US3146457A

US3146457A - Automatic control systems for hydrofoils

Info

Publication number: US3146457A
Application number: US244240A
Authority: US
Inventors: Schertel Hanns Von
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-12-10
Filing date: 1962-12-10
Publication date: 1964-08-25
Anticipated expiration: 1981-08-25

Description

Aug. 25, 1964 H. VON SCHERTEL 3,146,457

AUTOMATIC CONTROL SYSTEMS FOR HYDROFOILS Filed Dec. 10, 1962 2 Sheets-Sheet 1 rs 9 Z "43 2a A :5' m. l I r- 15/ )z/ g- 25, 1964 i H. VON SCHERTEL 3,146,457 I AUTOMATIC CONTROL SYSTEMS FOR HYDROFOILS Filed Dec. 10, 1962 2 Sheets-Sheet 2 United States Patent 3,146,457 AUTOMATIC CONTROL SYSTEMS FOR HYDROFOILS Hanns von Schertel, 450 Sonnenberg, Hergiswil am fies, Switzerland Filed Dec. 10, 1962, Ser. No. 244,240 11 Claims. (Cl. ILL-66.5)

The invention is concerned with an automatic control device, which serves to maintain the depth of immersion of hydrofoils, which are attached to watercraft, as Well as for the reduction of rolling and pitching, and of the vertical accelerations of such craft at sea. It is applied to foils, which have hinged flaps at their trailing edge for influencing of lift, and especially at such foils which during travel are submerged entirely below the watersurface.

As is well known, fully submerged hydrofoils are not autostable and they, therefore, need an automatic control of lift in dependence on their immersion depth, in order to maintain the stability of the craft. In a heavy sea, control of immersion depth alone will not achieve a suflicient seaworthiness and performance, since, on the one hand, the foil will try to follow the contour of the waves when cruising against or transversely to the sea, a fact which will lead to great vertical accelerations and to great rolling and pitching angles, and, on the other hand, the foil with the seas astern, will be unfavorably influenced by the orbital motion, changing its angle of attack or incidence from time to time. When emerging from the wave crest, the foil will be heaved considerably, so that it could easily come too close to the water surface and thus suffer from aeration, while the lift will diminish in front of the wave crest, so that the hull may enter or strike the crests of the waves.

In the case of automatic control systems for maintaining the immersion depth which have been known heretofore, the fully submerged hydrofoil has been arranged to pivot about a transverse axis, or it has pivoted flaps along its trailing edge. The adjustment of the angle of attack of the foil or of the flap, respectively, is accomplished through control elements which are sensitive to immersion either mechanically, hydraulically, or electrically. Feelers gliding on the surface of the water are used as a mechanical control, which feelers are attached to long forwardly projecting arms. Such control arrangements, however, have the disadvantage that the feeler arms are bulky and are easily subject to damage. Electronic arrangements are also known, where pairs of electrodes have been placed along the foil struts, which by galvanic action will close a circuit whenever they are submerged. The number of the pairs of electrodes thus short-circuited equals an electric value in proportion to depth of immersion which by amplifiers and servo-motor effects deflection of the flaps. Recently, sonic sensors have been used to maintain the depth of immersion, which emit impulses or continuous signals toward the water surface, and, in the case of deviations of the desired height or flying altitude of the boat, bring about changes of the angle of incidence or attack of the foils, or of the flaps respectively, in a corrective direction via electric and hydraulic amplifiers. Such electronic installations, which usually need two sources of energy, are extremely complicated, expensive and subject to breakdowns, all of which detract from maintaining of stability.

This present invention will eliminate the disadvantages described, by admission of air to the sub-pressure or low pressure regions of the foils profile for the automatic operation of the foil flaps, the inflow of air being produced during travel by the sub-pressure generated by the water flow on the foil or strut profile, and being changed 3,145,457 Patented Aug. 25, 1964 with the help of a simple installation as a fuction of the immersion depth, so that additional sources of energy are not required, and a control system is provided which is distinguished by its surprising simplicity and dependability. In order to diminish the vertical accelerations the rolling and pitching angles and the influence of the orbital movement, the sub-pressure could also be influenced by still other control valves. The control system has no unwieldy elements and those elements lying in the water are sturdy and are largely immune against collision with driftwood.

The invention consists in connecting a piston or diaphragm in a cylinder means, in a known manner, with the hinged flap at the trailing edge of the foil in such a manner that deflection of the flap is produced whenever the piston or diaphragm is moved. An element producing sub-pressure conditions, which is equipped with suction apertures, and a control member which has air intake openings which are arrange vertically one over the other and which are located partially above and partly below the normal surface of the water, are connected with the inernal space in the cylinder means. With increasing foil immersion, the increasing sub-pressure will move the piston in the direction to cause a positive deflection of the flaps; that is to say, downwards. At the same time, an air regulating valve is provided between the control member and the cylinder means which valve can be influenced through any given instruments responsive to the movements of the boat in the seaway and which can also be connected with the steering system setting the course of the craft.

