Abstract:
A valve assembly for receiving a fluid under pressure and comprising a plurality of valves in a single valve block. The assembly may include a plurality of check valves and including a counterbalance generating valve and a 3-way valve and including a method of use. The assembly may include an adjustable counterbalance valve, a pilot-operated check valve and a 3-way valve or combinations thereof.

Description:
RELATED APPLICATION 
       [0001]    The present invention claims priority to co-pending U.S. Provisional Patent Application Ser. No. 61/877,657, filed 13 Sep. 2013. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates in general to fluid pressure operated systems and devices, particularly pneumatic valve assemblies used to position heavy objects, such as boat gangways. 
       BACKGROUND OF THE INVENTION 
       [0003]    Systems and devices using fluid pressure for lifting and holding position are known. These systems and devices typically include check valves, which prevent sudden and potentially damaging loss of pressure when the supply of pressurized fluid unexpectedly decreases or fails. The present valve solves some of the problems related to the use of a standard dual. check or a. single check valve in applications which require better pneumatic control. In certain applications, using a dual check or single check alone, may cause the cylinder movement to be jerky and could cause a runaway condition when opening the valve after stopping. The present invention contemplates a single valve block configured to solve a number of design problems where pneumatic control of motion is required. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides a valve assembly for receiving a fluid under pressure and comprising a plurality of valves in a single block. The assembly may include a counterbalance valve to supply a continuous pressure to balance a load on a cylinder. The counterbalance valve is adjustable to maintain the load in an elevated position by applying constant back pressure to the air cylinder. Second, the assembly may include a pilot-operated check valve to trap air pressure on the opposite side of an air cylinder, to thereby reduce cylinder bounce. Third, the assembly may include a 3-way valve to quickly exhaust the pilot supply to the counterbalance valve, so that any movement due to load momentum does not further increase the pressure on the counterbalance valve, causing it to open, and the cylinder to drift until the system stabilizes. 
         [0005]    An alternative valve assembly may include a pair of counterbalance valves to supply a continuous pressure to balance a load on a cylinder. Second the assembly may further include the assembly may include a pair of 3-way valves to quickly exhaust the pilot supply to each respective counterbalance valve, so that any movement due to Load momentum does not further increase the pressure on a counterbalance valve, causing it to open, and the cylinder to drift until the system stabilizes. 
         [0006]    Another alternative assembly may include a counterbalance valve to supply a continuous pressure to balance a load on a cylinder. The counterbalance valve is adjustable to maintain the load in an elevated position by applying constant back pressure to the air cylinder. Second the assembly may include a 3-way valve to quickly exhaust the pilot supply to the counterbalance valve, so that any movement due to load momentum does not further increase the pressure on the counterbalance valve, causing it to open, and the cylinder to drift until the system stabilizes. Third, the system may include a check valve having a flow control mechanism to control air flow through the check valve. 
         [0007]    Yet another alternative assembly may include a counterbalance valve to supply a continuous pressure to balance a load on a cylinder. The counterbalance valve is adjustable to maintain the load in an elevated position by applying constant back pressure to the air cylinder. Second, the system may include a check valve having a flow control mechanism to control air flow through the check valve. 
         [0008]    The invention includes a valve comprising a valve body, the valve body including a first pilot bore, the first pilot bore including an input bore having an input port, an output bore having an output port, and a first cartridge spool disposed at least partially within the first pilot bore; and a second pilot bore, the second pilot bore including an input bore having an input port, an output bore having an output port, the second pilot bore including a second cartridge spool disposed at least partially within the second pilot bore. A valve according to the present invention includes a valve body which is a unitary member. A valve according to the present invention may include a flow control mechanism on one of a first pilot bore or a second pilot bore. The flow control mechanism may include a threaded adjusting screw and a bumper member mounted on a first end of the adjusting screw. The bumper member being in contact with one of a first or second cartridge spool to thereby limit the travel of the spool. The flow control mechanism may further include a lock nut threaded onto the adjusting screw and adapted to selectively prevent rotation of the adjusting screw with respect to the bumper member. A valve according to the present invention may further include a counterbalance mechanism for one of the pilot bores. The counterbalance mechanism may include a counterbalance adjusting screw and a counterbalance bias spring, the counterbalance adjusting screw biasing the bias spring in a direction against the cartridge spool to close the outlet port. A valve according to the present invention may further include a 3-way valve in fluid communication with at least one of the pilot bores. A 3-way valve may include a piston bore and a piston disposed at least partially within the piston bore, and a ball check. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a valve for use in a fluid flow system according to the present invention. 
