Patent Publication Number: US-9903396-B2

Title: Valve assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates to a valve assembly. In particular, the present disclosure relates to a pilot operated valve assembly for controlling the flow of a fluid to a plurality of actuators based on a load on the plurality of actuators. 
     BACKGROUND 
     Controlling an operation of a hydraulic actuator in a hydraulic circuit is conventionally accomplished using a single spool type valve. The single spool valve controls flow of hydraulic fluid in the hydraulic circuit including a flow of hydraulic fluid from an associated pump to the hydraulic actuator and a flow of hydraulic fluid from the hydraulic actuator to an associated tank. When the hydraulic output device is a hydraulic cylinder, these flows are commonly referred to as pump-to-cylinder flow and cylinder-to-tank flow, respectively. 
     The hydraulic circuit may include multiple hydraulic actuators. The hydraulic actuators are associated with operation of multiple systems. The hydraulic actuators receive hydraulic fluid from a single pump to operate the systems. The hydraulic circuit may include separate valves for each of the hydraulic actuator associated with each of the system. 
     Typically, valves include one of pressure compensators or priority based mechanisms to control and provide flow of hydraulic fluid to the hydraulic actuators. The pressure compensators or the priority based mechanisms enable proper flow of hydraulic fluid to the hydraulic actuators based on differential loads acting on the hydraulic actuators. However, the pressure compensators or the priority based mechanisms add to cost of the valves and the hydraulic circuit. 
     U.S. Pat. No. 4,117,862 discloses a pressure compensated control valve that includes a split spool valve with a common wall to provide a fluid to an actuator. The split spool valve controls opening of associated outlet ports of the valve assembly in response to a load on the actuator, and thereby controls flow of the fluid to the actuator. However, in fluid systems where a single pump delivers the fluid to multiple actuators, the pressure compensated control valve may not efficiently distribute and control the flow of fluid to the multiple actuators, based on differential loads acting on the multiple actuators. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present disclosure, a valve assembly is disclosed. The valve assembly includes a valve housing defining a bore, a first valve, and a second valve. The first valve and the second valve are disposed within the bore and each of the first valve and the second valve include a first end and a second end. Further, the first end of the first valve and the first end of the second valve are configured to contact each other. The valve assembly further includes a pilot chamber defined within the bore and configured to receive a pilot fluid. A pressure of the pilot fluid inside the pilot chamber is controlled to permit independent movement of the first valve and the second valve within the bore. 
     According to another aspect of the present disclosure, a valve assembly is disclosed. The valve assembly includes a valve housing defining a bore, a first valve, and a second valve. The first valve and the second valve are disposed within the bore and each of the first valve and the second valve include a first end and a second end. Further, the first end of the first valve and the first end of the second valve are configured to contact each other. Also, the second end of the first valve and the second end of the second valve are configured to be acted upon by a pilot fluid. The valve assembly further includes a pilot chamber defined within the bore between the first end of the first valve and the first end of the second valve. The pilot chamber is configured to receive the pilot fluid. Furthermore, the valve assembly is configured to operate in a first mode and a second mode. In the first mode, a pressure of the pilot fluid acting on one of the second end of the first valve and the second end of the second valve is manipulated such that the first valve and the second valve move together within the bore. In the second mode, the pressure of the pilot fluid acting on the second end of the first valve and the second end of the second valve is manipulated such that the first valve and the second valve move independently of each other within the bore. 
