EP0225415A1

EP0225415A1 - Rock breaking or crushing device

Info

Publication number: EP0225415A1
Application number: EP85308974A
Authority: EP
Inventors: Akiya Maeda; Mituya Sakai; Yukinobu Masaka; Masahiro Nomura; Yasuo Yamada; Tetsuro Tatsuhama
Original assignee: Seibu Polymer Kasei KK; Okumura Machinery Corp
Current assignee: Seibu Polymer Kasei KK; Okumura Machinery Corp
Priority date: 1985-12-10
Filing date: 1985-12-10
Publication date: 1987-06-16

Abstract

A rock breaking device is designed to crush rocks by the use of expansion pressure generated when a cylindrical elastic expansive member (1) is expanded by pressure fluid delivered to looped pockets (3) provided within the elastic member (1). The elastic member (1), made of rubber or the like, is arranged to fit tightly around a metal shaft (4) having a fluid passage (6) for delivering pressure fluid to the looped pockets (3) of the elastic member (1). Elastic rings (10) are interposed between the ends of member (1) and axially fixed abutments (12), and are of harder material than the member (1).

Description

The present invention relates to a rock breaking device for breaking or crushing rock or concrete by the utilisation of fluid pressure. In particular the invention relates to a device for breaking or crushing rock or concrete, which for use, is inserted into a hollow formed in the rock or the concrete to be broken.
Blasting with explosives has frequently been used for breaking up rocks or concrete. This, however, is disadvantageous in that noise and dust are inevitably generated at blasting, to the detriment of not only the environmental conditions in the surrounding area but also the working conditions in the pit or other work place, inducing critical influences on the safety of work in the work place. Therefore, a rock breaking method has been strongly desired, such which can reduce the amount of noise, vibrations and/or dust generated when breaking the rock or concrete, as compared with the prior, blasting method.
In recent years, a technique has been used in which rock or some other object to be broken up is first provided with hollow cavities and then, a fluid material is driven into the hollows. This method which utilizes the pressure of the fluid material is called a collapse method, and avoids at least some of the disadvantages of blasting. With this collapse method, however, there is a serious difficulty if there is any crack or any crevice in the object to be broken up. This is because the leakage of the pressure fluid out of the cracked portion means that necessary pressure for breaking the object cannot be obtained.
In another method, a lime-based filling is used. The lime-containing filling is preliminarily packed into hollow cavities formed in the object to be broken or crushed and then after the hollows are plugged, the filling is expanded through chemical action, whereby the object to be broken or crushed is statically broken. With this method, however, it takes a relatively long time for the lime-containing filling to be expanded through chemical action, and therefore, it is disadvantageous in low operational efficiency and high operational cost.
Furthermore, in the prior art methods as described above, the force against the wall of the hollows acts approximately uniformly on the object to be broken or crushed, that is to say uniformly around the circumference of the hollows, and many cracks are generated in the object. As a result, when the prior art method is employed in the case of a tunnel excavation for example, the wall surface of the resulting tunnel having a desired shape is formed with many cracks so as to be a coarse and rough surface, while the ground around the tunnel is loosened. Therefore, it is inconvenient that the prior art crushing method needs a taking-out operating under guidance or many coatings with concrete.
Consequently, in a tunnel excavation which requires that the destruction of the rock etc to be crushed or broken up should follow a predetermined line a method such as explained in Fig. 1 is employed. A lot of holes (not shown in the drawings) are driven at a given spacing around the peripheral shape of the tunnel; into each of these holes is injected a high pressure jet of water to connect with the other holes and thereby form slits H to be provided along the predetermined line, and then blasting powder is put into the blast hole S for blasting. However, since this method requires an additional operation for forming the slits in the blast hole, the operation of breaking up the rock to be removed becomes complicated, and moreover, since this method is accompanied with blasting, the generation of noise and/or vibrations cannot be avoided.
The present invention has been developed with a view to substantially solving or ameliorating the above-described disadvantages or inconveniences inherent in the prior art crushing methods, and has for its first object to provide an improved device which can accomplish a desired breaking or crushing of an object in a relatively short period of time with a favourable working environment and with no generation of noise and/or vibrations.
Broadly, in the present invention, an improved rock breaking or crushing device has a metal shaft covered with a cylindrical elastic expansive member, such as a rubber tube. To break rock, this device is inserted nto a hollow formed in the rock to be broken or crushed, and the cylindrical elastic expansive member is expanded by a pressure fluid, thereby to break the rock by the pressure of the expansion.
