A TRANSPORTABLE PONTOON

Abstract: A foldable, multi-hull pontoon suitable for use in bridging or as a ferry, comprises a sequence of trapezoidal hull plates (1) successively hinged to one another at their parallel edges so as to fold in concertina fashion, alternate pairs of the plates being mutually and transversely webbed at each end with collapsible triangular bulkheads (7) which define with the hull plates a series of triangular-section hulls (13). Gunwale spacing beams (40) are provided to stabilise the opened pontoon and to provide trackways.

Description: A TRANSPORTABLE PONTOON TECHNICAL FIELD This invention relates to a pontoon which can be folded for transportation upon a road vehicle. The pontoon is particularly, but not exclusively, applicable for use in bridging or as a ferry. BACKGROUND ART The majority of known transportable pontoons have the dis¬ advantage of being bulky and are disproportionately expensive to transport, a very large part of the transported volume being air. Attempts have been made to improve this situation by designing nestable pontoons, but even with these, a considerable amount of air space still requires transporting. Furthermore, mos existing pontoons must be launched and assembled individually and their deployment can be a time-consuming task in any bridging or ferrying operation. The present invention seeks to provide a foldable pontoon suitable for rapid deployment and having minimal enclosed air space in the transport mode. DISCLOSURE OF INVENTION According to the present invention a transportable pontoon includes: a multiplicity of substantially planar hull members each having a keel edge and a parallel gunwale edge, which members are successively hinged In sealed relationship at alternately conjoined keel edges and gunwale edges so as to fold respectively inwardly and outwardly in concertina fashion; and a collapsible bulkhead member extending in sealed relationship between each inwardly folding pair of hull members adjacent each end thereof, which bulkhead members define with the hull members a sequence of parallel hulls when the pontoon is extended. The bulkhead members may each converfi-ently comprise a flexible membrane which will fold between the hull members when they are closed towards one another. Alternatively each bulkhead member may comprise a centrally articulated pair of plates, hinged at their outer edges to the associated hull members so as to fold inwards when the pontoon is folded. Sealed hinged inter-connection of the hull and bulkhead members may be conveniently achieved by the use of flexible joints, sealed between the respective members. Alternatively, where a more robust OM construction is required, the hinges are -preferably of conventional, non-sealing pin type in combination with a supplementary sealing means , for example, a flexible membrane sealed to the conjoined members in parallel wi th the p in hinge so as to bridge the gap between the members. The hull members are pref erably of a buoyant material and weighted at the keel edges so as to have positive meta-centres to ensure that the pontoon will float upright when folded. This permits the pontoon to be speedily launched whilst still folded and easily unfolded whilst water-borne thus avoiding the necessity of employing cranes. The pontoon preferably further includes at least one gunwale s pacing beam f o r use when the p ontoon is opened , which beam is provided with spaced engagement means successively co-operative with each conjoined pair of gunwale edges so as to locate them. The beam also provides transverse stiff ening to the hulls . The spacing beam may also be us ed to connect together two similar pontoons by co-engaging the outer-most gunwales of both, thereby to extend the sequence of parallel hulls. These spacing beams may additionally be arranged to s erve as trackways or to support subsidiary trackways. BRIEF DESCRIPT ION OF DRAWINGS An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings of which Figures 1 and 2 a re a p lan vi ew and an end elevation view respectively of an unfolded , 6-hull pontoon, Figure 3 is a view of the same pontoon f olded for transporta¬ tion, and Figure 4 is a representation of the same pontoon during launch. BEST MODE FOR CARR ING OUT THE-INVE T I0 N The six-hull pontoon illustrated In . Figures 1 and 2 comprises twelve identical trapezoidal hull plates 1 of a bouyant composite material such as a resin honeycomb within an alloy skin, each plate having a keel edge 2 , a gunwale edge 3 and two bulkhead edges 4. The plates 1 are successively interconnected by inner hinges 5 at the keel edges 3 , and outer hinges 6 at the gunwale edges 4 so as to fold alternately inwardly and outwardly. A folding bulkhead plate 7 of equilateral triangular form is connected transversely between the bulkhead edges 4 at each end of each inwardly folding pair of hull plafes 1 by inner hinges 8, the bulkhead plate 7 being divided at its centre line 9 into two sym¬ metrical triangular portions 10 and 11 interconnected"by outer hinges • 5 12 so that the portions 10 and 11 will fold inwardly to lie between the hull plates 1 when the pontoon is folded. The relative sizes and the material densities of the hinges 5, 6, 8 and 12 are selected to provide that the assembled plates are preferentially weighted at the keel edges 3 so that the hull plates 10 will float upright in the folded condition. When the pontoon is open, the hull plates 1 and the bulkhead plates 7 conjointly define six parallel hulls 13, all the inter¬ connections of which are internally sealed against ingress of water by a flexible membrane strip 14 adhesively applied to the conjoined 15 members so as to bridge the gap between them. The pontoon is bound in folded condition with a securing strap 30 (see figure 3) and may be conveniently launched into a river from • " a conventional tilt truck 31. Subsequent unfolding of the launched pontoon is illustrated in 20 Figure 4. The folded hulls 13 are first brought into alignment with the bank and the nearest hull plate 1 is tethered to the bank. Two gunwale spacing beams 40, each having seven spaced gunwale engagement sockets 41, are then first engaged with the gunwale edge 3 of the outermost hull 13 and pushed outwardly from the bank so as to 25 open the pontoon and permit the sockets 41 to engage successively with the gunwale edges 3 of each of the hulls 13. A greater pontoon length may be provided by co-engaging the final socket 40 with the outermost gunwale of a second folded pontoon inserted between the already unfolded one and the bank, which second 30 pontoon is then similarly unfolded with further spacing beams 40. It will be apparent that this process can be continued with successive pontoons and spacing beams to provide a ribbon bridge of desired length. The spacing beams also serve as trackways across the pontoons or 35 may be provided with support means (not shown) for subsidiary track¬ ways. A typical pontoon having 22 hulls comprised by 44 hull plates each measuring 9m (at the gunwale edge) x 2m can be compacted for transportation into a block which is no more than 2.4m thick, and unfolded into a raft measuring 9m x 40πi having a depth of 1.8m In a few minutes without the use of cranes. The unladen pontoon, which « has a f ree-board of 0. 8m, will survive a 9 knot current in the ' direction of the keels and can be crossed in currents of up to 6 knots by normal bridge loads typically reducing the free-board to 0.5m. When, the pontoon is intended or use as a ferry, ie to be driven In the direction of the keels, an apron (not shown) is preferably fitted over the bow and stern bulkheads so as to shed water from a central ridge to the outer-most gunwale to prevent swamping. A particular advantage of the triangular multi-hull con¬ figuration of this embodiment of the invention over conventional flat-bottomed pontoons is the increased resistance offered by the folded plate structure to vertical crushing loads such as can be applied to a pontoon when it is in a grounded state. A further advantage offered by the inherent stability of the folded pontoon is the capability of deployment by dropping from a transport aircraf t. It will be seen that the equilateral triangular hull sections of the particular embodiment described provide a pontoon which floats with approximately one half of its depth submerged when not loaded. Other embodiments of the present invention having less draught can be provided by including pairs of hull plates of shorter gunwale height in the sequence. For example , a pair of short gunwale-height plates so as to provide consecutive pairs of hulls with intersecting V- sections, ie pairs mutually having an open W-section. In such an arrangement the conjoining bulkhead members would be extended to full gunwale height and the gunwale spacing bars would engage with the full-height gunwales only . Obviously the- number of pa irs of short plates intermediate each pair of full plates can be increased to reduce draught st ill further, but res is tance of the structure to crushing loads will of course decrease proportionally. INDUSTRIAL APPLICABILITY The invention may be used to p rovide self-contained bridge suppo rting pontoons or f errying pont oons as already described . Structures in accordance with the invention may also be attached as folding side panels to an amphibious vehicle so as to be extendable when the vehicle is afloat, thereby to increase the vehicle' s beam and buoyancy, and hence increase its stability and load bearing capacity.

