Abstract:
An ultrasonic liquid sensor for detecting liquid in a tube having sidewalls includes a first intermediate mounting plate held in physical communication with a first sidewall of the tube, a second intermediate mounting plate held in physical communication with the second sidewall of the tube. The plates are configured to allow the ultrasonic signal to pass therethrough. The sensor also includes a first and a second transducer element. The first and second transducer elements are mounted to the intermediate mounting plates and are configured to receive the ultrasonic signal passing through the sidewalls of the tube as well as the intermediate mounting plates to determine the presence or absence of liquid in the tube. The sensor can be enclosed in a self-contained unit and a support assembly can be used and formed of metal material or non-metal material to interface with the sensor and a secondary circuit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority of Provisional U.S. Patent Application Ser. No. 61/167,616, filed Apr. 8, 2009, entitled “SYSTEM AND METHOD FOR FABRICATING AN ULTRASONIC LIQUID SENSOR”. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention is directed to a sensing device. More particularly, the present invention pertains to a sensing device used to detect the presence or absence of liquid within a tube. 
         [0003]    Fluid or liquid within a tube or conduit may be detected using ultrasonic waves. Typically, a transmitting transducer is positioned on one side of a tube and a receiving transducer is positioned on the opposing side of the tube. The transmitting transducer emits an ultrasonic signal, which is propagated through the tube wall and into the tube itself. If the tube is empty, no signal is received by receiving transducer. If there is liquid present in the tube, however, the receiving transducer receives a signal and conveys the signal to, for example, a control circuit. 
         [0004]    Typically, the ultrasonic energy is generated and received by a pre-made joint sensor system consisting of a transmitting transducer and receiving transducer pre-fastened to a hollow, open-ended sleeve. In order to use the joint sensor system with a desired tube, a section of the tube is removed and the joint sensor system is joined to the tube at the area where the portion of tube has been removed. The tube is connected to the sleeve such that liquid passes through the sleeve, and the joint is then sealed at each end of the sleeve to the tube. The joint sensor system then becomes an integral part of the tube. While effective, such joints and seals are prone to leakage. In addition, placing the sensor integrally within the line of the tube is not only time-consuming, but also expensive. 
         [0005]    In another embodiment, transducers are applied directly to the tube sidewalls with fastening agents such as screws or chemical means, such as adhesive. Unfortunately, these fastening agents do not always maintain a secure connection and may absorb and/or distort the ultrasonic waves. In addition, in this configuration, the bottom electrode of the transducer may not be in electrical communication with the control circuit effectively, and thus, the signal becomes distorted and/or attenuated. 
         [0006]    Accordingly, there is a need for an ultrasonic liquid sensing device that maintains contact with the tube and does not distort or otherwise interfere with the transmission and reception of ultrasonic waves. Such a sensor is easy to mount and can be used and re-used with a variety of different sized and shaped tubes. Most desirably, no cutting of the tube is necessary and the tube maintains its structural integrity. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    An ultrasonic liquid sensor for detecting liquid in a tube having sidewalls includes a first intermediate mounting plate, a second intermediate mounting plate, a first transducer element, and a second transducer element. The first and second intermediate mounting plates are held in constant physical communication with a first and second sidewall, respectively, of the tube and are configured to allow an ultrasonic signal to pass therethrough. The plate can be fabricated from metal or non-metal materials. The non-metal plate can have conductive material included therein to provide an electrical connection path for the transducer circuitry. 
         [0008]    The intermediate mounting plates have first and second sides. The second sides of the intermediate mounting plates are held in close physical communication with the sidewalls of the tube, while the transducers are mounted to the opposing (first) sides of each of the intermediate mounting plates such that, in a use-position, the intermediate mounting plates are positioned between the tube sidewalls and the transducers. 