     According to an aspect of the present disclosure, a method for operating a valve assembly is disclosed. The valve assembly includes a valve housing defining a bore, a first valve, and a second valve. The first valve and the second valve are disposed within the bore and configured to contact each other. The method for operating the valve assembly includes controlling pressure of a pilot fluid acting on a first end and a second end of the first valve and a first end and a second end of the second valve for moving the first valve and the second valve within the bore. The method of operating the valve assembly further includes regulating flow of a fluid from one of a first outlet port and a second outlet port by moving the first valve and the second valve within the bore and positioning the first valve and the second valve within the bore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a fluid system including a valve assembly, in accordance with an embodiment of the disclosure; 
         FIG. 2  illustrates a sectional view of the valve assembly depicting positions of a first valve and a second valve in a neutral position, in accordance with an embodiment of the disclosure; 
         FIG. 3  illustrates a sectional view of the valve assembly depicting positions of the first valve and the second valve in a first mode, in accordance with an embodiment of the disclosure; 
         FIG. 4  illustrates a sectional view of the valve assembly depicting positions of the first valve and the second valve in a second mode, in accordance with an embodiment of the disclosure; 
         FIG. 5  illustrates a sectional view of the valve assembly depicting positions of the first valve and the second valve in a floating position, in accordance with an embodiment of the disclosure; 
         FIG. 6  illustrates a sectional view of a valve assembly depicting positions of a first valve and a second valve in a neutral position, in accordance with an alternative embodiment of the disclosure; 
         FIG. 7  illustrates a sectional view of the valve assembly depicting positions of the first valve and the second valve in a first mode, in accordance with an alternative embodiment of the disclosure; 
         FIG. 8  illustrates a sectional view of the valve assembly depicting positions of the first valve and the second valve in a second mode, in accordance with an alternative embodiment of the disclosure; 
         FIG. 9  illustrates a sectional view of the valve assembly depicting positions of the first valve and the second valve in a floating position, in accordance with an alternative embodiment of the disclosure; and 
         FIG. 10  illustrates a method for operating the valve assembly, in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts.  FIG. 1  represents an exemplary fluid system  100  incorporating a valve assembly  102 , according to an embodiment of the present disclosure. The fluid system  100  may be configured to manipulate one or more linkages, or any other fluidly powered components or systems of a machine. In an embodiment, the machine may be an excavator, a backhoe loader, a shovel, a wheel loader, etc. The machine may alternatively include any other mining, transportation, forestry, agricultural, construction, or industrial machine. 
     Referring to  FIG. 1 , the fluid system  100  includes an actuator  104 , a pump  106 , a first valve actuator  108 , a second valve actuator  110 , and a reservoir  112 . In an embodiment, the actuator  104  may be operatively connected with a boom or a stick of an excavator and configured to manipulate the boom or the stick. In the illustrated embodiment, the actuator  104  comprises a fluid cylinder. In another embodiment, the actuator  104  may be a fluid motor. The actuator  104  is configured to receive a fluid from the pump  106  and discharge the fluid to the reservoir  112 . The pump  106  may be a variable displacement pump or a fixed displacement pump. The pump  106  is also configured to provide fluid to an additional fluid circuit  100   a . The additional fluid circuit  100   a  may include similar components as that of the fluid system  100 . 
     Further, the valve assembly  102  is configured to control an amount and direction of flow of the fluid from the pump  106  to the actuator  104  and from the actuator  104  to the reservoir  112 . The valve assembly  102  is a pilot operated valve assembly. Further, a pilot circuit  114  is in fluid communication with the valve assembly  102  to actuate and operate the valve assembly  102 . Further, the first valve actuator  108  and the second valve actuator  110  are in fluid communication with the valve assembly  102 . The first valve actuator  108  and the second valve actuator  110  are configured to control flow of a pilot fluid to the valve assembly  102  for controlling actuation and operation of the valve assembly  102 . As shown in  FIG. 1 , the first valve actuator  108  and the second valve actuator  110  are solenoid-operated valves. Both the first valve actuator  108  and the second valve actuator  110  may be actuated to a first position and a second position. In the first position, the first valve actuator  108  and the second valve actuator  110  fluidly couple the valve assembly  102  to the pilot circuit  114 , thereby providing pilot fluid to the valve assembly  102 . In the second position, the first valve actuator  108  and the second valve actuator  110  fluidly couple the valve assembly  102  to the reservoir  112 , thereby draining the pilot fluid acting on the valve assembly  102  to the reservoir  112 . 
