US2470091A - Generator brush tool - Google Patents

Description

May 17, 1949. R. K. CLARK GENERATOR BRUSH, TOOL Filed April 10, 1946 Patented May 17, 1949 GENERATOR BRUSH TOOL Robert K. Clark, United States Army, St. Paul, Minn.

Application April 10, 1946, Serial No. 661,046

1 Claim.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for government purposes without the payment of any royalty thereon.

The present invention concerns the proper inspection of generators and the like, particularly such as exciters or battery charging generators of small internal combustion power plants.

In direct current generators the brushes ride on a commutator, inclosed by a ported case closed by a removable band covering ports over the brushes. They require occasional replacement for various reasons well known. Brushes are not easy to remove because of the lack of space to insert ones hand. A brush is held in place and caused to ride in close contact with the commutator surface by a spring which although capable of exerting a substantial force is easily sprung (permanently deformed) if pushed roughly aside. When the brush spring is sprung it is no longer capable of holding the brush in firm contact with the commutator. The resultant arcing under the brush accelerates wear and erosion of the brush and commutator, with impairment of generator efficiency and danger of shorting the armature windings and burning out of the gen erator. The invention offers a tool which enables clearing the brush spring from the path of removal of the brush with a minimum liability of damage to the spring.

Because of the diflicult it is not uncommon for generator inspectors to merely remove the cover band and attempt to inspect the commutator and the brushes without removing the latter. It is here sought to facilitate moving of the brush spring to clear the brush, and to enable removal of the brush with greater ease, so that liability of careless inspection will be counteracted.

It is an object of the invention to provide a simple tool which will grasp the brush spring and permit easy removal of the brush.

Referring to the drawing:

Fig. 1 is a side elevation of the tool, stretched, in lifting engagement with a brush spring, the latter indicated in dotted lines.

Fig. 2 is a front view of the tool, with a brush assembly and part of a generator case dotted in, the tool being dotted in its lifting engagement with the brush spring and in deflected position of the handle.

Fig. 3 is a view similar to Fig. 1 with the tool in a free state.

The tool comprises a pencil-shaped handle portion II] which may be of Wood or metal in a size suitable for insertion in a pencil pocket of a workmans garment, although its size may vary depending on the size of the generator installation with which it is used. The lower end may be tapered as at H. The larger upper end portion of a helical wire spring I2 is fitted over and around the end II and fastened to handle portion l0 by screw or other fastening means, so that the adjacent intermediate portion of the spring tends to be held coaxial with the handle.

Spring I2 is in the form of a conical helix normally close coiled, about two and a half inches long, more or less and is made of wire of about twenty-six S. W. G. In normal or free condition coils of the spring touch each other.

The tool is provided with a spring-engaging head I3 preferably of steel or other metal, having a shank portion I i fitting into and connected coaxially to the free end of spring l2. It will be noted that there is a central portion i5 of spring l2 between handle Ill and shank portion it which is free to flex or bend. Head 16 is provided with substantially parallel bifurcations iii of about three-sixteenths of an inch or more in length extending outwardly from shank portion i i substantially perpendicular to the axis of handle portion or rod l0, so that the head is generally L-shaped. The space ll between bifurcations it is such as to receive at least one turn of the coil of a generator brush spring.

Shank portion I4 is likewise fastened to spring l2 as described above by use of screws or equivalent means. Spring I2 may be tapered throughout its length from rod Hi to shank portion M if desired. In small jobs it may be replaced by a flexible strip of metal.

In use the band customarily fitted around the generator case, and covering openings in the case over the generator brushes, is removed, and the tool is inserted in the opening. The head it is manipulated so that bifurcations l5 grasp extend across (one over and one under) a coil of the generator brush spring which thus becomes engaged in space I1. In this condition, the major part of the spring I2 extends outwardly through the adjacent port of the case and beyond the latter, and the handle is movable by flexing of the spring l2 as may be required to effect the placement of the head l3. Handle It? is then raised symmetrically stressing the generator brush spring until clear of the brush, after which the brush may be readily removed. In this use of the tool the spring l2 may be bent to avoid obstruction of the handle by generator case parts or other parts, and after sufficient displacement of the end of the brush spring the handle may be pressed to one side while the brush spring remains confined by the head l3, so as to clear the case port and afiord free access to the and commutator. After removal and inspec o the brush is replaced or renewed and the spring readjusted on the brush and released from the tool.

It will be noted that the generator brush spring is compressed symmetrically, not pushed to one side and distorted so as to acquire a permanent ofi center set or be unable to firmly press the brush into contact with the commutator.

What I claim is:

A tool for lifting the brush spring of a dynamo electric machine of the general character described, comprising a handle body having a tapered helical spring extended therefrom, said spring having a normally rectilinear axis, but being extensible and flexible under stress of a handle laterally of a generator case opening while.

a brush spring is supported by the tool, said spring having a brush-spring-engaging head at its extremity comprising a substantially L-shaped rigid body having its shank portion secured coaxially to the extremity of said spring, two parallel closely spaced lateral arms being formed at the outer extremity of the head and spaced from each other in a plane coincident with the axis of said shank to receive a convolution of a spring therebetween.

ROBERT K. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,758,504 English May 13, 1930 Wiessner Jan. 5, 193 7

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