Patent Publication Number: US-6213007-B1

Title: Home yogurt/cheese making machine

Description:
This is a Continuation of application Ser. No. 09/352,062, filed on Jul. 14, 1999, now abandoned which is a divisional of application Ser. No. 09/183,833, filed on Oct. 30, 1998, now U.S. Pat. No. 6,012,383, which is a continuation-in-part application of Ser. No. 08/872,009, filed Jun. 9, 1997, now U.S. Pat. No. 5,829,344. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to kitchen appliances, and more particularly to a machine for automatically preparing any one of yogurt, soft frozen yogurt, hard frozen yogurt and cheese, at home. 
     II. Discussion of the Prior Art 
     Because of its taste and nutritional value, yogurt has been an increasingly popular food product. Many brand name yogurt products are available to the consumer in supermarkets. Traditionally, and because of the expense of these products, some consumers attempt to make yogurt at home. Warming devices for making yogurt at home are available and are discussed in the prior art. For example, U.S. Pat. No. 4,009,368 to Faivre et al. describes an electrically heated yogurt-making machine having an enclosure containing a receptacle into which boiled milk and a yogurt starter is placed. The enclosure contains an electrical heating element and a fusible material (wax) which is adapted to be heated to a melting point by the heating element. Heat from the melted wax is transferred to the milk container. The purpose of the wax is to provide a thermal mass exhibiting a temperature plateau at or near the optimum for incubating the bacteria used to transform the milk to yogurt. 
     The yogurt making process requires that the yogurt mix incubate relatively undisturbed for a somewhat unpredictable number of hours until the desired consistency and acidity is achieved. More frequent disturbance results in curdling of the milk product and the formation of cheese. If too high a temperature is employed, it accelerates the process to the point where it is difficult to catch the end-point where consistency and flavor are at their optimum. Traditional, home-based, room temperature yogurt techniques are slow, sometimes taking as long as 12 hours. The room temperature yogurt process does, however, offer the advantage of allowing it to be checked at reasonable intervals so that the incubation process might be terminated at or near its optimal point by initiating cooling. The incubation process can be accelerated to only about four hours by providing a warm environment for the yogurt mix, but if the optimal point is not detected accurately, the yogurt becomes more acidic and less palatable. Thus, considerable operator attention and care is required with prior art warming apparatuses. 
     The yogurt making appliances of the present invention obviate these problems. Specifically, the yogurt making machines of the present invention require no operator intervention or monitoring during the reasonably rapid, heating, cooling and warmed incubation process. The warming is automatically stopped at the desired point in the process with refrigeration being initiated automatically to terminate further incubation. 
     A further object and advantage of the present invention is that the same machine can be used to facilitate the preparation of frozen yogurt and ice cream as well as both cultured and artificially curdled cheese products. 
     SUMMARY OF THE INVENTION 
     The yogurt making appliances constructed in accordance with the present invention are particularly adapted for use in the home to automatically make yogurt, hard and soft frozen yogurt or ice cream and cheese products. There are at least six possible embodiments of these devices. The first, motor and detent (magnet) on top, is claimed in the above-referenced U.S. application and in European Union patent application 08/3043720. A second embodiment, motor and detent on the bottom, the third, motor on top and detent on the bottom, the fourth, motor on the bottom and detent on top, the fifth, motor and detent on the bottom with a center post and the sixth, motor on the bottom and detent on top with a center post, are described in the present specification. 
     The first embodiment, motor and detent on top, has an insulated container having a base and peripheral side walls defining a non-circular cross-section and an open top through which milk or dried milk and water is added to a yogurt starter, usually yogurt from the supermarket or a remanent of a previous batch. 
     One or more of (i) either the peripheral side walls, (ii) the base of the insulated container, and/or (iii) the paddle member have embedded therein or otherwise support an electrical or other warming element, such as a reversible, thermoelectric heating and cooling device and/or a nicrome filament that is adapted to apply warming to the contents of the container. 
     A cover member is configured to fit atop the peripheral side walls in covering relation to the open top of the container. The cover member includes at least one vent hole formed therethrough, along with a centrally located hole that is adapted to receive a paddle support shaft therethrough. The paddle support shaft has a rotating paddle secured to its lower end and the shaft for the paddle is sufficiently long so that when the paddle is disposed within the yogurt or cheese mix in the container, the shaft will pass upwardly through the central hole in the cover member. 
     Also disposed about the paddle support shaft and positioned atop the cover member is a rotatable occluding means for selectively covering and opening the vent hole(s) in the cover member. The means for selectively occluding and opening the vent hole(s) is releasibly secured to the cover member by a detent, such that a predetermined force must be applied to the vent hole occluding means before it is able to move relative to the cover member. 
     Finally, at least one drive motor with a built-in gear reduction transmission is affixed to the vent hole occluding means for rotating the paddle support shaft and paddle relative to the stationary container to periodically test the contents in the container. When the paddle stalls due to gelling and thickening of the contents, the motor then causes the occluding means to move from a vent hole occluding position to an open position. The motor is adapted to be driven either with predetermined duty cycles or continuously, dependent on the product being made. 
     Shifting of the occluding device from the covering position to the open position also triggers a switch, shutting off the motor, timer and the warming element and activating a cooling element. Alternatively, if the optional vent cover is not utilized, then cooling can rapidly occur if the device is disposed in a household refrigerator with its electrical cord extending out past the conventional, soft, door seal gasket used in most refrigerators. 
     The culturing container may, as an option, contain a double walled freezing bowl having a cylindrical, microwave heatable stainless steel interior wall and a non-cylindrical outer wall when preparing frozen yogurt. 
     The second embodiment has its motor and detent beneath a rotatable, un-insulated, non-circular culturing container. A double walled freezing bowl having a microwave heatable stainless steel inner wall may be enclosed within the culturing container and both disposed within an insulated chamber, consisting of a housing, base and cover. The housing also supports a fixed, downwardly directed, heatable paddle that extends into the mix. The base incorporates an air vent opening and/or an electrical or other warming element, such as a reversible thermoelectric warmer/cooler, with fans, mounted therein. A centrally located hole is formed through the base that is adapted to receive a drive shaft therethrough from a motor mounted on a rotatable occluding member. A gear reduced electrical motor is carried by the occluder for driving the culturing container. The occluding member is movable from a first position in which the air vent in the base is occluded to a second position in which the air vent opening is uncovered. The movement occurs when the consistency of the product being produced, as tested by the container motion, increases the resistance of the container to rotation relative to the stationary paddle. The means for selectively occluding and opening the vent hole is releasibly secured to the base member by a detent, such that a predetermined force must be applied to the vent hole occluding means before it is able to move relative to the base member. The motor is adapted to be driven either with a predetermined duty cycle or continuously, depending on the product being made. Shifting of the occluding device from the vent hole covering position to the open position also actuates a switch for deactivating the drive motor and the warming and timing elements and activating the cooling element. Alternatively, cooling can rapidly occur if the optional vent cover is not utilized and the device is disposed in a conventional refrigerator with its electrical cord extending outward past the soft door seal gasket, as with the first embodiment. 
     The third embodiment has the motor on the top of the container and the detent located in the base. It, too, has a rotatable, non-circular culturing container designed to be used with or without a freezing bowl. The culturing container is enclosed within a fixed insulated chamber, consisting of an exterior housing, a base and a cover. The cover, which is fixed to the housing, has a centrally located hole that is adapted to receive a paddle support shaft therethrough. 
     The paddle support shaft has a heatable paddle secured to its lower end. The shaft for the paddle is sufficiently long so that, with the paddle disposed within the mix in the container, the shaft will pass upwardly through the central hole in the cover member. 
     At least one drive motor with a gear reduction mechanism is affixed to the cover for rotating the paddle support shaft and paddle relative to the container to periodically test the contents of the container. Electrical slip rings permit warming and heating of the rotating paddle. At least one mix-adding hole and/or automatic yogurt starter adding hole, with a plug, is also formed through the cover. 
     The base incorporates an air vent opening. A centrally located hole formed in the base is adapted to receive a supporting shaft to which the container and the occluder are joined. The container and occluder are jointly movable only from a first position occluding the air vent opening to a second position in which the air vent opening is uncovered. This occurs when the consistency of the product being produced, as tested by the paddle motion relative to the mix in the container or freezing bowl, increases the resistance to paddle rotation sufficiently to overcome the force exerted by the detent means used to releasibly secure the yogurt container (and/or freezing bowl) and occluding member to the base. 
     The paddle motor is adapted to be driven either according to a predetermined duty cycle or continuously, according to the product being made. Shifting of the container and occluding member from the covering position to the open position also actuates a switch, shutting off the drive motor and timer and the thermoelectric warming element and activates the cooling element. Alternatively, cooling can rapidly occur if the optional vent cover is not utilized and the device is disposed in a refrigerator with the yogurt maker&#39;s electrical cord extending outward past the soft door seal gasket. 
     In a fourth embodiment, the motor is disposed in the base and the detent mechanism is on the top. It incorporates a rotatable culturing container, and optionally, a double-walled freezing bowl having a noncircular exterior and a stainless steel inner wall. Either or both are adapted to be enclosed within an insulated chamber consisting of a fixed, insulated, exterior housing, a base member and a cover. The cover is configured to fit firmly atop the housing and it includes at least one vent hole with an optional cover, and at least one pluggable mix adding hole. The cover also has a centrally located hole containing a bearing for journaling a paddle support shaft. The paddle support shaft has a paddle secured to its lower end and the shaft for the paddle is sufficiently long so that with the paddle disposed within the mix in the culturing container, the shaft will pass upwardly through the bearing in the cover member. 
