Abstract:
A string cheese-forming machine provides for extrusion of cheese into control volumes, for example, implemented with tubes each movably blocked with a piston having a stop. Complete filling of each tube is detected before ejection of the cheese from the tubes is undertaken, thereby ensuring consistent product volume and weight.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application 61/408,920 filed Nov. 1, 2010 hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to cheese processing equipment and in particular to a cutting machine for extruded string cheese. 
     String cheese is normally produced by extruding an Italian-style or “pasta filata” cheese, such as mozzarella, that has a grain structure producing string-like fibers. A “rope” of semi-molten extruded cheese is cut into short segments then cooled in a brine solution. 
     U.S. Pat. No. 4,759,704, describes a machine for extruding and cutting string cheese in which the cheese is extruded vertically downward toward a trip lever that activates a cutter, producing segments of the desired length. U.S. Pat. No. 4,902,523 describes a machine for extruding and cutting string cheese in which multiple sensors monitor horizontally extruded cheese ropes to trigger independent cutters at the appropriate lengths. 
     SUMMARY OF THE INVENTION 
     The present inventor has identified a substantial variation in the weight and volume of string cheese segments produced by current commercial machines believed to be inherent in length-based metering systems working on a semi-molten material. The present invention provides an improved cutting system for extruded string cheese that greatly reduces the variation among cut segments by constraining the semi-molten extruded cheese, before cutting, within a controlled volume provided by a sleeve and piston. By so constraining the semi-molten cheese, significantly greater uniformity in weight and volume is provided. 
     Specifically, the present invention provides apparatus and corresponding method for producing sections of extruded cheese employing a series of tubular sleeves having first ends adapted to receive cheese from an extruder. A series of pistons fit slidably within corresponding tubular sleeves, the pistons having first ends contacting cheese filling the tubular sleeves from the extruder and second ends moving in a direction of extrusion as the tubular sleeves are filled with cheese. A blocking element stops movement of the pistons when the tubular sleeves are filled with cheese to a predetermined volume and an ejector operates upon a filling of the tubular sleeves to the predetermined volume to eject cheese from the tubular sleeves. 
     It is thus one feature of at least one embodiment of the invention to provide an accurate method of providing uniform string cheese segments that addresses inherent inaccuracies of free-length measurement of a semi-molten material and the difficulty of weight measurement of a partially extruded rope. 
     The ejector may provide an actuator moving the second ends of the pistons counter the direction of extrusion to eject cheese from the first ends of the tubular sleeves. 
     It is thus one feature of at least one embodiment of the invention to provide a simplified mechanism that may employ a reciprocating piston motion for constraining then ejecting cheese segments. 
     The apparatus may provide a set of ports receiving cheese from the extruder and positioned between the extruder and the first ends of the series of tubular sleeves and the tubular sleeves may be mounted for reciprocation between a first and second position with respect to the ports in a direction substantially perpendicular to the axis so that a first set of tubular sleeves may align with ports in the first position and a different, second set of tubular sleeves may align with the ports in the second position. The ejector may operate to move the second ends of the pistons of the first set of tubular sleeves against the direction of extrusion for the first set of tubular sleeves when the tubular sleeves are in the second position and to move the second ends of the pistons of the second set of tubular sleeves against the direction of extrusion when the tubular sleeves are in the first position. 
     It is thus one feature of at least one embodiment of the invention to permit substantially continuous extrusion of the cheese through the use of two sets of tubular sleeves that may be alternately filled and ejected. 
     The interface between the ports and the tubular sleeves may provide a shearing of cheese extending between the ports and some tubular sleeves when the tubular sleeves move in the direction perpendicular to the axis between the first and second positions. 
     It is thus one feature of at least one embodiment of the invention to incorporate the cutting process into a movement of the tubes to further simplify the mechanism. 
     The ports may be spaced in a direction perpendicular to the axis at twice the distance of spacing of the tubular sleeves perpendicular to the axis and the ejector may provide an axially traveling ejector surface having spaced blocking elements contacting only every other piston. 
     It is thus one feature of at least one embodiment of the invention to provide an ejector that may interfere with the piston stops in a compact mechanism. 
     The direction of extrusion may be substantially horizontal and the ports may be separated by a distance no less than a diameter of a tubular sleeve and provide downwardly opening channels therebetween allowing cheese ejected from the first ends of the tubular sleeves to drop downward therefrom. 
