Zero force type connector block

[57] ABSTRACT

A zero force connector block having a number of snapover-center type terminals arranged along a circuit board receiving slot and a cam bar operable to engage the terminals serially and move contact portions on the terminals into engagement with a contact on a circuit board inserted into the slot. As the terminals move into engagement with the circuit board they move other terminals into engagement with different contact portions of the circuit board.

Claims, 13 Drawing Figures

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PATENTEOJUL 31973

SHEET 1 OF 4

3,744,005

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PATENTED JUL 31973

3,744,005

SHEET 2 OF 4

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BY

Thomas ΉοοΚβ-ρ, His ήΗοτηβι^

PATENTED JUL 31973

SHEET 3 OF 4

3.744,005

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INVENTOR.

FRED C. 5ITZLER BY

Thomas Hooker,

His -^ttorneij

PATENTED JUL 31973

3.744,005

SHEET U Of 4

<img file="US3744005A_D0006.tif" />

3,744,005

ZERO FORCE TYPE CONNECTOR BLOCK

THE INVENTION

The invention relates to zero force type connector blocks where a circuit board or like member is freely inserted into a slot formed in an insulated housing without engagement between the board and the terminals confined in the housing. The free insertion of the board into the block eliminates wear at the terminal contact areas during insertion. A row of snap-over-center type terminals is confined in the block along the open circuit board slot defined by ribs between adjacent terminals. The terminals are in the disengaged position during insertion of the board so that the contact portions are free of the board. The board may be directly inserted into the slot or it may be moved laterally along the slot to reach the contact position. After the board is inserted, a cam bar is moved longitudinally along the length of the block to engage the terminals serially and move or snap the same over-center to the engaged posi10

BACKGROUND OF THE INVENTION

Snap-over-center type contacts have been long used in small electrical switches of the push button type as disclosed in U.S. Pat. Nos. 1,960,020 and 2,172,673. In U.S. Pat. No. 2,901,568 an insulating button is provided between a pair of snap-over-center type contacts so that shifting of one contact causes the second contact to shift. U.S. Pat. No. 3,541,490 discloses a zero force type connector block in which spring terminals confined within the block are serially brought into electrical connection with pins extending into the block by inserting a cam bar along the length of the block to engage and stress the terminals. Other zero force type connector blocks for circuit boards have been proposed in which the terminals are removed from the circuit board slot during insertion and are then simultaneously brought into engagement with the contact on the circuit board through the use of a rotary cam or 20 longitudinally movable cam bar. The rotary cam and tion where the terminals contacts are spring biased against the contact areas on the circuit board. The cam bar may engage the snap-over terminals directly or may engage a slide member to move the slide member and thereby shift the terminals. The terminal contacts are 25 brought into engagement with the circuit board contact areas without protracted wiping along the surface of the circuit board so that the terminal contact areas are not worn away by frictional contact with the circuit board. This is important since the terminal contacts are frequently provided with a conductive coating or plating of a precious metal such as gold which improves the contact properties but is easily worn away. When the cam bar is fully inserted into the block, all of the terminals are in contact with contact portions along the circuit board.

Because the contacts are brought into engagement with the circuit board one at a time, or serially, with the insertion of the cam bar, the insertion force required to move the cam bar along the cam path is maintained at a relatively low level. This is important because of the present requirement of a large number of terminals per connector block row. Sometimes as many as 40 or more terminals are required per row. This means that the force required to shift all of the terminals simultaneously from the disengaged to the engaged positions is quite high. In some instances the force required to shift the terminals simultaneously would be too large to permit manual shifting of a cam bar. In other cases, the cam bar is not strong enough to transmit the required forces without buckling or breaking.

In some applications it is desirable to establish a second connection with a circuit board adjacent each snap-over-center terminal in the block. These connections may be used for the establishment of ground or reference voltages on the circuit board. Spring leaf terminals are located adjacent each snap-over-center terminal in the block and are biased toward the terminal so that an insulating button or spacer carried by the spring leaf is held against the terminal. Shifting of the snap-over-center terminal into engagement with the circuit board moves the leaf terminal so a contact point on the terminal engages the ground or reference voltage contact on the circuit board. The leaf terminal contact is free of the circuit board slot prior to engagement to prevent contact wear as the circuit board is positioned within the circuit board slot.

cam bar simultaneously engage the terminals to bring them into engagement with the circuit board at the same time. See, for instance, U.S. Pat. Nos. 3,478,301, 3,537,063 and 3,553,630.

other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings illustrating the invention, of which there are four sheets.

