Note: Descriptions are shown in the official language in which they were submitted.
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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.
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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.
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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.
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- 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.
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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~.
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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).
