Abstract:
A clamp apparatus for holding together two abutting pipe ends, in which the pipe ends have radial flanges to facilitate the exerting of axial compressive forces on the pipe ends. The clamp includes a first strap structure and a fastening mechanism for providing circumferential compressive force on retainer segments configured to transfer the compressive force onto the flanges of the pipe ends. The clamp apparatus also includes a secondary strap structure for providing independent redundancy, relative to the primary strap, to supply back-up circumferential force onto the primary strap structure, should a failure occur in either of the fastening mechanism or the primary strap structure, to enable the clamp to maintain clamping force on the abutting pipe ends.

Description:
BACKGROUND OF THE INVENTION 
     The Technical Field 
     The present invention is directed to clamping devices and systems that may be employed in ducting applications for holding two abutting pipe ends in a clamped, substantially fluid-tight configuration, without permanently affixing the pipe ends to one another. Such clamping systems may particularly be used in aerospace applications, such as connecting the ends of adjacent duct sections in an aircraft pneumatic system, in which turbine bleed gases are conducted from the engines throughout the aircraft. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a coupling apparatus for releasably connecting two closely-adjoining disposed pipe ends together, wherein each pipe end has a longitudinal axis, and wherein each pipe end has a flange extending radially therefrom, so that when the pipe ends are positioned to substantially adjoin one another. The flanges of the pipe ends are substantially juxtaposed to one another. 
     The coupling apparatus comprises an arcuate primary strap member, having two adjacent spaced-apart free ends, the arcuate primary strap member being configured to be placed circumferentially around the juxtaposed flanges of the two closely-adjoining ends. At least two retainer segments are provided, in which each of which at least two retainer segments is positioned within an inner surface of the arcuate primary strap member. Each retainer segment further has a concavity disposed therein to receive and exert at least an axial compressive force on each of the substantially juxtaposed flanges of the pipe ends, when the coupling apparatus is mounted about the pipe ends. 
     A fastening mechanism is operably connected to the ends of the primary strap member and configured to be selectively tightened and loosened, to selectively bring together or move apart the two adjacent spaced-apart free ends, respectively, so as to decrease or increase the total circumferential length of the primary strap member and the fastening mechanism, respectively, to, in turn, exert or remove axial compressive force on the flanges of the closely-adjoining pipe ends. 
     A secondary strap element encircles at least most of the circumference of the arcuate primary strap member, and cooperatively engages with the fastening mechanism, to facilitate maintenance of the coupling apparatus about the closely-adjoining pipe ends, in the event of a failure of the primary strap member. The secondary strap element provides a second structure to maintain the coupler apparatus in place on the pipe ends, which operates independently of the primary strap element to provide an independent redundancy therefor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation, in section of a representative typical prior art V-clamp fitting holding together two pipe ends. 
         FIG. 2  is an end elevation of the prior art V-clamp fitting of  FIG. 1 , in which the pipe ends have been omitted for clarity of illustration. 
         FIG. 3  is an end elevation of the clamping apparatus according to a preferred embodiment of the invention. 
         FIG. 4  is a perspective view thereof. 
         FIG. 5  is an enlarged right perspective view thereof. 
         FIG. 6  is an enlarged left perspective view thereof. 
         FIG. 7  is an enlarged perspective view of the fastening mechanism of the clamping apparatus of the present invention, with the bolt removed to show the loops at the ends of the secondary strap or cable. 
         FIG. 8  is a similar enlarged perspective view thereof, from a reverse point of view. 
         FIG. 9  is a plan view of a secondary strap or cable according to a preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention is susceptible of embodiment in many different forms, there are shown and described in the drawings and associated text, one or more specific embodiments, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. 
     The following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to one, or an, embodiment in the present disclosure can be, but not necessarily are, references to the same embodiment; and, such references mean at least one of the embodiments. 
     Reference in this specification to “one embodiment” or “an embodiment” is means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments, but not other embodiments. 
     The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Certain terms that are used to describe the disclosure are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the disclosure. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. It will be appreciated that same thing can be said in more than one way. 
     Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the is art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control. 
     In various industrial piping applications, such as in aerospace applications, it is desirable to be able to connect two abutting pipe ends in a substantially leakproof manner, without permanently attaching the pipe ends together (such as by welding, etc.). In such a situation, clamps may be employed which are configured to exert both radial and axial compression on the abutting pipe ends. 
       FIGS. 1 and 2  illustrate schematically, a typical clamp for connecting, in compression, two pipe ends. The clamp illustrated in  FIGS. 1 and 2  is of the type which corresponds to the requirements of Society of Automotive Engineers (“SAE”) Standards AIR860, AS4751, AS1960 (all as of 2009), and AS24563, the complete disclosures of which are hereby expressly incorporated by reference. Such clamps are configured to operate in temperature regimes of about −65° F. to about 1000° F., and pressure regimes of about 25 psi to about 300 psi. Referring to  FIG. 1 , clamp  10  is provided to connect together pipe ends  12  and  14 , respectively. Each pipe end  12 ,  14 , is provided with a radially extending connection flange  16 ,  18 , respectively. Flanges  16 ,  18  may be sheet metal flanges suitably attached to pipe ends  12 ,  14 , or they may be machined flanges integral to pipe ends  12 ,  14 , or otherwise suitably formed thereon. As shown in  FIGS. 1 and 2 , clamp  10  includes an encircling strap  20  (fabricated, e.g., from sheet metal of any suitable metal or alloy sufficient to withstand the conditions described above), which circumferentially surrounds and is configured, upon tightening of fastening mechanism  22 , to exert radially inwardly directed compression pressure on two or more retainer segments  24  (preferably configured from any suitable metal or alloy sufficient to withstand the conditions described above), which are attached to the inner surface of strap  20 . Two or more gaps  26  are provided, to enable the ends of retainer segments  24  to pivot slightly toward one another, to accommodate the reduction in circumference of strap  20 , upon tightening of fastening mechanism  22 , to enable the radial compression of the pipe ends (not shown in  FIG. 2 ) being joined. The retainer segments are typically configured so that up to 25% of the total retainer member circumference may fail, and still exert sufficient axial clamping force to maintain leakage to within predetermined maximum values, as established by SAE Standard AS4751. 
     Fastening mechanism  22  includes, in a typical clamp, bushings  28 ,  30 , which are received in loops  32 ,  24 , formed in the opposite ends of strap  20 . One bushing, e.g., bushing  28 , is configured to pivotably receive the cross-bar of a T-bolt  36 . The opposite bushing, e.g., bushing  30 , is configured to receive a trunion  38 , which is, in turn, configured to receive the shaft  40  of T-bolt  36 . A self-locking nut  42  is threadably received on shaft  40 . 
     In such a fastening mechanism  22 , to place clamp  10  on a joint between two pipe ends, nut  42  is loosened, and T-bolt  36  is pulled through, and pivoted out of and away from trunion  38 , thus permitting the opposed ends of strap  20  to be pulled away from one another, and placed over the abutted ends of the pipes to be joined. Once clamp  10  is positioned as desired, T-bolt  36  is pivoted around toward, and inserted through placed in trunion  38 , and nut  42  is tightened as desired, to bear against the outer end of the trunion, to impose the desired compression on the joint, with retainer segments  24  exerting both axial and radial compression on flanges  16 ,  18  of the pipe ends  12 ,  14 . 
     The specific structures which are shown as the trunion and the T-bolt in  FIGS. 1 and 2  are shown by way of example, and a number of bolt and trunion structures may be substituted therefor, without altering the operation of the clamp. 
     To provide a measure of independent redundancy for fail-safe protection, the T-bolt  36  and self-locking nut  42  in clamp  10  may be provided with a safety latch  44 , which, in the example of the prior art clamp shown in  FIGS. 1 and 2 , will be a tang or tab  43  of metal, extending from one end region of strap  20 , through an aperture typically provided in the opposed end of strap  20 . As a practical matter, strap  20  is far more likely to suffer catastrophic failure, than any other component of clamp  10 , especially, e.g., T-bolt  36 . 
