GB2574050A

GB2574050A - A cutter

Info

Publication number: GB2574050A
Application number: GB1808588.6A
Authority: GB
Inventors: T Taylor Scott
Original assignee: Horizon Tool Solutions Ltd
Current assignee: Horizon Tool Solutions Ltd
Priority date: 2018-05-24
Filing date: 2018-05-24
Publication date: 2019-11-27
Also published as: GB201808588D0

Abstract

A cutter 200 comprising a housing 210 for receiving and rotating around a workpiece, a counterweight 250 connected to the housing by a pivot 235, and a blade 240 coupled to the counterweight, the blade is coupled to the counterweight such that when the counterweight is pivoted away from the workpiece, the blade is displaced towards the workpiece. There may be a plurality of counterweights and blades coupled (mechanically or flexibly) to each other and connected by a pivot to the housing. A shank 260 may be provided on the housing, suitable for being held by the chuck of a drill or mill. The housing may have a socket or a passage therethrough for insertion of a workpiece. A cutter is disclosed in which a counterweight is merely supported by a housing and is coupled to a blade by a rack and pinion mechanism (fig 6a-7c).

Description

Field of the Invention

The present invention relates to a cutter for receiving and cutting workpieces, more specifically the invention relates to a cutter comprising one or more blades coupled to one or more counterweights which are displaced by a centrifugal force resulting from rotation around a workpiece.

Background to the Invention

Elongate members, such as bolts, pipes, rods, dowels, and tubes, are typically cut by sawing or chopping through them from one side to another. This may often produce a member with an asymmetrical or deformed end where the cut was made; it is especially difficult to cut through a member so as to produce a symmetrical end which is planar.

Alternatively, pipes, or other hollow tubular members may be cut using pipe cutters which typically comprise a rotating circular blade which is rotated around the circumference of the member to be cut. In this the radial depth into which a member may be cut is typically limited.

The present invention arose to overcome the above-mentioned problems and to provide a superior tool for cutting elongate members.

Prior Art

Korean Patent Application KR 20160080095A discloses a pipe cutting device which comprises a cutting plate supported on a body which is rotated around a workpiece. The cutting plate is displaced away from the axis of rotation by a centrifugal force such that a cutting tool comprised by the cutting plate cuts along a circumferential surface of the workpiece.

Statement of the Invention

According to a first aspect of the present invention there is provided a cutter comprising: a housing for receiving and rotating around a workpiece, a counterweight connected to the housing by a pivot, and a blade coupled to the counterweight; wherein the counterweight and blade are arranged such that when the housing rotates around the workpiece the counterweight is pivoted away from the workpiece by a centrifugal force and the blade is displaced towards the workpiece.

A centrifugal force is a fictitious force which appears to act on an object within a rotating reference frame. Within the rotating reference frame, the centrifugal force acts away from the axis of rotation and causes objects to accelerate away from the access of rotation unless the centrifugal force is balanced by centripetal force acting towards the axis of rotation.

The cutter may comprise one or more counterweights, each of which may be connected to the housing by a pivot such that when the housing rotates around the workpiece they are pivoted away from the workpiece. In some embodiments the cutter may comprise a plurality of such counterweights.

The cutter may comprise one or more blades each of which may be coupled to at least one of the one or more counterweights such that when the at least one counterweights to which a blade is coupled are pivoted away from the workpiece the blade is displaced towards the workpiece. In some embodiments the cutter may comprise a plurality of such blades. Each blade to may be coupled to one or more counterweights, and each counterweight may be coupled to one or more blades.

In use, as the housing is rotated around a workpiece to be cut, a centrifugal force acts upon the one or more counterweights within a frame of reference rotating with the housing. This force may displace the one or more counterweights away from the workpiece, thereby causing the one or more blades coupled to the one or more counterweights to be displaced towards the workpiece. The rotation of the housing may thereby cause the one or more blades to be displaced into contact with the workpiece.

It is to be appreciated that in some embodiments, the housing may be rotatable when no workpiece has been received by the housing such that centrifugal forces pivot the one or more counterweight away from the axis or rotation, thereby displacing the blade towards the axis of rotation. In alternative embodiments, the cutter may comprise a means to prevent rotation of the housing when a workpiece is not received by the housing.

In preferred embodiments, one, some, or all of the one or more blades are connected to, or supported upon the housing such that they rotate around the workpiece with the housing. These one or more blades are preferably connected to or supported on the housing, such that they are displaceable towards workpiece as they and the housing rotate. In use these one or more blades may be displaced into contact with the workpiece as they rotate so as to cut as they rotate.

The connection between the housing and one, some, or all of the one or more blades may be indirect. For example, in some embodiments, one, some or, all of the one or more blades are not connected directly to the housing but are each connected to the at least one of the one or more counterweights (which are connected to the housing by the pivots). As the housing rotates, the one or more counterweights and blades may rotate with the housing.

These connections between one, some or all of the one or more blades and counterweights may define the couplings which cause the one or more blades to be displaced towards the workpiece when the counterweights to which they are coupled are displaced away from the workpiece.

Each of the one or more blades is coupled to at least one of the one or more counterweights such that when these at least one counterweights are pivoted away from the workpiece, the blade coupled to these one or more counterweights is displaced towards the workpiece.

One, some, or all of the one or more blades may be coupled to one or more counterweights by one or more mechanisms, such as mechanical linkages, interlocking gears, rack and pinion gears, slider rocker mechanisms, levers, and/or elongate flexible linkages such as ligatures, cables, wires or chains.

Alternatively, or additionally, one, some or all of the one or more blades may be comprised by a rigid body which also comprises at least one of the one or more counterweights. Therefore, the rigid body couples these one or more blades to these at least one counterweights. In some embodiments the cutter may comprise a plurality of such rigid bodies, each of which comprises one or more counterweights and one or more blades. Each of the one or more rigid bodies may be connected to the housing by a pivot (thereby connecting the one or more counterweights comprised by the rigid body to the housing by a pivot). Such rigid bodies connected to the housing by a pivot are preferably arranged such that as the counterweights comprised by the rigid body pivot away from the workpiece, the one or more blades comprised by the rigid body pivot towards the workpiece. For example, the one or more counterweights comprised by the rigid body may be on an opposite side of the pivot to the one or more blades comprised by the rigid body.

Each individual blade may be coupled to one, two, some, or all of the one or more counterweights, and each individual counterweight may be coupled to one, two, some or all of the one or more blades. Preferably the mass of each blade is less than that of the counterweights to which the blade is coupled.

In preferred embodiments, one, some, or all of the one or more blades are each coupled to at least one of the one or more counterweights such that when these at least one counterweights are pivoted towards the workpiece, the blade to which they are coupled is displaced away from the workpiece.

Preferably, these couplings are the same as the couplings which displace the one or more blades towards the workpiece as the counterweights are pivoted away from the workpiece. Therefore, one, some, or all of the one or more blades may each be coupled to one or more counterweights such that when said counterweights are pivoted towards or away from the workpiece, the blade is displaced away from or towards the workpiece respectively.

One, some, or all of the couplings between one, some, or all of the one or more blades and the counterweights to which they are coupled may interconnect the coupled blades and counterweights, such that moving one of the coupled blades or counterweights causes a corresponding movement of the other blades and/or counterweights to which it is coupled.

In some embodiments, one, some, or all of the one or more counterweights may be arranged such that a user may displace them towards the workpiece manually. Alternatively, or additionally, one, some or all of the counterweights may be arranged such that they fall towards the workpiece under gravity when the cutter is held at certain orientations while not rotating and/or the cutter may comprise one or more return mechanisms or biasing means for displacing one, some or all of the counterweights towards the workpiece.

