Patent Publication Number: US-2006011411-A1

Title: Acoustic compressor

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to an acoustic compressor for a gas in which amplitude pressure change is utilized on the basis of acoustic resonance.  
      An acoustic compressor is known in which a piston is reciprocated axially with minute amplitude by an actuator in the larger-diameter base of an acoustic resonator thereby discharging a gas sucked into an acoustic resonator through the smaller-diameter end by pressure change in the acoustic resonator with reciprocation of the piston.  
      The acoustic compressor is constructed on the basis of amplitude pressure change of acoustic standing waves produced by resonance of a gas column in a tube involved by piston movement when the piston is reciprocated axially at minute amplitude. An operating portion is only an actuator for reciprocating the piston inside the base of an acoustic resonator. Thus, the structure is very simple and malfunction is not likely to occur. The acoustic compressor is expected to be used widely in the future.  
      However, in the acoustic compressor, a gas is sucked and discharged only by a piston that vibrates minutely. There is basic problem that a compression ratio obtained is small.  
     SUMMARY OF THE INVENTION  
      In view of the disadvantage, it is an object of the present invention to provide an acoustic compressor in which high-pressure compressed gas is obtained by very simple means, the compressor being small thereby increasing its application significantly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in appended drawings wherein:  
       FIG. 1  is a vertical sectional view of an embodiment of an acoustic compressor according to the present invention; and  
       FIG. 2  is a vertical sectional view of another embodiment of an acoustic compressor according to the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  is a vertical sectional front view of an embodiment of an acoustic compressor according to the present invention.  
      In the acoustic compressor, an actuator  2  is mounted to a larger-diameter base at the lower end of an acoustic resonator  1 , and a valve  3  is mounted on the smaller-diameter upper end.  
      The acoustic resonator  1  has a resonant cavity  4  in which the lower end is larger and the upper end is smaller in diameter. The inner surface of the resonant cavity  4  is shown by the following formula:  
         r   ⁡     (   x   )       =             r   p     -     r   o       2     ⁢     cos   ⁡     (       π   L     ⁢   x     )         +         r   p     +     r   o       2           
 
 where L is the length of the resonant cavity, r p  is the radius of the lower end or r o  is the radius of the upper end for suction and discharge. 
 
      The actuator  2  functions as support and reciprocates a piston  5 . The piston  5  is made of light alloy and engaged in the lower end of the resonant cavity  4 . A seal member  6  is engaged in the outer circumference of the piston  5 .  
      The acoustic resonator  1  has an outward flange  7  which is put on the upper surface of the actuator  2 . The outward flange  7  is fastened to the actuator  2  with a suitable number of bolts  8 .  
      The valve  3  comprises a suction chamber  12  which has an inlet  9  and a sucking bore  12  with an air-sucking inward nonreturn valve  10  at the lower surface of a bottom wall  3   a,  and a discharge chamber  16  which has a discharge bore  15  with a compressed-gas-discharging outward nonreturn valve  14  at the upper surface of the bottom wall  3   a.  The valve  3  is mounted on the upper end of the acoustic resonator  1 .  
      The inward and outward nonreturn valves  10 , 14  comprise reed valves or rubber-plate valves made of thin steel plates secured to the lower surface of the bottom wall of the suction chamber  12  and to the upper surface of the bottom wall of the discharge chamber  16  respectively. They may be made of ball-types or others.  
      Opening resistant force of the outward nonreturn valve  14  is much higher than that of the inward nonreturn valve  10 . The reasons will be described later.  
      The suction chamber  12  and the discharge chamber  16  are partitioned by a partition wall  17 .  
      Driving frequency of the actuator  2  is controlled by a function synthesizer (not shown) with the accuracy of about 0.1 Hz.  
      The piston  5  is reciprocated axially at minute amplitude at the larger-diameter base of the lower end of the acoustic resonator  1 . Accordingly when pressure amplitude in the acoustic resonator  1  becomes significant small value, air is sucked through the inlet  9 , introduced into the suction chamber  12  and sucked into the acoustic resonator  1  through the sucking bore  11  and the inward nonreturn valve  10 . Meanwhile, when pressure amplitude in the acoustic resonator  1  becomes significant large value, air is transferred from the acoustic resonator  1  and discharged from the outlet  13  of the discharge chamber  16  through the discharge bore  15  and the outward nonreturn valve  14  under pressure.  
      As mentioned above, in the embodiment as shown, opening resistant force in the outward nonreturn valve  14  of the discharge bore  15  is much higher than that of the inward nonreturn valve  10  in the sucking bore  11 .  
      At the beginning of operation, air which is sucked in the resonant cavity  4  through the sucking bore  11  and the inward nonreturn valve  10  is not discharged from the discharge bore  15  directly, but is discharged through the discharge bore  15  and the outlet  13  by opening the outward nonreturn valve  14  only after pressure in the resonant cavity  4  elevates to more than a certain value.  
      So, before the piston  5  moves, air is introduced into the resonant cavity  4  through the inlet  9  and the sucking bore  11  of the suction chamber  12 . Then, air is compressed by reciprocation of the piston  5  and discharged through the discharge bore  15  by opening the nonreturn valve  14  when pressure in the resonant cavity  4  exceeds a certain value. Thus, high-pressure air discharged through the outlet  13  is obtained.  
      Thus, compared with a case where the nonreturn valves  10 , 14  are equal to each other in opening resistant force, density of the gas sucked and discharged into the resonant cavity  4  with reciprocal motion becomes larger thereby increasing discharge pressure and amount.  
       FIG. 2  is another embodiment of the present invention.  
      A pressurizing rubber bag  18  is put on the inner surface of a resonant cavity  4  of an acoustic resonator  1 , and the upper end  18   a  is slightly lower than a sucking bore  11  and a discharge bore  15 , and a pressurized gas  19  is fed to the pressurized bag  18  through a feeding bore  21  in the side wall of the acoustic resonator  1  via a valve  20 .  
      The gas sucked in the resonant cavity  4  through the sucking bore  4  with reciprocal motion of a piston  5  is pressed on the upper end  18   a  of the pressurized bag  18  to deform at a certain amount, and with up-and-down motion of the upper end  18   a,  the external gas is sucked to the smaller-diameter upper end in the resonant cavity  4 . After the pressure of the gas in this part exceeds a certain value, it is discharged from the discharge bore  15 . The smaller-diameter upper end  18   a  of the pressurizing bag  18  is strongly reciprocated at a larger stroke compared with a stroke of the piston  5  and the upper inner space of a resonant cavity  4  is pressurized thereby achieving larger discharge pressure.  
      The foregoing merely relates to embodiments of the invention. Various changes and modifications may be made by a person skilled in the art without departing from the scope of claims wherein: