US 3634710 A
A brush holder intended to carry unfitted brushes, having a self-recoiling spring which surrounds a contact member connected to a current supply for securing current flow to and from the brush, the contact member being preferably axially symmetrical, with the shape of a spool, of two half-spools, or of a solid or a hollow circular cylinder which is preferably not stepped.
Claims available in
Description (OCR text may contain errors)
United States Patent Inventor Karl Woda Vienna, Austria Appl. No. 876,194
Filed Dec. 2, 1969 Patented Jan. 11, 1972 Assignee Elin-Union Aktiengesellschaft fur elektrische lndustrie Vienna, Austria Continuation of application Ser. No. 600,104, Dec. 8, 1966, now abandoned. This application Dec. 2, 1969, Ser. No. 876,194
BRUSH HOLDER FOR ELECTRIC MOTORS AND GENERATORS 10 Claims, 13 Drawing Figs.
US. Cl 310/239 Int. Cl 02k 13/00 Field of Search 310/239,
 References Cited UNITED STATES PATENTS 2,974,241 3/1961 Harter 310/246 3,158,772 11/1964 Krellner. 310/246 3,387,155 6/1968 Krulls 310/245 3,423,618 1/1969 Schmid... 310/246 3,466,481 9/1969 Sckerl 310/239 Primary Examiner-D. X. Sliney Assistant Examiner-R. Skudy Attorney-Cecily L. Frey ABSTRACT: A brush holder intended to carry unlined brushes, having a self-recoiling spring which surrounds a contact member connected to a current supply for securing current flow to and from the brush, the contact member being preferably axially symmetrical, with the shape of a spool, of two half-spools, or of a solid or a hollow circular cylinder which is preferably not stepped.
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hhtomuj BRUSH HOLDER FOR ELECTRIC MOTORS AND GENERATORS This is a streamlined continuing application of applicant's copending application Ser. No. 600,104, filed Dec. 8, 1966, now abandoned, entitled Brush-Holder for Electric Machines, now abandoned.
Brush holders using a self-recoiling spring have been manufactured for some years with good results. The advantage of such brush holders is to be seen in the fact that a pressure finger and consequently additional masses to be moved can be saved as the spring acts directly on the carbon brush by means of an insulating roller. The self-recoiling spring is a spiral (helical) spring which is coiled upon the insulating roller and exerts a rather constant pressure over the entire length of the brush, which length decreases with brush wear. Such advantageous brush holders, however, have generally been used only for fitted brushes, i.e., brushes having a flexible stranded copper cable which is secured in a drilled hole by tamped copper powder.
Unfitted brushes are preferably used for traction motors, exciters, and other direct-current motors and generators. Such brushes can easily be replaced, and their replacement can be performed also during operation which fact is of importance especially for exciter motors. I
The holders used hitherto for unfitted brushes usually have a pressure finger which owing to its mass has an adverse effect because of the tendency to be lifted by inertial forces.
A brush holder using a self-recoiling spring designed for unfitted brushes is known wherein a part of the self-coiling spring which is helically wound up and which bears against the carbon brush is surrounded by a cylindrical slotted metallic casing. Within this casing a pressure member is provided which is preferably manufactured from an insulating material upon which the part of the self-recoiling spring which bears against the carbon brush is helically wound.
A disadvantage of this brush holder is the fact that the selfrecoiling spring protruding through a slot of the metallic casing may touch the slot edges and in doing so may become current conductive which is undesirable.
A further disadvantage is the fact that the carbon brush is not provided with a trough on its top. Therefore the metallic casing may slide off in which case an additional unwelcome electrical contact with the holder casing results. With this known arrangement, moreover, only linear contact is given between the metallic casing and the carbon brush which fact impedes current flow.
The following invention makes it possible to avoid the above-mentioned disadvantages. Moreover, the brush holder in accordance with this invention distinguishes itself by a simpler and essentially sturdier construction which is of great importance with regard to possible chattering vibrations.
The object of this invention is a brush holder intended to carry unfitted brushes using a self-recoiling spring, having the characteristic features that the spring surrounds a one-part or multipart contact member connected to a preferably flexible cable and assuring current flow to or from the brush, said contact member preferably presenting rotation symmetry, e.g., a roller or a spool, and that current flow through the self-recoiling spring is prevented by an insulating barrier.
Preferably the contact member may surround the flexible cable or cables to beconnected therewith, preferably concentrically, if the cable is inserted into a central hole of the aforedescribed contact member.
In the accompanying drawings,
FIGS. 1 and 2 show a front elevation and a plan view, respectively, of a known brush holder with a self-recoiling spring;
FIGS. 3 and 4 show, likewise in front elevation and in plan view, by way of example, the changes made in a brush holder within the meaning of this invention;
FIGS. 5 and 6 show two modifications of the brush holder construction shown in FIG. 4;
FIGS. 7a through 7d show two further solutions for brush holders in accordance with this invention, in respective pairs of front and side views;
FIGS. 8a and 8b show modifications thereto on the understanding that the self-recoiling spring is attached to is holding part in an insulating manner; and
FIG. illustrates a possible example, in a vertical section, of such an attachment.
