Abstract:
A pneumatic cylinder system has a pneumatic supply at a first predetermined pneumatic pressure. A double acting cylinder is operably connected to the pneumatic supply and with a piston reciprocatingly mounted inside for retraction and extension of a piston arm connected to the piston. A high pressure pneumatic reserve chamber stores pneumatic reserve at a second predetermined pneumatic pressure that is higher than the first predetermined pressure. The high pressure pneumatic reserve chamber is operably connected to the double acting cylinder through a valve device such that when the pneumatic supply falls below a third predetermined pressure below the first predetermined pressure, the valve device opens communication between the high pressure pneumatic reserve chamber to a selected side of the double acting cylinder to selectively retract or extend the piston and the attached piston arm.

Description:
TECHNICAL FIELD 
       [0001]    The field of this invention relates to an air cylinder with a pressurized air-spring return cylinder. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    It is often desired that double acting cylinder and piston assemblies work off of a pressurized pneumatic supply to reciprocate the piston for retracting and extending the piston arm. It is often desired to provide a default position for the arm; i.e. the arm is in a normally extended or normally retracted position if the pneumatic pressure ceases or is otherwise shut off. This default retracted or extended position has been commonly accomplished with internal return springs that will mechanically retract or extend the piston arm. Coil springs for large bore air cylinders are fairly limited in availability, have limited range of bore sizes and are expensive. The working pneumatic pressure must also be increased to overcome the natural bias of the return coil spring. Furthermore, coil springs can rust and wear out. 
         [0003]    As such, alternate ways to automatically return the piston arm to its default retracted or extended position have been developed. One method is to use a secondary reservoir air tank that has enough air supply to completely fill the air cylinder to either retract or extend the working piston and its attached piston arm. These tanks have an air supply stored at the same pneumatic pressure as the working pneumatic pressure of the primary air supply. Thusly, the tanks need to be at least three to four times as large as the double acting cylinder so that a sufficient pneumatic pressure is maintained to completely push the working piston to its retracted or extended end position within the cylinder. Consequently, these tanks are expensive due to their large size and weight. 
         [0004]    What is needed is smaller return air spring tank that can house air at a second pneumatic pressure that is substantially above the pneumatic pressure of the working air supply. What is also needed is a pressure intensifier device that automatically fills the air tank to such a desired second pneumatic pressure. What is also desired is an air tank that is co-axially mounted with the working cylinder with a pressure intensifier mounted at a side thereof What is also needed is a pressure intensifier that runs off of a pneumatic supply at a first pneumatic pressure and has a pump section that can produce an increased pneumatic pressure output. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In accordance with one aspect of the invention, a pneumatic cylinder system has a pneumatic supply at a first predetermined pneumatic pressure. A double acting cylinder is operably connected to the pneumatic supply and has a piston operably mounted inside for reciprocating retraction and extension of a piston arm connected to the piston. A high pressure pneumatic reserve chamber stores pneumatic reserve at a second predetermined pneumatic pressure that is higher than the first predetermined pneumatic pressure. The high pressure pneumatic reserve chamber is operably connected to the double acting cylinder through a valve device such that when the pneumatic supply falls below a third predetermined pneumatic pressure below the first predetermined pneumatic pressure, the valve device opens communication between the high pressure pneumatic reserve chamber to a selected side of the double acting cylinder to selectively retract or extend the piston and the attached piston arm. 
         [0006]    Preferably, the high pressure pneumatic reserve chamber is operably connected to a pressure intensifier assembly that pumps gas to the high pressure pneumatic reserve chamber at the second predetermined pneumatic pressure. It is desired that the pressure intensifier assembly includes a stepped cylinder and stepped piston with the pneumatic supply being operably connected to the larger diameter section of the stepped cylinder for controllably and reciprocally moving the stepped piston. The smaller diameter section of the cylinder functions as a pump for receiving gas therein and pumps it to the high pressure reserve chamber. 