           [0010]      FIG. 2A  is a cross sectional view of the valve shown in  FIG. 1  and taken along lines  2 A- 2 A thereof. 
           [0011]      FIG. 2B  is a cross sectional view of the valve shown in  FIG. 1  and taken along lines  2 B- 2 B thereof. 
           [0012]      FIG. 2C  is an enlarged cross sectional view of a portion of the valve shown in  FIGS. 1 and 2A  showing the area referenced by  2 C in  FIG. 2A . 
           [0013]      FIG. 3  is a schematic representation of the valve shown in  FIG. 1  in use in a fluid flow system. 
           [0014]      FIGS. 4A-4D  are graphic representations of a fluid flow system according to the present invention using the valve illustrated in  FIGS. 1-3  and showing use thereof. 
           [0015]      FIG. 5  is a perspective view of another embodiment of a valve for use in a fluid flow system according to the present invention. 
           [0016]      FIG. 6  is a cross sectional view of valve shown in  FIG. 5  and taken along lines  6 - 6  thereof. 
           [0017]      FIG. 7  is a schematic representation of the valve shown in  FIG. 5  in use in a fluid flow system. 
           [0018]      FIGS. 8A-8B  are graphic representations of a fluid flow system according to the present invention using the valve illustrated in  FIGS. 5-7  and showing use thereof. 
           [0019]      FIG. 9  is a perspective view of another embodiment of a valve for use in a fluid flow system according to the present invention. 
           [0020]      FIG. 10A  is a cross sectional view of valve shown in  FIG. 9  and taken along lines  10 A- 10 A thereof. 
           [0021]      FIG. 10B  is a cross sectional view of the valve shown in  FIG. 9  and taken along lines  10 B- 10 B thereof. 
           [0022]      FIG. 10C  is an enlarged cross sectional view of a portion of the valve shown in  FIGS. 9 and 10B  showing the area referenced by  10 C in  FIG. 10B . 
           [0023]      FIG. 11  is a schematic representation of the valve shown in  FIG. 9  in use in a fluid flow system. 
           [0024]      FIGS. 12A-12C  are graphic representations of a fluid flow system according to the present invention using the valve illustrated in  FIGS. 9-11  and showing use thereof. 
           [0025]      FIG. 13  is a perspective view of another embodiment of a valve for use in a fluid flow system according to the present invention. 
           [0026]      FIG. 14A  is a cross sectional view of valve shown in  FIG. 13  and taken along lines  14 A- 14 A thereof. 
           [0027]      FIG. 14B  is a cross sectional view of the valve shown in  FIG. 13  and taken along lines  14 B- 14 B thereof. 
           [0028]      FIG. 15  is a schematic representation of the valve shown in  FIG. 13  in use in a fluid flow system. 
           [0029]      FIGS. 16A-16B  are graphic representations of a fluid flow system according to the present invention using the valve illustrated in  FIGS. 13-15  and showing use thereof. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0030]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the clams. 
       I. Counterbalance/3-Way and Check Valve 
       [0031]    With specific attention to  FIGS. 1-4D , a valve  10  according to the present invention may be seen. The valve configuration described and illustrated in these views is preferably used in applications requiring higher cylinder pressure in one direction of motion. An example of such an application is a vertical cylinder application, in which high pressure is required to lift the load and very little pressure is required to lower the load, because gravity does most of the work in one direction. Using a typical dual check or single pilot-operated check valve (not shown) may result in jerky motion and can cause a runaway condition when opening the valve after stopping. 
