Abstract:
A hand-held masher device for mashing of potatoes and like food stuffs; said device including a power unit providing a rotating shaft output; said device further including a masher assembly extending from said power unit; said masher assembly including a skirt element and a mashing element operating within said skirt element; characterized in that mashed potato and like food stuff is extruded through apertures disposed in a side wall of said skirt element; said masher assembly including internal guide surfaces; said guide surfaces in the form of an inverted portion of a conical structure depending from an underside of a supporting annular conical wall of said skirt element, and wherein upper portions of blades of said mashing element conform to said guide surfaces.

Description:
[0001]    The present invention relates to kitchen appliances and, more particularly, to powered devices for the preparation of food stuffs. 
       BACKGROUND 
       [0002]    In order to make mashed potato, the potato is first cooked as evenly as possible. If the starch grains in the potato are ruptured, they release Amilose, imparting a ‘gluey’ texture. Amilose is the thickening medium in gravy and custard. These starch grains can be ruptured by either excessive heat or kinetic energy. 
         [0003]    Best results are obtained by slicing the potato before boiling. Thick lumps overcook on the outside and release Amilose before the centre is softened. For perfect mash, the cooked potatoes should be washed before being mashed. 
         [0004]    Once softened the potato is crushed to remove lumps then blended with milk, butter, herbs etc to taste. Mashed potato is eaten in most countries under various guises. 
         [0005]    High speed choppers and food processors break down the starch grains and do not produce an acceptable result. They use high speed as a means of ‘catching’ the suspended lumps and breaking them up. 
         [0006]    The problem with a traditional hand masher in a saucepan is that hard lumps keep moving out of the way of the crushing bars. Unless the potato or the like is perfectly cooked it can become very difficult to remove all lumps. 
         [0007]    Commercial mashers, (or ricers as they are commonly called), use either a blade or a plunger to force material through a sieve. They have the limitation of being large and difficult to clean, and often difficult to use. 
         [0008]    At least one powered masher for domestic use is known. This device, marketed under the brand name Kenwood®, comprises an attachment for a “stick mixer” and includes a cylindrical skirt open at the underside and a top with apertures. A blade rotates in the skirt and forces food particle up through the apertures. Problems with this arrangement are firstly, it takes considerable force to repeatedly push the device into the food stuff to be mashed as the blade appears to push the food down against the bottom of the container and, secondly, food stuff extruded through the apertures in the top of the skirt tend to adhere thereon so that repeated impacting or scraping is required. 
         [0009]    A further problem of this masher is that to remove the blade for cleaning, the masher assembly must be attached to the power unit. The blade is attached to its drive shaft by means of a screwing “bayonet” fitting and it requires, the torque of the reduction gearing of the power unit to counteract the unscrewing force which must be applied. 
         [0010]    In the case of the masher appliance above, the blade speed is relatively low so that an inadvertent switching on of the power unit while attempting to remove the blade is unlikely to cause injury. However, other stick mixers operate at high revolutions in which the risk of injury is high and in these mixers the blades are not removable from the drive shaft for safety reasons. This makes the blades and the insides of the skirts in which they operate difficult to clean. 
         [0011]    It is an object of the present invention to address or at least ameliorate some of the above disadvantages. 
       Notes 
       [0000]    
       
         1. 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”. 
         2. The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country. 
       
     
       BRIEF DESCRIPTION OF INVENTION 
       [0014]    Accordingly, in a first broad form of the invention, there is provided a hand-held masher device for mashing of potatoes and like food stuffs; said device including a power unit providing a rotating shaft output; said device further including a masher assembly extending from said power unit; said masher assembly including a skirt element and a mashing element operating within said skirt element; characterized in that mashed potato and like food stuff is extruded through apertures disposed in a side wall of said skirt element. 
         [0015]    Preferably, said masher assembly is releasably attached at a lower end of said power unit. 
         [0016]    Preferably, said power unit comprises a generally vertically oriented cylindrical body when in use; outside surfaces of said body shaped to fit the grasping hand of a user. 
