GB2246803A

GB2246803A - An hydraulic hammer

Info

Publication number: GB2246803A
Application number: GB9116841A
Authority: GB
Inventors: Bernard Lionel Gien
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-06
Filing date: 1991-08-05
Publication date: 1992-02-12
Also published as: SE9102290D0; SE9102290L; CA2048374A1; AU8163291A; GB9116841D0; DE4125880A1

Abstract

A bit (2) in a down-the-hole drill rod (4) is driven down by a hammer (8) under the action of hydraulic pressure applied intermittently through fluid (19) to a stem (9) of the hammer. Compressed gas is applied through passages (15, 12, 13) to act between the hammer and bit for the return stroke of the hammer. The bit may be flushed by the gas through passage (6) or by the hydraulic fluid through a passage in the hammer. No internal valve is, therefore, required. <IMAGE>

Description

-1 1 AN RMRAULIC EMMER This invention relates to an hydraulic hammer

assembly used in jack hammers and drilling machines, particularly but not exclusively, down-the- hole drilling 5 machines.

Conventional hydraulic hammers utilise a high pressure pump and reservoir with fluid from the pump passed through a pressure operated valve which directs f low to one or other side of a piston in a piston and cylinder assembly. The piston forms the hammer for striking the drill bit.

There must be means for connecting the pump to the hammer and to return the hydraulic f luid, usually oil, back to the reservoir. This is usually a high pressure flexible hydraulic hose. A hose of this type cannot be used in down-the- hole hammer assemblies.

It is an object of the present invention to provide an hydraulic hammer which does not require an internal valve to control flow direction of the fluid passed the piston.

According to the invention there is provided an hydraulic hammer assembly comprising a piston and cylinder assembly with means for applying intermittent hydraulic pressure to one side of the piston and compressible means for constantly applying pressure to the opposite side of the piston. The invention also provides the compressible means to be mechanically supplied by means of a spring or the like or alternatively through a compressible fluid. 30 The intermittent hydraulic pressure can be supplied through an intermittently operated valve controlling a supply of fluid under substantially constant pressure. Further features of the invention provide for the valve to be a rotary valve or a sliding valve and f or there to be included means for rotating the hammer anvil.

Still further features of the invention provide for 1 2 the hammer assembly to be part of a down-the-hole drill with the pressures applied to the piston provided by fluid transported through separate passages in the drill rods, for the intermittent pressure fluid to be used for flushing the drill bit or for the intermittent pressure to be supplied through two different fluids. In the last mentioned case a second piston slidably operating in a sleeve will be provided.

The invention also provides for the constant pressure supply fluid to be used for flushing the drill bit in an assembly as defined above.

These and other features will become apparent from the following description of some examples of the invention, wherein reference will be made to the accompanying drawings, in which:

Fig. 1 is a longitudinal section through a downthe-hole drill assembly; Figs. 2 and 3 show modifications to the assembly of Fig. 1; - Figs. 4 and 5 show alternative valve assemblies for the intermittent fluid pressure supply; and Fig. 6 shows one form of drill rod suitable for use with the down-the- hole drill described.

As illustrated in Fig. 1 the hammer assembly 1 has a bit 2 at the free end and a backhead 3 secured to a drill rod 4. A casing 5 extends between the backhead 3 and the bit 2 which has a passage 6 for flushing fluid to pass through.

The casing 5 houses an inner sleeve 7 and a hammer in the form of a piston 8. The backhead end of the piston 8 extends as a stem 9 from the remainder of the piston and engages in the backhead 3 to form a sliding seal therewith.

The bore 10 through the backhead 3 is co-axial with a pressure fluid passage 11 in the drill rod 4.

The drawing also shows passages formed in the 1 1 i 3 1 hammer assembly for flushing fluid which can conveniently be compressed air. The passages extend as shown at 12 through the backhead 3, and as shown at 13 between the casing 5 and inner sleeve 7 extending between the backhead 3 ad bit 2. Apertures 14 are provided through the bit end of the inner sleeve 7 and the outer end of passage 12 communicates with a passage 15 in the drill rod 4 for the supply of compressed air.

