Abstract:
A compressor includes a cylinder having major and minor compression chambers. The major compression chamber includes an ambient intake and an outlet which can be directed either to the intake of the minor chamber or directly to a holding tank. The outlet from the minor chamber is likewise directed to the gas storage tank. In a preferred embodiment, the compressor includes two cylinders each with a major and minor chamber operated by a three-lobed cam. The compressor switches from single stage to dual stage operation with valves operable in response to attaining a preset gas pressure in the holding tank or output.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Multi-stage compressors act to compress air in a first chamber forcing it to a smaller second chamber and subsequently to an outlet. Thus, the piston in the smaller chamber is compressing already compressed air. This allows the compressor to achieve higher pressures. However, such operation is volumetrically inefficient at lower pressures.  
       SUMMARY OF THE INVENTION  
       [0002]     The present invention is premised on the realization that the efficiency of a compressor can be improved by switching from a single stage compressor having major and minor compression chambers to a two stage or dual stage compressor. The output from the larger major chamber is switched between either an outlet such as to a holding tank or to the intake of the smaller minor chamber which is in turn connected to an outlet and subsequently the holding tank. This allows for initial operation of the compressor in a single stage mode wherein the outputs from both the major and minor compression chambers are directed to a holding tank. When a predetermined pressure is achieved, the output from the major chamber is directed to the intake to the minor chamber, thus switching to a two stage compressor and allowing for greater pressures.  
         [0003]     This maximizes the efficiency of the compressor allowing it to maximize volumetric output initially and, subsequently, maximize pressure output.  
         [0004]     The present invention is described with respect to a three-lobed cam-operated dual-piston compressor which provides many advantages for the present invention. However, other compressor designs with more than one compression chamber will function in the present invention. A three lobed cam-operated dual piston compressor is shown in U.S. patent application Ser. No. 11/235,884, entitled ROTARY TO RECIPROCAL POWER TRANSFER DEVICE, filed on Sept. 25, 2005, the disclosure of which is hereby incorporated by reference. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is an elevational view of the present invention;  
         [0006]      FIG. 2A  is a cross sectional view of the present invention in a single stage mode with the pistons in a first stroke position;  
         [0007]      FIG. 2B  is a cross sectional view of the present invention in a single stage mode with the pistons in a second stroke position;  
         [0008]      FIG. 3A  is a cross sectional view of the present invention in a dual stage mode with the pistons in a first stroke position;  
         [0009]      FIG. 3B  is a cross sectional view of the present invention in a two-stage mode with the pistons in a second stroke position.  
         [0010]      FIG. 4  is an exploded perspective view of the follower of the present invention, partially broken away. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]     As shown, the compressor  10  includes an exterior housing  18 . Housing  18  includes a circular peripheral wall  24  and two side walls  26  and  28 . First and second cylindrical mounts  20  and  22 , located on peripheral wall  24 , support the first and second compressor chambers  14  and  16 . A shaft  30  extends through walls  26  and  28  and is fixed to cam  12 . The cam  12 , when rotated by shaft  30 , moves a follower  34  which, in turn, causes reciprocation of first and second pistons  36  and  38 .  
         [0012]     Cam  12  rotates within the follower  34  which includes a body portion  48  (see  FIG. 4 ) formed from first and second spaced body members  50  and  52  on either side of cam  12 . The first and second members  50  and  52  each include slots  54 ,  56  aligned with a central axis  58  of device  10 . The follower  34  has dogleg portions  55  and  57 , which are oppositely offset from central axis  58 . The follower  34  further includes first and second head portions  60  and  62  which hold the body members  50  and  52  together on either side of cam  12 . First and second rollers  64  and  66  are mounted to head portions  60  and  62 . Also fixed to head portions  60  and  62  are first and second rods  68  and  70  which, in turn, attach to the first and second pistons  36  and  38 , respectively.  
         [0013]     The dogleg portions  55  and  57  and follower  34  are directed toward the driving surface of the cam  12 , and opposite the direction of arrows  46 .  
         [0014]     As shown in  FIG. 4 , first head portion  60  is resiliently mounted to the first and second members  50  and  52  of the follower body, whereas second head portion  62  is fixedly attached to first and second members  50  and  52 .  
         [0015]     The first head portion  60  includes a top surface  72  and first and second legs  74  and  76 . The first roller  64  is attached to the first head  60  by a pin  78  which extends through first and second legs  74  and  76 . The head portion  60  is mounted to first and second members  50  and  52  with four hex screws  80  which run through axially stepped bores  82 . Shaft  84  of screws  80  extend through a resilient member which, as shown, is a series of Belleville washers  86  and a sleeve  88  and fastens to members  50  and  52  of the follower body  48 . The Belleville washers rest on a shoulder  90  secured by head  91  of screw  80 . Any suitable resilient member, such as a spring or the like, can be used in place of the Belleville washer.  
         [0016]     The second head  62  can be a mirror image of first head  60 , or, as shown, is simply a C-shaped cap with legs  92  and  93  attached with screws  81  to the members  50  and  52  of follower body  48 . The rods  68  and  70  are bolted to heads  60  and  62  at one end  61  and are attached to cylinders  36  and  38  at the opposite end.  
         [0017]     Compression chambers  14  and  16  are cylindrical which house pistons  36  and  38 . Rods  68  and  70  extend into chambers portion  14  and  16  through bushings  94 , 95  and oil seals  96 , 97  in circular plates  98 , 99  of discs  100 , 101 . Chambers  14  and  16  fit within discs  100 ,  101  forming sealed cylindrical chambers.  
         [0018]     Compression chamber  14  includes major and minor (by volume) compression chambers  125  and  126  separated by piston  36 . Likewise, compression chamber  16  includes major and minor compression chambers  127  and  128  separated by piston  38 . Compression chambers  14  and  16  also include intakes  104 ,  105 ,  106 , and  107 , and exhausts  108 ,  109 ,  110  and  111  leading to and from the respective major and minor compression chambers. Each of these intakes and exhausts utilizes flap valves  112  to allow air or gas in or out of the respective chambers.  
         [0019]     The exhaust output lines  108  and  109  lead from the minor compression chambers  128  and  126  directly to a holding tank  113 . These could lead to any output connected to the compressor. Further, intakes  106  and  107  lead from the ambient environment (or any source of low pressure gas) to the major compression chambers  125  and  127 . Exhaust line  110  leads from major compression chamber  125  to valve  114 , and exhaust line  111  leads from major compression chamber  127  to valve  116 .  
         [0020]     As shown in  FIGS. 2A, 2B ,  3 A and  3 B, the valve  114  and  116  can direct intake air for intake  104  and  105  respectively, either from the exhaust lines  110  and  111  or from the ambient intakes  118  and  120 . When inlets  104  and  105  are receiving intake airfrom ambient intakes  118  and  120 , the exhaust from lines  110  and  111  are directed through lines  122  and  124  to the holding tank  113 . Valves  114  and  116  are in turn controlled by a pressure sensor (not shown) located in the holding tank  113 . The pressure sensor will enable pre-set pressure switching of valves  114  and  116 .  
         [0021]     In operation, the shaft  30  will rotate, causing the cam  12  to rotate. The action of the cam  12  against rollers  64  and  66  causes the follower  34  to move in the direction of arrow  102  as shown in  FIG. 2A  and, subsequently, in the direction of arrow  103  shown in  FIG. 2B . This will in turn cause the rods  68  and  70  and associated cylinders  36  and  38  to move in the direction of arrow  102  and, subsequently,  103 . In the single stage operation, as shown in  FIG. 2A , with the follower fully extended in the direction of arrow  102  the piston  38  will be in an extended position as shown in  FIG. 2A  with piston  36  in a retracted position. As these pistons move, gas from chamber  125  will be directed through exhaust  111  through line  124  to holding tank  113 . Gas will be drawn into chamber  126  from intake line  120  into line  105 . Likewise, as the cylinder  36  moves in the direction of arrow  102 , gas will be drawn through intake  106  into chamber  127 . Gas in chamber  128  will be forced through exhaust  108  directly to holding tank  113 .  
         [0022]     As pistons  36  and  38  move in the direction of arrow  103 , the gas in chamber  125  is forced through exhaust  110  to holding tank  113 . Gas will be drawn in through intake  107  to fill chamber  127 . Likewise, gas will be directed from intake  118  through line  104  into chamber  126 , and gas from chamber  128  will be forced through line  111  through valve  116  and line  124  to the holding tank  113 .  
         [0023]     If a pre-determined pressure is sensed in the holding tank or output lines, valves  114  and  116  switch to the positions shown in  FIGS. 3A and 3B . As shown in  FIG. 3A , with the pistons  36  and  38  moving in the direction of arrow  102 , the compressed air from major chamber  127  will be driven through exhaust  111  through valve  116  to intake line  105  and into minor chamber  128 . Piston  36  will draw gas into chamber  125  through intake  106  and direct gas from minor chamber  126  through exhaust line  108  to holding tank  113 . When the pistons move in the direction of arrow  103 , gas will be drawn in through intake  107  into major chamber  127  and the gas in minor chamber  128 , which previously was directed from chamber  127 , will go directly to holding tank  113  through line  109 . Piston  36 , in turn, will force compressed gas from major chamber  125  through exhaust line  110  and valve  114  through intake line  104  into minor chamber  126 . Thus, in this embodiment, the gas initially is taken into major, or larger, chambers  125  and  127 , forced into minor, or smaller, chambers  126  and  128 , respectively, and, subsequently, compressed again forcing it into holding tank  113 .  
         [0024]     In the first mode of operation, the compressor  10  pumps the largest volume of gas with output from all four chambers  125 ,  126 ,  127 ,  128  directed to the holding tank to fill the holding tank  113  with gas as rapidly as possible. Once the tank reaches a pre-determined pressure, the valves  114  and  116  will be switched to the position shown in  FIGS. 3A and 3B , which will allow gas at a higher pressure and lower volume to be forced into holding tank  113 . Because the chambers  126  and  128  are smaller than chambers  125  and  127 , the air introduced in this mode into chambers  126  and  128  will be compressed, as opposed to ambient pressure, which will then be again compressed further when forced into the holding tank. This allows for higher pressure operation.  
         [0025]     Due to the design of this pump, only two valves are required, switching from one mode to a second mode. Further, these valves operate automatically in response to a preset pressure.  
         [0026]     Because the compressor is set up for operation in both directions of piston movement, both pistons  36  and  38  will be compressing gas regardless of the direction of movement of the pistons  36  and  38 .  
         [0027]     In this design, the oil seals  96 , 97  must also provide the compression seals for the minor chambers in addition to preventing oil in the housing  18  from entering the cylinders  14 , 16 . This allows the compressor cylinders  14 , 16  to operate without oil. This eliminates the need for any type of oil removal equipment downstream from the compressor in applications where the presence of oil cannot be tolerated.  
         [0028]     This has been a description of the present invention along with the preferred method of practicing the present invention. However, the invention itself should only be defined by the appended claims, WHEREIN