GB2203294A - Terminal in an electric motor - Google Patents

Abstract

A terminal 22 riveted to a brushleaf 18 of an electric motor provides for selectively either the dry connection of a terminal or a plain end of a wire lead from a power supply, or a touch connection. A resilient, bifurcated strip portion 27 of the terminal 22 projects within a recess 31 in the motor end cap. A terminal may be inserted through the opening 34 of the recess 31 (arrow A) to be squeezed between strip portion 27 and an opposing wall of a U-shaped part of terminal 22, or a tinned wire lead may be hooked into a slot 32 of the bifurcated portion 27. An aperture 33 extends from a bottom wall of the recess 31 through to the end face of the end cap to allow the terminal or wire end to be inserted alternatively from that direction (arrow B). A portion 23 of the terminal 22 is exposed on the side of the end cap to allow for a touch connection. Opposed L-shaped ribs 38 on the end cap 1 may anchor the supply leads. In an alternative embodiment, (Figs 5 to 9), the power supply terminal can only be inserted from the side of the motor to be gripped between a resilient, corrugated side arm (77) and an outer side of one arm of a U-shaped part of the terminal (74) on the brushleaf (70), an outer side of the base of that U-shaped part forming the touch contact (75). A brush gear carrier (57), (Fig 7), fits onto a pin (60) of a body (56) of an end cap assembly (55). <IMAGE>

Description

TERMINAL IN AN ELECTRIC MOTOR The present invention relates to the provision of a terminal in a fractional horsepower electric motor, in particular in a permanent magnet DC motor.

Typically, a terminal for connection of a power supply to an electric motor comprises a tag extending outside the motor, the tag may be received in a female terminal on the end of a supply lead or the supply lead may be soldered on the tag to electrically connect the lead and the tag. The tag itself is electrically connected to brushgear in the motor.

The present invention provides a fractional horsepower motor having a housing, a rotor comprising an armature and a commutator mounted in the housing, and brushgear mounted in the housing, wherein connection means is provided for electrical connection of a power supply to brushleaves of said brushgear, said connection means comprising a conducting metal strip, said strip having a first portion extending over an outside surface of said housing for forming a touch contact with said power supply, and a second portion housed within a recess in said housing and arranged to contact a terminal of a power supply when inserted in said recess.

The connection means greatly facilitates the connection of supply leads to the motor brushgear.

The connections may be arranged so that the supply lead may be inserted from the side of the motor or from an end of the motor. Also the arrangement may allow for a suppression element to be connected across the motor brushgear by utilising the connections not used for the supply leads.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is an enlarged perspective view of an end cap of a fractional horsepower PMDC motor according to a first embodiment of the invention; Figure 2 is an exploded perspective view, partly cut away, of a casing and motor assembly for use with the end cap of Figure 1; Figure 3 is an exploded, enlarged perspective view of part of the end cap of Figure 1; Figure 4 shows a tinned wire lead electric motor forming a second embodiment of the invention; Figure 5 is a side view of a second embodiment of the invention; Figure 6 is a plan view partly cut away of the inside of an end cap the embodiment of Figure 5; Figure 7 is a cross-sectional view on line VII-VII of Figure 6; Figure 8 is an underneath plan view of a brush holder and brushgear of the embodiment of Figure 5; and Figure 9 is a plan view of a brushleaf and terminal of the embodiment of Figure 5.

Referring to figures 1 to 4, a motor according to the invention comprises an end cap 1 of plastics material, the end cap carrying brushgear designated generally by the reference numeral 2. The motor further comprises a can-like steel casing 3 carrying two opposed permanent magnets 4, and a rotor which is journalled in bearings 5, 6 in the end cap 1 and casing 3 respectively. The rotor comprises a shaft 11 carrying a laminated armature 7 having coils 8 wound on arms of the armature. Coils 8 are connected to segments 9 of a commutator 10 on the shaft 11 which is received in the bearings 5, 6.

The end cap 1 closes the open end 12 of the casing 3 and is attached to the casing by lugs (not shown) which are pressed from the casing sidewalls 14 into recesses 15 in sides 16 of the end cap 1. A guide rim 17 is formed on the inner face of the end cap and fits within the open end 12 of the casing 3 to position the end cap 1 securely on the casing 3.