In some embodiments, when the housing stops rotating, one, some or all of the one or more counterweights pivot towards the housing. This may be a consequence of the one, some or all counterweights being biased towards the housing and/or the workpiece. For example, the counterweights may be biased by one or more springs or other resiliently deformable members.

Alternatively, or additionally, one, some, or all of the one or more blades may be biased away from the workpiece, for example, by one or more springs or other resiliently deformable members. These biased blades may be blades which are coupled to counterweights and consequently, when these blades are displaced away from the workpiece, the counterweights to which they are coupled may be displaced towards the workpiece, such that the biasing of the blades away from the workpiece biases the counterweights to which they are coupled towards the workpiece.

Blades biased away from the workpiece may be arranged such that a force is exerted on them when one or more counterweights to which they are coupled pivot away from the workpiece, displacing them towards the workpiece, and such that when the counterweight pivots towards the workpiece, the force is removed, thereby displacing the blades away from the workpiece.

Workpieces for cutting with the cutter may be or may comprise elongate members such as bolts, rods, screws, pipes, or other rod-like or tubular objects. The cutter may be configured to cut workpieces to a specific length, to remove a specific length of material from a workpiece, and/or to remove the length of a workpiece which protrudes beyond a specific point.

Alternatively, or additionally, the workpiece may be or may comprise one or more other objects, such as objects attached to elongate members as described above. For example the workpiece may comprise one or more nuts screwed onto a bolt.

The housing is preferably a body which into which a workpiece or an end thereof is inserted in use, and which is configured to be rotated around such a workpiece. In preferred embodiments, the housing comprises an aperture into which the workpiece is inserted in use.

In preferred embodiments the aperture has rotational symmetry of order at least two about the axis about which the housing rotates. In further preferred embodiments the aperture is circularly symmetric about the axis about which the housing rotates.

In some embodiments the aperture defines a socket comprised by the housing into which an end of a workpiece is inserted in use.

In use, a workpiece may be inserted into such a socket such that its end abuts the end or base of the socket, the blades of the cutter will therefore be a predetermined distance away from the workpiece, allowing a fixed length of the workpiece to be reliably cut. In some embodiments this distance may be adjustable by adjusting the depth of the socket or the position of the blades relative to the socket. For example, the socket may comprise a tubular wall upon which the blades are supported within which a cylindrical base is telescopically slide-able to a plurality of locations, or to any of a continuum of locations.

In such embodiments, the motor (or other torque-providing device) which drives the rotation of housing may be located on the far side of the base of the socket from the workpiece and may comprise a rotor which is rigidly connected to, or formed integrally with the housing, such that the housing rotates with the rotor.

In other embodiments the aperture may extend entirely through the body of the housing such that it defines a passage through the body. This may advantageously allow any length of workpiece to be inserted through aperture such that a cut may be made at any point along the length of the workpiece. In some embodiments this may also allow the housing to be attached around an elongate workpiece which does not have a free end over which a socket shaped housing could be fitted.

In such embodiments the motor (or other torque providing device) is preferably arranged such that it does not obstruct the passage. As such, the rotor of the motor (or other device) may not be coaxial with the axis or rotation of the housing, or rigidly connected to the housing. In such embodiments, the rotor may be connected to and may transmit rotation to the housing via one or more belts, chains, drive wheels and/or intermeshing gears.

In preferred embodiments, the housing is substantially tubular. The housing may comprise a substantially cylindrical body which partially encloses a cylindrical aperture extending partly or entirely therethrough.

In some embodiments the cutter may comprise inserts which may be inserted into the aperture of the housing to reduce its depth, width, and/or radius. Such inserts may be dimensioned such that they do not obstruct the blades as they are displaced towards the workpiece.

The one or more counterweights are each connected to the housing by a pivot such that as the housing is rotated, they are pivoted away from the workpiece by a centrifugal force. The cutter comprises one or more such pivots, each of which may connect one or more counterweights to the housing. The pivots define points about which the counterweight rotates in use.

In some embodiments, each individual counterweight may be connected to the housing by a separate pivot, in other embodiments individual pivots may connect multiple counterweights to the housing.

In some embodiments, one, some, or all of the one or more blades may also be connected to the housing by pivots, and these blades may pivot towards the workpiece when the counterweights to which they are coupled pivot away from it. Such blades may also pivot away from the workpiece when the counterweights to which they are coupled pivot towards it.

The pivots which connect one, some, or all of the blades to the housing may be the same pivots which connect counterweights to the housing. For example, in some embodiments one or more pivots may each connect a rigid body comprising at least one of the one or more blades and at least one of the one or more counterweights to the housing. Alternatively, or additionally, one, some, or all of the one or more blades may be connected to the housing by a pivot which does not connect any of the one or more counterweights to the housing, in such embodiments the blades are not comprised by the same rigid body as the counterweights to which they are coupled. These blades may instead be coupled and/or connected to at least one of the one or more counterweights by mechanisms such as interlocking gears, or interconnecting cords or ligatures.

Alternatively, one, some, or all of the one or more blades may not be connected to the housing by a pivot. For example, one, some or all of the one or more blades (which are not comprised by rigid bodies comprising one or more counterweights) may be slide-ably connected to the housing such that they slide towards and/or away from the workpiece as the counterweights to which they are coupled pivot away from and/or towards the workpiece.

In some embodiments, one, some, or all of the one or more counterweights, blades, and/or rigid bodies comprising one or more counterweights and/or blades, may be connected to the housing by a plurality of coaxial pivots about which they rotate when pivoting as described above.

In some embodiments, one, some, or all of the one or more counterweights, blades, and/or rigid bodies comprising one or more counterweights and/or blades, may pivot within a plane which contains the axis of rotation of the housing, and which rotates with the housing, the pivots by which they are connected to the housing having axes orthogonal to the rotating planes.

Alternatively, or additionally, one, some, or all of the one or more counterweights, blades, and/or rigid bodies comprising one or more counterweights and/or blades, may pivot within a plane orthogonal to the axis of rotation of the housing, the pivots by which they are connected to the housing being parallel to the axis of rotation of the housing.

One, some, or all of the pivots may be located on the exterior of the housing and/or may be located within slots or indents in a wall separating the exterior of the housing from the aperture for receiving the workpiece.

In preferred embodiments, the workpiece is received by the housing such that it is coincident with the axis of rotation of the housing, therefore when the housing is rotated apparent centrifugal forces displace the counterweights away from the axis of rotation and from the workpiece.

In preferred embodiments, when at least one of the one or more counterweights are pivoted away from the axis of rotation of the housing, the blades to which the at least one counterweight is coupled are displaced towards the axis of rotation of the housing. In further preferred embodiments the at least one counterweights may be displaced away from the axis of rotation as the housing rotates and/or the blades coupled to the at least one counterweights may be displaced towards the axis of rotation when the counterweights to which they are coupled are displaced by the centrifugal force. These displacements may be radial within a reference frame which rotates with the housing.

In some embodiments, one, some, or all of the one or more blades are displaceable to and from a first arrangement wherein they are not in contact with a workpiece received by the housing. This arrangement may be an arrangement where these blades do not obstruct or protrude into the aperture comprised by the housing, and/or where the blades are located exterior to, and/or within the walls of the housing.

In some embodiments, one, some, or all of the one or more blades are displaceable to and from a second arrangement in which these blades pass through a complete cross section of the aperture of the housing when the housing completes a full 360degree rotation. This may allow the cutter to fully cut through a workpiece when the blades are displaced to this extent. In some such arrangements, a plurality of, or all of the blades may meet at the centre of the aperture, which may be at the axis of rotation of the housing.

