Patent Publication Number: US-2017363217-A1

Title: Main Stage In-Line Pressure Control Cartridge with Optional Reverse Flow Function

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of Ser. No. 13/841,558, filed on Mar. 15, 2013, which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present general inventive concept is directed to a method and apparatus, and directed to a main stage cartridge. 
     Description of the Related Art 
     One trend in modern hydraulics is towards higher operating pressures in order to provide more work with a smaller actuator. There is also a desire to minimize energy consumption. 
     Currently, there is widespread use of hydraulic cartridge valve technology. Hydraulic cartridge valves do have high insertion losses due to small fluid passages coupled with multiple fluid directional changes 
     Hydraulic cartridge valves in present use are either of screw-in or slip-in construction. Screw-in cartridges are threaded into a cavity. The torque required to pre-load the cartridge in its cavity can be substantial in a larger valve. For example, a screw-in cartridge valve rated for a nominal flow of 200 gpm can have a pre-load torque requirement of 375 foot-pounds. 
     Slip-in cartridge valves, known as 2/2 valves or logic valves, are generally held in a cavity by a cover plate retained with socket head cap screws. The pre-load torques are much lower for a given nominal flow size. Most are designed to be used within cavities defined by standards DIN 24342 and ISO 7368. 
     For both screw-in and slip-in cartridge valves, the typical axis of fluid discharge is offset 90 degrees from the axis of fluid inlet. 
     Hydraulic cartridge valves currently utilize either a poppet or spool construction. Spool type hydraulic valves have disadvantages at higher pressures due to leakage between the valve sleeve and spool. Close fits are desired to minimize (but not eliminate) leakage. Despite this leakage may be unacceptably high as system working pressures increase. This results in wasted energy and heat as high-pressure hydraulic fluid is discharged to lower pressure without doing any useful work. 
     Silting is also a problem. Spool valves are vulnerable to fine fluid contamination. Debris deposited between the spool and the sleeve may result in erratic valve shifting, or the valve not shifting at all. Continuous leakage is present in spool type valves, even when the valve is closed, representing a continuous loss of energy. 
     Therefore, what is needed is a cartridge valve that can improve upon the deficiencies of the prior art. 
     SUMMARY OF THE INVENTION 
     It is an aspect of the present invention to provide an improved in-line cartridge valve. 
     These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1A  shows an end view of the body with a control or pilot module, the body which receives any cartridge of the present invention, according to an embodiment; 
         FIG. 1B  shows a top view of the body with a control module, according to an embodiment; 
         FIG. 1C  shows a cross section of the body with a cartridge inserted, according to an embodiment; 
         FIG. 2A  shows a thread-in valve assembly, according to an embodiment; 
         FIG. 2B  shows a cross section of a body used to house a thread-in valve assembly, according to an embodiment; 
         FIG. 3A  shows a slip-in valve assembly, according to an embodiment; 
         FIG. 3B  shows a cross section of a body used to house a slip-in valve assembly, according to an embodiment; 
         FIG. 4  shows a tubular poppet of a thread-in assembly, according to an embodiment; 
         FIG. 5A  shows a slip-in tubular poppet without a retainer collar control sleeve, or spring, according to an embodiment; 
         FIG. 5B  shows a cross section of a tubular poppet, according to an embodiment; 
         FIG. 5C  shows a cross section of a tubular poppet showing radial holes at an angle, according to an embodiment; 
         FIG. 6  shows a slip-in tubular poppet without a retainer collar, control sleeve, spring or seal, with a cone-shaped nose, according to an embodiment; 
         FIG. 7A  shows a top view of the control sleeve, according to an embodiment; 
         FIG. 7B  shows a side view of the control sleeve, according to an embodiment; 
         FIG. 7C  shows a cross section of the control sleeve, according to an embodiment; 
         FIG. 8A  shows a side view of a retainer collar, according to an embodiment; 
         FIG. 8B  shows a top view of the retainer collar, according to an embodiment; 
         FIG. 8C  shows a cross section of the retainer collar, according to an embodiment; 
         FIG. 9  shows a cross section of the tubular poppet with the retainer collar, control sleeve, and spring, according to an embodiment; 
         FIG. 10  shows a cross section of a slip-in valve assembly inside a body with forward flow, according to an embodiment; 
         FIG. 11  shows a cross section of a slip-in valve assembly inside a body in a neutral position, according to an embodiment; 
         FIG. 12  shows a cross section of a slip-in valve assembly inside a body with reverse flow, according to an embodiment; 
         FIG. 13A  is an orthographic view illustrating a front view of a slip-in valve assembly in a closed position, according to an embodiment; 
         FIG. 13B  is an orthographic view illustrating a front view of a slip-in valve assembly in assembly in open position, according to an embodiment; 
         FIG. 13C  is an orthographic view illustrating the tubular poppet opening of a slip-in valve assembly, according to an embodiment; 
         FIG. 13D  is an orthographic side view illustrating a slip-in valve assembly, according to an embodiment; 
         FIG. 14A  is an orthographic view illustrating a front of a body and control module, according to an embodiment; 
         FIG. 14B  is an orthographic view illustrating a back of a body and control module, according to an embodiment; 
         FIG. 15  is a cross section showing a thread-in assembly installed within a valve body, according to an embodiment; 
         FIG. 16  is a cross section showing the alternate slip in assembly (with the retainer collar) installed within a valve body, according to an embodiment; 
         FIG. 17  is a cross section illustration an example of a check valve configuration with control sleeve seals, according to an embodiment; 
         FIG. 18  is a cross section illustration of the check valve configuration with control sleeve seals in an open position, according to an embodiment; 
         FIG. 19  is a cross section illustration of the check valve configuration with control sleeve seals with an external drain, according to an embodiment; 
         FIG. 20  is a cross section illustration of a valve assembly with an external pilot signal, according to an embodiment; 
         FIG. 21  is a cross section illustration of a valve assembly with an internal pilot signal, according to an embodiment; 
         FIG. 22  is a cross section illustrating an internally piloted, internally drained relief valve with the reverse flow option, according to an embodiment; 
         FIG. 23  is a cross section illustration of a valve assembly with a remote control, according to an embodiment; 
         FIG. 24  is a cross section illustration of a valve assembly with a remote control connected to a 2-position, 2-way valve configured as a vented relief valve, according to an embodiment; 
         FIG. 25A  is a cross section illustration illustrating a slip-in insert and valve body configured to provide flow control function, according to an embodiment; and 
         FIG. 25B  is a cross section illustration of a slip in assembly including a tubular poppet configured to provide flow control function, according to an embodiment. 
     
    
    