The brush gear 2 comprises a pair of resilient brushleaves 18, each carrying a brush 19. The brushes 19 are mounted in apertures formed in ends of the brushleaves 18 as is well known in the art.

Opposite ends 21 of the brushleaves are mounted in a sidewall 20 of the end cap 1. The brushleaves 18 are formed of resilient, electrically conducting copper based alloy. The brushes 18 may be discrete carbon blocks, as shown, or may be formed by the brushleaves 18. In the latter case, a precious metal alloy is deposited on the brushleaf in the region where it contacts the commutator.

The brushleaves 18 are shaped to urge the brushes 19 onto the commutator 10 in the assembled motor.

The general motor construction thus far described is well known in the art and embodied with variations in many commercially available fractional horsepower PMDC motors.

The improvement provided by the present invention resides in the provision of a novel terminal construction 22 at the end 21 of the brushleaves.

As best seen by reference to Figure 3, the terminal portion 22 is formed by a conducting metal strip which is riveted by a rivet 39 to the brushleaf 18 to form an electrical contact therewith. The terminal is bent substantially at a right angle to form a first, contact portion 23, and then bent again substantially at a right angle to form a second, U-shaped portion 24, a first arm 25 of the U being connected at its outer end to the contact portion 23, and a second arm 26 of the U-shape being bent at its end to form a reentrant metal strip portion 27 which projects into the volume of the U-shape. The strip portion 27 is bifurcated, forming a tapering slot 32 (see the inset of Figure 3).

The terminal portion 22 fits into the side wall 20 of the end cap 1. A slot 28 extends across the width of the side wall and receives the brushleaf portion 21 and the end of the brushleaf 18 in the region of the rivet 39. The contact portion 23 is received in a shallow recess 29 in the outer face 30 of the side wall 20, so that the contact portion 23 is flush with the surface of the side wall 20. The U-shaped portion is received in a recess 31 in the side wall.

The recess 31 has an opening 34 at the outer face 30 of the side wall to allow a terminal or wire to be inserted into the recess from the side (arrow A).

The terminal portion 22 is held in the side wall by nibs 35 the terminal riding past the nibs so it is pressed down into the slot 28 and recess 31. The ribs 31 serve to keep the terminal portion 22 away from the casing end 12 when the end cap is attached to the casing 3.

Formed in the base 32 of the recess 31 is an elongate aperture 33 which extends through the remaining depth of the side wall 20.

To assemble the motor, the magnets 4 and the rotor are installed in the casing 3 with bearing 6. The brushleaves 18 are bent to shape and brushes 19 attached. The brushleaves 18 are inserted in the slots 28 and recesses 31 and the end cap attached to the casing 3.

A terminal of a supply lead may be connected to a brush leaf 18 from one of two directions. It may be inserted from the side of the motor into recess 32 through the opening 34 (arrow A), or from the end of the motor through the aperture 33 (arrow B). From either direction the terminal displaces the resilient strip portion 27 and so is squeezed between the strip portion 27 and the opposite arm 25 of the U-shape portion 24.

A wire lead 37 may be connected to the terminal portion by first tinning the lead with solder to form a slight blob 36 on the end of the lead. The end of the lead is then hooked into the slot 32, being fed through opening 34. The lead is pulled back slightly to trap the lead in the closed end of the slot 32, the solder blob preventing the lead from being pulled out of the slot. The lead may also be fed through the aperture 33. To facilitate attachment to the strip portion 27 the arms of the bifurcated end may be bent slightly out of plane and the slot may slope towards the aperture 33.

An anchor 37 comprising two oppositely facing L-shaped nibs 38 may be provided on the end cap 1 to hold the lead in place.

Figures 5 to 9 show a second embodiment of the invention.

In this embodiment an electric motor 51 has a housing comprising a casing 52 and an end cap assembly 53 as seen in Figure 57. The end cap assembly 53 and casing 52 carry bearings 54, 55 supporting an armature, as described in connection with Figures 1 to 4.

