Plastic fastener for detachably mounting a panel on a support member

A protective/decorative liner panel is mounted on a sheet metal support panel by molded plastic fasteners which allow the liner panel to be subsequently detached and reattached. Each fastener comprises a pin which is initially joined to a hollow grommet by a frangible web which aligns the pin shank with a bore in the grommet. The pin head is manually and twistably engageable with an installation hole in the liner panel and then the grommet is axially engaged with an installation hole in the support panel as the liner panel is moved toward the support panel. A hammer blow on the pin head fractures the web, forces the pin shank into the bore and moves the liner panel to its mounted position relative to the support panel. Serrations on the pin shank frictionally engage the bore wall to hold the pin and its attached liner panel in mounted position. First and second annular flexible resilient sealing flanges on the grommet and pin, respectively, seal the installation hole in the support panel against undesired liquid leakage. The sealing flange on the pin is large enough to encapsulate the sealing flange on the grommet when the pin shank is fully inserted in the grommet bore. The liner panel is detachable by pulling it away from the support panel and causing the pin shank to withdraw from the grommet bore, but the pin and grommet remain attached to their respective panels. The liner panel is re-attached by manually re-aligning the pin shank with the grommet bore and forcing it thereinto.

BACKGROUND OF THE INVENTION 
1. Field of Use 
This invention relates to a one-piece molded plastic fastener for mounting 
a first panel on a support member, such as another panel, so that the 
first panel can be detached and reattached. 
The fastener comprises a pin attachable to the first panel, a hollow 
grommet attachable to an installation hole in the support member, a 
frangible web initially interconnecting the pin and grommet but enabling 
the pin to be forcefully inserted into and subsequently withdrawn from the 
hollow grommet, and sealing means for the installation hole in the support 
member. 
2. Description of the Prior Art 
Various types of prior art fasteners are known or available for detachably 
mounting a first panel on a support member, such as another panel. Some of 
these fasteners are adapted to detachably mount a decorative and/or 
protective liner panel on the inside of an enclosed space in a piece of 
equipment such as an automobile or domestic appliance. In automobiles the 
passenger compartment and trunk use such liners. Domestic appliances, such 
as refrigerators or dishwashers, also use them. The liner panel needs to 
be removable and replaceable to enable servicing or replacement of 
components therebehind. Usually, a plurality of fasteners are used to 
secure each liner panel to the inside of a support member which, for 
example, typically takes the form of a rigid stamped sheet metal support 
panel forming part of the automobile or appliance structure. The support 
panel also provides mechanical support for other components in the 
structure. Some fasteners are one-piece or two-piece metal or plastic 
devices which are screwed or press-fitted in registering attachment holes 
in the liner and the support panel. Some attachment holes in the support 
panel are in locations where there is a risk of liquids leaking 
therethrough from the outside of the support panel and causing damage to, 
deterioration of or unsightliness in the associated liner or other 
components. In automobiles the liquid might be rain water, water splashed 
from the road, wash water, gasoline, oil or other liquid automotive 
products. Some fasteners are provided with separate or integral sealing 
washers or sealing devices to prevent leakage. 
U.S. Pat. No. 4,393,551 entitled "Rotatably Engaging Head For Fasteners", 
issued July 19, 1983 to Wollar and Schwind, and assigned to the same 
assignee as the present application, discloses a one-piece, 
injection-molded, self-sealing plastic fastener which is especially 
well-suited for the aforementioned purposes. This fastener has a special 
head which is twistably insertable manually into a pre-formed attachment 
hole in a liner panel and has an integral shank, with flexible resilient 
locking projections thereon, which is axially insertable into a 
registering pre-formed attachment hole in a support panel. To mount the 
liner panel with a plurality of such fasteners already attached thereto, 
the liner panel is placed adjacent the support panel in confronting 
relationship so that each fastener shank is axially aligned with the 
appropriate attachment hole in the support panel. Then, the liner panel is 
pressed-toward the support panel to cause the fastener shanks to enter the 
attachment holes therein, whereupon the flexible locking projections 
engage the edges of the attachment holes and secure the liner panel to the 
support panel. The flexible locking projections enable the liner panel to 
be detached merely by pulling it away from the support panel, carrying the 
fasteners with it, and also enable the liner panel to be reinstalled, as 
aforedescribed. This fastener comprises an annular flexible resilient 
sealing flange on its shank between the head and the locking projections, 
which flange engages the inside surface of the support member and seals 
the attachment hole therein against liquid leakage when the shank is fully 
inserted thereinto and the liner panel is properly mounted on the support 
panel. 
