PISTON COMPRESSOR WITH NO-LOAD OPERATION VALVE

Abstract

The invention concerns a piston compressor for compressing a compressible medium. The piston compressor includes a compressor stage, which includes a piston guided in a cylindrical space as well as an inlet valve chamber connected with the cylindrical space through art inlet valve and an outlet valve chamber connected with the cylindrical space through an outlet valve. The inlet valve chamber is connected with the cylindrical space through an idle control valve. The idle control valve includes a valve body and a control body. The valve body inner space presents a connection with the cylindrical space of the compressor stage and the valve body outer surface shows a compensation opening connecting the valve body inner space with the inlet valve chamber. The control body can move back and forth on the valve body, in an opening position releases the compensation opening, in a closed position locks the compensation opening and moves into closed position, if a pressure in the outlet valve chamber of the compressor stage arranged downstream exceeds a presettable value. The invention moreover concerns an idle control valve for a piston compressor for compressing a compressible medium.

Description

The invention concerns a piston compressor with an idle control valve.

Piston compressors are provided for compressing gases such as air, which should be used as a working medium for operating various systems. In operation such compressors are for instance used in such a way, that a compressed air container is filled with compressed air until a preset pressure level has been reached. When the preset pressure level is achieved, a control valve arranged between the compressor and the compressed air container opens, so that air forced from the compressor can escape into the atmosphere. The compressor itself is not often switched off, since it is fixedly coupled with a motor for a vehicle.

Longer pressure pipes are however generally situated between the control valve and the compressor. When the control valve is open, the compressor tries to overcome the resistance of the pipework and must hence generate a certain counterpressure. In particular with multistage compressors, the different displacements (displaced volume) of the various stages have additionally the consequence that the lower stages must still provide a significant amount of work.

It has been suggested to remedy the situation, to arrange an idle control valve between the cylindrical space of a compressor stage and the inlet valve chamber of this compressor stage. When achieving or exceeding a set differential pressure in the outlet valve chamber of the same compressor stage or of a compressor stage arranged furthermost downstream, this additional valve closes and pressure can be generated. Conversely the additional valve opens, if once the overflow valve has opened, the pressure drops in the outlet valve chamber on the pressure container.

The arrangement aforementioned indeed exhibits the shortcoming, that in certain balance conditions, wherein the force, which is exerted via the outlet valve chamber and a matching pipework on parts of the inlet valve chamber is equal to the force which is exerted via the compressor stage on the valve or parts thereof vibrations for instance of the valve tappet of the inlet valve chamber can be observed. This may damage the valve tappet as well as the valve seat plate. Moreover, the vibrations cause uncontrolled opening and closing of the inlet valve chamber and hence uncontrolled pressure fluctuations in the compressor, which again may damage the lamellae of the compressor.

It is hence an object of the invention to provide a piston compressor with an idle control valve as well as an idle control valve, whereas the problems mentioned in certain balance conditions do not occur.

According to the invention, the objective is resolved by a piston compressor with the features of claim 1. Additionally, the objective is also resolved by an idle control valve according to claim 14. Advantageous embodiments of the invention are disclosed in the dependent claims.

The single-stage or multistage piston compressor according to the invention for compressing a compressible medium includes at least one compressor stage. This compressor stage includes a piston guided in a cylindrical space as well as an inlet valve chamber connected with the cylindrical space through an inlet valve and an outlet valve chamber connected with the cylindrical space through an outlet valve. The outlet valve chamber may consist of the outlet valve chamber of the cylindrical space the first compressor stage (single-stage compressor) or of an outlet valve chamber of an additional cylindrical space, for instance of a multistage compressor arranged furthermost downstream. At the first compressor stage, the inlet valve chamber is connected with the cylindrical space through an idle control valve.

The idle control valve includes a valve body and a control body. The valve body inner space presents a connection with the cylindrical space of the compressor stage and the valve body outer surface, which faces away from the valve body inner space, shows a compensation opening connecting the valve body inner space with the inlet valve chamber. The control body can move back and forth on the valve body, releases in an opening position the compensation opening of the valve body outer surface and in a closed position locks said compensation opening. The control body moves into dosed position, if a pressure in the outlet valve chamber of the compressor stage arranged downstream exceeds a presettable value.

