US3688724A

US3688724A - Ground-effect machines

Info

Publication number: US3688724A
Application number: US44039A
Authority: US
Inventors: Jean Henri Bertin
Original assignee: Bertin et Cie SA
Current assignee: Bertin Technologies SAS
Priority date: 1969-06-10
Filing date: 1970-06-08
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05

Abstract

This invention is for improvements in or relating to groundeffect machines which are borne by land or water with the interposition of a number of cushions containing air or some other pressure fluid.

Description

United States Patent Bertin Sept. 5, 1972 [54] GROUND-EFFECT MACHINES [72] Inventor: Jean Henri Bertin, Neuilly-sur- [56] References Cited Seme, France UNITED STATES PATENTS 1 Assisnw Berlin & (fie, Plaisir, France 3,384,198 5/1968 Jones et al. ..1 14/67 A 22] Fil d: June 8, 1970 3,371,738 3/1968 Bertin ..l80/121 X PP 44,039 Primary Examiner-Andrew H. Farrell Attorney-Brufsky, Staas, Breiner and Halsey [30] Foreign Application Priority Data 57] ABSTRACT j g lg Stance This invention is for improvements in or relating to u e rance ground-effect machines which are borne by land or water with the interposition of a number of cushions lll. containing air or some other pressure fluid. v

Field of Search"; ..l14/67 A; 180/121 22 Claims, 21 Drawing Figures PATENTEDSEP s 1912 sum 2 or 5 PATENTEDSEP 5'912 SHEEI 3 0F 5 PATENTEDSEP 5|972 v I snw u 0F 5 GROUND-EFFECT MACHINES SUMMARY OF INVENTION It is an object of this invention to enable the various cushions to be supplied independently from a common pressure fluid source, a feature which, of course, helps stability and greatly reduces the space taken up by the supply facilities.

Another object of the invention is to provide a novel construction for a high tonnage sea-ship.

The invention accordingly comprises the combination of a substantially flat chamber which extends above the cushion-bounding curtains or walls or skirts or the like and which forms a header for supplying a number of cushions in parallel from a common pressure fluid source and which communicates with the cushions to be supplied by way of flow-limiting venturis, the same being disposed flat in the chamber.

The invention comprises also the arrangement, below the load bearing platform of the machine, of at least three projecting walls which extend parallel to the machine longitudinal axis and form at least two parallel channels, wherein the flexible skirts bounding the fluid cushions are arranged in files as near one another as possible.

This invention is for improvements in or relating to ground-effect machines which are borne by land or water with the interposition of a number of cushions containing air or some other pressure fluid.

It is an object of this invention to enable the various cushions to be supplied independently from a common pressure fluid source, a feature which, of course, helps stability and greatly reduces the space taken up by the supply facilities.

The invention accordingly comprises the combination of a substantially flat chamber which extends above the cushion-bounding curtains or walls or skirts or the like and which forms a header for supplying a number of cushions in parallel from a common pressure fluid source and which communicates with the cushions to be supplied by way of flow-limiting venturis, the same being disposed flat in the chamber. Preferably, the venturis are two-dimensional with a flat cross-section. Preferably too, the venturis are placed flat up against one of the chamber walls, such wall possibly forming one of the venturi walls.

The flat chamber contrived like a double bottom below the vehicle platform and supplying the air cushion chambers via venturis can be made rigid, and thus suitable for forming the load-bearing frame of the vehicle, if the walls of the flat chamber are interconnected at least in some places by tubes made of a rigid and strong substance such as steel. These tubes, which are closed on themselves and filled with gas or air, can be large enough to enable the vehicle to float and help to make the vehicle amphibious.

Advantageously, the tubes form the side wall of the flat chamber, interconnecting the two walls at their periphery. One or more tubes can also be disposed between the walls of the flat chamber so as to leave the air cushion supply paths therein unobstructed.

The invention also relates to the construction of a large ground-effect machine, more particularly a machine for long-distance sea travel, such as an oceangoing ground-effect machine. Of course, a machine of this kind needs a large surface to receive the air cushion pressure and thus produce the lift; unfortunately, when the transverse dimensions of skirts of this kind are increased, the forces withstood by the skirts also increase, and so large skirts must have thick and dense walls, a disadvantageous factor.