In the drawings, numeral 1 indicates a carbon brush sliding on a commutator or slip ring 2 and being fitted with two flexible cables 3 secured in drilled holes of the brush by tamped copper powder. The carbon brush is slidably supported by a holder 4. In a usual manner the latter is attached to a clamping part 5 to which also terminals 6 of cables 3 are screwed so as to make good contact. At 7 a self-recoiling spring is indicated, at 8 an U-shaped spring for holding spring 7, at 9 an insulating roller, by way of an example consisting of a plastic material commercially known under the trade name Teflon, upon which spring 7 is coiled.
The roller 9 rests in a top trough l of brush 1 and transmits to the same the pressure exerted by spring 7 without making electric contact between the spring and the top trough, guaranteeing in this way that ramification of the current and inadmissible current flow through the spring 7 are avoided.
As shown in FIGS. 3 and 4, in accordance with the invention, the use of an unfitted brush 10 is made possible by providing a roller or spool 11 made from an electric conducting material and being preferably hollow, which roller passes coaxially through a hollow insulating roller which in turn is surrounded by spring 7. The roller 11 may be rotatably supported within roller 90. Flexible cables 30 pass axially through roller 11 and are connected thereto e.g., by soldering.
Preferably a continuous cable 30 is drawn through roller 11 and is connected thereto by soldering at the outlet points or by clamping. Flanges ll, 11" of roller 11, of which at least one is only screwed on or soldered on in order to make it possible that roller 90 can be slipped over roller 11, have a greater diameter than roller 90 so that flanges 1 1, 11'' rest on a top trough 10 of the brush, making electrical contact as is shown in FIG. 3 by arrows 12 indicating flow of current. Spring 7 is also shown, as described earlier.
As shown in FIG. 5 the aforementioned conducting roller 11 may be replaced by two conducting end plates connected with cables 30 e.g., by soldering, which end plates are screwed or attached in another manner, if desired rotatably, to an insulating roller 900 provided with flanges or lateral insulating disks. Similarly to roller 11 and its flanges 11', l 1 shown in FIGS. 3 and 4, end plates 110 may be made from silver or may be provided with a silver coating in order to improve current transition to the brush 10.
The area being available for the current transition may be made sufficiently large by suitably choosing the thickness and also the diameter of the flanges 11', 11" or of the end plates 1 10 (see FIGS. 3, 4 and 5). However, it should be regarded as being within the scope of this invention to deviate from the axially symmetrical form of these end plates or flanges, in order to obtain a greater area of rest, and to prevent rotation which is now undesirable, e.g., by choosing a plane area of rest. In such a case brushes without a top trough are to be used.
Moreover, the flanges or end plates could be connected, on the side turned towards the brush, by a bridge as broad as possible, e.g., offering a rectangular area of rest. Preferably the flanges or the end plates, respectively, and the bridge form one piece.
In the embodiment shown in FIG. 6, spring 7 directly (e. g., surrounds contact member or roller 11, that is without the insertion of aninsulating roller (e.g. 9, 90) as it is used with the embodiments previously described. In this case, however, spring 7 is electrically insulated from roller 11 by an insulating layer 13 applied to roller 11 by a sintering process, a coat of paint or by another procedure. The spring 7 surrounds this insulation 13. The current conduction is again performed by flexible cable 30. The carbon brush does not need a fitting.
With carbon brushes having a small dimension in tangential direction, e.g., with small direct-current motors, generators and with traction motors, it is possible to use instead of a metallic roller (such as 11 in FIG. 6) for current transmission (indicated in FIGS. 3, 7a and 7b by arrows 12) from and to a carbon brush a a solid or hollow metallic pin 101, as shown in FIGS. 7a and 7b. The advantage is to be seen in the small diameter of pin 101 which can be used also with small dimensions of the holder casing in tangential direction. The pin 101 is made from an electrical conducting material, e.g., brass, with or without a silver coating.
A portion of pin 101 which is enveloped by spring 7 shows a contraction which hinders the pin from being displaced in axial direction. By insulation 13, which can be made in the same manner as described in connection with FIG. 6, spring 7 is electrically insulated from pin 101.
As with brushes which are very small in tangential direction the diameter of the spiral of spring 7 is far greater than the diameter of pin 101, and increases with increasing brush wear, the holder casing must be correspondingly recessed in a range covered by spring 7. The carbon brush 10a has a wedgeshaped recess 14 in the region of spring 7 which recess may likewise be used for removing the brush from its holder by means of a clamp. As it is shown in FIGS. 7a and 8a, cables 30 may be connected to pin 101 in any suitable manner. The carbon brush 10a is formed as a twin brush, as shown in FIG. 7b, and has e.g., a cylindrical continuous top trough.
