Apparatus for dispensing agricultural chemicals

Abstract: A manual applicator, for dispensing liquid agricultural chemicals, comprises a reservoir (11) for the liquid chemical and a hand-held dispensing apparatus (15). The reservoir (11) is provided with a non-return valve adapted to allow air to flow into the reservoir (11) when the head space in the reservoir falls below a predetermined pressure below atmosphere. In one embodiment an annular valve closure member (22) is mounted on a valve body (21) within the reservoir and one end (31) of the valve body (21) extends through the reservoir wall (W). The plane of the peripheral edge regions (26) of the diaphragm (22) is spaced from the plane of the central part (23) of said diaphragm (22) and is in pressure contact with an internal surface (W1) of the reservoir wall (W). That face of the diaphragm (22) within the peripheral edge region (26) is open to atmosphere via ducts (35 and 36) in the valve body (21).

Description: This invention relates to apparatus for dispensing agricultural liquid chemicals and, more particularly, to apparatus for manually dispensing such chemicals. Hand-held applicators for dispensing liquids, creams or gels, for domestic or personal use, are well known in the art and generally comprise a can-like sheet metal container, with the dispensing arrangement located one end thereof, or a jar or bottle arrangement with the dispensing arrangement formed with the neck closure for the jar or bottle. The sheet metal type containers are used extensively for so-called "aerosol" type dispensing arrangements and wherein a liquefied gas, forming part of the container contents, evaporates to a gaseous form to maintain the head space in the reservoir at a pressure above atmosphere such as to force the contents of the reservoir, under pressure, through the dispensing arrangement when the discharge outlet is open. In another well known type of dispenser, used extensively for jar or bottle reservoirs, the dispensing arrangement comprises pump means by which the container is pressurised, again to force container contents from the reservoir when the discharge outlet is open. In both of the above arrangements the reservoir is pressurised to force container contents from the reservoir when the discharge outlet is open and the reservoir is never at a pressure below that of the surrounding atmosphere. In another well known form of domestic or personal dispensing arrangement, known as the "squeeze" type, the reservoir has flexible, resilient walls and the container is manually deformed, by squeezing the flexible wall regions, to force container contents through the dispensing arrangement when the discharge outlet is open. With many such arrangements the discharge outlet is permanently open whereupon, when the flexible resilient walls are allowed to return to their unstressed form, air can flow readily through the discharge outlet and into the reservoir, so that the pressure in the reservoir can return to atmospheric pressure. The present invention is not concerned with dispensing arrangements wherein the reservoir contents are dispensed under a pressure greater than atmospheric pressure and such pressure dispensing arrangements are disclaimed herefrom. In other prior dispensing arrangements, according to the preamble of claim 1 as known from document FR-A-1577522, where it is necessary or desirable to allow atmosphere to enter the reservoir to replace liquid contents dispensed for the reservoir to allow the pressure in the reservoir to return to atmospheric pressure, it is a practise to include a non-return valve arrangement in the dispensing arrangement. The non-return valve is often in the form of an annular diaphragm element of uniform thickness, held at its peripheral regions and having a central bore through which a cylindrical element passes, said cylindrical element having an outer diameter greater that the unstressed bore of the diaphragm passing therethrough, whereupon, when the cylindrical element is axially displaced, the central regions of the diaphragm are displaced from the plane of the periphery of the diaphragm and, when the pressure difference across the diaphragm is above a predicted value air flows through the central bore of the diaphragm into the reservoir. With this type of non-return valve the central regions of the diaphragm are continuously distorted and, thereby, the actual pressure difference at which the diaphragm will allow air to flow through the central bore of the diaphragm cannot be accurately determined or maintained for long periods of usage. The difficulties of unpredictable opening valves and limited life for the diaphragm are not important for "throw away" reservoirs and dispensing arrangements but for long term usage of the dispensing arrangement the permanently distorted disc-like