GB2151362A

GB2151362A - A dispensing head

Info

Publication number: GB2151362A
Application number: GB08428991A
Authority: GB
Inventors: John Hamilton Mainstone
Original assignee: Ault & Wiborg Group PLC
Current assignee: Ault & Wiborg Group PLC
Priority date: 1983-12-15
Filing date: 1984-11-16
Publication date: 1985-07-17
Also published as: GB8333483D0; GB8428991D0

Abstract

A dispensing head for dispensing metered quantities of a number of different liquid media into a single container includes a number of pairs of dispensing valves 5, 6. Each pair includes a first valve 5 for dispensing liquid medium at a first rate and a second valve 6 for dispensing liquid medium at a second, slower rate, both valves of each pair being connected to a supply of the same particular liquid medium. All the dispensing valves 5, 6 are mounted around a common mounting plate 1 with their outlets located near the centre of the mounting plate. A load cell is located for monitoring the weight of a container which is located on it and into which the liquid media are dispensed. The required metered quantity of a particular liquid medium is dispensed against the weight monitored by the load cell with the final quantity of the liquid medium being supplied only through the second dispensing valve 6 of the pair connected to that particular liquid medium. <IMAGE>

Description

SPECIFICATION A dispensing head This invention relates to a dispensing head for dispensing metered quantities of a number of different liquid media into a single container to make a batch of liquid to a particular, predetermined recipe. A particular application for the present invention is for mixing a batch of printing ink having a particular colour from predetermined quantities of a number of different standard coloured printing inks.

At present the container in which a particular batch is to be mixed is moved manually between separate supplies of printing ink of standard colours. The container may be mounted on a portable weigh scale and then the printing ink of each of the different standard colours be weighed into the container or, alternatively each standard colour of printing ink may include its own metering device which meters the appropriate quantity into the container. This arrangement is very time-consuming and it would be extremely difficult to automate batch production using such a system.

Recently it has been proposed to have a single dispensing manifold containing a number of ink dispensing valves corresponding to the number of standard printing inks that are used. Typically there are more than ten standard printing inks used and the dispensing valves are arranged in a line along the manifold. To dispense a particular printing ink into a container located beneath the manifold the whole manifold is moved sideways until the dispensing valve for a particular standard colour is located above the centre of the container. Then the required quantity of printing ink of that standard colour is metered into the container. The manifold is then moved sideways until the dispensing valve connected to the next standard colour that is to be added is located immediately above the container.

This process is then repeated for each of the colours that are required. This system is again difficult to use and again difficu!t to automate.

According to this invention a dispensing head for dispensing metered quantities of a number of different liquid media into a single container comprises a number of pairs of dispensing valves, each pair including a first valve for dispensing liquid medium at a first rate and a second valve for dispensing liquid medium at a second, slower rate, both the first and the second valves of each pair being connected to a supply of the same particular liquid medium, all of the dispensing valves being mounted around a common mounting plate with their dispensing outlets located towards the centre of the mounting plate, and a load cell located beneath the outlets of the dispensing valves for monitoring the weight of a container which is located on it and into which the liquid media are dispensed, the required metered quantity of a particular liquid medium being dispensed against the weight monitored by the load cell with its final quantity being supplied only through the second dispensing valve of the pair connected to that particular liquid medium.

Preferably the vertical separation of the load cell and the common mounting plate is adjustable. Typically this is achieved by having the load cell fixed in position at floor level and having the mounting plate move up and down with respect to the load cell. In this case flexible connections are used to join each pair of dispensing valves to their ink supply. Also in this case it is preferred that the head includes a hydraulic ram to raise and lower the mounting plate and dispensing valves. It is important to be able to locate the dispensing valves at the minimum height above the load cell to allow the container to be inserted between them, so that the length of column of liquid medium which is "inflight" at any instant is reduced as much as possible.The column of ink in between the outlet of the dispensing valve and the top of the liquid level in the container is falling through space and thus the weight of this column of ink which is "in flight" is not recorded by the load cell. Accordingly, a greater accuracy can be achieved by reducing the height of this column of "in flight" liquid so that the smallest addition is made after the dispensing valve is closed. Naturally by dispensing the final quantity using the second valve for a particualr liquid medium the volum, and hence the weight, of the "in flight" liquid is reduced to a considerable extent, without increasing substantially the overall time required to dispense each liquid.

