US3358633A

US3358633A - Auto-pilot

Info

Publication number: US3358633A
Application number: US528723A
Authority: US
Inventors: Richard B Wallace
Original assignee: Oakland Corp
Current assignee: Oakland Corp
Priority date: 1966-02-21
Filing date: 1966-02-21
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19

Description

Dec. 19, 1967 R. B. WALLACE 3,358,633

AUTO-PILOT Filed Feb. 21, 1966 2 Sheets-Sheet 1 72 VACUUM SUPPLY F|G.l

2O 66 74 68 74 76 66 74 68 20 76 66 68 20 Min i1\\ IKE-73m l Mill WI). 6 IIIIAIIIVII" I6 56 FlG.2 FIG.3 56 F|G.4

VACUUM SUPPLY 94 8 l 56 I Y /70 INVENTOR. mo RD B. WALLACE ATTORNEYS Dec- 19617 R. B. WALLACE 3,

AUTO-PILOT Filed Feb. 21, 1966 2 Sheets-Sheet 2 VACUUM SUPPLY H2 oo INVENTOR. RICHARD B. WALLACE FIG. 9 BY Z Z/ ATTORNEY United States Patent 3,358,633 AUTO-PILOT Richard B. Wallace, Bloomfield Hills, Mich., assignor: to The Oakland Corporation, Troy, Mich., a corporation of Michigan.

Filed Feb. 21, 1966, Ser. No. 528,723 15 Claims. (Cl. 114-144) ABSTRACT OF THE DISCLOSURE An auto-pilot for a boat responsive to roll or turning of the boat about its longitudinal axis to apply a rudder correction.

The present invention relates to an auto-pilot and more particularly, to an auto pilot responsive to roll or turning of a boat about a longitudinal axis to apply a rudder correction.

It is an object of the present invention to provide an automatic pilot including steering mechanism responsive to roll to operate the steering mechanism.

It is a further object of the present invention to provide roll responsive means in the form of a pendulum to apply a steering correction to a boat in accordance with the magnitude and duration of the roll.

It is a further object of the present invention to provide an automatic pilot including fluid pressure means for operating a rudder including valve mechanism for controlling the fluid pressure means, the valve mechanism comprising a pair of independently movable valve elements, means responsive to roll of the boat for moving one of said valve elements, and means responsive to boat heading for moving the other of the valve elements.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is a diagrammatic view illustrating one embodiment of the present invention.

FIGURE 2 is an enlarged fragmentary sectional view on the line 22, FIGURE 1 showing one valve position.

FIGURES 3 and 4 are enlarged fragmentary sectional views similar to FIGURE 2, showing different valve positions.

FIGURE 5 is a diagrammatic view showing a steering system which includes the present invention.

FIGURE 6 is a diagrammatic view of a somewhat different embodiment of the present invention.

FIGURE 7 is an enlarged fragmentary view, partly in section, of adjustable pendulum control means.

FIGURE 8 is an enlarged fragmentary sectional view looking in the direction of the arrows 88, FIGURE 6.

FIGURE 9 is a diagrammatic view illustrating the provision of two devices responsive to different conditions for controlling the position of the rudder.

In prior Patent 3,148,654, in which I was a joint inventor, there is illustrated an automatic pilot intended primarily for use with small boats. This automatic pilot under ideal conditions operates very satisfactorily but use of this automatic pilot under varying conditions demonstrated that smaller boats could not be held closely to course in the presence of certain wave actions. It is common knowledge that typical power cruisers perform badly in a following or quartering sea, requiring a corrective turn of the boats wheel with each wave. While it appears superficially that only a boats rudder can cause a turn or change in course, it has been found that whenever the boat rolls about a longitudinal axis, the hull in effect becomes a rudder. A roll to the left without variaice tion in other factors produces a turn to the right and vice-versa. The condition may be made worse, depending in part on hull design, by an off-setting action of the wave on the stern of the boat relative to the bow.

An investigation demonstrated to me that with a normal sea resulting from perhaps a 15 mile per hour wind, the piloting or course holding problem was created for the most part by wave action and only to a minor degree by changes in direction requiring a magnetically based correction. It has been found that the wave-created factor rises steadily in direct proportion to wave size while it may reasonably be assumed that the magnetic course correction needs were substantially constant.

