Control valve

Abstract

 A control valve for a controlled supply of pressurized fluid from a source of pressurized fluid to a pressurized fluid system. The valve comprises a valve casing (1, 2) having a valve chamber (4), an inlet port (19) to be connected to the source of pressurized fluid, an outlet port (20) to be connected to the pressurized fluid system, and an exhaust port (21). A slide (8) movable in the valve chamber (4) is displaceable between a closing position and an opening position. In the opening position, a piston body (11) which is movable on the slide (8) can be displaced between an initial position, which secures a slow supply of pressurized fluid via a choke hole (28), and a final position, which permits a greater flow of pressurized fluid via a flow passage (27) having a substantially greater cross-sectional area than the choke hole (28).

Description

[0001] The invention relates to a control valve for a controlled supply of pressurized fluid, especially pressurized air, from a source of pressurized fluid to a pressurized fluid system, of the kind stated in the preamble of claim 1.

[0002] Such a control or air supply valve is known from SE-C-7906261-8 and ensures that the pressure increase will be relatively slow during a first phase of air supply, so as to avoid that work cylinders or other apparatus operable by pressure perform sudden movements under the influence of a pressure shock. When a pneumatic system has been left depressurized for some time, e.g. during a week-end, it could in fact occur that cylinder pistons or the like have arrived at such positions that, upon supply of air, the pistons have no counter-pressure and therefore perform an uncontrolled, jerky movement.

[0003] The object of the present invention is to considerably simplify the known valve structure in such a way that the main valve is integrated with the choke and pressure control valve, so that these valve parts can be accomodated in a common valve chamber in a valve casing.

[0004] This object is achieved, according to the invention, in that the inlet port(which is connected to the source of pressurized fluidjof the control valve communicates with the valve chamber via, on the one hand,a flow passage having a relatively large cross-sectional area and, on the other hand, a choke opening having a considerably smaller cross-sectional area, and that the slide of the valve is provided with a piston body, which is displaceable thereon and which, in the air supply positionα of the valve (wherein the inlet port communicates with the outlet port connected to the pressurized fluid system in question),is displaceable between an initial position, in which the inlet port communicates with the outlet port only via the choke opening and a final position, in which the inlet port communicates with the outlet port via the flow passage having a relatively large cross-sectional area as well.

[0005] By this means, the control valve may comprise only one valve chamber, in which the valve slide with the adjoining piston body is displaceable. Moreover, a considerable structural simplification is achieved by avoiding two separate valves each being arranged in a separate valve chamber and being connected to each other via a number of conduits or channels in the valve casing. Manufacture as well as operation and reliability will be enhanced thereby.

[0006] A particularly good operabiliy is isachieved if the piston body, being displaceable on the valve slide, is provided with a piston surface facing the outlet port and being so dimensioned that, upon reaching a predetermined pressure in the connected pressurized fluid system, it is subjected to a reversing force, which exceeds a counter-force, e_Jg_: exerted by a compression spring, so that the piston body is displaced to said final position.

[0007] Additional inventive features and advantages appear from the sub-claims and the detailed description below. Thus, the invention will be described further below with reference to the appended drawings illustrating a preferred embodiment.

[0008] 

Fig. 1 shows a central longitudinal section through a control valve according to the invention, wherein a slide valve is located in a first position being uninfluenced by outer control forces;

Fig.2 shows schematically the control valve according to Fig.1 with the slide valve located in a second position, during a first air supply phase; and

Fig.3 shows the control valve according to Fig. 1 with the slide valve located in a third position, permitting full air supply.

[0009] The control valve shown in Fig.1 comprises a two-part valve casing with an upper casing half 1 and a lower casing half 2 being screwed together into mutual contact in a parting plane and being sealed by means of a combination sealing element, which is formed in one piece and includes a planar portion (not shown) located in said parting plane as well as ring portions connected thereto and oriented perpendicularly to the planar portion. In Fig. 1 these ring portions are denoted 3a-3f. Each casing half 1,₂ has half-cylindrical recesses located adjacent to the parting plane and forming together a cylindrical valve chamber 4. The latter is lined with a cylinder tube 5, which is provided with several hole openings (to be explained further below) and is externally sealed in the axial direction by means of the above...mentioned sealing ring portions 3a-3f. At the ends of the cylinder tube 5, end portions 6,7 are inserted, so that the valve chamber 4 only communicates outwardly via the hole openings of the cylinder tube 5 and via recesses 6a, 7a in each end portion.

