US3007017A

US3007017A - Pressure switch

Info

Publication number: US3007017A
Application number: US21818A
Authority: US
Inventors: Frank W Dwyer; Phillip W Dwyer
Original assignee: F W DWYER Manufacturing CO
Current assignee: F W DWYER Manufacturing CO
Priority date: 1960-04-12
Filing date: 1960-04-12
Publication date: 1961-10-31
Anticipated expiration: 1978-10-31

Description

Oct. 3l, 1961 Filed April l2, 1960 F. W. DWYER EVAL PRESSURE SWITCH |Il 'INU 'MMIII um n I 39E 3g zep/ @MVM/340W? Oct. 31, 1961 F. w. DwYER ETAL 3,007,017

PRESSURE v,SWITCH Filed April 12, 1960 2 Sheets-Sheet 2 United States Patent O 3,007,017 PRESSURE SWITCH Frank Dwyer, Oak Park, Ill., and Phillip W. Dwyer, Michigan City, Ind., assiguors to F. W. Dwyer Mfg. C0., a corporation of Illinois Filed Apr. 12, 1960, Ser. No. 21,818 10 Claims. (Cl. 200-83) This invention relates to a huid actuated control unit responsive to fluid pressure differentials and more particularly is concerned with a pressure switch unit having a differential pressure capsule provided with externally mounted switch contacts `actuated from the power diaphragm of the capsule by an internally mounted rotatable actuating arm that projects through the capsule to operate the externally mounted switch contacts.

To provide a pressure switch construction for universal application, it is important that the switch contacts be mounted externally of the pressure capsule in order to isolate these contacts from the tluid to which the unit is connected. \It has long been a problem to provide an efficient arrangement for carrying motion from -an internally mounted pressure-operated element to externally mounted switch contacts. 'I'he actuating mechanism for carrying motion through the capsule must be mounted in gas-tight relation and should ol'rer a minimum of frictonal resistance to movement. In the past, sealing diaphragme have been utilized in conjunction with differential pressure capsules, but these act in opposition to the power diaphragm and impair the sensitivity of the unit.

The principal object of the present invention is to provide a pressure capsule with a gas-tight, low-resistance mounting for an actuating arm for transmitting motion from an internal diaphragm to an externally mounted switch device.

Another object of the invention is to provide a pressure capsule with a calibrated adjustable spring seat mounting for establishing a predetermined spring loading on a fluidpressure actuated diaphragm.

Still another object of the invention is to provide a pressure switch of the above-mentioned type-of economical construction that is reliable, accurate, and maintenance free.

lOther objects and advantages of the invention will be apparent during the course of the following description.

In the drawings:

FIG. l is a cross-sectional view through a pressure switch unit constructed in accordance with this invention;

FIG. 2 is a reduced top plan view of the unit of FIG. l;

FIG. 3 is an enlarged perspective view of the actuating arm element of the unit;

FIG. 4 is an enlarged sectional view illustrating the mounted relationship of the actuating arm;

PIG. 5 is lan enlarged detail view of a vcalibrated adjustable mounting for the diaphragm loading spring; and

FIG. 6 is a view similar to FIG. 5 and indicating a modified calibrated mounting mechanism of modified con struction.

Referring now to the drawings, the fluid-actuated control unit is illustrated in FIG. l as comprising a dilerential pressure capsule, designated generally at 10, having a switch device 11 mounted externally thereon and operably connected to an external portion of an internally mounted actuating arm, -designated in its entirety at 12, that is movable in response to differential pressure changes occurring in the capsule.

The capsule is provided with high-pressure and lowpressure connection taps 13 and 14, respectively, for connection to selected control points of a fluid pressure system while the switch device 11 is provided with con- 3,007,017 Patented Oct. 31, 1961 ice tacts for connection to a suitable control circuit yfor the uid pressure system.

The differential pressure capsule comprises a casing divided into high pressure and

low pressure chambers

15 and 16, respectively, by a movably mounted pressureoperated power diaphragm 17. The casing is comprised of mating

rigid shells

18 and 19 that define the highpressure and low-pressure chambers, respectively. "The shells are formed with annular marginal anges 18F and 19F for sealing Aengagement on opposite faces of the opposite marginal edges of the diaphragm 17. A gasket 20 is provided betwen the ange 18F and the diaphragm, and ya peripheral clamping ring 21 urges the auges of the shells together to establish a seal.

