APPARATUS FOR APPLYING A LIQUID MATERIAL AND METHOD FOR DETERMINING A FUNCTION USED TO OPERATE THE APPARATUS

Abstract

Provided is an apparatus for applying a liquid material to a plurality of parts, wherein the apparatus comprises at least a first gun through which the material can be applied to the parts; a reservoir for holding the material, the reservoir being fluidically connected to the first gun; a pressure system for providing a gas pressure acting on the material located in the reservoir, the pressure system having a pressure regulator, by which the gas pressure acting on the material can be adjusted, and a pressure sensor for detecting the gas pressure acting on the material; a temperature sensor for detecting the temperature of the material; and a control unit in which a material-specific function is stored which specifies a setpoint value for the gas pressure which depends on the detected temperature of the material. The invention also provides a method to determine the material-specific function.

Claims

1. An apparatus for applying a liquid material to a plurality of parts, said apparatus comprising: at least a first gun through which the material can be applied to the parts; a reservoir for holding the material, the reservoir being fluidically connected to the first gun; a pressure system for providing a gas pressure acting on the material located in the reservoir, the pressure system comprising a pressure regulator by means of which the gas pressure acting on the material can be adjusted, and a pressure sensor for detecting the gas pressure acting on the material; a temperature sensor for detecting temperature of the material; a control unit in which a material-specific function is stored which specifies a setpoint value for the gas pressure which depends on detected temperature of the material.

2. The apparatus according to claim 1, wherein the material-specific function outputs setpoint values which become smaller as the detected temperature of the material increases.

3. The apparatus according to claim 2, wherein the function is a straight line.

4. The apparatus according to claim 1, wherein the temperature sensor is arranged in the reservoir and detects the temperature of the material located in the reservoir.

5. The apparatus according to claim 1, wherein the control unit determines a signal from a difference between the setpoint value and the detected gas pressure, and with the signal the pressure regulator can be actuated.

6. The apparatus according to claim 1, comprising at least one second gun, wherein the reservoir for holding the material is fluidically connected to the second gun.

7. The apparatus according to claim 6, wherein the first gun and the second gun are connected to a gun carrier which is rotatably mounted about a main axis of rotation.

8. The apparatus according to claim 7, wherein the reservoir or at least a part of the reservoir is fixed and rotatably connected to the gun carrier.

9. The apparatus according to claim 7, wherein the gun carrier is connected in a rotationally fixed manner to a rotary plate which comprises a first part carrier and a second part carrier, the first part carrier being assigned to the first gun and the second part carrier being assigned to the second gun, the first part carrier and the second part carrier each mounted rotatably about their own axis of rotation.

10. A method for determining the material-specific function for the control unit of the apparatus according to claim 1, wherein different temperatures of the material are predetermined via a heat unit and the gas pressure, depending from the predetermined temperature, is set in such a way that a film weight per part emitted by the first gun is the same for the different temperatures in each case, wherein the function is determined on the basis of the set gas pressures and the predetermined temperatures.

11. The method of claim 10, wherein the heat unit comprises a double tube having an inner tube and an outer tube that encloses the inner tube; wherein the material is passed through the inner tube to the first gun and wherein through the outer tube a heat medium, which is heated or cooled the material, is passed.

12. The method of claim 11, wherein the temperature between the double tube and the first gun is detected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the following, the invention is explained in more detail by means of an exemplary embodiment and with reference to the attached figures. In the figures:

[0027] FIG. 1 shows an apparatus for applying a liquid material according to the invention in schematic view;

[0028] FIG. 2 shows a schematic view of a control circuit useful with the apparatus of FIG. 1; and;

[0029] FIG. 3 shows a schematic system for determining a function for a control unit of the apparatus of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0030] FIG. 1 schematically shows an apparatus 1 for applying a liquid material to a plurality of parts 100, in this case in the form of round metal can lids for example for food cans, beverage cans or beer cans. The apparatus 1 comprises a gun carrier 10 which is rotatably mounted about a main axis of rotation 2. A rotary plate 20 for receiving the parts 100 is non-rotatably connected to the gun carrier 10. Accordingly, the gun carrier 10 and the rotary plate 20 form a group which can rotate about the main axis of rotation 1.

[0031] The gun carrier 10, which is preferably substantially rotationally symmetrical, has retaining arms 11 for a first gun 30a and for a second gun 30b, respectively. The first gun 30a and the second gun 30b are intended to be representative of a plurality of guns which are uniformly distributed around the circumference of the gun carrier 10. The gun 30a is to be associated with a first part carrier 21a, which is rotatably mounted about its own axis of rotation 3. The gun 30b is associated with a second part carrier 21b, which can also rotate about its own axis of rotation. During operation of the apparatus 1, the assembly of the gun carrier 10 and the rotary plate 20 rotates about the main axis of rotation 2. At the same time, the part carriers 21a, 21b and the parts 100 arranged thereon rotate about the respective axis of rotation 3. During the rotation about the main axis of rotation 2, uncoated parts are continuously fed to the apparatus 1 and coated parts are continuously discharged.

[0032] A counter pad which presses the part 100 against each part carrier is not shown in FIG. 1. A proximity sensor can be installed below the counter pad for the detection of the part 100. If the proximity sensor indicates the presence of a part, the respective gun 30a, 30b receives an opening signal which opens a nozzle in the gun. Without any opening signal the gun 30a, 30b remain closed.

