LOCKING DEVICE

Abstract: The invention relates to a device for parts which are movable in tables and chairs, as well as being positionally adjustable and lockable in desired mutual relationship, by displacement of at least one supporting rod (2) carrying the respective part (1), this rod being accommodated in a guide tube (4) rigidly fixed to the supporting frame (3) of a chair or table, there being in the tube at least one positionally fixed sleeve (5) closely fitting round the rod, which is locked to the sleeve in a desired position with the aid of friction achieved by a compressive force applicable to the sleeve. The latter comprises two substantially equally great, circularly shaped portions (9, 10), mutually separated by at least one slot (6) extending the full length of the sleeve, both circularly shaped portions (9, 10) forming the sleeve being radially movable from an original position engaging the inside (11) of the guide tube (4) towards and away from each other inside the tube when the compressive force affects the curved outer surface (12, 13) of one of the circularly shaped portions (9, 10) for respectively locking and releasing the supporting rod (2).

Description: Locking device The present invention relates to a locking device for parts, which are movable in tables and chairs, as well as being positionally adjustable and lockable in desir¬ ed, mutual relationship, by displacement of at least one supporting rod carrying the respective part, this rod being accommodated in a guide tube rigidly fixed to the supporting frame of a chair or table, there being in the tube at least one positionally fixed sleeve closely fitting round the rod, which is locked to the sleeve in a desired position with the aid of friction achieved by a compressive force appliable to the sleeve. A usually available, movable part in chairs is an armrest, for example, which may be adjustable in height. At present, locking means are most often used to positionally fix the armrest with the aid of locking screws, which may be screwed into guide tubes on the chair frame, such as to lock the armrest in its desired position by bearing directly on the respective support rod carrying the armrest. This causes ugly marks on the rod. There are different arrangements for solving this problem, inter alia by fitting an intermediate sleeve in the guide tube, but these arrangements have proved less reliable or expensive in fabrication. There are the same problems in positionally fixing other movable parts of chairs and tables, e.g. depth adjustment means for back supports, locking means for leg supports, knee supports and other adjustable parts included in chair and table structures. The object of the invention is to provide a device of the kind mentioned above, where the disadvantages present up to now have.been eliminated. The dieting- uishing features of the invention are disclosed in the accompanying claims. As a result of the invention, there has been achieved a locking device for movable parts included in chairs and tables, which in an excellent way fulfils its object¬ ives, while it is also simple and cheap to manufacture. By the special implementation of the sleeve included in the device and situated in the guide tube, there is afforded, in accordance with the invention, very gentle engagement against the supporting rod carrying the part in question, when the rod is positionally fixed by a locking screw simultaneously as reliable, positional fixation of the part is attained. This is due, inter alia, to the great flexibility of the sleeve in the guide tube, this sleeve being adapted for locking the part to the supporting frame of a chair or table. The invention will now be described in more detail, with the aid of two preferred embodiment examples of the invention and with reference to the accompanying drawing, where: Fig. 1 is a schematic, perspective view of a chair having an armrest which is adjustable in height, an inventive locking device for posi¬ tional fixation of the armrest also being shown, Fig. 2 is a partial view of the device in Fig. 1, seen from above, Fig. 3 illustrates the device of Fig. 2 to a larger scale, Fig. 4 is a partially sectioned, schematic side view of an alternative embodiment, where the sleeve is accommodated centrally in the guide tube, with guide bushes fitted into either end of the guide tube, Fig. 5 is a schematic perspective view of the sleeve illustrated in Figs. 2 and 3 and Fig. 6 is a schematic, perspective view of a sleeve implemented in an alternative configuration. The inventive device comprises a locking means for movable parts included in tables and chairs. According to a preferred embodiment example illustrated in Figs. 1-3, a movable armrest 1 is adjustable to, and lockable at a desired height, which is accomplished in the following manner. At least one supporting rod 2 for the armrest 1 is accommodated within a guide tube 4 rigidly attached to the chair seat supporting frame 3. In the tube 4 there is at least one positionally fixed sleeve 5 fitting closely round the rod 2, and adapted to lock it at a desired height with the aid of friction gene¬ rated by applying a compressive force against the sleeve 5. In this embodiment the latter has a full- length slot 6, opposite to which there is a full-length groove 8 in the cylindrical surface 7 of the sleeve, which thus substantially comprises two circular por¬ tions 9 and 10. These portions can be urged against their resilience from their original positions engaging the inside wall of the tube 4 in a direction towards each other. This movement will take place when the com¬ pressive force is applied to the outer curved surface 12, 13 of one or other of the circular portions 9; 10, thus locking the supporting rod 2 in its assumed posi¬ tion. In an alternative embodiment illustrated in Fig. 6, the sleeve 5 may have both its circular portions 9 and 10 separated by diametrically opposing slots 6. To provide an axial fixation of the sleeve 5 in the tube 4, at least the edge portions of the circular portions 9 and 10 have the configuration of tongues projecting into corresponding recesses. The compressive force against the sleeve 5 is achieved by a locking screw 14 extending through guide sleeve 4 and support frame 3, such as to bear on the outer cylindrical surface 12, 13 of the sleeve when screwed into the frame 3. As will be seen in more detail in Fig. 5, in one em¬ bodiment of the sleeve 5 there is a groove 8 extending parallel to the symmetrical axis of the sleeve for its entire length. The groove has a rectangular cross- section corresponding to that of a keyway and has a depth preferably greater than two-thirds of the sleeve thickness. The sleeve is preferably made from a suit- able steel that will withstand the concentrated press¬ ure exerted by the screw 14, and it is positionally fixed inside the tube 4 by a protuberance 16, which may be provided by weld through a hole 17 in the tube 4. This may also apply to the embodiment in Fig. 6 as well. The sleeve is thus prevented from rotational or axial movement in the tube 4. As a result of providing groove 8 the sleeve will be sufficiently flexible to enable a desired locking force for the supporting rod 2 to be readily applied by tightening the locking screw 14. The width of the slot or gap 6 is made sufficient for the mutually opposing movements of the portions 9 and 10 when the armrest is locked at its desired height. In the alternative embodiment of the device as illu¬ strated in Fig. 4, the sleeve 5 is shorter than that in the other embodiments, and it is placed centrally in the guide tube 4. In this case, a guide bush 15 is fitted at either end of the guide tube, i.e. on either side of the sleeve, this solution affording a more pleasing implementation of the device, since the bushes 15 are hidden inside the tube. This alternative em¬ bodiment otherwise functions in the same way as the first one. Even other not more closely described or illustrated embodiments of the inventive locking device may be used, as mentioned in the introduction, for locking movable chair or table parts together in desir¬ ed, positionally fixed relationships.

