Low insertion force connector with wipe

A low insertion force connector contact assembly (122) has two contacts (136, 144) which are separated by insulation (143) from one another to provide separate circuit paths for separately engaging a mating contact (166) of a mating connector (22) in a Kelvin test configuration. The contact (144) engages the mating contact (166) of the mating connector (22) for applying current and voltage to the mating contact (166). The contact (136) engages the mating contact (166) for measuring the voltages of the mating contact (166). Preferably, the contact (144) is a spring biased plunger which is urged from a retracted position to an extended position. In the extended position, the contact (144) pushes the contact (136) aside of a position for engaging the mating contact (166). When the mating connector (22) is being engaged with the connector assembly (122), the mating contact (166) pushes the spring biased, plunger contact (144) from the extended position to the retracted position, releasing the contact (136) to engage with mating contact (166) with a wipe during a makeup stroke in which the mating contact (166) is engaged within the contact assembly (122). This type of contact assembly connection may be used with mating contacts (166) of various cross sections, such edge connector lands, and square, rectangular and round leads. In a production testing environment, the mating contacts (166) may be cleaned by spraying with a solvent or a discharge of air when being inserted into a connector contact assembly (202).

TECHNICAL FIELD OF THE INVENTION
 The present invention is related in general to low insertion force
 electrical connectors, and, in particular, to a low insertion force
 electrical connector having a wipe feature when the connectors are mated.
 BACKGROUND OF THE INVENTION
 Prior art connectors have been provided for electrically connecting two
 electric circuits, such as those found on circuit boards. One example is a
 pin-type connector and another example is an edge connector of printed
 circuit boards. Typically, an interference fit between the contacts of
 mating connectors provides a scraping action which wipes clean the
 surfaces of the mating contacts. However, when a large number of contacts
 are mated between two connectors with wiping engagement, the forces
 required to mate the two connectors often becomes quite large. Another
 problem with connectors having a wipe feature is that a full-stroke
 contact wipe causes excessive wear to the mating surfaces of the contacts.
 Some connector contacts are typically rated for a limited number of wipes,
 such as some gold contacts which are rated for only a few cycles. Other
 prior art connectors have been provided with a low insertion force feature
 in which a cam member is spring biased to separate two spaced-apart
 contacts with a clearance for passing the contact of a mating connector.
 Insertion of the mating connector into the low insertion force connector
 pushes the cam member against the bias spring, allowing the spaced-apart
 contacts to move toward one another and to engage the contacts of the
 connector being mated. These prior art low insertion force connectors have
 only one contact per mating connector contact, and not two separately
 insulated contacts.
 Another problem with prior art connectors occurs in those used for testing
 circuits using a high voltage potential, often called "High-Pot Testing."
 The high potential voltages applied in such tests often result in a large
 driving current being applied across the mating surfaces of the contacts.
 In some circumstances, a Kelvin test configuration may be used in which
 pairs of contacts are used for each connection to a unit under test,
 wherein one contact is used for driving the test current, or as the high
 voltage contact, and a second contact is used to take test measurements.
 When Kelvin test configurations are used, the electrical connections
 between mating leads are typically maximized by using wiping engagements
 and high contact pressures when the test contact connections are mated in
 order to reduce the voltage potential drop across the interface of the
 test contacts. However, with increasing miniaturization of circuitry,
 Kelvin test configurations have become increasingly difficult to implement
 due to significant decreases in contact spacings. With decreased contact
 spacings and further reductions in sizes of the contacts to fit within
 such spacings, the wear ratings of such contacts are rated for even fewer
 cycles of mating and breaking connections, especially if a full length
 wipe is used for the contacts during connector mating.
 SUMMARY OF THE INVENTION
 A low insertion force connector has contact assemblies which provide a
 limited wipe during the insertion stroke of a mating contact, and two
 separate circuit paths with each of the contacts of the mating unit in a
 Kelvin test arrangement. The contact assemblies include a plunger which is
 moveably mounted within a housing and has an exterior periphery which
 defines a cam surface and a contact surface. The plunger is moveably
 disposed within the housing for engaging the mating unit and moving from
 an extended position to a retracted position. The contact assemblies
 further include a bias member which biases the plunger into the extended
 position, and a contact member having a biasing portion, a contact portion
 and a mating periphery which is mounted to the housing and moved by the
 plunger to a position which is spaced apart from a contact position
 located adjacent to an aperture in the housing. An insulator extends
 between the biasing portion of the contact member and the plunger for
 electrically isolating the contact member from the plunger when the
 plunger is disposed in the retracted position. Insertion of the mating
 unit into the aperture engages the mating unit with the plunger, moving
 the plunger from the extended position to the retracted position with the
 plunger electrically coupled to the contact of the mating unit in a first
 electrical connection providing a first circuit path, and the contact
 portion of the contact member also engaging the contact of the mating unit
 in a second electrical connection providing a second circuit path. In a
 production testing environment, the mating contacts may be cleaned by
 spraying with a solvent or a discharge of air when being inserted into a
 connector contact assembly.

