US2313469A - Ladder - Google Patents

Description

March 9, 1.943. G. L. FORSMAN LADDER Filed March 18, 19.41 2 Sheets-Sheet l uowneys `March 9, 1943. G FORSMAN 2,313,469

LADDER Filed March 18, 1941 2 Sheets-Sheet 2 Patented Mar. 9, 1943 UNITED STATES PATENT FFICE LADDER George L. Forsman, Boston, Mass.

Application March 18, 1941, Serial No. 383,940

3 Claims.

This invention relates to ladders and more particularly to a novel combination step and extension ladder. I am aware that such combination is not broadly new and one object of my invention is to produce a superior and more substantial ladder of this nature and do so more economically than has been possible with ladders heretofore known.

My improved ladder is of tubular steel construction embodying tubular steel rungs rmly supported at their ends in tubular steel uprights, the uprights being elliptical in cross section whereby better to receive and support the rungs and to nest into compact relation when the two sections comprising the ladder are collapsed together. Other features contributing to the invention include novel and eiiicient means for connecting the two ladder sections together for pivotal movement to relations forming them into either a step ladder or an extension ladder, and cooperating latch means for securing the sections in these relations. The ladder is furthermore preferably provided with novel leveling devices attached to the feet thereof and serving to support the ladder firmly on uneven surfaces.

The production of an improved ladder of strong steel construction but of relatively light weight and embodying the novel features above and hereinafter described comprises the primary object of the invention. These features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof selected for purposes of illustration and shown in the accompanying drawings wherein:

Fig. 1 is t a front elevation of my improved ladder in step ladder arrangement,

Fig. 2 is a side elevation thereof,

Fig. 3 is an enlarged plan section taken on line 3-3 of Fig. 2,

Fig. 4 is a fragmentary plan section taken on line 4 4 of Fig. 2,

Fig. 5 is a front elevation of the ladder in extension ladder arrangement,

Fig. 6 is a side elevation thereof,

Fig. 7 is a side elevation of the ladder in collapsed relation,

Fig. 8 is an enlarged sectional view taken on line 8 8 of Fig. 6,

Fig. 9 is a vertical sectional View taken on line 9-9 of Fig. '7,

Fig. 10 is a plan section taken on line Ill-Ill of Fig. 9,

Fig. 11 is a sectional view taken on line lI-II of Fig. '7,

Fig. 12 is a fragmentary section taken on line |2-l2 of Fig. 3.

My improved ladder comprises two relatively simple and like sections l and l2 so pivoted together that they can be radily moved into the step ladder position of Figs. 1 and 2 or the extension ladder position of Figs. 5 and 6. `Each section embodies tubular rungs i4 supported at their ends in two uprights I6. The rungs are preferably circular in cross section and the uprights are elliptical in cross section and arranged to receive the rungs through the side walls thereof. The side walls are also preferably flat and parallel and theedge portions i8 connecting 15 the side walls are convexly V-shaped. Such construction is of 4substantial importance in providing better reception and support for the rungs, stronger construction, improved appearance and a superior arrangement permitting the two sections to collapse compactly together as illustrated in Fig. 7.

The rungs are reduced in diameter at their ends andthe uprights are provided with openings 29 and 22, respectively through the inner and outer walls for receiving the rungs, the opening 2E] being of a diameter corresponding to that of the rung and the opening 22 corresponding to the reduced end portion of the rung. A shoulder 24 is formed at each reduced end portion of the rungs for engaging against the inner face of the outer wall and the reduced ends of the rungs are riveted over at 26 to engage the outer wall securely between the shoulder and the upset end portion 26. Such construction provides a secure connection between the ends of the rungs and the outer walls of the uprights, supports the rungs on both side walls of each upright and presents each rung smooth and unbroken between the uprights.

It will be noted that the section I0 is somewhat longer than the section l2 and is slightly narrower whereby to dispose its uprights within and adjacent to the uprights of the section l2. The two sections are secured together by novel means permitting their movement to the step ladder position of Figs. y1-2, the extension .ladder position of Figs. 5-6 and the closely collapsed position of Fig. '7. This means embodies two steel straps 28 pressed to a shape to t closely on an upright and provide ears 3S disposed laterally of the uprights. These strap units are pressed into shape and seated rmly onto the uprights of the section l0 with the ears 3i) projecting laterally thereof. The straps are perforated to receive the second top rung I4 of the section and the ears 30 are also perforated to receive the top rung |42 of the section |2 (Figs. 2 and 4). The staps are thus anchored rmly to the uprights and to a rung |4 of the section Ill and provide a strong pivotal connection to the top rung |42 of the section I2. Spacers 32 are provided on the rung |42 to hold the section Il] evenly spaced within the section |2,

A latch yoke comprising two metallic straps 34 connected by a bar 36 is provided for holding the two sections in the step ladder relation. The straps are pivoted on a rung |43 of the section I2, two washer-like elements 3l being welded to this rung in position holding the two straps against the two uprights. Hooks 38 are formed on the free ends of the straps for engaging elements extending from the ends of a rung |44 of the section l0. Each of these extensions comprises a tubular element 40 extending into the rung and carrying a head 42 at its outer end, a cross pin 44 serving to secure the element in place in the rung. The hooks 38 are adapted to engage over the elements between the heads 42 and the uprights as illustrated in Fig. 12. The straps 34 are also recessed at 46 to receive a rung I4 when the ladder is collapsed to the position illustrated in Fig. '7.

