WO1991003931A1

WO1991003931A1 - Walkway unit

Info

Publication number: WO1991003931A1
Application number: PCT/GB1990/001428
Authority: WO
Inventors: Jonathan Michael Cassidy
Original assignee: Dunlop Limited
Priority date: 1989-09-20
Filing date: 1990-09-17
Publication date: 1991-04-04
Also published as: GB2236715A; DK34592A; IE903389A1; DK34592D0; IS3625A7; IE65266B1; GB8921259D0; AU6420690A; GB2236715B

Abstract

A walkway unit (40) for use in providing a walkway for a flexible buoyant structure such as that of a pair of hoses forming a part of the frame of a fish farming apparatus comprises a location portion (42) which supports a tread portion (41) and provides a pair of recesses (44) which face outwardly in opposite directions for location relative to a buoyant structure.

Description

WALKWAY UNIT

This invention relates to a walkway unit and in particular, although not exclusively, to a walkway unit for use in conjunction with a flexible buoyant structure. It relates also to a buoyant assembly comprising one or more of said walkway devices and a flexible structure typically but not necessarily of an elongate form.

One established use of an elongate and flexible buoyant structure is for forming a floatable frame of a fish farming apparatus. The floatable frame serves to support a submerged net or like device which acts as a fish enclosure, and the flexibility of the frame allows it to move horizontally and vertically in response to tide and wave action thereby to avoid or minimise the risk of the frame experiencing damaging forces. The floatable frame, particularly when of large size or shaped to have a plurality of cage sections, is used also to support a walkwa by means of which fish farming operatives can gain access either for the purpose of tending the fish or maintaining the fish farming apparatus.

In the case of buoyant structures of a kind comprising, for example, a pair of hoses or like flexible members arranged to extend side-by-side a particular problem can arise in providing a durable and effective walkway for support by the hoses. It is known (see for example International Patent Application Publication No. WO 85/03411) to provide a twin hose type frame section of a fish farming apparatus with a walkway which spans and is supported by the two hoses. The walkway comprises groups of battens which extend lengthwise of the hoses and are secured to ■ a tubular frame mounted on the hoses. Successive groups of battens may be flexibly interconnected but despite this flexible interconnection it is considered that the need firmly to secure the groups of battens to the hoses undesirably restricts the ability of the hoses to accommodate both vertical and horizontal deflections.

The present invention seeks to provide a walkway unit of a kind particularly suitable for forming a walkway for a buoyant structure such as one of the kind comprising a pair of elongate flexible members, for example flexible hoses, arranged to extend parallel with one another in a side-by-side relationship. The invention seeks also to provide a buoyant assembly of a flexible structure and one or more walkway units of the invention.

In accordance with one of its aspects the present invention provides a walkway unit for a flexible buoyant structure comprising a tread portion and location means, said location means depending from an underside of the tread portion and comprising a pair of retention surfaces each of which presents a recess, the two recesses being arranged to face in opposite directions and outwardly from the unit.

The retention surfaces may be defined by a substantially rigid location means which may be of a hollow or solid form. Preferably, however, the retention surfaces are defined by a pair of independently flexible retainers and more preferably said retainers are spaced whereby each may be deflected transversely, in a first direction parallel with the plane of the tread surface, towards the other retainer. It is further preferred that each said retainer have a distal portion which is substantially wholly flexible whereby at least said distal portion may be temporarily deformed for location or removal of the walkway unit relative to a flexible buoyant structure.

The length of each recess, as considered in a second direction parallel with the plane of the tread portion and perpendicular to said first direction, preferably is less than the distance for which the tread portion extends in said direction.

The length of the tread portion as considered in said second direction may be equal to or greater than the length of said portion in said transverse, first direction, but preferably is less than the transverse length in order to prevent undue restriction on flexibility of the flexible members.

The tread portion preferably has a pair of opposite edges which are parallel with one another and extend generally in said first, transverse direction. Suitable shapes for the tread portion include rectangular and trapezoidal shapes.

Where the retention surfaces are defined by a pair of independently flexible retainers, preferably the retainers are each of a web-like form of sheet- type material which is integral with the tread portion.

The tread portion and location means may each be formed from plastics material. Preferably they are of the same plastics material which is moulded to form an integral construction.

