US3181651A

US3181651A - Ladder and rung connection

Info

Publication number: US3181651A
Application number: US108895A
Authority: US
Inventors: Clayton E Larson
Original assignee: White Metal Rolling and Stamping Corp
Current assignee: White Metal Rolling and Stamping Corp
Priority date: 1961-05-09
Filing date: 1961-05-09
Publication date: 1965-05-04
Anticipated expiration: 1982-05-04

Description

May 4, 1965 c. E. LARSON LADDER AND RUNG CONNECTION 2 Sheets-Sheet 1 Filed May 9, 1961 24 CLAYTON E. LARSON r g2. fi w ATTORNEYS y 4, 1965 c. E. LARSON 3,181,651

LADDER AND RUNG CONNECTION Filed May 9, 1961 2 Sheets-Sheet 2 INVENTOR CLAYTON E. LARSON ATTORNEYS United Patented May 4, 1965 3,181,651 LADDER AND RUNS QONNEtCTlGN (Jlayton E. Larson, Weston, Conn, assigner to White Metal Rolling & Stamping Corporation, Brooklyn, N.Y., a corporation of New York Filed May 9, 1% Ser. No. 193,395 3 Claims. (6i. 182-228) This invention relates to ladders and a method of manufacturing the same. More particularly, it concerns an improved ladder construction incorporating a novel rung, and a unique method for forming the rungs thereof and connecting them to the ladder siderails.

Because of the functions served by ladders, it is essential that they possess two basic features, i.e., that they are sufficiently strong to carry the weight of a person or persons using them, and secondly that they be light in weight to facilitate movement from place to place as required without the use of special handling equipment. These requirements have led to the extended use by ladder designers and manufacturers or" light metals such as aluminum, magnesium or alloys including one or both of these metals, with the result that extremely light and strong ladders are presently available solely due to the inherent characteristics of these metals. Yet, there remains room for improvement, particularly in the assembly of the runes between the siderails and at spaced intervals along the length thereof. In ladders of this type heretofore available, perhaps the most common technique employed in connecting the ladder rungs to the siderail thereof has been to extend a tubular rung through a siderail aperture having a diameter substantially the same as or slightly larger than the rung diameter and swaging or upsetting the end of the rung outwardly to secure the connection. Examples of such constructions may be found in US. Patents No. 1,912,331 or No. 2,769,70. In other instances, rungs are secured in place by welding or brazing. Although such connections of the rungs to the siderails are satisfactory to prevent direct separation of these components, there results a considerable weakening of the ladder siderail due to the considerably large hole which must be formed necessarily in the siderails or, if welding or brazing is used, due to the heat stresses imposed on the metal from which the siderails are formed. Also, particularly where swaging or upsetting techniques are employed, the strength of the connection relies largely on the resistance of the upset portion or" the rung to deformation by bending. When such a ladder is subjected to rough handling, therefore, the severe bending stresses which occur between the rung and siderail result in a loosening of the joint and thus, a defective ladder. To circumvent this problem, further proposals have been advanced (see, for example, US. Patents No. 2,618,427 and No. 2,552,630), but have resulted in a comparatively complex arrangement which either gives rise to increased cost of manufacture or adds considerably to the overall weight of the ladder or both.

Also, it has been proposed, particularly where wooden siderails are used with metallic run s, to form the rungs having projections at their ends which are passed through the siderails and bent over at their ends to effect the attachment of the rung to the siderail (see, for example, US. Patents Nos. 1,445,573 and 1,503,880). Such construction afford a minimum of interference with siderail strength, but on the other hand, the only resistance orlercd to separation of the rung from the siderail resides in the bent over portion of the sheet metal prongs and any friction which may EXi between the prongs and the siderails in which they are imbcdded. As a result, when subjected to rough use, the extr me pull out forces due to bending moments incurred at the connection of the rungs to the sidcrails are likely to cause separation of the rung from the siderail producing a loose joint, and accordingly an unsafe ladder.

Another problem expericenced in the use of rungs or steps for ladders formed from like metals is the difiiculty in achieving a suitably light rung section. In rung constructions heretofore available, the direct bending moments imposed thereon in use have required suitably heavy rung cross-sections. To some extent, this problem has been mitigated by the use of tubular rungs but here, the requirement for a sufticient amount of material to etfect the joint between the rung and the siderail has restricted the lightness of rung cross-section employed. Although obviously, the rung could be built up at its end portions for this purpose, such would add materially to the cost of manufacture as compared with a rung having a continuous cross-section throughout its length.

