Aperture plugs

A plug for sealing an aperture in a panel includes a body portion adapted to close the aperture, a flange portion adapted to overlie an upper surface region adjacent the aperture, one or more insert portions adapted for insertion through the panel in contact or close adjacency to the edge surface of the aperture, and a body of sealant material in the form of a ring in contact with the under surface of the flange portion. The sealant material has the property of flowing when heated to an operating temperature lower than the melting point of the plug material, and the insert portion or portions of the plug and the body of sealant are formed so as to cause at least part of the sealant, upon being heated, to flow and adhere between the edge surface of the panel aperture and at least part of an insert portion.

FIELD OF THE INVENTION 
The present invention relates to a plug for closing and sealing an aperture 
in a panel and to a method of closing and sealing an aperture in a panel 
utilizing a plug. 
BACKGROUND OF THE INVENTION 
The invention has particular utility in closing paint drainage holes in 
motor car bodies. Such apertures are formed more usually in the floor plan 
of a motor vehicle to allow excess paint to drain before the body is 
transferred to the paint oven where the paint is dried. The apertures can 
vary from quite a small size up to e.g. 90 mm diameter and they may be of 
a variety of shapes for instance circular, elliptical or oblong. Such 
plugs are commonly called "floor plugs" although not all such apertures 
are necessarily in the floor of the vehicle. Recent examples on floor 
plugs are described in British Pat. Nos. 1,466,563 and 1,466,564. In such 
plugs a body of sealant material is used between the plugs and the upper 
surface of the panel which flows at least to a limited extent when 
subjected to high temperature, normally in the paint oven. Sufficient 
sealant material is used for this to flow when heated to fill any 
irregularities in the panel region adjacent the plug, and in the adjacent 
plug surface, to ensure a complete seal. 
While these plugs are generally successful in most applications, such 
plugs, particularly in the floor of the panel, are subjected to very 
considerable bombardment especially from rain water during travel of the 
motor vehicle and failures occur. The sealant or adhesive in such adhered 
plugs is restricted to the upper surface of the panel and normally between 
this surface and a flange portion of the plug which overlies the surface. 
The invention is aimed at improving the adhesion of aperture plugs 
generally and particularly floor plugs, to provide a secure fixing without 
complicating the insertion procedure. The insertion procedure of floor 
plugs has to be rapid and efficient. The plugs have to be inserted by an 
operative while the car bodies are moving on a conveyor system. 
SUMMARY OF THE INVENTION 
Essentially the invention relies upon causing at least a part of the 
sealant to flow into the aperture during the heating step and preferably 
to anchor against the under surface of the panel. 
In one form the invention provides a method of sealing in an aperture in a 
panel a plug which has at least one insert portion, a flange portion 
having an under surface, and a body of sealant material in contact with 
the under surface of the flange portion wherein said sealant material has 
the property of flowing when heated to an operating temperature lower than 
the melting point of the plug material, said method comprising inserting 
said at least one insert portion into said aperture, heating said sealant 
material and causing it to flow and adhere between the edge surface of 
said aperture and at least part of said at least one insert portion, and 
allowing said sealant material to cool. 
For example, the plug is preferably heated to cause the sealant material to 
flow to fill any irregularities in the adjacent surfaces of the flange 
portion of the plug and panel, and to flow within or through the aperture 
so as to engage between the insert portion(s) of the plug and the edge 
surface of the aperture. 
Preferably at least a part of the sealant flows through the aperture and is 
caused to adhere against the under surface of the panel. 
In another form of the invention there is provided a plug for an aperture 
in a panel comprising: 
at least one insert portion adapted for insertion into the aperture, 
a flange portion having an under surface adapted to overlie an upper 
surface region of the panel adjacent the aperture, and 
a body of sealant material in contact with said under surface of said 
flange portion, said sealant material having the property of flowing when 
heated to an operating temperature lower than the melting point of the 
plug material, and said at least one insert portion and said body sealant 
material being arranged such that at least a portion of said sealant 
material upon being heated when said at least one insert portion is 
inserted in the aperture, flows and adheres between the edge surface of 
the aperture and at least part of said at least one insert portion. 
