Abstract:
A claw pump includes: a housing; two rotating shafts which are disposed parallel; a pair of rotors respectively fixed to the two rotating shafts; a rotary drive device driving the pair of rotors; and a suction port and discharge ports formed in a partition wall of the housing. The discharge ports are constituted by a first discharge port and a second discharge port. The first discharge port is formed at a position that communicates with an initial stage compression space formed at an initial stage of a compression stroke in a compression space that is formed by joining a first pocket and a second pocket. The claw pump includes an opening/closing mechanism which opens the first discharge port when a pressure of the initial stage compression space reaches a threshold and closes the first discharge port when the pressure does not reach the threshold.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a claw pump capable of reducing the temperature of discharge gas. 
       BACKGROUND ART 
       [0002]    A claw pump includes a pair of rotors which have hook-shaped claws formed thereon and rotate in opposite directions to each other at the same speed in a non-contact manner while maintaining an extremely narrow clearance therebetween inside a housing that forms a pump chamber. The two rotors form a compression pocket, and compressed gas compressed in the compression pocket is discharged through a discharge port. The claw pump continuously performs suction, compression, and exhaust without using a lubricating oil or sealing liquid, thereby producing a vacuum state or pressurized air. As described above, since the lubricating oil or the like is not used, there are advantages that clean gas can be exhausted and discharged, and a higher compression ratio than that of a Roots pump that does not have a compression stroke can be realized. 
         [0003]      FIG. 5  illustrates an example of a claw pump according to the related art. In  FIG. 5 , a claw pump  100  includes a housing  102  that forms a pump chamber therein, and the housing  102  has a cross-sectional shape of two partially overlapping circles. Both end faces of the housing  102  are blocked by side plates (not illustrated), and a suction port  108  is formed in a circumferential wall of the housing  102 . Two parallel rotating shafts  110   a  and  110   b  are provided inside the housing  102 , and rotors  112   a  and  112   b  are respectively fixed to the rotating shafts  110   a  and  110   b.  The rotors  112   a  and  112   b  are provided with hook-shaped claws  114   a  and  114   b  which mesh each other in a non-contact manner. 
         [0004]    The rotors  112   a  and  112   b  rotate in opposite directions to each other (arrow directions), and gas g is suctioned into an inlet pocket P 0  that communicates with the suction port  108 . Thereafter, two pockets P 1  and P 2  are formed as the rotors  112   a  and  112   b  rotate (see  FIG. 5(D) ). Furthermore, the two pockets P 1  and P 2  join and form a compression pocket P (see  FIG. 5(F) ). In the compression pocket P, immediately after the pockets P 1  and P 2  join, an initial stage compression space Pe is formed. Thereafter, the initial stage compression space Pe is reduced as the rotors  112   a  and  112   b  rotate, such that an end stage compression space Pc is formed. The discharge port  116  is formed in one of the side plates at a position that communicates with the end stage compression space Pc. The gas g is compressed in the compression pocket P and is discharged from the discharge port  116 . 
         [0005]    In the claw pump, the gas is increased in temperature by compressing the gas, while a higher compression ratio than that of a Roots pump can be realized. The high-temperature gas comes into contact with the surrounding components and increases the temperatures thereof. Therefore, there is concern that contact between the claws of the rotors or contact between the claws and the inner surfaces of the housing may occur due to thermal expansion or deformation and breaking may occur due to insufficient heat resistance. To solve the problems, there is proposed a method of changing the shape of the discharge port or providing a plurality of discharge ports to increase the area of openings, reduce pressure loss, and prevent excessive compression, thereby preventing an increase in temperature. For example, in Patent Literature 1, there is disclosed an example in which discharge ports are formed in both of a pair of side plates that block both end faces of a housing to increase the area of openings. 
         [0006]    Otherwise, there has been an attempt to prevent an increase in temperature by reducing a compression ratio through a study of the shape of rotors. For example, in Patent Literature 2, there is disclosed a configuration in which a dent is formed in a face of a convex portion of a female rotor, which faces a claw of a male rotor, and gas in a compression pocket is allowed to escape to the dent when the compression pocket becomes distant from a discharge port, thereby relaxing excessive compression. 
