GB2109438A - Retaining means for use in mounting mining picks in pick bases - Google Patents

Abstract

A mineral mining pick 16 is rotatably mounted in a pick box 10 and is held in place by a spring steel retaining clip 30 fitted on a rear shank portion 14<1>. The clip 30 has a cup- shaped body comprising an apertured central base part surrounded by a shallow wall from the top edge of which extend radially directed folded limbs terminating in abutment feet which engage the rear face of the pick box. All bends are smoothly curved and rough edges are avoided. The pick can be removed by levering forwards to exert a force that deflects the limbs rearwards. <IMAGE>

Description

SPECIFICATION Retaining means for use in mounting mineral mining picks in pick boxes This invention relates to the mounting in pick boxes of mineral mining picks such as are used, for example, in rotary drum coal cutting machines.

More specifically, the invention is concerned with retaining means for holding in place a mining pick of the kind having a shank which is rotatably mounted in a through bore of a pick box.

In a known arrangement for holding in place mining picks of the above kind, the rear end portion of the shank projects beyond the rear face of the pick box and is provided with a wire retaining clip of a generally planar and somewhat U-shaped form having an open mouth which enables it to be fitted on the shank rear end portion, and to engage with an annular retaining groove therein, by a lateral displacement movement after the shank has been fully inserted into the pick box. When in position, part of the clip is seated in the annular retaining groove of the shank rear end portion and the remainder of the clip, lying in a plane transverse to the shank rear end portion, overlies the rear face of the pick box and acts as a stop limiting outwards axial displacement of the pick relative to the pick box.

Although this known arrangement is generally functionally satisfactory for the purpose of holding the pick in place in the pick box during use, when the pick is being mounted it is necessary for the clip to be fitted at the rear of the pick box as a separate operation after inserting the shank, and when the pick is being removed again a separate operation must be carried out at the rear of the pick box to remove the retaining clip before withdrawing the shank.This, however, is disadvantageous in practice because in mining operations such as coal cutting, on the one hand there is a tendency for dust and debris to accumulate and to become compacted at the rear of the pick boxes which makes it difficult to obtain access and fit and remove such retaining clips under working conditions and yet, on the other hand, the picks soon become worn and have a short working life so that frequent removal and replacement is essential.

An object of the present invention is accordingly to provide an improved form of retaining means for use in connection with the mounting of mining picks in pick boxes which can facilitate the operations of removal and replacement under working conditions and obviate the above-mentioned disadvantage of the prior art wire retaining clip referred to.

The invention is based on the concept of providing a mineral mining pick with a spring steel retaining clip which can be fitted in position on the rear end portion of the shank before inserting into the pick box, the clip having a plurality of radially directed resilient limbs which are adapted to flex or fold inwards to permit passage through the bore of the pick box during insertion of the shank from the front end thereof and to spring radially outwards when clear of the end of the bore so as then to overlie the rear face of the pick box and thereby to provide abutment stop limiting subsequent displacement of the shank in the axially outwards direction during working operation, the resilient limbs being such however that under the influence of a sufficiently large force urging the shank axially outwards, which force may be exerted by a crowbar or other levering tool applied at the front end of the pick box, they will deflect axially rearwards to such an extent as to again permit passage through the bore of the pick box and removal of the pick.

Thus, the pick can be fitted and removed entirely by operations carried out from the front end of the pick box and it is unnecessary for free access to the rear of the pick box always to be maintained for the purpose of manipulating the retaining clip into and out of position.

In designing satisfactory retaining clips in accordance with the invention, however, it is necessary to take into account the arduous working conditions under which they are to be used. In particular, as the pick shank is generally mounted so as to have some degree of axial play in the pick box, as well as being free to rotate therein, when the cutter is operating at speed with variable pressure, especially against mineral deposits of different hardness such as in coal seams mixed with rock for example, the pick and the retaining clip are both continuously subjected to heavy vibrational and percussive forces which tend to cause breakage and premature failure of the retaining clip.

Accordingly, in preferred embodiments, the retaining clip will be formed out of a single sheet steel blank shaped to provide a shallow cupshaped body part having a substantially flat base, pierced by a central aperture for receiving the rear end portion of the pick shank, which is surrounded by an upstanding wall portion, and a plurality of radially-directed limbs formed by strips of the sheet steel extending outwardly of the wall portion from the top edge thereof, each limb being bent round through a smoothly curved U-bend adjacent its root end so that its main portion lies in radiallyspaced relationship with the wall portion of the body part and extends below the level of the base of the latter to terminate in a foot portion providing a stop surface adapted to engage against the rear face of the pick box.It is important that all edges should be smooth and that there should be no sharp angular transitions likely to constitute areas of weakness for cracks to develop and the clip is desirably provided all over with a well polished finish, as by being subjected to a barrelling finishing process for example. Also, the size of the aperture in the base of the cup-shaped body part should not be unduly large in relation to the size of the base so that a substantial flat annular area of metal remains surrounding the aperture.

