GB2083567A

GB2083567A - Dispensing of Liquids

Info

Publication number: GB2083567A
Application number: GB8123690A
Authority: GB
Original assignee: Hundon Forge Ltd
Current assignee: Hundon Forge Ltd
Priority date: 1980-08-14
Filing date: 1981-08-03
Publication date: 1982-03-24
Also published as: GB2083567B

Abstract

Apparatus for dispensing measured doses of a liquid, for example for dispensing liquid veterinary preparations to be injected into domestic animals such as pigs, comprises a measuring chamber (6) having an inlet (10) adapted for connection to a liquid reservoir and an outlet (15), with one-way valves. A piston (27) is arranged for movement between an adjustable stop position in which the chamber defines a maximum volume and a fixed end position in which the chamber defines a minimum volume, means (41) being provided for causing movement of the piston between these positions. The volume of the doses may be varied by adjusting the stop 35. <IMAGE>

Description

SPECIFICATION Dispensing of Liquids Field of Invention This invention relates to the dispensing of liquids and concerns apparatus for dispensing measured doses of a liquid, for example for dispensing liquid veterinary preparations to be injected into domestic animals such as pigs.

Background to the Invention Dispensers are known for injecting doses of liquid veterinary preparations into animals in which a spring-loaded plunger in a cylinder is used by a hand squeeze-action to force liquid out of the cylinder through a hypodermic needle. In such devices the stroke of the plunger has not been adjustable and the squeeze-action has not included any mechanical advantage so that such devices have only been suitable for fixed doses and for relatively low viscosity liquid preparations.

It is an object of the present invention to provide dispensing apparatus which does not suffer from these disadvantages and which can therefore be of more general use. In particular it is an object to provide a dispenser having sufficient suction to cause complete evacuation of the contents of a collapsible container yet to still allow the dispenser to be operated by one hand.

The Invention According to the present invention there is provided apparatus for dispensing measured doses of a liquid, comprising a measuring chamber, a chamber inlet adapted for connection to a liquid reservoir, a chamber outlet, a respective one-way valve assoicated with each of said inlet and outlet, a piston arranged for movement with respect to the chamber between a stop position in which the chamber defines a maximum volume and a fixed end positon in which the chamber defines a minimum volume, actuating means for causing movement of the piston between said positions, and means for adjusting the stop position of the piston so as to adjust the maximum volume of the chamber.

In use of the apparatus, with the inlet connected to a reservoir containing a liquid to be dispensed, movement of the piston from its end position to its stop position causes liquid to be drawn into the chamber from the reservoir, via the chamber inlet and associated one-way valve, thus filling the chamber with liquid, the volume of the liquid depending on the location of the stop position of the piston. On subsequent movement of the piston from its stop position to its end position, a measured dose of liquid is expelled from the chamber via the outlet and associated one-way valve, flow of liquid in the opposite direction, i.e. towards the reservoir, being prevented by the one-way valve associated with the inlet.By repeating this sequence of actions, a series of successive doses of liquid each having an accurately measured volume may be easily and readily dispensed from the apparatus.

It is clear that the volume of each dispensed dose depends on the difference in the chamber volume when the piston is in its stop and end positions, so that by adjusting the location of the piston stop position the volume of dose dispensed by the apparatus may be readily varied. The apparatus may thus be used for dispensing successive doses of liquid of differing volumes, the necessary adjustment being easily effected by use of the means for adjusting the stop position of the piston.

The end positon of the piston is preferably such that the minimum volume of the chamber is substantially zero so that substantially all liquid is expelled from the measuring chamber during each cycle of action. This means that the apparatus can be easily emptied completely of liquid after use and there is no risk of any residual liquid remaining in the chamber, either during or after use, with possible risk of deterioration.

The outlet of the apparatus may be connected to, or adapted for connection to, a suitable fitting or the like, depending on the intended use of the dispensed doses. For example, in cases where the apparatus is intended for use in injecting doses of liquid into, say, domestic animals, the outlet may be connected to a hypodermic needle. In this case, the apparatus finds particular application in injecting measured doses of iron solution into pigs, the size of each dispensed dose being readily adjustable to suit each individual animal to be treated.

