Fluid handling – With repair – tapping – assembly – or disassembly means – Assembling or disassembling reciprocating valve
Reexamination Certificate
2000-03-27
2001-08-28
Walton, George L. (Department: 3753)
Fluid handling
With repair, tapping, assembly, or disassembly means
Assembling or disassembling reciprocating valve
C137S312000, C137S614180, C137S614190, C257S324000, C257S900000
Reexamination Certificate
active
06279602
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve with an improved piston with an elastomer O-ring intended in particular for the agrifoods and sanitation industries.
2. Description of the Prior Art
Valves for use in the above industries must be designed to avoid all risk of pollution of the liquid passing through the valves by bacteria that can grow within the valves.
Some prior art valves include a piston moving inside a cylindrical seat, the piston being fastened to an operating rod running along the axis of the cylindrical seat and the perimeter of the piston carrying an elastomer O-ring providing the seal between the piston and the cylindrical seat.
In the above type of valve, the elastomer O-ring is a force fit in a trapezoidal cross section groove in the piston. This arrangement has many disadvantages.
The most important of these disadvantages is that the product passing through the valve may become trapped between the groove and the O-ring, which can encourage the growth of bacteria.
Bacteria can also grow to the rear of the O-ring if it is defective (mechanically, chemically, thermally or otherwise).
The object of the present invention is to provide a piston type valve which does not have the above disadvantages and which has advantages of its own.
SUMMARY OF THE INVENTION
The invention therefore provides a piston type valve including a piston moving in a cylindrical seat, wherein the piston is fastened to an operating rod extending along the axis of the cylindrical seat, the perimeter of the piston carries an elastomer O-ring providing the seal between the piston and the cylindrical seat, the piston includes two piston members fixed axially together by clamping means, each of the two members includes an annular groove of substantially circular arc shaped cross section open toward the groove on the other member, and the elastomer O-ring is housed between the two annular grooves and clamped between them by the clamping means.
The O-ring, positioned between the two annular grooves, is deformed when the two piston members move toward each other and is therefore crushed into a shape complementary to the shape of the grooves.
Accordingly, when the two piston members are clamped together, the O-ring completely fills the two facing grooves. The O-ring can also deform radially inward and radially outward relative to the grooves.
This eliminates the risk of the product penetrating between the O-ring and the piston.
All risk of the growth of bacteria is therefore avoided, through leaving no empty space between the respective surfaces of the O-ring and the annular grooves, so making a perfect seal between the O-ring and said grooves; the seal between the piston and the seat is also improved.
In an advantageous version of the invention, a space remains between the two facing surfaces of said two piston members into which said O-ring can deform after fitting said O-ring and clamping said two piston members together.
The two piston members are preferably fixed axially together by a threaded rod carried by one of the members and screwed into a screwthread in the other member.
The two piston members are preferably clamped together sufficiently for the O-ring to become deformed and to project toward the empty space and toward the outside of the periphery of the two piston members so as to be pressed in a sealed manner against the cylindrical seat.
In an advantageous version of the invention, each edge connecting each annular groove and the adjacent surface of the corresponding piston member has a substantially rounded shape.
Accordingly, when the two piston members are clamped together, the O-ring is deformed and therefore crushed to provide a perfect seal not only at each of the grooves but also at the edges connecting each annular groove to the adjacent surface of the corresponding piston member.
The pressure of the O-ring against the cylindrical seat can therefore be adjusted to obtain the optimum conditions of sealing, of rubbing of the O-ring on the seat, of ease of operation and of reduced wear of the O-ring.
In a preferred version of the invention, the piston member opposite that carrying the operating rod carries a hollow rod whose interior communicates with the empty space between the two facing surfaces of the two piston members via at least one opening.
Thus in the case of a defective O-ring or a leak, the product passing through the valve can enter the space between the two piston members and from there the interior of the hollow rod so that it can be evacuated to the exterior.
There is therefore no risk of bacteria growing to the rear of the O-ring in the event of a leak.
Other features and advantages of the invention will become apparent in the course of the following description.
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patent: 3828815 (1974-08-01), Botnick
patent: 4037753 (1977-07-01), Brandau
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patent: 4373545 (1983-02-01), Knappe
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patent: 5699825 (1997-12-01), Norton
patent: 6009896 (2000-01-01), Van Oosten
patent: 2818787 (1979-11-01), None
patent: 247589 (1926-06-01), None
Bonnefous Jean
Maraud Bruns
Bachman & LaPointe P.C.
Defontaine
Walton George L.
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