US2699221A - Controllable reversible pitch marine propeller system - Google Patents

Description

Jan. 11, 1955 H. J. NlcHoLs CONTROLLABLE REVERSIBLE FITCH MARINE PROPELLER SYSTEM Filed April 19, 1950 3 Shets-Sheet 1 hummm HENRY J. W NULS Jan. 11`, 1955 H. J. NICHOLS TEM CONTROLLABLE REVERSIBLE FITCH MARINE PROPELLER SYS 3 Sheets-Sheet 2 Filed April 19, 1950 Jan. 11, 1955 H. J. MCHOLS 2,699,221

coNTRoLLAELE REVERSIBLE FITCH MARINE PRORELLER SYSTEM Filed April 19, 1950 5 Sheets-Sheet 3 'Hlld NHE'LLSV GHVMOJ. l HDlId GVEIHV EIIIOHOJ. BCIVIB GHVMOJ. Q *ca O o o e o O c?, o C O 1" l N i :i -lo I ANGLE BLADE PITCH aevINvAov IvolNvHoaw TWEE/m "Memor HENRY J. NICH S United States Patent O CONTROLLABLE REVERSIBLE PITCH MARINE PROPELLER SYSTEM Harry J. Nichols, Point Pleasant, N. J.

Application April 19, 1950, Serial No. 156,796

2 Claims. (Cl. 170-160.47)

This invention relates to a controllable, reversible pitch marine propeller system and particularly to such a system specially adapted for motor boats having inboard motors of considerable power.

The prior art discloses that many inventors have attempted to devise manually operable controllable pitch propeller systems intended for use in motor boats, but very few of these have met with any measure of success in practice. At the present time, the few such propellers in use are restricted to boats having engines of low power, usually less than ten horsepower. Among the main reasons for the lack of success of prior art inventions of this class, the following may be cited. The high propeller and boat speeds now prevalent make it necessary, in order to avoid loss of propulsion efficiency, to use a propeller having a streamlined hub of relatively small diameter, thus imposing rigid space limitations on the blade mountings and the mechanical movement in the hub for turning the blades about their axes. In direct conflict with this requirement of small diameter, the blade turning movement must be very rugged and must have a large angular range in order to reverse the pitch of the propeller. As a consequence, virtually all blade turning movements disclosed by the prior art are ruled out because they are not sufciently compact and rugged or else cannot provide the required angular range.

When a controllable pitch propeller is reversed to stop and reverse the motion of a motor boat while running under full power at top speed, upon reversal of the pitch powerful hydrodynamic forces tend to turn the blades about their axes, and these forces may cause the manual operating handle to kick-back suddenly, with consequent danger of loss of control or injury to the operator. But if the engine power is reduced before reversing the pitch, the available stopping power is likewise reduced, hence it is highly desirable to provide a manually operated pitch reversing mechanism which can be safely operated when the engine is delivering full power. Obviously, locking the operating handle in any set position will not overcome this danger, because such handle would have to be unlocked during the reversing operation. Furthermore, free or unlocked controls are essential if manual operation is to be exercised from a plurality of locations, as is often required in practice. To avoid the possibility of any accident, yet to provide convenience, special features must therefore be introduced to assure that the blade actuating mechanism is effectively selflocking in any position to which it may be set, so that tle operating handle does not have to be locked in p ace.

Further, if the engine power exceeds say ten horsepower and it is attempted to operate controllable-pitch propellers manually, the manual effort required may exceed the strength of the operator, unless the pitch actuating mechanism provides a large mechanical advantage. Such mechanical advantage is not provided practically by ordinary simple lever movements. Hence, for engine powers exceeding ten horsepower, say, some unusual pitch changing mechanism must be devised to meet the extraordinary requirements. The usual result has been that the special mechanism devised for this purpose became unduly complicated and costly, and hence impractical.

It is therefore the main object of the present invention to overcome the limitations and drawbacks of the prior art referred to above, and to provide a complete control- 2,699,221 Patented Jan. 11, 1955 ICC lable, reversible pitch propeller system for motor boats well adapted for manual operation and characterized by simplicity, compactness, ruggedness, low cost, and utmost reliability and safety.

