US763812A - Resistance for electrical uses. - Google Patents

Description

PATENTED JUNE 28, 1904.

J. F. TRACY. RESISTANGE FOR ELECTRICAL USES.

APPLICATION FILED DEC. 12, 1903.

N0 MODEL.

FIGJ.

WITNESSE S: KW

UNITED STATES Patented June 28, 1904:.

PATENT OFFICE.

JAMES F. TRACY, OF SHERIDANVILLE, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TO WILLIAM H. McFADDEN, OF PITTSBURG, PENNSYL- VANIA.

RESISTANCE FOR ELECTRICAL USES.

SPECIFICATION forming part of Letters Patent No. 763,812, dated June 28, 1904.

i Application filed December 12, 1903. Serial No, 184,949. (No model.)

To all whom, it may concern.-

Be it known that I, J AMES F. TRACY, a citizen of the United States, residing at Sheridanville, in the county of Allegheny and State of Pennsylvania,have invented or discovered certain new and useful Improvements in Resistances for Electrical Uses, of which improvement the following is a specification.

The invention described herein relates to certain improvementsin resistances for electrical purposes, the improvements being especially applicable for use in connection with starting-boxes for motors, circuit-controllers, heaters, &c.; and the-invention has for its 01 ject a construction capable of presenting any desired resistance without destruction or material injury to the resistance mechanism or parts controlled thereby.

The invention is hereinafter more fully described and claimed.

In the accompanying drawings, forming a part of this specification, Figure 1 is a side elevation of a starting-box embodying my improvement. Fig. 2 is a sectional elevation of the same on a plane indicated by the line II II, Fig. 1; and Fig. 3 is a transverse section on a plane indicated by the line III III, Fig. 1.

In applying my improvement to startingboXes a holder or shell 1, formed of a suitable insulating material, as indurated fiber asbestos, &c., is filled with finely-comminuted material 2. This material may be formed of any suitable substance, as cast-iron, steel,

wrought-iron, &c., or a mixture of two or more materials which when comminuted will give the desired resistance. Contact-pieces 8 are secured upon the holder or shell at suitable distances apart and electrically connected to the core 2. A convenient construction to this end consists in providing the contacts with jaws 1, embracing the shell and secured in position'by pins 5, passing through the jaws, the shell or holder, and the core, the material of the latter being compacted, by preference, so as to make good contact with the pins 5. The movable contact is formed by a U-shaped spring 6, having one leg sccured to a sliding block 7, movably mounted on a guide-rod 8, arranged parallel with the shell or holder. The other leg of the contactspring is adapted to bear against the contacts in succession as the supporting-block is shifted. It is preferred to secure the guide-rod 8 to the brackets 9, whereby the tubular shell or holder is secured to a suitable support. By movably mounting the block 7 on the rod or the latter in its bearing the block may be swung around for repairs, &c., ot' the spring or other part. Ordinarily one terminal, 10, of the starting-box is formed on or by the last one of the series, while the other terminal, 11, is electrically connected to the rod 8, which is electrically connected through the slide 7 to the contact-spring. It will be understood that the terminal 10 may be connected to any one of the contacts 3, dependent upon the resistance required. In case the comminuted material should become inoperative or defective, the plugs 12 at the end of the holder can be removed and the comminuted material discharged and new material placed in the holder.

I have found that with my improved starting-box ashunt-wound motor can be started when fully loaded without any injury to the motor or starting-box. A similar test made with the form of starting-box of the construction now in use resulted in the burning out of all the resistance-coils.

lVhile I have found that finely-comminuted cast-iron gives good results, the invention is not limited to such material, as I consider the employment or use of any comminuted material or mixture ofcomminuted n1aterials,many of which will suggest themselves to those skilled in the art, capable of giving the desired resistance effect as within the scope of my invention.

I claim herein as my invention 1. A starting-box having in combination a non-conducting tubular holder or shell, a core formed of comminuted conducting material, a series of contacts arranged in the shell or holder, and electrically connected to the core, ed to bear on the contact-pieces, substantially and a contact movable along the stationary as set forth. 1 contacts, substantiallyas set forth. In testimony whereof I have hereunto set 2. A starting-box having a tubular shell, a my hand. filling of comminnted conducting material, JAMES F. TRACY. contact-pieces provided With jaws gripping Witnesses: the shell and electrically connected to the fill- DARWIN S. WoLooTT,

ing, and a sliding block having a spring adapt- F. E. GAITHER.

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