US3774637A

US3774637A - Diaphragm actuated spool valve

Info

Publication number: US3774637A
Application number: US00285047A
Authority: US
Inventors: U Weber; G Janu
Original assignee: Johnson Service Co
Current assignee: Johnson Service Co
Priority date: 1972-08-30
Filing date: 1972-08-30
Publication date: 1973-11-27
Anticipated expiration: 1990-11-27
Also published as: AU5281273A; CA978442A; FR2198073A1; GB1408992A; AU469738B2; BR7306674D0; JPS5532921B2; ZA73739B; IT977449B; FR2198073B1; JPS4946069A; DE2307926C2; DE2307926A1

Abstract

A three-way spool valve includes a cylindrical, spool mounted within a bore including a pair of flexible annular lip seals. The seals are spaced somewhat less than the axial length of the spool to provide ''''break-before-make'''' switching. A load is connected to the chamber between the seals. The spool is connected to a snap action diaphragm operator secured overlying the bore with a transfer chamber connected to a vacuum source. An input chamber is connected to a relay or non-relay fluid control for positioning of the diaphragm and attached spool. An orifice interconnects the input chamber to the transfer chamber and the effective diaphragm area is greater in the input chamber than the transfer chamber to bias the spool valve to an initial position. A spring of a relatively low force may also bias the spool to the initial position.

Description

Assignee:

Filed:

DIAPHRAGM ACTUATED SPOOL VALVE Inventors: Urban A. Weber, George J.

Janu, both of Brookfield, Wis. 53005 Johnson Service Company,

Milwaukee, Wis.

Aug. 30, 1972 Appl. No.: 285,047

US. Cl 137/625.6, l37/625.61, 137/625.66 Int. Cl. F16k 11/00, Fl6k 31/385 Field of Search 137/6256, 625.66,

References Cited UNITED STATES PATENTS Zoller 137/6256 X Hamilton..... 137/625.61 X Hoffman 137/625.26 X Huntington 137/6256 X Dewberry 137/6256 VACUUM 1 SUPPLY 5 Nov. 27, 1973 Primary Examiner-Henry T. Klinksiek Assistant ExaminerRobert J. Miller Att0meyEugene R. Sawall [57] ABSTRACT A three-way spool valve includes a cylindrical, spool mounted within a bore including a pair of flexible annular lip seals. The seals are spaced somewhat less than the axial length of the spool to provide breakbefore-make switching. A load is connected to the chamber between the seals. The spool is connected to a snap action diaphragm operator secured overlying the bore with a transfer chamber connected to a vacuum source. An input chamber is connected to a relay or non-relay fluid control for positioning of the diaphragm and attached spool. An orifice interconnects the input chamber to the transfer chamber and the effective diaphragm area is greater in the input chamber than the transfer chamber to bias the spool valve to an initial position. A spring of a relatively low force may also bias the spool to the initial position.

11 Claims, 6 Drawing Figures VACUUM SUPPLY Pmzamsnmvm 7975 3. 774,637

VACUUM /i FIGJL 1 DIAPHRAGM ACTUATED SPOOL VALVE BACKGROUND OF THE INVENTION This invention relates to a diaphragm actuated pilot valve and particularly such a valve which functions satisfactorily as a fluidic flow amplifier in a vacuum powered control system.

In fluid flow and control systems, a pilot valve is often employed for coupling or connecting an operating fluid to a main valve as a load means. The fluid operated load may, for example, be alternately connected to an operating pressure source and to a reference source to establish two conditions or two load conditions. The operating pressure for both the pilot valve and the main valve may be a positive or a negative pressure. A single input three-way valve is particularly adapted to provide for the selective connection of the load to the two alternate pressure sources. In pneumatic systems, atmosphere is commonly employed as the reference pressure source.

The pilot valve in many applications is desirably diaphragm actuated and provides snap action switching so as to rapidly change the pressure connection. If the valve is constructed wtih minimal friction so as to operate with very low pilot pressures return forces promote snap action switching. In addition, for economic and commercial application the valve should not only be constructed of a relatively inexpensive and long life construction but should be adapted to easy assembly for mass production as well as repair and replacement of the seals and the like.