According to one aspect of the present invention, there is provided an improved rock breaking or crushing device, intended to be inserted into a hollow formed in a rock for then breaking the rock on the application of fluid pressure to the device, comprising:
a shaft, a length of which accommodates a fluid passage extending axially within the shaft for example along the centre axis thereof, one end of which passage opens at the end of the shaft to be connected to a pressure fluid source, while the other end of the passage debouches at an outlet opening in an axially central portion of the outer peripheral surface of the shaft;
an elastic member made of expandable material in cylindrical shape having an outer diameter suitable for insertion into the hollow in the rock with a small clearance, and an inner diameter capable of receiving the shaft therein, so that the elastic member is tight on the shaft, and provided with at least a pair of looped pockets each disposed within an axially central portion of the elastic member, opposite to the other in the axial direction of the elastic member and expandable by pressure fluid received therein, said looped pockets having port(s) disposed at position(s) biasing to the center on the inner surface of the elastic member in such a manner that pressure fluid supplied from the outlet opening of the shaft flows into the looped pockets through the port(s) without discharging to the outside; and
a paid of fixtures e.g. fixed abutments each mounted on the shaft at a respective end of the elastic member so as to prevent the elastic member from expanding along the axial direction of the shaft beyond the fixtures; whereby the elastic member is rendered able to expand only in its radial direction to break the rock when the pressure fluid is supplied into the pockets of the elastic member.
According to another aspect of the present invention, a crushing device comprises an elastic expansive member in a cylindrical configuration formed with looped pockets between the inner and outer peripheral surfaces thereof, said looped pockets having or communicating with at least one port at the inner periphery between the end portions of the elastic member, and extending towards the end portions, a metal shaft having an introduction passage for pressure fluid debouching at the center thereof, said elastic member being sleeved over the outer periphery of said shaft such that at least the inner peripheral surface of the end portions of the elastic member is closely adhered to said shaft, and a respective elastic ring harder than the the elastic member fixedly held to each end face of the elastic member by a fixture of a smaller diameter than said elastic ring, whereby pressure fluid can be injected from the fluid passage formed in the shaft to the inner peripheral side of the elastic member so as to expand the elastic member in the direction of an outer periphery thereof, thereby breaking or crushing an object to be broken up.
Preferably a deformable member is interposed between each end of the elastic member and the adjacent fixture. Such a deformable member may be an elastic ring, a spring washer, or one end portion of a part which also serves to cover the elastic member.
The adjoining surfaces of the deformable member and abutting end of the elastic member may taper, e.g. as conical surfaces, with smaller diameter axially closer to the adjacent fixture than the larger diameter of these surfaces. A cover tube may cover the whole outer periphery of the elastic member so as to reinforce the strength of the elastic member. Such a cover tube may include localised reinforcement.
When deformable members are interposed between the elastic member and the fixtures, they are preferably not softer than the elastic member, at least if a pair of deformable members is not connected together and/or abut tapering ends of the elastic member and/or if a cover tube over the elastic member lacks localised reinforcement. They may well be harder than the elastic member, e.g. in the case of spring washers or elastic rings of harder material than the elastic member.
The pockets in the elastic member suitably define annular cavities intermediately between inner and outer peripheries of the elastic member, communicating with a port or respective ports on the inner periphery of the elastic member, and extending from such port(s) axially towards the end of the elastic member.
The present invention will be explained further by means of the following description, which includes descriptionof the preferred embodiments of the invention, and makes reference to the accompanying drawings, in which;

Fig. 1 is an explanatory diagrammatic view of a tunnel formed with a blast hollow and slits therein;
Fig. 2 is an explanatory diagrammatic view showing a plurality of rock breaking or crushing devices for use in practice;
Fig. 3 is a cross-sectional view of a rock breaking or crushing device when being inserted into an object (e.g. rock) to be crushed;
Fig. 4 is an exploded perspective view of the device of Fig. 3;
Fig. 5 is a cross-sectional view of the device when an elastic expansive member therein is expanded; and
Figs. 6 to 13 are respective cross-sectional views of further devices according to other embodiments of the present invention.

