US3231023A

US3231023A - Variable pitch marine propeller

Info

Publication number: US3231023A
Application number: US431251A
Authority: US
Inventors: Don J Marshall
Original assignee: GOODALL SEMI METALLIC HOSE AND M
Current assignee: GOODALL SEMI METALLIC HOSE AND Mfg CO; GOODALL SEMI METALLIC HOSE AND M
Priority date: 1965-02-09
Filing date: 1965-02-09
Publication date: 1966-01-25
Anticipated expiration: 1983-01-25

Description

Jan. 25, 1966 D. J- MARSHALL VARIABLE PITCH MARINE PROPELLER Filed Feb. 9, 1965 INVENTOR: DON J. MARSHALL BY My ATTYS,

United States Patent 3,231,023 VARIABLE PITCH MARINE PROPELLER Don J. Marshall, Edgewater, Md, assignor to Goodall Semi-Wetallic Hose & Mfg. (10., Philadelphia, Pa., a corporation of Pennsylvania Filed Feb. 9, 1965, Ser. No. 431,251 Claims. (Cl. Mil-160.49)

The present invention relates to marine propellers, and more particularly to marine propellers having means for automatically varying propeller blade pitch depending upon the thrust requirements of the driven vessel under varying operating conditions.

Using a fixed blade propeller, the marine designer is seriously handicapped in his attempt to design an all purpose propeller in view of the variable conditions which occur during usage of the propeller on differing size and designed craft. If the propeller is designed for a particular craft or vessel, for example of the pleasure boat, cruiser class variety initially the boat handles excellently, which condition soon changes as the boat is used.

The marine architect in selecting a propulsion unit to be mounted in a newly designed hull, calculates the drag or power-consuming factor of the hull and selects an engine capable of developing the required power to move the hull through the water at a selected speed. The marine engineer simultaneously, selects a propeller of the diameter and pitch which will most effectively convert that power into useful thrust under varying water conditions. Some of the factors entering into his calculations are: underbody lines; gross weight; displacement at the design optimum speed (on plane); hull attitude or trim (weight placement within the hull); frictional effects of fouling on the bottom hull surface; screw placement; and rudder size and position. (For an excellent article on a comparison of the major methods of marine propeller design, see Comparing Four Methods of Marine Propeller Design, by Justin H. McCarthy, page 435, vol. 72, A.S.N.E. Journal.)

When the marine engineer bases his calculations on the'above-mentioned factors as well as others, he is able to predict the performance of the hull surprisingly accurately. However, in the hands of the average boat owner these factors are soon disturbed. For example, added weight in the form of extra equipment, added long range tankage, water absorption by the hull, overload of passengers and supplies, and their placement wherever space permits causing changes in the center of buoyancy, softening of the bottom finish and growth of marine fouling organisms and other factors add to the power demands and requirements of the hull. Adding to this adverse wind and rough water conditions, the propulsion unit designed by the marine engineer and architect for the specific craft is no longer in the hull for which it was designed, and a serious overload condition exists.

Under these conditions the propulsion unit is forced to operate under conditions of overload, the fuel consumption per mile raises, and as a result of power output loss, due to impaired breathing and the like, a decrease in the speed of the hull through the water is experienced.

Faced with these problems many boat owners try to find a new propeller for their vessel or craft. However, due to varying conditions of use, there is no single right propeller for all conditions. All of the hull slowing factors are variables. For example, leisurely cruises sometimes turn into a fast run to shelter in the face of sudden squalls; or a fishing trip with one or two passengers presents a different condition of loading than a family outing of six with hundreds of pounds of supplies; or a few hours'running to and from the best fishing grounds as opposed to four or five hours of slow speed trolling; each of these conditions merit a different screw having a different pitch.

Various cures are illustrated in the prior art, for example, the preset variable pitch propeller wherein the propeller is set before every outing based on some kind of guess of the days needs. Other cures illustrated in the prior art include manually variable propellers as well as supposedly automatic variable propellers. These systems require constant attention and have proved economically unfeasible because of high initial costs.

In view of the above, it is an object of the present invention to provide a variable pitch marine propeller having means to vary the pitch of its blades automatically to suit varying power demands of the hull and engine combination with which it is coupled to provide a high level of efficiency without overload of the engine.

Another object of the present invention is to provide a variable pitch marine propeller which changes the pitch of its blades primarily due to changes of thrust requirements so as to provide the pitch angle which will produce the maximum thrust under existing water conditions.

Another object of the present invention is to eliminate the fixed ratio which exists between hull speed and engine r.p.m. by providing an automatically variable pitch marine propeller.