DETAILED DESCRIPTION OF THE INVENTION
 FIG. 1 is a perspective view of a test station 12 made according to the
 present invention. The test station 12 includes a test unit 14 and an
 adaptor unit 16 which are connected by a cabling connection 18. In some
 embodiments, the adaptor unit 16 may be rigidly mounted to the test unit
 14. A unit under test ("UUT") 20 includes a connector 22. The UUT 20 is
 mounted within an enclosure 24 of the adaptor unit 16. The enclosure 24
 includes a housing 26 (shown in phantom) having a drawer 28 and a cover
 30. The cover 30 encloses a front opening 32 of the enclosure 24. Two
 mounting rails 34 are mounted on opposite sides of the housing 26 and
 extend in parallel in a horizontal plane. Two slide assemblies are rigidly
 mounted to opposite sides of the drawer 28 and slidably engage the
 mounting rails 34 to slidably mount the drawer 28 to the housing 26 such
 that the drawer may slide outward of the housing 26 in a horizontal plane.
 Two vertically disposed tracks 36 are mounted to the housing for slidably
 mounting the cover 30 to the housing 26. The cover 30 slides upward from
 the housing 26, preferably in a vertical plane.
 A cover operating assembly 38 and a drawer operating assembly 40 are
 interlinked such that the drawer 40 and the cover 38 are operated
 simultaneously. The cover operating assembly 38 includes two linkages 42
 which are mounted on the opposite sides of the cover 30 and which extend
 in parallel. Each of the linkages 42 have ends which are pivotally mounted
 to an upper portion of the cover 30 at pivot points 44, and opposite ends
 which are pivotally mounted to the opposite sides of an inward portion of
 the drawer 28 at pivot points 46. Movement of the drawer 28 outward from
 within the housing 26 of the enclosure 24 operates the linkages 42 such
 that the cover 30 will move upward within the tracks 36 to allow access
 through the opening 32 and into to the interior of the housing 26.
 Similarly, movement of the drawer 28 into the housing 26 will move the
 linkages 42 such that the cover 30 is moved downward within the tracks 36
 to enclose the opening 32.
 The drawer operating assembly 40 includes two halves, which extend on
 opposite sides of the drawer 28. Each of the two halves includes a handle
 50 which is rigidly mounted in an L-type configuration to a respective
 linkage 52. The two handles 50 and linkages 52 are pivotally mounted to
 the forward end of opposite respective sides of the drawer 28 at pivot
 points 54. The two linkages 52 are mounted on opposite ends from
 respective ones of the two pivot points 54 and the handles 50 to linkages
 56 at pivot points 58. The pivot points 58 are free floating, in that they
 are not disposed in a fixed relation to the housing 26, but rather are
 free to move relative to the housing 26 about respective arcs which
 preferably each have a continuous radius relative to pivot points 60 at
 which the two linkages 56 are pivotally mounted to the housing 26,
 respectively. Further included on the drawer 28 is a fixture 62 for
 securing the UUT 20 to an upper surface of the drawer 28. The drawer 28
 further includes a front portion 64 which extends upward to provide a
 forward lip which engages a lower portion of the cover 30.
 Disposed interiorly within the housing 26 is a connection assembly 70. The
 connection assembly 70 includes a low insertion force connector 72. The
 low insertion force connector 72 is mounted to a printed circuit board 74,
 which extends in vertical relation to the housing 26. The printed circuit
 board 74 has a lower end which defines an edge connector 76. The edge
 connector 76 fits within a low insertion force edge connector 78, which is
 preferably made according to the present invention. The connector 78 is
 mounted to a printed circuit board 80. A rearwardly disposed connector 82
 is also mounted to the board 80. The connector 82 is provided for mating
 to the cabling 18 connecting between the adaptor unit 16 and the test unit
 14. The connection assembly 70 is provided such that the connector 72 and
 the printed circuit board 74 may be replaced with a different connector
 and printed circuit board for mating with other units under test with
 connectors of different geometrical configurations from that of the
 connector 22. Thus, the adaptor unit 16 may be utilized to test a wide
 variety of units under test having different connector configurations.
