Servocontrolled valve for air-conditioning systems known as four pipes systems

The present invention relates to a servovalve for air-conditioning systems with terminal apparatuses formed of fan-convectors, inductors or the like, with contemporaneous supply of hot and refrigerated water by means of four pipes, two for the delivery and two for the return, known as "four pipes systems".

It is known that, at present, each terminal apparatus of this kind of system is associated to two batteries, one of which is passed through by hot water and the other one by refrigerated water, both being provided with a servovalve in order to control the water flow from the relevant delivery pipe. A generally electronic thermostatic device senses the temperature of the environment wherein the apparatus or "local unit" is installed and controls the two valves sequentially, by means of a rectilinear movement of a control means, such as a shutter. If the sensed temperature tends to rise above the calibration value, the "cold" battery controlling valve opens; on the contrary, if the temperature tends to lower, the "hot" battery controlling valve opens. It is absolutely necessary that, when one of the valves is open, the other one be closed in order to avoid the contemporaneous operation of the two batteries resulting in mixing of the two water flows and in a waste of energy. However, for various reasons, such a sequence may fail to occur, owing either to a thermostatic device defect or to a defect of the valve sealing.

It is also known that, due to overall size reasons, in the present local apparatuses the "hot" battery has a much smaller heat exchange surface than the "cold" one, thereby the hot water being fed must have a high temperature, which results in a considerable thermal dispersion from the pipes and does not allow the use of alternative energy sources such as heat pumps or solar collectors, by which particularly high temperatures cannot be obtained.

Therefore, the first object of the present invention is to eliminate one of the two valves and one of the two batteries for each local apparatus of a "four pipes" conditioning system, thus reducing the equipment's cost and avoiding that contemporary liquid flows having different temperatures occur in the apparatus, with notable economic advantages due to both a certain reduction in the equipment's cost, and the resulting energy gain.

Another object of the present invention is obtaining a better proportionality between valve stroke and liquid flow, with respect to the one obtainable with the rectilinearly moving valves of the prior art, as well as the independence of the valve operation from the hydraulic pressure of the circuit, with a simplification of the automatic control, since controlling two valves in sequence is no longer necessary, in addition to a simplification of the hydraulic connections.

A further object of the present invention is allowing to change in a particularly simple way the control valve characteristic, which is generally indicated with K_V, corresponding to the water flow rate in m³/h for a 1 bar pressure drop. In fact, by the valve according to the present invention it is possible to obtain different K_V values with the same valve, by adapting the characteristic thereof to that of the circuit that it has to control. Finally, it is possible to use alternative energy sources for heating the water that, with the valve according to the present invention, does not necessarily have to reach particularly high temperatures.

Said objets and advantages are obtained by means of a six-way rotating valve whose structural features are specified in claim 1.

Particularly preferred embodiments are obtainable through the features of the claims dependent from claim 1.

These and other objects, advantages and features of the valve according to the present invention will appear from the following detailed description of one embodiment thereof, which is reported as a non limiting example with reference to the accompanying drawings, wherein; <ul id="ul0001" list-style="none" compact="compact"><li><b>Figures 1 and 1a</b> are two sectional views, respectively along the line I-I of figure 1a and line A-A of figure 1, of a control valve assembly according to the present invention;</li><li><b>Figures 2, 2a and 2b</b> show the stationary ceramic collector disk 1 of the valve of figure 1 respectively in a top plan view of the same figure 1, that is taken from the side in engagement with movable disk 2, in a plan view taken from the opposite side and in a sectional view along the line B-B of figure 2;</li><li><b>Figures 3, 3a and 3b</b> show the movable ceramic distributor disk 2 respectively in a top plan view of figure 1, that is taken from the side in engagement with the control pin, in sectional views along line III-III of figure 3 and along line III'-III' of figure 3a;</li><li><b>Figures 4 and 4a</b> show the thrust compensator 3 of the valve of figure 1 respectively in a bottom plan view of figure 1, that is from the side of movable disk 2, and in a sectional view along the line IV-IV of figure 4; and</li><li><b>Figures 5, 6 and 7</b> show sectional views like in Figure 3b, in three different positions, of movable disk 2 with respect to the underlying stationary disk 1, with the corresponding positions of passage or shutting off of the ports on the stationary disk.</li></ul>