The fastener of U.S. Pat. No. 4,393,551 is satisfactory for its intended 
purpose, but there is a possibility that, if it is not properly installed, 
the sealing flange will not completely seal the attachment hole and a risk 
of leakage will exist. Furthermore, because the resilient flexible plastic 
locking projections directly slide across and engage sharp edges when 
inserted in an attachment hole in a support panel made of sheet metal, 
improper installation of the fastener or repeated insertion and withdrawal 
of the shank (occasioned by frequent detachment and reattachment of the 
liner panel) can damage the projections and render the fastener unfit to 
firmly secure the liner panel in place or unfit to enable an effective 
seal when mounted on the support panel. Therefore, there is a need for an 
improved fastener for this purpose. 
SUMMARY OF THE INVENTION 
In accordance with the invention, there is provided an improved one-piece 
molded plastic fastener for detachably mounting a first panel on a support 
member, such as a second panel. It is to be understood that the second 
panel has a fastener installation hole therethrough which is susceptible 
to undesirable fluid leakage. The fastener is especially well-adapted for 
use in equipment, such as automobiles or household appliances, wherein the 
aforementioned first panel is a detachable and reattachable decorative 
and/or protective liner panel, made of metal, plastic, fiber-board or the 
like, and wherein the second panel is a support panel, made of sheet 
metal, which forms part of the structure of the equipment. In practice, a 
plurality of fasteners are usually employed with a single liner panel. 
The fastener is made in one piece of resilient flexible plastic, such as 
Nylon (TM) or the like, and is preferably fabricated by a one-shot 
injection molding process. The fastener broadly comprises a hollow grommet 
having a bore therethrough and having mounting means enabling it to be 
mountable in an installation hole in the support panel; a pin having a pin 
shank and a pin head connectable to the first panel, preferably by means 
of an installation hole in the first panel; means, such as a frangible 
web, for initially and releasably connecting the pin and the grommet and 
enabling axial insertion of the pin shank into the grommet bore, as when 
the frangible web is broken; first sealing means on the grommet for 
sealing the installation hole in the support panel when the grommet is 
installed therein; second sealing means on the pin for engaging the 
support panel and cooperating with the first sealing means, as by 
encapsulation thereof, to form an additional seal for the installation 
hole in the support panel; and interengageable means on the pin and on the 
grommet to maintain the pin shank inserted in the grommet bore to thereby 
maintain the first panel mounted on the support panel. 
In a preferred embodiment of the invention, the pin head is constructed so 
as to be manually twistable into or out of engagement with a round (or 
elongated) installation hole in the first panel. Each first and second 
sealing means is an annular, conical, flexible, resilient sealing flange, 
with the second sealing flange being larger than and capable of overlying, 
surrounding and encapsulating the first sealing flange. The frangible web 
is annular in shape and integrally connected to and between the insertion 
end of the pin shank and the grommet edge around the grommet bore. The web 
initially aligns the pin shank with the grommet bore and also provides a 
one-piece fastener which, after fracture of the web, divides into two 
reusable pieces. The interengageable means which maintain the pin shank 
inserted in the grommet bore preferably comprise serrations on the pin 
shank which are frictionally engageable with the smooth, slightly 
resilient, deformable wall of the smaller diameter grommet bore. The 
frictional engagement is sufficient to maintain the pin shank firmly 
inserted in the grommet bore but, preferably, is not sufficient to prevent 
intentional withdrawal of the pin shank therefrom so as to enable the 
first panel to be detached from and subsequently reattached to the support 
panel. The grommet has flexible locking means or tabs which enable it to 
be secured in the installation hole in the support panel, and which, 
preferably, enable it to be removed therefrom if necessary or desirable. 
