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1. (WO2018224734) INLET VALVE FOR COMPRESSOR PRESSING GASEOUS MEDIUM, COMPRESSOR AND METHOD FOR CONTROLLING THE INLET VALVE OF THE COMPRESSOR
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INLET VALVE FOR COMPRESSOR PRESSING GASEOUS MEDIUM, COMPRESSOR AND METHOD FOR CONTROLLING THE INLET VALVE OF THE COMPRESSOR

TECHNICAL FIELD OF INVENTION

The object of the invention is an inlet valve for a compressor pressing gaseous medium, a compressor and a method for controlling the inlet valve of the compressor, according to what is disclosed about them in the preamble of the independent claims presented below.

STATE OF THE ART

Inlet valves for a compressor are per se known in the art. Patent specifications US5533873, US6027315, US2009/0028723 A1 , CN201779018 U and DE19916768 A1 , for example, disclose various inlet valves and their control ar-rangements.

Solutions according to the state of the art have many drawbacks. Often the structures are large and slow; for example, starting the compressor is slow if the flow path of the medium to be pressurized does not open sufficiently quickly. Gas may accumulate in the inlet valves being controlled with a fluid medium, and this impairs operation of the valve. Friction forces acting on components, such as piston seals, that are in contact with moving parts in a valve often rise to a high level. If large amounts of hot or cold air flow through a valve, the temperature of the valve can change disadvantageously. For example, devices operating in outdoor condi-tions in the wintertime are subjected to excessive cooling. Excessive cooling impairs the operational reliability of seals and causes stiffening of the lubricants, thus degrading the operational reliability of the entire apparatus.

In the solutions according to the aforementioned US specifications, there is, inter alia, no continuous circulation of control medium so that the temperature of the inlet valve cannot be adjusted in them with the control medium, e.g. in winter conditions it is not possible in them to warm the structures of the inlet valve sufficiently well. Also, gas that has accumulated in the control medium is difficult to remove in the solutions according to the aforementioned US specifications.

In the solution according to US patent specification No. US2009/0028723 A1 , one flow channel leads into the cylinder space of the piston and a second flow channel leads to inside the piston. High-pressure gas and low-pressure gas are used alternately as a control medium, and they are conducted into the cylinder and out of the cylinder along the same flow channel that leads to the end of the piston. In the flow channel leading to inside the piston is high-pressure gas, by means of which either the bottom part of the piston is pressed to close the flow path for the gas to be compressed, or the piston is raised for opening the flow path for the gas to be compressed. The specification also mentions that by using the pressure of the gas to raise and lower the piston, the use of springs and their drawbacks can be eliminated. This is a complex solution with multiple seals and a special piston, and also requires a separate valve for changing the direction of piston movement. Furthermore, a gaseous control medium cannot be efficiently used for warming the inlet valve.

AIM OF THE INVENTION

It is the aim of the present invention to reduce or even eliminate the aforementioned problems occurring in prior art.

One aim of the present invention is to provide an operationally reliable inlet valve for a compressor, in which inlet valve, inter alia, the loading of the seals can be reduced.

One aim of the present invention is to provide an inlet valve for a compressor, the operation of which inlet valve can be controlled precisely and quickly, in which case also gas bubbles in the control medium can be removed quickly and efficient-ly.

One aim of the present invention is to provide an inlet valve for a compressor, the temperature of the casing and other parts of which inlet valve being adjustable.

DESCRIPTION OF THE INVENTION

For achieving the aforementioned aims the compressor inlet valve, the compressor and the method according to the invention, as well as other objects of the in-vention, are characterized by what is disclosed in the independent claims attached hereto.

The embodiments and advantages referred to in this text relate insofar as applicable to the compressor inlet valve, to the compressor and also to the method ac-cording to the invention even when this is not expressly stated.

