FIELD OF THE INVENTION

The present disclosure relates to a food processing machine, comprising a receptacle for receiving food ingredients, and a flow-through cooling unit involving a cooling chamber for cooling the food ingredients. The disclosure particularly relates to ice cream makers, but also to cold beverage makers, sorbet makers, smoothie makers, and such like, and to multifunctional food processing appliances.

BACKGROUND OF THE INVENTION

An ice cream maker is a machine that is arranged to make small quantities of ice cream for consumption. Ice cream makers may prepare a mixture of selected ingredients and flavors by employing an electric motor mixer. Further, the resulting preparation is often chilled employing a cooling unit that freezes the mixture. Basically, for standard ice cream, an ice cream maker has to simultaneously - or nearly simultaneously - freeze the mixture while stirring it so as to aerate the mixture and avoid the formation of ice crystals.

The present disclosure also relates to domestic (household) food processing appliances. This is, the present disclosure is not limited to ice cream making appliances, but also to similar food processing machines.

WO 88/07331 Al discloses a machine for making ice cream and the like, comprising:

a receptacle for receiving liquid ingredients to be used for making the ice cream;

a mixing chamber having an egress from which the ice cream exits;

a cooling chamber surrounding said mixing chamber;

a rotor centrally mounted in said mixing chamber for atomizing and mixing the liquid ingredients and moving it through the mixing chamber to its egress, said rotor having a central post and outwardly projecting blade means; and

conduit means for feeding the liquid ingredients from the receptacle to the central post of the rotor, and outlet port means on said central post through which the liquid ingredients are ejected outwardly from the central post for action by the blade means. At the home user level, there is a certain need for instant ice cream makers and similar appliances. Conventional ice cream makers typically require time-consuming preparation, for instance chilling or freezing a bowl-shaped receptacle in a freezer. In this way, the receptacle, having a certain heat capacity, is cooled down and may therefore act as a cooling or freezing aid in a subsequent ice making procedure. However, this at least requires to place the receptacle in the freezer several hours ahead of the intended ice cream

preparation.

Further, so-called stand-alone instant ice cream makers are known. However, these appliances are somewhat bulky, due to their integrated freezing and/or cooling units. Typically, these appliances integrate therein a cooling cycle that is similar to the cooling cycle of a fridge or a freezer. Therefore, a certain size and energy consumption of the appliances has to be accepted. This is, however, a certain drawback in several home user environments, for instance when there is only little room in the kitchen.

Further, it has been observed that in conventional ice cream makers, often additives are used which may involve emulsifiers and/or congelation agents. In this way, a desired quality level of the finalized foodstuff product may be ensured. However, those additives do not have a positive impact on the taste as such, but serve as aids in the preparation. So as to make the prepared frozen foodstuff product even more elemental and natural, it is desirable to reduce the need for these additives. Preferably, the use of these additives may be dispensed with even in home user ice cream makers.

Further, a greater variety of frozen and/or chilled foodstuff products emerged on the market in recent years. This may for instance involve frozen yoghurt, fruit drinks, smoothies, coffee-based or milk-based drinks, or even tea-based drinks that are partially frozen or at least chilled. Hence, it would be beneficial to integrate freezing or chilling features in conventional kitchen appliances, such as blenders, juicers, beverage makers, etc.

There is also a certain need for dual-purpose or even multi-purpose appliances so as to obviate the need for several costly and space-consuming appliances.

Hence, there is still room for improvement in the field of food processing machines.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to provide a food processing machine, particularly an ice cream maker, that is arranged to produce ice cream and similar foodstuff products in short time, preferably without the need of time-consuming preparation. Further, it would be desirous to provide a food processing machine that is capable of producing ice cream and similar foodstuff products without the need or with only little need of using additives to achieve a desired structure of the foodstuff product.

Further, it would be beneficial to present a food processing machine that is arranged as a dual-purpose or multi-purpose machine. Preferably, the food processing machine is capable of ice cream making, but also of preparing cool drinks and similar foodstuff products. Further, it would be desirous to present a food processing machine that is less bulky than conventional appliances. Further, it would be desirous to present a food processing machine that is arranged to produce well-tasting ice cream and similar foodstuff products. Preferably, the machine is capable of ensuring a beneficial composition of the foodstuff product, for instance in terms of the size and distribution of ice crystals in the ice cream.

