BLENDER BASE MODULE

The present invention relates to motorized food blenders and, more particularly, to the arrangement of the base module and cooling of the drive motor for such blenders.

BACKGROUND

One of the important characteristics of a food blender, especially a food blender for domestic use, is its rated power output and noise level. Rated power for a given size is significantly influenced by the efficiency of cooling which can be provided to the motor. Significant factors influencing noise level (discounting impact noise of the blades against food ingredients) include the rigidity and mass of the motor mounting and that emitted by the cooling fan.

A problem in the design of blender base module motor assemblies is the need to balance these factors to achieve an acceptable noise level vis a vis power output. Another undesirable aspect of food blender design is that the need to accommodate a vertically oriented, direct driving motor, its commutator brushes assembly and the cooling fan, can make the base module unduly high.

It is an object of the present invention to address or at least ameliorate some of the above disadvantages.

Notes

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

Accordingly, in a first broad form of the invention, there is provided a food blender base module; said module adapted for supporting a blender jug and blade assembly; said base module containing a drive motor assembly, circuitry and controls; said base module characterised in that said drive motor is at least partly enclosed in a cooling shroud, wherein at least a lower portion of said shroud has a maximum diameter smaller than a length defined between outer ends of opposing brushes of said drive motor

Preferably, said drive motor assembly is arranged in said base module with the motor axis vertical; said opposing brushes arranged at an upper output shaft end of said

motor; an exhaust fan arranged at an opposite lower end of said motor assembly.

Preferably, said exhaust fan is located at a lower end of said cooling shroud.

Preferably, said exhaust fan is a radial fan; an upper flange of said radial fan enclosed by a cylindrical lower portion of said cooling shroud.

Preferably, said cooling shroud extends from said radial fan upwards; said cooling shroud extending at least to an underside of said opposing brushes.

Preferably, internal surfaces of at least a lower portion of said cooling shroud are substantially cylindrical.

Preferably, said motor assembly includes a single cast aluminium motor bracket; said motor bracket at said output shaft end supporting housings for said opposing brushes.

Preferably, upper portions of said motor bracket provide at least partial closure of an upper opening of said cooling shroud; said bracket restricting air flow between opposing coils of said motor; said upper portions arranged to direct cooling air over said coils and between the rotor and stator of said motor.

Preferably, said aluminium motor bracket at said output shaft end includes a pair of bridging elements supporting a

central output shaft bearing housing; space between said pair of bridging elements allowing flows of cooling air over said housings of opposing brushes.

Preferably, said housings of said opposing brushes are of brass; said housings in contact with said aluminium motor bracket .

Preferably, said motor bracket at said output shaft end is arranged to allow "line of sight" cooling air flow from upper portions of said bracket to said exhaust fan; said cooling air passing between said stator and said rotor of said motor.

Preferably, said base module is provided with a cooling air intake vent in an outer casing of said base module; said air intake vent located at a lower side portion of said casing.

Preferably, said shroud is provided with a cooling air guide channel along a side of said shroud; said channel guiding air drawn in through said air intake vent to a level above said upper portions of said motor bracket and said upper opening of said cooling shroud.

Preferably, said base module is provided with a cooling air outlet vent located around the periphery of said radial fan; said fan drawing cooling air through said inlet vent

to enter said upper opening of said cooling shroud; said cooling air drawn substantially over said coils and through central portions of said drive motor to exhaust through said outlet vent.

Preferably, the height of said base module from a supporting surface to a surface supporting said blender jug does not exceed 180mm.

The base module of any one of claims 1 to 15 wherein rated wattage output of said blade drive motor is not less than IkW.

Preferably, the emitted noise level of said base module when unloaded does not exceed 85dB at a distance of 0.5m from said base module.

In another broad form of the invention, there is provided a food blender base module drive motor arrangement wherein said drive motor is provided with commutator and opposing brushes at an upper output end of a vertically oriented motor shaft of said motor; said base module provided with an exhaust fan at an opposite end of said motor shaft, and wherein the diameter of a lowermost cylindrical portion of a cooling shroud of said motor is a close fit about the periphery said exhaust fan.

