GB2171948A

GB2171948A - Hydraulic impact tool

Info

Publication number: GB2171948A
Application number: GB08504900A
Authority: GB
Inventors: John Leslie Northwood; David Coy
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1985-02-26
Filing date: 1985-02-26
Publication date: 1986-09-10
Also published as: GB2171948B; GB8504900D0

Abstract

An hydraulic impact chisel comprises a trigger mechanism (28) including a flow control valve (18) drivably connected to a hand lever (25), the valve having two operational modes. A spring unit (42) includes a gas spring and an element (41) movable in a spring-compressing direction against the action of the spring and movable in a released direction under the action of the compressed spring. A piston component (45) is slidably movable to and fro under the action of pressurised fluid fed from the control valve in its two operational modes, respectively. The tool further comprises a releasable latch mechanism (50) which in a latched mode is adapted to fixedly connect a slidably-mounted hammer (30) and the piston component (45) for movement in a spring-compressing direction and which when the piston component has reached a preselected position is activated into an unlatched mode to release the hammer to move with the element of the spring unit under the action of the compressed spring. <IMAGE>

Description

SPECIFICATION Hydraulic impact tool This invention relates hydraulic impact tools.

In particular, although not exclusively the invention relates to hydraulic impact chisels used in underground mines for splitting nuts from bolts and shearing rivet heads etc.

Previously known hydraulic impact chisels used in underground mines have comprised hyraulic accummulators which store compressed fluid until a latch mechanism releases a chisel engaging hammer which during its impacting stroke is urged by the stored pressurised fluid to engage the chisel.

Unfortunately, such known impact chisels tend to be heavy and bulky tending to make them unsuitable for many tasks encountered in the confined working conditions met in underground mines.

An object of the present invention is to provide a hydraulic impact chisel which tends to be compact and therefore more widely acceptable in underground mines and which tends to be reliable and inexpensive.

According to the present invention a hydraulic impact tool comprises a housing assembly provided with a handle, a trigger mechanism including a pressurised fluid flow control valve having two operational modes, a hammer slidable to and fro within the housing assembly, a spring unit including a gas spring and an element movable in a spring compressing direction against the action of the spring and movable in a released direction under the action of the compressed spring, a piston component slidably movable to and fro within the housing assembly under the action of pressure fluid fed from the control valve in its two operational modes, respectively, and a releasable latch mechanism which in a latched mode is adapted to fixedly connect the hammer and the piston component when,in use, the trigger mechanism is triggered and the control valve is activated into the first of its two operational modes to feed pressure fluid to urge the piston component in the spring compressing direction against the action of the gas spring and which when the piston component has reached a preselected position in the spring compressing direction, is activated into an unlatched mode to release the hammer to move with the element in the spring released direction under the action of the compressed spring.

Preferably, the piston component is retained in the preselected position until the trigger mechanism is released and the control valve is activated into the second of its two operational modes to feed pressurised fluid to urge the piston component in a direction opposite to the spring compressing direction.

Conveniently, the control valve comprises a spool slidable along a bore between the two operational mode positions and the trigger mechanism comprises a trigger drivably engaging the spool.

Preferably, the releasable latch mechanism comprises a slide member slidably mounted on the piston component for limited movement with respect to the piston component.

Preferably, the slide member is connected to the piston component via a resilient bias.

Preferably, the releasable latch means comprises an abutment engageable with a formation when the piston component is in the preselected position.

Advantageously, when the abutment engages the formation, the slide member is slid relative to the piston component against the action of the resilient bias.

Preferably, the releasable latch mechanism comprises at least one ball which in the latched mode is engageable in a recess provided in the hammer to fixedly connect the hammer to the piston component and which in the latch released mode is disengageable from the recess to release the hammer.

Conveniently, in the latched mode the slide member retains the ball in the recess.

Advantageously, in the latch released mode the slide member is slid against the resilient bias to allow the ball to disengage the recess.

Preferably, the slide member comprises a recess for engagement by the ball in the latch released mode.

Conveniently, the recess provided in the hammer defines an outwardly directed taper tending to urge the ball towards the recess provided by the slide member.

Preferably, the released hammer impacts on an anvil.

Preferably, cushion means are provided between the anvil and the housing assembly.

Preferably, the anvil engages a chisel slidably retained by the housing assembly.

