Note: Descriptions are shown in the official language in which they were submitted.
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E;WI~C~ING E~ECT~ ECEPT~CLE~
BACKGROUND OF THE INVENTION
This invention is related to electrical receptacles
for use with electrical plugs. In particular, it is an
improved electrical receptacle that can be switched at the ~;
receptacle.
Electrical receptacles for currents of fifteen
amperes or more typically have contacts for three, four or five
wires. Such receptacles may injure an operator and may damage
the receptacle if they are connected or disconnected to the
electric power system under load. For these reasons, it is
conventional to provide some fQrm of switch with the
receptacle, often interlocked with the receptacle, to insure
that the plug is not removed from or inserted into the
receptacle under load. The switch is often a safety switch or
relay that is installed in a switchbox that serves as a mount
for the receptacle. In the alternative, the receptacle may be
combined with a circuit breaker. Either of these alternatives
increases the cost of installing a receptacle over the cost of
the receptacle itself.
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It would be useful to have a self-contained
receptacle that c~uld be switched to cut off eleatricity to a
plug before the plug is removed from or inserte~ in~o the
receptacle. Such a receptacle could be operated ~s a
stand-alone device or it could be combined with an interlock as
an additional assurance that the plug is not inserted into or
removed from the receptacle under load. It would also be
useful to have a switching electrical receptacle that would
meet requirements for rating for explosion-proof service. Such
a switching receptacle could be smaller than a combination
safety switch and receptacle, and would therefore be cheaper to
manufacture and easier to insta}l. It could also more easily
be made explosion-proof because its contacts open and close in
a relatively small volume within the receptacle.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
better electrical receptacle for currents of fifteen amperes or
more per phase.
It is a further object of the present invention to
provide a switching electrical receptacle that can be switched
manually at the receptacle.
~ t is a further object of the present invention to
prov;de a switching electrical receptacle that can be switched
at the receptacle by a manually-operated over-center linkage.
It is a further object of the present invention to
provide a switching electrical receptacle that can ke switched
electrically, pneumatically or hydraulically at the
receptacle.
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It is a further ob~ect of the present in~ention to
provide an electrical receptacls that can be switched on and
off by axial motion of a contact carrier.
It is a further object of the present invention to
provide an explosion-proof switching electrical receptacle.
Other objects will become apparent in the course of a
detailed description of the invention.
A switching electrical receptacle includes a fixed
set of female contacts mounted to be connected to electric
power lines. A housing supports a plurality of sliding
contacts of substantially cylindrical symmetry disposed
parallel to an axis. The housing can be slid axially into and
out of electrical contact with th~ female contacts to maXe or ~ ?~
break a circuit. The sliding contacts are in permanent sliding
contact with another set of female contacts that are connected
to load terminals that are adapted to receive an electric
plug. Each sliding contact is split along its axis and is
spring-loaded from within to exert radial forces that assure
good electrical connections between the sliding contact and ;~
each set of female contacts. Seals are readily installed in
the housing to make the receptacle explosion-proof and also
appropriate for outdoor use.
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BRIEF DESCRIPTION OF THE DR~WINGS
Fig. 1 is a central sectional side view of the
apparatu~ of the present invention with a switch in an open
position.
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Fig. 2 is a central sectional side view of the
apparatus of the present invention with the switch in a closed
position.
Fig. 3 is a central sectional side view of a sliding
contact for the practice of the present invention.
Fig. 4 is a top view of an apparatus for the present
invention including an actuator.
Fig. 5 is a central sectional side view of the
apparatus of Fig. 4.
~ETAI1ED DESCRIPTION OF THE INVENTION
Fig. l is a central sectional side view of an
apparatus for the practice of the present in~ention with a
switch in an open position, and Fig. 2 is a central sectional
side view of the apparatus with the switch in a closed
position. In Figs. l and 2, a receptacle l~ is affixed to a
wall 12. The receptacle 12 contains a plurality of female
terminals 14 that are connected to wire terminals 16. Wires,
which are not shown here, are inserted into the wire
terminals 16 to supply electric power to the receptacle l0.
Each wire terminal 16 has a screw 18 that can be tightened on
an inserted wire to establish a secure electrical and
mechanical contact between such a wire and each wire
terminal 16.