     Note that any portion of any part not explicitly shown in the drawings can be assumed to have a same structure as the visible corresponding/symmetrical portions of the part (unless such assumption would render the invention inoperative). Some figures illustrate cross-section views and (unless otherwise stated) other slices of the part(s) follow the same structure/pattern as the illustrated cross-section (unless such assumption would render the invention inoperative). Common sense can also be used to augment the figures knowing that the structure of the figures (and hence the invention) must be consistent with the stated operation(s) described herein. Thus, the figures can be augmented with any feature (described herein or not) which would be needed to render the invention operative. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     This invention is of a new pilot controlled two port straight flow thru hydraulic poppet valve with and without reverse flow capabilities. Control of the internal and external pilot flow together with control of the internal and external drain flow determines the function of the main poppet. 
     Note that fluid as used herein refers to any type of hydraulic fluid typically used in the art, including a fluid based on any kind of oil, mineral oil, water, and any commercially available hydraulic fluid such as SKYDROL, etc. 
     Existing hydraulic cartridge technology may be used to pilot or control the new main stage valve design. As the size and flow requirements of the pilot stage are small compared to the main stage, lost energy resulting from leakage and pressure drop may be minimized. 
     The new valve design has a positive metal-to-metal seal, and does not rely on very close clearance to minimize leakage and energy loss across the main flow stage. Larger clearances make the new valve design more resistant to the effects of dirt and contamination. The metal sealing minimizes or eliminates leakage associated with the valve in the closed position. 
     Socket head cap screws may be used to secure the valve in place, with relatively low pre-load torque requirements, when compared to a similarly sized screw-in cartridge. 
     The in-line orientation of the valve of the current invention is conducive to ‘sandwiching’ the main valve element between two components. Orientation of the fluid flow at the valve inlet and discharge is the same, as opposed to the 90 degree discharge offset associated with existing hydraulic cartridge designs. 
     Although the invention can be made to a variety of sizes, those depicted are optimized for use with the proprietary Unified Code 61 4-bolt flange standard disclosed in U.S. Pat. No. 6,715,798 (which is incorporated by reference herein in its entirety). Valves made for use with nominal port sizes 08, 12, 16, 20, 24, and 32 are made to the Unified Code 61 4-bolt standard. Sizes 40 and 48 are made to an industry Code 62 standard. 
     There are many advantages of putting valve and piping elements in line as stackable modular components using this standard, including but not limited to the use of high strength socket head cap screws as opposed to hex head cap screws in order to obtain higher working pressures in the same or smaller pressure containing envelope, the use of O-ring face sealing as a superior method to threaded connections, and how the use of this standard reduces leakage, labor costs, and system volume. 
     The valves illustrated in this patent are designed for hydraulic applications with operating pressures up to 5000 psi (350 bar). The valve assemblies described herein can be customized to further improve hydraulic systems that require other specific maximum hydraulic system pressures. 
       FIG. 1A  shows an end view of the body  0001  which receives (in a channel  0002  which passes through the entire body, although the bore is stepped so the diameter shown does not pass through the entire body) any cartridge of the present invention. The bolt mounting pattern shown can be a typical SAE 4-bolt mounting pattern that is common in the industry, and for which the slip in cartridges are designed for use with.  FIG. 1B  shows a top view of the body  0001  with a control module  0010 . 
     The sizes of straight flow through valves made to the teaching of this invention are favorable when compared to that of 90-degree discharge slip in cartridges in common use today.  FIGS. 0A and 0B  show end and side view of the envelopes of valves made to the teachings of this invention, including a pilot control valve. Dimensions (in inches) corresponding to the overall valve envelope, mounting pattern, bore diameter to receive the valve cartridge, and nominal flow rating at 40 psi pressure drop, are listed in Table 1 as follows: 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 NOMINAL 
               
               
                 NOMINAL 
                   
                   
                   
                   
                   
                   
                 RATED 
               
               
                 SIZE 
                 B 
                 W 
                 H 
                 E 
                 C 
                 L 
                 FLOW (GPM) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 8 
                 0.939 
                 1.75 
                 2.00 
                 1.500 
                 0.688 
                 2.88 
                 20.8 
               
               
                 12 
                 1.251 
                 2.06 
                 2.56 
                 1.875 
                 0.875 
                 3.42 
                 38.5 
               
               
                 16 
                 1.345 
                 2.25 
                 2.75 
                 2.062 
                 1.031 
                 3.38 
                 51 
               
               
                 20 
                 1.501 
                 2.75 
                 3.00 
                 2.312 
                 1.188 
                 3.38 
                 65 
               
               
                 24 
                 1.626 
                 3.00 
                 3.50 
                 2.750 
                 1.406 
                 4.13 
                 89 
               
               
                 32 
                 1.876 
                 3.00 
                 4.00 
                 3.062 
                 1.688 
                 4.88 
                 110 
               
               
                 40 
                 2.126 
                 4.38 
                 6.00 
                 3.500 
                 2.000 
                 5.25 
                 150 
               
               
                 48 
                 2.439 
                 5.38 
                 7.50 
                 4.188 
                 2.438 
                 5.75 
                 200 
               
               
                   
               
            
           
         
       
     
     Valves made to the teachings of this invention have a higher ‘power density’, or a better ability to transmit horsepower for a given unit of size. This is important given the trend in the hydraulic industry, particularly the mobile hydraulic industry, to provide more power with less weight. 
       FIG. 1C  shows a cross section of the body with a cartridge inserted. A cartridge  0015  is inserted into the channel in the body  0001 .  FIG. 1C  also show various nominal flow areas of slip-in cartridges made to the teachings of this invention for different nominal sizes. Table 2 is a tabular list of these areas: 
     
       
         
           
               
               
            
               
                   
               
               
                 NOMINAL 
                 AREA (SQUARE INCHES) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 SIZE 
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 8 
                 0.221 
                 0.130 
                 0.353 
                 0.148 
                 0.109 
                 0.221 
               
               
                 12 
                 0.442 
                 0.249 
                 0.627 
                 0.259 
                 0.300 
                 0.442 
               
               
                 16 
                 0.518 
                 0.338 
                 0.681 
                 0.344 
                 0.392 
                 0.690 
               
               
                 20 
                 0.519 
                 0.442 
                 0.883 
                 0.443 
                 0.491 
                 0.887 
               
               
                 24 
                 0.785 
                 0.601 
                 0.969 
                 0.616 
                 0.614 
                 1.108 
               
               
                 32 
                 1.108 
                 0.887 
                 1.141 
                 0.742 
                 0.748 
                 1.623 
               
               
                 40 
                 1.485 
                 1.227 
                 1.476 
                 1.118 
                 1.010 
                 2.159 
               
               
                 48 
                 2.074 
                 1.623 
                 1.909 
                 1.571 
                 1.360 
                 2.761 
               
               
                   
               
            
           
         
       
     
     In one embodiment a thread-in valve assembly is used (see  FIGS. 1A and 1B ), while in another embodiment a slip-in valve assembly can be used (see  FIGS. 2A and 2B ). Regardless of whether the thread-in valve assembly or the slip-in valve assembly is used, many of the components described herein can be used interchangeably with each version. The thread-in valve assembly and slip-in valve assembly can each be used for different purposes, for example the slip-in valve assembly can be used to allow for two-way flow. 
       FIG. 2A  shows a thread-in valve assembly, according to an embodiment. 
     A tubular poppet  0101  is integrally connecting to a threaded end  0102 . The threaded end  0102  and the tubular poppet  0101  have a hollow central region for fluid flow. The threaded end  0102  is configured for threaded engagement within a cooperating thread in a valve body. Alternatively, the tubular poppet  0101  can be engaged into the valve body through an interference fit or the like. A seal can be used adjacent the threaded end  0102 . 
     The tubular poppet  0101  has an expanded end that forms a conical seat  0105  for mating opposition to the control sleeve  0103 . The seat  0105  can also have a spherical or other geometry. The seat  0105  prevents any fluid inside the central region from escaping out the side opposite the side with the threaded end  102 , or vice versa thus in the closed position (shown) fluid can only enter/leave the valve assembly through the threaded end  0102 . Adjacent to the seat  0105  are radially oriented holes (not shown in  FIG. 2A ) that extend from the outer diameter of the tubular poppet  0101  to the inner diameter of the tubular poppet  0101 . The radially oriented holes can also be angled forward from inside to outside to improve flow characteristics. The outer diameter of the tubular poppet  0101  has limit rings (control sleeve limit ring  403 , first retainer collar limit ring  401 , and second retainer collar limit ring  402 ) to limit the movement of the control sleeve (and the retainer collar in the embodiment that uses the retainer collar, see  FIG. 3A ). 
     A control sleeve  0103  abuts to a spring  0104  which wraps around the tubular poppet  0101 . Oil grooves  0106  are present on the control sleeve  0103  that serve to center the control sleeve within its corresponding bore in the valve body. The control sleeve  0103  is configured to slide along the length of the tubular poppet  0101  between the seat and the limit ring  403  (see  FIG. 5B ). The spring  0104  is configured to naturally push the control sleeve  0103  closed (to the right in  FIG. 2A ). Fluid pressure coming from right to left (in  FIG. 2A ) pressing against a forward face  0107  of the control sleeve  0103  will urge the control sleeve  0103  to slide to the left towards the threaded end (when the pressure overcomes the force of the spring  0104  as well as any pressure induced force acting on face  108  of the control sleeve) and hence into an open position (not shown in  FIG. 2A ). In the threaded embodiment, the spring is sandwiched between the control sleeve and the bottom of a control cavity in the body that the tubular poppet is located in. If the tubular poppet is removed from the body, the spring can be removed from the poppet. 
     The control sleeve  0103  and the tubular poppet  0101  can be hardened for wear resistance. The control sleeve  0103  is annular. The inner diameter of the control sleeve  0103  is slightly greater than the outer diameter of the tubular poppet  0101  so that the control sleeve  0103  can move axially on the tubular poppet  0101 . The control sleeve  0103  has the forward face  0107 , and a control face  0108 . In the closed position, the internal diameter of forward face  0107  contacts a region of the tubular poppet  0101 , forming a metal to metal seal, in order to prevent the flow of high-pressure fluid into the central region of the tubular poppet  0101 . Note that when the control sleeve is in the closed position, the inner diameter of the control sleeve makes a tight seal with the seat  105 ,  205  of the poppet thereby obstructing the main channel of fluid flow from the central region through the holes and out past the control sleeve. The control sleeve  0103  can have a communication between forward face  0107  and control face  0108  (not pictured in  FIG. 2A ). At least a portion of this communication should be a passage to throttle the flow of fluid between the two faces. The inner diameter of the control face  0108  has a limit ring stop  631  which is formed for mating abutment against a corresponding control sleeve limit ring  0403  (see  FIG. 5B ). 
       FIG. 2B  shows a cross section of a body used to house a thread-in valve assembly, according to an embodiment. The channel (or cavity)  0130  in the body can be used to house the thread-in valve assembly illustrated in  FIG. 2A  or other variation. 
     Body threading  0131  can be used to screw the threaded end  0102  onto, thus the threaded end  0102  would always be pinned into the body and cannot move. Thus, when the valve assembly illustrated in  FIG. 2A  is inserted into the body shown in  FIG. 2B  (and the threaded end  0102  is screwed into the body threading  0131 ), the valve can operate as a check valve. Fluid would typically flow in the direction from right to left as illustrated in  FIG. 2B , but typically fluid would not be able to flow from left to right because there would be no mechanism to open the control sleeve this way. More details about how this operates are provided below. 
       FIG. 3A  shows a slip-in valve assembly, according to an embodiment. 
     The slip-in valve assembly is similar to the thread-in valve assembly but for the replacement of the threaded end  0102  with a retainer collar  0202 . In addition, the spring  0204  has a modified functionality than the thread-in valve due to the presence of the retainer collar  0202 . Thus, unlike the threaded end embodiment (in which the threaded end is always pinned in place), this embodiment uses the retainer collar  0202  which is capable of sliding. 
     The tubular poppet  0201  has an expanded end that forms a conical seat  0205  for mating opposition to a control sleeve  0203 . The seat  0205  can also have a spherical or other geometry. The seat  0205  prevents any fluid inside the central region from escaping out the end opposite the end with the retainer collar  0202 , thus in the closed position (shown) fluid can only enter/leave the valve assembly through the end with the retainer collar  0202 . Adjacent to the seat  0205  are radially oriented holes (not shown in  FIG. 3A ) that extend from the outer diameter of the tubular poppet  0201  to the inner diameter of the tubular poppet  0201 . The outer diameter of the tubular poppet  0201  has limit rings (control sleeve limit ring  403 , first retainer collar limit ring  401 , and second retainer collar limit ring  402 ) to limit the movement of the control sleeve (and the retainer collar in the embodiment that uses the retainer collar). 
     A control sleeve  0203  abuts a spring  0204  which wraps around the tubular poppet  0201 . Oil grooves  0206  are present on the control sleeve  0203  that serve to center the control sleeve within its corresponding bore in the valve body. The control sleeve  0203  is configured to slide along a length of the tubular poppet  0201 . 
     The tubular poppet  0201  has a sliding retaining collar  0202  on a first end of the tubular poppet  0201  that can slide along a portion of the outer body of the tubular poppet  0201 . Movement of the retainer collar is not necessary for proper valve operation, however it can be required for valve assembly. The retainer collar  202  should be moved a distance against the spring toward the poppet seat in order to install the first retainer collar limit ring  401  (see  FIG. 5B ). Whether or not the retainer collar actually moves along the poppet during use depends on the spring rate. To install the first retainer collar limit ring  401  requires that the retainer collar be pushed against the spring to expose the groove for first retainer collar limit ring  401 . After the ring is installed, the retainer collar can be released, and will rest opposed to first retainer collar limit ring  401  by being pushed by the spring. The first retainer collar limit ring is not visible, nor accessible, when in this position. Thus, the retainer collar should be moved out of the way. 
     The spring  0204  is interposed between the control sleeve  0203  and the retainer collar  0202  and is configured to naturally push the control sleeve  0203  closed (to the right in  FIG. 2A ) and also push the retainer collar  0202  to the end opposite the control sleeve  0203  (to the left in  FIG. 3A ). Any movement of the control sleeve  0203  and the retainer collar  0202  has to overcome the force of the spring  0204 . 
     Assuming the poppet is secured such that it cannot itself move in the left direction (in  FIG. 3A ), pressure coming from right to left (in  FIG. 3A ) pressing against a forward face  0207  of the control sleeve  0203  would urge the control sleeve  0203  to slide to the left (when the pressure overcomes the force of the spring  0204  and any force resulting from pressure applied to control face  0208 ) and hence into an open position (exposing the radial holes, not shown in  FIG. 3A ) while the position of the retainer collar cannot move further to the left (see  FIG. 10 ). When pressure is applied to the outward retainer face  0209  and to the inside diameter and left end (in  FIG. 3A ) of the tubular poppet (from left to right in  FIG. 3A ), the retainer collar  0202  (and hence the poppet) will be urged towards the control sleeve  0203  (to the right in  FIG. 2A ). In addition, pressure on the inside and end of the poppet will push the seat and thus the tubular poppet to the right direction which will also bring the retainer collar  0202  along in the right direction as well (since the first retainer collar limit ring  0401  will force the retainer collar  0202  to move along with the poppet) and compress the spring. Pressure acting from the left to right direction (in  FIG. 3A ) will also act on outward retainer face  209  urging it to the right (towards the control sleeve). Whether or not the retainer collar is “dragged” along by the tubular poppet is a function of the sum of the forces on the retainer (pressure forces and spring force). 
