A THREE-LEGGED ASSEMBLY

Abstract: A step ladder assembly has three legs (1, 5, 6) which are pivotably mounted at their upper ends, and which are associated with stop means (8) to define a limit of outward pivoting for the legs. One of the legs (1) has steps (2) mounted thereon. A wedging member (9) is movable upwards between the legs (1, 5, 6) to urge them outwardly against the stop means (8) thereby to define, with the stop means (8), predetermined pivotal positions of the legs (1, 5, 6). The wedging member (9) is coupled to a support rod (10) which is movable up and down with the wedging member (9) and which provides, in an upwards position of the wedging member (9), a support above a working platform (7) of the assembly. The stop means (8) is provided at least partly by edges of rigid sheet material forming the working platform (7) of the assembly, the edges being lower inner edges of the rigid sheet material after it has been folded-under along a rim of the working platform (7). One of the legs (1) is fitted at its lower end with an angularly rotationally adjustable bifurcation providing two feet for the leg.

Description: A Three-Leqqed Assembly This invention relates to a three-legged assembly and/or to a bifurcated end of a leg of such, or other, assembly. Three-legged assemblies are employed to provide support, structures of several different types, for example step ladders, seat supports, and tripod supports for cameras or telescopes. Examples of three-legged step ladders can be found more particularly in United States patent No. 4,524,849, and United States design patent No. 267,817. It is desirable for such an assembly to provide a rigid and stable configuration when in use, yet to be collapsible in order to take up little storage space when not in use. According to one aspect of the present invention there is provided an assembly having three legs which are pivotably mounted at their upper ends, the legs being associated with stop means to define a limit of outwards pivoting for the legs, and with wedging means moveable upwards between the legs to urge them outwardly against the stop means thereby to define, with the stop means, predetermined pivotal positions of the legs. The wedging means may preferably be coupled to a support member which moves upwardly with the wedging means to provide a support above for example a working platform of the assembly, preferably a hand-hold. When the wedging means is in an upper position the assembly will be in a rigid and stable condition, whilst when the wedging means has been moved downwards the legs may be pivoted inwardly to provide a collapsed and compact configuration of the assembly. The wedging means may comprise a wedging member (possibly in the form of a block) having one or more wedging surfaces to urge the respective legs outwardly as aforesaid. Such wedging member may be attached to a rod as the support member, which is moveable up and down with the wedging member, and there may be a fastening system associated with the wedging member and/or the support member to secure the wedging member in its upwards position. The support member may extend through an aperture in a working platform supported at the apex of the assembly, the support member preferably being moveable downwardly at a location from above the working platform. The top end of the support member can be formed with an actuating handle for moving the wedging means downwards, which may also serve as a steadying support for a person or object on a working platform when the assembly is in its erected configuration. The legs of the assembly may be pivoted at or just below a working platform such as has been mentioned, with the stop means being provided as part of, or being secured to, the working platform. In one embodiment the stop means may be provided at least partly by the edges of rigid sheet material. Possibly a working platform is itself formed of this rigid sheet material, with the stop means preferably being provided at least partly by the lower inner edges of the rigid sheet material after it has been folded- under along the rim of the working platform. The upper ends of the legs of the assembly may be pivoted onto cross-bars located in the working platform. Preferably, or according to another independent aspect of the present invention, at least one leg is fitted at its end with an angularly rotationally adjustable bifurcation providing two feet for the one leg. For a better understanding of the present invention and to show how it may be put into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a front view of a preferred embodiment of tripod step ladder according to the present invention, when in an erect configuration; Figure 2 is a front view of the step ladder of Figure 1 when in a collapsed configuration; Figure 3 is a side view of the erect step ladder of Figure 1; Figure 4 is a side view of the collapsed step ladder of Figure 2; Figure 5 is an exploded view of the pivotal assembly of the step ladder of Figures 1 to 4; Figure 6 is a side view of one of the legs of Figure 5 when in a coupled and erect