According to a feature of the invention, a large number of skirts are used which are small in relation to the machine dimensions but which are devised and distributed to make maximum use of the machine bottom surface and which are confined in at least two passages contrived below the machine by at least three walls which extend parallel to the machine longitudinal axis.

Preferably, the skirts are of the kind comprising a top polygonally shaped securing edge, for instance, in shape substantially square or oblong so as to contain the maximum available surface, on the ceiling surface of each of the corridors whereas the free bottom edge of the skirts is in shape substantially circular. These features combine very advantageously with the flat cushion supply capacity to reduce size and improve the efiiciency of the independent supply for a large number of air cushions.

The machine can also comprise means for bounding the longitudinal channels or passages at the front and/or rear so that an extra pressure fluid cushion supplied at least by leaks from the other cushions can be formed in each such channel or passage. For instance, the confining means can be formed by those of the flexible skirts which are at the front and/or rear of the machine in the longitudinal channels or passages, the walls of such skirts being disposed very near and/or in contact with such longitudinal walls. Of course, either the other skirts can be disposed similarly or a larger gap can be left between such other skirts and the passage walls.

A machine thus devised is very stable yet can be of very large dimensions and very great weight.

The following description, taken together with the accompanying exemplary non-limitative drawings, will show clearly how the invention can be carried into effect.

In the drawings:

FIG. 1 is a view in vertical projection and in section of a machine for travelling over water and comprising an embodiment of the invention;

FIG. 2 is a view in horizontal projection and in section on the line IIII of FIG. 1, the line Il of FIG. 2 denoting the trace of the section plane of FIG. 1:

FIG. 3 is a crosssection on the line III-III of FIG. 1;

FIG. 4 is a view to an enlarged scale, and in the same plane as FIG. 1, of an embodiment of a flat venturi;

FIG. 5 is a view corresponding to FIG. 4 but in horizontal projection;

FIGS. 6, 7 and 8 are sectioned views of other forms of venturi;

FIG. 9 is a view in horizontal projection of a venturi of the kind shown in FIG. 8;

FIG. 10 is a view in cross-section on the line X-X of FIG. 9;

FIGS. 11 and 12 are views in section of another form of venturi in two different operating positions;

FIG. 13 is an end view looking in the direction of an arrow F in FIG. 11;

FIG. 14 is a view in side elevation of an overland machine, but which can also float, embodied as a mixed truck;

FIG. is a cross-section on the line XV-XV of FIG. 14, the view being in the direction of the arrows in FIG. 14;

FIG. 16 is a plan view in horizontal section on the line XVI-XVI of FIG. 15;

FIG. 17 is a sectioned view in elevation on the line XVII-XVII of FIG. 19 of a ground-effect machine ac cording to the invention devised as an ocean-going craft;

FIG. 18 is a view in section on the line XVIII-XVIII of FIG. 17;

FIG. 19 is a view in section on the line XIXXIX of FIG. 18; 4

FIG. is a partial viewto an enlarged scale and in section on the line XX-XX of FIG. 19, showing constructional details of the flexible skirts at the front of the machine, and

FIG. 21 is a partial view in XXI of FIG. 20.

FIGS. 1-3 show a ground-effect machine assumed, in the particular example concerned, to move above the surface of water. The machine has a load-carrying platform 1, below the machine are facilities for producing air cushions to lift the machine above the water 2. The machine has, an appropriate propulsion facility which, in order to simplify the drawings, is not shown and which can be one or more air screws, a turbojet or the like. In the example shown the air cushions are of the plenum-chamber" kind and are each bounded by a flexible wall or skirt 3. The example has two rows of skirts disposed symmetrically one on each side of the vertical longitudinal plane of symmetry of the machine, such plane being parallel to the plane of FIG. 1. Each row comprises four skirts i.e., four cushions.

As the drawings also show, the skirt system has around it a skirt 4 which substantially follows the periphery of platform 1 and produces around the skirts 3 an extra air cushion energized by leakages from the air cushions bounded by the skirts 3; a separate supply may also be provided for the extra air cushion.

