Abstract:
A crankshaft driven positive displacement gear type air compressor enclosed within the engine housing forces air in between the compressor and reciprocating means. At approximately top dead center fuel is injected into the engine and burns. The high pressures of combustion transfer energy to the gears of the compressor and the reciprocating means and crankshaft assembly forcing them to accelerate. The reciprocating means accelerates to the bottom dead center position completely uncovering two exhaust ports. Exhaust passes through the exhaust ports and is scavenged with compressed air from the compressor flowing into the housing space enclosing the reciprocating means. The reciprocating means returns to the top dead center position compressing air in the housing space between the compressor and the reciprocating means. At approximately top dead center the process repeats itself. The improvement is the compressor gears are divided into sections to make several individual gear pumps used to pump all the working fluids in the engine, air, oil, fuel and water.

Description:
[0001]    This is a utility application based upon provisional patent application No. 60/223,733 filed Aug. 8, 2000. 
     
    
     
       ABSTRACT  
         [0002]    A crankshaft driven positive displacement gear type air compressor enclosed within the engine housing forces air in between the compressor and reciprocating means. At approximately top dead center fuel is injected into the engine and bums. The high pressures of combustion transfer energy to the gears of the compressor and the reciprocating means and crankshaft assembly forcing them to accelerate. The reciprocating means accelerates to the bottom dead center position completely uncovering two exhaust ports. Exhaust passes through the exhaust ports and is scavenged with compressed air from the compressor flowing into the housing space enclosing the reciprocating means. The reciprocating means returns to the top dead center position compressing air in the housing space between the compressor and the reciprocating means. At approximately top dead center the process repeats itself. The improvement is the compressor gears are divided into sections to make several individual gear pumps used to pump all the working fluids in the engine, air, oil, fuel and water.  
         DISCLOSURE INFORMATION STATEMENT  
         [0003]    In preparation for filing of this application, a pre-examination patent ability search was performed. Among the classes and subclasses reviewed were Class  123 , subclasses  27 R,  65 B,  65 BA,  68 ,  198 C,  213 ,  257 ,  268 ,  316 ,  528 ,  533 ,  559 . 1 ,  561 ,  565 , and  564 . Computer searching was also done on the PTO patent database.  
           [0004]    Designs for two stroke internal combustion engines are disclosed in the art that use positive displacement pumps to charge the cylinder with air prior to ignition. Compressed air is also used to scavenge the cylinder of combustion products during the exhaust cycle of the engine. Various methods of charging the cylinder with the compressed air produced by a positive displacement pump are disclosed in the art. Often a camshaft actuated poppet valve closing off the cylinder from the air passage leading from the air compressor is timed by the camshaft to open and allow the compressed air to enter the cylinder during part of the exhaust cycle to fill the cylinder and push out remaining exhaust gases before the exhaust port has closed.  
           [0005]    One such design is disclosed in the U.S. Pat. No. 4,671,218 issued to Weiland. In this patent there is disclosed a gear type positive displacement pump used to charge a holding chamber located above the cylinder with compressed air through which a valve stem projects to the valve face that seals the intake port located in the floor of the holding chamber from the cylinder beneath it. A crankshaft driven camshaft actuates the intake valve while the exhaust ports are open, which are located in the cylinder wall just above the face of the piston when it is at bottom dead center, allowing compressed air from the compressor to fill the cylinder and scavenge the cylinder of remaining exhaust gases. While this design appears to be simple and straightforward it has the disadvantage of using a camshaft to operate the intake valve and such a design adds to the cost and complexity of the machine and diminishes its performance by using engine output to operate the camshaft and valve. It also has the disadvantage of fresh air being able to enter the open exhaust ports before they close since the camshaft is timed to open the intake valve and allow compressed air from the compressor into the cylinder while the exhaust ports are still open. This will reduce the temperature of the exhaust gases reducing the effectiveness of catalytic converters designed to reduce exhaust emissions, which require high exhaust temperatures for maximum effectiveness. The solution to this problem is a combustion-operated valve between the compressor and the cylinder, sealing the cylinder from the compressor outlet that eliminates the need for a camshaft and closes before fresh air from the compressor can reach the exhaust port. No means are shown to transfer the energy of combustion directly to the compressor gears during the power stroke of the engine. Such a valve exposes the compressor gears to the forces of combustion thereby producing a transfer of power to them during the power stroke of the engine  
           [0006]    The blower types described and illustrated in the patents found during a patent search are usually of the Roots type as disclosed in the Toepel U.S. Pat. No. 4,539,948, the Green U.S. Pat. No. 5,746,163 and several others, turbocharger designs as disclosed in the Toepel Patent and Sweeney U.S. Pat. No. 5,878,703 and others, or of the radial type as disclosed in the Rocklein U.S. Pat. No. 4,860,699, the Covone U.S. Pat. No. 2,851,021, and others. Only in the Weiland Patent and Figliuzzi U.S. Pat. No. 5,179,921 do we see a positive displacement gear pump used as a means to force air into the engine. In neither of these designs or in any of the other patents listed is shown an engine in which the compressor is located in the engine and directly compresses air between the compressor and the reciprocating means without the use of intervening valve means to separate the compressor from the combustion process. Nowhere is such a valve means shown that does not use crankshaft power to operate it.  
