Abstract:
Booster valve ( 4 ) for pneumatic circuits, comprising: a hollow body ( 5 ), a pilot flow inlet/outlet gap ( 15 ) communicating directly with a control volume ( 16 ), an inlet/outlet gap ( 45 ) communicating with an actuator and communicating directly with an accumulation volume ( 29 ), a supplying gap ( 53 ) communicating directly with a supplying volume ( 38 ), a discharge gap ( 44 ), an amplified discharge shutter ( 25 ) which determines the sealing towards the discharge gap ( 44 ), a central device ( 43 ) comprising an amplified charge shutter ( 32 ) which determines the sealing towards the supplying gap ( 53 ), an activation piston ( 22 ) which, subjected to the pressure acting in the accumulation volume ( 29 ) and in the control volume ( 16 ), determines the movement of the amplified discharge shutter ( 25 ) or the amplified charge shutter, and having two separated and independent charge ( 47 ) and discharge ( 46 ); gain control devices which allow an independent adjustment between the charge and the discharge step and vice versa, and the central device ( 43 ) comprising a plurality of stakes ( 33 ), which, in combination with the passage sections determined by the opening of the amplified discharge shutter ( 25 ) and the amplified charge shutter ( 32 ) determine the flow amplification in discharge and charge steps.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to fluid flow control devices, and more in particular to a pneumatic booster valve. 
         [0003]    2. Brief Description of the Prior Art 
         [0004]    Continuous process industry, such for example the chemical, pharmaceutical and food industry, usually need to maintain and adjust the parameter values of the same process by means of pressure control. Therefore, there are used suitable manual or electric electro-pneumatic interfaces and pressure controllers. 
         [0005]    A manual pressure controller is a device, in which a pressure signal is provided by a handle control. 
         [0006]    Such controllers supply an outlet pressure favouring precision instead of dynamic behaviour. 
         [0007]    Anyway the obtainable precision has limitations due to mechanical problems caused by spring stiffness variations or caused by friction, and for this reason, there are also provided electric controllers which improve precision performance. 
         [0008]    The pressure transmitters and the pressure controllers are generally provided such that they produce a limited flow rate pressure signal, and when there are needed high flow rates it is needed to use suitable flow booster valves (or simply booster valves), characterized in that they can be controlled by a variable pressure, providing an outlet proportional pressure with high flow rates and equal to the control pressure. There exist also valves able to modify the ratio between these pressures by a constant value. Generally, a flow booster valve allows that the user chambers, normally a servo control, are rapidly filled, and that the excess air is discharged slowly from the outlet pipe. The actuation pneumatic systems of the valves comprise, generally, a compressed air source as working fluid, normally provided by an air compressor, which flows through a series of pipes. The compressed air flows into a positioner. The positioner, applied to an actuator, acquires a signal (for example an electric signal) proportional to the value of the position to be controlled (the position of the actuator determines the opening level of a valve shutter etc.). On the basis of the received input, the positioner controls the air flows to the actuator chambers determining the movements of the same actuator. The actuator is the device generating the desired movement. 
         [0009]    With the provision of actuators that manage great air volumes, the positioner, by itself, can supply and discharge a sufficient volume of compressed air during an excessively long time interval. As a consequence, such pneumatic circuits, having actuators with great volumes, can be unable to reach the piston suitable speeds. In this cases, between positioner and actuator there are generally provided booster valves. The booster valves allow the actuation system to reduce the working times increasing the air flow rate of the positioner in the first end of the cylinder and at the same time to deplete the air flow in the second end of the cylinder or vice versa. In the known booster valves this flow coefficient (CV) is equal to 1-10 GPM/psi. 
         [0010]    However, the advantages of the actuation system obtained by means of the addition of the booster valves are usually accompanied by a reduction in performance in the pneumatic circuit of the actuation system. In particular, the increase in the active elements number of the pneumatic circuit usually implies a dynamic instability of the piston positioning. As a consequence, while increasing the active elements number, due to the addition of the booster valves, the total air flow rate compressed by the positioner needed to activate the same elements is greater than the air flow rate of the pneumatic circuits having a lower number of active elements. In order to be activated and deactivated, the booster valves use the differential pressure variations generated by the pilot flow of the positioner. The amplification is activated when such pressure variation exceeds a determined value, thus implying an inevitable delay (phase lag) between positioner and boosters, both in activation and deactivation step. This delay or phase lag causes the dynamic performance reduction since in activation lengthens the time for reaching the desired position, while when this one is reached it can be overstepped owing to the deactivation delay. Therefore, there exists the need to define a new booster valve, which solves the cited problems. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention reduces or eliminates such performance inefficiency by means of a booster valve having the features described in the appended independent claim. 
         [0012]    Other preferred and/or particularly advantageous embodiments of the invention are described according to the features provided in the appended dependent claims. 