The element producing the sub-pressure conditions may be formed by the strut for the profiled foil, or by the upper surface of the foil, both of which have suction apertures. The air intake orifices, with which the cylinder means are connected, could also be located above the normal surface of the water, and the air intake openings located below the others and which preferably should overlap with those above, could be separately connected with air discharge openings on the upper side of the foil, in which case the flap would preferably have means for the limitation of the deflections in the negative direction.

In order to make the hydrofoil immune against the orbital movements within the waves of the sea, that is to say in order to obtain the deflections of the aps, which would balance out entirely or partially the fluctuations in lift as a result of the changes of the approach angle of the current, openings for sucking away of air which are located along the upper side of the foil near its leading edge, can be connected with that space of a second operating cylinder in which the under pressure will move the piston in the direction of a negative deflection of the flaps.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, illustrating several preferred embodiments thereof.

In the drawings:

FIGURE 1 is a front elevation view of hydrofoils and control elements of the present invention, on the hull of a boat which has been shown in cross section;

FIGURE 1a is a top plan view of the hydrofoils of FIGURE 1;

FIGURE 2 is a diagram of the control arrangement in section, wherein the sectional plane extends vertically and in cruising direction, which in this case is from the left to the right;

FIGURE 2a is a horizontal section view taken along the line Za-Za of FIGURE 2.;

FIGURE 3 is a diagram of a modified form control installation shown in section, similar to FIGURE 2;

FIGURE 4 is a further modification of the control arrangement shown in section;

FIGURE 5 shows the arrangement responding to the orbital movements in heavy seas in section, wherein the sectional plane runs the same way as in the preceding figures, the remaining elements of the control system being omitted;

FIGURE 6 shows a diagram of an arrangement responding to the inclination of the waves in section as in the preceding figures, and FIG. 7 is a vertical section view of a hydrofoil illustrating certain details of an exemplary flap construction.

The same elements in the various drawings are designated with the same numerals.

in FIGURES 1 and la the fully submerged hydrofoils 1 are shown, which at their trailing edges have hinged flaps 2 and which are attached to the hull 30 of a craft by means of struts 4. Instead of two divided foils, it would also be feasible to provide a continuous foil with divided starboard and port flaps. The most essential elements of the control system are the suction openings 8' at the upper side of the foils. The struts 4 serve as a control member which has lateral air intake openings and which, at the same time, as mentioned previously, serves as a connecting support between the hull 39 of the craft and the foil 1. A first cylinder 9 and a second cylinder 23 are provided, the latter for balancing of the orbital movements in the water. The other elements of the control system have been omitted in FIG- URE 1 for the sake of clarity.

The plan of the control system is shown in FIGURE 2. The flap is hinged at the trailing edge of the fully submerged hydrofoil 1 by means of a hinge joint 3. The flap 2 is linked with the piston 11 of the first cylinder 9 through a connecting rod 12. The foil 1 may have any desired profile.

The control member 4, formed by the strut, has a streamline-shaped profile which can be developed as a symmetrical circular segment profile, or preferably with a parabolic head and a blunt trailing edge (see FIGURE 2a). In the leading portion at the side of the control member 4, where during cruising a strong sub-pressure area will develop wherever the control member is submerged below the surface of the water, there are the air intake openings 6, which open intov ducts 5.

For the design according to FIGURE 2, the element producing the sub-pressure is formed by the lower part of the control member nearer the foil, along which element an increased sub-pressure occurs as. a result of the influence of the upper side of the foil.. There one or several suction openings 8 have been provided which open into the suction channel 7. While cruising, air will be sucked away from the channel 7 and from the space of the cylinder 9, connected with the channel 7 via channel 7a through the sub-pressure developing within the current, so that a low pressure will be produced in the cylinder space which will exert a downward force on the piston 11.

On the other hand and in. addition, the cylinder space 1% is also connected with the ducts 5 for the intake of air via the channels 7 and 7a and the valve 14 and the conduits 13. Anyone of these channels, of which one or any desired number may be provided, has a group of intake openings 6 arranged one above the other. The groups, as FIGURE 2 shows, are again arranged in the sequence of the channels, lying one above the other in such a manner that all of them together in a vertical direction form a continuous row of openings 6, which during cruising will lie partly above and partly below the surface of the water WL.

