WO2004029364A1

WO2004029364A1 - Mobile bridge and segment for such a bridge

Info

Publication number: WO2004029364A1
Application number: PCT/SE2003/001497
Authority: WO
Inventors: Torsten Höglund
Original assignee: Försvarets Materielverk
Priority date: 2002-09-25
Filing date: 2003-09-25
Publication date: 2004-04-08
Also published as: SE523664C2; SE0202830L; SE0202830D0; AU2003264574A1

Abstract

The invention relates to a mobile bridge, a segment and a sectional part for a mobile bridge. There are various types of mobile bridges; the invention relates mainly to a scissor-type bridge, which is usually transported on a tracked vehicle. The bridge according to the invention comprises two bridge halves (4, 5) joined by a link (6). Each bridge half (4, 5) has two segments (71, 72, 73, 74) comprising closed sectional parts (8) of extruded aluminium with stiffeners (9) in the form of a frame-work. The sectional parts (8) are joined by the welding method FSW (Friction Stir Welding) to form a load-bearing box section (10) comprising an upper part (11), two web parts (12, 13) and a lower part (14).

Description

MOBILE BRIDGE AND SEGMENT FOR SUCH A BRIDGE

The invention relates to a mobile bridge, a segment and a sectional part for a mobile bridge. There are various types of mobile bridges; the invention relates mainly to a scissor-type bridge which is usually transported on a tracked vehicle. Scissor-type bridges are used to bridge small watercourses and other types of obstacles that may exist on the ground.

Prior-art scissor-type bridges consist of two bridge halves which are articulated in the centre. During transport, the bridge is folded in two on the tracked vehicle. Laying out and recovery of the bridge are carried out by means of a hydraulic laying device on the tracked vehicle. Document US 5,276,930 discloses an example of such a bridge.

Mobile bridges are mainly used by the army to achieve accessibility for its vehicles which in recent years have become heavier and heavier. In order to manage increas- ingly heavy vehicles, the bridges have been reinforced and have thus also become heavier. The bridges that are currently used have reached a limit where bridge and bridge carrier cannot be heavier without significantly deteriorating mobility.

The object of the invention is to provide a bridge which is lighter and manages heavier loads than prior-art bridges.

The present-day bridges are often made of steel. The bridge parts are welded together and obtain their load-bearing capacity by means of box girders with stiffening bulkheads and/or a framework configuration. Steel bridges of this type cannot be made lighter while at the same time they should manage heavier loads. Other lighter materials, above all aluminium, have previously been used to save weight in mobile bridges, see for instance US 5,724,691. The bridge according to the US patent is manufactured according to the same principle as steel bridges, i.e. with box girders with welded stiffening bulkheads and/or a framework configuration. Welding in alu- minium, however, implies that the material is detrimentally affected by a reduced strength due to the action of heat. This can be taken care of by a stronger construction, which will be heavier, or an expensive and complicated heating process in order to restore the original properties of the aluminium. In order to avoid these drawbacks, the inventive bridge is mainly made of aluminium which is joined without the problems caused by ordinary welding.

Document DE 32 44 576 Al discloses a bridge beam section made of extruded alumi- nium sections and aluminium sheets which are joined by gluing. This results in elimination of the problems with reduced strength. On the other hand, the beam is made with stiffening bulkheads and metal sheets as upper part and web parts. To achieve the ultimate bearing resistance that is required in mobile bridges for heavy loads, this type of construction would nevertheless be too heavy.

The invention solves the above problems by a mobile bridge comprising a closed extruded sectional part of aluminium comprising stiffeners according to the appended claims.

The invention will now be described in more detail with reference to the following Figures:

Fig. 1 Bridge on tracked vehicle.

Figs 2a-b Side view and top plan view of laid-down bridge. Fig. 3 Sectional part.

Fig. 4 Top plan view of bridge half.

Fig. 5 a Side view of bridge segment.

Figs 5b-c Cross-sections AA and BB of bridge segment.

