GB Patent 957872 - Improvements in electric switch contacts

Claims

Claim 1 wherein the first contact element

consists of 70 % gold-30 % silver and the second contact element consists of 50 % palladium-50 % silver.

3 An electric switch according to Claim 1 or Claim 2, wherein the first contact element has a cylindrical contact surface.

4 An electric switch according to any one of the foregoing claims wherein the first contact element is located on a moving part of a driven mechanism.

An electric switch according to any one of the foregoing claims, wherein the second contact element has the form of a resilient elongated contact member of which one end is attached to a fixed part of a driven mechanism.

6 An electric switch according to any one of the foregoing claims, wherein the second contact element is arched at least about an axis parallel to the axis of the first contact element.

7 An electric switch according to Claim 6, wherein the second contact element is arched about a second axis at an angle to the other axis of this contact element.

8 An electric switch according to Claim 7 wherein the angle is a right angle.

9 An electric switch comprising a pair of contact elements substantially as herein described with reference to the accompanying drawing.

An electric clock or watch including the electric switch according to any one of the preceding claims.

practically no mechanical wear of the contact element.

In the embodiment illustrated in Figs.

3 to 6, parts common with Figs 1 and 2 have been given like references In this embodiment, a resilient contact element 40 replaces element 10 and has a narrow substantially rectangular cross-section and also a curved part 41 followed by a free arm 42 Element 40 may, for example, have a cross-section approximately 0 4 mm X 0.20 mm = 0 008 sq mm and a length of mm and is formed from the same materials as described for element 10 The curved part 41 is formed to give a partspherical contact surface, i e, it has a double curvature, as is best seen in Figs.

4-6.

Since gold-silver and silver-palladium alloys are used for the contact elements it is advantageous to connect the positive pole of the battery to the gold-silver contact and the negative pole to the silverpalladium contact.

Among the advantages of the switch contacts disclosed are that the mechanical contact wear is reduced to a minimum, and further that the self-resilient construction of the contact element 20 or 40 makes the switch simple and inexpensive to produce.

The element 10 or 40 itself can be made by relatively simple machining of precious metal alloys without it being necessary to laminate different materials.

WHAT WE CLAIM IS: 1 An electric switch for electric clocks or watches driven by direct current for periodically opening and closing the drive circuit, comprising first and second contact elements, wherein the first contact element contains 65 % to 80 % gold and 35 % to % silver, with up to 30 % of the silver being replaceable by copper, and the second contact element contains 40 % to less than 60 % palladium and the remainder silver, STEVENS, LANGNER, PARRY & ROLLINSON, Chartered Patent Agents, Agents for the Applicants.

Abingdon: Printed for Her Majesty's Stationery Office, by Burgess & Son (Abingdon), Ltd -1964.

Published at The Patent Office, 25 Southampton Buildings, London, W C 2, from which copies may be obtained.

957,872

Description

PATENT SPECIFICATION

DRAWINGS ATTACHED.

Date of Application and filing Complete Specification:

Feb 15, 1962.

No 5797/62.

c O Application made in Germany (No D 35487 VII Ic/21 g) on Feb 24, 1961.

Complete Specification Published: May 13, 1964.

(C) Crown Copyright 1964.

Index at Acceptance:-H 2 B( 2 C 1, 2 C 4, 2 C 6 C 2, 2 C 6 D, 2 C 6 X, 2 C 17); C 7 A( 8 K, 8 L, 85, 8 T, 19, X); G 3 T(A 5 81, A 5 B 2).

International Classification:-H 02 c (C 22 c, G 04 c).

COMPLETE SPECIFICATION.

Improvements in Electric Switch Contacts.

EP?,ATA SPECIFICATION 'NO 957, B 72 t l, DIENT NO 1.

Page 2, line e, for,rellabilit Y" read vreliably" page 3, line 11, for,0 4 " rea J " O 04 " Page 3, line 29, for " 20 " read " O " THE PATENT OFFICE, ist 'November, 1966 ana otner mecnamnisms by periodically interrupting the current given by a battery which furnishes driving power for moving parts of the mechanism in co-operation with a system of magnets Very high requirements are made of the switch contacts which periodically interrupt the current, in view of the number of interruptions and, in a wrist watch particularly, the dimensions of the contacts since the latter have to be accommodated in the watch case together with the mechanism and usually the battery A pair of contacts of this kind must, for example, perform over 150 million switching operations per year, given five breaks per second, and the surface properties of the contact materials hence should not vary to any marked degree Moreover, the contact system together with the necessary spring elements must be relatively small, particularly in wrist watches.

