US3383484A - Pressure responsive switch - Google Patents

Description

May 14, 1968 ARP ET AL 3,383,484

PRESSURE RESPONSIVE SWITCH 2 Sheets-Sheet 1 Filed Oct 13, 1965 May 14, 1968 J, m: ET AL 3,383,484

PRES SURE RESPONS IVE SWITCH Filed Oct. 13, 1965 2 Sheets-Sheei :2

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iwwk United States Patent 3,383,484 PRESSURE RESPONSIVE SWITCH Leon J. Arp, 1221 Marston, and James M. Varnum, 428 Ash, both of Ames, Iowa 50010 Filed Oct. 13, 1965, Ser. No. 495,649 1 Claim. (Cl. 200-83) ABSTRACT OF THE DISCLOSURE A pressure responsive switch comprising a pair of plates adapted to be locked together with a cavity formed therein. A pair of separate electric contacts are mounted in one plate, with the contacts being part of a normally open electrical switch, which switch can be connected to for operating any electrically responsive mechanism. A diaphragm is also mounted in the cavity which is responsive to a differential pressure on either side thereof. An opening is formed in the plate of the contacts to transmit, for example, the negative pressure of a person inhaling through the opening, and a positive pressure of a respirator system forcing air therethrough to the person. *On the side of the diaphragm facing the contacts, an electrically conductive disc is mounted which disc is operable to simultaneously engage the contacts, thereby closing the switch circuit. On the opposite side of the diaphragm, due to a series of holes formed in the other plate, air under atmospheric pressure is admitted therein for forcing the diaphragm and its disc against the contacts in response to a negative pressure on the disc side of the diaphragm. An electromagnetic device is also mounted on the opposite plate which is operable to vary the sensitivity of the pressure responsive switch by magnetically affecting the disc. The cavity on the electromagnetic device side of the diaphragm has a screen interposed between the diaphragm and the electromagnetic device to prevent the diaphragm from contacting the device, and for insuring air under atmospheric pressure on the entire surface of the diaphragm 'at all times irrespective of its position.

It is an object of this invention to provide a diaphragmtype switch wherein the diaphragm is movably responsive to a pressure differential induced by the inspiration or expiration of the patient to effect a closed electric circuit to actuate the respirator, and wherein further the response of the diaphragm to said pressure differential is electro-magnetically controllable, thereby varying the control sensitivity of the switch.

Yet another object of this invention is to provide 'a diaphragm-type pressure sensitive switch wherein the diaphragm is movable between a pair of positions effecting thereby an open or closed electric circuit, and further wherein the one side of the diaphragm exposed to atmospheric pressure is always substantially exposed thereto in both positions.

It is another object of this invention to provide a pressure sensitive switch capable of attaining the above designated objects which is extremely economical to manufacture, simple and rugged in structure, and effective in operation.

These objects, and other features and advantages of this invention will become readily apparent upon reference to the following description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a specific embodiment of the invention;

FIG. 2 is an exploded elevational view of the invention showing the relative position of the various parts, with certain parts thereof shown in sectional view;

3,383,484 Patented May 14, 1968 FIG. 3 is a bottom plan view of the upper housing;

FIG. 4 is a top plan view of the upper housing;

FIG. 5 is a sectional view taken along the line 5-5 in FIG. 4;

FIG. 6 is an enlarged, fragmentary sectional view of the invention, and showing the diaphragm in two alternate positions;

FIG. 7 is a top plan view of the base plate;

FIG. 8 is a sectional view taken along the line 8-8 in FIG. 7;

FIG. 9 is a bottom plan view of the base plate;

FIG. 10 is a plan view of the diaphragm;

FIG. 11 is an enlanged sectional view taken along the line 11-11 in FIG. 10;

FIG. 12 is a plan view of the wire screen.

Referring now to the drawings, a commercially 'available nose or face mask 10 (FIG. 1), adapted to fit a living creature, has two ports 11 and 12 formed therein. Fluidly connected to port 11 is a conduit 13 which is fluidly communicable at the other end 14 with the 'atmosphere. A second conduit 16, fluidly connected to the port 12 is fluidly communicable with a respirator 17 at a discharge port 18 formed therein. The conduit 16 (FIG. 1) branches off at 21 with a third conduit 22 which is fluidly connected to a tube 23 mounted in a pressure sensing device generally indicated 'at 24. The pressure sensing device 24 is electrically connected by lines 25 and 25a to the circuitry of the respirator 17 or other device responsive to inspiration or expiration for purposes hereinafter described.

