What is claimed is
1. A propulsion and control system for a minimum drag planing hull comprising the combination of: a pair of outboard stern-mounted counter-rotating propellers each having a hub and a plurality of variable pitch blades, said propellers being mounted so that during planing said propellers are in water contact substantially only to a depth not exceeding the length of any of said blades and said hubs are substantially out of water contact; means for supplying mechanical power to said propellers in such a way as to cause said counter-rotation; first pitch control means for controlling the pitch of said blades differently to vary the thrust contribution of each of said propellers and thereby to provide steering control; and second pitch control means for controlling the pitch of said blades together and in the same sense, thereby to effect speed control and control between forward and reverse.
2. The invention set forth in claim 1 further defined in that said blades are all of uniform size and shape.
3. The invention set forth in claim 1 further defined in that said first and second pitch control means both include means for maintaining all of the blades of each propeller always in the same sense and at the same pitch angle.
4. The invention set forth in claim 1 further defined in that each of said propellers includes means for maintaining all of its blades at substantially the same pitch angle and for varying the blade pitches of each of said propellers uniformly, said means including a pinion gear affixed to the shaft of each blade, and a gear rack in contact with each of said pinion gears, said gear racks being structurally integral with each other.
5. An inboard power boat propulsion and control system comprising: A pair of propellers mounted at the rear of said boat on respective shafts protruding through the transom of said boat, said propellers each comprising a hub assembly and a plurality of variable pitch blades, said shafts being so mounted as to position said propellers with respect to the surface of the water so that substantially only said blades are in water contract as said propellers turn and said hubs remain substantially above said surface of the water; means for supplying mechanical power to said propellers in a manner so as to cause clockwise rotation of one of said propellers and counterclockwise rotation of the other; means for varying the pitch of the said blades of one of said propellers in a first sense while simultaneously varying the pitch of the blades of the other of said propellers in the opposite sense to control the direction of the net propulsion force vector thereby to effect steering of said boat; and means for varying the pitch of the said blades of both of said propellers simultaneously in the same sense, thereby to control the magnitude and sense of the propulsion force vector parallel to the bow-stern axis of the boat.
This invention relates to aquatic vehicles, and more particularly to power propelled boats. It is most useful in connection with a "speed boat" having a planing hull.
It is normally considered necessary for "speed boats" to make use of the planing principle as contrasted from the principle of the displacement hull upon which larger vessels ordinarily depend. In connection with a planing hull it will be noted that there is no appreciable depth to the keel section of the boat and use is made of the fact that such a boat planes across the surface of the water over a cushion of water mixed with air bubbles. The familiar hydrofoil which is frequently driven by an air contact propeller is one approach to solving the problem of minimizing the drag introduced by rudders, propeller shafts, propeller hubs, and other structural and functional members which project downward into the water.
As compared to a hydrofoil driven by an air propeller the present invention provides a much more efficient and less expensive configuration. Obviously the air propeller drive is also a cumbersome and inherently dangerous device which tends to apply the forward thrust to the boat too far above the water line to be optimum. The present invention obviates the disadvantages of this type of boat drive, and as compared to the more conventional inboard and outboard motor boat configurations the following is to be noted.
Both inboard and outboard prior art motor boat propulsion systems require the use of drag producing members which project into the water. An outboard motor necessarily loses a large portion of its gross forward thrust end power efficiency because of the drag caused by the shaft housing, hub, skeg, and exhaust, all of which project downward into the water below the transom of the boat.
Conventional propellers used in the prior art inboard and outboard motor boat configurations are also relatively inefficient due to the large difference in speed between the blade tip and the portion of the blade nearest the center of rotation. Such conventional propellers, moreover, are necessarily thicker nearest the hub for structural reasons, and this results in a further loss of thrust producing capability. The present invention also tends to abviate another of the more familiar disadvantages of the conventional inboard or outboard motor boat configuration. This is the fact that the position of the propeller is, in these prior art situations, lower than is desirable for the production of maximum planing efficiency. In accordance with the present invention it will be seen that the net location of the forward thrust vectors is very nearly in line with the water contact surface of a planing hull, which is a great advantage from the point of view of maximum power efficiency through a more efficient thrust transfer.
The present invention moreover eliminates many of the conventional parts of prior art motor boat propulsion systems while providing such increased thrust efficiency and much greater operational flexibility including dock maneuvering and power braking.
In comparing the present invention with the usual prior art inboard motor boat it will be noted immediately that the present invention eliminates the need for clutching, shaft log, rudder, rudder packing gland, propeller shaft, and propeller shaft strut. Notwithstanding the elimination of these parts it will be shown that the configuration of the present invention is more efficient and maneuverable than any prior art signle or double propeller inboard motor boat configuration.
As compared to the usual prior art outboard motor boat arrangement, it will be noted that the present invention eliminates the outboard shaft housing, the outboard hub housing, the skeg, and the outboard exhaust pipe.
