US2957543A - Extension ladders - Google Patents

Description

Oct. 25, 1960 c. E. LARSON EXTENSION LADDERS 3 Sheets-Sheet 1 Filed May 23, 1956 INVENTOR CLAYTON E. LARSON ATTORNEY 5 /(amm win! Oct. 25, 1960 c LARSON EXTENSION LADDERS 3 Sheets-Sheet 2 Filed May 23, 1956 INVENTOR CLAYTQN E LARs'oN ATTORNEYS 3 Sheets-Sheet 3 C. E. LARSON EXTENSION LADDERS Oct. 25, 1960 Filed May 23, 1956 INVENTOR CLAYTON E. LARSON ATTORNEYS EXTENSHPN L'ADDERS iayton Elmore Larson, Weston, COBB. assignor to White Metal Rolling & Stamping Corporation, Brooklyn, N.Y., a corporation of New York Filed May 23, 19-56, Ser. No. 586,813

4 Claims. (Cl. 182-211) This invention relates to extension ladders. More particularly, it relates to extension ladders of the type in Which one section slides longitudinally upon another section, the new, improved ladders being so designed that they can be made of light metal such as aluminum or magnesium and yet be structurally strong and also have wide tread steps instead of rungs.

FIELD OF INVENTION Extension ladders of the sliding section type are standand commercial items which are indispensable to the present-day conduct of business and household activities. Although such ladders are sold in large numbers by many difierent manufacturers, and although many improvements for such ladders have been devised by designers and manufacturers from time to time, there are still several important disadvantages generally connected with the majority of extension ladders commercially available today.

The first such disadvantage can be referred to as the weight problem. Thus, most extension ladders are made of wood, and since a hard, strong wood is required to have a structurally safe ladder, the wooden ladders are undesirably heavy. This weight problem becomes especially acute with the longer ladders, particularly when they are in extended position, and must be moved from place to place. A partial solution to the weight problem has been provided in the past by fabricating the ladders from light metals such as aluminum or magnesium, e.g., see U.S. Patent 2,040,977. However, many of the metal extension ladders made heretofore have been constructed with certain structural Weaknesses so that they break rather quickly, or they have been so complicated or diflicult to manufacture that the price of the ladders has been so high that they have not appealed generally to the purchasing public.

A second disadvantage of extension ladders can be referred to as the rung problem. Thus, the use of rungs in the construction of step ladders has been considered desirable or essential in the past in order to provide crossmembers having adequate structural strength and still be of such size as to meet the dimensional limitations imposed by the relatively sliding sections of the extension ladders. However, the use of rungs in extension ladders is undesirable from the viewpoint of the user for several reasons. First, ladder rungs are uncomfortable to stand upon, and anyone who stands on one for any length of time becomes quite fatigued. Secondly, since there is very little surface contact between a round rung and a shoe sole, it is very easy for the user of a ladder to slip off a rung. Hence, this presents a very real safety hazard.

Numerous attempts have been made to overcome the fatigue defect of extension ladders by providing movable foot rests or plates, which may be placed over ladder rungs to give the user of the ladder a flat or extended standing surface, e.g., see U.S. Patents 2,500,559, 2,528,317 and 2,730,412. Although such movable foot rests can be used to mitigate the fatigue defect of exten- 2,957,543 Patented o r. 25, 1960 sion ladders, they do not help solve the safety problem, for they are employed with only one step at a time. Furthermore, they present the user of the ladder with additional trouble, since the movable foot rest is another item which must be moved or stored, and they are unhandy to use.

These drawbacks associated with extension ladders have been known for many years, and numerous attempts to mitigate or eliminate them have been made from time to time. However, the defects have not been satisfactorily overcome and there has existed a real need for new and improved extension ladders which eliminate in a practical and satisfactory manner the weight and rung problems discussed above, as well as some other problems, e.g., binding of the ladder sections when the ladder is being lengthened or shortened.

Objects A principal object of the present invention is the provision of new and improved extension ladders of the longitudinally slidable section type. Further objects include:

(I) The provision of extension ladders which have wide tread steps instead of round rungs.

(II) The provision of extension ladders which are so designed that they can be made of a light metal such as aluminum or magnesium, and at the same time, can be assembled and produced without complicated stamping or fabricating operations which substantially increase the manufacturing cost of the ladders.

(III) The provision of extension ladders made of light metal so that they will not rot, rust or splinter, but at the same time, which are so constructed that they are structurally strong and last indefinitely with normal use.