The fastener in accordance with the invention provides several advantages 
over the prior art. For example, it is manufactured and initially used as 
a one-piece unitary fastener, thereby eliminating the costly and 
time-consuming need to mold, subsequently handle, store, pre-assemble and 
install two or more separate pieces. The pin shank is initially 
pre-aligned axially with the grommet bore, thereby avoiding the need to 
deliberately effect such alignment, at least when the fastener is first 
employed. The pin shank is slidably received in the smooth-bored plastic 
grommet mounted in the installation hole in the support panel. This 
prevents any sharp edges of such hole from cutting or damaging the 
serrations on the pin shank and avoids the need to replace it because of 
serration damage. The relatively long grommet bore also ensures that the 
pin shank will be properly inserted and supported, either initially or 
subsequently, and also aids in proper positioning of the first panel and 
proper sealing against leakage. Two seals for the installation hole in the 
support plate provides a very effective seal, if both seals are properly 
engaged. Availability of two seals also ensures that leakage will not 
occur, even if one seal is improperly engaged. Because the two seals are 
integral with the fastener itself, storage and handling of separate seals 
is eliminated. As will be understood, the fastener could have other uses 
than those specifically disclosed herein. For example, it could be 
fabricated so as to have a pin head of a type other than that shown for 
attachment to something other than a first panel. Furthermore, it could be 
used to mount a first panel which never needs to be detached and 
re-attached. In such a case, the fastener could be constructed so that the 
pin shank could not subsequently be withdrawn from the grommet hole. Other 
objects and advantages of the invention will hereinafter appear.

DESCRIPTION OF PREFERRED EMBODIMENTS 
In FIGS. 1 and 8, numeral 10 designates a plastic fastener according to the 
invention for mounting a first member or panel 12 on a second member or 
panel 14 in confronting relationship and in such a way that panel 12 can 
be detached and reattached. Panels 12 and 14 have pre-formed installation 
holes 16 and 18, respectively, therethrough and hole 18 is understood to 
be subject to fluid (liquid) leakage therethrough which could adversely 
affect panel 12 or components (not shown) between the panels. Fastener 10 
is, therefore, further adapted to provide a dual seal to prevent such 
leakage. 
Panel 12 may, for example, be a decorative and/or protective panel (made of 
metal, plastic, fiber-board or the like) such as is used as a liner panel 
in a compartment in a vehicle (automobile, truck or the like) or domestic 
appliance (refrigerator, freezer, dishwasher or the like). Panel 14 may, 
for example, be a support panel (made of rigid sheet metal or the like) 
forming part of the structure of the vehicle or domestic appliance. Panel 
12 is detachable to afford access to components (not shown) located 
therebehind to enable servicing and/or replacement and needs to be 
reattached thereafter. Installation hole 16 in panel 12 is shown as round 
in FIGS. 1, 2 and 8, but could be an elongated hole 16A, as shown in FIG. 
2. Installation hole 18 in panel 14 is shown as round in FIGS. 1, 3 and 8. 
Fastener 10 is made of plastic which is resilient, flexible and deformable, 
such as Nylon (TM) or the like, and is fabricated in one piece, preferably 
by a one-shot injection molding process. Fastener 10 comprises a pin 
portion or pin 20, a grommet portion or grommet 22 and a frangible web 
portion or web 24 which is integrally connected between pin 20 and grommet 
22. 
FIG. 1 shows fastener 10 attached to both panels 12 and 14, out prior to 
fracture of web 24 and prior to movement of liner panel 12 to its fully 
installed or fully mounted position relative to support panel 14. FIG. 8 
shows fastener 10 attached to ooth panels 12 and 14, and after fracture of 
web 24 and after liner panel 12 has been moved to its fully installed or 
fully mounted position. 
