Note: Descriptions are shown in the official language in which they were submitted.
The invention relates to systems for detachably mounting a plurality
of daughter printed circuit boards ~PCBs) on a backplane.
Backplanes are printed circuit boards or metal plates on the upper
side of which "daughter" PCBs are detachably mounted perpendicularly to the
backplanes for easy removal and replacement while the circuit is still being
powered. One way of electrically connecting the daughter boards to other
daughter boards, the backplane, and other circuitry is by providing metallized
surface portions near the edges of the daughter boards and inserting them
between the forked prongs of electrical connectors that are secured to th0
backplane. Another way of making electrical connection to the daughter boards
involves using post and box connectors. The connectors secured to the back-
plane often have connector posts extending from the lower side of the backplanes
for receiving wires connecting selected pairs of posts, and bus bars are
often connected to a line of connector posts under the backplane to distribute
voltage to a plurality of posts. These connections to the daughter boards are
typically designed to carry small amounts of current; thus, a large number
of contacts are connected in parallel when large amounts of current are needed.
It has been discovered that space can be conserved and better elec-
trical connection between the components on the daughter boards and the bus
bars can be provided, to result in less current resistance and increased
reliability, by mounting the bus bar on the same side of the backplane as the
daughter boards, and providing the daughter boards with contacts that directly
mate with contact portions on the bus bars. In preferred embodiments, the bus
bar contact portions comprise a male portion extending along the length of
the bus bar and transversely to the backplane, the daughter board contacts
have forked prongs for engaging the male portion, and a daughter board has more
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than one forked contact for mating with a single bus bar to provide increased
current carrying capacity. In one embodiment the bus bar is connected to the
backplane via a dielectric housing, and in another embodiment the bus bar has
connector posts that extend through holes in the backplane.
The structure and operation of the presently preferred embodiment of
the invention will now be described after first briefly describing ~he
drawings.
Figure 1 is an elevation, partially broken away, of a system for
detachably mounting a plurali~y of daughter printed circuit boards on a back-
plane.
Figure 2 is a perspective view, partially broken away, of the Figure 1
system, with a daughter board shown disconnected from the backplane.
Figure 3 is a perspective view, partially broken away, showing an
alteTnative bus bar construction for use in said system.
Structure
Referring to Figures 1 and 2, there is shown daughter board mounting
system 10 including daughter boards 12 mounted on backplane 14 and electrically
connected to bus bars 16, 17 via female contacts 18 engaging mating male
contact por~ions 20 of bus bars 16, 17. Although not completely shown on
Figures 1 and 2, daughter boards 12 each have a plurality of female contacts 18
on them for making electrical connectionwith bus bars 16, 17 and other bus bars
not shown. On the portions of daughter boards 12 not shown, there also are
other contacts for making electrical connection between the components on
different daughter boards via, for example, wire wrapped connector posts.
Bus bars 16, 17 are made of copper and in their present embodiment
have 0.140" high and 0.150" wide base portions 22 under vertically extending
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male portions 20, which in this embodiment are 0.025" thick. Bars 16, 17are mounted on and electrically insulated from backplane 14 by dielectric
housings 24. Capacitor 30 is directly connected between bus bars 16, 17. Bus
bar 17 is connected to lead 32 by screw 34 for screwing into threaded hole 36,
and bus bar 16 has connector 38 attached toit for receiving lead 37, which is
held in place by a set screw 39. The bus bar used for ground is mounted
higher than the other voltage distributing bus bars to guarantee that when
daughter boards 12 are connected, they make electrical contact with the ground
bus bar first.
Female contacts 18 are the well known tuning fork type contacts
meeting military specification MIL-C-28754, and each can carry 5+ amps. They
are soldered to metallized portions on daughter boards 12 and are embedded in
insulators 26, which are shaped to provide a snug fit within the upwardly
extending portions of housings 24 when the forked prongs 28 are slid over
male portions 20. Portions of contacts 18 attached to daughter boards 12 are
positioned vertically in line, and are electrically connected in parallel, thus
providing increased current carrying capacity without using up space along
the width of boards 12.
Operation
In operation, daughter boards 12 can be easily attached and electrically
connected to backplane 14 by lowering them to engage the bus bars and other
connectors on the backplane. Because the ground bus bar is higher than the
other bus bars, the daughter boards make contact with ground first to prevent
damage to the components. Because the bus bars are on the same side of the
backplane as the daughter boards and are directly connected to the daughter
boards, space is conserved and there is good electrical conduction between the
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components on the daughter boards and the bus bars. Placing ~he bus bars
on the same side as the daughter boards also provides space for easily attach-
ing capacitors between the bus bars and avoids the problem of interference of
the bus bars with the wires wrapped to connector posts.
Other embodiments of the invention are within the scope of the
appended claims. By way of example, as is shown in Figure 3, one can use bus
bars 40, having connector posts 42 formaking electrical connection with conduct-
ing portions of backplane 44. Also, in addition to copper, other rigid,
electrically conducting materials such as phosphor bronze and brass can be
used for the bus bars.
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