US3189704A

US3189704A - Pneumatic switch actuator

Info

Publication number: US3189704A
Application number: US151475A
Authority: US
Inventors: Roland D Beck
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1961-11-10
Filing date: 1961-11-10
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15

Description

June 155 1965 R, i3. 55% 3,139,704

PNEUMATIC SWITCH ACTUATOR Filed 23cm. 16, 1961 F limmm; 56

TO VACUUM INVENTOR. ROLAND D. BECK ATTORNEY 3,189,704 PNEUMATIC SWITCH ACTUATOR Roland D. Beck, Anaheim, Calitl, assignor to Rohertshaw Controls Company, Richmond, Va, a corporation of Delaware Filed Nov. 10, 1961, Ser. No. 151,475 3 Claims. (Cl. 260$3) This invention relates to electric switches and more particularly to pneumatically operated electric switches.

An object of this invention is to effect snapping of a pneumatic snap switch by a relatively small actuating force.

Another object of this invention is to provide a snap switch with a small, compact construction which is comparatively inexpensive to manufacture.

This invention has another object in that a snap switch is furnished with a vacuum operation.

It is a further object of this invention to utilize a vacuum source to effect the snap action of a snap switch.

In the preferred embodiment of this invention, a switch casing houses a snap acting mechanism including a movable contact carrying arm for snap movement between a pair of fixed contacts. A pneumatic actuator is carried by the switch casing and includes a vacuum operated element acting on the switch arm to actuate the switch arm with a relatively small actuating force.

Other features and advantages of the present invention will become apparent from the following description of the preferred embodiment taken in connection with the accompanying drawing wherein:

FIG. 1 is a side elevation of a snap switch embodying this invention;

FIG. 2 is a partial section view of FIG. 1; and

FIG. 3 is an exploded view with parts in section of the actuating mechanism shown in FIG. 2.

Referring to FIG. 1, there is shown a casing or switch housing, indicated generally at 10, having three

terminal posts

12, 13, and 14 extending therefrom for connection to suitable electrical conductors (not shown). The in terior of the housing is substantially hollow and provides a mounting for a common contact 15 and fixed

spaced contacts

16 and 17, which contacts are electrically associated with the

terminal posts

12, 13 and 14, respectively. A movable contact 18 is secured to a free end of a current carrying blade 20 and is disposed for movement between the

spaced contacts

16 and 17.

The blade 20 constitutes the actuating switch arm of a snap acting mechanism as is well known in the art. As is illustrated in FIG. 2, the switch arm 20 has its fixed end secured to the mounting 22 for the common contact 15. A rigid support member 24 extends from mounting 22 in spaced parallel relation to the switch arm 20 and has a terminal shoulder portion which engages one end of a U-shaped rolling spring 36. The spring 26 is operatively disposed in an opening in the switch arm 20 and has its other end engaging a shoulder on the switch arm 20 to form a snap acting mechanism. With such an arrangement an actuating force on the switch arm 20 causes movement of the attached end of the rolling spring 26; as soon as the moving end of the rolling spring 26 passes a dead center position, the contact carrying end of switch arm 20 is moved with a snap action and contact 18 is snapped from the fixed contact 17 to the fixed contact 16. When the actuating force on the switch arm 20 is reduced, the snap action is reversed and the contact 18 transfers from the fixed contact 16 to the fixed contact 17.

The top cover of casing 10 is provided with an aperture 28 and the undersurface of such top cover has an annular recess 30 formed by a counterbore in axial alignment with the aperture 28. The annular recess 39 con- United States Patent stitutes a mounting surface for hermetically sealing a vacuum operated actuating means which is mounted through the aperture 28 and secured to the casing 10.

The vacuum operated means or pneumatic actuator for the switch arm 21 is best shown in FIG. 3 and includes a generally cup-shaped member or flexible boot 32 made of any suitable resilient material, such as molded rubber. The inner cylindrical wall of the cup-shaped member 32 has an annular recess 34 spaced just below its annular rim. The bottom wall of the cup-shaped boot 32 has a centrally located aperture 36 surrounded by a pair of spaced, upwardly extending annular ribs 38 and 40. A washer element 42 is securely fastened to the outer surface of the bottom wall by a rivet 44; a second washer element 46 encircles the annular ribs 38 and 40 and is seated in the bottom of the boot 32. The two

washers

42 and 46 sandwich the bottom wall of the boot 32 to lend rigidity thereto whereby the rivet 44 will always move perpendicularly and will not be tilted out of engagement with the switch arm 20.

An externally threaded tubular element 48 has an outwardly extending annular flange 50 on its lower edge, which is disposed in the annular recess 34 of the flexible boot 32; the upper end of tubular element 48 is connected to a vacuum source. The lower portion of tubular element 43 is provided with a counterbore 52 for receiving the upper portion of a coil spring 54 which maintains in axial alignment with its upper and lower ends by having its lower end disposed between the inner and outer ribs 38 and 40. The coil spring 54 is mounted in compression between the bottom wall of the flexible boot 32 and the shoulder of the counterbore 52 whereby it resiliently biases the rivet 44 into engagement with the switch arm 24}. The assembly is held together by a lock nut 56 threaded onto the tubular element 48 and bearing against the switch housing 10. The flexible boot 32 is drawn up firmly against the casing recess 30 causing the flexible boot 32 to expand against the walls of the casing recess 30 and thus elfect an hermetic seal for a chamber defined by the interiors of the boot 32 and the tubular element 48.

