Abstract:
A positive displacement chilled food dispenser is provided where liquid enters a portion of a housing where two screws reside. The housing is chilled below the freezing temperature of the liquid. The two screws, when rotating, move the liquid towards a dispensing end. The liquid freezes where it contacts the housing and is scraped by an outside diameter of the two screws. The frozen liquid is then dispensed through a dispensing end. At the dispensing end is an optional valve that selectively shuts the flow of frozen liquid off. Alternatively, a sensor determines how much frozen liquid is dispensed through the dispensing end.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Frozen treats such as ice cream, frozen yogurt, and the like have been a mainstay for people wanting to refresh themselves after a hot day, a meal, or just for a snack. Commonly, soft-serve ice cream or frozen yogurt is dispensed from a machine that both freezes a liquid into a flowable solid then dispenses it. In the current art, the machines use a spiral auger having a single straight blade that scrapes frozen product from the inside diameter of the dispensing cavity. The system has remained largely unchanged for many years and functions, except for the hassle and waste generated by cleaning and the inability to automatically dispense metered amounts. Currently in the art, a large cavity of unused product remains and must be discarded at the end of the day or when a flavor changeover is desired. An improved frozen treat dispenser is needed. 
       SUMMARY OF THE INVENTION 
       [0002]    The present disclosure describes a device for dispensing a metered amount of frozen product using a positive displacement pump. A set of helical screws reside inside a cavity that is chilled to below the freezing point of the product. One screw has the opposite thread of a second screw. As the helical screws rotate in opposite directions, the outside diameter continuously scrapes frozen product off of an inside wall of the cavity. Because the rotation of the screws positively displace the food product, a metered amount of product can be easily dispensed by controlling the rotation of the screws. Also because the inside available space is mostly consumed by the rotating screws, only a very small amount of product remains inside at any point in time. Another function of the positive displacement pump arrangement is that the system can be easily purged by dispensing any amount leftover. This minimizes the amount of waste when the machine is shut down at the end of use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    A preferred embodiment of this invention has been chosen wherein: 
           [0004]      FIG. 1  is a side section view of the system; 
           [0005]      FIG. 2  is a side section of the housing portion of the system in  FIG. 1 ; 
           [0006]      FIG. 3  is an isometric view of the housing portion with the upper and lower screws partially removed; 
           [0007]      FIG. 4  is an end view of the upper and lower screw showing the interface portion; 
           [0008]      FIG. 5  is a front view of section  5 - 5  in  FIG. 2 ; and 
           [0009]      FIG. 6  is an isometric view of the cover and housing. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]    A positive displacement dispensing device  10  is shown in  FIG. 1  that cools a liquid  12 ,  FIG. 2  into a frozen product  14 , such as ice cream or frozen yogurt. As shown in  FIG. 2 , the device has a housing  16  with an inlet port  18  and an outlet port  20   FIG. 1 . 
         [0011]    At the rear of the housing  16  is an input shaft  22  with a driven sprocket  24 . A motor  26  with a driving sprocket  28 ,  FIG. 1  as shown in  FIG. 1  connected to the driven sprocket  24  by a chain  30  transfers power to the input shaft  22 . A keyway and key secures the driven sprocket  24  to the input shaft  22 . It is contemplated that the input shaft  22  is driven directly by the motor  26 . 
         [0012]    Mounted to the input shaft  22  is a driving gear  32 ,  FIG. 2  that meshes with a driven gear  34 . The gears  32 ,  34  are located in the gear portion  35  of the housing  16 . Supporting the shaft  22  on the end closest to the driven sprocket  24  is a bearing  36 . As shown in  FIG. 2 , it is a ball bearing, but it could be any other type of device such as a bushing to allow the shaft  22  to rotate. Located past the driving gear  32  is a bushing  38  that supports the shaft  22  at the other end. The driven gear  34  is mounted to a driven shaft  40  which is also supported by a bearing  42  on one end and a bushing  44  on the opposite end. While it is not shown in the FIGS, shaft seals may be implemented on the shafts  22 ,  40  to prevent any liquid  12  from entering the part of the housing that contains the driving gear  32  and driven gear  34  and also to keep any lubricant from escaping the gearbox. The seal could be integrated into the bushing or other bearing device. It is further contemplated that the gear portion  35  would be capable of carrying a food-grade lubricant. Alternatively, moving parts in the gear portion  35  could have a food-grade coating with lubricating properties. 
         [0013]    Adjacent to the gear portion  35  of the housing  16  is a cooling portion  46 . Ends of the shafts  22 ,  40  protrude into the cooling portion  46 . On the end of the shaft  22  is a coupling portion  50 , and similarly, at the end of shaft  40  is another coupling portion  52 . Further located in the cooling portion  46  is a removable lower screw  54  and a removable upper screw  56 .  FIG. 3  shows the upper and lower screws  56 ,  54  partially removed. As is visible in  FIGS. 1 and 2 , the housing has an internal cavity. The internal cavity has an upper cylindrical surface  60  and a lower cylindrical surface  62 . This is visible in  FIGS. 2 and 5 . The internal cavity is formed by the two overlapping cylindrical surfaces  60 ,  62 . The internal cavity is sized to receive an upper screw  56  and a lower screw  54 . The upper screw  56  as shown is a double lead screw and the lower screw  54  is a single lead screw. Because of this, and in order to have proper meshing of the screws, the diameter of the upper screw  56  is double the lower screw  54 . It is contemplated that the upper screw  56  and lower screw  54  could be the same, either both being a single lead or double lead. 
