GB2113480A - Electrical test connector - Google Patents

Abstract

A pneumatically controlled electrical test connector 10 contains spring-loaded pins 34 whose ends are brought into electrical contact with the opposing ends of corresponding connector pins 4 of an electronic module 1 secured and orientated in a support frame 11 of the connector 10. The pins 34 of the pneumatically controlled connector 10 are recessed to centre the ends of the module connector pins 4. Pneumatic cylinders 25 secured to the support frame have piston rods 26 engaged with a slide 20 in which the spring-loaded pins 34 are longitudinally movably mounted, each pin 34 having a collar 36 and a spring 37 trapped between headers 31' and 31'' secured to opposite sides of the slide 20. When actuated, the cylinders 25 draw in the rods 26 and thus produce sufficient force between the opposing pins of the test and module connectors to thereby establish good electrical contact at the contacting pin ends. The spring 37 on each pin 34 accommodates the mechanical tolerances of the pin lengths and causes the force on each pin to be substantially equal. Commercially available connectors 39 are slipped onto the other ends 35' of the test connector pins 34 for wiring of the test connector 10 to a test set. <IMAGE>

Description

SPECIFICATION Electrical connector This invention relates to electrical connectors, and particularly but not exclusively to an electrical connector for use in production testing of electrical circuits having a fixed set of electrical contacts by an automated testing device.

A commonly used connector which is attached to printed circuit boards is of a type which has blades which extend for insertion into some form of pressure contact in a mating connector. An example is the female connector provided with a commercially available test set where the connector consists of individual "tuning fork" contacts which mate with the spade type terminals of the connector attached to the printed circuit board. This type of female connector has an advertised lifetime of 500 cycles which lifetime is governed primarily by the wiping contact wear on the tuning fork.

The limited life of this standard female connector requires that the connector be changed every few days. This requirement results in considerable labor costs and test set unavailabilty. Additionally, and perhaps more important, before the standard connector actually fails, random intermittent probelms arise which are difficult to isolate and result in increased trouble shooting labour costs.

Another undesirable feature of existing test set connectors is that the module to be tested is inserted manualiy. The difficulties of manual insertion limit the test set capability to less than 1000 units per eight hour shift because the high insertion and removal forces result in operator fatigue and possibly even hand injury. Hand insertion also results in the operators tending to "wiggle" the module when inserting and removing the module from its test connector which results in pin damage.

Attempts to replace the standard tuning fork type of connector contacts have been made using commercially available "Pogo Pins". The pogo pins have spring loaded plungers which contact the ends of the module terminals upon insertion. The primary advantage of this concept is that insertion and removal force is substantially less than for the tuning fork connector and results in decreased operator fatigue and module connector damage. The disadvantage with the pogo pin type of connector is that the low axial plunger force (less than 2 ounces) results in high and nonrepeatable contact resistance.

Further, the plunger spring and barrel design of the pogo pin results in a higher resistance path. The density of the pin components on the connector is such that small pin components are required, and these are easily bent and damaged.

Another approach for a test set connector works on the principle of inserting the module terminals into a receptacle followed by clamping the terminal pins by turning a dial or moving a lever. Although this technique minimizes connector wear and has low insertion/removal forces, it is difficult, if not impossible, to attain a low contact resistance. The absence of contact wiping coupled with low clamping force because of size constraints makes this approach unattractive.

it is therefore an object of the invention to eliminate the deficiencies of the prior art connectors by providing a connector which has low contact resistance, which produces minimum operator fatigue, and which has an extended lifetime requiring little "downtime" for maintenance.

In a preferred electrical connector mechanism in accordance with this invention, pneumatic cylinders have their pistons connected to a slide carrying electrical connecting pins. The pins have ends which are cupped to engage the ends of the pins of a standard electrical connector connected to the printed circuit board of a standard electronic module to be tested. The standard electric connector is accurately positioned in a frame with respect to the slide so that the pins of the slide are aligned with the pins of the connector. The pins of the slide are individually mounted within springs which are compressed when pin-to-pin end contact is made by moving the slide by the pistons of the pneumatic cylinders. The slide is mounted on precision screws to provide the required alignment accuracy.The desired pressure on the pin ends is determined by the regulated air pressure applied to the cylinders.

The springs acting on each pin individually equalize the pressure on each pin by removing the effects of difference in pin length caused by manufacturing tolerances.