(IV) The provision of sliding section extension ladders provided with rollers on the top section for contact with a wall or support and with pivoted safety feet on the bottom section of the ladder.

(V) The provision of sliding section extrension ladders in which the sections of the ladder are held together wtih new telescoping flange arrangements which permit the sections to slide smoothly relative to one another and substantially without any binding or the like between the ladder sections often encountered with extension ladders of the sliding section type.

(VI) The provision of extension ladders which are comfortable to stand upon, so that the user of the ladder can stand for long periods of time thereon without becoming appreciably fatigued or tired.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

General description These objects are accomplished according to the present invention by forming extension ladders with two or more sections which slide longitudinally relative to one another, the sections each being made from two side rails which are extruded in form of channels from light metal such as magnesium or aluminum, fixing extruded metal wide tread steps having integral reinforcing channels centrally disposed beneath the step treads between sections in sliding arrangement upon telescoping flange units formed integrally with the side rails.

A more complete understanding of the new and improved extension ladders of this invention and their method of use may be had by reference to the accompanying drawings in which:

Fig. 1 is a front elevation of the new and improved extension ladder constructions;

P Fig. 2 is a side elevation of the extension ladder of Fig. 3 is an enlarged fragmentary sectional view of the new ladders taken along the line 3--3 of Fig. 1;

Fig. 4 is an enlarged fragmentary front elevation showing the details of construction of the lower section of the ladder pictured in Fig. 3;

Fig. 5 is an enlarged fragmentary side sectional view showing the latch portion of the ladder in a slightly different position from that shown in Fig. 3;

Fig. 6 is an enlarged top plan view of the new ladders;

Fig. 7 is an enlarged fragmentary sectional view showing the top portion of the ladder as it appears when the ladder is fully closed;

And Fig. 8 is an enlarged fragmentary perspective view showing a portion of one of the wide tread steps of the new ladders and its method of attachment to a side rail.

Detailed description and modifications The new extension ladders basically comprise a lower section 2, an upper section 4 longitudinally slidable upon the lower section, latch means 6 and ladder section movement means 8.

The lower section 2 comprises a pair of side rails 10 and 12 which are preferably made from a light metal, such as magnesium or aluminum, by extrusion to have a special shape which will be described more fully hereinafter in connection with Fig. 8.

A plurality of wide tread steps 14 are fixed at equally spaced intervals between the side rails 10 and 12. An angle brace 16 is riveted to the under-side of the lowest step 14 by rivet 18, while the outer ends of the angle brace are fixed to the side rails 10 and 12 by rivets 20. This brace member 16 helps to hold the lower ends of the ladder section 2 firm and prevents undesirable vibration or spreading thereof.

Safety feet mounts 22 are fixed by rivets 24 to the bottom ends of side rails 10 and 12 and safety feet 26 are pivoted upon the mounts by bolts 28, which pass through the journals in the lower ends of the mounts. The feet are held in place by the cotter pins 30. The bottom face of the safety feet 26 are flanged to receive and hold the rubber pads 32.

The pivoted safety feet 26 permit the ladder to be extended, moved or used with greater ease and safety than ladders not equipped with such pivoted feet. Thus, the safety feet provide an extended'fiat surface upon which to rest the weight of the ladder and the person using the ladder, as compared with the pointed edge of a side rail. Similarly, the rubber pads 32 provide an anti-slip surface, aifording greater stability to the ladder.

The upper ladder section 4 comprises a pair of side rails 34 and 36 which, like the side rails of the lower section 2, have a plurality of wide tread steps 14 fixed between them at equally spaced intervals. The spacing between the steps in the upper section 4 is identical with the spacing between the steps in lower section 2. Similarly, as in the lower section, the upper section 4 also has an angle brace 38 fastened at its central bend to the lower-most step of the upper section by a rivet 40, while the outer ends of the brace are fixed by rivets 42 to the side rails 34 and 36.

The side rails of the upper ladder section, like the side rails of the lower section, are preferably made of light metal by extrusion in the form of a channel. The general shape of these extruded side rails can best be appreciated by reference to Figs. 6 and 8 of the drawings.

The side rails of both the upper and lower sections are the same except for the telescoping flange means which hold the two sections together. They comprise a channel member 44 which has a principal web 46 from which there extends two outwardly and perpendicularly extending rails 48. A pair of lugs 50 and 52 formed integral with the remainder of the side rail 44, extend perpendicularly and inwardly of the web 46 to form a longitudinally extending channel 54 on the inner face of each side rail. These integral lugs 50 and 52 and longitudinal channel 54 serve to mount the steps 14 upon the side rails. They also provide an important reinforcement for the side rails.

