Abstract:
An automatic flow rate control valve, includes a tubular body, defining a flow path between inlet apertures having a gradually variable cross-sectional area and a fluid outlet at one end; a flow control piston is axially movable within the tubular body, under opposite actions of the fluid pressure and a biasing spring, to choke the fluid inlet apertures, while maintaining a constant flow rate. The control piston is in the form of a first cup-shaped element sliding on a second cup-shaped element to define a hydraulic damping chamber, communicating with the flow path.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention refers to an automatic valve for controlling the flow rate of a hydraulic fluid; in particular it is directed to an automatic flow control valve and to a valve assembly to maintaining the flow rate of a fluid at a constant value, in response to pressure changes of the fluid.  
       STATE OF THE ART  
       [0002]     As is known, in the hydraulic circuits for heating or air-conditioning systems connected to several users, it is necessary to provide for a stabilisation of the flow rates of the fluid, when changes of the pressure or certain functional parameters occur, so as to comply at all times with the design conditions of the plants; for example, pressure changes in the fluid supplied to individual users are liable to modify the flow rates and consequently the heat exchange with the environment.  
         [0003]     A manual balancing of the flow rate, by means of special control valves, has not sufficiently solved the problem, in that the flow rates of the fluid in a system, for various reasons, can change in a wholly fortuitous manner.  
         [0004]     In order to solve this problem, presently use is made of special automatic valves for stabilising and controlling the flow rates in the return piping of the circuit of each individual user.  
         [0005]     These automatic valves for balancing and stabilising the flow rate comprise a tubular casing defining a passage between a fluid inlet and outlet of the valve.  
         [0006]     A fluid control piston is movably disposed in an axial direction into the tubular casing, and is subjected to the opposite actions of the pressure of the fluid and of a biasing spring. The control piston is in the form of a hollow member having apertures for the passage of the fluid in a side wall, which gradually narrows towards the fluid inlet end; a supplementary flow aperture can be provided on a bottom wall of the control piston.  
         [0007]     Such automatic flow rate control valves are shown, for example, in U.S. Pat. No. 5,174,330, U.S. Pat. No. 5,524,670, U.S. Pat. No. 6,311,712 and GB 2 370 096.  
         [0008]     Automatic control valves for stabilising the flow rates of a fluid, of the aforementioned type, have several problems and drawbacks in that, during their operation, as the fluid flow rate changes they can create pulsations and vibrations of the piston which give rise to irritating noise or which, at the most, can also damage the equipment of the individual users connected to them.  
         [0009]     After a careful analysis and suitable tests, it was discovered that these phenomena are due not only to the changes in pressure and/or flow rate of the fluid in a system, but also to the structural and functional features of the valves themselves.  
       OBJECTS OF THE INVENTION  
       [0010]     There is consequently a need to find new solutions for further improving the aforesaid valve devices.  
         [0011]     Therefore, a main object of this invention is to provide an automatic flow rate control valve whereby it is possible to remedy the problems inherent in the automatic valves of the known type.  
         [0012]     In particular, one object of the invention is to provide an automatic control valve for stabilising the flow rate of a pressurised fluid, in hydraulic systems, for example in heating and/or air-conditioning plants, whereby it is possible to eliminate or substantially reduce the causes of vibration and/or pulsation of the valve itself, and consequently the causes of generation of noise.  
         [0013]     A still further object of the invention is to provide an automatic control valve of the aforementioned kind, which is structurally simple, of extremely limited cost, and obtainable by moulding of plastic material.  
