WO1997026116A1

WO1997026116A1 - Linerbolt removing tool

Info

Publication number: WO1997026116A1
Application number: PCT/AU1997/000012
Authority: WO
Inventors: Alan John Russell; Peter Rubie
Original assignee: Russell Mineral Equipment Pty. Ltd.
Priority date: 1996-01-12
Filing date: 1997-01-13
Publication date: 1997-07-24
Also published as: AUPN751396A0

Abstract

A fluid actuated percussion device (8) including: a housing (20); an impact delivery member (10) supported for reciprocal movement along a hammer axis (22) by the housing (20); a piston assembly (16) moveable along the hammer axis (22) between a striking position at which the piston assembly (16) strikes the impact delivery member (10) and a retracted position remote from the impact delivery member (10); firing means (14) for firing the piston assembly (16) from its retracted position to its striking position; actuating means (18) for actuating the firing means (14); a reactive body assembly (13) moveable in the direction of the hammer axis (22); and driving means (15) for moving the reactive body assembly (13) in the direction of the hammer axis (22) towards the impact delivery member (10) prior to operation of the firing means (14) whereby the reactive body assembly (13) may be energised by movement and subsequently decelerated to substantially absorb the reaction generated by firing the piston assembly (16). The reactive body (13) may be driven away from the impact delivery member (10) by reaction forces only but preferably the driving means (15) also drives the reactive body (13) away from the impact delivery member (10) and subsequent to operation of the firing means (14). Most preferably the driving means (15) accelerates the reactive body assembly (13) towards the impact delivery member (10) a freely moveable state.

Description

"LINERBOLT REMOVING TOOL" — BACKGROUND OF THE INVENTION — This invention relates to percussion devices and it has particular application to manually guided hammers. A typical application of the present invention is in the removal of bolts from mining equipment, such as mills which utilise sacrificial segmented liners bolted to the internal casing of the mills which are regularly replaced during routine maintenance. Typically such mills may range in size from three metre to eleven metre diameter and are lined with replaceable heavy steel segments attached internally to the mill casing by through bolting. In such applications the bolts become corroded and clearances between bolts and holes become compacted with ore fines. This results in difficult bolt removal at liner removal time. As a result the many bolts which are utilised to attach the liners to the mill shell are often required to be freed manually by the use of large sledge hammers. This is a difficult and time consuming task which may result in injury to the workers. While it is well known to use percussive devices such as jack hammers and hydraulically powered hammers to provide repetitive impacts for many applications, they are not able to be manually guided into alignment with wall mounted bolts and other components. The applications of jack hammers are limited as the hammering effect produced by an electrically or pneumatically operated jack hammer does not provide the impact as would be provided by a sledge hammer, for example.

In known hammering devices capable of delivering such impacts, a high reaction force is produced which necessitates that such devices be carried by articulating machines or be rigidly attached to some support structure. This reduces their versatility and makes them unsuitable for many applications. Furthermore, it is difficult to quickly and accurately aligned such devices with the shank of a bolt or the like for effecting ready removal thereof. — SUMMARY OF THE INVENTION — The present invention aims to alleviate at least one of the abovementioned disadvantages and to provide percussion hammering devices which will be reliable and efficient in operation.

With the foregoing in view, this invention in one aspect resides broadly in a fluid actuated percussion device including:- a housing; an impact delivery member supported for reciprocal movement along a hammer axis by the housing; a piston assembly moveable along the hammer axis between a striking position at which the piston assembly strikes the impact delivery member and a retracted position remote from the impact delivery member; firing means for firing the piston assembly from its retracted position to its striking position; actuating means for actuating the firing means; a reactive body assembly moveable in the direction of the hammer axis, and driving means for moving the reactive body assembly in the direction of the hammer axis towards the impact delivery member prior to operation of the firing means whereby the reactive body assembly may be energised by movement and subsequently decelerated to substantially absorb the reaction generated by firing the piston assembly.

The reactive body may be driven away from the impact delivery member by reaction forces only but preferably the driving means also drives the reactive body away from the impact delivery member and subsequent to operation of the firing means. Most preferably the driving means accelerates the reactive body assembly towards the impact delivery member to a freely moveable state.