     It is thus one feature of at least one embodiment of the invention to permit a gravity-assisted ejection of cut cheese segments in a compact mechanism employing a reciprocating piston motion. 
     The ports may be second ends of forming tubes having first ends receiving cheese from the extruder and further including a mixer positioned between the extruder and the forming tubes providing first and second cheese input ports. The forming tubes may be mounted for rotation about axes of the forming tubes to impart a spiral pattern to an interface between first and second cheese received from the first and second cheese input ports into the forming tubes. 
     It is thus one feature of at least one embodiment of the invention to permit decorative spiraling of the cheese segments in a system that provides for controlled volume and weight of the segments. 
     The tubular sleeves may be in adjacent parallel configuration and the apparatus may further include a sensor system detecting positions of the pistons indicating that multiple of the tubular sleeves are filled with cheese to the predetermined volumes to trigger the ejector. 
     It is thus one feature of at least one embodiment of the invention to provide controlled back pressure on the extruded cheese by delaying the injector stage until each of the tubes is filled to ensure complete filling of each of the tubular sleeves. 
     The sensor system may be an optical beam interrupted by movable elements moving out of occlusion with the optical beam by each piston when a corresponding tubular sleeve is filled with cheese to the predetermined volume. 
     It is thus one feature of at least one embodiment of the invention to provide a simple and robust sensing system suitable for a food-manufacturing environment. 
     The tubular sleeves may be bores in a block of a fluorocarbon polymer. 
     It is thus one feature of at least one embodiment of the invention to provide a simple readily cleaned structure for constraining and releasing semi-molten extruded cheese. 
     These particular features and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is an exploded perspective view of the string cheese cutting apparatus per the present invention showing various components as controlled by a programmable controller or the like to provide for extrusion of cheese through forming tubes into a shuttle block having a precisely dimensioned bore and contained pistons; 
         FIG. 2  is a perspective detail view of the forming tubes of  FIG. 1  showing a rotating mechanism to provide for a spiral decoration of the cheese; 
         FIG. 3  is a top plan cross-section through the shuttle block of  FIG. 1  with the contained pistons in a first position before receipt of cheese; 
         FIG. 4  is a figure similar to that of  FIG. 3  showing the extrusion of cheese into alternate bores in the shuttle block; 
         FIG. 5  is a fragmentary detail view of a stop assembly and ejector bar used for constraining the extension of the pistons and sensing that all pistons are fully extended for the alternate bores, and further for pressing inward on the pistons to eject the cheese from the alternate bores of the shuttle block when the shuttle block is in an ejection position for those bores; 
         FIG. 6  is a figure similar to that of  FIG. 4  showing the shuttle block in a second ejection position for ejection of the extruded cheese from the alternate bores; and 
         FIG. 7  is a fragmentary detail of  FIG. 6  showing the ejection of the cheese in between the forming tubes while permitting filling of new bores in the shuttle block now aligned with the forming tubes. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a string cheese cutting apparatus  10  of the present invention may receive prepared pasta filata cheese along a horizontal axis  12  as indicated by an arrow into a funneling hopper  14 . The pasta filata cheese may be provided by conventional kneading equipment of a type known in the art that develops the grain structure characteristic of these cheese types. 
     The funneling hopper  14  may also receive a contrasting cheese  22  or other similar foodstuff. The contrasting cheese  22  may, for example, coat the upper surface of a planar slab  16  of the pasta filata in a thin colored layer  26  across the upper surface of the planar slab  16 . The funneling hopper  14  may further have various ports  20  receiving and outputting heating water to maintain the planar slab  16  and colored layer  26  at a proper consistency for extrusion. 
     The combined height of the planar slab  16  and colored layer  26  will approximate the cross-sectional dimension of the desired string cheese segments being produced and the horizontal width of the planar slab  16  and colored layer  26  will have a width greater than a combined cross-sectional dimension of the number of simultaneous extrusions being performed. 
     An exit port of the hopper  14  may deliver the combined planar slab  16  and colored layer  26  to a shaper die  31  fitting over the exit port. The shaper die  31  may divide the combined planar slabs  16  and colored layer  26  into adjacent square cross-sections defined by square entrance openings of the shaper die  31 . Each of these square openings funnels to a circular hole  33  having a cross-section matching that of the ultimately produced string cheese and permitting extrusion of the cheese into a cylindrical shape. 