The present invention moreover provides the advantage which would accrue from the use of a torque converter or a multispeed transmission, in that the adjustable pitch of the propeller blades according to the present invention provides the ability to match engine speed and torque to various boat load and speed conditions such that optimum throttle and pitch settings can be found for every condition.
It may be said that the general objective of the present invention is the provision of a motor boat propulsion system which has all the advantages of the prior art conventional inboard motor boat system while maintaining and even improving upon the flexibility and maneuverability afforded by the usual prior art outboard motor boat system. In addition it is an objective of the present invention to provide increased power and thrust efficiency and simple but very effective poser braking. Thses and other advantages of the present invention will be obvious as the description proceeds with reference to the drawings.
For clarity in the elucidation of the present invention drawings are provided as follows.
FIG. 1 illustrates pictorially the assembled elements typical of the invention.
FIG. 2 illustrates pictorially the details of the typical arrangement for providing variable propeller blade pitch in accordance with the present invention.
FIG. 3 a and 3 b illustrate partial sectional views of the propeller drive and pitch control mechanisms.
Referring now to FIG. 1 it will be noted that a relatively conventional motor boat hull is illustrated. The transom or stern section of the hull is shown as a flat substantially vertical member although this and the other specific details of the hull shape are arbitrarily selected for illustration and substantial variations will be seen to be possible as ordinary engineering design option. It will be noted that the depth of the keel as illustrated at 2 is minimal, which is typical of planing type hulls which are most useful in combination with the present invention. It will be noted that a pair of propeller assemblies 3 and 4 are mounted by means of straightforward shaft and bushing arrangements (not visible in FIG. 1). For each of the propeller assemblies 3 and 4 a direction of normal rotation which may correspond to forward motion of the hull or reverse motion (depending upon the specific pitch of the blades of the two propeller assemblies) is illustrated by means of rotational arrows. It will be noted that the two propeller assemblies counter-rotate. This is necessary particularly at high power levels corresponding to high speeds, since the placement of the two propeller assemblies is such that only the blades themselves are in contact with the water at or near the bottom of their travel when the boat is in the full planing mode of operation. Thus the hubs and internal hub mechanisms of the two propeller assemblies 3 and 4 remain substantially out of the water, except at lower or idling speeds when some settling of the hull into the water is normal. A single propeller or two propellers rotating in the same direction would necessarily produce a large side thrust which would obviously be undesirable.
In FIG. 1 the boat transom 1 is partially cut away to expose the gear case 5 mounted just inside the transom. A conventional engine 6 with conventional engine accessories such as an air cleaner 7, manifold 8, etc. is illustrated for driving the gear box 5 in a manner which will be more fully described as the description proceeds. A conventional stearing wheel 25 operates in connection with a wind-unwind drum and cables 10 and 12 which operate in conjunction with the pitch control yoke 9 to differentially vary the pitches of the two propellers as will be more fully described in connection with a later figure. Cable 11 will be seen to be associated with lever 13 to vary the pitches of the two propellers in the same sense at the same time (i.e. to increase or decrease the "bite" of the two propellers at the same time). The slideable bearing 29 will be described more fully in connection with a later figure.
It will be noted the the propeller blades 15, 16, 17 and 18 for the propeller assemblies 3 are shown pitched for forward motion when the propeller assembly is rotating as shown by the rotational arrows. Similarly blades 19, 20, 21 and 22 on propeller assembly 4 are pitched for forward motion in view of the arrows of rotation. Propeller hub mechanisms 23 and 24 are designed to control all the blades of each propeller simultaneously. The control cables of which 10, 11 and 12 are typical are supported by drilled blocks such as 14 in a conventional and well known way.
Referring now to FIG. 2 propeller assembly 3 has been chosen for discussion, however this is an arbitrary choice as the description will be seen to apply equally well to propeller assembly 4. A ribbed disc 23 which has its ribbed ends formed into racks of which 26 is typical is in contact with pinion gears, one to each root shaft of the variable pitch blades 15, 16, 17 and 18. In operation the entire assembly of FIG. 2 rotates and the ribbed disc 23 is only capable of moving with respect to the housing of the propeller assembly 3 along an axial direction for varying blade pitches, in response to the control cables. The ribbed disc 23 is however not permitted to rotate with respect to the housing 3 of the propeller assembly since it is necessary that the rack gears, of which 26 is typical, should always remain in firm contact with the pinion gears of which 28 is typical. In affixing the pinion gears such as 28 to the propeller root shafts such as 27 a keyed arrangement or some other arrangement known in the mechanical arts which is equally resistant of the reaction torque exerted on the shaft 27 by blade such as 15 as it makes high speed contact with the water is necessary. Referring now to FIGS. 3a and 3b, these partial sectional views will be described and referred to together for clarity. FIG. 3b is a sectional view of the gearing in the gear box 5 looking to the rear as depicted by the section cut line in FIG. 3a. It will be obvious from FIG. 3b that the four meshed gears 34, 35, 37 and 39 provide a convenient way of obtaining the necessary counter-rotation of the two propeller assemblies 3 and 4. In FIG. 3b typical blades 15 and 19 will be seen projecting below the bottom surface of the hull into the water thus providing thrust vectors which are very nearly in the plane of the hull bottom. In the configuration shown the application of power could be made either to shaft 36 or shaft 38 making gear 35 or gear 37 the primary driven gear. Gears 34 and 39 are keyed or otherwise firmly attached to the shaft sleeves 42 and 43 respectively. The sleeve 42 moreover is an integral part of propeller shaft assembly 4 as is sleeve 43 an integral part of the housing of propeller assembly 3. Inside shaft 40 is keyed so as to rotate with sleeve 42 and the same is true of shaft 41 with respect to sleeve 43. The keying of these later shafts to the sleeves through which they pass is the expedient which keeps the rack gears 26 in contact with the pinion gears 28 inside the typical propeller assembly as depicted in FIG. 2. Shaft 40 is however capable of sliding axially within sleeve 42 and the same applies to shaft 41 with respect to sleeve 43. Couplings (thrust bearings) 30 and 31 permit the axial push and pull necessary in changing propeller pitch while isolating the rotery motion of shafts 40 and 41 from the control yoke 9. The sleeve bushing 29 and shaft 32 provide an additional slideable freedom used when the propeller shafts are simultaneously varied as will be seen under the operational description to follow.
