US3016976A - Ladder construction - Google Patents

Description

Jan. 16, 1962 D. J. MUNSON LADDER CONSTRUCTION Filed Sept. 28, 1959 m m m w.

230M440 I Mam/501v @400 United States Patent 3,016,976 LADDER CONSTRUCTION Donald J. Munson, Minneapolis, Minn., assignor to The J. R. Clark Company, Spring Park, Minn., a corporation of Minnesota Filed Sept. 28, 1959, Ser. No. 842,702 1 Claim. (Cl. 182-194) This invention relates generally to stepladders and more particularly concerns step construction and means for mounting the steps between the ladder side rails.

The primary object of the invention is to provide a novel and improved stepladder construction which provides for secure mounting of metal cross members such as steps between wooden side rails without the use of nails, rivets, tie rods or other independent fastening devices and which appreciably strengthens the side rails in the area of mounting compared with conventional construction wherein the rails are weakened by grooving procedures.

Another object of the invention is to provide a new and improved stepladder construction which readily lends itself to automation in the manufacture and assembly thereof.

Still another object is to provide a ladder construction wherein the depth of step contact with the side rail and the rigid connection therebetween render the ladder more resistant to side sway.

With these and other objects in mind the invention broadly comprises a side rail and step assembly in a ladder wherein a sheet metal step is mounted between wooden side rails by providing the step with integrally formed tubular portions extending longitudinally of and endwise beyond the step, the tubular portions extending outwardly through apertures in the side rails and washer plates therebeyond and having their terminal end portions flattened against the washer plates to hold the rails firmly against the ends of the steps.

The above mentioned and additional objects of the invention will be brought to light during the course of the following specification, reference being made to the accompanying drawing, in which FIG. 1 is a perspective view of the upper portion of a stepladder embodying the improved construction of this invention.

FIG. 2 is a front elevation of one of the steps of the ladder partially broken away to show the connection between the step and one of the side rails.

FIG. 3 is a perspective view of one of the ladder steps before assembly with the other ladder components.

FIG. 4 is a cross section through one of the ladder steps taken on line 4-4 of FIG. 1.

Referring now more particularly to the drawing reference numerals will be used to denote like parts or structural features in the different views. The ladder is designated generally at and is the collapsible type with side rails 11 and brace legs 12 respectively having their upper ends pivoted as at 14 and 15 to a stop platform 16. A pail shelf 17 is mounted on the ladder by collapsible linkage 18 pivoted to the rails at 19 and the brace legs at 20 so that the shelf might be folded substantially into the common plane of legs 12 when the legs 12 and rails 11 are closed together for storage of the ladder. The brace legs 12 may be interconnected by a transverse brace member 21.

The side rails 11 are interconnected by a series of vertically spaced steps 22. In this construction the side rails and brace legs are made of wood while platform 16, pail shelf 17, brace 21 and steps 22 are of metal.

Each step 22 is formed of a single sheet of metal and will now be described in detail, reference being particularly made to FIG. 3. The sheet is formed in an elonice gated inverted channel shape with a broad central tread portion 24 being provided with longitudinally extending strengthening ribs 25, formed in the sheet itself. The front wall 26 of the step depends downwardly in substantial right angular relation to the tread 24 with the lower edge portion thereof curled inwardly in an annular direction to form an integral tube or bead 28 extending along the bottom of wall 26. The tube portion 28 of the step is longer than the channel or body of the step and projects beyond the ends of the step portions 24 and 26 as at 29.

The rear wall 27 of the step angles somewhat inwardly toward wall 26 in its downward extension and is provided with an integral tube 30 extending along its bottom edge. This tube is similar to tube 28 extending beyond the ends of the step proper as at 31. Each of the extensions 29 and 31 is somewhat longer than the transverse thickness of rail 11.

The steps are mounted in position between the side rails by inserting the tube extensions 29 and 31 through pre-drilled apertures 32 in the rails, the apertures being so located as to receive said extensions with the tread 24 disposed horizontally as the ladder is in erect condition. Washer plates 34 having apertures spaced to receive the extensions are placed over the extensions and against the outside surface of rail 11. The ends of the extensions are then flattened or clinched against the plate 34 as at 35 to tightly secure the step endwise against the side rail with the end edge of tread 24 bearing firmly against the rail.

The mounting is accordingly readily eifected without the use of nails, bolts, rivets or tie rods. Moreover, the assembly affords an extremely rigid connection between the step and rail without providing the side rail with step receiving gains which weaken the rail. The possibility of side sway in the ladder is greatly minimized by the depth of contact between the ends of the step walls 26 and 27 and the rails 11.

It is also significant that the step is so formed that the rail apertures for receiving tubes 28 and 30 are longitudinally offset to prohibit undue weakening of the rail at any one point.

Cross brace 21 utilizes a similar construction with tubes 37 being formed along the upper and lower edges thereof projecting through the legs 12 and washer plates 38 and being flattened thereagainst as at 39 to prohibit removal.

The construction described economically and effectively carries out the aforementioned objectives. It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claim. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

A step ladder comprising wooden spaced apart side rails and sheet metal step members, said step members extending between said side rails in vertically spaced apart position with the end edges thereof engaging one against each side rail, said sheet metal step members each being in the form of an inverted elongated channel in the provision of a central tread portion and having depending front and rear walls depending downwardly at substantially right angles from opposite sides of said central tread portion of the step, longitudinal elongated strengthening ribs formed in said step tread portion, said depending front and rear wall of each step having the lower edge curled inwardly in an annular direction on the lower edge of each respective wall, said lower curled edge of each wall extending beyond the length of said respective step members at each end in the provision of two spaced apart tubular extensions at each end of each respective step, said spaced apart wooden side rails each having oppositely positioned vertically spaced apertures therein, whereby the said tubular extensions of said respective vertically spaced steps project through said apertures, and a metal plate for each step likewise having oppositely positioned spaced apertures therein alignable with each of the respective spaced apertures of said Wooden side rails, to thereby receive the said respective tubular extensions of an adjacently positioned step memher, said plate serving as an anvil and said free ends of said tubular extensions being deformable into a flattened head portion against the exterior surface of said metal anvil plate to tightly secure the respective adjacent step endwise at each end between the said side rails.

References Cited in the file of this patent UNITED STATES PATENTS 901,755 Tiepolt Oct. 20, 1908 1,445,513 Wilford Feb. 13, 1923 1,683,422 Stevenson Sept. 4, 1928 2,090,331 Kutscheid Aug. 17, 1937 2,478,592 Nyberg Aug. 9, 1949 2,844,292 Rich July 22, 1958 2,951,550 Rich Sept. 6, 1960

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