As FIGS. 1, 4, 5, 6, 7 and 8 show, pin 20 generally comprises a pin head 
28, hereinafter described in detail, an annular flexible resilient sealing 
member 30 axially spaced from the pin head by a stem portion 33, and a 
cylindrical pin shank 32 having a cylindrical serrated portion 34, a 
cylindrical smooth guide portion 36 and a blunt tip portion 38. Grommet 22 
generally comprises a cylindrical grommet shank 40 having a smooth 
cylindrical grommet bore 42 therethrough, an annular flexible resilient 
sealing member 44 around the grommet shank, a plurality (four) flexible 
resilient locking projections or tabs 46 on the grommet shank and axially 
spaced from sealing member 44, and a conical tip portion 48. Web 24 takes 
the form of a thin frangible annular web, formed during molding, which is 
connected between the end of guide portion 36 of pin 20 and the grommet 22 
on a portion thereof surrounding grommet bore 42. 
As FIGS. 1, 4 and 5 show, pin head 28 on pin 20 is of the same type shown 
in aforementioned U.S. Pat. No. 4,393,551 and enables fastener 10 to be 
twistably secured to and twistably removed from installation hole 16 in 
liner panel 12 and reference should be had to that patent for a complete 
description thereof. Briefly, pin head 28 had a flat circular underside 27 
having a radial slit 29 therein and an integral tapered tongue 31 located 
above the underside 27. Tongue 31 is insertable into installation hole 16 
and fastener 10 is twisted so that head 28 gradually screws into hole 16. 
Removal is effected by twisting in the opposite direction. 
As FIGS. 1 and 8 show, the sealing members 30 and 44 are similar to each 
other in general configuration but member 30 is larger than member 44 in 
order to effect encapsulation thereof (see FIG. 8). The sealing members 30 
and 44 are resilient, flexible, conically shaped, annular flange-like 
members having cavities 45 and 47, respectively, therein. Cavity 45 is 
large enough to surround and encapsulate sealing member 44. Both are 
adapted to engage support panel 14, as FIG. 8 shows, to seal hole 18 
therein when fastener 10 is fully installed. 
Each tab 46 on grommet shank 40 is a thin flexible member of generally 
triangular shape integrally formed on the grommet shank and having sloped 
edges 49 and 51 which meet at an apex 53. When the tabs are fully 
extended, the distance between the apices of two diametrically opposed 
tabs 46 is greater than the diameter of installation hole 18 in support 
plate 14. The fully extended tabs 46 cooperate with sealing member 44 to 
entrap plate 14 therebetween and maintain grommet 22 releasably installed 
in hole 18. The tabs 46 flex or deform to enable intentional insertion or 
withdrawal of grommet 22 in hole 18. 
In a preferred embodiment of fastener 10, the following dimensions (in 
millimeters) were found satisfactory to enable fastener 10 to function 
properly for its intended purposes: 
diameter of grommet bore 42: 5.60 
diameter of pin guide portion 36: 5.60 
diameter (widest point) of pin blunt tip 38: 5.10 
outside diameter of serrated portion 34: 5.80 
root diameter of serrated portion 34: 5.00 
outside diameter of grommet sealing member 44: 12.00 
maximum thickness of grommet sealing member 44: 1.20 
diameter of cavity 45 in pin sealing member 30 greater than: 12.00 
depth of cavity 45 in pin sealing member 30 greater than: 1.20 
Fastener 10 is employed as follows. Assume that fastener 10 is in the 
condition shown in FIG. 1 and that web 24 is intact. The fastener is 
manually gripped and its pin head 28 is manually inserted and installed by 
twisting in installation hole 16 in liner panel 12 so that it is connected 
to liner panel 12 as shown in FIG. 1. Then, liner panel 12 is disposed in 
confronting parallel relationship to support panel 14 so that conical tip 
portion 48 of grommet 22 is axially aligned with insertion hole 18 in 
support panel 14. Liner panel 12 with fastener 10 attached thereto is then 
moved toward support panel 14 so that grommet 22 is inserted and installed 
by axial insertion in installation hole 18 in support panel 14, as shown 
in FIG. 1. In particular, the conical grommet tip portion 48 of grommet 22 
enters hole 18, the locking tabs 46 flex, enter hole 18 from one side and 
exit the other, and then flex back to the position shown in FIG. 1. Thus, 
support panel 14 is entrapped between sealing member 44 and the locking 
tabs 46. Such installation of grommet 22 causes sealing member 44 to flex 
and resiliently engage the side of support panel 14 closest to liner panel 
12 and effect an annular fluid-tight seal around installation hole 18. 
