Abstract:
A hydraulic circuit capable of both a regeneration mode of operation and a full force mode of operation includes a poppet valve controlled by a control valve operating in conjunction with a shuttle valve. The opening of the poppet valve enables the regeneration mode of operation, and the closing of the poppet valve enables the full force mode of operation.

Description:
RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from U.S. Provisional application No. 61/423,347 by Timothy L. Hand et al., filed Dec. 15, 2010, the contents of which are expressly incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to a hydraulic circuit, and more specifically to a hydraulic circuit for flow regeneration. 
     BACKGROUND 
     In many hydraulic circuits it is desirable to increase the movement speed of an implement by regenerating fluid flow from a discharge side of an actuator to an input side. However, when regenerating flow, the force the actuator is capable of producing may be lessened in exchange for the increased velocity. Accordingly, it may be beneficial to provide a hydraulic system capable of effectively switching between a regeneration state and a full force state. 
     SUMMARY OF THE DISCLOSURE 
     A hydraulic system is disclosed having an actuator with a first fluid chamber and a second fluid chamber; a poppet valve having an open position and a closed position, the poppet valve including a pressure chamber defined in part by a first working surface biasing the poppet valve toward the closed position; a shuttle valve in fluid communication with the first and second fluid chambers, the shuttle valve being configured to selectively pass fluid from the fluid chamber having a higher pressure; and a control valve movable between a first position facilitating fluid communication between the pressure chamber and the fluid selectively passed by the shuttle valve, and a second position facilitating fluid communication between the pressure chamber and the first fluid chamber. 
     In another embodiment of the disclosure, a hydraulic system is disclosed having an actuator with a first fluid chamber and a second fluid chamber; a poppet valve having an open and a closed position, the poppet valve including a pressure chamber biasing the poppet valve toward the closed position, and having a first port and a second port, wherein the first and second ports of the poppet valve are substantially fluidly isolated when the poppet valve is shut, and wherein the first and second ports of the poppet valve are in fluid communication when the poppet valve is open; a shuttle valve having a first port, a second port, and a third port, wherein the shuttle valve selectively communicates either the first port of the shuttle valve or the second port of the shuttle valve, whichever is at a higher pressure, with the third port of the shuttle valve; a first passage fluidly connecting the first fluid chamber, the first port of the shuttle valve, and the first port of the poppet valve; a second passage fluidly connecting the second fluid chamber, the second port of the shuttle valve, and the second port of the poppet valve; and a control valve having a first position facilitating fluid communication between the pressure chamber and the third port of the shuttle valve, and a second position facilitating fluid communication between the pressure chamber and the first passage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a machine having an implement; 
         FIG. 2  illustrates a first embodiment of a hydraulic circuit for control of the implement; and 
         FIG. 3  illustrates a second embodiment of a hydraulic circuit for control of the implement. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a machine  10  having an implement  12  and a body  14 . In the illustrated embodiment, machine  10  is a bulldozer; however, machine  10  may also be a wheel loader, motor grader, truck, excavator, scraper, or any other machine to which this disclosure may relate. Machine  10  also includes an actuator  16  configured to move the implement  12 . It is contemplated that a plurality of actuators may be working to working together to achieve the same functionality without departing from the scope of this disclosure. As illustrated in  FIG. 1 , actuator  16  is configured to move implement  12  relative to body  14  in a generally vertical motion; however, in alternate embodiments actuator  16  may cause implement  12  to move horizontally, to rotate, or to move in any other way known in the art. In the illustrated embodiment, implement  12  is a blade; however, implement may alternately be a bucket, a shovel, a bed, or other tool. 
       FIG. 2  illustrates a first embodiment of a hydraulic circuit  20  to control fluid flow in and out of actuator  16 . Hydraulic circuit  20  includes a source  22  of pressurized hydraulic fluid, a first control valve  24 , a poppet valve  26 , a shuttle valve  28 , and a second control valve  30 , and a low pressure reservoir  32 . As further illustrated in  FIG. 2 , actuator  16  includes a head end fluid chamber  34  and a rod end fluid chamber  36 . 
     In the first embodiment, a head conduit  40  fluidly connects the head end fluid chamber  34  to a port of the first control valve  24 . Similarly, a rod conduit  42  fluidly connects the rod end fluid chamber  36  to another port of the first control valve  24 . As illustrated, the first control valve  24  selectively fluidly connects the head conduit  40  and the rod conduit  42  with the source  22  and the reservoir  32 , selectively causing the actuator  16  to extend, retract, float, or substantially hold its position. 
