GB2294078A

GB2294078A - Jointing of tube sections

Info

Publication number: GB2294078A
Application number: GB9420502A
Authority: GB
Inventors: Sven Hultsjo
Original assignee: Peterson F O & Soener
Current assignee: Peterson F O & Soener
Priority date: 1994-10-11
Filing date: 1994-10-11
Publication date: 1996-04-17
Anticipated expiration: 2014-10-11
Also published as: SE9503477D0; GB2294078B; SE9503477L; SG50341A1; NO954029D0; GB9420502D0; NO954029L

Abstract

A method of producing a jointed tube, eg for piling, comprises connecting adjacent tube sections 1, 2 by an internal jointing sleeve 3 externally coated with a thermoplastics material, heating the plastics coating on the sleeve to a plastic state, and then pressing each tube section end onto the sleeve while heated plastics material at the outer circumference of the sleeve is pressed away, the tube sections having an inside diameter less than the outside diameter of the plastics coating. <IMAGE>

Description

ImProvements relatina to the pointing of tube sections e.g. for buildina niling.

This invention relates to the jointing of tube sections and is particularly but not exclusively, applicable to the jointing of tube sections which make up piles and to methods of piling using the methods of jointing.

A common method of reinforcing the foundations of buildings is to drive jointable piling members under or adjacent to load carrying structural components, and then transferring the load from the building to the finished pile in a suitable manner.

The object of the present invention is to provide a new method of jointing tube sections, applicable to tubes made of steel, particularly but not exclusively those for use in building piling, where the above mentioned problems of the prior art have been eliminated, and also to provide a jointing sleeve suitable for carrying out the method.

In GB-C-2 217 365 a method of producing a jointed steel tube is disclosed, the steel tube being externally coated with a thermoplastics to be corrosion resistant, which comprises connecting adjacent tube sections by an external jointing sleeve, the method comprising heating the jointing sleeve and the plastics coating on the tube sections to a highly plastic state, whereafter each tube section end is pressed into the jointing sleeve while heated plastics material at the outer circumference of the tube section is forced away, the jointing sleeve having an inside diameter somewhat less than the outside diameter of the plastics coating on the tube sections. Further, this method according to GB-C-2 217 365 results in an uneven external surface of the piling tube.

The features of the joint, i.e. strength, straightness, tightness etc., are obtained by plasticizing the thermoplastics by heating, so that the steel tubes can be pressed into the sleeve. The sleeve must withstand heating.

Thus, the objects set out below are achieved by methods in accordance with the invention by heating the coating on the jointing sleeve to a highly plastic state, the tube section ends then being pressed onto the jointing sleeve while forcing away heated plastics material on the outside circumference of the sleeve, the tubes having an inside diameter somewhat less than the outer diameter of the plastics coating on the jointing sleeve.

According to another aspect of the invention, a method of pile driving comprises driving a first tube section, connecting thereto a second tube section and driving the connected first and second tube sections, the connection being produced by a method according to the first aspect of the invention.

The present invention is based on the feature that the sleeve is coated with a termoplasticizable material and that the piling tubes, after plasticizing of the coating layer of the sleeve, are forced onto the sleeve, whereby the joint is accomplished with the desired characteristics. The applicability of the invention is no longer limitied to piling tubes with a thermoplastics coating, but instead every kind of steel tubes can be jointed in this way.

Piles cannot be inspected after installation. In case of steel piles the corrosion during the lifetime of the building has to be considered at the dimensioning. A particularly safe way is coating the steel with a glued, thick layer of stable thermoplastics (polyethylene). GB-C-2217365 has the disadvantage that the sleeve itself not can be given this exceptionally good corrosion protection, but instead you are referred to hot-dip galvanizing. The present invention makes it possible to give the total outer surface of the pile a smooth, high class corrosion protection.

The method according to the invention gives a rigid joint without the reduction of the material thickness of the piling tubes which occurs when using threaded muffs for jointing, and without the risk of damage to the protection against corrosion which occurs when the joint is welded.

When the temperature of the plastics layer drops, after pressing the tube ends onto the sleeve, the strength of the layer increases, and both tube sections will thus be securely jointed.

According to a preferred embodiment of the invention, mechanical means are arranged for preventing the movement of the sleeve inside the pile tubes. This mechanical means can be mounted in the form of shoulders above and below the sleeve, welded or otherwise, or by mounting a bolt through the piling tube and the sleeve.

The invention may be carried into practice in various ways but the manufacture of a joint in accordance with the invention will now be described by way of example with reference to the accompanying drawing in which the Figure is a longitudinal section through two tube sections and a jointing sleeve.

The Figure is a section along the central axis of pile members at the vicinity of a joint. The Figure shows tube ends 1, 2 forming part of a building pile. The tubes are made of steel coated with a polyethylene layer 1',2'. The joint between the tubes is achieved with the aid of a jointing sleeve 3 comprising an inner steel sleeve 4 with an external coating 5 of a thermoplastic material such as polyethylene. The inside diameter of the tubes is somewhat less than the outside diameter of the plastics layer on the sleeve and somewhat larger than the inside diameter of this layer.

