The present invention relates to a valve arrangement for an operation mode selector of an air conditioning system, the valve arrangement comprising a tube element which comprises a discharge port, a suction port and an evaporator port, the valve arrangement furthermore comprising two or more mode selecting valves being arranged for selectively establishing a fluid connection through either the discharge port or the suction port.

Furthermore, the invention relates to a pipe arrangement for an operation mode selector of an air conditioning system, the pipe arrangement comprising a discharge pipe, a suction pipe, and at least one valve arrangement fluidly connected to the discharge pipe and the suction pipe for selectively establishing a fluid connection with one of the discharge pipe and the suction pipe through the valve arrangement, the discharge pipe comprising one or more discharge port connecting zones, each fluidly connected to a corresponding discharge port of the valve arrangement, and the suction pipe comprising one or more suction port connection zones, each fluidly connected to a corresponding suction port of the valve arrangement.

Furthermore, the invention relates to an air conditioning system comprising a valve arrangement or a pipe arrangement.

Air conditioning systems, more specifically variable refrigerant flow systems (VRF-systems), comprising the operation mode selector in general are known. Usually, such an air conditioning system comprises one or more outdoor units for pumping a refrigerant through the system, one or more air conditioning devices comprising a heat exchanger and an expansion valve, and a tube system comprising a discharge pipe and a suction pipe fluidly connecting the one or more outdoor units to the one or more air conditioning devices, for example ceiling mounted devices, inside of a building, so as to supply the refrigerant to the air conditioning devices and to receive the refrigerant from the air conditioning devices. Typically, there are three operation modes for the air conditioning devices, heating mode, cooling mode and off mode. The operation mode selector allows controlling a fluid flow through the air conditioning system selectively so as to select one of the three modes accordingly.

To achieve this, the operation mode selector comprises two or more mode selecting valves being arranged for selectively establishing the fluid connection through either the discharge pipe or the suction pipe so as to supply refrigerant, hot gas at approx. 70°C, to the air conditioning devices in the heating mode and to supply refrigerant from the air conditioning devices back to the outdoor units in cooling mode.

To reduce noise during mode switching, especially in office buildings, usually four mode selecting valves are used allowing a stepwise increase of the fluid flow. The fluid flow from the discharge pipe is throttled by means of a first mode selecting valve having a comparably low maximum fluid flow and a second mode selecting valve having a comparably large maximum fluid flow. The fluid flow into the suction pipe is controlled by such two valves as well. One operation mode selector is provided between the discharge pipe and the suction pipe serving each air conditioning device or a group of air

conditioning devices. Due to the necessary tubes and the four mode selecting valves, such an operation mode selector is often quite complex and takes up considerable space.

US 2003/0132409 A1 discloses a valve arrangement for use in a vacuum system. It comprises an auxiliary valve and a main valve and is designed as a two-step opening valve. Valve arrangements having a similar function are also known from US 5,865,213, US 8,602,381 B2 and US 5,735,582. It is the object of the invention to provide a valve arrangement, a pipe arrangement and an air conditioning system having good integration while still being silent in operation. The object of the invention is solved by a valve arrangement as described in the outset in that one or more of the mode selecting valves are two-step opening valves.

Thus, the amount of separate mode selecting valves may be reduced which effectively leads to a reduced consumption of space and thus to a good integration. As still a stepwise control of fluid flow during mode change is possible, the system remains silent.

Preferably, the valve arrangement is in a planar configuration, the tube element and the mode selecting valves extending in the same plane. A preferred tube element is a valve housing. Planar means that the valve arrangement basically extends in two of the three spatial directions while the extension in the third spatial direction is comparably small. Thus, preferably, the mode selecting valves and the valve housing form a plate like structure. The mode selecting valves, the discharge port, the suction port, and the evaporator port may advantageously extend in the same plane. Therefore, preferably, the discharge port, the suction port and/or the evaporation port extend from the valve housing in the same extension plane radially in an outward direction of the plate like structure. A preferred valve housing is made from a metal. The valve housing preferably comprises valve mounting ports for mounting the mode selecting valves. Preferably, the extension of an edge of the plate like structure in one or two of the three spatial directions is larger by a factor of two, preferably larger by a factor of 2.5, more preferably larger by a factor of five compared to the longitudinal extension of the plate like structure in the third spatial direction. In a first spatial direction, the longitudinal extension of the valve arrangement is preferably larger by a factor of 1 .5, more preferably larger by a factor of 2 in comparison to a second spatial direction. For example, a preferred first edge of the valve arrangement has a length of 20 cm. A preferred second edge has a length of 10 cm. A preferred third edge of the valve arrangement has a length of 4 cm.

Preferably, one or more of the mode selecting valves provide a first opening step which involves throttling of a fluid flow through the mode selecting valve. This allows to establish a fluid flow through the mode selecting valve in the first opening step to establish a reduced pressure drop over the mode selecting valve.

It is preferred that one or more of the mode selecting valves provide a second opening step which is self-actuating depending on a predetermined reduced pressure drop across the mode selecting valve. This leads to a self- actuated full opening of the mode selecting valve in the second opening step once the predetermined reduced pressure drop over the mode selecting valve is established.