Preferably, the clip has a symmetrical form with a total of three limbs disposed equiangularly around the cup-shaped body part. The wall portion of the latter may be of reduced height between each pair of limbs but any variations in height are also preferably defined by a smoothly curved top edge which merges into the root portions and U-bends of the limbs.

The retaining clip is fitted coaxially on to a reduced diameter section of the rear end portion of the pick shank so that the underside of the base of the cup-shaped body part abuts against an annular shoulder, and the clip is conveniently held in place by a circlip or the like located on this reduced diameter section, preferably in an annular groove therein, immediately above the base of the cup-shaped body part, that is, in the axially rearwards direction of the pick shank.

In practice, the picks will be supplied by the manufacturers with the retaining clip already fitted so that they are all ready to be mounted when received by the user.

With the retaining clips having limbs of the configuration described it will be appreciated that, in mounting a pick in the pick box, as the shank is inserted into the pick box bore from the front end thereof the limbs will flex or fold inwards to permit passage through the bore. This action is facilitated by bevelled lead surfaces at the mouth of the bore and between different diameter sections of the bore within the interior of the pick box. It is only after the shank rear end portion has passed through the bore that the limbs are able to expand radially outwards so that the feet thereof overlie the rear face of the pick box.

It will further be appreciated that upon exerting a sufficient force axially outwards upon a mounted pick, a stage will be reached when the limbs will be deflected rearwards so that the shank can move forwards through the bore and the pick can be removed. As previously indicated, such axial force for removal may be applied by a crowbar or like leverage tool, and with the configuration described the limbs may snap suddenly into their rearwardly-deflected position when the axial force reaches a critical value.

By way of example, the construction and use of a typical mining pick retaining clip in accordance with the invention is illustrated in the accompanying drawings.

In said drawings, Figure 1 is a londitudinal sectional view showing a mining pick, fitted with the retaining clip, mounted in a pick box, fitted with the retaining clip, mounted in a pick box, as during use in a rotary drum coal cutting machine; Figure 2 is a rear end elevational view of the assembly of Figure 1; Figure 3 is a view similar to Figure 1 but showing the shank of the pick being inserted into the bore of the pick box; Figure 4 is also a view similar to Figure 1 but showing the pick being removed from the pick box; Figure 5 is a detail view of the rear end portion of the shank shown on its own; Figure 6 is a side view of the retaining clip on its own, shown on a larger scale; Figure 7 is rear elevational view of the retaining clip; and Figure 8 is a sectional view on line VIl-VIl of Figure 7.

Referring to the drawings, reference numeral 10 designates the pick box which has a through bore 12 to receive the shank 14 of the pick which is designated generally by the reference numeral 16.

The bore 12 is of cylindrical form and has a stepped diameter with a bevelled internal shoulder 1 8 between a narrower rear section 12b and a wider front section 1 2a, and there is also a bevelled lead-in surface 20 around the mouth of the bore at the front end.

The shank 14 of the pick 16 also has a stepped diameter with sections 14a and 1 4b which match the diameters of the bore sections 1 2a and 1 2b.

Forwardly of the shank section 1 4a there is a collar 22 which lies externally of the pick box, and at the front end the pick terminates in a cutting blade which is not shown in the drawings.

To the rear of the section 1 4b the shank 14 terminates in a rear end portion 14' which, although of smaller diameter than section 14b, is also stepped to provide a larger diameter section 1 4'c and a reduced diameter section 14'd defining a shouldered end face 24. The reduced diameter section 14'd is also formed with an annular groove 26.

As shown in Figure 1, in use the rear end portion 14' projects beyond the rear face 28 of the pick box 10 and is fitted with the retaining clip which is indicated generally by reference numeral 30.

Retaining clip 30 is formed in one piece from a blank of sheet spring steel and comprises a shallow circular cup-shaped central body part 32 from which extend three equiangularly-spaced radially-directed limbs 34. The body part 32 has a flat circular base 36 formed with a central circular aperture 38 of a diameter slightly greater than that of the section 1 4'd of the rear end portion 14' of the pick shank. It will be noted that the aperture 38 is surrounded by a substantial annular area of metal of which the width is greater than one third of the diameter of the aperture, the base itself 36 having a diameter which is approximately the same as that of the section 1 4'c of the shank rear end portion.

Around the base 36 is a shallow upstanding wall 40 and the root ends of the limbs 34 extend outwards from the top edge of this wall. Adjacent its root end, each limb 34 is bent round through a smoothly curved U-bend 42 so as to provide a main leg portion 44 lying beyond the wall 40 in radially spaced relationship therewith. Each main leg portion 44 is slightly inclined outwardly and termines in a flat out-turned foot portion 46 below the level of the base 36.

