Sealing rubber plug-fixing structure and method for clamping same to a wire

Abstract: To clamp a rubber plug to a wire without damaging the rubber plug, an insulation barrel is clamped to a clamping surface of a rubber plug, thereby retaining the rubber plug against withdrawal from the wire. An interposing ring is interposed between the insulation barrel and the rubber plug when the insulation barrel is to be clamped, so that side edges of the insulation barrel will not bite into the rubber plug, and hence will not damage the rubber plug.

Description: This invention relates to a sealing rubber plug-fixing structure and a method for clamping a rubber plug to a wire. A waterproof connector is used in environments requiring waterproof sealing. When a wire, having a metal terminal connected thereto, is to be inserted into a housing, a rubber plug for sealing purposes is fitted on the wire. Upon insertion, a watertight seal is formed between an inner wall surface of the housing and ring-shaped seal lips formed on and projecting from the outer periphery of the sealing rubber plug (see Fig. 11). This conventional rubber plug 50 includes a first portion having seal lips 51 that perform a sealing function, and a second portion 55 is adapted to be fixed to the sheathed wire 52. More specifically, an insulation barrel 54 of the metal terminal 53 is forcibly deformed to embrace the rubber plug over the entire periphery of the sheathed wire 52, thereby fixing the rubber plug to the wire 52. The force of clamping between the rubber plug and the metal terminal is provided by a clamping force applied by the insulation barrel. Therefore, the withdrawal of the rubber plug can be prevented merely by increasing the clamping force. However, the entire metal terminal is formed by blanking, and opposite side edges of the insulation barrel are defined by cut surfaces, thereby defining sharp edges. Therefore, when clamping is effected, the sheath of the wire may be partially cut, which would adversely affect the sealing function. This can be avoided by lowering the clamping force to such an extent that the biting of the edges into the sheath will not occur. However, if this is done, the originally - intended clamping function would be adversely affected. Another approach to avoid that the sheath of the wire may be partially cut by opposite side edges of the insulation barrel is disclosed in EP-A-0 520 291. This document discloses an electric terminal piece provided with a clinching portion for fastening a wire over an insulating or sealing member made of soft material covering the wire, such as an insulation coating of the wire, and a rubber seal for sealing the wire, without damaging the member, wherein an edge of the clinching portion is turned in a direction opposite to a direction in which the clinching portion is clinched, i.e. radially outwardly/upwardly. Accordingly, the member is not damaged by the edge of the clinched portion, and therefore insulation and waterproofing of the wire is maintained. However, bending or turning the clinching portion outwardly/upwardly away from the sealing member requires an additional production step and due to the raising rims or edges formed by such bending or turning, the clinched portion is no longer flat and thus exerts a considerable resistance against clinching forces for clinching him around the sealing member. The present invention has been made in view of the above problems, and an object of the invention is to provide a sealing rubber plug-fixing structure that prevents withdrawal of a sealing rubber plug from a metal terminal without damaging the rubber plug. According to a first aspect of the invention, there is provided a sealing rubber plug-fixing structure comprising: a sealing rubber plug fitted on an end portion of a sheathed wire, said sealing rubber plug being fixedly clamped to said wire for providing a seal between said wire and a cavity wherein the sealing rubber plug is to be inserted, wherein said clamping is provided by a metal terminal connector having an insulation barrel and a wire barrel, said insulation barrel fully embraces the entire outer periphery of a fixing region of the rubber plug, said connector being fixed to said end portion of said wire by means of said wire barrel embracing an exposed portion of an conductor of said wire; and an interposing member interposed between an outer clamping surface of said fixing region and an inner surface of said insulation barrel. The interposing member may have a ring-shape so as to fit on an outer peripheral surface of the rubber plug. In this event, the interposing member may have an interrupting groove formed at a portion thereof for allowing the interposing ring to be inwardly contracted in a radial direction. According to a second aspect of the invention, there is provided a waterproof seal comprising: a sealing rubber plug for fitting on an end