US1048670A - Contact for electromagnetic mechanism. - Google Patents

Description

R. A. PBSSENDEN. CONTACT FOR ELECTROMAGNETIC MECHANISM. APPLICATION rum) MAILIB, 1906.

7 Patented De0.31, 1912.

WITNESSES: i

(H 9.4 L3 WW wwzmmm UNITED STATES PATENT OFFICE.

REGINALD A. FESSENDEN, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, IBY MESNE ASSIGNMENTS, TO SAMUEL M. KINTNER, OF PITTSBURGH, PENNSYLVANIA, AND HALSEY M. BARRETT, OF BLOOMFIELD, NEW JERSEY, RECEIVERS.

Specification of Letters Patent.

Application filed March 16, 1906. Serial No. 306,387.

To all whom it may concern:

Be it known that I, REGINALD A. FEssEN- DEN, a citizen of the United States, and resident of Washington, District of Columbia, have invented certain new and useful Improvements in Contacts for Electromagnetlc Mechanism, of WhlCh the following is a specification.

The invention relates to electrical contacts, and is especially adapted for use'in sensitive relays.

Great difficulty has been experienced in the use of relays from the sparking and consequent weldln together of the contacts, even when a con enser is used across the contacts. And further the surfaces of the contacts become oxidized or otherwise deteriorated so that the pressure of one contact on the other is not suflicient to break or destroy the resisting film and permit of the completion of the circuit.

My invention has for its object the prevention of a weld between contacts and the rupture of such weld, if formed, without interference with the operation of the relay or other instrument.

It is a further object of the invention to prevent the formation of a non-conducting film on the surfaces of the contacts and its removal or breaking up if formed, as hereinafter more fully described and claimed.

In the accompanying drawing forming a part of this specification is shown diagrammatically a relay a bell.

In the practice of my invention a finger 1 is attached to the movable part or member of a relay, as for exam Ie the movable coil 2 of the Weston type 0 relays. This finger is preferably made so that it will bend or flex under slight pressure, and has suflicientresilience to return to normal position when relieved of the pressure. This finger is pro- .vided on one or both sides, dependent on the use to which the relay is put, with contacts 3., Similar contact or contacts, 4, are securedto springs or yielding members, 5 and 6, adapted to yield -read1ly under sli ht pressure and return to normal osition w en the pressure is relieved. ile I have shown my improvement as applied to the and circuits for operating operation of a bell, only one stationary con- The springsor yielding members, 5 and 6, are secured to suitable supports, 7 and 8, and means such as screws 9 are provided for adjusting such members. The springs 5 and 6 are connected to one pole of a battery, 10, which has its opposite pole connected to the finger, 1,. and a bell or other device, 11, is included in this circuit. A condenser, 12, or resistance, 13, or both, may be connected in shunt across the fixed and movable contacts.

It has been found experimentally that the sparking and welding 15 due to the chattering which occurs when the movable contact touches the fixed contact. If however the parts carrying the fixed contact or contacts, or the finger carrying the movable when one contact touches the other will be avoided. Any elasticity or flexibility will not attain the desired object,- but the proper elasticity must be attained empirically, when the vibrations will be damped and thus sparking avoided. It will also be noted that by means of the screw 9 the tension of the arm 5 may be varied and this will vary the period of vibration, so that the swing of the arms 5 and 1 may be made to coincide, which will eflect a further decrease in chattering,

In case sparking and welding should oc cur, provision is made by makmg the contacts in the form of segments of spheres, for

the rupture of such weld. Since the centers,

of motion of the arms are widely separated, the contacts in swinging will rub or roll one on the, other, thereby exerting such a leverage as will easily break any weld which may be formed.

It has been determined in a series of experiments with'electrical contacts, that almost all metal contacts deteriorate in time when the pressure of one contact on the other is very'slight. For example the resistance of silver or platinum contacts will run up to thousands of ohms in a few days or hours. I have ascertained that contacts made of any alloy of platinum and iridium, preferably an alloy containing 5% or 10% of ididium will not deteriorate, and the resistance will not rise materially if at all even when the contacts are pressed together very light, the pressure being of the order Patented Dec. 31, 1912.

of one tenth of a milligram. This discovery I of the benefit derived by the use of this alloy bears no relationto my previous discovery that the, high tem erature due to arcing in induction coils, di not deteriorate contacts formed of platinum iridium. In the present case the good results are due to the fact that thin high resisting coatings or filmswill not form on platinum iridium contacts, even when there is not any heating .from sparking. The arrangement of the spherical contacts on the yielding supports is further advantageous as when the movable contact bears against the other contact, both will move slightly in the same direction and there will be a rolling and a rubbing movement of one contact on the other tending to remove or break down any resisting film.

I claim herein as my invention:

'1. An electrical contact device comprising aplurality of contact members mounted respectively on resilient and upon resilient and pivoted supports, said members being of rounded form, whereby in making contact the members both'slide and rotate in contact with each other, substantially as described.

2. An electrical contact device comprising electrodes made of platinum iridium of general spherical form and mountings for said electrodes in the form of pivoted and resilient arms, whereby to prevent sparking.

In testimony whereof, I have hereunto set my hand and seal, the 12th day of March A. D. 1906.

REGINALD A. ZFESSENDEN. [1.. 'S.]'

Witnesses:

JESSIE E. BENT, PHILIP P051.

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