The maximum volume of the chamber and the possible degree of adjustment thereof may be selected heving regard tothe intended use of the apparatus. For example, for veterinary uses a maximum chamber volume of 2 ml, adjustable down to substantially zero, is suitable.

The piston may be slidingly sealed within the chamber by any suitable means, for example by use of an O-ring mounted on the piston.

Preferably, however, a suitable O-ring is fixed with respect to the chamber wall, for example by being mounted within an annular recess, so as to be slidingly engaged by the external surface of a piston rod that has been accurately machined to a specified diameter to within close tolerances. A consequence of this preferred arrangement is that it is not necessary for the bore of the chamber to be accurately manufactured to within close tolerances-a more difficult and costly machining operation than producing a rod with accurate external dimensions-because the seal is formed between the fixed O-ring and the external surface of the accurately-formed piston.

The means for adjusting the stop position of the piston conveniently comprise a micrometer screw arrangement including an axially movable member arranged to contact, directly or indirectly, the piston when in its stop position, and an actuating member, for example a micrometer thimble, provided with a measuring scale. By use of such an arrangement, the volume of each dispensed dose may be readily and accurately regulated.

The apparatus preferably includes means for biasing the piston to its start position, such means conveniently comprising a compression spring mounted between a head member fixed with respect to the piston and a stop ring fixed with respect to the chamber, for example fixedly mounted within a housing for the apparatus. The strength of such a spring is preferably selected having regard to the properties, particularly viscosity, of the liquid it is intended to dispense.

The actuating means preferably have a mechanical advantage and conveniently comprise a cranked lever pivotally-mounted for movement between start and end positions. The lever includes an operating arm adapted for engagement by the fingers of the user and an activating arm which is operatively linked to the piston so that movement of lever from its start position to its end position, for example by squeezing motion of the operating arm, causes the piston to be moved from its start position to its end position, and vice versa. Such a lever is preferably biased to its start position, and this is conveniently achieved in a preferred embodiment by the effect of a compression spring mentioned above.

The chamber is conveniently bounded in part by a window, for example in the form of a transparent disc of glass or suitable plastics material. This permits a user to monitor the functioning of the apparatus by checking that the chamber is properly filled, that no gas, e.g. air, bubbles are present in the liquid, that the liquid is the correct colour and so on.

The one-way valves may be of any suitable construction. In one preferred arrangement each valve includes a piston member housed within a chamber intO which an inlet passage (e.g. the chamber outlet or inlet) opens, the member being biased, for example by means of a spring, to a closed position in which it is seated sealingly about the inlet passage. With such an arrangement it is preferred that the diameter of the piston member is very much greater than the diameter of the bore of the inlet passage, and that the diameter of the chamber is very much smaller than the diameter of the piston member so that the piston member can easily and reliably seal off the inlet passage without requiring accurate guiding of the piston member in the chamber.

The inlet and outlet valves may be identical, or at least similar construction. It should be noted, however, that although liquid is positively expelled from the measuring chamber upon movement of the piston from its stop position to its end position, on reverse movement of the piston liquid is merely sucked into the chamber.

Accordingly, it may be advantageous for the bores of the chamber inlet and passages of the inlet valve to be relatively larger than the corresponding bores of the outlet in order to facilitate smooth and rapid flow of liquid into the measuring chamber. This is of particular importance for apparatus intended for use in dispensing relatively viscous liquids, such as iron solution intended for injection into pigs.

The inlet may be adapted for direct connection to a reservoir, for example by use of a container cap of the construction described in the specification of our co-pending Application No.

Alternatively, the inlet may be adapted for use with a remote reservoir, for example a tank carried on the backof the user, by having an inlet pipe to which suitable tubing, for example of plastics material, may be attached.

One embodiment of apparatus in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings.

Description of Illustrated Embodiment Figure 1 is a side elevational view of apparatus in accordance with the present invention; Figure 2 is the top plan view of the apparatus in Figure 1 and Figure 3 is a schematic, partly exploded, side elevation view of the apparatus of Figures 1 and 2 shown partly in section and with certain components omitted.