     According to the illustrated embodiment, the poppet valve  26  is disposed between the head conduit  40  and the rod conduit  42  such that when the poppet valve  26  is open fluid is capable of passing between the head conduit  40  and the rod conduit  42  via the poppet valve  26 , thereby facilitating fluid communication between the head end fluid chamber  34  and the rod end fluid chamber  36 . Conversely, when the poppet valve  26  is closed fluid is substantially prevented from passing between the head conduit  40  and the rod conduit  42  via the poppet valve  26 . In the illustrated embodiment, the poppet valve  26  is biased toward an open position by pressure in the head conduit  40  and pressure in the rod conduit  42 ; conversely, the poppet valve  26  is biased toward a closed position by a spring  44  and fluid in a pressure chamber  46 . As illustrated in  FIG. 2 , the pressure chamber  46  is defined, in part, by a first working surface  47 . Fluid pressure acting on the first working surface  47  tends to bias the poppet valve  26  toward the closed position. The poppet valve  26  also includes a second working surface  49 . Fluid pressure acting on the second working surface  49  tends to bias the poppet valve  26  toward the open position. According to the illustrated embodiment, the second working surface  49  includes a first portion  49   a  in fluid communication with the rod end fluid chamber  36  by way of the rod conduit  42 , and a second portion  49   b  in fluid communication with the head end fluid chamber  34  by way of the head conduit  40 . 
     With further reference to  FIG. 2 , the shuttle valve  28  is connected between the head conduit  40 , the rod conduit  42 , and a first port  48  of the second control valve  30 . The shuttle valve  28  is configured such that a pressure signal from either the head conduit  40  or the rod conduit  42 , whichever is at a higher pressure, is passed to the first port  48 . A second port  50  of the second control valve  30  is in fluid communication with the head conduit  40 . A third port  52  of the second control valve  30  is in fluid communication with the pressure chamber  46  of the poppet valve  26 . An orifice  54  may be provided between the pressure chamber  46  and the third port  52  to dampen movement of the poppet valve  26 . 
     The second control valve  30  has a first position in which the first port  48  is in fluid communication with the third port  52 , whereby the pressure chamber  46  is in fluid communication with the shuttle valve  28 . The second control valve  30  has a second position in which the second port  50  is in fluid communication with the third port  52 , whereby the pressure chamber  46  is in fluid communication with the head conduit  40 . In the illustrated embodiment, the second control valve  30  is biased toward the first position by a spring  58 , and the second control valve  30  is biased toward the second position by a solenoid  56 . 
       FIG. 3  illustrates a second embodiment of the hydraulic circuit  20  that is similar in configuration to the first embodiment, with a distinction in the manner in which the second control valve  30  is actuated. As illustrated in  FIG. 3 , a throttling orifice  70  is provided in the head conduit  40  in parallel with a check valve  72 . The check valve  72  is oriented such that fluid flow out of the head end fluid chamber  34  can pass through the check valve  72 , whereas fluid flow into the head end fluid chamber  34  can not pass through the check valve  72  and is channeled through the throttling orifice  70 . 
     A first pilot line  74  is connected to the head conduit  40  between the throttling orifice  70  and the head end fluid chamber  34 . A second pilot line  78  is connected to the head conduit  40  between the throttling orifice  70  and the first control valve  24 . The first pilot line  74  provides pressurized fluid to the second control valve  30  and biases the second control valve  30  towards the first position. In a similar manner, the second pilot line  78  provides pressurized fluid to the second control valve  30  and biases the second control valve  30  towards the second position. Similar to the embodiment illustrated in  FIG. 2 , a spring  56  also biases the second control valve  30  toward the first position. 
     Accordingly, as flow through the head conduit  40  toward the head end fluid chamber  34  increases, a pressure drop across the throttling orifice  70  increases, and thus the net force biasing the second control valve  30  toward the second position increases. Once this net force is sufficient to overcome the force of the spring  56 , the second control valve  30  will shift to the second position. 