When it is desired to use the ladder as an extension ladder, the yoke 34 is released and the operator, standing to the left of Fig. 2, grasps the top rung of the section l!) and swings this section to the position of Figs. 5 and 6. The novel latch means shown particularly in Fig. 8 is provided for holding the sections in this extended relation. This means comprises two U- shaped latches each having a leg 48 within and projecting outwardly of the ends of a rung I45 of the section I6 and a leg 5|! engaging within the ends of a rung I46 of the sections |2, where- 'by cooperating with the rung |42 to lock the two sections in extended and substantially parallel relation. A spring 52 within the rung I46 is connected to and serves to draw and hold the two latches inwardly to their locking position.

The ends of the ladder sections can be provided with rounded caps 54 preferably of rubber to form smooth and finished ends which also serve to contact a supporting surface without danger of slipping. I also preferably provide the ladder with novel leveling means to compensate for uneven supporting surfaces. This means comprises a steel housing 56 secured to the foot of the ladder as by welding at 5l, a plunger 58 in the housing, a steel plate 66 having a tongue extending into a slot in the back wall of the housing at 62 and having an opening receiving the plunger, and a spring 64 normally operative against a pin 66 to lift the plunger upwardly, the plunger preferably carrying a rubber shoe 68 at its bottom end. Should a leg of the ladder extend short of the supporting surface, the operator merely steps on the plunger and forces it downwardly through the plate into engagement with the supporting surface. The plate is canted upwardly by a spring lll into binding engagement with the plunger and prevents return movement of the plunger, whereby lengthening the leg tov compensate for the uneven surface. The plunger is released merely by depressing the outer end of the plate 6D whereupon the spring 64 retracts the plunger into the housing. The plate is held in position parallel with the upright i6 by its engagement through the opening in the top wall of the housing 56, The

plate engages over the plunger which holds the plate from moving out of the slot 62, the plate being entirely free except for its engagement with the plunger and in the slot 62.

It will now be apparent that I have not only produced a superior ladder of the nature defined, but have produced the same from stock material at a minimum of cost. The construction also is fully adaptable to mass production and can be made in varying lengths and varying modifications without departing from the normal manufacturing procedure. The two sections of the ladder are of like construction, whereby simplifying and reducing the cost of manufacture, and are of such configuration and so assembled that they can be readily moved to the three relative positions illustrated. 'I'he construction also permits easy handling of the ladder by one man even though the sections are of substantial lengths, the swinging of the section I6 about the axis I43 from the position of Fig. 2 to that of Fig. 6 being particularly convenient for one man. The strap connection of the sections at 28 together with the latches 48--50 also hold the ladder securely in the position of Fig. 6 with the two sections substantially parallel and equal to a single section. The elliptical shape of the sections, especially with the hat side walls, provides for secure seating of the rungs and such shape, together with the locating of the section I0 within and adjacent to the section |2 and the straps 34 therebetween, permits the two sections to nest closely together in collapsed relation as illustrated in Fig. '7. These and other novel features of the invention all contribute to produce a superior product as will be understood.

Having thus described my invention what I claim as new and desire to secure by Letters Patent ofthe United States is:

1. A combined step and extension ladder comprising two ladder sections each embodying tubular steel rungs supported at their ends in tubular steel uprights elliptical in cross section, the rungs extending through the shorter diameters of the uprights and having their ends secured to the uprights, two flat steel straps wrapped around the uprights of one section and having the ends thereof projecting laterally of the uprights in overlapped relation, a rung of said one section piercing the straps, and means, including a rung of the other section piercing the overlapped ends of the straps, pivotally connecting the two sections.

2. A combined step and extension ladder comprising two ladder sections each embodying tubular steel rungs supported at their ends in tubular steel uprights elliptical in cross section, the rungs extending through the shorter diameters of the uprights and being supported upon the walls thereof, two ears carried by the uprights of one section, means pivoting the other section to the ears for movement placing the two sections in step-ladder relation or extension-ladder relation, latch means comprising two U-shaped latches having two legs within and projecting outwardly of the ends of a rung of one section and two legs for engaging within the ends of a rung of the other section for holding the two sections in extension-ladder relation, and a spring within the first rung for drawing the two latches inwardly.

3. A combined step and extension ladder comprising two ladder sections each embodying tubular steel rungs supported at their ends in tubular steel uprights elliptical in cross section, the rungs extending through the shorter diameters of the uprights and being supported upon the walls thereof, two ears carried by the uprights of one section, means pivoting the other section to the ears for movement placing the two sections in step-ladder relation or extension-ladder relation, the two uprights of one section being disposed laterally within the two uprights of the other section, a locking unit having two legs pivoted to a rung of one section and located respectively adjacent to the two uprights thereof, the legs having hooks on their free ends, and means carried by the other section and extending outwardly from the ends of a rung thereof for receiving the hooks in position locking the two sections in step-ladder relation, the two legs of the locking unit being adapted to nest between the uprights of the two sections when the two sections are collapsed together.

GEORGE L. FORSMAN.

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