Abstract:
A vacuum hoist plate for moving slabs of cheese provides multiple plates positioned at the edges of the slab to bend those slab edges upward reducing suction between the slabs and preventing spalling as the cheese is lifted from a stack.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
     BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to cheese processing equipment, and in particular, to a vacuum hoist for lifting and transporting slabs of cheese.  
         [0002]     Referring to  FIG. 1 , in the manufacture of natural cheese, the cheese curd may be compressed into rectangular blocks of approximately 640 pounds and, for example, 28 inches high and with a horizontal base of 22 by 28 inches. At later steps in the manufacturing process, these blocks may be cut, in-place, to produce a stack  10  of horizontal slabs  12  approximately five to seven inches thick.  
         [0003]     The slabs  12  may be separated using a vacuum plate  14  which provides a manifold connecting a vacuum line  16  to a set of regularly spaced holes on the underside of the plate  14 . A vacuum may be drawn between the plate  14  and the uppermost slab  12  through the vacuum line  16 . Once a vacuum is drawn, the plate may be lifted by means of hoist tabs  24  and the uppermost slab  12  separated from the remainder of the stack  10 . The vacuum line  16  may be connected to a venturi-type vacuum pump  18 , the latter receiving a compressed air line  20  controlled by an electrically actuated valve  50  (shown in  FIG. 5 ), the latter receiving an electrical actuation signal  22  to switch on and off the compressed air through the compressed air line  20  and hence to switch on and off the vacuum through the vacuum line  16 .  
         [0004]     The slabs  12  of cheese of the stack  10  often stick together. This sticking can cause a spalling or tearing of the slabs  12  or can break the vacuum between the hoist plate  14  and the slab  12 . The operator of the hoist closely must monitor the slab pickup operation closely and may need to use a manual tool to pry up a corner of the uppermost slab  12  so as to break the suction between slabs.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The present invention provides a vacuum hoist for cheese manufacture that allows the separation of cheese slabs with reduced damage and/or spalling. The broad area of the vacuum plate is divided into one or more articulated sections that may be moved independently to peel the uppermost slab away from the remaining slabs of the stack. The invention thus reduces the need for close operator supervision of the pickup operation and damage to the cheese slab.  
         [0006]     Specifically, the present invention provides a cheese hoist having at least two vacuum plates having lower surfaces constructed to retain a vacuum between the lower surfaces and an upper surface of a cheese slab over an area sufficient to support the cheese slab. At least one vacuum plate is positioned adjacent to an edge of the cheese slab and an articulated connector between the vacuum plates allows one vacuum plate to move independently with respect to the other vacuum plate to peel a supported cheese slab away from a surface on which the supported cheese slab rests.  
         [0007]     Thus it is one object of at least one embodiment of the invention to apply a peeling action through the vacuum plate itself eliminating damage of the cheese slab from adhesion with the adjacent supporting slab or from insertion of a separating tool. The force applied by the vacuum plates is safely distributed over the area of the vacuum plates.  
         [0008]     The articulating connector may be at least one hinge allowing the outer edge of the vacuum plate to pivot upward about an inner edge near the other vacuum plate.  
         [0009]     It is thus another object of at least one embodiment of the invention to provide a simple mechanism that may produce a peeling action to separate slabs.  
         [0010]     The hoist may include an actuator operating between the two vacuum plates to provide an actuation force moving one vacuum plate with respect to the other vacuum plate.  
         [0011]     It is thus another object of at least one embodiment of the invention to provide a hoist that breaks the suction between adjacent slabs of cheese prior to hoisting of the cheese slab.  
         [0012]     The articulating connector may allow the two vacuum plates to move symmetrically with respect to each other to substantially simultaneously peel opposite edges of the supported cheese slab away from the surface on which it rests.  
         [0013]     Thus it is another object of at least one embodiment of the invention to provide a hoist that releases the slab evenly and that provides faster and more robust separation of the slabs by peeling two edges at once.  
         [0014]     The hoist may include a center plate and the two vacuum plates may flank the center plate and be attached to the center plates so that the center plate may remain substantially horizontal during independent movement of the vacuum plates.  
         [0015]     It is thus another object of at least one embodiment of the invention to distribute the bending of the cheese to reduce damage to the cheese. The multiple hinge lines to reduce the bending of the slab at any one point.  
         [0016]     The actuator may be supported by the center plate and connected to the outer edges of the two vacuum plates to simultaneously pull the outer edges of the two vacuum plates upward. The actuator may be a pneumatic cylinder having an actuator shaft extending vertically therefrom and connected via pivots to downwardly extending arms attached to pivots on each of the vacuum plates at points removed from the hinges.  
         [0017]     It is thus another object of at least one embodiment of the invention to provide a simple mechanism for providing the necessary movement of the vacuum plates and suitable for use in the food industry.  
         [0018]     The hoist may include a stop limiting the independent movement of the vacuum plates to a predetermined amount.  
         [0019]     It is thus another object of at least one embodiment of the invention to ensure that the cheese is not overstressed such as may cause damage.  