Fig. 6 Bridge segment in cross-section. Fig. 7 Bridge segment in cross-section.

Fig. 8 Transverse bracing.

Fig. 9a Side view of link.

Fig. 9b Top plan view of link.

Fig. 10 Bridge end. Figs 11 a-b First wire guide in a side view and in cross-section.

Figs 1 lc-d Second wire guide in cross-section and in a side view.

Fig. 12 Side view of one end of a bridge half.

Fig. 13 Bridge half in cross-section DD.

Fig. 14 Bridge half in cross-section EE. Fig. 1 shows a scissor-type mobile bridge (1) arranged on a carrier, usually a tracked vehicle (2). The tracked vehicle (2) is provided with a laying device (3) which comprises, inter alia, an arm which is releasably attached to the bridge (1).

Figs 2a-b show a laid-down bridge (1). The bridge consists of two bridge halves (4, 5) joined by a link (6). Each bridge half (4, 5) comprises two segments (71, 72; 73, 74) which form a roadway.

Fig. 3 shows a preferred embodiment of a sectional part (8). The sectional part (8) is made of extruded aluminium and has a closed profile, essentially square, and a stiffening interior in the form of a framework (9). The sectional part can also have a stiffener in some other shape or of some other material, such as foam.

Figs 4 and 5a show a bridge half (4) from above and in a side view. The bridge half comprises two segments (71, 72) which are held together by crossbars (50, 51). At one end of the segments (71, 72) there is a bridge end (30) which is used as an on-ramp for vehicles. The link (6) and a wire guide (20, 21) are arranged at the other end of the segments (71, 72). The load-bearing box section (10) has segments of different appearances. Figs 5a-5b show the cross-sections AA and BB respectively. The section CC is shown in Fig. 7.

Fig. 6 is a cross-section of a segment (71, 72, 73, 74). The cross-section has a closed profile, box section (10), consisting of four parts, an upper part (11), two web parts (12, 13) and a lower part (14). The parts (11, 12, 13, 14) are joined by a suitable method, for instance welding or gluing. All parts preferably consist of a number of sectional parts (8) joined by the welding method FSW (Friction Stir Welding).

The welding method FSW, Friction Stir Welding, implies that a pin is rotated between the edges that are to be welded together. The rotation causes the material to be stirred up and a very homogeneous and pore-free weld forms. The joint has essentially the same strength as the basic material. By making the welding depth somewhat greater than the thickness of connecting parts, the weld can be made stronger than connecting parts. In other welding methods, there will be a reduction of the strength in the heat-affected zone, HAZ. In the materials that are commonly used in extruded aluminium sections, the reduction is approximately 40% in the HAZ. In Fig. 6, four sectional parts (8) are joined to form an upper part (11). The web parts (12, 13) consisting of two sectional parts (8) are vertical and welded or glued to the upper part (11). As both the webs (12, 13) and the upper part (11) have great torsional rigidity in the transverse direction, no transverse bracings are required, possibly except in the link (6), in the abutments (40) and in the crossbars (50, 51).

The lower part (14) preferably consists of sectional parts (8) joined by the FSW method. They are possibly reinforced with strands of carbon fibre (not shown) which are secured by gluing to the link (6). Alternatively, the lower part (14) may comprise a metal sheet, girder construction or the like.

The webs (12, 13) according to the construction will be sufficiently flexurally rigid to make it possible to fasten crossbars (50, 51, 55), eye bolts, guide bars for wires etc. in a simple manner. Fastening suitably occurs by screw joints or gluing in order to prevent strength from being affected by e.g. welding. Fig. 8 shows an example of how crossbars (50, 51) and diagonal cross braces (55) can be fixed. The crossbars (50, 51) and the diagonal cross braces (55) are fixed to T beams (53, 54) which are attached to the underside of the upper part (11) and to the web parts (12, 13) of the different segments (71, 72; 73, 74). The lower T beams (54) are welded to a plate (56) and a transverse supporting beam (52). The plate (56) is fixed to the web (12, 13) by a number of screw joints (57).

