US2670805A

US2670805A - Controllable reversible pitch propeller

Info

Publication number: US2670805A
Application number: US735980A
Authority: US
Inventors: Harry J Nichols
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-03-20
Filing date: 1947-03-20
Publication date: 1954-03-02
Anticipated expiration: 1971-03-02

Description

March 2, 1954 H. J. NICHOLS 2,670,8 5

CONTROLLABLE REVERSIBLE PITCH PROPELLER Filed March 20, 1947 5 Sheets-Sheet l INVENTOR RY J. NICHOLS,

BY gymm ATTORNEY March 2, 1954 J NICHOLS 2,670,805

CONTROLLABLE REVERSIBLE PITCH PROPELLER Filed March 20, 1947 5 Sheets-Sheet 2 INVENTOR HARRY J. NICHOLS,

ATTORNEY March 2, 1954 H. .1 NICHOLS CONTROLLABLE REVERSIBLE PITCH PROPELLER Filed March 20, 1947 5 Sheets-Sheet 5 A l IIHHH FIG. 4

IIIHH 0 INVENTOR HARRY J NICHOLS.

ATTORNEY H. J. NICHOLS CONTROLLABLE REVERSIBLE PITCH PROPELLER March 2, 1954 5 Sheets-Sheet 4 Filed March 20, 1947 INVENTOR I HARRY J. NlCHOLS,

ATTORNEY March 2, 1954 H. J. NICHOLS CONTROLLABLE REVERSIBLE PITCH PROPELLER 5 Sheets-Sheet 5 Filed March 20, 1947 INVENTOR HARRY .J. NICHOLS BY MMM .g

Patented Mar. 2, 1954 CON TROLLABLE REVERSIBLE PITCH PROPELLER Harry Jr Nichols, Point Pleasant, N. J. Application March 20, 1947, Serial No. 735,980

16 Claims.

This invention relates to controllable reversible pitch propeller systems and more especially to such-propellersfor use on marine vessels, and has for its main object the provision of a propeller ofthe character described in which the pitch of the blades can be readily and accurately varied, and also reversed, while the propeller isin rotation under load. Another object is to provide an exceptionally simple, compact, and durable pitch changing mechanism which is economical to manufacture, easy to install andservice, and which embodies pitch limiting and pitch indicating devices, and other practical features tofacilitate operation by unskilledand non-technical operators.

Another object is to provide a strong and'ruggedblade turning mechanism adapted to be housed within a propeller hub of relatively small diameter which will: have a minimum of working parts and will hold the blades rigidly, thereby avoiding any possibility of flutter or vibration of the blade in operation due toexcessive back-lash or elasticity;'and which will also automatically lockthe blades against being turned by external forces at any position of pitch adjustment.

Another object is to provide a torque-amplifying actuating mechanism for driving th blade turning mechanism'which is-self-energizing, that is, it derives its operating torque from the propeller shaft; and which is adapted for remote control.

Another object is to provide a pitch varying mechanism of adequate angular range, including reversing, which iscapable-of changing the pitch in micrometric increments when desired, yet also is. capable ofv changing the pitch at-a rapid rate for maneuvering and. meeting emergencies.

Yet another object isto provide a pitch changing mechanism in which the actuating mechanism is relieved of any strain except when the pitch is being changed,- thus reducing wear and enabling relatively light mechanical parts to be employed.

A. further object is to provide a mechanical pitch limiting device to prevent the pitch being varied beyond the proper operating range, and an electrical pitch indicating device to indicate. visually at all times'the pitch of the blades.

With these-and other objectsin View, as Wellas other advantages incident to the improved construction, the invention consists invarious novel features and combinationsthereof set forth in the claims with theunderstanding that the several necessary elements constituting the same may be varied in proportionandarrangement without departing. from the nature and scope of the invention as defined in the appended claims. "I-o enable others skilled in the art to com- 7 prehend theunderlyingfeaturesof this invention that they may embody the sameby suitable modifications in structure and relation to meet the various practical: applications contemplated by the invention, drawings showing a preferred embodiment-of the invention form. part of this disclosure, and in such. drawings like characters of reference denote corresponding parts in theseveralviews in which:

Fig. 1". is .a side elevationin partial axial section of a marine variable pitch propeller and drive shaft therefor embodying certain features of the invention.

Fig. 2' is a transverse sectional-1 view taken substantially onlines- 2-Z of Fig. 1;

Fig. 3is a detaillviewof the inner end" of .a blade rootshowing the novel crown gear of the invention.

