Method of applying a retention ring to a disc rotor assembly

Details Method of applying a retention ring to a disc rotor assembly Method of applying a retention ring to a disc rotor assembly

1999-06-21

2001-03-06

Hall, Carl E. (Department: 3729)

Metal working

Method of mechanical manufacture

Electrical device making

C029S732000, C029S736000, C310S049540

Reexamination Certificate

active

06195869

ABSTRACT:

The present invention relates to a rotor for a rotary electrical machine such as an electrical generator or electric motor.
British Patent Specification GB 2 222 031 A describes an axial field electrical generator capable of operation at very high speeds. This document describes an axial field electrical generator having a disc rotor with a ring of permanent magnet segments equiangularly spaced around a hub. Engagement with the hub is maintained by means of a pre-stressed hoop. The hoop is formed initially as a push fit and stressed during assembly by expanding the hub by forcing into it, an oversize boss.
As a practical matter, this means of retention has severe disadvantages which have been overcome by the present invention.
Thus, a first aspect of the present invention provides a method of applying a retention ring to a disc rotor assembly comprising a plurality of substantially equiangularly spaced magnets, the method comprising expanding the retention ring by driving it over a tapered mandrel and onto a rim of the rotor assembly.
The complete rotor assembly may be used in any kind of electrical machine which utilizes a disc-type rotor, for example as described in GB 2 222 031 A or in the applicants' co-pending UK patent application No. 9123576.2 (GB 2 261 327 A). In such machines, usually a plurality of the rotors are spaced apart along a drive shaft, interspersed by thin annular stators.
Prior to fitment of the retention ring, it is preferred for the magnet to be maintained in position on a hub of the rotor by a temporary retention means, for example a temporary holding ring located over the rim of the rotor. It is also preferred to provide a second (outer) containment ring slidably located over the temporary holding ring, outside the tapered mandrel by means of push fit. When the retention ring is driven over the mandrel, the retention ring can then displace the outer containment ring so that the retention ring grips the temporary holding ring, and hence the rim of the rotor, through the mandrel by means of interference fit.
It is also convenient to support the retention ring on a slidable support means, for example a slidable support ring between itself and the tapered mandrel. The slidable support ring can then be driven over the rotor together with the retention ring so that it is trapped between the mandrel, the inner ring and the rotor itself.
After assembly, the temporary retention ring and slidable support ring can be machined smooth so that they do not obstruct the rotor in use.
The slidable support ring is preferably rested on a driver means such as a hollow driver cup partially surrounding the mandrel. Normally, the ring and driver means is acted upon by one part of a ram, for example mechanical or hydraulic, and a second part of the ram acts on the mandrel.


REFERENCES:
patent: 4759116 (1988-07-01), Jones
patent: 4918802 (1990-04-01), Schaefer
patent: 5144735 (1992-09-01), Stark
patent: 5175931 (1993-01-01), Ito
patent: 0353042 (1989-07-01), None
patent: 2632788 (1989-06-01), None
patent: 2299217 (1995-03-01), None

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