Abstract:
A low insertion force electrical connector comprising at least a plug and a base provided with a blind recess for receiving the plug. The base has pin contacts. The plug is connected to a bundle of electrical cables by means of electrical contacts. The base and the plug comprise conjugal means on the base and plug, which conjugal means include the base having a guide groove opening into a swing and lock hole formed in the base. The conjugal means permit a displacement in translation, with the plug in a first orientation, and when the plug is completely inserted at the end of the blind recess of the base a swinging displacement of the plug relative to the base, from the first to a second orientation, in which the plug is immobilized in translation by first locking means on the base and plug.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the field of electrical connectors of so-called low force of insertion, or zero force of insertion, more particularly with pin/lyre contacts. 
     To connect a layer of flexible cables to a rigid support of the printed card type, users require connectors needing a minimum insertion and blocking force, this latter remaining a necessity to permit any inadvertent disconnection. More generally, connectors are sought which will permit avoiding any accidental disconnection. 
     There is known for example a connector of zero insertion force described in U.S. Pat. No. 4,718,859, provided to receive a layer of cables. 
     Such a connector comprises two blocks: 
     a fixed block, generally connected to a support and provided for this purpose with blade contacts with a plug which are welded to the support, and 
     a movable block which coacts with the fixed block to immobilize the cables of the layer and ensuring contact between the cables of this layer and the blades, this requiring no insertion effort of the layer. 
     The movable block is mounted on the fixed block by translatory movement, guide means ensuring a suitable positioning of the two parts. The layer is then inserted between the two blocks. It then suffices to pivot the movable block relative to the fixed block to ensure pressing one portion of the blades against the cables, thereby ensuring the electrical connection. The locking is simultaneously ensured because any displacement in translation of the movable block relative to the fixed block is prevented. 
     The problem solved by this patent is that of the variations of thickness of the various layers to be inserted in this connector. Thus, these variations give rise to loss of pressure force of the plugs of the fixed block on the cables of the layer, unless different models are provided, each applicable to a type of layer. Given the very low sales price of these connectors, it would be of interest to provide a connector permitting receiving different thicknesses of layers of cables. 
     To solve this problem about different thicknesses, the base as specified in this American Patent have blades with a particular C-shaped profile, with offset ends thus forming two offset contact points, above and below the layer. Branches of the C shaped profile have a sufficient flexibility and adjust to thickness variations. The layer presents an S-shaped deformation when it is thin and the layer remains substantially flat when it is thick. The contact pressure is obtained in the same manner in both cases and only a contact at two points is possible. 
     SUMMARY OF THE INVENTION 
     The present invention provides a connector comprising a base and a plug, which requires very low insertion and locking force of the plug and the base, which gives rise to excellent electrical connection, which comprises first and if desired second blocking means, which is simple to produce, and which is easy to manipulate. 
     To this end, according to the invention, the electrical connector of low insertion force, comprises a base provided with a blind recess provided to receive a plug, this base carrying connection pins and this plug being connected to a bundle of electrical cables, and is characterized in that it is provided with translatory guide means, particularly comprising at least one guide ramp opening into a locking hole, which hole constitutes the first locking means so-called in translation, by coacting with at least one fixed rib of a suitable profile to assume a first orientation in which it can be moved in translation along said ramp and a second orientation in which it is immobilized in the locking hole by swinging relative to the plug and the base. 
     This electrical connector also comprises second locking means so-called in swinging. 
     According to a particular arrangement, the rib of the plug has a width equal to the width of the ramp of the base and its longitudinal axis is inclined relative to the plane of the lower and upper surfaces of the plug by an angle α, such that the base and the plug are aligned after locking. 
     According to the preferred embodiment, the second locking means comprise a ring mounted slidably on the upper end of the block of the plug and provided with two lateral tongues of a shape and position suitable to penetrate each one into the groove of the corresponding ramp. There are moreover provided retaining means for this ring in the active and inactive positions. 
     According to a particular application of the invention, each electrical contact of the plug is a blade contact of the lyre type with two branches provided to come into contact on opposite sides of each pin carried by the base. 
     According to some others features of the invention, particular dispositions of contacts of the connector are mentioned which allow the reinforcement of the electrical connection and make the cables installation easier while certifying the quality of such installations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described with respect to the accompanying drawings in which the different figures show: 
     FIGS. 1A and 1B a side elevational view of a connector according to the invention in a first position before locking and a second position after locking, 
     FIG. 2, a cross-sectional view in a transverse plane along the line  2 — 2 , 
     FIG. 3, a cross-sectional view in a transverse plane along the line  3 — 3 , 
     FIGS. 4A and 4B, views of the upper and lower surfaces of the plug of the connector according to the invention, and 
     FIGS. 5A,  5 B and  5 C, a sequence of emplacement of the plug in the base of the connector according to the invention, partially broken away so as to show the connecting pins and blades. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, there is shown a base  10  and a plug  12  in the insertion position. The plug is provided to receive a bundle  14  of electrical cables  16  disposed in a layer for example whilst the base comprises emergent pins  18 , positioned in the course of molding said base. 