A typical compressor inlet valve, according to the invention, compressing a gaseous medium comprises a casing; an inlet channel that is formed through the casing for bringing gaseous medium into the inlet valve, to its inlet side; an outlet channel that is formed through the casing for removing gaseous medium from the inlet valve, from its outlet side; a cylinder space that is arranged at least partly inside the casing; a piston that is arranged to be moved in the cylinder space in a first direction, i.e. towards the inlet channel, and in a second direction, i.e. away from the inlet channel; two or more flow paths for control medium that are formed through the casing into the cylinder space for conducting control medium into the cylinder space and out of it, and thereby for moving the piston; and a shut-off means for regulating and for closing the flow of gaseous medium, which shut-off means is arranged to be moved by means of the piston. Preferably at least one flow path for control medium is connected to the cylinder space in such a way that during regulation and closing of the shut-off means the pressure of the control medium on the aforementioned flow path is lower than in the cylinder space.

A typical method, according to the invention, for controlling the inlet valve of a compressor compressing a gaseous medium comprises at least the following phases: gaseous medium is brought into the inlet valve, to the inlet side, into the inlet channel of the inlet valve; gaseous medium is removed from the outlet side of the inlet valve, from the outlet channel of the inlet valve; the piston is moved in the cylinder space of the inlet valve, said cylinder space being arranged at least partly inside the casing of the inlet valve, in a first direction, i.e. towards the inlet channel, and in a second direction, i.e. away from the inlet channel; the inlet channel is, if so desired, closed with a shut-off means that is operatively connected to the piston in such a way that it moves along with the movement of the piston. Preferably con-trol medium is conducted along a first flow path for control medium through the casing of the inlet valve into the cylinder space, and along a second flow path away from the cylinder space at a lower pressure than the control pressure of the cylinder space, and thereby the piston and shut-off means are moved by controlling the pressure of the control medium in the cylinder space.

In one embodiment of the invention, the shut-off means is connected to the piston movably in relation to it, and a spring of the shut-off means is arranged between them, which spring is arranged to exert on the shut-off means a force moving it in a first direction. This solution enables evening out of the pressure differences mov-ing the shut-off means, and/or prevention of backflow through the inlet valve, even if the piston does not move.

In one embodiment of the invention, inside the casing of the inlet valve, between the cylinder space and inlet channel, is a slide surface supporting the piston at a clearance distance from the outer surface of the piston. In this case at least one flow path for control medium is connected to the cylinder space via the clearance and is arranged to lead from the clearance of the slide surface and the outer surface of the piston to outside the cylinder space, preferably e.g. to the reservoir line. The solution enables a simple and operationally reliable structure.

In one embodiment of the invention, at least one flow path for control medium is arranged to conduct control medium out of the cylinder space during regulation and closing of the shut-off means. In such a case the essentially continuous flow of control medium can be used for adjustment of the temperature of the structures of the inlet valve.

In one embodiment of the invention, in connection with the slide surface supporting the piston, is a seal that is arranged to seal the clearance between the slide

surface and the outer surface of the piston, and at least one flow path is connected to the cylinder space via the aforementioned clearance between the seal and the cylinder space. In such a case, by means of the aforementioned flow path, the pressure exerted on the piston clearance seal from the cylinder space side can easily be lowered. In this way sealing friction decreases and the service life of the seal increases. From the viewpoint of smooth operation of the valve, it is advantageous if the seal frictions can be kept low.

In one embodiment of the invention, the inlet valve comprises an outlet channel that is arranged to lead out of the cylinder space, typically from the top part of it, into the flow path for control medium. From the viewpoint of the operation of the control arrangement, it is important that as large a proportion as possible of the gases, even all the gases, can be removed from the cylinder space and from the control medium channels. The outlet channel is situated in such a way that the gases in the cylinder space and in the control medium can be efficiently removed.

In one embodiment of the invention, the control medium is a fluid medium, e.g. hydraulic oil. When it is desired to precisely adjust the amount of medium flowing into the compressor via the inlet valve, it is advantageous to use a fluid medium as a control medium.

One great advantage of the invention is the possibility of controlling the temperature of the inlet valve, e.g. of its casing, by means of the temperature of the control medium. Large amounts of gas can flow through the valve according to the inven-tion, e.g. air conducted in from the outdoor air, that tries effectively to change the temperature of the valve. In the inlet valve according to the invention the heat or coolness of the control medium used to control the valve can be utilized. For example, the casing or flow channel of the valve can be heated or cooled with it. In the structure according to the invention, the parts that are in connection with con-trol medium, i.e. the cylinder space, piston, spring and control medium channeling, for example, can be disposed inside the casing of the inlet valve. For example, these parts can be disposed inside the outlet channel of the inlet valve and in a part of the casing of the inlet valve surrounding it. If the casing is manufactured from a material that conducts heat very well, such as aluminum, control of the temperatures of the structure becomes more efficient than before.

