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Drawing from US Patent 5038091 |
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Electronic control for an appliance |
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| Publication Date |
August 6, 1991 |
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| Filing Date |
August 23, 1989 |
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| Parent Case |
This application is a continuation-in-part of two applications both
entitled "Electronic Control For an Automatic Washing Machine With a
Reversing PSC Motor" having U.S. Ser. Nos. 392,473 and 392,368 both filed
Aug. 11, 1989 by the same inventor as in the present application. Both
parent applications disclose control circuitry and logic similar to that
of the present application.
BACKGROUND OF THE PRESENT INVENTION
The present invention is directed to a control for an appliance and more
particularly to an electronic control for a compactor having a split-phase
induction drive motor.
In a conventional refuse compactor, a ram is driven into a refuse disposal
compartment to compact trash disposed therein and continues advancing
until the motor stalls. The ram is subsequently driven out of the refuse
disposal compartment. Various drive mechanisms for refuse compactors are
disclosed in U.S. Pat. No. 3,353,478 to Stephen Hawkin; U.S. Pat. No.
3,732,805 to Jerry W. Moon; U.S. Pat. No. 3,772,987 to Charles R. Difley;
U.S. Pat. No. 3,839,954 to Joseph F. Burgeois; U.S. Pat. No. 3,921,515 to
William A. Eckerle; U.S Pat. No. 4,007,678 to John K. C. Gustavson, et.
al.; U.S. Pat. No. 4,188,877 to Aman U. Khan; and U.S. Pat. No. 4,565,125
to Aman U. Khan.
Various mechanical and electronic controls have been designed for
regulating the operation of the drive mechanism of a trash compactor. For
example, Einar O. Engebretsen shows a compactor cycle control in U.S. Pat.
No. 3,962,964 wherein a dwell period is provided at the end of the
compaction cycle.
U.S. Pat. No. 3,855,919, Richard W. Potter shows a control system for a
compacting apparatus including signal lamps for showing the direction of
movement of the ram. The apparatus includes a time delay circuit for
automatically shutting down the compactor when any of the operational
cycles thereof continues beyond a predetermined time limit.
In U.S. Pat. No. 3,398,433 of Charles J. Borum, a trash compactor with a
clock timer control is disclosed for providing an extended delay period
after a compacting stroke. The clock is provided to permit the automatic
extended compaction at a period of time during the day when the compactor
is unlikely to be in use for a substantial length of time. The control
operates the ram independently of any manual initiation of the apparatus
to effect the compacting stroke at the predetermined time and to cause the
stopping of the ram for the delay period during that independently
initiated compaction stroke. In U.S. Pat. No. 3,543,676 of Gordon H.
Brown, another refuse compactor is shown having control circuitry for
regulating the operation of the compactor automatically.
Michael J. Bottas et al, in U.S. Pat. No. 3,613,560, show a refuse
compactor including a control circuit which permits operation of the ram
only when the drawer is substantially in the compacting position. The
control circuit includes a tilt switch which is arranged in the circuit to
permit reverse withdrawal movement of the ram by depression of a manually
operable pushbutton.
Jerome F. Stratman et al, in U.S. Pat. No. 3,821,927 show a refuse
compactor control system having a lower limit switch connected in parallel
with a centrifugal switch.
In U.S. Pat. No. 3,831,513 of Philip Tashman, a portable solid waste
compactor is shown having a compacting ram which has a stroke varying with
the reaction force of the waste material being compacted therein. An
interlock associated with the ram prevents operation of the compactor upon
removal of the container in which the refuse is compacted. A guard gate is
automatically closed across the refuse chute opening upon downward
compacting movement of the ram to prevent injury to the operator's hand.
If the guard gate is prevented from closing by an obstruction, a switch
causes immediate reversal of the ram to its uppermost position.
In U.S. Pat. No. 4,062,282, Samuel Jacob Miller et al show a refuse
compactor having a tilt switch for terminating operation of the compacting
ram in the event of a preselected tilt movement of the receptacle during
the compacting operation. Means are provided for preventing movement of
the receptacle sufficient to open the receptacle safety switch during the
compacting operation thereby preventing discontinuation of energization of
the ram motor during the compaction cycle which could immobilize the
compactor apparatus in midcycle.
While these prior art control patents teach that it is desirable to monitor
performance of a compactor to determine, for example, when compaction is
complete or when the bag is full, the prior art uses multiple sensors,
typically mechanical sensors, to monitor the operation. Furthermore, the
maximum torque applied is limited to the main winding breakdown torque.
A more generic control system for various appliances having an AC induction
drive motor, including examples of an automatic washing machine, a dryer,
an air conditioner, a refrigerator, and a dishwasher, is shown in my U.S.
