CN86108885A - Three-position five-way reversing valve unit - Google Patents

Abstract

The control element of the three-position five-way reversing valve is composed of two control spools. The first spool controls intake air at the first end of the cylinder and exhaust at the second end of the cylinder; the second spool controls intake air at the second end of the cylinder and exhaust at the first end of the cylinder gas. When the control pressure is lower than the pressure required to overcome the homing force acting on the spool, there is only a very small control pressure clearance space, which ensures high control action speed within the zero stroke range of the compact valve unit structure.

Description

Three-position five-way directional valve unit

The present invention relates to a three-position five-way directional valve unit for double-acting pneumatic cylinder positioning. The directional valve has a control element that can move in a housing with controllable medium joints under the action of a control pressure in the direction opposite to the return force. When the control pressure is lower than the pressure level required to overcome the return force, the control element is in a zero position that closes all medium joints.

For adjusting and positioning pneumatic cylinders, the valve's passage cross-section between zero and maximum must be precisely and easily adjustable in every intermediate position. To date, so-called non-sealing piston slide valves have mostly been used for this purpose. Due to their pressure-balanced design, these non-sealing piston slide valves can be operated with very low adjusting forces and, due to air lubrication, exhibit only low friction.

Positioning a double-acting pneumatic cylinder requires different controllability of the pressurized medium inlet and outlet on both sides of the piston. This is typically achieved using four 2/2-way, two 3/3-way, or one 5/3-way directional control valves (with a closed intermediate position). When using 2/2-way directional control valves, these valves can also be constructed as seat valves. While this offers a flexible design with diverse control possibilities, it also comes with the disadvantage of being extremely expensive. Using two 3/3-way directional control valves, one on the cover side and the other on the bottom side, simplifies control. This means that even when the pressurized medium in the cylinder is to be pre-pressurized (which is often necessary for rapid actuation), the control cannot be interrupted even after the piston reaches the desired position. Solutions using a 5/3-way directional control valve unit of the aforementioned type suffer from the disadvantage that the intermediate position is also closed when the position is switched off. This also results in the larger control air clearance associated with 3/3-way directional control valves. This disadvantage arises because the middle position of the control element is located in the middle of the control stroke due to functional limitations, and this disadvantage disadvantageously reduces the actuation speed of the proportional control valve.

The object of the present invention is to improve a directional control valve of the type described in the switch so that the above-mentioned disadvantages of the prior art are avoided and, in particular, a minimum control air clearance space is created around the zero position region in which all media connections are closed and a short actuation time is created in this region when the control pressure changes without high structural complexity and with high operational reliability.

One object is achieved according to the present invention by the following measure: the control element comprises two control valve cores arranged separately in a housing. Each control valve core cooperates with two media connections and has axially displaceable control edges that are each movable by control pressure. The control edge of the first control valve core controls the intake of air to the first end of the cylinder and the exhaust of air from the second end, while the control edge of the second control valve core controls the intake of air to the second end of the cylinder and the exhaust of air from the first end. This distribution of the control elements makes it possible, in a very simple manner and while retaining the aforementioned advantageous features of the 5/3-way valve, to achieve a very small control air clearance in the zero position of the control element. This control air clearance is actually derived solely from the control pressure supply line. From this zero position, both control valve cores are movable by control pressure, and each of the two control valve cores controls a direction of movement of the pneumatic cylinder or its working piston.

A further advantage of the solution according to the invention is that a very compact design is ultimately achieved, since the two separate control spools can be accommodated more compactly in the housing than a conventional 5/3-way directional control valve.

According to a further development of the present invention, two separate control valve cores can be placed in an insert sleeve in the housing. This sleeve has a control bore connected to the media connection. The control valve core and the sleeve are assembled as a set. This allows for the cost-effective manufacture of at least the required high-precision proportional control valve control components. The pipes in the housing connecting the media connection and the control bore do not require special precision and can, for example, be cast or formed together during the manufacture of the housing.

According to a further arrangement of the invention, the two control valve cores are pushed with a return force by separate pressure springs on the housing, which ensures that the movements of the two control valve cores are completely independent of each other and allows a valve unit structure that is symmetrical for the two control valve cores.

According to a preferred embodiment of the present invention, the two control valve cores are arranged parallel to each other in the housing, with the control pressure connection always located on the same side of the housing. This simplifies not only manufacturing but also connection and installation requirements, which is particularly advantageous when the valve unit is located directly near the cylinder to be controlled.

