US3231045A - Collapsible ladder - Google Patents

Description

Jan. 25, 1966 G. L. LAVRARD GOLLAPSIBLE LADDER 5 Sheets-Sheet 1 Filed Feb. 24, 1964 INVENTOR. GEORGES LOUIS LAVRARD BY MZMM M Beam AGENTS 5 Sheets-Sheet 2 Filed Feb. 24, 1964 FIG. 3

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AGENTS Jan. 25, 1966 G. L. LAVRARD 3,231,045

COLLAPSIBLE LADDER Filed Feb. 24, 1964 5 Sheets-Sheet 5 INVENTO GEORGES LOUIS LAV RD BY Wan M 38am AGE NTS United States Patent 3,231,045 COLLAPSIBLE LADDER Georges Louis Lavrard, 36 Ave. dn President Wilson, Chatellerauit (Vienne), France Filed Feb. 24, 1864, Ser. No. 346,747 Claims priority, application France, Feb. 26, 1963, 690

12 Claims. (Cl. 182-464) a This invention relates to collapsible ladders, and more particularly to a ladder having several hingedly connected sections.

More specifically, this invention is concerned with a modification of the ladder disclosed and claimed in my earlier United States Patent No. 3,073,414.

A principal object of this invention is the provision of a collapsible ladder the several sections of which are automatically locked when they pivot relative to each other into the operative position in which their side rails are longitudinally alinged.

' Another object is the provision of a ladder which is very rigid when in the operative position, yet light enough to be easily transported.

j A further object is the provision of a ladder the several elements of which are connected by form-fitting interengagement, and whichavoids-the use of stressed soldered,

welded, riveted, or bolted connections.

An additional object is the provision of a locking mechanism for rigidly holding the ladder sections in their operative position and more specifically of a locking mechanism which is simple and durable, and. which avoids concentration of stresses on individual ladder elements or their. parts. A

With these and other objects in view, the invention in one of its aspects mainly resides in a ladder whose side rails are constituted by longitudinal sections of tubular material connected by transverse rungsf The pairs of longitudinally adjacent sections are connected by hinges each of which comprises hinge plates respectively fixedly fastenedto the two connected sections, and arranged for pivoting movement about a pin whose axis is transverse of the direction of elongation of the rails. A first portion of each, hinge .plate is received. in the cavity of the associatedrail section, and asecond hinge plate portion projects outside of thatcavity and is oifset from the first portion in a direction transverse to the direction of elongation of the rail.

Cooperating abutment faces are provided on the rail sections of each pair,- and engage each other to limit pivoting movement of the rail sections in one direction to the operative position. vStop means in the cavity of one rail section cooperate with a latch member mounted on the projection portion of a hinge plate which is fastened to the other-rail section of the pair. The latch member is movable on the hinge plate toward and away from a position of engagement with the aforementioned stop means when the two rail sections are in the operative position. When the latch member. engagesthe stop means, it prevents pivoting movement of the two rail sections in the other direction that is, away from the operative position.v Otherfeatures ,andmany of the attendant advantages of this invention will bereadily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:.- FIG. 1 shows a portion of a sectional ladder of the invention in a perspective view which includes one complete section and portions of the two adjoining sections;

FIG. 2 is a perspective partly sectional end view of one of the, rungs of the-ladder on a larger scale that of FIG.. 1;

FIG. 3 shows a hinge portion of the ladder of FIG. 1 in plan section on the line lII-lll in FIG. 5;

FIG. 4 shows individual hinge elements of the ladder in plan view; and

FIG. 5 is a sectional elevational view of the hinge portion of FIG. 3 taken on the lines VV in FIGS. 1 and 3.

Referring now to the drawing in detail, and initially to FIG. 1, there is seen a portion of a sectional ladder which mainly consists of two parallel, longitudinal side rails 1, 2 connected by transverse rungs 3b, 30. Three sections 1a, 1b, 1c of the rail 1 and the corresponding rungs and sections of the rail 2 are seen in FIG. 1, but a ladder of the invention normally consists of substantially more than three sections.

The rail sections are respective portions of a rectangular tube of extruded aluminum which combines the desired properties of stiffness and lightness. Longitudinally adjacent sections of the rails 1, 2 are connected by hinges. The hinges of each rail-are identical, and are symmetrical to the hinges of the other rail. The hinge connecting the rail sections 112 and 1c will be described in detail hereinafter, and the description will be understood to be applicable to all the hinges of the ladder.

