Engine starter and accessory drive apparatus
FIELD OF THE INVENTION 
     This invention relates generally to starters and particularly to starters arranged to start an engine and having coupled thereto an accessory driven by the engine when the engine reaches its operating speed. 
     DESCRIPTION OF THE PRIOR ART 
     Engines are started by rotational power provided by starters. It is common practice to arrange the engine to drive accessories such as generators or the like coupled to the starter, upon the engine reaching its operating speed. Prior to the present invention separate means such as a gear system disposed between the starter and the accessory had to be used for the purposes intended. This resulted in the obvious disadvantages of a more complex and larger system than desirable, as for aircraft applications or the like. The present invention utilizes particular elements of the starter gearing to drive the accessory and hence obviates the aforenoted disadvantages. 
     SUMMARY OF THE INVENTION 
     This invention contemplates engine starter and accessory drive apparatus including first and second stage gear systems. A one-way drive, overrunning clutch is disposed between the output gear of the first stage and the input gear of the second stage. The arrangement is such that when power is developed at the input gear of the first stage the clutch drives the input gear of the second stage which causes an output drive member coupled to the engine to start the engine. When the engine reaches its operating speed the power input to the first stage decays. However, the engine continues to drive the output drive member and the second gear stage which in turn drives an accessory shaft. Hence, the second gear stage of the starter is active in starting the engine and driving the accessory shaft. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The single FIGURE in the drawing is a half-section schematic showing the significant elements of the invention. The Drawing does not show conventional elements such as bearings, seals and the like which are typically employed in arrangements of the type described and which are well known to those skilled in the art. 
    
    
     DESCRIPTION OF THE INVENTION 
     The device herein disclosed includes a first stage planetary gear system designated generally by the numeral 2 and a second stage planetary gear system designated generally by the numeral 3. 
     Each of the planetary gear systems 2 and 3 include pinion gears 8 and 9, respectively; planetary gears 10 and 11, respectively; and ring gears 14 and 15, respectively. 
     Between first stage ring gear 14 and second stage input pinion 9 is interposed a one-way drive, overrunning clutch 16. Clutch 16 is suitably mounted between inner and outer races 18 and 20, respectively. Inner race 18 is integral with an axially extending arm member 13 of ring gear 14, while outer race 20 is integral with an axially extending arm member 17 of an accessory shaft 6. Second stage input gear 9 is integral with outer race 20. Studs 22 and 24 are suitably mounted to a housing or the like 26 and rotatably support planetary gears 10 and 11, respectively, by bearings or the like (not shown). 
     A starter which may be used with the arrangement herein disclosed may be of the air turbine type designated generally by the numeral 28 and including a turbine wheel 29 having a plurality of blades 30, one of which is shown in the drawing. In operation, air flows through blades 30 developing driving power at pinion 8 of first stage planetary gear system 2. Pinion 8 drives planetary gear 10 which meshes with ring gear 14 and provides a reduction in speed and an increase in torque, relative to that of turbine wheel 29 of air turbine starter 28, at inner race 18 of clutch 16. 
     In this situation, clutch 16 is in contact with inner race 18 and outer race 20, thereby driving pinion gear 9 of second stage planetary gear system 3 and accessory shaft 6. In this connection it is noted that accessory shaft 6 may be coupled through a coupling means 32, which may be a gear arrangement or the like, to an accessory 33 such as a generator which is driven by an engine 35 as will be hereinafter described. 
     Second stage planetary gear 11 is caused to rotate by pinon gear 9 and, in turn, meshes with ring gear 15 causing an engine output drive coupling 34, which may likewise be a gear arrangement or the like, coupled to engine 35 to drive the engine. 
     When engine 35 reaches its operating speed and the aforenoted starting cycle terminates, air to turbine 28 is cut off and turbine wheel 29 begins to decelerate to rest. As this occurs, the power input to first stage planetary gear system 2 decays with the deceleration of the turbine. However, the engine, at its operating speed, drives second stage planetary gear system 3 through coupling 34 and planetary gear 11 which, in turn, drives second stage pinion gear 9. In this mode, overrunning clutch 16 rotates with outer race 20 and disengages inner race 18, thereby disconnecting planetary gear systems 2 and 3. The gear systems are not reconnected until the entire system is at rest, i.e., the engine is shut down. 
     As a result of the engine driving through the second stage planetary gear system as aforenoted, the speed of accessory shaft 6 is increased by the ratio of the second stage gearing. This ratio is selected to provide the desired speed increase at accessory output coupling 32 relative to engine drive coupling 34 driven by the engine. The gear ratio of first stage planetary system 2 is selected in combination with that of second stage planetary gear system 3 to provide the desired ratio between the speed of turbine wheel 29 and engine drive coupling 34. 
     It will now be seen that the second stage gearing of the starter is active during engine starting as well as during accessory driving, which occurs after the engine is at operating speed. This is a distinct improvement over prior art systems wherein, for example, an additional gear system was typically employed between the starter and the accessory driven by shaft 6, as will be understood by those skilled in the art. 
     The invention thus features imposing an overrunning clutch between the first stage gearing to the starter and the second stage gearing to the starter, utilizing the second stage gearing to achieve the desired speed increase between the accessory and the engine input drives.