US2705468A - Twin screw outboard motor - Google Patents

Description

April 5, 1955 3 mx TWIN SCREW OUTBOARD MOTOR Filed June 9, 1952 INVEN TOR. Syn/vs Y 0 .2

United States Patent TWIN SCREW OUTBOARD MOTOR Sydney Dix, Los Angeles, Calif.

Application June 9, 1952, Serial No. 292,527

3 Claims. (Cl. 115-18) This invention relates to outboard motors. It is particularly adaptable to outboard motors for driving watercraft at high speeds, comparable to the speeds of inboardmotor powered speed boats.

On all boats propelled by a single propeller, the propeller applies a torque to the boat acting about a generally horizontal axis, which tends to overturn the boat toward the right hand side of the boat, if the propeller turns clockwise, and toward the left hand side of the boat if the propeller turns counterclockwise. This torque is balanced by an upward thrust component on the downwardly urged side, which is the vertical component of the resistance of the water to the propelling force acting upon the boat. Also if the motor is suddenly stopped or greatly decelerated, this upward thrust continues as the boat travels under its momentum and since the propeller is no longer generating any torque, the upward thrust is unbalanced and tends to overturn the boat toward its opposite side.

This torque is present whether the boat is powered by an inboard or outboard motor. Ordinarily of little consequence, it may actually overturn high speed boats, which have hulls designed to plane the boat with the bow high out of the water. In the case of inboard motor powered speed boats, the boat may be designed as to beam, weight, displacement and hull lines to satisfactorily overcome this tendency to overturn. In an outboard motor propelled boat it is diflicult to design the boat to prevent its being overturned at high speeds, because the torque is applied well to the rear of the stern of the boat. Furthermore, the outboard motor is manufactured and sold for interchangeable use with boats of a wide variety of design. It would be impracticable to build boats specially designed for high speed without outboard motors, for the field of use of such boats would be very limited.

In accordance with this invention the outboard motor is provided with two oppositely rotating propellers, developing oppositely acting torques, which neutral ze each other. With the elimination of any torque m either direction of rotation, if the boat is planed to throw the bow well above the water line, so as to lower the resistance of the water to the movement of the boat, there will be no danger of the boat being overturned.

In inboard-motor powered boats planing 1s accomplished by a suitable and special design of the boat, and particularly of the hull of the boat. But any boat w th an all purpose hull may be made to plane sat sfactorily when powered by an outboard motor of this nvention. For this purpose the outboard motor is provided with an elongated transverse submerged body similar to an airplane wing. This body has upper and lower Skln surfaces of airfoil contour joined fore and aft to con stitute what may be termed a waterfoil body. When this body is adjusted to travel substantially horizontally through the water it has no effect upon the fore and aft pitch of the boat. But when tilted forwardly and downwardly on a horizontal axis it lifts the bow of the boat upwardly, causing the boat bull to act as a planing surface. The angle of pitch may be regulated to provide the desired planing effect by the hull, for any given distribution of weight in the boat. Thus by the use of twin propellers and an adjustable waterfoil on the outboard motor, any boat may be made to maintain an even keel and to plane at the proper angle of pitch for any desired speed, and under a wide variety of conditions.

While outboard motors are conventionally supplied with a rudder beneath the propeller, which turns with the entire outboard motor assembly upon manipulation of the tiller bar, steering is also facilitated by the change of direction of the propelling force, when the propeller axis is angled.

With this understanding of the advantages realized by an outboard motor of this invention, one embodiment of the invention is now described in connection with the accompanying drawings. The invention is not limited to this particular outboard motor but includes all outboard motors coming within the scope of the appended claims.

In the drawings:

Figure 1 is a perspective view of an outboard motor embodying the invention;

Figure 2 is a vertical sectional view taken along the line 2-2 of Figure 1;

Figure 3 is a horizontal sectional view taken along the line 33 of Figure 1;

Figure 4 is a perspective view of the control mechanism for the propeller assembly; and

Figure 5 is a fragmentary sectional view taken along the line 55 of Figure 4.

In the drawings, the outboard motor is shown as comprising a power unit generally indicated by the numeral 10, and a transmission and propeller unit generally indicated by the numeral 11, and a planing body 12.

The power unit 10 comprises a motor housing 13 in which is mounted the outboard motor on a vertical axis, and the fuel tank (not shown). The drawing shows on the motor unit a rope starting sheave 14, starter rope 15, throttle lever 16, fuel tank cap 17 of conventional design and relationship, and the tiller bar 26 and handle therefor.