           [0007]    It is therefore an important object of one embodiment the present invention to eliminate intake valves from a compressor charged two cycle engine by placing a positive displacement gear type air compressor in the engine head which compresses combustible material directly between the compressor and the reciprocating means thereby receiving a transfer of power to the compressor gears during the power stroke of the engine.  
           [0008]    It is an important object of another embodiment of the present invention to eliminate the need for a camshaft to operate a valve between the compressor and the cylinder with such a valve controlled to prevent a flow of fresh air into the exhaust port during the exhaust process of the engine.  
           [0009]    A third object of another embodiment of the present invention is to further simplify the engine design by combining the functions of the piston and rod into one reciprocating part to make the engine more durable.  
         SUMMARY OF THE INVENTION  
         [0010]    The invention comprises a two-stroke internal combustion engine. The simplest embodiment having a housing made of two identical parts bolted together for easy manufacture, strength or assembly and disassembly. The housing has an intake port located in the uppermost wall of the housing for passing air into a gear type air compressor. The engine includes the air compressor formed by two partial cylinders enclosing the two gear shafts of the air compressor within the upper part of the housing below the intake port. The gear shafts output shafts pass through holes in the outer housing walls for the takeoff of power, and one of them is connected by rotational means connected to the output shaft of the crankshaft for a transfer of power between them. A passage for holding compressed air connects the outlet side of the air compressor to the top end of the cylinder confining the piston of the engine so the compressor gears and the piston are simultaneously exposed to the forces of combustion during the power cycle of the engine. A fuel injector nozzle is located in the intake port for injection of fuel into the passage. The piston is rotatably connected to the rod which is rotatably connected to a crankshaft located in the lower part of the housing space for converting the forces of combustion into useful torque. The crankshaft output shafts pass through identical holes in the walls of the housing. The crankshaft, gear shafts and reciprocating part have internal passages (not shown) for the passage of lubricant to areas of the engine requiring lubrication. Lubricant is pumped into these passages by a conventional oil pump, which is located in the bottom of the housing, to lubricate the engine. An exhaust port is located in the cylinder wall above the bottom dead center position of the piston face and allows exhaust gases to escape the cylinder after the power stroke. Fuel timing and pressure regulation means are provided to allow correct amounts of fuel to be injected into the engine at the proper intervals. This machine has an improved performance compared to other types of two cycle engines because the piston and the compressor gears are exposed simultaneously to the forces of combustion. The power generated by them is combined through power transfer means connecting an output shaft of the crankshaft to an output shaft of a gear shaft.  
           [0011]    In any embodiment of this invention conventional sensors and engine management systems can be included to produce optimum engine performance. A conventional oil pump and oiling system can be included to provide oil to the cylinder walls, crankshaft bearings, rod bearings and gear shaft output rod bearings, conventional bearings means included for support of rotating parts. Conventional fuel supply means for supply of fuel to the fuel injector, conventional spark ignition means can be included to ignite the fuel and air mixture. A water jacket can be included to provide cooling means to embodiments that do not include a water jacket and if necessary an engine driven water pump included to circulate water through the water jacket and a radiator if needed, a fan to circulate air through the radiator.  