By way of example, two embodiments of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section taken through an hydraulic impact chisel construction in accordance with one embodiment of the present invention; Figure 2 is an incomplete end view of Figure 1; Figure 3 is an incomplete section taken along line Ill-Ill of Figure 1; Figure 4 is a detail of Figure 1; Figure 5 is a section taken along line V-V of Figure 4; and Figure 6 is a longitudinal section taken through a detail of an hydraulic impact chisel constructed in accordance with a second embodiment of the present invention.

Figures 1 and 2 of the drawings show the hydraulic impact chisel to comprise a housing assembly 1 held together by four bolts 2 (only the bolt holes are shown in Figure 2) extending substantially the length of the housing assembly. The housing assembly provides a handle 3, 4 secured in position by cross bolts 5. A chisel 6 extending from the nose of the housing assembly is slidably retained in position by a nose cap 7 fixedly retained by the aforementioned bolts 2. A lever 8 can be pivoted to an upright position as viewed in Figure 1 to permit the chisel to be removed from the nose cap. Pivoting the lever 8 turns pin 9 such that a flat 10 on the pin faces a retention pad or bush 11 thereby permitting removal of the pad followed by the chisel.

The handle section 3 defines two fluid flow passages 12 and 13 provided with connectors 14 for connecting the two passages 12, 13 to a source of pressurised hydraulic fluid and to exhaust, respectively. The exhaust passage 13 is provided with a non-return valve 15 preventing incorrect operation if misconnected to supply. The two passages connect with a bore 16 sealably containing a spool 17 of a directional flow control valve 18 (details of the control valve including further passages 19, 20, 21, 22 and 23 are shown in Figures 1 and3.

The spool is resiliently biassed by means of a coil spring 24 towards the operational mode as shown in Figure 1, the spool being slid along the bore towards its second operational mode by means of a pivotally mounted hand lever 25 having a forked end 26 engaging a recess 27 defined by the spool. The lever 25 constitutes part of trigger mechanism 28 for operating the impact chisel.

The lever is pivotally mounted on a pivot pin 29 for movement between the two positions indicated in Figure 1.

The impact chisel further comprises a hammer 30 slidable to and fro within the housing assembly and mounted two annular low friction bearing as semblies31, 32. The hammer is provided with an annular recess 33 having a outwardly directed tapered end 34. The end 35 is not tapered. The hammer is arranged to engage a slidably mounted anvil 36 which in turn is arranged to engage the chisel 6. The anvil has an outwardly directed flange 37 for engaging cushion means constituted by a stack of resilient washers 38. The cushion means retards movement of the anvil towards the end of its forward stroke to thereby reduce the reaction on the housing assembly should the chisel not fully absorb the force of the impact blow or if tool is 'fired' when chisel not fitted or not engaged on a nut.

The bearing assembly 31 is mounted in a guide member 39 fixedly mounted with the housing assembly 1. The guide member has an axially extending bore 40 for accommodating the hammer and a piston element 41 of a gas spring unit 42 which is abutted by the hammer. The piston element is slidable to and fro within the bore 40, the element being movable in a spring compressing direction (ie to the right as viewed in Figure 1) against the action of the spring and movable at high speed in a released direction (ie to the left as viewed in Figure 1) under the action of the compressed gas spring. The gas spring for example comprises nitrogen sealed within a cylinder 42 of the gas spring unit.

The guide member also provides a slideway for a piston component 45 which is sealed within chamber 46, 47 and constituting a double acting piston a cylinder device. The two sides of the chamber are hydraulically connected to the previously mentioned passages 22 and 23 communicating with the valve 18. The piston component 45 is provided with a forwardly extending tubularsec- tion 48 which carried the second of the aforementioned bearing assemblies 32 and which has four cross boreholes 49.

The hydraulic impact chisel also comprises a releasable latch mechanism 50 mounted on the end of the tubular section 48 of the piston component 45 in the vicinity of the cross boreholes 49. The releasable latch mechanism when in its latched mode (as seen in Figure 1) is adapted to fixedly connect the hammer and the piston component and when in an unlatched mode releases the hammer to move independently of the piston component. The latch mechanism comprises a slide member 51 slidably mounted on the tubular section of the piston component for limited movement with respect to the piston component.The slide member provides an annular recess 52 having a inwardly tapered end and is connected to the piston component via a resilient bias constituted by a plurality of tension coil springs 53 each secured between a pin 54 mounted on the tubular section of the piston component and a pin 55 mounted on the slide member. The rear end of the slide member provides an abutment 56 for engagement with an abutment formation 57 provided by an inwardly directed flange 58 of the housing assembly. The abutment 56 engages the formation 57 when the piston component reaches a preselected position assembly. The latch mechanism further comprises a plurality of balls 60 engaged in the cross boreholes 49 and alternatively in the recess 33 provided in the hammer or in the recess 52 provided in the slide member.The recess accommodating the balls depends upon whether the latch mechanism is the latched mode or in the unlatched mode as will be explained later in this specification. When, the balls are in the latched mode they are retained in the recess 33 by the radially inward face 61 of the slide member, the balls abutting the face.