portion of a sheathed wire, said sealing rubber plug having a sealing portion for providing a seal between said wire and a cavity wherein the sealing rubber plug is to be inserted, said sealing rubber plug is to be clamped to said wire by an insulation barrel of a metal terminal connector for fully embracing the entire outer periphery of a fixing region of the rubber plug adjacent the sealing portion; and an interposing member interposed between an outer clamping surface of said fixing region and an inner surface of said insulation barrel. According to a third aspect of the invention, there is provided a method for fixedly securing a seal to a wire, said wire being connectable to a metal terminal connector having an insulation barrel and a wire barrel, said method comprising: fitting a sealing rubber plug on an end portion of a sheathed wire and fixedly clamping said sealing rubber plug to said wire by fully embracing an entire outer periphery of a fixing region of the rubber plug with said insulation barrel; fixing said connector to said wire by means of said wire barrel embracing an exposed portion of the conductor of said wire; and interposing an interposing member between an outer clamping surface of said fixing region and an inner surface of said insulation barrel prior to embracing the entire outer periphery of said fixing region with said insulation barrel. During assembly, the wire is passed through a wire insertion hole in the rubber plug, and the metal terminal is forcibly deformed with the interposing member interposed between the rubber plug and the metal terminal so that the rubber plug is indirectly clamped and fixed. Additionally, the interposing member can be easily contracted radially inwardly when the rubber plug is clamped so that a uniform tightening force can be applied to the rubber plug over its entire periphery. Accordingly, the rubber plug is fixedly clamped with the interposing member interposed between the rubber plug and the metal terminal. Therefore, even if the clamping force applied by the metal terminal is increased, the rubber plug will not be damaged and the sealing property can be maintained. If the interrupting groove is provided, the interposing member can be easily contracted radially inwardly so that the rubber plug can be uniformly clamped, thus achieving a good tightened condition. These and other advantages will be described in or will become apparent from the following detailed description of preferred embodiments in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of a first embodiment of the present invention; Fig. 2 is a perspective view illustrating an interposing member and sealing rubber plug of the first embodiment; Fig. 3 is an enlarged, cross-sectional view illustrating a portion of the first embodiment; Fig. 4 is a perspective view of an interposing member of a second embodiment; Fig. 5 is an enlarged, top plan view illustrating the interposing member of the second embodiment; Fig. 6 is a perspective view of an interposing member of a third embodiment; Fig. 7 is an enlarged, cross-sectional view illustrating a portion of the third embodiment; Fig. 8 is a perspective view of an interposing member of a fourth embodiment; Fig. 9 is an enlarged, cross-sectional view of a portion of the fourth embodiment; Fig. 10 is a perspective view of an interposing member of a fifth embodiment; and Fig. 11 is a cross-sectional view of a conventional construction. A first preferred embodiment of the present invention will now be described with reference to Figs. 1 to 3. A rubber plug 1 is fitted on a front end portion of a sheath of a wire 2, and is clamped thereto by a metal terminal 3. In this condition, the rubber plug 1 is inserted into a cavity in a connector (not shown) to form a seal between the cavity and the wire 2. Reference is first made to the rubber plug 1 in detail. As shown in Fig. 2, the rubber plug 1 has a cylindrical shape as a whole, and is integrally molded of a rubber material having a suitable degree of elasticity. The rubber plug 1 has a wire insertion hole 4 formed therethrough along an axis thereof for passing the sheathed wire 2 therethrough. An outer peripheral surface of one side portion (the right side portion in Fig. 2) of the rubber plug 1 defines a seal region 6 on which two outer seal lips 5a,5 are formed. An outer peripheral surface of the other side portion (the left side portion in Fig. 1) defines a fixing region 8 that is adapted to be fixedly clamped to the wire by an insulation barrel 7 of the metal terminal 3. The rubber plug 1, when inserted into the cavity, is elastically deformed by an inner peripheral surface of the cavity, and is held in pressurized contact therewith, thereby maintaining the interior of the cavity in a watertight condition. The seal lip 5a that is closer to the fixing region 8 has at one end a stopper surface 9 formed over an entire circumference