US2966229A - Ladder construction - Google Patents

Description

Filed Feb. 15, 1955 2 Sheets-Sheet 1 Dec. 27, 1960 G. E. FREZIERES 2,

LADDER CONSTRUCTION Filed Feb. 15, 1955 2 Sheets-Sheet 2 5 b MAM United States Patent if LADDER CONSTRUCTIDN Grant E. Frezieres, 19350 Larne St., Pteseda, (Ialif.

Filed Feb. 15, 1955, Ser. No. 438,223

4 Claims. (Cl. 182219) My invention relates to ladder construction, and in general to the construction of ladders of all types but in particular to ladders of the type usually utilized in the average household and which, since such ladders are manipulated by persons unaccustomed to handling heavy weights, should be as light as possible.

It is very important that ladders should be strong and rigid since a person standing on a ladder that breaks or fails suddenly, at best takes a hard fall and may easily suffer severe fractures of the bones since he often finds himself falling encumbered with the broken ladder and is unable to soften his fall.

Ladders are generally given little attention or care in use, being often carelessly placed so that the users weight is not squarely supported and in any event are subjected to uneven loading as the user climbs up and down, this lack of care and constant racking usually resulting in one or more rungs becoming loosened and since the rungs are relied on to properly space the side rails, the whole ladder then soon deteriorates.

In order to produce ladders of less weight and greater strength, aluminum has been used for both side rails and rungs. Such ladders are relatively expensive to produce because of the metal forming required and the riveting on of brackets to secure the ends of the rungs to the rails and other mechanical operations adding much labor cost to the cost of materials.

Rungs of metal may become bent by accidental blows or excessive weight being placed on them and the work of replacing them is time consuming even when it is possible to do so.

Ladders are often leaned at larger angles against a Wall than is correct, thus imposing heavy shearing loads on the rails which in the case of wooden ladders when made strong enough to take such loads are quite heavy since it is impractical to brace the rails. In the case of metal ladders having properly braced side rails, the work required to build in such bracing adds considerably to the cost of the ladder.

It is an object of my invention to provide a ladder of high strength to weight ratio, having rungs of unusually strong construction.

A further object of my invention is to connect the rungs of a ladder to the side rails so that they will remain securely engaged therewith indefinitely, yet should a rung become bent by accident, it can be quickly disconnected from the side rails and be replaced by a new rung as securely attached as the original.

Another object of my invention is to produce a ladder of light but strong construction which may incorporate aluminum rungs but side rails of plastic material, the parts of the ladder being adapted for accurate and rapid production at a relatively low cost.

Still another object of my invention is to provide a ladder having side rails of plastic material which may be molded or otherwise formed with reinforcing elements incorporated therein to secure an unusually strong construction at little increase in weight as compared Z,%5,ZZ9 Patented Dec. 27, 1960 2 with side rails not provided with such reinforcement, the side rails in either case being lighter than wooden or metal side rails of usual construction.

A still further object of my invention is to provide a ladder construction comprising side rails which may be formed inexpensively by molding a single material such as plastic impregnated glass fabric, or of such material as an exterior layer and positioning a filling material such as a formed plastic within the outer layer.

It is to be understood that while my invention is hereinafter described as incorporated in a one piece ladder, the features thereof may equally Well be incorporated in extension ladders, or in step ladders of which latter type many millions are in use, or in step ladder like supports for planks as used in scaffolding.

Further objects and features of my invention will hereinafter appear from the following specification read in conjunction with the accompanying drawings which illustrate embodiments of my invention at present considered preferable by me.

In the drawings:

Figure l is a fragmentary perspective view of a ladder incorporating the novel features of my invention.

Figure 2 is a cross-section drawn on a larger scale, on the line 2-2 of Figure 1.

Figure 3 is a fragmentary perspective view, partly in section, showing the form of the holes provided in side rails of I beam form to receive the rungs.

Figure 4 is a detail, drawn on a larger scale, showing a form of spring plate detent used to maintain the rungs in engagement with the side rails of the ladder.

Figure 4a is a detail of view of another form of the member shown in Figure 4.

Figure 5 is a cross-section, drawn on a larger scale, on the line 55 of Figure 2.

Figure 6 is a fragmentary view, partly in section, of a modified construction of side rail.

Figure 7 is a fragmentary end view, partly in section, of another modified construction of side rail.

Figure 8 is a fragmentary cross-section through another modified construction of side rail.

Figure 9 is a fragmentary longitudinal section through the side rail shown in Figure 8.