         [0014]    The upper screw  56  has a continuous spiral  68  extending from one end to the other. A portion can be seen in  FIG. 3 . As shown in  FIGS. 2 and 3 , the upper screw  56  has a left-hand or reverse thread. The spiral  68  has a root  70  and a taper  72  that extends outwardly from the root  70 . The taper  72  terminates at a scraping surface  74 . The scraping surface  74  has an outer diameter that closely matches the internal surface  60 . The closer the scraping surface  74  matches the internal surface  60 , the more efficient the overall system. The upper screw  56  has an interface  76  that mates with the coupling portion  52  of the shaft  40 . When the upper screw  56  is mated to the shaft  40 , rotation of one will cause the other to rotate. The interface  76  and coupling portion  52  allow torque transfer. Because the assembly of the upper screw  56  to the shaft  40  is blind, misalignment could cause assembly difficulties. It is contemplated that the interface  76  and coupling portion  52  contains a ramped surface to allow misalignment as the two are mated but align them and allow single direction torque transfer. 
         [0015]    The lower screw  54  has a continuous spiral  78 ,  FIG. 2  extending from one end to the other. As shown, the lower screw  54  has a right-hand thread. It is contemplated that the lower screw  54  is a reverse thread and the upper screw  56  is a right-hand thread. The spiral  78  has a root  80  and a taper  82  that extends outwardly from the root  80 ,  FIG. 3 . The taper  82  terminates at a scraping surface  84 . The scraping surface  84  has an outer diameter that closely matches the internal surface  62 . The closer the scraping surface  84  matches the internal surface  62 , the more efficient the overall system. The lower screw  54  has an interface  86  that mates with the coupling portion  50  of the shaft  22 . When the lower screw  54  is mated to the shaft  22 , rotation of one will cause the other to rotate. The interface  86  and coupling portion  50  allow torque transfer. Because the assembly of the lower screw  54  to the shaft  22  is blind, misalignment could cause assembly difficulties. It is contemplated that the interface  86  and coupling portion  50  contains a ramped surface to allow misalignment as the two are mated but allow single direction torque transfer. 
         [0016]    Precise alignment of the upper screw  56  and the lower screw  54  is necessary for proper function and assembly of the device  10 . The coupling portion  50 , as shown, is a single projection that protrudes into a single receiver on the interface  86  on the lower screw  54 . The coupling portion  52  has  4  projections that protrude into corresponding receivers on the interface  76  of the upper screw  56 . As shown in  FIG. 4 , it is possible to assemble the upper screw  56  to the shaft  40  in four different orientations. It is possible to assemble the lower screw  54  to the shaft  22  in two different orientations. Alternate coupling styles are contemplated. 
         [0017]    When the lower screw  54  is meshed with the upper screw  56 , the root  70  is very close to the scraping surface  84 , the taper  72  is close to the taper  82 , and the root  80  is close to the scraping surface  74 . The close proximity of these surfaces improves the efficiency of the overall system. The combination of the lower screw  54  and the upper screw  56  form a screw-drive positive displacement pump for liquid  12 . 
         [0018]    The housing  16  is enclosed by a front removable cover  88 ,  FIGS. 1 and 2  that fits onto pins  94 ,  FIG. 2 . The removable cover  88  seals to the cooling portion  46 ,  FIG. 1  and has an upper bushing  96 ,  FIG. 2  that supports one end of the upper screw  56  on a bearing surface  98  and a lower bushing  100  that supports the end of the lower screw  54  on a bearing surface  102 . In the embodiment shown in all FIGS, removable cover  88  has captured screws  95 ,  FIG. 6  that serve to both secure the cover  88  to the housing  16  and drive it off of the housing for cleaning. The pins serve to properly align the cover  88  to the housing  16 , which then align the upper screw  56  and the lower screw  54  to their respective cylindrical surfaces  60 ,  62 . 
         [0019]    The coupling portion  50  engages with the interface  86  and is locked in rotation such that when the driving shaft  22  rotates, the lower screw  54  rotates in concert. Likewise, the coupling portion  52  engages with the interface  76  and is locked in rotation such that when the driven shaft  40  rotates, the upper screw  56  rotates in concert. The coupling portions  50 ,  52  allow the screws  54 ,  56  to be removed simply by pulling them out of the housing  16  when the cover  88  has been removed. 
         [0020]    On the ends of each screw are thrust surfaces. For example, the upper screw  56  has a thrust surface  104 ,  FIG. 4  that is adjacent to the interface  76 . Correspondingly, the lower screw  54  has a thrust surface  106  that is adjacent to the interface  86 . It is contemplated that the thrust surfaces  104 ,  106  are on the interfaces  76 ,  86 . The thrust surfaces  104 ,  106  carry the axial pressure from the reaction force created when the screws  54 ,  56  pump the liquid  12  from the inlet  18 ,  FIG. 5  to the outlet  20 . The gear portion  35  and bushings  38 ,  44  mate with the thrust surfaces  104 ,  106  to provide support. It is further contemplated that the shafts  22 ,  40  carry the axial load. 