FIGS. 70 and 7d show a modification of the arrangement shown in FIGS. 7a and 7b. In this case a metallic pin 101', similar to the aforementioned pin 101 in association with a carbon brush 10b, has no contraction for its guidance but a uniform diameter throughout its length. Axial movement of the pin is limited by suitably designing the top trough of the brush 10b. In the left half of FIG. 7c pin 101 is represented as being solid and in the right half as being optionally hollow. The portion of pin 101' which is enveloped by spring 7 is provided with insulating coating 13. Otherwise the embodiment is similar to that ofFIGS. 7a and 7b.
In the embodiments shown in FIGS. 8a and 8b, which are similar to FIGS. 7a through 7d, metallic pins 101, 101, respectively, are not insulated from the respective spring 7. In doing so, however, it becomes necessary to fix the latter to their holding parts in an electrically insulating manner, in order to avoid current ramification and undue current flow through the springs.
For this purpose spring 7 may be attached to a hardboard plate 16 by means of a rivet 15 as it is shown in FIG. 8c. The hardboard plate 16 in turn is riveted to a holding spring 17.
As can be seen in FIGS. 70 and 8b the troughs provided on the tops of the respective carbon brushes 10b, for the contact members in the form of pins 101', have limited lengths adapted to those of the respective contact members so that the latter are prevented from axial movement relative to these brushes.
From a technological and manufacturing standpoint it is of course simpler to provide an axially unlimited trough as shown, for example, in FIGS. 4, 5, 7a and 8a. In these cases an axial displacement of the respective contact member (e.g., roller 11 with flanges 11', or a similar roller with end plates 110, and/or the contact pins 101) can be prevented, if necessary, by the provision of suitably spaced conventional stops in terminal regions of the troughs. It will be understood that such stops would be disposed at a distance slightly larger than the axial length of the respective contact member so as to be effective in limiting its axial displacement with respect to the brushes (e.g., 10, 10a).
The inventive proposals for improving a brush holder are of great advantage, especially for traction motors. As the pressure finger having considerable mass falls away a jumping of the brush, as it is to be feared with high travelling speeds or heavy starts, is avoided. With traction motors, moreover, the small extension of the brush holder in the tangential direction is of importance in view of the restricted space in such cases.
The described brush holder with a self-recoiling spring may be constructed as a radial holder as well as an inclined holder.
1. A brush holder for carrying unfitted brushes, using a selfrecoiling spring, the holder comprising, in combination, a contact member (11, 110, 101, 101) surrounded by the spring (7) and at least partly contacted thereby, connected to a current supply (30) for securing current to and from the brush (10, 19a, 10b) within the holder, and having an axially symmetrical configuration at least in the portion of said contact member which is in contact with said spring, and an insulating member (90, 900) forming part of said contact member for preventing current flow through said spring.
2. The brush holder as defined in claim 1, wherein terminal portions of said contact member (11, 101) have a larger diameter than a portion thereof which is contacted by a portion of the innermost convolution of said spring (7), whereby intimate electrical contact is assured between said terminal portions and said brush (10, 10a).
3. The brush holder as defined in claim 1, in combination with said brush (10b), wherein the the latter has a troughshaped top for receiving said contact member (101') therein, with a length at least corresponding to that of said contact member, for preventing substantial displacement of the latter with respect to said brush.
4. The brush holder as defined in claim 1, in combination with said brush (10a, 10b), wherein the latter has a recess 14) for accommodating said spring (7) without being mechanically contacted thereby.
5. The brush holder and brush combination as defined in claim 4, wherein said recess (14) has a dovetail form, for permitting removal of said brush (10a, 10b) from the holder by means of a clamping tool which fits in part into said recess.
6. The brush holder and brush combination as defined in claim 4, wherein the largest diameter of said contact member (101, 101') is smaller than the largest expanded diameter of said spring (7), and the latter contacts a portion of said contact member with at least a portion of its innermost convolution.
7. The brush holder and brush combination as defined in claim 4, wherein said contact member (101) is in the form of a circular cylinder having a uniform diameter free from stepped portions.
8. The brush holder and brush combination as defined in claim 7, wherein said cylinder (101) is at least partly hollow.
9. A brush holder for carrying unfitted brushes, using a selfrecoiling spring, the holder comprising, in combination, a contact member (101, 101') surrounded by the spring (7) and at least partly contacted thereby, connected to a current supply (30) for securing current to and from the brush (10a, 10b) within the holder, and having an axially symmetrical configuration at least in the portion of said contact member which is in contact with said spring, and an insulating attachment (16) of said spring on its holding parts (15, 17), for preventing current flow through said spring.
10. A brush holder for carrying unfitted brushes, using a self-recoiling spring, the holder comprising, in combination, a contact member (101, 101') surrounded by the spring (7) and at least partly contacted thereby, connected to a current supply (30) for securing current to and from the brush (10a, 10b) within the holder, and having an axially symmetrical configuration at least in the portion of said contact member which is in contact with said spring, in combination with said brush, wherein the latter has a trough-shaped top for receiving said contact member therein, and is provided with stops for preventing displacement of said contact member with respect to said brush.