It is generally preferred to achieve a smaller size of the ice crystal since this results in a better taste of the ice cream resembling ice cream that is made by professional machines in ice cream shops.

In a first aspect of the present invention a food processing machine is presented, the machine comprising:

a receptacle for receiving food ingredients,

a flow-through cooling unit involving a cooling chamber for advancing and cooling the food ingredients,

wherein, in the cooling chamber, a stepped screw arrangement is provided that comprises a first screw section including at least one first thread helix, and a second screw section including at least one second thread helix,

wherein the first screw section comprises a first radial clearance between a spiral perimeter and a circumferential wall of the cooling chamber,

wherein the second screw section comprises a second radial clearance between a spiral perimeter and the circumferential wall of the cooling chamber, and

wherein the second radial clearance is greater than the first radial clearance.

This aspect is based on the insight that the stepped screw arrangement which may be regarded as a screw conveyor or a spiral conveyor and the cooling unit may be beneficially combined by actively cooling the cooling chamber in which the screw

arrangement is provided. Hence, both advancing and cooling the ingredients may be performed at the same time. As a result, the food processing machine is even better suited for instant or nearly instant ice cream making. In one and the same unit, the foodstuff product to be processed may be cooled/frozen, mixed, and fed towards a discharge outlet of the machine.

Further, a beneficial size and homogenous distribution of ice crystals in the ice cream and in similar foodstuff products may be achieved. Further, a small crystal size of ice crystals in the discharged/dispensed product may be ensured.

A further benefit is that the desired taste and quality may be achieved without the need or with only little need of adding emulsifiers, congelation agents, and similar additives. Hence, the prepared foodstuff product may be regarded as an "additive- free" or "low additive" foodstuff product.

The stepped screw arrangement comprises a first and a second section. The first screw section is arranged to scrape off the cooled/frozen product from a circumferential wall of the cooling chamber. Hence, the first screw section contributes to the formation of preferably small ice crystals.

The second section of the stepped screw arrangement, the second screw section, is not in tight contact with the circumferential wall. Hence, the second screw section is not arranged to scrape off the product from the circumferential wall. It has been observed that the scraping action of the first screw section involves a certain heating of the product to be processed. The main heating source in this context is the friction caused by the scraping action. Therefore, the second screw section further advances or conveys the product through the cooling chamber and along the circumferential wall. Hence, a certain re-crystallization of ice crystals may take place. Since in the region of the second screw section, no friction or only little friction occurs, only a limited or even no heat input into the product is present. This ensures the desired quality and composition of the finished product.

In an exemplary embodiment, the first screw section is an upstream section and the second screw section is a downstream section, wherein the food ingredients, when being advanced through the cooling chamber, firstly pass the first screw section and secondly pass the second screw section. In this way, a continuous instant or quasi- instant production of ice cream and similar foodstuff products may be ensured. One and the same module of the machine may cool down or freeze the product, and may convey the product and contribute to the formation of ice crystals.

In a further exemplary embodiment, the first screw section is a scraping section, wherein the second screw section is a non-scraping section. Hence, in the region of the second screw section, only a limited heat input into the product is present, wherein the cooling effect, caused by the circumferential wall of the cooling chamber, is still present. In accordance with the above embodiment, the second screw section may be referred to as advancing and mixing section.

Further, in the region of the first screw section, a certain pressurization of the foodstuff product takes place, as a tight contact between the helical coil of the first screw section and the circumferential wall is present.

In a further exemplary embodiment, a ratio between the second radial clearance and the first radial clearance is greater than 2: 1, preferably greater than 4: 1 , or may be even greater. Hence, a certain relaxation of the product is enabled in the region of the second screw section which, however, further propels the product towards a discharge outlet.

In a further exemplary embodiment, the first screw section and the second screw section are formed at a common screw shaft, wherein the circumferential wall is formed at a cooling cylinder, and wherein at least one of the cooling cylinder and the screw shaft is stepped along its axial extension.

Hence, in one embodiment, the cooling cylinder has a basically constant inner diameter, wherein an outer diameter of the first screw section is significantly greater than an outer diameter of the second screw section. In another embodiment, the cooling cylinder has a first section associated with the first screw section and a second section, associated with the second screw section, wherein the first section of the cooling cylinder has a smaller diameter than the second section. Hence, the cooling cylinder rather than the screw arrangement is stepped. Needless to say, also a combination of both a stepped cooling cylinder and a stepped screw arrangement may be envisaged.

