Conventional lifting platforms for motor vehicles usually function based on the piston hoist principle, the scissors jack principle or the lifting rack or lifting screw principle. Even though these types of lifting platforms in their various configurations fully satisfy operational and safety requirements of practical use, their acquisition costs are high, primarily because their lifting systems are technically complex.

It is the task of the invention to develop a technically simple lifting platform that requires little space. can be produced at low cost and requires little operational maintenance, while also fully complying with existing safety requirements.

This task is solved according to the invention in that the transmission of the lifting system contains at least one flexible pulling cord that is coupled to a rotating element positioned at the upper end of the column, and to the support arm.

As a pulling cord, it is possible to use commercial steel cables, belts, chains or the like, which are available at reasonable cost in many different configurations and strengths. The same applies for the other components of the lifting system.

To enable use of small electric motors, reduction gearing, containing simple gear combinations or possibly a chain drive, is expediently positioned between the motor shaft and the rotaLng element tor the pulling cora.

For single-track motor vehicles such as motorcycles, motor scooters or the like, the lifting platform according to the invention can be embodied as a single-column construction, and possibly be equipped with a movable chassis for mobile deployment. In this case, it is useful to position the drive unit and transmission elements in a box-shaped closed container below or to the side of the support arm, and to provide, on at least one side of the container, an access ramp over which the vehicle to be hoisted can be pushed into its hoisting position. For lightweight two-track vehicles such as passenger cars, as well, a correspondingly more robustly dimensioned single-column lifting platform incorporating the lifting system according to the invention can be used.

In a two-column version, a lifting platform according to the invention is characterized in that a separate pulling cord is provided for each column, in which case, if only one drive unit is used, its torque is evenly distributed to the rotating drive elements of both pulling cords, in order to exert the same pulling power on each of the support arms and in order to make sure they move at equal speed. This branching of the torque is accomplished in a simple manner by means of a shaft that extends between the columns and is driven by the drive unit either directly or via a gear train, e. g. a sprocket wheel. In order to ensure sufficient clearance for the vehicles, the shaft may be positioned, if necessary, on the upper extensions of the two columns or at the lower ends of the columns or under the floor level. The same applies for the drive unit, which, together with its gear elements, can be positioned either at the upper end of one of the columns or at its lower end.

A useful refinement of the invention is characterized in that the drive unit or an auxiliary drive can also be operated manually, to enable lowering a hoisted vehicle manually in the event of an operational failure.

According to another refinement of the invention, braking devices are provided for each support arm, which, in the event of a critical operational situation, e. g. if the pulling cord breaks or if the descent speed is too great, are actuated automatically, stopping the support arms.

Finally, additional control synchronism can be provided that would, for example, trigger an emergency stop if the two support arms are moving at different speeds and/or are positioned at different heights.

Finally, a so-called pulley block system can also be employed in the lifting system according to the invention, with the pulling cord being guided by a return element that is attached to the support arm, then running over a pulley or sprocket wheel positioned at the top end of the column and subsequently being taken up on a drum or the like located at the bottom end of the column. Apart from this, it is also an option to use a chain belt as a pulling cord.

Further characteristics and advantages of the lifting platform according to the invention can be found in the following description of embodiments based on the drawing.

The figures show: Figure 1 a two-column lifting platform in schematic frontal view; Figure 2 another embodiment of the lifting platform, also in schematic frontal view; Figure 3 an under-floor lifting platform in schematic frontal view.

The two-column lifting platform according to Figure 1 is designed for two-track vehicles, in particular for passenger cars, and it features two columns la, lb, which are firmly anchored in the floor foundations by means of an accompanying base 2a, 2b. To each column la, lb a horizontal support arm 4a, 4b is attached in a manner that permits it to be moved vertically. Each support arm 4a, 4b can be extended telescopically and features, at its end, a support Sa, 5b. At its other end, each support arm 4a, 4b is connected to a vertical guide 6a, 6b, which, in the embodiment shown, at least partially encloses correlated column 1a, lb, the length of these guides 6a, 6b guaranteeing a tilt-free retention of support arms 4a, 4b, even with the vehicles positioned on them, as well as an ability for smooth displacement.

