US3782640A

US3782640A - Valve mechanism for liquid applicator

Info

Publication number: US3782640A
Application number: US00230917A
Authority: US
Inventors: J Kirschmann
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-03-01
Filing date: 1972-03-01
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: AU6434574A

Abstract

A flow control valve for a liquid applicator having and outlet port formed in a filter assembly in the valve housing and a valve element urged towards a normally closed position against the outlet port by a compression spring guided by a shiftable carrier which also serves as a retainer and carrier for the valve element. The filter assembly is attached by a quick-disconnect joint to a removable bottom plug having a base wall for the valve housing through which a discharge orifice of predetermined size extends.

Description

United States Patent Kirschmann Jan. 1, 1974 [54] VALVE MECHANISM FOR LIQUID 3,632,043 l/l972 Kirschmann 239/575 X APPLICATOR v Primary ExaminerM. Henson Wood, Jr. [76] lnvemor' g g gzi g ggk gg gT Assistant Examiner-Michael Y. Mar

Attorney-George F. Williamson et al. [22] Filed: Mar. 1, 1972 [211 App]. No.: 230,917 ABSTRACT A flow control valvefor a liquid applicator having and [52] U S 239/571 239/575 outlet port formed in a filter assembly in the valve [51] Bosb 9/06 housing and a valve element urged towards a normally 7 [58] Fieid 570 571 closed position against the outlet port by a compres- 239/572' sion spring guided by a shiftable carrier which also serves as a retainer and carrier for the valve element. [56] References Cited The filter assembly is attached by a quick-disconnect joint to a removable bottom plug having a base wall' UNITED STATES PATENTS for the valve housing through which a discharge ori- 3,01 1,725 12/1961 Shames et al 239/575 X fice of predetermined Size extends 2,893,647 7/1959 Wortman i i 239/575 X 3,013,733 12/196! Williams et a]. 239/575 X 6 Claims, 7 Drawing Figures 40 g .32 #2 k 46 1 i 56 5% H 52 VALVE MECHANISM FOR LIQUID APPLICATOR BACKGROUND OF THE INVENTION This invention is directed to a flow control valve for liquid dispensing devices, such as applicators for fertilizer, insecticides and herbicides. For the purpose of distributing such liquids, spray attachments including a liquid supply tank, pump and distribution manifolds leading to a plurality of liquid applicator nozzles are incorporated on agricultural implements such as grain drills and planters with the individual liquid distribution nozzles being located so, as to distribute one of the aforesaid liquids along predetermined seed lines. Liquid applicator apparatus for such applications is disclosed in US. Pat. No. 3,632,043, issued on Jan. 4, 1972.

The hoses or lines leading to distribution nozzles on such liquid applicators conventionally employ a check valvewhich opens under'a predetermined liquid supply pressure to permit the distribution of liquid as desired. It is extremely important tht such check valves provide a positive shut-off to prevent the leakage of liquid onto the ground when the liquid applicator is not being used so as to avoid expensive waste of fertilizers, insecticides and heribicides. The check valve must also be readily accessable for cleaning and servicing because of its constant exposure to dirt and foreign particles; and to prevent the plugging of the valve, a filter device of some kind must be properly incorporated in the check valve assembly.

At the present time, there is no known check valve assembly which satisfactorily meets all of these requirements on liquid applicators for agricultural use. The check valve assembly of this invention has been developed with a view towards satisfying these needs with a valve unit which can be quickly and easily disassembled for cleaning and servicing, which is readily accessable, and which provides a tight, positive shut-off of the liquid applicator lines.

BRIEF SUMMARY OF THE INVENTION The flow control valve assembly of this invention is particularly characterized by a spring-loaded, positive shut-off check valve contained within a valve housing within which a filter assembly is positioned upstream of the check valve, the valve housing being of take-apart construction permitting quick and easy access to the valve and filter assemblies for cleaning and service.

