ELECTRICAL EDGE CONNECTOR

Abstract: Edge connector for a printed circuit board (35) comprises a housing (1) having terminals (21) therein. Terminals have spaced apart spring arms (26) which contact opposite surfa­ ces of the circuit board (35). The terminals (2) are in a first position when the circuit board (35) is inserted into the hous­ ing (1) such that the spring arms (26) are spaced apart and the circuit board can be readily inserted. After initial insertion, the circuit board (35) and terminals (21) are moved relative to the housing (1) and camming surfaces in the housing (1) cam the arms (26) towards each other and against the circuit board (35).

Description: This invention relates to an electrical edge connector for a printed circuit board, ceramic substrate, or the like, and is particularly concerned with a low insertion force for the board or substrate. There is described in GB-A-1039397, an edge connector for a printed circuit board or substrate, comprising an insulating housing formed with a contact-receiving through cavity and a slot for receiving an edge of the board or substrate traversing the cavity at one end, a contact in the cavity having a pair of divergent spring arms with the free ends presenting contact surfaces disposed at opposite sides of the slot for engaging opposite sides of the board or substrate, wherein the contact is moveable within the cavity in the insertion direction of the board or substrate between a first condition in which the contact surfaces are disposed outside opposite sides of the slot, and a second condition in which they are disposed within the slot width, and wherein the contact has a portion disposed between the spring arms which, in the first condition, projects into the slot whereby engagement of the connector with the board or substrate edge registers the projecting portion with the substrate edge to effect movement of the projecting portion rearwardly of the slot and movement of the contact to the second position, the cavity being of reduced width rearwardly of the slot whereby on movement of the contact between the first and second conditions, the spring arms are constrained by the reduced width cavity portion to move together to enter the contact surfaces into the slot, means being provided for biasing the contact towards its first condition. According to GB-A-1039397, said biasing means comprises a coil spring. The present invention is intended to provide biasing means which do not require the use of an additional metal part and which are economical of the contact material. According to the present invention, said projecting portion is formed with a spring arm having an end portion engaging a ramp surface formed on a wall of the cavity. Flexure of the spring arm against the ramp surface serving to bias the contact towards the first condition. Although US-A-4 118 094 discloses a low, or zero insertion force printed circuit edge connector having spring means formed integrally with the contacts of the connector, for biasing the contact spring arms towards said first condition. The spring biasing means are in the form of bellows springs, which are uneconomical of contact material. Each contact is provided with two such bellows springs and comprises two parts which are riveted together and are carried by a separate insulating member. A contact according to an embodiment of the invention may comprise a channel shaped body, the sides of the channel being extended at one end to define the spring arms, the base of the channel-shaped body being formed with said projecting portion which extends forwardly between the arms to a position rearwardly of the contact surfaces. Said projecting portion, is there folded back at a rearward inclination to provide said spring arm and said end portion being spaced from the base of the channel between the channel sides. Preferably, stops are formed in the cavity to limit movement of the contact between the first and second conditions. The invention will now be described, by way of example, with reference to the accompanying partly diagrammatic drawings, in which:- Figure 1 is an elevation of a connector housing from one side; Figure 2 is a section taken on the line 2-2 of figure 1; Figure 3 is an elevation of the connector of figure 1 from the opposite side with an end cavity shown in section; Figure 4 is a plan view of the connector of figure 1; Figure 5 is a side elevation of a contact for the connector of figures 1 to 4, but to an enlarged scale; Figure 6 is a plan view of the contact of figure 5; Figure 7 is a sectional view of a cavity of the connector viewed from an opposite direction to that of figure 2, and containing a contact according to figures 5 & 6, and in an initial condition of engagement with a substrate; Figure 8 is a section taken on the line 8-8 of figure 7, viewed in the direction of the arrows; Figure 9 is a view similar to that of figure 7 but with the substrate fully engaged with the connector, and Figure 10 is a view similar to that of Figure 8 but with the contact in a condition similar to that of figure 9. The connector housing of figures 1 to 4 is formed of resilient plastics insulating material as a unitary molding, and comprises a connector body portion 1 of generally rectangular slab-like form having at one major face, a mounting and retention section 2. The body 1 is formed with five through cavities, 3 arranged in a row and with a slot 4 for receiving a substrate edge extending