GB2136480A

GB2136480A - Pick holding arrangement

Info

Publication number: GB2136480A
Application number: GB08406211A
Authority: GB
Inventors: Leslie William Hindmarsh; Gerald Jacques Sanders; Robert George Knight
Original assignee: WIMET MINING Ltd
Current assignee: WIMET MINING Ltd
Priority date: 1983-03-10
Filing date: 1984-03-09
Publication date: 1984-09-19
Also published as: GB2136480B; GB8406211D0

Abstract

A cutter pick assembly comprises a point attack cutter pick (20) rotatably mounted in a pick box (2) through a sleeve (6) in a bore (4). In front of the sleeve a hardened metal thrust and seal ring (8) is mounted surrounding the forward end of the pick shank. The ring has a front face (8a) which engages in a recess (28) in a shoulder (26) of the pick and the ring both supports the pick against rearwardly directed cutting forces and provides a sufficiently close fit with the pick and the pick box bore to limit passage into the bore of foreign matter that may interfere with rotation of the pick in use. The thrust ring is retained axially in the bore by a spring clip (16) and a further spring clip (22) holds the pick axially in the sleeve (6), the later being trapped in the bore (4) by the thrust ring. <IMAGE>

Description

SPECIFICATION Pick holding arrangements This invention relates to holding arrangements for cutting picks, particularly but not necessarily exclusively point attack picks, which are intended to be free to rotate in use. It relates to rotatable cutter picks themselves and to assemblies of other picks with their holding arrangements.

To provide for rotatability it is known to provide a pick with a cylindrical shank fitting freely in a cylindrical bore of a pick box, which may be sleeved to make rotation easier.

These picks are usually employed in the severe conditions of mining and it is found that the freedom of a pick to rotate in the bore is impaired by build-up of foreign matter in the bore. As a result the working life of the pick will be considerably reduced because wear is concentrated on only a portion of the cutting tip.

According to one aspect of the invention there is provided an arrangement for holding a cutter pick comprising a pick box having a bore and sleeve receiving a shank of the pick lining at least a part of the length of said bore, the sleeve being rotatable in the bore to permit rotation of the pick about a longitudinal axis, a thrust ring at the front end of the bore being arranged to fit closely to the tool and the bore so as to impede the passage of foreign matter into the bore, said ring having an end face to support the pick against rearward axial forces.

According to another aspect of the invention, there is provided a cutter pick assembly comprising a point attack cutter pick rotatably mounted in a sleeved bore of a pick box, the forward end of said bore being substantially closed against the ingress of foreign matter by a metal thrust and seal ring closely fitting the pick and the pick box and having a forward annular face for supporting the pick against rearwardly directed cutting forces.

According to a further aspect of the invention, there is provided a point attack cutter pick comprising a cylindrical shank having an annular recess receiving a spring clip for retaining the pick shank axially in a bore of a sleeve and having a radially extending skirt at the forward end of the shank with a rearwardly directed recess for engagement by a thrust and seal ring supporting the pick against rearwardly directed cutting forces.

By way of example, the accompanying drawing illustrates an embodiment of the invention in axial section.

The drawing shows a pick box 2 with a cylindrical bore 4 in which a sleeve 6 is held axially between a front thrust ring 8 and an annular rear wall 10 of the bore. To hold the thrust ring axially in the pick box, the ring and the bore have annular recesses 12, 14 that come into registration with each other when the thrust ring is inserted, and a spring clip 1 6 that is resiliently deformable into the thrust ring recess during insertion but then springs out to engage both recesses.

The front face 8a of the thrust ring has a Vform cross-sectional form with the apex projecting forwards. Both the sleeve and the thrust ring are of a hard metallic material, e.g.

hardened steel.

A point attack coal-cutter pick 20 is inserted into the bore to seat in the sleeve 6 and be held there frictionally by a spring clip 22 located on a smaller diameter intermediate portion 24a of the pick shank 24. The axial retention of the thrust ring also traps the sleeve 6 in the bore.

