A pressure operable electrical switch having a diagonally supported flexure beam interposed between a pressure responsive diaphragm and a ball movable against a switch actuator. An exposed adjusting knob permits presetting pressure at which the instrument is to be operative and is located laterally displaced from the ball operatively connected to prevent beam movement at pressures below the setting thereof.

Current U.S. Class:	200/83S
Current International Class:	H01H 35/24 (20060101); H01H 35/26 (20060101); H01h 035/24 ()
Field of Search:	200/83,83.5,83.51,82.2 337/120

Robert W. Mayer Daniel Rubin Frank S. Troidl Roy L. Van Winkle William E. Johnson, Jr.

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Claims

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1. A pressure responsive device comprising: a. a housing having a central passage extending from a first end for connecting to a source of inlet pressure; b. a pressure yieldable diaphragm secured in pressure tight relation to said housing overlying said passage at a location displaced from said first end; c. movable means having one side operably engaging said diaphragm to be movable in direct response to yielding thereof and another side having a recess located in direct alignment with the axis of said passage; d. a ball member seated in the recess of said last-recited means for conjoint movement therewith; e. control means operative by an actuator movable in axial alignment with the axis of said passage; f. a pivotal flexure beam secured at one end and relatively free at the other end, said beam extending contiguously between said ball member and actuator and responsive to movement of said ball member to move said actuator between operative and inoperative position for said control means; and g. adjustment means to preset the operating pressure of said control means including means to apply a preset biasing force against the free end of said flexure beam acting in a direction to oppose pressure in said passage

2. A pressure responsive device according to claim 1 in which said adjustment means is located axially displaced from said adjustment means is located axially displaced from said central passage and acts in a

3. A pressure responsive device according to claim 2 in which said adjustment means includes a coil spring acting against the free end of said flexure beam and a control knob threadedly mounted to compress the

4. A pressure responsive device according to claim 3 including pressure unit calibrated indicia means correlated with a reference location on said control knob enabling visual observation of the set condition as the knob

5. A pressure responsive device according to claim 4 in which said control means comprises an electrical switch having contacts for connecting to a

6. In a pressure responsive device including a housing having a central passage extending from a first end for connecting to a source of inlet pressure, a pressure yieldable diaphragm secured in pressure tight relation to said housing overlying said passage at a location displaced from said first end; and movable means having two sides one side of which operably engages said diaphragm to be movable in direct response to yielding thereof and the other side of which has a recess located in direct alignment with the axis of said passage; the improvement comprising; a. a ball member seated in the recess of said last-recited means for conjoint movement therewith; b. control means operative by an actuator movable in axial alignment with the axis of said passage; c. a pivotable flexure beam secured at one end and relatively free at the other end, said beam extending contiguously between said ball member and actuator and responsive to movement of said ball member to move said actuator between operative and inoperative positions for said control means; and d. adjustment means to preset the operating pressure of said control means including means to apply a preset biasing force against the free end of said flexure beam acting in a direction to oppose pressure in said passage

7. In the improvement according to claim 6 in which said adjustment means is located axially displaced from said central passage and acts in a

8. In the improvement according to claim 7 in which said adjustment means includes a coil spring acting against the free end of said flexure beam and a control knob threadedly mounted to compress the spring against said

9. In the improvement according to claim 8 including pressure unit calibrated indicia means correlated with a reference location on said control knob enabling visual observation of the set condition as the knob

10. In the improvement according to claim 9 in which said control means comprises an electrical switch having contacts for connecting to a circuit to be controlled.

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Description

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1. The field of art to which the invention pertains includes the art of electricity, circuit makers and breakers as specifically including the art therein pertaining to switches operative by fluid pressure or other force and motion producing devices.

2. Condition responsive switches for various control purposes are well known in the industry and available from many sources of manufacture. While commercially available pressure actuated switches are known to function well, they are generally characterized by insufficient compactness, i.e., having too great a height dimension to meet particular customer needs and/or the inability to be adjustably and conveniently field set to the pressure at which the instrument is to be operative. Although many switches currently marketed contain one or the other of these features, none by virtue of their particular construction are readily capable of combining both features within a single instrument in an economic manner enabling the product to favorably compete in present markets against similar devices having one or the other of these features.

Typical of the prior art are pressure switches such as those disclosed for example in U.S. Pat. Nos. 2,249,208; 2,722,580; 2,807,686; and 2,919,321. It can be seen from a review of the mechanisms in the devices of these prior patents, that their relatively sophisticated constructions are not amenable to competitively low fabrication cost to provide a low height, compact pressure switching unit having integral means enabling field adjustable presetting of the pressure operating point.

