US 3902032 A
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United States Patent 11 1 Koepke 1451 Aug. 26, 1975 1 ELECTRICAL SWITCH WITH IMPROVED CONTACT STRUCTURE  lnventor: John A. Koepke, Des Plaines, 111.
 Assignee: Illinois Tool Workslnc., Chicago,
 Filed: June 7, 1974  Appl. No.: 477,219
 US. Cl 200/153 M; 200/159 A; 200/283  Int. Cl HOlh 13/52; I-IOlh 1/26  Field of Search..... 200/159 A, 153 M, 153 LA,
ZOO/159 R, 275, 279, 283, 246, 61.19
 References Cited UNITED STATES PATENTS 2,772,579 11/1955 Rohacs 200/77 2,903,540 9/1959 Gloviak et 211.... 200/159 R 3,239,629 3/1966 Lesser 200/153 3,361,888 1/1968 Brackett 200/153 M x 3,751,618 8/1973 Hallerberg ZOO/159 R Primary Examiner-Robert K. Schaefer Assistant Examiner-William J. Smith Attorney, Agent, or Firm--Robert W. Beart; Glenn W. Bowen 5 7 ABSTRACT An electrical switch with an improved contact structure of the type having a depressible plunger with a contact separator for separating two flexible contacts when the plunger is in one position and for allowing the contacts to close when the plunger is in a second position is disclosed. The improved contact structure consists of two identical bifurcated contacts, one arm of which has a flat contact surface and the other arm 7 of which has a curved contact surface. The contacts are positioned so that the curved arm of each contact engages the flat arm of the other contact when the switch is closed.
1 Claim, 4 Drawing Figures ELECTRICAL SWITCH WITH IMPROVED CONTACT STRUCTURE BACKGROUND OF THE INVENTION One particularly simple but effective type of electri cal pushbutton switch is constructed with a depressible plunger which has a separator member formed on it that is disposed between two contacts. The contacts are shaped so that they are normally biased toward each other. When the plunger has not been depressed, the separator member maintains the contacts separate so the switch is open; but when the plunger is depressed, the separator member moves downwardly so it is no longer in contact with the angled contact arms; and they are thereby allowed to engage each other to close the switch. In the described type of switch there is a tendency for the contacts to bounce when the arms contact each other. In addition, prior contact structures do not generally provide sufficient wiping action between the two contacts so as to keep the contact surface adequately clean. The contact structure of the present invention is designed to increase the reliability of the described type of switch while reducing the contact bounce problem and providing for increased wiping action.
It is. therefore, the object of the present invention to provide an improved contact structure for an electrical switch in which two contacts are positioned in the switch so that they are normally biased towards each other, and a plunger with a separator member on it de termines whether or not the two contact members remain separated or closed, wherein the improved contact structure is provided by two contacts which are identical and which have bifurcated ends constructed so that one arm of each contact is flat and the other arm of each contact is curved with the contacts being aligned so that the curved arm of each contact engages the flat arm of the other contact when the switch is closed.
DESCRIPTION OF THE DRAWINGS The present invention is illustrated by reference to the drawings in which:
FIG. 1 is a top view of a switch employing the improved contact structure of the present invention;
FIG. 2 is a perspective view of the improved contact structure of the present invention removed from the switch of FIG. I;
FIG. 3 is a cross-sectional view of the switch of FIG. 1 with the plunger in an undepressed position and the contacts in an open position; and
FIG. 4 is a cross-sectional view of the switch of FIG. I with the plunger depressed and the contacts in a closed position.
TECHNICAL DESCRIPTION OF THE INVENTION A switch constructed in accordance with the present invention is shown in FIGS.'1, 3, 4. The switch 10 comprises a housing 12 which has an upper panel member 14 formed with a boss 16 that has a central aperture I8. A plunger 20 is inserted into the central aperture 18 of the boss 16, which has a rim 21 that surrounds it so as to engage it to the upper end of a return spring 23. The lower end of the return spring 23 is retained in the groove 24 formed in the interior of the housing 12. A pair of contacts 28, are secured into the housing 12 with the upper contact portion 32 of the contacts 28,
30 extending into an internal cavity 26 and the plunger 20. The housing 12 is preferably formed of a plastics, and the contacts 28, 30 are preferably secured into the housing 12 by molding the sections 29, 31 of the contacts 28, 30 into the housing 12 when it is formed.
The contacts 28, 30 have angled sections 34, 36 between the contact portion 32 and the molded in sections 29, 31 which slope towards each other. The angled sections 34, 36 are biased towards each other so that they tend to engage each other. The plunger 20 of the switch 10, however, carries a separator member 27 which contacts the angled sections 34, 36 of the contacts 28, 30 when the plunger is not depressed so as to maintain the contacts 28, 30 open, as shown in FIG. 3. The plunger 20 is preferably formed of plastics and the separator member 27 is preferably integrally formed on the plunger 20. When the plunger is depressed, as shown in FIG. 4, the separator member 27 is lowered below the point where it no longer contacts the angled sections 34, 36 and the contacts 28, 30 are thereby allowed to close.
The improved contact structure of the present invention is best shown by reference to FIG. 2. The contacts 28, 30 are constructed with a pair of bifurcated arms 42, 44 and 38, 40 respectively. The bifurcated arms 40, 42 are formed with arcuate curved contact surfaces on the outer end of the straight segments 46 while the arms 38, 44 have substantially flat contact surfaces which engage the opposing curved contact surfaces 42, 40, respectively.
The design of the illustrated contacts 28, 30 provides a contact structure that has low contact bounce and increased reliability because of the bifurcated construction of the contact arms. The manufacturing cost of the contacts of the present invention is relatively low, since the arms 38, 40, 42 and 44are integrally formed on the contacts 28, 30. An additional feature of the contact structure of the present invention is that while the contacts 28, 30 are designed to be identical, the actual contacts will be slightly different due to manufacturing tolerances. This slight difference will provide slightly unbalanced forces that will aid in providing wiping action between the contact members 38, 42 and the contact members 40, 44 as they settle to their equilibrium positions.
The invention is claimed as follows:
1. In an electrical switch'comprising a housing, a depressible plunger, means for biasing the plunger to its undepressed state and a separator member which is depressible when said plunger is depressed; an improved contact structure comprising first and second contacts secured in said housing each of which comprise an angled section which provides a bias on said contacts that tends to force said contacts towards each other, and a bifurcated contact portion consisting of a first arm on I each contact having an arcuate curved contact surface and a second arm on each contact having a substantially flat contact surface wherein the curved contact surface of said first arm of said first contact is positioned so as to engage the flat contact surface of said second arm of said second contact and the curved contact surface of said first arm of said second contact is positioned so as to engage the flat contact surface of said second arm of said first contact when said first and second contacts are closed by movement of said separator member due to depression of said plunger to a position where it no longer separates said first and second contact members from each other.
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