US2656727A - Engine starter gearing - Google Patents

Description

Oct. 27, 1953 J. E. BUXTON ETAL 2,656,727

ENGINE STARTER GEARING Filed March 21, 1952 L ssai IN VEN TORS dwnes WITNESS: BY w- ,zsa'an/ Patented Oct. 27, 1953 ENGINE STARTER GEARING James E. Buxton and Frank T. Christian, Elmira, N. Y., assignors to Bendix Aviation Corporation, a corporation of Delaware Application March 21, 1952, Serial No. 277,864

6 Claims.

The present invention relates to engine starter gearing and more particularly to that type of drive in which a driving pinion is traversed into engagement with an engine gear responsive to acceleration of the starting motor.

In drives of this character which are used in extremely cold climates, it has been found that the oongealing of the lubricant for the traversing means retards the longitudinal movement of the pinion so that it may require repeated operation of the motor to secure engagement of the pinion, and sometimes the engagement does not occur until the starting motor has attained a high rotative speed. This is known as a spinning mesh and causes the parts of the drive to be subjected to abnormal stresses when the longitudinal movement of the pinion is arrested.

In the patent to Dunbar, No. 2,536,002, a solution of the cold meshing problem is provided by forming the pinion with a stub shaft extension which bears in a bracket fixed on the motor housing. By this arrangement, solidification of the lubricant in the pinion bearing resists the rotation of the pinion so as to counteract the effect of the stiffening of the lubricant on the threaded traversing means, and satisfactory meshing performance has been secured under very adverse conditions.

It is an object of the present invention to provide an engine starter drive which secures satisfactory cold weather operation in a novel and improved manner.

It is another object to provide such a device in which the pinion is of standard construction, and the armature shaft is supported in the outboard bearing similarly to conventional forms of drives.

It is another object to provide such a device incorporating means for reducing the tendency of the pinion to attempt to remesh with the engine gear after being thrown out of mesh when the engine starts.

It is another object to provide such a device in which the traversing means for the pinion is protected from foreign material such as water or mud which, on congealing, might interfere with the traversal of the pinion.

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, partially broken away and in section of .a preferred embodiment of the invention showing the parts in idle position;

Fig. 2 is a View similar to Fig. 1 showing a modified form of the pinion supporting means, with the parts in cranking position; and

Fig. 3 is a view similar to Fig. 1 illustrating a farther modification of the pinion supporting sleeve.

In Fig. 1 of the drawing there is illustrated a power shaft l on which a hollow sleeve 2 is rigidly mounted as indicated in dotted lines at 3. A screw shaft 4 is slidably journaled on the sleeve 2 and is provided at one end with overrunning clutch teeth 5 which are normally held in engagement with similar teeth 6 on a transmission member I, by means of a spring 8 which bears against a stop ring 9 anchored on the end of the sleeve 2 by means of a lock ring ll. Means for yieldingly driving the transmission member I from the sleeve 2 is provided in the form of a torsion and compression spring [2 which is anchored on the sleeve at one end by an anchor plate I3, and at its other end to the transmission member I by the anchor plate 14. Expansion of the spring I2 is limited by a thrust ring II! which limits longitudinal movement of the transmission member 1 toward the screw shaft. Compression of said spring is limited by a shoulder 20 on the sleeve which provides a thrust bearing for the transmission member I.

A control nut I5 is threaded on the screw shaft 4 and is provided with radial lugs I6 which pass through slots H5 in one end of a barrel member l1, and are retained by a lock ring I6 The other end of the barrel is rigidly connected to a pinion 18 as indicated at 9, whereby longitudinal movement of the control nut I5 is transmitted to the pinion to move it into and out of mesh with a gear 21 on the engine to be started.

A bearing bracket 2| is fixedly mounted on the frame of the starting motor, not illustrated, and has an opening 22 into which the. free end of the power shaft I extends. A sleeve 23 is rigidly mounted in the opening 22 of the bracket so as to provide an outboard bearing for the power shaft which is preferably bushed as shownat 24. Bearing sleeve 23 extends inwardly into engagement with the end of the sleeve 2, at which point it is piloted on the power shaft I as shown at 25. The power shaft is preferably reduced in diameter adjacent the pilot section as shown at 26 in order to reduce friction.

In installations which are exposed to weather conditions, it sometimes happens that water or mud which splashes on the drive will freeze on the screw shaft threads and associated parts so as to resist traversal of the control nut to move the pinion I8 into engagement with the engine gear 21. In order to obviate this difiiculty, the radial lugs It on the control nut are extended beyond the periphery :of the barrel, and a cylindrical shield 28 is mounted on the barrel with a terminal flange 29 pressed against a lock ring 3| by a spring 32 located between the flange and the lugs IE. to provide a step or shoulder 33 overlapping the lock ring 3| and preventing expansion of the lock ring by centrifugal force. Removal of the shield is accomplished by sliding the shield to the left against the compression of spring 32, and then removing the lock ring 3 I.

