US2154068A - Electrical contact - Google Patents

Electrical contact Download PDF

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Publication number
US2154068A
US2154068A US205360A US20536038A US2154068A US 2154068 A US2154068 A US 2154068A US 205360 A US205360 A US 205360A US 20536038 A US20536038 A US 20536038A US 2154068 A US2154068 A US 2154068A
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US
United States
Prior art keywords
per cent
tin
silver
electrical
electrical contact
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US205360A
Inventor
William C Ellis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to BE452819D priority Critical patent/BE452819A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US205360A priority patent/US2154068A/en
Application granted granted Critical
Publication of US2154068A publication Critical patent/US2154068A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/021—Composite material
    • H01H1/023—Composite material having a noble metal as the basic material

Definitions

  • This invention relates to electrical contacts and more particularly to electrical contact materials having good electrical conductivity combined with superior wear resisting properties.
  • An object of this invention is an improved contact material which has low contact resistance, superior wear resisting characteristics, is easily worked and can be readily attached to electrical apparatus by welding.
  • this object is attained by the-use of electrical contacts composed of an alloy containing between 90 and 99 per cent. silver and between 10 to 1 per cent. tin.
  • the electrical contact material comprises a binary alloy containing 95 to 97.5 per cent. silver and the remainder tin.
  • an alloy containing 95 per cent. silver and per cent. tin, and another containing 97.5 per cent. silver and 2.5 per cent. tin are admirably adapted for electrical contacts in panel dial and cross-bar dial systems.
  • These latter alloys may be easily fabricated into thin sheets or wires from which the electrical contacts are obtained. Contacts of these alloys may be welded without difficulty to electrical switches or relays and while possessing nearly as low contact resistance as pure silver, they have a considerably greater period of serviceability.
  • the range of proportions of silver and tin of the alloys in accordance with this invention is critical. If the binary alloys of silver and tin contain less than 1 per cent. of tin, the compositions are too soft and the specific resistivity of the contact materials are not sufficiently high to weld readily to the armatures of switches or relays. If the amount of tin exceeds per cent. 5 of the alloy, the material cannot be worked conveniently to obtain the contacts. Accordingly,
  • silver represent the compositions within the scope of this invention.
  • the alloys be restricted to compositions containing approximately 2 per cent. to 5 per cent. tin and the remainder silver without any substantial quantity of impurities.
  • the Rockwell hardness (B- -60) of annealed samples of electrical contact materials containing pure silver, an alloy containing 97.5 per cent. silver and 2.5 per cent. tin and an alloy containing 95 per cent. silver and 5 per cent. tin are 20, 30, and 39, respectively.
  • the resistivity and tensile strength of electrical contacts of pure silver and an alloy containing 95 per cent. silver and 5 per cent. tin are as follows:
  • Hard drawn Annealed Hardirawn Annealed 1. 99 1. 88 35, 000 26, 000 AgSn(95-5) 20.7 20.0 74,000 39,000
  • An electrical contact material containing from 90 to 99 per cent. silver and from 10 to 1 per cent. tin.
  • An electrical contact composed of an alloy containing approximately 97.5 per cent. silver and approximately 2.5 per cent. tin.
  • An electrical contact composed of an alloy containing approximately 95 per cent. silver and 5 per cent. tin.
  • An electrical contact composed of an alloy consisting of 95 to 97.5 per cent. silver and 5 to 2.5 per cent. tin.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Contacts (AREA)