         [0009]    The first transducer element, mounted to the first intermediate mounting plate, is configured to transmit an ultrasonic signal through the first intermediate mounting plate and the first sidewall of the tube. The second transducer element, mounted to the second intermediate mounting plate, is configured to receive the ultrasonic signal passing through the second sidewall of the tube and through the second intermediate mounting plate, in order to determine the presence or absence of liquid in the tube. The sensor can be enclosed in a self-contained unit. 
         [0010]    In an embodiment, the intermediate mounting plates have sufficient rigidity and strength to maintain continual and consistent direct, physical contact with the sidewalls of the tube while interfacing directly with a secondary electrical circuit. In another embodiment, a support assembly and/or a housing base assists in maintaining the intermediate mounting plates in direct, physical contact with the sidewalls of the tube. The support assembly and housing bases can both be formed of metal material or non-metal material and can serve to interface with the sensor and a secondary circuit. In an embodiment, the support assembly and/or housing bases provide rigid support to the intermediate mounting plates without the use of screws or adhesive while maintaining the shape and integrity of the tube and without attenuating or interfering with the sensor signal. 
         [0011]    These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein: 
           [0013]      FIG. 1  is a perspective view of a portion of an ultrasonic liquid sensor; 
           [0014]      FIG. 2  is a top view of the ultrasonic liquid sensor in accordance with the principles of the present invention; 
           [0015]      FIG. 3  is a perspective photograph of a plurality of the present sensors mounted to a printed circuit board; 
           [0016]      FIG. 4  is a perspective view of an intermediate mounting plate and transducer; 
           [0017]      FIG. 5  is a perspective view of a shared contact; 
           [0018]      FIG. 6  is a perspective view of an array of an embodiment of the present sensors; 
           [0019]      FIGS. 7  is a perspective view of the array of  FIG. 6 ; 
           [0020]      FIG. 7A  is a top view of the array of  FIG. 7  with a support assembly and housing bases; 
           [0021]      FIGS. 8 and 9  are perspective views of another embodiment of the present sensor; 
           [0022]      FIG. 10  is a perspective view of an array of the sensor embodiment of  FIGS. 8 and 9 ; and 
           [0023]      FIG. 11  is a top view of the array of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated. 
         [0025]    It should be further understood that the title of this section of this specification, namely, “Detailed Description Of The Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein. 
         [0026]    In the present ultrasonic liquid sensor, an ultrasonic signal is propagated between two transducers, through the material of intermediate mounting plates, and through a tube, in order to determine the presence or absence of liquid in the tube. In the present disclosure, “liquid” refers to any fluid medium capable of propagating an ultrasonic signal therethrough and includes any water-based or oil-based solution or mixture, gels and the like. In addition, a “tube” refers to any hollow conduit through which liquid may be passed and have any shaped cross-section, including but not limited to circular, rectangular, squared, oval, and the like. 
         [0027]    Referring now to the figures and in particular  FIGS. 1 and 2 , there is shown an exemplary embodiment of an ultrasonic liquid sensor  100  (“sensor”) in accordance with the principles of the present invention. The sensor  100  includes a pair of intermediate mounting structures, hereafter referred to as first and second intermediate mounting plates  110 ,  111  respectively, as well as a transmitting transducer  116  and a receiving transducer  117 . 
         [0028]    The first and second intermediate mounting plates  110 ,  111  can be relatively flat plates, discs, or other shaped elements. The first and second intermediate mounting plates  110 ,  111  may be fabricated from conductive or non-conductive materials and can include, but are not limited to, aluminum, steel, stainless steel, common die casting materials such as zinc, brass, plastics such as polyphenylene sulfide (PPS), fiberglass materials such as printed circuit board material (FR4), and mechanically rigid thermoset. It will be appreciated by those skilled in the art that this list is not exhaustive and includes any type of material which allows ultrasonic waves to pass through without distorting or attenuating the ultrasonic signal unduly. 
