CA2071643A1 - Process for joining workpiece part made of plastic - Google Patents

Abstract

In the process described for joining workpieces made of plastic along abutting edges, a permanently elastic compound adhering to the plastic and acting as a welding medium is applied along at least one of the edges and heated before the edges are brought into contact.

Description

~7~

Process for joining wor~piece parts made of plastic.

The present invention relates to a process for join-ing workpiece parts made of plastic along abutting edges which parts include at the joint mechanical coupling means, such a~ e.g~ groove and key.
At present processes for joining two adjacent or abuttiny edges of workpieces of plastic, such as e.g. strips, plates etc. commonly a simple mechanical lock is selected.
At other processes the edges or rims of the wor~pieces are heated and welded together by the own heated material. This process can be a2plied additionally at mechanical locks.
~ 7hen these techniques are applied at the production of tubes according to the winding process mechanical coup-ling means in form of slot and key are foreseen at the edges to be interconnected. In this case additionally a sealing element (e.g. rubber sealj can be inserted bet-ween the two wor]cpiece edges to be joined ("connecting seam"3 for increasing the soundness of the seal.
Inspite of these efforts the connections at exclusi-vely mechanical locks or at welding areas made by means of the own plastic material are not securely absolutely thight except at very high expenditures regarding production to-lerances and design.
Object of the present invention was the provision of a simple process for ~oining ~70rkpiece parts made of plastic, which is suitable for thermoplastic and also duro-plastic materials as well and ensure a completely sealed joint.
.

. ' ' .

~ v This object is solved at a method according to the initially mentioned kind in accordance with the invention in that at least along one of the edges to be joined a permanently elastic mass which adheres to the plastic is applied as welding mediuN at the area of the mechanical coupling means and that the workpiece parts which are to be coupled to each other are joined whereby previously the welding medium is heated.
The permanently elastic welding medium can thereby be installed already in the factory or only at jobsite, and specifically preferably in form of a continuous strand of material, i.e. extending uninterrupted along the joint.
A suitable permanently elastic,adhering welding mass is a caoutchouc mass, e.g. a copolymerisate of Isobutylene and (a little? Isoprene ~"Butyl").
The invention will hereinafter be explained some-what closer, whereby same embodiments of plastic workpie-ces equipped for the practicing of the inventive method are illustrated in the drawing.
There is shown in :
Fig. 1 a section through a plate or a plastic band, e.g. for the production of a wound pipe;
Fig. 2 a section through a joint between two edges of plastic parts ~e.g. seam of a wound pipe; and Fig. 3 a section through a plastic profile variant of which the edges for instance for forming a pipe (by a winding process) are to be joined together, whereby the welding medium can be applied eithex at the left edge in the groove or at the right edge at the key.

., , ~
" " ' ' f~ V ~

It shall again be repeated that the base of the in-ventive method is to join two adjacent, i.e. abutting edges of workpieces !strips, plates, etc.) of plastic ithermo-plastics, duroplastics) at the one side mechanically and at the other side at the same time by means of a perma-nently elastic mass which adheres to the plastic and ser-ves as welding medium. The permanently elastic mass, for instance a caoutchouc mass, e.g. a copolymerisate of Iso-butylene and ~a littlei Isoprene t]cnown e.g. under the trade mark "3utyl")is applied either in the factory or at jobsite to the workpiece. In the former case the applying of the welding medium strand and the producing of the plastic profile can be made simultaneously.
For the additional mechanical connection the edges of the workpiece which are to be interconnected are shaped as groove and key, resp. The groove and key combination allows only the mechanical locking together of the parts.
The welding medium which in any case has been applied previously is heated prior to the joining. This increases the flowability and the adhering capability of this caout-chouc mass. After the cooling of the parts welded to~et-her therewith the welded area remains elastic also at a low temperature.
Advantages of the joint produced in accordance with the invention:
- By the adherance and welding of the mass a comple-tely tight joint is produced.
- The joint is resistent against a growing in of roots.
- A positively locked ioint~ithin the framework of the limit of elasticity of the welding medium.

~, . . . :
, : ~ . ' ' ' ': , ' -,, ' ' ' ~
:

- The properties of the welding medium can be adjusted.
- The welding medium can be used together with various thermoplastic and duroplastic materials.
- Pipes produced by the inventive process keep their axial flexibility contrary to hard welded or bonded pipes; the same proves true for lag-ging plates.
- The inventive method secures a uniform seal and joint, also at unfavorable environmental condi-tions.
Fig. 1 illustrates a section through a plastic band 1 by means of which pipes are produced by a winding process;
thereby the key 3 foreseen at the one edge 2 of the band will snap into a correspondingly designed groove 5 at the other edge 4 of the band.
In order to secure in addition to the purely mecha-nical connection also a tight seal of the weld (at a pipe a spiral connection seam), a continuous strand 6 and 7, resp. of a mass(caoutchoucr e.g. "Butyl") of a permanent elasticity and adhering to the material of the profile is applied at the indicated areas. The applying proceeds at the factory or at jobsite, prior to the joining.
:
Fig. 2 illustrates on an enlarged scale a section through a sealed joint. The welding medium 6 and 7, resp.
adheres at the contact surfaces to the workpiece parts 1 and ~orms in this way an elastic, completely sealed joint (in addition to the mechanical cla~pin9 by groove 5 and key 3~.
. ~ , ' .

, ' ~' . :
.

_ 5 _ , ~, jL " -' Fig. 3 illustrates a further variant of a plastic profile 18 with groove 9 and key 10 at opposite edges.
The welding medium 11 and 12, resp. foreseen for the elastic joint is applied prior to the connecting either into the groove 9 or onto the key 10 (possibly also onto both parts).

Claims (6)

Patent Claims

1. Process for joining workpiece parts made of plastic along abutting edges which parts include at the joint mechanical coupling means, such as e.g. groove and key, characterized in that at least along one of the edges to be joined a permanently elastic mass which adheres to the plastic is applied as welding medium at the area of the mechanical coupling means and that the workpiece parts which are to be coupled to each other are joined.

2. Process according to claim 1, characterized in that the welding medium is applied to the workpiece in the factory, e.g. together with the production of the plastic part, or at jobsite.

3. Process according to claim 1 or 2, characterized in that a caoutchouc mass, e.g. a copolymerisate of Iso-butylene and Isoprene is used as permanently elastic, ad-hering mass.

4. Process according to one of the claims 1 to 3, characterized in that the welding medium is applied in form of a continuous or uninterrupted strand.

5. Process according to one of the claims 1 to 4, characterized in that the welding medium is heated prior to the joining.

6. A structural element formed of interconnected workpiece parts of plastic, specifically a pipe wound of plastic strips, produced in accordance with the method according to one of the claims 1 to 5.