[0033] The apparatus 1 comprises a reservoir 40 in which the material to be applied is stored. In the embodiment shown here, the reservoir 40 rotates with the gun carrier 10. A reservoir connection 41 is provided between the reservoir 40 and the gun carrier 10 and connects the reservoir 40 with the gun carrier 10. From the reservoir 40, the material is directed to the individual guns 30a, 30b via pressure lines 12.

[0034] A pressure system 50 of the apparatus 1 ensures that the material in the reservoir 40 is under a certain gas pressure or air pressure. The pressure system 50 comprises a pressure regulator 51 and a pressure sensor or gauge 52, which measures the pressure in a pressure conduit 53 between the pressure regulator 50 and the reservoir 40. The pressure regulator 51 is supplied with compressed air 4 from a compressed air system not shown here. The pressure regulator 51 and the pressure sensor 52 can be part of a single device.

[0035] The apparatus 1 further comprises a control unit 60, which is connected to the pressure regulator 51 via a signal line 61. In addition, a signal line 62 is provided between the pressure sensor or manometer 52 and the control unit 60. A signal line 63 connects the control unit 60 to a temperature sensor 70 arranged in the reservoir 40. The temperature sensor 70 measures the temperature of the material located in the reservoir 40.

[0036] The tasks of the control unit 60 are explained with reference to FIG. 2. FIG. 2 shows a control circuit for a set pressure pD. During operation of the apparatus 1, the control unit 60 receives a signal or a measured temperature value T from the temperature sensor 70. A function f(T) stored in the control unit (see transmission block 65) converts the measured temperature T into a setpoint value pD for the gas pressure/air pressure. The control unit 60 then compares this setpoint value pD (desired pressure) with a measured pressure pR (real pressure) and calculates a difference p between these two pressure values. From the pressure difference p, the control unit 60 determines a signal (see transmission block 64) and sends this to the pressure regulator 51. In the control circuit of FIG. 2, the pressure regulator 51 is represented by a transmission block 51.sup.I, where the transmission block 51.sup.I represents the conversion of the signal received from the control unit into a pressure value.

[0037] A way of determining the function f(T) stored or programmed in the control unit according to the invention is explained with reference to FIG. 3. Components which are similar or identical to the components in FIG. 1 are given the same reference signs.

[0038] A heat unit 80 may include a double tube 81, shown here only schematically, having an inner tube and an outer tube encasing the inner tube. The inner tube is connected to or forms part of the conduit 12, and material from the reservoir 90 passes through the conduit 12 and the inner tube to the first gun 30a. The gun 30a is a gun of the apparatus 1 or at least a gun of identical construction.

[0039] A heat medium, preferably heated water, flows through the outer tube. The water allows the material flowing through the inner tube of the heat unit to be heated or, if cooling water is used, to be cooled. The arrow 82 is to represent the water entering the outer tube. The arrow 83 denotes the outgoing water. With a temperature sensor 71, which is here arranged between the heat unit 80 and the first gun 30a, the temperature of the material before entering the gun 30a can be measured.

[0040] The reservoir 90 may be a reservoir being distinct from the reservoir 40 of the apparatus 1. However, the reservoir 90 may also be or represent the assembly consisting of the reservoir 40 and the gun carrier 10 of the apparatus 1.

[0041] The material can be heated (or cooled) to a certain temperature via the amount and temperature of the incoming water 82. In the method according to the invention, when determining the function f(T), a certain target film weight is predetermined, which expediently corresponds to the film weight with which the parts 100 are to be coated by the apparatus 1. Given the temperature and the predetermined target film weight or application amount, adjustment means 54, which may be a manual actuator, is used to adjust the pressure regulator so that the desired target application amount is obtained at the gun 30a. The temperature and the adjusted gas pressure detected by the pressure sensor constitutes a first pair of values I. By changing the parameters of the incoming water 82, the material can be brought to further different temperatures. In each case, the gas pressure must be re-adjusted so that the specified target film weight is again obtained. Thus, further pairs of values II to VI (any number of pairs is possible) can be formed, from which a function f(T) can then be calculated via a regression analysis. This function f(T), which has its validity only for a specific material, can be stored in the control unit 60 of the apparatus 1. For another material with different properties, in particular with regard to the temperature-dependent viscosity, the procedure described above must be carried out again.

LIST OF REFERENCE SIGNS

[0042] 1 apparatus [0043] 2 main axis of rotation [0044] 3 rotation axis [0045] 4 compressed air [0046] 10 gun carrier [0047] 11 retaining arm [0048] 12 conduit [0049] 20 rotary plate [0050] 21 part carrier (21a first part carrier; 21b second part carrier) [0051] 30 gun (30a first gun; 30b second gun) [0052] 40 reservoir [0053] 41 reservoir connection [0054] 50 pressure system [0055] 51 pressure regulator [0056] 51.sup.I transmission block for pressure regulator 51 [0057] 52 pressure sensor/manometer [0058] 53 pressure conduit [0059] 54 adjustment means [0060] 60 control unit [0061] 61 signal line [0062] 62 signal line [0063] 63 signal line [0064] 64 transmission block [0065] 65 transmission block [0066] 70 temperature sensor [0067] 71 temperature sensor [0068] 80 heat unit [0069] 81d double tube [0070] 82 incoming water [0071] 83 outgoing water [0072] 90 reservoir [0073] 100 part