US3395687A - Automatic starter for small engines - Google Patents

Description

Aug 6, 1968 J. R. HARKNEss 3,395,687

AUTOMATIC STARTER FOR SMALL ENGINES Filed March 20, 1967 5 Sheets-Sheet l Aug- 6, 1968 R. HARKNEss 3,395;687

AUTOMATIC STARTER FOR SMALL ENGINES Filed March 20, 1967 5 Sheets-Sheet 2 Aug 6, 1968 J. R. HARKNESS 3,395,687

AUTOMATIC STARTER FOR SMALL ENGINES Filed March 20, 1967 5 Sheets-Sheerl 5 ZZ /7 g zo @www Jug/vll 'Zirlmpis M ug- 6, 1968 J. R. HARKNi-:ss 3,395,687

AUTOMATIC STARTER FOB SMALL ENGINES Filed March 20, 1967 5 Sheets-Sheet 4 Aug 6, 1968 1. R. HARKNEss 3,395,687

AUTOMATIC STARTER FOR SMALL ENGINES Filed March 20, 1967 5 Sheets-Sheet 5 United States Patent O 3,395,687 AUTOMATIC STARTER FOR SMALL ENGINES Joseph R. Harkness, Germantown, Wis., assignor to Briggs & Stratton Corporation, Milwaukee, Wis., a corporation of Wisconsin Filed Mar. 20, 1967, Ser. No. 624,337 Claims. (Cl. 123-179) ABSTRACT OF DISCLOSURE The spring of a spring motor starter is wound by a small, low powered electric motor (rotating or reciprocating), driving through a high ratio transmission. A cyclically moving actuator, driven by the electric motor in synchronism with spring winding, automatically opens the motor energizing circuit when the spring is wound and concurrently releases the engine crankshaft for spring propelled cranking.

This invention relates to starting app-aratus for small internal combustion engines such as are used on power lawn mowers, snow blowers, garden tractors and similar equipment; and the invention has more particular reference to a fully automatic electric starter for such an engine that incorporates a very small, low powered electric motor.

The small engines with which this invention is concerned have provided a very versatile and dependable power source for Various implements and machines that make it possible and convenient for a person to perform many tasks that are beyond the normal limits of human strength and endurance. As such engines have lbeen sold in increasing numbers, implements powered by them are being used to an ever greater extent by men whose occupations do not accustom them to great exertion, by women, and even by older childrenf As a result, there is an insistent demand for an automatic starter for such engines, so that the tasksy performed with them can be accomplished with a minimum of muscular effort.

Although the price ofsuch engines has become so low (thanks to volume production economies) that purchasers are willing and able to pay some premium for the benefits of automatic starting, it goes without saying that low cost is still an extremely important desideratum in any automatic starter mechanism.

However, low cost is not the only consideration. The machines powered by engines of the type here under consideration are of such nature as to make sturdiness, simplicity and compactness essential features in any starter. In particular, an electric starter should preferably be powered by a small, compact and lightweight motor and should be adapted for energization from a very small battery. These requirements are incompatible with the heretofore conventional starter mechanisms, wherein an electric starting motor was arranged for directly driving the engine crankshaft during starting. To crankthe engine fast enough to start it, such a mechanism had to have a relatively heavy and powerful motor, energized from a substantially large battery.

The general object of this invention is to provide a fully automatic starter for internal combustion engines of the character described, powered lby an electric motor so small and so Ilow powered as to be normally incapable of turning over an engine at the required speed for starting if coupled to its crankshaft in the heretofore conventional direct driving relationship.

It follows that it is also an object of this invention to provide an automatic starter f-or engines of the character described that can be powered from a small, low-voltage battery of low ampere-hour rating.

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A further object of this invention is to provide an engine starter that is fully automatic, so that an operator need only press a button to etfect engine startingy while the mechanism automatically effects de-energization of the starting motor at the proper time.