The compressed air can be supplied at constant pressure through the passages and apertures above described to act on the bit striking surface 16 of the piston 8 to constantly tend to raise the piston 8 f rom, and to the bit 2.

When the piston 8 is raised from the bit 2 the compressed air can also act as a flushing fluid through the passage 6.

A chamber 17 is formed in the inner sleeve 7 around the stem 9 of the piston 8. The chamber 17 communicates through a passage 18 in the backhead 3 to ambient atmosphere.

A pressure f luid 19 acts through the bore of the drill rod 4 and backhead 3 as described below to enable the hammer assembly to operate.

The passage 18 to atmosphere is provided to prevent a build up of pressure in the chamber 17 which could occur if there is leakage either from the compressed air path through the assembly or of the pressure fluid passed the stem 9 of piston 8.

Fig. 2 illustrates the inclusion of a second piston 20 separating the pressure fluid 19 column into two secitons, thus enabling two different types of fluid to be used.

Fig. 3 illustrates a further modification wherein a gas accumulator is f ormed by a stem 21 on the striking end of piston 8 in sliding engagement with a sealing bush 22 providing an oil filled chamber 23 which is in 4 communication with the passages 13 between inner sleeve 7 and casing 5. These passages are sealed at the backhead end.

With gas under pressure introduced into passage 13, movement of the piston will enable the gas to expand or compress and always provide a pressure on the piston 8, tending to lift the piston 8 from the bit 2.

Flushing medium in this construction can be provided by the pressure fluid 19 passing through an axial bore 24 through the piston 8 and preferably a restriction 25 in the form of a suitable plug is provided in the bore 24 to limit the flow of pressure fluid 19 to the bit.

To enable the pressure fluid 19 to act intermittently on the piston 8 with a greater force than that provided by the compressed gas in passage 13, a pressure pump (not shown) and valve assembly are provided at the drill head.

Suitable valves are illustrated in Figs. 4 and 5 of the drawings.

Referring firstly to Fig. 4, the valve assembly 26 consists of a valve body 27 which has a passage 28 closed at one end 29 which is connected to a motor 30 for rotation. The open end of the valve is in alignment with the fluid passage 11 in the drill rod 4.

The body 27 rotates in a valve housing 31 which has a high pressure inlet port 32 from the pressure pump and an outlet port 33 connected to the reservoir for fluid for the pump.

The body 27 has a radial port 34 through the wall thereof and rotation of body 27 by the motor 30 in the housing 31 will bring port 34 alternately into alignment with ports 32 and 33. This has the result, in operation, of pressure of the pressure fluid down the drill rods intermittently varying from maximum pump pressure to exhaust pressure. Each time maximum pressure is exerted 1 i 1 I i i 1 i z 1 i 1 1 i i 1 1 down the column of pressure fluid 19 the constant gas pressure acting in the opposite direction on piston 8 is overcome and piston 8 is caused to strike the inner end of the bit 2. When the pump pressure on the pressure fluid is released the gas pressure will cause a return stroke of the piston.

Fig. 4 also illustrates a stepped piston 35 in the pressure fluid column to separate the fluid used through the pump from that in the drill rods 4. This will enable the f ormer to be a suitable oil while the latter is water. If the bores through the backhead 3 and end of the piston 8 are chromium plated or otherwise rendered rust resistant, water can be used directly in the hammer asembly 1. This will avoid the necessity for the second piston 20 illustrated in Fig. 2.

In Fig. 5 a suitable sliding valve assembly 36 is shown. The assembly consists of a sliding stepped valve member 37 movable in a valve casing 38 which is in communication with the column of pressure fluid 19.

Inlet and exhaust ports 39 and 40 are provided for connection to the delivery of the pressure pump and the reservoir for pump fluid respectively.

Reciprocation of valve member 37 will enable pump delivery pressure to be alternately applied to and relieved from the pressure fluid 19. This in turn will cause operation of the hammer assembly as described above.