         [0007]    In general, a claw pump suctions cooled outside air to obtain a cooling effect. However, in a case where the claw pump is particularly used as a vacuum pump, since the inflow of gas from the suction port is significantly reduced during an operation at a suction pressure of about the ultimate pressure, the cooling effect cannot be obtained. In addition, since the pump chamber is in a vacuum state, a pressure difference from the discharge side occurs, and there is concern that high-temperature gas discharged from the discharge port may flow back to the pump chamber. When the discharge gas that flows back to the pump chamber due to the backflow phenomenon is recompressed while maintaining a high temperature, the temperature thereof is further increased. Accordingly, there may be cases where the temperature of the discharge gas reaches 200° C. to 300° C. As a countermeasure, a method of providing a check valve in the outlet of the discharge port to prevent the backflow of the high-temperature gas is considered. 
       CITATION LIST 
     Patent Literature 
       [0008]    Patent Literature 1: Japanese Unexamined Patent Publication No. 2011-038476 
         [0009]    Patent Literature 2: Japanese Unexamined Patent Publication No. 2013-076361 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    However, in the method of changing the shape of the discharge port or increasing the area of openings as a countermeasure to prevent an increase in the temperature of the discharge gas, there is concern that the compression ratio may decrease, and desired performance cannot be exhibited, and the backflow of the high-temperature gas cannot be prevented. In addition, in the method of studying the shape of the rotor, there is concern that the shape of the rotor may become complex and design costs and production costs of the rotor may increase. Furthermore, in the method of providing a check valve in the outlet of the discharge port, there is concern that the flow resistance of the gas may be increased due to the installation of the check valve, which leads to excessive compression of the gas on the contrary, resulting in an increase in the gas temperature. 
         [0011]    In order to solve the aforementioned problems, an object of the present invention is to reduce the temperature of a discharge gas of a claw pump with low-cost means. 
       Solution to Problem 
       [0012]    In order to accomplish the object, the present invention is applied to a claw pump including: a housing which forms a pump chamber having a cross-sectional shape of two partially overlapping circles; two rotating shafts which are disposed parallel to each other inside the housing and synchronously rotated in opposite directions to each other; a pair of rotors which are respectively fixed to the two rotating shafts inside the housing, each of the rotors being provided with two or more hook-shaped claws, the claws meshing with each other in a non-contact state; a rotary drive device which drives the pair of rotors to rotate via the two rotating shafts; and a suction port and discharge ports which are formed in a partition wall of the housing and communicate with the pump chamber. 
         [0013]    According to an aspect of the present invention, the discharge ports are respectively formed in side plates which form both axial end faces of the rotating shafts of the housing and are constituted by a first discharge port and a second discharge port which are formed at positions that communicate with a compression pocket formed by a set of the claws. The claw pump includes an opening/closing mechanism of the first discharge port and the second discharge port for, while the pair of rotors rotate one revolution, discharging gas in the compression pocket formed by at least one set of the claws only via the first discharge port and discharging the gas in the compression pocket formed by at least another set of the claws only via the second discharge port, is included. 
         [0014]    In a case where two or more claws are provided in a single rotor, discharge gas is discharged two or more times while the rotor makes one revolution. Therefore, when the discharge gas is discharged from a single discharge port, the discharge interval is shortened, with a backflow phenomenon of the discharge gas that is increased in temperature, the temperature of the discharge gas is increased. In the aspect of the present invention, in the above-described configuration, the gas compressed in the compression pocket can be dispersed toward the first discharge port and the second discharge port so as to be discharged while the pair of rotors rotate one revolution. Accordingly, the discharge interval of the first discharge port or the second discharge port can be increased, and the time until the discharge gas that is compressed and is increased in temperature flows back to the discharge port can be increased. Therefore, the time for which the discharged gas is mixed with cooled outside gas so as to be cooled can be increased. Accordingly, gas at a lower temperature than that according to the related art flows back to the discharge port and thus the initial temperature of the gas that is recompressed after flowing backward can be reduced. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be prevented. 
