GB2113593A - Hydraulic tool - Google Patents

Abstract

The invention relates to a hydraulic tool for delivering a controlled high power blow for instance to a corroded or abraded nut to split the nut. The tool comprises an accumulator 5, a cylinder 2 in which is movable a piston 1, and a bit 26. A latching mechanism comprising, cylindrical member 11 is engaged with a sleeve 7, fixed to the piston, when the piston is adjacent the bit and a piston and cylinder device 17, 18 moves the cylindrical member 11 and thus the piston 1 away from the bit 26 against the pressure of the accumulator 5, at the same time supercharging the accumulator 5. At the end of its travel, the latching mechanism interacts with latch release means 43 to release the piston 1 which, under the influence of the supercharged pressure in the accumulator 5, moves violently towards the bit 26, striking it with a controlled and powerful blow. <IMAGE>

Description

SPECIFICATION Hydraulic tool This invention relates to a hydraulic tool particularly, but not exclusively, for use in recovery of equipment from mine workings.

In a coal mining operation, it costs about 3 million to equip a complete longwall face and to provide equipment in the roadways serving the face. Once the coal face has been worked out it is clearly desirable to recover as much equipment as possible for re-use on another face. Much mining equipment has to be transported into and around the mine workings in parts and is bolted together at its site of usage. In order to be able to recover this equipment, it is necessary to be able to undo the bolts. However, due to the arduous conditions in the mine workings and the movements of surrounding strata which frequently occur, it can be difficult, and in some cases impossible, to use a spanner, whether manually or power operated, to unscrew the nuts on the bolts.Even if a spanner can be located on the nut, the nut may be so rounded by abrasion, corrosion or bad fitting that it cannot be unscrewed.

In these cases it is common practice to try to remove the nut by use of a hacksaw, hammer and chisel or hydraulic pick. In the first two cases, and if the hacksaw is manually operated, a large amount of time and effort must be expended in removing the nut. If the hacksaw is hydraulically powered, it may not be possible to position it near enough the nut effectively to operate it. It is therefore generally preferred to use a hydraulic pick, especially to remove relatively inaccessible nuts.

However, the picks at present available are similar to those used in road repairs (usually known as hydraulic drills). These are operated on a multi blow principle. In general such a pick will be struck at a rate about 1000 times a minute by a piston reciprocated by a double acting hydraulic power supply. Each blow is not very powerful. The rate of striking causes a large degree of vibration and it is therefore very difficult to hold the pick in position on a nut for more than a few blows. Therefore, although the pick can be eventually effective in splitting nuts, it requires time, a degree of effort to control and can also cause damage to surrounding equipment. Another disadvantage of these picks is that they must be supplied at all times with high pressure hydraulic fluid.

It is an aim of the present invention to provide a hydraulic tool which at least in part overcomes the disadvantages of presently used hydraulic picks.

Accordingly the present invention provides a hydraulic tool comprising a bit slidably mounted for limited rectilinear movement, a piston for striking the bit to cause it to move in one direction, a fluid accumulator for supplying pressurised fluid for moving the piston towards the nut, and a latch mechanism for engagement with the piston, the latch mechanism being movable between a first position, in which it engages the piston when the piston is adjacent the bit, and a second position, in which a latch release means disengages the latch mechanism from the piston.

Preferably the bit is a chisel bit, although hammer head and pointed bits may also be used.

The latching mechanism may be moved between its two positions by any convenient means, and preferably the means comprises a piston and cylinder arrangement. In a preferred embodiment, the cylinder of the moving means comprises an annulus formed around the body of the tool.

Preferably, the latching mechanism comprises a system of abutments and ramps whose interaction causes a latching member to rotate from an engaged to a disengaged position or vice versa. Conveniently the ramps are locatd on each end of a cylindrical member rotatably and slidably mounted on the cylinder in which the striking piston moves.

Advantageously, the accumulator is connected to the hydraulic power supply through a non-return valve and the moving means may be operated by use of a manual pump.