 The adaptor unit 16 of the present invention further includes a safety
 switch 84 which grounds power leads of the adapter 28 when the drawer 28
 and the cover 30 are in outward positions, such that the opening 32 into
 the enclosure 24 is open to expose the power contacts of the test station
 12. The safety switch 84 preferably includes a reed switch 86 and a
 magnetic actuator 88. The actuator 88 is preferably a permanent magnet
 mounted to the handle 50.
 FIG. 2 is a perspective view of the test station 12 after the adaptor unit
 16 has been operated to move the drawer 28 into the housing 26 of the
 enclosure 24, and the cover 30 has been moved downward to cover the
 opening 32. The drawer 28 and the UUT 20 have been moved inward such that
 the connector 22 has engaged the connector 72. Additionally, a magnetic
 actuator 88 has been moved adjacent to a reed switch 86 such that the
 safety switch 84 is no longer disposed in a grounding position, in which
 power connections of the connection assembly 70 and the adapter unit 16
 are grounded. The safety switch 84 provides an important safety lock-out
 device to prevent electric shock hazards when the test station 12 is
 utilized for High-Pot Testing of various UUTs. The drawer operating
 assembly 40 has been moved to the inward position, closing the drawer 28,
 which causes the cover operating assembly 38 to move the cover 30 downward
 to enclose the UUT 20 within the enclosure 24.
 FIG. 3 is a sectional view of the connection assembly 70, taken along
 section line 3--3 of FIG. 1. The connector assembly 70 includes the
 connector 72 and the printed circuit board 74, with the edge connector 76
 of the printed circuit board 74 fitting within the connector 78 in a
 vertical mounting alignment. The connector 72 then extends forward of the
 board 74 in a horizontal mounting alignment for engaging the UUT 20 (shown
 in FIG. 2). The rearward end of the printed circuit board 80 has a
 connector 82. The connector 72 has a housing 92 having a forward opening
 aperture 94. Spaced apart on vertically opposite sides of the aperture 94
 are two contacts 96. A second housing 104 is mounted to an opposite side
 of the board 74 from the housing 92. A bias member 100, preferably
 provided by a coil spring, is disposed within the housing 104 for urging a
 plunger 98 from within the housing 104 and into a forward position in the
 housing 92. A moveable cam member 102 is mounted to the forward end of the
 plunger 98 and preferably has a U-shaped cross-section. The bias member
 100 urges the plunger 98 forward, pushing the moveable cam member 100
 between the two contacts 96. Insertion of a mating portion of the
 connector 22 of the UUT 20, as shown in FIG. 2, into the connector 72
 pushes the cam member 102 and the plunger 98 rearward against the bias
 member 100, removing the cam member 102 from between the contacts 96 which
 allows the contacts 96 to engage the contacts of the connector 22,
 preferably with a wiping engagement for the last thirty thousandths of an
 inch (0.030 in.).
 The connection assembly 70 further includes the connector 78, which
 preferably is identical to the connector 72. The connector 78 is
 configured for mating with the edge connector 76 of the printed circuit
 board 74, with the circuit board 74 being disposed perpendicular to the
 board 80. The connector 78 has two contacts 114 which are spaced apart on
 opposite sides of an opening 116 in the upper end of a housing 106 of the
 connector 78. A second housing 118 is mounted to an opposite side of the
 board 80 from the housing 106. A bias member 110, preferably a coil
 spring, is disposed within the housing 106 for urging a plunger 108 from
 within the housing 118 and into a forward position in the housing 106. A
 moveable cam member 112 is mounted to the forward end of the plunger 108
 and preferably has a U-shaped cross-section. The bias member 110 urges the
 plunger 108 forward, pushing the moveable cam member 112 between the two
 contacts 114 and spacing the two contacts 114 apart to prevent wiping of
 the edge connector 76 of the board 74 during an initial portion of a
 stroke for inserting the connector 76 into the connector 78. Engagement of
 the edge connector 76 of the board 74 pushes the moveable cam member 112
 and the plunger 108 rearward, allowing the two contacts to engage the
 contacts of the edge connector 76, preferably with a wiping engagement for
 the last thirty thousandths of an inch (0.030 in.) of the insertion
 stroke.