' To ensure that the skirt 4 is firm enough, its wall is formed, as can be seen in FIG. 2, in two parts each in shape resembling a large-radius circle arc, the arcs meeting at places 4a. This'feature provided considerable lift with improved efficiency, pitch stabilization, because of the lengthwise subdivision of the air cushions bounded by the skirts 3, and roll stabilization, because of the two rows of skirts 3 disposed one on either side of the longitudinal axis, providedthat the skirts 3 are supplied with compressed air independently of one another so that an excessive leakage from any one skirt at any one instant of time, for instance, because such skirt is between two waves, is not transmitted to the other skirts. The skirt supply facility shown enables the supplies to the various cushions to be made independent in this way and has other advantages. The facility comprises a flat chamber or capacity 6 which is disposed below the platform 1 and formed between the platform wall and a parallel wall 7 to which the skirts 3,4 are secured. Thechamber or capacity 6, which is rendered sealing-tight in appropriate manner except for the passages extending the skirts 3 and 4 through the wall 7, forms a sort of double bottom or flat header which is connected through a line 8 to a compressed air source comprising, in the example shown, two parallel operating air compressors 9 section on the line XXI- each disposed in a fairing 10 open to the front, so that as the machine moves air enters the fairings with the dynamic pressure due to the movement of the machine.

Each passage through which the skirts 3, 4 are supplied from the header 6 comprises a venturi tube i.e., and as can be seen in FIG. 4, a tube having a throat 11 following a convergent inlet part 12 which opens into the header 6 at a place 13. The venturis are two-dimensional i.e., flat in shape and are disposed horizontally in the double bottom 6 so that the axis of each venturi is substantially parallel to the walls 1, 7. This feature enables the venturis to be of adequate axial length, a dimension which is of course fairly important for satisfactory operation of a venturi tube if a large gap cannot be left between the walls 1 and 7. The space taken up by machinery is therefore reduced; also, the platform 1 and the center of gravity can be lowered. The arrows in FIG. 4 show the path taken by the air which enters the inlet orifice 13 of each venturi, then goes through the convergent part 12, throat 11 and divergent part 14 to reach the corresponding skirt through aperture 15 in wall 7. A blade lattice 16 helps to improve the-efficiency of the bend at the venturi exit;

FIGS. 4 and 5 also show an embodiment of a venturi formed by two parallel side plates or webs 17 which are secured to the wall 7 perpendicularly thereto by a cur vilinear cylindrically surfaced metal member 18 secured hermetically to the plates 17, the generatrices of the member 18 being perpendicular to the plates 17. Each venturi is therefore bounded by the plates 17, the member 18 and the wall 7. g I

FIGS. 1, 2 and 3 show the flat venturi a associated with each skirt 3 and four flat venturis b distributed over wall 7 between the skirts 3 to provide direct energization of skirt 4 in addition to the leakage air energization from skirts 3. The flat venturis can of course be embodied in many other ways.

With venturis designed so that the rate of flow at the throat in normal operation is slightly below or equal to the speed of sound, the flow through each venturi is limited automatically when the leakage flow from any skirt exceeds its nonnal operating value; this feature of course helps to make the skirts independent of one another.

Another way in which the flat venturis can be used to limit the rate of flow is for the venturi walls to be adapted to be moved relatively to one another to vary the constriction at the throat. A first embodiment of this kind is shown in FIG. 6 where the venturi comprises, between side members 17, two curvilinear

cylindrical walls

18, 18a articulated around stationary spindles 20. The two walls 18 can be moved towards and away from one another by being pivoted around the spindles 20 by actuators 21 which can be controlled by the pressure in the corresponding cushion. In a system of this kind, of course, the venturi exit orifice cannot be directly connected to the orifice l5 communicating with the skirt to be energized, and so in this case the walls 17 can co-operate with an extra fixed wall 22 rigidly secured to the walls 17 to form a closed box to which the venturi delivers and which communicates with the aperture 15.

