The present invention relates to an apparatus, in particular a pipe- pushing apparatus, for use in laying a length of pipe that is especially but not exclusively part of a replacement pipeline.

Modern utility pipes for water, gas, sewage and the like as well as electricity cable conduits are usually made of plastics, typically polyethylene. They are superior to the formerly used clay pipes as they do not readily crack or split. Conventionally, they are made with a smaller diameter than the pipes to be replaced and are laid by being inserted inside the pipes of an existing pipeline or conduit. This means that the replacement operation can be carried without a trench being dug to expose the full length of the existing pipeline. Instead, pits are dug at intervals along the length of the existing pipeline commensurate with the lengths of the new pipe. The existing pipeline is exposed and opened up in the pits. A length of new pipe is inserted into the pipeline through one pit and pulled through the existing pipeline using cables fed through the pipeline from an adjacent pit. The laid lengths of the new pipe are then coupled together prior to the pits being sealed.

GB2463169 describes a pipe-pushing apparatus comprising a pair of jaws having co-operating pipe-gripping surfaces. A hydraulic actuator is coupled to the jaws so that they can be opened and closed around a length of pipe. The jaws are rotatable about a pivot located above the pipe-gripping surfaces so that the pipe-gripping surfaces grip the sides rather than the top of bottom surfaces of the pipe and the apparatus approaches the pipe from above. One disadvantage of this arrangement is that the pipe can sag under its own weight. This can deform the new pipe and weaken it.

An object of the present invention is to provide a pipe-pushing apparatus for use in laying a length of pipe in an existing pipeline or ducting that is adapted to reduce sagging of the pipe and that places no tensile load on the pipe during insertion.

A further object of the present invention is to provide an apparatus that can be readily adapted to handle a range of pipe diameters.

According to the present invention there is provided a pipe-pushing apparatus for use in laying a length of pipe comprising

a bracket adapted for connection to an arm of an excavator vehicle; a pair of clamping jaws defining an interior clamping profile, an upper clamping jaw of the pair being mounted on the bracket and a lower clamping jaw of the pair being pivotally mounted to the upper clamping jaw along a pivot axis located at one side of the apparatus so that the lower clamping jaw is located beneath the length of pipe when the apparatus is in use; and

at least one ram for opening and closing the clamping jaws that is located on a side of the apparatus opposite the pivot axis, one end of the ram being connected to the upper clamping jaw and the other end of the ram being connectable to the lower clamping jaw to pivot the lower clamping jaw relative to the upper clamping jaw and being disconnectable from the lower clamping jaw to enable the lower clamping jaw to be located beneath the length of pipe.

Preferably, a first set of shims is locatable within the jaws to change the size and/or shape of the clamping profile formed when the jaws are closed.

Preferably also, a plurality of sets of shims is provided to enable the size of the cylindrical profile to be changed to a plurality of different diameters respectively.

Preferably also, the sets of shims nest inside one another. Preferably also, the clamping profile defined by the jaws and/or each of the sets of shims is that of a circular cylinder.

Preferably also, the upper clamping jaw is mounted on the bracket by a swivel unit whereby the clamping jaws are rotatable relative to the bracket.

Preferably also, the other end of the ram is connected to a pin that is releasably engageable in a locking mechanism attached to the lower clamping jaw.

Preferably also, a pair of rams is provided to operate the jaws, each of which rams is connected to respective ends of the pin.

Preferably also, the locking mechanism comprises a pair of locking jaws, one of which is fixedly mounted on the exterior of the lower clamping jaw and the other of which is pivotally mounted with respect to said one locking jaw.

Preferably also, said other locking jaw is pivotally mounted on said one locking jaw.

Preferably also, the locking jaws are clampable in a locked position around the pin by a nut and bolt arrangement. Preferably also, a two pairs of locking jaws are provided and located so as to lock around respective ends of the pin.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which :-

Fig. l is a side elevation of an apparatus for use in la) ng a length of pipe in accordance with the present invention; Fig. 2 is a view similar to Fig. ι but from the other side of the apparatus; and

Fig. 3 is an end view of the apparatus in the direction of the arrow III in Fig. l.

A pipe-pushing apparatus l, as shown in the drawings, is suitable for laying lengths of pipe in the ground by inserting them into an existing pipeline, conduit or ducting. The apparatus ι is adapted to form an attachment for a conventional excavator vehicle and to be mounted at the end of an arm (not shown) of such a vehicle instead of a conventional bucket. Preferably, therefore, the apparatus ι is adapted to be hydraulically or pneumatically powered and motive fluid lines are provided that link into those of the vehicle in order that operation of the apparatus l can be controlled from the cab of the vehicle. In use, the apparatus l is clamped around a length of pipe, the end of which is then inserted and pushed into the existing pipeline by operating the arm. Once a first section of the pipe has been inserted, the apparatus ι is undamped from the pipe, moved along it and reclamped so that a further section of the pipe can be pushed into position.