Fig. 4 is a side elevationin partial'cut away section of the propeller.shaft-coupling.and power mechanism forming part of. the invention;

Figs. 5 and 6 are transverse: sectional views taken substantially on. lines. 5-5 .and fi--E res spectively, ofFig. 4.

Fig. 7- shows thepitch limitcam sleeve in flat development to illustrate the principle cfthecontrol of the pitch blockv device of the invention.

Fig. 8'is aschematic diagram illustratingv the features and modeof" operation of the control apparatus.

Description Considered as a whole, and referring generally to the drawi'ngs, the construction of. the invention constitutes a complete machine comprising two main units namely a propeller'hubassembly including mechanism housed-within the propeller hubfor turningv the propeller blades axially in unison, asshown inFig. 1; and-a shaft'coupling assembly including torque-amplifying power mechanism foractuating the blade turning mechanism located within-the vessel, as-shown in Fig. 4. A tubular propellershaft and a connecting rod, slidably mounted coaxially in the propeller shaft-and moved by the power mechanism, operatively connect thesetwo main units. The invention also includes control apparatus for controlling the pitch of the -propeller blades from a remote station, including means for indicating the=pitch visually. 1

Referring now to the-drawings in. detail and particularly-toFigs; 1'and2, the'hub assembly of the invention is shown as including a two-piece hollow hub I!) having a forward driving portion l 1 which is tightly fixed to the tubular propeller shaft 30 by a tapered, keyed connection and retainer nut in conventional manner as shown, or by other suitable construction. A gasket i9 is provided to prevent leakage at the hub and shaft connection. The after part or cap l2 of the hub is tightly fixed to the forward part H by a plurality of longitudinally extending cap screws 23 located intermediate the blades as shown in Fig. 2. This hub structure mounts the blades and houses the blade turning mechanism.

The hub as a whole is formed with a plurality of radially extending bores comprising inner and outer circular seats and an intermediate annular shoulder 53. Blades 15, each having a circular boss 15 and cylindrical root H, are rotatably secured in the radial bores; each blade having a flanged blade gear l8 mounted concentrically on its root portion and fixed thereto by means of cap screws extending through the boss as shown. A packing or seal it of any preferred type is assembled between the blade boss l6 and shoulder i3 to prevent leakage of lubricant and entrance of water into the hub. Obviously, the gear 18 could be made integral with the blade root. The two-piece construction shown, however, permits of the gear being made of a harder and stronger metal than that of the blades, and facilitates manufacture.

The blades (5 can be rotated about their axes in the hub to vary their pitch in unison by means of novel mechanism now to be described. A combined gear and wedge 23 of hollow cylindrical form and having external herringbone gear teeth 2!, 2! as shown, is mounted for reciprocation axially in a closed axial bore formed in the two parts of the hub.. Wedge 20 is demountably fixed on the outboard end of connecting rod .25 by means of a tight splined connection and retainer rings, as shown, or in any other desired manner provided the connecting rod is not permitted to rotate. Wedge 29 has a splined internal bore adapted to slide without turning on a mating externally splined guide stud 24 fixed axially in the hub cap 12, preferably by pressing the knurled end of the stud into an internal axial hole drilled in the hub cap from inside as shown. This construction enables the wedge 26 to be reciprocated by the connecting rod 25, but neither the wedge nor the connecting rod can turn relative to the hub.

Referring to Figs. 2 and 3 in connection with Fig. 1, each of the blade gears I8 is provided with two sets of

skewed crown teeth

22, 22, which teeth are adapted to engage successively with the herringbone teeth 2 I, 2 l of wedge 20 in the usual manner of gear teeth. These two sets of teeth are located in opposite arcs of a common concentric circle and diametrically opposite teeth are inclined oppositely at the same angle of inclination as the herringbone teeth. (See Fig. 3.) As is well understood, the contour of the crown teeth must be conjugate to that of the herringbone teeth in order to provide proper meshing. The faces of the crown teeth are somewhat rounded, so asto avoid interference in action between the meshing teeth due to the perpendicular axes of the herringbone and crown gears.

It will be evident from the drawings that with the construction shown the blades i5 will be turned axially in unison when wedge 28 is translated axially by connecting rod 25. The wedge acts directly on the blade gears, hence intermediate gears as in the prior art are unnecessary, thus promoting simplicity and compactness while minimizing back-lash. It is also to be noticed that the novel mechanism described enables the wedge to act simultaneously in the same rotary direction on teeth of the blade gears located diametrically opposite, thereby applying a torque couple to turn each blade, rather than merely a single torque force. This feature is highly advantageous, since it tends to reduce greatly the load on the blade bearings incident to pitch change. It also provides a double operating connection between the wedge and the blades, doubling the strength of this connection and reducing wear. It is further to be noticed that although the wedge can turn the blades axially, the blades cannot rot-ate the wedge about its axis, because one set of crown teeth tends to rotate the wedge in the opposite direction from the other. The rotary action between the herringbone and crown gears is therefore irreversible and the only effective motion that the blades can impart to the wedge is that of axial translation. Moreover, the wedge turns the blades at a mechanical advantage due to the inclined plane effect provided by the sloping teeth, while the axial reaction of the blades is correspondingly reduced.