Each hinge in the rail 1 includes four plates 4, 5, 6, 7 of diecast aluminum, and each hinge in the rail 2 includes four corresponding plates 4, 5, 6', 7. The hinge plates have aligned circular openings in which a tubular cylindrical end portion of the associated rung 30 provides a hinge pin. Only the beaded rim 22 of the hollow hinge pin is visible in FIG. 1.

Respective portions of the hinge plates 4, 5 are conformingly received in the hollow interior of the rail section 1b, and are fixedly fastened to the rail section by rivets 15. The hinge, plates 6, 7 are similarly fastened in the rail section 10 by rivets 16. A flat latch bar 18 of cease-hardened steel projects outward from a recess between the portions of the hinge plates 4, 5 which project from the cavity in the rail section 112 are transversely offset thereform. The angularly bent free end of the bar 18 provides a handle 17. As will become apparent hereinafter the latch bar 18 locks the two adjacent side rail sec-tions 1b, 1c in a position in which the sections abuttingly engage each other along an interface 18.

Each rung is a section of an extruded aluminum bar whose cross sectional shape is best seen in FIG. 2. The rung consists of a cylindrical tube 8 from which short webs 8, 10 project in opposite radial directions. Flanges 11, 11 are integrally fastened to the respective webs. Theirou-ter faces extend in support planes obliquely inclined relative to each other, and are almost flat. They are provided with sharp-edge corrugations i2. Reinforcing ribs 13, 14 on the inner face of each flange 11, 11' make the flanges stiff enough so that they may serve as treads. The corrugations 12 prevents slipping. The web and flange portions are removed from the end portions of each rung so that the tube 8 projects on either side beyond'the treads of the rung. The tube provides the pivot pin for the aforementioned hinged plates.

The hinge structure is better seen in FIG. 3, and details of the individual hinge plates are most clearly evi dent from FIG. 4. The four hinge plates 4, 5, 6, 7 are formed with respective circular openings 24, 25, 26, 27 in which the tube 8 is coaxially received. The hinge plates are axially secured on the tube 8 between the aforementioned beaded rim 22 on the axial end of the tube 8 and the axial end faces of the webs 9, 10 and of the flanges 11, 11'. The openings 24, 25 are large enough to accommodate a tubular nylon washer 20 whichis coaxially arranged on the tube 8 tofacilitate rotation of the plates 4, 5 on the tube 8. Friction between the plates 4, 6 is reduced by a fiat, circular nylon washer 21, and a similar washer is interposed between the plates and 7.

The plate 4 has a recess or groove 23 which slidably receives the latch bar 18 as will become more fully apparent hereinafter from the description of FIG. 5. The plate 5 is shaped to conform to the plate 4 and to provide a cover for the recess 23. The plates 4, 5 are axially interposed on the tube 8 between the plates 6, 7 the inner faces of which are recessed to receive the plates 4, 5 therebetween.

The outer face of the hingle plate t5 carries two locking abutments 28, 29 each of which extends about the tube 8 in a circular arc of almost 180, and axially projects from the hinge plate 6. The abutments 28, 29 define therebetween two circumferential gaps 30. The abutments 28, 29 are received between the flanges 11, 11" of the associated rung 3c in the assembled condition of the ladder as indicated by the phantom view of the abutments in FIG. 2, and the gaps 30 receive terminal portions of the webs 9, it) therebetween as best seen in FIG.

'3. The abutments when interengaged with elements of the rung 3c prevent rotation of the rung relative to the associated rail section 10.

FIG. 5 shows how rotation of the sections 11), 1c relative to each other about the axis 36 of the tube 8 is prevented by the latch bar 18. The bar 18 is curved in a hat, aproxirnately circular arc. It is longitudinally guided in the aforementioned recess 23 of the hinge plate 4. The end portion of the bar 18-rernote from the handle 17 has a side face which abuts against a transverse stop pin 32 secured between the plates 6 and 7 in the rail section is so as to prevent rotation of the section about the axis 36 of the tube 8 in a clockwise direction, as viewed in FIG. 5. The other side face 31 is obliquely inclined relative to the direction of elongation of the bar 18.

counterclockwise rotation of the rail section .10 is prevented by abutting engagement of the sections 1b, 10 at the interface 19. Because the pin 32 is as far removed from the axis 36 as is possible in a structure of this kind, the stresses on the free end portion 31 during use of the ladder are relatively small. They are transmitted by the bar 18 to the sturdy hinge plate 4 along relatively large contact areas of a guide face which are indicated in the drawing by double arrows 4t) and 41.

The latch bar 13 is urged into the locking position illustrated in FIG. 5 by a helical compression spring 34 which is interposed between an integral transverse web 35 of the hinge plate 5 and an integral lug 33 of the latch bar 18. The longitudinal movement of the latch bar is limited by engagement of two abutment faces 37, 38 on a projecting portion of the hinge plate 4 with corresponding faces in a recess 39 of the latch bar.

The ladder described hereinabove may be folded or rolled up in a manner evident from my earlier US. Patent No. 3,073,414. If the ladder is to be folded, the latch bars 18 at the two lateral ends of each rung are simultaneously pulled outward of the associated hinges to unlock the same. If only one pair of hinges is unlocked, the two rigid portions of the ladder on either side of the unlocked hinges may be set up as a step ladder. The treads 11 of one ladder portion, and the treads 11' of the other portion face upward under such conditions. Because of the oblique inclination of the treads 11, 11' relative to each other, both portions of the ladder offer tread surfaces which are horizontal or nearly horizontal. If a folded or rolled ladder of the invention is straightened, the pins 32 cammingly engage the inclined faces 31' of the latch bars 18, and displace the bars against the pressure of their springs 34 until the bars can drop into their locking position shown in FIG. 5.

The ladder of the invention is very rigid in its operative position, yet quite light. The use of tubular rails made of aluminum or similar light metal partly accounts for the favorable combination of high mechanical strength and low weight. The specific hinge structure of the ladder safely prevents relative movement of the individual rafl sections. The use of a latch bar of a material which is very much harder and stronger than that of the cooperating ladder elements makes the hinge structure durable and reliable.

The useful life of the latch bar i-s greatly extended by the wide radial spacing of the stop pin 31 relative to the axis 36 from those portions of the hinge plate 4 to which the latch bar transmits the bending stresses which would move the rail sections away from their illustrated operative position. The anchorage of the latch bar is so firm that a ladder of the invention may be employed safely in an obliquely inclined position with the outwardly projecting portions of the hinge plates directed toward the person who climbs the ladder.

The ladder is free from solder joints, welded or bolted connections. The rivets 15, 16 merely hold the hinge plates in position, but they are not subjected to major stresses in the normal use of the ladder. The weight supported by the ladder is transmitted from rail section to rail section by the abutting relatively large faces at the interface 19. The bending stresses in the ladder are transmitted from the conformingly received hinge plate sections to the rail sections. The contact areas between hinge plates and rail sections are large, and stress con centrations are avoided.

The beaded rim 22 of the rungs is not normally sub. jected to severe stresses. The tube 8 transmits the weight of a person supported on the tread 11 to associated hinge plates which in turn abut against an edge of the associ atcd rail section. The treads are held in proper position by interengagement of respective portions of the tread and of an adjacent hinge plate.

A ladder having latch bars in each hinge of both side rails has been shown in the drawing, and such an arrangement is preferred where the ladder is to be subjected to high stresses. In most instances, it is sufficient to provide a single lockable hinge on each rung, and locking hinges are preferably arranged in one rail only. The manner in which the locking bars 18 are distributed over the several hinges of a ladder may be selected, however, to suit specific requirements without departing from the spirit and scope of this invention.

Obviously, many other modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A collapsible ladder comprising, in combination:

(a) two elongated side rails, each side rail being mainly constituted by a plurality of longitudinal'sections of tubular material defining respective cavities therein, each of said pluralities including a first section and a second section jointly constituting a pair of longitudinally consecutive side rail sections;

(b) a plurality of longitudinally spaced rungs transversely connecting said side rails;

(c) first and second hinge plate means respectively fixedly fastened to the first and second side rail section of each pair;

(d) hinge pin means connecting the first and second plate means of each pair of side rail sections for pivoting movement of said sections about a transverse axis;

(e) cooperating abutment means on the side rail sections of each pair for arresting said pivoting movement in one direction in an operative position in which the rail sections of;;said pair are longitudinally aligned;

(f)' stop pin means mounted in the cavity of the first section of one of said pairs, said stop pin means moving with said first section in an arcuate path when said first section is pivoted about said transverse axis away from said operative position,

(1) the second hinge plate means of said one pair having a guide face in the cavity of said first section spaced from said stop pin means in a direction opposite to said one direction when said sections are in said operative position; and

(g) latch means mounted on said second hinge plate means for sliding movement along said guide face toward and away from a position of engagement in which said latch means is interposed between said stop pin means and said guide face for simultaneous engagement with said stop pin means and said guide face.

