Closure element made of thermoplastic material

A closure element is provided made of plastic, particularly for sealing off at least one opening 2, 3 in at least one support member 20, 30, in particular, in a automotive body, the closure element including a head section 4 located above the support, and a basic body portion 5 extending through the support 20, 30. At least one region of the closure element is made of a material which expands under the influence of temperature. The basic body portion 5 and the head section 4 of the closure element 1' is preferably formed of a single piece of thermal plastic material, which, is with increased thermal influence, media-tight bondable via a gluing action within the openings 2, 3.

BACKGROUND OF THE INVENTION 
The subject invention is directed toward the art of plastic closure 
elements and, more particularly, to plastic closure elements or seal plugs 
that include a body section extending through at least one opening in at 
least one support or panel, an enlarged head section on one side of the 
support or panel, and a thermal expanding material disposed on at least 
one area of the closure element, the thermal expanding material being 
adapted to expand under the influence of temperature to seal the at least 
one opening. 
The invention is especially well suited for incorporation in automotive 
body panels and will be described with reference thereto; however, as will 
become apparent, the invention is capable of broader application and could 
be incorporated in a variety of components or used as a separate fastener 
for many purposes. 
Other closure elements made of plastic and a thermal expanding material are 
already known in the art such as shown in German patent number DE 40 18 
425 A1. In the above prior art example, the closure element includes a 
hollow space defined in the body of the closure element. The hollow space 
is filled with at thermal expanding medium which, after installing the 
closure lid in a support opening, expands under the influence of 
temperature to thus press areas of the closing lid against adjacent areas 
of the support opening. This results in producing a closure of the support 
opening. One problem with closure elements having the above-known 
construction is that it is necessary to take special design and 
manufacturing measures in order to provide the hollow space in the body of 
the closure element. 
In addition to the above, other closure caps are known which are made of 
plastic and which have, at respective opposing top and bottom ends 
thereof, a sealing lip, which acts upon the adjacent surfaces in the area 
of the support opening. Examples of this type of closure cap are DE-OS 35 
12 582, DE-OS 30 11 448 and GB-PS 1354973. 
One problem all of the above closure caps experience is the possibility of 
unintentional separation from the support opening before the thermal 
expanding material has had an opportunity to expand and seal the support 
opening and attach the closure element thereto. Thus, with the above 
closure caps, provisions must always be provided by means of additional 
fixtures or additional structural elements on the closure cap in order to 
ensure that the closure element remains fastened to the respective support 
opening until such time as the thermal expanding material has had an 
opportunity to expand and seal fastening the closure element to the 
opening. 
SUMMARY OF THE INVENTION 
The subject invention provides an arrangement which overcomes the 
shortcomings discussed above in connection with known seal plugs and 
provides a water-tight closure of at least one support opening and a 
relatively functionally safe and secure attachment to the support member 
with a closure element having a simple construction. 
In accordance with the invention, there is provided an improved plastic 
closure element for closing at least one opening in at least one 
operatively associated support member. The closure element includes a body 
portion and a head segment, each being formed from a single piece of 
thermoplastic material, which under the influence of an increase in 
temperature, is expandable and bondable through agglutination with the 
opening and its surrounding area within the support member. 
In accordance with another aspect of the invention, the closure element is 
formed having a simple design consisting of a basic body portion and a 
head section adjacent thereto whereby both areas are adapted to be 
manufactured quickly and inexpensively together using a thermoplastic 
material. The material forming the closure element is "media-tight" and, 
thus, seals against the flow of various fluids including water and oil. 
In accordance with yet another aspect of the present invention, the closure 
element is adaptable to serve simultaneously or separately as a base of a 
fastening element such as a bolt or screw or the like. In addition, the 
present invention is useful as a connection element for connecting at 
least two construction components. 
The thermoplastic material forming the closure element of the present 
invention has the advantageous property that, in the presence of an 
increase in temperature, the material expands and spreads out against the 
circumference of the respective support opening to impermeably seal the 
circumferential region of the support. After installation of the closure 
element according to the invention in at least one support opening formed 
in at least one support, the entire closure element needs only to next be 
exposed to an increase in temperature in order to ensure a media-tight 
seal of the at least one support opening. 
