DE1232047B - Device for optional electrostatic spraying of coating material - Google Patents

Description

Device for optional electrostatic spraying of coating material The invention relates to a device for the electrostatic spraying of coating material on workpieces with one applied to one pole of the electrostatic field Atomizing nozzle arrangement optionally through one of several supply lines for different Coating materials is supplied, with shut-off devices for the flow of the supply lines are provided.

A major problem occurs in the low consumption of the coating material and the high quality of the coatings produced, electrostatic Spray technique occurs when, for example, one color changes over to the other target. This is very common especially in mass production when of a workpiece color to be passed on to the other, as z. B. in the automotive industry occurs all the time.

The present invention is based on the object of a simple Way to create a centrally operated arrangement that is suitable for a fully or partially automatic Program control is suitable and takes up little space in the actual work area.

From the German patent specification 884 326 a non-electrostatic spray gun intended for spraying water, air and a solvent is known, which has the possibility of changing the liquid. This gun has several feed lines and in each one a pressure-actuated valve which releases the connection to a channel leading to the nozzle. A pressure member is adjustable so that it releases one or the other or more of the supply lines depending on its rotational position. This device is not suitable or intended as an automatically controlled device for coating with several colors in mass production. Each time after changing the spray material, the liquid in the supply line to the nozzle that was previously sprayed is still sprayed out.

Further, a manually operated shift mechanism for the well-known known in the hand-held compressed air spray guns, various colors in which the gun may be fed Patent 2,257,004 USA. from. The color change mechanism is connected to the hand spray gun by a single, relatively long feed line and has levers that can be operated by hand. If the person handling the spray gun wants to supply a different color, he turns one lever in order to close the valve in the paint line leading to the spray gun. The other lever is then turned by hand to adjust the mechanism so that one of the solvent lines is connected to the gun. The first lever is then moved to open the valve in the solvent line to the gun for cleaning purposes. The second lever then adjusts the mechanism so that another paint line is connected to the gun. Finally, the gun operator turns the first lever to open the valve in that new paint line, thereby feeding the paint from that line to the gun. Even with this device, which is very complicated in structure, the solvent in the line to the gun must first be sprayed after each color change. For this reason alone, this device is not suitable for automating the color change process. Furthermore, the loss of color and solvent when changing color is great.

Another known from German patent application S323621b / 75a System for paint spraying with a color change option has a control device with valves. The control device is manually operated to supplied from a plurality of paint sources to a plurality of spray guns Change color. This device is also not designed for automatic color change suitable, and with each change there must be a very long colored line in which the pistols lie in a row, first blown dry by paint and then by solvent.

The invention avoids the disadvantages of the known devices and provides a facility suitable for automatic or push button operation of the type outlined above in that the atomizing nozzle arrangement for each Supply line has a separate nozzle connected to this, that the nozzles are optional individually by means of a servomotor in spray position opposite the workpiece conveyor track can be brought and that a control for the servomotor and the shut-off devices is provided in the supply lines.

To change the color, all you have to do is switch off the nozzle that is currently spraying, the nozzle assembly rotated and the new nozzle put into operation.

The training is advantageously made so that the nozzles in a star-shaped grouping driven by an electric motor as a servomotor rotatable are stored.

A solid covering of the nozzle arrangement consisting of insulating material is advantageously provided with a jet outlet opening directed towards the workpiece conveyor track and laterally delimited by auxiliary electrodes. This covering renders any early or late insertion or stopping of the C nozzle, which is to be put into operation or switched off, harmless.

An embodiment of the invention is shown in the drawing. It shows Fig. 1 the plan of a coating system according to the invention, F i g. 2 shows a side view of the system according to FIG. 1, Fig. 3 shows a circuit diagram of the control device for the system according to FIGS. 1 and 2.

In the case of the coating device according to FIGS. 1 and 2, the atomizing device comprises a plurality of compressed air spray guns 60 which are arranged around a central hub 61 like the spokes of a wheel. A particular spray gun 60 is used for each color or type of liquid coating material to be sprayed. In the F 1 g. 1 shows eight such pistols. However, the control device will be described below only with reference to three of the spray guns - 60 a, 60 b and 60 c - described.

The hub 61 is attached to the upper end of a shaft 62 made of an insulating material. The lower end of the shaft 62 rotates in a bearing 63. The spray guns 60, hub 61 and shaft 62 are located within a cylindrical housing 64 made of insulating material. The upper end of the housing 64 is provided in an arc of about 451 with an opening 64 a, which is located directly opposite a conveyor track 65; the latter guides the objects 68 to be coated past the spray device.