As can be seen most clearly in Fig. 8, each of the steps 14 comprises a tread portion 56 of a width approximating the width of the side rails and an integral reinforcing tubular channel 58 which depends centrally from the bottom of the tread portion 56. The steps are preferably made by extruding the tread with the anti-slip reeding 57 in the top surface and depending channels 58 from light metal, cutting the extruded stock into suitable lengths and then removing, such as by punching or sawing, the corners of the tread portions to form four notches 60 in each step. These notches 60 extend back from both edges of the step tread portion 56 as far in as the vertical faces 62 of the depending reinforcing channels 58 to create step mounting lugs 64.

The integral lugs on the side rails 50 and 52 are so spaced that the inner channels 54 are of just the same width as the distance between the outside surfaces of the lug portions 64. These lugs 64 are extended into the longitudinal channels 54 and are fixed to the side rails by bolts 66, which pass through mating holes extending through the lugs 50 and 52 and the side walls 62.

As can be seen in Fig. 7, the side walls 62 of the reinforcing channels 58 do not run perpendicular to the tread portion 56 of the steps 14. Instead, the side walls are formed at a slight angle from the perpendicular to the tread portions 56, forming a tubular element beneath the step tread portion which is trapezoidal in cross-section, the plane of the tread portion forming an inside angle of between about and with the rear side 62 of the two parallel sides of the trapezoid. Consequently, the steps 14, when mounted between the side rails, slope down at a slight angle toward the front of the ladder when the ladder is held in a vertical position.

In order to strengthen the side rails and prevent their ends from being bent or broken when the ladder is accidentally bumped at its ends, angle pieces 68 are fitted in the channel space defined the rails 48 and the web 46 (see Fig. 6) at the top and bottom of section 4 and the top of section 2. The angle pieces 68 are held in position by rivets 70. When safety feet 26 are used with the ladder, an angle piece 68 is not used to strengthen the bottom edges of side rails 10 and 12 because the feet mounts 22 have side extensions 71 which serve this purpose. However, if it is desired to construct the ladder without pivoted safety feet 26, then the mounts 22 are replaced by angle pieces 68.

As previously mentioned, the only principal difference between the side rails in the upper and lower sections of the ladder is in the elements of the rails which make up the telescoping means 72 used to hold the two sections of the ladder in slidable engagement with one another. The means 72 comprises a longitudinal arcuate flange 74 which extends inwardly from the forward end of side rails 34 and 36. Longitudinal beaded lugs which are made integral with the main body of the side rails, extend inwardly from the rear of side rails 2 and 4. As can be seen clearly in Fig. 6, the beaded lugs 76 slide within the arcuate flanges 74 to form slidable 5 connect-ions between the upper and lower sections ofthe ladder.

Since the flanges 74 and beaded lugs 76 provide a very extended contact area between two ladder sections, this construction provides a very strong arrangement for holding the two ladder sections in slidable engagement. At the same time, it has been found that there is very little binding action between the two sections when they are moved relative to one another, even when they are in extended position, in contrast to the majority of prior known extension ladders which employ strap-like brackets to hold separate ladder sections in sliding engagement. If desired, the arcuate flanges 74 can be formed integrally with the side rails 2, and iof the lower ladder section and the beaded lugs 76 can be similarly formed integrally with the side rails 34 and 36 of the upper section. However, the ladder construction shown in the drawings is preferred, since it has been found that this arrangement has less tendency towards binding than the modified form.

The latch means 6 which holds the ladder sections in adjusted extended positions relative to one another can best be understood by reference to Figs. 3, 4 and 5. It comprises hooks 77 which are pivoted at the bottom end 78 upon flanged pins 86 carried in the pillow blocks 82 fixed in the inner channels 54 by bolts 84. The free end of hooks 76 have notches 84 in the upper end to fit over lug portion 64 of the ladder steps 14 (see Fig. 3).

