WO2004001176A1

WO2004001176A1 - Adjustable step ladder

Info

Publication number: WO2004001176A1
Application number: PCT/ZA2003/000083
Authority: WO
Inventors: Donald B. Freeman
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-06-24
Filing date: 2003-06-24
Publication date: 2003-12-31
Anticipated expiration: 2004-12-24
Also published as: AU2003252193A1; ZA200205046B

Abstract

An adjustable step ladder which includes a first pair of legs with spaced rungs, a second pair of legs, with spaced rungs, slidably fixed to the first pair of legs, mechanisms for locking the first pair of legs to the second pair of legs, a third pair of legs which are separately telescopically adjustable in length, to cater for uneven ground, and which support the first and second pairs of legs at inclined positions, and a stabiliser for bracing lower ends of the third pair of legs.

Description

ADJUSTABLE STEP LADDER

BACKGROUND OF THE INVENTION

[0001] This invention relates to an adjustable step ladder.

[0002] It can be dangerous to use a conventional step ladder on uneven ground, on steps and the like. A need exists for a step ladder which is of robust construction, which is collapsible for storage and transport purposes, and which can be adjusted, in use, on a substantially continuous basis to a significant height and to take account of an uneven, i.e. non-level, supporting surface.

SUMMARY OF THE INVENTION

[0003] The invention provides an adjustable step ladder which includes first and second legs, at least first and second cross pieces which are vertically spaced from each other and which are connected to the first and second legs thereby to keep the first and the second legs spaced from each other, each of the first and second legs including respective upper and lower telescopic members which are movable to vary the length of the respective leg independently of the other leg, third and fourth legs, a first plurality of rungs which are secured at spaced intervals between the third and fourth legs, fifth and sixth legs, a second plurality of rungs which are secured at spaced intervals between the fifth and sixth legs, a ground engaging load distributing member which is at lower ends of the fifth and sixth legs and which projects outwardly from respective opposing sides of the fifth and sixth legs, the third and fifth legs, and the fourth and sixth legs, including respective sets of complementary interengaged formations which permit sliding movement of the fifth and sixth legs, in their longitudinal directions, relatively to the third and fourth legs, two locking mechapisms which are used respectively for fixing the fifth leg to the third leg and the sixth leg to the fourth leg, each locking mechanism including a respective lug which is fixed to one of the respective legs, and a locking pin which is mounted to the lug and which is movable relatively thereto to engage with, or to disengage from, a selected formation on the other of the respective legs, first and second hinges which respectively connect an upper end of the first leg to an upper end of the third leg and an upper end of the second leg to an upper end of the fourth leg, and a flexible strap between the first and second legs and the third and fourth legs which permits limited pivotal movement of the first and second legs away from the third and fourth legs. [0004] The lugs may be respectively secured to the fifth and sixth legs near upper ends thereof and each of the first plurality of rungs may be a hollow rod, with opposed ends of these rungs defining the formations with which the locking pins are selectively engageable. The locking pins may be movable with a screw action, or they may be spring loaded, or they may be movable in any other suitable way.

[0005] Each hinge may include a body which is fixed to an upper end of a respective leg and a projection, through which is formed a hole, which extends from the body, a clevis which is fixed to an upper end of a corresponding respective leg and which includes two spaced limbs in which are formed holes which are in register with the hole in the projection, and a pin which is passed through the holes pivotally to secure the body to the clevis.

[0006] The ladder may include a stabiliser in the form of an elongate bar with two pins at respective opposing ends of the bar, each pin including a locking spring, and each pin being engageable with a respective complementary formation in the respective lower telescopic member of the first and second legs thereby to brace the lower ends of the first and second legs.

[0007] For storage or transport purposes the stabiliser bar may be detached from the first and second legs and may be secured to the first and second cross pieces.

[0008] The complementary formations may include interengaged longitudinally extending undercut formations on opposing surfaces of the third and fifth legs, and of the fourth and sixth legs, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention is further described by way of examples with reference to the accompanying drawings in which:

Figure 1 is a perspective view of an adjustable step ladder according to the invention in an extended state, from what is referred to herein as a front side,

Figure 2 illustrates the ladder of Figure 1 from a rear side,

Figure 3 is a view on an enlarged scale of a locking mechanism which is used in the ladder and which is designated by a circle marked "3" in Figure 1 ,

Figure 4 is a view on an enlarged scale of a hinge of the ladder which is designated by a circle marked "4" in Figure 1 , Figure 5 is a cross-sectional view illustrating how pairs of legs of the ladder are slidingly connected to each other, and

Figure 6 is a perspective view of a stabiliser which is used in the ladder of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

[0010] Figures 1 and 2 of the accompanying drawings illustrate an adjustable step ladder 10 according to the invention in an extended condition and mounted on an uneven surface which is formed by steps 11.

