Fluid handling – Systems – Sequentially closing and opening alternately seating flow...
Reexamination Certificate
1999-04-19
2001-09-25
Rivell, John (Department: 3753)
Fluid handling
Systems
Sequentially closing and opening alternately seating flow...
C137S596180
Reexamination Certificate
active
06293309
ABSTRACT:
The invention relates to a control valve apparatus, particularly to hydraulic directional control valves which in operation allows hydraulic fluid, usually oil, to perform a required function by shutting off one fluid port and opening another.
Such valves are often used in heavy machining, where components are required to be moved quickly, with consequent large momentum. Such valves therefore often find application in machinery such as a piling hammer. In such an application, switching of the control valve from one direction of flow to another is required to take place as quickly as possible in order to eliminate cavitation beneath a piston and to prevent a high pressure “spike” being generated on the other side of the piston by the large momentum of the moving parts. The control valve has to command the hammer to accelerate upwards, to retard it to zero velocity, and then to drop it under gravitational influence. These requirements have been previously achieved by passing metallic piston rings over open ports using a pair of piston rings, one to close and one to open. Generally this type of control valve works satisfactorily but it has the disadvantage in that eventually the metallic rings tend to break up, especially if no preventative maintenance is performed, and also to piston rings perform only a partial seal. Pieces of broken ring then migrate around the system until they finally end up in a filter of the system. In the process of such migration much consequential damage can be effected, leading to excessive downtime for repair and maintenance, which is expensive on time and equipment.
It is accordingly an object of the invention to seek to mitigate these disadvantages.
According to a first aspect of the invention there is provided a control valve apparatus providing reciprocal motion, comprising a spool and sleeve, a passage for fluid which is openable and closable by the spool and sleeve, ports for fluid, and at least one seal, the arrangement being such that a seat of one seal reacts with a seat of another seal, whereby to open the another seal.
Thus using the invention it is possible to provide substantially instantaneous switching, with no “overlapping” or “underlapping”.
There may be a seat device whereby the spool and sleeve are engageable for cutting off flow of fluid to the passage. This provides for substantially instantaneous cut-off of fluid particularly where the seat device may comprise a groove in the spool in which a nose of the sleeve may be received.
The groove and nose may have cooperable sealing surfaces. This seeks to obviate leakage, without requirement for additional seals.
The seating surfaces may be inclined surfaces. This provides for ease of construction, in that machining of the surfaces is relatively straightforward.
The spool may have a nose adapted for sealing cooperation with a seat of the seal, for cutting off fluid flow from the passage to a fluid port. This provides a relatively simple construction.
The seat of the seal and a nose of the spool may have cooperable inclined surfaces for effecting sealing. This again provides for relative ease of construction.
The ports may have relatively large cross-sectional are in relation to the fluid flow passage whereby to obviate building up of back fluid pressure. This seeks to ensure instantaneous operation.
There may be a low pressure port, a high pressure inlet port, and a pilot pressure inlet port. This arrangement provides for adequate control, particularly when the fluid may be a hydraulic fluid.
The sleeve may have a body, which body may have parts of different diameter, whereby a substantially constant (backward) force is applied to the sleeve, at system pressure. This provides for positive control, particularly when the spool may have a face exposed to hydraulic fluid which is of an area to provide substantially constant force to the spool in the forward direction, at system pressure.
The or each seal may be non-metallic. This arrangement can ensure that even in the event of failure, migration of valve apparatus seal ports will not cause damage to the apparatus as a whole, particularly when the or each seal may comprise a plastic material.
There may be separate seal(s) and port(s) whereby no port is scanned by any seal.
According to a second aspect of the invention there is provided valve apparatus as hereinbefore defined, in combination with a reciprocable device.
The reciprocable device may comprise a hydraulic piling hammer.
Control valve apparatus embodying the invention is hereinafter described, by way of example, with reference to the accompanying drawings.
REFERENCES:
patent: 3568571 (1971-03-01), Hoen et al.
patent: 3628571 (1971-12-01), Buchschlag et al.
patent: 5442992 (1995-08-01), Sanner et al.
Akerman & Senterfitt
Krishnamurthy Ramesh
Rivell John
Twinwood Engineering Ltd
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