Abstract:
An agitating retort ( 118 ) includes a drum ( 122 ) designed to fit closely within an outer shell ( 120 ) for rotation of the drum within the shell. The drum is perforated to permit water and/or steam to circulate through the drum during the retorting process. A plurality of interior transverse plates ( 130 ) are spaced apart along the interior of the drum to provide structural integrity thereto. The central portions of the plates ( 130 ) are open for receiving baskets ( 134 ) therein which receive containers of the foodstuffs or other products to be processed within the retort.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to retort systems for in-container preservation of foodstuffs, and more particularly to an agitating retort designed for high capacity.  
       BACKGROUND OF THE INVENTION  
       [0002]     Agitating retorts are widely used for in-container preservation of foodstuffs, either for pasteurization or sterilization processes.  FIGS. 1 and 2  illustrate the construction of a known agitating retort  18 , consisting of an outer retort shell  20  which in essence is a generally cylindrically shaped pressure vessel that houses a drum  22  that rotates within the shell. The drum is adapted to receive baskets  24  within which containers of foodstuffs are stacked. The containers may be in the form of cans, glass jars or of other types. Alternatively, the foodstuff containers may be arranged on trays carried by pallets, not shown. The baskets of foodstuff containers are clamped in place within the drum to retain the baskets and containers during rotation of the drum.  
         [0003]     Hot water, steam, or a combination of both (process fluid) are circulated through the drum to carry out the pasteurization or sterilization process. The process fluid may be introduced into the agitating retort  18  through a number of inlets that may be located above the drum over the length of the retort shell to partially or substantially fully fill the shell with process fluid. The process fluid may also be introduced onto the retort through distribution pipes extending lengthwise within the retort shell, exterior to and above the drum. Holes or spray nozzles may direct the water spray or steam/water spray downwardly from the distribution pipes onto the rotating drum and over and between the foodstuff containers carried by the baskets. The processing fluid from the holes or the nozzles collects at the bottom of the shell for removal.  
         [0004]     The drum  22  is shown of open design and is constructed from a number of spaced-apart vertical disks  30  that are joined together with a series of longitudinal tube structures  32  spaced about the perimeter portion of the disks to provide structural strength of the drum  22 . Reinforcing braces  34  may be welded between the tubes in a criss-cross pattern for further structural strength and/or rigidity. A door  36  is used to close off the open end of the shell  20  through which the baskets  24  holding the containers are loaded into and unloaded from the drum  22 . The drum  22  may be rotatably supported by rollers  38  located in the lower portion of the retort shell  24  and bearing against the outer surface of the drum  22 . A powered drive shaft  40  may be coupled to the end of the drum opposite the door  36  for rotation of the drum.  
         [0005]     As shown in  FIG. 2 , generally square or rectangular shaped openings  42  are formed in the disks  30  for receiving the baskets  24 . Various types of clamping systems, not shown, may be used to hold the containers and the baskets in place when the drum is rotated. As apparent, the tube structures  32  occupy a significant space within the drum and thus limit the cross-sectional size of the baskets  24  that can be accommodated by the drum. It will be appreciated that the throughput of an agitating retort can be increased if the drum were designed to accommodate baskets that occupy a larger cross-sectional area of the drum than is currently possible. The present invention seeks to address this issue as well as other issues, as described below.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the teachings of the present invention, an agitating retort is described as composed of an outer shell and a cylindrical drum sized to be closely receivable and rotatable within the shell. The drum is perforated about a substantial portion of its surface to allow passage of processing fluids into and out of the drum during operation of the retort. One or more reinforcing structures are used to reinforce the drum to enhance its structural integrity. Such reinforcing structure strengthens the drum in bending, torsion and/or in hoop strength.  
         [0007]     The reinforcing structures for the drum may be composed of a plurality of spaced apart transverse reinforcing walls positioned within the drum so that the outer perimeter of such circular walls fixedly engages the inside diameter of the drum. The central portions of such reinforcing plates are open for receiving baskets or other structures used to hold product containers.  
