GB2226522A - Pipe welding clamp - Google Patents

Abstract

The invention relates to a pipe clamping tool used for restraining the movement of small diameter pipes and couplings throughout the electrofusion jointing and cooling cycle. The two pipes to be jointed being held between two pairs of pre-machined profiles 5 which have crescent shapes removed from them. The form of these crescent shapes conforming to the outside diameter of the pipes being held. A number of crescent shapes being machined from each profile. The method of changing from one pipe size to another is by indexing round the profiles until the appropriate crescent shapes are adjacent and the profiles being closed together by a feedscrew 6 which draws arms, carrying the profiles 5, of each pair 1, 2 towards each other. <IMAGE>

Description

Pipe Welding Clamp for Couplings.

This invention relates to pipe welding clamps and is particulary, but not necessarily exclusively concerned with clamps for assistance in the welding of pipe jointing couplings onto pipes.

In the welding of thermoplastic pipes it is known that to form a successful joint using a thermoplastic coupling utilising a known welding technique such as electrofusion it is important to ensure that the pipes to be jointed are held securely to prevent movement of the pipes relative to the coupling which forms the joint. The said coupling may take the form of an equal coupling whereby both end sizes are similar, a reducing coupling whereby either end size may be disimilar or a Tee Shaped Coupling whereby either of the ends may be of a similar or disimilar sizes.The pipe sizes for which the welding clamp refers are particulary but not necessarily those within the range 16mm to 75mm outside diameter and can be in any combination of sizes within this range or alternatly the jointing of an outlet main or service from a saddle fitting whereby a branch of any size pipe up to 63mm is taken from a larger sized main by the known method of electrofused saddle, this saddle being of either the self tapping or non self tapping type.

Hither to, the common method of clamping these pipe sizes has been to clamp those sizes within the range 16mm to 32mm with a clamp of the open jaw type whereby the variation in size is accomodated by using inserts, liners or shims which make up the difference in size between the clamp profile and the relative pipe size to be clamped or changeable jaws. These inserts, liners and shims are easily misplaced, liable to damage and distortion require a degree of dexterity to fit and are often the cause of problems when jointing outlet mains and services to saddle fittings. For pipe sizes generally greater in outsize diameter that those above 32mm a second clamp is used of larger size but basically of the design described in the foregoing.An alternative method is to use fixed size jaws, this design requiring a number of clamps to provide for the various sizes of equal and reducing coupling in use.

The object of the present invention is to provide a pipe welding clamp which offers simplicity of operation, a greater range of pipe sizes which can be held, and a minimum of external components such as inserts liners or shims etc.

The design of the invention is as follows, two pairs of hinged arms (marked 1,2 on associated drawings) are hinged by screws but are sufficiently free to move away from or towards each other.

The hinged arm pairs are held at a fixed distance from each other by spacing bars (marked 3,4).

The distance between the spacer.:bars and consequently the open gap of the hinged arms is set and held by the screwing or unscrewing of a handwheel (marked 7) along a screwed section (marked 6).

The screwing in of the handwheel compresses a spring (marked 8) which is placed outside the screwed section. The position of the spring in relation to the spacer bars is between them, the action of the spring being to tension the spacer bars and hinged arms. Spacer bar (marked 3) having a clearance hole drilled into it through which passes the screwed section is free to move against the reaction of the compressed spring. Spacer bar (marked 4) has the screwed section fixed into it.

The basis of the invention is that to change the setting of the clamp when changing from one pipe size to another, or when it is required to clamp a reducing coupling the setting of the clamp is by indexing around profiles (marked 5) until the correct crescents, (The crescents being machines to the outside diameter of the pipe to be clamped) are adjacent to each other.

The coupling being positioned between opposing profile pairs and the pipe sections to be jointed are clamped between the adjacent crescents and held firmly by screwing the handwheel and closing together the spacer bars thereby positioning the hinged arms closer together at the unhinged end.

The operation of the index mechanism is carried out by loosening the thumbnut (marked 12) pulling forward the profile until it is disengaged from lockpin (marked 9) turning profile until new pipesize crescent is in the correct position. Re-engage the lockpin into locking hole and retighten thumbnut.

This operation to be carried out on all profiles individually.

Claims (6)

1. A pipe restraining clamp for pipe sizes 20mum to 63mm which securely holds the pipe, coupling assembly prior to electrofused jointing and has a mechanism which allows various pipe sizes within the range of the restraining clamps capability to be accomodated by moving pre machined profiles.

2. A pipe restraining clamp as claimed in 1, wherein the method of selection of pipe sizes to be accomodated is by the pre machined profiles being indexed round to the appropriate position.

3. A pipe restraining clamp as claimed in 1,2, wherein the method of precise location of the indexed profiles is made by a lockpin which locates into a pre drilled hole.

4. A pipe restraining clamp as claimed in 1,2 wherein the profiles which provide the location are positioned on the end of hinged arms and the position of the hinged arms is controlled by a handwheel moving on a threaded section.

5. A pipe restraining clamp as claimed in 1,2,4 wherein the pipe size range that can be accomodated is other than those generally accepted as being used in the United Kingdom such sizes may be but are not necessarily 40mm o.d., 75mm o.d. for example.

6. A pipe restraining clamp as claimed in 1,2,4,5 wherein the method of securing the profiles is other than by tightening a locking thumbscrew such a securing system may be for example a spring and ball locating system.