A LOCKING DEVICE

Abstract: A locking device (19) is adapted to releasably interlock a table frame (10) and a table top (11), the vertical level of which is adjustable. The locking device comprises a locking member (26) moveable between locking and releasing positions. The locking member (26) is connected to an operating pedal or handle (20) via a tension wire or Bowden cable (21). In order to prevent the locking member (26) from being released when a load placed on the table top (11) is too heavy, a tension spring (29) or another elastic member is inserted in the tension wire (21).

Description: A LOCKING DEVICE A locking device for releasably interlocking a table frame and a table top and table including such device. The present invention relates to a locking device for releas- ably interlocking a table frame and a table top which is adjustable in height in relation to the table frame. In the known tables of this type the weight of the table top and of possible objects supported thereby may be balanced by adjustable spring means, such as a gas spring or a torsion spring, which means that the resulting vertical force applied to the table top is about zero or at any rate rather small . The table top is releasably interlocked with the table frame by means of a locking member which may be moved to an inactive releasing position when the user operates a pedal or another operating member. However, if the user inadvertently releases the locking member while an extra force is being applied to the table top, for example because the user is leaning against the table top, the table top would move to its lowermost position very rapidly. Similarly, the table top may move very rapidly to its uppermost position if the locking member is released when a heavy object, which is usually supported by the table top, has been removed. In both cases the table may be damaged or the user may be injured. WO 8810081 discloses an adjustable table of the above type having a locking member which may be activated by a pedal via force transmission means comprising a wire and a two-armed lever which may be moved in abutting engagement with the locking member in the form of a second lever. A resulting vertical force applied to the table top is transformed into a torque applied to a spindle. If such torque exceeds a certain maximum value the locking member is moved out of the path of movement of the two-armed lever, which means that the force transmitting means are rendered inactive. The locking device according to the invention is of this known type comprising a locking member moveable between an active locking position, in which the table top is in an adjusted position in relation to the frame, and an inactive releasing position in which the height of the table top may be adjusted, an operating member being in force transmitting connection with the locking member by force transmitting means so that the locking member may be moved from its active locking position to its inactive releasing position by operating the operating member, and means for inactivating the force transmitting means when a resulting vertical force exceeding a predetermined maximum is applied to the table top, and the locking device according to the invention is characterized in that the force to be overcome for moving the locking member from its active locking position to its inactive releasing position increases in response to the resulting vertical force applied to the table top, and that the force transmitting means comprise resilient means having a resiliency so as to allow movement of the locking member from its active locking position to its inactive releasing position only when the resulting vertical force acting on the table top does not exceed said predetermined maximum. In the locking device according to the invention the force to be overcome for moving the locking member into its inactive releasing position may be the frictional forces acting between the locking member and the member being locked. Therefore, the force transmitting means may be a simple force transmitting connection between the operating member and the locking member via an elastic member, such as a spring. This means that the locking device according to the invention is considerably simpler than the known locking device described above . The locking device according to the invention may further comprise telescopically interengaging parts, which are connected to the table frame and to the table top, respectively, and which have a plurality of transverse openings or bores formed along the lengths of the telescopic parts, the locking member comprising one or more projections or pins, which may be moved into and out of engagement with aligned openings or bores in the telescopic parts. When the pull of gravity acting on the table top is approximately balanced by suitable means, such as gas springs, torsional springs, tension springs or the like, the frictional forces to be overcome for pulling the projections or pins of the locking member out of engagement with the aligned openings or bores in the telescopic parts is so small that the necessary force may without any problems be transmitted from the operating member to the locking member via the force transmitting means, which include the resilient means. If, however, the gravitational pull acting on the table top is not well balanced the force required for pulling the projections or pins of the locking member out of engagement with the aligned openings or bores of the telescopic part cannot be transmitted by the resilient means. Thus, when the operating member is actuated the resilient means will just be stretched or prolonged, while the locking member will remain in its active locking position. Alternatively, the locking device may comprise a rotatable member connected to the table top such that