US2471838A - Pressure switch - Google Patents

Description

A. E. ROSS PRESSURE SWITCH May 31, 1949.

Filed May 24, 1945 Patented May 31, 1949 UNITED STATES PTENT OFFICE PRESSURE SWITCH Arthur E. Ross, Chicago, Ill., assignor to Cook Electric Company, Chicago, 111., a corporation of Illinois 10 Claims.

This invention relates to pressure switches wherein an electric switch is made responsive to fluid pressure. Such switches are widely used, where dependability, compactness and convenience of adjustment to: operation at different pressures, of installation and replacement, are essential requirements. In such installations there are usually no facilities, time or mechanics skilled in the particular devices involved to dismantle or disassemble the apparatus to make adjustments or the like.

It is an object of this invention to provide a self-contained, compact, unitary pressure switch which is ruggedly constructed, readily installed or replaced, and which is readily and quickly adjustable after installation for operation of the switch at the desired fluid pressure without dismantling the installation or disassembling the device or any of its operative parts, and without disturbance of the installation or of the working parts of either the pressure-responsive elements or the electric switch elements or their individual adjustments.

A further object is to provide a compact, unitary, completely enclosed pressure switch in two parts or sections rotatively connected, the pressure point of operation of the switch being adjusted by the relative rotation of the parts or sections.

A still further object is the forming of such a pressure switch as a compact, unitary, cylindrical device having a body portion and a head portion with a threaded connection between, all in axial alignment. the body portion containing a pressure-responsive bellows, the head containing an electric switch, and the two being operatively connected through said threaded connection, the arrangement and construction being such that the relative rotation of the head provides an adiustrnent to operate the switch at a predetermined or desired operating pressure.

Still further objects and advantages will appear from the description. and claims to follow, in connection with the accompanying drawing. which illustrates an embodiment of the invention, and in which- Fig. 1 is a side elevation of the device, substantially at full scale, of one common size of the device;

Fig. 2 is a similar view at an enlarged scale and partly in section, except as to the electric switch;

Fig. 3 is a sectional plan view on the plane indicated by the line 33 of Fig. 1;

Fig. 4 is a similar view on the plane of line 4-4 of Fig. 2; and

Fig. 5 is a perspective detail with certain parts broken away to show a typical switch capable of use with the device of Fig. 1.

As shown in these figures, the complete two part or two-section enclosure consists of the lower larger part 59 and the upper or smaller part I! and the connection [2. Or it may be likened to a columnar body l0, head H and neck it. The are preferably cylindrical in form, in axial alignment, and the connection [2 threaded into the body iii, as indicated. The part or body it is of comparatively heavy tubing and threads at the lower end onto the boss or shoulder of a base it, which is preferably hexagonal in out line for the convenient application of a wrench. A threaded hole M through the base enables the device to be attached, as will be understood, to the pipe of the fluid pressure system to which the device is to be applied.

On the inside of this tube is an elongated pressure-responsive bellows E5 of any desired or suitable type and which, as is well understood, consists of a series of superposed spring metal discs alternately secured and sealed together at their inner and outer peripheries, as by soldering, brazing or welding, the whole being expansible and elongating under fluid pressure within and returnable to usual position by its own resilience when the pressure is relieved. The lower end of the bellows is operatively connected with the base is to receive pressure from the pressure pipe connected therewith, and at its upper end is uitably connected to and carries an end plate it. This end plate is provided with an extended inner lug or projection 11, into which threads the stem 58 of the head, plate or disc 59 which forms the actuator or operative element of the bellows. This head may be adjusted in any position desired with respect to the bellows and may be secured in adjusted position by the lock nut M. The hole for the threaded stem is does not extend through the projection ll of the end plate of the bellows, so that the pressure within the bellows is not affected thereby. This adjustment of the bellows operating head I9 and the assembly of same in the tubular casing Ill may all be done at the factory, the same being built, assembled and adjusted per specifications furnished it, so that to be installed it has merely to be screwed on the end of the pressure supply pipe where it is to be used.

Th electric switch of the device is located in the part, section, head or casing H referred to, and may be of the well known over-center spring type, as shown in Fig. 5; for example, that switch sold in. the trade as the Burgess micro-switch. This type of switch, which is shown by way of exemplification only, comprises an upper contact mounted on an insulating base 3| by a screw the movable contact 34 being adapted to be moved against the fixed contact 341. Movable contact 34 is carried on the resilient member comprising the central link 36 secured to the base it! of the switch by a screw 31. Over-center spring action is provided by the two integral arcuate tensioned members 38 and the free ends of the latter lying in Vshaped notches M 4l in the fixed plate s2, and hence deformed into the arcuate contour shown. By proper propontioning the relative lengths of the links 36 and members 38 and 39, a slight movement on the order of only a few thousandths of an inch applied to the link 36 suffices to move the contact 34 into engagement with the contact 38. Thus the switch is of the single-pole, single-throw type.

Suitable actuating movement is applied to the link 36 by the pin or button 2!, which in turn operates through the element 44 in contact with the link 36. Thus, although more than the necessary amount to operate the movable switch member is applied to the pin M, such excess movement is absorbed by the coiled spring 45, and the switch cannot be damaged.

