FLUID ACTUATED TOOL

Abstract: A fluid actuated tool in the form of a hydraulic hammer (20) comprises a body (22), a cylinder (26) and a chuck body (28). A piston (34) mounted within the cylinder (26) reciprocates and impacts on a chisel (36). Movement of the piston (34) results from the supply of hydraulic fluid, controlled by an apertured distributor valve sleeve (38) with a number of cylinder ports (40) communicating with a series of axial fluid carrying bores (42). Movement of the piston (34) and the sleeve (38) bring ports (40) and bores (42) into and out of alignment, so regulating movement of the piston (34).

Description: FLUID ACTUATED TOOL This invention relates to a fluid actuated tool, and in particular but not exclusively to a hydraulic percussive tool, such as a hammer. The invention also relates to a method of controlling the operation of a fluid actuated tool. Hydraulic percussive tools, such as hammers, are used in many applications, primarily in breaking up hard surfaces or structures . Larger hammers may be mounted on the arm of an excavator or on the backhoe of a tractor. A hammer comprises a body containing a reciprocating piston which strikes an anvil or tool piece, hereinafter referred to as the chisel. Conventionally, the flow of pressurised hydraulic fluid to the hammer is controlled by valves contained within a valve body mounted exter ally cf the hammer body, facilitating access to the valves for maintenance and repair. However, the valve body is vulnerable to damage and increases the mass and volume occupied by the hammer. It is among the objectives of embodiments of the present invention to provide a hydraulic hammer which is compact and includes a straightforward and reliable hydraulic fluid valving arrangement. According to the present invention there is provided a fluid actuated tool comprising: a body defining a cylinder; 2 a piston reciprocally moveable in the cylinder; a fluid inlet for providing fluid communication between a fluid source and the cylinder; a fluid outlet for providing communication between the cylinder and a fluid exhaust; and a sleeve valve around at least a portion of the piston in the cylinder, the sleeve valve being axially movable to control the flow of fluid between the fluid inlet and the fluid outlet and the cylinder. The invention also relates to a method of controlling the actuation of a fluid actuated tool utilising a sleeve valve . As the valve is located within the cylinder there is no requirement to provide a separate valve housing or the like on the tool body, and the valve is protected within the tool body. The tool is therefore compact and robust. The tool may be a hydraulic hammer, in which the piston impacts on a chisel bit . Preferably also, the fluid outlet defines flow restrictions for controlling the flow of fluid from the cylinder, to control the rate of movement of the piston in the cylinder on the exhaust or return stroke. Most preferably, the flow restrictions are orifices, and may be adjustable to vary the rate of fluid flow therethrough. Preferably, the valve sleeve defines fluid ports and fluid ports are also provided in the cylinder wall for communication with one or both of the fluid inlet and fluid outlet; when the ports are in alignment fluid may flow 3 through the ports into or from the cylinder. Preferably also, fluid communicating bores extend through the body for providing fluid communication between the cylinder ports and the fluid inlet and fluid outlet. Most preferably, the bores also provide fluid communication between axially spaced cylinder ports. Preferably also, the piston starts to move on its power stroke prior to the valve moving on its power stroke, and the piston and valve move together on the exhaust stroke. Preferably also, the valve and piston are locatable in initial power positions in which a sleeve inlet port is aligned with a cylinder inlet port so that high pressure fluid may flow from a fluid source into the cylinder, to act on the piston. Most preferably, the valve and piston are moveable from the initial power positions to exhaust positions in which the cylinder inlet port is closed and a cylinder exhaust port is open. Most preferably, in the exhaust position the valve closes the cylinder inlet port and exposes a cylinder exhaust port so that fluid may exhaust from the cylinder as the piston returns to the initial position. The valve may be moveable from the initial power position by application of fluid pressure to a portion of the sleeve. Most preferably, the sleeve defines an annular piston face positioned in an annular portion of the cylinder and application of fluid pressure to the face causes the sleeve to move in the cylinder. Preferably, 4 between the initial power position and the exhaust position, the sleeve and piston occupy a fluid transfer position in which a sleeve transfer port is aligned with a cylinder transfer port, the aligned transfer ports permitting high pressure fluid communication with the annular portion of the cylinder where the fluid acts on the annular piston face defined by the sleeve, to induce movement of the sleeve relative to the cylinder and piston. Most preferably, from the initial power position, the piston initially moves on its power stroke relative to the valve and subsequently uncovers the transfer ports to allow h ^ gh pressure fluid communication with the annular portion of the cylinder to induce movement of the valve. Preferably also, the valve is movable from its initial position to close the cylinder inlet port and limit or prevent further flow of high pressure