US2125171A

US2125171A - Brush for high intensity arc searchlights

Info

Publication number: US2125171A
Application number: US128202A
Authority: US
Inventors: John F Peters
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1937-02-27
Filing date: 1937-02-27
Publication date: 1938-07-26
Anticipated expiration: 1955-07-26

Description

July 26, 1 938. J. F. PETERS ,1

BRUSH FOR HIGH INTENSITY ARC SEARCHLIGHTS Filed Feb. 27, 1937 John F Defers.

Patented July 26, 1938 BRUSH FOR HIGH INTENSITY ARC SEARCH- LIGHTS John F. Peters, Edgewood, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvama Application February 2'7, 1937, Serial No. 128,202

13 Claims.

My invention relates to are searchlights and more particularly to the brushes used to conduct current to the electrodes of such searchlights.

In the operation of arc searchlights, it is common practice to feed the electrodes to the are as they are consumed in the are by moving the electrodes, which are usually round rods, toward the arc in the direction of their axes. In addition to the longitudinal motion, the electrodes,

and particularly the positive electrode, are rotated about their axes to secure even consumption of the electrode in the arc. Because of the relative motion of the electrode and the electrode holder, or electrode head as it is sometimes called,

it is necessary that contact brushes be mounted on the head to bear upon the electrode to conduct current thereto while the arc is burning.

High intensity searchlights such as operate on ciu'rents of from 150 to 250 amperes require that Lt. very good contact be maintained between the brush and the electrode to prevent excessive arcing and resultant burning of the brush. Poor contact between the brush and the electrode causes considerable power loss and voltage drop between the brush and electrode. Such power loss causes heating of the brush which in turn causes pitting and deterioration of the brush. Such pitting further increases the contact resistance between brush and electrode and so the condition is aggravated until it is necessary to replace the brush or refinish its contact surface. Pitting of the brush surface also'increases the sliding frictional resistance between the brush and the electrode thus placing an excessive burden upon the electrode feeding mechanism.

The contact surface of the brushes in common use heretofore has been in the form of a cylindrical surface intended to cover the electrode surface. It has been found that the diameters of 40 the electrodes vary both as between electrodes and in the individual electrodes. It is apparent that, in order to permit the brush contact surface to cooperate with all electrode diameters, it is necessary that the diameter of the brush con- AS tact surface be made at least as large as the largest electrode diameter that is likely to be encountered.

As a result of the construction just described, single line contact exists between the brush and the electrode except when the maximum diameter of electrode is engaged by the brush. This means that only line contact exists between the brush and the electrode. As a result a high contact resistance exists, causing the brush to pit 5 excessively and necessitating frequent reaming Cir of the brush contact surface. This repeated reaming shortens the brush life and causes excessive replacement and maintenance costs.

The object of my invention is to provide a brush for use with the electrodes of an arc searchlight which shall have a lower contact resistance than brushes now employed.

Another object of my invention is to provide a brush for use with the electrode of an arc searchlight which shall have its contact surface so shaped as to provide a plurality of line contacts between the brush and the electrode.

A further object of my invention is to provide a brush for use with the electrodes of an arc searchlight which shall have its contact surface so shaped as to minimize the contact resistance between the brush and the electrode.

A still further object of my invention is to provide a brush for use with the electrode of an arc searchlight which shall have its contact surface so shaped as to minimize the heat generated and consequent pitting at the brush contact surface.

Another object of my invention is to provide a brush for use with the electrode of an are search light which shall have its contact surface so shaped as to prolong the life of the brush thus obtaining increased maintenance and replacement economies.

Another object of my invention is to provide a brush for use with the electrode of an are search.- light which shall have its contact surface so formed as to provide two line contacts between the brush and the electrode thus insuring that the electrode be held securely against lateral movement.

Another object of my invention is to so shape the contacting surface of a brush for the electrode as to obtain a high contact pressure per unit of contact surface and to thus provide a better conducting contact between the brush and electrode.

