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TECHNICAL FIELD  
       [0001]    The present invention relates to apparatus for disintegrating food waste and particularly to such apparatus including a rotor to which blades are fixed. 
       BACKGROUND OF THE INVENTION  
       [0002]    For use in a kitchen a waste disposer must be sufficiently versatile to satisfactorily process not just soft materials or viscous materials (such as fruit or cooked cereals) but also hard and tough materials (such as some vegetables and bones). Particularly in processing these latter materials the duration of grinding required is an important consideration in the design of a disposer. 
         [0003]    Food waste in a conventional food waste disposer is forced by blades on a rotating grinding plate against teeth of a stationary grinding ring. Reduced processing times could be achieved if this action could be improved. 
         [0004]    Additional time is also required, for example, if harder food fragments such as carrot and bone pieces rotate at the same speed as the grinding plate without being ground. This results in increased noise and vibration, as well as residual food left in the grinding chamber after the disposer is turned off. Over time, this residual food may cause unpleasant odours. 
         [0005]    A further problem in designing a food waste disposer is jamming which occurs when hard objects such as bones enter the food waste disposer and get stuck between the blades of the rotating grinding plate and the stationary shredder ring. 
         [0006]    It is an object of the present invention to overcome or substantially ameliorate the above disadvantages or more generally to provide an improved apparatus for disintegrating food waste. 
       DISCLOSURE OF THE INVENTION 
       [0007]    According to one aspect of the present invention there is provided a food waste disposer comprising: 
         [0008]    a waste receptacle having a base; 
         [0009]    a grinding plate mounted at the base of the waste receptacle for rotation about an axis; 
         [0010]    apertures in the grinding plate for the passage of waste;. 
         [0011]    at least one blade mounted to the grinding plate for travel toward and away from the axis; 
         [0012]    a grinding ring about the periphery of the grinding plate for cooperating with the blade to disintegrate the waste, and 
         [0013]    inner and outer stop means engaging the blade at radially inner and outer travel limits of the blade respectively, the outer stop means engaging the blade as it is thrown outward by rotation of the grinding plate. 
         [0014]    Preferably the blade is slidably engaged with guide means fixed to the grinding plate. The guide means preferably restrain the blade to move linearly, more preferably the guide means restrain the blade to move radially, most preferably the guide means restrain the blade to move radially parallel to a plane of the grinding plate. 
         [0015]    Preferably the blade has at least one tooth having a leading face facing in a direction so as to confront materials to be disintegrated when the grinding plate is rotated, the leading face facing in the direction of rotation of the blade; a receding surface which extends away from the leading face in a direction directed outwardly from a tangent line, the receding surface having shear edges radially outward of the leading face for shearing waste. 
         [0016]    The tooth preferably projects from the grinding plate substantially in the axial direction and includes a receding surface which extends away from the leading face in a direction directed axially outwardly from the leading face. 
         [0017]    Preferably the guide means include upstands formed by stamping of the grinding plate. The blade preferably includes an elongate mounting portion extending in the radial direction from the tooth to an inner abutment, a saddle overlying the mounting portion and fixed to the grinding plate such that the abutment and tooth abut the saddle to limit the travel of the blade and provide the inner and outer stop means respectively. 
         [0018]    Preferably two blades are mounted to the grinding plate for coaxial radial movement on opposing sides of the axis. 
         [0019]    This invention provides a food waste disposer which is effective and efficient in operational use which, compared to comparable prior art disposers reduces processing times, especially for harder food fragments. The disposer is also less prone to jamming and moreover the device has an overall simple design which minimizes manufacturing costs and maximizes performance and reliability. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: 
           [0021]      FIG. 1  is a schematic section in an upright plane through a food waste disposer of the present invention; 
           [0022]      FIG. 2  is a pictorial view of the uppermost side of the grinding plate assembly of the disposer of  FIG. 1 ; 
           [0023]      FIG. 3  is a pictorial view of the uppermost side: of the grinding plate of the assembly of  FIG. 2 ; 
           [0024]      FIGS. 4   a  and  4   b  are pictorial views of a blade of the grinding plate of the assembly of  FIG. 2 ; 
           [0025]      FIG. 5  is a pictorial view of a saddle of the grinding plate assembly of  FIG. 2 , and 
           [0026]      FIG. 6  is a pictorial view of a rivet for fastening the saddle. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    Referring to the drawings, particularly  FIG. 1 , a food waste disposer includes a grinding chamber  1  having an inlet  2  at its upper end and a grinding plate  3  mounted at its base. In use the plane of the grinding plate  3  is substantially horizontal and it is rotated about its upright central axis  4  by a motor/gearbox assembly  5  to which it is connected by a drive shaft  6 . Adjacent the circular periphery  34  of the grinding plate  3  is grinding ring  7  fixed to the housing  8 . The grinding ring  7  includes peripherally spaced teeth  9  which cooperate with the grinding plate  3  to disintegrate the waste. 
         [0028]    As best seen in  FIGS. 2 and 3 , two like blades  10   a ,  10   b  are supported on the planar uppermost face  11  of the grinding plate  3 , each mounted for linear travel toward and away from the axis  4  by upstands  12   a - 12   h  formed in the grinding plate  3  and one of the saddles  28 . 
