US3667244A

US3667244A - Control system for freezers

Info

Publication number: US3667244A
Application number: US102284A
Authority: US
Inventors: Walter L Hock; William E Meyers
Original assignee: Kraft Inc
Current assignee: Kraft Inc
Priority date: 1970-12-29
Filing date: 1970-12-29
Publication date: 1972-06-06
Anticipated expiration: 1989-06-06
Also published as: CA944968A

Abstract

The present invention is directed to a freezing system of the hot gas type and a control system therefor. The freezing system is particularly directed to the type wherein a single motor is used to drive a dasher for a mix pump or pumps. The control system of the invention includes timing devices for controlling the start-up and shut-down of the freezing system in accordance with a predetermined sequence.

Description

C United States Patent [151 3,667,244

Hock et al. 1 June 6, 1972 54] CONTROL SYSTEM FOR FREEZERS 3,059,444 10/1962 Bickel et a1. ..62/1 35 [72] Inventors: nalter L. Hock, Skokie, 1.; William E. Primary Examiner wmiam E Wayne,

Monroe Attorney-Anderson, Luedeka, Fitch, Even and Tabin [73] Assignee: Kraftco Corporation, New York, NY.

[57] ABSTRACT [22] Filed: Dec. 29, 1970 The present invention is directed to a freezing system of the [21] APPLNO'Z 102,284 hot gas type and a control system therefor. The freezing system is particularly directed to the type wherein a single 52 US. Cl ..62/136, 62/233, 62/352 motor is used to drive a flasher for a mix p p or p The 51 control system of the invention includes timing devices for [58] Field of Search ..62/136, 135, 233, 352 controlling the P and Shut-down of the freezing System in accordance with a predetermined sequence.

[56] References Cited 7 Claims, 2 Drawing Figures PATENTEDJUN 6 I972 SHEET 10F 2 INVENTORS Maze .4. //0cx MLLMM Mrg5 A W i -IW, 6%,

ATTYS.

CONTROL SYSTEM FOR FREEZERS The present invention relates generally to a freezing device, such as an ice cream freezer, and more particularly relates to an improved control system for freezing devices wherein hot refrigerant gas from the refrigerant system is automatically injected into the freezing device upon shut-down so as to instantly warm the contents of the freezing chamber.

At the present time, many continuous ice cream freezers utilize the so-called hot gas refrigeration system in which hot refrigerant gas is automatically injected into the evaporator of the freezing system upon shut-down to instantly warm the contents of the freezing chamber so as to substantially eliminate troublesome freeze-up of the freezing chamber. in hot gas refrigeration systems, hot refrigerant gas is injected into the evaporator of the freezing system when the freezing system is shut down. The hot gas vaporizes the liquid refrigerant remaining in the evaporator. The vaporized refrigerant is then returned to the compressor and condenser of the refrigerant system and is returned to a liquid state. The use of hot gas permits remote starting and stopping of ice cream freezers by merely pushing a button.

A refrigeration system of the hot gas type is fully described in U.S. Pat. No. 3,059,444 to Fay D. Bickel et a]. However, the control systems used to date for freezers using the hot gas principle have not been entirely satisfactory. For those types of freezers using a common motor drive for the dasher and mix pump, there is a tendency to produce soft and unusable ice cream when the freezing system is started after a shutdown.

Accordingly, it is a primary object of the present invention to provide a control system for continuous ice cream freezers of the hot gas type that will enable the freezing operation to be instantly started without the production of soft ice cream. It is another object of the present invention to provide an improved continuous ice cream freezer of the hot gas type that will substantially reduce the amount of re-run upon start-up. It is a further object of the present invention to provide a continuous ice cream freezer of the hot gas type that has an improved control system and permits starting and stopping of the freezer by merely pushing a button.

These and other objects of the invention will become more clear from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a diagrammatic presentation of a freezing system embodying the present invention; and

FIG. 2 is a diagram of a basic control circuit for the freezing system of the invention.