In operation of the hydraulic impact chisel with pressurised hydraulic fluid fed to passage 12 and passage 13 connected to exhaust, the point (not shown) of the chisel 6 is positioned against a nut to be split. The lever 25 of the trigger mechanism is pulled to the position indicated by the broken line in Figure 1. The spool 17 of the control valve 18 is moved against the action of spring 24 into a first operational mode in which pressurised hydraulic fluid is fed to the portion 47 of the chamber. Simultaneously, the portion 46 of the chamber is connected to exhaust passage 13. The action of the pressure fluid in chamber portion 47 is to move the piston component to the right as viewed in Figure 1. The latch mechanism is in the latched mode as shown in Figure 1. Consequently, the hammer 30 is fixedly connected to the piston component and also moves to the right. Such a movement of the hammer causes the piston element 41 of the gas spring unit 42 to move tithe right in a spring compressing direction. The spring compressing movement continues until the piston component reaches a preselected position determined by the abutment 56 engaging the formation 57. Upon contact the slide member-51 is urged to slide against the action of the spring 53 until the recess 52 is adjacent to the cross boreholes 49.

The inwardly directed face 61 of the slide member disengages the balls and the action of the outwardly tapered ends of the recess 33 is to urge the balls outwardly into the recess 52 thereby activating the latch mechanism into an unlatched mode and releasing the hammer from the piston compo -nent. Immediately, the latch mechanism is unlatched the released hammer is free to move in a released direction under the action of the compressed gas spring. Consequently, the hammer impacts on the anvil which is held off its cushion means by the action of the chisel. Hence, the impact blow is delivered to the chisel which cuts into the nut.

Upon the hammer being released the piston component is held by the action of the pressurised hydraulic fluid in chamber portion 47 until the lever of the trigger mechanism is released allowing the spool 17 of the control valve 18 to move into the second of its two operational modes in which chamber portion 47 is connected to exhaust and chamber portion 46 is fed with pressurised hydraulic fluid. When the piston component 45 reaches the end of its return stroke (ie to the left as seen in Figure 1) cross boreholes once again are adjacent to the recess 33 provided in the hammer.

The action of the springs 53 of the latch mechanism is to urge the slide member towards the right as seen in Figure 1 thereby causing the inwardly tapered end of the recess 52 to urge the balls 60 through the cross boreholes 49 and into the recess 33. Thus, the latch mechanism once again is activated into its latched mode fixedly connecting the hammer to the piston component.

The impact chisel now is ready for delivering a second blow, if required.

It will be appreciated that the impact chisel does not have a continuous operational action but is designed to deliver one impact blow for each operation of the trigger mechanism. This is a particular safety feature of the tool and means that each blow is fully controllable being delivered exactly when and where required.

Figure 6 shows a detail of a second embodiment of a hydraulic impact tool comprising a different releasable latch mechanism to that shown in Figure 1. All other items of the tool construction are as shown in Figure 1 and further description on the identical features are not included.

The releasable latch mechanism 100 of Figure 6 comprises a slide member 101 slidably mounted on the forwardly extending tubular section 48 of the piston component. Movement of the slide member 101 is restricted in one direction by an abutment shoulder 102 defined by the tubular section which engages on corresponding abutment 103 provided on the slide member. Movement of the slide member 101 in the opposite ie forward direction is against the action of a compression spring 104 which seats on an abutment collar 105 retained in position by a circlip 106. The slide member 101 also defines a recess 52 for accommodating the balls 60 in the latch released mode, and a radially inward face 61 for retaining the balls 60 in the latched mode.