Air is sucked in through the openings 6 of the control member 4, located during cruising above the surface of the water and, as a result, the sub-pressure in the channels and in the cylinder space It is decreased in comparison to the sub-pressure existing along the suction openings 8. The openings lying underneath the surface of the water are closed against the entry of air by the waterflow causing a sub-pressure on these openings which approximately balances out the sub-pressure along the suction openings 8. The sub-pressure which at times appears in the cylinder space ltl, will depend on the relationship of the total cross-sectional area of the air intake openings to the constant cross-section area of the suction openings 8. Since the exposed cross-sectional area of air intake openings will change with the degree of submersion of the control member 4, the sub-pressure in the cylinder space it]: will also change as a function of the submersion. If the foil 1 with the control member 4 increases its immersion depth, then the cross-sectional area for the entry of air will diminish and the subpressure will increase until finally the same sub-pressure appears in the cylinder space 10 as on the suction openings 8, whenever all entry openings are submerged below the surface of the water. Conversely, the sub-pressure in cylinder space In will drop whenever the foil approaches the surface of the water, until finally when all openings which have been provided will be free, atmospheric pressure will almost have been reached. At the same time, one can gather from FIGURE 2 that the suction openings 8 and the entry openings 6 are connected with the internal space of the cylinder 9, in which the sub-pressure will move the piston 11 in the direction of the positive flap deflection, that is to say downwards.

The force which, as a consequence of sub-pressure, has been exerted against piston 11 will be transferred to flap 2 as a moment around the axis 3 through the rod system 12. Flap 2 on its part exerts a counter moment under the effect of the forces of flow. The flap-moment increases about linearly with the flap deflection. The moment created by the power of the piston and the counter acting flap-moment will balance each other out, so that to every magnitude of the sub-pressure in the space It), there corresponds a certain piston power and a certain flap deflection which again, and approximately linearly with the angle of deflection, will influence the lift of the foil. Since according to what has been said before, the sub-pressure is a function of the extent of immersion, the resulting flap deflection and the lift also are functions of the submersion of the foil.

From this arrangement the following function will result for the control:

If the foil leaves its normal position in cruising and if it increases its depth of immersion, an increase in lift will be caused through a positive flap deflection which directs the foil back to its normal submerged depth. Conversely, an approach to the surface of the water is corrected with a decrease of lift (negative flap deflection), so that therefore the stability of the craft is insured at a correct selection of the control values.

The process of control is largely independent of the speed, since both the sub-pressure alongside the suction openings 8 as well as the flap moment are a function of the speed, so that the condition of theequilibrium between the piston power and the flap moment will not be dis- 'turbed in case of changes in speed.

For the sake of understanding the function of the control it must also be mentioned that all hollow spaces, which during cruising are ventilated, will be filled with water when the craft is at a standstill. As soon as the craft begins to cruise, sub-pressure which will suck the spaces empty of air will develop along the suction openings 8 as well as alongside the air intake openings 6. The experiments have shown that this process requires only a few seconds. During cruising the sub-pressure always will remain alongside all openings, so that only at times will very small quantities of water enter through the openings lying directly at the surface of the water where an almost atmospheric pressure exists. These small quantities of water however do not impair the control.

FIGURE 2 shows that the air quantity regulating valve 14 has been switched into the connecting conduits 13 and 7 leading from the front air intake ducts 5 to the rear suction channel 7. This valve has the purpose of controlling additionally the quantity of air intake in order, thus, to influence the pressure in the cylinder 9 and the deflection of the flap 2. The quantity of air entering into this system, and the sub-pressure which will appear as a result, are therefore determined by the superimposed commands of the control member 4 and of the air quantity regulating valve 14.

In the example given in FIGURE 2 the valve 14 has been developed as a sliding valve member into which open the air intake ducts 5 of the control member in such a sequence that the mouth of the flow duct, together with the uppermost group of holes, will be closest to the valve member 15 and the rearmost ducts, with the lowest group of holes, will be the farthest removed from the valve member. The valve member 15 in its middle position as drawn, will open up the passage from the air intake ducts 5 to the suction channel 7. As it is moved in one direction (to left), it will choke off and close the ducts 5, that is to say first the uppermost group of holes, then the middle group and finally the lowest group, while the valve member will additionally admit air through the intake slit 17 whenever it is operated in the other direction (to the right).

The plurality of ducts 5, with groups of intake openings lying above one another, have been provided in order to achieve an even throttling of the quantity of air entering through valve 14. It is easy to understand that when providing only one single channel into which all entry holes open, and whose cross-sectional area of entry along the valve must naturally be equal to the total crosssectional area of all entry holes, a throttling of the quantity of air will occur only whenever the cross-sectional area of the throttling is smaller than the total crosssectional area of all intake openings which are above the surface of the water. Therefore, whenever the craft cruises, for example at the level indicated by the line WL, where approximately half of the openings 6 will be opened, then half the path of the valve member will exert no effect and throttling will start only after that. The sub-division of the three channels according to FIGURE 2 will result in a considerably more even throttling effect. The uppermost group of holes of the foremost channel during cruising will lie above the surface of the water, completely out of the water, so that here throttling will begin immediately through the valve member 15, which will have as a consequence a decrease in the submersion of the foil so that the middle group of holes of the middle channel too will be completely emerged whenever the valve member has completely closed the foremost opening along the valve. If now the valve member begins to close the entry of the middle channel, then here too a throttling of the quantity of air entering through the middle group of holes would occur immediately. The valve 14, therefore, will operate the more uniformly the more air intake channels have been provided.

