Abstract:
Beater assembly for mixing ingredients in the bowl of a stand mixer with planetary drive, the assembly ( 10 ) including upright arm members ( 12, 14 ) which repeatedly approach and pass close to the walls of the bowl in accordance with the motion imparted by the planetary drive. The arm members are provided with flexible wiping or scraping blades ( 22 ) which are capable of adapting themselves to fully conform to the bowl surface, each arm member ( 12, 14 ) is grooved ( 24 ) along its length and each blade ( 22 ) is formed of a length-wise resilient elastomer configured for mounting in the groove. The blades are formed at each end with fasteners ( 34, 36 ) and are held in position, under length-wise tension, by interlocking the fasteners with anchoring devices ( 38, 40 ) located near the ends of the arm members.

Description:
FIELD OF THE INVENTION 
     This invention relates to a beater assembly for a stand mixer. 
     BACKGROUND OF THE INVENTION 
     Stand mixers are well known and versatile kitchen appliances which generally (though not necessarily) comprise a somewhat C-shaped casing, including a support for a bowl in which ingredients are to be mixed, an upright section and a header portion which is supported by the upright section so as to dispose, overhead of the bowl, a socket housing a drive outlet capable of imparting rotational drive to a shaft inserted into the socket and coupled to the drive outlet. The drive outlet socket faces down towards the bowl and can accommodate, by temporary insertion thereinto, shafts of various tools designed to couple to the drive outlet and devised for such purposes as whisking, blending, kneading and beating ingredients. The drive outlet is configured to impart a planetary drive motion to tools attached thereto; whereby a tool is rotated about an axis and also processes around a circular path centered on the axis. 
     The beater tool is particularly useful, as it can perform a number of tasks, and such tools have evolved into a format whereby a pair of substantially rigid arm members, shaped to substantially conform to the profile of the inner upright surface and a portion of the base of the mixing bowl, are formed into a rigid frame structure by joining together their lower parts and providing a transversely-extending upper support, linking the upper parts of the arm members and supporting at its centre an upwardly-directed drive shaft, or a receptor for such a shaft; the shaft being in any event intended for insertion into the drive socket to couple with the drive outlet. 
     Such beater tools work reasonably well in general use. However, production tolerances make it difficult to ensure that the arm members of the beater accurately match the inner surface of the bowl. Accordingly, particularly when material of a clingy nature is being mixed, a problem can arise in that there is a tendency for some of the material to adhere to the surface of the bowl so that it is not thoroughly incorporated into the mixture being made. 
     GB 483,800 disclosed, as long ago as 1938, that this problem could be addressed by providing the arm members of the beater with flexible scraping members capable of adapting themselves to fully conform to the bowl surface, and thus provide a complete and systematic scraping or wiping action in order to remove adhering material from the surface of the bowl and redirect it back into the mixture. This “flexi-beater” concept has been revisited in recent years, as described for example in U.S. Pat. No. 7,314,308 to Fallowes et al, WO 2007/007202 to Kaas and WO 2006/083560 to Busick, but practical problems still exist in relation to fitting the scraping members to the arm members whilst allowing for cleaning, economical replacement of worn or damaged scraping members and/or the use of exchangeable scraping members with different operating characteristics, and it is an aim of this invention to address one or more of these problems. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a beater assembly for beating ingredients contained in a bowl supported under a planetary drive outlet of a stand mixer; the beater assembly comprising first and second arm members intended to depend into the bowl, and each configured so as to substantially follow the shape of the upright wall of the bowl; the arm members being further configured to adjoin near the base of the bowl, and the assembly further comprising a transverse member linking the non-adjoined ends of the arm members and supporting a shaft configured for temporary attachment to the planetary drive outlet of the stand mixer; the arm members being grooved along their length and each being provided with a respective anchoring device near its junction with said transverse member; and the assembly further comprising a blade member formed of a length-wise resilient elastomer and configured for mounting in said groove; the blade member comprising fasteners at its ends whereby the blade member can be secured to said arm members by interlocking of said fasteners with said anchoring devices; the retention of said blade member in said groove being enhanced by the length-wise resilience of said elastomer. This arrangement provides all of the benefits of a wiping beater and additionally permits the blade member to be readily removed for cleaning or replacement. 
     The ready removal and replacement of the blade member not only facilitates cleaning of the separate components and the economic replacement of worn or damaged blade members, but also advantageously permits the use, with the same beater assembly, of alternative blade members having wiper blades with differing characteristics, designed for use with, say, mixtures of widely different stiffness and/or with bowls made of different materials. Blade members intended for different applications are preferably made visually distinct, for example by colour coding, to aid user differentiation. 
