US2221084A - Engine starter - Google Patents

Description

' Nov 12, 1940. w, Fm GERALD 2,221,024

ENGINE STARTER Filed March 30, 1940 Lib/727 191F772 EPr'a/d tents 12,

ENGINE STARTER John w. Flt! Gerald, Milwaukee, Wis, assignor to Briggs & Stratton Corporation, Milwaukee, Win, a corporation of Delaware Application March so, 194a, Serial No. 327,053.v

This invention relates to improvements in engine starters.

Engine starters now in use may be divided into two classes or types, the automatic and the a manual. In the automatic type, the starter pinion is automatically propelled into mesh with the engine ring gear and automatically retracted upon starting of the engine; whereas,'in the manual type, the pinion is moved into mesh with the in engine rinla, gear either through a manually actuated system of levers or by an electromagnet.

Obviously, therefore, the latter type of engine starter is by far the more complicated and costly. However, notwithstanding the additional cost and complexity oi the manual type. the majority of present day automobiles use this type of engine starter. This follows from the fact that the engines are hard starting.

With the automatic type of starter, the pinion is thrown out of mesh with the ring gear at the first impulse or explosion of the engine. If the engine fails to start, the pinion must be re-engaged with the ring gear to again crank the engine; but such re-engagement cannot be effected until after the starting motor armature has come to rest.

The necessity for waiting ,between cranking cycles and the need for repeating the process several times is sumcient inconvenience to dissuade the use of the automatic type of starter except where the engine starts easily.

Another advantage of the manual type of starter over the automatic type is that excessive current drain is avoided. As is well known, the breakaway load which is applied each time the starter operates takes considerably more current than is required to keep the engine turning over in a continuous cranking operation. Hence, by obviating successive and separate starts, the'manual type imposes less load on the battery.

With the manual type of starter, the starting pedal is depressed and held down until the engine starts, for with this type of starter the pinion is moved manually into mesh with the ring gear and can be held in mesh as long as desired. When the engine starts, an overrunning clutch in the connection between the starter shaft and pinion permits the pinion to spin freely.

However, as often happens, this overrunning sequence, the starter armature is spun by the engine at very high speeds. Spinning the armsture shaft in this way loosens the armature windings and very often throws them out radially and ruins the entire motor.

clutch does not function properly and as a conl Thus, it is evident that although the manual type of starter can be held in engagement until the engine starts and in. this respectis advantageone over the automatic typeof starter, it does have objections in addition to itshigher cost and 6 greater complexity.

It is, therefore, an object of this invention to provide an engine starter which combines the advantages of the two presently known types of starters to enableholding the starter in mesh 10 until the engine starts without the possibility of subjecting the armature shaft to dangerously high speeds.

More specifically, it is an object of this invention to provide an engine starter wherein the i5 starter pinion is held in mesh with the engine ring' gear until the pinion reaches a predetermined speed of rotation, at which time it is released for automatic retraction.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, comblnation and arrangement of parts substantially as hereinafter described, and more particularly defined by the appended claims, it being under-' stood that such changes in the precise embo'die ment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates onecomplete example of the physical embodiment of the invention, constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view in side elevation of an engine starter construction in accordance with this invention, parts thereof being broken away and shown in section; a

Figure 2 is a cross sectional view taken through t Figure l on the plane of the line 22;

Figure 3 is a view similar to Figure '2 showing the parts arranged. to hold the pinion in mesh;

Figure 4 is a view similar to Figures 2 and 3, with the parts shown in the positions they occupy at the time the pinion is freed for retraction; and

Figure 5 is a perspective view of the latchelements used to hold the pinion in mesh with the I ring gear.

Referring now particularly to the accompanying drawing, in which like numerals indicate like parts, the numeral 5 designates the ringgear of an engine with which the starter of this invention,

lit

motor and on which the starter mechanism is V mounted as a unit.

ally and axially resilient coupling H of the type forming the subject matter of theJohn W. Fitz Gerald Reissue Patent No. 20,686, issued April 5, 1938, for Engine starter.

A screw threaded connection exists between the actuating or operating member ID and the pinion, which in the present instance consists of an externally threaded extension I! on the operating member and an internally threaded sleeve it to whichthe pinion is fixed.

The direction of screw pitch with relation to the direction of rotation is such that when the starting motor I is connected with the battery, the pinion l is automatically propelled forwardly into mesh with the ring gear 5. This position is defined by a stop It against which the pinion abuts.

when the engine starts and causes the pinion to travel at a speed in excess of that of the starter shaft, the screw threads function to retract 'the pinion out of mesh with the ring gear.

As pointed out hereinbefore, this type of starter is ideal from thestandpoint of simplicity and low cost; but because the pinion is thrown out of mesh with the ring gear substantially immediately upon the initial explosion of the engine,

it has proved disadvantageous for use with the engines that do not start readily.

. To overcome this disadvantage without sacrificing any of the desirable features of the automatic type of starter, the present invention provides speed controlled means for holding the starter .pinion 'in until the engine is fully started. This means consists of cooperating latch'parts or abutments l and it carried by the pinion operating member l0 and the pinion sleeve l3, respectively.

