US3004624A - Extensible ladder - Google Patents

Description

Oct. 17, 1961 c, GREEN 3,004,624

EXTENSIBLE LADDER Filed May 9, 1960 JOHN C. GREEN JNVENTOR.

A T TORNE Y United Stew P e 10."

, 3,004,624 EXTENSIBLE LADDER John C. Green, 2404 Hanley Drive, Fort Worth, Tex.

" FiledMa'y9, 1960, Ser. No. 27,686

3 Claims. i (Cl. 182-157) This invention relates to extensible ladders wherein the sides are comprised of hinged links pivoted'in a manner whereby the links define continuously straight parallel stringers when =the ladder is fully extended. Particularly, theinvention is directed to an improved latch mechanism for detachably securing adjoining side by side links in parallel relation when the ladder is extended its full length.

An object of the invention is to provide a lightweight and sturdy ladder of the lazy tong type and one which is capable of fabrication by mass production methods.

A particular object of the invention is to provide a practical latch mechanism for use in conjunction with a hinged ladder wherein the links form parallel straight stringers when the ladder is fully extended.

Another object of the invention is to provide a ladder of the described class which may be extended vertically from its collapsed position to fully extended position by one man standing on the ground.

Another object of the invention is to provide a lazy tong ladder having straight stringers when extended and latch means therefor which may be operated by a climber as he ascends or descends the ladder.

Another object is to provide a hinged ladder wherein adjoining links are provided with stirrups at their joints for lending rigidity to the ladder when fully extended.

A further object of the invention is to provide a rung construction which has pivot means for side by side pairs of links, yet which rungs are not subject to turning when stepped on by a person climbing the ladder.

These and other objects will become apparent from the following description and the accompanying drawing, wherein:

FIGURE 1 is a side elevation of a lazy tong type ladder in accordance with the invention and showing the ladder in its retracted or collapsed position.

FIGURE 2 is a side elevation of the ladder illustrated in FIGURE 1 and showing the same partially extended.

FIGURE 3 is a broken side elevational view corre sponding with FIGURES 1 and 2 but showing the ladder in its fully extended position.

FIGURE 4 is an enlarged broken perspective view showing inner and outer channels comprising parallel stringers along each side of the ladder and showing a hinge in an outer stringer.

FIGURE 5 is a view similar to FIGURE 4 but showing a hinge in the inner stringer.

FIGURE 6 is a broken perspective view showing hinges, such as illustrated in FIGURES 4 and 5, in side by side relation as occurs when the ladder is fully retracted.

FIGURE 7 is an enlarged sectional view taken on line 7-7 of FIGURE 5, and

FIGURE 8 is an enlarged broken elevation and sectional view showing one end of a rung pivotally con necting adjacent links of two stringers.

FIG. 9 is a view showing part of the hinge member illustrated in FIG. 6.

The form of the invention shown includes spaced parallel runners 10, each comprised of inner and outer hinged stringers 11 and 12 and rungs 13 connected between the inner stringers. The rungs 13 are regularly spaced with reference to each other and special rungs 13a hereinafter described. Each stringer 11 and 12 is comprised of inner and outer links 14 and 15 arrangedin side by side pairs which are pivotally connected with each other intermediate their ends by the special rungs 13a. The links 14- and 15 of each stringer 11' and 12 are oppositely hinged at their ends, and the hinge arrangement of one stringer isrthe reverse of the, other stringer so that each runner comprises a lazy tong construction.

Theindividual links 14 and are of channel stock and' the pairs of links have their webs adjacent each other.