In the operation of this embodiment of the invention, rotation of the power shaft l by the startin motor is yieldingly transmitted through the spring 12 and overrunning clutch teeth 6, to the screw shaft 4. Rotation of the barrel member [1 and pinion i8 is resisted by the inertia of the parts and also by the bearing friction between the pinion l8 and the stationary sleeve 23 on which it is mounted. The pinion and barrel assembly is thus constrained to move longitudinally and bring the pinion into mesh with the engine gear 21, the meshing movement being limited by the stop ring 9 on sleeve 2 which arrests the travel of the control nut IS. The screw shaft 4 then moves to the left, forcing together the clutch teeth 6, 5 and compressing the spring l2 until the backward movement of the transmission member 1 is stopped by the shoulder on the sleeve 2 after which the screw shaft, barrel, and pinion, rotate in unison to crank the engine. When the engine fires, the acceleration of the pinion, barrel and control nut [5 return the parts to idle position where they are re tained by the anti-drift detent 34.

It is to be particularly noted that if. the traversal of the control nut 15 on the screw shaft 4 is impeded by frozen lubricant, the same condition will be present in the bearing of the pinion l8 on the stationary sleeve 23, and this resistance to rotation will be operative to assist in securing traversal of the pinion into mesh with the engine gear.

In Fig. 2 of the drawing, the structure is substantially the same as that illustrated in Fig. 1, and the parts are similarly numbered. In this case, however, the bearing sleeve 23', instead of being rigidly mounted in the bracket 2|, is swiveled in the bracket, the terminal flange 35 of the sleeve being retained in the bracket by a lock ring 36. By this means the sleeve 23 constitutes a floating bearing member for the pinion I 8 which arrangement reduces the tendency of the pinion to be traversed back into engagement with the engine gear after it is thrown out of mesh when the engine starts. In other respects the operation of this structure is the same as that shown in Fig. 1.

In Fig. 3 of the drawing a further modification of the bearing sleeve structure for the pinion is illustrated. As there shown, the bearing sleeve 23" is fixedly mounted in the bracket 2| similarly to the sleeve 23 in Fig. 1, but sleeve 23" is reduced in diameter adjacent the idle position The flange is offset slightly so as of the pinion I8 as shown at 31, and the pinion is piloted directly on the power shaft as shown at 38 so that a small space 39 separates the pinion from the bearing portion of the sleeve 23".

When commercial forms of starter drive are operated at low temperatures, it rarely happens that the pinion does not move longitudinally at all when the power shaft is operated, but the usual condition is that the pinion moves a short distance each time the starting motor is energized until after three or four such operations, the pinion will engage the engine gear even under very adverse conditions. The sleeve 23" is so dimensioned that even a very slight movement of the pinion longitudinally will cause it to engage the sleeve, whereupon the sleeve becomes operative to assist the traversal of the pinion into mesh the same as in Fig. 1. Since however the sleeve does not engage the pinion when the pinion has been thrown back into idle position, the tendency of the pinion to attempt to remesh after it has been demeshed is reduced.

Although certain embodiments of the invention have been shown and described in detail, it

will be understood that other embodiments are possible and changes may be made in design and arrangement of the parts without departing from the spirit of the invention.

We claim:

1. In an engine starter drive a stationary bearing bracket, a hollow sleeve fixedly mounted at one end in the bracket, a bearing bushing within said end of the sleeve, a power shaft rotatably mounted in the bushing, a drive pinion journaled on said sleeve out of contact with the shaft and longitudinally movable on the sleeve into and out of mesh with a gear of an engine to be started, and means actuated by the power shaft for traversing the pinion into mesh with the engine gear and then rotating the pinion to crank the engine.

2. An engine starter drive as set forth in claim 1 in which the pinion, when in idle position, is supported on the power shaft out of contact with the sleeve.

3. In an engine starter drive, a power shaft, a screw shaft rotatably supported thereby, a yielding driving connection from the power shaft to the screw shaft, a control nut on the screw' shaft, a barrel member mounted at one end on the control unit, means connecting the barrel to the control nut for rotary and longitudinal movement therewith, a pinion fixedly mounted in the other end of the barrel, a fixed support member having an opening receiving the end of the power shaft, a sleeve rigidly mounted in the support member providing a bearing for said end of the power shaft, said pinion being slidably journaled on the sleeve out of contact with the shaft for movement into and out of mesh with a gear on the engine to be started.

4. An engine starter drive as set forth in claim 3 in which the bearing sleeve is piloted on the power shaft adjacent the idle position of the plIll0I1.

5. In an engine starter drive, a power shaft, a screw shaft rotatably supported thereby, a yielding driving connection from the power shaft to the screw shaft, a control nut on the screw shaft, a barrel member mounted at one end on the control nut, means connecting the barrel to the control nut for rotary and longitudinal movement therewith, a pinion fixedly mounted in the other end of the barrel, a fixed support member having an opening receiving the end of the power shaft, a sleeve mounted in the support member providing a bearing for said end of the power shaft, said pinion having a sliding bearing engagement on the sleeve for movement into and out of mesh with a gear on the engine to be started; including further a cylindrical shield fixedly mounted on the barrel member and surrounding the driving connection for the screw shaft.

6. An engine starter drive as set forth in claim 3 in which the power shaft is reduced in diameter so as not to bear on the interior of the sleeve except where it serves as a pilot for the sleeve and where it supports the pinion during the cranking operation, and including further an abutment fixedly mounted on the shaft for arresting the meshing movement of the control nut.

JAMES E. BUXTON. FRANK T. CHRISTIAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,403,022 Fornaca Jan. 10, 1922 1,445,949 Hirsch Feb. 20, 1923 1,778,012 Abell Oct. 14, 1930

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