ELECTRIC MOTOR BRUSH HOLDER

Abstract: A brush holder (31) for an electric motor comprising a tube member (31) which is provided with an opening at one end through which an electrode (30) slides. A compression spring (35) is held between the electrode and an abutment at the rear end of the tube. At least a pair of opposite side walls (44, 45) of the tube are generally cylindrically curved to define the area in which the compression spring is con­ tained. The cylindrically curved side walls are slit at (50, 51) at a point spaced from but adjacent the open end from which the electrode projects leaving a pair of short axial length, flat parallel walls (52, 53) adjacent the open end. The rear edges of the short walls extend across the curved tube at the front of the spring. The rear edges of the short walls furnish a stop for the spring and prevent it from being ejected from the tube. The electrode is attached to the spring at (36).

Description: Electric motor brush holder. The invention relates to a brush for an electric motor and more particularly to a holder for the brush. The electrode or contact of the brush of an electric motor is installed in a holder. The holder containing the electrode may be inserted in an appropriate positioning device in the housing of an electric motor and may be removed therefrom for replacement. The electrode comprises a contact member which is preferably of a carbon type. It has a profiled and usually rectangular cross-section. It is sufficiently elongated to continuously present a contacting surface to the commutator on the armature as the elongated carbon contact memb'er'5wCears. The elongated carbon contact member is housed in a hollow tubular holder of a cross-section which generally matches the crosssection of the electrode. But, the housing may be provided with other cross-sectional shapes, including a partly cylindrical cross-sectional shape on two opposing sides, in order to provide within the holder itself a support for other elements, like the electrode biasing spring, as hereinafter described. A contact pressure spring engages one end of the carbon con tact member or electrode and is preferably secured thereto. The spring is positioned in the holder and is compressed and charged between the end of the electrode within the holder and an abutment at the opposite end of the holder so that the electrode projects from an opening in the end of the holder. At least two opposite side walls of the holder are bowed out wardly in matching cylindrical form to accommodate the cylindri cal shape of the pressure spring. The bowed out walls extend substantially the length of the holder up to the end from which the electrode emerges. It is known to provide abutment means or other spring motion halting means in the holder to prevent the spring from extending all the way out of the holder when the carbon electrode is fully worn away. Known abutment means include a separate element, separate from and supported inside the holder. A brush and holder assembly of the type thus far described is disclosed in U.S. Patent 3,050,649. The present invention relates to means formed in the holder for preventing the electrode biasing spring from pushing fully out of the holder. Instead of a separate retention element having to be separately installed, according to the invention, the holder itself is configured upon initial fabrication to prevent the spring from moving out of the holder. Further the holder is shaped to properly guide and support the electrode against displacement and lateral and rotational motion. The holder has the previously mentioned generally cylindrically rounded, or outwardly bowed opposite side walls which are shaped for receiving the cylindrical profile of the bias spring. These bowed walls extend substantially up to the open end of the holder from which the electrode projects. Near that open end of the holder, the opposite side walls are slit across their width. This defines a transition that separates the spring motion stop section of the holder near the open end from the bowed wall main section of the holder. Instead of having the bowed walls, the section of the holder at the open end defines an opening into the holder that is completely rectangular. Thus, the end section of the holder provides two opposite sides which are essentially a chord or secant across the ends of the cylindrically curved walls of the main section of the holder. The rear edges of the unbowed sides provide an abutment against which the pressure spring, at the electrode end thereof, may bear so that the spring will not push itself out of the holder. The spring is thus retained in the holder at one end by the rear abutment of the holder and at the opposite end by the unbowed stop section of the holder at the open end. More generally expressed, in at least one dimension across the holder, the main section is wider than the spring stop section, so that the spring moving toward the stop section will be blocked from moving through that section. Interengagement or attachment of the electrode and of the spring which can-not leave the holder ensures that the electrode will not fall out of the holder while the entire brush=structure is being transported or inserted in or removed from a motor or at the end of the useful life of the electrode. The end of the holder away from tie open end carries an outwardly projecting abutment which limits the insertion of the entire holder into a retainer for the brush in the motor structure and thereby positions the brush holder within the motor structure. The open end of the holder