These basic objectives are realized by utilizing a two piece valve housing including a removable base plug having a discharge orifice of predetermined size therein, the base plug serving as an attachment means for a filter which is removable with the base plug as a subassembly. An outlet port formed at one end of a flow passage extending through the filter assembly is normally closed by a displaceable valve element carried on a holder contained within the removable base plug, the valve element holder also advantageously ineluding elongated guide means for a coil spring normally urging said valve element against the aforesaid outlet port in tight, sealing contact therewith.

The valve assembly is made particularly smooth working and tight closing by utilizing an I-I-shaped holder having a central web section to which a discshaped valve element is attached, and a plurality of upwardly and downwardly extending lugs and elongated spring guide means depending on opposite sides of the central web section and slidably bearing against upright side wall faces on the interior of the valve housing to assure the free movement and tight closing of the valve element under the compression force of the coil spring. The aforesaid, upwardly extending retainer lugs on the valve holder serve as retainer means for the valve element and define therebetween vertical spaces through which liquid passing through the valve outlet port may flow downwardly to the discharge orifice in the base plug.

A particularly beneficial aspect. of the flow control valve assembly resides in the provision of a quick disconnect snap-joint between the aforesaid base plug and the base end of a tubular stem forming a portion of the filter assembly, the valve outlet port being located at the bottom of the tubular stem. The snap connection between the filter stem and the base plug of the valve assembly permits the filter to be removed quickly and easily for cleaning or replacement, as well as to obtain access to the valve element of spring located in the base plug.

These and other objects and advantages of my inven- I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a portion of a drill and liquid applicator hose with which the flow control valve of this invention is used;

FIG. 2 is a vertical section view of the flow control valve assembly of this invention;

FIG. 3 is a horizontal section view taken along lines 3-3 of FIG. 2;

FIG. 4 is a side elevation view, partially in section, of the filter assembly for the control valve;

FIG. 5 is a bottom view of the filter assembly of FIG. 4;

FIG. 6 is a perspective view of a combined valve element holder and spring guide; and

FIG. 7 is a fragmentary, vertical section view of an enlarged scale showing the joint between the valve base plug and the rest of the valve housing.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, I have shown in FIG. 1 a disc opener 1 forming a portion of a grain drill of the type with which the liquid applicator valve of this invention is intended to be used. The particular ground opening drill shown in FIG. 1 is the double disc type having a pair of

discs

2 and 3 supported on an arm 4 of a frame assembly, not shown. A bracket arm 6 supports at its outer end a bracket link or finger 8 which is pivotally attached by a pin connection 10 to a mounting bracket 12 utilized for supporting and guiding the bottom end of a liquid distribution tube or hose l4. Bracket 12 is of elongated, arcuate shape at its lower end as shown to receive and guide the lower end of hose 14 at a desired angle and location between

discs

2 and 3. A liquid to be applied to the ground, such as liquid fertilizer, is distributed through hose 14, which extends at its lower end through split ring collars 16 and 18 attached to bracket 12. The control valve assembly of this invention is generally indicated by reference numeral 20, and is attached to the lower end of discharge tube 14 as illustrated in FIG. 1.

The valve housing is comprised of an upper, cylindrical housing portion 22 and a bottom cap or base plug 24 threadedly attached thereto, in the manner illustrated in FIGS. 2 and 7. The valve housing extends through lower, split ring collar 18 of mounting bracket 12 with base plug 24 projecting below collar 18 in the manner shown in FIG. 1. At its upper end, cylindrical housing 22 is provided with an elongated inlet extension 26 having an inlet passage 28 extending therethrough. The entire valve assembly may be quickly and easily attached to the lower end of discharge hose 14 by inserting inlet extension 26 within the bottom end of hose 14, teeth 30 formed on the peripheral surface of extension 26 serving to hold the valve assembly within hose 14. l have found it desirable from a manufacturing and use standpoint to mold the

valve housing components

22 and 24 from non-corrosive plastic material, such as polyethylene.