transversely of the cavities 3 between opposite sides of the body 1, at a lower end as seen in figure 2. At the upper end on a face opposite the mounting section 2, the body 1 is formed with a flap 5 extending from side to side of the body across all of the cavities 3 and integral with the body 1 at a hinge 6 at a middle portion of the body between upper and lower ends thereof. The flap 5, at its upper edge is formed with a series of latch projections 7, each having a latch aperture 8 and arranged to project transversely over walls 9, separating the cavities 3, the apertures 8 engaging projection 10 formed on walls 9 to secure the flap 5 in the position shown. It will be understood that the flap 5, with the latch projecting 7 disengaged from wall projections 10, is moveable by bending at the hinge 6 between an open position at 90 degrees counterclockwise from the position shown, to the closed position shown. The flap 5 is formed adjacent the hinge 6, and internally of the cavities 3, with a series of inwardly projecting shoulders 11, one to each cavity 3, the shoulders having downwardly facing shoulder surfaces for contact retention purposes as will be described later in connection with figures 7 to 10. Each cavity 3 is formed substantially at the level of hinge 6 and on one of the cavity sides bridging the slot 4 with an inward projection 12 having upper and lower ramp surfaces 13, 14 for camming engagement with a portion of a contact as will be described later. On the opposite side of each cavity there is formed a shallow groove 15 extending upwardly from the mouth of slot 4, beyond slot 4 and terminating opposite the projection 12 in a downward facing shoulder 16 for contact retention purposes as will be described later. These sides of each of the cavities are formed adjacent the other pair of sides with shallow projections defining upward facing shoulders 17 slightly above the level of the slot 4, which serve to limit contact insertion. The other pair of sides, below the shoulders 17 diverge to a lower cavity portion surrounding the slot 4, of enlarged width, as seen in figure 2. The mounting section 2 comprises a pair of spaced latch arms 18 depending from a bridge portion 19 stood away from the body 1. The arms 18 are of channel form open sides of the channels facing outwards as seen in figures 1 and 4, and lower ends of the channels being closed by latch portions 20 having upper and lower ramp surfaces. It will be understood that the lower ends of the arms can be resiliently flexed together to enable engagement or disengagement of the latch projections 20 with complementary means on a fixture for releasably securing the connector to the fixture. The contact of figures 5 and 6 comprises a channel shaped middle portion 21 having at one end a wire connecting section 22 of conventional form comprising a U-shaped wire crimp ferrule 23 and insulation support ferrule 24 extending from a carrier strip 25. At the other end of the portion 21, opposite sides of the channel are extended in divergent manner, as spring arms 26, to free ends which are turned inwards in arcuate manner to present opposed arcuate contact portions 27. As seen in figure 5 in side elevation the spring arms 26 are progressively reduced in width towards the free ends. The base of the channel shaped portion 21 is formed between the arms 26 with an extension 28 which, as seen in figure 6, is reduced in width forwardly and is stiffened by a central embossment 29. The extension 28 is further extended by a bent back portion 30 which extends rearwardly and upwardly between the arms 26 to project at its free end 31 above the channel portion 21. The free end 31 is bent down in arcuate manner to present an upwardly convex engagement surface. The base of the channel portion 21 is formed with a downwardly and rearwardly extending retention latch 32 pushed out of an aperture in the base behind the embossment 29. In use the contact of figures 5 and 6 is severed from the carrier strip 25 and crimped to a stripped wire end 33 in conventional manner to present a terminated lead for assembly to the connector housing of figures 1 to 4 as shown in figures 7 to 10. In figures 7 and 9 the mounting section 2 of the connector housing is not shown. For assembly of terminated leads to the connector housing, the flap 5 is moved to an open condition so that the shoulders 11 are clear of the cavities 3, The contacts are inserted into respective cavities 3, leading ends of the contact springs 26 initially engaging opposite sides of the cavities 3 below the hinge 6 and thereby flexed inwardly to allow passage into the cavities until the retention latch 32 enters the groove 15 and engages the shoulder 16 to secure the contact against withdrawal from the housing. During the insertion the bent back portion 30 engages the transition edge between the ramp surfaces 13 and 14 to flex the portion 30 inwardly until its free end 31 engages the ramp surface 14. At this condition, which corresponds to figures 9 and 10, the spring arms 26 are constrained inwardly by the cavity walls, and shoulders 34 at the lower end of the channel section 21 on opposite sides of the extension are spaced above the housing shoulders 17. The contact is thus capable of further downward movement through the cavity 3 and the flexure of the portion 30 against the ramp surface 14 exerts a downward force on the contact to move it downwardly until the shoulders 34 and 17 engage to resist further