The objects 68 are grounded by means of the conveyor track 65. The spray guns 60 are kept under a high voltage, on the order of 100 kilovolts, via the hub 61, which is connected to a high voltage source 73 by means of a spring 72 . Two parallel electrode wires 74, which are arranged on opposite sides of the opening 64 a, are also held by direct connection to the high voltage source 73 at a potential of about 100 kilovolts.

Each spray gun 60 has a special paint spray line 75 and a special compressed air line 76. These lines are flexible and of sufficient length that the shaft 62 can complete approximately one full revolution in each direction without damaging the lines. The flow of paint and compressed air to lines 75 and 76, respectively, for each spray gun is controlled simultaneously by a pair of shut-off valves 77 and 78, respectively, mounted adjacent to bearing 63. Each pair of valves 77, 78 is controlled by a single color and air solenoid 79 simultaneously.

The position of the spray guns 60 is changed by rotating the shaft 62 about its longitudinal axis. The rotation of the shaft 62 is carried out by a direct current motor 80 via a suitable gear transmission within a gear box 81. The shaft 62 can be rotated in any direction, depending on the direction of rotation of the motor 80. The operation of the motor 80 is controlled by several adjustment solenoids 82, which are arranged around the shaft 62 , a motor switch 83 which is arranged off-center on the side of the shaft 62 , and a motor switch 84 which is mounted next to the shaft 62. Each of the solenoids 82 has a spring-loaded, retracted core which protrudes into the path of the switch 83 when the solenoid concerned is energized.

A common, interconnected electrical control device, hereinafter referred to as the common control device, operates the feed control means (paint valves 77, compressed air valves 78 and motor 80) to selectively operate any pair of paint and air valves which operate a single preselected spray gun (e.g. the valves 77 a and 78 a for the spray gun 60 a), whereby the delivery of paint and air to any other spray gun is prevented, also for the purpose of setting the previously selected spray gun (for example 60a) in the cover position in the opening 64a. The common control device includes the 3 solenoid 79a, which controls the operation of the two valves 77 a and 78 a; other like color and air solenoids 79 control other pairs of color and air valves. This also includes the solenoid 82 a and other similar solenoids 82, which control the position of the spray guns 60 , as well as the switches 83 and 84, which control the rotation of the motor 80 .

The solenoids 79 and 82 and the switches 83 and 84 are interconnected by a control panel 85 which contains the mechanically operated device for setting the common operating device of the conveyor control means for a specific work sequence, namely the termination of the conveyance of paint and air to one of the spray guns Move another, previously selected spray gun into the overcoat position, then initiate the delivery of paint and air to the last-mentioned spray gun. The elements of one embodiment of the mechanically operated device are shown in detail in FIG. 3 shown. The elements built into the control panel 85 are shown in FIG. 3 is shown within the dashed line 85 , while the solenoids, the motor and the switches connected to the mechanically operated device are outside the dashed line. The mechanically operated device within the control panel 85 includes a number of push buttons PB 11 through PB 13, relays R 11 through R 18, a source of direct current 88 for operating the motor 80 and a variable braking resistor 89. Each relay has a plurality of contacts RC, some of which are normally open and some of which are normally closed. All of the aforementioned elements are operated from and connected to a 110 volt AC line as shown in FIGS. 3 shows.

In the figures, the container for the liquid überzuasmaterial and the main delivery line for compressed air are not shown, but it is assumed that the spray gun 60 a to a pressurized source for the liquid coating material A, the spray gun 60 b to a source for the material B. , the spray gun 60 c is connected to one for the material C. The conveyance of the coating material to the various spray guns 60 is controlled by a series of relays R 11, R 12 and R 13, which are initially energized by actuating the push buttons PB 11, PB 12 and PB 13. Each of these relays has three pairs of normally open contacts - RCI1, RC 12 and RC 13. The first of these contacts in each relay is connected to a holding circuit that bridges the relay control contacts of the associated pushbutton switch. The second contact pairs of the relays are in a circuit with the various setting solenoids 82 a, 82 b and 82 c, while the third contact pairs are in a circuit with the solenoids 79 , which convey the coating material and the compressed air to the various spray guns 60 taxes.