It is also an object of this invention to provide a fully automatic starter mechanism of the character described which incorporates readily available :heretofore conventional starting mechanism already present o-n many engines, and which thus lends itself well both to retrofitting and to production with existing facilities.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined :by the appended claims, it lbeing understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of physical embodiments of the invention, constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a view in top elevation, with portions cut away, of a vertical crankshaft engine equipped with a starter mechanism embodying the principles of this invention.

FIGURE 2 is a sectional view taken on the plane of the line 2-2 in FIGURE 1;

FIGURE 3 is a sectional view taken on the plane of the line 3 3 in FIGURE 2;

FIGURE 4 is a fragmentary perspective view looking obliquely upwardly at a portion of the starter mechanism shown in FIGURES 1 through 3;

FIGURE 5 is a view generally similar to FIGURE l but illustrating a modified embodiment of the invention;

FIGURE 6 is a View in side elevation, with portions broken away, of the embodiment of the invention shown in FIGURE 5; A

FIGURE 7 is a view generally similar to FIGURE 1 but showing another modied embodiment of the invention;

FIGURE 8 is a fragmentary view in side elevation, with portions broken away, of the embodiment of the invention illustrated in FIGURE 7;

FIGURE 9 is a view generally similar to FIGURE 1 but showing `still another modied embodiment of the invention; and

FIGURE 10 is a wiring diagram of the electrical circuit foi the starting mechanism illustrated in FIGURE 9.

Referring now to the accompanying drawings, the numeral 5 designates generally a single cylinder internal combustion engine of the type commonly used on power lawn mowers, having a vertical crankshaft 6 projecting upwardly above a shroud or housing 7 that embraces the body (not shown) of the engine to guide the iiow of cooling air over its crankcase and cylinder portions. The starting mechanism of this invention, designated generally by 8, is mounted on the shroud, over the upper end portion of the crankshaft 6.

The starting mechanism 8 comprises a spring motor 10, which can be very similar in construction to the spring motor starters disclosed in Coughlin et al. Patent No. 2,999,489, Svendsen Patents Nos. 3,040,853 and 3,165,- 100, and Harkness -Patent No. 3,270,732, except that it needs no manual crank for winding up its spiral spring 12. Instead, energy is stored in the spring 12 by means of a small, low-power electric motor 13, operating through a suitable driving transmission 14 which provides a high mechanical advantage for the electric motor whereby its high-speed, low-torque output is translated into low-speed, high-torque winding of the spring.

In addition to the spring powered starting motor 10 and theelectric winding motor 13, the starting mechanism 8 comprises a switch 16 connected in an energizing circuit for the electric motor and automatic holding and release means, designated generally by l (see FIGURES 3 and 4), by which the engine crankshaft is prevented from rotating in response to the energy stored in the spring until the spring has been wound to a predetermined extent. As more fully explained hereinafter, the switch 16 is manually closed to initiate engine starting ybut is automatically opened when the spring is fully wound, such opening of the switch occurring substantially concurrently with release of the crankshaft for spring propelled rotation.

The spring motor is enclosed in a housing 17 that `rests on downwardly projecting legs 18 secured at their lower ends to the upper portion of the shroud 7. As viewed from above, the spring motor housing 17 is substantially circular, and the legs 18 hold it in substantially concentric relation to the crankshaft 6, spaced above the upper end thereof. A cover 19, which can be detachably secured to the spring motor housing as by means -of sheet metal screws 20, overlies and encloses the electric motor 13 and the transmission means 14 that drivingly connects the electric motor with the spring motor, the top wall 21 of the cover being spaced above the top wall 2.2 of the spring motor housing. Y

The spring motor comprises an inverted cup-shaped spring carrier 23 inside of which the spring 12 is spirally coiled and to the side wall 24 of which the outer end of the spring is connected. An annular plate 25 on the bottom of the spring carrier cooperates with the top wall 26 thereof to confine the spring against edgewise displacement. A concentric pilot or hub portion 27 formed on the top wall of the spring carrier projects upwardly through a concentric hole 28 in the top wall 22 of the spring motor housing to provide a journal for the spring carrier; and a pair of coaxial gears 29 and 30 are anchored to the top of the hub portion. The gear 29, which is larger than the gear 30, is an element of the transmission 14 through which the spring carrier is rotatably driven by the electric motor 13 to effect winding of the spring.

