GB2115051A - Folding ladders - Google Patents

Abstract

A folding ladder has two parallel stiles (1) joined by rungs (2) which are pivoted to the stiles so that when the ladder is not in use the stiles may be closed together. The ladder is held in an "open" position by a locking means comprising a hinged strut arrangement (11, 12) between one stile and one rung and a spring- biassed catch bar (13). Two ladders may be joined together to form an extending ladder or a trestle ladder using guides at the ladder ends. <IMAGE>

Description

SPECIFICATION Folding ladder This invention relates to ladders.

In accordance with the invention, a ladder has a pair of parallel stiles joined by spaced-apart parallel rungs which are pivotally connected to the stiles for movement between 'open position' in which the rungs are at right angles to the stiles, and a 'closed position' in which the stiles lie adjacent to each other, the rung pivots being offset so that they are at different distances from the tread surface of each rung, and means being provided to hold the ladder in the open position.

In one preferred construction, the holding means comprises an intermediateiy hinged strut pivotally connected at its ends to one of the stiles and a rung which opens out as the ladder is brought into the open position, and a releasable hinged locking part which engages the intermediate hinge pin of the strut to lock it in the opened out position and thereby prevent the ladder returning to the closed position.

Two ladders according to the invention may be connected together to provide either an extending ladder or a trestle ladder by further means which include catch elements at one end of one such ladder to engage the other ladder at spaced-apart positions, and bracket members at one end of the other ladder forming stile engaging sliders with securing means to retain the two ladders in angular relationship.

Embodiments of the invention will now be described with reference to the accompanying drawings wherein Figure 1 shows an elevation of part of a simple folding ladder according to the invention, partly in section, Figure 2 shows a similar view to Figure 1 with the ladder in a folded position, Figure 3 shows a section on the line A-A in Figure 1, Figure 4 shows a section on the line B-B in Figure 1, Figure 5 shows, partly in section, a side view of two ladders connected to form an extending ladder, Figure 6 shows a section on the line D-D in Figure 5, Figure 7 shows a section on the line C-C in Figure 5, Figure 8 shows a part of Figure 5 with the ladders arranged to form a trestle ladder, and Figure 8a shows a modified structure, Figure 9 shows a plan view of the parts shown in Figure 8, Figure 10 shows an elevation in the direction E-E of the parts shown in Figure 8, Figure 11 shows an extending ladder in three different positions, Figure 12 shows diagrammatically a trestle ladder arrangement, Figure 1 3 shows a modification of the structure shown in Figure 6.

Referring to Figures 1-4, a simple folding ladder comprises a pair of U-section metal stiles 1 to which spaced apart U-section metal rungs 2 are pivotally connected at each end. A preferred metal is aluminium. The pivots 3 are offset on opposite sides of the centre lines of the flange members 4 of each rung, and the ends of the rungs are chamfered or rounded so that the rungs can freely rotate about their pivot axes in one direction to allow the stiles to be brought into abutment along their inward facing open longitudinal sides (as shown in Figure 2). Rotation of the rungs in the opposite direction from the open position shown in Figure 1 is prevented by the abutment of the flat rung ends 5 against the internal surface of the adjacent style.

To secure the ladder safely in the open position, a locking mechanism 10 is provided.

This mechanism comprises two struts 11, 12, which are pivoted together at one end, the other ends of the struts 11, 12 being respectively pivoted to one of the stiles and the lowermost rung 5. The mechanism further includes a catch bar 13 jointed to the end pivot 3A of the lowermost rung and provided with a part-circular recess 14 which embraces a stud 1 5 extending axially from the pivot 16 between the struts 11, 12. A hairpin spring 1 7 having ends abutting the bar 1 3 and the underside of the lowermost rung maintains the bar in engagement with the stud, as shown in Figure 1, so that the members 11, 12, 1 3 are retained in rigid relationship to lock the lowermost rung against rotation.The ladder may be collapsed to its closed position by lifting the bar 1 3 against the spring bias to disengage it from the stud and so allow the struts 11, 12 to fold together about their pivot axes. The edge of the bar 1 3 is recessed at 1 8 to house the stud when the ladder is closed as shown in Figure 2 so that the struts and bar of the collapsed mechanism do not prevent the stiles meeting.

Both ends of the stiles are fitted with resilient rubber or plastic buffers 19 to inhibit slip and protect surfaces against which the ladder ends are placed.

By the use of additional fittings two ladders as described above may be connected together to provide an extension ladder or a trestle ladder as shown in Figures 5-13.

As shown in Figures 11 and 12 one of the ladders 20 carries an extension guide 21 on each stile at its top end which also acts as a trestle connection for the other ladder 22. The ladder 22 is provided with a second extension guide 23 on each stile at its bottom end, the guide 23 further mounting an extension latch.

Referring to Figures 5, 6 and 7 each extension guide 23 comprises a bracket plate 24 pinned to its respective stile with inturned flanges 25, 26, the flange 26 limiting the separation of the two ladders when placed one adjacent the other.

The extension guides 21 (Figures 5 and 8-10) comprise flat brackets 27 fixed to the outside faces of the stile of the ladder 20 so as to overlie the stile of the ladder 2. A flange 28 on each bracket 27 is positioned so that an edge 29 thereof engages an adjacent stile of ladder 22 to prevent separation of the ladders in the region of the guide.

It will thus be appreciated that the guides move to allow free relative longitudinal movement between the two ladders and at the same time prevent separation in any direction transverse to the longitudinal direction.

To secure the ladders in an extended position, as shown in Figure 11, each plate 24 has a pin 30 secured by a pressed-on cup 36 which acts as pivot for a bolt 31 with a nose 32 to be selectively engaged in any one of a series of slots 33 spaced apart in an adjacent flange part of a stile of the ladder 20. A recess 34 in each bolt nose embraces the bottom edge of a selected slot when the two ladders are erected and prevent downward movement of the ladder 22 relative to the ladder 20. The degree of extension can be increased by simply lifting ladder 22. As the bolt nose reaches the slot top it is pushed downwardly so that the nose is disengaged from the slot and is kept in the downward position by abutment of the nose end against the stile until the next slot is reached when the bolt pivots back for reengagement. To reduce the extension the bolt is tipped manually to release it.As the next lower slot is reached, a sloping end surface 35 on the bolt end allows the bolt to start pivoting back just prior to full registry with the slot. This ensures that the bolt is in the correct engaging position before the bottom of the slot is reached and accordingly the downward movement is limited to only one inter-slot spacing, so preventing a dangerous "run away" when the extension is reduced.

To secure the two ladders in trestle formation as shown in Figure 12, each bracket 21 carries a flange 40 at right angles thereto on which is mounted a fixed pin 41. In the modification shown in Figure 8a, the pins 41 are mounted on the flanges 28. The axis of each pin is inclined to the longitudinal direction of the stile carrying the bracket at an angle corresponding to the required angular operation of the two ladders in trestle formation, e.g. 400. The orientation of the flange 28 is such that its inner surface 42 is at right angles to the pin axis. The plane of the surface 42 is spaced from the plane of the surface of the flange 30 which carries the pin by a distance equai to the width W of the stiles of the ladder 22.

To form the trestle from the two ladders they are placed in abutment in the position shown in Figure 8 with the lower guide 23 disengaged from the ladder 20, the guide 21 slid towards the top of the ladder 22 and the ladders relatively rotated towards an open position shown in Figure 12 until the pins 41 enter holes 44 in the adjacent flange parts of the stiles of ladder 22. With the pins fully home the surfaces 42 of the flanges 28 abut the opposite flange parts of the stiles of the ladder 22 (Figure 8) and the two ladders are firmly held together against further mutual rotation. The trestle can be closed by reversing the above described procedure and disengaging the pins from the stiles of ladder 22. In the modification shown in Figure 8a, the holes to receive the pins 41 are provided in the opposite flange parts of the ladder stiles.

