Abstract:
A clamp device that is used to maintain a consistent clamping pressure on a flanged connection despite changes in temperature and changes in internal pressure behind the flanged connection. The clamp device contains a rocking bolt assembly that is manually tightened with a wing nut. Should the wing nut loosen, the rocking bolt assembly contains internal springs that compensate for the loosened wing nut and maintain a relatively consistent tension in the rocking bolt assembly within a predefined range of conditions.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to clamping devices, commonly known as pipe clamps that are used to join together the flanged ends of two objects so that a fluid impervious seal is created between the opposing flanges. More particularly, the present invention relates to such clamping devices that are designed to provide a clamping tension that varies with changing conditions. 
     2. Description of the Prior Art 
     In the manufacture and processing of pharmaceutical products, dairy products and other materials that require a sanitary processing environment, it is common for materials to be stored and transported in stainless steel containers. Such stainless steel containers are manufactured by Eagle Stainless Container, Inc, of Ivyland Pa. The use of stainless steel is preferred because it enables the containers to be cleaned and sanitized in an autoclave or other harsh washing environment after they have been used. The stainless steel containers can therefore repeatedly be made sterile and can be used over and over again. 
     Since stainless steel containers are often used to house sterile materials or bioreactive materials, such containers typically do not contain threaded closures. Threaded closures provide confined areas between threads that may harbor contaminants or bioreactive material. Due to the physical shape of the threads, it is very difficult to properly clean threads to the sanitary standards needed. It is for this reason that threaded closures are generally not used. Rather, what is used are flanged caps. 
     Many stainless steel containers are manufactured with access ports that terminate with a flange connection. The flanged connection is a circular flange that radially extends from the neck of the access port. The access port can therefore be connected to a pipe with a similar flange connection or a cap that contains the proper sized flange connection. To join any two flanged connections together, the two flanges are placed in abutment so that the openings in the center of each of the flanges align. An O-ring or other sealer is placed between the two flanges. The flanges are then clamped together in a manner that compresses the O-ring and prevents the flanges from falling out of alignment. 
     In the prior art, there are many different types of clamping mechanisms that have been used to join together flanged connections. Typically, the clamps that have been used are annular in shape. Hinges are disposed along the annular structure to enable the annular structure to open. The clamps are opened and then closed over the span of the two adjoining flanges. The presence of the clamping device biases the adjoining flanges together and prevents the adjoining flanges from moving out of their aligned positions. 
     Prior art clamping devices with a single hinge are exemplified by U.S. Pat. No. 5,018,768 to Palatchy, entitled Pipe Coupling Hinge. Prior art clamping devices with multiple hinges are exemplified by U.S. Pat. No. 4,568,115 to Zimmerly, entitled Multi-Piece Pipe Clamp. Regardless of the number of hinges present, such prior art clamping devices typically contain a rocking bolt assembly that is pivotably connected to one end of the clamp. A wing nut is used to tighten the rocking bolt assembly. The wing nut passes over a slot that is positioned on the opposite end of the clamp. By tightening the wing nut, the diameter of the clamp can be reduced and the clamp can be tightened over the flanged connections. 
     In many applications, containers undergo severe temperature changes. For instance, a container may be filled at room temperature and then placed in a cryogenic environment, or vise versa. As the temperature of a container changes, the vapor pressure within the container changes and the forces on the cap of the container change. Additionally, as the container is moved into environments of differing temperatures, the temperature of the clamp used to hold a cap onto the container also changes. As a clamp experiences temperature changes, the metal of the clamp either expands or contracts. As such, a clamp that is very tight in one environment may become very loose in a different environment. 
     A need therefore exists for a new clamp design that is capable of providing a steady clamping pressure regardless of severe changes in temperature. This need is met by the present invention as it is described and claimed below. 
