US2264955A - Switch construction - Google Patents

Description

Dec. 2, 1941. N, c, H N ER 2,264,955

SWITCH CONSTRUCTION Original Filed June 3, 1935 F 16. a.=i.:\ 30 39' i INVENTOR. Newlarz fic/zeile e2; W/ @Mr&

ATTORNEY5.

Patented Dec. 2, 1941 UNITED STATES PATENT OFFICE SWITCH CONSTRUCTION Newton 0. Schellcnger, El Paso, Tex., assignor to Chicago Telephone Supply Company, Elkhart, Ind., a corporation of Indiana Original application June 3, 1935, Serial No.

24,752, new Patent No. 2,148,408, dated February 21, 1939. Divided and this application December 19, 1938, Serial No. 246,700

3 Claims. (01. 200-164) This invention relates to a new and improved switch and more particularly to a construction of fixed and movable switch contacts especially adapted for use in switches having low operating torque and requiring low contact resistance.

This application is a division of my copending application, Serial No. 24,752, filed June 3, 1935,

for Switch and variable high resistance, issued February 21, 1939,. as Patent No. 2,148,408.

Apparatus of this character as now usually designed and constructed are operated by the usual 110 volt commercial current and a switch limit of movement;

isrequired which will'handle safely and properly v a, current of this voltage at several amperes. In circuits of types used in such apparatus it is highly important that the switch not only have low resistance contacts but that the contact resistance remain substantially constant during 1 long continued operation of the switch. It is therefore important that the contacts be initially of low resistance and that means'be provided for maintaining such characteristics. To this end the switch should have a fast break to-minimize arcing and should have contact wiping action.

Other requirements are that the switch be of small size, with low operating torque and operable. by a driving movement through a relatively short arc. plifying equipment are now being made in very compact form and the dimensions of all their components must be correspondingly reduced. With a small switch combined with a small variable resistance the effective lever arm is small and consequently the operating torque must be I small to permit easy operation with usual types of control knobs. Also with small variable resistances the eflfective length of the resistance able contact as is possible for switch actuation.

It is an object of the present invention to provide new and improved switch contact construction.

having means coactingwith contact springs to Radio receiving sets and sound am-' It is an additional .object to provide'aiswitch Figure 2 is a view similar to Figure 1 but show ing the actuating cam and switch arm at their counterclockwise limit of movement;

Figure 3. is a view of Figure l as seen frombelow;

Figure 4 is a fragmentary section showing the spring and fixed contacts; i

Figure 5 is a section similar'to Figure 4 but showing the movable contact engaging the spring and fixed contacts;

Figure .6 is a section similar to Figure 4, show- I ing the parts in the off position;

maintain the parts in fixed relation with the switch in the off position.

It is a further object to provide a switch with Figure '7 is a fragmentary section on an enlarged scale showing a contact rivet before deformation;

Figure 8 is, a view similar to Figure 7 but showing the rivet after deformation.

The switch comprises the base.

notches 16 formed in its periphery. This base will normally be formed of non-conducting materials such as sheet fibre, Bakelite or other synthetic resinous material. The pivot ll'is secured to the base by riveting over its lower end l8 as shown in Figure, 3. 'Thepivotmember I! serves to support the switch arm 20 whichis rotatably mounted upon the pivot below the switch actuating cam 25. These parts are held upon the pivot ll by deforming its upper end against the upper face of the cam 24.

This pivot member ll preferably has an enswitch arm 20.

base member 15.

The form of switch shown is a double pole,

single throw switch. although it will be readily apparent that the various elements of the construction may be adapted to single pole, single throw, single pole, double throw and double pole,

l5 which in the form shown is a fiat dischaving, the locating v double throw switches without material modification.

The switch arm in the form shown carries a pair of contact members 2| which comprise rivets as shown in detail in Figures 7 and 8. The undeformed rivet shown in Figure 7 has a rounded contact face 21 surrounded by a shoulder 28 and a second contact face 29 surrounded by shoulder 30. When the rivet is deformed to clamp it to the switch arm, the shoulder 30 is deformed as shown in Figure 8, but the faces 21 and 29 are entirely undeformed. This swaging operation may be carried out by the means of tubular swaging elements which engage the shoulders 28 and 30 but do not contact the faces 21 and 29.

This will leave the contact faces 2'! and 29 with unbroken surfaces which will aid materially in effecting low resistance contacts. Rivets of this type having silver plating or other low resistance plating on their contact ends may be assembled by a circular swaging punch without injuring the low resistance surfaces.

