AU722226B2 - Apparatus for underground drilling - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: i Name of Applicant: Tracto-Technik Paul Schmidt Spezialmaschinen Docullents recoived on Actual Inventor(s): Franz-Josef Puttmann Frank Prutti Andreas Riekes Bernhard Kaufmann Address for Service: 3 (9 V1R 12 ;9 Batch No: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: APPARATUS FOR UNDERGROUND DRILLING Our Ref 577061 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- 2 "Apparatus for underground drilling" The invention relates to an apparatus for underground drilling, in particular for making or widening microtunnels and/or for replacing old pipework and for laying new pipework, consisting of a push-pull unit and a linkage in driven connection therewith and guided through the microtunnel or the pipework.

The making or widening of microtunnels and/or the replacement of old pipework and the laying of new pipework can be undertaken by means of pneumatic impact moles which dynamically generate the forward movement, or by means of jacks which generate a static pressure and drive or pull the .linkage forwards. Dynamically acting pneumatic impact moles entail the disadvantage that they cause loud noises during operation and can cause damage due to vibrations in the surrounding area, especially to other piping parallel to or crossing the microtunnel and release oil-containing waste air which pollutes the environment.

The statically acting jacks and winches are cumbersome to handle and can be used either for pushing only, with a linkage which is rigid when pushed, or for pulling, with the use of cables.

The linkage which is rigid when pushed has to consist of individual short linkage parts, since the pushing apparatus generally operates from a narrow pit or a small shaft. Gradually, as each linkage section corresponding to the diameter of the pit or of the shaft is forced into the soil or old pipework, the linkage has to be extended by the addition of a new linkage section. Since manhole shafts generally have an internal diameter of 1 m, the linkage sections often cannot be longer than 80 cm.

3 If winches are used to pull a widening apparatus by means of a cable through an existing microtunnel, the cable initially has to be threaded through this microtunnel or existing pipework, which is impossible with flexible cables.

In order to force a linkage into the earth by means of a pushing apparatus, the apparatus has to engage directly on the linkage, for which purpose clamping jaws are used which engage on the external surface of the linkage.

Since the application of force by means of the clamping jaws takes place by non-positive fitting, slippage under elevated soil resistance is inevitable, in view of the smooth surface of the linkage, resulting in wear and, as a consequence, even greater slippage. If the linkage is pulled or pushed through old pipework, in order to destroy the piping, dirt depositing on the linkage results in additional abrasion to the clamping jaws and the linkage, which facilitates slippage.

The existing linkages have threaded connections which are extremely sensitive to soiling. This applies even to coarse-pitch threads, which suffer from the additional disadvantage that they tend to break under elevated tensile stresses and with small radii of curvature. A further disadvantage of i'T ~threaded connections lies in the fact that a linkage section has to be Sunscrewed or screwed on approximately every 80 cm; this requires at least seven-fold to ten-fold rotation even with high thread pitches. With linkage lengths of 100 m, approximately 125 individual linkage sections have to be screwed together, with a corresponding expenditure of time.

Finally, linkages to be pressed stepwise into the earth possess the disadvantage that they are not each fixed in the earth between the individual steps of the forward movement and, accordingly, generally recoil to a greater or lesser extent under the action of the earth on the drilling head at the front end of the linkage. In this way, the advance of the linkage is shortened, at every stroke, to a greater or lesser extent depending on the composition of the earth. Since this happens after each forward step, and since a great 4 many steps are necessary when drilling over longer distances, the recoil inevitably leads to a substantial loss of performance.

This loss of performance is not only noticeable when the apparatus is being used for drilling, but also when, for example at the end of a pilot drilling operation or after a pipe has been laid in the earth, the drilling head is replaced by a widening or clearing head and this is drawn back through the pilot drilling or the pipework to the launch pit because in the case of widening, too, the earth exerts an action on the pulling linkage counter to the direction of movement of the widening or clearing head and the abovementioned recoil takes place.

The object of the invention is to improve an apparatus of the type mentioned .i initially in such a manner that it is suitable both for the pushing and for the pulling of a linkage and avoids wear resulting from slippage of the push-pull unit on the linkage. A further object of the invention is to avoid the loss of performance resulting from the abovementioned recoil of the linkage when making a drilling with a clearing head and/or when widening a pilot drilling, or in the destructive replacement of pipework laid in the earth by means of a bursting head.