The cavity of hub i0 is preferably provided with a supply of lubricant, such as light grease or solidified oil, to provide lubrication for the working parts of the mechanism in the hub.

Referring now to Fig. 4 which shows the power mechanism for reciprocating connecting rod 25, this mechanism is carried by an assemblage of parts serving as a coupling for connecting propeller shaft 30 to drive shaft 90, as for example an engine shaft. Drive shaft is shown as being provided with a conventional upset flange 9 I while propeller shaft 30 is preferably provided with a separable flange 3! of any desired construction. The coupling members comprise a short hollow coupling shaft 43 having an integral flange 69 at the driving end, and at the propeller shaft end a demountable coupling ring 32 keyed to the coupling shaft and held against axial movement .by a split lock-plate 33 whose inner perimeter is let into an annular groove in the coupling shaft. The flange 3| and the coupling ring 32 and lock-plate 33 are strongly clamped together by plural bolts in well known manner.

The inboard end of connecting rod 25, which extends into the coupling section, is formed with strong screw threads located some distance from the end to provide a screw 26 and is mounted so as to be slidable coaxially within the bore of the coupling shaft. A rotatable round nut 31, having external gear teeth, is mounted to turn freely on screw 2 6 and is held against axial movement by thrust washers 21 supported in circular recesses as shown, thus providing a thrust bearing for connecting rod 25. This part of the mechanism constitutes a screw jack.

Rotary nut 31 is provided with external gear teeth, thus constituting a sun gear as a whole as well as a nut. Sun gear 31 is driven by torque transmission gearing comprising a plurality of pinions 36 mounted in circular recesses in the coupling ring 32 and free to rotate on stud shafts 34 fit therein, and an annular gear 35 rotatably mounted on coupling ring 32. By referring to Fig. 5, it will be seen that when annular gear 35 rotates, the pinions 36 drive the sun gear 31, thereby turning it on screw 26 and forcing axial ing orbit gears as the carrier revolves.

planet pinion is tight on its shaft l't, the latter gra ers movement of the connecting .irod..by screwjack action.

Annular gear '35. is rotated for: pitch. changing purposes by torque-amplifying. epicyclic gearing capable of deriving energizing torque from the driveshaft, and applying bi-direction'al torque to gear 35. responsively to theselectiveapplication of one or the other of two control brakes .514, 54". This gearing eliminatesthe need of any. external source of power, such as a motor or pump, for driving the pitch changing mechanism. The torque amplifying gearing comprises. differential gearing, of spur gear type, mounted on coupling shaft 40 and consisting of two differential gear trains of opposite rotational effect connected: in tandem. External or internal orbitgears can'be used in the differential trains, the latter-being shown for illustrative purposes. Beginning at the drive-shaft end-of the-coupling, the initial member of the differential gearing is the first orbit gear 4!, fast oncoupling shaft lll, which gear is ineffect the primary driving member of the gear trains. The next member of the gearing is thefirst planet carrier 45, equivalent to an epicyclic train arm, mounted loose onshaft & and having a rim brake-drum. Planet carrier 45 carries a plurality of double planet pinions 46 mounted tomesh properly with the neighbor- Each being. journaled inbearings in the web of-planet carrier t5. The driven member of the firstdifferential gear train is the second or intermediate orbit gear 42, in thefor-m of a floating ring gear having double-width teeth, operatively connected to the first orbit gear 4t by planet pinions 46' and also serving as the driving member of the second differential gear train. The next member of the gearing is the second planet carri'er 55, identical in construction with the first planet carrier 45, likewise mounted loose on coupling shaft 40, and likewise'havinga rim brake-drum. Planet carrier 55 carries a plurality of double planet pinions 56 whose shafts 57 are journaled in hearings in the web thereof, as before. The final and driven member of the second differential gear trainisthe third orbit gear 43, operatively connected to the intermediate gear by planet pinions 56 and integral with or fast to annular gear 35.