         [0007]    The pneumatic supply is preferably operably connected to one side of the smaller diameter section of the stepped cylinder for delivering pneumatic supply at the first predetermined pneumatic pressure therein during a fill stroke of the stepped piston. The high pressure pneumatic reserve chamber is operably connected to the smaller diameter piston of the stepped cylinder for receiving pneumatic supply at the second predetermined pressure therefrom during a pump stroke of the stepped piston. 
         [0008]    In one embodiment, the high pressure pneumatic reserve chamber is co-axially mounted with the double acting cylinder and each are approximately the same diameter and length. The pressure intensifier assembly is mounted laterally on the side of the co-axially mounted high pressure pneumatic reserve chamber and the double acting cylinder. 
         [0009]    In one embodiment, the piston arm is operably connected to a knife gate valve and the piston arm is extendable to its default position by pneumatic pressure flowing from the high pressure pneumatic reserve chamber to the double acting cylinder to close the knife gate valve. 
         [0010]    According to another aspect of the invention, a pneumatic intensifier for supplying pneumatic pressure to a pneumatic pressure chamber has a stepped cylinder and a stepped piston slidably mounted in the stepped cylinder for reciprocating motion therein. A supply of pneumatic pressure at a first predetermined pressure is selectively and alternately in communication with each opposite side of a large diameter section of the stepped cylinder for reciprocally driving a large diameter section of the piston therein. The supply of pneumatic pressure is selectively in communication through a first port with one side of a smaller diameter section of the stepped cylinder for delivering the pneumatic supply at the first predetermined pneumatic pressure therein, when a smaller diameter section of the piston is retracting during a fill stroke with respect to the one side of the smaller diameter section. The one side of the smaller diameter section is also selectively openable through a second port to deliver pneumatic supply to the pneumatic reserve chamber during a pump stroke up to a second predetermined pneumatic pressure that is greater than the first predetermined pressure. 
         [0011]    According to another aspect of the invention, a pneumatic driven pneumatic intensifier has a driving section connectable to a pneumatic supply at a first pneumatic pressure with a pneumatic supply running the driving section. A pump section has an inlet selectively for receiving a gas and an outlet selectively openable to deliver pneumatic supply at a second pneumatic pressure that is greater than the first pneumatic pressure. It is further desired that the pump section receives the gas from the pneumatic supply at the first predetermined pneumatic pressure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Reference now is made to the accompanying drawings in which: 
           [0013]      FIG. 1  is a perspective view of a knife gate valve incorporating an embodiment of a double acting cylinder and air tank and intensifier pump according to the invention; 
           [0014]      FIG. 2  is a cross-sectional view of the intensifier pump shown in  FIG. 1 ; 
           [0015]      FIG. 3  is schematic view of the air flow through the double acting working cylinder, the air pump and the pressurized air spring return tank; and 
           [0016]      FIG. 4  is a schematic enlarged view of an actuator and normally closed three way valve shown in  FIGS. 2 and 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Referring now to  FIG. 1 , a double working cylinder and return air spring assembly  10  is operably connected to a knife gate valve  12 . The knife gate valve  12  is shown in a closed position in  FIG. 1 . An end of a piston arm  14  extends from one end of the double working cylinder  16  for opening and closing the valve  12  and is attached to the knife gate valve  12 . A return air spring tank  18  is coaxially mounted at an opposite end of the double acting cylinder  16 . An air pump intensifier assembly  20  is mounted on the side of the double acting cylinder  16 . 