An initial investigation of the problem was carried out with a pendulum activated valve in control of fluid pressure (vacuum) power steering mechanism. In practice, the pendulum actuated valve was substituted for the compass control valve of the system shown in the prior Wallace et al. Patent 3,148,654 previously referred to. The results obtained were astonishingly good. Even with no magnetic reference to the earths field, it was possible to hold a straight course for several minutes although the wakes of other boats and regular waves were present tending to upset the original direction. Moreover, a roll of the boat occasioned by the lateral shifting of weight of two men, which would normally cause a substantial turn, was cancelled completely by the counter-correction of the pendulum valve and the rudder correction which it applied.

The use of a pendulum controlled valve to counteract the tendency of wave action to produce a change in correction is useful in reducing the steering effort required by manual control of the rudder. In my prior copending application Ser. No. 391,381, new Patent 3,263,639 I have disclosed a steering system comprising an irreversible manually controlled device such as a wheel operating through a worm and worm gear to apply longitudinal movement to an elongated telescoping motion transmitting mechanism in association with power controlled means for effecting changes in the effective length of the elongated member. The present invention may be applied to control the mechanism for changing the effective length of the elongated member in place of the compass controlled mechanism illustrated in the copending application.

The most useful applicaton of the present invention however, contemplates the combination of course sensitive means including a compass such for example as a magnetic compass, and a roll responsive means such as a pendulum, together actuating a single valve mechanism for effecting automatic steering of a boat or automatic means for assisting manual steering of the boat.

Referring first to FIGURE 1 there is illustrated a mounting plate 10 to which is pivoted an assembly subplate 12, the pivot connection being illustrated at 14. Formed on the assembly sub-plate 1 2 is a boss forming a valve base 16 having valve ports therein as will subsequently be described. Pivoted to the valve base 16 'by a pivot connection 18 is a valve plate 20. Spring biasing means indicated generally at 20a are provided holding the valve plate 20 in sealing relation against the flat surface of the valve base. Details of the spring biasing means may be the same as illustrated and described in detail in connection with a second embodiment of the present invention.

Also pivoted to the assembly sub-plate 12 at 21 is a pendulum '22 including a pendulum weight 24. The pendulum includes a valve actuating arm 26 having a round head 27 received in the space between a pair of furcations 28 provided at the lower end of the valve plate 20.

The coaction between the valve structure incorporated in the valve base 16 and the valve plate 20 may be of different types depending on the type of power mechanism for shifting the rudder. In the present case the roll responsive mechanism is connected to a system as best illustrated in FIGURE 5, in which a boat rudder 30 is connected to be operated by a manually rotatable wheel 32 through suitable irreversible drive mechanism such for example as a worm and worm wheel which may be contained in a transmission housing 34. The connections between the transmission housing 34 and the rudder include elongated motion transmitting mechanism indicated generally at 36 which may take the form of rod means including a pair of

telescoping rod sections

38 and 40. Means are provided for effecting relative longitudinal movement between the

rod sections

38 and 40 and this means comprises a lever 42 pivoted at 44 on a bracket 46 connected to a tubular sleeve 48 carried by the rod section 38. The lever 42 has a motion transmitting connection 50 with the rod section 40. It will be understood that the tubular sleeve 48 is movable with the rod section 38 and in the absence of swinging movement of the lever 42 about its pivot 44, the sleeve, bracket and lever all move in unison with the rod sections '38 and 40.

Power actuated means for the lever 42 is provided and takes the form of a fluid motor such as the expansible bellows 52 having a tension spring 54 tending to move the bellows to open position against a controlled vacuum admitted through a vacuum supply line 56. The bellows includes a movable wall 58 to which the spring is connected and which also is connected to a rod 60 extending into one end of a flexible bowden wire device indicated generally at 62. The opposite end of the bowden wire device is connected to the bracket 46 and the flexible wire therein is connected to a rod 64 which in turn is connected to the lever 42. Accordingly, as the degree of vacuum in the bellows 52 is varied, movement of the wall 58 results in swinging of the lever 42 and corresponding movement of the rod section 40- relative to the rod section 38, thus resulting in a change in the effective length of the elongated motion transmitting mechanism 36 connecting the transmission housing 34 to the rudder 30. The roll sensitive valve mechanism described in connection with FIGURE 1 includes the valving structure best illustrated in FIGURES 2, 3 and 4. The valve base 16, as best seen in FIGURES 2 and 3, is provided with a pair of

ports

66 and 68. The port 66 maybe formed by the end of the tube or conduit 56 which applies vacuum to the bellows 52 as previously described. The tube or conduit 70 extends to a vacuum supply structure 72 which may be the manifold of an engine on the boat.