Preferably, all the planet pinions have the same number of teeth, and the first driving and final driven orbit gears have an equal number of teeth, but the intermediate orbit gear has a slightly different number of teeth'than theother orbitgears. It follows according to well known formulae that the two differentialgear trains would then have equal trainvalues or speed ratios, but of opposite algebraic signs, sometimes termed equal but contrary ratios. In the present case, it is essential that rotation of planet carriers 45 andv 5 in one directioniproduce rotation of driven orbit gear 63in opposite directions whereby a certain relative rotation of planet carrier; will cause a change of pitchinone direction, while like rotation of planetcarrier 55 will cause a change of pitch in the other direction. Moreover, it is; highly desirable that the gearing have alarge speed reduction ratio, which is char.- acteristic of thegearing described.

Brakes are providedtoapply retarding braking action independently to the two planet carriers.

While either mechanical or hydraulic brakescan be used, the preferred form-of; brakes i's;ofhydraulic typeand ccmprises two sets or closed hy-' 6: drauli'c. brake "cylinders' 511;. Bi, disposed radially withequ'al .spac'ingon ahousin'g 8|]; (See.l='ig.'.ti); Brakepiston's 541 836 mounted to work within'the closed brake cylinders and are provided. with means "to. prevent leakage past them, suchoas an 'O-ring seal 52"asshown. The'ipistonsare normally held in the inoperative .position-bycompression springs 53. The arrangement such that when hydraulic fluid under sufi-cient press sureiis appliedto the top space in either set ofcylinders, the brake pistons therein are thrust inwardly into frictional engagement. with the associated brake drum, thereby applying. braking force to the associated planet. carrier. Each set of brake cylinders is preferably located on the housing in staggered relation, as indicated in Fig. 4;

Operatiom The operating principle of the pitch changing mechanism is as follows: Normally, the gears and the planet carriers all rotate bodily as a unit with the coupling shaft, being stationary with respect to that shaft and to each other. Assume now that with the coupling shaft in rotation, brake fluid pressure is applied t-o the'brake'cylinders 50' operatively associated with the first plan: etary carrier 45, and the brake pistons thereof bear on the brake drum of the carrier with sufficient pressure to retard its rotation. As soon as the planet carrier starts to slow down dueto braking action, the planet pinions t6 carried thereby are caused to roll around andiplanetate in the two adjacent orbit gears. Due to theslight difference in the number of teethof thesucce'ssiv orbit gears, a differential angulardisplacement of intermediate orbit gear 42 relative to first orbit gear 41- occurs as the pinions pl'anetate, in well known manner, the torque producing such displacement being derived from the drive shaft. The second set of planet pinions ttmeanwhile act to lock the intermediate orbit gear '42 to final orbit gear 33. This locking action becomes apparent when it is considered that the teeth of the double pinions mesh with the teeth of the adjacent orbit gears at nearly the same pitch circle, and accordingly when not in rotation about their axes they act to key'the said gears together, thus positively preventing'their'relative rotation. Planet carrier in the absence of braking force will. therefore be compelled by the locking action of its planet pinions to revolve along with the adjacent orbit gears. Orbit gear 43 will accordingly be rotated along with the intermediate orbit gear and will transmit operating torque therefrom to annular gear "35. The

torque transmission gear train will be thus driven to rotate nut 3'1 on screw 28', thereby forcing connecting rod 25 to move in an axial direction to turn the blades to change their pitch, as previously described.

Next assume that retarding braking force is similarly applied to the second planetary carrier 55 by means of the associated brake: system. Since intermediate orbit gear 32 is locked by, planet pinions it'to drive gear El, theintermedi ate orbit gear now becomes the driving memberof the second differential gear train. As planet carrier 55 slows down, planet pinions 551 planetate in the adjacent orbit gears and the final, orbit gear 43' is driven relative to the shaft, but, in the opposite direction due to the opposite ratio of the second differential gear train.

The differential geartrains describe-d*are-therefore self-locking,- that is,- they canbeoperated as-geartrains only by relative rotation pf tlreplanet carriers. Another important aspect of these differential gear trains is that they act as drivecouplings when not functioning as gear. trains.

By reason of the mechanical advantage provided by the hub mechanism, the screw jack combination, and the difierential gearing, the braking torque required to actuate the pitch changing mechanism is very small, amountin to only a small fraction of the delivered torque. The brakes can therefore be of relatively light construction. And since the gears are used only during pitch change and then at light loading, comparatively light gears can be used without risk of undue wear.

