US3902569A

US3902569A - Extension ladder

Info

Publication number: US3902569A
Application number: US444023A
Authority: US
Inventors: Roger I Bair
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-02-20
Filing date: 1974-02-20
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02

Abstract

An extension ladder is disclosed having improved cable means adapted to assist in longitudinally moving one section of the ladder relatively to the other. In one form, a rail of one section has spaced-apart pulleys, and a cable trained around the pulleys for travel therearound as the sections move relatively to each other has a portion fixed with respect to an adjacent rail of the other section. Optionally, adjacent side rails of the two sections are adapted to interengage to keep the sections together and facilitate the relative longitudinal movement of the sections, and the ladder has releasable clamp means to fix one section to the other at a selected position reached in their relative, longitudinal movement.

Description

Unlted States Patent 1 [111 3,902,569

Bair Sept. 2, 1975 EXTENSION LADDER Primary ExaminerReinaldo P. Machado [76] Inventor: Roger 1. Hair, 806 E. Baltimore Rd Attorney Agent or Firm-Wesley Taylor Westminster, Md. 21 157 AB C STRA T 22 F] d: F b. 20, 1974 1 1 e e An extension ladder is disclosed having improved [21 Appl. NO-I 4 ,0 3 cable means adapted to assist in longitudinally moving one section of the ladder relatively to the other. In one form a rail of one section has 5 aced-a art ulle s ..Cl. ..1s2211 P P P Cl 2 E06C /1 2 and a cable trained around the pulleys for travel there- [58] Fieid i i i 210 209 around as the sections move relatively to each other 1822/21 has a portion fixed with respect to an adjacent rail of the other section. Optionally, adjacent side rails of the two sections are adapted to interengage to keep the [56] References cued S sections together and facilitate the relative longitudi- UNITED STATES PATENT nal movement of the sections, and the ladder has re- Huska leasable clamp means to fix one ection to the other at fi a selected position reached in their relative, longitudiramer..... 3,491,353 1 1970 Stillman 182/207 nal movement 10 Claims, 5 Drawing Figures EXTENSION LADDER BACKGROUND OF THE INVENTION Extension ladders are widely used both in industrial and home applications. Such ladders commonly comprise two sections adapted to move relatively to each other in the direction of their lengths so as to vary the effective length of the ladder. Hence the term extension ladder. The section of the ladder which rests on a ground support and normally does not move longitudinally has been called the base section, and the companion section which does move longitudinally and extends the ladder has been called the fly section. For convenience of reference, these terms are similarly used in the following description and claims.

Various means have been proposed to move the fly section relatively to the base section. Most are cumbersome to use and unduly add to the weight of the ladder. Since extension ladders are manually positioned for use, the over-all weight can be a factor. More seriously, a cable or rope is often employed to assist in moving the fly section relatively to the base section, and the rope becomes a safety hazard in that, by design, it passes around and becomes intertwined with the rungs of either or both sections. In this position, the rope limits the useful safe function of the ladder, since in climbing a section, the feet or legs of a user can accidentally catch on the rope, causing the user to trip or fall.

For example, in US. Pat. No. 3,331,468 to Redman, a rope runs directly along the longitudinal centers of both the base and fly sections, often leaving a length of the rope both in front and behind the midpoints of the rungs of the base section, and behind the midpoints of the rungs of the fly section. Further, in Redman different sections of the rope must be successively clamped and released by a sinuous clamp as the two sections are placed at different positions of extension. Moreover, the clamp itself is placed inside or between the ladder sections adjacent the center or midpoint of a rung and thereby further increases the safety hazard in climbing the ladder.

It would, therefore, advance the art to provide an extension ladder having improved means to move the base and fly sections relatively to each other.

SUMMARY OF THE INVENTION The present extension ladder has simple construction, is easy to operate, and yet is durable and safe in use. The ladder includes base and fly sections overlying and contacting one another in substantially parallel relation and adapted for relative, longitudinal movement. Cable means used to assist in the relative, longitudinal movement is confined to the sides of the sections and out of the way of a user of the ladder. The cable means does not intertwine with rungs, or even reach the rungs, nor wind about any other standard part of the sections of the ladder.