Particularly where the walkway unit is to be located between a pair of elongate members, such as reinforced hoses, of circular external cross-sectional shape, the recesses defined by the retention surfaces should be of a part-cylindrical shape which conforms or, subsequent to deformation of the retention surfaces when of a flexible kind, substantially conforms to the outer surface of a respective elongate member.

The present invention further provides a buoyant assembly comprising a pair of flexible members and a walkway unit of the present invention located between the flexible members with the flexible members extending at least partly into said recesses.

The invention envisages that securing means independent of the walkway unit shall restrain the flexible members from undue separation. If the flexible members are suitably restrained from undue separation it will be appreciated that the recesses can then be relied upon to co-operate with the flexible members to ensure that the walkway unit is restrained from being dislodged from the assembly in a direction perpendicular to the plane of the tread surface at least during normal use of the assembly.

The buoyant assembly may be buoyant by virtue of the flexible members being buoyant, e g buoyant hoses, by the location means of the or each walkway unit being buoyant or by attached buoyancy devices.

Preferably the buoyant assembly incorporates a walkway device of the kind having a pair of independently flexible retainers. The retainers may be provided in an arrangement in which, by virtue of their flexibility and the spacing of the flexible members, the walkway unit may be positioned or removed from between the flexible members without needing to separate the flexible members or with no more than a need to separate them only slightly.

In an alternative technique for constructing the buoyant assembly the flexible members may be moved towards one another from spaced apart positions so as to locate the flexible members in the respective recesses of the walkway unit and thereby lock the unit in position. In a further alternative the flexible members may be arranged in their required relative position, or substantially at that relative positioning and the walkway unit may then be slid into position from an open end of the pair of flexible members. These alternative procedures for construction may be utilised in a reverse sequence for removal and replacement of a walkway unit and they are particularly appropriate in the case of a walkway unit which has a location portion of a substantially rigid form.

Flexing movement of a buoyant assembly may tend to cause the walkway unit to move progressively along the length of elongate flexible members. Particularly in assemblies which do not have a plurality of walkway units sufficient to occupy substantially the whole of the length of the assembly or in which any intermediate securing means is not present to prevent such movement of a walkway unit, the surface of the or each recess for confronting a flexible member may be textured or otherwise adapted for securely frictionally engaging the flexible member; preferably the area of texturing is localised to a selective part of that area of the recess retention ourface which is for contact with a flexible member so that flexibility of the overall assembly is not unduly limited and so as to avoid undesirable abrasion of the surface of the flexible member.

It has been described that one or both of the flexible members may be of an elongate form and in particular may be in the form of a reinforced hose. The reinforced hose may be of a known kind, for example of a kind having buoyancy material built into the wall of the hose. It is to be understood, however, that the flexible member(s) need not be of elongate form, but may be of another form having an elongate edge or regions tor co-operation with location means of walkway units. Thus the walkway unit may be employed to provide continuity between two substantially flexible pontoon portions, the walkway units being located between confronting elongate edges of a pair of pontoon portions.

The buoyant assembly may be of a kind having flexible members which are elongate, and be utilised in forming the floatable frame of a fish farming apparatus. The buoyant assembly may be rectilinear for use in forming a polygonal frame or may be curved and thus suitable for forming a circular type frame.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:-

Figure 1 is a plan view of the outline of a floatable frame of a fish farming apparatus having a plurality of buoyant assemblies in accordance with the present invention; Figure 2 is a perspective view of a part of a buoyant assembly of Figure 1 and having walkway units in accordance with the present invention; Figure 3 is a perspective view of the walkway unit of Figure 2 with other parts of the assembly removed; Figures 4 to 6 are plan, end and side elevations respectively of a walkway unit of Figures 2 and 3; Figure 7 is a side view of a spacer for the hoses of the buoyant assembly of Figure 2; Figures 8 and 9 are perspective views respectively of two further embodiments of walkway units in accordance with the present invention, and Figure 10 is a side view of part of a walkway unit in accordance with a further embodiment of the present invention. A floatable frame 10 for a fish farm apparatus comprises six side members 11 interconnected in hexagonal form by six buoyant rigid connector units 12.

