US1915685A - Screw propeller - Google Patents

Description

June 27, 1933. R. o. MArrsoN 1,915,635v

Y SCREW PROPELLER med umn 1o, 1930 INVENTOR TToRNEY MQW' the collar .12 threadedly engages thearnt Patented June 2v, 1933r UNITED s'rifrasy ROBERT '0. HATTSON, 0F OAKLAND, CALIFORNIA A SCREW PBOPELLER Application led March 10, 1930., Serial No. 434,524. 'if

The .invention relates to a method of controlling the pitch of a screw ropelle'r blade and to a blade structure andp mounting for effecting said control.

.An object of the invention is to provide a device for so controlling the pitch of a propeller blade as to prevent the creation 0f an excessive tractive reaction thereagainst.

Another object is to provide an automatically operating control of the class described.

A further' object is to provide the means of my invention in a blade structure which may be substituted for present propeller blades.

Yet another object is to provide in the 'structure for certain required preliminary adjustments as to maximum allowable pitch and the allowed range of automatic pitchv variation.

The invention possesses other objects and features of advantage, some of which, with 'the foregoing, will'be set forth or be apparent in the following description of a typical embodiment of the invention which is illustrated in the accompanying drawing, in which v Figure 1 is a front face view of a propeller embodying the invention.

Figure 2 is a side view of the propeller and a supporting drive shaft therefor.

Figure 3 is an enlarged frontedge viewof a propeller blade Aand its mounting on the propeller hub, the hub being shown frag-' mentarily.v

Figure 4 is a section at 4 4 in Figure 3. Figure 5 is a section of the blade at 5);5 in

Fi re 4.'

particularly illustrated, the present invention is embodied in the structure of a pro- 4 peller 6 comprising a. hub 7 for mounting on a power operated shaft 8, arms 9 ixedto the hub 7 to form radial extensions thereof, and blades 11 mounted on the arms 9 for a limited swivelled movement thereabout. As particularly shown, the arms 9 are separate elements and their inner ends are arranged for Y threaded engagement in radial sockets provided in the hub. A collar 12 is mounted on each arm 9 at the base 'thereof as .shown outwardly of the hub and is arranged for abutment against the hub as a lock nut for fixing the arm in the hub.; the present ararm. As particularly illustrated, the blade 1l has a relatively fiat forward face 14 and is provided with transverse extensions or bosses l5 and 16 protruding from said face at the 65 outer and inner` blade ends respectively, said bosses havingl mutually aligned bores for the rotative reception of the arm 9 therethrough. While such is not shown, it is to be understood that for a relatively thick blade, an

arm-receiving longitudinal bore might be provided through and entirely within the blade. Preferably, and as particularly brought out in Figure 4, the opposed head and blade portions are formed to provide a racway for ball bearings 16 whereby to minimize frictional resistance to the turning of the blade on its arm, it being obvious that a` strong centrifugal force will constantly urge the blade against the head while the propeller is rotating.v

' Means are provided for limiting the swiv-v elled movement of each blade 11 about the arm 9 which carries it. As particularly shown in Fi ure 5, such means comprises the provision o a segmental and circumferential slot 17 in the arm 9 opposite the boss 15 and into which a set screw 18 mounted in said boss is arranged toextend as a stop for engaging the opposite Aslot ends 19 and 20. 90 A With the sto A end 2l of the set` screw 18 of a given size, t e angular acing of the slot ends 19. and 20 is seen to Y etermine themaxvimum swivelled movement of the blade about the arm. vShould vit be desired to change 95 5 wherein the' stop end 21V thereof is smaller v 109 t-han the end 21 of the screw 18; when the screw 18 is used, a greater swivelling range is rmitted than when the screw 18 is used.

eansare provided for yieldingly urging the blade to retain a limiting position wherein the working pitch thereof is a desired maximum. When the blade is disposed as desired, the stop screw 18 is arranged to engage an appropriate end of the slot 17 1n the present disclosure, the slot end 19 is arranged to be so engaged that a permitted rotation oi' the blade moves the stop pin toward the other slot end 20 and decreases the pitch of the blade. llt is noted that ad]usted disposal of the slot end 19 as required to provide for the desired 'maximum pitch of the blade is provided by the hereinbefore described xed mounting of the arm 9 in the hub by the use of the collar` 12 as a lock nut. As particularly shown, the means provided for urging said blade to maintain its position of maximum pitch comprises an helical torsion spring 22 disposed to generally encircle tliecollar 12 and having one end thereof fixed to the inner blade end and the other end fixed to the collar whereby a displacenient of the blade from its position of maximum pitch -is resiliently resisted.