The high pressure shell 18 has an internal passage IGP communicating between the chamber 15 and the highpressure connection tap 13. Similarly the low-pressure shell 19 has an internal passage 19P communicating between the chamber 16 and the low pressure connection tap 14.

The diaphragm sheet 17 may be of rubber or other similar tlexibly distortable material and is provided adjacent its outer marginal edge with an annular convolution 17C that surrounds and supports the central body region of this sheet for accommodating substantially free displacement thereof in accordance with the pressure differential acting upon it. A metal wear plate 22 is fixed to the high pressure face of the diaphragm 17 substantially central thereof for contact with the actuating arm 12. A second reinforcement plate 23 is fixed to the 10W pressure face of the diaphragm and provides -a seat for a calibration spring 24 that reacts between the low pressure shell 19 and the diaphragm 17 In the arrangement illustrated herein for purposesof disclosure, the spring 24 is shown as a compression spring and it resists diaphragm movement in a direction away from the actuating arm 12. llt will be apparent that a Itension spring could be substituted for resisting diaphragm movement in a direction towards the actuating arm. Obviously, the relationship of the high pressure and low pressure chambers may also be reversed, if desired.

In the lembodiment of the invention illustrated herein for purposes of disclosure, the high-pressure shell 18 has a centrally located mounting pocket 30, which, as best shown in FIG. 4, is recessed outwardly from the diaphragm 17 and is defined in part by spaced apart

wall portions

31 and 32. 'I'his mounting pocket 30 is in open communication with the high-pressure chamber and each of the

wall portions

31 and 32 bordering the pocket is provided with a bearing socket for rotatably mounting the actuating arm 12. 'Wall portion 31 has an external boss 31B that closes off the adjacent bearing socket to block leakage from chamber 1S.

As best shown in FIG. 3, the actuating arm 12 has a U-shaped body portion including opposed sides 12S and a closed end 12C connecting the sides, with the sides having oppositely outwardly extending lateral projections 12P journalled to rotate in the bearing sockets. The projection 12P that is rotatable in wall portion 32 extends completely therethrough and has a right-angled external extension 12E for connection to the pivotally mounted actuating arm 11A of the externally mounted switch device 11.

To complete the substantially frictionless, gas-tight, rotatable mounting -for the actuating arm 12, Ian eyelet 33 is provided on each of the axle-like lateral projections 1-2P .to function as thrust collars thereon and a washer 34 of lubric 4material such as vTetlon is provided on each projection for engagement against the eyelet. The boss 31B of the shell 18 provides a closed socket passage through which leakage is impossible, while the other T socket ypassage is sealed by a rubber O-ring 35 that is press-lit on its axle-like projection. The U-shaped body of the actuating arm 12 is formed so that when in its mounted relation within the pocket 31, its sides 12S tend to spread to spring-load the eyelets 33 to act-axially against the Teilon washers. Thisl applies a predetermined compression loading upon the rubber O-ring 35 to establish an axial seal against the 'wall portion 32. The press-tit mounting relationship of the O-ring establshes a radial seal against its axle-like projection 12P to complete the sealing of the bearing socket that opens through -wall portion 32. This arrangement provides a gas-tight, rotatable mounting for the externally vextending projection i12P, while the Teflon washers minimize frictional resistance to rotation of arm 12. The per- `formance of this dry type bearing arrangement remains constant over the useful life of the switch and it is important to the monitoring function of the control unit that its frictional resistance be held to a minimum and be maintained at some predictable constant value.

VIn order that the actuating arm 12 may respond properly to the pressure-induced diaphragm displacements, the arm is biased by an externally mounted spring wire coil 36, one end of which is iixed to the extension 12E and the other end of which is engageable with the shell 18 to urge the actuating arm in a direction of rotation `for holding its closed end 12C in abutting relation to the diaphragm 17.