Before the description proceeds, it is to be noted that like parts are designated by like reference numerals through the accompanying drawings. For convenience the concrete or rock breaking or crushing devices embodying this invention will frequently be referred to simply as "crushing devices".
It is also to be noted here that although the crushing device C of the present invention is most effective when it is used in plural numbers and disposed in parallel relation to each other as shown in Fig. 2, the following description will be directed to the case where only one crushing device is employed. In Fig. 2 each device is supplied from a common manifold through a stop valve 10.
Hereinafter, the crushing device of the first embodiment will be described with reference to Figs. 3 and 5. It includes an elastic member 1 detachably mounted on a shaft 4 with sealing means. The elastic member 1 is made of elastic materials such as rubber, or some synthetic resin having an expansive characteristic, in the configuration of a cylinder, with tapering end faces 1a extending outwardly at opposite end portions thereof. Within the elastic menber 1 a pair of looped pockets 3 are provided between the inner and outer peripheral surfaces facing each other and extending along the axial direction towards the opposite end portions of the elastic member 1, said pockets 3 having ports 2 disposed on the inner periphery with biasing to the center of the elastic member 1 for receiving pressure liquid into the pockets 3. As shown in the drawings, the pockets 3 of the elastic member 1 have cross-sections of lying L shape, so that there are portions of the elastic member 1 between the pockets 3 and the inner peripheral surface except at the ports 2. The portions form seals for pressure liquid. The shaft 4 to be employed as a solid core member, having a given length and a circular cross-section, is made of rigid materials such as metal or hard synthetic resin. It is provided with a central passage 6 for introducing pressure fluid from an inlet opening at the outer end surface of the shaft 4, which in use is coupled with a liquid source. The passage 6 levels to an outlet 5 opening at the outer peripheral surface of the middle portion of the shaft 4, to communicate with the ports 2 of the pockets 3 of the elastic member 1. Also, screw-threads 7 are provided at both end portions of the shaft 4 to secure fixtures 12 so that these are detachable. These serve for fixedly positioning both ends of the elastic member 1 sleeved on the shaft 4 at a given position in the middle portion of the shaft 4. The shaft 4 is forcibly inserted through the interior of the elastic member 1. Consequently, the elastic member 1 is sleeved onto the middle portion of the outer periphery of the shaft 4, with the elastic member 1 and shaft 4 tightly fitted against each other, while establishing communication between the ports 2 of the pockets 3 of the elastic member 1 and the outlet 5 of the passage 6 of the shaft 4. Sealing means includes a pair of elastic rings 10, metal washers 11 and metal rings 14, and a cover tube 13.
The elastic rings 10 are made of materials more rigid than the elastic member 1 and have the same outer diameter as the elastic member 1. Each has a tapering face at its end adjoining a tapering end face of the elastic member 1. Each of the elastic rings is provided between the outer end of the elastic member 1 and the metal washer 11 which is backed up by the fixture 12 secured onto the thread 7 of the shaft 4. Hence the tapering face of the elastic ring 10 is tightly held against a tapering end face of the elastic member 1 in order to prevent the outer end of the elastic member 1 from wrapping. In other words, the elastic ring 10 is assembled to be pressed against the elastic member 1 from the outside by the fixture 12 acting through the metal washer 11. This washer 11 has a similar or smaller diameter than the elastic ring 10, and the fixture 12, which is of a round nut type, has a smaller diameter than the elastic ring 10. Moreover, the elastic member 1 is closely surrounded by a cover tube 13 made of elastic material, serving to protect the outer peripheral surface over the whole length thereof. The protective cover tube 13 is made of extensible reinforcement material such as a spiral spring or the like and is fitted onto the outer periphery of the elastic member 1. A pair of metal rings 14 are formed as circular strips made of rigid material harder than the elastic member 1 made of metal, bead wire, reinforcing fabric and the like, and are respectively provided at both of the end portions of the elastic member 1 in order to prevent the elastic member 1 from wrapping at the end portions e.g. the end portions rolling over along the shaft, or otherwise distorting out of shape when pressure fluid is supplied into the pockets 3 of the elastic member 1. Each metal ring 14 is embedded integrally within the elastic member 1 so that one end contacts the elastic ring 10 and its inner surface contacts the outer peripheral surface of the shaft. However, the metal ring 14 may be embedded completely into the elastic member 1. Although it is so illustrated in Fig. 3 that a pair of the looped pockets 3 associated with ports 2 in the elastic member 1 are formed separately from each other, axially spaced in the elastic expansive member 1, a groove may be formed, as shown in Fig. 6 between the inner peripheral surface of the elastic member 1 and the outer periphery of the shaft 4 for connecting the ports 2 as one unit at the inner periphery of the elastic member 1.