The annular front shoulder 26 of the pick has a rear face 28 complementary to the front face of the thrust ring and these two faces normally fit closely together, as do the inner peripheral face of the thrust ring and the opposed periphery of the pick shank. The thrust ring therefore acts not only to react the rearwardly directed cutting forces on the pick, but also as a seal restricting the passage of foreign matter, in particular abrasive particles, into the bore. The rear of the bore may be sealed by a snap-in cap (not shown) which can be removed to allow a driver (not shown) to be inserted when the pick is replaced.

In use, the pick is intended to operate in the usual manner of a point attack pick, rotating randomly about its axis as it cuts in order to extend its useful life. For this purpose the sleeve is freely rotatable in the pick box bore, although rotation between the shank and the sleeve is also not excluded. The thrust ring 8 may be rotatably fixed to the pick box or may be left free to rotate in the box. A gap between the thrust ring and the sleeve ensures that its freedom to rotate is not restrained by axial forces transmitted through the thrust ring.

Because the bore 4 is closed at the front bythe thrust ring 8, the rotatability of the pick in use is less readily affected by the dirty conditions in which such picks are used and the life of the pick is thereby extended. At the same time, the choice of a hard material for the ring 8 ensures that it can be placed at the very front of the tool box bore where a seal is best effected and yet it is capable of withstanding the substantial axial forces generated during the cutting. The hardness of the thrust ring material also ensures that it has a long operational life.

1. A holding arrangement for a cutter pick comprising a pick box having a bore and a sleeve receiving a shank of the pick lining at least a part of the length of said bore, the sleeve being rotatable in the bore to permit rotation of the pick about a longitudinal axis,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pick holding arrangements This invention relates to holding arrangements for cutting picks, particularly but not necessarily exclusively point attack picks, which are intended to be free to rotate in use. It relates to rotatable cutter picks themselves and to assemblies of other picks with their holding arrangements. To provide for rotatability it is known to provide a pick with a cylindrical shank fitting freely in a cylindrical bore of a pick box, which may be sleeved to make rotation easier. These picks are usually employed in the severe conditions of mining and it is found that the freedom of a pick to rotate in the bore is impaired by build-up of foreign matter in the bore. As a result the working life of the pick will be considerably reduced because wear is concentrated on only a portion of the cutting tip. According to one aspect of the invention there is provided an arrangement for holding a cutter pick comprising a pick box having a bore and sleeve receiving a shank of the pick lining at least a part of the length of said bore, the sleeve being rotatable in the bore to permit rotation of the pick about a longitudinal axis, a thrust ring at the front end of the bore being arranged to fit closely to the tool and the bore so as to impede the passage of foreign matter into the bore, said ring having an end face to support the pick against rearward axial forces. According to another aspect of the invention, there is provided a cutter pick assembly comprising a point attack cutter pick rotatably mounted in a sleeved bore of a pick box, the forward end of said bore being substantially closed against the ingress of foreign matter by a metal thrust and seal ring closely fitting the pick and the pick box and having a forward annular face for supporting the pick against rearwardly directed cutting forces. According to a further aspect of the invention, there is provided a point attack cutter pick comprising a cylindrical shank having an annular recess receiving a spring clip for retaining the pick shank axially in a bore of a sleeve and having a radially extending skirt at the forward end of the shank with a rearwardly directed recess for engagement by a thrust and seal ring supporting the pick against rearwardly directed cutting forces. By way of example, the accompanying drawing illustrates an embodiment of the invention in axial section. The drawing shows a pick box 2 with a cylindrical bore 4 in which a sleeve 6 is held axially between a front thrust ring 8 and an annular rear wall 10 of the bore. To hold the thrust ring axially in the pick box, the ring and the bore have annular recesses 12, 14 that come into registration with each other when the thrust ring is inserted, and a spring clip 1 6 that is resiliently deformable into the thrust ring recess during insertion but then springs out to engage both recesses. The front face 8a of the thrust ring has a Vform cross-sectional form with the apex projecting forwards. Both the sleeve and the thrust ring are of a hard metallic material, e.g. hardened steel. A point attack coal-cutter pick 20 is inserted into the bore to seat in the sleeve 6 and be held there frictionally by a spring clip 22 located on a smaller diameter intermediate portion 24a of the pick shank 24. The axial retention of the thrust ring also traps the sleeve 6 in the bore. The annular front shoulder 26 of the pick has a rear face 28 complementary to the front face of the thrust ring and these two faces normally fit closely together, as do the inner peripheral face of the thrust ring and the opposed periphery of the pick shank. The thrust ring therefore acts not only to react the rearwardly directed cutting forces on the pick, but also as a seal restricting the passage of foreign matter, in particular abrasive particles, into the bore. The rear of the bore may be sealed by a snap-in cap (not shown) which can be removed to allow a driver (not shown) to be inserted when the pick is replaced. In use, the pick is intended to operate in the usual manner of a point attack pick, rotating randomly about its axis as it cuts in order to extend its useful life. For this purpose the sleeve is freely rotatable in the pick box bore, although rotation between the shank and the sleeve is also not excluded. The thrust ring 8 may be rotatably fixed to the pick box or may be left free to rotate in the box. A gap between the thrust ring and the sleeve ensures that its freedom to rotate is not restrained by axial forces transmitted through the thrust ring. Because the bore 4 is closed at the front bythe thrust ring 8, the rotatability of the pick in use is less readily affected by the dirty conditions in which such picks are used and the life of the pick is thereby extended. At the same time, the choice of a hard material for the ring 8 ensures that it can be placed at the very front of the tool box bore where a seal is best effected and yet it is capable of withstanding the substantial axial forces generated during the cutting. The hardness of the thrust ring material also ensures that it has a long operational life. CLAIMS

