GB2171051A

GB2171051A - Pipe compressing device

Info

Publication number: GB2171051A
Application number: GB08603647A
Authority: GB
Inventors: Maurice Henry Roberts; Emlyn Gurney Perrett
Original assignee: AVON LIPPIATT HOBBS; HAXEY ENG Ltd
Current assignee: AVON LIPPIATT HOBBS; HAXEY ENG Ltd
Priority date: 1985-02-15
Filing date: 1986-02-14
Publication date: 1986-08-20
Also published as: GB8503894D0; GB2171051B; GB8603647D0

Abstract

A pipe compression device has squeeze bars 1,2 adapted to fit around a flexible pipe 3; a first squeeze bar 1 is connected to a toggle mechanism 20 having one or more toggles and is slidably movable towards and away from a second squeeze bar 2. Means such as a motor-driven lead screw 26 are provided to operate the toggle mechanism 20 and cause squeeze bar 1 to move relative to squeeze bar 2, thus compressing flexible pipe 3. <IMAGE>

Description

SPECIFICATION Pipe compressing device This invention relates to devices for compressing flexible pipes, tubes or rods (hereinafter "pipes").

It is frequently desired to compress a flexible pipe in such a way as to wholly or partially close it off over a small part of its length. This is the case, for example, in fluid distribution systems in which modifications or repairs to a pipe are most conveniently made after closing off the pipe at two points in order to isolate the appropriate part.

Conventionally such pipes are closed by squeezing their opposing walls together between two bars (hereinafter referred to as squeeze bars).

For closure to be effective the compressing device must be capable firstly of exerting sufficient force to bring the pipe walls completely together, and secondly of maintaining the squeezed position without allowing the walls to work apart again. In addition, the device should be conveniently releasable, since the closures involved are generally temporary.

Orthodox compressing devices used for these purposes are of two main types; either a simple screw thread mechanism or a hydraulic jack is used to exert a force to bring the squeeze bars together. The simple screwthread mechanism is not suitable for exerting large forces, and can therefore not be used with large or strong pipes. Devices having a hydraulic jack are capable of exerting large forces, but difficulties due to worn or leaking systems are commonly encountered in applying maintaining or controlling this force.

The present invention overcomes these problems by applying the closing force to the squeeze bars using a toggle mechanism. By "toggle mechanism" is meant a mechanism having two elongate members hinged together forming an angle, the end of the first member remote from this angle being pivoted at a re-action member, and the end of the second member being pivoted where the load is to be applied-at a squeeze bar in this case. A force applied to the hinged angle and tending to increase that angle towards 180" therefore causes a considerable force to be applied at the squeeze bar via the second member. The nearer the angle to 180 , the greater the mechanical advantage obtained.

The movement of the toggle mechanism may be transmitted to a pipe to be compressed by a squeeze bar connected to one end of the toggle mechanism, which cooperates with a second, fixed, squeexe bar. By applying a suitable force to the hinge of the toggle mechanism, the two squeeze bars may be forced together, compressing the pipe between them.

A preferred arrangement has two toggles pivoted on a single squeeze bar, so that the two toggles operate together when force is applied at their hinged angles.

A preferred means of applying this force has a lead screw engaging with a thread mounted at the angle of two toggle members, so that the lead screw substantially bisects the angle between the two togglEmembers.

Rotation of the lead screw, for example, manually or by means of a motor drive, thus opens or closes the angle between the members. Where two toggles are used a single threaded member may be used to operate both.

For unity of construction the second squeeze bar and fixed point(s) of the toggle mechanism(s) may be held in a fixed relative position by mounting them on a common frame.

In order to prevent excessive deformation of the pipe walls, stops may be provided preventing the first and second squeeze bars from moving too close together. An alternative is the fitting of a gauge reaction member associated with the toggle mechanism by which gauge the load, stress, strain or similar applied to the pipe may be assessed. This gauge may simply be connected to a display and read by an operator. In such a case it would be advantageousion the display face to provide indications of unacceptable levels of stress, strain etc for a variety of pipe dimensions.

Alternatively the gauge (nay be connected to an automatic switch. Such a switch might for example become operative at pre-set values of load, stress, strain etc and upon operation might lock the toggle mechanism or drive unit appying the force.

An embodiment of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which Figure 1 shows a pipe compressing device according to the invention, and a pipe in a partially compressed condition and Figure 2 shows a similar apparatus into which a gauge has been incorporated.

With reference to Fig. 1, a pipe compressing device according to the invention has a frame consisting of a cross-bar 1 and downwardly extending frame members 2 and 3.

Each of the frame members 2 and 3 consists of two rails so that a channel is defined in each frame member. An upper squeeze bar 4 is slidably mounted across the frame, with its ends in the channels. Similarly, a lower squeeze bar 5 is removably mounted in the channels, downward movement of the lower squeeze bar 5 being prevented by the bottoms 6 of the frame members 2, 3 which extend across the channels to terminate them.

As illustrasted in the figure, the upper and lower squeeze bars 4 and 5 are positioned on opposite sides of a partially compressed pipe 7.

The squeeze bar 4 is provided with a guide rod 8 which can slide freely between guides 9, 10 on the cross bar 1; this is to keep the sqeeze bars 4 and 5 parallel and to provide a mechanical stop 11 whose operation will be described later.

Between the cross bar 1 and the upper squeeze bar 4 is a double toggle mechanism, generally designated 20. The double toggle mechanism 20 comprises two toggles, symmetrically disposed, each having an upper member 21 and a lower member 22. The upper members 21 are pivotally attached to a mounting 23, which is rigidly fixed to the cross bar 1, while the lower frame members 22 are pivotally attached to mounting 24, which is rigidly fixed to the upper squeeze bar 4.

