The present invention relates to an extendable working platform, in particularly for a personnel lift, comprising a frame, which is connected to the lifting mechanism of the personnel lift, said frame being connected to a fixed oblong platform portion, which has rectilinear guides for guiding a moveable platform portion, which can be extended from a retracted, the fixed platform portion overlapping, position to a extended position in which the moveable platform portion projects from the fixed platform portion.

For performing operations on a facade or on other elevated places usually personnel lifts are used. A personnel lift consists of a working platform which can be raised by means of a lifting mechanism, such as a scissor arm arrangement or a suitable telescopic hydraulic lift mechanism, to enable the personnel to perform their jobs. In order to enlarge the working surface for the personnel said working platforms are usually extendable in the longitudinal direction. This is especially important for operations over large surfaces within a limited time, such as cleaning windows and painting or cleaning facades. In the known personnel lifts the working platforms are extendable in a very limited way. This is due to the fact that in the present known constructions the moveable platform portion is arranged in a guide which is connected to the fixed platform portion. In the fully extended position of the moveable platform portion there must always be a considerable overlapping of both platform portions in order to achieve a sufficient support for the moveable platform portion. So the current extendable working platforms only allow an extension, which is much smaller than the length of the fixed platform portion.

It is an object of the present invention to provide an arrangement for an extendable working platform for a personnel lift, which can be extended over a considerable larger distance. This object is achieved according to the invention by the fact that the rectilinear guides are formed by I-profiles which are mounted on the longitudinal sides of the fixed platform portion, the inner sides of said I-profiles carrying an upper moveable platform portion situated above said fixed platform portion, and the outer sides of said I-profiles carrying a lower platform portion situated under said fixed platform portion, both

moveable platform portions having almost the same length as the fixed platform portion and said frame being connected to the fixed platform portion via the top sides of the said I- profiles.

By these measures a working platform is achieved, which has an extendable platform portion both under and above the fixed platform portion, so that an extension can be achieved at both ends of the fixed platform portion, said extension being somewhat smaller than the length of the fixed platform portion. With respect to the known working platforms this arrangement according to the invention allows an extension which is twice as large. Furthermore a lighter and compacter construction can be achieves because both moveable platform portions are moveable arranged in the same guides.

In a preferred embodiment van the invention the frame consists of one or more substantially C-shaped supports, which extend transversely under the working platform and its free ends are connected to the top sides of the said I-profiles. In this way the working platform can be supported on a lifting mechanism without restricting the moveability of the lower platform portion.

Further preferred feature and details of the present invention will become apparent from the subclaims 2-8.

The invention will be explained with reference to the drawings, in which: Figure 1 shows a partial cross section of the working platform according to the present invention.

Figure 2 shows a schematic side view of the working platform according to the invention in the totally extended position.

As can be seen in figure 1 the working platform according to the invention consists of a fixed platform portion 1, which in fact is formed by a rectangular oblong floor plate 2, which at the under side is provided with a reinforcement frame 3. On both longitudinal sides of the floor plate 2 an I-profile 4 is mounted on the floor plate 2. On top of the I- profiles a railing 5 is arranged, of which in this figure only a part of an upright is visible.

Between said I-profiles 4 an upper moveable platform portion 6 is arranged, which is carried in the inner sides of said I-profiles by means of guiding rollers 7, which are connected to the respective sides of said moveable platform portion. The moveable platform portion 6 is situated at a small distance above the fixed platform portion 1, and is also formed by un upper floor plate 8 and an reinforcement frame 9 arranged hereunder,

which also supports the guiding rollers 7. The floor plate 8 has at its longitudinal sides adjacent to the I-profiles upstanding walls 8a, which provide a stiffening for the floor plate 8 and also serve as support for a railing 10 which is arranged at its inner side and so is adjacent to the railing 5 of the fixed platform portion 1. Under the fixed platform portion 1 a lower moveable platform portion 11 is arranged, which also consists of a floor plate 12 having a reinforcement frame 13 at its under side. The floor plate 12 extends sideward beyond the fixed platform portion 1 and has upstanding side walls 12a which extend until the respective I-profiles 4. Near the ends of said upstanding walls guiding rollers are mounted by means of shafts, said rollers running in the outer side of the respective I-profiles 4.

At the upper side of each upstanding wall 12a is an in inwards directed flange 12b, which is situated in the outer side of the said I-profile 4, which flange 12b serves as a race for guiding rollers 14', which are mounted to the vertical body part of the respective I- profile. The lower moveable working platform is in this way guided in the outer side of both I-profiles by means of guiding rollers 14, said guiding rollers 14 being connected to the upstanding wall 12a through shafts, and by means of said guiding rollers 14' being connected to the vertical body part of the concerning I-profiles, the flange portion 12b running over said rollers 14'. In this way a reliable guiding is obtained of the lower moveable working platform 12 in the respective I-profiles 4. At the outer sides of the upstanding walls 12a a railing 15 is arranged, whereof only a part of an upright is visible. Said railing is thus situated at the outer side of the railing 5 of the fixed platform portion 1.

In order to be able to connect the whole working platform, consisting of the three interconnected platform portions, to a lifting mechanism (not shown in the drawings) of a personnel lift, supports 16, 16' are arranged near both ends of the fixed platform portion. Said supports are generally C-shaped and extend substantially under the working platform, while both end of the C each are connected to the upper side of the respective I-profile 4. In fact the supports each consist of a beam 16a , which is situated at some distance under the lower platform portion 11 at right angles to its longitudinal direction, said beam at both ends having upstanding beams 16b extending at right angles upwards along the sides of the working platform and these upstanding beams are at theirs ends provided with end beams 16c, extending at right angles to the beams 16b and directed inwards. The end

beams 16c each rest on the top of the respective I-profile and is connected thereto. In this way the whole working platform is supported by the beams 16a, without restricting the moveability of the platform portions 6 and 11. It is to be understood that the railing 15 of the lower platform portion 11 is constructed in such a way that it will not collide with the said supports.

Figure 2 shows a side view of the working platform according tot the invention in a totally extended position. As can be seen in said figure, the upper moveable platform portion 6 has been moved to the right and the lower moveable platform portion 11 has been moved to the left. The working platform is usually equipped with means for controlling the moveable platform portions. This may be realised electrical or manual. The moveable platform portions may be coupled to one another, for example by means of cables which are guided over pulleys, so that both moveable platform portions can be moved simultaneously inward and outward. Further the working platform may be provided with locking means in order to be able to lock said moveable platform portions in any desired position.

It will be clear that the invention is not limited to the embodiment described and illustrated here, but that numerous variants and modifications are possible for a person skilled in the art without departing from the scope of the appended claims. The construction of the platform portion may deviate from the construction as illustrated here. The frame consisting of the supports may be arranged in a different way. Essential is that said frame is connected to the top side of the I-profiles and also provide sufficient space to allow the moveability of the lower platform portion. Alternatively the working platform may also be used as suspended from cables, said cables being connected to the top sides of the I-profiles through a suitable connection.