         [0032]    An embodiment of the present invention as is depicted in the views of  FIGS. 1-4C , is directed to a valve  10  having three valves  20 ,  30 ,  40  in one body  12 . First, and as may be seen, a counterbalance valve  20  supplies a continuous pressure to balance a Load on a cylinder  14  (see  FIGS. 4A-4C ). The counterbalance valve  20  may be adjusted to maintain the Load in an elevated position by applying constant back pressure to the air cylinder  14 . Second, a pilot-operated check valve  30  traps air pressure on the opposite side of the air cylinder  14 , to thereby reduce cylinder  14  bounce. Third, a 3-way valve  40  quickly exhausts the pilot supply to the counterbalance valve  20 , so that any movement due to Load momentum does not further increase the pressure on the counterbalance valve  20 , causing it to open, and the cylinder  14  to drift until the system stabilizes. 
         [0033]    When lowering the Load, very little pressure is required, because the Load tends to move the cylinder  14  due to gravity. The effect of gravity may be a problem with known pilot-operated check valves (not shown), because known devices require a minimum pilot pressure to open the valve. Since the line to lower the cylinder requires very little pressure, the pressure may drop below the required minimum valve operating pressure, causing the Load to bounce undesirably as it moves downward. 
         [0034]    The counterbalance valve  20  of the present arrangement increases the pilot pressure by applying back pressure to the cylinder  14  that will increase the pressure required to lower the Load, and therefore, increase the pilot pressure, by providing a constant resistance to the cylinder  14 . 
         [0035]    The counterbalance valve  20  also reduces the chances of a runaway condition that may occur when the cylinder  14  is stopped, and then restarted without any back pressure on the cylinder  14 . The counterbalance valve  20  typically applies resistance to motion, so there is no sudden surge in motion. The runaway condition may occur if a typical dual check valve (not shown) is used instead of a counterbalance valve  20  and check valve  30  combination of the present invention. Likewise, a typical dual check valve (not shown) may quickly exhaust any back pressure on the cylinder  14 , allowing it to undesirably surge forward. 
         [0036]    The present valve  10  may further include a 3-way valve  40  to further reduce undesirable drift due to load momentum. When the system stops, the Load tends to stay in motion causing the air cylinder  14  to compress the air, thereby increasing the air pressure on the counterbalance valve  20 , causing it to stay open, until the system equalizes. The 3-way valve  40  greatly reduces this effect by closing the internal piston  42  that opens the counterbalance valve  20 , so that a surge in air pressure cannot continue to open the counterbalance valve  20  and cause the Load to drift. It is to be understood that while the present invention greatly reduces the amount of drift, a small amount of drift will always occur, due to the compressibility of air. 
       II. Operation of the Counterbalance/3-way and Check Valve 
       [0037]    Operation of the combination counterbalance/3-way and check valve  10  illustrated in  FIGS. 1-4C  may be particularly seen in the views of  FIGS. 4A-4C . As shown particularly in  FIG. 4A , air pressure from a supply source (not shown) is connected a control valve. When the control valve is energized to advance an air cylinder  14 , the air enters the control valve and the input port  22  of the counterbalance valve  20  in the direction of arrow A. The air further flows in the direction of arrow A′ via the air line  24 , to the main seat  32 , on the check valve  30 , by shifting the cartridge spool  34  in the pilot bore  38  in the direction of arrow B. Air enters the counterbalance valve  20  input port  22  in the direction of arrow A and opens the counterbalance main seat  26  by moving it, in the direction of arrow C. The counterbalance main seat  26  is lightly biased by seat spring  28  (see particularly  FIG. 2A ). The air continues to pass through the counterbalance main seat  26  in the direction of arrow A to the counterbalance valve output port  18 , thereby supplying air to the rod side  16 , of the air cylinder  14  and raising the Load in the direction of arrow E. The ball check  44  in the 3-way valve  40  is closed, so air cannot escape through air passage  45 . 
         [0038]    With further attention to  FIG. 4A , as the air cylinder  14  lifts the Load, air escapes from the cap side  17  of the air cylinder  14  in the direction of arrow 
         [0039]    F, and through the output port  36  of the check valve  30  in the direction of arrow F, out the main seat  32  of the check valve  30 . As previously mentioned, the main seat  32  of the check valve  30  will be open since air pressure is supplied by the air line  24 , to the check valve pilot bore  38 , Air escapes out the inlet port  37  of the check valve  30  in the direction of arrow F and through the control valve. 
