in fig1 , a worker 300 is in the process of installing a series of canisters 1 and injection nozzles 50 into a number of trees 320 . this is done by drilling holes in the trunks 310 , inserting an injection nozzle 50 into each hole and mating a canister 1 to each of the injection nozzles 50 . fig1 a depicts a vertical cross - section of the canister 1 of the fluid dispensing apparatus of the present invention . here , we can see the base 2 disposed at the bottom end of cylinder 3 . the base 2 is retained within cylinder 3 by a retaining ring 4 disposed in a groove 5 situated near the bottom end of cylinder 3 . compressed , nested coil springs 6 , 7 , 8 and 9 of differing gauges are shown disposed between the top surface 10 of the base 2 and the bottom surface 11 of the moveable partition 12 . the springs 6 , 7 , 8 and 9 are generally made of wire and are depicted here as having wire cross - sections 13 , 14 , 15 , and 16 that decrease with the spring label number and a number of turns per unit vertical length that increases with the spring label number . the number and properties of the multiple nested springs 6 , 7 , 8 and 9 govern the spring force provided for pushing on the moveable partition 12 . preferably , the collective springs 6 , 7 , 8 and 9 exert a force on the moveable partition 12 that does not collectively vary significantly over the travel range of the moveable partition 12 . it is preferred to choose the springs 6 , 7 , 8 and 9 such that each inner spring has a outside diameter only slightly smaller than the inside diameter of its outer spring to facilitate the nesting and positioning of springs 6 , 7 , 8 and 9 during assembly and operation . to prevent lateral interference of adjacent springs with each other during operation of the fluid dispensing apparatus , the base 2 and bottom surface 11 of moveable partition 12 are provided with grooves 17 , 18 , 19 , 17 ′, 18 ′ and 19 ′ for nesting of the springs . the potential for interference may otherwise result from a horizontal displacement of at least one spring into interference with an adjacent spring . alternately , and optionally as a supplemental feature , opposite winding lays for adjacent springs may be utilized to avoid interference . the state of the canister 1 depicted in fig1 a with the springs 6 , 7 , 8 and 9 compressed is the state where the canister 1 is filled with fluid ( not shown ). the fluid occupies the variable volume 20 delimited by the top surface 21 of the moveable partition 12 , the bottom surface 22 of the top end 23 of the cylinder 3 and the inside surface 24 of the cylinder 3 . surfaces 21 and 23 are profiled so as to minimize a volume of un - dispensed fluid present when the variable volume is fully dispensed . an output port 25 is disposed at the top end 23 of the cylinder 3 . disposed at the output port 25 , in the preferred embodiment , is a self - sealing valve / closure 26 having a hole ( not shown ), the hole being collinear with the dashed line 27 . when an object such as a needle ( not shown ) is inserted in the hole of the self - sealing valve / closure 26 , an internal pressure within the self - sealing valve / closure , the internal pressure arising from compression , will cause the valve / closure material to press against the perimeter of the needle as depicted later in fig3 a and 3c , affecting a seal around the needle . pressure present within the variable volume may increase the sealing ability of the valve / closure , and this effect may be further increased through a geometry of the valve / closure facets 28 that biases the valve material to seal - up . the preferred material for the valve 26 in its self - sealing format is an elastomer , such as styrene butadiene , but other suitable materials may be employed . in fig1 b the canister 1 in a state where the moveable partition 12 is at its topmost position with its top surface 21 substantially in contact with the bottom surface 22 of the top end 23 . a volume 40 for un - dispensed fluid is present immediately below the self - sealing valve 26 . the distance comprised between the bottom of the self - sealing valve 26 and the segment 29 of the top surface 21 of the moveable partition 21 allows for a protruding needle ( not shown ) to protrude from the surface of the self - sealing valve 26 without coming into forceful contact with the top surface 21 . also shown in fig1 b are the springs 6 , 7 , 8 and 9 in a state of partial compression . in a preferred embodiment , when the moveable partition