WO1999019583A1

WO1999019583A1 - Device for installing light-weight panel units

Info

Publication number: WO1999019583A1
Application number: PCT/FI1998/000798
Authority: WO
Inventors: Jukka Inkeroinen
Original assignee: Jukka Inkeroinen
Priority date: 1997-10-15
Filing date: 1998-10-14
Publication date: 1999-04-22
Also published as: FI108636B; FI973962A; ATE299980T1; DE69830915D1; EP1023510A1; AU9444798A; FI973962A0; EP1023510B1

Abstract

A lifting device (20) for installing lightweight prefabricated elements (21) in place on a wall or ceiling of a building. The lifting device comprises an intermediate storage (37) for the lightweight prefabricated elements and a lifting unit (22) provided with a gripping means (23, 36) for transferring the lightweight prefabricated elements from the intermediate storage to the installation site. According to the invention, the lifting device equipped with the intermediate storage incorporates at least one work station (26) for the installer (35) installing the lightweight element (21) in place. When there are two work stations (26a, 26b), the first work station (26a) is intended for the installer (35a) installing the first end of the lightweight prefabricated element (21) in place, and the second work station (26b) for the installer (35b) installing the opposite end of the lightweight prefabricated element in place. In a most preferred embodiment, the work stations (26a, 26b) are connected to turning booms (25a, 25b), which are mounted on the frame (24) of the lifting device so that the work stations are movable in both vertical and lateral directions.

Description

DEVICE FOR INSTALLING LIGHT-WEIGHT PANEL UNITS

The object of the invention is a lifting device for installing lightweight prefabricated elements in place at an installation site, which is, for example, a wall, ceiling or the like of a building, the said lifting device comprising an intermediate storage for the lightweight prefabricated elements connected with the lifting device, and a lifting unit provided with at least one gripping means for transferring the lightweight prefabricated elements from t e intermediate storage to the installation site.

As the building industπ' today is highly industrialised, many different types of prefabricated elements are used in building. The elements may vary from heavy load- bearing elements to light wall surface elements or insulation elements. Lifting and transferring heavy elements into place usually requires that the elements have, for example, lifting rings from which they can be suspended on the hook of a crane. Lightweight prefabricated elements, on the other hand, can be lifted, for example, by gripping the element's plane surface by means of suction pads. Alternatively, a lightweight prefabricated element can also be lifted by gripping the groove formed on the edge of a tongued and grooved lightweight prefabricated element, or other corresponding groove.

The lightweight prefabricated elements commonly used in buildings are the type of wall elements which consist of insulating wool in the middle and thin metal sheets on either side. The surface of the element is so smooth that it can easily be gripped with a suction pad lifter. Lightweight prefabricated elements comprised of insulating wool and metal sheets can, however, also be lifted by means of a lifting device that grips the groove of the tongue and groove seam. This is possible because the metal sheet on the surface of the element is folded over the edge of the element so that it forms a tongue and groove seam on the edge of the lightweight prefabricated element. When the element is lifted, the gripping means is guided into the groove, which it grips.

The suction pad lifter can also be used for installing other plane elements used in buildings, such as window elements, window panes, stone finished elements, etc. On the basis of the foregoing, it can be said that almost all elements in buildings may be considered as lightweight elements irrespective of their manner of lifting, with the possible exception of solid concrete load-bearing wall elements.

According to a known installation method, lightweight prefabricated elements to be installed on walls or the ceiling are lifted onto the wall or ceiling one by one. However, the installation work becomes substantially more efficient when an intermediate storage complying with the applicant's earlier invention is incorporated into the lifter. This solution is disclosed in the international publication WO 95/25210. According to the publication, the installation of elements on walls, ceilings or other installation sites is more efficient because the lifter takes a new element from the intermediate storage incorporated in the lifter in the vicinity of the installation site. Previously, the lifter had to fetch each element from further away on the ground or the actual storage site.

The aim of the present invention is to achieve a lifting device which will further improve the efficiency of installation of lightweight prefabricated elements. In known lifting devices there is the problem that although the elements can be conveyed to the installation site, their securing is still difficult.