Without deviating from the system of valve control, the valve can also be developed as a rotary slide valve. Also, in order to achieve a more even supply of additional air, it will be possible to provide air intake channels in the control member 4 in the same manner as prescribed and instead of the free entry at point 17 said air intake channels open, into the air quantity control valve 14, one behind the other, instead of the intake slit 17. Whenever the valve member 15 is moved to the right, it will then open up the intakes for the additional air beginning with the uppermost group of holes to the lowest group of holes.

In order to increase the sea worthiness of the craft controlled by the installation as described, to diminish the rolling and pitching and the vertical accelerations, the air quantity control valve 14 can be automatically regulated through control devices, which react to the movements of the craft at sea, such as gyroscopes, accelerometers and devices which will measure the submersion speed of the control member.

Such devices have been described in my earlier US. patent application S.N. 67,189, now Patent No. 3,117,546. In FIGURES 2 and 4 these devices have been indicated altogether by the number 20.

With the simultaneous application of several control devices for the control of a foil or a part of the foil, such devices may each operate a separate valve 14 and which together connected in parallel, are connected with the operating cylinder of one foil. It would also be possible that all devices would operate only one or perhaps two valves by means of the known mechanical or hydraulic super positions. It must be stressed as an advantage of the control system, that the forces for the operation of the air quantity control valve are extraordinarily small, so that the control devices can be connected directly with the valve without interposing any amplifiers, a fact which provides an essential simplification and increase in the reliability of the operation. Furthermore, through the described super position of the control caused by the control devices, with the control of the submerged depth, there is this further advantage, that in case the control devices fail (which devices in this case may be arranged in such a way that they will return to their middle position), the stability will still be maintained just the same through the control member 4. The craft with fully submerged, slight- 1y dihedral foils bank outward when cruising curves because of the centrifugal force, and, through the lateral resistance of the struts occurring when the sliding movement is introduced, a pair of forces will develop which banks outward. In order to counteract this moment and in order to bring about an inward banking in the curve, through an oppositely directed operation of the air quantity control valves of the starboard and port foil (see FIGURE 1) respectively of the two halves of the foils, additional air will be brought in at the foil which is located on the inside of the curve, while the supply of air to the operating cylinder of the foil located on the outside of the curve is being throttled. The operation of the valves takes place corresponding to US. patent application SN. 67,189, now Patent No. 3,117,546 in a guided manner, through a cam plate with spiral passages which is coupled with a directional control (steering wheel), a driving means attached to a lever meshing or operatively connecting with said cam plate. The two connecting elements, one of which is shown at 18 in FIGURE 2, lead towards the housing of the starboard and port air quantity control valve 14 which are movable in the bearings 19, said housing being arranged in such a manner that they will cause opposite control effects at movement in the same direc tion. Through a corresponding form of the spiral at the cam plate, every desired course of the transmission ratio between the turn of the steering wheel and the path of the valve can be achieved. In order to make possible the movement of the valve housings, the conduits 13 are made of flexible hose. The change of quantity of air which is brought about by the valve 14 is, therefore, brought forth both by the operation of the valve member 15, through the automatic control devices 20, as well as through the movement of its housing on the part of the course steering operation. The control arriving from both sides are superposed one over the other.

The air quantity control valve 14 of each foil, or of each half of each foil respectively, will preferably be located inside the hull of the craft as shown in FIGURE 1, where it is protected against entry of any water or dust. Correspondingly all automatic control devices which operate the valve member of the valve 14 can also be located protected inside the hull of the boat. In FIGURE 1 the operating cylinder 9 has also been located inside the hull of the boat with the help of a rocker arm 29, which takes 7 care of transferring the movement from the cylinder to the rod system 12.

In another exemplary form illustrated in FIGURE 3, the foil 1 forms the member creating the sub-pressure, said foil having suction openings 8' on the upper side of the foil. The openings. 8 are located on the rear part of the foil profile inFIGURE 3, and they open into a channel 28, which runs obliquely through the foil and which in turn is connectedwith valve 14.through the suction channel 7. The suction openings 8', according to FIGURE 1a may extend across only a part of the span width of the foil (left side of the figure), or they may extend across the whole span width corresponding to the right side of the figure. Since the lift of foils, whose upper side has air exit openings corresponding to US. patent application SerialNo. 67,189, can be regulated by changing the quantity of air supplied through these exit openings, the lift of the foil according to FIGURE 3 is not only influenced through flap 2 but also through the quantity of air emerging. from these suction openings 8'. Such influencing extends in the case of the right hand foil of FIGURE 1a, across the whole foil, and in the case of the left hand one, only across a part of said foil. The control process is also as follows:

Whenthe: quantity of. air flowing to the air exit openings 8" is increased through the control member or the valve 14; the lift of the foilwill decrease, but at the same time thepressure in the channels and in the cylinder space will decrease too. The deflection of the fiap will decrease through this decrease of pressure in the negative sense, so that the decreased lift of the foil will be brought about by both: the. change in the quantity of air supplied to the upper side of thefoil as well as'through the swinging of the flap.f If thevolume of air flowing to the air exit openings 8' is throttled down, then conversely the lift of the foil, first of all in consequence of the smaller quantity of air emerging and secondly in consequence of the positive deflectionof the flap, will be increased.