One of the important distinctions compared with prior-art scissor-type bridges that are made of box girders of steel and obtain their rigidity and load-bearing capacity by stiffening bulkheads and/or framework is that the invention uses extruded box sections which together form a large box section as a load-supporting construction.

In the shown bridge, deck, web and lower parts consist of identical sectional parts. The advantage is that only one section tool has to be developed. However, this results in the webs and the lower part being oversized. In large-scale production, a number of different sectional parts can be used instead. They can be more adjusted to their function and payload, which can reduce the weight still more.

Fig. 7 shows section CC in Fig. 5a. The box section (10) is, in the vicinity of the bridge end (30), provided with supporting web parts (41) outside the web parts (12, 13) and also a central support (42) in the middle of the segment. The additional support parts (41, 42) support the upper part within the on-ramp of the bridge. The part closest to the bridge end, about 1 m, is also used as abutment for the bridge, i.e. it abuts on the ground when in use. The Figure also shows lugs (40) which rest on corresponding lugs on the other bridge half when the bridge is folded. The lugs (40) are placed straight under the web parts (12, 13) in order to resist the shock load as the bridge halves are being folded up.

Figs 9a-b show an example of how a link between the bridge halves can be designed. The link comprises hinge parts (61, 62) which are arranged adjacent to the lower part (14) of the segments. The hinge parts (61, 62) in the Figure are made of extruded alu- minium and glued (64) to the segments (71, 73). Another embodiment of the link (6) involves the use of a milled and drilled section of aluminium or steel which is glued or welded to the segments (71, 73). The hinge parts (61, 62) are joined by a pin (63) extending along the entire length of the link (6).

Fig. 10 illustrates a bridge end (30). The upper part (11) of a segment is welded to the lower part (14) and also to an end section (31) of aluminium. The end section (31) has a fastening device, for instance in the form of a nut joint (33), which secures a wear section to the end section. The wear section (32) can also be made of aluminium, but is preferably made of stainless steel for better resistance to mechanical damage.

When being laid down, the bridge is first raised to a vertical position, after which the parts of the bridge are folded apart by means of a wire device according to prior-art construction, see for instance the Armoured Bridge Layer 971 A of the Swedish army.

The segments have a wire guide (20, 21) arranged at one end of the segments (71, 72, 73, 74). Figs 1 la-b show a first wire guide (20) arranged adjacent to one segment (71) of a bridge half. Figs 1 lc-d show a second wire guide (21) which is arranged adjacent to the other segment (72) of the same bridge half. Fig. l ie also shows how a first wire guide (20) from the second bridge half is accommodated between the box structure and the second wire guide (21) when the bridge has been laid out. The wire running in the wire guide (20, 21) is passed along the curved surface in a strip (25) which is screwed to the wire guide (20, 21) or releasable therefrom in some other way. When the strip (25) is worn out, it can easily be replaced instead of the entire wire guide (20, 21) being replaced. The wire guide (20, 21) can be made of steel or aluminium, but preferably a sectional part is used, which is cut to a suitable shape and provided with mountings for the strip (25). Fig. 12 shows one end of a bridge half with a link (6). Fig. 13 shows section DD from Fig. 12. Two bridge segments (71, 72) are juxtaposed with a gap between them. The wire guide (20) is fixed by screw joints to a web part (12) of one segment (71) and the other wire guide (21) is fixed to the web part (13) of the other segment (72).

Fig. 14 shows section EE in Fig. 13. The link (6) which comprises a hinge part (61) is arranged adjacent to the segment (72) and a corresponding hinge part adjacent to the corresponding segment of the other bridge half.

The top face of the upper part, the roadway, can suitably be provided with a non-skid coating; the outer areas of the bridge segments should have a thicker coating than in the inner area since wear caused by tracked vehicles is greater than wear caused by wheel-mounted vehicles. Without, or in combination with, a non-skid coating, antiskid protection can be provided by the grooves (81), see Fig. 3, in the roadway being given a deformation (82), being pressed down, at regular intervals.

