Electricity: circuit makers and breakers – Switch activation inhibitor – Removable actuator
Patent
1999-05-20
2000-07-04
Friedhofer, Michael
Electricity: circuit makers and breakers
Switch activation inhibitor
Removable actuator
200 17R, 200 6162, H01H 316, H01H 2700
Patent
active
060841850
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a safety switch having a switch housing with at least one key passage for receiving a key from exterior of the switch housing and with a plate cam rotatably mounted in the switch housing. Upon introduction of the key in the key passage, the key rotates the plate cam.
BACKGROUND OF THE INVENTION
Safety switches, such as disclosed in DE 44 08 024 A1, serve to make the current supply feeding electrical machinery dependent upon whether certain protection devices, which are integral with the machine, are positioned in the correct setting. With some embodiments, the safety switch does not connect the control current circuit supplying a current supply to the machine because the protection devices have greater tolerances than allowed by the safety switch.
EP-A1-0 707 329 discloses a safety switch with a plate cam mounted rotatably on an axis on which are arranged interlocking means. The interlocking means lock or secure the plate cam when the key is not introduced and are thrust out of their blocking position when the key is introduced. The plate cam is released with further introduction of the key, with the interlocking means being rotated together with the plate cam.
SUMMARY OF THE INVENTION
Objects of the present invention are to provide an improved safety switch in which the plate cam is prevented from rotating as a result of machine vibrations when the key is in or out of the key passage.
The foregoing objects are basically obtained by a safety switch comprising a switch housing, a first key passage in the switch housing, a key receivable in the key passage from a location exterior of the switch housing, and a plate cam projecting into the key passage and rotatable in the switch housing about a rotational axis upon introduction of the key. Securing means in the switch housing secures the plate cam against rotation when the key is completely introduced into the key passage and when the key is completely outside the key passage. It also allows the key to be introduced deeper into the key passage after the plate cam is secured by the securing means.
By securing the plate cam when the key is completely inserted, the plate cam is prevented from rotating as a result of vibrations of the machine occurring during key insertion, so that the key can no longer be pulled out. The key is inserted to a certain depth of introduction following termination of the rotary displacement of the plate cam. Since the securing means allows the plate cam to permit a deeper introduction of the key, in other words allowing for a "track alignment arrangement" of greater length, even imprecise switch-throwing protection devices can be reliably controlled. In advantageous embodiments, the plate cam is secured even when the key is not inserted.
In one preferred embodiment, the means for securing the plate cam are realized by the plate cam having at least one recess which cooperates with a blocking element movable relative to the plate cam.
The recess can be provided, for example, in an additional material part constructed on the side of the plate cam. The blocking element can be arranged on one side of the plate cam and constructed and shaped in conformation with a movable interlocking member. With this embodiment, parts can be used which are already present in known safety switches. This reduces the number of new required parts and reduces the required modifications of the tools. One especially space-saving embodiment is obtained when the interlocking member can be movable perpendicular to the rotary axis of the plate cam.
The recess and blocking element can also be realized, for example, in such a manner that the recess is provided in an area of the plate cam, which with rotation of the plate cam, projects into the key passage. Also the blocking arrangement can be provided as part of the key. An especially simple realization of the blocking element is obtained with a longitudinally slotted, fork-shaped key, and formed by recessed cutout sections provided on the interior of the
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Euchner GmbH & Co.
Friedhofer Michael
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