LADDER

Abstract: A ladder comprising a frame (2) pivotable between a folded-up and a folded-down position and connected to step members (3) via hinges (9) which, when the frame is folded up, allow the step members to lie in the plane of the frame and which, when the frame is folded-down, allow the step members to pivot to an active postion in which they extend substantially at right angles to the frame. Each step member (3) has its centre of gravity outside an imaginary plane extending through the associated hinges (9) and parallel to the plane of the frame (2). This causes the step members to be automatically and without external action unfolded to the position in which they extend at right angles from the frame, at the latest when the frame has reached its folded down, pendent position.

Description: LADDER Technical field of the invention The invention relates to a ladder comprising a frame pivotable between a folded-up inactive position and a folded-down and preferably vertically pendent position, said frame being connected to two or more step members via hinges which, when said frame is folded up, allow said step members to lie substantially parallel to or in the plane of the frame, and which, when said frame is folded down into its pendent position, allow said step members to pivot to a position in which they extend substantially at right angles to said frame. Such ladders are suitable for mounting on the drop- sides of platform vehicles, the step members being pi¬ voted, via axially spaced-apart hinges, to the inside of the associated dropside, such that, when the dropside has been raised to a position substantially perpendicular to the vehicle platform, said step members are hanging down substantially vertically from the pivot shaft on the inside of the dropside in a position in which they do not appreciably intrude upon the platform cargo space, and, when the dropside has been lowered and is hanging down preferably vertically, extend substantially at right angles from the dropside to facilitate climbing onto the platform. Background of the invention Ladders for platform dropsides are disclosed in U.S. patent specification 1,181,367 and GB patent speci¬ fication 181,485 and are convenient in that they facili¬ tate climbing onto the platform when the associated dropside is lowered/ and also do not intrude on the cargo space defined by all the dropsides. A drawback which they have in common is, however, that after lowering of the dropside, the step member must be released by a special manual operation from the position in which it is folded against the dropside. Thus, the ladder con¬ struction of U.S. 1,181,367 comprises a tongue attached to the free outer longitudinal side edge of the dropside and projecting perpendicular thereto. The tongue locks the step member in a recess in the dropside and is ex¬ tracted when the step member is to be pivoted to its active horizontally extending position. In addition, pivoting is rendered difficult by the two articulated tie rods at the opposite ends of the step member. Accord- ing to GB 181,485, the step member is kept locked in a recess in the dropside by means of a pivotable board or ruler which must be pivoted by hand from its locking position, before the step member can in turn be pivoted to its active position in which it extends at right angles from the dropside. The necessity of special manual release operations of the type described above of course makes folding-out of the step members rather time-consum¬ ing and is a source of irritation. A further drawback which the two prior art ladder constructions have in common is that they comprise but a single step member or foot plate and therefore are suitable merely for vehicles with comparatively low platforms, i.e. mainly city traffic vehicles having a low-clearance chassis. For the reasons above, these prior art ladder con- structions are directly unsuited for use on e.g. personnel carriers in the form of platform trucks. The chassis (and thus the platform) clearance of such vehicles is high so as to allow cross-country driving, and the ve¬ hicles must further be capable of quickly picking up a large or small number of combat troops. For military use in particular, where rapid embarkation may be a matter of life or death, it is crucial that climbing is not unnecessarily delayed, even by seconds, by for example the manual release of special locking means for the step members. Brief description of the inventive idea The present invention aims at eliminating the above- mentioned drawbacks of prior art ladder constructions of the relevant type and providing a ladder particularly suited for personnel carriers, which allows exceedingly rapid unfolding of the step members to their active position and convenient climbing onto vehicles having an extremely great chassis or platform height. Accord¬ ing to the invention, these and other objects are achieve in that each step member has its centre of gravity outsid an imaginary plane extending through the associated hinges and parallel to the plane of the frame, whereby said step members are automatically and without external action unfolded to the position in which they extend at right angles from the frame, at the