In the variant shown in FIG. 7, variation of throat cross-section and therefore the rate of flow, is controlled by the negative pressure produced in the throat zone in the venturi. Such'negative pressure depends upon the rate of flow of the fluid, and the rate tends of course to increase with the leakage from the skirt energized. The system is similar to FIG. 6 except that the

venturi walls

18, 18a are acted on by springs 23 which balance the action of the negative pressure. When the rate of flow of the fluid at the throat and the negative pressure increase, the two walls tend to move towards one another and reduce the throat cross-section.

In FIGS. 8-10 the same effect is produced by using for the venturi walls two flexible plates 18, 180 which are made of rubber or some other resilient and stretchable substance, the plates curving towards one another to an extent varying with the strength of the negative pressure. Conveniently, and as shown in FIG. 9, the plates are circular to facilitate deformation of the rubber.

In the embodiment shown in FIGs. 11-13, the main integers are those previously described with reference to FIG. 4; in this case, however, the foil 18, which can be of sheet metal or some other material, is deformable because its free end edge (the edge perpendicular to the plane of FIG. 11) has both its ends guided in slides 26 disposed in the members 17. For instance, and as can be seen in FIG. 13, edge 25 can be wound around a rod whose projecting ends 27 are guided in the slides 26. The same can be inclined to facilitate the move ment of the rod ends 27. Because of the possible movements which the edge 25 can make, and provided of course that the foil or sheet 18 is not rigidly connected, at least in its intermediate part, to the members 17 but can move thereon with satisfactory sealing-tightness (eg through the agency of a teflon-covered edge), the sheet 18 distorts to an extent varying with the negative pressure at the venturi throat and thus varies throat cross-section.

The facility described has various advantages. In ad dition to the advantages previously mentioned as regards space saving, since the skirts supply header can be made very flat, and as regards the reduction and substantial obviation of air leakages from any air cushions which happen to be too open to atmosphere, the machine bodywork is of improved sealing-tightness, since there is no need for a large number of ducts of relatively complicated shape to extend through the bodywork a great advantage for sea-going machines. Since the header is flat, a large number of generators of compressed air or some other pressure fluid can readily be associated with a large number of air cushions. Also, should the header bottom wall be damaged, a risk which is particularly likely in a sea-going machine, the air escapes below the vehicle so that there is a loss of stability but the general lift remains.

For buoyancy, sealed chambers can be provided, for instance, in the form of inflatable tubes disposed around platform 1.

The machine shown in FIGS. 14-16, also comprises plenum chamber air cushions each bounded by a flexible skirt 3 and can move either above land, denoted by the reference 20, or above water, for instance, across a river or lake. In the example, two skirt rows are disposed symmetrically one on either side of the longitudinal vertical plane of symmetry of the machine, such plane being represented by the line A- A in FIG. 16. Each row comprises three skirts i.e., three cushions. There is also an extra skirt at front and rear and positioned symmetrically of the line AA to leave space for wheels 32. The skirt supply facility providing independent skirt supplies from a common source is the same as hereinbefore described, the common source in this embodiment comprising an air compressor 9 driven by an e.g. electric motor 90. Compressor 9 has fairing 10 which is open to the front so that air is forced into the fairing by dynamic pressure as the machine moves. Each passage via which the skirts '3 are supplied from the header 6 is embodied, as described with reference to FIGS. 4 and 5, by a flat venturi placed horizontally in the capacity 6. The two horizontal walls 1, 7 thereof are interconnected by tubes 30 which are closed on themselves hermetically and filled with a gas, for instance, air; the tubes 30 are large enough to give the machine buoyancy in the water even if the air cushions do not operate; the capacity 6 cannot provide buoyancy, for when the air cushions are not in operation air can enter the capacity 6 via the venturis. The tubes 30 are made of steel or some other strong metal and are rigidly secured, e.g. by welding or in some other way, to the two walls 1, 7 and thus help to stiffen the system which the tubes 30 form in co-operation with the walls 1, 7, such system then being suitable on its own to form a vehicle frame or chassis to which arms 33 bearing the wheels 32 can be secured in any appropriate manner.