According to another further development of the invention, starting from the control pressure connection, the first control edge of the first control valve element controls the exhaust of the second cylinder end, the second control edge of the first control valve element controls the intake of the first cylinder end, the first control edge of the second control valve element controls the exhaust of the first cylinder end, and the second control edge of the second control valve element controls the intake of the second cylinder end. In this way, the control openings in the valve unit housing for controlling the intake and exhaust of the two cylinder ends can be arranged at approximately the same distance from the location where the control pressure connection is provided. This significantly simplifies the arrangement of the necessary connecting lines between the two separate control valve elements.

In order to move the two control valve spools separately with the control pressure, a particularly preferred embodiment of the present invention employs a pilot valve mounted directly on the control pressure connection on the housing. This ensures that the minimal pilot air clearance space available with the present embodiment is fully utilized and that this clearance space can be reduced by long connecting lines that do not lead to the pilot valves.

The present invention will be explained in detail below using the embodiments partially shown in the accompanying drawings: Figure 1 shows a double-acting pneumatic cylinder positioning circuit diagram with a valve unit according to the present invention, and Figure 2 shows a cross-section of an embodiment of a valve unit according to the present invention.

According to FIG1 , the double-acting pneumatic cylinder 1 essentially consists of a cylinder 2 and a piston 3 that moves axially in the cylinder and is connected to a piston rod 4 that extends outward from the cylinder 2. Connecting lines 7 and 8 for a pressure medium, particularly compressed air, are provided at a first end 5 and a second end 6 of the cylinder. These connecting lines are connected to a connection A or B on a 5/3-way directional control valve unit 9.

The valve unit 9, which positions the pneumatic cylinder 1 by controlling the air flow to and from the cylinder's two ends 5, 6, includes a control element that moves within a housing 10 and consists of two separate control valve cores 11, 12. These control elements are movable under the action of a control pressure applied to inlets X and Y in a direction opposite to the force generated by two separate pressure springs 13, 14, and control five media connections. P represents an uncontrolled pressure medium connection, i.e., an air supply connection to both cylinder ends, but the separate connection P can of course be replaced by a connection shared by both control valve cores. R represents the second cylinder end 6, i.e., the exhaust connection on the cover. S represents the exhaust connection at the first cylinder end 5; A and B have already been indicated above as connections directly to the cylinder ends.

In the circuit diagram of FIG1 , the two control valve slides 11 and 12 are depicted as 2/2-way directional valves with a corresponding function—their behavior is always equivalent to that of two mechanically coupled 2/2-way directional valves, as explained in detail below in the embodiment shown in FIG2 . The following briefly describes the operation of this valve unit 9: In the neutral position of the control elements, i.e., the two control valve slides 11 and 12, depicted in FIG1 , all five controllable media connections A, B, P, S, and R are closed under the action of the two compression springs 13 and 14, thereby also closing both cylinder ends to the outside. Depending on the pressure level, the piston 3 is held in its fixed position. For example, if the first control valve slide 11 slides out of the closed neutral position due to an inlet control pressure that exceeds the force of the compression spring 13, the inlet connection to the first cylinder end 5 and the outlet connection from the second cylinder end 6 open to a degree corresponding to the displacement of the control valve slide 11, and the piston 3 moves to the right as described. To move the piston 3 in the other direction, the control sequence described above must be initiated by applying a control pressure to the inlet Y of the second control valve element 12. Since the two control valve elements 11 and 12 can be moved independently of each other by control pressure via separate inlets X and Y, and can each control the movement of the piston 3 in one direction, it is also possible to easily brake the piston 3 when it approaches a desired position or hold it in that position, for example, by supplying air to both cylinder ends separately, jointly, or simultaneously.

To illustrate the structure of FIG. 2 , the same reference numerals as in FIG. 1 are used below, and generally speaking, the functions of corresponding components are the same.

In the housing 10 of FIG2 , two control valve cores are mounted in insert sleeves 15 and 16. These sleeves have control holes 17, 18, 19, 20, 21, 22, and 23 connected to the media connections A, B, S, and R. These control holes are in the form of slots or individual holes distributed around the sleeve and lead out of an annular space 24 around the sleeve. To establish the necessary connection between the annular space 24 and the connections, pipes 25 to 32 are provided in the housing and enter a threaded connection 33 outside the housing.