SUMMARY

This invention relates to control instruments and particularly to pressure responsive electrical switch devices for operating a control circuit of external equipment or the like. More specifically, the invention relates to a pressure responsive control switch characterized by a highly compact assembly affording a minimum instrument height yet having the capability of convenient field set adjustability of the instrument for accurately effecting the set pressure at which the instrument is to be operative. Not only are both of these features readily and compactly combined into a single instrument, but this result is achieved with a design affording high vibration resistance, low friction operation as to minimize inherent error as otherwise occurs in instruments of this type. Moreover, the simple construction hereof enables low production cost permitting the instrument to compete favorably in the market place against instruments marketed by others without these combined features.

These results are achieved in accordance with the invention by means of an assembled arrangement of components that includes a pressure sensitive diaphragm exposed to the pressure to which the instrument is intended to respond. A movable piston is supported in immediate follower engagement centrally aligned against the diaphragm and in turn responsively moves a ball on which is supported a diagonal flexure beam. Located opposite the beam is a switch actuator in the form of a plunger pin arranged in extended alignment with the ball and operating the switch to which the circuit leads are connected. The beam acts, via the ball, as a second class lever transmitting force to the switch actuator. Concomitantly opposing beam movement against the actuator is a loading spring acting against the beam axially displaced from the ball for applying a force at the free end thereof. The spring load is set at the desired operating pressure at which the instrument is to be responsive by means of a knurled adjusting knob movable relative to a fixed reference scale of pressure indicia.

Notwithstanding these combined operational features, the switch hereof can conveniently be constructed within an overall height of about 3 1/4 inches having a maximum lateral dimension of about 2 3/4 inches. Accordingly, by means of the invention hereof, features characterizing prior devices of this type are substantially improved on by a novel construction not previously known and affording a relatively low cost product satisfying a long felt need in the industry.

It is therefore an object of the invention to provide a novel pressure responsive control instrument characterized by a design affording convenient preset adjustment of the operating pressure at which the instrument is to be responsive yet having a higher degree of compactness than similar switch mechanisms of the prior art.

It is a further object of the invention to provide a novel pressure responsive control switch in accordance with the preceding object having a simplified construction affording relatively low fabrication cost as to enable competitive marketing of this unit against other units with lesser features.

FIG. 1 is an elevation view of the switch instrument hereof partly cut away to expose internal construction detail;

FIG. 2 is top plan view of the switch instrument hereof;

FIG. 3 is a sectional elevation taken substantially along the lines 3-3 of FIG. 2; and

FIG. 4 is sectional elevation taken substantially along the lines 4-4 of FIG. 2.

Referring now to the drawings, the illustrated embodiment of the invention includes a housing 10 representing the lower part of the instrument and having a shank 11 for connection to a system in which the instrument is to be employed. For these purposes the shank includes a male thread and a female thread at 21 enabling screw mounting to a well, bracket or other support on which the instrument is to be situated. Upward from the shank the housing enlarges to a hexagonal formation 12 on which to externally receive a wrench or the like used to install the instrument in place and in turn merging into an enlarged and squared cuplike formation 13 defining an internal recess 15. Supported and secured via bolts 14, 45 and 50 superposed overlying the cup end of the housing in pressure tight relation is a top plate 16 being exteriorly coextensive therewith.

Pressure of a system to which the instrument is to be responsive is received within the housing shank via a fluid passage 20 having a defined central axis 25. The passage extends upward to an annular shoulder 27 defining a coaxial bore 22 opening into the housing recess 15. Within the recess overlying bore 22 is supported a suitable preassembled pressure sensitive unit which may be of a type disclosed in Gorgens, et al. U.S. Pat. No. 3,393,612 incorporated herein by reference. As more fully disclosed in the Gorgens et al. patent, the pressure unit includes a diaphragm 34 attached to the underside of a piston 23, a cylinder 24 circumferentially surrounding the piston and a spring 26 in the form of a symmetrical spidershaped metal element overlying the piston to resist movement thereof. Cylinder 24 has an L-shaped cross section, the radially inward directed flange of which presents a flat seating surface 28 on which the piston can rest. For this purpose piston 23 is of two diameters, the larger being indicated at 30, and the smaller being indicated at 32. In radial dimension the piston and cylinder are closely situated but sufficiently spaced to permit axial movement of the former in a relatively friction-free relation.

On assembly of the unit, a thin piston flange or rim 33 is staked and deformed over the inner spring ring to secure the spring and piston in a firmly clamped relation while the fluid impervious rubber diaphragm 34 is sealed and clamped at its edges by an O-ring 36. In a manner similar to that described in the Gorgens, et al. patent supra, the piston and diaphragm are concomitantly urged in a vertical direction in response to pressure changes received at the fluid passage 20 being upwardly in response to increased pressure and downwardly in response to decreased pressure.

