US1925943A

US1925943A - Engine starting mechanism

Info

Publication number: US1925943A
Application number: US545757A
Authority: US
Inventors: Fred A Stein
Original assignee: Eclipse Aviation Corp
Current assignee: Eclipse Aviation Corp
Priority date: 1931-06-20
Filing date: 1931-06-20
Publication date: 1933-09-05
Anticipated expiration: 1950-09-05

Description

Sept. 5, 1933. F. A. STEIN ENGINE STARTING MECHANISI Filed June 20, 1931 2 Sheets-Sheet l INVENTOR Head 14, 6381/72.

Sept. 5, 1933.

F. A. STEEN ENGINE STARTING MECHANISEZ Filed June 20, 1931 2 $heecs-Sheei; 2

Patented Sept. 5, 1933 UNITED STATES PATENT OFFICE Eclipse Aviation Corporation,

East Orange,

N. J., a corporation of New Jersey Application June 20, 1931. Serial No. 545,757

8 Claims.

This invention relates to engine starting mechanisms, and particularly to those adapted to impart the initial turning force to a member, such as the crankshaft, of an engine having other means for maintaining itself in operation after such initial turning or cranking.

An object of the invention is to provide a power operated drive for a starter of the above class, characterized by the provision of a novel load limiting torque transmitting connections which are adapted to yield whenever the load exceeds a predetermined value, or in the event of a reverse rotation of they engine member due to premature ignition of the power charge, or other cause.

Other objects and advantages to be derived from the use of the invention herein disclosed reside in the construction and manner of combining the parts, and will become evident from the following description when read with reference to the accompanying drawings, wherein two embodiments of the invention are illustrated. It is to be expressly understood, however, that the said drawings are for the purpose of illustration only, and are not to be construed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings,

Fig. 1 is a longitudinal section of the device embodying the invention;

Fig. 2 is a sectional view along the line 2-2 of Fig. 1; and

Figs. 3 and 4 are similar views of a modification.

Referring to the drawings, and particularly to Fig. 1, the invention is shown embodied in a starter having a main casing l which is suitably supported, as by being detachably connected with the crankcase 2 of the engine in suitable manner as by bolts 3. Within a hub 4 of the casing there rotates a driving member comprising a nut or sleeve portion 5 and a flanged portion 6 extending laterally from one end thereof. Within such nut there is mounted for longitudinal and rotary movement, a driven member which is composed of a threaded shaft 7 having a hollow head 8 provided with radially disposed teeth adapted to engage the corresponding teeth of a jaw 9 of a suitable engine member 10, connected to, or part of, the engine crankshaft. In order to obtain its longitudinal and rotary movements, the threads of shaft 7 cooperate with corresponding threads on the interior of the nut 5, and'in order to enforce longitudinal movement of such shaft when the nut is rotated, detent fingers 11 are provided toengage the surface of the head 8 and prevent rotation of such shaft during the period of longitudinal advance into engagement with the engine member 10. The inner end of the shaft 7 is provided with a stop nut 12 which is adapted to contact the shoulder 13 of the sleeve 5 at th end of such longitudinal advance.

The means for imparting rotation to the sleeve 5 to first advance shaft 7 to establish driving connection with the engine, and to thereafter crank the engine through such driving connection, preferably includes a central shaft 14 which is in alignment with the shaft 7 and journaled in suitable bearings 15 supported in a hub 16 formed on a transverse wall 17 extending across the section In. of the casing. The shaft 14 is adapted to be driven by a prime mover which in the embodiment shown herein takes the form of an electric motor whose casing lb connects with the casing 1 through the intermediary casing section la above referred to, the section la being secured to the casing 1 by suitable bolts 22 and to the casing 122 by similar means 23. As herein shown, the shaft 14 is preferably an extension of the motor armature shaft and is drivably connected by a novel transmission mechanism next to be described, to the above described sleeve 5.

The novel transmission and torque limiting mechanism of the present invention is preferably constituted by a plurality of (as shown, two) planetary gear reduction assemblies, with which is associated a friction brake adapted to act upon one of the members of the gear reduction mechanism to hold said member normally stationary but to permit rotation thereof in the event of application of excess torque, or in the event of a suddenly applied tendency to reverse the direction of rotation, such as may occur in the event of back-kick or back-fire of the engine to be started.