Still another object of the present invention is to provide an automatically variable pitch marine propeller which will develop all of the desirable features of pitch variation automatically, at a lower initial cost, while effecting economies in operation.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawing in which:

FIG. 1 is a side elevation of an exemplary pleasure craft having portions thereof broken away to more clear ly illustrate apparatus used in conjunction with the propeller of the present invention;

FIG. 2 is an enlarged fragmentary view of a portion of a variable pitch marine propeller constructed in accordance with the present invention;

FIG. 3 is a fragmentary sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view taken along line 44 of FIG. 3; and

FIG. 5 is a fragmentary 'view of the device of the present invention and illustrating the propeller in a different position from the position shown in FIG. 2. Referring now to the drawing, and especially FIG. 1, a pleasure craft or boat 10 having a prime mover or engine 11 mounted within the hull 12 of the boat It is connected via a line shaft 13, supported by line bearing 14 and strut bearing 15, to a variable pitch propeller 20. Just beneath the stern of the boat It), and aft of the propeller 20, is a conventional rudder 16. Although the principle of operation of the propeller 20, as hereinafter described, is related to a boat having an inboard engine, it should be recognized at the outset that the variable pitch propeller of the present invention may be used in conjunction with outboard engines.

In accordance with the invention, the propeller 20 is provided with means to enable accommodation of the propeller to the varying thrust requirements of the hull 12. To this end, a shaped collar 21, in the present instance shaped in the form of a hexagonal parallelepiped with opposite parallel edges of unequal length, is mounted on and connected to the line shaft 13 just aft the strut bearing 15 and spaced from a tail stock 22 which is connected to the extended terminus of the line shaft 13 by,

' in the present instance, a bolt 23. As illustrated inthe drawing, the propeller assembly 20 comprises a hub 24 having a hollow frontal portion 25 and an after solid portion 26, coaxially mounted on the shaft 13 and axially movable between the tail stock 22 and the collar 21, Which acts additionally as a stop to limit forward axial movement of the hub. The hub 24 is keyed to the line shaft 13, in the present instance by a frontal plate 27 connected to the hub by bolts 28, and having a shaped aperture 29 to en gage the shaped collar 21 thus permitting rotation of the hub with the shaft 13.

Mounted circumferentially of the hub are a plurality of circumferentially spaced, radially projecting blades 30, each having an axle 31 extending into the hollow frontal portion 25 of the hub 24 and rotatably journalled thereto. The blades 30 may be of conventional marine design of the type normally found on pleasure craft and the like. However, preferably, in order to avoid undesirable reactions or moments on the blades when moving through the water, it is desirable that the axles 31 of the blades 30 be positioned at or along a line through the center of pressure of the resultant working section of the blade. In aeronautics, this point is sometimes referred to as the center of lift, but at any rate means the point in the chord of an airfoil section, prolonged if necessary, which is at the intersection of the chord and the line of action of the resultant water or air force.

In order to permit automatic adjustment of the blades 30 about their axles 31 dependent upon the thrust necessary to propel the craft through the water, means are provided interiorly of the hub to increase the pitch of the blades as thrust demands are increased. To this end, interiorly of the hub and mounted in the present instance on the terminus of each axle 31, is a lever arm 32 (see FIG. 4) having a leading and

trailing edge

33 and 34. Each of the levers has a first cam portion 35 on the leading edge 33 and spaced longitudinally of the lever, a second cam portion 36 on the trailing edge 34 thereof. In the present instance the first cam portion 35 of each lever arm 32 is aligned axially of the line shaft 13 with a portion 37 of the collar 21, for purposes which will hereinafter be explained. In the after solid portion 26 of the hub 24, mounted in bored holes 39 and aligned with the second cam portion 36 of each lever arm 32, is thrust reaction or biasing means, in the present instance comprising compression springs 38.

In operation, the biasing means or spring 38 engages the second camming portion 36 of the lever arm 32, which tends to maintain the blade 30 associated therewith at its finest pitch angle, such as illustrated in FIG. 2. As the blades commence rotation, in the counterclockwise direction as viewed in FIG. 3, and increased thrust demands are made of the propeller 20, the hub 24 moves axially of the shaft against the collar 21 causing bearing means 37 on the after side of the collar 21 to bear against the first cam portion 35 thereby causing rotation of each blade about its axle 31. As may be seen in FIG. 5, as thrust'demands are increased to a maximum, the second cam portion 36 moves against the spring 38 until the spring is fully compressed and the hub 24 is forward against the collar 21. In this position the blades are at their maximum pitch angle and attempt to move the boat through the water the maximum amount for each revolution of the shaft 13.

