Control valve assembly for an indirect pneumatic control, and method for controlling a working fluid pressure

Abstract

A control valve assembly for indirect pneumatic control and method for controlling a working fluid pressure, which enable precise, sensitive and speed-variable controlling. The assembly includes two valve units, a working fluid inlet, and a control fluid inlet. A working fluid channel connects the working fluid inlet through the two valve units to an outlet. A valve piston arranged within a valve cylinder of the valve units is movable between open and closed positions. A spring element biases the valve piston toward the closed position, and a control pressure chamber applies a control pressure counteracting the spring element's bias. When a control pressure is applied in the first chamber, the first valve piston is moved to the open position. Two opposite valve surfaces form a valve opening opened at varying widths when the valve piston is moved in the valve cylinder because of a changing control pressure, and the working pressure can be finely adjusted corresponding to the valve opening width depending on the control pressure.

Claims

1. A control valve assembly for an indirect pneumatic control, comprising two pneumatic sequentially arranged valve units, one working fluid inlet and one control fluid inlet, a working fluid channel connecting the working fluid inlet through the two valve units, to an outlet, in each valve unit, a valve piston arranged within a valve cylinder of the first and second valve unit and movable between an open and a closed position, in each valve unit, a spring element which biases the first and the second valve piston toward the closed position, in each valve unit, a control pressure chamber connected to the control fluid inlet for applying a control pressure counteracting the bias of the spring element to the respective valve piston, wherein the first valve unit is formed such that when a control pressure is applied in the first control pressure chamber, the first valve piston is moved from the closed to the open position, and wherein two opposite valve surfaces which are angled relative to each other are arranged on the valve cylinder and the valve piston so as to extend along the direction of movement in the second valve unit in a blocking and control region of the working fluid channel such that the valve surfaces form a valve opening opened at varying widths when the valve piston is moved in the valve cylinder because of a changing control pressure, and the working pressure is graduated adjustable corresponding to the valve opening width depending on the control pressure.

2. The control valve assembly according to claim 1, wherein at least one of the two valve surfaces of the second valve unit has two sequential sections, wherein an angle (a) between the valve surfaces in the first section following the closed position is smaller than an angle (b) of the valve surfaces in the second section adjacent to the open position.

3. The control valve assembly according to claim 2, wherein the two valve surfaces in the first and/or second section (A, B) are produced to run linearly, wherein the angle (a, b) between the two valve surfaces is between 0.1° and 10°.

4. The control valve assembly according to claim 2, wherein at least one of the two valve surfaces is formed to run nonlinearly in the first and/or second section, wherein an angle between the two valve surfaces increases between the closed and the open position and is between 0.1° and 45°.

5. The control valve assembly according to claim 2, wherein the first section and/or the second section of the valve surfaces extends in each case over at least 25% of the maximum adjustment path of the valve piston relative to the valve cylinder.

6. The control valve assembly according to claim 1, wherein at least the second valve piston is formed rotationally symmetrical, and the corresponding valve cylinder has a round cross-section so that the valve opening has the shape of an annular gap.

7. The control valve assembly according to claim 1, wherein the first and/or second control pressure chamber is arranged in a region of an end of the respective valve piston opposite the spring element, and/or the working fluid channel in the first and/or the second valve unit is arranged between a region (F) of the spring element and a region of the control pressure chamber.

8. The control valve assembly according to claim 1, wherein a single control fluid inlet that is connected to both control pressure chambers in an interior of the control valve assembly.

9. A method for controlling a working fluid pressure by a control fluid in a control valve assembly for an indirect pneumatic control, comprising the steps of: applying a working pressure by a working fluid to a working fluid inlet, controlling a control pressure in a control fluid and subjecting a control fluid inlet to the control pressure, feeding the control fluid into a control pressure chamber of each of a first and a second pneumatic valve unit, wherein the control fluid can move a first valve piston of the first pneumatic valve unit and a second valve piston of the second pneumatic valve unit, each arranged within a valve cylinder, to an open position, wherein each of the valve piston is biased by a spring element toward a closed position, wherein applying the control pressure in the first control pressure chamber moves the first valve piston from the closed into the open position, whereby the working fluid can flow through the first valve unit now being open to the second pneumatic valve unit through a working fluid channel connected to the working fluid inlet, wherein applying the control pressure in the second control pressure chamber causes a movement of the second valve piston against the force of the spring element into a position of the second valve piston in the valve cylinder associated with the control pressure between the closed and the open position, whereby the working fluid flows through the working fluid channel into the pneumatic second valve unit between two opposing valve surfaces at an angle from each other and extending along a direction of movement on a surface of the valve cylinder and the valve piston, wherein a valve opening in the working fluid channel formed between the valve surfaces is correspondingly graduated adjustable depending on the control pressure, and regulates the pressure of the working fluid applied to an outlet.

Description

(1) An exemplary embodiment of the control valve assembly according to the invention is explained in greater detail below with reference to the drawings. In the figures:

(2) FIG. 1 shows a sectional view of a control valve assembly with two closed valve units,

(3) FIG. 2 shows an enlarged sectional view of a blocking region of the second valve unit of the control valve assembly portrayed in FIG. 1,

(4) FIG. 3 shows a sectional view of the control valve assembly portrayed in FIG. 1 with an open first valve unit and a closed second valve unit, and

(5) FIG. 4 shows a sectional view of the control valve assembly portrayed in FIG. 1 with a fully open first valve unit and a partially open second valve unit,

(6) FIG. 5 shows a sectional view of the control valve assembly portrayed in FIG. 1 with two open valve units.

