Bus board connection apparatus

Electrical connection apparatus is disclosed for achieving versatile connections between bus boards and electrical devices having conductive pins which extend through holes in the boards. Connections are achieved through transversely expansible conductive washers within the holes around the pins. Transverse expansion is caused by compression of individual washers along central axes of the holes, the compression being produced by expander means associated with the washers. Two expansible washer configurations are disclosed, one comprising spring material preformed with protuberances which are flattened to cause transverse expansion, and the other comprising a conductive elastomeric material.

BACKGROUND OF THE INVENTION 
The present invention relates generally to electrical connectors, and more 
specifically to connector apparatus for achieving versatile connections 
between bus boards having one or more layers and electrical devices having 
leads which extend through holes in the bus boards. 
Various techniques and forms of apparatus have been devised for completing 
electrical connections between electrical devices and circuit boards or 
power supply bus boards. Many of these techniques and apparatus involve 
the use of holes in the circuit or bus boards through which leads of the 
electrical devices or device connectors can be inserted. It is, of course, 
known to solder the leads in place after insertion. Another known 
technique involves the use of deformable bushings, one of which at least 
partially surrounds each lead and is pressed into the surrounding hole in 
the circuit or bus board. Such an electrical coupling is the subject of 
U.S. Pat. No. 3,391,375 issued to W. D. Richards on July 2, 1968. These 
techniques are basically limited to single layer boards, and result in 
essentially permanent connections, thus complicating the process of making 
circuit modifications. 
It has relatively recently become common to assemble electrical and 
electronic apparatus from circuits fabricated on printed circuit boards 
which are electrically coupled by means of edge card connectors. Fixed 
portions of the connectors are frequently mounted on a back plane or 
ground plane, and are provided with pins which extend through holes in the 
back/ground plane. Interconnections may be made between some of the pins 
by wrapping flexible conductors around the pins. Such interconnections are 
produced by certain automatic equipment designated by the trademark Wire 
Wrap. 
A common bus board is frequently used for supplying electrical potential to 
predetermined pins of each of a plurality of connectors for powering 
circuitry on mating circuit boards. Where Wire Wrap type interconnection 
pins are provided, connections between predetermined pins and the back 
plane and/or bus board may be achieved with conductive bushings. Other 
pins may be insulated from the board by means of insulating bushings. 
Frequently the back plane/bus board/connector assembly is produced 
according to a user specification by a jobber who specializes in such 
assembly tasks. This procedure facilitates economical and uniform 
production of the assemblies. However, the assemblies so produced lack 
versatility in that the connections between the bus board and the 
connectors are firmly fixed at the time of assembly, and changes can be 
made thereafter only with considerable difficulty. In addition, this 
construction technique is not readily adaptable to electrical apparatus in 
which multilayer bus boards are needed to supply several different 
electrical potentials. 
The applicants have devised unique connection apparatus which permits 
versatile connections between electrical leads of the Wire Wrap type and 
multilayer bus boards. The connections may be altered in the field without 
special tools. Connections are easily made between any level in a 
multilayer bus board assembly and a pin extending through the assembly. 
Accordingly, many of the disadvantages of prior art electrical apparatus 
construction are reduced or eliminated. 
SUMMARY OF THE INVENTION 
The applicant's unique electrical connection apparatus basically comprises 
a transversely expansible conductive washer which is inserted in a hole in 
a bus board surrounding a pin to which it is desired to make an electrical 
connection. The washer is designed so that compression thereof along the 
central axis of the hole results in transverse expansion of the washer. 
The washer is compressed by expander means which includes first and second 
surfaces on opposite sides of the washer. The washer may be fabricated 
from spring material preformed with protuberant areas which are flattened 
to cause transverse expansion. The expander means may comprise base and 
driver members between which the washer is located and rotative coupler 
means for locking the base and driver members in a fixed axial 
relationship. 
The primary object of this invention is to provide improved electrical 
connection apparatus. 
It is a further object of this invention to provide easily alterable 
electrical connections between a bus board having holes therethrough and 
conductive pins extending through the holes. 
A further object is to provide versatile electrical connection apparatus 
for completing electrical connections between a multilayer bus board 
assembly at any level in the assembly and conductive pins extending 
through holes in the assembly. 
A further object is to provide improved bus board connection apparatus 
wherein electrical connections are achieved through transversely 
expansible conductive washers. 
Yet a further object is to provide a unique expansible washer configuration 
in which an external transverse dimension is increased and an internal 
transverse dimension is decreased by compression of the washer along an 
axis transverse to the transverse dimensions. 
Additional objects of the invention may be ascertained from a study of the 
disclosure, drawings and appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1, reference numeral 10 generally identifies a back plane assembly 
embodying various construction features common to prior art electronic 
apparatus. The back plane assembly includes a conductive ground plane 
member or board 11 on which are mounted the receptacle portions 12 of a 
plurality of conventional circuit card edge connectors. Ground plane 
member or board 11 is maintained at a zero reference electrical potential. 
