Low insertion force grommet

Abstract: A grommet for securement in a suitable aperture existing in a wall. The aperture has a diameter and the grommet comprises a body having a first portion formed to be secured to a cable which has a diameter. A flexible, second portion defines a closed chamber when the grommet is fixed to the cable, the second portion having a maximum unflexed outer dimension slightly greater than the diameter of the aperture and a maximum inner dimension substantially greater than the diameter of the cable. A third portion has a diameter substantially greater than the diameter of the aperture with a planar area between the second and third portions. An aperture engaging groove is formed in the planar area, the aperture engaging groove having a diameter substantially equal to the diameter of the aperture.

Description: This invention relates to a grommet according to the generic clause of claim 1 and more particularly to sealing grommets. Still more particularly, it relates to sealing grommets for bringing a radio antenna cable through the fire wall of an automotive vehicle. Such a grommet is already known from document US 5 453 579 which has a groove that corresponds in size to a hole in a wall, and a boot extending from the grommet in the shape of a nipple which forms an outer wall. The grommet also includes an inner wall that extends radially inwardly in the same plane as the wall to which the grommet is mounted, the inner wall defining an aperture through which the wire or bundle of wires passes. The outer wall and inner wall define a chamber for collecting water that enters the inside of the boot. The outer wall further defines a slot through which the collected water drains to remove the water from the inside of the boot. Prior art sealing grommets have comprised relatively massive, solid, hemispherical components of a flexible material, such as rubber. See, for example, U.S. Patent Nos. 2,225,472 and 5,353,472. The component would be provided with a groove for engaging the automotive vehicle fire wall and an extending flange preventing pull-through. Such grommets frequently required a setting force of up to 75 lbs. As the engine compartments of modern vehicles have become more and more crowded with electronic components, it has become more difficult to find the room necessary to be able to exert such pulling force. Improved grommets having a lesser setting force have been proposed wherein the flexible portion is substantially hollow. Examples of the latter grommets are shown in U.S. Patent Nos. 2,375,373; 3,244,802; 3,372,960; 4,041,241' 4,685,173; 5,337,447; and 5,452,494. Such grommets having collapsible compartments open to the environment have been known to allow foreign matter to accumulate therewithin, making removal, when such an action is desired, very difficult. It is, therefore, an object of this invention to obviate the disadvantages of the prior art. It is another object of the invention to enhance sealing grommets. It is yet another object of the invention to provide a sealing grommet with a reduced setting force. It is another object of the invention to provide a grommet having a flexible or collapsible section that will not accumulate foreign matter in use. These objects are accomplished, by the characterizing features of claim 1. The closed chamber is substantially sealed whereby ingress of foreign matter is prevented. Yet, this closed chamber is readily flexible when the grommet, after being fixed to a cable, is inserted into the wall aperture. The setting force is lower than that of the solid grommets and is comparable to the setting force of the grommets having open hollow portions. Fig. 1 is a sectional, elevational view of an embodiment of a grommet of the invention; Fig. 2 is a sectional, elevational view of a grommet attached to a cable; and Fig. 3 is a sectional, elevational view of a grommet of the invention inserted into a receiving aperture. For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings. Referring now to the drawings with greater particularity, there is shown in Fig.1 a grommet 10 having a body 12 of a suitable material, for example, SAE R4 15K butyl rubber, arranged along a longitudinal axis 16. The body 10 has a tubular, multi-diametered, central aperture 18 coaxial with the longitudinal axis 16. The body 10 further comprises a first portion 20 having a first outer diameter D1, a clamp receiving area 11 formed adjacent to the diameter D1, and a first inner diameter D2, which is formed to engage the outer, insulating layer of a coaxial cable 21 (see Fig. 2). A plurality of cable engaging ribs 19 are formed on the interior surface of first portion 20 to help grip the cable, especially after a clamp is installed in the clamp receiving area. A flexible, second portion 22 has a second outer diameter D3, a third outer diameter D4, a second inner diameter D5, and a third inner diameter D6, these differing diameters defining a tapered leading section 23 and a bulbous, hollow interior. In the embodiment shown, the second outer diameter D3 is equal to the first outer diameter D1; the second inner diameter D5 is equal to the first inner diameter D2; the third outer diameter D4 is greater than the second outer diameter D3; and the third inner diameter D6 is greater than the second inner diameter D5. A third body portion 28 defines a wall engaging flange and has a fourth inner diameter D7 equal to the first inner diameter D1 and a fifth outer diameter D8 greater than the third outer diameter D4. The body 10 has an area 30 between the flexible, second portion 22 and the third body portion 28, the area 30 having a circumferential, wall engaging groove 32 formed thereabout. The difference between the fifth outer diameter D8 and the third outer diameter D4 defines a plane 34 that lies substantially orthogonal to the longitudinal axis 16. The plane 34 has a circumferential groove 36 therein which, when the grommet is properly inserted into a wall aperture, provides a suction which helps to hold the grommet in place. Referring now to Fig. 2, grommet 10 is shown affixed to a cable 21 via a clamp 38 positioned at clamp receiving area 11. Since the fourth inner diameter D7 is equal to the first inner diameter D2, which in turn is equal to the diameter of the cable 21, the closed chamber formed by the tubular, multi-diametered central aperture 18 is substantially impervious to the entrance of foreign material and its flexibility is maintained. With the grommet 10 affixed to the cable 21 insertion thereof into an aperture 40 in a wall 42 is accomplished by feeding a leading portion of the cable 21 through the aperture in the direction indicated by arrow 44 and pulling until groove 32 engages the aperture wall. During the insertion process the bulbous chamber formed by the multi-diametered aperture 18 collapses sufficiently to allow this to occur. Insertion stops when the third body portion 28, which comprises the flange, engages the wall 42. The angled face of the flange in cooperation with the circumferential groove 36 provides a suction seal with great holding power; however, the insertion force remains low allowing ease of fitting even in confined areas such as the engine compartment of an automobile. Thus, there is provided an easily inserted grommet having great holding power that is still easily removed when necessary, thanks, in part, to the continued flexibility of the closed chamber which remains free of foreign matter. While there have been shown an described what are at present considered the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.

