US2153127A - Ladder - Google Patents

Description

April E. J. ARPS LADDER Filed Feb. 8, 1937 FIG. I. FIG. 2. :1) W

9--- ix INVENTOR EDMUND J. ARPS x ATTORNEYS UNITED STATES PATENT OFFICE LADDER Edmund J. Arps, Oshkosh, Wis., assignor to Duo- Safety Ladder Corporation, Oshkosh, Wis.

Application February 8, 1937, Serial No. 124,701

1 Claim.

My invention refers to ladders, and it has for its primary object to provide a non-conducting ladder for various purposes, comprising a combination of wooden and metallic elements, where- 5 by the ladder is not only insulated but is rendered by its structure strong, light, and durable. The ladder is especially designed for fire purposes, and embodies a plurality of telescopic elements for extension to various heights.

l I am aware of the fact that wooden ladders of this extension type have been heretofore manufactured, and, also, all-metal ladders, but in each instance the weight is detrimental to functioning, and the wooden ladders or ladder sections are 15 frequently weakened by coming in contact with fire hazards. The metal ladders have been found in practice to be heavy, and toact as ground conductors for any live wire contact that may develop in fighting fires..

20 With the above and other minor objects in view, the invention consists in certain peculiarities of construction and combination of parts, as will be hereinafter set forth in the drawing, and subsequently claimed.

25 In the drawing:

Figure 1 represents a sideelevation of a combination wood and metal ladder embodying the features of my invention.

2 is. a face. view, with parts broken away 30 and in section, to more clearly illustrate structural features.

Figure 3 is an enlarged, fragmentary, detail, side elevational view of a metallic bracket element associated with wood rails, parts being 35 broken away to more clearly illustrate structural features.

Figure 4 is a cross section of the same, the section being indicated by line 4-4 of Figure 1.

Figure 5 is a similar cross section of the ladder 40 element, illustrating a preferred form of bracket associated with the wood rails.

Referring by characters to the drawing, l-l' represent wood strips spaced apart to form skeleton side rails of the ladder. The upper and lower 45 ends of the ladder section are provided with filler blocks 2 and 3, respectively, which filler blocks are composed of wood in this instance, although in some cases they may be all-metal. The wood filler blocks are snugly fitted between the ends of 50 the strips l-l, and are glued thereto. The assemblage is further secured by bolts or rivets 4-4 and 5-5, which pass through the wood rail strips, filler, and preferably reinforcing metal bands 6-6. The upper metal band is bowed 55 around the end of the ladder, and is secured by the bolt 4, while the lower bands 6', in this particular instance, are simply shown to reinforce the elements secured by the bolts5, and the filler of this bottom. end section may be routed out, as indicated at X, whereby the prongs are formed 5 to prevent the last or bottom section from slipping.

It is understood, while I have shown only the bottom section, as indicated in dotted lines, Fig ures 3 and 4, a plurality of these sections may be 10 telescopically mounted one upon the other, whereby the proper height is obtained through extension of these Various sections, which arrangement is common in the art. The filler blocksZ and 3 each have a tubular rung l, which is rectangular in cross section, the ends being embedded in apertures formed in the blocks 2 and 3, said ends being further secured by bolts 5 passing therethrough. Another tubular tread rung 8 is provided for the blocks in this particular instance, but it is understood that one, or a series of said tread rungs, maybe employed. The ends of this tubular tread rung are initially fitted through apertured metallic plates 9, and the ends of the tubular rung are provided with pairs of expansions orbeads Ill-l0 upon opposite sides of the, plate, whereby these parts are permanently secured. Thereafter the ends of the tubular rung are fitted into apertures which are bored into the blocks, and the plates 9-9 are secured to said blocks by suitable screws, it being understood that the plates are fitted into the inner faces of the blocks.

In the event that the wood filler blocks should be formed from hollow metal elements, means for securing the rungs thereto would be similar to the means employed in connection with a plurality of metal brackets ll. As best shown in Figures 3 and 4 of the drawing, the metal brackets H are formed from a pair of plates l2-I2', which plates are spaced apart and provided with alined apertures for reception of the ends 1/ of metallic tubular rungs l3.