The invention will now be described in more detail, solely by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is an exploded view of a pneumatic connector embodying the invention; Fig. 2 is a top view in partial cross-section of the asembled pneumatic connector; Fig. 3 is a sectional view of Fig 2 shown along section line 3; and Fig 4 is an expanded view of a portion of Fig 3 modified to show the connector pins of the pneumatic connector in spring compression contact with the pins of an electric circuit module.

A test connector 10 which is a preferred embodiment of this invention is shown in an exploded view in Fig 1 and in assembled views of Figs 2-4. The test connector 10 comprises a module support member 11 adapted to support a standard electronic module 1 such as that described in the copending patent application No 8134821. The standard electronic module 1 has a body portion 2 in which a printed circuit board is secured. A standard connector having pins 4 is attached to the circuit board. The module has a pair of guides 5 on each side 6 and an extractor portion 7 which extends beyond the body 2 of the module, all as described in detail in patent application No 8134821.

The support member 11 has a bed 13 upon which the body 2 of the module may rest. The bed 13 is adapted to receive the module 1 in only one orientation, and has at one end, a vertical projection 12 bounding a slot 121 adapted to receive the downwardly projecting portion 8 of the extractor portion 7 of the module 1. The bed 13 has transverse projections 14 at its other end which serve as mechanical stops for the guide 5 of the module 1.

Another portion of the test connector 10 is the slide portion 20 which has a pair of guides holes 21 intro which sslf-lubricating bushings 22 have been fixed. The slide 20 is slidably connected to the support 11 by precision shoulder screws 23 which pass through the bushings 22 and are screwed into the support 11 at screw holes 231. The slide 20 is thus capable of sliding between the support 11 and the shoulders 24 of the screws 23. The slide is also attached at screw holes 28 to the threaded piston shafts 26 of a pair of air cylinders 25 which are attached to the support 11. The cylinders 25 are so secured to the threaded hole 252 of the support 11 that the piston shafts 26 of the cylinders 25 are parallel to the longitudinal axes of the precision screws 23.

The slide 20 has a slot 30 which extends transversely between the screw 23 and longitudinally through the slide to form an elongate hole in the direction of movement of the slide along the screws 23. Electrically insulating header 31' and 31", typical- ly one-sixteenth inch glass fiber sheeting, are mounted by mounting screws 32 on both sides of the slide 20 to cover the ssst 3Q. The heads 31' and 31" have pin aligning holes 33 which, when headers 31 are mounted on the slide 20, are in alignment with the connector pins 4 of the electronic module 1. The headers 31' and 31" also have clearance holes 331 which allow keyed pins 332 of the module to pass through the headers 31' and 31".Mounted in the holes 33 and extending beyond the headers 31' and 31" are contact pins 34. The pin 34 is preferably made of berrylium copper which has the desirable properties of hardness and good electrical conductivity. Each pin has a body 35 which is of substantially the same diameter as each hole 33 but is capable of sliding within the hole 33. A shoulder 36 larger in diameter than the body 35 prevents the pin 34 from completely sliding through the holes 33. A spring 37 slides over the body portion 35 and is stopped by the shoulder 36. The contact pin 34 when assembled between headers 31' and 31" has, inside the slot 30, its shoulder 36 pressed against the header 31' by one end of the spring 37, the other end of the spring 37 being pressured against the header 31".Electrical contact to the pin 34 is made by reducing the diameter of the pin body 35 at its end 35' beyond the header 31" to a diameter which allows a commercially available connector 39 to be used. The connectors 39 have electrical leads 38 through which electrical connection of the pins 4 of the module 1 is made to a test set (not shown).

A pneumatic control circuit is provided for the cylinders 25 and includes a normally closed air switch 17 having a actuating button 18 and connected to a pulse valve 53 which is connected to a 3-way air valve 50. The air valve 50 connects an air supply 51 through a regulator 511 to the cylinders 25 through a tube 52 in response to activation of the switch 17. Activation of another air valve 40 causes the air valve 50 to exhaust the air contained in the cylinders 25 through the tube 52 and an exhaust tube 54. Each cylinder 25 contains a piston 252 and a spring 250.

