US2205333A - Engine starting mechanism - Google Patents

Description

. H. BAER ENGINE STARTING MEGHANISM FiledJune l0, 1957 mvENToR. Hon/ard .Ba r- June 18,1940

l Patented June 18, 1940 UNITED ySTATES PATENT OFFICE ENGINE Y STARTING MECHANISM Howard Baer, Jersey City, N. J., assignor to Eclipse `Aviation 'Col-poration, E ast Orange, N. J., a corporation of New Jersey,

Application June 10, 1937, Serial No. 147,570

2' Claims.

`l novel means for converting an axially directed 'pressure into a rotation producing force whereby the axial4 movement of the driving member is translated to the engine cranking member.

A further object of the invention is to provide l a novel starting mechanism ofthe type employing a plurality of power actuated Ypistons one of which operates to produce engagement .between the starting mechanism and a member of the engine to be started, and the other of whichj operates to impart a cranking torque to the engine engaging member.

l Another object of the invention is toY provide a multiple power member starter ofthe foregoing character which makes it possible, by the 25 use of a novel construction, to obtain a quicker and more certain inter-engagement between the4 teeth of the engine engaging member and the engaged member of the engine, prior vto any appreciable axial movementof the larger of the 80 two power actuated pistons above referred to.,

A further'` object is to combine' the double screw teaching of Adolf Knig, in his German Patent No. 444,546, with the above described multiple piston concept of operation= 85 Other objects and advantages to be derived from the vuse of rthe invention reside in the l combination and interspecific construction, relation of parts whereby a compact,- emcient and easily operated and maintained unit is produced, all of which objects vand advantages will appear more clearly upon an inspection of the following specification, with reference to the accompanying drawing illustrating the preferred embodiment of the invention. It is to be expressly understood however, that the said drawing is for the purpose of illustration only and is not to be construed as a deiinition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawing, wherein like-reference characters refer to like parts throughout the several views:

Fig. 1 is a longitudinal axial section through a device embodying the invention; p

Fig. 2 is a slightly reduced end view partly in -.of a triple section intermediate transmission purpose threaded sections I9 and 20 receive balls section, and taken along line 2-2 of Fig. 1; and 3 is a fragmentary view along the inner assembly of Figl.

With reference to the drawing, and more particularly to Fig. 1, the piston actuated unit is contained within a sectional housing including cy.

lindrical parts I1 and I0, the latter having a flange I2 by which it is secured to the engine crankcase I3 as by bolts I4, theflange being conveniently of a size standardized for aircraft engine starters. .The engine crankshaft, or other drive shaft (not shown) is provided with a clutch element II engageable by the piston actuated clutch element scribed.

Cylinder I1 has a cup-shaped head I8, with a cylindrical portion lily to receive piston 23, said portion I9 being externally threaded to coact with a correspondingly internally threaded section I5 as will be later mo/re'fully de- 20 member A consisting of parts 20, 2| and24. A

second screw 22 is'drivably connected with the threaded section 24 by helical grooves or threads 29 and 3l which permit the axial travel of the piston 23 but cause rotation of the screw 22 because of friction reducing balls 36 assembled in cage 35 and inserted in the helical grooves 29 and 3|, stops 28a and 28h serving to limit the endwise movement of the cage. For a similar 6 .of a similarca'ge .'I, retained within its limits of movement by stops 8 and 9, corresponding to stops 28a and 2Iib, respectively.

, An anti-friction thrust bearing 32 is preferably interposed between a flanged skirt 34 on `the rear end of a spacer member (34h) and an inwardly extending circular portion 33 of the body I0, the said bearing 32 acting to take the axial thrust to which the inwardly extending rim 34a, on the forward end of the spacer member, is subjected. A spring 3l has one end resting against the closure plate I6 of the cylinder l1, and its opposite end abuts the thrust ring 38, which in effect, through the sleeve 24, abuts the outer ,race 39 o f a ball-bearing assembly 40 axially movable with but rotatably free of the piston 23, the intervening bearing balls. 40 facilitating free rotation of outer race 39 of the bearing, while the thrust ring 38 being possibly constrained to rotation by the natural twisting tendency of a spring such as the spring 31, as the latter is compressed in the forward travel of ths piston. Piston rings 4I insure against the loss of pressure as the pistonmoves forward,

Iandalso yieldably oppose any tendency towards rotation of the piston.

-engagement with the engine member II.

Due to the bolted split clamp connection 42 between the cylinder I1 and the body flange Illa, the former may be quickly detached for removing any fouling that may occur where combustible cartridges-are used as the source of fluid pressure to move the piston 23.

The present invention, as above indicated, includes improved means for automatically controlling both the meshing of parts I5 and II,

