Dec. 24, 1946. _H. D. HOEKSTRA 2,413,045 ‘ ENGINE STARTING MECHANISM Filed Feb. i9, 1941 3 Sheets-Sheet l 77 Y@ Z8 [Il \\\\\\ \ ` Ültmnuf îàI‘c. 24, 1946. H. D. HOEKSTRA . 2,413,045 ENGINE STARTING MECHANISM _ Filed Feb. 19, 1941 . 32 2 Wp?. ¿_? ' ' 5 Sheets-Sheet 2 '52g- r== A Y: l Z0 Y* _ ._ _ #____w 1MM» ä: 1 Dec.v24, 1946. 2,413,045 H. D. HOEKSTRA ÉNGINE STARTING MECHAN I SM Filed Feb. 19, 1941 - 3 Sheets-Sheet 3 Haro/Zd «DHoe/rS/?rcf, Ml i ¿ ¿___ ¿wel v 2,413,045 Patented Dec. 24, 1946 UNITED STATESÃ PATENT V OFFICE l 2,413,045l ' 4 ` ' v ‘ - - _ f ENGINE STARTING MECHANISM Harold D. Hoekstra, Rockville, Md. Application February 19, 1941, Serial No. 379,705 1 claim. (o1. 18s-_39) 1 er of the spring motor type adapted for use in cranking internal combustion engines of the air plane type. _ “An object of my invention is to provide a start er of this type which will be light weight, simple, 2 Fig. 7 is a fragmentary sectional view of the starter, showing to advantage the clutch with the rollers omitted; Fig. 8 is a sectional view taken on the line 8-8 of Fig. ’7, looking in the direction of the arrows, showing the clutch with rollers mounted in clutch My invention relates in general to engine starting mechanisms and in particular-to a start _ cage. » Fig. 9 is a fragmentary elevational view of the and inexpensive, being particularly adapted for starting motor drive shaft; use with low and medium powered aircraft. ’ Fig. 10 isla fragmentary sectional view of a modiñed form of clutch, for use in the present Another object is to provide a starter of this type in which a varying amount of energy may invention, the rollers being omitted. be stored (at a rapid or slow rate) ' and which Fig. 11 is a sectional View taken onV the line energy may be expended as' desired by the oper ll--H of Fig. 10, looking in the direction of the arrows, showing thismodiiied form of clutch in _end elevation, Fig. 12 is a fragmentary detail sectional view >taken. on the >une |2-a 2 of Fig. 11, poking in ' ator. It is also the object of this invention to provide a starter which canot be wound to an- ex cessive degree either by the operator, or by an engine back-nre. -the direction of the arrows, showing to advantage Still another object of my invention is to pro vide a novel release and clutching means -which _ the modified form of roller, the latter being shown in side elevation, and _ will insure ready release and positive clutching Fig. 13 is an elevational view of a tooth frag action and which will be free-running with no ment of the worm showing a conventional form 0I" rubbing action when disengaged. thread superimposed Íthereon, in dotted lines, A further object of this invention is 'to provide 25 pressure and pitch lines being also illustrated means whereby the eiiicient and desireable com- i .i _ thereon. pression type spring with its rectilinear motion In order to villustrate the application of my may be utilized to secure rotary motion. invention I have shown in Fig. 1 a fragment of Another object of this invention is to provide safety means to harmlessly dissipate the stored an airplane engine I5 and its crankshaft IS, a pilot’s seat I1, and an engine starting mecha energy in the starter in the event of clutch failure _ 30 `nism, generally designated I8. The engine start or inadvertent release. Other objects of the invention will be mani fest from the following description of the pre ferred form of the invention, taken in connec tion with the accompanying drawings, wherein Fig. 1 is a side elevational view of an airplane engine starter constructed in accordance with the present invention, illustrating its application to an engine, the latter being fragmentarily shown; Fig. 2 is a longitudinal sectional View of the starter motor, portions thereof being broken away to disclose details; Fig. 3 is an end elevational View of the starter ing mechanism is operatively connected to the crankshaft i6, said starting mechanism being fastened or secured tothe engine block by bolts 35 I9. Y My engine starting mechanism comprises a cylindrical shell 2B one end of which is closed, the opposite end being equipped with a housing 2 I, which latter, in'conjunction with the shell 20, provides a casing for details of the starter mecha nism hereinafter described.A These details in clude a shaft 22 which extends axially through said shell and housing and has formed on the engine end an inner race 23 of a roller clutch. vOn the shaft 22 a coarse