In accordance with the present invention, the above problems are solved very simply by using an electric switch comprising first and second contact elements, wvherein the first contact element contains lPrice 4 s 6 d l D 75 E is especially achieved the effect that if any protuberances or cavities appear on the surface of the element or the surface becomes roughened the surface will be smoothed over by wiping action of the second contact element and hence the surface remains smooth This effect is enhanced as the proportion of gold in the material increases and operates to ensure good contact between the contact surfaces and long life.

The precious metal alloys used for the first contact element are gold-silver alloys in the range 65 % to 80 % gold and 35 % to 20 % silver If desired, up to 30 % of the silver present in the alloy can be replaced by copper The alloys used for the second contact element are palladiumsilver alloys in the range 40 % to less than 60,' palladium and the remainder silver.

The silver present may be partly replaced up to 20 % by metals which form mixed crystals with the binary silver-palladium alloy, a preferred metal being copper The combination of a 70 % gold-30 % silver alloy as the first contact element and a 957,87 PATENT SPECIFICATION

957,872 DRAWINGS ATTACHED.

Date of Application and filing Complete Specification:

Feb 15,1962 No 5797/62.

Application made in Germany (No D 35487 VII Ic/21 g) on Feb 24, 1961.

Complete Specification Published": May 13, 1964.

C) Crown Copyright 1964.

Index at Acceptance:-H 2 B( 2 C 1, 2 C 4, 2 C 6 C 2, 2 C 61 D, 2 C 6 X, 2 C 17); C 7 A( 8 K, 8 L, 8 S, 8 T, 18, 19, X); G 3 T(A 5 B 1, A 5 B 2).

International Classffication:-H 02 c (C 22 c, G 04 c).

COMPLETE SPECIFICATION.

Improvements in Electric Switch Contacts.

We, Tim UNITED STATES TIME CORPORATION, a Corporation organized under the laws of the State of Connecticut, United States of America, of Middlebury, County of New Haven, Connecticut, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: -

This invention relates to improvements in electric switches, and provides electric switch contacts which are particularly suitable for use in electric clocks or watches.

It is known to drive clocks or watches and other mechanisms by periodically interrupting the current given by a battery which furnishes driving power for moving parts of the mechanism in co-operation with a system of magnets Very high requirements are made of the switch contacts which periodically interrupt the current, in view of the number of interruptions and, in a wrist watch particularly, the dimensions of the contacts since the latter have to be accommodated in the watch case together with the mechanism and usually the battery A pair of contacts of this kind must, for example, perform over 150 million switching operations per year, given five breaks per second, and the surface properties of the contact materials hence should not vary to any marked degree Moreover, the contact system together with the necessary spring elements must be relatively small, particularly in wrist watches.

In accordance with the present invention, the above problems are solved very simply by using an electric switch comprising first and second contact elements, wherein the first contact element contains lPrice 4 s 6 d l % to 80 % gold and 35 % to 20 % silver, with up to 30 % of the silver being replaceable by copper, and the second contact element contains 40 % to less than 60 % palladium and the remainder silver, with up to 20 % of the silver being replaceable by metals, particularly copper, which form mixed crystals with the binary silverpalladium alloy The second contact element is preferably connected in the form of a self-resilient bow-shaped member to the fixed parts of the mechanism, while the first contact element is preferably connected to a periodically moving part of the driven mechanism By including gold in the' alloy of the first contact element there is especially achieved the effect that if any protuberances or cavities appear on the surface of the element or the surface becomes roughened the surface will be smoothed over by wiping action of the second contact element and hence the surface remains smooth This effect is enhanced as the proportion of gold in the material increases and operates to ensure good contact between the contact surfaces and long life.

The precious metal alloys used for the first contact element are gold-silver alloys in the range 65 % to 80 % gold and 35 % to 20 % silver If desired, up to 30 % of the silver present in the alloy can be replaced by copper The alloys used for the second contact element are palladiumsilver alloys in the range 40 % to less than % palladium and the remainder silver.