SUMMARY OF THE INVENTION The present invention is particularly directed to an improved three-way pilot valve which has been particularly adapted to incorporation into vacuum powered pneumatic systems and which permits operation at very low signal levels. Generally, in accordance with the present invention, a spool valve is connected to a diaphragm operator including an input chamber and a transfer chamber. The spool is mounted within the transfer chamber and extends downwardly through a pair of axially spaced flexible annualr seals. In accordance with one aspect of this invention, the seals are spaced somewhat less than the axial length of the spool with the movement of the spool selected to provide an engagement with the spaced seal before disengaging the then engaged seal and thereby producing the desired break-before-make type of switching. The spaced seals define an intermediate connecting chamber having a passageway means providing for an output connection and for a connection to the transfer or control chamber of the diaphragm operator and to a secondary or reference source on the opposite end of the seals. The diaphragm operator in turn has the input chamber connected to a suitable pilot pressure source which can be modulated in any suitable manner, for example, through a variable diaphragm operated leakport unit, an on-off lid unit Or th like.

In accordance with a particularly important feature of this invention, the diaphragm operator further includes a metering orifice means interconnecting the input chamber to the transfer or control chamber. Further, the effective area of the diaphragm is greater in the input chamber than in the transfer chamber such that with an equal pressure supplied to both chambers, the diaphragm unit is biased to an initial position with the spool located in alignment with the immediately adjacent seal means and with the outer end of the spool spaced from the outermost seal means. The valve structure may, if desired, also include a return or bias spring which need, however, only have a realtively low force characteristic as a result of the initial fluid bias construction. This permits operation of the spool at very low supply pressures and permits or assures a snap action type switching.

Further, the valve assembly can conveniently and advantageously be constructed essentially as an all plastic unit. The spool is shaped to smoothly engage or spread the plastic seals. The plastic spool in combination with flexible plastic seals provides a cry simple and inexpensive low friction seal means which produces a bubbletight fluid seal without the need for precision machined parts and adapts the unit for vacuum powered systems without the necessity of any additional auxiliary seal mechanism. An all plastic construction also produces inherent corrosion resistance. In addition, the housing can be formed with multiple layered plate elements, with the annular seals and the diaphragm rigidly clamped between adjacent elements.

The present invention thus provides a very simple, reliable and inexpensive three-way fluid valve having minimal operating force requirements and which is particularly adapted for vacuum operated systems.

. BRIEF DESCRIPTION OF THE DRAWING The drawing furnished herewith illustrates a preferred construction of the present invention in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description.

In the drawing:

FIG. 1 is a bottom elevational view of a valve constructed in accordance with the present invention and interconnected into a vacuum powered control system;

FIG. 2 is an enlarged vertical section taken generally on line 22 of FIG. 1;

FIG. 3 is a fragmentary vertical section taken generally on line 33 of FIG. 1;

FIG. 4 is a horizontal section taken generally on a line 44 of FIG. 2;

FIG. 5 is an enlarged fragmentary view similar to FIG. 3 taken on line 5-5 of FIG. 1; and

FIG. 6 is an enlarged fragmentary view taken on line 6-6 of FIG. 2.

DESCRIPTION OF ILLUSTRATED EMBODIMENT Referring to the drawing and particularly to FIGS. 1 and 2, a vacuum powered spool type pilot valve 1, constructed in accordance with the teaching of the present invention, connects a pneumatic actuated load valve 2 to a vacuum source or supply 3 for selective opening of the valve 2. In the alternative, the pilot valve 1 disconnects the valve 2 from the vacuum supply 3 and connects it to a reference 4, shown as atmosphere, to establish teh alternate or closed position of the valve. As more clearly shown in FIG. 2, the pilot valve 1 of the present invention is a spool type valve including a cylindrical spool 5 coupled at one end to a diaphragm operator or actuator unit 6. An input chamber 7 is provided to the one side of the unit 6 and provided with a connecting input port 8 which is connected to establish a control pressure within the chamber 7. In the illustrative system, a restrictor 9 is shown in a signal line connecting the port 8 to the vacuum supply 3, with a relay switch connected to the line between the restrictor 9 and the port 8. The relay 10 is a conventional diaphragm unit preferably constructed in accordance with the teaching of U.S. Pat. No. 3,662,779. Generally, the diaphragm relay 10 includes a convoluted diaphragm 11 defining an output chamber 12 connected to the atmosphere via a connecting line 13. The diaphragm 11 is selectively positioned with respect to a nozzle 14 in the chamber 12 which correspondingly connects the chamber 12 and thus the atmospheric pressure to the input port 8 and the spool valve input chamber 7 or closes this connection, thus establishing an equal vacuum in both chamber 12 and chamber 7. Thus the position of the diaphragm establishes an adjustable leakport and thereby controls the pressure to the input port 8 for varying the pressure in the chamber 7 and the position of the diaphragm unit 6. The diaphgram 11 in turn is controlled by the pressure within a control chamber 16 connected to a signal line 17. For example, the pilot valve 1 is particularly adapted and may be incorporated into a vacuum powered sewage system such as shown in the co-pending application Ser. No. 284,775 of George J. Janu entitled TWO-POSITION LIQUID LEVEL CONTROLLER which was filed the same day as this application and is assigned to the same assignee.

