Abstract:
A tube or pipe clamp incorporates a clamping force measurement device. A support body is disposable around a threaded bolt of a locking assembly of the tube or pipe clamp. At least one spring element is held by the support body, a compression member being disposed in operative contact with the spring element for compressing the same in a clamp tightening operation. A scale is provided on one of the support body and the compression member for indicating a degree of compression of the spring element and concomitantly a magnitude of compressive force exerted by the compression member and the bolt on the tube or pipe clamp.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to tube or pipe clamps. More particularly, this invention relates to a device to be used with tube or pipe clamps or to be incorporated into such clamps for facilitating effective usage thereof. 
         [0002]    Flanged ferrule tube connections are used extensively in industry. The type of joint shown is a common clamped flange design. The ferrules have angled (conical) surfaces. The clamp captures the ferrules and contacts them on the conical faces. By clamping the clamp diametrically, the contact on the angled surfaces causes a linear force component to squeeze the ferrules together in a direction that squeezes the gasket between them. 
         [0003]    Industry has had various challenges with this type of clamp, including:
       1. Extrusion of the gasket into the liquid flow area of the tubes.   2. Difficulty determining the correct tightening torque to be applied at the wing nut.   3. Inability to give standard tightening instructions for various ferrule and clamp sizes.   4. Leaking joints due to heating and cooling of system fluid and clamped tubes.   5. Loosening of wing nuts, causing them to sometimes swing open.       
 
         [0009]    Participants in the industry and industry standards-creating bodies have attempted to solve this problem by introduction of standard component configurations and new products. Products include metal-to-metal ferrules with fixed gasket space, various durometer gaskets, hard gaskets, gasket appendages to achieve fixed ferrule-to-ferrule distance, torque-limiting nuts and live load nuts. 
         [0010]    The current state of the art includes spring clamping devices, which are meant to give some control or indication of clamping force. They are based on the expectation that the pull force on the clamping bolt is related to clamping force at the gasket. Two devices known to apply this theory are described in U.S. Pat. No. 5,653,481 to Alderman and U.S. Pat. No. 6,082,941 to DuPont. 
         [0011]    The Alderman patent is directed to a so-called live loading nut. Possible improvements over Alderman might include 1) a simplified design which eliminates second guide diameters on two components, 2) elimination of the need for a torque wrench for installation, and 3) reduction or elimination of friction and other forces within the prior art device itself and in the torque wrench. 
         [0012]    U.S. Pat. No. 6,082,941 discloses a device for tube clamps for the purpose of allowing an installer to tighten each nut to a specified torque matched to gasket material. Potential improvements over this prior art might include 1) simplified design, 2) reduction or elimination of friction and other forces within the prior art device itself, and 3) elimination of the need for a wrench or other tool for tightening. 
       OBJECTS OF THE INVENTION 
       [0013]    It is an object of the present invention to provide an improved tube or pipe clamp. 
         [0014]    A related object is to provide a tube or pipe clamp incorporating a device for alleviating at least some of the above-described problems with tube clamps. 
         [0015]    Another object of the present invention is to provide a device as part of a tube clamp to facilitate control and monitoring of clamping force on an inter-pipe gasket. 
         [0016]    A further object of the present invention is to provide such a device that is easy to install and easy to use. 
         [0017]    These and other objects of the present invention will be apparent from the descriptions and drawings herein. Although every object of the invention is attainable by at least one embodiment of the invention, there is not necessarily any single embodiment that achieves all of the objects of the invention. 
       SUMMARY OF THE INVENTION 
       [0018]    A tube or pipe clamp in accordance with the present invention comprises two clamp members, a locking device, and a clamp force measurement device. The clamp members are pivotably connected to one another at respective hinge-forming ends thereof. The locking device includes a shaft and a locking element operatively attached to the shaft, the shaft being pivotably attached to one of the clamp members, the other of the clamp members having a pair of prongs defining a slot for receiving the shaft so that the locking element is engageable with the prongs to lock the clamp members to one another at ends thereof opposite the hinge-forming ends. The clamping force measurement device includes a support body, at least one spring element, a compression member, and a scale or metric indication. The support body is disposable around the shaft of the locking device. The one or more spring elements are held by the support body. The compression member is in operative contact with the spring element for compressing same in a clamp tightening operation. The scale is disposed on the support body or the compression member for indicating a degree of compression of the spring element and concomitantly a magnitude of compressive force exerted by the compression member and the bolt on the tube or pipe clamp. 
         [0019]    Concomitantly, a clamping force measurement device comprises, in accordance with the present invention, a support body disposable around a threaded bolt of a locking assembly of a tube clamp, at least one spring element held by the support body, a compression member in operative contact with the spring element for compressing the same in a clamp tightening operation, and a scale on one of the support body and the compression member for indicating a degree of compression of the spring element and concomitantly a magnitude of compressive force exerted by the compression member and the bolt on the tube clamp. 