     Also attached firmly to the paddle support shaft and positioned in relation to the cover member is a means for selectively occluding and opening the vent hole in the cover member. The means for selectively occluding and opening the vent hole is releasibly secured to the cover member by a detent, such that a predetermined force must be applied to the vent hole occluding means before it is able to move relative to the cover member. A coiled conductive ribbon or otherwise supple electrical wire connection serves to conduct electricity to the paddle for warming/heating same. 
     The base contains an electrical heating element and/or a reversible thermoelectric warmer/cooler mounted therein. A motor with reduction gears is connected in driving relation with respect to the container. The occluding member mounted on the cover is movable with respect to the cover from a first position in which the air vent opening in the cover is occluded to a second position in which the air vent opening in the cover is uncovered. This again occurs when the consistency of the product being produced, as tested by the container motion, increases the resistance to rotation of the container against the paddle. The motor is adapted to be driven either according to a predetermined duty cycle or continuously, depending on the product being made. Shifting of the occluding device from the covering position to the open position also activates a switch, cutting off the drive motor and the warming element and activating a cooling element. Alteratively, cooling may rapidly occur if the optional vent cover is not utilized, and the device is dwelling in the refrigerator as previously explained. 
     In the fifth embodiment, the motor and detent are disposed in the unit&#39;s base. It has an insulated outer housing mounted on the base and its peripheral side walls define a chamber of a non-circular cross section and an open top through which whole milk or dried milk and water, or other constituents commonly used in preparing yogurt may be added to a yogurt starter, usually yogurt from the supermarket or a remanent of a previous batch. One or more of either the peripheral side walls or the base and/or the paddle member have embedded therein or otherwise support a warming and heating element, such as a tungsten filament. A reversible heat pump (thermoelectric heater/cooler) that is adapted to apply warming, and/or cooling, to the contents of the container may be employed as well. A cover member is configured to fit atop the peripheral side walls of the outer container in covering relation to its open top. The cover member includes at least one electrical connection with the housing and at least one slip-ring electrical connection with the rotating paddle or the center post. The outer housing has an integrally molded, tubular center post which has a centrally located sleeve-bearing that is adapted to receive a paddle support shaft therethrough. The paddle support shaft has a retainer preventing it from slipping downward. A rotating split paddle member is secured to its upper end. The paddle blades are sufficiently long so that they extend downwards into the yogurt or cheese mix placed in the container when used. 
     Also disposed around the paddle support shaft in the base is a motor, detent magnet and reed switch magnet supporting means. This supporting means is releasibly secured to the base member by the detent, such that a predetermined force must be applied to the aforementioned supporting means before it is able to move in relation to the base member. 
     Finally, at least one drive motor with a gear reduction mechanism is affixed to the supporting means for the rotatable motor, detent magnet and reed switch magnet for rotating the paddle support shaft and paddle relative to the stationary housing to thereby periodically test the contents in the chamber of the housing. The motor also rotates the supporting means, detent magnet and reed switch magnet with respect to the container upon the thickening of the contents in the container. The motor is adapted to be driven either with predetermined duty cycles or continuously, dependent on the product being made. 
     The culturing container may have a double walled freezing bowl inserted into it. The freezing bowl has a cylindrical, microwave heatable stainless steel interior wall and a non-cylindrical outer wall. Shifting of the detent magnet and reed switch magnet supporting device also triggers a switch, shutting off the motor, timer and the warming element and activating a cooling element. 
     In a sixth embodiment, the motor is disposed in the base and the detent is on the unit top. It has an insulated outer housing supported on a base, peripheral side walls defining a non-circular cross-section and an open top through which whole milk, dried milk plus water or other yogurt constituents are added to a yogurt starter, usually yogurt from the supermarket or a remanent of a previous batch. Integrally molded with the outer housing is a tubular center post. One or more of either the peripheral side walls or the base or the center post, and/or the paddle member have embedded therein or otherwise support an electrical or other warming and/or heating element or reversible, thermoelectric heat pump that is adapted to apply warming or cooling, to the contents of the container. A cover member is configured to rotate atop the peripheral side walls in covering relation to the open top of the container. The cover member includes at least one vent hole (and at least one automatic starter adding hole) formed therethrough, along with a centrally located hole that is adapted to receive a stub shaft on an occluder member therethrough. The cover has rotating paddle blades secured thereto which are sufficiently long so that they extend into the yogurt or cheese mix placed in the container during use. Slip rings connect the center post electrically with the cover. Also disposed about the occluder stub shaft and integral therewith is an occluding means for selectively covering and opening the vent hole in the rotating cover member. The means for selectively occluding and opening the vent hole is again releasibly secured to the cover member by a detent, such that a predetermined retarding force must be applied to the paddle before the occluder is able to move independent of the cover member. Finally, at least one drive motor with a gear reduction mechanism is affixed to the base for rotating the paddle support shaft within the tubular center post-sleeve. The motor is adapted to be driven either with predetermined duty cycles or continuously, dependent on the product being made. Periodic rotation of the top and its attached paddle tests the consistency of the contents in the container. As it thickens, the occluding means rotates away from a vent hole occluding position to an open position. 
     The culturing container may further contain or be replaced by a double walled freezing bowl having a cylindrical, microwave heatable stainless steel interior wall and a non cylindrical outer wall. Shifting of the occluding device from the covering position to the open position also triggers a switch, shutting off the motor, timer and the warming element and/or activating the cooling element. Alternatively, if the optional vent cover is not utilized, cooling can rapidly occur with the device dwelling in the refrigerator with its electrical cord extending out past the soft, door seal gasket. 
     When preparing yogurt, the machines of the present invention will preferably be placed on the kitchen counter, but may also, in most cases, be placed within the cooling compartment of a household refrigerator with the power cord for energizing the unit&#39;s motor and timing and heating/cooling elements extending out the door to a wall outlet. A solid-state timer is included as a part of the appliance for periodically energizing the motor(s) with a predetermined duty cycle whereby at relatively long periodic intervals, e.g., about every 15 minutes, the motor is energized for a relatively short time interval, e.g., about two seconds. This causes relative movement of the paddle with respect to the non-circular container, resulting in the consistency of the contents of the container being tested at infrequent intervals. As the incubation of the milk and yogurt starter continues in the warmed environment, a point will be reached where the mixture begins to rapidly gel. Under gelled conditions, the paddle and container will become locked against relative rotation and this results in the occluding means rotating from a vent hole occluding position to a vent hole open position. The rotation of the occluding means in the manner described also causes an electrical switch to open, shutting off power to the motor and to the warming element. With the power off and the vent hole open, cool air from the refrigerator will quickly absorb the heat energy within the appliance, terminating the culturing process. Alternatively, cooling can be achieved by having the switch reverse the polarity of the voltage applied to a thermoelectric heat pump. 
     The yogurt and cheese making container is preferably designed to have a non-circular periphery around its open upper end and around its inner peripheral side walls so that the gelled and curdled products provide a resistant lock between the paddle and the container. 
     In the first embodiment described, the cover may also be placed atop the container in any one of four positions. It has been found convenient to place a plurality of electrical switch actuators atop the wall of the container and surrounding the opening therein and then provide mating electrical switch contacts on the cover member such that when the cover is placed on the container in a first of the four possible positions, it causes the appliance to operate in a mode to produce yogurt. When the cover is rotated 90° and placed atop the container, only switches for causing the appliance to operate in a mode for producing soft frozen yogurt or ice cream will be actuated. Similarly, another 90° rotation of the cover relative to the container will result in only those switches for causing the appliance to produce hard frozen yogurt or ice cream to be actuated. The fourth possible position of the square cover relative to the square base will cause only those switches to be actuated whereby the appliance can be used to produce Ricotta cheese. Other alternative types of switching panels might be utilized. The cover and container of a device utilizing the switching scheme just described are appropriately color coded or otherwise marked to facilitate selection of a desired operating mode. 
     When the appliance of the first configuration of the present invention is to be used in preparing frozen yogurt or ice cream, the cover is placed on the container&#39;s open top in a different orientation such that cooperating switch and switch actuating devices on the container and cover disconnect the heating element from its source of power. A previously chilled freezing bowl dimensioned to fit into the opening in the container is removed from the refrigerator&#39;s freezer compartment and inserted into the opening of the container or inserted independently and rotation is commenced. The previously prepared mix is then poured into the freezing bowl, while the drive motor(s) are permitted to continuously drive either rotating paddle or container such that the frozen yogurt mix forming on the cylindrical inner wall of the freezing bowl is continuously scraped therefrom. The relative rotation of the container with respect to the paddle continues until the resistance on the paddle due to the presence of the hard or soft frozen yogurt overcomes stronger predetermined retaining forces to again allow the occluding means to rotate to the position wherein the electrical switch for applying power to the motor is opened. 
