Abstract:
Two disk-shaped pans are moulded with radial depressions each having a substantially V-shaped transverse profile, with a progressively increasing width and depth from the center of each pan to its border. Motor elements such as a four-bar linkage are arranged for rotating one of the pans around its axis with a reciprocating motion. The other pan can be pressed against the former to squeeze a lump of dough placed therebetween.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    In the preparation of pizzas, dough-spreading apparatuses for semi-professional use and also for home use are known in which a lump of leavened dough placed on a tray is squeezed by a flat pan that is lowered vertically upon the dough by manual or motorized pressure means. The dough-lump is spread because the applied pressure causes the dough to run in the only unconstrained direction, i.e. in a radial direction. 
         [0002]    A first drawback of this approach is that the dough is spread not only by plastic deformation, but also partly by elastic deformation, so that the squeezed pizza, after being released by the apparatus, tends to shrink back and swell again. Moreover, the strong pressure necessary for spreading the dough tends to expel the leavening gas scattered in the dough, thereby making the dough dense and noxiously affecting the quality of the pizza eventually resulting after cooking. 
       SUMMARY OF THE INVENTION 
       [0003]    The main object of the invention is to provide a dough-spreading apparatus for the preparation of pizzas, by which an unskilled operator can quickly obtain a thin pizza sheet from a lump of risen dough, while avoiding the above drawbacks. More particularly, the apparatus should not compact the dough excessively, and should break its grain in order to reduce its elastic return. 
         [0004]    Another object is to provide an apparatus of low complexity and cost. 
         [0005]    The above objects, as well as other objects and advantages, such as will appear from the following disclosure, are attained by the invention with a dough-spreading apparatus for the preparation of pizzas having the features set forth in claim  1 , whereby the dependent claims recite other advantageous features of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention will be described in more detail, by way of a non-limiting example, with reference to the attached drawings, wherein: 
           [0007]      FIG. 1  is a plan view of a preferred embodiment of the dough-spreading apparatus according to the invention; 
           [0008]      FIG. 2  is a partially cross-sectioned side view of the dough-spreading apparatus of  FIG. 1 ; 
           [0009]      FIG. 3  is a enlarged, perspective view of a pan used in the apparatus of  FIGS. 1 and 2 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0010]    With reference to the Figures, a disk-shaped flat pan  10 , preferably of stainless steel sheet, is coaxially carried on a shaft  12 , which is vertically and rotatably supported by bearings  14  in a sleeve  16  attached below a worktable  18 . 
         [0011]    With particular reference to  FIG. 3 , the surface of pan  10  has a coaxial starlike arrangement of identical radial depressions  20 . The depressions are shallow and have a substantially V-shaped profile, and are open at the pan border. Accordingly, the transverse cross-section of each depression  20  progressively widens from the pan center to its peripheral border, and the depth of the depression increases similarly. 
         [0012]    Preferably, pan  10  is cut from a stainless steel sheet of about 3 mm thickness, and is moulded under a press to form the depressions  20 . The diameter of the pan is proportionate to the desired diameter of the pizza: a typical value is, for instance, 250 mm. The number of depressions is, preferably, a score, although it may vary considerably, e.g. in the range 12 to 30. The depth of each depression in axial direction and at the pan border is preferably about 2 mm, although it can also vary, typically from 1 to 4 mm, also depending on the diameter of the pan. 
         [0013]    A motor  21  with reduction gear  22  is mounted under the worktable  18 . The driving shaft of the reduction gear carries a short crank  26 . A rod  28  connects crank  26  to a second crank  30  projecting from the lower end of shaft  12 , which carries pan  10 , thereby forming a four-bar linkage, whose geometry is such that when the output shaft  24  of reduction gear  22  turns, the end of crank  30  undergoes a reciprocating movement, whereby shaft  12  and consequently pan  10  execute a to-and-fro movement through a small angle, at a frequency determined by the turning speed of shaft  24  and reduction gear  22 . 
         [0014]    Four-bar linkage  26 - 28 - 30  is designed so that the angle of rotation of pan  10  around its axis is preferably about 15°, but, more generally, the range of movement of the pan might also be much narrower or wider, e.g. in the range 10° a 20°. The velocity ratio of reduction gear  22  with respect to motor  21  is such that the frequency of the reciprocating motion of pan  10  is in the range 100 to 200 oscillations, per minute. 
         [0015]    A bracket  32  is mounted above worktable  18 , and an arm  34 , provided with a handle  36  at its free end, is pivoted on the bracket. Arm  34  supports a second pan  38 , hinged at an intermediate point  39 . Pan  38  is similar to pan  10 , being shaped with identical depressions, so that an operator can manipulate handle  36  to lower arm  34  and press pan  38  coaxially onto pan  10 . 
         [0016]    In use, after the operator has floured pan  10 , he places a lump of leavened dough in the center of it and, while motor  21  is in motion so that pan  10  oscillates, the operator then lowers pan  38  onto it by manipulating handle  34 . The pressure exercized by pan  26  squeezes the dough, forcing it to flow in the directions not subjected to compression, i.e. in the radial directions. The flow of the dough is further helped by the rolling applied to the dough by the ridges between the depressions of both pans, which move reciprocally with respect to each other in a tangential direction. Such action breaks the grain of the dough, thereby weakening the internal ties among its fibers, and therefore helping the spreading of the dough and reducing the elastic return of the dough after spreading. 
         [0017]    Numerous changes can be made to the preferred embodiment disclosed above. 
         [0018]    Pans  10  and  38  might have different diameters. The profiles of depressions  20  could be different from a V-shape, e.g. they could be rounded or otherwise. The angular amplitude of depressions  20 , rather than being uniform in each case, might be different among the several depressions: for instance, wider and narrower depressions might alternate, and the same holds for the depth of the depressions. The number of depressions in both pans might also be different. 
         [0019]    The motion of pan  10  could of course be obtained by other kinds of mechanisms, and even rotary motor  21  with reduction gear could be replaced with a reciprocating actuator, not only electric, but also hydraulic or pneumatic, such as a cylinder. It should also be understood that, although the oscillating pan in the preferred embodiment is located in a fixed, lower position, the roles of both pans could be reversed.