US2815421A

US2815421A - Electrical contacts

Info

Publication number: US2815421A
Application number: US611364A
Authority: US
Inventors: Jr Childress B Gwyn
Original assignee: Metals and Controls Corp
Current assignee: Metals and Controls Corp
Priority date: 1956-09-21
Filing date: 1956-09-21
Publication date: 1957-12-03
Anticipated expiration: 1974-12-03

Description

United States Patent ELECTRICAL CONTACTS Childress B. Gwyn, Jr., North Attleboro, Mass, assignor to Metals & Controls Corporation, Attleboro, Mass, a corporation of Massachusetts No Drawing. Application September 21, 1956, Serial No. 611,364

9 Claims. (Cl. 200-166) This invention relates to electrical contacts, and more particularly, to electrical devices including pairs of cooperating contacts formed of improved compositions.

In direct current applications, and particularly such applications where vibratory inductive load characteristics (such as those encountered in automobile-type voltage regulators) exist, transfer or migration of metal between a contact of a given polarity and a cooperating contact of opposite polarity often has deleterious effects. One of these deleterious effects is that the surface of one of the pair of cooperating contacts or contact elements becomes built-up, with a resulting change in the effective height of the built-up contact element. In a precision instrument such as an automobile voltage regulator, such a change in the effective height of one of the contact elements may seriously impair the operating characteristics of the voltage regulator whereby its operational-life is substantially shortened.

Accordingly, an object of this invention is to provide electrical means embodying pairs of cooperating electrical contact elements which have a comparatively long operating life.

A further object of this invention is to provide improved electrical means comprising a pair of cooperating contact elements whereby deleterious effects due to metal transfer or migration between these contact elements are counteracted.

A further object of this invention is to provide electrical means including an improved pair of cooperating contact elements whereby build-up on the surface of either of these contact elements is prevented or substantially lessened.

A further object of this invention is to provide electrical means incorporating a pair of cooperating electrical contact elements whereby contact-surface resistance rise is inhibited and self-life failure is minimized.

A further object of this invention is to provide electrical means comprising a pair of cooperating electrical contact elements which during operation thereof inherently effect a surface fritting action against each other thereby tending to obviate localized hot spots at the cooperating surfaces of the respective contact elements.

A further object of this invention is to provide electrical means embodying a pair of cooperating electrical contact elements of opposite polarities and formed of respective compositions whereby the electrical means exhibits improved operatingcharacteristics.

Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements, combinations of elements, features of construction, arrangements of parts, the ingredients, combinations of ingredicuts, the proportions thereof, and features of composition which will be exemplified in the structures and products hereinafter described, and the scope of the application of which will be indicated in the following claims.

The alloys of which the respective contact elements of the cpoperating pairs of. contactelements .of

this invention are formed are particularly useful for the voltage limiting contacts of automobile-type voltage regulators. However, for such regulators, contact compositions which provide good performance characteristics when used as voltage limiting contacts usually also provide reasonably good performance characteristics when used as current limiting contacts. The same holds true of the improved compositions set forth herein. Furtherfore, while the particular compositions of this invention are primarily suited for direct current applications, they also perform highly satisfactorily in alternating current applications where the current through the contact element combination is in the range of 5 amperes or less, and more particularly in the range of from a few milliamperes to one ampere.

In an electrical device for making and breaking an inductive, direct current, electrical circuit, and incorporating the improved contact elements of this invention, the contact element of positive polarity for the voltage limiting pair of contact elements is formed of an alloy consisting essentially of 50% to by weight of gold and the remainder silver. The contact element of negative polarity of the pair of voltage limiting contact elements of this invention is formed of an alloy consisting essentially of 60% to 80% by weight of palladium, 0.5% to l..8% by weight of a modifying agent, and the remainder silver.

The modifying agent referred to herein has a hardening effect on the resulting alloy. Furthermore, this modifying agent acts as a migration-controlling agent having the effect (when a negative contact element of this invention is disposed in cooperating relationship with a positive contact element of this invention) of tending to reverse the direction of metal transfer or migration which, in electrical circuits using direct current, ordinarily takes place from the negative contact element to the positive contact element. The result is that, although metal transfer or migration of metal from one of the contacts to the other does occur to some extent, this metal transfer or migration so occurs (when a contact element combination of this invention is disposed in an inductive direct current circuit as described above) that the average or overall metal transfer or migration is substantially zero. In this regard, metal transfer normally occurs from the positive to the negative contact element of the combination of this invention throughout the regulator vibrational frequency range of from approximately 45 cycles per second to zero cycles per second. From approximately 45 cycles per second to approximately 80 cycles per second the metal transfer may go in either of the two directions between the positive and the negative contact element; and, above approximately 80 cycles per second, the metal transfer normally goes from the negative to the positive contact element. Since the vibrational frequency in an automobile-type voltage regulator generally varies from 0 to cycles per second during its normal use, the total metal transfer or migration amounts to substantially zero When the combinations of this invention areused for such installations.

