Abstract:
The invention provides a reversing valve for reversing a fluid flow, comprising a valve housing defining a cylindrical chamber, at least four passage outlets being formed in the valve housing and opening into the cylindrical chamber, and further comprising a valve core being received rotatably and hermetically within the cylindrical chamber of the valve housing, at least two passages being defined in the valve core, wherein the passage outlets and the passages are arranged such that the reversing valve can reverse the liquid flow once every time that the valve core rotates through 90°. The invention also provides a high frequency oscillation airflow generator. According to the invention, the reversing frequency of the gas flow and thus the efficiency of the high frequency oscillation airflow generator are improved.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to providing high frequency variable pressure to a patient to treat a respiratory disorder, and, in particular, to a reversing valve and a high frequency oscillation airflow generator comprising such a reversing valve. 
       BACKGROUND OF THE INVENTION 
       [0002]    A ventilation technique commonly known as “high frequency ventilation” is widely used to augment a patient&#39;s respiratory rate to assist with the patient&#39;s breathing and/or to remove an accumulated secretion from the patient&#39;s respiratory system. According to this technique, the pressure of the gas flow delivered to the patient&#39;s respiratory system oscillates between two levels at a relatively high frequency. Hence, high oscillation frequency is critical for this technique. 
         [0003]    U.S. Pat. No. 6,708,690B1 discloses an apparatus for providing high frequency variable pressure to a patient. The apparatus comprises a gas circuit, a valve disposed in the gas circuit, a driving assembly for driving the valve and two blowers disposed in the gas circuit. The valve includes a generally cylindrical valve member having a first axial surface, a second axial surface and a side surface. A first passage that extends from the first axial surface to a first portion of the side surface and a second passage that extends from the second axial surface to a second portion of the side surface are defined in the cylindrical member. When the valve is rotated to be in a first position and a second position that are spaced 180° apart around the central axis of the cylindrical valve member, the apparatus generates respectively a positive pressure that delivers a gas flow to the patient&#39;s respiratory system and a negative pressure that delivers a gas flow from the patient&#39;s respiratory system. Every time that the driving assembly for driving the valve rotates through 360°, the valve reverses the gas flow twice. 
         [0004]    To improve the efficiency of providing a high frequency variable pressure to the patient, there is a need to design a novel reversing valve to meet the requirement that the reversing frequency of the gas flow is as high as possible. 
       SUMMARY OF THE INVENTION 
       [0005]    Accordingly, it is an object of the present invention to provide a reversing valve and a high frequency oscillation airflow generator comprising such a reversing valve that overcomes the shortcomings of conventional pressure oscillation techniques. 
         [0006]    According to one aspect of the present invention, there is provided a reversing valve for reversing a fluid flow comprising:
   a valve housing defining a cylindrical chamber, at least four passage outlets being formed in the valve housing and opening into the cylindrical chamber; and   a valve core being received rotatably and hermetically within the cylindrical chamber of the valve housing, at least two passages being defined in the valve core;   wherein the passage outlets and the passages are arranged such that the reversing valve can reverse the liquid flow once every time that the valve core rotates through 90°.   
 
         [0010]    Preferably, four passage outlets opening into the cylindrical chamber are formed in the valve housing, a first passage outlet and a second passage outlet thereof are diametrically opposite to each other, a third passage outlet and a fourth passage outlet thereof are diametrically opposite to each other, a line connecting the third passage outlet and the fourth passage outlet is parallel to a line connecting the first passage outlet and the second outlet. The valve core is a cylindrical valve core, in which two passages are defined, wherein a first passage and a second passage of the two passages are spaced apart and extend perpendicularly to each other, and both the first passage and the second passage extend through and are perpendicular to a central axis of the cylindrical valve core, and the distance between the line connecting the third passage outlet and the fourth passage outlet and the line connecting the first passage outlet and the second outlet is equal to that between the first passage and the second passage. 