     When the appliance of the present invention is to be used in making agglutinated curd (Ricotta cheese), provision is made for the more nearly continuous rotation of the paddle in a warmed yogurt mix, stopped only about every 15 minutes for a shorter pause (about 5 minutes). A yogurt culture, which is stirred relatively continuously, agglutinates and forms a curd which, if subsequently not stirred, may settle as a firm mass sticking to the bottom of the irregular shaped container or, if stirred, may attach to and shrink on the stirring paddle, forming a ball. When the paddle increasingly becomes mired in an agglutinating mass which is attaching to the irregular shaped container, it causes a force resisting movement of the paddle. When the paddle, with an attached curd-ball, abruptly re-accelerates from a stop to a turning movement, the inertia of the curd ball on the paddle similarly causes a transient force sufficient to overcome the predetermined force between the occluding means and the cover so that the device opens up the vent hole in the cover and turns off the motor and timer and warming and/or may reverse a heat pump. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of the first embodiment home yogurt/cheese making machine; 
     FIG. 2 is a partial cross-sectional view of the first embodiment apparatus of FIG. 1; 
     FIG. 3 is a vertical cross-sectional view of the second embodiment home yogurt/cheese making machine of the present invention; 
     FIG. 4 is a cross-sectional view of the third embodiment home yogurt/cheese making machine of the present invention; 
     FIG. 5 is a cross-sectional view of the fourth embodiment home yogurt/cheese making machine of the present invention; 
     FIG. 6 is a cross-sectional view of the fifth embodiment home yogurt/cheese making machine of the present invention; 
     FIG. 7 is a cross-sectional view of the sixth embodiment home yogurt/cheese making machine of the present invention; 
     FIG. 8 is a schematic diagram of the electrical controls of the basic machine when used only for preparing yogurt or cheese; 
     FIG. 9 is a schematic diagram of the electrical circuitry incorporated in the machine for selectively preparing one of yogurt, hard and soft frozen yogurt or ice cream and cheese products; 
     FIG. 10 is a side elevational view of a yogurt “starter” adding attachment for the yogurt/cheese making machine; and 
     FIG. 11 is a top plan view of the attachment of FIG.  10 . 
    
    
     DESCRIPTION OF THE FIRST EMBODIMENT 
     Referring first to FIG. 1, there is indicated generally by numeral  10  a home appliance useful in preparing yogurt, soft or hard frozen yogurt or ice cream, and cheese from a starter and either pre-heated bottled milk or a mixture of dried milk and water as well as other ingredients for providing a desired taste and consistency. 
     It is recognized that yogurt can be prepared from nondairy products. Hence, the term “milk product” as used in the present application is intended to include both dairy and non-dairy products from which yogurt can be produced. The machine is seen to comprise a base container  11  of generally square configuration defined by a bottom  12  and four mutually perpendicular side walls  13 ,  14 ,  15  and  16 . The container  11  will preferably be molded from a suitable plastic and incorporated into the walls  13 ,  14 ,  15  and  16  and/or the bottom  12  is a thermostatically controlled warming element  17 , here shown as an elongated coil or serpentine arrangement of a nicrome wire that is arranged to warm the interior and, therefore, the contents of the container. A reversible thermoelectric heat exchanger for both warming and cooling might also be utilized. Other warming and heating element arrangements may be embedded in the paddle. The thermostat control is identified by numeral  18  in the drawings. As used herein “warming” is intended to mean raising or maintaining the temperature of the milk product to a culturing temperature which may be between about 113° F. while “heating” involves bringing the milk product to about 203° F. 
     The four walls  13 - 16  define an open upper top  19  having downwardly and inwardly sloping edges as at  20  and  21 . The mutually perpendicular side walls  13 - 16  and the bottom  12  are preferably formed of materials and insulation so that the heat energy derived by passing electrical current through the warming/heating element  17  will be inwardly directed. The upper edges of the four side walls include a plurality of post-like protuberances, as at  22 , which are spaced or otherwise distributed at predetermined intervals and, as will be further explained, function as electrical switch actuators. 
     Disposed above the base container  11  in the exploded view of FIG. 1 is an optional freezing bowl  23  that is used when preparing such products as hard or soft frozen yogurt or ice cream. The freezing bowl, which is also of a square outer shape, is dimensioned to be insertable into the base container  11 . The freezing bowl  23  has a substantially cylindrical inner wall  24 , preferably formed from microwave heatable stainless steel or aluminum. The inner wall may have a non-stick coating, such as Teflon, thereby to facilitate release of frozen product therefrom. Disposed between the cylindrical inner wall  24  and the square outer wall and nearly filling it is a chemical mixture exhibiting a low freezing point, a relatively high latent heat of fusion and a low coefficient of expansion. This material, when initially frozen, is capable of absorbing heat from the container contents over a reasonable period sufficient to cause the contents to freeze. The double-walled freezing bowl  23  has an inwardly and downwardly sloping surface  25  leading to the cylindrical chamber  24 . Prior to use, the insert  23  is adapted to be placed in the freezing compartment of a household refrigerator and chilled until the chemical material contained between the walls becomes frozen. 
     Sized to fit atop the rim of the base container  11  is a cover member  26 , preferably fabricated from a suitable insulated plastic and having a vent opening(s)  27 ,  28  and  29  formed through the thickness dimension thereof. A further central opening  30  is also provided for receiving the shaft  31  of a motor-driven drive member  32  therethrough. The square cover  26  further includes an additional opening  33  through which liquid ingredients may be poured into the freezing bowl  23  when the cover is in place thereon and the paddle is turning. The opening  33  is vertically aligned with the sloped upper edges of the freezing bowl so that when material is poured through the opening  33 , it will flow into the freezing bowl. An integrally molded, upwardly projecting annular wall  34  on cover  26  is designed to cooperate with the downwardly depending rim on drive member  32  to act as a baffle against inadvertent spillage when pouring ingredients into opening  33 . A snap-in, removable cap  35  is used to seal the opening  33 . 
     Positioned about the periphery of the cover  26  on the lower surface thereof are a plurality of cavities comprising normally opened switch contacts, as at  36 , and which are positioned so as to cooperate with the switch actuating pins  22  on the upper edge of the base of container  11 . The switch contacts  36  may comprise conventional diaphragm-type switches, each comprising first and second layers of metallization that are spaced apart from one another by an aperture insulating strip. One of the layers of metallization is deposited on a plastic (Mylar) membrane that when deformed through the aperture in the spacer layer, engages the second layer of metallization. Thus, when the cover  26  is assembled atop the base or container  11 , only those diaphragm switches  36  which are aligned with a switch actuator  22  will have their contacts closed. The switch contacts are adapted to be connected, via printed or other wiring  37 , to a control circuit  38  also mounted on the cover  26 . Rather than utilizing diaphragm switches, the switch actuators  22  themselves may be metal covered and function as a first electrical contact designed to cooperate with second contacts formed in recesses on the undersurface of the cover  26 . 
     Disposed atop the cover  26  and loosely surrounding the shaft  31  of the drive member  32  is an occluding member  39  having an integrally formed sleeve bearing  40  centrally disposed thereon. Washer-type spacers  41  and  42  fit over shaft  31  on opposite ends of the sleeve bearing  40  to prevent frictional engagement between the occluder  39  and cover  26  and drive member  32 . A pair of electrical drive motors  43  and  44  are mounted on the occluding member  39 . As best seen in the enlarged view of FIG. 2, the motor  43  and the motor  44  are slide mounted on the occluding member  39  and have shafts  45  and  46 , respectively, frictionally engaging an elastomeric band  47  deployed about an annular projection  48  that extends downwardly from the undersurface of the drive member  32 . 
     Tension springs  49  and  50  are operatively coupled via the magnetic cores  51  and  52  of the motors  43  and  44  as well as to the sleeve bearing  40  of the occluding member  39 . The springs function to maintain the motor shafts  45  and  46  in firm engagement with the elastomeric friction and  47  surrounding the annular projection  48  to inhibit slippage of the motor shafts on the friction band. A C-clip  53  holds the drive member, occluding member and cover together as a unit. 
     The paddle support shaft  31  is adapted to be coupled to a stub shaft  54  on a paddle member  55 . During use, the paddle is disposed within the container  11  and adapted to be driven by the drive shaft  31  when the motors  43  and  44  are simultaneously energized. The machine of the present invention may also be constructed so that a warming/heating element may be contained in the paddle with slip-ring contacts for coupling electrical power thereto. 
     The control circuit  38  disposed on the cover  26  is also wired to an electromagnet  56  having first and second coils of differing numbers of turns such that at least three different magnitudes of magnetic attractive force can be applied for respectively causing a relatively moderate magnetic attraction to a weak permanent magnet  57  on the occluder  39  or, alternatively, two selectively greater attractive forces. Reciprocally, the permanent magnet  57  can apply a weak attractive force to the core of the inactive electromagnet  56 . 
     The occluding member  39  is arranged to shift between first and second positions. In the first position, the occluding member  39  blocks the vent holes  27 ,  28  and  29  and in its second position uncovers those holes to expose the contents of the machine within the container  11  to the cooling temperature of a refrigerator in which the machine may be placed during use. When in the first position, a permanent magnet embedded in the occluding member  39  and identified by numeral  58  cooperates with a magnetic reed switch  59  disposed on the cover  26  to maintain the reed switch  59  closed. When the occluding member  39  is made to shift to its second position, the reed switch  59  is no longer under the influence of the permanent magnet  58  and its contacts open. 