The control valve assembly, as shown in FIGS. 2 and 4 includes a filter assembly generally indicated by reference numeral 32. This filter assembly is also preferably made of plastic components, including a head 34 having a transverse slot 36 and attached by downwardly depending lug 38 to a tubular stem 40. Formed along the length of stem 40 at longitudinally spaced locations thereon are a plurality of spacer elements in the forom of

shoulders

41, 42 and 43 which assist in supporting a cylindrical filtering screen 44 at a radially spaced location from stem 40. Cylindrical screen 44 abuts at its opposite ends against filter head 34 and base 45 of tubular stem 40. Radial ports 46 are formed through the walls of tubular stem 40 and communicate with an internal flow passage 48 defined by the inside wall surfaces of stem 40. As is hereinafter explained with respect to the operation of the control valve, fluid entering the valve housing through inlet extension 26 must pass through ports 46. Internal flow passage 48 extends through base end 45 of tubular stem 40 to form an outlet port 49, which is most clearly shown in FIG. 4. The base end 45 of stem 40 is flat on its outer surface so as to accommodate a disc-shaped valve element which normally closes port 49 in a manner hereinafter explained.

To facilitate disassembly and servicing of the valve assembly, a quick disconnect, snap-joint is provided between filter assembly 32 and the upper end of base plug or bottom cap 24. For this purpose, the base end 45 of tubular stem 40 of the filter assembly has a ring or bead 50 formed around its outer periphery, as clearly ap pears in FIG. 4. A complementary groove 52, most clearly shown in FIG. 7, is formed on the inside surface of the upper end of base plug 24 to receive ring 50. A horizontal shoulder 54 also formed at the top of base plug 24 serves as a stop for filter assembly 32. The filter assembly and base plug are quickly and easily coupled together to provide a subassembly by simply snapping ring 50 on the bottom end of filter assembly 42 into groove 52 at the top of base plug 24. The downward movement of the base end 45 of tubular stem 40 of the filter assembly into base plug 24 is limited by the engagement of filter base 45 with stop shoulder 54. This base plug and filter subassembly is quickly and easily assembled into upper valve housing 22 by screwing threaded base plug 24 into the lower, threaded end of cylindrical valve housing 22, this threaded joint being clearly shown in F lG. 7.

To accomplish a tight seal between base plug 24 and cylindrical valve housing 22, as well as between snap ring 50 and groove 52 of base plug 24, a tapered or beveled joint 56 is provided between the upper end of base plug 24 and the lower, inside peripheral surface of cylindrical valve housing 22. This'tapered joint 56, as is clearly shown in FIG. 7, is located radially outwardly from groove 52 at the top of base plug 24, with the mating beveled or tapered edges of plug 24 and cylindrical valve housing 22 tapering downwardly and outwardly, as shown. As base plug 24 is tightly threaded into the lower end of cylindrical valve housing 22, the mating beveled surfaces of these two housing components will be very tightly urged together. Simultaneously, the radial, inward force exerted on the upper end of threaded plug 24 as its beveled face tightly engages the tapered, complementary face on the bottom end of cylindrical valve housing 22, will have the effect of urging groove 52 inwardly into tight, sealing engagement with snap ring 50 on the base end of tubular filter stem 40. The tight joints thereby maintained at the top of base plug 24 with cylindrical valve housing 22 and the base end 45 of tubular filter stem 40 prevent any liquid from leaking around and bypassing valve outlet port 49.

In the bottom wall of base plug 24 a discharge orifice 58 of predetermined diameter is formed. Base plugs having discharge orifices of different diameters may be selectively utilized in combination with upper, cylindrical valve housing 22 for the particular flow conditions required. The base wall of plug 24 within which discharge orifice 58 is located serves as a closure wall for the bottom of the entire valve housing.

