GB2290050A

GB2290050A - Cutting blades

Info

Publication number: GB2290050A
Application number: GB9411754A
Authority: GB
Inventors: Mario Halbeisen
Original assignee: MARCRIST IND Ltd
Current assignee: MARCRIST IND Ltd
Priority date: 1994-06-11
Filing date: 1994-06-11
Publication date: 1995-12-13
Also published as: GB9411754D0

Abstract

A generally circular cutting blade 15 is rotatable about a central axis. The blade has a central hub 16 for mounting the blade on a rotatable drum (8, Fig. 3) and the outer periphery of the blade has a series of equi-angularly spaced segments 18 providing cutting edges, with adjacent segments being spaced by a corresponding inter-segment gap 19. Each segment 18 has a thickness greater than the thickness of the hub 16 so that when a plurality of similar blades 15 are clamped in face to face relationship with the hubs 16 in abutting relationship, the cutting edges of one blade 15, partially project into the gaps 19 of the adjacent blade 15 so that no ridges are left in a surface cut by the abutting blades 15. Each cutting segment subtends at the axis an angle no greater than the angle subtended at the axis by each gap. <IMAGE>

Description

TITLE: CUTTIBG BLADES This invention relates to cutting blades, particularly for use in machines which cut hard material such as concrete, stone, masonry, brickwork or the like.

A known machine for this purpose has a rotatable drum carrying a series of generally circular cutting blades, each having around its periphery a series of diamondimpregnated cutting segments which together provide the cutting edge of the blade. If the machine is required to remove the surface layer of, for example, a concrete floor, the drum is equipped with a series of such blades clamped together in face to face relationship so the passage of the rotating drum over the concrete floor cuts a channel equivalent to the axial length of the stack of blades. Notwithstanding that the blades are clamped together, the base of such a channel tends to have a series of longitudinal ridges (giving the channel base a slightly rippled shape in transverse cross-section) caused by a less effective cutting action along the lines where adjacent blades abut.This unwelcome result is made worse by two effects: the tendency for the blade edges to wear so as to produce a convex cutting edge; and the tendency for the abutting segments to separate as a result of the compressive force applied to the hub regions of the blades. The invention aims to provide a rotatable blade having a shape which, when assembled with other similar blades on a drum, provides an assembly which produces a smoother cut than that obtainable with known blade designs.

According to one aspect of the invention a generally circular cutting blade rotatable about a central axis has on its circumference an arcuate cutting edge extending for not more than half of the circumference of the blade, enabling a similar blade to be clamped in co-axial face to face relationship to provide an abutting pair of blades having cutting edges which partially overlap in the axial direction.

It will be appreciated that any number of blades may be clamped together in series, each abutting pair having cutting edges which partially overlap in the axial direction.

Preferably, the arcuate cutting edge is defined on a series of segments equi-angularly spaced around the circumference of the blade, an adjacent pair of blades being spaced by an inter-segment gap which subtends at the axis an angle at least as great as the angle subtended at the axis by a segment, so that when a pair of blades are clamped together the segments of one blade partially project into the inter-segment gaps of the other blade.

In a preferred arrangement, the blade has five segments each subtending an angle of substantially 30" at the central axis, meaning that each inter-segment gap subtends an angle of substantially 40 at the central axis.

The blade may have a central circular hole for mounting the blade, together with other similar blades, on a drum which in use is rotatably driven to cause the blades to rotate about the central axis.

Means are conveniently provided to prevent relative rotation between the drum and the blade, and such means may comprise rods which pass through aligned holes in the stack of blades.

According to another aspect of the invention a generally circular cutting blade rotatable about a central axis has a hub region for mounting the blade on a rotatable drum, the outer periphery of the blade having a series of equiangularly spaced segments providing cutting edges, with adjacent segments being spaced by a corresponding intersegment gap, each segment subtending at the axis an angle no greater than the angle subtended at the axis by each gap, each segment having a thickness greater than the thickness of the hub so that when a plurality of similar blades are clamped in face to face relationship to provide a series of blades with each hub region in abutting relationship, the cutting edges of one blade partially project into the gaps of the adjacent blade so that each abutting pair of blades present cutting edges which partially overlap in the axial direction.