For effecting a small or gradual change of pitch, braking action should be applied only sufficiently to retard but not to stop the proper one of the planet carriers. The rate of pitch change, which is proportional to the rate of rotation of the planet carriers relative to the shaft, will be correspondingly slow. For a fast change of pitch, as for example for an emergency stop of the vessel, the braking action can be increased so as to stop the proper planet carrier and then the pitch would be changed at the maximum rate, depending on the shaft speed and the over-all reduction ratio of the pitch changing mechanism. Thus it is apparent that the rate of pitch change can be regulated according to the application of th braking force. This feature contributes importantly to the flexibility and practicality of the pitch changing system of the invention, providing a smoothness of control comparable to that of hydraulic brakes on an automobile.

It is also to be noticed that pitch changes in both directions are effected by relative rotation of the carriers in the same direction. Should such rotation occur without brake action, as for example when accelerating or stopping the engine rapidly, both carriers would be similarly retarded or advanced relative to the drive shaft, and the rotation of one would offset the rotation of the other. This feature eliminates the need for brakes or looking devices to prevent unwanted changes in the pitch by reason of abrupt change in the engine speed, as has been the practice in the prior art.

Pitch block feature Referring now to Figs. 4, 6, and '7, the pitch changing mechanism of the invention is provided with a novel device for limiting the range of pitch change, usually called a pitch block device. The purpose of the pitch block device is to limit the pitch variation to a predetermined working range, in this case from full-forward to full-reverse pitch. Because of the large speed reduction ratio, and consequent high mechani cal advantage of the gearing and screw jack mechanism, to merely limit the travel of wedge 20 in its bore would risk breakage of some part of the kinematic chain when the motion of the wedge was blocked. Accordingly, in the embodiment now to be described, the pitch block device is made effective to block the relative rotation of one or the other of the planet carriers depending on the pitch limit reached. When the relative rotation of a planet carrier is thus blocked, the associated brakes will merely slip, limiting the consequences to some negligible amount of wear of the braking surfaces.

For purposes just explained, the connecting rod 25 is provided with an unthreaded cylindrical extension or mandrel 65 which extends into the bore of coupling shaft 40. A cam sleev 60, p'ro-. vided with a plurality of equally spaced longitudinal slots 6| (see Fig. 7), herein termed cam slots, is fixed on the end of mandrel 65 by a. taper pin 29. Two sets of radially disposed tilting wedges or sprags 63 are loosely positioned to work in radial slots cut in coupling shaft 40 and located in the median planes of

planet carriers

45 and 55 respectively. The cam slots are of course indexed with the shaft slots. Referring now particularly to Fig. 6, each sprag 63 is double tapered from the middle of its length, thereby providing fulcrums on the opposite flanks. The inner tapered ends of the sprags fit into the cam slots; and the outer end surfaces are slightly rounded, as shown.

The operating principle of the pitch block device is as follows: When in normal or inoperative position as shown in Fig. 6, the sprags are held by the cam slots in untilted position wherein the radial dimension of the sprags is only slightly less than the'space between the periphery of mandrel 65 and the inner bore of the

carrier

45, 55. In this position, the carriers can rotate freely on coupling shaft 40. When, however, the connecting rod 25 is translated by the screw jack device away from the median position a certain predetermined distance, indentations 62 notched in the sprag-controlling edge of cam slots Bl near the ends thereof are brought into registry with one set of sprags operatively associated with one of the carriers. When the sprags are free of the restraint of the cam slots, the friction on their outer ends due to the rotation of the carrier will tilt the sprags about one of their fulcrums to wedging position; or alternatively, the cam slots can be formed thus to tilt the sprags, if so desired. When so tilted, the sprags wedge between the mandrel 65 and the inner bore of the carrier, thus positively preventing further rotation of the said carrier. Since the pitch of the blades is directly related to the position of connecting rod 25 and hence of cam sleeve 60, it is evident that the pitch limits at which the carriers are prevented from further rotation can be determined by the position of the indentations 62.

It is to be noticed that when one of the carriers is blocked from further relative rotation by the Pitch indicating system Referring now to Figs. 4 and 8, for purposes of providing remote visual indication of the pitch angle an electric indicating system is provided as follows: A tubular variable resistor VB. is mounted by suitable means in an axial hole in drive shaft 90, but is insulated from electrical contact therewith. The variable resistor consists of a helical coil 1 I of resistance wire of high specific resistivity contained within an insulator sleeve 12, which sleeve in turn is contained within a metal flanged thimble '53. One end of the coil is electrically connected to thimble 13. A conducting metal connecting link 10, having ball ends split longitudinally to provide spring action, has one end 9. secured in :a socketprovided in the outward end of cam sleeve 60 in the manner of a ball and socket joint. The other end is slidable within the bore 01 the coil of resistance wire, being frictionally engaged in conductive contact therewith. This assembly constitutes a linear variable resistor VP. of sliding contacttype which is capable of functioning when submerged in oil or rease.

