ORBITAL SHAKER WITH BALANCING DEVICE

Abstract

An orbital shaker with a balancing device that automatically and passively compensates, without supply of external energy, forces and moments which are caused by imbalance and arise during operation, in particular as a result of a possible variable loading (mass, geometry of the containers, properties of the contents) and variable operating parameters (speed of rotation and shaking radius). The balancing device can be designed such that only the unbalance forces (static balancing) and/or the unbalance moments (dynamic balancing) are compensated.

Claims

1-21. (canceled)

22. An orbital shaker comprising a shaker table with a surface for supporting a load; a rotor rotatable around a rotational axis; a drive set up to produce the rotational movement of the rotor; a rotary joint, which connects the rotor and the shaker table together so that they can rotate freely around a joint axis, which has a parallel offset (e) from the rotational axis; a guide connected to the shaker table and configured so that all points of the surface of the shaker table describe a circular orbit with the same diameter as the rotor rotates, the diameter corresponds to twice the parallel offset; and a balancing device for the automatic compensation of imbalance-caused forces and/or moments including: at least one balancing plane perpendicular to the rotational axis; at least one orbit arranged concentrically around the rotational axis in each the at least one balancing plane; a plurality of compensating masses arranged to move freely on each orbit; a rotational damping mechanism configured to produce a moment acting on the compensating masses when there is a deviation between the rotational speed of the compensating masses and the rotational speed of the rotor around the rotational axis; and a guide system configured to allow at least one of a translational movement of the rotor within a plane which is perpendicular to the rotational axis or a tilting of the rotor around two axes which are at right angles to each other and lie in a plane perpendicular to the rotational axis.

23. The orbital shaker according to claim 22, wherein the drive is configured as an electric motor with a stator and the rotor as a movable part.

24. The orbital shaker according to claim 23, wherein the drive is mounted on a drive stand mounted on the guide system.

25. The orbital shaker according to claim 22, wherein the rotary joint comprises a pivot pin, which defines the joint axis and is arranged eccentrically to the rotational axis, and a bearing rotatably supporting the pivot pin.

26. The orbital shaker according to claim 22, wherein the parallel offset (e) between the rotational axis and the joint axis is adjustable.

27. The orbital shaker according to claim 22, wherein at least one circular guide is arranged on the rotor along each the at least one orbit to guide the compensating masses on the at least one orbit.

28. The orbital shaker according to claim 27, wherein the at least one circular guide comprises a ring-shaped cavity.

29. The orbital shaker according to claim 22, wherein the compensating masses are rolling elements.

30. The orbital shaker according to claim 28, wherein the rotational damping mechanism includes the ring-shaped cavity filled with a fluid.

31. The orbital shaker according to claim 30, wherein the at least one circular guide comprises at least two ring-shaped cavities with different diameters arranged concentrically around the rotational axis in each balancing plane, wherein the ring-shaped cavities are filled with fluids of different viscosities.

32. The orbital shaker according to claim 28, wherein each circular guide is divided into at least two segments representing part of a circle, and at least one of the compensating masses is arranged to move freely on the at least one orbit in each segment.

33. The orbital shaker according to claim 22, wherein the compensating masses arranged on each orbit are configured as pendulums, each of the pendulums having a center of mass and supported outside the center of mass rotatably around the rotational axis.

34. The orbital shaker according to claim 33, wherein the rotational damping mechanism is one of an eddy-current coupling or a hydraulic rotational damper arranged between the rotor and each of the pendulums.

35. The orbital shaker according to claim 22, wherein the guide system comprises a double-axis linear guide system configured to allow the rotor to move in two axes (X/Y) at right angles to each other in a plane perpendicular to the rotational axis.

36. The orbital shaker according to claim 35, wherein the drive is configured as an electric motor with a stator and the rotor as a movable part, and wherein the linear guide system is connected directly to the stator.

37. The orbital shaker according to claim 35, wherein the drive is configured as an electric motor with a stator and the rotor as a movable part, wherein the drive is mounted on a drive stand mounted on the guide system, and wherein the linear guide system is connected to the drive stand.

38. The orbital shaker according to claim 35, wherein a resistance of the linear guide system to displacement is adjustable in both directions.

39. The orbital shaker according to claim 24, wherein at least one restoring element always moves the drive stand back into a same starting position after the rotor has stopped rotating.

40. The orbital shaker according to claim 22, further comprising at least one stationary compensating weight arranged on the rotor to compensate for imbalance-caused forces and moments.

41. The orbital shaker according to claim 22, wherein the at least one balancing plane comprises at least two balancing planes arranged with an offset to each other in the direction of the rotational axis.