latest when the frame has reached its folded-down pendent position. Although the inventive ladder is particularly advantageou for mounting on platform dropsides, it can also be used in other contexts, for example in a cassette adapted to be built into a vehicle chassis. Brief description of the accompanying drawings in the drawings: Figs 1 and 2 are perspective views of the ladder ac¬ cording to the invention, as seen from in front and from behind, respectively, and in its active state, Fig. 3 is a perspective view of the same ladder in its inactive state, Fig. 4 is a rear end view of part of a platform vehicle provided with a ladder according to the invention, Fig. 5 is a lateral view of part of the same vehicle provided with said ladder, Fig. 6 is a perspective view of an alternative embodiment illustrating the frame of the ladder and the step members, Fig. 7 is an end view of the same ladder frame mounted in a cassette, the frame being shown in its folded-down active state, Fig. 8 is a lateral view of the same ladder construction as shown in Fig. 7, and Fig. 9 is a lateral view of the ladder frame retracted into the cassette. Detailed description of a preferred embodiment of the invention In Figs 1-3, a ladder according to the invention is generally designated 1 and comprises a frame 2 and, in this case, three step members, 3, 3', 3". The frame 2 consists of two spaced-apart cross members 4, 5 in the form of flat iron bars and two spaced-apart side bars 6, 6' interconnected via the cross members and being in the form of L sections whose one flange 7 is aligned with the flat iron elements 4, 5 and whose other flange 8 extends perpendicular to the plane of the flat iron elements. Each step member 3, 3 1 , 3" is pivoted to the two L sections 6, 6 ' , in the example shown by a pivot shaft 9 whose two opposite end portions 9', 9" project through holes in the flanges 8 of the side bars 6, 6'. Instead of using a through shaft 9, it is of course possible to connect the step members to the frame by individual hinges, e.g. in the form of short pivot pins positioned along a common geometric pivot axis. The individual step member, e.g. the member 3", comprises two spaced-apart side portions 10, 10' in the form of flat iron bars or flat bar-shaped elements which at their free end facing away from the pivot shaft 9 are interconnected by means of two or more, in this case three flat bar elements 11, 11' , 11" which are spaced-apart so as to conveniently let through any dirt and the like adhering to the climber's shoes. As is clearly shown in, for example. Fig. 1, the step member 3" which in the active position of the ladder is the lowest step member, is considerably deeper than the next step member 3' which, in turn, is deeper than the uppermost step member 3. In actual practice, all step members may have a width of 250-350 mm, the depth of the bottom member 3" being 280 mm, the depth of the intermediate member 3' being about 200 mm and that of the top member 3 about 120 mm. The distance between the intermediate member 3' and the bottom member 3" preferably equals the distance between the top member 3 and the intermediat member 3'. This distance can in practice be about 300 mm so that the ladder will have a total height of about 600 mm. It should finally be noted that the two flat bar elements 10, 10' forming the side portions of each step member are, at their inner ends, extended in wedge-shape so as to provide a relatively wide or high terminal edge 12 for engagement with the flanges 2 and 7 of the frame. In the active state of the ladder, these terminal edges 12 constitute abutments which serve to take up any forces acting on the step member during climbing. It should also be noted that the pivot shaft 9 is posi¬ tioned adjacent the upper edge 13 of the side portions 10, 10 ', which means that the centre of gravity of the step member is positioned outside an imaginary plane extending through the pivot shaft and parallel to the plane of the frame. Reference is now made to Figs 4 and 5 which show the ladder mounted on a platform dropside, more precisely a rear dropside 14 of a loading platform 15 of, for example, a personnel carrier generally designated 16. Fig. 5 indicates by full lines the rear dropside 14 in its lowered state in which it is hanging from the loading platform, dash-dot lines indicating the drop- side in its raised state in which it extends perpendicular away from the loading platform. In its lowered state, the dropside 14 abuts against a stop member 17 ensuring that the dropside is hanging substantially vertically from the platform. In practice, the rear dropside 14 may be provided with two ladders 1, one on each side of the platform. The ladder 1 is mounted on that side of the rear dropside which forms the inside in the raised position. The function of the ladder is obvious; when the dropside is raised, the individual step members 3, 3 1 , 3" are hanging down vertically from the associated pivot shafts in a position adjacent the inside of the rear dropside. In this state, the step members do not intrude on the cargo space as defined by all the platform dropsides. When the dropside is then lowered to the position in¬ dicated by full lines, the step