1. A holding arrangement for a cutter pick comprising a pick box having a bore and a sleeve receiving a shank of the pick lining at least a part of the length of said bore, the sleeve being rotatable in the bore to permit rotation of the pick about a longitudinal axis, a thrust ring at the front end of the bore being arranged to fit closely to the tool and the bore so as to impede the passage of foreign matter into the bore, said ring having an end face to support the pick against rearward axial forces.

2. An arrangement according to claim 1 wherein axial retaining means are provided to hold the thrust ring in the pick box.

3. An arrangement according to claim 1 or claim 2 wherein the thrust ring is held rotatably in the pick box.

4. An arrangement according to any one of claims 1 to 3 wherein the thrust ring has a forwardly tapering end face for said support of the pick.

5. An arrangement according to claim 4 wherein said end face has a vee cross-section with its apex frontmost.

6. An arrangement according to any one of the preceding claims wherein frictional retaining means are provided for engagement between the pick and the sleeve.

7. An arrangement according to any one of the preceding claims wherein the sleeve is retained in the bore by the thrust ring with clearance for a limited axial movement therein.

8. A cutter pick assembly comprising a point attack cutter pick rotatably mounted in a sleeved bore of a pick box, the forward end of said bore being substantially closed against the ingress of foreign matter by means of a metal thrust and seal ring closely fitting the pick and the pick box and having a forward annular face for supporting the pick against rearwardly directed cutting forces.

9. The assembly according to claim 8 wherein the thrust ring has a forwardly tapering end face and the pick has a rearwardly directed face with a recess complementary to said support face of the thrust ring.

10. An assembly according to claim 8 or claim 9 wherein frictional retaining means engage a peripheral recess in the pick to hold the pick shank in the sleeve.

11. A point attack cutter pick comprising a cylindrical shank having an annular recess receiving a spring clip for retaining the pick shank axially in a bore of a sleeve and having a radially extending skirt at the forward end of the shank with a rearwardly directed recess for engagement by a thrust and seal ring supporting the pick against rearwardly directed cutting forces.

1 2. A holding arrangement for a cutter pick constructed and arranged for use substantially as described herein with reference to the accompanying drawing.

1 3. A cutter pick assembly constructed and arranged for use substantially as described herein with reference to the accompanying drawing.

1 4. A point attack cutter pick constructed and arranged for use substantially as described herein with reference to the accompanying drawing.