Accordingly, a principal object of this invention is to provide a new and improved ladder incorporating a novel rung structure and method for its formation as well as a unique method of connecting the rung to the ladder siderails by which the aforementioned problems are substantially and effectively overcome.

Another object of this invention is the provision of a new and improved ladder construction by which the connection of the rungs to the siderails may be effected in an extremely economical manner, which connection is exceptionally strong and yet in no way sacrifices siderail strength characteristics or overall ladder weight.

A further object of this invention is that of providing a new and improved light metal ladder rung or step which is extremely resistant to bending loads imposed thereon while at the same time facilitating an extremely strong and eifective connection of the rung to the ladder siderail in an economical manner without in any way sacrificing overall lightness in weight.

A further object of this invention is the provision of a ladder of the type referred to in which the rungs are connected to the siderails in a manner such that maximum resistance to angular deformation or bending at the connection is aiford-ed without removal of any substantial portion of the ladder siderail and resulting weakening thereof.

Another object of this invention is that of providing a ladder rung structure of the type referred to and method for its manufacture which is adaptable to all forms of ladder rungs whether they be tubular, channel shaped, round, square or wide tread.

A still further object of this invention is the provision of a new and improved method for the manufacture of light metal ladders which is extremely economical in practice and which results a ladder having superior strength charact ristics and yet which is extremely light in Weight.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description, while indicating preferred embodiments of the invention is given by way of illustration only, since it will become apparent to those skilled in the art from this description that various changes and modifications can be made without departing from the true spirit and scope of this invention.

In general, the aforementioned objects are accomplished by extruding a li ht metal rung having a crosssection defining a plurality of rod-like rib portions interconnected by relatively thin integral wall portions and then cutting back the Wall portions at the ends of the rung to leave the rib portions extending as studs. These studs are then passed through corresponding apertures formed in the siderails and riveted or otherwise expanded to secure the rung-siderail connection. Preferably, the rung rib portions are arranged to be positioned at the top and bottom of the rungs when the ladder is in use to reinforce the rung against the compressive and tensile stresses which exist at these points respectively. 7 In one form of theinvention, the rung cross-section may be generally circular. and include at least tworeinforcing rib portions integrally formed with a pair of arcuate wall portions, the .wall portions being cut back at the ends to permit the rib portions to extend as studs for riveting to the ladder siderails. Alternatively, the rung cross section may be four sided so as to achieve a flat tread rung and three or four .rib portions may be formed therein and extended as the (rivet studs. Or, if a wide tread rung of the type used extensively in stepladders is to be desired, the rib portions may be formed at the corners of the step cross section interconnected by at least three integral wall portions, which are cut back at their ends to leave extending the .rib portions in the form of rivet studs. A more complete understanding of its various forms may be had by reference to the accompanying drawings in which: e FIG. 1 is a fragmentary side elevation in partial crosssection of the ladder of this invention; FIG.. 2 .is a cross section taken along line 2-2 of FIG. 1;

FIG. 3 is a perspective view of an extruded blank from which the ladder rung of this invention is formed;

FIG. 4 is a perspective view of the completed rung of this invention prior to its assembly with the ladder siderails;

FIG. 5 is an enlarged fragmentary elevation in partial section illustrating the connection of the rung to the ladder siderail;

FIG. 6 is a partial perspective view illustrating a modiiied form of the ladder rung of this invention; and

FIG. 7 is a cross-sectional view illustrating still another frnodified form of the invention.

Referring now to the drawings and particularly to FIGS. 1 and 2 thereof, a section of a ladder formed in accordance with the present invention is shown having a pair of siderails generally designated by the numeral 10,

and in the form illustrated are of I-shaped cross-section having a central web portion 12 between a pair of flanges 14. While a light metal sidera-il of this configuration is suitable for use with this invention, it is contemplated that other shapes may be used, such as for example, the siderails may be of C-shaped cross-section or in some instances if desired, may be of wood, in which case they would be of a rectangular cross-section. At intervals along the siderails corresponding to spacing between rungs, are

provided sets of at least two

holes

16 and 17 suitably shaped for attachment of rungs to the web 12 in a manner which will be more fully described hereinafter.