According to the framework of the invention, a valve body inner space is also provided into which the medium can flow in from the cylindrical space and flow off into the inlet valve chamber via compensation openings, if a control body arranged on the valve body releases one or several compensation openings. This enables on the one hand to arrange the inlet valve chamber, in particular said at least one compensation opening in a region, wherein the prevalent temperatures are not as high as immediately in or on the valve seat plate, wherein the outlet opening of the inlet valve chamber was provided until now. On the other hand, the arrangement according to the invention of at least of one compensation opening on the valve body outer surface offers the opportunity, to design the moving direction of the control body and the outflow direction of the medium from the cylindrical space into the inlet valve chamber in such a way that they rest on top of one another at a certain angle, in particular vertically, to thereby prevent any vibrations. Besides, the outflow direction of the medium from the valve body inner space can be provided in such a way, that said direction is arranged angularly or vertically to the valve body outer surface, so that the outflowing medium does not flow along the valve body outer surface or substantially not, thereby preventing the formation of coking on any corroding surface.

Another advantage of the invention lies in that the one and only component, namely the control body, may include a slider for selective locking of said at least one compensation opening in the valve body as well as a piston for applying a control pressure, in particular the pressure exiting from the outlet valve chamber.

As a matter of principle, the present invention can also be used with such a piston compressor, to be more accurate with such an idle control valve for a piston compressor, for which no special inlet valve chamber or outlet valve chamber is provided, but an inflow region and/or outflow region of different design for the medium to be compressed into the cylindrical space and/or from the cylindrical space. Another possibility, instead of applying the pressure exiting from the outlet valve chamber to the control body, consists in providing another control pressure acting on the control body, for moving the control body into closed position, if the control unit exceeds a preset value.

According to advantageous embodiments, the valve body is formed substantially cylindrical and the control body substantially hollow cylindrical. This enables straightforward assembly and easy fitting of both elements relative to one another. In particular, the inner diameter of the control body may substantially correspond to the outer diameter of the valve body.

In a particularly advantageous embodiment of the invention the control body is designed as a control piston in a control piston cylinder. Consequently, the relative movement of the control body as regards the cylinder body can be controlled by a pressure present in the control piston cylinder.

According to a particularly preferred embodiment in this respect the control piston cylinder is applied a pressure corresponding to the pressure prevalent in the outlet valve chamber. Consequently, the idea behind the invention, i.e. a particularly simple control unit, to be more accurate, simple regulation of the power produced by the piston compressor, is taken into account inasmuch as the pressure ratios prevailing in the outlet valve chamber directly influence the power produced by the compressor stage.

In this regard, a pipework can be provided between the outer valve chamber in the compressor stage and the control piston cylinder.

In a particularly advantageous embodiment of the invention both with small space requirements and cost-effective, the control piston cylinder is integrated in the inlet valve chamber. To do so, the side surface of the control piston cylinder can be directly incorporated into the casing of the inlet valve chamber. Alternately, the control piston cylinder can also be inserted as a stand-alone component into the net valve chamber.

In a further embodiment according to the invention the idle control valve includes a spring-loaded device, which applies a spring force to the control body. The resilience exerted by the spring-loaded device on the control body represents a counterforce opposite the one which is exerted on the control body by the pressure generated from the outlet valve chamber into the control piston cylinder. Only when the pressure exerted on the control body exceeds the resilience exerted by the spring-loaded device, the control body in the control piston cylinder moves from the opening position into the closed position.

In this regard it can be provided the valve body presents a receptacle for the spring-loaded device. The spring-loaded device may consist of a spiral pressore spring for instance which can be arranged in a hollow cylindrical receptacle of the valve body. In particular, the receptacle of the spring-loaded device can be separated relative to the portion of the valve body communicating with the medium of the cylindrical space.