         [0020]    The support body of the clamping force measurement device may take the form of a housing, casing, or enclosure. The one or more spring elements are then disposed in the housing. The spring elements may take the form of one or more helical springs or a plurality of spring washers arrayed in a stack. 
         [0021]    Pursuant to another feature of the present invention, the support body or housing of the clamping force measurement device has a set of walls, at least one of which is formed with a window. The scale is disposed on a surface of the housing proximate the window. 
         [0022]    An indicator element, which may be a feature of the compression element of the clamping force measurement device, such as an edge of the compression element or a marking disposed on a lateral surface thereof, is disposed in the housing and is visible through the window. The indicator element may be a separate member. In any event, the indicator element is movable relative to the scale to conform to the degree of compression of the spring element(s) and therefore to the amount of force exerted by the tube or pipe clamp. 
         [0023]    The compression member of the clamp force measurement device may take the form of a spacer slidably disposed inside the housing and disposed in contact with the locking element of the tube or pipe clamp, which may take the particular form of a tightening nut that is threadably connected to the shaft, e.g., bolt, of the locking device. Typically the tightening nut is a wing nut. The compression spacer may have a cylindrical form provided along one surface with a concavity that receives or seats the tightening nut. The indicator may be an edge of the spacer or a line printed on a lateral surface thereof. 
         [0024]    In an alternative embodiment of the invention, the compression member may be the locking element of the clamp&#39;s locking device. Where the locking element is a wing nut and the shaft of the locking device is a bolt threadably connected the wing nut, the portion of the compression member in contact with the at least one spring element may be a shaft of the wing nut. 
         [0025]    A clamping force measurement device in a tube or pipe clamp in accordance with the present invention compensates or accounts for variation in gasket durometer. It also facilitates the application of proper amounts of torque, regardless of clamp size. Where installed ferrules are misaligned or improperly distanced from one another, a clamping force measurement device as described herein helps determine that this is the case. 
         [0026]    The present invention improves the accuracy of measurement of the clamping force on a gasket, relative to all conventional devices. Use of the present invention can correct some root causes of leaking joints due to heating and cooling of a conduit system. 
         [0027]    The present invention can prevent or reduce the occurrences of clamps swinging open with temp changes and wing nuts becoming loose. 
         [0028]    When a pipe or tube clamp having a clamping force measurement device in accordance with the present invention is used properly and ferrules are properly set and aligned, the present invention can serve to reduce, if not eliminate, extrusion of gasket into the flow area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a perspective view of a tube clamp incorporating a clamping force measurement device, in accordance with the present invention. 
           [0030]      FIG. 2  is a perspective view, partially broken away, of the tube clamp and clamping force measurement device of claim  1 . 
           [0031]      FIG. 3  is a side elevational view of the tube clamp of  FIGS. 1 and 2 , showing the clamping force measurement device of  FIGS. 1 and 2  in cross-section. 
           [0032]      FIG. 4  is a side elevational view, on a larger scale, of the clamping force measurement device of  FIGS. 1-3 . 
           [0033]      FIG. 5  is an exploded perspective view, on an intermediate scale, of the clamping force measurement device of  FIGS. 1-4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    As depicted in  FIGS. 1-3 , a clamping force measurement device  10  in a tube clamp  12  is disposed around a shaft or bolt  14  of a clamp locking device  16  between a wing nut  18  for tightening or locking the locking device and a fork portion  20  of an upper clamp member  22 . A lower clamp half or member  24  is pivotably connected to upper clamp member  22  at a hinge  26 . 
         [0035]    Bolt  14  of clamp locking device  16  is pivotably attached to lower clamp member  24 . Specifically, bolt  14  is pivotably connected to a pair of flanges or prongs  28  of lower clamp member  24 . More specifically, an eyelet-bearing base portion  30  of bolt  14  receives a pivot pin  32  that extends between flanges or prongs  28 . 
         [0036]    In the closed and locked configuration of clamp  10  depicted in  FIGS. 1-3 , bolt  14  extends from lower clamp member  24  between two prongs  34  of fork portion  20  of upper clamp member  22 . Wing nut  18  is screwed onto bolt  14  and a shaft portion  36  of wing nut  18  extends into and operatively engages clamping force measurement device  10 . 
         [0037]    Clamping force measurement device  10  includes a support body  38  in the form of a housing or casing having a cylindrical sidewall  40 . On an upper side, an annular lip  42  extends inwardly from cylindrical sidewall  40  to define an opening  44 . Opening  44  is traversed by wing nut shaft portion  36  in the installed configuration of the clamping force measurement device. 