This object is achieved by a drilling apparatus having a push-and-pull drive, a linkage in driven connection therewith, coupling means of the drive engaging on the linkage and a linkage locking system.

The linkage locking system according to the invention fixes the linkage, for example a ladder-type linkage, after each forward step or stroke, when the coupling means of a linear drive releases itself from the linkage at the state of advancement achieved. The linkage locking system consists preferably of two mutually opposing retaining jaws or of a locking pawl which is lowered automatically after passing over, for example, the rung of a ladder-type linkage and engages behind the rung, until the rung moves on in the direction of advance during the next stroke.

The locking pawl can be so arranged that it can be pivoted through approximately 180' and, accordingly, exerts its locking action in both directions of the ladder-type linkage. This is readily possible if the locking pawl possesses, for example, two stopping faces arranged at an angle with respect to each other between which a stopping lug extends by means of which the locking pawl is supported in one or the other direction on a ladder rung.

When the linkage is moved in the working direction, the locking pawl is preferably moved outwards by the ladder rungs or linkage projections over a ramp, whereby their action is disabled.

The linkage preferably consists of individual sections which can be connected to each other via a plug-in coupling. The plug-in coupling may be such that it permits a degree of lateral play and, accordingly, steered drilling along a curved line. This is possible because the lateral play between the individual linkage sections has a cumulative effect such that drilling is possible on a curved track which, over relatively long distances, covers an angle of up to 900.

A frame of the apparatus is preferably telescopic and may possess an end plate which is guided in the frame via struts. The end plate serves as a support for the apparatus when, with the aid of the linkage, the clearing head is pulled through a pilot drilling or an ground-laid pipe towards the frame.

The end plate may be provided with a slide, which closes an aperture in the end plate. The aperture in the end plate offers the possibility that the clearing head, after it has moved through the pilot drilling or an ground-laid pipe, can completely leave the earth; in doing so, it moves, together with any earth and fragments of pipework destroyed by it which may be pushed in front of it, into the clear space between the end plate and the frame of the apparatus.

There, the clearing head can readily be released from the linkage, and from any follow-up pipe, without damaging the microtunnel created by it.

Since the clearing head is customarily used at the same time to pull new pipework, in the form of a follow-up pipe, into the widened microtunnel, a connection between the clearing head and the front end of the follow-up pipe is required. In the case of a follow-up pipe wound into a bundle, customarily of polyethylene, it is difficult because of the curvature of the pipe end caused by the winding and its powerful recoil to produce a sufficiently secure connection to the clearing head.

S:The invention provides a remedy here in the form of an articulated connection of at least three linkage sections which are connected to each other via, in each case, pivot pins extending at right angles to one another. In this manner, what is generally a type of universal joint is produced, with the aid of which the front end of the pipe can easily be drawn into the microtunnel created by the clearing head.

The linkage may possess projections and/or recesses, and the push-pull unit may possess positive-fitting coupling means which engage on these :.projections or in the recesses. The coupling means prevent slippage when the linkage is being pushed or pulled, so that the full performance of the push-pull unit can be utilized without excessive wear being caused to the linkage or the coupling means. The linkage may be designed as a rack or in the form of a ladder with rungs or may have annular or spiral grooves. The coupling means may engage as a pinion into the rack or the rungs of the ladder-type linkage or the annular or spiral grooves, or may consist of at least one latch member engaging into the rack or the annular or spiral grooves or onto the rungs or projections, so that the linkage can be moved 7either continuously by means of the pinion driven in rotation by the push-pull unit or stepwise with a linear drive by the push-pull unit.

The linkage may be composed of individual linkage sections with positive fitting and so as to be rigid when pushed, or may be designed merely for pulling as an articulated chain.

If the linkage consists of individual sections connected to each other, it is advantageous if these have at one end an aperture limited by transverse walls and at the other end a coupling head having a lug engaging through the aperture of a section to be coupled and a lug engaging under the transverse wall, a recess engaging over the other transverse wall and a lug engaging under the other transverse wall on the outside under the action of S.pushing.

