Abstract:
A sealing system for a food blending appliance; said sealing system providing a seal between a blade assembly and an open base of a jug of said appliance; said seal comprising a first upper sealing element and a seal-retaining element; wherein said first upper sealing element provides a substantially smooth transition between internal surfaces of said jug and an upper surface of said blade assembly.

Description:
[0001]    The present invention relates to food blenders and, more particularly, to food blenders intended for domestic kitchen use. 
       BACKGROUND 
       [0002]    Food blenders have become a popular appliances both for domestic and commercial use in the preparation of a wide variety of food ingredients. Blenders typically include a base which incorporates the motor and controls, a blade assembly and a jug. 
         [0003]    The cutting blade or blades are arranged with a vertical axis at the bottom of the jug and are usually directly driven from the motor at speeds in excess of 10,000 rpm, the high speed rapidly cutting food and even solid material such as ice into very fine particles. 
         [0004]    By having the blades situated at the bottom of the jug, food particles are repeatedly thrown outwards and upwards to fall back down to be recycled through the blades. 
         [0005]    It is clearly essential from a health point of view that the blades be accessible for cleaning. Again typically, in the case of domestic blender appliances this is achieved as shown in  FIG. 1 , by the jug having an open bottom which is releasably attached to the blade assembly and base, so that removal of the jug gives access to the blades without actually having to touch the sharp edges of the blades. 
         [0006]    This contrasts with the typical arrangement of commercial blenders shown in  FIG. 2 , in which the sides and base of the jug form a continuous whole and from which the blades are extracted from inside the jug for cleaning. This arrangement allows a larger diameter of blades relative to the sides of the jug and a smooth continuous transition between the blade supporting base and the sides of the jug. This arrangement makes it difficult for the blended material to “hang” on the walls and avoid being recirculated through the blades. 
         [0007]    The arrangement of the typical domestic blender is preferred for the convenient and safer means of access to the blades but comes with associated problems of effective sealing between the jug rim and loss of mixing efficiency because of the difficulty of providing a smooth transition between the blade supporting base and the sides of the jug. 
         [0008]    This latter is due to the inherent design limitations of the glass jugs preferred for domestic blenders. It is necessary (from a manufacturing point of view), to have the parting line for the jug core across the bottom of the jug. The parting line always leaves a jagged edge and must be machined off thereby providing a flat surface for sealing. However, for a jug with a square or hexagonal shaped upper section, this surface can only be provided at the base of a cylindrical wall portion which carries the external thread for attaching the jug to the blade supporting base. Even for a round upper section jug, a lower cylindrical wall portion at a smaller diameter to carry the securing thread is essential to avoid securing ring projecting outside of the jug profile. 
         [0009]    Again, the manufacturing process dictates that the internal surface of this cylindrical wall portion has a draft so that the surface is in effect a portion of an inverted cone. To then provide a blade supporting base for a smooth form of the jug would leave a gap between the jug and base as can be seen in  FIG. 3 . Such a gap will collect food particles and unless cleaned after every use, becomes a potential health problem. 
         [0010]    It is an object of the present invention to address or at least ameliorate some of the above disadvantages. 
       Note 
       [0011]    The term “comprising” (and grammatical variations thereof) is used in this specification in the inclusive sense of “having” or “including”, and not in the exclusive sense of “consisting only of”. 
       BRIEF DESCRIPTION OF INVENTION 
       [0012]    Accordingly, there is provided in a first broad form of the invention a sealing system for a food blending appliance; said sealing system providing a seal between a blade assembly and an open base of a jug of said appliance; said seal comprising a first upper sealing element and a seal-retaining element; wherein said first upper sealing element provides a substantially smooth transition between internal surfaces of said jug and an upper surface of said blade assembly. 
         [0013]    Preferably, said seal-retaining element comprises a semi-rigid collar; said collar comprising a cylindrical portion provided with an outwardly extending flange at a lower edge of said cylindrical portion. 
         [0014]    Preferably, said first upper sealing element at least partially envelops an upper edge of said semi-rigid collar. 
         [0015]    Preferably, said outwardly extending flange of said semi-rigid collar is retained between a planar annular surface at an underside of said jug and an upper surface of an annular flange of said blade assembly. 
         [0016]    Preferably, said system includes a second lower sealing element; said second lower sealing element at least partially enveloping said outwardly extending flange of said semi-rigid collar. 
         [0017]    Preferably, said second lower sealing element provides a seal between said planar annular surface at said underside of said jug and an said upper surface of said annular flange of said blade assembly. 
         [0018]    Preferably, said first upper sealing element provides a seal between an internal annular surface of said jug and an outer annular surface of said blade assembly. 