The transmission and propelling unit comprises the oppositely rotating propellers 21 and the power transmitting mechanism by which the motor drives the propellers. The shafts and gears of the propelling mechanism are enclosed within a vertical drive shaft housing 18 fixedly related in fluid tight manner to the motor housing 13, Within a cross shaft housing 36 (see Figure 3) fixedly related to the housing 18, and within two propeller drive shaft housings 20 fixedly connected to the cross shaft housing 36. The propeller drive shaft housings are each formed with a rudder 20a projecting downwardly therefrom. The drive shaft housing 18 and propeller housings 20 are preferably, as shown in Figure 3, of a cross-sectional contour such as to minimize retardation or drag of the outboard motor, due to fluid friction or to water turbulence.

The planing body 12 comprises an internal frame structure oscillatably mounted on the cross shaft housing 36, as will be described below, and an envelope 19 mounted on this frame structure of a sectional contour as illustrated in Figure 1 and in dotted lines in Figure 2 to likewise reduce resistance to the passage of the housing through the water but principally to convert the force of resistance of the water into a lifting or depressing pressure component acting upon the cross shaft housing and through it upon the outboard motor assembly as a whole. The cross shaft housing 19 may be said to have a hydrofoil contour similar to the airfoil contours characteristic of aircraft wings by which .the propelling force applied to the aircraft is utilized to overcome the force of gravity.

The vertical drive shaft housing 18 is formed with a forwardly projecting lug 25 and another lug (not shown) directly beneath the motor housing 13, between which a support 23 is mounted to pivot: on a vertical axis. This support is formed with a barrel portion 24 disposed between the lower lug 25 and its companion lug thereabove. To a forward portion of the support 23 are hinged a pair of transom brackets 22 by which the outboard motor is secured to the transom of the boat with which the outboard motor is used. Clamps 22a mount the outboard motor firmly upon the transom in conventional manner. The transom brackets 22 may be adjusted with relation to the support 2.3 to vary over a limited range the angle of pitch of the support 22 and with it the outboard motor assembly as a whole with respect to the boat.

Patented Apr. 5, 1955 The housing 18 encloses a vertical direct drive shaft 27 which is mounted in upper and lower bearings supported by and within the housing. The lower bearing 29 is carried by a cross plate 28 which extends outwardly from the shaft and its bearing to the forward and side walls of the housing 18 and rearwardly to the bulkhead 67 spaced a short distance forwardly from the rear meeting edges of the side walls of the housing 18. This cross plate 28 is joined to the housing 18 and bulkhead 67 in a manner to form a water-tight oint therewith and seal off the chamber 53 surrounding the shaft from contact with the water. A bevel gear 30 is keyed to the lower end of shaft 27.

A horizontal drive shaft 31 is mounted within the cross shaft cylindrical housing 36 in three bearings, each shown in Figure 3 with a designating numeral 38. The two end bearings 38 are mounted in bearing blocks 37 which are in turn secured within the cylindrical housing 36. The middle bearing 38 is mounted within a bearing block 39 which is also secured within the cylindrical housing 36. The shaft 31 has keyed or otherwise rigidly secured thereto a bevel gear 32 which meshes with the bevel gear 30 on the vertical shaft 27. Upon each end of the shaft 31 beyond the bearing blocks 37 is keyed or otherwise rigidly secured a bevel gear 33.

The propellers 21 and the propeller drive devices within the propeller drive shaft housings 20 are identical in construction. Each of the propeller drive shaft housings 20 is fixedly related to the cross shaft housing 36. In each of the propeller drive shaft housings a forward bearing 44 for the propeller shaft 35 is seated within a thickened nose portion 45 of the wall of the propeller drive shaft housing. Another bearing 48 is carried by a cross partition wall 46 which extends outwardly to the walls of the housing 20 and is suitably secured there to, as by fastening screws. A cylindrical block 47 which is shaped to fit snugly within the housing is bolted to the partition wall 46 and carries at its rear end a third bearing 49 for the propeller shaft 35. At the rear end of the bearing 49 a water sealing ring 50 is used to protect the bearings of the shaft 35 from Water and to exclude water from the chamber 51 within which the bevel gear 33 revolves. Bevel gear 34 fastened to shaft 35 meshes with the bevel gear 33 to transmit power from the cross shaft 31 to the shaft 35 and to the propeller 21 at the rear end of the shaft 35. It is apparent that the two propellers will rotate in opposite direction.

As stated above, the cross'shaft housing 36 and propeller shaft housings 20 are fixedly related. The planing body 12 may be tilted with respect to the transmission and propelling unit and the power unit about a horizontal axis extending longitudinally of the cross shaft housing 361 This horizontal axis is coincident with that of the horizontal drive shaft 31. The cylindrical housing 36 of the horizontal drive shaft 31 is fixedly secured to the vertical shaft housing 18 and the propeller drive shaft housings 20, by welding or other means at the junction of their respective envelopes.

The hydrofoil contoured skin of the envelope 19 of the planing body 12 is of given form and stiffened by an interior framework consisting of a pair of vertical end plates 40-40, and a pair of central rib plates 41-41. The propeller shaft housings 20 are adjacent the end plates 40-40. The rib plates enclose the lower end of the vertical housing 18 as is best seen in Figure 3. The rear ends of the stiffening rib plates 41 are joined by a yoke 43.

