GB2588831A

GB2588831A - A handheld circular cutter saw

Info

Publication number: GB2588831A
Application number: GB1916406.0A
Authority: GB
Inventors: Donson Simon; Bateman Ben; Holt Will; Stratford Mark
Original assignee: Evolution Power Tools Ltd
Current assignee: Evolution Power Tools Ltd
Priority date: 2019-11-11
Filing date: 2019-11-11
Publication date: 2021-05-12
Anticipated expiration: 2039-11-11
Also published as: GB2588831B; GB201916406D0

Abstract

A handheld disc cutter 10 having main body 12, front handle assembly 52 and rear handle assembly 16, the main body having a longitudinal axis (Y; Fig 5) and an elongate arm portion 18 extending along the longitudinal axis. The disc cutter has blade 24 arranged on the elongate arm of the main body which rotates about a horizontal axis of rotation (X; Fig 5) perpendicular to the longitudinal axis. The disc cutter power tool has electrical motor (62; Fig 8a) located within the main body and a gear arrangement, the gear arrangement has two reduction gears (66; 8c) located adjacent the electrical motor within the main body, a drive shaft (64; Fig 8a) in communication with the reduction gears and extending within the elongate arm and two drive gears (72; Fig 8c) at a distal end of the drive shaft and operable to drive the cutting blade about the axis of rotation. The rear handle assembly has a graspable handle arranged rearwardly from the main body. The front handle assembly has a graspable handle arranged forwardly of the motor and reduction gears when the disc cutter is held. This provides an improved ergonomic design of a handheld disc cutter.

Description

A Handheld Circular Cutter Saw The present invention relates to a circular cutter saw in the form of a disc cutter power tool.

Portable, manually-wielded circular cutter saw power tools are common in a number of applications. Such disc cutter saws generally comprise an abrasive circular blade which can be used to cut stone, concrete, metal and other materials. Such saws are commonly used in the construction and building industry, and in domestic environments, to make cuts with a substantially vertically arranged circular blade which rotates about a generally horizontal axis.

Commonly, the cutter saw power tools are powered by either a petrol engine or an electric motor. If an electric motor is used, then the motor can be either battery or mains (AC) powered.

However, known disc cutter power tools suffer from a number of disadvantages, not least in terms of ergonomics and usability. Often these power tools are heavy and unwieldy. This problem is exacerbated by the need to hold and wield the disc cutter power tool in use, which can be tiring for a user.

The present invention seeks, in embodiments, to address the ergonomic disadvantages of the known art.

According to a first aspect of the present invention, there is provided a handheld disc cutter power tool comprising a main body, a front handle assembly and a rear handle assembly, the main body having a longitudinal axis and comprising an elongate arm portion extending forwardly and substantially parallel to said longitudinal axis, wherein the disc cutter further comprises a circular cutting blade arranged on the elongate arm of the main body and operable, in use, to rotate about a substantially horizontal axis of rotation perpendicular to the longitudinal axis of the main body, wherein the disc cutter power tool further comprises an electrical motor located within the main body and a gear arrangement connected to the electrical motor and arranged to drive the cutting blade, wherein the gear arrangement comprises at least two reduction gears located directly adjacent the electrical motor within the main body, a drive shaft in communication with the reduction gears and extending within the elongate arm and at least two drive gears at a distal end of the drive shaft and operable to drive the cutting blade about the axis of rotation, wherein the rear handle assembly comprises a rear graspable handle arranged rearwardly from the main body, and the front handle assembly comprises a front graspable handle arranged forwardly of the motor and reduction gears when the disc cutter power tool is held in use.

By providing such an arrangement, a disc cutter according to an embodiment can be configured and arranged to be more ergonomic to use. The handle and component configuration means that, in use, the centre of gravity of the disc cutter lies between the user's hands which are spaced apart to give control and leverage. This provides a comfortable and accurate position in which to hold and use the disc cutter.

In one embodiment, the rear graspable handle is arranged substantially parallel to the longitudinal axis of the main body.

In one embodiment, the rear graspable handle extends rearwardly and upwardly from the main body.

In one embodiment, the main body has an upper surface and the rear graspable handle is spaced further from the longitudinal axis than the upper surface.

In one embodiment, the motor has a shaft which is rotatable about an axis substantially parallel to the longitudinal axis of the main body.

In one embodiment, the reduction gears rotate about an axis substantially parallel to the longitudinal axis of the main body.

In one embodiment, the drive shaft rotates about an axis substantially parallel to the longitudinal axis of the main body.

In one embodiment, drive shaft is hollow.

In one embodiment, the drive shaft further comprises a lock mechanism.

In one embodiment, the lock mechanism is arranged on the elongate arm and spaced from the drive gears.