In understanding the operation of the present invention let us assume that the engine 6 is permitted to idle or operate at some nominal speed. Although a clutch may be provided between the engine and the gear box 5 the system of the present invention is capable of operating very well without the use of a clutch, although clutching would permit easier engine starting. If it is assumed that the steering wheel 25 is in a neutral position and the lever 13 is essentially in a zero position the cable 11 will have pulled the control yoke to its approximate mid-position within the limits of its travel, and both shafts 40 and 41 will then be presumed to have positioned the ribbed discs 23 within the propeller hubs to an approximate mid-position so that the propeller blades are turned so as to afford "zero bite." That is to say that the plane of each propeller blade is essentially parallel to the plane of the transim 1. If the lever 13 is now advanced to one extreme position such that the ribbed discs 23 in both propeller hubs are moved together in the same direction, the blades of each of the propellers will be pitched to their nominal maximum (greatest "bite"). If the engine throttle is now advanced to provide a large amount of power it may be expected that the boat will accelerate very rapidly. Thus it is to be understood that the movement of the lever 13, which in the one extreme gives full forward and in the other extreme full reverse, operates to advance or retard the control yoke 9 as a unit such that shafts 40 and 41 are withdrawn or advanced within their respective sleeves 42 and 43 by the same amount. If now the steering wheel 25 is turned some amount in a predetermined direction, cables 10 and 12 effect differential movements of the shafts 40 and 41 through the flexible shaft housings in the ends of yoke assembly 9 thereby changing the propeller pitches differentially. As a matter of design, it is possible to provide for extreme turning of the steering wheel to actually throw one of the two propellers into reverse while the other propeller is providing a nearly maximum forward bite. In this way a large force couple in the horizontal plane is applied essentially at the transom of the boat and the result is very efficient close-quarter maneuvering.
Thus it will be obvious that the steering wheel 25 is arranged to cause differential pitching of the blades of either propeller as compared to the other while the blades of any given propeller all assume the same angle. Steering is thus a differential thrust proposition.
It will now be apparent that the present invention provides a ready means for effecting full power braking.
It is believed that it will be obvious to the reader after description to this point that a speeding boat according to the present invention could be changed to "full power astern" simply by full opposite movement of lever 13. No reversing of parts which have significant inertia is necessary, and no moving part needs even to be slowed during this process. There is moreover no need for loss of time because of shifting of gears or engaging or disengaging of clutches etc.
Concerning materials, it will be readily apparent that the engine, boat hull, steering wheel, and other control levers and cables would normally be made of conventional materials commonly used for these elements. The gear box 5, the yoke 9 and various other associated members within the boat hull would be expected to be made from metals customarily used for parts having similar functions in similar environments. The use of non metalic gears in the gear box 5 is of course a possibility but if the invention is to to be applied with a relatively high horsepower engine non metalic gears would normally not be considered. The propellers themselves might easily have their external housings or exterior cylindrical members constructed from bronze or some other metal or alloy which is relatively strong, machinable, and or castable and yet strong and relatively resistant to fatigue and corrosive environment such as encountered in salt water. The blades would preferably be made of a very strong and non corrosive material such as stainless steel, since it is important that their cross-sections be comparatively thin without sacrificing strength. The root shaft of each blade would normally be made of the same stainless steel also, especially where high engine power is involved.
The gears, of which 28 is typical, within the propeller housing should be understood to afford only one means for pitch adjustment. Those skilled in mechanical arts will realize that a crank arm arrangement or some other mechanical configuration could be substituted.
Many other modifications and variations falling within the scope of the present invention will suggest themselves to those skilled in these arts, and accordingly, it is not intended that the invention be regarded as limited to the embodiment illustrated. The drawings are to be regarded as illustrative only.