Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
2000-05-18
2001-12-18
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C091S524000
Reexamination Certificate
active
06330798
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydraulic control systems, and particularly to systems in which a pair of hydraulic operators can be driven either in parallel or in series to power a common load.
Construction equipment such as hoists have moveable members that are driven by a hydraulic operator, such as a hydraulicly powered motor or a cylinder/piston arrangement. Application of hydraulic fluid to the operator traditionally was controlled by a manually operated valve, such as the one described in U.S. Pat. No. 5,579,642. This type of valve had a manual operator lever mechanically connected to a spool which could slide within a bore of the valve body. The pump and tank lines of the hydraulic system connected to ports of the valve body and the operator was coupled to workports on that valve body. Movement of the spool into various positions with respect to cavities in the bore enabled pressurized hydraulic fluid to flow from the pump to the operator and return to the tank also through the valve.
Manual valves are required to be mounted in the operator cab of the equipment thus requiring that a pair of hydraulic lines be run from each valve to the associated operator. There is a present trend away from manually operated hydraulic valves toward electrical controls and the use of solenoid valves. This type of control simplifies the hydraulic plumbing as the control valves do not have to be located in the operator cab. Instead the solenoid valves are mounted adjacent the operator, thereby requiring that only a common hydraulic line be run from the pump and a common return line be run back to the fluid tank. The solenoid valves distributed throughout the equipment connect to this single pair of hydraulic lines. Electrical controls are mounted in the cab with wires running to the respective solenoid valves. Wires are easier to run throughout the equipment and are less prone to failure than pressurized hydraulic lines.
Some hydraulic applications utilize a pair of operators to power a common load and power those operators in parallel or in series in different operating modes. For example, lift hoists utilize a pair of hydraulic motors to drive the cable spool which raises or lowers a load. The motors usually are often connected in parallel for greater power to lift heavy loads. The motors are connected in series to lower the load permitting increased speed of the cable spool when less power is required as gravity aids that lowering. In this application, the two operators typically are connected to a four-way spool valve and a series-parallel circuit that changes mode as commanded by operation of the spool valve. Such systems require two valve housings and intricate valving.
SUMMARY OF THE INVENTION
A hydraulic valve assembly includes a main control valve with a main valve poppet slidably located within a first bore to control flow of fluid between a first inlet into the first bore and a first outlet leading from the first bore. The main valve poppet defines a first control chamber in the first bore on a side of the main valve poppet that is remote from the first outlet. A selectively moveable pilot poppet engages and controls movement of the main valve poppet.
A shadow valve includes a shadow poppet slidably located within a second bore to control flow of fluid between a second inlet and a second outlet into and from the second bore. The shadow poppet defines a second control chamber in the second bore on a side of the shadow poppet that is remote from the second outlet. The second control chamber is in fluid communication with the first control chamber.
Movement of the pilot poppet affects pressure in the first control chamber which produces movement of the main valve poppet resulting in the main control valve opening and closing. Because the first control chamber is connected to the second control chamber, the shadow poppet moves in unison with the main valve poppet so that the shadow valve opens and closes synchronously with the main control valve.
In the preferred embodiment of the valve assembly, the pilot poppet is driven by an electrical actuator, such as a solenoid. This lends the main control valve to being operated by a electronic controller.
This type of hydraulic valve assembly is especially adapted for selective control of two hydraulic operators in either series or parallel. In this application, first, second and third valve assemblies couple the first and second operators to the pump and tank of the hydraulic system. Each valve assembly includes a main control valve and a shadow valve. The system also includes a conventional solenoid operated proportional valve.
The main control valve of the first valve assembly couples the pump to the first port of the first hydraulic operator, and the shadow valve of the first valve assembly connects the first port of the first hydraulic operator to the first port of the second hydraulic operator. The main control valve of the second valve assembly couples the first port of the first hydraulic operator to the tank, while the shadow valve of the second valve assembly connects the second port of the first hydraulic operator to the first port of the second hydraulic operator. The main control valve of the third valve assembly connects the second port of the first hydraulic operator to the tank, and the shadow valve of the third valve assembly couples the second port of the first hydraulic operator to the second port of the second hydraulic operator. The solenoid operated proportional valve couples the pump to the second port of the second hydraulic operator.
In a first mode of operation, the electronic controller applies electricity to the electric actuator of the first valve assembly and to the electric actuator of the third valve assembly, thereby operating the first and second operators in parallel. In a second mode of operation, the electronic controller applies electricity to the electric actuator of the proportional valve and to the electric actuator of the second valve assembly, thereby operating the first and second operators in series. Because only one valve in each assembly has a electric actuator, the complexity of the hydraulic system and its control are reduced as compared to a system having separate electric actuators for each valve.
REFERENCES:
patent: 5421545 (1995-06-01), Schexnayder
patent: 6149124 (2000-11-01), Yang
Haas George E.
HUSCO International Inc.
Lazo Thomas E.
Look Edward K.
Quarles & Brady LLP
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