IN THE DRAWINGS:

FIG. 1 is a partially broken away perspective view of a connector block according to the invention;

FIG. 2 is a sectional view taken along line 2—2 of ³⁵ FIG. 1 with the terminals on the left of the view in the open or disengaged position, and the terminals on the right of the view in the closed or engaged position;

FIGS. 3,4 and 5 are sectional views taken along lines 3—3, 4—4 and 5—5 respectively of FIG. 2;

⁴⁰ FIG. 6 is a perspective view illustrating a pair of terminals removed from the block;

FIG. 7 is a broken away view illustrating engagement between the terminals and the block;

FIG. 8 is a perspective view of a cam rod used to ⁴⁵ move terminals in adjacent blocks from the open to the closed positions;

FIG. 9 is an enlarged view of a portion of FIG- 8;

FIG. 10 is a view of a cam rod similar to that of FIG. 8 for engaging the terminals on one side of a single block;

FIG. 11 is a sectional view taken through a connector block illustrating a further embodiment of the invention wherein the cam rods engage the free ends of the contacts. The block is in the open position;

FIG. 12 is similar to FIG. 11 but with the terminals in the closed position; and

FIG. 13 is a sectional view taken along line 13—13 of FIG. 12.

Connector block 10 includes an insulating body 12 which may be formed from a suitable plastic having a base 14 and a pair of upstanding sidewalls 16 and 18. Ribs 17 and 19 extend from the sidewalls and define the sides of a circuit board receiving recess 20 running longitudinally along the body from end 21. Terminal cavities 22 are formed between adjacent ribs 17 and 19 to each side of recess 20 and extend from the ends of sidewalls 16 and 18 below the bottom of the recess. A

3,744,005 cam path or recess 24 extends longitudinally along the outer surface of each sidewall past recesses 22 and is connected to each of the recesses by a passage 26.

A pair of contact terminals 28 and 30, best illustrated in FIG. 6, is confined in each recess 22 for engagement with the circuit board when positioned in slot 20. Each of the terminals is provided with a tail portion 32 which extends from the bottom of a recess 22 through an opening 34 provided in base 14 for engagement with printed circuitry or suitable circuit means on circuit board 36. U-shaped spring tabs 38 formed in the sides of tails 32 at the connection with the terminals are seated in recesses 40 at the upper end of holes 34 in order to secure the terminals to the body 12 in desired locations.

Each terminal 28 includes a tension leg formed from a flat thin strip of metal which extends from tabs 38 to terminal free end 44. As illustrated in FIG. 4, the edges of the medial portion 46 of leg 42 are bent together to reduce the width of the leg.

Compression leg 48 extends from free end 44 toward the tail 32 and is bowed away from the tension leg toward recess 20. A contact point 50 may be formed in leg 48 for engagement with circuitry on board 52 when positioned in slot 20. The tension leg 48 may be formed from an extension of the strip forming leg 28 and joined to leg 28 by means of a reverse bend at end 44. Crimp tabs 54 extending from the end of the tension leg engage the end of the compression leg so that the ends of both legs are held together securely at free end 44. The crimp prevents shifting of the compression leg along the longitudinal axis of the tension leg. Fingers 56 are formed in the free end 58 of tension leg 48 so that, as also illustrated in FIG. 4, the fingers may project past the reduced width portion 48 of the compression leg as in FIG. 2.

Ground terminal 30 includes an upwardly extending leaf spring 60 with a contact point 62 formed in the free end thereof. A pair of tabs 64 extend from the median portion of leg 60 in a direction away from point 62 and as indicated in FIG. 4 clasp insulating button or spacer 66.

With both snap-over-center terminals 28 and ground or follower terminals 30 mounted in body 12, the spring bias of leg 60 holds the spacer 66 against the tension leg 42 of terminal 28. Movement of terminal 28 between the opened and closed positions is transmitted to terminal 30 through the spacer 66 so that the terminal follows terminal 28 and is moved between the opened and the closed positions.

An insulating slide 68 is confined in each passage 26. The end of each slide which extends into a recess 22 includes a pair of spaced apart finger supports 70 located to either side of the reduced width portion 46 of tension leg 28. The ends of compression leg fingers 56 are seated in recesses 72 formed in the tops of supports 70 so that legs 48 are maintained under compression and bowed toward the circuit board recess 20. The sides of passages 26 extend into cam path 24 forming ridges 74 located to either side of slide 68. The width of the slides above ridges 74 is increased at 71 so that adjacent slides nearly touch each other. This increased width prevents the slides from moving into recesses 22 when positioned as illustrated on the left side of block 10 in FIG. 2. An upwardly projecting follower 76 is formed on the top of each slide 68. As indicated in FIG. 3 the projection 76 extends along the full width of the slide.

The follower 76 is generally rectangular with bevels 78 at opposite corners thereof.

FIG. 10 illustrates a cam bar 80 useful for insertion along a single cam recess or path 24 to engage the fol5 lowers 76 extending into the path and thereby move the slides 68 between the positions illustrated in FIG. 2. The cam bar 80 is used on the side of the block 10 which is not contiguous to additional blocks where insertion of the bar moves one side of the slides only. The 10 cam bars and slides are all formed of insulating material to prevent cross circuits between adjacent terminals 28.