         [0013]    According to an embodiment of the invention, the booster valve is characterized by inlet and outlet, separated and independent gain control devices. In this way, there is the possibility to control the discharge amplification without “being subjected” to the effect of the same control during the charge step, or vice versa. Moreover, the charge and discharge shutters result totally independent as well, both is static step (not amplified flow) and dynamic step (amplified flow). By suitably selecting preloading and stiffness of the discharge and charge contrast springs it is possible to obtain the dynamic behaviours desired of the charge amplification without influencing the discharge amplification behaviour, and vice versa. This does not occur in the known boosters. 
         [0014]    Moreover, the above cited booster valve design provides that the sealing strength between the discharge shutter and respective seat is independent of the sealing strength between charge shutter and respective seat. The sealing strengths are determined by the preloading and stiffness of the contrast springs. In the known booster valves, the increase in the contact strength of one of the two seals is detrimental to the sealing strength of the other one. 
         [0015]    In addition, said booster valve is characterized by an arrangement and a design of the inner organs 
         [0000]    (actuation piston, charge shutter, discharge shutter) which exemplifies the realization of the same elements and reduces the number of the portions in contact and respective movement between each other. As a consequence, at equal section of the chambers, it is obtained a better dynamic capacity or in other words an increase in the flow coefficient CV, near 20 GPM/psi in the here examined model. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and other advantages of the present invention are described in detail in the following by means of the appended figures. 
           [0017]      FIG. 1  is a section concerning the complex shown in  FIG. 1 , which shows a booster valve in charge amplification step. 
           [0018]      FIG. 2  is a scheme concerning the complex shown in  FIG. 1 , which shows the flow amplification in total rest step. 
           [0019]      FIG. 3  is a scheme concerning the complex shown in  FIG. 1 , which shows the booster valve in discharge amplification step. 
           [0020]      FIG. 4  is a scheme concerning the complex shown in  FIG. 1 , which shows the booster valve in charge amplification step. 
           [0021]      FIG. 5  is a scheme concerning the complex shown in  FIG. 1 , which shows the booster valve in not amplified discharge step.  FIG. 6  is a scheme concerning the complex shown in  FIG. 1 , which shows the booster valve in not amplified charge step. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    As it is shown in  FIG. 1 , the booster valve  4  comprises a body  5  made up of an upper portion  6 , a central portion  7 , a lower portion  8  and a side portion  9 . Suitable sealing rings  10 ,  11 ,  12 ,  13  guarantee that said portions are sealed between each other. 
         [0023]    The body  5  defined by the just cited portions is hollow inside and together with the other elements of the device defines various inner chambers, described in detail in the following. 
         [0024]    The upper portion  6  of the body  5  is provided with a pilot flow inlet/outlet gap  15 , which is communicating with a control volume  16 . The functioning of the control volume  16  is described in detail in the following. 
         [0025]    Always inside the upper portion  6  it is defined a cylinder recess  14 , seat of two contrast springs 
         [0000]      17 ,  17 ′, arranged concentrically and generally cylindrically configured. Such springs guarantee that the discharge gap is sealed, as it is explained in the following. Inside the upper end of the recess  14  of the portion  6  there are provided two seats  18 ,  19 , parallel between each other, the first seat  18  having with little lower diameter then the second seat  19 . The upper end of the two springs  17 ,  17 ′ strikes on the surface of the seats  18 ,  19 . The lower end of the recess  14 , inside the upper portion  6 , is characterized by another seat  20  with greater diameter then the one of the two springs  17 ,  17 ′ and little lower then the diameter of the cap  21 , which functions as seat of the second end of the springs  17 ,  17 ′. 
         [0026]    As it is described in the following, the seat  20  determines a stop surface for the cap  21 , when the springs  17 ,  17 ′ are in the position of maximum compression realizing the end stroke of an amplified discharge shutter  25 . 
         [0027]    The cap  21  is integral with the amplified discharge shutter  25  by means of a fixed coupling  24 . The amplified discharge shutter  25  is positioned partially in the upper portion  6 , inside the control volume  16 , and in the central position  7 , and it is positioned inside an activation piston  22 . 
         [0028]    The activation piston  22  comprises an outer surface 
         [0000]      26  tight coupled (by means of one or more O-ring
 
 28 ) with an inner surface  42  of the upper portion
 
 6 , so that the fluid sealing is guaranteed by the control volume  16  with respect to an accumulation volume  29 . Said accumulation volume  29  ends with the gap  45  communicating with the actuator, arranged in the central portion  7  of the body  5 . The activation piston  22  slides along the inner surface  42  of the upper portion  6  and at the upper end is provided with a central seat  30 . Such central seat  30  makes up the end stroke of the cap  21 , configured in the lower end as well so that it strikes on the activation piston  22  during the down stroke of the amplified discharge shutter  25 .
