GB2214069A - An adjustment device for adjusting the tilt and/or height of a bench or table top of a piece of furniture - Google Patents

Abstract

An adjustment device for adjusting the tilt or height of a table top has two lifting elements in the form of curved gear racks (109, 109') which engage gear wheels (116, 116') of a drive (131, 131'). Each gear rack is guided by a guideway (111, 111'). <IMAGE>

Description

AN ADJUSTMENT DEVICE FOR ADJUSTING.

THE TILT AND/OR HEIGHT OF A BENCH OR TABLE TOP OF A PIECE OF FURNITURE.

The invention relates to an adjustment device for adjusting the tilt and/or height of a bench or work top of a piece of furniture in accordance with the characterising clause of claim 1.

The tilt and/or height of the bench or table top of a piece of furniture can be adjusted with such known adjustment devices.

The lifting element is designed as a pair of lifting scissors by means of which the bench or table top can be raised or lowered.

When the bench or table top is in its lower position, the lifting scissors assume their lowest position, in which their legs subtend a large obtuse angle. To raise the top, therefore, a large expenditure of energy is required, because an unfavourable force distribution occurs as a result of the legs of the lifting scissors lying at an obtuse angle to one another. In addition, only a small displacement path of the lifting scissors produces a relatively large lift path of the bench or table top. As the adjustment process continues, the force relationships become more favourable, so that the lifting scissors can be operated with little force. However, the lift path now becomes smaller. This known adjustment device thus exhibits a non-uniform power-lift ratio.Moreover, the lifting scissors are susceptible to transverse loads, because as a result the legs of the scissors pinned together can become slightly twisted. This can result in the lifting scissors possibly ceasing to function. Moreover, the lifting scissors require considerable space for their installation.

The underlying task of the invention is to design the adjustment device of the generic type in such a way that it has an approximately constant power-lift ratio coupled with easy handling and small installation space.

For the adjustment device of the generic type, this task is solved according to the invention by the characteristic features of claim 1.

By means of lifting elements in the form of curved gear racks it is possible to develop the power-lift ratio so that it is approximately constant over the whole adjustment path of the adjustment device.

The energy expended on lifting is thus approximately constant in each position of the bench or table top. Also, the lift path is approximately constant in relation to the displacement path of the gear racks, so that the bench or table top can be adjusted effortlessly and accurately into the desired position. The gear racks are guided in the guideways in a trouble-free manner, so that the adjustment can be carried out in a simple fashion. Since the gear racks can be designed flat, they can be fitted close to the side of the piece of furniture, so that they require only a small amount of space.

The gear rack is a robust component part which has a long life.

Moreover, the gear rack drive guarantees an easy-running and accurate displacement of the bench or table top. If both lifting elements are actuated simultaneously, the bench or table top is displaced in height. It is also possible, however, to actuate just the one lifting element. In that case, the bench or table top will be adjusted in its inclination. The two lifting elements or gear racks thus enable a straightforward and trouble-free height and tilt adjustment. By means of the two lifting elements, relatively wide bench or table tops can also easily be adjusted.

Further features of the invention are provided in the further claims, the description and the drawings.

The invention is explained in greater detail with the aid of several examples of embodiment represented in the drawings.

Fig. 1 shows a first form of embodiment of an adjustment device according to the invention in a view through line 1-1 in Fig. 3, Fig. 2 shows a view from below the adjustment device according to Fig. 1, Fig. 3 shows a cross-section through the adjustment device according to Fig. 1, Fig. 4 shows the adjustment device according to Fig. 1 with a tilted bench top of the piece of furniture, Fig. 5 shows the adjustment device according to Fig. 1 with the bench top of the furniture adjusted in height, Fig. 6 shows another form of embodiment of a lifting element of the adjustment device according to the invention, Fig. 7 shows in a view from below a part of another form of embodiment of an adjustment device according to the invention, Fig. 8 shows a side view of the adjustment device according to Fig. 7, Fig. 9 shows a cross-section through the adjustment device according to Fig. 7, Figs. 10 - 12 show, in representations corresponding to Figs. 7 to 9, a further form of embodiment of an adjustment device according to the invention, Figs. 13 - 15 show, in representations corresponding to Figs. 7 to 9, a further form of embodiment of an adjustment device according to the invention, Figs. 16 - 18 show, in representations corresponding to Figs. 7 to 9, a further form of embodiment of an adjustment device according to the invention.