     The pins generally have in known manner a connection tail  20  to a printed circuit in the case in which the invention relates to a device for plug/base connection to a printed circuit or, again in a known manner, an attachment region for an electric wire when the connection device relates to a male/female connector. 
     The base  10  comprises a blind recess  22  for reception of the plug. 
     This recess  22  comprises: 
     a plugging wall  24 , 
     a bearing wall  26 , opposite the plugging wall, 
     two side guide walls  28  and  30 , only the wall  28  being seen in FIGS. 1A and 1B, the other wall facing it and being visible in FIGS. 2 and 3, and 
     a bottom  32 , slightly curved over a radius R. 
     The plugging wall  24  is inclined at an angle α, of the order of 10 to 20°, relative to the direction of introduction of the plug  12 , shown by the arrow  34 . Moreover, this plugging wall comprises a series of two canted surfaces p and q, shown in FIGS. 5A,  5 B and  5 C. 
     The bearing wall  26  is substantially parallel to the direction of introduction. It comprises a series of three canted walls a, b and c. 
     Each of the lateral walls  28  and  30  is provided with first guide and locking means  37 , comprising two guide ramps or grooves  38 ,  40  (see FIG. 2) each in the form of a groove disposed in the plane of the wall and with two holes or swing and lock holes  42 ,  44  for evident reasons of symmetry and stability. One  46 ,  48  of the ends of each of the ramps emerges from the edge of the blind recess  22  whilst the other  50 ,  52  of the ends emerges downwardly into the corresponding hole  42 ,  44 . 
     The holes  42 ,  44  have a particular shape, substantially in the form of a right triangle. Each large side  54  and  56  of the right triangle is aligned with the edge of each corresponding ramp  38 ,  40 , on the side of the plugging wall  24 . 
     Each small side  58 ,  60  is of a length greater than the width of the corresponding groove constituting each ramp. Adjacent to each small side, on the side surface  28 ,  30  at the outside, there is provided first locking means  61  in swinging, comprising a blocking notch  62 ,  64  as a depression. 
     The lower angle  66  of each of the holes which serves for a bearing, is provided with a hollow of a radius r. 
     The plug  12  comprises a block  68  of a shape partially conjugated to that of the blind recess  22  of the base with two upper and lower surfaces  69  and  70  substantially parallel and two later guide surfaces  71 ,  72 . This block comprises two surfaces a′ and b′ on the upper surface and a single surface p′ on the lower surface. 
     In known manner, this block  68  comprises a slot  73  for reception of a bundle  14  of electrical cables  16 . The conductive portion of each cable is prolonged in the juxtaposed sockets  74 . Each socket is provided with a hole  75  for passage of an electrical contact  76  in the form of a blade, each comprising a foot  78  and a head  80 . These electrical contacts with a profile of the lyre type are maintained in recesses  77  provided in said block, providing a comb and reaching around these blades with a profile of the lyre type, wrapping them laterally at least. This disposition insure to maintain a regular gap between blades, to maintain them rigid to have a good connection with the pins and to insulate them electrically speaking while keeping the possibility for pins to penetrate to insure electrical connection. 
     Each contact  76  can have two positions, one, before mounting, in which the foot  78  of the contact is outside the socket and the other, after mounting, in which the foot  78  of the contact projects into the socket  74  to penetrate into the conductive portion of the corresponding cable and to ensure the electrical connection. The foot is generally provided with barbs which prevent the retraction of each blade contact outside its recess after mounting. 
     In this embodiment, the head  80  of each contact  76  is in the shape of a lyre  82 , with two branches  82 - 1  and  82 - 2 . 
     Each of these branches has a particular profile of the lyre type which permits, as shown in FIG. 5A, a contactless introduction between the pin and the branches with a profile of the lyre type before swinging and a substantial contact at many points after swinging, as shown in FIGS. 5B and 5C. 
     The plug also has a portion of the first guide and locking means in the form of two ribs  84 ,  86 . Each rib comprises a rectilinear portion  88 ,  90  of a width equal to the width of the ramps of the base, with a sliding play similar to and a length equal at most to that of the greatest side  54 ,  56  of the hole  42 ,  44 . One of the ends  92 ,  94  of each rib is rounded with a radius of curvature equal to r to coact with the hollow  66  provided in the lower portion of the hole. 