Claims: A grommet (10) for securement in a suitable aperture (40) existing in a wall (42), said aperture having a diameter, said grommet (10) comprising: a body (12) having a first portion (20), a third portion (28) and a second portion (22) between said first portion (20) and said third portion (28), wherein said first portion (20) is formed to be secured to a cable (21) having a diameter; said second portion (22) having a maximum unflexed outer dimension (D4) slightly greater than the diameter of said aperture and a maximum inner dimension (D6) substantially greater than said diameter of said cable (21); said third portion (28) having an outer diameter (D8) substantially greater than said diameter of said aperture (40); an area (30) between said second and third portions (22,28); and an aperture engaging groove (32) formed in said area (30), said aperture engaging groove (32) having a diameter substantially equal to said diameter of said aperture, characterized in that said second, flexible portion (22) defines a closed chamber (18) when said grommet (10) is fixed to said cable (21), and in that said third portion (28) comprises a transversely extending flange which includes a circumferential flange groove (36) which is orthogonal to said aperture engaging groove (32). The grommet of claim 1, wherein said first portion (20) has an internal section formed to receive a cable (21) and said internal section has at least one cable gripping rib (19) formed therewith. The grommet (10) of claim 1 or 2, wherein said body (12) is arranged along a longitudinal axis (16), said body (10) having a tubular, multi-diametered, central aperture (18) coaxial with said longitudinal axis (16); said first portion (20) having a first outer diameter (D1) and a first inner diameter (D2); said second, flexible portion (22) having second outer diameter (D3) and a third outer diameter (D4) and a second inner diameter (D5) and a third inner diameter (D6), said second outer diameter (D3) being equal to said first outer diameter (D1), said second inner diameter (D5) being equal to said first inner diameter (D2), said third outer diameter (D4) being greater than said second outer diameter (D3), said third inner diameter (D6) being greater than said second inner diameter (D5); said third body portion (28) having a fourth inner diameter (D7) equal to said first inner diameter (D1) and a fifth outer diameter (D8) greater than said third outer diameter (D4). The grommet of claim 3, wherein the difference between said fifth outer diameter and said third outer diameter defines a plane (34) that lies substantially orthogonal to said longitudinal axis. The grommet of claim 4, wherein said plane (34) has said aperture engaging groove (36) therein. The grommet of claim 1 or 3, wherein said first portion is formed to provide a clamp receiving area (11).

Inventors: WRIGHT JOHN O, WRIGHT, JOHN O.
Applicants: OSRAM SYLVANIA INC, OSRAM SYLVANIA INC.
Application year: 1997
Main classification: H02G3
IPC codes: H02G15, H02G3, B60R16, F16L5, B60R13, H01B17