In one embodiment, the lock mechanism comprises a projection operable to engage with a recess formed in the drive shaft.

to In one embodiment, the projection is resiliently biased away from the recess.

In one embodiment, the front graspable handle is arranged substantially perpendicular to the longitudinal axis of the main body.

In one embodiment, the front graspable handle is arranged to extend around at least a part of the main body.

In one embodiment, the front handle assembly is arranged to connect to a part of the main body at a lower end thereof.

In one embodiment, further comprising a support skid located at a lower end of the main body and arranged to support the disc cutter power tool on a support surface.

In one embodiment, the front handle assembly is arranged to connect to the support skid.

In one embodiment, the front handle assembly is configured and arranged such that the front graspable handle is arranged substantially above the centre of gravity of the disc cutter power tool when the disc cutter power tool is resting on a substantially horizontal support surface.

In one embodiment, the front handle assembly is configured and arranged such that the front graspable handle is arranged forwardly of the centre of gravity of the disc cutter power tool when the disc cutter power tool is being held by a user in use.

In one embodiment, the front and rear handle assemblies are configured and arranged such that the centre of gravity of the disc cutter power tool is located below the front and rear graspable handles.

According to a second embodiment of the present invention, there is provided a guard housing for a handheld disc cutter power tool, the disc cutter power tool comprising a main body and a circular blade rotatably fixed thereto, the guard housing extending around and enclosing at least part of the circular blade, wherein the guard housing is pivotable about an axis parallel to the axis of rotation of the circular blade to enable the guard housing to be moved between a number of predetermined positions, wherein the guard housing further comprises a guard catch located on the guard housing, the guard catch being movable in a substantially radial direction between locked and unlocked positions, the guard catch being located and arranged to be actuated by a single hand of a user grasping the guard housing.

In one embodiment, the guard catch is resiliently biased into the locked position.

In one embodiment, the guard catch comprises a locking member arranged on the guard housing and operable to engage with a complementary recess formed on the main body.

In one embodiment, the locking member is movable linearly in a substantially radial direction.

In one embodiment, the guard catch further comprises a user-actuable button movable linearly in a substantially radial direction.

In a further aspect, there is provided a handheld disc cutter power tool comprising a main body, a circular blade rotatably fixed thereto and a guard housing according to the second aspect.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a front perspective view of a disc cutter power tool according to a first embodiment of the present invention; Figure 2 shows a rear perspective view of the disc cutter power tool of Figure 1; Figures 3 and 4 show respective side views of the disc cutter power tool of Figures 1 and 2: Figure 5 shows a plan view of the disc cutter power tool of Figures 1 to 4; Figures 6a and 6b show different views of a rear handle assembly forming part of the disc cutter power tool of Figures 1 to 5; Figures 7a to 7c show different positions of the disc cutter power tool representing different use states; Figure 8a shows a plan section view of the disc cutter power tool of Figures 1 to 5 taken along substantially horizontal plane; Figure 8b shows a side section view of the disc cutter power tool of Figures 1 to 5 taken along a substantially vertical plane; Figure 8c shows a perspective view of the disc cutter power tool similar to Figure 1 but with sections of a main body removed to illustrate internal components; Figure 9 shows a front perspective view of a disc cutter power tool according to a second embodiment of the present invention; Figure 10 shows a rear perspective view of the disc cutter power tool of Figure 9; Figure 11 shows a side view of the disc cutter power tool of Figures 9 and 10; Figure 12 shows a front view of the disc cutter power tool of Figures 9 to 11; Figure 13 shows a plan view of the disc cutter power tool of Figures 9 to 12; Figure 14 shows a magnified view of a part of the handle assembly of the disc cutter power tool of Figures 9 to 13; Figure 15 shows a view similar to Figure 14 but with a part of the handle assembly removed; Figure 16 shows a different view of a part of a handle assembly of the disc cutter power tool of Figures 9 to 13 with a different part of the handle assembly removed; Figure 17 is a section view through the handle assembly of Figures 14 to 16 taken through a plane substantially parallel to the longitudinal axis of the disc cutter power tool of Figures 9 to 13; and Figures 18 to 23 show magnified views of a part of a guard assembly of the disc cutter power tool of Figures 9 to 13.

The general configuration of a power tool in the form of a disc cutter according to a first embodiment of the present invention will be described with reference to Figures 1 to 8.

Figures 1 to 8 show an AC electrical disc cutter 10 according to a first embodiment of the present invention. Figure 1 shows a front perspective view and Figure 2 a rear perspective view. Figures 3 and 4 show side views of the disc cutter 10. Figure 5 shows a plan view of the disc cutter 10. Figures 6a, 6b, 7a-7c and 8a to 8c then illustrate specific aspects of the disc cutter power tool according to the first embodiment.