This type of coupling permits simple connection of the linkage sections, which may also be carried out automatically and requires no insertion of a mandrel or screwing together of the linkage sections.

By means of such a quick-action coupling head, the individual linkage sections, if they are pushed far enough into the earth or drawn far enough out of the earth, can be coupled and uncoupled to and from each other by a S. simple plugging action without this requiring a great expenditure of time and effort or interrupting the work of advancement for a relatively long period.

Preferably, the transverse walls have cut-outs adapted to the lugs engaging under them.

If the linkage sections are of ladder design, which means that they possess one or more struts, the transverse aperture may lie between the last and the penultimate rung, and rungs serving as transverse walls may limit the cutouts for the lugs. If, on the other hand, the linkage sections are of solid 8 design with regularly spaced recesses for the coupling means on at least one side, the transverse aperture can be arranged at one end of a linkage section, while a coupling head is provided at the other end.

Another method of connecting the linkage sections to each other is an arrangement wherein the linkage sections possess, at each end, a matching bayonet coupling head made from a longitudinal tab corresponding to about half the width of the section and having a recess at the front, outward end of the tab and a matching lug on the linkage section parallel to the tab and are provided with a transverse pin on the longitudinal tab of one linkage section and a matching transverse drilling in the longitudinal tab of the other section.

"i The drillings are so dimensioned that the transverse pin of one linkage section can be plugged into the transverse drilling, in an angled position of :the two linkage sections, and, after pivoting the linkage section that has been attached into an extended, flush position, are locked by the lugs engaging into the recesses.

00:0 In this manner, it is always possible, if a linkage section is pushed sufficiently far into a drilling or pipework, to attach a new linkage section obliquely to the S"rearward end of the last linkage section and, by pivoting, lock it into the extended position aligned with the other parts of the rod. When the linkage is being pulled, the analogous procedure can be adopted, a linkage section that has been pulled sufficiently far being released from its locking to the remaining parts of the rod by being pivoted back out of the extended position into an angled position.

If the transverse pin is displaceable within the transverse drilling towards the longitudinal axis of the linkage sections the bayonet coupling heads, under the action of pushing, engage into one another in a manner such that the linkage sections are coupled together with positive fitting and so as to be rigid when pushed.

9 If the push-pull unit consists of a linearly movable drive member and if the linkage has a thread at least at its end which can be coupled with positive fitting to the push-pull unit, the coupling means may consist of at least two radially movable gripping jaws engaging into the thread.

If, on the other hand, the linkage sections are designed as a rack or in the form of a ladder or with annular or spiral grooves, the latch member may consist of at least one transversely movable locking pawl coupling the pushpull unit In the drive direction to the linkage sections or an articulated chain.

A linearly movable push-pull unit must perform a return stroke after the "i working stroke. During this stroke, however, the linkage must not move or recoil; it is therefore advantageous if a locking pawl, movable transversely to the linkage and coupling or clamping the linkage contrary to the driving direction, is arranged on a non-movable part of the push-pull unit.

The invention is explained in detail below with reference to examples of embodiment shown in the drawing, in which: gi. shows the drilling apparatus in the course of making a S .pilot drilling, Eiq-2 shows a detailed lateral view of a push-pull unit and the linkages in driven connection therewith, Eiq 3 shows a linkage locking system according to the invention with retaining jaws, Eia shows a linkage locking system in the form of a simply acting locking pawl, shows a telescopic frame, 10 Fi. 6 shows a cardanic link consisting of a plurality of linkage sections in a lateral view and ig. 7 in a plan view of the connection according to Fig. 6, i 8 shows two linkage sections during coupling, iJg. 9 shows a plan view of other linkage sections coupled to one another, Eig. 10 shows a lateral view of the linkage sections according to S*Fig. 9, Fig. 11 shows a plan view of yet other linkage sections before they are coupled together, Sig. 12 shows a lateral view of the linkage sections according to Fig. 11 during coupling, Fi.. 13 shows the linkage sections according to Fig. 11 in the coupled state, Fig. 14 shows linkage sections of a further embodiment in the uncoupled state, Fig. 15 shows the linkage sections according to Fig. 14 in the coupled state and Fig 16 shows a drilling apparatus consisting of a push-pull unit and a ladder-type linkage in driven connection therewith in the destructive replacement of old pipework.