         [0014]     Another object of the invention is to provide a valve assembly comprising an automatic control valve for stabilising the flow rate, as mentioned previously, provided with a housing seat for the valve suitable to form a peripheral flow passage for the fluid towards an inlet aperture, or apertures of the valve, which is disposed around the body of the valve itself; in this way it is possible to provide the automatic flow rate control valve with suitable means for damping vibrations and/or pulsations.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0015]     According to a first embodiment of the invention, an automatic control valve for stabilising the flow rate of a hydraulic fluid is provided, comprising: 
        a tubular valve body defining a flow passage between at least one inlet aperture and an outlet aperture in the tubular body;     a flow control piston, axially movable within said tubular body; and     a biasing spring to urge the control piston in an open condition of the flow passage, against the pressure of the fluid,     wherein said inlet aperture is provided on a outer side wall of the valve body, said inlet aperture longitudinally extending to the valve body towards the fluid outlet end; and     in that the control piston comprises a cup-shaped element slidably movable between the outer side wall of the valve body and a coaxially arranged guide member having an inner wall which extends from the fluid outlet end into the piston member;     said piston member and guide member defining a piston damping chamber in communication with the internal flow passage of the control valve.        
 
         [0022]     According to a further embodiment of the invention, a valve assembly has been provided comprising a tubular element member extending between an inlet and an outlet for the fluid, and a seating for housing said automatic flow control valve, said control valve being in the form of a cartridge removably disposable in the seating between said inlet and outlet for the fluid in the tubular element of the valve assembly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The automatic control valve according to the invention, and some examples of valve assemblies comprising the control valve, are shown in the following drawings, in which:  
         [0024]      FIG. 1  shows a perspective view of the automatic control valve;  
         [0025]      FIG. 2  shows a longitudinal cross-sectional view of the valve of  FIG. 1 ;  
         [0026]      FIG. 3  shows an exploded view of the components forming part of the valve;  
         [0027]      FIGS. 4 and 5  show two different details of  FIG. 2 ;  
         [0028]      FIG. 6  shows a first assembly comprising the valve of  FIG. 1 ;  
         [0029]      FIG. 7  shows a second assembly comprising the valve of  FIG. 1 ;  
         [0030]      FIG. 8  is a graph showing the flow rate trough the valve for a large pressure range. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     As shown in  FIGS. 1 and 2  and in the exploded view of  FIG. 3 , the automatic control valve for stabilising the flow rate of a hydraulic pressurised fluid, indicated as a whole by reference number  10 , comprises a tubular body  11 , of moulded plastic material, having a cylindrical side wall delimited by an internal surface  12  and an outer surface  13  which extend along the longitudinal axis of the tubular body  11  of the control valve.  
         [0032]     One or more inlet apertures  14  are provided on the side wall  12  of the tubular body  11 , close to the outlet  15 , at the rear end of the body  11 ; in the event that more than one inlet apertures  14  are provided, they are angularly spaced apart from one another, and longitudinally extending towards the outlet aperture  15  at the rear end of the valve body  11 .  
         [0033]     The fluid inlet apertures  14 , as shown in  FIG. 1 , are appropriately shaped with a variable outline configuration to achieve a constant flow rate at different pressure values, as explained further on.  
         [0034]     In general, the geometrical shape of the outline of the inlet apertures  14 , must be such that the progression of the flow area is gradually decreasing, according to a fluid mechanics relationship, specifically Bernulli equation for flow, starting from an area  14 A of maximum flow passage, towards a small aperture  14 B designed to allow the minimum flow rate required for a user.  
         [0035]     In the case shown in  FIG. 1 , the aperture  14  has a substantially “T”-shaped profile, defined by two opposite curves, similar to hyperbolas, which converge towards the rear end of the valve body  11 ; however, the possibility of using other types of apertures  14 , differing from the one shown, in relation to specific requirements or requests of a user, is not excluded to provide a controlled rate of the flow.  
         [0036]     Inside the valve body  11 , on the side opposite to the fluid outlet, a control piston  16  has been provided for controlling the flow rate of the fluid through the inlet apertures  14 ; the piston  16  is in the form of an up-down turned cup-shaped element, having a closed bottom wall  16 A and a side wall  16 B provided with sealing means to seal against the inside cylindrical surface  12  of the tubular body  11 .  