It is possible to arrange a control medium heater or cooler and temperature control devices in connection with an inlet valve according to the invention. In this way adjustment of the temperature of the inlet valve can be made very precise if so required.

BRIEF DESCRIPTION OF FIGURES

In the following, the invention will be described in more detail by referring to the attached diagrammatic and simplified drawings, wherein

Fig. 1 presents an inlet valve according to the invention, as viewed from the side when cross-sectioned;

Fig. 2 presents a partial enlargement of point B of Fig. 1 ; and

Fig. 3 presents the fastening of the inlet valve according to Fig. 1 to the screw unit of the compressor, as viewed from the side when cross- sectioned.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE FIGURES

For the sake of clarity, the same reference numbers are used in the various figures and embodiments in the case of some parts that correspond to each other.

Fig. 1 presents a cross-sectioned inlet valve, according to the invention, intended for a flowing gaseous medium, which inlet valve is disposed on the inlet side of the compressor or in the piping of the inlet side. The inlet valve comprises a casing 1 , and an inlet channel 9 formed through it, and also an outlet channel 10, between which channels is a shut-off means 2 for regulating and closing the flow of the flowing gaseous medium. The inlet valve further comprises at least a control unit 1 1 arranged at least partly inside the casing 1 , which control unit comprises a cylinder space 7 and a piston 4 that is arranged to be moved in the cylinder space 7 in a first direction, i.e. towards the inlet channel 9, and in a second direction, i.e. away from the inlet channel 9. Preferably the shut-off means 2 and the piston 4, which is structurally a so-called plunger piston, is fitted into the casing 1 to be movable in the direction of the center axis K of the casing 1 .

Preferably the inlet valve further comprises two or more flow paths 5, 6, 17 that are formed through the casing 1 into the cylinder space 7 for conducting the control medium of the inlet valve into the cylinder space 7 and out of it, and thereby for moving the piston 4. The flow paths 5, 6, 17 are situated e.g. in the control unit 1 1 . Preferably the control medium flow paths 5 and 17 are arranged to conduct control medium into the reservoir line or directly into the reservoir so that control medium is removed from the cylinder space 7 via them. On the other hand, the flow path 6 is connected to the control system of the compressor in such a way that via the flow path 6 control medium is both fed into the cylinder space 7 and removed from it, in which case the control medium can travel reciprocally on the flow path 6.

Inside the casing 1 , preferably in a part of the control unit 1 1 that is in the outlet channel 10, arranged between the cylinder space 7 and the inlet channel 9, is a slide surface 14 supporting the piston 4, the slide surface surrounding the piston 4 at the clearance 19 distance from the outer surface 18 of the piston. Preferably the piston 4 is round in cross-section, in which case also the slide surface 14 is round in cross-section. In the slide surface 14 is a circular groove, in which is disposed a seal 15 for sealing the clearance 19 between the slide surface 14 and the outer surface of the piston 4, i.e. more briefly the clearance of the piston 4.

For displacing the shut-off means 2, a spring 3 is disposed between the shut-off means 2 and the piston 4, which spring 3 tries to displace the shut-off means 2 against the seal surface 12 at the bottom end of the inlet channel 9 by leaning on the piston 4. Preferably the shut-off means 2 is arranged into operative connection with the piston 4. The seal surface 12 is between the inlet channel 9 and outlet channel 10 and for implementing the sealing there is a seal 16 between the seal surface 12 and the shut-off means 2. By means of the inlet valve, the flow between the inlet channel 9 and outlet channel 10 is closable and adjustable and also the backflow of it is preventable.