The relays R 11, R 12 and R 13 are assigned further relays R 14, R 15 and R 16 , respectively. The push button PB 11 has a second set of normally open contacts in the circuit with the relay R 14, the push button PB 12 has a second pair of normally open contacts in the circuit with the relay R 15, the push button PB 13 a second pair of normally open contacts in the circuit the relay R 16. The relays R 14, R 15 and R16 have the normally open contact pairs RC14, RC15 and RC16 connected in parallel to the supply line in series with a motor control relay R 17 . Each of the relays R 14, R 15 and R 16 also has two pairs of normally closed contacts RC14, RC15 and RC16, respectively. The circuit of relay Rll includes the normally closed, series-connected contacts RC 15 and RC 16 of relays R 15 and R 16, the circuit of relay R 12 contains the normally closed, series-connected contacts RC14 and RC16 of relays R14 and R16, and the circuit of relay R 13 contains the normally closed, series-connected contacts RC 14 and RC 15 of relays R 14 and R 15. Relay R17 is a locking relay with a bolt which, when the relay is energized, the armature of the Relay sensed to hold it in the advanced position, even after de-energizing the relay, until an associated bolt release coil is energized.

The latch release coil of relay R 17 is controlled by switch 83 which allows the current to pass when it encounters the advanced none of any of the solenoids 82. Since the push buttons PB11, PB 12 and PB 13 are normally held in the open position, and since the holding circuit associated with each of these push buttons does not bridge the contacts which control the associated relays R 14, R 15 and R 16 , the relay R becomes 17 only temporarily excited. After the relay has been de-energized, its armature is only held in the advanced position by the bolt. As a result, when the switch 83 contacts the protruding core of the solenoid 82 to release the latch, all of the contacts of the relay R 17 return to their normal position. These contacts control the operation of the motor 80 in a manner to be described below.

To prevent damage to hoses 75 and 76 for paint and compressed air, respectively, rotation of shaft 62 is limited to slightly less than 3600 . Rotation of shaft 62 must therefore be provided in both directions. The direction of rotation of the shaft 62 and motor 80 is controlled by a relay R 18 with a set of contacts RC 18 which in effect form a double pole changeover switch. The relay R 18 is of the well-known type with two windings and is so constructed that when the armature is moved to one control position by the excitation of one winding, the armature remains in that position even if that winding becomes de-energized until the other Winding is achieved. The relay R 18 is controlled by a reversing switch 84 which is attached next to the shaft 62 and is actuated by a pin, not shown here, which sits on the shaft in an eccentric position. If, in the course of the rotation of the shaft 62, the pin detects the switching element of the switch 84, the latter switches the relay R 18 and its associated contacts RC18, whereby the direction of rotation of the motor is reversed. The switch 84 and its switch pin are arranged so that the switching of the switch 84 occurs while the shaft 62 rotates to bring a new spray gun 60 into the operating position.

The circuit of motor 80 receives power from a direct current source 88. The circuit of motor 80 includes two sets of normally open contacts RC 17 which must be closed by actuation of relay R17 in order for motor 80 to start. Relay R17 also includes two sets of normally closed contacts RC 17 which are connected in series to the armature of motor 80 with a braking resistor 89 . As long as relay R 17 passes power to motor 80 , it rotates in the direction determined by the position of relay R 18 until switch 83 engages the protruding core of one of solenoids 82 , thereby locking relay R17 is released and the latter returns to normal position to interrupt the power supply to the motor-80 and to switch the braking resistor 89 into the circuit of the motor armature, which delays the coasting of the motor and the shaft 62 is quickly brought to rest.

To be sure that none of the spray guns 60 is supplied with coating material as long as the latter change position, the circuits of the feed control solenoids 79 are closed by an additional set of normally closed contacts, lle 88 antacted RC 17 of the relay 17 to the Stronique. To the mode of operation of the device according to FIGS. To explain 1 to 3 , it should be assumed that the system was brought into the steady state by pressing down the push button PB 13. In this state, the spray gun 60c is in the operating position, as shown in FIG . 1 shows, and the relay R 13 is held in the state of energization via the holding circuit which bridges the switch PB 13. Since the movement of the spray gun 60 c in the operating position actuated the switch 83 to release the armature of the relay R17, the motor 80 stands still, and the contacts RC 17 of the relay R 17, which connect the power source to the circuits of the solenoids 79 control are closed. Since the relay R 13 is energized, its contact pairs RC13 are closed in the circuit of the solenoid 82 c and the solenoid 79 c, and the solenoids are thus energized. The valves 79c due to the excitation of the solenoid 77 c and 78 c -eöffnet. Air and coating material C are conveyed c to the located in the operating position of spray gun 60 and ejected from the same as a spray, the particles of the workpiece to be deposited on the latter by the electrostatic field between the high voltage electrodes 74 and.