the rotatable member is forced to rotate when the position of the table top is adjusted in relation to the table frame, the locking member comprising one or more projections or pins which may be moved into and out of engagement with openings or cutouts formed in the rotatable member. Also in this case the projections or pins of the locking member cannot be moved out of engagement with the rotatable member unless the gravitational pull acting on the table top is fairly well balanced. The rotatable member may be of any kind having a circular arrangement of openings or cutouts . In a preferred embodiment the rotatable member is a gear wheel and the projections or pins of the locking member may then be moved into and out of engagement with the spaces between the teeth of the gear wheel. The gear wheel may, for example, be rotatably mounted on the table frame and be in engagement with a rack mounted on the table top such that the gear wheel or pinion is rotated when the table top is moved in relation to the table frame. Preferably, the locking member is spring biassed towards its active locking position. This means that the locking member is automatically biassed into locking engagement when the operating member is released. In that case not only the frictional forces between the locking member and the member being locked, but also the spring bias should be overcome in order to move the locking member from its active locking position into its inactive releasing position. The force transmitting means interconnecting the operating member and the locking member may be of any suitable kind, such as a linked connection. In the preferred embodiment, however, the operating member is connected to the locking member by means of an elongated tension member, such as a wire or string, which may include the resilient means. The resilient means may, for example, be a coil spring, a spiral spring or any other kind of elastic member, such as a length of a string made from rubber or elastic plastic material. Preferably, the elongated tension member is a Bowden wire. The operating member may be a manually operateable handle or any other kind of operating member, such as a pedal. For some applications it is desirable that the force trans - mitting means, which may comprise an elongated tension member, defines a substantially right angle or an acute angle with the path of movement of the locking member. This may be obtained by an embodiment in which the force transmitting means comprise a pivotal member and an elongated tension member, which extends between the operating member and a first connecting point of the pivotal member. The locking member may then be connected to a second connecting point of the pivotal member and each of said first and second connecting points may be spaced from the pivot point of the pivotal member and said first and second connecting points may be mutually angularly spaced. The pivotal member may be a circular member, a sector of a circle or the like. Alternatively, the pivotal member may be an angular member comprising a pair of arms extending from said pivot point, said first and second connecting points being located at the free ends of said arms . According to a further aspect the present invention relates to a table comprising a frame and a table top which is adjustable in height in relation to the table frame, and the locking device of the type described above releasably interlocking the table frame at the table top. The invention will now be further described with reference to the drawings, wherein Fig. 1 is a perspective bottom view of part of a table accor- ding to the invention, Figs. 2, 3 and 4 are plan, side and end views, respectively, of a first embodiment of the locking device mounted on the table shown in Fig. 1, and Fig. 5 is a plan view as that shown in Fig. 2 where a cover member has been removed, Figs. 6-8 are a sectional views of a second embodiment of the locking device according to the invention shown in a locking position, an activated but still locked position, and in a released position, respectively, and Fig. 9 illustrates a table having a locking device as that shown in Figs. 6-8 mounted thereon. Fig. 1 shows the table having a table frame 10 and a table top 11 which may be moved vertically in relation to the table frame and locked in a desired vertical position. The table frame 10 comprises a pair of vertically extending posts 12 arranged at either end of the table top 11, and a transversely extending foot member 13 is connected to the lower end of each post 12. The shaft 14 extends longitudinally below the table top 11 and is rotatably mounted in rela- tion to the table top. A gear wheel 15 mounted at each end of the shaft 14 is engaging with a stationary, substantially vertically extending rack (not shown) , which is mounted within each of the posts 12. Thus, when the table top is moved up and down the interengaging gear wheels 15 and racks force the shaft 14 to rotate. The force of a torsion spring 16 mounted around the shaft 14 is substantially balancing the weight of the table top 11 and possible items supported thereby so that the table top 11 may rather easily be moved up and down in relation to the table frame 10. The shaft 14 and the spring 16 may be arranged within an elongated housing 17, and each of the gears 15 may be surrounded by a housing 18. When the height of the table top 11 has been adjusted the table top may be locked in its adjusted position in relation to the table frame 10 by means of a locking device 19 which may be operated by means of an operating handle 20, which is pivotally mounted on the bottom surface of the table top 11. The handle 20 is connected to the locking device 19 by means of a tension wire or Bowden cable 21. The locking device 19, which is shown in more detail in Figs. 2-5, comprises