Moreover, the metal washer 11 and the fixture 12 may be integrally formed. There is no particular limitation on the configuration of the fixture 12 except that it should have a smaller diameter than the elastic member 1. In the drawings, a reference A represents rock or other object to be crushed, and a reference B represents a hollow formed in the object A to be crushed. The internal diameter of the hollow B is considerably larger than the external diameter of the elastic member 1. The crushing device comprising the elastic member 1 and the shaft 4 is inserted into the hollow B for use.
As is clear from the foregoing description, in the crushing device of the present invention, the elastic member 1 has the looped pockets 3 formed between the inner and outer peripheral surfaces thereof. The looped pockets extend towards the opposite ends of the elastic member 1 and have ports 2 at the inner peripheral surface. Member 1 is sleeved over the outer periphery of the shaft 4, provided with the passage 6 for the pressure fluid on the central axis thereof, such that at least the inner peripheral surfaces at the opposite ends of the elastic member 1 are in close contact with the shaft 4. The elastic rings 10, harder than the elastic member 1, are brought into contact with the elastic member 1 at the opposite end faces, and further, the elastic member 1 and the elastic ring 10 are adhesively covered with the cover tube 13 at the outer periphery thereof. Moreover, each metal washer 11 of a smaller diameter than the cover tube 13 is pressed against an end face of the elastic member 1 by a fixture 12 smaller in diameter than the metal washer 11 and acting from outside at the end portion of the elastic ring 10 and the cover tube 13. Therefore, when the crushing device of the present invention is inserted into the hollow B in the object A to be crushed as shown in Fig. 3, and a pressure fluid is sent into the passage 6 formed in the shaft 4 from a supply source T (not shown) by a pump P, the pressure fluid L flows out to the looped pockets 3 of the elastic member 1 through the ports 2, thereby expanding the elastic member 1, as shown in Fig. 5, owing to the pressure of the fluid supplied into the looped pockets 3. This expansive force enables crushing of the object A to be crushed such as a rock or concrete having scanty resiliency, without generating blasting noises. Furthermore, the generation of vibrations and/or dust which is inevitable with the crushing operation can be remarkably limited, thus ensuring the safety in the crushing operation. Moreover, when the pressure within the looped pockets 3 becomes high due to the injection of the pressure fluid in the crushing opration, the elastic member 1 at the side of the outer peripheral surface is subjected to an outward expanding action, while at the same time, the inner peripheral part of the elastic member 1 is loaded with such force as to press the inner peripheral wall 1A against the outer periphery of the shaft 4. In this way, the inner peripheral portion of the elastic member 1, at the opposite ends thereof, is firmly and closely adhered to the outer periphery of the shaft 4, such that the pressure fluid can be effectively prevented from leaking. Furthermore, the elastic ring 10, which is harder than the elastic member 1 and is in contact with the end face of the elastic member 1, is pressed against the elastic member 1 by the fixture 12 of a smaller diameter than the elastic ring 10, acting through the metal washer 11. Accordingly, the expansion of the elastic member 1 towards the end faces thereof, because of the injection of the pressure fluid can be prevented by the elastic ring 10. At the same time, since the elastic ring 10 is made of an elastic material, the elastic ring 10 is able to follow the expansion of the elastic member 1.
Therefore, even if the end face of the outer periphery of the elastic ring 10 protrudes towards the metal washer 11 backed up by the fixture 12, the elastic member 1 can work normally, without any extraordinary change in the configuration thereof, thereby improving the durability of the elastic member 1. Further, this crushing device of the present invention displays a lot of useful effects, for example, capability of repeated use, with replacement of the elastic rings 10 only.
The rock breaking device according to the present invention may be modified, in addition to in the first embodiment, into various embodiments as will be described hereinbelow.
A crushing device shown in Fig. 7 comprises an elastic member 1 of a cylindrical configuration which has a looped pocket extending towards each end portion from ports 2 formed at the inner peripheral surface thereof, a shaft 4 provided with a fluid passage which has an outlet at the inner peripheral surface of the elastic member 1, said elastic member 1 being sleeved on the outer periphery of said shaft 4, and a cover sheet 15 in the form of a flexible sheet of tubular shape which is wound around the whole outer periphery of the elastic member 1 in place of the cover tube 13 employed in the first embodiment.
