Marine drive system with belt drive

An outdrive system for watercraft includes use of plastic or other relatively flexible material, e.g., compared to metal, especially as a housing material, and techniques which enable and/or at least facilitate use of such housing material. One of those techniques employs a flexible member, such as a belt, to couple power between the input and output of an outdrive and another employs a cooling system to remove heat. The invention also relates to use in a vehicle drive, especially for watercraft, of housing materials that are not subject to corrosion, galvanic action and the like.

TECHNICAL FIELD 
The present invention relates generally to drive systems for vehicles, 
especially watercraft. More particularly, the invention relates to 
outdrives for boats. 
In a preferred exemplary embodiment of the invention, features include, 
among others, use of plastic or other relatively flexible material, e.g., 
compared to metal, especially as a housing material, and techniques which 
enable and/or at least facilitate use of such housing material. One of 
those techniques employs a flexible member, such as a belt, to couple 
power between the input and output of an outdrive and another employs a 
cooling system to remove heat. The invention also relates to use in a 
vehicle drive, especially for watercraft, of housing materials that are 
not subject to corrosion, galvanic action and the like. 
BACKGROUND 
In an exemplary drive system for a vehicle, there usually is a power 
supply, an output mechanism, a power coupling system, and a housing and/or 
structural apparatus. The power supply typically is an engine or a motor, 
although other means also may be employed. The output mechanism converts 
power received from the power supply to motive force for the purpose of 
moving and directing the vehicle. In a boat, the output mechanism 
typically is a propeller. The power coupling mechanism couples, transmits 
or transfers power from the power supply to the output mechanism. Often 
the power coupling system includes one or more of a drive shaft, an output 
shaft, other coupling gears and shafts, a clutch, a transmission, etc. The 
housing and/or structural support apparatus typically holds one or more of 
the other components of the drive system in relation to each other in 
order to accomplish the appropriate interaction to effect the desired 
driving function. Additionally, the housing and/or structural support 
mechanism may provide, to the extent needed and/or desired, appropriate 
enclosure functions. 
The present invention preferably relates to drive systems for boats. As it 
is used herein, the term "boat" is intended to mean virtually any type of 
watercraft, vehicle, apparatus, device, etc., that is intended to be 
operated on, in and/or under water. The features of the present invention 
are particularly useful with surface craft, i.e., boats that float and/or 
are operated at the water surface, and especially drive systems therefor 
that are rated at from about 100 horsepower up to about beyond 1000 
horsepower. However, it will be appreciated that features of the invention 
may be used with other boat drive systems and at other power levels, e.g., 
those that are rated at less than 100 horsepower or more than several 
hundred horsepower, or even more than 1,000 horsepower, depending on the 
sizes of the several components of the outdrive. 
Moreover, although the features of the present invention are particularly 
useful in and relate to boat drive systems, it will be appreciated, and it 
is intended, that features of the invention may be used in drive systems 
for vehicles other than boats and/or in other applications, too. For 
compactness, though, the following description is directed to application 
of the features of the invention in drive systems for boats; application 
of features of the invention in other drive systems will be evident to 
those having ordinary skill in the art in view of the disclosure hereof. 
Conventional boat drive systems often are categorized by labels inboard, 
outboard, and inboard/outboard. In an exemplary inboard drive system the 
power supply, which will be referred to hereinafter for convenience as an 
engine although it may be a motor or some other source of power, and the 
majority of the power coupling system are located within the boat, which 
provides at least some housing and structural support functions. The 
propeller and at least part of the propeller shaft, of course, are located 
outside the boat in the water, as also is the case for outboard and 
inboard/outboard drive systems. One example of an inboard drive system is 
an in line system in which the engine, clutch, transmission and propeller 
shaft generally are in line facing from the front to the back of the boat, 
the propeller being at or near the back. Another example of an inboard 
drive system is referred to as a V-drive, as is known. In an outboard 
drive system typically the engine and the power coupling system are 
located outside or mostly outside the boat. Furthermore, in an 
inboard/outboard drive system an exemplary configuration employs an engine 
located in the boat and a power coupling system that has a substantial 
portion located outside the boat. The foregoing is exemplary; it will be 
appreciated that various hybrid combinations of the foregoing categories 
of boat drive systems, as well as other types of boat drive systems also 
exist and/or may exist in the future. 
The present invention includes features that may be useful in the various 
categories or types of boat drive systems mentioned above and in others 
that may not be specifically identified. However, according to the 
preferred embodiment and best mode, as is described in greater detail 
below, the present invention has particular utility when employed in 
and/or with the outdrive portion of the power coupling system of an 
inboard/outboard boat drive system and of outboard boat drive systems. 
Features of the invention also are especially useful in V-drive systems. 
The term outdrive typically means that portion of a vehicle drive system, 
usually excluding the engine, which is located outside the hull of a boat. 
The outdrive usually is part of or is the entire power coupling system of 
a boat drive system and also may include the output mechanism, typically 
the propeller. As they are used herein, the terms outdrive and power 
coupling system may be used synonymously, and such terms also may be used 
to designate non-overlapping parts or functions, i.e., not synonymously; 
the context will make the usage clear. For example, the engine drive shaft 
itself may be considered part of the power coupling mechanism, as is the 
universal joint, but only the latter usually would be considered part of 
the outdrive. 
In a conventional outdrive type of power coupling system, power is coupled 
between the engine and the output mechanism, which for convenience is 
referred to hereinafter as the propeller. Typically during use the engine 
drive shaft or at least the power input shaft for the outdrive and the 
propeller shaft are oriented in generally parallel horizontal directions 
and are vertically spaced apart. The conventional outdrive includes a 
rigid coupling shaft and associated gears to couple the rotary output from 
the drive shaft to the propeller shaft. Accurate positioning of the 
various parts of such a conventional outdrive is necessary in order to 
assure proper alignment and meshing of respective gears and shafts, as is 
well known. Relatively rigid metal castings typically are used as housings 
for such outdrives to provide the necessary stiffness to obtain the 
necessary accurate positioning functions mentioned. 
The gears, coupling shaft, and metal castings employed as housings and/or 
other parts for such conventional outdrives are relatively expensive to 
manufacture and are relatively heavy. A disadvantage due to the weight of 
such conventional outdrives is the difficulty in disassembling the 
outdrive for servicing. Frequently at least two people are needed to 
handle such a heavy apparatus. It would be desirable to reduce the weight 
of and the expense of manufacturing an outdrive. Moreover, by reducing the 
weight of the outdrive, the overall weight of the boat is reduced; and by 
maintaining the same horsepower capability for the outdrive, performance 
of the boat, e.g., the speed, can be improved. Other features of the 
invention, which will be described below also can be employed to reduce 
the weight of the boat and, thus, improve performance. 
The gears and coupling shafts of such conventional outdrives are usually 
located in an oil filled chamber. The oil provides usual lubricating 
function. Heat developed by the rotating gears and shafts heats the oil, 
which is cooled by thermal conduction through the metal housing of the 
outdrive to the water in which the outdrive, indeed the boat, are 
immersed. 
Due to the prior designs of outdrives and the mounting mechanisms for 
mounting the outdrive to a boat, and at least in part due to the 
relatively heavy weight of such prior outdrives, it was a difficult and 
time consuming task to remove the outdrive from the boat. Usually part of 
the disassembly and removal process required work to be performed from 
inside the boat to remove the tiller arm and gimbal ring, and in some 
circumstances the engine itself first had to be loosened or even removed 
to allow access to the mounting mechanism therefor. The gimbal ring 
mounting structure often used in conventional outdrives provides or 
permits for movement of at least part of the outdrive, about two axes, 
typically referred to as rudder and trim axes. The difficulty of removing 
a conventional outdrive is a disadvantage of such prior devices. 
One example of an outdrive which uses a flexible power coupling member in 
the form of a belt is disclosed in Dunlap U.S. Pat. No. 3,951,096. Such 
outdrive has a metal housing with two separate hollow down legs to enclose 
the two respective legs of the belt. Such hollow down legs extend between 
the upper housing portion where a drive sprocket is located and the lower 
housing portion (sometimes referred to as the torpedo) where a driven 
sprocket is located. The driven sprocket is coupled to the propeller. The 
present invention includes a number of improvements that may be employed 
with such a belt driven outside. 
Outdrives have included kickup features so that the outdrive kicks up or 
tilts out of the way when it strikes an object, such as a log, rock, lake 
bottom, etc. to avoid damage to the outdrive and/or other parts of the 
drive system or boat. Usually hydraulic cylinders having high pressure 
hydraulic fluid therein hold the outdrive, especially the propeller, at a 
particular trim angle to obtain a particular thrust angle for desired boat 
operation. If the outdrive strikes an object, hydraulic fluid in such 
cylinders is forced through small orifices to allow the outdrive to kickup 
out of the way of such object. The speed with which the fluid flows is a 
function of orifice size and fluid pressure, which in turn is a function 
of the force applied to the outdrive by the object struck. 
SUMMARY 
Briefly, according to the present invention, a power coupling apparatus, 
such as an outdrive or the like, employs a housing structure that is 
generally less rigid than a conventional metal casting (although, if 
desired, in principle it could be made equally rigid), such housing being 
formed, for example, of plastic or plastic-like material, together with a 
number of features which cooperate to enable and/or to facilitate the use 
of such housing material in an outdrive. The housing structure and the 
various features according to the present invention are described in 
detail below and are particularly pointed out and distinctly claimed 
independently and in combination in various ones of the claims. 
Another aspect of the invention is to employ techniques that enable use of 
plastic, polymer, resin or other materials that have similar properties as 
the material from which the housing and possibly other parts, too, of an 
outdrive may be made. 
According to one feature of the present invention, the housing, or at least 
a substantial portion of the housing, for an outdrive is a relatively 
lightweight material, such as a plastic material or plastic-like material. 
Compared to metal housings for outdrives, a number of advantages inure to 
the use of plastic material, including, for example, lightness of weight, 
convenience and low cost of manufacturing using molding techniques, 
insensitivity to problems due to corrosion, galvanic action, receptivity 
of paint (such as anti-fouling paint without associated galvanic corrosion 
problems, bottom paint, etc.), as well as others. 
However, compared to metal material, plastic material usually is more 
flexible and more susceptible to creep. Metal is stiffer and less 
susceptible to creep. Also, plastic material usually is less thermally 
conductive than metal, which therefore makes it unlikely that adequate 
heat removal by conduction through the outdrive housing into the water 
would be possible. Such flexibility may result in lack of adequate 
stability and/or accurate maintaining of relative placement and/or 
location of conventional outdrive parts, such as the gears, shafts, and/or 
other parts that effect coupling of power in a conventional outdrive. 
According to a feature of the invention, a flexible power coupling is used 
to couple power in the outdrive to obtain an effective transfer of power, 
for example, between the drive shaft and the propeller shaft. 
The use of such a flexible coupling allows the use of plastic for an 
outdrive housing, even though such plastic is susceptible to creep and is 
less stiff or rigid than metal. Such use of plastic desirably provides the 
benefits of reduced cost, lighter weight, corrosion resistance, etc., as 
are described in greater detail herein and will be evident from the 
description hereof. Such flexible power coupling may be a belt, a chain, 
or an equivalent flexible member, which is not so sensitive to precision 
alignment required for conventional power coupling apparatus that employ 
gears and shafts. The flexible member will be referred to below as a belt 
for convenience. However, it will be appreciated that other flexible 
members, such as chains or equivalent devices, may be used in place of the 
belt according to the principles of the invention. 