members are automatically and without external action folded out to the position in which they extend perpendicular away from the dropside as shown in Fig. 5, owing to their free mobility relative to the frame, combined with the fact that the centre of gravity of the step members is positioned outside the plane extending through all the pivot shafts. In other words, all step members are automatically folded out to their active position without any manual assistance whatsoever, at the latest when the dropside 14 has reached its lowered vertical position. Reference is now made to Figs 6-9 in which the ladder unit 1 is connected with a cassette or cassette- shaped unit which in its entirety is designated 18. The cross member 19 has, in this case, the shape of a shaft or rod the length of which slightly exceeds the width of the ladder 1 and which extends through holes in the flanges 8 of the frame side bars 6, 6' such that portions of the shaft project from the flanges 8 to form pivot pins 20. Each pivot pin 20 engages with an associated guide 21, 21' included in the cassette 18. More precisely, these guides are included in sections, each of which comprises a main web 22 and on one side a projecting upper flange 23 and, on the other side, two flanges 24, 24" extending inwardly towards the centre of the cassette, said flanges being spaced apart and parallel to form an elongate rectilinear groove. In the area of their one end, the two sections are inter¬ connected by means of a transverse metal sheet 25 which extends downwardly from the lower side of the cassette and which along its opposite short sides comprises trans¬ verse supporting metal sheets 25* whose upper edge is welded to the sections. This transverse sheet 25 serves as a support or abutment for the ladder unit 1 in its folded-down state. At the two opposite ends of the guides, stop members are arranged, in this case in the form of screws 26, 27, the first of which is situated very close to the outer or front end of the cassette and at a given distanc from the supporting sheet 25. More precisely, the distanc between the stop member 26 and the supporting sheet 25 should substantially equal the distance between the rod 19 and the plane in which the flanges 7 of the side bars of the ladder are positioned. To the outer or lower end of the ladder unit 1, a rubber loop 28 is attached to cooperate with a hook 29 on the supporting sheet 25 so at to lock the ladder unit 1 in its folded-up or inactive state. In practice, the above-mentioned cassette 18 may advantageously be mounted at the intended location by means of screws or bolts which are inserted through holes in the flanges 23 and are tightened on, for example, the lower side of a vehicle platform or a loading ramp. The ladder construction as described functions in the following way. Fig. 9 shows the ladder unit in its inactive position in which it is completely retracted in the cassette 18, i.e. the pivot pins 20 are engaged with the internal stop members 27; the ladder unit is locked in this position by means of the rubber loop 28 connected with the hook 29. When the ladder unit is to be folded down to its active position as shown in Figs 7 and 8, the loop 28 is disengaged from the hook 29, whereupon the ladder unit can be pulled horizontally out of the cassette 18. In interaction, the upper edge of the supporting sheet 25, the guides 21, 21' and the pivot pins 20 now forcedly guide the frame such that, while being pulled out, it is guided in one and the same horizontal plane as long as the pivot pins 20 are located at a distance from the stop members 26, which exceeds the distance between the stop members and the supporting sheet 25. However, as soon as the pivot pins 20 abut the stop members 26 and thus are in the area between the stop members and the supporting sheet 25, the ladder unit 1 is free to be pivoted to its folded- down position as shown in Fig. 8, in which it is hang- ing down vertically from the pivot pins 20. When the ladder unit is folded down in this way, the step members 3, 3 1 , 3" are automatically folded out to their active position in which they extend at right angles from the frame side bars 6, 6' as shown in Fig. 3. To move the ladder unit 1 back to the initial posi¬ tion shown in Fig. 9, the frame is pivoted upwards to a position in which it is slightly inclined upwards relative to the cassette 18, whereby the step members 3, 3', 3" are pivoted by gravity against the flanges 7 of the frame, whereupon the frame is pushed into the cassette while the pivot pins 20 guide the frame along the guides 21, 21' . The ladder construction illustrated in Figs 6-9 forms, in its folded state, a most compact unit which is readily mounted at any location, e.g. the loading platform or the frame of a vehicle (which need not be provided with platform dropsides) , the lower side of a loading ramp, a deck or the like. Conceivable modifications of the invention Of course, the invention is not limited to the embodiments described above and shown in the drawings. Thus, the construction of the step members may be varied in many ways. They can, for example, be designed as plates instead of the per se perferred grate structure shown in the drawings.