11 Fig. 17 shows a circuit diagram for the automatic control of the linear drive for the push-pull unit.

By means of the apparatus according to the invention, a drilling 2 is driven by steps into the earth 1, starting from a launch pit 3. To this end, a push-pull drive 4 is located in the launch pit 3. Its stationary mounting 5 is supported by means of an end plate 6 on the face of the earth 1 located in the direction of advance and is retained by means of one or more soil anchors 7. A coupling means 11 is connected to a carriage 9 and is so arranged that, during the pushing movement of the carriage, it engages behind a rung and, in this manner, drives the linkage consisting of the sections 14 by steps into the earth.

I: The mounting 5 is connected to a linear motor in the form of a preferably dual-action hydraulic piston/cylinder unit 8, having a piston 48 whose cylinder spaces 49, 50 are connected via two hydraulic lines 51, 52 having a 3/4-way valve 53, to a pressure medium source 54. From the hydraulic line 52 a branch line 55 leads via a shuttle valve 56 to the hydraulic line 51. The 9 shuttle valve 56 is connected via a line 57, with a manometer 58, to a control unit 59 from which two control lines 60, 61 lead to the 3/4-way valve 53.

The automatic control for the advancing trolley, shown in Fig. 17, operates by a method in which the pressure rise taking place shortly before the dead centre position of the piston 48 in the two cylinder spaces 49, 50 is converted by means of the manometer 58 into a signal for the control unit 59, which then switches the 3/4-way valve via the lines 60, 61 so that the cylinder space in which the pressure rise takes place is provided with hydraulic oil and the piston 48 begins its movement in the opposite direction.

Arranged on the mounting 5 is a hydraulic piston/cylinder unit 8 which reciprocally moves the carriage 9. Pairs of guide bolts 10 in the carriage 9 12 serve to guide the sections 14 of the drilling linkage. Other linkage sections 14 are connected to the linkage section 14 retained in the carriage 9 via a plug-in coupling.

The linkage sections 14 consist, in the manner of a ladder, of rungs 15, 16, 17 and parallel struts 18.

At one end of each linkage section 14 is the coupling head 19 of a rapidaction or plug-in coupling which interacts with the penultimate rung 16 and the last rung 17 of the neighbouring linkage section 14. The coupling head ~19 is provided with an approximately L-shaped recess 20, which engages over the last rung 17, while a lug 21 on the coupling head 19 engages into a cut-out 24 on the penultimate rung 16 and a lug 22 engages into a cut-out S. on the last rung 17. The coupling head is so dimensioned here that the connection between neighbouring linkage sections 14 possesses a degree of play which permits a linkage movement along a curved path.

In the making of a microtunnel 2 by the stepwise pressing into the earth of the linkage, consisting of individual sections 14, with a drilling head 13, a locking system 12 serves to fix the linkage axially when the carriage 9 returns to its starting position after completing its forward stroke.

The linkage locking system 12 consists, as shown in Fig. 3, of a frame with a retaining jaw 26 and two guide plates 27 with apertures 28 for the ladder linkage 14. A clamping jaw 29 is guided between the plates 27 and is pressed against the ladder linkage in the forward stroke cycle of the piston of a hydraulic cylinder (not shown).

Another linkage locking system 12 is shown in Fig. 4; it likewise consists of a frame with two mutually opposite apertures 28 in the plates 27 accommodating the linkage and possesses a locking pawl 32 mounted pivotably on a pin 31 whose stopping edge 33 comes to lie in a locking 13 manner against a linkage rung, while an oblique portion 34 of the locking pawl 32 slides in the opposite direction over the rungs.

A strut 36 is guided in a linearly movable manner in the frame 35 of the push-pull drive 4 at each of the corner points of a quadrilateral. The struts 36 support the end plate 6, in which there is an aperture 37 (cf. Fig. This aperture can be closed with the aid of a slide 38 and permits the passage of a clearing head pulled through a pilot drilling or an ground-laid old pipe into the free space 39 between the end plate 6 and the frame 35. In this free space, the clearing head can be separated without particular difficulties from the linkage 14 and from a new pipe pulled by it into the earth, which then projects out of the earth to a certain extent and can therefore be effortlessly connected to an adjoining new pipe.