' In the embodiment shown, a single tube 30 extends over the whole periphery of the capacity 6 and is embodied by welded-together sections. The tube 30 therefore forms the sealing side wall between the two horizontal walls 1, 7. Since the air from the compressor 9 to the various venturis takes a longitudinal path, another tube 31 can be placed on the longitudinal axis of capacity 6 between the two skirt rows. If there are more than two skirt rows, a further tube parallel to the longitudinal axis can be provided. The tube 31 can be independent of the peripheral tubes 30; in the example shown, the tube 31 is connected to the tubes 30, e.g. by welding. The extra front skirt is supplied through a venturi placed horizontally in a small flat capacity 60 bounded laterally by a tube 30a. The compressor output is branched at a place to supply the capacity 6a. The embodiment could of course be modified. More particularly, the tubes 30 could extend over only some of the periphery of the chambers 6, the remainder thereof being closed hermetically by any sort of side wall. Similarly, connecting means in addition to the tubes 30 and 31 could be provided between the walls 1 and 7.

Referring to FIGS. 17-21, a ground-effect machine is moving, in the direction indicated by an arrow F, along a bearing surface 2 which is water in this particular example, the machine being an ocean-going ground-effect machine. The machine structure 40 comprises a base member la which is hollow and sealing-tight to form a buoyancy reserve, and an operative part 41 which is connected to the base member 1a with partitioning such that the structure 40 forms a very rigid hollow member. Stifleners 42 increase the stiffness of member 1a. Inflatable chambers 43 disposed along and on each side of the machine protect the same and increase buoyancy. Members made of an expanded plsastics material can be used instead of the chambers 4 Rigid walls 44 which have a thin bottom edge and which are disposed lengthwise of the machine project below base member 1a towards surface 2 and thus bound longitudinal channels or passages. In the em bodiment described, there are four walls 44 bounding three such channels or passages. Disposed in each channel is a wall 7 which is substantiallyparallel to base member hand which co-operates with the associated walls 44 and the member la to bound a flat capacity 6 supplied with pressure fluid. Secured to each wall 7 are flexible skirts 3 each bounding a pressure fluid cushion 3a of the plenum chamber kind and extending between two walls 44 to near the surface 2. Advantageously, the skirts 3 have in plan near the wall'7 a polygonal shape which is substantially square in this embodiment (as represented by thin chain-dotted lines 3b in FIGS. 19 and 21) while their shape at their free edge near the surface 2 is substantially circular. Preferably, the polygonal surface is greater than the circular surface so that the pressure fluid contained by the skirts ensures vertical stability thereof. As is most readily apparent from F IGS. 17 and 19, the transverse size of the attached end of the flexible skirts 3 is substantially equal to the transverse width of the respective adjacent channels 44. Skirts of this' kind have already been disclosed in U.S. Pats. No.

3,369,623 and No. 3,414,075. Their advantage is that they make optimum use of the surface of the walls 7 for lift. Another possibility is to have skirts which are in plan near the wall 7 oblong-shaped and near the bearing surface substantially circular.

The cushions 3a bounded by the various skirts are supplied independently of one another by the corresponding capacity'6 via a two-dimensional convergent-divergent nozzle a in the form of a flat venturi. The capacities 6 are supplied from two fans or blowers 45 driven by motors 46, with dynamic intakes 47 for external fluid, the intakes 47 being disposed e.g. at the front of the machine. Each fan is associated with a lateral capacity 6 and supplies the same through a duct 48. The central capacity 6 is supplied through offshoots 480 from the ducts 48 and disposed in the base member la. Since they are separated from one another by the walls 4, the capacities 6 could also be supplied independently e.g. by means of three separate fans.

Advantageously, the longitudinal channels or passages bounded by the walls 44 are closed at their front and rear ends so as to bound the supplementary pressure-fluid cushions supplied by leakages from the cushions 3a bounded by the skirts 3. Accordingly, the skirts 3 at the front and/or rear of the longitudinal channels or passages bounded by the walls 44 have walls which are disposed very near the longitudinal walls 44, as can be seen in FIGS. 20 and 21. It would also be possible for the walls described as being very near the longitudinal walls 44 to be in contact therewith. Each longitudinal channel therefore bounds a pressure fluid cushion which is independent of the other cushions bounded by the other channels, so that the machine has very good lateral stability. Depending upon the conditions in which the machine is used, the free bottom edge of the skirts 3 can be substantially at the same level as the free edge of the walls 44, as shown in the figures, or higher or lower.

