Actuating system for a valve

Abstract

An actuating system for a valve which can be used as a control valve. The valve system having an outer housing, a receiving region for a switching spindle of the valve, at least one inductive sensor running in parallel to the receiving region, and at least one substantially circular cylindrical position encorder.

Claims

1. Actuating system for a valve, the actuating system comprising an outer housing adapted for connection to a valve body of the valve, the valve body containing an actuator and a switching spindle, said actuating system further comprising, and the outer housing containing,: a receiving region for receiving the switching spindle of the valve; at least one inductive sensor running in parallel to the receiving region and being arranged on a printed circuit board; a non-conductive inner housing at least partially enclosing the at least one inductive sensor and the printed circuit board, at least one position encoder, the position encoder being substantially circular cylindrical and comprising an encoder part and a connection part: the encoder part having a longitudinal axis with a circular bore running therethrough and including an electrically conductive material; and the connection part having a channel therethrough and an engagement element at one end configured to be engageable in a groove of the switch spindle; the connection part being insertable into the circular bore of the encoder part.

2. The actuating system according to claim 1, wherein a length (L.sub.41) of the encoder part is in a range of from 4 mm to 15 mm.

3. The actuating system according to claim 1, wherein the encoder part has an annular magnetic flux conductor which is wrapped with a wire made of the electrically conductive material.

4. The actuating system according to claim 1, wherein an outer diameter (d.sub.40) of the position encoder is at least twice as large as a diameter (d.sub.43) of the channel.

5. The actuating system according to claim 1, wherein the inner housing has a guide equipped to partially receive the position encoder.

6. The actuating system according to claim 1, wherein the inductive sensor has a measuring path(s) in a range of from 40 mm to 60 mm.

7. The actuating system according to claim 1, further comprising, in the outer housing, an electronic position regulator connected to the inductive sensor, and an actuating device having a port for connecting to the valve.

8. The actuating system according to claim 7 wherein the electronic position regulator is connected to a process regulator which has an interface for a sensor arranged outside the outer housing.

9. The actuating system according to claim 8, further comprising a user interface equipped to supply a position setpoint (S.sub.14) to the electronic position regulator and/or to supply a process setpoint (S.sub.16) to a process regulator.

10. The actuating system according to claim 1, wherein the switching spindle is guided by the position encoder.

11. The actuating system according to claim 10, wherein a distance (b) between a shell surface of the position encoder and the inductive sensor is at least 0.5 mm.

12. The actuating system according to claim 10, wherein the switching spindle has a connecting element with which an engagement element of the position encoder engages.

13. The actuating system according to claim 10, wherein the valve is a pneumatic valve connected to an electropneumatic actuating device of the actuating system.

14. The actuating system according to claim 1, wherein the non-conductive inner housing has a guide with a curved cross-section configured to partially receive the position encoder.

15. The actuating system according to claim 14, wherein the position encoder is positioned in the inner housing guide in such a way that the position encoder does not touch the non-conductive inner housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are shown in the drawings and explained in more detail in the subsequent description.

(2) FIG. 1 shows a schematic longitudinal depiction of a valve according to an exemplary embodiment of the invention.

(3) FIG. 2 shows a schematic view of a position encoder of a sensor element and a part of a switching spindle of the valve according to FIG. 1 from the viewing direction designated there as II.

(4) FIG. 3 shows a section through the depiction according to FIG. 2 along the line III-III.

(5) FIG. 4 shows a section through the depiction of FIG. 3 along the line IV-IV.

(6) FIG. 5 shows an isometric depiction of the position encoder and a part of the switching spindle according to FIG. 2.

(7) FIG. 6 shows another isometric depiction of the position encoder and a part of the switching spindle according to FIG. 2.

(8) FIG. 7 shows a position encoder and two sensor elements in an exemplary embodiment of the actuating system according to the invention.

(9) FIG. 8 shows an encoder part of a position encoder in an exemplary embodiment of the invention.

(10) FIG. 9 shows, in a diagram, signals of an inductive sensor of an actuating system according to an exemplary embodiment of the invention.

EXEMPLARY EMBODIMENTS OF THE INVENTION

(11) An actuating system 10 according to an exemplary embodiment of the invention, which is connected to a valve 20, is shown in FIG. 1. The valve 20 is designed as a pneumatic actuating valve and is arranged on a line 30. The actuating system 10 has an outer housing 11. In this housing, a receiving region 12 is defined, into which a switching spindle 21 of the valve 20 protrudes. A position encoder 40 is arranged on the switching spindle 21. A sensor element 13 is arranged in parallel to the receiving region 12. It supplies measurement data to an electronic position regulator 14, which controls an electropneumatic actuator 15. This has a port 151 to a pneumatic drive 22 of the valve 20. A vent valve 152 of the actuating device controlled by the position regulator 14 can feed compressed air from a pressure supply 50 through the port 151 into the pneumatic drive 22 in order to close the valve 20. An exhaust valve 153 of the actuating device 15, which is controlled by the electronic position regulator 14, can release air from the pneumatic drive into an exhaust air region 60 by means of the port 151. A process regulator 16 has an interface 161, to which a sensor 31 arranged in the line 30 downstream of the valve 20 can be connected. The sensor 31 is designed as a flow sensor in the present case. A user interface 17 with a display and buttons is applied to the outside of the outer housing 11. It allows the input of a position setpoint S.sub.14 and the input of a process setpoint S.sub.16. If the sensor 31 is not connected, a switch 18 in the outer housing 11 can be switched in such a way that the position setpoint S.sub.14 is fed to the position regulator 14. An actual position of the switching spindle 21 is then calculated in the position regulator 14 from a signal of the sensor element 13 generated by its inductive interaction with the position encoder 40 and the actual position is compared with the position setpoint S.sub.14. If there is a deviation between the actual value and the setpoint, the actual value is reset to the setpoint by means of a suitable control of the actuating device 15. If, on the other hand, the sensor 31 is connected, the switch 18 is switched in such a way that the position regulator 14 receives an input signal from process controller 16. This is calculated by comparing the process setpoint S.sub.16, which is a flow setpoint in the present case, with the actual value of the flow measured by the sensor 31. The calculated value is transferred to the position regulator 14 where it replaces the position setpoint S.sub.14.