     Referring now to the circuit diagram of FIG. 8, there is shown a circuit arrangement that may be used if the machine is only to be used in making yogurt or cheese. A power cord  801  has its input prongs adapted to be connected to a source of household current. A first insulated conductor in the power cord  802  connects to a first normally open contact  803  of the magnetic reed switch  804  ( 59  in FIG. 1) and its second contact  805  is connected by a conductor  806  to a junction point  807  to which one side of the warming/heating element  808  ( 17  in FIG. 1) is attached. The second conductor of the power cord  812  is connected through terminal point  3  within the control module  813  to the remaining terminal of the warming/heating element  808 . The junction  807  is also connected to terminal point  2  within the controller module. The drive motors  809  and  810  ( 43  and  44  in FIG. 1) are connected in parallel between the conductor  812  and a terminal point  1  in the controller module  813 . A set of normally open timer operated contacts  811  are connected in series between terminal points  1  and  2 . While mechanical switch contacts  811  are depicted in the drawings, the controller  813  will typically be a solid state device that will be biased to either a conducting or non-conducting state. 
     In use for preparing non-frozen yogurt, a yogurt starter and either previously heated bottled milk or dry, powdered milk plus warm water, is poured into the container  11  and the upper assembly, including the paddle  55 , the occluding member  39 , the drive member and the rectangular cover  26  are placed, as a unit, atop the container  11  and the drive member  32  is manually rotated in the counterclockwise direction (when viewed as in FIG. 1) by placing a finger in the recess  34  formed in the exposed upper surface of drive member  32  to thereby rotate the occluding member to which it is effectively locked, to the occluding member&#39;s initial position blocking the vent openings  27 ,  28  and  29  formed through the cover  26 . The assembly is then placed within a refrigerator with the power cord  801  extending through the flexible rubber seal of the refrigerator door and then plugged into a wall outlet. With the occluding member  39  in the position to occlude the openings  27 ,  28  and  29 , the permanent magnet  58  embedded in the occluder will cause the contacts of the normally open reed switch  59  ( 804  in FIG. 8) to be closed. As such, current will flow through the warming/heating element  17  ( 808 ) to maintain the warmth of the milk/starter mix within the container  11  at a desired culturing temperature. At this time, permanent magnet  57  is attracted to the iron of the unenergized electromagnet  56  ( 901  in FIG. 9) with a relatively weak force. 
     At relatively infrequent intervals, the timer control  813  will cause the contacts  811  to close for a relatively short interval. Without limitation, the contacts  811  may close about every 15 minutes for a time interval of about two seconds. When the contacts  811  close, an electrical current is supplied not only to the warming/heating element  17  ( 808 ), but also to the motors  43  and  44 . 
     Upon energization of the motors  43  and  44 , the drive member  32  will be rotated in the counterclockwise direction to also rotate the paddle  55  within the liquid mixture to thereby test the consistency of the constituents. After a few hours, the yogurt mixture will convert from a liquid to a somewhat firm gel. This transition occurs relatively rapidly. 
     Now, the next time that the timer contacts  811  are made to close, the motors  43  and  44  will attempt to rotate the drive member  32  and the paddle  55  which are keyed to one another. Because of the square shape of the container  11 , the paddle  55  will not only be unable to rotate within the gel but will also be unable to twirl the gelled yogurt and, as a result, the motors affixed to the occluding member  39  will overcome the relatively weak magnetic force provided by magnet  57  and will cause the occluding member  39  to rotate clockwise so as to uncover the vent openings  27 ,  28  and  29  and simultaneously cause the contacts  803 ,  805  of the magnetic reed switch  59  to open. Opening of the contacts  803  and  805  disconnects both the warming/heating element  17  and the controller/timer  813  from the power source and thereby shuts off the motors  43  and  44  in FIG.  1 . 
     Exposure of the gelled yogurt in the container  11  to the cool air within the refrigerator, via the vent openings  27 ,  28  and  29 , will allow the contents to cool rather rapidly, thereby terminating the warming process at a time when the consistency and flavor are optimum. Alternatively, the reversible thermoelectric heat exchanger is switched to cooling mode. 
     In making cheese, the controller is re-programmed so that the motors  43  and  44  run more continuously and the warming element  17  is also energized. Rather than continuous rotation, in the preferred mode for cheese making, the cycle allows about 15 minutes of rotation followed by about 5 minutes of interruption—long enough for the curd to settle and begin to agglutinate into a resistant mass. The cheese curd mass inhibits rotation of the paddle  55 . This causes the motors to now rotate the occluding means, opening the reed switch  59  and disconnecting power from the motors and warming element. The contacts  811  may open, for example, about every 15 minutes for a time interval of about five minutes. When the paddle, either with its attached curd-ball or mired in a firm or semi-firm mass, reaccelerates, the inertial or resistance force is sufficient to overcome the predetermined weak force between the occluding means and the cover so that the device opens up the vent hole(s) in the cover and turns off the motor and the timer and the heating element. 
     The operation thus far described involves the making of regular yogurt and cheese. By configuring the circuit as in the diagram of FIG. 9, additional capability is provided to the apparatus of FIG.  1 . Specifically, it can be used to prepare not only yogurt and cheese, but also soft and hard frozen yogurt or ice cream. 
     When it is desired to make soft frozen yogurt, the optional insert  23  is utilized. The freezing bowl  23  will have been thoroughly chilled in a freezer or in the freezing compartment of the refrigerator before it is placed into the base container  11 . Rotation is started and previously prepared frozen yogurt mix is then poured into the cylindrical cavity of the freezing bowl  23 , via access port  33  formed in the cover  26 . Also, the cover  26  will have been installed on the base container  11  in a different orientation than when the machine is being used to create yogurt in the first instance. As will be explained, the repositioning of the cover  26  relative to the base container  11  will result in different modes of operation. 
     FIG. 9 is a schematic electrical diagram of the apparatus of the present invention when designed for additional or multiple use application. In this arrangement, the electromagnet  56  of FIG. 1 is represented by two coils labeled T 1  and T 2  of electromagnet  901 . The coils T 1  and T 2  are adapted to be connected between the conductor  903  of the AC supply line when switches  904  and  905  are closed. In addition, a bypass switch  906  is provided which effectively removes the timer control  907  ( 38  in FIG. 1) from the circuit when it is closed. 
     The electromagnet  901  has fewer turns on coil T 1  than it does on coil T 2  and, as a result, the electromagnet  901  provides a lesser restraining force to the occluder  39  when the switch  905  is closed than is afforded when switch  904  providing energization to the coil T 2 , is closed. 
     It is to be further noted that a single pole, single throw normally open switch  908  is connected in series with the warming element  909  ( 17  in FIG. 1) between terminal  3  of the timer control  907  and junction point  910 . 
     The open/closed state of the switches  904 ,  905 ,  906  and  908  is determined by the orientation of the cover  26  relative to the top of the container  11 . When making regular yogurt, the switch actuator pins  22  will cooperate with the cover such that switch contacts  904 ,  905  and  906  remain open while contact  908  is closed. However, when making soft, frozen yogurt, the cover will be positioned such that the switch actuators  22  will cooperate with the switches  904 ,  906  and  908  so that contacts of switch  904  will be closed,  905  will be open,  906  will be closed and  908  will be open. As such, motors  911  and  912  ( 43  and  44  in FIG. 1) will operate continuously. With switch  908  open, no current will flow through the warming element  17 . As the paddle is continuously driven within the cylindrical chamber  24  of the freezing bowl  23 , when the yogurt freezes on the walls of the chamber  24 , it will be scraped off by the continuously rotating paddle  55  and will be mixed with the still somewhat liquid frozen yogurt mix remaining in the chamber. Of course, it is also possible to provide the desired scraping action by rotating the container  11  relative to a stationary paddle disposed in the cylindrical chamber, as in other embodiments yet to be described. 
     Once the consistency of the soft frozen yogurt becomes sufficiently stiff to overcome the attractive force due to current flowing through the coil T 1 , the occluder  39  will again rotate due to the stalled condition of the paddle  55 . The occluder will again reposition so as to open the reed switch contacts  913  and  914  to disconnect the motors  911  and  912  and to remove current from the coil T 1 . While not shown, it is also contemplated that the machine of the present invention be provided with an audible signaling device which would sound so that the soft frozen yogurt can be removed from the freezing bowl  23  before the yogurt becomes more firm due to the freezing action of the insert. Freezing of soft frozen yogurt to the inner wall of the bowl while attempting removal of the product can be countered by placing the bowl with its microwave-heatable, smooth-contoured, stainless-steel inner cylinder in a microwave oven and heating it briefly. A Teflon® lining might also be utilized. 
