Patent Publication Number: US-2007102048-A1

Title: Block coaxial valve for use in compressed air systems

Description:
FIELD OF THE INVENTION  
      This invention belongs to the field of the valves for the control of the delivery of fluids, and in particular it relates to a block coaxial valve to be used in compressed air systems.  
     PRIOR ART  
      The pneumatic block coaxial valves herein taken into consideration are the so-called full flow automatic valves. They can either be simple or double effect valves, normally closed or open.  
      Usually, these valves include a valve body with an aligned fluid input and output ports and, between said ports, a coaxial chamber in which a block piston is housed, functioning as a shutter, having an axial hole and movable between a closed position and opening position of a valve seat formed in the valve body on the side of the fluid input port.  
      For its movements between one position and the other, the piston can be piloted by supplying to the chamber an additional fluid flow fed from the external of the valve, or a part of the same fluid flow to be delivered taken upstream the valve seat. If the block piston is a simple effect one, the piloting fluid is supplied to the chamber from one side of the piston, opposite to a spring operating from the opposite side of the piston, whereas if the piston is a double effect one, the control fluid is loaded/unloaded from both sides of the piston in turns, depending of its direction of movement.  
      However, the currently known coaxial block valves, not only are voluminous and consequently bulky, but they are also relatively complex both in terms of body, size and the piston control system. In fact, the valve body e is usually produced by casting and subsequently machined, and the piston has two opposite stems that require a double control and sealing system within the body of the valve.  
     OBJECT OF THE INVENTION  
      However, it is an objective of this invention to provide a coaxial valve especially, but not only, for use in compressed air systems, that are easier to produce both technically and economically, valves of smaller dimensions lengthwise and with the advantage of having an intermediate part of the body simply made of a tubular element and a short piston having a sliding and sealing system only on one side.  
      This objective and said advantages are achieved with a coaxial valve basically in accordance with the claim  1  to follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will however be described in more details further ahead with reference to the enclosed drawings, in which:  
       FIG. 1  is a longitudinal cross-section of the valve when closed;  
       FIG. 2  is a similar section of the valve when opened; and  
       FIG. 3  is a section of the valve as assembled. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As illustrated, the valve is basically made up of a valve body  11  and a piston  12  functioning as a shutter. The valve body  11  is made up of an intermediate tubular element  13  and two coupling sleeves  14  and  15  positioned on its two opposite ends. The intermediate element  13  can profitably be obtained from a pipe, preferably made of aluminium. The coupling sleeve  14  and  15  are screwed to the ends of said tubular element  13  and they can also be made of aluminium, for example obtained through die-casting.  
      The valve body  11  thus made has a fluid input port  16  formed by a first coupling sleeve  14  on an end, a liquid output port  17  formed by the opposite coupling sleeve  15  on the other end. Between the input and output ports, there is a central chamber in which the piston  12  is housed, dividing it into a first compartment  18 , upstream, on the side of the first coupling sleeve and a second compartment  18 ′, downstream, on the side of the second coupling sleeve.  
      Each coupling sleeves  14 ,  15  has a threaded part  14 ′,  15 ′ or could be equipped with a quick coupling on which fluid circulation pipes my to be connected, compressed air in this case, to be supplied flowing towards the direction indicated by arrow F in  FIGS. 1 and 2 .  
      Facing the input port  16 , between the latter and the piston  12 , in the first coupling sleeve  14 , a deflector unit  19  around which radial apertures  20  are formed to connect the input port with the first central chamber compartment  18 .  
      On its surface facing the piston  12 , the deflector unit  19  forms a valve seat  21  with a relative gasket.  
      In one part of the second coupling sleeve  15 , which forms the output port  17 , a guide seat  22  is obtained.  
      The piston  12  can be obtained from an aluminium bar, it is formed with a through axial hole  23  and it has a flange  24  around which at least one sealing gasket  25  is mounted to operate on the internal surface of the chamber in which the piston moves.  
      On a surface of the flange  24 , around a mouth of the axial hole  23 , on the side facing the first compartment  18 , an annular protrusion  26  is obtained facing the seat  21  to interact with the latter.  
      On the opposite surface of said flange  24 , there is an extending guide stem  27  which houses and moves in the guide seat  22  formed by the second coupling sleeve, with the interposition of a sealing gasket  28  and a sliding pad  28 ′. Therefore, the piston is held and guided only on one side, that is on the side of its stem  27  that is coupled with the guide pad  22  in the second coupling sleeve through the sealing gasket  28  and the sliding pad  28 .  
      The piston  12  is movable between a closed and opening positions of the valve, in one direction by means of a spring  29  and towards the opposite direction by means of a piloting fluid under pressure, that gets to the first compartment  18  of the central chamber facing the piston, through the radial apertures  20  of the first coupling sleeve  14 .  
      In the intermediate tubular element  13  there are formed a radial hole  30  communicating with the first compartment  18  and another radial hole  31  communicating with the second compartment  18 ′ on the opposite sides of the piston.  
      In the example shown in the drawings, the spring  29  is positioned and placed behind the flange  24  of the piston, between this flange and the second coupling sleeve  15 . The spring is basically concentric to the guide stem  27  and usually maintains the piston advanced in the closed position on the valve seat  21 , thus avoiding the delivery of fluid— FIG. 1 .  
      The valve is opened by supplying a piloting fluid into the first compartment  18  of the central chamber, in opposition to the action of the spring  29 , in a way to move the piston  12  backwards, that is away from the valve seat  21 , thus allowing the flow of the fluid to be delivered from the input port  16  to the output port  17  through the radial apertures  20  in the first coupling sleeve and the axial hole  23  of the piston— FIGS. 2 and 3 .  
      Profitably and corresponding to the example of the valve illustrated in the drawings, as piloting fluid for the piston it is used the same conduit fluid that flows from the input port  16  into the first compartment  18  facing the piston  12 , through the radial apertures  20  of the first coupling sleeve  14 .  
      Basically, when the piston  12 , pushed by the spring  29 , is in the closed position against the seat  21 , the fluid, the compressed air, that gets into the input port  16  flows into the first compartment  18 , and also into the radial hole  30 , working on the piston with a force contrasted by the spring and which is equal to the conduit pressure by the surface of the piston flange exposed to the fluid. When said force exceeds the force of the spring  29 , the piston  12  retreats, opening the passage of the fluid from inlet port  16  to the output port  17 .  
      Likewise, the fluid under pressure, through the hole  30 , gets to an electric or manual valve—not illustrated—by which the conduit pressure may be directed to the balancing hole  31  and, through this, to the second compartment  18 ′ to the back of the piston. Until this does not take place, the valve is kept open to allow the delivery of the fluid. Instead, when a controlled delivery of fluid under pressure is supplied to the chamber  18 ′ at the back of the piston, the pressure on the two opposite sides of the flange of the piston is balanced, so the spring  29  moves the piston toward the closed position against the valve seat  21 .  
      Given that the pressure from both sides of the flange is balanced, the time and force for closing the piston shall always be the same and independent from the amount of conduit pressure.