Pushbutton hand dryer timer and method

Details Pushbutton hand dryer timer and method Pushbutton hand dryer timer and method

2000-02-07

2001-09-25

Jeffery, John A. (Department: 3742)

Electric resistance heating devices

Heating devices

Concentrated heated air stream

C219S492000, C219S507000, C034S563000, C200S0380FB, C200S0380FB

Reexamination Certificate

active

06295410

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to the field of appliance controls and, more particularly, to an improved pushbutton hand dryer timer.
BACKGROUND OF THE INVENTION
Timing mechanisms have been utilized for decades in the control of many different appliances. The present invention relates generally to electric dryers, and more particularly to a pushbutton hand dryer of the type commonly found in public rest rooms. With such a hand dryer, a user pushes a button or knob to start a drying cycle. During the drying cycle, a timing motor, a heater and a fan are turned on; and at the end of a drying cycle, as determined by the timing motor, the timing motor, heater and fan are automatically turned off. Such dryers must be simple, rugged and durable in construction and operate with great reliability over a long service life. To achieve such features, the hand dryer should have the fewest possible parts that operate in the simplest possible way.
As shown in
FIG. 6
, with known timer circuits, the heater H and fan motor FM are connected to the two non-neutral lines L
1
, L
2
of a 220 volt (“V”) source by a single switch S
1
. When the switch S
1
is open, one side of each of the heater H and fan motor FM is disconnected from one of the non-neutral lines L
1
; however, the other side of each of the heater H and fan motor FM remain connected to the other of the non-neutral lines L
2
. Therefore, any inadvertent electrical contact of the one side of the heater and/or fan motor to a ground, for example, the metal dryer housing or base etc., will result in 120 being applied thereto. Thus, the heater H and/or fan motor FM will be operated at half power. Such an inadvertent electrical contact with ground can result from a frayed, nicked or broken wire or other conductor accidently contacting a neutral or ground potential.
Therefore, there is a need to better isolate the heater and fan motor from the non-neutral wires of a power source.
SUMMARY OF THE INVENTION
The present invention provides an improved pushbutton hand dryer that reduces the probability of any inadvertent or uncommanded operation of the heater and fan motor. The improved pushbutton hand dryer reduces the chances that a frayed, nicked or broken wire or other electrical malfunction will result in the heater or fan motor operating at a reduced voltage. More specifically, the improved pushbutton hand dryer of the present invention provides an improved electrical isolation between the heater and fan motor and the non-neutral lines of a power source. Therefore, present invention has the advantage of providing a pushbutton hand dryer that operates more reliably with a longer service life.
In accordance with the principles of the present invention and in accordance with the described embodiments, the present invention provides a hand dryer operable with first and second nonneutral power wires having a voltage potential therebetween. The hand dryer includes a heater, fan motor and timer motor all rated to operate at the voltage potential. A first switch is operated by the timer motor and has a first side electrically connected to the heater and fan motor and an opposite side electrically connected to the timer motor and the first nonneutral power wire. A second switch is operated by the timer motor and has a first side electrically connected to the heater and the fan and timer motors and an opposite side electrically connected to the second nonneutral power wire.
In one aspect of the invention, the first switch includes first switch contacts that connect and disconnect the heater and fan motor respectively to and from the first nonneutral power wire, and the second switch includes switch contacts that connect and disconnect the heater and fan and timer motors respectively to and from the second nonneutral power wire. Thus, with two switches, the isolation of the heater and fan motor from the nonneutral wires is improved over hand dryers using only a single switch.
In a further embodiment of the invention, the first switch has an actuating arm switching a state of first electrical contacts at a consistent repeatable first time in response to operation of the timer motor, and the second switch has an actuating arm switching a state of second electrical contacts at a consistent repeatable second time in response to operation of the timer motor.
In one aspect of this further embodiment, the actuating arms are mechanically connected such that motion of the actuating arms causes the first switch to switch prior to the switching of the second switch. Therefore, the heater and fan motor will always be disconnected from the power source prior to disconnecting the timer motor, and both switches will always operate.
In another embodiment, the invention provides a method of operating a hand dryer in which a timer motor has a cam lobe initially engaged with an actuating arm of the first and second switches, thereby causing switch contacts to electrically disconnect the heater, fan motor and timer motor from the power source. The cam lobe is then disengaged from the actuating arm, thereby causing the first and second switches to electrically connect the heater, the fan motor and the timer motor to first and second nonneutral wires of the power source. Thereafter the timer motor moves the cam lobe into engagement with the actuating arm to operate the first switch and electrically disconnect the heater and fan motor from the first nonneutral wire. After that, the timer motor continues to move the cam lobe and actuating arm, thereby operating the second switch to electrically disconnect the timer motor, heater and fan motor from the second nonneutral wire.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description together with the drawings herein.


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