The disc cutter 10 comprises a main body 12, a blade assembly 14 and rear handle assembly 16.

The main body 12 is elongate and comprises a motor unit (not shown in Figures 1 to 2) as will be described later. The blade assembly 14 is connected to drive arm 18 forming part of the main body 12. The rotary blade assembly 14 is located at a distal end 20 of the drive arm 18. The blade assembly 14 comprises a drive hub 22 and a circular cutting blade 24 having a toothed cutting surface 26. However, this is not limiting and other types of circular blade, for example a circular blade with a continuous edge, may be used. The skilled person would readily appreciate the types of blade which could be used with the disc cutter of the present invention.

The cutting blade 24 has an arbor 28 and is rotatable about an axis of rotation X-X (Figure 5) which is substantially perpendicular to a longitudinal axis Y-Y (Figure 3 or 5) of the main body 12 and drive arm 18.

A guard assembly 30 is arranged on the blade assembly 14 and comprises a guard cover 32 which functions as a hood for at least a part of the cutting blade 24. The guard assembly 30 is pivotable through a range of angles as will be described later.

The rear handle assembly 16 is shown in detail in Figures 6a and 6b. The rear handle assembly 16 has a cutlass form and comprises a graspable handle 32 and a lower member 34. The graspable handle 32 has a first section 36 which extends upwardly and rearwardly from the main body 12 (i.e. extends upwards and rearwards of an upper surface of the main body 12), a graspable section 38 which forms a handgrip for a user of the disc cutter 10 and which extends substantially parallel to the longitudinal axis Y-Y of the main body 12 and a rear section 40 which extends downwardly from the graspable section 38 to meet the lower member 34.

A trigger 42 is located on an inner wall of the graspable section 38 and the graspable section 38 is shaped and contoured to enable a user to grasp the handle 32 with one hand and activate the trigger 42 with one or two fingers. A further safety button 44 (Figure 6b) is located on the side of the graspable section 38. When the safety button 44 is activated together with the trigger 42, the disc cutter 10 is caused to operate.

The lower member 34 is arranged at an angle to the longitudinal axis Y-Y of the main body 12 and is configured as a resting or support surface for the disc cutter 10 when placed on a ground surface. The angle of the lower member 34 is selected so that the bottom surface of the lower member 34 is substantially parallel to the ground surface when the disc cutter is in the resting configuration on the ground surface. This is shown in Figure 7a.

The lower surface of the lower member 34 has a clamshell construction and a slot guide 46 is formed therein. The slot guide 46 is arranged to receive a utility tool 48. The utility tool 48 in this embodiment is a simple mechanical tool used for tightening/loosening bolts, nuts, screws or the like. The utility tool 48 is substantially planar and, in this embodiment, formed from metal. The utility tool 48 is arranged to slide into the slot guide 46 and be held in a conformal arrangement with respect to the lower surface of the lower member 34. In other words, the utility tool 48 and storage arrangement in the form of the slot guide 46 are configured such that, when in situ, the utility tool 48 forms a part of the external surface of the disc cutter 10.

The location of a utility tool 48 in such a configuration has numerous benefits. The location on the rear handle assembly 16 and adjacent the graspable section 38 is intuitive and convenient for a user. Further, by storing the utility tool 48 in a conformal configuration forming part of the external surface of the disc cutter 10, the utility tool 48 can be easily identified and located by a user, whilst not increasing the footprint of the disc cutter 10 as a whole.

Further, the location of the utility tool 48 on the bottom part of the lower member 34 where the lower member 34 contacts a ground surface when in a resting position on a ground surface, the utility tool 48 can act as a "sacrificial" part which can be easily replaced in the event of wear or damage resulting from use on rough surfaces.

The main body 12 comprises a further handgrip assembly 50. The handgrip assembly 50 may be formed from any suitable material; for example, metal or reinforced plastic. If form from metal, the handgrip assembly 50 maybe powder coated or plastic coated for user convenience.

The handgrip assembly 50 comprises a looped handgrip 52 which extends from an upper portion of the main body 12 around the main body 12 to a base portion 54. The handgrip 52 is connected to the main body 12 at an upper connection 56 by means of screws or bolts or other fastening means. The handgrip 52 extends upwardly and forwardly of the upper connection 56, passes over the longitudinal axis Y-Y of the main body 12 and then passes down the left hand side of the main body 12 to loop under the main body to the base portion 54.

