US1405742A - Starter for engines - Google Patents

Description

S. W. RUSHMORE.

STARTER FOR ENGINES.

APPLICATION FILED DEC. 20, 1919.

1,405,742 Patented Feb.7, 1922.

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[HHHIIIHIIIHIIIIHXAIIWI F: G E E L J l S. W. RUSHMORE.

STARTER FOR ENGINES.

APPLICATION FILED 02020.1919.

1 ,405,742, Patented Feb. 7, 1922.

2 SHEETS-SHEET 2.

/ INl/E/VTOR HIS A TTORNE Y UNITED STATES PATENT OFF-ICE.

SAMUEL'W. RUSHMORE, 01" PLAINFIELD, NEW JERSEY.

STARTER FOR ENGINES.

Application filed December 20, 1919. Serial in. 346,481.

and State of New Jersey, have invented certain new and useful Improvements in Starters for Engines, of which the following is a specification.

My present invention relates to devices of the above type in which a motor driven pinion is shifted into driving engagement with a gear for rotating the crank shaft of the engine upon starting, and out of engagement after starting. It relates more particularly to devices of the above type in which the pinion is shifted by screwing endwise along a screw element on the driving member, when one rotates faster than the other. Such differential rotation is due to inertia effects upon sudden starting or stopping, either of the motor or the engine, and some auxiliar device such as an eccentric weight or friction drag is commonly employed to retard rotation of the pinion.

In starting devices of the above type employed on automobiles, the power for starting is commonly afforded by an electric motor operating on current derived from'the storage battery. Such motors accelerate with extreme rapidity the instant the circuit is closed. Consequently, the endwise screwing of the pinion either into or out of engagement with the engine gear is extremely rapid and the shock upon locking of the gear to rotate with its shaft and the simultaneous taking up of the load is very reat. A torque s ring may be employed or moderating sue shocks as set forth in another application of even date herewith.

Such spring when secured to a driving member at one end and to a driven member'at the other end permits the driven member to lag behind the driver and thus yieldingly applles' the powerso as to moderate the shocks. n I

Such torque springs, however, are noisy and frequently break and one object of my presentinvention is to secure similar results without the use of the torgue spring.

M present invention contemplates the emp oyment in this connection of friction driving means normally acting to appl to the pinion the maximum torque require for starting the engine but so arranged as to afford a certain amount of slip at the in- Specification of Letters Patent.

Patented Feb. '7, 1922..

stant of excessive shock due to locking of the pinion and simultaneous taking up of theload, when it contacts with the stop which limits its endwise screwing movement.

An additional feature of my invention is organizing the parts in such a way that the dl'lVlIlg plnlon itself will function mechanically through suitably related machine elements to automatically effect a slight release of the otherwise normally constant pressure of the friction coqipling, thereby permitting slip between the bers at the instant of abnormal power manifestation due to the momentum of the spinning shaft and armature. Preferably this mechanism is so organized that after such momentary release the full normal pressure on the friction members is automatically restored so that the full power normally available in the motor will be applied for driving the engine at the speed re uired for starting.

The above and other eatures of my invention may be more fully understood from the following descriptionin connection with the accompanying drawings, in which- Figure 1 is a schematic view partly in section showing the organization of parts according to one desirable embodiment of my invention; and

. Figure 2' is a detailed view on a'somewhat larger scale showing a modification.

In these drawings the crank shaft C of the internal combustion engine is provided with fly-wheel F having gear G formed'on the peripherythereof. In operative relation thereto are the electric starting motor 1,having an armature shaft 2 carrying a screwthreaded sleeve 3, carrying an internall threaded pinion 4 provided with gear teeth 5. The motor shaft is parallel with the crank shaft so that screwing of the pinion endwise along the sleeve sets it into and out of mesh with the gear teeth on the fly wheel. Inward movement of the pinion is limited by a collar 6 preferably integral with the armature "shaft 2. Any desired means may be employed for retarding rotation of the pinion when the starting of the engine operates to drive the pinion faster than the motor shaft, as, for instance, the friction spring 8.

Any suitable means may be employed for closingthe circuit of the motor as for in stance, the switch S connected in series with battery B.

The means for frictions-11y applying the riving and driven memdesired torque from the drive shaft 2 to the sleeve consist of the friction disc 9 integral with sleeve 3 and the cooperating annulus 10 carried by the box like structure 11 which is rigidly secured to the shaft 2 through bolts 12 and disc 13 which is secured to the shaft 2 by set screw 14.

The friction disc 9 is forced into frictional engagement with the annulus 10 by means of spring 15. The area of the frictional surface and the stiffness of spring 15 are predetermined with a view to transmitting from shaft 2 to pinion 4 the maximum torque required for rotating gear wheel G up to the starting speed.

It will be noted that spring 15 is not secured either to the driving or driven memb(r and serves none of the functions of a torque spring; also the sleeve 3 is secured to the shaftonly by pressure of said spring 15 forcing disc 9 into contact with annulus 10, Hence, said sleeve can be shifted endwise to the left to relieve the friction if sufiicient power be applied to compress the spring 15. Moreover, said sleeve may slip and rotate at slower speed or even remain stationary while shaft 2 is rotating whenever. suflicient power is applied to overcome the normal friction or when said friction is reduced or eliminated by the above described endwise movement of the sleeve to the left in opposition to the pressure of spring 15.