     SUMMARY OF THE INVENTION 
     The present invention is a clamping device that is used to maintain a consistent clamping pressure on a flanged connection despite changes in temperature and changes in internal pressure behind the flanged connection. The clamping device contains a plurality of arcuate segments. The first and the last of the arcuate segments contain base protrusions that align when the clamping device is closed. One of the base protrusions serves as the housing for a rocking bolt assembly. The rocking bolt assembly includes a threaded rod that joins to a shaft by a pivot. The threaded rod and shaft extend through a hole in the base protrusion. The shaft has an enlarged head that prevents the shaft and the threaded rod from passing through the hole. A wing nut engages the threaded rod and applies tension to both the threaded rod and the shaft. The amount of tension applied by the wing nut varies with changes in temperature. To compensate for variations in wing nut tension, at least one spring is provided around the shaft within the hole of the base protrusion. The spring, or springs, is compressed by the tension applied by the wing nut. When compressed, the spring, or springs, also applies tension to the shaft. The tension applied by the spring, or springs, compensates for any reduction in wing nut tension caused by a change in temperature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is an exploded perspective view of a container having a flanged access port that is sealed with a cap, wherein the cap is held in place with an exemplary embodiment of a clamping device; 
     FIG. 2 is a fragmented, exploded view of the rocking bolt assembly used in the clamping device shown in FIG. 1; 
     FIG. 3 is a selectively cross-sectioned view of the rocking bolt assembly shown in FIG. 1, illustrated in an open condition; and 
     FIG. 4 is a selectively cross-sectioned view of the rocking bolt assembly shown in FIG. 1, illustrated in a closed condition. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention clamping device can be used to connect any two objects have the same type of flanged connection, such as two pipes, the present invention is especially well suited for connecting a cap to a container. However, the present invention clamp can be applied to any application of flanged connectors that requires a clamp. 
     Referring to FIG. 1, there is shown a typical prior art container  10  with a flanged connection  12 . The container  10  is shown with a cap  14  that is used to selectively close the opening defined by the flanged connection  12 . The flanged connection  12  and the cap  14  both have corresponding sized surfaces that align when joined. An O-ring  16  is disposed between the flanged connection  12  and the cap  14 . The O-ring creates a seal between the flanged connection  12  and the cap  14  when it is compressed. 
     The present invention is a clamping device  20  that extends around the flanged connection  12  and the cap  14 , thereby biasing these two structures together and compressing the O-ring  16 . 
     From FIG. 1, it can be seen that the clamping device  20  contains at least two arcuate segments  22 ,  24 . The arcuate segments  22 ,  24  are joined together, thereby forming a structure that can be configured into a generally annular shape. The first arcuate segment  22  terminates with a base protrusion  26  that radially extends away from the center of curvature for the arcuate segment  22 . However, a unique rocking bolt assembly  30  is contained within the base protrusion  26 . The purpose of the rocking bolt assembly  30  is to retain the clamping device in a closed condition and apply a steady clamping force to the arcuate segments  22 ,  24  of the clamping device  20 , across a wide range of environmental conditions. 
     Referring to FIG. 2, it can be seen that the base protrusion  26  of the clamping device  20  defines a hole  34  in which the rocking bolt assembly  30  lay. The hole  34  is not uniform, but rather contains three different sections. Each of the sections has a different diameter. The first section  36  has the smallest diameter. The first section  36  is intersected by a slot  37  that extends from the first section  36  of the hole  34  to the side of the base protrusion  26 . The second section  38  of the hole  34  has a diameter larger than that of the first section  36  and is located next to the first section  36 . This causes a first ridge  39  at the interface between the first section  36  and the second section  38 . The third section  40  has a diameter larger than that of the second section  38  and is located next to the second section  38 . This causes a second ridge  41  at the interface between the second section  38  and the third section  40 . 
     The elements of the rocking bolt assembly  30  that extend through the hole  34  in the base protrusion  26 , are as follows. A threaded rod  42  is provided. The threaded rod  42  has an eyelet at one end. The threaded rod  42  has a diameter small enough to pass through both the first section  36  of the hole  34  and the slot  37  on the side of the base protrusion  26 . The threaded rod  42  is engaged by a wing nut  44  that is used to tighten the rocking bolt assembly  30 . 
     The eyelet at the end of the threaded rod  42  is connected to the end of a smooth shaft  46  with a pivot  47 . As a result, the threaded rod  42  can be moved about the pivot  47  relative the smooth shaft  46 . The end of the smooth shaft  46 , opposite the threaded rod  42 , terminates with an enlarged head  48 . The enlarged head  48  may have a cammed inner surface  49 , as will later be explained. 
     At least one disc spring  50  is placed around the smooth shaft  46 . A disc spring  50  is a spring where the center of the spring lay in a different plane from the periphery of the spring. Although a coil spring can be used, the use of disc springs are preferred. This is because disc springs generally have a higher spring constant per unit of space than do coil springs. Furthermore, due to their compact structure, disc springs are less sensitive to temperature changes than are coil springs. 
     The disc springs  50  lie around the smooth shaft  46  in the second section  38  of the hole  34 . The combined thickness of the disc springs  50  is larger than the width of the second section  38 , when the disc springs are uncompressed. As a result, the disc springs  50  must be slightly compressed in order to be contained completely within the second section  38  of the hole  34 . The disc springs  50  are confined within the second section  38  of the hole by the first transition ridge  39  and a cam housing  52 . The first transition ridge  39  between the first section  36  and the second section  38  of the hole  34  abuts against the first of the disc springs  50  and prevents the disc springs  50  from advancing into the first section  36  of the hole  34 . On the opposite side of the discs springs  50 , a cam housing  52  is placed around the smooth shaft  46 . The cam housing  52  has a diameter that fits into the third section  40  of the hole  34  but is too large to fit into the second section  38  of the hole  34 . As such, the cam housing  52  cannot be advanced into the hole  34  beyond the second transition ridge  41  between the second section  38  of the hole  34  and the third section  40  of the hole  34 . 