The handgrip 52 has a gripping portion 58 which is arranged perpendicular to, and elevated relative to, the longitudinal axis Y-Y of the main body 12 such that the gripping portion 58 extends across the longitudinal axis Y-Y. In other words, the gripping portion 58 crosses the central vertical plane of the main body 12. The gripping portion 58 is arranged to be gripped by a user in use and is the portion of the handgrip 52 most likely to be held by a user whilst the disc cutter 10 is in use.

The base portion 54 of the handgrip 52 connects to a lower part of the main body 12 and forms a frame for a skid portion 60 which, in use, acts as a support base for the disc cutter 10 when located on a ground surface.

As shown, the handgrip 52 has a relatively complex shape. This is so that the portion of the handgrip 52 most commonly gripped by a user (the gripping portion 58) extends forwardly of the centre of gravity (CG) of the machine when held by a user in an operational configuration, but is situated approximately directly above the centre of gravity when the machine is in a resting position on a surface. This makes it easier for a user to grip and lift the machine, but easier to wield in use. This is shown in Figures 7a to 7c.

As shown in Figure 7a, when the disc cutter 10 is resting on a ground surface, the skid portion 60 is arranged such that the centre of gravity (CG) of the disc cutter 10 is located rearwardly of the point where the skid portion 60 contacts the ground surface. This ensures that, in use, the disc cutter 10 sits back and does not tip forward so the blade 24 does not contact the ground surface.

The centre of gravity (CG) of the machine is shown generally in Figures 7b and 7c in different positions in use. As shown, the configuration of the handgrip 52 and graspable handle 38 mean that, in use, the centre of gravity of the disc cutter 10 lies between the user's hands which are spaced apart to give control and leverage. This provides a comfortable and accurate position in which to hold and use the disc cutter 10.

In other words, the bulk of the weight of the disc cutter 10 is arranged between the user's hands in use. In addition, the position of the rear handgrip 16 and graspable handle 38 above and behind the main body 12, and the position of the handgrip 58 above the main body 12 means that the CO of the disc cutter 10 is between and below a user's hands in use.

This improves the control a user has over the disc cutter 10 because the disc cutter 10 will naturally assume an orientation where the blade 24 is substantially vertically orientated because of a natural pendulum effect resulting from the CO being below both the user's hands. In addition, by concentrating the mass of the disc cutter 10 between the user's hands, the disc cutter 10 can be rotated and tilted more easily.

The configuration and ergonomics of the disc cutter 10 to achieve this weight balance will now be described in more detail.

Figures 8a to Sc show section views and/or views of the disc cutter 10 where part of the main body 12 adjacent the drive arm 18 has been removed to show the internal workings.

Figure 8a shows a plan section view showing the internal components. Figures 8b shows a side section view and Figure 8c shows a perspective view with a part of the drive arm 18 removed to see the internal components.

A motor 62 is located within the main body 12 of the disc cutter 10. The motor 62 comprises, in this embodiment, an electric AC motor driven from an electrical supply. The electrical connection to a mains AC supply is located on the rear handle 16 on the rear portion thereof. However, this need not be the case and a DC motor may be used, or a motor driven from a battery source.

The motor 62 is arranged longitudinally within the main body 12. By this is meant that a drive shaft 64 of the motor 62 rotates about an axis which is substantially parallel to the longitudinal axis Y-Y of the main body 12. In an embodiment, the motor 62 may have a shaft which is coincident with the longitudinal axis Y-Y.

The motor 62 has a gear arrangement 66 to drive the blade 24. In this embodiment, the gear arrangement 66 comprises a reduction gear assembly 68, a drive shaft 70 and bevel drive gears 72.

The reduction gear assembly 66 is the heaviest component within the gear arrangement 66. Therefore, in contrast to known arrangements, the reduction gear assembly 66 is located within the main body 12 adjacent the motor 62. In the present invention, the inventors have appreciated, for the first time, that location of the relatively heavy reduction gear assembly 66 within the main body 12 close to the motor 62 enables the centre of gravity of the machine to be located close to and rearwardly of the handle assembly 50 and handgrip 52.

In other words, by concentrating the heavier components of the drive assembly close to the centre of gravity, the moment arm between the blade 24 and the handgrip 52 is reduced, making the disc cutter 10 easier to wield about the centre of gravity and reducing the weight of the blade assembly. This means that, in use, the disc cutter 10 is easier to wield and manoeuvre, and is easier to position.

The reduction gear assembly 66 drives the drive shaft 70 which in turn utilises the pair of bevel gears 72 to rotate the drive by 90 degrees and drive the arbor 28 and blade 24. In this embodiment, the bevel gears 72 are press fitted to the drive shaft 70 and arbor 28 respectively. The drive shaft 70 takes the form of a solid cylindrical body but may, optionally, be hollow to reduce weight still further. This may further improve the advantages of the present invention by reducing the weight forward of the handle 52 still further.

