AU1546099A

AU1546099A - Percussion boring machine

Info

Publication number: AU1546099A
Application number: AU15460/99A
Authority: AU
Inventors: Alfons Hesse
Original assignee: Tracto Technik GmbH and Co KG; Tracto Technik Paul Schmidt Spezialmaschinen KG
Current assignee: Tracto Technik GmbH and Co KG
Priority date: 1998-02-07
Filing date: 1999-02-08
Publication date: 1999-09-02
Anticipated expiration: 2019-02-08
Also published as: DE19804919A1; GB2334053B; DE19804919C2; AU749893B2; GB2334053A; GB9902760D0

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: o e* Name of Applicant: Tracto-Technik Paul Schmidt Spezialmaschinen Actual Inventor(s): Alfons Hesse Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: PILE-DRIVE BORING IMPLEMENT Our Ref 570516 POF Code: 1282/308317 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- "Percussion boring machine" The invention relates to a percussion boring machine for the production and widening of boreholes in the ground, the destructive replacement of underground pipelines or ramming pipes or the like into the ground.

Percussion boring machines of this kind have proved extraordinarily useful; they are used in particular for trenchless laying of pipelines and comprise, like the machine known from German patent specification 21 57 259, a housing having an impact tip which can be fitted in the housing to move against the force of a spring. However, in place of the movable impact tip a tool mounted to move in the impact tip can be used. In the machine housing there is a reciprocating 15 striking piston, which is moved periodically to and fro between a forward and a rear end position or reversing position under the influence of a pressure medium supplied through a pipeline. Such percussion boring machines usually have a control sleeve adjustable mechanically, electrically or by means of a pressure medium to change the machine over from forward to reverse travel.

In the case of forward travel the impact piston imparts its kinetic energy to a front striking face of the housing, or in the case of reverse travel to a rear striking face of the housing. The front striking face may comprise an internal collar of the housing and have a central passage through it in 9 which the rear end of a longitudinally movable tool is guided.

When this is the case, the striking piston imparts its energy first to the tool and then the balance of it to the internal collar or to the housing.

In each case the striking faces of the housing, of the tool and also of the striking piston are subjected to extraordinarily high mechanical stresses. Thus in the case of large machines the impact energy may be as much as 10 000 joules. With a striking rate of 180 to 600 blows/minute this leads eventually to deformation of the striking faces and consequently to a correspondingly limited working life of the machine.

It is therefore the object of the invention to increase the life at least of the particularly stressed front striking face and hence of the percussion boring machine.

To this end, the invention provides that at least the more stressed, front striking face has a higher hardness than the housing. This can be achieved by plating, by hardening or by the use of an insert having a higher hardness, while the housing and also the striking piston normally consist of a steel having a lower hardness but greater toughness.

Although the striking piston can be replaced at less expense in the case of wear on its striking faces, at least its front striking face should have a higher hardness than the body of the piston.

Irrespective of the nature of the striking faces, the 15 machine housing may comprise a front and a rear part which are Sconnected together by a butt weld. This offers advantages in the manufacture of the housing, since the rear part of the housing can be made from a simple tube, while the front part with the striking face must be made from solid material. A further advantage comes from the fact that the front part or its striking face can be hardened before joining the parts of the housing, while the other part is left untreated or is S• given some other heat treatment.

The chisel can be guided by means of a collar in a bore in a housing having a front and a rear stop which limit the :stroke of the chisel and be provided with a peg which projects **,into the working chamber of the striking piston. If the Sprojecting length of the peg is shorter than the maximum stroke of the collar up to its front stop, the method of operation of the either one-piece or two-piece percussion boring machine, when it is used in soft ground, can be improved. For after the chisel has been moved forwards by an amount corresponding to the projecting length of the peg, in the case of a percussion boring machine having a housing tip screwed into the main housing the striking piston meets the then fully closed front face of the housing tip, so that the impact energy is received over a large surface, and jarring blows no longer occur. The front stop is not reached by the striking piston, for the collar has merely come nearer to the stop by the amount of the projecting length of the pin, without being able to come up against the front stop.

The invention will now be described in more detail, by way of example, with reference to an embodiment shown in the accompanying drawings, in which: Fig. 1 shows schematically a percussion boring machine, partly in section, Fig. 2 shows the front part thereof, formed in accordance with the invention, and Fig. 3 shows another embodiment of the front part.