The FIGURE 3 shows another design of the cylinder 9 which. in this case, has been developed in the preferred shape as a roller diaphr-agmacylinder and has complete water tightness with very low frictional forces, factors which for. the response sensibility of the device would be of significance. The transfer ofv the piston movement to the flap inFIGURE3 takes place by means of a rod'which r-uns protected inside of'the strut 4. The rod can be made with a very small quantity of material, a factor which is favorablefor achieving a great reaction speed of the control system.

In the practical example shown in FIGURE 4, the member producing the sub-pressure, as in FIGURE 2, is formed by the lower part of the strut where the suction openings 8' are located. The suction side of the foil, however, also has air suction openings 8' as in FIGURE 3, whereby the arrangement is made in such a manner that the; influencing of the lift takes place, not simultaneously through: the flap and the supply of air, but in sequence. For this purpose the air entry openings 6 of the duct 5 with which the operating cylinder 9 is connected through channel 7", are placed above the normal surface of the water WL, while theair entry openings 6' of the duct 5', which have been arranged to lie below the top ones, are connected through a, separate conduit 7 with the air exit openings 8' on the upper side of the foil. The upper air entry openings 6 for the operating cylinder 9 preferably overlap in, their position as to. height, with the air entry openings 6' for the upper side of the foil. The flap is preferably provided with a stop in order to limit the deflections in the negative direction, for example as in FIGURE 4, where the piston 11 joins the upper cylinder cover whenever the flap tands in the middle position as illustrated.

Just as in the preceding examples, one air quantity controlval've 14 or 1.4, corresponding to the tWo separate circuits, has been inserted in the connecting conduit running from the entry ducts 5 or 5, respectively, to the 1 a negative flap deflection.

8 suction channels 7 or '7', respectively. The two valves are connected with one another to co-ordinate their motion and they are operated together through the rod 16. They can, as shown in FIGURE 4, be arranged in such a manner that the entry of air to the two circuits is throttled down or enlarged simultaneously or else in such a manner that the throttling down of air moving to the foil takes place first before a deflection of the flap will be brought about through throttling down of air to the operating cylinders. For this purpose the mouth of the duct 5 in the left valve 14 must he moved to the left and, at the same time, a sufiiciently large path must be allowed for both valves. Also, the valves may be arranged in such a manner that the additional air will be first supplied to the operational cylinder, that is to say, first the flap is put in its zero position, before any additional air can emerge along the foil. In this case it will be necessary to move the air entry slit 17 of the right valve 1 toward the right and the two valves must be given a correspondingly greater path.

in this design the medium and the lower lift areas are controlled through the supply of air along the foil, While the high lift coetficients will be achieved through the flap deflections after ventilation of the foil has been closed down. T he described overlapping of the rows of holes serves the purpose of bridging the response time of the.

flap in order to obtain at the same time, with the submersion and closing down of the uppermost opening for the air supply to the upper part of the foil, a flap reaction and with it a steady course of the increase of lift.

In addition, FIGURE 4 shows the damper 33 of a known design, which serves. preventing or restraining the swings of the flap. The piston 34 is connected with the piston 11 of the operating cylinder. In a preferred design, the damper has an overflow channel 35 with a check valve 36, which will permit free passage of the liquid when the piston moves up, which however will close down in the direction of movement of the increasing positive flap deflections, so that the damping will occur. Through this arrangement a quick reaction of the flap will be guaranteed whenever the foil approaches the surface of the water, which fact brings with itself the danger of a foil aeration.

In FIGURE 5 the second operating cylinder 23 for v the flaps 2' is visible, whose space 24 is connected with the air suction openings 27 through the line 26 which is 10-- cated. on the upper side of the foil in the vicinity of the leading edge. The space 24 is located onthat side of the piston at which the sub-pressure acts in the direction or" The piston 25 has a smaller diameter than the main piston 11, so that during normal cruising conditions a constant force acts against the positive direction of the main piston. The piston 25 at great emersion, when only the lowest or no air entry opening 6 of the control member 4 will be located below the surface of the water, and the sub-pressure upon the piston 11 becomes small, will force the flap to negative deflections.