fluid into the cylinder. Preferably also, the piston defines a return piston face, preferably annular in form, which is positioned in a high pressure chamber and normally exposed to high pressure fluid, tending to return the piston and valve to the initial position. However, if the piston moves downwards in the cylinder beyond a predetermined relative position an opposite face moves into the chamber and is also exposed to said high pressure fluid, such that the piston remains stationary in the cylinder. This feature ensures that, when there is no load or resistance to movement of the piston, the piston will not oscillate in the cylinder. The 5 piston may be "reset" simply by applying a load to the piston to move the opposite face from the chamber. According to another aspect of the present invention there is provided a fluid actuated tool comprising: a body defining a cylinder; a piston reciprocally moveable in the cylinder along power and exhaust strokes; a fluid inlet for providing fluid communication between a fluid source and the cylinder; a fluid outlet for providing communication between the cylinder and a fluid exhaust; and a valve to control the flow of fluid between the fluid inlet and outlet and the cylinder, and the fluid outlet defining flow restrictions for controlling the flow of fluid from the cylinder and thus control the rate of movement of the piston in the cylinder on the exhaust stroke. The invention also relates to a method of controlling the actuation of a fluid actuated tool utilising an exhaust orifice. These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a fluid actuated tool in the form of a hydraulic hammer, in accordance with a preferred embodiment of the present invention; Figure 2 is an enlarged sectional view of a distributor valve of the hammer of Figure 1; 6 Figure 3 is an enlarged sectional view of the cylinder body of the hammer of Figure 1; Figure 4 is a plan view of the cylinder body of Figure 3 ; and Figures 5 through 12 are sectional views of the cylinder body, distributor valve and piston during a power and exhaust strokes. Reference is first made to Figure 1 of the drawings, which illustrates a fluid actuated tool in the form of a hydraulic hammer 20 in accordance with a preferred embodiment of the present invention. The hammer 20 comprises a body 22, a cylinder 26 and a chuck body 28. Mounted on the cylinder 26 is a transfer plate 30 and an accumulator 32. Mounted within the cylinder 26 is a piston 34 which, while the hammer 20 is in use, moves in a reciprocal manner within the cylinder 26 and impacts on a chisel 36 mounted in the chuck body 28. The movement of the piston 34 within the cylinder 26 is achieved by the controlled supply of high pressure hydraulic fluid from a suitable high pressure source (not shown) , typically a hydraulic pump on a tractor or tracked vehicle which supports the hammer 20. The flow of hydraulic fluid into and from the cylinder 26 is controlled by the interaction of an apertured distributor valve sleeve 38 (Figure 2) located in the upper part of the cylinder 26 with a number of cylinder ports 40 communicating with a series of axial fluid carrying bores 42, as may be seen more clearly in Figures 3 and 4 of the drawings. The 7 interaction between the valve 38 and the cylinder 26 will now be described in detail, with reference to Figures 5 through 12 of the drawings, which illustrate the relative positions of the piston 34 and the distributor valve 38 during a power stroke and a return exhaust stroke of the piston 34. Reference is first made to Figure 5 of the drawings, which illustrates the starting point in the operating cycle when the piston 34 and the distributor valve 38 are both at the top of their strokes. High pressure hydraulic fluid is being supplied from an appropriate source through a fluid inlet 44, the high pressure fluid charging the accumulator 32 and also pressurising six of the axial fluid bores 46, all of which communicate with the accumulator 32, and five of which extend axially through the cylinder 36 below the fluid inlet 44. The bores 46 are intersected by slots 48, 50, 52 and at various points along the length of the cylinder and which slots extend to intersect the cylinder and define fluid inlet ports. The first set of slots 48 are directly adjacent the fluid inlet 44. At the starting point of the operating cycle, as illustrated in Figure 5, the slots 48 are aligned with slots 54 in the distributor valve 38. The intermediate set of slots 50 communicate with an annular groove 56 within the cylinder allowing fluid communication with the cylinder via holes 58 in the lower part of the distributor valve 38. The holes 58 allow high pressure fluid to fill part of an annular chamber 60 formed between the piston head 62 and an annular piston 8 face 64 formed on the piston 34, the upper end of the chamber 60 being closed by a solid section 66 of the distributor valve, and the lower end of the chamber 60 being sealed by a solid section 68 of the distributor valve which includes an inner collar 70 in contact with the piston 34. The lower set of slots 52 provide communication with a return chamber 72 defined by the cylinder wall below a further annular piston 74. Commencement of the power stroke is triggered by the leakage of high pressure fluid between the piston head 62 and the distributor 38 at point 76 in Figure 5. This causes a slight separation of the piston 34 and the distributor 38 allowing the high pressure fluid stored in the accumulator 32 and fluid that is supplied by the pump to enter the main cylinder chamber 78 at