configuration; Figure 7 is a view of the working platform of Figures 5 and 6 from underneath; and Figure 8 is an exploded view of the bottom of the front leg. Figure 1 shows a three-legged tripod step ladder in erect configuration, resting on a flat surface. A hollow-section aluminium front leg 1 has fixed steps 2 welded at equal intervals along the front leg 1, each step being folded from sheet aluminium. In an alternative embodiment, the leg 1 could be provided by two uprights having steps connected therebetween as in a conventional step ladder. Two hollow-section aluminium rear legs 5 and 6 are provided behind the front leg 1. For maximum stability the three legs 1, 5 and 6 are arranged at equal angles of 120° around the vertical axis of the ladder assembly, and the legs 5 and 6 are provided with adjustable telescopic extensions. If required, leg 1 can be similarly telescopically adjustable also. Moreover the front leg 1 is provided with a divided support leg in the form of a bifurcation 3, whilst each of the two ends of the bifurcation 3 is provided with a hinged foot 4, as is the bottom end of each of the telescopic legs 5 and 6. The bifurcation 3 is angularly rotationally adjustable, and can be locked, as can better be seen in Figure 8. The three legs 1, 5 and 6 are pivoted at their upper ends within a working platform 7, as will be described in more detail hereinafter. The working platform 7 is provided by a shell made of folded sheet aluminium having a flat non-slip upper working surface. The non-slip feature may be provided by a patterned surface of the sheet aluminium, and may be provided for the steps 2 also. The sheet aluminium is folded-over downwardly at the lateral edges of the platform 7, to provide lower inner recessed edges 8 providing stops for the outward pivotal movement of the three legs 1, 5 and 6, as will be described in more detail hereinafter. The legs 1, 5 and 6 are wedged outwardly against the stop edges 8 by a wedging body 9 connected to the bottom of a support rod 10 having a handle 11 at its top end. Figure 2 shows the assembly of Figure 1 in a collapsed position, with the legs 5 and 6 being pivoted inwardly to lie paralle-1 with the front leg 1, and with the handle 11 being in its • downwards position to move the wedging body 9 itself downwardly. Figure 3 shows the erect assembly of Figure 1 from the side, and indicates how the bifurcation 3 extends forwardly to provide a broader support base for the erect assembly. Figure 4 similarly shows a side view of the collapsed assembly of Figure 2, showing the wedging body 9 and the handle 11 in their downwards position. Normally, the assembly will be stored in the collapsed position shown in Figures 2 and . To put the assembly into its erect condition, the user stands the assembly upright on its feet 4, and moves the three legs 1, 5 and 6 outwardly until they abut at their upper ends against their associated respective stops 8. In order to secure the rigidity and stability of the assembly, the user will grasp the wedging block 9 which is still in the downwards position shown in Figures 2 and 4, and (after rotational adjustment as described hereinafter) push it upwards into its uppermost position as shown in Figures 1 and 3, wherein the wedging block 9 abuts firmly against the inner surfaces of the legs 1, 5 and 6. In this way the wedging block 9 is moved upwards between the legs 1, 5 and 6 to urge them outwardly, by a wedging action, against the stop edges 8 thereby to define with the stop edges 8, a predetermined pivotal position of the legs 1, 5 and 6 as is shown in Figures 1 and 3- Of course no further outward pivoting movement is caused by the wedging block 9, because the legs 1, 5 and 6 have already been put into their extreme pivotal positions manually by the user. Nevertheless, the outwards urging on the legs 1, 5 and 6 by the wedging block 9 prevents any accidental collapse of the assembly. The reverse procedure is followed to collapse the assembly after use, except that the wedging block 9 is moved downwards from its wedging position by means of downwards pressure exerted by the user on support rod 10 via handle 11. Figure 5 is an exploded view of the top end of the ladder assembly, and provides a better understanding of the pivoting and securing mechanism. For the sake of clarity, only the top ends of the legs 1, 5 and 6 are shown, with just the top step 2 as welded to the front leg 1. The working platform 7 is formed of sheet aluminium, providing a flat hexagonal non-slip upper working area at the edges of which the sheet aluminium is folded-over to extend below the upper surface of the working platform 7. A square aperture 13 is provided at the centre of the upper surface of the working platform 7, and through it extends the support rod 10 having the handle 11 at its upper end. At its lower end the support rod 10 is securely push-fitted into a square socket at the centre of the wedging block 9. The wedging block 9 is seen to have three angled wedging surfaces 12 distributed around the edge of the wedging block 12 at equal angular distances of 120°. In this way the