The switch arm 20 is preferably formed of sheet material similar to that of which the base I5 is formed. from sheet material and the non-conducting raised portion 3| shown in detail in Figure 6 may be pressed from the sheet material during the stamping operation. These raised portions 3| are also clearly shown in Figures 1 to 3 and it will be apparent that when the switch is in the off position as shown in Figure 2, these nonconducting portions 3| will engage the spring contact portions 32 of the contact springs 33.

These portions 3| by engaging the springs in the off position of the single throw switch, such as that shown, will prevent anylooseness of the switch arm in that position. The contacts 2| engage the face of the base l5 or the fixed contacts supported thereby throughout the operation and in either on or off position.

By means of the extrusions 3| the spring contacts 33 serve to act as restraining forces urging the switch arm toward the base and prevent looseness in the switch when it is in the off position. These extrusions, in addition to performing this function of holding the arm down, also exert a cleaning action on the contacting surface of these upper contact springs 33 and serve to keep them clean and free from foreign matter or from products of the arcs which occur when the switch contacts are separated. The extrusions 3| may serve to apply a small amount of lubricant to the contacts.

The spring contacts 33 are shown in detail in Figures 4, 5 and 6. They include end portions which are held to the base l5 by rivets 34, and also connecting or soldering lugs 35 which extend to the outer face of the base through slots as shown in Figure 3. The spring contact members 33 include an intermediate portion 36 which extends at an acute angle away from the base I5 and which portion joins a re-entrant angular portion 31 which normally extends down to and in contact with the base |5, as best shown in Figure 5. The contact portion 32 extends beyond the re-entrant portion 31 and in a plane substantially parallel with the base l5, but with its ends rounded upwardly to ride over the contact rivets 2| as clearly shown in Figure 6. It will be apparent that the re-entrantportion 31 by normal contact with the base maintains these springs normally flexed a fixed amount. Their additional flexure is that caused by the thickness of the rivet 2| as clearly shown in Figure 6.

It may be formed by stamping The re-entrant portion 31 which strikes the base is in close proximity to the contacting portion 32 and the principal spring action is between the portion 31 and the securing rivet 34. This construction greatly simplifies the forming operation of making the springs and also their uniform assembly on the base. This construction maintains an accurate minimum distance between the contact surface 32 of the flexible spring and the contact surface 38 of'the fixed contact member 39. When the contact rivet 2| moves between the two contact surfaces 32 and 38 the portion of the flexible contact which bears against the base is raised from the base and the full pressure of the spring is exerted against the contact rivet. This construction accurately positions the flexible contact spring at the correct height above its associated stationary contact and prevents any tendency of the contact portion 32 of the spring 33 being too close to the switch base. If it were too close to the switch base this would result in the contact rivet not riding in under the spring properly and in the contacting spring riding on the arm after the contact rivet had moved away. Either of these conditions would materially hinder the switch action.

The stationary contact members 39 and their contact portions 38 fit into perforations 40 formed in the base member |5.' These contact portions are substantially in the plane of the inner face of the base member |5. The contact members 39 are formed with intermediate portions 4| which extend at right angles to the portions 38 through the perforations 40, and with outer portions substantially parallel to the portions 38 and secured to the outer face of the base member |5 by means of rivets 42. The contacts 38 are also preferably formed with integral connecting lugs 43 so as to avoid the necessity of additional connections. By having the contact face 38 flush with the surface of the base on which the contact rivet travels, there is no tendency for the switch arm 20 to move out of its normal plane of rotation and consequently no tendency for it to bounce and cause, an are as the switch makes contacts, which tendency would create a very undesirable condition and rapidly shorten the life of the switch.

In the operation of my improved switch with the parts in the position shown in Figure 1, the contact rivets 2| are in engagement with their respective spring and fixed contacts and both of the circuits are closed. In order to open the circuits it is necessary to move the switch arm 20 in the counterclockwise direction about the pivot H. To do this, the actuating cam 24 is moved in the counterclockwise direction about its pivot, which is also the pivot I! of the switch arm. This is accomplished by the movement of the drive pin 54 which is shown in Figure 1 as just entering the slot 53. The drive pin 54 engages the right-hand edge of the notch 53 as seen in this figure and begins the counterclockwise movement of the cam 24. This movement swings the pitrnan 49 past its center position and also brings the lug 45 against the edge of the notch 46 in the end of the contact arm 20. Its engagement against this edge of the notch causes the lug 45 to positively start counterclockwise movement of the switch arm 20. If the contacts on the arm and their associated spring and fixed contacts are smooth and clean, movement of the arm 20 may be initiated by the action of the spring 52 against the stop 50 and enlarged end 48 of the pitman 49. The toggle action may cause the cam 24 to move faster than the drive pin 54 so that the lug 45 engages the wall of notch 46 under the force of the toggle spring. A momentum will be acquired by the spring 52 moving the cam faster than the drive pin moves it and as soon as the pitman passes center the spring snaps the lug 45 against the wall of notch 45. This spring action will then complete the movement, swinging the parts to the position shown in Figure 2 where the switch contacts 32 ride on the non-conducting extrusions 3|.

