Technical Field

This invention relates to a craft having buoyancy members dimensioned and positioned to cause the craft to become stable and upright in a liquid medium without assistance in the event the craft is overturned.

Background Art

In United States patent No. 4,998,900 issued to Wright and in the corresponding international patent PCT/CA91/00218 (publication No. WO-91/ 19642), there is described and illustrated a self-righting inflatable craft having upwardly and outwardly extending inflatable tubes. These tubes are arranged to cause the craft to be unstable if inverted. In particular, the center of gravity of the craft, if inverted, will rotate and become vertically over the base of the craft so that it will by gravity topple back to an upright position.

If the inflatable tubes in these prior constructions do not fully inflate or, after inflation, are subsequently collapsed or distorted by strong winds or wave action, they may not adopt or retain their desired positions in which they extend upwardly and outwardly from the sidewalls of the main body. As a result the craft may not topple to the upright position.

Summary of the Invention

It is an object of the present invention to provide a life craft which can reliably return to an upright position if inverted.

According to the present invention there is provided a self- righting inflatable life craft, comprising: a craft body having inflatable sidewalls, a floor at or above a bottom of the sidewalls and a line of

rotation defined near the outer perimeter of the craft body upon which the craft body rotates on the surface of water when moved from an inverted position to an upright position, the craft body having a center of gravity which is spaced a first predetermined distance from the line of rotation when the craft is inverted, and at least three inflatable spaced apart tubular members, each tubular member extending upwardly and outwardly from a perimeter of the craft body at an angle from the perpendicular to the craft body sufficiently great and having a buoyancy sufficient such that the moment exerted on the craft about the line of rotation by its weight acting through its center of gravity causes the craft body to topple by gravity to an upright position, the improvement comprising a tie fixed to and extending between two points on the life craft to limit separation of the two points to the length of the tie during and after inflation of the tube members, the two points being chosen to inhibit distortion or collapse of the tubular members from their desired positions when inflated.

The tie may extend between a first point on one of the tubular members and a second point on the craft body. Alternatively, the tie may extend from a first point on one of the tubular members to a second point on a different one of the tubular members.

Preferably, the inflatable tubular members converge towards a common connecting member spaced upwardly from the craft body, the tubular members including top tubular portions extending from the outermost extent of the tubular members in a direction upwards and inwards towards the common connecting member. In this embodiment the tie may extend from a first point on a top tubular portion of one of the tubular members to a second point on the craft body. Alternatively, the tie may extend from a first point on the common connecting member to a second point on the craft body.

In this embodiment, the common connecting member preferably comprises an inflatable tube extending generally horizontally and at least two of the tube members being connected to the horizontally extending inflatable tube at points spaced along its length. In this construction, the tie may extend from a first point at one end of the horizontally extending inflatable tube to a second point on the craft body.

The tie may comprise a flexible substantially inextensible line. Alternatively, the tie may comprise an inflatable tube which extends in a straight line between the two points when inflated.

Preferably there are provided a plurality of the ties, at least two of the ties being symmetrically arranged relative to the arrangement of the tubular members so that one of the two ties inhibits distortion or collapse of the tubular members in one direction and the other symmetrically arranged tie inhibits distortion or collapse of the tubular members in the symmetrically opposite direction.

The present invention also provides a self-righting inflatable craft, comprising: a craft body including inflatable sidewalls having an upper edge and a sheer line being defined substantially between said sidewalls at said upper edge and the sheer line being defined substantially between the sidewalls at the upper edge, the sheer line having a midpoint substantially centered between the sidewalls; a means for righting the craft body including a plurality of inflatable tubular portions each having a central longitudinal axis which extends from the upper edge to a first predetermined position upwardly and outboard from the upper edge and which then extends inboard to centrally converge with a connecting member connected to others of the plurality of inflatable tubular portions at a second predetermined position above the sheer line, the first position

being spaced outward from the sheer line midpoint at least a horizontal distance substantially determined by the equation;

cos B°

the first position being spaced vertically above the sheer line midpoint at least a distance substantially determined by the equation:

V(C + D « tan E°) ² - C ²

the second position being spaced vertically above the sheer line midpoint at least a distance substantially determined by the equation:

