Abstract:
A load suspension stand includes a first stand member, a second stand member, a joint pivotably connecting the first with the second stand member, a cam plate rotatably fixed to the first stand member, a load transmission lever, an abutment pivotably supporting the load transmission lever at the second stand member, a load reservoir, acting on the second stand member and on the load transmission lever in order to exert a force F 1  on the cam plate by means of the load transmission lever, and a drive for displacing the abutment relative to the load transmission lever.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to German Patent Application No. 10 2008 060 725.8, filed Dec. 5, 2008, entitled “Load Suspension Stand and Microscopy System,” the contents of which is hereby incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    A conventional stand comprises a plurality of components or stand members articulating in pairs, whereby a base stand member is supported by an object like, for instance, a flooring or a wall, and a load is suspended by a final stand member. By shifting the stand members relative to each other using the links joining them, it is possible to shift the load with respect to the object. 
         [0003]    One example for such a stand is represented by a stand of a microscopy system carrying a load in the form of a microscopy optic. Such a microscopy system can be used for surgical interventions, whereby the microscopy optic is suspended by the stand such that a surgeon can shift it relative to a patient practically without exerting any force, i.e. by applying only minor actuating forces. This requires that the torsional moments exerted on the stand members by the weight of the microscopy optic and the weight of the stand members themselves are, as far as possible, compensated by the stand in all possible swiveling positions of the stand members relative to each other. The stand should further be adapted to support different microscopy optics differing from each other with respect to its weight and its center of mass position. Attaching additional components like a camera or additional eyepieces may, for example, modify the weight and the center of mass of a microscopy optic. To allow a compensation of the torsional moments exerted on the stand members independent of the swiveling positions, the stand has to be adjusted to such modifications. 
         [0004]    Examples of such stands are, for instance, known from DE 42 45 034 C2, DE 42 31 516 C2, EP 1 205 703 B1, EP 1 312 850 B1, U.S. Pat. No. 6,523,796 B2, and WO 2007/054327 A1. 
         [0005]    It has been found that conventional stands are inadequate for an adaptation to modified load situations practically independent of the swiveling positions. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention has been accomplished taking the above problems into consideration. 
         [0007]    According to embodiments of the present invention, a load suspension stand provides possibilities for an adaptation to different load situations. 
         [0008]    According to further embodiments of the present invention, a microscopy system provides options for modifying a microscopy optic. 
         [0009]    According to embodiments, a load suspension stand comprises at least a first component, a second component, a swivel joint linking the first to the second component, and a structure for providing a torsional moment at the joint between the two components. According to embodiments of the present invention, the structure is configured such that the torsional moment provided is modified subject to the swiveling position of the two components with respect to each other. 
         [0010]    According to embodiments, the structure is further configured to enable a modification of the characteristic with which the torsional moment provided varies subject to the swiveling position using a drive. The drive may comprise an actuator, such as a motor. The drive may be configured for manual operation and comprise a manually operable rotary knob for that purpose. 
         [0011]    According to embodiments, the structure comprises a cam plate rotatably fixed to the first component, and a load transmission lever being supported by the second component and configured to exert a force onto the cam plate. The force acting on the cam plate results in a torsional moment between the two components, whereby it is possible to adjust a desired characteristic of the torsional moment subject to the swiveling position of the two components relative to each other by a suitable configuration of the cam plate. 
         [0012]    According to an embodiment, the structure for providing the torsional moment comprises a cam plate being rotatably fixed to the first component of the stand, a load transmission lever, an abutment for a swiveling support of the load transmission lever on the second component of the stand, and a load reservoir acting on the second component and on the load transmission lever, in order to have the load transmission lever exert a force on the cam plate. 
         [0013]    According to embodiments of this, the load reservoir comprises a spring, like, for instance, a helical spring, a leaf spring or a gas pressure spring. In order to provide the required load, the spring can be biased in a compressed or in an expanded way. 
         [0014]    According to embodiments, the abutment for a swiveling support of the load transmission lever on the second component can be shifted, relative to the load transmission lever, by a drive enabling a modification of the position on the load transmission lever effective for supporting the load transmission lever relative to the second component. This allows modification of the lever action for transmitting the load provided by the load reservoir to the load transmission lever, which results in a modification of the force induced from the load provided by the load reservoir that is acting on the cam plate. 
         [0015]    According to embodiments herein, the load transmission lever can exert the force directly onto the cam plate, whereby the load transmission lever may provide options for reducing the friction force between the load transmission lever and the cam plate. These options may, for instance, comprise a roller being rotatably mounted on the load transmission lever or a provision of friction reducing surfaces on the load transmission lever, like, for instance, sliding faces of synthetic material. 
         [0016]    According to further embodiments, the load is transmitted indirectly from the load transmission lever to the cam plate by disposing, for instance, a further swiveling intermediate lever in the line of force from the load transmission lever to the cam plate. 
         [0017]    According to embodiments, the force transmitted from the load transmission lever onto the cam plate acts on a periphery of the cam plate. The cam plate is then configured such that a distance or a radius of the cam plate between its center and its periphery varies in the circumferential direction around the cam plate. According to alternative embodiments herein, the cam plate may further provide an inside circumferential surface on which a force directed radially outwards from the centre of the cam plate acts to generate the required swiveling position dependent torsional moment. 
         [0018]    According to embodiments, the abutment supporting the load transmission lever comprises a roller having the load transmission lever abutted against its outside periphery. According to an embodiment herein, the drive comprises a slide being displaced relative to the second component and being also abutted against the outer periphery of the roller. 
         [0019]    According to embodiments, the roller can be provided with cogs on its outer periphery and both the slide and the load transmission lever may be configured with a cog rail for engaging with the cogs of the roller. 
         [0020]    According to further embodiments, a microscopy system is provided comprising a stand according to the previously described embodiments and a load formed by a microscope. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The forgoing as well as other advantageous features of the invention will be more apparent from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings, wherein 