     Shown on the outside perimeter of the tubular poppet  0201  is control sleeve limit ring  0403  (prevents the control face  0208  of the control sleeve  0203  from moving too far along the tubular poppet  0201  past the control sleeve limit ring  0403 ). The second retainer collar limit ring  0402  prevents the retainer collar  0202  from moving further along the poppet past the second retainer collar limit ring  0402 ). First retainer collar limit ring  0401  is not shown in  FIG. 3A  because it is blocked by the retainer collar  0202 , but serves the purpose to prevent the retainer collar  0202  from sliding off the tubular poppet  0201 . 
     The control sleeve  0203  is annular. The inner diameter of the control sleeve  0203  is slightly greater than the outer diameter of the tubular poppet  0201  so that the control sleeve  0203  can move axially on the tubular poppet  0201 . The control sleeve  0203  has a forward face  0207 , and a control face  0208 . The internal diameter of forward face  0207  contacts the expanded region of the tubular poppet  0201  thereby forming a metal to metal circular sealing interface. There should be some clearance necessary between the inner diameter of the control sleeve and the outer diameter of the tubular poppet in order to allow them relative movement. This same clearance is also a leakage path. Although covering the holes  300  in the tubular poppet by the control sleeve will impede flow, the true sealing (flow obstruction) occurs between the circular edge of the inner diameter of the control sleeve where it contacts the sealing surface of the tubular poppet (the closed position). This contact between the forward face  0107 ,  0207  of the control sleeve and the seat  0105 ,  0205 , of the tubular poppet is completely sealed thereby preventing all fluid flow there between. The control sleeve  0203  can have a communication (passage) between forward face  0207  and control face  0208  (not pictured in  FIG. 3A ) to throttle the flow of fluid between the two faces. The inner diameter of the control face  0208  has a limit ring stop  0631  which is actually recessed from control face  0208  which is formed for mating abutment against a corresponding control sleeve limit ring  0403 . 
     Note in some embodiments there can be leakage between the outer diameter of the poppet  0201  and the inner diameter of the control sleeve  0203 . This is because in order to allow for there to be room for the control sleeve  0203  to slide along the poppet  0201 , there must be a slight space there between. This type of space is a “leakage path” and it is possible that (without the user of a poppet seal  820 ) a relative small volume of fluid can pass between one end of the control sleeve  0203  between the retainer collar and the poppet  0201  through this leakage path and out the other end of the control sleeve  0203 . However, the amount of fluid that can navigate this leakage path is relatively miniscule (and at very low pressure) as there is only a tiny space between the control sleeve  0203  and the poppet  0201 . An optional poppet seal  820  can be used to completely block this leakage path, see  FIG. 9 . Any leakage path is a restrained path because the space the fluid has to flow through is so slight compared with the main flow path (this will be discussed below in more detail). 
       FIG. 3B  shows a cross section of a body used to house a slip-in valve assembly, according to an embodiment. The channel (or cavity)  0230  in the body can be used to house the slip-in valve assembly illustrated in  FIG. 3A  or other variation. 
     Note that when the poppet is placed (housed) in the body, they are both configured such that the poppet has room in the body to slide through the control sleeve (in the right direction in  FIGS. 2A, 2B ) (thereby moving the seat rightward and away from contact on the inner diameter of forward face  0207  of the control sleeve) when the spring is compressed (see  FIG. 12 ) but the poppet cannot move in the left direction (in  FIGS. 2A, 2B ) relative to the retainer collar (see  FIG. 10 ). 
     Note that all parts shown in  FIGS. 1A and 1B  and all other figures (including but not limited to the tubular poppet  0101 , 0201 , retainer collar  0103 ,  0203 , oil grooves  0106 ,  0206 , seat  0105 ,  0205 , control face  0108 ,  0208 , forward face  0107 ,  0207 ) can be identical with the same function and can be used interchangeably herein. In fact all parts shown or described for the slip-in assembly can be used for the thread-in assembly (and vice-versa) without limitation, but for the threaded end  0102  (which is used for the thread-in assembly) and the retainer collar  0202  (which is used for the slip-in assembly) which are the main differences between the two versions. All features described herein can be used with any type of assembly (threaded, slip-in, or any other). 
       FIG. 4  shows a tubular poppet for use with a thread-in assembly, according to an embodiment. 
     The threaded end  102  is formed on the tubular poppet  0101  which has radial holes  0300  at an end of the tubular poppet  0101  closest to the seat  0105 . Note that there can be any number of holes (one or more) in any shape or configuration and are also referred to herein as a “hole set.” When the control sleeve (not pictured in  FIG. 4 ) is in the closed position (all the way to the right in  FIG. 4 ), the radial holes  0300  are covered by the control sleeve and thus fluid cannot flow through the radial holes  0300  because of a fluid-tight seal between the forward face  107 ,  207  of the control sleeve and the seat of the poppet (in which outward force from the spring helps form and maintain this seal). When the control sleeve is in the open position (wherein at least some of the radial holes  0300  are exposed) then fluid can flow through the radial holes  0300  and out of the entire assembly. Second poppet seal groove  0309  is used in the embodiment where a second poppet seal  0820  is used in order to hold the second poppet seal  0820 . In the embodiment where the second poppet seal  0820  is not used, then instead of the second poppet seal groove  0309  there can be poppet oil groove  0419  (see  FIG. 5B ). 
       FIG. 5A  shows a slip-in tubular poppet without a control sleeve, retainer collar, or a spring, according to an embodiment. 
     Retainer collar (not shown in  FIG. 5A ) would slidably attach to tubular poppet  0201  which has radial holes  0300  at an end of the tubular poppet closet to the seat  0205 . When the control sleeve (not shown in  FIG. 5A ) is in the closed position (all the way to the right in  FIG. 5A ), the radial holes  0300  are covered by the control sleeve and thus fluid cannot flow through the radial holes  0300  because of the tight seal between the control sleeve and the poppet which prevents fluid from flowing there between. Leakage from the control chamber into the hole set, and vice versa, may be prevented by seal  820  (not shown in  FIG. 5A ). When the control sleeve is in the open position (wherein at least some of the radial holes  0300  are exposed and the seal is broken) then fluid can continue to flow through the radial holes  0300  (in either direction) and continue flowing. Second poppet seal groove  0409  is used in the embodiment where a second poppet seal  0820  is used in order to hold the second poppet seal  0820 . In the embodiment where the second poppet seal  0820  is not used, then instead of the second poppet seal groove  0409  there can be poppet oil groove  0419  (see  FIG. 5B ). 
       FIG. 5B  shows a cross section of a tubular poppet, according to an embodiment. Note that this is a cross section (like most figures herein) and the parts shown all “wrap around” in a circular fashion. Thus, for example a first poppet seal  0400  is actually circular (e.g., a ring). The first retainer collar limit ring  0401 , the second retainer collar limit ring  0402 , and the control sleeve limit ring  0403  are also all rings. A central region  0405  is used for flow of fluid. 
     The first poppet seal  0400  abuts the retainer collar and is used to seal a control chamber (not shown in  FIG. 5B ) from fluid entering between the inner diameter of the retainer collar and the outer diameter of the poppet and can be made out of rubber, silicone, or any other material that can be used as a sealant. 
     A first retainer collar limit ring  0401  is used to stop a retainer collar (not shown in  FIG. 6 ) from sliding (in the left direction in  FIG. 6 ) past the first retainer collar limit ring  0401 . A second retainer collar limit ring  0402  is used to stop a retainer collar from sliding (in the right direction in  FIG. 6 ) past the second retainer collar limit ring  0402  (a retainer collar stopping point). A control sleeve limit ring  0403  is used to stop a control sleeve (not shown in  FIG. 6 ) from sliding past the control sleeve limit ring  0403  (in the left direction in  FIG. 6 ). The control sleeve would be stopped from sliding (in the right direction in  FIG. 6 ) by the seat. Also shown is poppet oil groove  0419 . 
       FIG. 5C  shows a cross section of a tubular poppet showing radial holes at an angle, according to an embodiment. 
     Two radial holes  0420  are shown. Also shown on the bottom are the nose and the view of the cross section shown. 
       FIG. 6  shows a slip-in tubular poppet without a retainer collar or a control sleeve with a cone-shaped nose, according to an embodiment. 
