GB2047605A

GB2047605A - Percussion tool

Info

Publication number: GB2047605A
Application number: GB7914525A
Authority: GB
Original assignee: Kone Corp
Current assignee: Kone Corp
Priority date: 1979-04-26
Filing date: 1979-04-26
Publication date: 1980-12-03
Also published as: GB2047605B

Abstract

Percussion tool with a hydraulically reciprocatingly movable piston 1, which strikes against a bit 2 on the end of the percussion tool, the movement of this bit being limited with the aid of a transversal locking pin 3 held by the body of the percussion tool. The locking pin is at its ends in the direction of the blow carried by hydraulic shock absorbers 5. <IMAGE>

Description

SPECIFICATION Percussion tool The present invention concerns a percussion tool comprising a hydraulically reciprocatingly movable piston which strikes against a bit on the end of the percussion tool, the movement of this bit being limited by the aid of a transversal locking pin held by the body of the percussion tool.

Percussion tools of prior art belonging to this type have the drawback that in overhead work, for instance, when working on the roof of a tunnel, such situations are often encountered in which the percussion tool is running but the point of the bit is not abutting on the material to be worked. In such instance the bit will slide under its own weight towards the piston and the piston will impart a blow to it.

The striking movement of the bit is now stopped by the transversal locking pin. Since the locking pin is held by the body, a striking motion in the direction of the stroke is produced on this part of the body. The longitudinal fixing screws of the percussion tool yield enough to set the accurately dimensioned, mutually abutting faces in the body of the percussion tool into small motions with reference to each other as a result of the impacts.

Through this the said surfaces may be damaged either mechanically or due to corrosion, to such extent that leakage and other kinds of trouble ensue.

The present invention may eliminate the said drawbacks. The percussion tool of the invention is characterized in that the locking pin is carred by hydraulic shock absorbers at its ends in the direction of stroke.

By the aid of the invention there will no longer be any so-called blank strokes which are directly transmitted to the body of the percussion tool; instead, such strokes are sufficiently damped by the hydraulic shock absorbers.

A favourable embodiment of the invention is characterised in that the shock absorber consists of an elongated pin-like piston having holes for throttling the flow of the hydraulic fluid and which is movable in a cylindrical space filled with hydraulic fluid. A shock absorber of this type is simple and favourable in manufacture and owing to the radial holes drilled in it the throttling can be made to increase in the direction of the stroke, whereby the damping is highly efficient.

Another embodiment of the invention is characterised in that the cylindrical space communicates with an annular space encircling the piston and which has been connected to the pressurized return system of the percussion tool's hydraulic system. After damping, the piston will therefore owing to the pressure present in the return system be urged back into its initial position, for the next damping operation.

A third embodiment of the invention is characterized in that the cylindrical space contains a helical spring for the returning of the piston. This is another simple design serving to return the piston.

A favourable embodiment of the invention is further characterized in that the shock absorber is a cartridge, attachable by threads to the body of the percussion tool. It is hereby a simple and fast operation to replace a damaged or worn out shock absorber.

The invention is described in the following by the aid of an example with reference to the attached drawing, wherein:- Figure 1 presents the percussion tool, in axonometric view.

Figure 2 shows the section carried along line ll-ll in Fig. 1.

Figure 3 displays a percussion tool according to another embodiment of the invention, sectioned.

The percussion tool of the invention comprises a hydraulically reciprocatingly movable piston 1, which strikes against the bit 2 on the end of the percussion tool, the movement of this bit being limited by means of a locking pin 3 transversal with regard to the bit. The locking pin 3 is carried at its ends by hydraulic shock absorbers 4 in the direction of the blow. The shock absorber 4 consists of an elongated pin-shaped piston 5 having in its cylindrical part throttling holes 11 and movable in a cylindrical space 6 filled with hydraulic fluid. The cylindrical space 6 communicates with an annular space encircling the piston 5, this space being connected by the passage 8 to the pressure-carrying return system of the percussion tool's hydraulic system.

In the embodiment depicted in Fig. 3, a helical spring 11 has been provided in the cylindrical space 6, for the returning of the piston. The shock absorber 4 is a cartridge, attachable to the body 9 of the percussion tool by threads 10.

Since the locking pin 3 of the bit 1 of the percussion tool is carried at its ends in the direction of the blow by hydraulic shock absorbers 4, no more blows directed immedi mately against the body of the percussion tool are experienced. The shock absorbers 4 damp quite sufficiently any blows directed against them if the bit 2 should happen to assume a position in which it slides towards the piston 1 and in which there is in front of its point no material to be hit.

It is obvious to a person skilled in the art that different embodiments of the invention may vary within the scope of the claims following below.

