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A manual applicator, for dispensing liquid agricultural chemicals, comprises a reservoir for the liquid chemical and hand-held dispensing apparatus. The reservoir is provided with a non-return valve adapted to allow ar to flow into the reservoir only when the pressure in the head space in the reserv

A manual applicator, for dispensing liquid agricultural chemicals, comprises a reservoir for the liquid chemical and hand-held dispensing apparatus. The reservoir is provided with a non-return valve adapted to allow ar to flow into the reservoir only when the pressure in the head space in the reservoir falls below a predetermined pressure below atmosphere.

대표청구항 ▼

1. A manual applicator, for dispensing liquid chemicals, comprising a reservoir for liquid chemicals to be dispensed, said reservoir when partially filled with liquid chemical defining a head space above the liquid chemical in the reservoir, an opening being formed in a wall of said reservoir in sai

1. A manual applicator, for dispensing liquid chemicals, comprising a reservoir for liquid chemicals to be dispensed, said reservoir when partially filled with liquid chemical defining a head space above the liquid chemical in the reservoir, an opening being formed in a wall of said reservoir in said head space, an outlet duct leading from said reservoir and through which duct liquid chemical is discharged from said reservoir, a dispensing apparatus connected to said outlet duct and a non-return valve arrangement including a diaphragm valve within said reservoir, said valve arrangement being located on said reservoir for communication with said opening, said diaphragm valve being arranged to open to allow air to flow into said reservoir only while the pressure in the head space above the liquid chemical in the reservoir is less than a predetermined pressure below atmosphere and wherein said diaphragm is of annular form and defines a central region having radial faces, a central bore passing axially through said central region and a surrounding region surrounding said central region and terminating at a peripheral edge region concentric with the axis of said central bore and wherein, in an unstressed condition of the diaphragm, said peripheral edge region of said diaphragm lies in a plane parallel to, but spaced from, the planes of the radial faces of the central region of said diaphragm. 2. A manual applicator according to claim 1, and wherein a thickness of said diaphragm reduces from said central region thereof towards said peripheral edge region. 3. A manual applicator according to claim 1, wherein said central bore passing through the diaphragm comprises a tapered bore having larger and smaller diameter end regions, the smaller diameter end region of said tapered bore being at the end region of said bore remotest from the plane of said peripheral edge region of the diaphragm. 4. A manual applicator, for dispensing liquid chemicals, comprising a reservoir for liquid chemicals to be dispensed, said reservoir when partially filled with liquid chemical defining a head spaced above the liquid chemical in the reservoir, an opening being formed in a wall of said reservoir in said head space, an outlet duct leading from said reservoir through which duct liquid chemical is discharged from said reservoir, a dispensing apparatus connected to said outlet duct and a non-return valve arrangement opening into said reservoir, said valve arrangement being located on said reservoir for communication with said opening, said non-return valve being openable to allow air to flow into said reservoir only while the pressure in the head space above the liquid chemical is less than a predetermined pressure below atmosphere and wherein the non-return valve includes a valve body and a diaphragm mounted on the valve body, said valve body being of generally cylindrical form and defining a blind bore extending axially into one end thereof and being continuously open to atmosphere, and a radial bore in open communication with said blind bore, said diaphragm being within said reservoir and defining a central region and a surrounding area surrounding said central area and terminating at a peripheral edge region, said peripheral edge region of said diaphragm lying in a plane parallel to, but spaced from, the planes of the radial faces of said central region of said diaphragm, said central region defining a central bore passing axially therethrough, and wherein said valve body enters into the said central bore of the said diaphragm to support said diaphragm within the reservoir. 5. A manual applicator according to claim 4, wherein said central bore passing through the central part of the diaphragm comprises a tapered bore and said valve body defines a tapered seat for said tapered bore of said diaphragm. 6. A manual applicator according to claim 4, wherein the said diaphragm is mounted on said valve body such that the plane of the said peripheral edge region of said diaphragm is at right angles to the axis of the said valve body. 7. A manual applicator according to claim 4, wherein the said valve body supports a single diaphragm such that when the diaphragm is mounted on the valve body, the plane of the axis of said radial bore defined by said valve body lies between said plane of the peripheral edge region of the diaphragm and the plane of the radial face of the central region of the diaphragm in closest proximity to said plane of the peripheral edge region. 8. A manual applicator according to claim 4, wherein said peripheral edge region of the diaphragm directly contacts a plane surface defining part of the internal surface within the reservoir when said diaphragm is in a closing condition. 