is also provided with an extension which, preferably after insertion of the brush assembly into the retainer therefor in the electric motor, may be bent up to assist in retaining the holder in the retainer and to provide a connector for an electric lead for the brush. The primary object of the present invention, therefore, is to provide a holder for a brush electrode for an electric motor, wherein a compression spring that is compressed within the brush holder drives the contact member or electrode out through one end of the brush holder. The invention further has for its object the arrangement of the holder so that a stop for the compression spring is provided adjacent the end of the holder through which the electrode projects. Apother object of the invention is to retain the electrode bias spring in the holder without the need for assembly of extra elements in the holder. A further object of the invention is to guide motion of the electrode as the motor operates and to keep a desired orientation for the electrode. A further object of the invention is to form the brush holder from a simple tubular structure which is rectangular at the open end from which the electrode emerges and which is cylindrical back from that open end to accommodate the compression spring and which inherently provides an abutment and stop for the compression spring to ensure that the compression spring always stays within the holder. Figure 1 is a generalized schematic view of an electric motor showing the position which the brush holder of the present invention occupies in an electric motor. Fig. 2 is a view, partly in cross-section, of the brush holder of the present invention. Fig. 3 is a view in perspective showing the brush and holder prior to completion. Fig. 4 is a view in perspective corresponding to fig. 3 showing the completed assembly of a brush. Fig. 5 is a cross-sectional view of the motor taken along line 5 - 5 of fig. 1 looking in the direction of the arrows and showing in particular a pair of brush retainers in the motor and the brush of the invention inserted therein. Fig. 6 is a view taken from line 6 - 6 of fig. 5 looking in the direction of the arrows and showing the brush in the electric motor. Fig 7 is a view of one side of the brush holder, without the electrode present, in the diction of arrows 7 - 7 of fig. 9. Fig. 8 is an end view of the brush holder taken from the right side in fig. 7. Fig. 9 is a top view of the brush holder of fig. 7 viewed in the direction of arrows 9 - 9 of fig. 7. Fig. 10 is the opposite side view of the brush holder of fig. 7 and showing the seam in the tube. Fig. 11 is a side view of the contact or electrode of the brush with the biasing spring connected thereto. In fig. 1 and 5 one embodiment of an electric motor 20 is here shown mounted on a support 19. The illustrated motor is a bypass-type blower motor for creating suction in an electric vacuum cleaner, but the application of the invention i not limited to any particular motor. The motor includes a conventional commutator 21 on the arma- ture 22 of the motor. The motor drives a shaft 23 to rotate and this in turn rotates the armature inside the stator pole pieces 24. The shaft 23 drives the blower motor main fan 25 and motor cooling fan 26 in the usual manner. The support 19 is provided with a lower bearing 27 and an upper bearing 28 which rotatively support the shaft 23 and support the electric motor 20. The bearings 27 and 28 are in turn supported in housings 28a and 28b at the top and bottom. The housings may be directly interconnected or may be connected together by the stator pole pieces 24 of the motor. The housings 28a and 28b are respective plastic moldings, for instance. The housing 28b carries integrally formed holder retainers 73, which are essentially tubular members, each adapted to receive the holder hereinafter described and retain it in position. When the holders are inserted into the respective retainers 73, the contact member or electrode 30 of each brush bears against the commutator 21 of the motor armature in order to provide appropriate contact therewith for electric current as is well known in the art. Each of the retainers 73 is provided with a removable cap 78 preferably of resilient insulating material in order to ensure that the brush remains within the holder retainer 73. Cap 78 is a snap-on cap having a re-entrant flange 79 which in turn engages a flange 80 on the holder retainer 73 to provide appropriate means for holding the brush in place and also for retaining the brush against being accidentally snapped out. Since the caps 79 are of resilient material they may be removed by prying against the re-entrant member section 79 in order to permit removal of the brush which is retained by the holder retainer 73 and permit replacement thereof. The brush includes a conventional carbon electrode 30 with an end 40 which engages the commutator 21. The electrode 30 has a rectangular cross-section, uniform along its length. The electrode is housed in the holder 31. The electrode holder 31 is a tubular member initially formed from flat sheet material that has been folded over to the generally rectangular hollow cross-section seen in fig. 8. The folded sheet is appropriately seamed at 32, as seen in fig. 10, in order to provide a brush holder structure which is substantially smooth inside and outside. The seam is either cold welded or otherwise interengaged and secured in order to integrate and interlock the seam ends. A coiled, cylindrical cross-section, compression spring 35 is positioned inside the brush holder 31 