[0011] The ladder includes first and second legs 12 and 14 respectively and three cross pieces 16, 18 and 20 respectively which are secured to the first and second legs at vertically spaced intervals and which keep the first and the second legs spaced from each other. The first leg includes an upper, outer, hollow tubular member 22 and a lower member 24 which is telescopically engaged with the upper member by inserting an upper end of the lower member into a downwardly facing end of the upper member. The leg 14 is similarly constructed with its corresponding members being designated 22A and 24A respectively.

[0012] As is evident from Figure 2 the lower members 24 and 24A are formed with a plurality of evenly spaced holes 26 on outwardly facing surfaces 28 and 28A of the lower members.

[0013] A stabiliser 30 is detachably engaged with the cross pieces 16 and 18. The stabiliser is shown on an enlarged scale in Figure 6 and includes an elongate bar 32 with two pins 34 and 36, which are preferably spring loaded, respectively at opposed ends of the bar. Figure 6 shows one of the pins detached from the bar. The pin includes a head 38, a shaped shank 40 which extends from the head and a curved locking spring 42 which is permanently fixed to the shank. The bar 32 is formed with holes 44 and the heads 38 of the pins are permanently fixed to the bar with the shanks extending through the holes. The locking springs 42 which surround the respective shanks 40 can be inserted into holes formed in the cross pieces 16 and 18 to secure the stabiliser in a detachable manner to the cross pieces.

[0014] The ladder includes third and fourth legs 50 and 52 and fifth and sixth legs 54 and 56 respectively. A first plurality of rungs 58 are fixed to the third and fourth legs at spaced intervals in a ladder arrangement. Similarly a second plurality of rungs 60 are fixed to the fifth and sixth legs at spaced intervals in a ladder arrangement. Each rung comprises a hollow rod 62 with a serrated upper surface 64, see for example Figure 4, which is fixed between opposing surfaces of the respective pairs of legs. Holes are formed in side walls of the respective leg and the rod is inserted into the holes and then an end of the rod is formed with a swaging formation 66, or any other appropriate technique is adopted, to secure the rod firmly to the respective leg. With this type of operation an open mouth 68 is formed by the rod on an outer surface 70 of the respective leg.

[0015] Figure 5 shows the legs 50 and 54 on an enlarged scale in cross-section. The legs 52 and 56 have a similar construction and this construction is therefore not described hereinafter.

[0016] Each of the legs 50 and 54 is formed from a hollow aluminium section 74 and has a protruding undercut formation 76 which extends longitudinally on an outer surface 78 of the section which, in use, opposes a corresponding outer surface 78A, of the other leg. The formations 76 are engageable with each other with a sliding action and permit one leg to be adjusted with a sliding action relatively to the other leg.

[0017] A load distributing member 80 is fixed to lower ends 82 of the fifth and sixth legs 54 and 56. This member is formed by an elongate bar 84 opposing ends 86 of which project outwardly from the respective legs 54 and 56. Rubber caps 90 are engaged with respective ends of the bar.

[0018] Hinges 92 and 94 pivotally connect upper ends of the first and third legs, and of the second and fourth legs, to each other. Figure 4 illustrates the hinge 94 The hinge 92 is of similar construction and therefore is not described in detail hereinafter

[0019] The hinge 94 includes a body 96 which is fixed to an upper end of the leg 52 and which includes a projection 98 which extends laterally relatively to the longitudinal direction of the leg 52. A clevis 100 is fixed to an upper end of the leg 14. The clevis has two spaced limbs 102 and 104 in which are formed registering holes 106. Only one hole is visible in the drawing. A corresponding hole, which is not visible in the drawing, is formed in the projection 98. When the holes are in register with each other a pin or bolt 108 can be passed through the holes thereby to retain the body pivotally engaged with the clevis.

[0020] The hinges 92 and 94 pivotally secure the legs 12 and 14 to the legs 50 and 52. A restraining member of any suitable kind e.g. a bar or rod, but preferably a flexible strap 120, is fixed to one of the rungs 58 and to the cross piece 18 and provides an effective mechanism which restricts pivotal movement of the legs 12 and 14 outwardly or away from the legs 50 and 52. This is necessary in order to stabilise the ladder in use. [0021] The legs 54 and 56 are, as indicated, slidingly movable relatively to the legs 50 and 52. When these pairs of legs have been moved to an appropriate selected length locking mechanisms 130 and 132 are used to secure the legs to each other.

[0022] Figure 3 illustrates the locking mechanism 132. The locking mechanism 130 is similar to the locking mechanism 132 and for this reason its construction is not described in detail hereinafter.

[0023] The locking mechanism 132 includes a lug 134 which is fixed to the leg 56 near an upper end thereof. The lug has a projection 136 and a pin 138 is threadedly attached to the projection. The pin has a shank 140 and an enlarged head 142 at one end of the shank. A thread 144 is formed on the shank and is engaged with a hole with a complementary thread in the projection 136. By rotating the head 142 in one sense the pin is advanced in the direction of an arrow 150 i.e. towards the leg 52. A protruding end 154 of the shank extends from an inner surface of the projection 136 and can be inserted into an open mouth 68 of one of the rungs 58 which extends between the legs 50 and 52. As an alternative to the threaded shank 140 use could be made of a spring which biases the pin towards the mouth 68 of a selected rung.

[0024] Particularly for storage and transport purposes the ladder can be adjusted to a compact mode. To achieve this the locking mechanisms 130 and 132 are disengaged from the legs 50 and 52 respectively and the legs 54 and 56 are slid upwardly along the legs 50 and 52, in the direction of an arrow 180 until the upper ends of the legs are more or less at the same height. The locking mechanisms are then engaged with the open mouth 68 on opposing sides of the uppermost rung, designated 58A between the legs 50 and 52.

[0025] The stabiliser 30 is detached from the lower members 24 and 24A and is engaged with the cross pieces 16 and 18.

[0026] The lowermost cross piece 20 includes locking pins 182 at its opposed ends which are similar to the locking pins 34 and 36 shown in detail in Figure 6. Although, for ease of use, the pins are preferably spring loaded, they could alternatively be movable with a screw-type action. The cross piece is however permanently engaged with the lower ends of the members 22 and 22A. The shanks of these pins normally engage with selected holes 26 in the lower members 24 and 24A respectively to retain the legs at selected extended positions. By pulling on the spring loaded pins 182 the shanks disengage from the holes and the lower members 24 and 24A can then be pushed home fully in the respective upper members 22 and 22A. [0027] The strap 120 collapses as the pairs of legs are folded towards each other, as required.

[0028] When the ladder is to be used the legs 54 and 56 are slid along the legs 50 and 52 respectively to a required extent thereby to adjust the overall length of the composite arrangement constituted by the legs 50, 52, 54 and 56. At the selected length the locking mechanisms 130 and 132 are used to secure the legs 54 and 56 to the legs 50 and 52.

[0029] The locking pins 182 on the members 22 and 22A are disengaged from the lower members 24 and 24A and these are telescopically extended as required. It is to be noted that the members 24 and 24A are movable independently of each other to respective required lengths. This feature, combined with the fact that the legs 54 and 56 can be adjusted independently of the legs 12 and 14, means that the ladder can be adjusted to take account of most kinds of uneven terrain. As shown in Figures 1 and 2 it is possible to adjust the ladder so that the lower members engage with different steps.

[0030] When the lower members are extended a reasonable length from the upper members it is necessary to make use of the stabiliser which is detached from the cross bars 16 and 18 and then engaged with selected holes 26 in the members 24 and 24A, as shown in Figure 2. It is to be borne in mind that the locking pins 182 in the cross piece 20 fix the lower members 24 and 24A to the upper members 22 and 22A respectively but that the stabiliser 30 which should, in practice, be attached as low as is possible to the members 24 and 24A is used to brace these components.

[0031] Pivotal movement of the legs 12 and 14 outwardly relatively to the legs 50 and 52 is restricted by the strap 120.

[0032] The step ladder of the invention provides a stable structure which is capable of being used in a safe manner on uneven ground, steps and the like. The ladder can be safely extended to a considerable height. The load distributing member 80 distributes the load which is carried by the ladder and also acts as a stabiliser due to the outwardly projecting ends 86.

Claims

1. An adjustable step ladder which includes first and second legs, at least first and second cross pieces which are vertically spaced from each other and which are connected to the first and second legs thereby to keep the first and second legs spaced from each other, each of the first and second legs including respective upper and lower telescopic members which are movable to vary the length of the respective leg independently of the other leg,

third and fourth legs, a first plurality of rungs which are secured at spaced intervals between the third and fourth legs,

fifth and sixth legs, a second plurality of rungs which are secured at spaced intervals between the fifth and sixth legs,

a ground engaging load distributing member which is at lower ends of the fifth and sixth legs and which projects outwardly from respective opposing sides of the fifth and sixth legs,

the third and fifth legs, and the fourth and sixth legs, including respective sets of complementary interengaged formations which permit sliding movement of the fifth and sixth legs, in their longitudinal directions, relatively to the third and fourth legs,

two locking mechanisms which are used respectively for fixing the fifth leg to the third leg and the sixth leg to the fourth leg, each locking mechanism including a respective lug which is fixed to one of the respective legs, and a locking pin which is mounted to the lug and which is movable relatively thereto to engage with, or to disengage from, a selected formation on the other of the respective legs,

first and second hinges which respectively connect an upper end of the first leg to an upper end of the third leg and an upper end of the second leg to an upper end of the fourth leg, and

a flexible strap between the first and second legs and the third and fourth legs which limits pivotal movement of the first and second legs away from the third and fourth legs.