The inner end of the spring 12 is connected with the driving element 31 of an overriding clutch which is designated generally by 32 and which can be of the type disclosed in the above mentioned Svendsen Patent No. 3,040,853. The driven element 33 of the overriding clutch is directly coupled to the upper end of the crankshaft 6. When the clutch is engaged, the energy stored in the spring is of course transmitted through the clutch directly to the crankshaft, to effect rotation of the latter; and when the engine starts, the clutch decouples automatically.

The automatic holding yand release means comprises a ratchet 34 which is coaxially secured to the driving element 31 of the overriding clutch, beneath the bottom wall of the spring carrier, and a pawl 3S that cooperates with the ratchet. The pawl 3S is swingably mounted on a pivot pin 36 that is ixed on the housing 17 with its axis parallel to that of the crankshaft, and the pawl is biased into engagement with the ratchet 34 by means of a suitable torsion spring 37 that reacts against a part of the housing 17. It will be apparent that when the pawl 35 is engaged with the ratchet 34, the driving member of the overriding clutch is confined against rotation, to allow the spring to be wound in consequence of rotation of the spring carrier.

In the embodiment of the invention illustrated in FIGURES 1 and 2, the electric motor 13 is of the conventional rotating armature type. It is mounted on a bracket 38 which projects laterally from the spring motor :housing and which holds the electric motor spaced to one side of the spring motor with its shaft 39 parallel to the axis of the crankshaft. A pinion 40 on the upper end of the motor shaft 39 meshes with a larger intermediate gear 41 that is coaxially anchored to an idler pinion 43,

4 and the latter meshes with the large driven gear 29 on the hub of the spring carrier. The electric motor thus drives the spring carrier 23 through substantially high ratio speed reduction gearing.

With a small motor rated at about 9 volts and having a no-load speed -of about 4,500 r.p.m. and a torque of about oz.in. at stall, and with a gear transmission ratio of about 50:1, about 7 seconds is required to wind ve turns on a spring motor adequate for starting a 3 or 4 horsepower engine. An electric motor of this size and rating is very small and light so that its presence on an engine is not likely to create installation problems, and its power requirements are such that it can be energized by a very small rechargeable battery. Such a motor could not reasonably be expected to be adequate for starting if it were directly cou-pled to the crankshaft of an engine, yet by using it to wind a spring in the arrangement contemplated by this invention, the mechanical energy that it produces during its seven seconds (approximately) of operation can be stored to be released very rapidly when the spring is permitted to unwind. The seven second delay between initiation of the starting cycle and completion of spring winding is not long enough to be objectionable, especially when measured against the advantages gained from the herein disclosed arrangement.

The switch 16 that controls energization of the motor is preferably mounted on the top wall of the cover 19 for the starter mechanism near the pivot axis of the pawl 35. The switch is preferably of the overcenter or toggle type. It is shown with a pushbutton 42 that projects from its top when the switch is open and from its bottom when the switch is closed. Hence manual downward actuation of the pushbutton 42 energizes the motor.

When the spring has been wound a predetermined number of turns (five turns would ordinarily be adequate to provide dependable starting), the pushbutton is automatically actuated to its raised switch open position by means of an actuator 44 which is cyclically driven by the electric motor and which also effects disengagement of the 4pawl 35 from the ratchet 34 substantially simultaneously with `de-energization of the motor.

As shown, the actuator 44 comprises an upright shaft 4S rotatably mounted at one side of the spring motor 17, a gear 46 on the shaft, just below its upper end, meshing with the smaller gear 30 on the spring carrier hub, a switch actuating cam or eccentric 47 on the top of the shaft, and a pawl releasing cam 48 on the bottom of the shaft. By means of the gear 46 on the actuator, the actuator is drivingly connected with the electric motor through the transmission 14. Gears 46 and 30 have `about a 5:1 ratio so that the actuator shaft makes one revolution when the spring is wound about five turns.