         [0018]    Referring now to  FIG. 3 , the double acting cylinder  16  has a working piston  22  slidably mounted for moving axially within the cylinder. The working cylinder  16  is operably connected to a working pneumatic pressure from air supply  23  that has line  19  in communication with a two position four way valve  24  that has a single actuation solenoid  21  and a return spring  25 . When the control valve  24  is in a first shown position, air flows from air supply  23  through line  19  through control valve  24  and then through line  37  to a valve  26 . The valve  26  has its position determined by a single air pilot  28  that biases the valve to the first position against bias of a return spring  27 . The valve  26  is normally in the position shown in  FIG. 3  when air pilot  28  is attached to air supply  23  that is at a normal working pneumatic pressure e.g. 60 p.s.i. When the valve  26  is in this normal position, pneumatic pressure from the control valve  24  flows therethrough and through line  30  to one side  29  of the cylinder to push the piston  22  to the right and extend the piston arm  14  to close the knife gate valve as shown in  FIG. 1 . Air from the other side  31  of the cylinder is exhausted though line  35  through the control valve  26 . 
         [0019]    When the control valve  24  is solenoid actuated, the valve  24  shifts to its other position to direct pneumatic pressure from air supply  23  directly to the other side  31  of the cylinder  16  to push piston  22  to the left and retract the piston arm  14  to open the knife gate valve  12 . The air within cylinder section  29  is exhausted through line  30 , back through valve  26 , through line  37  and through valve  24 . 
         [0020]    Pressurized air is reserved in tank  18  and is blocked from exhausting via a line  39  through to a blind port  33  in valve  26 . Thus, control of control valve  24  through it actuation solenoid  21  can controllably reciprocate the piston  22  within working cylinder  16 . 
         [0021]    When the air supply  23  decreases or completely depletes, due to power outage or other causes, the knife gate  12  automatically closes due to automatic extension of the piston arm  14 . The air pilot  28  in valve  26  no longer acts against the spring return and thus the valve  26  moves to its second position to the left from the position shown in  FIG. 3  which allows flow of pressurized air from tank  18  through line  39 , through the valve  26 , through line  30  and to the side  29  of cylinder to push the piston  22  to the right and extend the arm  14 . Control valve  24  is spring biased to the first position when not actuated as shown in  FIG. 3  and lets cylinder side  31  be exhausted through line  35 . If the air supply  23  loses its pneumatic pressure for other reasons besides a power outage and control valve  24  is still actuated, the cylinder side  31  is still exhausted through control valve  24  and back into supply line  19  because of the low pneumatic pressure in line  19 . 
         [0022]    Air supply  23  normally provides a pneumatic pressure of about 60 p.s.i. to the double working cylinder. The tank  18  is pressurized to a pneumatic pressure of about 200 p.s.i. and is sized to have the same diameter and approximately the same length as double working cylinder  16  to provide sufficient pneumatic pressure and air supply to complete one full stroke to fully extend piston arm  14  and close knife gate valve  12 . 
         [0023]    Air tank  18  is pressurized to a level that is well above the working pneumatic pressure of the air supply  23  (60 p.s.i.) through the use of a piston intensifier assembly  20 . The piston intensifier assembly  20  includes a stepped cylinder  40  having a stepped dual piston  42  inside. The larger diameter cylinder section  44  is connected to the air supply  23  through a two position four way valve  46 . More particularly, during a return fill stroke of the piston  42  as shown in  FIG. 3 , the one side  48  of the large cylinder section  44  is connected to the air supply  23  through line  49  leading to the valve  46 . Side  50  is exhausted through the valve  46  via line  51 . During the fill stroke the smaller diameter section  45  of cylinder  40  has its side  56  filled through the check valve  58  from pressurized air supply  23 . Side  55  is exhausted through an open port  53  in the cylinder housing as shown in  FIG. 2 . Check valve  57  is closed during this fill stroke to prevent air from escaping from tank  18 . 
         [0024]    As shown in  FIG. 2 , the stepped cylinder  40  has the normally non-actuated three way valves  62  and  72  housed at each end of large diameter section  44  where the large piston area  47  abuts the respective actuator  60  and  70  at each fill and pump stroke end. The large piston area  47  is connected to the small piston area  52  via a piston bar  75 . Side  55  is in open communication with ambient port  53 . Side  56  is in communication with ports  77  and  78  which can house check valves  57  and  58  respectively. 