Preferably, two or more of the mode selecting valves are two-step opening valves. In some embodiments, the valve arrangement comprises exactly two mode selecting valves which both are two-step opening valves. The two-step opening valve is preferably adapted to open partially in a first step and fully in a second step. This means that the fluid flow in the first step is comparably smaller than the fluid flow in the second step. Thus, it can replace two separate valves for allowing a comparably small fluid flow in a first step and a comparably large fluid flow in the second step as applied in valve

arrangements for operation mode selectors of air conditioning systems of prior art. A compact valve arrangement thus becomes possible which still allows silent changing of the operation mode. It is preferred that one or more of the mode selecting valves comprise an auxiliary valve, the auxiliary valve comprising an auxiliary valve element and an auxiliary valve seat, and a main valve, the main valve comprising a main valve element and a main valve seat, the main valve element being translatably arranged and providing the auxiliary valve seat. This allows having a very good integrated valve arrangement. Basically, this way two valve units are integrated into one mode selecting valve. A preferred main valve element is biased to the opening position by a biasing element. In a first opening step of the mode selecting valve, the auxiliary valve element is translated away from the auxiliary valve seat which is provided by the main valve element. By this, fluid may stream through the auxiliary valve seat to downstream of the main valve element which reduces a pressure drop over the main valve element. The biasing element biasing the main valve element away from the main valve seat is adapted to provide a force strong enough to overcome the reduced pressure drop only. Thus, in a second opening step, when the pressure drop has reduced by a predetermined amount, the main valve element is fully translated away from the main valve seat so as to allow full flow through the mode selecting valve. The main valve seat is preferably formed by an inner wall of the valve housing, preferably an end section of a cylindrical inner wall. Preferably, the main valve element comprises a cavity in which the biasing element is arranged. Thus, preferably the main valve element radially surrounds the biasing element arranged to bias the main valve element away from the main valve seat. A preferred biasing element is supported on an inner end surface of the main valve element and on a support shoulder arranged at the auxiliary valve element. Then, when the auxiliary valve element moves away from the auxiliary valve seat, the biasing element of the main valve element may be tensioned and when the force provided by the tensioned biasing element exceeds the force created by the pressure drop over the main valve element, the main valve element will move away from the main valve seat, thus providing full fluid flow through the throttling valve. Preferably, the main valve element comprises a cylindrical extension. The cylindrical extension extends preferably from the auxiliary valve seat into the direction of the main valve seat. The cylindrical extension, also called nozzle, has the purpose to supply low pressure to the cavity of the main valve element so as to prevent the main valve element to close when high speed fluid flows through the main valve seat. Thus, in a closed state, the cylindrical extension preferably extends towards the evaporator port or towards the suction port, respectively, depending on which of the two ports is to be blocked by the respective main valve element. In other words, it is preferred that a first mode selecting valve controls the fluid flow with respect to the suction port while a second mode selecting valve controls the fluid flow with respect to the discharge port. As the fluid flow will pass through the evaporator port in both the heating mode and the cooling mode, a third mode selecting valve controlling the fluid flow through the evaporator port can be omitted. In the heating mode, the fluid flow is established between the discharge port and the evaporator port. In the cooling mode, the fluid flow is established between the suction port and the evaporator port.

Preferably, a main flow direction through the auxiliary valve seat of the first mode selecting valve is arranged perpendicular to a main flow direction through the auxiliary valve seat of the second mode selecting valve. This may allow an especially good integration as a very space saving construction is possible. Thus, preferably, the nozzle of the main valve element defines the main flow direction through the auxiliary valve seat. If no such nozzle is present, the main flow direction is the direction which the orifice of the auxiliary valve seat faces. Preferably, an orifice of the main valve seat faces in the same direction as the orifice, or nozzle, of the auxiliary valve seat. A preferred inner diameter of the orifice of the main valve seat is between 8 mm and 1 6 mm. Preferred inner orifice diameters are for example 12 mm or 14 mm. Preferably, the main flow direction through the discharge port is arranged in parallel to the main flow direction through the suction port.

Preferably, the main flow direction through the evaporator port is arranged perpendicularly to the main flow direction through the discharge port.

Preferably, the main flow direction through the evaporator port is arranged perpendicularly to the main flow direction through the suction port. However, in some embodiments an angle larger than 0° is arranged between the main flow direction through the discharge port and the main flow direction through the suction port. This may have advantages for fluid dynamics and/or for connecting the discharge port to the discharge pipe and the suction port to the suction pipe. Thus, in view of the above, it is preferred that the auxiliary valve element of the first mode selecting valve is translatably arranged in a direction perpendicular to the main fluid flow through the discharge port and

translatably arranged in parallel with the main flow direction through the evaporator port. Preferably, the auxiliary valve element of the second mode selecting valve is translatably arranged in a direction perpendicular to the main flow direction through the evaporator port and translatably arranged in parallel to the main fluid flow through the discharge port and the suction port.

Furthermore, it is preferred that the main valve seat is arranged

perpendicular to the main flow direction through the evaporator port. This may further reduce fluid speed and thus noise. Additionally, lowering the fluid speed may reduce a risk of the main valve element moving back to the closed state when fluid passes by the main valve element and through the main valve seat. This feature is highly preferred for the second mode selecting valve controlling the fluid flow through the suction port.