diaphragms are unacceptable. Manual applicators for dispensing agricultural liquid chemicals are well known in the art and are available in many forms but, essentially, all such applicators comprise a reservoir, for containing the agricultural liquid chemical to be dispensed, and a hand-held dispensing apparatus, generally of tube-like form, with means for controlling the flow of liquid through the dispensing apparatus. The reservoir for the liquid chemical is generally made from a metal or plastics material, inert with respect to the chemicals to be dispensed, and may comprise; (1) a so-called "back-pack" or "knapsack" reservoir, wherein the reservoir is fitted with shoulder straps, or is supported by a frame including shoulder straps, by which the reservoir is carried on the back of the wearer, with a duct connecting the reservoir to the hand-held dispensing apparatus, or (2) a container-type reservoir, frequently in the form of a plastic bottle, presenting a mouth-like opening which is connectable directly to the hand-held dispensing apparatus. The knapsack type reservoir may include a hand-operated pump, for pumping liquid chemical from the reservoir, whilst the back-pack dispensing apparatus is generally a gravity feed arrangement. However, in both such embodiments the level of the liquid in the reservoir is higher than the point of outlet from the apparatus when the apparatus is in its position of use. As the liquid chemical flows through the said means for controlling the flow of liquid through the apparatus only when the flow passage through said means is open, the liquid flowing through the said means forms a seal preventing the flow of air from the liquid outlet upstream to the reservoir. Thus, in practise, as the level of liquid in the reservoir falls the pressure in the head space above the liquid chemical in the reservoir falls and the rate of discharge through the dispensing arrangement can be adversely affected. The prior art method for overcoming this problem is to provide an aperture in the top wall of the back-pack or knapsack reservoir, or in a filler cap closing a filling aperture in said top wall, so that the head space in the reservoir is always in open communication with the surrounding atmosphere. This often leads to spillage of expensive, and sometimes dangerous, chemical if the back-pack is taken off and placed where the level of liquid in the reservoir is above the venting aperture and, more seriously, should the user bend or accidentally fall forwardly, chemical can spill through the venting aperture onto the clothing and/or the upper body of the user and cause serious damage and injury thereto. The container-type applicator is also a gravity feed apparatus and the reservoir may conveniently present a screw-threaded mouth arranged to be threadedly engaged directly with the hand-held dispensing apparatus. In use, the container is inverted so that the threaded mouth of the container defines the lowermost part of the reservoir and liquid chemical can flow under gravity to the dispensing apparatus. The use of such a reservoir container, and its disposition in use, can lead to the creation of a low pressure in the head space above the liquid in the reservoir, which can adversely affect the controlled dispensing of the chemical. To overcome this problem prior art container-type arrangements are often fitted with a duct which extends into the reservoir, through the mouth closure and into the upper regions of the container, whilst externally the duct is attached to the outside of the container and is open to atmosphere at a point above the liquid level in the container whilst the apparatus is in its position for dispensing. Thus, the head space above the liquid in the container is continuously vented to atmosphere. With such an arrangement, chemical can spill from the container if the device is rested in such a position that the reservoir end of the duct is below the level of liquid in the reservoir and the outer end of the duct is also lower than the liquid level, whereupon liquid chemical can flow, under gravity from the reservoir through the duct to the external end thereof. The present invention seeks to provide a manual dispensing apparatus for dispensing liquid chemicals and which allows the reservoir to be vented without the danger of spillage of the liquid chemical through the venting means. According to the present invention there is provided a manual applicator, for dispensing liquid agricultural chemicals, comprising a reservoir for the liquid agricultural chemical to be dispensed and a hand-held dispensing apparatus, said applicator including a non-return valve arrangement adapted to prevent the leakage of liquid chemical therethrough whilst allowing air to flow into the reservoir only whilst the pressure in the head space in the reservoir