GB2149384A

GB2149384A - Liquid preparation apparatus

Info

Publication number: GB2149384A
Application number: GB08423156A
Authority: GB
Inventors: Armin Schultz; Eberhard Bartholomaus
Original assignee: Kombinat Polygraph Werner Lamberz VEB; Polygraph Leipzig Kombinat Veb
Current assignee: Kombinat Polygraph Werner Lamberz VEB; Polygraph Leipzig Kombinat Veb
Priority date: 1983-11-11
Filing date: 1984-09-13
Publication date: 1985-06-12
Also published as: DD219436B1; GB2149384B; DD219436A1; DE3428909A1; GB8423156D0

Abstract

Apparatus for the preparation of a moistening agent from a plurality of components in predetermined concentrations comprises a float system (9, 10) effecting switching on and off respectively in the case of a lower and an upper filling level in a mixing vessel (1). Evaluating and control means (36, 37), which evaluates the concentration of the components, controls component feed valves (5, 6, 7), sets an indicating device (27) into operation and actuates a suction pump (19). The suction pump (19) as well as the indicating device (27) are connected to respective outputs of the evaluating and control means, while a concentration measuring system (20, 21, 22) and the float system (9, 10) are connected to respective inputs of the evaluating and control means, inflow conveying pumps (14, 15) are associated by way of a control circuit (37) with the float system <IMAGE>

Description

SPECIFICATION Liquid preparation apparatus The present invention relates to liquid preparation apparatus for preparation of a liquid mixture, especially a moistening agent, from a plurality of components in predetermined concentrations, such apparatus being, for example, an accessory unit for the moistening mechanism of an offset printing machine.

In DE-PS 14 57 277 there is disclosed apparatus for the automatic production of solutions in predetermined concentration, which apparatus has for the metering of a chemical moistening agent additive, namely an etch concentrate, a measuring vessel arranged in a mixing vessel and constructed as a float body as well as two float systems functionally matched to each other for the metering of alcohol and the main liquid, namely water. A reservoir container containing the etch concentrate is connected to the mixing vessel.

As a consequence of sucking of moistening agent out of the mixing vessel into the circulating system of the offset printing machine by means of a suction pump installed for this purpose on a cover plate of the mixing vessel, a low state of the moistening medium level in this vessel is obtained. This has the effect that the associated switch for the suction pump is opened through one of the float systems, thus the excitation current circuit thereof is interrupted. At the same time, through the lower float of the other float system, the switch and thereby the excitation current circuit of the valve controlling the water inflow as well as the inflow of the chemical additive is closed.

As a result, this valve is opened and the water and the chemical additive are conducted by way of a siphon duct and the water feed duct to the mixing vessel through utilisation of the injector principle until the liquid has reached the level predetermined by the upper float of the second float system. At this instant, the measuring vessel has attained its highest position determined by the cover plate of the mixing vessel. The excitation current circuit and thereby the feed of the mixture of water and etch concentrate are now interrupted by means of the same switch. At the same time, a further valve, controlling the alcohol inflow, is actuated by this float system in such a manner that the associated excitation current circuit is closed and the valve is opened.The alcohol flows into the mixing vessel until the third liquid level, predetermined by the upper float of the first float system, is reached. The excitation current circuit of the alcohol valve and thus the alcohol inflow is interrupted by this float system and the suction pump is switched on by means of the initially mentioned switch.

Although this two-float system ensures, through the described regulation, that suction of the moistening agent mixture takes place only on attainment of a predetermined quantity, this occurs independently of the moistening medium concentration actually reached in the mixing vessel after the completed missing operation, thus independently of any disruptive influences. Thus, for example, the concentration of the chemical additive in the moistening agent is dependent on the pressure present at the water feed duct. If the necessary pressure is not present, less etch concentrate than intended is sucked in by way of the siphon duct. Disturbances arising in this apparatus are recognised only through inadequate print quality at an associated offset printing machine, thus when printer's waste occurs.A further factor impairing the print quality can be inadequate intermixing of the moistening agent components due to the addition of the alcohol as the last component, as homogeneously mixed moistening agent cannot be sucked out and conducted to the printing machine by the suction pump when the upper liquid level is reached. Moreover, the employed two-float system is relatively expensive, as its floats must be adjusted individually and relative to each other for the purpose of the required metering. In the case of high adjustment effort, fluctuations in the metering of the components in the moistening agent are difficult to avoid.