wedging surfaces 12 can cooperate with the inner surfaces of the three tripod legs 1, 5 and 6 respectively, to exert a strong wedging action thereon. In order to secure the wedging block 9 and the support rod 10 in their upper positions in the erect configuration of the ladder assembly, a screw-threaded bolt 14 is secured to the working platform 7 to extend downwardly below it, so that as the wedging block 9 is pushed by the user from below into its uppermost position, the bolt 14 enters with clearance an aperture 18 extending throughout the wedging block 9. When the assembly is in its erect configuration, with the wedging block 9 in its uppermost position, a securing nut 15 is screwed-onto the bottom end of bolt 14 by the user where the bolt 14 protrudes from the lower surface of the wedging block 9. The securing nut 15 is then tightened against the bottom surface of the wedging block 9, in order to maintain a fixed vertical relationship between the working platform 7 and the bolt 14 on the one hand, and the wedging block 9 and its actuating rod 10 on the other hand. Also shown in Figure 5 are three cross members 16 welded together at 120° intervals around the vertical axis, the welded assembly of cross members 16 being itself fixed onto the bottom of the upper surface of the working platform 7, thereby to be housed within the sheet aluminium shell providing the working platform 7. The support rod 10 passes through a gap between the inner ends of the three cross-members 16, whilst the top ends of the thrjee legs 1, 5 and 6 are pivotally secured to respective ones of the cross-members 16, by bolts (not shown) passing through holes 17 in the cross-members 16, and corresponding holes at the top ends of the legs 1, 5 and 6. In order to collapse the assembly, the securing nut 15 is first removed, to permit downwards movement of the wedging block 9. Then the user pushes down on the handle 11, which via the support rod 10 pushes the wedging block downwards out of its wedging position, until handle 11 abuts against the working surface of the working platform 7. Wedging block 9 is then forcibly pulled off the bottom of the support rod 10, and replaced thereon after rotation by 180°. In this way the wedging surfaces 12 are no longer aligned with the legs 1, 5 and 6, and sufficient clearance is achieved to allow the legs 1, 5 and 6 to be pivoted inwardly to the compact configuration shown in Figures 2 and 4. Figure 6 is a side view of a detail at the top end of the leg 1 when secured in the erect configuration of the ladder assembly as shown in Figures 1 and 3. The top end of the leg 1 is shown pivotally hinged to the associated cross-member 16, with the outer edge of the working platform being provided by sheet aluminium folded-over to provide inwardly a stop edge 8 defining a limit of lateral outwards pivoting for the leg 1. The wedging block 9 is shown in its upper position, with one of its wedging surfaces 12 urging the leg 1 outwardly against the stop edge 8 thereby to define, with the stop edge 8, a predetermined pivotal position of leg 1. The stop edge 8 is seen to be reinforced by a folded inner support 19 which improves the retaining action of the stop edge 8 and provides a larger support area. Each of the other legs 5 and 6, when seen from the side at the upper end, has the same appearance as is shown in Figure 6. Figure 7 shows from below the hexagonal working platform 7. It can be seen that the stop edges 8 are formed on flaps 20 and are spaced angularly apart by 120° around the vertical axis, with each stop edge 8 being provided by a recessed rim of the sheet aluminium material which is folded-over as shown in Figure 6. The recessed form of the stop edge 8 prevents excess sideways movement of the contained leg. Whilst the three flaps 20 of sheet aluminium material providing the stop edges 8 extend a relatively long way towards the centre of the working platform 7 after being folded over it can be seen that, between them, three intervening further flaps 21 of sheet aluminium, although still folded over at corresponding three edges of the working platform 7, nevertheless extend inwardly for only a relatively small distance at their central portions. Where the flaps 20, 21 meet along their inwardly directed edges, they are welded together for rigidity, with the intervening flaps 21 having inwardly-pointed extensions 22 at their inwardly directed edges for added strength. It will be appreciated that the illustrated and described step ladder assembly can be quickly and easily converted from the collapsed configuration shown in Figures 2 and 4, into the erect configuration ready for use, as shown in Figures 1 and 3 and as explained in more detail with respect to Figures 5 and 6. Once the user has pivoted the legs outwardly into the configuration shown in Figures 1 and 3, he can then first remove the wedging block 9 from the end of support rod 10, and then re-fit it rotated by 180° so that the wedging surfaces 12 again are aligned with the legs 1, 5 and 6. The user can then push the wedging block 9 upwardly, raising the support rod 10 and the