Valve unit for an electrostatic coating installation

The invention relates to a valve unit according to the preamble of claim 1 in particular for the operation under high voltage atomizer for the series coating For example, vehicle bodies.

In known electrostatic rotary or air atomizers this type (DE 4306800 A or Dürr / Behr "EcoGun ESTA") is the color line at the entrance to the atomization device with a Needle valve is opened and closed, the so-called Main needle valve whose valve needle from the plunger of a pneumatic valve actuator under the control of the parent Program control system of the coating system from the Closed position against the force of a return spring in the Open position is drawn.

For the supervisory control system is a feedback at least one and preferably two switching positions of the Main or paint needle valve desirable. For example, in no electrostatic air atomizers it was possible and usual, the desired shift position signals with the valve drive mounted Hall sensors or inductive sensors produce. These electrical sensors may not in electrostatic Atomisers are used, which during the Operation are under high voltage. Although here a Switching position sensing would be important for there was so far no realizable possibility.

The detection of the switching position of a valve needle for controlling of the ink flow takes place on the one hand for monitoring the Switching function through feedback and on the other hand to Valve control. By detecting the time between the start signal a valve needle and the feedback of the switch position change and the comparison with a predetermined Setpoint can operational deviations (for example, by component wear) recognized and compensated control technology will. This is particularly important in painting robots, the high Coating rates and frequent switching on / off Valve pins work better constancy of process sequences possible.

Although there are pneumatic sensors for interrogating the Shift position of valves, but the consideration for the here dynamic processes are too slow.

The invention is accordingly the object of providing a valve unit indicate their switching position even under high voltage is possible delay queried.

This object is solved by the features of the claims.

By the invention, a potential-free and therefore also for electrostatic sprayers suitable switch position signaling for example, allows for the main needle query. Also, the shift position other in an electrostatic under high voltage atomizer or in other Ingredients of a coating system befindlicher valves can be queried in the manner described herein. The valve may, for example, also be a diaphragm valve act.

At the illustrated embodiment as in the drawing electrostatic rotary atomiser for direct charging of Coating material, the invention is explained in detail. It show <dl tsize="17"><dt>Fig. 1</dt><dd>the rotary atomizer with the valve unit; and</dd><dt>Fig. 2 and Fig. 3</dt><dd>two modified embodiments.</dd></dl>

The atomizer shown in Fig. 1 has the usual main needle valve with the valve needle 1 to open and close the opening into the atomizer 4 color channel 2. The valve needle is along its axis in the containing the color channel 2 coaxial Farbrohr 3 displaced. For valve actuation is a pneumatic actuator with a piston 6 provided the opening of the main needle valve at 7 with Compressed air is applied, and consequently the attached thereto Valve needle 1 against the force of a on its back acting compression spring 8 in the drawing to the right pulls in the direction away from the atomizer 4 direction. In that regard, the atomizer is known per se. In operation, the entire color management system of the sprayer on a high-voltage potential in the order of magnitude of for example 100 kV are.

At its rear side remote from the valve needle 1 is at the Piston 6 a ram or shaft member 10 attached, the same axis with the valve needle 1, for example, within the Compression spring 8 can be arranged. Suitably the extent of his the piston 6 facing away from the end portion 11 has the shaft member 10 is shown having an optically reflective surface element 12. The reflective surface of the element 12 may be planar be and, for example, the entire circumference of the cross section quadrangular end portion of the shaft extend.

This is provided with the reflective element 12 end 11 is in the drawing in the two switching positions of the main needle valve shown. At 11, 12 are in the (left) To see closed position, at 11 ', 12' in their (right) valve opening position. The needle stroke H between these two can switch positions for example, about 5 mm.

The shaft 10 is in a coaxial to the needle axis recess 14 of the valve housing displaceable, into which a radial, ie transversely to the needle axis through the housing extending opening 15 leads. In the opening 15 is located a support and positioning body 17 for two optical fiber units 20 and 21, their optical end faces with the inner wall of the recess 14 are flush at the two points where the reflective element 12, 12 'in the two switching positions is. Thus, the reflective element is closed Main needle valve closely adjacent the face of the Optical waveguide unit 20 and with the valve open the Face of the unit 21 against. The mutual distance the central axes of the units 20, 21 corresponds to the valve needle H. Consequently, the two switching positions be reported by light signals, which occur when light supplied through the optical fiber unit in question from the outside, reflected by the element 11, 11 'and by the same A light guide unit (or possibly another optical waveguide) to an opto-electronic sensor (not shown) is returned, the outside of the high-voltage range may be located.