Description

Patented Apr. 11, 1939 UNITED STATES PATENT OFFICE ELECTRICAL CONTACT No Drawing. Application April 30, 1938, Serial No. 205,360
5 Claims.
This invention relates to electrical contacts and more particularly to electrical contact materials having good electrical conductivity combined with superior wear resisting properties.
In modern telephone practice, particularly in the panel dial and cross-bar dial systems, a tremendous number of electrical contacts are continuously made by automatic mechanisms. In such systems it is, of course, extremely important that a good contact be completed in order to obtain efficient transmission. Of necessity the contact points employed must be of materials which possess low contact resistance and good wear resis'ting characteristics. Further the contact ma- 15 terial in manufacture must be capable of easy I working and ready attachment by welding to relay armatures or other electrical apparatus. It has been found that certain of the alloys and metals heretofore employed for use as contact materials with other mechanisms and switches did not function satisfactorily when used in panel dial and cross-bar telephone switches.
An object of this invention, therefore, is an improved contact material which has low contact resistance, superior wear resisting characteristics, is easily worked and can be readily attached to electrical apparatus by welding.
In accordance with this invention, this object is attained by the-use of electrical contacts composed of an alloy containing between 90 and 99 per cent. silver and between 10 to 1 per cent. tin. Preferably the electrical contact material comprises a binary alloy containing 95 to 97.5 per cent. silver and the remainder tin. For example, an alloy containing 95 per cent. silver and per cent. tin, and another containing 97.5 per cent. silver and 2.5 per cent. tin are admirably adapted for electrical contacts in panel dial and cross-bar dial systems. These latter alloys may be easily fabricated into thin sheets or wires from which the electrical contacts are obtained. Contacts of these alloys may be welded without difficulty to electrical switches or relays and while possessing nearly as low contact resistance as pure silver, they have a considerably greater period of serviceability.
The range of proportions of silver and tin of the alloys in accordance with this invention is critical. If the binary alloys of silver and tin contain less than 1 per cent. of tin, the compositions are too soft and the specific resistivity of the contact materials are not sufficiently high to weld readily to the armatures of switches or relays. If the amount of tin exceeds per cent. 5 of the alloy, the material cannot be worked conveniently to obtain the contacts. Accordingly,
an alloy containing 1 per cent. tin and 99 per cent. silver and one containing 10 per cent. tin
and 90 per cent. silver represent the compositions within the scope of this invention.
For panel dial and cross-bar dial systems it is preferred that the alloys be restricted to compositions containing approximately 2 per cent. to 5 per cent. tin and the remainder silver without any substantial quantity of impurities. The Rockwell hardness (B- -60) of annealed samples of electrical contact materials containing pure silver, an alloy containing 97.5 per cent. silver and 2.5 per cent. tin and an alloy containing 95 per cent. silver and 5 per cent. tin are 20, 30, and 39, respectively. The resistivity and tensile strength of electrical contacts of pure silver and an alloy containing 95 per cent. silver and 5 per cent. tin are as follows:
Resistivity HllCl'0)hlIl- Tensile strength lbs/sq. cm. (23 C in.
Hard drawn Annealed Hardirawn Annealed 1. 99 1. 88 35, 000 26, 000 AgSn(95-5) 20.7 20.0 74,000 39,000
longer, are more easily welded to electrical apparatus, and due to the differential in cost between silverand tin, are more economical of manufacture.
What is claimed is:
1. An electrical contact material containing from 90 to 99 per cent. silver and from 10 to 1 per cent. tin.
2. An electrical contactcomposed of an alloy containing from 95 to 97.5 per cent. silver and from 5 to 2.5 per cent. tin.
3. An electrical contact composed of an alloy containing approximately 97.5 per cent. silver and approximately 2.5 per cent. tin.
4. An electrical contact composed of an alloy containing approximately 95 per cent. silver and 5 per cent. tin.
5. An electrical contact composed of an alloy consisting of 95 to 97.5 per cent. silver and 5 to 2.5 per cent. tin.
WILLIAM C. ELLIS.
US205360A 1938-04-30 1938-04-30 Electrical contact Expired - Lifetime US2154068A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
BE452819D BE452819A (en) 1938-04-30
US205360A US2154068A (en) 1938-04-30 1938-04-30 Electrical contact

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US205360A US2154068A (en) 1938-04-30 1938-04-30 Electrical contact

Publications (1)

Publication Number Publication Date
US2154068A true US2154068A (en) 1939-04-11

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
US205360A Expired - Lifetime US2154068A (en) 1938-04-30 1938-04-30 Electrical contact

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US (1) US2154068A (en)
BE (1) BE452819A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2548164A (en) * 1947-11-28 1951-04-10 Fansteel Metallurgical Corp Electrical contact
US3819897A (en) * 1972-01-21 1974-06-25 Siemens Ag Vacuum switch with contact material containing a minor percentage of aluminum
US4579787A (en) * 1983-12-14 1986-04-01 Degussa Aktiengesellschaft Material for low voltage current contacts
US5500304A (en) * 1992-02-05 1996-03-19 Beru Ruprecht Gmbh & Co. Kg Silver-nickel composite material for electrical contacts and electrodes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2548164A (en) * 1947-11-28 1951-04-10 Fansteel Metallurgical Corp Electrical contact
US3819897A (en) * 1972-01-21 1974-06-25 Siemens Ag Vacuum switch with contact material containing a minor percentage of aluminum
US4579787A (en) * 1983-12-14 1986-04-01 Degussa Aktiengesellschaft Material for low voltage current contacts
US5500304A (en) * 1992-02-05 1996-03-19 Beru Ruprecht Gmbh & Co. Kg Silver-nickel composite material for electrical contacts and electrodes

Also Published As

Publication number Publication date
BE452819A (en)

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