Preferably the insert portion or portions are so formed that at least part 
of the heated sealant is directed to flow against and adhere to the under 
surface of the panel. 
Preferably the plug includes an insert portion in the form of a continuous 
or discontinuous neck. In a preferred embodiment, a lower part of such 
neck projects outwardly from the remainder at a maximum point in alignment 
with the edge of the aperture. This causes the flowing sealant to be 
directed around the edge of the aperture and against the underside of the 
panel. 
The insert portion may also include means adapted to maintain the sealant 
under compression at least until it is heated. This will ensure that the 
sealant is squeezed so that upon being heated it flows to fill the 
irregularities in the surfaces and is forced at least in part through the 
aperture. 
Thus the insert portion may include resiliently flexible legs, which may be 
located within discontinuities in the neck. Such legs preferably have an 
outward and downward sloping portion adapted to engage the edge of the 
aperture upon insertion of the plug to resiliently clamp the plug to the 
panel and maintain the sealant under pressure. 
The shape of the body portion of the plug will be determined by the shape 
of the aperture to be sealed, which may vary and will not necessarily be 
circular.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2 there is shown a plug 1 having a body portion 2 
and a flange portion 3 continuous with the body portion 2, portions 2 and 
3 constituting a continuous circular plate. Extending downwardly from the 
under surface of the plate at the junction of the body portion 2 and 
flange portion 3 are three neck portions 4a, 4b, and 4c. Between every two 
adjacent neck portions is one of three retaining legs 5a, 5b and 5c. The 
legs are attached to the remainder of the plug only at their upper 
extremities, to ensure resilient flexibility and they lie close to the 
neck portions but are spaced therefrom by narrow channels 6 which extend 
upwardly to the under surface of the plate (2,3). 
Since each neck portion is similar to the others and likewise each leg is 
similar to the other legs, only one of each will be described. The neck 
portion 4a has a cylindrical inner surface 7 at right angles to the 
underside of the body portion 2, but its outward surface is shaped to 
provide an outward projection 8 formed by a thickening of the neck to an 
outwardly directed point, as the portion is viewed in cross-section. As 
shown in FIG. 1 the upper surface 9 of the projection is concavely curved 
and the lower surface 10 is convexly curved. 
The inner surfaces 11 of the legs are again cylindrical and aligned with 
the inner surfaces of the neck portions. The outer surfaces of the legs 
have a neck surface 12 parallel to the surface 11, and a downwardly and 
outwardly oblique shoulder 13 joining with a downwardly and inwardly 
oblique surface 14 which tapers to meet the surface 11. 
The flange portion 3 is rebated on its underside to house a sealant body 15 
which is clamped between the edge portion 16 of the flange portion 3 and 
the neck surface 12 of each leg. The sealant body 15 may be adhered in 
place if desired during manufacture by a heat softening step at a 
relatively low temperature. It is sufficient only that it does not come 
loose during handling and storage. 
It will be observed that the extremity of the projection 8 of each neck 
portion is generally in alignment with the neck surfaces 12 of the legs. 
FIG. 3 shows a part of the plug immediately after insertion into an 
aperture 18 in a panel indicated as 17. In this condition, the legs 5a, 5b 
5c are flexed inwardly so that the edge of the panel engages against the 
upper oblique shoulder 13 of each leg which clamps the flange portion 3 of 
the panel and the sealant downwardly against the panel 17 and maintains 
the sealant under compression until it is heated. The maximum or peak 
diameter of the neck portions 4a, 4b, 4c is equal to or slightly less than 
the diameter of the aperture 18 and is positioned approximately in line 
with the under-surface of the panel so as to substantially close the 
aperture. 