Y = C + (D • tan E°) where,

A = the distance from the sheer line midpoint to the axial center of the tube portion at the upper edge of the sidewalls; and

B = one-half the angle in degrees between the axial center of adjacent tube portions at the upper edge of the sidewalls; and

C = one-half the minimum lateral distance across the craft from one outermost side to the other;

C = one-half the minimum lateral distance across the craft from one outermost side to the other;

D = the vertical height of the sidewalls; and

E = the minimum angle in degrees beyond vertical that the sheer line must be tilted to cause the craft body to topple by gravity to an upright position, the inflatable tube portions being sized to provide buoyancy at least equal to the mass of the craft;

Y = distance from the beam or sheer line midpoint horizontally to the point at which the sheer line would intersect the line which extends at an angle E,

the improvement comprising a tie fixed to and extending between two points on the life craft to limit separation of the two points to the length of the tie during and after inflation of the tubular members, the two points being chosen to inhibit distortion or collapse of the tubular members from their desired positions when inflated.

In another aspect of the invention there is provided a self- righting craft having buoyant top and bottom sidewalls, a membrane affixed to the top sidewall around the perimeter thereof to form a floor and a canopy to shield occupants in an interior thereof, comprising a plurality of buoyant superstructure members affixed to at least one of the top and bottom tubular sidewalls. A canopy is affixed along the length of each of the buoyant sidewall members so as to reinforce the buoyant sidewall members against collapse. While other crafts disclose the use of canopies these are not disclosed as being used for structural reinforcement as well as for their ordinary use of shielding the occupants from the weather.

Other features and advantages of the present invention will become apparent from a reading of the following best mode of carrying out the invention and inspection of the accompanying drawings and claims, all of which are incorporated into this disclosure by specific reference.

Brief Description of the Drawings

Like reference numerals are used to indicate like parts throughout the various figures of the drawing, and wherein:

Fig. 1 is a schematic perspective view of an elongated self- righting life craft according to a preferred embodiment of the present invention;

Fig. 2 is a perspective view of an alternative embodiment of life craft according to the present invention; and

Fig. 3 is a perspective view of a further possible embodiment of life craft according to the present invention;

Fig. 4 is a top schematic view of the craft of Fig. 3 showing various calculated dimensions;

Fig. 5 is a schematic cross-sectional view taken substantially along line 14-14 of Figure 4 showing various calculated dimensions;

Fig. 6 is a schematic cross-sectional view taken substantially along line 15-15 of Figure 4 showing various calculated dimensions;

Fig. 7 is a perspective view of the craft of Figure 2 with a canopy over the outside and affixed to the exterior of the canopy tubular members;

Fig. 8 is a cross-sectional view of an alternative self-righting craft having circular arch members;

Fig. 9 is a side elevation view of craft of Fig. 8 without a canopy;

Fig. 10 is an end view of the craft overturned and floating in water;

Fig. 11 is a side elevation view of the craft of Fig. 8 with a canopy;

Fig. 12 is a side elevation view of a craft similar to that of Fig. 8 except that it is longer; and

Fig. 13 is a side elevation view of a craft with double arch members.

Best Mode for Carrying Out the Invention

Referring to Fig. 1, the craft 10 includes a craft body 13 comprising sidewalls 12, 14, 16, and 18, relatively short end walls 19 and a floor panel 20. The sidewalls and end walls are buoyancy members. The sidewalls 12, 14, 16, and 18 and endwalls 19 are made of inflatable tubes. A canopy superstructure 15 is formed by inflatable tubular members 22, 24, 26, 28, which extend upwardly from the sidewalls 12, 14, and initially extend outwardly to outermost points 29 and then inwardly to a ridge member 33. The ridge member 33 comprises an inflatable tube extending generally horizontally in the longitudinal direction of and parallel to the craft body 13. The craft 10 has a center of gravity 54 which is above a line of rotation 31 (the water line) so that the craft rotates about line of rotation 31 in returning to the upright condition.

