GB2129853A - Cutter picks and pick mounting arrangements - Google Patents

Abstract

A pick box (2) mounts alternatively two different pick types in an aperture (6, 8) within the box, with the aid of at least one removable bushing (12). The support locates a first of said pick types (F) non- rotatably by locking engagement with a rearwardly tapered shank thereof. The support also provides a forwardly facing abutment shoulder (10) for the transmission of axial forces from a second pick type (P) intended to be rotatable in the aperture. <IMAGE>

Description

SPECIFICATION Cutter picks and pick mounting arrangements This invention relates to cutter picks, e.g. for mineral cutting, and their mounting arrangements.

In a conventional coal cutting machine, for example, there are a large number of cutter picks, typically each located and supported in an individual pick box, a series of such boxes being mounted on a continuously driven chain or drum of the machine. Two particular types of pick which may be used in such a machine are the point attack pick which acts in the direction of cutting, with a conical cutting tip projecting obliquely forwards in the cutting direction from its pick box, in which the pick is so mounted as to be able to rotate about the longitudinal axis of the tool, and the forward attack pick which also projects obliquely forwards but which has a cutting tip that must be held in a fixed orientation.

The forms of cutting tip on these two types are intended to cope with different operating conditions and because of the different ways in which they act, the picks must be supported in different ways. The forward attack pick is located against rotation, e.g. by an abutting step on the pick box, and it may be provided with a tapered shank that engages a locking taper bore in the pick box when the pick is fully inserted. This contrasts with the rotational freedom ensured for the point attack pick generally in order to distribute wear over the tip. The shank is therefore usually cylindrical over at least a part of its length and sometimes a bush, which may itself rotate, is interposed between the shank and the tool box aperture.

According to the present invention, there is provided a pick box unit comprising a carrier or pick box arranged to mount alternatively either of two different types of pick with a shank of each type of pick supported within an aperture in the pick box, said aperture receiving at least one bushing by means of which at least one of said pick types is supported therein, the support for said pick types comprising (i) a tapered locking bore for the first of said pick types having a rearwardly tapered shank and arranged to secure the pick non-rotatably in the pick box, and (ii) a forwardly facing abutment face for the second of said pick types, which second type comprises a rearwardly facing abutment shoulder for the transmission of forces to said forwardly facing face and which is intended to be rotatable in the pick box.

Where said bushing or one of said bushings is employed to receive a forward attack tool for example, it advantageously takes the form of a split bush so as to be capable of radial movement to grip both the tool shank and the walls of the pick box aperture.

By the use of the invention, the shanks of the different types of tool can thus be interchangeably held in the carrier or pick box by, for example, using different bushings for the different types, using the unbushed aperture for one of the types, or by using the same bushing in different locations for the different types.

According to other aspects of the invention there are also provided forward attack picks and point attack picks which are adapted for use in an arrangement according to the invention, as well as novel forms of bushing.

The invention will be described in more detail by way of example, with reference to the accompanying schematic drawings in which: Figs. 1 and 2 illustrate a pick box unit according to the invention, the pick box holding in Fig. 1 a point attack pick, and in Fig. 2 a forward attack pick, and Figs. 3 to 7 illustrate features of a series of alternative forms of pick box unit according to the invention.

In Figs. 1 and 2 the pick box 2 has a stepped circular cross-section aperture 4 suitable for a standard point attack tool P (Fig. 1), and it may be of a known, standard size. It comprises forward and rearward coaxial cylindrical portions 6, 8 separated by a frusto-conical shoulder 10. The cylindrically formed aperture walls support the tool transversely while allowing it to rotate on its own axis, and the shoulder 10 supports the tool against the axial component of the cutting force.

When the forward attack pick F shown in Fig. 2 is to be used, a split bush 12 is inserted into the aperture 4 to form there a tapering passage that closely fits the tapering portion of the pick shank.

The passage has a circular cross-section to provide a taper lock for the pick shank after initial engagement of the pick with front step 1 4 on the pick box. Thus, as the pick is inserted into the box, firstly the step engages a front shoulder of the pick shank to locate the pick in the required orientation, then as the pick shank is fully inserted the taper portion expands the split bush so that it engages the passage walls and the pick is firmly held in a locking taper. Of course, the step 14 is so positioned that it does not contact the point attack tool.

In Fig. 3 a modified form of taper bush 30 is shown that extends only over the larger diameter forward portion 6 of the aperture but it provides a similar taper lock for the forward attack pick F, which can be of the same form as in Fig. 2.

In Fig. 4 the same two forms of pick shank are arranged to be held. The aperture of the pick box 40 has the same configuration rearward portion 8 as in Figs. 1 to 3 but a tapered forward portion 42 so that the forward attack pick F can be inserted and its shank locked directly with that forward portion. Orientation of the pick F as it is inserted is achieved by the front step 14. When it is required to mount a point attack tool P, a split bush 44 is inserted into the forward section of the aperture to provide a cylindrical receiving bore. The tool is thereby supported in the same manner as the example of Fig. 1.When a bushing is provided for the point attack tool, as in the example, it is also possible to employ a bush with a collar at its leading end bearing on the front face of the pick box whereby the axial force is transmitted from the tool through the collar to the box front face, although the greater exposure of the bearing faces in this arrangement with a tool shank that is intended to rotate will tend to increase their rate of wear.

