US 3912894 A
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Description (OCR text may contain errors)
Mullen et al.
[ CONVERTIBLE SWITCH  Inventors: John H. Mullen; Walter J. Kellogg,
both of Beaver, Pa.
 Assignee: Westinghouse Electric Corporation,
 Filed: Apr. 26, 1974  App]. No.: 464,730
 US. Cl 200/153 LA; 200/280  Int. Cl. HOlH 3/42  Field of Search 200/153 LA, 4 R, 280
 References Cited UNITED STATES PATENTS 2,714,637 8/1955 Schmocker ZOO/153 LA X 2,714,639 8/1955 Schmocker 200/153 LA X 2,991,343 7/1961 Norden ZOO/153 LA 3,369,100 2/1968 Kussy et al. 200/153 LA I YT F TY 3,912,894 Oct. 14, 1975  ABSIRACT A .convertible electric switch characterized by relatively movable contacts movable between open and closed positions. A contact carrier carrying one of the contacts and having a hole with a pair of opposite sides forming cam-following surfaces extending transversely to the direction of movement of the contact carrier. A contact actuator extending through the hole and having a pair of cam surfaces located at angularly disposed positions on the actuator to effect movement of the movable contact to one of the open and closed positions. The contact actuator is rotatable within the hole to present one or the other of the pair of cam surfaces to one or the other of the pair of cam follower surfaces.
7 Claims, 5 Drawing Figures 43 ,1 v 11: 45 t 1g 23 3| 1]:
k '1 F 2 l U.S. Patent Oct. 14, 1975 Sheet 2 of2 3,912,894
0 6 29 3 g I I 3? FIG. 4.
CONVERTIBLE SWITCH BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrical switching devices and, more particularly, to switches which are convertible from normally open to normally closed conditions.
2. Description of the Prior Art Selective switches of the cam type are particularly useful in control switching programs. U.S. Pat. Nos. 2,991,343, 3,539,736, and 3,675,168 disclose cam operated switches of the type generally involved in this invention. An advantage of such switches is that a switch actuator or plunger on which the cams are mounted moves transversely to the direction of movement of the contacts, thereby minimizing contact bounce which heretofore has been a source of arcing between contacts.
Notwithstanding various attempts to eliminate arcing, it is recognized that the possibility or arcing and re.- sultant welding between contacts is an ever present problem. The disadvantage of that problem is not avoided by most switches disclosed in the prior art, because the cam operation is useful only for moving the cams against a kick-out spring which does not have sufficient force to separate contacts if they are welded together. Thus, selective switches of the cam type would be more foolproof if the cam surfaces were also used to separate the contacts when necessary such as where they weld together.
SUMMARY OF THE INVENTION Generally, in accordance with this invention it has been found that the foregoing problem may be satisfied by providing a convertible switch comprising an insulating housing, fixed and movable contacts within the housing and movable between open and closed positions, mounting means mounting the movable contacts between open and closed positions and comprising a contact carrier having aperture means including a pair of spaced cam follower surfaces disposed along opposite sides of the aperture means, the cam follower surfaces extending transversely to the direction of movement of the movable contacts, a contact actuator having diametrically opposite pair of cam surfaces which are movable against one of the spaced cam follower surfaces to effect movement of the movable contact to one of the open and closed positions, the contact actuator extending through the aperture means and being rotatable to present one or the other of the cam surfaces to one or the other of the cam follower surfaces, and the cam actuator being biased longitudinally to a position corresponding to the bias position of the contact carrier.
The advantage of the switch of this invention is that it is not only convertible from normally open to normally closed positions by rotating the cam actuator or plunger 180 without disassembling any part of the switch, but it is operable to separate the contacts forcibly if the contacts are welded together.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view, taken on the line [-1 of FIG. 2, and showing the contacts in the open position;
FIG. 2 is a vertical sectional view taken on the line IIII of FIG. 1;
FIG. 3 is a horizontal sectional view taken on the line III-III of FIG. 1;
FIG. 4 is a view similar to FIG. 2 of another embodiment of the invention; and
FIG. 5 is an enlarged plan view taken on the line lV-IV of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1 and 2 a convertible switch is generally indicated at 5 and it comprises a housing 7, a contact assembly generally indicated at 9, and a contact actuator or plunger 11. The housing 7 is composed of electrically insulating material and encloses a chamber 13 in which the operating parts of the switch are located. The housing also comprises a plunger-receiver aperture 15, an access opening 17, and a hole 19, all of which communicate with the chamber 13.
The contact assembly 9 comprises a pair of stationary contacts 21, movable contacts 23, and a contact carrier 25 which is slidably mounted in the chamber 13 for moving the contacts 21, 23 between open and closed positions. The stationary contacts 21 are mounted on similar conductors 27 which extend through the housing 7 and are provided with external terminals 29.