Since in case of movement of the control body from the opening position into the closed position against the resilience, the medium situated in the receptacle of the spring-loaded device can be compressed, the invention may provide that in a preferred embodiment the receptacle and/or the control body each include one or several outlet openings, which in particular in the closed position of the control body are arranged so that the medium can overflow between the receptacle and the surrounding of the control body, i.e. in particular the inlet valve chamber. Hence, any unwanted influence of the pressure reaction characteristic of the inlet valve chamber is prevented.

A particularly preferred embodiment consists in that the main flow direction of the medium between the valve body inner space and the inlet valve chamber respectively, if no inlet valve chamber is provided, the surrounding of the valve body, substantially encloses an angle between 45° and 90° with the moving direction of the control body. The consequence is that when the medium is flowing with the control body in an opening position or a closed position, the influence on the position of the control body can be nil or negligible. Since the force component transmitted on the control body extensively works perpendicular to the moving direction of the control body the control body hardly moves or not at all and any unwanted vibration conditions are eliminated. In this context it may also be provided that several compensation openings are arranged in the valve body, which in particular may also be placed opposite.

On top of the possibility of arranging the outflow direction of the medium in such a way that no vibrations may occur inside the idle control valve, the arrangement according to the invention furthermore offers the advantage that in particular with single-stage or two-stage air compressors, with which further to an often coking of the valve seat plate, for instance an idle control valve designed as a slider sliding on the valve seat plate may get jammed, due to the medium flowing out far from the valve seat plate into the inlet valve chamber, whereas the compensation openings and the surrounding region which is brushed over by the control body, are not coked any longer.

Additional embodiments of the invention by way of example will be described more in detail below using the figures. Wherein

FIG. 1 shows a multistage piston compressor according to the invention and

FIGS. 2a, 2b show an idle control valve according to the invention in closed and opening position.

The multistage piston compressor 10 according to the invention for compressing compressible media shows two compressor stages 1, 2. Each compressor stage 1, 2 consists of or includes a piston (non represented) guided in a cylindrical space 11, 21 as well as each an inlet valve chamber 13, 23 connected with the cylindrical space 11, 21 through an inlet valve 12, 22 and an outlet valve chamber 15, 25 connected with the cylindrical space 11, 21 through an outlet valve 14, 24. The upstream compressor stage 1 arranged opposite the last compressor stage 2 includes an idle control valve 16, through which the inlet valve chamber 13 is connected with the cylindrical space 11.

The outlet valve chamber 25 of the last compressor stage 2 and hence arranged furthermost downstream is connected with the inlet valve chamber 13 of the first upstream compressor stage 1 through a pipework 3.

A heat exchanger 4 is provided between both compressor stages 1, 2 for cooling the compressible medium.

The idle control valve 16 is represented on FIG. 1 in the closed position. The compressed air container to be filled (non represented) has not reached the preset inner pressure. The overflow valve (non represented) arranged on the compressed air container is therefore closed and the multistage compressor 10 seeks to overcome the inner pressure of the closed system. The differential pressure delta p in the outlet valve chamber 25 of the compressor stage 2 arranged furthermost downstream is above a preset value. This differential pressure is applied via the pipework 3 on the idle control valve 16 and maintains the idle control valve 16 in the closed position. Thus, there is no permanent connection between the inlet valve chamber 13 and the cylindrical space 11 of the first compressor stage 1 and the medium is compressed in the first compressor stage 1.

FIGS. 2a and 2b show the idle control valve 16 in the closed position and the opening position. The idle control valve 16 includes a valve body 30, which is fastened to its side pointing to the cylindrical space 11 in the valve seat plate 32. The valve body 30 is cylindrical and possesses compensation openings 36 in its envelope surface 34. These are substantially circular or elliptical and distributed over the whole periphery of the envelope surface. Four compensation openings 36 are provided in the present embodiment. Instead of circular bores, slits or other opening geometries can be provided. The arrangement of the openings along the whole periphery is advantageous, so that the forces which are exerted when the medium flows through the compensation openings 36, extensively compensate each other.

