FLEXIBLE TRAP DOOR FOR ACCESS PLATFORMS

D E S C R I P T I O N

OBJECT OF THE INVENTION

The object of the present invention refers to a flexible trap door for access platforms.

BACKGROUND OF THE INVENTION

One of the most important topics in present-day is to guarantee the safety of workers. All social partners are making efforts to reduce the number of accidents, above all in construction, a sector where negative records are beaten.

With this in mind, improving scaffolding safety directly helps to reduce the accident rate, since 70% of accidents are caused by falls from different levels.

The EN-12810-1 2003 scaffolding Standard considers two ways to pass from one level to another:

- by means of a stepladder through an access platform

- by means of an access stairway

The EN 12811-1 Standard, in point 5.8.3, specifies:

"The free dimensions of the access opening on a platform shall be at least 0.45m in width, measured transversally across the platform and

0.60m in length. If it were not possible to close the opening by means of a permanently attached trap door, a protective guardrail must be able to be fitted. The trap door shall be lockable in the closed position".

Two types of trap doors may be found on the market:

a) opening lengthwise along the platform (figure 1 ) b) opening crosswise across the platform (figure 2)

In both cases, opening is manual and requires the use of at least one hand while going up, thus reducing safety on going up the stepladder.

Closing deserves separate treatment:

In case (a), a foreshortening is needed, since, while going down in one direction, in the other, with the arm over the head, the door must be held open. Moreover, and depending on the length of the platform, the door hampers the following section of the ladder.

In case (b), the opening position does not allow more than 90°, for which reason closing is caused by "gravity", which leads to accidents on being a rigid, heavy element.

Workers on scaffolding normally carry tools in their hands, and if it is necessary to go up a ladder of 40m or more, opening and closing doors, some to go upwards and others downwards, they are considered to be always open.

In case (a), they are simply not closed, which makes the situation worse, on the lower folding face of the trap door resting on the upper part, which is the part trodden on.

In case (b), they either keep it forced open so it does not close, causing broken hinges, or keep it fastened open with wires. Case (a) is curiously the most usual.

In both cases, the trap doors are normally made of two materials:

Plywood Aluminium plate

The load stipulated by the EN 12811-1 2003 Standard (point 6.2.4) corresponds to class 3, that is to say, 2.0 KN/m ² .

DESCRIPTION OF THE INVENTION

The present invention refers to a flexible trap door fastened to an access platform, that, when pushed by the worker's helmet, opens by rolling up and stays open while passing through the hole. Closing is "automatically" and progressively caused once the worker has gone through. Once closed, it may be used as a work surface, since it is strengthened by a cross-directional rigid reinforcement, allowing it to support the working load.

To open it from above, it has a tape to half-open it and place a foot on the first step of the ladder, opening it while going down. When not in use, it has a lock to avoid its opening while being transported and assembled.

This flexible trap may be used for access platforms in general and more preferably for scaffolding access platforms.

The trap door consists of a flexible, lengthwise rubber plate, cross- directionally reinforced inside, which enables it to open and support the working load of 2.0 KN/m ² stipulated by the EN 12811-1 2003 Standard. The materials that may be used are very varied, but have to fulfil the following requirements:

Rubber

- Resistance to environmental agents (UVA rays, temperature, humidity...) since scaffolding is generally used outdoors.

- Non-slip upper surface, since it is to be used as a work surface and walkway.

- Variable flexibility, more flexible at the front and less nearer its fastening point to the access platform, in order to facilitate its opening and guarantee self-closing.

- It shall resist chemical agents and show a certain fire-resistance (flameproof) especially where the scaffolding is to be used in industry.

- 15 mm maximum thickness.

Reinforcement

- They are profiles separated by a maximum of 4 cm.

- They have to be as light as possible to facilitate opening and not lead to an excessive weight being added to the access platform unit.

- It shall resist the working load of 2.0 KN/m ² , with a maximum flexion of 12mm to guarantee the feeling of safety while being trodden on.

Possible rubbers:

- Natural rubber with or without additives

- lsoprene - Neoprene

- Polybutadiene

- Butyl rubber

- Acrylic rubber

- Polyethylene rubber - Silicon

- Polysulphur

- Vinyl ethylene-acetate

- Fluorade ... etc. and its possible combinations

Possible reinforcements:

- Carbon fibre

- Glass fibre - Aluminium

- Copper

- Brass

- Steel - Wood - Combinations of different profiles and / or inter-connected, forming a mesh or chain.

The shape of these profiles could be:

- in round, square or rectangular pipe-shape - in T

- in I

- in triangle, etc.

Manufacturing process:

Depending on the quantity, it may be continuously cast or laminated, both in one direction as the other. The continuous lamination must be with heat in the remoulding process, so that the crosswise reinforcement sticks to the rubber.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 : Trap door opening lengthwise along the platform.

Figure 2: Trap door opening crosswise across the platform.

Figure 3: Flexible trap door: rubber body (1 ), access platform (2), rigid cross-directional reinforcement (3), tape (4) and lock (5).

Figure 4: Upwards sequence from one level to another.

Figure 5: Downwards sequence from one level to another.

Figure 6: Cross-directional reinforcement.

Figure 7: Initial section of the flexible trap door according to an embodiment method.

Figure 8: End section of the flexible trap door according to an

embodiment method.

Figure 9: Arrangement of the flexible trap door according to an embodiment method.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In a preferred embodiment of the invention, in the same way as shown in figure 3, the flexible trap door is fastened to the access platform

(2) that opens by rolling up when pushed by the worker's helmet and stays open while they pass through the hole. Closing "automatically" and progressively takes place once the worker has gone through. Once closed, it may be used as a work surface, since it is strengthened by a cross- directional rigid reinforcement (3), allowing it to support the working load.

To open it from above, it has a tape (4) to half-open it and place a foot on the first step of the ladder, opening it while going down.

When not in use, it has a lock (5) to avoid its opening while being transported and assembled.

Figure 6 shows a possible cross-directional reinforcement, which would be made up of round aluminium pipes with an inner diameter (D) of 5 mm, 1.5 mm (E 1) thick and 1.5x2 mm (E2xE3) flaps.

Figure 7 shows an example of configuration that would be made up of a silicon rubber body (1 ) with an inner polyester (6) mesh, 14 mm (E4) thick, with recesses of variable thickness (7) and transversely strengthened by the reinforcement (3), separated by a length (L) of 30

mm.

Figure 8 shows the end section of the trap door, finishing off in drillholes (8) to fasten it to the access platform with a diameter of 12 mm and a reinforcing flat bar (9).

Figure 9 shows the arrangement of elements on a 650mm-long (H), 550m-wide (A) trap door, displaying the typical profile of an access platform (2).