PLAIN END COUPLING

Priority Data and Incorporation By Reference

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 60/864,096, filed November 2, 2006 and to U.S. Provisional Application No. 60/948,741, filed July 10, 2007, each of which is incorporated by reference in their entirety. Technical Field

[0002] The present invention relates generally to the field of pipe couplings and the construction thereof. More specifically, the present invention relates to preferably rigid couplings for plain end or beveled pipe. The present invention provides a gripper element with a preferred geometry that can substantially prevent the relative movement between two coupled pipe elements and provides a coupling with a sealing performance that exceeds known couplings.

Background of the Invention [0003] Known pipe couplings for plain end or beveled pipes include a two piece housing that is disposed over the axially aligned ends of the two pipes to be joined. Within a central chamber of the housing is a gasket element to provide a fluid tight seal over the pipe end to pipe end junction. The gasket element is generally an annular elastomeric element having an inner circumferential surface that, when in use, circumscribes each pipe end to form a fluid tight seal between the pipe end and form a fluid tight pipe joint. The gasket is generally dimensioned to provide an expansion gap between the pipe ends thereby allowing for slight axial misalignment between pipe elements.

[0004] The housing elements of known pipe couplings further include lateral chambers disposed about the central gasket chamber. Within each lateral chamber is disposed one or more gripper elements for engaging and gripping the pipe end outer surface. The gripper elements circumferentially surround the pipe and create a depression in the pipe surface. Known gripper

elements include an edge surface or a plurality of teeth that form a depression in the pipe surface to grip the pipe, resist lateral or axial movement so as to provide a rigid type coupling. To secure and seal the coupling about the pipe joint, the coupling includes a bolting assembly to join the housing elements together.

[0005] Known plain or beveled end pipe couplings as described above include (i) the

GRUVLOK® Figure 7005 ROUGHNECK® Coupling from ANVIL INTERNATIONAL, INC.®; (ii) the Model 79 "WILDCAT™" Plain End Coupling from SHURJOINT®; and (iii) the Style 99 ROUST- A-BOUT® Couplings from VICTAULIC®. Each of the known couplings are generally configured to join steel pipe having a surface hardness less than 150 Brinell. Shown in FIGS. 1 and IA is one known gripper element that has a plurality of gripping teeth at its gripper surface 24o for engaging the pipe surface. In cross-section, the gripper element has lateral sides defining element heights H ₁ , H ₂ in which H ₂ is less than H ₁ . Table 1 shows various dimensions of the known gripper element shown in FIGS. 1 and IA: length Lo, angle from horizontal αo, upper surface radius of curvature R ₁ , lower surface of curvature R _2, and element width W ₀ Table 1 further shows how the various dimensions vary with coupling and pipe size accordingly. [0006] Table 1

[0007] In addition to the combinations of measurement parameters summarized above, a review of the various coupling dimensions establishes a series of dimensional relationships for the known gripper element, such as for example, a length-to-width ratio (L/W _o ) and a gripper surface 24 ₀ slope ((Hl-H2)/W ₀ ) as is summarized below in Table IA.

[0008] Table IA

[0009] Shown in FIGS. IB and 1C, is another known gripper element which has an edge surface 24o for engaging and gripping the pipe surface. Table 2 shows how the various gripper element dimensions vary with coupling and pipe size. Table 2A summarize the dimensional relationships for the known gripper element.

[0010] Table 2

[0011] Table 2A

[0012] Plain or beveled end couplings as described above can be used in a variety of piping applications including mining, oilfield services or other process piping. Generally, the coupling can be rated as having a designed maximum working pressure measured in pounds per square inch (PSI) or Bars, and/or by maximum end load measured in pounds (LBS) or Newtons (N). The pressure and/or load ratings can be a function of one or more factors such as, for example, (i) the nominal size of the coupling, (ii) the required number of bolts used to join the coupling housing elements; (iii) the required size of the bolts used; and (iv) the required bolt torque. The bolt assembly requirements, in addition to the pressure and/or load ratings, can further be a function of the gripper element configuration and its grip force. Disclosure of Invention