In a preferred embodiment, the main valve seat is arranged offset above a central diameter of the evaporator port. Thus, preferably the main fluid flow through the evaporator or port is arranged perpendicular to a cylindrical outer wall providing the main valve seat and perpendicularly directed onto said outer wall. This may further decrease fluid speed of a fluid entering or leaving the evaporator port. A preferred offset is one quarter of the diameter of the evaporator port above the center of the fluid flow passing though the evaporator port. The center of the main fluid flow through the evaporator port preferably coincides with the geometric center of the evaporator port. This feature is highly preferred for the second mode selecting valve controlling the fluid flow through the suction port.

Preferably, the auxiliary valve element is arranged to have a stroke length of 25 % or more of the inner diameter of the orifice of the main valve seat.

Preferably, the auxiliary valve element is arranged to have a stroke length of at least 4 mm. As comes clear from the above, the auxiliary valve element is arranged translatable so as to selectively open or close the auxiliary valve. Preferably, the auxiliary valve element is arranged to be actuated by a solenoid provided in the mode selecting valve. As the main valve element should have a comparably large stroke length so as to fully retract from the main valve seat and the main valve element provides the auxiliary valve seat, consequently, the auxiliary valve element should also have a comparably large stroke length. It is preferred that the stroke length is at least 4 mm, more preferably at least 8 mm. As follows from the above, the preferred stroke length of the main valve element is the same as the stroke length of the auxiliary valve element. The nozzle diameter, thus an inner diameter of a lumen through the nozzle, preferably is larger than 1 mm, more preferably larger than 1 ,5 mm. In a preferred embodiment, the auxiliary valve of one or more of the mode selecting valves is arranged to be opened by applying a peak electric power and is arranged to be held open by applying a holding electric power, the peak electric power being larger than the holding electric power. A preferred mode selecting valve comprises a power supply or is arranged to be fed by a power supply. A preferred power supply is a 24 V DC power supply. A comparably large peak electric power is needed to compensate for the comparably large stroke length of the auxiliary valve. Thus, the mode selecting valve is preferably arranged to provide a peak electric power of 25 W to 75 W, preferably 50 W, for an amount of time of 100 to 1000 ms, preferably 150 ms, more preferably 500 ms. Furthermore, the mode selecting valve is arranged to supply a holding electric power of preferably 1 to 5 W, more preferably 2.5 W, once the auxiliary valve element is in an open state and the auxiliary valve element shall be kept in the actuated, thus open, position. Preferably, the peak electric power is supplied by providing 2 to 3 A, more preferably 2.2 A. When the holding electric power is applied, the supplied current may be reduced to 0.05 A to 0.7 A, preferably to 0.1 A.

Thus, if the mode selecting valve is a solenoid valve, the solenoid may be arranged to actuate the auxiliary valve element in the way described above.

Preferably, the evaporator port comprises a cylindrical conduit which comprises at least one section having a radial outer wall extending in parallel to a main flow direction through the evaporator port and a tapering section having a radial outer wall tapering against the main flow direction, the main flow direction being directed into the tube element. Preferably, an angle of inclination between an inner surface of the radial outer wall the section arranged in parallel to the main flow direction and an inner surface of the radial outer wall of the tapering section is smaller than 15°. Preferably, the inclination is smaller than 10°. Preferably, there are two sections having the radial outer wall extending in parallel to the main fluid flow direction through the evaporator port and the tapering section is arranged in between the two parallel sections. Preferably, the tapering section results in a deceleration of fluid speed of a fluid entering the tube element through the evaporator port with a factor of preferably equal or larger than 1 .5, more preferably equal or larger than 2.5, most preferably equal or larger than 3.5, comparing a fluid speed at the end of the cylindrical conduit being distant from the tube element to a fluid speed at the end of the cylindrical conduit being adjacent to the tube element. Lowering the speed before the valve may reduce noise. Furthermore, the object of the invention is solved by a pipe arrangement as described in the outset in that at least one of the valve arrangements is a valve arrangement as described above.

The pipe arrangement thus has a compact size and reduced complexity while silent operation is still possible.

Preferably, one or more of the suction port connecting zones and/or one or more of the discharge port connecting zones are provided in a radial outer surface of the corresponding pipe. Having the ports arranged in a radial outer surface of the corresponding pipe allows high positioning flexibility for mounting the valve arrangement to the corresponding pipe. Preferably, two or more suction port connecting zones are provided in the radial outer surface of the suction pipe. Preferably, two or more discharge port

connecting zones are provided in the radial outer surface of the discharge pipe. Preferably, the suction pipe comprises two or more suction port connecting zones in the radial outer surface, more preferably three or more, more preferably four or more, more preferably five or more, more preferably six or more, more preferably seven or more, and most preferably eight or more suction port connecting zones in the radial outer surface. Mutatis mutandis, said numbers of discharge port connecting zones are provided preferably on the discharge pipe. In some embodiments, the respective port connecting zones are provided in a row. Each of the pipes may comprise two rows of port connecting zones facing each other. Via the respective port connecting zones the fluid connection between the pipes and the valve arrangement is established.

