US2395411A - Propeller handling mechanism - Google Patents

Description

Feb. 26, 19 46. 5 KITTEL 2,395,411

PROPELLER HANDLING MECHANISM Filed NOV. 10, 1943 4 Sheets-Sheet 1 I I 3 47 42 I 95 ,39 a Q Feb. 26, 1946. H. s. KITTEL PROPELLER HANDLING MECHANISM Filed Nov. 10, 1943 4 Sheets-Sheet 3 InfillII/IllllllIt!IIIllllI/IlIlIII/llllllllllllll III I! llllllllllI/IlllllIlII/IlillIY/l Feb. 26, 1946. H. s.- KlTTEL PROPELLER HANDLING MECHANISM Filed Nov. 10, 1945 4 Sheets-Sheet 4 I. a Y

NEH:

Patented Feb. 26, 1946 PROPELLER HANDLING MECHANISM Howard S. Kittel. Fort Worth, Tex., minor to Consolidated Vultee Aircraft Corporation, San Diego, Calif., a corporation of Delaware Application November 10, 1943, Serial No. 509,715

12 Claims.

The invention relates to apparatus for positioning aircraft propellers for coupling them to propeller shafts.

The propeller shaft in an airplane in a shop or hangar where overhaul or repairs are made or where airplanes are assembled is usually positioned at a considerable elevation above the floor. Heretofore it has been the usual practice to hoist propellers from the floor to the level of the propeller shaft in the airplane by an overhead crane with the propeller suspended from a hook. The work involved in positioning the propeller into axial alignment with the shaft was difficult and slow and required several or a group of workmen in manipulating the suspended propeller into correct position for sliding the propeller hub onto the propeller shaft because of the difi.lculties in controlling movements of the propeller while it is suspended from the crane.

One object of the invention is to provide apparatus by which the work involved in positioning an aircraft propeller into position to be slipped onto its drive shaft in the airplane will be expedited and lessened through means for positively controlling the vertical and lateral movements of the propeller.

Another object of the invention is to provide apparatus which makes it possible for a single workman to position the propeller and includes power-operated hoisting and shifting mechanism which facilitates the mounting and demountlng of the propeller.

Another object of the invention is to provide compact lifting apparatus for the propeller, which has a suflicient range of movement above the floor for elevating the propeller into position for coupling it to its drive shaft in the airplane and which comprises slidably and telescopically connected standards which are successively shlftable by power driven gear mechanism for cumulating the movements of the standards.

Another object of the invention is to provide a apparatus which is efficient in operation, simple I in construction, and greatly expedites the time required in mounting and demounting the propellers.

Other objects of the invention will appear from the detail description.

The invention consists in the several novel features which are hereinafter set forth and more particularly defined by claims at the conclusion hereof.

In the drawings: Fig. 1 is a side elevation of apparatus embody,- ing the invention, the propeller being elevated and in axial alignment with the drive shaft in readiness for sliding the propeller on the shaft.

Fig. 2 is a plan, parts being broken away.

Fig. 3 is a perspective of the retaining device for the propeller and its immediate support.

Fig. 4 is a detail section of onepf the tubular members of the supporting frame on which the lifting mechanism is mounted.

Fig. 5 is a vertical section through the column on the supporting frame with the slidable tele scopic standards of the shifting mechanism in their lowered positions.

Fig. 5 is a vertical section showing the position of the lifting racks while they are engaged with their respective pinions during a lifting operation.

Fig. 6 is a view similar to Fig. 5, the slidable telescopic standards being shown in partly elevated positions,

Fig; '7 is a vertical section taken on line l-l of Fig. '1.

Fig. 8 is a section taken online 8-8 of Fig. 7.

Fig. 9 is a section taken on line 9-9 of Fig. 6.

Fig. 10 is a perspective illustrating the latch for holding the lower slidable standard of the lifting mechanism in its lowered position while the other slidable standard is being independently shifted.

Fig. 11 is a vertical section taken on line I i-i i of Fi 9.

Fig. 12 is a horizontal section taken on line I2-i2 of Fig. 9.

Fig. 13 is a horizontal section taken on line l3i3of Fig. 9. v

Fig. 14 is a horizontal section taken on line i l-i4 of Fig.9.

Fig. 15 is a plan view, parts being broken. away, illustrating the latch for locking the lower slidable standard in its lowered position, and the retracting spring for the latch.

