GB2026572A

GB2026572A - Pneumatic percussion tool

Info

Publication number: GB2026572A
Application number: GB7827195A
Authority: GB
Original assignee: Institut Gornogo dela Sibirskogo Otdelenia Akademii Nauk SSSR
Current assignee: Institut Gornogo dela Sibirskogo Otdelenia Akademii Nauk SSSR
Priority date: 1978-06-17
Filing date: 1978-06-17
Publication date: 1980-02-06
Also published as: DE2825732A1; AT353185B; FR2433395B1; FR2433395A1

Abstract

A pneumatic percussion tool comprises a hollow cylindrical body 1 with a nut 3 which covers the open end of the body and has longitudinal channels 12 opening at one end 13 on the internal cylindrical surface of the nut, and a stepped ram 2 having an axial channel 9 and at least one inter-communicating radial channel 10, said ram reciprocating inside the body so that the front portion of said ram forms, together with the walls of the body, a reverse-stroke chamber 5 which is in communication periodically through channels 7, 9, 10 with a line of compressed air 4 which acts on the ram to retract it, air from the chamber 5 then escaping through channels 14, 15, 8. The external surface of the smaller-diameter step of the ram, the internal surface of the body, the end face of the nut and the face of the larger-diameter step of the ram form an annular space 6 which is charged with compressed air through channels 7, 11, 12, the ram 2 then striking the body 1, and used compressed air then being vented at 8. <IMAGE>

Description

SPECIFICATION Pneumatic percussion tool The present invention relates to percussion devices and more particularly, to pneumatic percus sion tools.

The invention will be used to the best advantage for driving wells through compacted ground.

It can also be useful for driving pipes, earthing electrodes, wooden and metallic slotted piles into the ground.

In accordance with the present invention, we provide a pneumatic percussion tool comprising a hollow cylindrical body with a nut which covers the open end of the body and has longitudinal channels opening at one end on the internal cylindrical surface of the nut and a stepped ram having an axial channel and at least one intercommunicating radial channel, said ram reciprocating inside the body so that the front portion of said ram forms, together with the walls of the body, a reverse-stroke chamber which is in communication periodically through said channels of the stepped ram with a line of compressed air which acts on the ram for dealing a blow followed by the discharge of air through discharge holes, the larger-diameter step of the ram being provided with longitudinal channels whereas the external surface of the smaller-diameter step of the ram, the internal surface of the body, the end face of the nut and the face of the larger-diameter step of the ram form an annular space which is periodically vented to the atmosphere. According to the invention, in said tool the smaller-diameter step of the ram interacting with the nut has at least one radial port arranged so that during forward stroke of the ram the compressed air is fed through said radial port of said ram and the longitudinal channel of the nut into said annular space.

Such a design raises the impact power of the tool because the entire cross-section area of the ram is subjected to the pressure of compressed air.

To improve operational reliability it is expedient that the larger-diameter step of the ram, closer to its smaller-diameter step, should have a circular recess receiving the open ends of the longitudinal channels of the larger-diameter step for communicating the reverse-stroke chamber with the atmosphere.

It is also expedient that the ram should be provided with an additional channel one end of which should open on the cylindrical surface of the largerdiameter step whereas its other end should open on the cylindrical surface of the smaller-diameter step of the ram and the smaller-diameter step should be provided with ports opening into said additional channel.

This ensures the discharge of the used air through the nut and thus dispenses with the side holes in the body which improves the strength of the latter.

Besides, in this manner there is no need in the protective housing which is installed on the body to keep dirt out of the tool space.

Simplicity of the design is achieved by forming the additional channels with the aid of a recess on the smaller-diameter step of the ram and by a cylindrical sleeve installed rigidly over said recess on the smaller-diameter step, said cylindrical sleeve having air admission and discharge holes.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which; Fig. 1 is a longitudinal section of a pneumatic percussion tool in accordance with the invention; Fig. 2 is a section taken along line ll-ll in Fig. 1; Fig. 3 shows a version of the tail portion of the pneumatic percussion tool in which a circular recess is made in the smaller-diameter step of the ram at the point of the radial port, with a partial cut-out; Fig. 4 shows a longitudinal section through a modified pneumatic percussion tool wherein the ram is provided with an additional channel for discharging the compressed air through the end portion of the ram;; Fig. 5 shows a longitudinal section through another modified pneumatic percussion tool wherein the additional channel is formed buy a recess on the smaller-diameter step and by a cylindrical sleeve installed rigidly over said recess on the smaller-diameter step of the ram; Fig. 6 is a section taken along line Vl-VI in Fig. 5; and Fig. 7 is a section taken along line VII-VII in Fig. 5.