The sub-pressure at the leading edge of the foil profile Where the suction openings 27 are located, changes considerably with the direction of the flow against the profile and, to be sure, increases with an increase in the angle of incidence. If, therefore, in the orbital movement of the waves a lift increase of the foil occurs as a result of the enlargement of the angle of incidence, then at the same time the sub-pressure on the piston 25 will increase and the flap is moved in an equalizing sense in the direction of negative deflections. If, conversely, the orbital movement decreasesthe angle. of incidence and lift, then the force acting upon the piston 25 will also'be decreased and the main piston will increase the deflection of flap 2.

In order todecrease the speed of response of the control system upon the changes in immersion of the control member 4, which from time to time is desirable in order to suppress a reaction to short waves, the channel 7 or the cylinder space, respectively, are connected with an air space 21 which is changeable as to volume (FIGURE 2). In the example, the change of volume is accomplished through movement of the piston 22. Instead of the smooth change, the increase of volume can also take place step by step by connecting one or several unvariable spaces, perhaps of varied size.

It is understandable that with the growing volume of air between the suction elements and the operating cylinder an increased dampening of the variations of pressure in the sea occurs and that the device permits an adaptation to each period of encountering specific wave crests.

In FIGURE 6 a design of the control arrangement has been shown which responds to the slope of the waves and, thus, acts in the way of a pre-control means. In this case, an additional auxiliary control member 4a with the air entry openings do has been attached at a distance behind the control member 4. The auxiliary control member 4a is connected with the second operating cylinder 23 through a conduit, the piston 25 of said operating cylinder responding to changes of the orbital angle. Under the effect of the control member 4a, the reaction of the piston 25 remains unaffected by changes of the angle of incidence against the member 4a, however, the control system responds also to inclinations of the water surface as follows:

In the case of changes in immersion with a parallel keel, the control system acts in the same sense as described before because the changes in force which occur along the main piston 11 outweigh those of the auxiliary piston 25. If the boat dips into a wave with an inclination of WLl, or if it will suffer a heavy trim by the bow, then the sub-pressure on the main piston will rise in consequence of the decrease of the area of air entry in the control member 4, while the counter force exerted by the auxiliary piston 25 will drop in consequence of the emersion of the entry opening 6a of the control member do, so that a great positive flap deflection will occur along foil 1. It is easy to understand that this deflection is essentially greater than will be reached in the case of a parallel increase of immersion, because in the latter case the counter force upon the piston 25 increases. The deflection angle will become the larger the greater the inclination of the waves. If, for example, in the wake when cruising through the crest of a wave, a diminishment of the angle of incidence occurs on the basis of the orbital movement, then the sub-pressure exisiting along the suction openings 27 will drop, which has as a consequence a further decrease of the force exerted on piston 25 and thus a further enlargement of the flap deflection. On the surface of the water WLZ, a negative deflection of the flap will take place which assumes even greater negative values, in correspondence with what has been said before, if for example an enlarged angle of incidence will occur along the front of the wave of following sea. It is self-evident that a third operating cylinder, for the control of the inclination of the waves with the suction point 27a of its own, can be provided instead of the cylinder 23 responding to the orbital movement. Such an additional suction point could be provided, for example, along the lower end of the auxiliary control member 4a or along the streamlined body 31, which is located at the end of said auxiliary member.

Subsequently some more partical design of the parts of steering arrangement will be described:

The air entry openings 6 can be circular or slit-shaped and they can be either on one side or, for the sake of greater security, on both sides of the strut, so that if the air should perhaps rush in, only half the submerged openings will be disturbed at any particular time on one side of the support.

The submersion characteristics of the hydrofoil (the course of the increase of the flap-angle and of the lift during submersion) is determined by the vertical distribution of the sectional area of the air entry across the control member, therefore, by the size and the distance from one another of the entry openings 6. This characteristic can be changed in order to adapt the behavior of the craft to the prevailing sea, whenever the control member for this purpose, has two or several channels with rows of variable openings, which according to choice, can be connected through a valve with the cylinder space. If the channel in action is equipped with a series of large distances of the openings from one another then the lift will only change little with the depth of submersion (small stability for cruising in short waves) whereas with smaller distances, a greater stability and a stronger adherence of the foil to the contour of the wave will develop.

Especially when using roller-membrzine-cylinders, whose membranes are exposed to possible damage, it would be possible-in order to increase the safety of the control arrangement-40 use two or even several operating cylinders into whose supply-conduits known by-pass valves have been built in, which would cut off the damage cylinder, whenever sub-pressure will drop in said cylinder as a result of the entry of air, and through this a difference in pressure between the cylinders would appear.

Since the sub-pressure along the upper side of the foil and along the struts is relatively small, and naturally at the maximum could only reach the complete vacuum, large diameters for the operating cylinders will result. They can be decreased through switching in of pressure transformers of a known kind between the element producing the sub-pressure and the operating cylinder. Through these devices, the sub-pressure carried to them, increased many times into super pressure (positive pressure), will be carried further to the operating cylinder 9. Correspending to the pressure reversal the pressure conduits toward the appropriate opposite sides of the piston are led as in FIGURE 2. The super pressure in the device will change proportionally to the sub-pressure supply. The pressure transformers must be fed compressed air which is produced by compressors, the disadvantage of the pressure reduction consisting in this.