Another aspect is to back bend an endless loop flexible drive member during 
use, especially by using generally non-moving surfaces. Another aspect is 
to remove heat from a drive system using such a flexible drive member. 
Another feature of the invention includes a technique for streamlining or 
reducing the profile of an outdrive that uses such a flexible coupling. 
Therefore, the outdrive will have an external appearance that is generally 
aesthetically pleasing in that it will be the same or similar to that of a 
conventional cast aluminum outdrive, for example. Also, the reduced 
profile improves the hydrodynamic characteristics, especially by reducing 
drag, compared to a large profile single leg housing that would be needed 
to contain the two belt legs, for example. 
Accordingly, a technique is employed to bend or to urge the belt legs back 
toward each other in at least part of the down leg of the outdrive 
housing, i.e., that zone between the upper housing portion and the lower 
housing portion (torpedo). To effect such back bending skid plates (also 
referred to herein as back benders) are provided in the housing, and the 
belt slides across the skid plates which urge the belt legs toward each 
other. A lubricant, such as an oil material, may be used to reduce 
friction at the sliding interface between the skid plates and the belt. 
Such back bending reduces the space required for the belt between the 
upper and lower housing portions and, thus, reduces the cross-sectional 
size dimensions or profile of the outdrive presented transverse to the 
travel direction through the water. Drag tends to be minimized while 
efficiency tends to be maximized. 
To remove heat from the outdrive is another feature of the invention, 
particularly since the preferred housing material usually would be less 
thermally conductive than prior metal housings. To remove heat, water from 
outside the outdrive is directed into heat exchange relationship with one 
side or surface of the mentioned skid plates outside of the belt chamber 
which is in the housing and contains the belt. The skid plates preferably 
are relatively thermally conductive, e.g., as a metal, especially 
aluminum. Heat generated at the skid plates and/or elsewhere in the 
outdrive is transferred to the skid plates, e.g., by the above-mentioned 
oil in the belt chamber, and that heat is conducted through the skid 
plates to the water at the other surface thereof. If desired, the water 
then may be directed to the engine for conventional engine cooling 
purposes. 
Still other features relate to use of plastic materials and molding 
techniques for other parts of an outdrive. 
It also will be appreciated that a preferred embodiment of the invention is 
described in detail below. However, the scope of the invention is intended 
to be limited only by the scope of the claims and the equivalents thereof. 
As it is used herein the term "plastic" means the conventional definitions 
of plastic, such as polymer material, synthetic material and so forth. 
Plastic includes both thermoset type plastic and thermoplastic. Plastic 
includes a material that preferably can be molded or laid up. It includes 
a material that will not encounter the types of corrosion and similar 
problems that may occur to a metal material. Usually a plastic material 
will be less stiff or rigid than metal, i.e., plastic typically is more 
flexible than metal. Plastic also usually has a greater tendency to creep 
than does a metal. Further, plastic often does not have as efficient a 
thermal conduction capability as does metal. 
Various examples of plastic material may be used in accordance with the 
present invention. 
One aspect of the invention relates to an outdrive for a boat including a 
power input shaft, a power output shaft, a flexible mechanism for coupling 
power between the shafts, and a single chamber housing the flexible 
mechanism during travel between the shafts. 
Another aspect of the invention relates to a drive system including a power 
input shaft, a power output shaft, an endless loop flexible mechanism for 
coupling power between the shafts, the flexible mechanism having plural 
legs extending between the shafts, and a bending device for bending the 
endless loop flexible mechanism so that at least one of the legs is bent 
toward the other. 
Another aspect relates to a plastic drive for boats including a plastic 
housing, a power input shaft, a power output shaft and a flexible 
mechanism in the plastic housing for transferring power between the 
shafts. 
Another aspect relates to the use of plastic for the housing of a power 
coupling system for boats or other vehicles. 
Another aspect relates to a technique for removing heat from an outdrive or 
the like which has a relatively non-thermally conductive housing. 
The outdrive of the invention also includes a trim feature and a kickup 
feature. 
Another aspect relates to a lock mechanism to prevent undesired tilting of 
an outdrive during reverse driving. 
Another aspect relates to a system for pretensioning a flexible drive 
member, such as a belt, chain or the like, including a support for 
supporting the flexible drive member for movement in the fashion of an 
endless loop, a housing for containing at least a portion of the support 
and the flexible drive member, and a mechanism for applying pressure to 
the support mechanism in a direction to increase tension on the flexible 
drive member. 
Another aspect relates to a system for pretensioning a flexible drive 
member, such as a belt, chain or the like, including a support for 
supporting the flexible drive member for movement in the fashion of an 
endless loop when driven by a power supply, for example, and a mechanism 
for changing tension on the flexible drive member as a function of the 
received power or the torque applied thereto. 
Another aspect relates to a mechanism for applying tension to a flexible 
member, such as a belt, chain or the like. 
Another aspect relates to a mechanism for applying tension as a function of 
engine torque to a flexible member, such as a belt, chain or the like. 
Another aspect relates to a mounting system for a boat drive including a 
gimbal structure, such as a gimbal ring to support the boat drive relative 
to a boat for movement of the boat drive relative to the boat about at 
least two different axes, a trim fastening mechanism for fastening the 
boat drive to the gimbal structure, the boat drive being pivotable about 
an axis including the trim fastening mechanism, and a trim adjusting 
mechanism for holding the boat drive at an angular relationship to the 
gimbal structure. 
Another aspect relates to a mounting system for a boat outdrive that 
facilitates mounting and demounting of the outdrive. 
Another aspect relates to a system for mounting an outdrive to a boat which 
enables mounting and demounting of the outdrive entirely from outside the 
boat, i.e., without having to disconnect fasteners and the like inside the 
boat. 
Another aspect relates to a boat drive including input and output shafts, 
variable ratio sprockets relatively coupled relative to the shafts to 
rotate at the same speed as the respective shafts, and a flexible coupling 
member, such as a belt, mounted on the sprockets for coupling power 
between the shafts. 
Another aspect relates to a power coupling system including input and 
output shafts, a flexible coupling mechanism for coupling the shafts to 
transfer power therebetween, a spacing device between the shafts for 
spacing the shafts relative to each other, and wherein the spacing device 
is a relatively nonrigid material. 
In a preferred embodiment, the spacing mechanism identified in the 
preceding paragraph is a plastic material. 
According to another aspect, a sprocket assembly for a flexible power 
transfer member, such as a belt, chain or the like, includes a sprocket 
for supporting the flexible power transfer member and for transferring 
power to and/or from the belt, bearings for supporting the sprocket for 
rotation, a seal to exclude water and to retain lubricant for the bearings 
and sprocket, and a cone clutch for selective engagement to transfer power 
between a further shaft and the sprocket. 
It will be appreciated that the various features of the invention may be 
employed alone and/or in combination with other features in plastic 
outdrive systems and in other drive systems for boats and/or other 
vehicles. 
The foregoing and other objects, features, advantages and embodiments of 
the invention will become apparent as the following description proceeds. 
The following description and the annexed drawings set forth in detail 
certain illustrative embodiments of the invention, these being indicative, 
however, of but a few of the various ways in which the principles of the 
invention may be employed. It is intended that the invention only be 
limited by the scope of the claims and the equivalents thereof.

DETAILED DESCRIPTION OF THE INVENTION 
Introduction 
Referring in detail to the drawings, wherein like reference numerals 
designate like parts in the several figures, and initially to FIGS. 1A, 1B 
and 2, a power coupling system 1 in accordance with the preferred 
embodiment of the present invention is illustrated coupled in a drive 
system 2 of a boat 3. An exemplary waterline is represented at 4 near the 
bow 5 of the hull 6 of the boat 3 when the boat is moving at or 
approximately on a plane. When the boat is at rest or is not at plane, the 
stern will be lower in the water than is illustrated, as is conventional. 
In the preferred embodiment, which is exemplary of the invention, the drive 
system 2 is of the inboard/outboard type, including a power supply 10, an 
output mechanism 11, the power coupling system 1, and a housing 12. The 
housing 12 provides functions of structural support, spacing and enclosing 
for the power coupling system 1 and the output mechanism 11. As was 
mentioned above, the power coupling system 1 of the invention may be 
employed with other types of drive systems for boats or other vehicles. 
As is described in further detail below, the invention employs a number of 
novel features. Several of these include a unique kickup feature, back 
bending of a drive belt, techniques for pretensioning and dynamic 
tensioning of a drive belt, and an hydraulically actuated cone clutch 
mechanism. Furthermore, a number of features in combination can be 
employed in accordance with the invention to provide an efficient and cost 
effective power coupling system for a boat drive or the like; and a number 
of these features include a plastic housing, a belt drive, a back bending 
technique for the belt drive, low pressure cylinders made of plastic for 
trim and kickup features, an hydraulically actuated cone clutch, and the 
ability to employ a reversible propeller. Several exemplary advantages of 
using primarily plastic material for the power coupling system of a boat 
drive include the elimination of corrosion problems, avoiding problems due 
to galvanic corrosion interaction caused by anti-fouling paints, due to 
stray electric currents, and/or other sources, and/or the like, facility 
and low cost of manufacturing, lightness of weight, and so on, to name but 
a few. 
Since a belt drive is used in the power coupling system, the housing 
therefor can be made of plastic, which is less stiff than metal. Back 
bending the belt, which is described in detail below, enables the power 
leg of the power coupling system, i.e., that portion which is in the 
water, for example, to have a relatively narrow profile or cross-sectional 
area transverse to the direction of travel through the water; and this 
characteristic improves hydrodynamics of the power leg, thus reducing drag 
in the water. 
In the exemplary (and preferred) embodiment of the invention, then, the 
power supply 10 is an engine 13. The engine has a drive shaft 14 which is 
rotated by the engine to provide power that ultimately causes rotation of 
the propeller 15, which is mounted on a propeller shaft 16. 
If desired, although not necessarily preferred, a conventional transmission 
17 may be included in the power coupling system 1 for the conventional 
purposes provided by a transmission. For example, the transmission may 
include reverse, neutral and forward gears to determine the direction of 
rotation of the propeller 15 and/or whether it rotates at all, as the 
drive shaft 14 is rotated. The transmission 17 also may include additional 
gears or other mechanism to change the ratio of the rotational speed of 
the propeller 15 with respect to the rotational speed of the drive shaft 
14. The transmission is shown in dotted outline in FIG. 1A because it is 
possible that such transmission may be omitted in the case that it is 
desired to have direct coupling of the engine 13 to the outdrive portion 
of the power coupling system 1. 
A clutch 18 also may be included in the power coupling system 1 of the 
drive system 2. The clutch 18 may be a conventional clutch that serves 
conventional clutch functions. Exemplary clutches may be an automotive 
clutch, a dog clutch, or some other clutch of conventional or special 
design, as may be desired. The clutch 18 may be operated in conventional 
fashion, for example, selectively to couple or to decouple the engine 
drive shaft 14 relative to the other parts of the power coupling system 1. 
Coupling would be effected, for example, when it is desired to turn the 
propeller 15 in order to move the boat 3. Decoupling would occur, for 
example, when the engine 13 is started, when it is desired to allow the 
engine 13 to run without turning the propeller 15, when gears in the 
transmission 17 are shifted, etc. 
The power coupling system 1 may be considered as including the drive shaft 
14, propeller shaft 16, transmission 17 and clutch 18, as those parts 
cooperate in the transmission of power from the engine to the propeller. 
