EP2532900B1 - Method for operating a pneumatic drive - Google Patents

Description

The invention relates to a method for operating a pneumatic drive, wherein a working space in a housing of the drive via a pressure line connected to a pressure accumulator under a network pressure and thereby a movably mounted in the housing piston, which limits the working space, starting from a starting position to a Stroke is moved until the piston reaches the stop, and a pneumatic drive with a housing, a working space in the housing, a pressure line through which the working space with a pressure accumulator is connected under a network pressure, and with a in the housing between a starting position and a stop movably mounted piston which limits the working space.

DE 11 2004 00504 T5 proposes such a method in which a displaceable magnetic sensor detects a specific position of the piston and interrupts the pressure line. In the background of the invention disclosed EP 1 820 974 A2 a pneumatic drive with a control that interrupts the pressure line when the piston reaches a stop.

Pneumatic drives with axially movable pistons belong to the order of the pressure medium transmissions, which move from the drive to the output with the aid of a pressure-only medium. A gas (in particular air) acts as a medium under a pressure above the ambient pressure on the drive member designed as a piston and displaces this in a cylindrical housing in the axial direction. In the subgroup of the rotary actuators the output member is a rotatable shaft, each axial displacement of the piston in the housing directly causes a rotation of the output shaft.

Pneumatic drives of the aforementioned type with adjustable start and / or end positions are generally known from the double-piston product series "actubar" of the applicant. The known part-turn actuators have a nominal pivoting angle of 90 ° between the start position and the stop of the output shaft, and in other embodiments also other angles (for example 180 °).

In the known rotary actuators proposes a mounted on the output shaft stop cam in the starting position and at the stop on stop surfaces, each at the tip of two acting as adjusting elements adjusting screws are formed. The heads of the adjusting screws are accessible from the outside of the housing, the adjusting screws are each secured with a fitting on the outside lock nut. By turning the adjusting screws in and out, the nominal swivel angle at the starting position and at the stop can be continuously reduced by 10 ° or increased by 5 °. So swivel angles between 70 and 100 ° are adjustable.

In such pneumatic actuators, if they can approach and hold any intermediate position, this position is maintained by pressure control of the active chamber.

If a drive, however, used to start the attack, then the working space is constantly filled with the current network pressure and held until the piston is to be returned to the starting position - regardless of whether in the working space of the full network pressure is required to the piston to move to the stop and to hold him there.

In the stop, the piston is in physical contact with the stop surface. In the broader context of the invention, similar quarter-turn actuators are also used as positioners for approaching defined intermediate positions between start position and stop without physical contact of the piston with a stop surface.

task

The invention has for its object to reduce the energy consumption of the drive.

solution

Based on the known method is proposed according to the invention that a control triggers an interruption of the pressure line at the expiration of a set waiting time when the piston reaches the stop. If the network pressure has not yet been reached in the working space at this time, the remaining pressure difference between working space and network pressure is no longer compensated by inflowing gas. The energy requirement of the pneumatic drive is the energy content of the "saved" gas decreases. On the one hand, in applications in which, after a defined waiting time after opening the valve always the stop is reached, the closing of the valve can be triggered only dependent on the waiting time, so that the use of a limit switch is unnecessary. On the other hand, the valve can be triggered after a defined waiting time after reaching the stop to build up a pressure surplus to hold the piston to the stop. According to the invention, this waiting time begins when the piston reaches the stop. On the one hand, in applications in which the stop is always reached with a defined holding pressure of the valve, the closing of the valve can be triggered exclusively depending on the holding pressure, so that the use of a limit switch is unnecessary. On the other hand, the valve can be triggered after reaching the stop only at the holding pressure to build a defined pressure surplus to hold the piston to the stop.

Preferably, in a drive, the piston is movably supported in the housing in an axial direction. The drive is then a single- or double-acting piston drive. Particularly preferably, the piston drives a transverse to the axial direction in the housing mounted output shaft, wherein the output shaft has at least one stop cam which abuts in the starting position and / or upon reaching the stop on a stop surface formed on the housing. The pneumatic drive is then a rotary actuator. Alternatively, a method according to the invention can also be used to operate a linear drive.