Any form of propulsion can be used. In the example shown, propulsion is by four screws 49 which are, with advantage, disposed infairings and which are placed at the front and rear of the machine respectively; the screws 49 are driven by motors 50 and can each make an appropriate angle with the machine axis so as not to cause disturbing interactions. The machine also has two fins 51 positioned, if required, outside the air stream produced by the screws 49.

The operative part of the machine comprises a central freight compartment 52 and, on either side thereof, engine compartments 53 and passengers compartments 54.

The interior of each skirt communicates with the flat capacity 6 above it, and receiving the compressed air from the fans 45, via a venturi tube of the kind previously described with reference to FIGS. 4 and 5. The space required for the equipment of the machine is therefore reduced, and the base member 1a and the center of gravity can be lower than previously.

The ground-effect machine according to the invention is very stable yet can be very large. For instance, the skirts 3 can readily be 20 meters in diameter, and the number of longitudinal channels in which the skirts 3 are disposed can be increased by increasing the number of walls 44. With skirts of this size and using three or four longitudinal channels, machines weighing from 1,600 to 3,000 tons can be constructed.

The invention is not of course limited to the embodiments described and covers embodiments arising from the use of equivalent technical means.

The walls 44 can be hollowed so as not to increase weight excessively and can be made of a rigid or slightly deformable material.

The means for bounding the longitudinal channels at the front and/or rear of the machine can differ from those described; for instance, a flexible wall which in plan preferably resembles a portion of circle arc can be used for each channel or passage.

I claim:

1. A ground-effect machine borne by a number of cushions of compressed air or some other pressure fluid, the cushions being bounded below the vehicle by separate curtains and being supplied with pressure fluid by a common source, said machine comprising a substantially flat capacity extending above the curtains of several cushions and receiving the output from the source, and venturis disposed horizontally in the capacity so that only their transverse dimension is presented between the top and the bottom of the capacity, each of said venturis opening into said capacity and into a sublying cushion respectively, in order to supply said cushion with pressure fluid.

2. A machine according to claim 1, wherein the venturis are two-dimensional, their-cross-section having a flat shape.

3. A machine according to claim 1, wherein the flat capacity has the form of a double skin between the load-carrying platform of the machine and a wall below at a reduced distance away, the cushion-bounding curtains being attached to the latter wall.

4. A machine according to claim 1, wherein the curtains are disposed in at least two symmetrical rows disposed one on either side of the vertical longitudinal plane of symmetry of the machine.

5. A machine according to claim 2, wherein the venturis are bounded by at least one curvilinear sheet.

6. A machine according to claim 5, wherein one of the venturi walls is the wall of the'header capacity.

7. A machine according to claim 5, wherein one ourvilinear wall of a venturi is movable or deformable for adjustment of the venturi throat cross-section.

8. A ground-effect machine according to claim 7, wherein the adjustment is controlled automatically in dependence upon the negative pressure at the throat.

9. A machine according to claim 1, wherein the two parallel walls of the flat capacity are interconnected at least in some parts by closed tubes filled with gas and made of a strong rigid substance.

10. A machine according to claim 9, wherein the tubes, which are closed hermetically,are large enough to give the machine buoyancy.

l 1. Machine according to claim 9, wherein the tubes form at least some of the side part of the flat capacity by interconnecting the two walls thereof at their periphery.

12. A machine according to claim 9, wherein a tube is disposed between the walls of the flat capacity in intermediate zones of the surface of such walls.

13. A machine according to claim 9, wherein the two walls of the flat capacity, interconnected by the rigid tubes, form the vehicle frame.

