US2708064A - Articulated ladder - Google Patents

Description

May 10, 1955 L R, MCGQWEN 2,708,064

ARTICULATED LADDER Filed Aug. 13, 1952 INVEN TOR.

Lebng d R. ML Galvan BY ATTORNEY United States PatentO ARTICULATED LADDER Leonard R. McGowen, East Alton, Ill., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application August 13, 1952, Serial No. 304,116

'3 Claims. (Cl. 228 -23) This invention relates to an articulated ladder. More particularly it relates to a ladder for traveling between the top of a floating roof tank or the like and its roof, Which ladder automatically adjusts for variation in roof height and embodies a platform at the juncture of ladder sections which is constantly horizontal.

The roof of a floating roof tank varies its distance from the top of the tank depending upon tank content. Various automatically adjustable ladders have been proposed for use in traveling between the roof and the top of the tank but most of these require roller guideways on the surface of the roof or other fixtures which complicate the structure as well as interfere with the removal of snow. An additional disadvantage of most ladders of the prior art is that they are unsuitable for use in tanks which are taller than they are Wide.

It is an object of the present invention to provide an automatically adjustable ladder for fluid storage tanks and the like having a vertically movable roof which ladder is particularly adapted for use in such tanks having a height which exceeds the diameter. A further object of this invention is to provide an adjustable ladder embodying a safety platform at the juncture of each pair of its articulated sections, which platform remains substantially horizontal irrespective of roof position. These and additional objects will be apparent from the following detailed description.

The invention will be described in conjunction with the drawings in which Fig. 1 is a partially diagrammatic plan view of the floating roof tank showing the relation of the novel ladder thereto.

Fig. 2 is a partially diagrammatic vertical section through the tank shown in Fig. 1 taken along 2-2.

Fig. 3 is an enlarged perspective view of the novel ladder and platform apart from the tank and roof.

Fig. 4 is a detailed partial view of the articulated platform supports, the shaft and the roller.

Referring to Fig. 1, indicates a volatile liquid storage tank having a floating roof 11 adapted to float on the liquid in tank 10. A spiral stairway 12 permits ascent from the ground to the upper edge of the tank at which is positioned platform 13. Hingedly attached to platform 13 is ladder section 14 which in turn is hingedly connected to platform 15. Juxtaposed to ladder section 14 is ladder section 16 which is similarly hinged to platform 15 as well as being hinged to section 14. Section 16 is hingedly connected to roof 11 at 17.

Referring now to Fig. 2 and Fig. 3, the components of the ladder and their relationship to the tank and roof can be more readily observed. Platform 15 is supported, at its unhinged end, upon support 18 which is pivotally connected to two sets of articulated support members 19 and 20 at each end of shaft 21. The other ends of articulated support members 19 and 20 are pinned to the stringers of the ladder sections 14 and 16 and supports 22 thereof, respectively. For purposes of the present description and the appended claims, the term ladder 2,708,064 Patented May 10, 1955 sections shall include supports 22. The action of the articulated supporting structure for platform 15 is such that shaft 21 and the axis of articulation of ladder sections 14 and 16 remains in substantially the same horizontal plane, irrespective of roof position. To accomplish this, support members 19 and 20 are preferably of equal length and are pivotally connected to the stringers and supports 22 at an equal distance from the axis of articulation. Platform support 18 comprises roller 23 and shaft 21. Roller 23 is rotatable about shaft 21 on bearings disposedat each end thereof. Short rollers at each end of the shaft are equally suitable. It is preferred to employ a roller such as that shown or other suitable friction reduction means upon which, the platform may ride. Such is not essential, however, and the platform may be slidably disposed on a simple nonrotatable cross member, e. g. shaft 21. Inasmuch as the horizontal relationship of shaft 21 and the axis of articulation of the ladder sections remains constant, platform 15 which is hinged to the ladder sections along said axis of articulation and disposed upon roller 23 at itsopposite end, likewise remains substantially in the same plane as the ladder opens and closes.

One skilled in the art can readily conceive alternatives for maintaining the platform horizontal without departing from the scope of the present invention. Thus, the platform support, instead of actually bearing the Weight of the platform, may be disposed in the space between the ladder sections. There, the horizontally movable platform support (similarly connected to the articulated supporting structure) may travel back and forth on top of an extension of the platform which likewise protrudes inwardly from the axis. By providing that the weight of the platform is in substantial excess of such an extension on the opposite side of the axis of articulation (which thus becomes a fulcrum), the extension is always held in contact with the movable platform support and the platform remains continually horizontal. Similarly, longitudinal guideways may be provided in one or more such extensions in which the end of the platform support may ride in a confined manner.

In Fig. 3 is shown the preferred construction of the ladder of the present invention. Sections 14 and 16 are strengthened by means of support members 22 which are permanently afiixed to the ladder sections and in turn hinged to the platforms 13 and 15 and to roof 11.

In Fig. 4 is shown the manner in which articulated support members 1? and 20 are pivotally connected to shaft 21 and roller 23 is rotatably disposed about shaft 21 on bearings 24 which are disposed within race 25.

A person desiring to reach the roof from platform 13 may descend ladder section 14 to platform 15, cross over to section 16 and readily descend to the roof surface. While not essential, hand rails are preferably included on the ladder.

The treads of the ladder may be narrow rungs as shown or of the wider tread type which are weighted in such a way as to remain substantially horizontal regardless of roof position. A ladder embodying such treads is described in U. S. 1,944,159.

Whereas the embodiment of the ladder shown in the drawings and described herein has only two sections, a greater number may, of course, be employed. In such case a plurality of platforms equivalent to platform 15 will be employed along the axis of articulation of each pair of juxtaposed ladder sections. It is preferred, although not essential, that all sections of a ladder be of substantially equal length. It is likewise preferred that articulated support members 19 and 20 be of equal length and that they be pivotally connected to the ladder and their supports at an equal distance on either side of axis of articulation.

Having thus described my invention, what I claim as novel and desire to protect by Letters Patent is as follows:

1. In a sectional ladder comprising articulated sections adapted to pivotally engage the top of a tank and to span the top of the tank down to its vertically movable roof, said articulated sections expanding and contracting vertically in accordance with the movement of the roof; the improvement comprising a platform articulated to said ladder sections at their axis of articulation, a horizontally movable support for said platform to maintain the same horizontal during the expanding and contracting movement of said sections, and supporting elements pivotally connected to said movable support and the respective ladder sections to maintain said support substantially horizontal with respect to said axis during said expanding and contracting movements.

-2, The improved sectional ladder of claim 1 wherein frame members comprising stiles are disposed laterally and parallel to the stiles of said ladder sections and are longitudinally coextensive therewith, said frame members being articulated on the same axis of articulation as said ladder sections and said platform, and said frame member of one ladder section being substantially vertically aligned with a stile of the ladder section articulated therewith.

3. The improved sectional ladder of claim 1 wherein the horizontally movable platform support comprises a roller means.

Tuell Apr. 12, 1870 Jagschitz July 26, 1927

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