The first planetary gear assembly includes a sun gear or pinion 25 drivably connected to the shaft 14 by suitable means such as the key 26, and adapted to mesh with a plurality of, planet gears or pinions 27 each of which is rotatably supported in a supporting plate or spider 28 which with annular plate 29 constitutes a housing for the unit, the spider 28 having a hub 30 rotatable about shaft 14, between which and the hub is preferably interposed a frictionless sleeve bearing 31 facilitating relative rotation between 27 are adapted to travel along the circular track constituted by the internally toothed annulus gear 33 which, in the embodiment shown in Fig. 1, is rigidly secured to the casing section .111, by screws 34.

The second planetary gear unit is composed of a similar set of planetary pinions 35 rotatable about their respective central pins 36 which, as shown, are in the form of screws having heads counter-sunk in a retaining disc 3'7, and having their ends threadedly engaging apertures provided for the purpose in the flange 6 of the sleeve 5. The planetary pinions 35 are adapted to mesh with and be driven by the teeth 40 formed on the hub 30 and constituting the sun gear, which, in conjunction with the internally toothed annulus gear 41, completes the second planetary unit.

-As shown, the friction brake mechanism takes the form of a pair of annular discs 43 and 44,

the former abutting the gear 41, and the latter the gear 33, the two discs being held in their abutting positions by the provision of a plurality of coil spring 45 surrounding each of the bolts 22 and preferably compressed sufficiently to produce a frictional pressure on the gear 41 to such an extent as to normally hold the said gear from rotation under the reaction produced on the teeth thereof by the rotation of the planet gears 35 in response to energization of the motor. Preferably, however, there is provided a series of manually adjustable devices for regulating the pressure of the friction disc 43 upon the gear 41. As shown. such means preferably takes the form of screws 47 passing through the flange 48 on the casing section 1a at equally spaced angular intervals, such screws alternating with the bolts 22 and having engagement at their ends with the disc 44. With this construction it is apparent that upon movement of the disc 44 to the left from the position shown in Fig. 1, by turning up of the screws 47, the stress of the springs 45 on the gear 41 will be increased, with the result that the gear 41 will be effective to withstand a stronger reaction, and hence transmit a greater driving torque before slipping.

In operation, when the motor is energized,

the shaft 14 will be rotated and the reduction gearing and drive will be operated. The torque of the motor is transmitted through the

gears

27, 40 and 35 to the flange 6, sleeve 5 and shaft 7. By virtue of the threaded connection 'between. shaft '7 and sleeve 5, the shaft will be advanced longitudinally into engagement with the engine member 10. The gear 41, as above explained, is normally stationary and the planetary pinions 35 cooperate therewith in the usual mamier to drive the shell 5. In the event however, of a backfire of the engine or other suddenly applied excess load, the resulting increased reaction on the gear 41 willcause the latter to slip around between the disc 43 and the flange 50, of the housing, and in this manner absorb the excess energy and protect the other parts of the assembly from injury. When the engine operates under its own power, the driven member will be automatically disengaged by reason of the inclination of the jaw teeth and the threaded connection with the sleeve 5.

There is thus disclosed a novel engine starter of the inertia type which is simple and rugged in structure, inexpensive to manufacture and efficient in operation. It is especially adapted for use with small engines because of its compactness and light weight, but since it is a selfcontained unit, it may be easily attached to any engine, and requires no external supporting means, the whole unit in the embodiment shown being mounted on an extension of the engine housing. Moreover, the arrangement shown is such as to permit of entry of the high torque necessary for cranking an airplane engine, by the use of a comparatively small diameter motor, such result being due to the novel coaxially arranged double planetary gear reduction.

