GB2093378A

GB2093378A - Tool-holding means

Info

Publication number: GB2093378A
Application number: GB8105391A
Authority: GB
Original assignee: AF Hydraulics Ltd
Current assignee: AF Hydraulics Ltd
Priority date: 1981-02-20
Filing date: 1981-02-20
Publication date: 1982-09-02
Also published as: GB2093378B

Abstract

A tool holding assembly for percussive apparatus comprises a body portion 1 with a through bore dimensioned to receive the hexagonal shank of a conventional tool 4 as a free sliding fit. A pivotal catch member 5 of the assembly has an inwardly projecting nose 6 which engages a retaining flange 7 on the tool 4. The catch member 5 is mounted on a mounting member 18 by a pivot 21 and is urged to the tool retained position by a torsion spring 22. The mounting member is retained on the body portion 1 by a screw 27 which allows a degree of resilient axial movement of the mounting member 18, in the axial direction of the tool, against a block of elastomeric material 29 contained in a recess formed between the mounting member 18 and the body portion 1. In the rest position the parts are held with the block 29 slightly compressed by a further elastomeric block 36 which is lightly compressed between the inner end of the mounting member 18 and a wall 37 on the body portion 1. <IMAGE>

Description

SPECIFICATION Tool-holding means This invention relates to tool-holding means in or for percussive apparatus such as roadbreakers and picks.

The tools normally used with a roadbreaker, for example, have a shank which is inserted into the body of the breaker and is retained therein while positioned so that the end of the shank is impacted by a reciprocatory striker. Various toolholding arrangements are employed which ensure retention but the usual arrangement comprises a spring-loaded catch member which engages a retaining flange on the shank of the tool. While working, the tool shank normally reciprocates freely within the body and without the flange striking the catch member, but if the tool breaks through the work, or is withdrawn therefrom with the breaker running, the flange impacts the catch member and is thereby retained in the tool mounting.

Due to the considerable inertial forces involved in arresting a free-running tool the tool-holding structure, particularly the catch member and the pivotal mounting thereof, have to be correspondingiy massive. With the development during recent years of high-powered hydraulic percussive apparatus the provision of tool-holding arrangements of sufficient strength and adequate life has resulted in such arrangements providing an undue proportion of the weight of the apparatus, particularly with hand-held apparatus such as a roadbreaker or pick. In fact, the required massiveness of conventional tool-holding arrangements has become a problem in the development of small hand-held apparatus of relatively high output power which is possible with modern technology associated with hydraulic percussive apparatus.

The object of the invention is to provide tool-holding means, in or for percussive apparatus, which is of relatively small overall dimensions and weight for a given output power of the apparatus.

A further object is to provide such an arrangement which can be designed so as to be usable with conventional tools the shanks of which are already provided with a retaining flange as described above.

According to the invention tool-holding means in or for percussive apparatus comprise a pivotal catch member, for engagement with a retaining shoulder or flange on the shank of a tool when fitted to the apparatus, and a carrier member on which the catch member is pivotally mounted and which is itself mounted so as to be capable of a limited degree of resilient movement relative to the body, in the axial direction of the tool shank, against a body of elastomeric material.

The means are conveniently embodied in a tool-holding arrangement forming a sub-assembly with a body portion having a tool receiving bore and which provides a nose piece of the main body of the apparatus. This body portion may be counterbored to receive the end of the striker which impacts the tool shank, and the subassembly is preferably a removable and replaceable component of the apparatus to facilitate servicing.

The body portion may be cut away on one side for mounting of the catch mounting member which, over an inner end region, may then be of generally semi-circular saddle-like section to sit on the cut-away region of the body portion and to define therewith a closed recess in which the elastomeric material is contained with a limited amount of radial clearance.

Alternatively, the catch mounting member may be in the form of a sleeve which surrounds the end of the body portion to define therewith a closed annular recess in an annular block of the elastomeric material is contained.

Preferably the mounting member is resiliently urged outwardly to a rest position in which said elastomeric material starts to be compressed, and this may be achieved by a further block of elastomeric material under light compression between the inner end of the mounting member and said body portion. This enables the contained body of elastomeric material to be freely positioned within said recess, i.e. not bonded to either of the components which between them define the recess, and thus it becomes itself a readily replaceable and disposable component.