In alternative embodiments, the one or more blades are not displaceable to a second arrangement as described above, and instead are instead displaceable to and from a second arrangement wherein the blades extend part of the way from the interior wall of the aperture of the housing towards the centre of the housing (which may coincide with the axis of rotation). Such a cutter may be used for cutting pipe, where extending the blades to the hollow centre of the workpiece in the centre of the aperture is unnecessary. This may allow shorter blades to be used which may advantageously allow the cutter to fit into confined spaces where such pipes may be located, for example within an excavation.

One, some or all of the one or more blades may be single edged blades, such as normal blades, clip-point blades, or sheepsfoot blades; may be double edged blades such as spear point blades (for example to allow rotation in either direction to cut the workpiece). In some embodiments one, some, or all of the one or more blades may be curved, for example such blades may be hawkbill or ulu blades. Alternatively, or additionally, one, some, or all of the one or more blades may be rotary cutters.

One, some, or all of the one or more blades may be sintered, electroplated, or vacuum brazed diamond cutters. Alternatively, or additionally one, some, or all of the one or more blades may be tipped with ultra-hard materials such as tungsten carbide or Polycrystalline Diamond (PCD).

In some embodiments, the one or more blades may be dimensioned and arranged such that each blade cuts through an equal amount of a workpiece as the housing is rotated. For example, a cutter comprising a pair of blades may be arranged such that as the housing is rotated each blade will cut through an equal amount of a workpiece, and if the workpiece is cut through completely, each blade will have cut through 50% of the cut. For example, the pair of blades may be adjacent and not overlapping such that each blade cuts through 50% of the thickness of a cut, but cuts through the full depth of the workpiece. In some such embodiments the cutting edges of the two blades may be arranged such that the portions of the workpiece into which they come into contact and which they cut are adjacent each other but do not overlap.

In some embodiments, the cutter may comprise a plurality of blades which are arranged to cut adjacent but not substantially overlapping portions of a workpiece in use. For example, a first blade may be located between first and second points along the length of the housing, aperture, socket or workpiece and a second blade may be located between the second point and a third point along such a length.

In some embodiments, one, some, a plurality of, or all of the one or more blades are each coupled to a different counterweight by a rigid arm which comprises the blade and the counterweight, and which is connected to the housing by a pivot (thereby coupling the blade to the counterweight and connecting the counterweight to the housing by a pivot).

The pivots may each connect a rigid arm to the housing intermediate the blade and the counterweight comprised by the rigid arm. For example, in some embodiments the blade and the counterweight may define or may be comprised by opposite ends of the rigid arm in-between which the pivot is located. In some embodiments the counterweight may be, may be defined by, or may comprise a portion of length of the rigid arm on one side of the pivot. The pivot may be located closer to the blade end of an arm than a counterweight end as described above.

In some such embodiments the cutter may comprise the same number of blades and counterweights, and each blade may be comprised by a different rigid arm which also comprises a single counterweight.

One, some, or all of the rigid arms may extend through slots or holes formed in a wall of the aperture comprised by the housing.

One, some or all of the rigid arms may be substantially straight and may pivot to and from a first orientation wherein the arms are substantially parallel to the axis of rotation and lies within or on the surface of the wall of the housing and/or a second arrangement wherein the arms extend substantially radially from, and perpendicular to, the axis of rotation of the housing, with the blades of the arms protruding into the aperture of the housing and the counterweights of the arms extending radially outwards from the housing. In some such embodiments the rigid arms may pivot within a plane containing the axis of rotation of the housing and which rotates with the housing.

In some embodiments, one, some, a plurality of, or all of the one or more counterweights are each connected to the housing by a pivot which is an elongate axle or shaft which is parallel to the axis of rotation of the housing. Each such counterweight may be connected to a separate axle or shaft which defines a pivot or alternatively multiple counterweights may be connected to a single axle or shaft.

One, some or all of the one or more blades may be connected to the axle or shaft, thereby coupling them to the one or more counterweights which are also connected thereto. These one or more blades may be spaced apart from the one or more counterweights along the length of the axle or shaft. Therefore, the counterweights and blades may rotate in different planes.

In such embodiments, the blades and/or counterweights connected to the pivot defining axle or shaft may be substantially flat and may be located within (and may rotate within) planes substantially orthogonal to the axle or shaft and the axis of rotation of the shaft.

For example, a counterweight may comprise a relatively flat weight connected to the axle or shaft by an arm which extends radially from the axle or shaft, such that the weight and arm lie within a plane orthogonal to the axle. In use the counterweight may rotate from an arrangement where the arm extends towards the axis of rotation of the housing, to one where it extends away from said axis, when the housing is rotated. Similarly, a blade may be a flat orthogonal blade attached to the axle or shaft at an end distal from its tip and may lie flat within a plane orthogonal to the axle or axis such that it rotates and cuts in a plane orthogonal to the axis of rotation. In some embodiments a single axle may be connected to both a blade and a counterweight as described above, and the blade and counterweight may extend in substantially opposite directions from the axle or shaft within two parallel but not coincident planes.

In some embodiments, the cutter may comprise a plurality of counterweights which are elongate weighted arms, each counterweight being connected to the housing by a separate pivot at or proximate to a first end of the arm. As the housing is rotated the counterweights rotate around the pivots such that their second ends (distal from their first ends and the pivots) are displaced away from the axis of rotation of the housing and the workpiece.

The cutter may further comprise a plurality of blades which are arranged to slide radially towards and away from the axis of rotation of the housing (into and out of the aperture of the housing). The cutter may comprise an equal number of counterweights and blades, and the blades and counterweights may be interspersed around the housing and the workpiece such that they alternate, and each blade is intermediate a pair of counterweights and each counterweight is intermediate a pair of blades.

Each blade may be coupled to the second ends of the two counterweights that it is between (such that the second end of each counterweight is also coupled to the two blades that it is between). The coupling being or comprising one or more rods, cords, chains, and/or flexible linkages which interconnect the blades and the second end of the counterweights.

Preferably the cutter comprises two or three blades and two or three counterweights. In use, as the second ends of the counterweights are displaced away from the workpiece and from each other as the housing is rotated. This may cause the linkages to become taught thereby pulling the blades (or the points thereof to which the linkages attach) towards a location directly intermediate the second ends of the counterweights to which they are connected, in such an arrangement they preferably extend into the aperture of the housing and/or are in contact with and arranged to cut the workpiece. The degree to which the counterweights are able to pivot may be limited by the lengths of the linkages therebetween and/or by some other retaining means.

In some embodiments the cutter comprises a means for connecting the housing to drill, mill, and/or other torque providing device, such that the housing is rotatable by the drill, mill, or other torque providing device.

For example, the cutter may comprise a shank, which may be dimensioned to be received and/or held by the chuck of a drill, mill or other torque providing device. The shank may be fixed to, or formed integrally with, the housing such that it rotates with the housing. Alternatively, the shank may be connected to or formed integrally with a rotor, wheel or gear from which rotation is conveyed to the housing by one or more interlocking gears, and/or belt and pulley systems.

In some embodiments, the cutter may comprise a torque providing device which may be coupled to the housing such that it rotates the housing in use. The torque providing device preferably comprises a motor and may be connected to the housing by one or more interlocking gears and/or belt and pulley systems.

In some embodiments the cutter may comprise an exterior housing which may surround, partially enclose, or entirely enclose the housing for receiving and rotating around a workpiece. The housing for receiving and rotating around a workpiece is preferably rotatable with respect to the exterior housing. The exterior housing may therefore provide a non-rotating exterior which may be handled by a user in use. One or more bearings may be provided between exterior housing and the housing for receiving and rotating around a workpiece.

The exterior housing may be clampable onto a workpiece, may be arranged to catch any material cut from a workpiece by the cutter in use, and/or may be arranged to provide a sealed cavity around the at least part of the housing for receiving and rotating around a workpiece. For example, an exterior housing may provide a sealed cavity within which the blades are located and which may be filled with a cooling fluid so as to prevent excess heat being generated during a cutting procedure. Alternatively or additionally, the sealed cavity may be configured to receive and extract gaseous and/or liquid coolant and/or cutting debris produced during cutting.

