GB2288220A

GB2288220A - Dispensing liquids

Info

Publication number: GB2288220A
Application number: GB9506228A
Authority: GB
Inventors: Alan Jeffrey Holmes; Glyn Robinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-03-26
Filing date: 1995-03-27
Publication date: 1995-10-11
Also published as: GB9506228D0

Abstract

Accurate dispensing of pigment and base liquids by weight to produce inks, paints, dyes, etc. is effected with a valve having a rod 25 carrying a valve needle 36, an annular closure member 60 defining a fine feed aperture 64 and a nozzle 14 which, together with the member 60 defines a fast feed aperture 62. Flanges 66, 68 on the rod 28 and member 60 co-operate after initial lifting of the valve needle 36 so that the member 60 is entrained to move to open the fast feed aperture 62. Compressed air is supplied simultaneously into bellows 54, 38, which act in opposition to produce a net force in the opening direction. A high pressure causes opening of both apertures. After a predetermined time, the pressure is reduced to close the aperture 62, while maintaining the aperture 64 open. This lower pressure may be pulsed to dispense drop by drop with subsequent manual cut-off. <IMAGE>

Description

Dispensing Liquids" This invention relates to a method, a valve and an apparatus for dispensing liquids.

The invention is intended for use, for example, in the dispensing of printing ink pigment liquids and base liquids by weight according to a predetermined recipe to produce a final colour with repeatable accuracy. There are typically 12 to 14 valves in an ink blending system, usually one valve for each pigment liquid and two or more valves for base liquids, varnishes and extenders. Inks may be water or solvent based. However, the invention can be used wherever liquids need to be dispensed accurately by weight or volume. Accordingly, other uses are in paint and dye manufacturing, in the mixing of resins for foam rubber production, and in the mixing of adhesives for application to components in the manufacture of assemblies.

The principal object of the invention is to dispense liquids of various viscosities with extreme accuracy.

Other objects and advantages will become apparent hereinafter.

According to one aspect of the invention, a method of accurately dispensing liquid comprises operating a valve so that the bulk of the liquid required passes through both a fast feed aperture and a fine feed aperture of the valve and the remainder of the liquid required then passes through only the fine feed aperture.

Preferably, the valve is operated in two stages by supplying valve-operating fluid first at a higher pressure to provide a continuous full flow of the liquid and then at a lower pressure to provide a continuous fine feed of the liquid.

At least said full flow may be provided for a preset time.

Preferably, the valve is lastly operated to provide a pulsed fine feed so that liquid can be dispensed one drop at a time.

The pulsed fine feed may be provided with a manual cut-off.

The rate of at least the fine feed may be controlled by varying the pressure of the valve-operating fluid so as to vary the extent of opening of the valve.

According to another aspect of the invention, a liquid dispensing valve has fast feed and fine feed apertures and means for enabling a supply of fluid to open both apertures or to open only the fine feed aperture, both apertures being allowed to close when the supply of fluid is cut off.

Preferably, the valve comprises a body, a spool slideable within the body, a valve member slideable on the spool to define the fast feed aperture between the member and the body and the fine feed aperture between the member and the spool, spring means confined between the body and the spool for urging the spool in the closing direction, spring means confined between the spool and the member for urging the member in the closing direction, and an abutment on the spool for moving the member in the opening direction when the spool is moved more than a predetermined distance in said direction by the supply of fluid.

Preferably, also, the means for selectively enabling the supply of fluid to open both apertures or only the fine feed aperture comprise a first bellows adapted when pressurised to urge the spool in the opening direction and a second bellows adapted when simultaneously pressurised to urge the spool in the closing direction, the area acted upon by the pressure in the first bellows being greater than the area acted upon by the pressure in the second bellows with the net result that the action of the first bellows on the spool preponderates over the action of the second bellows thereon so that the spool is urged with a moderating influence in the opening direction.

Preferably, the second bellows is disposed within a chamber in the body through which the liquid to be dispensed is fed, thus eliminating the need for sliding seals to keep separate the fluid under pressure and the liquid to be dispensed.

