US2233364A - Variable pitch propeller - Google Patents

Description

I Feb. 25, 1941.. B B, GEMENY 2233x564 VAMALE 'Prrcn PROPELLER v original Filed Jan. 2o. 193e 2 sheets-sheet 1 LUM Sme/nm g am Feb. 25, 1941. B. B.v GEMENY 2,233,364

VARIABLE PITJH PROPELLEK Original Filed Jan. 20, 1936 2 Sheets-Sheet 2 lazze Gemefz Q Chaman,`

Patented Feb. 25, 1941 UNITED srt-TissA PATEIWA OFFICE' Application Jamiary zo.' 193s, serial No. 59,967

. Renewed July 20, 1940 1o claims. (o1. 17o-162),

The invention relates to improvements in automatic variable-pitch propellers, and more particularly to a propeller for air craft and one in which the pitch is automatically self adjusted .under load and operating conditions, and one in which the Weight has not been materially increased over that of a standard xed propeller. v l

Decided advantages may be gained b-y the use of variable pitch propellers but, in structures heretofore produced, such advantages have been largely offset by the necessarily increased weight, complicated operating means such as gearing and fluid pressure devices to obtain the variable pitch characteristics, and by the extreme high cost of production. Furthermore, nearly all of the Variable pitch propellers hitherto produced depend on the pilot or operator for their variable pitch control.

This application is in part a continuation of my co-pending application Serial No. 711,245, filed February y14, 1934 issued as Patent No. 2,030,903, which relates to an automatic variable pitch propeller and defines such a structure wherein the centrifugal forces otherwise tending to turn the blades during operation of the propeller are balanced out and the air forces acting on the propeller blades during their operation .are utilized and controlled to automatically vary the pitch of the propeller to obtain an eiicient angle of Aattack in direct accordance with engine speed; speed of the plane and wind velocities.

It is one of the objects of this invention to provide an automatic variable pitch multiple blade propeller having more than two blades wherein al1 of the blades are synchronized in their oo ntrol, and in which the centrifugal forces tending to turn the blades in the hub during operation of the propeller are balanced out so that the angle of attack may be automatically varied in direct response to air forces acting on the blades while the propeller is in operation.

In the co-pending application, above identified, there is described a propeller structure with av plurality of propeller lblades having the center of the air forces acting thereon during operation of the propeller so disposed with respect to the center of gravity of the blade sections as to cause a. turning movement of the blades in the hub of the propeller and re'silient means controlling the movement .of the blades under such air force, together with movable weights interconnected With the blade shanks to synchronize the blades and balance Aout centrifugal forces acting therepellers having more than two blades with similar means for balancing out centrifugal forces and with means for automatically varying the pitch of the propeller in accordance with the air forces acting on the blades.

Automatic variation of the pitch of a propeller cannot be satisfactorily obtained by utilizing the centrifugal forces acting on the blades to produce the variation. The centrifugal forces depend only on the speed of rotation of the propeller, whereas the air forces acting on the blades thereof depend on engine speed, speed ofl the 4plane and wind velocities. In carrying out the objects of this invention, the centrifugal forces, otherwise tending to turn the blades in the hub, are balanced out at all positions of the blades by properly balanced weights interconnected with the hub ends of the blades and resilient means associated with the hub ends of blades control turning movements of the blades in accordance with air forces acting onthe blades during operation of thepropeller.

The invention will become apparent to those skilled in the art from the detailed description hereinafter set forth in which reference is made to the accompanying drawings wherein like reference numerals represent the same elements throughout'the several `figures of the drawings.

In the drawings:

Fig. 1 is a `View of a four blade propeller embodying the invention showing the structure partly in elevation and partly in central longitudinal section with the movable position of control elements indicated thereon by dotted lines.

lFig. 2 is a central longitudinal section taken on lines 2-2 or 3-3 of Fig. l.

Fig. 3 is an elevation of one of the weighted connections blades with concealed parts indicated thereon by dotted lines.

Fig. 4 is a transverse sectional view taken on line 4-4 of Fig'. 2.