If, however, the contact surfaces arerough or a weld has been formed, the lug 45, by its engagement with the edge of notch 45 under the direct thrust upon the cam 24 by the drive pin 54, will positively break the weld and start the movement of the switch arm, which movement will then be completed as a snap action by means of the spring toggle construction. The notch or opening 53 is made sufficiently large so that the break away of the switch arm contact from the fixed and spring contacts will be a snap action regardless of the speed of movement of the drive pin 54. This. movement can be completed before the rear end of the notch 53 engages the drive pin 54. The size of the notch 48 is important and the lug 54 does not engage the edge of the notch or opening 48 until the toggle has passed its center, as shown in Figure 2. Consequently it is impossible to make a slow, controlled break of the circuit. Although the construction provides for a positive break between the switch arm contacts and the fixed and spring contacts, if they tend to stick together suiliciently to fail to be separated by the initial spring action and require a positive start, the contacts are snapped apart by the toggle action of the switch once the sticking is broken.

Another important feature of the switch design is that the switch arm is entirely free from any lateral or twisting thrust from the spring toggle. This toggle is supported entirely free from the switch arm.

While I have shown certain preferred embodiments of my invention, it is capable of modification and'changes to meet varying-conditions and requirements, and I contemplate such changes and variations as come within the spiritand scope of the appended claims.

I claim:

1. In a switch of the character described: an insulated base having a flat surface; a spring blade fixed at oneend to said surface of the base so that its other free end portion may be flexed away from the base, said free end portion of the blade having a supporting foot formed thereon directed toward and normally contacting said surface of the base to flex the blade and hold the same under an initial degree of spring tension, the free end portion of the blade beyond the foot providing a stationary contact with its contact surface facing the base and held at a predetermined distance from the surface of the base by said foot; a contact movable across said surface of the base and having a contact surface spaced from said surface of the base a distance a little greater than the space between the .con-

tact surface of the stationary contact and the.

base; and means for moving said movable contact across the base and under said stationary contact to thereby bring the contacts into engagement and lift the stationary-contact so that the spring contact pressure is in excess of the I initial spring tension in the blade.

2. In a switch of the type wherein a movable conta'ctor is propelled across the surface of an insulated supporting base with a contact surface maintained at a definite elevation above the base: a co-acting stationary contact mounted on the base and comprising a spring arin blanked from resilient sheet metal and having one extremity anchored flatwise to the base in a manner such that a biasing force is exerted on the free length of the arm tending to hold the same to the base, the outer end portion of the free length of the arm being kinked to one side of the plane of the arm to provide a supporting foot which bears against the base to flex the spring arm and hold it under initial tension and continuing from the kinked portion back across the plane of the arm to the opposite side thereof, the extremital portion of said continuation being bent angularly to form a contact portion offset from the arm and projecting beyond the kinked portion to overlie the base, the contact surface of which faces the base and is spaced therefrom a distance determined by engagement of the foot with the base and which distance is less than the elevation at which said contact surface of the movable contact is maintained so that upon contact engagement the spring arm is additionally flexed to thereby provide substantial contact pressure at the instant of engagement and at final disengagementof the contacts.

3. An electric switch comprising: an insulated base; a pair of stationary contacts on the base and having superimposed contact surfaces, one

of said contacts comprising a spring arm fixed to the base at'a point remote from its contact surface and in a manner biasing its contact portion'towards the other stationary contact; asupporting foot on the spring arm bearing against the base to flex and tension the arm and hold its contact surface spaced from that of the other stationary contact; and a contactor movable across the base into bridging engagement with the stationary contacts, said contactor having its contact surfaces spaced apart a distance greater than the spacing between the contact surfaces of the stationary contacts so that disposition of the contactor between the stationary contactsadditionally flexes the spring arm. and firmly clamps the contactor between the stationary contacts.

NEWTON C. SCHELLENGER.

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