Plastic locking cover and process for attaching same in a support aperture

The specification and drawings disclose a plastic sealing or locking cover 1, and a process for using it to seal an aperture of a support 3, such as an opening in an automobile body component. At least one cavity 5 of the locking cover 1 is filled with a medium 6 which can expand under the influence of temperature after mounting of the locking cover 1 in the support aperture 2 to thus press areas of the locking cover against neighboring areas of the support aperture to create a tight seal.

BACKGROUND OF THE INVENTION 
The invention relates to a plastic locking cover and a process for mounting 
the same in an aperture of a support. The invention is especially suited 
for use as a body hole plug for automobile bodies and various design 
possibilities exist for such a locking cover. 
State of the art locking covers are already known which are made of plastic 
and which have at their top and bottom surfaces a sealing lip which act 
and sealingly engage upon the neighboring surface planes in the area of 
the associated support aperture. (See, for example, German Patent Nos. 35 
12 582 and 30 11 448 and British Patent No. 1,354,973). With all such 
known locking covers, there exists, however, the drawback of their 
unintentional detachment from the support aperture. Consequently, 
provisions must always be made, such as through additional attachment 
devices, to assure the respective locking cover is permanently mounted 
within the support aperture. 
By contrast, the objective of the present invention is based upon 
development and appropriate design of a locking cover, so that an 
operationally safe, permanent mounting in a support aperture, for example 
an opening in automobile body component, is guaranteed without use of 
additional attachment devices. 
SUMMARY OF THE INVENTION 
According to the invention, this task is solved by providing at least one 
cavity in the locking cover which cavity is filled with a medium that can 
significantly expand under the influence of temperature. After mounting 
the locking cover in the support aperture, the medium can be heated to 
expand and thus press areas of the locking cover against neighboring areas 
of the support aperture. This results in the advantage that the locking 
cover, consisting of two materials, is attached within a support aperture; 
the medium within the cavity of the locking cover expands under the 
influence of temperature, whereby in mounted state, the respective areas 
of the locking cover press themselves against the inner edge of the 
support or collar hole, and thus absolute sealing is guaranteed. It does 
not matter whether the respective support apertures are designed round, 
oval or angular. 
Into the cavity of the locking cover a known substance, which significantly 
expands under the influence of temperature is injected, for instance by 
the known two-component injection molding process. The substance 
preferably can, according to another characteristic of the invention, 
expand within a temperature range of, for instance, up to approximately 
200.degree. C. This results in simple mounting, whereby through 
temperature actuated swelling of the respective material positioned in the 
cavity, the corresponding area of the locking cover is pressed so firmly 
against the interior wall of the support aperture that tight seating, 
water-tightness and, possibly, impermeability to gas is guaranteed. 
In a further more limited aspect of the invention, the cavity in which the 
expanding substance is contained can be arranged symmetrically in the 
locking cover. The cavity may either extend through the entire locking 
cover or be designed in the locking cover in the shape of a ring adjacent 
the cover's edge. 
According to another possible aspect of the invention, the cavity can be 
joined via at least one aperture with the top surface side and/or the 
bottom surface side, so that the material which swells under expansion of 
heat, can be easily positioned in the cavity. 
Another refinement of the invention is in the possibility that the locking 
cover can be designed as a single piece or in two pieces. The two pieces 
of the locking cover can be bonded together with one another permanently, 
for instance through an adhesion process, to close the corresponding 
cavity securely.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As can be best understood from FIG. 1A, the purpose of the locking cover is 
for installation in an aperture 2 of a support member 3, for example, a 
structural or panel member of an automobile body. In the arrangement of 
FIG. 1A, the locking cover includes a radially facing circumferential ring 
area 7 arranged to act upon the inwardly facing neighboring area 8 of the 
support aperture 2. The arrangement produces interengagement in such 
manner that secure attachment of locking cover 1 in support aperture 2 is 
guaranteed, that is to say it can be water tight and even impermeable to 
gas. To that end, the locking cover 1 exhibits in its interior an internal 
cavity 5 which is adjacent the filled with a medium, for instance a 
plastic substance 6 capable of undergoing substantial expansion. The 
cavity 5 of locking cover 1 is produced through a conventional injection 
molding process, for instance gas pressure process. Accordingly, the 
appropriate plastic material 6 can be filled into the cavity 5 by means of 
known injection procedures. 
The material 6 filling chamber 5 is selected so as to be capable of 
undergoing significant selective expansion and remaining in the expanded 
state after once being expanded. Thus, after the cover has been installed, 
selective expansion of material 5 produces tight sealing and locking 
engagement between the exterior periphery of the cover and edge of the 
aperture. 
Although it is believed that many different materials could be used to form 
covers in accordance with the invention, a specific material combination 
is the use of a thermoplastic for the main body of the cover and a plastic 
such as polyvinylchloride, polypropylene, or polyurethane having a 
charging gas mixed therein used as the filling for chamber 5. A typical 
charging gas would be nitrogen. 
