U.S. patent number 3,698,203 [Application Number 05/112,559] was granted by the patent office on 1972-10-17 for consistency control for slush freezer.
This patent grant is currently assigned to Stoelting Brothers Company. Invention is credited to Carl R. Stoelting.
United States Patent |
3,698,203 |
Stoelting |
October 17, 1972 |
CONSISTENCY CONTROL FOR SLUSH FREEZER
Abstract
Liquid feeds from the upper reservoir to the lower refrigerated
chamber where it is frozen on the walls. The scrapers and blades in
the lower chamber scrape ice from the walls and keep the liquid/ice
mix agitated. The slush is drawn off to be served. As the ice
content increases, the load on the scraper drive increases. When
the desired consistency is reached, the control shuts down the
refrigeration. The control responds to torque and requires a
sustained torque for a predetermined period to respond and shut
down the compressor. The compressor is not restarted until the
torque has dropped to a predetermined lower value.
Inventors: |
Stoelting; Carl R. (Kiel,
WI) |
Assignee: |
Stoelting Brothers Company
(Kiel, WI)
|
Family
ID: |
22344580 |
Appl.
No.: |
05/112,559 |
Filed: |
February 4, 1971 |
Current U.S.
Class: |
62/136;
318/475 |
Current CPC
Class: |
G05D
24/02 (20130101); A23G 9/228 (20130101) |
Current International
Class: |
A23G
9/04 (20060101); A23G 9/22 (20060101); G05D
24/02 (20060101); G05D 24/00 (20060101); F25c
007/10 (); G05d 024/02 () |
Field of
Search: |
;62/136,233 ;73/59
;137/92 ;318/475,476 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wayner; William E.
Claims
I claim:
1. A slush machine including
a chamber adapted to contain liquid to be frozen to the consistency
of slush,
a refrigeration system including a compressor and an evaporator
surrounding the chamber for freezing liquid on the chamber
walls,
a scraper rotatably mounted in the chamber to scrape ice from the
chamber walls and including agitator blades,
a motor driving the scraper whereby the torque on the motor is an
indicia of the consistency of the slush,
means responsive to an uninterrupted sustained torque of
predetermined magnitude for a predetermined period of time to stop
the compressor,
and means responsive to lower predetermined torque for any period
of time to start the compressor.
2. A machine according to claim 1 in which the motor is mounted for
rotation relative to the machine and including means biasing the
motor to a first position corresponding to low torque, the torque
load on the motor tending to rotate the machine against the bias of
the biasing means.
3. A machine according to claim 2 in which the means to stop the
compressor includes timing means which operates only while the
predetermined torque obtains and which cancels the accumulated time
if the torque falls below the predetermined magnitude before
reaching said predetermined period.
4. A machine according to claim 3 in which the means for starting
the compressor includes a switch which is actuated when the motor
is in said first position,
said motor moving to a second position in response to torque of
said predetermined magnitude,
and a second switch actuated when the motor is in said second
position to energize the timing means.
5. A machine according to claim 4 in which said timing means
operates to stop the compressor and to cancel the accumulated time
in the timing means whereby the compressor may be restarted with no
time delay.
Description
BACKGROUND OF INVENTION
The most effective control for slush machines has heretofore
employed a drive motor which was rotatably mounted so the motor
casing rotated in response to increasing torque. The motor was
biased in one direction and rotation of the casing was resisted by
a shock absorber. Therefore, momentary increases in torque had no
effect. The greater the damping by the shock absorber, the greater
the time delay but the delay worked in both the torque increasing
and decreasing directions. And, from a practical matter, the time
delay available left something to be desired. Further, as the
torque gradually increased with interspersed shock loads, the motor
would work towards the shut-down position so that only a very short
time at maximum torque was required to initiate shutdown.
SUMMARY OF INVENTION
The present device does not start measuring the delay period until
the desired torque is reached and at that time the time delay
starts. Any decrease in torque below the set level will cancel the
accumulated time and require starting the period over again.
Therefore, there must be a sustained torque for a given period.
After the prescribed time delay, the refrigerant compressor shuts
down and can be restarted only after the torque has fallen to a
prescribed low value. With the positive control over the time
delay, the quality of the slush product is improved.
DESCRIPTION OF DRAWINGS
FIG. 1 is a vertical section through a slush machine to give the
environment of the control.
FIG. 2 is a perspective view of the motor and control switches.
FIG. 3 is a simplified schematic wiring diagram showing the
principles of the control.
DESCRIPTION OF PREFERRED EMBODIMENT
The slush machine shown in the drawings includes a cylinder 10
having an upper reservoir 12 and a lower freezing chamber 14. The
chambers are separated by a divider plate 16 which does not have a
tight fit to, therefore, allow liquid to flow from the upper
chamber to the freezer chamber to maintain the freezing chamber
full. The refrigerated or freezer chamber is surrounded by coils 18
which constitute the evaporator of a refrigeration system. The
chamber is provided with a central post 20 which extends up through
the chamber and, in effect, provides a standpipe preventing liquid
flowing out of the freezer chamber. The drive shaft 22 extends from
the lower end where it is guided in bushing 24 to the upper end
where it is connected to the agitator shaft 26 which extends back
down into the refrigerated chamber with its lower end guided on
bushing 28. The agitator shaft carries the scraper blades 30 and
the mixing blades 32 which function to scrape the ice from the cold
wall and move the ice particles upwardly in the refrigerated
chamber. The product is dispensed through the valve assembly 34.