a housing 22 which is formed in to part interconnected by means of screws 23. In Fig. 5 one of the housing parts has been removed. The housing 22 comprises a pair of lugs 24 each having an opening for a fastening screw 25 by means of which the locking device 19 may be fastened to the housing 18 as shown in Fig. 1. The locking device 19 comprises a locking member or pawl 26 having a number of locking fingers 27 extending therefrom. As best shown in Fig. 4 the locking fingers 27 are arranged along an arc of a circle, and the locking device 19 is mounted such in relation to one of the gear wheels 15 that the locking fingers 27 may be moved into engagement with the gear wheel and be received in spaces defined between adjacent teeth of the gear wheel . The locking member 26 is moveable in relation to the housing 22 between a locking position in which the locking fingers 27 extends outwardly from the housing 22 and engages with the gear wheel 15, and a releasing position in which the locking fingers 27 are out of engagement with the teeth of gear wheel 15. The locking member 26 is biassed towards its locking position by compression springs 28 and the locking member may be moved to its releasing position when a pulling force sufficient to overcome the spring bias of the springs 28 is applied to the locking member from the operating handle 20 via the Bowden cable 21. If the gravitational pull and other forces acting on the table top 11 is not properly balanced by the torsion spring 16 the table may be damaged and/or the user may be injured if the locking device 19 is released. In order to ensure that the locking device 19 can be released only when the forces acting on the table top 11 is properly balanced by the torsion spring 16 a tension spring 29 or another kind of elastic member is inserted between the tension wire 21 and the locking member 26. The tension spring 29 is less resilient than the compression springs 28. Therefore, when the handle 20 is operated so as to apply the pulling force to the locking member 26 via the tension wire 21 and the tension spring 29 the spring bias of the compression springs 28 may be overcome and the locking member or pawl 26 may be moved to its releas- ing position without any substantial elongation of the spring 29. If, however, the forces acting on the table top 11 is not properly balanced by the torsion spring 16 the gear wheel 15 will tend to rotate and the teeth of the gear wheel are forced into close engagement with the locking fingers 27 of the locking member 26. This means that a substantially increased pulling force must be applied to the locking member 26 in order to overcome frictional forces acting between the gear wheel 15 and the locking fingers 27 and to move the locking member into its releasing position. However, such increased pulling force can not be transmitted via the ten- sion spring 29 which just become stretched. Consequently, the locking device 19 can be released only when the weight of the table top 11 and other forces acting thereon are properly balanced by the torsion spring 16. This means, that the tension spring 29 is a kind of safety spring ensuring that the table top can not be released unless it is properly balanced. Figs. 6-8 illustrate an alternative embodiment of the locking device 19. The housing 22 of the locking device 19 comprises a body part 30 and a lid part 31 connected to the body part by snap locking means. The spring biased locking pawl 26 with the fingers 27 is moveable substantially at right angles to the main wall of the lid part 31, while the tension wire 21 extends into the housing substantially parallel to the lid part wall. An angular pivotal member 32 is mounted within the housing 19 so as to be pivotal about a pivot axis 33 between a locking position shown in Fig. 6 and a releasing position shown in Fig. 8. The end of the tension wire 21 extending into the housing 19 is connected to the free end of one of the arms of the angular member 32 via the tension spring 29 and the free end of the other arm of the angular member is connected to the locking member or locking pawl 26. Fig. 7 illustrates a situation where the tension wire 21 and the spring 29 have been tensioned in an attempt to release the locking device 19. However, because the table top has been unduly loaded the tension force of the spring 29 is not sufficient to overcome the frictional forces acting on the fingers 27 so as to release the locking device. Fig. 7 illustrates a table comprising a frame 10 supporting a table top 11 such that the vertical level of the table top may be adjusted. The table frame which may be of the type disclosed in Danish patent application No. 0519/98 comprises locking discs 34, which are connected to moveable link members 35 of the adjustable table frame 10. The locking discs are provided with openings or bores 36 for receiving the fingers 27 of locking devices 19, which are mounted on wall or plate members 37 mounted on the table top 11. The locking devices may be operated by a pedal or handle, not shown, via Bowden cables 21. As shown in Fig. 7 the ends of the Bowden cables adjacent to the locking devices 19 may extend along and closely adjacent to the posts 12. It should be understood that several other embodiments of the locking device could be made within the scope of the present invention. As an example, the table top and the table frame may comprise telescopically interengaging members defining openings or bores therein. The locking member could then comprise a pin which may be received in aligned openings or bores in the telescopic parts. The tension spring 29 may be replaced by any kind of elastic member having a modulus of elasticity allowing movement of the locking member to its releasing position only when the forces acting on the table top is balanced to an acceptable degree.