An outer wall 37 of the mounting pocket carries a lseries of externally tapped, inwardly extending, postlike projections 37P that engage -with mounting screws 38 for the switch device 111. These series of projections provide a range of mounting positions for the switch device to permit regulation of the dead band or makebreak diterential of the unit. The greater the spacing between the pivot axes of the Varm 11A of the switch device and the actuating arm 12, the greater is the travel of the diaphragm that is required to accomplish switch actuation, and hence, the greater is the required pressure diiferential. The outer end of the extension 12E has a hooked portion 12H and is also provided with a spring wire coil 39, with one end 39E vof the coil being extended aboutthe hook portion 12H to provide a loop through which the switch arm extends for operative connection to the arm 12.

A protecting shield 40 of angular configuration is provided to substantially enclose the delicate switch arm arrangement. This shield is tted in a groove defined between yadjacent integral guide ribs 18R on the outer face of the high-pressure shell 18 and is anchored in position by the mounting screws for the switch 11. A number of insulation shields 41, 42 and 43 are shown for protecting the external connection tongues 11T for the switch 11.

The low-pressure shell =19 is shown provided centrally thereof with a tubular sleeve section 19S extending outwardly away from the diaphragm 17 to provide a spring chamber that is in open communication with the lowpressure chamber 16. The spring 24, which extends axially in this chamber, has its outer end engaged in a cup-shaped spring seat 44 that is threadedly adjustable along the length of the sleeve section 19S to determine the spring force acting on the 'diaphragm to regulate the set point `for switch operation. A rubber ring gasket 45 is provided on the outer face 'of the spring seat 44 and a locking spud 46 is threaded within the sleeve section to sealingly compress this gasket 'against the spring seat after the desired spring-loading adjustment has been made.

In the Ialternative embodiment shown in FIG. a calibrated adjustable spring seat mounting is provided wherein the sleeve section 19S is in the form of a separate cup-shaped member of transparent plastic material and has an external flange 19F sealed to the shell 19 to surround a central opening .through which the diaphragm spring 24 projects. A rotatable adjustment rod 48 is extended through the rear wall of the cup member and along the axis of the spring to threadedly engage the adjustable spring seat 44 which is mounted for floating movement along the cup member. A stop shoulder 48S is provided on the rod to ix its position axially of the cup. A rubber O-ring 49 encircling the neck of the rod and a rubber O-ring 50 encircling the spring seat 44 provide a seal.

In accordance with the invention, indicia Iare provided along the length of the cup 19S to define a scale S calibrated in inches of water and a suitable reference mark which may be the O-ring 50 on the spring seat 44' indicates the pressure of the set point for switch operation.

Still another arrangement providing a calibrated spring seat mounting is shown in FIG. 6 wherein a cup shaped member 19S is shown sealed to the shell to surround a central opening through which the spring `24- is extended. Again indicia are provided to define a scale S along the exterior face of the member 19S and a rotatable adjustment rod 48 projects through the member 19S in threaded relation therewith and carries an adjustable spring seat 44. To indicate the switch setting, an external sleeve 51 is engaged over the head of the rod 48" for axial movement jointly therewith and its end edge 51E cooperates with the scale S. In this case the member 19S need not be transparent.

The foregoing description and the drawings are given merely to explain and illustrate our invention, and the manner in'which it may be performed, and the invention is not to be limited thereto, except insofar as the appended claims are so limited since those skilled in the art who have our disclosure before them will be able to make modifications and variations therein without departing from the scope and 'spirit of the invention.

We claim:

l. A pressure switch comprising `a diierential pressure capsule having a flexibly distortable partitioning diaphragm providing separate pressure chambers in said capsule, each of said chambers opening through said capsule for applying tiuid pressure to opposite sides of said diaphragm, a switch device mounted externally on said capsule, an actuating arm mounted internally on said capsule and including a rotatable portion projecting through said capsule in substantially Africtionless gas tight sealed relation therewith to engage and actuate said switch device upon a predetermined movement of said arm, and means for causing said actuating arm to follow the movements of said diaphragm to transmit motion from said internal diaphragm to said external switch device and wherein said capsule has an internal pocket defined by spaced apart wall portions that extend generally normal to the plane of said diaphragm, said pocket being in open communication with one of said chambers, each of said wall portions having a bearing socket, with one of said sockets opening through its wall portion and wherein said actuating arm comprises a U-shaped body portion including opposed sides and a closed end connecting the sides, said sides being provided at their free ends with lateral projections extending outwardly beyond the sides to rotate in said bearing sockets, with the projection that is in said one bearing socket constituting the said rotatable portion and having a further'extension externally of said capsule operatively connected to said `switch device.