The small space occupied by ladders in accordance with the invention makes them very suitable for non-professional users such as householders who only employ a ladder occasionally. For the convenience of such users it is predicted that a simple ladder of the kind shown in Figures 1-4 would be an initial purchase to be followed subsequently by the purchase of a ladder 20 (Figure 5) together with two extension guides 23 which the user would attach to the simple ladder. This attachment involves the insertion of pins 30 through predrilled holes in the ladder stiles. Figure 13 illustrates a modification in which the pins 30 enter blind holes in the bolts 31 and are secured by hammering in the pins, each pin being a light press fit into its hole.

The lengths of the ladders and the variation in extensibility can be selected to suit requirements.

For domestic use a simple ladder having six rungs at standard spacing in association with a matching trestle or extension ladder having five rungs has been found convenient, the slots 33 in the machining ladder stiles being located just above each rung.

The embodiments disclosed above are of metal, e.g. aluminium construction. However other materials, e.g. wood or rigid plastics, can be used.

Claims (14)

Claims

1. A ladder comprising a pair of parallel stiles joined by spaced-apart parallel rungs which are pivotally connected to the stiles for movement between an 'open position' in which the rungs are at right angles to the stiles, and a 'closed position' in which the stiles lie adjacent to each other, the rung pivots being offset so that they are at different distances from the tread surface of each rung, and means being provided to hold the ladder in the open position.

2. A ladder according to claim 1 wherein the holding means comprises an intermediately hinged strut pivotally connected at its ends to one of the stiles and a rung which opens out as the ladder is brought into the open position, and a releasable hinged locking part which engages the intermediate hinge pin of the strut to lock it in the opened out position and thereby prevent the ladder returning to the closed position.

3. A ladder according to claim 2 wherein the locking part comprises a catch bar pivoted on the rung pivot on the said one of the stiles, the catch bar having a part-circular recess to embrace a stud on the intermediate hing pin of the strut for holding the ladder in the open position, and a further recess in which the stud is housed when the ladder is in its closed position.

4. A ladder according to claim 3 having a biassing spring to urge the catch bar in a direction to maintain the stud within the part circular recess.

5. A ladder according to any of the preceding claims including an extension guide at or adjacent one end of each stil thereof, each said extension guide comprising a guide member to embrace a stile of a second ladder adjacent thereto and restrict separation of the ladders while allowing free relative movement between the ladders in the longitudinal directions thereof, and also comprising releasable latch means for holding the two ladders against relative longitudinal movement.

6. A ladder according to claim 5 wherein each latch means comprises a pivoted bolt engageable within a hole or any one of a series of holes spaced apart along each stile of the second ladder.

7. A ladder according to claim 6 wherein the bolt has a nose to enter the hole and the nose is provided with a transverse recess to receive an edge of the hole.

8. A ladder according to claim 7 wherein the nose has a sloping end and the or each hole is a slot longitudinally extending in relation to the stile of the second ladder such that upon relative movement of the ladders in one direction, the bolt automatically engages the hole or the next hole of the series.

9. A ladder according to any of claims 1-4 having at or adjacent one end of each stile an extension guide to embrace a stile of a second ladder and allow relative movement between the ladders in the longitudinal direction thereof and also angular movement between the ladders about a transverse axis, the extension guide also including means to limit angular separation of the ladders to a predetermined included angle to form a trestle.

10. A ladder according to claim 9 wherein the holding means of each extension guide comprises a pin having its axis inclined to the longitudinal edge of the stile to which the guide is attached at an angle corresponding to the said included angle, and for engaging a hole in the stile of the said second ladder, and a plate for engaging the surface of the second ladder stile, the base of the pin and the surface of the plate lying in parallel planes spaced apart by the width of the second ladder stile.

11. A ladder according to claim 10 wherein an edge of the plate engages the outer surface of the stile of the said second ladder when the ladders are parallel and adjacent.

12. A compound ladder capable of being arranged as an extension ladder or a trestle comprising a ladder according to any of claims 5-8 in combination with a ladder according to any of claims 9-11.

13. A ladder or compound ladder according to any of claims 1-12 wherein each ladder rung and stile is of metal and has a U-shaped cross section.

14. A ladder constructed and arranged substantially as hereinbefore described and shown with reference to Figures 1-4, 5-10, or 13, or in Figures 11 and 12 of the accompanying drawings.