Figure 10 is a fragmentary sectional View of a still further modified form of my invention.

Figure 11 is a detail view showing a head or foot member of the side rails by which the reinforcing rods shown in Figures 7 or 8 may be prestressed.

Figure 12 is a side view of a rung of modified shape adapted for use in a step ladder.

Referring now to Figures 1 through 5, the numeral 19 indicates generally the side rails of the ladder which rails are preferably though not necessarily of I beam form, having flanges 11 connected by a web 12.

In order to secure a light but strong construction I may form the rails by moulding two halves of each rail from a suitable strong but light thermo setting plastic reinforced material such as glass cloth or other strong woven plastic material and adhesive, or resin, and curing the molded parts under heat and pressure.

A reinforcing and weight bearing member 12, made for instance from laminated Wood or other plastic reinforcements with a setting adhesive bonding the lamina, is then fitted into one-half of the rail, the sides and edges, being coated with a suitable adhesive, or resin, and the other molded half of the rail pressed into position. The edges of the half rails are well overlapped as indicated at 13 and the overlapped surfaces coated with adhesive. Curing of the assembled rail is then completed under heat and pressure to produce a rigid tough yet relatively light construction. It is to be noted that the side walls of the rail form a solid piece of material in the web 12 while the overlapped edge portions 13 form a strengthening bead for the hollow flange portions 11.

The completed rails may be coated with a material acting as a sealant and fungicide and surface protector such as a plastic and solvent solution which will, when the solvent is driven off, deposit a dense adherent coating on the rails.

The web portion 12 of two lengths of rail are then punched or otherwise worked to produce openings extending through the web to receive the ends of rungs fitted therein. The lower edges of the openings 14 are provided with an offset recess 15b for a purpose that will later appear. Preferably the offset recess is arranged at an angle of about 15 to the longitudinal axis of the rail.

It is to be understood that while I will later describe various modifications of the side rail structure of my invention, these modifications all include the characteristic of strength and light weight and the various forms of ladder all utilize a tubular rung, preferably of aluminum or plastic having certain novel characteristics.

The rungs 15, best shown in Figures 4 and 5, comprise a tubular body portion 16, having a bead 17 extending along the underside and serving both as a reinforcing rib and locking member engaging with the offset recess 15b to prevent twisting of the rungs in the side rails. The rung is fabricated either by machining, extruding, or molding, and if of aluminum, annealing to have a lower smooth exterior surface as shown between points 1818 Figure 5, which is sufficient in extent to afford ample bearing surface between the rung and the web of the rail.

Around the remainder of the periphery of the rung the wall thickness is greater, affording a relatively thick tread portion 19 along the upper portion of the rung, and provided with strengthening corrugations 20 between the tread portion and a thick portion 21 below the corrugated portion of the rung periphery.

Peripheral slots 22 and 23 (see Figures and 6) are machined at each end of the rung, the slots being spaced apart so that they will lie on opposite sides of the web of the side rails.

The rungs are retained in the rails by positioning and retaining rings of resilient construction such as the arcuate dished member 24 shown in Figure 4, which comprises an interrupted annulus 25 having a number of spaced inwardly projecting wider portions 26 which engage in the peripheral slots 22 and 23. Two holes 27 are provided at the ends of the member 24. By means of a tool having laterally projecting pegs fitting the holes 27, the member 24 may be readily removed from position in the recess, but it may be readily pushed into position by bearing down on the periphery.

It is pointed out that the dished form of the member 24 causes the rings to exert pressure laterally between the rungs and opposite faces of each rail, thus members 24 do not only serve to prevent the rungs from slipping out of the rails but impart a desirable resilience or give to the ladder structure.

The members 24 are of dished form so that when in position with the dished edges 28 bearing against the sides of the web of the rail, the rungs are secured against working loose, but at the same time any small working of the rungs in the rails due to small fiexures in the latter may take place without causing wear of the fastening means between the rungs and rails as occurs in the usual form of ladder.

In the modified form of the locking and retaining member indicated at 29 in Figure 4a an interrupted ring 30 is provided with upstanding resilient laterally inclined fingers 31. The function and operation of member 29 is similar in all respects to the member 24.

In the form of the invention shown in Figure 6 rails 33 are arranged so that the flange and web can be extruded in unitary or monolithic form in continuous lengths. The rails are of generally I beam form, the

flanges 34 being strengthened by a central rib 35 and the web 36 by longitudinally extending ribs 37 formed integral with and joining the walls of the web at diametrically opposite areas. Holes can be cut at intervals in the length of the web for the rungs 15, preferably the holes being arranged so that the rungs are laterally abutted against a pair of ribs and rest upon three ribs, as shown in the figure.