         [0015]    As a result, the temperature of the discharge gas that is recompressed can be lowered, and an increase in the temperatures of components that come into contact with the discharge gas can be suppressed. Accordingly, contact between the claws of the rotors or contact between the claws and the inner surfaces of the housing due to thermal expansion or deformation and breaking due to insufficient heat resistance can be suppressed. In addition, the amount of thermal expansion of each of the components decreases. Therefore, as the amount of thermal expansion decreases, the gaps between the components can be further reduced, which leads to an increase in pump efficiency. Furthermore, the degree of request of each of the components for heat resistance can be reduced, and thus a reduction in costs can be achieved. 
         [0016]    According to an aspect of the present invention, the opening/closing mechanism can be constituted by a first partition plate and a second partition plate, which are fixed to one of the two rotating shafts on both sides of the pair of rotors in a rotational axis direction. In addition, the first partition plate is provided with an opening formed at a position that opens only the first discharge port and does not open the second discharge port when at least one set of the claws forms the compression pocket in the housing, and the second partition plate is provided with an opening formed at a position that opens only the second discharge port and does not open the first discharge port when at least another set of the claws forms the compression pocket in the housing. 
         [0017]    As described above, since the first partition plate and the second partition plate are used as the opening/closing mechanism, a wide installation space is not necessary. In addition, since the first partition plate and the second partition plate are fixed to the rotating shaft and are interlocked with the rotating shaft, a special drive device is not necessary, and the opening/closing mechanism can be simply formed with low costs. 
         [0018]    According to an aspect of the present invention, in a case where two claws are formed on each of the rotors, the first partition plate is provided with the opening formed at a position that opens only the first discharge port and does not open the second discharge port when one set of the claws forms the compression pocket in the housing. In addition, the second partition plate is provided with the opening formed at a position that opens only the second discharge port and does not open the first discharge port when the other set of the claws forms the compression pocket in the housing. 
         [0019]    In this configuration, the gas in the compression pocket is alternately discharged to the first discharge port and the second discharge port. In a claw pump having two claws for a single rotor, compressed gas is discharged from a single discharge port every half revolution. On the contrary, in the above-descried configuration, the compressed gas is discharged from a single discharge port every one revolution. Therefore, the time until the discharge gas that is compressed and is increased in temperature flows backward is increased twice that of the claw pump according to the related art. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be effectively prevented. 
         [0020]    According to an aspect of the present invention, in a case where three claws are formed on each of the rotors at equal intervals in a circumferential direction, the first partition plate is provided with the opening formed at a position that opens only the first discharge port and does not open the second discharge port when two sets of the claws form the compression pocket in the housing, and the second partition plate is provided with the opening formed at a position that opens only the second discharge port and does not open the first discharge port when another set of the claws forms the compression pocket in the housing. Accordingly, even in the case where three claws are formed on a single rotor, the time at which the compressed gas is discharged from a single discharge port can be increased, and thus gas at a lower temperature flows backward. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be prevented. 
         [0021]    According to an aspect of the present invention, the first partition plate and the second partition plate can be disposed between the pair of rotors and the side plates. Accordingly, a space in which the first partition plate and the second partition plate are disposed outside the housing is not necessary, and a compact pump configuration can be achieved. 
         [0022]    If there is no restrictions on space, the first partition plate and the second partition plate may also be disposed on the outside of the side plates. In this case, the management of gaps in the axial direction of the rotating shaft can be performed with lower accuracy than that of the housing, and workability and ease of assembly can be improved. Otherwise, the first partition plate and the second partition plate disposed on the outside of the side plates may be provided with blades, for example, in a structure such as a sirocco fan, to actively discharge the discharge gas to the outside. Accordingly, the backflow of high-temperature gas can be further suppressed. 
       Advantageous Effects of Invention 
       [0023]    According to some aspects of the present invention, the temperature of the discharge gas of the claw pump can be reduced by simple and low-cost means. Therefore, various problems caused by an increase in the temperature of the discharge gas can be solved. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0024]      FIG. 1  is an exploded perspective view of a claw pump according to a first embodiment of the present invention. 
           [0025]      FIG. 2  is a view viewed from arrow A in  FIG. 1 . 
           [0026]      FIG. 3  is an exploded perspective view illustrating a state after the claw pump makes a half revolution. 
           [0027]      FIG. 4  is an exploded perspective view of a claw pump according to a second embodiment of the present invention. 
