PROPULSION FIN FOR A FLOATING BODY
United States Patent 3773011
A propulsion fin for a floating body comprises a flat member adapted to be coupled externally to said body and extends, when at rest, in a plane substantially parallel to the direction of forward movement of said body, said member being intended to oscillate with a propulsive action during operation and comprising a diaphragm supported by a rigid frame coupled to said body, said frame extending laterally and towards the rear and being open at the rear so that the rear edge of the diaphragm is free, said diaphragm being constructed and mounted so as to be elastically deformable and having, when at rest, a mean position on said frame in which it is stretched with a pre-determined tension, and is mounted angularly movable on the frame in such manner as to move, during operation, from one side of said mean position to the other between two extreme positions in which the tension of the diaphragm is greater than said pre-tension, and in which the diaphragm is inflated in the form of a pocket and makes an angle with said mean position, starting from the frame. The invention is particularly applicable to floating bodies for water sports.
US Patent References:
N/A
Spangenberg - September 1971 - 3605676
SWIMMING APPLIANCE
McGowan - April 1969 - 3440994
Water sports toys
Vlacancich - February 1966 - 3232608
Self propelled toy fish
Oberg - October 1958 - 2854787
N/A
Spangenberg - September 1971 - 3605676
SWIMMING APPLIANCE
McGowan - April 1969 - 3440994
Water sports toys
Vlacancich - February 1966 - 3232608
Self propelled toy fish
Oberg - October 1958 - 2854787
Application Number:
05/227524
Publication Date:
11/20/1973
Filing Date:
02/17/1972
Export Citation:
Primary Class:
Other Classes:
440/22, 472/129
International Classes:
B63H1/36; B63H1/00; B63H1/36
Field of Search:
272/1B 46/91,92 115/28A,28R,4,21,22R,22.2,22.3 9/31D,31R,311,312
View Patent Images:
Primary Examiner:
Halvosa, George E. A.
Assistant Examiner:
Sauberer, Paul E.
Claims:
What I claim is
1. A propulsion fin for a floating body comprising a rearwardly opening rigid forked frame, an elastically deformable diaphragm stretched across the frame under an initial tension to normally maintain the diaphragm in a flat median position substantially coplanar with the frame, said diaphragm being pivotably mounted on the frame to rotate relative to the frame to positions on each side of said median position in which an angle is formed by the diaphragm at its attachment with the frame relative to the plane of the frame and in which the diaphragm is outwardly bulged forming a pocket under tension greater than the initial tension.
2. A propulsion fin as claimed in claim 1, in combination with a floating body on which the forked frame is secured.
3. A propulsion fin as claimed in claim 2, wherein the floating body is adapted to be pitched alternately nose-down towards the front and tail-down towards the rear causing the fin to oscillate to said positions thereby effecting forward movement.
4. A propulsion fin as claimed in claim 3, further comprising a strip disposed along the rear edge of the diaphragm and forming a free flap.
5. A propulsion fin as claimed in claim 3, in which the diaphragm is attached to the frame by a tubular sleeve.
6. A propulsion fin as claimed in claim 2, in which said diaphragm comprises at least one elastic portion allowing expansion thereof.
7. A propulsion fin as claimed in claim 6, in which the diaphragm also comprises at least one flexible portion.
8. A propulsion fin as claimed in claim 7, in which said elastic portion comprises an elastic fabric fixed to said flexible portion.
9. A propulsion fin as claimed in claim 7, in which said elastic portion comprises at least one elastic thread connection.
10. A propulsion fin as claimed in claim 6, in which a panel of the diaphragm is pivotally mounted on one portion of said frame and coupled by elastic lacing to another portion of said frame.
11. A propulsion fin as claimed in claim 6, in which said diaphragm is entirely elastic.
12. A propulsion fin as claimed in claim 2, in which said fin is of the caudal type in which the forked frame is joined to a central shaft for securing the frame to said floating body and in which each branch of the fork has a main portion extending from the shaft laterally and rearwardly and a rear projecting terminal portion substantially parallel to the longitudinal axis of the floating body.
13. A propulsion fin as claimed in claim 12, in which said main portion is substantially linear.
14. A propulsion fin as claimed in claim 12, in which said main portion is curved.
15. A propulsion fin as claimed in claim 1, in which said fin is of the lateral type, and in which supporting means is associated with said frame for stretching said diaphragm.