and it engages the inward or rearward end of electrode 30. The engagement is through the turn down section 36 at the end of the spring 35 being received in the opening 37 of the electrode 30. The engagement of the spring 35 with the electrode 30 ensures that the electrode 30 will not fall out of the brush holder 31 at the end of the useful life of the electrode and during transportation, insertion or removal of the entire brush structure in the holder retainer 73 of the motor. The brush holder 31 is tubular, and is a rectangular tube with at least two opposite, outwardly bowed sides. One pair of oppoeite side walls 41 and 42 are parallel to each other and are essentially planar. A second pair of opposite side walls 44 and 45 are, at their upper and lower margins adjacent the walls 41 and 42, parallel to each other, but they are bowed to a generally cylindrically curved form longitudinally thereof along the central areas 46 and 47 thereof. The bowed areas 46 and 47 of the walls 44 and 45 accommodate the cylindrical profile of the compression spring 35. Towards the open end of the holder 31, the bowed areas terminate at the slits 50 and 51 formed in the side walls 44 and 45, leaving the flat unbowed, front end stop sections 52 and 53 on the opposite side which are extensions of the walls 44 and 45. More generally stated, the distance across the holder 31 in at least one dimension, the dimension through the bowed areas 46 and 47 of the opposite walls 44 and 45, is greater than the same dimension through the unbowed corresponding side walls 41 and 42 defining the stop sections. The rearwardly facing edges of the flat stop sections 52 and 53 within the holder act together as a front stop for the front end 54 of the compression spring 35. Also, they guide the axial motion and the orientation of the electrode 30 through the holder. Furthermore, together with the holder side walls 41 and 42, the stop sections are shaped to define an opening of substantially the same cross-section as the contact member 30, which prohibits lateral shifting and rotation of the contact member 30. The rear end of the tube 31, at the end opposite the stop sections 52 and 53, is provided with extensions 60, 61 which are bent inwardly from the position of fig. 2 and 3 to the position shown in fig. 4 after the spring 35 has been inserted, to retain the spring compressed. The compression spring 35 is preferably made of a conductive metal. Because it bears between the rear or inside end of the electrode 30 and the bent in holder extensions 61, which hold the spring in position, an electrical path is provided from the connector 65 for the electric lead through the tube to the electrode 30. In addition, because the electrode 30 preferably has a current conducting fit with the stop sections 52 and 53 of the tube, current conduction occurs from the tube to the electrode at that point. When the brush holder 31 is inserted into the holder retainer 73, it is pushed in from the rear end of the retainer mechanism in a direction shown by the arrow 70 in fig. 5 and is pushed home entirely within the retainer 73 so that the contact surface 40 of the electrode 30 is pushed against the commutator 21. The spring 35 is thereby compressed. The cap 78 is snapped on over the flange 80 of the holder retainer 73 after the holder is inserted. The inward movement of the brush of the present invention into the retainer 73 is controlled by the lateral extension 74 from the rear end of one of the side walls of the brush holder 31, in this case an extension from the side wall 42 - 46 at the rear. The extension 74 bears against the rearward edge 75 of the holder retainer 73 and limits the inward movement of the brush holder. The brush is then retained in position by the electrode 30 bearing at its contact end 40 against the commutator 21 and by the rear end of the electrode being retained in position by the cap 78. The holder retainer 73 of the motor structure lacks longitudinal slots or openings. Therefore, the connector 65 on the holder for the electric lead which connects the brush into the motor circuit is initially arranged flat as shown in fig. 3. After the holder is inserted into the retainer 73, the connector 65 is bent and raised to a position where a motor lead 66 may be connected to it, as shown in fig. 6. The motor lead is, in turn, connected with the stator pole pieces 24. It will thus be seen that the brush holder of the present invention is one in which a simplified brush holder tube is created, wherein a compression spring is captured between the closed rear end of the tube and the opposite front end out of which the electrode is spring biased. The compression spring is thus compressed between the electrode and the rear end of the holder tube. However, when the tube is being transported and prior to ti8 insertion in the motor or its removal from the motor, and therefore when the electrode is not engaged with the commutator, a stop is provided in the holder for the spring so that it will not be ejected from the tube. The tube itself is configured at a stop section, which has a smaller cross-section than the spring, to provide the stop for the spring. Interconnection of the electrode and the spring prevents the electrode from being separated. The tube itself provides a simple way of connecting the electrode in circuit with the motor and provides inherently within it appropriate electrical connection to the electrode so that a connection to a tab extending from the tube will provide full electrical connection between the electrode and the remainder of the circuit.

