US494270A - Isaac t - Google Patents

Description

(No Model.)

.I. T. GROSS. EXTENSION LADDER,

Patented Mar. 28, 1893.

FICJI UNITED STATES PATENT OFFICE.

. ISAAC T. CROSS, OF VVATERTOWN, NEW YORK, ASSIGNOR OF ONE-HALF TO VICTOR F. THOMAS, OF SAME PLACEQ EXTENSION-LADDER.

A SPECIFICATION forming part of Letters Patent No. 494,270, dated March 28, 1893.

Application filed $epteml er 9, 1892. Serial No. 445 394. (N model.)

To all whom it may concern.-

Be it known that I, ISAAC T. CROSS, of Watertown, in the county of J eiferson and State of New York, have invented a new and useful 5 Iinprovementin Extension-Ladders,whichimprovement is fully set fort-h in the following specification.

This invention relates to the construction of extension-ladders, and particularly to lad- :o ders of the type described in Letters Patent No. 478,969, granted July 12, 1892. As described in said patent the outer section had a double set of rungs between which the inner, or movable section was normally inclosed, be-

ing adapted to slide in and out, and being retained in place and guided by the rungs. The latter were allowed to project a certain distance beyond the side supports, so as to allow room between for the play of the movable section. It is found in practical use that the projection of these rungs interferes with the convenient manipulation of the ladder when any corner or projecting portion of a building is encountered in setting the ladder up.

At the same time, to insert the rungs to their full thickness in the side supports would both impair greatly the strength of the latter, and also diminish the space for receiving the movable section. I have improved the construc- 0 tion at the same time avoiding the above defeet, by letting the rungs into the supports on one side to their full thickness, moving the opposite rungs outward a distance to compensate for the change. This results in a per- 3 5 fectly flush surface on the side of the ladder that is to be turned in use toward the building, without lessening either the strength, or the space in which the movable section slides. In the patent referred to, a curved or U- shapedlatch was pivoted near the upper end of the lower or relatively stationary section, into which any rung of the movable section dropped, and by which the movable section was sustained in its raised position. This '45 latch presents some difficulties in manufacturing, on account of its shape, and moreover, is liable to catch the rungs of the movable section on its descent. I make the latch with straight instead of curved holding sides, and make the distance between the rung upon which this latch rests and the one next below, less than the usual distance, by any amount equal to the thickness of the latch. This makes the spaces between all the rungs uniform when the ladder is extended. To the upper end of the movable section are pivoted two small rollers with sharp edges, which both serve to facilitate the extension of the ladder, and also by biting into the surface upon which it rests, diminish the danger of slipping sidewise. I also pivot to the lower section at its bottom, two dogs or holding devices, which can be pushed into the ground, and when not in use turned back so as not to catch the hands or clothing of the users.

The improvements will be better understood from the following detailed description, in which reference is made to the accompanying drawings, forming part of this specification.

In said drawings Figure I, is a front view of a portion of the ladder when extended. Fig. II is a vertical section thereof. Fig. III, is a cross-section on line III, and Figs. IV and V are detail views. 7

The lower section is composed of side supports or uprights A, and rungs a, 1) arranged in pairs, so as to form with said supports, a space of sufficient width to receive the upper or movable section. The rungs a are inserted in grooves in supports A, the grooves being of such depth that the surfaces of the rungs are flush with the edges of the supports. This side of the ladder is, in use, to be turned toward the building, and it will be seen that the rungs are clear of any obstruction which may be encountered in setting up the ladder. The opposite rungs b, on the other hand, project almost their entire thickness beyond the supports A. Thus the strength of the latter is 0 not impaired by the arrangement of the rungs a as described nor is the space for the movable section diminished. The movable section is made in the usual way, of supports 0 and rungs o, and is raised, as heretofore by 5 means of a cord 01 running over apulleyein a slot in support A and attached to the lower end of the movable section. To protect this pulley a block E is attached to the outside of the support A. This also permits the use of [co a larger pulley, and consequently less force is requiredto raise the movable-section. When raised it is supported by one of its rungs which rests upon the pivoted holding latch f, whichin turn rests upon the pair of rungs b, which are the next to the top rungs of the lower section. This latch, as shown in Fig. III, has straight supporting'sides. It follows that the rung c, which rests upon it is raised some-what above the level of rungs-b. make the distance uniform, the rungs b are set nearer to the rungs beneath and farther from those next above. Holding latch f is manipulated, as heretofore, by'a rod" g, eX- tending down the side of the lower section;

In extending the upper section by means of the cordd, considerable resistance is encountered if the ladder beinclined against the sideof abuilding; T-his'is greatly diminished by the small anti-frictionrollers h pi'voted atthe top of the section, (Fig. IV.) Theserollers are on the inside of the-supports O and'proj ect avery 'slightdistance beyond-them,;and the'width of these supports being diminished at their ends,-pern1its the" rollersto project far enough'to perform their specification'in the presenceof two subscriboffice without interfering withthe sliding of" the upper section in the lower. These rollersare grooved to present edges sufficiently sharp to take a-holduponthe surface against which I the ladder rests, and prevent later'als'lipping. I As a further precaution against slipping two dogs or catches k (Fig. V) having a tooth or the building; catches are turned to the position indicated point at the free end, are pivoted to the supports A near the bottom thereofr In use these dogs are turned so that their teeth engage in or against the surface upon which the ladder is placed, and tend to prevent slipping either laterally or in a direction away from When not inuse the dogs or in dotted lines.

I claim asmy invention- In an extension ladder the combination of a section having rungs arranged in pairs at- ,tached to opposite sides of uprights or supports, a'movable section adapted to slide in and out between the said rungs and uprights, and a holding latch pivoted to the lower section above and=adjacentto one of the rungs of the lower section and comprisingia frame ,with straightholdingsidesadapted-to extend across tothe'opposite rung of thepair,"-and form a'support'for a rung of the upper section when-extended, and which is turned 'up to a position parallel with the supportsor sides of the ladder when the'u'pper'section is beinglowered substantially ,as described. 1

In testimony whereof I- have signed" this ing witnesses.

ISAAO T. CROSS,

Witnesses:

FRED WENZEL, N. D. TERRILL;

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