Abstract:
An improved evaporator is provided for an ice making apparatus of the auger-type. The evaporator employs an evaporator body having spiral grooves cut or milled into its outer cylindrical surface and a cylindrical jacket disposed over the spiral groove formed on the outer cylindrical surface of the evaporator body, with the jacket being in interference-fit engagement against the groove of the evaporator body. The interference fit is formed by thermal expansion of the jacket prior to it being telescopically slid over the body, followed by a cooling-down of the jacket, by which it shrinks or compresses radially inwardly, to tightly seal against the outer periphery of the grooves, creating a sealed path for refrigerant flow, from inlet to outlet of the evaporator.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to auger-type ice making machines used in a commercial setting, which produce flaked or chipped ice. Ice is formed by water freezing on the inner wall of a hollow cylindrical freezing chamber. A rotatable ice auger, sized to enable the scraping of ice off the inner surface of the freezing chamber conveys the flaked ice toward an axial end of the freezing chamber whereby the flaked ice is compressed into a rigid mass of ice which is subsequently severed into discrete, generally uniform chunks of ice.  
           [0002]    The present invention is directed toward a new and improved auger-type ice making machine which has an improved evaporator.  
           [0003]    The present invention is an improvement upon U.S. Pat. No. 5,394,708, the complete disclosure of which is herein incorporated by reference.  
         SUMMARY OF THE INVENTION  
         [0004]    This invention relates to an auger-type ice making apparatus of the type wherein ice is produced on the inner walls of a cylindrical freezing chamber. A rotatable ice auger scrapes such walls producing flaked ice.  
           [0005]    In accordance with the present invention, the evaporator of the auger-type ice making machine comprises a cylinder comprising an evaporator body of significant wall thickness, which has a continuous spiral groove cut (preferably milled) on its outer cylindrical surface. This spiral groove embodies the refrigerant flow canal. A second cylinder comprises a jacket which is placed around the evaporator body. The jacket has an interference fit around the body and can only be slid into place after it is thermally expanded. Once the jacket has been expanded and slid into place, it is cooled and, upon being cooled, undergoes a radial contraction, whereby the inner cylindrical surface of the jacket seals tightly against the outer diameter of the spiral groove of the evaporator body, such that refrigerant will flow only along the spiral groove, confined outwardly of the spiral groove by the inner cylindrical surface of the jacket. Refrigerant inlet and discharge ports are provided through the jacket.  
           [0006]    This invention relates generally to an auger-type ice making apparatus where flaked ice is created on the interior wall of a cylindrical freezing chamber, scraped of the wall by an ice auger, and transferred out of the chamber, through a discharge aperture, to a discharge line.  
           [0007]    It is accordingly a general object of the present invention to provide a new and improved auger-type ice making apparatus, with an improved evaporator.  
           [0008]    It is another object of the present invention to provide a new and improved auger-type ice making apparatus which comprises an evaporator body having spiral grooves in its outer cylindrical surface, which grooves, together with the inner cylindrical surface of a jacket that is first heated or otherwise thermally expanded, and then allowed to cool, shrinks radially inwardly to form an interference fit against the continuous spiral groove, such that refrigerant delivered into and out of the spiral groove is confined between the evaporator body and the jacket, so as to flow only along the spiral groove from the inlet thereto, to the outlet thereof.  
           [0009]    Other objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a schematic diagram of an ice making apparatus of the prior art.  
         [0011]    [0011]FIG. 2 is an elevational view, partially broken away and shown in longitudinal section, of the auger-type ice generating apparatus embodied on the system shown in FIG. 1.  
         [0012]    [0012]FIG. 3 is a perspective view of the evaporator body and jacket of this invention, shown assembled at the left of FIG. 1, and shown longitudinally exploded at the right of FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    Referring now in detail to the drawings, wherein like reference numerals indicate like elements throughout the several views, there is shown in FIGS. 1 and 2 an ice making apparatus in accordance with one preferred embodiment of the prior art, of which the present invention is an improvement. The illustrated apparatus is shown generally as comprising an auger-type ice generating apparatus  10 , with a motor means  26  to drive the ice generating apparatus  10 , an input line for water  18  from a water source  16  to be frozen, an outlet delivery line  12  for delivery of chunks of ice to an ice retaining means  14 , a refrigeration means comprising a compressor means  20 , a condenser means  22 , an expansion valve  27 , and evaporator  24  to supply refrigeration to the ice generating means  10 .  
