The invention relates to a table having a height-adjustable tabletop which under the influence of an auxiliary mechanism provided with a driving means and being adjustable in dependence on the load on the table is substantially in equilibrium in arbitrary positions in which it can be adjusted and retained by a stop biassed in a brake position and releasable by a control member connected with the stop.

Tables of this type, for instance worktables or operating tables, are advantageous in that they may be adjusted with a minimum of effort from the user, because the auxiliary mechanism with the driving means is adjustable to compensate for the load on the table irrespective of the magnitude thereof. It is, however, an inconvenience of such tables that if the load is changed to a valueto which the table is not adjusted, the tabletop may perform a move¬ ment that according to circumstances may be even rather violent, if the stop is unintentionnally released, and it is the object of the invention to provide a table that does not suffer from said inconvenience .

In this respect a table of the above mentioned type according to the invention is characterized in that the connection between the stop and the control member is adapted to become ineffective due to a discrepancy between the load on the table and the load to which it is adjusted.

This may for instance be obtained in that the stop cooperates with a member that is rotated by the movement of the tabletop and which by its rotation makes the connection between the stop and the control member ineffective.

If the stop is released at a time when the load on the table differs from the load to which it is ad-

justed, the table will move only extremely slightly, e.g. one millimeter or less, following which the rotating member has rendered an unintentional release of the stop by the control member impossible. The invention will now be explained in detail as an example with respect to its use in a worktable illustrated in the drawings, in which

Figs IA and IB are schemtical views of an auxi¬ liary mechanism including a driving means in two dif- ferent positions of a worktable, and

Figs 2 and 3, on a larger scale, the particular brake or locking mechanism according to the invention, illustrated from the front and from the bottom.

In Fig. 1 the table proper is designated 1 and 2 designates the height-adjustable tabletop pro¬ vided with a supporting leg 3. Said leg is passed through an opening 4 in a frame portion 5 of the stationary section of the table accommodated with clearance in the lateral direction. The supporting leg 3 is via two levers 6 and 7 height-adjustably connected in a parallelelogram guide with a firm part S in the stationary section of the table.

At 9 the supporting leg 3 is pivotally con- nected with one end of a driving means, e.g. a pressure actuated member 10, which in this case is a gas spring. By a part 11 projecting from the other end of the gas cylinder the gas spring is guided in a guideway 12 in which it may be adjusted by a connecting piece 13 connected pivotally therewith at 11" and being provided with a piece of tube 14 having an internal thread that is in engagement with a thread spindle 14' having an external thread and being rotatable from the top surface of the table. One arm 6 of the parallelelogram guide com¬ municates with a thread spindle 16 over a universal

joint 15 provided with a connecting piece 15' having an internal thread, said thread spindle being rotatable by the movement of tabletop 2 and cooperating with a brake generally designated 17. Said brake is releasable over a cord drive 18 by activating a foot lever 19 against the force of a spring 20. When the brake is active, the mechanism and thus the tabletop 2 are maintained in the position into which it is adjusted. When the brake is released, the tabletop 2 may be displaced in the height direction, the thread spindle 16 being then not prevented from rotating.

In Figs 2 and 3 the brake or the locking arrangement is formed in such a manner that thread spindle 16 at its top is terminated by a nut 21 adapted to engage and disengage an opening 21 ' in locking member 22 biassed towards nut 21 by means of a spring 23. In the normal position of use a releasing member 25 is positioned opposite locking member 22 and is over cord drive 18 connected with the foot lever 19, the locking member being kept out of engagement with the releasing member by spring 20 but, on activation of foot lever 19 the releasing member is capable of lifting locking member 22 out of engagement with nut 21 so that tabletop 2 is adjustable for height, which as mentioned above is effected without requiring any particular effort from the user, provided the coupling point 11' in guideway 12 occupies a position corresponding to the load on the table. Tabletop 2 will then when actuated by the user merely move to the desired position in which it may be locked by stop 21, 22.

If, however, the load on tabletop 2 does not correspond to the positioning of coupling point 11' in guideway 12 or, if the load is changed in relation to the adjusted value and stop 21, 22 is released, table¬ top 2 will effect an uncontrollable movement upwards or downwards.

If the table is for instance loaded beyond the load to which it is adjusted, spindle 16 will over nut 21 effect a rotation restricted by spring 24 of locking member 22, cf. the position shown in dotted lines in Fig. 3, thereby moving it outside the activ¬ ating region of releasing member 25, and an uninten¬ tional actuation of foot lever 10 will then be inef¬ fective.

In the illustrated embodiment locking member 22 is connected with spring 24 via a stabilizing inter¬ mediate piece 26 that is pivotal about a pin 27.