handle 11. The legs 1, 5 and 6 are thereby urged outwardly by the wedging surfaces 12 on the block 9 so that the wedging block 9 defines, with the recessed stop edges 8, a predetermined pivotal position of the legs 1, 5 and 6. The ladder assembly thus assumes a rigid and stable erect configuration, whilst the provision of the bifurcation 3 at the bottom of the front leg 1, together with the hinged feet 4, can provide an especially stable arrangement. Maximum stability is thus provided both on flat and uneven terrains, and further adjustability for greater stability can be achieved by adjusting one or both of the telescopic legs 5 and 6 (or leg 1 if it is telescopic also) as is appropriate. Figure 8 shows the bifurcation 3 and how it is rotatably mounted at the bottom of leg 1. The feet 4 are shown as being rotatably mounted at the two ends of the bifurcation 3, whilst the bifurcation 3 itself is rotatably mounted at its apex onto the end of leg 1 via an overcentre locking clamp 23 which can fix the angle of adjustment of the bifurcation 3 by shortening itself to clamp together the surfaces it passes through. The bifurcation 3 is mounted on an end portion 24, of the leg 1, which extends frowardly at an angle to the remainder of the leg 1 above the end portion 24. The fact that the end portion 24 of the leg 1 is angled as aforesaid, makes the assembly more stable than if the leg 1 ended as is shown for legs 5 and 6 in Figures 1 to 4, even if a bifurcation such as 3 were to be fitted. This is due to the forwards and lateral support provided by the feet 4 of the bifurcation 3, owing to the forward extent of the angled end portion 24. It is to be noted however, that the forwards angle of the end portion 24 is a preferred and not an essential feature of the bifurcation 3. It is to be appreciated that the construction shown in Figure 8, and the broad principle thereof, can provide not just a preferred feature of the three- legged assembly, but can provide an independently inventive feature applicable to a leg of that or any other type of suitable assembly. A three-legged assembly according to the invention need not, of course, be restricted to the application of ladders. The inventive assembly could equally well be applied to a camera or telescope tripod, or a tripod supporting a high seat for observation purposes. The invention could even be applied to a tripod music stand or artist's easel. Although the preferred embodiment of the invention is described and illustrated as having only three legs, it is to be understood that the invention could be applied to an assembly having more than three legs, i.e. a three-legged assembly to which at least one other leg is added. Thus the invention is intended to cover within its scope for example a four-legged assembly, wherein only three or possibly all four legs are pivotably mounted at their top ends, three or all four legs being associated with stop means to define a limit of outwards pivoting for the legs, and with a wedging means which is moveable upwards between the three or all four legs to urge them outwardly against the stops thereby to define, with the stops, a predetermined pivotal position of the three or all four legs. Finally, whatever number of legs the assembly has, it is possible for two. of the legs to be effectively rigidly joined together at all times, to provide a rigid two-legged assembly. In the embodiments shown in Figures 1 to 4 therefore, for example the two legs 5 and 6 could be rigidly joined together at the angle between them shown in Figure 1, so that in the collapsed state of Figure 2 the legs 5 and 6 would remain at an angle towards another, although the side views of Figures 3 and 4 would remain approximately the same. Such an assembly is disclosed in United States design patent No. 267,817. In such an assembly as is envisaged, the collapsed configuration of the ladder assembly would of course occupy more storage space than that of the assembly of Figures 1 to 4 as described, but the construction of the pivotal assembly shown in Figure 5 could be designed more simply, since in this case the wedging means would move upwards between the legs to urge the leg 1 outwardly against one stop, and the combination of legs 5 and 6 outwardly against another stop thereby to define, with the two stops, a predetermined pivotal position of the three legs 1, 5 and 6 in the erect configuration of the ladder assembly. It is to be noted that in such an embodiment where the legs 5 and 6 are always fixedly arranged, the steps of the ladder could extend between legs 5 and 6 instead of being mounted on leg 1, and the rigid relative positioning of the legs 5 and 6 could be achieved by the rigid connections between the two legs 5 and 6 by the rigid steps, again as disclosed in United States design patent No. 267,817. Further developments of the illustrated and described embodiment could be: optional extensions to leg and step elements to give increased height; optional cable stays to legs for extra weight bearing to prevent leg splay; optional clip-on steps to fit to legs 5 and 6 for multiple person usage.