In some embodiments, the first screw section and the second screw section are arranged at a common screw shaft extending therethrough. Hence, a single rotation drive may be used to jointly rotate the first screw section and the second screw section.

In a further exemplary embodiment, at least the first screw section pressurizes the passing food ingredients. This has a positive effect on the taste of the prepared foodstuff product. In the vicinity of the second screw section, a relaxation of the passing food ingredients may take place.

In a further exemplary embodiment, a pitch of the thread helix of the first screw section is generally greater than a pitch of the thread helix of the second screw section, In a further exemplary embodiment, a radial extension of the thread helix of the first screw section is generally greater than a radial extension of the thread helix of the second screw section. This may as well have an influence on the formation of the ice crystals and the overall composition/structure of the foodstuff product. In a further exemplary embodiment, the thread helix of at least the first screw section has a profile comprising a first, upstream flank and a second, downstream flank, wherein, with respect to the longitudinal axis, the downstream flank is steeper than the upstream flank, and wherein, at an outer perimeter of the downstream flank, a spiral scraping edge is provided.

In some embodiments, the above applies to a cross-sectional profile of the thread helix of the first screw section that is parallel to a longitudinal axis of the first screw section. The spiral scraping edge corporates with the circumferential wall of the cooling chamber to scrape off ice crystals forming thereon. The downstream flank may be basically perpendicular or nearly perpendicular to the longitudinal axis of the screw section. Hence, the first screw section may pressurize and advance the passing food ingredients towards the second screw section.

In a further exemplary embodiment, the flow-through cooling unit is an active cooling unit that is arranged to freeze or cool down food ingredients that are advanced through the cooling chamber. This has the advantage that an instant cooling may be provided. Hence, at least in some cases, time-consuming preparation work can be omitted.

In a further exemplary embodiment, the flow-through cooling unit is arranged to cool down the circumferential wall of the cooling chamber and, mediately, the passing food ingredients. In this way, both freezing and advancing the food ingredients may be combined.

In a further exemplary embodiment, the flow-through cooling unit is a non- fluid cooling unit using at least one thermoelectric transducer.

At least one thermoelectric transducer that implements the thermoelectric effect may be utilized. For instance, at least one Peltier element may be used. Preferably, a number of Peltier elements is wrapped around the cooling chamber. Hence, an arrangement of Peltier elements may be used to cool down the circumferential wall of the cooling chamber and, consequently, the passing food ingredients.

In a further exemplary embodiment, the food processing machine further comprises a heat removal unit that is operatively coupled to the flow-through cooling unit, wherein the heat removal unit is arranged to remove excess heat from the flow-through cooling unit. This is particularly beneficial when a cooling unit is used that produces waste heat. The heat removal unit may involve a heat removal cycle. Hence, waste heat may be efficiently removed from the cooling chamber, i.e. from a waste heat side of cooling elements. In a further exemplary embodiment, the heat removal unit involves a tluid heat removal cycle operatively coupled with the flow-through cooling unit and a heat storage. In some embodiments, the heat storage is arranged to be detached. This may have the advantage that the heat storage may be cooled down or chilled in a fridge or freezer. Hence, in this way an even better heat removal performance, due to the present temperature gradient between the hot side and the cool side of the heat removal cycle, may be achieved. As a consequence, the cooling performance of the cooling unit may be further improved. The heat storage has a certain heat storage capacity. The heat storage may be attached and coupled to the heat removal cycle and, if necessary, detached and decoupled therefrom.

Needless to say, in alternative embodiments, the food processing machine may comprise a heat removal unit that is differently configured, for instance as an air ventilating cooler involving a fan or vent. Therefore, the term flow-through cooling unit may involve any of a liquid flow and a gas flow.

In a further exemplary embodiment, the food processing machine further comprises a mixing unit arranged upstream of the cooling chamber.

In a further exemplary embodiment, the mixing unit involves a mixing blade that is arranged in or operatively coupled to the receptacle. The mixing blade may be used to mix or blend food ingredients that are filled in the receptacle. Needless to say, at least in some embodiments, the receptacle may be detachable. Hence, also the receptacle may be placed in a fridge or freezer to provide some chilling performance. In some embodiments, the mixing blade is operatively coupled with the stepped screw arrangement, particularly with the common screw shaft. In alternative embodiments, the mixing unit is separately operated and driven.

