Abstract:
An ultrasonic flow meter permitting easy insertion and removal of a tube or conduit. A partial ring transducer or partial cylinder transducer is used to permit easy insertion and removal of a flexible tube in an ultrasonic flow meter for measuring fluid flow. In another embodiment a split ring or split cylinder transducer is used to facilitate easy removal and insertion of a tube or conduit in which fluid flow is to be measured. In another embodiment a clamping system is used to securely hold and couple a tube or conduit within the ultrasonic flow meter system. The present invention is conveniently adapted to hold flexible tubes and in particular disposable flexible tubes often used in the medical industry.

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to ultrasonic flow meters used to measure fluid flow in tubes or conduits, and more particularly to an ultrasonic transducer system permitting easy insertion of flexible tubes. 
     BACKGROUND OF THE INVENTION 
     The use of ultrasonic transducers to measure fluid flow is well-known. One such flow meter is disclosed in U.S. Pat. No. 5,594,181 entitled “Ultrasonic Flow Meter” and issuing to Stange on Jan. 14, 1997. Therein disclosed is an ultrasonic flow meter having two ring-shaped piezoelectric transducers with one operating as an ultrasonic transmitter and the other one as an ultrasonic receiver. The two ring-shaped piezoelectric transducers are embedded into the wall of a pipe. 
     Another ultrasonic flow meter is disclosed in U.S. Pat. No. 5,974,897 entitled “Ultrasonic Flow Meter” and issuing to Koyano et al on Nov. 2, 1999. Therein disclosed is an ultrasonic flow meter having three ring-shaped oscillators disposed longitudinally along a tube so as to intimately contact the inner peripheral surface of the ring-shaped oscillators with the outer peripheral surface of the tube. The center oscillator generates an ultrasonic wave that is detected by the forward and rearward oscillators to obtain the flow rate of a fluid flowing through the tube. 
     Yet another flow meter is disclosed in U.S. Pat. No. 6,055,868 entitled “Ultrasonic Flow Meter” and issuing to Koyano et al on May 2, 2000. Therein disclosed is an ultrasonic flow meter with two ring-shaped oscillators disposed longitudinally along the tube. 
     While these ultrasonic flow meters have adequately measured fluid flow they have been difficult to use in many applications, particularly where different sizes of tubes are used and where there is a need to frequently replace tubes. Accordingly, efforts have been made to accommodate different sizes of tubes or to facilitate the replacement of tubes in an ultrasonic flow meter. One such system is disclosed in U.S. Pat. No. 5,179,862 entitled “Snap-On Flow Measurement System” and issuing to Lynnworth on Jan. 19, 1993. Therein disclosed is a block having a channel therein and a retaining pin. Also disclosed therein is a semi-rigid body having a keyhole slot. The block or body is used to hold a conduit adjacent a transducer block. Another device for accommodating a conduit is disclosed in U.S. Pat. No. 7,469,598 entitled “Method of Employing a Transit Time Ultrasound Sensor” issuing to Shkarlet et al on Dec. 30, 2008. Therein disclosed is a measuring channel having an acoustic couplant contained therein for retaining a conduit in the measuring channel. 
     While these devices have adequately held a tube or a conduit or permitted their replacement, they have often encountered problems of coupling the ultrasonic transducer to the tube and fluid flow therein to obtain strong signals utilized for measuring the fluid flow. Therefore there is a need for an ultrasonic flow meter system that can accommodate tubing easily and yet permit the easy replacement of the tubing and in particular tubing that may be flexible and disposable tubing such as that used in medical applications in which the tubing is disposed of after each use. 
     SUMMARY OF THE INVENTION 
     The present invention comprises an ultrasonic flow meter system in which tubing can be easily inserted and removed, facilitating the use of a flexible disposable tube often used in the medical field to transport fluids into or out of the body. The ultrasonic flow meter comprises a plurality of partial ring transducers that have an opening for insertion of a flexible tube. In another embodiment the ultrasonic transducer comprises a split-ring transducer having ring segments that may be placed together holding a tube. In yet another embodiment an ultrasonic flow meter comprises a partial ring transducer having a clamp contacting the tube at the opening formed in the partial ring transducer. The partial ring or split ring transducers permit easy insertion and removal of a tube or conduit in which fluid flow is to be measured and yet permits good coupling of the ultrasonic energy from the partial ring or split ring transducer to the tube or conduit. 
     Accordingly, it is an object of the present invention to provide an ultrasonic flow meter that permits a tube or conduit to be easily inserted and removed. 
     It is a further object of the present invention to provide an ultrasonic flow meter that provides good coupling to the tube or conduit for measuring fluid flow therein. 
     It is an advantage of the present invention that the ultrasonic flow meter can accommodate flexible tubes that may be made readily disposable. 
     It is another advantage of the present invention that flexible tubing commonly used in the medical field may be used. 
     It is a feature of the present invention that a partial ring transducer is used. 