16. A propulsion fin as claimed in claim 2, in which said fin is of the lateral type and further comprising a supporting means associated with said floating body and adapted to stretch said diaphragm.
17. A floating body provided with at least one propulsion fin as claimed in claim 2, to be ridden astride by a user, said body having a generally domed shaped similar to that of a quarter of an orange, with a raised central portion straddled by the user and two lower end portions to remain continuously submerged during the course of the oscillations imparted by the user to said floating body for the forward propulsion of said body.
18. A floating body as claimed in claim 17, and further comprising, at the bottom of its central portion, two long lateral profiled members parallel to the longitudinal axis of floating body providing footrests and guiding and stabilizing said body.
1. A propulsion fin for a floating body comprising a rearwardly opening rigid forked frame, an elastically deformable diaphragm stretched across the frame under an initial tension to normally maintain the diaphragm in a flat median position substantially coplanar with the frame, said diaphragm being pivotably mounted on the frame to rotate relative to the frame to positions on each side of said median position in which an angle is formed by the diaphragm at its attachment with the frame relative to the plane of the frame and in which the diaphragm is outwardly bulged forming a pocket under tension greater than the initial tension.
2. A propulsion fin as claimed in claim 1, in combination with a floating body on which the forked frame is secured.
3. A propulsion fin as claimed in claim 2, wherein the floating body is adapted to be pitched alternately nose-down towards the front and tail-down towards the rear causing the fin to oscillate to said positions thereby effecting forward movement.
4. A propulsion fin as claimed in claim 3, further comprising a strip disposed along the rear edge of the diaphragm and forming a free flap.
5. A propulsion fin as claimed in claim 3, in which the diaphragm is attached to the frame by a tubular sleeve.
6. A propulsion fin as claimed in claim 2, in which said diaphragm comprises at least one elastic portion allowing expansion thereof.
7. A propulsion fin as claimed in claim 6, in which the diaphragm also comprises at least one flexible portion.
8. A propulsion fin as claimed in claim 7, in which said elastic portion comprises an elastic fabric fixed to said flexible portion.
9. A propulsion fin as claimed in claim 7, in which said elastic portion comprises at least one elastic thread connection.
10. A propulsion fin as claimed in claim 6, in which a panel of the diaphragm is pivotally mounted on one portion of said frame and coupled by elastic lacing to another portion of said frame.
11. A propulsion fin as claimed in claim 6, in which said diaphragm is entirely elastic.
12. A propulsion fin as claimed in claim 2, in which said fin is of the caudal type in which the forked frame is joined to a central shaft for securing the frame to said floating body and in which each branch of the fork has a main portion extending from the shaft laterally and rearwardly and a rear projecting terminal portion substantially parallel to the longitudinal axis of the floating body.
13. A propulsion fin as claimed in claim 12, in which said main portion is substantially linear.
14. A propulsion fin as claimed in claim 12, in which said main portion is curved.
15. A propulsion fin as claimed in claim 1, in which said fin is of the lateral type, and in which supporting means is associated with said frame for stretching said diaphragm.
16. A propulsion fin as claimed in claim 2, in which said fin is of the lateral type and further comprising a supporting means associated with said floating body and adapted to stretch said diaphragm.
17. A floating body provided with at least one propulsion fin as claimed in claim 2, to be ridden astride by a user, said body having a generally domed shaped similar to that of a quarter of an orange, with a raised central portion straddled by the user and two lower end portions to remain continuously submerged during the course of the oscillations imparted by the user to said floating body for the forward propulsion of said body.
18. A floating body as claimed in claim 17, and further comprising, at the bottom of its central portion, two long lateral profiled members parallel to the longitudinal axis of floating body providing footrests and guiding and stabilizing said body.
Description:
The present invention relates to a propulsion fin for a floating body, comprising a flat member which is intended to be coupled externally to the said body and which, when at rest, extends substantially in a plane parallel to the direction of forward movement of the said body, the said member moving with a propulsive action during the course of operation, for example when the said body is allowed to oscillate.
A fin of this kind is described in French Pat. No. 1,322,642 of the present applicant and in the first Certificate of Addition No. 82,572 attached to this patent.
Interesting results can be obtained with the object described in this French Patent and its Certificate of Addition, but in general starting-off is rather slow and the forward speed is fairly low. The applicant has made efforts in particular to improve the propulsion capacity of the fin, and after numerous tests and researches, it has been found that considerably improved performances can be obtained when the fin consists of a deformable diaphragm elastically stretched over a rigid frame in such manner as to be capable of being inflated in the form of a pocket alternatively on one side or on the other.