With reference to the drawings and particularly to Figures 1 and 1a, wherein the valve according to the present invention is represented in the whole, there can be seen that it is formed of a metal case 8 with lid 9 inside which a stationary collector disk 1, a movable distributor disk 2, both preferably made of self-lubricating ceramic, a thrust compensator 3, a polygonal terminal 4 integral with a central drive pin 5, connected to the servomotor which is not shown in the figure. The single elements 1-3 have been shown in greater detail in the figures 2-4a respectively. The valve comprises further a pressing spring 6 with thrust bearing 7 and a pin 10 for centering the assembly. Further, screws 21' fixing stationary disk 1 to case 8 of the valve and sleeve 22 with sealing O-rings 23 for connecting stationary disk 1 to the pipes passing through case 8 of the valve are also provided. In the valve body there are also indicated, for each port, two threaded connections, a radial one (which can be seen for all the ports in Fig. 1) and an axial one (14a and 14b for port 14 in figure 1), in order to allow the greatest connection flexibility with the hot and refrigerated water distribution piping and with the apparatus battery; the ports which are not used will be closed by suitable threaded plugs.

Now, with reference to figures 2-2b, there is particularly shown stationary ceramic collector disk 1 wherein six through ports are provided, which are so defined: 11 and 12 the ones with circular cross-section for connection to the battery; 13 and 15 the inlet and outlet curved trapezoidal ones, for example for hot water; and 14 and 16 the inlet and outlet curved trapezoidal ones for refrigerated water. Holes 21 for the screws connecting to the valve case and a hole 35 for pin 10 centering with respect to the movable disk can also be seen, while with 18 two diametrally opposite end stroke stops are indicated, and with 19 a central lowered area in order to reduce the surface of contact with the movable disk itself.

With reference to figures 3-3b there is particularly shown the movable ceramic distributor disk 2 wherein: 31 and 32 indicate two distribution channels, inscribed in the ring-shaped area defined by the six through ports of the stationary disk, 33 indicates a hole for connection with the thrust compensator, and 34 the hole, communicating with hole 33, for inserting the duct of the thrust compensator 3. There is then provided hole 35 for pin 10 which provides the centering with respect to the stationary disk, a housing 36 for the thrust compensator 3 with a polygonal impression 37 for engaging the end plate 4 of the control pin 5. It is worth while noting that, since disk 2 slips onto disk 1, the contact surfaces are worked with a very high plane-grinding grade, in order to ensure a perfect adhesion between the two surfaces for a safe contact hydraulic seal.

Thrust compensator 3 is represented in particular in figures 4 and 4a and is formed of two metallic disks 38 and 39 mutually connected by means of a corrugated metal circular wall 40. The inside of the chamber which is thus formed communicates with the outside through a pipe 41 which is intended to be inserted into hole 34 of movable disk 2 with hydraulic seal to be obtained by means of a suitable sealing material.

Polygonal end plate 4, being integral with control pin 5 of the valve, has not only the function of transmitting rotational motion from said pin to movable disk 2, but also that of opposing the thrust of compensator 3 by transferring it on pin 5, and, after all, on thrust bearing 7. It is to be noticed that it can have any profile, even different from the polygonal one, but not the circular one.

By referring again to figures 2-2b, it is to be noted that the three pairs of ports 11, 12; 13, 15 and 14, 16, respectively connecting with the battery and with the hot and refrigerated water pipes, the last two having preferably trapezoidal curved shape, are all inscribed in a ring-shaped area and spaced by 60° from each other, so that the ports of each pair are staggered from each other by 180°. Circular channels 31 and 32, of rectangular cross-section, formed in movable disk 2 (see Figure 3b), have the same width as said ring-shaped area, are diametrally opposite and their angular development is such that, when the disk is suitably rotated, the two battery ports (11 and 12 in the above assumption) are connected alternatively to the other two pairs of trapezoidal ports corresponding to the hot or refrigerated water. When the movable disk is in the intermediate position which is shown in figure 7, only battery ports 11 and 12 are uncovered, while the other four are shut off.