         [0038]    Support body or housing  38  further includes a nipple or extension  46  at an end opposite lip  42  and opening  44 . Nipple or extension  46  is insertable between prongs  34  of fork portion  20  and is provided at a free end with an aperture  48  ( FIG. 3 ) which is traversed by bolt  14 . 
         [0039]    Clamping force measurement device  10  further includes a plurality of spring washers or disk springs  50  which are disposed inside support body  38  around bolt  14  of locking device  16 . Disk springs  50  are held in contact with one another, in a compressed array, between (a) an annular shoulder or ledge  52  extending inwardly at a lower end of cylindrical sidewall  40  and (b) an annular compression member  54  in the form of a spacer slidably disposed inside housing  38  at an upper end thereof. 
         [0040]    Compression member or spacer  54  in turn is disposed in contact with shaft portion  36  of wing nut  18 . Compression member  54  has an annular or cylindrical form provided along an upper surface with a concavity or recess  56  that receives or seats a free end of wing nut shaft portion  36 . 
         [0041]    As shown in  FIGS. 4 and 5 , sidewall  40  of clamping force measurement device  10  is provided with a window  58  and a force indication scale  60  in juxtaposition to the window. A force magnitude indicator  62  ( FIG. 5 ) line printed, painted, cut, burned, molded or engraved on a lateral surface  64  of compression member  54 . Alternatively, the force magnitude indicator may be an edge (not separately designated) of compression member  54 . 
         [0042]    In using the clamp force measurement device  10  with clamp  12 , one slips support body  38  together with spring disks  50  about bolt  14 . Bolt  14  may have been already pivoted into its locking position, where it extends between prongs  34  of upper clamp member fork portion  20 . Wing nut  18  is then twisted onto the free end of bolt  14  so that the free end of shaft portion  36  is seated in concavity or recess  56  of compression member  54 . As wing nut  18  is turned, the clamp  10  is tightened about a pair of tubular conduit members (not shown) at a ferrule joint, about which the clamp is previously positioned. Compression member  54  compresses the array of spring disks  50  in direct proportion to the amount of force exerted on clamp  10  by locking device  26 . The magnitude of applied force may be read by comparing the location of indicator  62  with the markings of scale  60 . 
         [0043]    Clamping force measurement device  10  allows the installer to set clamp  12  to a specific force at the clamping bolt  14 , to see an indication of the force during installation, and to monitor the force visually without having to tighten wing nut  18  or use a torque wrench. The indication is done by direct indication of spring compression. The indication is almost entirely free of errors due to internal friction of the device or inaccuracies of an external torque wrench. The user tightens the wing nut  18  until indicating line  62  reaches a desired force-level line adjacent to window  58  on support body  38 . By easy calculations and testing, a manufacturer can relate the degree of spring compression to an amount of gasket compression between the ferrules. 
         [0044]    One limitation of clamping force measurement device  10  is the inability, in some installations, to distinguish whether the clamping force is just a result of compressing the gasket, or if ferrule misalignment or improper ferrule distance are also factors. This limitation exists for all known devices. However, the improvements provided by clamping force measurement device  10  exclude other error factors and may make detection of ferrule misalignment and ferrule misplacement easier. If one can always see accurately the clamping force being applied and know that only gasket compression and ferrule alignment are factors, it should be easier to troubleshoot any leakage or misalignment issues. 
         [0045]    One important benefit of clamping force measurement device  10  relative to prior art devices is eliminating the torque-limiting and/or torque-measuring functions that add error and complexity. The force of interest to be measured and controlled is the direct linear force on bolt  14 . By adding the torque aspect, the prior art devices add complexity, variables and errors, with not added benefit. 
         [0046]    Another benefit of clamping force measurement device  10  relative to prior art devices is no torque wrench is required. Users in quality-controlled environments must maintain calibration systems for accurate torque wrenches if the torque wrenches affect system performance and safety. 
         [0047]    A further benefit of clamping force measurement device  10  is that it can be used with the industry-standard wing nuts prevalent in industry. No wrench is needed. Yet another benefit is the clamp force can be monitored visually at any time. A further advantage is that clamping force measurement device  10  provides a live load that continues to exert clamping pressure even when the ferrules are pushed together by an external input, such as expansion of pipes and tubes due to heating of the system. The same feature; i.e., the ability of the clamp to continue applying force through the spring over some range of compression, also prevents the problem of wing nuts coming loose and swinging open. 
         [0048]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. For example, one or more helical spring members may replace disk springs  50 . Also, the scale markings may be provided on shaft portion  36  of wing nut  18  or even on compression member or spacer  54 , instead of on sidewall  40  of support body  38 . Furthermore, compression member or spacer  54  may be eliminated altogether, with a free end of wing nut shaft portion  36  placed directly in engagement with an uppermost spring disk  50 . In that case, wing nut  18  and particularly shaft portion  36  thereof performs the function of compression member  54 . 
         [0049]    Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.