GB2181068A

GB2181068A - Making frozen comestibles with over-run

Info

Publication number: GB2181068A
Application number: GB08623485A
Authority: GB
Inventors: Ronald D Howell; Robin J Goettsch
Original assignee: Cherry Burrell Corp
Current assignee: Cherry Burrell Corp
Priority date: 1985-10-04
Filing date: 1986-09-30
Publication date: 1987-04-15
Also published as: DE3633746A1; SE8604191D0; GB8623485D0; IT1199252B; BR8604853A; AU6328086A; SE8604191L; GB2181068B; DK471086D0; ES2002800A6; JPS6287057A; CA1270656A; FR2588160A1; DK471086A; IT8648513A0; FR2588160B1; AU597274B2

Abstract

A system for making frozen comestibles, and the like, having an over-run, and comprises a swept surface heat exchanger to which refrigeration means are connected. The system comprises a gas/mix system which includes a positive displacement pump (55) having a variable drive (57), with an inlet for a mix. A magnetic flow meter (59) receives mix from the pump outlet and provides a signal proportional to the flow of mix therethrough. The flow meter discharged into a conduit (61) which communicates with the inlet to the heat exchanger. A gas flow control means (67) is connected between the mix conduit and a source of pressured gas. A programmable computer (73) receives signals from the flow meter and controls the variable drive on the pump and the pressured gas through the gas flow control means. The system may include means responsive to viscosity changes in the heat exchanger to control the refrigeration means. <IMAGE>

Description

SPECIFICATION Frozen comestibles with over-run The present invention relates generally to a system for making frozen comestibles and the like having an over-run, and, more particularly, the invention relates to a system for making frozen desserts such as ice cream.

Background of Invention In the manufacture of frozen comestibles, the usual practice is to prepare a mix and provide over-run to the product by inclusion of air or inert gas, such as nitrogen, into the mix before entering a swept surface heat exchanger to chill or freeze the mix and provide a product with desired over-run. The heat exchanger is associated with a refrigeration system which connects to a manifold on the heat exchanger. In the normal functioning of the heat exchanger, the air or inert gas is,distri- buted throughout the mix by a dasher resulting in a chilled or frozen product having overrun.

As used herein the over-run is specified as a percentage, by volume, increase by inclusion of air or inert gas. For example, if the mix is increased in volume by the inclusion of 20% of the mix volume of gas, it is said to have a 20% over-run. If equal volumes of mix and gas are included in the final product, it is said to have 100% over-run.

It has been common to introduce the mix into a gear pump which has an inlet for receiving air to provide the over-run. The combination of mix and air are then pumped into the swept surface heat exchanger. The gear pump has had a number of limitations and the heretofore known systems of providing for air injection into the mix have also had limitations so that there have been substantial variations in the over-run. Thus, these previous known systems have not provided consistency in over-run control in the manufacture of frozen comestibles, including frozen desserts, ice crea, sherbet, and the like. In the manufacture of these products it is desired to provide between 20% and 200% over-run.

In heretofore known systems, as indicated, it is usual to provide the pump for feeding the mix and gas to the swept surface heat exchanger but also to provide a pump at the outlet of the heat exchanger, thereby requiring multiple pumps. Further, heretofore known systems have required major changes, such as sprocket changes, to accommodate a wide range of over-run. In addition, in systems known before this invention, the amount of inclusion of air was subject to variations in line pressure.

The use of gear pumps in systems for manufacturing frozen comestibles also had limitations in providing desired control of the overrun. The gear pump is affected by the viscosity of the mix, and the mix temperature likewise affects the gear pump operation. Upstream and downstream pressure had an effect upon the operation of the gear pump as well. Further, the gear pump tends to wear because of gear meshing whereas it would be desirable to avoid this wear in the operation of the system.

The prior systems had difficulty with shutdowns occasioned by the need for terminating the output of the swept surface heat exchanger as might result from a problem in the product packaging line. It is difficult, in many prior systems, to effect start-up after such a shut-down.

A principal object of this invention is to provide an improved system for making frozen comestibles and the like having over-run.

