PLASTIC SCREW GROMMET

RONDELLE PLASTIQUE POUR VIS

English Abstract

ABSTRACT
A plastic screw grommet provided with a through hole and
extending at one end in a sleeve which is connected to the remain-
der portion of the grommet through a thin section frangible upon
a blow struck on the sleeve and designed to receive a self-tapping
screw, said grommet being provided at the front face intended to
abut the wall to which the grommet is secured, with a flange and
internally with at least a frustoconical surface connected to said
flange with tapering directed against said flange.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A plastic screw grommet, characterized in that
it is provided with a through hole and extends a-t one end
in a sleeve which is connected to the remainder portion
of the grommet through a thin section, said -thin section
being frangible upon a blow struck on the sleeve, said sleeve
being designed to receive a self-tapping screw, said grommet
being provided with a flange at said one end intended to abut
the wall into which the grommet is secured, said grommet
externally having a pair of opposite frustoconical surfaces
connected to said flange with a reducing taper as the
grommet external surface approaches said flange, and said
sleeve being provided inside with a diaphragm for preventing
the outflow of any foam or other foaming material through
the sleeve hole from the apparatus to which said grommet
is applied.
2. A plastic screw grommet according to Claim 1,
characterized in that said sleeve is provided at both ends with
shoulders for engagement respectively with said flange at
said one end and with said other end of said grommet
arranged as said sleeve is inserted into the grommet.
3. A plastic screw grommet according to Claim 1,
characterized in that the hole and the outer surface of
said sleeve are substantially square in cross-section, and
said hole is provided at each of four corners with a relief
recess in order to make the grommet flexible.
4. A plastic screw grommet according to Claim 2,
characterized in that the hole and the outer surface of
said sleeve are substantially square in cross-section,
and said hole is provided at each of four corners with a
relief recess in order to make the grommet flexible.

5. A plastic screw grommet according to Claim 1,
characterized in that said diaphragm defines on the one hand
the hole receiving the self-tapping screw and on the other
hand a recess intended to make the sleeve flexible for
introducing it in the grommet.
6. A plastic screw grommet according to Claim 2,
characterized in that said diaphragm defines on the one hand
the hole receiving the self-tapping screw and on the other
hand a recess intended to make the sleeve flexible for
introducing it in the grommet.
7. A plastic screw grommet according to Claim 3,
characterized in that said diaphragm defines on the one hand
the hole receiving the self-tapping screw and on the other
hand a recess intended to make the sleeve flexible for
introducing it in the grommet.
8. A plastic screw grommet according to Claim 4,
characterized in that said diaphragm defines on the one hand
the hole receiving the self-tapping screw and on the other
hand a recess intended to make the sleeve flexible for
introducing it in the grommet.
9. A plastic screw grommet according to Claim 2,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.

10. A plastic screw grommet according to Claim 3,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.
11. A plastic screw grommet according to Claim 4,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.
12. A plastic screw grommet according to Claim 5,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.
13. A plastic screw grommet according to Claim 6,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.
14. A plastic screw grommet according to Claim 7,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.

15. A plastic screw grommet according to Claim 8,
characterized in that the shoulder at one end of said sleeve
is formed of two diametrically opposed projections and the
shoulder at the other end of said sleeve is formed of two
diametrically opposed lugs arranged substantially at 90°
to the projections.
16. A plastic screw grommet according to Claim 9, Claim 10
or Claim 11, characterized in that said flange of grommet is
provided with two diametrically opposed grooves, intended
to receive the lugs of said sleeve as the latter is inserted
into the grommet.
17. A plastic screw grommet according to Claim 12 or
Claim 13, characterized in that said flange of grommet is
provided with two diametrically opposed grooves, intended to
receive the lugs of said sleeve as the latter is inserted into
the grommet.
18. A plastic screw grommet according to Claim 14
or Claim 15, characterized in that said flange of grommet is
provided with two diametrically opposed grooves, intended to
receive the lugs of said sleeve as the latter is inserted
into the grommet.

Description

10503~Lo
PLASTIC SCl~W GRG~F~
.
This invention relates to a plastic screw grom~et intended
to act as an insert for a self-tapping screw.
In certain application where it is necessary -to secure a
¦screw to a thin wall, generally of sheet metal, it is necessary
to provide a support for the screw, because the en~agement a~o~e
¦of the screw with corresponding threads provided in a sheet hole
¦in which the screw is positioned would not be sufficient to pre-
¦vent a loosening or vibration of the screw. Such applications
¦occux for example in refrigerator cabinets in which such screws
¦can be required for fastening various internal components of the
refrigerator cabinet. In these applications there is also the
problem of providin~ a seal for the polyurethane ~oam during the
foaming operation necessary for filling with polyurethane foam
the hollow space between the walls of the cabinet. ~nother ex~mp e
of application occurs in the case of car body parts where there i
also the need to provide, by means of screws inserted into the
sheet, fastening locations of different devices to the body and
simultaneously to coat with polyurethane foam portions of the bod .
Solutions to these problems have been already proposed, but
they were elaborated and expensive~
~he object of this invention is to solve the above problems
in a simpler and more economical manner.
The object.is attained by the invention which contemplates
a plastic screw grommet that nas a through hole that extends at
one end in a sleeve. The sleeve is connected to the remainder
--1--