Another object is to provide a compact and powerful blade turning movement of adequate angular range adapted to be housed in a propeller hub of relatively small size which will have a minimum of parts, which will hold the blade rigidly, thereby avoiding any possibility of flutter or vibration during operation due to back-lash or elasticity, which will provide a substantial mechanical advantage, and which will be effectively self-locking in any position to which it may be set.

It is well known that the reverse gear and clutch usually employed on small marine engines to reverse the rotation of the propeller represent a disproportionate part of the cost, weight and size of the engine installation as compared to the engine proper, and this is particularly true in the case of inboard engines for motor boats. Moreover, the clutch and reverse gear are functionally useful only a few percent of the engine operating hours, and are therefore highly uneconomical in relation to their limited functions.

It is therefore a further object of this invention to provide an economical, manually operated pitch control mechanism particularly adapted for use with marine engines of the inboard class in place of, or as a replacement for, the ordinary clutch and reverse gear unit, which mechanism includes means for visually indicating the propeller pitch.

Yet another object is to provide a universal controllable pitch propeller system, that is to say a system well adapted for use with a wide variety of engines and boats, which can be supplied in kit form, and which can be readily installed by persons lacking mechanical skill.

With these and other objects in View, as well as other advantages incident to the improved construction, the invention consists in various novel features and combinations thereof set forth in the claims with the understanding that the several necessary elements constituting the same may be Varied in proportion and arrangement without departing from the nature and scope of the invention as defined in the appended claims.

To enable others skilled in the art to comprehend the underlying features of this invention that they may embody the same by 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 the several Views in which:

Fig. I shows a longitudinal view in half-section of a propeller assembly according to the invention,

Fig II and IIA show plan and right end views of the prismatic cam forming part of the propeller assembly,

Fig. III shows a front elevation of the: pitch control unit according to the invention,

Fig. IV shows a plan view in partial longitudinal section of the pitch control unit shown in Fig. HI,

Fig. V shows a section along plane V-V of Fig. III.

Fig. VI shows a graphic chart illustrating by curves typical relations between centrifugal torque on the blades of a propeller and the increasing leverage feature provided by the invention,

The system of the invention as a whole comprises a unitary propeller assembly as shown in Fig. I normally mounted under the stern of the boat; a manual pitch changing and indicating mechanism as shown in Figs. III-V, herein termed the pitch control unit, mounted in the boat; a hollow propeller shaft; and a control or connecting rod, mounted coaxially in the propeller shaft, which connects the pitch control unit and the blade turninlg movement in the propeller assembly in operative re ation.

T he propeller assembly Referring now to Fig. I, the propeller assembly consists generally of a one-piece streamlined hub 1 having an axial blind bore and radial open blade sockets, fastened tightly to the propeller shaft 20; propeller blades 2 mounted rotatably in the blade sockets so they can be turned each about its own axis; and a special compact mechanical movement for turning the blades axially in unison so as to vary their pitch.

The blades are each provided with a circular boss, and a cylindrical root for facilitating machining and accurately centering the blades. The blades are each detachably mounted for rotation in the blade sockets by means of a demountable anged journal 3, to which the blade boss is bolted by cap-screws 15, and a combination radial and thrust bearing. The bearing elements comprise an inner thrust ring 8, blade retainer ring 9, cover washer 10, resilient pad 11, outer thrust-ring 12, and sleeve bearing 14, all arranged as shown. A gasket 13, mounted in a groove in outer thrust-ring 12 as shown, seals the assembly against entrance of water or loss of lubricant.

The blades are turned in unison in their bearings to change their pitch by an irreversible positive motion mechanical movement of unusual compactness, ruggedness and simplicity, comprising an axially slidable prismatic cam 6 mounted coaxially in the bore of the hub and having on each lateral face onpositelv inclined curved grooves CG, herein termed cam grooves (see Fig. Il), in which two diametral or twin crank pins 4, mounted rigidly on the blade journals 3, are forced to turn as followers upon axial translation of the cam, which latter' is fastened tightly on connecting rod 21 by suitable means, such as taper pin 7. The twin crank pins are located substantially in line with the axis of the connecting rod, rather than at right angles thereto. The crank pins can thus be located close to the axis of the hub, thereby requiring a minimum of working space and enabling a hub of minimum diameter to be used.