For securing the spring ends as required, said ends are extended axially of the spring for respective engagement in a socket 23 provided in the opposed blade and in a socket 24 provided on an annulus 25 on th'e collar 12, said spring being compressedly -engaged between said blade end and annulus for retaining the blade ends in said sockets. 'llo permit adjustment of the torsional resistance of .the spring 22 to a swivelled displacement of the blade, the annulus 25 is threaded on the collar 12 and alock ring or annulus 26 is also mounted on said collar as a means to secure the annulus 25 in its adjusted position. Desirably, the springs 22 of the propeller 6 would bealike and would be adjusted to oder a like resistance to a rotation of the blades from their positions of maximum pitch.

lit will now be noted that the tractive reaction against a blade is 4arranged to be ntilized to eect a `displacement thereof from its position of maximum pitch when a desired draft, or traction, maximum is exerted by the propeller. 'llo this end, the blades 11 are so designed that the tractive lreaction thereagainst is arranged to urge their rotation to positions of lowered pitch and against the resistance of the springs 22, the torsional urge thus created prevailing if and-when the tractive reaction exceeds a desired value. lln the present pro eller, the desired effect is accomplished y providing a greater blade surtace behind the pivotal axisof the blade than ahead .of it, the type of thc blade determining the exact proportions. Since the net torsional or twisting eect on the blade is the diderence between rotativefurges lin remesa opposite directions, a minimum difference may be provided for in designing the blade. lln an airfoil blade, the aforesaid relation may not be necessary to insure a torsional ur e to decrease the'blade pitch as desired, it eing generally essential only ,that said torsional urge be created by the propeller draft reaction and increase with said reaction.

llt will now be clear that with a spring 2 set for a given resistance and the propeller in rotation whereby the effective torsion on a blade tends to urge it to a position of less than normal pitch, if the traction, and therefore said reaction, be increased, a point will be reached when the torsion will overcome the resistance of the springs 22 and the blade will assume a position of `decreased pitch, limited only by the range of adjustment permitted by the stop slot 17. Since the resistance of the spring 22 increases with its degree of distortion, a iully minimized pitch setting may not be reached.

Propellers embodying the novel features now set forth may be designed for the propulsion of both air and water vehicles. ln any case, should an excessive draft or traction be urged on the propeller by a driving mechanism, the eect thereof to decrease the propeller blade pitch prevents a slowing down or drag on the driving means, and may result in an increased rotative speed for the propeller, whereby a maximum application of the available power is maintained. It will thus be clear that the present device operi ates as a resilient shock absorbing means for the blades, prevents the imposition of an excessive traction'on the propeller, and automatically provides for a continued operation og a driving means at an emcient speed thereo lFrom the foregoing description taken in connection with the accompanying drawing, the advantages of the construction and method of operation will be readily understood by those skilled in the art to which the invention appertains, and while l have described the principle of operation, together with the device which 1 now consider to be the best embodiment thereof, I desire to have itunderstood that the device shown is merely illustrative, and that such changes may be'made, when desired, as fall within the scope of the appended claims.

Having thus describedmy invention, I claim as new and desire to secure b Letters Patent of the United States the ollowlng:

1. In a screw propeller, a hub, a'n arm threadedly secured to and extending radial- 1y from said hub, a blade swivelled on said arm for rotation between positions of maximum and minimum pitch, said blade having an annular groove at itsouter end surrounding the arm, ahead on the outer end of the arm, ball bearings between said groove and head, yielding means constantly urging said blade to retain its said position of maximum pitch, and means operative in accordance =51' with .the draft of the propeller to urge a rotation of said blade about said arm to its said position of minimum pitch.

2. In a screw. propeller, a hub, arms'extending radially from the hub, a` blade mounted to swivelupon said arm, said arm havingr a segmental slot formed therein and a pin carried by the blade and extending into said slot tolimit swivelling movement of said-blade to positions of maximumand minimum pitch, means to cause the blade to swivel under predetermined operating conditions, head members on the outer ends of said arms and antifriction thrust bearings rounding thearm'and fixed to said ringan'd blade, a second threaded ring for locking said first ring in position, head members on the outer ends of said arms and anti-friction thrust bearings'interposed between said head members and the outer ends of the blades.

In testimony whereof, I aiiiX my signature.

ROBERT 0. MATTSONL y ils

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