GB2173446A

GB2173446A - Mechanism for installing and holding a thermoweldable curved element to another thermoweldable curved element

Info

Publication number: GB2173446A
Application number: GB08514070A
Authority: GB
Inventors: Lucien Vaira
Original assignee: Toutelectric SAM
Current assignee: Toutelectric SAM
Priority date: 1985-04-12
Filing date: 1985-06-04
Publication date: 1986-10-15
Also published as: DE3611546A1; FR2580369A1; IT8667301A1; ES553846A0; GB8514070D0; ES8704247A1; IT1187978B; IT8667301A0; IT8653259V0

Abstract

Mechanism for installing and holding a thermoweldable curved element (3) to another thermoweldable curved element (1) characterised in that it consists in a strap system (5), one end of which is attached to a fixed point (4) of the first thermoweldable element, and the other is submitted, after going around the periphery of the second thermoweldable element, to a progressive traction by a stretcher consisting in a manoeuvre lever (10) which turns a roll (9) which drives the strap in the tensile direction, a pawl (13) blocking a ratchet wheel (12) preventing the roll from turning in the wrong direction, the frame (20) of this strap system being supported by a rim (4') on the first thermoweldable element opposite the rim (4) to which is attached the loop (8) that ends the strap (5), so as to balance the pressure put on the strap and to spread it out evenly along the whole periphery of the second thermoweldable element. <IMAGE>

Description

SPECIFICATION Mechanism for installing and holding a thermoweldable curved element to another thermoweldable curved element The present invention concerns equipment destined for implementation in procedures for connecting thermoplastic tubes by electrowelding them with parts generally designated as connecting parts, and which are based on a phenomena of progressive and limited heating resulting in the forming of a unitary block between the tubes and the connecting part.

Such procedures have been well known for about twenty years and the different improvements that have been made during these years were mainly to welding time, for exem ple the means described by the Filer in French patent 83/20429.

However, keeping the parts to be assembled in contact still causes different problems which have not yet been solved in a satisfactory way.

Therefore, first of all, these parts should remain fixed with respect to each other during the whole operation. However, especially in the case of the adapting of a by-pass to a tube, the welding is done on a plate which partially covers this tube, and which as described in the patent mentionned before, is used first to make the by-pass by means of an awl making a hole in the side of the tube and second to bring to the same point an electric conductor coil which allow to progressively bring the material of this plate and of this tube to melting point by heating, so as to ensure the welding under pressure of the plate supporting the by-pass and the tube.

The position of this plate on the tube must be kept fixed, axially as well as incliningly, which may be difficult if the defects or spaces in the mold dimensions do not allow a perfect contact between the plate and the tube.

Moreover, during welding, the plate must be maintained on the tube with as much pressure as possible.

Actually, several means are used to satisfy these various requirements: According to a first solution, the width of the edges of the plate slightly increase from one end to the other and into these cornershaped slopes is forcibly driven another plateshaped part which pushes againts the opposite side of the tube, this part remaining in place after welding. This solution is hard to realize with large diameter tube. Moreover it increases the price of the operation.

According to a second solution, a wringbolt is simply used to apply the plate to the tube.

But this requires the use of wringbolts according to the diameters of the tu'bes. Moreover, these tools are very heavy and hard to handle.

Finally, in the case of buried lines, the operator must come down the top of the excavation to do this work, and this represents a very important additional expense, per necessary excavation volume.

The present invention concerns a mechanism allowing to eliminate all of these problems, and calling, in its priciple, for a wellknown system, the functionning of which is sure and practical.

This known system is the one requiring a strap, one end of which is attached to a fixed point, and the other is submitted to a progressive traction by means of an stretcher consisting in a manoeuvre lever turning a roll which pulls the strap in the direction of the tension, a pawl blocking a ratchet wheel prevents the roll from turning in the wrong direction.

The mechanism according to the invention consists in equipment allowing to adapt such a system to an electroweldable by-pass dressing plate as described above.

To this effect, the plate has on its two lower edges two slopes parallel to the tube generators, the first acting as anchor for the loop of the fixed end of the strap and the second as stop to a supporting shoe which is submitted to the pressure of the stretcher mentionned above.