The valve plate 20 is provided with an elongated recess 74 which in the position of parts shown in FIGURE 2, affords connection between the passages formed by the tubes or

conduits

56 and 70. The valve plate 20 is further provided with a through opening 76 which is adapted to register with the port 66 formed at the end of thetube or conduit 56 so as to vent the interior of the bellows 52 to atmosphere when the parts are in the position shown in FIGURE 4. The valve occupies the position illustrated in FIGURE 3 when the boat is in a normal position. In this position it will be observed that the recess 74 connects the port 68 to the port 66 but the port 66 is also in limited communication with the opening or passage 76. Accordingly, the vacuum supply conduit 56 is bled to atmosphere an amount depending upon the exact position of the valve plate 20 relative to the valve base 16. At this time the eifectiveness of the partially bled vacuum suppliedto the bellows 52 is sufiicient to maintain the bellows in an intermediate position against the bias of'the spring '4 so as to maintain the rudder 30 amidships when the wheel 32 is in the amidships position.

If the boat rolls to port the pendulum remains in a veritical position and the valve plate 20 is swung in a counterclockwise direction as seen in FIGURE 1, or toward the limiting position shown in FIGURE 4. At this time the vacuum supply conduit 56 is in full communication with the bleed opening 76 and the vacuum port 68 is means 36. Assuming the manually operated wheel 32 is stationary at this time, this will result in a movement of the rudder to port sufficient to overcome the tendency induced by the wave action and resulting roll of the boat to cause the boat to change course.

Conversely, if the wave action causes roll of the boat to starboard the valve plate 20 is shifted from the intermediate position illustrated in FIGURE 3 toward the limiting position illustrated in FIGURE 2 which eliminates the atmosphere bleed to the vacuum supply conduit 56, and which affords unrestricted communication between the vacuum tube 70 and the vacuum supply line 56 connected to the bellows.

When the boat regains an even keelfollowing the roll induced by wave action, the valve plate 20 resumes the intermediate position shown in FIGURE 3 and the rudder returns amidships due to the water pressure on the rudder and leakage inthe system, the position of the valve plate 20 being suflicient to supply a partially bleed vacuum to balance the force exerted by the spring 54.

It is of course within the contemplation of the present invention to provide a valve port 66 which is elongated along the line connecting it to the port 68 so as to facilitate balancing of the vacuum in the bellows against reaction forces developed on the rudder and the action of the spring 54.

Means are provided for restricting movement of the pendulum 22 relative to the sub-plate 12 and this means constitutes abutment screws 80 extending through ears 82 provided on the sub-plate 12. By this means, move ment of the valve plate 20 beyond predetermined limiting positions is avoided.

The foregoing construction provides mechanism for effecting automatic adjustment of the rudder to anticipate and prevent changes in direction resulting from wave action and/or tilting of the boat. When employed in a system as illustrated in FIGURE 5, the-roll responsive auto-pilot is effective to eliminate a major portion of the steering effort required by the boat operator. How ever, it still requires the atention of the operator to maintain the boat on its true course over a substantial period of time. The present invention is however particularly well adapted to combine with course sensitive means to completely eliminate the necessity for attending the wheel.

As previously noted, the sub-plate, 12 is pivoted to the mounting plate 10 and swinging movement of the subplate 12 about the axis of pivot 14 is accomplished in response to changes in course. For this purpose a second bellows 82 is mounted on the mounting plate and includes a pivoted wall 84 connected by a link 86 to the sub-plate 12. The movable wall 84 is also connected to a tension spring 88 the oppositejend of which is suitably connected to a fixed spring support on the mounting plate 10. The interior of the bellows 82 is connected by a vacuum passage 90 to the vacuum supply source 72 through a restriction in the passage indicated at 92. The passage 90 includes a bleed valve indicated generally at 94 which is responsive to departures from a preset heading and includes a compass controlled valve element which may be of the type disclosed in prior Wallace et al. Patent 3,148,654. Accordingly, a vacuum, the degree of which is determined by changes in the boat heading, is applied to the bellows and is efiective' when the boat is on course to maintain the sub-plate 12 in its in termediate position.