[0013] A current coupling design provides for a 750 PSI maximum working pressure in a nominal two inch coupling requiring a bolt torque of 150 lb-ft. A preferred embodiment of the present invention provides a plain or beveled end coupling with a maximum working pressure of at least 750 PSI and a bolt or fastener torque minimum of about 150 LB-FT. The preferred coupling includes a housing having a centralized chamber and a central gasket member for sealing two joined pipe ends. The housing including a bolt assembly to support the housing about the piping. The chamber includes one or more chambers for housing at least one gripper element to engage the surface of a pipe end. The gripper element includes an elongated member having a plurality of surfaces, each having a length and a width to define a polygonal cross- section of the gripper element. At least one elongated surface of the gripper element defines an engagement surface for circumferentially engaging the surface of a pipe. The engagement surface preferably includes a plurality of vertices to define a plurality of engagement teeth for engaging a pipe surface with a grip force to define at least one of a torque requirement, maximum working pressure and maximum end load for the coupling.

[0014] One preferred coupling includes a housing defining a nominal coupling size ranging from about two inches to about ten inches. The coupling further includes a first plurality of gripper elements disposed in the housing to engage a first pipe, and a second plurality of gripper elements disposed in the housing to engage a second pipe. A sealing member is disposed in the housing between the first and second plurality of gripper elements to form a fluid tight seal between the first and second pipes. For a given nominal coupling size, the preferred gripping element has a length to width ratio less than that of previously known gripping elements and can provide a higher holding pressure and/or threshold pressure than that of known couplings. At least one gripper element has a length to width ratio preferably ranging from a minimum of about 1.7 to a maximum of about 3.5. In addition, the preferred gripping element has a pipe engagement surface slope of about zero.

[0015] Another preferred embodiment provides a gripping element for use in a pipe coupling. The gripping element includes a member defining a longitudinal axis and defining an axial length and a pipe engagement surface disposed along the member having a plurality of teeth for engaging the pipe member. The pipe engagement surface defines a width perpendicular to the longitudinal axis, a first lateral surface and a second lateral surface each disposed along the member and about the pipe engagement surface. The first and second lateral surfaces each define a height perpendicular to each of the width and the longitudinal axis, the length and the width of the element preferably define a length to width ratio ranging from about 1.7 to about 3.5.

[0016] In another preferred embodiment, a method is provided for coupling a first pipe and a second pipe each having plain ends. The method preferably includes providing a pipe coupling having a plurality of gripping elements to engage the plain ends and define a fluid tight seal between the first and second pipe. The method further preferably provides defining a failing limit of the fluid tight seal such that the pipe coupling fails to maintain the fluid tight seal when

the system is exposed to a hydrostatic pressure ranging between about 440 PSIG and 900 PSIG. In addition, the method can further preferably provide maintaining the fluid tight seal between the first and the second pipe for a period of at least five minutes under a hydrostatic pressure of about 600 PSIG. Brief Description of the Drawings

[0017] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the invention, and together, with the general description given above and the detailed description given below, serve to explain the features of the invention. It should be understood that the preferred embodiments provide examples of the invention as recited in the appended claims.

[0018] FIG. 1 is a plan view of a gripper element known in the art.

[0019] FIG. IA is a cross-sectional view of a gripper element known in the art.

[0020] FIG. IB is a plan view of another gripper element known in the art.

[0021] FIG. 1 C is a cross-sectional view of a gripper element known in the art. [0022] FIG. 2 is an exploded view of a preferred embodiment of a pipe coupling.

[0023] FIG. 3 is a cross-sectional view of the pipe coupling of FIG. 2 disposed about a pipe junction.

[0024] FIG. 4 is a detailed view of a housing used in the pipe coupling of FIG. 2.

[0025] FIG. 4A is a plan view of the preferred coupling assembly of FIG. 2. [0026] FIG. 5 A is a plan view of a preferred gripper element used in the pipe coupling of

FIG. 2.

[0027] FIG. 5B is a cross-sectional view of the gripper element of FIG. 5.