It is characteristic of the device relating to the invention that at least one work station is incorporated in the lifting device provided with an intermediate storage, for the installer installing the lightweight element in place. The work station may be a platform or, for example, a hoisting cage. The installer's work station is primarily movable to the vicinity of the installation site of the lightweight prefabricated element. It may, however, be so mobile that it will move a person as required to the intermediate storage unit or even lift a person from the ground to the desired place. By means of the installation device relating to the invention, the installation of elements is made substantially more efficient. This is because the device can move one or more installers continuously to the installation site or sites as required. It is also an excellent advantage of the invention that no separate personnel hoists are needed in addition to the device for lifting the lightweight prefabricated element. Work site conditions are indeed often so limited in space that there is no room for several different lifters.

The invention is described in the following by means of examples, with reference to the appended drawings, in which

Figure 1 shows the lifting device relating to the invention as seen diagonally from the side. Figure 2 shows the lifting device as seen from above.

Figure 3 corresponds to Figure 2 and shows the lifting device in another situation. Figure 4 shows the lifting device as seen from the side.

Figure 5 shows the lifting device as seen from the side, from another direction. Figure 6 corresponds to Figure 5 and shows the hoisting cages of the lifting device's work stations in another position.

Figure 7 corresponds to Figure 1 and shows a second embodiment of the lifting device.

Figure 8 corresponds to Figure 1 and shows a third embodiment of the lifting device,

Figure 9 shows the lifting device of Figure 8 when connected to a crane,

Figure 10 shows a lifting device suspended on the boom of a crane, as seen from the side.

Figure 1 1 shows a lifting device attached to a scissor lift, as seen from the side,

Figure 12 shows the lifting device of Figure 11 when attached to a forklift truck,

Figure 13 shows the lifting device when connected to a forklift truck, as seen from the side.

Figure 14 shows a fourth embodiment of the invention, as seen from the side,

Figure 15 shows the lifting device of Figure 14 when connected to a forklift truck,

Figure 16 shows the installer's work station unit as seen diagonally from the side,

Figure 17 corresponds to Figure 16 and shows the work station unit in another position.

Figure 18 shows a lifting device attached to a crane boom, as seen from the side,

Figure 19 shows an embodiment of the lifting device, as seen from the side,

Figure 20 shows the lifting device when attached to a crane boom, with the device on the ground.

Figure 21 shows the lifting device when attached to a crane boom, with the device lifted to installation height, as seen from the side.

Figure 22 shows a work station and the feeder device of a work machine, as seen from the side.

Figure 23 corresponds to Figure 22 and shows the feeder device in a different position,

Figure 24 shows the lifting device and the installation of the lightweight prefabricated element in place, as seen from above. Figure 25 corresponds to Figure 24 and shows the next stage in the installation of the lightweight prefabricated element.

Figure 1 shows the lifting device 20 relating to the invention for lifting and installing lightweight prefabricated elements in place. The lightweight prefabricated elements 21 are placed on top of each other in the intermediate storage 37 incorporated in the lifting device 20, from which they can be lifted one by one and transferred to the installation site, such as the wall or ceiling of a building. In Figure 1 , the lifting unit 22 of the lifting device 20 is provided with suction pads 23, which grip the lightweight prefabricated element to be lifted, then transferring it into place. The figure shows that at the moment depicted in the picture, lightweight prefabricated element 21c is being installed on top of the elements 21a and 21b, which are installed on the wall of a building.

The frame 24 of the lifting device 20 incorporates supporting legs 64a and 64b, which are lowered down onto the ground when the installers' work stations 26a and 26b are moved further to the sides. The frame of the lifting device 20 furthermore incorporates a telescopic extension part 65, which is used to stabilise the lifting device when the weight of the element 21 to be installed increases. The extension part 65 can also be used, for example, for moving the stairs, as shown in Figure 8.

According to the embodiment shown in Figure 1 , the work stations are personnel hoisting cages 26a and 26b located at the ends of the booms 25a and 25b fixed to the frame 24 of the lifting device 20. The booms 25a and 25b incorporate hydraulic cylinders 27a and 27b, by means of which the position of the hoisting cages can be changed both horizontally and vertically. Thus, the personnel hoisting cages 26 can be moved to almost any point to which the booms 25a and 25b reach. The hoisting cages 26 can be moved to the vicinity of the lightweight prefabricated element 21c to be installed, but they may also be lowered or lifted so that the person installing the elements may step into the hoisting cage 26 on the ground and be lifted by the hoisting cage to the desired installation site.