The control valve spools 11, 12, which are inserted into the housing inner bore 34 together with the component sleeves 15, 16, are supported on the lower housing cover 35 by separate compression springs 13, 14 and pressed into their neutral position by the action of these compression springs. In this neutral position, the control valve spools rest against the upper housing cover 36. Two axially eccentric control edges 37, 38 or 39, 40 are attached to each of the two control valve spools 11, 12, which open a larger or smaller control cross section of the control bores 20, 22, 23 depending on the axial position of the control valve spools. To enable the axial movement of the control valve spools 11, 12 in response to the force of the compression springs 13, 14, inlet openings 41 for the control pressure connections X, Y are provided in the upper housing cover 36.

In the position of the two control valve slides 11, 12 shown in FIG2 , there is no control pressure at inlets X, Y. The control bore 20 connected to the gas supply connection P is closed by the second pair of control edges 38, 40 of the control valve slides 11, 12. The same applies to the control bores 22, 23, which are connected to the connections A, B via lines 26, 28 and are closed by control edges 37, 39. Thus, the two cylinder ends 5, 6 in FIG1 are isolated from the valve unit 9. For example, when control pressure is applied to the first control valve slide 11 via inlet X, the first control edge 37 opens the control bore 22 and thus connects the exhaust connection R to the connection B leading to the second cylinder end 6. Simultaneously, the second control edge 38, which is mechanically fixed, creates a gap in the control bore 20, thereby connecting the pressurized gas connection P via the control bore 17 to the connection 5 leading to the first cylinder end 5. As a result, the piston 3 moves again to the right in FIG1 .

To achieve a reverse movement of the piston, a control pressure is applied to the inlet Y, whereby the first control edge 39 opens the control opening 23, the second control edge 40 opens the control opening 20, and the exhaust port S is connected to the first cylinder end 5, and the pressure port P is connected to the second cylinder end 6. However, the two control valve slides 11, 12 can also be actuated jointly, whereby different movement or pressure ratios are always achieved at the two cylinder ends, depending on the control pressure applied on both sides.

Auxiliary valves for the control pressure can also be arranged directly at the control pressure inlets X and Y, thereby achieving a very small control pressure clearance space and a rapid action according to the control pressure change, especially in the difficult area around the zero position of the two control valve cores. This is very beneficial for achieving precise positioning near the zero position.

Claims (6)

1. A double-acting, pneumatic cylinder positioning, three-position, five-way directional control valve unit, the directional control valve unit having a control element movable in a housing with controllable media connections under the action of a control pressure opposite to a return force, wherein when the control pressure is lower than the pressure required to overcome the return force, the control element is in its zero position in which all media connections are closed, characterized in that the control element comprises two control valve cores (11, 12) arranged separately in the housing (10), the control valve cores always having two axially movable control edges (37, 38 or 39, 40) cooperating with two media connections (A, B, S, P, R) and being respectively movable by the control pressure, wherein the control edges (37, 38) of the first control valve core (11) control the intake of the first cylinder end (5) and the exhaust of the second cylinder end (6), and the control edges (39, 40) of the second control valve core (12) control the intake of the second cylinder end (6) and the exhaust of the first cylinder end (5). 2. Valve unit according to claim 1, characterized in that the two separate control valve cores (11, 12) are located in an insert sleeve (15, 16) in the housing (10), the sleeve having control bores (17 to 23) connected to the media connections (A, B, S, P, R), and that both the control valve cores (11, 12) and the sleeve (15, 16) are manufactured as a single unit. 3. A valve according to claim 1 or 2, characterized in that the control valve element (11, 12) is urged by a return force by separate pressure springs (13, 14) on the housing (10). 4. Valve unit according to claim 1, characterized in that the two control valve slides (11, 12) are arranged parallel to one another in the housing (10) and the control pressure connections (X, Y) are always located on the same side of the housing. 5. Valve unit according to any one of claims 1 to 4, characterized in that, always starting from the control pressure connection (X, Y), the first control edge (37) of the first control valve element (11) controls the exhaust of the second cylinder end (6), the second control edge (38) of the first control valve element (11) controls the intake of the first cylinder end (5), the first control edge (39) of the second control valve element (12) controls the exhaust of the first cylinder end (5), and the second control edge (40) of the second control valve element (12) controls the intake of the second cylinder end (6). 6. The valve unit according to claim 1, wherein the pilot valves are arranged directly on the pressure connections on the housing in order to respectively move the control valve slides with the control pressure.