The present invention has for its object a propulsion fin for a floating body, characterized in that it comprises a diaphragm supported by a rigid frame which is intended to be coupled to the said body, the said frame extending laterally and towards the rear and being open at the rear in such manner that the rear edge of the said diaphragm is free, the said diaphragm being constructed and mounted so as to be elastically deformable and having, in the position of rest, a mean position on the frame in which it is stretched with a pre-determined tension, the said diaphragm being mounted angularly movable on the frame so as to be displaced, in operation, on each side of the said mean position, between two extreme positions at which the tension of the diaphragm is greater than the said pre-tension and in which the diaphragm is inflated in the form of a pocket and makes from the start of the frame, an angle with the said mean position.
The said floating body is preferably permitted to oscillate by pitching with a downward plunging movement towards the front and a tail-down movement towards the rear, the said frame and the said diaphragm extending in a position of rest in a substantally horizontal frame.
The fin according to the invention provides a substantial propulsive effect from the start, this being true both for the tail-down and nose-down positions, because the deformation to a pocket of the diaphragm assists the horizontal component of the forces in the direction of forward movement. The fin makes it possible to obtain high forward speeds, and in particular speeds of the order of 4 to 6 km. per hour.
The fin may be of the caudal type and in this case, the frame has preferably the shape of a fork with two arms and a central coupling handle to the floating body, each arm having a main front portion leaving the handle and extending laterally and towards the rear, and a rear end portion substantially parallel to the direction of forward movement.
The fin may also be lateral, and in this case, a supporting means is associated with the frame and/or with the floating body and serves to stretch the diaphragm.
The present invention has also for its object a floating body provided with at least one fin such as previously described, this floating body being intended to be ridden by a user like a horse. The floating body is characterized in that it has a generally domed shape similar to that of a quarter of an orange, with a rising central portion which is straddled by the user and two lower end portions intended to remain continouusly submerged during the course of the oscillations impressed on the floating body by the user in order to move the body forward.
Such a shape of the floating body has proved to be particularly effective for propulsion. In particular, the almost continuous submersion of the body, especially at the front and the rear, during the oscillations, permits a stabilization of the centre of thrust of the body, to the advantage of the operation.
The floating body preferably comprises, at the bottom of its central portion, two long lateral profiles parallel to the direction of forward movement, forming foot-rests and having a function of guiding and stabilization.
Forms of embodiment of the invention are described below by way of example, reference being made to the accompanying drawings, in which:
FIG. 1 is a view of a caudal fin according to the invention, this fin being in the position of rest;
FIG. 2 is a view of this fin in cross-section, taken along the line II--II of FIG. 1;
FIG. 3 is a view of the said fin in cross-section, taken along the chain-dotted line III--III of FIG. 1;
FIG. 4 is a view similar to FIG. 1, but in which the fin occupies one of its positions in which it is inflated in the form of a pocket;
FIG. 5 is a view in cross-section taken along the line V--V of FIG. 4;
FIG. 6 is a view in cross-section taken along the chain-dotted line VI--VI of FIG. 4;
FIG. 7 shows to a larger scale a pivotal mounting of the diaphragm on the frame;
FIGS. 8, 9, 10 and 11 are views similar to FIG. 1, but which relate respectively to four alternative forms;
FIG. 12 shows a plan view of two lateral fins in the position of rest;
FIG. 13 is a view in cross-section taken along the chain-dotted line XIII--XIII of FIG. 12, the fins being in the position inflated as a pocket;
FIG. 14 is a diagrammatic view in perspective of a floating body provided with fins according to the invention;
FIGS. 15, 16, 17, 18, 19 and 20 illustrate various phases of the operation of the floating body shown in FIG. 14.
Reference will first be made to FIGS. 1 to 3. A propulsion fin of a floating body comprises a diaphragm 10 supported by a rigid frame 11. The frame 11 has the shape of a fork with two arms 12 and 13 and with a central handle 14 for coupling to the floating body. Each arm 12 or 13 has a main portion 15 which is inclined to one side and towards the rear, and a rear transverse portion 16 substantially parallel to the direction of forward movement. It will be noted that the frame 11 is open at the rear.
The diaphragm 10 is constructed and mounted in such manner as to be elastically deformable and has, when at rest, a mean position on the frame 10 in which it is stretched with a pre-determined tension.