Figure 2 shows the lifting device 20 in a situation where the lifting unit 22 is about to grip the topmost lightweight prefabricated element 21 in the intermediate storage of the lifting device 20 by means of the suction pads 23. The personnel hoisting cages 26a and 26b, acting as the installer's work stations, are located on the sides of the lifting device so that the installation personnel in them are easily able to secure the lightweight prefabricated element 21c installed on the wall. It can be seen in the figure that the vertical pillars 28a and 28b of the wall construction are located in the vicinity of the hoisting cages 26a and 26b, which means that both ends of the lightweight prefabricated element 21c are easily secured to the vertical pillars 28a and 28b, for example by means of screws.

Figure 3 shows a situation corresponding to Figure 2, where the lifting device 20 is in the vicinity of the interior corner of a building. It can be seen from the figure that in such a case the personnel hoisting cage 26a can be moved closer to the frame 24 of the lifting device 20. Thus the lifting device 20 is able to move all the way to the corner of the building. If the hoisting cage 26 is suspended by means of the boom 25 shown in Figure 1 , the hoisting cage can easily be moved laterally either into the corner, to the vicinity of the pillar 28a, or away from it.

Figure 4 shows a situation where the personnel hoisting cage 26a of one of the work stations has been moved, by means of the boom 25a, momentarily away from the vicinity of the lightweight prefabricated element 21c being installed. This situation corresponds to that shown in Figure 3, where the lifting device 20 is required to come close to the interior corner of the building.

In Figure 5, the other personnel hoisting cage 26b of the lifting device 20 has been moved to the level of the floor 29. In this case, the person installing the elements is able to step into the hoisting cage 26b, which can then be lifted to the desired position in the vicinity of the lightweight prefabricated element 21c being installed. Thus the personnel hoisting cages 26 positioned for installation will also act as hoists for lifting personnel from the ground to the installation site. In Figure 5, the other hoisting cage 26a is depicted in a position suitable for the installer to secure the lightweight prefabricated element 21c to be installed.

Figure 6 shows that the work stations, that is, personnel hoisting cages 26a and 26b of the lifting device 20 are close to both ends of the lightweight prefabricated element 21c to be installed when lifted up. This means that the installers in the hoisting cages are in a suitable position for securing the lightweight prefabricated element 21c at both ends to the frame of the building, for example by means of screws.

Figure 7 shows a second embodiment of the invention, where only one boom 25 has been installed on the frame 24 of the lifting device 20, and at the end of the said boom there is only one work station. This type of structure is advantageous in cases where the lightweight prefabricated elements 21 are installed vertically in a space where the elements do not have to be installed on top of each other. In this case, the installer in the personnel hoisting cage 26 secures the top ends of the lightweight prefabricated elements 21c, and the other installer on the ground secures the bottom ends of the lightweight prefabricated elements 21c.

Figure 8 shows a third embodiment of the invention, where the lifting device 20 incorporates stairs 30, along which the installer can climb to the landing 31 connected to the boom 25 and move on from there to the work station 26. In Figure 9, the lifting device 20 is suspended at the end of the boom of a boom crane or the like. The boom crane itself is not shown in the figure, only its mounting unit 32. By means of this solution, the lifting device 20 can easily be moved to heights that cannot be reached by a lifting device supported on the ground.

Figure 10 shows an embodiment in which the type of lifting device 20 which has no wheels supported on the ground is mounted on the boom 33 of a boom crane. In the figure, the hoisting cage 26a of the first work station is incorporated in the top part of the frame 24 of the lifting device 20 as shown in Figure 1. The personnel hoisting cage 26b of the second work station, on the other hand, is incorporated in the bottom part of the frame 24 of the lifting device 20 so that the bottom ends of the lightweight prefabricated elements to be installed vertically can be secured by means of this hoisting cage 26b.

Figure 11 shows the lifting device 20 relating to the invention mounted on a scissor lift 34 provided with wheels. A work station, that is, a personnel hoisting cage 26 relating to the invention is also incorporated in the lifting device 20. The figure shows that the installer 35 is about to secure the lightweight prefabricated element 21c to the vertical pillar 28 of the frame of the building. In the embodiment shown in Figure 11 , the lifting device 20 is provided with the type of lifting unit 22, which comprises a gripping means 36 that lifts the lightweight prefabricated element 21 by the groove of a tongue and groove seam. This is why in this embodiment the lightweight prefabricated elements 21 in the intermediate storage 37 of the lifting device 20 are in a vertical position adjacent to each other.

