Abstract:
The present invention provides an improved rotor mechanism to improve the mechanism of the intermeshing displacement rotor and valve rotor. The main feature is that the displacement rotor and the valve rotor provide the operation curve from the carryover period to intake period, which includes a pair of convex curves with different radius merging smoothly with each other, thereby providing a smooth transference of the intake, exhaust, and carryover, etc. and avoiding noise and vibration during the working process. Moreover, the displacement rotor and the valve rotor provide the operation curve from the starting of exhaust to the period of ending, which is defined by an arcuated surface thereby providing a rotor mechanism with great diplacement transference and high compression ratio.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotor mechanism, more particularly, an improved rotor mechanism used in vacuum systems like a vacuum pump, an air compressor, a compressor, and those machines which includes a periodic compression operation of intake and exhaust, thereby providing enhancing those machines a high compression ratio and a smooth intake and exhaust process and avoiding noise and vibration. 
     2. The Prior Art 
     Referring to the U.S. Pat. Nos. 4,138,838, 4,224,016, 4,324,538, 4,430,050 and 5,149,256, the double lobes type rotor of multi-phases roots type compressor or vacuum pump relates to the present invention. Such double lobes type rotor mechanism comprises a pair of the intermeshing displacement rotor and valve rotor. A pair of lobes of each rotor provides periodic compression operation of air intake and air exhaust. Therefore, when intermeshing, the inosculation of two lobes of the rotors is very important. If the inosculation of the two lobes of the rotors is not good enough, noise and vibration may occur during the periodic air intake, air exhaust, and non-compression of the rotors. Moreover, wear may occur due to the improper intermeshing of the rotors thereby reducing the production useful life. The above-mentioned U.S. Pat. No. 5,149,256 obviously has those defects. Referring to FIG. 10, the lobes of a pair of rotors  8 ,  9  of U.S. Pat. No. 5,149,256 includes the tip portions  82 ,  92  formed at the junctions between the concave portions  80 ,  90  and the arcuated surface  81 ,  91  so that there is discontinuity of the rotors  80 ,  90 &#39;s curves at the tip portion  82 ,  92 . Therefore, during the moments from inefficient compression period to the period of air&#39;s starting intake, the top portions  83 ,  93  of the rotors  8 ,  9  will operate unsmoothly at the tip portion  82 ,  92  thereby resulting in noise and vibration. 
     SUMMARY OF THE INVENTION 
     To overcome those defects of the double lobes type rotor of the prior art, the object of the present invention is to provide an improved rotor mechanism which could operate smoothly and avoid noise and vibration during the periodic operation of intake, exhaust, and carryover, etc. 
     Another object of the improved rotor mechanism of the present invention is to provide an improved rotor mechanism which provides great displacement transference and high compression ratio to achieve the vacuum demanded for vacuum system by fewer stages of rotor sets in series. Therefore, such a improved rotor mechanism is cost efficient. 
     To fulfill the above-mentioned objects, the improved rotor mechanism of the present invention includes an improvement on the structure of the intermeshing displacement rotor and valve rotor, that is, to provide the two rotors a smooth operation curve during the carryover period. The main feature is that the operation curve provided by the displacement rotor and the valve rotor from the carryover period to the period of starting intake is defined by a couple of smoothly connected different curves rather than a couple of connected arcs. 
     Another feature of the improved rotor mechanism of the present invention is that the operation curve from the period of starting air intake to the period of ending provided by the displacement rotor and the valve rotor is defined by an arcuated surface thereby providing great displacement transference and high compression ratio. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is the perspective view of the displacement rotor and valve rotor of the present invention which are assembled within the cavity portion. 
     FIG. 2 is the planar view of one lobe of the displacement rotor of the present invention. 
     FIGS. 3,  4  are the perspective views of the corresponding rotation movement of the displacement rotor and the valve rotor about the hub. 
     FIG. 5 is the planar view of the displacement rotor of the present invention. 
