Tube shaking with circular motion and uniform orientation

A shaking device, comprising:

• a rotary input shaft defining an input axis and driven through a rotating input motion about the input axis;
• a rotary output shaft defining an output axis, driven through a rotating output motion about the output axis, offset from and parallel to the input shaft, and fixedly connected to a tube holder, wherein the tube holder is configured to hold one or more tubes that contain one or more samples;
• a connector extending between the output shaft and the input shaft, fixedly connected to the input shaft so that the connector rotates with the input shaft, and rotationally connected to the output shaft so that the rotating input motion of the input shaft drives the output shaft, and the fixedly connected tube holder, through a revolving motion about the input axis, but not through the rotating output motion, to shake the tubes through a circular motion profile;
• a counterweight connected to the input shaft and positioned opposite from the output shaft to counterbalance the tube holder during shaking;
• and
• an orientation-maintaining device including a fixed gear and a rotary gear, wherein the fixed gear is fixedly connected in place and not rotationally driven by the input shaft, wherein the rotary gear is rotational with and fixedly connected to the output shaft, wherein the rotary gear, and the fixedly connected output shaft, is driven through the rotating output motion, in an opposite angular direction and in a same angular degree relative to the rotating input motion, by indirect engagement with the fixed gear when the output shaft is driven through the revolving motion about the input axis, and wherein the rotating output motion of the output shaft maintains the tube holder and the tubes in a uniform orientation during shaking as the output shaft, and the fixedly connected tube holder, are driven through the revolving motion about the input axis such that uniform forces are applied to each of the tubes and the samples contained therein to homogenize the samples.