The apparatus is supported by a portable frame so that it can be quickly wheeled from any loadreceiving point over the floor to a position below and in front of the propeller shaft in the airplane. This frame is built up of three radially arranged tubular members 20, the inner ends of which are butt welded together. Members 20 are also rigidly secured together by a triangular plate 2| which is welded to the top of said members. Tubular sections 23 are slidably and tele- .able supporting frame or carriage composed of members which are adapted to be extended to spread the casters 24 sufficiently to adequately support the lifting mechanism against being tilted by the oil-center weight of the propeller and to permit the extension members to be moved together when desired for storage purposes, for clearing parts of apparatus on the shop floor, or for adjusting the spread of the casters for propellers of different weights. A tubular mast 28 has its lower end rigidly secured, for. example by welding, to the plate 2|.

A cradle is provided for retaining a propeller and is adapted to be raised and lowered by the lifting mechanism hereinafter described to bring the axis of the propeller to or from the axis of the propeller shaft. The cradle comprises a shelf 30 upon which the hub a of the propeller is' adapted to rest, a yoke 32 adapted to straddle one of the blades a of the propeller, and a bracket 29 to which said shelf and yoke are rigidly secured by welding. A flange or abutment 3| is provided at the outer end of shelf 30 to hold the hub on the shelf. The shelf 38 and abutment 3| are coveredwith a lining 33 of cushioning material, such as rubber or neoprene, and the inner face of yoke 32 is provided with a lining 34 of similar material to reduce the possibility of injury to the propeller. A strap 35 which is adapted to extend through notches 35 in the yoke 32 and around one of the blades of the propeller and around the inner side of bracket 29 is adapted to firmly secure and? position the propeller in the cradle. The form of the cradle may be modified for propellers of different constructions. The bracket 29 of the cradle is supported by a forked bracket 38 and is pivotally connected thereto so the cradle can swing horizontally relativ ly to bracket 36 by a pin or rod 31 which extends through overlapping lugson the upper and lower ends of said brackets. A pin 38 which is slidable through the upper lug of bracket 29 is adapted to enter a hole in the upper lug of bracket 36 to lock the cradle against horizontal swinging movement relatively to the bracket 36.

The cradle is supported for vertical movement by the lifting mechanism hereinafter described to bring the propeller retained therein to the elevation of the propeller shaft on the airplane and is horizontally and rectilinearly movable to permit the hub of the propeller to be coupled to and removed from the propeller shaft. The propeller shaft and the hub of the propeller are usually provided with interfit'ting splines for driving the propeller from the shaft. A horizontally extending tubular member 42 is vertically shiftable-by the lifting mechanism. A shaft 38 has one of its ends rigidly secured, as by welding, to the bracket 36 which supports the cradle and extends longitudinally through bushings 40, 4| in the end portions of tubular member 42 for sul porting the cradle for horizontal movement in coupling the propeller hub to the propeller shaft. A stop 39 is formed on the inner end of shaft 39 to limit the movement of the cradle away from, and the movement of shaft 39 in, the tubular member 42.

A device for manually sliding the shaft 39 in the tubular member 42 and horizontally shifting the cradle comprises a. gear rack 43 which is welded to shaft 39, a gear 46 housed in an extension of tubular member 42 and meshing with rack 43, a cross-shaft 44 journaled in the sides of said extension, and a crank 41 on the outer end of shaft 44 and at one side of the tubular member 42. By manually rotating the crank 41 and gear 46, rack 43 and shaft 39 will be shifted horizontally and rectilinearly for slid' ing the hub to or onto or off the propeller shaft. The rack 43 extends through a slot in bushing 4| which has sufllcient clearance for the rack 43 to permit the slight rotation of the propeller hub necessary to bring the splines on the hub and propeller shaft into position to slide into interfitting relation. In practice a staging or platform d, which may be portable,-is usually provided at a suitable elevation for a workman while coupling or uncoupling the propeller and the shaft.

The lifting mechanism for raising and lowering the cradle and the propeller retained therein comprises a tubular standard 50 which is telescopically slidable in the tubular column 28 which is fixed to the portable supporting frame, a tu- 40 bular standard 5| which is telescopically slidable in the tubular standard 58, and a tubular member 52 which is telescopically slidable in the upper end of tubular standard 5| and has its upper endwelded to the horizontal tubular member 42. The tubular standard 58 is slidable in column 28 and the standard 5| is slidable in standard 50 for cumulating their vertical movements to increase therange of lift of the propeller sufiiciently for raising the propeller from near floor level to the propeller shaft in the airplane.