     It will be appreciated that the invention provides a form of beater in which all parts may be cleaned in a dishwasher or by hand; the main body of the beater, comprising the first and second arm members and the transverse member, being made either from metallic material, such as stainless steel, or from a plastics material such as a polymer. 
     The first and second arm members and the transverse member are preferably formed as an integral framework. 
     The blade member preferably comprises a relatively thick root portion, configured to sit snugly in said groove, and an outwardly extending wiping part of thinner profile and formed to repeatedly flex when repeatedly wiped against the interior wall of the bowl during the planetary mixing motion. 
     In preferred embodiments of the invention, at least a major portion of the wiping part of the blade member has a thickness of 3.0 mm or more, and a length of 10.0 mm or more; the use of such dimensions providing unexpectedly good wear and damage resistance allied to good conformance to the bowl profile, as well as providing a substantial creaming surface. Indeed, it is considered that the use of such dimensions is inventive of itself and, accordingly, a further and independent feature of the invention provides for the incorporation, into beater assemblies generally, of blade members having wiping parts major portions at least of which conform to such dimensions. 
     Returning to specific embodiments and irrespective of whether or not the aforementioned preferred dimensions are employed, it is further preferred that the wiping part of the blade member is split, substantially centrally of the blade member&#39;s length, to more readily accommodate opposing flexure forces applied to the first and second arms of the beater during use. 
     In a particularly preferred form of the invention, walls defining the groove in said first and second arm members are cut away at or near the adjoined ends of said arm members to form a shaped cut-out, and said root portion of the blade member is thickened, substantially centrally of the length of said blade member, in a shape conforming to, and adapted to locate within, said cut-out. The cut-out may conveniently conform to a keystone-like shape. 
     In further preferred embodiments of the invention, the anchoring means may comprise undercut terminations of the walls defining the groove in the first and second arms, and the fasteners on said blade member may comprise tab-like terminations extending from said root portions and formed with lateral walls shaped to engage with said undercut terminations of the walls to hold the blade member in tension, stretched along said groove with its root portion snugly located therein. 
     In alternative embodiments, the anchoring means may comprise hook members formed on the first and second arm members or on said transverse member, and the fasteners may comprise apertured tab-like members extending from said root portion of the blade member, such that the apertured tab members can be fitted over the hook members to anchor the ends of the blade members, thereby to hold the blade member in tension, stretched along said groove with its root portion snugly located therein. 
     The shaft for driving the beater assembly may be integrally formed with the transverse member. Preferably, however, the transverse member is formed with a fitment, such as a screw-threaded socket, into which a shaft can be fitted and secured. 
     The beater assembly may be substantially flat in profile (i.e. the centre line of the groove may lie in a single plane), but it is preferred that the arm members are azimuthally twisted as this enhances the performance of the assembly in terms of encouraging ingredients that might otherwise escape upwards from the bowl area swept by the blade members, to move downwards for reincorporation into the mixture. 
     Where azimuthally twisted arm members are used, it is preferred to form the blade members flat, and to rely upon their resilience to enable them to conform to the azimuthal shape upon attachment to the arm members. The blades may be pre-shaped however, if desired, or if necessary to ease conformance to the azimuthal shape. 
     In preferred embodiments of the invention, no cross-bracing members are provided between the arm members. This provides an open-framework construction that is easier to clean than cross-braced frameworks and moreover avoids a disadvantage of cross-braced frameworks, whereby ingredients are undesirably collected on the cross-braces during use, meaning that the mixing process has to be interrupted for cleaning, from time to time. 
     Beater assemblies in accordance with the invention may be used both with conventional stand mixers and the more recently developed stand mixers which are capable of heating materials being mixed in the bowl. When used with such heated stand mixers, however, the invention is particularly beneficial since the intimate contact between the blade member and the bowl reduces the risk of ingredients burning and/or sticking to the bottom of the bowl if they become too hot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be clearly understood and readily carried into effect, one embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which: 
         FIG. 1  shows, in perspective view, a beater assembly in accordance with one embodiment of the invention; 
         FIG. 2  shows arm members and a transverse member integrally formed to create a framework of the beater assembly; 
         FIG. 3  shows a blade member of the beater assembly; 
         FIG. 4  shows another view of the blade member; and 
         FIG. 5  shows schematically the beater assembly in a stand mixer with planetary drive. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, a beater assembly in accordance with one example of the invention is shown at  10 . As aforementioned, the assembly  10  is intended for use in a stand mixer  100  with planetary drive  102 . In this example, the beater assembly  10  comprises an integral framework formed of first and second arm members  12  and  14  and a transverse member  16 . It will be appreciated that, although it is convenient for the purposes of description herein, to refer to the members  12 ,  14  and  16  as separate entities, they are in this embodiment (and, indeed, preferably) integrally formed, either of a high-strength plastics material such as a polymer or of a metallic material such as stainless steel. 