In this case it will be possible to charge and seal the accumulator, transport the tool to a remote site and operate it by use of the manual means. This is an advantage of the tool of the present invention when compared with presently used tools which require a continuous hydraulic fluid supply.

Conveniently, the accumulator is a gas accumulator, preferably using nitrogen, pressurised to a preset gas pressure, for instance of about 1 300 p.s.i.

Preferably, the action of the tool is controlled by a trigger such that the striking piston remains adjacent the belt until the trigger is operated. In this way it is possible to position the bit carefully before the tool is operated. This enables greater control to be exercised than is possible with the presently used devices. This ensures that the tool is used efficiently.

In use hydraulic fluid is supplied to the accumulator, through the non-return valve, causing the piston to move to a position adjacent the bit. The nitrogen accumulator is pressurised to a preset gas pressure, usually in the region of 1300 p.s.i. Since the hydraulic fluid is usually supplied at a pressure from 1,500 to 2,000 p.s.i., energy is stored in the accumulator as the hydraulic fluid enters. The latch mechanism is moved to its first position wherein it engages with the piston. Once engaged with the piston, it is moved to its second position. As the latch mechanism is connected to the piston, the piston is moved by the latch mechanism away from the bit against the pressure of the hydraulic fluid, thus supercharging the accumulator.As soon as the latch mechanism reaches its second position, the latch release means operates and the piston is free to move under the action of the pressure field. It thus moves violently towards the bit and strikes it, causing it to move away from the piston. The power in the movement of the bit is large because of the mass and distance of travel of the piston and the energy stored in the accumulator by the action of the initial inlet of the hydraulic fluid and by the supercharing effect of the movement of the latch/release mechanism.

In a normal hydraulic pick, the piston which strikes the bit is returned to its original position by hydraulic pressure. Therefore, when the piston moves back towards the bit, it must displace hydraulic fluid, thus dissipating some of its power. Moreover, since hydraulic fluid is supplied to both sides of the piston, valving systems must be incorporated, and, since these operate relatively inefficiently, they will reduce the power available to the bit. The tool of the present invention eliminates both these disadvantages as there is no hydraulic fluid acting on the piston to move it away from the bit and there are no valve systems affecting the movement of the piston.

It is envisaged that the tool of the present invention will be of particular, but not exclusive use, in the recovery of equipment from a coal face. It may be used to split corroded or abraded nuts. However, the tool may be used in many other areas where it is necessary to provide a controlled high power impact on a tool bit. For instance, the tool could be used with a hammer head bit to dislodge dowels, pins, bushes, etc. which have become tightly fixed in place through corrosion, wear or deformation.

The present invention will now be described by way of example only with reference to the accompany drawings, in which: Figure 1 shows a sectional side view of a tool according to the invention.

Figure 2 shows a side view of a part of the tool; Figure 3 shows a sectional view along line A-A of Fig. 1; Figure 4 shows a sectional view along line B-B of Fig. 1; Figure 5 shows a sectional view along line C-C of Fig. 1; Figure 6 shows a sectional view along line D of Fig. 4; Figure 7 shows a sectional view along line E of Fig. 4; and Figure 8 shows diagrammatically the hydraulic circuitry included in the tool.

Referring now to the Figures, a tool according to the invention is based on an elongated cylindrical striking piston 1 slidably mounted in a cylinder 2. The striking piston has an enlarged head portion 3 into the end of which is pressed a striker 4. The cylinder 2 is operatively and continuously connected to a hydraulic pressure accumulator 5 by means of bores 6.

A sleeve 7, screwed onto the outside of the head portion 3, extends towards the accumulator 5 and has an inner diameter greater than that of the cylinder 2. The sleeve 7 has a cylindrical chamber 8 and three radially spaced internal abutments 9. The sleeve 7 is provided with a key 7B which slides in keyway 7C in the cylinder 2, preventing rotation of the sleeve 7. (see especially Figs. 3 and 5).

A second sleeve 10 is fixed on the outside of the cylinder 2 adjacent the accumulator 5 and has three chamfered stubs 43 extending axially of the cylinder 2 away from the accumulator 5.