A further object of the invention is the provision of an improved system for making frozen comestibles and the like with closely controlled over-run which does not vary significantly during operation.

A still further object of the invention is the provision of an improved system for making frozen comestibles which can be readily varied to accommodate different through-puts and different over-runs in the system.

An additional object of the invention is the provision of an improved system for making frozen comestibles and the like having varied over-runs, which system can be placed on hold and readily started up.

Another object of the invention is the provision of an improved system for making frozen comestibles and the like, which has more life and can be easily maintained.

Still another object of the invention is the provision of an improved system for making frozen comestibles and the like, which does not require a pump at the output of a heat exchanger in addition to an input pump.

Further objects and advantages of the invention will be seen by reference to the foliowing drawings, and additional description.

Drawings In the drawings, Fig. 1 is an overall diagram of the system of the invention for making frozen comestibles and the like.

Description of the Invention The system of the invention is particularly adapted for making frozen comestibles and the like, having an over-run which is effected by the inclusion of air or an inert gas in a mix which is fed into a swept surface heat exchanger for chilling or freezing. The frozen comestibles can be frozen desserts, ice cream, sherbets, or the like.

Referring to Fig. 1, the system generally includes a swept surface heat exchanger 11, which has a liquid manifold 13 and a gas manifold 15 associated with cooling means.

The swept surface heat exchanger 11 includes a manifold cylinder 17 in which is disposed a tube 19. A dasher 20 is located within the tube 19, the dasher and tube being shown by dotted lines in Fig. 1. The manifold cylinder connects to the gas and liquid manifolds 15 and 13. The swept surface heat exchanger 11 has an inlet 21 and discharges through an outlet 23. The dasher 20 is driven by a shaft 25, which connects to a pulley 27. The pulley 27 is driven by means of a belt 29, which is, in turn, driven by a dasher motor 31. The dasher motor 31 may be controlled by a variable drive 33, which may be varied by changes in frequency of the electrical power.

The cooling means is a refrigeration unit, which is generally designated by the numeral 35, and is of conventional design and construction, and accordingly is only briefly described herein. Generally, the refrigeration unit 35 comprises an accumulator 37 for holding ammonia or other refrigerant.The accumulator 37 connects to an injector 39, which feeds liquid refrigerant through line 41 to the liquid manifold 13 of the swept surface heat exchanger 11. Gas from the heat exchanger 11 may be returned through a line 43 from the gas manifold 15. The level of refrigerant in the accumulator 37 is controlled by means of a float valve 45, which connects to a level controller 47, and allows liquid refrigerant to enter the accumulator through line 48. Liquid refrigerant may also enter through line 49.

The improvement of the invention comprises an air/mix system, generally designated 51, and particularly shown in Fig. 1, which includes a feed line 53 for introduction of the mix into a positive displacement pump 55.

While the pump 55 may be a conventional gear pump, it has been found more desirable to provide a lobe pump, such as a Waukesha pump, which provides longer life and less wear in the pump. In a gear pump, the gears normally mesh and typically one gear drives another gear, whereas in a lobe pump, the lobes do not contact one another and minimal wear occurs. The pump 55 is provided with a variable speed drive 57, which is preferably effected by frequency variation of the electrical power. This allows wide variation in the speed of the pump 55 which can be easily controlled to effect a wide range of mix flow.

It will be noted that no air or inert gas is introduced into the pump 55 as has been conventional. The pump discharges through conduit 56, which feeds mix into a magnetic flow meter 59. The magnetic flow meter is available on the market and includes a meter body and a signal conditioner associated with the meter body. The magnetic flow meter 59 relies on Faraday's Law of Electromagnetic Induction to generate a signal responsive to the flow of mix through the magnetic flow meter 59. As the mix flows through the magnetic field generated by high density coils of the flow meter, a voltage is generated which is directly proportional to the velocity of the mix flowing through. Electrodes in contact with the mix flow sends the flow induced voltage to the signal conditioner which converts this voltage to a pulse and/or analog current output through line 60.The magnetic flow meter is available on the market and a particularly satisfactory magnetic flow meter 59 is the Brooks Wafer-Mag Electromagnetic Flow Meter available from Brooks International Division of Emerson Electric Co.