It is of course evident from an inspection of FIG- URES 1-4 that the valve action may be obtained by movement of the valve plate 20 over the valve base 16 or alternatively, by movement of the valve base relative to the valve plate. Of course, it is possible for a change in course and rolling action of the boat to cause independent movement of the valve base and valve plate and these independent movements may be in the same direction or in opposite directions. In any case, movement of the sub-plate 12 in accordance with departures from preset course applies a rudder correction dependent upon the magnitude of the course change and in a direction tending to restore the boat to its true course.

Inasmuch as the transmission connecting the wheel 32 to the rudder 30 is irreversible, it is possible for the boat operator to bring the boat onto a desired course by appropriate manipulation of the wheel and to hold it on this course by appropriate adjustment of the rudder to the required position, which may or may not be strictly amidships. Then if the full auto-pilot system is connected in, the operator may release the wheel which remains in its last position, and the auto-pilot takes over completely, providing the repeated rudder corrections required to eliminate course changes due to roll and to provide the necessary changes in average rudder position as required to maintain the true course.

Referring now to FIGURES 68 a somewhat different embodiment of the invention is illustrated which however, operates on precisely the same theory. In this embodiment of the invention the mounting plate is indicated at 100 and the sub-plate 102 is pivoted thereto by a pivot mounting indicated at 104. In this case the valve plate 106 is pivoted on the same pivot mounting 104 as the sub-plate and hence it remains in undisturbed position when the sub-plate is tilted or pivoted in accordance with changes in course. A pendulum 108 is pivoted directly to the mounting plate 100 by pivot means 110 which extend through an opening 112 provided in the sub-plate 102. Thus, tilting of the subplate 102 in response to changes in course does not atfect the pendulum.

While valve means identical with those described in connection with FIGURES 1-4 may be provided in the embodiment of the invention illustrated in FIGURE 6, in this figure there is illustrated a specifically different arrangement in which a pair of

valve parts

114 and 116 are provided at the upper surface of the sub-plate 102 and are partially and equally closed by the valve plate 106 when it is in its intermediate position as illustrated in the figure. A rudder indicated generally at 118 is pivoted as indicated at 120 and has fixed thereto a pair of walls 122 and 124 each of which cooperates with a fixed intermediate wall 126 to provide two opposed expansible and contractable bellows chambers as illustrated.

A vacuum supply 128 which may be the manifold of the internal combustion engine on the boat, is connected through restrictions indicated at 130 by a conduit 132 to the chamber intermediate the walls 124 and 126, and by the conduit 134 to the chamber intermediate the

walls

122 and 126.

The bleed port 114 is connected by a conduit 136 to the vacuum conduit 134 and the bleed port 116 is connected by a conduit 138 to the vacuum supply conduit 132.

With the parts in the position illustrated in FIGURE 6, and with the

bleed ports

114 and 116 partially but equally restricted, it will be apparent that the vacuum provided to the interior of the chambers intermediate the

walls

122, 126 and 124, 126, is equal and accordingly the rudder will remain in intermediate position and move to the intermediate position if displaced from intermediate position when the valve plate 106 returns to the illustrated position.

As before, the sub-plate 102 is adapted to be pivoted from the illustrated intermediate position about the pivot axis 104 in accordance with changes in course from a preset heading as controlled by a bleed valve indicated diagrammatically at 140 in the vacuum supply line 142 6 connecting the vacuum supply 128 and a bellows 144. The bellows includes a fixed wall 146 and a movable Wall 143 connected by a link 150 to the sub-plate 102. The movable wall 148 of the bellows is connected by a tension spring 152 to the mounting plate 100. With this arrangement the sub-plate 102 will be maintained in an intermediate position when the compass controlled bleed valve 140 is maintained in a position corresponding to the desired heading. Upon a change in heading in either direction, the effectiveness of the bleed valve is either increased or decreased, thus correspondingly increasing or decreasing the degree of vacuum in the bellows and resulting in a corresponding shift in the subplate to a position in which the tension of the spring 152 is effective to counterbalance the changed vacuum.

The sub-plate 102 is provided with ears 154 carrying adjustable abutment screws 156 so that swinging movement of the pendulum 108 relative to the sub-plate 102, and accordingly movement of the valve plate 106 relative to the sub-plate, is maintained between predetermined limits. In addition, the mounting plate 100 is provided with ears 158 carrying set screws 160 adapted to engage the edges of the sub-plate 102 and additional set screws -162 adapted to engage the pendulum 108. With this arrangement set screws 160 may be set to limit swinging movement of the sub-plate 102, or they may be advanced to prevent movement of the plate, in which case the device is responsive only to roll and will require the attention of the boat operator to maintain the boat on true course over protracted periods. On the other hand, if the set screws 162 are advanced to engage the pendulum, the roll sensitive piloting action is eliminated and only the compass responsive piloting action is maintained.

