Patent Application
20060125236
This invention relates to retainers used with mechanical pipe couplings which effect a strong, reliable joint with a fluid-tight seal without the need for brazing or soldering.
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.
There are standard pipe fittings such as elbows (45° and 90°), tees and straight segments matched for use with standard tube diameters. 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 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.
The soldered joint is used to a great extent for pipe couplings. This 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 (especially 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 upon cooling and solidifying forms the solder joint. Excess flux is removed from the outer surfaces to prevent further acid etching of the pipe near the 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, as well as a personal burn 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 may comprise a housing having a socket for receiving the pipe end. Adjacent to the socket is an expanded region which accommodates components such as an elastomeric seal for sealing purposes, an annular retainer interposed between the outer diameter of the pipe end and the inner diameter of the coupling to mechanically hold the parts together, a washer positioned between the seal and the retainer and a support collar positioned between the retainer and the opening of the housing. The support collar, in conjunction with the socket, provides a two point support for the pipe end and augments the bending stiffness of the coupling. The washer prevents the seal from being displaced into the retainer under hydraulic pressure. Without the washer, the seal may ride up on the retainer teeth, unseat itself from the pipe end , and form a leak path within the coupling.
The retainer may have a band from which teeth extend radially inwardly to dig into the surface of the pipe end to resist extraction of the pipe end from the coupling after engagement. In such a coupling, the washer and the band have diameters that are close in size, and it is found that the washer may be forced within the band by pressure placed upon the washer by the seal as it deforms when a pipe end is engaged within the coupling or by the hydraulic pressure of the fluid within the pipe. If the washer “telescopes” into the retainer band then the seal is not properly confined within the housing and may lose its preload against the pipe and the housing, resulting in a leaky joint.
It is clearly advantageous to develop a retainer for a coupling wherein the telescoping of the washer into the retainer is prevented so as to maintain the fluid tight integrity of the joint.
The invention concerns a retainer positionable within a pipe coupling for retaining a pipe end within the coupling. The retainer comprises a circumferential band surrounding a central axis and having an outwardly facing surface engageable with an inwardly facing surface of the pipe coupling. The band has first and second edges oppositely disposed. A plurality of teeth are attached to the first edge of the band and project inwardly. The teeth are angularly oriented toward the second edge of the band and are engageable with the pipe positioned coaxially within the band. A plurality of projections are positioned along the second edge of the band. The projections are arranged in spaced apart relation and project inwardly toward the central axis.
Preferably, each projection is formed from an indentation in the outwardly facing surface of the band. The projections are preferably spaced around the band at equal angular intervals.
In alternate embodiments, the retainer may comprise a band having first and second oppositely disposed ends wherein teeth extend from the first end and a substantially continuous projection extends circumferentially around the second end of the band and projects inwardly toward the central axis; or, the retainer may comprise a band having first and second opposite ends wherein the teeth extend from the first end and the second end has a smaller diameter than the first end.
The invention also includes a coupling assembly for receiving an end of a pipe. The coupling assembly comprises a housing having a socket for receiving one of the pipe ends and an expanded region positioned adjacent to the socket. A seal is positioned within the expanded region adjacent to the socket. The seal is sealingly engageable with the housing and the pipe. A washer is positioned within the expanded region adjacent to the seal. The washer has an outer perimeter engaged with the housing. An annular retainer is positioned within the expanded region adjacent to the washer. The retainer comprises a circumferential band surrounding a central axis and having an outwardly facing surface engaged with the housing within the expanded region. The band has first and second edges oppositely disposed. A plurality of teeth project angularly inwardly from the first edge toward a peripheral surface portion of the pipe. The teeth are engageable with the peripheral surface portion of the pipe positioned coaxially within the housing. A plurality of projections are positioned along the second edge of the band. The projections are arranged in space apart relation and project inwardly toward the central axis. The washer engages the seal, the projections engage the washer and prevent any portion of the washer from moving into the band when the seal is subject to pressure within the housing. The projections also prevent the retainer from being forced over the washer when the pipe end is inserted into the coupling. The pipe end interacts with the retainer teeth and tends to force the retainer against the washer as it is inserted into the coupling.
In alternate embodiments of the coupling assembly, the retainer may have a substantially continuous circumferential projection or an end having a smaller diameter as described above.
As best shown in
Preferably, the projections 26 are formed by an indentation 28 in the outwardly facing surface 14 of the band 12. Indentations 28 preferably extend in a direction from the free edge 20 toward the leading edge 18, but only traverse between about ⅓ to ⅔ of the width of the band. Preferably, the depth of the indentation is about three times the thickness 30 of the band.
The retainer is preferably made from durable, corrosion-resistant metals such as stainless steel, and thus, the indentations 28 may be readily formed by application of a punch to the band. The band thickness will vary according to the size of the retainer with large diameter bands having greater thickness than smaller diameter bands. A maximum band thickness of about 0.020 inches is preferred to facilitate the incorporation of indentations 28.
As shown in
When seal 42, which is substantially incompressible, is subjected to pressure, for example, outward radial pressure from contact with pipe end 34 and hydraulic pressure from fluid within the pipe and coupling, it will tend to expand longitudinally and force the washer 46 into contact with the free edge 20 of retainer 10. The pressure exerted on the washer 46 by the seal 42 may be great enough to force the washer coaxially into the band 12. This condition is undesirable as it will tend to relieve the pressure between the pipe end 34 and the seal 42 as well as between the housing 36 and the seal. If the pressure on seal 42 is relaxed then it will tend to leak at a lower pressure. The inwardly oriented projections 26 positioned along free edge 20 engage the washer 46 and prevent the washer from “telescoping” coaxially into the band 12 and thereby maintain the pressure on the seal to ensure a fluid tight joint between the coupling housing 36 and the pipe 34. The projections 26 also prevent a portion of the washer 46 from being forced into the retainer. In the absence of projections, this may happen when the washer and the retainer are positioned eccentrically to one another within the coupling housing, as can occur due to varying manufacturing tolerances between the parts. With the eccentric positioning, a portion of the washer perimeter will not be supported by the free edge 20 of band 12, and thus, when the washer is subjected to pressure from the seal 42, the washer 46 may tend to rotate or bend and its unsupported portion may be forced into the retainer. With projections 26, however, there is always adequate support of the washer perimeter to prevent its entry into the retainer 10 regardless of the relative eccentricity between the washer and the retainer due to manufacturing tolerances.
Teeth 22, arranged around the leading edge 18 of band 12, project inwardly and engage the peripheral surface portion 54 of the pipe end 34. Because they are angularly oriented to slope toward the free edge 20 and are biased into engagement with pipe 34, the teeth allow the pipe to be inserted through opening 50 and into socket 38, but prevent extraction of the pipe end from the housing. The retaining action of teeth 22 may be augmented by the use of circumferential grooves 56 in the pipe end 34 as shown in
In yet another embodiment shown in
In another embodiment of a retainer 74, shown in
Couplings according to the invention provide a mechanical pipe coupling which can form a reliable fluid-tight joint without the hazards associated with brazing, welding or soldering. Use of the retainer ensures a reliable joint with a fluid tight seal that will not allow the seal to relax and thereby withstand relatively higher pressures.