A gear rack 55 is fixedly secured, as by weldins, to one side of the tubular standard 58. The tubular column 28 is provided with a vertical slot 28" in which'rack 55 is vertically slidable and the slot is bridged and closed by a channel bar 28. A rack 66 is welded .to the tubular standard 5|. Standard 58 is provided with a slot 5|] for the vertical movement of rack 66 and column 28 is provided with a second slot 28 for the vertical movement of rack '66 in said column. Racks 55 and 66 are disposed on diametrically opposite sides of the standards 50, 5| so that they may be independently shifted by pinions 56 and 51.

Pinions 56 and 51 are simultaneously driven from a common source of power, such as a reversible electric motor. When the standards 50, 5|

are lowered as illustrated in Fig. 5, pinion 61 will mesh with rack 86, while pinion 56 is clear from rack 55, for raising the standard 5| while the standard 50 remains in its lowered position. When the standard 5| and rack 65 are elevated to a predetermined point, standard 50 will be locked to the standard 5| by a device hereinafter described. so that rack 55 will be raised and pass into mesh with pinion 88 before the rack '88 is disengaged from pinion 81. Pinion 88 will then raise rack 85 and standard 88 for raising the standard 5| while said standards are locked together so that cumulative lifting movement will be imparted to standard 5| by the successive lifting of the racks 68 and 55. After the pinion 88 commences to lift rack 55, rack 68 will pass out a ement with pinion '81 so that continued movement of standard 50 will also lift standard This exemplifies lifting mechanism comprising a pair of telescopically connected standards which are slidable relatively to each other and in the column 28 and which are operable to cumulate the movements of the standards for lifting the propeller the necessary distance from near floor level to the propeller shaft in the airplane.

The mechanism for driving both of the pinions 58 and 81 from reversible electric motor 84 comprises speed reducing gearing 84 coupled to said motor, an output sprocket 83, a sprocket chain 82 driven by sprocket 83, a sprocket wheel 8| mounted on a shaft Bll, and a gear 58 fixed to rotate with sprocket 8|. The pinion 58 for shifting rack 55 onthe lower standard 58 is driven from gear 59 by a gear 89 which meshes with gear 58 and is connected to drive pinion 88. The pinion 61 for shifting rack '88 and the upper standard 51 is driven by an idler gear 81 which meshes with gear 59 and a gear 58 which meshes with idler 51 and is connected to drive pinion 81. Pinions E8 and 81 are driven in opposite directions. Motor 54 and gearing 84 are mounted upon a plate Iii which is secured on beams which are secured to the plate 2| of the portable supporting frame. A suitable housing 12 encloses the gearing for driving the plnions 58 and '68 and the latter are enclosed by an extension 13 of housing 12. Pinions 58 and 81 are supported by shafts which are carried by the walls of housing 12- and its extension 18. Shaft 58 and the shaft for idler gear 51 are supported by the inner wall of housing 12.

A suitable switching device e is mounted on the column 28 for controlling the operation of the reversible motor 54 for raising the liftin mechanism to raise the propeller and for lowering the lifting mechanism to lower the propeller. This switching device may include suitable limit switches for automatically stopping the operationof the motor at the end of predetermined lifting and lowering strokes, as well understood in the art.

The locking device for securing the standard iii to the standard 58 for conjoint vertical movement comprises a pair of pins 15 (Fig. 9) which are slidably mounted in a. cross-sleeve fixed in standard 5t, and are pressed outwardly by a spring 18, and are adapted to pass into holes 11 in the tubular standard 50. The ends of the pins 15 are inclined so they will be cammed inwardly by the upper end of the column 28 during the conjoint lowering movement of standards 58 and 5|. Stops 15 on pins 15 limit the outward movement of pins 15. After the pins 15 have been retracted during the lowering movement of the standards, their outer ends will slide on the inner periphery of the tubular standard 50 until the standard 5| is fully lowered in-standard 58. As

the standard 51 approaches. the upper end of the lifting stroke imparted thereto by pinion 81,

with its pinion 88 before rack 88 becomes disengaged from pinion 81. This exemplifies an automatically controlled device for locking together the standards which are slidabie in the column and relatively to each other, for imparting cumu lative movement to the standard ii.