Receptacles 12 each include a slot 13 for receiving the edge of a circuit 
card, and a plurality of contacts 14 for mating with contact elements 
along the edge of the card. A selected one or more of contact elements 14 
may be connected to board 11 as will hereinafter be described. In 
addition, selected contact elements 14 may be connected to predetermined 
bus boards 15, 16 and 17 of a bus board assembly in which the bus boards 
are insulated from one another by insulating sheets 18. 
The means by which selected contact elements 14 are electrically connected 
to bus boards 11, 15, 16 and 17 can best be seen in FIG. 2, wherein the 
various elements shown in both FIGS. 1 and 2 are identified by the same 
reference numerals as in FIG. 1. The bus board assembly, comprising bus 
boards 11, 15, 16 and 17, has a plurality of holes 19 therethrough 
extending along axes 20 transverse to the major surface planes of the bus 
boards. In FIG. 2, contact elements 14 of receptacle 12 are connected to 
conductive pins 21-25 which extend through holes 19 along the central axes 
20 thereof. Pins 21-25 are configured for Wire Wrap interconnections with 
the leads of other circuit components. Such pins have noncircular 
cross-sections with pronounced corners for insuring sound electrical 
connections with the leads wrapped therearound. It is common for such pins 
to be square in cross section. 
As shown in FIG. 2, the four contact elements 14 at the right end of 
receptacle 12 are intended for supplying various electrical potentials to 
components on the circuit card associated with the receptacle. The 
remaining two illustrated contact elements are shown for carrying 
electrical signals to or from the circuit card. Bus boards 11, 15, 16 and 
17 are shown of a solid conductive material. However, the boards may also 
be of a laminated construction in which only the outer surfaces and at 
least a portion of the surfaces bounding holes 19 are of a conductive 
material. 
Pins 21-25 are associated individual contact elements 14 from right to left 
respectively. Pins 25, associated with the two contact elements at the 
left side of FIG. 2, are insulated from board 11 by means of insulating 
bushings 26 inserted in the holes 19 around the pins. Pins 21, 22, 23 and 
24 are connected to boards 15, 11, 17 and 16 respectively through 
connection devices 28, 29, 30 and 31. The electrical connections are made 
through conductive washers 32-32c as will hereinafter be described. 
For purposes of illustrating the applicants' connection device in greater 
detail, device 28 of FIG. 2 is shown in exploded form in FIG. 3. Washer 32 
is located between a base member 33 having a first surface 34 thereon and 
a driver member 35 having a second surface 36 thereon. Conductive washer 
32 is transversely expansible as will be further discussed in connection 
with FIGS. 4 and 5. Surface 36 includes a diametral channel 37 therein 
which permits the desired functioning of washer 32. Base and driver 
members 33 and 35 are preferably molded of an insulating material so as to 
preclude formation of undesired electrical paths. 
Base member 33 and at least a portion of driver member 35 are shown with a 
diameter substantially equal to the diameter of holes 19, so as to fit 
therewithin. The base and driver members include a rotative coupler for 
locking the members together so as to maintain washer 32 in a compressed 
condition. For purposes of facilitating coupling and decoupling of base 
and driver members 33 and 35, base member 33 is provided with a central 
hole 38 configured to match the cross section of pins 21-25 so as to 
restrain the base member from rotation when it is in place. For 
illustrative purposes, and in accordance with typical Wire Wrap pin 
configurations, hole 38 is shown square in cross section. 
Driver member 35 has a central hole 39 therethrough to accommodate a 
conductive pin such as pins 21-25. Driver member 35 is provided with a 
portion 40 which is exposed when the driver member is in place. As shown, 
exposed portion 40 comprises a hexagonal head to facilitate rotation of 
the driver member relative to the base member. The rotative coupler shown 
in FIG. 3 is a bayonet type coupling which includes a pair of inwardly 
projecting dogs 41. Dogs 41 cooperate with a pair of diametrally located 
stepped indentations 42 in driver member 35. Each indentation 42 includes 
a first shallow channel 43 near surface 36 and a second deeper channel 44 
more remote from surface 36, with a small ledge between the channels. The 
purpose of the small ledge is to keep the several elements of connection 
device 28 together when the device is not in place for making an 
electrical connection. The portion of indentation 42 immediately adjacent 
the small ledge functions to accommodate one of dogs 41 when connection 
device 28 is in an unlocked state. Locking of the device is accomplished 
by rotating driver member 35 relative to base member 33 to a position 
where dog 41 can be moved along the deeper axial channel of indentation 
42. With dog 41 at an upper position in indentation 42, as seen in FIG. 3, 
driver member 35 can be further rotated so that the dog is moved into a 
locking portion 45 of the indentation. Ledge 46 of locking portion 45 
serves to maintain the base and driver members in a fixed axial 
relationship. 
The embodiment of washer 32 illustrated in FIGS. 4 and 5 comprises one form 
of transversely expansible conductive washer suitable for use in the 
applicants' connection device. Washer 32 is fabricated of a conductive 
spring material, and provided with a central hole 48 configured to closely 
conform to the cross section of conductive pins 21-25 after the washer is 
preformed into its desired shape. Washer 32 is also provided with a pair 
of notches 49 to accommodate the axial supports for dogs 41 on base member 
33. 