14. A surface effect machine having a platform movable above a bearing surface with the interposition of pressure fluid cushions, in a direction parallel to a longitudinal plane of symmetry, said machine comprising four laterally-spaced keel-like walls projecting from the under-surface of said platform towards said bearing surface and extending from prow to stern substantially parallel to said plane of symmetry to define three 1on gitudinally-extending and laterally-juxtaposed channels under said platform, namely a central channel and two side channels, and a plurality of flexible skirts dependfluid delivering fluid into said capacity, and venturis disposed horizontally in the capacity so that only their transverse dimension is presented between the top and the bottom of the capacity, each of said venturis opening into said capacity and into a sublying cushion respectively, in order to supply said cushion with pressure fluid.

16. A machine according to claim 15, comprising further into said platform a second flat capacity which is hermetic to provide buoyancy.

17. A machine as claimed in claim 14, further comprising a plurality of flexible skirts depending from said platform and positioned in fore-and-aft alinement behind each other in said central channel.

18. A machine as claimed in claim 14, wherein said skirts have a transverse size substantially equal to the transverse width of the respective channels, whereby said skirts extend across substantially the whole width of said respective channels.

19. A machine as claimed in claim 14, wherein said skirts alined in a same channel are substantially contiguous to each other.

20. A machine as claimed in claim 14, wherein said flexible skirts have an attached end adjacent to said platgorm and a free end remote therefrom, said free end being of substantially circular shape whereas said attached end is of a shape which differs from a .circle, the transverse size of said attached end being- I sbustantially equal to the transverse width of the respective channel whereby said attached end extends across substantially the whole width of said respective channel, the attached ends of the skirts alined in a same channel being substantially contiguing from said platform and positioned in fore-and-aft (ms to each otheralinement behind each other in each of said side channels.

15. A machine according to claim 14, comprising further a substantially flat capacity forming part of said platform above said flexible skirts, a source of pressure 21. A machine as claimed in claim 20, wherein said attached end is of generally polygonal shape.

22. A machine as claimed in claim 21, wherein said attached end is of generally square shape UNITED STATES PATENT 0mm QERTEFEATE @F CQREQTlGN Patent No- 3,688,724 Dated September 5, 1972 Inventor( s) JEAN HENRI BERTIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby. corrected as shown below:

In the heading, [30], insert additional priority application of'-- June 10, 1969 France. 69191 84 Column 1, line 12, "chamber" should read capacity Column 1, line 18, "chamber" should read capacity Column 10, line 25, claim 20, "platgorm" should read platform Signed and sealed this 25th day of December 1973.

(SEAL) Attest;

EDWARD M.FLETCHER,J-R. RENE D. TEGTMEYER Attesting Officerv Acting Commissioner of Patents F ORM PO-1050 (IO-69) USCOMM-DC 6O376-P69 U.S. GOVERNMENT PRINTING OFFICE 19.9 0-365-834, l ,1

Claims

2. A machine according to claim 1, wherein the venturis are two-dimensional, their cross-section having a flat shape.

6. A machine according to claim 5, wherein one of the venturi walls is the wall of the header capacity.

7. A machine according to claim 5, wherein one curvilinear wall of a venturi is movable or deformable for adjustment of the venturi throat cross-section.

10. A machine according to claim 9, wherein the tubes, which are closed hermetically, are large enough to give the machine buoyancy.

11. Machine according to claim 9, wherein the tubes form at least some of the side part of the flat capacity by interconnecting the two walls thereof at their periphery.

14. A surface effect machine having a platform movable above a bearing surface with the interposition of pressure fluid cushions, in a direction parallel to a longitudinal plane of symmetry, said machine comprising four laterally-spaced keel-like walls projecting from the under-surface of said platform towards said bearing surface and extending from prow to stern substantially parallel to said plane of symmetry to define three longitudinally-extending and laterally-juxtaposed channels under said platform, namely a central channel and two side channels, and a plurality of flexible skirts depending from said platform and positioned in fore-and-aft alinement behind each other in each of said side channels.

15. A machine according to claim 14, comprising further a substantially flat capacity forming part of said platform above said flexible skirts, a source of pressure fluid delivering fluid into said capacity, and venturis disposed horizontally in the capacity so that only their transverse dimension is presented between the top and the bottom of the capacity, each of said venturis opening into said capacity and into a sublying cushion respectively, in order to supply said cushion with pressure fluid.