Apparatus and method for keying an electrical assembly with a wiring backplane

An apparatus and method for keying an electrical assembly with a wiring backplane include an electrical assembly (1), a removable guide member (3), and a wiring backplane (8). The removable guide member (3) has a projection (7) perpendicular to the body (4) of the removable guide member (3) which is secured to the electrical assembly (1) by a flexible latching element (11). The electrical assembly (1) having a removable guide member (3) is received by a wiring backplane (8) adapted to receive the removable guide member (3).

TECHNICAL FIELD OF THE INVENTION 
This invention relates in general to electrical assemblies, and more 
particularly to an apparatus and method for keying an electrical assembly 
with a wiring backplane. 
BACKGROUND OF THE INVENTION 
Several known devices use keying or guide systems directed toward 
electrical board assemblies. However, many of these known devices are 
attached to the assembly connector or are integrated into the connector 
and used as part of the electrical circuitry to prevent electrostatic 
discharge. Thus, errors in connector keying or limitations in the number 
of possible connector keying combinations may still result in circuit 
incompatibility. Therefore, it is desirable to have a simple and efficient 
keying system in order to prevent erroneous circuit operation or damage to 
the circuitry of an electrical assembly. 
Some known devices have attempted to provide a keying system separate and 
apart from the assembly connector, but these systems may require 
installing additional hardware to the wiring backplane and electric 
circuit board. Additionally, these types of keying systems, as well as 
connector-type keying systems, require extensive record-keeping regarding 
the types and configurations of pins used and their respective keying 
orientation for subsequent modification or replacement. 
SUMMARY OF THE INVENTION 
From the foregoing, it may be appreciated that a need has arisen for an 
electrical assembly keying device and method that are simple, easy to 
install and modify, take up a minimal amount of space, and can be used 
independently from the electrical connectors. In accordance with the 
present invention, an electrical assembly keying method and device are 
provided that substantially eliminates or reduces disadvantages and 
problems associated with other types of keying devices and methods. 
According to an embodiment of the present invention, there is provided an 
electrical assembly containing an opening. A guide member is provided with 
a body having first and second ends. The first end of the guide member 
body has a projection perpendicular to the body. The projection is 
designed to cooperate with the electrical assembly opening for securing 
the guide member to the electrical assembly. A wiring backplane is 
provided and designed to receive the second end of the body of the guide 
member. The electrical assembly with the secured guide member will 
cooperate only with a wiring backplane that has been adapted to receive 
the second end of the guide member. 
The present invention provides various technical advantages. For example, 
one technical advantage is the simpleness and ease of installation of the 
keying device. Another advantage is the ability to limit the types and 
number of different connectors and hardware attached to the circuit board 
and wiring backplane while still providing a keying system preventing 
erroneous circuit connections. Other technical advantages are readily 
apparent to one skilled in the art from the following figures, 
descriptions, and claims.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIGS. 1, 2, and 3 where there is shown one embodiment of 
the electrical assembly keying invention. There is shown an electrical 
assembly 1 having a first opening 2. A guide member 3 has a body 4 with a 
first end 5 and a second end 6. The first end 5 has a first projection 7 
extending perpendicular to the body 4. The first projection 7 is designed 
to be received by the first opening 2 of the electrical assembly 1 and 
operable to secure the guide member 3 to the electrical assembly 1. 
Although the embodiment illustrated shows a first projection 7 having a 
latch element 11, any method of securing the guide member 3 to the 
electrical assembly 1 may be used. A wiring backplane 8 is designed to 
receive the second end 6 of the guide member 3. The embodiment illustrated 
shows a wiring backplane 8 adapted to receive the second end 6 of the 
guide member 3 by the use of a hole 12. The wiring backplane 8 may also be 
adapted to receive the second end 6 of the guide member 3 by coordinating 
any number of possible guide member 3 configurations with the wiring 
backplane 8. In operation, an electrical assembly 1 with a secured guide 
member 3 will be received only by a wiring backplane 8 adapted to receive 
the second end 6 of the guide member 3. 
