Patent Publication Number: US-5839920-A

Title: Electrical connector seal

Description:
The present invention relates to seals for use with electrical connectors; more particularly, the present invention relates to an electrical connector seal for receiving box shaped contacts therethrough without tearing the seal, and which provides a good sealing interface between the insulation of a conductor terminated to the electrical contact and the seal. 
     BACKGROUND OF THE INVENTION 
     Known electrical connector seals which are commonly available include apertures for receiving electrical contacts therethrough. The apertures generally include a frustoconical section for having a lead-in angle which accommodates the front end portion of the electrical contact as it is inserted through the seal. The function of the lead-in angle is to prevent tearing of the seal as the sharp edges and/or corners of the electrical contact are forced through the seal. However, when a plurality of electrical contacts are forced through a seal in a high density application, the seal material, being flexible and behaving somewhat as an incompressible fluid, has little room to flow, so that stress concentrations will be induced in the seal. Tension and compression concentration loci will be created in the seal, so that certain portions of the seal may fracture and tear when forced into engagement with the sharp edges of the electrical contact as it passes through the seal. Thus, as the electrical contact is forced through the seal, the seal material must flow to an area whereby the electrical contact can pass through the seal without fracturing or tearing the seal. 
     In light of the forgoing, what is needed is an electrical contact seal for high density applications which: will not tear or fracture when an electrical contact is inserted therethrough; includes a seal configuration which advantageously allows the seal material to flow in directions that tend relieve the stresses as the electrical contact is forced therethrough; and is of a compact design, is easy to manufacture, and is of a low cost. 
     SUMMARY OF THE INVENTION 
     The present invention provides a seal for use with an electrical terminal comprising at least one sealing unit, the sealing unit includes a contact receiving aperture comprising a front section, the front section comprises face surfaces which are offset at respective offset angles relative to the contact receiving aperture, a portion of the face surfaces are adjacent to a recess zone, the recess zone is offset at an angle relative to the contact receiving aperture, and the recess zone offset angle is relatively larger than the offset angle of at least one of the face surfaces. The front section of the sealing unit comprises a generally funnel-shaped portion disposed about the contact insertion aperture for providing a lead-in area for the contact. The contact receiving aperture comprises an annular recess disposed between a rib and a projection, each respectively formed of the seal, for sealing engagement with a conductor terminated to the contact, and the seal comprises at least one relaxation core adjacent to the sealing unit. The relaxation core comprises an essentially void space of a given volumetric magnitude, and the void space becomes relatively smaller as the contact is inserted through the sealing unit, thereby relieving stress in the seal. Additionally, the recess zone comprises a stress-relieving shape which is centered over the contact aperture, and, in a preferred embodiment, the recess zone is generally X-shaped. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an elevational view of a front side of the electrical connector seal of the present invention. 
     FIG. 2 shows a cross sectional view of a portion of the seal of FIG. 1 taken along line 2--2 of FIG. 1. 
     FIG. 3 shows a portion of the front seal of FIG. 1. 
     FIG. 4 shows a cross sectional view of a portion of the seal of FIG. 3 taken along line 4--4. 
     FIG. 5 shows the cross section of FIG. 2 with an electrical contact being inserted through the seal. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, the electrical connector seal 10 according to the present invention will be described. Seal 10 includes a sealing outer periphery 12 for engagement with a sealing wall of an electrical connector, a sealing inner periphery 14 for engagement with a sealing wall of an electrical connector, a front face 16, and a back face 18. The front face 16 includes sealing units 20, and relaxation cores 30 adjacent thereto. 
     Each sealing unit 20 includes a contact receiving aperture 21, a generally funnel-shaped section 22, an annular recess 24, an annular projection sealing profile 26, and a box shaped recess 28 extending from back face 18. Each generally funnel-shaped section 22 includes a pair of curved faces 22a and 22b with an recess zone 22c between them as shown in FIG. 3. Each face 22a and 22b comprises a respective contour, in a bulge-like relief relative to the recess zone 22c, which represents a boundary between the respective face and the recess zone 22c. The boundaries of respective faces 22a,22b comprise generally straight, sloping lines capped by an arcuate edge adjacent to aperture 21. The recess zone 22c is generally X-shaped and is centered over aperture 21, and the leg sections of the recess zone 22c which extend to the outer periphery of the sealing unit 20 are recessed relative to the face portions 22a and 22b. The innermost periphery of section 22 includes a sealing profile rib 22d for slidingly engaging an electrical contact 40, before the contact has been fully inserted in the seal, as shown in FIG. 5. 