More particularly as shown in FIG. 2, the illustrated pilot valve 1 is a multiple sectioned or layered housing including three disc-

like plates

18, 19 and 20 mounted in stacked relationship in combination with an outer inverted cup-shaped diaphragm cover 21 mounted overlying the uppermost plate 20. The diaphragm operator 6 is clamped between the cover 21 and the plate 20, as viewed in FIG. 2,.to define the input chamber 7 within the cover 21 and a ransfer or control chamber 22 within the housing section 20, which is formed with a suitable recess in the upper wall. The

housing plates

18, 19 and 20 further include an aligned bore 23 projecting downwardly form the chamber 22 with a pair of

annular seals

24 and 25 clamped one each between the

respective housing plates

19 and 20 and 18 and 19 to provide selective sealing engagement with the periphcry of spool 5. In the illustrated embodiment of the invention a bias spring 26 encircles the lower end of the spool 5 and acts between the spool 5 and the base of the recess in the housing section 18 to urge the spool 5 and the interconnected diaphragm operator 6 outwardly with respect to the

seals

24 and 25 and positions the spool 5 in sealing engagement with the seal 24 and spaced from the seal 25.

The housing plates are generally disc-shaped plates having the central bore and flat end surfaces projecting from such bore. The seal 25, as most clearly shown in FIGS. 3 and 4, is an annular flexible donut-shaped member which is located and firmly clamped between the opposed end faces of the

housing plates

18 and 19. The inner corners of

plates

18 and 19 adjacent bore 23 in turn are provided with an offset inner notch 27 and projection 28 defining a fluid tight junction. The seat 25 which projects inwardly therefrom to define a featuered sealing lip 29, which is formed to depend slightly away from chamber 22.

The

housing section

18, 19 and 20 are shown interconnected to each other in FIGS. 1 and 2 by a plurality of three equicircumferentially attachment screws 30 which extend upwardly through openings 31 in

members

18 and 19 and thread into an appropriately tapped opening 32 in the housing 20. The lower seal 25 thus defines a bottom chamber 33 which is connected via a laterally extending port or passageway 34 formed by a suitably drilled or molded radial opening in the side of the housing plate 18. The outer end of the passageway 34 is sealed by a suitable plug means 35. A tubular connector 36 is integrally formed with the bottom of the plate 18 and provides suitable connection to the passageway 34 for interconnection to the atmosphere 4 or other suitable reference.

As shown in FIG. 5, the seal 24 is similarly clamped between the housing sections 19 and 20 with an inner annular sealing lip 37 which with lip 29 defines an intermediate chamber 38 which is connected to a similar lateral passageway and connector tube 39 for connection to the load 2. The tube 39 is integrally formed with the intermediate housing section and extends downwardly through an opening in the housing section 18. The intermediate housing section 19 is of a length or depth which is less than the axial length of the spool 5 such that the sealing lips are spaced from each a distance less than the length of the spool 5. This produces a break-before-make type operation. Thus, as the spool 5 moves downwardly the circumference moves into sealing engagement with lip 29 before it disengages the seal lip 37. Therefore, it breaks the connection etween the reference source 4 and the load 2 before disengaging lip 37 and making the connection between the transfer chamber and the load 2.

In accordance with a significant aspect of this invention, the spool 5 is a cylindrical, smooth wall member having the sidewall joined to the opposite end walls by rounded or curved corners 39a. The sealing

lips

29 and 37 are formed of a suitable flexible material and are spread by the spool. The curved wall connections establish a smooth, progressive engagement of the seals by the spool to correspondingly spread the seals into I sealing engagement. This construction has contributed to the use of a low friction sealing material such as plastic and is particuarly useful in producing a valve which is operable at a low supply pressure.

