Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
1999-04-05
2001-03-27
Paladini, Albert W. (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C361S170000, C361S189000
Reexamination Certificate
active
06208042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to safety devices for electrical appliances, tools, and the like and, more particularly, but not by way of limitation, to a safety device that will prevent activation of an electrical appliance, tool, and the like upon the application or reapplication of power when an activation switch of the electrical appliance, tool, and the like has been left in a closed position.
2. Description of the Related Art
Electric appliances, tools, and the like include a power cord that inserts into a power delivery device which may be a generator but is most likely a standard AC outlet. Electrical appliances, tools, and the like include an activation switch that, when closed, permits the delivery of power to the electrical appliance, tool, and the like. If this activation switch is closed when the electrical appliance, tool, and the like is “plugged in”, the electrical appliance, tool, and the like will immediately power on. Similarly, when the activation switch remains closed after a power failure, the electrical appliance, tool, and the like will power on upon the reapplication of power. The unwanted activation of an electrical appliance, tool, and the like is highly undesirable because, at a minimum, property damage could result or, more importantly, dismemberment or even a death could occur.
Various devices have been designed to prevent inadvertent operation of an electric appliance, tool, and the like. These devices operate adequately, but still suffer disadvantages. Certain of the devices will not prevent inadvertent operation under some conditions, while others are expensive and complicated to manufacture. Accordingly, a safety device that will prevent inadvertent operation of electric appliances, tools, and the like under all conditions, yet is inexpensive and easy to manufacture is a highly desirable improvement over present safety devices.
SUMMARY OF THE INVENTION
In accordance with the present invention, an anti-reactivation safety device for an electrical load bearing device, includes a power input line for delivering current from a power source across the anti-reactivation device to the load bearing device. A current transfer switch positioned along the power-input line is provided. The current transfer switch includes a switch such as a thyristor or a relay for engagement in an open position and in a closed position to thereby control the flow of current across the power input line. The switch is normally in an open position.
The anti-reactivation safety device further includes a power return line. A latch circuit, linked with the power return line and linked with the current transfer switch, is provided for biasing the switch in an open position and in a closed position. The latch circuit includes a current divider. The anti-reactivation safety device includes a load sensor circuit for selectively engaging the latch circuit. The load sensor circuit includes a first line linked with the current transfer switch and a second line linked with the current divider of the latch circuit and linked with the power return line. In particular, the load sensor circuit may include an optoisolator for transferring current from the first line to the second line.
The anti-reactivation safety device may further include a control voltage step down and rectifier unit positioned along the power-input line for providing DC power to the latch circuit, the current transfer switch, and the load sensor. The control voltage step down and rectifier unit includes a voltage regulator for providing regulated DC power therefrom.
Accordingly, the load-bearing device includes a load bearing switch for selectively engaging the load-bearing device in an on position and in an off position. The load-bearing switch, while initially in an on position, completes a circuit provided by the anti-reactivation safety device, via the power input line and the power return line. As such, current flows across the power input line to the load sensor circuit, transfers from the first line to the second line, and flows across the current divider of the latch circuit. The current divider sufficiently draws current away from the latch circuit and the switch of the current transfer switch to render the switch in an open position, thereby safely preventing the load bearing device from powering up.
While initially in an off position, the load bearing switch does not complete a circuit provided by the anti-reactivation safety device, via the power input line and the power return line. As such, current only flows across the power input line to the latch circuit. The latch circuit receives sufficient current to bias the switch of the current transfer switch in a closed position, thereby enabling the load bearing device to power up upon election thereafter.
In one embodiment, an anti-reactivation safety device is integrally linked with a load bearing device, thereby defining a component of the load bearing device. Alternatively, one embodiment contemplates an anti-reactivation safety device as an independent unit. Accordingly, the independent anti-reactivation safety device includes a plug linked with the power input line and with the power return line for extracting power from a power source through the anti-reactivation safety device. The independent anti-reactivation safety device further includes a load-interface outlet linked with the power input line and with the power return line for facilitating connection with a load bearing device therefrom.
It is therefore an object of the present invention to provide an anti-reactivation safety device that will prevent activation of an electrical load bearing device upon the application or reapplication of power when an activation switch of the electrical load bearing device has been left in a closed or “on” position.
Still other objects, features, and advantages of the present invention will become evident to those skilled in the art in light of the following.
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Makay Christopher L.
Paladini Albert W.
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