2. A ladder according to claim 1 wherein the legs are respectively secured to the fifth and sixth legs near upper ends thereof and each of the first plurality of rungs is a hollow rod, and opposed ends of these rungs define the formations with which the locking pins are selectively engageable.

3. A ladder according to claim 1 wherein each hinge includes a body which is fixed to an upper end of a respective leg and a projection, through which is formed the hole, which extends from the body, a clevis which is fixed to an upper end of a corresponding respective leg and which includes two spaced limbs in which are formed holes which are in register with the hole in the projection, and a pin which is passed through the holes pivotally to secure the body to the clevis.

4. A ladder according to claim 1 which includes a stabiliser which includes an elongate bar, two locking pins at respective opposed ends of the bar, each locking pin being engageable with a respective complementary formation in the respective lower telescopic member of the first and second legs thereby to brace lower ends of the first and second legs.

5. A ladder according to claim 1 wherein the complementary formations include interengaged longitudinally extending, undercut formations on opposing surfaces of the third and fifth legs, and of the fourth and sixth legs, respectively.

6. An adjustable step ladder which includes first and second legs, at least first and second cross pieces which are vertically spaced from each other and which are connected to the first ^; and second legs thereby to keep the first and second legs spaced from each other, each of the first and second legs including respective upper and lower telescopic members which are movable to vary the length of the respective leg independently of the other leg, third and fourth legs, a first plurality of rungs which are secured at spaced intervals between the third and fourth legs, fifth and sixth legs, a second plurality of rungs which are secured at spaced intervals between the fifth and sixth legs, a ground engaging load distributing member which is at lower ends of the fifth and sixth legs, the third and fifth legs, and the fourth and sixth legs, including respective sets of complementary interengaged formations which permit sliding movement of the fifth and sixth legs, in their longitudinal directions, relatively to the third and fourth legs, the complementary formations including interengaged longitudinally extending, undercut formations on opposing surfaces of the third and fifth legs, and of the fourth and sixth legs, respectively, two locking mechanisms which are used respectively for fixing the fifth leg to the third leg and the sixth leg to the fourth leg, each locking mechanism including a respective lug which is fixed to one of the respective legs, and a locking pin which is mounted to the lug and which is movable relatively thereto to engage with, or to disengage from, a selected formation on the other of the respective legs, first and second hinges which respectively connect an upper end of the first leg to an upper end of the third leg and an upper end of the second leg to an upper end of the fourth leg, and a restraining member between the first and second legs and the third and fourth legs which limits pivotal movement of the first and second legs away from the third and fourth legs.

7. An adjustable step ladder which includes first and second legs, at least first and second cross pieces which are vertically spaced from each other and which are connected to the first and second legs thereby to keep the first and second legs spaced from each other, each of the first and second legs including respective upper and lower telescopic members which are movable to vary the length of the respective leg independently of the other leg, third and fourth legs, a first plurality of rungs which are secured at spaced intervals between the third and fourth legs, fifth and sixth legs, a second plurality of rungs which are secured at spaced intervals between the fifth and sixth legs, a ground engaging load distributing member which is at lower ends of the fifth and sixth legs, the third and fifth legs, and the fourth and sixth legs, including respective sets of complementary interengaged formations which permit sliding movement of the fifth and sixth legs, in their longitudinal directions, relatively to the third and fourth legs, two locking mechanisms which are used respectively for fixing the fifth leg to the third leg and the sixth leg to the fourth leg, first and second hinges which respectively connect an upper end of the first leg to an upper end of the third leg and an upper end of the second leg to an upper end of the fourth leg, each hinge including a body which is fixed to an upper end of a respective leg and a projection, through which is formed the hole, which extends from the body, a clevis which is fixed to an upper end of a corresponding respective leg and which includes two spaced limbs in which are formed holes which are in register with the hole in the projection, and a pin which is passed through the holes pivotally to secure the body to the clevis, and a restraining member between the first and second legs and the third and fourth legs which limits pivotal movement of the first and second legs away from the third and fourth legs.