Claims: CliAIMS 1. An assembly having three legs which are pivotably mounted at their upper ends, said legs being associated with stop means to define a limit of outward pivoting for said legs, and with wedging means movable upwards between said legs to urge them outwardly against said stop means thereby to define, with said stop means, predetermined pivotal positions of said legs. 2. An assembly as claimed in claim 1, wherein said wedging means comprises a wedging member having at least one wedging surface to urge the respective legs outwardly as aforesaid, and said wedging member is coupled to a support member which is movable up and down with said wedging member. 3. An assembly as claimed in claim 1, wherein said wedging means is coupled to a support member which moves upwardly with said wedging means to provide a support above a working platform of said assembly, said support member extends through an aperture in said working platform which is supported at the apex of said assembly, and said support member is movable downwardly at a location from above said working platform. 4. An assembly as claimed in claim 1, wherein said wedging means is coupled to a support member which moves upwardly with said wedging means to provide a support above a working platform of said assembly, and a top end of said support member is formed with an actuating handle or other member for moving said wedging means downwards, said handle or other member also serving as a steadying support for a person or object on said working platform when the assembly is in an erected configuration. 5. An assembly as claimed in any one of the preceding claims, wherein said legs of said assembly are pivoted at or just below a working platform of said assembly, with said stop means being provided as part of, or secured to, said working platform. 6. An assembly as claimed in any one of the preceding claims, wherein said stop means is provided at least partly by edges (possibly bent-over) of rigid sheet material forming a working platform of said assembly. 7. An assembly as claimed in claim 6 , wherein said stop means is provided at least partly by said edges of rigid sheet material forming said working platform of said assembly, said edges being lower inner edges of said rigid sheet material after said rigid sheet material has been folded-under along a rim of said working platform. 8. An assembly as claimed in any one of the preceding claims, wherein upper ends of said legs are pivoted onto cross-bars located in a working platform of said assembly. 9. An assembly as claimed in any one of the preceding claims, wherein at least one of said legs is fitted at its lower end with an angularly rotationally adjustable bifurcation providing two feet for said one leg. 10. An assembly having a plurality of legs, wherein at least one of said legs is fitted at its lower end with an angularly rotationally adjustable bifurcation providing two feet for said one leg. 11. An assembly as claimed in claim 9 or 10, wherein said bifurcation extends forwardly of the leg on which it is fitted. 12. An assembly as claimed in any one of the preceding claims, which is a step ladder. 13. An assembly as claimed in claim 12, wherein steps are supported by at least one of said three legs . 14. An assembly as claimed in claim 13, wherein said steps are mounted on and along a single one of said three legs . 15. An assembly as claimed in any one of the preceding claims, wherein the wedging means is associated with a fastening means to secure the wedging means in its uppermost position when the assembly is in use.

Inventors: KIRK-ALTON JULIAN WILLIAM, KIRK-ALTON, JULIAN, WILLIAM
Applicants: KIRK ALTON JULIAN WILLIAM, KIRK-ALTON, JULIAN, WILLIAM
Application year: 2000
Main classification: F16M11
IPC codes: E06C1, F16M11