Detailed Description of the Drawings Referring to the drawings, the illustrated apparatus comprises a two-part metal body 1 including a handle portion 2 that is appropriately contoured to fit easily and comfortably in the hand of the user and a nozzle portion 3. A hollow cylindrical housing 4, the inner wall 5 of which defines in part a cylindrical measuring chamber 6, is secured to the body 1 at the upper end of the handle portion 2, being retained in position by means of two opposed flanges 7 s 8 of the body 1 extending into an annular recess 9 formed adjacent to the lower end of the housing 4.

An inlet pipe 10 for the measuring chamber 6 extends from the rear of the housing 4 and terminates in an externally-threaded cylindrical connector portion 11 to which is secured an internally-threaded tubular member 12 formed with an externally-ridged inlet pipe 13. One end of a length of plastics tubing 14 is push-fitted onto the inlet pipe 13, the other end of the tubing 14 leading to a liquid reservoir (not shown). A oneway inlet valve (not shown) is provided within the chamber defined between connector portion 11 and the tubular member 12 to regulate the flow of liquid from the reservoir, via pipe 13, to the interior of said chamber, and the construction and functioning of this inlet valve will be described later.

An outlet pipe 15 for the measuring chamber similarly extends from the front of the housing 4, being diametrically opposed to the inlet pipe 10.

The outlet pipe 15 terminates in an increased diameter tubular body portion that is of internally stepped configuration and defined a narrower, inner, cylindrical chamber portion 17 and a wider, outer, chamber portion 18 that is internally threaded. A correspondingly threaded male connecting portion 19 of a tubular outlet member 20 is screwed within chamber portion 18, an 0 ring 21 being fitted within a suitable annular recess 22 in member 20 to form a seal. A hypodermic needle 23 (Figure 2) is fitted into the tip of outlet member 20 and is secured in position by means of a needle mount 24 screwed onto the member 20.

A one-way outlet valve of similar construction to the inlet valve is provided for regulating the flow of liquid from the outlet pipe 15 into chamber 17, and the construction and functioning of this valve will be described in detail later.

Referring particularly to Figure 3, the construction of the measuring chamber 6 will now be described further. The upper end of the chamber 6 is defined by a disc 25 of transparent material, e.g. glass or suitable plastics material, that is crimped in position and sealed with an 0ring 26. A circular section piston 27 is mounted within the body handle portion 2 so as to extend upwardly into the housing 4, with the upper end face 28 of the piston thus defining the lower end of the chamber 6. The piston 27 is slidingly sealed within the housing 4 by means of an Oring 29 licated within a rebate 30 at the lower end of the housing 4, the O-ring being held in position by a nylon guide ring 31.

It should be noted that a seal of such configuration, in which the O-ring is fixedly secured to the cylindrical housing, can be manufactured more simply and cheaply than comparable prior art seals in which the O-ring is secured to the piston. This is because in order to produce an effective seal with the present arrangement it is not necessary to use a cylindrical housing having an inner surface accurately machined to within close tolerances, as is the case with such prior art arrangements: instead, it is merely necessary to provide a piston with an outer diameter manufactured to within close tolerances-a simpler and cheaper machining operation than producing a bore to a close tolerance.

The piston 27 is thus arranged for axial sliding movement within the housing 4 between an adjustable rest or start position, shown in Figure 3, in which the chamber 6 has a maximum volume and a fixed upper or end position in which the chamber 6 has a minimum volume.

In this embodiment, the end position of the piston 27 is determined by engagement of the piston end face 28 with disc 25, hence the minimum volume of the chamber is substantially zero. The manner in which the location of the start position of the piston may be adjusted will be discussed below, but it should be noted at this stage that variation of this start position causes corresponding variation in the maximum volume of the chamber 6 and hence of the volume swept out by the piston 27 during movement between its start and end positions.