is at, or less than, a predetermined pressure below atmosphere, said valve arrangement comprising a diaphragm with a central bore therethrough, the diaphragm being of annular form and defining a central region and a surrounding outer wall region, characterised in that said diaphragm is mounted on a body passing through the said central bore and, in an unstressed condition for the diaphragm the peripheral edge of the diaphragm lies in a plane spaced from, but parallel to, the plane of the central region, and wherein the peripheral annular edge of the diaphragm engages a surface within the reservoir to define a closed condition for the non-return valve arrangement, the concave side of the diaphragm is continuously open to atmosphere, and the surrounding outer wall region of the diaphragm reduces in thickness from said central region to said peripheral edge. Preferably the diaphragm is mounted on a body of cylindrical form with the said planes of said diaphragm at right angles to the central axis of said body. In one embodiment the central bore through the diaphragm is a tapered bore the smaller diameter end of which is at that end of said bore most remote from the plane of the peripheral edge of the diaphragm and the body defines a tapered seat for the tapered bore of said diaphragm. In one preferred embodiment said body has a blind bore entered into one end thereof, said blind bore is open to atmosphere and said blind bore is in open communication with a radial bore or bores in the body which open to the concave side of said diaphragm. Preferably the body defines a flange engageable by the peripheral edge of the diaphragm to define a closure condition for the non-return valve arrangement. In one embodiment the body provides two oppositely tapering seats, two diaphragms are mounted on said seats in opposition so that their peripheral edges are in pressure contact, said body has a blind bore entered into one end thereof, said blind bore is open to atmosphere, said blind bore is in open communication with a radial bore or bores in the body, and wherein the plane of the axis of the radial bore or bores in the body lies in the plane of contact for the peripheral edges of the two diaphragms. In one preferred embodiment the said non-return valve arrangement is mounted on one end of a dip-tube within the reservoir and the bore of the dip-tube is open to atmosphere through a wall region of the reservoir. Preferably the non-return valve arrangement surrounds a liquid chemical discharge duct from the reservoir. In one embodiment he liquid chemical discharge duct is defined by the body, said body passes axially through a wall region of the reservoir, part of said body extends outwardly from the reservoir to permit a flexible discharge duct to be attached thereto, the diaphragm surrounds said body, within the reservoir and the concave side of said diaphragm is continuously in open communication with atmosphere via ducts through the reservoir wall surrounding the said body. The invention also envisages a manual applicator as defined herein in combination with a reservoir having a charging opening in its lower regions, characterised in that the non-return valve arrangement is directly fitted to a closure member for the said charging opening. The invention will now be described further by way of example with reference to the accompanying drawings in which, Fig. 1 shows, in diagrammatic side view, a back-pack type manual applicator. Fig. 2 shows, in axial cross-section, one form of non-return valve in accordance with the invention. Fig. 3 shows an axial cross-section through a diaphragm for a non-return valve according to the invention. Fig. 4 shows, in diagrammatic side view, a second embodiment for a manual applicator, Fig. 5 shows, in axial cross- section, a second embodiment non-return valve in accordance with the invention, Fig. 6 shows, partially in cross-section, an attachment for the reservoir for a manual applicator of the type shown in Fig. 4 including a valve arrangement in accordance with the invention. Fig. 7 shows an axial cross-sectional view through a valve arrangement in accordance with the invention, Fig. 8 shows an axial view of the valve arrangement in the direction of the arrow "A", shown in Fig. 7 and Fig. 9. shows an axial view of the valve arrangement in the direction of the arrow "B" shown in Fig. 7. The embodiment illustrated in Fig. 1 is a conventional "back-pack" applicator and comprises a reservoir 11, for a liquid agricultural chemical to be dispensed, provided with shoulder straps 12 by which the reservoir 11 can be supported on the back of the user. The reservoir 11 has an opening in its top wall 11 a , surrounded by a threaded boss (not shown), and a threaded closure cap 13 is screwed onto the threaded boss. Thus, the reservoir 11 can be charged with liquid