A latching or holding device is provided for holding the lower slidable tubular standard 88 in its lowered position during the upward shift of standard it by pinion 81, until the standard is lifted by the locking device between the standards. This latching device comprises an arm 18 which is pivoted at 18 to the top of the housing-extension 13 and is normally held into the path of the upper end of the tubular standard 50 by spring Si in the extension 18 of the housing 12. A pin and slot 82 between. the arm 18 and the top of extension 13 limit the inward movement of the latch by the spring 8! so that the curved end 84 of arm 18 will lap the upper edge of standard 58 when the latter is in its lowermost position. A cam 85 on one side of and adjacent the lowerend of the rack 88 on standard BI is adapted to shift arm 18 to release the standard 88 for upward movement before the locking-pins 18 enter the holes 11 in the standard pling them together, great accuracy is required which cannot be readily achieved by power driven gearing for the lifting mechanism. The invention provides a hydraulic device for accurately and vertically positioning the propeller retained in the cradle on the tubular member 42. This device comprises a vertical cylinder 81 which is fixed, andhas its lower end secured by a pin 88. in the tubular standard ii, a piston or plunger 88 which is slidable and rotatable in the cylinder 81 and is fixedly secured for vertical movement and rotation to a head 88 which is screw threaded into the lower end of tubular standard 52. A hydraulic pump 8| is secured at 82 on the top of tubular member 42 and its casing is connected by a flexible pipe 93 to the head 88 for the flow of fluid under pressure between the pump casing and the cylinder 81. The pump is provided with a handle or lever 98 which is pivoted at 88 to the pump casing, connected to the stem 81 of a piston in said casing. and adapted to force fluid through the pipe 98, head 80 and the duct 84 in piston 89 into the lower end of cylinder 81 for micrometrically and vertically lifting piston 88, the hollow standard 52 to which the member 42 is secured, and the propeller retained in the cradle which is supported by said member 42. This pump usually comprises a suitable valve through which fluid may be by-passed from cylinder 81 through pipe 88 to the casing of pump 8!, said valve being controlled by handle 88. This pump may be of standard construction used for hy-' draulic power. By imparting strokes to the lever 95, fluid in small and accurately controlled volume may be forced into the cylinder 81 for micrometrically lifting the propeller to bring it into horizontal alignment with the axis of the propeller shaft. By opening the by-pass valve, fluid in the cylinder 81 may be returned to the pump casing 8| for lowering the member 42. This exemplifies a hydraulic device for accurately or micrometically shifting the propeller vertically and supplementally to the power operable gear- 4 ing of the lifting mechanism.

In practice, the positioning of the propellers can sometimes be facilitated by horizontal rotation of the cradle on the portable supporting frame. The tubular standard 52 to which the horizontal supporting member 42 is fixed, is rotatable in the standard 5| through a complete circle. The piston 59, standard 52, tubular member 42, and pump 9| are conjointly rotatable horizontally for this purpose. In some instances it also facilitates the handling of the propeller to swing the cradle horizontally relatively to the horizontal slidable shaft 39. This can be done when the pin 33 is withdrawn from bracket 35.