It is also preferred that the firing means is disconnected from the piston assembly prior to the piston assembly reaching its striking position whereby the reactive forces are not felt as external shock loads. In the preferred form the piston assembly slides in a cylinder formed in the reactive body assembly and the firing means is an accumulator which provides pressurised gas to push the piston assembly through the cylinder towards the impact delivery member. Suitably the piston assembly includes a striking portion and an isolating portion, such as a cap, disposed intermediate the striking portion and the accumulator and being separable from the striking portion. In use the isolating portion is arranged to travel with the striking portion to a isolating position at which the isolating portion is held and isolates the striking portion from the accumulator whereby the striking portion may travel freely to the impact delivery member and preferably drawing a vacuum between it and the isolating portion in the process. For this purpose, the striking portion and the isolating portion are supported in the cylinder such that entry of gases or fluids therebetween is precluded. Preferably the piston assembly slides in a cylinder formed in the reactive body assembly which is accelerated to a free moving state prior to firing the piston assembly. It is also preferred that the driving means is hydraulically operated and further that the firing means is an accumulator which is charged for firing by hydraulically driving the piston assembly to its retracted position.

However the piston assembly and the reactive body could be disposed independent of one another with separate driving means which could be electrically, mechanically or pneumatically operated if desired. In addition the firing means could be powered by a solenoid or spring means if desired.

It is also preferred that the driving means accelerates the reactive body assembly to a freely moveable state with substantially constant acceleration prior to firing of the firing means. Furthermore for use as a bolt removing tool it is preferred that the mass of the a impact delivery member and the piston assembly are substantially equal and are less than the mass of the reactive body assembly. Suitable for use as a liner bolt removing tool these masses are in the range of 10 to 20kg for the piston assembly and about 100kg for the reactive body assembly and are accelerated to a terminal speeds in the range of 0.4 m/sec to 0.8 m/sec for the reactive body assembly and 8 m/sec to 12 m/sec for the piston assembly so as to deliver a blow which is greater than can be delivered by a sledge hammer.

While the fluid actuated percussion device may be of any desired size, for larger sizes it is preferred that it be associated with suspension means which permits the device to be easily manipulated by a single worker for alignment about both vertical and horizontal axes. In a preferred form the device is supported on an overhead rail assembly whereby its suspended location may be readily varied as well as its vertical location. — BRIEF DESCRIPTION OF THE DRAWINGS —

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a typical embodiment of the invention and wherein:- Fig. 1 illustrates a typical application of the present invention;

Fig. 2 is a plan view of the percussion tool;

Fig. 3 is a cut-away side view of the tool illustrated in Fig. 1. Figs. 4A and 4B Illustrate the sequence cylinder utilised in the tool of Fig. 1, in retracted and extended attitudes respectively;

Fig. 5 is a hydraulic schematic for the tool illustrated in Fig. 1; Fig. 6 is a cut-away perspective view of a further tool of the present invention, illustrated without the main housing;

Fig. 7 is a hydraulic schematic for the tool illustrated in Fig. 6, and Fig. 8a to 81 illustrate the operation of the embodiment illustrated in Fig. 6.

— DESCRIPTION OF THE PREFERRED EMBODIMENT — The liner bolt removing tool 8 illustrated in Fig. 1 is suspended by a length adjustable sling 9 supported by a track mounted overhead carriage above the access platform adjacent a cylindrical mill casing 11. As illustrated it is supported about a yoke 12 at or adjacent its centre of gravity whereby the bolt removing tool 8 may be readily pivoted about vertical and horizontal axes to align the moll 10 with the bolt to be removed. The bolt removing tool 8 is powered from a hydraulic pump assembly 28 connected to the tool through flexible pressure and return lines 29.

As illustrated in Figs. 2 to 4 the moil 10 of the bolt removing tool 8 is supported for limited reciprocal oscillation in the moil nose block 19 attached to the main housing 20 in which the hammer/piston assembly 21 is supported for reciprocal motion on guide tracks 17 along the moil axis 22. A handle 23 and adjacent actuating button 26 are provided at the opposite end of the housing 20. The hammer/piston assembly 21 comprises a heavy hammer body 13 which slides along guides 17 and is controlled by a sequence cylinder 15 which is mounted to the body 13 with its rod 51 connected fixedly to the moil nose block 19 and disposed parallel to a the moil axis 22. Initially the sequence cylinder 15 is disposed in its extended position shown in Fig 4B.

The hammer body 13 is formed with a cylinder 27 about the moil axis in which a piston 16 is sealably retained whereby it may be hydraulically driven to a retracted position adjacent the accumulator 14 supported at the rear end of the housing 20. A control module, shown in the schematic at 18, selectively supplies oil to the piston 16 and the sequence cylinder 15 to operate the tooll 8. The accumulator 14 consists of a nitrogen filled cylinder separated from the hydraulic oil by a flexible rubber bladder. When the piston 16 is released, that is fired, the nitrogen expands forcing the hydraulic oil out of the accumulator to accelerating the piston 16.