           [0022]      FIG. 1  shows a schematic representation of an embodiment a microscopy system, 
           [0023]      FIG. 2  shows an elevational view of a portion of an embodiment of a stand, and 
           [0024]      FIG. 3  shows a sectional view of the portion of the stand shown in  FIG. 2  along the section line II-II shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    In the exemplary embodiments described below, components that are alike in function and structure are designated as far as possible by alike reference numerals. Therefore, to understand the features of the individual components of a specific embodiment, the descriptions of other embodiments and of the summary of the invention should be referred to. 
         [0026]    Embodiments of a stand and of a microscopy system comprising a stand are explained below in relation to  FIGS. 1 to 3 . 
         [0027]    A microscopy system  1  as shown schematically in a perspective view in  FIG. 1  comprises a microscope  3  mounted on a stand  5 . The stand  5  comprises a base  9  provided with wheels  7  to form a base portion of the stand. The base  9  supports a stand member  13  by means of a swivel joint  11  so that the stand member  13  can be pivoted around a pivoting axis  15  extending vertically into space. A further stand member  17  is mounted on the stand member  13  by means of a joint  19  such that it can be swiveled around a horizontal swiveling axis  21 . A further stand member  23  is in turn mounted on the stand member  17  by means of a joint  25  so that it can be pivoted around a horizontal pivoting axis  27 . A further stand member  29  is in turn mounted on the stand member  23  by means of a joint  31  so that it can be pivoted around a horizontal pivot axis  33 . The stand member  29  in turn supports a stand member  35  by means of a joint  37  so that it can be pivoted around a pivot axis  39 . A further stand member  41  is in turn articulated to the stand member  35  by means of a joint  43  so that it can be pivoted around a pivot axis  45 , and finally a chassis  47  of the microscope is articulated to the stand member  41  serving as the final stand member of the stand  5  by means of a joint  49  so that it can be pivoted around a pivot axis  51 . This allows a shifting of the microscope  3  within an available space and an alignment of its orientation in space by swiveling the stand members around the pivot axes. 
         [0028]    Two counterweights  18  of the stand  5  are configured to substantially balance the microscope  3  with respect to the swiveling axes  21  and  27 , so that a user only has to overcome the residual friction force when swiveling the stand around these axes. Also for swiveling around a vertically aligned pivot axis  15 , a user only has to overcome the residual friction force. 
         [0029]    The weight of the microscopy optic  3  and the weight of the stand member  41  generate a torsional moment around the swiveling axis  45  that acts on the stand member  35  via joint  43 . The torsional moment depends on a swiveling position between the two stand members  35  and  41 . A structure, which is explained below in more detail with respect to  FIGS. 2 and 3 , for compensating for this torsional moment is provided on the stand members  35  and  41 . 
         [0030]    The two stand members  35  and  41  can be swiveled relative to each other around the pivot axis  45 , with the corresponding joint comprising a shaft  51  aligned coaxially to the axis  45  and rotatably fixed to the stand member  35  and pivot-mounted with respect to the stand member  41 . Limbs  53  and  54  arranged with a clearance between them and forming part of a U-profile  55  are interspersed with a shaft  51 . Stand member  41  is fixed to limb  54  of the U-profile  55 , and the U-profile  55  comprises a base plate  56  from which the two limbs  53  and  54  protrude in a perpendicular direction. A cam plate is located in the centre between the two limbs  53  and  54  and affixed to the shaft  51  in a rotationally fixed manner. The cam plate  57  has an outside circumferential surface  58  which distance r to the pivot axis  45  varies in the circumferential direction. In  FIG. 3  two distances r 1  and r 2  are shown as an example for different circumferential directions, whereby the directions of the two distances differ by an angle α of more than 20°, and whereby the ratio of r 2  to r 1  is more than 1.1. 
         [0031]    A roller  61  abuts against the outer periphery  58  of the cam plate  57  with a force F 1  such that, because of the configuration of the circumferential surface  58 , a torsional moment D acts on the shaft  51  around the axis  45 . The roller  61  is mounted rotatably around an axis  67  by means of a shaft  66  and between a pair of intermediate levers  63  and  64 . The two intermediate levers  63  and  64  can in turn be pivoted around a pivot axis  69  by means of a shaft  70  mounted on the limbs  53  and  54 , whereby the shaft  70  is on both sides fixed to the limbs  53  and  54  of the U-profile  55 . The two intermediate levers  63  and  64  jointly carry a pin  71  extending in parallel to the pivot axis  69  between the two intermediate levers  63  and  64 . A load transmission lever  73 , abutted against a slide  77  by means of a roller  75  serving as an abutment, pushes against the pin  71  with a force F 2 . A pin  79  further pushes against the load transmission lever  73  with a force F 3 . The force F 3  is provided by a spring  81 , which abuts against a cover plate  83  fixedly attached to the limbs  53  and  54  of the U-profile  55 , and against a spring receptacle  85  coupled to pin  79 . The load transmission lever  73  transforms the force F 3  provided by spring  81  in to force F 2 , mainly in the ratio of the lengths l 1  to l 2 , with length l 1  corresponding to the distance between pin  79  and the position at which the load transmission lever  73  abuts against the roller  75 , and with length l 2  corresponding to the distance between pin  71  and the position at which the load transmission lever  73  abuts against roller  75 . Intermediate lever  63  in turn translates the force F 2  into force F 1  pushing against the periphery  58  of the cam plate  51  and according to the ratio of the lengths l 3  and l 4 , whereby length l 3  corresponds to the distance between pin  71  and the pivot axis  69  of the intermediate lever  73 , and the length l 4  corresponds to the distance between the pivot axis  69  and the rotary axis  67  of roller  61 . 
         [0032]    Slide  77  abuts against the base  56  of the U-profile  55  by means of rollers  89  accommodated in a cage  87  such that the slide  77  can be shifted back and forth along a direction  91  and such that the forces F 3  and F 2  exerted by roller  75  on slide  77  are transferred by the rollers  89  onto the U-profile  55 . 
         [0033]    A drive  93  is provided for displacing the slide  77  in direction  91 , the drive comprising a motor  95  with a cog  97  mounted on its driven shaft  96  engaging into a cog wheel  98  for driving a shaft  99  mounted in a bearing block  101 . The shaft  99  extends into a recess  103  formed in slide  77 . Recess  103  is provided with a female thread engaging with a male thread  105  provided on shaft  99  for transforming a rotational movement of shaft  99  in a linear displacement of a slide  77  along direction  91 . The displacement of slide  77  along direction  91  results in a rotation of the roller  75  around its axis, thereby displacing it relative to the load transmission lever  73 . By displacing the roller  75  relative to the load transmission lever  73 , both lengths l 1  and l 2  vary and thus also the ratio with which force F 3  provided by spring  81  is transmitted into force F 2 , which is in turn transmitted by intermediate levers  63  and  64  into force F 1  acting on cam plate  57 . Force F 1  can therefore be characterized by: 
         [0000]    
       