     When the machine of the present invention is to be used to produce hard frozen yogurt or ice cream, the freezing bowl  23  is again used, but the cover will now be repositioned on the base container  11  such that the switch actuators  22  cooperate with the switches  36  on the cover  26  to cause switches  905  and  906  to be closed and switches  904  and  908  to be open, or switches  904  and  905  may both be closed. Also, the machine of the present invention may be inserted into the refrigerator&#39;s freezer compartment and the vent cover removed to permit access by ambient air. Given the fact that the coil T 2  of the electromagnet  901  ( 56  in FIG. 1) has a greater number of turns than the coil T 1  which is active in making soft frozen yogurt, the cover  26  and the occluder  39  will be attracted to one another with an increased force. With switch  908  open, the heating element  909  is not energized. Also, because switch  906  is closed, the timer circuit  907  is no longer functional and the motors  43  and  44  will run continuously, until such time as the magnetic reed switch  914  opens. As heat energy is removed from the yogurt mixture within the cylindrical compartment  24  of the freezing bowl  23  by the chemical contained between the walls of the insert and by the action of the refrigerator&#39;s freezing compartment, the yogurt will become more and more firm until a point is reached wherein the scraper paddle  55 , in attempting to scrape and stir the freezing yogurt, will overcome the force exerted by the coil T 2  of the electromagnet and the motors will then drive the occluding means  39  on which they are mounted so as to cause the magnetic reed switch contacts  913  and  914  to open and thereby disconnect the motors and the coil T 2  from the power lines. 
     Again, removal of the frozen product from the bowl  23  may be facilitated by briefly placing the freezing bowl with its microwave heatable inner cylinder and its frozen contents into a microwave oven and heating it for a short time sufficient to melt the bond of the yogurt to the wall of the bowl. If, after the hard frozen process has completed, the device has remained in the freezing compartment of the refrigerator and a hard block with the paddle frozen in has resulted, then the heating coils in the paddle can be activated to facilitate its extraction. 
     When the machine of the present invention is to be used in making Ricotta cheese, the freezing bowl is not used and the motors  43  and  44  run with a duty cycle in which they remain on for a relatively long interval and off for a somewhat shorter interval. The warming element will remain energized and the weak magnet  57  will provide the attractive force between the cover  26  and the occluding member  39 . Stated otherwise, the cover  26  will be positioned on the container such that the switch actuators  22  on the container will cooperate with the switches  36  to cause switch  904  to be open,  905  to be open,  906  to be open, and  908  to be closed. The milk and starter will be placed in the container  11  and the occluding member positioned so as to occlude the openings  27 ,  28  and  29  in the cover and to cause the magnetic reed switch contacts  913  and  914  to be closed. Because the mixture is being warmed, and largely, if not continuously stirred by the paddle over prolonged periods of time, a point will be reached wherein the mixture begins to flocculate and curdle and it may agglutinate into a rather firm mass on the bottom of the container if stirring ceases for a time. Also, some mixtures may tend to aggregate and form a curd ball on the paddle itself. When this process is complete to the point where the mass of the curd ball adds sufficient inertia to inhibit rotation of the paddle or an attempt to restart the paddle movement following an interruption in its rotation by opening of the timer switch  915  ( 811  in FIG.  8 ), the attractive force afforded by the permanent magnet  57  will be overcome and will result in the occluding member  39  shifting in position, due to the action of the motors, to the point where the magnetic reed switch  916  ( 804  in FIG. 8) again opens to thereby disconnect the heating element  909  and the motors  911  and  912  from the power source. 
     Rather than using a friction drive between the motor shafts and the elastomeric band on the drive member, an arrangement of gears driven by a single motor may be used instead. 
     Further, and as is mentioned in the foregoing specification, a heating (and warming) element may be located in the paddle member rather than in the walls of the container  11 . This would afford the additional advantage of allowing the paddle to be extracted from hard frozen yogurt or ice cream by heating the paddle for a short interval to melt the ice cream at its interface with the paddle. Any of a variety of electrical slip ring contacts can be used to provide electrical energy to a heating element in a rotating member. Another modification would be to sense changes in the current drawn by the motors as the consistency of the product varies from a liquid to a gel or to a solid and to use that sensed current change to shut off the current to the warming element and to the drive motor(s) and to switch on cooling by the reversible thermoelectric warmer/cooler. A safety switch may also be incorporated which would shut down all possibility of current flow whenever the cover is removed. A reduced voltage may be utilized for all functions to avoid electrical shock to the user. It is also contemplated that the appliance of the present invention can be modified to permit bread making and other food processing in addition to the functions described herein. 
     DESCRIPTION OF THE SECOND EMBODIMENT 
     Referring first to FIG. 3, there is indicated generally by numeral  310  a second embodiment of a home appliance useful in preparing yogurt, soft or hard frozen yogurt or ice cream, and cheese from a starter and either heated bottled milk or a mixture of dried milk and tap water. The machine is seen to comprise a culturing container  311  of generally non-circular (square or with baffles) configuration defined by a bottom  303  and mutually perpendicular side walls  304  and  305 . The container  311  will preferably be molded or shaped from a suitable plastic or metal. The four walls, as at  304  and  305 , define an open upper top  306  of non-cylindrical configuration. The bottom of the container is adapted centrally to be splined to a stub shaft  307  and is thereby able to be driven by the shaft of the motor  308  when it is energized. 
     Shown within container  311  is an optional freezing bowl  323  that is used when preparing such products as hard or soft frozen yogurt or ice cream. The freezing bowl  323 , which is also of a non-cylindrical outer shape, is dimensioned to be insertable into the container  311 . The freezing bowl  323  has a substantially cylindrical inner wall  324 , preferably formed from microwave heatable stainless steel or aluminum. Disposed between the cylindrical inner wall  324  and the non-cylindrical outer wall and nearly filling it is a chemical mixture exhibiting a relatively high latent heat of fusion and a low coefficient of expansion upon changing from a liquid to a solid state. Prior to use, the insert  323  is adapted to be placed in the freezing compartment of a household refrigerator and chilled until the chemical material contained between the walls becomes frozen. 
     The stationary insulated housing  309 , which is fastened to the stationary base  312 , is also locked removably to a stationary paddle supporting rim  313 , which in turn is roofed by the stationary removable cover  314 . 
     Sized to fit atop the opening rim of the housing and non-rotatably and electrically keyed to it is a paddle  315 , disposed within the mix in the container or freezing bowl. The machine of the present invention may also be constructed so that the stationary paddle  315  contains a thermostatically controlled electrical heating/warming element, here shown as a serpentine arrangement of nicrome wire  316 . 
     The insulated cover member  314  is sized to fit atop the rim of the paddle support member and the container. It is preferably manufactured from a suitable plastic. When the cover is removed, liquid ingredients can be poured into the freezing bowl even while the paddle remains in place and the bowl is rotating. Also the cover is adapted to support an insulated, solenoid-valved container for liquid yogurt or cheese starter which may be utilized to automatically add starter subsequent to the pre-heating and cooling steps when unheated bottled milk is utilized. There are electrical connections at  317  and  318  between the housing and paddle and cover to facilitate plugging in the unit for timed delivery of a starter through the cover opening  319  when plug  320  is removed. 
     The insulated base  312  has at least one vent opening  321  formed through the thickness dimension thereof, with a removable vent cover  322 . A further centrally disposed sleeve bearing is provided therethrough for receiving the stub shaft  307  of the motor drive member  308  therethrough. The stub shaft can be keyed to the container and/or the freezing bowl which are designed to be driven by the stub shaft. 
     Disposed in the base  312  and loosely surrounding the shaft  307  of the drive member is a rotatable occluding member  324  having an integrally formed sleeve bearing centrally disposed. The electrical motor with gear reduction  308  is fixed to the underside of the occluding member  324  and is arranged to rotate the container relative to the stationary paddle  315 , housing  309  and base  312 . A thermostatically controlled reversible heat exchanger  325  is also mounted within the base  312 . Both internal  326  (within the housing) and external  327  (outside the insulation) fans are mounted in relation to the reversible heat exchanger. The heat exchanger is preferably a reversible polarity thermoelectric device capable of both heating and cooling. The appropriate switches are adapted to be connected, via printed or other wiring, to a control circuit also mounted on (in) the base. A drain hole as at  328  provides egress for any spillage of liquid occurring within the housing. 
     The occluding member  324  is arranged to shift between first and second positions. In the first position, the occluding member blocks the vent opening  321  and in its second position uncovers the same to expose the contents of the machine within the container  311  to the cooling air of a refrigerator in which the machine may be placed during use, assuming the vent cover  322  is removed. The reversible heat pump  325  may also be switched to the cooling mode, in which case the vent cover remains in place. 
     When in the first position, a permanent magnet  330  embedded in the occluding member  324  cooperates with a magnetic reed switch  329  disposed on the base  312  to maintain the reed switch  329  closed. When the occluding member  324  is made to shift to its second position, the reed switch  329  is no longer under the influence of the permanent magnet  330  and its contacts open. 
     A timing control circuit like that earlier described is disposed in the base  312  and is wired to an electromagnet  331  having first and second coils of differing numbers of turns, such that as many as three different magnitudes of magnetic attractive force can be applied, respectively causing a relatively moderate magnetic attraction to a weak permanent magnet  332  on the occluder  324  or, alternatively, one or two selectively greater attractive forces. Reciprocally, the weak permanent magnet  332  can apply a weak attractive force to the core of the inactive electromagnet  331 . 
     A circuit like that depicted in the diagram of FIG. 8 may be used with the embodiment of FIG. 3 if the machine is only to be used in making yogurt or cheese. 
