Patent Publication Number: US-6217385-B1

Title: Sealing unit, particularly for electric connectors

Description:
TECHNICAL FIELD 
     The present invention relates to a sealing unit about one or more elongated elements such as cables, pipes or the like, and is particularly, though not exclusively, suitable for insertion between the casing and one or more cables of an electric connector, to which application the following description refers purely by way of example. 
     BACKGROUND OF THE INVENTION 
     The electric cable of sealed electric connectors is normally sealed by means of a sealing element having a through opening through which the cable is fitted. The sealing element may be a straightforward rubber ring for a single cable, as described for example in U.S. Pat. No. 5,069,639, or a multiple seal with a number of holes for respective cables, as described for example in U.S. Pat. No. 4,460,227. As the efficiency of the sealing element depends on its exerting a certain amount of pressure on the cable, the section of the opening must be smaller than the cross section of the cable to produce a certain amount of radial forcing when the cable is assembled. 
     Known sealing elements of the above type present several drawbacks. 
     One way of assembling the connector is to insert the cable through the sealing element before crimping the terminal on to the cable, which solution, however, involves a fairly complex, time-consuming assembly sequence. Alternatively, the sealing element may be assembled beforehand inside the casing, in which case the electric terminal, already crimped to the cable, must be fitted through the opening in the seal when the terminal is inserted inside the casing. On account of the small section of the opening in the seal, such a solution may result in severe distortion of the seal, and in tearing or cutting of the edge of the opening, thus impairing sealing efficiency in actual use. What is more, subsequent removal and reassembly may result in further damage, to the extent that the seal must eventually be replaced, with all the disadvantages this entails in terms of time and money. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sealing unit, particularly for an electric connector, designed to overcome the drawbacks typically associated with known seals of the aforementioned type. 
     According to the present invention, there is provided a sealing unit about an elongated element comprising first and second elastically deformable sealing elements facing each other and gripped against each other and against the elongated element interposed between the sealing elements. The sealing elements comprise respectively at least a first and at least a second portion complementary in shape, at least one of the portions being deformable by the other to cooperate in sealing manner with the elongated element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two preferred, embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: 
     FIGS. 1 and 2 show schematic partial views in perspective of a sealing unit in accordance with the teachings of the present invention and in two different operating positions; 
     FIG. 3 shows a partially sectioned longitudinal view of an electric connector featuring a pair of sealing units according to the present invention; and 
     FIG. 4 shows a cross section of the FIG. 3 connector, comprising a portion a along line IVa—IVa, and a portion b along line IVb—IVb in FIG.  3 . 
    