Also, with cooperating contact elements of a combination according to this invention, a surface fritting action occurs at the respective mutually engageable and disengageable surfaces of the contact elements whereby localized hot spots at these contact element surfaces are minimized. This, in turn, has a minimizing effect on the tendency for metal transfer or migration.

Best results have been effected when the modifying agent referred to above consisted essentially of nickel.

. Substantially identically good results have been obtained when the modifying agent consisted of a mixture of nickel and copper. In fact, unexpectedly good results are obtained by using as the modifying agent any one of nickel, cobalt, and copper and mixtures thereof, in substantially. this same proportion of 0.5 to 1.8% by weight,

Stated otherwise, so long as the modifying agent is in the proportion of from 0.5% to 1.8% by weight of the resulting alloy and is selected from the group consisting of nickel, cobalt and copper and mixtures thereof, the resulting composition is imbued with the migration-controlled and hardened characteristics which are discussed above.

A preferred example of a combination of contact elements of this invention is as follows: The contact element of negative purity is formed of an alloy consisting essentially of 72% by weight of palladium, 1.8% by weight of nickel and the remainder silver; and the contact element of positive polarity is formed of an alloy consisting essentially of 70% by weight of gold and the remainder silver. As another specific example of the respective contact element combinations falling Within the scope of this invention, the negative contact element is formed of an alloy consisting essentially of 65% by weight of palladium, 0.5% by weight of nickel and the remainder silver; and the contact element of positive polarity cooperating therewith being formed of an alloy consisting essentially of 60% by weight of gold and the remainder silver. As another preferred example of a contact element combination of this invention, the negative contact element is formed of an alloy consisting essentially of 72% by Weight of palladium, 0.4% by weight of nickel, 1.4% by weight of copper (the nickel and copper together making up the modifying agent), and the remainder silver; and the positive contact element is formed of an alloy consisting essentially of 70% by weight of gold and the remainder silver.

The efiicacy of the contact element compositions in the combinations of this invention is illustrated by the results of a series of life tests conducted under extremely severe operating conditions pointed out as follows. In particular, five contact element combinations formed of alloys presently in use in commercially-obtainable voltage regulators were compared with the contact element combinations formed of the improved alloys set forth herein. Each of these contact element combinations was placed in a 12 volt, Type No. 1119001, Delco Remy voltage regulator and each of these voltage regulators was disposed in electrically operative relationship with a partially-discharged, 12-volt storage battery and with a generator driven at a speed constantly varying from 1100 R. P. M. to 7000 R. P. M. and back to 1100 R. P. M.

The five presently-used contact element combinations referred to above appear as the first five combinations listed in the table below. The last two are combinations of this invention. All of the percentages listed below are by weight.

Voltage Limiting Contact Element Combination Average Life in Operational Hours Positive Polarity Negative Polarity 89% platinum, 11% 100% tungsten l, 100

ruthenium.

72% palladium, 1.8% -.do 1. 1,250

nickel, remainder silver 64% platinum, 25% do 1,000

palladium, 11% ruthenium.

77% silver, 22.7% cad- 3% palladium, 97% 700 mium, 0.3% nickel. silver.

95% silver, 5% manga- 99.5% silver, 0.5% 718 nese. car on.

70% gold, remainder 72% palladium, 1.8% 2,050

silver. nickel, remainder silver.

60% gold, remainder 65% palladium, 0.5% 1,765

silver. niickcl, remainder s ver.

Thus, the above-named preferred contact element combination (listed sixth, above) of this invention had an average operational-life of almost three times the length of one of the contact element combinations presently in use inautornotive type voltage regulators and approached an average operational-life of almost twice the length of that of the contact element combination presently used which had the longest average operational-life.

In the above-cited tests, operational failure occurred either as irregular action by the cooperating contacts of the particular combination which would have rendered the contacts unsuitable for their intended purpose, or as a closed circuit whereby the cooperating contacts of the particular combination remained mutually engaged with each other, either by sticking or by excessive build-up.