Claims: CLAIMS 1. A ladder comprising a frame (2) pivotable between a folded-up inactive position and a folded-down and preferably vertically pendent position, said frame being connected to two or more step members (3, 3', 3") via hinges which, when said frame is folded-up, allow said step members to lie substantially parallel to or in the plane of the frame and which, when said frame is folded down into its pendent position, allow said step members to pivot to a position in which they extend substantially at right angles to said frame, c h a r ¬ a c t e r i s e d in that each step member has its centre of gravity outside an imaginary plane extending through the associated hinges (9) and parallel to the plane of the frame (2), whereby said step members are automatically and without external action unfolded to the position in which they extend at right angles from said frame, at the latest when said frame has reached its folded-down, pendent position. 2. The ladder as claimed in claim 1, c h a r a c - t e r i s e d in that in the active or folded-down position of said frame, the bottom step member (3") is deeper than the next step member (3 1 ) which, in turn, is deeper than the top step member (3) . 3. The ladder as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that said frame (2) comprises two side bars in the form of L sections (6, 6 1 ) each of which has a flange (7) extending in a common plane, and a second flange (8) extending per¬ pendicular thereto, the width of said second flange at least equalling the height of the individual step member (3) . 4. The ladder as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that said step member (3) comprises two spaced-apart side portions (10, 10") in the form of flat iron bars or flat bar-shaped elements (10, 10') which at their- free end facing away from said pivot shaft are interconnected by means of two or more, preferably three flat bar elements (11, 11', 11"). 5. The ladder as claimed in claim 1, for hinged dropsides of a vehicle, particularly a personnel carrier, c h a r a c t e r i s e d in that said frame (2) is arranged on the inside of said dropside (14); when said dropside has been raised to a position substantially perpendicular to the platform, said step members (13, 13', 13") hanging down substantially vertically from the pivot shaft on the inside of said dropside in a position in which they do not appreciably intrude on the platform cargo space, and, when said dropside has been lowered and is hanging down preferably vertically, extending substantially at right angles from said dropside to facilitate climbing onto said platform, whereby all said step members (3, 3', 3") are automatically and without external action unfolded to the position in which they extend at right angles from said dropside, at the latest when said dropside has reached its lowered, vertically pendent position. 6. The ladder as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that said ladder frame (2) is connected with a cassette (14) adapted to be preferably horizontally mounted via two pivot pins or hinge projections (15) extending laterally from said frame and each engaging a guide (16, 16') in said cas- sette, and that below said guides, at least one support or abutment (20) is arranged at a distance from stop members (21) mounted at one end of said guides; said support (20), said guides (16) and said pivot pins (15) forcedly guiding said frame (2) in one and the same plane as said cassette as long as said pivot pins are spaced from said stop members (21) a distance exceeding the distance between said support (20) and said stop members, but allowing said frame to be folded down to its pendent, active position as soon as said pivot pins reach the area between said support and said stop members 7. The ladder as claimed in claim 6, c h a r a c - t e r i s e d in that said pivot pins (15) constitute parts of a shaft (5) the length of which exceeds the width of the ladder frame (2) and which extends through two spaced-apart and parallel frame side portions or flanges (8). 8. The ladder as claimed in claim 6 or 7, c h a r ¬ a c t e r i s e d in that said pivot pins (15) are located adjacent the upper or inner end of said ladder frame (2) and spaced from said top step member (3).

Inventors: JOHANSSON INGEMAR, JOHANSSON, INGEMAR
Applicants: SOEDERHAMNS KONSTBYRAA AB
Application year: 1987
Main classification: B60R3
IPC codes: B60R3, E06C5, E06C9