Cam bar 82, illustrated in FIGS. 8 and 9, is inserted into the cam recess or paths 24 of two adjacent blocks 15 10, as illustrated on the right of FIG. 2, to move the two sets of adjacent slides 68. A number of blocks 10 may be mounted in side by side relationship as indicated in FIG. 2 for mounting a number of daughter boards 52 upon a single mother board 36.

Cam bar 80 comprises a longitudinal body portion 84 having a bevelled lead end 86 and a handle 88 at the other end thereof. Groove 90 extends along the length of the bar and is provided with a rise section 92 adjacent lead end 86 so that the portion of the groove at 25 end 86 is laterally offset from the remainder of the groove. As indicated in FIG. 12, the cam bar 80 is inserted into recess 24 from one end of block 12 so that the projections 76 on the slides at the lower end of the recess are fitted in the end of the groove 90 at the lead ³⁰ end of the bar. Movement of the bar along the groove brings the rise section 92 of the groove 90 into successive engagement with one of the bevelled corners 78 on projections 76 in order to shift the slides outwardly of the recesses 20 from the position illustrated on the left ³³ in FIG. 2, to the position illustrated on the right in FIG.

2. Thus, as the bar is inserted the slides 68 are successively moved outwardly of the recesses. Because each slide is moved one at a time, the amount of force required to insert the bar is relatively low and relatively ⁴⁰ uniform.

Cam bar 82 is inserted in the double cam path defined by the pair of recesses or paths 24 between the abutting walls of the two adjacent blocks 10, as indicated in FIG. 1. Insertion of the bar sequentially moves ⁴⁵ both sets of slides 68 in the adjacent blocks 10 away from their respective recesses 22. In some cases it may be desirable to offset the rise sections 94 of the two cam recesses 96 on the bar longitudinally so that during insertion the slides in the two blocks are moved alterna⁵⁰ tively. In this way the cam bar does not shift opposing slides in the two blocks at the same time and the insertion force is reduced.

Terminal 28 is of the snap-over-center type having an engaged or contact position and a disengaged or open position. When in the disengaged position, illustrated by terminal 28 in the left hand recess 22 of FIG. 2, the tension axis of leg 42 is located to the left of the compression axis of leg 48. The two axes cross at crimp connections 54. The axial length of the tension leg 42 from the connection between the leg and the body 10 to the connection between the free end of the tension leg and the compression leg at crimp 54, is greater than the distance between such connection and the ends of fingers 56, as measured along the compression axis of leg 48, so that when the legs are positioned as on the left in FIG. 2, the compression leg 48 tends to lengthen and thereby rotate the tension leg in a counter3,744,005 minal at points other than the terminal free end. Thus, the shift force could be applied, by means of a cam or a slide actuated by a cam, to a point somewhere along the tension leg above the junction between the leg and 5 the body or even directly to the compression leg at a point above the junction between the leg and the body. As will be apparent from the description of the embodiment of FIGS. 11 and 12, the embodiment as illustrated does not require a slide interconnecting the cam and 10 each terminal.

Connector block 110 of FIGS. 11 and 12 includes an insulating body 112 having a number of recesses 114 formed therein to either side of a central longitudinally extending circuit board recess 116. A terminal 118 in15 eludes a tension leg 120, compression leg 122, tail 124 and locating tabs 126, all of which are similar to the corresponding elements of the previously described terminal 28 used in block 10. As in terminal 28, the free end of the compression leg 122 is provided with 20 spaced fingers 128. The ends of the fingers are seated in fixed pockets formed in spaced supports 130 which extend into the recess 114.

A crimp connection 132 secures the free end of the tension leg 120 to the end of the compression leg 122. 25 An extension 134 of terminal 118 past the crimp 132 is laterally offset at 136. The extension projects into cam path or recess 137 at the top of the block sidewall.

As illustrated in FIG. 12, a cam bar 138 having a recess 140 therein may be inserted along the top of each ³⁰ side of body 112 in path 137 with the recess 140 fitted around block ridge 142. Each cam bar 138 includes a cam recess 144 having an offset rise portion 146 located adjacent the lead end of the bar.