2. The pressure switch of claim 1 wherein each lateral projection of said actuating arm has a thrust collar and a washer of lubric material between the collar and the Iadjacent wall portion and wherein the one projection that has an external extension is provided with a rubber O- ring outboard of the washer to establish a seal radially against the said last-named projection and axially against the adjacent wall portion.

3. A pressure switch comprising a capsule composed of a pair of mating, rigid shells, a diaphragm spanning said shells-and engagedY therebetween to define separate adja-` cent chambers, each shell having an opening for external connection to apply differential fluid pressure to said diaphragm, a spring in one of said chambers and reacting against said diaphragm to urge it in a predetermined direction, a switch device mounted externally on said capsule, an actuating arm mounted internally on said capsule and including a rotatable portion projecting through said capsule in substantially frictionless gas tight sealed rela tion therewith to engage and actuate said switch device upon a predetermined movement of said arm, and means for causing said actuating arrn to follow the movements of said diaphragm to said external switch device.

4. A pressure switch comprising a casing composed of a pair of mating, rigid shells, a diaphragm spanning said shells and engaged therebetween to define separate adjacent chambers, each shell having an opening for external connection to apply fluid pressure to said diaphragm, a switch device mounted on said casing, means including an actuating arm mounted on said casing to follow the movement of said diaphragm and connected to said switch device for actuating the same in response to a predetermined movement of said diaphragm, one of said shells having a tubular sleeve section centrally thereof and extending outwardly from said diaphragm to provide a spring chamber opening into the pressure chamber defined by the said one shell, a spring in said spring chamber to react directly against said diaphragm, and means threadedly engaged with said sleeve section to provide an adjustable seat for said spring for setting the differential pressure loading required for actuation of said diaphragm.

5. A pressure switch comprising a casing composed of a pair of mating, rigid shells, a diaphragm spanning said shells and engaged therebetween to define separate adjacent chambers, each shell having an opening for external connection to apply fluid pressure to said diaphragm, a switch device mounted on said casing, means including an actuating arm mounted on said casing to follow the movement of said diaphragm and connected to said switch device for actuating the same in response to a predetermined movement of said diaphragm, one of said shells having a tubular sleeve section centrally thereof and extending outwardly from said diaphragm to provide a spring chamber opening into the pressure chamber defined by the said one shell, a spring in said spring chamber to react directly against said diaphragm, a yspring seat movable lengthwise in said sleeve section, means for adjusting and maintaining the axial position of said spring seat in said sleeve section, means defining a scale along said sleeve section, and means providing an indicator for cooperation with said scale, said indicator being movable axially conjointly with said spring seat.

6. In a pressure switch that includes a differential pressure capsule having a flexibly, distortable internal diaphragm defining separate pressure chambers within said capsule, 'an external switch device in fixed relation to said capsule and an actuating arm engageable with said diaphragm and connected to operate said switch mech- -anism in response to predetermined deflection of said diaphragm, the improvement 'wherein said switch device is externally mounted on said capsule and wherein said capsule has spaced apart wall portions defining a mounting pocket with said wall portions having cooperating bearing sockets, one of which opens through said capsule and wherein said actuating arm comprises a U-shaped body portion including opposed sides and a closed end connecting the sides, said sides being provided at their free ends with lateral projections extending outwardly beyond the sides to rotate in said bearing sockets, with the projecting that is in said one bearing socket constituting the said rotatable portion and having a further extension externally of said capsule operatively connected to said switch device.