         [0040]    With reference to  FIG. 4B , it may be seen that when the control valve is in the neutral, stopped position, an adjusting screw  60  may be set to hold the Load in position. The adjusting screw  60  is turned clockwise in the direction of arrow D to compress a spring  62 . The spring  62  thereby biases the main seat  26  to close the outlet port  18 . The screw is turned until the back pressure on the air cylinder  14 , holds the Load in a suspended position. 
         [0041]    Turning now to  FIGS. 4C and 4D , a method to reverse direction, or lower the Load utilizing the present valve  10  may be seen. As illustrated, the control valve supplies air to the input port  37  of the check valve  30  in the direction of arrow G, causing the main seat  32  to open in the direction of arrow H. The main seat  32  is lightly biased closed by a poppet spring  64 , Air is also supplied to the 3-way valve  40 , via air line  66  in the direction of arrow G′, which causes the piston  42  of the 3-way valve  40  to move downward in the direction of arrow K. Air line  66  usually taps into inlet port  37  of the check valve  30 , but may also be connected to another source of air pressure where the air is able to exhaust more quickly. The seal  48  on the piston.  42  closes the air passage  70  from the pilot bore  68  of counterbalance valve  20  to the exhaust passage  46  (see particularly  FIG. 2C ). The piston  42  also unseats the ball check  44 , and opens the air passage  45 , to the pilot bore  68  to allow air to flow in the direction of arrow J. The pressure shifts the cartridge spool  72  in the direction of arrow N to open the main seat  26  (see particularly  FIG. 2A ), causing air to flow in the direction of arrow N to a pressure differential required to hold the Load in position. 
         [0042]    With particular attention to  FIG. 4D , when the control valve is in the center position both ports  22  and  37  exhaust, and the pressure at the 3-way port  49 , drops to zero. At the same time, spring  50  (see  FIG. 2C ) of the 3-way valve  40  pushes the piston  42  away from the ball check  44  in the direction of arrow P. and spring  52  biases ball check  44  to close. Air passage  45  closes and the air passage  70  from the pilot bore  68  opens to atmosphere, exhausting through the exhaust passage  46  in the direction of arrow Q. It is to be understood that spring  50  may be replaced with various springs under differing tensions if back pressure so requires and if the valve  10  is required to close at a faster rate. 
         [0043]    The loss of pressure in pilot bore  66  causes the spring  62  to shift the cartridge spool  72  of the counterbalance valve  20  in the direction of arrow R and to close the main seat  26 . The 3-way valve  40  closes air passage  45 , so that any increase in pressure due to load momentum, will not open the counterbalance valve  20 , causing the air cylinder  14  to drift after stopping. 
       III. Counterbalance/3-Way and Counterbalance/3-Way Valve 
       [0044]    With specific reference to  FIGS. 5-8B , another embodiment valve  100  according to the present invention may be seen. The valve configuration described and illustrated in these views is preferably used in applications requiring high cylinder pressure in two directions of motion. An example of such an application is a heavy load application in which movement in two directions is required and drift due to momentum needs to be minimized in both directions. 
         [0045]    An embodiment of the present invention for use in such applications is depicted in the views of  FIGS. 5-8B . As seen, the valve  100  includes four valves  20 ,  20 A,  40 ,  40 A in one body  12 . A counterbalance valve  20 ,  20 A is applied during both cylinder  14  motions due to the effects of both gravity and momentum in both the elevating and lowering directions. Both counterbalance valves  20 ,  20 A may be adjusted for varying back pressures, depending on load and motion, as will be discussed. 
         [0046]    A 3-way valve  40 ,  40 A is also applied in both cylinder directions, to thereby reduce the amount of drift after stopping the cylinder  14 . As in the previous embodiment, the 3-way valve  40 ,  40 A quickly exhausts the pilot supply to the counterbalance valve  20 ,  20 A, so that any movement due to load momentum does not further increase the pressure on the counterbalance valve  20 ,  20 A causing it to open, and the cylinder  14  to drift until the system stabilizes. 
