WO1995016549A1

WO1995016549A1 - Accumulator

Info

Publication number: WO1995016549A1
Application number: PCT/GB1994/002738
Authority: WO
Inventors: Jarmo Uolevi LEPPÄNEN; Roger Robarts Briggs
Original assignee: Leppaenen Jarmo Uolevi; Roger Robarts Briggs
Priority date: 1993-12-17
Filing date: 1994-12-14
Publication date: 1995-06-22
Also published as: AU1198595A; ZA939448B

Abstract

A hydraulically operated rock drill which includes a cylinder (12), a piston (16), inside the cylinder, which includes an annular formation (26A) which moves into and out of a section (44) of reduced dimensions which is connected to an accumulator (18), the annular formation then pressurizing hydraulic fluid in the section whereby hydraulic energy, produced by kinetic energy developed over at least part of a return stroke of the piston (16), is stored in the accumulator (18).

Description

"Accu-Tiulator^*1'

BACKGROUND OF THE INVENTION

This invention relates generally to an accumulator and particularly to an accumulator which is suitable for use with a hydraulic rock drill.

It is known to make use in an hydraulic rock drill of one or more nitrogen gas charged accumulators which absorb hydraulic pressure peaks and store hydraulic power.

The main function of an accumulator on the oil return side of a rock drill is to reduce pressure peaks in the hydraulic fluid and prevent cavitation. On the high pressure side where oil is led to an operating piston the accumulator is charged upon retraction of the piston. The kinetic energy of the returning piston is stored in the accumulator and, when the piston stroke starts, the accumulator supplies extra oil and pressure to speed the' piston for the percussion stroke.

An accumulator of the aforementioned kind may include a rubber diaphragm which forms a first chamber which receives the charging oil and a second chamber, on the dampening side, which is charged with nitrogen. A relatively small volumetric capacity is required for the oil but a considerably larger capacity is required for the nitrogen. Thus the accumulator is fairly large. Consequently the moving space for the rubber diaphragm is also large. This, coupled with the fact that the pressure peaks may occur at a rate in excess of 10 000/minute, with a substantial difference in pressure between the low pressure and a pressure peak, means that the diaphragm can have a short operating life.

A broken diaphragm has the following negative effects:

a loss of power on the rock drill; reduced life for all hydraulic components; - increased downtime due to rock drill service; vibrating hoses become worn and burst; increased downtime due to hose changes; increased spare parts consumption and maintenance expenses; - broken accumulator mounting bolts.

SUMMARY OF THE INVENTION

The invention provides an accumulator which includes a diaphragm, a first gas-charged chamber with the diaphragm on a wall thereof, and a second gas-charged chamber which is in communication with the first chamber through at least one passage. In one form of the invention the accumulator includes a body in which are formed a first chamber, a second chamber which is adapted to be charged with a suitable gas, at least one hydraulic fluid port and at least one passage, and a diaphragm which divides the first chamber into a first section which is in communication with the hydraulic fluid port and a second section which is adapted to be charged with the said suitable gas and which is placed in communication with the second chamber by means of the passage.

Preferably the accumulator includes a plurality of the passages with each passage placing the second section in communication with the second chamber.

The cross sectional dimensions of each passage are relatively small. Each passage may have a diameter of less than 2mm and preferably the diameter of each passage is of the order of 1 ,2mm.

Support means may be provided inside the second chamber extending between opposing inner walls thereof. The support means may extend to that wall of the second chamber in which the said plurality of passages are formed.

Valve means may be provided for charging a gas such as nitrogen into the second chamber and the second section. Similarly the port may be adapted to be connected to a pressurized source of hydraulic fluid. Opposing inner surfaces of the first and second sections may have substantially similar recessed shapes.

BRIEF DESCRIPTION OF THE DRAWING

The invention is further described byway of example with reference to the accompanying drawing which illustrates from the side and in cross

section the construction of an accumulator according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

The accompanying drawing illustrates in cross section and from the side a hydraulic rock drill accumulator 10 according to the invention.