[0010] Inside the cylinder tube 5, a valve slide 8 is displaceably mounted. The valve slide 8 is provided, at its end portion to the left in the figure, with a fixed piston portion 8a with two sealing rings 9,10,whlch sealingly contact the inside of. the cylinder tube 5. The opposite end of the valve slide consists of a central, rather narrow shank 8b, on which an enclosing, cylindrical piston body 11 is displaceable between a first abutment 12 formed by a shoulder surface at the foot of the shank 8b, and a second abutment 13 consisting of a steel ring, e.g. a so called Seeger-ring, inserted in an annular groove on the shank 8b. The movable piston body has piston portions 14 and 15, respectively, each provided with a piston sealing ring 16 and 17, respectively, at each end. A helical compression spring 18 is inserted between the end portion 7 and the movable piston body 11, so that the valve slide 8 and the piston body 11 takes the position shown in Fig. 1 in the absence of other forces.

[0011] The valve casing 1,2 is provided with a number of connecting ports, which communicate with the valve chamber 4 via the hole openings of the cylinder tube and the recesses 6a, 7a of the end portions, respectively, namely an inlet port 19 to be connected to a source of pressurized fluid (not shown), e.g. a central compressor unit, an outlet port 20 to be connected to a pressurized fluid system, e.g. a pneumatic system having working cylinders and components belonging thereto, an exhaust port 21, e.g. for venting the connected pressurized fluid system, and an actuatirgport 22 to be pressurized for displacement of the valve slide 8 to the right against the action of the spring 18, and an evacuation port 23. In the right part of the valve casing 1,2, there is also inserted an adjusting screw 24 in a central through-bore in the valve casing and a threaded hole in the end portion 7 opposite to the end of the shank 8b of the valve slide 8. Thereby, an adjustable stop means is obtained for the valve slide 8. The adjusting screw 24 can be fixed in an adjusted position by means of a lock nut 25 which is tightened into contact with the outside of the valve casing.

[0012] In the shown position in Fig. 1, the control valve is closed. The source of pressurized fluid communicates via the inlet port 19, an adjoining ring chamber 26, a set of hole openings 27 having a relatively large cross-sectional area and a choke hole 28 having a substantially smaller cross-sectional area, with the limited annular chamber formed between the sealing rings 26 and 27 of the movable piston body. The pressurized fluid system is vented in that the outlet port 20, connected thereto, communicates with the exhaust port 21 via an annular chamber 3: a set of hole openings 29 in the cylinder tube 5, the annual space between the inside of the cylinder tube 5 and the outside of the valve slide 8, still another set of hole openings 30 in the cylinder tube 5, and an annular chamber 32.

[0013] From the first closing position according to Fig. 1, the valve slide 8 and the piston body 11 displaceable thereon can be reversed to a second, opening position according to Fig. 2 in that a control signal (e.g. pressurized air) is fed to the actuation port 22. Thereby, the connection between the outlet port 20 and the exhaust port 21 is broken, while the pressurized fluid from the source of pressurized fluid flows through the inlet port 19, the annular chamber 26, the choke hole 28, the hole openings 29, the annular chamber 31 and the outlet port 20 into the connected pressurized fluid system. Thus, in the latter a pressure build-up will occur relatively slowly, owing to the limited flow through the choke hole 28, so that possibly mal-positioned cylinder pistons or the like are displaced into distinct positions. During this first phase of pressure build-up, a desired flow rate can be set by means of the adjusting screw 24, whereby the position of the sealing ring 16 can be varied relative to the choke hole 28. Thus, the choke hole 28 may be more or less covered by the sealing ring 16, so that the effective cross-sectional area is adjusted correspondingly.

[0014] The pressure grows gradually in the pressurized fluid system and consequently also in the annular chamber between the fixed piston portion 8a of the valve slide and the displaceable piston body 11. Thus, the pressure acts on the end surface of the piston body 11 facing the outlet port 20, and when the pressure force caused thereby exceeds the counter-force of the spring 18, the piston body 11 will be displaced from the initial position according to Fig. 2 into a final position, which is shown in Fig. 3, wherein its opposite end surface engages with the stop ring 13. The distance (in the axial direction) between the choke hole 28 and the hole openings 27 is less than the displacement of the piston body 11, and the hole openings 27 will therefore be laid free on the same side as the choke hole 28 after the passage of the sealing ring 16. As a result, the inlet port 19 will communicate with the outlet port 20 also via these hole openings 27, which have a substantially larger cross sectional area than the choke hole 28. Therefore, the pressurized fluid flow can increase quickly, so that the further pressure build-up in the connected pressurized fluid system occurs relatively quickly during this second phase of the pressurized fluid supply.