Claims: CLAIMS 1. A transportable pontoon characterised by : a multiplicity of substantially planar hull members- (1) each having a keel edge (2) and a parallel gunwale edge- (3) , which members are successively hinged in sealed relationship at alternately conjoined keel edges and gunwale edges so as to fold respectively inwardly and outwardly in concertina fashion; and a collapsible bulkhead member (7) extending In sealed relationship between each inwardly folding pair of hull members adjacent each end thereof , which bulkhead members define with the hull members a sequence of parallel hulls ( 13) when the pontoon Is extended. 2. A pontoon as claimed in Claim 1 characterised in that each hull member ( 1) is of a buoyant material and weighted at the keel edge so as to float substantially vertically when the pontoon is folded. 3. A pont oon as claimed in Claim 2 further characterised by including at leas t one gunwale spacing beam ( 40) having spaced engagement means (41) co-operative with each gunwale edge. 4. A method of launching the pontoon claimed in Claim 3 character¬ ised by including the s teps of : a. dropping the folded pontoon into a water gap, b. tethering the near-end hull member to the bank , c. engaging the far-end gunwale edge with a far-end engagement means of the gunwale spacing beam, d. thrusting the far-end gunwale edge away from the bank with the gunwale spacing beam whilst successively co-engaging each of the engagement means and gunwale edges in inwardly directed sequence as the pontoon extends. OMPI

Inventors: FITZGERALD-SMITH JAMES PATRICK, FITZGERALD-SMITH, JAMES, PATRICK
Applicants: SECR DEFENCE BRIT
Application year: 1983
Main classification: B63B35
IPC codes: B63B7, B63B35, E01D15