GB2222491A

GB2222491A - Electric motor with modified bearing support for use in a food mixer

Info

Publication number: GB2222491A
Application number: GB8918624A
Authority: GB
Inventors: Kam Shing Mok; Chi Nung Wong
Original assignee: Johnson Electric SA
Current assignee: Johnson Electric SA
Priority date: 1988-08-31
Filing date: 1989-08-15
Publication date: 1990-03-07
Also published as: DE8910433U1; GB8820527D0; GB8918624D0; JPH0272657U

Abstract

For driving food mixer implement holders 35, a standard PMDC motor 1 is modified by omitting the standard shaft bearing the motor casing end, and an extension frame 22 incorporating a shaft bearing housing 21 is attached to the motor. The extension frame 22 may incorporate reduction gearing. <IMAGE>

Description

ELECTRIC MOTOR WITH MIXER IMPLEMENT HOLDER This invention relates to electric motors to be used for driving the implements or tools of a food mixer, food processor or the like.

Such appliances are commonly driven by AC motors, through reduction gearing.

There is a need for DC drives for such appliances, for use in rechargeable appliances, on board ships and vehicles, and so on.

In recent years, permanent magnet direct current (PMDC) motors have become widely used. Such motors commonly have the motor mechanism enclosed within a casing shaped like a pot or can. The motor shaft projects through a bearing mounted in the closed end of this casing.

It has proved difficult to adapt such motors for driving mixers and the like. The conventional reduction gearing used incorporates a shaft bearing. If such reduction gearing is driven from a conventional PMDC motor, the combination then has three shaft bearings in line, namely the two motor bearings, and the bearing incorporated in the reduction gearing. It is extremely difficult 'to achieve satisfactory alignment of three bearings in line, particularly in low-cost equipment.

It is an object of the present invention, to provide a simple adaptation of a PMDC motor which eliminates this difficulty.

According to the present invention, in an electric motor provided with a pot-shaped or can-shaped casing, the motor shaft extends through the end of the casing without contact, and an extension frame or bracket is attached to the said end of the casing, incorporates a shaft bearing or bearing housing spaced from the casing end, and incorporates or is adapted to be attached to an implement holder or holders to be driven by the shaft.

The invention makes it possible to connect the implement holder or holders to a standard PMDC motor with only minor modification of the standard motor construction. It is only necessary to omit the bearing, or the bearing holder, conventionally provided in the end of the motor casing, thereby leaving an aperture in the casing end large enough for the shaft to pass through it without contact.

In standard PMDC motors, this bearing holder may, depending on the size of the motor, be integral with the casing end or mounted in the casing end.

In the latter case, simply omitting the normal bearing holder will provide an ample aperture for the motor shaft. In the former case, it may be desirable to cut away the region of the casing end in which the motor shaft bearing is normally seated, so as to provide ample clearance between the shaft and the casing end.

The casing end of a PMDC motor commonly has in it screw holes for mounting the motor. These screw holes can be used for attaching the extension frame or bracket.

The casing end of a PMDC motor also commonly has indentations corresponding to projections within the casing which locate components of the motor, in particular the magnet. Such indentations or other formations normally provided on the casing end, can be used to provide positional location of the bearing extension frame or bracket.

The bearing extension frame or bracket may serve ,only to support the bearing, separate means being provided for supporting the reduction gearing to drive the implements. Alternatively, the extension frame or bracket may itself support the reduction gearing and means for holding one or more implements.

The invention will be further described, by way of example only, with reference to the accompanying drawings.

In the drawings: Figure 1 shows a bearing extension frame bracket for a PMDC motor, Figure 2 shows a PMDC motor fitted with a bearing extension frame or bracket and mixer implement holders.

Figure 3 is an exploded view of the motor and frame shown in Figure 2.

Figure 1 shows the end of a PMDC motor 1. This motor is of standard commercial construction. It comprises a metal can 2 with a integral end wall 3. Within the can is a DC rotor comprising a rotor winding and a commutator on a rotor shaft co-axial with the can, and a permanent magnet structure located adjacent to the inner surface of the can.

The end wall of the can is provided with ventilation slots 4, a pair of diametrically opposite threaded screw holes 5, and a pair of diametrically- opposed indentations 6 each corresponding to a projecting stud on the internal surface of the end wall. These studs locate the permanent magnets and space them from the internal surface of the end wall.

In a conventional PMDC motor, the rotor shaft projects through the centre of the end wall, and the end wall is provided with a central bearing housing, which accommodates a bearing for the rotor shaft. This bearing housing may be a cup pressed out of and integral with the metal of the end wall, particularly in small motors.

Alternatively the bearing housing may be a separate component located in a central aperture in the casing end wall.

In accordance with the present invention, the central bearing is omitted, leaving an aperture 7 larger than the rotor shaft, so that the rotor shaft extends through the casing end wall with a clearance. To achieve the necessary radial clearance between the rotor shaft and the casing end wall, it may be sufficient to omit the bearing from a conventional motor, without omitting the conventional bearing housing. However, it will usually be desirable to enhance the radial clearance by removing or omitting the bearing housing from a standard motor casing. In the case of standard motors fitted with bearing housings as separate components, the bearing housing is simply omitted from the motor assembly procedure.In the case of standard motors with integral bearing housings, the casing production method and tooling may be slightly modified to form the casing end wall with an enlarged central aperture instead of the integral bearing housing, or a standard motor casing with a formed integral bearing housing can have the bearing housing cut out for example by punching or stamping.

