Sealing Grommet Means

The present invention relates generally to a grommet means for being sealingly received onto an electrical wire, and, more particularly, to such a grommet means providing a sealing relation for a plurality of cable wires in an electrical connector.

In a typical form of electrical connector, plug and receptacle parts are each interconnected to separate multiwire cables, the connector parts including pin and socket contacts which releasably mate together when the parts are assembled. It is conventional to pass the cable wires through rubber grommets or inserts in the connector subsequent to their being affixed to a pin or socket contacts, as the case may be. In the past, these grommets have only been effective for sealing the connector interior from the ingress of moisture, dust and dirt and the like when the wires passing through the grommet are substantially straight and well aligned with the grommet opening axis. It has been found with prior known grommets that even a relatively few degrees of axial displacement of the cable wires produces a deformation of the grommet apertures preventing a completely satisfactory sealing relationship.

In the practice of the present invention there is provided a one-piece grommet constructed of a pliable material including a plurality of apertures extenting therethrough and wire-sealing wall portions, one for each cable wire. Each aperture is substantially greater than the cable wire diameter. Centrally located within the grommet and extending angularly inwardly from the aperture wall is a generally cone-shaped portion of the wall which terminates in an opening smaller than the wire diameter. The opening in the cone-shaped portion lies on the aperture axis and is encompassed by a bead. The wall thickness of the cone is relatively thin so that any wire movements transversely of the aperture axis will be take up by bending of the conical wall rather than by any tendency of the conical member opening bead to be stretched away from the wire breaking the seal about the wire.

As an alternative, two such grommets are arranged in back-to-back relationship with the apertures respectively aligned so that in the normal unstressed condition the cone-shaped portions extend away from each other.

FIG. 1 is an end elevational view of a grommet constructed in accordance with this invention.

FIG. 2 is a side elevational, sectional view of the grommet taken along the line 2--2 of FIG. 1 showing a cable wire in place.

FIG. 3 is a side elevational, sectional, partially fragmentary view similar to FIG. 2 showing the wire experiencing side-pull.

FIG. 4 shows an alternate embodiment of the invention in which two grommets of FIG. 1 are arranged in back-to-back relation.

FIG. 5 shows a partially fragmentary view similar to FIG. 4 with the wire experiencing side-pull.

FIG. 6 depicts the grommet assembled into a connector part.

With reference now to the drawings and particularly FIGS. 1 and 2, the wire sealing grommet of the present invention is identified generally as at 10 and is seen to include a generally disklike body 11 having a plurality of mutually parallel cylindrical apertures 12 passing therethrough from an entrance face 13 to an exit face 14. A longitudinally extending key ridge 15 on the circumferential peripheral surface of the body 11 is a visual means for aligning and locating the grommet in a given orientation with respect to the connector parts. The outer diameter of the grommet body 11 is such as to permit fitting receipt within an accommodating opening of a connector part as shown in FIG. 6, for example, as will be described in detail later herein.

The circular entrance face 13 in assembly will be directed outwardly of the connector whereas the exit circular face 14 will face to the connector internal parts. That is, in assembly, wires 16 of the cable will be introduced into apertures 12 from the face 13 side of the grommet and exit at the face 14.

It is important that the material composing the body 11 not only exhibit good resistance to abrasion, moisture and the like, but also be highly compliant and flexible in order to provide optimum wire sealing properties. Although various rubbers and plastics may be found suitable for this purpose, to date best results have been obtained by molding the grommet body 11 from a silicone or fluorosilicone rubber having a Shore durometer of 30-40. This type of rubber maintains its flexibility over a wide temperature range and ages well.

The aperture 12 has a diameter at least several and preferably four to five times that of a cable wire 16 to accommodate the sealing structure to be described at this time.

Each opening 12 has the walls thereof closely adjacent the exit or inner face 14 formed into a tube 17, the sides of which taper inwardly toward the entrance face 13 forming cone terminating in an opening 18 lying on the axis of aperture 12. The cone opening 18 is defined and reinforced by a circular bead 19. More particularly, the conical tubes 17 are integral with the main grommet body 11 beginning just inwardly of the exit face 14 where the tube bore diameter is substantially equal to the diameter of the aperture 12. The side walls of the tube 17 as they move away from the exit face 14 taper inwardly in a uniform manner terminating at a point beyond the center of the body 11 as measured along the aperture axis but substantially short of the entrance face 13. The diameter of the opening 18 as defined by the bead 19 is significantly less than the wire diameter so that when a wire is pressed through the opening the bead will be stretched and thereby be tightly and sealingly secured about the wire. With this construction, even when a wire 16 is subjected to a considerable side-pull as shown in FIG. 3 and the conical side wall deform to the point where the bead 19 contacts the aperture side wall, the bead still remains tightly and sealingly retained about the wire.

Although some variation in relative dimensions of the grommet parts may be found not to be detrimental to efficient operation of the invention, best results have been obtained in a practical construction where the body spacing between faces 13 and 14 was 0.200 inches (0.508 cm.), aperture diameter was 0.105 inches (0.267 cm.), the conical tube wall thickness was 0.018 inches (0.046 cm.) and the conical tube angle was 40 degrees. The opening formed by the bead 19 was 0.020 inches (0.051 cm.) which was specifically designed to accommodate an insulated wire having an outer diameter of approximately 0.040 inches (0.102 cm.).

In situations where a considerable amount of repetitive wire side-pull is to be encountered or the wire diameter is substantial (e.g., above about 0.079 inches in diameter) it may be advisable for insured reliability of sealing to employ the alternative embodiment shown in FIGS. 4 and 5. In essence, this version includes two of the grommets 10 and 10' with their respective exit faces 14 secured together by a suitable cementitious material 20. Accordingly, the corresponding apertures 12 of the two back-to-back grommets 10 are axially aligned with the conical tubes 17 in each common aperture being directed oppositely. Side-pull can produce deformation of both sealing tubes 17 as shown in FIG. 5, or if one end of the wire 16 is held centrally aligned and the other wire end subjected to side-pull only the one sealing tube will be deformed.

With reference now to FIG. 6, a typical connector part 21 is depicted with which the described wire sealing grommet 10 may be advantageously employed. Specifically, the connector part 21 is a hollow cylindrical body including an insert 22 within which a plurality of pin contacts 23 (or socket contacts) are secured. Cable wires 16 to be connected to the pin contacts as at 24 extend through individual apertures 12 of a grommet 10 and are thereby sealed in the manner described. The grommet is positioned within the connector part bore by using the ridge 15 to effect visual alignment.