Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
1999-09-07
2001-04-24
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C307S038000, C307S039000, C307S125000
Reexamination Certificate
active
06222285
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to power control circuits and, more particularly, to such circuits that may be used to control current consumption of a vacuum cleaner when operated in conjunction with a power tool.
BACKGROUND ART
It is often desirable when operating two motors simultaneously to provide for the automatic activation (or deactivation) of one of the motors, referred to as the secondary load, in response to the activation (or deactivation) of the other motor, referred to as the primary load. For example, operation of a vacuum cleaner motor (hereinafter “vacuum motor”) has been conditioned upon the operation of a power tool. In this way, the vacuum motor may be automatically activated to collect particulate matter generated by the power tool. Such conditioned operation has been provided by a control circuit that generally includes a current sensor to detect current flowing to the power tool (see, e.g., Samann U.S. Pat. No. 5,120,983). The current sensor, in turn, drives a triac or other switching element disposed between the power supply and the vacuum motor to permit current flow thereto.
It is also desirable to operate the vacuum motor independently of the power tool. Accordingly, such control circuits have included a three-position switch to determine whether the vacuum motor is to be inactive (“OFF”), operated independently from the power tool (“ON”), or activated in coordination with the power tool (“AUTO”). See Robitaille et al. U.S. Pat. No. 5,747,973. However, having to toggle between the three switch positions may be both inconvenient and confusing for a user of the vacuum cleaner.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a sensing circuit is useful with a power outlet and a device having power supplied thereto via the power outlet. The sensing circuit includes a generator that develops a first signal and a transmitter coupling the generator to a first terminal of the power outlet to supply the first signal thereto. The sensing circuit further includes a detector coupled to a second terminal of the power outlet. The detector is tuned to the high frequency of the first signal to develop a second signal indicative of whether the device is coupled to the power outlet.
In a preferred embodiment, the generator includes an oscillator and the transmitter includes a transformer coupling the oscillator to the first terminal of the power outlet. The detector may include a bandpass-tuned amplifier tuned in accordance with the high frequency of the first signal. Alternatively, the detector includes a receiver tuned in accordance with the high frequency of the first signal and a comparator coupled to the receiver to develop the second signal. The receiver may include an AC-to-DC converter that develops a DC signal supplied to the comparator for comparison with a threshold voltage.
According to another preferred embodiment, the sensing circuit is useful in combination with a load having the power outlet disposed thereon and a regulator coupled to the detector and enabled by the second signal to condition operation of the load on operation of the device. The load preferably includes a two-position switch that controls whether power is supplied to the load and the device. The regulator preferably includes a current sensor coupled to the power outlet for developing a third signal indicative of whether power is being supplied to the device. The device may include an auxiliary power tool and the power outlet may be disposed on a vacuum cleaner. The sensing circuit may be useful in further combination with a two-position switch such that the two-position switch couples the second terminal of the power outlet to a high voltage line of a power source.
In accordance with another aspect of the present invention, a control circuit controls operation of a first load in connection with operation of a second load powered via a power outlet. The control circuit includes a signal generator and a detector coupled to the power outlet to develop a first signal indicative of whether the second load is coupled to the power outlet. The control circuit further includes a sensor coupled to the power outlet to develop a second signal indicative of whether power is supplied to the second load and a switch circuit coupled to the first load and responsive to the first and second signals to provide for operation of the first load conditioned upon operation of the second load.
In a preferred embodiment, the power outlet has a first terminal coupled to the signal generator and a second terminal coupled to the detector. The control circuit preferably further includes a transmitter such that an oscillator of the signal generator is coupled to the first terminal of the power outlet by the transmitter.
According to another preferred embodiment, the switch circuit includes a triac coupled to the first load and a triac triggering circuit responsive to the second signal. The triac triggering circuit preferably includes a phase control circuit to adjust power supplied to the first load. The control circuit still further preferably includes a two-position switch that couples the power outlet and the first load to a power source when disposed in a closed position. The switch circuit may allow power to be supplied to the first load when the two-position switch is disposed in the closed position and the first signal indicates the second load is not coupled to the power outlet.
The switch circuit preferably does not allow power to be supplied to the first load when the two-position switch is disposed in the closed position, the first signal indicates that the second load is coupled to the power outlet, and the second signal indicates that current is not flowing to the second load.
The control circuit still further preferably includes a sensor that develops a third signal indicative of a parameter of the electrical energy supplied to at least one of the first and second loads. The phase control circuit variably adjusts power supplied to the first load in accordance with the third signal when the two-position switch is disposed in the closed position, the first signal indicates that the second load is coupled to the power outlet, and the second signal indicates that current is flowing to the second load.
In accordance with yet another aspect of the present invention, a vacuum cleaner is useful in conjunction with a power tool. The vacuum cleaner includes a power outlet configured to supply power to the power tool and a control circuit coupled to the power outlet. The control circuit, in turn, includes a generator coupled to a first terminal of the power outlet that develops a first signal and a detector coupled to a second terminal of the power outlet and tuned in accordance with the high frequency of the first signal to develop a second signal indicative of whether the power tool is coupled to the power outlet. The control circuit further includes a switch and a regulating circuit responsive to the second signal and the state of the switch to control power supplied to the motor of the vacuum cleaner.
According to a preferred embodiment, the switch includes a two-position switch and the regulating circuit supplies a predetermined maximum magnitude of power to the motor when the two-position switch is disposed in a closed position and the second signal indicates that the power tool is not coupled to the power outlet. The regulating circuit preferably includes a phase control circuit.
According to another preferred embodiment, the control circuit further includes a transmitter that couples the generator to the first terminal of the power outlet. The transmitter preferably includes a transformer and the generator includes an oscillator coupled to the transformer.
The detector may include a bandpass-tuned amplifier tuned in accordance with the high frequency of the first signal and the detector preferably further includes an AC-to-DC converter coupled to the bandpass-tuned amplifier and a comparator coupled to the AC-to-DC converter. The comparator is pref
Baer Mark E.
Crevling, Jr. Robert L.
Haley Edward M.
Robitaille James M.
Ballato Josie
Marshall O'Toole Gerstein Murray & Borun
Rios Roberto
Shop Vac Corporation
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