The adjustment device serves to adjust the tilt and/or height of a bench or table top of a piece of furniture, a table and suchlike.

In the case of the form of embodiment according to Figs. 1 to 5, the adjustment device has an L-shaped mounting plate 101, which lies with its horizontal leg 102 on a foot, a frame part 103 and suchlike. The vertical leg 104 lies parallel to the inner side 105 of the frame part 103. Close to its lower edge 106, the vertical leg 104 is provided with a slot 107 running in the longitudinal direction of the leg (Fig. 1) and being provided at the rear end of the leg 104, as seen from the viewpoint of the user sitting at the piece of furniture. Guided in slot 107 is a guide part 108 preferably in the form of a bolt which is attached to one end of a lifting element 109 in the form of a gear rack. As with the previous forms of embodiment, it is bent in the form of an arc through an angle of less that 1800.

At the other end facing the user sitting at the furniture, the gear rack 109 is provided with a further guide part 110 preferably in the form of a bolt, which engages a slot 111 of an intermediate plate 112, said slot being curved corresponding to the gear rack 109. The slot 111 extends over only a part of the length of the gear rack 109.

Provided directly adjacent to the gear rack 109 is a second gear rack 109', which is also bent in the shape of an arc and which subtends an angle of less then 1800. The gear rack 109' is provided with a preferably bolt-shaped guide part 110', which lies directly adjacent to the guide part 110 and engages a curved slot 111' in the intermediate plate 112. The slot 111' has the same curvature as gear rack 109' and extends over less than half the arc length of the gear rack. At the other end, the gear rack 109' is connected to the vertical leg 104 of the mounting plate 101.

As Fig. 1 shows, the gear racks 109, 109' are positioned in mirror-symmetric arrangement. They extend, moreover, over the same angular range and each have a convex curvature in relation to the bench or table top 113 of the piece of furniture.

Both gear racks 109, 109' are respectively supported by at least one support roller 114, 114' on their convex side facing the bench top 113. On the opposite side, the gear racks 109, 109' are provided with toothing 115, 115' which extends from the end of the gear rack having the guide part 110, 110' preferably over more than half the arc length of the gear rack. It is engaged by a gear wheel 116, 116' which is mounted torsion-resistant on a shaft part 117, 117'. It is connected torsion-resistant by a connection element 118, 118' to a dumb-bell shaft 119, 119' which extends to a frame part 103 lying opposite.

The two gear racks 109, 109' lie between two vertical legs 120, 121 of two L-shaped rails 122, 123 which are attached by their horizontal leg 124, 125 (Fig. 3) to the underside of the bench top 113. The two gear racks 109, 109' are guided trouble-free between the vertical legs 120, 121 of rails 122, 123.

The two gear wheels 116, 116' are mounted so as to be rotatable in openings in the vertical legs 120, 121. Two gear cases 126, 126' are attached to the side of leg 121 facing away from leg 120, there being positioned respectively in said gear cases a helical gear i27, 127' mounted torsion-resistant on the shaft parts 117, 117'. They each engage a helical gear 128, 128' housed in the gear cases 126, 126', only helical gear 128 being shown in Fig. 3. Both helical gears 128, 128' are mounted on an actuating shaft 129 which runs parallel to the vertical leg 121 of rail 123 (Fig. 2) and extends to the seating side of the piece of furniture. A crank 130 can be inserted into the actuating shaft 129. The helical gears 128, 128' and the actuating shaft 129 lie in the region above the dumb-bell shafts 119, 119'.

The gears 131, 131' housed in the gear cases 126, 126' can be actuated jointly by the actuating shaft 129. In gear case 126' there is a coupling 132 by means of which the gear 131' can be disengaged in such a way that it does not become active when the actuating shaft 129 rotates. To actuate the coupling 132, the actuating shaft 129 is axially displaced, as will further be explained below.

The two dumb-bell shafts 119, 119' lying at rightangles to the actuating shaft 129 connect the gears 131, 131' to the gears provided on the opposite frame part which have the same design.

The intermediate plate 112 lies between the vertical leg 104 of the mounting plate 101 and the vertical leg 120 of rail 122. The intermediate plate 112 has two slots 133, 134 (Fig. 1) parallel to one another and running in the height direction of the intermediate plate, into which there fits respectively a guide part 135, 136 which is attached to the vertical leg 120 of rail 122 and projects at rightangles from it.

