DEVICE FOR AN ELECTRIC MOTOR

Abstract: This invention relates to a device for an electric motor comprising a stator (10) with at least one stator winding (11), a rotor (14) with a commutator (18) and rotor windings (17) and at least one brush (21) which is pressed against the commutator the brush being slidably arranged in a brush holder (19) and being in electrical conducting connection with the stator winding (11). The electric motor also comprises a thermic motor protector (25) protecting the motor against overheating the motor protector (25) being arranged between the stator winding (11) and the brush (21) such that the stator winding is connected to a resilient element (12) pressing the motor protector (25) against the sleeve (20).

Description: Device for an electric motor This invention relates to a device for an electric motor comprising a stator with at least one stator winding, a rotor with a commutator and rotor windings and at least one brush which is pressed against the commutator the brush being slidably arranged in a brush holder and being in electrical connection with the stator winding the electric motor comprising a thermic motor protector protecting the motor against overheating. Electric motors provided with thermic motor protectors are previously known. The motor protectors are usually designed such that a heat sensitive element for instance a bimetallic spring switches off an electric circuit when the motor protector is heated which means that the current supply to the motor ceases. The motor protector is placed at a suitable place within or on the electric motor which means that it is neccessary to draw connecting electric conductors to this place. These installations complicate assembly and makes the motor more expensive. The purpose of this invention is to achieve an arrangemant decreasing the need for material and said need for conductor installation and which simplifies assembly. This is achieved by means of a device having the characteristics mentioned in the claims. An embodiment of the invention will now be described with reference to the accompanying drawing which shows a vertical section through an electric motor according to the invention. The electric motor comprises a stator 10 having at least one stator winding 11 with one end connected to a spring 12 which is fastened to a spring holder 13. The electric motor further comprises a rotor 14 supported by ball bearings 15 in a motor housning 16. The rotor in a conventional way is provided with rotor windings 17 which are connected to the commutator 18 of the rotor. The motor housing has a brush holder 19 of electrically insulated material, for instance plastic, the brush holder enclosing a sleeve 20 of electrically conducting material, for instance brass, which encloses a carbon brush 21 or the like. The sleeve 20 is fixed in the brush holder 19 whereas the brush 21 is slidably arranged in the sleeve 20 and is pressed against the commutator by means of a spring 22 which is inserted between the brush 21 and a folded end part 23 of the sleeve 20. The brush holder 19 is provided with a recess or a pocket 24 which is placed between the spring 12 and the sleeve 20 the pocket enclosing a motor protector 25 such that one side of the motor protector which is one of the contact means for the switch in the motor protector abuts the sleeve 20 whereas its other side, which is the other contact means, is connected to the spring 12. In order to safeguard a good electric contact between the motor protector 25 and the sleeve 20 the sleeve is provided with one or several embossings 26 extending towards the motor protector. This means that the motor protector 25 is arranged in the electric connection between the stator winding 11 and the brush 21. Thus, the arrangement shown has the advantage that the motor protector is very easy to assemble and to dismount since it is removably arranged in the pocket and is solely kept in position by the spring 12. It should also be mentioned that the spring 12a has such a shape and length that it abuts the sleeve 20 if a motor protector is not mounted in the pocket (see 12a in the figure).

Claims: Claims 1. Device for an electric motor comprising a stator (10) with at least one stator winding (11), a rotor (14) with a commutator (18) and rotor windings (17) and at least one brush (21) which is pressed against the commutator the brush being slidably arranged in a brush holder (19) comprising a metallic sleeve (20) or the like which at least partly surrounds the brush (21 ) and being in electrically conducting connection with the stator winding ( 11 ) the electric motor comprising a thermic motor protector (25) protecting the motor against overheating characterized in that the motor protector (25) is arranged between the stator winding (11) and the brush (21) such that the stator winding is connected to a resilient element (12) pressing the motor protector (25) against the sleeve (20). 2. Device according to claim 1 characterized in that the brush holder (19) is provided with a a recess or pocket (24) in which the motor protector (25) is placed. 3. Device according to claim 2 characterized in that the motor protector (25) has two opposite sides which are contact means for a switch arranged in the motor protector one side abutting the sleeve (20) when the motor protector being placed in the pocket whereas the other side is in engagement with the resilient element (12). 4. Device according to claim 2 or 3 characterized in that the resilient element (12) has such a shape and length that it abuts the sleeve (20) if a motor protector is missing in the pocket. 5. Device according to any of claims 2-4 characterized in that the sleeve (20) is provided with one or several extending contact areas (26) intended to abut the motor protector (25). 6. Device according to any of the preceding claims characterized in that the motor protector (25) is removably secured between the stator winding (11) and the sleeve (20). 7. Device according to any of the preceding claims characterized in that the brush holder (19) is made of electrically insulated material such as plastic.

Inventors: CARLSSON STEFAN, CARLSSON, STEFAN
Applicants: CARLSSON STEFAN, ELECTROLUX AB, AKTIEBOLAGET ELECTROLUX, CARLSSON, STEFAN
Application year: 2001
Main classification: H02K11
IPC codes: H02K11, H02K23