Washer 32 is preformed to have a first protuberant area 50 substantially 
bisecting the washer, and second and third protuberant areas 51 and 52 
located along chords on opposite sides of the first protuberant area. When 
washer 32 is in its relaxed condition, as shown by the solid line drawing 
in FIGS. 4 and 5, it has a diameter slightly smaller than the diameter of 
holes 19 so as to permit insertion of the washer into the holes. Base and 
driver members 33 and 35 are configured to compress washer 32 between 
surfaces 34 and 36, thereby flattening protuberant areas 51 and 52. When 
areas 51 and 52 are flattened, washer 32 is caused to transversely expand 
as indicated by dashed outline 53. 
Concurrently, protuberant area 50 becomes exaggerated as permitted by 
channel 37 in surface 36. This effect results in part from transverse 
forces exerted on the edges of washer 32, and in part from resistance to 
straightening of the knees identified by reference numeral 54. 
Exaggeration of protuberant area 50 causes a decrease in a transverse 
dimension of hole 48 as indicated by dashed lines 55. Accordingly, with 
connection device 28 in place, and as washer 32 is compressed, the washer 
is caused to grip both the interior surface of a hole in a bus board and 
the exterior surface of a conductive pin within the hole so as to achieve 
a sound electrical connection between the board and the pin. 
An alternate embodiment of the applicants' connection device is shown in 
FIG. 6, wherein elements similar to elements illustrated in FIG. 3 are 
identified by like reference numerals with a prime added. The principal 
differences reside in substitution of a conductive elastomeric washer for 
the preformed spring washer, and substitution of an interrupted thread 
rotative coupler for the bayonet type coupler of FIG. 3. The conductive 
elastomeric washer is identified by reference numeral 60. In use, washer 
60 is axially compressed between surfaces 34' and 36'. This compression 
causes the elastomeric material to expand in directions transverse to axis 
20', thereby gripping the interior surface of a hole in the bus board and 
the exterior surface of a conductive pin. In general, conductive 
elastomeric material has a higher resistance and less current carrying 
capacity than a similar spring washer configuration. Accordingly, 
connectors utilizing conductive elastomeric washers are principally useful 
in signal level applications in contrast to power supply applications. 
The interrupted thread rotative coupler illustrated in FIG. 6 comprises a 
pair of axially projecting shell portions 61 on base member 33'. Shell 
portions 61 are formed with an internal screw thread as shown. Driver 
member 35' includes a coupler portion 62 of reduced diameter formed with a 
pair of axial channels 63 configured to permit axial passage of shell 
portions 61. The remaining areas of coupler portion 62 are formed with an 
external screw thread, whereby after base and driver members 33' and 35' 
are axially mated, the driver member may be rotated relative to the base 
member to lock the members in a fixed axial relationship, thereby 
accomplishing the same function performed by the bayonet coupler of FIG. 
3. 
As is apparent from the foregoing discussion, the level in the bus board 
assembly of the bus board to which it is desired to make connection 
determines the required axial position of the conductive washer along the 
pin. Appropriate positioning can be accomplished by inversely varying the 
relative lengths of the base and driver members of the connection device. 
With reference to FIG. 2, it is desired to connect pin 22 to board 11 which 
occupies the closest level to connector 12. A connection device for making 
such a connection inlcudes a base member of minimum length and a driver 
member of maximum length. Conversely, it is desired to connect pin 23 to 
bus board 17 at the level furthest from connector 12. A connection device 
for making such a connection includes a base member of maximum length and 
a driver member of minimum length. Similarly, pins 21 and 24 are 
respectively connected to bus boards at intermediate levels. This can be 
accomplished by utilizing connection devices in which the base and driver 
members have correspondingly appropriate lengths. 
The applicants' connection device is easily installed by first selecting a 
device having base and driver members of the length which will locate the 
washer at the level in the bus board assembly at which it is desired to 
make connection. The connection device is then inserted over the pin and 
into the hole in the assembly. After the connection device is properly 
seated, further axial pressure sufficient to compress the conductive 
washer is exerted on the driver member and the driver member rotated to 
lock it together with the base member. The connection device can be 
removed with equal ease by reversing the foregoing steps. 
Accordingly, it is apparent that the applicants' connection device permits 
versatile electrical connections between electrical leads of the Wire Wrap 
type and multilayer bus boards. The connections are easily alterable and 
field repairable, thus providing exceptional utility. Connections and 
disconnections are easily accomplished at any level within a multilayer 
bus board. Finally, no special tools are required for installation or 
removal of the applicants' connection device. 
Although specific embodiments of the applicants' unique electrical 
connection apparatus have been shown and described for illustrative 
purposes, other embodiments within the applicants' contemplation and 
teaching will be apparent to those skilled in the art. The applicants do 
not intend that coverage be limited to the disclosed embodiment but only 
by the terms of the appended claims.