Contained within base plug 24 is a combined valve element holder and spring guide 60, which is shown in perspective view in FIG. 6. As is indicated in FIG. 2, holder 60 is l-l-shaped in vertical cross section, and is comprised of a horizontally extending, central web section 62, upwardly extending valve element retainer lugs 64, and a plurality of elongated spring guide legs 66 extending downwardly on the opposite side of central web section 62. Lug 64 and spring guide legs 66 are continuous, elongated members with their outside, vertical surfaces coextensive, the diametrical spacing between opposed pairs of these elongated members being such that they slidably bear against the inside, upright wall surfaces of base plug 24. A generally disc-shaped valve element 68, preferably made of rubber, is attached to the upper face of central web section 62, as by the use of an adhesive material, and is retained in place by upstanding lugs 64. Valve element retainer lugs 64 are circumferentially spaced around the periphery of central web section 62 and are offset radially outwardly from the peripheral edges of disc-shaped valve element 68 and web section 62 so that these lugs 64 define therebetween vertical spaces through which liquid passing out of outlet port 49 and past valve element 68 may flow downwardly through base plug 24 to discharge orifice 58. Valve element 68 is normally held in a closed position against outlet port 49, and against the flat, base wall of tubular stem base 45 in tight, sealing contact therewith by a compression spring 70. Coil spring 70 is contained within base plug 24 between the underside of central web section 62 of holder 60 and the base wall of plug 24, in the manner shown in FIG.

2. The upper end of spring 70 is contained and guided within downwardly depending legs 66 of holder 60.

It is to be noted that valve disc 68., valve holder 60 and spring 70 are all normally contained with base plug 24. In the course of assembling the valve unit, spring 70, holder 60 and valve disc 68 are first placed within base plug 24. Then, filter assembly 32 is attached to the upper end of base plug 24 by the snap attachment of ring 50 on the base end of tubular stem 40 within receiving groove 52 at the top of base plug 24. With compression spring 70 in its fully extended position, valve disc 68 will be located above the top of base plug 24. When base end 45 of filter assembly 32 is forced into snap attachment with the top of base plug 24, it engages valve disc 68 tightly and compresses spring 70 against the bottom or base wall of plug 24. Compressed spring 70, hearing upwardly against the bottom face of central web section 62 thereby serves to urge valve disc 60 into tight, sealing engagement with outlet port 49 and the bottom, flat face of tubular stem base 45. The subassembly of filter 32 and base plug 24 is then inserted within upper, cylindrical valve housing 22 and tightly attached thereto by the threaded coupling of plug 24 to the lower end of housing 22.

in operation, outlet port 49 will normally be held tightly closed by the action disc 68 and spring 70, when the pressure in the hydraulic system of a liquid applicator 0s below a predetermined level insufficient to overcome the pressure of spring 70. When a predetermined operating pressure is reached in the hydraulic supply system, fluid entering through inlet extension 28 will flow radially across slot 36 in filter head 34 in the manner indicated by the flow arrows in FIG. 2 and thence downwardly along the side walls of cylindrical housing 22 around filter screen 44. A filtering action removing foreign particles will then take place as the fluid flows inwardly through cylindrical screen 44 and into radial ports 46 formed in tubular stem 40. Fluid flowing downwardly through internal flow passage 48 of stem 40 and acting on the top of valve disc 68, will overcome the pressure of spring 70, at a predetermined fluid pressure level, thereby displacing valve element 58 and its holder 60 downwardly within plug 24 away from port 49. Valve element holder and spring guide 60 slides up and down within base plug 24, and serves to hold valve disc 68 in'the proper horizontal orientation for proper, tight seating against valve outlet port 49. Fluid passing out of outlet port 49 and over the top of valve disc 68 will flow downwardly through the annular spaces defined between adjacent lugs 64 of holder 60, these flow spaces being clearly shown in FIG. 3. Liquid flowing downwardly past holder 60? then is discharged through orifice 58 in the base wall of bottom plug 24 to be applied in the desired pattern.

