GB2069774A

GB2069774A - Rotary electric coupling

Info

Publication number: GB2069774A
Application number: GB8104007A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-02-20
Filing date: 1981-02-10
Publication date: 1981-08-26

Abstract

A stator (3) is fitted to an appliance and carries a rotor (17) via ball bearings (14). The inner races (15) of the bearings are electrically connected to a supply cable (31) via pins (21) which fit into sockets (20) in the rotor. The outer races (13) of the bearings are electrically connected to a supply cable (25) leading to the appliance motor. An electrical path is therefore provided from the cable (31) to the cable (25) via the balls of the bearings (14) and the cable (31) is free to rotate with the rotor (17) relatively to the stator and to the appliance during manipulation of the appliance in use. <IMAGE>

Description

SPECIFICATION Rotary electrical coupling The invention relates to an electrical coupling between two relatively rotatable members. Such couplings normally involve electrically conducting brushes or spring contacts which are carried by one of the members and wipe over an annular contact area on the other member. separate bearings are provided for supporting the two members so that they are relatively rotatable.

Such couplings are used in a wide variety of applications, for example between a trailing cable and a movable electrical appliance, to prevent twisting of the cable when the appliance is manipulated in use.

Another application is in the transmission of electrical energy to orfrom a rotor, such as a rotary shaft, in an electrical machine.

In accordance with the present invention, a rotatable electrical coupling between two members comprises at least one bearing with one race attached to one member, a second race attached to the other member, and rolling elements interposed between the races, the races and elements being made of electrically conducting material; one conductor which is non-rotatable relativelyto the one member and electrically connected to the one race; and a second conductor which is non-rotatable relatively to the other member and electrically connected to the second race; whereby the two members are supported for relative rotation by the bearing and an electrical path exists through the bearing from the one conductor to the second conductor.

This provides a very compact construction as the electrical path is through the bearing itself.

The rolling elements may be rollers or balls and the bearing may be an axial thrust bearing in which the races face one another axially, or radial bearings in which the outer races surround the inner races. In either case, when the bearing is under load in use, there will always be at least one of the rolling elements in hard contact with both races to provide a low resistance path between the races.

In a typical application, there will be two or more of the bearings, for example three bearings when three electrical paths for live, neutral, and earth are required. The type of electrical supply is comparatively irrelevant, and may be for example single or three phase AC or DC.

An example of a coupling constructed in accordance with the invention is illustrated in the accompanying drawings, in which: Figure 1 is an exploded side elevation with most parts in axial section; and, Figure 2 is an end elevation of a plug part of the coupling, as seen in the direction of arrow A.

The illustrated coupling is intended to be used for the supply of electrical power to a movable appliance, such as a vacuum cleaner or polisher. A hollow stator 3 is divided by a partition wall 4 into compartments 5 and 6. The stator 3 is enclosed within a cylindrical sleeve 7 which, like the stator 3, is made of the insulating material. The sleeve 7 and the cylindrical part of the stator 3, including the partition wall 4, are divided at a diametrical plane 8 and the stator 3 and sleeve 7 are divided from an end wall 9 of the stator at a breakline 10 which enables the lower half of the stator 3 and sleeve 7, to be separated downwards from the upper half of these parts and from the end wall 9 to provide access to the interior of the compartments 5 and 6. The two halves are held together by recessed screws which are not shown.

Within the compartment 6 the stator 3 is formed with three annular grooves 11 each of which accommodates a brass strip 12, extending partway around the upper half of the stator, and an annular steel outer race 13 of a respective ball bearing 14.

A steel inner race 15 of each bearing surrounds and a press fit on to a brass ring 16 and is pressed with the ring onto a hollow rotor 17 made of electrically insulated material. The inner bearings and rings 15 and 16 are separated by insulating spacer pieces 18 and are held in position on the rotor by means of an electrically insulating nut 19 which is screwed onto a screw threaded end portion of the rotor. The rotor is thus supported by the bearings for rotation within the stator 3.

At its other end the rotor 17 is provided with three sockets 20 which are arranged to receive conducting pins 21 carried by a plug 22 made of electrically insulating material. The plug can be held in secure engagement with the rotor, with the pins 21 in the sockets 20 by means of a grub screw 23 which screws into complementary sockets 24 in the rotor.

In use the stator 3 is fitted to a domestic appliance with a three core supply cable 25 to a motor of the appliance having one end entering the compartment 5 via a compression gland 26. The three cores 27 of the cable lead through the sleeve 7 to respective ones of the contact strips 12 to which they are electrically connected. The live core may be coupled through a fuse 28. Three insulated conductors 29 lead one from each of the brass rings 16 through the hollow interior of the rotor to respective contact terminals 30 which are shown diagrammatically within the sockets 20. Athree core electrical supply cable 31, connected at its remote end to an electrical supply, feeds into the plug 22 via a compression gland 32 and each core of the cable is connected electrically to a different one of the pins 21.

It is thus clear that when the plug 22 is fitted into the end of the rotor 17, three electrical paths are provided from a core in the cable 31, through a respective pin 21, contact terminal 30, conductor 29, brass ring 16, inner race 15, ball, outer race 13, contact strip 12, and core 27 to a corresponding core in the cable 25. Upon manipulation of the device rela timely to the cable 31, the drag of the cable will appropriately cause the rotor 17 to rotate relatively to the stator 3 without interferring with the electrical supply to the cable 25 and appliance motor.

It will be apparent that the illustrated example could be modified by extending the rotor 17 to the left in Figure 1 so that it forms the shaft along which the conductors 29 extend.