A receptacle 38 is provided on the side of the cylinder body 30 facing away from the cylindrical space 11, said receptacle being separated from the valve body inner space 42 through a side surface 40. A spiral spring 44 is arranged in the receptacle 38. The spiral spring 44 exerts a resilience against the side surface 40 and a control piston 46. The control piston 46 is hollow cylindrical. The inner diameter of the control piston 46 substantially corresponds to the outer diameter of the valve body 30. The control piston 46 can move back and forth along the common longitudinally X of valve body 30 and control piston 46 inside a control piston cylinder 48. The control piston cylinder 48 is formed in the present embodiment thanks to a judicious design of the side surface of the inlet chamber 13. The control piston cylinder 48 may also be provided as a separate component. The pipework 3 emerges in the outlet 50 in the control piston cylinder. The outlet 50 could be placed, instead of the illustrated positioning, radially outside and consequently covered by the control piston 46 at a distance also above the control piston 46, so that the control medium can flow freely into the control piston cylinder 48. The envelope surface 34, also designated as a side surface of the valve body 30, and in particular the side surface of the control piston 46 exhibit outlet openings, here 52, 54, which in the dosed position illustrated on FIG. 2a enable the air compressed by the closing process in the receptacle 38 to overflow in the inlet valve chamber 13.

As far as necessary, the control piston 46 can be sealed on its radially outer periphery against the control piston cylinder 48, for instance advantageously wire supported by means of a seal ring (non represented), in particular of PTFE, which is inserted in particular in a peripheral groove provided to that effect in the outer surface of the control piston cylinder 48. It goes without saying that other seals between the control piston 46 and the control piston cylinder 48 can be envisioned, for sealing the chamber subjected to the control pressure in the control piston cylinder 48. A seal can be provided, with or without additional sealant, in particular a seal ring, between the control piston 46 and the valve body 30. Particularly advantageously, the illustrated bands of control piston 46 and valve body 30 push against one another in the closed position of the control piston 46, for sealing the valve body inner space surrounded by the valve body 30, and hence the compensation openings 36.

If the pressure container (non represented) to be filled has reached the requested inner pressure, the overflow valve (non represented) opens and the multistage compressor 10 does not work against the inner pressure of the closed system any longer. The differential pressure delta p in the outlet valve chamber 25 of the compressor stage 2 arranged furthermost downstream is then close to zero, which means that the differential pressure delta p does not exceed the preset value. The preset value is for instance generated by the force of the spring 44 in the receptacle 38. The force of the spring 44 then moves the control piston 46 towards the longitudinal axis X away from the cylindrical space 11 into the control piston cylinder 48. This opening position is represented on FIG. 2b. The compensation openings 36 of the valve body 30 are then no longer properly closed by the control piston 46. The connection between the cylindrical space 11 and the inlet chamber 13 in the first compressor stage 1 is free, so that the medium in the first compressor stage 1 is not compressed in spite of a permanent piston movement, which means that the first compressor stage 1 is in idle mode. Simultaneously, the compensation openings 36 are filled with liquid freely and the risk, of formation of coking around said openings is minimal due to the comparatively reduced temperature level in the valve body 30.

Claims

1. A piston compressor (10) for compressing a compressible medium, fitted with a compressor stage (1), wherein the compressor stage (1) includes a piston guided in a cylindrical space (11) as well as an inflow region or an inlet valve chamber (13) connected with the cylindrical space (11) through an inlet valve (12) and wherein the piston compressor includes an outflow region or an outlet valve chamber (25) connected with a cylindrical space (21) through an outlet valve (24), wherein the inlet valve (13) or the inflow region is connected with the cylindrical space (11) through an idle control valve (16), characterised in that the idle control valve (16) includes a valve body (30), which encloses a valve body inner space and a valve body outer surface (34) facing away from the valve body inner space, and includes a control body (46), wherein the valve body inner space shows a connection with the cylindrical space (11) of the compressor stage (1) and the valve body outer surface (34) comprises a compensation opening (36) connecting the valve body inner space with the inlet valve chamber (13) or the inflow region, and wherein the control body (46) can move back and forth on the valve body (30), in an opening position releases the compensation opening (36), in a dosed position locks the compensation opening (36) and moves into dosed position, if a pressure in the outlet valve chamber (25) of the compressor stage (2) or another control pressure acting on the control body (46) exceeds a presettable value.