In some embodiments, the pipe arrangement comprises two or more valve arrangements having a planar configuration and being connected to the discharge pipe and to the suction pipe, the valve arrangements being separated from each other by an air gap. Preferably, the two or more valve arrangements are each connected to the suction pipe and the discharge pipe via port connecting zones arranged on the radial outer surface of the respective pipe. As the valves have a planar configuration, a space saving array, like a row of valve arrangements, may be provided on the pipe arrangement. The air gap between adjacent valve arrangements of the valve array should amount from 0,1 to 10 cm, more preferably from 0,3 to 1 cm. A good air gap could amount 0,5 cm, for example. Preferably, the pipe arrangement comprises a row of two or more valve arrangements, the discharge ports and the suction ports of the valve arrangements being arranged one after another on each of the two pipes, respectively. A row means that the valve arrangements are arranged such that the respective ports form a line on the respective pipe. This allows a compact configuration. However, in the alternative, neighboring port connecting zones may be arranged offset along the respective pipes. This may help to increase the air gap between two adjacent valve arrangements in a space saving manner. It is preferred that the pipe arrangement comprises two valve arrangements being arranged at the discharge pipe as a pair, the discharge port of one valve arrangement of the pair facing the discharge port of the other valve arrangement of the pair. This allows arranging two or more valve

arrangements on the same pipe while having a maximum air gap between them. The two or more pairs of valve arrangements are preferably arranged with an angular displacement of 180° between each of the valve

arrangements of each pair on the radial outer surface of the respective pipe. There may be one, two, three, four, or even more pairs of valve

arrangements per pipe arrangement. A preferred discharge pipe is an elongated pipe comprising two pipe connectors for fluidly connecting the discharge pipe to other elements of the air conditioning system. A preferred suction pipe is an elongated pipe comprising two pipe connectors for fluidly connecting the suction pipe to other elements of the air conditioning system. Preferred pipes are straight pipes. It is preferred that the pipe arrangement comprises two rows of two or more valve arrangements each, the discharge port and the suction port of each valve arrangement of one row being arranged facing the discharge port and the suction port of a corresponding valve arrangement of the other row. This allows arranging two rows of valve arrangements on the same pipe arrangement in a very efficient manner. In other words, the respective port connection zones of the discharge pipe and the suction pipe are preferably arranged on the radial outer surfaces of each of the two pipes and two rows of valve arrangements are arranged facing each other on each of the pipes. The port connection zones for one row of the valve arrangements are thus angularly displaced by 180° with respect to the port connection zones of the other row.

In an embodiment of the pipe arrangement each valve arrangement comprises an evaporator port, wherein the discharge pipe and the suction pipe are arranged in a common plane and the evaporator port extends perpendicular to the common plane. Such an arrangement has advantages when a plurality of valve arrangements is arranged one by one along the discharge pipe and the suction pipe. In an embodiment of the pipe arrangement there are at least two valve arrangements the evaporator ports of which extend in opposite directions. Accordingly the space on both sides of the pipe arrangement can be used to connect other pipings. In an alternative embodiment there are at least two valve arrangements the evaporator ports of which extend in the same direction. In this case the pipe arrangement can be located in a position in which access from one side is available.

In an embodiment of the pipe arrangement the evaporator ports of adjacent valve arrangements are offset relative to each other in a direction

perpendicular to the discharge pipe. In other words, the evaporator ports are arranged in a zig-zag-manner.

In an embodiment of the pipe arrangement the evaporator port extends from a pipe section in an area which is limited by a first plane through the discharge pipe and a second plane through the suction pipe and parallel to the first plane. In this way the evaporator port can extend, for example, through a space between the suction pipe and the discharge pipe. Furthermore, the object of the invention is solved by an air conditioning system as described in the outset which comprises a valve arrangement as described above or a pipe arrangement as described above. Such an air conditioning system has a compact configuration while allowing operation with low noise due to the stepwise throttling of the fluid flows when switching between the operation modes.

A preferred air conditioning system comprises one or more air conditioning devices. A preferred air conditioning device is connected to a liquid line and comprises an electronic expansion valve. Furthermore, a preferred air conditioning system can be switched between an off mode, a cooling mode, and a heating mode so as to either reduce the temperature of a room in which it is arranged or increase the temperature of the room in which it is arranged. Preferably, there is a connection pipe between the evaporator port of the valve arrangement and the air conditioning device. Thus, a preferred air conditioning device is an evaporator in cooling mode or a condenser in heating mode. Therefore, in view of the above, the first mode selecting valve is preferably a heating mode valve arranged to control the fluid flow between the discharge port and the evaporator port. Accordingly, the preferred second mode selecting valve is a cooling mode valve arranged to control the fluid flow between the suction port and the evaporator port. A preferred pressure at the suction port is between 7 and 10 bar. A preferred pressure at the discharge port is between 35 to 40 bar. A preferred pressure at the

evaporator port is between 20 and 30 bar.