42. The orbital shaker according to claim 41, wherein the guide system comprises circular guides configured to allow the rotor to tilt around two axes which are at right angles to each other and are in a plane perpendicular to the rotational axis.

43. The orbital shaker according to claim 41, further comprising at least one damper for damping the movements of the guide system.

44. The orbital shaker according to claim 22, wherein the guide system comprises circular guides configured to allow the rotor to tilt around two axes which are at right angles to each other and are in a plane perpendicular to the rotational axis.

45. The orbital shaker according to claim 22, further comprising at least one damper for damping the movements of the guide system.

Description

[0040] The invention is explained in greater detail below on the basis of several exemplary embodiments:

[0041] FIG. 1 shows a schematic diagram of an exemplary embodiment of the invention with automatic compensation of the imbalance force;

[0042] FIG. 2 shows a side view of the exemplary embodiment of FIG. 1;

[0043] FIG. 3a shows a top view of the exemplary embodiment of FIG. 1;

[0044] FIG. 3b shows a force polygon of the forces which occur during balancing according to FIG. 3a;

[0045] FIG. 4 shows a schematic diagram of an exemplary embodiment of the invention with automatic compensation of the imbalance force and of the imbalance moment;

[0046] FIG. 5 shows a perspective view of the exemplary embodiment illustrated in FIG. 4; and

[0047] FIG. 6 shows a schematic diagram of an arrangement of the compensating masses as pendulums.

[0048] A first exemplary embodiment of an orbital shaker with automatic compensation of the imbalance force is shown in the drawings of FIGS. 1, 2, 3a, and 3b and will be described in greater detail below:

[0049] A machine stand 1 in the form of a base plate is connected by a linear guide system 102, 103 to a drive stand 2 in the form of a motor plate so that relative motion is possible between the two stands. A drive is arranged on the drive stand 2. The drive drives a rotatably supported rotor 3. This rotor 3 is in particular the rotor—an external rotor in the present exemplary embodiment—of an electric motor.

[0050] Eccentrically, with a parallel offset “e” to the rotational axis 3a, a shaker table 5 is connected in freely rotatably fashion to the rotor 3 by a rotary joint 4. The rotary joint 4 comprises a pivot pin 4c, which defines the joint axis 4a and is eccentric to the rotational axis 3a, and it also comprises a bearing 4b, which rotatably supports the pivot pin 4c (compare FIG. 4) and is mounted on the bottom of the shaker table 5. The rotary joint 4 makes it possible for the rotor 3 and the shaker table 5 to rotate relative to each other around the joint axis 4a.

[0051] At the same time, a guide of the shaker table 5 prevents the shaker table 5 from rotating around the vertical axis. The guide has the effect that the shaker table 5, during its orbital movement, retains it orientation, and thus all points on the surface of the shaker table 5 describe the same orbit as they move, the diameter of this orbit being equal to twice the parallel offset “e” between the rotational axis 3a and the joint axis 4a. This blocking of the rotation of the shaker table 5 around the vertical axis—in the following also called rotational blocking—can be achieved by various types of guides, which are familiar to the expert active in the field of shakers and are therefore not illustrated in FIGS. 1, 2, and 3a for the sake of clarity, but are shown in the exemplary embodiment by way of example in FIGS. 4 and 5.

[0052] A tray 6 can be mounted on the shaker table, and the tray can be loaded in turn with the various containers to be shaken. However, these can also be placed directly on the shaker table 5.

[0053] In FIGS. 1, 2, and 3a, the variable load is shown by way of example as a holder 7 and an Erlenmeyer flask 8 to hold the material to be shaken. Although it does not itself rotate, the variable load describes an orbit defined by the parallel offset of the eccentric joint axis 4a to the rotational axis 3a. As a result of the movement of the variable load, a centrifugal force is produced, which causes the entire system to vibrate. The absolute value of the centrifugal force F depends on the mass of the load m, the shaker diameter d=2e, and the angular velocity Ω. The user of the orbital shaker can vary all three parameters within certain limits, which means that the centrifugal force is also variable. The following equation applies here:

[00001]$F=m.Math.\frac{d}{2}.Math.{\Omega }^2=m.Math.e.Math.{\Omega }^2$

[0054] So that the automatic compensating mechanism for compensating the imbalance force is functional, the driven rotor 3 is also movably supported in a plane which is perpendicular to its rotational axis 3a by means of the linear guide system 102, 103. This results in two additional degrees of freedom, namely, translational movement in the x and y directions in a plane perpendicular to the rotational axis of the imbalance. Optionally, this possible movement can be influenced by a restoring and/or damping force. The spring stiffness of the restoring force of a restoring element must be so low that the angular velocity Ω of the drive is in the supercritical range for all rotational speeds required for normal operation of the shaker (it must be greater than the angular eigenfrequencies ω.sub.0 of the movement of the system: Ω>ω.sub.0).