Each side member 11 is a buoyant assembly comprising a pair of flexible inherently buoyant reinforced hoses 13,14 of 370 mm outer diameter and which are interconnected with one another at their respective ends by the connector units 12. The pair of hoses is provided at 2 metre intervals with intermediate coupling means in the form of spacers 15 which maintain a small spacing of approximately 150 mm between the two hoses. An example of a suitable spacer is shown in Figure 7 and comprises a central link portion 16 and two adjustable ring portions 17. Subsequent to the spacers being provided on the hoses at the required positions (by sliding in the case of the type of spacer shown in Figure 7 and having an integral common link portion 16), the clamp means 18 is tightened to result in each ring portion 17 being secured to a respective hose 13,14.

Each side member 11 additionally comprises a plurality of walkway units 20 which will now be described in detail.

Each walkway unit 20 comprises a tread portion 21 which is of rectangular shape and in the form of an open type grating through which water may pass. The tread portion has associated therewith location means 22 for retention of the walkway units between the pair of hoses 13,14. The location means comprises a pair of flexible part-cylindrically shaped retention webs 23 which are spaced apart in a direction transverse relative to the length of the side member 11 and define a pair of oppositely and outwardly facing recesses 24. The retention webs 23 are formed from a plastics material such as polyethylene or polypropylene which is moulded to form an integral assembly of the web

23 and the tread portion 21. The flexibility of the plastics material is such that the tread portion, of a thickness in this case in the range 20 to 25 mm, may be substantially rigid especially as compared with the substantially flexible nature of the relatively thin retention webs 23 which in this case have a thickness typically of in the order of only 6 mm.

The webs 23 are each moulded to provide recesses

24 of an internal radius of curvature of approximately 185 mm, and the two webs 23 are spaced by a minimum of approximately 182 mm when in the absence of externally applied loads. The two webs 23 therefore are independently flexible and by virtue of their spacing they are each free to deflect inwards towards one another without at least initially coming into contact with one another.

Each tread portion has a width which is greater than its length as considered in the direction of the length of the frame, and typically is 33% greater than said length. The webs 23 each have a length as considered in said direction of the length of the frame which is less and in this case is half the length of the tread portion in that direction.

Each of the walkway units is positioned between the pair of hoses by flexing the webs 23 whereby their distal end portions 24 are moved together to a spacing of less than the 150 mm spacing of the hoses. The units are then inserted between the hoses, whereupon release of applied force on the webs allows them to return towards their initial shape. However, because the spacing of the hoses is less than the minimum spacing of the webs when unstressed, the webs bear positively against the outer surfaces of the hoses. The walkway units therefore are located by both a mechanical interlock of the hoses occupying the recesses 24, which restrains movement of the walkway unit out from between the hoses, and frictional engagement which restrains movement of the unit in a direction along the length of the hoses.

The walkway units are provided on each side member 11 in a number sufficient to result in the tread portions creating a substantially continuous walkway between the ends of the hoses. Accordingly any tendency for the units to move significantly along the length of the hose during flexing of the latter is resisted by the tread portions of successive walkway units coming into contact with one another, by end walkway units contacting the connector units and by walkway units contacting intermediate coupling spacers 15. To ensure that the tread portions do not abut to inhibit hose flexibility it is provided that their aggregate length in the direction of the length of the hose shall be less than the available length between the end connector units. Adjacent, confronting, edges of neighbouring walkway units may be provided with edge strips (not shown) of a substantially compressible material such as rubber so that the assembled walkway is rendered visually continuous without flexibility being impaired. In the aforedescribed side member 11 the tread portions of the walkway provide a substantially rigid walkway surface for the safe support of operatives whilst the flexibility of the webs 23 ensures that the flexibility of the twin hose assembly 13,14 is not significantly affected. The relatively shorter length of the web recesses as compared with the tread portion, as considered in the direction of the length of the hoses, further assists in avoiding undue restraint of hose flexibility. The flexibility of the web portions enables the walkway units to be inserted between a pair of hoses and removed therefrom without any need to separate the hoses.

In a further embodiment of the present invention (see Figure 8) a walkway unit 40 comprises a tread portion (shown in outline 41) substantially similar to the tread portion of the aforedescribed unit of Figures 4 to 6, and a location portion 42 of a substantially solid form. The location portion comprises a casing of pvc which encapsulates a buoyant filling of polyurethane foam. The pvc casing defines a pair of oppositely and outwardly facing recesses 44 which correspond in shape and positioning with the recesses 24 of the walkway unit of Figures 4 to 6. Because of the rigidity of this walkway unit, when being formed into an assembly with a pair of flexible hoses it is necessary either to separate the hoses or remove an end fitting whereby the walkway units may be slid lengthwise into position between the two hoses.

