Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR PRODUCING A PLASTIC HOLLOW BODY
WITH BUILT-IN PARTS AND A PLASTIC CONTAINER
WITH BUILT-IN PARTS
The invention concerns a process for the production of a plastic hollow
body and a plastic container.
The most widely varying production processes are known for the
production of hollow bodies of thermoplastic material, for example extrusion
blow moulding, deep drawing or injection moulding. In the extrusion blow
moulding process the hollow body can be seamlessly produced for example
from a single tubular preform. It will be noted however that there is also the
possibility of dividing a tubular preform into webs according to length,
placing
the webs separately in a two-part or multi-part tool and expanding or
shaping them within the tool by means of a reduced pressure or by
subjecting them to the action of a gas pressure.
Particularly in the production of technical components such as fuel
tanks which are produced in the above-described manner in one or more
parts from thermoplastic material, there is a need for various built-in or
installation parts or attachment parts to be fixed to the hollow body. That
can be effected in the first heat in the production procedure or also
subsequently. If the hollow body is intended to receive the installation parts
in its interior, it is often necessary, by virtue of the size of the
installation
parts, for them to be introduced into the hollow body in the production
thereof. The installation or attachment parts which 'are to be introduced or
attached to the hollow body can be clipped or welded to the hollow body, in
which case the welding operation can be effected in production of the hollow
body in the first heat or subsequently in the second heat, for example by
friction welding or heat-reflector welding.
Limits are often imposed on anchoring an installation part in positively
locking relationship in the interior of the hollow body by virtue of the
production process thereof. For example, when producing hollow bodies by
an extrusion blow moulding process, it is only limitedly possible to provide
in
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the contour of the hollow body, undercut configurations which permit
installation parts to be locked to the wall of the hollow body in positively
locking relationship. For that reason recourse is frequently had to welding as
a joining procedure.
Welding the components together however suffers from the
disadvantage that the plastic materials to be connected must form a material
pairing , which can be welded together. That limits the choice of the
installation or attachment parts for the hollow body.
By way of example, in the production of fuel tanks from plastic
material, this can represent a serious limitation as, in the presence of fuel,
certain plastic materials swell or are permeable for hydrocarbons. Certain
conduits and valves therefore require a choice of material which excludes the
possibility of welding to the container or tank or to the hollow body, from
the
outset.
Therefore the object of the invention is to provide a process for the
production of an article including installation parts in the form of a hollow
body of thermoplastic material, which permits particularly simple and secure
fixing of installation parts in the hollow body in the course of production
thereof.
A further object of the invention is to provide a plastic hollow body to
which installation parts or attachment parts are connected in positively
locking relationship in a particularly simple fashion.
That object is firstly attained by a process for the production of an
article enclosing installation parts in the form of a hollow body of
thermoplastic material, in which one or more preforms in web or tube form of
plasticised plastic material are disposed between the opened parts of a
moulding tool forming a cavity, at least one installation part to be enclosed
by the finished article is placed between the parts of the moulding tool and
the tool is closed around the preforms and the installation part and the
preforms acquire the external configuration of the article within the cavity
enclosed by the tool, wherein the installation part is pressed during or
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directly after shaping against the inside wall of the article while still
plastic so
that the plastic material of the hollow body passes through at least one
recess or opening in the installation part and flows therebehind.
In that way it is possible to provide that the installation part is
anchored to the wall of the hollow body in positively locking relationship
using
comparatively simple means. The inside wall of the hollow body passes
through and flows behind an anchoring opening in the installation part so that
a positively locking and non-releasable connection was achieved after cooling
of the components. There is no need for compatibility of the materials in the
sense of weldability of the parts'. The installation part can for example also
comprise metal or another material.
Due to the shaped configuration of the opening in the installation part,
the material of the wall of the hollow body, that flows through that opening
into the installation part, preferably forms a head which holds the connection
similarly to a rivet head.
In a preferred variant of the process, the operation of pressing the
installation part against the inside wall of the article is effected without
lost
aids which would have to be removed from the article again for example after
the article is finished.