The partial overlap of the cutting edges of adjacent blades means that the series of rotating blades presents cutting edges which, considered in the axial direction, have no discontinuity and therefore leave no ridges in the cut surface, in contrast to the result produced by known blades. Sometimes, it is required to cut grooves and this is conventionally done by using spacers of the appropriate width between blades or groups of blades of the known design. It will be appreciated that grooves can be cut with the inventive blades by the use of similar spacers. Further, slimmer spacers may be used between the inventive blades to give a rippled effect like that of the prior art, should this be required, and thicker spacers may be employed if a stepped profile is needed.Hence, one design of blade according to the invention can be used with thin spacers to impart a rippled profile to the cut, with thicker spacers to impart a stepped or grooved shape of a desired profile to the cut, and without spacers to impart a substantially smooth cut without longitudinal ridges. Moreover, any combination of these possibilities can be achieved on a single drum by mounting thereon a plurality of inventive blades, some in abutting relationship and others spaced as necessary by spacers of appropriate widths.

The invention also includes within its scope a machine having a rotatable drum carrying a plurality of cutting blades each in accordance with said one or said another aspect of the invention.

A machine incorporating cutting blades according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of the machine, Figure 2 is a plan view of the machine, Figure 3 is a fragmentary sectional view, to an enlarged scale, showing a drum of the machine and the profile of a groove cut thereby, Figure 4 is a perspective view showing two blades, Figure 5 shows how the blades may be mounted on the drum with the interposition of slim spacers between adjacent blades, the figure illustrating the resulting profile of the groove cut thereby, Figure 6 is a view similar to that of Figure 5 but with thicker spacers, Figure 7 is an elevation of a known cutting blade, and Figure 8 is a fragmentary sectional view showing a series of known blades mounted on a drum and the profile of the groove cut thereby.

Referring to Figure 1, the machine has a chassis 1, which is rendered mobile by four ground-engaging wheels 2 and which carries an electric motor 3. An upwardly projecting handle 4, terminating in a handgrip 5, enables the machine to be controlled and guided by a user.

The motor 3 drives, by means of a belt 6 and a pulley 7, a drum 8 rotatably mounted in the chassis 1 about a transverse horizontal axis. One end bearing 9 of the drum 8 is detachably connected to the chassis to enable the drum 8 to be removed from the chassis for replacement of cutting blades, in known manner.

Referring to Figure 3, the drum 8 has a central cylindrical body 10 to one end of which is welded an end flange 12. A further end flange 13 has a central circular aperture and is a sliding fit over the body 10. A pair of threaded rods 14 are used to retain a stack of cutting blades 15 on the drum. One end of each rod 14 is threaded into the flange 12, the other end having threaded thereon a nut which, when tightened, presses the flange 13 against the stack of blades 15 which are thus clamped on the body the body 10 between the fixed flange 12 and the movable flange 13. Release of the rods 14 enables the blades 15 to be replaced.

A pair of the blades 15, each according to the invention, are shown in Figure 4. Each blade 15 has a metal hub 16 surrounding a central circular aperture 17 which is a sliding clearance fit on the tubular body 10. Around its outer periphery, each blade has five equi-angularly spaced segments 18 each having diamond fragments embedded therein to provide the blade with a radially outer segmented cutting edge. Between adjacent segments 18, there is a corresponding inter-segment gap 19. Each segment 18 subtends at the centre of the blade (ie in use at the rotational axis of the drum 8) an angle of 30 , and each gap 19 subtends at the centre of the blade an angle of 42" Each blade has in its hub 16 a first pair of holes 20a, 20b and a second pair of holes 22a, 22b.The holes 20a, 20b are diametrically opposite one another, the hole 20a being radially aligned with the centre of a segment 18 and the hole 20b being radially aligned with the centre of the opposite gap 19. The second pair of holes 22a, 22b are also diametrically opposed and are angularly displaced by 36 from the first pair of holes such that the hole 22a is radially aligned with a gap 19 and the hole 22b is radially aligned with the opposite segment 18.

