Abstract:
An apparatus for forming a rising crust comprises a dough-manipulating unit adapted to apply a vacuum at the peripheral edge portion of an underlying sheet of dough to hold and lift the peripheral portion. The manipulating unit is inwardly contractible while holding the peripheral edge portion of the sheet of dough and movable downwardly while being in a contracted state to provide for the formation of a peripheral fold in the sheet of dough. The dough-manipulating unit allows for high volume production of rising crust pizzas.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to food products and, more particularly, to a method and an apparatus for preparing a rising crust from a sheet of dough. 
   2. Description of the Prior Art 
   Originally, pizza pies were made by hand. With the increasing demand, various devices have been developed to allow a pizza to be made in large-scale production assemblies, frozen or freeze-dried before packaging, and shipped to grocers nationwide. 
   In large scale, commercial bakeries, pizza crusts are typically formed in a press comprising a die that can be operated to apply pressure onto a dough ball to flatten the dough ball into a circular, square or rectangular sheet of dough. Cavities can be defined in the die to form corresponding raised ridges in the dough. 
   While high volume pizza processing machines allow for the formation of a raised ridge around the outer peripheral edge of a pizza pie, they suffer from several drawbacks. Often the so formed industrial crust will have a poor flavor and taste as compared to a hand-made pizza crust. Unlike hand-made dough pizza, the peripheral ridge of dough formed by pressing will often not raise during the baking process. 
   There is therefore a need for a new high volume processing method and apparatus for use in the preparation of rising crust pizzas. 
   SUMMARY OF THE INVENTION 
   It is therefore an aim of the present invention to provide an apparatus for forming pizza dough with a ridge or crust that will rise when baked. 
   It is a further aim of the present invention to produce a rising crust that is close in taste and texture to a hand-made rising crust. 
   Therefore, in accordance with the present invention, there is provided an apparatus for use in the preparation of a rising crust from a sheet of dough having a peripheral edge portion, the apparatus comprising a dough manipulating unit for lifting from above the peripheral edge portion of an underlying sheet of dough, the manipulating unit being inwardly contractible while holding the peripheral edge portion of the sheet of dough and movable downwardly while being in a contracted state to provide for the formation of a peripheral fold in the sheet of dough. 
   In accordance with a further general aspect of the present invention, there is provided a method of forming a contour ridge on a sheet of dough, comprising the steps of: applying a vacuum at a peripheral portion of a sheet of dough to hold the peripheral portion and allow it to be lifted from a support surface, bringing the lifted peripheral portion inwardly towards a central portion of the sheet of dough so as to form a Z-shaped fold, and pressing down the Z-shaped fold. 
   In accordance with a still further general aspect of the present invention, there is provided an apparatus for forming a contour ridge in a sheet of dough, the apparatus comprising a folding station whereat a peripheral edge of the sheet of dough is folded over inwardly to form a peripheral fold, a rolling station whereat the peripheral fold is rolled in to create a double fold, a pressing station for pinching the double fold to prevent the fold from subsequently unrolling, and a conveyor for moving the sheet of dough from one station to another. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: 
       FIG. 1  is a side view of an apparatus for forming a rising crust from a sheet of dough in accordance with a first embodiment of the present invention; 
       FIG. 2  is a top plan view of the apparatus of  FIG. 1 ; and 
       FIG. 3  is an enlarged elevation view of a folding station forming part of the apparatus of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates an apparatus  10  suited for use in the preparation of pizza crusts from raw dough sheets. As will be seen hereinafter, the apparatus  10  provides for the formation of a contour ridge in the form of a roll edge of dough or a peripheral piped flange of dough around the periphery of the dough sheet. The piped flange is made by folding the outer edge of the sheet of dough D ( FIG. 3 ) inwardly and by subsequently rolling in the so formed peripheral fold so as to create a contour ridge that, unlike dough ridges made by pressing, will rise during baking, thereby providing for the production of so called rising crust pizza. 
   The apparatus  10  generally comprises a frame  12 , a conveyor belt  14  supported by the frame  12  and driven by an indexing mechanism  16  for sequentially carrying successive dough sheets from a positioning station  18  to a cutting station  20 , a dough folding station  22 , a dough rolling station  24 , and to a pressing station  26 . 
   The conveyor belt  14  preferably comprises an endless Nylon belt  28  offering a smooth conveying surface for the sheets of dough D. According to a preferred embodiment of the present invention, the endless belt  28  has a 16 inches width. The belt  28  extends over a tension roller  30  and a driven roller  32  respectively mounted at an upstream end and a downstream end of the apparatus  10 . The rollers  30  and  32  are mounted on respective shafts  34  and  36 . A braking mechanism (not shown) is mounted on the shaft  34  of the tension roller  30  to act against the inertia that the belt  28  may have after having been indexed by the indexing mechanism  16 . 