In a particularly preferred variant of the process according to the
invention the head of the connection is formed without aids for producing
deflection (restraining the plastic material of the wall of the hollow body,
that
flows into the opening).
Desirably two preforms in web form are extruded between the opened
halves of a two-part blow moulding mould, wherein the mould halves are
firstly closed against an installation carrier frame arranged between them,
arranged within the installation carrier frame are means for positioning
installation parts, with which the installation part is pressed out of the
plane
of the frame against the inside wall of the article, and wherein in a further
process step the installation part carrier frame is removed and the mould
halves are closed against each other to finish the article. The last process
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step provides for welding of the two halves of the article while still in the
first
heat.
It will be appreciated by the man skilled in the art that it is also
possible to provide an installation carrier plate in place of an installation
carrier frame. The installation carrier frame moreover does not necessarily
have to be in the form of an open or opened element.
The object of the invention is further attained by a plastic hollow body
having at least one installation or attachment portion, which was connected
to the hollow body in the production thereof, wherein the hollow body and
the installation or attachment part are connected together in positively
locking relationship in such a way that the installation or attachment part in
the region of its contact surface with the wall of the hollow body has at
least
one through opening through which passes the plastic material of the wall of
the hollow body and behind which said plastic material engages.
The through opening is desirably in the form of a circular bore.
Alternatively the through opening can be profiled, which is advantageous in
particular when the installation part has only one through opening and a
unique orientation of the installation part in relation to the wall of the
hollow
body is desired. Preferably the plastic material which passes through the
through opening forms in the installation or attachment parts an enlarged
head which provides for anchoring of the two components in positively
locking relationship.
In accordance with a preferred variant of the plastic hollow body
according to the invention it is provided that the installation part has at
least
one foot element which forms a set-off or stepped contact surface with the
wall of the hollow body. In that way, with the same pressing force, the
pressure in relation to surface area on the wall of the hollow body is
increased in the region of the contact surface. The foot element or elements
produce a punch-like action which reinforces the flow of the thermoplastic
material of the wall of the hollow body into the through opening. The
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through opening desirably passes through the contact surface of the foot
element.
In a variant of the plastic hollow body it is provided that the contact
surface of the foot element is of a concave or conical configuration and the
5 through opening forms approximately the deepest location of the trough
configuration, whereby the flow movement of the plastic material of the wall
of the hollow body through and behind the through opening is positively
influenced.
In a further desirable configuration of the plastic hollow body it is
provided that the through opening is of an undercut configuration at its end
which is remote from the wall of the hollow body. The undercut configuration
forms the support means for the enlarged head of the molten projection
when it has cooled.
If the plastic hollow body according to the invention is for example in
the form of a fuel tank, installation parts of the fuel tank can be equipped
with a plurality of foot elements in the above-described manner. Accordingly,
increasing the number and distribution of the connecting locations makes it
possible to achieve a connection or anchoring of the installation parts in the
interior of the fuel tank, with the connection or anchoring being secure and
reliable for any operating condition of the motor vehicle.
The invention is described hereinafter by means of an embodiment by
way of example illustrated in the drawing in which:
Figures 1 and 2 show a diagrammatic view of the connection of an
installation part to the wall of the hollow body, and
Figures 3 to 12 show a diagrammatic view of the production process
for a fuel tank of plastic material according to the invention.
As illustrated in highly simplified form in Figures 1 and 2 the
installation part 1 shown in section has a foot element 2 with a through
opening 3.
As already mentioned hereinbefore the process according to the
invention is described hereinafter by way of example by reference to the
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production of a fuel tank of plastic material. The invention however is to be
interpreted in such a way that any hollow body whatsoever can be produced.
The connection can be made both within and also outside the hollow body.
In the present case the installation part 1 is in the form of a surge pot in a
fuel tank.