thereof in perpendicular relation to the axis of the rubber plug 1, as shown in Fig. 3. Another stopper surface 12 is formed on the rubber plug in perpendicular relation to the axis of the rubber plug, and is spaced a predetermined distance from the stopper surface 9 in opposed relation thereto. The two stopper surfaces 9 and 12 cooperate with each other to limit the displacement of an interposing ring (interposing member) 10 and the insulation barrel 7 in the axial direction, as more fully described below. The stopper surface 12 at the fixing region 8 is defined by an inner surface of a withdrawal prevention flange 11 formed on and extending radially outwardly from the front end of the fixing region 8 over an entire circumference thereof. The outer peripheral surface extending between the two stopper surfaces 9 and 12 defines a clamping surface 8a that can be compressively grasped by the insulation barrel 7. The distance between the two stopper surfaces 9 and 12 is slightly larger than the width of the interposing ring 10 and the width of the insulation barrel 7. In this example, the stopper surface 12 at the fixing region 8 is slightly smaller in diameter than the other stopper surface or annular extension 9, and the radially-outward dimension of the stopper surface 12 is larger than the sum of the thicknesses of the interposing ring 10 and insulation barrel 7, as shown in Fig. 3. Before the insulation barrel 7 is forcibly deformed, the interposing ring 10 shown in Fig. 2 is provisionally fitted on the fixing region 8. In this embodiment, the interposing ring 10 is made of a soft resin, and has an interrupting slit 13 extending parallel to the axis thereof. With this construction, although the inner diameter of the interposing ring 10 is normally smaller than the outer diameter of the clamping surface 8a, the interposing ring 10 can be forcibly expanded to resiliently fit on the clamping surface 8a. The width of the interposing ring 10 is slightly larger than that of the insulation barrel 7, and the interposing ring 10 has an elasticity that allows the insulation barrel 7 to bite thereinto, depending on the degree of deformation of the insulation barrel 7, thereby limiting the displacement of the insulation barrel 7 in the axial direction. As shown in Fig. 1, the metal terminal 3 includes a connection portion 14 formed at its front end for receiving a mating metal terminal (not shown) and a wire barrel 16 disposed rearwardly of the connection portion for clamping an exposed portion of a conductor 15 of the sheathed wire 2. The insulation barrel 7 is disposed rearwardly of the wire barrel 16. In the blanking of the metal terminal 3, a pair of arms of the insulation barrel 7 extends substantially perpendicularly to the axis of the metal terminal 3, and are symmetrical with respect to the axis. The insulation barrel 7 has a sufficient length to fully embrace the entire outer periphery of the interposing ring 10 fitted on the fixing region 8 of the rubber plug 1. The operation of this embodiment will now be described. The wire 2 is passed through the wire insertion hole 4 in the rubber plug 1, and the rubber plug 1 is positioned at the front end portion of the sheath of the wire. In this condition, the conductor is clamped by the wire barrel 16. Before or after the clamping operation, the interposing ring 10 is forcibly expanded, and is provisionally fitted on the clamping surface 8a of the fixing region 8. Then, the insulation barrel 7 is forcibly deformed to embrace the interposing ring 10. When the insulation barrel 7 is thus forcibly deformed, the interposing ring 10 is deformed into a smaller diameter so that the clamping surface 8a is tightly grasped indirectly by the insulation barrel. In this case, depending on the degree of the clamping force, the insulation barrel 7 bites into the interposing ring 10. Therefore, the insulation barrel is more positively secured to the interposing ring 10, thereby preventing relative axial displacement between the two. Moreover, the two stopper surfaces 9 and 12 limit the axial displacement of the insulation barrel 7 and the interposing ring 10 so that the insulation barrel 7 is prevented from disengagement from the rubber plug 1. In this case, even if the insulation barrel 7 has sharp edges, these edges only bite into the interposing ring 10 and will not come into direct contact with the rubber plug 1. Therefore, the sealing property of the rubber plug 1 can be maintained without damaging the rubber plug 1. Only those portions of a second embodiment of the invention different from the above first embodiment will now be described with reference to Figs. 4 and 5. In this embodiment, an interposing ring 20 has an interrupting groove 21 extending at an angle with respect to the axis of this ring, as shown in Fig. 4. If the interrupting groove 21 is formed along the axis, a gap could be formed between