downward movement. The contact is now in the condition of figures 7 and 8. In this condition the spring arms 26 enter the lower cavity portion of increased width and flex apart on opposite sides of the slot 4 with the contact ends 27 outside the slot 4. The forward or lower end of the extension 28 is disposed within the slot 4, and the retention latch 32 is spaced below the shoulder 16. When all of the contacts have been assembled into respective cavities 3, the flap 5 is closed to the condition shown in figures 7 and 9 so that the projections 11 enter respective cavities behind and above the channel portion 21 in a position to register with rear or upper edges of the channel portion 21 as shown in figures 9 and 10 to provide a secondary contact retention to that provided by latch 32 and shoulder 16. In the condition of figures 7 and 8, the connector can be assembled to a substrate 35 by entering the edge of the substrate 35 into the slot 4 between the contact portions 27 until the edge of the substrate 35 engages the forward lower end of the contact extension 28. In this position, shown in figure 7, the contact portions 27 are clear of the slot and are not engaged by the substrate 35, so that risk of damage of the contact surfaces by sharp edges of the substrate 35 and by abrasion is avoided. Further movement of the substrate 35 into the slot 4 drives the contact upwardly or rearwardly in the cavity 3, the portion 30 being flexed inwardly by the ramp 14 and the spring arms 26 being flexed inwardly by being drawn into the cavity portion of reduced width. The contact portions 27 are thus urged against opposite sides of the substrate, as shown in figure 9 to exert contact force. The substrate 35 is suitably supported in a fixture, not shown, having means complementary to the latch arms of the mounting section 2 of the connector so that the latch arms 18 at their ends 20 engage the complementary means in a snap fit releasably to secure the connector in the condition of figures 9 and 10. To release the connector, the latch arms 18 may be flexed together, and the connector withdrawn from the substrate 35 by upward movement of the housing in the figure 9 position to that of figures 7 and 8. The spring portion 30 and the engagement of its free end 31 with the ramp, serves to drive the contact downwards relative to the housing so that the contact portions 27 flex apart from the substrate to the figure 7 condition before the connector is withdrawn from the substrate 35. In this way abrasion of the contact portions 27 with the substrate 35 and engagement with any sharp edges is avoided.

Claims: An edge connector for a printed circuit board or substrate, comprising an insulating housing (1) formed with a contact receiving through cavity (3) and a slot (4) for receiving an edge of the board or substrate (35) traversing the cavity at one end, a contact (21,22) in the cavity having a pair of divergent spring arms (26) with free ends presenting contact surfaces (27) disposed at opposite sides of the slot (4) for engaging opposite sides of the board or substrate (35), wherein the contact (21,22) is movable within the cavity (3) in the insertion direction of the board or substrate (35) between a first condition in which the contact surfaces (27) are disposed outside opposite sides of the slot (4), and a second condition in which they are disposed within the slot (4) width, and wherein the contact (21,22) has a portion (28) disposed between the spring arms (26) which, in the first condition, projects into the slot (4) whereby engagement of the connector with the board or substrate (35) edge registers the projecting portion (28) with the substrate edge to effect movement of the projecting portion (28) rearwardly of the slot (4), i.e. in the insertion direction of the substrate,and movement of the contact (21,22) to the second condition, the cavity (3) being of reduced width, rearwardly of the slot (4) whereby on movement of the contact (21,22) between the first and second conditions, the spring arms (26) are constrained by the reduced width cavity portion to move together to enter the contact surfaces (27) into the slot (4), means (30) being provided for biasing the contact (21,22) towards its first condition; characterized in that the projecting portion (28) is formed with a spring arm (30) having an end portion (31) engaging a ramp surface (14) formed on a wall of the cavity (3), flexure of the spring arm (30) against the ramp surface (14) serving to bias the contact (21,22) towards the first condition. A connector as claimed in claim 1, characterized in that shoulders (11,16,17) are formed in the cavity (3) to limit movement of the contact (21,22) between the first and second conditions. A connector as claimed in claim 1 or 2, characterized in that the contact comprises a channel shaped body (21), the sides of the channel being extended at one end to define said spring arms (26), the base of the channel shaped body (21) being formed with said projecting portion (28) which extends forwardly between the arms (26) to a position rearwardly of the contact surfaces (27), said projecting portion (28) being there folded back at a rearward inclination to provide said spring arm (30), said end portion (31) being spaced from the base of the channel between the channel sides.

Inventors: HOSCHEK, WOLFGANG, RYLL, JUERGEN
Applicants: AMP INCORPORATED
Application year: 1984
Main classification: H01R23
IPC codes: H01R12, H01R24