These and other objects of my invention will be apparent after reading the following detailed description in connection with the accompanying drawing, in which Figure 1 is a diagrammatic illustration of the electrodes and electrode feeding mechanisms of an arc lamp with the brushes in their cooperative relationships.

Fig. 2 is an end elevational view showing the contact relation between an electrode and a brush which has a cylindrical contact surface.

Fig. 3 is an end elevational view showing the contact relation between an electrode and a brush embodying the principles of my invention.

the best results.

Fig. 4 is a perspective View of the brush shown in Fig. 3; and,

Figs. 5 and 6 illustrate the contact relation between an electrode and modified forms of brushes embodying my invention.

In carrying out my invention, I have provided on the arc head unit of a'searchlight, a pair of brushes with V-shaped slots in that end of the brushes which bears on the electrode, with the slots running longitudinally of the electrode and each side of the slot contacting the electrode.

Referring to Fig. 1, I have illustrated the positive and negative electrodes i and 2 of an arc Searchlight with the mechanism for feeding the electrodes to the are 3 and 4, and the mechanism 5 for rotating the positive electrode, these feeding and rotating mechanisms being driven by a constantly rotating motor 6 through suitable gearing. Power for energizing the arc is supplied to the electrodes through brushes 1 and these brushes are energized from a suitable power source, as illustrated.

It is understood that this mechanism is only illustrative and the gearing mechanisms are not drawn to scale. The mechanism for rotating the positive electrode is provided to insure even burning of the positive electrode. The mechanism for feeding the electrodes to the are are provided to compensate for the consumption of electrodes in the arc and to maintain the arcing tips in a fixed position.

It will be seen that the positive electrode has both a rotational and a sliding movement relative to its brushes. In Fig. 2, I have shown the usual form of brush contact surface. Heretofore, this has been a cylindrical surface and because of the variation in the diameter of the electrode along its length and the variation in diameter as between electrodes it is apparent that a brush surface diameter could not be chosen that would fit all electrodes, that the surface diameter would have to be at least as large as the largest expected electrode diameter, that electrode diameter in most cases would be smaller than the brush surface diameter and that contact between the brush and the electrode would be only line contact at the point A.

Furthermore, the cylindrical contact surface of the brush might vary from line contact to surface contact depending on the relative diameters of the brush surface and the electrode. This gives a variation in contact pressure between the brush and the electrode and as this contact more nearly approaches the surface contact, there is not sufficient unit pressure between these surfaces to insure good conduction between the brush and the electrode.

For these reasons, it was necessary that as near as possible to line contact be maintained between the brush and the electrode at all times. This line contact is obtained by providing the brush shown in Fig. 3. This brush has a V-shaped slot lengthwise of the brush and the electrode fits into this slot, as illustrated. Such an arrangement provides line contact between the brush and electrode at the two points B, thus insuring high unit pressure between the brush and electrode and providing two of these high pressure contact surfaces.

The angle between the sides of this V-shaped slot shown in Fig. 3 may be taken as merely illustrative of the principle of this invention and is not necessarily the exact angle which will give The angle for obtaining the best results would probably vary with the diameter of the electrode to be used with the brush and such angle would have to be determined by experiment.

If it should be desirable to increase or decrease the brush contact pressure above or below that obtained by the plane surfaces of the V-shaped slot shown in Fig. 3, the V-shaped slot may have side surfaces which are convex or concave as illustrated in Figs. 5 and 6. It will be noted that the same principles apply in these modifications, that line contact is obtained between the brush and electrode at two separated positions on the electrode and that the contact of the two sides of the V-shaped slot with the electrode serves to maintain the electrode at a fixed position and prevent lateral movement of the electrode.