           [0028]      FIGS. 5(A) to 5(H)  are front sectional views illustrating a claw pump according to the related art in a stroke order. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0029]    Hereinafter, the present invention will be described in detail using embodiments illustrated in the drawings. Here, the dimensions, materials, shapes, and relative arrangements of components described in the embodiments are not intended to limit the scope of the invention thereto if not particularly defined. 
       First Embodiment 
       [0030]    Next, a claw pump according to a first embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . In  FIGS. 1 and 2 , a claw pump  10 A according to the embodiment includes a housing  12  that forms a pump chamber therein. The housing  12  is constituted by a cylinder  14  having a cross-sectional shape of two partially overlapping circles, and a pair of side plates  16   a  and  16   b  which block both end faces of the cylinder  14 . The cylinder  14  is provided with a suction port  18 , and the suction port  18  is disposed at a position that communicates with an inlet pocket P 0  in which suctioned gas g is not compressed. 
         [0031]    Inside the housing  12 , two rotating shafts  20   a  and  20   b  are arranged parallel to each other. Inside the housing  12 , rotors  22   a  and  22   b  are respectively fixed to the rotating shafts  20   a  and  20   b.  The rotating shafts  20   a  and  20   b  extend toward the outside of the housing  12 , and end portions of the rotating shafts  20   a  and  20   b  are connected to a rotary drive device (not illustrated). The rotating shafts  20   a  and  20   b  are synchronously rotated in opposite directions to each other by the rotary drive device. The rotors  22   a  and  22   b  are rotated in the opposite directions to each other at the same speed by the rotary drive device. The rotors  22   a  and  22   b  are provided with two claws  24   a  and two claws  24   b  which have a hook shape and mesh with each other in a non-contact state (with a fine gap therebetween). The two claws are disposed at positions at 180 degrees to each other in the circumferential direction. The rotor  22   a  is provided with a first concave portion  25   a  formed on the downstream side of the first claw  24   a.  The rotor  22   a  is provided with a second concave portion  25   a  formed on the downstream side of the second claw  24   a.  Here, the downstream side mentioned here is the downstream side with respect to the rotational direction of the rotor  22   a.    
         [0032]    The gas g is suctioned into the inlet pocket P 0  from the suction port  18  by the rotation of the rotors  22   a  and  22   b.  Next, the inlet pocket P 0  into which the gas g flows is divided into a first pocket P 1  enclosed by the housing  12  and the rotor  22   a,  and a second pocket P 2  enclosed by the housing  12  and the rotor  22   b.  As the rotors  22   a  and  22   b  further rotate, the first pocket P 1  and the second pocket P 2  join such that a compression pocket P is formed. Immediately after the joining, an initial stage compression space Pe is formed. Thereafter, the compression pocket P is reduced in size and an end stage compression space Pc is formed. In this compression process, the gas g in the compression pocket P is compressed. 
         [0033]    The side plates  16   a  and  16   b  are respectively provided with discharge ports  26   a  and  26   b  which are formed in regions closer to the rotating shaft  20   a  than the rotating shaft  20   b.  The discharge ports  26   a  and  26   b  are disposed at positions which communicate with the end stage compression space Pc when the end stage compression space Pc is formed by the claws  24   a  and  24   b.  The discharge ports  26   a  and  26   b  are disposed at the same position in the circumferential direction of the rotating shaft  20   a  and have the same shape. 
         [0034]    A partition plate  28   a  having a circular outer shape is fixed to the rotating shaft  20   a  between the side plate  16   a  and the rotor  22   a  inside the housing  12 . In addition, a partition plate  28   b  having a circular outer shape is fixed to the rotating shaft  20   a  between the side plate  16   b  and the rotor  22   a.  The partition plates  28   a  and  28   b  are respectively provided with openings  30   a  and  30   b.  The openings  30   a  and  30   b  are disposed substantially in the same region in the radial direction from the rotating shaft  20   a.  The openings  30   a  and  30   b  are disposed at positions at 180 degrees to each other about the rotating shaft  20   a  in the circumferential direction. In other words, the openings  30   a  and  30   b  are formed to substantially have point symmetry (that is, twofold symmetry) about the rotating shaft  20   a.  Fine gaps are provided between the outer circumferences of the partition plates  28   a  and  28   b  and the inner circumference of the housing  12  to an extent that the gas g does not leak. 