Claims: Claims 1. Locking device for parts which are movable in tables and chairs as well as being positionally adjust- able and lockable in desired, mutual relationship, by displacement of at least one supporting rod (2) for carrying the respective part (1) , this rod being accom¬ modated in a guide tube (4) rigidly fixed to the sup¬ porting frame (3) of a chair or table, there being in the tube (4) at least one positionally fixed sleeve (5) closely fitting round the rod (2) , which is locked to the sleeve in a desired position with the aid of fric¬ tion achieved by a compressive force appliable to the sleeve, characterised in that the sleeve (5) includes two substantially similarly as great, circularly shaped portions (9, 10) separated from each other by at least two slot formations (6, 8) in diametrically opposed relationship, both of which extend the full length of the sleeve (5) , said portions (9 and 10) being radially movable from original engagement against the inside (11) of the guide tube (4) in a direction towards, and away from each other inside said tube, when said com¬ pressive force affects the outer curved surface (12, 13) of the respective circularly shaped portion for respectively locking and releasing said rod (2) . 2. Device as claimed in claim 1, characterized in that the slot formations comprise two diametrically opposing through slots (6) , of which at least one extends over the full length of the sleeve, there also being formed an interlocking configuration between the mutually opposing edge portions of said sleeve (5) , this configuration taking the form of at least one tongue and its corresponding recess. 3. Device as claimed in claim 1, characterized in that the slot formations comprise a through slot (6) and a groove (8) diametrically opposed to it, made in the curved surface (7) of the sleeve (5) , both slot and groove extending the full length of said sleeve. 4. Device as claimed in claim 3, characterieed in that the groove (8) made in the curved surface (7) of the sleeve (5) extends parallel to the longitudinal axis of symmetry of the sleeve and has a rectangular cross-section with a position and shape substantially conforming to that of a keyway. 5. Device as claimed in claim 4, characterized in that the depth of the groove (8) is greater than two- thirds of the sleeve thickness. 6. Device as claimed in any one of the preceding claims, characterised in that the compressive force is obtained using a locking screw (14) extending through guide tube (4) and supporting frame (3) for bearing against one of the outer curved surfaces (12, 13) of the sleeve (5) . 7. Device as claimed in any one of the preceding claims, characterised in that the screw (14) may be caused to bear against a centrally situated area of one of the circularly shaped portions (9; 10) of the sleeve (5), the other portion (9; 10) being positionally fixed in the guide tube (4) with the aid of a protuberance (16). 8. Device as claimed in claim 1, characterised in that the guide tube (4) extends past the sleeve (5) at either end thereof for accommodating guide bushes (15) with the sleeve (5) situated therebetween.

Inventors: DU REES STEPHAN, DU REES, STEPHAN
Applicants: MERCADO MEDIC AB, REES STEPHAN DU, DU REES, STEPHAN
Application year: 1995
Main classification: F16B12
IPC codes: A47B9, A47C1, F16B7, F16B12