     A cone-shaped nose  0530  has radii  0531 . This construction can be preferable from a fluid dynamics perspective. 
       FIG. 7A  shows a top view of the control sleeve, according to an embodiment. 
     Forward face  0600  of the control sleeve (same as control sleeve  0103 ,  0203 ) is typically positioned on the tubular poppet facing the seat (opposite the threaded end or the retainer collar) and contains a passage  0606 . The passage  0606  extends between the two faces of the control sleeve (the forward face  0600  and the control face  0602 ) and allows fluid to flow there between (in either direction). 
       FIG. 7B  shows a side view of the control sleeve, according to an embodiment. 
     Forward face  0600  (same as  0107 ,  0207 ) is opposite control face  0602  (same as  0108 ,  0208 ). Oil grooves  610  are the same as oil grooves  0106 ,  0206 . 
       FIG. 7C  shows a cross section of the control sleeve, according to an embodiment. 
     Cross section diagram  620  shows the actual cross section of the control sleeve illustrated in  FIG. 7C . The passage  0606  comprises an aperture  0601 , an orifice  0604 , and an expanded area  0605 . The aperture  0601  allows fluid to flow in from the forward face  0600  and allows fluid to flow through the aperture  0601  to the orifice  0604 . The orifice  0604  can have a reduced diameter (in comparison to the diameter of the aperture  0601 ) in order to throttle the flow of fluid. The orifice  0604  connects to the conical opening  0605  which is an expanded area with a chamfered conical opening which can prevent the spring  0104  from obstructing flow out of the orifice  0604 . Thus fluid can flow from the forward face  0600  through the aperture  0601  through the orifice  0604  and out the conical opening  0605 , or it can flow in the reverse direction as well. While  FIG. 7C  illustrates the aperture  0601  having a constant diameter, this is not required and the aperture  0601  can have a varying diameter. Control sleeve opening  0603  is an opening which fits onto the tubular poppet. It is noted that the passage  0606  can take many forms and the orifice  0604  and/or the conical opening  0605  can be optional, as long as fluid is enabled to flow through the passage  0606  from one side of the control sleeve to the other. Control sleeve opening  0603  is an opening which fits onto the tubular poppet. 
     Aperture  601  is part of the passage  0606  which runs throughout the entire control sleeve so that fluid can flow in one side and out the other (typically in the aperture  0601  on the forward face  0600  and out the conical opening  605  in the control face  0602  into the control chamber, although fluid can flow in the reverse direction as well). The passage  0606  is open at both sides so that fluid can travel through the control sleeve in either direction. 
     It is noted that the passage  0606  in the control sleeve can be optional, and any embodiment described herein can have the passage  0606  or not have one (which means where the passage  0606  is illustrated would be solid so as not to allow flow therein). 
     Limit ring stop  0631  cooperates with the control sleeve limit ring  0403  to stop the control sleeve from sliding further along the tubular poppet in the direction opposite the seat. Control sleeve opening  0603  is an opening with a slightly larger diameter than the outer diameter of the tubular poppet so it can fit over the tubular poppet and slide as described herein. 
     While the drawing in  FIG. 7C  is a cross section and “wraps around” the circular control sleeve, note that the passage  0606  (comprising the aperture  0601 , orifice  0604 , and conical opening  0605 ) does not “wrap around” and exists as a hole going through the control sleeve (as illustrated in  FIG. 7A ). 
     The diameter of the conical opening  0605  on control face  0602  should preferably be greater than the wire size of the spring  0104  so that the spring  0104  does not block flow through the orifice. A chamfer can be used to accomplish this. 
       FIG. 8A  shows a side view of a retainer collar, according to an embodiment. 
     Retainer collar  0700  (same as retainer collar  0202 ) has forward face  0209  which faces away from the control sleeve (thus fluid flowing against the retainer collar  0700  coming from outside of the body but not from the central region would exert pressure against the forward face  0209 ). Retainer collar seal  0707  is used to seal the control chamber so that fluid does not leak in and out of the control chamber between the outer diameter of the retainer collar  700  and the inner diameter of the corresponding bore in the valve body (cavity). All seals used herein can be made of a material such as rubber, silicone, etc. and are used to seal potential leakage paths. 
       FIG. 8B  shows a top view of the retainer collar, according to an embodiment. 
     Retainer opening  0706  is a hollow section inside the retainer collar  0700  adapted to fit over the tubular poppet so the retainer collar  0700  can slide along a portion of the length of the tubular poppet. 
       FIG. 8C  shows a cross section of the retainer collar, according to an embodiment. A first limit ring stop  0709  cooperates with the first retainer collar limit ring  0401  (see  FIG. 6 ) to prevent the retainer collar  0700  from sliding off the tubular poppet. A second limit ring stop  0708  cooperates with the second retainer collar limit ring  0402  (see  FIG. 5B ) to prevent the retainer collar  0700  from sliding too far along the tubular poppet towards the control sleeve. The retainer opening  0706  is an opening with a diameter slightly larger than the outer diameter of the tubular poppet so that the retainer collar  0700  can fit onto the tubular poppet and slide. 
       FIG. 9  shows a cross section of the tubular poppet with the retainer collar and the control sleeve, according to an embodiment. 
     The retainer collar  202 , control sleeve  203  and spring  204  (and other parts such as the radial holes, etc.) as described herein are shown. Note how the first limit ring stop  0709  (see  FIG. 8 ) cooperates with the first retainer collar limit ring  0401  (see  FIG. 5B ) to prevent the retainer collar  0700  from sliding off the tubular poppet. A second limit ring stop  0708  (see  FIG. 8 ) cooperates with the second retainer collar limit ring  0402  (see  FIG. 5B ) to prevent the retainer collar  0700  from sliding too far along the tubular poppet towards the control sleeve. Limit ring stop  0631  cooperates with the control sleeve limit ring  0403  to stop the control sleeve from sliding further along the tubular poppet in the direction opposite the seat. 
     Note that the control sleeve  0203  is currently in the closed position and thereby the radial holes are covered by the control sleeve  0203  and sealed by interaction between the control sleeve  0203  and the seat of the poppet. When the control sleeve  0203  slides into the open position (to the left in  FIG. 9 ) from the closed (sealed) position, the inner diameter of the control sleeve comes off of the seat on the poppet, and the radial holes are exposed (in their entirety or at least a portion) and the seal is opened/broken permitting fluid to flow from the side of the forward face through the central region  0803  of the poppet and out a tubular poppet opening  0804  wherein the fluid would then flow through the body onto the next part of a hydraulic circuit. 
     Without any pressure against the forward face  0107 , the spring  0204  naturally urges the control sleeve  0203  into the closed position. The spring  0204  will also naturally urge the retainer collar  0202  in a direction opposite the control sleeve. 
     The dashed line  0801  shows the diameter of the channel in the body that the valve assembly is inserted into (see  FIG. 1A , channel  0002  which is also labeled as dia ‘B’ in  FIG. 1A ). A control chamber  0802  is a hollow volume that surrounds the tubular poppet. In other words, the control chamber  0802  exists in the region between the tubular poppet and the channel (which would have a toroid with a square cross section shape). The control chamber  0802  is a volume which is sealed on one end by the retainer collar (including retainer collar seal  707 ) and is closed on the other end by the control sleeve. Aside from potential leakage between the outer diameter of the control sleeve and the inner diameter of the valve body bore, the only path for fluid in/out of the control chamber (not including any pilot paths which are not shown in  FIG. 9 ) is the passage (which comprises the aperture  0601 , orifice  0604 , and conical opening  0605 ). Note that there is a potential leakage path between the outer diameter of the control sleeve and the inner diameter of the valve body bore when the control sleeve does not have an outside diameter seal like the retainer collar. Note that in an embodiment control sleeve seals  1601  can be used on the control sleeve to prevent this leakage (see  FIG. 17 ). In any embodiment described herein, seals on the control sleeve may or may not be used. 
     The purpose of the control chamber is to receive pressure that is against the forward face  0107  by receiving the pressurized fluid through the passage  0606 . The pressure inside the control chamber when the valve is in the closed position should approximately equal the pressure exerted onto the forward face  0107  therefore making it difficult if not impossible for the control sleeve to open (without any other external forces). Therefore, the fluid in the control chamber can be used in numerous ways depending on the function of the cartridge. For example, a pressure relief pilot valve can be connected to the control chamber so that only when the pressure inside the control chamber exceeds a certain amount, the control chamber would be drained thereby lowering the pressure in the control chamber thus permitting the control sleeve to slide to the open position. Or the control chamber can be connected to an externally piloted valve so that upon a signal the externally piloted valve can open (or close) thus draining the control chamber and causing the control sleeve to open. 