[0028] FIG. 6 is a schematic of a test piping assembly for evaluating a pipe coupling having with coupling of FIG. 2 installed in the test position.

Mode(s) of Carrying Out the Invention

[0029] Shown in FIGS. 2 and 3 are respective exploded and cross-sectional views of an illustrative embodiment of a coupling 10. The coupling 10 preferably includes a housing 12 formed of two housing elements 12A and 12B configured to surround a pipe junction, defining axis B-B, formed by the pipe ends of two axially joined pipes. Disposed within the housing is an elastomeric annular member 16, preferably a gasket member 16, configured to surround the pipe ends and form a fluid tight seal therebetween. Preferably located adjacent the annular member is one or more gripper elements 20 configured to grip the outer surface of the pipe ends. The housing elements 12A and 12B are joined together by one or more mechanical fasteners 18 such as, for example, threaded bolt 18 A and nut 18B. Although only two pieces are shown to form the housing 12, the housing can be formed by more than two pieces. The fasteners 18 join the halves together to secure and seal the housing 12 and gasket member 16 about the pipe junction and further apply a gripping force about the pipe end outer surfaces via the gripper elements. The housing elements 12 A, 12B can be configured for a union as shown and described in U.S. Patent No. 6,139,069 entitled "Universal Mechanical Coupling with Interfitting Ends" which is shown and described in U.S. Provisional Patent Application No. 60/864,096 and incorporated by reference in its entirety. Accordingly, the housing element 12A can, for example, include a tongue and recess for joining corresponding recess and tongue on element 12B. Preferably, the coupling 10 is configured such that application of a maximum torque of at least 150 LB-FT at the fasteners 18 provides the coupling 10 with at least one of a maximum working pressure of at least 750 PSI.

[0030] Preferably, housing elements 12 A, 12B each include a semi-circular surface such that when elements 12A and 12B are aligned and joined, their semi-circular surfaces form a circumferential inner surface for circumscribing a junction between two pipe ends. Moreover, the joined housing elements 12A and 12B work with gasket member 16 and the gripper elements

20 to apply a sealing and gripping force about the pipe junction. Shown in FIG. 3 is a cross- sectional view of an assembled coupling 10 disposed about a pipe junction formed by the axially aligned pipe ends IOOA and 10OB. The pipe ends IOOA and IOOB are preferably formed from metal pipe, more preferably steel pipe having a hardness no greater than 150 Brinnell. As seen in FIG. 3, the housing 12 includes a centralized chamber 11 for housing the gasket member 16. The gasket member 16 is preferably an elastomeric member such as, for example, GRINNELL' S EPDM gaskets as described in TYCO FIRE & BUILDING PRODUCTS data sheet G610 (April 2006), which is shown and described in U.S. Provisional Patent Application No. 60/864,096 and incorporated in its entirety by reference. The gasket 16 is dimensioned so as to have an axial thickness sufficient to axially receive a portion of each pipe end 10OA and 100B. Moreover gasket 16 is preferably dimensioned so as to allow for a gap between pipe ends IOOA and IOOB to allow for axial expansion and/or movement of pipe ends IOOA and IOOB. [0031] Preferably disposed laterally about the central chamber 11 is at least one lateral chamber 13 defined by the inner surface of housing elements 12 A, 12B for housing one or more gripper elements 20. The chamber 13 is preferably continuous about the inner surface of the housing elements 12 A, 12B or alternatively can be formed by a plurality of chambers circumscribed along the inner surface of the housing 12. The chamber 13 is preferably located within the housing so as to locate and apply a gripper element 20 medial of a pipe end IOOA, IOOB. Preferably, the chamber 13 includes a surface substantially normal to the axis B-B to which the gripper element 20 can be secured. The chamber 13 further includes sidewalls to surround the lateral sides of the gripper element 20. As seen in FIG. 3 and 4, the sidewalls are preferably disposed at an angle β relative to a line parallel to the axis B-B. The dimensions of the housing 12 A, 12B vary with the size of the coupling 10. FIG. 4 A schematically shows the existence of a preferred gap G between the housing halves 12A and 12B. Table 3 below provides preferred dimensions of the: chamber depth F, shoulder diameter SD, chamber diameter

GD and gap G between housing halves 12 A, 12B. Although the dimensions are preferred, they may each be varied provided such variation configures a coupling 10 to perform and/or function in a manner as described herein.