         [0029]    The first intermediate mounting plate  110  has a first side  112 A and a second side  112 B. Similarly, the second intermediate mounting plate  111  also has a first side  113 A and a second side  113 B. Each intermediate mounting plate  110 ,  111  is rigid, and in a use-configuration is positioned with second sides  112 B and  113 B placed in physical communication with the outer sidewalls of the tube T. 
         [0030]    The transmitting transducer  116  is mounted to the first intermediate mounting plate  110 . The transmitting transducer  116  has a top side  118  (with a top electrode  119 ) and a bottom side  120  (with a bottom electrode  121 ). The bottom side  120  of the transmitting transducer  116  is mounted to the first side  112 A of the intermediate mounting plate  110 . The bottom side  120  may be bonded to a conductive pad  122  on the intermediate mounting plate  110  or may be bonded to the intermediate mounting plate  110  directly if the intermediate mounting plate  110  is formed of a conductive material. 
         [0031]    Similarly, the receiving transducer  117  is mounted to the second intermediate mounting plate  111 . The receiving transducer  117  has a top side  128  (including a top electrode  129 ) and a bottom side  130 . The bottom side  130  (including a bottom electrode  131 ) of the receiving transducer  117  is mounted to the first side  113 A of the intermediate mounting plate  111 . The bottom side  120  of the receiving transducer  117  may be bonded to a conductive pad  123  on the intermediate mounting plate  111  or may be bonded to the intermediate mounting plate  111  directly if the intermediate mounting plate  111  is formed of a conductive material. 
         [0032]    In an embodiment shown in  FIGS. 2 and 3 , sensor  100  includes a support assembly  140  for the intermediate mounting plates  110 ,  111 . The support assembly  140  may be manufactured from plastics or metals, from conductive, non-conductive, or a combination of conductive and non-conductive material. Such materials, as discussed above, can include, but are not limited to, aluminum, steel, stainless steel, common die casting materials such as zinc, brass, plastics such as polyphenylene sulfide (PPS), common injection molding materials, fiberglass materials such as printed circuit board material (FR4), and mechanically rigid thermoset. The support assembly  140  may include any circuitry necessary to interface with a secondary circuit  150  and the sensor  100 . 
         [0033]    It will be appreciated by those skilled in the art that a support assembly may not be required; the intermediate mounting plates may be formed with sufficient rigidity and strength to maintain physical contact with the sidewalls of the tube without additional support. It will also be appreciate by those skilled in the art that in an embodiment having no support assembly as described, an interface between the sensor and a control circuit or other secondary circuit may still be required and is anticipated and contemplated by the present disclosure. 
         [0034]    In another exemplary embodiment shown in  FIGS. 4-7 , a sensor  400  includes an intermediate mounting plate  410 , a transducer  416 , and a shared contact  460 . The transducer  416  can be configured as a transmitting transducer or as a receiving transducer. In a use-position, as shown in  FIG. 6 , the shared contact  460  is positioned between two sensor assemblies  400  ( 400 A and  400 B), contacting the transducers  416  of each of the two sensor assemblies. Tubes T 1 , T 2 , and T 3 , may be positioned between the intermediate mounting plates with additional support for the intermediate mounting plates provided by the support assembly  440  and/or the housing base  470 , as shown in  FIGS. 6 ,  7 , and  7 A. 
         [0035]    In yet another exemplary embodiment shown in  FIGS. 8-11 , sensor  800  includes a pair of intermediate mounting plates  810 ,  811  with a transducer  816  sandwiched between intermediate mounting plates  810 ,  811 . In a use-configuration, as shown in  FIG. 10 , sensor  800 A is paired with other sensors  800 B,  800 C, and  800 D. In the example shown in  FIG. 10 , three tubes T 1 , T 2 , and T 3  are positioned between two adjacent sensors  800 , such that the intermediate mounting plates  811  of each sensor  800  is in physical contact with the sidewall of one tube and the intermediate mounting plate  810  is in physical contact with the sidewall of an adjacent tube. In the embodiment shown in  FIG. 10 , a housing base  870  and/or support assembly  840  is also present. 
