US2209049A - Engine starter - Google Patents

Description

July 23, 1940.

R. CHILTON ENGINE STARTER Filed March s, 19:58

3 Sheets-Sheet 1 Q ATToRNE f July 23, 1940.- RQ cHlL'roN ENGINE STARTER Filed March 3, 1958 3 Sheets-Sheet 2 lNvENToR oLa/m @mimi ATToRNx-:f

ENGINE STARTER Filed MaICh 3, 1938 3 Sheets-Sheet `3 0 Tl 5. A0

INVENTOR Kamm) CHILTON Jua-1w A/ AT1-ORNE Patented July 23, 1940 rATENT oEFicE ENGINE STARTER Roland Chilton, Ridgewood, N. J. Application March 3, 1938, Serial No. 193,808

l 2 Claims.

` My invention `relates to starters, and particularly to starters for aeronautical engines.

A prime object of the invention is to provide a starterand associated gearing of greater com- '5' pactness than that obtaining in conventional designs, or alternately, to provide greater torque capacity within current dimensions.

It will be understood that these starters mount on engine accessory sections where they are surlO rounded by magnetos, generators, oil pumps, fuel pumps, etc., resulting in extreme congestion. The demands upon, and accordingly, the dimensions of, the various accessories tend to increase as the h art develops. This development also introduces l additional accessories from time to time. Great difficulty, therefore, is now experienced in meeting all ofthe requirements in the space available on current engines.

In the case of the starter, the necessary high ratio reduction gearing is the bulkiest element, and this gearing is normally placed at the engine end of the starter with the electric motor mounted on the rear. The diameter of the motor is a relatively small dimension but, in most cases, it is found that the worst interferences with adjacent accessoriesoccur at the engine end of the starter. Accordingly, in this invention, novel means are provided whereby the normal disposition may be reversed and the gearing placed at the end of the starter remote from the mounting flange whereat, due to the relative shortnessof certain of the other accessories, more space is afforded.

Another object of the invention is to provide a novel planetary cage structure permitting the use `of an abnormally large number of gear driven planet pinions whereby the capacity of a gear of given diameter is substantially increased.

Other objects and advantagesof the invention will be obvious from, or will be pointed out in, the `following description with reference to the drawings, in which:

Fig. 1 comprises axial half sections through the starter, the upper portion showing the parts in engaged condition and the lower portion showing the parts disengaged;

Fig. 2 comprises segmentaltransverse sections in which segment (a) is on the line a of Fig. 1, segment (b) is on the line b of Fig. 1, and segment (c) ison the line c of Fig. 1;

Fig. 3 is a perspective detail view of a planet member;`

Figs. 4 and 5 are detail views of a split friction ring;

Fig. 6 is an end view of a standard three-Way starter jaw, vand (Cl. 'i4-7) Fig. 7 is an end View of a ne tooth jaw associated with the standard jaw in this invention.

, position shown in the lowerI half of Fig. 1 to the engaged position indicated in the upper half. The disengaged position of the armature is offset axially from the center of the field to effect this automatic magnetic mesh.

Carried along with the armature during this engaging motion are the following elements:

The tubular armature shaft 2t which has splines 28 at its rearward end is slidable in a hub 3l) of a driving gear 32. At its inner end the armature shaft carries rigidly a sleeve .Se having an enlarged annular portion 3B within which is frictionally engaged a spring cuff member 38 (seen in detail views of Figs. 4 and `5) having a projecting key member il which is engaged with a Slot 42 formed in the periphery of an engine engaging jaw 44 having the standardized three jaw engagement with a companion jaw on'the engine to be l started and indicated by dotted lines at dii.

The back of the engine jaw d4 is equipped `with very fine ratchet teeth i8 and engaged with these teeth is a companion ratchet member 5f! (also shown in Fig. '7), which member has splines 52 slidable on a main driving shaft 5i (which does `not partake of the axial movement) The ratchet teeth 43 are urged into Aengagement by a light spring 5E. The parts above described are urged to the disengaged or right hand position (of the D lower half of Fig. 1) by a long spring 58 disposed `in a bore in the shaft 5@ and engaging a long tension rod Bil through a bushing 62, this rod being securedto the engine engaging jaw lil by a suitable head member fifi. ,5

As before stated, the main shaft 54, on which the hollow armature 26 rotates and slides axially on split bushings 88, does not partake of this axial motion, being provided at its 4right hand end lwith a flange 68 and with a suitableoutboard support 1.540 bearing lil. An internally toothed gear l2 is Asecured tothe flange 68 by screws "M,