 
         [0029]    The sealing between amplified discharge shutter  25  and activation piston  22  is guaranteed by the provision of O-rings  31  arranged in parallel between each other. The amplified discharge shutter  25  is not stiffly fixed to the activation piston  22  but it slides therein. 
         [0030]    The activation piston  22 , in its lower end, is integral with an amplified charge shutter  32  by means of three stakes  33  mutually arranged at 120°. The activation piston  22  and the three stakes  33  are integral with the amplified charge shutter  32  and make up a central device  43 . The functioning of the central device  43  is described in detail in the following. 
         [0031]    The amplified charge shutter  32  is positioned outside an amplified discharge sealing seat  34  which is extended radially in a flange element  35 . The amplified discharge sealing seat  34  and the flange  35  make up a plug  37  as a whole, integral with the portion  8  of the body  5  (an 0-ring  39  guaranteeing its sealing) and arranged in the lower end of a supplying volume  38  of the air in pressure. The plug  37  is provided with a discharge gap  44 . 
         [0032]    The amplified charge shutter  32  is not stiffly fixed to the amplified discharge sealing seat  34  of the plug  37 , but it can be positioned in sliding way. Between these two elements there are positioned two contrast springs  36 ,  26 ′, with sealing function towards a supplying gap  53 , as shown in  FIG. 2 . 
         [0033]    The sealing between amplified charge shutter  32  and the amplified discharge sealing seat  34  of the plug 
         [0000]      37  is guaranteed by the provision of 0-rings  40 , arranged in parallel between each other. In the same way and for the same aim, between the amplified charge shutter  32  and the flange element
 
 35  of the plug  37  there are suitable O-rings  41 .
 
         [0034]    The amplified charge shutter  32  striking on a sealing wall  50  of the central portion  7  defines a frustum conical sealing surface  51  in engagement with the frustum conical sealing surface  52  of the sealing wall  50 . Such sealing is guaranteed by the provision of a suitable gasket  58 . 
         [0035]    The amplified discharge shutter  25  at the end stroke on the lower end with the amplified discharge sealing seat  34  of the plug  37  defines a frustum conical sealing surface  48  in engagement with the frustum conical sealing surface  49  of the amplified discharge sealing seat  34 . Such sealing is guaranteed by the provision of a suitable gasket  59 . 
         [0036]    As it is shown in  FIG. 2 , in addition to the above described elements, the booster valve  4  comprises two gain control devices, respectively discharge  46  and charge  47  ones, coupled with the relative discharge  54  and charge  55  gain control screws. The use of the gain control devices  46 ,  47  is described in detail in the following. 
         [0037]      FIG. 2  shows the booster valve  4  in its neutral position, in which the pilot flow is null. The fluid volume connected to the inlet/outlet gap  15  of the pilot flow has the same fluid volume pressure connected to the inlet/outlet gap  45  communicating with the actuator. 
         [0038]    When the booster valve  4  is in its neutral position, the contrast springs  17 ,  17 ′ (represented schematically in figure by only one spring  17 ″) bring the amplified discharge shutter  25  at end stroke, avoiding the fluid passage between the frustum conical surface  48  of the amplified discharge shutter  25 , and the frustum conical surface  49  of the amplified discharge sealing seat  34 ; therefore the accumulation volume  29  remains isolated from the discharge gap  44 . 
         [0039]    When the booster valve  4  is in its neutral position, the compression springs  36 ,  36 ′ (represented schematically in figure by only one spring  36 ′′) bring the amplified charge shutter  32  at end stroke, avoiding the fluid passage between the frustum conical surface  51  of the amplified charge shutter  32  and the frustum conical sealing surface  52  of the sealing wall  50 : therefore the accumulation volume  29  remains isolated from the supplying volume  38 . 
         [0040]    So, in such a configuration, the device maintains both the supplying gap  53  and the discharge one  44  closed. 
         [0041]      FIG. 5  shows the booster valve  4  during the not amplified discharge step wherein the pilot flow is in discharge. The flow passes through the discharge gain control device  46 , suitably controlled by the discharge gain control screw  54 , so that a wide opening is allowed and a light pressure drop is generated. This implies a light upstream and downstream pressure difference of the discharge gain control device  46 . In particular the fluid volume connected to the gap  15  of the pilot flow has a little lower pressure with respect to the fluid volume connected to the gap  45  and communicating to the actuator (the charge gain control device  47  remains instead in contact with the respective seat  56  since the generated pressure difference tends to maintain it in the closing position). 