For example, if the inlet valve is in the open position, i.e. when the flow of the medium being compressed presses the shut-off means 2 downwards in Figs. 1 and 3, then when the drive motor of the compressor stops the structure according to the invention allows displacement of the shut-off means 2 upwards, i.e. into the closed position, even if the piston 4 was stationary. The spring 3 assists in displacing the shut-off means 2 into the closed position, i.e. in Figs 1 and 3 upwards, in which case the shut-off means 2 presses against the seal surface 12. In this way back-flow between the inlet channel 9 and the outlet channel 10 of the inlet valve can be prevented.

On the bottom end, i.e. on the second end, of the piston 4, in line with the center axis K is disposed a spring 8, the purpose of which is to displace the piston 4 into the initial position, i.e. Into the bottom position in the embodiment presented in the figures, when the pressure of the control medium has left the cylinder space 7 via the control medium flow paths 5, 6, 17, i.e. flow channels. For closing and/or regulating the flow, the control pressure of the control medium is conducted into and removed from the cylinder space 7 typically via the first flow paths 5 and 6, whereas the second flow path or flow channel, i.e. the seepage flow path 17, is preferably used exclusively for removing control medium and gas from the cylinder space 7 and its channeling.

The inlet valve presented in Fig.1 can be fastened e.g. into the screw unit 23 of the compressor in the manner presented in Fig. 3. The inlet valve is fastened to the casing of the compressor in such a way that the lower flow channel of the inlet valve, i.e. the outlet channel 10, is tightly connected to the suction orifice 21 of the screw unit 23 of the compressor, or to piping leading to it.

After the compressor has started, negative pressure forms in the outlet channel 10, which negative pressure acts on the shut-off means 2. In this case the spring 2 is compressed and the shut-off means 2 displaces into the open position, in Figs. 1 and 3 downwards, and at the same time towards the suction orifice 21 of the screw unit 23 of the compressor. Air or some other gas to be compressed is then able to flow into the inlet channel 9 and via the outlet channel 10 into the compres- sor. The compressor starts to produce pressure, which is discharged via the pressure orifice 22. When the pressure of the gaseous medium to be compressed has risen to the desired level, pressurized control medium, controlled by the compressor control system, comes e.g. via the first flow channel 6 into the cylinder space 7. In this case the piston 4 starts to move towards the inlet channel 9 and simultaneously moves, via the spring 3, the shut-off means 2, which moves in Figs. 1 and 3 upwards towards the inlet channel 9 and at the same time restricts the amount of gas flowing through the inlet channel 9. At the same time control medium escapes from the first flow channel 5 via some part (not presented) of the control system. A suitable amount of control medium also escapes via the seepage flow path 17. Preferably control medium can escape directly into the reservoir line for control medium, in which line the pressure is lower than the control pressure prevailing in the cylinder space 7. In such a case a pressure lower than the control pressure of the cylinder space 7 also prevails in the seepage flow path 17. After the control pressure has risen in the cylinder space 7 to a sufficiently high level, the piston 4 displaces the shut-off means 2 against the seal surface 12, in which case flowing of the gas into the compressor is prevented.

The parts that are in connection with control medium, i.e. the cylinder space 7, piston 4, spring 8 and control medium flow paths 5, 6, 17, are disposed in the control unit 1 1 inside the casing 1 of the inlet valve. For example, these parts can be disposed inside the outlet channel 10 and in a part of the casing 1 of the inlet valve surrounding it. In this way the temperature, i.e. the heat or coolness, of the control medium used for control of the inlet valve can be used for warming or cooling the inlet valve.

In the structure according to the invention presented by the figures, the spring force of the spring 8 exerts a force on the piston 4 that pushes the piston towards its initial position, i.e. towards the second end of the piston. A typical piston 4 ac-cording to the invention is structurally a so-called plunger piston. From the viewpoint of seal frictions, this is an advantageous solution because only one piston clearance seal 15 is needed. During operation of the inlet valve, the control pressure varies in the cylinder space 7 and therefore also on the seal 15. A rise in con- trol pressure increases to some extent the compression of the seal 15 against the outer surface 18 of the piston 4. At the same time the friction increases. It is advantageous if the pressure exerted on the seal 15 can be reduced with a suitable structure. In the structure according to Figs. 1 -3, the seepage flow path 17 leads from the piston clearance 19 into the reservoir line, in which the pressure is lower than the control pressure acting in the cylinder space 7. In this case the seepage flow path 17 is connected to the cylinder space 7 via the piston clearance 19 between the seal 15 and the cylinder space 7. Suitably, the junction of the seepage flow path 17 with the piston clearance 19 is near the seal 15.