Operation of the latch mechanism 100 is similar to that of the previously described first embodiment. Upon the tubular section being urged by pressurised fluid in the gas spring compressing direction and upon reaching the aforementioned preselected position an abutment face 107 on the slide member engages the abutment formation presented by the tool housing and urges the slide member to slide against its resilient bias until the recess 52 is opposite the cross boreholes 49. The balls then are urged by the action of the inclined end 34 of the recess 33 on the hammer 30 into the recess 52 to release the latch mechanism.

Further operation of the second embodiment of latch mechanism is similar to that of the first described embodiment.

Claims

1. A hydraulic impact tool comprising a housing assembly provided with a handle, a trigger mechanism including a pressurised fluid flow control valve having two operational modes, a hammer slidable to and fro within the housing assembly, a spring unit including a gas spring and an element movable in a spring compressing direction against the action of the spring and movable in a released direction under the action of the compressed spring, a piston component slidably movable to and fro within the housing assembly under the action of pressure fluid fed from the control valve in its two operational modes, respectively, and a releasable latch mechanism which in a latched mode is adapted to fixedly connect the hammer and the piston component when, in use, the trigger mechanism is triggered and the control valve is activated into the first of its two operational modes to feed pressure fluid to urge the piston component in the spring compressing direction against the action of the gas spring and which when the piston component has reached a preselected position in the spring compressing direction, is activated into an unlatched mode to release the hammer to move with the element in the spring released direction under the action of the compressed spring.

2. A tool as claimed in claim 1, in which the piston component is retained in the preselected position until the trigger mechanism is released and the control valve is activated into the second of its two operational modes to feed pressurised fluid to urge the piston component in a direction opposite to the spring compressing direction.

3. A tool as claimed in claim 2, in which the control valve comprises a spool slidable along a bore between the two operational mode positions and the trigger mechanism comprises a trigger drivably engaging the spool.

4. A tool as claimed in claim 1, 2 or 3, in which the releasable latch mechanism comprises a slide member slidably mounted on the piston component for limited movement with respect to the piston component.

5. A tool as claimed in claim 4, in which the slide member is connected to the piston component via a resilient bias.

6. A tool as claimed in claim 5, in which the releasable latch means comprises an abutment engageable with a formation when the piston component is in the preselected position.

7. A tool as claimed in claim 6, in which when the abutment engages the formation, the slide member is slid relative to the piston component against the action of the resilient bias.

8. A tool as claimed in claim 7, in which the releasable latch mechanism comprises at least one ball which in the latched mode is engageable in a recess provided in the hammer to fixedly connect the hammer to the piston component and which in the latch released mode is disengageable from the recess to release the hammer.

9. A tool as claimed in claim 8, in which in the latched mode the slide member retains the ball in the recess.

10. A tool as claimed in claim 9, in which in the latch released mode the slide member is slid against the resilient bias to allow the ball to disengage the recess.

11. A tool as claimed in claim 10, in which the slide member comprises a recess for engagement by the ball in the latch released mode.

12. A tool as claimed in claim 11, in wich the recess provided in the hammer defines an outwardly directed taper tending to urge the ball towards the recess provided by the slide member.

13. A tool as claimed in any one preceding claims, in which the released hammer impacts on an anvil.

14. A tool as claimed in claim 13, in which cushion means are provided between the anvil and the housing assembly.

15. A tool as claimed in claim 13 or 14, in which the anvil engages a chisel slidably retained by the housing assembly.

16. A hydraulic impact tool substantially as described herein and substantially as shown in the accompanying drawings.

New claims or amendments to claims filed on 28th May 1985.

Superseded claims 1.

New or amended claims:

1. A hydraulic impact tool comprising a housing assembly provided with a handle, a trigger mechanism including a pressurised fluid flow control valve having two operational modes, a hammer slidable to and fro within the housing assembly, a spring unit including a gas spring and a piston element abutting the hammer and movable in a spring compressing direction against the action of the spring and movable in a released direction under the action of the compressed spring, a piston component slidably movable to and fro within the housing assembly under the action of pressure fluid fed from the control valve in its two operational modes, respectively, and a releasable latch mechanism which in a latched mode is adapted to fixedly connect the hammer and the piston component when, in use, the trigger mechanism is triggered and the control valve is activated into the first of its two operational modes to feed pressure fluid to urge the piston component in the spring compressing direction against the action of the gas spring and which when the piston component has reached a preselected position in the spring compressing direction, is activated into an unlatched mode to release the hammer to move with the element in the spring released direction under the action of the compressed spring.