The base plate 26 of the pressure sensing device (FIGS. 2 and 8), constructed of a non-metallic material, has an aperture 27 (FIG. 8) formed in the center thereof which receives the tube 23, and which opens into an inverted frustro-conical cavity 28 formed in the top of the plate 26 as illustrated in FIG. 8.

Two diametrically opposite, parallel holes 29 and 31 (FIG. 6) are formed in the plate 26 on each side of the opening 28. Stainless steel screws 32 and 33, with their shank end-s 34 and 35 ground to a point, for purposes hereinafter described, are threadably inserted through back-up nuts 37 and 38 and into the holes 29 and 31. The nuts 37 and 38 are provided to lock and to position the screws 32 and 33 to enable the ends 34 and 35 thereof to protrude into the opening 28 for a predetermined distance. Fastened to the heads of the screws 32 and 33 are the wires 25 and 25a (FIG. 1). In this arrangement the screw ends 34 and 35 are the open contact-s of a normally open electric switch, closeable as hereinafter provided.

The base plate 26 is completed by 'a quartet of tapped holes 39 (FIG. 7) formed, one in each corner, therethrough.

The upper housing 36 (FIGS. 2 and 5) of the pressure sensing device, constructed of Plexiglas or like nonmetallic material, is provided with an aperture 41 formed centrally therein, and which opens into an intermediate, circular cavity 42 having a larger diameter. The intermediate cavity 42 leads into a larger circular cavity 43 formed in the housing 36 on the under side thereof as best illustrated in FIG. 5. A plurality of arcuately spaced openings 44 (FIG. 3) are bored through the housing 36 and extended into the peripheral area of the cavity 43 as 'best seen in FIG. 3. Four holes 46 are axially drilled through the housing 36, one in each corner, for

alignment with the holes 39 in the plate 24. Secured to the surface 47 of the shoulder formed between the cavity 43 and the cavity 42 is a fine mesh circular screen 48 (FIGS. 6 and 12) which has 'a diameter greater than that of the cavity 42. It is seen that the screen 48 completely covers the cavity 42.

Four screws 49 (FIGS. 2 and 6) are provided to secure the plate 26 to the housing 36 by insertion through the aligned holes 46 and 39. When the plate 26 and housing 36 are secured together a chamber 50 consisting of the cavities 43 and 28 is created therein, with the cavity 42 in fluid communication therewith through the screen 48.

Between the plate 26 and the housing 36 (FIG. 6), and thereby dividing the cavity 50 into two parts, is stretched a circular, silicone rubber diaphragm 51, also shown in FIG. 10, which under normal conditions because of its tautness assumes the position shown by the dotted lines in FIG. 6. Bonded to the center of the diaphragm 51 and on the side thereof facing the screw ends 34 and 35 is a circular stainless steel disc 52, best shown in FIG. 2.

An electromagnet 53 (FIG. 2) is mounted on the housing 36 with its core 54 (FIG. inserted into the aperture 41. The magnet 53 may be varied as to the strength of its field relative to attracting the disc 52, by means of a potentiometer 56 electrically connected thereto.

In operation of the system, air under atmospheric conditions enters the pressure sensing device 24 by flowing through the openings 44 (FIG. 6) and into the portion of the chamber 50 located above the diaphragm 51 as shown in FIG. 6. 'On the nose mask side of the diaphragm 51, or in the lower portion of the chamber as seen in FIG. 6, atmospheric conditions also exist when the respirator 17 is not functioning.

In use, the mask is placed over the face of the patient. Upon inspiration by the patient, a negative pressure is created in the conduits 16 and 22, as both are closed off from the atmosphere. With a negative pressure in the cavity 50 below the diaphragm 51, the positive atmospheric pressure on the top side of the diaphragm 51 forces the diaphragm 51 to the distended full line position shown in FIG. 6, wherein the disc 52 contacts the ends 34 and of the screws 32 and 33, thereby closing the electrical circuit leading to the respirator 17, which is thereby activated. The activated respirator 17 then forces a proper supply of fluid through the conduit 16 to the nose mask and the lungs of the patient, while at the same time transmitting fluid through the conduit 22 into the chamber below the diaphragm, thereby creating a positive pressure against the diaphragm 51. This positive pressure forces the diaphragm upwardly and away from the full line position as illustrated in FIG. 6, and thereby breaks the contact between the disc 52 and the screw ends 34 and 35, thus opening the circuit and deactivating the triggering section of the respirator 17.