In a further exemplary embodiment, the food processing machine further comprises a modelling unit through which the processed foodstuff product is dispensed. The modelling unit may involve a discharge opening through which the prepared foodstuff product may be discharged.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter. In the following drawings

Fig. 1 shows a schematic block diagram illustrating an exemplary embodiment of an ice cream making procedure; Fig. 2 is a schematic simplified illustration of a food processing machine in accordance with the present disclosure;

Fig. 3 is a simplified schematic block diagram implementing modules of an exemplary food processing machine in accordance with the present disclosure;

Fig. 4 is a simplified schematic illustration of a cooling unit of a food processing machine, and a heat removal unit associated thereto;

Fig. 5 is a simplified side view of a cooling chamber of a cooling unit wherein a screw shaft is arranged that involves a first screw section and a second screw section;

Fig. 6 is a simplified partial side view of a cooling unit involving a cooling cylinder in which a screw shaft is arranged, wherein a heat removal sleeve is provided that surrounds the cooling cylinder;

Fig. 7 is a simplified, schematic cross-sectional view through the arrangement shown in Fig. 6 indicated by VII-VII therein, to illustrate a layer structure; and

Fig. 8 is a more detailed enlarged partial view of the arrangement of Fig. 6 indicated by VIII in Fig. 6.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following, several aspects and embodiments of the present disclosure will be further detailed and explained with reference to ice cream making and/or ice cream making machines. However, this shall not be understood in a limiting sense. Consequently, aspects, embodiments and insights of the present disclosure may also be applied in the context of juice making, smoothie making, and generally in the field of the preparation of at least partially cooled beverages.

Therefore, whenever reference is made to ice cream in this following, it should be understood that also other foodstuff products may be processed and prepared.

Fig. 1 is a simplified block diagram illustrating several steps of an ice cream making procedure.

The sequence illustrated in Fig. 1 involves a blending or mixing step 10, a pasteurization step 12, a homogenization step 14, a cooling step 16, a freezing step 18, a modelling step 20, and a hardening step 22.

In the step 10, ingredients involving milk fat, solid ingredients, stabilizers, and emulsifiers are blended. In this way, a certain mixing degree, preferably a complete mixing, of liquid and non- liquid ingredients may be ensured. In the step 12, pasteurization may take place to kill microorganism, such as bacteria. In this way, the keepability of the resulting product may be improved. Needless to say, the pasteurization step is not always necessary, particularly for domestic ice cream making applications.

The step 14 involves a homogenization in which fat contents of the milk are broken into smaller sizes, thereby avoiding a separation of the fat from water contents. This has a positive effect on the creaminess of the resulting ice cream. In the step 14, as the case may be, emulsifiers and stabilizers may be added to the composition of ingredients.

The step 16 involves a cooling and an aging of the mixture. For instance, cooling may take place at about 5 °C (Celsius) for some hours. This may involve that some milk fat may already at least partially crystallize. Further, protein stabilizer may hydrate. As a result, the mixture may be stabilized for a whipping procedure.

The step 18 involves a freezing procedure. Further, air may be mixed in in the step 18. As a consequence, air bubbles are present in the mixture which improves the softness of the resulting cream.

In the step 20, the mixture is modeled and packed, if necessary. Modelling may involve forming mixed ice cream involving a mixture of several types of ice cream, arranging the ice cream in a good-looking shape, etc.

Further, if it is intended to consume the ice cream at a later time, a deep freezing procedure may be present in the step 22. For instance, rapid cooling to no more than -25 °C may be applied. In this way, water contents will freeze quickly. Hence, small ice crystals may be formed. As such, the prepared ice cream may be kept for a considerably long time, provided that a sufficiently low storage temperature may be ensured.

Fig. 2 is a schematic, simplified side view of a food processing machine 30. The food processing machine 30 is arranged as an ice cream maker or as a dual-purpose or multi-purpose appliance that is also capable of ice cream making.

The machine 30 involves a housing 32 having a base plate 34 and a column or frame 36. In the housing 32, a control unit or controller 40 is provided. Further, a motor 42 is provided. The motor 42 is arranged as an electric motor.