The present invention relates to a scissor-type mobile bridge, a segment and a section for such a bridge. The section is made of extruded aluminium and has a closed profile with a stiffener, preferably a framework. The segment is made up of a plurality of sections joined by the welding method FSW. The segment has a load-bearing box construction, which, when the segments are joined by a link to the bridge, gives the bridge its rigidity and load-bearing capacity. The segment and the sectional part can with, or without, modification also be used for other types of mobile or stationary bridges.

Claims

1. A scissor-type mobile bridge, comprising two bridge halves (4, 5) joined by a link (6), c h a r a c t e r i s e d in that a bridge half (4, 5) comprises a segment (71, 72, 73, 74), which comprises at least two closed sectional parts (8) made of extruded aluminium, comprising stiffeners (9), and joined to form a load- bearing box section (10).

2. A scissor-type mobile bridge as claimed in claim 1, c h a r a c t e r - i s e d in that the stiffeners (9) form a framework.

3. A scissor-type mobile bridge as claimed in claim 1 or 2, c h a r a c t e r - i s e d in that the sectional part (8) and the stiffeners (9) are made as one part by extrusion.

4. A scissor-type mobile bridge as claimed in any one of claims 1-3, c h a r - a c t e r i s e d in that the segment (71, 72, 73, 74) comprises at least two sectional parts (8) joined by the welding method FSW (Friction Stir Welding).

5. A scissor-type mobile bridge as claimed in claim 1, c h a r a c t e r i s e d in that the box section comprises an upper part (11), two web parts (12, 13) and a lower part (14), and that at least one of the parts comprises two sectional parts (8) with a closed profile containing a stiffener (9) and made of extruded aluminium, which are joined by the welding method FSW (Friction Stir Welding).

6. A scissor-type mobile bridge as claimed in any one of claims 1-5, c h a r - a c t e r i s e d in that the sections are reinforced with strands of carbon fibre which are secured by gluing to the link (6).

7. A scissor-type mobile bridge as claimed in any one of claims 1-6, c h a r a c t e r i s e d in that a segment (71, 72, 73, 74) is joined to the link (6) by gluing.

8. A scissor-type mobile bridge as claimed in any one of claims 1-7, c h a r - a c t e r i s e d in that the link (6) comprises a hinge part (61, 62) made of extruded aluminium.

9. A scissor-type mobile bridge as claimed in any one of claims 1-8, c h a r a c t e r i s e d by a laying device comprising a wire guide (20,21) arranged at the end of each segment (71, 72, 73, 74), comprising at least one sectional part (8) and a wear strip (25) which is releasably arranged along the curved part where the wire runs.

10. A segment for a mobile bridge, comprising three parts, an upper part (11), a web part (12, 13) and a lower part (14), c h a r a c t e r i s e d in that at least one of the parts comprises two sectional parts (8), with a closed profile containing stiffeners (9), made of extruded aluminium and joined by the welding method FSW (Friction Stir Welding).

11. A segment as claimed in claim 10, c h a r a c t e r i s e d in that an upper part (11), a lower part (14) and two web parts (12, 13) are joined to form a closed load-bearing box section ( 10) .

12. A segment as claimed in claim 11, c h a r a c t e r i s e d in that the upper part (11) and the web parts (12, 13) comprise two or more sectional parts (8) joined by the welding method FSW (Friction Stir Welding).

13. A segment as claimed in claim 12, c h a r a c t e r i s e d in that the lower part (14) comprises two or more sectional parts (8) joined by the welding method FSW (Friction Stir Welding).

14. A segment as claimed in claim 12, c h a r a c t e r i s e d in that the lower part (14) comprises a metal sheet, girder construction or the like.

15. A segment as claimed in any one of claims 11-14, c h a r a c t e r i s e d in that the upper part (11), the lower part (14) and the web parts (12, 13) are joined by welding or gluing.