US2572775A - Extension ladder - Google Patents

Description

Oct. 23, 1951 M. SMITH 2,572,775

EXTENSION LADDER Filed March 24, 1949 l 2 SHEETS- SHEET 1 Oct. 23, 1951 M. SMITH EXTENSION LADDER Filed March 24, 1949 2 SHEETS--SHEET 2 1N VEN TOR. /Vtfrzw 5mm BY w, 6M, ym

Patented Oct. 23, 1951 .mesne assignments, to McCabe-Powers Auto Birdy '09 S;tfl0iiis, 1Mo... a entnommen .0f

Missouri Application March 24, 1949, Serial No.-83,1-91

This invention relates to an extension ladder provided withmeans for readily effecting the extension of one section with reference to the other. The object of the invention is to provide not only simple means for-effecting fthe-extension but also means lfor readily controlling the vdescent of'the extendable portion bygravity, so that there will `be no danger of injuring the operator or damaging the apparatus. My extension ladder is .well adapted for mounting in any suitablefmanner as for example-on a vehicle where it may lie in 'a horizontal position for transportation and be raised into an inclined or approximately vertical position for use.

The invention is illustrated in the drawing hereof and hereinafter fully explained and the essential novel features are summarized in the claims.

In the drawings, Fig. 1 is a side elevation of my extension ladder indicated as mounted on a vehicle, part of which is shown; Fig. 2 is a fragmentary elevation on a larger scale of the ladder in a plane transverse to Fig. l; Fig. 3 is a side elevation of mechanism for controlling the extension; Fig. 4 is a cross section through the elevating mechanism, in a plane indicated by the line 4-4 on Fig. 3; Fig. 5 is a fragmentary sectional elevation on a larger scale of a portion of the operating mechanism shown in Fig. 4.

The base portion of my extension ladder indicated at Ill in Figs. 1 and 2 comprises a pair of parallel side bars and various cross bars I I. The extension member I2 also has a pair of parallel side bars connected by cross bars I3. The side bars of the extension are slidably connected, as by tongue and groove or other suitable means, with the side members of the base I0.

I have indicated the base I as mounted on suitable supporting mechanism carried by a standard rising from a vehicle 2|. The supporting mechanism indicated in general at 22 is not shown in detail as it constitutes no portion of the present invention. It may be constructed in accordance with Patent No. 2,422,507, issued June 17, 1947 to my assignee, The American Coach & Body Company, as assignee of Herman J. Troche and Elton J. Farrar.

To effect the extension of the ladder member I2 along and beyond the member I0, I provide a cable anchored at its upper end to the upper portion of the base ladder I0 as, for instance, by looping around a top cross rod I I of the base ladder. This cable then extends along the extension ladder to the lower portion thereof where it passes around two pulleys 3| carried by brack- 2 Claims. (Cl. 25p-14g) ets f32 extending inwardlyfrom .the side barsfof the extension ladder. rThe cable then passesupwardly to a pulley 33 and .also secured ttowthe uppermost cross bar .II and'thence downwardly to a winding drum .40 carried'bythe basemember I0.

The windingdrum :40, .shown in `detailin Fig. 4, comprises ahollow barrel 4I and two disc heads 42yandx43. These :heads aretightly mounted on a rota-ry shaft .45 journaled in bearings -46 4and 41 carried by brackets 156 and 51 respectively. The Ibrackets .in turn Iare Acarried by the side members of the base ladder I0. I have shown a collar 48 welded to the head 42 and keyed to the shaft 45 so that the drum is locked to the shaft to rotate therewith while allowing the shaft to be shifted slightly longitudinally thereof, as indicated by the broken lines in Fig. 4 for a purpose hereinafter described. A suitable disc crank 5U slidably keyed to the shaft, furnishes means for rotating the shaft and drum to wind in the cable 30 and thus cause the extension of the ladder I2.

Between the hub of the disc crank 50 and the bearing 41 I mount a distance sleeve 5 I. Threaded on the shaft on the outer side of the hub of the disc crank is a hand wheel 53 which bears against the hub. A cotter pin or other suitable stop 55 prevents inadvertent removal of the hand wheel 53 from the shaft. Secured to the inner face of the bracket 5'I is a rub disc 58 with which the drum head 43 may be caused to contact by a slight lateral shifting of the drum.

Fig. 4 shows in full lines the drum and shaft in position with the drum head 43 in snug engagement with the friction disc 58, which is the braking or lowering position. This view indicates in broken lines the position of the drum and shaft during the raising operation.

In the operation of my invention, the rotating of the hand crank rotates the shaft 45, the hand wheel 53, the shaft 45 and the drum as a unit to wind in the cable to raise the extension. When the extension is descending by gravity the same is controlled by the hand wheel 53, which, being turned manually on the screw thread of the shaft, operates to pull the shaft outwardly and thereby shift the drum slidably toward the hand wheel causing retarding friction between the head 43 and the rub disc 58 on the bracket 51.

The friction, produced by the braking disc may, if desired, be suiiicient to firmly hold the extension member elevated or it may be such that the extension gradually and slowly slides down within the base ladder.

A suitable gravity latch (not shown) may if desired be applied to the extension ladder to overhang successive rungs of the base ladder and hold it positively in any elevated position which may be given to it, until the latch is manually thrown to idle position preceding the descent.

It will be seen that my elevating mechanism is very simple in construction, readily operated to effect the extension desired without requiring much force by the operator on the handle 59 of the disc crank. During such elevation the shaft and drum rotate freely without binding friction. On the descent of the ladder the mere turning of the hand wheel 53 controls descent so that the ladder may gradually return to its initial position without danger to the operator or causing damage to the mechanism.

I claim:

1. The combination of a base, a member to be raised, a pair of bearings carried by the base, a shaft rotatably mounted in said bearings, a drum between the bearings secured to the shaft, a cable connecting the drum and said member, a hand crank keyed to the shaft in a manner to allow some movement between them axially of the shaft, a member threaded on the shaft and bearing against the hub of the hand crank, means to resist axial movement of the hand crank toward the adjacent bearing, and a friction device between such adjacent bearing and the adjacent end of the drum adapted to coact with the drum when the shaft is shifted axially.

2. The combination of a base, a member to be raised, said base having a pair of bearings, a shaft rotatably mounted in said bearings, a drum between the bearings tightly keyed to the shaft, a cable wound on the drum and leading to said member over a pulley carried by the base, a crank keyed to the shaft in a manner to allow axial movement of the shaft through the crank, a distance sleeve between the hub of the crank and the adjacent bearing, a hand Wheel threaded on the shaft and bearing against the outer side of the hub of the crank, and a friction disc between such adjacent bearing and the adjacent end of the drum, adapted to frictionally clamp the drum to the bearing when the shaft is shifted by the hand wheel.

MERTON SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Smith Nov. 21, 1950

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