Generally, the present invention is directed to a freen'ng system of the hot gas type and a control system therefor. The freezing system includes a condenser, a receiver, an expansion device, an evaporator, which includes a freezing tube for congealing a product supplied thereto, and an accumulator. All of the components of the freezing system are connected in seriesflow relationship to form a refrigeration system. The freezing system also includes a dasher for agitating a product within the freezing tube and pumps for supplying a product to the freezing tube. The freezing system of the invention particularly is directed to the type wherein a single motor is used to drive the dasher and a mix pump or pumps. The control system of the invention includes timing devices for controlling the start-up and shut-down of the freezing system in accordance with a predetermined sequence.

More particularly, referring now to the drawings, as seen in FIG. 1, the principal components of the freezing system of the invention are illustrated. These components include a compressor 11, a condenser 13, a receiver 15, an accumulator l7 and an evaporator 19, all of the principal components being connected in series-flow relationship. The evaporator 19 includes a freezing tube 21, into which an ice cream mix is introduced for freezing. Liquid refrigerant flows from the receiver through duct 23 to an automatically controlled expansion valve 25, which may be of any conventional type. Valve 27 is controlled by solenoid 29, and is used to shut off the flow of liquid refrigerant through duct 23 as required.

The liquid refrigerant flows from the expansion valve 25 through duct 31, which is connected at its other end to jet injector 33. The jet injector 33 is located in accumulator 17 at a point below the liquid level that is maintained therein by float valve 35. Float valve 35 controls the flow of refrigerant into the accumulator through a line 36 connected with duct 23.

A duct 37 connected to the jet injector 33 carries the liquid refrigerant into the evaporator 19, and a return line 39 carries vaporized refrigerant from the evaporator 19 back to the accumulator 17 from where it is withdrawn by compressor 11 through suction line 41. The vaporized refrigerant is then compressed, condensed and again circulated through the system.

A back pressure regulator valve 43 is located in line 41 to maintain the desired pressure within the evaporator and thereby provide control of the freezing temperature. The regulator valve 43 variably restricts the amount of refrigerant gas flow in line 41 and thereby maintains the pressure in line 41 and the evaporator 19 at a desired value. The regular 43 may be of any suitable type; however, regulator 43 is preferably of a type that is controlled by a pilot valve 45 located in a line 46 which connects the control portion 47 of the regulator valve 43 with line 41 at a point upstream from the regulator valve 43. When pilot valve 45 is fully open, the control portion 47 of regulator valve 43 senses the full pressure of line 41 and acts to fully open regulator valve 43 and permit full flow of refrigerant gas through line 41 from evaporator 19, which results in maximum cooling of the refrigeration system. Pilot valve 45 is normally maintained in a partially open condition so as to restrict the pressure to the control portion 47 of regulator valve 43 and to thereby restrict and control flow of refrigerant gas through line 41 at less than maximum cooling. Regulator valve 43 may be fully closed by shutting off the flow of gas to the control portion 47 of valve 43. The flow of gas to the control portion 47 may be shut off by valve 48, which is controlled by solenoid 49;

Bypass line 50 is provided which routes the flow of refrigerant gas around pilot valve 45 so as to remove the function of pilot valve 45 as a control on the regulator valve 43. When bypass line 50 is open, the flow of gas to the portion 47 of regulator valve 43 is sufficient to cause regulator valve 43 to remain in a fully open position. Bypass line 50 is controlled by valve 51, which is actuated by solenoid 52.

Ice cream mix is supplied from a suitable source (not shown) and is pumped into the freezing tube 21 through a duct 53 by means of motor-driven mix pump 54. Air is incorporated into the mix to provide the desired amount of overrun through air line 55. The air is sucked into pump 54 from the atmosphere through an adjustable air valve (not shown). The flow of air through air line 55 is further controlled by valve 56, which is actuated by solenoid 57. Booster pump 58 may be used to feed ice cream mix through line 61 at a positive pressure to mix pump 54. A motor-driven dasher 59 constantly agitates the ice cream mix in the freezing tube 21 to provide uniform freezing. Dasher 59 and mix pump 54 are driven by a common motor 60.