In the following, preferred embodiments of the invention will be described referring to the attached drawings in which

Fig. 1 shows a perspective view according to a first embodiment of the invention;

Fig. 2 shows a cross-sectional view through the first embodiment of the invention;

Fig. 3a shows a first controlling state in a heating mode according to the first embodiment;

Fig. 3b shows a second controlling state in a heating mode according to the first embodiment;

Fig. 4a shows a first controlling state in the cooling mode according to the first embodiment;

Fig. 4b shows a second controlling state in the cooling mode according to the first embodiment;

Fig. 5 shows a perspective view of a second embodiment according to the invention;

Fig. 6 shows a third embodiment of the invention;

Fig. 7a shows a cross-section through the second embodiment of the invention;

Fig. 7b shows a side-view of two pipe arrangements according to the second embodiment which are serially connected to each other; Fig. 8 shows a cross-section of a mode selecting valve used embodiment of the invention;

Fig. 9 shows a main valve element used in an embodiment of the

invention;

Fig.10 shows a fourth embodiment of the invention in a perspective view;

Fig. 1 1 shows a section through the fourth embodiment of the

invention;

Fig. 12 shows a fifth embodiment of the invention in a perspective view;

and

Fig. 13 shows a front view of the embodiment of fig.12.

In order to increase readability, reference signs were added to the following detailed description of embodiments and to the attached patent claims. The reference signs are in no way meant to be limiting. Furthermore, it should be understood that features shown in one embodiment may be freely combined with features shown in other embodiments and with any feature described above as long as they do not conflict with each other. Furthermore, as should be understood, the invention is not limited to the exemplary embodiments.

Figure 1 shows a first exemplary embodiment according to the invention. A pipe arrangement 1 for an operation mode selector of an air conditioning system is depicted. The pipe arrangement 1 comprises a valve arrangement 2 comprising a tube element 3, here a valve housing, which comprises a discharge port 4, a suction port 5 and an evaporator port 6. The pipe arrangement 1 comprises a discharge pipe 7 and a suction pipe 8. The valve arrangement 2 is fluidly connected to the discharge pipe 7 via the discharge port 4. Furthermore, the valve arrangement 2 is fluidly connected to the suction pipe 8 via the suction port 5. For this reason, the discharge pipe 7 comprises a discharge port connection zone fluidly connected to the corresponding discharge port 4 of the valve arrangement 2. Additionally, the suction pipe 8 comprises a suction port connecting zone fluidly connected to the suction port 5 of the valve arrangement 2. For selectively establishing the fluid connection with one of the discharge pipes 7 and the suction pipe 8 through the valve arrangement 2, the valve arrangement 2 comprises two mode selecting valves 9, 10. More specifically, the valve arrangement comprises a first mode selecting valve 9 which is arranged to control a fluid flow from the discharge pipe 7 to the evaporator port 6. In addition, the valve arrangement 2 comprises a second mode selecting valve 10 arranged to control a fluid flow from the evaporator port 6 to the suction pipe 8.

As shown in figure 1 , the pipe arrangement has a very compact design. This is due to the first mode selecting valve 9 and the second mode selecting valve 10 being two-step opening valves. The two mode selecting valves 9, 10 each provide a first opening step which involves throttling of a fluid flow through the mode selecting valve 9, 10 and a second opening step which is self-actuating depending on a predetermined reduced pressure drop across the first mode selecting valve 9 and the second mode selecting valve 10, respectively. Thus, instead of four separate valves for ensuring a quiet change between operation modes, two two-step opening valves are provided. Thus, a silent change between off mode, heating mode and cooling mode can be provided with a compact configuration.

As shown, the valve arrangement 2 is in a planar configuration, the tube element 3 and the mode selecting valves 9, 10 extending in the same plane. This means that the tube element 3, the discharge port 4, the suction port 5, the evaporator port 6, the first throttling valve 9 and the second throttling valve 10 all extend basically in the same plane.

Figure 2 now discloses further details about the first embodiment in a cross- sectional view. As both mode selecting valves 9, 10 are identical with respect to their design and functionality, here reference is made only to the details of the first mode selecting valve 9. The state depicted in figure 2 is the off mode. Thus, both, the first mode selecting valve 9 and the second mode selecting valve 10 are in a fully closed state. Therefore, no fluid flow takes place between the discharge port 4 and the evaporator port 6 or between the suction port 5 and the evaporator port 6. The first mode selecting valve 9 is a solenoid valve. Therefore, it comprises a solenoid 1 1 a. The solenoid 1 1 a can be energized by a power source fixed with a screw to a casing of the first mode selecting valve 9. When the solenoid 1 1 a is energized, an auxiliary valve element 12a will be pulled upwards against a biasing force of a first biasing element 13a, a coil spring. The auxiliary valve element 12a is radially surrounded by a main valve element 14a and a second biasing element 15a, a coil spring, arranged for biasing the main valve element 14a in an opened position. Furthermore, the main valve element 14a comprises an auxiliary valve seat 1 6a which comprises a longitudinal nozzle. As can be seen, in the closed state of the first mode selecting valve 9, the nozzle extends through an orifice of a main valve seat 17a into a lumen provided by a cylindrical wall providing the main valve seat 17a. Thus, in a first opening step the solenoid 1 1 a is energized which translates the auxiliary valve element 12a away from the auxiliary valve seat 1 6a provided by the main valve element 14a. By this, a comparably small fluid flow through the auxiliary valve seat 1 6a becomes possible and the second biasing element 15a becomes tensioned so as to create a force pushing the main valve element 14a away from the main valve seat 17a. However, the biasing force created by the second biasing element 15a is pre-set so that it is smaller than a biasing force created by a pressure drop over the main valve element until a predetermined reduced pressure drop over the main valve element 14a is established. At this point in time, the pressure drop over the main valve element 14a has sufficiently reduced so that the main valve element 14a is pushed away from the main valve seat 17a, thus performing the second opening step. As the orifice of the main valve seat 17a has an inner diameter of 8 mm, which is larger than the inner diameter of the orifice of the auxiliary valve seat 16a, the fluid flow in the second opening step is considerably larger than in the first opening step in which only the orifice of the auxiliary valve seat 1 6a is open.