Fig. 5 illustrates a pick box 50 for which the aperture is formed by two concentric cylindrical portions 6, 8 as in Figs. 1 and 2, joined by the frusto-conical shoulder 1 0. A cylindrical bushing 52 fits the larger cross-section forward portion of the aperture when the point attack tool P is inserted, the bush functioning to assist the rotation of the tool, but leaving clear the major part of the shoulder 10 that provides rearwards support for the tool. A tapered split bush 54 is used instead when the forward attack tool F is to be mounted, to co-operate with the tapered faces of the tool shank.

In the example of Fig. 6, each of the two tool types is supported in the box 60 with the aid of a bushing, but in this instance the same split bush 62 provides the bushing for both, its position being reversed depending upon the tool type to be inserted. The split bush thus has a cylindrical outer face fitting forward cylindrical portion 64 of the tool box aperture and an inner tapered face 66, with oblique end faces 68a, 68b that each match the conicity of the aperture shoulder 1 0.

In the first part of Fig. 6, the bush is inserted so that it tapers rearwardly and in this postion it can receive the tapered shank of a forward attack tool F. There may be some clearance between the front end of the bush and the rearwardly facing shoulder of the tool shank. As in preceding examples, the tool is located against rotation by the front step 14.

When the position of the bush is reversed, its larger oblique end face 68b provides a location for the conical shoulder on the point attack tool P through which axial forces are transmitted. The bush 62 terminates short of the forward end of the cylindrical portion 64 of the tool box aperture and the tool shank is located transversely by this extreme forward end of the tool box aperture and by the cylindrical rear portion 8 of the aperture, rearwards of the bushing.

In Fig. 7, a reversible bushing 72 similar to that shown in Fig. 6 is used. In this instance, however, prevention of rotation of a forward attack pick F is achieved by means of a locating pin 74 lying within the receiving aperture in the tool box. This engages a complementary recess or flat in the forward attack pick shank, but the shank of the point attack pick P has a cylindrical form of sufficiently small radius to clear the locating pin so that rotation of the tool is not hindered by it. In other respects the tools are located and supported in the manner already described.

Fig. 7 shows a spring clip 76 used to retain the point attack pick in its aperture. It will be understood that in all the illustrated examples the point attack picks will be provided with retaining means, which may take entirely conventional forms. Although the forward attack picks will normally be rigidly held by their locking taper connection, axial retaining means may also be provided for these picks if desired.

It will also be understood that where split bushes are provided they may be one-piece sleeves or they may be made up of a number of parts - e.g. as a diametrically split sleeve - the latter alternative of course being required where the inside dimensions of the bushing are less than the dimensions of the rear portion of the tool shank, as in the case in Fig. 7.

While the foregoing examples illustrate how different pick types can be secured interchangeably in a pick box, the taper bushings can be usefully employed to secure picks that are required to have a fixed orientation whether or not provision is made for interchangeability with other pick types, however. For example, the radial type of pick, which projects from its box substantially at right-angles to the direction of cutting movement and which is provided with a rectangular section shank that is a loose fit in the pick box aperture, can with advantage be secured more firmly using a taper lock bushing. Preferably, the pick shank and the pick box aperture are given a circular cross-section and it may also be more convenient to use a split bushing so as to be capable of tight engagement between shank and aperture walls by radial expansion.

Claims (11)

1. A pick box unit comprising a carrier or pick box arranged to mount alternatively either of two different types of pick with a shank of each type of pick supported within an aperture in the pick box, said aperture receiving at least one bushing by means of which at least one of said pick types is supported therein, the support for said pick types comprising (i) a tapered locking bore for the first of said pick types having a rearwardly tapered shank and arranged to secure the pick non-rotatably in the pick box, and (ii) a forwardly facing abutment face for the second of said pick types, which second type comprises a rearwardly facing abutment shoulder for the transmission of forces to said face and which is intended to be rotatable in the pick box.

2. A unit according to claim 1 wherein said bushing provides said tapered locking bore.

3. A unit according to claim 2 wherein said bushing is in the form of a split bush.

4. A unit according to any one of claims 1 to 3 wherein said forwardly facing abutment face is formed by a shoulder within the aperture spaced from its forward end.

5. A unit according to claim 2 or claim 3 together with claim 4 wherein the bushing extends both forwardly and rearwardly of said abutment shoulder.

6. A unit according to claim 2 or claim 3 together with claim 4 wherein the bushing terminates rearwardly at said shoulder.

7. A unit according to claim 6 wherein said bushing is reversible in the aperture to an alternative position in which it forms means for the transmission of forces between said abutment shoulder of the pick support and the associated rearwardly facing abutment shoulder of the second pick type.

8. A unit according to any one of claims 1 to 6 wherein said bushing or a further bushing provides a cylindrical bore for at least one portion of the length of the shank of the second pick type within said aperture.

9. A unit according to any one of the preceding claims wherein means within the aperture locate the first pick type angularly with respect to the central axis of the aperture.

10. A pick box unit constructed and arranged for use substantially as described herein with reference to any of the examples in the accompanying drawings.

11. A bushing for use in a pick box unit according to the invention and being in the form of a split bush having a cylindrical outer surface and a rearwardly tapered bore, there being either an outer step intermediate the length of the bushing or an outer end face at the smaller end of that bore, which step or face is tapered in the same sense as the bore, but at a more acute angle.