     Referring to  FIGS. 1, 2, 3, 4, and 5 , the valve assembly  102  includes a valve housing  116  defining a bore  118 , a first valve  120 , a second valve  122 , a first outlet port  124 , a second outlet port  126 , a first inlet port  128 , a second inlet port  130 , a first drain port  132 , and a second drain port  134 . The first valve  120  is positioned within the bore  118  and configured to slide within the bore  118 . The first valve  120  controls flow of the fluid between the first outlet port  124 , the first inlet port  128 , and the first drain port  132 . The first valve  120  includes a first end  136  and a second end  138 . Both the first end  136  and the second end  138  are configured to be acted upon by the pilot fluid for moving the first valve  120  within the bore  118 . Further, a first spring  140  may be coupled to the second end  138  to bias the first valve  120  in a neutral position. In the neutral position, the first end  136  of the first valve  120  contacts the second valve  122  (as shown in  FIG. 2 ). 
     The second valve  122  includes a first end  142  and a second end  144 . Both the first end  142  and the second end  144  are configured to be acted upon by the pilot fluid for moving the second valve  122  within the bore  118 . The second valve  122  controls flow of the fluid between the second outlet port  126 , the second inlet port  130 , and the second drain port  134 . Further, a second spring  146  coupled to the second end  144  to bias the second valve  122  in a neutral position. In the neutral position, the first end  142  of the second valve  122  contacts the first end  136  of the first valve  120  (as shown in  FIG. 2 ). 
     Further, the valve assembly  102  includes a pilot chamber  148  defined within the bore  118  configured to receive the pilot fluid. A pressure of the pilot fluid inside the pilot chamber  148  is controlled to permit independent movement of the first valve  120  and the second valve  122  within the bore  118 . As shown in  FIG. 2 , the pilot chamber  148  is defined within the bore  118  between the first end  136  of the first valve  120  and the first end  142  of the second valve  122 . The pilot chamber  148  is in fluid communication with the pilot circuit  114  and receives the pilot fluid from the pilot circuit  114 . In an embodiment, a valve may be positioned between the pilot circuit  114  and the pilot chamber  148  to control flow of the fluid from the pilot circuit  114  to the pilot chamber  148 . The pressure of the pilot fluid acting on the first end  136  and the second end  138  of the first valve  120  and the first end  142  and the second end  144  of the second valve  122  may be controlled to enable movement of the first valve  120  and the second valve  122  within the bore  118 . 
     In the neutral position (as shown in  FIG. 2 ), the valve assembly  102  is configured to block flow of the fluid between the pump  106  and the actuator  104 , and between the actuator  104  and the reservoir  112 . As shown in  FIG. 2 , in the neutral position, the first valve  120  contacts the second valve  122 . Further, in the neutral position, the pressure of the pilot fluid acting on the first end  136  and the second end  138  of the first valve  120  and the first end  142  and the second end  144  of the second valve  122  may be a maximum pressure of the pilot fluid. With the pilot fluid acting on the first end  136  and the second end  138  of the first valve  120 , and the first end  142  and the second end  144  of the second valve  122 , both the first spring  140  and the second spring  146  force the first valve  120  and the second valve  122  to a center position. As shown in  FIG. 2 , in the neutral position, the first valve  120  is positioned within the bore  118  such that the first valve  120  closes the first inlet port  128  and the first drain port  132 . Similarly, the second valve  122  is positioned within the bore  118  such that the second valve  122  closes the second inlet port  130  and the second drain port  134 . 
     Further, the valve assembly  102  is configured to move from the neutral position to allow flow of the fluid from the pump  106  to the actuator  104  and from the actuator  104  to the reservoir  112 . The valve assembly  102  is configured to operate in a first mode and a second mode. In the first mode, the first valve  120  and the second valve  122  contact each other and move together within the bore  118 . In the second mode, the first valve  120  and the second valve  122  are spaced from each other within the bore  118  and move independently of each other. The valve assembly  102  is operated in the second mode to control an opening of the first inlet port  128  or the second inlet port  130  to provide a controlled flow to the actuator  104  from the pump  106 . 