A plurality of rungs 18 are spaced at intervals between thesidera-ils, the cross section ofeach rung defining a plurality of relatively heavy rod-like reinforcing rib portions, there being two

such ribs

20 and 21 in the embodiment of FIGS. 1 and 2 diametrically opposed and interconnected by relatively light semicircular wall portions 22 formed integrally therewith to form a rung of circular externalcross-section. Desirably, the external surfaces of therungs are fluted or serrated to provide a traction sur- :face on the exterior of the rung.

The walls 22 on each end of the rungs are cut back 7 to leave a portion of the ribs extending as

rivet studs

24 and 25 respectively. The studs extend through the

apertures

16 and 17 and are expanded over the web 12 adjacent the apertures by riveting, to form

heads

26 and 27.

As shown in FIG. 1, the angular position of therungs with respect to the longitudinal center-line 28 of the siderails is such that a line 30 passing through the center of the

heads

26 and 27 and correspondingly the axes of

ribs

20 and 21 make with the line 28 an angle a. vpreferably approximates 15, so that when the ladder is placed against a building or other support in use, the line 30 assumes a ppmximatelyvertical position. Accord- The angle a ingly, the rib portions 29 and 21 are positioned, in use, at the extreme lower and upper portions of the rung, the positions of maximum loading in tension and compression respectively imposed by central loading of the rung from above. Thus, it will be seen that in the new and improved ladder rung of this invention, there exists a concentration or relatively heavy cross-section of material at the points of maximum stress, permitting an extremely thin wall portion interconnecting these rib portions and a corresponding reduction in weight as compared to a uniform or conventional cross-section. Further, the extension of the rib portions as studs. extending through the

apertures

16 and 17, and the expansion or riveting of the end thereof to form the

rivet heads

26 and 27 results in pressure between the heads and their adjacent holding surfaces in the siderail web to add substantial strength to the joint to resist forces in shear, tension, torsion, or bending. Yet, because of the relatively small apertures required in the siderail web 1 2, the siderail is weakened an insubstantial amount as compared with prior art teachings. p

The unique method for forming the ladder of the present invention may be understood by reference to FIGS. 3, 4 and 50f the drawings. As shown in FIGURE 3, the rungs are formed by extruding continuously a cross-section defining the

ribs

20 and 21 and integral wall portions 22 and severing the extrusion into lengths to form blanks 32. A portion of the walls 22 near each end of the blank 32 are cutback such as by machining, abrading or other well known techniques to leave end portions of the

ribs

20 and 21 extending as

studs

24 and 25 respectively. After the rungs 18 are thus formed, they are aligned with the

apertures

16 and 17 in the siderail web 12, inserted therethrougliand the outer ends thereof expanded or riveted to form the

heads

26 and 27. In this manner, the highly desirable ladder structure is formed and assembled in an extremely simple and economical manner.

In the embodiment of FIG. 6, the rung takes the form of a'channel-shaped wide tread step 34, the cross-section of which is defined by a plurality of longitudinally extending rib portions 36, formed integrally with connecting side wall portions 38 and a top wall or tread portion 40 having upwardly facing treads 42. As in the first mentioned embodiment, the

walls

38 and 40 are cut back at the end of the rung to leave extensions of the ribs 36 in theform. of-studs 44 to be inserted in correspondingly spaced apertures in the ladder siderail and riveted thereto.

A still further preferred modified embodiment of the ladder rung of this invention is illustrated in FIG. 7 of the drawings. As shown in this figure, a rung incorporating the present invention may be formed having a quadrangular or trapezoidal cross-section to define anupper wall or tread 46 under which a rib portion 48 is integrally formed, sidewalls 50 and a bottom wall 52. A pair of rib portions 54 are provided at the corners of the

walls

50 and 52 to resist the tensile stress imposed on the lower portion of the rungs when loaded. Again, as in the preceding embodiments, the

walls

46, 50 and 52 in use will be cut back to leave extending the

ribs

48 and 54, as rivet studs for connection of the rung to the ladder siderails.

Thus, is will be apparent to one skilled in the art that the foregoing objectives are completely and effectively fulfilled by the present invention. Because of the unique cross-sectional configuration of the rungs, an extremely strong and light rung section is afiorded, while at the tachment of the rung to the ladder siderails. The ability to attach the rungs by riveting materially enhances the strength. of the connection because of the inherent qualities which derive from a rivet-type connection. In other words, after the

studs

24 and 25 are inserted through the

apertures

16 and 17 and the ends thereof riveted, not only is the rung held against removal from the siderails by the rivet heads 26 and 27, but also thatportion of the stud'which remains in the aperture is expanded so as to develop extreme pressure against the sides of the holes and thus firmly anchor the rung in place. Accordingly, the resulting ladder is light in weight, exceptionally strong to Withstand the loads imposed thereon, and further is resistant to the damaging effect of forces resolved into the rung-side rail joints by rough handling.

