GB2063965A - Improvements in or relating to mining tools - Google Patents

Abstract

A mining tool has a shank main part (6) that is mounted in a closely fitting bore (10, 16) of the support block (14) from the front. At the rear of the shank there is an extension carrying a yieldable washer (32) with outwardly projecting tabs held in place by a smaller diameter locking washer (34). The locking washer is smaller enough to pass freely through the bore (10, 16) and the tabs (36) of the yieldable washer can flex to allow it to pass through the bore as the tool shank main part is inserted. When the tool reaches it final position in the support block the tabs have emerged from the rear of the bore and spring outwards through their own resilience. Return movement of the tool through the bore is then resisted by the tabs, the locking washer provided support that increases their flexural resistance. <IMAGE>

Description

SPECIFICATION Improvements in or relating to mining tools This invention relates to mining tools, in the form of cutter picks or point attack tools, for example. It is also concerned with the combination of such mining tools with their mounting blocks or boxes.

It is known to support a mining tool in a mounting comprising a support block or box having a stepped bore into which the tool shank is inserted from the front, the tool shank having a stepped shank with a configuration complementary to that of the bore. This configuration comprises a larger diameter forward region and a smaller diameter rearward region which both engage the tool shank closely to support it against transverse forces. A rearwardly facing shoulder on the shank engages a forwardly facing shoulder in the bore between the forward and rearward regions to provide a support face against the axial forces of the cutting action of the tool.It is also necessary to provide some means of retaining the tool against sliding forwardly out of the bore, although this 5 counter to the direction of the cutting forces themselves, and that may be done by attaching a locking metal snap ring or washer in a groove at the rear of the shank where the shank protrudes from its support block so that the washer bears against a rear face of the block.

This is inconvenient, in that the user must attach the locking washer in a separate operation, and must also remove the washer in a separate operation before he can change the tool. It has been proposed to mount a resilient locking ring on a tool shank before inserting the tool in its bore, the ring being located in a groove in a region of the shank that lies within the mounting bore. The ring is deformed as the shank is pushed into the bore but engages with a rearwardly facing peripheral shoulder of the bore when the tool is in place. This form of locking has also been proposed for an arrangement in which the bore is not stepped and the tool is supported against rearward axial forces by a flange or skirt that bears on a forward face of the support block.In either case, the resilient ring is placed on the shank beforehand, and on insertion a relatively large force is required to push the tool into place; there is therefore a risk of damage to the ring, so that a relatively low force will be sufficient to draw the tool forwards again, as might occur randomly during the operation of the tool.

According to the present invention, there is provided a mining tool comprising a shank having a main part for insertion into a bore of a mounting for engagement with the bore to support the tool transversely thereof, and having a rearwardly directed face intermediate the length of the tool for engagement with the mounting to support the tool against the cutting forces acting rearwardly on the tool, rearwardly of said main part the shank being provided with an extension of smaller crosssection than said main part and on which there is mounted a retaining arrangement comprising resiliently yieldable means having a maximum transverse dimension greater than at least the region of the main part of the shank adjacent said extension, and locking means having a maximum transverse dimension not greater than said adjacent region of the shank main part, said locking means being mounted on said extension with at least its region of maximum transverse dimension disposed behind the yieldable means for support thereof against flexure rearwardly.

Preferably said yieldable means and said locking means are provided by members of different materials, but which may however be secured together before being assembled onto the tool shank.

Analogously to the known forms of tool already referred to, said rearwardly directed face on the shank may be in the form of a shoulder between larger and smaller cross-section portions of the shank and arranged for engagement with a complementary shoulder in the mounting bore, or in the form of a flange or skirt arranged for engagement with a face at the entry to the mounting bore.

Preferably, said continuation is itself of stepped form, with a smaller cross-section part rearmost behind a larger cross-section part that however still has a cross-section smaller than that of the preceding portion of the main part of the shank.

The yieldable means can then be held in position by the locking means against a shoulder that will be formed between said two parts of the continuation.

Conveniently, the locking means is located wholly or mainly by friction, for which purpose it may have a resilient portion or portions that engage the adjoining peripheral surface of the tool shank. In a preferred arrangement, said resilient portion or portions seat in a slight forward taper of said smaller part of the continuation so as to hold the locking means more firmly against accidental displacement rearwards.

The invention will be described in more detail by way of example with reference to the accompanying diagrammatic drawings, in which Fig. 1 is a side view of a point attack tool according to the invention, Fig. 2 is a rear view of the yieldable and locking washers on the tool of Fig. 1, Fig. 3 is a cross-sectional detail view of part of the tool of Fig. 1, further illustrating the manner in which the washers are located on the tool shank, and Fig. 4 is a view similar to Fig. 1 illustrating some possible modifications of the embodiment of the invention in Figs. 1 to 3.