Claims: CLAIMS 1. A locking device for releasably interlocking a table frame and a table top, which is adjustable in height in relation to the table frame, said locking device comprising a locking member moveable between an active locking position, in which the table top is locked in an adjusted position in relation to the frame, and an inactive releasing position, in which the height of the table top may be adjusted, an operating member being in force transmitting connection with the locking member by force transmitting means so that the locking member may be moved from its active locking position to its inactive releasing position by operating the operating member, and means for inactivating the force transmitting means when a resulting vertical force exceeding a predetermined maximum is applied to the table top, characterized in that the force to be overcome for moving the locking member from its active locking position to its inac- tive releasing position increases in response to the resulting vertical force applied to the table top, and that the force transmitting means comprise resilient means having a resiliency so as to allow movement of the locking member from its active locking position to its inactive releasing posi- tion only when the resulting vertical force acting on the table top does not exceed said predetermined maximum. 2. A locking device according to claim 1, further comprising telescopically interengaging parts, which are connected to the table frame and to the table top, respectively, and which have a plurality of transverse openings or bores formed along the lengths of the telescopic parts, the locking member comprising one or more projections or pins, which may be moved into and out of engagement with aligned openings or bores in the telescopic parts. 3. A locking device according to claim 1, further comprising a rotatable member connected to the table top such that the rotatable member is forced to rotate when the position of the table top is adjusted in relation to the table frame, the locking member comprising one or more projections or pins, which may be moved into and out of engagement with openings or cutouts formed in the rotatable member. 4. A locking device according to claim 3 , wherein the rotatable member is a gear wheel . 5. A locking device according to any of the claims 1-4, wherein the locking member is spring biassed towards its active locking position. 6. A locking device according to claim 5, wherein the operating member is connected with the locking member by means of an elongated tension member, such as a wire, which may include the resilient means. 7. A locking device according to claim 5 , wherein the force transmitting means comprise a pivotal member and an elongated tension member which extends between the operating member and a first connecting point of the pivotal member, the locking member being connected to a second connecting point of the pivotal member, each of said first and second connecting points being spaced from the pivot point of the pivotal member and said first and second connecting points being mutually angularly spaced. 8. A locking device according to claim 7 , wherein the pivotal member is an angular member comprising a pair of arms extending from said pivot point, said first and second connecting points being located at the free ends of said arms. 9. A locking device according to any of claims 6-8, wherein the elongated tension member is a Bowden wire. 10. A locking device according to any of the claims 1-9, wherein the operating member is a pedal. 11. A table comprising a frame and a table top which is adjustable in height in relation to the table frame, and a locking device according to any of the claims 1-10 for releasably interlocking the table frame and the table top.

Inventors: OHLSEN HENRIK ALMEGAARD, OHLSEN, HENRIK, ALMEGAARD
Applicants: OHLSEN HENRIK ALMEGAARD, SIS INT AS, OHLSEN, HENRIK, ALMEGAARD, SIS INTERNATIONAL A/S
Application year: 1998
Main classification: A47B9
IPC codes: A47B9