US1552993A - Electric-switch contact - Google Patents

Description

Sept. 8, 1925'. 1,552,993

H. E. LEPPERT ELECTRIC swmcu CONTACT Filed Jan. 13. 1923 Fig. 1..

7 0 w INVENTOR Henry E. L qaperi Patented Sept. 8, 1925.

v UNITED STATES PATENT OFFICE.

HENRY E..LEPPERT, OF NEW BRITAIN, CONNECTICUT, ASSIGNOR TO THE TBUMBULL ELECTRIC MANUFACTURING COMI A'NY, 0F PLAINVILLE, CONNECTICUT, A COR" IPQRATION CONNECTICUT.

ELECTRIG-SWITCH CONTACT.

Application filed January 13, 1923. Serial No. 612,467.

To all whom it may concern;

Be it known that I, HENRY E. Lnrrnnr, a

citizen of the United States of America,

of having only about one third the current.

carrying capacity of copper. It has such a decided grain or texture that it is liable to.

fracture unless the switcl1 contact is designed so as to have the grain extend in the right direction, in fact, contacts which are :of angularform and have parts extending in various directions are necessarily weak inspots. Fulthermore, bronze is quite expensive and difficult to manipulate. On the other hand, copper which is comparatively cheap and uniform in character and easy to bend into shape, and which has a high current carrying capacity, is comparatively v angular bends.

one of the contact soft and not so durable as bronze where there is rapid and repeated operation of the switch.

I have found however that satisfactory switch contacts can very easily be made of copper by compressing, swaging or squeczing the metal at the part where actual contact occurs so as to compress, condense and harden the metal.

Figure 1 is a perspective view showing the arrangement of contacts and terminals for what is sometimes termed a four-way push button switch.

F ig. 2 is an enlarged sectional view of portions and the supporting arm,"

Fig. 3' is a plan view of the rotatable contact member of what is commonly termed a rotary snap switch.

Fig.4 is an enlarged sectional view on the plane of the line l-4 of Figure 3.

Fig. 5 is a perspective View of one of the stationary contacts for a rotary snap switch. Fig. 6 is an enlarged sectional view on the plane of the line 6-6 of Fig. 5.

Figure 1 illustrates a form of construction whichit is particularly difficult to make of phosphor bronze on account of the many In a construction of this tions without fracturing kind, it will be obvious that it is impossible to lay out the contact so as to have the grain of the metal running longitudinally throughout all the parts. By making such contacts of copper however which is of uniform character it is very easy to bend the arms and terminal portions into the desired posi the metal. In this case the bracket portion or carrier arm 7 has a number of contact portions such as 8 which are swaged or squeezed, for instance in a power press, so as to make the metal more dense at the point where the actual physical contact is to occur. In some cases a hve per cent reduction in thickness .is'

sufficient to materially stiffen the metal and prolong its life against the thousands of rapid repeated openings and closings of the circuit to which such switches are subjected. The switch member 9 of Figure 8 has oppositely disposed contact portions 10 which have been condensed as above described. In some cases two are employed secured face to face as in many rotary snap switches.

Figure 5 shows the invention as applied to a stationary type of terminal and contact having a body portion 11 and a contact portion 12 which has been compressed to harden it. Although I consider this invention as formed of copper, I anticipate that the same principle may be applied to contacts formed ofsoft brass which material is easily worlrc l and. has a fairl good current carrying capacity, ,and which does not have the disadvantageous characteristics of bronze.

It has been the practicetoarrange the contact members of snap switches of the several types either with a solid movable contact member adapted to contact between a pair of spring fingers carried by a stationary member or with a movable contact member having two-part spring ends adapted to contact on opposite sides of a solid stationary contact member.

it has been the practice to'makc the solid member of con'iparatively hard brass and the spring members of bronze or, in some cases, of extra hard brass; bronze is expcnsive, difficult to work, liable to fracture because of 91a drawing grain and its conductivity is relatively low; brass is far from of such switch members particularly applicable to contacts manner, it is equal to copper in conductivity and is objectionable because, in many cases, sharp ends are necessary and metal which is soft enough to stand these bends without fracturing the metal is too soft to stand up well mechanically in the many operations of the switch.

Copper has been considered to be too softh for use as contact members for such except, in some cases, as for contacts. The hardest copper is soft enough to be bent at any angle relative to the drawing grain'of the metal but it has been too soft to stand up well in the rep ea ed operation of the switch. now find in actual practice that hard drawn copper possesses s'uflicient spring qualities to function as spring contacts and that it wears well mechanically after the contact ends have been 'hardened or compressed in the manner specified.

lVith the contact ends hardened in this possible and practical to make any or all of the switch contacts of copper which possesses the maximum mechanical strength and electrical conductivity and the method applies equally well when comparatively'soft brass is used for making the contacts.

Obviously the compressed portion of these contacts could be drawn in the sheet metal as it passes through the drawing rolls and the blanking dies could be laid out accordingly but, as a rule, it would be more economical to blank the parts out of regular commercial metal at the most advantageous cutting angle and to then compress the eontact ends.

Contacts made in this manner possess several very advantageous characteristics.

First: The body portion is of comparatively soft metal which is not likely to break through the impact or momentum of the snap switch action because it is not at all brittle and has practically no grain due to the metal drawing-process yet it possesses sullicient spring to serve its purpose.

Second: The squeezing or con'ipressing of the contact head portion produces a comparatively hard surface which resists the operating wear and obviates the natural tendency of soft metal to ball up when subjected to friction.

Third: The compressin heads between polished dies produces a perfectly finished surface well adapted to re sist friction and all burrs, pins or projections are also removed by the same compressing or squeezing operation.

switches solid stationary drawn commercial of the contact shown in Fig. 3

Fourth: By making the snap switch contact of copper particularly in the form it is possible to use comhighly conductive metal and still have the necessary resiliency in the arms and the necessary hardness in the com- It is also easier to andle and assemble such copper snap with the usual supporting accuracy on account of their greater thickness.

claim: i

1. A sheet copper snap switch cont-act having a body portion and a contact head,

the said body portion being relatively soft portion being hardened y compression to increase its resistance to mechanical wear.

2. An electric switch contact member formed of comparatively soft conductin sheet metal of low resistance principally copper and having a contact portion compressed and hardened and having smooth contact faces.

3. The method of forming a switch member which comprises blanking a piece of comparatively soft highly conducting sheet metal and hardening the contact portion by compressing the same to a less thickness than too remaining portion.

4. A switch contact member formed from commercial drawn sheet metal having a supporting portion and a consaid' contact head being condensed by mechanical pressure to'increase the density of the metal of the head.

11 electric switch contact member hav-' ing a supporting portion of readily bendable metal and a contact head compressed to increase the density and hardness of the metal thereof.

7. An electric switch contact member having a supporting portion of commercially rolled sheet copper and a contact portion condensed and hardened for the purpose specified.

8. An electric switch member having a supporting portion of relatively soft easily bendable metal and a contact head, said contact head being hardened solely by compression for the purpose specified.

HENRY E. LEPPERT.

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