Abstract:
A pneumatic valve includes a cylinder having at least one gas port for providing inflow and outflow of a gas; a piston arranged in the cylinder and performing a reciprocating, straight-line movement in response to the inflow and outflow of the gas; a first valve shaft passing through the piston and having a first end portion including a first coupling portion; and a second valve shaft including a second coupling portion and having a first end portion protruding from the cylinder, wherein the second coupling portion is coupled to the first coupling portion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a pneumatic valve. More particularly, the present invention relates to a pressure-controlled valve for creating mechanical movement.  
           [0003]    2. Description of the Related Art  
           [0004]    A conventional air valve is typically installed between a vacuum pump generating a vacuum pressure and a reactor using the vacuum pressure. The air valve serves to connect the vacuum pump and the reactor when needed. Such an air valve is operated by air pressure and includes a bellows that can be constricted by an applied air pressure. One such conventional air valve includes a cylinder, a piston interior to the cylinder, and a valve shaft. A plurality of ports are included in the cylinder to allow pressurized air to be supplied to, or discharged from, a head of the piston. In response to such an inflow or outflow of air, the piston is forced in a reciprocating, straight-line mechanical movement. The straight-line movement of the piston is transferred to the bellows by the connecting valve shaft, which connects a central portion of the piston to the bellows using a nut. The movement of the bellows in turn opens or closes a ventilation passage of a valve body.  
           [0005]    A significant disadvantage of such a valve configuration is that, over time, the nut may loosen due to the repeated movement of the piston, eventually causing the piston to be separated from the bellows. In order to re-attach the piston and the bellows or to tighten the nut the cylinder must be disassembled.  
         SUMMARY OF THE INVENTION  
         [0006]    A feature of an embodiment of the present invention provides a pneumatic valve having an improved coupling mechanism between a valve shaft and a piston.  
           [0007]    Another feature of the present invention provides a pneumatic valve having a piston with a long life span.  
           [0008]    According to a preferred embodiment of the present invention, a pneumatic valve includes a cylinder having at least one gas port for providing an inflow and an outflow of a gas; a piston arranged in the cylinder that performs a reciprocating, straight-line movement in response to the inflow and outflow of the gas; a first valve shaft passing through the piston having a first end portion including a first coupling portion; and a second valve shaft including a second coupling portion and having a first end portion protruded from the cylinder, wherein the second coupling portion is coupled to the first coupling portion, such that straight-line movements of the piston are transferred in a longitudinal direction of the first and second valve shafts.  
           [0009]    Preferably, the first and second coupling portions have a threaded interface capable of mating, wherein the first coupling portion includes a male threaded screw portion, and the second coupling portion includes a female threaded screw portion.  
           [0010]    The second valve shaft further includes a second end portion having a flange portion contacting the piston. The first end portion of the second valve shaft includes a tightening protrusion that may be tightened using a tightening tool. The tightening protrusion may have a groove into which a wrench may be inserted or a polygon-shaped protrusion suitable for tightening by a spanner wrench. Preferably, the pneumatic valve further includes a bellows arranged around a second end portion of the first valve shaft, an elastic member arranged between an outer surface of the cylinder and the bellows, and a lubricant injection apparatus for injecting a lubricant, such as oil, to an inner surface of the cylinder through the second valve shaft, which preferably includes at least one lubricant passage therein.  
           [0011]    The present invention provides several advantages over conventional air valves. One, since a connection between the first and second valve shafts may be tightened by tightening the protruding second end portion of the second valve shaft without disassembling the cylinder, a loosened coupling between the first valve shaft and second valve shaft may be facilely repaired. Second, since friction between the piston and an inner surface of the cylinder is reduced by the application of a lubricant, a pneumatic valve having a piston with a long life span may be achieved.  
           [0012]    These and other features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon review of the detailed description that follows.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which like reference numerals indicate like elements throughout.  
         [0014]    [0014]FIG. 1 illustrates a cross-sectional view of a pneumatic valve according to a preferred embodiment of the present invention.  
         [0015]    [0015]FIG. 2 illustrates a cross-sectional view of the pneumatic valve of FIG. 1 in a compressed operational state.  
         [0016]    [0016]FIG. 3 illustrates a perspective view showing a state wherein a second valve shaft of the pneumatic valve is coupled to a lubricant injection apparatus.  