From the above descri tion of the parts the operation of the device will be readily understood. When the switch S is closed the armature shaft 2 with its integral collar 6 and carrying with it the sleeve 3 will be rotated. Rotation .of the pinion 4 will be revented or at least retarded by inertia. ence the pinion will screw endwise into mesh with gear G. The starting speed of the motor being very great. and practically unimpeded up to the moment when the gear 4 butts against collar 6 and the pinion 4 being then practically stationary and in mesh wth stationary fiy-wheel gear G, there is an instant when the momentum stored up in the rapidly rotating armature and shaft apply an abnormally excessive torque. With the arrangement shown in the drawings, the effect of this is to tend to screw the pinion still farther to the right but as the pinion cannot screw farther. toward the right because it is already butting against collar 6, the tendency is to screw the sleeve in the opposite direction thus tending to relieve the frictional pressure of disc 9 on annulus 101 This permits the pinion and sleeve to lag behind the drive shaft during the time needed to take up the shock and start the fly-wheel of the engine. The pressure of spring 15 being constant, will operate automatically to restore disc-10 to full frictional engagement with annulus 9 as soon as the abnormal or shock conditions have been equalized by getting the fly-wheel of the engine in motion and corresponding slowing down of the motor armature.

It will be understood that the above de scribed endwise movements of the sleeve are likely to be minute and in many cases will manifest themselves merely as decrease of pressure of the frictional surfaces rather than as observable movements of the sleeve.

It will be evident also that if the pressure of spring 15 be properly gauged so as to afford a closely regulated pressure slightly greater than the maximum normal torque, the friction surfaces may slip suflicient to take up the shock without any endwise movement of the sleeve 3.

In the embodiment of my invention shown in Figure 2, the number and nature of the essential elements is the same but the organization of the parts is different in detail. In this figure, the fly-wheel Gr, pinion 4, spring 8, screw sleeve 3 with friction disc 10 may be the same as before. The pinion 4, however, when screwed to the end of the sleeve, comes into contact with collar 16 rigidly secured on sleeve 3 by set screws 4. Hence, screwing the pinion 4 until it butts against the collar cannot have any tendency to screw the sleeve 3 to the left. An equivalent function is performed in a better and more easily determinable manner by the cooperating. friction disc 19 which is internally screw-threaded as at 1 20 so as to fit the multiple thread steep pitch screw 21 cut in the outer portion of the armature shaft 2. This friction disc 19 is forced endwise into frictional engagement with disc 10 by stifiothrust spring 25. This spring like spring 15 previously described is not a torque spring but operates merely by its endwise thrust to force disc 19 against disc 10 with the pressure required to transmit the normal maximum torque required for starting the engine.

he operation of this form of my invention is similar to that of Figure 1 except that in Figure 2, it is the disc 19 that screws rearwardly to relieve the friction pressure at' the inst-ant of maximum shock, the pinion and sleeve being at thisv instant relatively locked by reason of the strew forcing pinion 4 into contact with the collar 16 which, as before stated, is rigid with the sleeve 3, and thus prohibits further relative movement of sleeve and pinion until the direction of rotary stress is reversed by the starting of the engine and consequent driving the pinion at a speed overrunning the speed of the armature shaft.

One functional advantage of the arrangement shown in Figure 2 over that shown in Figure 1 is that the endwise movement for relieving the pressure and friction of the friction members is predetermined by the ing an electric starting motor, a shaft driven thereby, a screw element rotated by said shaft, a pinion adapted to screw endwise into and out of engagement with a gear for starting the engine according as said screw element rotates faster or slower than said pinion, and, in combination with said parts,

a friction coupling interposed between the electric starting motor and the engine, said coupling having frictional engagement suflicient to transmlt the normal power required for driving the-engine up to starting speed, but insufiicient to withstand the abnormal torque developed by the momentum of the drivin members acquired during the shifting 0 said pinion, together with means whereby abnormal torque, applying abnormal endwise screwin efl'ort, operates aut0- matically to reduce t e pressure of the friction elements of said friction coupling.

2. The combination specified by claim 1 in which a. spring. is arranged as the means to oppose reduction of the pressure of the fricment onthe armature shaft and formed with a friction surface as one element of said friction coupling, the cooperatin friction surface being mounted upon an by the armature shaft, said parts being located and relativel arranged so that the abnormal torque wil cause endwise screwing of one of said friction elements in a direction to relieve the surfaces.

4. The combination specified b claim 3, in which asgring is arranged as t e means to oppose uctlon of the pressure of the frictlonal elements. I

5. The combination specified by claim 3, in which the shaft-driven frictional element is screw. threaded to the drive shaft, by a screw of opposite twist to that of the sleeve screw,

.and in which a thrust spring is employed as the means for preventing unscrewing of said shaft engaging friction element under nor-j mal torque but is adapted to yield and permit such movement under abnormal torque.

Si ed at New York city in the county of New ork, and State of New York, this 13th day of December A. D. 1919. l

- SAMUE W. RUSHMORE.

being driven pressure on their frictional u

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