The power coupling system 1 also includes other portions, as will be 
described further below. 
A number of controls 21 (and, if desired, displays) of conventional 
electrical, mechanical, hydraulic and/or pneumatic type (or other type), 
may be included to operate and/or to control various functions of the 
drive system 2. For example, the controls 21 may be operated by the boat 
operator to start the engine 13 and/or to determine the engine speed. The 
controls 21 also may be coupled to the transmission 17 and to the clutch 
18 to adjust gears and/or clutching functions in conventional fashion. 
Further, the controls 21 may be coupled to a power steering actuator which 
operates a tiller arm 22 to steer the boat. Still further, the controls 21 
may be coupled to the power coupling system 1 to control trim and tilt 
functions, as are described in further detail below as well as locking to 
avoid tilting when driving in reverse. The controls 21 may include 
mechanical, electrical, hydraulic, and/or pneumatic controls and/or 
linkages, and so on, which are available to effect the desired control 
functions of the drive system 2. The controls 21, engine 13, transmission 
17 and clutch 18 may be mounted in the boat 3 in a conventional fashion 
and are operative, for example, in conventional fashion, to supply power 
in the form of rotational energy via the various other portions of an 
outdrive 30 of the power coupling system 1 to rotate the propeller 15. 
The Outdrive 30 
A significant component of the outdrive 30 is the housing 12, and according 
to the preferred embodiment and best mode of the invention that housing is 
made of plastic material or of a material that has the characteristics of 
plastic material. Since plastic ordinarily is less stiff than metal, such 
as an aluminum housing, and tends to creep more than metal would, a belt 
drive assembly 31 is used to couple power from the upper housing portion 
32 through the down leg 33 portion of the housing to the lower housing 
portion or torpedo 34. 
The belt drive assembly includes a pair of upper and lower sprockets 35, 36 
and a flexible belt 37, for example of rubber or polymer material, which 
is rotated about and between the sprockets. The belt 37 runs in a chamber 
38 in the housing 12. A belt drive, especially the belt itself, is more 
forgiving as to positional alignment or tolerances than is a gear and 
shaft drive typically used in conventional outdrives. To avoid the need 
for two down legs, as is shown in the above U.S. Pat. No. 3,951,096, while 
minimizing the cross-sectional area of the down leg 33 required to house 
the legs 40, 41 (FIG. 2) of the belt 37 and presented transversely of the 
direction of travel through the water, the belt legs are bent toward each 
other. Such bending is effected by skid plates or back benders 42, 43, 
which in the preferred embodiment are of metal material that have smooth 
surfaces 44, 45 over, on, across, etc., which the belt 37 slides. 
It will be appreciated that a belt 37 is but one form of flexible coupling 
member that may be employed in the invention, as was mentioned above. 
Preferably that flexible coupling member is in the form of a continuous 
loop or endless loop and is able to transmit rotary motion, torque, and, 
thus, power from the power input portion to the power output portion of 
the outdrive 30. 
Heat may be developed in the outdrive 30, for example by the belt 37 as it 
is bent and flexed by the back benders 42, 43 and the sprockets 35, 36 and 
as it slides on the back benders. Heat also may be developed at other 
parts of the outdrive, for example, at the respective sprockets 35, 36 due 
to friction losses or the like. Against the outside surfaces 46, 47 of the 
back benders (i.e., outside relative to inside the belt chamber 38) a 
cooling flow 48 of water is provided through flow paths 49, 50, to remove 
heat from the back benders and, thus, from the outdrive. 
A fluid 51 in the belt chamber, which provides a lubricating function for 
the belt and, if desired, for the sprockets 35, 36, transfers heat from 
the outdrive to the back benders 42, 43, for example at the surfaces 44, 
45. Whether the fluid 51 provides boundary lubrication or fluid film 
lubrication, e.g., depending on thickness of the lubricant between the 
belt and back bender surfaces 44, 45, it has been found that there is 
adequate heat transfer to the back benders. Therefore, the belt and/or 
other related parts in the outdrive will not overheat. 
Preferably the back benders are made of a relatively efficient thermally 
conductive material, such as metal, especially aluminum. The cooling flow 
48 of water flowing against the outside surfaces 46, 47 of the back 
benders conducts the heat away from the back benders and from the 
outdrive. The source of the cooling water flow 48 may be from the water in 
which the boat is immersed. For example, an opening in the housing 12 may 
provide an inlet for such water. Since the water flow 48 usually would 
have adequate cooling capacity after having removed heat from the back 
benders, the flow paths 49, 50, may be joined at 52 (FIG. 1B) and directed 
to couple the water flow to the engine 13 for cooling the engine in 
conventional fashion. 
An exemplary trim, tilt and kickup mechanism provided the outdrive 30 is 
shown at 53. Other conventional trim, tilt and kickup mechanisms 
alternatively may be used. The mechanism 53 includes a relatively large 
area, relatively low pressure actuator 54, which has a piston 55, cylinder 
56, rolling diaphragm 57 and rod 58. By changing hydraulic fluid pressure 
in the chamber 59 of the actuator 54, the piston 55, diaphragm 57 and rod 
58 are moved relative to the cylinder 56 to trim the angle of thrust of 
the outdrive 30, more specifically of the propeller 15, and/or to tilt the 
outdrive, e.g., for servicing, trailering, etc. 
In response to application of a kickup force against the outdrive 30, the 
outdrive tends to tilt out of the way. The cylinder 56 then moves relative 
to the piston 55 and rod 58 tending to create a vacuum in the actuator 
chamber 59. The force required to kickup the outdrive can ramp up to that 
required to draw the vacuum, namely the product of atmospheric pressure 
times (against) the outside surface 60 of the piston 55 and then remains 
constant. After the kickup force is removed, the weight of the outdrive 30 
and the atmospheric pressure acting against the outside surface of the 
piston 55 urging it into the cylinder 56 serve as a restoring force 
promptly to return the outdrive to the pre-kicked up orientation. 
In accordance with the present invention, the outdrive 30 is included in 
the power coupling system 1 and, for convenience, also may be considered 
to include the output mechanism 11, namely, the propeller 15. The outdrive 
30 is mounted at the stern 70 of the boat 3. The engine drive shaft 14, or 
at least an extension portion 14a thereof on the output side of the clutch 
18 (if such clutch, the transmission, or some other part(s) were used 
between the engine and the outdrive), passes through an appropriate 
opening 71 in the stern transom 72 of the boat to couple rotary power to 
the outdrive 30, as is described in greater detail below. Moreover, 
steering functions for the outdrive 30 are effected via the tiller arm 22, 
which also is coupled to the outdrive 30 via an appropriate opening 73 in 
the transom 72. Other connections such as for hydraulic lines, pneumatic 
lines, mechanical connections, and electrical connections, etc., also may 
be provided to the outdrive 30 via appropriate openings through the rear 
transom 72 of the boat or may be otherwise provided to the outdrive 30, as 
may be desired. 
Outdrive Mounting Structure 80 
Referring, now, to FIGS. 1 and 3-8, the outdrive 30 includes a mounting 
structure 80 for mounting and supporting the outdrive from the boat 3. The 
mounting structure 80 is designed to permit movement of the outdrive 30 
about the tilt axis T and about the rudder axis R, while supporting the 
outdrive 30 from the boat 3 and also permitting connections of the drive 
shaft 14a, tiller arm 22, and other hydraulic, pneumatic, water and/or 
electrical lines, for example, through the transom 72 of the boat. Rudder 
function may be effected by rotating the outdrive in response to torque 
applied by the tiller arm 22; steering function primarily is accomplished 
as a function of the direction of thrust by the propeller 15 and/or as a 
function of rudder action effected by submerged surface area portions of 
the outdrive 30 that are relatively long in the direction of travel 
through the water compared to the thickness or width dimension thereof 
transverse to the water flow direction. 
The mounting structure 80 includes a transom housing portion 81 directly 
secured to the boat 3 and a gimbal mounting portion 82, which interfaces 
between the transom housing portion 81 and the outdrive housing 12 and 
permits desired tilting and rudder movement thereof. The transom housing 
portion 81 includes an inner transom housing 83 and an outer transom 
housing 84. The inner transom housing 83 and the outer transom housing 84 
preferably are coupled to each other and to the boat transom 72 in 
sandwich relation, as is seen in FIG. 3, for example. The sandwich 
connection provides substantial reinforcement of the transom 72 to provide 
support for the outdrive 30. The inner and outer transom housings 83, 84 
may be plastic, metal or other material. The inner and outer transom 
housings 83, 84 and the stern transom 72 are secured together by bolt and 
nut fasteners 85, as is seen in FIG. 3, and seals are provided as needed 
to prevent water leakage into the boat. The seal would be external of the 
fasteners, e.g., circumscribing them, so that the fasteners ordinarily 
remain dry. Conventionally, openings are provided in the inner and outer 
transom housings 83, 84 and through the transom 72 for passing the tiller 
arm 22 through tiller opening 73 and for passing the drive shaft 14a 
through opening 71 between the inside and outside of the boat. 
A main gasket 90 extends about the outer transom housing 84 facing the boat 
and prevents water leakage into the boat. The drive shaft 14a passes 
through a gimbal bearing 91, which is enclosed in a gimbal bearing housing 
92 that is part of the outer transom housing; and the drive shaft is 
covered by a water tight flexible boot 93, for example, of rubber, at the 
connection thereof to the power input 94 for the outdrive 30. The gimbal 
bearing housing 92 and boot 93 prevent water leakage at the drive shaft 
14a. The tiller opening 73 is made water tight to prevent water leakage 
into the boat, as is described further below. 
Various parts of the drive system 2 may be coupled to the inner transom 
housing 83, such as engine mounts, power steering cylinders, fasteners to 
secure plumbing conduits, such as engine cooling, hydraulics, exhaust, 
etc., e.g., for support and/or positioning. As an example, a bracket 96 
for mounting a power steering cylinder (not shown) that moves the tiller 
arm 22 to rotate the outdrive is shown in FIG. 5. Such power steering 
cylinder may be controlled by operation of controls 21 by the boat 
operator in conventional manner. 
The outer transom housing 84 supports the rudder functions (steering 
functions) for the outdrive 30. The outer transom housing 84 also provides 
a load path from the outdrive 30 to the boat 3. 
The gimbal mounting portion 82 includes a gimbal ring 100 to which the 
outdrive housing 12 is connected for mechanical support. The gimbal ring 
100 (FIGS. 6-8) preferably is made of plastic (which is non-corrosive) or 
aluminum material, although other materials that have appropriate 
strength, corrosion resistance and weight characteristics may be used. The 
gimbal ring 100 has top, middle and bottom straps or arms 101-103, side 
straps or arms 104, 105, and a central opening 106 through which part of 
the housing 12, drive shaft 14a and/or other portions of the outdrive may 
pass. It is mounted in and between an upper support 107 and a lower 
support 108 of the outer transom housing 84 in a manner that secures the 
gimbal ring relative to those supports while permitting rotation of the 
gimbal ring about the rudder axis R. 
At the top strap 101, the gimbal ring 100 is attached to the upper support 
107 by the upper rudder pin 110. Such connection is provided with a water 
tight seal to prevent water entering into a tiller chamber 111 that faces 
tiller opening 73. The tiller chamber 111 is enclosed between upper, lower 
and side walls 112-114 seen in FIG. 3, for example. The upper wall 112 has 
an access opening (not shown) for access into the chamber 111 to fasten 
and unfasten the nut 116 secured to the threaded end of the upper rudder 
pin 110. The lower wall 113 has a circular cross sectional opening 118 
through which the upper rudder pin passes for securing to the tiller arm 
22. 