     The cam housing  52  has an internal cammed surface  54  that faces away from the disc springs  50 . The internal cammed surface  54  of the cam housing  52  engages the cammed surface  49  of the enlarged head  48  at the end of the smooth shaft  46 . 
     When the wing nut  44  is tightened, the wing nut  44  applies a tension force to the threaded rod  42 . The threaded rod  42  transfers that tension force to the smooth shaft  46 . The tension force biases the enlarged head  48  of the smooth shaft  46  toward the hole  34  in the base protrusion  26  of the clamp assembly. As the enlarged head  48  of smooth shaft  46  advances toward the hole  34 , the cammed surface  49  on the enlarged head  48  meshes with the cammed surface  54  within the cam housing  52 . The tension force in the smooth shaft  46  is then transferred as a compression force to the cam housing  52 . The cam housing  52  itself is then biased into the third section  40  of the hole  34  by the compression force. As the cam housing  52  is biased into the third section  40  of the hole  34 , the cam housing  52  pushes the disc springs  50  into the second section  38  of the hole  34 . If the compression force surpasses the spring coefficient of the disc springs  50 , the disc springs  50  compress until the cam housing  52  abuts against the second transition ridge  41 . 
     If the wing nut  44  is over rotated., the tension force applied to the smooth shaft  46  may surpass a predetermined maximum threshold value. The cammed surface  49  on the enlarged head  48  and the cammed surface  54  in the cam housing  52  are designed to engage each other until the maximum threshold value is reached. If a tension force is experienced that surpasses the maximum threshold value, the cammed surface  49  on the enlarged head  48  and the cammed surface  54  in the cam housing  52  slip passed each other. As such, the smooth shaft  46  is free to spin with the threaded rod  42  and the wing nut  44 , thereby making further tightening impossible. 
     Referring to FIG. 3, it can be seen that to use the clamp assembly, both base protrusions  26 ,  27  of the clamp assembly are aligned. The wing nut  44  is then rotated so that the threaded rod  42  and the smooth shaft  46  linearly align. Once aligned, the wing nut  44  is tightened so that the wing nut  44  biases the two base protrusions  26 ,  27  of the clamp assembly toward each other. 
     Referring now to FIG. 4, it can be seen that when the wing nut  44  is fully tightened, the disc springs  50  become compressed. There are now two elements that are applying tension to the threaded rod  42  and the smooth shaft  46 . The first element is the wing nut  44  as it abuts against the base protrusion  27  of the clamp assembly. The second element is the disc springs  50 . The disc springs  50  apply tension to the smooth shaft  46  throughout their range of compression. Accordingly, should the wing nut  44  become loose, the tension in the smooth shaft  46  would remain constant because the disc springs  50  would partially decompress to compensate for the loosening wing nut  44 . If the disc springs  50  were compressed a total of ¼ inch, then the wing nut  44  can be retracted ¼ inch without effecting the tension in the smooth shaft  46  and thus the clamping strength of the assembly. 
     Furthermore, should the force applied to the clamp by the wing nut  44  become greater due to changes in temperature, the excess tension force can be absorbed by further compressing the disc springs  50  and the tension applied to the clamp assembly remains relatively constant. 
     The clamping device therefore provides a means to maintain a relatively constant clamping pressure on a flanged opening throughout a wide range of changing temperatures and internal vessel pressures. The result is a more reliable and versatile clamp that creates a more reliable and versatile seal. 
     In the described embodiments, a cam housing was used to prevent the wing nut from being over tightened. This feature is optional. All components in the clamp assembly are preferably made of stainless steel. Accordingly, it is unlikely that enough force can be applied by hand to damage the clamp assembly. The described cam housing can simply be replaced with a flat washer if desired. Similarly, the cammed surface on the enlarged head of the smooth shaft can also be eliminated. 
     It will be understood that the various figures described above illustrate only one preferred embodiment of the present invention. A person skilled in the art can therefore make numerous alterations and modifications to the shown embodiment utilizing functionally equivalent components to those shown and described. For example, there are numerous types of spring elements and spring configurations that can be substituted for the disc springs described. All such modifications are intended to be included within the scope of the present invention as defined by the appended claims.