Claims: CLAIMS: 1. A brush holder for the brush electrode of an electric motor, said brush holder comprising a tube that is open at one end for receiving and retaining an electrode which is slideably mounted in said tube and which is slideable out of said tube open end; said tube being adapted to retain a compression spring therein for biasing an electrode out of said tube open end; an abutment in said tube away from said tube open end for being abutted by a spring in said tube, wherein a spring in said tube is adapted to be compressed between said abutment and an electrode-within said tube; said tube having a main section with a cross-section sized for receiving a spring for movement through said tube and for compression in said tube, characterized in that a stop for a spring has been defined in and by said tube near said tube open end; said stop being shaped and placed to be engaged by and block the pathway of a spring out of said tube open end while permitting the electrode in said tube to move through said tube open end. 2. Brush holder according to claim 1, wherein said stop comprises a stop section of said tube having an opening with a cross-section that is narrower in at least one dimension than the cross-section of a compression spring to be supported in the other, main section of said tube, and the opening defined by said stop section defining the opening of said tube through which an electrode is slideably movable. 3. Brush holder according to claim 1 or 2, wherein said spring is connected to said electrode for retaining said electrode mechanically connected to said brush holder. 4. Brush holder according to claim 1, 2 or 3, wherein said tube consists of electrically conductive material. 5. Brush holder according to claim 1, 2, 3 or 4, wherein said electrode has a predetermined profile in crosssection and said stop section defines an opening in said tube having substantially the same cross-sectional profile for orienting said electrode and for guiding said electrode for moving axially of said tube. 6. Brush holder according to claim 5, wherein said electrode is substantially rectangular in cross-section and said spring is substantially cylindrical in cross-section; said tube main section including opposite walls which are curved generally to match the cylindrical curvature of the cross-section of said spring and to provide a complete retainer for said spring; said stop section defining an opening in said tube which is generally rectangular and which is shaped correspondingly to the crosssectional profile of said electrode passing through said stop section; said main tube section opposed walls projecting outwardly of said tube holder further than the corresponding walls of said tube stop section. 7. Brush holder according to claim 6, wherein for defining a transition between said main tube section and said stop section, said opposite side walls of said tube being slit between said curved portions thereof at said main tube section and the same said side walls at said stop section, defining edges of said stop section facing towards said main section for serving as an abutment for said spring moving out of said holder open end. 8. Brush holder according to any one or more of the preceding claims, wherein said tube carries an electrical connector thereon for electrically connecting said brush holder to a notor. 9. Brush holder according to claim 8, wherein said connector comprises a tab located at said open end of said tube; said tab being bendable with respect to said holder to a position where it may receive a connection to the motor. 10. Brush holder according to any one or more of the preceding claims, characterized by a stop member provided on the said brush holder and any from said brush holder open end for serving as an index with respect to the structure of an electric motor for positioning said brush holder with respect to an electric motor.

Inventors: WACEK, RUDOLPH W.
Applicants: SHOP-VAC CORPORATION
Application year: 1981
Main classification: H01R39
IPC codes: H02K13, H01R39