As is seen in FIGS. 3, 7, 7A, 7B and 8, the upper rudder pin 110 preferably 
is reinforced by a metal pin 120 or bolt, for example, stainless steel, 
that has adequate strength characteristics to carry the clamp load of the 
nut 116. Such pin 120 has a head end and a thread at the other, as is 
illustrated in FIG. 3. Preferably a threaded opening 121 is formed part 
way into the head end to facilitate removing the upper rudder pin 110. 
Molded about and to the pin 120 is a cylindrical body 122 with a keying or 
locking feature. Such keying feature may be wings, extending tabs, or the 
like shown at 122w that are operative to lock the upper rudder pin 110 to 
turn the gimbal ring 100. Also molded about and to the pin 120 nearer the 
center of the axial length thereof is a generally cylindrical body 123, 
which is intended to rotate in a circular cross sectional opening provided 
in the lower wall 113 of the upper support of the outer transom housing 
84, so that the rudder pin 110 and gimbal ring 100 can rotate relative to 
the outer transom housing 84. Further, molded about and to the pin 120 
near the top threaded end is a polygonal shape body 124, e.g., of 
hexagonal cross section, and preferably being tapered from one end toward 
the other to facilitate insertion and tightening into a correspondingly 
shaped mating opening in the tiller arm 22 and to facilitate separating 
such body from the tiller arm opening when desired. The bodies 122, 123, 
124 may be made of plastic material that is molded directly to the pin 120 
using, for example, insert molding techniques. 
An opening 125 is formed in the top strap 101 of the gimbal ring 100. A 
bushing 126 fits in that opening 125, and the keyed cylindrical body 122 
of the rudder pin 110 fits securely in that bushing as is illustrated in 
FIG. 3. The bushing 126 has reliefs in the wall thereof to pass the keys 
122w into locking slots 122s formed in the gimbal ring. Further, a 
cylindrical pivot bearing 127 fits in the stepped cylindrical opening 110 
in the lower wall or arm 113 of the upper support 107 of the outer transom 
housing 84. The cylindrical body 123 of the upper rudder pin 110 fits in 
such pivot bearing 127 for rotation. An o-ring seal 130 at the top end of 
the pivot bearing 127 prevents water leaking into the tiller chamber 111. 
Moreover, relatively close fit of the pivot bearing 127 with the 
cylindrical body 123 and relatively close fit of other portions of the 
upper rudder pin square body 122 with the square bushing 126, and 
relatively close fit of other parts of the upper rudder pin 110, gimbal 
ring 100 and wall 113 help prevent leakage of water into the tiller 
chamber 111 and into the boat 3. 
With the gimbal ring 100 positioned in the manner illustrated in FIG. 3, 
with the outdrive 30 not yet coupled to the gimbal ring, and with the 
upper rudder pin 110 in place, as is illustrated, the nut 116 can be 
fastened onto the threaded end of the pin 120 to hold the gimbal ring to 
the upper support 107 of the outer transom housing 84. A cover 128 (also 
seen in FIG. 4) then can be installed to cover the opening 129 (FIG. 4) 
into the tiller chamber 111. As the nut 116 is tightened, the hexagonal 
body 124 is drawn into a correspondingly shaped opening in the tiller arm 
to make a secure connection therewith. Due to the features of the upper 
rudder pin 110 (including bodies 124, 122) and the connections thereof 
with the tiller arm 22 and with the gimbal ring 100, turning of the tiller 
arm will cause turning of the gimbal ring about the rudder axis R. Since 
the outdrive 30 is mounted to the gimbal ring 100, as is described in 
further detail below, such turning of the gimbal ring will turn the 
outdrive to steer the boat and to change the direction of thrust by the 
propeller 15. The arrangement of parts and the cooperative interaction 
thereof as was just described facilitates the assembly and disassembly of 
the gimbal ring and the tiller arm relative to the outer transom housing 
from outside the boat. 
To remove the upper rudder pin 110, access to the nut 116 is provided by 
means (not shown) such as a removable plate 128 in the front wall of the 
chamber 111. The nut 116 can be removed. Thereafter, a u-shape jig can be 
placed beneath the head end of the upper rudder pin to place the legs of 
the jig in engagement with the bottom of the upper strap 101 of the gimbal 
ring. A screw then can be placed through an opening in a bridge portion of 
such jig and threaded into the countersunk opening 121 in the head end of 
the rudder pin 120. As such screw is tightened to bear against the bridge 
of the jig and to penetrate the threaded opening 121, the upper rudder pin 
110 will be drawn out of secured relation with the tiller arm and will 
become free for removal. This removal action is analogous to that employed 
with a typical bearing puller type of device. 
As is seen in FIGS. 1, 3, 4 and 7, the bottom strap 103 of the gimbal ring 
100 is mounted to and between a pair of tines 130, 131 of the lower 
support 108 of the outer transom housing 84 and is held there by the lower 
rudder pin 132, which preferably is a shoulder screw. The screw 132 passes 
through opening 133 in the tine 131 and opening 134 in the strap 103, 
which fits in a space 135 between the tines 130, 131. The screw 132 is 
threaded securely into a threaded opening 136 in the upper tine 130. 
Bushings 137, 138 are located in the openings 133, 134 in the tine 131 and 
strap 103. The lower rudder pin 132 may be tightened to hold the overall 
assembly of the gimbal ring strap 103 to the lower support 108 of the 
outer transom housing 84 for securement therein while permitting rotation 
about the rudder axis R. 
The side straps or arms 104, 105 of the gimbal ring 100 extend between the 
top and bottom straps or arms 101, 103 and have openings 140, 141 
therethrough for connection to the housing 12 of the outdrive 30 by 
conventional pivot bolts, shoulder screws, or the like, which are 
generally designated 142, 143, respectively, at opposite sides of the 
gimbal ring. Such pivot bolts may be secured to threaded openings 144, 145 
in the housing 12. Those threaded openings may be reinforced with metal 
material, if desired. Appropriate bushings, bearings, and the like also 
may be employed. The objective is to secure the housing 12 to the gimbal 
ring by such pivot bolts 142, 143 while permitting tilting of the housing 
12 and apparatus therein about the tilt axis T. Preferably the pivot bolts 
142, 143 are tightly secured to the housing 12 and rotate in the openings 
140, 141 as the tilt angle of the housing 12 varies. 
A conventional position sensor 145 may be mounted at one of the pivot bolts 
142, 143 in conventional fashion. The position sensor 145 may be a device 
that produces an electrical signal representative of absolute position or 
relative position or movement of the outdrive relative to a fixed 
position, for example. Such position sensor may operate by detecting the 
tilt angle of the pivot bolt relative to the gimbal ring 100. Information 
concerning such relative tilt angle can be coupled electrically, as by 
leads 146, to the controls 21 for displaying the actual relative tilt 
angle to the boat operator or for use in automated trim adjusting 
equipment. An example of a position sensor is a device that has an 
electrical resistance characteristic which varies with respect to tilt 
angle; such a device may be, for example, a potentiometer type of device, 
such as one available from Allen-Bradley Company. 
The middle arm or strap 102 of the gimbal ring 100 extends generally 
horizontally between the side straps 104, 105. The strap 102 provides a 
mechanism to which the trim, tilt and kickup mechanism 53 is attached to 
the gimbal ring 100. Such attachment enables the gimbal ring to serve as 
the structure against which the outdrive 30 may be urged to effect trim 
and tilt functions and also to receive force when the propeller 15 is 
turning to drive the boat in the water. Thus, forward thrust is applied 
via the mechanism 53 to the gimbal ring 100, which in turn transmits the 
forward thrust to the boat 3 to move the boat through the water. 
As is seen in FIGS. 1, 2, 7 and 8, the rod 58 is bifurcated to portions 
58a, 58b, which extend through passages 150, 151 in the housing 12 in 
isolation from the belt chamber 38. Therefore, water which may enter the 
passages 150, 151 will not enter the belt chamber 38. The ends 152, 153 of 
the rods 58a, 58b have openings 154, 155 therein and fit into slot-like 
openings 156, 157 in the middle strap or arm 102 of the gimbal ring 100. A 
locking rod 158 placed through a locking passage 159 in the strap 102 
through the openings 156, 157 of the bifurcated arms 58a, 58b holds the 
rod 58 to the gimbal ring. The bifurcated arrangement described 
facilitates coupling the rod 58 to the gimbal ring 100 without interfering 
with the belt 37. 
Power Input Mechanism 160 
Referring to FIG. 3, mechanical power is supplied the outdrive 30 via the 
outdrive power input 160, which includes a conventional universal joint 
161, the gimbal bearing assembly 91, engine drive shaft 14, 14a as an 
input shaft, and a rotatable shaft 162 at the output side of the universal 
joint. The universal joint 161 is a conventional device having respective 
input and output connectors 163, 164, which are respectively coupled to 
the drive shaft extension portion 14a and rotatable shaft 162 and are 
coupled to each other via the universal joint housing 165. As is 
conventional, the universal joint 161 couples rotary motion between the 
input and output connectors 163, 164 thereof while also permitting 
relative movement of those connectors in one or more planes and/or along 
one or more axes. The center of pivot of the universal joint 161 is 
located at the intersection of the rudder axis R and the tilt axis T. This 
arrangement permits freedom of rotation for the outdrive 30 about the 
rudder axis R and/or tilt axis T without interfering with the coupling of 
rotary power or torque through the universal joint 161. 
The gimbal bearing assembly 91 includes a stepped cylindrical gimbal 
bearing housing 92. Preferably the gimbal bearing housing 92 is part of 
the outer transom housing 84. The gimbal bearing 91 is self-centering in 
the gimbal bearing housing 92. O-ring seals 166 on the drive shaft 14a at 
the gimbal bearing 91 retain lubricant in the gimbal bearing 91, and/or 
prevent dirt from entering the gimbal bearing. A lip seal 167 is 
positioned between the drive shaft 14a and the opening 168 in the housing 
92 through which the shaft 14a passes into the housing. The lip seal 167 
prevents lubricant in the housing 92 exiting through the opening 168 and 
prevents dirt, water or other material from outside the housing entering 
the same. 
A power input chamber 170 of the housing 12 circumscribes the connector 164 
of the universal joint 161 and part of the shaft 162. The flexible boot 93 
circumscribes the universal joint 161 and associated parts and is fastened 
between the outdrive housing 12 at the power input chamber 170 and the 
gimbal bearing housing 92 primarily to prevent water and dirt from 
entering the area 172 where the universal joint and associated parts are 
located. The flexible boot prevents water from entering such area 172 and 
from there gaining access into the boat. The flexible boot 93 permits the 
outdrive 30 to tilt about tilt axis T and to rotate about rudder axis R 
while still maintaining the function of enclosing the area 172. 
The gimbal bearing 91 facilitates aligning of the drive shaft 14 and/or the 
extension portion 14a with the universal joint 161. The engine is aligned 
to the gimbal bearing. The gimbal bearing provides for support of the 
shaft and provides a gimbal function to facilitate alignment and to 
accommodate slight misalignment of the engine drive shaft with the 
universal joint. 