In use, it i5 desired to make connections between the
female terminals 14 of the receptacle lO and a corresponding
set of female terminals 24 that are part of a plug 26. The :
female terminals 24 are also adapted to be connected by a se~
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of screws 28 to wires that are not shown here. A contact
carrier 32 carries a sliding contact 34 for each associated
pair of wire terminals 14 and 24. Fig. 1 shows the contact
carrier 32 in a position where each of the female terminals 14
is connected to a corresponding one of the ~emale terminals 24
by the sliding contact 34 that moves with the contact
carrier 32. This is the "on" position for the switching
receptacle 10. Fig. 2 shows the opposite situation, with the
contact carrier 32 moved to a position where contact is
interrupted between the female terminals 14 and 24. A
detent 40 is inserted in a hole 42 in the casing ~4 of the
plug 26 when electric power is connected so that the plug 26
c~nnot be removed from the receptacle 12 under load. In
Figs. 1 and 2, the detent 40 i5 operated by a rod 48 that can
be lifted only when a cam 50 is moved out of a blocXing
position by a rod 52. An interlock to a circuit breaker or
disconnect switch, none of which is shown here, operates the
cam 50 to permit the detent 40 to be raised only when the power
is off. S~ch an interlock could equally as well be operated by
a conventional over-center mechanism connected to operate the
contact carrier 32.
In Figs. 1 and 2, the plug 26 is in the
receptacle lO, holding a hinged cap 58 in an open position. If
the plug 26 is removed from the receptacle 10, the hinged
cap 58 closes to protect the female terminals 24 from dirt,
moisture and the like.
Fig. 3 is a sectional side view of one of the sliding
contacts 34 of Figs. 1 and 2. In Fig. 3, the sliding
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contact 34 exhibits cylindrical symmetry about an axis 62. A
first half 64 is attached to a second half 66 by rivets 68 : i
and 70. The rivets 68 and 70 are sized to permit the first
half 64 to move radially with respect to the second half 66,
but are ~eaded to keep the first half 64 and second half 66
together. It should be evident that other means such as screws
threaded into tapped holes or nuts and bolts could equally as
well be used ~o keep the first half 64 and second half 66
together w~ile permitting them to move radially with respect to
each other. In the alternative, the halves 64 and 66 could be
held together by retaining rings inserted in qroov~s so that
the rings would not contact the female terminals 14 and 24.
The rivets 68 and 70 are preferred because they provide guides
for relative radial motion between the halves 64 and 66.
Two springs 76 and 78 that are placed between the
halves 64 and 66 exert forces on the halves 64 and 66 that will
tend to keep them apart and will thus make good electrical
connections between the sliding contact 34 and the female
terminals 14 and 24. A shoulder 82 has a diameter that is
greater than the diameter of the contact regions 86 and 88. A
relieved regi~n 90 is given a diameter slightly less, of the
order of 0.001-0.010 ", to reduce sliding friction upon
insertion of the sliding contact 34 ~nto a female terminal 14
or its removal from the terminal 14. Chamfers 94 and 96 at
opposite ends of the sliding contact i4 aid in connecting the
plug 26 to the receptacle 10 and in moving the sliding
contact 34 into the female terminal 14. The construction
described here insures good electrical contact-without
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requiring the machining of especially close tolerances, and it
does no~ use the elasticity of the brass or similar matPrial of
the sliding cc,ntact 34.
Fig. 4 is a top view of an apparatus for the practice
of the present invention including an actuator for the switch,
and Fig. S is a central sectional side view of the apparatus of
Fig. 4. In Figs. 4 and 5, a frame llo, which may be part of a
wall or of a switch box, provides support for a housing 112
which in turn supports a contact carrier 114. A sliding
contact 116 is shown in an open position in which it does not
make contact with a female terminal 118. The contact
carrier 114 has a male terminal 120 that will be slid axially ;
into contact with the female terminal 118 by an actuating
rod 126 that may be moved manually, hydraulically,
pneumatically or by an electrical relay. None of these
actuating means is shown here. The receptacle of Fig~ 5 also
differs from that of Fig. 1 in having a ground contact 128 that
is not switched but that makes continuous contact with a plug '
(not shown) that may be inserted into the receptacle of
Fig. 5. To do so, an operator must lift a cover 130 and also
rotate a rod 134. This rtates a linkage 136 to raise a
detent 138, allowing insertion of a plug. The r~d 134
connected by a rod 140 to a cam plate 142 which prevents ~,
insertion of a plug when the contact carrier 114 is in the "on"
position.
The embodiments of the invention described above are
intended to describe the best mode for the practice of the
invention, and should be taken as exemplary and not as
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limiting. The scope of the invention is that of the appended
claims and their equivalents.
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