US2139479A

US2139479A - Adjustable ladder

Info

Publication number: US2139479A
Application number: US223485A
Authority: US
Inventors: Harvey C Wertz
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-08-06
Filing date: 1938-08-06
Publication date: 1938-12-06
Anticipated expiration: 1955-12-06

Description

Dec. 6, 1938. H. c. WERTZ 2,139,479

' ADJUSTABLE LADDER Fil ed Aug. 6, 1 938 Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE Application August 6,

7 Claims.

The invention relates to ladders for use on sloping or uneven surfaces, and more particularly to a ladder adapted for quick and easy adjustment to accommodate it to varying uneven surfaces.

Prior constructions have included means for adjusting the supporting legs of a ladder, but such constructions have required manipulation of cam levers or locking pins in order to unlock the supporting legs and to lock them in adjusted positions.

Such locking devices are apt to become diflicult to operate because of corrosion or lack of lubrication, and do not always function efiiciently to positively lock the supporting legs' in adjusted position.

Accordingly, it is an object of the present invention to provide an improved ladder construction having adjustable legs for supporting the ladder on uneven surfaces.

Another object is to provide an adjustable ladder having improved means for automatically locking the supporting legs in adjusted positions.

A further object is to provide improved means for positively locking the supporting legs in adjusted positions in such a Way that the weight of a person on the ladder increases the locking action.

A still further object is to provide improved means for normally locking the supporting legs of an adjustable ladder in adjusted position, said means being in position to be released by grasping the ladder for adjusting the supporting legs thereof.

These and other objects are accomplished by the improvements comprising the present invention which is illustrated by way of example in the accompanying drawing, described in the specification, and defined in the appended claims.

In general terms the invention may be stated as including a ladder having a step frame with spaced cross bars pivoted thereon and supporting legs pivoted to the ends of the cross bars for relative movement longitudinally of the step frame, one cross bar being movable away from said step frame on its pivotal connection therewith and normally held in engagement with locking bars secured on said step frame.

Referring to the drawing forming part hereof:

Figure l is a rear perspective view of the improved ladder in adjusted position for resting on an uneven surface;

Fig. 2 is a front elevation of the improved ladder showing an adjusted position in dot-dash lines;

1938, Serial No. 223,485

Fig. 3 is a fragmentary side elevation thereof;

and

Fig. 4 is a fragmentary sectional view as on line 4-4, Fig. 2.

Similar numerals refer to similar parts throughout the several views of the drawing.

The invention is shown and described as applied to a short step ladder by way of example, but it will be understood that it may be equally well applied to ladders of different sizes and types without departing from the scope of the appended claims.

The improved ladder preferably includes side rails 5 connected at intervals by steps 6 forming a step frame F. The rear supporting leg member 1 may be fork-shaped including two members 8 pivoted as at 9 to the top of the frame F, so that the frame and rear leg member I can be folded together when the ladder is not in use.

Preferably a link II] is pivoted at one end to a bar ll secured between rear leg members 8, and has an angular flange [2 at its other end for engaging in a slot formed by the U-shaped metal piece l3 on one of the steps 6, for holding the frame F and rear leg 1 in spread apart position. A coil spring l4 may be secured between rear legs 8 at a position spaced below bar II over which the flange l2 may be hooked for yieldingly holding the link In out of the way when the frame F and rear leg member 1 are folded together.

The means for supporting the step frame F preferably includes adjustable supporting legs l5, located one at each side of the frame and preferably converging toward each other at their upper ends. The legs I5 are pivoted adjacent their lower ends as at I6 to the outer ends of a lower cross bar ll, which is in turn pivoted midway between its ends at l8 to a cross member l9 secured to the side rails 5.

At their upper ends the legs l5 are pivoted by pivots 20 to the outer ends of an upper cross bar 2|, and the cross bar 2| has a pivotal connection midway between its ends with a cross member indicated generally at 22 secured to the side rails 5. The cross member 22 may consist of two overlapped pieces 23 and 24 secured to the side rails under one of the steps 6, as shown in Fig. 4, and the pivotal connection of cross bar 2| therewith preferably includes a bolt or pivot pin 25 extending through said pieces 23 and 24 and extending slidably through said cross piece 2|, so that the cross bar is movable on the pivot.

An angular bracket 26 is secured on the rear side of .crosspiece 24, and has a flange 21 spaced from cross piece 24 in which the rear end of pivot pin 25 is fixed. A spring 28 is provided around pivot pin 25 for yieldingly urging cross bar 2| rearwardly against the flange 21 of bracket 26, as best shown in Fig. 4. A metal sleeve 29 may be provided in cross piece 24 around the spring 28 for shielding the same.

The cross bar 2| is preferably of metal and angular in cross section having a rearwardly extending flange 30. Means for automatically locking the cross bar in adjusted positions preferably includes substantially U-shaped locking bars 3| secured at their ends to the side rails 5, as by screws 32, and having their intermediate portions spaced rearwardly from said side rails.

The cross bar 2| extends between the bars 3| and the side rails, that is, through the openings provided by the locking bars, and the intermediate portions of the locking bars 3| are provided with series of notches or serrations 33 in which the flange 30 of cross bar 2| is adapted to be engaged.

As shown in Fig. 4, the notches 3-3 are preferably substantially Y-shaped in cross section, so that the flange 30 of cross bar 2| is easily entered and held. therein.