Outdrive Power Leg 180 
The outdrive 30 includes a so-called power leg portion 180 intended to 
transfer or to couple power received via the outdrive power input 160 to 
the propeller 15. In the illustrated embodiment of the invention, the 
propeller 15 is a constant pitch propeller. Therefore, rotation of the 
propeller in one direction will tend to drive the boat forward and 
rotation of the propeller in the opposite direction will tend to drive the 
boat in reverse direction. Reversing of the propeller rotation direction 
can be achieved by appropriate adjustment of the transmission 17, as is 
conventional. Alternatively, other means may be provided to change or to 
reverse the pitch, rotational direction and/or direction of thrust of the 
propeller 15. 
Briefly referring to FIG. 20, a locking mechanism 500 for locking the 
outdrive in fixed position to prevent inadvertent kickup action when the 
propeller is operating to drive the boat in reverse direction is 
illustrated. The locking mechanism 500 includes a modified lower rudder 
pin 501 mounted in the lower support 108 of the outer transom housing. The 
lower rudder pin includes a movable plunger 502 slidable in a chamber 503 
within the lower rudder pin 501. A spring 504 spring loads the plunger 502 
to a withdrawn condition. However, in response to application of fluid 
pressure to the a pressure chamber 505 in the lower rudder pin, the 
plunger is forced to move against the spring 504 so as to protrude through 
the bottom of the lower rudder pin and to lock into a notch 506 in a notch 
plate 507. The notch plate 507 is fixedly carried on the housing of the 
outdrive power leg. Plural notches 506 are provided in the notch plate 507 
so that the plunger 502 can fit into a respective notch substantially 
without regard to the particular trim angle at which the power leg is 
oriented. 
In operation of the locking mechanism, fluid is provided to the pressure 
chamber 503 via fluid line 508 when it is intended to operate the 
propeller in reverse direction, i.e., to move the boat in reverse 
direction. Such fluid pressure may be supplied in response to actuation of 
a gear shift and/or controls 21 associated with the drive system for the 
boat. In response to such pressure the plunger is extended from its 
previous retracted position against the force of the return spring 504 so 
as to enter, to engage, and to lock into a respective notch opening 506 in 
the notch plate. When the propeller tries to pull the boat backwards, the 
outdrive will not kickup due to the locking action of the locking 
mechanism 500. When the gear shift is moved out of reverse gear, the fluid 
pressure in the pressure chamber 503 would be relieved; the plunger 502 
would be withdrawn into the lower rudder pin under the force exerted by 
the return spring 504; and the outdrive then would be free to kickup if 
necessary upon striking an object. 
Water spray may be directed to the area of the notch openings 506 through a 
water intake opening 509 (through the anti-ventilation plate, which is 
described below [reference number 283]) to keep them clean as the boat 
moves through the water. Such cleaning water flow or spray flows through a 
chamber area 510. A drain 511 may be provided to remove such sprayed 
water. For convenience, said drain 511 may pass said cleaning water out 
through an opening(s) (not shown) in the side(s) of the anti-ventilation 
plate 283; or other convenient draining flow path may be provided. 
The housing 12, which encloses the power leg 180 preferably is formed of 
plastic material, which has a lower degree of stiffness than metal. The 
flexible member 37 is employed to transfer power or torque in the power 
leg 180. Such flexible member may be a belt, a chain or some other 
flexible member. Preferably the flexible member 37 is in the form of an 
endless loop. The advantage of using such a flexible member is the 
forgiveness or forgiving nature thereof in that precise alignment and 
positioning of parts, e.g., the upper and lower sprocket assemblies 35, 36 
on which the flexible member 37 is mounted, for example, do not have to be 
maintained in a high precision relative position arrangement as would 
usually be necessary when a shaft and gears are used in the power leg of a 
conventional outdrive. 
An exemplary flexible member 37 is a toothed belt sold by Gates Rubber 
Company under the name POLYCHAIN. Alternatively, a belt sold under the 
trademark HTD (also of Gates) may be used. Virtually any belt can be used 
that will withstand power transmission. One exemplary belt is formed of 
polyurethane construction reinforced with fiberglass and/or Kevlar and 
possibly including Nylon facing material. The width of the belt and the 
strength characteristics of the belt are a function of the amount of power 
or torque intended to be coupled via the belt. Other types of belts, 
toothed or not, also may be used. The half length of the belt is 
approximately the distance between the relatively outer spaced-apart 
portions of the upper and lower sprocket assemblies 35, 36. A chain or 
other relatively flexible member may be used as a substitute for the belt, 
although the noise generated by a chain, for example, may be undesirable 
and/or unacceptable. Exemplary belts which might be used are disclosed in 
U.S. Pat. Nos. 3,964,328; 4,605,389; or 4,652,252. 
Upper Sprocket Assembly 35 
The upper sprocket assembly 35, which is seen in FIGS. 1, 2, 3 and 9, 
includes a sprocket 181 having a plurality of teeth or grooves 182 
intended to cooperate with the teeth 183 (shown in FIG. 9) in the belt 37 
to move the belt, such motion being referred to as rotation of the belt, 
as the upper sprocket assembly is turned. In this regard, the rotatable 
shaft 162 from the universal joint 161 is coupled to the upper sprocket 
assembly 35 to turn the same and, thus, the belt 37. 
Preferably the upper sprocket assembly 35 is of a cartridge design in that 
it can be inserted as a unit into an appropriate opening and recess 
arrangement 184 provided therefor in the housing 12 facilitating 
installation, removal, and replacement, for example. The upper sprocket 
assembly 35 includes a sprocket 181, a pair of bearings 185, 186 mounted 
to permit the sprocket to rotate about the axis B as it is turned by the 
rotatable shaft 162, a closed-end rear cartridge housing 187 and a forward 
cartridge housing 188 with an opening 189 therein. The opening 189 is for 
passing the rotatable shaft 162 into the enclosed cartridge area 190 for 
mechanical connection to the sprocket 181 to turn the sprocket in the 
bearings 185, 186 as the universal joint 161 is turned by the drive shaft 
14a. A seal 191 prevents dirt from entering the sprocket housing area 190 
via the opening 189 and also retains lubricant, such as oil, grease, etc., 
in the area 190 to lubricate the bearing 186. Similarly, the cartridge 
housing portion 187 may contain in the cartridge housing area 192 a 
lubricant, such as grease, etc., to lubricate the bearing 185. 
The various portions of the upper sprocket assembly 35 may be made of 
plastic material or of metal. For example, one or more of such parts may 
be made of various plastic materials so as to be relatively strong, 
relatively light in weight and not subject to corrosion. Preferably such 
parts can be made using relatively inexpensive methods, such as molding or 
extruding. The seal 191 may be of rubber, plastic or other material that 
provides an adequate sealing function for the described purpose. 
As seen in FIG. 2, preferably the housing 12 of the outdrive 30 is formed 
of two halves 200, 201 that are assembled in a clam shell type of 
construction. The two halves may be substantially the same (e.g., 
respective mirror images) and may be secured together at a seam so as to 
facilitate placement of, support of, enclosing of, and functioning of the 
various parts contained therein. In FIGS. 1B and 3 the inside of the port 
side clam shell housing 200 is illustrated; the starboard side clam shell 
housing may be similarly formed and joined by adhesive material, sealant, 
gaskets, screws or other threaded fasteners, rivets, etc., to the port 
side half of the housing 12 along the various interfacing surfaces, one 
being designated 202, for example. In FIG. 2 the clam shell portions 200, 
201 of the housing 12 are illustrated divided along the center line 203 of 
the outdrive 30. The seam at which the two clam shell halves are secured 
would be along the center line 203. However, if desired, other modified 
clam shell housings where parts interfit with each other also may be 
employed in accordance with the spirit and scope of the present invention. 
In the illustrated embodiment the shell is split front to back; however, 
it will be appreciated that the shell can be split in different ways, too, 
such as port to starboard, angularly, etc. 
As is seen in FIGS. 1 and 3, since the upper sprocket assembly 35 is of a 
cartridge form, it can fit in and among a number of bosses, protrusions, 
etc., such as those identified at 210, 211 at which the cartridge housings 
187, 188 are secured to hold the bearings 185, 186 and the sprocket 181 in 
position illustrated for operation. The cartridge housings may have flat 
wall surfaces and angled corners that cooperate with rail-like structures 
formed by the bosses 210, 211 to hold the cartridge in position in the 
housing 12. If desired, a different type-of upper sprocket assembly 35 may 
be substituted for the one illustrated so long as the outside dimensions 
thereof are appropriate to fit within the areas provided by the bosses 
210, 211 and/or other mounting structure provided therefor in the housing 
12. For example, different respective upper sprocket assemblies 35 may be 
used to substitute sprockets 181 that have different respective numbers of 
teeth thereon and/or effective diameters thereof and/or that have other 
associated mechanisms, such as a cone clutch, which will be described 
further below with respect to FIG. 19. 
In the preferred embodiment, after the power leg 180 of the outdrive 30 has 
been manufactured, in most instances it would not be intended to 
substitute and/or to repair various parts thereof in the field, although 
repair of various parts and/or replacement of various parts may be 
effected at the factory where the clam shell halves 200, 201 may be 
separated for access to the parts therein. It may be possible to repair 
the outdrive in the field; but it is preferred to effect repair at the 
factory. Moreover, since the power leg is relatively lightweight, removal 
thereof from the gimbal ring 100 can be done by one person in many 
instances, thus facilitating such return for servicing. 
Belt Tensioning 
It is desirable, and in many instances necessary, to apply tension to the 
belt 37. The invention employs a pretensioning mechanism and also may 
include a dynamic tensioning mechanism. The tension should be appropriate 
to assure that the belt remains securely mounted on the upper and lower 
sprocket assemblies 35, 36 and that it does not slip during operation of 
the outdrive 30 to transfer the appropriate amount of power. Also, the 
belt needs to be pretensioned to offset the torque developed by the engine 
on the power leg 180. Specifically, as torque is applied, one side of the 
belt would tend to become slack. The tension helps to prevent this from 
occurring. The appropriate amount of tension may be from several hundred 
to several thousand pounds of tension, depending on the torque developed 
by or in the outdrive 30. 
The cartridge housings 187, 188 may have rectangular exterior shape to fit 
in and to slide in rails formed by the bosses 210, 211 across the top, 
bottom and especially the sides of the cartridge housings 187, 188. The 
cartridge housings then can slide within the rails vertically, e.g., away 
from the lower sprocket assembly 36 to apply the desired static tension 
forces. 
In the embodiment illustrated in FIGS. 1 and 3, for example, a permanent 
type of pretension may be applied by providing chambers 220, 221 in the 
housing 12 facing the upper sprocket assembly 35. This pretensioning 
sometimes is referred to as a jack up tensioning, e.g., as in an 
automobile jack. Material then can be applied to such chambers. That 
material tends to urge the upper sprocket assembly 35 away from the lower 
sprocket assembly 36 to tension the belt 37. Such material supplied to the 
chambers 220, 221 may be, for example, a fluidic material that can be 
injected or pumped into the chambers after the outdrive 30 has been fully 
assembled with the clam shell halves 200, 201 secured to each other having 
the sprocket assemblies 35, 36 and belt 37 properly positioned and the 
rotatable shaft 162 properly installed in the manner illustrated in FIGS. 
1 and 3. Such fluid material may be, for example, an epoxy material or 
some other material that has incompressible or controlled compression 
characteristics to apply the desired pressure in the chambers 220, 221 and 
can solidify, especially while under pressure, to maintain continuing 
tension on the belt. Alternative means also may be employed to apply the 
desired tension of the belt. As one example, rigid means may be inserted 
into the chambers 220, 221. Alternatively, other means may be used to 
apply the desired tensioning forces. In any event, it will be appreciated 
that by applying force or pressure within the chambers 220, 221 the upper 
sprocket assembly 35 is urged away from the lower sprocket assembly 36 
thereby to apply tension to the belt 37. 