and the exhaust of the fluid pressure from the cylinder upon completion of the cranking operation. This combined meshing and exhaust control may be effected by providing a path along which fthe pressure fluid may, flow to act directly and immediately upon the head portion 22a of the sleeve 22 whereby said sleeve 22 may move axially forward prior toand independently of the beginning of axial movement of the main piston 23, as is explained more fully hereinafterthe said head portion 22a-of the sleeve 22 thus constituting,- in effect, a separate piston with exposed surface area greater than the initial exposed surface areas of the piston 23 and parts integrated therewith-the annular boss SI of the cylinder head serving to "block off the major' annular chamber 45, may instantly pass directly into along annular chamber between the rod 46 and the4 tube 41, which constitutes a centrally disposed extension of the piston 23, to which piston the flanged rear end of the tube 41 is connected by suitable screws 48 ,or equivalent means, as illustrated; the 4forward end of the annular chamber thus formed having communication with the bore of the sleeve 22 by virtue of the area surrounding radial projections 43 formed on the forward end of the rod 4 6, and also by virtue-f of the passage-way continuing i through the thickened forward portion 50 of the tube 41.l This forward Vportion 50 is`provided with sealing rings 5I which prevent seepage of fluid or -particles contained therein backwardly into the 4space surrounding the tube 41, while at the same time facilitatingand permitting free sliding movement of the tube within the bore of sleeve 22 as the piston 23 moves forward in the cylinder I3. The valve 43 is carried by the rod 46 and is of such a length that with the parts in the'positions indicated in Fig. l, a collar 52 extending inwardly of piston 23 will bear against f the fingers 44 on the valve 43. to hold said valve on the seat 53a formelfn the head 53. At the commencement of an operative cycle` of fthe motor, such as is occasioned` by the delivery of fluid pressure to the chamber 45, this fluid prissure will tend to maintain the exhaust valve 43 closed; but as the piston nearly reaches the end of its movement, the collar 52 will be brought into engagement with the projections 4.3 'to unseat the exhaust valve 43. 4In this connection the central opening in collar 52 is so formed as to provide a plurality of corresponding inwardly extending projections or fingers for abutment with vthe radial projections 49 of the rod 46 as' the piston 23 approaches the end of its stroke, while at the same time this construction permits constant clearance between the said collar 52 and the rod 46 (asI shown clearly in Fig. 1) whereby the pressure uid is always free to pass between the chamber 45 and the bore of sleeve 22, passage being ilrst from chamber 45 to the bore 22 (at the beginning of the cycle of operations) and subsequently in the reverse direction to allow the pressure fluid to be exhausted in responseto the opening of the exhaust valve 43-that is, its removal from'jits s'eat in the housing 53-by the engagement of the collar 52 with the projections 49 at the end of the stroke of the piston 23 as above described. The exhaust valve having been thus unseated, the bead 54 thereon will engage he conical end of valve guide 55 to yieldably old` the valve in the openv position, to

, permit exhaust by way of outlet passage 51, outlet ports 58 in the cage 59, and exhaust pipe 6l.

The piston having4 completed its operative stroke, and the exhaust valve having been opened, the piston will beurged on its return stroke by the coil spring 31. f During this return movement, the exhaust valve being held open,

` the cylinder will be eifectively'scavenged. Due

to the action of the parts 54 and 55 the valve will remain open until such time as the piston collar 52 is brought to bear against the lingers 44 at the end of valve stem 43 for again seating the valve. This insures closing movement of the valve'at the time the piston has substantially completed its return movement. It is thus apparent that the exhaust means is of such construction as to remain' openduring the major portion of the return stroke of the piston so as to insure substantially complete scavenging. In order to permit the movement of the sleeve 22;- for the purpose of meshing the parts I5 and II independently of the movement of the piston- 23-without at the same time creating too severe an axial thrust on the driving sleeve 24 with which the said driven sleeve 22is threadedly engaged, the ball-cage assembly is preferably of a length somewhat less than the distance between retainer rings 28h and 28a whereby forward movement of thesl'eeve 224 to ythe extent necessary to induce complete mesh between parts I5 and I I occurs prior toA taking'up o f the thread-clearance between the end-balls 36 on the one hand, and the retainer rings 28h and 28a on` the other.

If during this meshing movement a collision should occur between the corners of the teeth of the two parts. I5 and Il thus temporarily interfering with full engagement thereof the piston 22a and sleeve 22 will nevertheless continue to move axialllforward in response to the urgeof the pressure-fluid which has entered its bore by way of the communicating passage-ways above described, such continued forward movement of the piston 22a beingpossible because of the clear ance between the forward end of the said piston and the jaw I5 to which the forward end is splined as indicated at 56, the spring 42a also being sufficiently compressible to permit such relative axial movement. During this relative axial movement a certain amount of rotary movement reverse to the rotary movement ofthe cranking will alsooccurdue to the effect of the relatively stationary threads 3I of -the outer" sleeve 24 upon thoseof the sl'eeve 22 and such rotary movement will therefore relieve the condition of cornered tooth contact, whereupon spring v42a will expand from its compressed condition and thereby press the jaw member I5 into full' threaded extension I9 ofthe cylinder head I8.

'This threaded extension i9 therefore corresponds to the threaded extension "r of the Knig patent, in`that it remains in the rear of the -piston 23 as the pistn advances (as is also true of Knigs part r) rather than being disposed in advance of the piston at all times, as in certain other devices nowin use. 0n the other hand it diflers'from Knig in the sense that it permits the use of a more nearly solid piston surface area.

In order to secure the increased amount of rotation referred to in the preceding paragraph, the helical grooves in section 20 of the member A are pitched in the opposite direction from those of section 2 4; the elements I9 and 22 being threaded to correspond'to the helical grooves or threads of sections 20 and 24, respectively.

What is claimed is:

l. In a motor, the combination with an externally -threaded cylindrical element, fixed ,against rotation and provided with a smooth inner surface, of rotatable driven means, and means .for driving said rotatable driven means, said driving means including a piston movable along the smooth inner surface of said fixed cylindrical element, a part threadedly engageable i,

with the threaded outer surface of said iixed cylindrical element, and means including a member moved by the piston and integrated with said last-named `.part for causing the vlongitudinal movement of 'said piston to be translated into a rotary movement of said driven means.

2. In a motor, rotatable driven means, longitudinally moving driving means having an annular pocket therein, said driving means also having helical grooves along' one side of said annular pocket, a plurality of balls `disposed in said helical grooves, means including a stationary `means to rotate as the latter moves longitudinally, and means .for transmitting said rotation to the driven means at an increased rate of speed.

HOWARD BAER.

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