opposed ends of the interposing ring 20, thus forming an area on which the clamping force applied from the insulation barrel is not exerted. However, because the interrupting groove 21 is formed obliquely, such a gap is not formed over the entire periphery, and therefore the clamping force is applied to the rubber plug 1 uniformly over the entire periphery. This prevents the withdrawal of the rubber plug 1 more positively. Only those portions of a third embodiment of the invention different from the above first embodiment will now be described with reference to Figs. 6 and 7. In this embodiment, means for preventing axial displacement of the insulation barrel 7 is provided directly on an interposing ring 30. More specifically, a pair of retaining flanges 32 is formed respectively on opposite ends of an outer surface of the interposing ring 30 over an entire periphery thereof, and they are directed radially outwardly. The outer peripheral surface extending between the two retaining flanges 32 defines a clamping surface 31 that can be compressively grasped by the insulation barrel 7. In the third embodiment, the retaining flanges 32 prevent the insulation barrel 7 from being axially displaced, either to the right or to the left, on the interposing ring 30. Therefore, the displacement of the insulation barrel 7 is prevented during the forcible deformation of the barrel so that the clamping operation can be carried out smoothly. Only those portions of a fourth embodiment different from the above third embodiment will now be described with reference to Figs. 8 and 9. In this embodiment, a retaining recess 31 and retaining surfaces 32 are formed on an outer peripheral surface of an interposing ring 35 as in the third embodiment. In addition, a retaining convex portion 36 is formed on an inner peripheral surface of the interposing ring 35 over an entire circumference thereof, the convex portion 36 being disposed centrally of the width of the interposing ring 35. The width of the retaining convex portion 36 is generally equal to the width of the insulation barrel 7, and the convex portion 36 bites into the clamping surface 8a of the fixing region 8 when the insulation barrel is clamped relative to the rubber plug 1. In the fourth embodiment, when the interposing ring 35 is provisionally fitted on the clamping surface 8a of the rubber plug 1, the retaining convex portion 36 of the interposing ring 35 slightly bites into the clamping surface 8a because of a resilient restoring force of ring 35, thereby slightly limiting the displacement of the interposing ring 35. Therefore, until the clamping is effected by the insulation barrel 7, the displacement is prevented, thus achieving an advantage that the clamping operation can be carried out smoothly. Only those portions of a fifth embodiment different from the above first embodiment will now be described with reference to Fig. 10. In the fifth embodiment, an interposing ring 40 comprises a pair of ring pieces 41. The two ring pieces 41 correspond to those obtained by dividing the interposing ring 10 of the first embodiment into two sections symmetrical with respect to the axis of the ring. An inner diameter of the ring configuration formed by the oppositely-mated ring pieces 41 is slightly smaller than the outer diameter of the fixing region 8. In the fifth embodiment, when the insulation barrel 7 is to be forcibly deformed, the two ring pieces 41 are first opposed to each other to surround the fixing region 8. When the insulation barrel 7 is forcibly deformed to embrace the ring pieces 41, the insulation barrel 7 is fixed in such a manner that the insulation barrel 7 slightly bites into the two ring pieces 41. The interposing ring 40 in this embodiment is of the split type, and therefore the ring 40 is not required to have resiliency for allowing the fitting of the ring on the fixing region 8. Namely, the interposing ring does not need to be made of an elastic material, and therefore the degree of freedom of material choice can be increased. The present invention is not to be limited to the above embodiments and, for example, the following modifications fall within the scope of the present invention. (1) The interposing member may be made of any suitable material such as, for example, paper and vinyl, as long as the interposing member prevents the edges of the insulation barrel from coming into direct contact with the rubber plug. Also, the interposing member should not be made of a material that will damage the rubber plug when it is interposed between the rubber plug and the insulation plug. (2) Furthermore, the interposing member may comprise a tape-like material wound on the rubber plug. Having now described the invention, it will be apparent to those skilled in the art that many changes and modifications can be made without departing from the scope of the invention as set forth in the appended claims.