         [0017]    [0017]FIG. 4 illustrates a cross-sectional view of the portion of the pneumatic valve shown in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Korean Patent Application No. 2001-19636, filed on Apr. 12, 2001, and entitled: “Air Valve,” is incorporated by reference herein in its entirety.  
         [0019]    In the following description, the term “air” and “pneumatic” should be interpreted broadly to include any compressed, gaseous compound that may be satisfactorily used to power the mechanical movements of the elements of the present invention. Further, although in the following description, drawing orientations are occasionally referenced as being “up” or “down,” this is for explanatory purposes only and not meant to be limiting, since the pneumatic valve of the present invention may be arranged in any useful orientation.  
         [0020]    [0020]FIG. 1 illustrates a cross-sectional view of a pneumatic valve  100  according to a preferred embodiment of the present invention. Pneumatic valve  100  includes a cylinder  110 , a piston  113 , a first valve shaft  115 , and a second valve shaft  119 .  
         [0021]    The cylinder  110  further includes a gas port  111  through which pressurized gas inflows or outflows. The piston  113 , which is preferably made of rubber, performs a reciprocating, straight-line movement in a longitudinal direction of the first and second valve shaft in response to the pneumatic pressure being applied or released through gas port  111 .  
         [0022]    The first valve shaft  115  is installed to pass through a central portion of the piston  113  and has a male threaded screw portion  115   a  on a first, lower end portion thereof. A bellows  117  is arranged to surround a second, upper end portion of the first valve shaft  115 . The second valve shaft  119  includes a female threaded screw portion  119   a  into which the male threaded screw portion  115   a  of the first valve shaft  115  is inserted and rotated in a tightening direction so that first valve shaft  115  is securely coupled to second valve shaft  119 . Second valve shaft  119  has a sufficient length so that a first, lower end portion thereof protrudes outwardly from the cylinder  110  when the piston  113  is at the uppermost location of the cylinder  110 , i.e., nearest the bellows.  
         [0023]    Bellows  117  further includes pneumatic sealing plates  117   a  and  117   b  on lower and upper portions thereof, respectively. An elastic member  121  having an elastic force for returning piston  113  to an un-pressurized position is arranged to surround a portion of the first valve shaft  115  between cylinder  110  and bellows  117 .  
         [0024]    The second valve shaft  119  further includes a second, upper end portion having a flange portion  119   b  and the first, lower end portion having a tightening protrusion  119   c . The flange portion  119   b  supports a bottom surface of the piston  113 , so that pressure applied to piston  113  forces second valve shaft  119  in a direction that compresses bellows  117  and elastic member  121 , and release of that pressure causes elastic member  121  to force second valve shaft  119  and piston  113  in a direction that allows expansion of bellows  117 . Tightening portion  119   c  may be tightened using a tightening tool, such as a wrench or a spanner wrench, when the coupling between the first and second valve shafts,  115  and  119 , respectively, becomes loosened due to a repeated reciprocating, straight-line movement of the piston  113 .  
         [0025]    Operation of the pneumatic valve of FIG. 1 is explained below with reference to FIG. 2, which illustrates a cross-sectional view of a pressurized operational state of the pneumatic valve of FIG. 1. First, when pressurized gas is supplied to cylinder  110  through the gas port  111 , piston  113  and the coupled first and second valve shafts  115  and  119 , respectively, are forced to move in a direction indicated by the arrows in FIG. 2. This movement causes bellows  117  and elastic member  121  to be compressed.  
         [0026]    When gas pressure on piston  113  is released via a discharge through the gas port  111 , elastic member  121  pushes up the sealing plate  117   a  by its restoration, such that the piston  113  and the first and second valve shafts  115  and  119  move up.  
         [0027]    The supply and discharge of gas through the gas port  111  may be accomplished using an apparatus for changing a flow direction of gas, such as a solenoid valve installed on an end portion of a gas line (not shown) to be coupled to the gas port  111 . More specifically, the solenoid valve opens a gas-supplying passage during a gas-supplying operation, or closes the gas-supplying passage while simultaneously opening a gas-discharging passage during a gas-discharging operation, according to a movement of a spool built therein.  