chemical to be dispensed by removing the cap 13, charging the reservoir 11 through the opening in the threaded boss and then refitting the closure cap 13. A flexible duct 14, from the lower regions of the reservoir 11, connects the reservoir 11 with a hand-held dispensing apparatus, generally indicated by reference 15, which includes a valve 16 for controlling the flow of liquid chemical from the reservoir 11 through the apparatus 15 to an outlet (not shown in the drawings) and which outlet, when the dispensing apparatus is in its position of use, is always lower than the surface of the liquid in the reservoir. As described hereinbefore, as liquid chemical flows from the reservoir 11 to the apparatus 15, the level of the liquid in the reservoir 11 will fall, increasing the head space in the reservoir 11 above the free surface of the liquid in the reservoir 11, and as the liquid level in reservoir 11 falls the pressure in the head space will be continuously reducing until it can reach a point at which the free flow of liquid through the valve 16 is severely impaired, and thereby dosage rates are adversely affected. One valve arrangement, for use with the reservoir 11 illustrated in Fig. 1, is illustrated in Fig. 2, and comprises a valve body 21 and a flexible diaphragm 22. The diaphragm 22 (see Fig. 3) is of substantially truncated conical form and comprises a central region 23 with a tapered bore 24 therethrough. In its un-stressed condition the outer wall regions 25 of the diaphragm 22 are inclined to the central axis through the diaphragm 22 such that the peripheral edge 26 of the diaphragm 22 lies in a plane P parallel to, but spaced from, the central region 23 and at right angles to the central axis through the diaphragm 22. The tapered bore 24 through the diaphragm 22 has its smaller diameter end most remote from the plane P of the peripheral edge 26 of the diaphragm 22. The diaphragm may be made of any natural or synthetic flexible resilient material that is essentially inert with respect to the chemical to be dispensed. As will be seen from Figs. 2 and 3, the outer wall region 25 of the diaphragm 22 reduces in thickness from the central regions 23 to the peripheral edge 26. The valve body 21 is of general cylindrical configuration and defines a plurality of sections along its axial length. Thus, the valve body 21 presents a threaded end section 31 which terminates at the radial face 32 a of a cylindrical section 32, at the end of cylindrical section 32 most remote from the threaded end section 31 the body 21 presents a tapered seat 33 for the diaphragm 22, the smallest diameter of the tapered seat 33 being most remote from the threaded end section 31, and the tapered seat 33 terminates at the inner radial wall 34 a of a flange 34. The valve body 21 also includes an axial bore 35, open at the radial face of the threaded end section 31, and which axial bore 35 extends into the body 21 to radial bores 36, which open to the cylindrical surface of the cylindrical section 32. A diaphragm 22 is mounted on the body 21 by flexing the diaphragm 22 so that it can pass over the threaded end 31 and over the cylindrical part 32 to seat on the tapered seat 33 with its central region 23 most remote from the peripheral edge 26 in seating contact with the radial face 34 a of the flange 34. The axial length of the diaphragm 22, when properly located on the valve body 21 and un-stressed, is slightly greater than the axial distance between the radial face 34 a of the flange 34 and the radial face 32 a of the cylindrical part 32. Thus, when the threaded end section 31 of the valve 21, 22 is located in an aperture A in a wall W of a reservoir, and which wall W may comprise the radial face of the filler-cap 13 or the top wall 11 a , and secured by a nut N externally of the reservoir engaged on the threaded end section 31, the radial face 32 a is in abutting relationship with the inner surface W1 of the wall W and the diaphragm 22 is under a small axially compressive loading, whereupon the peripheral edge 26 is in pressure contact with the inner surface W1 of wall W. When so located, the radial bores 36 open at the cylindrical part 32 of the body 21 between the central region 23 and the peripheral edge 26 of the diaphragm 22 and whereby the volume defined by the concave face of the diaphragm 22 is continuously open to atmosphere. With the non-return valve 21-22 so located and secured within the reservoir, with the peripheral edge 26 of the diaphragm 22 in pressure contact with the internal surface W1 of wall W, liquid in the reservoir cannot leak between the peripheral edge 26 of the diaphragm and surface W1 of the wall W of the container, even when the liquid level in the reservoir is above the diaphragm 22. In the event now that the pressure in the head space falls below a predetermined