A cylindrical member 11 having an external groove 12 is rotatably and slidably mounted in the cylinder 2. A split, annular ring 13 is rotatably mounted in the groove 12. The cylindrical member 11 and the groove 12 are show in Fig. 2. On the side of the groove 12 nearest the head 3 of the piston 1, the cylindrical member 11 is provided with three ramps 14 and catch pieces 44. On the other side of the cylindrical member 11 there are provided three ramp sections 15. The ring 13 is keyed to the inside of a housing 28 to prevent it from rotating. The cylindrical member 11 is biased by springs 16 to rotate relative to the ring 13.

The annular ring 13 is fixedly attached to piston 17 which is located in annular cylinder 18 comprising cylindrical members 19 and 20. The cylindrical member 19 also forms a housing for the piston head portion 3 and first sleeve 7. The piston 17 and cylinder 18 arrangement is double acting, and fluid is supplied to the opposite sides of the piston 17 by conduits 21 and 22 respectively (shown in detail in Figs. 6 and 7).

The cylinder 18 is closed off by member 23 which also closes off the end of the internal housing 19 for the piston head 3. An air hole 24 is formed in the member 23. The member 23 is internally screw threaded and a bearing 25 is screwed therein. In the bearing 25 is slidably mounted a chisel type bit 26 which is co-axial with the piston 1 A stop member 27 is screwed onto the outside of the bearing 25 to limit the rectilinear movement of the bit 26.

The other end of the cylinder 18 is closed off by member 23B and the release mechanism is surrounded by the housing 28. The three members 23, 23B and 28 are held together by four threaded rods 28A. A control section comprising a spool valve 29 and trigger 30 are mounted on a handle 32 on the housing 28. Pressure fluid is supplied to the tool via connection 31 and is vented to tank by a similar connection 45 (see Fig. 8). The operation of the control section and the ar rangement of hydraulic connections will be obvious to anyone skilled in the art and will therefore not be described in detail here. The spool valve 29 is movable axially against a spring bias to direct pressure fluid to one or the other sides of piston 17.

The tool is used in the following manner. In the position shown in Fig. 1 the ramps 15 have co-operated with stubs 43 on the second sleeve 10 to cause the cylindrical member 12 to rotate against the spring bias as far clockwise (as seen in Fig. 3) as it can. At this stage the abutments 9 are at the point marked X on the cylindrical member 11 and are therefore ready to disengage.

Therefore, as pressure fluid is fed to the accumulator 5 via the connection 31, the piston 1 will move slowly towards the bit 26 and will eventually abut the member 23. The accumulator is then pressurised to the hydraulic supply pressure, which may be as much as 2,000 p.s.i. The hydraulic fluid also flows along conduit 21 and causing piston 17 to move from right to left as seen in Fig. 1. The piston 17 causes the ring 13 and annular member 11 to move in register with it.

As the annular member 11 approaches the abutments 9, they cooperate with the ramps 14 to cause the member 11 to rotate against the bias of the springs 16. Once the abutements 9 reach point X, the springs 16 cause the member 11 to rotate in the opposite direction. The ramps 14 move into the chamber 8 and the abutements 9 engage with the catch pieces 44 operatively to connect the sleeve 7 and therefore the piston 1 to the member 11.

The trigger 30 is pulled towards the handle 32 moving the spool valve 29 to redirect the flow of pressure fluid to the other side of the piston 17 via conduit 22 causing it to move in the opposite direction. Thus the piston 1 is moved against the pressure exerted on it by the fluid in the accumulator 5, thereby supercharging the accumulator 5.

Towards the end of the movement of the piston 17, the ramps 15 on the member 11 come into contact with the stubs 43 on the second sleeve 10 and co-operate to cause the member 11 to rotate against the bias of the springs 16. As soon as the member 11 reaches the position shown in Fig. 1, the abutments 9 and catch pieces 44 disengage.

As the accumulator is now supercharged the piston 1 is forced violently towards the bit 26, striking it with great force and causing it to move explosively to the left as seen in Fig. 1 until the energy has been absorbed by the cutting action of the bit 26 or until stopped by the member 27.