A coaxial rod 32 extends from the lower end of the piston 27, the rod 32 passing through a guide ring 33 that may be fixed within the handle portion 2 of body 1, but is preferably integrally formed therewith. The rod 32 terminates in a disc-shaped head member 34 that normally rests on the upper end of an adjustable stop rod 35 housed within the body handle portion 2 and arranged for axial movement with respect thereto, resulting in corresponding axial movement of the piston 27.

A compression spring 36 is located around rod 32, extending between and butting against the lower face of the guide ring 33 and the upper face of head member 34. The spring 36 thus biases the piston 27 in a downwards direction, i.e.

towards its start position, and normally acts to bring the lower face of the head member 34 into engagement with the upper end of the stop rod 35. It can thus be seen that the position of the stop rod 35 determines the start position of the piston 27.

As mentioned above, the position of the stop rod 35, and hence of the start position of the piston, is adjustable. Such adjustment is achieved by means of a micrometer screw arrangement comprising a threaded rod (not shown) fitted with a terminal thimble 37, the rod being adjustably received in an internally-threaded sleeve 38 extending from the lower end of the handle portion 2 such that the upper end of the threaded rod engages the lower end of the stop rod 35 to permit adjustment of the axial position of the stop rod. The sleeve 38 is marked with a scale 39, the thimble 37 including a co-operating pointer 40.

In the presant embodiment the pitch of the thread of the micrometer screw arrangement is such that one turn of the threaded rod (not shown) produces an axial movement thereof of 1.5 mm, such movement causing a similar axial movement of the piston 27 and resulting in a change in the maximum volume of the chamber 6 of 0.25 ml. Thus, four complete turns of the rod are required to produce a chamber volume adjustment of 1 ml.

An operating lever is interconnected with piston 27 for causing movement thereof between its start and end positions. The lever comprises a U-section cranked member 41 that is pivotally connected to the body 1 about a pivot point 42a.

The member 41 includes an outer, operating arm 42, the outer surface of which is appropriately contoured for easy and comfortable engagement by the fingers of the user, and an inner, activating arm 43, the free end of which rests within a square section aperture 44 within the piston 27.

A roller 45 is pivotally mounted at the free end of the arm 43 about a pivot point 46 to facilitate movement of the free end of the arm 43 within the aperture 44.

The member 41 is pivotable about point 42 between a rest or start position, shown in full lines in Figure 3, in which the piston is also located in its rest or start position, as also shown in Figure 3, and an inner or end position, shown in dashed lines in Figure 3, in which the piston 27 is located in its upper or end position.

The member 41 is biased towards its start position by the action of spring 36 but can be moved to its end position by moving the outer arm 42 towards the body handle position 2, i.e. in the direction of arrow A shown in Figures 1 and 3, such movement conveniently being achieved by squeezing the arm 42 towards the handle portion 2, Such movement causes the inner arm 43 to move upwardly with respect to the handle portion 2, with the free end of the arm 43 describing an arc of a circle, moving upwardly and laterally with respect to the handle portion. Such upwards movement causes corresponding upwards movement of the piston 27, the roller 45 facilitating smooth lateral movement of the free end of arm 43 within the aperture 44 of the piston 27.

It is apparent that such upwards movement of the piston 27 causes corresponding upwards movement of the rod 32 and head member 34 connected thereto, resulting in the head member 34 being lifted out of engagement with the upper end of the stop rod 35, thus compressing the spring 36 between it and the guide ring 33.

When the squeeze grip (or other force) on the arm 42 is released, the compressed spring 36 acts to move member 34 downwardly until it engages the upper end of stop rod 35, causing consequential downwards movement of the piston 27 and arm 43, thus returning the piston 27 and member 41 to their respective start positions.

The construction and functioning of the oneway inlet and outlet valves will now be described in detail.

Considering firstly the outlet valve, as shown in Figure 3, a piston member 47 is located within the inner chamber portion 17 of body portion 16, the piston member 47 comprising a tubular body closed at one end and adapted to be seated on end face 48 of chamber portion 17 about the opening of the bore of outlet pipe 15 into that chamber portion. An O-ring 49 is fitted in a rebate 50 at the closed end of the piston member body for providing sealing contact between the piston member body and end face 48.

