Electricity: circuit makers and breakers – Special application – Change of inclination or of rate of motion responsive
Patent
1996-11-21
1998-05-05
Gellner, Michael L.
Electricity: circuit makers and breakers
Special application
Change of inclination or of rate of motion responsive
200 6152, H01H 3502
Patent
active
057477620
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an oscillation switch and a portable electrically driven machine which is fixed to a workpiece by means of a clamp or an electromagnet, and more particularly to a highly stable electrically driven machine provided with an oscillation switch which stops the drive of an electrically driven tool fixed to the workpiece by the attraction of an electromagnet base to the workpiece, as soon as the electrically driven tool begins to slide laterally due to cutting resistance or the like which is generated during cutting operation.
BACKGROUND ART
There have been known many portable electrically driven machines which can be fixed to a workpiece by means of a clamp or an electromagnet. Recently, there has been proposed a drilling machine of a portable type which has an automatic feeder and an electromagnet base formed integrally with the drilling machine and which drills a workpiece after the workpiece is attracted to the workpiece so that the drilling machine is fixed to the workpiece.
The attracting force of the electromagnet of the drilling machine with the electromagnet base is set to such a value as fully withstands the cutting resistance generated due to the drilling operation or due to the feed load of the drilling machine so that the drilling machine is prevented from displacing during the drilling operation.
However, the following unexpected phenomena may occur: when a workpiece having a forged surface is drilled; built-up edge when the drilling time has elapsed to some extent from the starting time of drilling; or or the automatic feeder of the drilling machine when the space between the drill and the workpiece is clogged with chips so as to cause the drill to bite the workpiece.
On such unexpected occasions, the attracting force cannot withstand these loads and there occurs such trouble that the electromagnet base is lifted and/or is moved with respect to the workpiece.
Under these conditions, the drilling machine with the electromagnet base may rotate around a stabilizing thread or the spindle of the drill, fall down or slide laterally without being attached to the workpiece. In these cases, at least the drive of the drilling machine must be stopped instantaneously.
Under these circumstances, the inventors of the present invention proposed a drilling machine provided with an electromagnet base (hereinafter referred to as "the proposed machine") which stops the drive of the drilling machine as soon as the machine laterally slides even slightly, as disclosed in Japanese Unexamined Patent Application Publication No. 3-19708.
In the proposed machine are provided such elements as a mercury switch which comprises a tubular member filled with mercury and a pair of contacts which extends horizontally in the tubular member or an oscillation switch comprising a fixed contact and oscillation contacts which is provided in the vicinity of the fixed contact via spring means.
Such a switch used in the drilling machine with the electromagnet base detects the lateral sliding of the machine so as to instantaneously stop the drive of the drill motor and/or a feed motor. Thus, a workpiece can be drilled safely.
However, the directions in which the mercury switch or the oscillation switch is operated are limited. When the drilling machine with the electromagnet base is used in an inclined state in such a case in which the drilling machine with the electrode is attached to the inclined surface of the workpiece, the switch which is provided in parallel with the attracted surface of the electromagnet base may fail to operate or the switch may be maintained in an ON state so that the switch cannot perform its own function even if the machine slides laterally. In order to avoid this failure, the machine is attached to the workpiece in such a way that the switch is kept in a horizontal state, or alternately the direction of the switch must be changed with respect to the machine.
The first object of the present invention is to provide an oscillation switch which can securely
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Asano Osamu
Fukuda Kenji
Friedhofer Michael A.
Gellner Michael L.
Nitto Kohki Co. Ltd.
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