         [0042]    After the generated pressure difference, the activation piston  22  exerts a light strength on the amplified discharge shutter  25 , which is not sufficient to win the strength of the discharge contrast springs  17 ,  17 ′. Therefore, the amplified discharge shutter  25  does not free the discharge gap  44 . Both the contrast springs  17 ,  17 ′ and  36 ,  36 ′ (represented by only one spring  17 ″ and  36 ″ in  FIGS. 2-6 ) maintain the amplified discharge and amplified charge shutters  25  and  32  in contact with the respective sealing seats, i.e. with the sealing wall  50  and the discharge sealing seat  34 , maintaining both the supplying gap  53  and the discharge one  44  closed.  FIG. 3  shows the booster valve  4  during the amplified discharge step, in which the pilot flow is in discharge. The flow passes through the discharge gain control device  46 , suitably controlled by the discharge gain control screw  54 , so that a partial opening is guaranteed and a relevant pressure drop in generated. Such pressure drop depends on the pilot flow rate and on the adjustment of the same control screw  54 . This implies a not negligible upstream and downstream pressure difference of the discharge gain control device  46 . In particular, the fluid volume connected to the pilot flow gap  15  has a definitely lower pressure with respect to the fluid volume connected to the gap  45  and communicating with the actuator (the charge gain control device  47  remains instead in contact with the relative seat  56  since the generated pressure difference tends to maintain it in the closing position). 
         [0043]    After the generated pressure difference, the activation piston  22  exerts a strength on the amplified discharge shutter  25  such that the strength of the contrast springs  17 ,  17 ′ is won, which are then compressed until reaching the balance condition. The movement of the amplified discharge shutter  25  depends on the strength exerted by the activation piston  22  and the discharge contrast springs  17 ,  17 ′. 
         [0044]    Therefore, the amplified discharge shutter  25  goes away from the respective sealing seat  34 , thus freeing the discharge gap  44  and causing the amplified discharge. The contrast springs  36 ,  36 ′ maintain the amplified charge shutter  32  in contact with the sealing wall  50  maintaining the supplying gap  53  closed. 
         [0045]      FIG. 6  shows the booster valve  4  during the not amplified charge step, in which the pilot flow is in charge. The flow passes through the charge gain control device  47 , suitably controlled by the charge gain control screw  55 , so that a wide opening is guaranteed and a light pressure drop is generated. This implies a light upstream and downstream pressure difference of the charge gain control device  47 . In particular, the fluid volume connected to the pilot flow gap  15  has a little higher pressure with respect to the fluid volume connected to the gap  45  and communicating with the actuator (the discharge gain control device  46  remains instead in contact with the relative seat  57  since the generated pressure difference tends to maintain it in the closing position). After the generated pressure difference, the activation piston  22  exerts a light strength on the 
         [0000]    &lt;′&gt;amplified charge shutter  32 , which is not sufficient to win the strength of the contrast springs  36 ,  36 ′. Therefore, the amplified charge shutter  32  does not free the supplying gap  53 . Both the contrast springs  17 , IT and  36 ,  36 ′ maintain the amplified discharge and amplified charge shutters  25  and  32  in contact with the respective sealing seats, i.e. with the sealing wall  50  and the discharge sealing seat  34 , maintaining both the supplying gap  53  and the discharge one  44  closed. 
         [0046]      FIG. 4  shows the booster valve  4  during the amplified charge step, in which the pilot flow is in charge. The flow passes through the charge gain control device  47 , suitably controlled by the charge control screw  55 , so that a partial opening is guaranteed and a relevant pressure drop is generated. Such pressure drop depends on the pilot flow rate and on the adjustment of the same control screw  55 . This implies a not negligible upstream and downstream pressure difference of the charge gain control device  47 . In particular, the fluid volume connected to the pilot flow gap  15  has a definitely higher pressure with respect to the fluid volume connected to the gap  45  and communicating with the actuator (the discharge gain control device  46  remains instead in contact with the relative seat  57  since the generated pressure difference tends to maintain it in the closing position). 
         [0047]    After the generated pressure difference, the activation piston  22  exerts a strength on the amplified charge shutter  32  such that the strength of the contrast springs  36 ,  36 ′ is won, which are compressed until reaching the balance condition. The movement of the amplified charge shutter  32  depends on the strength exerted by the activation piston  22  and by the charge contrast springs  36 ,  36 ′. 
         [0048]    Therefore, the amplified charge shutter  32  goes away from the sealing wall  50 , thus freeing the discharge gap  53  and causing the amplified charge. 
         [0049]    The contrast springs  17 ,  17 ′ maintain the amplified discharge shutter  25  in contact with the sealing wall  34  maintaining the discharging gap  44  closed. 
         [0050]    In addition to the above described embodiments of the invention, it is to be intended that there exists many other variants. It is also to be intended that said embodiments are only examples, not limiting the scope of the invention or its applications or configurations. On the contrary, even if the above description offers those skilled in the art at least on example configuration, it is clear that there are many possible variations of the elements described without departing from the scope of the invention as defined in the appended claims literally interpreted and/or according to legal equivalents thereof.