As mentioned, the invention has been developed in particular in connection with treatment couches, tables, hospital beds etc., i. e., means where height adjustment is desirable.

In many cases, when, for example, the weight of the manoeuvred element, e. g., a couch top, is low, the element might not be not lowered when the actuator goes down, because the cord drive device is intended primarily for action during the drawing out of the telescopic supporting column. This problem might also arise when the element which is to be raised or lowered is attached to the supporting column via a lever arm According to the invention, it is therefore proposed to connect the actuator between an end of the supporting column and the intermediate supporting column section, and to construct the cord drive device to include a pulley in each end of the intermediate supporting column section and, placed around the pulleys, a cord drive which is connected to the inner and the outer supporting column sections. Designing the supporting column in this way will cause the cord drive to be double-acting, i. e., a positive effect on the telescopic supporting column is obtained both on extension and retraction.

The telescopic supporting column according to the invention may to advantage have an external actuator. This results in a supporting column of simpler structure, and at the same time the actuator is more easily accessible.

According to the invention, the cord drive may to advantage be an endless cord. This endless cord is then placed around the pulleys and is secured in a suitable way to the inner and outer supporting column sections.

It is especially desirable that the telescopic supporting column be designed to have a rectangular cross-section. A telescopic supporting column designed in this way will have flat lateral faces which will facilitate attachment or connection to other elements, for example, a base frame and a couch top or its supporting frame.

An especially advantageous embodiment according to the invention is one where the outer supporting column section is the upper section of the telescopic supporting column. This permits a particularly favourable embodiment wherein, for example, a couch supporting frame may be made of vertical plate elements, which can be attached in a simple manner to the rectangular outer, upper supporting column section.

The invention will now be explained in more detail with reference to the drawings, wherein: Figure 1 is a perspective view of a telescopic supporting column according to the invention, when drawn in or retracted; Figure 2 shows the telescopic supporting column in Fig. 1 when drawn out, i. e., extended; Figure 3 is a sectional view through the supporting column in Fig. 1; Figure 4 is a sectional view through the supporting column in Fig. 2; Figure 5 is a perspective view of a telescopic supporting column according to the invention, having a supporting frame for a non-illustrated couch top attached thereto; Figure 6 is a front elevation of the supporting column in Fig. 5, where one side of the supporting frame has been removed; and Figure 7 shows a section through the supporting column in Fig. 6.

Figures 1 to 4 show a tripartite supporting column. The supporting column has three supporting column sections 1,2 and 3. An actuator 4 is articulately attached to the lower supporting column section 3 at 5, and at 6 is articulately attached to a bracket 7 connected to the middle supporting column section 2, which bracket also supports a pulley 8.

Inside the telescopic supporting column, a pulley 9 (see Figs. 3 and 4) is mounted on the middle supporting column section 2, at the lower end thereof. An elongate element 10, for example, a belt, wire or cord, is placed around the two pulleys 8 and 9, as is shown in Figures 3 and 4. The elongate element 10 is connected to the upper supporting column section 1 at 11 and is connected to the lower supporting column section 3 at 12.

In respectively the upper and lower supporting column sections 1,3, an opening 13 and 14 respectively has been made for the passage of the elongate element 10, which in the exemplary embodiment is in the form of an endless cord.

When the actuator 4 is extended from the retracted position in Fig. 3, the upper and middle supporting column sections 1,2 are drawn out as shown in Fig. 4. When the actuator 4 is shortened, the upper and middle supporting column sections 1,2 will be drawn down into the lower, outer supporting column section 3 and so back the state illustrated in Fig. 3. The illustrated and described cord drive arrangement ensures a double action, i. e., that the supporting column is extended and shortened in a positive manner by means of the actuator 4, and there is no dependence on the weight of the element manoeuvred by the telescopic supporting column being sufficient to compress the supporting column when drawing down or retracting the telescopic supporting column.

Bearing pads 15 that are known per se are provided between the supporting column sections 1,2,3, and these afford favourable guiding of the supporting column members relative to one another and to a great extent prevent the effects of overturning moments which are due to the external location of the actuator.

The telescopic supporting column illustrated in Figures 1 to 4 has a rectangular cross- section and is so constructed that it is the inner supporting column section 1 which is the upper section of the telescopic supporting column. The sections may of course be arranged in the reverse fashion, and an embodiment of this kind is shown in Figures 5 to 7.

Figures 5 to 7 show a telescopic supporting column (when retracted) and this telescopic supporting column has an upper, outer supporting column section 20, a middle supporting column section 21 and a lower, inner supporting column section 22.

The lower, inner supporting column section 22 is connected to a base 23, shown only schematically, intended to rest against, e. g., a floor 24. In this case, the outer, upper supporting column section 20 is attached to a couch top 25, primarily by means of two mutually parallel generally triangular plate elements 26,27.

Uppermost on the upper supporting column section 20, there is provided a bracket 28 to which an actuator 29 is articulately attached at 30. The other lower end of the actuator 29 is articulately attached at 31 to a projection 32 on the middle supporting column section 21. A pulley 33 is supported in this projecting part 32. A pulley 34 is supported at the top in the intermediate supporting column section 21, and as in the preceding exemplary embodiment, an endless cord 35 runs around these pulleys 33,34. The endless cord 35 is passed through and secured to the middle supporting column section 21 at 36 and at 37 is passed through and secured to the outer, upper supporting column section 20.

It will be appreciated that the telescopic supporting column in Figures 5 to 7 functions in the same way as that shown in Figures 1 to 4, and that also this telescopic supporting column benefits from a double-acting cord drive which is actuated by means of the actuator.

As in the preceding exemplary embodiment, guide pads or bearing pads 38 are arranged between the supporting column sections 20,21 and 22.

The plates 26 and 27 are screwed or spot welded to the plane-parallel sides of the outer, upper supporting column section 20, so demonstrating what is favourable about having a"reverse"supporting column of this kind.