Figure 12 shows the lifting device 20 shown in Figure 11 , when positioned in the fork of a forklift truck 38. In other respects the lifting device 20 with its work station personnel hoisting cage 26 corresponds to the lifting device 20 shown in Figure 11.

In the embodiment of Figure 13, the lifting device 20 is positioned in the fork of a forklift truck 38, where the lifting device 20 can be lifted to the desired height. The hoisting cage 26 of the installer's 35 work station will then also move to the suitable height for installation. In this lifting device 20 also, the lifting unit 22 is provided with a gripping means 36 which lifts the lightweight prefabricated element 21 by the groove. On the other hand, the lightweight prefabricated elements 21 located in the intermediate storage 37 of the lifting device 20 are in a horizontal position on top of each other and lean on the vertical frame 24 of the lifting device 20. In this case, when a lightweight prefabricated element 21 is lifted from the intermediate storage 37, the gripping means 36 of the lifting unit 22 may press the lightweight prefabricated element against the vertical frame 24 of the lifting device 20 when it grips the topmost lightweight prefabricated element 31. The advantage of this arrangement is that at the stage when the gripping means 36 grips the groove of the lightweight prefabricated element 21 , the lightweight prefabricated element 21 cannot slip and will thus stay in place making it easier to grip the groove.

Figure 14 shows a lifting device 20 comprising wheels for moving on the ground. The hydraulic system of the device is operated by an electric motor, which is powered by a cable 39. The installer's 35 work station in this embodiment is a personnel hoisting cage 26 mounted on a hydraulic cylinder 40, which hoisting cage can be lifted to the desired height by means of the hydraulic cylinder.

Figure 15 shows a lifting device 20 similar to that shown in Figure 14, but which is, however, mounted on the fork of a forklift truck 38 in this embodiment. The lifting device 20 can thus be lifted to the desired height by means of the forklift truck 38. The personnel hoisting cage 26 mounted on the hydraulic cylinder 40 is also provided with stairs 30.

Figure 16 shows an embodiment in which the personnel hoisting cages 26a and 26b of the work stations are connected to the same boom 25, thus forming a separate work station unit 41. This unit can be incorporated, for example, into known lifting devices as an accessory. In this embodiment, the mobility of the hoisting cages 26 is not as versatile as in the solution shown in Figure 1 , but it is nevertheless advantageous when a simple accessory solution is required. In a preferred embodiment, the work station hoisting cage unit 41 shown in Figure 16 can be incorporated, by means of connecting projections 61 , for example, into the lifting devices 20 shown in Figures 14 and 15 or 20 and 21. The work station unit 41 can be connected to the lifting device 20 by means of the connecting projections 61 for example to a lifting device mounted on the spikes of a forklift truck. This accessory may, however, equally well be mounted on a lifting device mounted on the hook of a crane. In their simplest form, the work stations 26 of the work station unit 41 can be moved manually by means of telescopic tubes 63. These may, however, be replaced for example, by hydraulic cylinders.

Figure 17 shows the work station unit 41 shown in Figure 16 in another position, where the telescopic tubes 63 are turned around the joints 62 into a vertical position. The distance between the work stations 26 can then be adjusted by means of the telescopic tubes 62. Figure 18 shows a lifting device 20 which is suspended, for example, on the boom of a crane by means of a mounting unit 32. During installation, this mounting unit 32 is locked so as to be rigid, in such a way that the lifting device 20 will not be able to move with respect to the top end of the crane boom. In this way it is ensured that the lifting device 20 remains firmly in place when the lightweight prefabricated element 21c is being secured to the vertical pillar 28 of the frame of the building. The mounting unit 32 can, however, be released to enable the lifting device 20 to turn by means of the joint 42. In such a case the lifting device 20 may be allowed to tilt, for example, when the crane boom performs a wide movement in lifting the lifting device 20 off the ground to installation height. For installation, the joint 42 is, however, again locked so as to be immobile.

Figure 19 shows diagrammatically a lifting device 20, the work station hoisting cage 26 of which is provided with a roof 43 or safety bar, which protects the installer 35 from any objects falling from above.