In the example shown in FIGS. 1 to 7, the diaphragm 10 is composed of two flexible lateral portions 17 and 18 and a central portion 19 formed by an elastic fabric. The portions 17, 18 and 19 may be assembled together by any appropriate means, for example the portion 19 may be double and fixed by a seam at 20 to the portions 17 and 18.
The diaphragm 10 is mounted so as to be angularly movable on the frame 11. For example, the front edge of the diaphragm is made tubular at 21. (see FIG. 7) and is pivotally mounted with play on the frame 11 for a rotating movement of the diaphragm 10 at that place. It will be appreciated that the pivotal movement of the diaphragm 10 on the frame is carried out under excellent conditions, although the arms 12 and 13 are neither straight nor coaxial, due to the fact that the diaphragm 10 is deformable.
With this arrangement, the diaphragm 10 moves, during operation, on each side of the means position between two extreme positions 10a and 10b (see FIG. 6) which are more or less distant from this mean position, depending on the tilting torque. In each extreme position, the tension of the diaphragm 10 is greater than the pre-tension in the mean position and the diaphragm is inflated in the form of a pocket (see in particular FIGS. 5 and 6). In each extreme position, starting from the frame 11, the diaphragm 10 forms an angle A (FIGS. 5 and 6) with the mean position.
It will be observed from FIG. 1 that the rear edge of the diaphragm comprises a strip 22 free from any mounting on the frame 11 and forming a free flap. There can be seen in FIGS. 1 and 4, the line L in chain-dotted lines which separates the diaphragm proper from the flap 22. The line L has a slightly elbowed general shape. It will be noted from FIG. 1 that the section line III--III is substantially coincident with the line L.
It can be seen from FIG. 5 that in the extreme position of the diaphragm 10 inflated like a pocket, the flap 22 forms an inflexion with the running portion of the diaphragm 10. This flap 22 has the function of a trailing edge and ensures continuity of the streams of liquid by preventing a return of liquid towards the front.
It will also be noted from FIGS. 1 to 6 that the diaphragm 10 is advantageously made of a sheet material of constant thickness and is provided with stiffening ribs 23 parallel to the direction of forward movement. In an alternative form, the stiffening may be obtained by a gradual variation of the thickness of the diaphragm. It will be appreciated that the stiffening means by ribs 23 or the like extend on each side of the line L, which enables excellent continuity of the working profile to be obtained.
The fin, such as this has been described with reference to FIGS. 1 to 7 is a caudal fin adapted to be arranged to the rear of a floating body.
When this floating body is permitted to oscillate while pitching with a nose-down movement towards the front and a tail-down movement towards the rear, the fin moves with a particularly effective propulsive action both for the tail-down and nose-down positions, enabling it to effect an immediate start and to obtain a high forward speed, in particular of the order of 4 to 6 km. per hour.
In the example of FIGS. 1 to 7, the diaphragm is composed of two flexible portions 17 and 19 and an elastic portion 19, but the diaphragm may also be made uniformly elastic, as shown at 10' in FIG. 8.
As shown in FIG. 9, the elastic fabric 10 may also be replaced, on the one hand by a system of elastic threads 19" coupling together the flexible portions 17 and 18, and on the other hand by a simple central closure portion 19" 1 . The diaphragm can be seen at 10'.
In FIG. 1, each arm 15 is substantially straight, but the arms may also be provided in an arcuate form at 15'" as has been shown in FIG. 10. The diaphragm can be seen at 10'".
In another alternative form shown in FIG. 11, the diaphragm shown at 10 iv , comprises a flexible non-extensible panel 24 articulated at 25 on a part of the frame 11, and coupled by elastic lacing 26 to another part of the frame.
Reference will now be made to FIGS. 12 and 13, in which the arrangement is similar to those which have just been described, but in which the fin is not a caudal but a lateral fin.
In the example of FIG. 12, two lateral fins are provided. A supporting means 27 is preferably associated with the frame and/or with the floating body and serves to stretch the diaphragm. For example, each frame, indicated by 111, receives an auxiliary rod 27 which extends along the floating body and which serves to stretch the diaphragm, designated by 110. In FIG. 12, the fins are shown in the position of rest, and in FIG. 13 in the position inflated as a working pocket.
The lateral fins described with reference to FIGS. 12 and 13 also make it possible to obtain an effective propulsive effect.