[0055] If a restoring force is not used, the spring stiffness and thus also the angular eigenfrequency ω.sub.0 will both be zero. All operating speeds Ω are therefore greater than the eigenfrequency ω.sub.0 of the movement, and supercritical operation is always guaranteed. Nevertheless, the drive stand 2 in this case is not necessarily always in the same position after balancing. By means of the damping of the linear guide system 102, 103, the movement of the linear guide system 102, 103 can be kept low during start-up and possibly even when passing through the eigenfrequency. The damping can be achieved by friction in the linear guides of the linear guide system and/or by additional components (for example, fluid dampers or eddy-current dampers).

[0056] The linear guide system 102, 103 can also comprise mechanical stops, which limit the maximum deflection in the direction of the X and Y axes in the plane perpendicular to the rotational axis. Neither the stops nor any elastic and/or damping elements are shown in FIG. 1, 2, or 3a.

[0057] The above-mentioned supercritical operation guarantees a phase angle of more than 90° (ideally, of)180° between the exciting imbalance force and the deflection of the system in the plane perpendicular to the rotational axis. If, therefore, a resultant residual imbalance force is acting in one direction, the system is deflected in the opposite direction.

[0058] The balancing device also comprises at least two compensating masses 101, 110, the centers of mass of which move concentrically on an orbit around the rotational axis 3a of the rotor 3. Such motion on the orbit is possible because, in the one case, the compensating masses 110, which are configured here as pendulums, are provided with a support 111 outside their centers of mass (FIG. 6), and, in the other case, because the compensating masses 101, which are in the form of rolling elements (balls or cylinders) and/or sliding elements are able to roll and/or slide along a circular guide on one or more orbits. In the exemplary embodiment according to FIGS. 1, 2, and 3a, a ring-shaped channel 100, in which the compensating masses 101, configured as balls, can roll serves as the circular guide. The compensating masses 101 must be able to move in such a way that they can change their position relative to the variable load 7, 8.

[0059] Simultaneously, it must be ensured that, in the balanced state, the compensating masses 101 rotate at the same speed as the variable load 7, 8. This is made possible by a velocity-dependent rotational damping between the rotor 3 and the compensating masses 101. What is meant here by rotational damping is a means which generates, as a function of the relative rotational speed between the compensating masses 101 and the rotor 3, a directional moment, which reduces the relative rotational speed. The ring-shaped channel 100, in which the compensating masses 101 move, is filled with a fluid to provide the rotational damping function. When pendulums 110 are used, an eddy-current coupling can be used to provide the rotational damping.

[0060] If the orbital shaker is not balanced, the imbalance force brings about a deflection of the drive stand 2 in a plane perpendicular to the rotational axis 3a, i.e., a deflection which trails the force by approximately 180°. Because the compensating masses 101 in this case no longer rotate around the midpoint (MP) of their support, i.e., of the ring-shaped channel (see FIG. 3a) but rather around the unbalanced midpoint, called here the coordinate origin (KU), the centrifugal forces acting on them also have a component acting tangentially to the orbit, designated the restoring force 1, 2 in FIG. 3a. Because of the way in which the pendulums 111 and the ring-shaped channel 100 are supported, however, only forces (except for friction) acting in the direction normal to the orbit can be absorbed, so that the tangential force (restoring forces 1, 2) must generate a change of position of the compensating masses 101 or 110 relative to the joint axis 4a. As soon as the compensating masses 101 or 110 have reached a position which compensates the original imbalance force, the resultant imbalance force and thus also the radial deflection Δr of the motor stand 2 are equal to zero. The points MP and KU then coincide. The compensating masses 101 or 110 now retain their position during operation until the balance state changes. To obtain optimal balancing results, the friction of the compensating masses in the circular guide should be minimized, because otherwise this friction will negatively influence the optimal arrangement of the compensating masses.

[0061] The guide system realized in the exemplary embodiment as a linear guide system 102, 103 must first allow the desired translational motion of the rotor 3 in a plane perpendicular to the rotational axis 3a and, second, it must block all other movements. In addition, the guide system absorbs the weight forces. In addition to the linear guide system shown with two crossing linear guides with plain bearings, it is also possible to use linear guides with roller bearings.

[0062] The guide system for the rotor 3 can also be built up out of elements with spring elasticity. These must comprise a low spring stiffness in the direction of motion in the plane perpendicular to the rotational axis 3a, so that supercritical operation can be guaranteed and must be as stiff as possible in the other directions (blocking of the motion and absorption of the forces and moments).

