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WO1992011425A1 - Echelle amelioree a trois pieds - Google Patents

Echelle amelioree a trois pieds Download PDF

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Publication number
WO1992011425A1
WO1992011425A1 PCT/US1990/007498 US9007498W WO9211425A1 WO 1992011425 A1 WO1992011425 A1 WO 1992011425A1 US 9007498 W US9007498 W US 9007498W WO 9211425 A1 WO9211425 A1 WO 9211425A1
Authority
WO
WIPO (PCT)
Prior art keywords
leg
collar
ladder
braces
shaft
Prior art date
Application number
PCT/US1990/007498
Other languages
English (en)
Inventor
William H. Baker
Original Assignee
Baker William H
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Baker William H filed Critical Baker William H
Priority to PCT/US1990/007498 priority Critical patent/WO1992011425A1/fr
Publication of WO1992011425A1 publication Critical patent/WO1992011425A1/fr

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
    • E06C—LADDERS
    • E06C1/00—Ladders in general
    • E06C1/02—Ladders in general with rigid longitudinal member or members
    • E06C1/38—Special constructions of ladders, e.g. ladders with more or less than two longitudinal members, ladders with movable rungs or other treads, longitudinally-foldable ladders
    • E06C1/382—Tripod ladders
    • E—FIXED CONSTRUCTIONS
    • E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
    • E06C—LADDERS
    • E06C1/00—Ladders in general
    • E06C1/02—Ladders in general with rigid longitudinal member or members
    • E06C1/14—Ladders capable of standing by themselves
    • E06C1/16—Ladders capable of standing by themselves with hinged struts which rest on the ground
    • E06C1/20—Ladders capable of standing by themselves with hinged struts which rest on the ground with supporting struts formed as poles
    • E—FIXED CONSTRUCTIONS
    • E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
    • E06C—LADDERS
    • E06C7/00—Component parts, supporting parts, or accessories
    • E06C7/08—Special construction of longitudinal members, or rungs or other treads