   The indexing mechanism  16  comprises a pneumatic cylinder  38  having an 18 inches stroke. The pneumatic cylinder  38  has a reciprocating piston  39  drivingly engaged at a distal end thereof with a first toothed belt  40  extending over a pair of idle pulleys  42  journaled to the frame  12  underneath the conveyor belt  14 . The movement communicated to the first toothed belt  40 , when the piston  39  is retracted, is transmitted to the shaft  36  and ,thus, the driven roller  32  of the conveyor belt  14  by a second toothed belt  44  operatively engaged with a pulley (not shown) mounted to the shaft  36 . A one-way clutch (not shown) is provided between the belts  40  and  44  to prevent that the movement imparted to the belt  40 , when the piston  39  is extended, be transmitted to the conveyor belt  14 . A tension roller  46  is provided to maintain an appropriate tension in the toothed belt  40 . The above-described indexing mechanism  16  provides for the sheets of dough D on the belt  28  to be incrementally advanced under the action of the pneumatic cylinder  38  towards the downstream end of the apparatus  10  by a predetermined distance (18 inches) each time the piston  39  is retracted. However, when the piston  39  is extended, no movement is transmitted to the belt  28  because of the one-way clutch. It is understood that other indexing mechanism could be used as well. 
   The positioning station  18  is located at the upstream end of the apparatus  10  and essentially comprises a laser source  48  and a mirror  50  mounted to a drum  52 , which is, in turn, adjustably mounted to a cantilever arm  54 . The mirror  50  is slightly inclined and is rotated upon itself by an air motor (not shown) so as to reflect the laser beam generated by the laser source  48  into a luminous circle on the underlying top surface of the belt  28 . The diameter of the circle projected onto the belt  28  can be adjusted by varying the vertical position of the drum  52  relative to the belt  28 . According to a preferred embodiment of the present invention, the diameter of the circle is 14.50 inches. The generation of a luminous circle onto the belt  28  allows an operator to manually place a sheet of dough D on the belt  28  in a predetermined position so that when the sheet of dough D is subsequently incrementally advanced by the conveyor belt  14 , the dough sheet D will be accurately positioned with respect to the cutting station  20 , the folding station  22 , the rolling station  24  and the pressing station  26 . 
   After having been properly placed within the luminous circle projected on the belt  28 , the sheet of dough D is advanced to the cutting station  20 . The cutting station  20  includes a vertically movable overhead blade assembly  56 . The overhead blade assembly  56  includes a pair of rods  58  slidably mounted in two linear bushings  60  provided on a support structure  62  located at a given elevation over the conveyor belt  14 . As shown in  FIG. 2 , a circular cutting blade  64  with a pair of diametrically opposed linear wings  66  projecting respectively towards the upstream and downstream ends of the apparatus  10  along a central axis thereof is mounted to a tool holder  68  ( FIG. 1 ) which is, in turn, securely mounted to the distal lower ends of the rods  58 . A pneumatic cylinder  70  ( FIG. 1 ) or the like is provided for vertically displacing the tool holder  68  and, thus, the circular blade  64  towards to and away from the underlying sheet of dough D on the belt  28 . The vertical movement of the tool holder  68  is guided by the rods  58  in the bushings  60 . A pair of radially extendible/contractible semi-circular ejectors  72  are mounted about the circular cutting blade  64  to remove from the belt  28  the excess dough extending about the cutting blade  64  after the dough sheet D has been cut down. A pair of pneumatic cylinders, one of which is shown at  74  in  FIG. 2 , extends between the semi-circular ejectors  72  for controlling the operation thereof. The tool holder  68  also carries an annular stamping member  69  concentrically disposed within the circular cutting blade  64  to leave a circular indentation I ( FIG. 3 ) or fold line in the dough while the same is being cut by the blade  64 . According to a preferred embodiment of the present invention, the annular stamping member  69  is spaced inwardly from the circular cutting blade  64  by a distance of ½ inch. It is understood that the annular stamping member is slightly vertically recessed in the bottom face of the tool holder  68  relative to the circular blade  64  to ensure that the annular stamping member  69  has a penetration depth into the dough that is less than that of the circular cutting blade  64 . The annular stamping member is vertically adjustable to prevent the sheet of dough from being cut by the stamping member. The annular stamping member  69  is preferably made of Nylon. 
   In operation, the overhead blade assembly  56  is lowered onto an underlying sheet of dough so that the circular cutting blade  64  cuts the sheet of dough and the annular stamping member creates a circular indentation I in the dough at a distance inwardly of the cutting line. Then, the ejectors  72  moves radially outwardly to remove the excess dough at the periphery of the sheet of dough D and the overhead assembly  56  moves vertically upwardly away from the conveyor belt  14  to a stand-by position before being lowered once again for the next sheet of dough. 