         [0037]     The sealing means comprise a lip seal  18  housed in an annular seat  18 ′,  FIG. 3 ; in a position opposite to the bottom wall  16 A of the piston, an annular rib  19  has been provided to choke the flow area for the fluid through the inlet apertures  14  when the piston  16  is moved axially; a plurality of longitudinal ribs  20 , see  FIG. 3 , extend longitudinally between the seat  18 ′ for the seal and the annular rib  19 .  
         [0038]     Lastly, the automatic flow rate control valve  10  comprises a biasing spring  21 , which acts to balance the force generated by the pressure of the fluid on the opposite side the control piston.  
         [0039]     In the example shown, the biasing spring  21  is housed within a damping chamber  22  for damping the vibrations or pulsations of the control piston.  
         [0040]     In particular, as can be seen from  FIG. 2 , the damping chamber  22  is defined between two opposite cup-shaped elements, in particular between the downwardly facing piston  16  and an upwardly facing cavity, defined by an inner cylindrical wall  23  coaxially arranged to the outer wall of the valve body, to provide an annular gap for sliding movement of the piston more precisely the wall  13  extends from the outlet  15  towards the piston  16 , coaxially and inside the cylindrical wall  13  of the valve body  11 . In this way, in addition to forming the damping chamber  22 , an annular flow passage  24  for the fluid is simultaneously formed between the inlet apertures  14  and the outlet aperture  15 , as shown. The opposite cylindrical surfaces of the valve body  11  and the inner walls  23 , in addition to forming the annular passage  24  also provide guide means for the longitudinal movement of the piston  16 .  
         [0041]     The inner wall  23  of the valve body is made in one piece with the tubular body  11 , being connected to the latter by means of three spokes  25  disposed at 120°, only one of which is shown in  FIG. 2 , or in any other suitable way. Therefore, both the valve body  11  and the control piston  16 , thanks to their simple configuration, can be obtained simply by moulding from plastic material; in this way, not only is it possible to give the control valve or its parts any whatsoever configuration, but it is also possible to substantially reduce their manufacturing costs.  
         [0042]     Moreover, the use of plastic material both for the valve body and the control piston helps to reduce the noise during operation of the control valve.  
         [0043]     In order to allow the movement of the piston  16  and to dampen the vibrations, it is necessary for the damping chamber  22  to be in communication with the flow path  24  inside the valve itself. Consequently, as shown in the detail of  FIG. 4 , between the inner surface  19 A of the annular rib  19  of the control piston  16 , and the outer surface  23 ′ of the inner wall  23  of the valve body  11 , there is a narrow annular slit  27 A or slits  27 B which enable communication between the damping chamber  22  and the inner flow passage  24  for the fluid.  
         [0044]     The communication between the damping chamber  22  and the flow passage  24  for the fluid could be differently shaped, for example by providing the internal surface of the ribbing  19  with a plurality of small longitudinal slits  27 B, or vice versa, or in any other suitable way, as shown in  FIG. 5 .  
         [0045]     To prevent the piston  16  from being pushed by the spring  21 , outside the tubular body  11  of the valve, use has been made of a small U-shaped stop clip  26 , suitably shaped to be seated into a circumferential slit  28 , on one side of the outer wall of the valve body  11 , to engage by the two legs  26 A with opposite detents  29  on both sides of the valve body  11 , as shown. The detents  29  have a slanted upper surface  29 ′,  FIG. 1 , which facilitate the snap-on engagement of the two legs  26 B of the stop clip  26 .  
         [0046]     The valve  10  may be in the form of a cartridge insertable into a respective housing, of a duct, tubular connecting element or hydraulic assembly, as shown by way of example in  FIGS. 6 and 7  of the drawings, where the same reference numbers as in the preceding figures have been used to indicate similar or equivalent parts.  