         [0047]    In this application, the counterbalance valves  20 ,  20 A increase the pilot pressure by applying back pressure to both sides of the cylinder  14  to increase the pressure required to both lower and raise the Load, and therefore, increase the pilot pressure, by providing a constant resistance to the cylinder  14  in either movement. 
         [0048]    The counterbalance valves  20 ,  20 A also reduce the chances of a runaway condition that may occur when the cylinder  14  is stopped, and then restarted without any back pressure on the cylinder  14 , as described above. The counterbalance valves  20 ,  20 A typically apply resistance to motion, so there is no sudden surge in motion. 
         [0049]    The present valve  100  may further include two 3-way valves  40 ,  40 A to further reduce undesirable drift due to load momentum. When the system stops, the Load tends to stay in motion causing the air cylinder  14  to compress the air, thereby increasing the air pressure on the counterbalance valve  20 ,  20 A causing it to stay open, until the system equalizes. The 3-way valves  40 ,  40 A greatly reduce this effect by closing the internal piston  42 ,  42 A that opens the counterbalance valve  20 ,  20 A so that a surge in air pressure cannot continue to open the counterbalance valve  20 ,  20 A and cause the Load to drift. It is to be understood that while the present invention greatly reduces the amount of drift, a small amount of drift will always occur, due to the compressibility of air. 
       IV. Operation of the Counterbalance/3-Way and Counterbalance/3-Way Valve 
       [0050]    Operation of the combination counterbalance/3-way and counterbalance/3-way valve  100  illustrated in  FIGS. 5-7  may be viewed particularly in  FIGS. 8A-8B . With specific attention to  FIG. 8A , air enters the control valve and input port  22  of counterbalance valve  20  in the direction of arrow A. The air further flows in the direction of arrow A and opens the main seat  26  of the counterbalance valve  20  by moving it in the direction of arrow C. The counterbalance main seat  26  is lightly biased by seat spring  28  (see particularly  FIG. 6 ). The air continues to pass through. the counterbalance main seat  26  in the direction of arrow A to the counterbalance valve output port  16 , thereby supplying air to the rod side  16 , of the air cylinder  14  and moving the Load in the direction of arrow E. The ball check  44  in the 3-way valve  40  is closed, so air cannot escape through air passage  45 . 
         [0051]    With continued attention to  FIG. 8A , it may be seen that as the air cylinder  14  is moving the Load, air must be able to escape from the cap side  17 , of the air cylinder  14  in the direction of arrow F. The air moves through the output port  18 A of counterbalance valve  20 A in the direction of arrow F, and out the main seat  26 A of counterbalance valve  20 A. The main seat  26 A will be open because pressure supplied via air line  74 , causes the piston  420 . of the 3-way valve  40 A to move in the direction of arrow K to unseat the ball check  44 . The seal  48  on the piston  42 A closes the exhaust passage  46 . 
         [0052]    Air flows from air passage  45  to the pilot bore  68  in the direction of arrow J. The increase in air pressure will cause the cartridge spool  72 A to shift in the direction of arrow B and to open the main seat  260 . Air may now escape through outlet port  22 A in the direction of arrow F and exhaust through the control valve. 
         [0053]    As in the previous embodiment, when the control valve is in the neutral, stopped position, an adjusting screw  60  may be set to hold the Load in position. The adjusting screw  60  is turned clockwise in the direction of arrow D to compress a spring  62  (see  FIG. 4B ). The spring  62  thereby biases the main seat  26  or  26 A to close the outlet port  18  or  18 A. The screw is turned until the back pressure on the air cylinder  14  holds the Load in a suspended position. 