If you want to stop the supply of coating material C and feed another material, for example A, then the switch PB 11 is temporarily closed to energize the relays R 11 and R 14. The energization of relay R 14 opens normally closed contacts RC14 in the circuit of relay R13, thereby de-energizing the latter and opening its normally closed contacts RC13 to break the holding circuit around switch PB13 and de-energize solenoids 79c and 82c . Thus hears the supply of coating material C to the spray gun 60 c, and the No of the solenoid 82c is retracted. Energizing relay R14 also closes contacts RC14 in the circuit with relay R17, starting motor 80 and rotating spray gun adjustment shaft 62 . Although the energization of the relay R 14 is only temporary, so that the relay R 17 is only temporarily energized, the latch of the latter keeps the contacts RC 17 closed in the motor circuit and the motor continues to rotate. The excitation of the relay R 11, which occurs by closing the switch PB 11 together with the excitation of the relay R 14, completes the holding circuit around the switch PB 11 to keep the relay Rll energized; likewise, contacts RC 11 in circuit with solenoid 82a are closed to advance the solenoid. The contacts RC 11 in the circuit with the solenoid 79 a close at this point in time, but without any effect, since the contacts RC 17 connected in series with them were opened at the same time by the excitation of the relay R 17.

Assuming that the shaft can rotate far enough 62, to bring the spray gun 60 a into the operating position without triggering the switch 84, the motor 80, the spray gun further rotates until 60a of the operating position at the opening 64a approaches and the switching element of the switch 83 detects the protruding core of the solenoid 82a. When this occurs, the armature of the relay R 17 is free to open the motor circuit and to close the motor braking circuit, with the result that the spray gun 60a comes to rest in the operating position. When the relay R 17 is released , the contacts RC17 close in the circuit with the solenoid 79 a in order to excite the latter via the associated and previously closed contacts RCII. When the solenoid 79a is energized, the valves 77a and 78a are opened and the coating material1A is now sprayed from the spray gun 60a, which is in the operating position.

If it is then desired to coat the objects with material B, the pushbutton PB 12 is pressed to energize relay R 12 and temporarily relay R 15 . The normally closed contacts RC 15 of the relay R 15, which are connected in series with the relay R 11 , open temporarily to switch off the spray gun 60 a. The relay R 17 is latched by the temporary closure of the normally open RC15 of the relay, which is connected with the relay R17 in series, again. The normally closed relay contacts RC17, which are connected in series with the supply line, are opened and locked in order to de-energize all paint and compressed air solenoids when the spray guns are set again.

At the same time, the normally closed relay contacts RC 17, which are connected in series with the resistor 89 , are opened and the normally open contacts RC 17 between the direct current source 88 and the motor 80 are closed to supply the armature of the motor 80 with current. The normally open contacts RC 12 b with the Einstellsolenoid 82 are connected in series, close to the solenoid 82 to excite b. The motor 80 rotates the shaft 62 until the spray gun 60 b is in the operating position at the opening 64 a. Then, the motor is made currentless 80 b through contact between the switch 83 and the pin of the Einstellsolenoids 82nd This unlocks the relay R17 so that the normally closed contacts RC 17, which are connected in series with the solenoids 79, close; the coating material B is fed to the spray gun 60 b and atomized by the same.

If the switch 64 is triggered when a selected spray gun 60 is brought into the operating position, the relay R 18 and its contacts RC 18 are switched to reverse the motor 80 and the shaft 62. The shaft then rotates in the opposite direction until the previously selected spray gun has reached the operating position.

Claims (3)

Patent claims: 1. Device for the electrostatic spraying of coating material on workpieces, in which an atomizing nozzle arrangement applied to one pole of the electrostatic field is optionally supplied by one of several supply lines for different coating materials, with shut-off devices being provided for the flow of the supply lines, characterized in that, that the atomizing nozzle arrangement (60, 61) for each supply line (75) has a separate nozzle (60) connected to it, that the nozzles (60) can optionally be brought into the spraying position individually by means of a servomotor (80) opposite the workpiece conveyor track (65) and that a control (82, 83, 84, 79) for the star motor (80) and the shut-off device (77) is provided in the supply lines. 2. Device according to claim 1, characterized denotes Ge, that the nozzles (60) are rotatably driven in a star-shaped array of an electric motor (80) as actuator. 3. Device according to claim 1 or 2, characterized by a solid covering of insulating material (64) of the nozzle arrangement, which has a beam outlet opening directed towards the workpiece conveyor track (65) and laterally limited by auxiliary electrode wires (74). Documents considered: German Patent No. 884 326; German interpretation document S 32362 Ib / 75 a (published on December 8, 1955); USA. Pat. No. 2,257,004.