Abstract:
A none intrusive pressure sensing device that clamps on to a pressure line and detects the internal pressure of the pressure line by detecting the resultant changes in the diameter of the pressure line. The clamp is held together by a fastener having a sensing element, such as a strain gage, that is able to detect the change in length of the fastener as the pressure line and the clamp expand and contract with the internal pressure of the pressure line.

Description:
FIELD OF THE INVENTION 
   The invention relates to pressure sensors and, more particularly, relates to non-intrusive devices for detecting pressures of a pressurized fluid or gas in a pressure line without breaching a wall of the pressure line or contacting the fluid or gas inside the pressure line. 
   BACKGROUND OF THE INVENTION 
   Most conventional pressure transducers used to detect pressures in the pressure lines of machinery are intrusive, requiring exposure to the pressurized fluid or gas in the pressure line. This involves an assembly process requiring a breach in the wall of the pressure line or some other method of direct exposure of the pressure transducer to the pressurized fluid or gas. 
   SUMMARY OF THE INVENTION 
   The assembly processes for the intrusive transducers tend to increase assembly and maintenance costs for the machinery and to increase the potential for contamination of the fluid or gas. The complexity of some of the conventional non-intrusive pressure transducers tends to be costly and to make such transducers difficult to fabricate. The bulkiness of a remainder of the conventional non-intrusive pressure transducers tends to decrease the range of use, especially in machinery where space is at a premium. 
   Described herein is a device and method for non-intrusively detecting an internal pressure of a pressure line. A clamp with two arms is closed over the outer diameter of the pressure line for a snug fit having first ends of the clamp arms pivotally connected and second ends of the clamp arms connected by a sensor fastener. As the internal pressure in the pressure line increases and decreases, the outer diameter of the pressure line expands and contracts causing a diameter of the clamp to expand and contract and the length of the sensor fastener to change. The sensor fastener includes a sensing element that detects the length of the sensor fastener as it changes with the pressure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will be described in detail, with references to the following figures, wherein: 
       FIG. 1  is a side view of an exemplary embodiment of the clamping cuff assembly of the invention; 
       FIG. 2  is a front view of the clamping cuff assembly of  FIG. 1 ; 
       FIG. 3  is a top view of the clamping cuff assembly of  FIG. 1 ; 
       FIG. 4  is an exploded view of the clamping cuff assembly of  FIG. 1 ; 
       FIG. 5  is a view of an exemplary embodiment of a sensor fastener; 
       FIG. 6  is a side view of a second embodiment of the clamping cuff assembly of the invention; 
       FIG. 7  is a front view of the clamping cuff assembly of  FIG. 6 ; 
       FIG. 8  is a top view of the clamping cuff assembly of Fib.  6 ; 
       FIG. 9  is a side view of a third embodiment of the clamping cuff assembly of the invention; 
       FIG. 10  is a top view of the clamping cuff assembly of  FIG. 9 ; and 
       FIG. 11  is a functional diagram illustrating the connections between strain gages, a controller and a display. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  is a side view of an exemplary embodiment of the clamping cuff assembly of the invention. As illustrated in  FIG. 1  as well as  FIGS. 2–4 , the clamping cuff assembly includes a clamping cuff  10  and a sensor fastener  20 . 
   The clamping cuff  10  includes: a first arm  11  having a first arm first end  11   a  and a first arm second end  11   b ; a second arm  12  having a second arm first end  12   a  and a second arm second end  12   b ; a bolt  13  and a nut  14 . The nut  14  and bolt  13  pivotally connect the first arm  11  and the second arm  12  via holes  11   c  and  12   c  in the first arm first end  11   a  and the second arm first end  12   a , respectively, as illustrated in  FIGS. 1–4 . The first arm and second arms  11 ,  12  are made of strong and relatively rigid materials. These materials include, but are not limited to, aluminum and steel. 