         [0017]    Preferably, a shaft of said mashing element engages with said rotating shaft of said power unit when said device is assembled for use. 
         [0018]    Preferably, said side wall of said skirt element forms a portion of a cone; said side wall extending downwardly and outwardly from a supporting annular conical wall of a connection portion of said masher assembly; said connection portion provided with mating elements for said releasable attachment to said power unit. 
         [0019]    Preferably, said apertures in said side wall comprise a plurality of generally rectangular elongate slots extending from proximate a lower edge of said side wall to proximate an upper edge of said side wall; said plurality of slots spaced at equal intervals around said side wall. 
         [0020]    Preferably, said masher assembly includes internal guide surfaces; said guide surfaces in the form of an inverted portion of a conical structure; an upper edge of said conical structure proximate an inside annular junction between said side wall and said connection portion of said masher assembly. 
         [0021]    Preferably, said conical structure is closed at a lower end by a generally planar disc. 
         [0022]    Preferably, said mashing element includes a central boss; said boss approximating an inverted portion of a sphere; a planar upper portion of said boss approximately equal in diameter to said generally planar disc; said mashing element further comprising at least one mashing blade extending outwardly from said boss. 
         [0023]    Preferably, said at least one mashing blade comprises three mashing blades. 
         [0024]    Preferably, each of said mashing blades comprises an arm element extending outwardly from said central boss to a sweeping blade tip; said blade tip comprising an elongate trailing edge extending from an inside lower edge of said skirt element to proximate said inside annular junction; said trailing edge substantially coplanar with the axis of said drive shaft of said mashing element. 
         [0025]    Preferably, a lower portion of said arm element lies in a plane defined by said lower edge of said skirt element; an upper portion of said arm element formed so as to sweep along side surfaces of said conical structure of said guide element. 
         [0026]    Preferably, said sweeping blade tip includes a curved surface portion extending from said elongate trailing edge and merging with said arm element; said curved surface convex relative direction of rotation of said mashing element. 
         [0027]    Preferably, said mashing element and said shaft of said mashing element are removable for cleaning from said mashing assembly. 
         [0028]    In another broad form of the invention, there is provided a method of mashing potatoes and like food stuffs with a hand-held powered masher device; said method including the steps of:
       a. lowering a mashing assembly of said hand-held masher device into precooked potatoes or other suitable food stuffs,   b. periodically lifting and re-positioning said hand-held masher device in a container of said precooked potatoes or other suitable food stuffs.       
 
         [0031]    Preferably, said hand-held masher comprises a power unit and a masher assembly releasably attached to said power unit. 
         [0032]    Preferably, said masher assembly includes an annular skirt and a mashing element rotating within said annular skirt when said masher device is in use. 
         [0033]    Preferably, said annular skirt is provided with elongate generally rectangular slots; said slots arranged at intervals around said annular skirt. 
         [0034]    Preferably, said mashing element includes outwardly extending arms; each of said arms including a trailing edge substantially sweeping an inner surface of said annular skirt; said arms shaped such that lower edges of said arms lie in a plane defined by a lower edge of said skirt; upper edges of said arms conforming to surfaces of a guide structure within said annular skirt, such that when said mashing element is urged into rotation by said power unit said mashing element substantially sweeps a space between internal surfaces of said skirt and said guide structure. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0035]    Embodiments of the present invention will now be described with reference to the accompanying drawings wherein: 
           [0036]      FIG. 1  is an assembled perspective view of a preferred embodiment of a hand-held masher device according to the invention, 
           [0037]      FIG. 2  is a partially sectioned view of the masher device of  FIG. 1 , 
           [0038]      FIGS. 3 to 5  are partially sectioned views of a further embodiment of the invention showing a shaft locking mechanism. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Preferred Embodiment 
       [0039]    With reference to  FIGS. 1 and 2 , a preferred embodiment of a hand-held masher device  10  according to the invention, comprises a power unit  12  and a masher assembly  14 , releasably attached to the power unit  12 . 