pitch multiple thread .45 being fragmentarily shown; 24 is provided and mating therewith a large Fig. 4 is a top plan View of a starter made in diameter iianged nut 25. Formed on twosides accordance with my invention, the starter motor of nut 25 are grooves 26 which mate with splines being fragmentarily shown; _ ‘ ,2l formed in the shell 20 to prevent rotation of Fig. 5 is a fragmentary side elevational view of my starter showing in detail portions v`of Athe 50 nut 25 while allowing _translational movement motor, and associated appurtenances, the latter “wind-up” mechanism; _ _ Fig. 6 is a sectional view taken on line ß-S of Fig. 5 looking in the direction of the arrows, showing the motor casing engaging spring in `,side elevation; thereof along the longitudinal axis of the hous ing. Compression springs 28 and 29, coaxial with shaft 22, react against the housing 2| and nut 25 and serve to store energy when nut 25 is dis placed towards the engine end of >starter mecha 2,413,045 3 4 nism, Bearing 3B carries the thrust load from shaft 22 into housing 2|. Fixedly attached to Starting is accomplished by depressing the starting pedal 51 in Fig. 1`Which operates cable shaft 22 is worm wheel 3| which reacts with a worm 32 attached to shaft 33 as shown to advan 58 and pulls down lever 59. Lever 59 is rotatably attached to bolt 43' by means of boss 44. Formed vin lever 59, is slot 60 which mates with pin 6| anchored in housing 35. Spring 62 tends to ro tate the lever 59 in a direction opposite to that tage in Fig. 3. Shaft 33 is carried by a bearing 34 formed in a drum housing 35. Worm 32 and shaft 33 are rotatable, in one direction only, by the drum 3S of a drum housing 35 through a con produced by tension in cable 58 and acts to pre ventionalratchet and pawl mechanism 31 and vent unintentional release of the starting mecha 38 respectively. The pawls are engaged, for 1a 10 nism. Clutch engaging spring 63 is attached to manifest purpose, by springs 39 as shown to ad lever 59 and through a portion of the travel of vantage in Fig. 5. Worm 32 and shaft 33 are ro- . lever 59 bears upon button 53 depressing the tated in a direction to cause rotation of worm same. As the button 53 is depressed, it operates wheel 3| in the “wind” direction as shown by the to advance the clutch rod 52 and places the clutch arrow in Fig. 3 by means of cable 40 passing in an operative position and at the same time around drum 36. Cable 40 is trained around pul lever 59, by means of pin 6|' and slot 60, disen ley 4| and passes into the cabin or’cockpit ofthe `gages the worm 32 from the worm wheel 3| airplane and is there attached to handle 42. The thereby allowing the springs to utilize the stored handle 42 is positioned adjacent the seat -|1 for energy and rotate the engine to be started. convenient; accessibility to the pilot for winding 20 In the event that the starter springs have been partially or fully compressed and the lever 59 is the motor of the starter mechanism, as shown in Fig. 1. The return rotation of drum 36 is ac operated while the engine is running or if there complished by means of a torsion' spring 43, the is clutch slippage, the stored energy in springs 28 two ends of which are anchored in housing 35 and 29 cannot be utilized in the usual manner and drum 36 respectively. The worm and hous and must be dissipated in some other manner to ing assembly is rotatably mounted on bolt 43' avoid damage to the starter. This is accom which is anchored in boss 44 formed on shell 29, plished by means of a seal 64 attached to the to permit disengaging worm 32 from worm wheel flange of nut 25 thus forming an air buffer cyl 3|. inder in shell 29, as shown to advantage in Fig. 2. A basically ~conventional roller type over 30 A metering valve 65 is provided in shell 20, con running clutch, such as shown in Figs. 2, '1, and 8, sisting of an orifice setscrew 66 to permit adjust is mounted in the engine end of the starter ment of the airflow therethrough and conse mechanism. The clutch comprises an outer race quently to allow adjustment to the proper de 45 which is attached to engine I5, inner race 23, gree of buil‘lng to prevent injury to the starting and rollers 45. A novel arrangement is provided mechanism. ` to prevent the rollers contacting the outer race Preferably, as shown in Fig. 13, the threads of 45 during the over-running or disengaged period. the worm 32 and Worm wheel 3| have the meshing This consists of roller cage 41 with spring mem