GB2178507A

GB2178507A - Speed reducing mechanism

Info

Publication number: GB2178507A
Application number: GB08618338A
Authority: GB
Inventors: Dieter Haage
Original assignee: RINEFAS Ltd
Current assignee: RINEFAS Ltd
Priority date: 1985-07-29
Filing date: 1986-07-28
Publication date: 1987-02-11
Also published as: BR8603553A; GB8618338D0

Abstract

In a ceiling fan having a central drive hub 11 within which there is located an electric motor 15 including a stator 16 and rotor 17, drivingly connecting the rotor 17 and hub 11 is a speed reduction assembly 21 comprising a drive member 22 attached to the rotor, a driven member 26, and rotatable elements 25 contacting both members 22, 26. A stationary cage 24 is provided with apertures for receiving the rotatable elements 25. The elements 25 are in frictional engagement with surfaces 23 and 27 or the drive and driven members, with the diameters of said surfaces 23, 27 being different from one another. <IMAGE>

Description

SPECIFICATION Speed reducing mechanism The present invention relates to a rotary power transmission device which may be used to increase or decrease the rotational speed transmitted thereby, and more particularly but not exclusively to such devices which are employable with axial flux induction electric motors.

In the construction of ventilating machines, air pumps, and fans, particularly ceiling fans, it has been found desirable to have the blades of the fan rotate within a desired speed range.

Since this speed range does not always correspond with the rotating speed of the electric motor, it is desirable to provide a rotary power transmission device to increase the speed or decrease the speed of the blades relative to the rotor of the motor.

The use of gear mechanisms, chains or belts in order to effect the above discussed rotary power transmission, the resulting contruction would be generally complex and therefore expensive to manufacture. Still further, the complexity would generally detract from the overall life of the assembly as well as the reliability thereof.

It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a drive assembly to transmit rotary power from the rotor of an electric motor, said drive assembly comprising a drive member to be attached to said rotor so as to rotate therewith, said drive member having a generally circular drive surface coaxial with respect to the axis of said rotor, a stationary cage, a plurality of drive elements supported by said cage and each having a circular cross-section and rollingly engaged with said drive surface, a driven member rotatably supported so as to be rotatable about the axis of said motor, said driven member having a generally circular driven surface coaxial with said member and engaged by said drive elements so that upon rotation of said rotor, rotary power is transmitted to said driven member via said driven elements, and wherein the diameter of said drive surface is different to the diameter of said driven surface so that the angular velocity of said driven member is different to said drive member.

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a schematic perspective view of a ceiling fan; Figure 2 is a schematic sectioned side elevation of the drive hub of the ceiling fan of Fig. 1; Figure 3 is a schematic sectioned enlarged view of a portion of the drive hub of Fig. 2; and Figure 4 is a schematic perspective view of a cage and power transmitting portion of the drive hub of Fig. 2.

In the accompanying drawings there is schematically depicted a ceiling fan 10 having a central drive hub 11 supporting a plurality of blades 12. The hub 11 and blades 12 are supported by a shaft 13 having an upper flange 14 enabling mounting of the fan 11 on a ceiling surface. Accordingly the shaft 13 is held stationary and provides a reaction for the axial flux induction electric motor 15 located within the drive hub 11. The motor 15 may be constructed in accordance with the axial flux induction electric motor as described in U.S. Patents 450,947, 4,410,820, 4,395,815 and 4,320,645. The motor 15 has a stator 16 and a rotor 17. The rotor 17 is rotatably supported by means of a bearing 18 mounted on an axle 19 fixed to the shaft 13.

The stator 16 is attached to a flange 20 forming the lower end of the shaft 13.

The drive hub 11 provides a hollow housing encompassing the motor 15 and a rotary power transmission assembly 21. The assembly 21 transmits rotary power from the rotor 17 to the hub 11. The assembly 21 includes a drive member 22 providing a generally circular drive surface 23 which has its axis coaxial with the shaft 13 and the axle 19.

Fixed to the lower end of the axle 19 is a cage 24 providing a plurality of apertures which receive power transmitting elements 25, which in this particular embodiment are spherical elements. However it should be appreciated that other elements may be used. All that is required is that they have a circular cross section, with the circular part of the element 25 engaging the surface 23. Attached to the hub 11 is a driven member 26 having a driven surface 27 which is also circular and coaxial with the axis of the shaft 13, axle 19 and drive surface 23. The elements 25 are in frictional engagement with the surfaces 23 and 27 and accordingly as the surface 23 rotates, due to the rotation of the rotor 17, the driven member 26 is caused to rotate in the opposite direction due to rotation of the elements 25. Since the member 26 is fixed to the hub 11, the hub 11 is in turn driven thereby.

It should be appreciated that since there is a difference in the diameter of the surface 23 in comparison to the diameter of the surface 27, a speed reduction results when rotary power is transmitted from the rotor 17 to the hub 11. Accordingly it should be appreciated that the speed difference between the rotor 17 and the hub 11 is dependent upon the difference between the surfaces 23 and 27. For example, if the surface 23 had a larger diameter than the surface 27, then there would be an increase in speed.

In conventional ceiling fans, it is most com mon to employ 18 or 24 pole induction motors in order to provide the fan with the desired rotational speed (about 300 rpm). However 18 and 24 pole induction motors are generally inefficient.

The abovedescribed preferred form of the present invention enables a four pole motor to be employed, which in comparison to 18 and 24 pole motors, is far more efficient.

Claims

1. A drive assembly to transmit rotary power from the rotor of an electric motor, said drive assembly comprising a drive member to be attached to said rotor so as to rotate therewith, said drive member having a generally circular drive surface coaxial with respect to the axis of said rotor, a stationary cage, a plurality of drive elements supported by said cage and each having a circular crosssection and rollingly engaged with said drive surface, a driven member rotatably supported so as to be rotatable about the axis of said motor, said driven member having a generally circular drivens surface coaxial with said member and engaged by said drive elements so that upon rotation of said rotor, rotary power is transmitted to said driven member via said drive elements, and wherein the diameter of said drive surface is different to the diameter of said driven surface so that the angular velocity of said driven member is different to said drive member.

2. The drive assembly of claim 1 wherein said drive member is an annular member fixed to said rotor and said driven member is an annular member.

3. The drive assembly of claim 2 further including a housing to encompass said drive assembly and the motor to be attached thereto, and wherein said driven member is attached to said housing.

4. The drive assembly of claim 3 wherein said housing is adapted to drive fan blades of a ceiling fan.

5. The drive assembly of any one of claims 1 to 4 wherein said elements are spherical and are rotatably supported by said cage.

6. The drive assembly of claim 5 wherein said cage has a plurality of apertures which receive said elements so that said elements are freely rotatable relative to said cage.

7. A drive assembly substantially as described herein with reference to the accompanying drawings.

8. A ceiling fan having an axial flux induction electric motor and a drive assembly driven by said motor by said drive assembly being drivingly connected to a rotor of said motor.

9. A drive assembly to transmit rotary power from the rotor of an electric motor, substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.