Upon axial translation of cam 6, the twin crank pins are forced to move as followers in the cam grooves CG in opposite linear directions but in the same rotary direction, and thus apply a torque couple to the blade journals to turn the blades about their axes. The angle through which the blades can be turned may be 45 or more, which is quite adequate for reversing the pitch. The cam grooves CG are of special curvature so as to produce uniform angular displacement of the blades in direct proportion to the axial translation of the wedge. In mathematical terms, the curves of the cam grooves represent intersecting arcs of complementary trochoids. as explanied in detail in my copending application Ser. No. 770,640 led August 26, 1947.

The crank pins are each fitted with a hardened roller sleeve to reduce friction and wear, in the well-known manner of roller chains. The crank pins are of replaceable type and are notched to break off clean in case of an excessive blow to a blade. This is a safety feature to prevent damage to the actuating mechanism in case the propeller strikes an obstruction, and to facilitate and expedite repairs when necessary.

The mechanical movement in the hub, herein termed the twin crank-pin movement, provides a substantial mechanical advantage according to the well-known inclined plane principle, thereby enabling a relatively light control or connecting rod to be used. The blade mechanism is rigid and the working parts can fit with negligible backlash. When the blades are bolted to the journal, the resilient pad 11 is compressed thereby preloading thc bearings and eliminating shake of the blades.

The propeller assembly as a whole is characterized by simplicity, compactness, ruggedness, ease of manufacture and assembly, and ease of replacement of the blades and working parts. The hub is provided with a supply of suitable lubricant at assembly and requires no further lubricant unless dismantled. Due to the compactness of the hub, the propeller blades can be located in normal relation to the hull, rudder, and strut or stern bearing. Due to the streamline form of the hub, there is no loss of propulsion efficiency. despite the necessarily somewhat larger diameter and length of the hub. Due to the efflcient blade turning movement, the connecting rod can be of such small diameter that no increase in the normal diameter of the propeller shaft is necessary. Because of' the irreversible action of this movement blades are effectively locked in any pitch to which they are set, hence any axial force acting on the connecting rod when at rest is negligible.

The pitch control unit Referring now to Figs. III to V, inclusive, the pitch control unit, which enables the operator to change or reverse the pitch at will, has a basic structure or frame comprising a pair of sideplates 23, these plates being held in rigid relation by five cross-members 24 and being rigidly mounted astride propeller shaft 20 on any suitable foundation or bed, as indicated. The pitch changing mechanism is operated by an operating lever 40 which is provided with forks 26 pivotally mounted on slide-plates 23 by shoulder screw pivots 25 and operatively connected by toggle-links 27 to cross-head assembly 30, so as to slide the latter along propeller shaft 20. Cross-head assembly 30 comprises a hollow trunnion block 31 provided with stepped bores adapted to receive a pair of ball bearings 32 which are fixed therein by retainer rings 33; and a pair of thrust rings 34 locked together by the inner races of the ball bearings and slidable on the propeller shaft.

The connecting rod 21 extends coaxially through the propeller shaft 20 into the cross-head assembly 30, and is provided near the inboard end with a demountable cross-tenon 35 having projecting ends adapted to slide in longitudinal slots cut in the walls of the propeller shaft. The projecting ends of the tenon fit into notches provided in the faces of the thrust rings 34. Trunnion block 31- is also provided with diametral trunnions 36 horizontally disposed, and adapted to slide longitudinally in guide slots 28 cut in each of the side-plates 23. The toggle-links 27 are hinged on forks 26 of the operating lever by hinge studs 37, the opposite ends of the links being pivotally connected to trunnions 36.

Increasing leverage feature A novel feature of the invention is provided by thc special toggle linkage mechanism for producing progressively increasing mechanical advantage as the operating lever is angularly displaced to increase the pitch of the blades. Since mechanical advantage obtained by the action of levers and links is commonly called 1everage, this feature is termed the increasing leverage feature.