 FIG. 4 is a sectional view of the connector 72 of the connection assembly
 70, taken along section line 4--4 of FIG. 3. The connector 72 includes a
 nonconductive plate, preferably provided by the printed circuit board 74.
 The circuit board 74 has guide holes 75. The guide holes 75 in the board
 74 provide bearing surfaces through which the plungers 98 slidably extend,
 and by which the plungers 98 are guided in to extend in parallel
 directions for engaging the moveable cam member 102. The housing 92 is
 formed such that retaining shoulders are provided to retain the moveable
 contact member within the housing 92, such that the moveable contact
 member will not pass through the aperture 94. The housing 104 is
 preferably formed of a nonconductive material, and includes a plurality of
 bores 105, preferably provided by blind holes. Bias members, preferably
 coil springs 100, are disposed in the bores 105. The plungers 98 have
 enlarged heads 103 which are entrapped within the bores 105 by the size of
 the guide holes 75 in the circuit board 74 being smaller than that of the
 heads 103. The bias springs 100 urge the plungers 98 into extended
 positions pushing the moveable cam member 102 into an extended position,
 which increases the spacing between opposing pairs of the leads 96.
 The moveable cam member 102 is preferably continuous and extends the full
 length of the connector 72, but in other embodiments may be provided in
 sections. Preferably, the moveable cam member 102 is of a length such that
 a selectable number of the bias springs 100 may be removed in order to
 reduce the force required to push the moveable cam member rearward during
 makeup of the connector 22 of the UUT 20 with the connector 72, thereby
 selecting the insertion force required for makeup. In some embodiments,
 the bores 105 may extend through the housing 104 and then the ends thereof
 may be threaded for receipt of a threaded plug member to allow for
 removable of the bias springs 100 without requiring disassembly of the
 connector 72. In the alternative, removable blanking member, such as a
 small rod or flat plate, may be provided which fits flush with a surface
 of the housing 104 such that the connector 72 will have a more compact
 profile than if threaded blanking plugs are used to retain the springs 100
 within the bores 105. Preferably, the bores 105 are blind holes and the
 housing 104 is removed from the circuit board 74 for installation and
 removal of the selectable number of springs 100 from within the bores 105
 to determine the insertion force required for makeup of a mating connector
 with the connector 72.
 FIG. 5 is a longitudinal sectional view of a collet-type contact assembly
 122, such as may be used as a first alternative embodiment for the contact
 assemblies of the connector 72, as would be viewed from the rear of a
 sectioning plane taken along section line 3--3 of FIG. 1 when used in
 place of the contact assemblies of the connector 72. The embodiment shown
 for the contact assembly 122 may be sized for accommodating 0.025 inch
 square or round mating contact leads on 0.100 inch centers. The contact
 assembly 122 includes an enclosure 124 having an aperture 126. The
 aperture 126 includes a tapered guide portion 128 for guiding mating
 contacts through the aperture 126 and into the interior of the enclosure
 124 in alignment for mating with the contact assembly 122. The tapered
 guide portion 128 is preferably coaxial with and concentric with the
 aperture 126. The enclosure 124 is mounted to a printed circuit board 130.
 The contact assembly 122 further includes a collet-type contact 132. The
 collet contact 132 has a continuous, solid rear body portion 134 and a
 forward body portion having slots 164 which define collet fingers 136. The
 slots 164 and the collet fingers 136 extend parallel to a longitudinal
 axis 168 of the collet contact 132. The inward facing portions of the
 collet fingers 136 define two pairs of oppositely disposed, inwardly
 facing collet contact faces 138. The rearward end of the solid,
 continuous, rear body portion 134 of the collet contact 132 defines a
 contact connection 140.
 The contact assembly 122 further includes a spring biased pin assembly 142.
 An insulator 143 separates the pin assembly 142 from the rear body portion
 134 of the collet contact 132. The spring biased pin assembly 142 includes
 a plunger 144 which is slidably mounted within a sleeve 146. A bias spring
 148 urges the plunger 144 into an extended position from within the sleeve
 146. The plunger, the sleeve 146 and the spring 148 are preferably formed
 of metal. The forward end of the plunger 144 defines a contact face 150.