For draining purposes a lower valve 36 is provided.
At the bottom of the machine there is an electric motor 38 which
drives shaft 22 through reduction gearing in housing 40. The
housing is supported on bearing 42 so that the motor and reduction
gearing is rotatable relative to the slush machine. FIG. 2 shows
the manner in which the motor and gear assembly is biased clockwise
by spring 44 which is compressed between the bushing 45, anchored
to the machine frame by lug 47, and the end of rod 49 connected to
arm 46 extending from the mounting plate 48. The mounting plate is
provided with two switch actuating arms 50,52. The bias, therefore,
acts to urge the motor in a direction whereby the arm 50 will
contact the plunger of switch S.sub.1. The motor stub 54 connects
into the bottom of the shaft 22. Shaft 22 turns the scraper and
blades and increasing consistency of the slush in the refrigerated
chamber will act to increase the torque load on the motor whereby
the motor will tend to rotate as the load increases. This will move
the actuating arm 50 away from switch S.sub.1 and eventually bring
actuating arm 52 into contact with switch S.sub.2 when a
predetermined load is reached as determined by the spring
characteristics. This is utilized to derive the control function to
obtain and maintain the desired consistency in the slush. FIG. 3
shows a simplified schematic of the control system.
As may be seen in the schematic, when the on-off switch is closed,
the motor is energized and the mixing blades and scraper are placed
into operation. These will continue in operation so long as the
slush machine is in use. Due to the action of the bias spring on
the motor mount, the normally open switch S.sub.1 will be closed.
This will cause relay No. 1 to be energized through the normally
closed time delay switch S.sub.3 which is operated by relay No. 2.
Energization of relay No. 1 will close normally open switches
S.sub.4 and S.sub.5. Closure of switch S.sub.5 puts the
refrigeration compressor 56 across the line L.sub.1 ,L.sub.2 and
starts the freezing operation. Closure of switch S.sub.4 puts a
shunt around switch S.sub.1 so that the compressor 56 will continue
in operation after switch S.sub.1 opens by reason of the torque
load increasing slightly and the actuating arm 50 moving away from
switch S.sub.1.
With switch S.sub.4 closed there is a voltage supply to the
resistor R and the silicone controlled rectifier SCR which is
initially in its non-conducting state. The voltage supplied through
the dropping resistor R tends to build a charge on the capacitor C
but since switch S.sub.2 is closed the charge cannot build up, the
charge being leaked off to ground.
After the torque increases sufficiently for the motor to rotate
against the spring load to open the normally closed switch S.sub.2,
the charge can start building up on the capacitor and will do so at
a rate determined by the RC time factor of the components.
Desirably in about 75 seconds the charge on the capacitor and,
hence, at junction 58 will build up to the breakdown voltage of
neon bulb NE whereupon the neon will trigger the SCR to the
conductive state. This, in turn, will energize relay No. 2 which
will open switch S.sub.3. This will de-energize relay No. 1 and
open switches S.sub.4 and S.sub.5 which stops the compressor and at
the same time takes away the voltage supply to the timing circuit
RC. At this point the compressor is stopped and cannot be restarted
until the torque drops down low enough for switch S.sub.1 to be
reclosed which would then provide voltage to relay No. 1 through
switch S.sub.3 which has reclosed since the voltage has been
removed from relay No. 2 and it has gone back to its normally
closed state.
With this circuit arrangement it is necessary that the torque
continue at a predetermined high value for an uninterrupted time
delay period which, as stated, is preferably about 75 seconds.
Should there be any momentary decrease in the torque, the motor
mount would swing away from switch S.sub.2 permitting the switch
S.sub.2 to close and thereby ground the charge on the capacitor.
This, then, means that subsequent reopening of switch S.sub.2 in
response to the high torque will require initiation of the entire
time delay period again. This system, therefore, is not additive of
the periods that the torque may be above the predetermined high
torque. The reason that the additive feature is not desirable is
that as the ice builds up and the desired consistency is
approached, there may be lumps or hard spots in the ice which cause
momentary excursions in the torque load which are not truly
indicative of the consistency. All other systems heretofore
proposed for control of the slush consistency have, in effect, been
additives. This statement would include those systems which use
shock absorbers in controlling the movement of the motor. Those
systems had no way to, in effect, cancel out the effect of
momentary excursions in torque. The present system which requires a
sustained torque in excess of the predetermined high gives a more
accurate indication of the consistency. Once the refrigeration
system is shut down, the consistency has to be reduced to that
which permits reclosure of switch S.sub.1. If there is a period of
heavy draw resulting in very rapid reduction in the consistency,
this system will go back into operation much quicker than any of
the prior devices which required a time delay subsequent to
stopping the compressor. There is no fixed time delay with this
arrangement and restarting of the compressor is dependent strictly
upon consistency of the product.
* * * * *