GB1585117A - Percussive tools particularly casing constructions thereof - Google Patents

Description

(54) PERCUSSIVE TOOLS, PARTICULARLY CASINO CONSTRUCTIONS THEREOF (71) We, GULLICK DOBSON LIMI TED, a British Company of Ince, Wigan, Lancashire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The invention relates to percussive tools and has particular, but not exclusive, reference to impact-type mineral winning machine heads.

Our Patent Specification No. 1,356,022 discloses a mining head or other impact tool, with control valve gear and in which an impact chisel or other tool bit is driven on its impact stroke by a compressible fluid that is compressed successively by a pressure-fluid, preferably hydraulically, driven piston serving as, or driving, the chisel hammer.

According to this invention there is provided a percussive tool of the type utilising a hammer piston reciprocable within a cylinder to strike a tool-bit drive head, comprising a hammer piston housing body of modular construction having three axially successive body parts fixedly secured one to another to define said cylinder, and within and extending through the intermediate one of those body parts into both of the other body parts sleeve means for positively slidably guiding the hammer piston. This type of construction facilitates maintenance and allows versatility of interfitment of component parts.

Our co-filed applications Nos. 9704176 (Serial No. 1580025) and 23538/76 (Serial No. 1585112) concern selective mining systems requiring a high degree of manipulability of the mining head, which bring with them the desirability of a compact structure for the mining head itself.

To this end, in embodiments of the invention the intermediate body part is adapted via the sleeve means to guidingly mount a hammer drive piston, serves to communicate driving pressure fluid thereto, and affords at opposite faces thereof mounting facilities for relatively forward and rearward drive piston cylinder defining body parts.

Preferred embodiments relate to a percussive tool comprising a rearward body part including a chamber for a compressible pressure fluid to be compressed on rearward movement of the drive piston and to drive the hammer piston by expansion thereof. A forward body part may serve in guiding a striker part of the hammer piston.

The intermediate body part may include or provide a mount for main pressure fluid valve means for controlling rearward movement of the hammer drive piston and initiation of forward movement thereof.

Such a main pressure fluid valve means may conveniently have access porting for a pilot control valve and / or access porting for accumulator means. Preferably, said access porting allows interchanging of said pilot valve and said accumulator means, say being on opposite faces of a body of the main pressure fluid valve means.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view partly cut away of a percussive mineral winning head; Figure 2 is a rear view of the head of Figure 1, also partly cut away; and Figure 3 is a front view of the head of Figure 1.

In the drawings a mineral winning head is shown as comprising an intermediate body portion 10 incorporating a main control valve 11 and having a bore 12 fitted with a locating and sealing sleeve 13 for a hammer drive piston 14. An annular clearance 15 between the sleeve and the bore 12 communicates via a relatively eccentric step 16 (see Figure 2) with a pressure fluid inlet passage 17 from the main valve 11, the sleeve having circumferentially spaced apertures 18 for feeding the pressurised fluid to the piston 14.

The sleeve 13 extends from both sides of the intermediate body portion 10 and engages stepped bores in a rear body part 20 and a front body part 21 with a sealing relationship. The rear body part 20 cooperates with rear face 22 of the drive piston 14 to define a cavity 23 for a compressible pressure-fluid with the drive piston 14, in operation, being driven by hydraulic fluid from the main valve into the cavity 23 to compress the fluid therein until a required pressure is reached when the main valve 11 under the influence of the pilot valve 32 removes the hydraulic pressure-fluid as the drive piston 14 is driven in the opposite direction by expansion of the compressible fluid in the chamber 23.The front body part 21 slidably guides a forward portion of the drive piston 14 that is of relatively reduced diameter and is recessed 25 at its end to accommodate an impact tool such as a chisel 26 running in a sleeve 27. The recess 27 has at its base a central crown 28 acting as a striker for the chisel 26.

The rear, intermediate and front body portions are shown as being bolted together with mating and sealed stepped edge parts about their mating central bores.