Preferably the piston clearance 19 in connection with the cylinder space 7 can be made to be suitably large so that the pressure acting on the seal 15 is, in practice, the same as the pressure of the reservoir line. With this arrangement, the pressure exerted on the seal 15 can be reduced and thus the seal friction can also be low-ered.

The performance of the seals also affects their temperature. In the structure presented by Figs. 1 -3, the piston 4 and cylinder space 7 surrounding it, as well as the seal 15, are disposed inside the casing of the inlet valve 1 . Two or more flow paths 5, 6, 17 for control medium lead into the cylinder space 7. Of these, one can be connected to the control system of the compressor and one of the others to the return flow piping or to the control system of the compressor. Owing to this kind of arrangement, the control medium can efficiently warm or cool the structure. Heat transfer is particularly efficient if the material of the casing 1 is aluminum, which as a good thermal conductor evens out the temperatures of the structure.

When using several flow paths 5, 6, 17 for control medium, the removal of air or other gas from the control channeling of the inlet valve and from the cylinder space is more efficient than in a system comprising one flow path. The flow path 5 is used mainly to boost the transfer of control medium temperature into the parts of the inlet valve. In such a case, the control medium is removed from the cylinder space 7 via the flow path 5, in which case the circulation speed of the control medium in the cylinder space 7 increases.

The removal of gases from the control channeling and from the cylinder space 7 can be made more efficient by disposing a suitably sized outlet channel 24 in the structure to connect the cylinder space 7 and the seepage flow path 17 directly or indirectly to each other. In such a case, all the gas does not need to travel via the piston clearance 19. Preferably the outlet channel 24 is disposed between the top part of the cylinder space 7 and the seepage flow path 17. The placement is best seen in the partial enlargement B in Fig. 2. Air and other gases flow in the fluid upwards so that, owing to the placement of the outlet channel 24, gas removal from the structures of the inlet valve is more efficient.

In one embodiment of the invention, compared to the embodiment presented by Figs. 1 -3, the flow channel 5 and outlet channel 24 can be completely omitted. In this case, the piston clearance 19 is formed to be suitable in such a way that the flow of the control medium between the flow paths 6 and 17 is made to be such that the control medium is able to warm the casing 1 of the inlet valve efficiently. At the same time, any air that has collected in the channeling of the inlet valve is efficiently removed.

As presented above, in the solution according to a preferred embodiment the seepage flow path 17 is connected to the cylinder space 7 at least via the piston clearance 19, but in addition a separate outlet channel 24 can also be used to connect the cylinder space 7 and the seepage flow path 17 directly to each other. Depending on the structure, the piston clearance 19, alone or together with the outlet channel 24, is arranged to form a passage for the control medium from the cylinder space 7 into the seepage flow path 17. Preferably the combined cross-sectional area of the aforementioned passage is adapted to be smaller than the cross-sectional area of the first flow channel 6 feeding control medium into the cylinder space 7, in which case the aforementioned passage forms a choke, between the cylinder space 7 and the seepage flow path 17, for the flow of control medium. In this case a part of the control pressure of the control medium goes to controlling the movement of the piston 4 and a part circulates via the seepage flow path 17 to the reservoir line that is at a lower pressure. According to this solution, the seep- age flow path 17 for control medium is connected to the cylinder space 7 via a choke in such a way that, during regulation and closing of the shut-off means 2, the seepage flow path 17 conducts control medium out of the cylinder space 7, but the pressure of the control medium on the seepage flow path 17 is lower than in the cylinder space 7. In the solution according to a preferred embodiment, during regulation and closing of the shut-off means 2, a part of the control medium is conducted from the cylinder space 7 into the seepage flow path 17 as an essentially continuous flow, and another part of the control medium is conducted to control the piston 4.

The invention is not intended to be restricted to the embodiments presented above, but instead the independent claims define the scope of protection. The dependent claims present a few preferred embodiments of the invention.