Patent Publication Number: US-2023156877-A1

Title: Microwave heating apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heating apparatus, especially to a microwave heating apparatus. 
     2. Description of the Prior Art(s) 
     Nowadays, one way of heating corrosive liquid is usually indirect heating. However, since said indirect heating is time-consuming and energy-consuming, efficiency of the whole process of the indirect heating is low. With reference to  FIGS.  4  and  5   , another way of heating the corrosive liquid is microwave heating. The theory of the microwave heating is the process of heating a dielectric material in an alternating electric field. Due to properties of the dielectric material, the dielectric material is heated by means of dielectric loss produced in the dielectric material when the dielectric material is subjected to an electromagnetic field. In practice, the microwave heating is applied to chemical process or liquid for rapid heating, distillation, thermal catalysis, thermal chemical reaction, etc. 
     A conventional microwave heating apparatus includes a magnetron  90 , a circulator  91 , a tuner  92 , a heating tube  93 , and a moving short  94 . The magnetron  90  is used to generate microwave. The circulator  91  is used to protect a microwave source from microwave that is reflected from a rear end of the conventional microwave heating apparatus. The heating tube  93  is provided with a guiding tube  95  that is mounted through the heating tube  93 . The guiding tube  95  extends perpendicular to a propagation direction of the microwave and is for liquid to be heated to flow through. The tuner  92  and the moving short  94  is used to adjust impedance matching of the microwave, such that the liquid to be heated can be well heated by the microwave while passing through the heating tube  93 . 
     However, when chemical liquid is heated by the microwave and temperature of the chemical liquid increases, the relation between dielectric constant or dielectric loss of the chemical liquid and frequencies of the microwave is functional, and the dielectric constant and the dielectric loss of the chemical liquid are highly correlated with the temperature of the chemical liquid. With increase of the temperature of the chemical liquid, the dielectric constant and the dielectric loss change dramatically. 
     Thus, electrical properties of material to be heated change during the heating process, which causes the impedance matching to change constantly. Consequently, efficiency of the microwave heating is constantly changing during the heating process, such that the efficiency of the microwave heating and the heating effect are unstable. 
     In order to overcome the above-mentioned problem, the expensive and automatic tuner  92  is used to automatically adjust the impedance when the impedance changes during the heating process. However, in addition to be expensive, the tuner  92  is mechanically operated to adjust the impedance. The impedance that changes rapidly is often unable to become perfect match. 
     To overcome the shortcomings, the present invention provides a microwave heating apparatus to mitigate or obviate the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     The main objective of the present invention is to provide a microwave heating apparatus having a magnetron, a circulator, a heating assembly, and an end assembly. A front end of the circulator is connected to the magnetron. 
     The heating assembly has a base waveguide tube and a guiding tube. The base waveguide tube has an inlet port and a connecting port. The inlet port is formed in a front end of the base waveguide tube, and the front end of the base waveguide tube is connected with a rear end of the circulator. The connecting port is formed in a rear end of the base waveguide tube. The base waveguide tube has an imaginary axis defined through the front end of the base waveguide tube and the rear end of the base waveguide tube. The guiding tube is mounted through and securely mounted on the base waveguide tube and has an imaginary central line defined along an elongation direction of the guiding tube. An included angle between the imaginary central line and the imaginary axis is smaller than 90 degrees. 
     The end assembly includes a reflecting component and an adjusting module. The reflecting component is movably mounted in the base waveguide tube, is disposed between the guiding tube and the connecting port and has a reflecting surface facing toward the guiding tube. The adjusting module is mounted on the rear end of the base waveguide tube, is connected to the reflecting component, and selectively drives the reflecting component to adjust a distance defined between the reflecting component and the guiding tube. 
     By adjusting the included angle between the imaginary central line and the imaginary axis, an inclined angle of the reflecting surface of the reflecting component and the distance defined between the reflecting component and the guiding tube, a best impedance matching of the microwave can be set according to impedance change of liquid to be heated, so as to be suitable for different liquids. Moreover, an expensive auto tuner can be omitted, such that cost of the microwave heating apparatus can be saved and system complexity of the microwave heating apparatus can be reduced. 
     Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a microwave heating apparatus in accordance with the present invention; 
         FIG.  2    is a cross-sectional side view of the microwave heating apparatus in  FIG.  1   ; 
         FIG.  3    is an operational cross-sectional side view of the microwave heating apparatus in  FIG.  1   ; 
         FIG.  4    is a perspective view of a conventional microwave heating apparatus in accordance with the prior art; and 
         FIG.  5    is an enlarged side view of the conventional microwave heating apparatus in  FIG.  4   . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIG.  1   , a microwave heating apparatus in accordance with the present invention comprises a magnetron  10 , a circulator  20 , a heating assembly  30 , and an end assembly  40 . 