Fig. 1 shows a circular cross-section point attack tool with a conventional hard metal insert 2 at its tip, and behind a protective flange or skirt 4 a main supporting part 6 of the tool shank comprises a larger diameter forward portion 8 and a smaller diameter rearward portion 10, these being separated by a rearwardly facing shoulder 1 2. The tool is mounted in a support block or box 14, shown only fragementarily, that has a stepped bore with larger and smaller diameters 1 6, 1 8 and a forwardly facing shoulder 20 each complementary to the associated parts of the shank. The front face (not shown) of the box lies immediately behind the tool skirt 4 and the rear face 22 lies a little behind the rear end of the smaller diameter portion 10 of the shank.

Continuing from the rear of its smaller diameter portion of the shank has an extension 24 also of stepped form, with a forward part 26 of a diameter intermediate that of the smaller diameter portion 10 of the main part of the shank and that of a rear part 28 of the extension. Against the rearwardly facing shoulder 30 between these parts a washer 32 of resiliently yieldable plastics material is held by a metal locking washer 34.

The yieldable washer 32 has a series of external tabs 36 at its outer periphery, while the locking washer 34 has a series of internal tabs 38 at its inner periphery. The external tabs 36 project from an inner annular region 40 of the yieldable washer that has a diameter smaller than the rear bore of the box, but the tabs give the washer a maximum transverse dimension greater than that bore. The locking washer has an outer diameter smaller than the rear bore 1 8 of the box, but larger than the diameter of the forward part 26 of the shank extension: its internal tabs 38 project inwards in the unstressed state to a diameter less than the rear part 28 of the extension, so that they are resiliently deformed when the locking washer is pushed into place and grip the extension surface to hold the yieldable washer securely in position.

The rear part of the extension has a slight peripheral relief 42 in its region adjoining the shoulder, tapering inwardly forwards from its main cylinderical region, and the locking washer tabs engage this tapering surface to be retained firmly against accidental displacement as they hold the yisldable washer against the shoulder 30. The washers are both put in position on the tool shank during manufacture.

In use, the shank is inserted into the box bore from the front and both washers 32, 34 are of a size to pass without hindrance through the forward larger cross-section bore 1 6. In the smaller cross-section bore 18, the external tabs 36 of the yieldable washer as able to flex to allow it to pass through the bore, while the locking washer is small enough to move freely along the bore. The yieldable washer snaps back into shape as it emerges from the bore and then acts to retain the tool in position. Thus, at the end of this simple insertion operation the tool is held in place and it is very easily possible to check visually that the yieldable washer has assumed its correct position.

Because the locking washer has a diameter greater than the forward part 26 of the extension, the resistance to flexure of the external tabs of the yieldable washer will be greater if the tool is urged forwards than it was during rearwards insertion into the bore 1 8. It is therefore possible to arrange that the insertion can be made with very little force without correspondingly weakening the retaining action once the tool is inserted.

Nevertheless, it remains possible by the deliberate application of force to remove the tool for replacement without removing the washers in a separate operation.

The yieldable washer 32 is shown with six external tabs 36 and the locking washer 34 with seven internal tabs, but in practice either or both may have smaller or larger numbers of tabs.

In Fig. 4 the tool is shown with a shank having a main supporting part 46 of constant crosssection disposed in a plain bore 48 of support block or box 50. In this case, a forward flange or skirt 52 serves to support the tool against the axial forces of the cutting action of the tool. At the rear of the shank part 46 the stepped extension 24 carries the washers 32, 34 in the manner already described. These may lie behind the rear face of the support block, in the manner shown in Figs. 1 and 3, but as illustrated in Fig. 4 at the rear end of the bore 48 there is a larger diameter counterbore 54 and the tabs 36 are located in the counterbore to retain the tool in the support block.

As with the embodiment of Figs. 1 to 3, the tool is inserted from the front of the support block, and when it reaches its final position the washer tabs 36 emerge from the bore 48 to spring into the counterbore 54. Preferably it is arranged that the counterbore has a smaller diameter than the maximum free radial dimension of the washer 32, so that the flexible tabs 36 tend to grip the counterbore and therefore hold the flange or skirt 52 against the front face of the support block. It will be understood that a similar counterbore can also be employed with the stepped form of shank shown in Fig. 1.