Pawls 86 are pivoted upon the pin 88, which are carried upon the latch hooks 76 so that the lower heavy ends 90 of the pawls will cause the pawls to fall into a generally vertical position when they are not in contact with a step lug. The other ends 92 f pawls 8'6 are bent over toward the side rails of the ladder so that when the weighted ends 96 of the pawls cause them to drop, the bent ends 92 will come in contact with the tips 94 of the hooks 76. Hence, the pawls 86 serve to close oif the notches 84 in the hooks 76 as the upper section 4 of the ladder is being closed down upon the lower section 2. Consequently, the pawls 86 cause the latch means 6 to ride up over each step lug as the upper section descends. Conversely, when the upper section 4 is being raised to extend the ladder, the bent ends 92 of pawls 84, which extend forward a slight distance beyond the tips 94 of the hooks 76, will be caught by the associated step rung 64 (see Fig. so that as soon as the tip $4 of hook 76 passes over the top of the lugs 64, the hook 76 will be snapped by the action of the leaf spring 96 bearing against pin 98 fixed to the hook 76 to snap over the step lug 64. Then, the upper section 4- can drop back slightly and the hooks 76 will become supported upon the step lug 64, as shown in Fig. 3. The leaf springs 96, which bias the hook toward the lower section steps, are fastened to the side rails by nuts and a bolt 100.

Raising and lowering of the upper section 4 of the ladder, particularly when the upper section is in an extended position, is accomplished using the section movement means 8. This comprises a pulley 102 journaled on the shaft 164, which is carried by the bearing member 106 fastened by rivets 108 upon the under surface of the reinforcing channel 58 of the top step 1 1 of the lower section 2. A rope or cable 114 passes over the pulley 102, one end of the rope being suitably fastened to the bottom step 14 of the upper ladder section 4, while the other end of rope 110 is left free. By pulling upon the free end of the rope, the upper section 4 will be moved up relative to the lower section 2.

In order to prevent the upper corner of the ladder from marring or damaging walls or surfaces against which the ladder may be placed or come in contact, and also as an aid in raising and lowering the ladder, the ladder is fitted with rollers 112. These rollers are carried upon the upper end of the upper section 4 on hearing pins 114, which are fastened in the forked end 116 of the standard 120. The standard 126 is fixed to the side rail of the upper section 4 by having the block shapeden'd 122. fit into the inner channel 54 of the side rail and be held in place in the inner channel by a pair of rivets 124.

Method of use The new ladders of this invention are preferably stored when not in use in a closed position, i.e., with upper section 4 moved down upon section 2 so that the latch devices 6 fit over the step lugs 64 of the bottom step of lower section 2. In this position, since the side rails of the upper and lower sections are both of the same length, the bottom edges of lower section side rails 10 and 12 will be in line with the lower edges of upper section side rails 34 and 36. The same will be true of the upper edges of all of the side rails. Furthermore, the treads of all of the steps of the upper section 4 will lie in the same plane as the treads of the juxtapositioned steps of the lower section 2. This alignment of the step treads is accomplished, as can be seen by reference to Fig. 3, by positioning the latch devices 6 upon the upper section 4 to bring the tread of at least one step of the upper section in the same plane with the tread of one step of the lower section. Then, since all steps of both upper and lower sections are the same spaced distance from one another, this alignment of the steps of the upper and lower sections will take place automatically regardless of what step the latch devices 6 are supported upon.

With the ladder in a fully closed position, it may be extended by resting the feet 26 on a suitable surface and then raising the closed ladder to a generally vertical position, or resting the rollers 112 against a wall or other surface against which the ladder is to be used. With either the ladder being held vertically by the user or with it resting on the rollers against a surface, the free end of rope is pulled to cause the upper section 4- to move upwardly with the arcuate flange 74 sliding over the beaded lug 76. As the upper section 4 proceeds upwardly, the hooks 76 will engage step lugs 64 and be pushed slightly backward against the biasing action of leaf spring 96, as shown in Fig. 5, while the pawl will be caught at end 92 and held out of the way to permit the book 76 to snap over the step lug 64 and then drop into position around the step lug,'as shown in Fig. 3. If this step extension of the ladder does give the desired height, the upper section is'pulled up step by step until the desired amount of extension is obtained. At each position where the latches fall into supporting arrangement, the tread portions 56 of both the front and back steps of the ladder will lie in the sameplane where the steps of the two ladder sections remain juxtapositioned.

When it is desired to shorten the ladder or return it to completely closed condition for storing, the upper section is first raised by pulling on rope 116 a sufficient amount to cause the latch hook 76 to raise up off step lug 64 and permit the pawl 86 to move under the action of gravity to enable the bent end 92 to clear the step lug and engage the tip 94 of the latch hook. Then, the upper section will drop on down with the latch devices 6 being pushed out of the way of each step because of the closing of hook opening 84 by the pawls 86. If it is desired to locate the ladder at some intermediate lowered position, the upper section '4 is brought down sufiiciently so that the latch devices 6 arefar enough below the particular step upon which they are to be supported to bring the lugs of that step above the ends 92 of the pawls 86. Then, the upper section is raised to cause the pawls to be moved away, as shown in Fig. 5, and permit the latch hook 76 to again snap over the desired step.