The end plate 6 can readily be moved out with the aid of the linkage 14 after the insertion of a bolt 40 between two rungs 15, 16, 17.

The new pipe is drawn in with the aid of a connection consisting of at least ~three linkage sections 14, which are connected to each other via pivot pins 41 extending in each case at an angle of 90 to each other (Figs. 6, In this manner, a cardanic connection is produced between the new pipe and the clearing head, which substantially facilitates the drawing-in of the front end of the pipe into the microtunnel created by the clearing head.

If a linkage section 14 is pressed so far into the microtunnel 2 that the penultimate rung 16 is situated shortly in front of the end plate 6, approximately in the position shown in Fig. 1, the upper guide bolts 10 are drawn out from the mounting 9 and a further linkage section 14 is, as shown in Fig. 8, coupled to the preceding linkage section 14. This is achieved in that the new linkage section 14 to be coupled on is guided, with the lug 21 of its coupling head 19 in an angled position, through the transverse aperture between the penultimate rung 16 and the last rung 17 and then pivoted -14downwards into the extended position shown in Figs. 1, 2, aligned with the preceding linkage sections 14. Thereafter, the upper guide bolts 10 are again inserted into the carriage 9, and the stepwise advance by means of the push-pull unit 4 begins again, until the new linkage section 14 has again almost disappeared within the microtunnel 2.

As a consequence of the thrust acting on, in each case, the last linkage section 14, the lugs 21, 22 push forward within the cut-outs 24, 25 on the penultimate and last rungs 16, 17; they thus ensure a coupling between the linkage sections 14 which is rigid when pushed. At this time, each lug 21, 22 engages under a rung 16, 17.

Figs. 9 and 10 show linkage sections 42 of solid design and having lateral projections 43 on which coupling means can engage for the advance of the linkage, similarly to the coupling means 11, 12 according to Figs. 1 to 4.

A coupling head 19 is arranged at one end of each linkage section 42 and is provided with a recess 20 and lugs 21, 22, while at the other end there is a transverse aperture 25 which is limited by rungs 15 so that the coupling head 19 can be inserted through this transverse aperture 25 for coupling with a further linkage section 42 and subsequently pivoted.

The lug 21 then engages into the transverse aperture 25, so that in this embodiment also a coupling is guaranteed which is rigid when pushed.

Figs. 11 to 13 show a further embodiment of a coupling between linkage sections which is rigid when pushed. These linkage sections again are of ladder-type design; however, only the parallel longitudinal struts 18 and a cut-out 46 adjoining bayonet coupling heads 44, 45 are shown. The bayonet coupling head 44 is designed as a tab extending in the longitudinal direction of the linkage section and having a thickness of approximately half the width of the linkage section. The end of the bayonet coupling head 44 is provided 15 with a recess 47, which interacts with a matching lug 48 on the neighbouring linkage section. The bayonet coupling head 44 possesses a transverse pin 49, which interacts with a transverse drilling 50 on the bayonet coupling head It is apparent from Fig. 11 that the bayonet coupling heads 44, 45 are of matching design, so that, in the position shown in Fig. 12, the transverse pin 49 can be inserted into the transverse drilling 50 and the linkage sections can be brought into the extended, i.e. aligned, position by pivoting and locked there (cf. Fig. 12).

If the transverse drilling 50 is designed as a slot, a slight relative displacement may occur under the action of pushing on the linkage sections, which brings the mutually perpendicular surfaces of the bayonet coupling heads 44, 45 to rest against each other, so that the linkage sections are connected to each other so as to be rigid when pushed.

Figs. 14 and 15 show linkage sections 51 which possess a round cross section and are provided at one end with a conical external thread 52 and at the other end with a drilling 53 having a conical internal thread 54. The linkage sections 51 can thus be simply screwed together and, in this manner, form a linkage which is rigid when pushed. The coupling means of the pushpull unit can engage into the recesses 55, designed as annular grooves.

Instead of the annular grooves, spiral grooves may also be arranged on the external surface of the linkage sections 51.

