Apparatus for manufacturing frozen confection

An aerated mixture of unflavored ice cream, yogurt or other food base mix is applied to one end of the interior of an elongated freezing chamber and is advanced along the chamber by a rotating screw or auger. As the mix is advanced within the chamber, it is cooled and worked to form a semi-solid product. Prior to discharge from the remote end of the chamber, flavor is injected and mixed into the product. The free volume in the system from chamber inlet to the discharge point is carefully limited to a minimum amount so that most of the product is cleared from the system during each individual serving. The result is the availability of individual servings of a fresh, high-quality frozen food product.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
The invention relates to the manufacture of high-quality frozen foods such 
as ice cream, yogurt, and the like. 
B. Prior Art 
Frozen food products are typically produced in batch form, i.e., a quantity 
substantially larger than the amount commonly required by a single user is 
produced in advance of a specific request and is held available for 
subsequent dispensing. For example, in machines for dispensing "soft" ice 
cream to the individual consumer, although an individual consumer might 
want a serving of only a few ounces, it is common to dispense this from a 
machine which makes a quantity measured in quarts or gallons in advance of 
the request and which stores the excess for subsequent sale. The product 
necessarily deteriorates during this storage, both through oxidation and 
through the growth of ice crystals which detract from whatever smoothness 
the product originally possessed when fresh. 
Novel apparatus and methods suitable for producing, on demand, quantities 
of frozen food product such as ice cream, yogurt or the like that range 
from in the order of ounces to gallons or unlimited amounts is described 
in a series of patents of which two of the inventors of the present 
invention are co-inventors, namely, U.S. Pat. No. 5,292,030, "Method And 
Apparatus For Producing And Dispensing Aerated Products", issued Mar. 8, 
1994; U.S. Pat. No. 5,433,967, "Method And Apparatus For Producing And 
Dispensing Aerated Or Blended Food Products", and U.S. Pat. No. 5,473,909, 
"Method And Apparatus For Producing And Dispensing Aerated Or Blended 
Fluid Products", issued Dec. 12, 1995. The teachings of these patents are 
expressly incorporated herein by reference. 
SUMMARY OF THE INVENTION 
A. Objects of the Invention 
Accordingly, it is an object of the invention to provide a method and 
apparatus for forming a frozen confection, food, or the like of high 
quality and in amounts that extend down to the order of ounces or less. 
Further, it is an object of the invention to provide a method and apparatus 
for producing "on demand" a high quality frozen confection, food or the 
like. 
Another object of the invention is to provide apparatus for producing "on 
demand" a high quality frozen confection, food or the like which is simply 
constructed, readily serviceable, and easily maintained in a sanitary 
condition. 
Yet a further object of the invention is to provide a method and apparatus 
for producing "on demand" a high quality frozen confection, food or the 
like in which different flavors may readily be imparted to a base mixture 
during the "on demand" production of the resultant product and with 
minimum carry-over from one serving to the next. 
Another object of the invention is to provide method and apparatus for 
producing "on demand" flavoring for a frozen food product. 
B. Brief Description Of The Preferred Embodiment of The Invention 
In accordance with the present invention, an aerated base mixture of 
unflavored ice cream, yogurt or other food base or mix is fed in liquid 
form to the interior of an elongated freezing chamber having a rotating 
screw therein. The chamber wall is cooled to a temperature below freezing 
by means of cooling fluid applied to the exterior thereof. The liquid base 
in the screw threads is moved longitudinally along the chamber by the 
screw and increasingly cools as it contacts the wall of the chamber in 
traveling down the chamber. The device functions more or less as a 
positive displacement pump pumping the base along the chamber such that 
there is microcirculation of the base within the valleys of the screw 
thread(s). Liquid base is continuously circulated under positive pressure 
into heat exchange contact with the chamber walls and freezes 
progressively. This minimizes air cell and ice crystal size and uniformly 
distributes these elements throughout the food product. 
Thus, the operation of the present apparatus contrasts sharply with prior 
devices with rotating blades which scrape frozen material from the surface 
of the chamber and remix it into the bulk of unfrozen material within the 
chamber. 