Preferably, also, the liquid to be dispensed is continuously recirculated through the chamber in the body to prevent constituents of the liquid from settling out and to purge any air from said chamber.

The valve preferably comprises a two-stage valve operable selectively by a supply of fluid at a higher pressure to open both apertures and at a lower pressure to open only the fine feed aperture According to a further aspect of the invention, apparatus for producing accurate mixtures of different liquids includes a plurality of valves as hereinbefore defined for dispensing different pigment liquids into a first container, means for weighing the first container, means for discharging the combined pigment liquids into a second container, at least one valve for dispensing base liquid directly into the second container, and means for weighing the second container.

Preferably, the or each valve for dispensing base liquid is as hereinafter defined.

The invention will now be described, by way of example only, with reference to the accompanying drawings of which: Figure I is a side view of a liquid dispensing valve; Figure 2 is a top view thereof; Figure 3 is a side view of the valve with most of the body omitted on one side of the centre-line and the internal components thus revealed shown in cross-section in full flow position; Figure 4 is a front view of apparatus for producing accurate mixtures of different liquids; and Figure 5 is a side view of said apparatus.

Referring now to Figures 1 to 3 of the drawings1 a liquid dispensing valve has a generally cylindrical body indicated generally at 10 comprising a block 12, an outer cone 14, a centre spool guide 16, a barrel 18 and an end cap and spool guide 20 which are secured together by screw threads. The block 10 has a hole 22 for a fixing bolt and contains a cylindrical chamber 24 with two ports 26 for the inlet and return of liquid to be dispensed, said liquid being continuously recirculated to prevent its constituents from settling out and to purge said chamber of any air which may cause some liquids to congeal. A spool indicated generally at 28 is slideable within the body 10 and comprises a tubular section 3O, a section 32 having a blind bore 34, and a needle valve 36 which are secured together by screw threads.Part of the tubular section 30 projects through the end cap 20 and constitutes an inlet and exhaust passage for a supply of compressed air for operating the valve. A first flexible metallic bellows 38 is secured by welding, soldering or high performance adhesive between the centre spool guide 16 and a flange 40 formed on the section 30. and the interior of said bellows communicates by way of a radial port 42 in said section with the bore of said section. A flanged nut 44 secured by a lock-nut 46 is adjustable along a threaded portion 48 of the end cap 20, and the flange 40 is adapted to abut against the nut 44 as shown to limit movement of the spool 2s in the opening direction A helical compression spring 50 is confined between the end cap 20 and the flange 40 to urge the spool 28 in the closing direction.A small flange 42 formed on the section 30 is intended to contact the guide 16 to prevent excessive movement of the spool 28 in the closing direction, which might damage the bellows 38, when the valve is partially dismantled. A second flexible metallic bellows 54 of significantly smaller diameter than the bellows 38 is secured by welding, soldering or high performance adhesive between the guide 16 and a flange 56 formed on the section 32, and the interior of the bellows 54 communicates by way of a radial port 58 in said section with the bore of said section. The arrangement is such that the area of the flange 40 capable of being acted upon by pressure in the first bellows 38 is greater than the area of the flange 56 capable of being simultaneously acted upon by pressure in the second bellows 54 with the net result that the action of the first bellows 38 on the spool 28 preponderates over the action of the second bellows 54 thereon so that said spool is urged with a moderating influence in the opening direction. The bellows 54 is disposed within the chamber 24 and thus avoids the need for sliding seals such as O-rings to keep separate the compressed air and the liquid to be dispensed, thereby, eliminating static friction, which can adversely affect repeat accuracy, and greatly reducing the risk of seal failure.An annular valve member 60 of high molecular density polyethylene is slideable on the needle valve 36 and defines a fast liquid feed aperture 62 between said member and the outer cone 14 and a fine liquid feed aperture 64 between said member and the needle valve 36. A small abutment flange 66 formed on the needle valve 36 is adapted to contact an internal flange 68 screwed to the valve member 60 and move said member in the opening direction as shown when the spool 28 is moved more than a predetermined distance in said direction.