     Second poppet seal  0820  (which is actually a ring like the other seals) can be used to seal any leakage between the outer diameter of the poppet and the inner diameter of the control sleeve  0203 . If the second poppet seal  820  is not used then the poppet would not have the second poppet seal groove  0409  (see  FIG. 5A ) but instead would have the poppet oil groove  0419  (see  FIG. 5B ). Any of the seals described herein can be used or omitted in any embodiment described herein in any combination. Seals are typically used to control leakage paths, and may be desirable (will prevent leakage) or less desirable (can cause more friction and wear) based on the valve function. 
       FIG. 10  shows a cross section of a slip-in valve assembly inside a body with forward flow, according to an embodiment. 
     In  FIG. 10 , the fluid flows from right to left in the forward direction (from face 0 to face 1). In this example, the fluid enters the tubular poppet from an outside of the tubular poppet  900  (near the control sleeve end), flows through the hole set, through the central region, and exits out the end of the tubular poppet opposite the control sleeve (at face 1). The fluid exerts enough pressure onto the forward face which overcomes the resistance of the spring and pushes the control sleeve into the open position, thereby exposing the radial holes. Note that the retainer collar does not move even though the control sleeve is pushed open. The fluid then freely flows into the radial holes and through the central region of the tubular poppet and out the tubular poppet opening. Thus, the opening of the control sleeve creates an unrestrained main channel of fluid flow between the central region and an outside of the poppet through the hole set. This is considered an unrestrained main channel because there is a relatively good amount of clearance for the fluid to freely flow as intended so the fluid can effectuate its purpose in the hydraulic circuit. Note that there are a number of potential leakage paths in the valve assembly. All potential leakage paths can be sealed by using optional seals. In some embodiments, no seals (or some but not all) are used thereby enabling fluid to flow through available leakage paths. For example, leakage paths can potentially exist: i) between the inner diameter of the retainer collar and the outer diameter of the poppet; ii) between the outer diameter of the retainer collar and the inner diameter of the bore in the body used to house the valve assembly; iii) between the inner diameter of the control sleeve and the outer diameter of the poppet; iv) between the outer diameter of the control sleeve and the inner diameter of the bore in the body used to house the valve assembly. Note that all such leakage paths are restrained. That is, the clearance between the two adjacent parts in any leakage path is extremely slight and does not allow for significant fluid flow there between when compared with the main flow path of the valve. 
       FIG. 11  shows a cross section of a slip-in valve assembly inside a body in a neutral position, according to an embodiment. The control sleeve is in the closed position. 
     Either no fluid enters from the control sleeve end or fluid does enter from the control sleeve end (from face 0 flowing towards face 1) but not with enough pressure to open the control sleeve (e.g., the closing force of the spring is greater than the fluid pressure on the forward face). In either case, the control sleeve remains in the closed position and the retainer collar also does not move (stays in its position at the end of the tubular poppet opposite the control sleeve). This is the neutral position. 
     Also shown in  FIG. 11  (and other figures) is end cap  1000 . The end cap  1000  is the plate of steel or other suitable material that mates with the valve body and is retained by screws. It holds the slip-in assembly within its cavity in the valve body. There is a face sealing O-ring  1001  around the perimeter of a bore in the valve body that contacts an opposing face of the end cap to prevent leakage. An O-ring groove  1002  is a groove where the O-ring is located. Annular space  1003  is an annular space defined on the outer diameter by the end cap and the inner diameter by that portion of the poppet that extends beyond the outward face of the limit collar (also referred to as retainer collar). 
       FIG. 12  shows a cross section of a slip-in valve assembly inside a body with reverse flow, according to an embodiment. 
     The slip-in valve assembly can also be configured for reverse flow (from left to right in  FIG. 12 ) as well. This would operate as follows. Fluid would enter into the tubular poppet opening (the end opposite the control sleeve or from face 1). The central region would initially fill with the fluid but because it would not initially be able to exit out face 0 because the radial holes would initially be blocked by the control sleeve, particularly the metal-to-metal seal formed by the ID of the control sleeve against the poppet seat. The fluid would exert pressure on the inside diameter and left face of the tubular poppet and on retainer face  0209  which would push the entire tubular poppet towards face 0 (the poppet and retainer collar can move together as a unit). Note that the control sleeve might shift in position a little in the direction of face 0 (to the right in  FIG. 12 ). A shoulder  1100  prevents the control sleeve from continuing to move towards face 0. As the fluid pressure forces the seat of the tubular poppet to move to the right (towards face 0 in the “reverse” direction), the retainer collar will also move along with the seat/tubular poppet towards face 0 (or to the right in  FIG. 12 ). This compresses the spring as shown in  FIG. 12 . The radial holes (also referred to as hole set) in the tubular poppet are now exposed and even though it is the tubular poppet, not the control sleeve that has moved relative to the valve body, this is still considered the “open position” of the control sleeve. 
     Once the control sleeve is open, then the fluid inside the central region can exit the central region through the radial holes and out of the cartridge in a same (reverse) direction (from left to right in  FIG. 12  or from face 1 to face 0). Thus, in this configuration, the fluid is able to flow in the reverse direction (the “forward” or “normal” direction being from face 0 to face 1 in  FIG. 12 ). 
       FIG. 13A  is an orthographic view illustrating a front view of a slip-in valve assembly in a closed position, according to an embodiment. 
     A notch  1200  is shown on an end of the valve assembly near the control sleeve  203 . The notch  1200  is merely a slight recess with no ability for fluid or anything to pass through and serves no purpose other than allowing processing (grinding) operations of the poppet. Also shown are the aperture  0601 , retainer collar  0202 , and first poppet seal  0400 . 
       FIG. 13B  is an orthographic view illustrating a front view of a slip-in valve assembly in assembly in open position, according to an embodiment. 
     Radial holes  0300  (also referred to as a hole set) are exposed in the open position. Also shown is the seat  0205 . 
       FIG. 13C  is an orthographic view illustrating the tubular poppet opening of a slip-in valve assembly, according to an embodiment. 
     Tubular poppet opening  0804  is a hollow area which allows fluid to fill a central region inside the valve assembly. 
       FIG. 13D  is an orthographic side view illustrating a slip-in valve assembly, according to an embodiment. The tapered end of the seat  0205  is shown. The seat can be shaped as a toroid with a rectangular trapezoidal cross section (as shown), and the control sleeve in the closed position abuts a tapered part of the region, thereby forming a fluid-tight (and air-tight) seal thereby preventing flow of fluid through/out the control sleeve. When the control sleeve is in the closed position, any fluid inside the central region would typically have no passage out of the valve assembly except through the tubular poppet opening  0804 . 
       FIG. 14A  is an orthographic view illustrating a front of a body and control module, according to an embodiment. 
     Body  0001  houses the valve assembly which is placed in the channel (also referred to as cavity)  230  in the body  0001 . A control module  0010  as affixed to the body  0001  and can be configured as described herein to configure the valve assembly for different operations. 
       FIG. 14B  is an orthographic view illustrating a back of a body and control module, according to an embodiment. 
     As known in the art, multiple bodies can be bolted together in an enclosed hydraulic circuit (which would also typically include a pump and a reservoir) which can be utilized in any manner (e.g., drive machinery, etc.) 
       FIG. 15  is a cross section showing a thread-in assembly installed within a valve body, according to an embodiment. The control chamber  0802  stores fluid in between the outer diameter of the tubular poppet and the diameter of the channel in the body  1400  which houses the valve assembly. If there is no passage in the control sleeve (as illustrated in  FIG. 15 ) then the control chamber  802  should typically be initially empty since there would be no way for fluid to enter/exit the control chamber  802  in this example (except for the potential for leakage around a small annular clearance around the outer diameter of the control sleeve as discussed above). 