Since the canopy superstructure 15, which consists of inflatable tubular members 22, 24, 26, and 28 and ridge member 33 illustrated in Fig. 1, may be susceptible to distortion or collapse in the longitudinal direction, i.e. in the general direction of arrow A in Fig. 1, the craft includes a tie 35 fixed to and extending between points 37 and 39.

SISSTITUTE SHEET (RULE 26)

The point 37 is provided at the end of the ridge member 33 and the point 39 is provided on the short end wall 19 of the craft body 13. The tie 35 is a flexible strap secured at each of its ends by suitable reinforcing patches affixed to the material of the ridge member 33 and the end wall 19. The tie or strap 35 is flexible so as to collapse and be packed with the craft when it is deflated and inside a protective storage casing (not shown) but is substantially inextensible so as to inhibit distortion or collapse of the canopy superstructure 15 in the direction of arrow A. A symmetrically arranged tie 35A is provided at the opposite longitudinal end of the craft for inhibiting distortion or collapse of the canopy superstructure 15 in the direction opposite to that shown by arrow A.

Although the ties 35, 35A are illustrated as flexible straps, they could be made for example as cables, or even rigid links, such as a tie being composed of a number of rigid rods hinged together so that when the craft is erected by inflation, the links adopt a straight line configuration the same as the illustrated tie 35.

Referring to Fig. 2 a variation of the embodiment of Fig. 1 comprises inclined tubular ridge members 45 and 45A which are inflated simultaneously with the other inflatable components of the craft 10. The inflatable tubular ridge members 45 and 45A function in the same manner as the tie straps 35 and 35A of Fig. 1 by inhibiting distortion or collapse of the canopy superstructure 15 from the illustrated position in the direction of arrow A.

Also shown in Fig. 2 are lateral ties 55, 57. These extend between points 65, 67 and 75, 77, respectively, located on the upper portions 32 of opposed tubular members 26, 28 and 22, 24, respectively. The lateral ties 55, 57 inhibit distortion or collapse of the tubular members in a direction away from each other transverse to the general longitudinal

line of the elongated craft 10, e.g. as would occur upon distortion of the canopy superstructure 15 of the downward direction illustrated by arrow B. The lateral ties 55, 57 can be used in addition to the ties 35 and can be made of similar materials such as flexible lines, straps or rigid links.

Referring to Figure 3 there is shown a rectangular craft 10 with a canopy superstructure 17 consisting of four sets of inflatable tubular members 22, 24, 26 and 28 joined to the upper sidewall 12 and extending upwardly and outwardly to a point outboard of the sidewalls 12 and 14, and then inclined upwardly and inwardly to a common junction 25. Ties 85 and 87 connect each of the tubular members 22, 24, 26 and 28 to the upper sidewall 12 on either side of thereof. A canopy 34 is affixed to the tubular members 22, 24, 26, and 28 and extends down to and is affixed to the upper sidewall 12. A door 20 provides access to an interior thereof.

The various ties 35, 35A, 55, 57, 85, 87 illustrated in the drawings can be all used simultaneously in one craft, although this may not be necessary. For example the ties 35, 35A in Fig. 1 provide substantially the same function as the ties 85, 87 would provide if associated with each of the inflatable tubular members 22, 24, 26, 28 in Fig. 1.

Referring to Figures 4, 5 and 6 there is shown the various dimensions that are appropriate for the craft of Figure 3

Referring to Fig. 7, rather than utilizing ties or straps, it is possible to apply a canopy 49 affixed to the interior side of the inflatable tubular members 22, 24, 26, 28, 45 and 45A. By affixing the canopy 49 along the length of the latter members, the cloth of the canopy 49 itself serves as the ties 35 and 35A. The canopy 49 can equally as well be affixed to the exterior side of the inflatable tubular members 22, 24, 26, 28, 45 and 45A

and serve the same function. As a further alternative two canopies may be used, one connected to the interior side of the inflatable tubular members 22, 24, 26, 28, 45 and 45A and one to the exterior thereof. Yet a further alternative is to incorporate the ridge member 33 and inflatable tubular members 45 and 45A into the canopy itself.

