EP1245291B1 - Valve unit for an electrostatic coating installation - Google Patents

Abstract

A main needle valve for an electrostatic sprayer has an optoelectronic sensor device with light wave conductors (20,21) with their front surfaces facing a reflex element (12) for a structural link (10) moved by the valve needle (1), which is remotely controlled to slide between two indexing positions. The optoelectronic sensor senses an indexing position and generates a corresponding sensing signal.

Description

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

In known electrostatic rotary or air atomizers of this type (DE 4306800 A and Dürr / Behr "EcoGun ESTA"), the paint line is opened and closed at the entrance to the atomizer with a paint needle valve, the so-called main needle valve, the valve needle of the piston of a pneumatic valve drive is pulled under control by the parent program control system of the coating system from the closed position against the force of a return spring in the open position.

For the higher-level system control feedback is desired at least one and preferably both switching positions of the main or paint needle valve. For example, in non-electrostatic air atomizers, it was possible and common to produce the desired switching position signals with mounted on the valve drive Hall sensors or inductive sensors. However, these electrical sensors can not be used in electrostatic atomizers that are under high voltage during operation. Although a switching position query would also be important here, there was no feasible option for this.

The detection of the switching position of a valve needle for controlling the color flow on the one hand to monitor the switching function by feedback and on the other hand also for valve control. By detecting the time between the drive signal a valve needle and the feedback of the switching position change and the comparison with a predetermined setpoint operational deviations (eg by component wear) can be detected and compensated control technology. As a result, a better constancy of the process sequences is possible especially in painting robots that work with high coating speeds and frequent switching on / off of valve needles.

Although there are also pneumatic sensors for interrogating the switching position of valves, which are too slow for the dynamic processes considered here.

From EP-A-0 846 498, for example, an electrostatic atomizer with an example optical sensor for the valve position of the atomizer is known. The sensor is arranged on a displaceable with the valve needle of the atomizer sensor bolt. The signal from the sensor is intended to indicate open-close as well as intermediate positions of the movable valve body and may be used by a signal processor for diagnostic purposes.

From GB-A-2 159 942 an optical switch position sensor with optical fibers for fluid valves is known in which the amount of light transmitted from a transmitter to a receiver changes with the switching position.

From US-A-4 356 397 a device for monitoring the switching position of valves is also known in which a magnet arranged on a displaceable valve stem rotates a polarizer and analyzer arrangement located in the light path between two optical waveguides.

The invention has for its object to provide a valve unit whose switching position is interrogated as quickly as possible even under high voltage.

This object is solved by the features of claim 1.

By the invention, a potential-free and therefore also suitable for electrostatic atomizer switch position signaling is possible, for example, for Hauptnadelabfrage. The switching position of other valves in an electrostatic atomizer or in other high-voltage components of a coating system can also be interrogated in the manner described here. The valve may, for example, also be a diaphragm valve.

Fig. 1

den Rotationszerstäuber mit der Ventileinheit; und

Fig. 2 und Fig. 3

zwei abgewandelte Ausführungsformen.

The invention is explained in greater detail in the electrostatic rotary atomizer for direct charging of the coating material shown in the drawing as an exemplary embodiment. Show it

Fig. 1

the rotary atomizer with the valve unit; and

Fig. 2 and Fig. 3

two modified embodiments.

The atomizer shown in Fig. 1 has the usual main needle valve with the valve needle 1 for opening and closing the opening in the atomizer 4 color channel 2. The valve needle is along its axis in the color channel 2 containing coaxial color tube 3 slidably. For the valve actuation, a pneumatic valve drive with a piston 6 is provided, which is acted upon to open the main needle valve at 7 with compressed air and consequently attached to it valve needle 1 against the force of acting on its back compression spring 8 in the drawing to the right in the the atomizer bell 4 opposite direction pulls. In that regard, the atomizer is known per se. In operation, the entire paint conduit system of the nebulizer may be at a high voltage potential of the order of, for example, 100 kV.

On its rear side facing away from the valve needle 1, a plunger or shaft member 10 is attached to the piston 6, which can be arranged coaxially with the valve needle 1, for example within the compression spring 8. Expediently on the circumference of its end part 11 facing away from the piston 6, the shank member 10 has an optically reflecting surface element 12 as shown. The reflecting surface of the element 12 can be flat and extend around the entire circumference of the end portion of the shank which is quadrangular in cross section, for example.