         [0028]    A threaded screw coupling between the first valve shaft  115  and the second valve shaft  119  may become loosened by repeated up and down movements of the piston  113 . However, unlike in conventional air valves, a loosened screw coupling between the first valve shaft  115  and the second valve shaft  119  in the present invention may be facilely repaired or tightened without disassembling piston  113  from cylinder  110 . This tightening may be accomplished by simply rotating or adjusting the tightening protrusion  119   c , preferably using a wrench or a spanner, which would fit a corresponding mating groove or polygon-shaped protrusion on tightening protrusion  119   c.    
         [0029]    Additionally, unless adequately lubricated, repeated movement of piston  113  produces friction between piston  113  and an inner surface of the cylinder  110 , thereby reducing the life span of the piston due to degradations, such as scratching and/or warping. In order to provide such lubrication, pneumatic valve  100  preferably includes a lubricant injection apparatus, such as that shown in FIGS. 3 and 4, wherein the second valve shaft  119  is coupled to a lubricant injection apparatus  200 .  
         [0030]    As shown in FIGS. 3 and 4, the second valve shaft  119  further includes a plurality of lubricant passages  19   d  formed therein. The second valve shaft  119  is coupled to the lubricant injection apparatus  200  through a coupling member  201 . Preferably, the coupling member  201  may be configured to be tightened using a tightening tool in order to perform the same function as the tightening protrusion  119   c  of FIG. 1.  
         [0031]    The lubricant injection apparatus  200  includes an injection pipe  210  and a lubricant cylinder  220 . The injection pipe  210  and the lubricant cylinder  220  are coupled to each other through a lubricant port body  215 . The injection pipe  210  further includes an injection opening  211  formed at the junction with coupling member  201 , as shown in FIG. 4, to provide a path for the lubricant to be injected into lubricant passages  119   d  of second valve shaft  119 .  
         [0032]    Lubricant port body  215  includes a lubricant port  215   a  formed at a side thereof. An upper portion of the lubricant port body  215  is coupled to a lower portion of the injection pipe  210  through a coupling means  217 , such as a crown nut, and the lower portion of the lubricant port body  215  is coupled to a lubricant cylinder  220  through a coupling means  221 , such as a crown nut.  
         [0033]    The lubricant cylinder  220  includes a suction open  220   a  formed at end of the lubricant cylinder  220  opposite from the coupling member  201 . A lubricant piston  225  is arranged in lubricant cylinder  220 , and includes a piston rod  225   a  and an elastic member  223  having an elastic force, such as a spring. The piston rod  225   a  is coupled to a valve rod  213 , which passes through an opening in a camping  227  and the lubricant port body  215  to extend into injection pipe  210 . A valve head  213 a of the valve rod  213  serves to open or close injection opening  211  of the injection pipe  210 . A tube  229  having an uneven interior surface is arranged around valve rod  213  to prevent the lubricant from flowing into the opening of camping  227 .  
         [0034]    A cycle of operation of lubricant injection apparatus  200  of FIGS. 3 and 4 preferably includes: first, when gas is withdrawn from the lubricant cylinder  220  through the suction opening  220   a , the lubricant piston  225  together with piston rod  225   a , valve rod  213 , and valve head  213   a  move down, compressing elastic member  223  and opening injection opening  211  of injection pipe  210 . An externally supplied lubricant, such as oil, flows into the injection pipe  210  through the lubricant port  215   a  of the lubricant port body  215 , and then passes through the injection opening  211  to lubricant passages  119   d . When gas pressure is re-applied to suction opening  220   a , lubricant piston  225  is forced upward, injecting the lubricant into lubricant passages  119   d  in second valve shaft  119  and then to an inner surface of the cylinder  110  of the pneumatic valve shown in FIGS. 1 and 2, thereby lubricating the interior of the cylinder of the pneumatic valve. Note that lubricant flowing into the injection pipe  210  does not flow into the opening in camping  227  due to the uneven interior surface of tube  229 , thereby maintaining a clean atmosphere outside of the lubricant injection apparatus.  
         [0035]    As described previously, the present invention features two primary advantages over conventional air valves. First, since the first and second valve shafts may be tightened by the tightening protrusion of the second valve shaft without disassembling the cylinder, a loosened coupling between the first and second valve shafts may be facilely repaired. Second, since friction of the piston against the cylinder is reduced, preferably by supplying a lubricant to the inner surface of the cylinder, a longer life span of the piston may be realized.  
         [0036]    A preferred embodiment of the present invention has been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the invention as set forth in the following claims.