In this connection, the main fact to be considered is that the tendency of centrifugal force acting on thc blades of a propeller when in rotation is to turn the blades to a slightly negative pitch. This tendency is illustrated in Fig. Vl, which shows a typical curve of the centrifugal torque acting on the blades of a marine propeller running at a certain number of revolutions plotted against the pitch angle of the blades, the data for the curve shown having been determined by spinning the propeller in air. It may be mentioned that the hydrodynamic forces acting on a marine propeller in operation normally oppose to some extent the effect of centrifugal force, since their general tendency is to increase the pitch of the blades. However, in practice the resistance to turning the blades generally increases with the pitch, and hence it is highly advantageous to provide a pitch changing mechanism having increasing leverage, which is here provided in the following manner.

The operating member, which comprises the pitch control lever 40 and associated parts, constitutes a bell crank lever, since it is pivoted about a fixed axis or fulcrum 25 and transfers turning motion from one direction to another direction. The portion of the operating member between axis 25 and hinge studs 37 constitutes the crank arm of the bell crank lever, and it is upwardly inclined from the axis 25. The toggle-links 27 connect the crank arm to the cross-head assembly so as to slide the latter along the shaft upon angular displacement of the operating lever, this portion of the mechanism constituting what is customarily called a toggle joint. Considering that the lever mounting aXis 25 is disposed at the level of the propeller shaft 20, and hence of the connecting or control rod 21, the aforesaid arrangement of crank arm and toggle links 27 results, when the pitch control lever 40 is moved in a direction as to increase the pitch of the blades, in the point of pivotal connection between said crank arm and toggle links moving towards a straight-line relationship with said axis 25 and the point or line of pivotal connection of said toggle links and the control rod; that is to say, it lowers throughout the angle A. Fig. III. The mechanical advantage or leverage of the linkage mechanism comprising the operating lever, crank arm, toggle-links and crosshead can be calculated in any particular case from the formula:

where L1=effective length of operating lever Lz :length of crank arm L3=length of toggle-links A--angle of crank arm from shaft axis These quantities are indicated in Fig. Ill, from which it may be seen that the linkage mechanism of the invention comprises essentially a combination of the elementary mechanical movements customarily called a bell crank lever and a toggle-joint.

The overall mechanical advantage of the pitch changing mechanism is equal to the leverage of the linkage mechanism multiplied by the mechanical advantage of the twin crank-pin movement in the hub, which latter can be assumed as approximately 2:1. As a practical example, assume that the ratio L1/L2=5, the ratio L2/L3=.67 and the crank angle A=5. Then the theoretical overall mechanical advantage would be Thus, assuming further that the mechanical efficiency of the mechanism is 60%, the actual mechanical advantage would be .6X 69:41; which means that any manual effort applied to the pitch control lever 40 would be multiplied about 40 times upon application to change the pitch of the blades.

As illustrative of the advantage of the increasing leverage feature, a typical curve of overall mechanical advantage plotted on angular displacement of the blades from zero pitch angle is also shown in Fig. Vl. It is apparent from comparison with the blade torque curve that the increasing leverage feature will tend to enable the operator to increase the pitch from neutral to full ahead without substantially increased manual effort. Whereas, greatly increased effort would be required by simple lever mechanism having a fixed leverage, typical of the prior art. Since the main limitation in the practical application of manually operated controllable-pitch propellers is to be found in the manual effort necessary to control the pitch at maximum pitch settings, it becomes evident that the increasing leverage feature materially extends the range of application of such propeller systems. For example, in the typical case illustrated in Fig. Vl, the overall mechanical advantage is quadrupled due to the increasing leverage feature, in effect extending the range of application upward fourfold.

Operating lever retaining and indexing device Referring now to Fig. V, a friction device is provided to retain the operating lever 40 in any position to which it may be set. This device, which is carried by the operating member, comprises compression springs 38 slidably mounted on a cross-pin 39 and bearing against domeshaped caps 41 which work in holes drilled in side forks 26 and over the ends of cross-pin 39. The caps 41 frictionally engage the inside surfaces of side plates 23, each of the latter being preferably provided with a hollow or hole located opposite the neutral position of the operating lever 40. The purpose of this latter feature is to provide a tactually perceptive index or indication of the neutral position of the operating lever 40, for the convenience of the operator. ln other words, the operator is apprised, merely by the feel of the lever, when the operating lever is in neutral position.