The installation part 1 shown in Figure 1 is pressed with its foot
element 2 against the wall 4 of the hollow body to be produced, more
specifically when the plastic material of the wall 4 is still or is again in
the
plastic state. In the production process described hereinafter the connection
is made in the first heat in the production of the hollow body so that the
material of the wall 4 is still in the molten state and, when a sufficient
pressure is applied to the foot element 2 in the direction of the arrow shown
at the right in Figure 1, the material of the wall 4 forms the head 5 which is
shown in Figure 2 and which engages behind the through opening 3 in the
installation part 1. The through opening 3 is preferably in the form of a
round bore which is chamfered or undercut at its end remote from the wall 4.
For the purposes of improving the flow characteristics of the plastic
material the foot element 2 has a concave contact surface 6 which has a
through opening 3 passing therethrough centrally, that is to say at the
deepest location of its trough configuration. That shaping of the contact
surface 6 and the foot element 2 which is stepped in relation to the
installation part 1 promotes the flow characteristics of the molten material
through the through opening 3. With a given pressing force, the stepped
configuration of the foot element 2, in a punch-like form, increases the
pressure in relation to surface area in the region of the contact surface. The
concave configuration of the concave surface in conjunction with the
increased pressure in relation to surface area that occurs there causes the
molten material to be guided into the through opening 3.
On its side remote from the contact surface 6 the through opening 3 is
.30 provided with an undercut configuration 7 serving as a support means for
the
head 5. The head is formed even if the undercut configuration 7 is not
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present, it is then necessary under some circumstances to make the
thickness of the foot element 2 smaller.
As already mentioned hereinbefore the process according to the
invention is shown diagrammatically in Figures 3 to 12.
The process according to the invention includes the production of the
article 8 in the form of a fuel tank by extrusion blow moulding.
The moulding tool includes two mould halves 9a, 9b which are of a
mutually complementary configuration and which in the closed condition
define a mould cavity 10 which determines the external configuration of the
article 8 to be produced. Placed between the mould halves 9a, 9b is an
installation carrier frame 11 which is arranged displaceably between the
mould halves 9a, 9b. Installation part holders 12 are arranged variably in
position within the installation carrier frame 11. They are displaceable or
adjustable within the installation carrier frame 11 hydraulically or
pneumatically in the plane of the installation carrier frame and transversely
thereto. The installation part holders 12 are fitted with installation parts
1,
as shown in Figure 4. In the present case the installation parts 1 are
connected together by way of a line which is not identified in greater detail.
Each of the installation parts is approximately of the configuration shown in
Figures 1 and 2.
After the installation carrier frame 11 has been positioned between the
mould halves 9a, 9b preforms 13 in web form are extruded between the
opened mould halves 9a, 9b from one or more extrusions heads (not shown).
It is equally possible for the preforms 13 not to be extruded at the place of
installation of the tool but remote therefrom, and to be moved into position
between the opened mould halves 9a, 9b with a handling apparatus.
The preforms 13 respectively extend in the position shown in Figures 5
and 6 between a mould half 9a, 9b and the installation carrier frame 11. In a
further process step the preforms are applied by means of a reduced
pressure against the contour of the mould halves 9a, 9b in the mould cavity
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11. That can be effected with closure of the mould halves 9a, 9b against the
installation carrier frame 11, or it can already be effected previously.
The preforms 13 are caused to bear completely against the contour of
the mould cavity 10 by means of reduced pressure or also by an increased
pressure.
The installation part holders 12 then move out of the plane of the
frame and press the installation parts 1 against the wall 4 of the article 8
or
against the preforms bearing against the mould cavity 10. The above-
described anchoring effect for the installation parts 1 to the wall 4 of the
article 8 takes place.
The installation carrier holders 12 then move back into their starting
position. The mould halves are moved away from each other, in which case
the previously formed half-shell portions of the article 8 remain in the mould
cavity. The installation carrier frame 11 is moved away between the mould
halves 9a, 9b, the tool closes again and welds the two half-shell portions of
the article together.
The operation of shaping and removing the finished article 8 are
diagrammatically illustrated in Figures 11 and 12.
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List of references
1 installation part
2 foot element
3 through opening
4 wall
5 head
6 contact surface
7 undercut configuration
8 article
9a, 9b mould halves
10 mould cavity
11 installation carrier frame
12 installation part holder
13 preforms
a