     Cheese extruded through the holes  33  passes through bearings  37  held by a bearing block  35  (as will be described below) and is received by corresponding forming tubes  28  in a forming assembly  27  and having ends fitting within the bearings  37 . Each of the forming tubes  28  is mounted parallel to the axis  12  and arrayed across the horizontal width of the combined planar slab  16  and colored layer  26  and aligned with holes  33  in the shaper die  31 . Generally the forming tubes  28  are spaced horizontally by slightly more than twice their width to provide a gap between each forming tube  28  slightly larger than the outer diameter of a forming tube  28 . These gaps will provide an exit path for extruded cheese as will be described below. 
     First, open ends of the forming tubes  28  pass through a support plate  30  that abuts the bearing block  35  which in turn is aligned with the exposed planar face of the shaper die  31 . Second, opposite open exit ends of the forming tubes  28  pass through a slide plate  32  displaced from but parallel to the support plate  30 , as will be described below. The slide plate  32  includes apertures or cutouts  34  aligned with the gaps between the forming tubes  28  to provide openings between the openings of the forming tubes  28  for ejection of cheese as will be described. The forming tubes  28  are mounted to rotate about their respective axes within the support plate  30  and the slide plate  32 . 
     Referring to  FIGS. 1 and 2 , the first ends of the forming tubes  28  extending through the support plate  30  are received by correspondingly sized bores of spur gears  36  which are around the outer diameter of ends of the forming tubes  28  and attached thereto. The forming tubes  28  extend slightly through the spur gears  36  to provide a support lip  39  that may be received by the bearings  37  of the bearing block  35  described above to support the forming tubes  28  for rotation. The spur gears  36  inter-engage so that each forming tube  28  rotates in unison with the others in alternate counter-cyclic directions  38 . An idler gear  40  communicates between one spur gear  36  and a corresponding drive gear  42  on a motor  44  permitting rotation of these forming tubes  28  during the extrusion by the motor  44 . This rotation will produce a spiraling of the colored layer  26  and the planar slab  16  in the manner of a barber pole. 
     The motor  44  may be controlled by a control system  46 , for example, a programmable logic controller executing a stored program for operating the string cheese cutting apparatus  10  the structure of which will be understood from the following description. The control system  46  may include a user console  48  for the entry of data or control parameters according to techniques well known in the art. 
     It should be understood that the above-described spiraling mechanism is optional and required only if the spiral form is desired. 
     Referring again to  FIG. 1 , the slide plate  32  may smoothly abut a leading edge of a shuttle block  50 . The shuttle block  50 , for example, may be formed of machined Teflon and a spring biased to ride against the trailing face of the slide plate  32  as it reciprocates back and forth in a horizontal direction  52  with respect to the slide plate  32  between the first and second positions. The spring biasing may be accomplished, for example, by air cylinders operating under control of the predetermined pressure. 
     The reciprocation of the shuttle block  50  may be controlled by an actuator  54 , such as an air cylinder and valve, also under control of a stored program in control system  46 . 
     The shuttle block  50  includes multiple bores  56  numbering twice the number of the forming tubes  28  and having half the horizontal spacing. In this way, in the first position, a first set of alternate bores  56  are aligned with the forming tubes  28  and a second set of bores  56  between the first set are aligned with cutouts  34 . Conversely, in the second position, the second set of bores  56  is aligned with the openings of the forming tubes  28  and the first set of bores is aligned with cutouts  34 . 
     Each of the bores  56  may receive a mold plug  58  being a cylindrical metal rod having a diameter closely fitting with the inner diameter of the bores  56  to form a piston-like structure there in. Trailing ends of the mold plugs  58  provide for stop heads  59  limiting insertion of the mold plugs  58  into the bores  56 . In one embodiment, the mold plugs  58  excluding the stop heads  59  may have a length substantially equal to the axial length of the bores  56 . As cheese is extruded through the forming tubes  28 , the cheese will fill alternate bores  56  (depending on the position of the shuttle block  50 ) and push outward against a leading face of the corresponding mold plugs  58 . 
     The rearward movement of the mold plugs  58  is arrested before the mold plugs are fully disengaged from the bores  56  by stop pins  60  (to be described in more detail below) aligned only with every other mold plug  58  in those bores  56  receiving cheese from a forming tube  28 . A castellated ejection pusher  62  provides upward extending projections  64  positioned between stop pins  60  and, after the shuttle block  50  shifts, may be used to push the extended mold plugs  58  back into the bores  56  of the shuttle block  50  by the agency of an actuator  66  also controlled by control system  46 . 