Thimble 13 is suitably mounted in the central hole of an insulated flanged metal disc 15, sandwiched, between two insulator rings 16; as for example by screws 14, which screws also serve to make electrical contact between thimble 13 and ring 15.. Disc 15 and the insulator rings Hi are firmly clamped in position betweenfiange ill of drive shaft 90 and flange 49 of coupling. shaft. 40. The periphery of disc 15 serves electrically as a collector ring with which a brush 8!, mounted in a conventional insulated brush holder 82. supported by housing 80, makes electrical contact in well known. manner. A conductor 83 connects brush 8! to an external electrical circuit including pitch indicating instrument PI of Fig. 8.

Control system Referring now to Fig. 8 which shows schematically the control system for controlling the pitch changing mechanism already described from. a remote station, selective control of the hydraulic brakes is provided by a double-cylinder hydraulic controller E of conventional type, having a three-wayneutral biased control handle 85 adapted to actuate the hydraulic brakes selectively. The cylinders of the controller are hydraulically connected to the hydraulic brakesby'iluid transmitted by small tubing 86, 8'! in the usual manner. The control handle has a neutral position N, and the direction of pitch change responsive to operation of the handle is indicated by F for forward or increase of pitch, and R for reverse or reduction of pitch.

electrical pitch indicator instrument PI, of known ohmmeter type, is provided at the control station, this indicator being connected in series circuit with variable resistor VR and a battery B, as indicated in the diagram or as desired, provided link To is included in the circuit. The pitch indicator instrument, whose response should be-proportional to the change of resistance of variable resistor VB, is preferably of voltagecompensated type, in which casethe batteryB maybe the engine battery. lfhe died of the pitch indicator has a scale calibrated to indicate the blade pitch, the relative pitch also being indicated, as by the letter F for forward and the letterR'for reverse, as indicated: The position of neutral or zero effective pitch, that is the pitch at which the residual forward and reverse thrusts are in balance, is also indicated, as by the letter 'N.

The operation of the controls may be illustrated bythe following example: Assume that a vessel equipped with the propeller system of" the invention is stationary alongside a dock, with the/engine running and lines cast oiT; further that the propeller is in neutral pitch and the control handle free. In that condition, the cohtrol handle would be in the neutral or N position, the indicator would indicate neutral pitch N as shown in the diagram, and no efiecti've pressure would exist in the hydraulic brake cylihders. Then to go ahead, the control handle wohldabe moved slowly towards. the Flt-posi tion, thereby applying increasing pressure to the proper hydraulic brake. Braking force being thereby applied to retard the proper planet carrier, the pitch changing mechanism will be actuated to increase the pitch of the blades as previously-described. As the pitch is increased, the propeller becomes effective to drive the vessel ahead. Assuming the engine to run at constant speed, after acceleration the speed of the vessel would be related to the blade pitch, up to the power limit of the engine. When the desired pitch is reached, as indicated by the pitch indicator whose pointer follows the blade pitch, the control handleis released and thereupon returns'itself to neutral N position.

To stop the vessel when underway, the control handle is. moved towards the reverse or R" position, thereby applying hydraulic pressure to the other hydraulic brake and retarding the planetary carrier to actuate the pitch changing mechanism to reduce the pitch. As soon as the pitch becomes negative with respect to the angle of attack of the water entering the propeller blades, the propeller produces a reverse thrust to oppose the forward motion .of the vessel. The vessel can accordingly be brought to rest by slow- 1y reducing the pitch to neutral in correlation with the loss of speed; Meanwhile, as before, the pointer of the pitchindicator follows the pitch of the blades, visually indicating same.

For more rapid stopping or for reversing the motion of the vessel, the control handle should be moved gradually further towards the reverse R position. The pitch reducing mechanism would accordingly be actuated at maximum speed and. full reverse thrust obtained. In this case the control handle should be held in reverse until the pitch of the blades is reduced to a. negative pitch, wherein reverse thrust only is produced.

but general less negative than positive pitch will be used.