FIG. 4 illustrates an alternative embodiment of the invention where the 
guide member 3 has a second projection 9 extending perpendicular to the 
body 4 and parallel to the first projection 7. The first projection 7 is 
designed to be received by the first opening 2 of the electrical assembly 
1. The first opening 2 receives the first projection 7 and is thereby used 
to secure the guide member 3 to the electrical assembly 1. The second 
projection 9 is positioned on the body 4 of the guide member 3 to align 
the body 4 of the guide member 3 with the wiring backplane 8. In the 
depicted embodiment, the second projection 9 aligns the body 4 of the 
guide member 3 with the wiring backplane 8 by using the edge of the 
electrical assembly 1 to prevent excessive rotation of the guide member 3. 
Also, the embodiment illustrated shows a wiring backplane 8 adapted to 
receive the second end 6 of the guide member 3 by the use of a cavity 13 
in the wiring backplane 8. 
FIGS. 5 and 6 illustrate an alternative embodiment of the invention. The 
electrical assembly 1 has a first opening 2 and a second opening 10. The 
guide member 3 has a first projection 7 and a second projection 9 
perpendicular to the body 4. The first projection 7 is parallel to the 
second projection 9. The first projection 7 is designed to be received by 
the first opening 2 of the electrical assembly 1. The first opening 2 
receives the first projection 7 and is thereby used to secure the guide 
member 3 to the electrical assembly 1. The second projection 9 is designed 
to be received by the second opening 10 and cooperates with the second 
opening 10 to align the body 4 of the guide member 3 with the wiring 
backplane 8. The second projection 9 and the second opening 10 may be 
located anywhere along the body 4 of the guide member 3 and can be 
coordinated with different body 4 diameters or shapes to increase the 
number of possible keying combinations. FIG. 7 illustrates the second 
opening 10 located on the edge of the electrical assembly 1 in the form of 
a slot 14 to cooperate with the second projection 9 in aligning the body 4 
of the guide member 3 with the wiring backplane 8. 
FIGS. 8 and 9 illustrate additional embodiments of the invention. In FIG. 
8, the first opening 2 of the electrical assembly 1 is of rectangular 
cross section and cooperates with the first projection 7 of the guide 
member 3 also of rectangular cross section. The non-circular cross section 
of the first projection 7 and first opening 2 in the electrical assembly 1 
prevents excessive rotation of the guide member 3 and is operable to align 
the body 4 of the guide member 3 with the wiring backplane 8. Though not 
shown, first projection 7 may have a latch element similar to latch 
element 11 in order to secure guide member 3 to electrical assembly 1. 
FIG. 9 illustrates a guide member 3 with a non-circular body 4 to prevent 
rotation and allow for a combination of keying devices. 
It should also be noted that, although one guide member 3 is shown in the 
drawings, other similar members can be located elsewhere along the 
electrical assembly 1 to increase the number of keying combinations. Also, 
the geometric shape and size of the guide member 3 can be varied to 
increase the number of possible keying combinations. 
Guide member 3 may be constructed out of a variety of materials, including 
plastics, and may be made by a variety of techniques, including injection 
molding. Preferably, guide member 3 is made out of nylon 6/6 having a 94VO 
UL rating for electronic equipment. This provides a safe, nonflammable, 
and cost effective device for providing a viable keying apparatus. 
Thus, it is apparent that there has been provided, in accordance with the 
present invention, a guide member that satisfies the advantages set forth 
above. Although the present invention has been described in detail, 
various changes, substitutions, and alterations can be made herein. For 
example, though described with regard to electrical assemblies and 
backplanes, the present invention is not limited thereto and may be used 
for a variety of keying and aligning applications. Other examples are 
readily ascertainable by one skilled in the art and may be made without 
departing from the spirit and scope of the present invention as defined by 
the following claims.