Processed frozen ice cream is forced out of an outlet in the end of freezing tube 21 and into line 62. Throttle valve 63 regulates the flow of ice cream through line 62. Throttle valve 63 is air-controlled by controller 65. Controller 65 is actuated by pressure sensor 67 located in duct 53 which feeds ice cream mix from pump 54 to the freezing tube 21. The operation of throttle valve 63 will be more fully described hereinafter in connection with a discussion of the control system of the invention. Check valve 69 is in duct 53 to prevent ice cream from freezing tube 21 from backing up in duct 53 to pump 54 when the freezing-system is shut down.

The system as thus far described operates as follows: Liquid refrigerant is supplied from the high pressure side of compressor 11 to condenser 13 and receiver 15. The liquid refrigerant is expanded and cooled by expansion valve 25. The expansion valve 25 maintains the liquid refrigerant at a suitable operating pressure for the jet injector 33. Liquid refrigerant in passing through injector 33 withdraws additional refrigerant from accumulator 17. Liquid refrigerant is then directed against the heat exchange surfaces of the freezing tube 21 to cool the contents of the tube. As the refrigerant evaporates from the freezing tube 21, the vapor thus formed is returned through the duct 39 to the accumulator 17 where gas and entrained liquid within the gas are separated. The gaseous refrigerant is withdrawn from the accumulator 17 through the suction line 41 to the compressor 1 1 for recirculation through the system. Regulator valve 43-maintains the desired pressure and temperature in the evaporator 19. The desired pressure and temperature are set by manually adjusting pilot valve 45 which feeds a gas pressure signal to the control portion 47 of regulator valve 43.

The freezing system is alsoprovided with meanswhereby hot gas may be automatically injected into the evaporator 19 to warm the contents of the freezing tube 21 upon shutdown. in the hot gas portion of the free freezing system, warm, vaporized refrigerant from the high pressure side of compressor 11 is removed through a duct 71 that leads directly to the evaporator 19. The admission of the hot gas into the evaporator 19 is controlled by valve 73 which is actuated by solenoid 75. To warm the contents of the freezing tube quickly, the pressure setting of the regulator valve 43 is changed to allow a higher than normal operating pressure so as to build up the pressure of the hot gas in the evaporator 19 rapidly. The pressure setting of regulator valve 43 is changed by providing in duct 46 a valve 48 controlled by a solenoid 49 which shuts ofi theflow of gas through the pilot valve 45 and allows a secondary pilot 77' to control regulator valve 43. The secondary pilot 77 is set so that the regulator valve 43 remains closed until valve 73 is closed to stop the admission of hot gas, or until apredetermined higher pressure of approximately 60 psig is reached. A pressure limit switch 79 is provided to close the hot gas valve 73 when the pressure reaches a predetermined value of about 40 psig. The normal mode of operation of the hot gas valve in the control system of the present invention is such that the pressure limit switch 79 is not used to inactivate the hot gas valve 73, as will be explained more fully hereinafter.

Referring now to FIG. 2, the electric control system of the present invention will be described in detail. The circuit is supplied from a source of electrical energy (not shown) which terminates in electrical supply lines L1 and L2. The circuit includes an upper power circuit 80 and a lower control circuit 81. A push button start switch 82 and a push button stop switch 83 are connected across L1 and L2. The two switches are used to start and stop the freezer system from a remote location be means of the control circuit 81. The control circuit 81 can be duplicated for each of several freezer systems so that each freezer system can be remotely started and stopped by the switches 82 and 83. The two switches 82 and 83 are connected in series with a main holding coil 85 and a time delay holding coil 87. The main holding coil 85 controls a set of main contacts 85a. When multiple freezer systems are being controlled, main holding coil controls a set of contacts in the control circuit of each freezer system. For purposes of simplicity in description only a single control circuit for a single freezer system is shown in FIG. 2. When the start button 82 is pressed, the main holding coil 85 is energized, closing the contacts 85a. This permits current to flow to holding coil 91. Holding coil 91 controls contacts 91a and 91b. When holding coil 91 is energized by closing the contacts 85a, holding coil 91 closes contacts 91a which act to lock holding coil 91 in an energized condition. Main holding coil 85 also controls the contacts 85b which act to lock in the main holding coil 85 after the start switch is pressed..Current is supplied to lower control circuit 81 through normally closed contacts 131a, whose function is described hereinbelow.