         [0014]    In operation of the ice maker according to the prior art, conventional refrigerant under pressure is sent from the compressor means  20  via line  37  to the condenser means  22 . The refrigerant is thereafter liquefied within the condenser means  22  and then passed through an expansion valve  27  to the evaporator  24 . Evaporator  24 , which completely surrounds the ice making machine  10 , boils the liquid refrigerant under low pressure to extract heat from, and accordingly cool, the generally cylindrical ice freezing chamber. Evaporator  24  additionally comprises an evaporator cover  29  which serves as an insulator and protective cover. Water is supplied to the cylindrical freezing chamber  30 , which houses an ice auger  28 , from a water source  16  through water input line  18 . A constant level of water  25  is maintained in the freezing chamber. Water freezes on the inner wall  38  of the freezing chamber  30  and is scraped off by means of the ice auger  28 .  
         [0015]    The ice generating apparatus  10  according to the prior art is shown in greater detail in FIG. 2. The auger  28  is disposed vertically in the interior of the freezing chamber  30  and is driven by shaft  44 . Actuation of the motor means  26  results in a rotation of the auger  28  which causes ice to be scraped off the inner wall  38  of the freezing chamber  30  in flaked form. The ice generating apparatus  10  includes a water inlet  32 , formed on its lower end for receiving water from the inlet line  18 , and an ice discharge  34 , formed on the upper end for delivering generated ice to the delivery line  12 . Tubing  36  is also included, wrapped a plurality of times around the freeing chamber  30  which defines the aforementioned evaporator  24 . Evaporator  24  includes an inlet  33  for receiving the refrigerant from the expansion valve  27 , and refrigerant vapor is passed out through an outlet  35 , into outlet line  54  where, as shown in FIG. 1, it is carried back to the compressor means  20 . The refrigerant extracts heat from the ice generating apparatus  10  through the walls of freezing chamber  30  as it is passed through the evaporator  24 . This causes some of the water contained within the freezing chamber  30  to freeze along the inner wall  38 .  
         [0016]    Auger  28  includes at least one coiled band of scrapers  42  extending outward from the auger surface  56 , in close proximity to the inner wall  38  of the freezing chamber  30 . A drive shaft  44  connects to the motor means  26  extending axially through the auger  28 . Accordingly, as auger  28  is rotated, the scraper  42  shaves the ice formed on the inside walls  38 , carrying it axially upward, in the form of slush, to be compacted against an annular compacting head  51 .  
         [0017]    As indicated above, the ice discharged through the discharge  34  is sent via line  12  to the retaining means  14 .  
         [0018]    The use of a prior art evaporator that includes a wrapping of copper tubing around a cylindrical body is avoided. In accordance with the prior art, such a copper tube, when brazed into a refrigeration circuit, embodies the refrigerant flow canal of the evaporator. Attachment of the wrapped tube to the cylinder body is typically accomplished by using a solder to bond them together. Often the wrapped assembly is dipped into a molten solder tank, allowing the solder to flow underneath and in between the copper tubing wrap. Such attachment and subsequent insulation of the copper tubing wrap is a labor and process intensive endeavor. Additionally, evaporator performance and reliability depend on proper execution of the process because proper copper tube attachment is critical to ensure heat transfer from the water within the evaporator to the refrigerant in order to freeze the water, and it is vital that moisture be sealed out of the wrapped tubing area of the evaporator assembly. If moisture is not sealed out and ice is formed between the copper tubing wrap and body, the subsequent expansion and contraction due to freeze/thaw operation cycles may cause copper wrap separation and/or structural failure of the body itself. Generally the solder is used not only to bond the copper tube to the body, but also acts as a moisture seal.  
         [0019]    The problems associated with a wrapped and dipped evaporator manufacturing process are numerous. For example, the wrapped tube may tend to distort as it is wrapped around the body, creating voids and air gaps that can harm performance. Furthermore, the wrap may tend to “spring” when the assembly is removed from the wrapping apparatus, so the ends of the copper tube must be attached, typically via spot welding, to the body, in order to counter such tendency to “spring”. If the wrap is too tight, the solder will not flow properly. If the wrap is too loose, the heat transfer may not be appropriate. Furthermore, solder adhesion is problematic, especially when the body is stainless steel. At a minimum the body needs to be fluxed in an acid prior to dipping it into a solder, if not actually pre-tinned prior to wrapping. It has been found that solder adhesion is critical to evaporator performance. Additionally, in a wrap assembly, the assembly must be pre-heated prior to solder dipping, in order to avoid dangerous eruption of the solder tank which could occur should a cold assembly be introduced into molten solder. Furthermore, solder must never flow to the interior of the evaporator body, because of the lead content of the solder, but sealing of the ends of the evaporator during the dipping process has been found to problematic. Additionally, attaching insulation to the exterior of the dipped assembly is difficult due to the uneven outer surface. Typically, a shell is placed around the assembly, and a foam-in-place operation is performed, with the intent of having the insulation flow into the voids, further sealing the dipped area from moisture.  