The flow meter 59 discharges into conduit 61 for carrying the mix to the swept surface heat exchanger 11, and particularly to its inlet 21. Downstream of the magnetic flow meter 59 air or inert gas is introduced into the conduit 61 by means of a tee 63, which connects to an air line 65. The tee is provided with a check valve.(not shown). The amount of air which enters the conduit 61 from air line 65 is controlled by an air mass flow control means 67, which receives filtered and pressured air through line 69. The air mass flow control means 67 is also available in the market and automatically controls the air mass flow through the air line 65. One particularly satisfactory air mass flow control means is the Brooks Model 5850C sold by Brooks Instrument Division of Emerson Electric Co.The flow control means 67 receives input signals through line 71, so as to control the amount of air introduced into the conduit 61.

A programmable computer 73 serves to control the flow rate of the mix through the pump 55, and to control the air into the conduit 61 by means of the input signals to the flow control means 67 through line 71. The programmable computer 73 is set at a given flow rate and also set to provide air for a desired over-run. The signal from the magnetic flow meter 59 is provided in proportion to the actual flow of the mix. This signal also simultaneously. serves to control the over-run, which is set in the programmable computer 73, and feeds a control signal to the air mass flow control means 67. The programmable computer 73 is available in the market and a particularly satisfactory programmable computer is identified as PiC 49, sold by Giddings and Lewis Electronics Company. Because various software programs can be developed from the described functions within the skill of the art for the operation of the computer 73, it is not necessary to further describe the software program.

The computer 73 also provides control of the pump 55 by means of the signal from the flow meter 59 which controls the frequency for the variable drive 57. Thus, the flow is set, monitored and controlled regardless of temperature fluctuations and/or viscosity changes in the mix. Further, wide variations in the set flow can be made without difficult drive changes to the pump 55 as by having to change sprockets. Further, the signal from the flow meber 59 simultaneously through the computer 73 adjusts the set flow of air through the flow controller 67, thereby maintaining consistency of over-run.

Thus, the programmable controller 73 serves to control the speed of the pump 55 for a desired flow rate, and varies the speed by change of frequency in the event that the feed through the line 56 is not in accord with the set flow rate. Likewise, the output of the flow meter 59 may vary and provide a variable signal to the programmable computer 73 to adjust the air passing through the air mass flow controller 67. Thus, the overall system serves to provide precise and continuous control of over-run at a predetermined value. Variations in the operation of the pump or in the mix are accommodated automatically in the system providing a highly advantageous system.

A feature of the invention is in the allowance for hold times when the output of the swept surface heat exchanger 11 is not required, such as in the case of a packaging line shutdown. When such condition occurs, a hold back valve 81 in the output line 85 from the swept surface heat exchanger 11 is closed by means of a solenoid 83 operated by the computer 73. When the hold back valve is closed, i.e., the swept surface heat exchanger being placed on hold, the viscosity of the mix in the heat exchanger 11 will increase, thereby causing an increased power requirement from the dasher motor 31. This increased power is read by a power transducer 87. This increase in power requirement is indicated as a signal to the computer 73 through line 89. The computer 73 controls the pressure in the refrigeration means 35 suction line 91.The computer 73 also controls flow through line 90 by means of a solenoid valve 97. The refrigerant suction line 91 connects to a back pressure valve 95, which is operated by the computer 73 in response to the signal from the power transducer 87. The back pressure valve 95 controls the flow from the accumulator through line 96. The flow in the refrigerant liquid line 90, which feeds the injector 39, is controlled by a solenoid valve 97. The liquid control valve 97 is operated by the computer 73 as well. By programming the computer, the pressure in the swept surface heat exchanger gas manifold 15 is controlled so as to reduce the cooling and thereby allows the dasher 20 to continue to rotate during a hold period.The advantage of this particular system is that the swept surface heat exchanger 11 can continue to function while the holdup in the output of the swept surface heat exchanger is being corrected or adjusted.

At the same time that the hold back valve 81 is closed by the computer 73, the pump 55 is stopped by the computer 73.