In accordance with a somewhat more limited aspect of the invention, a 
second embodiment of the invention includes a first section formed into 
the shape of a flange on an end of a basic body portion formed into the 
shape of a cone. In this embodiment, the cone-shaped basic body portion is 
alternatively selectively shaped into a truncated cone, the truncated cone 
having a bowl-shaped recess formed therein, a narrow bottom end, and a 
wide top portion connected to the flange. For adjustment to the 
circumference of the respective support opening, the truncated cone is 
formed to change shape or transition into a cylindrical-shaped portion at 
the wide top portion facing the underside of the flange. The 
cylindrical-shaped portion preferably has a smaller diameter than the 
cross-section surface of the truncated cone region. Moreover, at the 
underside of the flange, there is preferably provided a circumferential 
groove which functions as a provisional auxiliary seal. 
In accordance with still yet a somewhat more limited aspect of the 
invention, a third embodiment includes a projecting spreader region on the 
basic body portion of the closing element. The projecting spreader region 
is connected to the cylindrical region traversing the support opening. In 
this embodiment, a spreader element is receivable into the basic body 
portion and the flange, the spreader element being moveable into positions 
effecting an opened and closed spreader region position and further, the 
spreader element includes a cover portion for covering the flange formed 
in the first section of the plastic closure element. 
In accordance another aspect of the invention, the spreader region consists 
of several spreader arms which are moveable into a spread position through 
interaction of a cylindrical region of the spreader element. In this 
embodiment, the basic body portion has two successively arranged axially 
spaced apart openings of different diameters whereby the opening of the 
smaller diameter is located in the area of the spreader arms and is 
selected to substantially correspond to the outer diameter of an imbedded 
region formed on the spreader element. The spreader element preferably 
consists of a plastic material which is stable, even under the influence 
of high temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring more particularly to the drawings wherein the showings are for 
the purposes of illustrating the preferred embodiments of the invention 
only and not for purposes of limiting same, 
FIG. 1 generally illustrates a closure element 1 according to the present 
invention, made of plastic, which, in the first embodiment, serves to 
close two openings 2, 3 respectively formed in two operatively associated 
support members 20, 30. As shown, each of the two openings 2, 3 have 
different diameters. The closure element 1 includes a head segment 4 
located above support 20. The head segment is preferably formed in the 
shape of a flange 4'. The flange 4' is followed by a cone formed as a 
basic body portion 5, the basic body portion extending through the two 
openings 2, 3 of the two support members 20, 30. 
It will be appreciated by those of ordinary skill in the art that the 
closure element of the present invention is useful separately as shown in 
FIG. 1 or simultaneously as a base member of a fastening element. Further, 
the present invention is useful as a connection element for connecting at 
least two construction components. 
According to the present invention, the basic body portion 5 and the flange 
4' of the closure element 1 is made from a thermoplastic expandable 
extruded material. The material, as shown best in FIG. 2, when exposed to 
an increase of temperature, enters into a blister-formation state and 
effects a gluing into a media-tight connection and closure of the openings 
2, 3 when exposed to an increase of temperature. The blister formation 
state is also realized with the employed materials. 
FIGS. 3-5 show a second preferred embodiment of a closure element 1' 
according to the invention. In this embodiment, a truncated cone 5' is 
formed below the flange 4'. The truncated cone 5' serves as the basic body 
portion. The truncated cone 5' preferably includes a bowl-shaped recess 6. 
As is best shown in FIG. 3, the truncated cone region 5' changes shape 
over at an expanded region B facing the underside of the flange 4' into a 
cylindrical region 7. The cylindrical region 7 preferably has a diameter 
which is less than a cross section of the surface of the region B of the 
truncated cone portion 5'. The cylindrical region 7 is particularly useful 
for connecting the closure element into the support openings. 
Further as shown in FIGS. 3 and 4, the underside of the flange 4' is 
equipped with a circumferential groove 8. In that manner, the exterior 
circumference of the flange 4' forms a sealing lip between the closure 
element and the support opening. The sealing lip engages the surface of 
the support 20 in an annular region surrounding the opening 2. As best 
shown in FIG. 4, the circular region of engagement between the sealing lip 
and the support opening is preferably circularly continuous and spaced 
apart from the edge of the rim of the support opening. 