     FIG. 6 is the planar view of the valve rotor of the present invention. 
     FIGS. 7A to  7 D, FIGS. 8A to  8 D and FIG. 9 are the perspective views of the periodic operation of the intake, the exhaust and the carryover, etc. of the displacement rotor and the valve rotor of the present invention. 
     FIG. 10 is the planar view of the intermeshing double lobes type rotor of the U.S. Pat. No. 5,149,256. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a rotor mechanism of the present invention comprises a pair of intermeshing displacement rotor  71  and valve rotor  72 . The rotors  71 ,  72  are accommodated within a cavity portion  73 . The cavity portion  73  includes an inlet  730  and an outlet  731 . The valve rotor  72  is disposed adjacent to the outlet  731  and is rotatable to occlude or open the outlet  731 . Also referring to FIG. 5, the displacement rotor  71  of the present invention includes a pair of lobes  711 ,  712  which has the same structure and is symmetrical about a rotary hub C 1 . For facilitating the description and avoid the complexity of drawings, only the lobe  711  shall be described about the designated detailed structures as follows. The lobe  711  includes a first arcuated surface  713  to provide the operation process from air intake starting period to the period of ending, a second arcuated surface  714  corresponding to the first arcuated surface  713  to provide the operation process from the period of air exhaust starting to the period of ending, and a third arcuated surface  715 , a fourth arcuated surface  716 , a first convex surface  717 , a second convex surface  718 . The first and second convex surfaces  717 ,  718  are connected between the first arcuated surface  713  and the second arcuated surface  714  to provide an operation process of carryover. The third arcuated surface  715  is smoothly connected with the second arcuated surface  714 . The fourth arcuated surface  716  is connected between the third arcuated surface  715  and the the first convex surface  717 . The second convex surface  718  is connected between the first convex surface  717  and the first arcuated surface  713 . 
     Referring to FIG. 6, the valve rotor  72  includes a pair of lobes  721 ,  722  which has the same structure and is symmetrical about a rotary hub C 2 . Each lobe  721 ,  722  includes the corresponding arcuated surfaces  723 ,  724 ,  725 ,  726  and the convex surfaces  727 ,  728  which is defined by the relative rotation movement of the arcuated surfaces  713 ,  714 ,  715 ,  716 , and the convex surfaces  717 ,  718  and intermeshes with the arcuated surfaces  713 ,  714 ,  715 ,  716 , and the convex surfaces  717 ,  718  (For facilitating the description and avoid the complexity of drawings, only the lobe  721  shall be described about the designated detailed structures as following.) 
     The arcuated surfaces and the convex surfaces of the displacement rotor  71  are defined in an ordinal manner, i.e. the third arcuated surface  715 , the fourth surface  716 , the first convex surface  717 , the second convex surface  718 , the first arcuated surface  713 , and the second arcuated surface  714 . The description for defining each arcuated surface and convex surface is as follows. 
     1. Referring to FIG. 3, the maximum external radius of the displacement rotor  71  and the valve rotor  72  is designated R. The distance between the centers of the hubs C 1 , C 2  of the rotors is designated 4R/3. A pair of parallels P 1 , P 2  is defined as drawing assistant lines. A pair of rounds  60 ,  61  are respectively drawn out with the maximum radius R and circle center C 1 , C 2 . 
     2. Referring to FIG. 2 again, a third arcuated surface  715  is defined by a round  62  which has a radius of 23R/60 and is tangent to both the round  60  defined by the maximum external radius of the displacement rotor and the parallel P 1 . The surface on the round  62  which is between the point of tangency  1  of the round  62  and the round  60  defined by the maximum external radius of the displacement rotor, and the point of tangency  2  of the round  62  and the parallel P 1 , is the third arcuated surface  715 . 
