TITLE : "Apparatus for dispensing predetermined proportions of liquids of different specific weights contained in the same tank" DESCRIPTION The present invention relates to an apparatus for feeding predetermined proportions of liquids of different specific weights which are contained in the same tank, in particular for feeding water and solvent to apparatus for cleaning the cylinders in printing machines, The invention relates to systems for cleaning the cylinders in printing machines which are usually fitted with means for spraying a cloth or other means-which are subsequently brought into contact with the cylinder-with predetermined proportions of water and solvent in order to remove traces of paper and ink. In apparatus of known type, the water and solvent are kept in separate containers and the two liquids are cyclically sucked up and employed in the predetermined proportions using separate suction and distribution circuits. The invention proposes a major simplification to these systems by containing both the water and solvent, in the predetermined proportions, in a single tank. Since agitation of the two liquids could in certain cases cause them to become denser or coagulate, which could lead to the mixture-spraying nozzles becoming blocked or could cause other complications, the invention envisages allowing the said two liquids to separate out into layers inside the tank as a result of their specific weights and also envisages providing a submerged element of variable position inside the tank, this element having a plurality of suction holes spaced out along its entire length, having one end positioned such that it can rotate in the region of the bottom of the tank, having its upper end anchored to float means and being connected to suction means. As the level of mixture in the tank changes, the submerged element modifies its position so that its holes always remain submerged in the liquid, these holes being spaced out along the entire height of the column of the said mixture so that, each time the suction means connected to the submerged element are activated, a mixture made

up of the same proportions of liquids as those fed into the tank at the outset will always come out.

Further characteristics of the invention, and the advantages deriving therefrom, will be more clearly apparent on reading the following description of a preferred embodiment of the said invention, illustrated purely by way of non-limiting example in the figures of the attached sheets of drawings, in which: -Fig. 1 illustrates a perspective view-partially cut away to show the internal components-of the tank for the mixture of liquids, with the submerged element of variable position shown in its position of maximum elevation, i. e. when the tank is full ; -Figs 2,3,4, and 5,6,7 illustrate the tank sectioned through its height and the various positions of the submerged element during use of the mixture, respectively with the mixture made up of 50% water and 50% solvent and with the mixture made up of 70% water and 30% solvent ; -Fig. 8 illustrates the tank sectioned through its height and with the liquid mixture in a state where it has separated out into differentiated layers, which could, for example, occur soon after a new supply of mixture is fed into the said tank; and -Figs 9 and 10 illustrate two variant embodiments of the apparatus, with the suction unit positioned horizontal and vertically, respectively.

Figure 1 shows that floats 3 are mounted inside the tank 1 so that they can slide on a pair of guide rods 2 which are, for example, positioned along a side wall of the said tank. A hole 4 is formed in one of the walls of the tank adjacent to the wall close to the guides 2, in line with the said guides, which hole 4 is preferably suitably raised off the bottom of the tank in order to prevent any dirt, which by its very nature tends to precipitate there (see below), from being sucked up. Passing through the hole 4, with a side seal and such that it can rotate, is an elbow joint 5 which, at its end located inside the tank, is fixed to and communicates with a tube 6 whose length is preferably shorter than the width L of the said tank. The other end of this tube is fixed to and communicates with an elbow joint 7, in turn fixed to and

communicating with a horizontal extension 8 which is closed for example at the end 108 and which is in turn hinged to and communicates with the head end of a T joint 9, the leg of which is connected to and communicates with a tube 10 of length approximately equal to that of the first tube 6 and essentially lying in a plane midway between the guides 2. The tube 10 is closed at its upper end, at which point a round crossbar 20 passes rotatably through it, its looped ends 120 encircling the guides 2 in a slidable manner and resting on the floats 3. The tubes 6 and 10 have a series of holes 11,11'evenly spaced out along their entire length with a small filter being mounted in each hole ; alternatively, the said tubes are made from a suitable sintered material so that they are able to suck up the liquids uniformly along their entire length. In the example shown in Figure 1, the tubes 6 and 10 have an internal diameter of 6 mm and each has ten holes 11,11', for example 0.8 mm in diameter and spaced approximately 20 mm apart. A suction hole can optionally also be provided on the end 108 of the extension 8. So that the system in question can operate correctly, it is necessary for the sum total of the cross sections of the holes 11,11'of the entire hinged submerged element P, made for example in the manner described, to be less than or equal to the internal cross section of the said submerged element.

The submerged element P is connected, via at least any one intermediate or end point, for example via the elbow joint 5, to the suction pipe 12 of any suitable pump (see below). In order to understand how the apparatus described operates, the reader's attention is firstly directed to Figure 2, which shows that the tank 1 contains a quantity of liquid made up of 50% water and 50% solvent. Under rest conditions the layer of solvent S settles above the layer of water A which has a greater specific weight. When the tank is full, as shown in Figure 2, the tubes 6 and 10 are in an essentially vertical position, with the tube 6 submerged in the layer of water A and the tube 10 submerged in the layer of solvent S. By applying suction to the pipe 12 a mixture made up of 50% water and 50% solvent comes out of the latter. As the level of liquid in the tank 1 falls, as illustrated successively in Figures 3 and 4, the floats 3 drop and the tubes 6 and 10 become incline, with each

remaining in its respective layer A or S, so that a mixture of liquid made up of half water and half solvent always comes out of the pipe 12.