Experimentation and use in practice have shown that the shaping of the brush contact surface after the manner illustrated and described has prolonged the life of the brushes and has made it necessary to refinish the contact surfaces of the brushes less often than when the cylindrical contact surface illustrated in Fig. 2 is used. It has also been found that the centering effect of the V-shaped contact surface on the electrode has resulted in a better beam projected from the Searchlight, since the variations in the beam intensity and focus have been eliminated by preventing lateral movement of the electrode.

In compliance with the requirements of the patent statutes, I have shown and described herein a preferred embodiment of my invention. It is understood, however, that the invention is not limited to the precise construction shown and described, but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustrative of the principles of my invention.

I claim as my invention:

1. In an arcing device in which the electrode is rotated about its axis and is moved axially to feed it to the are, means for conducting current to the electrode comprising a fixed brush having a V-shaped slot, the sides of the slot serving as the contact surfaces between the brush and the electrode.

2. In a brush for conducting current to an electrode of an are, which electrode rotates and is moved into the arc, said brush being so formed as to maintain substantially line contact with the electrode at a plurality of circumferentially spaced positions on the electrode.

3. In an arc Searchlight having means for rotating an electrode and feeding the electrode to the are, a fixed brush for conducting current to the electrode, said brush being so formed as to provide a plurality of surfaces in different planes as surfaces of contact with the electrode.

4. In a means for maintaining electrical contact with a substantially cylindrical surface which rotates about its axis and which moves in the direction of its axis, a brush made of conducting material and having a slot in one side thereof, said slot being so formed that, when the brush is placed in contact with said cylindrical surface, with the cylindrical surface lying in the slot, each of the slot surfaces will maintain substantially line contact with the cylindrical surface.

5. In a device for maintaining electrical contact with a body having a substantially cylindrical surface which has a motion in the direction of its axis and rotation about its axis and Whose dimensions may lack uniformity, a brush made of conducting material and having a slot so shaped that each of its surfaces acts as a contact surface between the brush and said body.

6. In a device for maintaining electrical contact with a body having a substantially cylindrical surface which has a rotational movement about its axis and a movement in the direction of its axis and whose dimensions may vary from point to point along the length of the body, a brush made of conducting material and having a V- shaped slot, the sides of the slot being curved and serving as the contact surfaces between the brush and the bodies.

'7. In a device for maintaining electrical contact with the electrodes of an electric arc, which electrodes are rotated about their axes and moved in the direction of their axes, are substantially circular in cross section and may vary in dimensions, cross sectional shape and degree of straightness both as between points along the individual electrodes and as between electrodes, a brush made of conducting material and having a slot with curved sides, said slot being so disposed that its sides form contact surfaces between the brush and the electrode.

8. In an arcing device having an electrode which is rotated and fed to the are as it is consumed in the arc, a brush for conducting current to said electrode, said brush having a surface for contacting the electrode which comprises a V-shaped slot having sides which are plane surfaces.

9. In an arcing device having an electrode which is rotated and fed to the arc, a brush for conducting current to the said electrode, said brush having a contact surface in the form of a V-shaped slot whose sides are curved surfaces.

10. In an arcing device having an electrode which is rotated and fed to the arc, a brush for conducting current to the said electrode, said brush having a contact surface in the form of a V-shaped slot whose sides are convex.

11. In an arcing device having an electrode which is rotated and fed to the arc, a brush for conducting current to the said electrode, said brush having a contact surface in the form of a V-shaped slot whose sides are concave.

12. In an arcing device in which an electrode of substantially circular cross-section is rotated about its axis and is moved axially to feed it to the arc, means for conducting current to the moving electrode comprising a fixed brush bearing against the electrode, said brush having a V-shaped slot, the sides of said slot serving as contact surfaces between said brush and the electrode.

13. In an arcing device having an electrode which is rotated and fed to the arc, a brush for conducting current to the electrode, said brush having a contact surface in the form of a V- shaped slot whose sides are surfaces generated by the movement of a substantially straight line while maintaining the line parallel to a predetermined line.

JOHN F. PETERS.