         [0036]    In the embodiments discussed above, the sensor operates in a manner such that an ultrasonic signal is transmitted from the transmitting transducer, propagates through the first intermediate mounting plate, through the tube first sidewall, through any liquid present, through the opposite sidewall (second sidewall) of the tube, and through the second intermediate mounting plate of the sensor until it is finally received by the receiving transducer. The signal is then transformed by the transducer and relayed to a control circuit or the like to indicate the presence or absence of liquid within the tube. It will be appreciated by those skilled in the art that the transducers themselves are not in physical contact with the sidewalls of the tubes; it is the intermediate mounting plates which maintain physical contact with the sidewalls. 
         [0037]    For example, in  FIGS. 1-3 , the sensor  100 , the transmitting transducer  116 , mounted to the first intermediate mounting plate  110 , emits an ultrasonic signal. The material of the first intermediate mounting plate  110  is capable of allowing the ultrasonic signal to pass through without modifying, attenuating, or distorting the ultrasound signal. The intermediate mounting plate  110  is in physical communication with the sidewall of the tube T such that the ultrasound signal then passes into the tube T. If there is no liquid present in the tube T, the ultrasound signal will stop or not continue to propagate. 
         [0038]    If, however, there is liquid present, the ultrasound signal will propagate through the liquid and penetrate the opposing sidewall of the tube T. As with the first intermediate mounting plate  110 , the second intermediate mounting plate  111  is also made from a material which allows the ultrasound signal to pass through, again without modification, attenuation, or distortion. The ultrasound signal is received by the receiving transducer  117 . The receiving transducer  117  can then convert the ultrasound signal to an electrical signal and relay that signal to a secondary circuit  150  such as a control circuit. The electrical signal may be relayed through the circuitry enclosed in the support assembly interface, or directly from the transducer through another form of electrical interface. 
         [0039]    In the embodiments shown in  FIGS. 4-7  and  8 - 11 , the number of individual components needed when used with a plurality of tubes can be decreased. In the embodiments of  FIGS. 4-7  and  8 - 11 , because the transducers serve as dual mode transducers (i.e. act as both transmitting and receiving transducers) fewer components are necessary in these embodiments. 
         [0040]    For example, in  FIGS. 4-7 , the sensors  400 A,  400 B, and  400 C operate in essentially the same manner as the embodiment shown in  FIGS. 3  and described above, with a slight modification. The pair of mounting plates  400  provide the same ultrasonic function as mounting plates  110  and  111  above, but with the use of the shared contact  460 , the plates  410  and shared contact  460  provide an electrical path for both the transmitting and receiving transducer pairs. 
         [0041]    In another example shown in  FIGS. 8-11 , the sensors  800 A,  800 B,  800 C, and  800 D operate the same way as the embodiment shown in  FIGS. 3  and described above, again with a slight modification. The pair of mounting plates  800  provide the same ultrasonic function as mounting plates  110  and  111 , but with the use of plates  810  and  811  an electrical path for both the transmitting and receiving transducer pairs is provided and when placed between a pair of liquid tubes, for example, T 1  and T 2  or T 2  and T 3  as shown in  FIG. 10 , a single transducer and plate assembly  800  situated between the tubes can alternate between the function of a transmitter for one tube and a receiver for the other tube. 
         [0042]    The advantages to the present ultrasonic liquid sensor will be appreciated by those skilled in the art. The sensor provides a cost-effective assembly and method for determining the presence or absence of liquid in a tube. The present sensor eliminates the need for the tube to be cut in order for the sensor to be inserted, thus maintaining the integrity of the tube. The present sensor is easy to install and maintain. In addition, the sensor can be re-used with different tubes and can be adjusted to fit any diameter tube. 
         [0043]    All patents referred to herein, are incorporated herein by reference, whether or not specifically done so within the text of this disclosure. In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
         [0044]    From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.