LADDER WITH SELF-ADJUSTING EXTENSION LEGS

Abstract: The invention relates to a ladder provided with an arrangement for maintaining the ladder in upright position independent of the contour of the supporting surface. This is obtained, according to the invention, by providing the ladder with two extension legs (9,10) which are slidably carried by the side legs (1, 2) of the ladder. The extension legs are suspended by a flexible connection (11) running through a hollow step member (3) at the upper part of the extension legs. The extension legs are journalled movable on the side legs (1, 2) lockable to the side legs by locking controls (16) movable downwards on the side legs. For operating the locking controls there is a further flexible connection (14) arranged between the locking controls (16) and running through a hollow step member at the bottom part of the extension legs (9, 10). Hence, the two extension legs are movable in opposite directions a decided distance, but when the extension legs are moved upwards the locking controls are pulled downwards by the flexible connection (14) causing locking of the extension legs (9, 10) to the side legs (1, 2).

Description: LADDER WITH SELF-ADJUSTING EXTENSION LEGS. The present invention relates to a ladder of the kind set forth in the preamble of the accompanying claim 1. Ladders of this kind are known, which have a slidable and manually lockable extension leg at one side leg of the ladder. The object of that arrangement is to make it possible to position a ladder leaning against for instance a wall and placed upon an uneven supporting surface without assuming a more or less tilted position of the ladder. In that case it is necessary to use two hands for holding the ladder, and, hence, it is necessary to obtain a self-adjusting operation and secure locking of the extension leg, which is not the case with known ladders. The object of the present invention is to obtain a ladder, which fulfills the above mentioned demands, and which is easily obtained by completion of existing ladders with uncomplicated fittings. This is achieved, according to the invention, by equipping the ladder with the characterizing features of claim 1. When the ladder is positioned with the foot end against a supporting surface the extension legs will be automatically adjusted depending upon the supporting surface, and then at pushing the ladder against the supporting surface the extension legs becomes locked. Then, at lifting of the ladder the extension legs becomes automatically released. Preferable embodiments of the ladder according to the invention are set forth in claims 2-4. The invention is more closely clarified in the following with reference to the attached drawings, which show schematically an embodiment of a ladder according to the invention as example, and in which Fig.l is a front view, partly in section, of the ladder, Fig.2 is a longitudinal section of one extension leg of the ladder, Fig.3 is a side view of the ladder, and Fig.4 is a front view of the ladder positioned upon a stepped surface. Fig.l illustrates the bottom part of a standard ladder made of light metal and having two side legs 1,2 with tubular step members 3 extending between the side legs and having open ends at the outer sides of the side legs. In these openings of the two bottom step members, stems 4 are inserted, which have apertures in which a rod 5 is attached at one side of the ladder and a rod 6 is attached at the other side of the ladder. Both rods are directed in parallel to the side legs and are cylindrical with a circular cross section area. Each rod ,5,6 supports a slidable holding device 7,8 to each of which an extension leg 9,10 is attached by a screw joint. The extension legs enclose the stems 4 and are guided by them. Fig.2 illustrates more clearly that the holding devices 7,8 and accordingly also the extension legs 9,10 are suspended from two parallel wires 11 which are. attached to each of the holding devices 7,8 at each side of the. rods 5,6 and which run each through a separate curved channel 12 in the upper stems 4 and in the tubular step member 3. The bottom stems 4 are further provided with similar channels 13 through which two further wires 14 are running between the holding devices 7,8 via the hollow bottom step member 3. These wires have enlarged end portions 15 which form locking controls, that are attached to the upper side of a clamp ring system consisting of four steel rings 16 which are thread on to each rod 5,6 and a spring 17 that is supported by the bottom wall of each holding device and pushes the steel rings 16 upwards against the wire end portions 15. The wire system is kept stretched by the springs 17 and therefore also the stems 4 are kept in position without the use of fastening screws, if desired. Further, by that, also the steel rings 16 are kept in position perpendicular to the rods 5,6 and permit the holding devices to slide on the rods 5,6. It is obvious, thus, that the extension legs together with the holding devices 7,8 are movable such that if the ladder is kept lifted one of the extension legs is permitted to move a distance in one direction at the same time as the other extension leg is forced by the wire system to move the same distance in the opposite direction. But if the extension legs 9,10 are pressed rather hard against a supporting surface and, thus, are pressed upwards, the wire ends 15 and the wires 14 will pull one side of the steel rings 16 downwards against the action of the springs 17 such that the steel rings become inclined and by that lock the holding devices 7,8 and the extension legs 9,10 to the rods 5,6. This state will exist until the pressure of the ladder against the supporting surface ceases and the springs 17 can push back the steel rings 16 to the position perpendicular to the rods 5,6. As illustrated by Fig.3 the extension legs 9,10 may be a bit narrower than the usual standard ladder and preferably run edge to edge with the flanges that normally are present on standard ladders made of light metal. Fig.4 discloses the ladder placed upon a stepped surface, at which the extension legs, when the ladder is lowered towards the stepped surface, are automatically adjusted depending upon the support surface, and at depressing of the ladder, for instance by placing a foot on the bottom step member, are locked in this position. The invention is of course not restricted to the exemplifying embodiment here shown and described but may be modified in various ways within the scope of the invention defined by the claims. The wires may, of course, be substituted by two thin chains, and if desired the rods of circular cross section may be substituted by rods of sguare cross section. Moreover, the equipment is preferably designed such that a standard ladder is easily equipped with the necessary equipment for forming a ladder according to the invention.

Claims: C L A I M S ' 1. A ladder with two side legs (1,2) and a number of tubular step members (3) extending between the side legs, and at the foot end of each side leg an extension leg (9,10) slidably mounted in parallel to the side leg, in addition to which the extension legs (9,10) are mutually connected by a flexible connection (11,14) running in a closed path along the foot ends of the side legs and two step members and permitting movement of the extension legs (9,10) in opposite directions a decided maximum distance, and which connection causes a locking of the extension legs to the side legs when a tightening of the flexible connection occurs due to a simultaneous depression of the extension legs towards a supporting surface, characterized in that a holding device (7,8) of a locking member, comprising a locking control (15) that can be actuated against the action of a spring member (17) , is fixedly attached each to one of the extension legs for locking the extension legs with respect to the respective side legs at an actuation of the locking controls in the direction towards the foot ends of the extension legs, and that the flexible connection is separated into an upper part (11) having ends which are attached to each holding device (7,8) and a bottom part (14) having ends which constitute the locking controls (15) . 2. A ladder according to claim 1, characterized in that the extension legs (9,10) are journalled on each a cylindrical rod (5,6) attached to each side leg in parallel to said side leg, and on which a clamp ring means (16) attached to the holding device (7,8) is slidably carried movable to obliquity to said rod in clamping direction by said locking control (15) to lock the extension legs (9,10) to respective rod (5,6). * 3. A ladder according to claim 1 or 2, characterized in that at least the two bottom step members (3) are tubular with open ends at the outer sides of the side legs in each of which openings a stem (4) is inserted that is provided with a securing device for an end of said rods (5,6), and at least one curved channel (12,13) for guiding said flexible connection (11,14) into or out from corresponding step members. 4. A ladder according to any of claims 1-3, characterized in that each of the two parts of the flexible connection comprises two in parallel running wires (11,14) having ends positioned on opposite sides of said rods (5,6). - o - o - o -

Inventors: WALLENIUS JAN FOLKE, WALLENIUS, JAN, FOLKE
Applicants: WALLENIUS JAN FOLKE, WALLENIUS, JAN, FOLKE
Application year: 2001
Main classification: E06C7
IPC codes: E06C7