US2720789A - Engine starter gearing - Google Patents

Description

Oct. 18, 1955 J. J. DIGBY ENGINE STARTER GEARING Filed June 3o, 1953 7 m |.H 9 u Pw .w. .0 m Z m \MM /m \4 Mm www 9 5 Q09 44%? i @o 1,7||H|I 4 /Qu H W /8l1n% ,4% H ,a H 1 H :Pw Hu ...x

1N V EN TOR. 7a/nes j @@,z

A TT ORNE Y WITNESS m. jizz;

United States Patent Oiiice 2,720,789 Patented Oct. 18, 19755 ENGINE STARTER GEARIN G James J. Digby, Elmira, N. Y., assigner to Bendix Aviation Corporation, a corporation of Delaware Application June 30, 1953, Serial No. 364,993

2 Claims. (Cl. 74--7) The present invention relates to engine starter gearing and more particularly to a drive of the automatically engaging and disengaging type incorporating means for holding the gears in engagement until the engine is reliably self-operative.

In devices of this character it is necessary to provide some form of overrunning connection between the drive pinion and the starting motor in order to prevent acceleration of the starting motor to excessive speeds when the engine becomes self-operative, and also to avoid having the starting motor act as a load on the engine during the initial period when the engine cylinders start tiring. Various types of overrunning clutches have been and are employed for this purpose, but it has been found that the type which employs clutch members having interengaging teeth which are wedged together by screw-jack action under load is in many respects the most satisfactory. This type of clutch as previously embodied in drives of this character has, however, been subject to the disadvantage that if the yielding means for closing the clutch is such as to exert a rm pressure on the parts, the clutch is likely to be somewhat noisy while overrunning, and there is a tendency for gradual attrition of the points of the teeth.

It is an object of the present invention to provide a novel device of this type incorporating a dentil overrunning connection between the starting motor and engine gear which is eciently operative over long periods of use.

It is another object to provide such a device incorporating means for reducing noise and wear of the overrunning clutch.

It is another object to provide such a device in which the dentil clutch members are held out of engagement with each other as long as the engine overruns the starting motor above a predetermined speed of rotation.

It is another object of the invention to provide such a device in which the reengagement of the dentil overrunning clutch takes places in a positive manner without clashing or milling of the clutch teeth.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which Fig. l is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in idle or normal position;

Fig. 2 is a similar view showing the parts in cranking position; and

Fig. 3 is a similar view showing the parts in the positions assumed when the engine starts and causes the drive pinion to overrun the starting motor shaft.

In Fig. 1 of the drawing there is illustrated a power shaft 1 which may be the extended armature shaft of a starting motor not illustrated. A sleeve 2 is anchored at one end on the power shaft by suitable means such as illustrated at 3, and has a smooth reduced portion 4 on which a screw shaft 5 is slidably journaled. The screw shaft is provided at one end with clutch teeth 6 (Fig. 3) arranged to cooperate with similar clutch teeth 7 on a driving clutch ring 8 which is also slidably journaled on the reduced portion 4 of the sleeve 2 and confined thereon between a lock ring 9 and a thrust washer 11 seated against a shoulder 12 of the sleeve formed by its reduction in diameter.

An anchor plate 13 is non-rotatably mounted in any suitable manner on the anchored end of the sleeve 2 against a terminal flange 14 thereon, a second anchor plate 15 is similarly mounted on the driving clutch ring 8 against a rib 16 formed thereon, and a drive spring 17 is anchored at its ends in the plates 13, 15 to form a yielding driving connection between the sleeve 2 and the driving clutch ring 8. Spring 17 is normally maintained under a small amount of endwise compression by virtue of the positioning of the clutch ring 8 by the lock ring 9.

A pinion 18 is slidably and rotatably mounted on the power shaft 1 for longitudinal movement into and out of engagement with the gear 19 of the engine to be started. Means for actuating the pinion is provided comprising a control nut 21 threaded on the screw shaft 5 and having peripheral lugs 22 slidably mounted in slots 23 formed in one end of a barrel member 24, the opposite end of which is reduced in diameter as shown at 25 and provided with an inwardly extending ange 26 rigidly secured to the pinion 18 as indicated at 27. The control nut 21 is retained in the barrel 24 by a lock ring 28, and a meshenforcing spring 29, located between the control nut and a shoulder 31 formed in the interior of the barrel by its reduction in diameter, normally holds the control nut seated against the lock ring 23.

The meshing position of the pinion 18 is defined by means of an abutment ring 32 which is conned on the end of the sleeve 2 by means of a lock ring 33, in position to arrest the travel of the control nut 21 when the pinion is fully meshed with the engine gear 19. A thrust washer 34 is interposed between the control nut and abutment ring, and a light compression spring 35 is located between the thrust washer 34 and the abutment ring, which spring is effective to yieldingly press the clutch teeth 6 of the screw shaft into engagement with the teeth 7 on the clutch ring 8. Abutment ring 32 is preferably provided with a recess 36 in its surface for the reception of the spring 35 when the parts are pressed together during the cranking operation as shown in Fig. 2.

A spring-pressed centrifugally-released detent and latch member 37 is mounted in a radial aperture 38 in the control nut 21 in position to engage and bear on the screw shaft 5. The screw shaft is formed with an inclined shoulder 39 which cooperates with the detent 37 to yieldingly resist meshing movement of the pinion and thus perform the function of preventing the pinion from drifting away from idle position while the engine is running. The screw shaft is also provided with a recess 41 in position to receive the latch 37 as the control nut approaches the end of its meshing movement. The shoulder 42 of the recess 41 cooperates with the latch to prevent demeshing movement of the control nut until the rotational speed of the control nut and its associated parts is sufficiently high to withdraw the latch from the recess by centrifugal force.

Centrifugally operated means are provided for holding the clutch teeth 6, 7 out of engagement during the overrunning of the clutch above a predetermined speed. As here shown this means comprises an annular disc 43 seated on the driving clutch ring 8 against the rib 16, a dished collar 44 anchored on the adjacent end of the screw shaft 5 as by means of lugs 45 which traverse conforming slots in a rib 49 formed on the screw shaft and enter a groove 46 in the surface of the screw shaft.

A plurality of balls 47 are located betwe'en the disc and collar, arranged to wedge them apart under the inuence Vof centrifugal force by engagement with an inclined por tion 48 of the collar 44. In order to ensure rotation of the balls with the collar, the latterpis preferably provided V with recesses 50- in which the balls are conned.

the power shaft causes the screw shaft V- toghe movedf to the left, compressing the VVdrive spring, I7A until' the clutch ring 8 is arrested by the thrust washer 11. lThereafterl the lclutch teeth 6, 7 are tightly compressed by the screw-jack action ofthe screw shaft 5' and control nut 21, and torque'i's transmitted to the pinion 18 to crank f the engine.

When Ythe engine res, the Ypinion 1S is accelerated faster than the rotative speed of the starting motor where- Vby4 the control nut 21 is moved back on the screw shaft until the latch member 37 engagesl against the shoulderV 42 of the screw shaft. Further backward movement of the control nut and associated -parts is thereby prevented, and the screw shaft is caused4 to overrun the clutch ring 8- as illustrated in Fig 3. The rapidV rotation of the screw shaft causes the balls 47I to move out and wedge the clutch teeth 6, 7 apart against the actiony of the clutch spring 35,. so that the overrunning action takes place quietly and without wear on the clutch teeth. If the engine should not remain self-operative, the consequent slowing down of the screw shaft permits' the spring 35 to become effective to reengage the clutch teeth 6, 7` and cranking is resumed.

When the engine runs evenly, the speed of the pinion and barrel assembly'is such as to cause withdrawal of the latch member 37 by centrifugal force, whereupon the parts are permitted to return to idle position where they are yieldably maintained by the detent action of the latch member 37 in cooperation with the shoulder 39 onrthe screw shaft. V

If, during the meshing action, toothy abutment should occur between the pinion and engine gear, the meshing movement of the pinion is momentarily arrested while torque is built up during continued movement of the control nut 21 as yieldingly permitted by thel mesh-en# forcing spring 29. When such torque has built up sutli-V cent'ly to index the pinion teeth into proper registry with the tooth spaces of the engine gear, the spring 29 snaps the pinion into initial mesh whereupon meshing and cranking continues'as usual. Y

Although but one form of the invention has been shown and described in detail, it will be understood that modications in the details and arrangements of the structure may be made without departing from the spirit of the invention. t

I claim:

l. In an engine starter drive a power shaft, Aa sleeve fixed thereon, a screw shaft slidably' journaled on the sleeve having overrunning clutch teeth on-one end and a peripheral latching recess adjacent thereto, a driving ring having cooperating clutch teeth journaled on the sleeve with freedom for limited longitudinal movement, yielding driving means for rotating the drivingring from the sleeve, a pinion slidably journaled on the power shaft for movement into and out of meshr with an enginegear,V a barrelmember fixed to the pinion, a control 'nut' threaded on the screw shaft having a splined connection with the barrel with freedom for limited relative longitudinal movement, a stop on the sleeve for arresting ,the control nut when the pinion is in mesh with the engine gear, a centri-fugally released latch in the control nut engageable with said recess on the screw shaft forprevent ing the return ofthe control nut to idle position, spring means normally holding Vthe screw shaft andl the driving clutch ring in engagement, and centrifugally-actua'ted means for holding the clutch teeth of the screw shafty and clutch ring apartras long as the screw shaft is rotating above a predetermined speed.

2.A An engine starter drive as set forthinA claim 1V inl which said means for holding the overrunning clutch teeth apart comprises anannular disc on the' driving clutch ring, a dishedcollar on the screw shaft adjacent.

thereto, and afplurality of balls located between the disc andl collar and arranged to wedge them apart responsive to centrifugal force. V

References Cited in the file of this patent Y Miller .V .V... Ian. 6, 1953iA

Images