    
     PREFERRED EMBODIMENT 
     Number FIGS. 1 and 2 shows a sealing unit  1  comprising a pair of sealing elements  2 ,  3 , which are placed together and pressed against each other to cooperate in sealing manner with a number of parallel electric cables  4  (only one shown in FIG. 1) interposed between elements  2  and  3 . 
     Elements  2  and  3  are molded from elastomeric material, and comprise respective shaped surfaces  5 ,  6  facing and cooperating with each other. Each of surfaces  5 ,  6  presents a number of first portions  7  and second portions  8  defining bands of surfaces  5 ,  6  extending transversely in relation to cables  4  and alternating in a direction parallel to cables  4 . Portions  7 ,  8  of element  2  are offset axially in relation to portions  7 ,  8  of element  3 , so that a portion  7  of one element mates with a portion  8  of the other. 
     Portions  7  and portions  8  are complementary in shape. More specifically, first portions  7  comprise a number of pairs  9  of sealing lips  10 ; the lips  10  in each pair  9  define a C-section seat  11  of a depth greater than the diameter of cables  4 , and housing a portion of a respective cable; and the adjacent lips  10  of two adjacent pairs  9  are separated by a C-section gap  12  shallower than seats  11 . Second portions  8 , on the other hand, present an undulated contour defined by a number of crests  13  located at gaps  12  of adjacent first portions  7 , and alternating with a number of grooves  14  located at seats  11  of adjacent first portions  7 . 
     Second portions  8  are sunk in relation to first portions  7  so as to form a shoulder  15  between the bottom of seat  11  and the bottom of adjacent groove  14 . Lips  10  present a substantially trapezoidal axial section; and the lips  10  of adjacent portions  7  define respective gaps  16  also presenting a substantially trapezoidal section but slightly less than the section of lips  10  when undeformed. 
     Sealing elements  2 ,  3  present respective flat supporting faces  17  opposite surfaces  5 ,  6  and which cooperate in sealing manner with respective pairs of gripping elements (not shown) between which unit  1  is compressed in use. 
     Unit  1  operates as follows. 
     In FIG. 1, sealing elements  2 ,  3  are shown in the open position facing each other to permit insertion of cables  4  (only one shown) between respective surfaces  5 ,  6 . 
     Cables  4  are inserted so as to engage seats  11  in portions  7  of each element  2 ,  3  when elements  2 ,  3  are placed together and pressed against each other (FIG. 2) to mate surfaces  5  and  6 . Pairs  9  of lips  10  of portions  7  of one element  2  or  3 , which almost entirely surround a respective portion of cable  4 , fit inside the corresponding grooves  14  of respective portions  8  of the other element  3  or  2 ; and, at the same time, crests  13  of each portion  8  engage in forced manner the gaps  12  between pairs  9  of lips  10 , so that lips  10  in each pair  9  are deformed about respective cable  4  and cooperate end to end. 
     Lips  10  thus provide for sealing the entire periphery of the cable, with the exception of the portion at which they cooperate end to end; which portion, however, is located at shoulder  15  defined by the adjacent portion  7  and which provides for preventing any infiltration. The alternating arrangement of portions  7  and  8  therefore defines a labyrinth seal for ensuring absolutely airtight sealing of cables  4 ; which performance is further improved by the axial force produced by the trapezoidal section of lips  10  and dimensional interference with respective gaps  16 . 
     FIGS. 3 and 4 show an electric connector  19  featuring a pair of sealing units  20  in accordance with the teachings of the present invention. 
     Connector  19  comprises an insulating casing  21  in turn comprising a main body  22  with two rows of cavities (not shown) housing respective electric terminals  23 ; and two shells  24  snapped together on either side of an intermediate wall  25  of body  22  separating the two rows of cavities and projecting from body  22  so as to separate the two rows of cables  4  of respective terminals  23 . 
     Each shell  24  defines with wall  25  a chamber  29  housing a respective sealing unit  20 . Each unit  20  comprises a sealing element  2  and a sealing element  3  with respective surfaces  5 ,  6  as described with reference to unit  1  in FIGS. 1 and 2; and elements  2 ,  3  are compressed against each other between respective shell  24  and wall  25 , and cooperate in sealing manner with opposite sides of cables  4 . Shells  24  are secured to each other by means of elastic snap-on fasteners, and are retained on wall  25  in the direction parallel to cables  4  by retaining means not shown. 
     To ensure stable transverse positioning of elements  2 ,  3  and enhance the sealing effect due to interaction of portions  7  and  8 , wall  25  and shells  24  are conveniently undulated and defined by a number of equally spaced projections  27  cooperating with respective recesses  28  formed in surfaces  17  of sealing elements  2 ,  3  at crests  13  of portions  8  and gaps  12  of portions  7 . 
     The advantages of units  1  and  20  according to the present invention are as follows. 
     By virtue of the sealing unit being formed in two separate parts between which the cables are inserted, it may be assembled and disassembled with the terminals already crimped to the respective cables  26 , with no need to force the terminals through small-section openings as with known one-piece seals. Moreover, when gripped together against the cable, the complementary shape of the two sealing elements causes them to flex into sealing contact with the cable. And finally, the axially alternating arrangement of portions  7  and  8  defines a labyrinth seal ensuring substantially airtight sealing of the unit. 
     Clearly, changes may be made to units  1  and  20  as described and illustrated herein without, however, departing from the scope of the present invention. For example, changes may be made to the number of portions  7 ,  8 ; to the number of cables  4  for sealing; or to the shape of lips  10  and respective seats  11 .