In one form, the present ladder includes spaced-apart pulleys located along one side of one of the sections and remote from the rungs or steps that one would use in climbing that section. A cable trained over the pulleys and adapted to ride around them as the two sections move relatively, has a length or portion of the cable fixed to the other section, likewise along a side of that section and remote from the rungs or steps of that section.

In addition, the adjacent sides or rails of the two sections are preferably shaped to interengage in a sliding relation and thereby facilitate the relative longitudinal movement of the sections while helping to keep the sections together. Optionally, the ladder also may include releasable clamping arms pivotally mounted on one section and adapted to clamp onto a selected part, such as a rung, of the other section, tentatively to lock the two sections together at some desired position reached in their relative longitudinal movement.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. I is a perspective view of one embodiment of the present ladder placed in position against a wall;

FIG. 2 is a side elevational view of the ladder of FIG.

FIG. 3 is an enlarged, fragmentary view of a side rail of the fly section and shows a hook or catch for a cable;

FIG. 4 is a fragmentary, horizontal cross-section taken through two adjacent side rails of the overlying sections and illustrates how these sides may interengage for sliding movement; and

FIG. 5 is a fragmentary, vertical cross-section taken between the side rails of the two sections and shows releasable clamping arms for locking the two sections together at some desired position of extension.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the embodiment illustrated includes a base section, generally indicated at B, ineluding spaced-apart rails 10 and II interconnected by rungs 13, and a fly section generally represented at F and including spaced-apart rails 13 and I4 interconnected by rungs 15. The base and fly sections including their rungs may be made of any suitable material, such as wood or metal, and especially extruded aluminum, the die for which is configured to produce the crosssectional shapes illustrated in the drawing. For example,

rungs

12 and 15 are generally circular in crosssection but may have a flattened

upper land

12a and 15a, respectively, (FIG. 2) for the convenience and comfort of a user.

A cable system used to assist in moving section F relatively to section B is mounted outboard or to the side of the two sections. As shown in FIG. 2, two

strips

16 and 17 are bolted to the outside of the rail 11 of the base section B near its upper and lower ends. The strips extend toward fly section F and their forward ends are folded back on themselves in a direction toward rail 14 of the fly section to form bearings 16a and 17a in which pulleys l8 and 19 are freely mounted, respectively, for rotation on stub shafts 20. It will be noted that this construction places pulleys 18 and 19 in a vertical plane that passes through rail 11 as viewed in FIG. 2 and parallel to that view.

A cable 22 is trained around pulleys l8 and 19 for travel thereover. By the term cable or cable means is meant rigging, rope, roping, cord, and the like. The cable may be considered to be effectively continuous with a portion of the cable fixed to side rail 14 of the fly section. In the embodiment illustrated, cable 22 has free ends which are fixed to side rail 14 in proximity to each other by a hook or catch 23. The hook includes a metal strip fixed by a bolt 24 to side rail 14 and having its ends folded back on itself and bifurcated to define opposed, cooperating

claws

25 and 26. The free ends of cable 22 are knotted as at 27 and 28, with one knot caught between each of the

opposed claws

25 and 26. The length of cable 22 is initially adjusted to be substantially taut as shown in FIG. 2. Thereafter, no further adjustment of any kind is ever necessary, even as sections B and F move relatively to each other to the maximum amount of extension possible.