The piston 1 will not strike the bit 26 again until the trigger 30 is pulled again. Thus after each blow the bit 26 can be repositioned on its objective so that it can effectively strike it every time the trigger 30 is operated. Due to the supercharging effect of the action of the piston 17 and cylinder 18, the force exerted on the objective is higher than would be possible with a previously used hydraulic tool.

Moreover, there is no dissipation of the power available because of any valving systems, which are not necessary in the present invention, and because the striking piston 1 has only to displace air though hole 24 and not hydraulic fluid before it strikes the bit 26.

Using this tool it has been found possible to split a nut, having an annular thickness of about 1 cm., a depth of about 1.5 cm., and made from strong steel, with as few as three blows. Using a conventional rapid blow tool of sufficient power, it would generally take about 2 minutes to split the nut.

In an alternative embodiment of the tool the accumulator is charged at a source of high pressure hydraulic fluid. The connection 31 is released and the accumulator 5 is sealed by check valve 40. The tool is then taken to a remote site for operation. Connection 31 is connected to a hand operated hydraulic pump which is used in conjunction with the trigger 30 to move the piston 17 backwards and forwards to effect the operation of the tool.

Since the accumulator section (shown in Fig.

8) is sealed by check valve 40 the tool may be used at the remote location many times without the necessity of having a constant source of high pressure hydraulic fluid.

The hydraulic system tool used on the tool is shown schematically in Fig. 8 with the piston 1 having just struck the bit 26. The presence of check valves 40 and 41 prevent the tool from being used with its connections wrongly made and relief valve 42 ensures that the tool cannot be over pressurised, if for instance it is inadvertently connected to a very high pressure supply.

Thus the tool of the present invention provides significant advantages over previously used tools and will prove of much use in especially mine salvage operations.

Claims (6)

1. A hydraulic tool comprising a bit slidably mounted for limited rectilinear movement, a piston for striking the bit to cause it to move in one direction, a fluid accumulator for supplying pressurised fluid for moving the piston towards the bit and a latch mechanism for engagement with the piston, the latch mechanism being moveable between a first position, in which it engages the piston when the piston is adjacent the bit, and a second position, in which a latch release means disengages the latch mechanism from the piston.

2. A tool according to claim 1, wherein the bit is a chisel, hammer head or pointed bit.

3. A tool according to either one of claims 1 and 2, wherein the latching mechanism is movable between its two positions by a piston and cylinder arrangement.

4. A tool according to claim 3, wherein the cylinder of the moving means comprises an annulus formed around the body of the tool.

5. A tool according to any one of the preceding claims, wherein the latching mechanism comprises a system of interating abutments and ramps.

6. A hydraulic tool substantially as hereinbefore described with reference to the drawings.

6. A tool according to claim 5, and including a rotatable latching member having on it either the abutments or the ramps.

7. A tool according to any one of the preceding claims, and including a non-return valve between the accumulator and the hydraulic power supply.

8. A hydraulic tool substantially as hereinbefore described with reference to the drawings.

CLAIMS (12 Apr 1983)

1. A hydraulic tool comprising a bit slidably mounted for limited rectilinear movement, a piston for striking the bit to cause it to move in one direction, a fluid accumulator for supplying pressurised fluid for moving the piston towards the bit and a latch mechanism for engagement with the piston, the latch mechanism being moveable, by moving means comprising a piston and cylinder arrangement, between a first position, in which it engages the piston when the piston is adjacent the bit, and a second position, in which a latch release means disengages the latch mechanism from the piston, the cylinder of the moving means comprising an annulus formed around the body of the tool.

2. A tool according to claim 1, wherein the bit is a chisel, hammer head or pointed bit.

3. A tool according to any one of the preceding claims, wherein the latching mechanism comprises a system of interacting abutments and ramps.

4. A tool according to claim 3, and including a rotatable latching member having on it either the abutments or the ramps.

5. A tool according to any one of the preceding claims, and including a non-return valve between the accumulator and the hydraulic power supply.