Figure 3a now depicts a state in which the heating mode is to be started. A peak electric power of 50 W is provided to the solenoid 1 1 a of the first mode selecting valve 9 by means of a 24 V DC power supply at 2.2 A for 500 ms in the first embodiment. However, instead of a 24 V DC power supply, any power supply can be used which may supply sufficient peak electric power to actuate the auxiliary valve element 12a. As shown in figure 3a, in the first opening step, the second biasing element 15a is compressed between a shoulder provided on a front end of the auxiliary valve element 12a and a surface of the main valve element 14a arranged opposite to the auxiliary valve seat 16a. In this state, the force provided by the second biasing element 15a is still not large enough to overcome the force created by the pressure drop over the main valve element 14a. When the pressure drop reduces due to fluid passing through the orifice of the auxiliary valve element 16a, after a predetermined reduced pressure drop is established, the force created by the second biasing element 15a will be strong enough to overcome the force created by the pressure drop. Then the main valve element 14a will lift from the main valve seat 17a, as depicted in figure 3b.

Figure 3b then shows the heating mode in full effect. The main valve element 14a has lifted completely from the main valve seat 17a as the pressure drop over the first throttling valve 9 has reduced due to the auxiliary valve being in the opened position. Therefore, the second biasing element 15a, biasing the main valve element 14a away from the main valve seat 17a, produces the force strong enough to translate the main valve element 14a into the opened position. To hold the auxiliary valve element 12a in the opened position, a holding electric power supplied by the power supply to the solenoid 1 1 a is sufficient, the peak electric power being larger than the holding electric power. In the depicted embodiment, the holding electric power is 2.5 W, applied for example for 60 seconds or longer, as long as the heating mode is selected. After the heating mode is deactivated by closing the first mode selecting valve 9, the first mode selecting valve 9 returns to the state depicted in figure 2.

Figure 4a now refers to a state in which the cooling mode is to be started. In this state, the second mode selecting valve 10 is actuated so as to allow a fluid flow between the evaporator port 6 and the suction pipe 8. As said before, the design and function of the second mode selecting valve 10 is identical with the design and function of the first mode selecting valve 9.

Accordingly, a peak electric power of 50 W is provided to the solenoid 1 1 b of the second mode selecting valve 10 by means of a 24 V DC power supply at 2.2 A for 500 ms. The power supply is attached to the second mode selecting valve 10 by a screw connection, as shown in figure 4a. However, instead of a 24 V DC power supply, any power supply can be used which may supply sufficient peak electric power. The auxiliary valve element 12b is lifted from the auxiliary valve seat 1 6b which allows fluid flow from the evaporator port 6 to the suction port 5. Thus, refrigerant may be transferred from the air conditioning device fluidly connected to the evaporator port, through the valve arrangement 2, to the suction port 5 and out into the suction pipe 8.

Figure 4b shows the cooling mode in full effect. The main valve element 14b has lifted from the main valve seat 17b as the pressure difference over the second mode selecting valve 10 has reduced due to the auxiliary valve element 12b being in the opened position. Therefore, the second biasing element 15b, biasing the main valve element 14b away from the main valve seat 17b, provides a force strong enough to translate the main valve element 14b into the opened position. To hold the auxiliary valve element 12b in the opened position, a holding electric power supplied by the power supply is sufficient, the peak electric power being larger than the holding electric power. In the present embodiment, the holding electric power is, like for the first mode selecting valve 9, 2.5 W. The holding electric power is applied, for example, for 60 seconds or longer, as long as the cooling mode is selected. After this, the cooling mode is deactivated by fully closing the second mode selecting valve 10, thus returning to the state depicted in figure 2.