While the embodiment above described possesses considerable practical merit, the invention is not limited to such embodiment since the novel principles may be incorporated in struc tures varying considerably from that above described. Thus, for example, as shown in Figs. 3 and 4, the friction brake may be caused to act upon the annulus gear of the first planetary unit rather than upon the second unit. Referring to these figures, it will be seen that in this embodiment, the annulus gear 41 is rigidly held to the casing by screws 60 while the annulus gear 33 is only frictionally held, the torque transmitting capacity thereof being governed by the setting of the adjusting screws 61, corresponding to screws 47 of Fig. 1, but engaging clutch disc 43 rather than clutch disc 44. Thus it will be seen that the arrangement of Fig. 1 is reversed but the effect is the same, namely to transmit a predetermined torque and to yield in the event of the application of a sudden load beyond such predetermined torque value.

It is to be understood that various other changes may be made in the form, details of I construction and arrangement of the parts and the uses to which they are applied, without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. In an engine starter, a drive including a driving member mounted for movement into engagement with a member of the engine to be started and for rotary movement to crank the engine, reduction means connected with such drive and including a normally stationary gear, a normally rotatable gear coaxial therewith, friction discs abutting each of said gears, and spring means interposed between said discs to exert a yielding restraining force on said normally stationary gear.

2. In an engine starter, a drive including a driving member mounted for movement into engagement with a member of the engine to be started and for rotary movement to crank the engine, reduction means connected with such drive and including a normally stationary gear, a normally rotatable gear coaxial therewith, friction discs abutting each of said gears, spring means interposed between said discs to exert a yielding restraining force on said normally stationary gear, and means for relieving said normally stationary gear of the frictional pressure of said discs.

3. In an engine starter, a drive including a driving member mounted for movement into ongagement with a member of the engine to be started and for rotary movement to crank the engine, reduction means connected with such drive and including a normally stationary gear,

a normally rotatable gear coaxial therewith,

friction discs abutting each of said gears, spring means interposed between said discs to exert a yielding restraining force on said normally stationary gear. and means for relieving said normally stationary gear of the frictional pressure of said discs, said means comprising a manually operable adjusting member for moving said disc out of engagement with said gear.

4. In an engine starter, a drive including a driving member mounted for movement into engagement with a member of the engine to be started and for rotary movement to crank the engine, reduction means connected with such drive and including a normally stationary gear, a normally rotatable gear coaxial therewith, friction discs abutting each of said gears, spring means interposed between said discs to exert a yielding restraining force on said normally stationary gear, and means for transferring the frictional pressure from said normally stationary gear to said normally rotatable gear.

5. In an engine starter, a drive including a driving member mounted for movement into engagement with a member of the engine to be started and for rotary movement to crank the engine, reduction means connected with such drive and including a normally stationary gear, a normally rotatable gear coaxial therewith, friction discs abutting each of said gears, and spring means interposed between said discs to exert a yielding restraining force on said normally stationary gear, and means for transferring the frictional pressure from said normally stationary gear to said normally rotatable gear comprising a manually adjustable member for moving said discs away from said first named gear whereby the springs interposed between said discs are caused to exert a stress upon said second named gear.

6. In an engine starter, a driving member adapted to engage a member of the engine to be started, means for rotating said driving member during such engagement to effect cranking of the ,engine, said rotating means including a motor driven shaft, a plurality of planetary gear assemblies each including a normally stationary gear, one of which is movable when excessively loaded, and a friction mechanism interposed between said planetary gear assemblies for limiting the torque capable of being transmitted therethrough.

7. In an engine starter, a drive including a driven member engageable with a member of the engine to be started to impart initial rotation thereto, a driving member, and reduction means connecting said members, said reduction means including a pair of normally stationary gears and a plurality ofnormally rotating gears, the latter being drivably connected with said driven member, and a casing enclosing said reduction means, one of said normally stationary gears being immovable with respect to said casing and the other of said normally stationary gears being rotatable in said casing on application of excessive load thereto.

8. In an engine starter, a drive including a driven member engageable with a member of the engine to be started to impart initial rotation thereto, a driving member, reduction means including a pair of normally stationary gears and a plurality of normally rotating gears, the latter being drivably connected with said driving and driven members, and means interposed between said normally stationary gears for preventing movement thereof except upon application of an excessive load.

FRED A. STEIN.