Fig. 5 is a view corresponding to Fig. l, showing a three bladepropeller structure. 1

Referring to Figs. l and 2, the numeral I indicates a conventional engine shaft on which the propeller 2 is mounted. The propeller consists of the blades `3 whose roots extend into the hub 4. The hub is of the split housing type consisting of two counterpart portionsA orvhalves 5 and 6, which are arranged to be squeezed tightly around the blade Shanks' andV bearings within the hub. The squeezing or clamping engagement is accomplished by through bolts 'l which pass through registering bolt holes 8 drilled through intermediate adjacent propeller the counterpart portions and by clamping rings 9 at the ends ofthe housing. The counterpart portions are duplicates, machined along meeting faces to insure proper registry and cooperation with each other. The half portions are machined to provide a central transversely extending bore to receive the engine shaft in mounting the propeller. The hub members are provided with an lenlarged central recess I to accommodate for movement therein movable counterweights connected between the adjacent shanks of the propeller blades for balancingthe centrifugal force exerted on the blades and presently to be described. Extending inwardly thereof, eachl of the counterpart portions of the housing is provided adjacent the outer ends with integral semicircular flanges or bearing retaining members II.- These flanges or members are surfaced on opposite sides to receive and support bearings included in the hub assembly and serve to define, in conjunction with similarly surfaced, outwardly facing shoulders I2, recesses in which the bearings are received. Adjacent to the outwardly facing shoulders I2, the hub housing portions are provided with an inwardly extending lug I3, and either side thereof with concave recesses I4 adapted to form, in conjunction with means on the blade Shanks, a housing for a helical spring I5. i'

The blades 3 have their Shanks provided with a series of reduced or stepped portions extending within the hub for cooperation with bearing and control members therein. The innermost stepped portions of the shanks are threaded to receive thereon, in adjustable relationship, lever vcontrol members in the form of crank collars I6 which have concave recesses in their outer periphery extending therear'ound from opposite sides of lugs I'I. The' concave recesses are ar-` ranged to register with the recesses I4 in the hub sections and form therewith housings for the springs I5 which are interposed, respectively,

. between the lugs I3 on the hub housing and the lugs I'I on the collars. The lugs I3 and I1 are in overlapping relationship and cooperate as steps in limiting turning of the blade shanks in a clockwise direction as viewed in Fig. 4 of the draw- 1ngs. The springs I5, interposed between the lugs on the hub and crank collars, normally tend to turn the blade shanks in a clockwise direction but allow turning of the Shanks in a counterclockwise direction under forces tending to compress the springs.

The crank collars I6 are adjusted with respect to the hub housing by screw threaded adjustment along the reduced shanks of the blades, and are held in adjusted positions by means of keys I8 engaging keyways in the blade shanks and the collars-see Fig. 4. This precludes any movement of the collars with respect to the blades after proper adjustment has been made.

The control members I6 are provided .at diametrically opposed points with stub shafts I9 extending into the central recess in the hub housing. These stub shafts I9 afford 'supports and mounting means for weight mechanism for balancing the centrifugal forces tending to cause a turning movement of the blades in the hub when the propeller` is rotated. 'This mechanism comprises a plurality of identical weight lever arm assemblies each of which are connected be` tween a stub shaft on one blade control element and another stub shaft on the control element for an adjacent blade.- Referring in particular to Fig 3, each weight lever assembly consists of vfor accurate counterweight balance.