The cross-members 24a and 24h may also be utilized as stops to limit the travel of the operating lever 40; the ends of cross-member 24b being mounted in elongated slots provided in side-plates 23, so as to be adiustable in position, thereby to limit the maximum forward pitch. Adjustment of the reverse pitch limit is not usually required. but can be proxided for in the same way as the forward pitch limit by mounting the ends of cross-member 24b in slots in the side-plates.

Special shaft couplings' Referring again to Fig. l, it may be noted that the propeller assembly is fastened tightly to the propeller shaft by a special keyless flange coupling. thereby avoiding weakening the propeller shaft by cutting a key-way in it. This special coupling, called the Myriad Lock coupling, is described in detail in my copending application Serial No. 34,641 tiled June 23, 1948.

While a conventional flange coupling, or the Myriad Lock coupling could be provided to couple the propeller shaft 20 to the engine shaft, preferably a special flange coupling, as illustrated, is provided for convenience in installation. This coupling comprises a flanged coupling 42 adapted to fit the propeller shaft and 'to be fastened to the engine shaft flange (not shown) by bolts in the usual manner. ln lieu of the usual keyed connection between the ordinary flange coupling and shaft, the flange coupling 42 is preferably connected rigidly to the shaft by two taper pins 43 located 90 apart and tightly driven into tapered matching holes in the flange member and shaft. The purpose of this construction is as follows. When the propeller equipment of the invention is supplied in kit-form, the propeller shaft and connecting rod are provided in maximum lengths, and usually have to be cutoff to proper length for the particular installation. To cut a key-way in the shaft, as for the usual flange coupling, requires machine shop facilities. But by providing the proper sizes of taper pins, drills and taper reamers as part of the equipment supplied in kit form, the fitting and assembly of the propeller shaft to the shaft coupling and of the connecting rod to the wedge can be performed by means of hand tools, thereby facilitating the installation of the propeller while saving expense.

Operation The pitch control lever is shown in .neutral position indicated by N in Fig. III, that is, the position in which the blades have insufficient pitch t0 produce driving action; altho they absorb some engine torque, which prevents the engine over-speeding while the blades are in neutral pitch. The pitch changing mechanism is usually arranged to provide greater ahead pitch than astern pitch. since full pitch is only required when the boat is going full speed ahead.

The operation of the pitch changing mechanism is as follows: For purposes of starting the engine and when idling. the pitch control lever is positioned in the neutral or N position. To get underway, the pitch control lever is moved ahead towards the forward or F position, thereby sliding the cross-head assembly forward along the propeller shaft. The motion of the cross-head assembly is transmitted by the control rod to the cam, which is thereby translated and applies a torque couple to each of the blades so as to increase their pitch and thus to drive the boat ahead. Meanwhile, the throttle of the engine is usually opened by the operator to provide greater power, as required to drive the boat at increasing speed.

As previously described, the mechanical advantage of the pitch changing mechanism increases rapidly as the pitch control lever is moved toward the forward position due to the action of toggle-joint Lz-Ls (see Fig. III), thereby facilitating the pitch advancing operation. When the pitch control lever is moved to full forward position, indicated by F, the toggle-linkage becomes straight and cannot be reversed by the blades. The operating mechanism is therefore positively self-locking in the normal running position. At intermediate vpitch positions, the pitch control lever is effectively maintained in any position to which it may be set by the friction clutch device shown, taking into consideration that the twin crank-pin movement in the hub is effectively irreversible.

To reduce or reverse the pitch, thereby to slow-down, stop, or reverse the motion of the boat, the pitch control lever is merely moved towards the reverse or R position, thereby moving the various parts of the pitch changing mechanism in the reverse direction to reduce or reverse the pitch of the blades.

By reason of the positive mechanical connections of the links of the operating mechanism, the angular position of the pitch control lever always indicates the pitch of the blades, hence there is no need for other pitch indicating means. Further, the pitch can always be set to any desired intermediate degree merely by properly positioning the pitch control lever, which latter will be held in that position by the friction clutch device against displacement by vibration or reaction forces. Due to the mechanical efficiency of the operating mechanism, and the large and progressively increasing mechanical advantage which it provides, the reaction force to be overcome by the operator is greatly diminished, with the practical result that the pitch changing mechanism of the invention can be applied to the manual control of the pitch of propellers directly driven by high speed engines of considerable power, say up to one hundred horsepower. Further, due to the non-reversing characteristics of the mechanism, any possible recoil force or kickback at the pitch control lever is reduced to negliglble proportions, eliminating any danger of loss of control by or injury to the operator.