The end cap assembly 53 comprises a body 56 and a brushgear carrier 57. The brushgear carrier 56 carries brushgear 59 and is mounted on a pin 60 in the end cap, the carrier 56 having an aperture 61 which receives the pin 60, as seen in Figure 6 and 7.

The brushgear comprises a pair of brush assemblies 69, one of which is illustrated in side view in Figure 9. A brushleaf 70 carries a brush 71 at one end and is rivetted at its other end 72 to end 73 of a terminal 74. Terminal 74 is similar to terminal 22 of Figures 1 and 3 and comprises a first touch contact portion 75 and a second, U-shaped portion 76. U-shaped portion 76 has a side arm 77 which is corrugated and has a reinforcing rib 78.

Figure 8 shows the underside of the brush holder 57 which is hidden in Figure 6. The brushleafs 70 are shown in their relaxed position, whereas in Figure 6 they are shown spaced apart to receive a commutator.

The brush holder 57 comprises a plastics body 62 having a through aperture 61 for receiving pin 60 as described previously. Two slots 63 extend from an inner wall 64 to an outer wall 65 of the motor and each receive a brush assembly 69, the slot housing the rivet connection between the brushleaf 70 and terminal 75. The outer wall 65 is recessed, the touch contact portions 75 sitting in the recess.

U-shaped portions 75 are each received in a recess 66 in the body 62, between sidewalls 67, 68 thereof.

The recesses 66 have a narrow opening 79 for insertion of a terminal (not shown) of a power supply lead. A terminal inserted through opening 79 into the U-shaped portion 75 will resiliently deform the corrugated sidewall 78 and be gripped in the recess by the U-shaped portion.

The brush assemblies 69 are mounted in the holder 57 by sliding them downwards into the slot 63 and recess 66. The holder 57 is then attached to the end cap body 56 by pushing it onto pin 60.

The holder 57 has two integrally formed upstanding pins 80 which cooperate with a rim 81 to locate the end cap assembly in the casing 52.

Various modifications may be made to the described embodiments and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims (11)

1. A fractional horsepower motor having a housing, a rotor comprising an armature and a commutator mounted in the housing, and brushgear mounted in the housing, wherein connection means is provided for electrical connection of a power supply to brushleaves of said brushgear, said connection means comprising a conducting metal strip, said strip having a first portion extending over an outside surface of said housing for forming a touch contact with said power supply, and a second portion housed within a recess in said housing and arranged to contact a terminal and/or lead of a power supply when inserted in said recess.

2. A motor as claimed in claim 1, wherein the second metal strip portion bears resiliently against the terminal to secure it in the recess.

3. A motor as claimed in claim 1 or 2, wherein the second metal strip portion is generally U-shaped and the terminal is received in the U-shape.

4. A motor as claimed in claim 2 or 3, wherein the second metal strip portion has a free end which projects into the volume of the recess and is resiliently displaced by a terminal inserted in the recess.

5. A motor as claimed in claim 2 wherein the first conducting metal strip portion comprises a U-shaped portion, an end of an arm of the U-shaped portion being connected to the brushleaf, and a contacting portion extending from an end of the other arm of the U-shaped portion into the region bounded by the U-shape, the contacting portion being resiliently displaced by a terminal inserted in the recess.

6. A motor as claimed in any one of claims 1 to 5 wherein an aperture or slot is provided in the conducting metal strip for receiving and gripping a wire power supply lead.

7. A motor as claimed in claim 6, wherein a slot is provided, the slot being tapered towards one end thereof so that a tinned lead may be drawn into the slot to be gripped thereby.

8. A motor as claimed in claim 7, wherein anchoring means is provided on the housing for anchoring a said lead to the housing.

9. A motor as claimed in any one of claims 1 to 8, wherein said recess has a first opening at a side of the motor for -receiving a terminal or wire lead and a second opening at an end of the motor for receiving a terminal or wire lead.

10. A motor as claimed in any one of claims 1 to 9, wherein the brushleaves and terminal portions are mounted on an end cap of the motor housing.

11. A motor as claimed in claim 10, wherein the brushleaves and terminal portions are mounted on a holder which is mounted on the end cap.