US3025925A - Lazy-tongs mechanisms, with particular application to foldable ladders - Google Patents

Description

March 20, 1962 B LAZY-TONGS MEC APPLICATI Filed March 10, 1959 T. T. PO

HANISM ON TO FO 0 3,025,925 WITH PART LAR BLE LADDE 2 Sheets-Sheet 1 March 20, 1962 B. T. T. POOK 3,025,925

LAZY-TONGS MECHANISMS, WITH PARTICULAR APPLICATION To FOLDABLE LADDERS Filed March 10, 1959 2 Sheets-Sheet 2 ilnite States This invention is concerned in general with the provision of improved lazy-tongs mechanism with particular application to an improved ladder capable of being told ed up when not required and adapted to be opened out quickly and easily in order to be ready for use. Our improved ladder may be used as a loft ladder, or in connection with aircraft or ships and for many other purposes.

Ladders making use of lazy-tongs mechanisms are quite well known and such ladders fold up and open out in an efiicient manner and application of the present invention to ladders relate to ladders of this type. One disadvantage of known lazy-tongs mechanism and particularly ladders based upon this principle is that when folded they take up rather too much space. It is an object of the present invention in general to provide an improved lazy-tongs mechanism which takes up less space when folded than known mechanisms of this type, and in particular to provide an improved foldable ladder using the lazy-tongs principle.

According to the present invention we provide mechanisms of the type referred to in which the rods of the lazy-tongs are so interconnected that when the mechanism is folded the outer pivots are arranged in staggered and overlapping relation so that the mechanism folds into smaller space than heretofore. To achieve this result each rod instead of being pivoted to an adjacent rod at an inner pivot in the centre is connected to the adjacent rod oif-centre so that each rod has a longer arm and a shorter arm. Looking at the lazy-tongs as a whole the two shorter arms of one pair of rods are pivoted at their free ends to the two shorter arms of the adjacent pairs of rods and so on with the result that the outer pivots align themselves in two rows at each side of the inner pivots when the mechanism is folded.

The invention also includes a ladder comprising a pair of spaced mechanisms each of the type referred to, wherein the rods of each lazy tongs mechanisms are so interconnected that, when the mechanisms are folded simultaneously, rungs pivotally connecting corresponding ends of the rods of the pairs and spacers connecting the corresponding other ends of the rods are arranged in staggered and overlapping relation so that the ladder folds into a smaller space than heretofore.

In order that the invention may be clearly understood and readily carried into effect, reference is now directed to the accompanying drawings which illustrate the application of the invention to a foldable ladder and in which:

FIGURE 1 is a side elevation of a ladder in accordance with this invention shown in the extended position;

'FIGURE 2 is a side elevation to an enlarged scale showing the ladder folded, and

FIGURE 3 is a part plan of FIGURE 2.

In the drawings a foldable ladder consists of a lazy tongs indicated generally at 1 and having a ground engaging member 2 at the lower end and a strap 3 at the upper end to engage the aircraft or the like with which atent the ladder is associated. The lazy tongs at each side 4 of the ladder is made up of pairs of rods 4, 5 pivotally connected in crossed over relation at 6. The pivots 6 form what is referred to in this specification as the inner pivots. In known lazy tongs mechanisms generally and as applied to ladders in particular the inner pivots 6 aredisposed centrally of the pairs of rods but that is not so in accordance with the invention and as illustrated each pair of rods 4 and 5 have longer arms 7 and shorter arms 8. The shorter arms 8 of each pair of rods 4, 5, are pivotally connected at 9, 10 to the shorter arms 8 of one adjacent pair of rods and the longer arms 7 of each pair of rods 4, 5 are pivotally connected at 11, 12, to the longer arms 7 of another adjacent pair of rods. The pivots 9 and 10, 11 and 12 forms what are referred to in this specification as the outer pivots and the arrangements are such that the outer pivots align themselves in two rows at each side of the inner pivots when the ladder is folded up.

FIGURE 2 illustrates this very clearly and it will be observed that the outer pivots are arranged in staggered and overlapping relation so that the ladder is foldable into a smaller space than heretofore with ladders having the outer pivots foldable into exact alignment.

The top rod 13 of the lazy tongs has a recess 14 on the underside for engagement behind a locking nut 15 as illustrated in FIGURE 1 so that the ladder may be locked in its operative position.

In the embodiment illustrated the pivots 9 and 11 support the rungs 16 of the ladder and the pivots 10 and 12 support spacers 17. As illustrated the spacers 17 are smaller in diameter than the rungs 16 but naturally this is simply a matter of convenience.

Our improved ladder is preferably made from light and strong metal; and it forms a substantially rigid structure. By providing a series of recesses 14 on the locking rod 13, or otherwise, the ladder can be designed to be simply adjustable so as to cover a limited height range for a given angle of inclination or to vary the inclinations for a given height.

Means may also be provided for connecting two such ladders together to form a pair of steps.

If desired means may be provided to pull the ladder up into the folded position, for example a chain, wire, cable, rope or strap may be used for this purpose and such an arrangement is essential when the ladder is used in aircraft or the like.

What I claim is:

1. A ladder which comprises a pair of spaced lazytong mechanisms; each of said mechanisms comprising a plurality of end-to-end connected pairs of crossed, substantially uniform rods of substantially uniform length, there being inner pivotal connections between the crossed rods of each pair and outer pivotal connections between the ends of adjacent pairs to permit the mechanism to be moved between folded and extended positions; each pair of outer pivot connected rods being arranged to collapse toward generally parallel alignment, said inner pivotal connections of all adjacent pairs of crossed rods being substantially equidistantly spaced from the intervening outer pivotal connections between said adjacent pairs, and said inner pivotal connections being positioned olf center of said crossed rod-s so that, with the mechanism folded, said outer connections are arranged in staggered relation to permit their overlapping; and a plurality of equidistantly spaced rungs interconnecting said 3 4 mechanisms and extending between the outer pivotal con- 936,681 Union Oct. 12, 1909 nections on one side of said pairs. 942,683 Vaghi Dec. 7, 1909 2. A ladder as recited in claim 1 further comprising 1,203,545 Moore Oct. 31, 1916 means for locking the mechanism in an extended position. 1,570,863 Simmons J an. 26, 1926 5 1,952,494 Gafford Mar. 27, 1934 References Cited in the file of this patent 2,697,845 Broner D 23, 1954 UNITED STATES PATENTS FOREIGN PATENTS 93,877 Haasz Aug. 17, 1869 147,241 Germany Jan. 2, 1904

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