(12) The inductive interaction between the sensor element 13 and the position encoder 40 enables the exact positioning of the switching spindle 21 to be determined. These are shown in detail in FIGS. 2 to 6. The sensor element 13 has a 0.5 mm thick inner housing 131 made of a plastic in which an inductive sensor 132 is arranged on a printed circuit board with connecting cables 133. This is thermally fixed to the inner housing 131 by means of bores not shown. The position encoder 40 consists of an encoder part 41 and a connection part 42. The encoder part 41 is designed as a cylinder made of copper in the present case, having a length L.sub.41 of 12.5 mm. Its outer diameter corresponds to the outer diameter d.sub.40 of the position encoder 40 and is 18 mm in the present case. Along the longitudinal axis of the encoder part 41, a circular bore runs, into which the connecting part 42 is inserted. This consists of a plastic and has a channel 43 with a diameter d.sub.43 of 4.9 mm inside it. This diameter d.sub.43 corresponds to the outer diameter of the switching spindle 21. The connecting part extends over the entire length L.sub.41 of the encoder part 41 and beyond. Its length is 25.1 mm. It ends in spring-shaped engagement elements 421, which engage in a groove 211 in a ring around the switching spindle 21 in the manner of a tongue and groove connection. On the side of the position encoder 40, on which the engagement elements 421 are located, the connecting part is substantially widened in one section to the outer diameter of the encoder part 41 and adhered to it there. The distance between the shell surface of the position encoder 40 facing towards the inductive sensor 132, which corresponds to the shell surface of the encoder part 41, and the surface of the inductive sensor 132 is 1.0 mm, and the distance a between the shell surface and the surface of the inner housing 131 is 0.5 mm. The inner housing 131 has a guide 134 which faces towards the position encoder. This has the shape of a recess with a curved cross-section, such that the distance between the shell surface and the inner housing is constant in the radial direction of the encoder part 41 in the region of the guide 134.

(13) FIG. 7 shows that, in a different embodiment, the actuating system 10 can have two sensor elements 13a, 13b, which both run in parallel to the receiving area 12 but are arranged at an angle of 90 degrees to each other. This enables a redundant position measurement for safety-relevant applications of the valve 20. In this simplified depiction, which is not true to scale, it is also shown that the distance b between the shell surface of the position encoder 40 and the inductive sensor 132 is large enough to include the thickness c of the inner housing 131a of the sensor element 13a, as well as to ensure a sufficient installation tolerance. The same applies to the second sensor element 13b.

(14) In an alternative exemplary embodiment, the encoder part 41 of the position encoder 40 is not a copper cylinder. As shown in FIG. 8, the encoder part instead has a ring-shaped magnetic flow conductor 411, which consists of ferrite. This is wrapped with a copper wire 412. A capacitor 413 is connected in series with the wire 412. Thus the wire 412 and the capacitor 413 form a resonator. This encoder part 41 functions as an active encoder part, while an encoder part 41 made of copper functions as a passive encoder part.

(15) In the exemplary embodiment described in FIGS. 1 to 6, the inductive sensor 132 has a measuring path s along the receiving region 12 of 50 mm and a length of 78 mm. In FIG. 9, the course of the measured voltage U.sub.mess and the course of the calibrated voltage U.sub.kal are plotted, by way of example, over this measuring path s. Furthermore, the course of the linearity L over the measuring path s is shown. After the calibration, there is only a non-linearity of approximately ?0.4%.

(16) The actuating system 10 and the valve 20 can be manufactured together in the manner shown. However, it is also possible to retrofit a valve 20 to the actuating system 10. To do so, the position encoder 40 is applied to the switching spindle 21 by pushing the switching spindle 21 through the channel 43 until the engagement elements 421 engage in the recess 211. Then the actuating system is placed on the valve 20 in such a way that the switching spindle 21 protrudes into the receiving region 12 and the pneumatic drive 22 of the valve 20 is connected to the port 151 of the positioning system. If there is a sensor 31 in line 30, it is connected to the interface 161. The actuating system 10 is subsequently ready for operation. There is no danger of incorrect adjustment of the position encoder 40 during installation. As soon as it has reached a position defined by the recess 211 along the longitudinal axis of the switching spindle 21, it can be rotated about the switching spindle 21 as desired, without impairing the position measurement using the inductive sensor 132.