two collars 20 having integral therewth'on opposite sides, stub shafts 2I rotatably supporting weight lever arms 32 and 33 apertured and fitted over the collar stub shafts. The weight lever arms 32 are each provided at their free ends with a cylindrical housing 34 open at each end. Weight lever arms 33 are each in the form of a fiat plate, abutting and closing one end of the cylindrical housing of the other weight lever arm and having two oppositely disposed laterally extending lugs 35 that engage within matched recesses in the ends of the cylindrical housing portion of cooperating arm 32. Screws 3E, or any other suitable detachable fastening means, may be vemployed to maintain the two engaging leverarms `in the assembled position described. A floating weight in the form of a pinv 3l telescopically and slidably engages within adjacent cylindrical housings, with its ends each in abutting relationship with a coil spring 38 within one of the cylindrical housings. By this construction, it will be noted that the weight lever arms may rotate and have lsliding movement on the ends l The entire Weight mechanism connectingthe several control elements on the shanks of the propeller blades acts as a unit to counterbalance the centrifugal forces acting on the blades when the propeller is operated. The -arrangement is such that when the propeller blades turn in the hub, the stub shafts I9 on the controlelements may move in two directions over a circular path, whereas the main body of the counterweight, of which the floating pin and housing is the principal part, moves in a straight line. When the blades turn from a low pitch angle to a. high pitch angle, the connected stub' -shafts I9 move closer togetherin two directions. The turning of the lever on the floating pinsland the stub shaft I9 permits this movement in one direction and the sliding of the lever arms on the floating pins permits the movement in the second direction. The showing of the weight mechanism assembly of Fig. 3 is in o-pen position, whereas in a closed position the space between the cylindrical housings is substantially closed. When the propeller is not being operated, the weights assume a position wherein the engine shaft may serve as a stop. 'I'he arms and counterweights being creasing the leverage applied to the control elements in counterbalancing centrifugal forces act- .ing on the blades.

The weights are so selected and arranged with relation to a particular propeller design as to result in accurate counterbalancing, at any position of the blades, thecentrifugal forces that otherwise cause the blades to turn in the hub.

There are two controllable factors in providing One is the weight of the arms and. the counterweight itself,

blade shanks. The collar 28 serves as an adjust-y and the other is .the distance from the center of the hub to the center of the stub shaft on the control element or collar which determines the leverage and throw or the extremev open position of the weights.. The full open position of the counterweights corresponds to the full open position of the blade angle so that the centrifugal force acting on each blade is in exact relation to the blade angle at all times. The counterweights are so arranged as to oil'er no obstruction to the engine shaft at anytime. It will be understood that the size and diameter of the collar I6 will be determined by the leverage required for the counterweights and the exact shape of the hub recess will be governed by the necessary clearance to provide for travel of the counterweights. As the diameter of the collar or control element is increased, the greater is the leverage of the counterweights, permitting finer tuning of the counterweight action. Also, the collars act as part of the housings for the springs and are deter- `mining factors in the design of the spring if the springs are located in the position as shown for purpose of illustration.

The relative distances of the center of the air pressure on a blade andthe center of gravity of the blade sections from the leading edge ofthe blade are so arranged that the air forces acting on the blades during operation of the propeller may be utilized to produce a turning movement of the blades in one direction in the hub of the propeller. In this arrangement, the center of the air pressure acting on a blade is always displaced laterally a predetermined distance from the center of gravity of a blade section, always at -one side of the gravity center, but this distance is so small that the leverage of the air force causing a turning of the blade in the hub is also small. Therefore, the spring force required to regulate the effect of 'the air force will be relatively small and does not require springs of excessive dimensions. These springs may be accurately designed for the. ranges of control necessary in diierent propeller structures. Adjustments of spring length and tension can be obtained by introducing adjusting means between the springs and the lugs in many different ways well known to the art.

The springs tend to hold the blades in. an extreme open position or a maximum blade angle until the propeller is rotated and the air pressure thereon is suilicient to turn the blades to a smaller blade angle and to oifer a positive resistance to the air forces closing-the blade angle to less than the calculated angle of attack at normal cruising speed of the engine. In cooperation with the spring control, it will be noted that the movement of a blade in one direction is limited by engagement of the lugs, as previously described and in theopposite direction by engagement of the counterweights with the engine shaft.

. inwardly directed bearing retaining iiange Il.

This bearing consists of the .two' outer roller race plates 25 and 26 and the single intermediateroller plate 21 interposed between the rollers. The bearing assembly is adjusted to position against the retaining ange by means of a collar 28 which has a screw-threaded relationship with one of the reduced or steppedl portions of the ing member for the main thrust bearing and has a reduced portion 29 screw-threaded in part and extending within the inner member of one of the radial thrust bearings positioned against the outwardly facing shoulder I2. An adjusting means 30 has threaded engagement with the reduced portion 2'9 of the main adjusting collar 28 to provide for clamping engagement of the inner radial thrust bearing against the outwardly'facing shoulder I2 on the hub portion. The other radial thrust bearing is positioned within the outer end of the hub against the inwardly directed bearing retaining ange Il, where it is held in 'position of adjustment by an internally threaded collar 3| engaging a threaded portion on the shank of the propeller blade. The bearing assemblies are duplicated at each end of the hub and the above description suillces for each assembly. With the arrangement described, it will be noted lthat very tight adjustments of the bearings can be obtained and yet have all of the main centrifugal force acting on each blade effectively applied to a single axial thrust bearing. The radial thrust bearings take all of the torque and may be positioned' as tightly as possible against their seats on the hub housing by the adjusting collars, yet when in operation, the centrifugal force, which amounts to many thousand pounds for each propeller blade, is applied to the axial thrust bearing, it will tend to relieve the radial thrust bearings from their original tight adjustment sufficiently to enable the centrifugal thrust to be taken solely by the axial thrust bear-ings.