y7. In a pressure switch that includes a differential pressure capsule having a flexibly, distortable internal diaphragm defining separate pressure chambers within said capsule, a switch mechanism and an actuating arm engageable with said diaphragm and connected to operate said switch mechanism in response to predetermined deflection of said diaphragm, the improvement wherein said capsule comprises mating rigid casing shells cooperable to grip said diaphragm therebetween, one of said shells having a tubular sleeve section centrally thereof and extending outwardly from said diaphragm to provide a spring chamber opening into the pressure chamber defined by the said one shell, a spring in said spring chamber to react directly against said diaphragm, and means threadedly engaged with said sleeve section to provide an adjustable seat -for said spring -for setting the difierential pressure loading required lfor actuation of said diaphragm, the other of said shells having a mounting pocket centrally thereof and defined :by spaced apart wall portions of said other shell, and an actuating arm engageable with said diaphragm and connected to operate said switch mechanism in response to predetermined deflection of said diaphragm, the improvement wherein said switch device is externally mounted on said capsule and wherein said capsule has spaced apart wall portions defining a mounting pocket with said wall portions having cooperating bearing sockets, one of which opens through said capsule and wherein said actuating arm comprises a U- shaped body portion including opposed sides and a closed end connecting the sides, said sides being provided at their free ends with lateral projections extending outwardly beyond the sides to rotate in said bearing sockets, with the projection that is in said one bearing socket constituting the said rotatable portion and having a further extension externally of said capsule operatively connected to said switch device.

8. A pressure switch comprising a capsule composed of a pair of mating, rigid shells, a diaphragm spanning said shells and engaged therebetween to define separate adjacent chambers, each shell having an opening for external connection to apply differential fluid pressure to said diaphragm, a spring in one of said chambers and reacting against said diaphragm to urge it in a predetermined direction, one of said shells having a series of switch-mounting positions, a switch device for external mounting on said one shell and having a pivotally mounted switch arm, an actuating arm mounted internally on said one shell and including a rotatable portion projecting through said capsule for Aconnection to the pivotally mounted arm of said switch device, means for connecting said actuating Iarm in operative engagement with said switch arm, means for biasing said actuating varm for following the movements of said diaphragm to transmit motion from said diaphragm to said switch arm, and means for securing said switch device at any selected one of said positions to vary the dead band of said pressure switch.

9. A pressure switch comprising a differential pressure capsule having a fiexibly distortable partitioning diaphragm providing separate pressure chambers in said capsule, each of said chambers opening through said capsule for applying ttiuid pressure to opposite sides of said diaphragm, said capsule having a series of external switch mounting positions, a switch device for external mounting on said capsule and including a switch operating arm, an actuating arm mounted internally of said capsule and including a rotatable portion projecting through said capsule for engagement with said switch operating arm, means for connecting said actuating arm in operative engagement with said switch arm means for causing said actuating arm to follow the movements of said diaphragm to transmit motion from said diaphragm to said switch operating arm and means for securing said switch device at any selected one of said positions to vary the dead band of said pressure switch.

l0. A pressure switch comprising a differential pressure capsule having a flexible distortable partitioning diaphragm providing separate pressure chambers in said capsule, each of'said chambers opening through said capsule for applying uid pressure to opposite sides of said diaphragm, a switch devicer mounted on said capsule, means including an actuating arm mounted on said casing to follow the movement of said diaphragm and connected to said switch device for actuating the same in response to la predetermined movement of said diaphragm, said capsule having a tubular sleeve section extending away from said diaphragm and providing a spring chamber opening into one of said pressure chambers, a spring in said spring chamber tovreact directly yagainst said diaphragm, and means threadedly engaged with said sleeve section to provide anadjustable seat for said spring for setting the diierential pressure loading required for actuation of said diaphragm.

References Cited in the tile of this patent UNITED STATES PATENTS 1,459,218 Knaak June 19, 1923 UNITED STATES PATENT oEEICE CERTIFICATE OE CORRECTION Patent No. 3OO7,017 October 31V 196 Frank W. Dwyer et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column line l after "diaphragm" insert to transmit motion from said internal diaphragm m,

signed and sealed this 10th day of April 1962.

(SEAL) Attest:

ERNEST W. SINIDEB.

Attesting Officer DAVID L. LADD Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. BYOOT ,017 October 3l u 196 Frank W. Dwyer et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column line IEMl after "diaphragm" insert -w to transmit motion from said internal diaphragm n signed and sealed this 10th dy of April 1962.-.

(SEAL) Attest:

ERNEST wy. SWTDEE Attesting Officer DAVID L. LADD Commissioner of Patents