Pipe joints or couplings – Essential catch – Leaf spring
Reexamination Certificate
2000-07-18
2002-12-31
Binda, Greg (Department: 3679)
Pipe joints or couplings
Essential catch
Leaf spring
C285S340000
Reexamination Certificate
active
06499771
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to couplings for pipes and especially to couplings which effect a strong, reliable joint with a fluid-tight seal without the need for brazing or soldering.
BACKGROUND OF THE INVENTION
The construction of piping networks requires couplings that can form fluid-tight joints between pipe ends which can withstand external mechanical forces, as well as internal fluid pressure and reliably maintain the integrity of the joint. Many forms of joints are known, such as brazed or soldered joints, threaded joints, welded joints and joints effected by mechanical means.
For example, copper tubing, which is used extensively throughout the world to provide water service in homes, businesses and industry, is typically joined by means of couplings which are soldered to the pipe ends to effect a connection.
The use of copper tubing for piping networks is so widespread that standard tubing sizes have been established in various countries. For example, in the U.S., there is the ASTM Standard entitled “Specification B88-99e1 Standard Specification for Seamless Copper Water Tube” copyright 2001, in Germany, the DIN Standard and in the United Kingdom, the British Standard (BS) both of which are defined by the European Standard EN 1057, dated April, 1996 and entitled “Copper and Copper Alloys—Seamless, Round Copper Tubes For Water and Gas in Sanitary and Heating Applications”. Chart 1 below shows a portion of the range of outer diameters of the various standard copper tubes listed above.
CHART 1
Standard Outer Copper Tube Outer Diameters
ASTM
DIN
BS
½″
15 mm
15 mm
¾″
22 mm
22 mm
1″
28 mm
28 mm
1.25″
35 mm
35 mm
1.5″
42 mm
42 mm
2″
54 mm
54 mm
Naturally, there are standard pipe fittings such as elbows (45° and 90°), tees and straight segments matched for use with the standard tube diameters. These standard fittings are defined in the U.S. by ASME/Standard B16.22a-1998, Addenda to ASME B16.22-1995, entitled “Wrought Copper and Copper Alloy Solder Joint Pressure Fittings”, dated 1998. In Europe, the standard fittings are defined by EN 1254, dated Jul. 15, 1998 and entitled “Copper and Copper Alloys—Plumbing Fittings—Part 1 Fittings With Ends for Capilary Soldering or Capilary Brazing to Copper Tubes”. The standard fittings have open ends with inner diameters sized to accept the outer diameter of a particular standard tube in mating contact for effecting a soldered joint.
In addition to the standard fittings described above, other components, such as valves, strainers, adapters, flow measurement devices, and other components which may be found in a pipe network will have a coupling which is compatible with the standard pipe, and it is understood that the term “coupling”, when used herein, is not limited to a standard elbow, tee, or other fitting but includes the open end of any component useable in a piping network which serves to couple the component to the pipe end.
A soldered joint is effected between a standard diameter tube end and its associated standard fitting by first cleaning the surfaces to be joined, typically with an abrasive such as a wire brush or steel wool, to remove any contaminants and the oxide layer which forms on the surfaces. Next, the cleaned surfaces are coated with a flux material, usually an acid flux, which further disrupts the oxide layer (when heated) and permits metal to metal contact between the fitting, the pipe end and the solder. The pipe end is next mated with the fitting thereby bringing the cleaned, flux coated surfaces into contact. The fitting and pipe end are then heated to the melting temperature of the solder, and the solder is applied to the interface between the tube and the fitting. The solder melts, flows between the surfaces of the pipe end and the fitting via capillary action and forms the solder joint.
While the soldered joint provides a strong, fluid-tight connection between pipe end and fitting, it has several disadvantages. Many steps are required to make the soldered joint, thus, it is a time consuming and labor intensive operation. Some skill is required to obtain a quality, fluid-tight joint. Furthermore, the solder often contains lead, and the flux, when heated, can give off noxious fumes, thus, exposing the worker to hazardous substances which can adversely affect health over time. The joint is typically heated with an open gas flame which can pose a fire hazard.
To overcome these disadvantages, many attempts have been made to create mechanical couplings which do not require solder or flame to effect a strong, fluid-tight joint. Such mechanical couplings often use an over-sized opening accommodating an O-ring for sealing purposes and an annular ring interposed between the outer diameter of the pipe end and the inner diameter of the coupling to mechanically hold the parts together. The annular ring often has radially extending teeth which dig into the facing surfaces of the coupling and the pipe end to resist extraction of the pipe end from the coupling after engagement.
While these mechanical couplings avoid the above identified problems associated with soldered joints, they can suffer from one or more of the following disadvantages. The annular ring may not provide adequate pull-out strength, and the pipe end could be inadvertently separated from the coupling, for example, during thermal contraction of a long run made of several segments of mechanically coupled pipes. If both ends of the pipe run are fixed the thermal contraction will put significant tension loads on each joint, tending to pull them apart. If the pipes carry water and the water in the pipe freezes, the expansion of the water upon freezing will also put significant tensile load on the mechanical joints. Pressure spikes within the pipe, caused by a sudden closing of a valve (the “water hammer effect”) also place the joints under tension, and could lead to a joint failure.
The annular ring also does not help keep the pipe end concentric with the coupling upon insertion, allowing the pipe end to tip and deform the annular ring and gouge the inside surface of the coupling or an elastomeric seal, such as an O-ring. The annular ring cannot be relied upon to provide electrical continuity between the pipe end and the coupling, sometimes resulting in a relatively poor ground for electrical purposes. In such a joint, there is furthermore little or no resistance to axial rotation of the pipe relatively to the coupling (i.e., relative rotation of the pipe and coupling about the longitudinal axis of the pipe). Thus, valves or other items mounted on the pipe will tend to rotate. Use of an enlarged section to accommodate the annular ring may cause energy loss impeding fluid flow if the fluid is forced to flow into a coupling having a larger cross-sectional area. In general, when mechanical couplings are designed to overcome the aforementioned inherent disadvantages, they tend to suffer from a high part count, making them relatively complex and expensive.
SUMMARY AND OBJECTS OF THE INVENTION
The invention concerns a coupling for engaging a pipe end without the use of solder. The coupling comprises a first receptacle, preferably cylindrical in shape for receiving the pipe end, and a second receptacle, also preferably cylindrical, arranged coaxially and in tandem with the first receptacle. The second receptacle is smaller than the first receptacle so as to form a shoulder within the coupling between the first and second receptacles.
The coupling also includes a retainer having a perimetrical surface, preferably cylindrical and positioned within and coaxial with the first receptacle. Locking teeth are positioned circumferentially around the retainer and project from the perimetrical surface, the locking teeth being engageable with the first receptacle and the pipe end to resist removal of the pipe end from the coupling.
An elastomeric seal, for example an O-ring, is positioned coaxially within the first receptacle between the shoulder and the retainer and effects a fluid-tight seal between the pipe end and
Dole Douglas R.
Snyder, Sr. Ronald R.
Thau, Jr. Lawrence W.
Wilk, Jr. Charles E.
Binda Greg
Synnestvedt & Lechner LLP
Victaulic Company of America
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