Electricity: circuit makers and breakers – Switch activation inhibitor – Actuator blocking device
Reexamination Certificate
1999-12-06
2001-07-10
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Switch activation inhibitor
Actuator blocking device
C200S321000, C200S332200
Reexamination Certificate
active
06259047
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to power tools, such as power grinders for polishing, abrading or cutting workpieces, having improved switch devices for starting and stopping the power tool motors.
2. Description of the Related Art
A known power grinder is shown in FIG.
10
and is generally indicated by reference numeral
41
. The grinder
41
comprises a substantially cylindrical housing
42
and a handle
43
connected to the rear end of the housing
42
. A motor
49
is disposed centrally within the housing
42
and serves to drive a spindle
44
that downwardly extends from the front end of the housing
42
. A grinding disk
45
is mounted on the spindle
44
.
A grip portion
46
and a switch device
47
are mounted on the handle
43
. The switch device
47
includes a switch circuit that is connected between the motor
49
and a power supply cable
48
. The power supply cable
48
extends outward from the rear end of the handle
43
for connection with a power source. The handle
43
has a joint portion
43
a
that is joined to the housing
42
and that has a substantially cylindrical configuration corresponding to the configuration of the housing
42
. The grip portion
46
is adapted be grasped with one hand of an operator, and therefore, the grip portion
46
has a configuration suitable for hand-held operation. More specifically, the grip portion
46
has a substantially cylindrical configuration that has a diameter smaller than the housing
42
. The switch device
47
has an operation member
47
a
that can pivot about a pivotal axis
47
b
like a seesaw so as to open and close the switch circuit. In addition, the position of the switch device
47
is determined such that the operator can press either side of the operation member
47
a
with respect to the pivotal axis
47
b
so as to turn on and off the switch circuit while he grasps the grip portion
46
.
However, with the known power grinder
41
, the switch device
47
may be accidentally turned on an off, because the operation member
47
a
can be freely accessed.
SUMMARY OF THE INVENTION
It is, accordingly, one object of the present invention to teach power tools having improved switch devices, in which accidental switching operations can be reliably prevented.
According to the present invention, a power tool is taught that includes a motor and a switch device for starting and stopping the motor. The switch device preferably includes an operation member and an on-operation prevention device. The operation member can pivot about a pivotal axis from an on position to an off position and has an on-operation arm and an off-operation arm on either side of the pivotal axis for operation by an operator. The on-operation prevention device preferably serves to prevent the operation member from moving from the off position to the on position.
Therefore, the operator cannot turn on the switch device unless the on-operation prevention device has been moved to a position that permits the operation member to move from the off position to the on position. As a result, switch device can be reliably prevented from accidentally or unintentionally being turned on.
In one representative embodiment, the on-operation prevention device includes an on-operation prevention member that can move between an on-operation prevention position and a releasing position. The on-operation prevention member substantially covers the on-operation arm of the operation member when the on-operation prevention member is in the prevention position and substantially uncovers the on-operation arm when the on-operation prevention member is in the releasing position. Therefore, the on-operation arm can be reliably prevented from being accessed by the operator when the on-operation arm is in the on-operation prevention position.
Preferably, the on-operation prevention member can move from the on-operation prevention position to an on-operation position via the releasing position so as to move the operation member from the off position to the on position by means of the on-operation arm. Therefore, the on-operation prevention member can be operated to release its on-operation prevention function and then to turn on the switch device. As a result, the switch device can still be conveniently operated, despite the incorporation of the on-operation prevention device.
In addition, preferably, the power tool further includes a biasing member for applying a first biasing force to move the on-operation prevention member from the on-operation position to the releasing position and for applying a second biasing force to move the on-operation prevention member from the releasing position to the on-operation prevention position. Therefore, when the operator releases the on-operation prevention member after turning on the switch device, the on-operation prevention member can automatically return to on-operation prevention position. As a result, the operability can be improved.
Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.
REFERENCES:
patent: 4002874 (1977-01-01), Brown
patent: 4598182 (1986-07-01), Breslin
patent: 4910365 (1990-03-01), Kuo
patent: 5045648 (1991-09-01), Fogleman, Sr.
patent: 5047598 (1991-09-01), Osika et al.
patent: 5723833 (1998-03-01), Thrasher
patent: 2315841-B2 (1974-10-01), None
patent: 8514075-U1 (1985-06-01), None
patent: 4443797-A1 (1996-06-01), None
Catalog page—1988 Ackermann+Schmitt “Elektrowerkzeuge”.
Kimata Hirokazu
Sugiura Shin
Dennison, Scheiner Schultz & Wakeman
Friedhofer Michael
Makita Corporation
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