Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
1999-12-14
2001-04-03
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C137S596140, C137S596150, C251S025000, C251S043000
Reexamination Certificate
active
06209580
ABSTRACT:
TECHNICAL FIELD
This invention relates to valve assemblies for use in hydraulic power systems for controlling reversible piston-cylinder drive units or the like. More particularly, it relates to the provision of an improved valve assembly which combines together a switching valve, an off-on valve and a directional valve. The invention also relates to various subassemblies, components and features of the valve assembly.
BACKGROUND INFORMATION
I own many patents relating to various aspect of reciprocating slat conveyors. Such patents include U.S. Pat. No. 4,712,467, granted Dec. 15, 1987, and entitled, Combined Linear Hydraulic Motor And Transfer Valve; U.S. Pat. No. 4,793,469, granted Dec. 27, 1988 and entitled Reduced Size Drive/Frame Assembly For A Reciprocating Floor Conveyor; U.S. Pat. No. 4,821,868, granted Apr. 18, 1989 and entitled, Drive/Frame Assembly For A Reciprocating Floor; U.S. Pat. No. 5,103,866, granted Apr. 14, 1992, and entitled, Poppet Valve And Valve Assemblies Utilizing Same; U.S. Pat. No. 5,193,661, granted Mar. 16, 1993, and entitled, System Of Linear Hydraulic Motors; U.S. Pat. No. 5,361,679, granted Nov. 8, 1994, and entitled, Directional Control Valve With Pilot Operated Poppet Valve; and U.S. Pat. No. 5,622,095, granted Apr. 22, 1997, and entitled, Hydraulic Drive And Control System. The valve assembly of the present invention is particularly suited for use with reciprocating slat conveyors but it is believed to also have general utility.
The reciprocating slat conveyors disclosed by U.S. Pat. Nos. 4,712,467; 4,821,868 and 5,622,095 operate on what has been described the 1-2-3 cycle. This cycle is illustrated and described in my U.S. Pat. No. 4,793,469, with reference to FIGS. 2-6 in that patent. The conveyor is composed of slats that are divided into “sets” and “groups”. In a typical conveyor, there are twenty-four slats divided into three “sets” and eight “groups.” Each “group” consists of one slat from “set.” Starting from one side of the conveyor, and moving inwardly, the first “group” of slats is composed of one slat from “set 1”, then one slat from “set 2”, and then one slat from “set 3.” The next “group” ( “group 2”) repeats this pattern and the pattern is repeated all the way across the conveyor, from “group 1” to “group 8.”
FIG. 2 of U.S. Pat. No. 4,793,469, shows all of the conveyor slats in a retracted position in which common ends are aligned at a start station a. A load L is shown centrally positioned on the conveyor. FIG. 3 of that patent shows all of the conveyor slats being advanced together to move the load L forwardly. Movement continues until the opposite end of the conveyor slats are moved to a fully advanced position b. FIG. 4 shows the “set 1” slats being retracted while the “set 2” and “set 3” slats are held stationary. The load does not move because the frictional forces exerted on it by the stationary “set 2” and “set 3” slats are larger than the frictional forces exerted on it by the retracting “set 1” slats. FIG. 5 shows the next step in the sequence. The retracted “set 1” slats and the advanced “set 3” slats are held stationary while the “set 2” slats are being retracted. Again, the load L does not move. FIG. 6 shows retracted “set 1” and the “set 2” slats stationary and the “set 3” slats being retracted. Again, the load L does not move. In this example, the load L is moved a distance equal to the endwise movement of the slats, viz. a-c or d-b.
U.S. Pat. Nos. 4,712,467; 4,821,868, and 5,622,095 disclose a popular style of drive assembly for reciprocating slat conveyors. Each set of slats is connected to a separate transverse drive beam. Thus, in the example given above, there are three transverse drive beams. Each transverse drive beam is connected to a reversible linear hydraulic motor. The control system for the linear hydraulic motor includes a reversing valve, an on/off valve and a directional valve. The reversing valve is also quite commonly referred to as a switching valve. Example reversing valves are disclosed in the aforementioned U.S. Pat. Nos. 5,103,866; 5,193,661; 5,361,679 and 5,622,095. A typical on/off valve is designated OOV in U.S. Pat. No. 5,193,661. A typical direction control valve is designated DCV in U.S. Pat. No. 5,193,661.
A problem in existing systems is that the switching valve, the on/off valve and the direction control valve are separate valves that are spaced apart and connected together by conduits. This results in the system having a large number of conduits. The number of conduits dictates the overall space requirements for the system. The use of separate valves connected by conduits also can result in a positioning of the valves to where one or more of them are not be readily accessible.
There is a need for an approved assembly of the three valves in which the amount of tubing is minimized and the three valves are grouped close together and are rendered accessible to a user. It is a principal object of the invention to fill this need and provide such a valve assembly.
DISCLOSURE OF THE INVENTION
A valve assembly of the present invention includes a switching valve in a valve housing. The valve housing includes a pressure port, a pressure passageway leading from the pressure port to the switching valve, a return port, a return passageway leading from the switching valve to the return port, a first inlet/outlet port, a first in/out passageway leading from the switching valve to the first in/out port, a second in/out port and second in/out passageway leading from the switching valve to the second in/out port. The switching valve has first position in which the pressure passageway is connected to the first in/out passageway and the second in/out passageway is connected to the return passageway. The switching valve also has a second position in which the pressure passageway is connected to the second in/out passageway and the first in/out passageway is connected to the return passageway. A shunt passageway in the valve housing extends between the pressure passageway and the return passageway at a location between the pressure and return ports and the switching valve. A off/on valve in said housing includes a valve plug movable into the shunt passageway, to close the shunt passageway. It is also movable out from the shunt passageway, to open the shunt passageway. When the shunt passageway is closed, pressure at the pressure port is connected to the pressure passageway leading to the switching valve and the switching valve is connected by the return passageway to the return port. When the shunt passageway is open, pressure at the pressure port is shunted away from the switching valve to and through the shunt passageway and to the return passageway and the return port.
Preferably, the valve housing includes a valve seat surrounding the shunt passageway, generally where it meets the return passageway. The valve plug has a plug end facing the valve seat and an opposite rear end. The valve plug is movable axially to move the plug end into and out from a closed position on the valve seat.
In one embodiment, the housing includes a cam passageway rearwardly of the valve plug. A cam in said cam passageway is rotatable between first and second positions. The cam is operatively connected to the rear end of the valve plug and is adapted to permit rearward movement of the valve plug into its open position when the cam is in its first position. Movement of the cam from its first position to its second positions imposes an axial force on the valve plug, moving the valve plug into its closed position.
In one embodiment, the valve plug includes an axial passageway. When the valve plug is seated, and the cam is in its second position, pressure in the pressure passageway is connected by the axial passageway in the valve plug to a region rearwardly of the valve plug where at it exerts and axial force on the valve plug, urging it towards a seated position.
In this embodiment, the cam may include a vent passageway that is blocked when the cam is in its second position and which connects the region rearwardly of the val
Barnard Delbert J.
Michalsky Gerald A.
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