     The valve assembly  102  may be operated in the first mode by reducing the pressure of the pilot fluid acting either on the second end  138  of the first valve  120  or on the second end  144  of the second valve  122 . In an embodiment, when flow of the fluid from the pump  106  to the actuator  104  is required through the second outlet port  126 , the pressure of the pilot fluid acting on the second end  138  of the first valve  120  is reduced. The pressure of the pilot fluid acting on the second end  138  of the first valve  120  may be reduced by actuating the first valve actuator  108  to the second position. The actuation of the first valve actuator  108  in the second position allows the pilot fluid acting on the second end  138  of the first valve  120  to be drained to the reservoir  112 . Further, the pressure of the pilot fluid in the pilot chamber  148  and the pressure of the pilot fluid acting on the second end  144  of the second valve  122  is kept unchanged. Therefore, the reduction of the pressure of the pilot fluid acting on the second end  138  of the first valve  120  causes, the first valve  120  and the second valve  122  to move together within the bore  118 . This allows positioning of the second valve  122  within the bore  118  such that the second inlet port  130  and the second outlet port  126  are opened and fluidly coupled to each other (as shown in  FIG. 3 ). In so doing, the pump  106  provides fluid to the actuator  104  via the second outlet port  126 . Similarly, when flow of the fluid to the actuator  104  from the pump  106  is required via the first outlet port  124 , the pressure of the pilot fluid acting on the second end  144  of the second valve  122  is reduced by actuating the second valve actuator  110  in the second position. 
     Further, the valve assembly  102  may be operated in the second mode by manipulating the pressure of the pilot fluid acting on the second end  138  of the first valve  120  and the second end  144  of the second valve  122 . In the second mode, the first valve  120  and the second valve  122  is configured to move independent of each other within the bore  118  to regulate and reduce flow of the fluid to the actuator  104  from the pump  106 . Flow of the fluid from the pump  106  to the actuator  104  is reduced by either reducing the opening of the first inlet port  128  or the opening of the second inlet port  130 . The reduction in the opening of the first inlet port  128  or the opening of the second inlet port  130  may be achieved by sliding and thereby suitably positioning the first valve  120  and/or the second valve  122  inside the bore  118 . In the second mode, the movement and positioning of the first valve  120  and/or the second valve  122  within the bore  118  is controlled by controlling the pressure of the pilot fluid acting on the second end  138  and/or the second end  144 . 
     In an embodiment, as shown in  FIG. 4 , to reduce flow of the fluid through the second outlet port  126 , the second valve  122  is positioned such that the second inlet port  130  is partially opened. This is achieved by first reducing the pressure of the pilot fluid acting on the second end  138  of the first valve  120  and thereby moving the first valve  120  and the second valve  122  within the bore  118  such that the first spring  140  is compressed and the second spring  146  is extended. Thereafter, the pressure of the pilot fluid acting on the second end  144  of the second valve  122  is reduced by actuating the second valve actuator  110  to the second position. This allows retraction of the second spring  146 , thereby moving the second valve  122  within the bore  118  such that the second inlet port  130  is partially opened. Once the second valve  122  is suitably positioned within the bore  118 , the second valve actuator  110  is actuated to the first position, thereby stopping the movement of the second valve  122  within the bore  118 . 
     In an embodiment, a first position sensor (not shown) may be used to determine the position of the second valve  122  within the bore  118 . The first position sensor may be a linear voltage differential transformer based sensor, a hydro-mechanical feedback device, or any other suitable position sensor known in the art. 
     Similarly, when the reduced flow is required through the first outlet port  124 , the first valve  120  and the second valve  122  are moved within the bore  118  by reducing the pressure of the pilot fluid acting on the second end  144  of second valve  122 , at first. Thereafter, the pressure of the pilot fluid acting on the second end  138  of the first valve  120  is reduced by actuating the first valve actuator  108  to the second position. Thereafter, the first valve actuator  108  may be actuated to the first position based on a position of the first valve  120  within the bore  118  such that the first valve  120  partially opens the first inlet port  128 . 
     In an embodiment, the position of the first valve  120  within the bore  118  may be monitored by a second position sensor. The second position sensor may be a linear voltage differential transformer based sensor, a hydro-mechanical feedback device, or any other suitable position sensor known in the art. 
     Referring to  FIG. 5 , a floating position of the valve assembly  102  is shown. In the floating position, the first valve  120  and the second valve  122  is positioned within the bore  118  such that the first outlet port  124 , the second outlet port  126 , the first drain port  132 , and the second drain port  134  are in opened state. Therefore, in the floating position, the first outlet port  124  is in fluid communication with the first drain port  132  and the second outlet port  126  is in fluid communication with the second drain port  134 . As shown in  FIG. 5 , in the floating position, the first inlet port  128  and the second inlet port  130  are in closed state. The valve assembly  102  may be actuated in the floating position by reducing the pressure of the pilot fluid acting on the second end  138  of the first valve  120  and the second end  144  of the second valve  122 . The reduction in the pressure of the pilot fluid may be achieved by actuating the first valve actuator  108  and the second valve actuator  110  in the second position. 