Fig. 2 shows a top plan view of the assembled connector 10 of Fig 1 in which a portion of the module 1, depicted by dashed lines, is shown resting on the bed 13. The guides 5 of the module 1 are in contact with the stops 14 of the support 11 The extension 7 is seen to extend over the rib 12. The module 1 fits snugly between the slides 141 of the support 11 when resting on the bed 13, its pins 4 being in vertical and lateral alignment with corres ponging pins 34 of the slide 20. The back edge 9 of the module 1 is seen to be closely spaced from the rib 12.Fig 2 shows the slide 20 in its most remote position relative to support 11 which occurs when the cylinders 25 are nct activated by air from the supply 51, the springs 250 pushing the respective pistons 252 to cause the shafts 26 to hold the slide 20 out against the head 24 of the screws 23.

Fig 3 shows a cross-sectional view of Fig 2 along the section line 3 and illustrates more clearly the placement of the module 1 on the bed 13. The back edge 9 of the module is shown adjacent the ridge 12.

Fig 13 also shows the downwardly projecting portion 8 of the module 1 extending into the slot 121 with the module extension 7 extending over the top of the ridge 12.

Fig. 4 is an expanded view of a portion of a sectional view similar to Fig 3 and shows in more detail the contacting of the connector pins 4 of the module 1 with the ends 351 of the pins 34 of the slide 20. The connection is made by pressure contact of the ends of the pins 4 and 34, the pressure being provided by the partially compressed springs 37.

The springs 37 are compressed by the movement of the slide 20 toward the support 11 by the retraction of the piston rods 26 caused by the application of air pressure to the cylinders 25 from the supply 50 through the valve 50 by the actuation of the air switch 17 attached to the support member 11. The actuating button 18 of the air switch 17 projects above the surface of the bed 13 to make contact with a module 1 when the module is properly inserted on the bed 13 of the support 11.

In the operation of the test set connector 10, the module 1 to be tested is placed on the bed 13 of the support 11 and rests upon the actuating button 18 of the air switch 17. The module 1 is oriented so that its pins 4 are in the direction of the slide 20. The transverse projections 14 prevent the module 1 from being improperty inserted on the bed 13 in a position too close to the slide 20. The asymmetrical mechanical configuration of the extended portion 7 of the module 1 is such that the module 1 will seat on bed 13 only when the downwardly directed portion 8 can drop into the slot 121. This arrangement allows the module 1 to be correctly oriented before it may be tested.

After inserting the module 1 in the correct position in the support 11, the operator applies finger pressure in a downward direction on the module 1 which causes the module 1 to depress the actuating button 18 of the switch 17. Closing the switch 17 provides air pressure from the supply 51 to the pulse valve 53 which provides a single pulse of air to the 3-way valve 50 which then allows air to flow from the regular 511 of supply 51 through the pipe 52 to the cylinders 25. The air pressure from the supply 51 causes the piston 252 and the shaft 26 of the cylinder 25 to retract into the cylinder pulling the slide 20 toward the support 11.Movement of the slide 20 also causes the ends 351 of the pins 34 to make contact with the ends of the pins 4 of the module 1 as shown in Fig. 4. The module 1 is prevented from moving by the ridge 12 which engages the back edge 9 of the module 1. Movement of the slide 20 subsequent to the time that the pins 34 meet the pins 4 causes compression of the spring 37. The pressure provided by the air supply 51 through the regulator 511 to the air cylinders 25 and the elastic constant of the springs 37 are chosen so that the desired amount of mechanical pressure on each pin 4 is obtained when spring 37 is approximately compressed to half the distance between the headers 31' and 31".

Typically, the spring 37 will compress one eighth inch with one pound of force; therefore, each cylinder 25 exerts about twenty pounds of force. The compression springs 37 provide accommodation for differences in length of the terminal pins 4 or the contact pins 34.

The end 351 of each contact pin 34 which makes electrical connection to the end of a terminal pin 4 of the module is concave to provide a self-aligning capability for the contact pin 34. The opposite end 35' of contact pins 34 is reduced in diameter to fit into a commercially available connector 39. Electrical conductors 38 of the electrical connector 39 provide direct electrical connection between the test set (not shown) and the module 1 under test.

After actuation of the air cylinders 25 causes electrical connection to be made between the test set and the module 1, the operator causes the test set to commence testing. Upon completion of testing, as indicated by a signal from the test set, the operator actuates the air valve 40 which actuates the air valve 50 to close off the air supply to the line 52 from the regulator 511 and to allow the air within the cylinder 25 to escape through the line 54 to the atmosphere. With the release of air pressure, the springs 250 contained within the cylinders 25 cause the slide 20 to be pushed away from the module 1 under test and to remove contact between the contact pins 34 and the module pins 4. With the release of the contact pin pressure, the module 1 may be removed from the support member 11 and an indication placed thereon as to whether the module has passed or failed the test.