           [0012]    This discussion has outlined some of the more important objects of the invention. These objects should be construed as illustrative of the more salient features and applications of the present invention. Many other important results can be obtained by applying the disclosed invention in different ways and modifying it within the scope of the disclosure. Accordingly, by referring to the detailed descriptions of the various embodiments taken together with the accompanying drawings and claims a more complete understanding of the invention may be ascertained. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS (SUBMITTED WITH PRELIMINARY DRAWINGS)  
       [0013]    [0013]FIG. 1 is a side section view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0014]    [0014]FIG. 2 is a side elevation view of the internal combustion engine shown in FIG. 1.  
         [0015]    [0015]FIG. 3 is a side elevation view of the internal combustion engine shown in FIG. 1.  
         [0016]    [0016]FIG. 4 is a top plan view of the internal combustion engine shown in FIG. 1.  
         [0017]    [0017]FIG. 5 is a transverse section view taken through a plane indicated by section line  5 - 5  in FIG. 1.  
         [0018]    [0018]FIG. 6 is a view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0019]    [0019]FIG. 7 is top plan view of the internal combustion engine shown in FIG. 6  
         [0020]    [0020]FIG. 8 is a side section view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0021]    [0021]FIG. 9 is a partial side section view taken through a plane indicated by section line  2 - 2  in FIG. 1.  
         [0022]    [0022]FIG. 10 is a side elevation view of a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0023]    [0023]FIG. 11 is a top plan view of the internal combustion engine shown in FIG. 1.  
         [0024]    [0024]FIG. 12 is a view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0025]    [0025]FIG. 13 is a partial side section view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0026]    [0026]FIG. 14 is a partial side section view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0027]    [0027]FIG. 15 is a partial side section view through a two-cycle internal combustion engine in accordance with one embodiment of the invention.  
         [0028]    [0028]FIG. 16 is a transverse section view taken through a plane indicated by section line  9 - 9  in FIG. 1.  
         [0029]    [0029]FIG. 17 is a transverse section view taken through a plane indicated by section line  10 - 10  in FIG. 7.  
         [0030]    [0030]FIG. 18 is a transverse section view taken through a plane indicated by section line  10 - 10  in FIG. 7. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Referring now to the drawings in detail, FIGS.  1 - 6 , and  18  illustrate a two-cycle internal combustion engine constructed in accordance with one embodiment generally referred to by reference number  10 . In this embodiment the engine is enclosed by a housing assembly  12 , which is formed from two housing sections,  14  and  16 . Bolts  19  pass through holes  17  in the flanges  11  and  13  surrounding sections  14  and  16  and nuts  18  secure the two housing sections against gasket  23 . As clearly illustrated in FIG. 1 and FIG. 4 an intake port  20  is formed in the top wall of housing sections  14  and  16 . The lower end of intake port  20  connects to two parallel partial cylinders  33  and  34  formed in housing section  14  and in housing section  16 . They are parallel with the crankshaft and contain hollow gear shafts  46  and  47  (teeth not shown in side section views) which are meshed together as can be more clearly seen in FIG. 4. These gear shafts are divided into sections that form five separate gear pumps used to pump all the working fluids in the engine, the water, fuel, oil, and air. Gear pump  100  and  101  are located at the ends of the gear shafts  46  and  47  and they pump the oil used in the engine through passages not shown. Gear pump  102  pumps the fuel used by the fuel injector and passes through fuel regulation means not shown. Gear pump  103  pumps the water used to cool the engine that passes through cooling passages  41  and  48 . Gear pump  104  pumps the air into the engine and functions as the compressor. Passage means are provided in the engine to carry the working fluids to their appropriate locations but are in most cases not shown. Seals  110  are spaced between the gear pumps to prevent mixing of the fluids. Gear shafts  46  and  47  have output shafts  42 ,  43 ,  44  and  45  extending through holes formed in the outer vertical walls of housing section  14  and  16 . The gear shafts  46  