It would thus be desirable for liquid preparation apparatus, especially for the automatic production of a moistening agent, to be capable of a simpler and more exact setting, compared with the known apparatus, of the concentration of the components of the liquid.

In the case of apparatus for use in association with a printing machine, fluctuations in the metering of the components contained in the moistening agent should be without influence on the print quality, thus the metering should be able to take place in narrow tolerance ranges required for quality printing and causes of faults should be able to be detected and eliminated relatively quickly.

According to the present invention there is provided liquid preparation apparatus for preparation of a liquid mixture from a plurality of components in predetermined concentrations, comprising a mixing vessel, a respective flow control valve to control inflow of each component into the vessel, inflow conveying means operable to convey at least one of the components to the vessel, outflow conveying means operable to convey liquid mixture out of the vessel, quantity measuring means to provide output signals indicative of predetermined quantities of liquid mixture in the vessel, concentration detecting means to provide a respective output signal indicative of a predetermined concentration in the vessel of at least one of the components, indicating means to provide indications as a function of said out put signals, and control means responsive to said output signals to control opening and closing of the valves and operation of the inflow and outflow conveying means and of the indicating means.

In a preferred embodiment, the control means is arranged in front of gate valves of the liquid mixture feed system and evaluates the concentration of the mixture components, controls the gate valves, sets the indicating means into operation and actuates a suction device. The suction device and the indicating means are each connected to a respective output of the control means, while the concentration detecting means and the quantity measuring means are each connected to a respective input. The inflow conveying means, in the form of pumps, are associated by way of a control circuit with the quantity measuring system.It is advantageous to construct the control means and interlink it with the connected systems in such a manner that the gate valves of two components of the liquid mixture are connected with timing elements or throughflow quantity meters which are disposed in the control means and are respectively connected through delay elements to the output means of the quantity metering means. This output means can also be connected to a first negated input of each of a first and a second AND-gate and to the negated resetting input of each of a first and a second bistable multivibrator, the setting inputs of which are connected to output means of the concentration detecting means. A second input of the first AND-gate is connected to the output of the first bistable multivibrator and a first input of a third AND-gate is connected to the output of the second bistable multivibrator.Second and third inputs of the second AND-gate are also connected to, respectively, the two outputs of the bistable multivibrators. The output of the second ANDgate is connected through an output of the control means with a control device of the suction device, while the indicating means is connected to the outputs of the first and third AND-gates and to a third bistable multivibrator which is connected at its inputs to the output means of the quantity measuring means. The concentration detecting means can comprise an areometer measuring the density, changed due to a chemical additive, of the liquid mixture as well as an areometer measuring the density, changed due to the alcohol additive, of the mixture.It is also possible for the concentration detecting means to comprise merely one areometer to measure the densities, changed through the chemical additive and through the alcohol additive, of the mixture. Moreover, it is expedient to construct the quantity measuring means as a float system detecting upper and lower levels of the mixture and delivering a signal in these limit cases. It is also possible to provide, in place of the float system, a timing element with a delay element connected in front thereof and to interlink these elements in terms of signals with the control circuit of the suction device.Advantageously, respective signal sources are arranged in the indicating means to serve for the indication of deviation of the chemical additive concentration and the alcohol concentration in the mixture from target values and for the indication of attainment of the upper level state of the mixture in the vessel, wherein these signal sources can be light-emitting diodes and can be arranged in a control panel of, for example, an offset printing machine. By means of such apparatus, when used for preparation of a moistening agent for the moistening mechanism of an offset printing machine, the agent can be sucked out of the vessel and conducted to the printing machine only when the concentration, which has been set in correspondence with the desired print quality, of all components has actually been reached, while any error source is indicated to the operator of the machine.As a result, misprints, which have hitherto become apparent only after a relatively large time interval by reason of the gradual change in the moistening agent concentration and thereby gradual worsening in quality, may be avoided. In addition, shutdown times of the printing machine to enable fault location may be reduced.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, which is a schematic diagram of apparatus embodying the invention.