         [0054]    When the control valve is in the center position both ports  22  and  22 A exhaust, and the pressure at the port  49  of 3-way valve  40 , drops to zero. At the same time, spring  50  (see  FIG. 22 ) of the 3-way valve  40  pushes the piston  42  away from the ball check  44  in the direction of arrow P (see  FIG. 4D ), and the spring  52  biases ball check  44  to close. Air passage  45  closes and the air passage  70  from the pilot bore  68  opens to atmosphere, and exhausts through the exhaust passage  46  in the direction of arrow Q. It is to be understood that spring  50  may be of any type suitable to deliver an acceptable tension and may be under differing tensions if back pressure so requires, and if the valve  100  is required to close at a faster rate. For example, higher spring rates would close the valve  100  more quickly and alleviate the effect of back pressure. An adjustable spring rate would be ideal. 
         [0055]    With attention to  FIG. 8B , a method to reverse direction or to lower the Load using valve  100  may be seen. As illustrated, the control valve supplies air to the input port  22 A of counterbalance valve  20 A in the direction of arrow G, causing the main seat  26 A to open in the direction of arrow H. As in the discussion regarding  FIG. 8A , the counterbalance main seat  26 A is lightly biased by seat spring  28  (see particularly  FIG. 6 ). The air continues to pass through the counterbalance main seat  26 A in the direction of arrow G to the counterbalance valve output port  18 A, thereby supplying air to the cap side  17 , of the air cylinder  14  and moving the Load in the direction of arrow E. The ball check  44  in the 3-way valve  40 A is closed, so air cannot escape through air passage  45 . 
         [0056]    As may be further seen in  FIG. 8B , as the air cylinder  14  is moving the Load, air must be able to escape from the rod side  16 , of the air cylinder  14  in the direction of arrow N. The air moves through the output port  18  of counterbalance valve  20  in the direction of arrow N, and out the main seat  26  of counterbalance valve  20 . The main. seat  26  will be open because pressure supplied via air line  66 , causes the piston  42  of the 3-way valve  40  to move in the direction of arrow K to unseat the ball check  44 , The seal  48  on the piston  42  closes the exhaust passage  46 . Air flows from air passage  45  to the pilot bore  68  in the direction of arrow J. The increase in air pressure will cause the cartridge spool  72  to shift in the direction of arrow M and to open the main seat  26 . Air may now escape through outlet port  22  in the direction of arrow N and exhaust through the control valve. 
         [0000]    V. Counterbalance/3-Way and Check Valve with Flow Control 
         [0057]    Turning now to  FIGS. 9-12C , another embodiment valve  200  according to the present invention may be seen. The valve configuration described and illustrated in these views is preferably used in applications requiring movement of heavy load in one direction, and drift due to momentum needs to be minimized in one direction. In situations utilizing valve  200 , the reverse direction requires movement of a heavy load, however drift is not as important, so a flow control is sufficient to control the movement. 
         [0058]    An embodiment of the present invention for use in such applications is depicted in the views of  FIGS. 9-12C . As seen, the valve  200  includes three valves  20 ,  30 A,  40  in one body or block  12 . A counterbalance valve  20  and 3-way valve  40  is applied to the heavy side (gravity added) and a check valve  30 A having a flow control mechanism  72  is applied to the reverse motion, as will be discussed. 
         [0000]    VI. Operation of the Counterbalance/3-Way and Check Valve with Flow Control 
         [0059]    Operation of the combination counterbalance/3-way and check valve with flow control  200  illustrated. in  FIGS. 9-11  may be seen in the views of  FIGS. 12A-12C . With specific attention to  FIG. 12A , air enters the control valve and the input port  22  of counterbalance valve  20  in the direction of arrow A. The air further flows in the direction of arrow A′ via air line  24 , to the main seat  32 , on check valve  30 A, by shifting the cartridge spool  34  in the pilot bore  38  in the direction of arrow B. Movement of the cartridge spool  34  is limited a flow control mechanism  76 . Specifically, the flow control mechanism  76  includes a bumper  78  (see  FIGS. 10B and 10C ) attached to an adjusting screw  80  which can be set to vary the travel of the cartridge spool  34 , and thus, vary the height h that the main seat  32  opens and thereby control flow (see  FIGS. 12A and 12C ). A locking nut  82  holds the adjusting screw  80  in position. 
