US908782A - Counterbalanced stair. - Google Patents

Description

UNiTED sTATEs PETER L. LARSON, OF CHICAGO, ILLINOIS.

C-OUNTERBALANCED STAIR...

Specicationof Letters Patent.

ratented Jan. 5, 190e.

Application led Hay 2 5, 1908. -Serial No.'434=,964

To all whom it may concern:

Be it known that I, PETER L. LARsoN, a citizen of the United States, and resident of Chicago, county of Cook, and State of Iplli nois, have invented a certain neT and useful Improvement in Cor-.nterbalanced Stairs, of

`which the following is a specification, and

which is illustrated in the accompanying drawings, forming apart hereof.

The invention relates to stairs adapted to turn about a horizontal pivot and, more particularly, to' those which are pivotally -seeired at theirupper end to the edge of .a

platform such as t at of the' balcony of a fire escape. In practice these stairs are employed for connecting the balcony of afir'e escape with the groundand in order that.

when not in use they may not provide a means of access to the building to which the fire escape is ap lied and may notv obstruct the assageway elow, they are so counter- -Weig ted that they normally rest in 'a substantially horizontal position, but are easily depressed to connect with the ground by pressure aplplied to the treads of the stairs.

As usua y constructed the counterweights of these stairs take the form ofan extension of the stair projecting beyond its pivot at the higher end. In order thaty this counter- Weight may clear the platform to the edge.

of which t stair is connected it is neces,- sarily applied to one side only/of thestair frame. n this construction t ere is a tendency of that part of the uncounterweighted weightedstair embodying the features of the invention; Fig. 2 showsvin side elevation a .-mimerals 10 an 11 in t detail of the construction' separated from other parts; Fig. 3 is a detail transverse sectional view of the stair illustrated in Fig. 1; Fig. 4 is a lside elevation of the. stair illustrating the relative disposition 'f its parts before being hung upon itspivotal support.

Figs. 5and 6 aredetail sectionalviews, andv taken on the lines 5-5 and' 6-6 of Figs. V1`

and 3 respectively.- v

As shown, the. stair comprises side members which are enerall' designated by the fiedrawings. ,hese

-side members are connected by the treads generally designated 12. Preferably each of the side members comprises a pair of fparallel bars 15 l-oneof which'is shown in 'detail in Fig. 2 of the drawings. The bars of each pair are connected adjacent .the higher end of the stair by plates 17, which are apertured to receive the pivotal support 18. i Thepivotal support which is 'shown takes the form of a rod 18 projecting hori- Zontally from the Wall 19 of the building to which the stair is applied. At the lower end of the stair thebars 15, 16 of eachpair are connected by foot pieces 20. rI'he treads 12 may be of any convenient form of construction and as shown, each comprises a plurality of parallel rods 2.1, each having its ends itted into cross pieces 22, 23 and the treads are secured to the side members 10,

. 11 of the stair by securing the cross pieces f 22, 23 to the bars 15, 16, of which the side members are composed, ,by bolts 24, as most clearly shown in Figs. 3J and 6 of the drawings. j

Preferably the counter weight provided for normally supporting the stair in a substantially horizontal position, takes the form of a plurality of weights 25. As shown', these weig its are fitted into' a channel member 26 to which they are detachably secured by bolts 30. 'I he channel member may be alpplied to one of the side members, as 10,;.of t e stair adjacent its higher end and extends beyon`d the pivot 18,'as shown at 27. A secondchannel member 28 is secured to the channel y member 26 adjacent its outer end for su porting additional counter weights 29. s this counter weight is applied to but one 'of the side members, as 10, of the stair, there is a tendency for the free end of the uncounter- Weighted side member 11' to sag. Such a sagging would give the-stair a distorted and unsightly a pearance. In carrying out the invention, t is distortion is prevented by so a plying the treads 12 to the side member 10 tllfatbefore the stair is hung upon the pivotal 'support 18 and before the application of the, counter weights 25, 29. to the channel members 26, 28, the treads occu ya spiral rela# tion, as shown' in Fig. 4 o the drawings. Most convenientl this spiral `relationof the` treads is eHected y twisting each of the side members -land 11 about itslongitudinal axis 'before the` connection of the `treads thereto.

las

i ro

When each of the side members 10` andll .is formed ,from a pair of'bars 125,116, y

Cir

- 3 of the drawings.

as'shown, this twisting of the 'side'members stair presents a distorted ap earance when 1s en'ected by a twisting of the bars 15, .16 the parts have been assemble and mounted before their connection by the pivot plates 17 and foot pieces 2 0 tothe form illustrated in Fig. 2. In then connecting the treads 12 to the side members 10 and 11, the bars 15,

16 are strained byva drawing up of the bolts 24 to it snugly against the end pieces 22,23

of the treads and this straining of the bars 15 16 causes the end of the side member 11 to inclineupwardly towards .its outer free end, as shown in big. 4. Villen constructed in this AWay and hnng upon a rhorizontal pivot 18, the greater sagging of the outer free end of the side member 11 ofthe stair than of the outer freeend of the member 10, because of the application of the cosnter Weights, 25, 29 to the channel bars 26, 28 secured to the member 10, produces a suiiicient torsional strain in the bars 15,' 16 of each of the side members 10 and 11 .to arrest the sagging when the parts have been broLght to the undistorted position illustrated in 1* igs. 1 and If, however, from any chance, as by too great a twisting ofthe bars 15,' 16 of the side members 10 and 11, the

in the position of service, this distortion may be-corrected by a twisting of the stair as a Whole by grasping the outer free ends of the lside members 1 0 and 11 and by then ham.-

mering upon the twisted parts of the bars I claim as my invention In combination, a stairI adapted to turn' about a horizontal pivot comprising side members and treads connecting the -side members, and a counterweight applied to one side only of the stair, the treads of the stair being secured to the side member at the counterweiglited side of the'stair in spiral relation, Wliereby they are brought into parallel relation by the torsional strain produced -in that side member by the tendency of that part of the nncounterweighted side of the stair remote from the pivot to sag.

PETER L. LARSON.

Witnesses:

CHARLES B. GILLsoN, LoUis K. GiLLsoN.

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