US2927660A - Self-starter for model engines - Google Patents

Description

March 8, 1960 P. M. DE GROAT SELF-STARTER FOR MODEL ENGINES Filed Feb. 21, 1958 BY g T4; ou

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SELF-STARTER FOR MODEL ENGINES Philip M. De Groat, Newark Valley, N.Y., assignor to L. M. Cox Manufacturing Co., Inc., Santa Ana, Calif, a corporation of California Application February 21, 1958, Serial No. 716,792 8 Claims. c1. 185-41) This invention relates to model internal-combustion engines, and more particularly to an improved springactuated starter for such engines, especially as employed for operating small scale models of airplanes, boats, automobiles and similar toys. 2,751,898, entitled Model Engine Starter, filed August 3, 1954 and issued January 26, 1956, I broadly disclose a self-releasing spring starter which stores energy when the drive shaft is rotated in a reverse or contranormal direction as part of the starting operation.

The present inventionincorporates improved means whereby the starting mechanism automatically engages and disengages itself as required. Although my earlier patent broadly comprehends automatic disengagement of the starting mechanism after the stored energy has been released from the spring, the present invention allows for automatic engagement as well, for all positions of the drive shaft. Reference may be made to my earlier patent for additional illustration or for a better understanding of any features of construction that might be common to the two devices.

A principal object of the present invention is to provide a new and improved type of starter for model internal-combustion engines which includes a clutch mechanism and means for automatically engaging the clutch when the drive shaft is reversed from any starting position; another object is to provide improved means for disengagement of the starting mechanism when the Starting spring has become de energized; a further object is to utilize a clutch device that is simple and effective' in operation, and yet which produces a minimum frictional drag when in the, disengaged position; a further object is to provide improved means for causing normal centrifugal forces to assist in further reduction of theclutch drag in the disengaged position; and to provide means for locating the starting spring in concentric relation to the drive shaft and to oppose unbalancing tendencies of centrifugal forces. These and other objects of the invention will become more apparent from the following description and from the appended drawing showing one form of the invention as applied to a model internal-combustion engine.

In the drawing:

I Figure 1 is a side view of a propeller-driven engine showing one form of the improved starter in operating position.

Figure 2 is a front view of the same engine with the propeller removed to show one manner of connecting the starting spring to the drive shaft; and

Figure 3 is an enlarged'side view of the engine drive shaft and starter mechanism with some parts shown in section.

Generally speaking, the improved starter comprises an energy storage device, herein more readily defined and illustrated as a spring member, with automatic clutch means for operatively connecting the storage device to the. propeler shaft. The clutch mechanism is unidirectional in its operation in the sense that it provides a In my earlier Patent No.

2,927,660 Patented Mar, 8,

ice

and is illustrated as terminating in a mounting flange 15 for convenience in making a driving connection .witha propeller or similar energy-dissipating device 16. Ener gy developed by the engine 12 is transmitted to the shaft 13 which accordingly rotates relative to the stationary portions of the engine, and the motion is transmittedto the propeller through the mounting flange, all in con ventional manner. 7

As pointed out in my earlier patent, more effective, quicker and safer starting of the engine can be accomplished over earlier methods it the drive shaft is rotated in a reverse direction for one or more revolutions, while at the same time storing energy in the starting'mechanism. When the propeller is released, the shaft is urged to rotate in the normal or operating direction until theenergy of the starting device is dissipated, during which time the engine normally is set into operation.

In my earlier patent, a clutch mechanism has been shown which becomes operable by having the. propeller blade engage a-retractable hook-like extension of the starting'spring. With the improved mechanism, herein disclosed, energy storage is efiected immediately by re versal of the drive shaft, irrespective of the angular ,position or phase of the drive shaft" at the time of. such reversal. Various energy storage means utilizing rubber bands, compressed air cylinders and the like might be utilized for the purpose, but for the sake of simplicity, I prefer to show a helical spring 17, substantially of the proportions illustrated in the drawing' Although the requirements naturally varyaccording to the size of the engine, a spring suitable for many of the popular small aircraft engines in current use, employs six to eight turns of approximately .040 spring steel wire, coiled to a diam eter of inch. Clutch means is provided for operatively engaging the starting spring 17 and the shaft 13. It is patentably immaterial whether the free end ofthe spring normally is stationary and engages the drive, shaft during the shaft reversing operation, or whether the spring normally rotates with the. shaft and selectively engages a stationary part of the engine at the time of shaft reversal. To illustrate the principles of the invention, I show the spring as one that normally rotates when the engine is operating, the motion being cover 22 may be used for centering the starting spring,

and it also may be held in position by the screw 19.