 The contact assembly 122 further includes a socket contact 152, having a
 contact face 154 for engaging the rearward end of the pin assembly 142. A
 contact connection 156 is defined on the rearward end of the socket
 contact 152. The forward end of the plunger 144 has a periphery which
 defines a cam surface 158 for engaging a mating surface 160 defined on an
 interior portion of the periphery of the collet fingers 136. The forward
 end of the collet fingers 136 provide guide surfaces 162 which provide a
 tapered entrance hole.
 FIG. 6 is a partial section view of the collet-type contact assembly 122 of
 FIG. 5, after a mating contact 166 has been inserted and engaged with the
 contact assembly 122. The plunger 144 has been pushed inward within the
 sleeve 146 to a retracted position and the face 150 of the plunger 144
 engages the forward end of the mating contact 166. Movement of the plunger
 144 rearward and into the sleeve 146 will allow the collet fingers 136 to
 move inward toward the longitudinal access 168 of the collet contact 132,
 such that the collet contact 140 will engage the exterior surface of the
 mating contact 166. Preferably, the shape of the cam surface 158 and the
 mating surface 160 is formed such that the contact surface 140 of the
 collet fingers 136 will engage the exterior of the mating contact 166 in a
 scraping engagement to wipe the surfaces of the contacts 136 and 166 clean
 for an insertion travel of approximately thirty thousandths of an inch
 (0.030 inches) as the mating contact 166 is inserted within the collet
 contact 132. The insulator 143 separates the collet 132 from the sleeve
 146 of the pin assembly 142 to provide two separate circuit paths to the
 mating contact 166.
 FIG. 7 is an elevation view of the forward end of the collet contact 132.
 Slots 164 are shown extending into the forward end of the collet contact
 132, defining the collet fingers 136. The contact surfaces 128 are
 arcuately shaped.
 FIG. 8 is an elevation view of the forward end of the collet contacts 132,
 showing flat contact surfaces 138 for the collet fingers 136.
 FIG. 9 is an elevation view of the forward end of the collet contact 132.
 Notches 172 are formed into the contact faces 138. The notches 172 have
 square profiles. The contact face 138 of the collet fingers 136 are shown
 having notches 172 formed therein. The notches 172 are preferably formed
 with sides at substantially right angles, and the notches 172 are aligned
 such that they together define a square profile for mating with a mating
 contact 166 having a square-shaped cross section.
 FIG. 10 is an elevation view of the forward end of the contact 132, showing
 an alternate embodiment in which an alternative contact member 174 is used
 having a square-shaped cross section, rather than a cylindrical shaped
 cross-section. The contact member 174 may be formed of a tubing having a
 square-shaped cross section. The forward end of the contact member 174 has
 four slots 176 cut therein to define contact fingers 178. The contact
 fingers 178 preferably have inwardly facing contact faces 180 which are
 preferably aligned for receiving a mating contact 166 having a
 square-shaped cross section. The plunger 144 may have a cylindrical-shaped
 cross section. In other embodiments, a piston of square-shaped cross
 section may be used.
 FIG. 11 is a perspective view of a contact assembly 202 of a second
 alternative low insertion force connector, preferably for engaging 0.025
 inch square leads on 0.300 inch centers, and having leaf-spring type
 contact members 214 and 216. The contact assembly 202 includes a boss 204,
 preferably having a rectangular-shaped cross-section, or a square-shaped
 cross section. A guide member 206 is rigidly mounted to the boss 204 and
 extends forward of the boss 204. A movable cam member 208 is slidably
 engageable upon the guide member 206. The movable cam member 208 includes
 cam surfaces 210 and 212, which are angularly spaced apart equal angular
 distances around a longitudinal axis 238 of the contact assembly 202. The
 forward cam surfaces 210 are disposed on the forwardmost end of the
 moveable cam member 208, on opposite sides from one another. The cam
 surfaces 212 are spaced rearward from the forward end of the moveable cam
 member 208, and disposed on opposite sides from one another, and rotated
 90 degrees from the cam surfaces 210 in a plane which is transverse to the
 longitudinal axis 238 of the contact assembly 202. The contact assembly
 202 has two leaf-spring type contacts 214 and two leaf-spring type
 contacts 216 which are angularly spaced apart equal distances and extend
 parallel to the longitudinal axis 238 of the contact assembly 202. The
 contacts 214 are preferably longer than the contacts 216, and aligned for
 fitting against respective ones of the cam surfaces 210. A slot 218 is
 formed in the forward end of the moveable cam member 208 for receiving the
 two contacts 216 in alignment for engagement with respective ones of the
 cam surfaces 212. The moveable cam member 208 is shown in FIG. 11 as being
 extended in a forward position, such that the corresponding ones of the
 contacts 214 and 216 are spaced apart by engagement with respective ones
 of the cam surfaces 210 and 212. The boss 204 and the moveable cam member
 208 are preferably formed of nonconductive materials to isolate the
 contacts 214 and 216 from one another, such that four separate circuit
 paths are provided. In other embodiments, insulation layers may be
 provided to insulate the contacts 214 or 216 from one another.