In place of the bearing normally provided in the motor casing end wall, the output shaft of the motor is extended and is supported in a bearing 10 which is located in a bearing housing 11 integral with or carried by a spider or bracket 12 which is mounted on the motor casing so that its bearing housing is spaced from the end of the casing and is co-axial with it.

In the embodiment illustrated in Figure 1, this bearing bracket 12 has a central boss 13 incorporating the bearing housing, and four splayed legs 15 each ending in a radially outwardly extending foot 16 or 17.

A first pair of diametrically opposite feet 16 are provided with respective screw holes 18 corresponding in size and position to the internally threaded holes 5 in the motor casing end wall.

Each of the other pair of diametrically opposite feet 17 is provided with a projecting stud 19, corresponding in position and size to the indentations 6 in the motor casing end wall.

The bearing support bracket 12 is fitted against the motor casing end wall with its projecting pins or studs seated in the indentations 6, and it is secured by screws inserted through the holes 18 into the threaded holes 5.

,The bearing support bracket 12 in turn, carries or is attached to a transmission and drive system for driving implements of a food mixer, beater, food processor or the i like. This drive system, and holders for the implements if provided, can be of any suitable kind, including constructions already known and conventional.

By this arrangement, an essentially standard PMDC motor can be used to drive food-processing implements directly, without problems of shaft and bearing alignment which would arise if the standard bearing were retained in the motor casing end wall.

Figure 2 shows a similar PMDC motor 1 to the end wall of which has been attached a cast metal bracket 22 corresponding generally to the bracket 12 shown in Figure 1. Corresponding components of the bracket 22 are identified by reference numerals corresponding to those in Figure 1 increased by ten.

The motor output shaft 31 projects through the central aperture 7 in the motor casing end wall and through the bearing mounted in a bearing housing 21. The outer end of the motor shaft is provided with or attached to a worm gear 32.

Plates 33, 34 are attached to the bracket 22 parallel to the motor shaft and extending outwards away from the motor. Openings 36 are formed in plates 33, 34, these providing bearing surfaces for receiving a rotatable implement 38 for a food mixer on axes perpendicular to and spaced on opposite sides of the motor shaft. Each implement holder is integral or attached to a gear wheel 40 which measures with the worm gear 32 so that when the motor rotates, the mixer implement holders 35 are rotated in opposite directions.

The plate 33 is also provided with integral lugs 42 in which are holes for mounting screws to mount the assembly of motor and bracket in the food mixer or other appliance.

Claims

1. In combination, an electric motor provided with a pot-shaped or can-shaped casing, and with a motor shaft which extends through an aperture formed in an end wall of the casing without contact; and an extension frame or bracket which is attached to said end wall of the motor casing, incorporates a shaft bearing or bearing housing spaced from the casing end, and incorporates or is adapted to be attached to an implement holder or holders to be driven by the shaft.

2. The combination claimed in claim 1 in which the motor is a standard PMDC motor omitting the bearing, or the bearing holder, normally provided in the end of the motor casing.

3. The combination claimed in claim 2 in which the motor casing has screw-threaded apertures in its end wall, to which the extension frame or bracket is screwed.

4. The combination claimed in claim 2 or 3 in which the motor casing has one or more indentations corresponding to internal projections, and the extension frame or bracket is provided with locating means mating with the said indentation(s).

5. The combination claimed in any of claims 1 to 4 in which the extension is in the form of a spider having a boss forming a bearing housing and a plurality of legs extending from the boss to engage the motor casing.

6. The combination claimed in any of claims 1 to 5 in which the extension frame or bracket further includes at least one bearing housing for a said implement holder.

7. The combination claimed in any of claims 1 to 6 in which the extension frame or bracket carries reduction gearing for transmitting rotation from the motor shaft to said implement(s).

8. A motor unit comprising a pot or can-shaped casing and an armature shaft extending through the closed end of said casing, the shaft being unsupported at said closed end.

9. In combination, a motor unit as claimed in claim 8 and an extension frame or bracket attached to said end, the bracket incorporating a shaft bearing or bearing housing spaced from the casing end and incorporates or as adapted to be attached to an implement holder or holders to be driven by the shaft.

10. Mixer driving apparatus comprising a motor unit as claimed in claim 8 and transmission means for transmitting power to a mixing implement, the transmission means comprising an extension frame or bracket which is attached to the said end of the casing, incorporates a shaft bearing or bearing housing spaced from the casing end and incorporates or is adapted to be attached to an implement holder or holders to be driven by the shaft.

11. A motor unit substantially as hereinbefore described with reference to figure 1 or figure 2 and 3 of the accompanying drawings.

12. The combination of a p.m.d.c. motor and a bearing housing substantially as hereinbefore described with reference to figure 1 or figures 2 and 3 of the accompanying drawings.