         [0011]    Preferably, eight passage outlets opening into the cylindrical chamber are formed in the valve housing, a first passage outlet and a second passage outlet thereof are diametrically opposite to each other, a third passage outlet and a fourth passage outlet thereof are diametrically opposite to each other and a second line connecting the third passage outlet and the fourth passage outlet is parallel to a first line connecting the first passage outlet and the second passage outlet, a fifth passage outlet and a sixth passage outlet are diametrically opposite to each other and a third line connecting the fifth passage outlet and the sixth passage outlet is parallel to the first line, a seventh passage outlet and an eighth passage outlet are diametrically opposite to each other and a fourth line connecting the seventh passage outlet and the eighth passage outlet is parallel to the first line. The valve core is a cylindrical and hollow valve core forming a central passage, one end of the central passage is closed and the opposite end is open, a first group of holes including four first holes, a second group of holes including two second holes, a third group of holes including four third holes, and a fourth group of holes including two fourth holes are formed in a wall of the cylindrical and hollow valve core, and each group of holes is spaced from every other group of holes along a central axis of the cylindrical and hollow valve core, the four first holes are distributed equidistantly in a first plane perpendicular to the central axis of the cylindrical and hollow valve core, two diametrically opposite first holes thereof are in communication with each other via a conduit to form a first passage, the two second holes are distributed so as to be diametrically opposite in a second plane perpendicular to the central axis of the cylindrical and hollow valve core, a line connecting with the two second holes is parallel to the first passage, the two second holes are in communication with each other via a conduit to form a second passage, the four third holes are distributed equidistantly in a third plane perpendicular to the central axis of the cylindrical and hollow valve core, a line connecting with two diametrically opposite third holes thereof is perpendicular to the first passage, the two diametrically opposite third holes are in communication with each other via a conduit to form a third passage, the two fourth holes are distributed diametrically opposite in a fourth plane perpendicular to the central axis of the cylindrical and hollow valve core, a line connecting with the two fourth holes is perpendicular to the first passage, the two fourth holes are in communication with each other via a conduit to form a fourth passage, the distances between the first line and the second line, between the second line and the third line and between the third line and the fourth line are equal to those between the first plane and the second plane, between the second plane and the third plane and between the third plane and the fourth plane, respectively. 
         [0012]    Preferably, four passage outlets opening into the cylindrical chamber are formed in the valve housing and distributed equidistantly along a circumferential direction. The valve core comprises two circular bodies and a spacer centrally interconnecting said two circular bodies when the valve core is received rotatably and hermetically within the cylindrical chamber of the valve housing to form the reversing valve, and the two circular bodies, the spacer and the valve housing together define a first passage and a second passage. 
         [0013]    According to another aspect of the present invention, there is provided a high frequency oscillation airflow generator comprising a reversing valve for reversing a gas flow, at least one blower, a driving assembly for rotatably driving the reversing valve and a plurality of connecting lines connecting the reversing valve with the at least one blower, the reversing valve comprising:
   a valve housing defining a cylindrical chamber, at least four passage outlets being formed in the valve housing and opening to the cylindrical chamber; and   a valve core being received rotatably and hermetically within the cylindrical chamber of the valve housing, at least two passages being defined in the valve core;   wherein the passage outlets and the passages are arranged such that the reversing valve can reverse the gas flow once every time that the driving assembly drives the valve core to rotate through 90°.   
 
         [0017]    Preferably, four passage outlets opening into the cylindrical chamber are formed in the valve housing, a first passage outlet and a second passage outlet thereof are diametrically opposite to each other, a third passage outlet and a fourth passage outlet thereof are diametrically opposite to each other, a line connecting the third passage outlet and the fourth passage outlet is parallel to a line connecting the first passage outlet and the second outlet. The valve core is a cylindrical valve core, two passages are defined in the cylindrical valve core, a first passage and a second passage of the two passages are spaced from and perpendicular to each other, both the first passage and the second passage extend through and are perpendicular to a central axis of the cylindrical valve core, and the distance between the line connecting the third passage outlet and the fourth passage outlet and the line connecting the first passage outlet and the second outlet is equal to that between the first passage and the second passage. The at least one blower comprises a first blower and a second blower, the plurality of connecting lines comprises a first connecting line, a second connecting line and a third connecting line, the first connecting line has a free end and connects at the opposite end with the second passage outlet and the fourth outlet, the second connecting line connects at one end with the first passage outlet and at the opposite end with an outlet of the first blower, the third connecting line connects at one end with the third passage outlet and at the opposite end with an inlet of the second blower, and an inlet of the first blower and an outlet of the second blower open into the atmosphere or other gas source. 
