US3297973A

US3297973A - Floating-brush contact assembly

Info

Publication number: US3297973A
Application number: US305760A
Authority: US
Inventors: George E Wendell
Original assignee: POLY SCIENT CORP
Current assignee: POLY SCIENT CORP; POLY-SCIENTIFIC Corp
Priority date: 1963-08-30
Filing date: 1963-08-30
Publication date: 1967-01-10
Anticipated expiration: 1984-01-10
Also published as: FR1405104A; GB1020378A; DE1489080A1

Description

Jan. 10, 1967 G. E. WENDELL 3,297,973

FLOATINGBRUSH CONTACT AS S EMBLY Filed Aug. 50, 1963 2 Sheets-Sheet l Geo/ye a. [Jan/2% Jan. 10, 1967 G. E. WENDELL FLOATING-BRUSH CONTACT ASSEMBLY 2 Sheets-Sheet 2 Filed Aug. 50, 1965 United States Pate 3,297,973 FLOATING-BRUSH CONTACT ASSEMBLY George E. Wendell, Blacksburg, Va., assignor to Poly- Scientific Corporation, Blacksburg, Va. Filed Aug. 30, 1963, Ser. No. 305,760 11 Claims. (Cl. 339) This invention relates to sliding or rotating contact assemblies, and, more particularly, to contact assemblies in which very light contacting pressures are employed.

A great deal of study has gone into the mechanism of electric conduction between two relatively movable conductors. Despite this extensive work and the many prior constructions which have been proposed, a number of significant problems remain. Initially, contact life and the reliability of conduction over long periods of time are not as high as would be desirable. This problem is attributable, at least in part, to the common use of high contact pressures, and to the presence of harmful organic vapors which tend to attack the contacting surfaces and increase their resistance. The organic vapors are frequently a result of soldering or potting operations which occur when the relatively movable contacts are assembled.

Accordingly, principal objects of the present invention include reduction in the contact pressure of moving electrical contacts and elimination of the need for soldering and potting at the time the contacting assemblies are manufactured.

In the case of multiple contacts, such as those found in brush block assemblies, where as many as 20 or 30 or more brushes engage corresponding commutator or slipring elements, it is frequently difi'icult to assemble or disassemble the units or to replace brushes. Furthermore, the alignment and adjustment of contact pressures is a serious problem in the tiny space which is allocated to each brush within the brush block assembly.

Another object is the simplification of assembly and replacement of brushes without contamination of the contacting surfaces.

In accordance with the present invention, the foregoing objects are achieved by the use of a piece of conductive wire having a bend along its length, a conducting tube into which the bent wire fits loosely, and a grooved conductor, such as a slip-ring or commutator, which is engaged tangentially by the Wire.

In a preferred embodiment of the invention, four separate bent conductive Wires are loosely inserted in a single conductive tube, a doubly grooved slip-ring is provided, two of the wires engage separate grooves in one direction from the tube; and the two remaining wires face in the other direction and tangentially engage the same two grooves at points spaced around the periphery of the slipring from the points of engagement of the first two wires.

One of the important features of the construction described above is that the individual wires are free to rotate about the axis of the conductive tube in which they are inserted. This permits a relief of strain and a free-floating contact relationship between the wires and the groove or grooves.

With this arrangement, automatic alignment is achieved and contact pressure may be reduced from the normal pressure of four or five grams down to one or two grams, or even less. The assembly, disassembly and cleaning, and the replacement of brushes may be accomplished in a clean room with no soldering, potting or other source of noxious vapors present which could contaminate or corrode the moving contact surfaces.

Other advantages of the present construction involve a greater range of selection of brush materials, since soldering or welding to the wire brush is eliminated, a reduction in size of brush block assemblies, simplified construction, lower costs, and increased product reliability.

Patented Jan. 10, 1967 tice The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which several embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.

