GUARDRAIL FOR AN ELEVATED WORKING PLATFORM

Abstract

A collapsible structure is described that can be erected to provide an elevated working platform having two ends and two sides. Two telescopically collapsible ladder frames (10, 12) are disposed above the level of the platform, one on each end of the platform. Each ladder frame (10, 12) is formed of two stiles (20, 22) having telescopically collapsible sections, rungs each extending between respective sections of the two stiles and latch mechanisms for locking the stile sections in the extended position of the ladder frame. Each of the ladder frames (10, 12) further incorporates a guardrail (30, 32) that lies parallel to the rungs (24) when the ladder frame is collapsed. The guardrail (30, 32) is mounted for rotation about a first stile and releasably secured to the second stile. After release from the second stile of the same ladder frame and rotation about the first stile each guardrail is connectable to the second stile of the other ladder frame to lie parallel to a side of the platform.

Description

FIELD OF THE INVENTION

The present invention relates to a guardrail for an elevated working platform of a telescopically collapsible structure.

BACKGROUND OF THE INVENTION

EP 1392940 discloses a collapsible scaffolding tower having an elevated working platform. There has also previously been proposed a podium in which a working platform is pivotably connected to the tops of two ladders, that may be telescopically collapsible and are used to climb onto the platform. To meet safety requirements and regulations, any such elevated working platform needs to be surrounded by guardrails.

In EP 1392940, the scaffolding tower consists of two telescopically collapsible ladder frames that are connected to one another by suitable stays and braces and the ends of the elevated working platform rest on two opposed rungs. In such a construction, the rungs of the ladder frames that are higher than the working platform can act as guardrails on two sides of the tower but at least two further guardrails are required at the front and the back of the tower.

Similarly, in the case of a podium, it has been proposed to provide two short collapsible ladder frames, one at each end of the platform, that can be pivoted to lie parallel to the platform. The rungs of these ladder frames can serve as guardrails at the ends of the platform but once again two further guardrails are required at the front and the back of the podium.

OBJECT OF THE INVENTION

The present invention seeks to provide a collapsible structure that affords adequate protection to a person standing on an elevated platform yet does not require guardrails to be stored and transported separately from the collapsible structure.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a collapsible structure that can be erected to provide an elevated working platform having two ends and two sides, wherein two telescopically collapsible ladder frames are disposed above the level of the platform, one on each end of the platform, each ladder frame being formed of two stiles having telescopically collapsible sections, rungs each extending between respective sections of the two stiles and latch mechanisms for locking the stile sections in the extended position of the ladder frame, wherein each of the ladder frames incorporates a guardrail that lies parallel to the rungs when the ladder frame is collapsed, the guardrail being mounted for rotation about a first stile and releasably secured to the second stile, and wherein the guardrail after release from the second stile of the same ladder frame and rotation about the first stile is connectable to the second stile of the other ladder frame to lie parallel to a side of the platform.

In accordance with a second aspect of the invention, there is provided a collapsible structure that can be erected to provide an elevated working platform having two ends and two sides, wherein two telescopically collapsible ladder frames are disposed above the level of the platform, one on each end of the platform, each ladder frame being formed of two stiles having telescopically collapsible sections, rungs each extending between respective sections of the two stiles and latch mechanisms for locking the stile sections in the extended position of the ladder frame, wherein each of the ladder frames incorporates two guardrail parts each rotatable about a respective one of the stiles of the ladder frame, the guardrail parts lying parallel to the rungs when the ladder frame is collapsed and being releasably connected to one another, and wherein each of the guardrail parts, after release from the other guardrail part mounted on the same ladder frame and rotation about the ladder frame stile is releasably connectable to a guardrail part mounted on the other ladder frame to form a guardrail extending parallel to a side of the platform.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows two collapsed ladder frames for positioning one at each end of a raised platform to provide hand and knee level guardrails all round the platform,

FIGS. 2 to 4 show different stages in the deployment of the guardrails of the ladder frames shown in FIG. 1, and

FIGS. 5 and 6 show sections through a releasable latch for locking a guardrail to a latch pin secured to one of the stiles of the ladder frames.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 shows two ladder frames 10 and 12 in their collapsed state. The two ladder frames are intended to be located at opposite ends of a raised platform. The raised platform may be the platform of a scaffolding tower, as described in EP 1392940 or it may form part of a podium. In the case of a scaffolding, the platform may rest on a collapsible frame incorporating the two ladder frames 10 and 12. In the case of a podium, the platform is permanently pivotably connected to two support ladders that can collapse for storage under the platform whereas the two illustrated ladder frames 10 and 12 may be similarly connected to the platform to fold away above the platform. When fully erected, as shown in FIG. 4, the ladder frames 10 and 12 provide a secure cage surrounding the platform on all sides with guardrails at both waist height and knee height.

Each of the ladder frames 10 and 12 includes two stiles 20 and 22, made up of telescopically collapsible tubular sections labelled 20a, 20b, 20c and 22a, 22b, 22c of progressively smaller diameter. Rungs 24a, 24b and 24c extend between and are mounted on the respective pairs of sections 20a, 22a; 20b, 22b; and 20c, 22c. When the ladder frames 10 and 12 are extended, the rungs 24a to 24c themselves serve as guardrails at the opposite ends of the raised platform.

In addition, each of the two ladder frames 10 and 12 includes components for erecting two further guardrails 30a and 30b arranged at waist height and two still further guardrails 32a and 32b arranged at knee height. When deployed, these further guardrails 30 and 32 lie parallel to the sides of the raised platform, i.e. perpendicular to the planes containing the rungs of the two ladder frames 10 and 12.

It is important to note that all components of the guardrails 30 and 32, when collapsed, lie in the planes of the rungs of the ladder frames so that they may be stored neatly and no further separately stored components are required for their assembly.

The guardrails 30 and 32 are constructed differently from each other on account of their location. In the case of the guardrails 30a and 30b, each is connected at its opposite ends to two tubes that are of a diameter to fit snugly in the uppermost stile sections 20c and 22c. In FIG. 1, the two guardrails 30a and 30b lie above the top rungs 24c of the respective ladder frames and the tubes of each guardrail 30 are received in the top sections 20c and 22c of the same ladder frame 10 or 12. As shown in FIG. 2, the guardrails 30 can be pulled out of the upper sections 20c, 22c of the ladder frame on which they are stored and reinserted into the stiles after rotation through ninety degrees. Thus, one of the tubes of the guardrail 30a is received in the top stile section 22c of the ladder frame 10 while its other tube is received in the top stile section 20c of the ladder frame 12. The guardrails 30a and 30b are in this way used to connect the two ladder frames 10 and 12 to one another to form a stable self-supporting framework.

It is preferred for one of the tubes connected to the guardrails 30a and 30b to be longer than the other and to provide a stop collar on the longer tube so that it cannot be separated from its associated ladder frame, in the same way as the stile sections are prevented from separating from one another. Deployment of each guardrail 30a and 30b can thus be carried out by simply raising the guardrails until its shorter end separates from the associated stile, rotating it by 90° then lowering the shorter tube into the stile of the other ladder frame.

This method of coupling the ends of the guardrails to the stiles cannot be used for the guardrails 32a and 32b that are at knee height. Instead, one of each guardrail may be permanently connected to a collar that can rotate about one of the stiles 20, 22 while the other may be releasably connected to a rotatable collar on the other stile. FIGS. 5 and 6 show sections through a releasable latch for locking a guardrail to a latch pin secured to one of the stiles of the ladder frames.

The guardrail 36 in FIGS. 5 and 6 is pivotable at one end about an axis normal to the plane of the drawing and is formed with a slot 38 near its illustrated opposite. The slot 38 can receives a latch pin 40 that forms part of collar mounted on the opposite stile of the ladder frame. A sleeve 42 is slidable over the end of the guard rail and is biased into the locking position shown in FIG. 6 by a spring 44. In this position a tongue 46 of the sleeve 42 engages under the latch pin 40 and prevents it from slipping out of the slot 38, thereby securing the guardrail 36 to the opposite collar. When the sleeve 425 is urged to the left, as viewed in FIG. 5, the latch pin 40 is no longer obstructed by the tongue 46 and the guardrail may be rotated clockwise to release it from the collar.

The tongue 46 has a ramped surface 48 so that the engagement of the pin 40 with the tongue 46 moves the sleeve 42 to the left. Thus, operation of the latch is automatic when the guardrail 36 is lowered onto the latch pin 40. Release of the latch however requires the sleeve 42 to be moved towards the opposite stile. An unstable person standing on the platform and gripping the sleeve 42 accidentally to steady himself would attempt to pull the sleeve 42 away from the direction of the adjacent stile and would not therefore unintentionally unlatch the guardrail.

In the alternative construction of the knee height guardrail 32 shown in FIGS. 1 to 4, each guardrail is formed in two similar parts. Each part comprises a first collar 50 located above the rung 24b and slidable relative to the stile section 22c and a second collar 52 disposed between the rung 24a and slidable over the stile section 22a. A bar 54 extends between the two collars 50 and 52 and carries half a guardrail 56 and an inclined brace 58 to forms a rigid gate leg assembly. The gate leg assemblies on opposite stiles can be connected to one another by a sliding sleeve 60. Preferably, permanent magnets in the sleeve 60 and in the guardrail halves 56 hold the sleeve in the locked position in which it overlies the ends of both gate leg assemblies.

In FIG. 2, the gate leg assemblies on the same ladder structure are connected to one another, resulting in the guardrails resting parallel to the rungs 24, whereas in FIG. 4, the gate assemblies are rotated through 90° and connected to one another with the guardrails extending parallel to the sides of the platform.

Claims

1. A collapsible structure that can be erected to provide an elevated working platform having two ends and two sides, comprising: two telescopically collapsible ladder frames disposed above a level of the platform, one ladder frame located on each end of the platform,wherein each ladder frame comprises a first stile and a second stile, the first and second stiles having telescopically collapsible sections,rungs each extending between respective sections of the first and second stiles, andlatch mechanisms for locking the respective sections in an extended position of the ladder frame,wherein each of the ladder frames incorporates a guardrail that lies parallel to the rungs when the ladder frame is collapsed, the guardrail being mounted for rotation about the first stile and releasably secured to the second stile, andwherein the guardrail after release from the second stile of a same ladder frame and rotation about the first stile of the same ladder frame is connectable to the second stile of the other ladder frame to lie parallel to a side of the platform.

2. A collapsible structure as claimed in claim 1, wherein the guardrail is connected to two tubes each slidably received in an uppermost section of a respective stile of the ladder frame.

3. A collapsible structure as claimed in claim 2, wherein the tubes connected to each guardrail are of unequal length, wherein a shorter tube may be disengaged from the second stile while the other tube remains engaged within the first stile to permit the guardrail to rotate about an axis of the first stile.

4. A collapsible structure as claimed in claim 1, wherein one end of the guardrail is secured to a first collar rotatably secured on the first stile and the opposite end of the guardrail is releasably secured to the second stile by a releasable latch.

5. A collapsible structure as claimed in claim 4, wherein the releasable latch comprises a latch pin that forms part of a collar mounted on the second stile, a slot in the end of the guardrail to receive the latch pin and a sleeve slidably mounted on the end of the guardrail and having a tongue operative when in a locking position to prevent the latch pin from escaping from the slot.

6. A collapsible structure as claimed in claim 5, wherein the sleeve is spring biased to urge the tongue into the locking position, and wherein the tongue has a ramped surface configured to cause the sleeve to retract automatically against an action of the spring when engaged by the latch pin.

7. A collapsible structure as claimed in claim 6, wherein an orientation of the tongue is such that release of the latch pin is effected by sliding the sleeve along the guardrail towards a second collar.

8. A collapsible structure as claimed in claim 1, wherein, when deployed, the guardrail is arranged at waist height above the platform to serve as a handrail.

9. A collapsible structure as claimed in claim 1, wherein, when deployed, the guardrail is arranged at knee height above the platform to serve as a knee rail.

10. A collapsible structure that can be erected to provide an elevated working platform having two ends and two sides, comprising: two telescopically collapsible ladder frames are disposed above the level of the platform, one ladder frame located on each end of the platform,wherein each ladder frame comprises two stiles having telescopically collapsible sections,rungs each extending between respective sections of the two stiles, andlatch mechanisms for locking the stile sections in the extended position of the ladder frame,wherein each of the ladder frames incorporates two guardrail parts,, each guardrail part rotatable about a respective one of the stiles of the ladder frame, the guardrail parts lying parallel to the rungs when the ladder frame is collapsed and being releasably connected to one another, andwherein each of the guardrail parts, after release from the other guardrail part mounted on a same ladder frame and rotation about a ladder frame stile is releasably connectable to a guardrail part mounted on the other ladder frame to form a guardrail extending parallel to a side of the platform.

11. A collapsible structure as claimed in claim 10, wherein the collapsible structure is a podium, wherein the guard rail is arranged at knee height above the platform and each guardrail part is connected to a brace of which a lower end is connected to a collar slidable over and rotatable about a lowermost section of the ladder frame.

12. A collapsible structure as claimed in claim 11, in which a collar rotatably mounted on the stile and secured to the knee rail and the collar connected to the lower end of the brace are coupled to one another by a rigid inextensible bar lying parallel to the axis of the stile about which the knee rail is rotatable.

13. A collapsible structure as claimed in claim 10, wherein the guardrail parts are releasably connectible to one another by a retractable sleeve retained on one of the guardrail parts and slidable over the end of the other guardrail part.

14. A collapsible structure as claimed in claim 13, wherein the sleeve is retained in a position overlying both guardrail parts by permanent magnets mounted on the sleeve and one of the guardrail parts.