The main control valve 11 for pressurised hydraulic fluid is indicated as being integral with the intermediate body part 10, but need not be. Internally, the intermediate body portion of the control valve will have transverse bores for flow and return of the hydraulic fluid as indicated generally at 30, hydraulic fluid passages 17 to the drive piston cylinder and a displaceable valve element for allowing communication either for such flow lines or for such return lines. This action of the main control valve is produced by a pilot valve 32 in a valve body 33 shown secured to the forward face of the intermediate body portion or control valve, and affording communication between the transverse bores 30 and hydraulic fluid ports 34 integral with the pilot valve body 33.A pair of accumulators, one for each of the transverse bores 30 are shown in an integral structure bolted to the relatively rearward face of the intermediate body portion or main control valve. These accumulators 36 are preferably of the general type shown in our co-pending Application No. 3446/76 (Serial No.

1581441) with a hollow piston 37 sliding in a closed and pressurised chamber 38, the accumulator body being provided with passageways 39, 39b communicating with a charging valve 39a and a safety vent 40.

Preferably, the pilot valve body 33 and the accumulator unit are interchangeable.

The main control Valve 11 is shown (Figure 2) as having a hollow valve spool 41 slidable relative to the bores 30 and 17 in a main valve bore 42. Although only one end is shown the valve spool 41 has, at each end, a hollow land 43 for engagement by an actuator rod 44 slidable in an end bore 45 of the main valve body and having an apertured crown 46 for bearing on the interior of the corresponding hollow land 43 with through communication thereto. The end bores 45 have hydraulic fluid-flow and return channels 47 and 48 controlled by the pilot valve.When, as for the end shown in section, pressurised hydraulic fluid is applied to the end of a valve actuator 44 it will move out of its bore 45 to shift the main control valve spool 41 so that the corresponding land 43 blocks the transverse bore 30 from communication with the relatively reduced centre portion of the valve spool that is in permanent communication with the channel 17. When that bore 45 is opened to the return hydraulic line, and pressurised fluid is applied to the other bore 45 the valve spool 41 will shift in the opposite direction so that its hollow land engages the seat 49 to give communication between the previously blocked bore 30 and the bore 17.

A diagrammatic representation of the valves and pressure-fluid circuitry associated with the mineral winning head for operating purposes is given in Figure 4.

In this Figure, it will be seen that individual high and low pressure pilot valve parts are shown separately at 32A and 32B with both connected by gas pipes 51 to the gas chamber 23 to respond, differentially, to high and low pressures of the gas so as to constitute high and low pressure gas operated switches of predetermined or preset characteristics say according to variable spring rating or settings. A hydraulic pilot start line 52 is shown connected to one port of the low pressure pilot valve 32B which has other ports connected to the cylinder of one of the pilot pistons of the main valve via line 53 and to a hydraulic drain pipe 56, respectively. Drain connections 60, 61 are also shown together with intercoupling bored paths 62.

Hydraulic flow and return mains are shown at 30A and 30B respectively, connected to corresponding ports of the main valve 11 and, via branch pipes, to ports of the high pressure pilot valve 32A which has a further port connected via a spring loaded shuttle valve device 54 to the cylinder of the other pilot piston of the main valve via line 55. The device 54 also has a port connected to a pilot reset line .57.

In describing operation, it is first assumed that the piston 14 is in its forward position and there is no pressure-fluid supplied to the head. On applying hydraulic fluid pressure, the main valve pilot pistons will set to positions corresponding to the states shown in Figure 4, if they are not already in such positions, due to pressurisation of the pilot reset line 57. Hydraulic pressure in the pilot start line 52 will act via the low pressure pilot valve part 32B and the relevant main valve pilot piston to cause the main valve to operate as described above to admit hydraulic fluid to retract the piston 14 and compress the gas in the chamber 23.

Rising gas pressure will act first to cancel the low pressure pilot valve part 32B and positionally lock the piston 14, and then to operate the other pilot valve part 32A to switch the main valve position to allow exhaustion of hydraulic fluid as the piston 14 is driven on its impact stroke by the compressed gas. Subsequent cycles will be self-starting for as long as hydraulic pressure is applied over lines 30A and 52.

If desired, a controlled pressure nonreturn air line branch can be connected to the front end of the piston 14 to impose a higher than atmospheric pressure and both an air pump action and dirt ingress inhibition.