In use, hydraulic oil flows from the pump 28 via pressure reducing valve 30 to the piston which is retracted against the accumulator 14 which is thus charged. This action suitably increases the pressure within the accumulator 14 from about 600psi to 800psi. Once the accumulator 14 is charged the sequence valve 32 opens and oil flows to the sequence cylinder 15 which holds the hammer body in the retracted position. A proximity sensor 39 is activated and its switch is closed.

When the power pack 28 is switched on but before operation of the hammer body 13 is initiated by the operator the hammer/piston assembly 21 is configured as shown in Figs. 2 and 3. When the start button 26 is depressed a solenoid on valve 33 shifts the valve spool and oil flow is reversed to the sequence cylinder which accelerates the hammer body 13 forwar . The sequence cylinder consists of a piston/rod 51 supported within a sleeve 52 with a series of orifices 53 opening to one end thereof. The sleeve 52 is retained by a cylinder barrel 54 and end caps 55. In the extended position the piston portion 50 covers all but one of the orifices 53. When hydraulic oil flows to retract the cylinder the piston portion 50 begins to move through the sleeve 52 and sequentially uncovers the remaining orifices 53 thus providing the hammer body 13 with a motion that is approximately constant acceleration towards the moil end of the housing 20. This motion is felt by the operator as a constant reaction force which can be easily resisted.

Oil also flows to the bottom end of the piston 16 via check valve 34 and orifice 35 which communicates with the annular groove 38 about the cylinder 27. This causes the piston 16 to retract, further charging the accumulator 14. The logic element 36 remains closed shutting off the by-pass passage 45 across the piston 16.

After the sequence cylinder 15 has accelerated the hammer body 13 towards the moil end block 19, the piston 51 exits the sleeve 52, allowing the hammer body to move freely. As the piston 51 exits the sleeve 52 the cam 41 for valve 33 strikes the abutment 42 shifting the spool and reversing the flow to the sequence cylinder 15. However as the piston 51 is outside the sleeve 52 this does not immediately affect the motion of the hammer body 13. The plunger 40 on valve 37 of logic element 36 then strikes the abutment 43 which vents the logic element 36 allowing it to open. This allows oil to flow from one side of the piston 16 to the other through the by-pass passage 45 and the accumulator discharges accelerating the piston 16. The by¬ pass passage 45 is a large bore passage so as to provide minimum restriction to acceleration of the piston 16.

Before the piston 16 strikes the moil 10 a spring loaded end cap 24 strikes against the collar 25 sealing the passage to the cylinder 27 and thus halting the flow from the accumulator. This ensures that there is no external hydraulic pressure acting against the piston 16 when it strikes the moil 10 as this would result in the hammer body 13 being accelerated unduly. The piston 16 continues its travel along the moil axis 22 drawing a vacuum in the void between itself and the cap 24. The piston 16 then strikes the moil 10 which in turn strikes the object it is pressed against.

As the piston portion 50, and thus the hammer body 13, is moving freely in the sleeve 52 at the instant of firing the piston the reaction generated by the firing is not, transmitted to the operator. This reaction, caused by the acceleration of the piston 16, decelerates and reverses the direction of travel of the hammer body 13. This action causes the sequence cylinder piston portion 53 to re-enter the sleeve 52 where its motion is again controlled by the orifices 53 in sleeve 52 which now uniformly decelerate the hammer body. Again this is felt by the operator as a constant reaction force. The action of the vacuum and the spring on the cap 24 plus recoil from striking the moil returns the piston 16 to its extended rest position. The plunger 40 on valve 37 when not in contact with stop 13 closes under the action of a spring. Logic element 36 then closes, its closing speed controlled by an internal orifice.

If the start button 26 is still depressed the sequence will be repeated when the hammer body 13 triggers the proximity sensor 39. In this embodiment the masses of the moil 10 and piston 16 are each about 12 kg and the mass of the hammer body 13 is 90 kg.

The pump assembly 28 supplies oil at 2400psi with the result that continuous blows at the rate of about 80 per minute may be delivered by the moil at 600 Joules per blow. This compares with a maximum of about 450 or 150 Joules which may be delivered vertically and horizontally, respectively by a sledge hammer. The tool 8 may be readily aligned to deliver blows at any angle from vertically down to just below horizontal. As the tool 8 has a low reaction can be operated continuously without undue fatigue on the operator. The tool 8 also requires minimal supporting structure and plant interface.