Many other modifications are possible within the scope of the invention. For example, instead of a ring-form locking member or washer, a cap-like member can be provided that also covers the rear end of the tool shank. Whether or not this form is chosen for the locking member, it is possible to secure it and the yieldable member together so that they are assembied as a unit on the tool shank. It is also possible to provide an integral unit that comprises means fulfilling the functions of the yieldable and locking members, i.e. to permit relatively easy insertion of the tool from the front of the mounting bore while affording greater resistance to release of the tool therefrom. In this last case, however, the yieldable means and the locking means would both be furnished by elements of the same material and rely on their form and disposition for their different functional properties.

The tool mounting may also take other forms than those illustrated. For example, a peripheral groove or recess can be formed near the rear of the bore to receive the tabs or the like of the yieldable member. If a counterbore is provided, as exemplified in Fig. 4, such a groove may also be formed in it.

Claims (14)

1. A mining tool comprising a shank having a main part for insertion into a bore of a mounting for engagement with the bore to support the tool transversely thereof, and having a rearwardly directed face intermediate the length of the tool for engagement with the mounting to support the tool against the cutting forces acting rearwardly on the tool, rearwardly of said main part the shank being provided with an extension of smaller crosssection than said main part and on which there is mounted a retaining arrangement comprising resiliently yieldable means having a maximum transverse dimension greater than at least the region of the main part of the shank adjacent said extension, and locking means having a maximum transverse dimension not greater than said adjacent region of the shank main part, said locking means being mounted on said extension with at least its region of maximum transverse dimension disposed behind the yieldable means for support thereof against flexure rearwardly.

2. A mining tool according to claim 1 wherein the yieldable means comprises a resiliently yieldable member having a maximum transverse dimension greater than at least the region of the main part of the shank adjacent said extension, and the locking means comprises a locking member mounted on said extension behind the yieldable member, said locking member having a maximum transverse dimension not greater than said adjacent region of the shank main part.

3. A mining tool according to claim 2 wherein the locking member and the yieldable member are secured together as a unit before being mounted on the tool shank.

4. A mining tool according to any one of claims 1 to 3 wherein the locking means comprises a cap-like portion covering the rear end of the tool shank.

5. A mining tool according to any one of the preceding claims wherein said extension of the shank is of stepped form, comprising a smaller cross-section part rearmost behind a larger crosssection part that has a cross-section smaller than that of said adjacent region of the main part of the shank, the locking means holding the yieldable means against a shoulder formed between said larger and smaller cross-section parts of the extension.

6. A mining tool according to any one of the preceding claims wherein the locking means comprises a resilient element or elements engaging frictionally with the adjoining peripheral surface of the tool shank extension.

7. A mining tool according to any one of the preceding claims wherein the locking means comprises an inner peripheral region formed by a series of inwardly projecting tabs engaging with the tool shank extension.

8. A mining tool according to any one of the preceding claims wherein the locking means engages a forwardly tapering region of said shank extension.

9. A mining tool according to any one of the preceding claims wherein the resiliently yieldable means comprises an outer peripheral margin formed by one or more outwardly projecting tabs.

10. A mining tool according to any one of the preceding claims wherein the tool shank main part forwards of said extension comprises a larger cross-section forward portion and a smaller crosssection rearward portion of greater cross-section than the larger cross-section part of said shank extension and being separated from the main part larger cross-section forward portion by support shoulder providing said rearwardly directed face for engagement with a complementary shoulder in the bore of the tool mounting.

11. A mining tool according to any one of the preceding claims in combination with the support block having a bore in which the tool shank main part is received by insertion from the front and which is formed to locate and support the tool against transverse forces in use, and an engagement face at the rear of said bore for retaining the tool against forwards movement.

12. A combination according to claim 11 wherein the support block has a larger crosssection counterbore at the rear of said bore with a cross-section larger than the locking means maximum transverse dimension and having said yieldable means located in it.

13. A combination according to claim 12 wherein said counterbore has a cross-section smaller than the free maximum transverse dimension of the yieldable means.

14. A mining tool according to any one of claims 1 to 10 in combination with the support block having a bore in which the tool shank main part is received by insertion from the front and which is formed to locate and support the tool against transverse forces in use, a peripheral groove or recess being formed adjacent the rear of said bore for engagement by the yieldable means to retain the tool against forwards movement.

1 5. A mining tool according to claim 14 together with claim 12 or claim 1 3 wherein said groove or recess is formed in the counterbore.

1 6. A mining tool constructed and arranged for use substantially as described herein with reference to the examples in the accompanying drawings.

1 7. A combination of mining tool and support block constructed and arranged for use substantially as described herein with reference to the examples in the accompanying drawings.