US1701123A - Extension ladder - Google Patents

Description

Patented Feb. 5, 1929.

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PERCY. WILLIAM nomm'rs', or FITZROY, NEW PLYMOUTH, NEW ZEALAND, ABSIGNOB or 'rnmmtrmrns 'ro REGINALD CHARLES HENRY SANDERS AND LESLIE ALLAN BROWN, BOTH or mew P YMOUTH, NEW ZEALAND, AND ome'rnn'rn To mm: emuismoam surprise, or JOHANNESBUBG, TRANSVAAL, soon: AFRICA.

EXTENSION LADDER.

Application filed November 6, 1926, Serial No. 146,714, and in New Zealand July 14, 1926.

This invention relates toladders of the type known as extension ladders wherein the ladder sections are held in their extended position by means of gravity pawls or catches pivoted to the upper ladder section and adapted to engage or lock on the rungs of the lower ladder section, and wherein means such as a pulley and rope are provided for hoisting the upper ladder section on the lower section.

The object of this invention is to provide improved locking means for use on ladders of the above type whereby a more positive action and greater security and rigidity is obtained when the ladder is extended. It is well known that accidents have occurred through the breakage of the rung of a ladder engaged by the pawls. The present invention provides means for preventing such accidents.

According to the invention, the upper section of the ladder has secured to one side rail near its lower end, a sprin actuated pawl adapted to be normally pressed outwards, and

engage one of the rungs of the lower laddersection to prevent sliding or collapsing of said ladder sections one upon the other.

The spring actuated pawl is connected by a link to one arm of a bell crank lever, to the other arm of which is attached one end of a rope or cord which is reeved through a pulley secured to the top bar or guide of the lower ladder section. a

By exerting a hoisting strain on this rope or cord to raise or extend the upper ladder section on the lower section of the ladder, the bell crank lever is given turning movement and by its connecting link, causes the spring actuated pawl to be withdrawn from its operative position to permit the ladder sections to be freely slid one upon the other. Immediately the hoisting strain is released on the rope or cord the spring actuated pawl is free to resume its operative position and engage the nearest rung of the lower ladder section, thereb retainlng the said sections in their exten ed positions.

A further object of the invention is to provide an improvement in the present gravity hung pawls or catches, in order to provide for the moving of the latter to positions where they will not en age the rungs of the lower section of the la der, without having to tilt scribed with reference to the accompanying drawing wherein Figure 1 is a'pers ective view of a portion of an extension la der fitted with the improvements,

Figure 2 is a side elevation ofzthe spring actuated pawl and means for operating the same, and

Figure 3 is a side elevation of an improved gravity operated pawl orlever. i

The ladder comprises a lower section 1 and an upper section 2 slidable one upon the other and glield together by the usual guide mem- Gravit operated pawls 4 hinged one on either si e of the lower end of the upper ladder section 2 are connected together by means of a stay rod 4 to cause them to operate together, and are adapted when the ladder is raised in an inclined osition, to engage the run tion 1 in the we 1 known manner.

Secured on one rail of the upper ladder section 2 slightly above the gravity pawls i 1s a pawl 5 adapted to be normally forced or held outwards over the rungs of the ladder of the lower adder secsection 1 by means ofa spring 6 acting on a bell crank lever8.

This spring actuated pawl 5 is connected by a link 7 to one arm of the bell crank lever 8 the other end of the latter having attached thereto one end of a rope or cord 9 reeved through a pulley 10 secured to the upper guide member 3 on the ladder section 1.

By pulling on the rope or cord 9 the ladder section 2 can be slidabl raised or extended on the section 1, the hoisting strain on said rope or cord 9 at the same time operating the bell crank lever 8, and through the link 7, withdrawing the pawl 5 from its position in line with the rungs of the ladder section 1.

On the ladder being extended to the desired time engage the rung of the ladder section 1 nearest to them to provide additional support for the ladder section 2 and also to provlde for additional security 111 case of acc1-,

dent to, or releasing of the spring actuated pawl 5.

One of the gravity pawls 1 is provided at its upper end with an arm 11 to which is attached a rope or cord, preferably the other end of the rope or cord 9, so that when lowering the section 2, said pawls 4 can be kept clear of the rungs of the lower section 1, by maintaining a light strain on the endof the rope attached to the arm 11 during the paying out of the other end of said rope or cord, the section 2 being first slightly raised on the section 1 to permit the pawls to be disengaged from the rungs with which they were engaged.

In the event of the breakage of the rung engaged by the pawls 4, the latter hang by gravity,'so that in the descent oil the section 2, the rung of the section 1 next below the broken rung is engaged by said pawls, which are prevented by the casing 12 of the pawl 5,

from makingcomplete turns on their pivots and so stop the further descent of the section 2.

.What I doclaim and desire to obtain by Letters Patent of the United States of America,is: H.

'lhecombination with an extension ladder having extensible ladder sections, of a pair of sustaining catch devices on one ladder section adapted to engage the rungs of the other adacent ladder section, a rope for extending said ladder sections having one end connected with one of said catch devices, said latter catch device being constructed'to operate to disengage a rung of the adjacent ladder section under the hoisting strain on said rope, the other of saidcatch devices being connectcd to the other end of said ro e, whereby the same may be moved from run engaging position, at will, during the hoisting movement.

in testimony whereof I have signed my name to thissp ecification.

PERCY WILLIAM ROBERTS.

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