When the ladder is supported on aneven or flat surface, as indicated in full lines in Fig. 2, the cross bars ll and 2| are substantially horizontal and the spring 28' yieldingly urges the cross bar 2| rearwardly to hold the flange 30 thereof in engagement with horizontally opposite notches 33,

When it is desired to adjust the supporting legs l5 to rest on an uneven surface without tilting the frame F laterally, the operator grasps the side rails 5 and the adjacent upper ends of the legs l5 in such a way as to squeeze them together. This operation moves the cross bar 2| on its pivot 25 forwardly against cross piece 24, compressing the spring 28 and releasing the flange 30 from engagement with the notches 33.

While the cross bar 2| is held in this position, both the cross bars 2| and I1 may be swung easily about their pivots 25 and I8 respectively, to move one leg upwardly and the other downwardly to the desired adjusted position, such a position being shown in Fig. l and in dot-dash lines in Fig- 2. The legs |5 are then released and the spring 28 automatically engages the flange 30 in angulariy opposite notches 33 to hold the legs l5 in adjusted position. In other words, as shown in Fig. l. the flange 30 engages an upper notch of one lockingrbar 3| and a lower notch of the other locking bar 3|.

It is natural to grasp the side rails of a ladder intermediate their top and bottom ends when lifting, transporting or adjusting the ladder. In the present improved adjustable ladder, the cross bar 2| is released from engagement with the looking bars 3| for adjusting the ladder by merely grasping the side rails at the usual places in the accustomed manner and at the same time squeezing the upper ends of the adjustable legs |5 and the side rails together. Accordingly, the ladder may always be held with both hands on the side rails even though the supporting legs are being adjusted.

Obviously, the Weight of a person on the ladder will increase the frictional locking engagement between the. locking bars 3| and the cross bar 2| so as to more securely hold the legs in any adjusted position within the limits of the series of notches 33.

The improved: ladder is simple, compact and inexpensiveto make, and is easily manipulated and adjusted. When the operator releases his hold on the side rails of the ladder the supporting legs are automatically locked in position.

It should be understood that various modifications in details of construction and arrangement may be made in the present improved ladder as shown and described, without departing from the scope of the appended claims.

I claim:

1. An adjustable ladder including a step frame, cross bars spaced longitudinally of said step frame and pivotally connected thereto intermediate their ends, supporting legs at the sides of said step frame pivoted to the ends of the cross bars, one of said cross bars being movable away from said step frame on its pivotal connection therewith, a locking bar secured on said step frame adjacent said movable cross bar, and means yieldingly urging said movable cross bar into engagement with said locking bar.

2. An adjustable ladder including a step frame, cross barsspacedlongitudinally of said step frame andpivotally connected thereto intermediate their ends, supporting legs at the sides of said step frame pivoted to the ends of the cross bars, one of. said cross bars being movable away from saidstep frame on its pivotal connection therewith, a locking bar having notches secured on said step frame adjacent said movable cross bar, and springv means yieldingly urging said movable cross bar into engagement with said locking bar notches.

3'. An adjustable ladder including a step frame having side rails, spaced upper and lower cross bars pivotally connected intermediate their ends 2 on said step frame, supporting legs at the sides of said step frame pivoted to the ends of said cross bars, the upper cross bar being movable on its pivotal connection with said frame in a direction toward and away from said frame, serrated looking bars secured on said step frame side bars, and spring means yieldingly urging said movable cross bar into' engagement with the serrations of said locking'bars, I

4. In an adjustable ladder having a step frame, spaced cross bars pivoted on said frame, and supportinglegs pivoted to said cross bars, means for locking said legs in adjusted position, said means including a lockingbar'secured to the frame, and a' spring urging one of said cross bars away from said f-rameand into locking engagement with said lockingbar.

5.v Anadjustable ladder including a step frame having side rails, U-shaped locking bars having their'endssecured to said side rails and including notched portions spaced rearwardly thereof, upper and lower cross bars pivotally connected intermediate their ends on said step frame, said upper'cross bar extending between said side rails and said locking bar notched portions, spring means urging said upper cross bar into locking engagement with said locking bar notched portions, and supporting legs pivoted to the ends of said cross bars at the sides of said step frame.

6;. An adjustable ladder including a step frame having siderails, U-shaped locking bars having their ends secured to said side rails and including notched portions spaced rearwardly thereof, upper and lower cross bars pivotally connected intermediate'their ends on said step frame, said upper cross bar extending between said side rails and said locking bar notched portions and having a rearwardly directed flange, spring means at the pivotal connection: between the upper cross bar for urging said cross bar rearwardly to engage said flange with the notched portions of said looking bars, and supporting legs pivoted to the ends of said cross bars at the sides of said step frame.

7. An adjustable ladder including a step frame having side rails, a lower cross bar pivoted intermediate its ends on said step frame, a pivot pin on said step frame spaced upwardly from said lower cross bar, an upper cross bar mounted intermediate its ends on said pivot pin and slidable axially thereof, a locking bar on said step frame, a spring on said pivot pin between said step frame and said upper cross bar for urging said cross bar into engagement with said locking bar, and supporting legs pivoted to the ends of said cross bars at the sides of said step frame.

HARVEY C. WERTZ.

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