In use, it is necessary to be able to lock the motion of the blade 24. This may be, for example, to prevent movement of the blade for safety, or to allow repair or replacement of the blade 24. In conventional arrangements, this is achieved by means of a connection to one or more of the bevel gears driving the blade. However, the inventors of the present invention have realised, for the first time, that an improved ergonomic arrangement can be achieved by providing an arbor lock on the drive shaft 70 itself.

As shown, in Figures 8b and 8c, an arbor lock button 74 is located on an upper surface of the drive arm 18. The arbor lock button 74 comprises a pin 76 which is biased into a normally open position by a resilient means such as a spring. In use, the button 74 and pin 76 are pushed downwardly by a user's action to engage with an aperture 78 formed in the drive shaft 70. This locks the arbor 28 and blade 24 preventing rotational movement thereof.

By locating the arbor lock button 74 in such a position, the operation is more convenient and economically efficient for a user. For example, such a push-button operation is achieved closer to the centre of gravity of the disc cutter 10 than in conventional arrangements. Therefore, application of force at that point will not disturb the disc cutter 10 from, for example, a sitting position on a ground surface and will enable a user to push the button 74, lock the blade 24 and then reach to the blade 24 with their other hand. This separation enables much more controlled operation of the disc cutter 10 than in conventional arrangements.

A second embodiment of disc cutter in accordance with the present invention is shown in Figures 9 to 23. A disc cutter 100 according to a second embodiment is shown.

The disc cutter 100 differs, in one aspect, from the disc cutter 10 of the first embodiment in that the blade size is larger. The first embodiment is optimised for a blade size of 9 to 10 inches. However, the second embodiment has a larger blade size of 12 inches. This means the entire machine is necessarily larger. As a result, the structure is different to enable ergonomic use.

The disc cutter 100 of the second embodiment comprises a main body 102, a blade assembly 104 and rear handle assembly 106.

Components in common with, or functionally similar to, the first embodiment will not, for brevity, be described again in detail here.

As for the first embodiment, the main body 12 is elongate along a longitudinal axis Y-Y and comprises a motor unit as will be described later. The blade assembly 104 is connected to drive arm 108 forming part of the main body 102. The rotary blade assembly 104 is located at a distal end 110 of the drive arm 108. The blade assembly 104 comprises a drive hub 110 and a circular cutting blade 114 having a toothed cutting surface 116. The cutting blade 114 has an arbor 118 and is rotatable about an axis of rotation X-X (Figure 13) which is substantially perpendicular to the longitudinal axis Y-Y of the main body 102 and drive arm 108.

A guard assembly 120 is arranged on the hub assembly 104 and comprises a guard cover 121 which functions as a hood for at least a part of the cutting blade 114. The guard assembly 120 is pivotable through a range of angles as will be described later.

The rear handle assembly 106 is generally similar to the rear handle assembly 106 of the first embodiment and again has a cutlass form and comprises a graspable handle 122 and a lower member 124 (Figure 10). The graspable handle 122 has a first section 126 which extends upwardly and rearwardly from the main body 12, a graspable section 128 which forms a handgrip for a user of the disc cutter 100 and which extends substantially parallel to and above the longitudinal axis Y-Y of the main body 102 and a rear section 129 which extends downwardly from the graspable section 128 to meet the lower member 124.

Again, the lower member 124 is arranged at an angle to the longitudinal axis Y-Y of the main body 102 and is configured as a resting or support surface for the disc cutter 10 when placed on a ground surface. The angle of the lower member 124 is selected so that the bottom surface of the lower member 124 is substantially parallel to the ground surface when the disc cutter 100 is in the resting configuration on the ground surface as shown and described in the first embodiment.

A key difference for the second embodiment is the forward handle structure. The disc cutter 100 comprises a handle assembly 130 which forms (as shown in a front view in figure 12) a substantially symmetrical and rectangular box structure around the outside of the main body 102.

The handle structure 130 has a gripping portion 131 which is arranged perpendicular to, spaced from and elevated above the longitudinal axis Y-Y of the main body 102 such that the gripping portion 131 extends across the longitudinal axis Y-Y. In other words, the gripping portion 131 crosses the central vertical plane of the main body 102. The gripping portion 131 is arranged to be gripped by a user in use and is the portion of the handgrip 131 most likely to be held by a user whilst the disc cutter 100 is in use.

In common with the first embodiment, the handle assembly 130 is connected to the main to body 102 at two points -at a lower portion 132 and a connection 134 to an upper part of the main body 102. At the lower portion 132, the handle assembly 130 is connected to a skid portion 136. In the second embodiment, each side of the lower portion 132 passes into a respective side of the skid portion 136 such that a part of the handle assembly 130 is located on either side of the skid portion 136. However, the connection 134 to the upper part of the main body 102 differs from that of the first embodiment as described below.