The pawl actuating cam 48 has a finger-like radially projecting lobe 49 that is adapted to engage a similar lobe 50 on the pawl 35 at each revolution of the cam, to thereby swing the pawl out of engagement with the ratchet 34 when the spring has been wound to the desired extent, thus releasing the driving element of the overriding clutch to allow the crankshaft 6 to be turned by the spring. j

The cam or eccentric 47 that cooperates with the switch 16 comprises a finger-like lobe that engages the downwardly projecting end of the pushbutton 42 of the switch to raise the same and thus open the switch at about the same time that the pawl actuating cam 48 is swinging the pawl 35 out of engagement with ratchet 34. The switch of course remains in its open (pushbutton up) condition until the pushbutton is manually depressed for the purposes of a subsequent engine start.

The lobe 49 on the pawl actuating cam 48 is arranged to hold the pawl 35 out of engagement with the ratchet 34 through a small period of dwell, so that even though the electric motor coasts to some extent after the switch 16 is opened, the pawl will not re-engage the ratchet to interfere with rotation of the driving element of the clutch. Preferably the switch 16 is actuated to its open position Very slightly after the pawl 35 is disengaged from the ratchet 34. The pawl 35 is of course re-engaged with its ratchet 34 shortly after the motor 13 is energized for a subsequent winding cycle.

It will be apparent that the starter mechanism of this invention can readily incorporate the expedient disclosed in the above mentioned Svendsen Patent No. 3,165,100, or that of Harkness Patent No. 3,270,732, whereby the pawl would be positively prevented from engaging the ratchet so long as the engine is running.

The spring 12 will of course exert upon the spring carrier 23 a torque equal and opposite to that which it applies to the crankshaft 6, and when the electric motor is de-energized such torque will tend to turn it in the reverse of its running direction. However, because of the high ratio of the gearing that comprises the transmission 14 connecting the electric motor with the spring carrier, the inertia of even a light motor armature should satisfactorily resist such rotation. In cases where the electric motor does not sufficiently resist tlorque, as where the gear ratio is low or the armature of the motor is very light, a pawl 51 can be arranged for cooperation with the gear 30 to hold'it against-rotation in the spring unwinding direction but permit its rotation in the winding direction. v

The embodiment of the invention illustrated in FIG- URES 5 and 6 avoids the possibility of reverse rotation of the electric motor during cranking of the engine, without the need for an expedient like the pawl last described and also has some advantage in compactness. In the FIGURES 5 and 6 embodiment the transmission 14 which 4provides the driving connection between the electric motor 13 and the spring carrier 23 comprises a worm 140 coaxially connected with the shaft 39 of the electric motor and having direct meshing engagement with the larger gear 29' on the spring carrier hub. If the gear 29 has about 50 teeth, the same electric motor to spring carrier drive ratio will be provided as in the FIGURES 1-2 embodiment, without the need for intermediate gearing like the gear 41 and -pinion 43, and the worm arrangement will of course prevent torque from being imposed upon the motor shaft as the spring unwinds. Obviously the worm 140 should be journaled in bearings 52 that accommodate the end thrust imposed upon the worm by spring reaction.

In other respects the embodiment of the invention illustrated in FIGURES 5 and 6 can be identical with that lillustrated in FIGURES 1 and 2.

In the embodiment of the invention illustrated in FIG- URES 7 and 8 a rotating electric motor 13, which can be similar to the motors of the FIGURES 1 2 and 5-6 embodiments, is again employed to effect winding of the spring mechanism, but in this case the rotation of the motor shaft 39 is translated into endwise reciprocation of a winding pawl 54 that drivingly cooperates with a ratchet 129 coaxially secured to the hub or pilot 27 of the spring carrier 23. It will be apparent that the ratchet 129 is the functional equivalent of the gear 29 of the FIGURES 1-2 embodiment of the invention and the gear 29 of the FIGURES 5-6 embodiment.