2. A ladder as set forth in claim 1, wherein each hinge plate means has a first portion received and fixedly fastened in the cavity of the associated rail section and a second portion outside said cavity, said hinge pin means pivotally connecting said second portions.

3. A ladder as set forth in claim 1, wherein said hinge pin means is secured to one of said rungs.

4. A ladder as set forth in claim 3, further comprising interengaging locking means on one of said hinge plate means and on said one rung for preventing pivoting movement of said rung about said axis relative to said one hinge plate means.

5. A ladder as set forth in claim 4, wherein said one rung has a substantially flat tread face.

6. A ladder as set forth in claim 4, wherein said rung has two substantially flat tread faces oppositely spaced from said axis and obliquely inclined relative to each other.

7. A ladder as set forth in claim 1, wherein each of said rungs is a unitary elongated structure having two longitudinally terminal portions, one of said terminal portions constituting said hinge pin means, and a portion intermediate said terminal portions, said intermediate portion having a tread face defining a plane of support, the ladder further comprising locking means on one of said hinge plate means and engaging said rung for preventing pivotal movement of said rung about said axis relative to said one hinge plate means.

8. A ladder as set forth in claim 7, wherein said rung has a second tread face defining a second plane of support obliquely inclined relative to said first-mentioned plane of support.

9. A ladder as set forth in claim 1, wherein said second hinge plate means is formed with a recess, and a portion of said latch means is conformingly received in said recess for said sliding movement.

10. A ladder as set forth in claim 9, further comprising handle means on a portion of said latch means outside said recess for actuating said sliding movement.

11. A ladder as set forth in claim 9, further comprising yieldably resilient means urging said latch means toward said position of engagement.

12. A ladder as set forth in claim 11, wherein said latch means has a cam face obliquely inclined relative References Cited by the Examiner UNITED STATES PATENTS 3,073,414 1/1963 Lavrard 18224 X FOREIGN PATENTS 921,383 3/1963 Great Britain. 346,989 6/ 1960 Switzerland.

HARRISON R. MOSELEY, Primary Examiner.

REINALDO P. MACHADO, Examiner.

Claims (1)

1. A COLLAPSIBLE LADDER COMPRISING, IN COMBINATION: (A) TWO ELONGATED SIDE RAILS, EACH SIDE RAIL BEING MAINLY CONSTITUTED BY A PLURALITY OF LONGITUDINAL SECTIONS OF TUBULAR MATERIAL DEFINING RESPECTIVE CAVITIES THEREIN, EACH OF SAID PLURALITIES INCLUDING A FIRST SECTION AND A SECOND SECTION JOINTLY CONSTITUTING A PAIR OF LONGITUDINALLY CONSECUTIVE SIDE RAIL SECTIONS; (B) A PLURALITY OF LONGITUDINALLY SPACED RUNGS TRANSVERSLY CONNECTING SAID SIDE RAILS; (C) FIRST AND SECOND HINGE PLATE MEANS RESPECTIVELY FIXEDLY FASTENED TO THE FIRST AND SECOND SIDE RAIL SECTON OF EACH PAIR; (D) HINGE PIN MEANS CONNECTING THE FIRST AND SECOND PLATE MEANS OF EACH PAIR OF SIDE RAIL SECTIONS FOR PIOVOTING MOVEMENT OF SAID SECTIONS ABOUT A TRANSVERSE AXIS; (E) COOPERATING ABUTMENT MEANS ON THE SIDE RAIL SECTIONS OF EACH PAIR FOR ARRESTING SAID PIVOTING MOVEMENT IN ONE DIRECTION IN AN OPERATIVE POSITION IN WHICH THE RAIL SECTIONS OF SAID PAIR ARE LONGITUDINALLY ALIGNED; (F) STOP PIN MEANS MOUNTED IN THE CAVITY OF THE FIRST SECTION OF ONE OF SAID PAIRS, SAID STOP PIN MEANS MOVING WITH SAID FIRST SECTION IN AN ARCUATE PATH WHEN SAID FIRST SECTION IS PIVOTED ABOUT SAID TRANSVERSE AXIS AWAY FROM SAID OPERATIVE POSITION,

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