According to a second aspect of the invention, there is provided a cutter comprising: a housing for receiving and rotating around a workpiece, at least one counterweight supported by the housing and at least one blade coupled to at least one of the at least one counterweights; wherein the at least one counterweights and at least one blades are arranged such that when the housing rotates around the workpiece the at least one counterweights are displaced away from the workpiece by a centrifugal force and the at least one blades are displaced towards the workpiece.

One, some, or all of the one or more mechanical actuators may be or may comprise rack and pinion mechanisms or other linear actuators. For example, in some embodiments the one or more counterweights may comprise or support one or more rack gears which may mesh with one or more pinion gears on one or more axles which be connected directly to one or more blades such that the blades are rotated with the axles. Alternatively, the axles may be connected to or support an additional set of pinion gears which may mesh with rack gears on the one or more blades such that the blades are displaced linearly when the axles are rotated.

In such embodiment the one or more counterweights and/or blades may slide generally or substantially radially towards or away from the workpiece, for example along one or more tracks comprised by the housing.

The second aspect of the invention may comprise any suitable optional feature or modification described above with reference to the first aspect of the invention.

Preferred embodiments of the invention will now be described by of example only and with reference to the figures.

Brief Description of the Figures

Figure 1a is an overall view of a first cutter according to the present invention;

Figure 1 b is a cross-sectional view of the first cutter when stationary;

Figure 1c is a cross sectional view of the first cutter when rotating;

Figure 2a is an overall view of a second cutter according to the present invention;

Figure 2b is a partially cut away view of a third cutter according to the present invention mounted on a workpiece;

Figure 2c is an exploded overall view of a fourth cutter according to the present invention;

Figure 3a is an overall view of a fifth cutter according to the present invention;

Figure 3b is an overall view of a connected blade and counterweight of the fifth cutter;

Figure 3c is a top-down view of the fifth cutter;

Figure 3d is a bottom-up view of the fifth cutter;

Figure 3e is a partly cut-away overall view of a sixth cutter according to the present invention;

Figures 4a is a partially cut-away overall view of a seventh cutter according to the present invention when stationary;

Figure 4b is an overall, partially cut-away view of the seventh cutter when rotating;

Figure 4c is a top-down cut-away view of the seventh cutter when stationary;

Figure 4d is a top-down cut-away view of the seventh cutter when rotating;

Figure 4e is a view of the underside of the fourth cutter;

Figure 5a is an overall view of a first blade for a cutter according to the present invention;

Figure 5b is a side-on view of the first blade;

Figure 5c is a top-down view of the first blade;

Figure 5d is an overall view of a second blade for a cutter according to the present invention;

Figure 5e is a side-on view of the second blade;

Figure 5f is a top-down view of the second blade;

Figure 6a is an overall partially cut-away view of an eighth cutter according to the present invention;

Figure 6b is a top-down cut-away view of the eighth cutter when stationary;

Figure 6c is a top-down cut-away view of the eighth cutter when rotating;

Figure 7a is an overall partially cut-away view of a ninth cutter according to the present invention;

Figure 7b is a top-down partially cut-away view of the ninth cutter when stationary; and

Figure 7c is a top-down partially cut-away view of the ninth cutter when rotating.

Detailed Description of the Figures

Referring to the Figures generally there are shown eight cutters according to the first aspect of the present invention and a single cutter according to the second aspect of the present invention. Each of the cutters comprising a housing for receiving a workpiece, and a plurality of counterweights, and a plurality of blades each directly or indirectly coupled to one or more of the counterweights.

Referring to Figures 1a, 1b and 1c, there is shown a first cutter 100 according to the first aspect of the present invention. The cutter 100 comprises a cylindrical housing 110 with an aperture 120 for receiving and rotating around a workpiece, a pair of arms 130 which comprise bladed ends 140 and counterweight ends 150, and a shank 160.

The housing 110 is in the form of a cylindrical body with a central coaxial cylindrical aperture 120 formed therein. The cylindrical aperture 120 extends from a first end face 121 of the cylindrical body, where it defines a circular opening, along approximately three quarters of the length of the body. The housing 110 is therefore in the form of a cylindrical tube with an open first end and a closed second end.

The shank 160 is rigidly connected to the second end of the housing 110 and is coaxial with the cylindrical housing 110 and aperture 120. In use the shank is received and gripped by the chuck of a torque providing device, such as a drill. The torque providing device may therefore be used to rotate the shank 160 and the housing 110.

A pair of generally rectangular apertures 115 are formed in the cylindrical wall portion of the housing 110 which surrounds the aperture 120. The two apertures 115 being on opposite sides of the cylindrical aperture 120 and central axis of the housing 110 about which the cutter 100 is rotated in use.

A pin 135 extends across each aperture between opposite sidewalls thereof. The pin 135 being perpendicular to the central axes of the housing 110 and aperture 120 and to an imaginary radial line extending from the central axes through the pin 135. Each pin extends through a portion of a rigid arm 130 which pivots around the pin 135.

Each arm 130 comprises a first end 140 which is bladed, and a second end 150 which acts as a counterweight. The pins 135 pass through each arm in a direction perpendicular to their length, approximately one third of the way from their first end to the second end, such that the length of the arm between the pin 135 and the second end 150 is greater than the bladed length between the pin 135 and the first end 140.

The bladed first end 140 of the arm comprises a single concave cutting edge, such that the end 140 is in the form of a hawkbill blade. The portion of the arm 130 on the second end 150 side of the pin is asymmetrically and comprises a generally lobeshaped protrusion on the opposite side of the arm to the cutting edge of the bladed first end 140.

The arms 130 are arranged with the generally lobe-shaped protrusions of their second ends 150 extending out of the housing 110, with the apertures 115 being too small for the arms to be rotated to an arrangement where the second ends are located inside the aperture 120. In use, as the cutter 110 is rotated, the second ends 150 of the arms (which are larger and consequently heavier than the first ends 140) are displaced away from the housing 110, the aperture 120, and any workpiece received therein. Within a reference frame rotating with the cutter 100 the second ends 130 will experience an outwardly directed apparent centrifugal force. This causes the arms 130 to pivot to an orientation wherein they extend generally radially from the axis of rotation. This causes the bladed first ends 140 to be pivoted into the aperture 120 until their tips meet at the axis of rotation. This allows the blades 140 to cut through any workpiece located within the aperture as they are rotated.

In use a workpiece such as a bolt, rod, pipe, or other elongate object to be cut may be inserted into the aperture 120, to be cut to a desired length by the pivoting blades 140. The blades may be shaped to produce a desired cut shape on the workpiece.

Figure 1b shows the cutter 100 at rest with no external forces acting thereon, and Figure 1c shows the cutter 100 as it is being rotated with the arms 130 in their fully pivoted positions.

Referring to figure 2a there is shown a second cutter according to the first aspect of present invention. The second cutter 200 has a similar overall structure to the first cutter 100 described above but differs in that the shape of the arms and in that the arms rotate about axes parallel rather than perpendicular to the axis of rotation of the.

The second cutter comprises a cylindrical housing 210 and a pair of arms 230 with bladed first ends 240 and counterweighted second ends 250 which are connected to the housing 210 by pivots 235.

As in the first cutter 100, the housing 210 of the second cutter 200 is a cylindrical body with a central cylindrical aperture 220 extending from a first end face 221 of the cylindrical body, where it defines a circular opening, along approximately three quarters of the length of the cylindrical body. A shank 260 is supported on and extends from a second end face of the cylindrical body distal from the first end 221 with the cylindrical aperture. The shank 260 is coaxial to the cylindrical body and the cylindrical aperture 220.