         [0008]     In alternative to, or in addition to, the reinforcing plates, the structural integrity of the drum can be enhanced by using interior and/or exterior rings at the ends of the drum or at locations intermediate the ends of the drum. Further, structural members may be positioned lengthwise of the drum on the interior and/or exterior of the drum. Such structural members may include rods, tubes, angles, channels, or other structural shapes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing aspects and many other attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a schematic side elevational view of a prior art agitating retort structure;  
         [0011]      FIG. 2  is a schematic cross-sectional view of  FIG. 1 , taken substantially along lines  2 - 2  thereof;  
         [0012]      FIG. 3  is a partially schematic longitudinal view partially in cross-section of an agitating retort constructed in accordance with one embodiment of the present invention;  
         [0013]      FIG. 4  is a substantially schematic view of  FIG. 3 , taken substantially along lines  4 - 4  of  FIG. 3 ;  
         [0014]      FIG. 5  is an isometric view, partially in schematic, of a segment of a drum constructed according to the present invention taken from one end thereof;  
         [0015]      FIG. 6  is a view similar to  FIG. 5 , but taken from the opposite end of the drum segment;  FIG. 7  is a partial cross-section view of a further embodiment of the present invention corresponding to  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Referring initially to  FIGS. 3-6 , the agitating retort  118  includes a generally cylindrically shape shell  120 , having a closed end portion  119  which is convex in shape in a manner typical of pressure vessels, and an open opposite end portion  121  that is closable by a door  136  in a manner typical of agitating retort constructions. Thus, these features of the present invention will not be described in detail.  
         [0017]     The focus of the present invention includes a new and novel drum construction  122 , which may be utilized in conjunction with existing retort shells or new retort structures. The drum  122  is designed to be close fitting within the retort. The clearance between the exterior of the drum and the interior of the shell  120  may be in the range of from about 2 to 6 cm.  
         [0018]     As shown in  FIG. 3 , the drum  122  is in the form of a perforated cylinder  123 . The drum can be composed of a single structural member, for example, a flat perforated plate that is rolled into a cylindrical shape. Alternatively, the drum  122  could be constructed of sections of perforated plates that are rolled to form segments of the drum, with the segments then welded or otherwise attached together in both the axial and circumferential directions.  
         [0019]     The perforations  124  in the drum cylinder  123  are provided for the purpose of enabling water, steam or other process fluids to enter and exit the drum. The perforations  124  are illustrated as being circular in shape, but can be of numerous other shapes, such as square, triangular, oval, diamond or slot shaped. Also, though the round perforations  124  are shown as arranged in circumferential rows and straight lines along the length of the drum, the perforations can be arranged in numerous other patterns, such as offset from each other from row to row, or in a spiral pattern about the drum cylinder  123 . The drum cylinder may also be only partially perforated in a pattern that provides higher strength and/or stiffness in function of the mechanical loads during operation. Also, the size and number of perforations may vary with different factors, for example, the thickness of the drum wall, the speed of rotation of the drum, the type of working medium, whether water, steam, or a combination, as well as other factors. As one specific but non-limiting embodiment, the circular perforations may be approximately 50 mm in diameter and arranged on 90 mm centers, providing an open area of about 28%. Other percentages of open area provided by the perforations may be utilized. One design criteria of the present invention in this regard is to provide sufficient open area in the drum to allow for adequate circulation of the working medium into and out of the drum, while at the same time maintaining the strength and structural integrity of the drum.  
         [0020]     The drum may be composed of numerous different types of materials, including carbon steel, stainless steel, and other appropriate materials. The diameter and length of the drum, as well as the material composition of the drum, will be a factor in the wall thickness of the drum cylinder. Another factor in the wall thickness of the drum cylinder is the type(s) of bracing and amount of bracing utilized with the drum, as described below.  
         [0021]     One type of bracing or reinforcement utilized with drum  122  consists of generally circularly shaped plates or disks  130  disposed transversely in the interior of the drum and spaced apart along the length of the drum. The plates  130  are sized to be closely receivable within the interior of the drum, with the perimeter of the plates fixedly attached to the interior surface of the drum by welding, bolting, or otherwise. It will be appreciated that such plates can vastly increase the torsion strength and hoop strength of the drum. Openings  132  of generally square or rectangular shape are formed in the central portion of the plates  130  for reception of baskets  134 . Rollers  138  may be axle to the bottom portions of the baskets  134  to ride within grooved rails  140  extending longitudinally of the drum  122 . Alternatively, a series of rollers  138  can be axle within the drum in aligned relationship to support the bottom portions of the baskets  134 . As shown in  FIG. 4 , the openings  132  may extend almost to the outer perimeter of the plates  130 , thereby maximizing the cross-sectional size of the baskets  134  receivable within the drum. Although the plates  130  are shown in  FIG. 4  as being of solid construction (other than opening  132 ), the plates can be perforated or otherwise include openings to lighten the construction of the drum and also to allow for circulation of water and/or steam through the plates.  
