Electricity: circuit makers and breakers – Switch activation inhibitor – Actuator blocking device
Reexamination Certificate
2000-02-22
2001-08-14
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Switch activation inhibitor
Actuator blocking device
C200S321000
Reexamination Certificate
active
06274828
ABSTRACT:
The present invention relates to an on-off switch for use in an electric power hand tool.
BACKGROUND OF THE INVENTION
The operation of an electric power hand tool is usually controlled by an on-off switch. As power hand tools would inevitably be subject to impact during arduous handling, care should be taken not to cause the switch to be turned on unintentionally, which may otherwise result in an accident. Most existing switches used in this field are not sufficiently robust.
The invention seeks to mitigate or at least alleviate such a problem by providing an improved on-off switch of this type.
SUMMARY OF THE INVENTION
According to the invention, there is provided an on-off switch for use in an electric power hand tool, which switch comprises a body, a switching mechanism provided within the body, an operator supported by the body for movement between a first position to turn on the switching mechanism and a second position to turn off the switching mechanism, a first spring resiliently biasing the operator towards the second position, and a movable locking device resiliently biased by a second spring for locking the operator in the second position against accidental switching on of the hand tool, the operator and locking device including respective first and second metal parts for abutment with each other to lock the operator in the second position.
Preferably, the first metal part is provided internally of the operator for reinforcement.
More preferably, the first metal part has a shape corresponding to the shape of the operator.
In a preferred embodiment, the locking device includes an actuator movable in opposite first and second directions, being resiliently biased by the second spring in the first direction, for moving the second metal part in the first direction into the path of movement of the first metal part for blocking the movement of the operator from the second position and in the second direction away from the path of movement to allow the operator to move to the first position.
More preferably, the actuator is movable in opposite directions past a central position to reach a side position on either side of the central position, and is resiliently biased by the second spring towards the central position.
Further, more preferably, the actuator has opposite ends to facilitate movement by a person using the hand tool on either side of the switch.
It is preferred that the body include a third metal part which is located behind the second metal part for providing reinforced support for the second metal part when the second metal part is abutted by the first metal part.
Advantageously, the locking device is releasably connected to the body for use and is removable such that the remainder of the switch may be used independently without the locking device.
More specifically, the body includes a pair of opposed hooks for connecting the locking device to the body between them through a snap-fit action.
The invention also provides an electric power hand tool incorporating the on-off switch, in that the hand tool has a body including a handle at which the switch is located for use.
The power hand tool may be an electric saw incorporating a motor-driven circular saw blade.
REFERENCES:
patent: 3847233 (1974-11-01), Glover et al.
patent: 3873796 (1975-03-01), Worobec, Jr.
patent: 4180716 (1979-12-01), Suzuki
patent: 4549097 (1985-10-01), Ulmer
patent: 5346342 (1994-09-01), Winchester
patent: 6057518 (2000-05-01), Bascom et al.
patent: 6091035 (2000-07-01), Campbell et al.
Defond Manufacturing Limited
Leydig , Voit & Mayer, Ltd.
Scott J. R.
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