In an upper portion of the housing 32, a receptacle 46 is arranged. In some embodiments, a cover 48 is provided to cover the receptacles 46 and the ingredients contained therein, if necessary.

The receptacle 46 may for instance comprise a bowl 50. In some embodiments, the bowl 50 is made from metal, and be formed from stainless steel that qualifies for use in food processing environments. In certain embodiments, the bowl 50 may be, arranged as a detachable bowl. For instance, the bowl 50 may be arranged to be temporarily stored in a fridge or freezer. This may contribute to a fast ice cream making procedure. Further, the detachable arrangement simplifies cleaning.

In the receptacle 46, a mixing unit 54 is provided. The mixing unit 54 involves a mixing blade 56 which may be arranged to stir ingredients contained in the receptacle 46. Hence, a mixture of the ingredients may be prepared.

The motor 42 may be operatively coupled with the mixing blade 56. A curved arrow 60 indicates a rotation of the mixing blade 56.

Downstream of the receptacle 46, a cooling unit 64 is provided. The cooling unit 64 involves a cooling chamber 66 having a circumferential wall 68. The circumferential wall 68 may be formed from stainless steel that qualifies for use in food processing environments.

In at least some embodiments, the cooling chamber 66 extends through a cooling cylinder 70 defined by the circumferential wall 68. In the cooling chamber 66, a screw shaft 72 is provided. Needless to say, also the screw shaft 72 may be coupled with the motor 42. Hence, also the screw shaft 72 may be rotated, refer to the arrow 60.

In some embodiments, one and the same motor 42 is coupled with both the mixing blade 56 and the screw shaft 72. However, in alternative embodiments, two separate motors are provided, one of which is coupled with the mixing blade 56 while the other one is coupled with the screw shaft 72.

The screw shaft 72 in the cooling chamber 66 is arranged to propel or advance the pre-mixed ingredients through the cooling chamber 66.

Further, the cooling unit 64 is arranged to cool down the circumferential wall 68 of the cooling chamber 66 and in this way to freeze the passing mixture of ingredients (also referred to as slurry).

In accordance with major aspects of the present disclosure, a first screw section 74 and a second screw section 76 are formed at the screw shaft 72. The first screw section 74 may also be referred to as upstream screw section. The second screw section 76 may also be referred to as downstream screw section.

The machine 30 further involves a modelling unit 32. The modelling unit 32 involves a discharge opening 84 through which the prepared ice cream may be dispensed. Needless to say, the discharge opening 84 may involve a sieve or mask, depending on the intended purpose. In Fig. 2, an arrow designated by 86 indicates a general flow direction of the processed foodstuff product.

Fig. 3 is a block representation of major modules of an ice making machine. As already described in Fig. 2, a controller 40, a mixing unit 54, a cooling unit 64, and a modelling unit 82 is provided. Further, indicated by 90, a heat removal unit is provided. The heat removal unit 90 is operatively coupled with the cooling unit 64. The heat removal unit 90 is arranged to remove excess or waste heat from the cooling unit 64. Hence, cooling performance of the cooling unit 64 may be further increased.

The controller 40 is arranged to control the operation of the mixing unit 54, the cooling unit 64, and the heat removal unit 90. To this end, the controller 40 may control at least one motor, for instance to operate mixing blades, screw blades, etc. Further, the controller 40 may be arranged to control a cooling action, for instance a cooling flow, cooling elements, etc. Embodiments of cooling elements will be discussed in more detail further below.

In addition, the controller 40 may be arranged to control the operation of the heat removal unit 90. To this end, for instance a heat removal cycle may be operated which may involve the operation of a pump, a valve, etc.

Fig. 4 is a schematic, simplified view illustrating the operation of an exemplary embodiment of a cooling unit 64.

At an inlet end, a mixing unit 54 is provided. At an outlet end, a modelling unit 82 involving a discharge opening 84 is provided. Between the inlet and the outlet, a cooling chamber 66 is arranged in which a screw shaft 72 is arranged. At the screw shaft 72, a first screw section 74 and a second screw section 76 are provided. The second screw section 76 is downstream of the first screw section 74.