Time delay holding coil 87 is of the type which is cocked when current is applied and which is triggered when current is removed. When current is removed from time delay holding coil 87, such as by pressing stop switch 83, the time delay sequence is triggered. Time delay holding coil 87 comes into use during the stop sequence, which is explained more fully below. Y

A bypass circuit around start switch 82 and stop switch 83 is provided. The bypass circuit includes an on-off switch 93, normally closed contacts 850 and timer 95. Normally closed contacts c are controlled by main holding coil 85. When the start switch is pressed, which activates holding coil 85, the normally closed contacts 850 are opened. The on-off switch 93 is then placed in the On" position. Subsequently, when the freezer system is stopped and main holding coil 85 is deenergized, the normally closed contacts 850 become closed and timer 95 is started. This provides a-check on the elapsed time that the freezer is maintained in a stop condition.

As previously indicated, energization of holding coil. 91

closes contacts 910 and 91b. This permits current to flow through contacts 91a and 9lb and energizes time

delay holding coils

105, 107, 109 and 1 11. Time delay holding coils 105, l07 and 109 are of the type which are cocked when no power is applied and which are triggered by the application of power. Time delay holding coil 111 is of the type which is cocked by the application of power, and which is triggered upon the cessation of power.

Upon the application of power through contacts 85a, 91a and 91b, time delay holding coil closes immediately and controls contacts 105a. Contacts 1050 are normally open and are closed when time delay holding coil 105 is activated. The contacts 105a are maintained closed for the timing cycle of time delay holding coil 105. This time period is usually maintained at about 15 seconds, but may be adjusted within the range of from about 5 to about 30 seconds. Closing of contacts 105a activates holding coil 115. Holding coil 115 controls contacts 115a and 115b. When holding coil 115 is energized, contacts 115a and l15b are closed and power is supplied to holding coil 133 and to

solenoids

29 and 49, which open valves 27 and 48 respectively.

The closing of contacts 115a and 115!) also energizes holding coil 119. Holding coil 119 controls contacts 119a, 119b, 1l9c and 119d. Contacts 1 19a are used to lock in holding coil 119 when independent start switch 121 and stop switch 123 are used. Independent stop and start switches 121 and 123 are 4 located at individual freezers and are used to effect manual operation of the system.

Contacts 1l9b are used to energize holding coil 125 when the timing sequence initiated by time delay holding coil 107'is terminated. Time delay'holding coil 107, upon energization opens immediately and closes after a time delay of from about 3 to about l5 seconds, preferably about 5 seconds. Time delay holding coil 107 controls normally closed contacts 107a. Dur ing the time period of time relay holding coil 107, contacts 107a are open and holding coil 125 remains unenergized. After time delay holding coil 107 closes contacts 107a are closed and holding coil 125 is energized. Holding coil 125 activates contacts 125a which, in combination with contacts 1 19c, lock in holding coil 125 to the circuit after energization. Holding coil 125 also controls contacts 125b, which lock in holding coil 1 19 to the circuit, and contacts 125C, which lock in

solenoids

29 and 49, which hold valves 27 and 48 in the open position. Holding coil 125 also closes contacts 125d, which completes the circuit to solenoid 57 (which opens valve 56), pump 58 and motor 60. Thus, solenoid 57, pump 58 and motor 60 are not activated until after the time delay period introduced by time delay holding coil 107 has terminated. Contacts 119d are used to open the circuit to solenoid 75 when holding coil 119 is energized. Solenoid 75 controls valve 73 which controls the flow of hot gas to the evaporator 19. Thus, hot gas is not admitted to evaporator 19 when holding coil 119 is energized.