After the end of each rung is fitted through the plate apertures, it is crimped or beaded at the points l4 and M, to form shoulders between the inner and outer faces of the wall l2, whereby endwise movement of the rung is eliminated. The extreme end of the rung or tube l3, as best shown in Figure 4, is then crimped or beaded at the point IE, to form a shoulder which impinges against the inner face of the wall 12, and the opening in said wall is slightly depressed about the end surface of the tube, whereby said end surface is soldered or welded to the outer surface 56 of the bracket plate I2, to thus insure a permanent connection which is smooth in finish, and at the same time connects the parts, forming in effect a homogeneous mass.

The plate elements I2 and I2 are each inwardly formed with flanges I Ii-I 6, which flanges are in sliding fit, and have nested thereagainst the wood rail strips II it being understood that the flanges are then secured to the wood rails by bolts or screws II. Thus, the brackets not only form metallic supports for the tubular rungs, but they also act as braces for the skeleton rail structure, whereby each ladder section will result in a strong and durable assemblage. Owing to the fact that the rail elements are composed of wood, and the transversely disposed rung and supporting brackets are of metal, preferably aluminum, the structure is interrupted, or insulated, whereby stray currents of electricity will not be grounded through the ladder sections, due to this insulation, which is a vital and important feature accomplished by my composite structure. From the foregoing description of the plate elements and ladder rungs, it should be understood that prior to assemblage of the hollow bracket embodying the spaced plates I2I2 the rung is first fitted in the aperture of the inner plate and beaded upon opposite sides to lock it. Thereafter, just back of the end of the rung I3 the same is beaded to form a shoulder I5. The next operation for assemblage is that the plate I2 is slit over the end of the round, and secured thereto by welding, or analogous means. Hence, it will be observed that I provide an integral all-metallic fitting, a series of which can be thereafter readily inserted along the length of the ladder, whereby the skeleton or spaced strips Will be secured to the bracket elements by bolts, to thus securely stiffen the ladder as a whole, bracing the spaced wood elements in a vertical direction, and also transversely, due to the rungs I3 which constitute tie rods.

In Figure 4 of the drawing, the inner plate or wall of the bracket element is illustrated as having a depression I8, which serves as a stirrup or guide shoe for the rail strip I, which rail strip is indicated by dotted lines as fitting into the depression of the shoe. However, as shown in Figure 5 of the drawing, this depression may be dispensed with, and the rail strips and bracket surfaces in themselves will form the shoes or interlocking elements.

In the above referred to modified construction, the surface of the plate I 2 forms a sliding shoe for the rail element, indicated in dotted lines of Figure 4. For example, this rail element will abut the projection of the strip I with the bottom surface of said rail element riding upon the plate. Briefly, the projecting surface of the rail element I serves to prevent side play of the sliding ladder section, thus dispensing with the depression I8.

While I have shown and described the brackets as being composed of two metallic strips bolted and secured together, it is obvious that this hollow bracket element may be formed from a single strip folded upon itself without departing from the spirit of my invention. Furthermore, it is understood that in manufacturing intermediate ladder stretches for the extension assemblage, the lower ends of such intermediate sections will be provided with finishing blocks 2 and 3, but the forked or spurred end in such instances will be eliminated. Furthermore, in manufacture the spurred or lower end of the bottom ladder section can be indefinitely varied in structural features, it being simply necessary to provide any type of spur element to prevent the ground or initial ladder section from slipping when these ladder sections are used independently of a truck.

While I have shown and described one example of my invention minutely as to all details, it is understood that I may vary the structural features within the scope of the claim.

I claim:

In a ladder, rails of skeleton-like form including longitudinally extending spaced strips, and an all-metal fitting disposed between the strips, said fitting comprising a pair of inner and outer spaced plates having alined openings, rightangular interengaging flanges extending from the plates for connection with the strips, tubular rungs having ends fitted through the alined openings of the plates, beads formed on the rung on opposite sides of the inner plate forming shoulders against the inner and outer surfaces of the inner plate, means securing the end of the rung to the outer plate, whereby the plates and the rung form a single unit, and means for securing the flanges of the plates to the strips.

EDMUND J. ARPS.

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