The other ends of members 21 and 22 of each toggle are hinged together at hinges 25, so that the two toggles form a diamond shape which changes in width as the upper squeeze bar 4 is raised or lowered relative to the cross bar 1. The hinges 25 are each provided with co-axial threads and a lead screw 26 passes through and engages with the threads of both the hinges. The lead screw 26 has opposite helices at each end, so that rotation of the lead screw 26 causes the hinges 25 either both to move outwardly or both to move inwardly, depending on the direction of rotation.

One end of the lead screw 26 is connected to a motor drive unit 27. Since the lead screw 26 can move vertically relative to the frame when the toggle mechanism operates, the drive unit is left free to slide vertically in a drive unit mounting 28, fixed to cross bar 1.

Alternatively, a telescopic connection could be used.

In order to prevent the squeeze bars from closing too far and possibly damaging the pipe, various forms of stops may be provided.

As illustrated, stops 30 and 31 take the form of thick flanges at the ends of the upper squeeze bar 4. These will abut on the lower squeeze bar 5 when a predetermined clearance between the working faces of bars 4 and 5 is reached, and prevent further compression of the pipe 7. They may also act as guides for the upper squeeze bar 4. There is also, as previously mentioned, an adjustable stop 11 in the form of a projecting block at the top of the guide rod 8. Stop 11 will abut on cross bar 1 and prevent further compression when a particular clearance between squeeze bars 4 and 5 is reached. This particular clearance is predetermined by the adjusted position of the stop 11 on the guide rod 8.

In order to squeeze-off e.g. the pipe of a live gas main in a trench the lower squeeze bar 5 is removed (by sliding it sideways out of the channels) and the device is fitted over the pipe with the upper squeeze bar 4 in a raised position. The lower squeeze bar 5 is then passed under the pipe and fitted into the channels in the frame members 2 and 3 so that it rests on the bottoms 6 of the frame members 2, 3. The drive unit 27 is then operated, rotating the lead screw 26 in the sense appropriate for compression. Engagement of the lead screw 26 with the threads in the hinges 25 then forces the hinges 25 towards one another, thereby applying a strong downward force on the upper squeeze bar 4 by action of the toggle mechanism 20 via mountain 24. This continues until the pipe is compressed to the desired degree. As long as lead screw 26 is not then rotated the device will not work loose.

Motor driven unit 27 may be electrically, pneumatically or hydraulically powered, with appropriate stalling levels or cut-off switches.

This makes the device according to the invention particularly suitable for use as an "emergency squeeze-off unit" to provide a remotely operated safety valve at a constantly changing position on a "live" pipe when renewing a main by "live insertion".

In case of failure of the motor drive unit 27, means for manually moving the lead screw 26, e.g. a ratchet mechanism,. may be provided.

Fig. 2 shows a device similar to that of Fig.

1 in which a strain gauge 20 has been incorporated between the crossbar 1 and the upper toggle members 21. The operation of the toggle mechanism 20 exerts a force on the gauge, the magnitude of which force may be read from the visible display 32. The display 32 may incorporate indications (not shown) such as coloured arcs, as to acceptable limits of strain for particular pipe sizes and wall-todiameter ratios.

Alternatively the gauge 30 may be connected to the motor unit 27 by a switch which operates automatically to prevent further force being applied when a certain strain level has been reached. The strain at which this occurs would be preset at a value according to the dimensions of the pipe being compressed.

Clearly such an arrangement is- of great advantage when the pipe being compressed is of a non-standard size or wall-to-diameter ratio.

Claims

1. A device for compressing a pipe comprising a frame which includes a support for supporting a pipe, a squeeze bar to compress a supported pipe, the squeeze bar being slidably mounted for movement towards and away from the pipe support and a reaction member remote from the support, a pair of elongate members joined pivotally at their first ends, the second end of one of the members being pivotally attached to the reaction member, the second end of the other member be ing pivotally attached to the squeeze bar such that a change in the pivot angle between the two members causes the squeeze bar to move towards or away from the pipe support, and means for applying a force to the elongate members such that the pivot angle between the members tends to change and so to cause the squeeze bar to move.

2. A pipe compressing device according to claim 1 wherein there are two said pairs of pivoted elongate members between the reaction member and the squeeze bar.

3. A pipe compressing device according to claim 2, wherein the two pairs of elongate members are symmetrically arranged about the line of the compressive force.

4. A pipe compressing device according to claim 3 wherein the means for applying the force to the elongate members includes a lead screw engaging both pairs of elongate members and a drive means for rotating the screw.

5. A pipe compressing device according to claim 4 wherein a screw-threaded element engaged by the lead screw is provided at the pivot of the pairs of elongate members and an increase in pivot angle causes the squeeze bar to move towards the support.

6. A pipe compressing device according to any one of the preceding claims wherein the squeeze bar is slidably mounted in parallel guiding members of the the frame.

7. A pipe compressing device according to any one of the preceding claims wherein the pipe support is removable.

8. A pipe compressing device according to any one of the preceding claims including a load measuring gauge by which the magnitude of the load being applied to a pipe may be assessed.

7. A pipe compressing device according to claim 8 wherein the load measuring gauge constitutes part of the reaction member.

10. A pipe compressing device according to claim 10 or claim 11 wherein the load measuring gauge includes or activates control means for modulating the force being applied.

11. A pipe compressing device substantially as herein described with reference to and as illustrated in Fig. 1 or Fig. 2 of the accompanying drawings.