The housing section 20 is formed with a recess closed by the diaphragm actuator 6 and defining the transfer chamber 22. An integral connector tube 40 extends downwardly through appropriate openings in the

housing sections

18 and 19 for connection to the vacuum supply 3. The vacuum pressure is thus impressed in chamber 22 and selectively applied via the bore 23 to the chamber 37 by transfer to the load 2 upon movement of the spool 5 downwardly to space the upper end of the spool below he lip 37 of the seal 24.

The illustrated spool 5 includes a spring guide shaft 41 formed on the lower end thereof and projecting downwardly into the bias spring 26. A stop 41a is secured to the base of chamber 33 in alignement with shaft 41 and limits the downward movement of the spool. The upper end of the spool 5 includes a connecting stem 42 which projects upwardly with the upper end of a reduced cross section extending through the diaphragm actuator 6. The upper or extended end of the stub 42 is threaded to define a clamp bolt 43 with a clamping nut 44 threaded thereon to firmly interconnect the spool 5 to the diaphragm unit 6. The diaphragm unit 6 includes a convoluted diaphragm 45 having an outer peripheral clamping portion located within a recess in the upper end of th housing section 20, with the cup-shaped cover 21 telescoped downwardly into the recess and solvent welded or otherwise secured therein to securely clamp the diaphragm in position and to establish a fluid tight seal at the junction. A pair of washers 46 are disposed over stem 42, one each to the opposite sides of the diaphragm to support the control portion of the diaphragm.

In accordance with the present invention the threaded stem portion 43 extending through the diaphragm 45 is provided with axial passageway 47 which is connected to the chamber 7 by a lateral passageway 48 formed by recess or notch in the outermost ends of the stem. The passageway 47 extends downwardly through the stem and terminates in an orifice 49 which is connected by a lateral passageway 50 to the chamber 22. Thus restricted communication is established between the chambers 7 and 22. Further, the fact that the bottom of the transfer chamber 22 is sealed by the spool within the

seal

37 or 29 respectively results in a different effective diaphragm area in the chambers 7 and 22. Thus, the effective area in chamber 7 is greater than the effective area in chamber 22 by the cross section of the spool 5. Thus, if the port 8 is closed or connected to the same full supply as chamber 22 such that the pressures in chambers 7 and 22 equalize, the diaphragm operator 6 will be biased to move upwardly as a result of the differential area to the full line position shown. With this construction the diaphragm operator produces a snap action response and the spring 26 can be eliminated or formed as a very low force spring.

The operation of the illustrated pilot valve is breifly summarized as follows. When the vacuum supply 3 is connected to the support port connector 40, a corresponding vacuum is established in chamber 22. Assume that in this position, the switch 10 is fully open to establish essentially atmospheric pressure at port 8. The force exerted by the vacuum on the control diaphragm 6 will overcome the force of the spring 26 and the spool 5 moves downwardly to its lower position, as determined by the stop 41a provided in the exhaust plate 18. As noted previously, the straight portion of spool 5 is longer than the spacing between the

seals

24 and 25. Thus, during the downward movement the spool first engages seal 25 to break the connection of the load connector 39 to the exhaust connector 36 and only then disengages the seal 24 to open the connection between the connector 40 and the load connector 39. As a result the supply port 40 is never connected directly to the exhaust port as may occur in other known types of pilot valves with the possible malfunction. Even a momentary connection of the supply and the exhaust or reference sources may result in a very substantial decrease in the level of the vacuum force acting on he diaphragm with the resultant failure of the pilot valve due to the diaphragm and spool not reaching its lowermost position. Thus, the connection of the supply source to the exhaust source would create a pressure condition which would prevent the net forces acting upon the diaphragm being of sufficient magnitude to actually close the exhaust and thereby result in the malfunction of the main valve operation.

In the above assumed condition, the chamber 7 is connected to atmosphere through the nozzle 14 and passageway 13 of the switch 10. This will result in a bleeding of air through the orifice 49 and through the orifice 9 with a very large pressure drop such that the pressure in the control chamber 7 is practically equal to the atmosphere. The spool 5 will therefore be maintained in the lower or actuated position. If the connection of the chamber 7 to atmosphere is effectively closed, the flow through the connecting passageway in orifice 49 and through orifice 9 will subside or gradually diminish to a point where a vacuum is formed in chamber 7 equal to the vacuum in chamber 22 and essentially equal to full supply vacuum. The resulting force on the diaphragm 45, however, is not equal as a result of the different effective areas. A slightly greater vacuum net force will exist in chamber 7 than in chamber 22, with the difference proportional to the cross section of the spool 5. This creates a net negative raising force on the diaphragm unit 6 which, in the illustrated embodiment, is added to the force of a compression spring 26 and causes the spool 5 to rapidly move upwardly to the uppermost position shown in FIG. 2. During this return movement, the spool 5 will first effect engagement with the seal 24 to seal off the load connector 39 from the chamber 22 and only thereafter disengage the seal 25 to open the connnection of the load connector 39 to the exhaust or reference connector 36.

In a preferred construction, the net differential force applied on the diaphragm 45 is sufficient to overcome the friction between the spool 5 and the

seals

24 and 25 and to rapidly move the diaphragm unit 6 to the cutofi position. The compression spring 26 under such a circumstance can be completely eliminated or the force can be very low. The full stroke of the spool 5 is achieved practically without any change in the control force on the diaphgram unit 6 and thereby produces a highly desirable snap action switching.

The above described system includes the switching relay 10 for controlling the signal to the spool control port 8, by connecting it alternatively to vacuum and atmosphereic pressure conditions. If desired, a non-relay type circuit component can be employed. For example, a lid unit 51 can be mounted overlying the port 8 to selectively open and block flow through the control port and thereby change the condition created in chamber 7. The'pilot valve of this invention may therefore accommodate various types of sensing control units and the like and can be used in various application. The spool 5 and the

seals

24 and 25 for optimum construction are formed of a plastic material minimizing friction and permitting the use of very low supply and input pressure levels while maintaining highly effective bubble-free seals. Applicants have found that the pilot valve of this invention can be readily applied to vacuum control systems with only the two relatively simple,

annular seals

24 and 25. Thus, a valve as shown in the drawing has been constructed with the housing section formed of an injection molded polysulfone, with the spool seals 24 and 25 formed of a low density polyethylene and the control diaphragm similarly vacuumformed of a polyethylene. The several parts were solvent welded and assembled with the clamping screws as illustrated. The valve operated satisfactorily at vacuum pressure level between 2 and 30 inches of mercury column and was readily controlled by a vacuum signal of approximately one-half the supply pressure level as well as by a mechanical lid closure of the control port. The plastic design not only results in a relatively readily mass produced unit at a low cost but provides the highly desirable inherent corrosion resistance characteristics.

The present invention thus provided an improved low cost pilot valve employing a diaphragm actuator.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims, particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. A three-way spool valve comprising a first annular flexible seal member, a second corresponding annular flexible seal member mounted in concentric axially spaced relation to said first seal member and defining a valved chamber therebetween, a spool reciprocably mounted coaxially of said seals, a diaphragm actuator coupled to one end of said spool and defining a transfer chamber coupled to the first valve chamber through said first seal member and having an input chamber to the opposite side of the diaphragm unit, said spool being a cylindrical member of a length greater than the spacing between said first and second seal members, said spool being formed with a smooth outer wall and of a diameter in excess of the corresponding seal members to define a low friction outer seal therebetween.

2. The three-way spool valve of claim 1 wherein said seal members are formed of a flexible plastic and said outer wall is a plastic establishing a firm fluid type seal when engaged with the spool with a minimum friction.

3. The three-way spool valve of claim 1 wherein said diaphragm actuator including a restricted passageway means interconnecting the transfer chamber and the input chamber whereby closing the input chamber results in an equalized pressure in such chambers, said diaphragm assembly having a greater effective area in said input chamber than in said transfer chamber.

4. The three-way spool valve of claim 3 including a bias spring means coupled to said diaphragm actuator and spool to correspondingly urge the spool and actuator in the direction opposite from that created by a positive pressure in said input chamber.

5. The three-way spool valve of claim 1 wherein said flexible seal members are similar flexible circular members having inner angularly oriented sealing lips, a plurality of three valve plates being interconnected in stacked relation with the seal members clamped one each between the interfaces of said plates, said plates having central, aligned bores with said sealing lips projecting into said bores, said spool being mounted within said bore.

6. The three-way spool valve of claim 5 wherein a first end plate includes a recess encircling said bore, said diaphragm actuator being connected to said first end plate with said recess defining said transfer chamber, said diaphgram actuator having a cover plate secured to the first end plate to define said input chamber, said actuator including a coupling stem secured to said spool and extended between said chambers and having a restricted passageway means interconnecting the transfer chamber and the input chamber whereby closing of the input chamber results in an equalized pressure in said chambers, said diaphragm assembly having a greater effective area in said input chamber than in said transfer chamber.

