Abstract:
A lifting device is provided. The lifting device includes a top part and a bottom part. A lifting linkage connects the top part to the bottom part and has at least two sub-linkages connected to one another via a central articulation. A drive unit is operable to adjust the height of the top part and act on the central articulation.

Description:
[0001]     The present patent document is a continuation of PCT Application Serial Number PCT/EP2005/051223, filed Mar. 16, 2005, designating the United States, which is hereby incorporated by reference. 
     
    
     BACKGROUND  
       [0002]     1. Field  
         [0003]     The present embodiments relate to a lifting device.  
         [0004]     2. Related Art  
         [0005]     Lifting devices are generally known from the prior art. For example, WO 98/46137 discloses a lifting device that adjusts the height of a patient support. Parallelogram structures are used as lifting linkages. The known structures require a large amount of installation space. Large lifting forces are necessary for height adjustment. These lifting forces are not constant. Different displacement speeds arise during height adjustment. The known solutions, for example, are too large, involve too much design outlay and require excessively complicated controls.  
       SUMMARY  
       [0006]     In one embodiment, a lifting device includes a top part and a bottom part. A lifting linkage connects the top part to the bottom part and has at least two sub-linkages connected to one another via a central articulation. A drive unit is operable to adjust the height of the top part and act on the central articulation.  
         [0007]     The drive unit acts on a central articulation of a multi-part lifting linkage. This allows the lifting device to be of particularly straightforward and compact construction.  
         [0008]     In one embodiment, a scissors structure is used as a sub-linkage (lifting rod). The amount of installation space which is required for the lifting device is greatly reduced in comparison to the known constructions. In another embodiment, the lifting linkage comprises two scissors structures connected to one another in an articulated manner. This double scissors structure may be used to adjust the height of a top part, for example, a patient support, provided on the top scissors assembly. In this embodiment, the top part can be adjusted in an extremely confined amount of space.  
         [0009]     In another embodiment, it is also possible to use, for example, a triple or quadruple scissors mechanism. A multiple scissors structure has a high level of rigidity and bending strength when laterally occurring forces are absorbed.  
         [0010]     In one embodiment, the drive unit is designed to provide a rectilinear movement of the central articulation (joint) in the vertical direction. The drive unit is provided directly beneath the central articulation. The drive unit provides a constant displacement speed to the central articulation. The drive unit provides operative forces and particularly precise synchronization to the central articulation. In this embodiment, because a single drive unit is used, there is no need for a separate synchronization control. In this embodiment, the lifting device does not require arcuate pivoting of the lifting linkage or an associated need for more space.  
         [0011]     In another embodiment, the drive unit has a spindle and a motor. A spindle and a motor have relatively less maintenance than a hydraulic cylinder. In one embodiment, a vertically running spindle is driven, via a corresponding gear mechanism, by an electric motor with its axis of rotation perpendicular to the spindle axis. This embodiment allows a space-saving construction of the lifting device.  
         [0012]     In one embodiment, the spindle is a trapezoidal spindle. The spindle is not limited to a self-locking type of spindle. Other spindles may be used, for example, ball screw spindles. In one embodiment, the spindle, motor and gear mechanism are embodied such that the spindle flanks are always subjected to the load. Hydraulic cylinders have varying operating paths depending on design. In one embodiment, the drive unit is fixed, for example, there is no return play.  
         [0013]     In another embodiment, the motor is fastened on the bottom part, for example, on a base plate. Accordingly, there is sufficient space for the motor-control above the motor and there is no need for any moveable cable guide.  
         [0014]     In an alternative embodiment, a moveable motor is fastened on the central articulation and moves up and down on the spindle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  illustrates a perspective view of lifting device according to a first embodiment,  
         [0016]      FIG. 2  illustrates a perspective view of a lifting device according to a second embodiment, and  
         [0017]      FIG. 3  illustrates a plan view of a lifting device according to the second embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0018]     In one embodiment, as shown in  FIG. 1 , a lifting device  1  includes a bottom part, in the form of a base plate  2 , a top part, in the form of a patient support  3 , and a lifting linkage. The lifting linkage is configured as a double scissors mechanism or double scissors structure  4 . The double scissors structure  4  comprises, for example, two scissors assemblies  5 ,  6  as sub-linkages, which are connected to one another by a central articulation (joint)  16 .  
         [0019]     The bottom scissors assembly  6  is supported by the base plate  2 . The bottom scissors assembly  6  includes front scissor feet  7  and rear scissor feet  8 . The front scissor feet  7  are connected to the base plate  2 . As shown in  FIG. 2 , the rear scissors feet  8  of the bottom scissors assembly  6  are connected to one another via a slide  9 . For example, when the double scissors structure  4  is opened and closed, the slide runs back and forth in the running direction  11  on a running rail  10  fastened on the base plate  2 .  
         [0020]     In one embodiment, a horizontally arranged electric motor  12  is fastened on the base plate  2  between the front and the rear scissors feet  7 ,  8  of the bottom scissors assembly  6 . In an alternate embodiment, a hand crank (not illustrated) for emergency operation of the lifting device  1  is attached at that end of the electric motor  12  which is directed toward the rear scissors feet  8 . The axis of rotation  13  of the electric motor  12  runs parallel to the running direction  11  of the slide  9 . There is sufficient space for arranging a motor-controller (not depicted) above the electric motor  12 . A toothed gear mechanism  14  that converts the rotary movement of the electric motor  12  into a linear movement of a telescopic spindle  15  is located between the front scissors feet  7 . The spindle  15  is operable perpendicular to the axis of rotation  13  of the electric motor  12  and is arranged between the front scissors feet  7  and beneath the front central articulation  16  of the double scissors structure  4 . In one embodiment, the spindle  15  is designed as a trapezoidal screw spindle (ACME spindle) and has its spindle head connected in an articulated manner to the front central articulation  16  of the double scissors structure  4  via a transverse connection  17 . In another embodiment, the spindle  15  is a telescopic spindle.  
         [0021]     For example, for a height adjustment of the patient support  3 , the electric motor  12  is switched on and the telescopic spindle  15  is extended and retracted. The central articulation  16  of the double scissors structure  4  executes a rectilinear movement in the vertical direction  18  at a constant displacement speed and the slide  9  moves in the running direction  11 . The axis of rotation  13  of the electric motor  12  runs perpendicular to the spindle  15  axis. In one embodiment, the gear mechanism  14  is a self-locking gear mechanism. The spindle flanks are subjected to load and the telescopic spindle  15  does not exhibit any return play. The absolute-value sensor of a measuring system is fitted directly (not depicted) on the telescopic spindle  15 .  
         [0022]     In an alternative embodiment, as shown in  FIG. 2 , the lifting device includes a moveable motor  19 . In this embodiment, the electric motor  19  is fixed on the central articulation  16  of the double scissors structure  4 . For example, when the double scissors structure  4  opens and closes, the electric motor  19  moves up and down on a screw spindle  20  fixed on the base plate  2 .  
         [0023]     As shown in  FIG. 3 , a lifting device  1  requires only a particularly small base surface area.  
         [0024]     While the invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made without departing from the scope of the invention. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.