Preferably, said diameter of said lowermost cylindrical portions of said cooling air shroud is substantially smaller than a length defined between outer ends of said opposing brushes at said upper output end.

Preferably, a cooling air guide channel provides a cooling air path from an inlet vent at a side of said base module; said guide channel directing said cooling air between an inside surface of a casing of said module and said guide channel to an upper opening of said cooling air shroud.

Preferably, cooling air entering said upper opening of said cooling air shroud is biased to flow over hotter portions of said drive motor; said hotter portions including coils and central portions of said drive motor.

In still another broad form of the invention, there is provided a method of maximising cooling air flow around and through a motor assembly in a food blender base module; said method including the steps of:

(a) arranging opposing brushes of a blade drive motor of said assembly at an output shaft end of said drive motor,

(b) arranging a cooling fan at an opposite lower end of said drive motor,

(c) providing a cooling shroud around said blade drive motor wherein a maximum internal diameter of said shroud is smaller than a length defined by outer ends of said opposing brushes.

Preferably, said exhaust fan is a radial fan; said radial fan including an upper disc with central opening, and a lower disc; an array of blades linking said upper disc and said lower disc.

In another broad form of the invention, there is provided a method of assembling a base module of a food blender; said base module including a main cover portion, a motor assembly, a cooling air shroud and a base cover portion; said method including the steps of:

(a) attaching said motor assembly to an inside upper portion of said main cover portion,

(b) fitting said cooling shroud over said motor assembly,

(c) attaching said base cover portion.

Preferably, said motor assembly includes commutator and brushes arranged at an upper end of the motor shaft of a drive motor of said motor assembly.

Preferably, said cooling shroud includes a lowermost cylindrical portion; said cylindrical portion forming a

close fit around the periphery of a radial cooling fan mounted to a lowermost end of said motor shaft.

BRIEF DESCRIPTION OF DRAWINGS Embodiments of the present invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is an exploded perspective view of the major components of blender base module according to a preferred embodiment of the invention,

Figure 2 is an assembled partly sectioned side view of the blender base module of Figure 1 when viewed in a first direction,

Figure 3 is an assembled partly sectioned side view of the blender base module of Figure 1 when viewed in a second direction normal to the direction of Figure 2,

Figure 4 is an exploded perspective view of the base module components of Figure 1 viewed from below,

Figure 5 is a plan view of the motor and shroud assembly viewed from the output shaft end.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to Figures 1 to 5, a base module 10 for a food blender includes an outer casing 11 made up of a main cover portion 12 and a base cover portion 14, a drive motor assembly 16 and an internal cooling air shroud 18. In

rne present arrangement of the invention the drive motor is oriented within the base module with the motor shaft vertical.

Motor assembly 16 includes upper and lower cast aluminium motor brackets 20 and 22 respectively, electric motor components 24 and a radial exhaust fan 26 located at the base of the motor assembly. Attached to upper motor bracket 20 are housings 28 and 29 for a pair of opposing brushes 30 and 31 acting on a commutator 32. Commutator 32 and brushes 30 are located at the output shaft end 34 of the motor shaft 33 of motor assembly 16. A splined blade shaft connector 36 is affixed at the outer end 38 of motor shaft 33.

The greater portion of motor assembly 16 is located within the cooling shroud 18 (as best seen in Figure 2) such that the upper surfaces 40 of the side elements 42 of upper motor bracket 20 are approximately flush with the rim 44 of the upper opening 46 of the shroud 18. At least the lower portions 48 of shroud 18 are approximately cylindrical, closely shrouding the lamination stack 50 and coils 52 of the motor. The lowermost part of cylindrical portions 48 of the shroud 18 encloses the upper disc 54 of the radial exhaust fan 26. As can best be seen in Figure 2 and 3, this lowermost cylindrical portion of the cooling shroud is of a diameter to closely confine the periphery of

the radial exhaust fan disc 54 so that the fan acts with maximum efficiency to draw cooling air through the shroud.

Radial exhaust fan 26 comprises disc 54 with central opening 58, and lower disc 61. An array of radial blades 63 link the upper and lower discs, with the lower disc 61 being fixed to the lowermost end of motor shaft 33.