Since the present invention may take many diverse forms, it is to be distinctly understood that the foregoing description is illustrative only and not limiting, the true spirit and scope of the invention being defined by the appended claims:

I claim:

1. A ladder comprising in combination:

a pair of side rails having sets of holes formed therein at longitudinally spaced intervals, each of said sets having at least two holes;

and a plurality of rungs extending between said side rails, said rungs each including an extruded length of light metal of a generally circular cross section defining two rod-like rib portions, said rib portions being diametrically opposed and interconnected by semicircular wall portions, the wall portions at each end of said length being cut back to leave said rib portions extending as studs;

said studs being received in said holes and expanded to connect said rungs to said side rails, said rib portions and said studs in each of said rungs being spaced along the length of said side rails to provide resistance to bending of said rungs together with resistance to bending between said rungs and said side rails in a direction of length of said side rails.

2. A ladder comprising in combination:

and a plurality of rungs extending between said side rails, said rungs each including an extruded length of light metal of a channel-shaped cross section, said channel-shaped cross section defining a wide tread step including four rib portions connected by a pair or integral side wall portions and a top wall portion, the wall portions at each end of said length being cut back to leave said rib portions extending as studs;

said studs being received in said holes and expanded to connect said rungs to said side rails, said rib portions and said studs in each of said rungs being spaced along the length of said side rails to provide resistance to bending of said rungs together with resistance to bending between said rungs and said side rails in a direction of the length or" said side rails.

3. A ladder comprising in combination:

and a plurality of rungs extending between said side rails, said rungs each including an extruded length or" light metal of a quadrangular cross section to define top, bottom and side wall portions, said rung having rod-like rib portions, at least one of said rib portions in said top wall and at least two of said rib portions being disposed at the corners defined by said bottom and side walls, the wall portions at each end of said length being cut back to leave said rib portions extending as studs;

References Cited by the Examiner UNITED STATES PATENTS 347,608 8/86 Jackson 182-194 488,428 12/92 Frye et a1. 182216 901,755 10/08 Tiepolt 182194 1,246,709 11/17 Brown 182-228 2,090,331 8/37 Kutscheid 182222 2,630,175 3/53 Dickerman 29-513 X 2,790,586 4/57 Troche 182-216 3,016,976 1/62 Munson 182-194 FOREIGN PATENTS 211,308 2/24 Great Britain.

468,907 7/37 Great Britain.

561,625 10/57 Belgium.

HARRISON R. MOSELEY, Primary Examiner. G. L. BREHM, Examiner.

Claims

1. A LADDER COMPRISING IN COMBINATION: A PAIR OF SIDE RAILS HAVING SETS OF HOLES FORMED THEREIN AT LONGITUDINALLY SPACED INTERVALS, EACH OF SAID SETS HAVING AT LEAST TWO HOLES; AND A PLURALITY OF RUNGS EXTENDING BETWEEN SAID SIDE RAILS, SAID RUNGS EXTENDING BETWEEN SAID SIDE OF LIGHT METAL OF A GENERALLY CIRCULAR CROSS SECTION DEFINING TWO ROD-LIKE RIB PORTIONS, SAID RIB PORTIONS BEING DIAMETRICALLY OPPOSED AND INTERCONNECTED BY SEMICIRCULAR WALL PORTIONS, THE WALL PORTIONS AT EACH END OF SAID LENGTH BEING CUT BACK TO LEAVE SAID RIB PORTION EXTENDING AS STUDS; SAID STUDS BEING RECEIVED IN SAID HOLES AND EXPANDED TO CONNECTED SAID RUNGS TO SAID SIDE RAILS, SAID RIB PORTIONS AND SAID STUDS IN EACH OF SAID RUNGS BEING SPACED ALONG THE LENGTH OF SAID SIDE RAILS TO PROVIDE RESISTANCE TO BENDING OF SAID RUNGS TOGETHER WITH RESISTANCE TO BENDING BETWEEN SAID RUNGS AND SAID SIDE RAILS IN A DIRECTION OF LENGTH OF SAID SIDE RAILS.