high velocity. As shown in Figure 6, the piston 34 is accelerated very rapidly downward due to the combined flow from the pump and the accumulator 32. Initially, the distributor 38 is held at the top of its stroke due to the differential pressure created by the areas of the distributor 38 exposed to the high pressure fluid. As illustrated in Figure 7, as the piston 34 travels downwards relative to the cylinder 36 and the distributor 38, the piston head 62 uncovers holes 80 in the distributor 38 which communicate with slots 82 in the cylinder 26 intersecting three of the axial bores 84. The bores 84 communicate with passages in the transfer plate which lead into the upper end of the cylinder, above the enlarged end 9 of the distributor valve 38. The bores 84 are also intersected by drain slots 88, the purpose of which will be described in due course. Thus, on the piston 34 reaching the position as illustrated in Figure 7, high pressure fluid may flow via the main piston chamber 78 into the bores 84 allowing high pressure fluid to reach the top of the distributor 38 and change the pressure forces acting on the distributor 38. This "unlocking" of the distributor 38 allows it to move downwards under the influence of the high pressure fluid, which is also acting continuously on the upper surface of the annular area formed by the collar 70. This initial downward movement of the distributor valve 38 is illustrated in Figure 8 of the drawings. As the distributor 38 continues to move downwards as illustrated in Figure 9 of the drawings, it first closes off the flow from the high pressure fluid inlet 44 as the distributor slots 54 are moved out of alignment with the cylinder slots 48. Continued downward movement of the distributor 38, as illustrated in Figure 10, then opens a fluid outlet 92 as the upper end of the distributor 38 uncovers three cylinder slots 94 which intersect three of the axial bores 96 which act as low pressure exhausts. A further set of slots 98 intersect the lower end of the bores 96, opening into an annular groove 100 in the cylinder wall, which provides communication with the lower part of the chamber 60. A further lower set of slots 101 is, at this stage, located opposite the piston 64. Uncovering the slots 94 causes the collapse of the high 10 pressure regime in the upper part of the main cylinder chamber 78. However, the distributor 38 and the piston 34 continue on their downward travel, the piston 34 due to its momentum and the distributor 38 due to the high pressure which continues to act on the upper surface of the collar 70. While the high pressure fluid inlet 44 remains closed by the distributor 38, the accumulator 32 is charged from the external fluid supply to provide extra capacity for the next power stroke. The piston distributor return is effected by the continual high pressure feed to the return chamber 72 acting on the annular piston 74, as illustrated in Figure 11 of the drawings. This supplies the returning force, in addition to any rebound after the impact with the chisel 36. A similar high pressure feed is maintained to the annular chamber 60, as illustrated in Figure 12 of the drawings, and the high pressure fluid acts as a fluid spring which serves to reseat the distributor 38 on top of the piston head 62 before the piston 34 has reached the top of its stroke, thus preparing the hammer for the next firing stroke. As the distributor 38 and piston 34 rise up to the firing point, the main low pressure drain, provided by the slots 94, is closed. The fluid remaining in the chamber between the piston 34 and the distributor 38 is then only able to discharge via orifices 102 in the transfer plate 30 11 and into the transfer bores 84 and then into the low pressure bores 96 via the slots 88, 101 and the annular piston groove 104 between the annular pistons 64, 74. This ensures that a low pressure regime exists in the transfer bores, ensuring correct seating of the distributor 38 prior to the next firing point . The orifices 102 in the transfer plate 30 effectively control the return speed of the piston 34 and the distributor 38 and also provide damping at the end of the stroke. To ensure that the piston 34 does not oscillate rapidly under "no-load" conditions, known as blank firing, the axial extent of the piston 74 is such that the upper face of the piston 74 will move into the return chamber 72 if the chisel 36 is not in contact with, for example, a hard surface which is being broken up. When the piston 74 moves into the chamber 72, the axial pressure forces acting on the piston 74 are balanced, such that there is no upward axial pressure force acting on the piston 34, and the piston 34 therefore remains stationary. To "re-set" the hammer 20, a load is applied to the chisel 36, pushing the piston 34 upwardly, and as soon as the piston 74 closes the top of the return chamber 72, the high pressure fluid acting in the return chamber 72 is no longer balanced and the piston 34 will be moved upwardly. From the above-described embodiment it will be clear to those of skill in the art that the provision of a distributor valve 38 in the form of a sleeve, mounted 12 within the cylinder and around the piston, provides a simple and effective means of controlling the flow of hydraulic fluid into the cylinder, and thus controlling actuation of the piston 34. It will also be clear to those of skill in the art that the above-described embodiment is merely exemplary of the present invention, and that various modifications and improvements may be made thereto, without departing from the scope of the invention.

