Positive gear engagement mechanism
BACKGROUND OF THE INVENTION 
     This invention relates generally to starters for engines and the like and more particularly to pneumatically driven starters having an output on a pinion gear which engages an engine flywheel or the like. The invention further relates to so-called &#34;soft&#34; engaging starters including a prestart engaging cycle followed by a full powered start. 
     In a number of prior art starters the pinion shaft carrying the pinion was extended by several means. Three of these include pneumatically pre-engaged, inertia driven, and electrically pre-engaged. A pneumatically pre-engaged pinion requires extra hoses to shuttle air to a piston. An inertia driven system requires elaborate helical splines. An electric starting system requires a solenoid for engagement, which may be bulky in size, and costly. In addition, either timed or signal operated air solenoids were utilized to accomplish the pre-engagement or soft engagement function. 
     The foregoing illustrates limitations known to exist in present pneumatic and electric starters. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, this is accomplished by providing a positive gear engagement mechanism comprising an elongate casing, an elongate liner mounted for reciprocation within the casing, a motor mounted within the liner having its rotary output transmitted to a pinion for selective engagement with a gear means for rotating the engine, and means for supplying motive media to the motor at a reduced rate in one selected position of the liner and for transporting the liner to a second operating position whereby the pinion engages the gear and the motor receives motive media at an increased rate. 
     The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a sectional view of the generally cylindrical form starter according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a positive gear engagement mechanism 1 according to the present invention is generally cylindrical in form having a hollow cylindrical outer housing 2. An inner housing or liner 3 is disposed within the outer housing 2 for longitudinal reciprocation therein. The inner housing or liner 3 has contained within its hollow center a motor 5 and a transmission 6 which in turn drives a drive pinion shaft 25 which extends from the liner 3 through a housing cover 26 which closes one end of the housing 2. The shaft 25 has mounted on its exposed outside end a drive pinion 35 which is retained on the drive shaft 25 by means of a drive pinion screw 28. 
     By way of further explanation in the form of a preferred embodiment, a pneumatically operated engine starting motor of the radial inward flow type is utilized to power the starter. The air turbine motor 5 is comprised of a front deflector 10 and a rear deflector 11 generally forming the ends of a housing which along with the liner 3 contain the front stator 8 and the rear stator 9. 
     A rotor 7 is mounted for rotation in front and rear shaft bearings 14a and 14b, respectively. The bearings are positioned in the front stator 10 and rear stator 11. Suitable rotor shaft seals 12a and 12b are provided to prevent loss of pressure fluid between the rotor bearing spacers 13a and 13b and the stators 8 and 9. The rotor 7, bearing spacers 13a and 13b, rotor shaft seals 12a and 12d, and shaft bearings 14a and 14b are assembled on the rotor shaft and maintained thereon by means of a rotor lock nut 16. Proper compression between the seal components is maintained by a wavy washer 17 interspaced between the rear shaft bearing 14b and the rear rotor bearing spacer 13b. 
     It should be appreciated by one skilled in the art that air entering the motor through nozzle 44 is expanded through the stator blades 47 against the rotor blades 57 to impart rotation to the rotor and power to drive the starter. 
     The gear reducer shown is of the conventional idler gear form having its output on a ring gear 18 which is mounted for rotation within the liner 3 by means of a bearing 19. The rotary output of the ring gear is imparted to the shaft 25 through a one way clutch 20 which permits drive in the starting rotation direction only and permits overrun of the drive shaft 25 once the engine has started without overspeed of the remainder of the starter components. 
     The shaft 25 is retained in the one way clutch 20 and ring gear 18 by means of retainers 17a and 17b. A shaft seal 21 prevents foreign matter from entering the gear reducing cavity and retains lubricant therein. A return spring 4 is provided to translate the liner 3 and its contained components to the rear of the starter housing 2. 
     The drive shaft 25 is positioned within the housing cover 26 by means of a drive shaft bearing 31. The housing cover 26 is secured to the housing 2 by means of cap screws 27. A drive housing seal 29 is provided to prevent foreign matter from entering the starter cavity. 
     The starter is further mounted to an engine to be started by means of a flange 30 which positions the starter to engage the drive pinion gear with a mating gear on the engine when the pinion shaft 25 is extended from the housing. 
     The housing 2 is provided with a pneumatic fluid or air inlet 40. A passageway 42 transmits the pressure fluid to a chamber 43 formed at the rear end of the starter between the rear deflector 11 and back plate 33. Back plate 33 is secured to the housing 2 by means of cap screws 49. 
     It may now be appreciated by one skilled in the art that once pressure fluid is applied to the starter the chamber 43 will become pressurized and will translate the liner 3 towards the front end of the starter against the force of return spring 4 carrying with it the motor 5, gear reducer 6, and shaft 25. 
     During the initial movement a limited amount of pressure fluid is permitted through restricted passage 45 to enter liner inlet port 51 and circumferential distribution passage 46 which communicates with the nozzles 44. Air passing through the nozzles 44 is expanded through the stator blades 47 and the rotor blades 57 to impart rotation to the rotor 7 as previously described. 
     Expanded pressure fluid exits the motor by means of exhaust ports 52a and 52b in the liner 3 and corresponding exhaust holes 41a and 41b. 
     In addition to the restricted inlet air flow afforded by the restricted passageway 45, it should be appreciated that on initial operation the rear port 52b is blocked by the housing 2 thereby permitting only flow through the forward port 52a. This effectively halves the power available until the liner 3 has been translated to the forward position (i.e., to the right as viewed from the right side of the FIG. 1). This permits the drive pinion 35 to encase the flywheel or similar gear of an engine to be started before full power is applied to the starter. 
     Upon reaching the fully engaged position the inlet port 51 is in register with the inlet 40 and the exhaust ports 52a and 52b are in register with the exhaust holes 41a and 41b thereby permitting full flow of pressure fluid through the starter motor and obtaining its full output power during the starting cycle. 
     Once the engine has started the pressure fluid is removed from inlet 40. Chamber 43 is exhausted rearward through passage 42 and through the motor 5 thereby reducing the pressure in chamber 43 and permitting the return spring 4 to translate the liner to the rear position wherein the cycle is completed. 
     It should further be appreciated that once the engine has started the one way clutch 20 permits overrunning of the drive pinion without damage until such time as the return spring withdraws the drive pinion 35 from engagement with the engine.