Given the nature of the larger disc cutter 100 of the second embodiment and the increased weight, there is a risk that a machine used roughly on a building site, for example, may be subject to significant shock forces and potential damage in use.

It is likely that any potential shocks or impacts (e.g. from a machine being thrown into a storage bin or rear of a truck) will be experienced by the handle assembly or a part thereof because this section surrounds the disc cutter 100. Therefore, relatively large shock forces may be transmitted from the handle assembly 130 through to the main body 102. This may be exacerbated given that the handle assembly 130 is spaced from the main body 102, thereby creating a turning force between the handle assembly 130 and the main body 102 when an impact shock to the handle assembly 130 occurs.

The main body 102 may be form from a cast material or another material that is necessarily structurally rigid due to the need to support the motor and drive assembly. Therefore, shock or impact damage to the main body 102 may necessitate complex repair or replacement and may result in the disc cutter 100 being out of operation for some time.

In the context of time-demanding operations on building sites and construction work, this may be unacceptable. Therefore, the inventors of the present invention have realised, for the first time, that this problem can be addressed by providing a sacrificial or relatively weak link element connecting the handle 130 to the main body 102.

In other words, the handle assembly is connected to the main body 102 by means of a link connection 134 which is designed to sever in the event of a sharp shock or impact. Under normal use conditions, the handle connection 134 will be sufficiently robust to enable use without separation of the handle 130 or connection 134, but in the event of a sharp impact the connection 134 is designed to sever to prevent damage to the main body 102.

By providing such a sacrificial linkage, replacement of the linkage 134 is simple and straightforward, in contrast to damage to the main body 102 which may necessitate delayed repair.

The handle connection 134 is shown in Figures 14 to 17. As shown, the handle connection 134 comprises first and second clamshell parts 138a, 138b formed on the handle assembly 130 and a mounting connection 140 formed internally on the main body 102. The mounting connection 140 may be formed on a gearbox housing or a motor housing forming part of the main body 102. Indeed, a gearbox housing and/or motor housing must necessarily be formed of sufficiently strong material to withstand and support the internal components therein. Consequently, such a part of the main body 102 may be a cast or machined part where structural integrity is required. Thus, such a part may not be easily replaceable and may be costly and time consuming to repair.

The mounting connection 140 may take any suitable form. In this embodiment, the mounting connection 140 comprises a pair of through-holes and accompanying bolts. However, any suitable mounting connection 140 may be provided as required.

To mitigate damage to the main body 102, a link part 142 connects the first and second clamshell parts 138a, 138b to the mounting connection 140.

The link part 142 is shown in Figures 15 to 17 and comprises a substantially L-shaped and substantially flat structure which is connected to the mounting connection 140 at a first end 142a and to the clamshell parts 138a, 138b at a second end 142b. As shown in Figures 15 to 17, the second end 142b of the link part 142 is sandwiched between the first and second clamshell parts 138a, 138b and connected by a bolt or other fixing means passing therethrough.

The link part 142 is designed to fail first in an impact situation to protect the surrounding parts. The link part 142 may be configured to be either materially or structurally weaker to than the parts to which it is connected. As shown in Figures 15 and 16, the link part 142 has a frangible portion 142c which is thinner and therefore weaker than the surrounding elements.

Consequently, in an impact situation, the frangible portion 142c will sever before damage to the main body 102 occurs. In such a situation, it is straightforward to remove the broken link part 142 from the handle assembly 134 by separating the clamshell parts 138a, 138b, and removing the remaining part of the link part 142 from the mounting connection 140. The link part 142 can then be replaced easily and the disc cutter power tool 100 restored to fully operational status quickly.

Alternatives may be provided. For example, the link part 142 may be formed from a weaker material than the surrounding parts (e.g. milder steel or weaker plastic) or may be shaped differently to be structurally thinner or more frangible than surrounding elements. The skilled person would be readily aware of variations which could be used with the present invention.

A further addition to the second embodiment is in the form of the rotating guard assembly 120. This is shown in Figures 18 to 23. In this embodiment, the guard assembly 120 is operable to rotate or pivot about an access generally parallel to the axis of rotation X-X of the blade 114 and arbor 118. This is to allow use of the disc cutter 100 at different angles.

For example, if a doorway is to be cut then during the cut the user will rotate the machine from an elevated angle above the users head to cut the upper part of the doorway and then will cut downwardly towards a low angle close to the floor surface. This must be achieved without the guard assembly 120 contacting the surface to be cut or obstructing the blade 114, while still protecting the user from part of the rotating blade 114 and the associated dust generation. This is achieved by having a rotating guard assembly 120.