- These latch parts or abutments are so positioned with relation to each other that when the I pinion is propelled forwardly into mesh with the ring gear, the latch parts or abutments engage,

asshownin Figure 3, to prevent retrograde rotation of the pinion and thus preclude retraction of the pinion as long as the latch parts are engaged and effect a direct torque transmitting connection from the pinion sleeve to the flange One of the cooperating latch parts yields or came out of the way during engagement; and to facilitate this camming action, the two abutments have their approaching faces beveled or inclined, as illustrated.

' In the specific embodiment of the invention illustrated, the latch part or abutment i6 is rigidly fixed to the pinion sleeve. l3 and the other being movable; and

enemas yieldingly maintains the abutment It in the path of the abutment l6. This spring is anchored to the inner end of the arm it by a screw ill and has its outer end bifurcated to form two spring fingers 22 which press the block I! against the arm ll. Hence, as the pinion moves out into mesh with the ring gear, the abutments or latch partsare operatively engaged.

When the starter revolves, centrifugal force acting on the block ll and the latch part It tends to throw the same outwardly against the tension of the spring fingers 22. At cranking speed, the centrifugal force is wholly inadequate to move the latch part it out of its operative position so that the starter can be held in" as long as necessary to effect complete starting of the engine.

When the engine begins to operate under its own power and drives the starter pinion at a speed substantially in excess of cranking speed, the centrifugal force overbalances the spring tension and moves the latch part it out of engagement with the latch part It to free the pinion for retraction.

The speed at which centrifugal force overbalances the spring tension may be determined by varying the tension of the spring in any suitable manner, as by an adjusting screw 28 threaded into the am It and bearing down on the arched medial portion of the spring. In this manner, retraction of the pinion may be controlled to occur at any predetermined speed between cranking speed and safe armature speed.

The normal cranking speed of an engine is approximately 100 R. P. 101.; and since the gear ratio between the starter and engine is generally ten to one, the starter motor armature turns over at approximately 1000 R. P. M. during cranking of the engine. No danger of damaging the armature exists at speeds of 10,000 R. P. M. and even 12,000 E. P. M. Hence, there is a relatively wide range within which the speed responsive means may be set to function and release the pinions for retraction.

From the foregoing description taken in connection with the accompanying drawing, it will be readily apparent to those skilled in the art that this invention provides an engine starter which incorporates the advantages of both the automatic and the manual type of star-ten What I claim as my invention is:

1. An engine starter of the type having a motor and wherein the pinion is automatically projected into mesh with an engine gear and is automatically demeshed upon starting of the engine:

the combination of a smooth shaft adapted to be driven by the starting motor; an externally threaded screw freely slidable and rotatable on said shaft; an outwardly extended annular flange on said screw; a resilient driving connection be-.

tween the shaft and the screw including a rubber-like collar encircling the shaft and frictionally engaging said flange; a pinion movable longitudinally and rotatably with respect to said smooth shaft; an internally threaded sleeve on the pinion threaded on the screw so that a speed differential between the screw and pinion propels the pinion longitudinally; cooperating abutments on the flange and the sleeve engageable upon projection of the pinion into mesh with the engine gear to effect a direct torque transmitting connection from the pinion sleeve to said flange which prevents premature retraction of the pinion from the engine gear, one of said abtuments centrifugally responsive means carried by the flange and operable to displace the movable abutment and free the pinion for retraction upon the attainment of a predeflange on said screw; a resilient driving connection between the shaft and the screw including a rubber-like collar encircling the shaft and frictionally engaging said flange; a pinion movable longitudinally and rotatably with respect to said smooth shaft; an internally threaded sleeve on the pinion threaded on the screw so that a speed differential between the screw and pinion propels the pinion longitudinally; an arm fixed to said annular flange and projecting therefrom to overlie the internally threaded pinion sleeve; cooperating abutments on said arm and internally threaded pinion sleeve providing a latch engageable upon projection of the pinion to its operative position to establish a direct torque transmitting connection between the pinion sleeve and flange to prevent relative rotation between the pinion and the screw in the direction effecting retraction of the pinion; and centrifugally responsive means mounted on the arm and operable to disengage said latch and release the pinion for retraction upon the attainment of a predetermined speed of rotation onthe part of the screw.

3.Inanenginestarterofthetypehavinga motor and wherein the pinion is automatically projected into mesh with an engine gear and is automatically demeshed upon starting of the engine: the combination of a smooth shaft adapted. to be driven by the starting motor; an externally threaded screw freely slidable and rotatable on said shaft; an outwardly extended annular flange on said screw; a resilient driving connection between the shaft and the screw including a rubber-like collar encircling the shaft and frictionaiiyengaging said flange; a pinion movable longitudinally and rotatably with respect to said smooth shaft; an internally threaded sleeve on the pinion threaded on the screw so that's speed differential between the screw and pinion propels the pinion longitudinally; an arm on said flange projecting axially toward the pinion said arm being of such length as to at all times overlie the pinion sleeve; a centrifugally responsive weight guided for movement on said arm; a leaf spring connecting the weight with said arm and and arranged to oppose movement of the weight in response-to centrifugal force; and cooperating radially disposed abutments on the weight and pinion sleeve providing a latch engageable to effect a direct torque transmitting connection between the pinion sleeve and said flange which prevents premature retraction of thepinion, said weight and spring being so coordinated that the centrifugal force developed at a predetermined speed of rotation of the sleeve releases the latch to free the pinion for retraction.

JOHN W. FITZ GERALD. 851

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