The arrangement preferably also includes means to urge the tool shank towards the outer retained position, i.e. into engagement with the catch member, so that when the apparatus is free running the tool will remain id this outward position and not be continually impacted by the striker which will reciprocate freely and itself be arrested in the normal manner. This tool position may be achieved by mounting a spring or a springloaded plunger or the like in said body portion of the tool-holding means, which spring or plunger engages the tool shank.

The invention will now be further described with reference to the accompanying drawings which show, by way of example, two illustrative embodiments of the invention. In the drawings: Figure 1 is a side view of one tool-holding arrangement in accordance with the invention; Figure 2 is an end view thereof; Figure 3 is a cross-sectional view on the line A-A of Figure 1; Figure 4 is a cross-sectional view on the line B-B in Figure 1; Figure 5 is a view similar to Figure 3 but only partly sectioned to show a method of attachment of the illustrated arrangement to the main body of associated percussive apparatus; and Figure 5 illustrates diagrammatically, in longitudinal cross-section, a second tool-holding arrangement in accordance with the invention.

The arrangement illustrated in Figures 1 to 5 is a self-contained assembly designed to provide a nose-piece of the percussive apparatus with which it is used. It comprises a body portion 1 with a hexagonal through bore 2 dimensioned to receive the hexagonal shank 3 of a conventional tool 4 as a free sliding fit. The tool 4 is shown in broken lines in Figure 3, and a pivotal catch member 5 of the assembly has an inwardly projecting nose 6 which engages the usual flange 7 on the tool 4 to retain the latter when fitted.

At the inner end the body 1 has a projecting spigot portion 8 which locates in the end of the main body 9 of the percussive apparatus (Figure 5) which forms no part of the invention and hence will not be described in detail herein. At this end the body 1 has a counterbore 10 which receives, with free radial clearance, the outer end of a striker 11 of the apparatus which striker impacts the end of the shank 3 in the usual manner. At the inner end of the spigot portion 8 the body 1 has an external screw-thread 1 2 for securing purposes, and in the manner of attachment illustrated in Figure 5 this is achieved by a double-threaded coupling ring 1 3 which also engages a screwthread 14 of opposite hand formed on the main body 9.A sealing/locking sleeve 1 5 is swaged in position around the screw coupling and, as this method of attachment requires separate angular location of the bodies 1 and 9, a radial dowel 1 6 is fitted to the spigot portion 8 and engages a locating slot at the end of the body 9.

At the outer end the body 1 has on one side a generally arcuate cut-away portion 17 (see particularly Figures 3 and 4) on which a generally saddle-shaped catch mounting member 1 8 is slidably mounted. The recess 1 7 extends around one half of the periphery of the body 1 and has radial side walls 1 9 on which the side edges of the member 18 are slidably supported for a limited degree of resilient movement in the axial direction of the tool shank 3. The body 1 is foreshortened at the other end over the 1800 span of the cut-out 1 7 and the mounting member 1 8 projects forwardly over the foreshortened region in which the catch 5 is positioned.This projecting end of the mounting member 18 is bifurcated to provide parallel side limbs 20 between which the catch member 5 is pivotally mounted on a pivot 21 provided by a roll pin pressed into aligned bores in the limbs 20. A torsion spring 22 mounted around a further roll pin 23 fitted between the limbs 20 has an end limb 24 which engages a spring abutment 25 on the catch 5 to urge the latter, in the anti-clockwise direction as viewed in Figure 3, to the normal resting position shown. In this position a tail portion 24 of the catch member rests against an abutment surface 26 on the mounting member 18.

The other end limb 24a of the spring 22 engages a spring abutment 25a on the mounting member 18, and the tail portion 24 enables the catch member 5 to be moved by hand, against the spring force, free of the flange 7 to allow removal of the tool 4. On insertion of the tool the flange 7 engages the catch 5 and automatically displaces the nose portion 6 out of the way, the catch member 6 springing back to the retaining position illustrated after passage of the flange 7.

The mounting member 1 8 is retained on the body 1 by a screw 27 which passes through a longitudinal slot 28 in the member 1 8 which permits the required axial movement of the latter.