         [0020]    Referring now to FIG. 3, it will be seen that the improved evaporator  125  of the present invention is generally designated in place of the evaporator  24  of FIGS. 1 and 2, and comprises an evaporator body  130  and a jacket  131 .  
         [0021]    The evaporator body  130  has an inner cylindrical wall  138  and, on its outer cylindrical surface, a spiral groove  140 , which is milled, or otherwise cut into the exterior cylindrical surface of the evaporator body  130  to define a spiral groove  140  from a location above the lower end  141  of the body  130 , to a location below the upper end  142  thereof. At opposite ends of the spiral groove  140  there are circumferential grooves  143 ,  144 .  
         [0022]    A refrigerant inlet port  145  is provided in the cylindrical jacket  125 , fed by the refrigerant delivery line  39  of FIG. 1, with the refrigerant being carried off via refrigerant discharge port  146 , to the refrigerant outlet line  54  of FIG. 1.  
         [0023]    It will be apparent that, except for the evaporator construction, the ice making apparatus of this invention is in accordance with the apparatus of FIGS. 1 and 2, with the evaporator of FIGS. 1 and 2 being replaced by the evaporator construction of FIG. 3.  
         [0024]    The cylindrical jacket  131  has an interference fit against the outer peripheral edges  147  of the spiral cut  140 , to seal refrigerant that enters via port  145 , to remain within the spiral groove  140 , from its inlet location  145 , to its discharge location  146 .  
         [0025]    The manner in which the interference fit is achieved is by heating the jacket  131  prior to sliding it into place over the body  130  of the evaporator  125 , whereby the jacket  125  thermally expands to a greater diameter, or outwardly, in the radial direction. After the jacket  125  is in place over the body  130 , it is cooled and shrinks or reduces in diameter, or in a radial direction, until the inner cylindrical surface  148  thereof tightly engages against the outer peripheral edges  147  of the continuous helical or spiral groove  140  formed on the outer surface of the body, whereby it tightly seals thereagainst.  
         [0026]    Thus, refrigerant entering via inlet port  145 , into circumferential groove  143 , is caused to pass along the helical groove until it reaches the upper circumferential groove  144 , whereby it can exit the evaporator via exit port  146 , to line  54 , and back to the compressor  20 .  
         [0027]    An auger  28  disposed inside the auger body thus, as set forth in the description above with respect to FIGS. 1 and 2, scrapes ice from the inner cylindrical wall  138  of the body, delivering the same upward through the evaporator, to discharge via ice discharge port  134 , to an ice delivery line  12 , back to an ice retaining means  14 .  
         [0028]    The jacket  131  is welded to the evaporator body  130  at upper and lower ends thereof, at locations  150  and  151 , as shown in FIG. 3, to ensure proper refrigerant sealing within the groove  140 .  
         [0029]    It will be seen that, in accordance with this invention, the manufacturing process for forming an evaporator is greatly simplified, in that it is not necessary to use a wrapped tube construction, and the problems associated with a wrapped tube construction are thereby avoided. Moreover, the spiral groove that is formed in accordance with this invention is no longer subjected to variations that are inherent in a wrapped dipped tube construction. Additionally, with the present invention moisture can no longer affect the integrity of the refrigerant path or evaporator structure. Additionally, in accordance with the present invention, more simplified forms of insulation can be used, for example, a simple foam material can be fastened in place to insulate the evaporator. Additionally, by employing circumferential grooves at each end of the body, the heat transfer between thick-walled ends of the evaporator and the spiral groove is minimized. Furthermore, by locating the refrigerant inlet and outlet ports  145  and  146  as disclosed herein relative to the spiral groove  140 , refrigerant turbulence can be effected to the highest degree, with minimal loss due to pressure drop.  
         [0030]    It will be recognized by those skilled in the art that changes may be made in the above described embodiments of the invention without departing from the broad inventive concepts thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover all modifications which are within the scope and spirit of the invention as defined by the appended claims.