     The magnetron  10  is disposed at a front end of the microwave heating apparatus and is used to generate microwave. Since the magnetron  10  is conventional, a more detailed description of the magnetron  10  is omitted. 
     The circulator  20  has a front end connected to the magnetron  10 . The circulator  20  is used to protect a microwave source from microwave that is reflected from a rear end of the microwave heating apparatus. Since the circulator  20  is conventional, a more detailed description of the circulator  20  is omitted. 
     With further reference to  FIGS.  1  to  3   , the heating assembly  30  has a base waveguide tube  31 , two mounting seats  315 , and a guiding tube  32 . 
     The base waveguide tube  31  is hollow, is rectangular in cross-section, and has an inlet port  311 , a connecting port  312 , an upper mounting hole  313  and a lower mounting hole  314 . The inlet port  311  is formed in a front end of the base waveguide tube  31 . The front end of the base waveguide tube  31  is connected with a rear end of the circulator  20 . The connecting port  312  is formed in a rear end of the base waveguide tube  31 . The upper mounting hole  313  and the lower mounting hole  314  are obliquely formed through an upper sidewall and a lower sidewall of the base waveguide tube  31  respectively and are coaxial with each other. 
     The two mounting seats  315  are securely mounted on an outer side surface of the base waveguide tube  31 . Each of the mounting seats  315  has a through hole  316  and multiple threaded holes  317 . The through hole  316  is formed through the mounting seat  315 . The through hole  316  of one of the mounting seats  315  aligns with the upper mounting hole  313 . The through hole  316  of the other one of the mounting seats  315  aligns with the lower mounting hole  314 . Each of the threaded holes  317  has an internal thread. 
     Moreover, the base waveguide tube  31  has an imaginary axis  318 . The imaginary axis  318  is an imaginary line of a central axis of the base waveguide tube  31  and is defined through the front end of the base waveguide tube  31  and the rear end of the base waveguide tube  31 . 
     The guiding tube  32  is hollow and is made of quartz. However, material of the guiding tube  32  is not limited to quartz, and the guiding tube  32  may be made of any material that allows the microwave to pass through and does not absorb the microwave. 
     The guiding tube  32  is mounted through the through holes  316  of the two mounting seats  315  and the upper mounting hole  313  and the lower mounting hole  314  of the base waveguide tube  31 , is securely mounted on the base waveguide tube  31 , and has an imaginary central line  324 . The imaginary central line  324  is defined along an elongation direction of the guiding tube  32 . 
     An included angle θ between the imaginary central line  324  and the imaginary axis  318  is smaller than 90 degrees. 
     The guiding tube  32  is further is provided with two fastening seats  322 . The two fastening seats  322  are securely mounted around the guiding tube  32 , are separately disposed on the guiding tube  32 , and are securely connected with the two mounting seats  315  respectively. Specifically, each of the fastening seats  322  has multiple fastening holes  323  aligning with the threaded holes  317  of a corresponding one of the mounting seats  315  respectively. Multiple fasteners are mounted through the fastening holes  323  of the fastening seats  322  respectively and are engaged in the threaded holes  317  of the two mounting seats  315 . However, the way of securely mounting the guiding tube  32  on the base waveguide tube  31  is not limited to the above-described structure. The guiding tube  32  may be directly connected with the upper sidewall and the lower sidewall of the base waveguide tube  31 . 
     The end assembly  40  includes a reflecting component  41  and an adjusting module  42 . 
     The reflecting component  41  is elongated and corresponds in shape to an interior of the base waveguide tube  31 . The reflecting component  41  is movably mounted in the base waveguide tube  31 , is disposed between the guiding tube  32  and the connecting port  312 , and has a reflecting surface  411  and a connecting hole  412 . The reflecting surface  411  is formed on a front end of the reflecting component  41 , is an inclined plane, and faces toward the guiding tube  32 . An inclined angle of the reflecting surface  411  can be decided according to actual needs of users. The connecting hole  412  is formed in a rear end of the reflecting component  41 . An internal thread is formed around the connecting hole  412 . 
     The adjusting module  42  is mounted on the rear end of the base waveguide tube  31 , is connected to the reflecting component  41 , and selectively drives the reflecting component  41  to adjust a distance defined between the reflecting component  41  and the guiding tube  32 . 
