Abstract:
An apparatus ( 10 ) for producing an orbital movement in a plane ( 20 ) is disclosed. The apparatus ( 10 ) comprises a lower shaft ( 40 ) and an upper shaft ( 30 ), being parallelly and eccentrically  attached to one another, and a platform ( 50 ) mounted on the upper shaft ( 30 ). A ring gear ( 60 ) is attached to the platform ( 50 ) and coaxially rotatable about the upper shaft ( 30 ). A gear wheel ( 80 ) is coaxially rotatably mounted on the lower shaft ( 40 ) and engages with the ring gear ( 60 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    None 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The field of the invention relates to an apparatus and method for producing an orbital movement in a plane, particularly for shaking and/or rotating a fluid sample. 
         [0004]    2. Brief Description of the Related Art 
         [0005]    Existing systems are known for creating an orbital shaking movement for ensuring that particles in fluids in sample holders do not settle down at the bottom of a container forming the sample holder. 
         [0006]    Existing systems are also known that use a belt for driving one or more pulleys and having two shafts. A first one of the shafts is coaxial to the main axis of the pulley and is located on one of the flat sides of the pulley. A second one of the shafts is located on an opposite flat side of the pulley with an offset to the main axis. These pulleys are mounted with a coaxial shaft in a structure, which does not orbit, and with the other shafts in an orbiting structure, which orbits when a drive motor drives the belt. The orbiting structure can be attached to or be part of a platform on which the sample holders can be placed. These prior art systems often have two or more eccentric shaft pulleys to support the weight of the sample holders including the fluid samples. 
         [0007]    The prior art systems often include a counterweight to balance the orbiting mass. The center of counterweight needs to be aligned at 180° to the center of gravity of the orbiting parts. A mechanism or method is needed to ensure alignment of the rotation angles of the pulleys and the counterweight. 
         [0008]    The sample holders of the prior art need to be moved to a so-called pipetting position reachable by a pipettor to be filled or emptied. The structure with the sample holders is rotated by a second motor to move the sample holder for filling or emptying to the pipetting position. In an alternative manner, the sample holders can be placed on a rectangular plate for positioning the sample holders to the pipetting position with a second motor moving the rectangular plate in an X- and Y-direction. 
         [0009]    Another system is known which uses a planetary drive with round holders for the sample holders. The planetary drive comprises a plurality of small gear wheels, which orbit around a larger gear wheel. The orbiting movement of the gear wheels and the movement of the sample holders into the pipetting position is carried out by the same motor. The motor turns the supporting structure carrying the sample holders on its upper surface and the corresponding small gear wheels on the lower surface in a manner such that the fluid holders and the gear wheels can rotate about a common axis. The small gear wheels engage with a fixed center wheel. The sample holders turn about their own axis and orbit the center wheel at the same time when the planetary drive is in operation. Thus, the fluid in the sample holders is moved sufficiently to prevent particles from settling down at the bottom of the sample holder. The sample holders can be placed in the required pipetting position. 
         [0010]    It is known that the belts of the prior art systems are prone to failure from elongation and excessive wear over time. This problem can be aggregated in high temperature environments. The belt drive systems and the planetary drive systems of the prior art also require a certain amount of space for their operation. In particular, the planetary drive system requires a separate holder for each one of the sample holders. Thus, there is a limitation on the maximum number of sample holders that can be placed on the system or the required space may be too large in order to enable high performance system specifications. It is also known that belt drives require more maintenance in general than the gear wheel drives. The belt drives can also be more difficult and time-consuming to assemble. There is also a risk of wrong assembly. 
         [0011]    One of the further issues associated with the planetary drive is that it does not allow positioning of the sample holders without shaking the fluids in the sample holders and this can lead to difficulties with pipetting in a short time frame. 
       SUMMARY OF THE INVENTION 
       [0012]    An apparatus for producing an orbital movement in a plane of a sample holder is disclosed. The apparatus comprises an eccentric shaft with a lower shaft and an upper shaft. The lower shaft and the upper shaft are parallelly and eccentrically attached to one another. A platform is rotatably mounted on the upper shaft. A ring gear is attached to the platform and is also able to coaxially rotate about the upper shaft. The ring gear comprises a plurality of interior teeth on radially inward facing circumferential surface. A gear wheel having a plurality of exterior teeth on a peripheral circumferential surface is arranged to be coaxially rotatably mounted on the lower shaft. The gear wheel and the ring gear are so placed that at least some of the plurality of the interior teeth engage with at least some of the plurality of exterior teeth. 