The planing body 12 with its envelope 19 may oscillate over a limited are around the cylindrical housing 36. To provide for this relative oscillatory movement, the two end plates 40-40 and two rib plates 41-41 are journaled upon the housing 36 by means of four bearings, each shown and designated by the numeral 42 in Figure 3. Thus it is evident that the hydrofoil contoured envelope 19 may be oscillated about the axis of the housing 36 with respect to the motor unit and the transmission and propeller unit to vary the angle of pitch of the hydrofoil contoured skin of the envelope 19 with respect both to the rest of the outboard motor and to the boat.

Control of the pitch of the envelope 19 is accomplished in the following manner. A link rod 54 is pivotally connected at its lower end to a lug 43a on the yoke 43 and at its upper end to an arm 55 of a bell crank lever. The link 54 is bent near its lower end and disposed to reciprocate vertically in a chamber 68 between the bulkhead 67 and the rearmost portion of the sidewalls of the housing 18. The lower end of the rear edge of the housing 18 is slotted for the accommodation of the link rod 54.

The forward end of the arm is secured to a cross shaft 56 (see Figure 4) which is rotatably mounted in a bearing 57 provided in the sidewall of the upper end of the housing 18. The other arm 58 of the bell crank lever is secured to the outer end of the cross shaft 56 outside of the housing 18. To the free end of arm 58 is pivoted a rod 59. The other end of this rod is threaded to engage a nut 60 as best shown in Figure 5. This nut is held against longitudinal movement through the engagement of a screw 64 with a circumferential groove on the reduced end 62 of the nut 60. The screw 64 is disposed in a bracket arm 63 suitably secured to the outboard motor housing 13. The outer end of the nut 60 has a knurled surface 61. It is evident that by manually rotating the knurled end of the nut the rod 59 may be moved longitudinally in either direction and that this motion is communicated by arms 58 and 55 of the bell crank lever to vertically move the link rod 54 and correspondingly elevate and lower the rear portion of the envelope 19. Thus the hydrofoil surfaces of the housing envelope may be angled with respect to the rest of the outboard motor assembly and with respect to the boat.

It will be seen that the chamber 51 in which the bevel gears 33 and 34 have meshing engagement, is sealed off from the water surrounding the outboard motor and that proper lubrication of these gears and associated shafts may be maintained. The same is true of the chambers 52 surrounding the cross shaft 31 and of the chamber 53 surrounding the vertical shaft 27. The arm 55 may operate within a chamber at the upper end of the housing 18 which is suitably sealed from communication either with the vertically upright chamber 53 or the chamber within the motor housing 13 in which the motor and its associated control devices are positioned.

The manner of operation of the outboard motor will be understood from the foregoing description of this embodiment of the invention. A forward upward pitch of the boat hull may be brought about to any desired degree by manipulation of the nut 60 to elevate the rear of the envelope 19. The boat may thus be planed in just the right amount to drive the boat at the desired speed. The optimum angle of pitch of the boat with respect to the water level may be maintained for any given distribution of weight of the passengers and cargo. The boat will not roll to either side, either when driven by the motor, or when the motor is suddenly decelerated or stopped. All danger of the boat capsizing is eliminated.

I claim:

1. In an outboard motor, the combination of: a support provided with means for fixed securement to a boat transom; a vertically extending first housing pivotally mounted on a vertical axis on said support; a motor at the upper end of said housing; a vertical motor driven shaft in the lower portion of the housing; a horizontal cross member horizontally pivotally mounted centrally of its ends on a cross axis at the lower end of said first housing and having an upper and lower skin of hydrofoil cross section; a cross drive shaft housing secured to said first housing and a cross shaft mounted therein and geared to said vertical drive shaft, said cross shaft being mounted in its housing on an axis coincident with said horizontal cross pivotal axis; two propeller housings at the ends respectively of said second housing; drive shafts in said propeller housings respectively geared to said cross drive shaft to rotate in opposite rotational directions; and propellers mounted on said propeller shafts respectively.

2. The combination defined in claim 1 and in addition thereto: control means mounted on the first housing for pivotally moving the cross member over a limited are.

3. The combination defined in claim 1 and in addition thereto: a pair of rudders, associated with the propeller housings respectively and disposed in the central vertical longitudinal plane of said propeller housings.

(References on following page) References Cited in the file of 'this patent UNITED STATES PATENTS Manker Aug. 23, 1904 Bivert May 2, 1916 5 Owen July 4, 1922 Richey Mar. 10, 1925 Shively Sept. 25, 1951 6 FOREIGN PATENTS Great Britain of 1902 Great Britain Sept. 26, 1923 Italy Ian. 19, 1932 France Jan. 2, 1930

Images