Pipe joints or couplings – Flexible joint – rigid members – Bellows
Reexamination Certificate
1999-03-12
2001-05-22
Nicholson, Eric K. (Department: 3627)
Pipe joints or couplings
Flexible joint, rigid members
Bellows
C285S299000
Reexamination Certificate
active
06234542
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to fluid piping systems. More particularly, this invention pertains to expansion joints for relieving heat expansion stress in a fluid piping system.
It will be appreciated by those of skill in the art that fluid piping systems designed to transport fluids in settings such as dialysis clinics, research laboratories, certain manufacturing facilities and food processing plants must be periodically disinfected.
The prior art fluid piping systems, with multiple solvent-welded joints and cavities which are relatively inaccessible for disinfection provide a suitable environment for growth of a number of pathogenic microorganisms, such as Pseudomonas species. The inventors have described, in U.S. patent application Ser. No. 09/206,904, for a “System for Fluid Delivery in a Dialysis Clinic,” filed Dec. 7, 1998, the details of which are incorporated herein by reference, a novel fluid piping system which minimizes the recessed surfaces where bacteria may freely grow. However, since Pseudomonas, particularly, can grow along internal surfaces of a tube filled with sterile water, periodic disinfection of the piping system is required.
Currently, disinfection of fluid piping systems in health care clinics, particularly dialysis clinics, utilizes a combination of chemical and high temperature disinfection means. The high temperatures required for heat disinfection of conventional systems place considerable expansion stress on the piping systems. Chemical disinfectants are therefore used to allow heat disinfection temperatures to be decreased.
Chemical disinfectants, however, provide an added risk to patients in a dialysis clinic. Formaldehyde, for example, may cross dialysis membranes to enter the patient's bloodstream and stimulate antibodies to the patient's own DNA. Therefore, a more acceptable disinfection program would provide disinfection using heat alone.
What is needed, then, is a component for a fluid piping system that would facilitate heat disinfection by reducing expansion stress within a fluid piping system exposed to high temperatures for prolonged periods of time and capable of repeated cycling without compromising the integrity of the expansion compensating component.
SUMMARY OF THE INVENTION
An expansion joint is provided for connecting pipes in a fluid piping system. The expansion joint is particularly designed to reduce heat expansion stress in a fluid piping system.
The expansion joint includes a cylindrical bellows connected between pipes in the fluid piping system. Also included is a sheath enclosing the cylindrical bellows. During heat disinfection, distortion of the cylindrical bellows is limited by the sheath, while the lack of fixed attachment of the sheath allows the couplings connecting the expansion joint to the adjacent pipes in the fluid piping system to freely slide towards each other as the pipes expand due to heat expansion.
The cylindrical bellows is preferably formed of corrugated polymer tubing. In a preferred embodiment of the invention, the bellows is formed of a corrugated polytetrafluoroethylene tube that is stable at a temperature of 105 degrees Celsius applied for a period of at least 20 hours.
Couplings at the ends of the corrugated bellows provide connectors for attachment to complementary couplings at the ends of adjacent pipes in the fluid piping system.
In a preferred embodiment, the couplings allow replacement of the expansion joint, most preferably by providing threaded connections that can be easily installed and removed.
Installation of the removable sheath is accomplished by fitting the sheath over the length of the corrugated bellows and adjacent couplings, facilitated by a lengthwise split in the sheath. The sheath is preferably formed of polymer tubing.
An object of the present invention is to provide a means to reduce heat expansion stress in a fluid piping system. Another object of the invention is to provide a component of a fluid piping system which facilitates the use of high temperatures for prolonged periods of time during heat disinfection.
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Brochure entitled “Quadra-Side High Pressure Expansion Compensators” (undated, but admitted to be prior art).
Peterson Michael J.
Russell Richard M.
Dialysis Systems, Inc.
Nicholson Eric K.
Waddey & Patterson
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