         [0020]     The lower surface of the vacuum plates are substantially planar plates with regularly spaced holes communicating via manifold to a vacuum line. The plate may include a peripheral ridge sealing the cheese to the plate.  
         [0021]     It is thus another object of at least one embodiment of the invention to provide an improved method of separating cheese slabs that still provides a broad area support to the cheese such as may be provided by a vacuum plate.  
         [0022]     These particular objects 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 DRAWINGS  
       [0023]      FIG. 1  is a simplified perspective view of a prior art vacuum hoist used for separating cheese slabs;  
         [0024]      FIG. 2  is a perspective view of the articulated vacuum hoist of the present invention with vacuum lines, vacuum valve, and actuator structure removed for clarity and in partial cutaway;  
         [0025]      FIG. 3  is a side elevational view of the vacuum hoist of  FIG. 2  showing a first planar configuration of the vacuum plates when the vacuum hoist is initially placed on a cheese slab;  
         [0026]      FIG. 4  is a figure similar to that of  FIG. 3  showing a second convex configuration of the vacuum plates used to peel the cheese slabs apart prior to hoisting of an upper slab;  
         [0027]      FIG. 5  is a cross-sectional view through one vacuum plate of  FIG. 2  showing the airflow, and a block diagram showing the control structure for controlling the vacuum hoist of the present invention; and  
         [0028]      FIG. 6  is a figure similar to that of  FIG. 2  showing an alternative embodiment of the invention in which a diagonal hinge axis is used to allow upward flexure of a corner of the vacuum plate. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]     Referring now to  FIGS. 2 and 3 , a vacuum plate hoist  15  of the present invention provides a left and right generally rectangular vacuum plate  14   a  and  14   b  separated by a hinge plate  26 . Hinge plate  26  has a left edge attached to the right edge of vacuum plate  14   a  by means of hinges  28  and has a right edge attached to a left edge of vacuum plate  14   b  by means of hinges  28   b.    
         [0030]     The vacuum plates  14   a  and  14   b  may thus swing upward about hinge axes  30  of the hinges  28   a  and  28   b  so that the vacuum plates  14   a  and  14   b  are angled with respect to hinge plate  26  to present a convex lower surface (shown generally in  FIG. 4 ) or may swing downward to present a planar lower surface (shown generally in  FIG. 3 ) where each of the vacuum plates  14   a  and  14   b  and hinge plate  26  are coplanar together to define an area  32  substantially matching an upper surface of a slab  12 .  
         [0031]     The hinges  28   a  and  28   b  joining vacuum plates  14   a  and  14   b  to hinge plate  26  are attached to the upper surfaces of the vacuum plates  14   a ,  14   b , and hinge plate  26  so that the edges of the vacuum plates  14   a  and  14   b  abutting against edges of the hinge plate  26  naturally stop the vacuum plates  14   a  and  14   b  from angling downward past a planar configuration.  
         [0032]     A hoist mount  37  may be attached to the center of the upper surface of the hinge plate  26  to provide a point of attachment between the present invention and a hoist.  
         [0033]     Also attached to the upper surface of the hinge plate  26  is a pneumatic actuator  40  having an actuator shaft  42  that may move under the influence of air pressure in a vertical direction. The actuator  40  may have controllable stroke, for example, through the use of a threaded stop of the like, to allow adjustment of the maximum upward extent of the actuator shaft  42 . The actuator shaft  42  is connected by means of a pivot joint  44  to two downwardly extending arms  46   a  and  46   b  which attach, respectively, to pivot points  48   a  and  48   b  on outer edges of vacuum plates  14   a  and  14   b  spaced from the hinges  28   a  and  28   b.    
         [0034]     Referring to  FIGS. 2 and 5 , each of vacuum plates  14   a  and  14   b  provides a manifold formed by an internal hollow chamber  34  joining an upwardly extending vacuum fitting  36  with a series of regularly spaced holes  39  through the lower surface of the vacuum plates  14   a  and  14   b . The lower surface of the vacuum plates  14   a  and  14   b  may further include a downwardly extending peripheral ridge  58  sized to engage the soft surface of the cheese slab  12 . Air may pass through the holes  39  into hollow chamber  34  and out vacuum fitting  36  so as to establish a low pressure between the lower surface of the vacuum plates  14   a  and  14   b  and the upper surface of a cheese slab  12  retained by a pressing of the upper surface of the slab  12  against the lower surface of the vacuum plates  14   a  and  14   b  and the downwardly extending peripheral ridge  58 .  
         [0035]     The hinge plate  26  may be a solid plate without lower holes  39 , however, it will be understood to one of ordinary skill in the art that the manifold construction of vacuum plates  14   a  and  14   b  may also be applied to hinge plate  26  so as to provide additional lift if necessary.  