         [0035]    More specifically, the opening  30   a  overlaps the first concave portion  25   a  formed on the downstream side of the first claw  24   a  of the rotor  22   a.  The opening  30   a  is disposed at a position that overlaps discharge port  26   a  when a first set of the claws  24   a  and  24   b  (one set of claws) of the rotors  22   a  and  22   b  forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port  26   a  to communicate with each other. The opening  30   b  overlaps the second concave portion  25   a  formed on the downstream side of the second claw  24   a  of the rotor  22   a.  The opening  30   b  is disposed at a position that overlaps discharge port  26   b  when a second set of the claws  24   a  and  24   b  (the other set of claws) of the rotors  22   a  and  22   b  forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port  26   b  to communicate with each other. 
         [0036]    In this configuration, when the first set of claws  24   a  and  24   b  forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port  26   a  via the opening  30   a . Next, when the second set of claws  24   a  and  24   b  forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port  26   b  via the opening  30   b.  Therefore, the compressed gas is alternately discharged from the discharge ports  26   a  and  26   b.    FIG. 1  illustrates a state in which the end stage compression space Pc formed by the claws  24   a  and  24   b  and the discharge port  26   b  communicate with each other via the opening  30   b  of the partition plate  28   b.    FIG. 3  illustrates a state in which the rotors  22   a  and  22   b  make a half revolution from the state of  FIG. 1  and the end stage compression space Pc and the discharge port  26   a  communicate with each other via the opening  30   a  of the partition plate  28   a.    
         [0037]    According to this embodiment, since the compressed gas is alternately discharged from the discharge ports  26   a  and  26   b,  compared to a claw pump according to the related art, the interval at which the discharge gas is discharged from the discharge ports  26   a  and  26   b  can be increased twice. Therefore, the time for which the discharged gas is mixed with cooled outside gas so as to be cooled can be increased. Accordingly, in a case where the pump chamber is at a low pressure, gas at a lower temperature than that according to the related art flows back to the discharge port and thus the initial temperature of the gas that is recompressed after flowing backward can be reduced. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be prevented. 
         [0038]    As a result, the temperature of the discharge gas that is recompressed can be lowered, and an increase in the temperatures of components that come into contact with the discharge gas can be suppressed. Therefore, contact between the claws  24   a  and  24   b  of the rotors  22   a  and  22   b  or contact between the claws  24   a  and  24   b  and the inner surfaces of the housing  12  due to thermal expansion or deformation and breaking due to insufficient heat resistance can be suppressed. In addition, the amount of thermal expansion of each of the components decreases. Therefore, as the amount of thermal expansion decreases, the gaps between the components can be further reduced, which leads to an increase in pump efficiency. Furthermore, the degree of request of each of the components for heat resistance can be reduced, and thus a reduction in costs can be achieved. 
         [0039]    In addition, since only the partition plates  28   a  and  28   b  need to be used, a wide installation space is not necessary. In addition, since the partition plates  28   a  and  28   b  are fixed to the rotating shaft  20   a  and are interlocked with the rotating shaft  20   a,  a special drive device is not necessary, and an opening/closing mechanism can be simply formed with low costs. Furthermore, since the partition plates  28   a  and  28   b  are disposed between the rotors  22   a  and  22   b  and the right and left side plates  16   a  and  16   b,  a space in which the partition plates  28   a  and  28   b  are disposed outside the housing  12  is not necessary, and a compact pump configuration can be achieved. 
       Second Embodiment 
       [0040]    Next, a second embodiment of the present invention will be described with reference to  FIG. 4 . In a claw pump  10 B according to this embodiment, a pair of rotors  40   a  and  40   b  are provided with three claws  42   a  and three claws  42   b  having a hook shape. The claws  42   a  or  42   b  are disposed at equal intervals in the circumferential direction of the rotor  40   a  or  40   b.  The rotor  40   a  is provided with a first concave portion  45   a  formed on the downstream side of the first claw  42   a.  The rotor  40   a  is provided with a second concave portion  45   a  formed on the downstream side of the second claw  42   a.  The rotor  40   a  is provided with a third concave portion  45   a  formed on the downstream side of the third claw  42   a.  A partition plate  44   a  having a circular outer shape is fixed to the rotating shaft  20   a  between the side plate  16   a  and the rotor  40   a.  In addition, a partition plate  44   b  having a circular outer shape is fixed to the rotating shaft  20   a  between the side plate  16   b  and the rotor  40   a.    
