Patent Application
20080169647
1. Field of the Invention
A pipe coupling assembly connects a first pipe to a second pipe.
2. Description of the Prior Art
Current methods for joining components of fluid handling systems, such as air conditioning systems, typically use fittings with elastomeric seals, such as o-rings or seal washers, to contain the fluid. Elastomeric seals work well in applications of moderate temperature and pressure condition and where some small amount of leakage or permeation of the refrigerant or working fluid is tolerable. The fittings themselves are often machined and brazed or welded to the pipes, adding another potential leak location. Some fittings form the pipe itself to create the surface on which the seal is located.
In applications where temperatures or pressures become extreme however, elastomeric seal properties degrade or exhibit excessive fluid/refrigerant emission. One such application, for example, is an air conditioning (A/C) system utilizing CO2 as the refrigerant. The CO2 A/C system typically has refrigerant temperatures exceeding 300 degrees F. and pressures exceeding 2000 PSIG. These conditions exceed the capabilities of elastomeric seals.
Currently, applications involving high temperature or pressure sometimes use a flared pipe style fitting or ferrule type fitting to provide a metal-to-metal seal. Both of these designs typically involve the plastic deformation of the pipe seal surface resulting in a one-time-use connection.
Examples of pipe fittings include U.S. Pat. No. 5,332,267 to Harrison, U.S. Pat. No. 5,362,229 to Yamaga, U.S. Pat. No. 4,928,998 to Brandener, and U.S. Pat. No. 4,343,499 to Dumar, Jr. et al.
Brandener, Harrison and Dumar all disclose a coupling assembly for connecting two pipes in which the second pipe forms the coupling having a spherical outer surface. This adds costs due to the requirement of manufacturing two different pipe ends.
The Harrison patent teaches a pipe coupling assembly for connecting a first pipe having a socket to a second pipe. The end of the second pipe is spherical and has a flow passage with a diameter slightly less than the diameter of the pipe to accommodate misaligning. The second pipe forms the coupling and is inserted into the first pipe and a clamping mechanism is disposed over the pipes. A ferrule is disposed between the first pipe and the clamping mechanism forming two contact areas in order to deform the socket of the first pipe to contact the surface of the second pipe. Initial contact of the flared surface of the first pipe and the spherical surface of the second pipe is along a line of contact, as distinguished from surface contact. However, the clamping mechanism compresses on the first pipe forcing the flared surface of the first pipe to conform about the line of contact and into the spherical surface of the second pipe to increase the contact from the line to a sealing land of definitive width, i.e., a band of contact.
The Yamaga patent discloses a pipe coupling assembly including a first pipe having a socket and a second pipe having a spherical-shaped end and a flow passage. The second pipe forms the coupling and is inserted into the socket of the first pipe and secured using a clamping mechanism. An o-ring in conjunction with a groove on the socket of the first pipe forms a seal between the first pipe and the second pipe.
Although the prior art provides a coupling assembly having sealing capabilities, there remains a need for a coupling assembly able to align itself with a pipe. More specifically, there is a need for an assembly is able to be aligned with two identical pipes, thus requiring a minimum number of components, while simultaneously providing unrestricted flow through the assembly.
The invention provides for a first pipe and a second pipe each having an end extending radially outwardly into a hemispherical socket. An insert having a bulbous shape engages the sockets of the pipes and defines a flow passage extending along an axis between the pipes. A clamping mechanism is disposed about the pipes for holding the sockets into engagement with the insert. The insert has a first neck extending axially around the flow passage and fitting into the first pipe and a second neck extending axially around the flow passage and fitting into the second pipe for substantially aligning the pipes with the axis.
The present invention overcomes the shortcomings of relying on elastomeric seals and also allows re-use by creating a unique metal-to-metal seal geometry staying within the metal's elastic limits. Furthermore, the invention does not require threaded parts or o-rings. Also, because the ends of each pipe can be identical, it reduces manufacturing costs by allowing for the use of identical pipe ends as well as a minimum number of components. Moreover, the invention self aligns the insert with the two pipes while allowing for small movement between the two pipes within the elastic limit of the insert material. Additionally, the assembly provides unrestricted flow therethrough by providing a substantially uniform diameter, and thus cross-sectional area, between the pipes and the insert.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a pipe coupling assembly is generally shown.
A first pipe 20 has an end which extends radially outwardly into an enlarged first collar 22 and then into a first hemispherical socket 24 having a first socket radius RS1. A second pipe 26 has an end which extends radially outwardly into an enlarged second collar 28 and then into a second hemispherical socket 30 having a second socket radius RS2. In one embodiment, the first and second pipes 20, 26 are identical in shape and size to one another and the first and second sockets 24, 30 are identical in shape and size, i.e., the first socket radius RS1 is equal to the second socket radius RS2. Similarly, the first and second collars 22, 28 are identical in shape and size to one another, thus requiring one tool to form the sockets 24, 30 on each pipe, lowering the cost of manufacturing the assembly.