When the assembly is heated, e.g. in a paint oven, the sealant melts and 
flows and in so doing fills the irregularities in the panel and the flange 
portion and also flows into the spaces between the edge of the panel and 
the neck portions as shown in FIG. 4. This out-flowing of the sealant 
reduces the volume of sealant on the upper surface of the panel. As this 
occurs the shoulders 13 ride down the underside edge of the panel aperture 
so that the peak diameter of the neck portions 4a, 4b, 4c also move 
downwardly opening up a gap through which the sealant can flow freely. At 
the same time, the edge portions 16 of the flange portions of the plug are 
brought down into engagement with the upper surface of the panel 17. The 
released sealant 15 flows through the aperture and fills the spaces 
between the edge of the panel and the neck portions of the plug. Some of 
the sealant is caused by the concavely curved surfaces 9 of the neck 
portions to flow against the underside of the panel. Furthermore some of 
the sealant flows through the channels 6 between the neck portions and the 
retaining legs and engages the shoulders 13 of the legs and the underside 
of the panel in the vicinity of the legs. In this way a complete seal is 
formed not only between the top surface of the panel and the plug but also 
all around the edge surface of the aperture and the adjacent underside 
region of the panel. This in turn forms a very secure anchorage for the 
plug when the assembly has cooled. 
It is not necessary for the neck regions to be shaped as in FIG. 4. FIG. 5 
shows a slightly different cross-section in which the chamfer between the 
inner surface 7 and the outer surfaces is outward and downward. This 
enables part of the sealant to flow under the projection to form a more 
secure anchorage to the neck portion. 
The preferred sealant is an EVA material (ethylene vinyl acetate), which 
can be compounded to flow at a variety of temperatures. The normal 
temperature in a paint sealing oven is between 140.degree. and 170.degree. 
C. and a suitable flow point for the EVA material would be from 
100.degree. to 135.degree. C. The material is present in a fairly 
substantial volume sufficient to fill the various channels as shown in the 
drawings. A material which tends to shrink on being heated is preferably 
avoided. Many other materials would be suitable as the sealant, e.g. soft 
polyethylene. If desired a thermosetting material could be used, if 
necessary with a blowing agent. Certain PVC plastisols containing blowing 
agents and which tend to expand and cross-link when heated, may be used, 
e.g. a material as sold by W. G. Grace & Co. under the name PLASTICOLE 
compound No. 1268. Polyurethane compositions containing blowing agents may 
also be used, but in general it has been found that a low softening 
thermoplastic material having good flowing and adhesive properties to 
metal and other plastic materials is to be preferred. 
The plug is preferably moulded from a suitable plastic material, which 
should be of good impact strength and abrasion resistance. A suitable 
material is Nylon (Trademark) 66. 
However in general the invention is not limited to plugs moulded from 
plastics materials and is not limited to the embodiment shown as regards 
structure. It may be applied to other known types of plug used, e.g. in 
vehicle body floor apertures, e.g. a snap-fit type as described in British 
Pat. No. 1,350,558, in which part of the plug engages underneath the panel 
when inserted, or a plug as described in British Pat. No. 735,044 in which 
a tool is used to dimple or spin a portion of the plug to engage under the 
panel. The invention is also generally applicable to the type of plug 
fitted with spring legs as described in British Pat. No. 1,466,563. 
Clearly it is not necessary that the sealant engages in the aperture or 
under the panel in all regions provided that a complete seal is obtained 
and a secure anchorage is afforded. In plugs provided with a continuous 
neck or collar region which is inserted through the aperture, provision 
may be necessary in the form of recesses or channels, to allow part of the 
sealant to flow through the aperture into contact with the edge surface of 
the aperture. 
It is not necessary for the sealant body to be confined (before insertion) 
to the flange region of the plug. In certain embodiments it may be 
desirable for at least part of the sealant body to project downwardly, 
e.g. against part of the insert portion so as to enter the panel aperture 
when the plug is inserted. 
The plug may be provided with any suitable number of retaining legs. While 
the illustrated embodiment has three retaining legs equiangularly spaced 
around the plug body and is suitable for use in a circular hole it may be 
desirable to have a larger number of retaining legs if the plug is 
designed to be used in an elliptical or rectangular hole.