     The transverse member  16  is provided in its central region  16   a  with a threaded socket; the socket being configured to accommodate a stub shaft  18  which is screwed into the threaded socket and fixed in place with a lock-nut  20 . The shaft  18  is adapted at its upper, free, end to fit into the drive socket of a stand mixer and to couple to a planetary drive outlet therein; thereby, in known manner, to simultaneously rotate the beater assembly about the axis of the shaft  18  and cause it to process around a circular orbit centred on the shaft axis. The length of the shaft  18 , and thus the operating height of the beater assembly relative to the base of a mixing bowl, can be varied somewhat, if desired, by releasing the lock-nut  20 , screwing the shaft  18  into or out of the socket and re-tightening the lock-nut  20 . 
     A flexible, wiping blade member  22  is releasably secured to the edges of the arm members  12  and  14 , in a manner that will be made clear hereinafter. This wiping member  22  is made of an elastomeric material which is length-wise resilient and can thus be stretched into place and, once properly anchored, is self-retaining. The wiping blade member  22  makes repeated, intimate wiping contact with the interior sides of a bowl in which ingredients are being mixed as the beater assembly executes its planetary mixing motion. The repeated intimate contact is effective to cream soft mixes, such as margarine with sugar, and to move back into the mix ingredients that would otherwise have adhered to the walls and/or the base of the mixing bowl. Furthermore, if the stand mixer with which the assembly is used is capable of heating ingredients being mixed, the repeated intimate wiping contact reduces the risk of ingredients sticking to the bottom of the bowl and/or burning on. 
     It will be appreciated that the elastomeric material forming the wiping member  22  must be suitable for food contact, resistive of high temperatures, non-hydrolytic, and resistant to hot water and detergents; as, of course, must be the plastics or metallic material forming the framework  12 ,  14 ,  16 . 
     In order to accommodate the wiping member  22 , the arm members  12  and  14  are formed, as shown in  FIG. 2 , with a continuous groove  24  formed as a U-shaped channel section, and defined by upstanding walls  26  and  28 . As shown in  FIGS. 3 and 4 , the wiping member  22  comprises a thickened root portion  30 , shaped and dimensioned to fit snugly into the groove  24 , and an outwardly extending wiper blade  32  which is thinner than the root portion and can flex as it wipes against the internal bowl surface. 
     The member  22  is resilient length-wise and can be stretched into position and, when properly anchored to the arm members  12  and  14 , is held in place by its own resilience; the groove  24  following a smooth, curved path along the arms  12  and  14  to avoid causing damage to the elastomeric wiping member  22 . 
     As described thus far, therefore, the beater assembly comprises first and second arm members  12  and  14 , intended to depend into a mixing bowl, and each configured so as to substantially follow the shape of the upright wall of the bowl; the arm members  12  and  14  joining near the base of the bowl. The assembly further comprises a transverse member  16  linking the non-adjoined ends of the arm members  12  and  14 , and supporting a shaft  18  configured for temporary attachment to the planetary drive outlet of a stand mixer. The arm members  12  and  14  are grooved (as at  24 ) along their length and the assembly further comprises a blade member  22 , formed of a length-wise resilient elastomer and configured for self-retained, elastic mounting in the groove. 
     In this example, the stronger root portion  30  of the blade member  24  is formed with tab-like fasteners  34  and  36  at its ends, whereby the blade member  22  can be secured to the arm members  12  and  14  by interlocking of the fasteners  34  and  36  with respective anchorage points  38  and  40  formed by shaping the ends of the walls  26  and  28  of the groove  22 . Preferably the ends of the walls  26  and  28  are formed at  38  and  40  with a slight undercut to improve retention of the fasteners  34  and  36  respectively. 
     This arrangement provides all of the benefits of a wiping beater and additionally permits the blade member to be readily removed for cleaning or replacement. Moreover, all parts of the assembly may be cleaned in a dishwasher or by hand. The simple and convenient anchoring means is effective to hold the blade member  22  in tension, stretched along the arms  12  and  14  and with its root portion  30  snugly located in the groove  24 . 
