US3068957A - Ladder construction - Google Patents

Description

Dec- 18, 1962 c. L. BEST ETAL 3,068,957

LADDER coNsTRUcTIoN Filed Nov. 4. 1960 3 Sheets-Sheet 1 3o INVENToRs CHARM-SL. Basr- BY Orr@ .S1 A//azse/v ArfoxA/Er:

Dec. 18, 1962 c. L. Bl-:s'r ETAL 3,053,957

LADDER CONSTRUCTION Filsd Nov. 4. 1960 5 Sheets-Sheet 2 Irrokwegs Dec. 18, 1962 c. L. BEST ETAL 3,068,957

LADDER CONSTRUCTION Filed NQV. 4. 1960 5 Sheets-Sheet 3 mi f2 f5 INVENToRs CHARM-.s L. Beas-r BY Orr-o .5', /V/zsa-w Marg/La# United States Patent Olice 3,068,957 Patented Dec. 18, 1962 3,068,957 LADDER CONSTRUCTION Charles L. Best, Watertown, and Otto S. Nielsen, Minneapolis, Minn., assignors to The J. R. Clark Company, Spring Park, Minn., a corporation of Minnesota Filed Nov. 4, 1960, Ser. No. 67,401 Claims. (Cl. 182.-246) This invention relates to stepladders.

Stepladders normally comprise a ladder section having steps and ay prop section pivoted to the ladder section and adapted to support the ladder section in a relatively upright position for use over a floor or other supporting sur'- face. It has become a relatively common practice in recent years to also build steps or rungs into the prop section and to provide a means for aligning and locking the sections in extended overlapping condition to provide an extension ladder of substantially greater length than the ladder section alone.

It is also desirable that the prop section be so connected to the ladder section as to be longitudinally adjustable with respect to the intersection pivot whereby the prop section and ladder section may rest upon different levels such as when used on a stairway.

The present invention is concerned with the type of stepladder having the characteristics above described and which ladder for convenience may be referred to as a convertible ladder.

An object of the present invention is to provide such a convertible ladder wherein one section is longitudinally slidable relative to its pivotal connection with the other section and with a singular means for locking said slidable section against such sliding movement regardless of whether the sections are arranged in stepladder or extension ladder formation.

Another object of the invention is to provide a spreader brace for limiting spreading of the ladder and prop sec tions of a stepladder which is also adapted to lock the sections against each other in substantial parallelism.

Still another object of the invention is to provide a convertible ladder having sections adapted to be arranged to form an extension ladder and in which the sections can be freely and relatively moved in an expanding or contracting direction and automatically locked in any selected position of length adjustment of the ladder.

Still another object of the invention is to provide a convertible ladder having two sections and an interconnecting bracing structure for supporting the section in angular step-ladder relation and which same bracing structure is adapted to lock the sections togetheron parallel planes and against relative contracting movement when the sections are in extension ladder relation.

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 r FIG. l is a side elevation of the ladder with they ladder sections relatively arranged for use of `the ladder as a conventional stepladder on a horizontal supporting surface.

FIG. 2 is a front elevation of the ladder in the condition shown in FIG. 1.

FIG. 3 is a horizontal section taken along line 3 3 of FIG. 1 through one side of the ladder'and looking downwardly upon the spreader brace.

FIG. 4 is a side elevation of the ladder, similar to FIG. l, but showing the ladder sections relatively arranged for use of the ladder on a staircase or with one section at rest upon an elevated supporting surface.

-tions at one side of the ladder.

FIG. 7 is a side elevation of the ladder with the ladder sections relatively arranged for use of the ladder as an extension ladder.

FIG. 8 is a vertical section through the upper portion of the ladder taken along line 8 8 of FIG. 6.

FIG. 9 is a vertical section through the upper portion of the ladder taken along line 9 9' of FIG. 5.

FIG. l() is an enlarged section taken through one side of the ladder, along line 1ll 10 of FIG. 7 and looking downwardly.

FIG. ll is a view similar to FIG. 8 but with the ladder in extension ladder condition as in FIG. 7 and with the ladder sections between positions of adjustment.

Referring now more particularly to the drawings reference numerals will be used to denote like parts or structural features of the invention in the different views. The ladder has two straight ladder sections denoted at 10 and 11 and hereinafter respectively referred to as the rear and front ladder sections. The rear section 10 comprises a pair of parallel side rails 12 which are interconnected by a plurality of spaced rungs 14 extending therebetween. The front section 11 has side rails 1'5 which are interconnected by a series `of cross steps 16 in conventional manner. Rails 15 may diverge in their downward eX- tension, as shown in FIG. 2, for improved lateral stability of the ladder.

The present invention lies in the structure interconnecting the sections 10 and 11 and inasmuch as this structure is identical on both sides of the ladder only the elements on the near side as the ladder is viewed in FIGS. 1, 4 and 7 will be described in detail.

An elongated channel 17 is disposed around the side rail 12 and serves as a guide for longitudinal sliding movement of the rail therethrough. The channel has its side edges turned inwardly along the inner face of the rail as at 18 (FIG. 6) to hold the channel on the rail. A relief 19 is provided in the outer wall of the channel to allow free passage of the projecting ends 20 of the rungs 14 therethrough.

A bracket 21 is mounted on the channel 17 near the upper end thereof. This bracket conforms closely around the outside of the channel to which it is secured and then has a rearwardly extending mounting flange 22 and terminaties in an inwardly set ear 24. Ear 24 is pivoted to side rail 15 by bolt and nut assembly 25 best shown in FIG. 6.

Horizontally opposite the lower end portion of channel 17 a Ushaped clip 27 is mounted on the front edge of side rail 15. This clip is connected to the lower end portion of the channel 17 by a spreader brace designated generally at 28. This brace, best shown in FIG. 3, comprises end links 29 and 30 respectively pivoted at 31 and 32 to channel 17 and clip 27 and a center link 34 having its ends pivoted at 35 and 36 to the swingable ends of the end links 29 and 30. A snubber member 33 of rubber or other resilient material is mounted on rail 15- projecting toward the channel 1'7.

Link 34 is a downwardly opening channel prohibiting upward movement of links 29 and 3l) about their pivotal connections therewith. The length of link 34- between its pivots 3S and 36 is equal to or slightly greater than the length of link 30 between its pivots 36 and 32. The length of link 29 between its pivots is substantially equal to the distance between pivots 31 and 32 when the channel 17 is against the snubber as in FIGS. 7 and l0. The spreader brace 28 not only serves to limit spreading movement of the sections 10 and 11 about pivot 25, but it also is adapted to serve asa locking mechanism to hold the channel 17 firmly against the side rails 15 when the assembly is used as an extension ladder as shown in FIG. 7.

Turning now to FIG. 9, it will be understood that this aceites? .3 view shows the bracket 21 as viewed from the inner side of the side rail 12. The mounting flange 22 on the bracket lies substantially on the plane of the inner face of the rail (FIG. 6) and an offset wall 22a lying parallel with rail 12 faces forwardly and connects ear 24 with the ange 22.

A flat elongated latch or hook member 4) has its lower fend portion pivoted as by pin 41 to mounting flange 22. The upper portion of member 40 has a rearwardly opening hook portion 42 adapted to engage under and around the front side of rung 14. The upper end of member 4b has a rearwardly slanting edge 44. Between edge 44 and the hook opening a dog-leg shaped gate 45 is pivoted .as by pin 46 at its center or balance point for opening and closing movement over the mouth of the hook. The lower front edge of member 4t) is cut at an angle as at 47 (FIG, 9) to engage flush against wall 22a when the hook 42 is at rest against rung 14. A wire scar spring 48 has one end extending through an aperture 49 in the member 4() and its other end extending through Wall 22a, said spring being held under compression to yieldably hold the member 49 `in its rearward position against rung 14 with edge 47 in engagement with wall 22a.

A clip 50 is secured to the side rail 15 and has a laterally extending flange 51 which extends outwardly in front of the member 4i! when the ladder sections are .spread for stepladder use. This assures positive engagement of the hook with rung 14 when the ladder is in this condition. However, when the sections are moved together about pivot for extension ladder use the liange 51 will be moved away from the member 40, as in FIG. ll, allowing the member 40 to be forced forwardly about its pivot 41 against spring 43. A flange on the upper rear edge of gate 45 limits entrance of the gate into the hook opening.

Operation and use of the ladder will now be understood. When the ladder is used as a conventional stepladder as shown in FIGS. l and 2, or as a stairway ladder as in FIG. 4, the spreader braces 2S will be extended in a rigid condition and the members 46 will be locked against the opposing rung 14 preventing any movement of the side rails 12 through channels 17.

When it is desired to collapse the ladder for storage or to use it as an extension ladder as in FIG. 7, the braces 28 are broken by pushing upwardly on links 34. This allows the end links 29 and 3i) to swing upwardly about their outer end pivots and the channels 17 and the ladder section 1t) carried thereby can be swung inwardly about the pivots 25 and against the front section 11. The channels 17 will engage the snubbers 33. During the collapsing movement the front links 30 are swung upwardly and forwardly through 180 degrees about their pivots 32 until said links enter the channels 34 with both extending forwardly as shown in broken lines in FG. 7. At this point the channels 17 are against snubbers 33. As the links 34 are then swung downwardly about pivots 35, to the position shown in full lines in FIG. 7, pivots 32 and 35 are disposed in near coaxial alignment and the spreader braces become over-center locking devices for securely holding the guide members 17 against the side rails 15.

when the guide channels 17 are so locked the member 4G will still be held in engagement with rung 14 by the pressure of spring 48. However, it will be understood that flange 51 will now have been moved in a forward direction away from the hook 4G' allowing the hook to be urged forwardly against the spring 48 (FIG. 11). Accordingly, the section 10 can be moved upwardly in the channels 17 with the rungs 14 passing over the hook opening until the desired extension ladder length has been reached with a selected rung 14 engaged by the hook member. inasmuch as the load of section 10 is applied endwise to the member 4t), with `the member 4t) and rung 14 engaged thereby in the same relative position as in FlQS. 8 and 9, the sections it) and 11 are locked against relative contracting movement and the ladder may be safely used as an extension ladder.

When it is desired to again collapse or contract the sections they are tirst extended slightly until the locked rung 14 passes upwardly beyond the hook and gate 45. As section i0 is then lowered it will engage the inclined edge 44 on the hook member and force the hook forwardly. It will then close the gate 45 and move along the rear edge thereof past the hook opening. The inclined edge 44 cannot move rearwardly past the rung path due to engagement of the hook member edge 47 with wall 22a. If the ladder is to be shortened only slightly, section 10 is lowered only until the rung 14 to be locked passes over the gate 45, and is then raised until the hook engages the selected rung.

It will be understood that whenever the section 1) is to be relatively adjusted along the channels 17, such as to convert the ladder from a conventional stepladder (FIG. l) to a stairway ladder (FIG. 4) or vice versa, the braces 28 must be collapsed and channels 17 moved against side rails 1S. Section 10 is then moved upwardly or downwardly to the desired position in the manner described above.

The member 40 accordingly provides a positive lock f' against movement of section 10 in either direction when the sections 10 and 11 are angularly disposed in stepladder relation. Moreover this device in conjunction with the brace 23 serves to lock the sections together and against contraction when used as an extension ladder, thus eliminating the need of a second independent extension ladder hook.

It is understood that suitable modications may be made in the structure as disclosed, provided such modications come within the spirit and scope of the appended claims. Having now therefore fully illustrated `and described our invention, what we claim to be new and desire to protect by Letters Patent is:

1. In a combination stepladder and extension ladder a irst ladder section, guide means pivotally mounted on the first ladder section, a second ladder section mounted in said guide means for movement therewith about said pivot between an angular spread position relative to the tirst section to form a stepladder therewith and a position parallel to the first section, the second section also being longitudinally slidable in said guide means to form an extension to the first section when in parallelism therewith, the second section having a plurality of cross rungs spaced therealong which are round in cross section, a hook member pivoted on the first section and having a hook element engageable with portions of any selected rung which are opposed longitudinally of the section to prohibit said sliding movement of the second section in either direction in said guide means, and a stop member rigidly mounted on said first section adjacent the hook member in such position as to move into engagement with and retain the hook member in its rung engaging position when the sections are moved to their relatively spread position.

2. In a stepladder having first and second elongated ladder sections pivotally and slidably interconnected for relative spreading and closing movement about the pivot between a spread position and a closed parallel position as well as longitudinal extending and retracting sliding movement of the second section relative to the rst when the sections are in closed position, the second section having a plurality of cross sectionally circular cross rungs spaced therealong, a rung latching element pivotally mounted on the first section for movement between a retracted position toward the first section and an advanced position in the path of sliding movement of said cross rungs, said latching element having a substantially semicircular rung seat for seating any selected rung, said seat opening toward said second section to engage peripherally around at least the entire rung halt lying at one side of the path of movement to so seat the rung as to prohibit sliding movement of the second section in either direction when the latching element is in its advanced position, and means on the first section for locking the latching element in its advanced position.

3. A convertible ladder, comprising in combination, a first upright ladder section, a second upright ladder section having side rails and a plurality of cross rungs spaced along thev side rails, a guide device mounted on the lirst section and holding said side rails for longitudinal sliding movement of the second section upwardly or downwardly to extend or contract the height of the ladder, said guide device pivoted to the first section for swinging movement of the device and the second section held thereby between a closed position against and substantially parallel to the first section and a spread position at an angle to the rst section, a latching element mounted on the guide device adjacent the guide device pivot, said latching element having a hook portion positioned to engage under any selected rung to prohibit downward movement of the second section in the guide device when the sections are in either closed or spread position, and a fixed stop on the irst section above the guide device pivot for movement about said pivot relative to the second section between an out of the way position when the sections are closed and a stop position prohibiting upward movement of the second section when the sections are spread.

4. A convertible ladder comprising in combination, a first upright ladder section, a second upright ladder section having side rails and a plurality of cross rungs spaced along the side rails, guide means mounted on the iirst section and holding said side rails for longitudinal sliding movement of the second section upwardly or downwardly to extend or contract the height of the ladder, said guide means pivoted to the first section forswinging movement of the second section between a spread position at an angle to the first section and a closed position substantially parallel to the iirst section, hook means movably supported on the first section to lock the second section against downward movement by engaging a rung thereof but movable to permit unlimited upward movement of the second section when the second section is in closed position, an extendable and contractable locking linkage having one end connected to the first ladder section and the other end connected to the guide means, and means for locking the linkage in its contracted condition to secure the guide means against the first section and thereby hold the ladder sections in substantially parallel position.

5. In a stepladder, a rst ladder section, guide means pivotally mounted on the first ladder section, a second ladder section slidably mounted in said guide means for longitudinal sliding movement therein and movable with said guide means about said pivotal mounting between relatively angular and parallel positions with respect to the first section, one of said sections having longitudinally spaced rungs, a hook swingably supported by the other section and movable between rung engaging and releasing positions, and a hook stop positioned on said other section to move into the path of movement of the hook as the sections are moved to their relatively angular position to lock the hook against movement to its releasing position.

References Cited in the lile of this patent UNITED STATES PATENTS 551,073 Burgedahl Dec. 10, 1895 1,342,881 Udell lune 8, 1920 1,942,849 Thrasher Jan. 9, 1934 2,521,114 Campbell Sept. 5, 1950 2,896,830 Blair July 28, 1959 2,942,686 Osovski June 28, 1960 2,991,484 Willis Iuly 1l, 1961

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