     Referring to  FIGS. 6, 7, 8, and 9 , a valve assembly  102   a  is shown according to an alternative embodiment of the disclosure. The valve assembly  102   a  includes a valve housing  116   a  defining the bore  118 , a first valve  120   a , a second valve  122   a , the first outlet port  124 , the second outlet port  126 , a first inlet port  150 , a second inlet port  152 , a first drain port  154 , and a second drain port  156 . In the present embodiment, the first drain port  154  and the second drain port  156  are positioned between the first inlet port  150  and the second inlet port  152 . 
     The first valve  120   a  and the second valve  122   a  are disposed within the bore  118 . The valve assembly  102   a  further includes the pilot chamber  148  defined within the bore  118  between a first end  136   a  of the first valve  120   a  and a first end  142   a  of the second valve  122   a . Further, a second end  138   a  of the first valve  120   a  may be coupled to the first spring  140  and a second end  144   a  of the second valve  122   a  may be coupled to the second spring  146 . The first spring  140  and the second spring  146 , respectively bias the first valve  120   a  and the second valve  122   a  in a neutral position (shown in  FIG. 6 ). In the neutral position, the first outlet port  124  and the second outlet port  126  are closed, while the first inlet port  150 , the second inlet port  152 , the first drain port  154 , and the second drain port  156 , are opened. Further, in the neutral position, the first end  136   a  of the first valve  120   a  and the first end  142   a  of the second valve  122   a  contact each other. 
     Further, the valve assembly  102   a  is configured to be operated in a first mode and a second mode by controlling the pressure of the pilot fluid acting on the first end  136   a  and the second end  138   a  of the first valve  120   a , and the first end  142   a  and the second end  144   a  of the second valve  122   a . The valve assembly  102   a  is operated in the first mode and in the second mode in a similar manner as described earlier in conjunction with the valve assembly  102 . 
     In the first mode, the first valve  120   a  and the second valve  122   a  contact each other and move together within the bore  118  (shown in  FIG. 7 ). In the first mode, the first valve actuator  108  or the second valve actuator  110  is controlled, in a similar manner as described earlier with respect to the valve assembly  102 , to reduce the pressure of the pilot fluid acting on either the second end  138   a  of the first valve  120   a  or the second end  144   a  of the second valve  122   a.    
     In the second mode, the valve assembly  102   a  is configured to provide a reduced flow of the fluid to the actuator  104  though the first outlet port  124  or the second outlet port  126 . In the second mode, the first valve  120   a  and/or the second valve  122   a  is positioned within the bore  118  such that the either the first outlet port  124  or the second outlet port  126  is partially opened to reduce flow of the fluid to the actuator  104 . The positioning of the first valve  120   a  and/or the second valve  122   a  is performed by reducing the pressure of the pilot fluid acting on the second end  138   a  of the first valve  120   a  and the second end  144   a  of the second valve  122   a  in a similar manner as described earlier in reference to the actuation of the valve assembly  102  in the second mode. As shown in  FIG. 8 , in the second mode, the second valve  122   a  moved and positioned within the bore  118  so as to partially open the second outlet port  126  to reduce flow of the fluid through the second outlet port  126 . 
     Referring to  FIG. 9 , a floating position of the valve assembly  102   a  is shown. In this floating position, the first valve  120   a  and the second valve  122   a  is positioned within the bore  118  such that the first outlet port  124 , the second outlet port  126 , the first drain port  154 , and the second drain port  156  are in opened state. Therefore, in the floating position, the first outlet port  124  is in fluid communication with the first drain port  154  and the second outlet port  126  is in fluid communication with the second drain port  156 . The valve assembly  102   a  may be actuated in the floating position by reducing the pressure of the pilot fluid acting on the second end  138   a  of the first valve  120   a  and the second end  144   a  of the second valve  122   a . The reduction in the pressure of the pilot fluid may be achieved by actuating the first valve actuator  108  and the second valve actuator  110  in the second position. 