1. Percussion tool with a hydraulically reciprocatingly movable piston (1), which strikes against a bit (2) on the end of the percussion

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Percussion tool The present invention concerns a percussion tool comprising a hydraulically reciprocatingly movable piston which strikes against a bit on the end of the percussion tool, the movement of this bit being limited by the aid of a transversal locking pin held by the body of the percussion tool. Percussion tools of prior art belonging to this type have the drawback that in overhead work, for instance, when working on the roof of a tunnel, such situations are often encountered in which the percussion tool is running but the point of the bit is not abutting on the material to be worked. In such instance the bit will slide under its own weight towards the piston and the piston will impart a blow to it. The striking movement of the bit is now stopped by the transversal locking pin. Since the locking pin is held by the body, a striking motion in the direction of the stroke is produced on this part of the body. The longitudinal fixing screws of the percussion tool yield enough to set the accurately dimensioned, mutually abutting faces in the body of the percussion tool into small motions with reference to each other as a result of the impacts. Through this the said surfaces may be damaged either mechanically or due to corrosion, to such extent that leakage and other kinds of trouble ensue. The present invention may eliminate the said drawbacks. The percussion tool of the invention is characterized in that the locking pin is carred by hydraulic shock absorbers at its ends in the direction of stroke. By the aid of the invention there will no longer be any so-called blank strokes which are directly transmitted to the body of the percussion tool; instead, such strokes are sufficiently damped by the hydraulic shock absorbers. A favourable embodiment of the invention is characterised in that the shock absorber consists of an elongated pin-like piston having holes for throttling the flow of the hydraulic fluid and which is movable in a cylindrical space filled with hydraulic fluid. A shock absorber of this type is simple and favourable in manufacture and owing to the radial holes drilled in it the throttling can be made to increase in the direction of the stroke, whereby the damping is highly efficient. Another embodiment of the invention is characterised in that the cylindrical space communicates with an annular space encircling the piston and which has been connected to the pressurized return system of the percussion tool's hydraulic system. After damping, the piston will therefore owing to the pressure present in the return system be urged back into its initial position, for the next damping operation. A third embodiment of the invention is characterized in that the cylindrical space contains a helical spring for the returning of the piston. This is another simple design serving to return the piston. A favourable embodiment of the invention is further characterized in that the shock absorber is a cartridge, attachable by threads to the body of the percussion tool. It is hereby a simple and fast operation to replace a damaged or worn out shock absorber. The invention is described in the following by the aid of an example with reference to the attached drawing, wherein:- Figure 1 presents the percussion tool, in axonometric view. Figure 2 shows the section carried along line ll-ll in Fig. 1. Figure 3 displays a percussion tool according to another embodiment of the invention, sectioned. The percussion tool of the invention comprises a hydraulically reciprocatingly movable piston 1, which strikes against the bit 2 on the end of the percussion tool, the movement of this bit being limited by means of a locking pin 3 transversal with regard to the bit. The locking pin 3 is carried at its ends by hydraulic shock absorbers 4 in the direction of the blow. The shock absorber 4 consists of an elongated pin-shaped piston 5 having in its cylindrical part throttling holes 11 and movable in a cylindrical space 6 filled with hydraulic fluid. The cylindrical space 6 communicates with an annular space encircling the piston 5, this space being connected by the passage 8 to the pressure-carrying return system of the percussion tool's hydraulic system. In the embodiment depicted in Fig. 3, a helical spring 11 has been provided in the cylindrical space 6, for the returning of the piston. The shock absorber 4 is a cartridge, attachable to the body 9 of the percussion tool by threads 10. Since the locking pin 3 of the bit 1 of the percussion tool is carried at its ends in the direction of the blow by hydraulic shock absorbers 4, no more blows directed immedi mately against the body of the percussion tool are experienced. The shock absorbers 4 damp quite sufficiently any blows directed against them if the bit 2 should happen to assume a position in which it slides towards the piston 1 and in which there is in front of its point no material to be hit. It is obvious to a person skilled in the art that different embodiments of the invention may vary within the scope of the claims following below. CLAIMS

1. Percussion tool with a hydraulically reciprocatingly movable piston (1), which strikes against a bit (2) on the end of the percussion tool, the movement of this bit being limited with the aid of a transversal locking pin (3) held by the body of the percussion tool, characterized inthat the locking pin (3) is at its ends in the direction of the blow carried by hydraulic shock absorbers (4).

2. Percussion tool according to claim 1, characterized in that the shock absorber (4) consists of an elongated pin-like piston (5) having holes (11) forthe throttling of the hydraulic fluid and being movable in a cylindrical space (6) filled with hydraulic fluid.

3. Percussion todl'according to claim 1 or 2, characterized in that the cylindrical space (6) communicates with an annular space (7) encircling the piston (5) and which latter space is connected to the pressurized return system of the percussion tool's hydraulic system.

4. Percussion tool according to claim 1 or 2, characterized in that the cylindrical space (6) contains a helical spring (11) for the returning of the piston (5).

5. Percussion tool according to any one of the claims 1-4, characterized in that the shock absorber (4) is a cartridge attachable tothe body (9) of the percussion tool by threads (10).

6. A percussion tool, substantially as described herein with reference to and as illustrated by the accompanying drawing.