         [0047]     In particular,  FIG. 6  shows a tubular pipe fitting  30  provided with a seat  31  for housing the cartridge of the automatic control valve  10 . The valve  10  is tightly disposed into the seat  31  so as to prevent a direct flow passage for the fluid between both ends  32  and  33  of the pipe fitting, while allowing the flow passage through the valve  10  only.  
         [0048]     Therefore, the valve body  11 , in correspondence with its outlet end  15 , is provided with an annular seat  34  for a seal  35 .  
         [0049]     The body  11  of the valve, for example in correspondence with its fore end, opposite the fluid outlet, or in any other suitable position, is provided with radial protrusions  36  which cooperate with the annular flange  34 , to maintain the valve body  11  centred in the seat  31  of the pipe fitting  30 . Since the inner diameter of the outer cylindrical surface  13  of the valve body  11  is smaller than the diameter of the inner cylindrical surface of the seat  31 , an annular passage  37  is formed between the two facing surfaces, on the outside of the valve body, which allows the passage of the fluid towards the inlet apertures  14 , without flowing through the control piston  16  and the damping chamber  22 ; in this way it is possible to prevent any variation in the flow and other external factors from causing fluctuations and/or vibrations, with the consequent elimination of any cause of noise.  
         [0050]     With reference to  FIG. 6 , the valve  10  operates as follows: the fluid which enters from the end  32  of the pipe fitting  30  is diverted by the valve  10  towards the annular path  37 , and then enters through the inlet apertures  14  towards the outlet  15  of the valve at the other end  33  of the pipe fitting  30 .  
         [0051]     Simultaneously, the pressure of the fluid which acts on the piston member  16 , pushes the latter forward, against the force of the biasing spring  21 , until reaching a balanced condition in which the annular rib  19  of the piston  16  has partially choked the inlet apertures  14  with an area of the flow passage capable of achieving the desired flow rate.  
         [0052]     If, for any cause the pressure and therefore the flow rate of the fluid tends to change, the combined and opposite actions of the pressure and the biasing spring, will move the piston  16  forward or backward, bringing it to rest in a new balanced position corresponding to a new flow passage area through the inlet apertures  14 , so as to maintain the flow rate at a constant value; any fluctuations and/or vibrations of the valve will be eliminated thanks to the hydraulic damping of the fluid contained in the damping chamber  22 .  
         [0053]     Several tests have been conducted with different types of biasing springs  21  and seals  18 , for different values of flow rate and pressure. During all the tests a regular behaviour of the valve was observed together with a satisfactory regulation of the flow rate at the design value.  
         [0054]     The graph in  FIG. 8  shows a typical trend of the flow rate, in relation to the pressure for a control valve according to the invention; from said figure it can be seen that the value Q (1/h) of the flow rate, as the pressure P varies, has a substantially rectilinear trend and a substantially constant value within a wide working range, with total absence of fluctuations.  
         [0055]      FIG. 7  of the drawings shows another possible application of a cartridge-type valve according to the invention.  
         [0056]     Again, in  FIG. 7  the same reference numbers as in the preceding figures have been used to indicate similar or equivalent parts.  
         [0057]     In the case of  FIG. 7 , the casing  40  of the pipe fitting comprises a slanted seat  41  for the valve  10 , on one side of the pipe fitting itself, between the inlet end  41  and the outlet end  42 , to enable the valve  10  to be inserted and removed or to be inspected and replaced, by removing a plug  43 .  
         [0058]     In this case, the valve  10  is locked in the seat  41  by means of a spring  26  which extends rearwardly from the valve body, ending with an annular ring  26 ″ to rest against the closing plug  43 .  
         [0059]     From what has been described and shown, with reference to figures it will be clear that the invention is addressed to a new type of control valve for stabilising to a constant value the flow rate of a hydraulic fluid, and to a valve assembly comprising a tubular housing and a control valve of the aforementioned type. Therefore, other modifications or variations may be made to the housing and to the control valve or their parts, without thereby departing from the scopes of the claims.