The clutch means, as previously described, functions at any position of the drive shaft to secure one end of the starting spring for motion relative to the opposite end. In the preferred embodiment, best seenin Figure 3, such a clutch device 23' anchors the freeiendoff the spring opposite the terminal 18 to a stationary portion of the engine as required. The clutch may be defined functionally as a uni-directional clutch, or an over-running clutch in that it engages whenever the initial shaft motion occurs in one particular direction, specifically aaeaeeo the direction opposite to normal engine operation. As illustrated in Figure 3, this may be accomplished by utilizing a spiral or helical spring 27 that constricts, and hence tightly engages a stationary part of the engine such as the sleeve 14 when the spring is twisted so as to constrict the turns. While the starter spring 17 and the clutch spring 27 are coiled in the same direction and might be made integral, I find it preferable to employ separate springs for energy storage and clutch operation respectively, primarily because of differences in the required physical size and properties of the two units. Hence I prefer to employ a spirally coiled leaf spring 27 for the main clutch member, the inner winding of which conforms closely to the shape of the stationary part of the engine with which it cooperates, in the present case the sleeve 14. Sufficient frictional drag is allowed in the initial condition that any constricting forces acting on the leaf spring create a positive lock between it and the sleeve. Successful operation has been obtained with spring material measuring from .003 in. to .005 in. in thickness, and having a width of approximately in. The clutch member 27 resembles a clock spring in appearance, and requires several convolutions for most effective operation. The leaf spring has an outer termination 24 that may be secured to the starter spring 17 as shown in Figures 1 and 3 by having the hooked free end 25 of spring 17 extend through an aperture 26 in the termination 24. The aperture may be reinforced as shown with a suitable grommet, or the parts may be successfully secured as by spot welding or other conventional techniques. Other clutches, functioning in a similar way may of course be substituted, but I find the spirally coiled leaf spring to be light in weight, durable and reliable.

In operation, the shaft is rotated in a reverse direction, that is in a clockwise direction when viewing Figure 2, causing a slight constriction force to be transmitted through the starter spring from the left terminal 18 to the opposite end 25. This same force acts on the spiral spring 27 reducing the diameter of the inner convolution slightly, and causing the spring to act as a clutch, and arresting further rotation of the end 25. As the shaft continues to be rotated, the turns of spring 17 be come energized, creating a force which operates the shaft in the opposite or normal direction when the shaft is released. The propeller and shaft thus rotate through one or more revolutions in the counter-clockwise direction when viewing Figure 2, permitting the engine to start in a normal manner. As soon as the shaft 13 has rotated sufficiently that no energy remains in the spring 17, the convolutions of clutch 23 likewise are no longer constricted and both springs rotate as a unit with the propeller. Any slight frictional drag that might exist between the inner convolution of the clutch 23 and the sleeve 14 is reduced by centrifugal force as the propeller rotates, causing the convolutions to increase slightly in diameter, and hence to reduce the frictional contact. Inertia effects also operate to reduce the drag since the acceleration forces transmitted by the propeller shaft tend to open up the turns of the spring in the clutch 23 while the engine is operating. g

The cover 22 adds some desirable operating qualities; in that it protects the starter spring and the clutch from corrosion and physical damage, and additionally centralizes the starter spring 17 by the close interfitting relationship between the outer diameter of the spring and the inner diameter of the cover. This cover also opposes any centrifugal tendencies to throw parts of the spring out of the normal illustrated position.

Although I have earlier disclosed a preferred embodiment of the present invention, it is to be understood that various modifications may be made from the specific arrangement herein disclosed without departing from the spirit of the invention, as I comprehend all modifications properly within the scope of the appended claims.