         [0018]    Preferably, eight passage outlets opening into the cylindrical chamber are formed in the valve housing, a first passage outlet and a second passage outlet thereof are diametrically opposite to each other, a third passage outlet and a fourth passage outlet thereof are diametrically opposite to each other, and a second line connecting the third passage outlet and the fourth passage outlet is parallel to a first line connecting the first passage outlet and the second passage outlet, a fifth passage outlet and a sixth passage outlet are diametrically opposite to each other, and a third line connecting the fifth passage outlet and the sixth passage outlet is parallel to the first line, a seventh passage outlet and an eighth passage outlet are diametrically opposite to each other, and a fourth line connecting the seventh passage outlet and the eighth passage outlet is parallel to the first line. The valve core is a cylindrical and hollow valve core forming a central passage, one end of the central passage is closed and the opposite end is open, a first group of holes including four first holes, a second group of holes including two second holes, a third group of holes including four third holes, and a fourth group of holes including two fourth holes are formed in a wall of the cylindrical and hollow valve core, each group of holes is spaced from every other group of holes along a central axis of the cylindrical and hollow valve core, the four first holes are distributed equidistantly in a first plane perpendicular to the central axis of the cylindrical and hollow valve core, two diametrically opposite first holes thereof are in communication with each other via a conduit to form a first passage, the two second holes are distributed so as to be diametrically opposite in a second plane perpendicular to the central axis of the cylindrical and hollow valve core, a line connecting with the two second holes is parallel to the first passage, the two second holes are in communication with each other via a conduit to form a second passage, the four third holes are distributed equidistantly in a third plane perpendicular to the central axis of the cylindrical and hollow valve core, a line connecting with two diametrically opposite third holes thereof is perpendicular to the first passage, the two diametrically opposite third holes are in communication with each other via a conduit to form a third passage, the two fourth holes are distributed so as to be diametrically opposite in a fourth plane perpendicular to the central axis of the cylindrical and hollow valve core, a line connecting with the two fourth holes is perpendicular to the first passage, the two fourth holes are in communication with each other via a conduit to form a fourth passage, the distances between the first line and the second line, between the second line and the third line and between the third line and the fourth line are equal to those between the first plane and the second plane, between the second plane and the third plane and between the third plane and the fourth plane, respectively. The at least one blower comprises one blower, the plurality of connecting lines comprises a first connecting line, a second connecting line, a third connecting line, a fourth connecting line and a fifth connecting line, the first connecting line has a free end and connects at opposite ends with the third passage outlet and the seventh passage outlet, the second connecting line connects at one end with the fifth passage outlet and at the opposite end with an inlet of the blower, the third connecting line connects at one end with an outlet of the blower and at the opposite end with the first passage outlet, the fourth connecting line connects at one end with the second passage outlet and at the opposite end with the fourth passage outlet, and the fifth connecting line connects at one end with the sixth passage outlet and at the opposite end with the eighth passage outlet, the free end of the central passage of the hollow valve core opens into the atmosphere or other gas source. 
         [0019]    Preferably, four passage outlets opening into the cylindrical chamber are formed in the valve housing and distributed equidistantly along a circumferential direction. The valve core comprises two circular bodies and a spacer centrally interconnecting said two circular bodies; when the valve core is received rotatably and hermetically within the cylindrical chamber of the valve housing to form the reversing valve, the two circular bodies, the spacer and the valve housing together define a first passage and a second passage. The at least one blower comprises one blower, the plurality of connecting lines comprises a first connecting line and a second connecting line, the first connecting line connects at one end with an outlet of the blower and at the opposite end with a first passage outlet of the four passage outlets, the second connecting line connects at one end with a second passage outlet of the four passage outlets which is diametrically opposite to the first passage outlet and at the opposite end with an inlet of the blower, one of a third passage outlet and a fourth passage outlet remains unobstructed and the other one opens into the atmosphere or other gas source. 
         [0020]    Preferably, a reversing frequency of the gas flow generated by the high frequency oscillation airflow generator is adjusted by changing a rotating frequency of the driving assembly. 
         [0021]    Preferably, the flow rate of the gas flow generated by the high frequency oscillation airflow generator is adjusted by changing the rotational speed of the blower. 