The accumulator includes a body 12 in which are formed a first chamber 14, a second chamber 16, a port 18, a plurality of passages 20 in a wall 22 between the first chamber 14 and the second chamber 16, a valve 24 which leads to the second chamber, and a rubber diaphragm 26.

The rubber diaphragm includes a flange 28 which is clamped between opposing surfaces of two mating parts 12A and 12B of the body. The rubber diaphragm is relatively thick and of a simple design. The diaphragm divides the chamber 14 into a first chamber section 30 which is in communication with the port 18 and a second chamber section 32 which is bounded by the wall 22. The passages 20 thus place the second section 32 in communication with the interior of the second chamber 16.

Depending on the design of the accumulator there are a substantial number of the passages 20, of the order of 80 passages. Each passage is of reduced cross sectional area and typically has a diameter of the order of 1,2mm.

10

Opposing surfaces 31,33 of the chamber 14 have substantially similar recessed shapes which determine the extent to which, and the manner in which, the diaphragm is stretched and deformed, in use.

15 The chamber 16 is contained in a separately formed portion of the body which is attached to the portion of the body accommodating the chamber 14 in any appropriate way. In use of the accumulator the wall 22 may be subjected to substantial forces and to prevent deformation of the wall the chamber 16 may include an internal support 34 which extends from the

20 wall 22 to an opposing wall 36 of the chamber.

«

In use of the accumulator the port 18 is connected in a known manner to the pressure side of operating fluid lines of a hydraulic rock drill. The chamber 16, and hence the second section 32 which is in communication with the chamber via the passages 20, is charged with nitrogen through the valve 24. The second section is relatively small compared to the construction of a conventional accumulator and consequently only a relatively small volume is provided for diaphragm movement. The additional gas required for storage of all the hydraulic energy is held in the chamber 16. Thus the diaphragm, in use of the accumulator, is not extended unduly and unnecessary stretching of the diaphragm rubber is obviated. The life expectancy of the diaphragm is increased and this means that there is less downtime and maintenance. Operating costs are reduced. Since the diaphragm is not unduly stretched in operation it can be made from a thicker material which means that it lasts longer.

It is necessary to make the passages 20 relatively small in cross section to avoid the rubber of the diaphragm from being pushed into the passages or extruded through the passages if the gas pressure is reduced or if the gas leaks out from the chamber 16.

Claims

1. An accumulator (10) which includes a diaphragm (26), a first gas-charged chamber section (32) with the diaphragm (26) on a wall thereof, and which is characterised by a second gas-charged chamber

(16) which is in communication with the first chamber section (32) through at least one passage (20).

2. An accumulator according to claim 1 which is characterised in that it includes a third chamber (30) which is adapted to be connected to a source of hydraulic fluid, the diaphragm (26) forming a wall of the third chamber.

3. An accumulator according to claim 2 characterised in that respective surfaces (31,33) of the first chamber (32) and of the third chamber (30) , which oppose the diaphragm (26), have substantially similar recessed shapes.

4. An accumulator (10) which includes a body (12) in which are formed a first chamber (14), at least one hydraulic fluid port (18), and a diaphragm (26) and which is characterised by a second chamber which is adapted to be charged with a suitable gas, in that the diaphragm divides the first chamber (14) into a first section (30) which is in communication with the hydraulic fluid port (18), and a second section (32) which is adapted to be charged with the said suitable gas and which is placed in communication with the second chamber (16) by means of at least one passage (20).

5. An accumulator according to claim 4 which is characterised by a plurality of the passages (20), each passage placing the second section (32) in communication with the second chamber (16).

6. An accumulator according to claim 4 or 5 which is characterised by support means (36) extending between opposing inner walls of the second chamber (16).

7. • An accumulator according to any one of claims 4 to 6 which is characterised in that it includes valve means (24) through which the said suitable gas can be charged into the second chamber (16) and the second section (32).

8. An accumulator according to any one of claims 4 to 7 characterised in that the port (18) is adapted to be connected to a pressurized source of hydraulic fluid.

9. An accumulator according to any one of claims 4 to 8 characterised in that opposing surfaces (31;33) of the first and second sections (30;32) have substantially similar recessed shapes.