Definitions

  • This invention relates to the field of folding ladders, especially to stepladders, and stepladders of a triangular or tripod aspect.
  • Step Ladders provide a means for an individual to climb to a height for manipulating objects or performing work in locations where the ladder must be free standing, not resting against a support.
  • the ladder depends solely upon its construction and erection to insure its stability, in contrast to extension ladders which are braced against a structure in use.
  • a typical step ladder is designed to be folded into a convenient size for storage and carrying, and the requirement that it be portable is a major design constraint, restricting the weight of the ladder.
  • a typical step ladder will be found to weigh thirty pounds ( approximately 15 kilograms) or less in weight, in order to ensure that it may be easily handled. It is also designed to be folded into a package that, insofar as possible, is not of significantly increased size over a folded ladder of similar height reaching capability.
  • step ladders The stability of step ladders is dependent upon the user's movement on the ladder during use.
  • the requirement that the ladder be portable tends to reduce the weight to the minimum consistent with required structural strength.
  • an average user will weigh about One Hundred Fifty pounds (about sixty eight kilograms), in use practically all the weight involved in the dynamic couple of ladder and user will be concentrated in the user, and there will be very little static weight tending to stabilize the ladder.
  • the location of the users weight determines the static stability of the ladder in use; if a vertical line down from the user's center of gravity falls out of the footprint of the ladder, then the ladder will topple.
  • the invention shows an improved form of tripod ladder having a coordinated, folding extension and collapsing mechanism which substantially avoids binding and yet provides extremely rigid construction especially for the individual rear legs which are otherwise susceptible to bending.
  • the invention comprises in a tripod ladder, an improved erection and support mechanism based on a vertically extending, triangular cross section center post, fastened at an upper end to the upper platform of the ladder, defining a central axis about which the ladder vertically extends.
  • This center post acts as a vertical guide or tracking device at the vertex of the planes of extension of each of the major support legs.
  • a sliding collar of improved design slides along the center post to both control and coordinate the movement of these extending parts.
  • Single, tension, compression and torsion resistant braces are pivotaily affixed at one end to the sliding collar and at the other end to a leg assembly. Collar movement along the center post thus controls the opening of the ladder, coordinating the opening motion in that all legs extend and contract uniformly together.
  • the triangular center post defines angles of extension.Alignment lips on the triangular sliding collar maintain each of the leg braces in a substantially equal angular relationship, 120 degrees apart, during extension and in the open position.
  • the sliding collar and center post eliminate binding within the ladder mechanism.
  • the braces for each of the legs, being pivoted at each end are loaded principally in tension.
  • Alignment channels on the collar, and matching alignment channels upon each of the legs maintain the braces in an equal angular position, preventing misalignment of the ladder, and maintaining the entire structure as a rigid well braced tripod, substantially free from torsion or twisting moments induced by placing the ladder on an uneven surface, or induced by the shifting of the weight of the user, which creates unequal loads on the supporting legs.
  • Fig. 1 is a front view with a cutaway showing the tripod ladder in an extended position with the extension mechanism activated.
  • Fig. 2 is a section view of the extension mechanism showing the legs in a closed position.
  • Fig. 3 is an oblique view of the top cap or upper platform of the ladder.
  • Fig. 4 is a side view section from Fig. 3, showing the attachment of a front leg section to the top cap of the ladder.
  • Fig. 5 is a bottom view of the top cap or upper platform of the ladder.
  • Fig. 6 is a section from Fig. 5, in view perpendicular to the view of Fig 4, showing the attachment of the front leg section of the ladder.
  • Fig. 7 is a cross section view vertically downward through the center post and sliding collar of the ladder showing the individual leg braces.
  • Fig. 8 is a view of the control latch of the sliding collar in an engaged locked position.
  • Fig. 9 is a cross section of the control latch of the sliding collar showing the locking pin retracted during movement.
  • Fig. 10 is a cross section of the control latch of the sliding collar of the invention showing activation of the latch to withdraw the locking pin from engagement.
  • Fig. 11 is a detailed sectional view in two positions showing the mutual engagement of the rear leg braces, the sliding collar, and the rear legs of the ladder showing the captive alignment of the rear leg braces within the alignment channels of the rear legs and the sliding collar.
  • Fig. 12 is a view of the foot of the rear leg of the ladder.
  • Fig. 13 is a side view of the foot of the rear leg of the ladder.
  • Fig. 14 is an oblique view of the foot of the front leg of the ladder.
  • Fig. 15 is a side section view of the foot of the front leg of the ladder.
  • Fig. 16 is a view depicting various cross sections possible for the rear leg sections of the ladder.
  • the tripod ladder 2 comprises a front leg section 6 and two independent rear leg sections 8, all joined and pivoted from a top cap 10.
  • the front leg section 6, in order to permit climbing, is in the form of two slightly inwardly tapered side rails 12 having individual horizontal steps 14.
  • the side rails 12 are in the form of extruded channels within which the steps 14 are mounted and secured, typically by riveting.
  • the side rails 12 comprising the front leg section 6 terminate in insulated, friction producing feet 16, typically in the form of molded or cast rubber or plastic feet 16 having a high friction and load absorbing capability.
  • the two rear legs 8 likewise terminate in molded or cast rubber or plastic feet, having a frictional base, load absorbing and insulating capabilities.
  • Such feet 16 are shown in Figs. 12-15; in the preferred embodiment of the invention, they have a serrated lower ground gripping face 18 and have upper extensions 20 engaging with the channels 22 of the leg sections 6,8 to securely support the same against impacts and forces of sliding.
  • the feet 16 By enclosing the ends of the leg sections 6,8, the feet 16 also serve as protective padding, to lessen impact damage by the ladder as it is moved about.
  • Each of the three leg sections 6,8 of the ladder 2 are independently pivoted from the top cap 10.
  • the front leg side rails 12 are fastened to the top cap 10 by a pivot pin 24, preferably a rivet, about which the front legs 6 pivot in extension and retraction.
  • a second supporting pin 26 engaged within the top cap 10 is free to slide within an arcuate recess 28 within each front leg side rail 12 to permit the front leg 6 to pivot about the first pivot pin 24.
  • the rear legs 8 each are independently fastened between rear leg extensions 30, molded into the top cap 10, by means of a single rear leg pivot (not shown), extending through the rear leg channel 22 and the rear leg extensions 30, and about which the rear legs 8 pivot.
  • FIGs. 1 and 7 show the extension mechanism 4 of the invention.
  • a triangular cross section center post 34 is fastened within the top cap 10 of the invention in a center post receiving receptacle 36.
  • This center post 34 extends vertically downward from the top cap 10 and defines the center axis 38 about which the ladder 2 extends and retracts.
  • Each of the rear legs 8 is in the form of a hollow channel or extrusion 22 having high compressive strength and rigidity against bending. From one side of this extrusion 22 extend two parallel lips 40, forming an alignment channel 42. Although these alignment channels are required only for that portion of the leg 8 within which the leg braces 44 may be captive, for additional strength and rigidity of the rear leg 8, alignment channels 42 extend the length of the leg 8.
  • Journaled around the center post 34 is a triangular sliding collar 46 having three pairs of parallel lips 40 forming three alignment channels 42.
  • the center post 34 defines three sides, 120 degrees apart, forming equal angular faces 48.
  • the alignment channels 42 of the sliding collar 46 extend radially outward from these three equal angular faces 48 and define equal angles of support 120 degrees apart.
  • Within each set of alignment channels 42 is pivotaily affixed a leg brace 44.
  • the two rear leg braces 44 are extrusions of rectangular cross section pivotaily affixed within their respective sliding collar alignment channel 42.
  • the front leg brace 44a is in the form of two separate angled bars 52. Each angled bar 52 is pivotaily affixed to one side rail 12 of the front leg 6 of the ladder 2 at one end; both angled bars 52 are pivotaily affixed through a single pivot pin, typically in the form of a closed rivet, through the front alignment channel 42 of the sliding collar 46.
  • the front leg brace 44a angled bars 52 are angled so as to form, in combination with a front leg side rail 12, through a step 14 to a second side rail 12, a triangular bracing structure, the vertex 56 of the triangle being formed through the pivot pin 54 and the two alignment channel lips 40 of the sliding collar 46.
  • an actuating handle 58 On each of the two front leg brace angled bars 52 is provided an actuating handle 58, a shaped plastic or wooden grip amenable to being grasped by one hand.
  • the latching mechanism 60 comprises an open sided lock release lever 62, a section of extrusion pivoted within front alignment channel 42 by the front pivot pin 54.
  • Lock release lever 62 holds a ladder extension locking pin 64.
  • An internal spring and washer 66 force the locking pin 64 against the center post 34 of the ladder 2.
  • Lock release lever 62 is cut away to form an angled lower section 72 so that it may pivot, when depressed, about front pivot pin 54 against the head 70 of the locking pin 64, and has an internal bracing spring 74 maintaining it in an undepressedposition.
  • the sliding collar 46 is moved along the center post 34 by reaching through the steps 14 and gripping one or two of the hand grips 58 on the front leg brace 44a.
  • the sliding collar 46 may be moved along the center post 34 until the locking pin 64 engages with one of the provided engagement locking holes 68, at which point the locking pin spring 66 forces the locking pin 64 into a hole, latching the sliding collar 46 at a fixed vertical position along the center post 46.
  • One such vertical position is provided as a substantially closed position, the inner ends of the rear leg braces 44 being raised with respect to the outer ends of the rear leg braces 4 , drawing the rear legs 8 into the front legs 6 of the ladder 2 and providing a closed ladder form for storage or carriage.
  • a lower engagement locking hole 68 is provided wherein the rear leg and front leg braces 44 approach a horizontal position, being slightly tilted, providing maximum extension of the rear legs 8 with respect to the front legs 6; this is the principal operable position. Additional engagement locking holes 68 may be provided for intermediate open positions as desired, although the stability of a tripod ladder 2 is based upon the width of the base and therefore maximum extension within a working space is considered most desirable for maximum stability of the ladder 2.
  • the ladder 2 may be readily adjusted to another extension by grasping the handle 58, placing a thumb upon the lower portion of the lock release lever 62 and pushing the lock release lever 62 against the resistance of the locking lever bracing spring 74.
  • the lock release lever 62 then pivots against the bottom of the head 70 of the pin 64, pulling the locking pin 64 free of the engagement locking hole 68.
  • handle 58 movement will move sliding collar 46 past engagement locking hole 68, and lock release lever 62 may be released.
  • the pin 64 although spring biased, rides upon the outer surface of the center post 34 until it engages another engagement locking hole 68, at which point it snaps into engagement, locking the sliding collar 46.
  • the center post 34 thus acts as a vertical guide or tracking device defining the vertex of planes of extension of the legs 6,8.
  • Each leg 6,8 in turn is braced in a triangular brace comprising the leg meeting at one pivoting vertex in the top cap 10 extending through the top cap 10 down through the center post 34, through the sliding collar 46 to the inner end of the leg brace 44 then through the leg brace 44 to its outer end pivotaily fastened to the leg 6,8.
  • This support triangle being formed of members which are pivoted at each end, has all of its members essentially in compression or tension load, with bending moments being much reduced.
  • the legs 8 and leg braces 44 may be made of relatively hollow thin wall extrusions 22 in shapes known to be strong under tension.
  • these members may be formed of composite material in the form of hollow wall regular sections 22 which are strong in tension. Since the ends of the leg braces 44 are pivoted only low bending movements are imposed . The rear legs 8 are supported against bending by the leg braces 44.
  • each leg, leg brace and the center post defines a plane of extension.
  • the imaginary plane of extension of the front legs is along a bisector of the angle formed by the two front leg braces meeting at the sliding collar.
  • the construction of the center post and the sliding collar with the sliding collar alignment channels maintains and coordinates each of these planes so that they are equal angular, substantially 120 degrees apart. It is found that if the braces are maintained in coordination by means of the sliding collar and center post and if the planes of extension are maintained at 120 degree equi-angular spacing, then binding does not occur during retraction or extension of the legs. Working loads are more equally distributed over the primary support components of the ladder structure, thereby reducing torsional stresses and enhancing the inherent stability of the structure.
  • the front leg braces and handles are easily grasped through the front steps of the ladder; the handles are offset, in both the extended and the closed position, from the center post and from the front legs.
  • the danger of pinching of the user's hands during extension and retraction of the ladder is substantially eliminated.
  • locating the hand grips along the front braces optimally positions the hands so that the user's thumb can readily press upon the actuating lever of the sliding collar lock, releasing the sliding collar from engagement, then letting the sliding collar engage in a second locked position.
  • the ladder may be opened, extended or retracted by an individual standing in front of the front steps, reaching through the opening provided between two adjacent front steps, and free of danger of pinching the hands or fingers in the mechanism as it folds to a closed position or extends to an opened position.
  • the mechanism as described provides for an improved actuating mechanism for a tripod ladder having substantial freedom from unwanted motions even on uneven surfaces, being free from binding during the extension or retraction of the ladder 2 and being substantially free from danger of pinching or finger catching during actuation of the ladder 2, and being able to be actuated from an open to a closed position and back by an individual standing in front of the ladder 2 in the normal operating position.
  • the preferred embodiment has described a preferred form of the locking mechanism and the channel. It can be seen that the apparatus may be made of various materials, and in several detailed forms, all of which will be apparent to designers skilled in the art.
  • the form of the extrusions which form the braces and legs is particularly one admitting a wide variety of forms, some of which are illustrated in the figures. It should be apparent that the Claims therefor admit of a wider variety of equivalents than the specific illustrative embodiment here described, and the patent is not limited to that embodiment, but extends to those equivalent structures claimed.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Ladders (AREA)

Abstract

Echelle à trois pieds (2) comprenant un mécanisme (4) de support et de montage fixé sur une barre centrale (34) à section transversale triangulaire, s'étendant verticalement. Cette barre centrale (34) est fixée au niveau de son extrémité supérieure sur la plate-forme supérieure (10) de l'échelle (2), définissant un axe central (38) autour duquel s'étend verticalement l'échelle (2). La barre centrale (34) sert de guide vertical ou de système d'alignement vertical au niveau du sommet des plans d'extension de chacun des pieds de support principaux (6, 8). Un collier (46) coulisse le long de la barre centrale (34) pour coordoner le déplacement des pieds (6, 8) étirés. Des attaches (44) sont fixées pivotantes au niveau d'une de leurs extrémités au collier (46) et à l'autre extrémité à un pied (6, 8). Le déplacement du collier le long de la barre centrale (34) commande ainsi l'ouverture de l'échelle (2). La barre centrale triangulaire (34) définit les angles d'extension. Des voies d'alignement (42) situées sur le collier triangulaire (46) maintiennent chaque attache de pied (44) de manière à ce qu'elles aient toutes pratiquement le même angle.
PCT/US1990/007498 1990-12-19 1990-12-19 Echelle amelioree a trois pieds WO1992011425A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US1990/007498 WO1992011425A1 (fr) 1990-12-19 1990-12-19 Echelle amelioree a trois pieds

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1990/007498 WO1992011425A1 (fr) 1990-12-19 1990-12-19 Echelle amelioree a trois pieds

Publications (1)

Publication Number Publication Date
WO1992011425A1 true WO1992011425A1 (fr) 1992-07-09

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Family Applications (1)

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PCT/US1990/007498 WO1992011425A1 (fr) 1990-12-19 1990-12-19 Echelle amelioree a trois pieds

Country Status (1)

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WO (1) WO1992011425A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2341884A (en) * 1998-09-18 2000-03-29 Steadman William D A ladder
US6206139B1 (en) 1996-10-17 2001-03-27 Robert C. Bogart, Jr. Folding tripod ladder having extendable legs
US6874598B1 (en) 2002-10-15 2005-04-05 William H. Baker Ergonomically improved tripod stepladder
US9534443B1 (en) 2011-12-27 2017-01-03 Robert C. Bogart Ladder and related methods

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US124518A (en) * 1872-03-12 Improvement in step-ladders
US947409A (en) * 1909-01-22 1910-01-25 Everett Hudson Step-ladder.
US1778898A (en) * 1927-10-15 1930-10-21 Konigsberg Joseph Stepladder
US2650014A (en) * 1951-01-05 1953-08-25 Harrison Henry Stepladder
US4754845A (en) * 1987-02-06 1988-07-05 Baker William H Step ladder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US124518A (en) * 1872-03-12 Improvement in step-ladders
US947409A (en) * 1909-01-22 1910-01-25 Everett Hudson Step-ladder.
US1778898A (en) * 1927-10-15 1930-10-21 Konigsberg Joseph Stepladder
US2650014A (en) * 1951-01-05 1953-08-25 Harrison Henry Stepladder
US4754845A (en) * 1987-02-06 1988-07-05 Baker William H Step ladder

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6206139B1 (en) 1996-10-17 2001-03-27 Robert C. Bogart, Jr. Folding tripod ladder having extendable legs
GB2341884A (en) * 1998-09-18 2000-03-29 Steadman William D A ladder
US6874598B1 (en) 2002-10-15 2005-04-05 William H. Baker Ergonomically improved tripod stepladder
US9534443B1 (en) 2011-12-27 2017-01-03 Robert C. Bogart Ladder and related methods

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