GB2116610A - Improvements in cutter-bit assemblies for mining - Google Patents

Abstract

A cutter bit assembly comprises a holder 10 in which a cutter-bit 11 is detachably secured with the aid of an arcuate wedge 23 and a deformable strip 33. <IMAGE>

Description

SPECIFICATION Improvements in cutter-bit assemblies for mining The present invention relates to cutter-bit assemblies. Such assemblies are widely used in mining and tunnelling and generally known assemblies are composed of a holder mounted to some cutting appliance or machine and a cutterbit which is inserted into the holder. To clamp the cutter-bit in the holder it is usual to employ a locking element which is inserted between the cutter-bit shank and the inside of a socket of the holder receiving the shank.

German patent specification 1 291 708 describes an assembly wherein a thin metal filler plate is inserted into a gap between a front wall of the holder, nearest the cutting edge of the cutterbit, and a corresponding front face of the cutter-bit shank. A clamping sleeve can be driven into aligned bores in the metal plate and the cutter-bit shank. When it is necessary to replace the cutterbit the sleeve must be loosened and the metal plate removed before the shank can be manoeuvred out of the socket. German patent specification 2355554 describes a similar assembly where instead of a clamping sleeve a crimping plate is crimped over the metal filler plate and is secured to the holder or cutter-bit.

During use of cutter-bit assemblies and especially where the assembly is subjected to impact stress, deformation and wear occurs at the zones where the cutter-bit is seated. As a result of such wear and deformation the cutter-bit can become loosened and chattering occurs.

A general object of the present invention is to provide an improved cutter-bit assembly.

A cutter-bit assembly constructed in accordance with the invention comprises a cutterbit with a shank received in a pocket of a holder.

The shank engages with a rear face, remote from the cutting edge of the cutter-bit, against an abutment in the pocket and locking means is provided in a gap between a front face of the shank and an inner face of the pocket. In accordance with the invention the gap is arcuate and tapered and the locking means is composed of a tapered arcuate locking element or wedge received in the gap. A crimping element or strip is preferably retained on a dog or similar projection on the arcuate wedge and is crimped over a front wall of the holder.

The wedge is readily accessible from its lower larger region via a window in the front wall.

Consequently, the wedge can be retightened if necessary by hammering on the end of the larger region. The cutter-bit can be secured more reliably than is the case with prior constructions.

Replacement of the cutter-bit is easily accomplished by breaking or deforming the crimping strip and by hammering on the end of the upper reduced region of the wedge which is accessible beneath the cutter-bit cutting edge.

The arcuate wedge provides a relatively large contact area with both the cutter-bit shank and inner surface of the pocket which are similarly curved. This avoids unduly high contact pressures when the cutter-bit assembly is in use.

The wedge or arcuate locking element may extend over an arc of about 1 500 to 1800. The crimping strip may be hooked onto the projection of the element prior to location in the arcuate gap or channel and once the element has been hammered in the strip can be deformed around the front wall of the holder. The locking element can be reduced in a step-like manner around its central region so that the projection over which the crimping strip engages is located in a recess delimited by a lateral shoulder. The projection may be shaped and dimensioned as discussed hereinafter.

At the rear face, remote from the wedge, the shank of the cutter-bit preferably has a curved recess which seats on a bolt or pin mounted in the pocket. The shank then possesses a nose or projection engaging beneath the pin.

The invention may be understood more readily, and various other aspects andfeatures of the invention may become apparent, from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein: Figure 1 is a part-sectional side view of a cutter-bit assembly constructed in accordance with the invention; Figure 2 is a front view of the assembly taken in the direction of arrow II of Figure 1; Figure 3 is an enlarged side view of the locking element of the assembly of Figures 1 and 2; Figure 4 is a sectional view of the locking element shown in Figure 3, the section being taken along the line lV-lV of Figure 3; and Figure 5 is a sectional side view of the holder of the assembly of Figures 1 and 2.