In the lowered horizontal position of the bench top 113 represented in Fig. 1, the guide part 108 of the gear rack 109 is positioned against the end of the slot 107 facing towards the gear rack 109'. The other guide part 110 of rack 109 is positioned against the end of the curved slot 111 facing towards the gear rack 109'. The guide part 110' is positioned against the end of slot 111' facing towards the gear rack 109. The intermediate plate 112 is lowered to the extent that its chamfered edges 137, 138 are adjacent to the guide part 108 of gear rack 109 and to the swivelling axle 139 of gear rack 109'. The guide parts 135, 136 of rail 122 are positioned at this time at the lower end of the slots 133, 134 of the intermediate plate 112. It lies concealed behind the vertical leg 120 of rail 122.The gear wheels 116, 116' are positioned at the ends of the toothing 115, 115' of gear racks 109, 109' said ends being those facing away from one another. In order to adjust the bench top 113 into an inclined position (Fig. 1), the actuating shaft 129 is shifted axially backwards as viewed from the seating side of the piece of furniture. This puts gear 131' out of operation by means of coupling 132. If the actuating shaft 129 is now rotated using crank 130, the gear wheel 116 is rotated via the gear 131. The gear rack 109 is thus shifted relative to rail 122 along an arc.

Since the gear rack 109 is guided by the guide part 108 in slot 107 of the mounting plate 101, the bench top 113 is raised at the end n facing away from the seating side as the gear rack 109 is displaced.

At this point, the guide part 135 of rail 122 is shifted in slot 133 of the intermediate plate 112, until it comes into contact against the other end of the slot and then drives the intermediate plate 112 with it (Fig. 4). At the opposite end the intermediate shaft 112 is supported by its chamfered edge 138 in a swivelling fashion on the swivelling part 139 of gear rack 109. At the same time, the gear rack 109' swivels about the swivelling part 139, but in doing so it is not shifted in relation to the rail 122. The guide part 110 of gear rack 109 is displaced in the slot 111 of rail 122. The bench top 113 is at its greatest inclination when the guide part 110 comes into contact with the end of slot 111 facing away from gear rack 109'.As a result of the gear wheel 116 engaging gear rack 109, the bench top 113 is held in each tilt position, being supported on the frame part 103 via the gear rack 109, its guide part 108 and the mounting plate 101. Moreover, the bench top 113 is also supported on frame part 103 via the swivelling part 139 and the mounting plate 101. The gears 131, 131' of a swivelling part 103 are connected in a drivable manner via the dumb-bell shafts 119, 119' to the corresponding gears on the opposite swivelling part, so that the bench top 113 can be raised uniformly on both sides or can be adjusted in its inclination.

If the gear rack 109' facing the seating side of the furniture is to be displaced, the actuating shaft 129 must firstly be drawn back again axially, so that the coupling 132 of gear 131' is engaged.

Both gears 131, 131' are then actuated simultaneously by the actuating shaft 129. The two gear racks 109, 109' are then displaced synchronously roughly in opposite directions out of the initial position according to Fig. 1, whereby the guide part 110 of gear rack 109 is displaced in slot 111 of the rail 122 and the guide part 108 in slot 107 of the mounting plate 101. The guide part 110' of the other gear rack 109 is also displaced in slot 111' of rail 122. Moreover, the gear rack 109' swivels via its swivel part 139 relative to the mounting plate 101. As a result of the motions of gear racks 109, 109' in opposite directions, the bench top 113 is raised uniformly.

Via the guide parts 135, 136 of rail 122, the intermediate plate 112 is also raised as soon as the guide parts strike against the upper ends of slots 133, 134 of the intermediate plate. The extreme upper position of the bench top 113 is reached when the guide parts 110, 110' of gear racks 109, 109' strike against the ends of the slots 111, 111' facing away from one another.

When the bench top 113 is returned, the intermediate plate 112, which hangs on the guide parts 135, 136, is lowered until its chamfered edges 137, 138 come to a stop on the guide part 108 and the swivelling part 139. The sequence of motions here are coordinated in such a way that the intermediate plate 112 only comes to a stop when the guide part 108 is almost in its end position according to Fig. 1. The use of the freely suspended intermediate plate 112 allows a large adjustment path without the rail 122 having to be particularly high. When the bench top 113 is in the lowered position (Fig. 1), the vertical leg 120 of the angle rail 122 does not therefore project downwards beyond the horizontal part of the frame part 103. The intermediate plate 112, viewed in the axial direction of the dumb-bell shafts 119, 119', is also concealed behind the vertical leg 120.With this form of embodiment too, the bench top 113 can be lowered to the extent that it is only a short distance from the frame 103. Consequently, the adjustment device is only slightly visible from the outside.