In the drawings:

FIG. 1 is a schematic view of a brush and slip-ring contact assembly shown in partial cross-section, in accordance with the invention;

FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG. 1;

FIG. 3 is an enlarged view of a portion of the contact assembly of FIG. 2;

FIG. 4 is a partial cross-sectional view taken at right angles to FIG. 3; and

FIG. 5 is a cross-sectional view taken along lines 55 of FIG. 3.

With reference to the drawings, FIG. 1 shows a brush block aassembly including an inner subassembly 12 having a set of grooved conducting rings, and an outer subassembly 14 including many sets of brushes. The active elements of the brush subassembly are the wires 16 which engage the grooved conducting rings in the assembly 12. Other components shown in FIG. 1 include the outer housing 18, the brush leads 20 and the slip-ring leads 22. The slip-ring assembly 12 is mounted on

ball bearings

24 and 26 for relative movement with respect to the electrical brush assembly 14.

In practice, either the brush assembly 14 or the slipring assembly 12 may be fixed while the other rotates. The leads 20 are connected to the conductive sleeves 28 which hold the wires 16v The leads 22 are potted within an insulating core inside the slip-ring assembly 12 and are brought out through the cylindrical member 30 which is secured to the right-hand end of slip-ring assembly 12, as shown in FIG. 1.

FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG. 1. It shows the relative positions of the brush assembly 14 and the slip-ring assembly 12 to advantage.

FIG. 3 is an enlarged view of a portion of FIG. 2 showing the precise arrangement of the brush wires 16 and the slip-rings of assembly 12. As clearly shown in FIGS. 2 and 3, the wires 20 pass through the insulating cylinder 32 and are soldered to the sleeve 28. The wires 16 are bent and slip freely into the conducting sleeves 28. The wires 16 are bent and slip freely into the conducting sleeves 28. The slip-ring assembly 12 is provided with a series of conductive rings including the ring 34 shown in FIGS. 2 and 3. These rings are spaced and insulated from one another. One of the leads 22 is connected to slipring 34.

Other views of wires 16 and their engagement with the doubly grooved slip-ring 34 are shown in FIGS. 4 and 5. Thus, FIG. 4 shows a view of the wires 16 which is taken at right angles from the view of FIG. 3. Similarly, FIG. 5 is a partial cross-sectional view taken along lines 5-5 of FIG. 3.

The wires 16 are held in the conductive tube 28 solely by the pressure exerted against the tube 28 and the tangential pressure against slip-ring 34. This permits free rotation of each of the wires 16 about the axis of tube 28 and therefore secures precise alignment of the wire in the grooves of slip-ring 34. In actual practice, the wires 16 are preformed and bent to a precise angle before insertion onto tube 28.

In one particular case, a wire of an alloy known as Paliney-7 was mounted in a brush block assembly having an inner diameter of 0.170 inch to run on a slip-ring having an outer diameter of 0.122 inch. The wire had a diameter of 0.0027 inch. In order to obtain a two-gram pressure on the commutator, the wire was initially bent to tangentially engage a cylinder having a diameter of 0.106 inch. For completeness, it may be noted that the alloy Paliney-7 has a composition of 10 percent gold, 10 percent platinum, 35 percent palladium, 30 percent silver, 14 percent copper and 1 percent zinc.

In each case, the contact pressure is determined as a function of the mechanical properties of the contact wire, and the geometry of the assembly. Normally, for miniature sizes, contact pressures will be greater than one-tenth gram and less than the usual four or five grams employed in prior devices of the same genera-l size, and would characteristically be one or two grams. For larger size brushes, heavier pressures would be employed; in the normal case, however, contact pressures in arrangements fabricated in accordance with the invention will be a fraction of that of prior art units of comparable size.

With regard to another aspect of the present invention, it has been determined that brushes and commutators of the same material may actually be employed without adverse effects. Thus, a slip-ring plated with gold was successfully employed with a wire brush having gold plated onto beryllium copper wire. This experiment was considered to be particularly interesting and indicative of the advantages of the present invention in view of the fact that it is contrary to most of the known principles in the field of sliding contacts to use both brushes and sliprings or commutators of the same material. In most cases, such contact surfaces are rapidly degraded through galling and fail within short periods of time. However, with the lack of contamination and the relatively light pressure, life-times equal or superior to normal contact wear was achieved even with identical metal surfaces.