     3. The fourth surface  716  is defined by the point of tangency  1  of the third arcuated  715  and the round  60  defined by the maximum external radius of the displacement rotor, the tip portion A 1  defined by the corresponding rotation movement of the two rotors about the hubs (Referring to FIG. 3, the two tip portions A, A 1  are defined by the corresponding rotation movement of both the maximum external radius R of the two rotors  71 ,  72  about the hubs C 1 , C 2 .). The surface of the round  60  defined by the maximum external radius of the displacement rotor which is between the tip portion A 1  and the point of tangency  1  is the fourth arcuated surface  716 . 
     4. After the fourth arcuated surface  716  is defined, the convex surface which is defined by the corresponding rotation movement of the tip portion A 1  cooperating with the tip portion A of the valve rotor  72  with the above-mentioned the maximum external radius R of the two rotors  71 ,  72 , as the radius about the hubs C 1 , C 2  is the first convex surface  717 . 
     5. The second convex surface  718  is defined by the corresponding rotation movement of the fourth arcuated surface  716  about the hubs C 1 , C 2  of the two rotors  71 ,  72 , respectively. 
     6. The first arcuated surface  713  is defined as follows. A round  63  with a radius of 16.45R/60 is defined to be tangent to both the second convex surface  718  and the parallel P 2 . The surface which is between the point of tangency  4  of the round  63  and the second convex surface  718 , and the point of tangency  5  of the round  63  and the parallel P 2  is the first arcuated surface  713 . 
     7. The second arcuated surface  714  is defined as follows. The enantiomorphous round  64  is defined by the 180 degree rotation of the round  63  which defines the first arcuated surface  713  about the hub C 1  of the displacement rotor. Moreover, another round  65  with the radius of 20R/3 is defined to be tangent to both the above-mentioned enantiomorphous round  64  and the third arcuated surface  715 . The surface which is between the point of tangency  6  of the round  65  and the enantiomorphous round  64 , and the point of tangency  2  of the round  65  and the third arcuated surface  715  is the second arcuated surface  714 . 
     Also referring to FIG. 7A to FIG. 7D, FIG. 8A to FIG. 8D, and FIG. 9, the period of the intake, exhaust and carryover of the displacement rotor  71  and valve rotor  72  of the present invention is described. Referring to the FIG. 7A to FIG. 7D, from the period of starting intake to the period of ending, the first arcuated surface  713 ,  723  of the displacement rotor  71  and the valve rotor  72  provide the whole operation process. Referring to FIG. 8A to FIG. 8D, from the period of starting exhaust to the period of ending, the second arcuated surface  714 ,  724  of the displacement rotor  71  and the valve rotor  72  provide the whole operation process. Referring to FIG. 9, during the period of carryover the third arcuated surfaces  715 ,  725 , the fourth arcuated surfaces  716 ,  726 , the first convex surfaces  717 ,  727 , and the second convex surfaces  718 ,  728  of the displacement rotor  71  and valve rotor  72  provide the whole operation process. It should be noted that (referring to FIG.  9  and FIG. 7A) during the transition of the present invention from the carryover to intake, the second convex surfaces  718 ,  728  smoothly operate corresponding to the first convex surfaces  717 ,  727  so that no noise or vibration would occur during the operation. The second arcuated surfaces  714 ,  724  provide great displacement transference and high compression ratio, which is over 3 times higher than the compression ratio of the conventional Roots rotors. Moreover, during the simulating process of the rotors of the present invention, the maximum gas intake volume and the minimum volume of the rotor compression limit could be calculated. The carryover volume, etc. of the rotor during the operation could be evaluated. According to the theory of polytropic process of classic thermodynamics, the theoretic single stage compression ratio of the double lobes type rotor of the present invention is about 29 with air as the inlet material and is much higher than the compression ratio of the conventional Roots pump which is 2˜8, while discharging to atmosphere. 
     While the rotor mechanism of the present invention has been described with reference to a specific embodiment, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications to the present invention can be made to the preferred embodiment by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.