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

The shaft 10 is displaceable in a recess 14, which is coaxial with the needle axis, of the valve housing and into which an opening 15 extends radially through the housing, ie transversely to the needle axis. In the opening 15 sits a holding and positioning body 17 for two optical waveguide units 20 and 21, the optical end faces with the inner wall of the recess 14 are aligned at the two points where the reflective element 12, 12 'is located at the two switching positions. Thus, when the main needle valve is closed, the reflective element lies closely adjacent to the end face of the optical waveguide unit 20 and, when the valve is open, faces the end face of the unit 21. The mutual distance of the central axes of the units 20, 21 corresponds to the valve needle H. As a result, the two switching positions can be signaled by light signals, which arise when light supplied by the relevant optical fiber unit from the outside, from the element 11, 11 'and reflected by the same Fiber optic unit (or possibly another optical fiber) is returned to an opto-electronic sensor (not shown), which may be located outside the high voltage range.

For the purpose described, suitable optical waveguide sensor systems are known and require no further description.

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

The switching position query can also be done at other locations of the valve needle itself or a sliding member with her.

Further, in some cases, a single fiber optic unit may satisfy only one of the two switch positions.

Instead of the radial arrangement of the optical waveguides of the illustrated embodiment, it is also possible to arrange an optical waveguide axially along the shaft member whose switching position is detected by different degrees of reflection.

Another variant is the arrangement of at least one opto-electronic light barrier, for example on the shaft member 10 for potential-free query one or both switch positions. Fig. 2 shows an embodiment guide with two radially on opposite sides of the shaft member aligned with each other arranged optical waveguides LWL1 and LWL2. In the illustrated switching position, the conductor LWL2 from the conductor LWL1 sent light pulses to the opto-electronic converter, while in the other position, the shaft member end closes the photocell. On the other hand, in the embodiment according to FIG. 3, both switching positions can be actively interrogated, since a bore 30 is provided radially through the shaft member and positioned between two mutually aligned optical waveguides LWL1, LWL2 or LWL1 ', LWL2'.

According to another possibility (not shown), the main needle valve shown in the drawing can be modified such that at least one magnetically active transmitter element is arranged on or in the displaceable shaft member 10, eg instead of the reflecting element 12 in FIG. 1 or the bore 30 in FIG FIG. 3. In this modification, at least one sensor element which uses the magneto-optical Faraday effect or Kerr effect and which contains an optical polarization device with an analyzer is used as the sensor device arranged to interrogate the switching position on the displaceable shaft member. The donor element may be a permanent magnet, or else an element of iron or other material with ferromagnetic properties, with which the magnetic field of a magnetic element contained in the sensor element is variable. By approaching the encoder element which is displaced with the shaft member 10, the polarization direction of light conducted through the polarization device in the sensor element can be rotated in order to generate a light signal. An optical waveguide device connected to the polarization device leads to a remote electronic device located outside the high-voltage region for generating an electrical signal corresponding to the light signal. The sensor element may include a reflector which redirects the light coming from the polarization device to the analyzer, wherein a refraction element (Faraday effect element) or a prism is located between the polarization device and the reflector and an optical fiber for the sensor element to the polarization device supplied light and to the analyzer, a light guide for the light supplied to the remote electronic device are connected. Such optical sensors are known per se and commercially available. In the case described here, however, they have the special and surprising advantage that they can work under high voltage without problems. Depending on expediency here can or two sensors may be arranged, for example, at the locations of the optical fibers 20 and / or 21 in FIG. 1.

In particular, when only one optical waveguide unit is arranged on the displaceable shaft member 10 and, for example, the second optical waveguide 21 in FIG. 1 or the second unit with the optical waveguides LWL1 ', LWL2' in FIG. 3 are to be saved, it may be expedient that at the displaceable shaft member 10 are provided two spaced in the displacement direction signal generating elements, of which the first element triggers a binary signal of the sensor device when the valve needle 1 is in its one switching position, while the second signal generating element triggers a binary signal of the sensor device when the valve needle. 1 is in its other switching position. According to Fig. 1 and Fig. 3, the two signal generating elements may be formed by reflective surfaces, between which there is a non-reflective or less reflective surface, or by spaced light barrier openings. An embodiment with two spaced apart in the shaft member 10 permanent magnet or magnetically effective donor elements for the above-described Faraday effect or Kerr effect sensor system is possible.