     It is another feature of the present invention that a split ring transducer is used. 
     It is yet another feature of the present invention that a partial ring or split ring transducer is driven radially. 
     It is a further feature of the present invention that a partial cylinder or split cylinder transducer is driven axially. 
     It is yet another feature of the present invention that a clamp is used in combination with a partial ring transducer for holding the tube and providing good coupling. 
     These and other objects, advantages, and features will become more readily apparent in view of the following more detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an ultrasonic flow meter of the present invention using three partial ring transducers. 
         FIG. 2A  is a partial cross section of a partial ring transducer holding a tube or conduit. 
         FIG. 2B  is a perspective view illustrating a partial ring transducer. 
         FIG. 2C  is an elevational view illustrating a partial ring transducer. 
         FIG. 3  schematically illustrates an ultrasonic flow meter system using three partial ring transducers. 
         FIG. 4  schematically illustrates an ultrasonic flow meter system using two partial ring transducers. 
         FIG. 5  is a perspective view schematically illustrating an ultrasonic flow meter system utilizing two partial ring transducers that are driven radially. 
         FIG. 6  is a perspective view schematically illustrating an ultrasonic flow meter system utilizing two split ring transducers driven radially. 
         FIG. 7  is a perspective view schematically illustrating an ultrasonic flow meter system utilizing two partial cylinder transducers driven axially. 
         FIG. 8  is a perspective view schematically illustrating an ultrasonic flow meter system utilizing two split cylinder transducers driven axially. 
         FIG. 9  is a perspective view illustrating an ultrasonic flow meter system utilizing two partial ring transducers and a clamp. 
         FIG. 10  schematically illustrates an ultrasonic flow meter using a housing or damper. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a perspective view illustrating an ultrasonic flow meter of the present invention. The ultrasonic flow meter  10  holds a soft or flexible tube  12  having a fluid flow moving in the direction of arrows  14 . The tube  12  may be made of polyvinyl chloride or PVC, silicone, or other soft or flexible material. A plurality of partial ring transducers  16 ,  18  and  20  are placed around the tube  12 . Each of the plurality of partial ring transducers are coupled through a wire or conductor  22  to a controller containing electronics, not shown, for controlling the transmission and reception from the plurality of transducers  16 ,  18  and  20 . The center partial ring transducer  16  may act as a transmitter with the upstream partial ring transducer  18  and the downstream partial ring transducer  20  acting as receivers. The plurality of partial ring transducers may be made of a piezoelectric material, such as lead zirconate titanate or PZT, or other materials with piezoelectric properties. 
       FIGS. 2A-C  more clearly illustrates one of the partial ring transducers.  FIG. 2A  is a partial cross section illustrating the partial ring transducer  18  holding the tube  12 . The tube  12  is inserted into the partial ring transducer  18  through the opening  24  formed by a first end  26  and a second end  28 . The opening  24  is preferably less than one hundred and eighty degrees of the circumference of the partial ring  18  and it is preferably between sixty and ninety degrees of the circumference. The opening  24 , illustrated in  FIG. 2A , is approximately ninety degrees of the circumference.  FIG. 22  is a perspective view more clearly illustrating the shape and the two ends  26  and  28  of the partial ring transducer  18 .  FIG. 2C  additionally illustrates the two ends  26  and  28  between the opening  24  in the partial-ring transducer  18 . 
       FIG. 3  schematically illustrates the ultrasonic flow meter  10  with the plurality of partial-ring transducers  16 ,  18  and  20  coupled to a controller  30 . The controller  30  may control the plurality of partial ring transducers  16 ,  18  and  20  so as to drive the central partial ring transducer  16  as a transmitter forming an ultrasonic wave within the fluid contained in tube or conduit  12  to the upstream partial ring transducer  18  and the downstream partial ring transducer  20  that act as receivers. The time difference or time lag between the received signal at the upstream partial ring transducer  18  and the downstream partial ring transducer  20  is proportional to the fluid flow in tube  12 , represented by arrows  14 . Accordingly, the controller  30  may operate similarly to the operation of the ultrasonic flow meter disclosed in U.S. Pat. No. 5,974,897, which is herein incorporated by reference. 
       FIG. 4  illustrates another embodiment of an ultrasonic flow meter  110  utilizing two partial ring transducers  116  and  118  coupled through wires or conductors  122  to a controller  130 . The fluid flow represented by arrows  14  may be measured by driving the two partial ring transducers similar to that as disclosed in U.S. Pat. No. 6,055,868, which is herein incorporated by reference. 
       FIG. 5  illustrates another embodiment of the present invention wherein the ultrasonic flow meter  210  comprises two partial ring transducers  216  and  218  holding the tube or conduit  12 . The two partial ring transducers  216  and  218  are driven by a flow meter circuit  230 . The flow meter circuit  230  preferably drives the partial ring transducers  216  and  218  so they vibrate radially causing a wave to travel within the fluid in the tube  12 . The radially driving of the two partial ring transducers  218  and  216  causes an ultrasonic wave to propagate initially radially and then axially within the tube  12 . Arrow  232  represents the direction of radial vibration of the partial ring transducers  216  and  218 . 