In order to reduce fluid speed and thus noise in the cooling mode depicted in Fig. 4a and 4b, the evaporator port 6 comprises a cylindrical conduit which comprises two sections having a radial outer wall extending in parallel to a main fluid flow direction through the evaporator port 6 and one section having a radial outer wall tapering against the main fluid flow direction in the cooling mode. The tapered section is arranged between the two parallel sections. The angle of inclination between inner surfaces of the parallel sections and inner surfaces of the tapered section is smaller than 15°. Thus, as the cylindrical conduit widens along the flow direction in the cooling mode, the fluid speed decreases. In the embodiment as shown the fluid speed is decelerated with a factor of 2.5 through the cylindrical conduit. Furthermore, the main valve seat 17b of the second mode selecting valve 10 is arranged perpendicular to the main flow direction through the evaporator port 6. The main valve seat 17b is furthermore arranged offset with respect to a central diameter of the evaporator port 6. Both features further decrease fluid flow speed of fluid passing through the second mode selecting valve 10 and entering the suction pipe 8. This may reduce noise during operation mode switching, which is highly preferred in office environments. Therefore, in view of the figures 3 and 4, it becomes clear that it is highly advantageous when two or more of the mode selecting valves 9, 10 are two- step opening valves. A very good stepwise opening is possible when one or more of the mode selecting valves 9, 10 comprise an auxiliary valve, the auxiliary valve comprising an auxiliary valve element 12a, 12b and an auxiliary valve seat 1 6a, 1 6b, and a main valve, the main valve comprising a main valve element 14a, 14b and a main valve seat 17a, 17b, the main valve element 14a, 14b being translatably arranged and providing the auxiliary valve seat 16a, 1 6b, as depicted in the figures 3 and 4. As shown, the main flow direction through the auxiliary valve seat 1 6a of the first mode selecting valve 9 is arranged perpendicular to a main flow direction through the auxiliary valve seat 16b of the second mode selecting valve 10. This is very advantageous in order to have a planar configuration of the valve

arrangement 2, thus a plate-like valve arrangement 2. A preferred size of the valve arrangement 2 is 20 x 10 x 4 cm ³ . The valve arrangement 2 according to the invention is very space saving.

In general, in the state depicted in figure 2, before the heating mode is activated, thus in start-up, an electronic expansion valve (EEV) of the air conditioning device (not shown) connected to the evaporator port 6 is in a closed state, allowing no fluid flow. In the state depicted in figure 3a, the EEV is in a closed state, preventing fluid flow. In the state depicted in figure 3b, the EEV is in an opened state, allowing fluid flow. When the heating mode is deactivated, the EEV is put in the closed state, as are the first mode selecting valve 9 and the second mode selecting valve 10. Before the cooling mode is activated, the EEV is in a closed state. When the cooling mode is ready, as shown in figure 4a, the EEV is still in the closed state. When the cooling mode is running, thus the state according to figure 4b, the EEV is open. When the cooling mode is deactivated, the EEV, the first mode selecting valve 9 and the second mode selecting valve 10 are all put in a closed state.

Figure 5 shows a second embodiment of a pipe arrangement 1 for an operation mode selector of an air conditioning system, the pipe arrangement 1 comprising a discharge pipe 7, a suction pipe 8, and four valve

arrangements 2 fluidly connected to the discharge pipe 7 and the suction pipe 8 for selectively establishing a fluid connection with one of the discharge pipe 7 and the suction pipe 8 through each of the valve arrangements 2. The discharge pipe 7 comprises four discharge port connecting zones, each fluidly connected to a corresponding discharge port 4 of each valve arrangement 2, and the suction pipe 8 comprises four suction port connection zones, each fluidly connected to a corresponding suction port 5 of each valve arrangement 2. As shown in figure 5, all four of the valve arrangements 2 are two-step opening valves, more specifically solenoid valves as explained above. This becomes possible due to the fact that the suction port connecting zones and the discharge port connecting zones are provided in a radial outer surface of the corresponding pipe 7, 8. Thus, each of the valve arrangements 2 is fluidly connected to the discharge pipe 7 and the suction pipe 8 through the radial outer surface. Therefore, the four valve arrangements 2 have a planar configuration. This allows, as shown, to arrange the valve

arrangements 2 side by side along the extension of the discharge pipe 7 and the suction pipe 8. More specifically, as shown in figure 5, a row of four valve arrangements 2 is provided, the discharge ports 4 and the suction ports 5 of the valve arrangements 2 being arranged one after another on each of the two pipes 7, 8 respectively. Figure 6 shows a third embodiment according to the invention. Here, the pipe arrangement 1 comprises several pairs of two valve arrangements 2 being arranged at the discharge pipe 7, the discharge port 4 of one valve

arrangement 2 of the pair facing the discharge port 4 of the other valve arrangement 2 of the pair. Three pairs of valve arrangements 2 and thus six valve arrangements 2 in total are provided connected to the discharge pipe 7 and the suction pipe 8. Thus, there are two rows of two or more valve arrangements 2 each, the discharge port 4 and the suction port 5 of each valve arrangement of one row being arranged facing the discharge port 4 and the suction port 5 of a corresponding valve arrangement 2 of the other row. A highly compact pipe arrangement 1 is thus provided. Figure 7a shows a cross-section of a pipe arrangement 1 according to figure 5. The discharge pipe 7 and the suction pipe 8 each are covered on a first end by a plug 18 while the other end is arranged to be fluidly connected to fluid circuits of the air conditioning system. As can be seen in this drawing, the four valve arrangements 2 have a planar configuration and are connected to the discharge pipe 7 and to the suction pipe 8, the valve arrangements 2 being separated from each other by an air gap 19. The air gap has a width of 0,5 cm. Thus, the distance between two neighboring valve arrangements 2 is 0,5 cm in this embodiment. The distance between two centerlines of two neighboring valve arrangements 2 is 3,8 cm.

As shown in Fig. 7b, when the respective plugs 18 are removed, two or more pipe arrangements 1 may form a set. The discharge pipes 7 and the suction pipes 8 of each pipe arrangement 1 are serially connected to each other, respectively. Thus, eight valve arrangements 2 are provided in a compact manner in the shown example, using a solder joint.