As previously pointed out, one of the important features of this invention is the utilization of the air pressure to decrease the angle of attack to the position of maximum eiciency. This is done by employing blades so designed that the distance' of the center of gravity of the blade. sections from the leading edge and the distance of the center of air pressure on the blades are so related that the ain forces will tend to produce a turning movement of the blade in opposition to the spring pressuresV acting on the blade Shanks. 'I'his feature of Adesign of the blade is set forth in detail in the copending application, above identified,l and it suffices for this description to define the blades as those having the center of gravity and the center of the air forces thereon as described above.

The invention contemplates the use of blade structures whereon the center of air pressure is always to occur at a greater distance from the leading edge than the center of gravity to obtain desired control over the air` forces. The center of air pressure occurring below the center of gravity of the blade section would cause the blade to turn in the hub so as to reduce the angle of attack, which is the desired action. Howi ever, to control the amount of reduction of this `and full throttle speeds of the engine, regardless of the speed of the plane or the velocity of the wind up to the limit of the maximum blade angle, so that the uctuations of wind velocity are automatically compensated for. In taking oil, divthe operation of the propeller above described,l

the air force is utilized to decrease the angle of attack under control of the springs tending to hold the blade in the extreme open position or tially triangular in shape.

maximum blade angle. spring employed will be determined by the con-l ditions dealt with in each case of structure variation, but in all cases the resultwill be that described in connection with the illustrated embo'diment of the invention. Thel centrifugal forces acting on the propeller blades tend to turn the blades in the hub, this action being counterbalanced by the free swinging weights of the governor. The governor and the springs, to-` gether with the utilization of the air force by suitably designed propeller blades, result in a self-adjusting variable pitch propeller free from gearing and other pitch varying agencies, and further results in a propeller having a minimum number of parts so that assembly and adjustment thereof is a simple matter.

In the modied form in Figure 5, showing application of the invention'to a three blade propeller, the central recess in the hub 'is substan- The general structure, however, including that for the weight governor connections, is substantially the same in detaillexcept for size as previously described for the four blade propeller. It will be understood that the size and weight of the lever arms and oating weight pins will be determined by the been used are words of description rather than of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in all of its aspects I claim:

1. In a variable pitch propeller, the combination of, a hub, a plurality of propeller blades spaced less than 180 apart rotatably mounted coplanar in said hub and having crank members xed to their inner ends, collars on the crank members diametrically opposed with relation to the longitudinal axis of a blade, a movable weight lever arm pivotally mounted on each'of said collars, a movable weight member slidably and pivotally supported between a lever arm extending from one crank member and a lever arm from an adjacent crank member, said movable Weight and lever' arm assemblies being relatively movopposed laterally extending lever mounting mem-l bers thereon, a weight lever arm pivotally mount- The type and design of ed at one end on each of said lever mounting members and having a cylindrical housing at its free end, weight members slidably mounted in and between a pair of cylindrical housings on lever arms extending from adjacentcrankcollars whereby all of thefweight lever: arms areconnected in pairs by a plurality vof Aweight members, said lever arms having-sliding vand rotative engagement with said. weight members to -permit free movement of the weights to oppose centrifugal forces tending to turn the blade in the hub when thev propeller' is rotated.