Concerning material which may be used, Neoro-28A, a high gold alloy, and Neoro-G wire have been successfully employed. Neoro-ZSA includes 75 percent gold, 22 percent silver, and 3 percent nickel. Neoro-G includes 72% percent gold, 4 percent silver, 1 percent zinc, 8 /2 percent platinum and 14 percent copper. Coin gold, including 10 percent copper and 90 percent gold, and other known precious metal contact materials may also be employed. With any of the foregoing materials, it has uniformly been found that the use of brush and slip-ring or commutator assemblies in accordance with the present invention produces much longer contact life and greater reliability than arrangements which have been proposed heretofore employing the same or comparable materials.

In closing, advantages of the present invention include reduction in the required torque for driving the commutator, and the other advantages mentioned above. Some of these advantages which were previously discussed include simplification of construction, ease of assembly and brush replacement, reduction in cost, redundancy of contacts in the case of the multiple wire slip-ring units, reduction in size of the over-all assembly, a greater range of selection of brush materials, and greatly increased reliability and contact life.

It is to be understood that the above-described arrangements areillustrative of the application of the principles of the invention. Numerous other arrangements within the scope of the invention may be devised by those skilled in the art. Thus, by way of example and not of limitation, one, two or six br-ushes could be employed instead of the four brushes used in the preferred embodiment of the invention; the grooved conductive rings may .be segmented to form commutators and employed with brushes extending in but one direction; linear relative movement of brushes and matching grooved surfaces may be employed with curved wire brushes; and materials other than those specified could also be used. Accordingly, from the foregoing, it is evident that various changes may be made in the present invention without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. In combination:

a brush assembly comprising a hollow conductive tube and four bent wires each having one end extending loosely into said tube; and

a doubly grooved slip-ring mounted for relative rotation with respect to said brush assembly, two of said wires engaging respective grooves in the slip-ring in one direction from said conductive tube, and the other two wires engaging the respective grooves in the other direction from said tube.

2. In combination:

a doubly grooved slip-ring mounted for relative rotation with respect to said brush assembly, two of said wires tangentially engaging respective grooves in the slip-ring in one direction from said conductive tube, and the other two wires tangentially engaging the respective grooves in the other direction from said tube.

3. In a floating brush contact arrangement:

a brush assembly comprising a plurality of hollow conductive tubes;

four bent wires associated with each tube, each wire having one end extending loosely into each of said tubes; and

a corresponding plurality of doubly grooved slip-rings mounted for relative rotation with respect to said brush assembly, two of the wires in each set engaging respective grooves in one of the slip-rings in one direction from each of said conductive tubes, and the two other wires engaging the respective grooves in the other direction from said tube.

4. In combination:

a brush assembly comprising a hollow conductive tube and four bent wires each having one end extending loosely into said tube, and a doubly grooved slipring mounted for relative rotation with respect to said brush assembly; and

two of said wires engaging respective grooves in the slip-ring in one direction from said conductive tube, and the other two wires engaging the respective grooves in the other direction from said tube with less than four grams of pressure.

5. In combination:

a brush assembly comprising a plurality of hollow conductive tubes;

a set of four bent wires associated with each tube, each wire having one end extending loosely into each of said tubes; and

a corresponding plurality of doubly grooved conductors mounted for relative movement with respect to said brush assembly, two of the wires in each set tangentially engaging respective grooves in one of the conductors in one direction from each of said conductive tubes, and the two other wires of the same set tangentially engaging the respective grooves of the same conductor in the other direction from said tube.