In this way, the manoeuvring of the strap causes the development of a progressiv tension of the strap on the part of the tube located above the plate, and the pushing with a corresponding pressure of the plate on the tube.

When this tension, and afterwards this pressure are sufficient, electric current is sent to the coil contained in the plate and the welding is done without any risk of movement of the plate with respect to the tube.

Moreover, under the effect of the same tension, any unevenness or defect in the adaption of the plate to the tube is made good for the effect of the strap being to bring the two edges of the plate against the tube.

Even better, thanks to the same effect, a single type of plate is necessary, for a series of different tube diameters, however remaining in the same sizes, a difference in curve radius of 20% being acceptable, the resulting stress lessening during welding, whatever the tube diameter, because in any case, when tension is applied, the plate will anyhow be pushed under pressure against the tube, bending out of shape until it adapts itself exactly to the tube, to which it is then welded.

According to another characteristic of the invention, the mechanism has flexible means against which strap tension is exerted, i.e. the compression of the plate to the tube. Moreover, these means are preferably associated to taring means acting as stress indication al lowing to limt the compression to the desired value.

According to another characteristic of the invention, the box containing the pawl coil system of the strap has an extending element allowing to manoeuver the device at the top of an excavation, and the operator does not have to go down into it.

Finally, according to a last characteristic, the supporting shoe is associated to a tilting hood allowing to put the mechanism in the middle on the axis of the by-pass when it si put into place.

The invention is now going to be described referring to the annexed drawing on which: Figure 1 is a perspective view with several partial cut-aways of the mechanism according to the invention, fixed to the parts to be assembled by electrowelding and, Figure 2 is a cut-away according to the vertical plane Il-Il of Fig. 1.

On this drawing, reference 1 indicates the tube or main line, to which a dressing must be attached by electrowelding. This dressing consists in a radial tube 2 interdependent on a plate 3 containing, according to a know procedure, an electric conductor ornament causing, during the current flow, the melting of the material of the plate 3 then of the tube 1 in the welding zone.

This plate has two edges 4 and 4' on its two lower sides whose role will be described in detail hereafter.

The mechanism according to the present invention consists in the combining of a strap 5, of stretcher system indicated by the general reference 6, and a system indicated by the general reference 7, allowing the implementation of this stretcher when this strap is associated to the parts to be welded together 1 and 3.

At one end, the strap 5 is ended by a loop 8, to be attached to edge 4.

At the other end, the strap 5 winds around the stretcher 6 onto the roll 9, being revolved by a lever 10, interdependantly fixed to the axle 11 of the roll 9 to which are also attached the ratchet wheels 12-12', co-operating with the pawls 13-13' (not on drawing).

In this way, and in a know way, when the lever 10 is moved in the direction of the arrow F, the strap 5 winds around the roll 9, in such a way that, being attached by the loop 8 to the edge 4, it si submitted to more and more traction.

According to the invention, the bolt 14 bearing the axle 11 of the roll 9 is attached by the screws 15-15' to the box 16, vertically mobile along an axle 17 (see Fig. 2) reversely to a couple of springs 18-18' being supported, on the one hand, by the bottom of a lodging 19-19' of this box 16, and on the other hand by the corresponding bowls 20 A of a shoe 20, which is supported on its superior side 21 by the edge 4' opposite the edge 4 of the plate 3. These springs are preferably lodged in the cases 18 A.

To the top of the box 16 is attached a rod 22 whose level indicates the sinking level, i.e.

the compression of springs 18.

On the lodging 23 the box 16, a return spring is lodged, parallel to the springs 18, and pushing a rod 24 parallel to the fixed rod 22 against the top of the shoe 20.

The compression level of the springs 18, i.e. the traction exerted on the strap 5, i.e.

finally the compression of the plate 3 to the tube 1, can therefore visually be seen by the space between the tops of respectively rod 22 and rod 25.

A tilting hood 27 is articulated around an axle 26 to the front of the box 16, hood into which are embedded the top 28 of the bypass 2.