It will be apparent to those skilled in the art that the signal provided by the test set as to whether the module has passed or not passed can be used to actuate air cylinders (not shown) which provide an appropriate marking stamp on the test module prior to its being released by the switch 43. It will also be apparent that the test set could provide a signal after completion of testing which would actuate the air valve 50 to remove the pressure from the air cylinders 25.

It will be further apparent that the invention may be used with any connector connected to wires onto a printed circuit board without being part of a module. The support member and the bed upon which the connector rests need only be compatible with the particular connector and the structure to which the connector is attached. The connector needs only to have pins which are strong to withstand moderate end pressure, e.g. one pound, without bending; the pressure being adequate to provide good electrical contact with the test connector of the invention.

The invention is described in general terms in the following claims.

Claims (11)

1. An electrical connector for making electrical contact with another electrical connector and comprising a mounting frame for securing the said other connector in a fixed position; a slide connected to the mounting frame; a plurality of electrically conducting pins movably mounted in the slide, the pins being in electrical isolation from each other and each pin being resiliently mounted in the longitudin- al direction thereof; means for securing the other connector so that the pins of the other connector are aligned with the movably mounted pins; and means for securing the slide so that the ends of the movably mounted pins make contact with the ends of the pins of the other connector.

2. An electrical connector according to claim 1, wherein the frame contains a recess adapted to hold the said other connector in a fixed position relative to the frame so that the electrical connector pins of the other connector are in longitudinal alignment with the movably mounted pins.

3. An electrical connector according to claim 1 or 2, wherein the ends of each of the movably mounted pins are recessed along the control axis of each in relative to the peripheral portion of the end of the pin.

4. An electrical connector according to any preceding claim, wherein the means for moving the slide comprises pneumatic cylinder means connected to the slide; a regulated air supply; and means for applying air from the said supply to the cylinder means so as to cause the movably mounted pins to have their ends come into contact with the ends of the pins of the other connector and to cause the movably mounted pins to move longitudinally against their respective resilient means.

5. A connector mechanism comprising: a frame having a recess adapted to secure a module having connector pins; means for holding a plurality of test pins, each in lateral alignment with a corresponding one of the said connector pins, each of the test pins being resiliently mounted for movement in the longitudinal direction thereof and each of the test pins and the said connector pins having their ends of opposite concavity; means for causing the holding means and the frame to move toward each other to cause the secured module connector pin ends to make contact with the ends of the test pins, the moving means providing sufficient force to cause resilient longitudinal movement of the test pins; and a plurality of electrical conductors, the test pins having their other ends adapted to make electrical connections with the plurality of electrical conductors.

6. A connector mechanism according to claim 5, wherein the recess is adapted to prevent actuation of the said means for causing the holding means and the frame to move toward each other except for one orientation of the module.

7. A connector mechanism according to claim 5, wherein a plurality of wire connectors are connected to the said plurality of electrical conductors, and the said other ends of the test pins are adapted to make sliding electrical connection with each wire connector attached to a different one of the electrical conductors.

8. A connector mechanism according to claim 5, 6 or 7, wherein means for resiliently mounted the test pins comprises a slide; a pair of electrically insulating headers, each having a plurality of holes and being mounted to the slide, the holes of each header being arranged to be aligned with the connector pins, the test pins being mounted between the headers and protruding through the said holes, and each of the test pins having a collar greater in diameter than the said holes through which the test pin protrudes; and a spring on each of the test pins between the said collar and one of the headers, the pin end adapted to make electrical connection being the end nearer the said collar than the spring.

9. A connector mechanism according to claim 6, wherein the means for causing the pin holding means and the frame to m'e toward each other comprises at least one force producing means connected between the pin holding means and the frame; and means responsive to the said one orientation of the module in the frame to actuate the said force producing means.

10. A connector mechanism according to claim 9, wherein the said force producing means comprises a pneumatic cylinder; a source of pressure regulated air; air valve means responsive to the said one orientation of the module to allow flow of air from the source to the cylinder; and means for releasing the air from the cylinder to remove the said force from the test pins and to allow the module to be removed from the frame.

11. An electrical connector substantially as described hereinbefore with reference to the accompanying drawings.