The provision of the abutment screws 162 for immobilizing the pendulum may be considered as illustrative only of any suitable means for preventing operation of the auto-pilot system in response to roll or listing of the boat. Obviously, similar results may be accomplished by the provision of valves in the vacuum supply lines leading to the

valve ports

114 and 116. Similarly, the compass controlled system may of course be selectively disalzled by operation of a valve in the vacuum supply line 1 2.

Referring now to FIGURE 7 there is illustrated adjustable means connected to the pendulum as by an extension '164 comprising a pair of relatively large light pistons 166 movable with considerable freedom in cylinders 168 having small axial extent and having a relatively large opening 170 adapted to be closed by a swinging valve element 172 pivoted for example as at 174 and having a manipulating finger piece 176. The pistons 166 constitute dashpot mechanism effective to modify and somewhat slow the action of the pendulum 108 as the boat rolls.

Referring now to FIGURE 8, mechanism for maintaining the

valve plates

20 or 106 in firm position against the ported valve base surfaces is illustrated. In this figure the valve plate 106 is shown as connected by the pivot 104 which serves as a common pivot for the sub-plate 102 and the valve plate 106 and the mounting plate 100. The valve plate 106 must swing freely and freedom must be provided for independent swinging of the sub-plate 102, but at the same time it is essential for the abutting surfaces of the sub-plate and valve plate to maintain firm contact. Accordingly, a screw is threaded into a tapped recess 182 in the sub-plate 102 and extends through an enlarged opening in the valve plate 106. A washer 184 is provided and interposed between the washer and the head of the screw 180 is a resilient washer or spring device 186 adapted to maintain a light but constant pressure contact between the abutting surfaces of the sub-plate 102 and the valve plate 106.

While in the foregoing reference has been made to a rudder correction, or movement responsive to roll, or movement of the boat about a longitudinal axis, it is sometimes desirable to provide independent substantially similar devices one of which is responsive to periodic roll as induced by a more or less regular succession of waves, and the other of which may be induced by listing of the boat which remains in a canted or listing position for a substantial interval.

In FIGURE 9 such a system is diagrammatically illustrated and comprises a wheel 19% connected to a rudder 191 through elongated motion transmitting means 192. Diagramrnatically indicated at 193 is the mechanism responsive to periodic rolling motion of the boat for effecting correction by shortening and lengthening the elongated motion transmitting means, the details of which are clearly illustrated in FIGURE and have been described at length in the foregoing. Intermediate the roll responsive mechanism for shortening the length of the elongated motion transmitting means 192 is a second similar device 194 which may be identical in all respects except that the pendulum of the type shown at 22 in FIG- URE 5 is heavily damped as for example by dashpot means of the type illustrated in FIGURE 7 but differing specifically therefrom in that the fluid displaced by move ment of the pistons is preferably in the form of a hydrau lic fluid displaceable through relatively restricted passages. Thus, the pendulum associated with the mechanism 194 will not be significantly responsive to back and forth roll but will instead be responsive to a listing of the boat which is maintained for a substantial interval, for example 30 seconds or a minute, or more. This device will also of course be responsive to the average list so that the fact that the'boat, in addition to listing, is subjected to a rolling motion, will not prevent the list responsive mechanism from operating.

A prime advantage of the use of the two mechanisms, one of which is responsive to fairly rapidlyrecurring rolling motion and the other of which is responsive to list or average list, is that the range of control provided by the roll responsive mechanism is not restricted and the total control is the additive result of the control exerted by the roll responsive mechanism and by the list or average list responsive mechanism.

Attention is called to the essentially modular construction of both of the embodiments of the invention previously described. It. is possible to install the auto-pilot mechanism responsive solely to rolling of the boat without obtaining the compass control mechanism although the pivoted sub-plate used in connection with the compass controllcd auto-pilot mechanism will be present. The roll controlled auto-pilot will then function as described, eliminating the major portion of the effort required by the helmsman to overcome the wave action normally shifting the boat off course. At any future time it is then a simple matter to add the compass controlled part of the mechanism by simply connecting the bellows device associated therewith to the sub-plate and connecting it to the compass modifying source of vacuum.

