US3431378A

US3431378A - Hermetically impervious switch

Info

Publication number: US3431378A
Application number: US670950A
Authority: US
Inventors: Robert R Hellman
Original assignee: Westport Development and Manufacturing Co Inc
Current assignee: Westport Development and Manufacturing Co Inc
Priority date: 1967-09-27
Filing date: 1967-09-27
Publication date: 1969-03-04
Anticipated expiration: 1986-03-04

Description

United States Patent 8 Claims ABSTRACT OF THE DISCLOSURE A snap action electric switch that is enclosed by a hermetically impervious container and is actuated by distortion of a side wall of a tube that is not sensitive or distortable by external environmental pressure.

The present invention as herein specifically disclosed is shown used with an electric switch of the snap action type which has a single blade that is normally in one position. A force producing a determined linear movement of an actuator on a portion of the blade causes the blade to move or snap to an unstable another position where it is maintained until the determined movement is removed when it returns to its one position. The blade is engageable with a first contact at its one position to produce a circuit therethrough and is engageable with a second contact at its another position to produce a second circuit therethrough. While the blade shown is a shaped onepiece blade, it will be appreciated that the present invention is applicable to other types of electrical switches which require a determined movement of an actuator to effect a change from one circuit to another.

In many instances it has been found desirable or necessary to position an electric switch to be actuated by a movement that occurs in an environment that is harmful to the switch or in which switch operation may be a hazard. While the switch could be located remote from the environment it is usually desirable to locate it in the environment to be as directly reactive to the movement as possible. However, in such environments, the switch should maintain its mechanical operating characteristics and an important characteristic is the operating point or position of the actuator which effects the sh1fting from one contact to the other. In heretofore hermetically impervious switches, they have not been found satisfactory in that the mechanical operatiing characteristics of the switch have been subject to change when a change occurs in an environmental condition. Particularly, pressure has heretofore effected the operating pomt especially if the movement was transmitted through a flexible, flat diaphragm. Unsatisfactory operation in many situations has been found to occur when the switch operating point shifts on the order of one or a few ten thousands of an inch from its set position because it is then no longer exactly related to the movement for its actuation.

It is accordingly an object of the present invention to provide an electrical switch which is hermetically imprevious but which retains its operating characterist cs even over wide extremes of environmental conditions mcluding pressure.

Another object of the present invention is to provide an electric switch that achieves the above object but yet which is extremely simple in construction, relatively economical to manufacture and durable in use.

A further object of the present invention is to provide a hermetically sealed electrical switch which is operable by an actuating movement that is similar to the normal actuating movement of the switch when it is not contained in a hermetically impervious container and which may be mounted in the same manner as if it were not hermetically impervious.

In carrying out the present invention, the particular switch disclosed in the hereafter described embodiment is essentially identical to the switch disclosed in U.S. Patent No. 3,278,700 granted to me on Oct. 11, 1966 and assigned to the assignee of the present invention. This switch includes a body of ceramic material upon which three posts are mounted, one carrying a first contact, another carrying a second contact and the third supporting one end of a distortable switch blade. The other end of the blade carries a contact which is engageable with either the first or second contact and is caused to move from one position to another by a linear movement of an actuator on the blade. The position where the blade shifts from one position to the other is known as its operating point and is controlled with respect to the switch body to be repeatable within very small tolerances. The hermetic container for the switch includes a tube that is secured around the bottom portion of the body and has an interior shape that conforms to the shape of the body. Secured to the exterior of the tube is a cover that is box-shaped, hollow and extends above the switch. Opposite sides of the cover are formed with apertures and a tubular member has its ends sealed to the sides of the apertures to form a cylindrical through cavity.

The cover further includes an operating member having a portion positioned outside of the cover and another portion that extends within the tubular cavity to engage the exterior surface of the tube. A movement of the outside portion causes a similar movement of the portion within the cavity and the latter is forced against a side of the tubular member to cause it to axially distort by in effect bending its axis. The switch has its actuator positioned to engage the interior surface of the tube so that a movement of the side is transmitted to it and hence eflfects the operation of the switch.

Other features and advantages will hereinafter appear.

In the drawing:

FIGURE 1 is a side view of the switch of the present invention with the container being shown in section.

FIG. 2 is a section taken on the line 2i-'2 of FIG. 1.

FIG. 3 is a section taken on the line 3-3 of FIG. 1.

