LINING UNDERGROUND DUCTS

This invention relates to the lining of underground ducts.

In my co-pending Applications Nos.83 15982 and 84 31174 I disclose apparatus and methods for enlarging or profiling an existing sewer to accept a lining or new pipe. It is convenient to attach a new pipe to the rear of the enlarging or profiling apparatus so that a separate pass through the existing bore is avoided. However, when the new pipe is fed into the bore in sections, the friction between the pipe and the sides of the bore is often such that excessive stain is placed on the connections between the pipe sections, particularly when the distance between manholes is relatively large and a long pipe has to be towed by the device as it approaches the end of the bore.

This invention avoids placing excessive tension on the pipe connections by providing a method in which the cable or chain previous- ly attached to the forward end of the enlarging or profiling device is instead fed through the device and through the pipe sections to a rearward pipe section where it is secured by, for example, a plate or fork fitted to the rear end of the pipe. This has the effect of putting the pipe connections under compression rather than tension, so that the pipe sections are held together as the profiling device and the pipe are pulled through the bore. Weaker, and hence less expensive, pipe sections can therefore often be used.

According to another aspect of the invention, there is provided apparatus for lining an underground duct, wherein the apparatus comprises a device having an expandable portion for removing irregularities in or enlarging the duct and having a plurality of radially movable leaf members forming a segmented outer shell, and drive means for driving the leaf members from a retracted configur¬ ation outwardly from a longitudinal axis of the apparatus to an expanded configuration, wherein the apparatus is arranged so as to provide a substantially unobstructed axial passage for allowing a chain, cable or the like to pass through the complete length of the apparatus.

In certain circumstances the amount of friction resisting the movement of the profiling device and new pipe may be such that the tension required on the chain or cable is sufficient to cause the pipe to flex sideways and jam in the bore. To overcome this, in one embodiment of the invention a towing chain is temporarily secured to the profiling device. This may be achieved by including a clamp inside the profiling device, operable by remote control using, for example, a small hydraulic ram. Thus, each time as new pipe section is to be added to the rear end of the new pipe, all tension on the chain is released and the plate removed. The new section is attached to the pipe and the plate refitted. As tension is applied by a winch at the forward end of the bore, the clamp is .operated when the tension reaches a predetermined level, to limit the compression of the pipe sections, and any increase in tension above this figure is applied directly to the profiling device.

The clamp preferably comprises a pivotable stop member arranged such that in an operative position its end engages the chain by, for example, pinching it against the surface of a chain guide in the machine or by entering one of the chain links. The stop member is coupled to the ram, the force applied to the stop member and hence the chain being controlled by the fluid pressure fed to the ram.

In a preferred embodiment the clamp acts as a ratchet, movement of the chain in one direction being completely prevented, but movement in the opposite direction being permitted when the force pulling the chain in that direction exceeds a value determined by the ram pressure.

The invention will now be described by way of example with reference to the drawings in which:-

Figure 1 is a sectional diagram of an underground sewer in the process of enlargement and lining;

Figure 2 is a partly sectional view of apparatus for- enlarging the duct and housing the front end portion of a lining pipe section; and

Figure 3 is a more detailed diagrammatic view of the apparatus showing a device for clamping a towing chain.

Referring to Figure 1, a hydraulically powered profiling apparatus 10 expands the bore of an existing sewer 12 to allow a new lining pipe comprising a plurality of interconnected pipe sections 14 to be pulled into the sewer behind the apparatus 10. ^• The apparatus 10 is in two main parts 10A and 10B to give it sufficient length to avoid the tendency of deviating from the required centre line, yet allowing separate insertion of the two parts into the sewer using a manhole 16 of limited width. The forward part 10A of the apparatus comprises apparatus as described in my co-pending Patent Application No.84 31174 the disclosure of which is incorporated herein by reference. Referring to the partly sectioned side view of Figure 2, this part 10A is bolted or otherwise connected to the rear part 10B which is a tube having the same diameter as the maximum diameter of the front part 10A and an inside diameter slightly greater than the outside diameter of the pipe sections 14 to allow the leading pipe section to move axially inside the rear part 10B. Alternatively the leading pipe section may be clamped to the apparatus 10. A chain 18 passes through the whole apparatus 10 and the pipe sections 14 to be attached to a winch (not shown). A trapdoor opening 24 provides access to nuts 26 which hold the rear part 10B to the front part 10A.