For the purpose described suitable fiber optic sensor systems are known per se and require no further Description.

Instead of the illustrated arrangement of the reflective surface element 12 at various or all the peripheral parts of the end the shaft member 10, the desired rotational positions of the shaft allowed with respect to the optical waveguides 20, 21, is sufficient to a reflective surface only on the said optical waveguides facing peripheral part.

The switching position sensing can also elsewhere in the Valve needle itself or a sliding her Baugliedes done.

Further, in some cases, a single optical fiber unit to query only one of the two switch positions suffice.

Instead of the radial arrangement of the optical waveguide of the illustrated Embodiment, it is also possible to use a Optical fiber axially to place along the shaft member, its switching position by different strong reflection is recognized.

Another Abwa ndlungsmöglichkeit the arrangement is at least an optoelectronic photocell example to the shaft member 10 to the floating query one or both Switching positions. FIG. 2 shows an embodiment with guide two radially on opposite sides of the shaft member aligned with each other arranged optical waveguides and FOC1 FO2. In the illustrated switch position, the LWL2 sent by LWL1 light pulses to the optoelectronic conduct transducer while in the other position Shaft member end closes the light barrier. In the embodiment according to Fig. 3, however, can both switch positions be actively queried, since a radially through the shaft member leading, between two mutually aligned Optical waveguides FOC1, FO2 or FOC1 'FO2' positioned Hole 30 is present.

According to another (not shown) can possibility the main needle valve shown in the drawing to the effect be modified such that on or in the displaceable Shaft member 10 at least one magnetically active transducer element is arranged, for example, instead of the reflective element 12 in FIG. 1 or the bore 30 in Fig. 3. When the query arranged at the switching position of the displaceable shaft member Sensor device used in this modification, at least a the magneto-optical Faraday effect or Kerr effect -use sensor element an optical polarization device includes an analyzer. The transmitter element can be a permanent magnet, or a member of iron or anything else material with ferromagnetic properties, with which the magnetic field of a contained in the sensor element is changeable magnetic element. By approaching the with the shaft member 10 shifting donor element, the polarization direction of geleitetem through the polarizer Light in the sensor element for producing a light signal be rotated. One of the polarization means connected fiber optic array results in a remote, located outside the high voltage range electronic means for generating a signal to the light corresponding electrical signal. The sensor element may comprise a reflector of the said polarizing means light coming to the analyzer back passes, wherein between the polarizer and the reflector a refractive element (Faraday effect) element or a prism is and the polarization means is a light guide for the sensor element and light supplied to the analyzer a light guide for the remote electronic device applied light are connected. Such optical Sensors are known per se and commercially available. but in the case described here, they have the special and surprising advantage that they easily under high voltage can work. Depending on their suitability to a case or two sensors, for example at the positions of the light waveguides be 20 and / or 21 are arranged in FIG. 1.

In particular, if only one of the displaceable shaft member 10 A light guide unit are arranged and, for example, the second optical fiber 21 in Fig. 1 or the second unit saved with the optical waveguides FOC1 'FO2' in Fig. 3 to be, it may be expedient that sliding on the Shaft member 10 two in the direction of displacement spaced signal generation elements provided are, of which the first element is a binary signal of the sensor device triggers when the valve needle 1 in its one Shift position, while the second signal generating element a binary signal of the sensor device triggers, when the valve needle 1 in its other switching position is. According to FIG. 1 and FIG. 3, the two Signal-generating elements formed by reflective surfaces be, between which a non-reflective or less Surface is, or by spaced photocells openings. Also an embodiment with two in the shaft member 10 spaced permanent magnets or magnetically active transmitter elements for the above-described Faraday effect or Kerr-effect sensor system is possible.

Of the sensor in the two switching positions in each case triggered binary signals have the same binary value appropriately. The binary signals are from the electronic sensor device generated the remote at one of the valve Outside the high voltage range is and with connected to the valve unit via the optical fiber array is. When the shaft member 10 between its two positions is moved, the sensor signal changes due to lying of the two signal generating elements First region into the opposite binary value, before upon reaching the other valve position again the first binary value is produced. With the aid of an electronic control device it can be determined whether, for example, by Generating a control signal for switching the valve (and after the disappearance of the first binary value) within a prescribed time again the first binary value as a message the other valve position is generated. Is not the Case, there is a fault that reported by an alarm signal becomes.