It will be appreciated by those skilled in the art, that the above described valve assembly can be very easily taken apart for servicing and cleaning by simply threadedly disconnecting base plug 24 from the bottom end of valve housing 22. Filter assembly 32, being attached to the top of base plug 24 will be withdrawn with it. The filter screen can be easily cleaned if desired, and may be quickly and easily replaced by simply snapping it out of engagement with groove 52 in the top of base plug 24. This quick-disconnect removal of filter assembly 32 6 I anticipate that various changes may be made in the size, shape and structural arrangement of my valve assembly without departing from the spirit and scope of my invention as defined by the following claims.

I claim:

I. A positive shut-off flow control valve for a liquid applicator comprising:

a valve housing having an inlet fitting at one end thereof;

a closure wall at the opposite end of said valve housing having a discharge orifice of predetermined size therein;

a filter assembly inside of said valve housing, said filter assembly comprising a filtering element and a flow passage so constructed and arranged that liquid entering said housing through said inlet fitting must pass through said filtering element before flowing into said flow passage;

an outlet port at one end of said filter flow passage;

a displaceable, disc shaped valve element normally seated against said outlet port in closing relation thereto;

an l-l-shaped holder for said valve element on which said valve element is carried, said holder comprising a central web section with valve element retainer means depending on one side thereof and elongated spring guide means depending from the opposite side thereof, said valve element being affixed to said one side of said holder web section; and

a coil spring contained between said holder and said closure wall in compression, and urging said valve element against said outlet port in tight, sealing contact therewith, said spririg being contained and guided within said guide means of said holder and bearing against said opposite side of said web section.

2. A flow control valve as defined in claim 1 wherein:

said valve element retainer means comprises a plurality of upstanding retainer lugs circumferentially spaced around the periphery of said central web Section, the outer, upright faces of said lugs slidably bearing against upright side wall faces on the interior of said valve housing and being offset radially outwardly from the peripheral edges of said discshaped valve element and said web section so that said lugs define therebetween vertical spaces through which liquid passing through said outlet port and past said valve element may flow downwardly to said discharge orifice.

3. A positive shut-off flow control valve for a liquid applicator comprising:

a valve housing comprised of an upper, cylindrical housing portion having an inlet passage at one end therof, and a base plug removably attached to the opposite end of said cylindrical housing portion, said plug having a base wall with a discharge orifice of predetermined size extending therethrough;

a filter assembly inside of said valve housing, said filter assembly being comprised of a filtering element and a tubular stem having flow passage means extending therethrough and terminating at an outlet port in the base of said stem adjacent to said base p g;

a displaceable valve element normally seated against said base end of said filter stem in closing relation a compression spring in said base plug urging said valve element towards a normally closed position engagement with said ring on said filter stem by the engagement of said tapered surfaces with each other as said base plug is screwed into said cylindritubular stem placing said flow passage in fluid flow communication with the space between said valve housing and said tubular stem within which said screen is contained; said tubular stem having a base over said outlet port against said base end of said and through which said flow passage extends to filter stem; and form an outlet port;

a quick disconnect, snap-joint between said base end displaceable disk-shaped valve element normally of said filter stem and the upper end of said base seated against said outlet port in closing relation plug opposite said base wall, whereby said filter asthereto; sembly and base plug form a removable subassem- 10 holder for said valve element on which said valve bly, the snap attachment of said filter stem to said element is carried, said holder including dependbase plug serving to compress said spring and ing, elongated spring guide means; and thereby hold said valve element in tight, sealing ena coil spring contained between said holder and said gagement with said outlet port under the reaction closure wall in compression, and urging said valve force of said spring in the assembled condition of element against the outer surface of said base and said filter stem and base plug. of said tubular stem in closing relation to said out- 4. A flow control vavle as defined in claim 3 wherein: let port in tight, sealing contact therewith, said said quick disconnect, snap-joint between said base spring being contained and carried within said end of said filter stern and said base plug is comguide means of said holder. prised of a peripheral ring on said base end of said 6. A positive shut-off flow control valve for a liquid filter stem and a complimentary groove formed in applicator comprising: the upper end of said base plug within which said a valve housing comprised of an upper, cylindrical ring is received; and housing portion having an inlet passage at one end said base plug is threadedly attached to said cylindrithereof, and a base plug removably attached to the cal housing portion, the upper, outside face of said opposite end of said cylindrical housing portion, base plug opposite said groove and the mating, said plug having a base wall with a discharge orifice complimentary surface of said cylindrical housing of predetermined size extending therethrough; portion being tapered downwardly and outwardly a filter assembly inside of said valve housing, said filtowards said base wall of said plug, whereby said ter assembly being comprised ofa filtering element groove on said base plug is urged into tight, sealing and a tubular stem having flow passage means extending therethrough and terminating at an outlet port in the base of said stem adjacent to said base a displaceable valve element normally seated against said base end of said filter stem in closing relation cal housing portion. 5. A positive shut-off flow control valve for a liquid applicator comprising: to said outlet port within the confines of said base a valve housing having an inlet fitting at one end plug;

thereof; a compression spring in said base plug urging said a closure wall at the opposite end of said valve housvalve element towards a normally closed position ing having a discharge orifice of predetermined size over said outlet port against said base end of said therein; filter stern; and a filter assembly inside of said valve housing, said fildisconnectable joint between said base end of said ter assembly comprising a filtering element and a filter stem and the upper end of said base plug opflow passage so constructed and arranged that liqposite said base wall, whereby said fitler assembly uid entering said housing through said inlet fitting and base plug form a removable subassembly, the must pass through said filtering elelment before snap attachment of said filter stem to said base plug flowing into said flow passage, said filter assembly serving to compress said spring and thereby hold comprising a tubular stem, the inside wall surfaces said valve element in tight, sealing engagement of which define said flow passage, a cylindrical with said outlet port under the reaction force of screen extending around said tubular stem and held said spring in the assembled condition of said filter in spaced apart relation thereto to serve as said filstem and base plug. tering element, and flow port means through said UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent l qo. 3,782,640 Dated January 1, 1974 Invent0r(s) John D. Kirschmann It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 8, line 5, change "and followed by through which" to -end--; change "and" preceded by "said base" in column 8, line. 1.5 to --end-..

Si d and sealed this 5th day of November 197 (SEAL) Attest;

c. MARSHALL DANN Commissioner of Patents MCCOY M. GIBSON JR. Attesting Officer F ORM PO-105O (10-69) USCOMM-DC 60376-P69 fir U45, GOVERNMENT PRIN OFFICE: I569 O--366-334

Claims

1. A positive shut-off flow control valve for a liquid applicator comprising: a valve housing having an inlet fitting at one end thereof; a closure wall at the opposite end of said valve housing having a discharge orifice of predetermined size therein; a filter assembly inside of said valve housing, said filter assembly comprising a filtering element and a flow passage so constructed and arranged that liquid entering said housing through said inlet fitting must pass through said filtering element before flowing into said flow passage; an outlet port at one end of said filter flow passage; a displaceable, disc-shaped valve element normally seated against said outlet port in closing relation thereto; an H-shaped holder for said valve element on which said valve element is carried, said holder comprising a central web section with valve element retainer means depending on one side thereof and elongated spring guide means depending from the opposite side thereof, said valve element being affixed to said one side of said holder web section; and a coil spring contained between said holder and said closure wall in compression, and urging said valve element against said outlet port in tight, sealing contact therewith, said spring being contained and guided within said guide means of said holder and bearing against said opposite side of said web section.

2. A flow control valve as defined in claim 1 wherein: said valve element retainer means comprises a plurality of upstanding retainer lugs circumferentially spaced around the peripherY of said central web section, the outer, upright faces of said lugs slidably bearing against upright side wall faces on the interior of said valve housing and being offset radially outwardly from the peripheral edges of said disc-shaped valve element and said web section so that said lugs define therebetween vertical spaces through which liquid passing through said outlet port and past said valve element may flow downwardly to said discharge orifice.