 FIG. 12 is a side elevation view of the contact assembly 202 after the
 moveable cam member 208 has been pushed rearward by a mating contact 200
 of a mating connector. The cam surfaces 210 and 212 have been moved
 beneath respective ones of mating surfaces 223 of the contacts 214 and
 216, such that the contacts 214 and 216 will be urged inward and engage
 the outer periphery of the mating contact 200. Preferably, the geometrical
 relationships of the contact surfaces 222 and the shape of the mating
 surfaces 223 of the cam surfaces 214 and 216 is such that the contact
 surfaces 222 of the contacts 214 and 216 will scrape or wipe the outer
 periphery of the mating contact 200 for approximately thirty thousandths
 of an inch (0.030 in.). The forward end of the boss 204 preferably
 provides a stop for preventing further rearward movement of the moveable
 cam member 208 when the mating contact 200 is being engaged therewith. The
 contacts 214 and 216 thus provide four separate circuit paths to the
 mating contact 200.
 FIG. 13 is an exploded view of the contact assembly 202. Preferably, a
 recess 224 is formed in the forward end of the boss 204. The boss 204
 preferably has a rectangular cross section. The guide member 206 is
 preferably cylindrical in shape and mounts within the recess 224. A bias
 spring 226 extends exteriorly around the guide member 206. A recess 228 is
 formed in the rearward end of the moveable cam member 208 for receiving
 the guide member 206 and the bias spring 226 in a sliding engagement.
 The contact assembly of FIG. 13 further includes a cleaning flow ports 236
 for cleaning the mating contacts, and cleaning flow ports 240 for cleaning
 the contact 214 and 216 with a discharge of cleaning fluid, such as
 solvent, air, a combination of solvent and air, or the like. Flow passages
 230, 232 and 234 connect with the recess 228 and extend through exterior
 surfaces of the moveable cam member 208 to define respective ones of the
 flow ports 236 and 240. A flow passage 242 extends through the guide
 member 206 and into the boss 204 for connecting the recess 228 to a supply
 of solvent, air, or the like. A seal member, such as an O-ring, a
 chevron-shaped seal or lip seal, may be used to seal between the guide
 member 206 and the recess 226. Alternatively, a small leakage of cleaning
 fluids may be tolerated from the space between the guide member 206 and
 the recess 226. The recess 226 is pressurized to spray a discharge of
 cleaning fluid through the flow ports 238 and 240.
 FIG. 14 is a sectional view of a contact assembly 250 of a third
 alternative low insertion force connector. The contact assembly 250 is for
 engaging a mating contact 288, which is preferably one of 14.0 gauge leads
 on 0.200 inch centers, and applying a 30.0 amp drive current to the mating
 contact 288. The contact assembly 250 includes a connector housing having
 a forward housing 252 and a rearward housing 254 which are fastened
 together. The forward housing 252 includes a forwardly disposed aperture
 256 having a tapered guide surface 258. The aperture 256 extends into an
 interior cavity 260, which is formed into the interior of the forward
 housing 252. Two contact leads 262 extend within the interior cavity 260
 on opposite sides of a contact pin assembly 264. Two bores 266 are formed
 on opposite sides of the rearward housing 254 for receiving the contact
 leads 262. A central bore 268 is formed within a central interior portion
 of the rearward housing 254, preferably concentric with a central
 longitudinal axis 269 of the contact assembly 250. A cylindrical insulator
 portion 270 is defined by the portion of the rearward housing 254 which
 extends between respective ones of the two bores 266 and the central bore
 268. A fastener 296 secures the forward housing 252 to the rearward
 housing 254. Preferably, the forward and rearward housings 252 and 254 are
 formed from a non-conductive material, such as a plastic.