is as depicted in fig1 b , the springs 6 , 7 , 8 and 9 , of progressively decreasing diameter , would each preferably be compressed to at least 30 % of their total allowable deflection , or optionally by 60 % or more of their allowable deflection . fig1 c provides an exploded view of fig1 b . the recessed bottom end 30 provided immediately below the base 2 together with the taper 31 provided at the top end 23 of the canister 1 allow for stable stacking of a plurality of canisters as depicted in fig4 . this stacking feature reduces the storage volume required for storing the canisters . an additional feature of the canister 1 is that the moveable partition 12 comprises a groove 38 for receiving a seal ring 32 for sealing the variable volume 20 . fig2 depict in vertical cross - section an injection nozzle 50 that includes an injection nozzle bottom end 51 having a recess 52 delimited by a recess wall 53 , a recess lower end 54 and a recess top end 55 . the injection nozzle 50 further includes a bore 60 extending therethrough wherein a needle 61 having a bore 62 extending therethrough is provided . the recess 52 is shaped for mating to the canister 1 output port 25 by aligning the injection nozzle bottom end 51 with the output port 25 of the canister 1 and then pushing and / or twisting the canister 1 towards the injection nozzle 50 . the recess wall 53 then penetrates into an annular opening 41 of the canister top end 23 ( shown in fig1 a . 1b . upon mating of the injection nozzle 50 to the canister 1 , the tip of the needle 61 protruding from the recess top end 55 penetrates the self - sealing valve / closure 26 and accesses the variable volume 20 of the canister 1 . when the nozzle 50 is fully mated to the output port 25 , the length of the tip of the needle 61 protruding from the cavity top end 55 is such that the needle end 63 is not in forceful contact with the moveable partition 12 . upon mating of injection nozzle 50 to canister 1 , a fluid contained in the variable volume 20 of the canister 1 , the fluid being under a positive pressure provided by the moveable partition 20 being pushed towards the canister top end 23 by the springs 6 , 7 , 8 and 9 , will be pushed through the bore 62 of the needle 61 and further pushed through the bore 60 of the injection nozzle . thereby , the fluid will be dispensed from the dispensing apparatus comprising the injection nozzle 50 and the canister 1 . additionally , the nozzle 50 may be provided with an elongated portion 70 for inserting into a hole of a tree or plant for dispensing fluid , or treatment chemicals , into the tree or plant . the length of the elongated portion 70 may be provided with tapered segments . for instance , a first , more tapered segment 71 may be provided for facilitating the insertion of the nozzle 50 into a hole of a tree or plant . furthermore , a second , less tapered segment 72 may be provided for providing a tight fit / seal between the injection nozzle 50 and the hole of the tree or plant as the injection nozzle 50 is inserted into the hole . moreover , a third tapered shouldersegment 73 may be provided for limiting the penetration depth of the injection nozzle 50 into the tree . depending on the treatment plan for the tree or plant to be treated , injection nozzles having different penetration depths may be provided . another feature of injection nozzle 50 is that it may be tapped or hammered at its cavity lower end 54 for insertion into a hole of a tree or a plant without causing damage to the needle 61 . this needle - preserving feature is afforded by the fact that the end of the needle 61 protruding from the cavity top end 55 does not extend beyond the cavity lower end 54 . moreover , the width of the nozzle bottom end 51 may be chosen so as to facilitate gripping by an operator or allow prying with a prying device thereby facilitating the removal of the injection nozzle 50 from a hole in a tree or plant . fig3 c shows the canister 1 mated to the injection nozzle 50 at the stage where and a fluid or treatment chemical 81 is dispensed from the dispensing apparatus 80 . the area of the cross - section surface of the moveable partition 12 , and / or the spring force exerted by the springs 6 , 7 , 8 and 9 on the moveable partition 12 can be altered to achieve desired fluid dispensing pressure . the bore diameters of the injection nozzle 50 and the needle 61 and the fluid or chemical treatment 81 viscosity may be chosen so as to control the fluid or chemical treatment 81 flow rate . as injection rate into trees is often dependent on dispensing pressure , this device offers quick injection times because of its high and consistent injection pressure and maximum flow rate . a method for using the preferred embodiment of the dispensing apparatus 80 shown in fig3 would comprise the steps of : determining at which depth a fluid or treatment chemical 81 should be dispensed in a tree or plant ; drilling a hole in the tree or plant to a depth no shallower than the determined depth ; providing an injection nozzle 50 in dependence of the determined depth ; inserting the injection nozzle 50 into the hole ; providing a canister 1 filled with fluid or treatment chemical 81 ; and mating the canister 1 to the injection nozzle 50 . once the canister has been depleted , it may be recharged through use of the refilling nozzle 100 depicted in fig5 a and 5b , fig5 b depicting an exploded view of fig5 a . the refilling nozzle contains a refilling needle 101 carried in a shaft 102 terminating at an end 103 remote from the needle tip 104 in a groove 105 for a first “ o ” ring 106 . the shaft 102 is included in a housing 107 . when assembled as shown in fig5 a , the first “ o ” ring 106 seals against an inner rim 110 within the refilling nozzle 100 . a compressed spring 111 extending around the shaft 102 is seated at one end on the inner rim 110 , and at the other end on a seat 112 surrounding the refilling needle 101 . until further compression of spring 111 , the first “ o ” ring 106 provides a seal that can block refilling fluid flow from the top 120 of the refilling nozzle to the tip 104 of the refilling needle 101 . compression of spring 111 raises the shaft 102 with respect to the housing 107 thereby raising the first “ o ” ring 106 off of rim 110 . refilling fluid ( not shown ) entering from the top 120 of the refilling nozzle 100 may then flow pass the first “ o ” ring and channel through a gap ( not shown ) comprised between the interior diameter 113 of the housing and the shaft 102 . from there , the refilling fluid flows along a portion of the shaft 102 to a hole 114 , said hole being in contact with the proximal end 115 of the refilling needle 101 , and through the refilling needle 101 . compression of the spring occurs when the nozzle 50 is fully mated to the output port 25 of the canister . the spring force is such that it prevents a displacement of the shaft 102 towards the top 120 of the refilling nozzle before insertion of the needle 101 into the variable volume 20 through the valve / closure 26 . on retraction of the refilling nozzle 100 , the shaft 102 is such that the “ o ” ring seals against the inner rim 110 before the tip 104 of the refilling needle 101 becomes exposed . furthermore , once the refilling nozzle 100 is fully mated to the output port 25 of the canister , a friction force or physical connection between the refilling nozzle and the output port overcomes the tendency of the force provided by the spring 111 to separate the refilling nozzle and the canister 1 . mating threads on the refilling nozzle and canister top end or the like can be employed to maintain the connection against the refilling nozzle &# 39 ; s spring . three mating stages of the refilling nozzle 100 to the canister 1 are shown in fig6 a to 6c . fig7 depicts the refilling of a canister 1 . the canister 1 is mated to a refilling nozzle 100 attached to a hose 202 . the hose 202 is connected to a pump 201 via a port 203 . the pump is connected to a refilling fluid reservoir 200 and provides a pressured refilling fluid output to hose 202 . the foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use . these embodiments are only exemplary . the invention in its broadest , and more specific aspects is further described and defined in the claims which now follow . these claims , and the language used therein , are to be understood in terms of the variants of the invention which have been described . they are not to be restricted to such variants , but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein .
a dispensing apparatus for dispensing fluid is disclosed . a fluid contained in a canister is pressurized by a moveable partition driven by spring means mounted within the canister . the canister is mated to an injection nozzle to allow fluid flow from the canister though the nozzle and possibly into a body to be provided with fluid . a preferred embodiment of the dispensing apparatus is for dispensing fluid or treatment chemicals into trees and plants .