In order to facilitate a relative, sliding movement between the ladder sections, it is preferred to have the adjacent side rails of the two sections slidably interengage. FIG. 4, which is a horizontal cross-section of

rails

10 and 13 of the two sections, illustrates one manner of accomplishing this. A corresponding horizontal cross-section of interengaging rails 11 and 14 may be the same. The width of section F is less than the width of section B, so that

side rails

13 and 14 lie between side rails 10 and 11. Each side rail has front and rear flanges shown at 10a and 10b and at 13a and 13b in FIG. 4 for

rails

10 and 13, respectively. Flanges 10b and 13a overlap, with flange 13a lodged between flange 10b and rungs 12 of section B. This prevents sections B and F from laterally separating. On the other hand, further nesting or movement of the sections toward each other is arrested by flange 14b of rail 14 (FIG. 2) striking against the bearings 16:: or 170. Additionally, there is a T-shaped rubber strip 30 fixed in any suitable manner, such as by bolts passing through the stem of the T, to the top of each of the side rails 10 and 11 of the base section. Strips 30 bear against the forward flange 14a of rail 14 and forward flange 13a of rail 13 to limit the nesting movement of section F into and between the side rails of section B.

The present invention does not rely on any particular releasable clamping means to lock the sections together at a selected, extended position. Various means known in the art can be used. FIGS. 1 and illustrate a preferred clamping device, one such device being installed along each side of the ladder, inwardly of the rails. Since these clamping devices are the same, except for being mirror images of each other, that is, of right and left hand order, only one is described in detail.

A bolt 32 secures a pocket 33 formed of strip metal to an inner side of rail 13 and also serves as a pivot pin for a swinging arm 34 around which the arm turns. The arm has a downwardly pointing finger 35 defining a notch 36 and an upwardly extending cam finger 37 which curves to the other side of the pivot pin 32 away from notch 36 as shown in FIG. 5. Midway of arm 34 and on a side of notch 36 opposed to finger 35, a pivot pin 38 Secures a lever 39 for free rotation with respect to arm 34. Lever 39 has a small flange 41 passing beneath finger 35 and is fairly evenly balanced, so that it normally assumes a substantially horizontal position as shown in FIG. 5. A leaf spring 42 has one end secured by rivet 43 to pocket 33 and to rail 13, its free end bearing against arm 34 and urging it to the left as viewed in FIG. 5.

An inverted, U-shaped holder 45 having a telescoping rubber sleeve 46 is bolted to the front and rear flanges of each of the

rails

13 and 14 of the fly section. These serve as hand-grippers, and rubber sleeve 46 minimizes marring of a surface against which the upper portion of the ladder may rest. Shoes 47 are pivotally mounted to the bottom ends of rails and 11 of the base section by transverse pivot pins 48. By virtue of being free to turn, shoes 47 readily accommodate to any support surface even should the surface slant from the horizontal. To increase frictional contact, the soles of shoes 47 may have a rubber strip 49 suitably secured to the shoes.

In use, fly section F may be readily moved longitudinally with respect to base section B without any concern for or, indeed, attention to cable 22. It is not necessary periodically to tie or loosen the cable with respect to other parts of the ladder as is required in other types of extension ladders. Since the front flange of

rails

13 and 14 overlap the rear flanges of rails 10 and 11 and lie between those rear flanges and rungs 12 of the base section, as shown in FIG. 4, the two sections are prevented from separating. The flanges of

rails

13 and 14 in cooperation with bearings 16a and 17a and in cooperation with rubber strips 30 prevent excessive inward, nesting movement of the two sections as previously described. Meanwhile, the relative longitudinal movement of the two sections is guided and strengthened by cable 22, pulleys 18 and 19, and

holders

16 and 17. Still other means can be used to prevent forward or rearward or lateral displacement of the two sections.

With respect to the clamping device of FIG. 5, it is not necessary for a user of the ladder to touch this device when lifting the fly section. As section F rises, cam finger 37 strikes a higher rung 12 of section B, pivoting arm 34 clockwise about pivot pin 32. The same rung contacts the left hand portion of lever 39 and turns it in a counter-clockwise direction, such that notch 36 of arm 34 and lever 39 are poised like open jaws about to close upon a rung. When fly section F is allowed a slight drop from this position, notch 36 catches about an upper portion of a rung l2, and lever 39 turns clockwise to contact a lower portion of the rung. The two sections are now locked relatively to each other.