When the liquid media being dispensed are liquid inks or paints that dry by solvent evaporation it is preferred that there is no pipework downstream from the dispensing valves and as little of the valve as possible downstream of its seat. The solvent from liquid ink or paint tends to evaporate and dry out with the result that the pigments clog any pipework or portions of the valve downstream from its seat. In this case it is preferred that the dispensing valves are all formed by ball plug valves with the dispensing outlet of the valves effectively being defined by the end of the bore of the ball plug. Again in this case it is especially preferred that the valves include a polytetrafluoroethylene seat.

Preferably the valves are each controlled by an actuator. Again for working with inks or paints which include an inflammable solvent it is preferred that the actuators are pneumatically operated. Preferably the actuators are of a type in which they bias the valves into their closed position and require a supply of compressed air to open them. Tyhpically actuators are very much larger in size than the valves that they control. It is for this reason that the present invention is particularly useful since by arranging the valves towards the centre the mounting plate with the valves close together, the actuators are then arranged radially outwards from the valves and so are arranged around a circle of larger diameter.Thus, the valves are close together and arranged around one, or two circles of small pitch circle diameter whilst the actuators are arranged around a cricle having a very much greater pitch circle diameter to accommodate the greater size of the actuators than that of the valves. In this case the actuators are joined to the valves by extension spindles. Preferably the first valves of each pair are arranged almost touching on a circle having a first pitch circle diameter and the second valves of each pair are arranged on a circle having a second pitch circle diameter which is slightly larger than the first. Typcially there are more than ten pairs of dispensing valves mounted on the mounting plate and there may be, for example, fourteen pairs of valves.

The dispensing valves may be manually controlled in accordance with the weight dispensed as monitored by the load cell but preferably the dispensing head forms part of an automatic dispensing system including a programmed computer. In this case, once a particular recipe has been selected the programmed computer is arranged to dispense predetermined weights of each of the number of different liquid media required for that particular recipe.

A particular example of a dispensing head in accordance with this invention will now be described with reference to the accompanying drawings, in which: Figure 1 is an under plan of a quarter of the dispensing head; Figure 2 is a radial section through the dispensing head showing only a single valve and associated actuator; Figure 3 is a detail of a connecting pipe for connecting a pair fo valves; and, Figure 4 is a diagram of the entire ink dispensing system.

The dispensing head comprises a circular mounting plate 1 made from polypropylene with twenty-eight ball plug valves 2 and actuators 3 mounted around it. The mounting plate 1 and dispensing valves are mounted above a weigh platform mounted on load cells 4 which is only shown in Figure 4. The ball plug valves 2 are standard half-inch full bore polytetrafluoroethylene seated ball plug valves and are arranged in pairs around the mounting plate 1. Valves 5 are arranged around a pitch circle diameter of 1 94 millimetres and constitute the coarse pour valves whilst valves 6 are arranged around a pitch circle diameter of 266 millimetres and have their balls partially filled by a plug to restrict the flow through them. The valves 6 constitute fine pour valves. The actuators 3 are air openspring closed valves and may be Model No.

790-0015 manufactured by Keystone Valves (U.K.) Limited. The actuators 3 are connected to the mounting plate 1 by angle brackets 7.

The actuators 3 are connected to the vales 2 by extension spindles 8 and 9 of different length. Valve 5 and its immediately adjacent valve 6 are linked together by a Y-shaped connecting pipe 10 shown in Figure 3 and linked to a common ink supply by a flexible pipe (not shown). The mounting plate 1 is connected to a hydraulic ram, not shown, so that its height can be adjusted.