6. In a rotary contact assembly,

a brush support,

a ring having a conductive surface mounted for relative rotational movement with respect to the brush support,

said brush support having means defining an elongated opening confronting the ring and containing an electrically conductive means permitting angular movement of the brush and making electrical contact with the brush for all angular positions thereof,

a resilient electrically conductive brush with one end thereof having a substantially straight portion, said brush being of smaller dimension than said opening and inserted loosely into said opening in the brush assembly and in electrical engagement with said conductive means,

said brush having a bend along its length, with said one end thereof on one side of the bend,

means for limiting the penttration of the brush into said opening,

a portion of the brush on the other side of the bend tangential-1y engaging the ring,

the respective size of said opening and said brush, and

the location of said opening in the brush support relative to the surface of the ring being such that the brush is maintained in continuous contact with the conductive means in the brush support and with the ring solely by the opposing pressures on the brush exerted by the ring and the brush support,

whereby the brush is free to shift angular position in the brush support and maintain continuous alignment with the ring during relative rotational movement of the brush support and ring.

7. In the rotary contact assembly of claim 6, said electrically conductive means comprising a hollow conductive tube.

8. In the rotary contact assembly of claim 6, said means for limiting the penetration of the brush into said 6 opening comprising a portion of the brush support engaging the bend in the brush.

9. In the rotary contact assembly of claim 6, said electrically conductive means comprising a hollow conductive tube, and said means for limiting the penetration of the brush comprising the lip of the tube engaging the References Cited by the Examiner UNITED STATES PATENTS 2,242,273 5/1941 Taylerson 3395 2,473,526 6/1949 Hood et al. 3395 2,509,931 5/1950 Krantz 339-5 3,054,098 9/1962 Jacoby 339-244 X EDWARD C. ALLEN, Primary Examiner. ALFRED S. TRASK, Examiner.

Claims

6. IN A ROTARY CONTACT ASSEMBLY, A BRUSH SUPPORT, A RING HAVING A CONDUCTIVE SURFACE MOUNTED FOR RELATIVE ROTATIONAL MOVEMENT WITH RESPECT TO THE BRUSH SUPPORT, SAID BRUSH SUPPORT HAVING MEANS DEFINING AN ELONGATED OPENING CONFRONTING THE RING AND CONTAINING AN ELECTRICALLY CONDUCTIVE MEANS PERMITTING ANGULAR MOVEMENT OF THE BRUSH AND MAKING ELECTRICAL CONTACT WITH THE BRUSH FOR ALL ANGULAR POSITIONS THEREOF, A RESILIENT ELECTRICALLY CONDUCTIVE BRUSH WITH ONE END THEREOF HAVING A SUBSTANTIALLY STRAIGHT PORTION, SAID BRUSH BEING OF SMALLER DIMENSION THAN SAID OPENING AND INSERTED LOOSELY INTO SAID OPENING IN THE BRUSH ASSEMBLY AND IN ELECTRICAL ENGAGEMENT WITH SAID CONDUCTIVE MEANS, SAID BRUSH HAVING A BEND ALONG ITS LENGTH, WITH SAID ONE END THEREOF ON ONE SIDE OF THE BEND, MEANS FOR LIMITING THE PENETRATION OF THE BRUSH INTO SAID OPENING, A PORTION OF THE BRUSH ON THE OTHER SIDE OF THE BEND TANGENTIALLY ENGAGING THE RING, THE RESPECTIVE SIZE OF SAID OPENING AND SAID BRUSH, AND THE LOCATION OF SAID OPENING IN THE BRUSH SUPPORT RELATIVE TO THE SURFACE OF THE RING BEING SUCH THAT THE BRUSH IS MAINTAINED IN CONTINUOUS CONTACT WITH THE CONDUCTIVE MEANS IN THE BRUSH SUPPORT AND WITH THE RING SOLELY BY THE OPPOSING PRESSURES ON THE BRUSH EXERTED BY THE RING AND THE BRUSH SUPPORT, WHEREBY THE BRUSH IS FREE TO SHIFT ANGULAR POSITION IN THE BRUSH SUPPORT AND MAINTAIN CONTINUOUS ALIGNMENT WITH THE RING DURING RELATIVE ROTATIONAL MOVEMENT OF THE BRUSH SUPPORT AND RING.