A technique for dynamic tensioning may be employed in the invention, as is 
illustrated in FIGS. 10, 11, 12A and 12B. By using the dynamic tensioning 
mechanism 229, the belt 37 would not be tensioned or at least not 
tensioned tightly unless the belt is being driven by the engine. Depending 
on the set up, spring constants, various other dimensions, etc., the 
actual tension applied to the belt would be a function of the loading of 
the belt. As loading increases, e.g., as the belt RPM increases, so does 
the loading, at least over a range. Thus, at low power, idle or engine off 
condition, the belt is only lightly tensioned, and this eliminates strain 
on the belt and on the plastic housing 12. 
In the dynamic tension mechanism 229 a modified upper sprocket assembly 35' 
is employed. The upper sprocket assembly 35' is similar to the sprocket 
assembly 35 described above except that a modified housing 230, 231 is 
provided at the respective opposite ends of the sprocket 181. Seals 232, 
233 in the forward housing 231 retain lubricant and prevent dirt and/or 
water from entering the housing 231. The housings 230, 231 are split, each 
including an upper portion 230a, 231a in which the sprocket is mounted for 
rotation, and each including a lower portion 230b, 231b for supporting the 
upper housing portion. The upper and lower housing portions are coupled by 
a pivot pin 234, 235, and a spring 236, 237 at each housing biases the 
upper housing portion away from the respective lower housing portion to 
provide pretensioning. 
As the sprocket 181 is counterclockwise relative to the illustration of 
FIGS. 12A and 12B, for example, the upper housing portions 230a, 231a 
pivot about the pivot pins 234, 235 to increase the tension on the belt. 
In FIG. 12A no pivoting motion has occurred, and in FIG. 12B such pivoted 
motion is depicted as having occurred to increase tension on at least one 
leg of the belt 37. The amount of tension applied to the belt is generally 
proportional to the torque applied to the belt by the sprocket. The total 
amount of tension is limited to the maximum pivoting permitted of the 
upper housing 230a, 231a relative to the lower housing 230b, 231b. 
An important advantage inures to the dynamic tensioning mechanism 229 shown 
in FIGS. 10, 11 and 12. The belt 37 is not tensioned, other than a 
relatively small amount due to the springs 236, 237, or by other means 
that take up initial belt tension, e.g., a shim, a wedge, etc., which is 
placed at the appropriate location in or relative to the sprocket during 
assembly of the sprocket and/or of the belt drive system. The jack up 
feature described elsewhere herein also may be used for such tensioning 
purpose. Therefore, when the belt is not loaded or at least is not 
relatively heavily loaded (e.g., at idle or engine off) strain on the belt 
is reduced or even substantially eliminated. The fact that the belt is not 
tensioned all the time reduces long term housing loading and resulting 
creep. 
It will be appreciated that the dynamic belt tensioning mechanism 
illustrated in FIGS. 10, 11 and 12 may be employed by itself or in 
combination with the above-described pretensioning mechanism. 
Lower Sprocket Assembly 36 
Referring to FIGS. 1 and 13, the lower sprocket assembly 36, too, 
preferably is generally of a cartridge design mounted in the housing 12 by 
pairs of horizontal and vertical bosses 240, 241 that form rails in the 
manner described above with respect to the upper sprocket assembly 35. The 
lower sprocket assembly 36 includes a sprocket 242 that has a plurality of 
teeth 243 which mesh with the teeth 183 of the belt. The diameter of the 
lower sprocket 242 is generally larger than the diameter of the upper 
sprocket 181 and the sprocket assemblies have a correspondingly different 
number of teeth. Therefore, a rotational speed reduction is effected 
between the rotatable shaft 162 and the propeller 15 due to the ratio of 
the diameters and number of teeth on the respective sprockets 181, 242. 
Using different ratios, different speed reduction effects can be obtained 
without using additional gears, transmissions, or the like. Of course, if 
desired, a 1:1 ratio of diameters and teeth also may be used. Further, if 
a non-toothed belt were used, the sprockets preferably would not have 
teeth. 
Preferably the space between teeth on the upper and lower sprockets 181, 
242 is about the same and the ratio of the number of teeth on the larger 
to the smaller is from about 2:1 to about 1:1; and more preferably from 
about 1.7:1 to about 1.5:1. In an example, the lower sprocket 242 may have 
on the order of 39 teeth and the upper sprocket 181 may have on the order 
of 22 teeth. Using the sprockets to effect a reduction in speed between 
the rotatable shaft 162 and the propeller 15 provides a desired speed 
reduction of the type accomplished in the past by conventional gears in 
prior art outdrives. 
The sprocket 242 is supported for rotary motion by a pair of bearings 244, 
245, which are secured in position in the manner illustrated by respective 
cartridge housing portions 246, 247 and generally in the manner described 
above with respect to the upper sprocket assembly 35. The lower sprocket 
preferably is fixed and does not move for adjustment. At the rear end of 
the sprocket 242 are a pair of seals 250 which circumscribe part of a 
stepped-down diameter output shaft portion 251 of the sprocket 242 to 
prevent water from reaching the bearing 244 and/or other interior portions 
of the sprocket assembly 36 and the belt chamber 38. The seals also help 
to prevent lubricant or other fluid material intended to be in the belt 
chamber 38 from leaking out. 
The propeller 15 may be mounted directly onto the output shaft portion 251 
of the sprocket 242, for example, by using a threaded fastening 
connection, a conventional screw fastener, or adhesive material placed at 
the interfacial area 253 of connection between the propeller and the shaft 
251. Other means also may be employed to secure the propeller 15 onto the 
shaft 251. 
It will be appreciated, then, that as the engine produces a rotary output, 
which is coupled by the drive shaft portion 14a to the universal joint 
161, the upper sprocket 181 is rotated to cause the belt 37 to be rotated. 
As the belt 37 is rotated, belt tension is increased by preferably using 
the dynamic tensioning mechanism of FIGS. 10, 11, and 12 of an upper 
sprocket assembly 35' and the lower sprocket 242 is rotated, which then 
turns the propeller 15. 
Variable Pitch/Reversing Pitch Propeller Actuator Embodiment 
In an embodiment of the invention, the propeller 15 may be of a type that 
has variable pitch and/or reversing pitch blades 260. The pitch thereof 
may be changed by a mechanism included within the propeller 15 that is 
actuated by a push rod 261 located within and along the center line of the 
lower sprocket 242. The push rod 261 may be sealed within a cylindrical 
opening 262 of the lower sprocket 242 by an o-ring 263 to prevent leakage 
of water into the belt chamber 38 or lubricant out from the belt chamber 
38. The push rod may be actuated by a conventional fluid actuator 265. 
Such push rod is spring loaded to the position illustrated in FIGS. 1B and 
13 by a return spring 268 or may be so urged by the reaction force against 
the propeller, i.e., being urged to the right against a piston 266. The 
piston 266 is coupled to a rolling diaphragm 267 that forms a relatively 
low pressure hydraulic (or pneumatic) chamber 270 in a cylinder 271 that 
is secured to an open end of the cartridge housing 247 of the lower 
sprocket assembly 36. A flange portion 272 of the diaphragm 267 is trapped 
between a pair of flanges 273 of two generally cylindrical portions of the 
cylinder 271. 
In response to application or removal of fluid pressure from a fluid 
connection 274 to the chamber 270 of the fluid actuator 265, pressure in 
the chamber can be altered to determine whether the piston 266 is driven 
to the left or not against the return spring. When the piston is driven to 
the left, push rod 261 would be driven to the left and, accordingly, a 
mechanism in or associated with the propeller 15 would respond to alter 
the pitch or direction of the blades 260. However, upon release of the 
pressure in the chamber 270, the blades 260 in response to the return 
spring urge the push rod 261 to the right tending to reduce the volume in 
the chamber 270. The fluid inlet 274 may be coupled to a source of 
hydraulic fluid or pneumatic fluid that is controlled by controls 21 to 
effect the desired operation of the blades 260, as was described. 
An advantage to using a variable pitch or reversing pitch propeller, 
especially a propeller that is able to assume a forward pitch or a reverse 
pitch to drive the boat 3 in forward or reverse directions, is that there 
is no need for a transmission for determining forward or reverse rotation. 
This helps to minimize cost and also can reduce boat weight. 
The various portions of the lower sprocket assembly 36 preferably also are 
made of plastic material or metal. The diaphragm 267 may be of rubber or 
similar material. Moreover, if desired, the propeller 15 itself may be 
made of plastic material. Use of plastic, as was described above, 
facilitates manufacturing, reduces the cost of manufacturing, avoids 
corrosion problems and minimizes weight of the various parts of the 
outdrive 30. 
External Features 
As is seen in FIGS. 1, 2 and 14-16, at the bottom of the power leg 180 is a 
replaceable skeg 280. Such replaceable skeg is mounted by a dovetail 
groove connection 281 to the clam shell halves 200, 201 where they are 
secured together at the bottom 282 thereof. The skeg 280 provides 
direction control with a rudder-type action for the outdrive 30 and boat 
3. The skeg 280 also helps provide a measure of protection for the 
propeller 15 to prevent the blades 260 from striking the bottom of the 
body of water in which the outdrive is operated and also provides a 
measure of protection for the blades 260 from striking a solid object, 
such as a rock, submerged log, etc. In the event the skeg 280 becomes 
damaged or destroyed, it can be slid out from the groove in which it is 
connected to the bottom 282 of the housing 12, and an undamaged skeg then 
can be reinstalled by sliding the same into the dovetail groove connection 
281. 
The skeg may also be made in various "winged" configurations to provide a 
prescribed amount of lift to affect the trim of the boat. Such a winged 
configuration is illustrated at 280a in FIGS. 14A and 16A. Such winged 
skeg may help enable the boat to go up on a plane under appropriate 
conditions. 
A plate 283 is molded as part of the housing 12. The plate 283 provides the 
usual function of anti-ventilation, i.e., to tend to prevent air from 
becoming entrained in the stream of fluid, e.g., the water, through which 
the propeller turns and propels the boat. Another function of plate 283 is 
to block spray of water upward. Since the plate 283 preferably is 
integrally molded and formed as part of the respective clam shell halves 
200, 201, no additional work effort is required to manufacture and/or to 
install such plate on the outdrive 30. 
As is seen in FIG. 15, the passages 150, 151 for the bifurcated portions 
58a, 58b of the rod 58 extend in the upper housing portion 32. Since much 
of the outdrive housing 12 is likely to be submerged at least when the 
boat is at rest, it is likely that water will enter such passages. A drain 
opening 284 (FIG. 1B) in the back of the upper housing portion 32 may be 
provided to drain such water when that drain is above the water level. 
Trim, Tilt, Kickup Mechanism 53 
Referring, now, to the trim, tilt and kickup mechanism 53, which is shown 
in FIGS. 1, 3, 17 and 18, the actuator 54, including the piston 55, 
cylinder 56 and rod 58 preferably are made of plastic material to minimize 
cost of materials and of manufacturing, to minimize weight, and to 
eliminate corrosion problems. The rod 58 is generally linear, relatively 
long, and bifurcated, although other shape of rod may be employed, as may 
be desired, depending on the particular design and structure of the 
outdrive 30. 