Referring now more particularly to Figure 5, it can be seen that the side elements 42 of the upper motor bracket 20 provides a partial closure of the upper opening 46 of the shroud 18. The configuration of the upper bracket 20 is such that air flow into the shroud 18 is restricted over the regions between the coils 52 of the motor but is biased to flow over the coils and adjacent portions of the lamination stack 50. As well, the drive motor of the invention is structured to maximise the spaces between rotor and stator are so as to allow "line of sight" cooling air flow through the centre of the motor from the upper portion down to the centre opening 58 of the radial fan upper disc 54 at its base. The structure of the lower cast aluminium bracket 22 with its pair of narrow bridging structures supporting the fan end shaft bearing housing 78 further assists in this free flow of cooling air.

This minimal obstruction of cooling air flow over and through the hottest parts of the motor is also aided by the similar narrow pair of bridging elements 60 supporting the central motor shaft upper bearing housing 62. The space

between the pair of bridging elements 60 also allows unimpeded cooling air flows over the housings 28 and 29 of the opposing brushes 30 and 31. Cooling of the brushes 30, 31 is further aided by the housings 28 and 29 being of brass and in contact with the relatively massive side elements 42 of the upper cast aluminium motor bracket 20 to which they are attached, and which act in effect as heat sinks.

Cooling air shroud 18 is provided with a cooling air guide channel 64 at one side of the shroud 18. As best seen in Figure 2, when the motor assembly 16 and cooling air shroud 18 are assembled into the main cover portion 12 and base cover portion 14, guide channel 64 forms an air flow path between the inside of the casing and the shroud. Cooling air drawn in through inlet vent 66 is guided up to the top of the motor assembly and the upper opening 68 of the shroud 18. When so assembled, the radial exhaust fan 26 is nested in outlet vent structure 70 in base cover portion 14 of the casing. Assembly of the components of the base module proceeds with firstly the motor assembly 16 being attached to the projecting mounting posts 80 inside the upper portion of the main cover portion 12 by the four resilient vibration mountings 84. The cooling shroud 18 is then fitted over the motor assembly and also attached to similar mounting posts 86 and wiring (not shown) connected. The shroud also serves

to lock down the printed circuit board of the motor control system (not shown) . Finally, the base cover portion 14 is attached to the posts 88 of the cooling shroud 18, completing the assembly of the base module. The arrangement of locating the commutator 32 and brushes 30. and 31 at the output shaft end 34 of the motor assembly allows the lamination stack, coils and rotor of the motor to be located much closer to the exhaust fan 26 than is possible with a conventional motor layout. Four advantages flow from this arrangement-.

Firstly it allows for a relatively close fitting of the lower portions 48 of cooling air shroud 18 around the motor with an internal maximum diameter of the cylindrical lowermost portions less than the length defined between the outer ends 71 and 72 of the opposing brushes 30 and 31. Thus the outer ends of the brushes and their electrical connector terminals are able to project well beyond the confines of these lowermost portions of the shroud.

Secondly, as described above, it allows a close fit of the rim 74 of the lower opening 76 of the lowermost cylindrical portions of the cooling air shroud around the periphery of the blade flange 54 of the radial exhaust fan 26. This ensures maximum efficiency of the fan in drawing air through the shroud and the motor. Thirdly, the arrangement provides for a considerably lower overall profile of the base module, providing a more

compact base module than would be possible in a conventional motor layout with a similar power rating. The particular arrangement of the base module of the invention is capable of a power output of 1000 watts, yet has an overall height from support surface to the top of the main cover portion 12 of less than 180mm.

The combination of radial exhaust fan, the close fitting lower portion of the cooling air shroud, the open yet very rigid structure of the cast aluminium brackets, as well as the relatively open central structure of the drive motor, all provide significantly improved cooling of the motor compared with known blender motors of the same size. This provides a significant increase in rated wattage output power for a given size of motor. Fourthly, cooling fans are a major contributing factor to the noise level of blenders. Because of the improvement in cooling air flow efficiency provided by the arrangement of the present invention, there is a significant reduction in the decibel level of the present base module which has a noise level of under 85dB at a distance of 0.5m at its maximum speed setting.

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.