Around the hub 3l) of the driving gear 32, previously described as splined to the armature shaft 26, there is rotatably floated, on a bushing 16, a

cage member comprising a hub 'l0 and a flange 0i! which has a circumferential plurality of bearing bores 82. Aligned with the bores 82 are companion bores 83 formed in a rim 84 extending from a flange 86 secured by bolts 88 to the member 30 to form a composite planet carrier. This carrier, it may be pointed out, comprises an important feature of the present invention.` The member 84-06 is shown in detail in the perspective view of Fig. 3 which is turned end-for-end with respect to Fig. 1 in order to better show'the construction. Two of the tapped holes in the in-turned flange member 86, whereby the cage elements are secured together, appear in this view which also shows all of the plurality of bearing bores in theV rim 04. It will be seen that the outside diameter of this rim will clear the tips of the teeth in the ring gear l2 while the inner diameter clears the tops of the teeth of the driving gear 32. Backv of the rim 34 the member has counterbores extending through to the rear face of the flange 86, these counterbores being large enough to clear the tops of the teeth of planet pinions later to be described. These counterbores dene intermediate hollow sided stumps, seen in transverse section at 00 (Fig. 2-c) which stumps integrally unite the rim 84, and the ange 85 which is assembled rigidly With the companion flange 80, by the screws 03, as previously described.

Supported in this composite cage structure are a plurality of composite planets comprising right hand pinions 92, having extending journal shafts S34-96, to the latter of which is fitted a second pinion 98. This latter pinion is clamped for unitary rotation with the pinion 02 by means of nuts |00, distance pieces l02 and spacer washers |04. The pinions 98 engage with a ring gear |06 splined into a housing lll to comprise the fixed member of the differential planetary gear. The housing 108 has bars H0 (also seen in section Z-a) integral with a flange H2 by which the gear housing is secured to the motor fiange I4 by long tubular nuts H4. The housing is provided With a cover Il6 to enclose the brush gear and with a gear housing H8 which supports the outboard bearing l0 previously described.

The operation of the starter is as follows: As soon as the motor is energized it drives the gear 32 through the spline connection at the hub 30 and this gear in'turn causes the pinions to planetize with the cage 86-04. The fixed annular gear |06 has a slight differential in tooth member relative to the driven gear l2 which is, accordingly, rotated at reduced speed, driving the main shaft '54 through the flange 6B and with it the ratchet jaw 52; these parts comprising the low speed, high torque elements of the starter. Simultaneously with energization of the motor,

'the armature shaft is moved leftward by the offset disposition of the armature, under the magnetic pull from the motor field l0, establishing axial contact with the standard three-tooth jaw 44 with the engine jaw 4S. It will be seen that 'these jaws afford a possible one-third of a turn rotational backlash which, in the case of a typical reduction ratiol of to 1, corresponds to 40 turns of the motor armature, during which it is free, in conventional starters, to accelerate under no-load, which would produce destructive impacts due to the flywheel effect of the high speed motor armature. However, the starter jaw 44 is at all times lightly urged to rotate with the sleeve member 3S (already described as rigid with the armature) by the friction cuff 38, and will so rotate until arrested by complete rotational engagement of the jaws 44-46; this overrunning of the jaw 44 being permitted by the ratchet teeth 43 which take up the starting drive at slow speed from the gearing the instant the jaw 44 is so arrested.

It will also be seen that by the novel disposition here disclosed the reduction gearing is disposed at the rear-end of the starter where it is more accessible and where there is, in general, more room on current engines than at the conventional disposition next to the mounting flange. It will also be seen that, by the novel planet cage disposition of this invention, it is possible to accommodate a very large number of planet pinions meshecl with a central gear whereby the capacity of the gear may be increased and/or its diameter reduced.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. In an engine starter organization, a casing having an inner end portion of substantially less diameter than the outer end portion thereof, said inner end portion being adapted for attachment to the engine, an engine-engaging jaw, a low speed drive shaft organized for unitary rotation with said jaw, said drive shaft being substantially coextensive in length with the overall length of said casing, an armature rotatable on said shaft within the small diameter inner end portion of said casing, and reduction gearing drivably connecting said shaft and armature, said reduction gearing having an overall diameter greater than that of said armature and being wholly confined within the larger diameter outer end portion of said casing.

2. In an engine starter organization, a casing having an inner end portion and an outer end portion, said two portions being adapted for attachment one to the other, and said inner end portion having an overall diameter substantially less than the corresponding diameter of said outer end portion whereby the latter is adapted to overhang the circle of bolt holes through which the bolts for attaching the starter toI the engine extend, an engine-engaging jaw, a low speed shaft organized for unitary rotation with said jaw, said shaft being substantially coextensive in length with the overall length of said casing and being mounted concentrically therewithin, an armature rotatable upon said shaft,

said armature being confined within the smaller ROLAND CHILTON.

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