         [0022]    These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a perspective view of a valve core of a reversing valve according to a first embodiment of the present invention; 
           [0024]      FIG. 2  is a perspective view of a valve housing of a reversing valve according to a first embodiment of the present invention; 
           [0025]      FIG. 3  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a first embodiment of the present invention, in which the high frequency oscillation airflow generator generates a negative pressure to deliver a gas flow from a patient&#39;s respiratory system; 
           [0026]      FIG. 4  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a first embodiment of the present invention, in which the high frequency oscillation airflow generator generates a positive pressure to deliver a gas flow to a patient&#39;s respiratory system; 
           [0027]      FIG. 5  is a perspective view of a valve core of a reversing valve according to a second embodiment of the present invention; 
           [0028]      FIG. 6  is a perspective view of a valve housing of a reversing valve according to a second embodiment of the present invention; 
           [0029]      FIG. 7  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a second embodiment of the present invention, in which the high frequency oscillation airflow generator generates a negative pressure to deliver a gas flow from a patient&#39;s respiratory system; 
           [0030]      FIG. 8  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a second embodiment of the present invention, in which the high frequency oscillation airflow generator generates a positive pressure to deliver a gas flow to a patient&#39;s respiratory system; 
           [0031]      FIG. 9  is an exploded perspective view of a reversing valve according to a third embodiment of the present invention; 
           [0032]      FIG. 10  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a third embodiment of the present invention, in which the high frequency oscillation airflow generator generates a negative pressure to deliver a gas flow from a patient&#39;s respiratory system; and 
           [0033]      FIG. 11  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a third embodiment of the present invention, in which the high frequency oscillation airflow generator generates a positive pressure to deliver a gas flow to a patient&#39;s respiratory system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]      FIG. 1  is a perspective view of a valve core of a reversing valve according to a first embodiment of the present invention and  FIG. 2  is a perspective view of a valve housing of a reversing valve according to a first embodiment of the present invention. As shown in  FIGS. 1 and 2 , a reversing valve  10  according to a first embodiment of the present invention comprises a cylindrical valve core  11 . The cylindrical valve core  11  defines a first passage  1 A and a second passage  1 B. The first passage  1 A and the second passage  1 B are spaced from and perpendicular to each other. Both the first passage  1 A and the second passage  1 B extend through and are perpendicular to a central axis of the cylindrical valve core  11 . 
         [0035]    The reversing valve  10  further comprises a valve housing  13 . The valve housing  13  defines a cylindrical chamber  15 . Four passage outlets  1 A 1 ,  1 A 2 ,  1 B 1  and  1 B 2  opening into the cylindrical chamber  15  are formed in the valve housing  13 . The first passage outlet  1 A 1  and the second passage outlet  1 A 2  are diametrically opposite to each other. The third passage outlet  1 B 1  and the fourth passage outlet  1 B 2  are diametrically opposite to each other. A line connecting the third passage outlet  1 B 1  and the fourth passage outlet  1 B 2  is parallel to a line connecting the first passage outlet  1 A 1  and the second passage outlet  1 A 2 . The distance between the line connecting the third passage outlet  1 B 1  and the fourth passage outlet  1 B 2  and the line connecting the first passage outlet  1 A 1  and the second passage outlet  1 A 2  is equal to that between the first passage  1 A and the second passage  1 B. Thus, the first passage  1 A may align with the first passage outlet  1 A 1  and the second passage outlet  1 A 2  and the second passage  1 B may align with the third passage outlet  1 B 1  and the fourth passage outlet  1 B 2  when the cylindrical valve core  11  is received rotatably and hermetically within the cylindrical chamber  15  of the valve housing  13  to form the reversing valve  10 . 
         [0036]      FIG. 3  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a first embodiment of the present invention, in which the high frequency oscillation airflow generator generates a negative pressure to deliver a gas flow from a patient&#39;s respiratory system.  FIG. 4  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a first embodiment of the present invention, in which the high frequency oscillation airflow generator generates a positive pressure to deliver a gas flow to a patient&#39;s respiratory system. As shown in  FIGS. 3 and 4 , the high frequency oscillation airflow generator  100  comprises the reversing valve  10  according to the first embodiment of the present invention, a first blower  1 G 1 , a second blower  1 G 2  and a driving assembly  17  for rotatably driving the reversing valve  10 . The driving assembly  17  is coupled with the cylindrical valve core  11  via a shaft  19 . The driving assembly  17  may be an electrical motor. However, driving assembly  17  may also be a pneumatic or hydraulic motor. 
         [0037]    The high frequency oscillation airflow generator  100  also comprises a first connecting line  21  which has a free end  23  and which connects at the opposite end with two of four passage outlets of the reversing valve  10 , for example, the second passage outlet  1 A 2  and the fourth outlet  1 B 2 . The high frequency oscillation airflow generator  100  further comprises a second connecting line  25  which connects at one end with the first passage outlet  1 A 1  of the reversing valve  10  and at the opposite end with an outlet of the first blower  1 G 1  and a third connecting line  27  which connects at one end with the third passage outlet  1 B 1  of the reversing valve  10  and at the opposite end with an inlet of the second blower  1 G 2 . An inlet  29  of the first blower  1 G 1  and an outlet  31  of the second blower  1 G 2  open into the atmosphere. Of course, the inlet  29  of the first blower  1 G 1  and an outlet  31  of the second blower  1 G 2  may open into any other suitable gas source. 
