US2428750A - Engine starter - Google Patents

Description

Oct. 7, 1947.

J. E. BUXTON ENGINE STARTER Filed Dec. 21, 1945 WITNESS Patented Oct. 7, 1947 ENGINE STARTER James E. Buxton, Elmira, N. Y., assignor to Bendix Aviation Corporation, Elmira Heights, N. Y., a corporation of Delaware Application December 21, 1945, Serial No. 636,373

Claims.

The present; invention relates to an engine starter and more particularly to that type of starter in which the mechanism remains operatively connected to the engine to be started until said engine is properly self-operative.

It is an object of the present invention to provide a novel engine starter of the above type which is simple and economical in construction and easy to assemble.

It is a further object to provide such a device in which the friction between the actuating and. control members for the engine driving member is increased through the action of centrifugal force to resist the disengaging movement of the engine driving member when momentary or isolated impulses are received from the engine during cranking.

It is a further object to provide such a device in which a ring of material having a high coeflicient of friction is placed between the actuating and control members in position to engage and frictionally clutch said members together when the control member is misaligned by centrifugal force.

It is a further object to provide such a device wherein the control member is provided with means for cocking or moving it out of alignment on the actuating member responsive to centrifugal force to thereby cause the control member to bind frictionally on the actuating member.

- Further objects and advantages will be apparent to those skilled in the art from the following description and accompanying drawing, in which:

Fig. 1 is a side elevation partly in section of a preferred form of the present invention shown inidle position;

Fig. 2 is a view similar to Fig. 1 showing the starter drive in overrunning position;

Fig. 3 is a detail view in perspective of the actuating member of the starter, with the anti-drift means partly broken away;

Fig. 4 is a side elevation partly in section of a form of the actuating member embodying a friction ring; and

Fig. 5 is a perspective view of the casing and clutch housing members showing the method of assembly.

In Fig. 1 of the drawing, there is illustrated a power shaft l, which may be the armature shaft of an electric motor, not shown, having a smooth reduced extension l providing a stop shoulder 2 against which thrust washers 2' are seated. An actuating member in the form of a screw shaft 3 is fixed thereon in any suitable manner as by means of the drive pin 4 extending through the power shaft, and retained therein by suitable means such as a set screw 4'. A control member in the form of a nut 5 is threaded on the screw shaft 3. An engine driving member in the form of a pinion 6 is slidably journalled on the reduced portion 1' of the power shaft I in position to engage and rotate an engine member such as a gear I when the pinion is pressed into cranking position against stop shoulder 2. A yielding driving connection between the control nut and pinion is provided comprising a yielding member in the form of a sleeve 8 of elastically deformable material such as rubber seated on the control nut 5 against a flange 9, and a normally engaged 'overrunning clutch comprising a driving clutch plate I! having saw-tooth dentals l2 and a driven clutch plate l3 having similar dentals l4. Driving plate II is demountably attached to a barrel or casing member l5 by means of inte ral lugs l6 fitted within longitudinal slotsl'! in the barrel and held therein by a combination lock member and clutch housing member l8. The driven plate I3 is fixed in any suitable manner such as welding at H] to the pinion 6 and is held in contact with the driving plate H by a spring 21 seated at one end against a shoulder 22 on the periphery of plate l 3 and bearing at the other end against the radial flange 23 of clutch housing l8. The rear of barrel I5 is formed with an inwardly extending rib 24 against which the flange 9 of the control nut 5 rests with a slight pressure imparted thereto by the initial compression of rubber sleeve 8.

According to the present invention, means are provided for inclining or misaligning the control nut 5 on the screw shaft 3 responsive to centrifugal force so as to cause the control nut to bind frictionally on the screw shaft and thereby resist traversal thereon when the parts are rotating at high speed. For this purpose, suitable clearance is provided between the threads 21 and 28 on the nut and screw shaft respectively, the nut is counterbored at its rear end as shown at 25, and an eccentric mass 26 is formed thereon. The thread clearance is so chosen in conjunction with the l-engthof the threads 21 as to permit substantial misalignment of the parts so as to cause a progressive increase in the inter-thread friction as the .rotative speed of the control nut 5 increases at the moment when the engine fires.

Anti-drift means for the pinion 6 while in idle position are provided in the form of a pin 29 held within a radial hole 30 in the eccentric portion .26 of control nut 5. The anti-drift pin 29 is pressed intoa recess 3| in the screw shaft 3 by a spring 32, the upper end of said spring being seated against a ring 33 which is pressed on the control nut in position to cover the hole 30 and is provided with an opening 34 forming a guide for the pin 29. The location of the anti-drift pin in the eccentric portion of nut 5 causes the pressur of the pin on the screw shaft to assist the action of the eccentric mass in causing the cocking action of the nut on the screw shaft.

In the operation of this embodiment of the invention, rotation of the power shaft I and screw shaft 3 causes the control nut 5 and its associated parts to traverse to the right in Fig. 1 pushing the pinion 6 into mesh with the engine gear 1 and upon contact of the pinion against thrust washers 2' to close the clutch II, I3. Further traversal of the control nut -5 compresses the rubber s1eeve8 until sufficient torque is transmitted to the engine gear 1 to cause it to rotate and crank the engine.