Another method to attain a smaller diameter for the operating cylinders consists in the diminishment of the flap moment through the design of the flap as shown in FIGURE 7. The pivot axes 3 of the flap 2, in this instance, are removed from the leading edge of the flap so far, that the part 32 which is located in front of the axis, serves as an unloading surface for the reduction of the flap moment. In other words the axis 3 has been moved up closely to the center of lift of the flap. When swinging the flap, the front part 32 carries out the movement as compared to the fixed profile of the foil. The leading edge of the flap is narrower than the back wall of the fixed profile of the foil, so that in the middle position of the flap (solid line) a step will develop above and below. However at the greatest positive deflection, the upper part of the flap is alined with the upper part of the profile (dotted line) and at the greatest negative deflection, the lower side of the profile is alined with the underside of the flap. If the air suction openings 8 are provided directed rearwardly into the upper step, then this will result in a favorable arrangement, where the suction openings at negative deflection angles at which great quantities of air will exit, are completely opened but which, with increasing positive deflection and a decreasing quantity of air, will close down more and more, finally completely closing at the greatest positive deflection where no more air will escape. The suction side contour of the profile then will have no more non-uniformity.

In the case of water craft, where the control system according to the invention is being applied, bow foils only, which are attached to the forepart of a ship, for example, corresponding to FIG. 1, may be provided with the control system, while the stern foil may be rigid and have no flap, and remain uncontrolled. This stern foil will maintain its submerged depth automatically through the fact that every change in submerged depth which it will experience is associated with rotation of the craft about the front foils which are kept constant in their submerged depth, a fact Which has as a consequence a change of the angle of attack in a recovery sense. In order to be more effective in decreasing the pitching vibrations, the stern foil can be provided with a flap whose operating cylinder however will only be influenced by the instruments responding to inclinations and accelerations, that is to say no control member for the stern foil has been provided and the entry of air is solely controlled by an air quantity regulating valve operated by the instruments.

Naturally this control system can also be used in the case of partially emerging foils of smaller dynamic stability.

While several modifications have been illustrated and described, it will be apparent that other variations may be made within the spirit of the invention, and it is desired therefore, that only such limitations be placed on the invention as are imposed by the prior art and set forth in the appended claims.

What is claimed is:

1. Apparatus for automatically controlling the immersion depth of hydrofoils supporting a hull of a Watercraft and having at least one fiap hinged to the trailing edge or the hydrofoil, comprising cylinder means having a piston therein, linkage means interconnecting said flap with said piston for pivoting said flap about a hinge axis therefor responsive to pressure changes in said cylinder means, sub-pressure generating means communicating with said cylinder means for subjecting said piston to sub-pressure conditions produced thereby to effect movement of the piston in a positive flap deflection direction responsive to increasing sub-pressure, control means for modifying said sub-pressure conditions applied to said cylinder means including air ducts connected with said cylinder means and having air intake openings disposed to occupy positions above and below the normal waterline when the watercraft is in motion for changing said sub-pressure conditions applied to said piston in relation to changes in the level of the air intake means relative to the water surface, and an air regulator valve between said control means and said cylinder means for variably restricting communication of air and admitting additional air from said control means to said cylinder means.

2. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, wherein a supporting strut is provided for said hydrofoil ex tending from the watercraft to the hydrofoil, and wherein said sub-pressure generating means is formed in said strut by generally vertically extended air channel means projecting downwardly to a location adjacent to the hydrofoil, said air channel means having suction openings in a lower region thereof, which remain constantly submerged, opening through surface portions of the strut where suction conditions are produced by movement of the strut through the water.

3. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, wherein said sub-pressure generating means. is formed in the hydrofoil by air channel means therein having suction openings along. the upper side of portions of the hydrofoil where suction conditions are produced by the hydrofoil configuration during movement of the same through the water.

4. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, wherein said air intake openings of said control means connected with said cylinder means lie above normal waterline and air intake openings of said control means which lie below the normal waterline separately communicate with means along the upper side of the hydrofoil having suction openings and stop means for said piston limiting the deflection of the flap in a negative direction.

5. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, where in said control means comprises a plurality of separate air ducts, each having a group of air intake openings therein located in vertical array, said ducts being spaced along the direction of travel of the watercraft, and the air intake opening region thereof being located at different levels.

6. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, wherein said control means comprises a plurality of separate air ducts, each having a group of air intake openings therein located in vertical array, said. ducts being spaced along the direction of travel of the watercraft, and the air intake opening regions thereof being located at different levels, said sub-pressure generating means including a vertical air suction channel terminating in suction openings located continuously below the water line in suction pressure zones created during movement of the watercraft, communicating duct means common to all of said ducts of said control means extending from the forwardmost of said ducts to the rearmost of said ducts and said air suction channel, and said regulating valve having a valve member in said communicating duct for terminating communication with said cylinder means progressively from the foremost duct to the rearmost duct and for admitting additional air to said cylinder eans.

7. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, wherein a supporting strut is provided for said hydrofoil extending from the watercraft, said control means being formed of a plurality of generally parallel, vertically elongated air ducts projecting downwardly in said strut to locations spaced selected distances above the hydrofoils in the lower ends thereof, the air intake openings in said air ducts being located at progressively lower levels progressing from the front to the rear of said strut and the air intake openings in adjacent air ducts overlapping each other a selected extent, an elongated manifold duct communicating with the upper ends of each air duct and with said cylinder means, and said air regulating valve having a valve member movable in two directions axially of said manifold in one direction to progressively close off the upper ends of said air ducts from communicating with said cylinder means in a progressing manner from the forwardmost air duct to the rearmost air duct and in the other direction to admit additional air to said cylinder means.

8. In apparatus for controlling the immersion depth of hydrofoils, the combination in claim 6, wherein the air intake openings in said ducts are at progressively lower levels progressing from the forwardmost duct to the rearmost duct.

9. In apparatus for controlling the immersion depth of hydrofoils, the combination in claim 1, wherein a damper cylinder having a piston and an overflow duct from one side of the piston to the other is coupled to said cylinder means, said overflow duct having a check valve therein operative to close the overflow duct opening upon movement of the piston of said cylinder means in the direction of increasing positive flap deflection.

10. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, wherein a second cylinder having a reciprocative piston is in communication with the first mentioned cylinder means, said second cylinder and piston having a relatively smaller diameter than said first-mentioned cylinder means, air duct means having air suction openings located on the upper side of the hydrofoil adjacent to the leading edge thereof communicating with said second cylinder to apply sub-pressure to the piston thereof in a senset'o cause the piston of said first-mentioned cylinder means to move in the direction of negative flap deflection.

11. In apparatus for controlling the immersion depth of hydrofoils, the combination recited in claim 1, Wherein a second cylinder having a reciprocative piston is in communication with the first mentioned cylinder means, said second cylinder and piston having a relatively smaller diameter than said first-mentioned cylinder means, air duct means having air suction openings located on the upper side of the hydrofoil adjacent to the leading edge thereof communicating with said second cylinder to apply sub-pressure to the piston thereof in a sense to cause the piston of said firstmentioned cylinder means to move in the direction of negative flap deflection and a second References Cited in the file of this patent UNITED STATES PATENTS 2,709,979 Bush et al. June 7, 1955 FOREIGN PATENTS 549,266 Italy Oct. 9, 1956

Claims

1. APPARATUS FOR AUTOMATICALLY CONTROLLING THE IMMERSION DEPTH OF HYDROFOILS SUPPORTING A HULL OF A WATERCRAFT AND HAVING AT LEAST ONE FLAP HINGED TO THE TRAILING EDGE OF THE HYDROFOIL, COMPRISING CYLINDER MEANS HAVING A PISTON THEREIN, LINKAGE MEANS INTERCONNECTING SAID FLAP WITH SAID PISTON FOR PIVOTING SAID FLAP ABOUT A HINGE AXIS THEREFOR RESPONSIVE TO PRESSURE CHANGES IN SAID CYLINDER MEANS, SUB-PRESSURE GENERATING MEANS COMMUNICATING WITH SAID CYLINDER MEANS FOR SUBJECTING SAID PISTON TO SUB-PRESSURE CONDITIONS PRODUCED THEREBY TO EFFECT MOVEMENT OF THE PISTON IN A POSITIVE FLAP DEFLECTION DIRECTION RESPONSIVE TO INCREASING SUB-PRESSURE, CONTROL MEANS FOR MODIFYING SAID SUB-PRESSURE CONDITIONS APPLIED TO SAID CYLINDER MEANS INCLUDING AIR DUCTS CONNECTED WITH SAID CYLINDER MEANS AND HAVING AIR INTAKE OPENINGS DISPOSED TO OCCUPY POSITIONS ABOVE AND BELOW THE NORMAL WATERLINE WHEN THE WATERCRAFT IS IN MOTION FOR CHANGING SAID SUB-PRESSURE CONDITIONS APPLIED TO SAID PISTON IN RELATION TO CHANGES IN THE LEVEL OF THE AIR INTAKE MEANS RELATIVE TO THE WATER SURFACE, AND AN AIR REGULATOR VALVE BETWEEN SAID CONTROL MEANS AND SAID CYLINDER MEANS FOR VARIABLY RESTRICTING COMMUNICATION OF AIR AND ADMITTING ADDITIONAL AIR FROM SAID CONTROL MEANS TO SAID CYLINDER MEANS.