The drawings and the foregoing specification constitute a description of the improved auto-pilot in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. An auto-pilot system for a boat having a rudder including a power device for moving the rudder, means responsive to roll or movement of the boat about a longitudinal axis for operating the power device.

2. An auto-pilot system as defined in claim 1 in which the means responsive to roll or tilting of the boat about a longitudinal axis comprises a pendulum.

3. An auto-pilot system as defined in claim 2 in which the power device is a fluid pressure operated device, valve means for controlling the device, and means connecting said pendulum to said valve means.

4. An auto-pilot system as defined in claim 3 in which said power device is vacuum operated, and in which said valve means comprises one or more atmosphere bleed valves.

5. An auto-pilot system as defined in claim 21 comprising means for limiting the amount of movement of thependulum from intermediate position.

6. An auto-pilot systemas defined in claim 2 comprising means for controlling the rate of response of the pendulum to roll or tilting of the boat about a longitudinal axis.

7. An auto-pilot system as defined in claim 1 comprising in addition means responsive to departure of the boat from a preset course for operating the, device in a direc-. tion to restore the boat to the preset course.

8. An auto-pilot system for a boat as defined in claim 7 which comprises a pair of cooperating valve members, means responsive to roll or tilting of the boat about a longitudinal axis for shifting one of said members, means responsive to variations in course to shift the other of said members, the course responsive means being separable from and selectively applicable to the valve member adapted to be controlled thereby, whereby the course responsive part of the system is an option which may be added to the roll responsive system at any time.

9. An auto-pilot system as defined in claim 7 in which the power device is a fluid operated. motor, valve means in control of the motor, said valve means comprising first and second independently movable cooperating valve members, means connecting one of said valve members to the means responsive to roll or tilting of the boat about a longitudinal axis, and. means connecting the other of said valve members to the means responsive to departure of the boat from a preset course.

10. An auto-pilot system as defined in claim 9 in which the means responsive to roll or tilting of the boat about a longitudinal axis comprises a pendulum, and means connecting said pendulum to one of said valve members.

11. An auto-pilot system as defined in claim 9 comprising means for selectively disabling the means responsive to roll or tilting of the boat about a longitudinalaxis and the means responsive to departure of the boat from a preset course to provide for operation of the steering mechanism in response solely to departure of the boat from a preset course or solely to roll or tilting of the boat about a longitudinal axis, or jointly in response to both roll or tilting of the boat about a longitudinal axis and departure of the boat from a preset course.

12. An auto-pilot system for a boat having a rudder, a wheel, elongated motion transmitting means interposed between the rudder and wheel, and a one-Way driving connection from the wheel to the motion transmitting means, means for effecting variations in length of the motion transmitting means so as to produce movement of the rudder independent of or in the absence of movement of the wheel, power means for producing effective changes in length of the motion transmitting means, and means responsive to roll or tilting of the boat about a longitudinal axis to control operation of said power means to effect changes in the effective length of said motion transmitting means.

13. Apparatus as defined in claim 12 comprising in addition means responsive to departure of the boat from a preset course to effect changes in the length of the motion transmitting means, the means responsive to departure of the boat from a preset course being operable simultaneously with the operation of the means responsive to roll or tilting of the boat about a longitudinal axis so as to produce variations in the length of the motion transmitting means dependent jointly on roll or tilting of the boat about a longitudinal axis and departure of the boat from a preset course. i

14. Apparatus as defined in claim 13 comprising means for disabling the means responsive to roll or tilt- 15. Apparatus as defined in claim 12 in which the eifective change in the efiective length of the motion means responsive to roll or tilting of the boat about a transmitting meanslongitudinal axis is responsive essentially to rolling mo- References Cited tron repeated at relatively short intervals, 1n eombmat on 5 UNITED STATES PATENTS with a second power means for producing addltlve 176 8 7 10/1939 W h 114 144 h h h r t 'ttin 3135 gigs t o l isfin Z; a ve rZ i l istin 3 t l 1 ei b a 1 2498223 2/1950 Rommel 114144 S P g g g 3,263,639 8/1966 Wallace 114 144 to control the operation of the second power means to efiect with the first mentioned power means an overall 10 ANDREW H. FARRELL, Primary Examiner.