The pneumatic percussion tool in accordance with the invention comprises a hollow cylindrical body 1 (Fig. 1) accommodating a stepped ram 2, and a nut 3 which covers the open end of the body 1 and serves for connecting a compressed air line 4. Said line 4 is connected to a source of compressed air (not shown in the drawing) of any conventional type, e.g. a compressor.

The ram 2 consists of two interconnected cylindrical steps, the front step being larger in diameter. The front portion of the larger-diameter step of the ram 2 and the walls of the body 1 form a reverse-stroke chamber 5. The cylindrical surface of the smallerdiameter step of the stepped ram 2, the face of the nut 3 andtheface of the larger-diameter step of the ram 2 form an annular space 6. The faces of the smaller-diameter step and of the nut 3 form a rear working chamber 7 which is in constant communication with the compressed air line 4.

The side walls of the body 1 have discharge holes 8 located at such a distance from the front end of the body 1 as to ensure the discharge of compressed air from the reverse-stroke chamber 5 when the ram 2 is in the rearmost position as shown in Fig. 1.

The stepped ram 2 has an axial channel 9 and a radial channel 10 communicating with the axial channel, both being intended to deliver compressed air into the reverse-stroke chamber 5 from the rear working chamber 7. The radial channel 10 opens on the cylindrical surface of the larger-diameter step.

The smaller-diameter step is provided with a radial port 11.

The nut3 has longitudinal channels 12 (Figs. 1,2) opening on the internal face surface of the nut 3 (Fig.

1) at one end and on its cylindrical surface interact ing with the ram 2 at the other. The nut 3 has a recess 13 receiving its admission channel 12.

The recess 13' can also be made on the stepped ram 2 (Fig. 3) in which case the radial port 11' opens into said recess. The surface of the larger-diameter step of the ram 2 (Fig. 1) is provided with longitudi nal channels 14 which open at one end into the reverse-stroke chamber 5, and with a circular recess 15 located closer to the smaller-diameter step of the ram 2 and receiving the other ends of the longitudinal channels 14. The body 1 has a recess 16 located in the front portion of the body 1. To ensure the discharge of compressed air through the end portion of the tool and to improve the strength of the body 1" (Fig. 4), the stepped ram 2" is provided with an additional channel 17 one end of which opens on the cylindrical surface of the larger-diameter step whilst its other end opens on the cylindrical surface of the smaller-diameter step of the ram 2".Fig. 4 shows the additional channel 17 made by drilling. At the side of the rear chamber 7" the additional channel 17 is closed with a plug 18. The smaller-diameter step of the stepped ram 2" is provided with ports 19 and 20 opening into said additional channel 17. The body 1" has a recess 21 located in its middle portion, approximately. The nut 3" has a discharge channel 22 for discharge of the compressed air, one end of said channel opening on the external face surface of the nut 3" whilst its other end opens on its cylindrical surface interacting with the smaller-diameter step of the ram 2".

To simplify the design of the tool and reduce the forces of friction between the cylindrical surface of the smaller-diameter step of the stepped ram 2" ' (Fig. 5) and the nut 3" ', the additional channel 17" ' of the stepped ram 2" ' can be formed by the recess 23 on the smaller-diameter step and by a cylindrical sleeve 25 rigidly fixed over said recess 23 on the smaller-diameter step of the ram 2"', said sleeve having a hole 25 (Fig. 5, 6) coinciding with the port 11"' of the stepped ram 2" ' for admitting compressed air into the annular space 6" ', and discharge holes 26 (Fig. 5, 7) and 27 (Fig. 5) opening into the additional channel 17" 'of the stepped ram 2"' for discharge the compressed air out of the reversestroke chamber 5"' and annular space 6"'.

The percussion tool according to the invention functions as follows.

As compressed air is supplied from the line 4 (Fig.