1. A rotatable electrical coupling between two members, the coupling comprising at least one bear

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Rotary electrical coupling The invention relates to an electrical coupling between two relatively rotatable members. Such couplings normally involve electrically conducting brushes or spring contacts which are carried by one of the members and wipe over an annular contact area on the other member. separate bearings are provided for supporting the two members so that they are relatively rotatable. Such couplings are used in a wide variety of applications, for example between a trailing cable and a movable electrical appliance, to prevent twisting of the cable when the appliance is manipulated in use. Another application is in the transmission of electrical energy to orfrom a rotor, such as a rotary shaft, in an electrical machine. In accordance with the present invention, a rotatable electrical coupling between two members comprises at least one bearing with one race attached to one member, a second race attached to the other member, and rolling elements interposed between the races, the races and elements being made of electrically conducting material; one conductor which is non-rotatable relativelyto the one member and electrically connected to the one race; and a second conductor which is non-rotatable relatively to the other member and electrically connected to the second race; whereby the two members are supported for relative rotation by the bearing and an electrical path exists through the bearing from the one conductor to the second conductor. This provides a very compact construction as the electrical path is through the bearing itself. The rolling elements may be rollers or balls and the bearing may be an axial thrust bearing in which the races face one another axially, or radial bearings in which the outer races surround the inner races. In either case, when the bearing is under load in use, there will always be at least one of the rolling elements in hard contact with both races to provide a low resistance path between the races. In a typical application, there will be two or more of the bearings, for example three bearings when three electrical paths for live, neutral, and earth are required. The type of electrical supply is comparatively irrelevant, and may be for example single or three phase AC or DC. An example of a coupling constructed in accordance with the invention is illustrated in the accompanying drawings, in which: Figure 1 is an exploded side elevation with most parts in axial section; and, Figure 2 is an end elevation of a plug part of the coupling, as seen in the direction of arrow A. The illustrated coupling is intended to be used for the supply of electrical power to a movable appliance, such as a vacuum cleaner or polisher. A hollow stator 3 is divided by a partition wall 4 into compartments 5 and 6. The stator 3 is enclosed within a cylindrical sleeve 7 which, like the stator 3, is made of the insulating material. The sleeve 7 and the cylindrical part of the stator 3, including the partition wall 4, are divided at a diametrical plane 8 and the stator 3 and sleeve 7 are divided from an end wall 9 of the stator at a breakline 10 which enables the lower half of the stator 3 and sleeve 7, to be separated downwards from the upper half of these parts and from the end wall 9 to provide access to the interior of the compartments 5 and 6. The two halves are held together by recessed screws which are not shown. Within the compartment 6 the stator 3 is formed with three annular grooves 11 each of which accommodates a brass strip 12, extending partway around the upper half of the stator, and an annular steel outer race 13 of a respective ball bearing 14. A steel inner race 15 of each bearing surrounds and a press fit on to a brass ring 16 and is pressed with the ring onto a hollow rotor 17 made of electrically insulated material. The inner bearings and rings 15 and 16 are separated by insulating spacer pieces 18 and are held in position on the rotor by means of an electrically insulating nut 19 which is screwed onto a screw threaded end portion of the rotor. The rotor is thus supported by the bearings for rotation within the stator 3. At its other end the rotor 17 is provided with three sockets 20 which are arranged to receive conducting pins 21 carried by a plug 22 made of electrically insulating material. The plug can be held in secure engagement with the rotor, with the pins 21 in the sockets 20 by means of a grub screw 23 which screws into complementary sockets 24 in the rotor. In use the stator 3 is fitted to a domestic appliance with a three core supply cable 25 to a motor of the appliance having one end entering the compartment 5 via a compression gland 26. The three cores 27 of the cable lead through the sleeve 7 to respective ones of the contact strips 12 to which they are electrically connected. The live core may be coupled through a fuse 28. Three insulated conductors 29 lead one from each of the brass rings 16 through the hollow interior of the rotor to respective contact terminals 30 which are shown diagrammatically within the sockets 20. Athree core electrical supply cable 31, connected at its remote end to an electrical supply, feeds into the plug 22 via a compression gland 32 and each core of the cable is connected electrically to a different one of the pins 21. It is thus clear that when the plug 22 is fitted into the end of the rotor 17, three electrical paths are provided from a core in the cable 31, through a respective pin 21, contact terminal 30, conductor 29, brass ring 16, inner race 15, ball, outer race 13, contact strip 12, and core 27 to a corresponding core in the cable 25. Upon manipulation of the device rela timely to the cable 31, the drag of the cable will appropriately cause the rotor 17 to rotate relatively to the stator 3 without interferring with the electrical supply to the cable 25 and appliance motor. It will be apparent that the illustrated example could be modified by extending the rotor 17 to the left in Figure 1 so that it forms the shaft along which the conductors 29 extend. CLAIMS

1. A rotatable electrical coupling between two members, the coupling comprising at least one bear ing with one race attached to one member, a second race attached to the other member, and rolling elements interposed between the races, the races and elements being made of electically conducting material; one conductor which is non-rotatable relatively to the one member and electrically connected to the one race; and a second conductor which is nonrotatable relatively to the other member and electrically connected to the second race; whereby the two members are supported for relative rotation by the bearing and an electrical path exists through the bearing from the one conductor to the second conductor.

2. A coupling according to claim 1, in which the or each bearing is a radial bearing with the outer race surrounding the inner race.

3. A coupling according to claim 2, in which there are two or more of the bearings, the inner races of the bearings being fitted onto one of the members and separated by at least one insulating spacer piece.

4. A coupling according to any one of the preceding claims, in which one of the members incorporates a plug orsocketwith at least one contact connected to a respective one of the conductors, and there is a complementary socket or plug having at least one contact connected to a conductor in a traiiing lead.

5. A coupling according to claim 1, substantially as described with reference to the accompanying drawings.