Three circumferentially spaced radial ports 70 are formed in the annular valve member 60 whereby its bore communicates with the chamber 24 containing the liquid to be dispensed, and a helical compression spring 72 is confined between the flange 56 and the flange 62 to urge the member 60 in the closing direction, Those parts of the outer cone 14, the member 60 and the needle valve 36 which define the fast feed aperture 62 and the fine feed aperture 64 are of such shapes as to provide a clean uniform flow without spray or spread and a clean cut-off on closing, and to eliminate accumulation of material which would cause drips or eventually congeal and fall off as dried solids. Said shapes and/or their dimensions can readily be changed to provide different flow rates. The bellows 38 and 54 can be formed of brass, phosphor bronze or stainless steel.The majority of the parts of the dispensing valve can be made of various metals or plastics according to the intended use. Aluminium is frequently suitable and will normally have all wetted parts anodised with a coating of polytetrafluoroethylene to improve surface release properties, prevent build-up of solids, increase resistance to aggressive chemicals and solvents, and aid cleaning and routine maintenance.

In operation, both of the co-axial apertures 62 and 64 are held closed by the springs 50 and 72 when the supply of compressed air to the projecting tubular section 30 of the spool 28 is cut off. When a batch of liquid is required to be dispensed1 compressed air at a higher pressure, say 60 to 75 pounds per square inch, is first supplied continuously to the section 30 for a preset time by way of a conventional solenoid valve of electro-pneumatic or proportional pressure type. This moves the dispensing valve into its full flow position shown in Figure 3 in which both the fast and fine feed apertures 62 and 64 are open to allow the bulk of the required amount of liquid to be dispensed rapidly.

Compressed air at a lower pressure, say 30 to 40 pounds per square inch, which can be varied so as to vary the extent of opening of the fine feed aperture 64, is then supplied continuously to the section 30 for a preset time by way of another solenoid valve. This moves the spool 28 sufficiently far in the opening direction to open the fine feed aperture 64, but not far enough to cause the abutment flange 66 to contact the internal flange 68 screwed to the valve member 60 so that said member holds the fast feed aperture closed under the action of the spring 72. The resulting fine flow of liquid ensures accuracy as the target weight is approached. Finally, compressed air at the lower pressure is supplied in rapid pulses to the section 30 whereby the fine feed aperture 64 repeatedly opens and closes so that liquid can be dispensed one drop at a time.This pulsed fine feed is provided with a manual cut-off which enables a batch of liquid to be dispensed with a weight accurate to, say 0.1 gram.

In one modification, the dispensing valve can be operated by hydraulic fluid under pressure, in another modification it can be adapted to vacuum control, in a further modification it can be adapted to proportional control so that the dispensing rate can be infinitely variable from fully open to fully closed1 in yet another modification it can be adapted to closed loop control so that the flow rate can be kept constant despite changes in viscosity, and in yet a further modification air pressure can be used to assist spring-closure of the dispensing valve in order to increase the closing force and closing speed.

Referring now to Figures 4 and 5. apparatus for producing accurate mixtures of various liquids is constructed in the form of a weighing machine gsntry and access platform. More specifically, the apparatus comprises a multiplicity of drums 100 of different pigment liquids which are continuously recirculated by respective pump means 102 through respective liquid dispensing valves of the kind hereinbefore described. Said valves are not individually illustrated but are secured in close proximity to one another in a head 104 disposed immediately above a first container 106 The head 104 also has a washing function, and includes solenoid valves not individually illustrated for successively operating selected dispensing valves under the control of an operator. Control panels 109 include means for weighing the container 106 after each batch of pigment liquid has been dispensed When all the requisite pigment liquids have been dispensed into the container 106, a valve 110 on said container is activated to discharge the combined pigment liquids into a second container 112. At least one base liquid is also dispensed into the container 112 from source means not illustrated by one or more of a plurality of liquid dispensing valves 114 of the kind hereinbefore described. The container 112 rests on a scale 116 for weighing it before and after the or each batch of base liquid is dispensed. A gantry 118 with access steps 120 facilitates maintenance of the dispensing valves and replenishment of the drums 100. This apparatus produces accurately repeatable recipes of inks, paints and the like.