Reference will now be made to FIG. 14, in which there is shown at 28 a floating body for a water sports game intended to be ridden astride by a user and having at the rear a caudal fin 10 such as that which has been described with reference to FIGS. 1 to 7, and at the front two lateral fins 110 such as those which have been described with reference to FIGS. 12 and 13.
The floating body 28 has a generally domed shape similar to that of a quarter of an orange with a raised central portion 29 which is straddled by the user, and two extreme portions 30 and 31 which are lower and are intended to remain continuously submerged during the course of the oscillations of the body 28. It will be understood that the body 28 is wider at the top than at the bottom.
At the bottom of its central protion, the body 29 further comprises two long lateral profiled members 32 parallel to the direction of forward movement. Each member 32 is composed of an upper portion 32a inclined downwards and towards the exterior, and a lower horizontal portion 32b. The profiled members form, on the one hand guides for maintaining the direction of forward movement, and on the other hand they constitute foot-rests at 32b. It will be appreciated that the members 32 have a stabilizing effect against a pitching movement or pounding, and, by virtue of the length, enable the feet to be placed either towards the front or the rear or in the centre at the will of the user.
There can be seen in FIG. 15 a device in the position of rest, in which the fins 10 and 110 are flat and horizontal.
In FIG. 16, the user begins a nose-down movement, of which the completion of travel is shown in FIG. 17.
In FIGS. 18 and 19, the user leans back by a tail-down movement and there is shown in FIG. 20 the device at the end of the tail-down movement and at the beginning of another nose-down operation.
There will be observed from FIGS. 16 to 20 the inflated shapes in the form of a pocket taken by the fins 10 and 110.
It will be understood that the improved qualities of the floating body and the fins permit a harmonious equilibrium of the effort required from the user for the nose-down and tail-down movements, which both ensure a propulsive effect and may have substantially the same duration.
It will be noted that the front fins 110 could be replaced by rigid lateral ailerons froming simple stabilizers. These ailerons may be shaped in the form of a shovel and may be mounted with a slight dihedron to the horizontal.
A fin of this kind is described in French Pat. No. 1,322,642 of the present applicant and in the first Certificate of Addition No. 82,572 attached to this patent.
Interesting results can be obtained with the object described in this French Patent and its Certificate of Addition, but in general starting-off is rather slow and the forward speed is fairly low. The applicant has made efforts in particular to improve the propulsion capacity of the fin, and after numerous tests and researches, it has been found that considerably improved performances can be obtained when the fin consists of a deformable diaphragm elastically stretched over a rigid frame in such manner as to be capable of being inflated in the form of a pocket alternatively on one side or on the other.
The present invention has for its object a propulsion fin for a floating body, characterized in that it comprises a diaphragm supported by a rigid frame which is intended to be coupled to the said body, the said frame extending laterally and towards the rear and being open at the rear in such manner that the rear edge of the said diaphragm is free, the said diaphragm being constructed and mounted so as to be elastically deformable and having, in the position of rest, a mean position on the frame in which it is stretched with a pre-determined tension, the said diaphragm being mounted angularly movable on the frame so as to be displaced, in operation, on each side of the said mean position, between two extreme positions at which the tension of the diaphragm is greater than the said pre-tension and in which the diaphragm is inflated in the form of a pocket and makes from the start of the frame, an angle with the said mean position.
The said floating body is preferably permitted to oscillate by pitching with a downward plunging movement towards the front and a tail-down movement towards the rear, the said frame and the said diaphragm extending in a position of rest in a substantally horizontal frame.
The fin according to the invention provides a substantial propulsive effect from the start, this being true both for the tail-down and nose-down positions, because the deformation to a pocket of the diaphragm assists the horizontal component of the forces in the direction of forward movement. The fin makes it possible to obtain high forward speeds, and in particular speeds of the order of 4 to 6 km. per hour.
The fin may be of the caudal type and in this case, the frame has preferably the shape of a fork with two arms and a central coupling handle to the floating body, each arm having a main front portion leaving the handle and extending laterally and towards the rear, and a rear end portion substantially parallel to the direction of forward movement.
The fin may also be lateral, and in this case, a supporting means is associated with the frame and/or with the floating body and serves to stretch the diaphragm.
The present invention has also for its object a floating body provided with at least one fin such as previously described, this floating body being intended to be ridden by a user like a horse. The floating body is characterized in that it has a generally domed shape similar to that of a quarter of an orange, with a rising central portion which is straddled by the user and two lower end portions intended to remain continouusly submerged during the course of the oscillations impressed on the floating body by the user in order to move the body forward.