Each of the respective alloys forming the contact elements of the combinations of this invention can be formed by conventional melting processes.

The contact elements of this invention may constitute electrical contacts or merely the portions of electrical contacts which engage and disengage respectively cooperating contacts for making and breaking an electrical current.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

I claim:

1. A pair of cooperating electrical contact elements, one of said contact elements comprising an alloy consisting of 60% to by weight of palladium, 0.5% to 1.8% by weight of a modifying agent selected from the group consisting of nickel, cobalt and copper and mixtures thereof, and the remainder silver; and the other of said contact elements comprising an alloy consisting essentially of 50% to 80% by weight of gold and the remaindersilver.

2. A pair of cooperating electrical contact elements, one of said contact elements comprising an alloy consisting of 60% to 80% by weight of palladium, 0.5% to 1.8% by weight of nickel and the remainder silver; and the other of said contact elements comprising an alloy consisting essentially of 50% to 80% by weight of gold and the remainder silver.

3. A pair of cooperating electrical contact elements, one of said contact elements comprising an alloy consisting of 60% to 80% by weight of palladium, 0.5% to 1.8% by weight of cobalt and the remainder silver; and the other of said contact elements comprising an alloy consisting essentially of 50% to 80% by weight of gold and the remainder silver.

4. A pair of cooperating electrical contact elements, one of said contact elements comprising an alloy consisting of 60% to 80% by weight of palladium, 0.5% to 1.8% by weight of copper and the remainder silver; and the other of said contact elements comprising an alloy consisting essentially of 50% to 80% by weight of gold and the remainder silver.

5. A pair of cooperating electrical contact elements, one of said contact elements comprising an alloy consisting of 72% by weight of palladium, 1.8% by weight of nickel, and the remainder silver; and the other of said contact elements comprising an alloy consisting essentially of 70% by weight of gold and the remainder silver.

6. A pair of cooperating electrical contact elements, one of said contact elements comprising an alloy consisting of 72% by weight of palladium, 0.4% by weight of nickel, 1.4% by weight of copper, and the remainder silver; and the other of said contact elements comprising an alloy consisting essentially of 70% by weight of gold and the remainder silver.

7. In an electrical device for making and breaking an inductive, direct current, electrical circuit; a first electrical contact element of negative polarity, said first contact element comprising an alloy consisting essentially of 60% to 80% by weight of palladium, 0.5% to 1.8% by weight of a modifying agent selected from the group consisting of nickel, cobalt and copper and mixtures thereof, and the remainder silver; and a second electrical contact element of positive polarity, said second electrical contact element .comprising .an alloy consisting .,essentially of 50% to 80% by weight of gold and the remainder silver; said contact elements being cooperable to make and break said circuit.

8. In an electrical device for making and breaking an inductive, direct current, electrical circuit; a first electrical contact element of negative polarity, said first contact element comprising an alloy consisting essentially of 72% by weight of palladium, 1.8% by weight of nickel, and the remainder silver; and a second electrical contact element of positive polarity, said second electrical contact element comprising an alloy consisting essentially of 70% by Weight of gold and the remainder silver; said contact elements being cooperable to make and break said circuit.

9. In an electrical device for making and breaking an inductive, direct current, electrical circuit; a first electrical contact element of negative polarity, said first contact element comprising an alloy consisting essentially of 72% by weight of palladium, 0.4% by weight of nickel, 1.4% by weight of copper, and the remainder silver; and a second electrical contact element of positive polarity, said second electrical contact element comprising an alloy consisting essentially of 70% by weight of gold and the remainder silver; said contact elements being cooperable to make and break said circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,048,647 Feussner et al. July 21, 1936 2,151,905 Emmert Mar. 28, 1939 2,300,286 Gwyn Oct. 27, 1942

Claims

1. A PAIR OF COOPERATING ELECTRICAL CONTACT ELEMENTS, ONE OF SAID CONTACT ELEMENTS COMPRISING AN ALLOY CONSISTING OF 60% TO 80% BY WEIGHT OF PALLADIUM 0.5% TO 1.8% BY WEIGHT OF A MODIFYING AGENT SELECTED FROM THE GROUP CONSISTING OF NICKEL COBALT AND COPPER AND MIXTURES THEREOF, AND THE REMAINDER SILVER; AND THE OTHER OF SAID CONTACT ELEMENTS COMPRISING AN ALLOY CONSISTING ESSENTIALLY OF 50% TO 80% BY WEIGHT OF GOLD AND THE REMAINDER SILVER.