     As noted above, relaxation cores 30 are located adjacent to respective sealing units 20. Each relaxation core includes an annular wall 32, and a bottom wall 34, and is preferably of a cylindrical shape, although other shapes may be used. As shown in FIG. 1, the relaxation cores 30 are disposed adjacent to sealing units 20 on a generally two-to-one basis. However, some sealing units 20 which are located adjacent to inner periphery sealing surface 14 would not require a relaxation core 30 because the sealant material will flow by virtue of the inner periphery 14 being adjacent to the sealing unit 20. 
     Now referring to FIGS. 3 and 4, the seal 10 will be further described. FIG. 3 shows the interface 22c which extends between faces 22a and 22b of sealing unit 20. Referring to FIG. 2, angle α depicts a lead-in angle for sliding engagement with an electrical contact to be inserted into contact receiving aperture 21. Angle α is found generally at the intersection of lines X and Y with faces 22a,22b, respectively, as shown in FIG. 3. Referring now to FIG. 4, angle β depicts an angle of the surface of recess zone 22c, between faces 22a and 22b of sealing unit 20, and represents the recess zone corners, i.e. between faces 22a and 22b, as shown in FIG. 3. In a preferred embodiment of the invention, the lead-in angle α is about 35° ±10° or less depending on the thickness of the seal 10, measured from the contact insertion axis; and the interface angle β of recess zone 22c is about 40° ±10° or less depending on the thickness of the seal, as measured from the contact insertion axis. Therefore, there is a gradual increase in steepness, along the curved surfaces of faces 22a and 22b, from the 35° lead-in angle α to the 40° interface angle β, which advantageously allows the corners of the sealing units 20 to slidingly deform around, for example, the sharp corners of a box contact without tearing or fracturing of the seal material. Additionally, the angles α and β are calculated to minimize the amount of required seal thickness, between the front and back faces 16,18, so that the seal 10 is a compact design which prevents fracturing or cutting of the seal material as the box contact 40 is inserted therethrough. 
     Referring now to FIG. 5, the behavior of the seal 10 as an electrical contact 40 is inserted therethrough will now be described. FIG. 5 shows an electrical contact 40 being inserted through contact receiving aperture 21. The contact 40 is, for example, a box shaped receptacle contact. FIG. 5 is shown adjacent to FIG. 2 in the appended drawings for ready comparison between the two. Relaxation cores 30 are shown to have a different shape 30&#39; in FIG. 5, which represents a narrower, or smaller volumetric space, as compared to the relaxation core 30 of FIG. 2. This is due to the fact that rib 22d will be in engagement with the outer surface of electrical contact 40 and the seal material will flow away from contact 40 as the contact is inserted into contact receiving aperture 21 thereby making the volumetric space of relaxation core 30&#39; relatively smaller. Additionally, annular projection 26 is in engagement with the box contact 40 further outwardly moving the seal material away from contact 40. Furthermore, the annular projection 26 and rib 22d are allowed to flow toward backface 18 by virtue of: annular recess 24, which provides a space for rib 22d to flow; and the box shaped recess 28, which provides a space for annular projection 26 to flow. 
     However, it is important to note that the funnel-shaped section 22 initially engaged the box contact 40 and the corners of the box contact 40 did not tear the seal material because of the lead-in angle α, and the steepness associated with interface angle β, which cooperate to relieve stress in the area of the box contact&#39;s sharp outer corners. Additionally, FIG. 5 shows two relaxation cores 30 or 30&#39; associated with a respective sealing unit 20, but some sealing units 20 are disposed adjacent to sealing inner periphery 14, and the seal material can therefore flow towards sealing inner periphery 14, thereby obviating the need for a second relaxation core 30 for that particular sealing unit 20. 
     After the electrical contact 40 has been fully inserted through the sealing unit 20, the annular projection 26 and rib 22d will relax, and relaxation cores 30&#39; will revert to a volumetric space close to their original shape; however, the engagement of rib 22d and annular projection 26 with the conductor terminated to contact 40, will result in some deformation of the seal of relaxation core 30. Thus it is seen that as the electrical contact 40 is inserted into a respective sealing unit 20, three major movements of the seal material occur, namely: the funnel-shaped section 22 will move towards a respective relaxation core 30, rib 22d will move towards annular recess 24, and annular projection 26 will flow towards box shaped recess 28. But it is important to note that stress will be relieved from rib 22d by interface angle β of recess zone 22c as well, and stress will be relieved from annular projection 26 by having the axial length of the relaxation core extend all the way to an area adjacent to the annular projection 26, especially in that the backwall 34 of relaxation core 30 will extend to a point which is substantially in alignment with a face of box shaped recess 28. 
     Thus, while a preferred embodiment of the invention has been disclosed, it is to be understood that the invention is not to be strictly limited to such embodiment but may be otherwise variously embodied and practiced within the scope of the appended claims. For example, it is contemplated that a funnel portion 22 can be formed on back face 18 instead of recess 28, with recess 24 taking a medial position in the seal 10, so that the contact 40 can be inserted from the front or back faces 16,18.