In practice the spring pressure rates of the springs 38 can be made linear or curvilinear so as to more closely match the torque curve of a particular engine for a particular boat. One of the advantages of the above-(la scribed arrangment of the biasing means or springs is that the springs do not have to be closely matched in manufacture as the blades are effectively coupled together via the hub, levers and collar.

The manner in which spring force for a single blade may be calculated is: Spring force developed thrust+ No. of blades+distance from the center of an axle to the second cam portion/distance from the center of the axle to the first cam portion. For example, assume a HP. engine develops 900 lbs. thrust at full power and a three-bladed propeller is provided on the shaft of the engine. Further assume that the ratio of distances of the second cam portion to the first cam portion from the center of the axles is 3/1. Spring force (force to close the spring)=9-00 lbs/3 blades/M1 lbs.

Many existing outboard and inboard propellers are provided with slip clutches which prevent damage to the propeller blades by effecting slip between the blades and the prime mover upon the blades striking a hard object. The conventional slip clutch normally comprises a compressed sleeve or disk of rubber mounted between the drive shaft and the hub connecting the blades, which compressed rubber is capable of movement relative to the hub if a blade associated with the hub strikes, for example, the sandy bottom or other objects impeding the free rotation of the blades through the water.

The variable pitch marine propeller of the present invention lends itself for easy adaptation of a slip type clutch which may be mounted in either the tail stock or forward of the hub. For example, if a slip clutch were to be mounted in the tail stock, a slip clutch could comprise a pair of concentrically mounted radially spaced sleeves, the inner sleeve being secured to the shaft extension and the outer sleeve splined or connected to the after portion of the hub. Between the inner and outer sleeve a compressed sleeve of rubber is mounted, which sleeve of rubber affords driving connection between the shaft extension and the outer sleeve thus affording rotation of the hub. Of course in an arrangement such as above described, the collar mounted forward of the hub would preferably be circular in cross section thus providing no keying of the collar to the hub, rotation being caused solely by the connection of the hub to the aforementioned outer sleeve.

Thus, at slow speeds such as when trolling or the like, when thrust requirements are at a minimum, the propeller pitch will be automatically suited for slow speed, minimum thrust requirements, i.e. a fine pitch. 0n the other hand, when the boat is being subjected to increased drag conditions, such as when cruising at high speeds, thrust requirements are increased and. accordingly, the blades of the propeller will attain automatically a pitch best suited for existing requirements. The result is that the pitch of the blades is automatically adjusted to accommodate any water state, hull condition and speed of hull.

Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and combination and arrangement of parts may be made without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. In a boat having a hull and a prime mover carried thereon, a line shaft connected to said prime mover at one end and extending exteriorly of the hull and terminating in a tail stock, a variable pitched propeller mounted on said shaft adjacent said tail stock; a shaped collar mounted on and connected to said shaft and spaced from said tail stock, said propeller comprising a hub, having a hollow portion and a solid portion, axially movable on said shaft between said tail stock and said collar and keyed to said shaft to rotate therewith, circumferentially spaced, radially projecting blades each having an axle and extending into the hollow portion of said hub and rotatably connected thereto, a lever having a leading and a trailing edge, secured to each of said axles interiorly of said hub in said hollow portion, each of said levers having a first camming portion on said leading edge and a second camming portion on said trailing edge, thrust reaction means in said solid portion of said hub for engaging said second camming portion and means on said collar to engage said first camming portion whereby upon rotation of said shaft the resulting thrust from said blade rotation causes said hub to move axially of said thrust rotating said blades about their axles until said thrust reaction means force equals the thrust on said hub.

2. Apparatus in accordance with claim 1 wherein said blades are mounted on their axles along a line through the center of pressure of said blades.

3. Apparatus in accordance with claim 1 wherein said thrust reaction means comprises a spring.

4. Apparatus in accordance with claim 3 wherein said spring has a curvilinear pressure rate closely approximating the torque curve of said prime mover.

5. Apparatus in accordance with claim 1 wherein said hub is mounted coaxially of said shaft and contains means References Cited by the Examiner UNITED STATES PATENTS Kellogg et al 170--160.49 Bellman 170-160.51 Irgens 170164.54 Bugatti 170-160.53 Miller 170-16049 Gansert 170-160.59 X Coleman 170-16053 Italy.

defining a shaped aperture to receive and engage said 15 JULIUS E. WEST, Primary Examiner.

collar therein.