By the time the base reaches the remote end of the chamber, the base is in 
the form of a highly viscous slurry or paste that is cooled to a 
temperature at or near its freezing point. 
The base product exits the chamber into an end cap that both supports the 
screw and provides convoy channels that carry the product to a discharge 
bore from which the product may exit the chamber. Extending into the bore 
from the exterior is one or more flavoring channels, and a drive shaft for 
a mixer blade positioned in the bore or the chamber and on the end of the 
shaft. The blade intermixes the flavoring and the base product before 
discharge of the product from the bore. 
The convoy channels in the end cap are desirably of limited total volume in 
relation to the volume of a typical ice cream cone serving in order to 
minimize the amount of product resident in the machine at any time. For 
similar reasons, as well as to achieve rapid and thorough cooling of the 
product, the clearance between the screw and the inner wall of the chamber 
is very small, e.g., on the order of a tenth of an inch or less.

PREFERRED EMBODIMENT 
In FIG. 1, a longitudinally extended freezing chamber 10 is supplied with 
cooling fluid through a supply tube 12. The cooling fluid traverses the 
chamber 10 through channels 14 in the interior thereof (see FIG. 2) and 
exits through a discharge tube 16. A reservoir 18 of confection or food 
product mix in the liquid state is supplied to the chamber 10 at an inlet 
end thereof via feed tube 20. The product preferably comprises an 
unflavored base mix that has been aerated and is ready for chilling or 
near freezing. A suitable method and apparatus for forming the base mix is 
described in U.S. Pat. Nos. 5,292,030, 5,433,967, and 5,473,909, referred 
to above. 
Although we have shown chamber 10 oriented horizontally and the mix being 
introduced through the side wall of the chamber, the chamber 10 could just 
as well be vertical and the liquid flowed into the upper end of the 
chamber from any suitable source of aerated mix, e.g., a turbulence tube 
as disclosed in the above-identified patents. 
The liquid mix is carried through the chamber 10 by means of a screw 22 
(see FIG. 2) and is discharged from the chamber at an outlet end thereof 
via a discharge nozzle 24. The screw 22 is driven by a spindle 26 
connected to a shaft 28 of a motor 30. A flavoring head 32 is located at 
the outlet end of the chamber 10 and imparts different flavorings to the 
mix inside the chamber through separate nozzles 34a, 34b, 34c (see FIG. 3) 
before the mix exits the chamber. The specific flavor may be selected by 
actuating selector buttons 32a, 32b, 32c, respectively. Three such nozzles 
and buttons, and thus three such flavors, have been shown for purposes of 
illustration, although more or less may be used. A motor 36 drives a 
perforate mixer blade 38 (see FIG. 3) via a shaft 40 in order to intermix 
the flavoring with the base mix before the latter is discharged through 
the nozzle 24. 
Turning now to FIGS. 2 and 3, the interior of the chamber 10 is shown in 
more detail. For purposes of illustration, the chamber is shown as 
comprising an elongated double-walled cylinder having an inner wall 50 and 
a concentric outer wall 52 enclosing between them a spirally-wound cooling 
coil 14 in contact with, and encompassing, the inner wall 50. The coil 14 
is connected at an inlet end 14a to coolant inlet tube 12 and at an outlet 
end 14b to coolant discharge tube 16. A removably attached end plate 60 
adjacent the fluid mix inlet 20 seals the interior of the chamber at one 
end thereof, and a removably-attached end plate 62 adjacent the chilled 
mix outlet tube 16 seals the chamber at the other end thereof. The screw 
22 is supported at one end by the shaft 26 which extends through the end 
plate 60, and is supported at the other end by a shaft extension 22a which 
rotates in a mating recess in plate 62. 
The screw 22 is spaced a slight distance "d" from the interior wall 50. 
Plate 62 has a circumferential groove 64 formed on its interior face of 
radial dimension "d" matching the spacing between the screw and the 
interior wall and of relatively slight depth. A bore 64b extends 
longitudinally (as seen in FIG. 2) from a lower portion of the groove 64a 
into a transverse bore 66. The bore 66 communicates with nozzle 24. 