         [0060]    Air enters the counterbalance valve  20  input port  22  in the direction of arrow A and opens the counterbalance main seat  26  by moving it in the direction of arrow C. The counterbalance main seat  26  is lightly biased by seat spring  28  (see particularly  FIG. 2A ). The air continues to pass through the counterbalance main seat  26  in the direction of arrow A to the counterbalance valve output port  18 , thereby supplying air to the rod side  16 , of the air cylinder  14  and moving the Load in the direction of arrow E. The ball check  44  in the 3-way valve  40  is closed, so air cannot escape through air passage  45 . 
         [0061]    With further attention to  FIG. 12A , as the air cylinder  14  moves the Load, air must escape from the cap side  17  of the air cylinder  14  in the direction of arrow F, through the output port  36  of the check valve  30 A, and out the main seat  32 , of the check valve  30 A. The main seat  32  will be open to a predetermined height h set by the adjusting screw  80 . As illustrated in the views of  FIGS. 12A and 12C , the height h can be varied to increase or restrict the flow of the air through the main seat  32  by the flow control mechanism  76 . As shown in  FIG. 12C , rotation of the adjustment screw  80  in the direction of arrow T positions the bumper  78  and therefore the travel boundary of the cartridge spool  34 . The ability to control air flow through the main seat  32  also controls the speed of the cylinder  14  and therefore the Load movement. 
         [0062]    As in the previous embodiments, when the control valve is in the neutral, stopped position, an adjusting screw  60  on the counterbalance valve  20  may be set to hold the Load in position. The adjusting screw  60  is turned clockwise in the direction of arrow D (see  FIG. 4B ) to compress a spring  62 . The spring  62  thereby biases the main seat  26  to close the outlet port  18 . The screw is turned until the back pressure on the air cylinder  14 , holds the Load in a suspended position. 
         [0063]    Also similar to the embodiment illustrated in  FIGS. 1-4D , when the control valve is in the center position both ports  22  and  37  exhaust, and the pressure at the 3-way port  49 , drops to zero. At the same time, spring  50  (see  FIG. 2C ) pushes the piston  42  away from the ball check  44  in the direction of arrow P, and spring  52  biases the ball check  44  to close. Air passage  45  closes and the air passage  70  from the pilot bore  68  opens to atmosphere, exhausting through exhaust passage  46  in the direction of arrow Q (see  FIG. 4D ). It is to be understood that spring  50  may be of any type suitable to deliver an acceptable tension and may be under differing tensions if back pressure so requires, and if the valve  200  is required to close at a faster rate. For example, higher spring rates would close the valve  200  more quickly and alleviate the effect of back pressure. As in the previous embodiments, an adjustable spring rate would be ideal. 
         [0064]    Turning now to  FIG. 12B , a method to reverse direction, or lower the Load utilizing the valve  200  may be seen. As illustrated, the control valve supplies air to the input port  37  of the check valve  30 A in the direction of arrow G, causing the main seat  32  to open in the direction of arrow H. The main seats  32  is lightly biased closed by a poppet spring  64  (see  FIG. 10B ). Air is also supplied to the 3-way valve  40 , via air line  66  in the direction of arrow G′, which causes the piston  42  of the 3-way valve  40  to move downward in the direction of arrow K. The seal  48  on the piston  42  closes the air passage  70  from the pilot bore  68  of counterbalance valve  20  to the exhaust passage  46  (see particularly  FIG. 2C ). The piston  42  also unseats tie ball check  44 , and opens the air passage  45 , to the pilot bore  68  to allow air to flow in the direction of arrow J. The pressure shifts the cartridge spool  72  in the direction of arrow M to open the main seat  26  (see particularly  FIG. 2A ), causing air to flow in the direction of arrow N to a pressure differential required to hold the Load in position. 
         [0065]    As in previous embodiments the loss of pressure in pilot bore  68  causes the spring  62  to shift the cartridge spool  72  of the counterbalance valve  20  in the direction of arrow R and to close the main seat  26 . The 3-way valve  40  closes air passage  45 , so that any increase in pressure due to load momentum, will not open the counterbalance valve  20  and cause the air cylinder  14  to drift after the control valve is set to a stopped, neutral position. 