level, the fall in pressure generates a pressure difference across the diaphragm 22 with the greater pressure acting on the concave face of the diaphragm 22, whereupon the diaphragm 22 deflects, reducing the sealing pressure between the peripheral edge 26 and the surface W1, and air can flow past the peripheral edge 26 of the diaphragm 22 to the head space in the reservoir. It will now be seen that with the non-return valve 21, 22 liquid within the reservoir cannot escape past the diaphragm 22 whilst air can flow through the non-return valve 21-22 to the head space to prevent said head space from falling to that low pressure at which the flow of liquid from the reservoir is impaired. In the embodiment illustrated in Fig 2, the periphery 26 of the diaphragm 22 is illustrated as making direct contact with the inner surface W1 of the wall W. However, when the surface W1 is rough or is otherwise unsuitable for making a seal by direct contact with the diaphragm 22, the valve body 21 may include an annular flange 32 b , shown in broken line in Fig. 2, presenting one radial surface engageable by the periphery 26 of the diaphragm 22 and an opposite surface for engagement with the surface W1, conveniently via a resilient sealing member (not shown) between the said flange and the surface W1. In the applicator arrangement shown in Fig.4 a reservoir 41 comprises a bottle, which may be of glass or a convenient plastics material, with a threaded neck outlet (not shown) and said threaded neck is attached to a cap element 42, internally threaded to receive the threaded neck of the reservoir 41, of a manual applicator 43 and which applicator 43 includes a valve 44 for controlling the flow of liquid through the applicator 43. Fig. 5 shows a second non-return valve arrangement and which is particularly suited to the type of applicator illustrated in Fig. 4. In the Fig. 5 embodiment a valve body 51 comprises a generally cylindrical body defining, from one radial end, a connecting section 52 having a serrated cylindrical periphery 52 a , intended to be inserted into and retained by the bore of a dip-tube 53. The connection section 52 terminates at a radial flange 54 and, at that side of the flange 54 remote from the connecting section 52, the body 51 defines a first conical valve seat 55 for a first diaphragm 22. Adjacent the large end of the conical valve seat 55 the body defines a cylindrical section 56, which terminates in the large diameter end of a second conical valve seat 57 for a second diaphragm 22. The smaller diameter end of the conical seat 57 terminates at an annular flange 58. The body further includes a blind bore 59, extending axially from the radial face of the connecting section 52, in open communication with radial bores 60, which open in the cylindrical surface of cylindrical section 56. The plane of the axes of the radial axial bores 60 lies midway between the flanges 54 and 58. Two diaphragms 22, which may be identical to the diaphragm 22 illustrated in Fig. 3, are mounted on the valve body, each diaphragm being supported on a conical seat 55 or 57 individual thereto. The axial length between the diaphragm-engaging surfaces of the flanges 54 and 58 is slightly less than the axial length of the two diaphragms 22 in an un-stressed condition so that, when assembled on the valve body 51, the two diaphragms 22 are in pressure contact at their peripheral edges 26. The cap element 42 for the reservoir 41, shown in cross-section in Fig. 6, includes a threaded bore 42 a for engagement with the threaded mouth of the reservoir 41 and includes an annular flexible seal 61 engageable by the radial face of the threaded mouth of the reservoir 41. A cylindrical wall 62, surrounds an aperture through the cap element 42 and projects externally of the element 42. The wall 62 is received into the tubular element 43 a of the dispensing arrangement 43, whereupon the interior of the reservoir 41 is in open communication with the tubular element 43 a of the dispensing arrangement 43. The said cap element 42 also supports a cylindrical wall 63 which surrounds an aperture through the cap element 42, and which wall 63, is firmly received into the end of the dip-tube 53 remote from the valve body 51. Thus, the bore of the tubular element 63 and the bore of the dip-tube 53 are always open to atmosphere. With the bore of dip-tube 53 at atmosphere pressure the axial bore 59, radial bores 60 and the volume enclosed by the two diaphragms 22 are also at atmosphere pressure. The length of the dip-tube 53 will normally be selected so that the valve arrangement 52 to 60 inclusive will lie in the upper regions of the reservoir 41 when the reservoir 41 is in its position for use and the said valve will be located within the head space of the reservoir 41 in an early stage in the discharge. It will now be seen