Rectangular hollow brackets 16 areprovidedin corresponding ends=of the glinks and have integral bearings 17 projecting from corners thereof vfor receiving hinge pins 18. The axis of each pin 18 lies substantially within the plane defined by-the outer surface of the adjacent channel link 14 or 15. I

A feature of the invention is directed to a special latch assembly :shown in detail in FIGURES 4 through 7. Each latch assembly includes a hook portion 19 and a hook receiving portion 20. Each hook portion 19 and hook receiving portion 20 is comprised of formed sheet metal substantially U-shaped in transverse section so as to provide ears, not numbered, which receive extending ends of the hinge pins 18. Each book portion 19 extends longitudinally beyond the link 14 or 15 to which it is secured where it is provided with a lateral book 21 adapted to be positioned through a slot 22 in a laterally extending flange 23 on the hook receiving portion 20 and positioned to engage an adjacent stringer 11 or 12 when the latter is fully extended. The outer surfaces of the lateral flanges 23 may be reinforced by plates, not shown, if desired. Similarly, the books 19 may be reinforced by additional plates 24, and which plates are of the same thickness as washers 25 around the special rungs 13a between links 14 and 15 as shown in FIGURE 8. Latches 26 are mounted by means of pivot pins 27 on the hook receiving portions 20 and are arranged to receive the hooks 2 1 when the latter are extended. As shown in FIG- URE 7, the latches 26 are outwardly bowed, as at 28, to provide spring engagement with the hooks 21. The links 14a and 1511 at the foot of the ladder are of half length and their extending ends are joined by one of the special rungs 13a. Channel shaped feet 29 may be provided around the extending ends of the outer half links as shown in FIGURES 1 and 2.

Referring now to FIGURE 8, each special rung 13a extends through the inner and outer links 14 and 15 which are provided with inner and outer bearings 30 and 31. The outer ends of the special rungs 13a, which are of tubular material, are peened so as to be rigidly secured to the outer bearings 31. The intermediate rungs 13 are reinforced by channel shaped brackets 32 in the inner links 14 and shown in FIGURE 4.

The retracted ladder, as shown in FIGURE 1, may be extended horizontally along the ground or may be raised vertically by the operator by placing his foot on the lowermost special rung 13a and pulling upwardly on any rung 13a thereabove.

For the purpose of describing the operation, the hook portions 19 and their integral hooks 21 are designated by the letter C and the hook receiving portions including the lateral flanges 23 and hook receiving slots 22 are designated by the letter D.

Referring now to FIGURE 2, the joining of opposite hinged portions C and D is illustrated by means of arcuate arrows. The letters A and B and arrows thereby designate the ultimate alignment of outer links 15 when the ladder is extended as shown in FIGURE 3. In view of the foregoing description, it will be apparent that the latches 26 may be caused to engage the hooks 19 as a person ascends or descends the ladder.

The invention is not limited to the exemplary construction herein shown and described, but may be made in many ways within the scope of the appended claims.

What is claimed is:

1. An extensible ladder wherein the runners thereof Patented Oct. 17,1961

are comprised ofinner and outer stringers and wherein each stringeris comprised" of'links oppositely-hinged at the end corners thereof, the links of said inner and outer stringers being arranged in side by side relation and pivotally connected intermediate =their--ends",thel hinged" links semblies' including-"stumps extending fronrone-said"link 10 so" as *to. engage an adjacent said li'nk of the-same stringer and amadjacent-istringerwhen the-ladderis in its fully extended fposition; and rungsconnected between the-inner I said stringers;

23"A1rextensible ladder-as defined in clainrd and wherein each said latch assembly is comprised of aih'oole portion including awigidly; projecting hook on an extending end thereof opposite-its mounting, and "a hooku'eceivmg portion mounted on the ends of adjoining links opposite the'hinge" thereof; said hook" receiving-portion" including a slot adapted to receive the hook of said hook portion, and a latch pivotally 'mounted on said hook receiving portion adapted toenggge said book.

3. An extensible ladder asa= definedinclaim 1, and wherein vthmpivotaliconneetiorr:betweerr said side thy-side links are rungs extendingtherethrough}(and:wherein the ends of said rungssareusecured against rotation to the outer said links.

References inzthe fiie=of-"th-is patent NfITED. STAIE S: PATENTS;

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