The operation of the mechanism is as follows: A by-pass having to be welded by electrowelding according to known procedures, to a main tube 1, by means of a plate 3, this place is placed in the desired place and fixed first by inserting the loop 8 into the edge 4, and then by inserting the top 28 into the hood 27, thus ensuring its positionning; The edge 21 of the shoe 20 is then fixed above the edge 4' of the plate, and one only has to make enough pushes on the handle 10 in the direction F to make the two markers constituted by the rods 22 and 25 correspond.

The traction exerced by the strap on the periphery is considered as sufficient. It is generally of about 1500 to 2000 Newtons, so that the material of plate 3 is bent out of shape, which brings it into contact with tube 1. The electric current is then sent into the coil contained in the plate 3, and, until the time control mechanisms intervene, the material of the plate and of the tube 1 are going to melt to one another, ensuring the required welding.

During this time, the whole mechanism is of course fixed, and this ensure its position and direction with respect to the tube.

A lug 29 cut from the edge of the loop 8 co-operates with a lodging corresponding to the edge 4, to ensure an even more precise longitudinal positionning, and especially to avoid that, under the tensile effect, the loop escapes from the edge 4.

It is clear that in this way the positionnind and holding in place operations of everyting to be welded are solved in a very simple way, that the safety of this positionning and of the welding are ensured, even in the case of unevenness or radius differences between the surfaces of tube 1 and plate 3.

In the case of an underground line, the operator should remain at the top of the excavation. To this effect the box 16 may be extended to the corresponding height, or an extension bar may be inserted between the box and the bolt 14, for example simply by screwing.

According to a utilization variation, the loop 8 can first be attached to the edge 4, the strap 5 hanging free, then this strap can be passed under the tube 1 and then attached to the roll 9 of the stretcher. The positionning operation of the by-pass to the tube at the top of the excavation is therefore easier, the by-pass first being lowered into the line with the device, being maintained there by its c#ap 28, and the strap is attache to it by its loop 8. The free end of the strap can then be caught by a hook for example, passed under the line and brought up th the roll 9 of the extendable strap to be attached. The disassembly of the operation after welding is also made easier this way.

According to another variation of the invention, the control of the tension of the strap is obtained, not visually by lugs 22 and 25 but by a couple limitor placed in the handle 6, for example of a known type of friction.

Claims

1. Mechanism for installing and holding a thermoweldable curved element to another thermoweldable curved element, characterized in that it consists in a strap system, with one end attached to a fixed point of the first thermoweldable element, and the other, after going around the periphery of the second thermoweldable element, is submitted to a progressive traction by a stretcher consisting in a manoeuvring lever turning a roll driving the strap in the direction of the tension, a pawl blocking a ratchet wheel preventing the roll from turning in the wrong direction, the frame of this stretcher system being supported by the edge of the first thermoweldable element opposite the edge to which is attached the loop at the end of the strap, so as to balance the tension exerced on the strap, and to distribute it evenly along the periphery of the second thermoweldable element.

2. Mechanism according to claim 1, characterized in that between the anchoring shoe and the frame of the stretcher system, tiring springs are installed, allowing to control the tension exerted by the strap, and therefore the pressure exerted by the first thermoweldable element on the second.

3. Mechanism according to claim 2 characterized in that the control of the pressure from the visual lining-up of the interdependent rods, respectively of the shoe and of the part of the mechanism interdependent on the stretcher system.

4. Mechanism according to claims 1 to 3 characterized in that the second thermoweldable element is a cylindric tube, and the first thermoweldable element is a by-pass destined to be radially welded to this tube before making a hole in it, this by-pass being interdependent on a plate in the shape of a saddel, whose curve conforms in shape to the superios surface of the tube, and in which is sunk the electric welding resistance.

5. Mechanism according to claim 4 characterized in that the shoe is associated to a tilting hood which comes above the top part of the by-pass so as to hold it when it is installed.

6. Mechanism according to any one of the previous claims, characterized in that the box containing the stretcher is extended enough to allow the use of this mechanism on underground lines without having to come down from the top of the excavation.

7. Mechanism according to claim 2 characterized in that the control of the pressure is obtained by a couple limiting mechanism associated to the handle of the stretcher.

8. Mechanism for installing and holding a thermoweldable curved element to another thermoweldable curved element, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.