GB2239071A - A grommet assembly for a panel fastener - Google Patents

Abstract

A grommet assembly is mounted in a countersunk hole 18 in a panel of an aircraft, and comprises an upper portion 20 having an outwardly flared portion 21 conforming to countersunk hole 18, an enlarged portion 23, and a thin walled portion 25, and a lower portion 26 having an upper thin walled portion 27 extending upwardly into said hole 18 from the blind side of said panel with an inner tapered wall and a lower enlarged portion having an inner annular wall of a diameter generally greater than the diameter of said hole 18, the thin walled portion 25 being swaged against said inner tapered wall of the lower portion, thereby trapping said panel 16 between the flared portion 21 and the upper surface of the enlarged portion of the lower portion 26. <IMAGE>

Description

A GROMMET ASSEMBLY FOR A PANEL FASTENER The invention relates to a grommet assembly for panel fasteners; and, more particularly, to captive panel fasteners suitable for securement to aircraft panels or the like.

According to the present invention there is provided a grommet assembly mounted in a countersunk hole in a panel of an aircraft or the like comprising: a first upper body portion having an outwardly flared portion at the top thereof conforming to said countersunk of said hole with a downwardly extending thin walled portion extending within said hole with an enlarged portion between said flared portion and said thin walled portions;; a second lower body portion having an upper thin walled portion extending upwardly into said hole from the blind side of said panel with an inner tapered annular wall and a lower annular enlarged portion forming an inner annular wall of a diameter generally greater than the diameter of said hole, said thin walled portion of said first upper body portion being swaged against said inner tapered annular wall of said second lower body portion thereby trapping said panel between the flared portion of said first upper body portion and the upper surface of the enlarged portion of said second lower body portion.

Reference is now made to the accompanying drawings, in which: - Figure 1 is an elevational view, partly in crosssectional, showing the bolt captivated to a panel; Figure 2 is an exploded view of the bolt assembly and grommet assembly of Figure 1; Figure 3 is an elevational view, partly in section, of the bolt assembly alone of Figure 1; Figure 4 is a view taken along lines IV-IV of Figure 3; Figure 5 is a view taken along lines V-V of Figure 3; Figure 6 is an elevational view, partly in section, of the panel 16 alone of Figure 1 showing the assembly of the grommet assembly thereto; Figure 7 is a view similar to Figure 6 showing the swaging of the lower grommet portion to the upper grommet portion;; Figure 8 is an elevational exploded view, partly in section, illustrating the assembly of the bolt, washer and spring to panel 16 after installat ~.. of the grommet assembly; Figure 9 is a view similar to Figure 3 showing a modified hold out spring for co-operation with a grommet according to the present invention; Figure 10 is a view taken along lines X-X of Figure 9; Figure 11 is a view similar to Figure 3 showing another embodiment of a hold out spring for co-operation with a grommet according to the present invention; Figure 12 is a view taken along lines XII-XII of Figure 11; Figure 13 is a sectional view illustrating the assembly of ring 29 to the bolt assembly of Figure 11; Figure 14 is a view similar to Figure 3 showing still another embodiment of a hold out spring for co-operation with a grommet according to the present invention; and Figure 15 is a view taken along lines XV-XV of Figure 14.

Figure 16 is an elevational view similar to a portion of the apparatus in the apparatus Figure 1; and Figure 17 is a view similar to Figure 16 showing the apparatus of Figure 16 installed on a thicker panel.

Referring now to Figure 1 of the drawing, a bolt 10 is shown adapted to mate with a receptacle assembly 11.

Receptacle assembly 11 may be of any suitable type, as for example, the assembly 12 described in my co-pending UK patent specification 2197412 the teachings of which are incorporated herein by reference. Receptacle assembly 11 herein is secured to subpanel 12 by rivets 13 or the like.

A hole 14 is provided in subpanel 12 coincident with a hole 15 in main panel 16 and a resilient gasket 17 may optionally be provided between panels 12 and 16.

As seen in Figure 1, a tapered countersunk 18 leads into opening 15 in panel 16. As seen in Figure 2, a two piece grommet assembly 19 is provided. First upper portion 20 has a conically shaped portion 21 and an integral lower generally cylindrical portion 22. An enlarged area 23 surrounds the exterior of upper portion 20 between portions 21 and 22 and an annular cut-out area 24 (see also Figure 1) is provided on the inner wall of upper portion 20 at the intersection of portions 21 and 23. It can be seen in Figure 2 that grommet portion 20 terminates at bottom in a thin-walled end 25.

Grommet assembly 19 further includes a lower grommet portion 26 having an upper generally cylindrical portion 27 and a lower generally enlarged portion 28.