Claims: 13 CLAIMS 1. A fluid actuated tool comprising: a body defining a cylinder; a piston reciprocally moveable in the cylinder; a fluid inlet for providing fluid communication between a fluid source and the cylinder; a fluid outlet for providing communication between the cylinder and a fluid exhaust; and a sleeve valve around at least a portion of the piston in the cylinder, the sleeve valve being axially movable to control the flow of fluid between the fluid inlet and the fluid outlet and the cylinder. 2. The tool of claim 1 wherein the tool is a hydraulic hammer, in which the piston impacts on a chisel bit. 3. The tool of claims 1 or 2 wherein said fluid outlet defines flow restrictions for controlling the flow of fluid from said cylinder, to control the rate of movement of said piston in said cylinder on the exhaust or return stroke. 4. The tool of claim 3 wherein said flow restrictions are orifices. 5. The tool of claims 3 or 4 wherein said flow restrictions are adjustable to vary the rate of fluid flow therethrough . 14 6. The tool of any preceding claim wherein the valve sleeve defines fluid ports and fluid ports are also provided in the cylinder wall for communication with one or both of the fluid inlet and fluid outlet. 7. The tool of claim 6 wherein fluid communicating bores extend through said body for providing fluid communication between the cylinder ports and the fluid inlet and fluid outlet . 8. The tool of claim 7 wherein said bores also provide fluid communication between axially spaced cylinder ports. 9. The tool of any preceding claim wherein said piston starts to move on its power stroke prior to said valve moving on its power stroke, and said piston and valve move together on the exhaust stroke. 10. The tool of any preceding claim wherein said valve and piston are locatable in initial power positions in which a sleeve inlet port is aligned with a cylinder inlet port so that high pressure fluid may flow from a fluid source into said cylinder, to act on said piston. 11. The tool of claim 10 '.-.'herein said valve and piston are moveable from said initial power positions to exhaust positions in which said cylinder inlet port is closed and a cylinder exhaust port is open. 15 12. The tool of claim 11 wherein in the exhaust position said valve closes said cylinder inlet port and exposes a cylinder exhaust port so that fluid may exhaust from said cylinder as said piston returns to the initial position. 13. The tool of any one of claims 10 to 12 wherein said valve is moveable from said initial power position by application of fluid pressure to a portion of the sleeve. 14. The tool of claim 13 wherein said sleeve defines an annular piston face positioned in an annular portion of the cylinder and application of fluid pressure to the face causes said sleeve to move in said cylinder. 15. The tool of claim 14 wherein between said initial power position and said exhaust position, said sleeve and piston occupy a fluid transfer position in which a sleeve transfer port is aligned with a cylinder transfer port, the aligned transfer ports permitting high pressure fluid communication with said annular portion of said cylinder where the fluid acts on the annular piston face defined by the sleeve, to induce movement of the sleeve relative to the cylinder and piston. 16. The tool of claim 15 wherein from said initial power position, said piston initially moves on its power stroke relative to the valve and subsequently uncovers said transfer ports to allow high pressure fluid communication 16 with said annular portion of said cylinder to induce movement of said valve. 17 The tool of claim 16 wherein said valve s moveable from its initial position to close said cylinder inlet port and limit or prevent further flow of high pressure fluid into said cylinder. 18. The tool of claim 17 wherein said piston defines a return piston face which is positioned m a high pressure chamber and normally exposed to high pressure fluid, tending to return said piston and valve to the initial position and wherein if said piston moves downwards in the cylinder beyond a predetermined relative position an opposite face moves into the chamber and is also exposed to said high pressure fluid, such that the piston remains stationary in the cylinder. 19. A fluid actuated tool comprising: a body defining a cylinder; a piston reciprocally moveable m the cylinder along power and exhaust strokes; a fluid inlet for providing fluid communication between a fluid source and the cylinder, a fluid outlet for providing communication between the cylinder and a fluid exhaust; and a valve to control the flow of fluid between the fluid inlet and outlet and the cylinder, and 17 the fluid outlet defining flow restrictions for controlling the flow of fluid from the cylinder and thus control the rate of movement of the piston in the cylinder on the exhaust stroke.

Inventors: NAISMITH GEORGE, NAISMITH, GEORGE
Applicants: CALDERVALE ENGINEERING SERVICE, NAISMITH GEORGE, CALDERVALE ENGINEERING SERVICES LIMITED, NAISMITH, GEORGE
Application year: 1999
Main classification: B25D9
IPC codes: B25D9