     The assembly in  FIG. 15  can allow fluid flow from face 0 to face 1 but not from face 1 to face 0. Flow from face 1 to face 0 would not urge the spring to open the control sleeve, while flow from face 0 to face 1 would put pressure on the forward face and thus urge the control sleeve open breaking the seal between the control sleeve and the seat of the poppet thereby allowing fluid to flow from outside the poppet through the hole set and hence through the poppet. Note that if fluid attempts to flow from face 1 to face 0 the fluid would pass up the drain path  1401  in the control module  1402 ) and into the control chamber  0802  which would provide more force to urge the control sleeve closed (to the right in  FIG. 15 ). 
       FIG. 16  is a cross section showing the alternate slip in assembly (with the retainer collar) installed within a valve body, according to an embodiment. 
     The control chamber  0802  stores fluid in between the outer diameter of the tubular poppet and the diameter of the channel in the body  1500  which houses the valve assembly. If there is no passage  0606  in the control sleeve (as shown in  FIG. 16 ) and seals are used on the control sleeve (no seals are used on the control sleeve in  FIG. 16 ) then the control chamber  802  should typically be empty since there would be no way for fluid to enter/exit the control chamber  802  in this example. If there is no passage in the control sleeve and seals are not used on the control sleeve (as illustrated in  FIG. 16 ) then the control chamber  802  may eventually fill due to the slight leakage path between the outer diameter of the control sleeve and the inner diameter of the valve body bore). In order for the valve to operate as shown in  FIG. 16 , any air or fluid in the control chamber would need to be compressed in order to allow the control sleeve to open, unless the air or fluid is somehow allowed to exit the chamber. The only way this may happen as shown in  FIG. 16  is for the air or fluid to follow the leakage path around the outer diameter of the control sleeve. In the other embodiments shown with a drain, once the valve has been opened to flow, and then closes, the chamber will then at least partially fill with fluid. The action of the control sleeve closing will result in the control chamber drawing a partial vacuum. Fluid will be drawn into the control chamber from the region of face 1 through the drain. The chamber may initially be empty, but will at least partially fill after the first cycle. The embodiment shown in  FIG. 16  is not, from a practical perspective, an ideal embodiment. 
     The slip in assembly illustrated in  FIG. 16  can also be used with the control module configured as illustrated in  FIG. 15  (with the drain path as illustrated). 
       FIG. 17  is a cross section illustration an example of a check valve configuration according to an embodiment. This is a simple embodiment of the inventive concept. No pilot or passage in the control sleeve is used in this embodiment. Note that the cross section illustrated is shown in the legend in  FIG. 17  (in fact all cross sections illustrated herein can be based on the same legend).  FIG. 17  illustrates a closed valve (closed control sleeve). Flow is allowed from face 0 to face 1 but prevented from face 1 to face 0. 
       FIG. 17  is similar to the configuration in  FIG. 15 , but note that in  FIG. 17 , the control sleeve has two control sleeve seals  1601  (although other numbers of control sleeve seals can be used from 1 to 4). Not using control sleeve seals  1601  may be adequate at lower system pressures, but it may not be ideal for use with higher system pressures due to the leakage around the control sleeve. Control sleeve seals  1601  are located around the outer diameter of the control sleeve to eliminate any flow from the control cavity outward to face 0 (and vice versa). This can occur because there is a slight clearance between the outer diameter of the control sleeve and the inner diameter of the bore used to house the assembly in order to provide room for the control sleeve to slide. The control sleeve seals  1601  can be made of any sealing material (e.g., rubber, silicone, etc.) and prevent fluid from passing through the clearance between the control sleeve and the bore of the body. Thus, in  FIG. 17 , by virtue of the control sleeve seals  1601 , the control chamber  0802  should be empty unless there is any reverse flow.  FIGS. 17 and 18  also illustrate control sleeve seals on the control collar. 
     Note that in any embodiment described or illustrated herein, control sleeve seals  1601  (and in fact any of the seals described herein such as the first poppet seal  400 , second poppet seal  820 , the retainer collar seal  0707 ) may or may not be used at the user&#39;s option. For example, any embodiment described or illustrated herein that uses control sleeve seals (or other type of seal) can also be implemented without control sleeve seals. Any embodiment described or illustrated herein that does not use control sleeve seal(s) (or other type of seal) can also be implemented using one or more control sleeve seal. Any seals described herein can also be used in any combination. For some embodiments of the invention, particularly where the control sleeve is provided with a passage  0606 , and the valve response time must be relatively fast to modulate pressure, the control sleeve seals shown in  FIG. 17  may not be advantageous due to issues of stiction, longer response time, and possible premature seal wear. 
     In a further embodiment, a control module orifice  1600  may be added to the control module to slow the response time of the valve opening and closing. This may be advantageous in certain applications, particularly where valve chatter is a problem. The control module orifice  1600  is entirely optional and may or may not be used in any embodiment described or depicted herein as per the user&#39;s preferences. 
     In this embodiment, the poppet is threaded into the flanged body. Pressure coming from the side opposite the threaded end (the right side in  FIG. 17 ) acts on the forward face  0107  of the control sleeve, which urges the control sleeve open. This is opposed by the spring force acting in the opposite direction. The control sleeve opens when the force urging the control sleeve open (pressure on the forward face  0107  multiplied by the area of the forward face  107 ) is greater than the spring force. This is the valve cracking pressure. Selecting various spring attributes such as K factor and spring compression in the closed state may vary the cracking pressure.  FIG. 18  is an illustration of this embodiment after the control sleeve opens. 
       FIG. 18  is a cross section illustration of the check valve configuration in an open position, according to an embodiment. 
     After the pressure urges the control sleeve open from  FIG. 17 , the control sleeve will be open as illustrated in  FIG. 18 . The fluid can now flow from the control sleeve side to the threaded side (from right to left in  FIG. 18 ). The fluid comes from the right side, enters the radial holes (which were blocked in  FIG. 17  when the control sleeve is in the closed position), travels through the central region inside the poppet and out through the threaded end. When the pressure on the forward face is not great enough to continue to maintain the control sleeve in the open position (e.g., the spring force becomes greater than the force on the control sleeve (pressure on the forward face  0107  multiplied by the area of the forward face  107 ), then the spring will force the control sleeve back into the closed position again and stop further fluid flow through the poppet. 
     Reverse flow is prevented. The spring naturally urges the control sleeve closed, and thus fluid entering through the threaded end would not escape through the radial holes since the control sleeve would be closed. Reverse flow fluid could also enter the drain  1700  and into the control chamber, further serving to urge the control sleeve in the closed position. 
     Thus, when pressure on the line is greater than a particular amount, the valve will open and thus provide pressure relief to the line. If the K factor of the spring is small enough to allow easy opening of the control sleeve, then this valve assembly would operate as a simple check valve permitting flow in only one direction. Note that the control chamber would typically be empty in this embodiment, unless there is reverse flow from the threaded end which would fill the control chamber via drain  1700  but the fluid would not pass through the control sleeve (and hence would not exit the check valve except for a small amount of leakage through the annular clearance around the outer diameter of the control sleeve) but would provide additional resistance to the control sleeve opening. When there is forward flow, the forward flow would open the control sleeve and release some of the fluid in the control chamber through the drain  1700 . This embodiment could also function as a direct operating relief valve or direct operating sequence valve, by selecting a spring appropriate for the application. 
     In the simplest embodiment, the control module merely serves to vent the control chamber to allow movement of the control sleeve. Note that the control module may be either internally drained such as internal drain  1700 , or externally drained (the drainage path would be independent of the discharge flow path of the valve as in  FIG. 19 ). 
       FIG. 19  is a cross section illustration of the check valve configuration with an external drain, according to an embodiment. 
     Backpressure on the valve may affect the valve cracking pressure. Backpressure on the valve will affect the fluid pressure in the control chamber. This will tend to assist the spring force in urging the control sleeve closed (control chamber pressure multiplied by control sleeve area  2 ). In those circumstances where this is not desirable, then external drainage of the control module is preferred using an external drain  1801  which leads to a fluid reservoir  1800 . 