3. A positive shut-off flow control valve for a liquid applicator comprising: a valve housing comprised of an upper, cylindrical housing portion having an inlet passage at one end therof, and a base plug removably attached to the opposite end of said cylindrical housing portion, said plug having a base wall with a discharge orifice of predetermined size extending therethrough; a filter assembly inside of said valve housing, said filter assembly being comprised of a filtering element and a tubular stem having flow passage means extending therethrough and terminating at an outlet port in the base of said stem adjacent to said base plug; a displaceable valve element normally seated against said base end of said filter stem in closing relation to said outlet port within the confines of said base plug; a compression spring in said base plug urging said valve element towards a normally closed position over said outlet port against said base end of said filter stem; and a quick disconnect, snap-joint between said base end of said filter stem and the upper end of said base plug opposite said base wall, whereby said filter assembly and base plug form a removable subassembly, the snap attachment of said filter stem to said base plug serving to compress said spring and thereby hold said valve element in tight, sealing engagement with said outlet port under the reaction force of said spring in the assembled condition of said filter stem and base plug.

4. A flow control vavle as defined in claim 3 wherein: said quick disconnect, snap-joint between said base end of said filter stem and said base plug is comprised of a peripheral ring on said base end of said filter stem and a complimentary groove formed in the upper end of said base plug within which said ring is received; and said base plug is threadedly attached to said cylindrical housing portion, the upper, outside face of said base plug opposite said groove and the mating, complimentary surface of said cylindrical housing portion being tapered downwardly and outwardly towards said base wall of said plug, whereby said groove on said base plug is urged into tight, sealing engagement with said ring on said filter stem by the engagement of said tapered surfaces with each other as said base plug is screwed into said cylindrical housing portion.

5. A positive shut-off flow control valve for a liquid applicator comprising: a valve housing having an inlet fitting at one end thereof; a closure wall at the opposite end of said valve housing having a discharge orifice of predetermined size therein; a filter assembly inside of said valve housing, said filter assembly comprising a filtering element and a flow passage so constructed and arranged that liquid entering said housing through said inlet fitting must pass through said filtering elelment before flowing into said flow passage, said filter assembly comprising a tubular stem, the inside wall surfaces of which define said flow passage, a cylindrical screen extending around said tubular stem and held in spaced apart relation thereto to serve as said filtering element, and flow port means through said tubular stem placing said flow passage in fluid flow communication with the space between said valve housing and said tubular stem within which said screen is contained; said tubular stem having a base and through which said flow passage extends to form an outlet port; a displaceable disk-shaped valve element normally seated against said outlet port in closing relation thereto; a hoLder for said valve element on which said valve element is carried, said holder including depending, elongated spring guide means; and a coil spring contained between said holder and said closure wall in compression, and urging said valve element against the outer surface of said base and of said tubular stem in closing relation to said outlet port in tight, sealing contact therewith, said spring being contained and carried within said guide means of said holder.

6. A positive shut-off flow control valve for a liquid applicator comprising: a valve housing comprised of an upper, cylindrical housing portion having an inlet passage at one end thereof, and a base plug removably attached to the opposite end of said cylindrical housing portion, said plug having a base wall with a discharge orifice of predetermined size extending therethrough; a filter assembly inside of said valve housing, said filter assembly being comprised of a filtering element and a tubular stem having flow passage means extending therethrough and terminating at an outlet port in the base of said stem adjacent to said base plug; a displaceable valve element normally seated against said base end of said filter stem in closing relation to said outlet port within the confines of said base plug; a compression spring in said base plug urging said valve element towards a normally closed position over said outlet port against said base end of said filter stem; and a disconnectable joint between said base end of said filter stem and the upper end of said base plug opposite said base wall, whereby said fitler assembly and base plug form a removable subassembly, the snap attachment of said filter stem to said base plug serving to compress said spring and thereby hold said valve element in tight, sealing engagement with said outlet port under the reaction force of said spring in the assembled condition of said filter stem and base plug.