It should be noted that the power transducer 87 functions during normal operation to provide input to the computer 73 as a result of sensing viscosity changes in the mix in the tube 19. This provides further control and consistency of over-run.

The system of the invention further includes a "hot gas" system for melting down the product in the swept surface heat exchanger 11.

This hot gas system is generally designated 99, and is not unusual in the art so that it will not be further described, although the drawing generally illustrates the manner of operation of the hot gas system. The hot gas is supplied through line 101 to the hot gas system 99.

In operation of the system, mix is fed into the system through line 53 and into the pump 55. The pump is controlled by a variable frequency drive 57 and the output of the pump passes through line 56 to the magnetic flow meter 59. The mix, after being sensed by the magnetic flow meter 59, passes through line 61 and into tee 63 into which air is introduced from the air mass flow control means 67. The mixture of air and mix then passes to the inlet 21 of the swept surface heat exchanger 11, wherein it is chilled and/or frozen while being whipped by means of the dasher 19. The product with the desired over-run leaves the swept surface heat exchanger 11 through outlet 23- and passes through line 85 through the hold back valve 81 to a packaging line.

As indicated, the flow meter 59 provides a signal in proportion to the flow rate of mix therethrough. This signal serves to provide an input to the computer 73, which provides output signals for controlling the variable frequency drive 57 and controlling the air mass flow control means 67. The computer 73 has set points for the through-put of the system and provides variable adjustment of the overrun between wide ranges.

In the event that the hold back valve 81 is shut because of a cut-off in the need for the product, viscosity increases in the swept surface heat exchanger 11, causing an increased power requirement to dasher motor 31, whereupon this power increase is sensed by the power transducer 87, which signals the computer 73. The refrigeration means 35 for the swept surface heat exchanger 11 is controlled by the computer 73 to reduce the refrigerant going to the manifold cylinder 17. The computer 73 also causes the pump 55 to stop. Thus, the swept surface heat exchanger 11 can readily be placed upon hold without shutdown of the whole system with consequent loss of product.

The overall system of the invention provides unique results and advantages over the heretofore known systems for the making of frozen comestibles with over-run. The various advantages have been outlined in the foregoing.

Claims

1. In a system for making frozen comestibles and the like having over-run comprising a swept surface exchanger which includes a manifold cylinder in which is disposed to a tube having a dasher, refrigeration means connected to the manifold cylinder, an inlet to the tube, an outlet from the tube and an air/mix system; an improved air/mix system comprising a positive displacement pump having an inlet for a mix, a variable drive and an outlet, a magnetic flow meter for receiving mix from said pump outlet and providing a signal proportional to the flow of mix therethrough, a mix conduit connected between said flow meter and the inlet to the tube, air mass flow control means connected between said mix conduit and to a source of pressured air, a programmable computer receiving said signal from said flow meter and controlling both said variable drive for said pump and the pressured air through said air mass flow control means.

2. A system in accordance with Claim 1 wherein said positive displacement pump is a lobe pump.

3. A system in accordance with Claim 1 or 2 wherein said programmable computer sets the flow of said mix and the over-run set point.

4. A system in accordance with Claim 1 or 2 or 3 wherein said variable drive is responsive to variation in frequency.

5. A system in accordance with any preceding claim wherein said signal simultaneously controls the flow of said mix and the air mass flow control means.

6. A system in accordance with any preceding claim which further includes a motor connected to the dasher and a power transducer connected to the motor which conducts a signal to said computer.

7. A system in accordance with Claim 6 which further includes a hold back valve at the outlet from the cylinder, a motor connected to the dasher, a power transducer connected to the motor for sensing power requirements of said motor and providing input to said computer, means for controlling the refrigeration means connected to said computer, and means in said computer for stopping said pump.

8. A system in accordace with any preceding claim which further includes a hold back valve at the outlet of the tube.

9. A system for producing frozen comestibles including means for controlling the proportion of gas added to the prepared comestible mix prior to freezing.

10. A system for producing frozen comestibles with means, including means for sensing and compensating for changes in the system, for temporarily stopping production of the frozen comestible.

11. A system for producing frozen comestibles substantially as described hereinabove with reference to the accompanying drawings.