A spring 51 is located within tubular body portion 16, with one end of the spring extending into the body of piston member 1 7 and the other end being engaged by an adjacent end face of tubular outlet member 20. The spring 51 thus acts to bias the piston member 47 into a closed position in which the end face thereof is sealingly seated on face 48 about the opening of the outlet pipe 15 into the chamber portion 17, thus preventing flow of liquid in either direction between the outlet pipe 15 and the chamber portion 17. It is clear, however, that the piston member 47 can be unseated and moved to an open position by application of sufficient liquid pressure to the end face thereof to overcome the action of the spring 51, and thus to permit liquid to flow from the outlet pipe 1 5 into the chamber portion 17, but that liquid flow in the other direction is not possible.

It is to be noted that the diameter of the end face of piston member 47, as defined by O-ring 49, is very much less than the internal diameter of chamber portion 17, and that the diameter of the bore of outlet pipe 15 is very much less than the diameter of the end face of piston member 47. A consequence of such construction is that the piston member 47 can easily and reliably seal off the bore of outlet pipe 1 5 without requiring accurate guiding of the piston member 47 in chamber portion 17.

The one-way inlet valve is of similar construction to the outlet valve, and comprises a piston member (fitted with an O-ring) and a spring identical in construction to the piston member 47 and spring 51 of the outlet valve. The piston member and spring are fitted within the chamber defined between connector portion 11 and tubular member 12 such that the piston member is arranged to seat sealingly around the entrance of inlet pipe 13 to that chamber, thus acting as a one-way valve that permits liquid to flow from inlet pipe 13 into the chamber, but not in the opposite direction.

For reasons that will be discussed below, the bore of the inlet pipe 1 3 and of the inlet pipe 1 0 are slightly greater than the bores of the corresponding pipes of the outlet valve.

Otherwise, the inlet and outlet valves are identical in construction.

In use of the above-described apparatus a reservoir containing a liquid to be dispensed is attached to the free end of plastics tubing 14. The reservoir may conveniently be in the form of a bottle, tank or like container and may for certain applications be adapted to be carried by a user, for example by being strapped onto the user's back.

The apparatus is prepared for use by squeezing the arm 42, thus causing the piston 27 to be moved to its end position, and then releasing the arm so that the piston returns to its start position, causing liquid to be sucked in from the reservoir.

This action is repeated a sufficient number of times to fill the plastics tubing 14 with liquid from the reservoir and also, finally, to fill the chamber with such liquid.

The apparatus is then ready for use. Upon further squeezing movement of the arm 42 piston 27 is again moved from its start position to its end position, causing the liquid contained in the chamber 6 to be expelled to the outlet pipe 15, via the outlet valve and ultimately to be ejected from the hypodermic needle 20. On subsequent releasing of the handle 42 and movement of the piston 27 to its start position, a further measured dose of the liquid is drawn into the chamber 6 and the operation may then be repeated any desired number of times.

It is clear that the maximum volume of the chamber 6, and hence the volume of a dose expelled from the apparatus, can be simply and easily adjusted to any desired amount by use of the micrometer screw adjustment.

Further, the user can monitor that the apparatus is functioning correctly by viewing the chamber 6 through the transparent disc 21 to check that there are no gas, e.g. air, bubbles in the liquid within the chamber, that the chamber is filling properly, that the treatment liquid is the correct colour, and so on.

It should be noted that although liquid is positively ejected from the chamber 6 under the squeezing action of arm 42 forcing piston 27 upwardly, liquid is merely sucked into the chamber from the reservoir upon downwards movement of the piston 27 under the action of return spring 36. It is for this reason that the bore of the inlet pipes is made wider than the bore of the corresponding outlet pipes, thus facilitating ready flow of liquid from the reservoir into the chamber. This feature is of particular importance when using dispensing liquids of relatively high viscosity, such as certain iron solutions used for treating pigs. Similarly, the strength of the compression spring 36 may be appropriately selected having regard to the properties, particularly viscosity, of the liquid it is intended to use the apparatus to dispense.