Time delay holding coil 109 opens immediately and closes after a period of from about 5 to about 60 seconds, preferably about 15 seconds. Time delay holding coil 109 controls contacts 109a. During the time period initiated by holding timing coil 109, contacts 109a are closed and solenoid 52 is activated. Solenoid 52 opens valve 51 which permits a full pressure signal to be sent through bypass line 50 to the control portion 47 of regulator valve 43. This holds regulator valve 43 in a fully open position for the time period that time delay holding coil 109 is set. This permits a maximum flow of refrigerant through the freezing system to effect maximum freezing during the timing period of time delay holding coil 109.

In summary of the control system to this point, after start switch 82 is pressed, main holding coil 85 is energized and power is supplied to time

delay holding coils

105, 107, 109 and 111. Timing coils 105, 107 and 109 act to supply full refrigeration to freezing tube 21 for a time period. At the end of another time period, pump 58 and motor 60 are started. Motor 60 starts dasher 59 and mix pump 54. Solenoid 57 is activated and air is introduced through valve 56 and line 55. At the end of a further timed period, full refrigeration is stopped and normal controlled refrigeration is supplied to freezing tube 21. The use of a controlled sequence for starting dasher 59, mix pump 54 and effecting full refrigeration for a controlled period acts to supply refrigeration sufficient to reduce the amount of soft ice cream that is produced during start-up of the freezing system.

Throttling valve 63 is located at the output of freezing tube 21. Throttling valve 63 is controlled by a sensor which senses the pressure in mix line 53. The pressure in mix line 53 is controlled by the consistency and hardness of the ice cream in freezing tube 21. When the consistency and hardness of the ice cream in freezing tube 2l-are too low, the pressure in mix line 53 drops and sensor 67 transmits a signal to controller 65 which sets throttling valve 63 so as to reduce the output of ice cream from freezing tube 21. This further reduces the amount of soft ice cream that is produced upon start-up of the freezing system.

When it is desired to stop the freezing system, stop switch 83 is depressed. This interrupts current to main holding coil 85. When main holding coil 85 is de-energized, contacts 850 are opened and holding coil 91 is de-energized. Time delay holding coil 87 is also de-energized. This triggers the timing cycle of time delay holding coil 87 which closes for a few seconds and then opens. Time delay holding coil 87 controls contacts 870, which close during the timing cycle. Closing of contacts 87a energizes holding coil 131. Holding coil 131 controls normally closed contacts 131a and holds these contacts open during the timing cycle of time delay holding coil 87. This interrupts power to the lower control circuit 81 by having

contacts

131a and 85a open simultaneously. After the timing cycle of time delay holding coil 87 ends, contacts 131a are closed and power is again supplied to the lower control circuit 81 to permit manual operation and to operate the hot gas control sequence described hereinbelow.

interruption of power to the lower control circuit 81 drops out holding coils 125 and 115 and interrupts power to time delay holding coil 111. This stops motor 60, pump 58 and closes

valves

56, 27, 48 and 51.

Upon interruption of current to time delay holding coil 111, the timing period is triggered and time delay holding coil 111 closes for a period of from about three-fourths to about 5 minutes, preferably about 2 minutes, and then opens. Time delay holding coil 111 controls normally open contacts 111a. Contacts 111a when closed during the timing cycle of time delay holding coil 111 supply current to solenoid 75 which opens valves 73 and permits hot gas to move into the freezing tube 21. As indicated, the hot gas is permitted to flow into freezing tube 21 for a timed period which is controlled by time delay holding coil 111. Pressure switch 79 is present to permit closing valve 73 if the pressure within the freezing tube should rise to above about 40 psig.