When th engine fires, the sudden acceleration of the engine gear is multiplied by the gear ratio of the gear and pinion and transmittedthrough the closed clutch I I, I3 to the control nut 5, causing it to overrun and move backward on the screw shaft 3 thus relaxing the rubber sleeve 8 and allowing the clutch II, I3 to overrun. The high speed of rotation of the control nut at this time causes the eccentric mass 26 thereon to cock the nut on the screw shaft thus causing the nut to bind and resist traversal back to idle position in a manner similar to the action of the pinion 6 on its screw shaft 4 as shown and described in the patentto Bendix, 1,274,369. The screw 3 while in idle position. The operation of this form of the invention is similar to that of the first embodiment except that when centrifugal.

force produces misalignment of the nut 5', on the shaft 3, the ring 35 is caused to engage and bind frictionally on the tops of the threads of the screwshaft. The ring 35 is preferably formed of a material such as rubber, fiber or plastic having a highcoefficient of friction-whereby the frictional-connection thus established between nut '5' and shaft 3 is effective in retarding relative motion therebetween. 1

Although certain embodiments of the invention have-been shown and described in detail, it will 7 be understood that other embodiments are possible and changes may be made in the formand arrangement of the parts without departing from the spirit of the invention as definedin the claims appended hereto.

shaft is also rapidly accelerated by the release 7 of, the cranking load, whereby the nut remains clutched to the screw shaft by the cocking action of the eccentric mass as long as the operator maintains the starting switch'closed, and the pinion is consequently held in mesh with the engine gear.

If the engine should fail to continue. self-operative, the engine gear slows down, retardingthe pinion 6 and its clutch member I3. When the latter slows down to the speed of they clutch member II, the saw-tooth dentals of the. clutch members engage under the action of the spring 2!, whereby the nut 5 is also retarded and'consequently traversed by the screw shaft to the right in Fig. '1, and cranking is resumed. The engine is thus cranked continuously until it is reliably self-operative. When the engine is properly functioning, the operator deenergizes the starting motor whereupon the armature shaft I and screw shaft 3 come to rest. Th control nut simultaneously slows: down until the cocking effect of the eccentric mass 26 is reduced to the point where the torque transmitted from the pinion through the overrunning clutch II, I3 is sufficient to move the nut back to idle position,

thus drawing the pinion out of mesh'with the engine gear. Thereafter the parts are yieldably maintained in idle position by the engagement of anti-drift pin 29 in recess 3I in the screw shaft.

In Fig. 4 of the drawing, a second embodiment of the present invention is shown in Which-the inter-thread friction between the control nut'5" and screw shaft 3 is either augmented or. supplanted by a friction ring 35having a high coeflicient of friction interposed between said nut and shaft. The ring 35 may have any suitable location between the nut 5 and shaft 3'but is preferably pressed'into the bore at the forward end of the control nut'and held therein in' any desired manner as by friction. The inner diameterv of the ring 35 i -radially spaced from shaft What is claimed is: 1. In an engine starter, the combination of a power shaft, an actuating member fixed thereon,

a control member having an inclined connection to said actuating member, said connection having means for permitting relative misalignment between said members, an engine driving member Slidably journalled on said power shaft for engagement with and rotation of a member of an engine to be started, means for driving said en-- 2. In an engine starter, the combination oil-a power shaft, a screw shaft fixed thereon, a control nut having a female threadfor a portion of its length mounted onsaid screw shaft with sufficient clearance to permit relative inclination of the respective aXes of rotation thereof, an engine driving member slidably journalled on'said'power shaft for movement into and out of drivingengagement with a member of an engine to be started, means for traversing and rotating said engine driving member from said control nut,

said means including an overrunning clutch; and

means on said'control nut responsive to centrif ugal force for inclining'said nut on said shaft and thereby increasing the friction therebetween :to-resist disengagement of said engine driving member from the engine member.

V 3. In an engine starter, the combination of a power shaft, a screw shaft fixed thereon, a control nut loosely threaded on said screw shaft and provided with a counterbore for a substantial part of its length to permit said nutto' tilt out of the axis'of rotation of said shaft, an engine driv ing member slidably journalled; onsaid power shaft for engagement withla'nd rotation of a member of an engine to 'bestarted,;means' including a clutch for driving, said enginge driving member from said control nut, and means includment of the nut'thereon' to thereby cause the nut to" bind ,frictionaily on the screwshaft','means on said control nut including an anti-drift member acting on said screw shaft for producing said misalignment, a pinion slidably journalled on said motor shaft for movement into mesh with and rotation of an engine gear, and means including an overrunning clutch and a yieldable member for driving said pinion from said control nut.

5. In an engine starter, the combination of a power shaft, a screw shaft fixed thereon, a control nut having a substantial counterbore at its rear end and loosely threaded on said screw shaft to permit relative inclination thereon, a, pinion slidably journalled on said power shaft for engagement with and rotation of an engine gear, means including an overrunning clutch for driving the pinion from the control nut, a member having a, high coefiicient of friction located between said nut and screw shaft in position to establish a, frictional connection therebetween when the nut is inclined on the screw shaft, and a centrifugally responsive mass on said control nut for causing inclination of the nut responsive to high speed rotation thereof.

JAMES E. BUXTON.

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