Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Reexamination Certificate
1999-07-01
2001-01-16
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
C137S498000
Reexamination Certificate
active
06173737
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of vehicular wheelchair lifts which enable persons who are physically challenged or otherwise have limited mobility to board and leave a vehicle. More particularly, the present invention relates to the field of flow control valves used in hydraulic systems for vehicular wheelchair lifts or the like.
2. Description of the Prior Art
Specifically, hydraulic vehicular wheelchair lifts are well known in the art. Many of these lifts utilize a hydraulic actuating system with a flow control valve for moving the lift platform between a ground level position to an entry level position and from the entry level position to a stowed position. Furthermore, these lifts are also designed to be gravity-down during the platform movements from the stowed position to the entry level position and from the entry level position to the ground level position.
One of the disadvantages with prior art flow control valves is that they are restricted in one direction. Another disadvantage is that the main orifice port which is used for restricting hydraulic fluid flow has a narrow diameter opening and can get clogged by small particles in the hydraulic fluid. A further disadvantage is that there are three fluid routes in which the hydraulic fluid flows through the flow control valve.
U.S. Pat. No. 5,639,066 issued to Lambert et al. on Jun. 17, 1997 discloses a bidirectional flow control valve. The valve regulates flow in either direction between two ports having a valve with one of the ports formed in the housing at a proximal end and coaxial with the main bore and with a second one of the ports formed in the housing and opening into a side of the bore. A tubular spool is slidably received in the bore, and the spool has a lumen which is coaxial with the first port and a radial opening in the wall of the spool, with an edge of the opening being positioned to wipe across an edge of the second port so as to vary the cross-sectional area of a flow passage between the first and second ports in an area defined between the edges of the opening and of the second port.
U.S. Pat. No. 5,308,215 issued to Saucier on May 3, 1994 discloses a hydraulic drive passenger lift with a flow control structure for accommodating various distinctive motion patterns, including lifting “up and down” (loading and unloading) and “fold and unfold” (storage and deploy) patterns. The flow control arrangement with different attenuation degrees is designed for the purpose of having similar reduced platform movement speeds during the storage phase and the deployment phase of the storage movement pattern. The flow control structure includes multiple paths between a source and an actuator, with control for selecting the appropriate path to yield predetermined flow rates. A solenoid driven spool valve and a biased movable orifice member select the desired path. While the flow is substantially unrestricted during “up and down” movement, it is somewhat restricted for reduced speed during the “unfold” movement and is more restricted during the power-driven “fold” movement.
U.S. Pat. No. 5,320,135 issued to Pierrou on Jun. 14, 1994 discloses a flow compensator valve that is used in a hydraulic system which includes a cylindrical body having inlet and outlet ports, and a slidable spring-biased hollow piston insert disposed within a center bore of the body, which insert has a plurality of ports for flow control depending on the position of the insert as it reciprocates axially within the center bore of the valve body.
It is desirable to provide a hydraulic system with an improved bidirectional flow control valve to eliminate the disadvantages mentioned above. It is also desirable to provide an improved bidirectional flow control valve in which the hydraulic flow can be restricted in either direction of flow of the valve and the relative restricted flow rates may be the same or various.
SUMMARY OF THE INVENTION
The present invention is a bidirectional flow control valve used in a hydraulic system for regulating fluid flow in either direction through the valve and providing the same or various restricted flow rate at either direction of the flow through the valve. The valve comprises a housing, a slidable sleeve, two opposite springs, and two opposite cap nuts. The housing has a central bore and a sidewall with first ports located adjacent to one end and second ports located adjacent to the other end. The slidable sleeve is slidably disposed within the central bore of the housing and movable among a first position, an equilibrium position and a second position. The slidable sleeve has an interior wall disposed therein to form a first chamber and a second chamber. The interior wall has an axial port to permit flow of fluid theretlirough. The first spring is disposed within the first chamber of the slidable sleeve and constrained therein by the first cap nut or other suitable means. The second spring is received by the second chamber of the slidable sleeve and constrained therein by the second cap nut or other suitable means.
The slidable sleeve is initially positioned (without any flow pressure) in the equilibrium position within the valve housing which is not blocking both the first and second ports of the valve housing. When hydraulic fluid flows from the first ports to the second ports, the hydraulic fluid pressure in the first chamber of the valve is greater than in the second chamber, the slidable sleeve is biased by the fluid and the first spring moves toward the second position which in turn partially blocks the second ports and restricts the flow from the first chamber of the valve.
The slidable sleeve is automatically adjusted to the equilibrium position where forces applied on two opposite sides of the slidable sleeve are equal to each other due to the unique bidirectional valve. Specifically, as an example, while the slidable sleeve moves toward the second ports, it partially blocks the second ports and restricts the flow from the first chamber. The flow from the first chamber is more restricted if the second port openings are partially obstructed by further movement of the slidable sleeve. The flow pressure in the second chamber will build up to a certain level to automatically push the slidable sleeve back to the equilibrium position so as to maintain the second ports partially open to allow the restricted flow to exit therethrough. Even in the event that the slidable sleeve fully blocks the second ports, thereby preventing the hydraulic fluid from exiting the hollow housing, the slidable sleeve will still automatically move back to the equilibrium position by the second spring. In this way, the second ports are self-adjusting and maintained partially open to allow flow with certain restricted flow amount to exit therethrough. Reversed movements operate when the hydraulic fluid flows from the second ports to the first ports.
As one of the demonstratable embodiments of the invention, the bidirectional flow control valve is applied on one kind of electric-hydraulic controlled wheelchair lift which travels between a stowed position, an entry vehicle floor position and a ground landing position. The flow control valve is mounted in the hydraulic system to have a restricted flow rate during movements of the swing-up movement (from the floor position to the stowed position) and the swing-down movement (from the stowed position to the floor position). The first ports of the housing are connected to a hydraulic actuator means, such as a pump, and the second ports of the housing are connected to a hydraulic moving means, such as a cylinder. One unique feature is that by using the present invention bidirectional flow control valve, the restricted flow rate remains the same regardless of the load changes on the wheelchair lift which leads to many advantages.
The restricted flow rates from either direction of flow through the bidirectional flow control valve may be the same or different upon pre-selection or design and arrangements made in the dimensions
Chen Tony D.
Fong Jerry
Hepperle Stephen M.
Ricon Corporation
Rozsa Thomas I.
LandOfFree
Bidirectional flow control valve does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bidirectional flow control valve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bidirectional flow control valve will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2507462