The silver present may be partly replaced up to 20 % by metals which form mixed crystals with the binary silver-palladium alloy, a preferred metal being copper The combination of a 70 % gold-30 % silver alloy as the first contact element and a % silver-50 % palladium alloy as the second contact element has proved very satisfactory.

When such alloys are used the contacts have a surprisingly long life and hence operate reliability over a long period much in excess of a year and, in many forms, a considerable number of years.

Since the resilient contact element may, and indeed preferably does, consist of the same self-resilient material integrally throughout, its construction is simple and inexpensive and it is adapted to take up a minimum amount of space, which is particularly important in the case of watches.

To improve the "smoothing" effect and reduce wear still further, it is advantageous for the contact elements to slide past one another during the making and breaking of contact Sliding is promoted by appropriately curving the contact surfaces and preferably both the contact surfaces are curved The curvature is advantageously cylindrical over the contact surface of one contact element, preferably the first contact element, and again cylindrical or, better still, domed or part-spherical over the contact surface of the other contact element, preferably the self-resilient element This latter configuration provides the contact surface of the contact element in question with at least two curvatures the axes of curvature being preferably substantially normal In this case, contact between the contact surfaces is theoretically limited to a point, and in these conditions an extremely good "smoothing" effect and no appreciable wear are obtained.

Further features of the invention will become apparent from the following description of preferred embodiments thereof, reference being made to the accompanying drawing wherein: Fig 1 is a plan view of one embodiment of the invention; Fig 2 is a side view in the direction of the arrow A in Fig 1; Fig 3 is a side view, similar to Fig 2, of a further embodiment of the invention; Fig 4 is a partial view in the direction of the arrow B in Fig 3 of the resilient contact element to a larger scale than Fig 3; Fig 5 is a section on the line 5-5 in Fig 4; and Fig 6 is a section on the line 6-6 in Fig 4; In the embodiment of the invention illustrated in Figs 1 and 2, a self-resilient contact element 10 of circular cross-section is clamped or fastened 'by its right-hand end in the drawing to a stationary part 11 of a clock or watch At its free end the element 10 is bent back upon itself so as to give a curved part 12 which forms the contact surface, and a straight free arm 13.

An oscillating element 20, for example, the balance wheel 22 of a watch, periodically oscillates to and fro about a pivot 21 70 A contact element 23 having a cylindrical contact surface is fastened on balance wheel 22 and its axis extends parallel to the axis of rotation of the wheel and hence perpendicular to the general direction of move 75 ment In addition to this contact element, a check element 24 of insulating material, for example a ruby, is fastened on the balance wheel and serves to improve contact conditions On oscillation of the 80 balance wheel 22 the check element first meets the part 12 of the resilient contact element 10 and imparts a certain initial tension to the latter, so that on further movement of the balance wheel 22 the 85 energy stored in resilient element 10 is released suddenly to snap the contact surfaces on the contacts 10 and 23 into engagement A circuit (not shown) is then closed through a current source e g a go battery so as to result in a current used to drive the balance wheel During the further movement of balance wheel 22 the contacts slide upon one another After a certain distance the contacts separate again 95 so that the current is interrupted.

In the example described above the contact element 10 is made of the self-resilient material Particularly suitable materials for forming the contact elements 10 and 23 100 are alloys of the precious metals; for element 23 gold-silver alloys consisting of from 65 % to 80 % gold and 35 % to 20 % silver are used If desired, up to 30 % of the silver present in the alloy can be re 10 a placed by copper Far element 10, the alloys used are silver-palladium alloys consisting of from 40 % to less than 60 % palladium and the remainder silver The silver present may be partly replaced by 110 metals which form mixed crystals with the binary silver-palladium alloy, a preferred metal being copper.

A pair of contact elements were constructed using a 70 % gold-30 % silver alloy 115 to form the one contact element and a % silver-50 % palladium alloy to form the other, self-resilient contact element, and these have proved very satisfactory in service, operating reliably over a long 120 period The resiliency and the hardness of the material forming the resilient contact element can be increased, if necessary, by subjecting it to cold working during manufacture 125 The use of a hard self-resilient precious metal alloy for the resilient contact element gives the additional advantage that when it meets a check element 24 consisting of hard insulating material there is 130 957,872 with up to 20 % of the silver being replaceable by metals, particularly copper, which form mixed crystals with the binary silverpalladium alloy.

2 An electric switch according to