The cooling unit 64 is arranged as a flow-through cooling unit. This does not necessarily involve that a fluid cooling medium is provided. Rather, as used herein, the term flow-through cooling unit emphasizes that the processed foodstuff product is basically passing through the cooling chamber 66. Hence, a continuous cooling operation may be provided. Therefore, not the cooling medium, but the cooled or frozen foodstuff product is actually "flowing" through the cooling unit 64.

In the embodiment illustrated in Fig. 4, the cooling unit 64 involves at least one thermoelectric transducer 94. Thermoelectric transducers 94 are generally known. They may involve, but are not limited to, Peltier elements. Peltier elements basically create a temperature difference when a voltage is applied thereto. Hence, a cool side and a hot side is present. By cooling down the hot side, the cooling efficiency of the Peltier elements may be improved. For instance, a series of Peltier elements may be used. Hence, even without employing a conventional cooling circle, heat may be removed from the cooling chamber 66, thereby cooling or freezing the passing foodstuff product.

In Fig. 4, also the heat removal unit 90 is schematically illustrated. The heat removal unit 90 involves a heat removal cycle 98 that is operatively coupled with the cooling unit 64, particularly the thermoelectric transducer(s) 94.

By way of example, a heat exchanger 100 is provided that is arranged as a cylindrical sleeve 102. The heat exchanger 100 is wrapped around the thermoelectric transducer(s) 94. Hence, waste heat may be removed therefrom.

Via at least one fluid line 104, a heat removal fluid may flow between the sleeve 102 and a heat exchanger 106.

Hence, the heat removal cycle 98 involves a heat exchanger 100 at the hot side, and a heat exchanger 106 at the cold side. At the heat exchanger 100, waste heat may be transferred from the cooling unit 64 to the heat removal fluid. Further, at the heat exchanger 106, the heat removal fluid may cool down. To this end, a heat storage medium 108 may be provided in or operatively coupled with the heat exchanger 106. Hence, assuming that the heat storage medium 108 is actually colder than the passing heat removal fluid, a heat transfer may be established.

Further, a pump 110 may be provided in the heat removal cycle 98 to propel the fluid flowing therethrough.

In some embodiments, the heat storage medium 108 may be arranged to be attached or detached from the heat exchanger 106. This has the advantage that the heat storage medium 108 may be placed in a fridge or a freezer, in advance of a use of the machine 30. Hence, the greater the temperature difference between the heat storage medium 108 and the passing heat removal fluid, the better the cooling unit 64 may be cooled down. The heat storage medium 108 may involve a solid or a fluid medium. Generally, the storage medium of the heat storage medium 108 may have a considerable heat storage capacity.

In Fig. 5, an exemplary embodiment of a screw shaft 72 having a first screw section 74 and a second screw section 76 is illustrated. The screw shaft 72 may generally be used in a cooling unit 64, refer to Fig. 2.

In Fig. 5, a flow direction of the processed foodstuff product is indicated by an arrow 86. The screw shaft 72 is arranged in a cooling cylinder 70 of the cooling unit 64. Hence, a circumferential wall 68 of the cooling cylinder 70 surrounds the screw shaft 72.

As already explained in connection with Fig. 2, the screw shaft 72 may be operatively coupled with a motor to rotate the screw shaft 72 about its longitudinal axis 112.

The first screw section 74 comprises at least one first thread helix 114. The second screw section 76 comprises at least one second thread helix 116. Each of the first screw section 74 and the second screw section 76 may also involve a plurality of helixes or, in the alternative, a segmented or partially interrupted helix.

As can be readily seen in Fig. 5, the first screw section 74 is in close contact with the circumferential wall 68. This is indicated by a first radial clearance 118 in Fig. 5. Consequently, an outer diameter dl of the first screw section 74 almost corresponds to an inner diameter Di of the cooling cylinder 70, i.e. is only slightly smaller.

By contrast, between the second screw section 76 and the circumferential wall 68, a much greater clearance is provided, refer to the second radial clearance 120 in Fig. 5. Consequently, a diameter D2 of the second screw section 76 is significantly smaller than both the inner diameter Di of the cooling cylinder 70 and the diameter D 1 of the first screw section 74.

In Fig. 5, a pitch of the first thread helix 114 is indicated by pi and pi. Further, a pitch of the second thread helix 116 is indicated by p2. In the exemplary embodiment shown in Fig. 5, a mean pitch of the first thread helix 114 is greater than the pitch p2 of the second thread helix 116. However, also deviating arrangements are conceivable that do not comply with this arrangement.