It is not essential that each retention surface forming a recess be of a continuous form. Thus the retention surfaces 50 may each comprise a pair of arcuate limbs 51 as shown in Figure 9. In a further form of a walkway unit (see Figure 10) the retention surfaces 60 defining the recesses may be formed from a grid type plastics moulding having a surface shape or texture which is well adapted for frictionally engaging the surface of a hose but which is of good flexibility so as to move in conformity with changes in the normally truly cylindrical outer contacting surface of the hose.

Claims

[received by the International Bureau on 18 February 1991 (18.02.91); new claims 12,16,17,21 and 22 added; remaining claims renumbered accordingly; original claims 1-11 unchanged (3 pages)]

11. A walkway unit according to any one of the preceding claims wherein each retention surface is of or substantially of a part-cylindrical shape.

12. A walkway unit according to any one of the preceding claims wherein the retention surfaces are substantially smooth curved surfaces of a concave shape.

13. A walkway unit according to any one of the preceding claims wherein the length of each recess, as considered in a second direction parallel with the plane of the tread portion and perpendicular to a direction in which the recesses face outwardly away from one another is less than the distance for which the tread portion extends in said second direction.

14. A walkway unit according to any one of the preceding claims wherein the length of the tread portion in the direction in which the recesses face outwardly and oppositely is greater than the length of the tread portion in a direction perpendicular thereto.

15. A walkway unit according to any one of the preceding claims wherein the walkway unit has at least one edge which extends substantially in a transverse direction parallel with the plane of the tread surface, and said edge is provided with an element of compressible material.

16. A walkway unit according to any one of the preceding claims wherein the length of the tread portion in a first, transverse direction parallel with the plane of the tread surface and with the direction in which the recesses face outwardly away from one another is at least equal to the maximum spacing, in said first direction, of structure defining the recesses.

17. A walkway unit according to any one of the preceding claims wherein said unit is bereft of securing means to restrain separation of a flexible buoyant structure from the unit.

18. A walkway unit according to claim 1 and constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings. 19. A buoyant assembly comprising a pair of flexible members and a walkway unit according to any one of the preceding claims located between the flexible members with the flexible members extending at least partly into said recesses.

20. A buoyant assembly according to claim 19 wherein securing means is provided independent of the walkway unit to restrain separation of the flexible members.

21.. A buoyant assembly according to claim 19 or claim 20 wherein the recesses co-operate with the flexible members to ensure that the walkway unit is restrained from being dislodged from the flexible members in a direction perpendicular to the plane of the tread surface at least during normal use of the assembly.

22. A buoyant assembly according to any one of claims 19 to 21 wherein the length of the tread surface of a walkway unit in a direction perpendicular to the elongate flexible members is greater than the spacing of those members.

23. A buoyant assembly according to any one of claims 19 to 22 wherein the assembly is provided with flexible members which are buoyant.

24. A buoyant assembly according to any one of claims 19 to 23 wherein at least one of the flexible members is a flexible reinforced hose.

25. A buoyant assembly according to any one of claims 19 to 24 wherein at least one of the flexible members is of an elongate rectilinear form.

26. A buoyant assembly according to any one of claims 19 to 24 wherein at least one of the flexible members is of an elongate and curved form.

27. A buoyant assembly according to any one of claims 19 to 26 wherein a plurality of walkway units is provided and at least one of the confronting edges of a neighbouring pair of walkway units is provided with an element of compressible material arranged for contact with the other walkway unit of the pair.

28. A flexible buoyant assembly for forming at least a part of the floatable frame of a fish farming apparatus, said flexible buoyant assembly comprising a pair of flexible buoyant hoses arranged to extend substantially parallel with one another and maintained against separation by end connectors and intervening spacers, and supported by said hoses a plurality of walkway units each comprising a tread portion and a location means which depends from an underside of the tr.ead portion and comprises a pair of independently flexible retainers each of substantially part-cylindrical shape and arranged to define a pair of oppositely and outwardly facing recesses which in the assembly are occupied by portions of the respective hoses, a plurality of the walkway units being provided whereby the tread portions of successive units form a substantially continuous walkway surface along the length of the assembly.

29. A buoyant assembly constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

30. A floatable frame for fish farming apparatus comprising a buoyant assembly according to any one of claims 19 to 29.

31. A floatable frame for fish farming apparatus constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.