US3021921A - Ladder extension - Google Patents

Description

LADDER EXTENSION 2 Sheets-Sheet 1 Filed May 22, 1959 Illllllll:

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LADDER EXTENSION 2 Sheets-Sheet 2 Filed May 22, 1959 FIG. 4

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ATTORNEY United States. Patent 3,021,921 LADDER EXTENSION Clement C. Poelvoorde, 1002 W. 7th .St., Mishawaka, Ind. and Stanley A. Kapusta, 19519 E. Reasor St., South Bend, Ind.

Filed May 22, 1959, Ser. No. 815,005 '3 Claims. Cl. 182-201) The present invention relates to ladders, and more particularly to a mechanism for use in adjusting a ladder or similar device to uneven ground, floors or other supporting surfaces.

One of the principal objects of the present invention is to provide a mechanism for adjusting the legs of a ladder or similar devices to uneven ground, floors and the like, which can easily be varied in length to give the desired extension and which automatically locks in its adjusted position when released, to safely and firmly maintain the position until intentionally released.

Another object of the invention is to provide a mechanism for varying the length of the legs of ladders and the like which can be readily mounted on and firmly secured to the legs of conventional step and straight ladders, and which canbe so installed without the use of any special tools, skills or the necessity of placing the mechanism in any exact position on the respective legs of the ladder.

Still another object of the invention is to provide an extension mechanism of the aforesaid type which can be adjusted to an infinite number of positions within maximum and minimum limits to give a firm, level position to the ladder after the ladder has been raised or placed in its desired upright position. A further object of the invention is to provide a relatively simple, easily operated ladder extension which will fit a standard ladder and which will give long, trouble-free service without any special attention or conditioning.

Another object is to provide a mechanism for adjusting the leg length of ladders and the like, which can be constructed as an integral part of the ladder during the fabrication of the ladder or as a separate unit which can be installed on the ladder in the factory, store or home.

Additional objects and advantages will become apparent from the following description and accompanying drawings, wherein:

FIGURE 1 is a perspective view of a step ladder shown in its unfolded position and with our present extension mechanism mounted on the legs thereof;

FIGURE 2 is an enlarged front elevational view of the present extension mechanism removed from the ladder;

FIGURE 3 is a side elevational view of the extension mechanism shown in FIGURE 2;

FIGURE 4 is an elevational view of the other side of the mechanism shown in FIGURES 2 and 3;

FIGURE 5 is a top plan view of the extension mechanism shown in the preceding figures;

FIGURE 6 is a vertical cross sectional view of the present mechanism, taken on line 66 of FIGURE 4, showing the mechanism in its locked position;

FIGURE 7 is a vertical cross sectional view of the mechanism, taken on line 7-7 of FIGURE 4, showing the mechanism in its unlocked position;

FIGURE 8 is a horizontal cross sectional view of the mechanism taken on line 8-8 of FIGURE 2;

FIGURE 9 is a plan view of one of the elements of the means for locking the extension mechanism in its adjusted position; and

FIGURE 10 is a plan view of a spring forming a part of the locking means.

Referring more specifically to the drawings, numeral 12 designates a conventional step ladder having front upright side members 14 and 16, with legs 18 and 20, respectively,

3,021,921 Patented Feb. 20, 1962 ice steps 2.2, top step '24, rear legs 26 and 28 and chains 30 and 32 for retaining the ladder in its unfolded upright position during use. Numeral 34 indicates the present leg extension mechanism mounted on the outer side of all four legs of the ladder, and secured thereto by screws or bolts extending into or through the legs. The extension may be mounted on only one or two legs, for example, on legs 18 and 20 or on legs 18 and 26. The step ladder 12 is shown merely for the purpose of illustrating the manner in which the present extension mechanism is installed and is not to be a limitation on the present invention, which may be used equally as well on straight ladders, and scaffolding, on chairs, stools, saw horses and benches. For convenience of description, however, the term ladder will be used in the specification and claims to include and mean any of these aforementoined devices unless specifically stated otherwise.

The present ladder extension mechanism is constructed of metal, preferably aluminum, and consists of a plate 40 and a shaft 42 slidably mounted on said plate by brackets 44 and 46 formed integrally with the plate and having aligned rectangular holes 48, 49 and 50, respectively, for receiving the shaft. The plate-is secured to the ladder legs bya plurality of'screws or bolts (not shown) extending through holes 52, the position and size of which may be varied to fit any particular installation. Shaft 42 is rectangular in-cross section and slightly smaller in transverse dimensions than holes 48, 49 and 50 so that the shaft will slide freely therein, and is held in locked position by three fingers '54, 56 and 58, 'each' of said fingers having a broadened portion 60, as shown in FIGURE 9, with a rectangular hole 62 therethrough and a tongue-like portion for use in operating the lock means.

The three fingers are assembled inhollow bracket 44, and are held firmly against a shoulder 66 by a spring 68, of the shape shown in FIGURE 10, reacting between the bottom wall 70 of bracket 44 and the underside of the lower finger 58. The loop 72 of spring '68 extends substantially around hole 62 of the lower finger and bears against the lower face thereof. To assist in operating the fingers to release the locking means, an arm 74 is rigidly connected to bracket 44 above the opening 76 through which the fingers extend so that the operator can raise the fingers by merely squeezing the fingers upwardly against or toward the arm, shoulder '66 functioning as a pivot point for the fingers so that as the outer ends 64 of the fingers are pulled toward the arm, portions 60 move to a horizontal position perpendicular to the shaft, retracting corners 80 and 82 on the opposite sides of hole 62,fr0m the shaft, thereby releasing the shaft for free longitudinal movement, as soon as the operator releases the fingers, spring 68 returns the fingers from the position shown in FIGURE 7 to the position shown in FIG- URE 6, again locking the shaft in its adjusted position. A shoe 88 of rubber or of metal with a rubber sole is preferably secured to the lower end of shaft 42 to prevent slipping while the ladder is being used.