         [0021]    The refrigeration system is shown in  FIG. 1  with a compressor  110 , evaporator coils  112 , a condenser  114 , and a condenser fan  116 . These items are all connected by tubing  118  to allow refrigerant to circulate. Refrigeration of this type is well known in the art. When the compressor  110  is running, the refrigerant is compressed into a liquid in the condenser  114 , which is then cooled by the condenser fan  116 . The coolant then travels through an orifice, where it expands into the evaporator coils, causing it to lose a significant amount of heat, cooling the cooling portion  46 ,  FIG. 6 . Because the cooling portion is made from a heat-conductive material, the evaporator coils heat or cool the cooling portion effectively. A controller can be implemented using temperature sensors to control the compressor&#39;s activity, thereby controlling the temperature of the cooling portion  46 . 
         [0022]    Because the screws and cooling portion form a positive displacement pump, dispensing only occurs when the screws rotate. In order to control the screws, several different methods can be implemented. First, a switch can be connected to the motor  26  such that the motor only turns when the switch is activated. Further, the switch could be attached to a dispensing valve that the user can open or close. When the switch indicates that the valve is open, the motor  26  can be enabled, causing product  14  to be dispensed. When the limit switch indicates the valve is closed, the motor  26  is then turned off to prevent excessive pressure buildup in the housing  16 . Alternatively, a pressure sensor (not shown) can be implemented in the housing  16  that can control the motor  26  based on the pressure inside. Another option is to have a sensor or encoder (not shown) located on one of the shafts  22 ,  40 , or the motor  26  such that a controlled amount of product  14  be dispensed, based on the number of revolutions of the screws  54 ,  56 . Because the amount of displacement is known for each revolution, the user could control the amount of product  14  being dispensed using that method. This could eliminate the need for the valve. It is contemplated that the aforementioned controls could be used singularly or in combination with each other to control the dispensing of product  14 . 
         [0023]    For operation, the user fills a reservoir  90 ,  FIG. 2  with liquid  12 , usually some form of frozen dessert, such as ice cream or frozen yogurt. The liquid  12  passes through the inlet port  18  and into the cavity inside the cooling portion  46 . The cooling portion  46  is chilled by refrigeration either through an integral or external cooling jacket  92 ,  FIG. 1 . As the liquid  12  begins to fill the cavity, it contacts the screws  56 ,  54 . The motor  26  begins to turn, causing the shaft  22  to rotate. The shaft  22 , in turn, causes the driving gear  32  and therefore the driven gear  34  to turn. Because these gears directly mesh, the driven gear  34  turns in the opposite direction of the driving gear. As shown, the gear ratio is 2:1 but could be other ratios, depending on the screws  54 ,  56  they drive. 
         [0024]    The cooling portion  46  is cooled sufficiently below the freezing point of the liquid  12 , such that the liquid  12  hardens and accumulates on the cylindrical surfaces  60 ,  62 ,  FIG. 5 . The upper screw  56 , namely the scraping surface  74  shears off accumulated hardened liquid from the upper cylindrical surface  60  and moves it toward the outlet port  20  as it rotates. Simultaneously, the lower screw  54 , namely the scraping surface  84  shears off accumulated hardened liquid from the lower cylindrical surface  62  and moves it toward the outlet port  20  as it rotates. 
         [0025]    For cleaning, liquid  12  is removed from the inlet port  18  and the motor  26  is enabled, rotating the screws  54 ,  56 . This drives any remaining liquid  12  from the cooling portion  46  and out of the cooling portion  46 . At any point, the refrigeration system is disabled to allow the cooling portion  46  to warm up. Once the cooling portion is devoid of most liquid  12 , the cover  88  can be removed, allowing access to the upper and lower screws  56 ,  54 . The user then pulls the screws  56 ,  54  away from their respective coupling portion  52 ,  50  and out of the housing. As shown, the upper screw  56  has a grabbing handle  58 ,  FIG. 3  located inside, allowing the user to grasp it and pull the upper screw  56  directly out. It is contemplated that the lower screw  54  has a similar feature. 
         [0026]    After cleaning, reinstallation of the components of the system  10  are largely the reverse of their removal. Firstly, the screws  56 ,  54  are mated where the root  80  meets the scraping surface  74  and the scraping surface  84  meets the root  70 . The screws  56 ,  54  are aligned to allow the coupling portion  52  to mate the interface  76  while simultaneously allowing the coupling portion  50  to mate the interface  86 . The cover  88  is then secured to the cooling portion  46 . 
         [0027]    It is understood that while certain aspects of the disclosed subject matter have been shown and described, the disclosed subject matter is not limited thereto and encompasses various other embodiments and aspects. No specific limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. Modifications may be made to the disclosed subject matter as set forth in the following claims.