Conventionally, such rotation is managed by a screw thread connector located on the main body or on a part of the guard housing. This is typically done by unscrewing a connection bolt, rotating the guard housing and then re-tightening the connection screw thread. This process is sub-optimal since it will take effectively three steps for the user to adjust the guard and will take a user considerable time to complete the adjustment.

In contrast, the inventors of the present invention have developed a guard catch 144 which is operable to move radially to enable the user to adjust the guard housing more conveniently and easily than known arrangements.

In embodiments, this is achieved by the provision of a catch 144 which is located on the guard cover 121 and comprises a user-operable handle 146a, a rod 146b connected to the handle 146a and a resilient biasing means in the form of a compression spring 146c. In use, the rod 146b engages with a toothed wheel 148 on a part of the drive arm 108 of the main body 102 and is resiliently biased into the locked position as shown in Figures 19 and 20 by the spring 146c.

To release the guard cover 121 from a currently locked position, a user pulls the guard catch handle 146a radially outwards (relative to the axis of rotation of the blade 124) releasing the guard catch pin 146b from the socket 148 on the drive arm 108. The guard cover 121 can then be angularly adjusted and the catch 144 released to lock again in a different position on toothed wheel 146 of the drive arm 108.

To assist with this, a gripping portion 150 is provided. The gripping portion 150 acts as a useful grip location for a user whilst adjusting the guard cover 121. At least a portion of the gripping portion 150 is located radially outwardly of the guard catch 144 along a radial axis of movement of the guard catch 144. However, the gripping portion 150 may take any suitable form.

This is an ergonomically-efficient motion for a user who can grip the gripping portion 150 (or indeed any upper part of the guard cover 121 if so desired) with one hand and pull the catch 144 with a finger or thumb of the same hand. The user can hold the guard catch handle 144a with the respective finger/thumb whilst rotating the guard cover 121, and then release the catch 144 when the desired position is reached. In other words, the release of the catch 144, rotation of and relocking of the guard cover 121 can be achieved in one motion by a user using only one hand. This is efficient and pleasant for user and results in much greater usability of the disc cutter 100.

A further feature on the second embodiment is that of water injection. A common problem with disc cutters in general is that when cutting material such as stone or brick, considerable airborne dust, dirt and debris is generated. This can be problematic for a user of the machine in terms of health and safety considerations. One way to address this is to provide water injection either side of the cutting blade which forms a paste or slurry of cutting waste instead of airborne dust and debris. Conventionally, such water injection utilises a single pipe with two apertures either side of the blade, where the water outlet apertures are in series in a single pipe. This is suboptimal and can lead to an even pressure distribution between the water jets.

However, the inventors have realised, for the first time, that an alternative arrangement can be provided whereby a water supply pipe is split into two separate pipes utilising a Y junction or U junction. This insures that equal pressure is provided to each side of the water injectors.

This configuration is shown in Figures 21 to 23. Figures 21 to 23 show the water pass from inlet to outlet in the second embodiment. The water inlet pipe (not shown) feeds into a valve mechanism 152 (Figure 11) which is located adjacent to the rear handle assembly 106. The valve has a control which is movable by a user gripping the handle 106 and is activated by a finger to move the valve from an on to an off position or vice versa. A pipe 152a leads to the gripping portion 150 which, in addition to the graspable function described above, also functions as a housing unit for the water injection pipes as will be described. As described above, the gripping portion 150 is connected to the upper part of the guard cover 121.

The gripping portion 150 acts as a mounting position for the inlet pipe 152a. A Y-junction is formed therein and two separate pipes 154, 156 split either side of the gripping portion 150 and pass inside the guard cover 121 such that the outlet nozzles 158, 160 are located internally of the guard cover 121 in order to spray water onto both sides of the cutting disc 114 during a cutting operation.

Advantageously, as described above, the use of a Y or U junction enables equal water pressure to be applied on both sides of the cutting disc 114, improving cutting performance. In addition, as described above, the gripping portion 150 also functions as a convenient handgrip for a user manipulating the guard cover 121 and this may further improve the control and positioning of the guard cover 121 in relation to the guard catch aspect as described above.

Variations of the above embodiments will be apparent to the skilled person. The precise configuration of components may differ and still fall within the scope of the present invention.

Embodiments of the present invention have been described with particular reference to the examples illustrated. While specific examples are shown in the drawings and are herein described in detail, it should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. It will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention.