Reinforcing rods or cords 37a may be located between certain of the ribs. Such reinforcements are more fully described with relation to Figure 7.

Rung 15 is shown as being in all respects similar to that described with reference to Figure 5, but as will later appear modified forms of rung may be utilized.

Another form of the invention shown in Figure 7 is designed to be formed by molding the outer skins or portions of each half rail 38a, 38b and web 39a, 3% from a suitable thermo setting plastic impregnated fabric and then setting the molded parts under heat and pressure. The parts are produced in predetermined lengths and each half rail and web are fitted with longitudinal rods or cords of high stress material 39 such as spun nylon or glass fiber impregnated with a suitable thermo setting resin. If preferred the elements 39 may be strong metal wires.

The reinforcing elements may be positioned under stress between end "members 46 as shown in Figure 11, which shows twisted glass fiber and plastic cords with expanded ends 41 gripped in tapered openings 42 moulded in the members 49 shaped to fit over the top and bottom of the rail ends and which may be divided vertically, the halves being clamped together by screw studs 43 after the meeting faces and the openings 42 have been coated with thermo setting plastic. The members 4%) may then be permanently secured together and to the ends of elements 39.

It will be understood that the tensioning end members may be formed in sections to fit over the rails and the web and secured into a solid block by thermo setting adhesive between the sections.

In assembly, the top and bottom end members 40 are held apart under tension and one-half of the ladder fitted into place. The interior of the ladder half may then be coated with thermo setting plastic adhesive.

repared plastic preparations (indicated at 44) in dough-like form containing ingredients eifective to foam the plastic when heated may then be built up around the reinforcing members 39. The other ladder half may then be treated in a similar manner. Preferably sleeves 45 are positioned in holes provided in the rails to receive the rungs and are put in position, and the ladder halves pressed together with overlapped edges 46 provided with a coating of thermo setting adhesive between their overlapped faces, and the whole ladder then set by heat and pressure. 7

If preferred, the halves of the ladder with sleeves 45 and reinforcements in place is sealed up and the foam plastic material in liquid form is poured therein and then foamed.

Suitable foaming materials are known in the art as for instance in Patent No. 2,576,073, issued to E. L. Kropa et al. and numerous others.

The ladder is then fitted with rungs as previously described in connection with the previously described embodiments of the invention.

In the form of the invention shown in Figures 8 and 9, a ladder construction of the same general form as that of Figure 7 is shown but the reinforcement consists of cross braced high stress rods or cords 47 in the rails and if desired also in the web.

The rods or cords which may be formed of plastic impregnated fiber glass are tightened around tubularsleeves or spacers 48 and the remainder of the space is filled with foamed plastic, indicated at 49.

It will be 'notedthat by utilizing alternate spacers 48 to support the rungs 15, the intermediate spacers provide lightening holes.

The embodiment of the invention shown in Figure shows ladder rails each half being formed with semicircular rolled over edges 50 and having a sheet of plastic or aluminum honeycomb 51 inserted into the web to strengthen and stiffen it. The outer skin of the web and rails may be formed from plastic impregnated woven fiber glass material, the edges 52 of the re-entrant portion of the rails being coated with thermo setting adhesive which will be set when setting the ladder halves under heat and pressure. Thereafter the sheets of honeycomb material are positioned on the plastic adhesive coated inner face of one member, sleeves 53 are positioned in openings cut through the web and honeycomb, the meeting faces 54 of the rail halves are coated with plastic adhesive together with the inner face of the remaining half of the web, and the whole set under heat and pressure.

The final step is then to insert the rungs of the ladder as previously described.

It is believed unnecessary to explain in detail that ladder ends of suitable impact resistant plastic can be fitted to the ends of lengths of ladder, these ends may be utilized to secure hinge elements embedded therein when making ladders of the step ladder type or of the kind used in scaffolding.

In Figure 12 a modified form of rung is shown which is suitable for use in step ladders and comprises a rung 15a of the form and mounted in the rails and secured therein all as previously described, but a wide step 55 is provided by lengths of aluminum provided with upstanding ridges 56 which fit into the grooves in the surface of the rungs and are securely held therein by screws 57 passing through holes drilled in the plate and engaging in tapped holes in the thick tread portion of the rung.