With this type of valve a relief valve should also be used when the inlet port is closed. To overcome unnecessary energy loss an accumulator can be included in the system. It will be appreciated however that alternative porting arrangements can be used to avoid the necessity for the relief valve.

It will be understood that the methods of applying the intermittent pressure supplied through the pressure fluid 19 to the piston 8 need not be effected 6 hydraulically as set forth in the above example. It may be applied by mechanically reciprocating a piston to cause pressure and release of pressure in the fluid 19. This arrangement could readily be set up by those skilled in the art and would also preferably include the relief valve and accumulator referred to above.

Also. the examples given above describe the use of a compressible f luid to provide a constant pressure on the piston to raise it from the bit. Mechanically resilient means such as compression springs or blocks of suitable resilient material recessed to extend and contract into the piston or drill bit, may also be used.

Fig. 6 shows a form of drill rod 4 which can conveniently be used with this invention.

The drill rod 4 has an inner pipe 41 which is used as the drive rod and provides the passage for the pressure fluid 19. An outer pipe 42 is welded at 44 to the inner pipe 41 and this welding can conveniently take place at the-position on the drill rod where flats 43 are f ormed to enable the rods to be manipulated with spanners. This will readily be understood by those who make such drill rods.

It is to be understood that the invention above described can be widely varied from the specific examples described and illustrated without departing from the scope of the invention. The drill rod assembly and pressure fluid valving can be varied, as can the shape and configuration of the hammer assembly components. What is essential is that there be different pressures applied to each side of the hammer piston.

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Claims

CLAIMS:

1. An hydraulic hammer assembly comprising a piston and cylinder assembly with means for applying intermittent hydraulic pressure to one side of the piston and compressible means for constantly applying pressure to the opposite side of the piston.

2. An hydraulic hammer as claimed in Claim 1, in which the compressible means is a resilient mechanical means.

3. An hydraulic hammer as claimed in Claim 1. in which 10 the compressible means is provided through a compressible fluid.

4. An hydraulic hammer as claimed in any one of the preceding claims, in which the intermittent hydraulic pressure is provided through a column of liquid to which hydraulic pressure is applied through an intermittently operated valve controlling a supply of fluid under substantially constant pressure.

5. An hydraulic hammer as claimed in any one of Claims 1 to 3, in which the intermittent hydraulic pressure is applied through a column of liquid to which pressure is applied by a mechanically reciprocated piston acting on the column of liquid.

6. An hydraulic hammer as claimed in Claim 4, in which the valve is a rotary valve.

7. An hydraulic hammer as claimed in Claim 4, in which the valve is a sliding valve.

8. A down-the-hole drill including an hydraulic hammer as claimed in any one of the preceding claims.

9. A down-the-hole drill as claimed in Claim 8, in 30 which the pressures applied to the piston are provided by fluid transported through separate passages in the drill rods.

10. A down-the-hole drill as claimed in Claim 9, in which the passage for the liquid applying the intermittent pressure to the piston includes a passage for flushing the drill bit.

8

11. A down-the-hole drill as claimed in Claim 9 or Claim 10, in which the passage for the liquid to apply intermittent pressure to the piston includes a separating piston enabling different fluids to be used in the hammer 5 and in the drill rods.

12. A down-the-hole drill as claimed in Claim 9, in which the passage for applying a constant pressure to the piston includes a passage for flushing the drill bit.

13. A down-the-hole drill substantially as described 10 with ref erence to Figs. 1 and 2 and 4 and 6 or Figs. 1 and 3 and 5 and 6 of the accompanying drawings.

Published 1992 at The Patent Office, Concept House, Cardiff Road. Newport. Gwent NP9 IRH. Furiher copies may be obtained from Sales Branch, Unit 6. Nine Mile Point. CwTnfelinfach, Cross Keys, NewporL NP I 7HZ. Printed by Multiplex techniques lid, St Mary Cray. Kent.

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