     In use for preparing non-frozen yogurt, a yogurt starter and either previously heated liquid milk or dry, powdered milk plus water, is poured into the container  311  and the cover  314  is placed on top. (Alternatively, non-heated milk can be utilized and heating and cooling and starter adding can be carried out automatically by the device prior to the machine&#39;s automatically proceeding on with the following operations). The occluding member in the base (occluder and motor and permanent magnets) is manually rotated in the clockwise direction (when viewed from above) by placing a finger against the tab  333  protruding through the base from the occluding member to thereby rotate the occluding member to its initial position blocking the vent openings  321 . Without the vent cover, the assembly may then be placed within a refrigerator with the power cord extending through the soft, compressible gasket of the refrigerator door and plugged into a wall outlet. Alternatively, the device may be placed on the counter top, the electrical cord plugged in and, with the vent cover in place, the reversible heat exchanger permitted to function consecutively in both its warming and cooling modes. With the occluding member  324  in the position to occlude the opening  321 , the permanent magnet  330  embedded in the occluder will cause the contacts of the normally open reed switch  329  to be closed. As such, current will flow through the warming element  325  and/or  316  in the paddle to warm the milk and starter mix within the container  311 . At this time, permanent magnet  332  is attracted to the iron of the unenergized electromagnet  331  with a relatively weak force. 
     At relatively infrequent intervals, the timer control will cause the contacts  811  to also close for a comparatively short interval. Without limitation, the contacts  811  may close about every 15 minutes for a time interval of about two seconds. When the contacts  811  close, an electrical current is supplied not only to the warmer  316  and/or  325 , but also to the motor  308 . Upon energization of the motor  308 , and assuming a stationary paddle  315 , the shaft and stub shaft  307  will be rotated in the clockwise direction to also rotate the container  311  around the liquid mixture to thereby test the consistency of the constituents. After a few hours, the yogurt mixture will convert from a liquid to a somewhat firm gel. This transition occurs relatively rapidly. 
     Now, the next time that the timer contacts  811  are made to close, the motor will attempt to rotate the stub shaft  307  and the container which are keyed to one another. Because of the rectangular shape of the container  311 , the container will not be able to rotate around the gel and will also be unable to swirl the gelled yogurt and, as a result, the motor  308  affixed to the occluding member  324  will overcome the relatively weak magnetic force provided by the magnet and will cause the occluder to rotate counterclockwise so as to uncover the vent opening  321 , and simultaneously cause the contacts of the magnetic reed switch  329  to open. Opening of the contacts disconnects both the heating element and the timer from the power source and shuts off the motor  308 , all as previously explained. 
     Exposure of the gelled yogurt in the container  311  to the cool air within the refrigerator, via the vent opening will allow the contents to cool rather rapidly, thereby terminating the incubation process at a time when the consistency and flavor are optimum. Alternatively, the polarity to the thermoelectric heated/cooler  325  may be reversed, similarly commencing cooling. 
     In making cheese, the controller time-ratio switch is adjusted and the motor  308  is made to run intermittently for approximately fifteen minutes and permitted to rest for approximately five minutes. After a period of time, the milk and starter mix will curdle and fall to the bottom of the container and agglutinate and become a solid mass. At this point, the cheese mass will inhibit rotation of the container in relation to the paddle  315 . This causes the motor to now rotate the occluding member, opening the reed switch and disconnecting power from the motor and warming element and either opening up the vent if it is not further covered or switching on the cooling mode. 
     The operation thus far described involves the making of regular yogurt and cheese. By configuring the circuit as in the diagram of FIG. 9, additional capability is provided to the apparatus of FIG.  3 . Specifically, it can be used to prepare not only yogurt and cheese, but also soft and hard frozen yogurt or ice cream in the same manner as earlier explained. 
     When it is desired to make soft frozen yogurt, the optional insert  323  is utilized. The freezing bowl  323  will have been thoroughly frozen in a freezer or in the freezing compartment of the refrigerator before it is placed into the container  311 . After rotation has been started, previously prepared frozen yogurt mix is poured into the cylindrical cavity of the quick freeze insert  323 , via the hole  319  in cover  314  or with the cover removed. 
     Once the consistency of the soft frozen yogurt becomes sufficiently stiff to overcome the attractive force due to current flowing through the coil T 1  of the electromagnet  901 , the occluder  323  will again rotate due to the stalled condition of the bowl in relation to the paddle  315 . The occluder will again reposition so as to open the reed switch contacts  913  and  914  to disconnect the motor  308  and to remove current from the coil T 1 . While not shown, it is also contemplated that the machine of the present invention be provided with an audible signaling device which would sound so that the soft frozen yogurt can be removed from the freezing bowl  324  before the yogurt adheres to it due to the freezing action of the insert. 
     Also, while making hard frozen yogurt or ice cream, the machine of the present invention may be inserted into the refrigerator&#39;s freezer compartment. Given the fact that the coil T 2  of the electromagnet  901  has a greater number of turns than the coil T 1  which is active in making soft frozen yogurt, the electromagnet and the occluder magnet will be attracted to one another with an increased force. With switch  908  open, the warming element  909  ( 316  in FIG. 3) is not energized. Also, because switch  906  is closed, the timer circuit is no longer functional and the motor  308  will run continuously until such time as the magnetic reed switch  329  opens. As heat energy is removed from the yogurt mixture within the cylindrical compartment of the freezing bowl  323  by the chemical contained between the walls of the insert and by the action of the refrigerator&#39;s freezing compartment, the yogurt will become more and more firm until a point is reached wherein the scraper paddle.  315 , in attempting to scrape and stir the freezing yogurt, will overcome the force exerted by the coil T 2  of the electromagnet and the motor will then drive the occluding means  324  on which it is mounted so as to cause the magnetic reed switch contacts to open and thereby disconnect the motor and the coil T 2  from the power lines. Electrical resistance heating of the paddle and microwave heating of the inner wall of the freezing bowl may aid the process of removing hard frozen yogurt that has been neglected for some period of time from the freezing bowl. 
     When the machine of the embodiment of FIG. 3 is to be used in making Ricotta cheese, the freezing bowl is not used and, as earlier explained, the motor is run more continuously with a duty cycle in which it remains on for a relatively long interval and off for a somewhat shorter interval. The warming element will remain energized and the weak magnet will provide the attractive force between the base  312  and the occluding means  324 . The milk and starter will be placed in the container  311  and the occluder positioned so as to occlude the opening  321  in the base and to cause the magnetic reed switch  329  to be closed. Because the mixture is being warmed and stirred by the stationary paddle in the irregular shaped rotating container over prolonged periods of time, a point will be reached wherein curd forms and gravitates to the bottom of the mix during non-stirring intervals and begins to agglutinate and form into a rather firm mass on the bottom of the container. When the process is complete to the point where this mass inhibits rotation, the increased resistance will be enough to overcome the attractive force afforded by the permanent magnet  332  and will result in the occluding means  324  shifting in position due to the action of the motor to the point where the magnetic reed switch  329  again opens to thereby disconnect the heating element  316  and the motor  308  from the household power source. 
     A modification would be to sense changes in the current drawn by the motor as the consistency of the product varies from a liquid to a gel or a solid and to use that sensed current change to control the movement of the occluding means and/or to shut off the current to the heating element and/or to the drive motor(s). A safety switch might be incorporated which would shut down all possibility of current flow whenever the cover is removed and, also, a reduced voltage might be utilized for all functions to avoid electrical shock to the user. It is also contemplated that the appliance of the present invention might be further modified to permit bread making and other rotation based food processing in addition to the functions described herein. 
     DESCRIPTION OF THE THIRD EMBODIMENT 
     A third preferred embodiment of the invention is illustrated in the cross-sectional view of FIG.  4 . It is similar in many respects to the previously described first and second embodiments, but differs therefrom primarily in the fact that the drive motor for a rotating paddle is disposed on the unit&#39;s cover member while the occluding device is located in the unit&#39;s base. 
     Referring to FIG. 4, there is indicated generally by numeral  401  a home appliance useful in the preparation of yogurt, soft frozen yogurt, hard frozen yogurt and Ricotta cheese. It comprises an outer, molded plastic housing  402  having an outer wall  403  and an inner wall  404  spaced from the outer wall, leaving an insulating air chamber  405 . The housing includes a base  406  that, as in the earlier embodiments, includes a timer and control circuit like that illustrated in FIGS. 8 and 9. 
     Insertable within the housing  402  is a container  407 . The container  407  is designed to have a non-circular cross-section. As in the earlier embodiments, the container  407  will typically hold the milk during the preparation of regular soft yogurt, but optionally, may receive a freezing bowl  408  therein. The freezing bowl  408  is a double-walled structure having a freezing liquid  409  contained between the walls. The freezing bowl is, again, used when it is desired to prepare soft frozen or hard frozen yogurt using the machine of the present invention. 
     A top member  410  is adapted to fit on the housing  402  in covering relation to its open top. The cover  410  includes a central aperture  411  containing a sleeve bearing  412  which journals a shaft  413  of an electric motor  414 . The shaft  413  is designed to mate with a stem  415  of a rotatable paddle  416 . The width of the paddle is designed to closely conform to the inner wall of the freezing bowl. 
     In order to deliver electrical power to the motor  414 , an electrical conductor  417  connected to a motor terminal at one end also connects to an electrical contact  418  on the cover  410  and a mating contact on the housing  402 . A further conductor, not shown, traverses through the housing wall into the base  406  for connection to the control circuit contained therein, like that shown at  38  in FIG. 1, but not specifically illustrated in FIG.  4 . 