Such a shape of the floating body has proved to be particularly effective for propulsion. In particular, the almost continuous submersion of the body, especially at the front and the rear, during the oscillations, permits a stabilization of the centre of thrust of the body, to the advantage of the operation.
The floating body preferably comprises, at the bottom of its central portion, two long lateral profiles parallel to the direction of forward movement, forming foot-rests and having a function of guiding and stabilization.
Forms of embodiment of the invention are described below by way of example, reference being made to the accompanying drawings, in which:
FIG. 1 is a view of a caudal fin according to the invention, this fin being in the position of rest;
FIG. 2 is a view of this fin in cross-section, taken along the line II--II of FIG. 1;
FIG. 3 is a view of the said fin in cross-section, taken along the chain-dotted line III--III of FIG. 1;
FIG. 4 is a view similar to FIG. 1, but in which the fin occupies one of its positions in which it is inflated in the form of a pocket;
FIG. 5 is a view in cross-section taken along the line V--V of FIG. 4;
FIG. 6 is a view in cross-section taken along the chain-dotted line VI--VI of FIG. 4;
FIG. 7 shows to a larger scale a pivotal mounting of the diaphragm on the frame;
FIGS. 8, 9, 10 and 11 are views similar to FIG. 1, but which relate respectively to four alternative forms;
FIG. 12 shows a plan view of two lateral fins in the position of rest;
FIG. 13 is a view in cross-section taken along the chain-dotted line XIII--XIII of FIG. 12, the fins being in the position inflated as a pocket;
FIG. 14 is a diagrammatic view in perspective of a floating body provided with fins according to the invention;
FIGS. 15, 16, 17, 18, 19 and 20 illustrate various phases of the operation of the floating body shown in FIG. 14.
Reference will first be made to FIGS. 1 to 3. A propulsion fin of a floating body comprises a diaphragm 10 supported by a rigid frame 11. The frame 11 has the shape of a fork with two arms 12 and 13 and with a central handle 14 for coupling to the floating body. Each arm 12 or 13 has a main portion 15 which is inclined to one side and towards the rear, and a rear transverse portion 16 substantially parallel to the direction of forward movement. It will be noted that the frame 11 is open at the rear.
The diaphragm 10 is constructed and mounted in such manner as to be elastically deformable and has, when at rest, a mean position on the frame 10 in which it is stretched with a pre-determined tension.
In the example shown in FIGS. 1 to 7, the diaphragm 10 is composed of two flexible lateral portions 17 and 18 and a central portion 19 formed by an elastic fabric. The portions 17, 18 and 19 may be assembled together by any appropriate means, for example the portion 19 may be double and fixed by a seam at 20 to the portions 17 and 18.
The diaphragm 10 is mounted so as to be angularly movable on the frame 11. For example, the front edge of the diaphragm is made tubular at 21. (see FIG. 7) and is pivotally mounted with play on the frame 11 for a rotating movement of the diaphragm 10 at that place. It will be appreciated that the pivotal movement of the diaphragm 10 on the frame is carried out under excellent conditions, although the arms 12 and 13 are neither straight nor coaxial, due to the fact that the diaphragm 10 is deformable.
With this arrangement, the diaphragm 10 moves, during operation, on each side of the means position between two extreme positions 10a and 10b (see FIG. 6) which are more or less distant from this mean position, depending on the tilting torque. In each extreme position, the tension of the diaphragm 10 is greater than the pre-tension in the mean position and the diaphragm is inflated in the form of a pocket (see in particular FIGS. 5 and 6). In each extreme position, starting from the frame 11, the diaphragm 10 forms an angle A (FIGS. 5 and 6) with the mean position.
It will be observed from FIG. 1 that the rear edge of the diaphragm comprises a strip 22 free from any mounting on the frame 11 and forming a free flap. There can be seen in FIGS. 1 and 4, the line L in chain-dotted lines which separates the diaphragm proper from the flap 22. The line L has a slightly elbowed general shape. It will be noted from FIG. 1 that the section line III--III is substantially coincident with the line L.
It can be seen from FIG. 5 that in the extreme position of the diaphragm 10 inflated like a pocket, the flap 22 forms an inflexion with the running portion of the diaphragm 10. This flap 22 has the function of a trailing edge and ensures continuity of the streams of liquid by preventing a return of liquid towards the front.