faces thereof rounded so that the pitch line is bers 48, pin 49, slots 50 vand 5| of the inner race substantially as indicated at X while the pressure 23 and cage 41 respectively, clutch rod 52, but 40 angle lines are as indicated at Y. This embodi ton 53, and spring 54. The rollers are kept free ment'of the invention taken with the preferred of the outer race 45, except when starting. The location of bolt 43’ in close proximity to the axial movement of clutch rod 52 is transformed extension of the pressure angle line Y, whilst into rotary motion by means of pin 49 and slot being a substantial distance from pressure angle 59 in the inner race 23. Then by means of pin .line Z, permits reversibility in the “wind” direc 49 and slot 5| in cage 41, the roller cage is ro tion, to prevent damage from reverse engine rota tated thus bringing the rollers out of engagement tion due, for-example, to back-nre during contact with outer race 45. of worm Wheel 3| and Worm 32 because of sud den release of pedal 51 immediately after start Another type of over-running clutch which has been found to work very satisfactorily is shown 50 ing. It will be readily seen that the tendency of in Figs. 10, l1 and 12 wherein conical rollers 46’ worm wheel 3| to rotate in the “start” direction are employed and react between the inner race shown on Figure 3 Will, due to the shape of the 23’ and the conical outer race 45’. This type of meshing teeth on both worm wheel 3| and worm over-running clutch permits direct axial move 32,'eXert a force substantially along the line Y ment of clutch rod 52 to engage or disengage. C71 Cil of Figure 13. Since by specification bolt 43’ is in The operation of the starting mechanism is as close proximity to line Y extended, there is no follows: To’store energy or to wind-up the starter appreciable tendency for the worm and drum motor, the pilot or operator pulls handle 42 and assembly and the housing 35 in which they are cable 49 rotates drum 36 and the worm 32 -Which mounted to pivot about bolt 43’. Hence the teeth in turn rotates worm Wheel 3| in the direction of 60 will remain in mesh and the system may be con the “wind-up” arrow shown in Fig. 3.. Rotation sidered irreversible. However, rotation of Worm of the worm wheel 3| turns the threaded shaft 22 wheel 3| in the “wind” direction applies force to and nut 25 is moved in a direction to compress the worm 32 along a line normal to the mating springs Y28 »and 29. Storage of energy in the teeth faces subjected to the force and hence dis springs can be stopped at any point desired and placing the Worm 32 out of contact with worm it "is impossible-to compress springs 28 and 29 to wheel >3| by pivoting of housing 35 and its as an excessive degree through manual energy sembled components about bolt 43’. Hence, in storage or through back-fire since the nut 25 this direction the system is reversible. As is well travels oif the- threads of shaft 22 when a pre known to those versed in the art, spring 54, determined compression value is reached, 'as' though it will tend to disengage the Vclutch upon shown at 55 in Fig. 2. The ends of the threads on release of pedal 51, will not normally have suin cient force to overcome clutch friction and hence shaft 22 and in nut 25 may beA rounded, as at 55 in-Fig. 2, to avoid a “dead center” position, when the above described worm reversibility is neces vthe starter is fully wound, thus'insuring positive, quick release for starting. sary. It is to be understood that various changes may 2,413,045 5 6 be made in the details of construction, proportion and arrangement of parts Within the scope of the claim hereto appended. What is claimed is: said Worm wheel and located in close proximity to the projection of a line passing through the pitch circle of the said worm Wheel normal to the teeth faces having the lesser pressure angle and A spring motor, means to store energy in the mo tor including a worm and Worm wheel, the teeth of the said Worm and Worm Wheel having faces on at the point of Worm and Worm Wheel contact so as to permit relative translation between said Worm and worm Wheel substantially parallel to one pair of mating tooth faces and at an appre one side inclined at a greater pressure angle than ciable angle to the adjacent pair of mating tooth the faces on the opposite side of the said teeth, the said Worm being pivotally mounted with the 10 faces. pivot axis substantially parallel to the axis of the HAROLD D. HOEKSTRA.