GB2145648A - 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 28, a cylinder 2 in which is a striking piston 1, and a bit 4. The striking piston 1 is moved away from the bit 4, latched to a piston 6, by hydraulic means. The accumulator 28 is supercharged by a supercharging piston 19 which subsequently releases the latch allowing the striking piston 1, under the influence of the supercharged hydraulic fluid in the accumulator 28, to move violently against the bit 4 thus delivering a very powerful blow to, for instance, a corroded nut. <IMAGE>

Description

SPECIFICATION Hydraulic tool This invention relates to a hydraulic tool, more particularly to a hydraulic chisel for splitting nuts from bolts, shearing rivet heads etc. particularly but not exclusively in mine workings.

In a coal mining operation, it can cost in excess of 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 workplace. In order to be able to recover this equipment, it is necessary to remove the nuts and 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 manual or power operated, to unscrew the nuts from 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 to the nut to operate it effectively. It is therefore generally preferred to use a hydraulic pick, especially to remove relatively inaccessible nuts.

In ourcopending patent application no. 81135347 we describe a hydraulic nut splitter deveoped as an alternative to the more common hydraulic pick (usually known as hydraulic drill). This is a device that operates on a single blow principle rather than the multiblow principle of the hydraulic pick. It delivers a harder blow than existing hydraulic picks.

However various shortcomings have emerged: the device as used in certain locations weighs approximately 30 kgs. Bearing in mind that the device is essentially a hand tool this poses a serious ergonomic problem which will have a bearing on the usefulness of the tool.

The removal of certain nuts from inaccessible places e.g. certain places within an A.F.C. linepan, requires a smaller and more manoeuverable tool than the present hydraulic nut splitter.

An object of the present invention is to provide an improved hydraulic tool that overcomes in part the disadvantages of existing hydraulic picks and nut splitters.

Accordingly the present invention provides a hydraulic tool comprising a bit slidably mounted for limited rectilinear movement, a striking piston for striking the bit to cause it to move in one direction, a fluid accumulator for supplying pressurised fluid for moving the striking piston towards the bit, a super charging piston for supplying pressurised fluid to the fluid accumulator, and a latch mechanism for engagement with the striking piston, the latch mechanism being moveable by hydraulic moving means comprising a latch piston and cylinder arrangement between a first position in which it engages the striking piston when the striking piston is adjacent the bit, and a second position in which the super charging piston, having pressurised the fluid accumulator, disengages the latch allowing the striking piston to strike the bit.

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

Preferably the latching mechanism comprises a rod and tube slideably mounted in and on the axis of the striking piston, said tube having a number of radially spaced holes and said rod having a ramped neck containing a number of balls such that on moving the rod relative to the tube the balls are forced up the ramp into the radially spaced holes where they sit proud of the outside of the tube and lock the tube to an annular grove within the striking piston.

Conveniently the fluid accumulator is an inert gas accumulator. Preferably the fluid accumulator contains nitrogen.

Preferably the fluid accumulator is pressurised to a preset gas pressure of about 1300 pounds per square inch.

Preferably there is a non return valve between the hydraulic supply and the fluid accumulator.

Preferably the action of the tool is controlled by a trigger such that the striking piston remains adjacent the bit until the trigger is operated. In this way it is possible to position the bit carefully before the tool is operated.

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

Figure 2 is a schematic circuit diagram showing the hydraulic circuit within 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 first cylinder 2. The striking piston 1 having a reduced diameter striking head 3 which delivers blows to the end of bit 4. To absorb any excess striking piston energy a buffer comprising a number of spring washers 5, 5', 5" is provided within the tool. This will prolong the service life and reduce damage to the tool in the event of accidental firing when the bit is not in contact with anything.

The striking piston 1 cooperates, at its other end with a latch piston 6 which has associated with it a latch rod 7 having a ramped neck 8, a detent groove 9, and two steel balls 10 and 10'. An extension of the latch piston 6 forming a latch tube 12 runs coaxially about latch rod 7 and within cylindrical striking piston 1. Cylindrical striking piston is further provided with a diametrical enlargement forming an annular groove 13. The latch piston 6 operates within a second cylinder 14 and further contains a sprung ball to cooperate with the detent groove 9.

An annular protrusion 16 separates the second cylinder 14 from a third cylinder 17 which opens out into a fourth larger diameter cylinder 1 8. A super- charging stepped piston 19 sits within the third cylinder 17 and fourth cylinder 18 which is sealed by end plate 21.

Hydraulic fluid is fed to the tool via an inlet connector 20 and outlet connector 23 and is controlled by a spool valve 24 with associated trigger 25, a pressure relief valve 26, a non-return valve 29, a sequence control valve 27 and an accumulator 28 which distribute the hydraulic fluid via a network of conduits shown schematically in Figure 2. The hydraulic circuitry will be easily understood by a person skilled in the art by reference to Figure 2.

After firing the striking piston 1 is adjacent the bit 4, latch piston 6 is disengaged from striking piston 1 and is adjacent annular protrusion 16 with latch rod 7 pushed into latch piston 6 and therefore with balls 10, 10' sitting down in ramped neck 8 and not proud of latch tube 12. Super charging piston 19 is at the left hand end of its travel (on Figure 1) where it is in contact with the end of latch rod 7.