[0063] An alternative embodiment of a guide system which allows only the desired movements in a plane perpendicular to the rotational axis 3a can be realized by means of, for example, a Schmidt or Kärger coupling.

[0064] For additional compensation of the moment produced by the imbalance force, the rotor 3 and its rotational axis 3a must be able to move not only in the plane but also to tilt around two axes at right angles to each other in a plane perpendicular to the rotational axis (compare FIGS. 4 and 5). The guide system shown in FIG. 5 comprises an intermediate member 108, which is connected to the machine stand 1 in such a way that it can move translationally and rotationally in and around an x-axis in the plane perpendicular to the rotational axis 3a. This is possible by means of, for example, a combination of rotary joints 106 and sliding joints 107. On this intermediate member 108, the stator of the motor is mounted in such a way that it can move in and around the y-axis in the plane perpendicular to the rotational axis 3a. By means of this serial arrangement, the stator of the motor can, in sum, rotate around the x and y axes and be freely pushed along these axes as well. It therefore has four degrees of freedom.

[0065] So that the imbalance moments can be compensated, furthermore, at least two compensating masses 101 in at least one additional balancing plane, which are guided on an orbit in the additional balancing plane, are needed. The exemplary embodiment according to FIGS. 4 and 5 has two ring-shaped channels 100a and 100b, which are offset from each other in the direction of the rotational axis 3a; the compensating masses 101, configured as balls, travel around these channels.

[0066] So that the rotor can always be brought back to the same starting position after the end of a shaking operation, it is also possible in this embodiment to use restoring elements, especially to use the springs 104 and 105 shown in FIG. 4, to reverse the tilting and the displacement.

[0067] As in the case of an orbital shaker with pure imbalance force compensation, the movements can be damped to avoid large deflections when passing through the eigenfrequency and during the start-up phase.

[0068] In FIGS. 4 and 5 as well, the shaft of the motor represents the driven rotor, but here it is configured as an internal rotor. The two ring-shaped channels 100a, 100b are mounted on the rotor 3, so that they rotate with the rotor. In the ring-shaped channels 100a, 100b, an oil is provided for the rotational damping of the compensating masses 101, which are in the form of the balls. The shaker table 5 is connected to the rotor 3 by a rotary joint 4, which is arranged eccentrically to the rotational axis 3a on the outward-facing end surface of the rotor 3.

[0069] As a guide or rotational block for the shaker table 5, several rods 12 are provided, each with a universal joint 13 at both ends. One of the universal joints 13 is connected to the shaker table 5, the other to the drive stand 2, on which the drive is mounted. The guide or rotational block has the effect that the shaker table 5 describes a circular orbit without any change in its orientation. A barrel 9 containing the material to be shaken, representing the load, is present on the shaker table 5.

[0070] As long as an imbalance moment is acting, the rotational axis 3a will tilt around the x and y axes. Because the two balancing planes with the ring-shaped channels 100a, 110b are a certain vertical distance away from the x and y axes, the midpoint of the ring-shaped channels 100a, 110b moves back to an orbit around the coordinate origin KU. Here, too, the associated eigenfrequency of the system must be selected so that a phase delay of over 90° is obtained. This is made possible by selecting the lowest possible eigenfrequency. In this case, the deflection of the midpoint (MP) of the ring-shaped channels 100a, 100b leads to actuating forces on the compensating masses, and these continue to act until the imbalance is compensated (similar to the forces shown in FIGS. 2 and 3a for the compensation of the imbalance force alone).

[0071] In the embodiment according to FIG. 4, furthermore, a compensating mass 10 is used, which is permanently connected to the rotor 3. This can compensate the imbalance caused by the shaker table 5 and the rotary joint 4 and possibly other components as well, i.e., the imbalance which remains constant upon variation of the load, with the result that only the variable load itself must be balanced by the compensating masses. In addition, this additional mass can also compensate a typical load, especially a load equal to half the maximum load, which means that fewer compensating masses are required in the automatic system.

LIST OF REFERENCE NUMBERS

[0072]

TABLE-US-00001 No. Designation  1 machine stand  2 drive stand  3 rotor  3a rotational axis  3b stator  4 rotary joint  4a joint axis  4b pivot pin  4c bearing  5 shaker table  6 tray  7 holder  8 Erlenmeyer flask  9 shaker vessel  10 stationary compensating mass  11  12 rod  13 universal joint 100 ring-shaped channel 100a upper ring-shaped channel 100b lower ring-shaped channel 101 compensating mass (ball) 102 guide system (anti-friction bush) 103 guide system (coordinate axes) 104 spring for translational movement 105 spring for rotational movement 106 circular guide 107 translational support 108 intermediate member 109 — 110 compensating mass (pendulum) 111 support