The patient on exhaling forces fluid from the nose mask 10 through passage 13 to the atmosphere and at the same time into the pressure sensing device 24 via the passages leading thereto. This exhalation maintains the positive pressure on the disc side of the diaphragm created therein by the activation of the respirator 17. For an instant, between the inspiration and the expiration of the patient the entire system will again be under atmospheric conditions as described hereinabove. The patient again inhales and the above described sequence is again set in motion.

The potentiometer 56 controlled electromagnet 53 is mounted on the pressure sensing device 24 to regulate the sensitivity of the diaphragm 51. If the electromotive force is increased by changing the setting of the potentiometer 56, the magnetic force created by the magnet requires a greater negative pressure on the disc side of the diaphragm 51 to overcome the force holding the disc away from contacting the screw ends 3-4 and 35. Therefore it can readily be seen that the pressure sensing device 24 can be used in a respirator system for either an infant or an adult by merely regulating the potentiometer.

The screen 48 is so mounted to prevent the diaphragm 51 and accompanying disc 52 from being forced into the cavity 42 and against the core of the electromagnet 54 during operation of the device 24. Atmospheric air entering the chamber 50 via the holes 44 can pass through the screen to be on the top side of the diaphragm so as to act on substantially the entire surface thereof. If the screen was not so mounted, atmospheric air would only act on the annular peripheral portion of the diaphragm 51. This could result in a disadvantageous sticking of the disc 52 to the core 54 which would adversely eflect the operation of the device.

It can, of course, be visualized that the pressure sensing device could be connected to a signal device instead of a respirator, whereby a change in pressure would cause an alarm or the like to be activated.

Although a preferred embodiment of this invention has been described and disclosed hereinbefore, it is to be remembered that various modifications and alternate constructions may be made thereto without departing from the true spirit and scope of the invention as defined in the appended claims. For example, many minute changes in the position of the diaphragm 51 as caused by the presence of a slight negative pressure in the cavity 50, or even caused by a slight positive pressure therein, can be sensed by means substituted for the screw electrodes 32 and 33; such as a variable reluctance unit operatively connected to the circuitry of the respirator 17, or to another device responsive to inspiration or expiration. Furthermore, in the place of the variable reluctance arrangement, variable capacitance, variable inductance, or variable resistance arrangements could be used, as could the interruption of a light beam as a means for sensing changes in the position of the diaphragm.

Each of these aforementioned arrangements could be built into the plate 26 for detecting minute changes in the position of the diaphragm 51, and as a means for utilizing said changes for controlled operation of the respirator 17.

We claim:

1. A pressure sensing device consisting in combination:

base plate means;

upper housing means mounted on said plate means and forming a cavity therebetween, said cavity fluidly communicable with the atmosphere;

a diaphragm secured between said plate means and said housing means and disposed within said cavity, wherein one side of said diaphragm is exposed to the atmosphere;

fluid means fluidly connected to said plate means for communicating a fluid with said cavity on the other side of said diaphragm;

said diaphragm movably responsive to a pressure-differential between said fluid means and the atmosphere;

a normally open electrical switch means having a pair of spaced contacts mounted on said plate means and extending into said cavity; and

electrically conductive disc means mounted on said diaphragm and operable to simultaneously engage said contacts and close said switch in response to movement of said diaphragm;

electro magnetic means mounted on said housing means, said magnetic means operable to control the attraction thereto of said disc means whereby to control the sensitivity of said diaphragm; and

screen means mounted in said cavity adjacent said one side of said diaphragm and interposed between said magnetic means and said diaphragm, said screen means located within said cavity such that air under atmospheric pressure is on either side of said screen means at all times regardless of the position of said diaphragm, said screen means operable to prevent said diaphragm from engaging said magnetic means, and operable further to allow air under atmospheric conditions to impinge substantially the entire ex- References Cited UNITED STATES PATENTS Halbleib ZOO-83.6 Dashner et a1. 340270 Hueber et a1. 20083 Tobias 200-83 10 Lusted 200-83 X CPL 6 6/1963- Horowitz 20083 10/ 1963 Caldwell 128140 2/1966 Bird et a1. 128145.6 2/ 196 6 Fullman 222250 FOREIGN PATENTS 2/ 1912 Austria. 9/1896 Germany.

RICHARD A GAUDET, Primary Examiner.

K. L. HOWELL, Assistant Examiner.

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