Advantageously, a drive is a double-acting rotary piston drive.

In a particularly advantageous embodiment, a drive has a valve in the pressure line, wherein the control closes the valve for interrupting the pressure line.

embodiment

Fig. 1

eine Schaltskizze eines ersten pneumatischen Antriebs,

Fig. 2

eine Schaltskizze eines zweiten pneumatischen Antriebs und

Fig. 3

Schematische Kennlinien der Antriebe

The invention will be explained below with reference to an embodiment. Show it

Fig. 1

a circuit diagram of a first pneumatic drive,

Fig. 2

a circuit diagram of a second pneumatic drive and

Fig. 3

Schematic characteristics of the drives

The in the FIGS. 1 and 2 shown switching sketches show a first pneumatic drive 1 and a second pneumatic drive 2, each with a rotatable output shaft 3. The drives 1, 2 are each connected via a valve 4 in a pressure line 5 with a pressure accumulator 6 under a network pressure. The drive 1, 2 each has a housing 7 with a first working space 8 and a second working space 9 delimited from the first working space.

The first drive 1 shown in FIG. 1 is a double-acting one

Axial piston rotary actuator with two in the housing 7 in an axial direction 10 movably mounted piston 11, each delimiting the first working space 8 of the second working space 9. The pistons 11 drive the toothed output shaft 3 mounted transversely to the axial direction 10 in the housing 7.

The second drive 2 shown in FIG. 2 is a double-acting one

Rotary-wing actuator with a connected to the output shaft 3 rotary wing 12, which delimits the first working space 8 of the second working space 9.

The output shaft 3 has in each case a stop cam 13, which abuts in the starting position and when reaching the stop in each case on a stop surface, not shown. In addition, the drive 1, 2 each have a control element 14 for the starting position and a control element 15 for the stop. The controls 14, 15 are arranged in the stop surfaces contact switch.

The valve 4 is a 5/3-way valve with electromagnetic control and spring-loaded center position. In the middle position all connections are closed.

The valve 4 is connected via a first electrical switch 16 for movement from the starting position to the stop and a second electrical switch 17 for the movement from the stop back to the starting position. For the movement to the stop becomes the first Working chamber 8 connected to the accumulator 6 and the second working chamber 9 vented. For the movement back to the starting position, the first working space 8 is vented and the second working space 9 is connected to the pressure accumulator 6. As soon as the stop cam 13 abuts in one of the stop surfaces, the respective control element 14, 15 triggers the corresponding push-button 16, 17 via a control line 18, so that the valve 4 returns to the middle position by the spring load.

FIG. 3 schematically shows the operation of one of the drives 1, 2 for opening and closing a flap, not shown, the pressure 19 in the first working space 8 and the pressure 20 in the second working space 9 respectively between ambient pressure 21 and system pressure 22 and the position 23 of the piston 11 between the position 24 ("open") and the position 25 ("closed") each at the stop of the flap.

At the starting point 26 of the FIG. 3 the flap is closed and the first working chamber 8 is acted upon by the system pressure 22, the second working space 9 is below ambient pressure 21. The difference between the system pressure 22 and ambient pressure 21 via the first working space on the piston 11 a holding force, the flap in the position 25 "Closed" stops.

In the first switching point 27, the valve 4 is switched and the first working space 8 ent, the second working space 9 vented. The holding force is reduced until the courses of the two pressures 19, 20 intersect. Then, a pressure difference 28 and thus a corresponding release force from the second working chamber 9 is built on the piston 11. In the first breakaway point 29, the release force overcomes the adhesion of the sealing rubber of the flap, the piston 11 and the flap move to the position 24 "open", wherein the pressure 19 in the first working space 8 decreases and the pressure 20 in the second working space 9 increases.

