IE43174L

IE43174L - A motor having permanent magnet field magnets

Info

Publication number: IE43174L
Application number: IE761967A
Authority: IE
Original assignee: Thomson Brandt
Priority date: 1975-09-05
Filing date: 1976-09-03
Publication date: 1977-03-05
Also published as: FI762517A; NO141625C; CH597710A5; GR61613B; YU209976A; DK144228C; GB1549876A; AT346416B; DE2639779A1; IT1063654B; DK399276A; NO141625B; NL7609756A; SE7609761L; ATA655576A; NO763036L; ES451174A1; IE43174B1; LU75709A1; DK144228B

Description

4 317 4 The present invention relates to motors having permanent magnet field magnets.

Electric motors are frequently provided with a magnetic frame which supports the working members made 5 of magnetic material such as the pole pieces, field ina<)nel:;, <-tc. The motors ..uiy - frame with a metal cover termed an end-shield which includes a bearing for the armature shaft.

In the prior art, the pole pieces or permanent 10 magnet field magnets, which are formed e.g. by ferrite slabs, art; generally held in position on the frame by bonding with Araldite ( Trade Mark) or some other substance. To position and attach the end-shields on the framef systems of nuts and bolts or bonding means 15 are generally used.

The means mentioned above for holding the various component parts in place on the frame have proved to be costly and complicated and time-consuming. In addition, when nuts and bolts are used, it is not possible to 20 dismantle the motor quickly while the use of bonding means makes it difficult to dismantle the motor at all.

The present invention has as an object substantially to reduce or overcome the above disadvantages. 43174 Accordingly the invention consists in an electric motor having a hollow stator frame provided with end shields and with internal permanent magnet field magnets, and further comprising attachment devices for attaching 5 said end shields and field magnets to said frame, said attachment devices extending through holes in said frame and each having one* end which engages and presses one of the end shields against one end of said frame, and another end which presses one of said field magnets 10 against the interior of said frame.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a dlagrammatic perspective view of part 15 of an embodiment of m electric motor according to the invention, having permanent magnet field magnets. For reasons of clarity, the rotor of the motor and its associated components are not shown, and Fig. 2 is a schematic view, in longitudinal 20 section along A-A' oi: Fig 1, of part of an electric motor according to the invention naving permanent magnet field magnets.

The motor in Fig. 1 is a D.C. motor which has a hollow frame 1 of magnetic material which has permanent 25 magnet field magnets 2 mounted against its inside face. The magnets 2, in tho embodiment being described, are formed by ferrite slabs. At either end the frame is provided with an end-shield, one of which is shown at 3 in Fig. 1. The end-shield 3 has a groove defining 30 annular flange 4 which defines a plurality of spaced grooves around its circumference, one of which is shown at 8, and which are intended to provide a firm seating for the outer portio; 9 of a device 5 for attaching and positioning both the end-shield 3 and the permanent 35 field magnets 2 on o: against, the .said frame 1. The attachment and positioning device 5, which is shown in the form of a clip, is formed by a steel wire whose elasticity is such as to allow it to act as a spring.

Clip 5, whose shape is substantially that of a U, has a plurality of portions, namely the portion 9 which represents the base of the U, and portions 6 which represent the ends of the sides of the U. The shape of the portion 9 corresponds to or is identical with the shape of the respective groove 8 in the end-shield. The portions 6 and the portion 9 are connected by linking portions 10, which are parallel in the embodiment being described and which represent the sides of the U. The function of the clip is to hold the end-shield 3 rigidly in position on the end of the frame 1 by means of its portion 9 and to attach the permanent field magnets 2 riyidly against the frame 1 by means of its portions 6.

To attach the end-shield 3 Lo the frame I, portion 9 of the clip engages elastically in the groove 8 of slightly larger dimensions which is formed in the flange 4, and to hold the magnets 2 in place, the portions 6 of the clip, which pass through holes 11 in the frame 1, fit into respective recesses 7 in the field magnets 2. The number of grooves 8 is equal to the number of clips. The clips thus form a means of positioning or angularly locating the end-shield 3.

The shape of the clip 5 enables pressure effects to be obtained from its outer portion 9 and its portions 6 to press the end-shield 3 and the field magnets 2 against the said frame 1, the pressures being represented by vectors P and P' in Figure 2.

Irrespective of the elastic characteristics of the material forming the clip 5, its overa]1 elastic action is produced, in particular, by bends formed in the clip which are shown at C, D, E, F, ir. Figure 2.

In the embodiment described, qiven that the motor 4 317 4 has two field magnets, the clips 5, which are two in number {at each end of the motor) and one of which is shown in Figs. 1 and 2, are symmetrical about the axis of symmetry of the motor and consequently about the 5 axis of symmetry of the frame.

The clips which form the attachment and positioning means perform two functions namely, attaching and positioning the end shields on the one hand, and on the other hand the permanent field magnets on or to the 10 frame 1.

They also make it possible to reduce assembly time, by allowing the whole operation to be performed at the same time, which makes a considerable saving. 43174

Claims

CLAIMS:-

1. An electric motor having a hollow stator frame provided with end shields and with internal permanent magnet field magnets, and further comprising attachment 5 devices for attaching said end shields and field magnets to said frame, said attachment devices extending through holes in said frame and each having one end which engages and presses one of the end shields against one end of said frame, and another end which presses one of 10 said field magnets against the interior of said frame.

2. A motor as claimed in claim 1, wherein each end shield has an annular groove-defining flange to receive the ends of the attachment devices associated therewith. 15

3. A motor as claimed in claim 1 or claim 2, wherein the field magnets have recesses for receiving the ends of the said attachment devices associated therewith .

4. A motor as claimed in any one of the preceding 20 claims, wherein each attachment device comprises a wire folded into the general shape of a U, the base of the U forming said end of the device which engages one end shield, and the arms of the U having end portions which press against the associated field magnet. 25

5. An electric motor substantially as hereinbefore described with reference to the accompanying drawings. F. R. KELLY £ CO. AGENTS FOR THE APPLICANTS.