It is to be expressly understood that While the general form of the invention selected for illustrative purposes is what may be termed the universal form adapted for general use with small engines of various types and sizes, the invention can be readily adapted for use with any particular engine within the power range where the propeller system of the invention may be applicable. For example, it is contemplated that the pitch control vmechanism may be mounted on the engine about the drive shaft in the manner of clutch and reverse gear mechanisms, and supplied as an integral part of the engine. It is also contemplated that the pitch control lever may be powered by so-called booster devices, whereby the operator merely controls the application of power for pitch changing purposes. It is also to be particularly noted that the propeller system of the invention is readily adaptable to equipping existing vessels with that system as a replacement for fixed pitch propeller, and without alteration of conventional propulsion arrangements.

It is thought evident without further discussion that the invention provides a thoroughly practical and reliable controllable reversible pitch propeller system well-adapted for manual operation and having outstanding advantages over the prior art.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. The appended claims are therefore intended to cover all such modifications and changes.

I claim:

l. A controllable pitch marine propeller system comprising, in combination; a hollow propeller shaft; a controllable pitch propelelr aflixed to the outboard end of said shaft, said propeller including a hollow hub with propeller blades journaled therein so as to be axially rotatable and an irreversible mechanical movement within said hub for applying a torque couple to each of said blades, said movement comprising a pair of diametral crank pins on the inner end of each blade and a prismatic cam translatable coaxially in said hub and having complementary trochoidal cam grooves positively driving said crank pins; a control rod afxed to said cam and mounted coaxially translatable within said propeller shaft for translating said cam; and pitch control mechanism mounted about said propeller shaft away from said propeller and comprising a stationary frame, a pitch control lever pivotally mounted in said frame at the level of said propeller shaft, a cross-head assembly mounted slidably upon said propeller shaft and operatively connected to said control rod to translate the latter, and a toggle linkage connecting said control lever to said cross-head assembly and operative to produce a progressively increasing mechanical advantage as said control lever is moved in a direction as to increase the pitch of said blades, said toggle linkage comprising a crank arm xed to said control lever and a toggle link pivotally connected to said crank arm and said cross-head assembly and being arranged so that as said control lever is moved as aforesaid the point of its connection with the crank arm moves toward straight-line relationship with the control lever mounting and the control rod.

2. A controllable pitch marine propeller system comprising, in combination; a hollow propeller shaft; a contrallable pitch propeller affixed to the outboard end of said shaft, said propeller including a hollow hub with propeller blades journaled therein so as to be axially rotatable and an irreversible mechanical movement within said hub for applying a torque couple to each of said blades, said movement comprising a pair of diametral crank pins on the inner end of each blade and a prismatic cam translatable coaxially in said hub and having complementary trochoidal cam grooves positively driving said crank pins; a control rod affixed to said cam and mounted coaxially translatable within said propeller shaft for translating said cam; and pitch control mechanism mounted about said propeller shaft away from said propeller and comprising a stationary frame, a pitch control lever pivotally mounted in said frame at the level of said propeller shaft, a cross-head assembly mounted slidably upon said propeller shaft and operatively connected to said control rod to translate the latter, and a toggle linkage connecting said control lever to said crosshead assembly and operative to produce a progressively increasing mechanical advantage as said control lever is moved in a direction as to increase the pitch of said blades, said toggle linkage comprising a crank arm integral with said control lever and extending upwardly at an angle to said lever from the lever mounting, and a toggle link pivotally connected to the upper end of said crank arm and to said cross-head assembly and being arranged so that as said control lever is moved as aforesaid the point of its connection with the crank arm moves toward straight-line relationship with the control lever mounting and the control rod.

References Cited in the tile of this patent UNITED STATES PATENTS 484,382 Wattles Oct. ll, 1892 1,203,557 Gallaudet Oct. 31, 1916 FOREIGN PATENTS 760 Great Britain Oct. 3l, 1907 16,473 Great Britain lune l, 1905 20,776 Great Britain Sept. 8, 1894 7,666 Sweden May 4, 1896 686,214 France July 23, 1930

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