         [0025]      FIG. 4  illustrates in schematic fashion the actuator  60  and normally non-passing three way valve  62 . The spring  63  normally biases the valve to close off line  19  to connected air supply  23  and exhausts air pilot  64  when actuator  60  is not pressed. When actuated, line  19  is open to air pilot  64 . Valve  72  is similarly constructed to be normally biased to close off line  19  and exhaust air pilot  74 . When valve  72  is actuated, line  19  is open to air pilot  74 . 
         [0026]    When the dual stepped piston  42  is fully returned and the fill stroke has ended, the piston  42  hits an actuator end  60  of the normally three way valve  62  to commence the pump stroke. The valve  62 , when actuated, allows air from air supply  23  to pass through line  19  to the air pilot  64  of the valve  46  such that valve  46  shifts position to the right from the position shown in  FIG. 3  to now let the air supply  23  be in communication with the side  50  of intensifier  20 . Air lock behind air pilot  74  is prevented by air being exhausted through non-actuated valve  72 . The pneumatic pressure exerted in cylinder side  50  pushes the larger piston area  47  to the right as shown in  FIG. 3 . Cylinder side  48  is exhausted through line  49  and through valve  46 . During this pump stroke, smaller piston area  52  is pushed to the right and forces the air within side  56  of smaller cylinder section  44  to go through check valve  57  and to the tank  18 . Check valve  58  is closed during this pump stroke. Ambient air is drawn in through open port  53  to side  55  to prevent vacuum lock behind piston area  52 . 
         [0027]    At the end of the pump stroke, the large piston area  48  engages an actuator end  70  of a normally closed three way valve  72  which similarly sends air to an air pilot  74  on the other side of valve  46  to shift it back to the left as shown in  FIG. 3  to commence another fill stroke. Three way valve  62  is in the normal bias position that allows exhausting of air pilot  64  therethrough and prevents air lock. At the end of the full stroke, the cycle is repeated. 
         [0028]    Because of the difference in diameter of the large piston area  48  compared to the small piston area  52 , the air supply pressure  23  will continue to operate the intensifier  20  and pump air into the tank  18  until the pneumatic pressure within the tank  18  is well above the pneumatic pressure of the working air supply, in other words, the ratio of the two piston areas  48  and  52  will be approximately the ratio of the final pressure within tank  18  and the working pressure of air supply  23 . While it is foreseen that a pressure ratio of three or four to one is foreseen, other pressure ratios can be easily accomplished merely by changing the ratio of working areas of pistons areas  48  and  52 . The intensifier pump  20  will continue to work until an equilibrium is reached and it can no longer pump more air into tank. 
         [0029]    While it is shown that the piston arm  14  will automatically extend upon cessation of air supply  23  to close knife gate  12 , the high pressure tank  18  and working cylinder assembly  10  can be used with other applications and also can be used to automatically retract piston arm  14  upon the cessation of pneumatic pressure from air supply  23 . A simple reversing of the two lines  30  and  35  to the double working cylinder  16  will cause the piston arm  14  to automatically retract as opposed to automatically extend during absence of air supply  23 . 
         [0030]    By having the tank  18  coaxially mounted with the working cylinder and being approximately the same size as the working cylinder, an easily manufactured assembly using duplicate parts is accomplished. Furthermore, the side mounting of the intensifier  20  onto the tank and cylinder assembly  12  provides for a compact package that can be easily mounted. 
         [0031]    While the intensifier is described as being operating off of air supply  23 , it is also foreseen that the intensifier  20  can be electrically driven. While air is the most common source for pneumatic pressure, other gases, e.g. nitrogen may be used for certain oxygen free application. While it is shown that the intensifier uses a reciprocating piston, other shaped pumps for example Wankel, spiral or rotary shaped pumps are also foreseen. 
         [0032]    While not as efficient, it is also foreseen that the side  56  may draw in and receive ambient air from outside of cylinder section  45  rather than receive air from air supply  23 . 
         [0033]    Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.