         [0038]    When the high frequency oscillation airflow generator  100  is in operation, the driving assembly  17  drives the cylindrical valve core  11  to rotate hermetically within the valve housing  13  along a direction indicated by arrow R. When the cylindrical valve core  11  rotates to a position as shown in  FIG. 3 , the first passage  1 A of the reversing valve  10  is blocked by the valve housing  13  while the second passage  1 B communicates with the third passage outlet  1 B 1  and the fourth passage outlet  1 B 2 . At this moment, under the action of the second blower  1 G 2 , the gas flow flows along a direction indicated by a hollow arrow from the free end  23  of the first connecting line  21  to the outlet  31  of the second blower  1 G 2  through the first connecting line  21 , the second passage  1 B and the third connecting line  27 . 
         [0039]    When the cylindrical valve core  11  further rotates through 90° from the position as shown in  FIG. 3  to a position as shown in  FIG. 4 , the first passage  1 A of the reversing valve  10  communicates with the first passage outlet  1 A 1  and the second passage outlet  1 A 2 , while the second passage  1 B is blocked by the valve housing  13 . At this moment, under the action of the first blower  1 G 1 , the gas flow flows along a direction indicated by a solid arrow from the inlet  29  of the first blower  1 G 1  to the free end  23  of the first connecting line  21  through the second connecting line  25 , the first passage  1 A and the first connecting line  21 . The gas flow is reversed at the free end  23  of the first connecting line  21  compared with that shown in  FIG. 3 . 
         [0040]    When the cylindrical valve core  11  further rotates through 90° from the position as shown in  FIG. 4 , the reversing valve  10  returns to the position as shown in  FIG. 3 . This process is repeated periodically. The free end  23  of the first connecting line  21  usually couples to an airway of a patient so that the high frequency oscillation airflow generator  100  generates alternately a negative pressure and a positive pressure to deliver the gas flow from and to the patient&#39;s respiratory system, respectively. Obviously, every time that the driving assembly  17  drives the cylindrical valve core  11  to rotate through 360°, the reversing valve  10  reverses the gas flow at the free end  23  of the first connecting line  21  four times. In other words, every time that the driving assembly  17  drives the cylindrical valve core  11  to rotate through 90°, the reversing valve  10  reverses the gas flow once at the free end  23  of the first connecting line  21 . 
         [0041]      FIG. 5  is a perspective view of a valve core of a reversing valve according to a second embodiment of the present invention and  FIG. 6  is a perspective view of a valve housing of a reversing valve according to a second embodiment of the present invention. As shown in  FIGS. 5 and 6 , a reversing valve  40  according to a second embodiment of the present invention comprises a cylindrical and hollow valve core  41  to form a central passage  42 . One end of the central passage  42  is closed and the opposite end is open. A first group of holes including four first holes  2 A 1 ,  2 A 2 ,  2 A 3  and  2 A 4 , a second group of holes including two second holes  2 B 2  and  2 B 3 , a third group of holes including four third holes  2 C 1 ,  2 C 2 ,  2 C 3  and  2 C 4 , and a fourth group of holes including two fourth holes  2 D 1  and  2 D 4  are formed in the wall of the hollow valve core  41 . Each group of holes is spaced from every other group of holes along a central axis of the cylindrical and hollow valve core  41 . Four first holes  2 A 1 ,  2 A 2 ,  2 A 3  and  2 A 4  are distributed equidistantly in a first plane perpendicular to the central axis of the cylindrical and hollow valve core  41 . Two diametrically opposite first holes  2 A 2  and  2 A 3  are in communication with each other via a conduit to form a first passage  41 A. Two second holes  2 B 2  and  2 B 3  are distributed so as to be diametrically opposite in a second plane perpendicular to the central axis of the cylindrical and hollow valve core  41 . A line connecting with two second holes  2 B 2  and  2 B 3  is parallel to the first passage  41 A. Two second holes  2 B 2  and  2 B 3  are in communication with each other via a conduit to form a second passage  41 B. Four third holes  2 C 1 ,  2 C 2 ,  2 C 3  and  2 C 4  are distributed equidistantly in a third plane perpendicular to the central axis of the cylindrical and hollow valve core  41 . A line connecting with two diametrically opposite third holes  2 C 1  and  2 C 4  is perpendicular to the first passage  41 A. The two diametrically opposite third holes  2 C 1  and  2 C 4  are in communication with each other via a conduit to form a third passage  41 C. Two fourth holes  2 D 1  and  2 D 4  are distributed so as to be diametrically opposite in a fourth plane perpendicular to the central axis of the cylindrical and hollow valve core  41 . A line connecting with two fourth holes  2 D 1  and  2 D 4  is perpendicular to the first passage  41 A. The two fourth holes  2 D 1  and  2 D 4  are in communication with each other via a conduit to form a fourth passage  41 D. 