The assembly includes an insert 32, generally indicated, having a bulbous, or nearly spherical shape, e.g., an apple shape, for engaging the sockets 24, 30 of the pipes 20, 26. The insert 32 is bulbous to accommodate some misalignment of the insert 32 relative to the pipes 20, 26 without changing the contact area or, more importantly, the sealing function.
The insert 32 defines a flow passage 34 extending along an axis A A between the pipes 20, 26. The insert 32 has a center diameter d d about the axis A A with a first hemisphere 36 having a first insert radius RI1 on one side of the diameter d d and a second hemisphere 38 having a second insert radius RI2 on the other side of the diameter d d. In one embodiment, the first insert radius RI1 is equal to the second insert radius RI2.
The first socket radius RS1 is greater than the first insert radius RI1 and the second socket radius RS2 is greater than the second insert radius RI2 such that insertion of each of the hemispheres 36, 38 of the insert 32 into each of the respective sockets 24, 30 forms a circular contact line between each of the sockets 24, 30 and the insert 32, e.g., a latitude line. The difference between each socket radius RS1, RS2 and the corresponding insert 32 radius RI1, RI2 directly depends on the elastic limit of the materials used. If the materials of the insert 32 and the pipes 20, 26 have higher elastic limits the difference between the radii may be greater. Similarly, if the materials have lower elastic limits, the difference between the radii must be smaller to avoid plastic deformation.
A clamping mechanism 40, generally indicated, is disposed about the pipes 20, 26 for holding the sockets 24, 30 into engagement with the insert 32. The clamping mechanism 40 includes a first block 42 disposed about the first pipe 20 and a second block 44 disposed about the second pipe 26. Each of the blocks 42, 44 includes a clamping ring 46 extending circumferentially about the clamping portion 48 and defining a plurality of holes 50 extending axially.
Each of the blocks 42, 44 of the clamping mechanism 40 includes a throat portion 52 having a diameter d smaller than the collars 22, 28 and axially engaging one of the collars 22, 28 and a spherical clamping portion 48 extending from the throat portion 52 and about one of the sockets 24, 30. The throat portion 52 and the spherical clamping portion 48 of each block profile each of the pipes 20, 26 leaving a small space between the throat portion 52 of the blocks 42, 44 and the collars 22, 28 of the pipes 20, 26 in order to evenly transfer the load from the clamping mechanism 40 to the perimeter of the sockets 24, 30 of the pipes 20, 26. Each of the blocks 42, 44 defines an annular recess 54 extending axially thereinto between the clamping portion 48 and the clamping ring 46 for allowing a small amount of movement of the clamping ring 46 relative to the throat portion 52.
The clamping mechanism 40 includes a plurality of bolts 56 disposed in the holes 50 in the clamping ring 46 of the blocks 42, 44 for clamping the first block 42 to the second block 44. The bolts 56 move the sockets 24, 30 into engagement with the insert 32 along the line contact between each of the hemispheres 36, 38 and each of the sockets 24, 30 as the blocks 42, 44 are moved together. In theory, the geometry of the contact area remains a line while the blocks 42, 44 move together, however, in practice, the surface of the insert 32 is matched closely to that of the pipe so that it produces a contact band, with the highest load at the center, due to elastic deformation of the pipe and the insert 32 adjacent to this line of contact.
A layer of polymeric material may be disposed on the hemispheres 36, 38 of the insert 32 for forming a seal between the insert 32 and the sockets 24, 30 by filling surface imperfections in the insert 32 and the sockets 24, 30. The polymeric material may be coated on the surface of the insert 32 or the insert 32 may be impregnated with the polymeric material.
The assembly is distinguished by the insert 32 having a first neck 58 extending axially around the flow passage 34 and terminating in a chamfered end and a second neck 60 extending axially around the flow passage 34 and terminating in a chamfered end. The first neck 58 fits with loose clearance into the first collar 22 of the first pipe 20 and the second neck 60 fits with loose clearance into the second collar 28 of the second pipe 26 to substantially align the pipes 20, 26 with the axis A. A small space is provided between the chamfered ends of the necks 58, 60 and each of the collars 22, 28.
Although the first and second necks 58, 60 may be inserted into the first and second pipes 20, 26 respectively, the necks 58, 60 are preferably inserted into the first and second collars 22, 28 so that the inside diameters d of the pipes 20, 26 are substantially equal to the diameter d of the flow passage 34, thus creating unrestricted flow through the assembly.
As shown in
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