At its captive end the winding pawl 54 is journaled on a circular eccentric 55 which is fixed on the shaft of the motor 13 and which imparts reciprocating motion to the pawl. The pawl 54 is biased laterally toward engagement with the ratchet 129 by means of a suitable leaf spring 56, reacting against the side wall of the cover 17.

As the pawl 54 is moved lengthwise in the direction toward the motor shaft 13, it effects incremental advance of the ratchet 129 in the spring winding direction by a circumferential distance equal to the pitch of a ratchet tooth. As the pawl is moved in its return stroke, a holding pawl 51 engages the ratchet to prevent retrograde Irotation of the spring carrier. Inasmuch as the ratchet 129 can have about fifty teeth, the pawl and ratchet spring winding transmission of FIGURES 7 and 8 can provide the same drive ratio betweenthe motor 13 and the spring carrier 23 as the reduction gear 4transmission of FIG- URES l and 2.`

The actuator 44 in the FIGURES 7 and 8 embodiment of the invention can be identical with the actuators 44 of the previously described embodiments, being similarly driven by a gear 46 on its shaft that meshes with a gear 30- fixed on the spring carrier pilotv 27 coaxially with the ratchet 129.

The embodiment of the invention illustrated in FIG- URE 9 is generally similar to that of FIGURES 7 and 8, except that a reciprocating electric motor 13 replaces the rotating armature motors of the previously described embodiments.

The reciprocating motor 13', which drives a ratchet 129 on the spring carrier 23 through a pawl 54, comprises a solenoid 57 having a hollow core in which a magnetically permeable plunger 58 is reciprocable, a breaker mechanism 59 which controls energization of the solenoid 57, and a lever 60 to which the plunger 58 and pawl 54 are connected and which actuates the breaker mechanism 59.

The lever 60, which extends generally transversely to the plunger 58 and pawl 54, is fulcrumed about a pivot pin 61 that is fixed to the spring motor housing 17 with its axis parallel to that of the spring carrier 23 and spaced therefrom. The fulcrum of the lever 60 is intermediate its ends, but nearer one end than the other so as to define a shorter arm 62 and a longer arm 63 of the lever. The plunger 58 has a pivotal connection 64 to the longer arm 63 of the lever, at a substantial distance from its fulcrum 61, and the pawl 54 has a pivotal connection 65 with the lever that is intermediate its fulcrum and the plunger connection 64. A tension spring 66 is yconnected to the free end of the longer arm 63 of the lever and reacts against a fixed part of the structure to bias the lever in the direction to carry the plunger 58 axially out of the solenoid and to move the pawl 54 in its return stroke.

The breaker mechanism 59 comprises a fixed contact 67 and a cooperating movable contact 68 carried on one arm of a short, medially pivoted lever 69. The other arm of the lever 69 is bifurcated, and the shorter arm 62 of the lever 60 is disposed between the bifurcations to provide a lost motion connection between the two levers.

As illustrated in FIGURE 10, the fixed contact 67 of the breaker mechanism is connected in series with a current source through the switch 16. The movable breaker contact 68 is connected with the solenoid. When the switch 16 is closed and the breaker mechanism is in the position to maintain its contacts 67 and 68 engaged, the solenoid 57 is energized to attract the plunger 58 and thus propel the pawl 54 through a winding stroke. As the pawl reaches the end of its winding stroke the lost motion connection between the levers 60 and 69 is effective to swing the lever 69 to its position in which the contacts 67 and 68 are separated, breaking the energizing circuit to the solenoid and permitting the spring 66 to propel the pawl 54 in itsreturn stroke. As the pawl 54 nears the end of its return stroke, the lost motion connection between levers 60 and 69 again becomes effective, this time, however, swinging the lever 69 to its position in which the oreaker mechanism contacts are engaged, initiating another cycle of reciprocation of the winding pawl 54.

As in the FIGURES 7 and 8 embodiment of the invention, a holding pawl 51 cooperates with the ratchet 129 to prevent retrograde rotation of the spring carrier.