The screws 32% and 3?, respectively, receive the terminals 22 by means of which the switch may control the external circuit.

Suitable terminals 22, in this instance two in number, are provided at the end of the section II of the casing for connection with the conductors of the external electric circuit in which the switch is to be included, such connection or conductors, however, being loose enough or such as to permit rotation of the casing H, as hereinafter' explained.

Theswitch in the assembled device is operated by the disc is of the bellows striking and pushing on the end of pin ill passing through the connection l2 and engaging the switch mechanism inside the section H, and this occurs when pressure in the bellows expands and lengthens the samev sufficiently to do so. The upper face of the disc I!) is carefully smoothed and in a plane perpendicular to the axis of the device, and the adjacent end of pin 2! is slightly rounded so that its axial central point is adapted to engage the flat actuating disc is of the bellows. This pin 2i is preferably of suitable hard insulating material of smooth exterior and slides freely end- Wise in the tubular connection !2.

Pressure adjustment is relatively simple and easily made. When the device is initially assembled, adjustment of member is and the lock ing of nut 2c thereafter will permit operation. of

the device at a predetermined pressure. Bellows l-5 will expand and member Hi will. be brought into: engagement to engage and actuate pin of. switch ll. Pin 2i will alsobe adjusted so that its position will be predetermined with respect to the adjustment of member l9 described above. This is accomplished by threading stud l2 into position upon casing ill to place pin. 2.! in relative operating position with member is at thev time it is adjusted. Lock nuts 23 are then tightened to maintain this positioning of pin 2!. If then, further adjustment is desirable during time of operation, say when some new operating conditions obtain, or when the device is used differently, or at another place, lock nuts 23 may then be untightened and switch it turned until pin 2| is newly positioned with respect to memher is. to secure actuation of switch H at a pre determined pressure in the system. Lock nuts. 23 are again tightened and the adjustment rigidity maintained until another change is desirable. This adjustment is simple and allows attendants to make the same without giving them access to the interior of the device. Tools and other instruments are thus kept away from the 4 bellows unit and the operating characteristics are thereby effectively preserved. Slight bending or distortion of any of the bellows flanges will destroy a sensitive adjustment of the switch unit ii, while injury to or rupture of the wall of these flanges or to their peripheral joints by a sharp tool will cause leaks to occur and therefore the stroke of the bellows for a given pressure will be changed. Normally such injuries or rupturing require replacement of the device. It will be apparent that member iii is so shaped as to prevent insertion of sharp or pointed tools through the threaded opening in the top of housing iii to a point where they will come into contact with bellows I5.

The initial adjustment of member iii provides therefor a satisfactory setting of the same for the bellows employed while more minute or sensitive adjustments, or changes thereof, can be made by turning switch unit I l to determine the relative distance between the engaging face of member i9. and the end of pin 2i and therefore the pressure at which engagement occurs between these two parts and actuation of switch ii is effected.

As thus constructed, the device constitutes a rugged, unitary, enclosed structure with no outside parts to be injured or knocked out of adjustment even by rough handling, the bellows part or section is strongly made to form a rigid support for the switch part or section which requires no other care, it is applied in operative position merely by screwing it to the pressure pipe and connecting the other end to the circuit, it is readily and quickly adjustable for accurate operation at different pressures wholly from the exterior by merely turning the switch member, and may be used in any position the installation may require. When not in use, it may be stored in any convenient way without derangement of its parts or individual adjustment; extras may be carried along, and replacements are readily made. It is complete within itself and ready for use at all times.

Without further elaboration, the foregoing will so fully explain the gist of my invention that others may, by applying current knowledge, readily adapt the same for use under varying conditions of service, without eliminating certain features, which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured to me by the following claims.

I claim:

1. A pressure switch comprising a cylindrical tubular enclosin casing forming a body and a smaller enclosing casing forming a head with a threaded neck between the two casings, all in axial. alignment, said body having an enlarged base portion with a threaded aperture therethrough for connection with a fluid-pressure pipe, an elongated pressure-responsive bellows in said body and secured to said base to receive fluid under pressure from the said pipe, an actuator carried. at the opposite end of said bellows, an electric switch inv said head, conductor terminals therefor on the exterior of said head, a push-pin slidablein said threaded neck to operate said switch and having an end adjacent the said actuator, the position of said pin with respect to said actuator being adjustable by turning the head on said. threaded neck, and means to lock said neck in adjusted. position, the said body forming a rigid support for said head.

2. A. pressure-operated device comprising a and the latter being made in conl necting the two casings together for operation of the device at the desired pressure.

3. A pressure switch comprising a rigid tubular enclosed body casing having a supporting base at one end with an aperture therethrough for attaching the switch to the pipe of a pressure systern, said casing having a threaded opening in its opposite closed end, a longitudinally expansible bellows within said body casing mounted at one end on said base and communicatin with said aperture, an end plate for the other end of said bellows, an actuator disc within said casing opposite and adjacent the said opening in the end thereof and adjustably connected with said end plate of the bellows, a relatively small head consisting of a completely closed casing having a threaded tubular neck adapted to be inserted in said threaded opening in the end of the body casing to support the head on the body, a switch in the head casing, and an operating pin for the switch extending through said neck and adapted to be engaged by said actuator disc in the body casing to operate the switch upon a predetermined pressure in the bellows, the threaded neck enabling the head casing and its operating pin to be adjusted with reference to the said actuator to adjust the operation of the said pin and switch at the desired pressure.

