Refrigeration – Time or program actuator
Reexamination Certificate
2001-12-14
2004-09-21
Ford, John K. (Department: 3753)
Refrigeration
Time or program actuator
C062S303000, C165S232000, C165S095000, C165S097000
Reexamination Certificate
active
06792769
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
This invention relates generally to a refrigeration system and particularly to a system for maintaining the condenser in a clean, dirt-free and lint-free condition.
Refrigeration systems which include a compressor, a condenser coil, and an electric motor driven fan for blowing air on the condenser coil suffer from reduced efficiency as the condenser coil collects dirt and lint over time. Because of this reduced efficiency it is necessary to subject the condenser coils to periodic cleaning resulting in down time of the system and in some cases costly repairs.
Various cleaning systems have been used in an attempt to obviate this problem. In particular, attempts have been made to eliminate the collection of lint and dirt resulting from the continuous blowing of air in one direction over the condenser by reversing the direction of the air stream over the condenser to blow collected lint and dirt off the condenser. The patents discussed below which relate to this problem are incorporated by reference herein.
An early patent which utilizes this principle of air stream reversal is U.S. Pat. No. 1,967,019 which discloses a fan arranged to blow cooling air through a condenser. Reversal of the fan motor, a single phase induction motor, is accomplished by changing polarity of the current in the starting winding. A solenoid pawl and cam arrangement is used to operate the switching. The solenoid operates a reversing switch and is actuated by energization of the compressor motor.
U.S. Pat. No. 2,525,462 discloses air flow reversal through a condenser in a refrigerator which is accomplished by a switching arrangement controlled by a modified compressor motor circuitry so that the fan direction is reversed each time the refrigerating unit stops and starts so that the fan operates in reverse when the refrigerating unit is idle. U.S. Pat. No. 3,344,854 discloses an anticlog device for automobile radiators which provides a movable endless belt screen such that foreign matter deposited on the screen when the belt is on to one side of the radiator is blown off the screen when the belt is moved to the other side of the radiator. U.S. Pat. No. 5,050,667 discloses a ventilation system in which a fan is pivotally mounted in a duct for rotation from a first position blowing air out of one end of the duct to a second position blowing air out of the other end of the duct. U.S. Pat. No. 5,226,285 discloses a self-cleaning fan assembly in which a reversible fan is located between two condensers and reversal is effectuated by means of pressure switches so that an increase in refrigerant flow reverses the rotation of the fan motor. These systems tend to be complicated, to operate at a constant cleaning speed and suffer from a lack of control of the operation and cleaning speed and operate in reverse for relatively uncontrolled time periods. In addition, these system do not offer flexibility in the choice of cleaning duty cycles, choice of fan speed in cleaning cycles, and require fairly complicated electromechanical devices which reverse air flow to the detriment of equipment reliability.
The present reversible fan arrangement solves these and other problems in a manner not disclosed by the known prior art.
SUMMARY OF THE INVENTION
This invention provides a condenser cleaning system in which the fan runs continuously for long periods at one speed in one direction during a normal operating cycle and intermittently for short periods in a reverse direction during a cleaning cycle.
This cleaning system for the condenser of a refrigeration unit comprises a compressor including a motor, a condenser, a cooling fan including a motor and a fan blade; and control means for running the fan motor drive system at a first preselected speed in a forward direction to direct air toward the condenser for a first determined period of time and in a reverse direction to direct air away from the condenser at a second selected speed for a second predetermined period of time, the speed and the time periods being effective to prevent formation of lint on the condenser.
It is an aspect of this invention to provide that the first selected speed is less than the second selected speed in one embodiment of this invention.
It is another aspect of this invention to provide that the first predetermined time period is longer than the second predetermined time period.
It is still another aspect of this invention to provide that the fan is continuously run at the lower speed and the motor drive system reversed several times a day to run at the higher speed in the opposite direction.
It is yet another aspect of this invention to provide that the first selected speed is about 1500 rpm during normal operating cycles and the second selected speed is about 2000 rpm during cleaning cycles.
It is an aspect of this invention to provide that the reversing motor drive system is powered directly off terminals associated with the compressor motor.
It is yet another aspect of the invention to provide that the control means includes a timer.
It is another aspect of the invention to provide that the timer causes the motor drive system to run in the reverse direction for about 14 minutes after every 8 hours of compressor running time.
It is still another aspect of the invention to provide that the motor drive system includes a solid state commutated (SSC) direct current motor in one embodiment of this invention.
It is an aspect of this invention to provide that, in the case of the SSC motor, the first selected speed is less than the second selected speed.
It is another aspect of this invention to provide that, in the case of the SSC motor, the forward speed is about 1500 rpm and the reverse speed is about 2000 rpm.
It is an aspect of this invention to provide that the solid state commutated motor and the timer are electrically connected to the terminals of the compressor motor.
It is another aspect of this invention to provide that the motor drive system includes a reversible permanent split capacitor (RPSC) ac induction motor in another embodiment of this invention.
It is yet another aspect of this invention to provide that, in the case of the reversible permanent split capacitor (RPSC) motor, the first selected speed and the second selected speed are equal.
It is still another aspect of this invention to provide that, in the case of the RPSC motor, the forward speed and the reverse speed are about 1500 rpm.
It is an aspect of this invention to provide a kit for retrofitting a refrigerator unit of the type comprising a compressor, a condenser and a motor and a fan blade, with a condenser cleaning system, the kit comprising a replacement reversible condenser fan motor; control means for running the replacement motor at a first selected speed to direct air toward the condenser for a first predetermined period of time, and in a reverse direction of the motor to direct air away from the condenser at a second selected speed for a second predetermined period of time, the speed and the time periods being effective to prevent formation of lint, the control means including a timer.
It is another aspect of this invention to provide that the kit reversible motor is a solid state commutated motor.
Another aspect of this invention is to provide that the kit reversible motor is a reversible permanent split capacitor motor.
It is an aspect of this invention to provide a method of retrofitting a refrigerator unit, of the type comprising a compressor, a condenser, a condenser fan having an existing motor and a blade, with a condenser cleaning system including a reversible condenser fan motor and a timer. The method comprises the steps of disconnecting the power supply to the refrigerator unit; disconnecting the existing condenser fan motor leads from the compressor; removing the condenser fan motor; removing the condenser fan blade; installing the condenser fan blade in the same direction on the reversible condenser fan motor; installing the reversible condenser fan m
Ford John K.
Polster Lieder Woodruff & Lucchesi L.C.
True Manufacturing Co. Inc.
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