If the proportions of water and solvent in the tank 1 are changed, for example as illustrated in Figure 5 which shows a case in which the liquid load is made up of 70% water and 30% solvent, it can be seen that the submerged element P formed by the tubes 6 and 10 is positioned such that approximately 70% of the holes 11,11'are located in the lower layer A and the remaining 30% of the holes 11' are located in the upper layer S. This state is automatically maintained as the level of liquid in the tank gradually drops, as illustrated successively in Figures 6 and 7, so that a mixture made up of 70% water and 30% solvent will always come out of the suction pipe 12.

If the suction pipe 12 is activated immediately after a new quantity of mixture which has been stirred beforehand is fed into the tank 1, the system in question would still operate correctly since a mixture with an equal proportion of water and solvent would enter through all the holes 11,11'. A short time after the new supply of mixture had been fed into the tank 1, the condition illustrated in Figure 8 would apply, with an upper solvent-rich layer S, a lower water-rich layer A and intermediate layers SA having different proportions of water and solvent. In this situation too, the system would operate correctly since the holes 11,11'in the submerged element are spaced out along the entire height of the column of liquid fed into the tank, so that a mixture made up of the same proportions of water and solvent as the new supply of mixture fed into the tank would always come out of the suction pipe 12.

Figures 9 and 10 illustrate that the pipe 12 can be connected to a positive-displacement pump 13, for example of reciprocating type, which is connected via its discharge pipe 14 to the set of solenoid valves 15 which feed the mixture of water and solvent to the apparatus for cleaning the printing cylinders. If a quantity of mixture is left in the pumping circuit at the end of a cycle, this mixture would tend to separate out into layers. If the pump, the solenoid valves and the associated pipes 12 and 14 are positioned horizontally as shown in Figure 9, the fact

that the residue separates out into layers does not cause any problems since the next time the said pump is started up, the two layers of liquid come out mixed together. Contrary to the illustration in Figure 9, the couplings between the pipes 12 and 14 and the pump 13 are positioned in a horizontal imaginary plane. If, on the other hand, the pump 13, the valves 15 and the associated pipes 12 and 14 are positioned vertically, as shown in Figure 10-given that the residual mixture would tend to separate out into layers and that, the next time the said pump was started up, first the solvent and then the water would come out of the pumping system- provision would have to be made in that case for an additional solenoid valve 115 to be activated at the end of the cycle, which valve would connect the discharge pipe 14 of the pump to a re-circulating pipe 16 which would discharge into the tank 1.

Provision would also have to be made for the pump 13 to complete its delivery stroke so that any residual mixture is discharged into the said tank. At the beginning of the next cycle-given that liquid from the previous cycle has been left and has separated out inside the delivery pipe 14 and in the vertically positioned solenoid valves- provision would have to be made, once the pump 13 has sucked up the mixture from the tank 1, for an initial part of the first delivery stroke of the said pump to take place with the solenoid valve 115 activated, so that the said residual liquid inside the pipe 14 can be discharged into the tank 1, after which operation the solenoid valve 115 would be closed and the solenoid valves 15 would be activated in the pre- established order, while the pump remains activated. It goes without saying that instead of the solenoid valve 115 other suitable valve means can be used, for example a throttle which has been set at a pressure greater than the operating pressure of the user machine connected to the solenoid valves 15 and which, via its pipe 16, is in constant communication with the tank 1.

Having made repeated observations, it has been found that the problems mentioned above in connection with the liquids separating out are nevertheless minimized by the fact that the mixture coming out of the submerged element P described in the present invention tends to remain stable for at least twelve hours, presumably by virtue of the vigorous and uniform mixing that the liquid

undergoes, first as it passes through the holes 11,11'and then as it passes through the submerged element P, as a result of the fact that there is a pressure drop inside the pipe 12 of about approximately 1 bar. Needless to say, a pump of any other suitable type may be employed in place of the positive-disptacement pump 13.

It is clear from Figures 9 and 10 that, by keeping the hole 4 suitably raised off the bottom of the tank, it is possible to keep the suction circuit separate from the dirt which tends to precipitate on the bottom layer Z of the said tank and which can be periodically drained off via a drainage tap 17.

It should be understood that the description referred to a preferred embodiment of the invention, to which numerous variations and modifications can be made, especially structural ones, which could, for example, apply to the submerged element P which could be made differently-with a single rigid tube to fit inside a very wide tank, or with more than two rigid tubes which are hinged together, or with one or more flexible tubes.