It will also be noted from FIGS. 1 to 6 that the diaphragm 10 is advantageously made of a sheet material of constant thickness and is provided with stiffening ribs 23 parallel to the direction of forward movement. In an alternative form, the stiffening may be obtained by a gradual variation of the thickness of the diaphragm. It will be appreciated that the stiffening means by ribs 23 or the like extend on each side of the line L, which enables excellent continuity of the working profile to be obtained.
The fin, such as this has been described with reference to FIGS. 1 to 7 is a caudal fin adapted to be arranged to the rear of a floating body.
When this floating body is permitted to oscillate while pitching with a nose-down movement towards the front and a tail-down movement towards the rear, the fin moves with a particularly effective propulsive action both for the tail-down and nose-down positions, enabling it to effect an immediate start and to obtain a high forward speed, in particular of the order of 4 to 6 km. per hour.
In the example of FIGS. 1 to 7, the diaphragm is composed of two flexible portions 17 and 19 and an elastic portion 19, but the diaphragm may also be made uniformly elastic, as shown at 10' in FIG. 8.
As shown in FIG. 9, the elastic fabric 10 may also be replaced, on the one hand by a system of elastic threads 19" coupling together the flexible portions 17 and 18, and on the other hand by a simple central closure portion 19" 1 . The diaphragm can be seen at 10'.
In FIG. 1, each arm 15 is substantially straight, but the arms may also be provided in an arcuate form at 15'" as has been shown in FIG. 10. The diaphragm can be seen at 10'".
In another alternative form shown in FIG. 11, the diaphragm shown at 10 iv , comprises a flexible non-extensible panel 24 articulated at 25 on a part of the frame 11, and coupled by elastic lacing 26 to another part of the frame.
Reference will now be made to FIGS. 12 and 13, in which the arrangement is similar to those which have just been described, but in which the fin is not a caudal but a lateral fin.
In the example of FIG. 12, two lateral fins are provided. A supporting means 27 is preferably associated with the frame and/or with the floating body and serves to stretch the diaphragm. For example, each frame, indicated by 111, receives an auxiliary rod 27 which extends along the floating body and which serves to stretch the diaphragm, designated by 110. In FIG. 12, the fins are shown in the position of rest, and in FIG. 13 in the position inflated as a working pocket.
The lateral fins described with reference to FIGS. 12 and 13 also make it possible to obtain an effective propulsive effect.
Reference will now be made to FIG. 14, in which there is shown at 28 a floating body for a water sports game intended to be ridden astride by a user and having at the rear a caudal fin 10 such as that which has been described with reference to FIGS. 1 to 7, and at the front two lateral fins 110 such as those which have been described with reference to FIGS. 12 and 13.
The floating body 28 has a generally domed shape similar to that of a quarter of an orange with a raised central portion 29 which is straddled by the user, and two extreme portions 30 and 31 which are lower and are intended to remain continuously submerged during the course of the oscillations of the body 28. It will be understood that the body 28 is wider at the top than at the bottom.
At the bottom of its central protion, the body 29 further comprises two long lateral profiled members 32 parallel to the direction of forward movement. Each member 32 is composed of an upper portion 32a inclined downwards and towards the exterior, and a lower horizontal portion 32b. The profiled members form, on the one hand guides for maintaining the direction of forward movement, and on the other hand they constitute foot-rests at 32b. It will be appreciated that the members 32 have a stabilizing effect against a pitching movement or pounding, and, by virtue of the length, enable the feet to be placed either towards the front or the rear or in the centre at the will of the user.
There can be seen in FIG. 15 a device in the position of rest, in which the fins 10 and 110 are flat and horizontal.
In FIG. 16, the user begins a nose-down movement, of which the completion of travel is shown in FIG. 17.
In FIGS. 18 and 19, the user leans back by a tail-down movement and there is shown in FIG. 20 the device at the end of the tail-down movement and at the beginning of another nose-down operation.
There will be observed from FIGS. 16 to 20 the inflated shapes in the form of a pocket taken by the fins 10 and 110.
It will be understood that the improved qualities of the floating body and the fins permit a harmonious equilibrium of the effort required from the user for the nose-down and tail-down movements, which both ensure a propulsive effect and may have substantially the same duration.
It will be noted that the front fins 110 could be replaced by rigid lateral ailerons froming simple stabilizers. These ailerons may be shaped in the form of a shovel and may be mounted with a slight dihedron to the horizontal.