For manual operation of the dasher and mix pump, which is desirable during cleanup, switch 135 is closed so as to energize holding coil 125. When the switch 135 is closed, holding coil 125 is energized;

contacts

125a, 125b, 125C and 125d are then closed. Contact 125d supplies power to and starts pump 58, motor 60, and energizes solenoid 57. Contacts 125k and 125C have no effect since holding coil 91 is not energized and contact 91b is open. The start system of the invention maybe manually initiated and stopped by depressing start switch 121 or stop switch 123. When start switch 121 is depressed the timed relay sequences controlled by contact 91b are started.

Two-way switch 139 is used to supply power to

solenoids

29 and 49 in its down position and to DPST momentary switch 141 in its up position. Switch 141 controls power to hot gas solenoid 75 or to solenoid 52. Power to hot gas solenoid 75 may be manually applied by depressing switch 141 when switch 139 is in the up position. Power is applied through normally closed contacts 119d and pressure limit switch 79. When switch 141 is in its normal uppermost position, power is applied to solenoid 52 which opens by pass valve 51. This power is applied through normally .closed contacts 111k and 133a. This permits a full flow of refrigerant gas to the control portion 47 of regulator valve 43 when the refrigeration system is oh. This maintains a maximum flow of refrigerant gas throughout the system during shut-down so as to keep the refrigerant in the accumulator as cold as possible during shutdown. This further reduces the amount of soft ice cream.

The freezing system of the present invention provides a control system for minimizing the amount of soft ice cream produced upon start-up of a hot gas freezing system which uses a common motor drive for the dasher and mix pump. The control system of the invention provides a unique time delay actuation of the freezing system so as to effect minimization of soft ice cream.

What is claimed is:

l. A freezer apparatus comprising an evaporator, including a freezing tube to which the product to be frozen is supplied, first conduit means for conducting liquid product to said freezing tube, second conduit means for conducting frozen product away from said freezing tube, pump means in said first conduit means for supplying product to said freezing tube, dasher means within said freezing tube for agitating said product during cooling thereof, single motor means for driving both said dasher means and said pump means, a first supply line to carry liquid refrigerant to said freezing tube, a second supply line to carry hot refrigerant gas to said freezing tube, a normally closed valve in sad second supply line, a refrigerant discharge line leading from said freezing tube to carry gaseous refrigerant therefrom, pressure regulator means in said refrigerant discharge line to control pressure at preselected values, first timing means to inactivate said pressure regulator means for a first predetermined period and provide a maximum flow of liquid refrigerant to said freezing tube during said first predetermined period and second timing means for delaying activation of said motor means for a second predetermined period occurring during at least a portion of the time period of said first predetermined period.

2. A freezing apparatus in accordance with claim 1 wherein said first timing means and said second timing means are activated upon start-up of the freezing apparatus.

3. A freezing apparatus in accordance with claim 1 which further includes third timing means for controlling the opening of said valve in said second supply for a predetermined period.

4. A freezing apparatus in accordance with claim 3 wherein said third timing means is activated upon shut-down of the freezing apparatus.

5. A freezing apparatus in accordance with claim 1 which further comprises throttle valve means in said second conduit means and pressure sensing means in said first conduit means, said pressure sensing means controlling said throttle valve means at preselected values to control the softness of said frozen product.

6. An electrical control circuit for freezing apparatus having an evaporator including a freezing tube, a pump to supply liquid product to the freezing tube, a dasher within the freezing tube to agitate the product while it is being frozen, a single motor for driving both the pump and the dasher, a pressure regulator for controlling the pressure of refrigerant supplied to the evaporator, an adjustable valve for controlling a pressure signal to the pressure regulator, a bypass line around the adjustable valve, a first solenoid controlled .valve in the bypass line, a second solenoid controlled valve for controlling the supply of refrigerant to the evaporator, and a third solenoid controlled valve for controlling the supply of hot gas to the evaporator, said control circuit comprising an electrical power source, a stop switch, a start switch, a main holding coil c011 nected in series with said start and stop switches across said power source, first and second solenoids for said first and second solenoid controlled valves to open said valves when the respective solenoid is energized, a first time control relay and a second time control relay, said main holding coil being energized when said start switch is pressed, said first and second time control relays being energized by said main holding coil, first and second solenoid being controlled by said first time control relay, said motor starter circuit having a set of contacts operated by said second time control relay, said first and second time control relays being set in a way so that said first and second solenoids are opened a predetermined period before said motor starter circuit is energized.