     INDUSTRIAL APPLICABILITY 
     Referring to  FIG. 10 , a method  1000  for operating any one of the valve assembly  102  and the valve assembly  102   a  is provided. Although the method  1000  is explained in conjunction with the valve assembly  102 , it may be understood that the valve assembly  102   a  may be operated in a similar manner. Further, the references will be made to  FIGS. 1-9  for describing the method  1000  in detail. 
     The method  1000  includes a step  1002  for controlling the pressure of the pilot fluid acting on the first end  136  and the second end  138  of the first valve  120 , and the first end  142  and the second end  144  of the second valve  122 , to enable movement of the first valve  120  and the second valve  122  within the bore  118 . The pressure of the pilot fluid acting on the second end  138  and second end  144  may be controlled by respectively controlling the first valve actuator  108  and the second valve actuator  110 . In an embodiment, the pressure of the pilot fluid acting on one of the second end  138  of the first valve  120  and the second end  144  of the second valve  122  may be reduced to move the first valve  120  and the second valve  122  together within the bore  118 . The pressure of the pilot fluid acting on either the second end  138  or the second end  144  may be reduced to actuate and operate the valve assembly  102  in the first mode. 
     Further, the pressure of the pilot fluid acting on the second end  138  of the first valve  120  and the second end  144  of the second valve  122  may be reduced to move the first valve  120  and the second valve  122  independently within the bore  118 . The pressure of the pilot fluid acting of the second  138  and the second end  144  may be reduced to actuate and operate the valve assembly  102  in the second mode. The pressure of the pilot fluid acting on the second end  138  may be reduced by positioning the first valve actuator  108  in the second position. Similarly, the pressure of the pilot fluid acting on the second end  144  may be reduced by actuating the second valve actuator  110  in the second position. 
     The method  1000  further includes a step  1004  for regulating flow of the fluid through the first outlet port  124  or the second outlet port  126  by moving the first valve  120  and the second valve  122  within the bore  118 . The first valve  120  and the second valve  122  may be moved to suitably position the first valve  120  and the second valve  122  such that flow of the fluid through the first outlet port  124  or the second outlet port  126  is regulated. In an embodiment, the first valve  120  and the second valve  122  is moved and positioned within the bore  118  such that the first inlet port  128  or the second inlet port  130  is partially opened so as to restrict flow of the fluid respectively through the first outlet port  124  or the second outlet port  126 . To partially open either of the first inlet port  128  or the second inlet port  130 , the valve assembly  102  operates in the second mode. 
     Further, an operation of the fluid system  100  having the valve assembly  102  is disclosed. Although the operation of the fluid system  100  is explained in conjunction with the valve assembly  102 , it may be understood that fluid system  100  having the valve assembly  102   a  may be operated in a similar manner. 
     In operation, the pump  106  provides flow of the fluid to the actuator  104  via the valve assembly  102 . When there is requirement to solely actuate the actuator  104 , the valve assembly  102  operates in the first mode. For actuating the valve assembly  102  in the first mode, a controller may actuate either the first valve actuator  108  or the second valve actuator  110  to the second position, thereby reducing the pressure of the pilot fluid acting on the second end  138  or the second end  144  by draining the pilot fluid to the reservoir  112 . 
     When the pump  106  provides flow of the fluid to both the actuator  104  and the additional fluid circuit  100   a  which has a higher load as compared to the actuator  104 , the valve assembly  102  operates in the second mode. For this purpose, the controller actuates both the first valve actuator  108  and the second valve actuator  110  to the second position. This allows a restricted flow of the fluid to the actuator  104  from the pump  106  and relatively more flow of the fluid to the additional fluid circuit  100   a.    
     Therefore, the disclosed valve assembly directs a flow of the fluid to systems or circuits based on loads acting on fluid systems or circuits, when a single pump provides flow of the fluid to actuate multiple systems of a machine. Therefore, additional components such as a pressure compensator valve may be removed from such fluid systems or circuits connected to a single pump. This helps in reducing the cost and overall size of the valve assembly and the fluid system.