         [0022]     In place of or in addition to plates  130 , the drum  122  may be reinforced in other ways. For instance, reinforcing rings  150  may extend around the exterior of the drum in registry with the locations of the plates  130  or at other locations along the length of the drum. Corresponding or other rings, not shown, may be positioned in the interior of the drum, bearing against the inside surface of the drum. Also reinforcing rings  152  and  154  may be positioned to extend longitudinally from the opposite ends of the drum. The rings  150 ,  152  and  154  may be fixedly attached to the drum by welding, bolting, clamping or otherwise.  
         [0023]     The drum  122  may be alternatively or additionally reinforced by structural members extending longitudinally of the drum. These structural members could be rods, tubes of round, square or rectangular shape or profiles of various shapes including U, L or T profiles. The structural members are spaced apart from each other about the exterior or interior circumference of the drum cylinder  123  or both, not shown, and may be fixedly attached to the drum by welding, bolting, clamping or otherwise.  
         [0024]     As an example,  FIG. 7  illustrates a series of exterior channels  160  extending lengthwise along the exterior surface of the drum. The channels  160  can be spaced apart from each other about the exterior circumference of the drum cylinder  123 . Interior channels  162  may in addition or alternatively extend along the interior of the drum, being positioned at spaced-apart locations about the inside surface of the drum. The interior channels  162  may be similar or of different size than the exterior channels  160 . The exterior and interior channels may be fixedly attached to the drum by welding, bolting, clamping or otherwise. If plates  130  are used in conjunction with drum  122 , then the plates may have openings to provide clearance for the interior channels, or the interior channels may extend between adjacent plates  130 . It will be appreciated that the size and number and location of the channels or other structural members may be varied to achieve the desired level of reinforcement. The important factor is that the structural members do not occupy a large distance in the radial direction relative to the drum, while significantly enhancing the structural integrity of the drum, including its bending strength, torsion strength, and hoop strength.  
         [0025]     Referring again to  FIGS. 3 and 4 , the drum  122  is supported for rotation about its longitudinal axis  190 . This support may be provided by roller sets  200  adapted to rotate about axes  202 , disposed parallel to the drum axis  190 . As shown in  FIG. 4 , the shell  120  may be enlarged at the location of the rollers to house the rollers. Alternatively, a portion of the rollers  200  may extend outwardly of the shell. The rollers  200  are shown in  FIG. 3  as positioned adjacent the end of the drum at the open end portion  121  of the shell. However, rollers similar to rollers  200  may also be positioned at the opposite end of the drum as well as at one or more locations intermediate the ends of the drums. In addition, the rollers  200  may ride against the exterior of the drum itself or ride against a ring formed around the drum, for example, rings  150 ,  152 , and  154 , described above. The rollers  200  may not only support the drum  122 , but also may be powered to rotate the drum. Various systems may be provided to apply rotational torque to the rollers  200 .  
         [0026]     The drum  122  may be driven other than by powering one or more rollers  200 . For example, the drum  122  may be driven by a powered drive shaft  220  that may be coupled to an end structure  222  attached to the end of the drum  122  corresponding to the closed end  119  of the shell  120 . A radial thrust bearing structure  224  may be mounted to the shell end structure  119  to support and constrain the drive shaft  220  as it is powered to rotate the drum  122 . The end structure  222  may be of various constructions, including composed of a plurality of radial arms  226  extending outwardly from a central hub  228 . The outer end portions of the arms  226  may be attached to drum ring  154 . By this construction, the end portion of the drum  122  is substantially opened so as not to, significantly restrict the circulation of water and/or steam into and out of the drum. If drive shaft  220  is utilized to rotate the drum  122 , rollers similar to rollers  200  may or may not be utilized at the adjacent end portion of the drum  122 .  
         [0027]     Various embodiments of the present invention have been illustrated and described. In each of these embodiments, the outer diameter of the drum is sought to be maximized with respect to the interior diameter of the shell, thereby maximizing the capacity of the drum to receive baskets  134  or other structures used to hold and support food product containers or other types of containers for processing within the agitating retort  118 . Simultaneously, the drum is designed to provide for good circulation of the water and/or steam utilized as the working medium in the retort  118 . In the present invention, this is accomplished by providing holes or other perforations or openings in the retort drum  122 .  
         [0028]     While preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.