         [0029]    The grinding plate  3  is a metal plate (for instance of stainless steel) and each of the upstands  12   a - 12   h  is formed by shearing and bending a section of the plate in a stamping operation. The upstands are arranged in two rows on either side of a radially-extending line  13  that bisects the grinding plate  3  and in sets of four symmetrically positioned either side of a line  14  bisecting the grinding plate perpendicular to line  13 . Guide faces  15   a - 15   d  on each of the upstands  12   a - 12   d  are coplanar and parallel to the line  13  while respective opposing guide faces  15   e - 15   h  of the upstands  12   e - 12   h  offset to the other side of line  13  are also coplanar and parallel to the line  13 . 
         [0030]    Each of the blades  10   a ,  10   b  has an elongate mounting portion  18  extending in the radial direction and having parallel edges  16   a ,  16   b  that are received between the guide faces  15   a - 15   h . A slot  80  parallel to the edges  16   a ,  16   b  in the base of the blades  10   a ,  10   b  reduces the contact area between the blades and the face  11 , leaving the blades  10   a ,  10   b  supported upon coplanar support surfaces  17   a ,  17   b . In this manner the blades  10   a ,  10   b  are restrained to move radially parallel to a plane of the grinding plate  3 . 
         [0031]    At the outer end of the mounting portion  18  a tooth  19  extends in the axial direction away from the face  11 . The tooth  19  has a leading face  20  facing in the direction of rotation of the blade and aligned perpendicular to the tangent line  21  and to the support surfaces  17   a ,  17   b  so as to confront materials to be disintegrated when the grinding plate is rotated. 
         [0032]    A receding surface  22  extends away from the leading face  20  to the trailing face  81  in a direction directed outwardly from the tangent line  21 . The receding surface  22  is stepped, having first and second shear edges  24  radially outward of one another and of the leading face  20  for shearing waste. 
         [0033]    The leading edge of the tooth  19  is chamfered to produce a planar chamfer face  26  extending away from the leading face  20  and inclined obliquely to the leading face  20  toward the axial end surface  28  on the axial tip of the tooth  19 . The end surface  28  is planar and substantially parallel to the support surfaces  17   a ,  17   b . Extending outwardly from the end surface  28  an upper oblique surface  27  is planar and inclined acutely to the end surface  28 . 
         [0034]    At the inner end of the mounting portion  18  an inner abutment nub  25  is formed, having an abutment face  46  on an outer side thereof. The abutment face  46  is positioned opposite an abutment face  27  formed on the tooth  19 . At radially inner and outer ends of the blades  10   a ,  10   b  are arcuate surfaces  39 ,  41  respectively. The surface  39  is complementary to the cylindrical hub  40  and the surface  41  has the same radius of curvature as the peripheral edge  34 . 
         [0035]    A saddle  28  made, for instance, of corrosion-resistant steel has a symmetrical shape comprising parallel legs  29  joined by a web  30  to form a U-shape. The concave side  31  is complementary to the mounting portion  18  providing a sliding fit therebetween. The saddles  28  are permanently fixed to hold the blades  10   a ,  10   b  in place by rivets  90  extending through openings  32   a - 32   d  in the grinding plate  3 . The nub  25  and tooth  19  provide stop means, the faces  46 ,  47  abutting the saddle  28  to limit the travel of the blades  10   a ,  10   b.    
         [0036]    Through-extending apertures  36  are provided in the grinding plate  3  for the passage of waste. Two protrusions  35   a ,  35   b  are formed in diametrically opposite positions in the plate by a stamping operation. The protrusions  35   a ,  35   b  have a smooth convex surface bounded by an irregular quadrilateral-shaped edge. A projecting lug  37  is formed in like manner to the upstands  12   a - 12   h  by shearing and bending a section of the plate in a stamping operation. Notches  38   a - 38   c  in the peripheral edge  34  provide additional cutting surfaces. The notches  38   a - 38   c , lug  37  and protrusions  35   a ,  35   b , like the blades  10   a ,  10   b  assist in breaking up the waste and driving it outwardly against the grinding ring  7 . 
         [0037]    When the grinding plate  3  is stationary the blades  10   a ,  10   b  are free to move radially, for instance, in response to water or waste being directed into the grinding chamber  1 . In operation, rotation of the grinding plate  3  serves to throw the blades  10   a ,  10   b  outwardly, the nub  25  abutting the saddle  28  in a position where the arcuate surface  41  is radially aligned with the edge  34  adjacent the grinding ring  7 . Material entering the tapering space between the receding face  22  and the grinding ring  9  tends to push the blade inwards, and in addition to the reaction forces acting to disintegrate the waste, clamping action may be provided, the blades holding the waste against the teeth  9  of the grinding ring  7 . 
         [0038]    Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Summary:
Blades on a rotating grinding plate force waste against a stationary grinding ring. The blades are mounted on radially aligned guides on the grinding plate, allowing the blades to move freely inwardly and outwardly between opposing stops. The blades are thrown outward by rotation of the grinding plate. A receding face on the blades cooperates with the grinding ring for moving the blades inwardly and for forcing waste against the grinding ring.