Toothed segments 140 can also be used as the lifting element instead of the gear racks 109, 109', as is represented in Fig. 6. It has a cut-out 141, whose one edge 142 curved in the shape of an arc has the toothing 143. The gear wheel 116, 116' engaging this toothing projects partly through the cut-out 141. The length of the cut-out 141 roughly corresponds to the length of the toothing 143. The toothed segment 140 further has an opening 144 to accommodate the guide part 108 or the swivelling part 139 as well as an opening 145 to accommodate the guide parts 110 and 110'. The toothed segment has a high degree of stability and can easily be manufactured.

The adjustment device according to Figs. 7 to 9 again has the one mounting plate 201 which is attached to the inner side of a side piece 202. A further mounting plate, designed the same as mounting plate 201, is attached to the opposite (not shown) side piece. In order to adjust the tilt and/or height of the table or bench top 203, there are two toothed segments 204, 204' which are arranged in alignment beside one another with a small spacing between them.

The mounting plate 201 is L-shaped and has a horizontal leg 205 with which it rests on the side piece 202 of the foot, frame part or suchlike. The vertical leg 206 lies parallel to the inner side 207 of the frame part 202. Close to its lower edge, the vertical leg 206 is provided with a slot 209 running in its longitudinal direction (Fig.

8) which is provided at the rear end of the leg 206, as viewed by the user sitting at the piece of furniture. In slot 209 there is preferably a guide part 210 in the form of a bolt which is attached to one end of the toothed segment 204. On the other end facing towards the user sitting at the piece of furniture, the toothed segment 204 is provided with a further guide part 211 preferably in the form of a bolt, which engages a curved slot 212 of an intermediate plate 13.

As Fig. 8 shows, the arc-shaped edge of the toothed segments 204, 204' facing towards the top 203 runs through an angle of less than 1800. The slot 212 runs parallel to the curved edge 214 of the toothed segment 204, but extends only over a part of the length of this edge.

The tooth segment 204' also has an arc-shaped edge 215 facing towards the top 203 and extending over an angle range less than 1800. The toothed segment 204' is provided with a preferably bolt-shaped guide part 211' which is immediately adjacent to the toothed segment 204 and engages a curved slot 212' in the intermediate plate 213. The slot 212' has the same curvature as the edge 215 of the toothed segment 204' and extends over less than half the arc length of this edge. On the other end, the toothed segment 204' is attached to the vertical leg 206 of the mounting plate 201.

The two toothed segments 204, 204' are arranged mirror-symmetric to one another. Their edges 214, 215 each have a convex curvature relative to the top 203.

Both toothed segments 204, 204' are supported on their convex side facing the top 203 by at least one support roller 216, 216' respectively.

The toothed segments 204, 204' have respectively cuts-outs 217, 217', whose edges 218, 218' facing towards the edges 214, 215 have respectively toothing 219, 219'. The edges 218, 218' run parallel to the edges 214 and 215 of the toothed segments 204, 204'. The cut-outs 217, 217' are provided in the region of the ends of the toothed segments lying beside one another. The toothing 219, 219' is engaged respectively by a gear wheel 220, 220' which is mounted torsion-resistant on a shaft 221, 221'. The shafts 221, 221' extend to the opposite (not shown) frame part.

The two toothed segments 204, 204' lie between two vertical legs 222, 223 of two L-shaped rails 224 and 225, the horizontal legs 226 and 227 of which are attached to the underside of the top 203.

The two toothed segments 204, 204' are guided trouble-free between the vertical legs 222, 223 of rails 224, 225.

The gear wheels 220, 220' penetrate the vertical legs 222, 223 of rails 224, 225 (Fig. 9). Two gear cases 228, 228' (Fig. 7) are attached to the side of the vertical leg 223 facing away from leg 222, helical gears 229, 229' arranged respectively on the shafts 221, 221' being positioned in said gear cases. As Figs. 7 and 9 show, the helical gears 229, 229' project out from the gear cases 228, 228'. Inside the gear cases, the helical gears 229, 229' engage respectively a helical gear 230, 230'. Both helical gears 230, 230' are mounted on a common actuating shaft 231 which runs parallel to the vertical leg 223 of rail 225 (Fig. 7) and extends to the seating side of the piece of furniture. A crank 232 can be inserted into the actuating shaft 231. The helical gears 230, 230' and the actuating shaft 231 lie in the region above the dumb-bell shafts 221, 221'.