In order, as shown in Fig. 16, to replace old pipework 56 with new pipework 57, linkage sections 14, progressively coupled together to form a linkage, are pushed, for example from a manhole shaft 58, through the old pipework 56 to a neighbouring manhole shaft (not shown). A bursting head 59 is then coupled to the coupling head 19 of the last linkage section 14, while the successive linkage section 14, which Is In the manhole shaft 58 in the region 16 of the push-pull unit 4, is drawn by the hydraulic piston/cylinder unit 8 into the manhole shaft 58 in order to displace the carriage 9. In this manner, the old pipework 56 is fragmented by means of the bursting head 59; at the same time, an expanded microtunnel 60 is produced and a new line, connected to the bursting head 59, is drawn into the microtunnel 60 in the form of a followup pipe 57.

In order to make it possible to pull the linkage consisting of the linkage sections 14, the coupling means 11, 12 and locking pawls 32 are shown twisted through 180* by comparison with the illustration in Fig. 1.

In order to assist the fragmentation of the old pipework 56, a hydraulically S* driven mole 61 may be arranged in the bursting head 59, to which mole a pressure medium is fed via pressure medium line 62 in the follow-up pipe 57.

The impacts of the mole 61 cause rapid fragmentation of the old pipework 56.

Instead of the mole 61, or in cooperation therewith, extensible cutters may be arranged on the bursting head 59, these applying locally intensified, powerful forces on the old pipework 56 by means of a radial movement and destroying this pipework.

Claims (29)

1. Apparatus for the making or widening of microtunnels and/or for the fragmentation of old pipework, and for the laying of new pipework underground, having a push-and-pull drive a linkage (14) in driven connection therewith, coupling means (11) of the drive engaging on the linkage, and a linkage locking system (12, 32).

2. Apparatus according to Claim 1, characterized in that the linkage locking system (12, 32) possesses a retaining jaw (26) and a movable clamping jaw (29).

3. Apparatus according to Claim 1, characterized in that the linkage locking system (12) consists of a locking pawl (32).

4. Apparatus according to one of Claims 1 and 2, characterized in that the linkage consists of individual sections (14) coupled together with lateral play. Apparatus according to one of Claims 1 to 4, characterized in that the push-and-pull drive is provided with a frame

6. Apparatus according to one of Claims 1 to 5, characterized in that an end plate is guided in the frame (35) via struts (36).

7. Apparatus according to Claim 5 or 6, characterized in that the end plate is provided with an aperture (37) and a slide (38). 18

8. Apparatus according to one of Claims 1 to 7, characterized in that the linkage is provided with projections (43) and/or recesses (20, 24,

9. Apparatus according to Claim 8, characterized in that the linkage (14) is designed as a rack.

10. Apparatus according to Claim 8, characterized in that the linkage (14) is of ladder design.

11. Apparatus according to Claim 8, characterized in that the linkage (14) has annular or spiral grooves

12. Apparatus according to one of Claims 1 to 11, characterized in that the linkage (51) possesses a thread (52, 54) at least at its end capable of being positively coupled to the push-and-pull unit

13. Apparatus according to one of Claims 8 and 9 to 11, characterized in that the coupling means consist of a pinion engaging with the linkage and driven to rotate by the push-pull unit.

14. Apparatus according to one of Claims 8 and 9 to 12, characterized in that the coupling means consist of a latching and unlatching latch member (11, 12, 33) engaging on at least one projection (15, 43) or in a recess (20, 25, 46, 55) and driven linearly by the push-pull unit Apparatus according to one of Claims 9, 10, 11 and 13, characterized in that the linkage (14) consists of linkage sections (14, 42) which can be coupled via a plug-in coupling so as to be rigid when pushed. -19

16. Apparatus according to one of Claims 1 to 15, characterized in that the plug-in coupling consists of a male and a female coupling member which can be connected so as to be rigid when pushed by lengthwise displacement and rotation of the linkage (14) about an axis substantially perpendicular to the linkage axis.

17. Apparatus according to Claim 16, characterized in that the linkage sections (14, 42) possess at one end a transverse aperture (20, 24, and at the other end a coupling head (19) with a lug (21) passing e. through the transverse aperture (20, 24, 25) of a linkage section (14, 42) to be coupled and engaging under a transverse wall a recess (20) engaging over the other transverse wall (17) and a lug (22) engaging under the other transverse wall (17) on the outside under the action of pushing.