To transmit piston movement in accordance herewith there is provided a spherical ball 38 freely supported within bore 39 of top plate 16. The ball is normally seated in drilled recessed 40 on the topside of piston 23 to be movable conjointly therewith. Bore 39 likewise has an axis extension coincident with axis 25 and is of a diameter providing radial clearance to the ball sufficient to permit frictionless axial movement thereof.

Overlying the ball in normally force contact engagement therewith (see FIG. 4) is a flexure beam 44 secured to top plate 16 at one end via bolt 45 and relatively free at its opposite end whereat it is formed with a central bore 46 and an upward-turned flange 47. Received through the bore 46 is a centering bolt 50 extending axially upward parallel and displaced from axis 25 to threadedly support an adjusting knob 52 at its uppermost end. The knob is formed at its underside with a counterbore 53 in which to receive a coil spring 54 loaded by compression against flange 47 as will be explained. In this arrangement the compressive force of spring 54 acting against the flexure beam resists upward movement of the ball imposed by pressure acting against the underside of diaphragm 34.

For these purposes, beam 44 is of a relatively firm inflexible strip material having a window 48 defining a hinge location and is initially supported without preloading. The rate of spring 54 is matched to the beam arm deflection corresponding to scale travel for pressure calibrations on scale 68. At zero load, the spring is in its natural uncompressed state with the beam barely contiguous to the ball without any preloading thereon. Likewise, the operating switch differential between "on" and "off," can be governed by appropriate selection of the spring rate. Preferably, a 2 and 3 percent differential is employed for 15 and 20 amperage service respectively.

Switching operation of the device is conducted by switch unit 57 having a switch actuator in the form of a vertical plunger or pin 56 downwardly depending into engagement against the topside surface of beam 44. Pin 56 is supported in axial alignment with axis 25, and endures vertical movement in a follower relation to beam 44. The switch is of a suitable type commercially available for either line voltage or control line voltage having terminals 58, 59 and 60 to receive wire leads of the circuit in which it is to be connected.

Securing the switch in position on top plate 16 is a vertical bracket 62 having horizontally extending opposite ends 63 received beneath the nut of each bolt 14. On the opposite face of switch 57 bracket 62 forms a nameplate 65 bent into a springlike engagement against the knurled surface of knob 52. This serves to provide a frictional detent against the knob whereby inadvertent resetting of the latter from vibration or the like is prevented. Along the rightmost edge of the nameplate, as viewed in FIG. 1, is a reference scale 68 of calibrated pressure indicium at which the instrument can be preset to operate. In accordance herewith the indicium are calibrated to coincide with the under-edge 69 position of knob 52.

To set switch operating pressure knob 52 is hand-rotated by an operator until bottom edge 69 is opposite the desired pressure reading on scale 68. Rotating the knob advances it up or down on the threaded shank of center bolt 50 to move under-edge 69 relative to pressure indicia on scale 68 corresponding to pressures at which the unit will operate when the knob is stayed. Downward movement of the knob increases spring compression against flexure beam 44 thus increasing the force which ball 38 must overcome to operate the switch. The converse is also true. In this relation therefore, flexure beam 44 forms a second class lever transmitting force to the switch actuator via the ball 38. By means of control knob 52 being located offset with respect to ball 38 the leverage effect permits using a coil spring 54 having a generally lower spring rate than would otherwise be required if the latter were located in axial alignment between the ball and plunger.

With the arrangement thus described there is disclosed a simply constructed, highly compacted, pressure responsive electrical switching unit. The unit is comprised of a minimum number of operating components in which pressure received in the fluid passage 20 acts via the piston 23 in a linearly direct axially aligned movement against the switch actuator 56. Adjustment can be easily and readily operator set in the field by mere appropriate setting of adjustment knob 52 relative to indicia scale 68. Once the knob has been set to the desired operating point, the detent effect of plate 65 prevents inadvertent self change. While a pressure range of 0--100 p.s.i.g. is illustrated, appropriate force matching of spring 54 to arm 44 and/or substituting piston assemblies 23 of different capacity as disclosed in the Gorgens et al. patent supra will permit any plausible range to be employed. Not only does the simplicity of this design have a minimum of operative and cooperating components which affords economical fabrication but it likewise contributes to a high degree of compactness having a minimum height dimension. At the same time, by virtue of the tight-knit compactness, the unit has a high resistance to vibration which could in time otherwise affect its operating performance. Yet further, the manner in which the flexure beam loads the ball against the switch actuator plunger, eliminates backlash and prevents impact damage which could otherwise occur.

By the above description there has been disclosed a novel switching unit responsive to operating pressure of a system for which it is employed to operate an appropriate number of control circuits as a function of pressure change. By the assembly arrangement provided, the switch is of a highly economical construction affording the combined features of minimal height and convenient field setting adjustment of the appropriate pressure at which the unit is to be operative.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense.

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