The gears 233, 233' housed in the gear cases 228, 228' can be jointly actuated by means of actuating shaft 231. In each of the gear cases 228, 228' there are couplings 234, 234' which each have a coupling part 235, 235' mounted torsion-resistant on the actuating shaft 231. In the position represented in Fig. 7, the coupling parts 235, 235' are engaging the helical gears 230, 230'. Both helical gears 230, 230' are thus driven in a rotating manner when the actuating shaft 231 is rotated.

The actuating shaft 231 can be displaced axially relative to the helical gears 230, 230'. If the actuating shaft 231 is displaced axially to the left by means of the crank 232 in Fig. 7, the coupling part 235' becomes disengaged from the helical gear 230'. As a result, only the helical gears 229, 230 are driven in a rotating manner when the actuating shaft 231 is rotated. If, on the other hand, the actuating shaft 231 in Fig. 7 is displaced to the right, the coupling part 235 disengages from the helical gear 230. When the actuating shaft 231 is then rotated, only the helical gears 229', 230' are driven in a rotating manner.

At a distance from the gear cases 228, 228', a brake track 236, 236' is mounted torsion-resistant on the respective dumb-bell shafts 221, 221', into which brake track there is fitted one end of a helical spring 237, 237' which surrounds the shaft 221. The other end of the helical springs 237, 237' is fitted into the helical gears 229, 229'. The brack tracks 236, 236' are encompassed by clamping rings 238, 238' which can be actuated by a common actuating rod 239 (Fig. 7). The clamping rings 238, 238' have ends 240, 240a and 240', 240a' (Fig. 8) lying at a distance from one another, which have aligned drill holes in each of which a threaded section of the actuating rack 239 lies.The threads in the ends of the clamping rings are designed contra-rotating to one another, so that both ends of each clamping ring 238, 238' are moved in opposite directions to one another when the actuating rod 239 is rotated. The end of the actuating rod 239 facing towards the user of the piece of furniture is preferably bent, so that this end lies in the region of crank 232 of the actuating shaft 231.

As Fig. 7 shows, the clamping rings 238, 238' are provided with coupling bushes 241, 242 directed towards one another, said bushes being penetrated by the actuating rod 239. It can be displaced axially relative to the coupling bushes 241, 242. The coupling bushes 241, 242 are provided with slots 243, 244 running axially, through which guide pins 245 and 246 standing out radially from the actuating rod 239 project. The torsion-resistant connection between the actuating rod 239 and the coupling bushes 241, 242 is produced by these guide pins 245, 246. In the position shown in Fig. 7, both coupling bushes 241, 242 are driven in a rotating manner by the guide pins 245, 246 when the actuating rod 239 is rotated.If the actuating rod 239 in Fig. 18 is displaced to the left, the guide pin disengages from edge-open slot 244 of coupling bush 242, so that when the actuating rod is rotated, only the coupling bush 241 is driven in a rotating manner. If the actuating rod 239 in Fig. 7 is displaced to the right, the guide pin 245 is released from the edge-open slot 243 of the coupling bush 241, so that now only the coupling bush 242 is driven in a rotating manner when the actuating rod 239 is rotated.

Usually the clamping rings 238, 238' are located in their clamping position, in which they firmly surround the brake tracks 236, 236'.

The two helical springs 237, 237' serve as counter-weight devices, by means of which the weight of the top 203 during adjustment can be taken up and equalised. Depending on the weight of the top 203, the prestressing of the helical springs 237, 237' can be adjusted simply by means of the gears 233, 233'. To do this, the actuating shaft 231 is merely rotated in the appropriate direction by means of the crank 232. If both couplings 234, 234' are in the coupling position, as in Fig. 7, then both helical gears 230, 230' are rotated when the actuating shaft 231 is rotated. The helical gears 229, 229' engaging them and mounted rotatably on shafts 221, 221' are thereby rotated.Since one of the ends of the helical springs 237, 237' is fitted into these gear wheels 229, 229' the prestressing of the helical springs is increased or reduced depending on the direction of rotation. The brake tracks 236, 236', into which the other ends of the helical springs 237, 237' are fitted, cannot be rotated during this adjustment procedure, because they are held firmly in position by the clamping rings 238, 238'.