.3.l In a multiple blade variable pitch propeller having a metal hub and a plurality of blades having their shanks mounted for turning movement in the hub, an .annular crank member attached to each blade shank, each crank member having diametrically opposed laterally extending lever mounting members thereon, spring means interposed between the hub and each crank member tending to turn the crank member in one direction, a weight lever arm pivotally mounted at one end on each of said lever mounting members and having a cylindrical housing at its free end, a weight member-having cylindrical portions slidably mounted in and bctween a pair of cylindrical housings on lever arms extending from crank members ofv adjacent blades whereby all of the weight lever arms are connected in pairs by a. plurality of weight members, said lever arms having sliding and rotative engagement with said weight members to permit free movement of the weights to oppose centrifugal forces tending .to turn the blade in the hub when the propeller is rotated.

4. In a multipley blade variable pitch propeller having a metal hub and a plurality of blades having their shanks mounted for turning movement in the hub, an annular crank member attached to each blade shank and mounted in a plane which intersects mounting planes of crank members on adjacent blades, each crank mem' ber having diametrically opposedlaterally extending stub shafts thereon, a weight levervarm pivotally mounted at'one end on each of said stub shafts and having a cylindrical housing with one end open at its free end, al weight member having cylindrical portions slidably mounted in and between a pair of cylindrical housings on lever arms extending from crank members of adjacent blades whereby all of the weight lever arms are connected in pairs by a plurality of weight members, said lever arms having sliding and rotative engagement with said weight members to permit free movement of the weights to oppose centrifugal forces tending to turn the blade in the hub when the propeller is rotated.

5. In a variable pitch propeller, the combination of a hub, a plurality of blades rotatably mounted in said hub and having crank members iixed to their inner ends, vsaid crank members each having stub shafts diametrically opposed with relation to the longitudinal axis of the associated blade, a collar support rotatable on each of said stub shafts, a movable weight lever arm pivotally mounted on each collar support, a movable weight member slidably and rotatably supported between a lever arm extending from one crank member and a leverv arm from an adjacent crank member, said movable weight and lever arm assemblies being relatively movable with respect to the crank members to counterbalance centrifugal forces-tending to turn the blades in the hub when the propeller is rotated.

6, In a variable pitch propeller, the combination of a hub, a plurality of blades rotatably mounted in said hub and having crank members fixed to their inner ends, resilient means opposing' movement of the crank members in one direction, each'of said crank members having stub shafts diametrically opposed with relation to the longitudinal axis of an associated blade, a support member rotatable on each of said stub shafts, a movable Weight lever arm pivotally mounted on each of said support members, a movable weight member slidably and rotatably supported between a; lever arm extending from one crank member and a lever arm from an adjacent crank member, spring means between each Weight and its supporting lever arms tending to centralize the- Weight between the supporting lever arms, said movable weight and lever arm assemblies being relatively movable with res'pect to the crank members to counterbalance centrifugal forces tending to turn `the blades in vthe hub when the propeller is rotated.

7. In an automatic variable pitch propeller having a hub and at least three equally spaced radiating blades mounted for turning movement on their axes, means connecting the blades for automatically balancing out centrifugal forces acting on the blades during rotation ofthe propeller, and means for automatically controlling the pitch of the blades in accordance with the air forces acting thereon during operation of the propeller, said first mentioned means including of weights and movable lever arms supporting said Weights, said lever arms and Weights con' Vthree or more equally spaced radiating blades mounted for turning movement in the hub, means for varying the angles of the blades in relation to air forces on the blades during rotation of the propeller, means including movable Weight lever arms and radially movable weight members connecting each blade with the next adjacent blade on opposite sides thereof to provide a series connectionof all of the blades to automatically balance centrifugal forces tending to turn the blades in the hub during rotation of the propeller, and connections between said weight lever arms and blades providing universal movement of the arms.

10. In 'a variable pitch propeller, the combination with a motor shaft, a hub mounted on said shaft, three or more equally spaced radiating propeller blades rotatably mounted in said hub and each blade having a crank member fixed on the inner end thereof, a series of movable weighted connections enclosed Within the hub for connecting the crank members in series from diametrically opposite points thereon, means pivotally connected with the cranks and pivotally associated with the weighted connections to provide outward radial movement of the connection between said blades, said weighted connections serving to counterbalance centrifugal forces tending to turn the blades when the propeller ls rotated. 5

BLAINE B. GEMENY.

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