With respect to said position, it can be noted with reference to figure 5 that, if movable disk 2 is completely rotated by 30° counterclockwise, it connects port 11 with port 14 and port 12 with port 16 by means of channels 31 and 32 respectively, thus allowing refrigerated water to supply the battery in the above assumption, while ports 13 and 15 or shut off.

On the contrary, with reference to figure 6, when movable disk 2 is completely rotated by 30° clockwise, port 11 is connected to port 13 and port 12 to port 15, again through channels 31 and 32, thus allowing hot water to supply the battery, while ports 14 and 16 are shut off. In this regard it is to be noted that, with particular reference to figure 2b, the ports having trapezoidal shape take, through the thickness of stationary disk 1, a circular shape on the lower opposite side in order to allow connection with the corresponding holes provided on case 8 of the valve by means of suitable sleeves, such as the one indicated with 22.

The function of the thrust compensator 3 particularly shown in figures 4, 4a is automatically balancing static and dynamic thrust exerted by the water of the system onto movable disk 2 through the ports. In fact, the inside of the compensator defined by the two disks 38 and 39 and by the peripheral wall made of corrugated sheet 40 is communicating, through pipe 41, with one of the two channels 31, 32 of movable disk. The plane surfaces of compensator 3 have preferably an area which equals the sum of the four ports 13-16 which can be shut off and of the two channels 31, 32, whereby the valve operation is not influenced by the hydraulic pressure existing in the supply circuits.

It is also to be noticed that adhesion between disks 1 and 2 is obtained by means of a spring 9 pressing against movable disk 2 and that, by virtue of compensating device 3, the pressure exerted by the spring can be greatly reduced with positive effects both for the disks life and for the torque which is necessary for the valve handling, as the servocontrol is subjected to a rotating movement of ± 30°. Obviously, the movable disk can assume any position within the 60° of stroke, that is, within the positions shown in figures 5 and 6, in either direction with respect to the central neutral position of figure 7, when considering that such a position depends on the response of the servocontrol, with modulating effect, to the signal sent by the thermostatic system, with consequent regulation of the water flow rate in a linear way from 0 to 100%. In such a way, the desired proportionality requirement is obtained, which consists in a fluid flow rate directly proportional to the stroke of the shutting off member. In the rectilinearly moving valves, said member is normally formed of a shutter with respect to the valve seat, but in that case such a requirement is very difficult to be obtained, due to the stroke being reduced with respect to the diameter. On the contrary, with the six-way rotating valve according to the present invention, said requirement is met, because movable disk channels 31 and 32 uncover portions of trapezoidal port pairs which are directly proportional to the angles of rotation.

Last point to be considered, for the valve according to the invention, is the value of the previously mentioned characteristic K_V. This value is very important because it allows adapting the valve characteristic to that of the circuit to be controlled. According to the present invention, valves having different characteristics can be obtained without having to build them every time, but starting from a single basic valve. It will be enough to vary the internal diameter of duct 22 inserted into one of the two connections to the battery, starting from the maximum value, equal to that of the hole in which it is inserted, in order to obtain, with the same pressure drop (1 bar), a smaller water flow in the time unit and therefore a reduction of the characteristic K_V.

For example, the yield of the cooling battery of "four pipes" fan-convectors is normally calculated for a medium logarithmic temperature of about 10K, never going with the refrigerated water temperature at the battery inlet under 9°C, in order to avoid atmospheric condensation effects on the battery itself and with a dry bulb temperature of the air at the battery inlet of 26°C. On the contrary, the heating battery can be calculated for a medium logarithmic temperature up to 45K. Since the heating and cooling thermal loads are substantially similar, the hot battery surface can be much more reduced than the cold one, but with the need of reaching rather high temperatures, as previously mentioned. With a single battery, as provided for and made possible by using the six-way rotative valve of the present invention, the logarithmic temperature in the cooling phase would be always 10K, while the one in the heating phase would be about 12K. This means that the temperature of the water being fed could also be only 40°, with air at the battery inlet of 20°C, resulting in the possibility to use alternative energy sources for heating, such as heat pumps or solar collectors.