that with the valve arrangement 52 to 60 illustrated in Fig. 5, arranged as illustrated in Fig. 6 for use with the dispensing arrangement illustrated in Fig. 4, the diaphragms 22 are in pressure contact at their respective peripheries 26 for all conditions of the reservoir when the pressure acting on the external surfaces of the diaphragm is greater than a predetermined pressure below atmosphere. When now, the with discharge of liquid from the reservoir 41, the level of liquid in the reservoir falls and the pressure in the head space reduces to, or below, said predetermined pressure below atmospheric pressure in the atmospheric volume contained by the diaphragms 22 will cause said diaphragms 22 to deflect, reducing the contact pressure at the peripheral edges 26, until air flows between the peripheral regions 26 of the said diaphragms 22 into the reservoir 41. With the flow of air between the diaphragms 22 into the head space, the pressure in the head space will increase and, when the pressure in the head space rises above the said predetermined pressure level, the diaphragms 22 will close at their peripheral edges 26 to seal the reservoir 41. The said predetermined pressure below atmospheric pressure at which the diaphragm 22 or diaphragms 22, will allow air flow into a reservoir is wholly determined by the configuration of the diaphragm(s), the flexibility of the diaphragm(s) 22 and the degree of axial compression applied to the diaphragm(s) 22 and these parameters can be readily adjusted to obtain the desired predetermined pressure difference at which air will flow through the valve arrangement to the head space. It will be appreciated that, by removing the dip tube 53 and wall 63, the non-return valve arrangement 21, 22 illustrated in Fig. 2 may be applied to the cap 42 for the small volume applicator illustrated in Fig 4. Further, when the valve body 21 presents a flange 32 b as described hereinbefore, the single diaphragm valve arrangement 21, 22 may be substituted for the double diaphragm arrangement illustrated in Figs. 5 and 6 on the inner end of the dip tube 53. In like manner, the valve arrangement illustrated in Fig. 5 may conveniently have a screw thread formed on its connection section 52 to allow the said valve arrangement 22, 51 be applied directly to a reservoir wall W, in identical manner to the valve 21, 22, In the embodiment illustrated in Fig. 7, 8, and 9, intended for use with an applicator as shown in Fig. 4, the valve arrangement comprises a support element 71, a tubular element 72, a valve closure member 73, and a filter element 74. The support element 71 comprises a body of revolution and defines a cylindrical wall 71 a an annular inwardly directed radial wall 71 b at one end of the wall 71 a , an outwardly directed flange 71 c at the end of wall 71 a remote from wall 71 b , an inner cylindrical wall 71 d extending from the radially innermost part of radial wall 71 b and terminating short of the plane of the flange 71 c , and a radial wall 71 e extends from the end of wall 71 d remote from wall 71 b to support an annular boss 71 f . The element 71 has an axial bore 71 g through the boss 71 f and a plurality of ducts 75 in the illustrated example four cylindrical ducts 75, equally spaced about a pitch circle concentric with the bore 71 g , pass through boss 71 f parallel with the bore 71 a . The tubular element 72 is also a body of revolution and comprises a tubular part 72 a having an outer diameter which is a friction fit in the bore 71 g in the support element 71, a tubular part 72 b which has a diameter greater than the bore 71 g , a radial shoulder 72 c between the external diameters of the parts 72 a and 72 b which then limits the entry of the tubular element 72 into the bore 71 g , and a cup-like part 72 d supported on that end of the tubular part 72 b remote from the shoulder 72 c . The cup-like part 72 d is arranged to frictionally receive and retain the hemispherical filter 74 therein. The valve closure member 73 is also a body of revolution and is made from a flexible resilient material, conveniently a natural or synthetic rubber, and comprises a central cylindrical part 73 a with a bore 73 b therethrough and an annular wall 73 c extending axially and radially outwardly from one end of the central part 73 a . The axially and radially extending wall 73 a preferably tapers from its connection with the central part 73 a to a minimum thickness at its outermost peripheral regions. The bore 73 b through the valve closure member 73 is slightly smaller than the diameter of the tubular part 72 b so that when the tubular part 72 b is inserted into the bore of member 73, by flexing the member 73, the bore 73 b is in frictional contact with the cylindrical outer surface of the part 72 b and, in its operative position, the radial face, of the cylindrical part 73 a remote from the axial and radially extending wall 73 c abuts the undersurface of the cup element 72 d of tubular element 72. The axial length of the valve closure member 73, when unstressed is slightly greater than the axial length of the cylindrical surface of the part 72 b , whereupon, when the element 72 is inserted into the bore 71 g , entering first through the surface 71 h , and the part 72 b is driven through the bore 71 g until the annular shoulder 72 c abuts the surface 71 h , the periphery 73 d of the axially and radially extending wall 73 a abuts the surface 71 h , and the member 73 is axially deformed between the undersurface of the cup part 72 d and the surface 71 a . The outer periphery 73 d of the wall 73 a engages the surface 71 h at an annulus having a diameter greater than the radially outmost regions of the ducts 15 so that the ducts 15 open into the concave chamber defined within the valve closure member 73. The parts 71, 72, 73 and 74 are most preferably selected from materials which are inert with respect to the liquid chemicals to be dispensed. The part 71 may be made from a plastics material and conveniently made by a moulding process. The tubular element 72 may also be made from a plastics materials, and again made by a moulding process. The valve closure member may be made from any flexible resilient material inert with respect to the chemical material to be dispensed and may conveniently be made by a moulding process. The filter 74 may be made from plastics or metallic wire material or may comprise a sintered body of a plastics or metal material. In use the part 71 is inserted into the open outlet of a bottle reservoir for the liquid chemical to be dispensed, the outer cylindrical surface on wall 71 a being a friction fit into the smooth bore of the outlet, and the element 71 is inserted into the outlet until the flange 71 c , or a resilient sealing ring 76 on the cylindrical wall 71 a , abutting flange 71 c , abuts the radial face of the reservoir surrounding the outlet. When the reservoir bottle has a screw neck surrounding the outlet the element 71 may be secured to the reservoir by a screw cap (not shown) having a central aperture therethrough of such diameter as to allow the ducts 75 to be open to the surrounding atmosphere. With the element 71 closing the mouth of the bottle reservoir the duct to the manual controls for the applicator is attached to the tubular element part 72 a protruding externally of the element 71 and the assembly can then be inverted, so that the valve arrangement is in the lower regions of the reservoir, ready for use. With the reservoir in its position for use chemical liquid can flow readily through the filter 74 and through the bore in tubular element 72 to the duct supplying the liquid chemical to the manually actuable dispensing arrangement for the applicator and, in this position, the liquid chemical in the reservoir is continuously in contact with those surfaces of the valve closure 73 exposed within the reservoir. Whilst the liquid pressure acting on the axially and radially extending wall 73 c is greater than atmospheric pressure the closure member 73 maintains the peripheral edge of wall 73 c in sealing contact with the surface 71 h of element 71, thus preventing chemical leakage through the valve arrangement. When now, with the applicator dispensing liquid chemicals, the pressure in the headspace falls the liquid pressure acting on the closure 73 also falls until, at a predetermined liquid pressure on the closure 73, and which predetermined pressure is below atmospheric pressure, the peripheral regions 73 d of the wall 73 a are deformed by the atmospheric pressure beneath the wall 73 a and air flows from atmosphere, up the ducts 15 and between the surface 71 h and the deflected peripheral edge 73 d into the reservoir to form bubbles in the liquid which rise to the headspace. The predetermined liquid pressure at which the closure member 73 will deflect to allow air flows into the reservoir is determined by the composition of the valve closure member 73 and the axial compression of the closure member 73 between the cup-like part 72 d and the surface 71 h . Preferably, the closure member 73 is arranged to deflect to allow air flow into the reservoir before the reduction in liquid pressure in the lower regions of the container reaches that level at which the flow through the applicator becomes interrupted and the dosage dispensed thereby rendered variable. Whilst in the specific embodiment the valve arrangement has been described with reference to a bottle reservoir, which may be a conventional 1 litre or 5 litre bottle, the invention is not restricted thereto and, for example, the valve arrangement could be inserted into an aperture in the lower regions of a back-pack or knapsack reservoir.

Claims: A manual applicator, for dispensing liquid agricultural chemicals, comprising a reservoir (11, 41) for the liquid agricultural chemical to be dispensed and a hand-held dispensing apparatus, said applicator including a non-return valve arrangement adapted to prevent the leakage of liquid chemical therethrough whilst allowing air to flow into the reservoir (11, 41) only whilst the pressure in the head space in the reservoir is at, or less than, a predetermined pressure below atmosphere, said valve arrangement comprising a diaphragm (22, 73) with a central bore (24, 73 b ) therethrough, the diaphragm (22, 73) being of annular form and defining a central region (23, 73 a ) and a surrounding outer wall region, (25, 73 c ) characterised in that said diaphragm (22, 73) is mounted on a body (21, 51 or 72) passing through the said central bore (24, 73 b ) and, in an unstressed condition for the diaphragm (22, 73) the peripheral edge (26, 73 d ) of the diaphragm (22, 73) lies in a plane spaced from, but parallel to, the plane of the central region (23, 73 a ), and wherein the peripheral annular edge (26, 73 d ) of the diaphragm (22, 73) engages a surface (W1, 26 or 72 c ) within the reservoir (11, 41) to define a closed condition for the non-return valve arrangement, the concave side of the diaphragm (22, 73) is continuously open to atmosphere, and the surrounding outer wall region (25, 73 c ) of the diaphragm (22, 73) reduces in thickness from said central region (23, 73 a ) to said peripheral edge (26, 73 d ). A manual applicator according to claim 1, characterised in that, the diaphragm (22, 73) is mounted on a body (21, 51 or 72) of cylindrical form with the said planes of said diaphragm (22, 73) at right angles to the central axis of said body (21, 51 or 72). A manual applicator according to claims 1 or 2, characterised in that the central bore (24) through the diaphragm (22) is a tapered bore (24) the smaller diameter end of which is at that end of said bore (24) most remote from the plane of the peripheral edge (26) of the diaphragm (22) and the body (21) defines a tapered seat (33, 55 or 57) for the tapered bore (24) of said diaphragm (22). A manual applicator according to claims 1, 2 or 3, characterised in that said body (21, 51) has a blind bore (35, 59) entered into one end thereof, said blind bore (35, 59) is open to atmosphere and said blind bore (35, 59) is in open communication with a radial bore or bores (36, 60) in the body (21, 51) which open to the concave side of said diaphragm (22). A manual applicator according to claims 1, 2, 3 or 4, characterised in that the body (21) defines a flange (32 b ) engageable by the peripheral edge (26) of the diaphragm (22) to define a closure condition for the non-return valve arrangement (21 to 36). A manual applicator according to claims 1, 2, 3, 4 or 5, characterised in that the body (51) provides two oppositely tapering seats (55, 57), two diaphragms (22) are mounted on said seats (55, 57) in opposition so that their peripheral edges (26) are in pressure contact, said body (51) has a blind bore (59) entered into one end thereof, said blind bore (59) is open to atmosphere, said blind bore (59) is in open communication with a radial bore or bores (60) in the body (59), and wherein the plane of the axis of the radial bore or bores (60) in the body (51) lies in the plane of contact for the peripheral edges (26) of the two diaphragms (22). A manual applicator according to any one of the preceding claims, characterised in that the said non-return valve arrangement (21 to 36, or 51 to 60) is mounted on one end of a dip-tube (53) within the reservoir (11, 41) and the bore of the dip-tube (53) is open to atmosphere through a wall region of the reservoir (11, 41). A manual applicator according to any one of the preceding claims, characterised in that the non-return valve arrangement (71 to 76) surrounds a liquid chemical discharge duct from the reservoir (11, 41). A manual applicator according to claim, 8, characterised in that said liquid chemical discharge duct is defined by the body (72), said body (72) passes through a wall region (71 e ) of the reservoir (11, 41), part of said body (72) extends outwardly from the reservoir (11, 41) to permit a flexible discharge duct (14, 43 a ) to be attached thereto, the diaphragm (73) surrounds said body (72), within the reservoir and the concave side of said diaphragm (73) is continuously in open communication with atmosphere via ducts (75) through the reservoir wall (71 e ) surrounding the said body (72). A manual applicator according to any one of the preceding claims, in combination with a reservoir (11, 41) having a charging opening in its lower regions, characterised in that the non-return valve arrangement (21 to 36, 51 to 60 or 71 to 76) is fitted to a closure member (42, 71) for the said charging opening.

Inventors: ROBINSON RODRICK CHARLES, ROBINSON, RODRICK CHARLES
Applicants: HORSTINE FARMERY LTD, HORSTINE FARMERY LIMITED
Application year: 1991
Main classification: A01M7
IPC codes: A01M7, F16K15