As shown in Figures 1 and 2, a cutter-bit assembly is composed of a holder 10, a cutter-bit 1 and locking means 23, 33. The locking means includes a locking element 23 depicted in Figures 3 and 4. The holder 10 is itself depicted separately in Figure 5. As is known the holder 10 is fixed or detachably mounted to some appliance e.g. a mineral winning machine such as a plough or shearer or to a hewing or tunnel driving machine or to the cutter means thereof. The cutter-bit 11 is then detachably mounted to the holder 10. The cutter-bit 11 takes the form of a metal plate with a shank portion received in the holder and a hardmetal insert 12 forming a cutting edge.

The holder 10 is of generally rectangular configuration provided with an open pocket 13 to receive the shank of the cutter-bit 11. The pocket 13 is defined between front and rear walls, side walls and a bottom wall of the holder 10. In Figures 1 and 2, the side walls of the holder 10 are designated 38, 39, the front wall is designated 17, the rear wall is designated 14 and the bottom wall is designated 1 8. The front wall 17 is provided with an opening or window 1 6 near the bottom wall 18 and a wedge-shaped upper recess 36. The bottom wall 18 itself has an aperture 1 5 extending to the rear wall 14.The rear surface of the shank of the cutter-bit 11 and the inner face of the rear wall 14 of the holder 10 are formed with similar arcuate recesses 20, 26. A pin or bolt 25 is located in the recess 26 of the wall 24 to engage as a press-fit in bores 37 in the side walls 38, 39.

The recess 20 of the shank of the cutter-bit 11 can be fitted onto the peripheral surface 21 of the pin 25. The lower region of the shank of the cutter-bit 11 beneath the recess 20 forms a projection 1 9 which engages in hook-like manner beneath the pin 25. The front region of the shank of the cutter bit 11 opposite the recess 20 extends in arcuate manner around a curvilinear rear surface 24 of the front wall 17 of the holder 10. This arcuate face 22 of the shank of the cutter-bit 11 defines with the curved surface 24 of the wall 17 an arcuatelytapered gap or channel which opens to the window 1 6 and narrows upwardly of the assembly.

The locking element 23 shown in Figure 3 and 4 takes the form of an arcuate wedge, shaped to locate within the arcuate channel. The arcuate channel and the element 23 extend over an arc of about 1 60O to 1 80a. As shown in Figures 3 and 4, the lower end region 27 of the locking element 27 has a greater cross-section than that of the upper end region 28 and the cross-section reduces progressively from x to the upper end region 28.

The front face 29 of the locking element 23 is approximately semi-circular. The front face 29 of the element 23 engages with the rear surface 24 of the wall 1 7 of the holder 10 while the rear face 30 of the element 23 engages against the front face 22 of the shank of the cutter-bit 11. As shown in Figure 4, in the central region of the locking element 23 there is a step-like reduction designated y and y' which forms a lateral shoulder 31 of domed or pitched profile. A recess is thus formed between the shoulder 31 and the region 28 in which a shaped projection or dog 32 is located on an arc coinciding with the centre of the element 23. The dimension y between the lower end region 27 of the element 23 and its shoulder 31 approximately corresponds to the width of the front face 22 of the shank of the cutter-bit 11 and the width of the wall 17.The dimension y' in the region between the shoulder 31 and the upper region 28 of the element 23 is about one half to two thirds of the dimension y. The dog 32 serves to receive a crimping strip 33 (Figures 1 and 2) which looks in the recess around the dog 32 and bears around the wall 1 7. The dog 32 is disposed at a distance z from the shoulder 31 and this distance z is slightly greater than the thickness of the crimping strip 33. As shown in Figures 1 and 3, the dog 32 narrows in width in the direction towards the thinner region 28 of the element 23.

The distance z' between the dog 32 and the respective arcuate faces 29 and 30 is somewhat greater than the thickness of the strip 33.