         [0019]    Preferably, said second lower sealing element and said first upper sealing element comprise elastomer rings, said elastomer rings joined by said semi-rigid collar. 
         [0020]    Preferably, said blade assembly includes a blade supporting base member; said blade supporting base member comprising a circular base portion and a peripheral skirt depending substantially vertically from said circular base portion; an outer surface of said skirt defining said outer annular surface. 
         [0021]    Preferably, said annular flange of said blade assembly extends outwardly from a lower edge of said peripheral skirt. 
         [0022]    Preferably, said jug is open at said underside; a base portion of said jug forming a cylindrical wall at said underside; an internal surface of said cylindrical wall defining said internal annular surface of said jug; an underside of said cylindrical wall defining said planar annular surface. 
         [0023]    Preferably, the diameter of an internal lower edge of said cylindrical wall is larger than the outer diameter of said peripheral skirt; respective diameters differing by an amount adapted to leave a gap between said internal lower edge and said skirt sufficient for the thickness of a said cylindrical portion of said collar. 
         [0024]    Preferably, said second lower sealing element is held in compression between said planar annular surface and said annular flange of said blade assembly. 
         [0025]    Preferably, said internal annular surface forms a portion of an inverted cone between said internal lower edge and an internal upper edge of said internal annular surface, such that a gap between said internal upper edge and said skirt is larger than said gap between said internal lower edge and said skirt. 
         [0026]    Preferably, said first upper sealing element is held in compression between said internal upper edge and said skirt. 
         [0027]    Preferably, said circular base portion of said blade assembly, an upper outer surface of said first upper sealing element and internal surfaces of said jug are arranged to form a continuous substantially smooth surface extending from a vertical drive shaft of blades of said food blending appliance to upper edges of said jug. 
         [0028]    Preferably, an outer surface of said cylindrical wall at said underside of said jug is provided with thread formations; said thread formations adapted to engage with thread formations of a securing ring; said securing ring adapted to connect said blade supporting base member to said jug; said securing ring provided with an inwardly extending flange adapted to apply said compression of said second lower sealing element. 
         [0029]    Preferably, said first upper sealing element is substantially of triangular cross section; said elastomer material of said upper sealing element overmoulded over said upper edge of said semi-rigid collar. 
         [0030]    Preferably, said second lower sealing element is substantially of rectangular cross section; said elastomer material of said lower sealing element overmoulded over said outwardly extending flange of said semirigid collar. 
         [0031]    In a further broad form of the invention, there is provided a seal for the junction between the blade assembly of a food blending appliance and a jug of said appliance; said seal including a first upper sealing element and a second lower sealing element; said first upper sealing element and said second lower sealing element joined by a collar. 
         [0032]    In yet another broad form of the invention, there is provided a method of providing a smooth transition between an upper surface of a blade assembly of a food blending appliance and internal surfaces of an open base jug of said appliance; said method including the step of providing a dual seal sealing system between said blade assembly and an open base of said jug. 
         [0033]    Preferably, said dual seal includes an elastomer first upper sealing element and an elastomer second lower sealing element. 
         [0034]    Preferably, said first upper sealing element and said second lower sealing element are joined by a semi-rigid collar. 
         [0035]    Preferably, said first upper sealing element provides a seal for a gap formed between a skirt of said blade assembly and an outwardly tapering internal surface of said jug. 
         [0036]    Preferably, said second lower sealing element provides a seal between a planar annular surface at an underside of said open base jug and an outwardly projecting flange of said blade assembly. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0037]    Embodiments of the present invention will now be described with reference to the accompanying drawings wherein: 
           [0038]      FIG. 1 , is a cross section of the upper portion of a typical blade assembly and jug of a domestic kitchen food blender according to the prior art, 
           [0039]      FIG. 2 , is a cross section of a typical blade assembly and jug of a commercial food blender according to the prior art, 
           [0040]      FIG. 3 , is a cross section of an upper portion of a blade assembly and a glass jug configured according to a preferred embodiment of the invention, 
           [0041]      FIG. 4 , is a cross section of the blade assembly and glass jug of  FIG. 3  with a preferred embodiment of a sealing system according to the invention installed, 
           [0042]      FIG. 5 , is a detailed view of the installed sealing system of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Preferred Embodiment 
       [0043]    With reference to  FIGS. 4 and 5 , a food blending appliance  10  intended primarily, though not exclusively, for domestic kitchen use, includes a blade assembly  12  and glass jug  14 . Blade assembly  12  includes a blade supporting base member  16  provided with a central bearing and conventional seal assembly  18  for support of a vertical drive shaft  20  and blades  22 . Vertical drive shaft  20  and blades  22  are urged into rotational movement by a conventional drive motor mounted in a base enclosure (not shown). 