The sheet 15 wound around the outer periphery of the elastic expansive member 1 is provided in order to prevent the elastic member 1 from being damaged by being pressed directly against the object to be broken such as rock, when in use, that is, when it is expanded within the hollow B formed in the object to be broken. For the purpose of meeting the expansion of the diameter of the elastic member 1, the cover sheet 15 is formed into a spiral shape, or it is wound up such that at least both end portions of the protective sheet are overlapped around the elastic member 1. For this cover sheet 15, there are favourably employed such flexible sheets as metal sheet, plastic sheet, fiber woven sheet or non-woven cloth.
As is clear form the above description, the crushing device according to the present embodiment is so constructed that the elastic member 1 of a cylindrical shape provided with looped pockets 3 extending towards the end portions from openings formed at the inner peripheral surface is sleeved over the outer periphery of the shaft 4 having the fluid passage 6 with the outlet 5 opening at the inner peripheral surface of the elastic member 1, with the cover sheet 15 of a flexible sheet being wound around the outer periphery thereof. Accordingly, when a pressure fluid is injected from a fluid supply source (not shown) into the fluid passage 6, the elastic member 1 expands in the direction of the outer diameter thereof, the force of which expansion acts on the object to be broken, through the cover sheet 15, and therefore, the object to be broken such as a rock A can be broken with reduced amount of noise and vibrations. Moreover, since the inner peripheral wall of the looped pockets 3 is pressed against the shaft 4 through injection of the fluid into the looped pocket 3, the elastic member 1 is closely adhered to the shaft 4 with increased strength, and accordingly, the pressure loss of the fluid can be prevented with assured prevention of leakage of the pressure fluid in the axial direction of the elastic member 1.
In addition, even when there is a crack in the wall of the hollow into which the rock breaking device is inserted for breaking or crushing the object by the use of the expansive force of the elastic member 1, or a crack is formed at the moment of fracture, a possible type of damage is effectively prevented. Because the cover sheet 15 is wound around the outer periphery of the elastic member 1, it prevents the possibility of a part of the outer peripheral surface of the elastic member 1 entering the crack, and thereupon being damaged by so entering the crack. This improves the service life of the elastic member 1.
A crushing device shown in Fig. 8 does not employ the cover tube 13 which is used in the crushing device of the first embodiment. Specifically, the crushing device of Fig. 8 is constructed in such manner that an elastic member 1 which has looped pockets 3 formed between the inner and outer peripheral surfaces of the elastic member 1 and extending towards the opposite ends of the elastic member 1 is sleeved onto the outer periphery of the shaft 4 provided with fluid passage 6 at the central portion thereof so that at least the inner peripheral surfaces of the elastic member 1 at the opposite ends thereof are in close contact with the shaft 4. Furthermore, the elastic rings 10, harder than the elastic member 1, are brought into pressed contact with the opposite end faces of the elastic member 1 by the fixtures 12 which have smaller diameter than the elastic ring 10.
According to a further embodiment shown in Fig. 9, the crushing device is characterised in that the cover tube 13 is integrally formed with the elastic member 1 at the outer peripheral surface of the elastic member, as a reinforcement material 16. Simultaneously with this, a spring washer 17 of conical type is employed in place of the elastic ring 10 of the first embodiment. In other words, both the elastic member 1 embedded in the outer periphery of the shaft 4 and the shaft 4 are, according to this embodiment, screwed into male screws provided at the end portions of the shaft, and integrally formed into one unit at a predetermined position by a fixture 12 which has the spring washer 17 inserted between the nut and the elastic member 1 so that the spring washer is in contact with the end face of the elastic member 1, and therefore, the member 1 can be prevented from expanding in the axial direction thereof when in use. The deformable spring washer is, of course, harder than the elastic member 1.
As for the above-described extensible reinforcing material 16 embedded at the outer periphery of the elastic member 1, a bias cord, woven fabric, wire-netting or other extensible synthetic fiber cloth may be used, which should be embedded into the shape of a cylinder in parallel relation to the outer peripheral surface of the elastic member 1, to prevent localised expansion of the elastic member 1.