The tool 60 illustrated in Figs. 6 without the main housing which is similar to that of the Fig. 1 embodiment differs from that embodiment in that it has been simplified. In this further embodiment of the invention, the nitrogen in the accumulator 61 acts directly onto the piston 62 such that there is no requirement to charge and relieve the hydraulic pressure in the accumulator 61. As a result, items 30, 31 and 32 of the previous embodiment are not required. Thus a simplified hydraulic circuit may be utilised.

In order to keep the hammer assembly 63 as light and simple as possible a remotely mounted single solenoid valve is utilised to fulfil the functions provided by the valve 33 and the firing plunger 40. The simplified hydraulic circuit is shown in Fig 7. The firing of the piston 62 is achieved by one small and one large logic element. The small element 65 controls the pilot on the large element 66. This allows rapid opening of the large element for more efficient firing of the piston 62.

Upon start up, the solenoid valve 80 is de-energised and pressure is applied to both the port 67 of the hammer assembly 63 and the port 68 of the sequencing cylinder 64. The solenoid valve 80 is shown energised in Fig. 7. The sequencing cylinder 64 extends retracting the hammer assembly while the piston 62 remains stationary, held in position by the check valve 70. The logic element 71 is shut because it requires a pressure drop across it to open. The solenoid valve 80 is activated by two proximity sensors 72 and 73. The sensor 72 is located so that it is triggered when the hammer assembly 63 is in its retracted position, as at start up, and the other sensor 73 is activated as the hammer assembly 63 moves forward into the firing position.

The rear proximity sensor 72 is in series with the start button and the solenoid valve 80 will not be energised until both rear proximity sensor and the start button are activated. When activated pressure is supplied to both the port 78 and the port 79 of sequence cylinder. Ports 67 and 68 are open to tank. The piston 62 retracts charging the accumulator 61 and the sequencing cylinder 64 retracts accelerating the hammer body forward. The logic elements are held shut by pressure at pilot line 81. When the hammer reaches the forward proximity sensor 72/73 the solenoid valve is de-energised and pressure is again applied to ports 67 and 68. Ports 78, 79 and 81 are open to tank. This causes the logic elements to open and the hammer to fire. As the piston accelerates forward the hammer body is decelerated at the same time the sequence cylinder reverses and the body returns to its start position. In order to facilitate reversing of the sequence cylinder after firing the sequence cylinder rod 85 has a rubber cushion on its end to smooth out any slight discrepancies between the piston firing and the sequence cylinder changing direction. Furthermore the sleeve is fluted longitudinally at the free floating position so as to maintain engagement between the sleeve and the piston portion.

The piston cap 74 is formed as a nylon cup that encloses the end of the piston 62. The cup 74 is fitted with an internal seal between itself and the piston. When the end of the cup 74 strikes the seal ring 87 a vacuum is drawn between the cup and the piston and the piston continues forward without further acceleration by the accumulator.

In addition the hammer assembly is supported by linear bearings mounted on a pair of spaced parallel guide rails 88 disposed at opposite sides of the sequence cylinder rod 85. The rails 88 are cantilevered out from the moil nose block 89.

In the drawing series of Figs 8a to 81, the hydraulic components are shown with all passages open in Fig 8a. When power is initially turned on as illustrated in Fig. 8b, the proximity sensor 72 and start trigger are in series. The solenoid valve 80 is energised when proximity sensor 72 is activated and the start trigger 26 is depressed. In this state the proximity sensor 73 is not sensing and the logic element 65 is open.

Oil is trapped in front of the piston 62 by the check valve 70. The piston has equal area both sides - therefore the pressure is balanced across the piston and the piston is stationary.

After the trigger 26 has been depressed, as illustrated in Fig. 8c pressure in line A causes logic element 65 to close and hold logic element 66 closed. The piston 62 retracts further compressing the gas in the accumulator 14. Pressure is applied to the staggered orifices in the sequence cylinder 64 and as it moves it uncovers more orifices and accelerates in near linear manner.

Just before firing, as illustrated in Fig. 8d, the proximity sensor 73 is about to be activated. The hammer assembly 63 has accelerated to the required speed and the piston is fully retracted. At firing, as illustrated in Fig. 8e, when proximity sensor 73 is activated it de- energises the solenoid valve 80 and applies pressure to connection B. This opens logic element 66. Oil is still trapped in front of the piston 62 by the check valve 70.

Momentarily this pressure increases above the pressure at 'B' due to the force on the piston of the charged accumulator.