     The cover also is molded so as to include voids as at  419  and  420  which improves the thermal insulating properties of the cover. Also formed in the cover  410  is a circular opening  421  adapted to be sealed by a removable plug  422 . With the plug removed, it is possible to pour ingredients through the opening  421  into the container  407  or the freezing bowl  408  as the case may be. 
     Further conductors, as at  423 , connect between power contacts  424  on the cover and housing for applying power to a protected electrical socket  425  on the cover  410 . This socket is adapted to receive a yogurt starter introducer device in FIGS. 10 and 11 having a solenoid actuated shutter which is made to open by the timed delivery of a control signal from the control circuit to the solenoid, via contacts  424  and  425  and the conductors  423  connecting them. With the shutter open, the contents of the starter adding device flow into the container  407  at an appropriate time in the cycle, all as will be further explained hereinbelow. 
     With continued reference to FIG. 4, it can be seen that there is formed in the base a passageway  426  through which cool air may flow when the removable plug  427  is absent. This plug is not used when the yogurt making appliance of the present invention is to be used in combination with a household refrigerator. Placement of the unit  401  in a household refrigerator would then permit cool air to flow through the apertures  428  in the base and through the aperture  426  to circulate in the space  429  between the inner wall  404  of the housing and the adjacent wall of the container  407 . 
     By providing a thermoelectric heat exchanger, as at  433 , it can assist in both the heating and cooling functions employed in the yogurt making process. The thermoelectric device  433 , is of a well known type where when a voltage of first polarity is applied the unit will provide a heating function and when the polarity is reversed, cooling takes place. In addition to the heating that may be provided by the thermoelectric unit  433 , the paddle  416  includes a heating element  434  therein which is adapted to be energized by way of slip rings  435 . In that the paddle  416  remains in intimate contact with the yogurt constituents, the warmth given off thereby aids in the culturing process. 
     As in the earlier embodiments, there is shown cooperating with the vent opening  426  in the base, an occluder member  436  that extends through a radial slot  437  formed in the base  406 . It is fixedly attached to a turntable shaft  438  that passes upward through the base and connects to an extendable splined drum  439  that mates with a recessed area  440  formed in the bottom of the container  407  or the freezing bowl  409 . Thus, rotation of the container  407  will also result in rotation of the occluder member  436 . 
     A detent in the form of an electromagnet  441 , as before, cooperates with a permanent magnet  442  attached to the occluder member  436  for applying a predetermined force resisting rotation of the occluder member and, accordingly, rotation of the container  407  by virtue of the connection afforded by the shaft  438  and the spline drum  439  connecting the two. 
     The base further incorporates a magnetic reed switch  444  therein having contacts that are under the influence of a permanent magnet  443  mounted in the occluder member when the occluder member  436  is in a first orientation where the passageway  426  is being occluded. An extension  445  of the occluder protrudes laterally through the side wall of the base so that it is accessible for manually setting the device in its vent-covered starting mode. 
     In that the control circuit depicted in FIGS. 8 and 9 has already been explained in connection with preceding embodiments, no further explanation and mode of operation is deemed to be necessary for an understanding of the construction and operation of the embodiment of FIG.  4 . 
     In use, with the occluder  436  initially set in its starting position and with the freezing bowl  409  removed, pre-heated bottled milk or a mixture of warm water and dried milk may be added into the container  407  through the opening  421  in the cover. At this point, the power plug may be connected to a source of household current for initially energizing the filament  434  in the paddle  416  as well as the thermoelectric heater/cooler  433  mounted in the unit&#39;s base. The combination or either of these two heat sources causes the ingredients to be warmed. At periodic intervals determined by the timer used in the control circuit, the motor  414  will be energized to rotate the paddle momentarily so as to “test” the consistency of the contents of the container. Stated as before, motor  414  may be energized for about two seconds every fifteen minutes for this purpose. When the point is reached where the ingredients begin to gel, because of the non-circular cross-sectional profile of the container  407 , the paddle will become somewhat bonded to the container to the point where the container itself will begin to rotate with the paddle and thereby rotate the occluder member  436  against the magnetic force provided by the magnet  441  comprising the detent member. The occluder member thus will swing to a position no longer occluding the vent hole  426 . Movement of the occluder  436  also increases the separation between the reed switch  444  and its cooperating permanent magnet  443 , allowing the switch contacts of the reed switch to reverse, shutting off the motor and disconnecting the heating element from the power source. 
     Assuming that the unit has been placed in a refrigerator, cooling air can now propagate through ports  428  and through the vent  426  and up and around the container to terminate the culturing process at an optimum point. 
     If it is assumed that the device includes the thermoelectric unit  433 , it would not be necessary to place the yogurt maker within a refrigerator. Here, movement of the occluder so as to cause the reed switch contacts to reverse may be used not only to shut off the motor  414 , but also to reverse the polarity of the voltage applied to the thermoelectric unit from its heating mode to its cooling mode. The way in which soft frozen yogurt, hard frozen yogurt and Ricotta cheese can be made using the present invention applies equally to the embodiment of FIG. 4 and, hence, it is deemed unnecessary to repeat that explanation. 
     DESCRIPTION OF THE FOURTH EMBODIMENT 
     Referring first to FIG. 5, there is indicated generally by numeral  501  a further embodiment of a home appliance useful in preparing yogurt, soft or hard frozen yogurt or ice cream, and cheese from a starter and either bottled milk or a mixture of dried, powdered milk and water. As in the previously described embodiments, the machine is seen to comprise a rotatable container  502  of generally square or baffled irregular, non-cylindrical construction defined by a bottom  503  and mutually perpendicular side walls as at  504  and  505 . The container  502  will preferably be molded or formed from a suitable plastic or metal. The bottom  503  is keyed centrally at  506  to mate with a stub drive shaft  507  having a splined hub  508  thereon. The four walls of container  502  define an open upper top  509 . 
     Displayed within the container is an optional freezing bowl, indicated generally by numeral  510 , that is used when preparing hard or soft frozen yogurt or ice cream. The freezing bowl is identical in construction to what has earlier been described and need not be explained further. 
     Surrounding the container  502  and/or the optional freezing bowl  510  is an insulated housing  511  composed of a base  512 , enclosure  513  and cover  514 . The insulated base contains a motor  515  with the stub drive shaft  507  that is keyed to interact with and support the container  502 , or the freezing bowl  510 . The motor is underneath the base and there is a bearing (not shown) for the shaft to pass through to the top of the base  512 . There is also a drain duct  516  through the base. A thermoelectric heat exchanger  517  with a drip guard cover  518  is disposed in an air vent  519  that is formed in the top of the base  512 . An air circulation path between the inside of the enclosure  513  and the outer wall of the container  502  is in fluid communication with air vent  519  allowing for the passage of warming and cooling air from the thermoelectric heat exchanger to act on the container  502 . 
     The insulating cover member  514  is preferably fabricated from a suitable plastic and it has an opening  530  through the thickness dimension thereof. The cover further includes an additional opening through which liquid ingredients can be poured into the freezing bowl while the freezing bowl is rotating and the cover is in place thereon. The cover furthermore includes an integrally formed sleeve bearing  521  centrally disposed therethrough for receiving the shaft  522  of a paddle  523 . The insulated cover furthermore supports an electromagnet  524  and a reed switch  525 . 
     An occluding member  526  sits atop the cover, with two permanent magnets  527  and  528  embedded in and attached to its periphery for interaction with the reed switch  525  and the core of the detent electromagnet  524 , respectively. The occluding member is integral with the paddle support shaft  522 . During use, the paddle  523  is disposed within the container in a stationary, but potentially rotatable mode. The machine of the present invention may be constructed so that a warming-heating element as at  529  can be contained in the paddle, as well as or rather than having a thermoelectric heat exchanger  517  in the base. 
     A control circuit like that of FIG. 8 is disposed on the cover or in the base  512 . It is also wired to the electromagnet having a pair of coils of differing numbers of turns such that two different magnitudes of magnetic attractive force can be applied for respectively causing a relatively moderate magnetic attraction to the weak permanent magnet  528  on the occluding member  526  or, alternatively, a greater attractive force. 
     The occluding member  526  is arranged to shift between first and second positions. In the first position, it blocks the vent hole  530  and in its second position uncovers this hole to expose the contents of the machine within the housing  511  to the cooling temperature of a refrigerator in which the machine may be placed during use. When in the first position, the permanent magnet  527  embedded in the occluding member cooperates with the magnetic reed switch  525  disposed on the cover to maintain the reed switch closed. When the occluder is made to shift to its second position, the reed switch is no longer under the influence of the permanent magnet and its contacts open. 
     From what has been described in explaining the operation of the embodiments of FIGS. 1 through 4, the reader will clearly understand how the present embodiment functions in preparing yogurt, frozen yogurt and Ricotta cheese. 
     Upon energization of the motor  515 , the container  502  will be rotated in the clockwise direction to also relatively rotate the paddle within the liquid mixture to thereby test the consistency of the constituents. After a few hours, the yogurt mixture will convert from a liquid to a somewhat firm gel. This transition occurs relatively rapidly. 