4. A pressure switch comprising a base, a pressure bellows mounted on and connected with said base, said base having means for supportingly connecting it to a pressure supply system, an adjustable actuator head connected with and carried by the opposite end of the bellows, a rigid tubular casing enclosing said bellows and actuator and firmly engaging and secured to said base, said casing havin a threaded opening in its closed end over the said bellows and head, a tubular neck threaded into said opening, a relatively small head casing neck, an electric switch in said head, a longitudinally slidable pin in said neck for operating the switch contacts by pressure on the pin, the free end of the said pin being adjacent the bellows head or actuator within the body casing for operation thereby, said threaded connection of said neck with the end of the bellows casing permitting the accurate adjustment of said switch pin toward and from the bellows actuator head by turning the head casing to vary the operative pressure of the switch, and means to lock said neck in its adjusted position.

5. A pressure-operated device comprising a tubular casing having an enclosing end wall with a restricted opening therein, a pressure-responsive bellows in said. casing, an actuator disc wholly within the casing and carried by the bellows opposite and adjacent the said opening, an external device secured to said end wall of the casing and having an operating pin projecting through said opening and into the casing to be engaged and opera ed by said actuator, the surface of said actuator for engagement with the pin being laterally extended beyond the axial line of contact to insure proper operation of the pin even if the carried and supported by said point of engagement of the actuator and pin be laterally displaced slightly from said axial line.

6. A pressure switch comprising an enclosed tubular supporting body casing and a head casing exteriorly mounted on said body casing and having a longitudinally adjustable threaded tubular neck of less diameter than the body casing and head casing, said neck extending into the body casing and adjustably supporting the head casing on the body casing, a pressure-responsive bellows in the body casing arranged to be connected with an external fluid pressure system, an electric switch in the head casing arranged to be connested in an electric circuit system, and a longitudinally sliding pin in and through said neck for operating said switch by said bellows, said adjustable neck enabling the head to be adjusted toward and from the body to operate the switch at diiferent predetermined pressures in the bellows.

'7. A pressure switch comprising a tubular body casing having a base at one end and an enclosing end wall across the other end of the casing, a fiuid-pressure-responsive bellows in said body casing connected to the base and therethrough to the pressure supply system, an exteriorly mounted head casing on said body casing and having a threaded tubular neck of less diameter than the said casings and threading into the end of said body casing and supporting the head casing thereon, an electric switch located in said head casing and having terminals to connect it in an electric circuit, and an operating pin for said switch slidable in and through said tubular neck and projecting into said body casing. in position to be operated by said bellows, the said threaded neck enabling the head and switch to be adjusted toward and from the body casing to operate the switch at predetermined pressures in the bellows.

8. A pressure-operated device comprising a tubular body casing having an enclosing end wall with a r stricted opening therein, a pressureresponsive bellows in said casing, an actuator disc wholly inside the casing adjacent said opening and connected with said bellows in line with said opening to transmit motion from the bellows through said opening in the operation of the said device, said actuator disc being substantially larger in diameter than the said opening and relatively close to said end wall whereby to prevent tampering with the bellows by inserting a tool through said opening and around the actuator.

9. A pressure switch comprising an enclosed supporting body casing, a pressure-responsive device in said casing adapted to be connected with a fluid pressure system, an enclosed head casing, an electric switch in said head casing, said head casing having a threaded neck adapted to be adjustably secured in the wall of said body casing and thereby to support the head casing on the body casing, and a sliding pin extending through said neck and operatively connecting the pressure-responsive device in the body casing with the switch in the head casing, the adjustment of said casings with respect to each other through said threaded neck determining the pressure at which the switch is operated by said pressure-responsive device.

10. A pressure switch comprising, in combination, a rugged elongated tubular casing having a supporting base at one end and an enclosing wall at the other end, a bellows in said casing 7 8' adapted to be connected through said base with FE a fluid pressure system, a tubular head casing RE RENCES CITED I enclosing an electric switch, said head casing T wine re ces ar of r cord in the having a threaded supporting neck screwing into file 0f thls patent! the Said. end- Wall Of the body casing, and a Slid- UNITED STATES PATENTSv ing pin extending through said neck and operatively connectingthe switch in the head casing Number I Name Date with the bellows in the body casing, said head 1,932,983 Rainfly 31, 3 casing being adjustable to and from the said body 2 2 Houmshea'd Aug. 27, 1935 casing by said threaded neck to determine the 10 2,033,417 Dfizoteu M 10, 9 pressure at which the switch is operated by the 8 2 H111 May .3 be-H ,6 uthe Feb. 6, 1940 2,395,007 Leupold Feb. 19, 1946 E. RO 22,432,312 HQLSSBlhOII'l Dec. 9, 1947

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