At the stage of assembly shown in FIG. 1, fastener 10 is attached to both 
panels and liner panel 12 is temporarily supported on support panel 14 but 
is not yet in its final mounting position shown in FIG. 8. Web 24 of 
fastener 10 is still unfractured and intact and pin 20 is not yet inserted 
into bore 42 of grommet 22. 
Now assume that fastener 10 and the panels 12 and 14 are in the relative 
positions and conditions shown in FIG. 1. As FIG. 7 shows, blunt tip 38 of 
pin 20 already extends into bore 42 of grommet 22, but the smooth pin 
guide portion 36 does not. In order to effect movement of liner panel 12 
to its fully installed position shown in FIG. 8, a strong blow is 
delivered to pin head 28, as by means of a hammer or mallet, to effect 
axial movement of pin 20 toward grommet 22. As this pin movement 
commences, web 24 fractures and smooth guide portion 36 of pin 20 slidably 
enters smooth grommet bore 42, being guided for such entry, if necessary, 
by blunt tip 38. As pin movement continues, serrated portion 34 of pin 20 
enters and is inserted into grommet bore 42, being guided by pin guide 
portion 36. Although the outside diameter of serrated portion 34 is larger 
than that of bore 42, the serration tips 35 and wall 45 of the bore are 
sufficiently flexible, resilient and compressible to enable such entry, if 
the blow is forceful enough. 
As FIG. 8 shows, when pin 20 reaches its fully inserted position, sealing 
member 30 thereon overlies, surrounds and encapsulates sealing member 44 
of grommet 22 and engages the side of support panel 14 closest to liner 
panel 12 and effects an additional of back-up annular fluid-tight seal 
around installation hole 18 in support panel 14. FIG. 8 also shows that 
liner panel 12 is then in fully mounted position relative to support panel 
14. Liner panel 12 is maintained in fully mounted position and pin 20 is 
maintained in fully inserted position because, as FIG. 8 shows, the 
serration tips 35 dig into and frictionally engage resilient wall 45 of 
plastic grommet bore 42 with sufficient force to prevent unintentional 
axial withdrawal of pin 20. 
Liner panel 12 can be detached from support panel 14 by manually pulling it 
away from support panel 14 with sufficient force to overcome the 
aforementioned force of frictional engagement and effect complete axial 
withdrawal of pin shank 32 from grommet bore 42. The flexibility, 
resiliency and deformability of the plastic of fastener 10 enable this to 
occur. However, when the panels 12 and 14 are detached from each other, 
pin 20 and grommet 22 remain attached to the panels 12 and 14, 
respectively. 
Liner panel 12 can be reattached to or remounted on support panel 14 as 
follows. The liner panel 12, with pin 20 still attached thereto is 
disposed in confronting parallel relationship to support panel 14 on which 
grommet 22 is still attached. Blunt tip portion 38 of pin 20 is aligned 
with and inserted into grommet bore 42 and it guides pin guide portion 36 
into grommet bore 42 as liner panel 12 is moved toward support panel 14. 
At this stage, a hammer blow is delivered to head 28 of pin 20 and guide 
portion 36, in turn, guides serrated portion 34 of pin 20 into grommet 
bore 42, as hereinbefore described. 
If it so happens that either pin 20 or grommet 22 or both are damaged and 
unsuitable for use, each may be removed from its associated panel, while 
the panels are detached from one another, and a new fastener 10 may be 
installed. Removal of pin 20 from its installation hole 16 in liner panel 
12 is effected by twisting it in the direction reverse to its installation 
direction. Removal of grommet 22 from its installation hole 18 in support 
panel 14 is effected by pulling on it axially (by means of sealing member 
44) with sufficient force to cause the locking tabs 46 to flex and bend 
relative to grommet shank 40 and pass through hole 18.