       FIG. 6  illustrates an embodiment of the invention utilizing two split ring transducers. This embodiment may be used to hold more rigid pipe or tubing, such as made from polytetrafluoroethylene or PTFE, glass, or steel. The ultrasonic flow meter  310  comprises two split ring transducers  316  and  318  that are assembled around the tube  12  in two halves. Split ring transducer  316  is comprised of a first half  316   a  and a second half  316   b  and split-ring transducer  318  is comprised of a first half  318   a  and a second half  318   b . The halves are placed together to securely hold the tube or conduit  12 . While two halves are illustrated in  FIG. 6 , multiple segments may be used to form the split ring transducer and to hold the tube or conduit  12  when assembled. The use of a split ring permits the tube or conduit  12  to be easily removed and replaced in the ultrasonic flow meter  310 . The split ring transducers  316  and  318  are driven by a flow meter circuit  330  similarly to that described with respect to  FIG. 5 . Arrow  332  represents the direction of radial vibration of the split ring transducers  316  and  318 . 
       FIG. 7  illustrates yet another embodiment of the present invention utilizing an axially driven transducer. Ultrasonic flow meter  410  comprises partial cylinder transducers  416  and  418  holding the tube or conduit  12  and driven by a flow meter circuit  430 . The flow meter circuit  430  drives the partial cylinder transducers  416  and  418  at a certain frequency so they vibrate axially as represented by arrow  434 . The axial driving of the partial cylindrical transducers  416  and  418  provide a positive wave transmission improving the detection of the fluid flow within the tube or conduit  12 . 
       FIG. 8  illustrates yet another embodiment of the present invention in which the ultrasonic transducers are driven axially. Ultrasonic flow meter  510  comprises split-cylinder transducers  516  and  518 . Split cylinder transducer  516  is comprised of a first half cylinder  516   a  and a second half cylinder  516   b  and split cylinder transducer  518  is comprised of a first half cylinder  518   a  and a second half cylinder  518   b . By utilizing split cylinder transducers  516  and  518  the tube or conduit  12  can readily be removed from the ultrasonic flow meter  510 . The flow meter circuit  530  drives the split cylinder transducers  516  and  518  axially as represented by arrow  534 . 
       FIG. 9  is a perspective view of another embodiment of the present invention utilizing a clamp. The ultrasonic flow meter  610  comprises partial ring transducers  616  and  618  holding a tube or conduit  12  when placed through the opening  624  formed by the split ring transducers  616  and  618 . A housing  638  is formed around the partial ring transducers  616  and  618  and is formed as part of a clamp  636 . The clamp  636  has a lever or handles  640  coupled to a spring hinge  642 . The spring hinge  642  provides a predetermined amount of force. A tube support  644  is placed adjacent the opening  624  and contacts the tube or conduit  12  so as to improve coupling between the partial ring transducers  616  and  618  and the tube or conduit  12 . Accordingly the tube or conduit  12  can easily be removed when desired and replaced within the ultrasonic flow meter  610  by pressing on lever or handle  640  so as to lift the tube support  644  off of and away from the tube or conduit  12  permitting the tube or conduit  12  to be easily removed through the openings  624  formed in the partial ring transducers  616  and  618 . The use of the tube support  644  assures that the tube  12  stays in position and improves the coupling providing an improved signal representative of fluid flow. 
       FIG. 10  schematically illustrates an embodiment of the invention using housings or dampers  746  and  748  adjacent partial ring transducers  716  and  718 . The housings or dampers  746  and  748  help to hold the tube  12  and to dampen the ultrasonic energy on the side of the tube  12  on which the fluid flow is not being measured. The tube  12  is inserted through openings  724  and  750  formed in the partial ring transducers  716  and  718  and housings or dampers  746  and  748 . Controller  730  is coupled to the partial ring transducers  716  and  718  by wires or conductors  722 . 
     Accordingly it should readily be appreciated that the present invention, by utilizing a partial ring or partial cylinder transducer as well as a split ring or split cylinder transducer makes possible the use of an ultrasonic flow meter with disposable or flexible tubing that can readily and easily be replaced permitting the use of ultrasonic flow meters in application that were previously not possible or practical. One such application is in the medical field where the tubes are usually made disposable. Additionally, by providing a partial ring or cylinder the present invention permits different sizes of flexible tubes to be utilized in a single device and yet permitting relatively good coupling so as to accurately measure fluid flow. If needed, an acoustic coupling material, such as gel or grease, may be applied between the transducer and the tube to achieve improved coupling. 
     While the present invention has been described with respect to several different embodiments, it will be obvious that various modifications may be made without departing from the spirit and scope of this invention.