and  47  are crankshaft driven, counter rotating in opposite directions drawing intake air through intake port  20  and force the intake air into passage  30 , from which it passes into cylinder  40 . A fuel injector  32  projects into passage  30  through the rear wall of housing section  14  for injecting fuel into passage  30 . Partial cylinders  33  and  34  are centrally connected at their lower side to outlet passage  30  traversing the length of partial cylinders  33  and  34  within housing sections  14  and  16  and extending through internal housing wall  15  to cylinder  40  that contains piston  56 . As illustrated in FIG. 1 and FIG. 5 formed within the cylinder  40  is a horizontal generally elongated exhaust port  22  passing through housing section  14  and having flat upper and lower horizontal sides and curved vertical sides. The lower horizontal side of exhaust port  22  is aligned horizontally with upper horizontal surface face  54  of piston  56  when piston  56  is positioned at bottom dead center within cylinder  40 . As can be more clearly seen in FIG. 1 and FIG. 6, piston  56  has an upper exterior horizontal surface face  54 , a circular exterior curved surface  53  tangent with the wall of cylinder  40 . Piston  56  is rotatably connected to connecting rod  59  rotatably connected to rod journal  61  of crankshaft  65 . As can be seen more clearly in FIG. 2, FIG. 3 and FIG. 5 the crankshaft output shafts  63  and  64  pass through holes in housing section  14  and  16  for external power transfer from the crankshaft. Crankshaft output shaft  64  is centrally attached to a drive pulley  75 . The power transfer belt  72  circumscribes drive pulley  75  and extends around drive pulley  76 , which is attached to the output shaft  45  of gear shaft  47 . An oil pump  68  pumps oil through passages in the engine to areas of the engine requiring lubrication. Coolant flows through water jackets  41  and  48  to remove excess heat from the engine. The other necessary cooling means are not shown on the engine. Throttle plate  80  is located in the intake  20  to control the amount of air the engine receives.  
         [0032]    During operation of the engine the crankshaft output shaft  64  rotates the drive pulley  75  transferring power to the drive belt  72  causing drive pulley  76 , which is attached to gear shaft output shaft  45 , to rotate and turn gear shaft  47 . The teeth of gear shaft  47  rotate and force the teeth of gear shaft  46  to move forcing rotation of gear shaft  46 . The rotation of the gear shafts  46  and  47 , which are closely confined within parallel partial cylinders  33  and  34  moves air received from intake port  20  along the circumference of partial cylinders  33  and  34  and into passage  30  from which it passes into cylinder  40 . As crankshaft  65  rotates piston  56  is pushed by crankshaft connecting rod  59  towards internal horizontal housing wall  15 , thereby reducing the volume within cylinder  40  and compressing the air held therein between piston  56  and rotating gear shafts  46  and  47  of the air compressor. When piston  56  reaches approximately top dead center the fuel injector  32  injects fuel into passage  30  containing the compressed air from the compressor. The high temperature of the compressed air confined within passage  30  ignites the incoming fuel mixture from the compressor.  
         [0033]    The forces of combustion transfer energy to the teeth of gear shafts  46  and  47  and to the piston  56  simultaneously causing these parts to accelerate. The acceleration of the gear shafts  46  and  47 , transfers power to their output shafts  42 ,  43 ,  44  and  45 . The acceleration of the piston  56  transfers energy to the crankshaft  65  thereby transferring power to the output shafts  63  and  64  which is combined with the power output of the gear shaft output shaft  45  through power transfer belt  72 . As the gear shafts  46  and  47  accelerate they pump more air into the engine for combustion causing greater power to be generated. The fuel injector  32  is timed to turn off before piston  56  passes below exhaust port  22  so the combustion occurring within cylinder  40  can finish before exhaust gases begin to pass out of the engine. Fresh air from the compressor enters cylinder  40  and scavenges it of exhaust gases while the exhaust port  22  is exposed to the volume of cylinder  40  above the face of piston  56  and fills that portion of cylinder  40  with fresh air. As piston  56  moves towards top dead center, air between the gear shafts  46  and  47  and piston  56  is compressed into passage  30  making the engine ready for another power stroke.  
         [0034]    [0034]FIG. 7 illustrates a different embodiment of the described invention. FIG. 7 shows the embodiment wherein a poppet valve  85  seals passage  30 ′ from cylinder  40 ′. The valve stem of poppet valve  85  projects upwards through housing section  14 ′ and  16 ′ into a compartment containing the helical spring  86  and retainer  87  that keep valve  85  tensioned against the bottom of the lower wall of passage  30 . When combustion of the fuel and air in passage  30 ′ occurs the forces of combustion push valve  85  down against the face of the piston  56 ′ forcing it towards bottom dead center, there it uncovers exhaust port  22 ′ and exhaust gases escape through it from the cylinder. The valve  85  closes when fuel injector  32  (not shown) stops injecting fuel into the engine at which time the fresh air from the compressor flowing into passage  30 ′ burns the remaining fuel within passage  30 ′ and the valve then closes. This design does not need a camshaft. The pressures that are caused by combustion occurring in passage  30 ′ actuate valve  85 . Throttles  80 ′ and  81  control the amount of air flowing into the engine. Screw on cap  84  covers the compartment  88 , containing helical spring  86 , retainer  87  and the valve stem of valve  85 . The valve stem of valve  85  passes through valve guide  90 .  
         [0035]    Referring now to the drawings in detail, FIGS.  8 - 17  illustrate a two-cycle internal combustion engine constructed in accordance with one embodiment generally referred to by reference number  10 ′. In this embodiment the engine is enclosed by a housing assembly  12 ′, which is formed from three housing sections,  14 ″ and  16 ″ and  18 . Bolts  19 ″ pass through holes  17 ″ near the corners in sections  14 ″ and  16 ″ and thread into threaded holes passing through section  18  thereby bolting the three housing sections securely together. As clearly illustrated in FIG. 8 and FIG. 11 an intake port  20 ″ is formed in the top wall of housing section  14 ″, and a fuel injector  32 ″ projects into intake port  20 ″ through the rear wall of housing section  14 ″ for injecting fuel into port  20 ″. The lower end of intake port  20 ″ connects to two parallel partial cylinders  33 ″ and  34 ″ formed in the bottom of housing section  14 ″ and in the top of housing section  16 ″. They are parallel with the crankshaft and contain hollow gear shafts  46 ″ and  47 ″ (teeth not shown in side section views) which are meshed together as can be more clearly seen in FIG. 11. Gear shafts  46 ″ and  47 ″ have output shafts  42 ″,  43 ″,  44 ″ and  45 ″ extending through holes formed in the outer vertical walls of housing section  14 ″ and  16 ″. The gear shafts  46 ″ and  47 ″ are crankshaft driven, counter rotating in opposite directions drawing intake air through intake port  20 ″ and forcing the intake air into passage  30 ″ from which it passes into cylinder  40 ″. Partial cylinders  33 ″ and  34 ″ are centrally connected at their lower side to outlet passage  30 ″ traversing the length of partial cylinders  33  ″ and  34 ″ within housing section  16 ″ and extending through internal housing wall  15 ″ to cylinder  40 ′ that contains reciprocating part  56 ″. As illustrated in FIG. 8 and FIG. 12 formed within the cylinder  40 ″ is a horizontal generally elongated exhaust port  22 ″ passing through housing section  16 ″ and having flat upper and lower horizontal sides and curved vertical sides. The lower horizontal side of exhaust port  22 ″ is aligned horizontally with upper horizontal surface face  54 ″ of reciprocating part  56 ″ when reciprocating part  56 ″ is positioned at bottom dead center within cylinder  40 ″. As can be more clearly seen in FIG. 8 and FIG. 9 reciprocating part  56 ″ has an upper exterior horizontal surface face  54 ″, a circular exterior curved surface  53 ″ that is tangent with the wall of cylinder  40 ″ and a lower depending section  58 . Lower depending section  58  has a transverse bearing hole  51 ″ formed therein surrounding rod journal  61  of crankshaft  65 ″. The upper section of reciprocating part  56 ″ has a sectioned ball shape having a slightly smaller diameter than the cylinder diameter so it can rotate and slide within cylinder  40 ″ with lower section  58  acting as lever arm that forces the rotation of upper section having curved sides  53 . The reciprocating part  56 ″ and crankshaft  65 ″ are assembled together so the reciprocating part can be one solid part. When crankshaft  65 ″ rotates reciprocating part  56 ″ rotates and the exterior curved surface  53  rotates as it slides up and down the cylinder wall  40  allowing constant contact with the wall of cylinder  40 ″. As can be seen more clearly in FIG. 9, FIG. 10 and FIG. 12 the crankshaft output shafts  63 ″ and  64 ″ pass through holes in housing section  16 ″ and  18  for external power transfer from the crankshaft. Crankshaft output shaft  64  is centrally attached to a drive pulley  75 ″. The power transfer belt  72 ″ circumscribes drive pulley  75 ″ and extends around drive pulley  76 ″, which is attached to the output shaft  45 ″ of gear shaft  47 ″.  
         [0036]    During operation of the engine the crankshaft output shaft  64 ″ rotates the drive pulley  75 ″ transferring power to the drive belt  72 ″ causing drive pulley  76 ″, which is attached to gear shaft output shaft  45 ″, to rotate and turn gear shaft  47 ″. The teeth of gear shaft  47 ″ rotate and force the teeth of gear shaft  46 ″ to move forcing rotation of gear shaft  46 ″. The rotation of the gear shafts  46 ″ and  47 ″, which are closely confined within parallel partial cylinders  33 ″ and  34 ″ moves air received from intake port  20 ″ along the circumference of partial cylinders  33 ″ and  34 ″ and into passage  30 ″ from which it passes into cylinder  40 ″. As crankshaft  65 ″ rotates reciprocating part  56 ″ is pushed by crankshaft rod journal  61 ″ towards internal horizontal housing wall  15 ″, thereby reducing the volume within cylinder  40 ″ and compressing the air held therein between reciprocating part  56 ″ and rotating gear shafts  46 ″ and  47 ″ of the air compressor. When reciprocating part  56 ″ reaches approximately top dead center the fuel injector  32 ″ injects fuel into the incoming air stream within intake port  20 ″ and the fuel flows with the air into the air compressor. The air compressor discharges the fuel and air mixture received from intake port  20 ″ into passage  30 ″ containing the compressed air from the compressor. The high temperature of the compressed air confined within passage  30 ″ ignites the incoming fuel mixture from the compressor. The forces of combustion transfer energy to the teeth of gear shafts  46 ″ and  47 ″ and to the reciprocating part  56 ″ simultaneously causing these parts to accelerate. The acceleration of the gear shafts  46 ″ and  47 ″ transfers power to their output shafts  42 ″,  43 ″,  44 ″ and  45 ″. The acceleration of the reciprocating part transfers energy to the crankshaft  65 ″ thereby transferring power to the output shafts  63  ″and  64 ″ which is combined with the power output of the gear shaft output shaft  45 ″ through power transfer belt  72 ″. As the gear shafts  46 ″ and  47 ″ accelerate they pump more air into the engine for combustion causing greater power to be generated. The fuel injector  32 ″ is timed to turn off before reciprocating part  56 ″ passes below exhaust port  22 ″ so the combustion occurring within cylinder  40 ″ can finish before exhaust gases begin to pass out of the engine. Fresh air from the compressor enters cylinder  40 ″ and scavenges it of exhaust gases while the exhaust port  22 ″ is exposed to the volume of cylinder  40 ″ above the face of reciprocating part  56 ″ and fills that portion of cylinder  40 ″ with fresh air. As reciprocating part  56 ″ moves towards top dead center, air between the gear shafts  46 ″ and  47 ″ and reciprocating part  56 ″ is compressed into passage  30 ″ making the engine ready for another power stroke.  
         [0037]    [0037]FIGS. 13, 14 and  15  illustrate different embodiments of the described invention. FIG. 13 shows an embodiment wherein the fuel is injected into the intake port and ignition means placed in the wall of passage  30 , for ignition of the fuel mix in passage  30 . FIG. 14 shows the embodiment wherein fuel is injected into the passage  30  instead of into the intake port by fuel injector  32 , which is located in the rear wall of passage  30 . In this embodiment is illustrated in FIG. 17, taken through section lines  17 , the two sets of gears to each side of the compressor gears positioned in partial cylinders  33  and  34 . These two gear sets are comprised of gears  90 ,  92 ,  94 , and  96  which are immersed in oil to reduce wear and function as a means to control the rate of wear of the main compressor gears. They can be used to pump cooling oil through the hollow gear shafts and through the oil cooler (not shown) to cool the gear shafts  46  and  47 . Oil control rings