         [0013]    This arrangement allows the epicycloid and rotary movement of the platform to produce orbital shaking and enable stopping of the sample holders in a correct position for pipetting. The apparatus requires little space and can operate in high-temperature environments, as the eccentric shaft can be driven by a motor attached to the lower shaft. 
         [0014]    In one aspect of the invention the ring gear can be independently driven either by a further gear wheel engaging with teeth on the lower part of the gear wheel or by a pulley. 
         [0015]    The platform and ring gear may be formed as one piece. 
         [0016]    The apparatus may comprise a counterweight connected to the upper shaft. 
         [0017]    The apparatus may further comprises a sample holder mounted on the platform. 
         [0018]    The apparatus may further comprise a first transmission device for driving the lower shaft to rotate coaxially. 
         [0019]    The first transmission device may be pulley coaxially attached to the lower shaft, or a first transmitting gear wheel coaxially attached to the lower shaft. 
         [0020]    The apparatus may further comprise a second transmission device for driving the gear wheel to rotate coaxially. 
         [0021]    The second transmission device may be a pulley coaxially attached to the gear wheel or a second transmitting gear wheel coaxially attached to the gear wheel 
         [0022]    The apparatus may further comprise a first motor operatively connected to the first transmission device. 
         [0023]    The apparatus may further comprise a second motor operatively connected to the second transmission device. 
         [0024]    A method for producing an orbital movement in a plane of at least one fluid sample on a platform is disclosed. The method comprises driving interior teeth of a ring gear attached to the platform to roll off exterior teeth of a gear wheel; driving the ring gear to rotate about its center; and superposing the rolling off and the rotating of the ring gear 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0025]      FIG. 1  shows an example of the apparatus. 
           [0026]      FIGS. 2A-C  show an example of the eccentric shaft, and the ring gear and the gear wheel in a cross section ( FIG. 2A ) and a bottom view ( FIG. 2B ). The offset of the eccentric shaft is shown in  FIG. 2C . 
           [0027]      FIGS. 3A and 3B  show the gear wheel with the exterior teeth and drive teeth ( FIG. 3A ) and the ring gear within the eccentric shaft ( FIG. 3B ). 
           [0028]      FIGS. 4A-C  show an example of the orbital shaking. 
           [0029]      FIGS. 5A-C  show a further example of the shaking. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protector&#39;s scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with the feature of a different aspect or aspects and/or embodiments of the invention. 
         [0031]      FIG. 1  shows an example of the apparatus  10  of this disclosure. The apparatus  10  is used to produce an orbital movement, such as a shake or rotation, in a plane indicated by the reference numeral  20  in  FIG. 1 . 
         [0032]    The apparatus  10  comprises an eccentric shaft having an upper shaft  30  and a lower shaft  40  about which is attached a platform  50 . The platform  50  can rotate co-axially about the upper shaft  30 . The platform  50  is mounted on a ring gear  60  having interior teeth  70 . The interior teeth  70  engage with exterior teeth  90  of a gear wheel  80 . The platform  50  and the ring gear  60  could be made from a single piece. One or more sample holders  55  can be mounted on the platform  50 . A drive wheel  110  is connected to the lower shaft  40  to rotate the lower shaft  40 . The drive wheel  110  is connected by a belt driven pulley  115  to a drive motor (not shown). 
         [0033]      FIGS. 2A-C  show an example of the eccentric shaft  30 ,  40 , in cross section ( FIG. 2A ) and in a bottom view ( FIG. 2B ) of the eccentric shaft illustrating the interior teeth  70  and the exterior teeth  90 .  FIG. 2C  shows the eccentric shaft  30 ,  40  with an offset marked. The same reference numerals are used in  FIGS. 1 and 2 . 
         [0034]    It will be seen from  FIG. 2B  that some of the exterior teeth  90  engage with some of the interior teeth  70 . 