     Reverse flow through the valve (flow from face 1 to face 0) is prevented by the seat at the control sleeve/poppet interface. Flow from face 1 to face 0 would be induced by a pressure gradient higher at face 1, and lower at face 0. The net forces on the control sleeve in this instance will urge the control sleeve closed and prevent flow from face 1 to face 0). 
     As the sleeve is guided over the poppet, this design has advantages over unguided disc or ball type check valves in applications where turbulence induced premature wear may be a concern. 
     The control module can be changed to affect the operation of the valve. For example, instead of a simple direct operating check valve as noted above, the control module may be enhanced to make the valve a pilot to open a check valve. 
       FIG. 20  is a cross section illustration of a valve assembly with an external pilot signal, according to an embodiment. 
     In this example, a normally closed pilot valve  1900  is in a control module  1901  and replaces the simple drain in the control module as described above. This pilot valve  1900  allows flow from the threaded end to the control chamber, but prevents flow from the control chamber to the drain unless the pilot valve  1900  is acted upon by a pilot signal. In this example, an external pilot signal  1902  is used to open the pilot valve  1900 , and permit the control chamber to drain. The control sleeve may then open providing that the inlet pressure at face 0 acting on the forward face of the control sleeve exceeds the spring force. If the control chamber is full of fluid, then the valve would not allow flow in either direction until the signal is received to open the pilot valve  1900  in which flow is then enabled from face 0 to face 1. 
     Any pilot valve used and the main valve (the valve assembly that enables or disables flow from face 0 to face 1 via opening/closing the control sleeve) interact in a master-slave relationship. Thus, the pilot valve can be altered to result in any number of functions for the main valve element. 
       FIG. 21  is a cross section illustration of a valve assembly with an internal pilot signal, according to an embodiment. This configuration can be used as a pressure relief valve. 
     This is the same valve assembly (main valve) from  FIG. 20  but controlled with a direct operating pilot relief valve  2000  (which opens only when its incoming pressure is greater than a preset pressure otherwise it remains closed) in the control module. In this example, the control sleeve is provided with a communication between the fluid entering from face 0 and the control chamber (e.g., from the forward face  2002  to the control face  2003 ), which is passage  0606  (which can comprise an aperture, orifice, and conical area) which provides a controlled leakage between the upstream control face and the control chamber. In some embodiments, this can enable piloted versions of the valve assembly to operate based on a pressure in the control chamber. 
     Pressurized fluid coming from face 0 onto the forward face  2002  will urge the control sleeve to open as described above. Due to the flow of fluid through the passage  0606  across the control sleeve, pressurized fluid will fill the control chamber. This will act on the control face  2003 , tending to urge it closed. The spring force will also tend to urge the control sleeve closed. Thus, absent another exit path for the fluid from the control chamber, the control sleeve will typically remain closed regardless of how much pressure is exerted on the control face from face 0 (coming from right to left). 
     Fluid is prevented from exiting the control chamber due to the direct acting pilot relief valve  2000  in the control module, which is blocking the path from the control chamber to the drain. Fluid can travel up pilot path  2004  and stops at relief face  2005  of the relief valve  2000 . 
     When the pressure at relief face  2005  of the pilot relief valve  2000 , and thus the pressure in the control chamber, exceeds the setting of the pilot relief valve  2000 , the pilot relief valve  2000  will open, allowing the fluid in the control chamber to drain (through the pilot relief valve  2000  and into the drain exit  2006 ). As there is an orifice in the passage  0606  in the control sleeve, fluid is drained from the control chamber faster than it can be replenished. The hydraulic forces on the control sleeve will become unbalanced and tend to urge the control sleeve open. The valve will open when the net hydraulic force on the control sleeve exceeds the spring force. The control sleeve will attempt to maintain a steady state position such that the pressure drop across the control sleeve, resulting in a net hydraulic force on the control sleeve, balances the spring force on the control sleeve. 
     This type of valve is said to be internally piloted. The pilot relieve valve  2000  receives its pilot signal from the same source as the main pressure source acting upstream on the valve. 
       FIG. 22  is a cross section illustrating an internally piloted, internally drained relief valve with the reverse flow option, according to an embodiment. 
     The valve assembly shown in  FIG. 22  is similar to the valve assembly shown in  FIG. 20  but for instead of the threaded end, the retainer collar is used (as described herein). This would accommodate reverse flow, as described herein. 
       FIG. 23  is a cross section illustration of a valve assembly with a remote control, according to an embodiment 
     In this example, the remote control  2201  is connected to a fluid tank  2204  and can adjust the pressure setting below the maximum pressure setting of the pilot valve  2200  in the control module. This configuration can also be used with the retainer collar embodiment as well. 
     In an embodiment, a remote control can be used where the state of the remote control (set by an operator) is infinitely variable between fully open and fully closed, rather than having discrete positions. This type of valve can be controlled with a proportional electrical signal or the like. Thus, the pilot valve controlled by the remote control is not limited to discrete open and closed position but also is capable of having continuous degrees of open/close based on the signal. Thus the rate of flow through the pilot valve can be controlled by the remote control (in addition to just on/off). 
       FIG. 24  is a cross section illustration of a valve assembly with an external pilot  2300  connected to a 2-position, 2-way valve  2302  configured as a vented relief valve with a fluid tank  2204 , according to an embodiment. 
     When the 2-way valve  2302  is closed (as shown) the pilot valve  2300  behaves as an internally piloted valve (will open automatically when the pressure inside the control chamber  0802  reaches a certain level). When a signal is sent to the solenoid of the 2-way valve  2302  causing it to shift (the second control envelop with an arrow), the control chamber is vented to the tank  2204  at very low pressure, removing the hydraulic resistance on the control face of the control sleeve, and allowing it to shift. 
     This configuration can also be used with the retainer collar embodiment as well. 
     Different valve elements in the control module can make the main valve behave in a number of ways. For example, the main valve can be made to perform as a counterbalance valve, pressure reducing valve, sequence valve, unloading valve, etc. The valve and body may be configured in other ways to provide still more functions. 
       FIG. 25A  is a cross section illustration illustrating a slip-in insert and valve body configured to provide flow control function, according to an embodiment. 
     In this embodiment, the passage in the control sleeve is replaced with a poppet orifice (not shown in  FIG. 25A  but see  FIG. 25B ) in the body of the tubular poppet. By selecting a pilot valve in the control module to maintain a constant pressure drop across the orifice in the poppet, the main valve can be made to provide a constant rate of flow. 
       FIG. 25B  is a cross section illustration of a valve assembly with a tubular poppet configured to provide flow control function, according to an embodiment. 
     A poppet aperture  2411  is in communication with a poppet orifice and opening  2410  permitting flow between the central region  0405  inside the tubular poppet and the control chamber  0802 .  FIG. 25B  is illustrated as a cross section and note that this poppet aperture  2411  and poppet orifice  2410  and opening do not exist as a ring (for example like the seals) but exists only as a small passage/opening. 
     Unlike the passage  060  in the control sleeve  0103 , the poppet aperture  2411  and poppet orifice  2410  permit flow directly between the central region  0405  and the control chamber  0802 . Since the control chamber  0802  can be piloted (using an internal, external, or any other type of pilot) this enables additional functionality to be used for flow control. 
     All features described and/or illustrated herein (or the absence of any such feature) can be combined with each other in any combination without limitation. For example, any embodiment described herein may or may not have a threaded end, may or may not have a retainer collar, may or may not have a passage in the control sleeve, etc. Any combination of feature(s) can be used without limitation with any other combination of feature(s). Any feature described herein can also be optional. The illustrations shown herein are exemplary but any illustration can be augmented with any feature described herein or any feature shown can also be removed without limitation. 
     The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. Further, 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 illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.