     The ready removal and replacement of the blade member  22  not only facilitates cleaning of the separate components and the economic replacement of worn or damaged blade members, but also permits the use, with the same framework  12 ,  14 ,  16 , of alternative blade members having wiper blades with differing characteristics, designed for use with, say, mixtures of widely different stiffness and/or with bowls made of different materials. Blade members intended for different applications may with advantage be made visually distinct from one another; for example by colour coding, to aid user differentiation. 
     It is preferred that the wiping blade part  32  of the blade member  22  is split, substantially centrally of the blade member&#39;s length, to more readily accommodate opposing flexure forces applied to the first and second arms  12  and  14  of the beater during use. 
     In this embodiment of the invention, at least a major portion of the wiping part  32  of the blade member  22  is about 3.0 mm thick and about 10 mm long and, in practice, it is generally preferred to use or exceed these dimensions. Blades of such thickness exhibit surprisingly good wear and damage resistance, and blades of such length conform well to variations in the bowl profile, as well as providing a substantial creaming surface. 
     As has been previously mentioned, it is considered that the use of such dimensions is inventive of itself and, accordingly, a further and independent feature of the invention provides for the incorporation, into beater assemblies generally, of blade members having wiping parts major portions at least of which conform to such dimensions. It will be appreciated that blade members having wiping parts with at least a major portion conforming to such dimensions can be used to significant advantage irrespective of how the blade members are applied and secured to the arm members. For example, blade-like wiping members that are over-moulded onto arm members can benefit from conformance with the dimensions recited herein, provided that such dimensions are adhered to over at least a major portion of the blade member&#39;s wiping part. 
     Returning now to the particularly preferred form of the invention shown in the drawings, the walls  26  and  28  defining the groove  24  in the arm members  12  and  14  are cut away where the arm members join to form a shaped cut-out  42 , and the root portion  30  of the blade member  24  is thickened, substantially centrally of the length of said blade member, as shown at  44 , in a shape conforming to, and adapted to locate within, the cut-out  42 . This expedient is intended to provide a central location point to assist the user when fitting the blade member  22  to the arms  12  and  14 , but may be omitted if desired. The cut-out  42  and the thickening  44  at the root  30  of the blade member  24  (if provided) may conveniently conform to a keystone-like shape. 
     In the present example of the invention, as described above, the anchoring points for the blade member  22  are constituted by undercut terminations of the walls  26  and  28  defining the groove  22  in the arm members  12  and  14 , and the fasteners on said blade member  22  comprise tab-like terminations  34  and  36 , extending from the root portion  30  of the blade member  22 . The terminations  34  and  36  are formed with lateral walls such as  46  and  48 , and shaped to engage with the undercut terminations  38  and  40  of the walls  26  and  28  to hold the blade member  22  in tension, stretched along the groove  24  and with its root portion  30  snugly located therein. 
     In alternative embodiments, the anchorage points may comprise hook members formed on the arm members  12  and  14  or on said transverse member  16 , and the fasteners may comprise apertured tab-like members extending from the root portion  30  of the blade member  22 , such that the apertured tab members can be fitted over the hook members to anchor the ends of the blade member  22 , thereby to hold the blade member in tension, stretched along the groove  24  with its root portion  30  snugly located therein. 
     The shaft  18  for driving the beater assembly may be integrally formed with the transverse member. Preferably, however, and as described above, the transverse member  16  is formed at  16   a  with a centrally located fitment, such as a screw-threaded socket, into which the shaft  18  can be fitted and secured. 
     The beater assembly may be substantially flat in profile (i.e. the centre line of the groove  24  may lie in a single plane), but it is preferred that the arm members  12  and  14  are azimuthally twisted, as shown in  FIGS. 1 and 2 , as this enhances the performance of the assembly in terms of encouraging ingredients that might otherwise escape upwards from the bowl area swept by the blade member  22 , to move downwards for reincorporation into the mixture. 
     Where azimuthally twisted arm members  12  and  14  are used, it is preferred to form the blade member  22  flat, and to rely upon its resilience to enable it to conform to the required azimuthal shape upon attachment to the arm members  12  and  14 . The blade member  22  may be pre-shaped however, if desired, or if necessary to ease conformance to the azimuthal shape. 
     It will be noted that, unlike conventional beater assemblies, the assembly exemplified herein has no cross-bracing members between the arms  12  and  14 . An advantage of this open-framework construction is that the assembly afforded thereby is easier to clean. Moreover, cross-braces tend, when moving through the mixture to undesirably collect ingredients, meaning that the user has to stop processing from time to time to scrape the beater clean. This disadvantage is avoided by means of the open-framework construction used in this example of the beater assembly.