This invention relates to a step ladder and, in particular, to a step ladder having three supporting legs.

A typical step ladder has two side rails connected together by a plurality of steps to form a ladder, and a pair of supporting rails, which are attached to the top of the ladder such that they can be folded out to support the ladder. Thus, such a step ladder has four supporting legs.

A ladder, known as an orchard ladder, has three supporting legs, two of which are at the ends of the supporting rails for the ladder and the third being at the end of a support which folds out from the top centre of the ladder to form a tripod type support. US Patent No. 1,139,990 discloses an orchard ladder of light weight having two leg members to which a series of steps are attached and a prop hingedly connected to the upper end of the ladder. Orchard ladders are designed for outdoor use, such as for picking fruit off the branch of a tree. Thus the apex of the ladder can be positioned below the fruit to be picked, and the prop will extend beyond the branch. However, such a ladder is not practical for use indoors, as it can be difficult to extend the prop when positioning the ladder close to the area of work.

Japanese Patent Publication No. 2000-257362A discloses a step ladder constructed from two trapezoidally shaped ladder frames, hingedly connected to each other along adjacent side rails, such that the step ladder can be folded for storage and opened out for use. The steps on each ladder frame are parallel to each other and the height of the steps on each frame matches. When the step ladder is in the open position, the outer side rails are connected together by a stay to hold the step ladder in the open position.

A person using the step ladder, as disclosed in JP 2000-25736A, can place a foot on each frame and straddle the connected side rails, thereby leaving his hands free to carry out some work. The step ladder can also be positioned towards the work making it easier to carry out the work while on the step ladder.

However, since the outer side rails are only connected by the stay they can pivot about the stay connection points, which compromises the stability of the step ladder when the user's weight is above the

connection points. It is an object of the present invention to overcome the

disadvantages of the step ladders hereinbefore described.

Thus, the invention provides a step ladder, comprising a first and second ladder frame with each ladder frame being of a triangular shape with two side rails of equal length connected together at one end to form the apex of the frame, a central rail connecting the first and second frames together, such that the central rail forms one side rail of the first frame and one side rail of the second frame and such that the first and second frames can move about the longitudinal axis of the central rail, with the end of the central rail opposite the apex of each frame and the other ends of the remaining side rails, to the outside of the step ladder, forming three ground engageable legs, at least one step on each ladder frame, the steps being at the same height and parallel to the line joining the ends of the ground engageable legs, such that, in use, the first and second ladder frames are moveable from a closed position, wherein the first ladder frame is superimposed on the second ladder frame, and a free standing, open position, wherein the step ladder is supported on the ground engageable legs in a generally V-shaped orientation. An advantage of the step ladder according to the invention is that, since the side rails on the first and second ladder frames are connected together at the apex of each frame, the stability of the step ladder, in the open position is improved.

The stability of the step ladder is also enhanced by the central rail and the three point engagement with the ground.

Thus, the weight of a user is distributed across the step ladder as a whole and movement of the user on the step ladder will not cause any flexing thereof.

Furthermore, a user can use the apices of the ladder frames as a gripping point, when at the top of the step ladder. Also, as the ladder frames, in the open position, are in a generally V-shaped orientation, a user may have one foot on a step of the first ladder frame and the other foot on a step of the second ladder frame, whilst straddling the central rail for extra support.

A further advantage of the step ladder in accordance with the invention is that it can be placed close to the work area, such as a wall of a building and the user does not have to stretch in order to carry out the work.

Preferably, the and each step is fixed at one end thereof to the side rail to the outside of the step ladder and is pivotally attached at the other end thereof to the central rail. An advantage of this method of attaching the steps is that, once assembled, each ladder frame will form a stable structure, with the outer rail and central rail being spaced apart by the steps.

Further, preferably, the central rail is an elongate bar of circular cross-section, wherein the and each step has an collar extending from the other end thereof, through which the elongate bar passes, with a pair of stops on the elongate bar, to each side of the and each step, for maintaining each step in position along the elongate bar.

An advantage of this attachment method is that the collar attached to each step is free to move about the elongate bar, thereby providing the means for moving the ladder frames between the closed and open positions. In one embodiment of the invention, a plurality of hinges are mounted along the central rail and a step on the first ladder frame and a corresponding step on the second ladder frame are attached to each side of a particular hinge. An advantage of this arrangement of the steps is that if a step is damaged it can be easily replaced, without having to dismantle the whole step ladder.

In a further embodiment of the invention, formations on the central rail define the open position of the step ladder and prevent it from being opened beyond the open position.

An advantage of the formations is that the maximum opening of the step ladder is fixed, and the ladder cannot open further, during use.

In a further embodiment of the invention, the central rail is formed from one side rail of the first ladder frame, which is hingedly connected, along the length thereof, to a corresponding side rail on the second ladder frame.

Preferably, the hingedly connected side rails are connected by a plurality of hinges.

A plurality of hinges can be arranged along the connected side rails in positions that will suit a particular size of step ladder. In a further embodiment of the invention, the hingedly connected side rails are connected by a piano hinge, which extends along the length of the inner rails from the other ends thereof to adjacent the apices of the ladder frames. The use of a piano hinge adds strength to the connection between the side rails.

In a further embodiment of the invention, cooperating formations on the hingedly connected side rails abut when the step ladder is in the open position. An advantage of the abutting formations is that the maximum opening of the step ladder is fixed, and the ladder cannot open further during use.

Preferably, the cooperating formations include a plurality of reversible biscuit joints between the hingedly connected side rails. By a reversible biscuit joint in this context is meant an oval shaped biscuit mounted in a crescent shaped groove on one side rail which biscuit locates in a corresponding crescent shaped groove in the other side rail. The joint in this case is a dry joint such that the joint may be formed, when the step ladder is moved to the open position, and broken as the step ladder is moved to the closed position. An advantage of the use of reversible biscuit joints is that they impart extra strength and stability to the connected side rails when the step ladder is in the open position.

In a further embodiment of the invention, the ratio of the height of the first or second ladder frames to the distance between the side rails of the respective ladder frame, at the other ends thereof, is 1.6 -1.8 to 1.

This range of ratios has been found to produce a stable step ladder.

Preferably, when the step ladder is in the open position, the step on the first ladder frame defines an angle of 80° to 90° with the

corresponding step on the second ladder frame, to the inside of the step ladder.

An angle of between 80° to 90° has been found to provide a stable step ladder, when in the opened position.

The invention will be further illustrated by the following description of embodiments thereof, given by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of a step ladder in accordance with the invention;

Fig. 2 is a side elevation of the step ladder of Fig. 1 in the closed position;

Fig. 3 is a cross section on line III - III of Fig. 2; Fig. 4 is a side view of a further embodiment of a step ladder in accordance with the invention in the closed position;

Fig. 5 is a cross section on line V - V of Fig. 4;

Fig. 6 is a perspective view of a further embodiment of a step ladder in accordance with the invention in the open position; and

Fig. 7 is a schematic view of the centre rail of the step ladder of Fig. 6.

Referring to Fig. 1, there is indicated generally at 10, a step ladder in accordance with the invention, in an open position. The step ladder 10 comprises a first ladder frame 11 and a second ladder frame 12, both being of a triangular shape. The first ladder frame 11 has a pair of side rails 13, 14 connected together, at one respective end 15, 16 thereof, to form the apex 17 of the frame 11. The other ends 18, 19 of the side rails 13, 14, respectively form ground engageable legs 20, 21. Similarly the second ladder frame 12 has a pair of side rails 22, 23 connected together, at one respective end 24, 25 to form the apex 26 of the frame 12. The other ends 27, 28 of the side rails 22, 23, respectively form ground engageable legs 29, 30.

A set of five steps 31 on the first ladder frame 11 is mounted between the side rails 13, 14 and is parallel to the line joining the ground engageable legs 20, 21. A complementary set of steps 32 is mounted between the side rails 22, 23 of the second ladder frame 12 at the same heights as the set of steps 31.

The side rail 14 of the first ladder frame 11 is hingedly connected, along the length thereof, to the corresponding side rail 22 of the second ladder frame 12, such that the first and second ladder frames 11, 12 are moveable from a closed position (not shown), wherein the first ladder frame 11 is superimposed on the second ladder frame 12, and a free standing, open position (as shown), wherein the step ladder 10 is supported on the ground engageable legs 20, 21, 29, 30 in a generally V- shaped orientation.

In the open position, as shown, each step 31 on the first ladder frame 11 defines an angle of 85° with the corresponding step 32 on the second ladder frame 12, to the inside of the step ladder 10.

Referring to Fig. 2, the step ladder 10 of Fig. 1 is illustrated in a closed position and from the side. The side rail 14 of first ladder frame 11 is hingedly attached to the side rail 22 of second ladder frame 12 by four hinges 33, 34, 35, 36. A surface 37 on the side rail 14 abuts with a corresponding surface 38 on side rail 22 when the step ladder 10 is in the open position. Referring to Fig. 3, the surface 37 on the side rail 14 is sloped and the corresponding surface 38 on the side rail 22 slopes in the opposite direction. Thus, the surfaces 37 and 38 will abut as the side rails 14 and 22 come together around the hinge 34. Referring to Fig. 4, there is indicated generally at 40, an

alternative embodiment of a step ladder in accordance with the invention, which is illustrated in a closed position and from the side. The features in common with the embodiment of Figs. 1 to 3 have been assigned the same reference numerals.

In this embodiment the hingedly connected side rails 14, 22 include three reversible biscuit joints 41, 42, 43 therebetween. Each reversible biscuit joint 41, 42, 43 comprises an oval shaped biscuit 44, 45, 46, respectively, mounted in a crescent shaped groove (not shown) on the side rail 14, which biscuits 44, 45, 46 locate in a corresponding crescent shaped groove 47, 48, 49, respectively, located in the

corresponding side rail 22. The reversible biscuit joints 41, 42, 43 are dry joints such that the reversible biscuit joints 41, 42, 43 are formed, when the step ladder 40 is moved to the open position, and broken as the step ladder 40 is moved to the closed position (as shown).

Referring to Fig. 5, the shape of the biscuit 45 can be seen.

Referring to Fig. 6, there is indicated generally at 50, a further embodiment of a step ladder in accordance with the invention, in an open position. The step ladder 50 comprises a first ladder frame 51 and a second ladder frame 52, both being of a triangular shape. The first ladder frame 51 has an outer side rail 53 connected to a central rail 54 at one respective end 55, 56 thereof, to form the apex 57 of the frame 51. The other ends 58, 59 of the outer side rail 53 and of the central rail 54, respectively form ground engageable legs 60, 61. Similarly the second ladder frame 52 has an outer side rail 62, connected to the central rail 54, at one respective end 63, 56 thereof, to form the apex 64 of the frame 52. The other end 65 of the outer side rail 62 forms a third ground engageable leg 66. A set of five steps 67 on the first ladder frame 51 is mounted between the outer side rail 53 and the central rail 54, and each step 67 is parallel to the line joining the ground engageable legs 60, 61. A complementary set of steps 68 is mounted between the outer side rail 62 of the second ladder frame 52 and the central rail 54, at the same heights as the set of steps 64.

A plurality of hinges 69 are mounted along the central rail 54 and a step 67 on the first ladder frame 51 and a corresponding step 68 on the second ladder frame 52 are attached to each side of a particular hinge 69, such that the first and second ladder frames 51, 52 are moveable from a closed position (not shown), wherein the first ladder frame 51 is superimposed on the second ladder frame 52, and a free standing, open position (as shown), wherein the step ladder 50 is supported on the ground engageable legs 60, 61, 66 in a generally V-shaped orientation.

Referring to Fig. 7, there is illustrated a schematic view of the central rail 54 of the step ladder 50 of Fig. 6. A step 67 and a

corresponding step 68 are shown attached to a hinge 69. A formation 70 mounted on the central rail 54 supports the hinge 69 on a particular position 71 on the central rail 54. A further hinge 69, to which steps have yet to be attached, is shown at position 72 on the central rail 54.