Figure 20 shows a lifting device 20 which is mounted on the boom 33 of a crane 44. Between the boom 33 and the lifting device 20 is a mounting unit 32 which is locked so as to be immobile at the installation stage. The work stations, that is, personnel hoisting cages 26a and 26b belonging to the lifting device 20 are provided with frames 45, which are, for example, booths covered with transparent material. These frames 45 thus protect the installers 35 both from rain and from any falling objects. The frames 45 are obviously open on the side on which the installation work takes place. In this embodiment, the work stations 26a and 26b cannot be lifted with respect to the lifting device 20. The work station personnel hoisting cages 26a and 26b may also be provided with a heating device, and they may comprise a heated accessory box, for example, for gaskets being installed.

Figure 21 shows the lifting device 20 shown in Figure 20 when mounted on the boom 33 of a crane 44. In the embodiment shown in the figure, the lifting device 20 has been connected by means of a lockable mounting unit 32 to the fixed extension part 46 of the crane boom 33. When the mounting unit 32 is locked, the lifting device 20 is like a fixed part of the extension part 46 of the boom 33. This means that the installation work can be carried out while the lifting device 20 remains firmly in place.

In Figure 22, a work machine feeder device 47 is connected to the work station personnel hoisting cage 26 incorporated in the lifting device relating to the invention. In the embodiment shown in the figure, the feeder device 47 comprises a cylinder 48, the piston 49 of which is movable, for example, by a foot pedal 50. The construction may be executed mechanically, pneumatically or hydraulically. In Figure 22, reference numeral 51 refers to the tube between the foot pedal 50 and the cylinder 48. It is essential that the installer 35 does not have to support the work machine, which is a drilling machine 52 in Figure 22. The work machine 52 may, however, equally well be, for example, a power screwdriver. In the figure, the installer 35 may move the drilling machine 52 supported by the eccentric arm 53 to the desired position and then press the foot pedal 50, in which case the feed motion of the piston 49 also brings about a feed motion of the drilling machine 52.

Figure 23 shows the work machine feeder device 47 connected to the work station hoisting cage 26 shown in Figure 2, in a horizontal position. The cylinder 48 of the feeder device 47 is fixed to the hoisting cage 26 by means of a joint 54, which means that the cylinder 48 can be turned from the vertical position shown in Figure 22 to the horizontal position shown in Figure 23. When the cylinder 48 is in the horizontal position, the foot pedal 50 causes the horizontal feed motion of the piston 49 and at the same time of the drilling machine 52. By means of the eccentric arm 53 the drilling machine 52 can be moved to the desired position before the actual drilling feed. It is obvious that the installer's 35 work is speeded up and facilitated substantially, when he does not have to support the heavy drilling machine 52 or power screwdriver in his hands.

Figure 24 shows the lifting device 20 and an installation situation where the first stage of installing the lightweight prefabricated element 21c has been carried out. By means of the boom 57 of the lifting unit 22, the vertical lightweight prefabricated element 21c, supported by the suction pads 23, is placed against the vertical pillars 28a and 28b of the wall of the building. The lifting unit 22 also comprises a joint 59, by means of which the lightweight prefabricated element 21c can be brought to a position parallel with the wall surface. The lifting unit 22 also comprises a slide 60, which moves longitudinally and by means of which the element can be brought into place at the installation site in this direction.

Figure 24 shows that there is a gap 55 between the previous, secured lightweight prefabricated element 21b and the lightweight prefabricated element 21c now being installed. This is because the tongues and grooves 56a and 56b of the lightweight prefabricated elements 21b and 21c require that the final installation movement takes place in the direction of the plane of the element, as shown in Figure 25. It is only after this that the tongues and grooves 56a and 56b of the lightweight prefabricated elements 21b and 21c will be placed tightly against each other and thus the joint between the elements 21 b and 21c will be locked in place.

Figure 25 shows the securing of the lightweight prefabricated element 21c, after the second stage of the installation of the lightweight prefabricated element 21c, that is, the lateral installation movement, has been carried out. The lateral movement is brought about by means of the slide 58 between the boom 57 and the frame of the lifting device 20. The slide 58 always moves the boom 57 horizontally but the slide 60 at the opposite end of the boom always moves the lightweight prefabricated element longitudinally. As shown in the previous Figure 24, this adjusting movement of the vertical lightweight prefabricated element 21c also takes place vertically.