The provision of the two pairs of holes 20a, 20b, 22a, 22b enables the blades 15 to be mounted on the drum, with the rods 14 passing through aligned holes, and with adjacent blades relatively angularly displaced so that the segments 18 of one blade lie across the gaps 19 of the adjacent blade. This is illustrated in Figure 4 where the arrow 23 indicates how one of the rods 14 passes through holes 22a and 20a alternately, and arrow 24 indicates how the other rod 14 passes through holes 22b, 20b alternately. The blades are mounted on the drum in sequence, alternately in the two orientations shown in Figure 4. Two pairs of holes in each blade 15 are necessary because the blade 15 has a particular direction of rotation, indicated by an arrow in Figure 4.

Each segment 18 has a thickness greater than the thickness of the hub, and each segment projects from the face surface of the hub by an equal distance of the order of 1/2mm. Hence, when the blades 15 are arranged in a clamped series in the manner described, the segments 18 of one blade project into the gaps 19 of the adjacent blade, as illustrated in Figure 3. The axial overlap of about 1mm of the segments of adjacent blades means that a groove 25 cut by the stack of blades 15 has a smooth base, as illustrated in Figure 3. By making repeated passes, the machine can completely remove a surface layer from a concrete floor.

If it should be required to produce a groove with the rippled effect of the prior art, slim spacers 26 (in the form of annular packing pieces) can be incorporated between the blades 15, as indicated in Figure 5. The result is a groove 27 with longitudinal ridges 28 along the lines where the segments abut. The incorporation of wide spacers 29 (Figure 6) between the blades 15, gives a stepped profile 30 to the resulting cut surface.

Figures 7 and 8 show the prior art, to contrast with the invention. The known blade 32 of Figure 7 has a plurality of segments 33 and a single pair of holes 34 for clamping a plurality of such blades 32 onto a drum by means of rods 14. When this is done (Figure 8) the segments abut one another and the resulting groove 35 unavoidably has ridges 36.

Because blades according to the invention can cut without leaving longitudinal ridges, it is expected that they will prove particularly useful in machines for removing surface layers of concrete from floors, walls or ceilings in order to clean the latter (eg remove contaminated surface layers) or to prepare such surfaces for the application of a new surface finish.

Claims

1. A generally circular cutting blade rotatable about a central axis, the blade having on its circumference an arcuate cutting edge extending for not more than half of the circumference of the blade, enabling a similar blade to be clamped in co-axial face to face relationship to provide an abutting pair of blades having cutting edges which partially overlap in the axial direction.

2. A generally circular cutting blade according to claim 1, wherein the arcuate cutting edge is defined on a series of segments equi-angularly spaced around the circumference of the blade, an adjacent pair of blades being spaced by an inter-segment gap which subtends at the axis an angle at least as great as the angle subtended at the axis by a segment, so that when a pair of blades are clamped together the segments of one blade partially project into the inter-segment gaps of the other blade.

3. A generally circular cutting blade according to claim 2, wherein the blade has five segments each subtending an angle of substantially 30 at the central axis, meaning that each inter-segment gap subtends an angle of substantially 40 at the central axis.

4. A generally circular cutting blade according to any of the preceding claims, wherein the blade has a central circular hole for mounting the blade, together with other similar blades, on a drum which in use is rotatably driven to cause the blades to rotate about the central axis.

5. A generally circular cutting blade according to claim 4, wherein means are provided to prevent relative rotation between the drum and the blade.

6. A generally circular cutting blade according to claim 5, wherein said means comprise rods which pass through aligned holes in the stack of blades.

7. A generally circular cutting blade rotatable about a central axis, the blade having a hub region for mounting the blade on a rotatable drum the outer periphery of the blade having a series of equi-angularly spaced segments providing cutting edges, with adjacent segments being spaced by a corresponding inter-segment gap, each segment subtending at the axis an angle no greater than the angle subtended at the axis by each gap, each segment having a thickness greater than the thickness of the hub so that when a plurality of similar blades are clamped in face to face relationship to provide a series of blades with each hub region in abutting relationship, the cutting edges of one blade partially project into the gaps of the adjacent blade so that each abutting pair of blades present cutting edges which partially overlap in the axial direction.

8. A plurality of blades each in accordance with any of the preceding claims, spacers being provided between at least certain of the adjacent blades, so that the plurality of blades cut a groove or cut to yield a rippled effect.

9. A machine having a rotatable drum carrying a plurality of cutting blades each in accordance with any of the preceding claims.

10. A generally circular cutting blade constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.