As is fully described in the foregoing description, since the crushing device of the present embodiment is reinforced by the reinforcing material 16 embedded at the outer peripheral region of the elastic member 1, localised expansion of the member 1 is resisted. Even when there is exists a crack or crevice in the crushing device itself or in the hollow B into which the crushing device is inserted for the process of breaking the rock or the like by the utilization of the expansion pressure of the elastic member 1, or even when a part of the outer peripheral surface of the elastic member 1 enters the above crack, the elastic member 1 is effectively prevented from locally expanding to a burst. This is of advantage to improve the service life of the elastic member. Moreover, the crushing device of the present embodiment has a practical advantage that only the elastic member 1 needs to be exchanged for a fresh one in the event that it is damaged.
A crushing device of Fig. 10 employs both the spring washer 17 of Fig. 9, and the flexible cover sheet 15 of Fig. 7.
A crushing device of Fig. 11 has the cover sheet 15 shown in Fig. 10 further covered with an elastic tube 13 such as, for example, a rubber tube. According to this embodiment, the elastic cover tube 13 is expanded in diameter simultaneously with the expansion of the elastic member 1 when in use, and at the same time, the former is reduced in diameter simultaneously with the contraction of the elastic member 1 when the crushing operation is completed. Therefore, the crushing device of the instant embodiment is advantageous in that the tube 13 prevents it from remaining wedged within the hollow B, with the protective cover sheet 15 still expanded in diameter, when it is desired to remove the crushing device after the completion of the breaking or crushing operation.
Referring now to Fig. 12, there is shown a still further embodiment of crushing device wherein the cover sheet 15 is fixedly fastened at both ends thereof by the metal washer 11 and the fixture 12, acting through the encircling elastic ring 10 made of, for example, synthetic resin, the outer periphery of which is covered with the cover tube 13.
In Fig. 13, a crushing device is shown in accordance with yet a further embodiment. An elastic moulded member 18 of a tubular configuration, functioning as the cover tube 13 covering the cover sheet 15, is integrally formed with the elastic rings 10. Member 18 extends over the whole outer peripheral surface of the elastic member 1, and both the cover sheet 15 and the moulded member 18 are fastened to the surface of the elastic member 1 by the metal washer 11 and the fixture 12. In the present embodiment as in other embodiments described earlier, the moulded member 18 and the cover tube 15 increase in diameter concurrently with the expansion of the elastic member 1 in the crushing operation, while they reduce in diameter simultaneously with the contraction of the elastic member 1, and accordingly, they are easily removed out of the hollow B after the completion of the rock breaking operation. The moulded member 18 may be of harder material than the elastic member 1.
As is clear from the foregoing description, the above embodiments of rock-breaking device of the present invention comprise a cylindrical elastic member 1 provided with at least one pair of encircling pockets 3 associated with port(s) 2 and a metal shaft 4 on which said elastic member 1 is sleeved. The outer peripheral surface of the shaft is in close communication with said port(s) of the elastic member. The pockets 3 encircle the shaft 4. Deformable members, such as elastic rings 10 are mounted onto said shaft 4 in touch with the end faces of the elastic member 1. A fluid injection passage extends axially within the metal shaft 4 from one end thereof, to communicate with the looped pockets formed between the inner and outer peripheral surfaces of the elastic member. By injecting a fluid into the looped pockets through the fluid passage, the elastic member is expanded in the direction of an outer periphery thereof, and accordingly, the elastic member expands only in the transverse, e.g. radial direction of the hollow formed in the rock or concrete while being restrained from expanding in the longitudinal direction thereof by the elastic rings and/or other parts secured to the shaft at each end of the elastic member 1. Thus, in the crushing device of the present invention, the rock or concrete can be easily broken or crushed by a large pressure produced in proportion to the area of the outer periphery of the elastic member by the pressure fluid pressed into the looped pockets. Moreover, since the rock or concrete is broken merely by injecting a fluid by a pump into the looped pockets after insertion of the crushing device into the previously formed hollow cavity, the breaking or crushing operation can be carried out speedily, without causing such unfavourable influences to the operational environments as noise and/or vibrations.
Furthermore, since the device of the present invention is able to be reused, the rock breaking or crushing operation can be performed highly efficiently and ecnomically.
Although various embodiments of the present invention have been described by way of example with reference to the accompanying drawings, it should nevertheless be appreciated that numerous further changes and modifications can be made.