Referring to the drawing, a snap action electrical switch is generally indicated by the reference numeral 10 and is of the type disclosed in my above-noted U.S. patent. Accordingly, it includes a body 11 on which are mounted three

posts

12, 13 and 14. The post 12 supports one end of a cont-act blade 15 whose other end carries a blade contact 16 while the post 13 carries a normally closed contact 17 and the post 14 carries a normally open contact 18. The contacts are connected to

lead wires

19 and 20 for contacts 17 and 18 respectively while a lead 21 is connected to the blade member.

The post 12 further supports a pre-load bracket 22 having an aperture 23 in which is positioned a sapphire ball 24. The top part of the ball is engaged by a portion of an actuator 25 that is also mounted on the post 12 with the ball being held between the blade and the actuator. The unsupported end of the actuator has an up-turned lip 26 terminating in an arcuate edge 27.

With this construction of a switch, it will be understood that slight bending movement of the actuator 25 causes the ball 24 to move downward and as it moves it distorts the blade 15 to cause movement of the blade contact 16 from its solid line position to its dotted line position. In the solid line position, a circuit is formed through the lead 21 to the lead 19 while in its dotted line position, it engages the normally open contact 18 to form a circuit from the lead 21 to the lead 20. Upon an upward movement of the actuator the blade will snap by its own inherent construction to its solid line normal position. The particular position of the actuator wherein it causes the snap action movement of the blade from its normally closed to its normally open position is called the operating point and its maintenance with respect to the remainder of the switch is normally required to be extremely precise and repeatable.

The body 11 of the switch is formed to have an integral ledge 28 extending about its lower periphery. A metal tube 29 which has an interior shape mating with the exterior periphery of the ledge, in this instance rectangularly shaped, is fitted over the ledge and is secured thereto by a sealed joint using hardened fused metal 29a. A hollow metal cover 21 having the shape shown is open at its bottom and the tube 29 and switch placed therewithin. The opposite sides of the cover 31 are formed with circular apertures 31a and 31b and a tubular member 32 is positioned to extend lengthwise through the cover above the switch. The ends of the tubular member are welded as at 33 and 34 to the sides of the cover defining the apertures to form a sealed connection therebetween. The cover is also welded as at 35 at its bottom edge to the bottom edge of the tube 29.

The body 11 is formed to have a pair of transverse support holes 36 by which the switch may be supported to be against a surface (not shown). The cover has on its other two sides, holes which mate with the holes 36 and a pair of cross tubes 37 are positioned within the holes 36 to extend therethrough to have their ends welded as at 38 to the sides of the container. In this manner, the switch is supported within the container while being hermetically sealed therein in view of the fused metal at 30, the weld 35 and the

welds

33 and 34. As disclosed in my abovenoted patent, the

leads

19, 20 and 21 extend through the base to be secured to the

posts

12, 13 and 14. The posts are secured by fused metal 12a, 13a and 14a to the base and thus any opening about the leads is sealed against fluid. The fused metal joints for both the posts and the ledge 28 may be effected when the base is formed of ceramic material by coating the portions of the base with a vacuum deposited metallic material, such as a molybdenum manganese alloy that is then nickel plated, forming the posts and tube 29 of nickel and brazing with an 80% gold brazing alloy. By having the bottom of the tube 29 and cover open, the leads are free to have connections made thereto in a conventional manner.

In order to produce the movement on the actuator 25 to effect the actuation of the switch, there is supported on the top portion of the cover a U-shaped operator 39 having an outer arm 40 and an inner arm 41. A flexible spring bracket 42 having the shape shown has one end welded as at 43 to the cover and its other end welded as at 44 to the outer arm. The inner arm has its end formed with a depending arcuate flange 45 that mates with the exterior surface of the tubular member in approximate alignment with the lip 26 of the actuating arm. The operator 39 is of relatively rigid construction so that a force or movement applied in the direction of the arrow 46 will cause the operator to effectively pivot on the spring bracket 42 and move the flange 45 a distance which is related to the amount of movement of the outer arm 40 by the ratio of the lever arms.

With the above-described structure of a hermetically sealed switch, it will thus be understood that a linear movement in the direction of the arrow 46 on the outer arm 40 of the operator will cause a pivoting movement of the inner arm with the movement being accommodated by the spring bracket 42. The movement is essentially a linear movement of the depending flange 45 of the inner arm and this movement produces a downward distortion of the tubular member 29 which distortion is transmitted to the actuator 25. As the actuating parts are relatively rigid and their flange 45 and lip 26 abut the opposite surfaces of the tubular member, there is effectively no lost motion and no part in which changes could occur to alter the relationship of the movement.