 A contact pin assembly 264 preferably includes a plunger or a cam member
 272 and a sleeve 274. Preferably the plunger 272 is spring biased to
 extend forwardly of and from within the sleeve 274. A bias member 148,
 which is preferably is a coil spring, is mounted within the sleeve 274 to
 bias the plunger 272 outward from within the sleeve 274, as shown for the
 contact pin assembly 122 of FIG. 5. A stop 276 extends outwardly of the
 sleeve 274 for engaging a forward end of the central bore 268. The forward
 end of the plunger 272 has a contact face 278. The forward periphery of
 the plunger 272 defines a cam surface 280. The forward ends of the contact
 leads 262 are preferably formed to define mating surfaces 282 for engaging
 the cam surface 280, contact surfaces 284 for engaging a mating contact
 288, and guide surfaces 286 for guiding the mating contact 288 to extend
 between opposing ones of the contact leads 262. Preferably, the contact
 leads 262 are flat, leaf-spring type contacts, such as those having a
 rectangular cross section. The mating contact 288 extends through the
 aperture 256 of the forward housing 252, and engages the contact face 278
 of the piston 272. Movement of the mating contact 288 further into the
 forward housing 252 pushes the piston 272 back into the sleeve 274 until
 the cam surface 280 of the piston 272 is moved from between the mating
 surfaces 282 of the oppositely disposed contact leads 262, allowing the
 contact surfaces 284 of the contact leads 262 to engage upon the forward
 end of the mating contact 288. Preferably, the mating contact 288 will
 move for another thirty thousandths of an inch (0.030 in.) between the
 contact surfaces 284, and the mating contact surface is wiped. Then, the
 forward face of mating contact 288 will be engaged by the contact face 278
 of the piston 272, and the outer periphery of the mating contact 288 will
 be engaged by the two contact surfaces 284 of the contact leads 262.
 Electrical connections 290 and 292 are provided for respective ones of the
 contact leads 262. A contact 294 is electrically coupled to the contact
 pin 264.
 FIG. 15 is an elevation view of the forward end 252 of the connector
 housing, showing apertures 256 and the tapered guide surfaces 258. Two of
 the apertures 256 are shown.
 FIG. 16 is an elevation view of the rear housing 254 of the connector
 housing of the contact assembly 250. The contact 294 of the rear contact
 connections is shown. The rearward end of respective ones of the contact
 leads 262 are shown as the connections 290 and 292.
 FIG. 17 is a side elevation view of one of the contact leads 262. The
 contact lead 262 preferably has a biasing portion 302, and a forwardly
 disposed contact portion 306. A mounting portion 304 is disposed rearward
 of the biasing portion 302. The forward end of the contact portion 306 is
 formed to define a mating surface 282 for engaging the cam surface 280 of
 the piston 272. Also formed on the contact portion 306 is the contact
 surface 284 and the guide surface 286. The guide surface 286 is forward of
 the contact surface 284. The contact member 262 has a central longitudinal
 axis 308 which on a rearward end is spaced apart from a line 310. The
 rearward end of the axis 308 of the contact 262 is spaced apart a distance
 312 of 0.090 inches from the line 310 and the contact portion 284 touches
 the line 310. Preferably, the contact lead 262 is formed of a spring
 steel, or of another resilient material, that will provide a spring force
 or biasing force for engaging the contact surface 284 against a mating
 contact lead with a wiping engagement therebetween.
 FIG. 18 is a longitudinal sectional view of a contact assembly 322 of a
 fourth alternative connector, preferably sized for connecting to 14.0
 gauge leads aligned in rows on 0.200 inch centers, with the rows also
 being spaced apart on 0.200 centers, and applying a 30.0 amp drive current
 through the plunger 272 of the contact pin assembly 264 to a mating
 contact 332. A contact lead 262 is used for measuring the voltage applied
 to the mating contact 332. The plunger 272, the contact pin assembly 264
 and the contact lead 262 are similar to those shown above and described
 for FIGS. 14 and 17. The contact assembly 322 has a forward housing 324
 and a rearward housing 326. An aperture 328 is formed in the forward
 portion of the rearward housing 326 and includes a tapered entrance guide
 portion 330. The mating contact 332 extends through the aperture 328 for
 engaging the plunger 272 of the contact pin assembly 264 and the contact
 lead 262. A bore 334 is provided for receiving the contact lead 262, and a
 bore 336 is provided for receiving the contact pin assembly 264. An
 insulator portion 338 extends between the bore 334 and the bore 336.