The mechanism for actuating the switch 16 and for releasing the driven clutch element when spring winding is terminated can be the same in the FIGURE 9 embodiment of the invention as in those previously described.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides a compact, inexpensive and dependable fully automatic starting mechanism for Small internal combustion engines, capable of being powered by a very small, low powered electric motor.

What is claimed as my invention is:

1. Mechanism for starting a small internal combustion engine comprising:

(A) a coiled spring;

(B) a rotatable winding element connected with one end of the spring for winding the same;

(C) a rotatable output element connected with the other end of the spring and drivingly connectable with the crankshaft of an engine to be started;

(D) ya latching element movable between a locking position 'in which it restrains the output element iagainst rotation and a releasing position freeing the output element for rotation;

(E) an electric motor drivingly connected with the winding element for winding the spring;

(F) an actuator driven by the electric motor and cyclically movable in a predetermined relationship to rotation of the winding element so that the actuator attains a predetermined position whenever the winding element has been driven through a predetermined number of turns;

(G) cooperating means on the latching element and the actuator for effecting motion of the latching element to its releasing position in consequence of motion of the actuator to its 4said predetermined position; and

(H) switch means connected with the motor and actuable by the actuator to effect de-energization of the motor in consequence of motion of the actuator to its said predetermined position.

2. Mechanism for 'starting a small internal combustion engine comprising the combination of:

(A) an energy storage motor of the type comprising:

(l) a coiled spring which is adapted to be wound (2) a rotatable output element connected with the spring to lbe driven thereby and drivingly connectable with the crankshaft of an engine to be started, and

(3) holding means movable to an operative position preventing rotation of the output element and to a releasing position permitting rotation of the output element;

(B) an electric motor so connected with the spring as to be operative to wind the same;

(C) release means operatively associated with said holding means for moving the latter to its releasing position in consequence of the spring being wound to a predetermined extent;

(D) switch means connected with the motor for controlling energization of the same; and

(E) actuator means synchronized w-ith the release means and operatively associated with the switch means to elect de-ener-gization of the motor concurrently with movement of the holding means to its inoperative position.

3. The mechanism of claim 1, further characterized the electric motor being of the rotating type and hav- 8 ing a geared connection wit-h the Winding element.

4. The mechanism of claim 1 wherein the winding element comprises a ratchet, further characterized by:

(A) the electric motor comprising (1) a solenoid,

(2) an armature reciprocable between defined limits of motion, `said armature being 4biased in one direction of its motion and adapted to be magnetically moved in the opposite direction in consequence of energization of the solenoid, and

(3) circuit breaker means connected with the armature for actuation thereby 'and electrically connected with the solenoid, :said circuit breaker means providing for energization of the solenoid as it nears the limit of its motion in the first mentioned direction and for de-energization of the solenoid as it nears the limit of its motion `in said other direction; and

(B) the connection between the electric motor and the winding element comprising a pawl connected with said armature to be reciprocated thereby and engageable with the ratchet to ecct incremental rotation thereof in consequence of reciprocation of the armature.

5. Means for utilizing a substantially small and low powered electric motor to effect :starting of an internal combustion engine, comprising:

(A) a spring motor having 1) a coiled spring,

(2) a rotatable winding element by Whic'h the spring can be wound, and

(3) a rotatable output element by which the spring is drivingly connectable with the crankshaft of an engine to be started;

(B) means so connecting the electric motor with the winding element that a substantially large number of cycles of electric motor operation is required to eiect one turn of the winding element;

(C) releasable holding means for restraining rotation the output element while the spring is being wound;

(D) switch means connected with the electric motor for controlling energization thereof;

(E) an actuator cyclically driven by the electric motor;

(F) means operatively associated With the actuator and with the holding means for releasing 'the output element when the actuator reaches a predetermined point in its cycle; and

(G) means operatively associated with the actuator and with the switch means for effecting de-enengization of the electric motor substantially concurrently with release of the output element.

References Cited UNITED STATES PATENTS 1,022,087 4/1912 Jenney 123-179 FOREIGN PATENTS 677,251 8/ 1952 Great Britain.

WENDELL E. BURNS, Primary Examiner.

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