9. A manual applicator according to claim 4, wherein the valve body includes a flange and said flange defines a plane surface engageable by said peripheral edge region of the diaphragm to define a closing condition for the valve arrangement. 10. A manual applicator, for dispensing liquid chemicals, comprising a reservoir for liquid chemicals to be dispensed, said reservoir when partially filled with liquid chemical defining a head space above the liquid chemical in the reservoir, an opening being formed in a wall of said reservoir in said head space, an outlet duct leading from said reservoir and through which duct liquid chemical is discharged from said reservoir, a dispensing apparatus connected to said outlet duct and a non-return valve arrangement opening into said reservoir, said non-return valve being arranged to open to allow air to flow into said reservoir only while the pressure in the head space above the liquid chemical is less than a predetermined pressure below atmosphere, said valve arrangement being located on said reservoir for communication with said opening, the non-return valve including a valve body and two identical diaphragms mounted on the valve body in oppositely facing relationship, said valve body being of generally cylindrical form and defining a blind bore extending axially into one end thereof and being continuously open to atmosphere, and a radial bore in open communication with said axial bore and wherein said two diaphragms are both within said reservoir, each diaphragm defining a central region and surrounding region surrounding said central region and terminating at a peripheral edge region, said peripheral edge region of said diaphragm lies in a plane parallel to, but spaced from, the planes of the radial faces of said central region of said diaphragm, and central region defining a central bore therethrough, said valve body entering into the said central bores of the said two diaphragms to support said diaphragms within the reservoir, the two diaphragms being supported on the valve body such that their peripheral edge regions are in contacting relationship and the plane passing through the axis of the radial bore lies between the central regions of the two diaphragms. 11. A manual applicator according to claim 10, wherein said central bore passing the central part of each said diaphragm comprises a tapered bore, the smallest diameter of said tapered bore being at the part of the central region remotest from the plane of the peripheral edge region of the diaphragm, and said valve body defining two oppositely tapering seats for receiving said tapered bores of said two diaphragms. 12. A manual applicator according to claim 10, wherein the plane passing through the axis of said radial bore at right-angles to said axis of said valve body lies in the plane of contact of the peripheral edge regions of the two diaphragms. 13. A manual applicator according to claim 10, wherein the valve body is directly connected to a wall defining the reservoir and that end region of the said valve body including the opening communicating with said axial bore passes through the reservoir wall to continually expose said blind bore to atmosphere. 14. A manual applicator according to claim 10, wherein said reservoir includes a closure member and the valve body is directly connected to said closure member. 15. A manual applicator according to claim 10, wherein said non-return valve is mounted on one end of a dip-tube located within the reservoir, and said dip-tube is open to atmosphere through an apertured wall region of the reservoir. 16. A manual applicator, for dispensing liquid agricultural chemicals, comprising a reservoir for liquid chemical to be dispensed, an outlet duct leading from said reservoir and a dispensing apparatus being connected to said outlet duct, and a non-return valve arrangement connected to said reservoir, said non-return valve arrangement being located on said outlet duct and communicating with an opening formed in said reservoir, comprising a tubular body having a bore which defines the liquid chemical outlet from the reservoir, and a diaphragm mounted on said tubular body, and wherein said diaphragm comprising a central region defined between two, parallel radial faces, a surrounding region surrounding said central region and terminating at a peripheral edge region, said peripheral edge region of said diaphragm lying in a plane parallel to, but spaced from, the planes of said radial faces defining said central region and said central region defining a central bore therethrough for receiving said tubular body therein, the peripheral edge region being arranged to contact an internal surface of the reservoir when the valve is in a closing condition, and air ducts passing through the wall of the reservoir within the area bounded by the area of contact of said peripheral edge with said internal surface of the reservoir. 17. A manual applicator according to claim 16, wherein said tubular body has one end open to the interior of the reservoir and an opposite end projecting from the reservoir to enable said outlet duct to be attached thereto. 18. A manual applicator according to claim 16, wherein said reservoir includes said opening in the lower region of said reservoir when the reservoir is in a normal position for dispensing liquid chemical, said opening being closed by a closure member, a surface region of said closure member constituting a part of the reservoir wall, and said tubular body being passed through said closure member and being supported thereby.