         [0000]    VII. Counterbalance and Check with Flow Control Valve 
         [0066]    With reference now to  FIGS. 13-16B , another embodiment valve  300  according to the present invention may be seen. The valve configuration described and illustrated in these views is preferably used in applications requiring movement of a light load in one direction and where control of drift due to momentum is not required. In this application, movement in the reverse direction also does not require drift control, therefore use of a flow control mechanism is sufficient to control movement. 
         [0067]    An embodiment of a valve for use in such applications may be seen in the views of  FIGS. 13-14B . As illustrated, the valve  300  includes two valves  20 ,  30 A in one block or body  12 . A counterbalance valve  20  is applied during lifting of the Load to the cylinder  14  side where the force of gravity adds to the pressure. A flow control mechanism  76  on the check valve  30 A is applied during reverse motion of the Load to regulate motion. 
       VIII. Operation of the Counterbalance and Flow Control Valve 
       [0068]    Operation of the Counterbalance and Flow Control Valve  300  may be seen in the views of  FIGS. 16A and 16B . As is shown in  FIG. 16A , air enters the control valve and the input port  22  of the counterbalance valve  20  in the direction of arrow A. The air further flows in the direction arrow A′ via. the air line  24 , to the main seat  32 , on the check valve  30 A, by shifting the cartridge spool  34  in the pilot bore  38  in the direction of arrow B. Movement of the cartridge spool  34  is limited by a flow control mechanism  76 . Specifically, and similar to the embodiment illustrated in  FIGS. 9-12C , the flow control mechanism  76  includes a bumper  78  (see  FIG. 14B ) attached to an adjusting screw  80 . The movement of the cartridge spool  34  is limited by the bumper  78  attached to the adjusting screw  80  which can be set to vary the travel of the cartridge spool  34 , and thus, vary the height h that the main seat  32  opens. Turning the screw  80  clockwise in the direction of arrow T will limit the flow through the main seat  32  (see  FIG. 12C ). A locking nut  82  holds the adjusting screw  80  in position. 
         [0069]    As mentioned with regard to previous embodiments, air also enters the counterbalance valve  20  input port  22  in the direction of arrow A and opens the counterbalance main seat  26  by moving it in the direction of arrow C. As in the previous embodiments, the counterbalance main seat  26  is lightly biased by seat spring  28 . The air continues to pass through the counterbalance main seat  26  in the direction of arrow A to the counterbalance valve output port  18 , thereby supplying air to the rod side  16 , of the air cylinder  14  and moving the Load in the direction of arrow E. 
         [0070]    With further attention to  FIG. 16A , as the air cylinder  14  moves the Load, air must escape from the cap side  17  of the air cylinder  14  in the direction of arrow F, through the output port  36  of the check valve  30 A, and out the main seat  32 , of the check valve  30 A. The main seat  32  will be open to a predetermined height h set by the adjusting screw  80 . As was previously discussed with regard to  FIGS. 12A and 12C , the flow control mechanism  76  may set the height h to restrict and vary the flow of the air, and therefore, limit the speed of the air cylinder  14 . 
         [0071]    When the control valve is in the neutral position (stopped), the adjusting screw  60  is turned clockwise until the back pressure on the air cylinder  14 , holds the load in a suspended position. 
         [0072]    Turning now to  FIG. 16B , a method to reverse direction, or lower the Load utilizing the valve  300  may be viewed. As illustrated, the control valve supplies air to the input port  37  of the check valve  30 A in the direction of arrow G, causing the main seat  32  to open in the direction of arrow H. The pressure increases in the air cylinder  14 , and the cylinder  14  begins to move downward, causing the air pressure in the rod side  16  of the cylinder  14  to increase. The increased air pressure travels to the pilot bore  68 , via air passages  45  and  70  in the direction of arrows N and N′, respectively. The pressure overcomes the adjusting spring  62  and shifts the cartridge spool  72  in the direction of arrow M to open the main seat  26  (see particularly  FIG. 2A ), causing air to flow in the direction of arrow N, allowing the air to escape out port  22  to the control valve, where it will vent to atmosphere. 
         [0073]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention.