US3037581A

US3037581A - Self-levelling ladder

Info

Publication number: US3037581A
Application number: US109773A
Authority: US
Inventors: Floyd L Feltrop
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-05-12
Filing date: 1961-05-12
Publication date: 1962-06-05
Anticipated expiration: 1979-06-05

Description

`une 5,

Filed. May

F. L. FELTROP SELF-LEVELLING LADDER 2 Sheets-Shea?l 1 INV EN TOR.

FLoYo L. F'ELTRQP AT'TQIZNEYS June 5, 1962 F. L.. FELTROP SELF-LEVELLING LADDER 2 Sheets-Sheet 2 Filed May 12. 1961 l lll ..,..,|||H.,w....f.w -JWN INVENToR.

FLoYO L. FE L-rraop ATTORNEYS United States Patent O 3,037,581 SELF-LEVELLING LADDER Floyd L. Feltrop, Eldon, M0. Filed May 12, 1961, Ser. No. 109,773 8 Claims. (Cl. 182-202) This invention relates to a novel self-levelling ladder.

The primary object of the invention is the provision of a more practical and eflicient ladder of the kind indicated whose legs or rails have vertically slidable feet or extensions, on their lower ends, which are adapted to move vertically in opposite directions to accommodate them to different levels of uneven ground when contacted therewith, and wherein spring-retracted locking means is provided for the extensions or feet, which act to lock the same in adjusted positions, upon the'imposition of effective weight upon the ladder.

Another object of the invention is the provision of novel and improved locking means of the character indicated, in conjunction with hollow lower ladder leg portions and hollow extensions or feet sliding in said portions, the locking means comprising a spring-retracted locking assembly located within each lower leg portion and its extension or foot, the locking assemblies having normally retracted detent elements which are adapted to engage in detent openings provided in the leg portions and the extensions or feet only while the assemblies are extended by effective weight imposed on the ladder.

A further object of the invention is the provision of locking assemblies of the character indicated above, which are operatively connected to related ends of a rockable equalizing bar which is pivoted, intermediate its ends, on a stationary cross bar which extends between and is fixed to the lower ladder leg portions.

Other important objects and advantageous features of the invention will be apparent from the following description and the accompanying drawings, wherein, for purposes of illustration only, a specific form of the invention is set forth in detail.

In the drawings:

FIGURE l is a perspective view of a self-levelling ladder of the present invention;

FIGURE 2 is an enlarged fragmentary front elevation of said ladder, showing its leg extensions or feet resting upon different levels of the ground; t

FIGURE 3 is a fragmentary side elevation looking from right to left in FIGURE 2;

FIGURE 4 is a fragmentary vertical transverse section taken on the line 4-4 of FIGURE 2;

FIGURE 5 is a horizontal section taken on the line 5 5 of FIGURE 2;

FIGURE 6 is a further enlarged vertical transverse section taken on the line 6-6 of FIGURE 2, showing a locking assembly in relaxed or retracted position;

FIGURE 7 is a view like FIGURE 6, showing the locking assembly in compressed or extended locking position;

FIGURE 8 is a fragmentary vertical longitudinal section taken on the line 8-8 of FIGURE 6; and

FIGURE 9 is a fragmentary vertical longitudinal section taken on the line 9--9 of FIGURE 7.

Referring in detail to the drawings, wherein Vlike numerals designate like parts throughout the several views, the illustrated ladder comprises a pair of similar parallel vertical legs or rails 12, which are spaced and connected by vertically spaced rungs 14. 'I'he legs 12 can be of C-shaped channel form throughout their lengths, as shown, or be of any other suitable cross section, except for lower end portions 16 which are of C-shaped channel cross section. The lower leg portions 16 having front and

back walls

18 and 20, and inner and outer side walls. 22 and 24, respectively, opposed pairs of these walls being Mice parallel, and the inner side walls 22 having central vertical slots 26 therein, which extend to the lower ends of the leg portions 16. The outer side walls 24 are formed with central vertical slots 28, which open to the lower ends of the leg portions 16, and have closed upper ends 30, which are preferably spaced downwardly from the lowermost of the ladder rungs 14. The place of what would ordinarily be the lowermost rung of the ladder is taken by a fixed cross bar 32 which extends between and is fixed at its ends to the inner side walls 22 of the legs 12, at locations behind the slots 26 and 2S, the cross bar 32 being thereby rearwardly offset out of the vertical plane of the rungs 114.

A generally horizontal equalizer bar 34, which is longer than the distance between the outer side walls 24 of the ladder legs 12, is pivoted, at its midpoint, as indicated at 36 to the forward side of the xed cross bar 32, at the midpoint thereof, and end portions of the equalizing bar extend through the

slots

26 and 28 in the ladder leg side walls. The equalizer bar 34 has parallel side end portions, which work closely but freely in the slots 28, and which are formed with longitudinally elongated closed slots 38 which have parallel upper and

lower sides

40 and 42, respectively, the upper sides 40 being, in effect, cam surfaces.

Rectangular C-cross section channel extensions or feet 44 are upwardly and slidably and conformably engaged in the lower ends of the lower ladder leg portions 16, and have closed lower ends 46 to rest upon a surface, such as the ground G. The feet 44 have front and

back walls

48 and 50, and inner and

outer side walls

52 and 54, respectively. The inner and

outer side walls

52 and 54 are provided with central vertical closed

slots

56 and 58, respectively, which are preferably horizontally aligned with each other, and which, as shown in FIGURE 9, are greater in vertical dimension than the end portions of the equalizer bar 34, so as to provide for substantial upward and downward tilting of the equalizer bar in the

slots

56 and 58.

The front and back walls 18 and 20' of the lower portions 16 of the ladder legs 12 are provided with centered vertical rows of vertically spaced horizontal detent slots 6l) which are in horizontal alignment with each other, and which start upwardly from points close to the lower ends of the legs 14. At similar locations spaced from their upper and lower ends, the extensions y44 are formed, in their front and

back walls

48 and 50, with similar horizontally aligned circular openings 62.

As shown in FIGURES 6 to 9, fixed lower half-round bars 64, which are narrower than the circular openingsy 62, extend between the front and

back walls

48 and 50 and have their convex lower sides 66 fixed, at theiry ends, as indicated at 68, to the bottom of the circular openings 62. The lower half-round bars 64 are provided with central vertical bores 70 extending therethrough and receiving vertical pins 72 which are fixed centrally to and extend downwardly from upper half-round bars 74, which have their convex sides 76 disposed upwardly. The upper half-round bars 74 are of -the same dimensions as the lower half-round bars 64 and have their ends freely disposed in the circular openings 62, and their convex upper sides 76 freely engaged with the upper cam sides 40 of the closed slots 38 in the ends of the equalizer bar 34.

Flat upwardly bowed leaf springs 78 have flat horizontal middle portions 80 having centered openings 82, which receive the vertical pins 72, and downwardly and longitudinally outwardly curved end portions 84 in the ends of the middle portions 80, which have terminal ends 86. In the retracted and uncompressed condition of the springs 78, shown in FIGURE 6, their terminal ends 86 are located within the circular openings 62, and the ladder leg extensions 44 are free to be moved upwardly or downwardly in the ladder legs 12. In the fully compressed or extended condition of the springs 78, shown in FIGURE 7, produced by imposition of weights upon the ladder, the springs 7S are flattened, so that their end portions 84 are pushed longitudinally outwardly, so that the terminal ends 86 thereof reach through the circular openings 62 and into detent slots 60 in the front and

back walls

18 and 20, respectively, of the lower ladder leg portions 16, so as to securely lock the extensions 44 in vertically adjusted positions relative to the ladder legs 12.

In use and operation, in order to adjust the ladder so that its extensions 44 supportably bear upon different levels of ground as shown in FIGURE 2, with the ladder in erect position, the extensions 44 are permitted to slide downwardly in the ladder legs 12, until their lower ends 46 rest upon the different ground levels. These movements of the extensions 44 are accompanied by rocking of the equalizer bar 34, so that, in effect, the rise of one extension is accompanied by a fall, to a similar extent, of the other extension. When the lower ends of the extensions 44 have reached the ground, exertion of downward pressure upon the ladder, either by grasping the ladder legs 12 or a rung 14, or by stepping upon a rung 14, the upper sides 40 of the closed slots 3S in the ends of the equalizer bar 34 engage and force the upper half-round bars 74 downwardly and compress and extend the springs 78, so that their terminal ends 86 are forced against the inner surfaces of the front and back walls, 18 and 20 of the leg portions 16 until the terminal ends 86 reach related detent slots 60, whereat the terminal ends engage therein and lock the extensions in their adjusted positions. This locked condition of the extensions 44 continues only as long as sufiicient weight is imposed on the ladder. When such weight is removed from the ladder, the springs 78 retract or resume their uncompressed condition, wherein their terminal ends 86 are withdrawn from the detent slots 60, and the extensions 44 are again free to slide in the ladder legs 14.

Although there has been shown and described a preferred form of the invention, it is to be understood that the invention is not necessarily confined thereto, and that any change or changes in the structure of a-nd in the relative arrangements of components thereof are contemplated as being within the scope of the invention as defined by the claims appended hereto.

What is claimed is:

l. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and fixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and iixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said iixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only While the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements.

2. A self-levelling ladder comprisin'J a pair of spaced vertical legs, rungs extending between and fixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and fixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies cornprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said fixed detent elements being vertically spaced detents on walls of the lower end portions.

3. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and fixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and fixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said fixed detent elements being vertically spaced detents on walls of the lower end portions, the ends of said equalizer bar extending within said lower end portions and extensions and having slots in which said springs are located.

4. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and fixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and fixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said fixed detent elements being vertically spaced detents on walls of the lower end portions, the ends of said equalizer bar extending within said lower end portions and extensions and having slots in which said springs are located, said equalizer bar slots having upper sides, upper bars extending across the interior of the extensions and freely vertically movable therein, lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending through the equalizer bar slots, said springs being rupwardly bowed leaf springs engaged between the upper and lower bars and having terminal ends constituting said movable detent elements, opposed walls of the extensions having openings through which said terminal ends can extend, opposed walls of the lower end portions of the legs having vertically spaced detent slots constituting said xed detent elements, into which the terminal ends of the springs are engageable only in the compressed condition of the springs.

5. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and fixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and fixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition ofthe springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress lthe springs only when weight is imposed'on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said fixed detent elements being vertically spaced detents on walls of the lower end portions, the ends of said equalizer bar extending within said lower end portions and extensions and having slots in which said springs are located, said equalizer bar slots having upper sides, upper bars extending across the interior of the extensions and freely vertically movable therein, lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending through the equalizer bar slots, said springs being upwardly bowed leaf springs engaged between the upper and lower bars and having terminal ends constituting said movable detent elements, opposed walls of the extensions having openings through which said terminal ends can extend, opposed walls of the lower end portions of the legs having vertically spaced detent slots constituting said fixed detent elements, into which the terminal ends of the springs are engageable only in the compressed condition of the springs, said upper bars having central downwardly extending pins fixed thereto, said lower bars and mid-length portions of the springs-having openings through which the pins extend.

6. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and xed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and fixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said fixed detent elements being vertically spaced detents on walls of the lower end portions, the ends of said equalizer bar extending within said lower end portions and extensions and having slots in which said springs are located, said equalizer bar slots having upper sides, upper bars extending across the interior of the extensions and freely vertically movable therein, lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending across the interior of the extensions beneath the upper bars and fixed to the extensions, said upper and lower bars extending through the equalizer bar slots, said springs being upwardly bowed leaf springs engaged between the upper and lower bars and having terminal ends constituting said movable def tent elements, opposed walls of the extensions having openings through which said terminal ends can extend, opposed walls of the lower end portions of the legs having vertically spaced detent slots constituting said fixed detent elements, into which the terminal ends of the springs are engageable only in the compressed condition of the springs, said upper bars having central downwardly extending pins fixed thereto, said lower bars and mid-length portions of the springs having openings through which the pins extend, said opposed wall openings of the extensions being wider than the combined widths of the upper and lower bars and the springs, said lower bars having ends fixed on the lower ends of the extension wall openings.

7. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and fixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and fixed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the aoszeel springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the xed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said xed detent elements being vertically spaced detents on walls of the lower end portions, the ends of said equalizer bar extending within said lower end portions and extensions and having slots in which said springs are located, asid equalizer bar slots having upper sides, upper bars extending across the interior of the extensions and freely vertically movable therein, lower bars extending across the interior of the extensions beneath the upper bars and tixed to the extensions, said upper and lower bars extending through the equalizer bar slots, said springs being upwardly bowed leaf springs engaged between the upper and lower bars and having terminal ends constituting said movable detent elements, opposed walls of the extensions having openings through which said terminal ends can extend, opposed walls of the lower end portions of the legs `having vertically spaced detent slots constituting said fixed detent elements, into which the terminal ends of the springs are engageable only in the compressed condition of the springs, said opposed walls of the extensions having closed slots not substantially larger than the cross section of the equalizer bar ends, through which the ends of the equalizer bar work.

8. A self-levelling ladder comprising a pair of spaced vertical legs, rungs extending between and iixed to the legs, said legs having lower end portions, extensions slidably engaged on said lower end portions and extending therebelow, a fixed cross bar extending between and xed to the lower end portions of the legs, an equalizer bar pivoted at its midpoint on the midpoint of said fixed cross bar, locking assemblies on said extensions, with which ends of the equalizer bar are operatively engaged, said assemblies having movable detent elements, and said lower end portions having fixed vertically spaced detent elements with which the movable detent elements are adapted to engage only while the lower ends of the extensions are engaged with the ground and effective weight is imposed on the ladder, said locking assemblies comprising springs having said movable detent elements thereon, the movable detent elements being disengaged from the fixed detent elements in an uncompressed condition of the springs, the ends of the equalizer bar being operatively connected to the springs and adapted to compress the springs only when weight is imposed on the ladder for compressing the springs and engaging their movable detent elements with the fixed detent elements, said lower end portions of the ladder legs being tubular and said extensions being tubular and engaged in the lower end portions, said locking springs being positioned within the extensions, and said fixed detent elements being vertically spaced detents on walls of the lower end portions, the ends of said equalizer bar extending within said lower end portions and extensions and having slots in which said springs are located, said equalizer bar slots having upper sides, upper bars etxending across the interior of the extensions and freely vertically movable therein, lower bars extending across the interior of the extensions beneath the upper bars and xed to the extensions, said upper and lower bars extending through the equalizer bar slots, said springs being upwardly bowed leaf springs engaged between the upper and lower bars and having terminal ends constituting said movable detent elements, opposed walls of the extensions having openings through which said terminal ends can extend, opposed walls of the lower end portions of the legs having vertically spaced detent slots constituting said fixed detent elements, into which the terminal ends of the springs are engageable only in the compressed condition of the springs, said opposed walls of the extensions having closed slots not substantially larger than the cross section of the equalizer bar ends, through which the ends of the equalizer bar work, other opposed walls of the lower end portions of the ladder legs having vertical slots through which the ends of the equalizer bar work.

References Cited in the le of this patent UNITED STATES PATENTS 1,280,741 Hunn Oct. 8, 1918 2,476,650 Biery July 19, 1949 2,854,180 Brunckhorst Sept. 30, 1958 2,894,670 Anderson July 14, 1959 2,969,126 Gardner Ian. 24, 1961