Electricity: circuit makers and breakers – Interlocking – Between plural switches
Reexamination Certificate
1999-12-30
2001-02-27
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Interlocking
Between plural switches
C200S01700A, C200S018000
Reexamination Certificate
active
06194675
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention is generally directed to linkages for controlling switches and more particularly to a linkage assembly for use as a double throw safety switch for controlling a first switch and a second switch so that both switches cannot be “on” at the same time.
2. Background of the Invention
There are many instances when more than one switch is used in connection with operation of a machine or system. However, in such situations, it is not always desirable to allow two switches to be “on” at the same time. The present invention provides a mechanical linkage to control two conventional single throw switches to create a double throw safety switch. The linkage ensures that both switches cannot both be in an “on” position at the same time. Instead, either both switches are “off,” or only one of the two switches is “on” and the other is “off.” Prior linkages were difficult to manufacture and to repair. The present linkage can be assembled top-down with a minimum of fasteners. Additionally, the single throw switches are not required to be rigidly mounted to the linkage and can be removed independent of the linkage assembly.
SUMMARY OF THE INVENTION
The present invention is directed to a linkage assembly for a double throw safety switch. In one embodiment, the linkage assembly includes a main frame having a first slider plate moveably fastened to the frame and a second slider plate also moveably fastened to the frame. A driver arm, also connected to the frame, is connected the first slider plate and to the second slider plate to effect movement of both plates. A first follower arm is connected to the frame and to the first slider plate, and a second follower arm is connected to the frame and to the second slider plate. The first and second follower arms control a first and second single throw switch, respectively, and can be connected to ensure that both switches are not “on” at the same time.
The first slider plate includes a first guide defined to allow for movement of the first slider plate, preferably linear, upon movement of the driver arm. Similarly, the second slider plate also includes a first guide defined to allow for movement, again preferably linear, of the second slider plate. The first slider plate also includes a second guide defined to either maintain the position of the first follower arm, or to move the first follower arm, preferably by rotating the first follower arm, upon linear movement of the first slider plate away from a central portion of the driver arm. The second slider plate also includes a second guide defined to either maintain the position of the second follower arm, or to move the second follower arm, preferably by rotating the second follower arm, upon linear movement of the second slider plate away from the central portion of the driver arm.
The first guides in the first and second slider plates can be in the form of slots which cooperate with slider supports on the frame which extend through the slots. The profile of each slot defines a range of movement of the respective slider plate. Similarly, the guides in each slider plate for the follower arms can be profiled to effect a particular range of movement of the follower arm upon movement of the slider plate.
The first and second follower arms can be connected, preferably by a shaft in the follower arm, to a first and a second switch, respectively. Movement of the first follower arm is utilized to control the first switch and movement of the second follower arm is utilized to control the second switch.
In operation, rotation of the driver arm effects linear movement of the first slider plate and the second slider plate. The linear movement of the first slider plate either maintains the position of the first follower arm or effects rotational movement of the first follower arm depending on the direction of the driver arm and the position of the follower arm prior to movement of the driver arm. Similarly, linear movement of the second slider plate either maintains the position of the second follower arm or effects rotational movement of the second follower arm. The first and second slider plates, and the first and second follower arms are configured such that the first switch is not “on” when the second switch is “on.”
The linkage assembly can further comprise a cover connected to the frame and an engaging mechanism which engages the cover when either the first switch or the second switch is “on,” to prevent removal of the cover. In addition the linkage assembly may include an override mechanism which disengages the engaging mechanism when either the first switch or the second switch is “on” to allow removal of said cover. The override mechanism may comprise a defeat slider connected to frame. A defeat arm and a defeat shaft can be utilized to move the defeat slider to disengage the engaging mechanism.
In an alternative embodiment, the linkage assembly can utilize a single slider plate to control the movement of both the first and the second follower arms. The single slider plate would include first guides, preferably one or more slots, to control movement of the slider plate with respect to the frame, and a second guide to control movement of the first follower arm, and a third guide to control movement of the second follower arm. The profile of the second and third guides can be defined to either maintain the position of the follower arm, or to move the follower arm to either an “on” or “off” position depending on the direction of movement of the slider plate. A driver arm can be pivotally mounted to control movement of the slider plate.
Further aspects of the invention are described in the detailed description of the preferred embodiment and the claims, and are shown in the drawings.
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Friedhofer Michael
Golden Larry I.
Shrout Larry T.
Square D Company
Stacey David R.
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