In use, the shank 260 is being received and gripped by the chuck of a torque providing device such as a drill. The torque providing device may then be used to rotate the shank and by extension the entire cutter 200.

The housing 210 of the second cutter 200 differs from that of the first cutter 100 in that the pair of generally rectangular apertures 215 formed in the cylindrical wall of the housing 210 extend lengthways around the circumference of the housing 210 perpendicular to the central axis of rotation of the housing 210.

As in the first cutter 100, one of a pair of pins 235 extends across the width of each of the two rectangular apertures 215. The pins 235 therefore extend parallel to the axis of rotation of the housing 210, the shank 260 and the cutter 200, rather than extending perpendicular thereto as in the first cutter 100 described above.

The two arms 240 are each supported on and rotate around one of the two pins 235 such that their lengths are perpendicular to, and they rotate within a plane orthogonal to the axis of rotation of the cutter 200. The arms 230 comprise counterweights 250 at their second ends (which are located outside of the housing 210) and single edged blades 240 at their first ends (which are located within and displaceable between the interiors of the rectangular apertures 215 and the cylindrical aperture 220 as the cutter 200 is rotated).

When the cutter 200 is rotated a centrifugal force acts on the counterweights 250 in the reference frame rotating with the cutter 200, displacing them outwards away from the housing 210 and the axis of rotation. This causes the arms 230 to pivot around the pins 235 and the bladed ends 240 of the arms to be displaced out of the rectangular apertures 215 into the cylindrical aperture 220. If a workpiece is located inside the cylindrical aperture 220 the bladed ends 240 will contact and cut it as they rotate. If the cutter 200 continues to rotate the bladed ends 240 will be displaced inwards until they meet at the centre of the cylindrical aperture 220.

Referring to Figure 2b there is shown a partially cut-away view of a third cutter 200 according to the first aspect of the present invention mounted on a workpiece 222. The third cutter comprises an inner housing 210 and a pair of pivoting arms 230 of similar structure to those of the second cutter 200 described above and illustrated in Figure 2a. The inner housing 210 of the third cutter 200 differing from the housing 210 of the second cutter 200 in that it is open at both ends and designed to be fitted over any point on an elongate workpiece 222 rather than only over an end thereof. The third cutter 200 further comprises an exterior housing 285 for enclosing the housing 210 and the pivoting arms 230, a clamp 270 for securing the cutter to a workpiece and a torque providing device 265 for driving rotation of the cutter inner housing 210 of the cutter.

The inner housing 210 of the third housing 200 being cylindrical and comprising a central coaxial cylindrical aperture similar to that of the second cutter 200 described above. The cylindrical aperture of the third cutter 200 differs from that of the second cutter 200 in that it extends through the full length of the cylindrical body 210, the cylindrical body 210 having two open ends and no shank such that it defines a tube.

The inner housing 210 comprises a pair of arms 230 with counterweights 250 and cutting blades on opposite ends of the same shape and function as those of the second cutter 200 described above with reference to Figure 2a. The arms 230 are located within rectangular apertures 215 of substantially the same shape and function of those of the second cutter 200 described above.

The inner housing is located within and rotated with respect to an exterior housing 285. The exterior housing 285 comprises a pair of internal cavities 288 each of which contains a portion of the inner housing 210. One of the cavities provides space for the counterweighted ends 250 of the arms 230 be displaced into as the inner housing 210 is rotated. The other cavity 288 encloses a belt drive 262, 263, 264 for driving rotation of the inner housing. Any offcut material produced by the cutter 200 cutting through a workpiece may advantageously be contained within the cavity 288.

The exterior housing comprises a pair of circular apertures one or both of which are defined by collets 225 which fit around the workpiece 222 are clamped onto the workpiece 222 by a clamp 270 and provide a seal between the cavity 288 of the exterior housing 285 and the environment in which it is located. The seal may optionally allow the cavity 288 containing the arms 230 to be filled with a gaseous or liquid coolant and/or cutting fluid. The exterior housing 285 may optionally be connected to a means of debris dust and/or cutting fluid extraction.

A pair of clamped collet 225 ends may advantageously hold a workpiece 222 on both sides of a cut such that after the workpiece 222 is cut through by the cutter, both resulting pieces are gripped and neither will be dropped.

In some embodiments this clamp 270 may be in the form of a clamp that conforms to the application, for example the cutter may be arranged to cut scaffolding tube and the clamps 270 may be scaffolding clamps for conforming to a particular scaffolding system.

Bearings 280 are provided between the inner housing 210 and the exterior housing 285 at each of the apertures between the cavities 288 and the exterior of the cutter and between the two cavities 288. The bearings 280 allow the inner housing 210 to rotate freely with respect to the exterior housing 285. A portion of the exterior surface of the inner housing 210 defines a belt engaging portion 262 around which one end of a belt loop 263 passes. The other end of the belt loop 263 passes around a drive wheel 264 of significantly greater radius than the belt engaging portion 262 of the inner housing 210. The drive wheel 264 is connected by an axle to the torque providing device 265 which is mounted to the exterior housing 285. In use a user may actuate the torque providing device 265 to rotate the axle, the drive wheel 264, the belt loop 263 the belt engaging portion 262, the inner housing 210 and by extension the arms 230, thereby causing the blades to pivot and any workpiece 222 received by the cutter 200 to be cut.

Referring to Figure 2c there is shown a partially cut-away exploded view with enlarged detail of a fourth cutter 200 according to the first aspect of the present invention which is arranged to be mounted on a workpiece with no free end.

The fourth cutter 200 has a similar structure to the third cutter 200 described above and comprises an inner housing 210 with a pair of pivoting cutting arms 230 and an exterior housing 285 for enclosing the inner housing 210 and being clamped onto a workpiece.

The inner housing 210 of the fourth cutter 200 has a similar structure to that of the third cutter 200 described above and shown in Figure 2b. The inner housing 210 comprises a tubular cylindrical body with a coaxial cylindrical aperture 220, a pair of rectangular apertures and a pair of pivoting arms 230 with counterweights 250 extending through and pivoting within the rectangular apertures. The inner housing further comprises a ring gear 267 connected to and surrounding a central portion of the cylindrical body. The inner housing is bipartite and comprises two hemi-tubular parts which interlock to define the tubular cylindrical body and the ring gear 267.

The ring gear 267 is spaced apart from the cylindrical tubular body by a pair of arms on opposite sides of the body, each of which is comprised in part by each of the two hemi-tubular parts of the inner housing. The two hemi-tubular parts are interconnected by a pair of sliding dovetail joints 205 on interior surfaces of the two arms.

The cutter 200 further comprises an exterior housing 285 arranged to enclose the inner housing 210 and the portion of the workpiece onto which the inner housing is fitted. The exterior housing 285 encloses an interior cavity between two circular apertures with collets 225 which may be clamped onto a workpiece as in the third cutter 200 described above and illustrated in Figure 2b. The cavity has a wide central portion surrounding the cutting arms 230 and the ring gear 267, and two narrow portions intermediate the wide portion and the apertures with collets 225. Bearings 282 are provided in alcoves in the walls of the narrow portions of the cavity, these bearings 282 contact the exterior surface of the cylindrical tubular body allowing the inner housing 210 to rotate with respect to the exterior housing 285.

The outer housing 285 is in a clamshell arrangement and comprises two part which are interconnected on one side by a hinge 290, 292 such that the outer housing can be fit over the inner housing 210 and the workpiece. A latch 295 is provided on the opposite sides of the two parts from the hinge 290, 292 such that the outer housing 285 can be locked in position.