At firing as illustrated in Fig. 8f the logic element 65 is no longer holding logic element 66 closed, and the high pressure forward of the piston causes logic element 66 to rapidly open. Pressure across the piston 62 is now balanced. The force of the gas in the accumulator causes the piston to accelerate. Oil in front of the piston flows through logic element 66 to the rear of the piston. The force of the gas accelerating the piston also decelerates the hammer assembly 63 and reverses its direction. This is aided by the sequence cylinder 64.

At end of firing, as illustrated in Fig. 8g, the piston cap 74 strikes the tool body 59 and seals the piston from the accumulator and prevents further acceleration of the piston by the gas. The piston 62 may strike the moil 58 at this time, as illustrated in Fig. 8h, or if as illustrated in Fig. 8i, the moil 58 is further away from the piston, the piston will continue its movement towards the miol 58, drawing a vacuum in sealed space 76 between itself and the cap 74.

After firing, and the piston has come to rest, pressure across the piston balances and logic element 66 closes. As the cylinder rod returns it covers orifices which causes it to uniformly decelerate the body. The hammer assembly 63 continues to its rest position as illustrated in Fig. 8b.

It is to be understood that the above has been given by way of illustrative embodiment of the invention, all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as is defined in the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A fluid actuated percussion hammering device including:- a housing; a impact delivery member supported for reciprocal movement along a hammer axis by said housing; an piston assembly moveable along the hammer axis between a striking position at which the piston assembly strikes the impact delivery member and a retracted position remote from the impact delivery member; firing means for firing the piston assembly from its retracted position to its striking position; actuating means for actuating the firing means; a reactive body assembly moveable in the direction of the hammer axis, and driving means for moving the reactive body assembly in the direction of the hammer axis towards said impact delivery member prior to operation of the firing means whereby the reactive body assembly may be energised by movement and subsequently decelerated to substantially absorb the reaction generated by firing the piston.

2. A fluid actuated percussion hammering device as claimed in claim 1, wherein said driving means also drives said reactive body away from said impact delivery member and subsequent to operation of the firing means.

3. A fluid actuated percussion hammering device as claimed in claim 1 or claim 2, wherein said driving means accelerates said reactive body assembly towards said impact delivery member to a freely moveable state.

4. A fluid actuated percussion hammering device as claimed in any one of the preceding claims, wherein said firing means is disconnected from said piston assembly prior to the piston assembly reaching its striking position.

5. A fluid actuated percussion hammering device as claimed in claim 4, wherein said piston assembly slides in a cylinder formed in said reactive body assembly and said firing means is an accumulator which provides pressurised gas to push said piston assembly through said cylinder towards said impact delivery member.

6. A fluid actuated percussion hammering device as claimed in claim 5, wherein said piston assembly includes a striking portion and an isolating portion disposed intermediate said striking portion and said accumulator, said isolating portion being separable from striking portion and being arranged to travel with said striking portion to a isolating position at which said isolating portion is held and isolates said striking portion from said accumulator.

7. A fluid actuated percussion hammering device as claimed in claim 6, wherein said striking portion and said isolating portion are supported in said cylinder such that entry of gases or fluids therebetween is precluded.

8. A fluid actuated percussion hammering device as claimed in any one of claims 5 to 7, wherein said accumulator is charged for firing by hydraulically driving said piston assembly to its retracted position.

9. A fluid actuated percussion hammering device as claimed in claim 8, wherein said accumulator is fired by quick release of the hydraulic fluid utilised to drive said piston assembly to its retracted position.

10. A fluid actuated percussion hammering device as claimed in claim 9, wherein said quick release is provided by controlling the outflow of the hydraulic fluid utilised to drive said piston assembly to its retracted position through cascade connected logic elements.

11. A fluid actuated percussion hammering device as claimed in any one of the preceding claims, wherein the mass of said impact delivery member and said piston assembly are substantially equal and are less than the mass of said reactive body assembly.

12. A fluid actuated percussion hammering device as claimed in any one of the preceding claims, wherein said driving means is a hydraulic ram assembly having a plurality of fluid inlet ports which are sequentially opened to the working chamber of the ram assembly as the length of the working chamber extends.

13. A fluid actuated percussion hammering device as claimed in claim 12, wherein said hydraulic ram assembly is a double acting ram assembly having a working chamber which converts to a drain chamber upon reverse operation of the hydraulic ram assembly and wherein said plurality of fluid inlet ports become drain ports which are sequentially closed during contraction of the drain chamber.

14. A fluid actuated percussion hammering device as claimed in any one of the preceding claims, wherein said reactive body is supported on linear bearings on a pair of spaced parallel bars which extend parallel to the hammer axis.