   After having been cut to the proper size, the sheet of dough D is moved to the folding station  22  whereat the peripheral edge of the sheet of dough is folded over inwardly about the indentation I formed therein so as to form a peripheral Z-shaped fold in the sheet. 
   The folding station  22  generally comprises a plurality of circumferentially distributed suction members  76  ( FIGS. 2 and 3 ) mounted on a linkage structure depending from the circumference of a horizontal mounting disc  78 . According to a preferred embodiment of the present invention, there are  32  suctions fingers  76 . As best shown in  FIG. 3 , the mounting disc  78  is fixed to the lower ends of two guiding rods  80  mounted for vertical movement in a pair of linear bushings  82  forming part of the support structure  62 . A pneumatic cylinder  84  is provided on the support structure  62  for vertically displacing the disc  78  and, thus, the suction members  76  towards and away from the belt  28 . 
   Each suction member  76  is mounted at the lower end of an arm  86 . The arm  86  is pivotally mounted at an opposed upper end thereof to a bracket  88  fixed to the circumferential edge of the mounting disc  78 . The lower end portion of each arm  86  is pivotally connected via a link  90  to a vertically movable hub structure  92  depending from a central portion of the mounting disc  78 . The link  90  is pivotally connected at a first end thereof to the arm  86  and at a second opposed end thereof to the hub structure  92 . This linkage structure allows the arms  86  to pivot conjointly about their respective pivot axes in response to a vertical movement of the hub structure  92  relative to the disc  78 , thereby allowing increasing or reducing the diameter of the circle defined by the suction members  76 . A pneumatic cylinder  94  is provided for vertically moving the hub structure  92  relative to the mounting disc  78 . 
   As shown in  FIG. 3 , each suction member  76 , includes an end fitting  96  mounted at a lower end of a hollow cylinder  98 , a piston  100  mounted for sliding movement within the cylinder  98 , and a cover  102  mounted to the lower end of the arm  86  for closing the upper end of the cylinder  98 . The end fitting  96 , the cylinder  98  and the cover  102  are structurally attached together by threaded fasteners, such as the ones illustrated at  104 . The piston  100  has a stem portion  106  adapted to extend outwardly of the end fitting  96  through a passage defined therein. A spring  108  is provided within the cylinder  98  for normally urging the piston  100  upwardly to a retracted position wherein the stem portion  106  of the piston  100  is withdraw from the passage in the end fitting  96 . The interior of the cylinder  98  defines a chamber that is divided into first and second chambers  110  and  112  by the piston  100 . The first chamber  110  is connected to an air compressor (not shown) via a port  114 . The second chamber  112  is operatively connected to a pump (not shown) via a port  116 . The pump is preferably mounted within the frame  12  underneath the conveyor belt  14 . A number of slots (not shown), for instance four, are defined in the end fitting  96  for connecting the passage, the second chamber  112  and the port  116  in fluid flow communication, thereby allowing the second chamber  112  to be used as a vacuum chamber. 
   In use, the pump is powered to withdraw air from the second chamber  112  via port  116  of each suction member  76 . While air is being drawn out of the second chamber  112 , the piston  100  of each suction member  76  is biased to its retracted position so as to clear the passage in the end fitting  96 . Also, the pneumatic cylinder  94  is operated to position the suction members  76  along a circle generally corresponding to the peripheral edge portion of the underlying sheet of dough, i.e. outwardly of the indentation I previously defined therein by the annular stamping member. The pneumatic cylinder  84  is then operated to lower the mounting disc  78  and, thus, the suction members  76  onto the sheet of dough D. Once the peripheral portion has been grasped by the suction members  76  due to the vacuum effect, the pneumatic cylinder  84  is operated to lift the peripheral portion of the sheet of dough D from above and the pneumatic cylinder  94  is operated to pivot the arms  86  inwardly so as to displace the suction members  76  radially inwardly. This combination of movements results in the creation of a Z-shaped fold at the periphery of the sheet of dough D. Thereafter, the pneumatic cylinder  84  is operated to displace the mounting disc  78  and the suction members  76  downwardly, the source of vacuum is shut down and the pistons  100  are displaced to their extended positions against the biasing force of the springs  108  so as to cause the stem portions  106  of the pistons  100  to project outwardly of the end fittings  96  in order to press the three-ply fold in a way such that the same maintains its configuration after the pressure exerted thereon has been released. The pistons  100  are moved to their extended position by pressurized air fed by the air compressor into the first chambers  110  through port  114 . Once the three-ply fold has been formed at the periphery of the sheet of dough D, the same is moved to the next station, namely: the rolling station  24 . 
   At the rolling station  24 , the three-ply fold formed at the periphery of the sheet of dough D is rolled upon itself to form a double fold on the periphery of the sheet of dough D. 