The outer housing further 285 comprises a drive gear 266 which is located and rotatable within a rectangular aperture in the wall of the wider portion of the cavity of the outer housing 285. A portion of the drive gear 266 extends into the cavity and meshes with the ring gear 267 of the inner housing 210 which is supported by the bearings 280 in the walls of the narrow portions of the cavity of the outer housing 285. Consequently, the inner housing 210 may be rotated within the cavity of the outer housing 285 by rotating the drive gear 266 which extends from the exterior of the outer housing.

Referring to Figures 3a to 3d there is shown a fifth cutter 300 according to the first aspect of the present invention. The cutter 300 comprises a cylindrical housing 310 with an aperture 320 for receiving workpieces to be cut, a shank 360 for rotating cutter 300 and a pair of axles 333 to which are attached a pair of blades 330 and counterweights 332, 350.

The fifth cutter 300 comprises a housing 310 with a similar structure to those of the first and second cutters 200 described above. The housing 310 is a cylindrical body with a central cylindrical aperture 320 extending from an open first end 321 part of the way to a closed second end, at which a shank 360 is located. The shank 360 in use being received by the chuck or a torque providing device, and a workpiece to be cut being inserted into the aperture 320 of the housing 310.

A pair of elongate axles 333 are each located within one of two elongate apertures which extend parallel to the axis of rotation of the housing 310 from the second closed end of the housing 310 to a notch 315 formed in the wall which surrounds cylindrical aperture at the open distal end 321 of the housing 310.

The axles 333 are longer than the elongate apertures formed in the housing 310 and protrude from the closed second end of the housing 310 and into the notches 315 at the open end 321 of the housing 310. A cutter arm 330 is attached to a first end of each axle 333 within the notch 315 at the first open end of the housing 310, such that the blades 340 rotate with the axle 333 within a plane at the open end 321 of the cylindrical aperture of the housing 310 and orthogonal to the axis of rotation of the cutter 300. A counterweight 350 is attached to a second end of each axle 333 at the second closed end of the housing 310, such that the counterweights are located generally within, and rotate within a plane slightly on the far side of the housing 310 from the opening of the aperture 320. This allows the counterweights to rotate without protruding substantially past the curved exterior surface of the housing 310, which may advantageously allow the cutter 300 to be used in confined areas.

The blades 340 are single edged and curved and are dimensioned such that they can meet at the central axis of rotation of the housing following the cutter path 341 shown in Figure 3d.

The counterweights comprise generally cylindrical weights 350 attached to the axles by arms 332, such that the centre of mass of the counterweights 350 is distant from the axles 333. The counterweights 332 350 may be asymmetrically lobe shaped.

The counterweights 350 extend from the axles at approximately 90 degrees to the cutting edge of the blades 340. As such when the counterweights 350 are oriented radially inwards towards the axis of rotation, the associated blades 340 which are attached to the same axles do not substantially protrude beyond the exterior of the housing 310. When the counterweights 350 are aligned with the perimeter of the housing, the blades 340 are oriented radially inwards towards the axis of rotation so as to cut the workpiece.

In use, as the housing 310 is rotated the counterweights 350 are displaced outwards under an apparent centrifugal force, thereby rotating the axles 333, and consequently rotating the blades into a workpiece received by the aperture 320 of the housing 310.

The first end face 321 of the housing surrounding the opening of the cylindrical aperture may have a rasp, saw, abrasive or other cutting surface that would allow the cutter 300 to cut a soft material such as wood surrounding the head of a fastening while the blades 340 or counterweights 350 are restrained. Once the cutter is at a desired depth the cutter blades 340 or counterweights 350 would be released so as to part-off the head of the fastening.

Alternatively, the first end face 321 may be formed from a soft bearing surface such as bronze, brass, a graphite composite or other self-lubricating material and/or may be a replaceable sacrificial surface so as to reduce frictional damage to a surface surrounding a workpiece to be cut.

In some embodiments the cutters 340 may be recessed a set distance from the first end 321 and employ an insert comprising a socket and bearings so as to accurately position the cutters above a fastening to remove surplus length.

Referring to Figure 3e there is shown a partially cut-away view of a sixth cutter 300 according to the first aspect of the present invention. The sixth cutter 300 comprises an inner housing 310 with a pair of axles 333 each supporting a blade 330 and a counterweight which has a similar structure to the fifth cutter 300 described above.

The inner housing 310 has a similar structure to that of the fifth cutter 300 described above but differs in that it does not comprise a shank, and instead comprises a belt engaging circumferential portion 362 formed on its curved exterior surface. The inner housing 310 comprises an aperture 320 and supports a pair of axles 333, blades 330 and counterweights which are identical to those of the fifth cutter 300 described above.

The inner housing 310 is located partially within an outer housing 385 attached to a torque providing device 365. The outer housing 385 encloses a cavity within which the closed end and the belt engaging portion 362 of the inner housing 310, along with a drive belt 363 and a drive wheel 364. The open first end 321, notches 315 of the housing and the blades are located outside of the exterior housing and protrude out of a circular aperture therein. A plurality of bearings 380 are provided between the inner housing 310 and the exterior housing 385 such that the inner housing is free to rotate with respect to the exterior housing 385.

A first end of the drive belt 363 engages with and fits around the belt engaging portion 362 of the inner housing and a second end of the belt engages with and fits around the drive wheel which has a greater radius that the inner housing. The torque providing means 365 drives rotation of the drive wheel 364 thereby rotating the belt 363 and the inner housing and causing the counterweights and blades 330 to be displaced outward and inward respectively.

The sixth cutter is particularly suited to applications in confined spaces such as engine bays.

Referring to Figures 4a, 4b, 4c, 4d and 4e there is shown a seventh cutter 400 according to the first aspect of the present invention arranged to cut a length of a bolt 422 which protrudes beyond a nut 423.

The cutter 400 comprises a generally cylindrical hollow housing 410 with a curved wall intermediate flat upper 411 and lower end walls 412. A circular aperture is formed in the centre of the lower wall 412, the circular aperture being dimensioned to receive the nut 423 within a socket 424 (as figure 4e) that is held within a bearing race 480 and the length of the bolt 422 protruding therefrom. A rectangular aperture 416 is formed in the centre of the upper wall of the housing 411. The rectangular aperture 416 permits a bolt 422 of any length to be inserted through the housing 410; the rectangular aperture also receives upper ends of the two counterweights 450. A passage 420 is defined through the cutter 400 from the circular aperture in the centre of the lower wall 412, through the rectangular aperture 416 and into the shank 460.

The two counterweights 450 are generally rectangular weights located on opposite sides of the passage 420 extending through the housing 410 where a bolt 422 is located in use. The upper ends of the two counterweights 450 are held in the rectangular aperture 416 by pins 435 extending thereacross, and about which the two counterweights 450 are free to pivot about the pins 435.

In a resting position (as shown in Figures 4a and 4c) the counterweights hang substantially parallel to the bolt 422; as the housing is rotated, the free ends of the counterweights 450 are displaced away from the bolt 422 by an apparent centrifugal force in the rotating reference frame, this is shown in Figures 4b and 4d.

The cutter 400 further comprises a pair of blades 440 mounted on radial tracks 442 in the lower face of the housing 412 on opposite sides of lower aperture 424 and the passage 420 for the bolt 422 such that the blades are able to slide radially into and out of contact with the bolt 422. The blades 440 each being located intermediate the two counterweights 450.

Each of the blades 440 is coupled to the lower ends of each of the two counterweights 450 by inelastic flexible or rigid linkages 434 of fixed length, such as wires or chains or rods. As the cutter 400 is rotated around the bolt 422, the lower ends of the counterweights 450 are displaced outwards away from the bolt 422, thereby pulling the two blades 440 along the track towards the bolt 422 which is located between the two counterweights 450. This pulls the blades 450, which rotate with the housing 410 into contact with the bolt 422 such that they cut it.