The operation of the apparatus in raising the propeller for positioning it adjacent the propeller shaft will be as follows: The hub of the propeller a will be placed on the shelf 33 and one of its blades a will be secured by strap 35 in the yoke 32 while the slidable standards 55 and 5| are lowered. as illustrated in Fig. 5. The portable frame may be easily wheeled to any convenient loading point to receive the propeller and then wheeled into position adjacent the airplane where the propeller, when elevated, will be at the front of the propeller shaft in the airplane. The motor 54 will then be operated under control of the switching device e to drive pinions 55 and 51 in the proper direction for raising the lifting mechanism. The pinion 51 then meshes with gear rack 55 and the pinion 55 is disengaged from rack 55. The latching arm 15' will overlie the upper end of standard 55 and prevent upward movement of said standard with the standard 5|. The rack 55 will slide the standard 5| upwardly in the standard so. Shortly before the standard 5| and rack 55 reach the limit of the upward stroke imparted thereto by the pinion 51, cam 85 on rack 55 will shift latch arm 15 to release the standard 55 for upward movement and the spring-pressed pins 15 will snap into holes 11 in standard 55 and lock standards 55 and 5| together for conjoint vertical movement. This locking occurs before the lower end of rack 55 clears the pinion 51. The initial lift of standard 55, after it is locked to standard 5| by pins 15, will engage the rack 55 with the rotating pinion 55. The pinion 55 will then continue the lifting movement of standard 55 and the-standard 5| which is locked thereto, and rack 55 on standard 5| will be disengaged from pinion 51. The continued movement of standard 55 by pinion 55 and rack 55 will conjointly lift the standards 55 and 5| for cumulative lift of the upper standard 5|. Standard 5| will then be raised sufficiently to elevate the propeller approximately to the level of the propeller shaft and the motor 54 will be stopped. The shaft 39 will usually be retracted in the tubular horizontal member 42 while the propeller is being elevated. The operator will next rotate the crank 41 and gear 45 to slide rack 43 and shaft 39 in the tubular member, 42 and toward the front end of the propeller shaft to bring the rear end of the propeller hub in close proximity to the front end of the propeller shaft. If necessary, the supporting frame may be wheeled to bring the propeller hub and propeller shaft into vertical coaxial alignment. In order to bring the axes 'of the propeller hub and propeller. shaft into accurate horizontal coaxial alignment, theoperator will impart the necessary number of strokes to pump lever 95 to force sufficient fluid into the lower end of cylinder 31 to raise piston 59, standard 52, and the horizontal tubular member 42. The propeller and cradle may then be rocked slightly as permitted by the slight clearance of shaft 35 in the groove in bushing 4| which is fixed in tubular member 42 to bring the splines on the hub and,the propeller shaft into position to be slipped into interfltting relation. Next, the operator will rotate crank 41 and gear 45 to horizontally slide rack 43 and shaft 33 in the tubular member 42 to slide the propeller onto the propeller shaft. After the propeller hub has 'been coupled to the propeller shaft, the strap 35 can be removed and the cradle lowered slightly by returning some of the fluid from cylinder 31 into the casing of pump 9| so that abutment 3| will clear the propeller hub. The cradle can then be withdrawn from the propeller. leaving the latter coupled to the propeller shaft.

The apparatus may also be used to demount the propeller from the shaft. For that purpose the lifting mechanism will be operated to its raised position and the cradle will be secured to the propeller hub on the shaft. The crank 41 can then be operated to shift the cradle hori-.-

over the upper end of said standard and hold it lowered. Before the rack 55 becomes disengaged from pinion 55, rack 55 will engage pinion 51.

Pinion 51 will then lower rack 55 in standard During this lowering movement and slightly before the standard 55 is fully lowered, the inclined ends of pins 15 will engage the upper end of column 25 and be forced inwardly so that standard 5| will be released for downward sliding movement in the standard 55, the pins being then held retracted by engagement with the inner periphery of standard 55.

The invention exemplifies apparatus for handling aircraft propellers: which makes it possible for a single operator to position a propeller for coupling it to a propeller shaft; which comprises telescopically and slidably connected standards which are successively and slidably shifted for cumulative movement of the upper standard to provide the desired range of lift for bringing the propeller from a. position near the floor to the propeller shaft on the airplane; means for accurately or micrometrically shifting the propeller for bringing the propeller and the propeller shaft in exact coaxial relation horizontally to facilitate coupling them together; means on the lifting mechanism for slidably and horizontally shifting the propeller to or from the propeller shaft; a propeller retaining cradle which is supported on the lifting mechanism to swing laterally to facilitate handling of the propeller; means for locking the standards together while one is being raised I or lowered from the other; means for locking one of the standards against sliding movement for the independent shift of the other; which greatly facilitates the positioning of the propeller relatively to the propeller shaft and its removal therefrom; and which is simple in construction and efficient in operation.

The invention is not understood as restricted to the details set forth since these may be modified within the scope of the appended claims without tdieparting from the spirit and scope of the invenscopically siidable in the standard which is slidable in the column, gear racks on opposite sides of the standards, respectively, gearing, comprising pinions, for separately and successively. engaging the racks and lifting the standards relatlvely to the column, means for lifting one of the standards for cumulative movement from the other, and a propeller support carried and shiftable by the standard'having the cumulative movement.