     Extending from tang or tab  43  will be two wings  45  which, once clamp  10  has been positioned in place and tightened down over the pipe ends, are bent upwardly, parallel to one another, and perpendicular to the plane of strap  10 . In this way, should strap  20  fail, the wings  45  of latch  44  will engage the edge of the opening in the strap through which the tang passes, and prevent the tang or tab from being pulled through the aperture in that end of the strap  10 , and maintain a certain level of tension in the strap to help prevent the pipe ends from being pulled apart. Typically, latch  44  is provided with a relatively short tab or tang, so that wings  45  abut the edges of the aperture in the adjacent strap end (i.e., there is little or no “slack” in the tab or tang, once fastening mechanism  20  has been suitably tightened. 
     In certain industrial applications, it may be desirable to provide additional safeguards for the integrity of the joint connector, other than the single safeguard of the safety latch shown in the prior art apparatus of  FIGS. 1 and 2 . 
       FIGS. 3-6  show an embodiment of the present invention. Clamp apparatus  46  may be used in a variety of industrial applications, such as in ducting for aerospace applications, such as conveying bleed air from turbine engines that is used for aircraft Environmental Control Systems and for purposes such as deicing. Such pneumatic systems employ duct gas bleed leak detectors, which are temperature sensitive. Clamp  46  may be substantially similar to clamp  10 , having a strap  48 , and two or more retainer segments  50 . Fastening mechanism  58  will include a safety latch  52 , having wings  54 , and an elongated tang  56 , which will be operably configured to be long enough, so that, if T-bolt  60  fails, strap  48  will be permitted to loosen enough, to enable the pipe ends to separate enough to leak (and thus be detected by the duct gas bleed leak detection system), but not enough that clamp  46  falls off the joint and permits the pipe ends to become completely separated. 
     T-bolt  60  is pivotably mounted in bushing  70 , held in loop  72  of strap  48 . Trunion  73  is pivotably mounted in bushing  74 , which is held in loop  76  of strap  48 . 
     The present invention also includes a secondary strap mechanism, to hold clamp  46  onto the pipe ends, should strap  48  fail, especially near or in the zone of the gaps between retainers  50 . Secondary strap mechanism  62  includes wire or cable  64  ( FIG. 9 ), which is held in place on the outside of strap  48  by guide structures  66 , which are permanently affixed to cable  64 , and, in turn, affixed, such as by welding, to the outside surface of strap  48 . The end of wire or cable  64  terminate in loops  68 , which are placed over shaft  61  of T-bolt  60  (see  FIGS. 7 and 8 ). 
     When clamp  46  is mounted over a pair of duct ends to create a joint connection, and tightened in place, strap  48  and fastening mechanism  58  is under tension. However, cable  64 , especially in the portion between loops  68  and the nearest guide structures  66 , is slack at that time. In the event of a catastrophic failure of strap  48 , because T-bolt  60  will be intact, loops  72 ,  76  of strap  48  will remain in fixed positions relative to one another. Therefore, loops  68  attached to the ends of cable  64  will be held in place. However, the remaining portions of strap  48  will tend to expand, pushing radially outwardly against strap  68 , and placing it under tension. Preferably, the amount of slack initially provided in strap  68  will not be sufficient to permit clamp  46  to come off of the flanges of the adjacent pipe ends, though some amount of leakage may occur, the amount of which may be controlled by the amount of initial slack provided in cable  64  at the time of installation. 
     By providing secondary cable  64 , coupler  46  is provided with an independent redundancy (relative to primary strap  48 ) for holding retainer segments  50  in position about the flanges of the pipe ends. Because cable  64  is directly anchored, at its ends to T-bolt  60 , it is capable of operating independently of strap  48 . 
     The foregoing description and drawings merely explain and illustrate the invention, and the invention is not limited thereto, except as those skilled in the art who have the present disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.