Linkage mechanism

Abstract

A linkage mechanism for mounting a movable support to a fixed member for movement between a first position and a second position. The mechanism includes a first linkage arm respectively connected at each end to the fixed member and the movable support and second linkage arm having one end connected to the movable support and the other to a connector located intermediate the ends of the first linkage arm. A third linkage arm extends between the movable support and the connector. The connector controls the movable support during the movement between the first and second positions. A two link arrangement is also disclosed having a pair of linkage arms extending between a movable support and a fixed member. The linkage arms being linked by a connector intermediate their respective ends.

I claim:  
     
         1 . A linkage mechanism for mounting a movable support to a fixed member for movement between a first position and a second position, the mechanism including: 
 a first linkage arm that extends between a first end and a second end that are respectively connected to the fixed member and the movable support;    a second linkage arm that extends between a third end and a fourth end, wherein the third end is connected to the fixed member;    a third linkage arm that extends between a fifth end and a sixth end, wherein the sixth end is connected to the movable support; and    a connector for connecting the fourth end and the fifth end to the first linkage arm intermediate the first end and the second end for controlling the movable support during the movement between the first and second positions.    
     
     
         2 . A linkage mechanism according to  claim 1  wherein the connector further controls the attitude of the movable support during the movement of between the first and second positions.  
     
     
         3 . A linkage mechanism according to  claim 1  wherein the first linkage arm includes a control formation and wherein the connector slideably connects the fourth end and the fifth end to the control formation.  
     
     
         4 . A linkage mechanism according to  claim 3  wherein the control formation is a slot in the first arm and the connector is a pin that connects the fourth and the fifth ends and which is slideably received in the slot.  
     
     
         5 . A linkage mechanism according to  claim 1  wherein the connector is a fourth linkage arm that extends between a seventh end and an eighth end that are respectively connected to the fourth end and the fifth end by respective pins, and wherein the control formation includes two slots that are spaced apart in the first linkage arm and which receive respective one of the pins.  
     
     
         6 . A linkage mechanism according to  claim 5  wherein the two slots are joined to form a single slot.  
     
     
         7 . A linkage mechanism according to  claim 1  wherein the first, second, third and sixth ends are pivotally connected to the respective fixed member and movable support.  
     
     
         8 . A linkage mechanism according to  claim 7  wherein the first, second, third and sixth ends are pivotally attached at a fixed point to the respective fixed member and movable support.  
     
     
         9 . A linkage mechanism according to  claim 7  wherein one of the first, second, third and sixth ends are pivotally and slideably connected to the respective fixed member and movable support.  
     
     
         10 . A linkage mechanism according to  claim 9  wherein the pivotal and slideable connection allows selective locking of the support against relative movement.  
     
     
         11 . A linkage mechanism according to  claim 10  wherein the pivotal and slideable connection allows selective locking at one of a plurality of discrete further positions between the first and second positions.  
     
     
         12 . A movable support for a load, the movable support being mounted to a fixed member by a linkage mechanism for movement between a raised position and a lowered position, the support including: 
 a platform having an upper surface for supporting the load, the upper surface extending substantially along a plane; and    a mount extending upwardly from the platform for engaging with the linkage mechanism at an upper mounting point and a lower mounting point that is spaced apart from the upper mounting point, the mounting points being on opposite sides of the plane.    
     
     
         13 . A movable support according to  claim 12  wherein the lower mounting point is adjacent to the plane.  
     
     
         14 . A movable support according to  claim 12  wherein the mounting points are equally spaced from the plane.  
     
     
         15 . A movable support according to  claim 12  wherein the mount extends below the platform for providing additional load bearing capacity.  
     
     
         16 . A movable support according to  claim 15  wherein the mount includes two spaced apart support formations that each extend from one end that is connected to the linkage mechanism to another end that is disposed beneath the platform.  
     
     
         17 . A movable support according to  claim 16  wherein the support formations are mechanically linked by a cross member.  
     
     
         18 . A movable support according to  claim 12  wherein the platform includes a front edge, a rear edge spaced apart from the front edge, and two side edges joining the front edge and the rear edge.  
     
     
         19 . A movable support according to  claim 18  wherein the mount extends normally from the platform and defines the front edge.  
     
     
         20 . A movable support according to  claim 18  wherein the rear edge is bevelled or otherwise rounded to reduce the risk of inadvertent contact with the rear edge causing injury to a user of the support.  
     
     
         21 . A movable support according to  claim 12  wherein the linkage mechanism includes a lock for selectively preventing and allowing the movement between the raised and the lowered positions.  
     
     
         22 . An adjustable support for a load, the adjustable support being mountable to a fixed member by a linkage and including: 
 a base extending from the linkage and providing two spaced apart guide formations;    a platform for supporting the load, wherein the platform is mounted to the base for movement between a first position and a second position; and    two spaced apart control formations being associated with the platform for respectively inter-engaging with the guide formations such that the movement of the platform between the first position and the second position results in a change of inclination of the platform with respect to the base.    
     
     
         23 . An adjustable support according to  claim 22  wherein the guide formations are respective slots formed in the base and the control formations are respective sliders that extend from the platform and which are received within the corresponding slots.  
     
     
         24 . An adjustable support according to  claim 22  wherein the platform includes a platen having a substantially planar upper surface upon which the load is supported and a lower surface to which the sliders are mounted.  
     