Claims

What we claim is:

1. A method of accurately dispensing liquid comprising operating a valve so that the bulk of the liquid required passes through both a fast feed aperture and a fine feed aperture of the valve and the remainder of the liquid required then passes through only the fine feed aperture.

2. A method according to Claim 1, comprising operating the valve in two stages by supplying valve-operating fluid first at a higher pressure to provide a continuous full flow of the liquid and then at a lower pressure to provide a continuous fine feed of the liquid.

3. A method according to Claim 2, comprising providing at least said full flow for a preset time.

4. A method according to Claim 2 or Claim 3, comprising lastly operating the valve to provide a pulsed fine feed so that liquid can be dispensed one drop at a time.

5. A method according to Claim 4, comprising providing the pulsed fine feed with a manual cut-off.

6. A method according to any one of Claims 2 to 5, comprising controlling the rate of at least the fine feed by varying the pressure of the valve-operating fluid so as to vary the extent of opening of the valve.

7. A liquid dispensing valve having fast feed and fine feed apertures and means for enabling a supply of fluid to open both apertures or to open only the fine feed aperture, both apertures being allowed to close when the supply of fluid is cut off

8. A liquid dispensing valve according to Claim 7, comprising a body, a spool slideable within the body, a valve member slideable on the spool to define the fast feed aperture between the member and the body and the fine feed aperture between the member and the spool, spring means confined between the body and the spool for urging the spool in the closing direction, spring means confined between the spool and the member for urging the member in the closing direction, and an abutment on the spool for moving the member in the opening direction when the spool is moved more than a predetermined distance in said direction by the supply of fluid.

9. A liquid dispensing valve according to Claim 8, wherein the means for selectively enabling the supply of fluid to open both apertures or only the fine feed aperture comprise a first bellows adapted when pressurised to urge the spool in the opening direction and a second bellows adapted when simultaneously pressurised to urge the spool in the closing direction, the area acted upon by the pressure in the first bellows being greater than the area acted upon by the pressure in the second bellows with the net result that the action of the first bellows on the spool preponderates over the action of the second bellows thereon so that the spool is urged with a moderating influence in the opening direction.

10. A liquid dispensing valve according to Claim 9, wherein the second bellows is disposed within a chamber in the body through which the liquid to be dispensed is fed, thus eliminating the need for sliding seals to keep separate the fluid under pressure and the liquid to be dispensed.

11. A liquid dispensing valve according to Claim 10, wherein the liquid to be dispensed is continuously recirculated through the chamber in the body to prevent constituents of the liquid from settling out and to purge any air from said chamber.

12. A liquid dispensing valve according to any one of Claims 7 to 11, comprising a two-stage valve operable selectively by a supply of fluid at a higher pressure to open both apertures and at a lower pressure to open only the fine feed aperture.

13. Apparatus for producing accurate mixtures of different liquids, including plurality of valves according to any one of Claims 7 to 12 for dispensing different pigment liquids into a first container, means for weighing the first container, means for discharging the combined pigment liquids into a second container, at least one valve for dispensing base liquid directly into the second container, and means for weighing the second container.

14. Apparatus according to Claim 13, wherein1 the or each valve for dispensing base liquid is in accordance with any one of Claims 7 to 12.

15. A method of accurately dispensing liquids substantially as hereinbefore described.

16. A liquid dispensing valve constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 3 of the accompanying drawings.

17. Apparatus for producing accurate mixtures of different liquids, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, Figures 4 and 5 of the accompanying drawings.

18. Apparatus for producing accurate mixtures of different liquids, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 5 of the accompanying drawings.