In some embodiments the tracks 442 may comprise springs or other resiliently deformable members which may act to displace the blades 440 away from the bolt 422 when the cutter 400 is not rotating.

The cutter 400 has been described as if it is in the orientation shown in figures 4a and 4b. It is to be appreciated that terms indicative of this orientation such as upper, lower, vertical etc. are with reference to this orientation and do not limit the cutter to such an orientation. The cutter is able be used, held or rotated in any orientation and may be reoriented in order to cut bolts 422 in other orientations, such as horizontal bolts.

The cutter 400 comprises a hollow shank 460 coaxial with the bolt 422, which is attached to the upper face 411 and surrounds the upper aperture 416, although this will limit the length of a bolt which may be removed in a single cut. The hollow shank 460 may form the basis of an extended shank for a coaxial drive means or the basis for an orthogonal belt drive wheel.

When dealing with hard materials such as stainless steel, any cutting device according to the present invention may be limited by the magnitude of the cutting force which is practically generatable at practical rotational velocities with counterweights of given dimensions. The cutting force may be increased by using heavier materials for the counterweights and/or lighter materials such as titanium for elements which are displaced towards a workpiece during rotation, such as the blade arms. The size or volume of such elements may also be reduced, for example by cutting holes or indents therein so as to reduce their mass.

Referring to Figures 5a to 5f there is shown a pair of blades for use with cutters according to the present invention. Figures 5a, 5b and 5c show a first blade and Figures 5d, 5e and 5f show a second blade; the two blades being mirror images of each other.

Each blade comprises a cutting edge 545 half the thickness of the main blade body 540, the cutting edges of the two blades being on opposite sides of the blade body such that when the two blades are located at equal points along the length of a workpiece (for example on opposite sides of a cutter according to the present invention) their cutting edges 545 will contact separate but adjacent portions of the workpiece as they are rotated around the workpiece. This has the effect of allowing a blade substantially of a given thickness (for example so as to be sufficiently rigid) to exert a greater cutting force as it is rotated. The two blades each comprise sloped portions 546 which taper from the narrow cutting edge 545 to the wider remainder of the blade 540.

Cutters according to the present invention for cutting large diameter workpieces such as large pipes may comprise a large number of blades each of which may be shaped to a separate portion of the length of the workpiece such that the combination of all of the plurality of blades produces a wider cut. One some or all blades may be cut to form a specific shape such as a chamfer to the finished edge of the workpiece.

Referring to Figures 6a to 6c there are shown partially cut-away views of an eighth cutter 600 according to the first aspect of the present invention. The eighth cutter has a similar overall structure to the fifth cutter 300 described above and shown in Figures 3a to 3d.

Similarly, to the fifth cutter 300 the sixth cutter 600 comprises a cylindrical housing 610 with a first end with an aperture 620 and a closed second end 611 upon which a shank 660 is supported. The aperture 620 in the first open end of the body opens onto a cylindrical first cavity 614 for receiving a workpiece such as a bolt protruding from a nut 622 as shown in Figures 6b and 6c. A second cavity 638 is located intermediate the first cavity 614 and the closed second end 611 of the housing 610. The two cavities are separated by a bulkhead 613. The second cavity enclosing a pair of counterweights 650, 651 and a set of interlocking gears and toothed elements 632, 634, 635 for connecting the counterweights to an axle 633.

The eighth cutter 600 comprises an elongate axle 633 located within an elongate aperture formed in the wall surrounding the first cavity 614 and extends between a blade 630 located adjacent the open end of the housing 610 and the second cavity 638. An axle gear 634 with teeth around a subset of its edge is connected to the end of the axle 633 in the second cavity 638.

The axle gear 634 meshes with a secondary gear 635 with teeth around a portion of its border. The secondary gear 635 is connected to by an axle 639 to a first counterweighted body 652 with a counterweight 651 at its first end and a toothed gear portion 636 at its second end distal from the counterweight. This partially toothed gear portion meshes with a partially toothed gear portion at and end of a second counterweighted body 650 of similar structure to the first counterweighted body.

In use as the housing 610 is rotated the counterweighted ends of the counterweighted body are subject to a centrifugal force and are displaced outwards away from the axis of rotation of the cutter 600. This drives rotation of the axle 633 through the gear chain

634, 636, 637, 639, 635, 634 causing the blade to be pivoted inwards towards the axis of rotation.

For purposes of clarity, the second cavity 638 is shown substantially extended, and in variant embodiments the ends of the gear axles 639 would be set into the bulkhead 613 and the closed second end 611 of the housing 610.

The two counterweighted arms 652 are lobe shaped and comprise narrower portions to provide clearance for the axle gear 634 and secondary gear 635 while maximising the counterweight mass at their ends

The blade 630 and the toothed end of the first counterweighted body 652 comprise lightening holes 631 to maximise the force of the cutting blade.

Figure 6b shows a partially cut-away top-down view of the cutter 600 at rest configured to remove a seized fastening 622 in a confined space. The bulkhead 613 has been partially cut-away to show the first cavity as has part of the first counterweighted body 652. It is envisaged that the cutter 600 could comprise return springs on the gear mechanism to displace the counterweighted ends of the bodies 650 652 away towards the axis of rotation when the cutter is not rotating.

Figure 6c shows a corresponding partially cut-away view of the cutter 600 during or after a rotation where the path of the cutting blade 640 has passed through the thickness of the fastening 622. If the present cutter is required to cut the full diameter of the aperture 620 an arrangement of ratchet and pawls could be employed about the main axle 633 and between the secondary gear 635 and the first counterweighted body 652 the cutting edge 640 of the blade 630 could traverse from the start position at the outer diameter of the housing aperture 620 to the central axis of rotation of the cutter 600. This would be achieved in two cycles of the counterweight 650 from its position at figure 6b to its position at figure 6c. After the first cut cycle a return spring mechanism on the counterweight would engage once the rotation stops, returning the second counterweighted body 650, via a ratchet and pawl between the secondary gear 635 and the first counterweighted body 652, back to its start position while a corresponding ratchet and pawl on the main axle 633 would hold the axle gear 634 and secondary gear 635 in partially displaced positions. The cutter 600 would be rotated for a second cut cycle to complete the desired cut path. If a still greater cutting force is desired an appropriate gear ratio could be employed which would in turn necessitate a corresponding number of start-stop cut cycles of the counterweight 650 to complete the desired cut path of the cutting edge 640 of the blade 630.

Such ratchet mechanisms might be selectively engageable and disengage-able via a means external to the housing 610. For example, the arrangement of the second counterweighted body 650 may be manually reset-able between cut cycles via a means external to the housing 610.

It is also envisaged that the blade 630 shown in Figure 6b could be reduced to a length capable of only cutting the illustrated fastening, for example, half its illustrated cutting distance. This would increase the cutting force and subsequently require, by the previously described ratchet arrangement, that two start-stop cut cycles be completed to complete a cutting procedure.

In other variants of the eighth cutter 600, the cutter may comprise interchangeable parts such as blade arms of various length, adjustable gear ratios and or counterweights with adjustable masses or which are removable or replaceable.

It will be appreciated that a second blade 630, 631, axle 633 and gear and counterweight set 634, 635, 639, 632, 634, 650, 651 could be added to the eighth cutter on an opposite side of the cutter to the first such components.

Referring to figures 7a to 7b there is shown a ninth cutter according the second aspect of the present invention. The ninth cutter comprises a cylindrical housing 710 for receiving and rotating around a workpiece, a pair of counterweights 750 which are displaced radially by a centrifugal force as the housing 710 is rotated and a pair of blades 740 coupled to the counterweights by mechanical actuators 733, 735, 737.