A rigid retaining ring 29 is provided having a plurality, such as three, of inwardly extending tabs or ears 30. A hold out spring 31 is provided, of generally a single piece of spring material, having a lower generally circular ring portion 32 with an upwardly extending upper portion 33.

Upper portion 33 extends first upwardly at portion 34 from a point integral with ring portion 32, then curves back on itself at first curved portion 35, then curves outwardly and back inwardly to form a second curved portion 36.

Bolt 10 is best shown in Figure 3 wherein bolt 10 has a tapered enlarged head 37, an elongated shank 38, and a plurality, such as three, of spaced elongated slots 39-41 (see also Figures 2 and 4). It is noted that slots 39 to 41 extend from a point adjacent the underside of head 37 all the way along and through the bolt shank 38 through tapered nose 42 thereof. Bolt shank 38 is bored out in the interior to form a cavity 43 and a through slot 44 is provided through the wall of shank 38. An annular groove 45 is provided adjacent nose 42. A slot 100 (Figures 4 and 5) is provided through the wall of bolt 10 adjacent nose 42. The assembly of the components of Figure 2 will now be described.As seen in Figure 6, upper grommet portion 20 is inserted into a hole 15 in panel 16 from the access side thereof and lower grommet portion 26 is inserted from the blind side with upper portion 27 disposed in the area formed between lower cylindrical portion 22 and the walls of panel 16 forming opening 15. As seen in Figure 7, end 25 of lower portion 22 is swaged against portion 27 to securely hold the grommet assembly 19 to panel 16. The spacing or area 46 between portions 23 and 26 (Figures 6 and 7) allows for varying panel thicknesses.

As seen in Figure 8, bolt 10 is inserted through grommet assembly 19 and washer 29 is now assembled to the shank 38 of bolt 10 by merely placing washer 29 onto bolt 10 with tabs or ears 30 riding in slots 39 to 41. Spring 31 is now inserted into bore 43 passing through slot 100 until retaining ring portion 32 snaps into groove 45 and curved portion 36 snaps out of slot 44 as seen in Figure 3. The final assembled position is shown in Figure 1. It can be seen that the curved portion 36 of resilient spring 31 rests into the cut-out area 24 of grommet assembly 19 thus holding bolt 10 in an out position with respect to panel 16. Bolt 10 can be merely pushed with spring 31 moving inwardly so that the outer threads 47 of bolt 10 can mate with the internal threads 48 of receptacle assembly 11 as is well known in the art. Washer 29 is stopped in its downward movement by its engagement with ring portion 32 (see also Figure 5).

It can thus be seen that hold out means and a retaining member for the washer is provided for both holding bolt out from panel 16 and washer retaining 29 to the bolt 10 without any additional parts.

Cut-out area 24 is thus a counterbore into which spring 36 detents into when installed. In order to standardize spring 36 and its location in bolt 10, area 24 will always remain in the same position in relation to the blind side of panel 16. That is, area 24 and grommet portion 20 will vary in thickness depending upon the thickness of panel 16.

However, a constant dimension is maintained between the depth of area 24 and the terminal flat bottom of the lower flat bottom of grommet portion 26.

Thus, as seen in Figure 16, a distance A is shown between counterbore of area 24 and the bottom of portion 28.

However, if a thicker main panel is used, such as panel 160 in Figure 17 wherein like numerals refer to like parts of Figure 16, the portion 230 is made longer than portion 23 to accommodate the increased thickness of panel 160 while the distance A remains the same allowing standardization of the spring 36 and its location. This constant dimension ensures a proper detent force on spring 36. Gap 46 (Figure 6) as heretofore discussed compensates for variation in the panel thickness.

Although a particular type of hold out spring has been disclosed, which may be circular in cross-section throughout, as seen in Figure 9, wherein the like numerals refer to like parts of the embodiment of Figures 1 to 8, a hold out spring 49 is shown having an integral retainer ring portion 50, which is semi-circular in cross-section, and an upwardly extending integral portion which curves first outwardly to form curved portion 51, then returns to a vertical straight integral portion 52 abutting against the inner wall of cavity 43. As seen in are 10, washer 29 abuts against the flat upper surface 53 of ring portion 50.

The assembly of spring 49 to bolt 10 is identical to the assembly of spring 31 to bolt 10 described with respect to the embodiment of Figures 1 to 8, and to the installed grommet assembly 19, so further discussion is deemed unnecessary.

Although in both embodiments of Figures 1 to 8, and Figure 9, the hold out springs 31 and 49 are installed after installation of washer 29, it is possible to install the washer after installation of the hold out spring while retaining the benefits of the integral retaining ring portion. This is shown in Figure 11 wherein again like numerals refer to like parts of the embodiment of Figures 1 to 8. In this embodiment, hold out spring 54 is shown again having an integral retaining ring portion 55, an integral upwardly extending portion 56, an integral first curved top portion 57, and a second curved portion 58 which functions as a hold out means similar to curved portions 36 and 51.