It will be appreciated that the tubular element 29 as shown is in effect a bellows formed of resilient metal to have corrugated walls consisting of a series of convolutions. When the switch is placed in an environment wherein there are pressure changes, the tubular member 29 is capable of withstanding extreme pressures without deformation such as radial expansion by reason of its shape inherently providing this characteristic and by the pressure being exerted throughout the entire exterior surface of the tubular member. Pressure change accordingly will fail to distort the side walls and produce an actuating movement on the actuating arm or change the side walls so as to vary the movement required for actuation. While the tubular member is extremely resistant to structural changes due to pressure, it is naturally inherently capable of lengthwise expansion and contraction and offers little resistance to such a change. The movement of the inner arm to cause actuation may be only on the order of a few thousands of an inch which while distorting the axis of the tubular member is so relatively small as to be easily accepted by the tubular element with essentially no resistance thereto. Moreover, the inner arm acts in the intermediate portion of the tubular element, wherein distortion meets its least resistance. The operator is returned to its normal position by the flexed spring bracket 42, the distorted tubular member and the distorted blade 15.

Accordingly, the cover is hermetically impervious and yet the movement for actuation is made unaltered by environmental conditions such as pressure. The shape of the cover and the use of the tubes 37 enable the switch to be mounted as if it did not have the cover in the conventional manner as by screws passing through the tubes. Moreover, the switch is actuated by a movement in the same direction as the movement of the actuator and hence the switch may be easily installed in the same manner as if it was not hermetically sealed.

While the switch may be mounted by the use of the tubes 37, flanges could also be welded to the cover for providing support if for example it was desired to place the switch in an opening in a container with the leads being on one side and the operator on the other.

It will accordingly be appreciated that there has been disclosed an electric switch which is responsive to a linear movement but which is hermetically impervious. The sealed switch maintains its operating characteristics even when subjected to extreme changes in pressure by the use of a tubular member which is essentially radially unexpansible but which is easily axially distortable. By applying the actuating movement through the side wall of the tubular member the movement is effectively transferred without change to the actuator of the switch.

Variations and modifications may be made within the scope of the invention and portions of the improvements may be used without others.

I claim:

1. A hermetically sealed electric switch comprising a base, first and second contact means mounted on the base, movable contact means mounted for movement between the first and second contact means, actuating means for actuating the movable contact means to move it from engagement with the first contact means to the second contact means and including an actuator, a cover enclosing said contact means and actuating means and being sealed to the base, a tubular element secured to said cover and having a wall portion adjacent said actuator, an operator having an operating end positioned adjacent said wall portion on the opposite side thereof from the actuator, means mounting the operator for movement to radially distort the wall portion in a direction towards the actuator to effect actuation of the switch and in which the cover is formed to have an opening on one side and a corresponding opening on its opposite side, the tubular element is elongate and extends from the opening on one side to the opening on the other and means connecting and sealing the edges of the openings and the ends of the tubular element.

2. The invention as defined in claim 1 in which the tubular element is shaped to resist radial distortion caused by pressure and is capable of radial distortion by the operator.

3 The invention as defined in claim 2 in which the tubular element includes a series of convolutions and is formed of flexible metal.

4. The invention as defined in claim 1 in which the operator has a pair of spaced apart arms, spring means supporting the operator on the cover with one of said arms being outside the cover and the other of said arms extending into the tubular element and carrying the operating end.

5. The invention as defined in claim 4 in which the operating end includes a surface that is shaped to mate with the exterior surface of the tubular element engaged thereby and in which the actuator includes a surface that is shaped to mate with the interior surface of the tubular element.

6. The invention as defined in claim 1 in which the base includes a pair of transverse apertures, open-ended tubes positioned in said apertures and means securing the ends of the tubes to opposite walls of the cover to form through openings by which the switch may be supported.

7. The invention as defined in claim 1 in which there is a tube secured to the base and depending therefrom and the cover is secured to the tube.

8. The invention as defined in claim 7 in which the tube and the cover are formed with an open bottom, leads connected to the first and second contact means and accessible through the open bottom and means securing the leads to the base with a hermetic seal.

References Cited UNITED STATES PATENTS 4/1962 Roeser 200-168 8/1964 Cooper 200-168