When the trigger 25 is released the spool valve 24 allows hydraulic fluid into cylinders 14 and 17 via annular protrusion 16 thus forcing supercharging piston 19 to the right (Figure 1) and latch piston 6to the left (Figure 1). Super charging piston 19 comes to rest against the end plate 21. As latch piston 6, with associated latch tube 12 and latch rod 7 move to the left (Figure 1) the left hand end of latch rod 7 is first to contact the back of striking piston 1. As the latch piston 6 continues to move leftward the balls 10 and 10' are forced up the ramp of ramped neck 8. When the latch tube 12 reaches the back of the striking piston 1 the balls 10 and 10' are right out of ramped neck 8 and are sitting proud of the outside diameter of latch tube 12 ready to lock against the shoulder at the end of the annular groove 13.Also the spring biased ball has located the detent groove 9 to lock latch piston 6 to latch rod 7 and hence ensure that the latch assembly is in engagement with the striking piston 1 via balls 10 and 10'.

On firing, the spool valve allows the hydraulic fluid between latch piston 6 and supercharging piston 19 to be vented to the drain side of the hydraulic system whilst forcing high pressure liquid via the non-return valve into the left hand end of cylinder 18, the accumulator and the left hand end of cylinder 14, all 3 of these spaces being in fluid communication with one another. Under the influence of the high pressure hydraulic liquid latch piston 6 moves to the right (Figure 1) towards the annular protrusion 16, taking with it the striking piston 1. When the latch piston 6 comes to rest against annular protrusion 16 the pressure of the hydraulic fluid within the tool rises to the supply pressure. This activates the sequence control valve 27 which allows hyydraulicfluid at the supply pressure, into the right hand end of cylinder 18.This moves the supercharging piston 19 to the left (Figure 1) forcing the supply pressure fluid from the annular space at the left hand end of cylinder 18 via conduits to the accumulator thus supercharging it. The degree of supercharge is controlled by the ratio of the differential areas of the right hand face and step face of supercharging piston 19. As supercharging piston 19 moves to the left and forces hydraulic fluid into the accumulator non-return valve 29 prevents this pressure being lost back down the supply line. When the supercharging piston 19 reaches the annular protrusion 16, it pushes latch rod 7 into latch piston 6 allowing balls 10 and 10' to drop into the necked ramp 8. This frees the striking piston 1 from the latch.Due to the supercharged hydraulic fluid pressure in the accumulator and within cylinder 14 with which it communicates via a large bore conduit striking piston 1, which extends up to the left hand side of latch piston 6 (Figure 1), is accelerated under great force to the left where it strikes bit 4.

Pressure relief valve 26 is provided in the event of the supercharged pressure going too high. The supercharging effect of this embodiment provides a pressure increase from an 1100 psi supply pressure to 3500 psi on the striking piston. The only large flow of hydraulic fluid is from the accumulator 28 into the cylinder 14 as the striking piston 1 fires. This is provided for by using a large bore conduit machined in the body of the tool.

The pressure relief valve 26 allows the safe use of this tool on supply pressures of anything from about 1000 psi to about 2500 psi and can therefore be operated from the hydraulic supply on powered roof supports. If no supply line is available the tool can be used with a hand operated hydraulic pump.

Atool according to the invention is mechanically simpler than other prior art devices but most important it is smaller, more manoeuverable and lighter weighing approximately 1/2 that of the tool according to our application no. 81135347. This means the tool can reach nuts and bolts that our previous invention cannot but more importantly the tool according to our present invention is light enough to substantially solve the ergonomic problem associated with our earlier application.

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 to 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.

Claims (9)

1. A hydraulic tool, comprising a bit slidably mounted for limited rectilinear movement, a striking 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, a supercharging piston for supplying pressurised fluid to the fluid accumulator, and a latch mechanism for engagement with the striking piston, the latch mechanism being moveable by hydraulic moving means, comprising a latch piston and cylinder arrangement, between a fist position in which it engages the striking piston when the said striking piston is adjacent the bit, and a second position in which the supercharging piston, having pressurised the fluid accumulator, disengages the latch allowing the striking piston to strike the bit.

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

3. A hydraulic tool according to claim 1 or claim 2 wherein, the latching mechanism comprises a rod and tube slidably mounted in and on the axis of the striking piston, said tube having a number of radially spaced holes and said rod having a ramped neck containing a number of balls such that on moving the rod relative to the tube the balls are forced up the ramp into the radially spaced holes where they sit proud of the outside of the tube and lock the tube to an annular groove within the striking piston.

4. Ahydraulictool according to any of the preceding claims, wherein the fluid accumulator is an inert gas accumulator.

5. A hydraulic tool according to claim 4, wherein the inert gas is nitrogen.

6. A hydraulic tool according to claim 4 or 5, wherein the gas is pressurised to a preset gas pressure of 1300 pounds per square inch.

7. A hydraulic tool according to any of the preceding claims, wherein there is provided a nonreturn valve between the hydraulic supply and the fluid accumulator.

8. A hydraulic tool according to any of the preceding claims, wherein the action of the rod is controlled by a trigger such that the striking piston remains adjacent the bit until the trigger is operated.

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