In a similar manner to the housing of the eighth cutter 600 described above, the housing 710 of the ninth cutter 700 is a cylindrical body with a first end 712 with a central circular aperture 720 opening onto a first cavity 714 and a second closed end 711 supporting a shank 760 for rotating the housing 710 around its central axis. The housing 710 comprises a first aperture for receiving a workpiece and containing the blades 740, as well as a second cavity 738 separated from the first cavity 714 by a bulkhead 713 and located between the first cavity 714 and the second closed end 711. The second cavity 738 contains the counterweights 750. The first and second cavities 714, 738 being substantially cylindrical.

The second cavity 738 is shown substantially enlarged for visual clarity and the length of the cavity 738 (between the bulkhead 713 and the closed end 711 of the housing) would typically be equal to or slightly larger than the lengthwise thickness of the counterweights 750 and the counterweight pinion gears 734. This would advantageously prevent the counterweights 750 becoming displaced off of the counterweight pinion gears 734 within the cavity 738. In some variants of the cutter an enlarged second cavity 738 may be required for additional and or larger counterweights 750.

In some variants of the cutter, the bulkhead 713, the counterweights 750, and optionally the second closed end 711 and shank 760 may comprise central apertures, indents, notches, or cut-outs so as to define an unobstructed central passageway through the housing coaxial with the central circular aperture 720 in the first end 712 of the housing 710. This may allow a longer workpiece to be received by the cutter 700.

The profiles of the two counterweights 750 when they are viewed from either end of the cutter 700 are in the shape of a segment of a circle of equal radius to the second cavity 738 of the housing 710. The two counterweights 750 being displaceable between an outer arrangement where their curved edges are in contact with the interior wall of the second cavity 738 (as shown in Figure 7c) and an inner arrangement wherein their straight edges are in contact with each other at the centre of the second cavity 738 (as shown in Figure 7b).

Each of the counterweights 750 comprises a pair of parallel slots 753 which extend perpendicular to their straight edges, one of the long edges of each of the slots defining the rack gear 735 of a rack and pinion mechanism. A counterweight pinion gear 734 being located within each slot 753 and meshing with the rack gear 735 defined thereby.

The counterweight pinion gears 734 are each supported on and connected to a corresponding axle 733 which extends from the second cavity 738, through the bulkhead 713 and across the first cavity to the closed first end 712 of the housing 710. A blade pinion gear 737 is supported on and connected to each of the axles adjacent to the closed first end 712 of the housing 710.

Each of the blade pinion gears 737 meshes with a blade rack gear 736 supported on one side of one of the two blades 740 so as to define a rack and pinion mechanism. Each of the blades 740 having a blade rack gear 736 extending along each side, each of which engages with a single blade pinion gears 737. The counterweight rack gears 735 are on opposite sides of the axles 733 from the blade rack gears 736 such that when the counterweights 750 are displaced radially outwards (for example, under a centrifugal force) the axles 733 rotate in a first direction and the blades 740 are displaced radially inwards and when the counterweights 750 are displaced radially inwards the axles 733 are rotated in an opposite second direction and the blades 740 are displaced radially inwards.

Each of the blades 740 is secured within a housing 741 which is mounted on a radial track 742 formed in the inside face of the closed second end 712 of the housing 710 extending between the aperture 720 and the inside curved walls of the first cavity 714. Consequently, the blades 740 are restricted to radial displacement and are coupled to counterweights 750 such that they are displaced together.

Figures 7b and 7c show the cutter 700 in stationary and rotating arrangements respectively with the central bulkhead 713 cut away to view the components of the first and second cavities simultaneously. In Figure 7c part of one of the counterweights 750 is also partially cut away.

In some variants of the cutter 700, the cutting force may be increased by employing a mechanically advantageous gear arrangement which may include a ratchets and pawls between the blades 740 and the counterweights 750. In some embodiments several stop start cut cycles as described with reference to the seventh cutter may be required to complete a cut.

The invention has been described by way of example only and it will be appreciated that variation may be made to the embodiments described above without departing from the scope of the invention as defined by the claims. For example, features of one described cutter according to the present invention may be combined with features of one or more of the other described cutters.

Claims

1. A cutter comprising: a housing for receiving and rotating around a workpiece, a counterweight connected to the housing by a pivot, and a blade coupled to the counterweight; wherein the counterweight and blade are arranged such that when the housing rotates around the workpiece the counterweight is pivoted away from the workpiece by a centrifugal force and the blade is displaced towards the workpiece.

2. A cutter according to claim 1 comprising a plurality of counterweights each connected to the housing by a pivot such that when the housing rotates around the workpiece the counterweights are pivoted away from the workpiece by a centrifugal force.

3. A cutter according to claim 2 comprising a plurality of blades each coupled to at least one of the counterweights such that when the at least one counterweights to which they are coupled are pivoted away from the workpiece the blades are displaced towards the workpiece.

4. A cutter according to claim 3 wherein the blades are each coupled to at least one of the counterweights such that they rotate with the at least one counterweight to which they are coupled.

5. A cutter according to claim 3 or 4 wherein the blades are each coupled to at least one of the counterweights by a mechanical linkage.

6. A cutter according to claim 3 or claim 4 wherein the one or more blades are each coupled to at least one of the counterweights by an elongate flexible linkage.

7. A cutter according to claim 3 or claim 4 wherein each of the blades is comprised by a rigid body which also comprises at least one of the counterweights, thereby coupling the blade to the at least one counterweight.

8. A cutter according to claim 7 comprising a plurality of rigid bodies, each of which comprises a single blade and a single counterweight to which the blade is coupled.

9. A cutter according to claim 8 wherein each of the plurality of rigid bodies is connected to the housing by a pivot at a point intermediate the blade and the counterweight comprised by the rigid body.

10. A cutter according to any of claims 7 to 9 wherein the rigid bodies are arms.

11 .A cutter according to claim 10 wherein the counterweight comprised by the arm is a portion of the length of the arm.

12. A cutter according to any of claims 3 to 11 wherein the blades are each coupled to at least one of the counterweights such that when the at least one counterweight to which a blade is coupled is pivoted away from the workpiece, the blade is displaced towards the workpiece, and when the at least one counterweight is pivoted towards the workpiece the blade is displaced away from the workpiece.

13. A cutter according to any of claims 3 to 12 comprising one or more biasing means each arranged to bias at least one of the counterweights towards the workpiece.

14. A cutter according to any of claims 3 to 13 wherein the housing comprises an aperture into which a workpiece is inserted in use.

15. A cutter according to claim 14 wherein the aperture defines a passage through the body, through which a workpiece is inserted in use.

16. A cutter according to claim 14 wherein the aperture defines a socket into which an end of a workpiece is inserted in use.

17. A cutter according to any of claims 3 to 16 wherein the blades are each connected to the housing by a pivot.

18. A cutter according to any of claims 3 to 17 wherein each of the blades is connecting to the housing by a pivot which also connects a counterweight to which the blade is coupled to the housing.

19. A cutter according to any preceding claim comprising a means for connecting the housing to a drill or mill.

20. A cutter according to claim 19 wherein the means for connecting the housing to a drill or mill is a shank dimensioned to be held by the chuck of a drill or mill.

21. A cutter comprising: a housing for receiving and rotating around a workpiece, at least one counterweight supported by the housing and at least one blade coupled to at least one of the at least one counterweights; wherein the at least one counterweights and at least one blades are arranged such that when the housing rotates around the workpiece the at least one counterweights are displaced away from the workpiece by a centrifugal force and the at least one blades are displaced towards the workpiece.

22. A cutter according to claim 22 wherein the at least one blades are each coupled to at least one of the at least one counterweights by one or more rack and pinion mechanisms.