         [0035]      FIGS. 3A  show an example of the gear wheel  80  mounted on the eccentric shaft  30 ,  40 . It will be seen that the gear wheel  80  has drive teeth  95 , which can engage with a set of gears (rather than the belt driven pulley  115 ) to drive the gear wheel  80 .  FIG. 3B  shows a further example of the eccentric shaft  30 ,  40  about which is located the ring gear  60  with the interior teeth  70 . It will be understood from  FIGS. 3A-B  that the gear wheel  80  can be mounted inside the ring gear  60  such that some of the interior teeth  70  engage with some of the exterior teeth  90 , as shown in  FIG. 2B . The ring gear and the gear wheel  80  are pivot-mounted on the shaft  30  and it is therefore possible to rotate the eccentric shaft  30 ,  40  without rotating the gear wheel  80 . 
         [0036]    The apparatus  10  may require a counterweight  130  if the system exceeds a certain size and balancing of centrifugal forces is required. The counterweight  130  is attached to the upper shaft  30  in such a way that it is able to counter act the centrifugal forces exerted on the apparatus  10 . 
         [0037]    An example of the orbital movement of the apparatus  10  is shown in  FIGS. 4A-B . This aspect of the invention assumes that the gear wheel  80  is not rotated, but that the eccentric shaft  30 ,  40  is rotated by the drive wheel  110 . The center C of the larger ring gear  60  circles the axis A of the gear wheel  80 . The radius of this circle O (shown as a dotted line) equals the offset of the eccentric shaft  30 ,  40 , as shown in  FIG. 2C . The interior teeth  70  of the ring gear  60  roll off the exterior teeth  90  of the gear wheel  80  and thus the ring gear  60  also turns about its axis. This turning means that the angle of rotation α of the eccentric shaft  30 ,  40  changes faster than the angle of rotation β of the ring gear  60 . A point P on the ring gear  60  thus moves on a path shown in  FIG. 4B  about the axis A of the gear wheel  80 .  FIG. 4C  shows the movement of the gear wheel  80  and the ring gear  60  with respect to each other. 
         [0038]      FIGS. 5A-C  show a second aspect of the rotation in which the gear wheel  80  is also driven. The ring gear  60  is rotated about its center C. Thus, the point P on the ring gear  60  can travel at any position on the circular path B. It was noted in connection with  FIG. 4  that the circle O equals the offset of the eccentric shaft  30 ,  40 . This is represented by a virtual circle O′ in  FIG. 5B . Thus, any point can be moved to any position at the intersection of the circle B and the virtual circle O′. 
         [0039]    An orbital shaking movement is therefore produced when the eccentric shaft  30 ,  40  rotates continuously and the gear wheel  80  simultaneously rotates in an opposite direction. It will be appreciated that the rotational speed of the gear wheel  80  needs to be adapted to the speed of the ring gear  60  according to the transmission ratio of the ring gear  60  and the gear wheel  80 . The point P then travels on the virtual circular path O′ through which the eccentric shaft  30 ,  40  rotates. The diameter of the virtual circle O′ equals the diameter of the circle O and therefore the offset of the eccentric shaft  30 ,  40  and the center of the virtual circle O′ always stay in the same position. The platform  50  is attached to the ring gear  60  and therefore follows this movement. An orbital shaker for fluid samples  120  in the sample holder  55  is therefore created. 
         [0040]    In a further aspect of the invention, a pipettor can be used to reach the platform  50  for adding and/or removing fluid samples  120  from the sample holder  55 . The sample holder  55  needs to be positioned on the platform  50  reachable by the pipettor. The rotation of the eccentric shaft  30 ,  40  and the position of the ring gear  60  therefore needs to be coordinated such that the sample holders  55  are stopped in a position reachable by the pipettor. 
         [0041]    A sensor could be located on the lower shaft  40  to detect the rotation angle of the lower shaft  40 . This allows the drive wheel  110  to place the offset of the upper shaft  30  in a particular position so that the sample holder  55  can then be placed in the pipetting position reachable by the pipettor by rotating the gear wheel  80  on the upper shaft  30 . 
         [0042]    In one aspect of the invention it would be possible also to add a stirring mechanism to stir the fluid samples  120 . 
       REFERENCE NUMERALS 
       [0000]    
       
           10  Apparatus 
           20  Plane 
           30  Upper Shaft 
           40  Lower Shaft 
           50  Platform 
           55  Sample Holder 
           60  Ring Gear 
         Interior Teeth 
           80  Gear Wheel 
           90  Exterior Teeth 
           95  Drive Teeth 
           100  Drive Motor 
           110  Drive Wheel 
           115  Belt Driven Pulley 
           120  Fluid Sample 
           130  Counterweight