Seal for a rotary valve for high temperature and high...

Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for a pipe – conduit – or cable

Reexamination Certificate

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Details

C277S616000, C277S435000, C277S637000, C277S652000, C277S946000, C251S314000, C251S317010

Reexamination Certificate

active

06398225

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an improved seal for a rotary valve for controlling the flow of fluids at high temperature and pressure. More particularly, the invention relates to an improved seal for a valve for use in a device for sterilizing dental tools known in that art as a “Harvey” sterilizer.
In the medical arts there is a continual need to sterilize surgical instruments. The Harvey sterilizer, in particular, was developed over 50 years ago for use in the art of sterilizing dental instruments, and is in common use today in substantially the same form. It is presently marketed by Barnstead/Thermolyne, of Dubuqe, Iowa, as the HARVEY CHEMICLAVE.
The Harvey sterilizer is similar to an autoclave, but employs higher temperatures and pressures for its sterilizing agent, typically a formaldehyde/alcohol solution. For example, the sterilizing chamber of the Harvey sterilizer employs temperatures and pressures of about 270 degrees Fahrenheit and about 28-30 p.s.i.g., as compared to about 250 degrees Fahrenheit and about 15 p.s.i.g. used in an autoclave.
The action of the Harvey sterilizer is critically dependent on that of a rotary valve described in Hendershot, U.S. Pat. No. 3,650,305, incorporated by reference herein in its entirety. Basically, the valve may be rotated to provide selectable fluid paths between various components of the sterilizer. Particularly, in a first limit position of the valve, a measuring or metering chamber is connected to a reservoir, for filling the metering chamber with a sterilizing agent, typically a formaldehyde/alcohol solution. A second limit position of the valve empties the measuring chamber into a sterilization chamber. A third, intermediate position of the valve vents the measuring chamber and a fourth intermediate position vents the sterilizing chamber.
The valve comprises a valve member and a valve body rotatably mounted inside the valve body. The valve member has a frusto-conical shape and is received by a similarly shaped aperture in the valve body. A coil spring presses the valve member into the valve body. The valve member includes a plurality of ports and internal passages connecting selected ports together. The valve body has a mating plurality of ports connected to the various structures mentioned above.
It is undesirable for hot, high pressure sterilizing fluid and vapor to leak between the ports, or between the ports and the atmosphere. To prevent this, the valve member has been treated to accept a coating of polytetrafluoroethylene (“PTFE”), and the coated surface is subsequently machined to high tolerance for mating to a particular, selected valve body. Manufacturing costs are high and degradation of the seal requires replacing the entire valve assembly.
Prior attempts to provide economical leak-proof sealing in a Harvey sterilizer valve have employed “O” rings, rubber or silicone seals around the ports. However, these leave space between the valve body and the valve member, permitting the unwanted transmission of hot liquid and vapor between the ports once the valve member is turned so that the ports are not aligned.
Accordingly, there is a need for an improved seal for a rotary valve for high temperature and high pressure fluids that provides for more economical manufacture and repair of the valve.
SUMMARY OF THE INVENTION
An improved seal for a rotary valve for high temperature and high pressure fluids according to the present invention solves the aforementioned problems and meets the aforementioned needs by providing a removable seal member adapted for disposition between a valve body and a valve member rotatably disposed in the valve body. The seal member is removably retained with respect to a selected one of the valve body and valve member, and has one or more apertures through a side-wall thereof corresponding to one or more ports associated with the selected one of the valve body and valve member.
In one aspect of the invention, the seal member is adapted so that pressure exerted thereon by the valve is sufficient to induce cold flow in the seal member, to better seal between the valve body and the valve member and to better absorb mechanical tolerances. Preferably, the seal member has a constant thickness, which is particularly advantageous in the Harvey sterilizer. Preferably as well, the seal member substantially fills the space between the valve body and the valve member, exclusive of its apertures.
In another aspect of the invention, the seal member is elongate and has two ends, and includes a pair of longitudinally disposed slots extending through the side-wall. Each slot extends from one of the ends and extends more than half-way across the elongate dimension of the seal member toward the other end and “overlaps” the other slot, as discerned when traveling circumferentially around the seal member.
Therefore, it is a principal object of the present invention to provide a novel and improved seal for a rotary valve for high temperature and high pressure fluids.
It is another object of the present invention to provide such a valve that provides for increased economy of manufacture.
It is still another object of the present invention to provide such a valve that provides for increased economy of repair.
It is yet another object of the present invention to provide such a valve that provides for improved leak resistance.
The foregoing and other objects, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the following drawings.


REFERENCES:
patent: 2183296 (1939-12-01), Marx
patent: 3650304 (1972-03-01), Hendershot
patent: 4073308 (1978-02-01), Smith
patent: 4365646 (1982-12-01), Sandling
patent: 4410003 (1983-10-01), Sandling
patent: 4478388 (1984-10-01), George
patent: 4494730 (1985-01-01), George
patent: 4564044 (1986-01-01), Biller et al.
patent: 4711264 (1987-12-01), Medvid
patent: 5901944 (1999-05-01), Ramakrishnan

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