         [0042]    The reversing valve  40  further comprises a valve housing  43 . The valve housing  43  defines a cylindrical chamber  45 . Eight passage outlets  2 A 1 ′,  2 A 2 ′,  2 B 1 ′,  2 B 2 ′,  2 C 1 ′,  2 C 2 ′,  2 D 1 ′ and  2 D 2 ′ opening into the cylindrical chamber  45  are formed in the valve housing  43 . The first passage outlet  2 A 1 ′ and the second passage outlet  2 A 2 ′ are diametrically opposite to each other. The third passage outlet  2 B 1 ′ and the fourth passage outlet  2 B 2 ′ are diametrically opposite to each other and a second line connecting the third passage outlet  2 B 1 ′ and the fourth passage outlet  2 B 2 ′ is parallel to a first line connecting the first passage outlet  2 A 1 ′ and the second passage outlet  2 A 2 ′. The fifth passage outlet  2 C 1 ′ and the sixth passage outlet  2 C 2 ′ are diametrically opposite to each other and a third line connecting the fifth passage outlet  2 C 1 ′ and the sixth passage outlet  2 C 2 ′ is parallel to the first line connecting the first passage outlet  2 A 1 ′ and the second passage outlet  2 A 2 ′. The seventh passage outlet  2 D 1 ′ and the eighth passage outlet  2 D 2 ′ are diametrically opposite to each other and a fourth line connecting the seventh passage outlet  2 D 1 ′ and the eighth passage outlet  2 D 2 ′ is parallel to the first line connecting the first passage outlet  2 A 1 ′ and the second passage outlet  2 A 2 ′. The distances between the first line and the second line, between the second line and the third line and between the third line and the fourth line are equal to those between the first plane and the second plane, between the second plane and the third plane and between the third plane and the fourth plane, respectively. Thus, when the cylindrical and hollow valve core  41  is received rotatably and hermetically within the cylindrical chamber  45  of the valve housing  43  to form the reversing valve  40 , two diametrically opposite holes of four first holes  2 A 1 ,  2 A 2 ,  2 A 3  and  2 A 4  may align with the first passage outlet  2 A 1 ′ and the second passage outlet  2 A 2 ′ respectively, two second holes  2 B 2  and  2 B 3  may align with the third passage outlet  2 B 1 ′ and the fourth passage outlet  2 B 2 ′ respectively, two diametrically opposite holes of four third holes  2 C 1 ,  2 C 2 ,  2 C 3  and  2 C 4  may align with the fifth passage outlet  2 C 1 ′ and the sixth passage outlet  2 C 2 ′ respectively, two fourth holes  2 D 1  and  2 D 4  may align with the seventh passage outlet  2 D 1 ′ and the eighth passage outlet  2 D 2 ′ respectively. 
         [0043]      FIG. 7  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a second embodiment of the present invention, in which the high frequency oscillation airflow generator generates a negative pressure to deliver a gas flow from a patient&#39;s respiratory system.  FIG. 8  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a second embodiment of the present invention, in which the high frequency oscillation airflow generator generates a positive pressure to deliver a gas flow to a patient&#39;s respiratory system. As shown in  FIGS. 7 and 8 , the high frequency oscillation airflow generator  200  comprises the reversing valve  40  according to the second embodiment of the present invention, a blower  2 G, and a driving assembly  47  for rotatably driving the reversing valve  40 . The driving assembly  47  is coupled with the cylindrical and hollow valve core  41  via a shaft  49 . The driving assembly  47  may be an electrical motor. However, driving assembly  47  may also be a pneumatic or hydraulic motor. 
         [0044]    The high frequency oscillation airflow generator  200  also comprises a first connecting line  51  which has a free end  53  and which connects at the opposite end with two out of eight passage outlets of the reversing valve  40 , for example, the third passage outlet  2 B 1 ′ and the seventh passage outlet  2 D 1 ′. The high frequency oscillation airflow generator  200  further comprises a second connecting line  55  which connects at one end with the fifth passage outlet  2 C 1 ′ of the reversing valve  40  and at the opposite end with an inlet of the blower  2 G, a third connecting line  57  which connects at one end with an outlet of the blower  2 G and at the opposite end with the first passage outlet  2 A 1 ′ of the reversing valve  40 , a fourth connecting line  59  which connects at one end with the second passage outlet  2 A 2 ′ of the reversing valve  40  and at the opposite end with the fourth passage outlet  2 B 2 ′ of the reversing valve  40 , and a fifth connecting line  61  which connects at one end with the sixth passage outlet  2 C 2 ′ of the reversing valve  40  and at the opposite end with the eighth passage outlet  2 D 2 ′ of the reversing valve  40 . The free end  63  of the central passage  42  of the hollow valve core  41  opens to the atmosphere. Of course, the free end  63  of the central passage  42  may open into any other suitable gas source. 