     Now, the next time that the timer contacts are made to close, the motor will attempt to rotate the container. It will be impossible for the container to swirl a gel around the paddle and because of the irregular shape of the container and the shape of the paddle, the container and paddle will in effect be locked together. As a result, the motor being keyed to the container will overcome the relatively weak magnetic force provided by magnet  528  and will cause the paddle and occluder to rotate so as to uncover the vent opening  530  and simultaneously cause the contacts of the magnetic reed switch  525  to open. Opening of the contacts disconnects both the warming element and the controller/timer from the power source and thereby shuts off the motor. 
     Exposure of the gelled yogurt in the container  502  to the cool air within the refrigerator, via the now open vent will allow the contents to cool rather rapidly, thereby terminating the incubation process at a time when the consistency and flavor are optimum. 
     DESCRIPTION OF THE FIFTH EMBODIMENT 
     Referring next to FIG. 6, there is shown a fifth embodiment of the invention. It resembles the second embodiment (FIG. 3) in that the drive motor and occluder are disposed in the base. However, it differs therefrom in the manner in which relative motion is created between the container and the paddle. In the embodiment of FIG. 3, the container is adapted to be rotated by the motor, whereas in the embodiment of FIG. 6, the container remains stationary and it is the paddle that is the motor-driven member. 
     In implementing the yogurt maker of FIG. 6, the outer molded plastic housing  601  has an integrally formed, centrally disposed tubular center post  602  projecting upwardly from the housing base  603 . Contained within the central bore of the tubular center post  602  is a drive shaft  604  that is adapted to be driven by the motor/gear reduction device  605  located in the base portion  606  of the outer housing  601 . Affixed to the shaft  604  proximate its upper end is a split paddle  607 , which, during use, fits within the chamber defined by the inner wall  608  of the housing  601  or within a specially formed freezing bowl  609  in those instances where the machine is being used to prepare soft or hard frozen yogurt. 
     The freezing bowl  609  has an outer wall  610  and an inner wall  611  that are spaced apart from one another, allowing a freezable liquid  612  to be trapped there between. The inner and outer walls  610  and  611  abut one another in the center of the freezing bowl and form an upwardly extending tubular projection  613  whose inside diameter is slightly greater than the outside diameter of the molded plastic center post  602 . As such, the freezing bowl  609  can be inserted into the chamber defined by the outer housing by slipping the freezing bowl over the center post  602 . 
     A cover  614  is designed to fit onto the open upper end of the housing  601  in covering relation thereto. Voids, as at  615  and  616 , are formed in the top to add to its insulating qualities. An opening is formed through the top  614  at  617 , allowing ingredients to be poured into the container or freezing bowl as the machine is operating. A cap or plug  618  can be used to seal the opening  617 . 
     The top  614  also includes a bearing  619  into which the upper end of the shaft  604  is fitted. Furthermore, electrical slip rings  620  and  621  mounted in the cover and in the paddle, respectively, permit an electrical current to flow from a conductor  622  disposed within the cover to a heating element (not shown) disposed within the paddle  607 . Also not visible in the embodiment of FIG. 6 are conductors leading from the power cord through the housing  601  to mating contacts  623  and  624  between the cover  614  and the upper rim of the housing  601 . Again, in FIG. 6, provision is made for positioning a yogurt starter adder device atop the cover  614 . Specifically, and as earlier described, the adder device includes a solenoid actuated shutter at the base of an insulated funnel which can fit through the opening  617  when the plug  618  is removed. An electrical connection to the solenoid is provided via contact  624 , conductor  625  and socket  626  into which contacts on the starter adder device are insertable. 
     The motor  605  is shown as being affixed to an occluder member  627  and it has a handle portion  628  extending out through a slot  629  formed in the base  606  of the housing. Mounted on the occluder  627  is a permanent magnet  629  adapted to cooperate with a magnetic reed switch  630  affixed to the housing closely adjacent the reed switch when the occluder is in a first position. The occluder also supports a permanent magnet  631  positioned to cooperate with a pair of coils of an electromagnet  632 . The control circuit for the embodiment of FIG. 6 is the same as for the previous embodiments and is shown in detail in FIGS. 8 and 9. In that the construction and mode of operation of that control circuit has already been explained in conjunction with the description of the earlier embodiments, it is deemed unnecessary to repeat that description. Suffice it to say, that when the machine is first turned on, the yogurt mix is maintained warm by the resistance element disposed in the paddle  607  and/or by a thermoelectric heat exchanger  633  shown mounted in the side wall of the housing  601 . Periodically, the timer portion of the control circuit closes contacts for energizing the motor  605  to thereby “test” the consistency of the yogurt mix as culturing takes place. When the point is reached in the culturing process where the yogurt begins to gel, a resistance is imparted to the paddle  607  causing the paddle to stall but with the motor  605  continuing to run, the occluder pivots from its home position to a position which breaks the magnetic attraction between the reed switch  630  and the permanent magnet  629  to thereby disconnect the motor and timer from the electrical supply and reversing the polarity of the voltage applied to the thermoelectric unit causing it to cool rather than warm. 
     DESCRIPTION OF THE SIXTH EMBODIMENT 
     Comparing the yogurt maker illustrated in FIG. 7 with that in FIG.  6  and having described the earlier embodiments make it apparent that the only substantial difference is that the occluder device is moved to the housing&#39;s top. In this arrangement, the split paddle  701  is molded integrally with the cover  702 . The motor  703  has its output shaft  704  extending upwardly through the tubular center post  705  of the molded plastic housing  706 . This shaft is keyed to a downwardly projecting stem  707  of the occluder  708 . 
     The occluder supports a permanent magnet  709  thereon which cooperates with a magnetic reed switch  710  mounted in a recess of the cover  702  when the occluder  708  is in its home position. Also mounted in the cover  702  is an electromagnet  712  adapted to cooperate with a permanent magnet  711  disposed on the occluder. 
     In this apparatus, when the motor  703  is driven, it rotates the occluder member  708  which is magnetically coupled to the top  702  by the attractive force between the permanent magnet  711  and the core of the electromagnet  712 . Thus, the top  702  rotates with the occluder and with the paddle member  701  until a point is reached in the cycle where the yogurt mix begins to firm-up and gel. The gelling of the yogurt mix stalls the paddles  701  and the cover  702  is prevented from rotating. However, the occluder, being driven by the motor  703  breaks the magnetic coupling and rotates out of covering relation relative to the vent opening  713 . That rotation of the occluder  708  relative to the top  702  also causes the reed switch contact  710  to open to shut off the motor  703  and to disconnect the power from the heating element disposed in the split paddle  701 . Where the unit is disposed in a refrigerator, cooling air passes through the vent  713  to terminate the culturing process. If the unit is to be used on a countertop, then, as with earlier embodiments, the thermoelectric heat exchanger  714  has its power reversed when the occluder swings independently of the cover so as to function in a cooling mode rather than a heating mode. 
     In any one of the described embodiments, rather than testing the consistency of the milk product by its viscosity, a pH or chemical change measuring device may be used to detect when the hydrogen ion concentration of the mix reaches a predetermined level of acidity or other chemical change occurs and for automatically turning off the warming and initiating cooling thereof in response to such condition. As mentioned earlier, the motor current can be sensed using a comparitor circuit. As the yogurt gels, the motor current increases and when it exceeds a threshold established by the comparitor, a control signal is developed that can be used to terminate warming and initiate cooling. 
     Yogurt Starter Introducer 
     FIGS. 10 and 11 respectively show a side elevational view and a top view of an attachment for the preceding six embodiments of the invention which allows for the automatic introduction at a predetermined time point in the cycle of operation of a yogurt starter mix. The starter mix may comprise yogurt purchased from a grocery store and may comprise a small amount of a previously prepared batch of yogurt. The introducer comprises a molded plastic container indicated generally by numeral  1001  and, as shown in FIG. 11, it includes downwardly and inwardly sloping end and side walls  1005 . Each of these side walls terminates at its lower end in a rectangular base  1006  having an aperture  1007  formed therethrough. Aligned with this aperture is a downwardly extending tube  1008  that is adapted to fit through an opening in the top of the housing of the yogurt maker when plug-in electrical contacts  1009  are fitted into an electrical jack or socket formed on the cover of the housing. 
     The electrical contacts  1009  are connected by electrical conductors (not shown) to the terminals of a solenoid device  1010  disposed within a compartment of the device  1001 . A hinged lid, as at  1011  is used to close the container  1001  following the placement of the starter material within the adder device. 
     The solenoid  1010  is operatively coupled by a linkage  1012  to a shutter  1013  that normally occludes the aperture  1007 , preventing the starter material from flowing down through the tube  1008 . Upon the timed actuation of the solenoid  1010 , however, the shutter  1013  swings out of the way of the aperture  1007  and allowing the starter material to flow through the tube  1008  into the container of the yogurt making machine. Rather than employing a solenoid to actuate the shutter  1013 , a current activated bimetal strip may be used instead. 
     As should be apparent from what has been described, the device of FIGS. 10 and 11 is adapted to be plugged into the sockets  318  of the embodiment of FIG. 3, socket  425  in the embodiment of FIG.  4  and socket  626  in the embodiment of FIG. 6. A set of contacts (not shown) in the solid state timer  810  may be used to complete a circuit between the power supply and the solenoid  1010  (or bimetal strip) at an appropriate time when the contents in the container of the yogurt preparing machine are at an appropriate culturing temperature. 
     This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself. 
     The above descriptions are thus intended by way of example only and are not intended to limit the present invention in any way except as set forth in the following claims.