WHAT WE CLAIM IS:- 1. A percussive tool of the type utilising a hammer piston reciprocable within a cylinder to strike a toolbit drive head, comprising a hammer piston housing body of modular construction having three axially successive body parts fixedly secured one to another to define said cylinder, and within and extending through the intermediate one of those body parts into both of the other body parts sleeve means for positively slidably guiding the hammer piston.

2. A tool according to claim 1, wherein the intermediate body part has passageway means for communicating driving pressure fluid to the hammer piston and affords at opposite faces thereof mounting facilities for the relatively forward and rearward of said three body parts.

3. A tool according to claim 2, wherein the rearward body part includes a chamber for a compressible pressure fluid to be compressed on rearward movement of the drive piston and to expand in driving the hammer piston forwards.

4. A tool according to claim 1, 2 or 3, wherein a or said forward body part serves for guiding a striker part of the hammer piston.

5. A tool according to any preceding claim, wherein the intermediate body part includes, or provides a mount for, main pressure fluid valve means for controlling rearward movement of the hammer drive piston and initiation of forward movement thereof.

6. A tool according to claim 5, comprising a said main pressure fluid valve means having access porting for a pilot control valve.

7. A tool according to claim 5 or claim 6, wherein a or the said main pressure fluid valve means includes access porting for accumulator means.

8. A tool according to claims 6 and 7, wherein said access porting allows interchanging of said pilot valve and said accumulator means.

9. A tool according to claim 8, wherein said access porting is on opposite faces of a body of the main pressure fluid valve means.

10. A pressure fluid operated percussive tool arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. In describing operation, it is first assumed that the piston 14 is in its forward position and there is no pressure-fluid supplied to the head. On applying hydraulic fluid pressure, the main valve pilot pistons will set to positions corresponding to the states shown in Figure 4, if they are not already in such positions, due to pressurisation of the pilot reset line 57. Hydraulic pressure in the pilot start line 52 will act via the low pressure pilot valve part 32B and the relevant main valve pilot piston to cause the main valve to operate as described above to admit hydraulic fluid to retract the piston 14 and compress the gas in the chamber 23. Rising gas pressure will act first to cancel the low pressure pilot valve part 32B and positionally lock the piston 14, and then to operate the other pilot valve part 32A to switch the main valve position to allow exhaustion of hydraulic fluid as the piston 14 is driven on its impact stroke by the compressed gas. Subsequent cycles will be self-starting for as long as hydraulic pressure is applied over lines 30A and 52. If desired, a controlled pressure nonreturn air line branch can be connected to the front end of the piston 14 to impose a higher than atmospheric pressure and both an air pump action and dirt ingress inhibition. WHAT WE CLAIM IS:-

1. A percussive tool of the type utilising a hammer piston reciprocable within a cylinder to strike a toolbit drive head, comprising a hammer piston housing body of modular construction having three axially successive body parts fixedly secured one to another to define said cylinder, and within and extending through the intermediate one of those body parts into both of the other body parts sleeve means for positively slidably guiding the hammer piston.

2. A tool according to claim 1, wherein the intermediate body part has passageway means for communicating driving pressure fluid to the hammer piston and affords at opposite faces thereof mounting facilities for the relatively forward and rearward of said three body parts.

3. A tool according to claim 2, wherein the rearward body part includes a chamber for a compressible pressure fluid to be compressed on rearward movement of the drive piston and to expand in driving the hammer piston forwards.

4. A tool according to claim 1, 2 or 3, wherein a or said forward body part serves for guiding a striker part of the hammer piston.

5. A tool according to any preceding claim, wherein the intermediate body part includes, or provides a mount for, main pressure fluid valve means for controlling rearward movement of the hammer drive piston and initiation of forward movement thereof.

6. A tool according to claim 5, comprising a said main pressure fluid valve means having access porting for a pilot control valve.

7. A tool according to claim 5 or claim 6, wherein a or the said main pressure fluid valve means includes access porting for accumulator means.

8. A tool according to claims 6 and 7, wherein said access porting allows interchanging of said pilot valve and said accumulator means.

9. A tool according to claim 8, wherein said access porting is on opposite faces of a body of the main pressure fluid valve means.

10. A pressure fluid operated percussive tool arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.