Between the limbs 34, the wall 40 is of reduced height but its top edge is smoothly curved, as shown at 48, to merge with the root portions of the limbs.

The retaining clip 30 is given a well-polished surface overall by being subjected to a barrelpolishing process and all burrs and sharp edges are eliminated to reduce any tendency to crack and failure when in service.

In use, as will be seen from the drawings, the clip 30 is fitted on the rear end portion 14' of the pick shank 14 so that the base 36 seats on the reduced diameter section 14'd with the underside abutting against the shouldered face 24. The retaining clip is then held in place by a circlip 50 (see Figure 2) engaged in the annular groove 26.

The clip 30 is fitted to the pick 1 6 before mounting the latter in the pick box 1 0. As shown most clearly in Figure 3, in mounting the pick the shank 1 4 is inserted through the front end of the bore 12 and, upon then being moved axially rearwards, the resilient limbs 34 of the clip are forced radially inwards permitting passage through the bore. This action is facilitated by the bevelled lead surface 20 around the mouth of the bore, and also by the bevelled internal shoulder 1 8 between the different diameter sections 1 2a and 12b.

When the shank 14 is fully inserted, however, the rear end portion 14' projects beyond the rear end face 28 of the pick box and the limbs 34 expand outwards so that the out-turned feet 46 overlie the pick box end face thereby to provide a stop limiting subsequent axially-outwards movement of the pick, as shown in Figures 1 and 2.

To remove the pick, for replacement purposes for example, a crowbar levering implement 60 is applied between the front end of the pick box 10 and the collar 22 so as to exert a powerful force in the axially-outwards direction. This then results in the resilient limbs 34 of the clip 30 being forced rearwards and eventually they move with a snap action into a rearwards directed position which will again permit passage through the bore 12.

This operation is shown, somewhat diagrammatically, in Figure 4.

As illustrated, when the pick is mounted in the pick box for normal use there is a certain amount of axial play permitted which provides space for the tip of the crowbar levering implement 60 to be inserted between the front of the pick box and the collar 22. If necessary, however, the front end of the pick box could be recessed to facilitate engagement of the implement 60.

It will of course be understood that the abovedescribed specific embodiment is presented only by way of example, and numerous modifications in detail features thereof can be made within the scope of the invention.

Claims (5)

1. A mineral mining pick having a shank for rotatably mounting in a through bore of a pick box, said pick being provided with a retaining clip which can be fitted in position on the rear end portion of the shank before inserting into the pick box, said clip being integrally formed, out of a single sheet steel blank, as a spring steel collar fashioned to provide a shallow cup-shaped body pierced by a central shank-receiving aperture and having a plurality of radially directed resilient limbs which are adapted to flex or fold inwards to permit passage through the bore of the pick box during insertion of the shank from the front end thereof and to spring radially outwards when clear of the end of the bore so as then to overlie the rear face of the pick box and thereby to provide abutment stops limiting subsequent displacement of the shank in the axially outwards direction during working operation, the resilient limbs being such that under the influence of a sufficiently large force urging the shank axially outwards, which force may be exerted by a levering tool such as a crowbar for example, applied at the front end of the pick box, they will deflect axially rearwards to such an extent as to then permit outwards passage through the bore of the pick box and removal of the pick, said shallow cup-shaped body part of the clip having a substantially flat base surrounded by an upstanding wall portion and the radially-directed limbs being formed by strips of the sheet steel extending outwardly of the wall portion from a top edge thereof, each limb being bent round through a smoothly curved U-bend adjacent its root end so that its main portion lies in radially-spaced relationship with the wall portion of the body part and extends below the level of the base of the latter to terminate in a foot portion providing a stop surface adapted to engage against the rear face of the pick box.

2. A mineral mining pick as claimed in claim 1 wherein the clip has a symmetrical form with a total of three limbs disposed equiangularly around the cup-shaped body part.

3. A mineral mining pick as claimed in claim 1 or 2 wherein the wall portion of the cup-shaped body part of the clip is of reduced height between each pair of limbs, variations in said height being defined by a smoothly curved top edge which merges into the root portions and U-bends of the limbs.

4. A mineral mining pick as claimed in any of the preceding claims wherein the retaining clip is fitted coaxially on to a reduced diameter section of the rear end portion of the pick shank so that the underside of the base of the cup-shaped body part abuts against an annular shoulder, and the clip is held in place by a circlip or the like located on said reduced diameter section, immediately above the base of the cup-shaped body part, that is, in the axially rearwards direction of the pick shank.

5. A mineral mining pick retaining clip substantially as herein described and illustrated with reference to the accompanying drawings.