It is to be understood that various plastic materials mentioned in the preceding specification are given by way of example only since improved materials are constantly being developed in this field. For instance, the mention of Fiberglas as a suitable fabric which is laid up in layers with suitable thermo setting adhesives is to be understood to be equivalent to synthetics, asbestos or other high modulus materials which may be readily manipulated under heat and pressure to form very light yet strong ladder structures. These structures will provide rails preferably having dense high strength walls spaced apart and stiffened by light expanded material such as foam rubber or honeycomb material and further strengthened by the inclusion of internal flanges of the same material as the outer walls. In addition or in place of internal structural reinforcement, bracing of high strength material either of metal or the polyester material forming glass fishing rods for instance, may be utilized.

The rails may also be produced by an extrusion process from suitable plastic materials such as polyesters, phenolic, epoxy, silicone, rigid thermo plastics or altered combinations of thermo setting types.

A weatherproof and fungus resistant coating may be applied to the ladders by spraying or painting with liquid solutions of plastics such as Acron weather coating and others.

The rungs and steps are preferably produced from extruded aluminum or of course other suitable light but strong metals, and processed casting, but may also be produced from suitable plastics such as polyesters, phenolic, epoxy, silicone, reinforced type or rigid thermo plastic types, scaffolding, rigid vinyls, styrene, etc.

The construction of the rails aflords a safety feature in that the annular removable detent rings are protected from accidental blows from tools or from being caught by clothing.

In view of the many suitable materials which may be utilized, and the variety of configurations in which the ladders, step ladders, extension ladders, etc. may be produced, I do not intend to limit the scope of the invention by the examples given by way of illustration but only as intended to be defined by the scope of the appended claims.

What I claim is:

1. A ladder comprising: side rails having outer walls of a tough dense plastic and a filling material of foamed plastic enclosed within said walls; interior reinforcing elements spaced throughout said foamed material, holes being provided through said reinforcing elements; reinforcing rod-like members of high tensile strength material wound around said reinforcing elements throughout the length of said ladder; and tubular rungs having their ends extending through openings in the walls of the rails and certain of said interior reinforcing elements, said rungs being provided with recesses at each end; and detent means releasably engaging in the recesses in the ends of the rungs and engaging with the faces of said side rails to prevent separation of the rungs from the side rails until removal of said detent means has been effected.

2. A plastic ladder comprising: side rails having outer walls of strong hard plastic of uniform thickness and of I-beam form with flanges connected by a web portion; an interior cellular re-einforcement material, filling the whole interior faces of the ladder walls throughout the length of the ladder; vertically spaced openings in the hard outer wall of the web portion and the re-enforcement; and rungs extending at each end into said openings and secured therein.

3. A ladder as set forth in claim 2 wherein said reenforcement is made of expanded honeycomb material positioned between and bonded to said walls, said openings each having a smaller offset opening cut in the lower edge thereof, tubular rungs each provided with a longitudinally extending rib along the whole length of the lower side of said rung, said rib being effective to engage with said offset opening to lock said rungs against turning in the rung receiving openings and to reinforce the rung; and laterally resilient means engaging against both faces of the side rails and removably mounted on said rungs to secure the rungs in the rails.

4. A ladder as set forth in claim 3 and in which said tubular rungs are provided with a thickened smooth lower peripheral portion to transmit the weight of the user to the rail, an upper thickened longitudinally extending portion serving as a tread for the user, and longitu dinal corrugations extending between said smooth and thickened portions, the form of the rung being uniform throughout the length of the rung.

References Cited in the file of this patent UNITED STATES PATENTS 785,901 Mallory Mar. 28, 1905 983,213 Dahill et al. Jan. 31, 1911 1,912,331 Wikstrand May 30, 1933 1,915,640 Alsaker June 27, 1933 2,411,761 Stolberg Nov. 26, 1946 2,417,586 Crosley Mar. 18, 1947 2,418,929 Glassbrook Apr. 15, 1947 2,487,803 Heimann Nov. 15, 1949 2,509,081 Bluth et al May 23, 1950 2,552,630 Hutchinson May 15, 1951 2,571,717 Howard et al. Oct. 16, 1951 2,594,561 Huck Apr. 29, 1952 2,639,252 Simon et al. May 19, 1953 2,656,087 Sharrock Oct. 20, 1953 2,776,080 Hopfeld Jan. 1, 1957 2,779,066 Gaugler et a1. Jan. 29, 1957 FOREIGN PATENTS 178,274 Austria Apr. 28, 1954 654,320 Great Britain June 13, 1951 667,843 Great Britain Mar. 5, 1952

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