The cylinder 56 is formed by two housing parts 291, 292, both of which 
preferably are generally of hollow cylindrical configuration. The housing 
parts 291, 292 are coupled together at a flange connection 294 where the 
annular flange 295 of the rolling diaphragm 57 also is connected. The 
diaphragm 57 may be of rubber, reinforced rubber, or other material, which 
is available commerically, for example, from Bellofram Corporation. The 
diaphragm 57 cooperates with the housing 291 to form a variable volume 
fluid chamber 59 into which fluid, such as hydraulic fluid or pneumatic 
fluid, for example, may be delivered to increase or to decrease the 
pressure in the chamber and, thus, the volume thereof. The piston 55 is 
mounted behind the cap-like portion 296 of the rolling diaphragm 57 both 
to support the diaphragm and to support the rod 58 relative to the 
diaphragm and the balance of the actuator 54. Such fluid actuators are 
well known in the art. 
The cylinder 56 is mounted at the flanges 294 between several bosses 
generally designated 297 (FIG. 1B) to secure the actuator 54 in the 
outdrive housing 12. As a result, as the cylinder 56 and the piston 55 
undergo relative movement, relative movement must occur between the 
housing 12 and the gimbal ring 100 at which the rod 58 is connected. Such 
latter relative movement is in effect a trimming or tilting type of 
action. The axis of rotation of the outdrive 30 in response to such 
relative movement of the piston 55 and cylinder 56 is the trim axis T, as 
was described above. 
To change the trim of the power leg 180, one may increase or decrease fluid 
pressure in the chamber 59. Such change may be effected by the operator of 
the boat adjusting the controls 21 to adjust an appropriate hydraulic 
control line coupled, for example, at 301 to the fluid chamber 59. 
Moreover, it it were desired fully to tilt the power leg a maximum degree 
of tilt, say, for example, 50 degrees to about 60 degrees, preferably 
about 52 degrees, i.e., angle A, as is illustrated in FIG. 1B, fluid 
pressure may be applied to the chamber 59 to move the cylinder 56 to a 
maximum extended position relative to the back of the boat and the piston 
55. As long as fluid volume in the chamber 59 is maintained, then, the 
power leg would remain fully tilted, e.g., for servicing, transporting, or 
other reason. 
The actuator 54, cylinder 56 and the piston 55 may have a relatively large 
cross-sectional area transverse to the direction of relative movement 
thereof, say on the order of about eighteen square inches. The large 
surface area against which fluid pressure in the chamber 59 acts, then, 
enables a relatively low pressure fluid to develop a relatively large 
force to move the cylinder 56 relative to the piston 55 to tilt the power 
leg 180. The relatively large cross-sectional area of the actuator 54 and 
the operability thereof in response to only relatively low fluid pressure 
enables the cylinder 56 and the piston 55 to be of molded plastic. One 
exemplary material is a thermoplastic polyester. The rod 58 also 
preferably is made of high strength plastic able to withstand the 
compression and tension forces applied thereto, as is described herein. 
Kickup allows the power leg 180 to tilt about the axis T when the leading 
edge 302 of the power leg 180, the propeller 15, or some other part of the 
outdrive 30 strikes an object, such as a rock, log, the bottom, etc. Such 
tilting allows the lower portion of the outdrive to tilt out of the way of 
such object, preferably without damaging the outdrive 30. 
The force tending to kickup the power leg 180 initially is balanced against 
the sum of the forces created by the weight of the power leg itself, 
atmospheric pressure acting against the back side of the piston 55 in the 
actuator 54 and the thrust of the propeller. When that kickup force is 
large enough to overcome that sum and the inertia of the power leg 180, a 
vacuum tends to be created in the chamber 59 of the actuator 54 as the 
power leg is kicked up to tilt about the tilt axis T. After kickup has 
begun, the force required to create that vacuum to continue the tilting 
remains substantially constant. 
Hydraulic fluid in the chamber 59 ordinarily does not have to flow during 
kickup. After the force tending to kick up the power leg 180 terminates, 
atmospheric pressure acting against the surface area of the piston 55 
tends to return the piston to the original position in the chamber 59 and 
the power leg 180 back to the original pre-kickup orientation. The weight 
of the power leg 180 and the propeller thrust responding to gravity force 
also helps return the power leg 180 back to the pre-kickup orientation. 
Summarizing, then, when the leading edge 302 of the power leg 180 strikes 
an object and the force of that strike is adequate to overcome the 
atmospheric pressure times the area at the back of the piston 55 plus the 
weight of the power leg 180, then the power leg 180 will tilt about the 
axis T. The piston 55 actually remains in position relative to the gimbal 
ring 56, as the cylinder 56, which is fixedly mounted in or to the housing 
12, is moved to pull a vacuum in the cylinder chamber 59. The kickup force 
remains constant because the force needed to be overcome is atmospheric 
pressure times the area of the back side of the piston 55. Since the 
kickup force, then, is so limited, the possibility of damage to the 
outdrive is minimized. Moreover, since the kickup force is uniform, the 
entire power leg kicks up in a substantially continuous action, and it is 
less likely to deform or to distort as it achieves a higher tilt, e.g., as 
a log pushes past. If the kickup force were variable and/or in particular, 
if the force exceeded a certain relatively high level, e.g., as a function 
of tilt, then such a high force could distort and/or damage the plastic 
housing 12. 
After the kickup force has been eliminated, the power leg 180 will return 
to the original position it had assumed prior to having been kicked up. 
Back Benders 42, 43 
It is desirable that an outdrive have a relatively small cross-sectional 
area transverse to the direction of travel through the water. See FIGS. 2, 
15 and 16. A potential disadvantage in using a belt 37 or other flexible 
member which has two legs 40, 41 is that space is required to house each 
of the belt legs. In the past such space requirement would have required a 
relatively broad cross-section or two down legs as in the above Dunlap 
patent. 
However, it has been discovered in accordance with the present invention 
that the belt 37 can be bent backwards to compress the legs 40, 41 thereof 
toward each other in a way that tends to minimize the cross-sectional area 
profile of the outdrive transversely to the direction of travel through 
the water. 
Turning to FIG. 2, a front elevation view, partly in section, of the belt 
drive assembly 31 forming part of the power leg 180 is illustrated in 
detail. The respective clam shell housings 200, 201 near the bottom of the 
outdrive define a bulbous shape, often referred to as the torpedo 34 of 
the outdrive 30 behind which the propeller 15 (not shown) would be 
mounted. The torpedo 34 houses the lower sprocket assembly 36. 
The back bending function is accomplished by a pair of relatively strong 
curved plates 42, 43, sometimes referred to as skid plates or back 
benders. Such plates 42, 43 are of relatively strong material able to urge 
the legs 40, 41 of the belt 37 toward each other with adequate force 
without damaging the clam shell housing parts 200, 201 on which the plates 
42, 43 may actually be mounted. The plates 42, 43 preferably are formed of 
stainless steel material or aluminum. Alternatively, they may be formed of 
some other metal material. The plates 42, 43 may be precoated with a low 
friction material, such as that sold under the trademark Teflon, to 
facilitate sliding of the belt 37 over the surfaces of the plates. For 
example, the plates may be coated with a Teflon impregnated anodizing 
material. 
The plates 42, 43 preferably are bent or curved in the manner illustrated 
so as to form a segment of an arc of a circle. Such circle preferably if 
extended would be tangent or approximately tangent with the travel 
direction of the belt about the lower sprocket 242. 
A lubricating medium 319, such as oil, transmission fluid, gear oil, or the 
like, is in the belt chamber 38. The belt chamber 38 is coupled to a sump 
320, which extends from the bottom of the lower sprocket 242 part way up 
along the sides thereof, between the belt 37 and the housing 12, as is 
illustrated in FIG. 2. It has been found that an adequate amount of 
lubricant is available when the sump 320 is filled to a level that is less 
than about one-half the diameter of the lower sprocket 242. 
Such lubricant fluid 319 preferably is splashed by the rotating sprocket 
242 and by the belt 37 at both surfaces thereof and particularly at the 
surface that faces the respective plates 42, 43 to provide a thin sliding 
surface interface between the belt legs 40, 41 and the plates 42, 43. The 
fluid 319 also provides a cooling or heat transfer function to remove heat 
from the outdrive 30. It has been found that a relatively small amount of 
lubricant 319 will enable the belt 37 to slide smoothly and with minimal 
friction over the surfaces of the plates 42, 43 without encountering 
unusual belt wear. Belt wear is therefore, preferably kept to a minimum. 
In fact a layer of lubricant 319 that is on the order of from one to 
several molecules thick has been found especially desirable between the 
belt legs 40, 41 and the smooth surfaces 44, 45 of the plates 42, 43. 
Preferably such surfaces are smooth and polished further to minimize 
friction and belt wear. Also, preferably the back surface of the belt 37 
facing the back bender surfaces 44, 45 may have grooves that extend in the 
width direction or dimension of the belt 37. Such grooves appear to 
enhance the thermal energy transfer between the belt and the surfaces 44, 
45. It appears that such grooves carry fluid 319 to the surfaces 44, 45 
from the sump 320, contribute to splashing of such fluid elsewhere in the 
belt chamber-38, and/or cause turbulence in the carried fluid 319, all of 
which appear to cooperate to improve efficiency of heat transfer between 
the fluid 319 and the plates 42, 43. The fluid reduces the amount of 
friction and, therefore, the amount of heat generated; and the amount of 
heat dissipation is reduced significantly. 
According to the invention, the belt 37 is pinched together near the bottom 
by passive structural means, namely, the plates 42, 43 and/or the housing 
12 itself. According to the preferred embodiment, there is no need for any 
rotating elements, such as idler wheels, to pinch the belt. The belt is 
dragged across the plates 42, 43. The belt tends to float on the lubricant 
fluid hydrodynamically slightly away from the surfaces of the plates 42, 
43, thus minimizing wear of the belt. 
The radius of the back bend desirable is circular and is not so severe as 
to cause undue wear of the belt. In the preferred embodiment, the radius 
of curvature may be, for example, on the order of 24 inches. The actual 
radius of curvature of the back bend tends to determine the size of the 
cross-sectional area of the submerged portion of the power leg; while it 
is desirable to maximize the radius of curvature of the plates 42, 43 to 
minimize wear of the belt 37, it also is desirable to minimize that radius 
of curvature to minimize the mentioned cross-sectional area. 
The use of back bending of the belt tends to improve the overall 
hydrodynamics of the submerged portion of the outdrive, and, as a result, 
drag through the water is reduced. If desired, other means may be used to 
back bend the belt. 
If desired, lubricant from the sump 320 may be specially sprayed at 
particular locations in the area of the torpedo 34 and/or plates 42, 43, 
or on the belt 37 itself to achieve a desired lubricating function 
vis-a-vis the belt and the plates. However, it has been found that normal 
splashing without specific directing of jets of lubricant toward strategic 
spots adequately achieves the desired lubricating function. 
If desired, the lubricant 319 may be directed through a heat exchanger to 
cool the fluid to reduce belt wear due to heat. More preferably, though, a 
cooling water flow 48 is provided in chamber areas 49, 50 behind the back 
benders 42, 43. Seals 332, 333 prevent leakage between the water chambers 
49, 50 and the belt chamber 38. An inlet 334 for receiving cooling water 
flow is provided at or approximate the torpedo 34. Ordinarily such inlet 
preferably is under water. Conventional means may be used otherwise to 
seal the chambers 49, 50 to prevent leakage, and flow lines may be 
provided otherwise to conduct cooling water flow 48, as may be desired. 