[0015] When the control valve is to be closed again and the pressurized fluid system is to be vented, the valve slide 8 is relocated in that the pressure on the signal port 22 is brought to cease, whereby the compression spring 18 displaces the valve slide and the piston body 11 to the left in the figures, and the position according to Fig. 1 is reached.

[0016] It will be apparent that a number of detail changes can be made within the scope of the claims.

[0017] Thus, the choke opening 28 does not have to be an elongated hole, as shown, but can be constituted by e.g. a number of small holes distributed axially and/or circumferentially in such a way that the effective cross-sectional area is adjustable. One or several of these holes may furthermore consist of an elongated slot extending all the way to the hole openings 27. Even the latter may have a different configuration and a variable, effective cross-section, The essential feature is that the choke opening 28 has a considerably smaller cross sectional area than the one of the flow passage formed by the hole openings 27.

[0018] Although the shown embodiment having a cylinder tube 5 provided with holes is rather practical, said cylinder tube may in principle be eliminated and, instead, the various openings may be located directly in the valve casing. Likewise, the adjusting screw 24 may be eliminated or replaced by a stop displaceably arranged on the shaft 8b of the valve slide, e.g. a nut which is screwed onto the shank and replaces the stop ring 13 as well.

Claims

1. Control valve for a controlled supply of pressurized fluid to a pressurized fluid system, comprising a valve casing (1,2) having a valve chamber (4), an inlet port (19) to be connected to a source of pressurized fluid, an outlet port (20) to be connected to the pressurized fluid system and an exhaust port (21), wherein a valve slide (8) movable in the valve chamber (4) is displaceable between a first position, in which the outlet port (20) communicates with the exhaust port (21), and a second position, in which the inlet port (19) communicates with the outlet port (20), and means (28) for restricting the flow of pressurized fluid in said second position of the valve slide (8) during a first phase of the pressure build-up in the connected pressurized fluid system, characterized in that said inlet port (19) communicates with the valve chamber (4) via, on the one hand, a flow passage (27) having a relatively large cross-sectional area and, on the other hand, a choke opening (28) having a considerably smaller cross-sectional area, and that the slide (8) of the valve is provided with a piston body (11), which is displaceable thereon and which, in said second position of the valve slide (8), is displaceable between an initial position, in which the inlet port (19) communicates with the outlet port (20) only via the choke opening (28), and a final position, in which the inlet port (19) communicates with the outlet port (20) via said flow passage (27) having a relatively large cross-sectional area as well.

2. Control valve as defined in claim 1, characterized in that the piston body (11) is provided with a sealing (16), which in said initial position is located between the choke opening (28) and the flow passage (27), wherein a piston surface facing the outlet port (20) is so dimensioned that, upon reaching a predetermined pressure of the pressurized fluid supplied to the pressurized fluid system, it is exposed to a reversing force exceeding a counter-force and thereby displaces the piston body (11) into said final position.

3. Control valve as defined in claim 2, characterized in that said counter-force is generated by a compression spring (18) .

4. Control valve as defined in anyone of the preceding claims, characterized in that the piston body (1.1) is displaceable on a shaft (8b) of the valve slide (8).

5. Control valve as defined in anyone of the preceding claims, characterized in that the initial position of the piston body (11) is adjustable by means of separate adjustment means (24),whereby the effective cross-sectional area of said choke opening (28) may be varied.

6. Control valve as defined in anyone of the preceding claims, characterized in that the valve chamber (4) is defined by a cylinder tube (5), the inside of which communicates with the various valve ports (19,20,21) via hole openings (27,28,29,30) in the cylinder tube (5), whereby said flow passage (27) and choke opening (28) are constituted by such hole openings.

7 . Control valve as defined in claim 6, characterized in that the valve casing is divided into two casing parts (1,2) and that the central axis of the cylinder tube (5) is located in the parting plane.

Drawing