It is to be noted that the mechanical advantage of the operating lever enables the apparatus to be easily used one-handed. Further, this mechanical advantage, coupled with the action of the return compression spring 36, enables the apparatus to exert sufficient suction to cause complete evacuation of the contents of a collapsible container.

It is clear that the above-described apparatus may be modified in various ways. For example, instead of utilising a remote reservoir attached to the apparatus by means of plastics tubing 14, a suitable reservoir may be attached directly to the apparatus, for example by a suitable connector secured to connector portion 11 in place of tubular member 12. For example, the tubular member 12 may be replaced by a container cap of the construction described in the Specification of our co-pending Application No.

with the outlet valve piston member and spring being housed within a chamber designed between the connector portion 11 and container cap outlet sleeve and seated over the inlet orifice thereof. In this case, a bottle or other container containing liquid to be dispensed may then be attached directly to the apparatus by being pierced upon the apertured pin of the container cap and secured thereto by means of the spring arms.

Claims

1. Apparatus for dispensing measured doses of a liquid comprising a measuring chamber, a chamber inlet adapted for connection to a liquid reservoir, a chamber outlet, a respective one-way valve associated with each of said inlet and outlet, a piston arranged for movement with respect to the chamber between a stop position in which the chamber defines a maximum volume and a fixed end position in which the chamber defines a minimum volume, actuating means for causing movement of the piston between said positions, and means for adjusting the stop position of the piston so as to adjust the maximum volume of the chamber.

2. Apparatus according to claim 1 , wherein the end position of the piston is such that the minimum volume of the chamber is substantially zero.

3. Apparatus according to claim 1 or 2, wherein the outlet is connected to a hypodermic needle.

4. Apparatus according to claim 1,2 or 3, wherein the piston is slidingly sealed within the chamber by means of a suitable O-ring fixed with respect to the chamber wall so as to be slidingly engaged by the external surface of a piston rod that has been accurately machined to a specified diameter to within close tolerances.

5. Apparatus according to any one of the preceding claims, wherein the means for adjusting the stop position of the piston comprise a micrometer screw arrangement including an axially movable member arranged to contact the piston when in its stop position, and an actuating member provided with a measuring scale.

6. Apparatus according to any one of the preceding claims, including means for biasing the piston to its start position.

7. Apparatus according to claim 6, wherein the biasing means comprise a compression spring mounted between a head member fixed with respect to the piston and a stop ring fixed with respect to the chamber.

8. Apparatus according to claim 7, wherein the strength of the spring is selected having regard to the properties, particularly viscosity of the liquid the apparatus is intended to dispense.

9. Apparatus according to any one of the preceding claims, wherein the actuating means have a mechanical advantage.

1 0. Apparatus according to any one of the preceding claims, wherein the actuating means comprise a cranked lever pivotally mounted for movement between start and end positions, the lever including an operating arm adapted for engagement by the fingers of the user and an activating arm which is operatively linked to the piston so that movement of lever from its start position to its end position causes the piston to be moved from its start position to its end position, and vice versa.

11. Apparatus according to claim 10, when the lever is biased to its start position.

12. Apparatus according to any one of the preceding claims, wherein the chamber is bounded in part by a window in the form of a transparent disc of glass or suitable plastics material.

13. Apparatus according to any one of the preceding claims, wherein each one-way valve includes a piston member housed within a chamber into which an inlet passage opens, the member being biased to a closed position in which it is seated sealingly about the inlet passage.

14. Apparatus according to claim 13, wherein the diameter of the piston member of each valve is very much greater than the diameter of the bore of the inlet passage, and the diameter of the chamber is very much smaller than the diameter of the piston member.

1 5. Apparatus according to any one of the preceding claims, wherein the bores of the chamber inlet and passages of the inlet valve are relativelv laraer than the corrnspondinq bores of the outlet.

16. Apparatus for dispensing measured doses of a liquid, substantially as herein described with reference to, and as shown in, the accompanying drawings.