According to an exemplary embodiment of the invention, the belt 37 is one 
sold under the trademark POLYCHAIN having an 8 millimeter pitch. Coarser 
and finer pitches also are available and may be employed. However, coarser 
pitches tend not to be as pliable for bending around short radii, such as 
those employed using the upper and lower sprockets of the present 
invention. Pitch is the distance between teeth when the belt is laid out 
flat. Preferably the present invention uses a relatively small pitch 
series belt to enable bending around relatively short radii of the 
sprockets. 
An advantage to the use of the back bent belt in addition to the low 
cross-sectional area provided is the increase in the number of belt teeth 
and sprocket teeth that are engaged as the belt goes around the respective 
sprockets, as compared to the number of interengaged teeth when the belt 
legs run "straight" between sprockets. The increased number of 
interengaged teeth enhances the power coupling efficiency and 
effectiveness between the belt and the sprockets. 
Cone Clutch Upper Sprocket Assembly 
Turning to FIG. 19, a cone clutch assembly 600 is shown. The cone clutch 
assembly 600 may be substituted for the upper sprocket assembly 35 in the 
outdrive 30 of the present invention. The cone clutch assembly 600 is 
selectively operable to couple rotary motion from the universal joint to 
the belt 37 via a sprocket 601 that is able to be rotated. Actuation of 
the cone clutch assembly 600 may be carried out by a connection to and 
operation of the controls 21. 
A rotatable shaft 602 of the cone clutch 600 assembly is mounted in a 
hollow opening 603 of the sprocket 601 for rotation independently or 
coextensively therewith as a function of whether or not the cone clutch is 
actuated. Accordingly, the sprocket 601 and the shaft 602 are concentric; 
and although they are in relatively close fit relation, they are able to 
rotate relative to each other when the cone clutch is not actuated. The 
shaft 602 is connected to the connector 163 of the universal joint for 
rotation thereby. The sprocket 601 is mounted in bearings 604, 605 which 
in turn are mounted in housings 606, 607 that can be mounted in the 
housing 12 of the outdrive 30, e.g., as the upper sprocket assembly 35 
described above is mounted. If desired, pre-tensioning means and/or 
dynamic tensioning means, as were described above relative to the upper 
sprocket assembly 35, may be employed with the cone clutch assembly 600 
and the mounting thereof if the housing 12. 
A cone clutch mechanism 610 of the cone clutch assembly 600 particularly 
includes a cone 611 and a cup 612. The cone and cup are positioned for 
relative axial movement along the axis C about which the sprocket 601 and 
the shaft 602 are concentrically arranged. When the cone 611 and cup 612 
are relatively separated along the axis C, no motion is coupled from one 
to the other, and one can rotate relative to the other. However, when the 
cone 611 and cup 612 are engaged with each other at confronting surfaces 
611s, 612s, rotational effort from one causes the other to rotate 
therewith. 
In the illustrated embodiment the cone 611 is mounted at an end of the 
shaft 602 at a threaded connection 613. The thread preferably is a spiral 
thread, the male being on the shaft and the female being interiorly of the 
cone. Preferably the cone 611 can be rotated on the male thread to move 
the cone along the axis C toward or away from the cup 612. A resilient 
member 614, such as a belleville spring or washer, normally urges the cone 
to the left relative to the illustration of FIG. 19, away from engagement 
with the cup 612. Other types of resilient members alternatively may be 
used for such purpose. 
The cup 612 is mounted on the sprocket 601, for example by a secure 
threaded connection 615. The cup rotates with the sprocket 601. In 
particular, when the cone 611 engages the cup 612, rotary motion of the 
shaft 602 is coupled to the sprocket 601 to rotate the sprocket and, thus, 
to drive the-belt. 
A fluid actuator mechanism 620 is used to actuate the cone clutch assembly 
600 to couple rotary motion from the power supply and universal joint to 
the sprocket 601. (Other types of actuators, such as mechanical or 
electrical type, may equivalently be used.) A fluid connection 621 couples 
the fluid actuator to the controls 21 to receive fluid pressure, volume or 
other fluid input to actuate the cone clutch mechanism 600; and may 
relieve such fluid pressure, drain fluid volume, etc., to deactuate the 
cone clutch mechanism. 
A diaphragm 622 is secured in the housing 607 by a retaining ring 623 in 
conventional fashion to define a fluid chamber 624. The diaphragm 622 is 
reinforced by a retainer plate 625 and a washer 626, which are secured to 
each other by a rivet 630. The fluid connection 621 is coupled to the 
fluid chamber 624 to supply or to drain fluid with respect thereto. The 
head of the rivet 630 is positioned to be in and/or to move into 
engagement with a wear plate 631 that is attached to the cone 611. 
When the cone clutch mechanism is not actuated, ordinarily the quantity 
and/or pressure of fluid in a chamber 624 is minimal, and the spring 614 
urges the cone 611 along the spiral thread 613 away from the cup 612. In 
response to application of fluid and/or fluid pressure via the fluid 
connection 621 to the fluid chamber 624, the rivet head 630 working 
against the wear plate 631 urges the cone 611 against the spring 614 and 
to the right along as the cone rotate along the thread 613. The angle on 
the thread is selected such that it is not self-locking; yet it is 
adequate to provide the required amount of axial motion along the axis C 
by the cone 611. As the surfaces 611s and 612s engage, the forces and/or 
resistances developed are such that the cup is tightened along the thread 
and is further secured into engagement with the cone. For example, the cup 
tends to resist rotating due to its inertia and that of the belt, etc., 
thus causing it to try to slow down the rotating cone, which, therefore, 
tends to undergo relative rotation to the shaft 602; as a result, the 
thread pulls the cone tightly against the cup. A secure connection between 
the cone and cup thus being made, the rotary motion of the shaft 602 turns 
the sprocket 601 and drives the belt 37. When fluid pressure in the fluid 
chamber 624 subsequently is relieved, the spring 614 urges the cone to the 
left relative to the illustration to disengage from the cup. 
It will be appreciated, then, that the cone clutch mechanism 600 may be 
operated by the controls 21 or by some other means to engage and to 
disengage the belt 37 and, thus, the propeller of the boat, for example. 
Additional details of the cone clutch assembly 600 include a rotatable 
shaft seal 640 which prevents water from entering the housing 606, for 
example, and retains lubricant in the housing. A retaining ring 641, ball 
key 642, and thrust washer 643 prevent the shaft 602 from moving along the 
axis C, and the key causes the thrust washer to turn with the shaft. A 
flange 644 helps hold the bearing 604 in place and prevents the belt 37 
from moving off the sprocket 601. A retaining ring 645 retains a thrust 
washer 646 in place on the shaft 602; and the spring 614 bears against 
such thrust washer. 
It is noted that the cone clutch assembly 600 is a single acting cone 
clutch. This is as compared to a dual acting cone clutch in which one 
actuator mechanism is required for forward and the for reverse movement. 
In the present invention, though, actuation is via fluid; and return or 
deactuation is by the force of the spring 614. 
The following summarizes a number (although not all) of features of the 
invention: 
As to the plastic housing, preferably it is formed of plastic structural 
members, either of the thermoset or thermoplastic type. The housing is of 
clam shell construction, which provides strength, convenience of assembly, 
convenience of manufacturing, and minimum expense. For example, both 
halves of the clam shell may be mirror images of each other, thus 
facilitating engineering and designing, as well as making of a mold to 
mold the same. The clam shell halves may be secured together by rivets, 
screws, or even may be glued. The skeg at the bottom is replaceable by 
sliding out from the dovetail connection thereof to the housing 12. Metal 
skegs tend to become damaged, but typically cannot easily be replaced, 
whereas the instant plastic one can easily be replaced. 
A plastic housing does not have to be painted because the color may be an 
integral part of the plastic material of which the housing is molded. 
Although some anti-fouling paints cannot be applied to aluminum casting 
outdrives due to galvanic action of the paint with the aluminum material 
of the outdrive, virtually any paint can be applied to a plastic material. 
A plastic outdrive will not corrode, is cost effective, and is relatively 
lightweight. 
Due to the lightweight of the plastic outdrive of the invention, the power 
leg of the outdrive can be easily disassembled from the gimbal ring 100 by 
a single individual without having to enter the boat. Moreover, the gimbal 
ring structure itself may be removed from the outer transom housing by 
disconnecting the upper and lower rudder pins from the mounting structure 
thereof, also preferably without having to enter the boat. 
Various component parts of the outdrive 30 may be of plastic material, as 
is described in further detail above. Examples include the bearing 
housings, tilt cylinder structure, transom housing, actuator shafts, and 
so on. The various fittings to which hydraulic and/or pneumatic lines are 
connected and the lines themselves can be plastic since relatively low 
pressures are used in the invention. Such parts can be assembled by gluing 
together. Such plastic parts are cost effective, will not corrode, are 
lightweight and can be manufactured and/or replaced easily. Because of 
heat, it is desirable to use metal, e.g., aluminum, for the sprockets to 
displace heat from the belt. It is desirable to use thermally conductive 
sprockets to dissipate heat from the belt. Moreover, to extend the belt 
life under severe load it is desirable to provide a very smooth finish on 
the surface of the sprockets where they engage the belt 37. For example, 
such surface can be polished and coated with anodizing or nickel for 
smoothness. 
The way the belt 37 is mounted permits the use of the internal trim, tilt 
and kickup mechanism 53 compared to the external trim/tilt cylinders of 
prior art devices, which encounter snagging and spray problems and are 
somewhat unsightly. Specifically, in the present invention the actuator 
rod of the trim/tilt assembly may pass outside the two legs 40, 41 of the 
belt 37, but still within the housing 12 so that the cylinder 56 can be 
located in line therewith and not outboard the major front/rear axis of 
the boat. 
The toothed belt drive is oil lubricated and will be oil cooled. Back 
bending of the belt permits reduced hydrodynamic drag on the portion of 
the outdrive which is located in the water. 
A rolling diaphragm cylinder is used in the trim/tilt structure 45, and the 
cylinder thereof utilizes atmospheric pressure in conjunction with the 
kickup and return features of the outdrive. 
Since the trim/tilt cylinder and the actuator on the lower sprocket for 
changing or reversing the pitch of the propeller are low pressure 
actuators, they can be made of plastic, which is relatively inexpensive. 
Since those actuators operate at relatively low pressure, the various 
hydraulic lines and/or fittings associated therewith can be of plastic and 
relatively inexpensive rubber material, respectively; and the hydraulic 
lines and fittings can be glued together. 
As was mentioned earlier, the outdrive can be easily removed from the boat 
and sent back to the factory for servicing or replacement. To remove the 
power leg 180, for example, the trim bolts or shoulder screws 142, 143 can 
be removed; the bellows or boot 93 can be disconnected; the hydraulic 
lines can be disconnected; the pin 158 is removed; and then the power leg 
180 can be easily removed from the gimbal ring 100. 
To remove the gimbal ring 100, which is attached to the outer transom 
housing 84, the stop nut 116 is removed. A washer and screw may be 
installed in the bottom of the upper rudder pin 110 and using a bearing 
puller type device, the upper rudder pin can be pulled out toward the 
bottom. The lower rudder pin 132 can be removed by unscrewing it. The 
gimbal ring 100 then can be removed. 
It is noted here that the invention has been described with respect to an 
outdrive 30; but it will be appreciated that the features of the invention 
may be used with other drives, such as outboards, inboards, and various 
hybrid drives, especially for watercraft, and also for other vehicles.