Claims: A sealing rubber plug-fixing structure comprising: a sealing rubber plug (1) fitted on an end portion of a sheathed wire (2), said sealing rubber plug (1) being fixedly clamped to said wire (2) for providing a seal between said wire (2) and a cavity wherein the sealing rubber plug (1) is to be inserted, wherein said clamping is provided by a metal terminal connector (3) having an insulation barrel (7) and a wire barrel (16), said insulation barrel (7) fully embraces the entire outer periphery of a fixing region (8) of the rubber plug (1), said connector being fixed to said end portion of said wire (2) by means of said wire barrel (16) embracing an exposed portion of an conductor (15) of said wire (2); and an interposing member (10; 20; 30; 35; 40) interposed between an outer clamping surface (8a) of said fixing region (8) and an inner surface of said insulation barrel (7). The sealing rubber plug-fixing structure according to claim 1, wherein said interposing member (10; 20; 30; 35) has a ring-shape, said interposing member also having an interrupting groove (13; 21) formed at a portion thereof for allowing said interposing member (10; 20; 30; 35) to be inwardly contracted in a radial direction. A waterproof seal comprising: a sealing rubber plug (1) for fitting on an end portion of a sheathed wire (2), said sealing rubber plug (1) having a sealing portion (6) for providing a seal between said wire (2) and a cavity wherein the sealing rubber plug (1) is to be inserted, said sealing rubber plug (1) is to be clamped to said wire (2) by an insulation barrel (7) of a metal terminal connector (3) for fully embracing the entire outer periphery of a fixing region (8) of the rubber plug (1) adjacent the sealing portion; and an interposing member (10; 20; 30; 35; 40) interposed between an outer clamping surface (8a) of said fixing region (8) and an inner surface of said insulation barrel (7). The waterproof seal according to claim 3, wherein said clamping surface (8a) is bounded by first and second stopper surfaces (12, 9). The waterproof seal according to claim 4, wherein said first stopper surface (12) is defined by a flange (11) located a remote distance from the sealing portion (6), and the second stopper surface (9) is defined by an annular extension integrally formed with said sealing portion (6). The waterproof seal according to claim 5, wherein a diameter of the flange (11) is less than a diameter of the annular extension, the diameter of the flange (11) being approximately twice as large as a thickness of the interposing member (10; 20; 30; 35; 40). The waterproof seal according to anyone of claims 3 to 6, wherein said interposing member (10; 20; 30; 35) includes a slit (13; 21) that is flexibly expandable so as to allow the interposing member to fit over the fixing region (8). The waterproof seal according to claim 7, wherein said slit (21) is formed at an angle with respect to an axis of the interposing member (20). The waterproof seal according to anyone of claims 3 to 8, wherein said interposing member (30; 35) includes flanges (32) that extend radially away from said fixing region (8), said flanges defining a seating surface for clamping portions of said insulation barrel (7). The waterproof seal according to claim 9, wherein said interposing member (35) includes a convex portion (36) having a diameter that is slightly less than a diameter of the seating surface of the interposing member (35), said convex portion (36) biting into the fixing region (8, 8a'). The waterproof seal according to claim 10, wherein said convex portion (36) and said seating surface are formed on opposite sides of said interposing member (35). The waterproof seal according to claim 3, wherein said interposing member (35) includes a convex portion (36) having a diameter that is slightly less than a diameter of a main surface of the interposing member (35), said convex portion biting into the fixing region (8, 8a'). The waterproof seal according to claim 3, wherein said interposing member(40) is a two-part structure including at least two ring pieces (41) each having an arc that substantially matches a corresponding portion of the fixing region (8)., The waterproof seal according to claim 3, wherein said interposing member comprises tape-like material wrapped around said fixing region (8). A method for fixedly securing a seal to a wire, said wire being connectable to a metal terminal connector (3) having an insulation barrel (7) and a wire barrel (16), said method comprising: fitting a sealing rubber plug (1) on an end portion of a sheathed wire (2) and fixedly clamping said sealing rubber plug (1) to said wire (2) by fully embracing an entire outer periphery of a fixing region (8) of the rubber plug (1) with said insulation barrel (7); fixing said connector to said wire (2) by means of said wire barrel (16) embracing an exposed portion of the conductor (15) of said wire (2); and interposing an interposing member (10; 20; 30; 35; 40) between an outer clamping surface (8a) of said fixing region (8) and an inner surface of said insulation barrel (7) prior to embracing the entire outer periphery of said fixing region (8) with said insulation barrel (7). The method according to claim 15, further comprising providing the interposing member (35) with flanges (32) to define a seating surface for said insulation barrel (7). The method according to claim 15, further comprising providing the interposing member (35) with a convex portion (36) that bites into the clamping surface (8a). The method according to claim 15, wherein the wire (2) is inserted through the seal before the clamping of the interposing member (10; 20; 30; 35; 40).

Inventors: KATSUMA TAKATOSHI, KATSUMA, TAKATOSHI, KATSUMA, TAKATOSHI, C/O SUMITOMO WIRING SYST., LTD
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1995
Main classification: H01R13
IPC codes: H01R13, H01R43, H01R4