If the top 203 is to be adjusted in height, the clamping rings 238, 238' are loosened by rotating the actuating rod 239. The height adjustment of the top 203 can now be carried out. Since the brake tracks 236, 236' are no longer blocked against rotation, they are driven by the prestressed helical springs 237, 237'. Moreover, since the brake tracks 236, 236' are mounted torsion-resistant on the shafts 221, 221', the latter are driven via the brake tracks 236, 236'. In this way, the gear wheels 220, 220' mounted torsion-resistant on the shafts 221, 221' are driven, said gear wheels engaging the toothing 219, 219' of the toothed segments 204, 204'.

In position represented in Fig. 8, the top 203 is in its lowermost position. The gear wheels 220, 220' lie against the ends - facing away from one another - of the cut-outs 217, 217' in the toothed segments 204, 204'. The guide part 210 of the toothed segment 204 lies against the end - facing the gear wheel 220 - of the slot 209 in the verticle leg 206 of the mounting plate 201. If the gear wheels 220, 220' are rotated in the manner described above, the toothed segments 204, 204' are swivelled upwards towards one another from opposite directions. In doing so, the toothed segment 204' swivels about the axle 247, by means of which the toothed segment 204' is attached at its end facing away from the toothed segment 204 to the vertical leg 206 of the mounting plate 201. At the same time, the guide part 211' is shifted in the slot 212' with this swivelling motion.

The other toothed segment 204 also swivels upwards, whereby the guide part 210 is displaced in the horizontal slot 209 of the vertical leg 206 of the mounting plate 201. Both toothed segments 204, 204' swivel uniformly so that the top 203 is displaced horizontally in height. The gear wheels (not shown) provided on the other frame part are also rotated via shafts 221, 221'. As soon as the desired height of the top 203 is reached, the actuating rod 239 is rotated in the opposite direction, as a result of which the clamping rings 238, 238' again firmly embrace the brake tracks 236, 236', so that the shafts 221, 221' can no longer be rotated. The actuating rod 239 is held on the furniture in a manner not shown.

If the top 203 is to be tilted, the actuating rod 239 is firstly displaced axially in the desired direction, so that either the guide pin 245 or the guide pin 246 engages the corresponding coupling bush 241 or 242. The actuating rod 239 is then rotated and released by the respectively engaged coupling bush 241 or 242 of the corresponding clamping ring 238 or 238'. The respective shaft 221 or 221' with the associated gear wheel 220 or 220' is then rotated via the prestressed helical spring 237 or 237'. In this way, only one of the two toothed segments 204, 204' is swivelled, so that the top 203 is tilted.

In order to adjust the prestressing of the given helical spring for the inclination adjustment of top 203, the actuating shaft 231 can be shifted axially in the desired direction, so that either the coupling part 235 or the coupling part 235' engages the helical gear 230 or 230'. By rotating the actuating shaft 231, the respective helical spring 237, 237' is then prestressed in the manner described with blocked brake tracks 236, 236'.

The clamping rings 238, 238' are loosened in the adjustment process to such an extent that a trouble-free adjustment is ensured.

The top 203 has its greatest inclination when the guide part 211 of the toothed segment 204 strikes against the end of the slot 212 of intermediate plate 213 facing away from the- toothed segment 204'. As a result of the gear wheels 220, 220' engaging the toothing 219, 219', the top 203 is held secure in each tilt position. It is supported on the frame part 202 via toothed segment 204, its guide part 210 and the mounting plate 201. Moreover, the top 203 is also supported on the frame part via the axle 247 of the toothed segment 204' and the mounting plate 201. The upper extreme position of the top 203 is reached when the guide parts 211, 211' of toothed segments 204, 204' strike against the ends of slots 217, 217' facing away from one another.

The top 203 can also be adjusted in height in an inclined position by translation. To achieve this, it is simply a matter of pushing back the actuating rod 239 out of its axially displaced position into the middle position shown in Fig. 7. If the actuating rod 239 is then rotated, both clamping rings 238, 238' are again loosened, so that both gear wheels 220, 220' are then rotated towards one another from opposite directions in the manner described via the prestressed helical springs, such that the two toothed segments 204, 204' are displaced towards one another from opposite directions in the described manner. As a result, the top 203 is displaced by being translated in its given inclined position.

The form of embodiment according to Figs. 10 to 12 differs from the previously described example of embodiment solely in the fact that separate actuating rods 239a, 239b are provided for the brake tracks 236, 236'. The clamping rings 238, 238' located on the brake tracks are actuated by these rods in the described manner.