In use and operation, the present leg extension mechanism is secured to the legs of a ladder or the like, preferably one on each of the four legs, using screws or bolts extending through holes 52, and shoe 88 is placed on the lower end of shaft 42 with the lower side, as seen in FIGURE 2, facing outwardly away from the ladder. When the ladder is first placed on uneven ground or floor, the extensions are preferably all in their retracted position i.e. with the shoes adjacent the lower ends of the ladder legs. Shaft 42 on the leg above the lowest part of the ground or floor is pulled downwardly until the shoe comes in contact with the ground or floor. The shaft can be pulled downwardly to its adjusted position without manipulation of fingers 54, 56 and 58 and the shaft will be automatically locked in its adjusted position by spring 68 urging corners 80 and 82 into engagement with the shaft with the fingers positioned at the inclined angle shown in FIGURE 6. Any pressure on the ladder tending to move the shaft longitudinally will only result in a better gripping action between the fingers and the shaft so that no slippage will occur. Two and possibly three of the extension mechanisms may be adjusted before the ladder is fully level. When the ladder is moved to a place where the floor or ground is level, the shaft is released from its adjusted position and returned to the retracted position by the op erator merely squeezing fingers 54, 56 and 58 upwardly toward arm 74 to the position shown in FIGURE 7. This causes the fingers to pivot on shou-lder'66 and to become substantially level or directly perpendicular to the' axis of the shaft, thus resulting in the withdrawal of corners 80 and 82 from the sides of the shaft, releasing the latter so that it can move freely to its retracted position. When the fingers are released by the operator, spring 68 returns the fingers to their angular position shown in FIGURE 6. In a modification of the invention, shaft 42. may be round and the holes through brackets 44 and 46 and fingers 54, 56 and 58 circular to accommodate and operate satisfactorily in conjunction with the round shaft. Further, one, two, ormore than three fingers may be used in the locking means. Various other changes and modifications maybe made without departing from the scope of the present invention. i

We claim: g 1. An extension mechanism for the legs of ladders and the like, comprising a plate having a plurality of holes for securing said mechanism to the legs of the ladder, two generally vertically arranged brackets secured to said plate and having aligned rectangularly shaped openings therethrough, a shaft having a rectangularly shaped cross section slightly smaller than said openings extending through said openings and downwardly beyond said plate, a shoe of rubber or rubber-like material on the lower end of said shaft, three fingers in face-to-face contact with each other in the upper bracket and extending outwardly therefrom and having a position substantially perpendicular to said shaft, each of said fingers having a rectangularly shaped hole for receiving said shaft in said bracket, a rigid arm secured to the bracket adjacent to and above said fingers, a rigid shoulder on said arm serving as pivot point forsaid fingers between the holes therein and the portion extending from the respective bracket, and a spring operatively positioned in said upper bracket exerting a force on said fingers and urging said fingers about said pivot point upwardly away from said perpendicular position.

2. An extension mechanism for use with ladders and the like, comprising a plateadapted to be secured to a ladder, a bracket secured to said plate and having a rectangularly shaped opening therethrough, a shaft having a rectangularly shaped cross section extending through said opening and downwardly beyond said plate, three fingers in face-to-face' contact with each other in the bracket and extending outwardly therefrom and having a position substantially perpendicular to said shaft, each of said fingers having a rectangularly shaped hole for receiving said shaft in said bracket, an arm connected to said bracket, a fixed shoulder on said arm serving as pivot point for said fingers between the holes therein and the portion extending from said bracket, and a spring operatively positioned in said upper bracket exerting a force on said fingers and urging said fingers about said pivot point upwardly away from said perpendicular position.

3. An extension mechanism for use with ladders and the like, comprising a bracket having a rect-angularly shaped opening therethrough, a shaft having a rectangularly shaped cross section extending through said opening and downwardly substantially below said bracket, a shoe on the lower end of said shaft, a plurality of fingers in face-to-face contact with eachother in brackets and extending outwardly therefrom and having a position substantially perpendicular to said shaft, each of said fingers having a rectangularly shaped hole for receiving said shaft in said bracket, an arm secured to the bracket adjacent to and above said fingers, a fixed shoulder onsaid arm serving as pivot point for said fingers between the holes therein and the portion extending from the bracket, and a spring operatively positioned in said upper bracket exerting a force on said fingers and urging said fingers about said pivot point upwardly away from said perpendicular position. as

References Cited in the file of this patent UNITED STATES PATENTS 1,844,760 Hayne Feb.'9, 1932 1,978,855 Ha ne Oct. 30, 1934 2,432,245 Lundquist Dec. 9, 1947 2,555,036 Hosted May 29, 1951 2,608,794 Matter Sept. 2, 1952 2,806,723" Fairclough Sept. 17, 1957 2,890,824 Derby June 16 1959 2,914,135 1959 Crouch Nov. 24,

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