Claims

1. A rock or concrete breaking device, to be inserted into a previously formed hollow in rock or concrete, for breaking the rock or concrete on the application of fluid pressure to the device, comprising:-
a shaft, a length of which is provided internally with a fluid passage extending axially within the shaft, one end of which passage opens at the end of the shaft to be connected to a pressure fluid source, while the other end of the passage is provided with an outlet opening, which opens to the outside in a central portion of the outer peripheral surface of the shaft;
an elastic member made of expandable material in cylindrical shape having an outer diameter suitable for insertion into the hollow in the rock with a small clearance, and an inner diameter capable of receiving the shaft therein in a tightly engaged relationship therebetween, and provided with at least a pair of pockets each disposed within a portion of the elastic member between its axial ends, opposite to the other in the axial direction of the elastic member and expandable by pressure fluid received therein, said pockets having at least one port on the inner surface of the elastic member in such a manner that pressure fluid supplied from the said outlet opening of the shaft flows into the pockets through the port(s) without discharging to the outside; and
a pair of fixtures each mounted on the shaft at respective ends of the elastic member so as to prevent the elastic member from expanding along the axial direction of the shaft beyond the fixtures;
whereby the elastic member is constrained to expand only in its radial direction, so as to break the rock or concrete when pressure fluid is supplied into the said pockets of the elastic member.

2. A device as defined in claim 1, further comprising: a pair of elastic rings each having almost the same diameter as that of the elastic member and interposed between a respective fixture and the elastic member so as to protect the elastic member from expanding beyond the fixture.

3. A device as defined in claim 2, wherein the said elastic rings are made of material harder than the elastic member.

4. A device as defined in claim 3 wherein the end of each elastic ring, proximate the elastic member, tapers axially from a smaller diameter closer to the adjacent said fixture to a larger diameter further from said fixture.

5. A device as defined in any one of the preceding claims, further comprising a cover tube for covering the whole outer periphery of the elastic member so as to reinforce the strength of the elastic member.

6. A device as defined in claim 5, wherein said cover tube is made of materials including reinforcing elements therein.

7. A device as defined in any one of claims 1 to 3, further comprising a cover sheet for covering the whole outer periphery of the member so as to reinforce the strength of the elastic member.

8. A device as defined in claim 7, wherein said cover sheet is made of a sheet of flexible material.

9. A device as defined in any one of the preceding claims, wherein said elastic member includes reinforcing wires embedded therein at a position close to the outer periphery.

10. A device as defined in any one of the preceding claims, wherein said elastic member is provided with a pair of metal rings each embedded at a respective end portion of the elastic member for preventing the elastic member from wrapping at the end poriton.