~IL()503~0
portion of the grommet through a thin section, with the
thin section being frangible upon a blow struck on the
sleeve. The sleeve is designed to receive a self-tapping
screw, and the grommet is provided with a flange at the
one end intended to abut the wall into which the grommet
is secured. The grommet externally has a pair of opposite
frustoconical surfaces connected to the flange with a
reducing taper as the grommet external surface approaches
the flange, and the sleeve is provided inside with a
diaphragm for preventing the outflow of any foam or other
foaming material through the sleeve hole from the apparatus
to whicll the grommet is applied.
By means of this arrangement, if measures have been taken
to shape the frustoconical surface in such a manner that, once
a screw is introduced in a suitable hole provided in the wa11
to which it is to be fastened, the hole wall presses on the
grommet thereby reducing the diameter of the through hole
thereof, a blow struck on the sleeve causes the fracture
of the thin section connecting the sleeve to the remainder of
the grommet and the penetration of the sleeve into the grommet
with the grommet being locked against the wall, because the
sleeve tends to expand the grommet compressed by the wall
hole. In this position the sleeve is ready to receive the
self-tapping screw.
According to a feature of the invention the sleeve is
internally provided with a diaphragm for preventing the
polyurethane foam or other similar foaming material of the
apparatus to which said grommet is applied to fall out of
the sleeve hole during the foaming operation.
According to another feature of the invention the sleeve is
provided at both ends with a pair of shoulders for engagement with

- ~05~3~
a front wall of the grommet ~nd the flange of the grommet arrarl-
ged at the other front wall of the grommet as the sleeve is insert _
ed into the grommet.
The above and other features will be apparent from the follo~ _
ing detsiled description merely given by wa~ of example and there-
fore not intended in a limiting sense, of an embodiment of the
invention in connection with the accompanying drawing, wherein:
Fig. 1 is an elevation view of a screw grommet according to
the invention before it is applied to a wall; .
~lg. 2 is a sectional view taken along the line 2-2 of Fig~ ;
Fig 3 is a front view of the screw grommet of Figs. 1 and 2
looking in the direction of arrow 3 of these figures;
Fig. 4 is a fragmentary view taken along the line 4-4 of Fig
3, appearing with Fig. 1; and
~ ig. 5 is a fragmentary front view of the screw grommet look-
. ing in the direction of arrow 5 of Fig. 1 once a screw shank isinstroduced into the grommet, appearing with Fig. 1.
Referring to the ~igures of the drawing, there is seen. that
the screw grommet 1 is provlded with a through hole 2 and a pair
of outer frustoconical surfaces 3 and 4.
The hole 2 is square in cross-section with a recess 5 at the
four corners in order to make the screw grommet flexible. The
screw grommet is provided also at one of the fron-t faces thereof
with a flan~e 6 which extends from this flange in a sleeve 7 whic~
`) is9luare in cross-section, having a-t the free end a hole 8 separa-

1050310ted b~ means of a diaphragm 9 from a cavity 10 of trapezoidal shaI e
the function of which is to make the sleeve 7 resilient. q'he lst-
ker is connected to t~e remainder of the screw grommet by means
of a pair of frangible -thin sections 11 and is provided in . dia-
metrically opposed locations with a pair of projections 12. At
the free end the sleeve 7 is provided with a pair of ~u~s 1~ dia~
metrically opposed and oriented with an angle of 90 degrees to
the pro~ections 12~ In the ~lange 6 of the screw grommet 1 a pair
of grooves 14 are provided in diametrically opposed locations,
said grooves being designed to receive the lugs 13 as will be
discussed hereinafter.
Assuming the screw grommet is to be secured to a wall 15 (se~
~ig. 2)~ the screw grommet is introduced into the hole 16 suitabl~
provided in the wall by taking advantage of the resiliency impar-
ted to the screw ~rommet by the presence of the recesses 5 pro-
vided at the four corners ol the hole 2. The screw grommet is
thereby compressed on its frùstoconical surface 4 as a result of
the engagement of this surface with the hole wall 16. At thi.s
point a blow is struck on the end of the sleeve 7 so as to break
the sections 11 connecting the sleeve to the screw grommet 1 and
to cause the sleeve to penetrate the hole 2 and slide therein
until the projections 12, which have entered the hole 2 as a re~
sult ol the resiliency imparted to the sleeve by the recesses 5,
come out of the hole 2 and due to the resiliency take again their
_ 4 _

~6~5~313~G~
¦non compressed condition wherein the projec-tions engage the front
¦surface of the screw grommet 1O At the same time the lugs 13 eng
. Ige in the grooves 14 of the f~ange 6 50 that the sleeve 7 is axial -
ly adjusted with respect to the screw grommet~
¦ As the sleeve 7 has entered inside the screw grommet 1, the
¦sleeve expands the screw grommet which was compressed by the hole
¦wall 16 causing thereby the screw grommet to be locked within the
hole~
¦ It is seen that the diaphragm 9 prevents the polyurethane
¦foam to ~all out of the inside of the wall 15 during the foaming
. ¦operation which is necessary in apparatus or parts (for example
¦parts of a car body) -to which the screw grommet is being applied
¦ As the foamin~ operation is finished the screw grommet is
¦ready to receive a self-tapping screw, not shown, which is intro-
¦ duced into the wall of the sleeve 7 by cutting therein the threadc
J necessary to the engagement be-tween screw and grommet. Due to
the square shape of the hole 2 and the sleeve 7~ the screw grommet
cannot rotate as the screw is being tightened.
I While an embodiment only of the invention has been described
~ and illustrated it is obvious that various changes and modifica-
¦tions can be made thereto without departing from the scope of the
¦invention.