Claims

CLAIMS1. A handheld disc cutter power tool comprising a main body, a front handle assembly and a rear handle assembly, the main body having a longitudinal axis and comprising an elongate arm portion extending forwardly and substantially parallel to said longitudinal axis, wherein the disc cutter further comprises a circular cutting blade arranged on the elongate arm of the main body and operable, in use, to rotate about a substantially horizontal axis of rotation perpendicular to the longitudinal axis of the main body, wherein the disc cutter power tool further comprises an electrical motor located within the main body and a gear arrangement connected to the electrical motor and arranged to drive the cutting blade, wherein the gear arrangement comprises at least two reduction gears located directly adjacent the electrical motor within the main body, a drive shaft in communication with the reduction gears and extending within the elongate arm and at least two drive gears at a distal end of the drive shaft and operable to drive the cutting blade about the axis of rotation, wherein the rear handle assembly comprises a rear graspable handle arranged rearwardly from the main body, and the front handle assembly comprises a front graspable handle arranged forwardly of the motor and reduction gears when the disc cutter power tool is held in use.
2. A disc cutter power tool according to claim 1, wherein the rear graspable handle is arranged substantially parallel to the longitudinal axis of the main body.
3. A disc cutter power tool according to claim 1 or 2, wherein the rear graspable handle extends rearwardly and upwardly from the main body.
4. A disc cutter power tool according to claim 2, wherein the main body has an upper surface and the rear graspable handle is spaced further from the longitudinal axis than the upper surface.
5. A disc cutter power tool according to any one of the preceding claims, wherein the motor has a shaft which is rotatable about an axis substantially parallel to the longitudinal axis of the main body.
6. A disc cutter power tool according to claim 5, wherein the reduction gears rotate about an axis substantially parallel to the longitudinal axis of the main body.
7. A disc cutter power tool according to claim 6, wherein the drive shaft rotates about an axis substantially parallel to the longitudinal axis of the main body.
8. A disc cutter power tool according to any one of the preceding claims, wherein the drive shaft is hollow.
9. A disc cutter power tool according to any one of the preceding claims, wherein the drive shaft further comprises a lock mechanism.
10. A disc cutter power tool according to claim 9, wherein the lock mechanism is arranged on the elongate arm and spaced from the drive gears.
11. A disc cutter power tool according to claim 10, wherein the lock mechanism comprises a projection operable to engage with a recess formed in the drive shaft.
12. A disc cutter power tool according to claim 11, wherein the projection is resiliently biased away from the recess.
13. A disc cutter power tool according to any one of the preceding claims, wherein the front graspable handle is arranged substantially perpendicular to the longitudinal axis of the main body.
14. A disc cutter power tool according to any one of the preceding claims, wherein the front graspable handle is arranged to extend around at least a part of the main body.
15. A disc cutter power tool according to any one of the preceding claims, wherein the front handle assembly is arranged to connect to a part of the main body at a lower end thereof.
16. A disc cutter power tool according to claim 15, further comprising a support skid located at a lower end of the main body and arranged to support the disc cutter power tool on a support surface.
17. A disc cutter power tool according to claim 16, wherein the front handle assembly is arranged to connect to the support skid.
18. A disc cutter power tool according to any one of the preceding claims, wherein the front handle assembly is configured and arranged such that the front graspable handle is arranged substantially above the centre of gravity of the disc cutter power tool when the disc cutter power tool is resting on a substantially horizontal support surface.
19. A disc cutter power tool according to claim 18, wherein the front handle assembly is configured and arranged such that the front graspable handle is arranged forwardly of the centre of gravity of the disc cutter power tool when the disc cutter power tool is being held by a user in use.
20. A disc cutter power tool according to any one of the preceding claims, wherein the front and rear handle assemblies are configured and arranged such that the centre of gravity of the disc cutter power tool is located below the front and rear graspable handles.
21. A guard housing for a handheld disc cutter power tool, the disc cutter power tool comprising a main body and a circular blade rotatably fixed thereto, the guard housing extending around and enclosing at least part of the circular blade, wherein the guard housing is pivotable about an axis parallel to the axis of rotation of the circular blade to enable the guard housing to be moved between a number of predetermined positions relative to the main body, wherein the guard housing further comprises a guard catch located on the guard housing, the guard catch being movable in a substantially radial direction between locked and unlocked positions, the guard catch being located and arranged to be actuated by a single hand of a user grasping the guard housing.
22. A guard housing according to claim 21, wherein the guard catch is resiliently biased into the locked position.
23. A guard housing according to claim 21 or 22, wherein the guard catch comprises a locking member arranged on the guard housing and operable to engage with a complementary recess formed on the main body.
24. A guard housing according to claim 23, wherein the locking member is movable linearly in a substantially radial direction.
25. A guard housing according to any one of claims 21 to 24, wherein the guard catch further comprises a user-actuable button movable linearly in a substantially radial direction.