The binary signals respectively triggered by the sensor at the two switching positions expediently have the same binary value. The binary signals are generated by the electronic sensor device located outside the high voltage region at a location remote from the valve and connected to the valve unit via the optical fiber array. When the shaft member 10 is displaced between its two positions, the sensor signal initially changes to the opposite binary value due to the region lying between the two signal generating elements before the first binary value is generated again when the other valve position is reached. With the help of an electronic control device it can be determined whether, for example, after 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 is generated as a message of the other valve position. If this is not the case, there is a fault that is signaled by an alarm signal.

Claims (13)

1. Valve unit for an electrostatic installation for the series coating of workpieces,
   with a valve which can be switched over by remote control and of which the movable valve member (1) is displaceable between two switching positions and in one switching position frees the path for a medium flowing through the valve whilst the valve is closed when the valve member (1) is located in its other switching position,
   in particular for an atomiser which is at high voltage in operation,
   wherein for querying the switching position of the valve and for generation of a corresponding query binary signal an opto-electronic sensor device with at least one optical waveguide (20, 21) is provided on a structural element (10) which is displaceable with the valve member (1) or forms a part of the valve member,
   characterised in that by means of an electronic monitoring device it is ascertained whether the binary signal appears within a predetermined time after the generation of a control signal for switching over the valve, and that otherwise an alarm signal is generated.
2. Valve unit as claimed in Claim 1, characterised in that the displaceable structural element (10) has at least one optically reflecting surface (12) which is positioned opposite the sensor surface of the optical waveguide (20, 21) when the valve member (1) is located in its switching position to be reported.
3. Valve unit as claimed in Claim 1 or 2, characterised in that an opto-electronic sensor device with at least one optical waveguide (20, 21) in each case is provided for each of the switching positions.
4. Valve unit as claimed in any one of Claims 1 to 3, characterised in that the movable valve member (1) is the valve needle of a needle valve.
5. Valve unit as claimed in Claim 4, characterised in that the displaceable structural element (10) is a stem member which is attached coaxially to the piston (6) of the pneumatic valve drive and is displaceable in a recess (14) of the valve housing into which an opening (15) for the optical waveguide(s) (20, 21) leads which is radial with respect to the needle axis.
6. Valve unit as claimed in any one of Claims 1 to 3, characterised in that the movable valve member is connected to the diaphragm of a diaphragm valve.
7. Valve unit as claimed in Claim 1, characterised in that the optical waveguides (LWL1, LWL2) form at least one light barrier for the structural element (10).
8. Valve unit as claimed in Claim 1, characterised in that a magnetically acting transmitter element is disposed on or in the displaceable structural element (10),
   that a sensor element is provided which contains an optical polarising device,
   that due to the approach of the transmitter element the polarisation of light passed through the polarising device is changed magneto-optically in the sensor element for the generation of a light signal,
   and that an optical waveguide arrangement which leads to a remote electronic device for the generation of an electric signal corresponding to the light signal is connected to the polarising device.
9. Valve unit as claimed in Claim 8, characterised in that the sensor element contains a reflector by which the light coming from the polarising device is led back to an analyser of the polarising device, wherein between the polarising device and the reflector there is located a refracting element or prism which rotates the polarising device, and that a light guide for the light supplied to the sensor element and a light guide for the light supplied to the electronic device are connected to the polarising device.
10. Valve unit as claimed in any one of the preceding claims, characterised in that on the displaceable structural element (10) there are provided two signal generating elements which are spaced from one another in the direction of displacement and of which the first element emits a binary signal from the sensor device when the valve member (1) is located in one of its switching positions, whilst the second signal generating element emits a binary signal from the sensor device when the valve member (1) is located in its other switching position.
11. Valve unit as claimed in Claim 10, characterised in that the two signal generating elements of the displaceable structural element (10) are formed by optically reflecting surfaces.
12. Valve unit as claimed in Claim 10, characterised in that the two signal generating elements are formed by light barrier openings.
13. Valve unit as claimed in any one of Claims 10 to 12, characterised in that the two binary signals have the same binary value, and that the sensor signal from the sensor device is switched over to the opposite binary value when the displaceable structural element (10) is displaced between its two positions.

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