   As shown in  FIG. 1 , the rolling station  24  generally comprises a plurality of circumferentially distributed fingers  118  connected to each other by means of a flexible latex cord  119 . According to a preferred embodiment of the present invention, the plurality of fingers  118  includes  28  fingers having a 1-inch width. Each finger  118  is mounted to the lower end of an arm  120  which is, in turn, pivotally mounted to the outer circumference of a mounting disc  122 . The mounting disc  122  is secured to the lower ends of a pair of guiding rods  124  mounted for vertical sliding movement in a pair of bushings  126  forming part of the support structure  62 . The vertical movement of the mounting disc  122  and, thus, of the fingers  118  is controlled by a pneumatic cylinder  128 . The lower end portion of each arm  124  is connected via a link  130  to a vertically movable hub structure  132  depending from a central portion of the mounting disc  122 . The link  130  is pivotally connected at a first end thereof to the arm  120  and at a second opposed end thereof to the hub structure  132 . This linkage structure ensures that the arms  124  will pivot conjointly at unison about their respective pivot axes in response to a vertical movement of the hub structure  132  relative to the disc  122 , thereby allowing increasing or reducing the diameter of the circle defined by the fingers  118 . A pneumatic cylinder  134  is provided for vertically displacing the hub structure  132  relative to the mounting disc  122  and, thus, cause the arms  120  to rotate inwardly or outwardly about their respective pivot axes. 
   In operation, the mounting disc  122  is lowered to position the fingers  118  outwardly about the outer edge of the sheet of dough D. Then, the cylinders  128  and  134  are conjointly operated to raise the mounting disc  122  and pivot the arms  120  radially inwardly so as to roll the tree-ply fold inwardly upon itself. 
   From the rolling station  24 , the sheet of dough is moved to the pressing station  26 . As shown in  FIG. 1 , the pressing station  26  includes a central disc  138  securely mounted at the lower end of a pair of guiding rods  140  slidably engaged in a pair of linear bushings  142  forming part of the support structure  62 . A pneumatic cylinder  144  is provided for vertically displacing the central disc  138  towards and away from the conveyor belt  14 . The vertical movement of the central disc  138  is guided by the guiding rods  140  in the bushings  142 . The pneumatic cylinder  144  extends between the support structure  62  and a collar  146  adjustably mounted to the guiding rods  140 . By varying the vertical position of the collar  146  on the guiding rods  140 , it is possible to adjust the stroke of the central disc  138 . A spring-loaded annular fence  148  is mounted to the central disc  138  for encircling the sheet of dough D when the central disc  138  is displaced to a lowered position thereof. The spring-loaded annular fence  148  is arranged so as to rest on the conveyor belt  14  when the central disc  138  is displaced to its lowered position. An annular die  150  is mounted to a downwardly facing surface of the central disc concentrically within the spring-loaded annular fence  148 . The annular die  150  has an undersurface defining an annular recess (not shown) having a rounded shape generally corresponding to that of the contour ridge on the sheet of dough D. The annular die  150  is provided on an inner circumference thereof with a downwardly depending circumferential lip (not shown) to pinch the interior circumference of the contour ridge and, thus prevent the contour ridge from unrolling. Four circumferentially distributed pneumatic cylinders  152  are mounted on the central disc  138  to vertically displace the annular die  150  relative to the central disc  138 . 
   In operation, the pneumatic cylinder  144  is activated to press down the central disc  138  onto the sheet of dough D with the spring-loaded annular fence  148  abutting against the belt  28  about the sheet of dough D so as to create an exterior barrier. The central disc  138  exerts a pressing force on the central portion of the sheet of dough D, while at the same time forming an interior barrier for the contour ridge at the periphery of the sheet of dough D. At the same time, the annular die  150  is pressed against the previously formed contour edge in order to confirm its shape and pinch the dough at its inner circumference, thereby ensuring the integrity of the contour ridge. Once the inner portion of the contour ridge has been pinched off, the pneumatic cylinder  144  is activated to displace the central disc  138  and the spring-loaded annular fence  148  upwardly away from the sheet of dough. During this operation, the pneumatic cylinders  152  are activated so as to press the annular die  150  on the dough to prevent the sheet of dough D from being lifted off the conveyor  14  with the central disc  138  and the spring-loaded annular fence  148 . 
   After having been pressed at the pressing station  26 , the sheet of dough D is moved to the downstream end of the conveyor belt  28  where the sheet of dough D is removed from the apparatus  10  for further processing. 
   The above-described manner of forming the contour ridge on the sheet of dough D advantageously allows for the contour ridge to rise during baking, thereby providing for the production of a pizza pie with a crispy crust, a good puffiness and a good taste. 
   Although a circular formed sheet of dough has been exemplified, it is understood that the present invention could be adapted to any shape of pizza dough, such as square or the like.