Valves and valve actuation – Fluid actuated or retarded – Flexible wall expansible chamber reciprocating valve actuator
Patent
1996-03-06
1997-01-14
Lee, Kevin
Valves and valve actuation
Fluid actuated or retarded
Flexible wall expansible chamber reciprocating valve actuator
251331, 251359, F16K 712
Patent
active
055931308
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a valve of the type that employs a flexible membrane to close or open the valve, particularly a valve that is included in fluid networks for handling various types of fluids, gaseous as well as liquid.
A known type of membrane valve consists of a valve body and a flexible membrane. Two liquid flow channels formed in the surface of the valve body are separated by a land portion, or valve seat, having a contact surface for the membrane, which can be actuated so that the membrane surface in a first position sealingly contacts the land portion to block the flow between the two channels, and in a second position is spaced from the land portion to allow liquid flow between the channels.
In U.S. Pat. No. 4,304,257 the land portion is flat and coincident with the rest of the surface of the valve body, and the membrane is flexed mechanically between the two positions by means of a solenoid operated rod member attached to the membrane, and more particularly such that the membrane in the state of rest contacts the land portion and to open the valve is pulled downwardly into an aperture below the membrane.
This valve has several disadvantages. In addition to the mechanical solenoid operation of the membrane being relatively complicated and requiring sensitive adjustment, the membrane is subjected to great stresses with the risk of permanent stretch. Further, liquid flow through the valve does not take place directly when the membrane is withdrawn from the land portion, but the void formed must first be filled with liquid, which causes a prolonged valve opening time.
Developments of the above described valve where several of the mentioned drawbacks are overcome are described in U.S. Pat. Nos. 4,848,722, 4,852,851 and 4,858,883. First of all, the mechanical actuation of the membrane is replaced by a considerably simpler pneumatic actuation in all these valve constructions.
Further, in the construction according to U.S. Pat. No. 4,848,722, the land portion is replaced by a spherically concave recess in the valve body, in which recess the two flow channels terminate. By virtue of such a concave contact surface for the membrane, the sealing area is maximised and the stresses on the membrane are reduced as membrane wrinkles and sharp membrane bends are avoided. The enlarged contact area is, however, disadvantageous in that it makes the valve opening slower.
The valve construction according to U.S. Pat. No. 4,858,883 is therefore provided with a groove or a channel in the bottom of the concave recess, which channel in the closed position of the valve is also sealed by the membrane, but which when the valve is opening is rapidly uncovered by the membrane to connect the two flow channels so that liquid flow is allowed almost immediately and before a larger gap or void has been created between the membrane and the valve seat. Hereby, the response time of the valve is reduced to a considerable extent.
U.S. Pat. No. 4,852,851 describes a similar construction in which, however, a reduced continuous flow is maintained through the valve by means of a flow through channel formed in the concave surface and having such a depth that it can not be sealed by the membrane.
The present invention relates to a further improved valve construction of the above-mentioned type which provides for better sealing with low actuating pressure, quicker valve opening and valve closing, more reproducible control of the valve position states, and minimised material fatigue of the valve membrane as well as of the valve seat.
According to a basic concept of the invention, this is accomplished by a membrane valve of the mentioned pneumatic type where the valve seat surface is divided into a, preferably smaller, primary sealing surface, or top sealing surface, and a, preferably larger, secondary sealing surface, so that opening and closing, respectively, of the valve takes place in two steps, and more particularly such that when the valve is closing, the membrane first rapidly seals against the top sealing surface, and then pr
REFERENCES:
patent: 4304257 (1981-12-01), Webster
patent: 4848722 (1989-07-01), Webster
patent: 4852851 (1989-08-01), Webster
patent: 5203368 (1993-04-01), Barstow et al.
patent: 5313264 (1994-05-01), Ivarsson et al.
patent: 5496009 (1996-03-01), Farrell et al.
Hansson Thord
Sjolander Stefan
Lee Kevin
Pharmacia Biosensor AB
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