Figure 8 now shows a longitudinal section through the first mode selecting valve 9 disclosing more details. As is shown, the auxiliary valve element 12a comprises a cavity which houses the first biasing element 13a. The biasing element 13a biases the auxiliary valve element 12a into the closed position, thus pressed on the auxiliary valve seat 1 6a. The auxiliary valve seat 1 6a is part of the main valve element 14a. The main valve element 14a is made of brass. However, in some embodiments, the auxiliary valve seat 1 6a is made from a molded polymer or Teflon. Having the molded part allows to omit further sealing means for sealing the main valve element 14a. The tip of the auxiliary valve element 12a is equipped with a spherical element 20a. The spherical element 20a ensures good sealing of the auxiliary valve seat 1 6a in the closed state. In alternative embodiments (not shown), a substantially cylindrical element is provided instead of the spherical element 20a. As shown in figure 8, the second biasing element 15a is radially surrounded by the main valve element 14a. This allows a compact design. The second biasing element 15a, a coil spring, biases the main valve element 14a into the opened position, thus away from the main valve seat 17a. However, the force provided by the second biasing element 15a is strong enough only after the predetermined reduced pressure drop over the first mode selection valve 9 is established. As shown, the second biasing element 15a is supported on a shoulder on the front end of the auxiliary valve element 12a, neighboring to the spherical element 20a. When the auxiliary valve element 12a translates backwards into a space 21 a, in this embodiment by 4 mm, the second biasing element 15a gets compressed, being able to force the main valve element 14a away from the main valve seat 17a once the pressure drop over the main valve element 14a has reduced by a predetermined amount. The stroke length is 50 % of the inner diameter of the orifice of the main valve seat 17a. However, in other embodiments the stroke length may just be more than 25 % of the inner diameter of the orifice of the main valve seat 17a to provide sufficient flow capacity. Same goes for the second mode selecting valve 10 which follows the same principles, mutatis mutandis and in view of figures 4a and 4b.

Finally, figure 9 shows a main valve element 14a as applied in the first mode selecting valve 9 of the three embodiments. The main valve element 14a comprises a feeding hole 22a passing through a radial outer surface of the conically shaped main valve element 14a. The feeding hole 22a is arranged adjacent to a sealing face 23. The feeding hole 22a also serves as a bleeding hole. The sealing face 23a ensures sealing when the main valve element 14a is in the fully opened state, thus the main valve element 14a is lifted from the main valve seat 17a, for example by a full stroke of 4 to 10 mm. Fluid may flow through the discharge pipe 7 or the suction pipe 8, respectively, and through the feeding hole 22a, the auxiliary valve seat 1 6a, the nozzle and the evaporator port 6 when the auxiliary valve element 12a is distant from the auxiliary valve seat 16a. It should be noted that the length of the tubular nozzle of the auxiliary valve seat 1 6a depends on the stroke length of the auxiliary valve element 12a. The length of the nozzle is selected so that the forward end of the nozzle pointing away from the auxiliary valve element 12a remains radially surrounded by the cylindrical wall of the main valve seat 17a even in the fully opened state of the main valve element 14a, as can be seen in figure 3b. By this, low pressure is fed from upstream the main valve element 14a to the interior of the main valve element 14a, preventing the main valve element 14a to close once fluid streams along its outer surfaces and through the main valve seat 17a. This opposes a suction effect caused by the flowing fluid. Again, the description above also pertains to the main valve element 14b of the second mode selecting valve 10.

As described above, a valve arrangement 2, a pipe arrangement 1 and an air conditioning system (not shown) may be provided which are compact in view of prior art while still allowing a silent changing between the operation modes. This is due to the fact that one or more, in the embodiments as described two two-step valves instead of a multiplicity of single step opening valves are used in each valve arrangement 2 which allows a space saving design while keeping the function the same.

Fig. 10 and 1 1 shows a fourth embodiment of the invention in which eight valve arrangements are arranged in a very compact manner. To this end the discharge pipe 7 and the suction pipe 8 are arranged one above the other in a common plane 30.

The evaporator ports 6 of a first group 31 of valve arrangements extends perpendicular to the plane 30 in one direction and the evaporator ports 6 of another group 32 of valve arrangements extends perpendicular to the plane 30 in the opposite direction. Fig. 12 shows a fifth embodiment of the invention which is similar to the embodiment of fig. 10 and 1 1 . However, the evaporator port 6 of both groups 31 , 32 of valve arrangements extend in the same direction perpendicular to the plane 30.

As can be seen in fig. 13, the evaporator ports 6 of adjacent valve

arrangements are offset relative to each other in a direction perpendicular to the discharge pipe 7. In other words, the evaporator ports 6 are arranged in a zig-zag-manner so that the space available can be used optimally.

As can be seen in particular from fig. 1 1 at least one evaporator port 6 (in the embodiment shown all evaporator ports) extends from a pipe section 33 in an area which is limited by a first plane 34 through the discharge pipe 7 and a second plane 35 through the suction pipe 8, wherein the first plane 34 and the second plane 35 are parallel to each other. The pipe section 33 forms part of the valve arrangement 2