7. The three-way spool valve of claim 6 wherein said spool is fornred of a plastic having said smooth outer wall, and said seal members being formed of a flexible plastic for establishing said firm fluid type seal, said plates being formed of a plastic.

8. The three way spool valve of claim 1 wherein flexible seal members are secured to a housing having an axial bore with the seal members axially spaced within said bore to define the valved chamber therebetween, said diaphragm actuator being secured to one end of said housing and having a diaphragm defining a transfer chamber communicating with the bore, the opposite end of the bore defining a reference chamber, said diaphragm being mounted normal to said bore, said spool having a stem extending through said control chamber and having a reduced portion extending through the diaphragm into said input chamber, said input chamber having an outer wall engaged by said stem in response to selected movement of the diaphragm, said stem including a passageway means including an orifice interconnecting the transfer chamber and the input chamber, said diaphragm including an annular convolution means to establish an essentially zero spring rate.

9. The three-way spool valve of claim 8 wherein said seal members are formed of a flexible plastic, said housing and spool being formed of a rigid plastic, said spool having rounded engaging corners and said spool and seal members being formed of a plastic defining a low sliding friction for establishing said firm fluid type seal with a minimum friction.

10. The three-way spool valve of claim 8 including a vacuum source coupled to said transfer chamber, and said reference chamber being coupled to atmosphere.

11. A three-way spool valve comprising a first annular flexible seal member, a second corresponding annular flexible seal member mounted in concentric axially spaced relation to said first seal member and defining a valved chamber therebetween, a diaphragm actuator coupled to one end of said spool and defining a transfer chamber coupled to the first valve chamber through said first seal member and having an input chamber to the opposite side of the diaphragm unit, a spool reciprocably mounted coaxially of said seals for selectively opening and closing of the passageway therethrough and said diaphragm actuator including a restricted passageway means interconnecting the transfer chamber and the input chamber whereby closing of the input chamber results in an equalized pressure in such chambers, said diaphragm assembly having a greater effective area in said input chamber than in said transfer chamber.

Inventor(s) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated November 27, 1973 Column 3,

Column 4,

Line

Line I Line Line Line

Line

Line Line -It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

after "constructed". cancel "Wtih" and insert with before "or" cancel "ransfer" and insert transfer after "downward1 cancel and insert from after "The" cancel "seat" and insert seal at the beginning of the line cancel "etween'l and"insert,' I between before "lip" cancel ""he". and insert the'-- after "in" cancel "a'lign'ement" I and insert alignment---; 1

before "housing" cancel "th" and insert the.

FORM PO-1 050 (0-69) u'sc'oMM-Dc scan-Poo W U.S. GOVERNMENT PRINTING OFFICE III O O-8ll,

UNITED STATES PATENT OFFICE Page 2 Patent No. 3,774,637 Dated November 27, 1973 Inventor(s) URBAN A. WEBER and GEORGE J. JANU 1 It is certified that error appears in the abo e-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Page 2 Column 5, Line 31, at the end of the line, cancel 7 "breifly" and insert briefly Line 53, after "on" cancel "he" and insert the Column 6, I Line 37, before "pressure" cancel "mosphereic" and insert mospheric Coluxm- 7, '7 Line 6 17, after "diaphragm" cancel 'v'unit" CLAIM l i v and insert actuator Column 7, Line 26, before "with" cancel "spool" and CLAIM 2 a insert seal members olumn 7, Line 30, C after "closing" insert .of-

CLAIM 3 Line 32 after "diaphragm" cancel "assembly" 1 and insert actuator r55;

Column 8 Line 6, after "is" cancel 'fomred" and CLAIM 7 I insert formed- Signed and sealed this lfithday of June 1974,

(SEAL) Attest: p p

EDWARD M.FLEI'CHER,JR. c. MARSHALL 1mm Attesting Officer I Commi's sionerfof Patents FORM Po-wso (10-69) v a uscoM'M-oc wan-P69 U.S. GOVER NMINT PRINTING OFFICE 2 1.. o ali-fllb

Claims

7. The three-way spool valve of claim 6 wherein said spool is fomred of a plastic having said smooth outer wall, and said seal members being formed of a flexible plastic for establishing said firm fluid type seal, said plates being formed of a plastic.