GB2246671A

GB2246671A - Terminal assembly for pmdc motor

Info

Publication number: GB2246671A
Application number: GB9016820A
Authority: GB
Inventors: Georg Strobl; Tung Sing Choi
Original assignee: Johnson Electric SA
Current assignee: Johnson Electric SA
Priority date: 1990-07-31
Filing date: 1990-07-31
Publication date: 1992-02-05
Anticipated expiration: 2010-07-31
Also published as: GB9016820D0; CN2110948U; GB2246671B; JPH0511761U; DE9109492U1; HK37595A

Abstract

An end cap 10 assembly for a d.c. fractional horsepower motor has brush leaves 11 anchored by mounting plates 12 radially separated from a central motor axis. Power supply terminals 17 are provided relatively close together, intermediate the anchor points and the motor axis to accept a supply socket (not shown) and electrically connected to the plates 12 by radial (elbow) links 18. A bearing housing 15 is fitted to the end cap 10 after the terminals and links are fitted and before the plates 12 are rivetted to the links 18. <IMAGE>

Description

Electric motor end cap The invention relates to electric motors.

The invention relates more particular to an end cap for a permanent magnet fractional horsepower motor.

The end cap is conventionally arranged to support brush gear for contacting a commutator of the motor, and is provided with power supply terminals extending externally of the end cap. The terminals are located opposite the anchoring points of the brush leafs on generally the same radius. Such a motor a fully described for example GB Patent Application 8823993.4 with reference to Figure 1 . Because the supply terminals are significantly separated from the central axis of the motor and from one another, supply sockets cannot normally be used to connect to the motor supply terminals.

t4oreover, the supply sockets required for use by various motor end users vary to some extent and there is a requirement to provide an end cap which can be adapted to accept a number of generally small but different sized supply sockets.

According to one aspect of the invention there is provided an end cap for an electric motor having a commutator mounted on a motor shaft rotatable about a central axis, brush gear for contacting the commutator having brush leaves supported by the end cap at anchor points radially separated from the central axis, a bearing for supporting one end of the shaft, and power terminals mounted in and extending axially and externally of the end cap radially separated from the central axis but closer thereto than the anchor points, in which electrically conductive links extend radially to connect between each respective terminal and a brush leaf at its anchor point, and in which the bearing is mounted in a separate housing which fits inside the end cap and at least partially over the conductive links.

Each terminal may be connected to its respective brush leaf by two radial links connected together in electrical series.

The bearing housing may have limbs which extend radially outwards and fit against an inside surface of the end cap. The limbs may be formed of plastics material and have apertures which fit over axial probes integrally formed in the end cap. The limbs may be secured to the probes by applying heat and pressure to rivet the limbs to the probes.

According to another aspect of the invention there is provided a method of preparing an end cap assembly, the assembly comprising an end cap, power terminals extending externally and axially through the end cap, a radial link extending outwards from each terminal to an anchor point for a brush leaf mounting plate and an end shaft bearing supported in a separate housing, the method comprising entering the power terminal from outside the end cap into an aperture in the end cap, fixing each terminal to an inner end of its radial link, the link resting against an inside surface of the end cap, mounting the bearing housing inside the end cap, and then fixing the brush leaf mounting plate to the outer end of the link.

The method normally comprises fixing the brush leaf to the mounting plate before fitting the plate to the link.

An end cap assembly for a permanent magnet fractional horsepower motor will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is an inside end view of the end cap with brush gear and a bearing fitted to the end cap; Figure 2 is a sectional side view of the cap assembly of Figure 1; Figure 3 is a sectional view of a power terminal and part of a bearing and bearing housing; and Figure 4 is an inside end view of the end cap.

In use, the end cap fits to a motor, such as fully described in GB Application 8823993.4, to support a bearing for one end of the motor shaft and to provide brush gear and power supply terminals for the motor.

Referring to the drawings, a plastics end cap 10 supports two brush leaves 11 at anchor points A against respective brush leaf holder plates 12. A central bearing 13 is held in a separate plastics bearing housing 14 which has three radially extending limbs 15 provided with apertures which fit over axial probes 16 integrally formed with the end cap 10.

Power terminals 17 extend axially through the end cap for external connection to a power supply adapter (not shown). The power terminals 17 are respectively electrically connected by radially extending elbow links 18 to a bent-over end of each of the plates 12. The connections between the terminals 17, the links 18 and the plates 12 are formed by rivotting, as shown clearly in Figure 4. The probes 16 are also connected by a rivoting or swaging procedure to the limbs 15.