The construction and operation of the percussion boring machine correspond in principle to those of the machine described in German patent specification 21 57 295. It has a housing 1 with a front part 2 into which an impact tip is 15 screwed, and a striking piston 3. The striking piston 3 has in o. its rear part a compressed air chamber 4 with radial control openings 5 and is guided in the machine housing 1 to move longitudinally along a control pipe 6. When it meets an internal collar 7 of the machine housing 1 it imparts its S 20 impact energy thereto. In the rear part of the machine housing there is a stop ring 8 through which the control pipe 6 projects and is connected on the far side of the stop ring with a compressed air hose.

In place of the screwed-in impact tip with the tool 10, a head which is axially movable or is fixed to the housing part 2 may be used. However, a screwed-in impact tip has the advantage that in case of wear it can be quickly replaced.

When the machine is advancing the striking piston 3 moves to and fro under the influence of the compressed air supplied to the striking piston chamber 4 through the compressed air hose 9 and the control pipe 6: it imparts its impact energy substantially exclusively to the internal collar 7. Only in the relatively rare event of a reversal of the direction of movement (reverse travel) becoming necessary is the striking piston 3 controlled so as to strike the stop ring 8 with its rear end. This is described in more detail in German specification 21 57 295.

In the front part 2 of the housing with the impact tip a tool 10 is axially movably guided with its rear end 12 'Q40jprojecting through the internal collar 7 having the striking face 13. The tool 10 is supported on the impact tip or on the machine housing 1 as the case may be by means of a collar 14 and a prestressed spring The internal collar 7 has a hardened surface 13 and accordingly a higher resistance to wear and deformation than the material from which the front part 2 of the housing is made. In the same way the striking piston 3 also has a hardened surface 16, although this is not essential, since it is possible to exchange the striking piston in the event of its front face becoming worn. To do this it is only necessary to unscrew the stop ring 8 with the control pipe 6 from the housing.

Furthermore, the rear, annular striking face 17 of the piston 3 and the opposed striking face 18 of the stop ring 8 15 are hardened, although this is not essential, since the machine is only exceptionally operated so as to travel S backwards. Consequently the faces 17, 18 are subjected to far less mechanical stress than the striking faces 13, 16.

The housing consists independently of the nature of the striking faces of two parts which are joined together by a weld 19, though it may be formed in one piece.

In the percussion boring machine shown in Fig. 3 the main housing 1 is provided at its front end with an internal screw thread 20 into which a housing tip 21 is screwed by means of a peg-like extension of the thread 22. In an axial bore 23 of the housing tip 21 a chisel 10 formed at its front end as an impact tip 10 is guided. The impact tip 9 is provided with a stepped head which is fixed to the chisel 10 by means of pins 24. The pins 24 pass through the housing bore 25 of the housing tip 21.

In the housing bore 25 a collar 26 of the chisel 10 is also located: in the starting position shown the collar 26 touches the rear stop 27 defined by the housing bore 25. A peg 28 of the chisel 10 extends through the threaded extension 22 of the housing tip 21 and projects into the working space 29 of the striking piston 3. The projecting length 30 of the peg 28 is shorter than the maximum stroke 30 of the chisel 10 in the direction of impact 32; the length of stroke 30 is given by the distance which the chisel collar 26 could theoretically ,.cover from the rear stop position shown to the pins 24 which simultaneously define the front stop. However, since the projecting length 30 is shorter than the length of stroke 31, the striking piston 3 strikes directly on the front face 33 of the housing tip 21 after a stroke of the chisel corresponding to the projecting length 30. The chisel 10 can then not move any farther forward, and the collar 26 cannot reach the pins 24 or the front stop 14.

Again, the front striking face or front face 33 is hardened.

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Claims

2. A percussion boring machine according to claim 1, wherein said striking face (13, 33; 16; 17; 18) is hardened.
3. A percussion boring machine according to claim 1 or claim 2, wherein said striking face (13, 33; 16; 17; 18) is :15 provided with an insert.
4. A percussion boring machine according to any preceding claim, wherein the front striking face (13, 33) has a oo through passage for the rear end (12) of a tool movably guided in the tip of the machine.
5. A percussion boring machine according to any preceding claim, wherein the front and/or the rear striking face (16; 17) of the piston has a higher hardness than the body of the piston.
6. A percussion boring machine, particularly one according to any preceding claim, wherein the housing comprises a front and a rear part and the parts of the housing are welded together.
7. A percussion boring machine according to any of claims 4 to 6, wherein the tool (10) is guided by means of a collar (26) in a housing bore (23) having a front and a rear stop (12, 27) and is provided with a pin (28) projecting into the working chamber of the striking piston and wherein the projecting length (30) of the pin is shorter than the maximum stroke length (31) of the collar (26) between the stops (12, 27) DATED: 22 April, 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: EC TRACTO-TECHNIK PAUL SCHMIDT SPEZIALMASCHINEN