1) into the rear working chamber 7, it flows through the axial channel 9 and the radial channel 10 of the stepped ram 2 into the reverse-stroke chamber 5.

Owing to the difference of areas of the face surfaces of the ram 2 directed to the rear working chamber7 and reverse stroke chamber 5, said ram starts mov ing towards the nut 3. During its movement the radial channel 10 is covered by the internal surface of the body 1 so that the further movement of the ram 2 will be effected due to expansion of compres sed air in the reverse-stroke chamber 5. At the end of the stroke of the stepped ram 2, its circular recess 15 gets aligned with the hole 8 in the side walls of the body 1 and puts the reverse-stroke chamber 5 in communication with the hole 8 of the body 1 through the longitudinal channel 14 on the largerdiameter step of the ram 2. The compressed air escapes into the atmosphere from the reverse stroke chamber 5 through the longitudinal channel 14 of the ram 2 and the hole 8 in the body 1.

At the end of the stroke of the ram 2 the radial port 11 on the smaller-diameter step of the ram 2 gets in line with the recess 13 of the nut 3. Compressed air flows from the axial channel 9 of the ram 2 through the radial port 11, the recess 13 of the nut 3 and the longitudinal channels 12 of the same nut into the annular space 6 and acts on the entire face surface of the ram 2. Being pressed by the compressed air contained in the rear working chamber 7 and in the annular space 6,tha stepped ram 2 stops and starts moving forward. At a preset distance from the beginning of motion of the stepped ram 2 its radial port 11 on the smaller-diameter step is covered by the internal surface of the nut 3 whilstthe recess 13 of the nut 3 is covered by the smaller-diameter step of the ram 2.Further movement of the stepped ram 2 is effected due to the energy of the expanding air in the annular space 6 and the pressure of compressed air in the rear working chamber 7. At the end of the forward stroke (foremost position of the ram 2 shown in Fig. 1) the ram 2 strikes the body 1. At the same time the ram 2 uncovers the holes 8 in the side walls of the body 1 and the used compressed air is expelled into the atmosphere from the annular space 6. The radial channel 10 of the stepped ram 2 opens into the recess 16 in the front part of the body 1 thereby putting the reverse-stroke chamber 5 in communication with the rear working chamber 7.

The compressed air flows from the supply line 4 into the rear working chamber 7 and, through the axial channel 9 and the radial channel 10 of the ram 2, enters the reverse-stroke chamber 5. Then the working cycle is repeated over again.

The circular recess 13 of the nut 3 (Fig. 1) and the circular recess 23 (Fig. 5) on the smaller-diameter step of the stepped ram 2" ' as well as the circular recess 15 (Fig. 1) on the larger-diameter step of the stepped ram 2 are necessary in order to maintain uninterrupted admission of compressed air into the annular space 6 (Fig. 1) and 6" ' (Fig. 5) and discharge of compressed air from the reverse stroke chamber 5 (Fig. 1) and 5" ' (Fig. 5) into the atmosphere in case the stepped ram 2 (Fig. 1) and 2"' (Fig.

5) turns around the longitudinal axis.

If the tool is realized as shown in Fig. 4, it functions in a similar manner exceptforthe fact that the compressed air is discharged from the reverse-stroke chamber 5" and annular space 6" through the rear end of the tool, passing through the additional channel 17 of the stepped ram 2" and the discharge channels 22 of the nut 3".

In the position shown in Fig. 4 the compressed air flows through the axial channel 9" and the radial channel 10" of the stepped ram 2" into the reverse stroke chamber 5". In this period the annular space 6" is vented to the atmosphere through the port 19, additional channel 17, port 20 of the stepped ram 2" and the discharge channel 22 of the nut 3".

The compressed air acts on the face surface of the smaller-diameter step of the stepped ram 2" directed to the rear chamber 7" and on the face surface of the larger-diameter step of the stepped ram 2" directed to the reverse-stroke chamber 5".

Due to the difference in the areas of the faces of the steps of the stepped ram 2" the latter begins to move towards the nut 3". In the course of its movemenu the port 19 gets in line with the recess 13" of the nut 3" whilst the longitudinal channel 14" on the larger-diameter step of the stepped ram 2" opens into the recess 21 of the body 1". The additional channel 17 of the ram 2" also opens into the same recess 21. The compressed air escapes into the atmosphere from the reverse-stroke chamber 5" through the longitudinal channel 14" of the ram 2", the recess 21 of the body 1" the additional channel 17 and the port 20 of the stepped ram 2" and through the discharge channel 22 of the nut 3".