FIG. 5 illustrates the plastic closure element of the second preferred 
embodiment after having undergone the thermal expanding effect. As shown 
in that figure, the closure element 1' is installed in a support opening 2 
of an operatively associated support member 20. As shown there, the 
closure element has undergone blister formation and gluing action to bond 
the closure element to the opening 2 at a circumferential region of the 
support 20 so that the support opening 2 is media-tight sealed. 
The closure element 1 according to the first preferred embodiment as shown 
in FIGS. 1 and 2 and the closure element 1' according to the second 
preferred embodiment as shown in FIGS. 3-5 are each respectively 
constructed as a single piece having a unitary construction. That is, the 
closure elements 1, 1' are formed entirely of the thermal expanding 
plastic material. According to FIGS. 6-8, the third preferred embodiment 
of the present invention is a closure element 1" which is formed in two 
pieces, each piece being formed of a different material. 
With reference now to FIGS. 6-8, the basic body portion 5 includes a 
spreader region 10 which protrudes from the support opening 2, 3. The 
spreader region 10 is followed by a cylindrical region 7' traversing and 
extending through the respective support openings. According to FIGS. 6 
and 7, the spreader region preferably consists of several spreader arms 
10, 10" circumferentially disposed around said cylindrical region 7'. 
In addition to the above, the basic body portion includes two successively 
arranged internal openings 12, 12', the openings 12, 12' are axially 
spaced apart as shown and, in addition, each is preferably formed having a 
diameter different from the other. The opening 12' has a smaller diameter 
and is located in the region of the spreader arms 10, 10". 
The closure element of the third preferred embodiment includes a separate 
spreader element 15 which, as best illustrated in FIG. 7, consists of a 
cover flange 26, a cylindrical region 25, and a lead-in inbedment region 
27. Preferably, a bowl-shaped recess 28 is formed in the cylindrical 
region 25 of the spreader element 15. 
FIG. 6 illustrates the delivery state of the third preferred embodiment of 
the invention. With reference now particularly to that figure, the 
embedment region 27 is located in the opening 12' having the smaller 
diameter formed in the basic body portion 5. The cylindrical region 25 is 
located above the flange 4'. In this delivery state, the two-piece closure 
element 1" is easily installed into the two openings 2, 3 having different 
diameters in a manner that the cylindrical-shaped region 7' of the basic 
body traverses both of the openings 2, 3, whereby flange 4' is positioned 
on the upper side of the support member 20. 
FIG. 7 illustrates the connection state of the closure element whereat the 
spreader element 15 is pressed into the two openings 12, 12' of the basic 
body portion 5. In that position, the spreader region 10 opens up and the 
plurality of spreader arms 10, 10' assume a spread-open position. The 
longitudinal or axial motion of the spreader element is facilitated by the 
shape of the cone region 27' between the cylindrical region 25 and the 
inbedment region 27. In the position illustrated, the cylindrical region 
25 traverses the openings 12, 12' formed in the basic body portion. 
In the installed state as shown in FIG. 7, the cover flange 26 of the 
spreader element 15 includes a free space 29 formed on an underside 
thereof covering the flange 4'. 
Upon exposure to a temperature increase, the material forming the basic 
body portion 5 undergoes a deformation, for example a blister formation 
and gluing state, and thereby expands and seals off the openings 2, 3 as 
best shown in FIG. 8. The result is a media-tight closure of the two 
openings 2, 3. In addition, an aesthetically pleasant effect achieved 
because the cover flange 26 of the spreader element 15 covers over the 
thermoexpanded body portion on the side of the top support member 20. 
Although the spreader arms 10, 10' are illustrated as being elongated 
members, those of ordinary skill in the art would appreciate that the 
spreader arms can be formed of any type or number. However, it is 
important that the spreader arms be moveable to radiate outwardly as 
illustrated from the delivery position depicted in FIG. 6 to the installed 
position depicted in FIG. 7 at which position the spreading operation of 
the spreader arms takes place behind the support 20 or 30 to grip the 
closure element to the support members 20, 30. 
Thus, according to the present invention, the closure element 1, 1', 1" 
easily media-tight seals openings having a range of different diameters 
without regard for whether the multiple openings 2, 3 have different 
diameters in each of the respective stacked support member openings. 
The invention has been described with reference to the preferred 
embodiments. Obviously, modifications and alterations will occur to others 
upon a reading and understanding of this specification. It is intended to 
include all such modifications and alterations insofar as they come within 
the scope of the appended claims or the equivalents thereof.