     Referring now to  FIG. 3 , the operation of the string cheese cutting apparatus  10  may start, for example, with the shuttle block  50  in a leftmost position with respect to the tube assembly  27  with mold plugs  58   a ,  58   c ,  58   e , and  58   g  (and their corresponding bores  56 ) aligned with forming tubes  28  to receive cheese therefrom. 
     Referring now to  FIG. 4 , as cheese  70  is received into the bores  56  associated with the mold plugs  58   a ,  58   c ,  58   e , and  58   g , those mold plugs travel backward displaced by the cheese  70 . Generally, the mold plugs  58  will move at different rates because of an inherent uneven pressure in the extrusion process such as contributes in the prior art to inconsistent product weights. 
     Referring now momentarily to  FIG. 5 , each of the stop pins  60  may be mounted on a corresponding pivoting tab  72  that may pivot about a horizontal axis perpendicular to axis  12  backward within the gaps between projections  64  of the ejection pusher  62 . This pivoting proceeds until the stop pins  60  are vertical and abut a stop plate  74 . As the tabs  72  pivot backward they raise opaque flags  80  whose weight generally causes the stop pins  60  to be displaced forward before they contact the mold plugs  58 . When the opaque flags  80  are in the lowered position they align along a horizontal axis of light beam  82  to block a light beam between a light transmitter  86  and light receiver  88 . The light receiver  88  is connected to the control system  46  to detect when all of the flags  80  have been raised indicating that all of the mold plugs  58  are fully extended and the corresponding mold tabs  72  abut the stop plate  74 . At this point of equal extension, the pressure in each of the bores  56  equalizes and the volumes (and weight) of cheese in each of the bores  56  is substantially equal. With the flags  80  fully raised out of the light beam  82 , a signal is provided to the control system  46  to slide the shuttle block  50  leftward. 
     As shown in  FIG. 6 , this leftward sliding of the shuttle block  50  moves the bores  56  of mold plugs  58   b ,  58   d ,  58   f , and  58   h  into alignment with forming tubes  28  and the bores  56  of mold plugs  58   a ,  58   c ,  58   e , and  58   g  into alignment with the cutouts  34  (shown in  FIG. 1 ) providing a shearing action between the leading edge of the shuttle block  50  and the abutting surface of the slide plate  32  cutting the cheese  70  within the bores of mold plugs  58   a ,  58   c ,  58   e , and  58   g  cleanly to length. This movement moves the mold plugs  58   a ,  58   c ,  58   e , and  58   g  off of the stop pins  60  and into alignment with the projections  64  of the ejection pusher  62 . The ejection pusher  62  may then be moved inward by the actuator  66 , shown in  FIG. 1 , by the control system  46  using a simple delay timer from the motion of the shuttle block  50 . 
     Referring to  FIG. 7 , the inward motion of the ejection pusher  62  ejects the cheese  70  in the bores  56  of mold plugs  58   a ,  58   c ,  58   e , and  58   g  backward toward the extruder. Then the cheese  70 , as cut to length, may pass in between the forming tubes  28  of the assembly  27  through the cutouts  34  in the slide plate  32  shown in  FIG. 1 . Cheese sticks of precise length and volume may then drop downward, for example, into chilled brine or onto a carrier. 
     During this ejection process, the alternate bores, for example, associated with mold plugs  58   b ,  58   d ,  58   f , and  58   h  may be simultaneously filled from forming tubes  28  providing a substantially continuous process. In this way back-and-forth motion of the shuttle block  50  and the motion of the ejection pusher  62  may provide for a steady stream of precisely formed cheese sticks. 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     References to “a controller” and “a processor” can be understood to include one or more controllers or processors that can communicate in a stand-alone and/or a distributed environment(s), and can thus be configured to communicate via wired or wireless communications with other processors, where such one or more processor can be configured to operate on one or more processor-controlled devices that can be similar or different devices. Furthermore, references to memory, unless otherwise specified, can include one or more processor-readable and accessible memory elements and/or components that can be internal to the processor-controlled device, external to the processor-controlled device, and can be accessed via a wired or wireless network. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications, are hereby incorporated herein by reference in their entireties.