7. An electrical control circuit in accordance with claim 6 which further comprises a third solenoid for controlling said third valve and a third time control relay, said third time control relay being energized when said stop button is pressed and said third time solenoid being controlled by said third time control relay so as to admit hot gas to the evaporator for predetermined period of time.

Patent No. 3,667 Dated June 6 1972 lnventofls) Walter L Hock & William Myers I .It is certified that error appears in the. above-identified patent .and that said LettersPaten't are hereby corrected as shown below:

Column 2, actual line 65, (indicated line 66) after "is" insert located-.

Column 3, line 17 delete "free" Column 4, actual line 47, (indicated line 48) after v"3" insert -seconds.

Column 5, actual line 57 (indicated line 58) change "three-fourths" to l/4 minute.

' Column 6 actual line 44 (indicated line 4 5 after "control" insert --refrigerant (Claim 1) Signed and sealed this 2nd day of January 1973.

(SEAL) Attest:

EDWARD M.CFLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PC3-1050 USCOMM-DC 60376-P69 v 5.5. GOVERNMENT PRINTING OFFICE l (939 O 356334

Claims

1. A freezer apparatus comprising an evaporator, including a freezing tube to which the product to be frozen is supplied, first conduit means for conducting liquid product to said freezing tube, second conduit means for conducting frozen product away from said freezing tube, pump means in said first conduit means for supplying product to said freezing tube, dasher means within said freezing tube for agitating said product during cooling thereof, single motor means for driving both said dasher means and said pump means, a first supply line to carry liquid refrigerant to said freezing tube, a second supply line to carry hot refrigerant gas to said freezing tube, a normally closed valve in sad second supply line, a refrigerant discharge line leading from said freezing tube to carry gaseous refrigerant therefrom, pressure regulator means in said refrigerant discharge line to control pressure at preselected values, first timing means to inactivate said pressure regulator means for a first predetermined period and provide a maximum flow of liquid refrigerant to said freezing tube during said first predetermined period and second timing means for delaying activation of said motor means for a second predetermined period occurring during at least a portion of the time period of said first predetermined period.

6. An electrical control circuit for freezing apparatus having an evaporator including a freezing tube, a pump to supply liquid product to the freezing tube, a dasher within the freezing tube to agitate the product while it is being frozen, a single motor for driving both the pump and the dasher, a pressure regulator for controlling the pressure of refrigerant supplied to the evaporator, an adjustable valve for controlling a pressure signal to the pressure regulator, a bypass line around the adjustable valve, a first solenoid controlled valve in the bypass line, a second solenoid controlled valve for controlling the supply of refrigerant to the evaporator, and a third solenoid controlled valve for controlling the supply of hot gas to the evaporator, said control circuit comprising an electrical power source, a stop switch, a start switch, a main holding coil connected in series with said start and stop switches across said power source, first and second solenoids for said first and second solenoid controlled valves to open said valves when the respective solenoid is energized, a first time control relay and a second time control relay, said main holding coil being energized when said start switch is pressed, said first and second time control relays being energized by said main holding Coil, first and second solenoid being controlled by said first time control relay, said motor starter circuit having a set of contacts operated by said second time control relay, said first and second time control relays being set in a way so that said first and second solenoids are opened a predetermined period before said motor starter circuit is energized.

7. An electrical control circuit in accordance with claim 6 which further comprises a third solenoid for controlling said third valve and a third time control relay, said third time control relay being energized when said stop button is pressed and said third time solenoid being controlled by said third time control relay so as to admit hot gas to the evaporator for a predetermined period of time.