     Each rib is provided with a boss  96 ,  98  provided to coact with notches  62 ,  64  provided in the base as will be explained later. 
     So as to take account of the remaining thickness of each side wall, the rib is spaced from the side wall which carries it. 
     Moreover, the longitudinal axis of the rib also forms an angle α with the longitudinal axis  66  of the block  68  whose four surfaces are substantially parallel two by two if the canted surfaces are excluded. As to the end of the block, it is slightly rounded with a radius R identical to the radius R of the bottom  32 . 
     The base and the plug are also provided with second guide means  70 , in this case two wings  100 ,  102  carried by the plug and two grooves  104 ,  106  provided in the base and of a complementary profile to permit precise positioning. It is thus desirable to limit the play of penetration such that the blade contact of the lyre type will occupy a position, by its two branches  82 - 1  and  82 - 2 , on opposite sides of the corresponding pin  18 . 
     The connector according to the present invention can also be completed by second locking means  108 . 
     These second locking means comprise a ring  110  mounted slidably on the upper end of the plug, which end remains outside the base after plugging in. 
     This ring comprises two lateral tongues  112 ,  114  of a shape and position adapted to penetrate each one into the corresponding groove of the ramp  38 ,  40 . 
     This ring can have two positions, one shown in FIG. 1A in which the ring is in the upper inactive position and the other shown in FIG. 1B in which the ring is in the lower active position, for swinging locking, the tongues  112 ,  114  entering into the ramps in the direction of the arrows. 
     According to the preferred embodiment, there is also provided means  120  for retaining the second locking means in each of the active and inactive positions, comprising a double boss  116 ,  118  provided within the ring, and outside of the plug, the assembly forming a hard point. 
     The emplacement of such a connector is carried out as will be explained. 
     The base is considered as stationary in the present case, the pins  18  projecting into the blind recess  22 . 
     The plug  12  is inserted into the blind recess and in the first step, the plug is guided in vertical translation by the ribs  84 ,  86  which slide along the ramps  38  and  40 . The block  68  of the plug is in the inclined position. 
     Upon introduction of the block, each electrical contact  76  of the blade lyre type comes onto opposite sides of the associated pin with its branches  82 - 1  and  82 - 2 , but without contact with the pin. 
     The wings  100  and  102  of the plug complete guidance by coaction with the grooves  104  and  106  of the base. 
     When the plug is entirely inserted into the base with the end of the block against the bottom  32 , the block bears with a portion of its surface b′ against the surface c of the base and with its surface p′ against the surface p of the plugging surface. 
     Each rib  84 ,  86  is then in line with the hole  42 ,  44 . 
     To obtain final mounting, the block  68  of the plug is manipulated by swinging in the direction of the arrow of FIG. 5A, which is to say such that the longitudinal axis  66  of the block coincides with the longitudinal axis of the base, the angle α becoming zero. 
     The boss  96 ,  98  of each rib snap connects with the corresponding notch  62 ,  64  of the lateral surface  28 ,  30  of the base. This snap connection, by its resilience, permits the operator to sense the maneuver and to see that the locking point has been reached. 
     Each electrical contact  76  comes into contact with its branches with the corresponding pin  18  as shown in FIGS. 5B and 5C. 
     The block  68  is then located in abutment by its surfaces a′ and b′ of its upper surface against the surfaces a and b of the base, which provides a stable bearing, the more so that the rear surface bears with its surface p′ against the surface q of the base. 
     The first locking means prevents the retraction of the plug from the base. Nevertheless, the plug can be brought into inclined position by reverse swinging, providing a reduced force to pass the hard point constituted by the boss/notch couples, these couples ensuring breaking of undesired swinging, particularly arising from vibrations or light shocks. 
     It is also useful to provide the present connector with second locking means  108  which prevent this return swinging movement. It suffices to manipulate the sliding ring  110  from the upper end of the plug toward the base, in the direction of the arrow  34  of introduction of the plug into the base. 
     Each tongue  112 ,  114  then penetrates the corresponding ramp  38 ,  40  as is visible in FIG.  1 B and the cross-sectional view of FIG.  2 . 
     It will be noted that the plug is nevertheless removable by successive performance of the reverse steps. On the contrary, any undesired disconnection is prevented without deliberate intervention. 
     The snap-in system could be modified with a boss/notch couple disposed between the rib and the facing slide surface by a rib as described above by replacing it with a boss or a notch at any point along the rib from the moment at which a notch or a conjugated boss come face to face in the base.