I claim:

1. A self-starter for a model internal-combustion engine of the type having an engine-driven shaft extending through a stationary collar supported by said engine, said starter comprising a spring member having means at one end for attachment to said drive shaft, and having clutch means operative at the opposite end of said spring memher for mechanically securing said spring member to said collar whenever said drive shaft is rotated in a contranormal direction, thereby to energize said spring, said clutch means being operative to release said opposite end from said collar when said spring member has become de-energized.

2. A self-starter for a model internal-combustion eugine of the type having an engine-driven drive shaft extendin through a stationary collar supported by said engine, said starter comprising a spring member having means at one end for attachment to said drive shaft, and an over-running clutch extending between said collar and the opposite end of said spring, and being operative when said shaft is rotated in a reverse direction to con nect said opposite end to said collar thereby to energize said spring, and being operative when said spring is deenergized to disconnect said opposite end from said collar.

3. A self-starter for a model internal-combustion engine of the type having an engine-driven propeller shaft rotatable relative to a stationary portion of said engine, said starter comprising a spring member having one end attached to said shaft, and over-running clutch means attached to the opposite end of said spring member, and being operative to lock said opposite end against rotation whenever said shaft is rotated in a reverse direction, thereby providing storage of energy within said spring.

4. A self-starter for a model-combustion engine of the i type having an engine-driven propeller shaft operated by said engine, said starter comprising a spring member hav ing one end attached to said shaft, and over-running clutch means attached to the opposite end of said spring member, and being operative to lock said opposite end against rotation Whenever said shaft is rotated in a reverse direction, thereby providing storage of energy within said spring, said over-running clutch being operative to release said opposite end to permit free rotation of said spring with said shaft when said shaft has rotated in a forward direction sufficiently to de-energize said spring.

5. A self-starter accessory for a model internal-combustion engine of the type having a propeller shaft for rotation relative to a stationary portion of said engine, said starter comprising a starting spring member having a connection at one end for attachment to said shaft, means secured to the opposite end of said spring member, said means being automatically engageable with such stationary portion of said engine, whereby said spring is energized whenever said shaft is rotated in a contra-normal direction, said means being free to disengage itself from said stationary portion whenever said shaft has rotated sufficiently in a normal direction as to de'energize said spring.

6. A self-starter accessory for a model internal-combusion engine of the type having a propeller shaft for rotation relative to a stationary portion of said engine, said starter comprising a starting spring member having a connection at one end for attachment to said shaft, means secured to the opposite end of said spring memher, said means being automatically engageable with said stationary portion of said engine, whereby said spring member isenergized whenever said shaft is rotated in a contra-normal direction, said means comprising a helicaily coiled leaf spring secured at one end to said opposite end of said starting spring member, and being free to disengage itself from such stationary portion whenever said shaft has rotated sufficiently in a normal direction as to tie-energize said spring member.

7. A self-starter accessory for a model internal-combustion engine of the type having a propeller shaft pro- "fem 1) iecting through a stationary cylindrical sleeve extending from said engine, said starter comprising a starting spring member having a connection at one end for attachment to said shaft, clutch means secured to the opposite end of said spring member, said means being automatically engageable with said cylindrical sleeve, whereby said spring member is energized whenever said shaft is rotated in a contra-normal direction, said clutch means comprising a helically coiled leaf spring secured at one end to said opposite end of said starting spring member, and having its inner convolutions closely encircling said cylindrical sleeve and being free to disengage itself from said sleeve whenever said shaft has rotated sufficiently in a normal direction as to de-energize said spring member.

8. A self-starter for a model internal-combustion engine of the type having an engine-driven propeller shaft rotatable relative to a stationary portion of said engine, said starter comprising a spring member, said spring member comprising a coil spring wound about said propeller shaft and having one end cngageable with said shaft and the other end engageable with said stationary portion, whereby energy may be stored in said spring for urging said shaft to rotate in a normal direction, and an overrunning clutch disengageable upon rotation of said shaft in said normal direction to free one of said ends from its engagement.

References Cited in the file of this patent UNITED STATES PATENTS

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