As can be further seen from Fig. 5, the pitch pi, pi of the first thread helix 114 is gradually reduced towards the second thread helix 116. In other words, a downstream pitch pi of the first thread helix 114 is smaller than an upstream pitch pi of the first thread helix

114. As the gap between neighboring coils becomes smaller in the downstream direction, the foodstuff product passing through the cooling chamber 66 is gradually pressurized.

A (cross-sectional) profile of the coil or blade that forms the first thread helix 114 is indicated in Fig. 5 by 126 (dashed line). The profile 126 is generally trapezoid-shaped. The profile 126 involves an upstream flank 128, a downstream flank 130, and a

circumferential surface 134 arranged therebetween. At the outermost edge of the downstream flank 130, a scraping edge 132 is present. The scraping edge 132 and/or the circumferential surface 134 of the first thread helix 114 define the diameter Dl thereof. A respective profile of the second thread helix 116 is indicated in Fig. 5 by 138. As can be readily seen, the profile 126 is much more prominent than the profile 138.

While the screw shaft 72 is rotated, the scraping edge 132 scrapes off the processed foodstuff product from the circumferential wall 68 of the cooling unit 74. Further, the downstream flank 130 urges or propels the foodstuff product downwards towards the second screw section 76.

The scraping action involves the formation of ice particles. Hence, a desired composition and particle size may be ensured. However, it has been observed that the scraping process as such involves a certain amount of friction and, consequently, heat generation in the vicinity of the first screw section 74. Hence, the second screw section 76 is arranged such that no scraping between the second thread helix 116 thereof and the circumferential wall 68 takes place. Hence, little or even no heat is generated in the foodstuff product in the vicinity of the second screw section 76. Nevertheless, also the second screw section 76 contributes to the ice cream making process by stirring and propelling the processed slurry.

With reference to Fig. 6, Fig. 7 and Fig. 8, a layer structure of the cooling unit 64 will be explained in more detail.

Fig. 6 is a simplified cross-sectional side view; Fig. 7 is a cross-sectional view along the line VII-VII in Fig. 6. Fig. 8 is a detailed view of a region indicated by VIII in Fig. 6.

The general layout of the cooling unit 64 corresponds to the layout already explained herein before. The cooling unit 64 involves a cooling cylinder 70 having a circumferential wall 68 that defines a cooling chamber 66. In the cooling chamber 66, a screw shaft 72 having a first screw section 74 and a second screw section 76 is arranged. Cooling elements involving at least one thermoelectric transducer 94 are placed around the circumferential wall 68. At an outer side of the thermoelectric transducer(s) 94, a sleeve 102 that forms part of a heat exchanger is provided. Through the sleeve 102 a heat removal fluid may flow and remove waste heat from the thermoelectric transducer(s) 94.

Hence, at least three cylindrical layers are provided, the circumferential wall 68, the thermoelectric transducer(s) 94, and the sleeve 102.

In Fig. 6 and Fig. 7, hatching is used to distinguish the respective layers 68, 94, 102. Needless to say, at least through the sleeve 102, a fluid flow may be present.

Fig. 8 is a more detailed partial view of a side region of the arrangement shown in Fig. 6 and Fig. 7. As with Fig. 6 and Fig. 7, from the inside to the outside, the screw shaft (here the first screw section 74), the circumferential wall 68, the thermoelectric transducer(s) 94 of the cooling unit, and the sleeve 102 of the heat removal unit are provided in a concentrically arranged series.

Fig. 8 further shows that between the circumferential wall 68 and the thermoelectric transducer(s) 94, a heat transfer film 142 is present. Similarly, between the thermoelectric transducer(s) 94 and the sleeve 102, a further heat transfer film 144 is present. The heat transfer films 142, 144 improve the heat transfer between the respective layers. Hence, the circumferential wall 68 may be cooled down by removing heat therefrom at an outer side thereof. Further, at an outer side of the thermoelectric transducer(s) 94, a heat removal from the hot side thereof to the sleeve 102 may take place.

The heat transfer films 142, 144 may involve materials having a great thermal conductivity, for instance appropriate metal alloys. The heat transfer films 142, 144 provide a conductive layer improving the heat transfer between the involved surfaces.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limiting the scope.