     INDUSTRIAL APPLICABILITY 
     With respect to  FIGS. 1 and 2 , when it is desirable to lower the implement  12 , the first control valve  24  may be actuated to connect rod conduit  42  with the low pressure reservoir  32  and the head conduit  40  with the source of hydraulic fluid  22 . When it is desirable to operate the actuator  16  in a full force mode, such as when digging, the solenoid  56  in the illustrated configuration may be disengaged. With the solenoid  56  disengaged the spring  58  will tend to bias the second control valve  30  toward a position in which the pressure chamber  46  is connected with the shuttle valve  28 . In this manner the poppet valve  26  will tend to remain closed because the pressure chamber  46  will be connected to whichever of the head conduit  40  or the rod conduit  42  is at a higher pressure. The area of surface  47  is greater than that of surface  49 , so if the pressure in chamber  46  is equal to that in rod conduit  42 , poppet valve  26  will still remain closed. As the poppet valve  26  under these conditions will tend to prevent fluid from passing between the head end fluid chamber  34  and the rod end fluid chamber  36 , the actuator  16  is capable of operating at its full potential force. 
     Conversely, when it is desirable to operate the actuator  16  in a quick drop or regenerative mode, such as to rapidly lower the implement  12  from a raised position, the solenoid  56  in the illustrated configuration may be engaged, thereby connecting the pressure chamber  46  with the head conduit  40 . In this manner, when the head end fluid chamber  34  is at a lower pressure than the rod end fluid chamber  36 , such as when the implement  12  is raised and gravity or external force is acting to extend the actuator  16 , the lower pressure in the pressure chamber  46  may allow the poppet valve  26  to open, and allow fluid from the rod end fluid chamber  36  to flow into the head end fluid chamber  34 . In this manner, the speed of the actuation of the actuator  16  may be increased because it is not limited by the flow of hydraulic fluid provided from the source of hydraulic fluid  22  or by flow through first control valve  24 . 
     When external force, such as, for example, gravity, is countered or reduced significantly, for example, when the implement  12  hits the ground, fluid chamber  36  pressure decreases, actuator  16  extension speed slows down or comes to a stop, while at the same time, pump flow still reaches the fluid chamber  34  and boosts up the pressure, hence the pressure in poppet chamber  46  increases accordingly. Once the latter becomes high enough so that the force it exerts on area  47  is able to overcome the force on area  49  of the poppet valve  26 , which connects to chamber  36  with decreased pressure, the poppet valve  26  closes up. As a result, the regeneration path is cut off and the actuator  16  extends with full hydraulic force mode. This transition is done automatically without additional command. 
     The embodiment illustrated in  FIG. 3  may operate in a manner similar to the embodiment illustrated in  FIG. 2 , except that a pressure differential over a throttling orifice  70  is used to actuate the second control valve  30  rather than a solenoid  56 . According to this embodiment, when fluid the implement  12  is being raised, fluid may flow out of the head end fluid chamber  34  through a check valve  72  so that the flow out of the head end fluid chamber  34  is not restricted by the throttling orifice  70 . 
     When the implement  12  is being lowered and fluid is flowing into the head end fluid chamber  34 , the fluid is channeled through the throttling orifice  70 , and the pressure differential over the throttling orifice  70  increases with the flow rate of fluid through the orifice. Accordingly, when the rate of fluid flow into the head end fluid chamber  34  is sufficiently low, the spring  56  will overcome the pressure imbalance between the first pilot line  74  and the second pilot line  78 , causing the pressure chamber  46  to be in fluid communication with the shuttle valve  28 , which will tend to keep the poppet valve  26  shut in a manner similar to the embodiment described above and illustrated in  FIG. 2 . Once the flow into the head end fluid chamber  34  reaches a flow rate that creates a pressure differential between the first pilot line  74  and the second pilot line  78  sufficient to overcome the force of the spring  56 , the second control valve  30  will shift positions such that the pressure chamber  46  is in fluid communication with the head conduit  40 , which will tend to allow the poppet valve  26  to open when the head end fluid chamber  34  is at a lower pressure than the rod end fluid chamber  36 . In this manner, the implement  12  may quickly be lowered from a raised position, while still allowing the implement  12  to operate with full force for operations such as digging. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed invention without departing from the scope or spirit of the invention. Additionally, other embodiments of the disclosed invention will be apparent to those skilled in the art from consideration of the specification and practice of the apparatus and method disclosed herein. It is intended that the specification and examples be considered as exemplary only.