In the operation of conventional snap switches, an actuating force of a predetermined value x is required to eiiect initial snap over of the snap acting mechanism. For return action, the actuating force must be reduced to a lesser predetermined value y whereupon the snap acting mechanism operates in the opposite direction. In accordance with the present invention, the coil spring 54 is so designed as to exert an actuating force having a predetermined value slightly larger than x; thus the rivet button 44 is biased against the switch actuating arm 20 which is normally held in its actuated position. The relative positions of the various switch elements are illustrated in FIG. 2 as being in this normal actuated condition.

In order to eflect snap action of the switch from its normal position, the construction of this invention pre sents an arrangement whereby the actuating force on the switch arm 20 requires a reduction of the value of x minus y. Inasmuch as the value of x minus y is relatively small, the effective pressure area of the flexible boot 32 can be quite small resulting in a compact construction that will easily fit into the confines of a miniature snap acting switch casing.

The tubular element 48 of the pneumatic actuator has its outer portion adapted to be connected to a vacuum conduit so that when a suitable valve in the vacuum conduit is opened, the chamber defined by interiors of the tubular element 48 and the flexible boot 32 will be in communication with a vacuum source. If desired, the tubular element 48 may extend through a panel and the lock nut 56 utilized to mount the casing 10 to such a panel. In accordance with some predetermined sequence D a i of operation with which the switch is associated, the interior of the flexible boot 32 is subjected to a vacuum; because of its resiliency and the exterior pressure area, the flexible boot 32 will contract and reduce the actuating force on the switch arm 2%. By the use of vacuum, a small reduction in the actuating force is obtained so that when such reduction reaches the value x minus y, the switch arm 20 causes movement of the attached end of rolling spring 26 and the movable contact 13 is transferred to the fixed contact 1'7 with a snap action.

With the above arrangement,,it is possible to construct a snap switch that will operate in response to an extremely small actuating force and that may 'be economically fabricated from relatively simple components into a compact structure. J

Inasmuch as various changes and modifications may be made to the present invention, it is intended that the foregoing description of the preferred embodiment shown in the drawing be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A pneumatic actuator for a switch mechanism comprising a switch casing, switching device in said casing, means defining an opening in said casing, a peripheral recess surrounding the opening, a cup-shaped flexible member having a bottom wall engaging said switching device for operating the same and having a rim portion disposed in said recess, an internal groove adjacent said rim portion, a tubular element having a flange portion disposed in said groove and a connecting portion extending through the opening, fastening means on said connecting portion engaging said casing whereby said flange portion arsa'roa seals said rim portion against said recess to define a pneumatic chamber in said flexible member, coil spring means mounted between said tubular element and said bottom wall to maintain said bottom wall in biased engagement with said switching device, and means on said tubular element for subjecting the pneumatic chamber to a pneumatic condition, said cup-shaped flexible member being flexed in response to the pneumatic condition whereby said bottom wall is moved to actuate said switching device. Y

2. The combination as recited in claim 1 wherein said bottom wall comprises a pair of spaced rib elements and 7 said coil springmeans has one end mounted between said spaced rib elements.

bottom wall further comprises washer means to define a rigid end for engaging said switching device.

References Cited 'by the Examiner BERNARD A. GILHEANY, Primary Examiner.

: WALTER STOLWEIN, Examiner.

3. The combination as recited in claim 2 wherein said

Claims

1. A PNEUMATIC ACTUATOR FOR A SWITCH MECHANISM COMPRISING A SWITCH CASING, SWITCHING DEVICE IN SAID CASING, MEANS DEFINING AN OPENING IN SAID CASING, A PERIPHERAL RECESS SURROUNDING THE OPENING, A CUP-SHAPED FLEXIBLE MEMBER HAVING A BOTTOM WALL ENGAGING SAID SWITCHING DEVICE FOR OPERATING THE SAME AND HAVING A RIM PORTION DISPOSED IN SAID RECESS, AN INTERNAL GROOVE ADJACENT SAID RIM PORTION, A TUBULAR ELEMENT HAVING A FLANGE PORTION DISPOSED IN SAID GROOVE AND A CONNECTING PORTION EXTENDING THROUGH THE OPENING, FASTENING MEANS ON SAID CONNECTING PORTION ENGAGING SAID CASING WHEREBY SAID FLANGE PORTION SEALS SAID RIM PORTION AGAINST SAID RECESS TO DEFINE A PNEUMATIC CHAMBER IN SAID FLEXIBLE MEMBER, COIL SPRING MEANS MOUNTED BETWEEN SAID TUBULAR ELEMENT AND SAID BOTTOM WALL TO MAINTAIN SAID BOTTOM WALL IN BIASED ENGAGEMENT WITH SAID SWITCHING DEVICE, AND MEANS ON SAID TUBULAR ELEMENT FOR SUBJECTING THE PNEUMATIC CHAMBER TO A PNEUMATIC CONDITION, SAID CUP-SHAPED FLEXIBLE MEMBER BEING FLEXED IN RESPONSE TO THE PNEUMATIC CONDITION WHEREBY SAID BOTTOM WALL IS MOVED TO ACTUATE SAID SWITCHING DEVICE.