To unlock the sections, section F is again raised slightly so that finger 35 clears the rung. Arm 34 is then pulled back (clockwise in FIG. 5) as by pulling on the cam finger 37, and section F is then allowed to drop by its own weight without obstruction.

It is also possible to position the clamping device intermediate rungs 12 as shown in FIG. 5. In this case, notch 36 does not seat about a rung. Arm 34 is allowed to pivot counterclockwise (under the influence of spring 42) sufficiently above a rung, so that lever 39 is also above the rung. Now when section F drops, lever 39 strikes the rung and is turned clockwise about its pivot pin 38 (FIG. 5) until flange 41 of the lever hits finger 35. The arm 34 and lever 39 then rest on the rung as illustrated in FIG. 5.

Although the foregoing describes a preferred embodiment of the invention, it is understood that the invention may be practiced in still other forms within the scope of the following claims.

I claim:

1. In an extension ladder comprising a base section and a relatively longitudinally movable fly section, the improvement of means for moving one section relatively to the other including spaced-apart pulley means fixed with respect to one section and extending to a side of said other section, and cable means having spaced-apart portions trained over said pulley means for travel therearound as the sections move relatively to each other, and unitary catch means rigidly fixed with respect to the other section comprising strip means having spaced-apart hook means adapted releasably to engage said spaced-apart portions of said cable means.

2. The extension ladder of claim 1 in which said pulley means and said unitary catch means are so fixed to said sections along sides thereof.

3. The extension ladder of claim 1 in which said spaced-apart portions of said cable means are fixed to said unitary catch means in proximity to each other.

4. An extension ladder including a base section having side rails and a fly section having side rails, the two sections overlying and contacting one another and being adapted for relative longitudinal, slidable movement, spaced-apart pulley means mounted on a side rail of said base section and extending to a side of said fly section, cable means having spaced-apart portions trained around said pulley means for travel thereover as the sections move relatively to each other, and a single, integral catch means rigidly fixed with respect to an adjacent side rail of the fly section including strip means having opposed hook means adapted releasably to engage said spaced-apart portions of said cable means.

5. The extension ladder of claim 4 in which the adjacent side rails of the two sections are adapted to interengage to facilitate such relative, longitudinal, slidable movement.

6. The extension ladder of claim 4 in which the width of one section is less than the width of the other section whereby the side rails of said one section lie between the side rails of said other section, and the adjacent side rails of the two sections are adapted to interengage to facilitate such relative, longitudinal, slidable movement.

7. The extension ladder of claim 4 in which the adjacent side rails of the two sections have interengaging flange means to facilitate such relative, longitudinal, slidable movement.

8. The extension ladder of claim 4 in which said spaced-apart portions of said cable means are fixed to said integral catch means of the other section in proximity to each other.

9. The extension ladder of claim 4 in which said spaced-apart portions of said cable means comprises free ends, and the integral catch means of said adjacent side rail of the other section secures said free ends.

10. An extension ladder including a base section having side rails and interconnecting rungs and a fly section having side rails and interconnecting rungs, the two sections overlying and contacting one another and being adapted for relative longitudinal, slidable movement, spacedapart pulley means mounted on a side rail of said base section and extending from that section toward a side of said fly section, a single, unitary integral catch means provided with turned, bifurcated opposed ends to define hook means mounted on a side rail of said fly section adjacent the side rail of said base section having the spaced-apart pulley means, and cable means having free ends trained around said pulley means and having said free ends secured to said

Claims

10. An extension ladder including a base section having side rails and interconnecting rungs and a fly section having side rails and interconnecting rungs, the two sections overlying and contacting one another and being adapted for relative longitudinal, slidable movement, spaced-apart pulley means mounted on a side rail of said base section and extending from that section toward a side of said fly section, a single, unitary integral catch means provided with turned, bifurcated opposed ends to define hook means mounted on a side rail of said fly section adjacent the side rail of said base section having the spaced-apart pulley means, and cable means having free ends trained around said pulley means and having said free ends secured to said hook means.