2. Apparatus for handling and positioning an aircraft propeller for coupling it to a propeller shaft comprising, a supporting frame, a tubular column on the frame, a tubular standard telescopically siidable in the column, a standard telescopically siidable in they'standard which is slidable in the column, gearing for separately and successively lifting the standards relatively to the column, means for lifting one of the standards for cumulative movement from the other, means for locking the standard which is slidable in the column against v rtical movement while the other standard is being shifted, and a propeller support carried and shiftable by the standard having the cumulated movement.

3. Apparatus for positioning an aircraft propeller for coupling it to a propeller shaft comprising, a supporting frame, a tubular column on the frame, a tubular standard telescopically siidable in the column, a standard telescopically siidable in the standard which is siidable in the column, gearing for separately and successively lifting the standards relatively to the column, means forlifting one of the standards for cumulative movement from the other, automatically controlled means for locking the standard which is siidable in the column against vertical movement while the other standard is being shifted, and a propeller support carried and shiftable by the standard having the cumulated movement.

4. Apparatus for handling and positioning an aircraft propeller for coupling it to a propeller shaft comprising, a supporting frame, a tubular column on the frame, a tubular standard telescopically siidable in the column, a standard telescopically siidable in the standard which is slidable in the column, gearing for separately and successively lifting the standards relatively to the column, means automatically controlled by relative movement between the standards for lifting one of the standards for cumulative movement from the other, means for locking the standard which is siidable in the standard against vertical movement while the other standard is being shifted, means for releasing said locking means by relative movement between the standards, and a propeller support carried and shiftable by the standard having the cumulated movement.

5. Apparatus for positioning an aircraft propeller for coupling it to a propeller shaft comprising, a portable supporting frame, a tubular column on the frame, a standard slidably supported for vertical movement by the column, power driven gearing for lifting the standard, a propeller support shiftable vertically with the standard, and hydraulic means between the standard and the propeller support for micrometrically lifting the support for accurately positioning the propeller relatively to a propeller shaft.

6. Apparatus for positioning an aircraft propeller for coupling it to a propeller shaft comprising, a portable supporting frame, a tubular column on the frame, a standard slidably supported for vertical movement by the column, power driven gearing for lifting the standard, a horizontally siidable propeller support, means in which the propeller support is slidably mounted and shiftable vertically with the standard, and hydraulic means between the standard and the propeller support for micrometrically lifting the support for accurately positioning it relatively to a propeller shaft.

7. Apparatus for positioning an aircraft propeller for coupling it to a propeller shaft comprising, a portable supporting frame, a tubular column on the frame, a standard slidably supported for vertical movement by the column, power driven gearing for lifting the standard, a stem slidable in the upper end of the standard, a horizontally extending tubular support on the-stem, a propeller support comprising a shaft siidable in said tubular support, a cylinder and piston in the standard and a pump carried by the horizontally means for the siidable support mounted on the frame.

9. Apparatus for positioning an aicraft propeller for coupling it to a propeller shaft comprising, a portable supporting frame, a cradle, including an under support and a yoke for straddling a portion of the propeller for retaining the prising, a portable supporting frame, a cradle,

including an under support and a yoke for straddling a portion of the propeller for retaining the propeller, a shaft for slidably supporting the cradle for horizontal movement, means for slidably shifting the shaft, a pivotal connection between the shaft and. the cradle for permitting lateral pivotal movement of the cradle relatively to the shaft, means for locking the cradle and shaft against pivotal movement, and raising and lowering means for the shaft mounted on the frame.

11. Apparatus for positioning an aircraft propeller for coupling it to a propeller shaft comprising, a portable supporting frame, lifting mechanism mounted on the frame, a standard mounted for horizontal rotation on the lifting mechanism,

. and a cradle including an under support and a propeller blade for retaining a propeller supported by and rotatable with the standard.

12. Apparatus. for positioning an aircraft propeller for coupling it to a propeller shaft comprising, a portable supporting frame, lifting mechanism mounted on the frame, a standard mounted for horizontal rotation on the lifting mechanism, a horizontal tubular member fixed on the upper end of and rotatable with the standard, a shaft slidably supported in said member, and a cradle including an under.eupport and a yoke for straddling a portion of the propeller for retaining a propeller supported by the shaft.

HOWARD S. KITTIL.

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