The movable contacts 23 are disposed at opposite ends ofa bridging contact member 31 which extends between the space pair of stationary contacts 21. The member 31 extends through a window 33 at one end of the contact carrier 25. In the window a compression spring 35 holds the associated bridging contact member 31 in place to provide a resilient contacting engagement between the corresponding movable contacts 23 and the stationary contacts 21 in a manner similar to that set forth in US. Pat. No. 3,296,567. A spring 37 is disposed between a shoulder 39 on the plunger and the housing to maintain the contacts 21, 23 in the open position. However, if the spring 37 is a tension spring, the contacts 21, 23 may be maintained in the closed position.
As shown in FIG. 3 the contact carrier 25 comprises opening means or hole 41 through which the plunger 1 1 extends. Inasmuch as the plunger 11 comprises cam surfaces 43 and 45, opposite surfaces 47 and 49 of the hole 41 are cam follower surfaces which engage the cam surfaces 43 and 45 when the plunger 11 is operated.
The contact actuator or plunger 11 is an elongated member, the upper end portion of which extends through the aperture 15 of the housing 7 where it is retained by suitable biasing means such as a compression spring 51. The cam surfaces 43 and 45 are located at diametrically opposite positions on the plunger and at longitudinally spaced positions thereof. The plunger 11 is movable longitudinally as well as rotatably as indicated by the arrow 53 (FIG. 1).
In operation, when the plunger 11 is depressed against the spring 51, the surface 49 of the contact carrier 25 follows the inclined cam surface 45 under the influence of the spring 37 and the inclined cam surface 43 engages the cam following surface 41 to move the contact carrier 25 to the broken line position, whereby the movable contacts 23 close a circuit through the stationary contacts 21 as shown by the broken line positions 23.
When the plunger 11 is rotated 180, the inclined cam surfaces 43 and 45 are disposed in the broken line positions as shown in FIG. 1. Thus, when the plunger 11 is in the uppermost position, under the force of the spring 51, the contact carrier is in the broken line position 25 with a circuit closed through the contacts 21, 23. When the plunger 11 is moved against the spring 51, the cam surface 45 moves from its broken line position and the cam surface (broken line) 43 engages the cam follower surface 49 and moves the contact carrier 25 to the contact open position against the pressure of the spring 37. If for any reason the contacts 21, 23 are welded together, the cam surface 43 may be used to force them apart.
Moreover, reversing the position of the plunger 11 from the solid line position to the broken line position of the cam surfaces 43, 45, reverses the condition of the switch 5 from a normally open to a normally closed condition, as shown more particularly in FIG. 5 the top surface of the plunger may be provided with an indicator or'arrow 55 for indicating whether the plunger is in the normally closed or normally open position with respect to the contact carrier 25.
The embodiment of the invention shown in FIG. 4 differs from that of FIG. 3 in that the movable contacts 23a and stationary contacts 21a are reversed and shown in a closed circuit condition against the pressure of the spring 37. Thus the plunger 11 is in the position shown in FIG. 1 with the cam surface 45 in the solid line position. Manifestly, lowering of the plunger 11 causes separation of the contacts 21a, 23a under normal conditions in response to pressure of the spring 37. If the contacts 21a, 23a are slightly welded together, continued depression of the plunger 11 brings the cam surface 43 into contact with the cam follower surface 47 and thereby forces the contacts 21a, 23a apart. Rotation of the plunger 11 to the dotted line position of the cam surfaces 43, 45 enables closing of the circuit through the contacts 21a, 23a. The indicator 55 (FIG. 5) does not obtain for the embodiment of the invention shown in FIG. 4.
Accordingly, the convertible switch of this invention provides for simple conversion of the switch from a normally open to a normally closed position without the necessity of removing or adding parts or changing wiring. The convertible switch also provides for means for readily separating the contacts where they are welded together.
What is claimed is:
l. A convertible switch comprising an insulating housing, fixed and movable contacts movable between open and closed positions, mounting means mounting the movable contact between open and closed positions and comprising a contact carrier having a pair of spaced cam follower surfaces extending transversely to the direction of movement of the movable contact, a contact actuator having one cam surface on one side thereof and another cam surface on the other side thereof, the cam surfaces being operable on opposite sides of the contact carrier, the contact actuator being movable longitudinally to effect movement of the contact carrier, the one cam surface moving the contact carrier to one of the open and closed positions of the contacts when the actuator is moved in one direction, the other cam surface moving the contact carrier to the other of the open and closed positions of the contacts when the actuator is moved in the other direction, the contact actuator also being rotatable to turn the cam surfaces to diametrically opposite sides of the actuator, the contact carrier being biased in one direction against the contact actuator, and the actuator being movable against the cam surfaces to effect movement of the movable contact to one of the open and closed positions.
2. The convertible switch of claim 1, in which the contact carrier is movable longitudinally in a direction that is transverse to the movement of the contact actua- 3. The convertible switch of claim 2, in which the contact carrier comprises aperture means through which the contact actuator extends.
4. The convertible switch of claim 3, in which the aperture means is a hole and the cam follower surfaces are disposed along opposite sides of the hole.
5. The convertible switch of claim 4, in which the contact actuator is rotatable to present one or the other of the cam surfaces to one or the other of the cam follower surfaces.
6. The convertible switch of claim 2, in which the mounting means is biased in one of the open and closed positions.
7. The convertible switch of claim 6, in which the mounting means is biased in the open position.