When the cam bars 138 are withdrawn from the ³⁵ block 110, as illustrated in FIG. 11, the compression axes of legs 122 are located nearer the circuit board recess 116 than the tension axis of legs 120 so that the compression legs bias the tension legs against the bottom of recesses 114. The block is provided with a pair ⁴⁰ of ground contact terminals 148 indentical to terminals 30 in FIG. 2. With the cams withdrawn the contacts 150 of terminals 118, and contacts 152 of terminals 148 are withdrawn from recess 116 thereby permitting ready insertion of circuit board 154 without engage⁴⁵ ment of the contact during insertion. After the circuit board has been seated in recess 116 the cam bars 138 are inserted along ridges 142 with the terminal projections 136 seated in recess 144. Movement of the cam bars serially moves the projections 136 toward recess ⁵⁰ 116 so that tension axes of terminal legs 120 passes the compression axes of the legs 122 and the contacts 150 are biased toward and into engagement with contacts 156 on the board 154. The movement of terminals 118 into engagement with circuitry 156 also moves the con⁵⁵ tacts 152 of terminals 148 into engagement with printed circuitry 158 on the board. This position is illustrated in FIG. 12.

While in both embodiments the compression legs and tension legs are formed from an integral strip of metal with the joining ends secured together by a crimp, obviously separate compression and tension legs could be used with their legs secured together. The disclosed construction has the advantage of avoiding contact resistance in the circuit path extending from the contact point to the connection at the terminal tail.

Daughter boards are frequently inserted into connector blocks when there is an applied voltage between the clockwise direction to bias the free end 44 of the terminal against the bottom of recess 22. In this position the contact 50 is withdrawn from the circuit board recess 20. The spring bias of terminal 30 maintains the insulating spacer 66 against the tension leg 42 at all times so that when the terminal 28 is positioned as in the left of FIG. 2, contact tip 62 is also located within recess 22. With cams 80 and 82 withdrawn the slides 68 in walls 16 and 18 are all extended into their respective recesses 22 and all terminal contact points 50 and 62 are withdrawn from the circuit board holes 20. The daughter board 52 may be freely inserted into the recess without wear on any of the terminal points 50 and 62. As mentioned, the board 52 may be inserted directly into cavity 20 or may be moved laterally into the cavity from block end 21.

After the circuit board 52 has been positioned within the block 10, the cam bars are inserted within the recesses 24 and the slides 28 are serially withdrawn from the recesses 22. As the slides are withdrawn, the compression axis of each compression leg 48 is pivoted back toward the tension axis of each tension leg. When the compression axis pivots past the tension axis, the compression leg 48 then rotates the tension leg away from the bottom of the recess 22 toward the circuit board 52 thereby moving the contact point 50 into engagement with circuitry 98 on the board. Movement of the tension legs toward the circuit board pivots the spring leaves 60 of terminals 30 toward the circuit board to bring contact points 62 thereof into electrical connection with printed circuitry 100 on the board. A resilient high pressure electrical connection is formed between each of the contact points 50 and 62 and their respective contacts 98 and 100. Spring pressure urging contact points 62 against pads 100 is provided in part by the resiliency of strip 60 and in part by the compression leg which biases the tension leg 42 toward the circuit board.

The tabs 54 at the free end of the terminal 28 secure together the ends of legs 42 and 48 so as to prevent any movement of the end of leg 48 relative to the end of leg 42. The rigid connection is required to prevent lengthening of leg 48 along the axis of leg 42. Other means, such as a rivet or weld, may be used in place of the tabs to secure the ends of the two legs together and prevent relative axial movement thereof.

In the connector block 10 the terminals are serially brought into engagement with the circuit board by the insertion of the cam bar. When the cam bar is withdrawn from the block the terminals are held in the disengaged position by the tension leg permitting ready insertion and withdrawal of the circuit board.

The embodiment of FIGS. 1 thru 11 uses a snap-overcenter terminal in which the snap action is achieved by moving the free end of the compression leg so that the compression axis is brought past the axis of the tension leg. In this way the terminals 28 are either biased toward the bottom wall of recess 22 or toward the circuit board. This snap-over-center action may be achieved in other ways whereby the compression axis is moved past the tension axis. Thus, as in the embodiment illustrated in FIGS. 11 and 12, the free end of the compression leg may be fixed and the cam bar may engage the free end of the terminal in order to move the same so that the axis of the larger compression leg is moved past the axis of the longer tension leg. In this embodiment the force required to shift the terminal may be applied to the ter3,744,005 terminals in the block. By removing the contacts of both terminals in each of the terminal pairs, it is possible to move the daughter board to the contact position without engagement between the terminal contacts and contact pads on the daughter board other than those with which connections are desired. It is not possible in conventional connector blocks to have two electrically hot terminals at a given location along a series of terminals because during insertion of the circuit board past the contacts of the pair the contact of one of the terminals engages a circuit contact on the daughter board intended for connection with the other terminal contact. Such connections, even if momentary, are highly undesirable since the application of an undesired voltage to a contact pad on the daughter board could ruin circuitry on either the mother or daughter board. In the connector blocks as disclosed, the contacts of each terminal pair are located at the same distance along the series of terminal pairs at each side of the circuit board cavity. By using this construction, together with zero force terminals, the undesirable cross circuits are prevented.

While I have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.