The brake tracks 236, 236' can be much longer than in the case of the above form of embodiment. It is also connected torsion-resistant to the shafts 221, 221'.

In order to adjust the top 203, the clamping rings 238, 238' are loosened by means of actuating rods 239a, 239b. The toothed segments 204, 204' are then adjusted by means of the prestressed helical springs in the manner described. Since separate actuating rods 239a and 239b are provided for the clamping rings 238, 238' with this form of embodiment, the actuating rods no longer need to be capable of being displaced axially. If the top 203 is being adjusted in height, both actuating rods 239a and 239b are rotated to loosen the clamping rings 238 and 238'. If the top 203 is to be tilted, then either the actuating rod 239a or 239b is rotated depending on the tilt direction. As for the rest, the adjustment of the top 203 takes place in the same way as with the example of embodiment according to Figs. 7 to 9.Since the actuating rods 239a, 239b do not need to be axially displaceable, they can be designed very simply and can also be connected to the clamping rings 238, 238' in a simple manner.

With the example of embodiment according to Figs. 13 to 15, motor drives 248, 248' are respectively provided for the clamping rings 238, 238' instead of the actuating rods. The motor drive can be provided in the form of servo-motors, operating magnets and suchlike, which can be actuated from the side of the furniture facing the user. The motor drives 248, 248' each have a threaded spindle 249, 249' which screws into the threaded holes at the ends 240, 240a, 240', 240a' of the clamping rings 238, 238'. As for the rest, this example of embodiment has the same design as the form of embodiment according to Figs. 7 to 9. Using the motor drives 248, 248', the clamping rings 238, 238' can be readily actuated when adjusting the top 203.

With the example of embodiment according to Figs. 16 to 18, the actuating shaft 231 is motor-driven and is displaced axially by motor. One end of the actuating shaft 231 is connected to a motor sliding drive 250, which is an actuator and by means of which the actuating shaft can be displaced axially. The other end of the actuating shaft 231 is connected to a drive motor 251 by means of which the actuating shaft 231 can be rotated.

The drive motor 251 has a drive bush 252, into which the actuating shaft 231 projects. The drive bush 252 is provided with a slot 253 which runs axially, into which a guide pin 254 standing out radially from the actuating shaft projects. The slot 253 is so long and the guide pin 255 so provided on the actuating shaft 231 that the drive connection between the drive bush 252 and the actuating shaft 231 is ensured in every axial position of the actuating shaft.

The coupling parts 235, 235' are again mounted on the actuating shaft 231, the former being able to engage the helical gears 230, 230' in the manner described.

There are no helical springs with this form of embodiment. In contrast, the gear wheels 220, 220' are driven in a rotary manner directly by the helical gears 229, 229'. They are mounted torsion-resistant on the shafts 221, 221'. Depending on the axial position of the actuating shaft 231, both gear wheels 220, 220' or only one of the two gear wheels are driven in a rotary manner, so that both toothed segments 204, 204' or only one of these toothed segments is accordingly swivelled.

The drive motor 251 does not have to be arranged on an end of the actuating shaft 231. It can, for example, also be provided in the area between the two gears 233, 233', as indicated in Fig. 16 by dot-and-dash lines. In this case, the drive shaft 255 of the drive motor 251 is connected to it in a drivable fashion via a bevel gear 256 which permits axial movements of the actuating shaft 231.

With forms of embodiment described, the toothed segments can also be replaced by gear racks curved in the shape of an arc.

Claims (31)

1. An adjustment device for adjusting the tilt and/or height of a bench or table top of a piece of furniture, with a lifting element which engages the bench or table top and is connected to a drive, characterised in that the adjustment device has a further lifting element, anc; in that both lifting e;ements lie beside one another and are each designed as curved gear racks, each of which engages a gear wheel of the drive and each of which is guided by a guideway.

2. An adjustment device according to claim 1, characterised in that the gear rack has at least one guide part by means of which it is guided in the guideway.

3. An adjustment device according to claim 2, characterised in that the guide part is a bolt, a roller or such like, which engages the guideway made in the form of a slot.

4. An adjustment device according to any one of claims 1 to 3, characterised in that the drive is formed by two intermeshing helical gears whose axes are at rightangles to one another.

5. An adjustment device according to any one of claims 1 to 4, characterised in that the gear rack on its side facing away from the bench or table top is supported on at least one supporting part which is preferably a roller.

6. An adjustment device according to any one of claims 1 to 5, characterised in that the adjustment device has a synchronous operation which exhibits a shaft which extends perpendicular so the gear rack and is connected to the drive such that it can be driven.