     
         25 . An adjustable support according to  claim 22  wherein the guide formations are inclined with respect to each other to allow the application of an automatic locking force to lock the platform at one of a plurality of further positions intermediate the first and the second positions.  
     
     
         26 . An adjustable support according to  claim 25  wherein the locking force is increased with the weight of the load.  
     
     
         27 . An adjustable support according to  claim 22  wherein the platform, during movement between the first and second positions, follows a predetermined path due to the inter-engagement between the guide formations and the control formations.  
     
     
         28 . An adjustable support according to  claim 27  wherein the predetermined path includes both transverse and rotational components.  
     
     
         29 . An adjustable support for a load, the adjustable support being mountable to a fixed member and including: 
 a base for mounting to fixed member and having two spaced apart guide formations;    a platform for supporting the load, wherein the platform is mounted to the base for movement between a first position and a second position; and    two spaced apart control formations being associated with the platform for respectively inter-engaging with the guide formations such that the movement of the platform between the first position and the second position results in a change of inclination of the platform with respect to the base.    
     
     
         30 . An adjustable support according to  claim 29 , wherein the guide formations are slots and the control formation are sliders that are received within the respective slots, and wherein the slots are inclined with respect to each other so that the platform is gravitationally biased into locking engagement with the base.  
     
     
         31 . An adjustable support according to  claim 30  wherein the locking engagement is overcome by a force that is applied by a user such that, upon the removal of that force the platform returns into locking engagement with the base.  
     
     
         32 . A linkage mechanism for mounting a movable support to a fixed member for movement between a first position and a second position, the mechanism including: 
 an arm that extends between a first end and a second end that are respectively connected to the fixed member and the movable support;    a linkage that extends between a third end and a fourth end that are respectively connected to the fixed member and the movable support, the linkage further being connected, intermediate the third end and the fourth end, to the arm intermediate the first end and the second end for controlling the attitude of the movable support during the movement between the first and second positions.    
     
     
         33 . A linkage mechanism according to  claim 32  wherein the movement of the movable support between the first and second positions is along a predetermined path.  
     
     
         34 . A linkage mechanism according to  claim 32  wherein the attitude of the movable platform remains substantially constant throughout the movement between the first and second positions.  
     
     
         35 . A linkage mechanism according to  claim 32  wherein the linkage includes a first linkage member and a second linkage member that are respectively connected to the fixed member and the movable support, the members being rotatably mounted to each other at a mounting point.  
     
     
         36 . A linkage mechanism according to  claim 35  the mounting point corresponds to the connection between the arm and the linkage.  
     
     
         37 . A linkage mechanism according to  claim 32  wherein the linkage includes a first, second and third linkage members, where the first and the second linkage members are respectively connected to the fixed member and the movable support and the third linkage member extends between and is connected to the first and the second linkage members.  
     
     
         38 . A linkage mechanism according to  claim 32  wherein the arm includes a guide formation intermediate the first and second ends and the linkage includes a control formation intermediate the third and fourth ends wherein the guide and control formations define the connection between the arm and the linkage.  
     
     
         39 . A linkage mechanism according to  claim 38  wherein the control formation is mounted for relative movement with respect to the guide formation during the movement of the movable support between the first and second positions.  
     
     
         40 . A linkage mechanism according to  claim 39  wherein the guide formation is a slot formed in the arm and the control formation is a slider that extends from the linkage and which is received in the slot for slideable progression along the slot during the movement of the movable support between the first and second positions.  
     
     
         41 . A linkage mechanism according to  claim 40  wherein the slot has two ends that are abutted by the slider when the movable support is in the first and second positions respectively.  
     
     
         42 . A linkage mechanism according to  claim 32  further including a lock for selectively preventing and allowing the movement between the first and second positions.  
     
     
         43  A linkage mechanism according to  claim 42  wherein the lock includes a key element positioned on said arm and selectively engageable with said fixed member to prevent and allow said movement.  
     
     
         44 . A linkage mechanism according to  claim 43  wherein said key is operated by translational movement of said movable support relative to said fixed member.  
     
     
         45 . A linkage mechanism according to  claim 32  wherein at least one of the connections of the arm or linkage to the respective fixed member or movable support is a pivotal and slideable connection.  
     
     
         46 . A linkage mechanism for mounting a movable support to a fixed member for movement between a first position and a second position, the mechanism including: 
 a first linkage arm that extends longitudinally between a first end and a second end that are respectively connected to the fixed member and the movable support;    a second linkage arm that extends longitudinally between a third end and a fourth end that are respectively connected to the fixed member and the movable support;    a first connection element disposed intermediate the first end and the second end; and    a second connection element disposed intermediate the third and the fourth end and being mechanically linked with the first connection element during movement between the first and second positions for ensuring that a transverse load applied to any one of the arms is shared by both arms.    
     
     
         47 . A linkage mechanism according to  claim 46  wherein the first connection element includes a slot in the first linkage arm and the second connection element includes a pin that travels along the slot during the movement between the first and second positions.  
     
     
         48 . A linkage mechanism according to  claim 47  wherein the second linkage arm includes a first link that extends between the third end and a fifth end and a second link that extends between the fourth end and the fifth end.  
     
     
         49 . A linkage mechanism according to  claim 48  wherein the pin extends from the fifth end.