At the same moment the radial port 11" of the ram 2" gets in line with the recess 13" of the nut 3" and the compressed air enters the annular space 6" from the rear working chamber 7" through the axial channel 9", the port 11" of the ram 2", the recess 13" and the admission channel 12" of the nut 3". Being acted upon by compressed air in the rear working chamber 7" and annular space 6", the stepped ram 2" stops and begins to move forward to strike the body 1".

At the end of the stroke of the ram 2" its port 20 gets in line with the admission hole of the channel 22 and the compressed air escapes into the atmosphere from the annular space 6", through the port 19, additional channel 17, port 20 of the ram 2" and the discharge channel 22 of the nut 3".

Compressed air enters the reverse-stroke chamber 5" and the cycle is repeated over again.

This layout of the tool makes it possible to make a solid body 1" without side holes which improves its strength. Besides, this makes it possible to dispense with the protective housing installed on the body 1" to keep dirt out of the spaces of the ram 2", this promotes the reliability in service.

If the tool is realized as shown in Fig. 5, it operates in a similar manner as the version illustrated in Fig.

4. The compressed air is discharged into the atmosphere from the annular space 6" ' (Fig. 5) through the hole 26 of the sleeve 24, the additional channel 17" ' formed by the walls of the stepped ram 2" ' and of the cylindrical sleeve 24, through the hole 27 of the cylindrical sleeve 24 and the discharge valve 22"' of the nut 3" '.The compressed air contained in the reverse-stroke chamber 5" ' is discharged into the atmosphere through the longitudinal channel 14" ' of the ram 2" ',the recess 21'" of the body 1'", additional channel 17' ",the hole 26 in the cylindrical sleeve 24 and the discharge channel 22' " of the nut 3"'.

The compressed air is admitted into the annular space 6' " from the rear chamber 7' " through the axial channel 9' ", the port 11"' of the ram 2" ', the air admission hole 25 of the cylindrical sleeve 24, the recess 13" ', and the admission channel 12' " of the nut 3" Such a layout adds to simplification of the design.

Claims

1. A pneumatic percussion tool comprising a hollow cylindrical body with a nut closing the open end of the body and having longitudinal channels opening at one end on the internal cylindrical surface of the nut, a stepped ram with an axial channel and at least one intercommunicating radial channel, said ram being accommodated in said body, being reciprocated by the compressed air and forming by its front portion, together with the walls of said body, a reverse-stroke chamber which is in communication periodically through said channels of the stepped ram with the compressed air line; the surface of the larger-diameter step of the ram is provided with longitudinal channels for communicating said reversestroke chamber with the atmosphere whilst the external surface of the smaller-diameter step of the ram, the internal surface of the body, the face of the nut and the face of the ram larger-diameter step form an annular space which is put periodically in communication with the atmosphere; the portion of the smaller-diameter step of the ram interacting with the nut is provided with at least one radial port arranged in such a manner that in the course of forward movement of said ram compressed air is fed into said annular space from the compressed air line through the radial port of the ram and the longitudinal channel of the nut.

2. A pneumatic percussion tool according to Claim 1 wherein the larger-diameter step of the ram, closer to its smaller-diameter step, has a circular recess communicating with the longitudinal channels of the larger-diameter step for venting the reverse-stroke chamber to the atmosphere.

3. A pneumatic percussion tool according to Claim 1 wherein the ram is provided with an additional channel one end of which opens on the cylindrical surface of the larger-diameter step whilst its other end opens on the cylindrical surface of the smaller-diameter step of the ram and wherein the smaller-diameter step has ports opening into said additional channel.

4. A pneumatic percussion tool according to Claim 3 wherein the additional channel of the ram is formed by a recess made on the smaller-diameter step of the ram and by a cylindrical sleeve installed over said recess on the smaller-diameter step of the ram, said sleeve having air admission and discharge holes.

5. A pneumatic percussion tool realized substantially in accordance with any one of the above Claims as disclosed in the description with reference to the accompanying drawings.