In the first measuring point 30 when striking the flap in the position 24 "open" lie in the first working space 8 63 v. H. and in the second working space 9 66 v. Chr. H. of the system pressure 22 at. Here, the valve 4 switches to the middle position, so that the respective pressures are kept in both working spaces.

In the second switching point 31, the first working chamber 8 is vented via the valve 4 and the second working chamber 9 is vented. Since the pressures are already close to each other, they reach very quickly in a second breakaway point 32 the same values. The piston 11, which has to overcome a very low adhesion of the rubber seal, is essentially in motion at the same moment. In the figure, the second switching point 31 and the second breakaway point 32 are separated for illustrative reasons.

The flap moves back in the direction of the position 25 "closed" to a contact point 33, in which the sealing rubber touches the opening to be closed. To move the flap further into position 25 "closed", a larger force and thus a larger pressure difference 34 between the work spaces is required.

In the second measuring point 35, this required pressure difference 34 is reached and the flap is again in position 25 "closed". In the first working space 8 are 85 v. H. and in the second working space 9 27 v. H. of the system pressure 22 at. Again, the valve 4 switches to the middle position and keeps the pressures in the two workrooms.

In the third switching point 36, as in the first switching point 27, the first working space 8 is released again, the second working space 9 is ventilated and the piston 11 and the flap again move to the position 24 "open" to a third measuring point 37. The course of the pressures and the position 23 of the piston 11 between the second measuring point 35 and the third measuring point 37 are repeated for each subsequent switching operation.

The illustrated course of the pressures and the position 23 of the piston 11 between the measuring points 30, 36, 37 measured by way of example are not based on measurements, but serve only for qualitative illustration.

Compared to the known state of the art, in which between the first measuring point 30 and the second switching point 31 and between the second measuring point 35 and the third switching point 36, the working spaces are completely ventilated or vented, spares the inventive method the purpose spent for this purpose or drained without benefit Compressed air and the corresponding energy.

The work areas are not abrupt, but vented via a throttle silencer, not shown. In alternative drives, the valves used pneumatically or hydraulically or programmatically controlled by a processor. In a programmatically implemented control element 14, 15, the delay elements described above can be particularly easily integrated depending on minimum duration, minimum pressure, time delay or pressure surcharge.

In the event of a sudden pressure surge or other mechanical load on the flap, which in position 25 "Closed" exceeds the holding force due to the pressure reduced below the system pressure, the flap opens first. By opening the flap, the control 15 again switches the system pressure to the first working space 8. The drives 1 and 2 according to the invention automatically report this fault to higher-level control.

At the drives 1 and 2 optionally the maximum pressure in the first working space 8 can be limited to a value below the system pressure. The flap then takes over the function of an adjustable pressure relief valve for the underlying space, such as an exhaust duct.

In the figures are

1

drive

2

drive

3

output shaft

4

Valve

5

pressure line

6

accumulator

7

casing

8th

first working space

9

second workspace

10

axially

11

piston

12

rotary wing

13

stop cams

14

Control for the starting position

15

Control for the stop

16

first button

17

second button

18

control line

19

Pressure in the first workspace

20

Pressure in the second workspace

21

ambient pressure

22

system pressure

23

Location of the piston

24

Position "open"

25

Position "Closed"

26

starting point

27

first switching point

28

pressure difference

29

first breakaway point

30

first measuring point

31

second switching point

32

second breakaway

33

contact point

34

pressure difference

35

second measuring point

36

third switching point

37

third measuring point

Claims (1)

1. Method of operating a pneumatic actuator (1, 2) wherein a working chamber (8, 9) in a housing (7) of the actuator (1, 2) is connected via a pressure line (5) with a pressure store (6) at a mains pressure and through this a piston (11), which is displaceably borne in the housing (7) and delimits the working chamber (8, 9), is moved from a starting position towards a stop until the piston (11) reaches the stop, characterised in that on expiry of a determined waiting period a control element (14, 15) triggers an interruption of the pressure line (5) when the piston (11) reaches the stop and in that the waiting time begins when the piston (11) reaches the stop.

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