         [0045]    When the high frequency oscillation airflow generator  200  is in operation, the driving assembly  47  drives the cylindrical and hollow valve core  41  to rotate hermetically within the valve housing  43 . When the cylindrical and hollow valve core  41  rotates to a position as shown in  FIG. 7 , the first connecting line  51  communicates with the fifth connecting line  61  via the fourth passage  41 D between two fourth holes  2 D 1  and  2 D 4 , the fifth connecting line  61  communicates with the second connecting line  55  via the third passage  41 C between two diametrically opposite third holes  2 C 1  and  2 C 4 , the third connecting line  57  communicates with the free end  63  of the central passage  42  via the central passage  42 , the fourth connecting line  59  and the branch of the first connecting line  51  connecting with the third passage outlet  2 B 1 ′ are blocked by the wall of the hollow valve core  41 . At this moment, under the action of the blower  2 G, the gas flow flows along a direction indicated by an arrow from the free end  53  of the first connecting line  51  to the free end  63  of the central passage  42  through the first connecting line  51 , the fourth passage  41 D, the fifth connecting line  61 , the third passage  41 C, the second connecting line  55 , the blower  2 G, the third connecting line  57  and the central passage  42 . 
         [0046]    When the cylindrical and hollow valve core  41  further rotates through 90° from the position as shown in  FIG. 7  to a position as shown in  FIG. 8 , the third connecting line  57  communicates with the fourth connecting line  59  via the first passage  41 A between two first holes  2 A 2  and  2 A 3 , the fourth connecting line  59  communicates with the first connecting line  51  via the second passage  41 B between two diametrically opposite second holes  2 B 2  and  2 B 3 , the second connecting line  55  communicates with the free end  63  of the central passage  42  via the central passage, the fifth connecting line  61  and the branch of the first connecting line  51  connecting with seventh passage outlet  2 D 1 ′ are blocked by the wall of the hollow valve core  41 . At this moment, under the action of the blower  2 G, the gas flow flows along a direction indicated by an arrow from the free end  63  of the central passage  42  to the free end  53  of the first connecting line  51  through the central passage  42 , the second connecting line  55 , the blower  2 G, the third connecting line  57 , the first passage  41 A, the fourth connecting line  59 , the second passage  41 B and the first connecting line  51 . The gas flow is reversed at the free end  53  of the first connecting line  51  compared with that shown in  FIG. 7 . 
         [0047]    When the cylindrical and hollow valve core  41  further rotates through 90° from the position as shown in  FIG. 8 , the reversing valve  40  returns to the position as shown in  FIG. 7 . This process is repeated periodically. The free end  53  of the first connecting line  51  usually couples to an airway of a patient so that the high frequency oscillation airflow generator  200  generates alternately a negative pressure and a positive pressure to deliver the gas flow from and to the patient&#39;s respiratory system, respectively. Obviously, every time the driving assembly  47  drives the cylindrical and hollow valve core  41  to rotate through 360°, the reversing valve  40  reverses the gas flow at the free end  53  of the first connecting line  51  four times. In other words, every time that the driving assembly  47  drives the cylindrical and hollow valve core  41  to rotate through 90°, the reversing valve  40  reverses the gas flow once at the free end  53  of the first connecting line  51 . 
         [0048]      FIG. 9  is an exploded perspective view of a reversing valve according to a third embodiment of the present invention. As shown in  FIG. 9 , a reversing valve  70  according to a third embodiment of the present invention comprises a valve core  71 . The valve core  71  comprises two circular bodies  71   a  and a spacer  71   c  centrally interconnecting said two circular bodies  71   a . The two circular bodies  71   a  and the spacer  71   c  may be formed separately and then assembled together. Of course, the two circular bodies  71   a  and the spacer  71   c  may be formed integrally. 
         [0049]    The reversing valve  70  further comprises a valve housing  73 . The valve housing  73  defines a cylindrical chamber  75 . Four passage outlets  3 A 1 ,  3 A 2 ,  3 B 1  and  3 B 2  opening into the cylindrical chamber  75  are formed in the valve housing  73  and distributed equidistantly along a circumferential direction. When the valve core  71  is received rotatably and hermetically within the cylindrical chamber  75  of the valve housing  73  to form the reversing valve  70 , two circular bodies  71   a,  the spacer  71   c  and the valve housing  73  together define a first passage  3 A and a second passage  3 B. 
