US1879303A - Switch blade - Google Patents

Description

Sept. 27, 1932. I A KEMPTQN 1,8519303 SWITCH BLADE Filed Oct. 30, 1929 InVenov-I Les|iev \.Kernpcc-n b5 His Attornegl ranges.

o practice that arcing Patented Sept. 27, 1932 UNITED s'rArss "PATENT OFFICE mean: a. xmrr'ron,

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Application am October so, me. lerhl no. team.

The present invention relates to blades for sna switches and especially to switchesinten ed for controlling the circuits of electric heating devices, as for example electric Such switch blades have to carry large amounts of current and are frequen y operated. Although means. are provided for actuating the movable member or blade with a snap action, it is found in takes place when the cirrelativel contacts and movable blades. For example, the structure shown in my Patent 1,670,07 3 granted May 15, 1928 may be used.

5 indicates a four arm switch blade or spring contact brush, two of said arms being lon er than the others so as to engage a di erent set of stationary contacts, one pair of arms extending at ri ht angles to the other pair. They are ma e of good spring material, such as phosphor bronzeor equivcuit is 0 ed WlllCh causes burning or pitalent metal. They are assembled in the ting of t e surfaces thereof. When the surswitch in pairs as shown in Fig. 2, and as faces become rou hened in this .manner the contact between 51c moving and stationary parts is impaired, which in turn causes local heating of the arts which is ob'ectionable as will readily appreciated. 11 order to improve the operation it We standard practice to coat the contacting surfaces with some kind of grease or heavy oil which while it makes the parts move easily has the effect, es cially where an excess of (grease is used, 0 increasing the trouble inci ent to arcing. My invention has for its object to improve the construction of switch members or blades or both by providing embossments thereon to the end that the arcing or burning is confined to portions of the surfaces or parts of the members or blades other than at the embossments through which the current flows when the switch is closed.

Fora consideration of what I believe to be novel and my invention, attention is directed to the accom anying description and the claims appende thereto. I

In the accompanying drawing, which is illustrative of my invention, Fig. 1 is a plan view of a rotatable switch blade, Fig. 2 is an edge view showin how the parts are arranged in a switch, ig. 3 is an end view of one of .the blade arms, and Fig. 4- is a sectional view on an enlarged scale of a pair of moving blades and a stationary contact;

In order to simplify the descr1 tion of my invention, the details of the switc operating mechanism as Well as some of the other parts have been omitted. It is to be understood, however, that in this particular an suitable operating mechanism may be emp oyed and practice, each many pairs may be provided as are necessary for controlling the circuits of the heating or other devices associated with the switch.

The blades or brushes are so made and assembled as to be biased toward each other so as to make good contact with the'stationary contacts. 6 indicates stationary contacts which are bridged by the blades to close the circuit between them.

Instead of makin the contact surfaces at the ends perfectly at and smooth and flush with the body of the blade as is the standard is provided with a shallow embossment 7 which rises slightly above the metal forming the other part. he embossments are formed b suitable dies, and their surface area should great enough to carry 'the current without appreciable local heatin The amount that each embossment is raised will depend chiefly upon the thickness of the stationary contact and on the shape or curvature of the edges of the blades. For example, and 36 amperes, as shown, the embossment may be raised by an amount of the ,order. of to 0ne-quarter of the thickness/of the blade. The object is to raise it aslittle as possible and yet provide a surface 'which will remain smooth and free from burning due to arcing when the circuit is broken. The end portions of each blade arm are bent or curved away from the plane of the blade to a lower level as indicated at 8 startin at or near the base of the embossment so that all danger of the parts 'amming when the blade is moved is obviated, and to cause whatever arc is formed to be beyond the embossment.

in switches designed for 225 volts any suitable arrangement of the stationary The amount that the ends are bent or curved will depend chiefly u on the thickness of the stationary contacts. he oint is they should afiord an easy entrance or the contact between the blades as well as form arcing surfaces below the level of the embossment.

The entering edges of the stationary-contacts'are-beveled or sharpened as shown at 9 in Fig. 4. As the air of moving blades is rotated by a suitab e means (not snown) to interrupt the circuit, the embossments pass out of en agement with the stationaryicontact and due to the spring of the blade arms they move toward each other, still graspmg the contact between them but'in regions beyond the embossments. This has the efiect of causing the arcing to take place not at or on the embossments but m are on or regions outside thereof, for examp e as at 10 and 11, the are following the metal outward from the embossments until broken by relaf tive movements of the stationary and moving parts. To state the matter in other words,

I the embossments ride on the stationary contact,then move toward each other while other parts ofthe blade maintain the electric circuit and the arc is finallylbroken at the level or region belowlandbeyond the embossments. As a preferred arrangement, I have shown a pair of blades engaging op osite sides of the same stationary contact at where the currents to be carried are small a single blade may be employed, having of course, the embossment arranged in the manner described.

In this case the arc will be obliged to follow one path instead of two.

Tests made with switches embodiyrng my improved blade show substantial mprovement over the prior smooth or non-embossment type in the absence of roughenlng, pitting and local heating. For example, switches fitted with my improvement have been given a rotary test of 12,000 cycles without any trouble from flashin or burning, and the embossments remained smooth and clean, such roughening and pitting as took place being wholly outside the embossments. In the particular test referred to, the voltage was 255 and the current 36 amperes. In one test the switch was placed in circuit with a high heat coil of a range on a 112 volt circult with a current of 48 amperes, and after 144 hours of operation had a temperature of 125 F., with a room temperature of 92 F., or a rise of only 33 F. over room temperature, which is substantially less than is normally the case. Due to the fact that the contacting surfaces remain smooth, the local heatin of the switch at the contacts as'indicated a bove is small, and the life of the switch is thereby increased.

What I claim asnew and desire to secure by Letters Patent of the United States is:

1. In combination, a pair of'sheet metal switch blades, each of which has a shallow embossment pressed therefrom to form a fiat ammo:

contact surface of considerable area which rises above the level of the surrounding part of the blade, said embossments facing each other, with a stationary contact adapted to be engaged on opposite sides successively by the embossments and the surrounding parts of the blades as the blades move out of enga'gement with the stationa contact.

2. In combination, a rigi contact and a spring contact brush adapted to e age said rigid contact and having an er iliossment forming a contact surface and an adjacent surface adapted to engage the ri 'd contact as the contact brush is separate from said rigid contact to open an electric circuit, and provide an arcingsurface for said contact rus 3. In combination, a rigid contact and spring contact brushes adapted to engage said rigid contact and having embossments forming contact surfaces and surfaces adjacent said contact surfaces adapted to engage the rigid contact as the contact brushes se arate from said rigid contact to open an e ectric circuit, and rovide arcing surfaces for said contact bruslies. I

4. In combination, a rigid contact and two spring contact brushes adapted to engage said rigid contact and having embossments forming contact surfaces engaging opposite sides 0 said rigid contact and surfaces adjacent said contact surfaces adapted to en gage the rigid contact as the contact brushes separate from said rigid contact to open an electric circuit, and rovide arcing surfaces for said contact brushes.

5. Aswitch member comprising twos ring contact brushes having em ents orming contact surfaces on the inner sides of the brushes and surfaces adjacent to the embossments forming arcing surfaces which are adapted to engage a contact after the em bossments have passed out of engagement with the contact whereby the arcing of the contact brushes is limited to an area which is not in normal engagement with the contact when an electric current is passing therethrou h.

6. switch member com rising two rin contact brushes biased towfrd each othz r an having shallow embossments on the inner side of the contact brushes forming flat contact surfaces raised above the adjacent surface of the contact brush whereby the surfaces adjacent to the embossments engage a contact. as the electric circuit is opened through the switch member to prevent the

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