US1950574A - Extension ladder latch - Google Patents

Description

M. w. SMITH 1,950,574

EXTENSION LADDER LATCH Filed Jan. 13, 1933 Patented Mar. 13, 1934 PATENT OFFC EXTENSION LADDER LATCH Martin Watson Smith, Somerville, Mass., assignor of one-half to Elmer N. Hutchins, Somerville,

Mass.

Application January 13, 1933, Serial No. 651,600

1 Claim.

The invention relates to latches for holding the upper sections of extension ladders in any desired position and for permitting said upper sections to either be raised or lowered at will.

The object of the invention is to provide a latch which is exceptionally simple and inexpensive, yet will be eiilcient, easy to operate, and safe.

With the foregoing in view, the invention resides in the novel subject matter hereinafter described and claimed, description being accomplished by reference to the accompanying drawing.

Fig. l is a vertical sectional view partly in elevation showing the parts in their normal positions for supporting the upper ladder section.

Fig. 2 is a view similar to Fig. 1 but showing the parts related to allow lowering of the upper ladder section.

Fig. 3 is a vertical sectional view partly in elevation as indicated by line 3-3 of Fig. 2.

In the drawing above briefly described, the numeral 5 denotes the lower ground-supported section of an extension ladder and 6 has reference to the slidable upper section, said sections 5 and 6 having the conventional rungs 7 and 8 respectively. Secured to the inner side of one of the stiles of the upper section 6, is a fiat attaching plate 9, screws 10 being preferably employed for securing said plate to said stile. Pivotally mounted at its lower end upon the attaching plate 9, is a substantially vertical hook 11, said lower end of said hook being provided, in the present disclosure, with a bearing 12 which surrounds a stamped out stud 13 on the plate 9, said bearing being held upon said stud by the head 14 of a bolt 15 which passes through said stud and through the stile which carries the plate 9. Near its upper end, the hook 11 is provided with a bill 16 to engage the rungs 7 of the lower ladder section 5, and said hook is provided with a bevel 17 extending upwardly from said bill 16. When raising the ladder section 6, this bevel 17 strikes the rungs 7 successively so that the hook cannot interfere with such raising, but on the contrary will be retracted each time the bevel engages a rung. The hook movements may be limited by stops 26 and 27 carried by the plate 9.

Spaced downwardly from the bill 16 is a substantially horizontal balanced lever 18 which is fulcrurned between its ends at 19, upon the supporting plate 9, the outer end 20 of this lever being normally under the rung '7 engaged by the bill 16, as shown in Fig. 1. This .end 20 of the lever 18 is co-operable with a lateral projection 21 on the bill 16, to swing the entire hook 1l to retracted position each time said lever engages a rung 7, when lowering the upper ladder section 6, as illustrated in full lines in Fig. 2. lThe hook 11 is provided also with another lateral projection 22 which co-acts with the end 23 of the lever 18 when raising the ladder section 6. After the bill 16 has passed any rung 7 when raising the section 6, the lever end 20 will strike the same rung and said lever will therefore be tilted to the dotted line position shown in Fig. 2, in which position its end 23 engages the projection 22, so that slight further ascent of the ladder section 6 further swings the lever 18 and again swings the hook toward the rung 7 so that the bill 16 will be in readiness to engage the rung which it just cleared. In order to engage the hook bill with this rung, the ladder section 6 must be lowered a trie, and during such lowering, the lever 18 returns to the normal position shown in Fig. 1.

In order to lower the section 6 from a position such as that shown in Fig. 1, it is necessary to rst raise said section until the outer end of the lever 18 will overlie the rung '7 previously engaged by the bill 16. The lowering of the section 6 may then be effected, and as the outer end 2O of the lever 18 successivly strikes the rungs 7, said lever is swung as shown in full lines in Fig. 2, so that said end 20 engages the projection 21 and retracts the hook 11 so that the latter cannot interfere with the lowering operation. When the section 6 has been lowered to the required extent, the hook 11 may have a tendency to remain in the position shown in Fig. 2, but by then raising said section 6 sufciently to cause the lever 18 to engage the superposed rung 7, said lever is rocked as shown in dotted lines in Fig. 2 causing its end 23 to engage the projection 22, thereby again projecting the hook so that the bill 16 may properly engage the rung '7.

Preferably, a casing 24, open only at one edge, 1

which the hook is engageable, a lateral projection on said hook bill spaced above the rungengaging end of said lever to be struck by the same for the purpose of swinging the hook away from the rungs when said rung-engaging lever end is swung upwardly during retraction of the ladder, and a second lateral projection on said hook spaced above the other end of said lever to be struck by the same for the purpose of swinging the hook toward the rungs when said rung-engaging lever end is swung downwardly during extension of the ladder.

MARTIN WATSON SMITH.

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