         [0040]    Power unit  12  comprises a body  16  which houses at least an electric motor  17 , and one or more control switches  18  for operation of the device. The body  16  is of a generally cylindrical shape but is preferably formed with outer surface shaped to suit the grasping hand (not shown) of a user. An extension  20  of the power unit houses a drive shaft  22  driven into rotary motion by the electric motor  17  of the power unit  12 . 
         [0041]    A set of reduction gears  23  housed in the base of the power unit  12 , reduces the rpm of the driven shaft  22  to a fraction of the rpm of the electric motor, thereby significantly increasing the torque output of the drive shaft  22 . The low rpm, suited to the mashing operation of the device, demands a relatively low powered electric motor so that in one preferred form of the masher, the device  10  is cordless and the power unit body  16  is provided with a rechargeable battery pack in the manner described in the present applicant&#39;s earlier Australian application No. 2005270712. 
         [0042]    Extension  20  is provided with mating structures  25 , for example in the form of bayonet elements, for releasable engagement with the masher assembly  14 . Masher assembly  14  comprises a connection portion  26 , a skirt element  28  and a mashing element  30  located within the skirt element  28 . The connection portion  26 , in the form of a substantially cylindrical housing, is provided with bearings  31  and a short mashing element drive shaft  32 . The mashing element  30  is rigidly connected to an outer end of the mashing element drive shaft  32 . Drive shaft  32  is releasably retained within the connection portion  26 , for example by spring-loaded detent balls acting on an annular groove on the drive shaft, so that the shaft  32  and mashing element  30  may be removed from the assembly  14  for cleaning. 
         [0043]    The lower end of the drive shaft  22  of the power unit  12  is adapted to engage automatically with the upper end of the mashing element drive shaft  32  when the masher assembly  14  is assembled to the power unit  12  for use. 
         [0044]    The skirt element  28  is in the form of a section of a cone, open at its underside  34 , with a aide wall  36  sloping outwardly from a supporting annular conical wall  38  extending from the connection portion  26 . Spaced at regular intervals around the side wall  38  is a plurality of apertures  40 . Preferably apertures  40  are formed as elongate, generally rectangular slots  40 , each slot  40  extending from proximate the lower edge  42  of the side wall  36 , to proximate its upper edge  44 . Although the slots shown in  FIGS. 1 and 2  are preferred, tests have shown that other arrangements of patterns of apertures in the side of skirt  36  perform similarly in the efficient extrusion of the material being mashed. 
         [0045]    The skirt element  28  is further provided with an internal guide structure  46  in the form of an inverted conical structure depending from the underside of the supporting annular conical wall  38 , and with its upper edge  48  proximate an inside annular junction between the side wall  36  and the supporting annular conical wall  38  of the skirt. The side wall  50  of the guide structure  46  is preferably somewhat concave. The guide element is closed at its lower end by a generally planar disc  52 , through the centre of which projects the short mashing element drive shaft  32 . 
         [0046]    A particular feature of the invention resides in the characteristics and form of the mashing element  30 . In a preferred form, the mashing element  30  comprises three mashing blades  54  extending radially from a central boss  56  which is rigidly attached to the outer end of the mashing element drive shaft  32 . The boss  56 , is in the form of an inverted section of a sphere with an upper planar surface  53  in close proximity to the underside of the closing planar disc  52  of the guide structure  46 . 
         [0047]    Each of the mashing blades  54  comprises an arm element  58 , extending outwardly from the central boss  56 , to a sweeping blade tip  60 . This sweeping blade tip  60  is in the form of an elongate trailing edge  62  extending upwardly from proximate an inside lower edge of the skirt element side wall  36  to proximate the inside annular junction, and is oriented generally coplanar with the axis of drive shaft  32 . The sweeping blade tips  60  include a curved surface portion  62  extending from the elongate trailing edge  62  and merging with the arm elements  58 , with the curved surface being convex relative the direction of rotation of the mashing element  30 . The relatively small swept area of the blade arms adjacent the central boss  56 , prevents material accumulating in this region and rotating with the blades. This feature, together with the curved surface portions  62  ensures that material is continually forced radially outwards to be forced up against the internal surface of the skirt  36  and extruded through the apertures  40 . 