Conclusions New and improved designs for extension ladders have been discussed above. These new ladder constructions make it possible to fabricate step ladders of the slidable section type from light metals such as aluminum or magnesium in an efficient manner which permits them to be produced by large volume production methods resulting in reduced manufacturing costs. At the same time, the ladders are structurally strong, since they incorporate unique reinforcing features at all vital points, and they do not include inherent points of weakness found in many prior metal ladders which cause them to break or become unsafe after being used for a short while.

Probably the most significant aspect of the new extension ladders is their wide tread steps. As far as known, this is the first time that a ladder of this type has been available with wide tread steps instead of the usual narrow rungs. The steps of the new ladders provide a wide tread, reeded surface upon which a ladder user can stand for extended periods of time without becoming fatigued, and these treads are strong enough to support the heaviest person, even if the person stands on only a small section of the tread, e.g., an over-hanging front section. Nevertheless, the steps still meet the dimensional limitations imposed by the sliding sections of the ladder.

Finally, the new ladders are provided with novel telescoping means for holding the separate sections slidably together in a fashion which is structurally very strong and also is generally free of the binding action experienced in many extension ladders, particularly when they are in an extended condition.

I claim:

1. A bisectional extension ladder including a lower stationary section comprising side rails which each have a pair of integral lugs extending therefrom to form a longitudinal channel on the inner face of the side rail, and a plurality of steps fixed between said side rails at equally spaced intervals, each step comprising a fiat tread portion and an integral depending reinforcing channel, said tread portion being shorter in length than the distance between said side rails with the reinforcing channel extending beyond the tread portion at each side of the step forming mounting lugs for the step, the width of the step lugs being substantially equal to the distance between the inner walls of said side rail channels, said step lugs extending into said channels, the steps being fixed to the side rails by bolts which pass through mating holes in the inner face channels and step lugs, an upper movable section formed of side rails and steps substantially identically arranged as aforesaid in the lower section, said lower and upper sections being held together in slidable engagement by longitudinal arcuate flanges which extend from the side rails of one of the ladder sections and longitudinal lugs which telescope within said flanges extending from the side rails of the other ladder section, and latch means carried by said upper section adapted to hold said upper section at a plurality of separate positions relative to the lower section with the treads of the steps of the upper section in the same plane as the tread of the juxtapositioned step of the lower section.

2. A ladder as claimed in claim 1 wherein the sides of said step reinforcing channels are all at a slight angle off the perpendicular to the tread of their respective steps whereby the steps slopes slightly downwardly toward the front when the ladder is held in a vertical position.

3. An extension ladder comprising a plurality of slidably connected together ladder sections, each section comprising parallel side rails and a plurality of wide tread steps fixed at spaced intervals along said ladder sections, each of said steps comprising a fiat, tread portion of a width approximating the width of said side rails and an integral structural member coextensive therewith, depending centrally from the underside of said tread portion forming a reinforcement element longitudinally across the bottom of the tread portion, the steps in at least one of said ladder sections being notched out back to said structural member creating side extending lugs out of the portions of the structural member where the tread portion is notched out, the steps in said last mentioned ladder section being supported upon the side rails thereof by said lugs, and latch means carried by at least another one of said ladder sections to hold the ladder in an extension position, said latch means comprising hooks pivotally mounted on the inside of said side rails for enga ement over said side extending lugs.

4. A ladder as claimed in claim 3 wherein said steps are formed of extruded metal and the depending integral structural member is a tubular element.

References Cited in the file of this patent UNITED STATES PATENTS 70,016 Quackenbush Oct. 22, 1867 598,430 McBride Feb. 1, 1898 790,807 Schilling May 23, 1905 856,683 Davis June 11, 1907 975,223 Ferguson Nov. 8, 1910 989,570 Cooper Apr. 18, 1911 1,645,232 Ferguson Oct. 11, 1927 2,126,171 Carbis Aug. 9, 1938 2,214,935 Perry Sept. 17, 1940 2,388,415 John Nov. 6, 1945 2,466,838 Buell Apr. 12, 1949 2,636,659 Salisbury Apr. 28, 1953 2,680,555 Nilsson June 8, 1954 2,760,706 Pearl Aug. 28, 1956 FOREIGN PATENTS 16,710 Great Britain 1904 211,308 Great Britain Feb. 21, 1924 140,391 Australia Mar. 5, 1951 178,274 Austria Apr. 26, 1954

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