(7) With a control valve assembly 1 portrayed in FIG. 1 for the indirect pneumatic control of the working pressure for a pneumatic vane motor of a hoist, a first and a second valve unit 2, 3 are arranged parallel to each other in a common housing.

(8) Each of the two valve units 2, 3 is formed as a spring-biased pneumatically operated valve. Correspondingly, a movable valve piston 9, 10 is arranged in a valve cylinder 7, 8 in each of the valve units 2, 3 such that a pressure fluid, in particular compressed air, guided through the valve unit 2, 3 can be blocked, or respectively regulated by means of a surface section of the valve cylinder 7, 8 and of the valve piston 9, 10.

(9) On one side, the valve piston 9, 10 is biased by a spiral spring 11, 12 toward a closed position, wherein one end of the spiral spring 11, 12 braces against a round face of the valve cylinder 7, 8, whereas the other end is secured within a hole in the valve piston 9, 10. At the other end E of the valve piston 9, 1o, a control pressure chamber 13, 14 is produced in the valve cylinder 7, 8. The control pressure chambers 13, 14 of both valve units 2, 3 are jointly connected to an inlet for a control pressure airflow so that pressure can build up in the control pressure chamber 13, 14 that counteracts the spring tension of the spiral spring 11, 12 and allows the valve piston 9, 10 to be moved by applying the control pressure to the face of the valve piston 9, 10.

(10) The control valve unit 1 has a working pressure air inlet 4 as well as a corresponding outlet 5 that provides a pressure-controlled compressed air flow for the vane motor of the hoist. The outlet 5 is connected to the working pressure air inlet 4 through a working pressure air channel 6, wherein the working pressure air channel 6 runs sequentially through both valve units 2, 3 and can be blocked and regulated in each case in a blocking and control region 15 by means of the valve units 2, 3.

(11) A valve surface 16, 17 is arranged on both the second valve piston 10 as well as the associated valve cylinder 8 that lie against each other when the valve unit 2, 3 is in a closed state. Both valve surfaces 16, 17 are arranged at an angle to each other so that when the valve piston 10 moves in the valve cylinder 8, an enlarging valve opening forms in the shape of an annular gap as movement increases.

(12) FIG. 1 shows a control valve assembly 1 with both valve units 2, 3 in the closed position so that the first valve unit 2 blocks the working pressure air flow just after the working pressure air inlet 4, and no pressure in the region of the working pressure air channel 6 is applied to the second valve unit 3. In this state of the control valve assembly 1, there is also no control pressure, or respectively the control pressure of the control pressure air in the control pressure chambers 13, 14 lies below a fixed threshold value of approximately 1.2 bar for opening the valve units 2, 3.

(13) FIG. 3 shows a control valve assembly 1 in a state that only occurs briefly, or respectively exactly upon reaching a threshold value of the control pressure for opening the valve units 2, 3. The first valve unit 2 is completely open, whereas the second valve unit 3 is still closed. The control pressure in the first control air pressure chamber 13 counteracts the first spiral spring 11 enough to just open the valve opening of the first valve unit 2 in that the two valve surfaces 16, 17 of the first valve unit 2 disengage.

(14) As the control pressure increases, the second valve piston 10 of the second valve unit 3 now is also moved against the spring force of the spiral spring 12 toward the open position, wherein the spring force is selected so that the valve piston 10 is shifted over the maximum adjustment path W within a predefined pressure range, preferably between 1 bar and 6 bar.

(15) In order to first of all enable a sensitive control and then a quick and forceful release of the working air pressure as the control pressure increases, the valve surfaces 16, 17 of the second valve unit 3 are formed by a changing angle a, b within the control surface 17 of the valve piston 10 (see FIG. 2). The valve surface 16 of the valve cylinder 8 is produced as a linearly running cylindrical surface as part of the wall of the valve cylinder 8. The valve surface 17 of the valve piston 10 has two sections A, B at an angle to each other which are each also arranged at an angle a, b to the opposing valve surface 16. Both sections A, B have a linear contour. The angle a of the first section of the valve surface 17 to the opposing valve surface 16 is 5°, whereas the corresponding angle b of the second section B is 45°. The two sections A, B extend over 85% of the maximum adjustment path W of the valve piston 10 in the valve cylinder 8.

(16) FIG. 4 shows a control valve assembly 1 with the first valve unit 2 in the completely open position and the second valve unit 3 in a partially open position, wherein the working pressure air is guided through an annular gap formed by the control surfaces 16, 17 of the second valve unit 3, and a reduced volumetric flow through this annular gap can flow through the working pressure air channel 6 from the working air pressure inlet 4 to the outlet 5 of the control valve assembly.

(17) Finally, FIG. 5 shows a control valve assembly 1 with both valve units 2, 3 in the completely open position, wherein the working pressure air can flow unhindered through the working pressure air channel 6 from the working air pressure inlet 4 to the outlet 5 of the control valve assembly through the control surfaces 16, 17 of the two valve units 2, 3.

LIST OF REFERENCE NUMBERS

(18) 1 Control valve assembly 2 First valve unit 3 Second valve unit 4 Working fluid inlet 5 Outlet 6 Working fluid channel 7 First valve cylinder 8 Second valve cylinder 9 First valve piston 10 Second valve piston 11 First spring element 12 Second spring element 13 First control pressure chamber 14 Second control pressure chamber 15 Blocking and control region 16 First valve surface 17 Second valve surface A First section B Second section E End of the valve piston F Region of the spring element S Region of the control pressure chamber V Adjusting direction W Maximum adjustment path a Angle of the first section b Angle of the second section