         [0048]    A lower portion of each arm element lies in a plane defined by the lower edge of the side wall  36 . The upper portions  64  of these arm elements  58  are formed so as to sweep along the side surface of the inverted portion of the guide structure  46 . Thus, as the mashing element rotates within the skirt element  28 , the entire space between internal surfaces of the skirt element and the guide structure  46  is swept by the mashing blades, with the elongate trailing edges  60  maintaining a minimum clearance from the inside surface of the skirt element side wall  36 . 
       Second Preferred Embodiment 
       [0049]    In a second preferred embodiment of the invention, a food preparation appliance again comprises a power unit as described above and a blade extension unit. A blade extension unit according to this embodiment, may take the form of the masher assembly described above but may be any assembly comprising housing with a skirt at its distal end, a drive shaft extending through the housing and a food preparation blade rotatable within the skirt. 
         [0050]      FIG. 3 , shows a food preparation appliance  112  comprising a power unit  117  (lower portion shown only) engaged with a blade extension unit  114  for use. Located within housing  104  of the blade extension unit  114 , is a sliding member  106 , movable within the housing between a non-engaged position as shown in  FIG. 3  and an engaged position as shown in  FIG. 5 . 
         [0051]    Sliding member  106  is automatically urged into the engaged position of  FIG. 5  by a spring  105 , acting between a support structure  107  at the lower end of the blade extension unit  114  and the sliding member  106 , as the power unit  117  is withdrawn from the blade extension unit. 
         [0052]    It can be seen from  FIG. 3 , that when the extension  120  of the power unit  117  is pushed into and engages with the blade extension unit  114 , the lower end  109  of the power unit forces the sliding member  106  into its disengaged position. 
         [0053]    Drive shaft  132  of the blade extension unit  114  is provided at its proximate end with a boss  134  provided on its external surfaces with engagement elements  140 . Boss  134  includes a drive socket  138  for engagement with the rotating shaft output  142  of the power unit  117 . These engagement elements  140  of the boss  134 , engage with complementary engagement elements  144  of the eliding member  106 , when the sliding member is urged into the engaged position shown in  FIG. 5 . 
         [0054]    Sliding member  106  is prevented from rotation relative to the housing  104  of the blade extension unit  114 , through sliding engagement with non-rotating control elements  146  of the support structure  107 , fixed within the lower end of the blade extension unit. 
         [0055]    Blade element  130  is removably attached to the drive shaft  132  of the blade extension unit  114  by a screwed connection  136 , with the thread of the screwed connection selected opposite in sense to the rotation of the drive shaft  132 . 
         [0056]    By means of the locking mechanism of the invention, as soon as the power unit is removed from blade extension unit, the drive shaft is locked and prevented from rotation. This then allows the blade element  130  to be grasped and unscrewed from the shaft  132  for ease of cleaning both the blade element and the internal surfaces of the skirt  128 . 
         [0057]    In Use 
         [0058]    The masher device of the present invention is adapted to the mashing of pre-cooked potatoes and many other foodstuffs such as bananas, vegetables and avocado for example, in a flat-bottomed container. The device is repeatedly lowered down into the food until the lower edge of the skirt element is in contact with the surface of the container. Once the mashing process is underway, the action of the blades allows the device to sink downward into the food volume with no effort required of the user. There is little or no suction of the device into the material allowing it to be readily lifted free for several re-positionings to cover the area of the base of the container. 
         [0059]    The slowly rotating mashing element has been found to initiate a pumping, or screw compression type action in which the food is continually pushed outwardly by the trailing edges of the blades and forced out through the apertures. While the trailing edges of the blade tips sweep against the apertures, the undersides of the lower portions of the arms of the blades, scrape the bottom of the container, pulling the food stuff into the skirt and ensuring that no lumps remain. 
         [0060]    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 of the present invention.