The end cap assembly, comprising the component parts shown in Figures 1 and 2, is normally formed as follows: Each terminal l7 is fitted from externally of the end cap 10 into an aperture 20 (Figure 4) and pushed through the aperture 20. The link 18 which bears against an inside surface of the end cap 10 is then fixed (rivotted) to the terminal 18. . The bearing housing 14 is then fitted by entering the probes 16 in the apertures of the limbs 15. Heat and pressure is applied to fix the limbs to the probes 16. Each brush leaf already rivotted to its holder plate is placed in position and rivotted to the outer end of a respective link 18. Apertures 21 (Figure 4) are provided to accept a rivotting tool head. This completes the assembly and it will be noted that the housing 14 partially covers the links 18.

The assembly can also be formed by first fixing the outer end of the radial link 18 before the terminal is entered in an aperture 20 and fixed to the inner end of the radial link. In that case the brush leaf is fixed to the holder plate after the housing 14 have been fitted to the end cap 10.

It is also possible in some circumstances to form the terminal 17, the link 18, the plate 12 and the brush leaf as a sub-assembly before the terminal is fitted into and pushed through an aperture 20.

The parts l7, 18 and 12 may also be wholly or partially integrally formed.

In the arrangement described and shown in Figures 1 to 3, the brush leaf (and brush) comprises a component currently used in motors and so no especial new design or new tooling is required.

The links 18, formed as described as simple metallic (e.g. brass) elbows, can be made to have any chosen effective radial length and so the terminals 17 can be fitted at virtually any chosen radial distance from the motor axis by simply providing apertures 20 with centres appropriately spaced from that axis.

Thus, not only can the terminals 17 be arranged relatively close together to accommodate a relatively small adapter but can also be simply arranged to be displaced from one another to accept any particular power supply adapter size that a customer or end-user of the motors may require.

It will be noted that there is provision in the end cap described and shown in Figure 4, for a third terminal (there are three apertures 20). The third terminal may be required for a temperature sensor or other motor control signal supply.

Claims

1. An end cap for an electric motor having a commutator mounted on a motor shaft rotatable about a central axis, brush gear for contacting the commutator having brush leaves supported by the end cap at anchor points radially separated from the central axis, a bearing for supporting one end of the shaft, and power terminals mounted in and extending axially and externally of the end cap radially separated from the central axis but closer thereto than the anchor points, in which electrically conductive links extend radially to connect between each respective terminal and a brush leaf at its anchor point, and in which the bearing is mounted in a separate housing which fits inside the end cap and at least partially over the conductive links.

2. An end cap according to claim 1, in which each terminal is connected to its respective brush leaf by two radial links connected together in electrical series.

3. An end cap according to claim 1 or 2, in which respective connections between an end of each terminal, the links and to the anchor points of the brush leaf are all rivetted connections.

4. An end cap according to any one of claims 1 to 3, in which the housing has limbs extending radially outwards which are arranged to be fitted against an inside surface of the end cap.

5. An end cap according to claim 4, in which the limbs are formed of plastics material and have apertures which fit over axial probes integrally formed in the end cap.

6. An end cap according to claim 5 in which the limbs are secured to the probes by applying heat and pressure to rivet the limbs to the probes.

7. An end cap according to any one of claims 1 to 6, in which each power terminal is permanently connected to a respective radial limb or limbs before being fitted to the end cap.

8. An end cap according to claim 7, in which a respectively brush leaf is fitted to a respective radial link before the power terminal is fitted to the end cap.

9. A method of preparing an end cap assembly, the assembly comprising an end cap, power terminals extending externally and axially through the end cap, a radial link extending outwards from each terminal to an anchor point for a brush leaf mounting plate and an end shaft bearing supported in a separate housing, the method comprising entering the power terminal from outside the end cap into an aperture in the end cap, fixing each terminal to an inner end of its radial link, the link resting against an inside surface of the end cap, mounting the bearing housing inside the end cap, and then fixing the brush leaf mounting plate to the outer end of the link.

10. A method according to claim 9, which includes fixing the mounting plate to the outer end of the link before fixing the inner end of the link to the terminal.

11. An end cap for an electric motor substantially as herein described with reference to any one or more of Figures 1 to 4 of the accompanying drawings.

12. An electric motor having an end cap according to any one of claims 1 to 8.

13. A method of preparing an end cap assembly substantially as herein described with reference to any one or more of Figures 1 to 4 of the accompanying drawings.