Referring now to the drawing, there is shown apparatus for preparing a moistening agent for the moistening mechanism of an offset printing machine, the apparatus comprising inflow pipes 2, 3 and 4, for the components water, alcohol and a chemical additive, which project into a mixing vessel 1.

The inflow of these components is regulated through gate valves arranged in the inflow pipes, in particular electromagnetic valves 5, 6 and 7. A float system 9 is disposed in the vessel 1 to be displaced by moistening agent 8 in the vessel. Associated with the float system 9 is a switch 10. The float system 9 serves to close the switch 10 on the attainment of a predetermined lower level of the moistening agent 8 and to open the switch 10 on the attainment of a predetermined upper level of the agent. Delay elements 11, 1 2 and 13, which are arranged in front of the valves 5, 6 and 7, are addressed by the electrical signal provided on closing of the switch 10. In accordance with the fixed inflow sequence of the components, the time delays of the delay elements 11, 1 2 and 1 3 are set in such a manner that first the alcohol, then the additive and finally the water flow in. The time delay for the actuation of the valve 6 is so selected that the required flow pressure of the alcohol builds up in front of the valve 6 after addressing of conveying pumps 14 and 1 5 by the signal of the switch 10 supplied through a control device 37. The valve 6 is opened after this delay time. The opening time of the valve 6 and thereby the inflow quantity of the alcohol is determined by a timing element 16 connected between the delay element 1 2 and the valve 6.The time delay for the actuation of the valve 7 is so set that a timing element 1 7 connected to the output of the delay element 1 3 opens the valve 7 when the timing element 1 6 has closed the valve 6. After the timing element 1 7 has closed the valve 7, the valve 5 is opened through the delay time of the delay element 11 connected between the switch 10 and the valve 5. The inflow quantity of the third component, water, is limited through the opening of the switch 10 on attainment of the upper level of the moistening agent 8.

The function of the timing elements 1 6 and 1 7 as well as of the float system 9 can be taken over by throughflow quantity meters or similar. In this case, the negated closing signal of an electromagnetic valve 18 which is connected behind a suction pump 1 9 and regulates the outflow of the moistening agent 8 is utilised as an address signal for the delay elements 11, 12 and 13.

Areometers 20 and 21 are arranged at the mixing vessel 1 for checking of the actual concentrations of the additive and alcohol, respectively. The areometers 20 and 21, each at an adjustable height, have respective wiper contacts 22, which each correspond to the target density value of the component concerned within the permissible tolerance range in the moistening agent 8. When the target density values are reached after inflow of the respective components, current circuits are closed by way of the associated wiper contacts 22 and the signal are stored by bistable multivibrators 23 and 24 associated with the areometers 20 and 21.The control of the suction pump 1 9 by way of a control circuit 25 takes place when the switch 10 is opened, thus when the upper level of the moistening agent 8 is reached, and the two set outputs of the bistable multivibrators 23 and 24 display an H-signal, thus the target density values have been attained. This interlinking is realised through an AND-gate 26, the input of which connected with the switch 10 possesses a negating function.

An associated indicating equipment 27 is so arranged that optical signal sources 28 and 29 light up when the switch 10 is opened and the bistable multivibrators 23 and 24 are set, thus the target densities of the additive and the alcohol are present, and that an optical signal source 30 extinguishes as soon as the upper level of the moistening agent 8 is reached. The lighting-up of the sources 28 and 29 takes place simultaneously with the extinction of the source 30 and sucking-out of the moistening agent 8, provided that the target densities of both components have been attained. A second, differently coloured signal source may be associated with each of the optical signal sources 28, 29 and 30.

Simultaneously after reaching the lower level of the moistening agent 8, the suction pump 19 is switched off and the bistable multivibrators 23 and 24 are reset. A bistable multivibrator 33, provided for the control of the optical signal source 30, is also set by way of its dynamic setting input (L/H-step).

The optical signal sources 28, 29 and 30 are thereby reset to their original state.