As seen in Figure 11, the material comprising spring 54 is a wire form material having a cross-section forming an outer tapered wall at ring portion 55. In assembling washer 29 and spring 54 to bolt 10 of Figure 11, the spring 54 can be installed first in the manner previously discussed with curved portion 58 exiting slot 44 and retaining ring portion 55 snapping into groove 45. Washer 29 can now be installed by sliding over tapered surface 59, (see Figure 13) the flat upper surface 60 providing a stop for washer 29 (Figure 12).

As seen in Figure 14, wherein like numerals refer to like parts of the embodiment of Figure 11, spring 61 is identical to spring 54 except that it is rounded in crosssection at the bottom forming an outer rounded surface 62.

Washer 29 moves over this rounded area and tabs or ears 30 enter slots 39-41 as heretofore discussed, the downward movement of washer 29 being arrested by engagement with flat surface 60 (Figure 15). In the embodiments of Figures 11 and 14, the inherent resiliency of retaining ring portion 55 allows the same to move slightly inwardly, as seen in Figure 13, then spring back out as washer 29 moves therepast.

In all embodiments, the washer 29 can be a rigid and close fitting washer and is retained to the bolt 10 by engagement with a retaining ring portion that is an integral portion of the hold out means of the hold out spring. There is no need to machine grooves or slots that must terminate at some point along the bolt body; grooves or slots 39 to 41 extend all the way through the nose of the bolt.

The unique two piece grommet assembly compensates for varying door or panel thicknesses and is swaged against itself, not directly against the door or panel. This is particularly important in doors or panels of composite materials where stress thereon is to be avoided. The washer is engaged with the bolt slots by merely sliding the same thereon without need of special tools. The integral ring portion on all embodiments of the hold out spring retains the washer to the bolt. The cut-out area of the unique two piece grommet assembly, which compensates for varying door or panel thicknesses, provides an area into which the curved portion of the hold out spring rests allowing proper engagement therewith. No added parts for retaining the washer to the bolt-spring assembly are required.

The present specification has been divided out of UK patent specification 2213896 to which reference should be made.

Claims (4)

1. A grommet assembly mounted in a countersunk hold in a panel of an aircraft or the like comprising: a first upper body portion having an outwardly flared portion at the top thereof conforming to said countersunk of said hold with a downwardly extending thin walled portion extending within said hole with an enlarged portion between said flared portion and said thin walled portions;; a second lower body portion having an upper thin walled portion extending upwardly into said hole from the blind side of said panel with an inner tapered annular wall and a lower annular enlarged portion forming an inner annular wall of a diameter generally greater than the diameter of said hold, said thin walled portion of said first upper body portion being swaged against said inner tapered annular wall of said second lower body portion thereby trapping said panel between the flared portion of said first upper body portion and the upper surface of the enlarged portion of said second lower body portion.

2. A grommet assembly according to Claim 1, wherein the first upper body portion is counterbored on the inner surface thereof.

3. A grommet assembly according to Claim 1 or 2, wherein the lower end of the enlarged portion is spaced from the upper end of thin walled portion by the second body portion to permit fixing of the grommet assembly to different thicknesses of panel.

4. A grommet assembly according to claim 1 substantially as described herein with reference to and as illustrated in Figures 1,2,6,7,8,16 or 17 of the accompanying drawings.

4. A grommet assembly substantially as described herein with reference to and as illustrated in Figures 1,2,6,7,8,16 or 17 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A grommet assembly mounted in a countersunk hole in a panel of an aircraft or the like comprising: a first body portion having an outwardly flared portion at one axial end thereof conforming to said countersunk of said hole with an axially extending walled portion extending within said hole with an enlarged portion between said flared portion and said thin walled portion;; a second body portion having an axially extending thin walled portion extending into said hole from the side of said panel opposite to the side having the countersunk, the second body portion having an inner tapered annular wall and an annular enlarged portion at one axial end forming an inner annular wall of a diameter generally greater than the diameter of said hole, said thin walled portion of said first body portion being swaged against said inner tapered annular wall of said second body portion thereby trapping said panel between the flared portion of said first body portion and the enlarged portion of said second lower body portion.

2. A grommet assembly according to Claim 1, wherein the first body portion is counterbored on the inner surface thereof.

3. A grommet assembly according to Claim 1 or 2, wherein the axial end of the enlarged portion of the first body portion is spaced from the axial end of the thin walled portion of the second body portion to permit fixing of the grommet assembly to different thicknesses of panel.