When a cover formed as described above is installed and then heated to a 
temperature up to about 200.degree. C., the plastic softens and the 
charging gas expands thus expanding the softened plastic and forcing it 
radially into sealing and locking engagement with the edge of the 
aperture. 
After installation of the locking cover 1 containing the material 6 in 
cavity 5, the entire unit is subjected to heat treatment, by being heated 
to a temperature range where the material 6 expands, for example, from 
+90.degree. C. to .ltoreq.180.degree. C. Thus, the locking cover 1 is 
caused to be seated securely in support aperture 2 through swelling of 
material 6. In this arrangement, locking cover 1 exhibits, respectively, 
in the upper and lower area, sealing lips 9 and 10, which extend 
circumferentially about the cover and which position themselves, after 
completion of the heat treatment, against neighboring areas of the support 
aperture. By proper design of the lips 9 and 10 relative to the cavity 5, 
it is possible to have the lips rotate or shift into more firm engagement 
with the areas surrounding the aperture. 
In the embodiment according to FIG. 2, the locking cover 1 is designed 
identically to that described with reference to FIGS. 1A and 1; its 
purpose, however, is for the sealing and locking of a support aperture 2 
of the type which is equipped with a circumferential collar 4. Thus, the 
cover can be used with different apertures with equal facility. 
In the embodiment according to FIG. 3, the locking cover 1 is designed 
differently in that on the upper side 13 and the bottom side 14, there is 
present a somewhat ring-shaped recess 11, 12, respectively, Again, a 
cavity 5 is employed which is filled with the plastic material 6, which 
expands under the influence of temperature and remains in the expanded 
condition after being heated above a predetermined temperature. 
In the embodiment according to FIG. 4, once again, like FIG. 2, there 
exists the possibility of sealing aperture 2 of the support 3, which is 
equipped with a circumferential collar 4. 
While in the embodiments according to FIGS. 1 to 4, the cavity 5 extends 
across the entire locking cover 1, the cavity in the embodiment according 
to FIG. 5 is designed as ring 17 and is also filled with the previously 
discussed plastic material 6. 
In such an arrangement, there exists the possibility according to the FIG. 
6 embodiment to provide, on the upper side 13 of locking cover 1, a 
cup-shaped recess 11. Moreover, the ring-shaped cavity 5, 17', 
respectively can have any selected geometric shape. 
Again, the locking cover 1 according to FIG. 1 and FIG. 6 has 
circumferential sealing lips 9 and 10 in the upper and lower area. These 
lips can have other shapes and can be either rigid or flexible depending 
upon the environment in which they are to be used. 
In the embodiment according to FIG. 7, the cavity 5 is connected via at 
least one opening 15 with the upper side 13 of locking cover 1. Thus, 
material 6 can be easily installed via opening 15 into the ring-shaped 17 
cavity 5 of locking cover 1. 
According to FIG. 8, the possibility also exists that at least one 
aperture, 15, 16, respectively, leads from the upper side 13 and lower 
side 14, respectively, to the cavity 5, which is designed in the shape of 
a ring. In such an arrangement as well, the corresponding plastic material 
6 can be placed in simple fashion into the cavity 5. However, the material 
6 must be of such consistency that there can be no undesired slipping of 
the plastic material out of the locking cover 1. 
All the aforementioned designs of locking cover 1 have in common that they 
are each designed in one piece and exhibit in the interior a randomly 
shaped cavity 5. 
According to the embodiment of FIGS. 9 and 10, the locking cover 1' can be 
designed in two pieces with a cavity 5 built into either or both of the 
two parts is, 19 which are subsequently joined permanently together. These 
two pieces 18 and 19 are joined at the adjacent areas 20, 21, for instance 
through gluing or bonding, and after such joining, they form a one-piece 
locking cover 1'. Again, the appropriate material 6 can be placed into the 
rectangularly designed cavity 5, according to FIG. 9. 
The possibility also exists to form the two half-dish pieces 18, 19 so that 
they are connected by means of a hinge-joint and to fold them together, 
for instance, for gluing. 
In the embodiment according to FIG. 10, the cavity 5' is designed to have a 
"U"-shaped cross-section. It should be appreciated that the cavity 5 could 
have other cross-sectional shapes. Likewise, the two pieces 18, 19 of the 
locking cover can again have circumferential sealing lips 9, 10, 
respectively. 
The two-piece locking cover 1' can also be divided, in an embodiment which 
is not specifically illustrated in the drawings, in the area of its 
longitudinal axis into two semi-circular pieces. The pieces are, for 
example, connected with each other by means of a hinge joint. The pieces 
can be folded together to form one unit containing the cavity with 
adjacent areas glued together. 
As a result of the specific design of locking cover 1, 1', respectively, 
containing a material 6 placed into cavity 5, 5', respectively, which 
expands under the influence of temperature, for instance up to 200.degree. 
C. and above, operationally secure attachment of the locking cover in a 
support aperture is guaranteed in simple fashion. Moreover, firm seating 
and water tightness results. Under certain circumstances, even 
impermeability to gas can be attained. 
The invention has been described with reference to the preferred 
embodiment. 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.