         [0044]    Glass jug  14  is of typical and conventional construction, comprising a base region  24  open at the underside, from which rise outwardly sloping side walls  26 . Side walls  26  may be of circular or square cross section, but base region  24  comprises a cylindrical wall  28  provided with an external thread formation  30 . The underside of cylindrical wall  28  is machined flat (as explained above) to provide a planar annular surface  32  and, in this first preferred embodiment, forms a first sealing surface for a second lower sealing element  34 . 
         [0045]    As also explained above, the internal annular surface  36  of cylindrical wall  28  is provided with a draft for manufacturing purposes-. Thus the internal annular surface  36  in effect is a portion of an inverted conical surface between two parallel planes, the respective planes defining an internal lower edge  38  and an internal upper edge  40 . An annular region of the internal surface immediately below the internal upper edge  40  forms a first sealing surface for a first upper sealing element  42 . 
         [0046]    Blade supporting base member  16  comprises a circular base portion  44  and a peripheral skirt  46  depending vertically from the periphery of base portion  44 . Peripheral skirt  46  is provided with an outwardly extending annular flange  48  the upper surface  50  of which forms a second sealing surface for the second lower sealing element  34 . 
         [0047]    The outer diameter of peripheral skirt  46  is such that a gap  50  is left between the outer annular surface  52  of skirt  46  and the internal lower edge  38  of cylindrical wall  28 . Because of the conical geometry of the internal annular surface  36  of cylindrical wall  28 , the gap  50  between the outer surface of skirt  46  and the internal upper edge  40  of internal annular surface  36  is larger than that between the skirt and the internal lower edge  38  (as can best be seen in  FIG. 3 ). The peripheral edge of circular base portion  44  is provided with a chamfer  54 , forming a second sealing surface for the first upper sealing element  42 . 
         [0048]    The seal  56  of the present invention comprises the first upper sealing element  42  and second lower sealing element  34 , preferably linked together by a semi-rigid collar  58 . Preferably collar  58  has a cross sectional configuration in the shape of an “L”, comprising a cylindrical portion  60  and an outwardly extending flange  62  from the lower edge of cylindrical portion  60 . The semi-rigid collar  58  acts to prevent the first upper seal  42  from being drawn down into the tapering gap  50  when blade assembly  12  is extracted from jug  14 , causing jamming and preventing a smooth separation of jug and blade assembly. 
         [0049]    The second lower sealing element  34  comprises a rectangular cross section moulding, overmoulded over outwardly extending flange  62 , while the first upper sealing element  42  comprises a generally triangular cross section moulding, overmoulded over the upper edge of cylindrical portion  60  of collar  58 . Both sealing elements are moulded in a food grade elastomer. Preferably, the material of collar  28  is of a semi-rigid plastic such as for example a polypropylene. 
         [0050]    As shown in  FIG. 5 , second lower sealing element  34  is adapted for sealing compression between the planar annular surface  32  of cylindrical wall  28  and the upper surface  64  of outwardly extending flange  48 . Compression is provided in a conventional manner by an internally threaded securing ring  66 , provided with an inwardly extending flange  68 . First upper sealing element  42  is adapted to seal the gap between the chamfer  54  of circular base portion  44  and the surface below internal upper edge  40  of cylindrical wall  28 , thereby preventing the ingress of food material into the gap between peripheral skirt  46  and internal annular surface  36 . 
         [0051]    The arrangement of the dual sealing elements  34  and  42  of the present invention allows for a virtually smooth continuation of the surface of the blade supporting base member  16  and the internal surfaces of the jug  14 . This virtually smooth internal surface formed by the assembled jug and blade assembly contrasts strongly with the arrangement of conventional blenders shown in  FIG. 1 , ensuring that material flung outwardly by the blades flows efficiently upwards along the walls of the jug, reducing undesirable pooling of the material. The sealing system of the present invention thus combines the features of convenient access to the blades for cleaning and the greater efficiency of blending usually only found in commercial blenders. 
       Second Preferred Embodiment 
       [0052]    This preferred embodiment is identical to the first embodiment described above except that in this case the sealing system is simplified to comprise of the semi-rigid collar with first upper sealing element only. The semi-rigid collar is again provided with an outwardly extending flange as described above, but does not have an overmoulded elastomer sealing element, so that in this embodiment, the semi-rigid collar forms a seal-retaining element. The outwardly extending flange on assembly of the jug to the blade assembly is locked between the underside of the jug and the surface of the securing ring, thereby securing the upper sealing element in its correct sealing position between the inside surface of the jug and the peripheral skirt of the blade assembly. 
         [0053]    The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope and spirit of the present invention.