During assembly, the shank of the cutter-bit 11 is introduced and orientated into the pocket 13 of the holder 10 to engage with its projection 1 9 beneath the pin 25 with the recess 20 engaging on the periphery 21 of the pin 25. The strip 33 is then fitted on to the element 23 so that a hooked end region 34 engages around the dog 32. The wedge element 23 with the fitted crimping strip 33 is then introduced into the arcuate channel between the surfaces 22, 24 from below. The element 23 is driven in with hammer blows on lower end of the region 27 to clamp the bit 11 firmly in the holder 10. To retain the wedge element 33 in position the forward end region 35 of the crimping strip 33 is deformed over the wall 1 7 into the wedge-shaped recess 36 as shown in Figures 1 and 2.As shown in Figures 1 and 2 the end 28 of the element 23 is readily accessible so that after release of the bent-over region 35 of the crimping strip 33 the wedge element 23 can be driven out by hammer blows on the end 28 for replacement of the bit 11.

Preferably, the locking element 23 is made from stainless steel in order to prevent it from rusting within the assembly. Similarly the pin 35 is preferably made from stainless steel. The element 23 is intended for re-use but the crimping strip 33 is intended to be used once and then replaced.

The holder 10 is preferably made as a casting. As shown in Figure 5, raised abutments 40 can be formed in the interior of the side walls 38, 39 of the holder 10. These abutments 40 need only project by about 0.5 to 1 mm into the pocket 13.

These abutments 40 can compensate for manufacturing tolerances and they can be machined, e.g. ground, to match the thickness of the shank of the cutter-bit 11 and provide a precise fit for the latter.

Claims (14)

1. A cutter-bit assembly comprising a holder defining an open pocket, a cutter-bit having a shank mounted with the pocket, an arcuate tapered gap between the shank and an inner face of the pocket and a removable arcuate tapered locking element fitted in said gap.

2. An assembly according to claim 1, wherein there is further provided a deformable crimping strip engaged around a projection of the locking element and around a wall of the holder defining said inner face.

3. An assembly according to claim 2, wherein the locking element is reduced over a central region in a step-like manner and the projection lies in a recess formed by the reduced region.

4. An assembly according to claim 2 or 3, wherein the projection has a curved profile matching the arc describing the locking element.

5. An assembly according to claim 4, wherein the projection is tapered in the same direction as the locking element.

6. An assembly according to claim 3, 4 or 5, wherein the reduced region provides a lateral shoulder extending across the locking element and the shoulder is spaced from the projection by a distance slightly greater than the thickness of the crimping strip.

7. An assembly according to any one of claims 2 to 6, wherein the locking element has a first arcuate surface engaging with the inner face of the pocket and a second arcuate surface engaging with a curved face of the shank, and the projection is spaced from the first and second surfaces by a distance slightly greater than the width of the crimping strip.

8. An assembly according to any one of claims 2 to 7, wherein the wall of the holder is provided with a wedge-shaped recess for accommodating the crimping strip.

9. An assembly according to any one of claims 1 to 8, wherein the locking element is made from stainless steel.

10. An assembly according to any one of claims 1 to 9, wherein the shank has a curved recess opposite the gap which seats on a pin mounted in the pocket.

11. An assembly according to claim 10, wherein the pin locates in a recess in an inner surface of a rear wall of the pocket and the shank has a projection which engages beneath the pin.

12. An assembly according to claim 10 or 11, wherein the pin is made from stainless steel.

13. An assembly according to claim 10, 11 or 12, wherein the pin is fitted into the bores in lateral walls of the holder defining the pocket.

14. An assembly according to any one of claims 1 to 12, wherein the holder is a casting and the pocket has side walls formed with raised abutment faces which can be machined to compensate for tolerances and ensure an accurate fit with the shank.

1 5. An assembly according to claim 14 when appended to claim 10, 11 or 12, wherein the pin is fitted into bores in the side walls.

1 6. An assembly according to any one of claims 1 to 1 5, wherein the inner face of the. pocket is defined by a front wall of the holder and a window is provided in said wall to permit access to the larger end of the locking element for hammering and locking.

1 7. An assembly according to any one of claims 1 to 1 6, wherein the smaller end of the locking element is accessible beneath a cutting edge of the cutter-bit for hammering and release.

1 8. A cutter-bit assembly substantially as described with reference to and as illustrated in the accompanying drawings.

1 9. A cutter-bit, a holder or a locking element for use in the assembly according to any one of the preceding claims and substantially as described with reference to and as illustrated in the accompanying drawings.