7. An adjustment device according to any one of claims 1 to 6, characterised in that the drive has a shaft stub which is connected in a torsion-resistant manner to an intermediate shaft.

8. An adjustment device according to claim 7, characterised in that the one helical gear of the drive is mounted in a torsion-resistant on the shaft stub.

9. An adjustment device according to any one of claims 1 to 8, characterised in that the gear rack is arranged such as to be concealed for the greater part of its length.

10. An adjustment device according to any one of claims 1 to 9, characterised in that the gear rack with one end on a mounting plate and with the other end on a rail connected to the bench or table top is moved by sliding.

11. An adjustment device according to claim 10, characterised in that the mounting plate has a slot running in its longitudinal direction, which is engaged by the one gear rack with the guide part.

12. An adjustment device according to claim 10 or 11, characterised in that the rail has a curved slot in the form of an arc, which is engaged by a gear rack with the guide part.

13. An adjustment device according to any one of claims 1 to 12, characterised in that the other gear rack with the one end on the rail is moved in a sliding manner preferably on a curved slot in the form of an arc, and is attached with its other end to the mounting plate.

14. An adjustment device according to any one of claims 1 to 13, characterised in that the gear racks can be displaced roughly synchronously in opposite directions.

15. An adjustment device according to any one of claims 1 to 14, characterised in that the two gear racks are guided between two metal parts.

16. An adjustment device according to any one of claims 1 to 15, characterised in that there is connected to the one metal part an intermediate plate which preferably lies between the metal part and the mounting plate and is preferably adjustable in the height direction relative to the one metal part and the mounting plate.

17. An adjustment device according to claim 16, characterised in that the one metal part has at least two driver pins which fit into the slots of the intermediate plate, which slots preferably extend in the height direction of the intermediate plate.

18. An adjustment device according to claim 16 or 17, characterised in that the intermediate plate in its lower end position rests on the guide part of the one gear rack and on the swivelling part of the other gear rack.

19. An adjustment device according to any one of claims 1 to 18, characterised in that the drive connection between the drive of the one gear rack and the actuating shaft can be removed by a coupling.

20. An adjustment device according to any one of claims 1 to 19, characterised in that the gear rack is provided on a toothed segment which preferably has a cutout, one edge of which is provided with toothing.

21. An adjustment device especially according to any one of claims 1 to 20, characterised in that it has two gear trains which can be connected by an axially displaceable actuating shaft, which is connected to two coupling parts which can optionally engage the gear wheels of the gear train.

22. An adjustment device according to claim 21, characterised in that the coupling parts are mounted on the actuating shaft.

23. An adjustment device, especially according to claim 21 or 22, characterised in that at least one helical spring is located, as a power transmission agent, in the drive connection from the gear train to the gear wheel of the lifting element.

24. An adjustment device according to claim 23, in which the gear train is connected to a further gear train via a dumb-bell shaft, characterised in that the one end of the helical spring is rigidly connected to the one gear wheel of the gear train and the other end is rigidly connected to a brake track which is mounted torsion-resistant on the dumb-bell shaft, and that the one gear wheel of the gear train is mounted rotatably on the dumb-bell shaft.

25. An adjustment device according to claim 24, characterised in that there is mounted on the brake track a clamping ring with which the brake track can be clamped in place and which can preferably be displaced by means of an actuating rod or by a motor drive out of the clamping position into a release position.

26. An adjustment device according to any one of claims 23 to 25, characterised in that the helical spring encompasses the actuating shaft.

27. An adjustment device according to any one of claims 23 to 26, characterised in that both gear trains and both lifting elements are connected by two actuating shafts to two further gear trains and lifting elements, and that on each actuating shaft a brake track is mounted torsion-resistant and can in each case be clamped by means of a clamping ring.

28. An adjustment device according to any one of claims 21 to 27, characterised in that there is provided between the two clamping rings at least one coupling part through which an actuating rod can be coupled optionally with both or one of the clamping rings, and which is preferably a pin projecting at rightangles from the actuating rod, which in the coupling position engages a slot from counter-coupling parts of clamping rings.

29. An adjustment device according to any one of claims 21 to 28, characterised in that the actuating shaft can be axially displaced by means of a motor or magnetic drive.

30. An adjustment device according to any one of claims 21 to 29, characterised in that the actuating shaft can be rotated by a drive motor.

31. An adjustment device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.