18. Apparatus according to Claim 17, characterized in that the transverse walls (16, 17) possess cut-outs (24, 25) adapted to the lugs (21,22) engaging under them.

19. Apparatus according to Claim 15 or 17, characterized in that the linkage sections (14) are of ladder design, the transverse aperture (20) lies between the last and penultimate rungs (15, 16, 17) forming the transverse walls, and the rungs define the cut-outs (20, 24, 25) for the lugs. Apparatus according to Claim 15 or 17, characterized in that the linkage sections (42, 51) are of solid design with regularly spaced projections (43) on at least one side for the coupling means (11, 12, 32).

21. Apparatus according to Claim 15, characterized in that the linkage sections (42) possess, at each end, a matching bayonet coupling 20 head (44, 45) made from a longitudinal tab corresponding to about half the width of the linkage section (14) and having a recess (47) at the front, outward end of the tab and a matching lug (48) on the linkage section parallel to the tab and are provided with a transverse pin (49) on the longitudinal tab of one linkage section and a matching transverse drilling (50) in the longitudinal tab of the other linkage section, which are so dimensioned that the transverse pin (49) of one linkage section can be plugged into the transverse drilling in an angled position of the two linkage sections, and, after pivoting into an extended, flush position, are locked by the lugs (48) engaging into the :recesses (47).

22. Apparatus according to Claim 21, characterized in that the transverse pin (49) is displaceable within the transverse drilling towards the longitudinal axis of the linkage sections (14) and, under the action of pushing, the bayonet coupling heads (44, 45) engage into one another in a manner such that the linkage sections (14) are coupled together with positive fitting and so as to be rigid when pushed.

23. Apparatus according to one of Claims 14 to 22, characterized in that the latch member consists of at least one transversely movable locking pawl (11) interacting in the drive direction of the push-pull unit with the linkage sections (14, 42, 51).

24. Apparatus according to one of Claims 14 to 22, characterized in that a transversely movable locking pawl (12) locking the linkage sections (14, 42, 57) counter to the drive direction is arranged on a non- movable part of the push-pull unit VI 21 Apparatus according to one of Claims 1 to 24, characterized by at least three linkage sections (14) whose neighbouring pivot pins (41) in each case extend at right angles to each other.

26. Apparatus according to one of Claims 1 to 25, characterized by a remote control for the push/pull unit.

27. Apparatus according to one of Claims 1 to 26, characterized in that the carriage and/or the hydraulic cylinder is connected to end switches to reverse the hydraulic cylinder.

28. Apparatus according to Claim 27, characterized In that the hydraulic lines (51, 52) are connected to the two cylinder spaces (49, 50) of the hydraulic cylinder (48) via a 3/4-way valve (53) with a pressure medium source and, between the hydraulic lines, branch lines are connected via a shuttle valve (56) to a manometer (58) measuring the respectively current pressure, the manometer switching the 3/4- way valve via a control unit (59) when the maximum pressure is reached and thus connecting one or the other hydraulic line to the *pressure source. I

29. Method for coupling two linkage sections (14, 42, 51), characterized in that the linkage section (14) to be coupled is positioned obliquely relative to the other linkage section (14) and is plugged by means of a lug (21) arranged at the front end (19) into a transverse aperture 24, 25) in the other linkage section and is then pivoted into an extended position with the other linkage section. Method according to Claim 29, characterized in that the linkage sections (14) are locked together by axial pushing after being pivoted. 22

31. Method according to Claim 29 or 30 for making or widening microtunnels and/or for replacing old pipework and for laying new pipework, wherein, by means of a push/pull unit, a linkage consisting of individual sections and in driven connection therewith is progressively pushed or pulled through the microtunnel or through the pipework and, after each step, a section is coupled to the linkage or removed from the linkage.

32. Method according to Claim 31, characterized in that the linkage is fixed in the axial direction after each step.

33. Method for inserting and/or pulling linkages, characterized in that the carriage of the push/pull drive moves automatically and reciprocally.

34. Method according to one of Claims 29 to 33, characterized in that the push/pull unit is operated from a remote control device. DATED: 30th March, 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: TRACTO-TECHNIK PAUL SCHMIDT SPEZIALMASCHINEN 2