   As illustrated in  FIG. 5 , the sensor fastener  20  includes four strain gages  21   a – 21   d , a nut  22  and a bolt  23  having a threaded portion  23   a , a shank  23   b  and a head  23   c . The nut  22  is a conventional locking nut. The four strain gages  21   a – 21   d  are attached at equal angular positions around the circumference of the shank  23   b . The strain gages  21   a – 21   d  are then electrically connected to a conventional measuring device or controller  50  for receiving signals from the strain gages  21   a – 21   d , converting those signals to read in units of pressure, and displaying the converted results on a display  40  as illustrated in  FIG. 11 . 
   In operation, the first and second cuff arms  11 ,  12  are placed around the pressure line  30 . The first arm second end  11   b  and the second arm second end  12   b  are then connected via the sensor fastener  20 , slot  11   d  and slot  12   d  as illustrated in  FIGS. 1–4 . Finally the sensor fastener  20  is tightened, i.e., pre-loaded in tension for a snug fit between the pressure line  30  and the cuff assembly  10 . 
   As the pressure line  30  expands and contracts with increasing and decreasing internal pressure, the shank  23   b  lengthens and shortens accordingly as the sensor fastener  20  holds the cuff assembly  10  together via tension. Thus, the strain gages  21   a – 21   d  detect any changes in a length of the sensor fastener  20  as they, i.e., the strain gages  21   a – 21   d , lengthen and shorten in concert with the shank  23   b.    
     FIG. 6  is a side view of a second embodiment of the clamping cuff assembly of the invention comprising: a first arm  111  having a first arm first end  111   a  and a first arm second end  111   b ; a second arm  112  having a second arm first end  112   a  and a second arm second end  112   b ; and a sensor fastener  120  including two nuts  122   a ,  122   b , a screw  123 , and four strain gages  121   a – 121   d . The first arm second end  111   b  includes a slot  111   d  and the second arm second end  112   b  includes a hole  112   d . The screw  123  includes a first connecting portion  123   a , a second connecting portion  123   b  and a shank  123   c . All other components remain the same as in the first embodiment. As illustrated in  FIGS. 6 and 7 , in this particular embodiment the first arm second end  111  and the second arm second end  112  extend past each other. Thus, in the second embodiment of the invention, the sensor fastener  120  is compressive as it holds the clamping cuff assembly  100  together via a compressive load. The compressive nature of the sensor fastener  120  is the primary functional difference between the first and second embodiments of the invention. The pivotal connection between the first arm first end  111   a  and the second arm first end  112   a  is established after the first arm  111  and the second arm  112  are placed in position about the pressure line  30  to avoid interference between the first arm second end  111   b  and the second arm second end  112   b.    
   In operation the first and second arms  111 ,  112  of the clamping cuff  100  are placed around the pressure line  30  and held in place by assembling the sensor fastener  120  as illustrated in  FIGS. 6 and 7 . The first arm first end  111   a  and the second arm first end  112   a  are then pivotally connected via the holes  111   c  and  112   c  using the nut  14  and the bolt  13 . Finally, as indicated in  FIG. 6 , the sensor fastener  120  is assembled by: placing the first connecting portion  120   a  into the hole  112   d ; sliding the second connecting portion into the slot  111   c  such that nuts  122   a  and  122   b  are on opposite sides of the slot  111   d ; and adjusting the nuts  122   a  and  122   b  for a frictional connection to the opposite sides of the slot  111   d  as well as a compressive pre-load on the shank  120   c . The sensor fastener  120  then, respectively, shortens and lengthens as the clamp  100  expands and contracts with the internal pressure of the pressure line  30 . 
     FIG. 9  illustrates a third exemplary embodiment of the invention. This embodiment is essentially the same as the first embodiment illustrated in  FIG. 1 . However in this embodiment the clamp  200  comprises a first flexible arm  211  with a first arm first end  211   a  and a first arm second end  211   b ; a second flexible arm  212  with a second arm first end  212   a , and a second arm second end  212   b . In this particular embodiment, the first ends  211   a ,  212   a  are directly joined and indistinguishable from each other as the first and second flexible arms comprise a single and continuous piece of flexible material. The flexible material may include, but is not limited to, nylon and leather. 
   Having described the illustrated embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.