[0032] Table 3

[0033] Shown in FIGS. 5 A, 5B is a preferred embodiment of a gripper element 20 in plan and cross-sectional views. The gripper element 20 is preferably a metallic member elongated along a longitudinal axis A-A. Preferably, the gripper element 20 is constructed from ASTM A- 29 Grade 1017 carbon steel case hardened to Rc 50, 0.010 case depth, although other materials of adequate hardness and/or treatment can be employed. The gripper element 20 can further include a finish such as, for example, zinc electroplate to ASTM B633 Type III, SC 1. The axial length L of the gripper element 20 can range from about 0.5 inches to about 1.5 inches. Preferably, the axial length L of the gripper element 20 varies directly in relation to the nominal coupling size. [0034] The gripper element 20 can further preferably include a first elongated portion

2OA and a contiguous second portion 2OB. Preferably, at least one of the first portion 2OA and second portion 20 B is angled with respect to the longitudinal axis A-A so as to define an angle α therebetween. The angle α allows a plurality of circumferentially aligned gripper elements 20 to line the housing 12 and circumscribe a pipe end 10OA, 10OB. The number of gripper elements 20 to be disposed within the housing 12 can accordingly vary as a function of the axial length L and the angle α of the gripper elements 20. The angle α is preferably a function of the nominal

coupling size. For example, where the coupling 10 has a nominal coupling size of about 2 inches, the angle α is 6.25°. The angle α is preferably inversely related to the nominal size of the coupling.

[0035] Table 4 shows a preferred schedule of the gripper element 20 dimensions: length

L, angle α, width W, and height H. From the schedule of preferred dimensions, a set of preferred dimensional relationships and combinations of dimensional parameters are realized such as for example, a length-to-width ratio (L/W), a gripper surface 24 slope ((Hl-H2)/W) as is summarized below in Table 4A. Other dimensional parameter combinations include, for example, the preferred length and angle combinations. Although the tables below provide the preferred schedule of dimensions and relationships, it is to be understood that the dimensions can be varied so long as they provide the performance and function of the preferred coupling 10 as is described herein.

[0036] Table 4

[0037] Table 4A

[0038] As previously mentioned one or more gripper elements 20 can be aligned and secured within a single housing element 12 A, 12B to approximate and engage a semi-circular perimeter of the pipe end 10OA, 10OB. The gripper element 20 can be secured in the housing by any known fastening means such as, for example, bonding, welding, mechanical fastening etc. In one preferred embodiment, the gripper element 20 is secured to the housing 12 by adhesive bonding, preferably a clear silicone sealant such as SUPER SILICONE SEALANT CLEAR as provided by 3M™. A description of the preferred sealant is shown in the 3M product data sheet, "TS Data Sheet 08661; 08662; 08663; 08664" (Rev. 1 May 1999) shown and described in U.S. Provisional Patent Application No. 60/864,096 and incorporated in its entirety by reference. Alternatively, other adhesives can be used. Preferably, one surface is secure to the interior surface of the housing element 12 A, 12B, and an opposite surface is exposed for engaging and gripping the outer surface of the pipe end 10OA, 10OB.

[0039] Shown in FIG. 5B is a cross-sectional view of the gripper element 20. The gripper element 20 is preferably rectangular in cross-section having a width W and a constant height H. However, other geometries are possible such as for example, polygonal or oblong provided the gripper element presents at least one surface for securing the element 20 in the housing and one surface for engaging and gripping an outer surface of the pipe end 10OA, 10OB. Accordingly, the gripper element 20 includes a first surface 22 for engaging the interior of a housing element 12 A, 12B. In addition, the gripper element 20 includes a second surface 24 for engaging the pipe.

