This invention relates to a movable scaffold as set forth in the preamble of claim 1.

In prior known scaffolds, having the four corners thereof provided with an adjustment feature, such as e.g. in a scaffold described in US patent 4,293,054 which has a vertically movable hoisting platform, the scaffold has its vertical adjustment elements consisting of adjustable legs not allowing for a displacement of the scaffold during or after the adjustment procedure. With these scaffolds, the disengagement/engagement of adjustment in rough terrain causes the scaffold to topple over.

An object of the invention is to eliminate this drawback and to provide a scaffold capable of being displaced as well as adjusted from four corners simultaneously even in terrain with major height differences. The scaffold is safe during its displacement, nor does it topple over.

According to the invention, this object can be accomplished with a scaffold which is characterized by what is set forth in the characterizing clause of claim 1.

The invention will now be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 shows schematically one scaffold of the invention in erected condition,

Fig. 2 shows one structural element for the scaffold of fig. 1, and

Fig. 3 shows in more detail one vertical adjustment mechanism useful in a scaffold of the invention.

A scaffold 20 shown in fig. 1 comprises tubular corner members 1, which are connected to each other at the ends of the scaffold by means of substantially horizontal tubular cross-members 2, preferably by welding, thus producing gable elements 23 (see fig. 2). The tubular material comprises preferably aluminium, e.g. aluminium of alloy T6. In this exemplary case, the aluminium tube has a diameter

of 50 mm and a wall thickness of 2 mm. The gable elements 23 present at the opposite ends of the scaffold are connected to each other by means of work platforms 21 and by substantially horizontal rear-side tubes 2b and diagonal front- side bracing tubes 2b. The passage between work platforms at various levels is provided by means of ladders 22, extending adjacent to the work platforms between the gable elements 23 within a frame structure established by the tubular corner members 1 and the tubular cross-members 2, 2a, 2b connecting the same. Each tubular corner member has its bottom end provided with a wheel 15 for enabling a displacement of the scaffold. When the scaffold is in its erected position, the wheels are locked and thus prevent an inadvertent displacement of the scaffold. In addition, the scaffold can be fitted with adjustable extra bracing legs 24 for ensuring that the erected scaffold stays securely upright, especially in the case of high-rise scaffolds, and/or for preventing its inadvertent movement. The scaffold is intended for use both outdoors with its top work platform at the height of 8 m according to standard EN 1004 and indoors with its top work platform at the height of 12 m according to standard EN 1004. A ballast for steadying the scaffold is indicated by reference numeral 25.

A vertical adjustment between the wheel 15 and a tubular corner member 1 associated therewith during erecting the scaffold and/or during moving the scaffold to another position on an uneven foundation is implemented by means of a vertical adjustment mechanism 5 depicted more closely in fig. 3. As shown in fig. 3, the vertical adjustment mechanism comprises a casing element 5a attached to the scaffold's 20 gable element 23, and a lifting element 5b movable relative to the casing element in the longitudinal direction of the casing element. A movement of the lifting element 5b relative to the casing element 5a can be effected e.g. mechanically or hydraulically. To the casing element 5 is preferably welded a connecting piece 14, to which is in turn attached, preferably likewise by welding, an attachment element 4, having its bottom end provided with a hook member 4a which is adapted to bear from below against the substantially horizontal tubular cross-member 2 of the scaffold's gable element. The attachment element 4 is adapted to be clamped to at least one tubular cross-member 2 with a clamping means 3, e.g. a bolt, the attachment element 4 and the tubular cross-member 2 having necessary holes drilled therein for this purpose. In the depicted embodiment, the attachment element 4 is connected to three lowermost tubular cross-members 2

of the scaffold's gable element. In the exemplary case, the vertical adjustment mechanism 5 has a height of 114 mm, it has a lifting height of 760 mm and a lifting load of 900 kg max. In the exemplary case, the attachment element 4 is made of steel and 750 mm in length, 10 mm in thickness, and 50 mm in width.

The wheel 15 has connected therewith an adjustment tube 9, which is preferably made of steel and disposed inside a tubular corner member 1 to travel longitudinally relative to the tubular corner member. By way of example, the adjustment tube is 45 mm in diameter, 1800 mm in length, and has a wall of 3 mm and has preferably a steel flange 10 welded thereto, said flange having holes drilled in its corners. The wheel 15 has its body 13 fitted respectively with a flange element 12 with matching holes drilled in its corners. The flange elements 10, 12 are coupled to each other with bolts 11. The lifting element 5b has its bottom end provided with guide elements 6-8 for displacing the wheel 15 and its associated adjustment tube 9 relative to the tubular corner member 1 in the process of moving the lifting element 5b relative to the casing element 5a. The guide elements at the lifting element's 5b bottom end include a tubular member 8 preferably of steel, which is linked, e.g. by way of a T-shaped bracket 7, to a plate member 6 mounted on the lifting element's bottom end. The adjustment tube 9 is extended through the tubular member 8 to the interior of the tubular corner member 1. In the exemplary case, the tubular member has a diameter of 51 mm, a height of 100 mm, and a wall thickness of 3 mm.

In the process of moving the scaffold, the vertical adjustment mechanism 5 provided in each corner can be operated whenever necessary by means of a crank 16, the adjustment tube 9 moving within the tubular corner member up or down depending on the rotating direction of the crank, and the wheel 15 is moving concurrently relative to the scaffold frame, thus adapting the wheel 15 to undulations of terrain to maintain the scaffold always essentially upright throughout the displacement. The scaffold is intended for a slow walking-pace movement by human effort, whereby the moving crew has time to respond to variations in terrain.