         [0041]    Two openings  46   a  and  46   b  are bored in the partition plate  44   a , and a single opening  46   c  is bored in the partition plate  44   b.  The openings  46   a,    46   b,  and  46   c  are disposed at substantially the same position in the radial direction from the rotating shaft  20   a.  The openings  46   a,    46   b,  and  46   c  are disposed at equal intervals of  120  degrees in the circumferential direction about the rotating shaft  20   a.  In other words, the openings  46   a,    46   b,  and  46   c  are formed to have threefold symmetry about the rotating shaft  20   a.  In addition, fine gaps are provided between the outer circumferences of the partition plates  44   a  and  44   b  and the inner circumference of the housing  12  to an extent that the gas g does not leak. 
         [0042]    More specifically, the opening  46   a  overlaps the first concave portion  45   a  formed on the downstream side of the first claw  42   a  of the rotor  40   a.  The opening  46   a  is disposed at a position that overlaps discharge port  26   a  when a first set of the claws  42   a  and  42   b  (one set of claws) of the rotors  40   a  and  40   b  forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port  26   a  to communicate with each other. The opening  46   b  overlaps the second concave portion  45   a  formed on the downstream side of the second claw  42   a  of the rotor  40   a.  The opening  46   b  is disposed at a position that overlaps discharge port  26   a  when a second set of the claws  42   a  and  42   b  (another set of claws) of the rotors  40   a  and  40   b  forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port  26   a  to communicate with each other. The opening  46   c  overlaps the third concave portion  45   a  formed on the downstream side of the third claw  42   a  of the rotor  40   a.  The opening  46   c  is disposed at a position that overlaps discharge port  26   b  when a third set of the claws  42   a  and  42   b  (yet another set of claws) of the rotors  40   a  and  40   b  forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port  26   b  to communicate with each other. The other configurations are the same as those of the first embodiment. 
         [0043]    In this configuration, when the first set of claws  42   a  and  42   b  forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port  26   a  via the opening  46   a.  Next, when the rotors  40   a  and  40   b  rotate 120 degrees and the second set of claws  42   a  and  42   b  forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port  26   a  via the opening  46   b . When the rotors  40   a  and  40   b  further rotate 120 degrees and the third set of claws  42   a  and  42   b  (the remaining set of claws) forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port  26   b  via the opening  46   c.    
         [0044]    According to this embodiment, the time interval at which the compressed gas is discharged from the discharge ports  26   a  and  26   b  can be increased, and thus the gas at a lower temperature flows backward. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be prevented. 
       INDUSTRIAL APPLICABILITY 
       [0045]    According to the embodiment, a claw pump in which an increase in the temperature of a discharge gas can be avoided and problems caused by the temperature increase can be solved can be realized by simple and low-cost means. 
       REFERENCE SIGNS LIST 
       [0046]      10 A,  10 B,  100  CLAW PUMP 
         [0047]      12 ,  102  HOUSING 
         [0048]      14  CYLINDER 
         [0049]      16   a,    16   b  SIDE PLATE 
         [0050]      18 ,  108  SUCTION PORT 
         [0051]      20   a,    20   b,    110   a,    110   b  ROTATING SHAFT 
         [0052]      22   a,    22   b,    40   a,    40   b,    112   a,    112   b  ROTOR 
         [0053]      24   a,    24   b,    42   a,    42   b,    114   a,    114   b  CLAW 
         [0054]      26   a,    26   b  DISCHARGE PORT 
         [0055]      28   a,    28   b,    44   a,    44   b  PARTITION PLATE 
         [0056]      30   a,    30   b,    46   a,    46   b,    46   c  OPENING 
         [0057]      116  DISCHARGE PORT 
         [0058]    P COMPRESSION POCKET 
         [0059]    Pe INITIAL STAGE COMPRESSION SPACE 
         [0060]    Pc END STAGE COMPRESSION SPACE 
         [0061]    P 0  INLET POCKET 
         [0062]    P 1  FIRST POCKET 
         [0063]    P 2  SECOND POCKET 
         [0064]    g GAS