Each column la, lb features a stable extension upright 7a, 7b, each with a top bearing 8a, 8b for a cross shaft 9, which bears, on its right hand side (in Figure 1) a sprocket wheel 10. In the upper area (in Figure 1) of the right hand extension upright 7b, a drive unit is installed in the form of an electric motor 11, which sets cross shaft 9 in rotational motion via a sprocket wheel 12 and endless chain 13 that runs over the two sprocket wheels 10 and 12. Respective pulling cords 15a, 15b, which can be steel cables, belts or chains run over each of two reels 14a, 14b that are permanently attached to endless chain 13. In the embodiment shown, each pulling cord 15a, 15b is a steel cable that is attached with one end to the corresponding vertical guide 6a, 6b via a connection 16a, 16b, and with the other end to the corresponding reel or drum 14a, 14b.

By switching on electric motor 11, cross shaft 9, together with its two reels or drums 14a, 14b, is set in rotation, via chain drive 10 through 13, so that both pulling cords: 15a, 15b are rolled up with equal speed, causing the two support arms 4a, 4b to be lifted synchronously.

Arms 4a, 4b are usefully lowered by virtue of their own weight, or of the additional weight of vehicle they carry, the speed being determined by a brake or by the electric motor 11.

In Figure 2, only the right hand part of a lifting platform is schematically shown, the second column of which is constructed in the same manner with the additional assemblies, according to the embodiment in Figure 1. Here, electric motor 11 is located together with chain drive 10,12,13 inside a box-shaped housing at the lower end of column lb, which is configured as a hollow section. Accordingly, cross shaft 9 extends within a cross channel 21 contained in floor slab 3 and covered with a plate 22. Drums, of which only drum 14b on the right hand side is shown here, are attached to both ends of the cross shaft drums in a manner free of rotational play. As in the embodiment. in Figure 1, when support arms 4b are lifted and lowered, the corresponding parts of each pulling cord 15b are rolled up on drums 14 that are located, at least in part, inside the hollow section of the column. Also, in the embodiment according to Figure 2, a steel cable 15b extending inside the hollow section is used as a pulling cord, with one end being attached at 16b at the bottom of vertical guide 6b and running over a return pulley 23 attached rotatably in the upper area of column 1 b, and with the dashed part of the pulling cord being rolled up on bottom drum 14b.

Especially in the embodiment according to Figure 2, the so-called pulley block system can be particularly easily applied by attaching one end of pulling cord 15b to the upper part of column lb and by positioning another return pulley in longitudinal guide 6b by which the pulling cord then runs to upper return pulley 23.

While the embodiment according to Figure 2 requires greater constructive expense due to floor channel 21 and its cover, it also offers the advantages that the clearance between the two columns is not limited by cross shaft 9 as in Figure 1, and the columns themselves do not have extensions.

Even though two-column lifting platforms are shown in the drawing, each of the embodiments can also be embodied as a single-column lifting platform, in which case only cross shaft 9 is omitted. In particular, the embodiment according to Figure 2 is preferably suited for use as a single-column lifting platform for lightweight two-track motor vehicles, e. g. passenger cars, in which case two support arms 4b are provided that can be pivoted with respect to one another at the same height level.

The lifting system shown in the embodiments according to Figures 1 and 2 can also be used in other embodiments for mobile one-column lifting platforms of the type preferably used to repair or service motorcycles. In such an embodiment, the column can also comprise several parts that retract and expand telescopically, and it can be mounted on a moving chassis.

The under-floor lifting platform shown in Figure 3 features two vertical support surfaces 25a, 25b, with each having a horizontal support arm 4a, 4b with a telescopically adjustable loading arm 5a, 5b attached to its upper ends. Installed in the upper part of a pit 26 in floor slab 3 is a support framework 27, schematically sketched, to which guiding elements 28a, 28b for each vertical support surface 25,25b are attached. Support framework 27 is expediently embodied together with guiding elements 28a, 28b and the other assemblies as a pre-assembled unit, so that they can be installed and anchored in pit 26 in a simple manner. The bottom ends of the two vertical support surfaces 25a, 25b are permanently connected by means of a rigid crossbeam 29 that guarantees synchronized movement of the vertical support surfaces as they are lifted or lowered. Attached with their lower ends to this crossbeam 29 are pulling cords embodied as steel cables 30a, 30b, each running parallel to a corresponding vertical support surface 25a, 25b. The upper ends of steel cables 30a, 30b are each attached to a drum 31a, 31b, both fitted on a common shaft 32. This shaft 32 rotates in fixed bearings 33a, 33b that are located at the ends of the shaft and that may be mounted on support framework 27. An electric motor 34, which is also attached to support framework 27 together with an integrated transmission, and which is