Above and below the jointing sleeve 3 shoulders 9,10 are arranged for preventing the movement of the sleeve during piling. These shoulders could e.g. be welded.

In making the joint, the end portions of the members adjacent the joint faces are heated, the plastics material of the plastics layer of the sleeve then becomes highly plastic. The tube ends are then pressed onto the joint sleeve until they meet each other at 6. During this procedure some of the plastics layer has been pressed away or otherwise removed by the tube ends, yet leaving a plastics layer between the inner surface of the tubes and the outer surface of the sleeve, such as to achieve a bond between the sleeve and tube ends after the plastics has been allowed to cool. By chamfering the tube ends 7, 8 the plastics material layer on the sleeve will be compressed and not sheared away, thus avoiding the risk for the plastic to cumulate at the interface between the tube ends.

The heat can be provided through electrical heating elements with means adapted to be placed around the tube ends and the sleeve, respectively.

In applying the method according to the invention for provid ing building piles, it is advantageous to start from factory produced units including a tube section and a jointing sleeve attached thereto in accordance with the invention. At the piling site itself it is then only necessary to heat the jointing sleeve and the end portion of the tube section which is to be applied onto the sleeve, i.e. the tube that upwardly terminates the pile being driven. This technique is also advantagous in many other applications.

Before applying the tube ends onto the jointing sleeve, they can be internally coated with a layer of a glue or a plastics material having a melting point which is higher than the temperature at which the plastics coating of the sleeve becomes highly plastic. After the joint described above has been made, the sleeve can be heated in a separate operation so that the melting point of the glue is attained, the glue then forming a reliable bonding layer at the interface between the outside surface of the tube and the remaining plastics layer of the sleeve after the glue has cooled.

It has been found that a superior result in the jointing method is achieved if the following steps are taken.

1. The dimension of the jointing sleeve is selected in relation to the dimension of the pile tube cross-section such that the gap between sleeve and tube section does not exceed 2 mm.

Thereby is ensured the necessary straightness and tensile strength of the jointed pile.

2. The gap between the jointing sleeve and the tube section shall not be below 0.2 mm. There is thus ensured that the plastics is not stripped off from the sleeve during the jointting process.

3. The interior surface of the tube ends is chamfered at the ends thereof. In this way the plastics material coating the sleeve will be more effectively pressed into the above-mentioned gap between the sleeve and the tubes.

4. The plastics coating of the sleeve is heated to a softening temperature over 70 C before the jointing operation. There is thus ensured good plasticity of the plastics during this operation. However, the temperature of the plastics must not be higher than about 4000C to avoid carburization.

The invention is not restricted to what has been described above in connection with the description of an embodiment. For example the method and jointing sleeve in accordance with the invention are also utilizable for jointing tube elements other than pile members, although the invention is primarily intended for jointing pile members.

Claims

Claims:

1. A method of producing a jointed tube,gor piling, comprising connecting adjacent tube sections by an internal jointing sleeve externally coated with a thermoplastics, bringing the plastics coating on the sleeve to a

plastic state by supply of heat, whereafter each tube section end is pressed onto the jointing sleeve while heated plastics material at the outer circumference of the sleeve is pressed away, the tube sections having an inside diameter

less than the outside diameter of the plastics coating on the jointing sleeve.

2. A method as claimed in claim 1 in which heat is applied to the jointing sleeve and/or directly to the thermoplastic coating.

3. A method as claimed in Claim 1, in which the tube sections are heated.

4. A method as claimed in Claim 1, in which the coating on the jointing sleeve and the tube sections are heated.

5. A method as claimed in any of the preceding claims in which the inside diameter of the tube sections selected in relation to the outside diameter of the jointing sleeve such that an annular gap with a width of between 0.2 and 2 mm is obtained between the sleeve and the tube sections.

6. A method as claimed in any one of the preceding claims in which the plastics material on the jointing sleeve is heated to at least about 750C before the jointing sleeve are inserted into the tube sections.

7. A method as claimed in any of the preceding claims in which the tube section ends to be jointed are fitted onto the jointing sleeve successively as follows: a first tube section end and the sleeve are heated; the sleeve is inserted into the first tube section; the sleeve and the first tube section are returned to normal temperature; the first tube section end, the sleeve and the second tube section end are heated; the sleeve is inserted into the second tube section end; and the joint is finally returned to normal temperature.

8. A method as claimed in any of the preceding claims in which the tube section ends have an internal chamfer.

9. A method of jointing a tube substantially as described herein with reference to the accompanying drawing.

10. A method of pile driving comprising driving a first tube section, connecting thereto a second tube section and driving the connected first and second tube sections, the connection being produced by a method as claimed in any of the preceding claims.

11. Tube sections for carrying out the method according to any one of the preceding claims, wherein said tube sections are chamfered on the inside of its ends such as to form a conically widening portion.

12. Tube sections for carrying out the method according to any one of the preceding claims, wherein they comprise means for restricting longitudinal movement of the jointing sleeve in the tube sections during piling.

13. Tube sections for carrying out the method according to any one of the preceding claims, wherein they are made of steel.

14. Jointing sleeve for carrying out the method according to any one of the preceding claims, wherein said sleeve is coated with plastics.