         [0036]     Referring now to  FIG. 3 , in use, the vacuum plate hoist  15  may be placed on a topmost slab  12  of a stack of slabs, resting on a lower slab  12 ′, with the area  32  of the vacuum plate hoist  15  aligned with the upper area of the slab  12 . Initially, the actuator shaft  42  is in its lowermost position allowing the vacuum plates  14   a  and  14   b  to start in planar configuration with coplanar vacuum plates  14   a  and  14   b  and hinge plate  26 .  
         [0037]     A low pressure is then established between the lower surface of the vacuum plates  14   a  and  14   b  and the upper surface of the slab  12  by means of vacuum lines  38  communicating with vacuum fittings  36  as described above. Referring also to  FIG. 5 , the vacuum line  38  may be connected to a venturi-type vacuum pump  18  which receives through an air line  20  a source of compressed air controlled by an electrical valve  50  of a type well known in the art. The vacuum pump  18  may include a vacuum gauge  21 . An electrical signal to the electrical valve  50  may come from an operator or an automatic controller  52  as will be described below.  
         [0038]     Referring now to  FIG. 4 , once the vacuum plate hoist  15  is in place on top of the stack  10  of slabs  12 , and a vacuum is drawn through vacuum lines  38 , the actuator  40  is activated to move the actuator shaft  42  upward. Referring also to  FIG. 5 , the actuator  40  may be connected to an electrical valve  54  of a type well known in the art and placed in series between a primary pneumatic line  56  fed by an external pump (not shown) and an air line  41  connected to the actuator  40 . An electrical signal to the electrical valve  54  may come from an operator or an automatic controller  52  as will be described below.  
         [0039]     As the actuator shaft  42  rises, arms  46   a  and  46   b  are simultaneously raised, in turn, lifting the outer edges of vacuum plates  14   a  and  14   b  and, as a result of the low pressure drawn through vacuum lines  38 , lifting the slab  12  so as to peel the outer edges of the slab  12  back away from the outer edges of the supporting slab  12 ′.  
         [0040]     Although the inventor does not wish to be bound by a particular theory, this peeling action is believed to both break the suction between the slabs  12  and  12 ′ and, by concentrating any adhesive forces between the slabs at a boundary that sweeps back from the edge of the slabs  12  and  12 ′ toward its center, to reduce adhesive spalling that can break off chunks of cheese from the interface surface.  
         [0041]     The actuator  40  provides an internal or external stop (not shown) limiting the height of the actuator shaft  42  and thus limiting the amount of upward flex of the vacuum plates  14   a  and  14   b  about the hinge plate  26 . This flexure amount is set so as to provide the necessary peeling action, but not to unduly stress the cheese by bending such as might cause it to fracture. A reduction of bending fracture is also obtained through the use of two sets of hinges  28   a  and  28   b  which distribute the bending of the cheese slab  12  over two hinge axes  30  (shown in  FIG. 2 ).  
         [0042]     Once the peeling action is complete, a hoist may be activated lifting the vacuum plate hoist  15  upward by the hoist tabs  24  (shown in  FIG. 2 ) to move the cheese slab  12  away from the slab  12 ′ as required for further processing.  
         [0043]     Referring to  FIG. 5 , the steps described above may be controlled manually or by an electrical controller  52  which provides necessary sequencing to the operations if automatic operation is desired. The controller  52  may also communicate with valves  50  and  54  to first establish the vacuum between the vacuum plates  14  and the cheese slab  12  (not shown in  FIG. 5 ) and then to operate the actuator  40  after a sufficient time has passed for the low pressure to be established. Thus, for example, a single operator button may cause both an establishment of the vacuum, and a peeling away of the cheese slab from the cheese slab  12 ′.  
         [0044]     Optionally, the controller  52  may moderate a hoist signal so as to automatically begin these operations prior to any lifting by the hoist after positioning of the vacuum plate hoist  15  is established. In this case, the sequence of operations is triggered by the hoist signal itself. A manual release signal may release the slab  12  via valve  50  after moving of the slab  12  is complete.  
         [0045]     Referring now to  FIG. 6 , in an alternative embodiment of the present invention, a triangular vacuum plate  14   a  (being a corner of the generally rectangular lifting surface) may be separated from a trapezoidal hinge plate  26  along a diagonal hinge axes  30  to swing upward therefrom. In this embodiment, only a single vacuum plates  14   a  may be required and the hinge plate  26  may have a vacuum fitting  36  (not shown) so that the full area of the combined plates may be used for lifting. This configuration allows the slab  12  to be separated from the other slabs  12 ′ starting at a corner of the slab  12  in a natural peeling action. In other respects this embodiment may work as described above with respect to  FIGS. 3-5 .  
         [0046]     It will be understood from the above description to those of ordinary skill in the art that variations in the invention may include additional vacuum plates  14  in various sizes to accommodate different sizes of cheese slabs and joined with a variety of mechanisms. Further it will be understood that, although the preferred embodiment uses an actuator  40 , that the articulation of the vacuum plates  14   a  and  14   b  may be provided by other means including, for example, the hoisting action itself and that other types of actuators may be used.  
         [0047]     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but 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.