The apparatus l comprises a bracket 2 that is adapted for connection to the arm of an excavator vehicle. Mounted on the bracket 2 is a pair of clamping jaws 3, 4, each of which defines an interior clamping profile 5. Although this profile 5 could take any shape, preferably the profile is that of a circular cylinder so as to be complementary to the shape of the pipe to be handled by the apparatus. The jaws 3 and 4 comprise upper and lower clamping jaws respectively. The upper clamping jaw 3 is mounted on the bracket 2 by a swivel unit 6. The swivel unit 6 enables the jaws 3, 4 to be rotated relative to the bracket 2. Preferably, the swivel unit 6 is hydraulically or pneumatically powered and enables the jaws 3, 4 to be rotated through 360° relative to the bracket 2 and held fast in any preferred position relative thereto. The lower clamping jaw 4 is pivotally mounted to the upper clamping jaw 3. The pivot axis 7 may be formed by a series of bolts that locate through strengthening flanges 8 which project from the exterior of the jaws 3, 4 at their ends and at the centre of their length, as shown in Fig. 2. Alternatively, the pivot axis may be formed by a bar (not shown) that passes through holes formed in all of the flanges 8 and that has nuts secured to its ends adjacent the outer flanges 8. However formed, the pivot axis 7 is located at one side of the apparatus 1 when in use. This means that the lower jaw 4 locates beneath a clamped length of pipe, which is advantageous as it means that the lower jaw 4 supports the pipe to prevent it from sagging that in turn reduces deformation of the pipe and thereby reduces the risk of the pipe structure from weakening. Opening and closing of the jaws 3, 4 is effected by at least one but preferably a pair of rams 9, which are also hydraulically or pneumatically powered via fluid lines 10 that are preferably connectable into the power unit and controls of the vehicle to which the apparatus 1 is connected, as described above. The rams 9 are located on a side of the apparatus 1 opposite the pivot axis 7. Upper ends of the rams 9 are pivotally connected via a pin 11 to a plate 12 that is attached to the exterior of the upper jaw 3. Lower ends of the rams 9 are pivotally connected to a second pin 13 which is releasably engageable in a locking mechanism 14 attached to the lower clamping jaw 4 so that the lower clamping jaw 4 can be pivoted relative to the upper clamping jaw 3. However, the rams 9 and pin 13 are disconnectable from the locking mechanism and thereby from the lower clamping jaw 4 to enable the jaws 3 and 4 to be opened so that the lower clamping jaw 4 can be located beneath a section of pipe to be clamped. This section can be offered up to the side of the apparatus 1 adjacent the rams 9 without it the pipe having to be fed between the jaws 3, 4 from its end, which would otherwise be the case if the lower clamping jaw 4 were not capable of being disconnected from the rams 9. Although not shown in the drawings, a guard is also provided to cover the rams 9 to reduce the risk of accidents when they are in use.

Preferably a pair of locking mechanisms 14 is provided, one at each end of the pin 13. Each locking mechanism 14 comprises a pair of locking jaws 15 and 16. One jaw 15 is fixed to the exterior of the lower clamping jaw 4 and the other jaw 16 is pivotally mounted with respect thereto. In the present embodiment the jaw 16 is pivotally mounted on the other jaw 15 but it could be pivotally mounted adjacent the jaw 15 to the lower clamping jaw 4. The locking jaws 15, 16 are lockable in a closed position by a nut and bolt arrangement 17. This is to ensure that the jaws 3, 4 cannot open by accident during use of the apparatus 1, for example if the motive fluid line to the rams 9 were to be accidentally cut. In order to enable the clamping jaws 3, 4 to be used with a wide range of pipe shapes and sizes, a set of shims 18, typically comprising a pair of shims, is locatable within the jaws 3, 4 so that the size and/or shape of the clamping profile 5 formed when the jaws 3, 4 are closed can be changed. Preferably, a plurality of sets of shims 18a, 18b, etc., are provided to enable the clamping profile to be changed to one of a number of different profiles, as desired. Advantageously, the sets of shims 18 nest inside one another for ease of storage within the jaws 3, 4 when the apparatus 1 is not in use and to provide a large number of alternative clamping profiles. Again, while the clamping profile 5 provided by each of the sets of shims 18 could be different, it is expected that in practice the clamping profile 5 defined by each set of shims 18 will be that of a circular cylinder.

The size of the apparatus 1 can vary dependent on the type of pipes it is intended to handle. However, for most applications it is expected that the clamping profile 5 of the jaws 3, 4 and sets of shims 18a, 18 b, etc., will enable pipe diameters between 63 mm and 400 mm inclusive to be accommodated. The length of the jaws 3, 4 is preferably around 400 mm to ensure a firm grip around the pipe to be laid and to ensure sufficient friction between the pipe and the jaws 3, 4 or shims 18 to prevent slippage of the pipe in the jaws 3, 4 during use.

In use, the apparatus 1 is connected to the arm of an excavator vehicle, as indicated above, and the fluid lines 10 are connected to an appropriate source of motive fluid, typically under control of the excavator vehicle controls. The rams 9 are extended to pivot the lower jaw 4 open. The locking mechanism 14 is then unlocked so that the pin 13 can be disengaged from the mechanism 14 to permit the jaws 3, 4 to be opened fully. A length of pipe can then be located between the jaws 3, 4, an appropriate set of shims 18 being used if necessary to ensure that when the jaws 3, 4 are closed the pipe is firmly clamped. Once the pipe is located, the pin 13 is engaged under the upper locking jaw 14 and the lower locking jaw 15 is clamped in the closed position. Retraction of the rams 9 will then close the jaws 3, 4 so that the pipe is then firmly clamped in the apparatus 1. The apparatus 1 can then be manipulated by the excavator vehicle as described above to insert and push the pipe down an existing pipeline.