Liquid supplied to the chamber 10 from reservoir 18 is confined between the 
exterior surfaces of the threads of the screw 22 and the interior surface 
of wall 50, which is chilled by the coolant fed through the conduit 56. As 
the screw is rotated by the motor 30, the mix is advanced longitudinally 
(i.e., left to right in FIG. 2) within the screw thread and along the 
cylinder wall. As this occurs, the mix is increasingly chilled and has the 
form of a highly viscous slurry or paste by the time it reaches the 
discharge end of the chamber at the end plate 62. On reaching the end 
plate, it is forced into the circumferential groove 64 and thence through 
the port 64b into bore 66. 
As it traverses the chamber, the mix is confined to a limited volume 
defined by the volume between the outermost (peak) diameter of the screw 
and the interior wall of the chamber, as well as the volume contributed by 
the thread itself (i.e., the volume in the valleys between the peaks and 
roots of the screws). The former volume is limited by limiting the 
clearance between the screw and the interior wall of the chamber. The 
latter can be limited by controlling the thread depth and pitch. The 
overall volume is desirably limited so as to promote microcirculation of 
the mix around the longitudinal axes of the thread valleys. Mix is thus 
circulated into contact with the chilled wall 50 as the mix is, pumped 
along the chamber by the screw. This results in the formation of ice 
crystals and air cells in the mix which are quite small, i.e., tens of 
microns, and a uniform distribution of these cells and crystals throughout 
the product thereby optimizing product overrun. 
As seen more clearly in FIG. 3, flavoring head 32 contains flavoring 
reservoirs 33a, 33b, 33c which are connected to the bore 66 via tubes 
34a-34c. When a particular flavor selector 32a-32c button is operated, it 
causes head 32 to dispense a corresponding flavor into bore 60. This 
flavoring is intermixed by rotary mixer 38 with the base mix being 
supplied to bore 66 through bore 64b before the mix is discharged through 
discharge nozzle 24. Mixer 38 is advantageously a cruciform paddle wheel 
having apertures 38a in its blades through which the mix may flow for 
thorough intermingling with the flavoring. 
As an example of a particular configuration for a system in accordance with 
the present invention, a multiple thread-start screw having a length of 
5-20 inches, a pitch of 1-5 inches, a thread depth (peak to root) on the 
order of 0.1 inch, a clearance (distance between outer screw diameter and 
inner wall) of about 0.010 inch and rotated at between 100 and 400 rpm can 
be constructed to chill the base mix to a suitable serving temperature at 
the time of discharge. Acceptable serving rates on the order of four 
ounces in ten seconds should readily be achievable. This system provides a 
thin mix layer which dynamically cools the mix as it is forced along the 
chamber by the screw and is also believed to microcirculate or "work" the 
mix as it is advanced to thereby avoid large ice-crystal formation. It 
also avoids scraping the interior wall where such crystals would most 
readily form. 
It will be understood that the foregoing description is illustrative only, 
and the invention is not limited to the specific parameters and details 
shown and described. For example, longer or shorter screws may be used, of 
different pitch, diameter and number of "starts",and rotated at different 
speeds. The screw material is preferably plastic, such as Delrin (a 
trademark of DuPont), but may be any of a variety of other plastic or 
non-plastic materials. More than one screw may be used, e.g., two or more 
screws in co- or counter-rotating interlocking fashion to more positively 
advance the material through the chamber. Also, the starting mix could 
itself be flavored and to which other flavors may be added during the 
process. 
The volume of the conduits at the discharge end, such as groove 64a and 
bore 64b should be kept as small as practicably possible in order to 
minimize the amount of chilled mix resident in the system after a serving. 
A variety of base mixtures may be used, and these may be fed from the side 
(as illustrated herein) or from the end, under gravity feed or under 
pressure, etc. The mix is preferably a dairy mix, but other food mixes may 
be used. 
CONCLUSION 
From the foregoing it will be seen that there is described a method and 
apparatus for manufacturing frozen confection or other foods that is 
particularly adapted to providing fresh single-serving portions on demand. 
The system avoids batch processing, is simple, and is expected to be 
readily maintainable in sanitary condition without excessive labor.