 Preferably, the rearward housing 326 and the forward housing 324 are
 formed from an insulating material, such as a plastic. The contacts 290
 and 294 will extend at the rearward end of the rearward housing 326.
 FIG. 19 is an elevation view of the rearward end of the rearward housing
 326, showing the contacts 290 and 294 extending rearwardly therefrom.
 Preferably, the contact 294 is soldered, or braised, to the rearward end
 of the contact pin assembly 264. The contact 290 is preferably the
 rearwardly end portion of the contact lead 262.
 FIG. 20 is a sectional view of an alternative low insertion force contact
 assembly 362 of a fifth alternative embodiment. The contact assembly has
 contacts 364 and 366 for engaging a mating lead. A plunger 368 provides a
 moveable cam member and may be formed of a nonconductive material, such as
 plastic, or formed of a conductive material to provide a contact for
 engaging a mating contact of a mating unit. If the plunger 368 is formed
 of a conductive member, than insulator layer 369 may be provided by an air
 gap, as shown, or by an insulator member, or the like, which separates the
 contacts 364 and 366 from the plunger 368, as shown for the embodiments of
 FIGS. 5, 14 and 18. Alternatively, the plunger 368 may be formed of a
 nonconductive material, and have a conductor which extends interiorly
 therein for connecting to a mating lead, or a combination of the above. A
 housing 370 includes a bore 372 for enclosing a head portion of the
 plunger 368. The housing 370 is mounted to a plate 373, preferably
 provided by a printed circuit board 373. A flow passage 374 extends
 through the housing 370 and into the bore 372. A flow passage 376 extends
 through the length of the plunger 368 to define a flow port 378 on the
 outward end of the plunger 368. A spray of a pressurized solvent, a blast
 of air, or a combination thereof, may be passed through the passages 374
 and 376 for discharge through the flow port 378 to clean the end of a
 mating contact. Additionally, the spray of solvent, air, or the like, may
 be directed from the cleaning port 378 in directions for cleaning the
 mating contact surfaces of the contacts 364 and 366, or additional flow
 port may be provided which are similar to the flow ports 236 and 240 for
 the moveable member 208 of FIG. 13.
 FIG. 21 is a schematic diagram of a reed switch 342 which may be used for
 the reed switch 86 of the safety switch 84 shown in FIGS. 1 and 2. The
 reed switch 342 includes a stationary contact 346, a moveable contact
 element 348 and a contact portion 350 of the contact 348. A housing 356
 encloses the mating portions of the contacts 346 and 348. Preferably, a
 magnet 352 is rigidly secured to the housing 356 to bias the reed contact
 348 to engage the contact 346, which preferably shunts the power circuit
 of the adaptor unit 16 to ground. A permanent magnet 354 may be used for
 the magnetic actuator 86 of FIGS. 1 and 2. When the drawer 28 is fully
 within the enclosure 16 and the cover 30 fully covers the opening 32, the
 magnet 354 will be aligned adjacent to the switch 344, overcoming the bias
 of the magnet 352 and pulling the reed contact 348 away from the contact
 346, such that the power circuit of the adaptor 16 is no longer shunted to
 ground. Power may then be applied to test the circuitry of the UUT 20.
 The present invention provides several advantages over the prior art. A low
 insertion force connector is provided which includes connector assemblies
 having separate circuit paths for connecting to a single mating contact of
 a mating connector. The two circuit paths have first and second contacts,
 respectively, which engage the mating contact at separate engagement
 points. An insulator extends between the first and second contacts,
 insulating at least rearward portions of the first and second contacts
 from one another. The first contact preferably has a cam surface and is
 moveable from an extended position to a retracted position. In the
 extended position, the cam surface pushes the second contact aside of a
 position for engaging the mating contact. Engagement of the mating
 connector with the low insertion force connector pushes the mating contact
 against the first contact, which moves the first contact from the extended
 position to the retraced position. When the first contact is disposed in
 the retracted position, the second contact engages the mating contact, and
 wipes the mating contact during a later portion of an insertion stroke for
 engaging the mating contact with the first and second contact. Mating
 leads may also be cleaned of contaminates with a spray of solvent or a
 blast of air when being mated to a contact assembly.
 Although the preferred embodiment has been described in detail, it should
 be understood that various changes, substitutions and alterations can be
 made therein without departing from the spirit and scope of the invention
 as defined by the appended claims.