Pat. No. 4,481,786, assigned to the assignee of the present invention.
That control system employs a ferrite core sensor having a primary winding
that is formed of two turns of the drive motor's run winding, the sensor
having a single turn secondary winding that forms a sense winding coupled
to a motor phase monitoring circuit. The sense winding provides a signal
representing a polarity change in the run winding current. The current
polarity change signal is used by the motor phase monitoring circuit to
provide a voltage compensated motor phase angle pulse to a microcomputer
for the appliance to control various operations of the appliance More
particularly, a digital representation of the motor phase angle pulse is
used by the microcomputer to monitor the starting of the drive motor by
detecting a characteristic decrease in the motor phase angle
representation. The motor phase angle representation is further used by
the microcomputer of an automatic washing machine to determine the
agitator torque which is in turn used by the microcomputer to
automatically control the water level of the washing machine. An average
motor torque number is also determined from the motor phase angle
representation wherein the average motor torque number is used to provide
an end of drain control for the washing machine.
While my prior patent application suggests that the control may be used to
control any AC induction motor controlling any appliance, including a
split phase induction motor controlling a trash compactor, the
applicability or desirability of such a control to the specific needs of a
compactor was neither addressed nor considered. The present invention is
directed to a control utilizing some of the teachings of my aforementioned
U.S. patent to a refuse compactor but applying a novel circuit and novel
logic to detect the onset of stalling as the ram compacts the refuse and
using that information to control the operation of a compactor in a novel
way.
SUMMARY OF THE INVENTION
The present invention provides a control for a split phase induction motor
that detects the onset of stalling and temporarily boosts the torque of
the motor in order to perform more work at precisely the time when the
motor is beginning to stall. In particular, the control provides more
torque to the ram of a refuse compactor at the time when the ram of the
compactor engages the refuse and begins to stall as a result of the
resistance of the refuse to compaction.
The present invention also provides a force level control for compactor
that permits manual selection from three different force levels which
result in three different compaction rates.
The preferred embodiment of the present invention provides a control for
refuse compactor with a split-phase induction drive motor. The control
includes a ferrite core sensor on the main winding of the drive motor
sampling circuitry sampling the lagging phase angle of the motor main
winding current at a predetermined sample rate through a refuse compaction
stroke, a selector for manually selecting high, medium or low compaction
force, a controller selectively operable to obtain medium force by
terminating the stroke when the compaction force exceeds the main winding
breakdown torque, a controller for selectively applying a high force by
selectively reactivating the start winding of the motor instead of
terminating the cycle, and a controller selectively operable to obtain a
low force by terminating the stroke of the ram when the phase sample falls
below a predetermined threshold level. The predetermined threshold level
for the low force cycle is preferably defined at the start of each cycle
by a locked rotor main winding phase sample acquired prior to starting the
motor
The present invention further provides a control for a refuse compactor
that monitors the phase angle of a motor winding and determines a no load
and a full bag condition.
In the preferred embodiment, the present invention provides a control for a
refuse compactor having a ram driven by a split phase induction drive
motor. The control includes sampling circuitry sampling the lagging phase
angle of the motor main winding current during the compaction stroke, a
controller detecting the onset of compaction from the lagging phase angle
information, such that a no load condition is detected by the failure to
detect compaction after a first predetermined time and such that a full
bag condition is detected by the detection of compaction by a second
predetermined time.
It is therefore the primary object of the present invention to provide a
reliable refuse compactor control for a refuse compactor with a
split-phase induction drive motor.
It is another object of the present invention to provide a compactor
control providing two or more force level selections to thereby allow the
user to control the approximate full trash bag weight.
It is still another object of the present invention to provide a control
for a refuse compactor that applies or selectively applies increased
torque and thereby provides increased compaction at the onset of
compaction than was previously available from the motor.
It is yet another object of the present invention to provide a control for
refuse compactor that detects the onset of compaction without the use of a
centrifugal switch.
It is another object of the present invention to provide a control for a
refuse compactor that monitors the characteristics of a motor winding to
determine the onset of compaction, as well as a no load and a full bag
condition.
It is a further object of the present invention to provide an electronic
control for a split phase induction motor that temporarily activates the
start winding of the motor up on the onset of a motor stalling condition
such as to boost the torque of the motor at the time of peak load on the
motor where the onset of stalling is detected by monitoring the lagging
phase angle of the motor main winding.
These and other objects, advantages and features of the present invention
will become apparent to those skilled in the art upon review of the
following description of the preferred embodiment in conjunction with the
drawings appended. |
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