Connector with a plug and base of low insertion force, particularly of the type with pin/lyre contacts

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.

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 .alpha., 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.

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 .alpha., of the order of 10 to
 20.degree., 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, 5B and 5C.
 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 .alpha. 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 .alpha. 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. 1B 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.