Referring to Figure 3, the front part 10A of the apparatus has a body portion 10C housing a ram 28 which drives a set of pivot- able leaf members 10D radially outward by means of connecting links 30. The leaf members 10D form an inner part of an expandable portion of the machine, their front ends being pivotally attached to a second set of leaf members 10E forming the outer part of the expandable portion. These outer leaf members are in turn pivoted on a nose piece 10F.

The ram 28 is different from that shown in my Application No.84 31174 in that it has an opening centred on the longitudinal

axis of the machine to allow the chain 18 to pass through the machine as shown. The ram cylinder 28A is annular, as is its piston 28B, the latter being coupled to a ring 32 sliding on an axial tube 34 which encloses the chain 18. As an alternative, the ram 28 may be replaced by two or more rams arranged off-axis and each coupled to the ring 32.

To enable the chain 18 to be gripped in the machine 10, the body portion IOC houses a short hydraulic ram 36 pivotally mounted on the outer wall of the body portion IOC, the piston rod being pivotally attached to a stop member 38. In the drawing the stop member

38 is shown in its operative position with its free end bearing against the chain 18 between two links so that the chain is pinched between the stop member and an opposing support in the form of chain guide 40. It will be noted that, subject to the force applied by the clamping ram 36, the angle of the stop member, as determined by the position of its pivot, is such that movement of the chain 18 forwardly

(to the right) relative to the machine is prevented completely since movement in that direction serves only to increase the clamping or pinching force. Rearward movement of the chain is, however, possible provided that the resultant rearward force on the chain is sufficient to overcome the force exerted by the clamping ram 36.

The clamping device allows the lining of a sewer as follows. The plastics lining pipe sections 14 are attached one by one at the entrance to the sewer as the machine 10 and lining pipe move through the sewer. The chain 18 extends from the winch through the apparatus 10 and through the lining pipe section 14 to a plate or fork 42 placed over the end of the rearmost pipe section. Each time a new pipe section is fitted to the rear end of the pipe, tension on the chain 18 is released, the plate or fork 42 removed, the chain 18 threaded through the new section, and the plate or fork 42 placed over the rear end of the new section.

The apparatus 10 is now operated to expand the leaf me ebers outwards and tension applied to the chain with the stop member 24 raised. The pipe is now under compression, having butted up against a shoulder or end plate of the rear part 10B of the apparatus 10, and

it can be towed through the duct behind the apparatus 10. It has been found that too large a compressive force can cause the pipe to snake and thus jam in the duct. This can be detected by an increase in chain tension at the winch end, and the snaking can be largely pre- vented if the compression of the pipe is limited. The clamping device disclosed in the present application allows the correct compressive force to be applied in a relatively simple manner. By operating the clamping ram 36 to bring the stop member 38 to bear against the chain 18, and adjusting the fluid pressure in the ram 36 to a predetermined value, the winch can be stopped and tension on the chain 18 ahead of the apparatus 10 reduced to allow the chain 18 to move rearwardly past the stop member 38 until the tension in the chain behind the machine has reduced to the value (determined by the clamping ram pressure) at which no further movement past the stop member 38 takes place. The lining pipe is now under limited compression, and subsequent operation of the winch pulls both apparatus 10 and pipe sections 14 forward without further forward movement of the chain 18 relative to the apparatus 10. With only limited compression applied to the pipe sections 14, snaking can be largely avoided. The whole assembly moves forward step by step as described above until the profiling apparatus 10 emerges at the opposite end of the sewer.

The invention is not restricted to the use of a chain. A cable, wire or rope can also be used, in which case the clamp or gripping means may be modified to achieve the best clamping effect.