From the above, it will be "evident that the control handle can be manipulated to control the direction and rate of pitch change, and the vessel speed accordingly, while the pitch indicator indicates the existing pitch of the blades, thus serving as a guide to the operator in manipulating the control handle. isv driven by an engine under the control of a constant speed governon the direction of motion and the speed of the vessel can be controlled merely byfinger tip manipulation of the pitch control lever. The need for a clutch and reversing gear; and of manipulating the throttle, throwing out the clutch, and operating the re verse gear lever in coordination during maneuvering, according to present practice, can all be eliminated by the system provided by the present invention. Moreover, the controllable reversible pitch propeller provides superior and smoother maneuvering ability, and improved performance and economy in operation. It will be evident to those skilled in the art that the pitch control system described provides exceptional flexibility and versatility of control, and other substantial operating advantages.

Without. further analysis the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge,read-' ily adapt it. for various applications without omitting certain features that, from. the standpointerthe prior art, fairly constitute essential chara'cteri'stics of the generic or specific. aspects The reverse speed of the vesselwill be related to the degree of negative pitch,

When the vessel of the invention, and therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalency of the following claims.

I claim as my invention:

1. A variable pitch propeller system of the type having a tubular propeller shaft, a drive shaft, and a mechanical drive coupling therebetween for drivingly connecting said shafts, and having, in combination; a hub assembly fixed to said propeller shaft including a hollow hub having radial blades rotatable about their axes mounted thereon, and a mechanical movement mounted in said hub for turning said blades axially in unison; means for operating the aforesaid mechanical movement including a connecting rod slidable axially in the bore of said tubular propeller shaft to operate the said mechanical movement, and a screw-jack mechanism for translating said connecting rod axially; power mechanism carried bodily by said coupling for operating said screw-jack mechanism including torque-amplifying differential gearing characterized by a large speed reduction ratio for deriving, upon individual application of two minor control braking actions, driving torque from said drive shaft and applying operating torque in one or the other rotational direction to said screw-jack mechanism at a slow speed relative to the shaft speed; a pair of brakes for applying control braking action selectively to said differential gearing to operate said screw-jack mechanism in one or the other direction; and control means for actuating said brakes at will from a remote station, thereby to vary the pitch as desired.

2. The combination of the propeller system of claim 1 and an automatic safety device carried bodily by said coupling and operative to block said gearing against improper actuation by said brakes at predetermined limits, thereby limiting the pitch variation to a predetermined working range.

3. In combination with the propeller system of claim 1, of electrical means actuated by the axial translation of said connecting rod for indicating the pitch visually at a remote station.

4. In a variable pitch marine propeller including a hollow hub and radial blades having their roots secured in said hub so as to be rotatable about their axes to vary their pitch, a mechanical movement housed within said hub for so rotating said blades in unison comprising; a slidable cylindrical wedge having external herringbone teeth mounted coaxially in said hub, means mounted in said hub coacting with said wedge so as to allow axial movement without rotation relative to the hub, and a crown gear fast to the root of each blade and, having diametral oppositely inclined teeth operatively meshing in the manner of gear teeth with the herringbone teeth of said wedge.

5. A variable pitch marine propeller system, including a hollow propeller shaft and a driving shaft, a power unit for rotating said driving shaft, and a mechanical coupling for drivingly connecting said shafts, having, in combination; a hollow hub fast to said propeller shaft mounting radial blades rotatable about their axes to vary their pitch and housing a mechanical movement for so rotating said blades in unison; means for operating said mechanical movement including a connecting rod movable in the bore of said propeller shaft to operate said movement; power mechanism carried bodily by said coupling for actuating said connecting'rod including speed-reducing differential gearing normally capable uponselective application of braking action thereto of deriving adequate power from said power unit to actuate said connecting rod so as to vary the pitch of said blades in a gradual but positive manner when said blades are in rotation under load; selective braking means for actuating said dilferential gearing; control means for controlling said braking means at will from a remote station; and a pitch block device for blocking said differential gearing against improper actuation by said brakes in a manner to exceed predetermined pitch limits.

6. In a variable pitch marine propeller having a tubular propeller shaft and a hollow hub fast to said shaft mounting axially rotatable blades, in combination, a mechanical movement housed within said hub adapted to rotate said blades axially in unison to vary their pitch, a mechanical drive coupling connected to drive said propeller shaft, power transmission means for driving said mechanical movement, differential gearing mounted bodily on said coupling in driven relation to said coupling and in driving relation to said power transmission means, brake means for actuating said difierential gearing to increase or decrease the blade pitch, control means for actuating said brake means at will from a remote station, and mechanical means for blocking said differential gearing against improper actuation by said brake means at predetermined pitch limits.