[0040] The second surface 24 preferably includes a means for gripping about the pipe end 10OA, 10OB. Preferably, the second surface 24 includes one or more teeth 26 for gripping about the pipe end 10OA, 10OB. The teeth can axially extend along the longitudinal axis for the full length of the gripper element 20. Alternatively, a plurality of teeth may be spaced along the axial length of the gripper element 20. More preferably the second surface includes at least three

gripping teeth 26 extending the full axial length of the gripper element 20 and uniformly disposed about the width W. The teeth 26 are preferably defined by two surfaces angled relative to one another and meeting at a vertex for engaging the pipe end 10OA, 10OB. Preferably, the two surfaces of the teeth 26 define an included angle of about 90°, and the teeth further preferably define a peak-to-peak spacing of about 0.090 inches.

[0041] As the configuration of the gripper elements preferably varies with the size of the coupling and pipe size, the number of gripper elements 20, bolt fasteners 18 A and nuts 18B employed in a single coupling assembly 10 also varies accordingly. Table 5 below shows the preferred count of gripper elements 20 and the number of fastener assemblies 18 and the torque requirements varied with the coupling size. Accordingly, it should be understood that the number of gripper elements 20, the number of fastener assemblies 18 and the torque requirements thereof can vary so as to provide the preferred coupling 10, its performance and function.

[0042] Table 5

[0043] A preferred embodiment of the coupling 10 was assembled and evaluated for performance in a comparison test with the Style 99 ROUST- A-BOUT® Coupling from VICTAULIC®. Shown in FIG. 6 is a test stand piping assembly 200 configured to evaluate the performance of a coupling. The test assembly 200 includes a first pipe segment 21 OA and a second pipe segment 210B coupled together by the coupling to be tested. Each end of the test assembly 212, 214 is capped so as to define a substantially fluid-tight piping assembly.

Disposed at one end of the assembly 212, is an inlet 216 for coupling to a fluid source such as water.

[0044] According to the test procedure, with the test coupling in place, water is introduced into the assembly 200 so as to displace and/or compress any air that may be within the assembly 200. Fluid is continuously fed into the assembly 200 until the assembly achieves an internal pressure of 600 PSIG. To evaluate the test coupling, a hydrostatic pressure test is conducted in which the 600 PSIG test pressure is held for five minutes. During the five minute period, the test coupling and its surrounding pipe joint are evaluated for deformation, leakage and/or other failure. If the test coupling and the assembly 200 are able to maintain the 600 PSIG test pressure for the entire five minute test period, the pressure is increased until the coupling fails. The pressure at failure is then recorded.

[0045] A 6-inch Style 99 ROUST-A-BOUT® Coupling and a prototype coupling,

GRINNELL FIG. 909 from GRINNELL® of Tyco Fire Products LP constructed in accordance with the present invention were each subjected to the above described test. The test assembly was constructed using nominal 6 inch steel pipe. The results of the test are summarized below. [0046] Table 6

[0047] The pressure tests demonstrate that a preferred embodiment of the coupling 10 provides improved performance over known couplings. Specifically, the Grinnell Fig. 909 coupling was able to maintain the 600 PSIG hydrostatic pressure for substantially the full five minutes. In addition, the preferred coupling demonstrated a failure threshold that was more than two times the pressure threshold of the known coupling. In light of the preferred dimensional relationships and dimensional parameter combinations described above, one or more

configurations of a preferred gripper element 20 can provide a preferred coupling 10 with improved performance over known couplings using known gripping configurations. Thus, it has been demonstrated for a given nominal size coupling having a preferred gripping element with a length to width ratio less than previously known does provide a higher holding pressure and/or threshold pressure than that of known couplings. Additionally, the preferred gripping element has a pipe engagement surface defining a preferred slope of about zero to contribute to the improved coupling performance. Moreover, the preferred gripper elements 20, may define working pressures and torque requirements, corresponding to a particular nominal coupling size, which were not previously known in coupling design and/or standards. [0048] While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present invention. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.