         [0050]      FIG. 10  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a third embodiment of the present invention, in which the high frequency oscillation airflow generator generates a negative pressure to deliver a gas flow from a patient&#39;s respiratory system.  FIG. 11  is a schematic diagram of a high frequency oscillation airflow generator comprising a reversing valve according to a third embodiment of the present invention, in which the high frequency oscillation airflow generator generates a positive pressure to deliver a gas flow to a patient&#39;s respiratory system. As shown in  FIGS. 10 and 11 , the high frequency oscillation airflow generator  300  comprises the reversing valve  70  according to the third embodiment of the present invention, a blower  3 G, and a driving assembly (not shown in the drawings) for rotatably driving the reversing valve. The driving assembly is coupled with the valve core  71 . The driving assembly may be an electrical motor. However, the driving assembly may also be a pneumatic or hydraulic motor. 
         [0051]    The high frequency oscillation airflow generator  300  also comprises a first connecting line  81  which connects at one end with an outlet of the blower  3 G and at the opposite end with the first passage outlet  3 A 1  of the reversing valve  70  and a second connecting line  83  which connects at one end with the second passage outlet  3 B 1  of the reversing valve  70  which is diametrically opposite to the first passage outlet  3 A 1  and at the opposite end with an inlet of the blower  3 G. The third passage outlet  3 A 2  may open into the atmosphere while the fourth passage outlet  3 B 2  may open into an airway of a patient or vice versa. Of course, the third passage outlet  3 A 2  may open into any other suitable gas source. 
         [0052]    When the high frequency oscillation airflow generator  300  is in operation, the driving assembly drives the valve core  71  to rotate hermetically within the valve housing  73 . When the valve core  71  rotates to a position as shown in  FIG. 10 , under the action of the blower  3 G, the gas flow flows along a direction indicated by an arrow from the fourth passage outlet  3 B 2  of the valve housing  73  to the third passage outlet  3 A 2  of the valve housing  73  through the second passage  3 B, the second connecting line  83 , the blower  3 G, the first connecting line  81  and the first passage  3 A. 
         [0053]    When the valve core  71  further rotates through 90° from the position as shown in  FIG. 10  to a position as shown in  FIG. 11 , the spacer  71   c  moves to a position perpendicular to that shown in  FIG. 10 . At this moment, under the action of the blower  3 G, the gas flow flows along a direction indicated by an arrow from the third passage outlet  3 A 2  of the valve housing  73  to the fourth passage outlet  3 B 2  of the valve housing  73  through the first passage  3 A, the second connecting line  83 , the blower  3 G, the first connecting line  81  and the second passage  3 B. 
         [0054]    When the valve core  71  further rotates through 90° from the position as shown in  FIG. 11 , the reversing valve  70  returns to the position as shown in  FIG. 10 . This process is repeated periodically. If the fourth passage outlet  3 B 2  couples to an airway of a patient, the high frequency oscillation airflow generator  300  generates alternately a negative pressure and a positive pressure to deliver the gas flow from and to the patient&#39;s respiratory system, respectively. Obviously, every time that the driving assembly drives the valve core  71  to rotate through 360°, the reversing valve  70  reverses the gas flow at the fourth passage outlet  3 B 2  four times. In other words, every time that the driving assembly drives the valve core  71  to rotate through 90°, the reversing valve  70  reverses the gas flow once at the fourth passage outlet  3 B 2 . 
         [0055]    Only one blower is required for the high frequency oscillation airflow generator according to the second and third embodiments, while two blowers are required for the high frequency oscillation airflow generator according to the first embodiment. The high frequency oscillation airflow generator according to the second and third embodiments is compact and low-weight in comparison with the high frequency oscillation airflow generator according to the first embodiment. 
         [0056]    According to the present invention, the reversing valve reverses the gas flow generated by the high frequency oscillation airflow generator four times every time the valve core rotates through 360°. The reversing frequency of the gas flow and thus the efficiency of the high frequency oscillation airflow generator according to the present invention are twice that of the conventional pressure oscillation techniques. 
         [0057]    The reversing frequency of the gas flow generated by the high frequency oscillation airflow generator according to the present invention may be adjusted by changing the rotating frequency of the driving assembly. The flow rate of the gas flow may be adjusted by changing the rotation speed of the blower. 
         [0058]    In the above mentioned embodiments, the reversing valve according to the present invention is used to reverse the gas flow. It should be understood that the reversing valve according to the present invention is used to reverse a liquid flow. 
         [0059]    Although the invention has been described in detail for the purpose of illustration, based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims.