US2704939A - Engine starter gearing - Google Patents

Description

March 29, 1955 c.- A. MENDENHALL ENGINE STARTER GEARING Filed Jan. 25. 1954 A TTDRNE Y United States Patent ENGINE STARTER GEARING Charles A. Mendenhall, Horseheads, N. Y., assignor to Bendix Aviation Corporation, Elmira Heights, N. Y., a corporation of Delaware Application January 25, 1954, Serial No. 405,692

Claims. (Cl. 74-7) The present invention relates to engine starter gearing and more particularly to a starter drive of the type in which the gearing is automatically engaged and maintained in mesh until the engine has attained a sufficient rotary speed to indicate that it is reliably self operative.

It is an object of the present invention to provide a novel starter drive of the above type which is effective and reliable in operation and readily adapted for installations with a wide variety of requirements.

It is another object to provide such a device in which the sub-assembly which is operative to secure traversal of the drive pinion into mesh has a comparatively large polar moment of inertia relative to its mass, whereby satisfactory cold weather engagement of the drive is promote It is another object to provide such a device in which the parts which remain connected to the engine while the engine is overrunning the drive are comparatively small and light so that problems of vibration and binding are minimized.

It is another object to provide such a device incorporating a centrifugally released latch for holding the gearing in mesh with means including a centrifugal clutch for rotating the element carrying the latch whereby the forces exerted on the latch are controlled, and a time delay is secured which assists in preventing demesh responsive to a false start.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation, partly broken away and in section, of a preferred embodiment of the invention with the parts in normal or idle position;

Fig. 2 is a view similar to Fig. 1 showing the parts in cranking position;

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

Fig. 4 is a section taken substantially on line 4-4 of Fig. l; and

5 is a section taken substantially on line 5--5 of In Fig. 1 of the drawing there is illustrated a power shaft 1 on which a hollow sleeve 2 is fixedly mounted as by means of a cross pin 3. A driving Qverrunning clutch member 4 is slidably journalled on; the sleeve between a shoulder 5 formed on the sleeve and a lock ring 6 seated in a groove in the periphery of the sleeve and contained in a counter-bore 7 in said clutch member.

Clutch member 4 is normally held against the stop ring 6 by the initial compression of a drive spring 8 which yieldably connects said clutch member for rotation with the sleeve 2.

A hollow screw shaft 9 is also slidably journalled on the sleeve 2 and is provided with overrunning clutch teeth 11 which are adapted to cooperate with similar clutch teeth 12 on the driving clutch member 4. A pinion 13 is rotatably mounted on the power shaft 1 and is slidable thereon into and out of mesh with a gear 14 of the engine to be started; and means for actuating the pinion from the screw shaft are provided including a control nut and clutch member 15 threaded on the screw shaft, a driven clutch member 16 having teeth 17 arranged to cooperate with similar teeth 18 on the control nut, and a barrel member 19 rigidly mounted at one end on the pinion as indicated at 21, and coupled rigidly to the driven clutch member 16 at its other end as shown at 22.

The meshing movement of the driven clutch member 16, barrel 19 and pinion 13 is limited by an abutment ring 23 fixed on the end of the sleeve 2, a thrust washer 24 being preferably interposed therebetween. A dished spring washer 25 is interposed between the abutment ring 23 and the thrust washer 24, and serves normally to maintain the teeth 12, 11 of the driving clutch member 4 and screw shaft 9 in engagement.

An outer barrel member 26 is non-rotatably mounted on the control nut 15 and encloses the inner barrel 19. A centrifugally actuated frictional clutch is provided for transmitting torque from the inner barrel 19 to the outer barrel 26 when the inner barrel is rotated above a predetermined speed. For this purpose a band 27 of suitable frictional material such as brake lining is anchored at one end as indicated at 20 (Fig. 4) to the exterior of the inner barrel 19 and is wrapped around the inner barrel in the direction of rotation of the drive. By this arrangement, when the clutch band 27 is moved outward by centrifugal force into contact with the interior of the outer barrel 26, it engages therewith in the manner of a self-energizing clutch, and torque is transmitted thereby to rotate the outer barrel and consequently the control nut 15.

The screw shaft 9 is provided with a peripheral notch 28, and a spring pressed latch 29 (Fig. 3) is mounted in the control nut with freedom for radial sliding movement, in position to enter the notch 28 as the pinion 13 approaches its fully meshed position. The latch thus prevents the control nut from threading itself back to idle position on the screw shaft until the latch is withdrawn by centrifugal force.

The screw shaft is also provided with an inclined shoulder 30, best seen in Fig. 2, adjacent the position of the latch 29 when the parts are in normal or idle position. The latch thus serves as a detent to prevent the pinion from drifting away from idle position. In some installations it has been found desirable to provide a plurality of anti-drift detents as best shown in Fig. 5 where a second detent 31 is shown.

A light coiled compression spring 32 interposed between the control nut and the driven clutch member 22 normally holds the teeth 18, 17 of these members out of engagement.

In operation, starting with parts in the positions illustrated in Fig. 1, rotation of the power shaft 1 by the starting motor, not illustrated, is transmitted through sleeve 2 and drive spring 8 to the driving clutch member 4, and through overrunning clutch teeth 12, 11 to the screw shaft 9. Rotation of the control nut 15 is resisted by the outer barrel member 26 which has a high polar moment of inertia due to its large diameter, so that the control nut is traversed to the right pushing ahead of it the driven clutch member 16 inner barrel 19 and pinion 13. When the pinion is fully meshed with the engine gear 14, the longitudinal movement of the driven clutch member 16 is arrested by the abutment ring 23. The clutch teeth 18, 17 as well as the overrunning clutch teeth 11, 12 are then wedged tightly together by the screwjack action of the screw shaft and control nut, and the pinion 13 is rotated to crank the engine.

When the engine fires, the acceleration of the pinion 13 by the engine gear 14 causes it to overrun and move the control nut 15 back on the screw shaft until arrested by engagement of the latch 29 in the end of the notch 28. This permits the spring 32 to separate the clutch teeth 18, 17 whereby the pinion, inner barrel 19 and driven clutch member 16 are permitted to overrun freely.

If the engine remains self-operative, the inner barrel 19 is rotated at sufiiciently high speed to cause the centrifugal clutch band 27 to move out and engage the interior of the outer barrel 26 and frictionally transmit torque thereto causing the barrel 26, control nut 15 and screw shaft 9 to overrun the driving clutch member 4. When the torque so transmitted is sufiicient to rotate the outer barrel 26 and control nut 15 faster than the critical speed, the latch 29 is withdrawn by centrifugal force, permitting the parts to be returned to idle position.

Although but one form of the invention has been shown and described in detail it will be understood that changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a sleeve fixed thereon, a driving overrunning clutch member slidably journalled thereon, yielding driving means connecting the sleeve and clutch member, a hollow screw shaft slidably journalled on the sleeve having overrunning clutch teeth adapted to cooperate with similar teeth on said clutch member, a pinion rotatably mounted on the power shaft and slidable thereon into and out of mesh with a gear of an engine to be started, and means for actuating the pinion including a control nut and clutch member threaded on the screw shaft, a driven clutch member adapted to cooperate with the control nut, a barrel member connecting said driven clutch member to the pinion, and an abutment ring on the sleeve limiting the meshing movement of the driven clutch member.

2. An engine starter drive as set forth in claim 1 ineluding further an outer barrel member fixedly mounted on the control nut and enclosing the inner barrel and a centrifugal clutch connection between said barrels.

An engine starter drive as set forth in claim 2 in which the centrifugal clutch connection comprises a flexible band anchored at one end on the inner barrel, and bearing frietionally on the interior of the outer barrel when pressed into contact therewith by centrifugal force.

4. An engine starter drive as set forth in claim 1 in which the screw shaft is provided with a peripheral notch, and including further a spring-pressed centrifugally released latch carried by the control nut in position to enter said notch as the pinion approaches its fully meshed position.

5. An engine starter drive as set forth in claim 1 including further a spring normally holding the teeth of the screw shaft in engagement with the teeth of the driving clutch member, and a second spring normally holding the teeth of the driven clutch member out of contact with the teeth of the control nut.

No references cited.

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