     Specifically, the adjusting module  42  includes a screw rod  43 , a connecting rod  44 , a holding rod  45  and a connecting plate  46 . 
     The screw rod  43  has an external thread, a front end, and an axial hole  431 . The front end of the screw rod  43  is securely connected to the rear end of the base waveguide tube  31 . The axial hole  431  is formed through the front end of the screw rod  43  and a rear end of the screw rod  43  and aligns with the connecting port  312  of the base waveguide tube  31 . 
     The connecting rod  44  is mounted through the axial hole  431  of the screw rod  43  and the connecting port  312  of the base waveguide tube  31  and has an external thread and an annular protrusion  441 . The external thread of the connecting rod  44  is formed around a front end of the connecting rod  44 . The front end of the connecting rod  44  protrudes in the connecting hole  412  of the reflecting component  41  and the external thread of the connecting rod  44  engages with the internal thread that is formed around the connecting hole  412 . The annular protrusion  441  is formed around a rear end of the connecting rod  44 . 
     The holding rod  45  is mounted around the rear end of the connecting rod  44  and the rear end of the screw rod  43  and has a combining recess  451 , a bottom hole  452 , and a bottom panel  453 . The combining recess  421  is formed in a front end of the holding rod  45 . An internal thread is formed around the combining recess  421  and engages with the external thread of the screw rod  43 , such that the holding rod  45  is rotatable relative to the screw rod  43 . The bottom hole  452  is formed through a bottom defined in the combining recess  421 . The bottom panel  453  is formed around the bottom hole  452 . 
     The connecting plate  46  has a combining portion  461  and a limiting portion  462 . The combining portion  461  and the limiting portion  462  are oppositely formed on the connecting plate  46 . An outer diameter of the combining portion  461  is smaller than an outer diameter of the limiting portion  462 . The combining portion  461  is mounted in the bottom hole  452  of the holding rod  45  and abuts against the connecting rod  44 . The connecting plate  46  is fastened to the connecting rod  44  via a fastener. The bottom panel  453  of the holding rod  45  is loosely held between the limiting portion  462  of the connecting plate  46  and the annular protrusion  441  of the connecting rod  44 . When the holding rod  45  rotates relative to the screw rod  43 , the connecting rod  44  and the reflecting component  41  are driven to rotate accordingly. However, the way of driving the reflecting component  41  to rotate is not limited to the above-described structure. The adjusting module  42  may be designed according to users&#39; needs as long as the distance between the reflecting component  41  and the guiding tube  32  can be adjusted. 
     With reference to  FIGS.  1  and  2   , when the microwave heating apparatus is in use, an input pipeline and an output pipeline are connected to two ends of the guiding tube  32  respectively. The liquid to be heated is transported by the input pipeline and the output pipeline to flow through the guiding tube  32 . With decrease of the included angle θ formed between the guiding tube  32  and the base waveguide tube  31 , impedance bandwidth becomes wider and a length of the guiding tube  32  in the base waveguide tube  31  becomes longer. Thus, when assembling the microwave heating apparatus of the present invention, the mounting seats  315  allowing the guiding tube  32  to have a suitable inclined angle can be chosen according to the kind of the liquid to be heated. With the proper included angle θ between the guiding tube  32  and the base waveguide tube  31 , a suitable impedance bandwidth can be formed. 
     Specifically, by using the mounting seats  315  with their through holes  316  having different inclined angles, the guiding tube  32  incline in different angles, such that the included angle θ can be set. Moreover, the inclined angle of the reflecting surface  411  of the reflecting component  41  can be adjusted according to the inclined angle of the guiding tube  32 , and the inclined angle of the reflecting surface  411  can be adjusted simply by replacing the reflecting component  41  with another reflecting component  41  having the reflecting surface  411  of another inclined angle. 
     When the magnetron  10  emits the microwave to heat the liquid flowing through the guiding tube  32 , impedance properties of the liquid change with temperature of the liquid. The impedance bandwidth can be adjusted according to change of the impedance of the liquid. With reference to  FIGS.  2  and  3   , when heating different liquid with microwave, the best impedance matching of the microwave can be set by turning the holding rod  45  to adjust the distance between the reflecting surface  411  of the reflecting component  41  and the guiding tube  32 , so as to be suitable for different liquids. 
     As all possible change in the dielectric properties of the liquid fall within range of the matching bandwidth, dramatic change in efficiency of the microwave heating can be avoided and heating efficiency can be increased. Moreover, an expensive auto tuner can be omitted, such that cost of the microwave heating apparatus can be saved and system complexity of the microwave heating apparatus can be reduced. 
     Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.