The resilient force against which the mounting member 18, and hence the catch 5, can move axially to absorb the impact of the flange 7 on the catch member 5, to retain the tool 4 should the latter break through or be withdrawn from the work, is provided by a block of elastomeric material 29 contained in a generally annular recess between the arcuate base wall of the cutaway 17 and the mounting member 18. This recess is defined (Figures 3 and 4) by an inner end wall 30 and an outer wall 31 formed in the member 18, and an outer end wall 32 and an inner wall 33 formed on the body 1 as well as the radial side walls 1 9 previously referred to. The elastomeric block 29, which is conveniently a polyurethane moulding of the saddle-shape illustrated, has a limited degree of radial clearance to allow the desired amount of resilient compression.To this end the block 29 is moulded with spaced internal projections such as 34, which sit on the inner surface 33, and spaced external projections such as 35 which similarly sit against the outer surface 31 of the containing recess.

The parts are held in the rest position illustrated with the block 29 slightly axially compressed within the containing recess by an elastomeric block 36 lightly compressed between the inner end wall 37 of the cut-away 1 7 and the inner end 38 of the mounting member 1 8. So that when the apparatus is free running the tool shank 7 will not continuously impact the catch member 5, a spring-loaded plunger 39 is slidable axially in the body 1 at a position diametrically opposite to the catch member 5. This plunger 39 is urged by a compression spring 40 into engagement with the flange 7 which is thus urged to a free resting position illustrated in Figure 3 in which it iightly engages the catch member 5.With the tool 4 in this position the end of the striker 11 can reciprocate freely in the end counterbore 10 without impacting the tool shank 3.

The slot 28 and screw-fixing 27 are sealed against the ingress of dirt by a closure plate 41 retained by a circlip 42.

Figure 6 illustrates, somewhat diagrammatically, a modified construction in which the saddle-shaped catch mounting member 1 8 is replaced by a sleeve member 11 8 axially slidable in the nose portion of the body 101 which it surrounds. It has a counterbore 131 to provide an annular recess in which the annular block of elastomeric material 129 is now retained, axially between an end wall 1 30 of the recess (formed on the member 118) and a retaining ring 141 fitted around the body 101 and itself retained by a circlip 142. The elastomeric block 36 of the first embodiment is also replaced by an annular block 136. A spring 140, between the ring 141 and the tool flange, replaces the spring/plunger arrangement 39, 40.

Claims

1. Tool holding means in or for percussive apparatus, comprising a pivotal catch member for engagement with a retaining shoulder or flange on the shank of a tool when fitted to the apparatus, and a catch-mounting member on which the catch member is pivotally mounted and which is itself mounted so as to be capable of a limited degree of resilient movement relative to the main body of the apparatus, in the axial direction of the tool shank, against a body of elastomeric material.

2. Tool handling means according to claim 1, embodied in a tool-holding arrangement in the form of a sub-assembly with a body portion having a tool receiving bore and which provides a nose piece of the main body of the apparatus.

3. Tool holding means according to claim 2, wherein said body portion is counterbored to receive the end of a striker which impacts the tool shank during operation of the apparatus.

4. Tool handling means according to claim 2 or claim 3, wherein the sub-assembly is a removable and replaceable component of the apparatus to facilitate servicing.

5. Tool holding means according to any of claims 2 to 4, wherein said body portion is cut away on one side for mounting of the catchmounting member.

6. Tool holding means according to claim 5, wherein the catch mounting member is of generally semi-circular saddle-like section over an inner region so that it sits on the cut-away region of the body portion and defines therewith a closed recess in which the body of elastomeric material is contained with a limited amount of radial clearance.

7. Tool holding means according to any one of claims 2 to 4, wherein the catch-mounting member is in the form of a sleeve which surrounds the end of said body portion to define therewith a closed annular recess in which an annular block providing said body of elastomeric material is contained.

8. Tool holding means according to any one of the preceding claims, wherein the catch mounting member is resiliently urged outwardly to a rest position in which said body of elastomeric material starts to be compressed.

9. Tool holding means according to claim 8, wherein the catch-mounting member is resiliently urged to said rest position by a further body of elastomeric material positioned under light compression between the inner end of the catchmounted member and said body portion.

10. Tool holding means according to claim 8 or claim 9, wherein said first-mentioned body of elastomeric material is freely positioned, so as to be a readily replaceable component.

11. Tool holding means according to any one of the preceding claims, wherein means are provided to urge the tool shank member, so that when the apparatus is free running the tool remains in this position and is not continually impacted by the striker.

12. Tool holding means according to claim 11, wherein the tool shank is urged towards said outer retained position by a spring, or a spring loaded plunger or the like, which engages said shoulder or flange of the tool shank.

1 3. Tool holding means for percussive apparatus, constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.