2. A piston compressor according to claim 1, characterised in that the valve body (30) is substantially cylindrical.

3. A piston compressor according to claim 1 or 2, characterised in that the control body (46) is substantially hollow cylindrical.

4. A piston compressor according to one of the preceding claims, characterised in that the control body is designed as a control piston (46) in a control piston cylinder (48).

5. A piston compressor according to claim 4, characterised in that the control piston cylinder (48) is applied a pressure corresponding to the pressure in the outlet valve chamber (25).

6. A piston compressor according to any of the claim 4 or 5, characterised in that the control piston cylinder (48) is connected with the outlet valve chamber (25) via a pipework (3).

7. A piston compressor according to any of the claims 4 to 6, characterised in that the control piston cylinder (48) is integrated in the inlet valve chamber (13).

8. A piston compressor according to one of the preceding claims, characterised in that the idle control valve (16) presents a spring-loaded device (44), which applies a spring force to the control body (46).

9. A piston compressor according to claim 8, characterised in that the valve body (30) includes a receptacle (38) for the spring-loaded device (44).

10. A piston compressor according to claim 9, characterised in that that the receptacle (38) and the control body (46) each present an outlet opening (52, 54).

11. A piston compressor according to claim 10, characterised in that the outlet openings (52, 54) of the receptacle (38) and control body (46) are arranged in closed position in such a way that the medium can overflow between the receptacle (38) and the inlet valve chamber (13).

12. A piston compressor according to one of the preceding claims, characterised in that the main flow direction of the medium between the valve body inner space and the inlet valve chamber (13) with the moving direction of the control body (46) encloses an angle substantially between 45′ and 90′.

13. A piston compressor (10) according to any of the preceding claims, characterised in that the piston compressor presents an upstream (1) compressor stage and a downstream (2) compressor stage, wherein each compressor stage (1, 2) includes a piston guided in a cylindrical space (11, 21) as well as an inlet valve chamber (13, 23) connected with the cylindrical space (11, 21) through an inlet valve (12, 22) and an outlet valve chamber (15, 25) connected with the cylindrical space (11, 21) through an outlet valve (14, 24), wherein at the compressor stage (1) arranged upstream, the inlet valve chamber (13) is connected with the cylindrical space (11) through an idle control valve (16), and wherein the valve body inner space of the inlet valve chamber (16) includes a connection with the cylindrical space (11) of the compressor stage (1) arranged upstream and wherein the control body (46) moves into closed position, if a pressure in the outlet valve chamber (25) of the compressor stage (2) arranged downstream exceeds a presettable value.

14. An idle control valve (16) for a piston compressor (10) for compressing a compressible medium, fitted with a compressor stage, wherein the compressor stage includes a piston guided in a cylindrical space as well as a inlet valve chamber connected with the cylindrical space through an inlet valve or an inflow region and an outlet valve chamber connected with the cylindrical space through an outlet valve or an outflow region, wherein the idle control valve is designed in order to connect the inlet valve chamber or the inflow region with the cylindrical space at the compressor stage, characterised in that the idle control valve includes a valve body (30), which encloses a valve body inner space and a valve body outer surface (34) facing away from the valve body inner space, and includes a control body (46), wherein the valve body inner space shows a connection with the cylindrical space of the compressor stage arranged upstream and the valve body outer surface comprises a compensation opening (36) connecting the valve body inner space with the inlet valve chamber or the inflow region, and wherein the control body (46) can move back and forth on the valve body (30), releases the compensation opening (36) in an opening position, locks the compensation opening (36) in a closed position and moves to the closed position, if a pressure in the outlet valve chamber of the compressor stage or another control pressure acting, on the control body (46) exceeds a presettable value.

15. An idle control valve (16) according to claim 14, characterised in that the control body is designed as a control piston (46) in a control piston cylinder (48).