It is thus ensured that all error sources, which are possible before the concentration measurement in the feeding and mixing of the components of the moistening agent 8 and which may be caused by, for example, false charging of reservoir containers 34 and 35, functional disturbances at one of the timing and/or delay elements 11 to 1 7 or at the valves 5 to 7, or a defect in or congestion of the inflow pipes 2 to 4, particularly between the valves 5 to 7 and the vessel 1, are detected by reason of their effects on the concentration and are evaluated and indicated with a view to their recognition. As a result of this evaluation, sucking-out of the mixed agent is prevented even on the occurrence of only one fault in that the suction pump 1 9 is not switched on. Due to the thorough intermixing of the components through the water inflow up to the attainment of the upper level, there is no falsification of the measurement results. Moreover, the metering of the other components of the moistening agent 8 is no longer dependent on factors such as, for example, water pressure.

Claims

1. Liquid preparation apparatus for preparation of a liquid mixture from a plurality of components in predetermined concentrations, comprising a mixing vessel, a respective flow control valve to control inflow of each component into the vessel, inflow conveying means operable to convey at least one of the components to the vessel, outflow conveying means operable to convey liquid mixture out of the vessel, quantity measuring means to provide output signals indicative of predetermined quantities of liquid mixture in the vessel, concentration detecting means to provide a respective output signal indicative of a predetermined concentration in the vessel of at least one of the components, indicating means to provide indications as a function of said output signals, and control means responsive to said output signals to control opening and closing of the valves and operation of the inflow and outflow conveying means and of the indicating means.

2. Apparatus as claimed in claim 1, the control means comprising a first control device connected at respective input means thereof to output means of each of the quantity measuring means and the concentration detecting means and at respective output means thereof to control elements of the outflow conveying means and of at least one of the valves and to the indicating means, and a second control device connected at input means thereof to the output means of the quantity measuring means and at output means thereof to a control element of the inflow conveying means.

3. Apparatus as claimed in claim 2, wherein the first control device comprises a respective timing element or throughflow quantity meter connected at output means thereof to electromagnetic actuating means of each of a first and a second one of the valves and at input means thereof to the output means of the quantity measuring means by way of a respective delay element.

4. Apparatus as claimed in either claim 2 or claim 3, wherein the first control device comprises a respective bistable multivibrator connected at one input thereof to the output means of the concentration detecting means to receive each said output signal of the concentration detecting means and at another input thereof to the output means of the quantity measuring means, and an AND gate connected at one input to the output means of the quantity measuring means, at a respective further input thereof to the output of the or each multivibrator, and at an output thereof to the control element of the outflow conveying means.

5. Apparatus as claimed in claim 4, wherein the first control device comprises a respective further AND gate connected at one input thereof to the output means of the quantity measuring means and at another input thereof to the output of the or each multivibrator, and a further bistable multivibrator connected at input means thereof to the output means of the quantity measuring means, the indicating means being operable by output signals of the or each further gate and of the further multivibrator.

6. Apparatus as claimed in claim 5, the indicating means comprising a respective optical indicating device connected to the output of the or each said further gate and operable to provide an optical indication of deviation of the instantaneous concentration of a respective one of the components from said predetermined concentration thereof, and a respective optical indicating device connected to an output of the further multivibrator and operable to provide an optical indication of a predetermined maximum quantity of liquid mixture in the vessel.

7. Apparatus as claimed in claim 6, wherein each of the indicating devices comprises a light-emitting diode, the diodes being arranged in a control panel.

8. Apparatus as claimed in any one of the preceding claims, the concentration detecting means comprising an areometer to provide output signals indicative of densities of the liquid mixture influenced by a chemical additive component and an alcohol additive component.

9. Apparatus as claimed in any one of claims 1 to 7, the concentration detecting means comprising a first areometer to provide an output signal indicative of the density of the liquid mixture influenced by a chemical additive component and a second areometer to provide an output signal indicative of the density of the liquid mixture influenced by an alcohol additive component.

10. Apparatus as claimed in any one of the preceding claims, the quantity measuring means comprising a float responsive to the filling level of the vessel and a switch operable by the float to provide output signals respectively indicative of a predetermined minimum and a predetermined maximum filling level of the vessel.

11. Apparatus as claimed in any one of claims 1 to 9, the quantity measuring means comprising a delay element and a timing element connected at input means thereof to output means of the delay element, and means being provided to interlink signals of those elements with a signal of a control device for the outflow conveying means.

12. Apparatus substantially as hereinbefore described with reference to the accompanying drawing.

1 3. An offset printing machine comprising apparatus as claimed in any one of the preceding claims for preparation of a moistening agent for a moistening mechanism of the machine.