Figure 4 shows the remainder of the ink dispensing system but shows only a single ink storage tank 11. In practice, with head shown in Figures 1, 2 and 3 fourteen such ink storage tanks would be provided and each would be connected to its respective pair of dispensing valves 5 and 6. Ink is drawn from its tank 11 via outlet pipe 12, three-way valve 1 3 and double-diaphragm air-operated pump 14 to a pipeline 1 5 which leads to the pair of dispensing valves 5 and 6. The pump 14 can also be used to fill the storage tank 11 from drums 16 via a dip tube and flexible hose 17.

Under these circumstances a float valve 1 8 prevents the tank 11 from being overfilled by automatically closing valve 1 9.

The system also includes a programmed computer, typically a BOFORS D4 mini-processor which is preferably located in a FA SEEFA certified enclosure. The weighing platform 4 is preferably a BOFROS PV3 electronic load cell weighing platform which is connected to the computer. Typically the computer has a memory capacity to enable it to store seventy recipes when controlling fourteen different colours and once a particular recipe is selected manually the programmed computer automatically controls the quantity of ink dispensed from each pair of valves 5 and 6 in accordance with the weight signals obtained from the weighing platform 4.

The dispensing head in accordance with this invention is able to dispense into any container having a minimum diameter of 300 millimetres without the container having to be moved during dispensing of up to all fourteen separate colour units. Naturally the system includes interlocks such as a whisker valve 20 to ensure that a container is in position on the load cell platform before allowing any inks to be dispensed and emergency stop switches such as 21 to interrupt the dispensing at any instant. It is also preferred that the processor is arranged to lock out the dispensing operation in the even that any dispensing operation takes longer than a preset time thereby to ensure that in the event of the storage tank 11 becoming exhausted or a dispensing valve 5 or 6 not closing, further operation of the dispensing system is prevented until remedial action is taken.

Claims

1. A dispensing head for dispensing metered quantities of a number of different liquid media into a single container comprising a number of pairs of dispensing valves, each pair including a first valve for dispensing liquid medium at a first rate and a second valve for dispensing liquid medium at a sec- ond, slower rate, both the first and the second valves of each pair being connected to a supply of the same particular liquid medium, all of the dispensing valves being mounted around a common mounting plate with their dispensing outlets located towards the centre of the mounting plate, and a load cell located beneath the outlets of the dispensing valves for monitoring the weight of a container which is located on it and into which the liquid media are dispensed, the required metered quantity of a particular liquid medium being dispensed against the weight monitored by the load cell with its final quantity being supplied only through the second dispensing valve of the pair connected to that particular liquid medium.

2. A dispensing head according to claim 1, in which the vertical separation of the load cell and the common mounting plate is adjustable.

3. A dispensing head according to claim 2, in which the load cell is fixed in position at floor level and in which the mounting plate is movable up and down with respect to the load cell.

4. A dispensing head according to claim 3, in which the head includes a hydraulic ram to raise and lower the mounting plate and dispensing valves.

5. A dispensing head according to any one of the preceding claims, in which the dispensing valves are all formed by ball plug valves with the dispensing outlet of the valves effectively being defined by the end of the bore of the ball plug.

6. A dispensing head according to any one of the preceding claims, in which the valves are each controlled by an actuator.

7. A dispensing head according to claim 6, in which the valves are arranged close together around one or two concentric circles of small pitch circle diameter towards the centre of the mounting plate and the actuators are arranged radially outwards from the valves around a circle having a very much greater pitch circle diameter, the actuators being joined to the valves by extension spindles.

8. A dispensing head according to any one of the preceding claims, in which there are fourteen pairs of the valves mounted on the mounting plate.

9. A dispensing head according to any one of the preceding claims, in which the operation of the dispensing valves is controlled by a programmed computer in response to a particular recipe programmed into the computer and the output of the load cell.

10. A dispensing head substantially as described with reference to the accompanying drawings.

11. An ink dispensing system including a dispensing head in accordance with any one of the preceding claims.