         
           
             
               
                 F 
                 1 
               
               = 
               
                 
                   
                     l 
                     3 
                   
                   
                     l 
                     4 
                   
                 
                 × 
                 
                   
                     l 
                     1 
                   
                   
                     l 
                     2 
                   
                 
                 × 
                 c 
                 × 
                 Δ 
                  
                 
                     
                 
                  
                 S 
               
             
             , 
           
         
       
     
         [0000]    whereby c represents the spring rate of spring  81 , and ΔS represents the length of the biased springs  81 . 
         [0034]    Since the relation l 1  to l 2 , as well as the spring rate c of the spring, are factors in the above equation, the roller or abutment  75 , the slide  77  and its drive  93  thus combine to form a drive for varying the effective spring rate of spring  81 . The product c×l 1 /l 2  can therefore be interpreted as the spring rate of spring  81  effective at the periphery  58  of cam plate  57 . An operation of motor  83  therefore results in a variation of the effective spring rate, which could otherwise only be achieved by replacing spring  81  with a stronger or weaker spring. 
         [0035]    The structure explained with reference to  FIGS. 2 and 3  can therefore be used effectively for operatively compensating the torsional moments generated by microscopy optic  3  and stand member  41  which acts on the pivot axis  45 . The structure can in particular be used to compensate for variations of the microscopy optics  3  centre of mass using motor  95 . 
         [0036]    For achieving a precise displacement of roller  75  relative to the load transmission lever  73 , roller  75  is formed by a cog wheel with cogs  105  formed at its periphery, whereby the slide  77  and the load transmission lever  73  comprise corresponding cog rails with cogs  106  and  107  adapted to engage with cog wheel  75 . 
         [0037]    In the embodiment described above, the load transmission lever  73  transmits the force provided by springs  81  first to the intermediate levers  63  and  64 , which eventually transmit the force to the cam plate  57 . It is, however, possible to omit the intermediate levers so that the load transmission lever  73  transmits the force directly to the cam plate. 
         [0038]    The structure for providing a variable torsional moment as explained with reference to  FIGS. 2 and 3  is provided between the stand members  35  and  41  of a microscopy system according to an exemplary embodiment as explained with reference to  FIG. 1 . However, it is appreciated that a respective structure can also be provided between other stand members. 
         [0039]    The present invention has been described by way of exemplary embodiments to which it is not limited. Variations and modifications will occur to those skilled in the art without departing from the scope of the present invention as recited in the appended claims and equivalents thereof.