Referring to Figs. 8 to 11, an alternative self-righting design, having advantages over the Wright design, has arch tube members 42 and 43 which have a diameter wider than the width of the bottom and top tubular sidewalls 40 and 41, respectively, and may join the bottom tubular sidewall 40. The top tubular sidewall 41 passes through the arch tubes members 42. With this design the center of mass 48 of the craft is located along the center of the craft slightly above the bottom tubular sidewall 40 but below the top tubular sidewall 41. The centre of rotation 17 of the arch tube members 42 and 43 (see Fig. 9) is above the centre of mass. The separation of the center of mass 48 from the radius center of rotation 17 is known as the eccentricity, e. Where the centre of rotation is significantly above the sheer line 47 the arch members will extend outboard of the craft but where the centre of rotation is closely above or below the sheer line the arch members will not extend outboard beyond the vertical edge 58 of the craft. It should be noted that the bottom tubular sidewall 40 is not vertically below the top tubular sidewall 41 but its center is located at radius R from point 17 as with the top tubular sidewall 41, thereby not inhibiting the self-righting motion. Where the sidewall members are of different size (radius) it is important to ensure that the outboard edge of the bottom sidewall member is at or within the arc made from the centre of rotation to the outboard edge of the upper sidewall member, R'.

The complete tubular structure shown in Figure 9 includes bottom tubular sidewall 40 and top tubular sidewall 41, a pair of arch tube members 42 and 43 joined to the top tubular sidewall 41. Tubes 44 and 36

SϋBSmUTE SHEET (RULE 26)

which connect the longitudinal tube 46 to the curved ends of the top tubular sidewall 41, function as added reinforcement against collapse of the tubular members along the length of the craft 11. A flexible upper membrane 56 is affixed around the top of the top tubular sidewall 41 around the perimeter thereof to provide a floor. Ordinarily a lower flexible membrane is affixed between the sidewalls around the perimeter thereof to form an insulating shield to prevent water from directly contacting the upper membrane and to provide insulation.

Referring to Fig. 10, the craft after inflation and in a non- upright position will normally move to a position in which the bottom and top sidewalls 40 and 41, respectively, are floating at the surface of the water and the sheer line 47 makes an angle of A with the vertical. In this position the center of mass of the craft is displaced to the left of the line 30 where the craft rotates on the water and so the craft is tipped upright in the direction of the arrow. The buoyancy of the raft acting vertically upward substantially through the center of rotation and the weight force of the craft acting through the center of mass provide a couple or moment which acts to rotate the craft to a stable position. Point 30 is essentially a line on the water upon which the craft rotates. When in the stable position the line effectively becomes the width of the base but during rotation the line is quite narrow and may be considered a line. In the cross sectional view this line is delineated by point 30 (refer Fig. 10). In the event the craft is temporarily moved opposite to the direction of the arrow C shown in Fig. 10, it will return with some speed and immediately tip about line 30 and right itself. Consequently, there are no stable positions available in which the craft is not upright.

Referring to Fig. 11, the complete craft of Fig. 9 is shown with a canopy 49 attached along the length of each of the arch tube members 42

and 43 and the longitudinal tube 46 and top tubular sidewall 41. A door 50 provides access to the interior of the craft 11.

Fig. 12 illustrates another embodiment in which the length of the craft is increased by simply adding another arch member to provide three arch members 63, 64 and 70 with an associated increase in the length of the longitudinal member 60 and the sidewalls 61 and 62. The canopy in this case has two doors 66 and 71 and is attached along line 38 to the bottom sidewall member 61.

In order to provide greater strength against collapse, a double arch member construction may be used as shown in Figure 12.

It will be seen that the craft according to the present invention can enable improved reliability in self-righting of the craft, particularly if it is inverted when it is first being inflated. When this occurs, the tendency of the inflatable tube members is to fail to inflate to their finally desired operative positions and will not be as effective in preventing inversion. However, the provision of ties between points whose separation is increased upon distortion or collapsing or a canopy affixed to these members facilitates more efficient erection and therefore self-righting of the craft.

Each of the craft in Figures 1 to 10 can be non-inflatable as long as the superstructure is buoyant. Other craft with buoyant superstructures as shown in the drawings herein can also function as self- righting craft.