'7. In a variable-pitch marine propeller system, the combination of a hollow propeller shaft, a hollow hub fast thereto mounting axially rotatable radial blades, mechanism for rotating said blades axially in unison including an operating rod extending through the bore of said propeller shaft and movable therein to operate the aforesaid mechanism, a mechanical coupling for driving said propeller shaft, power transmission means operatively connected to move said operating rod when under load, differential speedreducing gearing carried bodily by said coupling and operatively connected in driven relation to said coupling and in reversible rotary driving relation to said power transmission means, hydraulic braking means for selectively actuating said differential gearing to produce forward or reverse rotation of said power transmission means, control means for controlling said braking means to var the pitch of said blades, and electrical means independent of said control means and actuated by the movement of said operating rod for indicating the pitch of said blades.

8. In combination with a propeller having a pitch varying mechanism, of means for limiting the variation in blade pitch to a certain working range comprising an operating member of the pitch varying mechanism having a movement proportional to the blade pitch, a rotary member for actuating the pitch varying mechanism, a plurality of wedges adapted to block under controlled conditions the relative rotation of said rotary actuating member, and automatic control means actuated by said operating member adapted to retain said wedges in non-blocking position normally, to free said wedges for movement into blocking position when a certain pitch limit is reached and to displace said wedges from blocking position when the said pitch limit is thereafter departed from in the direction of the working range.

9. In variable pitch propellers having radial blades with roots secured-in bearings in a hub for axial rotation thereby to change their pitch, a mechanical movement for so rotating said blades in unison, comprising, a crown gear fast to the root of each blade and having two sets of oppositely inclined skew teeth located diametrically opposite, and a cylindrical wedge having herringbone teeth oppositely inclined at the same angles as the said skew teeth and mounted with its axis concentric with said hub and in meshing engagement with said crown gears.

10. In a variable pitch propeller having axially rotatable blades with roots secured in bearings in a hub, means for rotating said blades axially in unison comprising a crown gear having two sets of diametral oppositely inclined skew teeth fast to each blade root, a cylindrical wedge having herringbone teeth adapted to mesh with the aforesaid skew teeth, and means for guiding the movement of said cylindrical wedge so that it can move only in axial translation.

11. In a variable pitch propeller system adapted for changing the pitch of its own blades responsively to the manipulation of control means lo cated at a remote station, the combination of power means including spur-gear differential gearing for moving said blades for pitch variation, selective brake means for actuating said difierential gearing, remote control means for operating said brake means under the control of said gearing, automatic pitch block means for blocking and unblocking the rotation of said differential gearing selectively and regardless of the action of said brake means thereby to limit the pitch variation to a predetermined working range, and means actuated by said gearing for indicating the pitch visually at said remote station.

12. In a variable pitch propeller system, the combination of power means for changing the propeller blade pitch, including spur-gear diiierential gearing having two independent planetary members, and automatic pitch-limit means for blocking the rotation of said planetary members selectively at predetermined limits thereby to limit the range of pitch variation, said pitch limit means also being adapted to unblock the rotation of a blocked planetary member responsively to the movement of said power means in the opposite direction.

13. A mechanical movement for adjusting the angle in unison of radial propeller blades so mounted as to be capable of angular adjustment each about its own axis thereby to vary their pitch comprising, a crown gear having two sets of oppositely inclined diametral teeth fast to the root of each blade, a cylindrical wedge member having external herringbone teeth mounted with its longitudinal axis concentric with respect to and meshing as a gear with said crown gears, and means for moving said wedge member axially.

14. Actuating mechanism for varying in unison the pitch of a plurality of radial propeller blades symmetrically mounted with respect to a common center so as to be each rotatable about a radial axis converging at said center including, a cylindrical wedge member having uniformly spaced external teeth mounted concentrically between said blades, and individual crown gears each mounted fast on the root of one of said blades and having teeth located in two diametrically opposite" segments adapted to mesh operatively with the teeth of said wedge member.

15. The mechanism of claim 14 in which the said wedge member is provided with herringbone teeth and the said crown gears with diametral oppositely inclined skew teeth having the same helical angle as said herringbone teeth.

16. In a variable pitch marine propeller, the combination of a hollow driving shaft, a plurality of blades carried thereby and so mounted as to be capable of angular adjustment each about its own longitudinal axis for varying the blade pitch, an operating rod movable axially within said driving shaft for imparting angular movement to said blades, power means capable of deriving power from said driving shaft to drive said operating rod, control means for actuating said power means, and an automatic mechanical safety device carried bodily by said driving shaft and actuated by movement of said operating rod so as to block said power means against improper actuation by said control means at predetermined limits of movement of said operating rod thereby limiting the pitch variation to a predetermined working range.

HARRY J. NICHOLS.

References Cited in the file of this patent UNITED STATES PATENTS Nichols July 1,