In Figure 25, when the lightweight prefabricated element 21c has been moved laterally into place by means of the lifting boom 57 and its slide 58, the joint formed by the tongues and grooves 56a and 56b is tight. After this the installer 35a in the work station personnel hoisting cage 26a drills a hole with the drilling machine 52 at the end of the lightweight prefabricated element 21c, after which the installer turns a screw into the hole, the said screw locking the end of the lightweight prefabricated element 21c to the vertical pillar 28a of the wall. Similarly, the installer in the other personnel hoisting cage 26b secures the opposite end of the lightweight prefabricated element 21c to the vertical pillar 28b. After this the lifting device 20 takes the next lightweight prefabricated element from its intermediate storage and moves it to the site where it is to be installed. Self-drilling screws can obviously also be used, in which case only a power screwdriver will be needed for installation. In such a case the drilling machine can also be used as a power screwdriver.

It is obvious to a person skilled in the art that the different embodiments of the invention may vary within the scope of the claims presented below.

Claims

1. A lifting device (20) for installing lightweight prefabricated elements (21) in place in the installation site, which is, for example, a wall, ceiling or the like of a building, the said lifting device comprising an intermediate storage (37) for the lightweight prefabricated elements connected with the lifting device, and a lifting unit (22) provided with at least one gripping means (23, 36) for transferring the lightweight prefabricated elements from the intermediate storage to the installation site, characterised in that incorporated in the lifting device (20) equipped with an intermediate storage (37) is at least one work station (26), for the installer (35) installing the lightweight element (21) in place.

2. A lifting device as claimed in claim 1, characterised in that the lifting device (20) comprises two work stations (26a, 26b), the first work station (26a) of which is intended for the installer (35a) installing the first end of the lightweight prefabricated element (21) in place, and the second work station (26b) for the installer (35b) installing the opposite end of the lightweight prefabricated element in place.

3. A lifting device as claimed in claim 1 or2, characterised in that the installers' (35a, 35b) work stations (26a, 26b) form a detachable or fixed work station unit (41) so that the work stations are mounted at opposite ends of the same horizontal boom (25).

4. A lifting device as claimed in claim 1,2 or 3, characterised in that the installers' (35a, 35b) work station (26a, 26b) is movable vertically and/or horizontally by means of a telescopic structure (40).

5. A lifting device as claimed in claim 1 or2, characterised in that the installer's (35a, 35b) work station (26a, 26b) is connected to a turning boom (25a, 25b), which is fixed to the frame (24) of the lifting device so that the work station is movable both vertically and laterally.

6. A lifting device as claimed in any of the claims 1to5, characterised in that turning booms (25a, 25 b) are incorporated in the frame (24) of the lifting device (20) adjacent to each other, at the end of which booms are the installers' (35a, 35b) work stations (26a, 26b).

7. A lifting device as claimed in any of the claims 1to5, characterised in that the first work station (26a) is connected to the upper part of the frame (24) of the lifting device (20) for installing the upper part of the lightweight prefabricated element (21), and the second work station (26b) is connected to the lower part of the frame (24) of the lifting device (20) for installing the lower part of the lightweight prefabricated element.

8. A lifting device as claimed in any of the claims 1to7, characterised in that the installer's (35) work station (26) is a personnel hoisting cage, which comprises a roof (43) or a corresponding safety bar in its upper part for protecting the installer from objects falling from above.

9. A lifting device as claimed in any of the claims 1to8, characterised in that the installer's (35) work station (26) is a personnel hoisting cage, one or more sides of which are furnished with a transparent or non-transparent protective wall.

10. A lifting device as claimed in any of the claims 1to9, characterised in that the installer's (35) work station (26) is furnished with one or more protective walls and the work station has a heating device.

11. A lifting device as claimed in any of the claims 1to10, characterised in that a support and feeder device (47) for a tool (52), such as a drilling machine or a power screwdriver, the feed motion of which device is horizontal and/or vertical, is connected to the installer's (35) work station (26).

12. A lifting device as claimed in any of the claims 1 to 11, characterised in that the lifting unit (22) of the lifting device (20) is provided with at least one actuating device (57, 59, 60) which moves the lightweight prefabricated element (21c) to be installed to the installation site so that the end of the element provided with a tongue and groove is in the vicinity of the installer's (35) work station (26), and with an actuating device (57, 58) which moves the tongue (56b) of the lightweight prefabricated element in the vicinity of the work station laterally into the groove (56a) of the adjacent lightweight prefabricated element (21b), which is already installed in its place.