Magnetic coupling assembly for coupling stir bar in magnetic stirrer mixer and magnetic stirrer mixer using the same
View Patent ↗A magnetic coupling assembly for a magnetic stirrer includes a non-magnetic disc embedded with two or more pairs of magnets. The two magnets of each pair are oriented with opposite magnetic poles pointing in the upward direction. When the magnetic coupling assembly is driven to rotate, it can bind one or more axially magnetized stir bar in a mixer at a relatively higher speed to achieve better mixing result without causing spin-out or jumping-flea phenomena, compared to when only one pair of magnets is used.
1. A magnetic stirrer for a magnetic stirrer mixer, the magnetic stirrer comprising:
a magnetic coupling assembly comprising:
a non-magnetic block; and
a first coupling pair of magnets and a second coupling pair of magnets mounted in a top side of the non-magnetic block, wherein
the two magnets of each of the two coupling pairs are oriented such that one has its north pole (N-pole) pointing upwards and the other has its south pole (S-pole) pointing upwards;
the four magnets of the two coupling pairs of magnets are respectively positioned at four corners of an imaginary first quadrangle on the top side of the non-magnetic block; and
the two magnets having their respective N-poles pointing upwards are positioned at two adjacent corners of the first quadrangle; and
a drive mechanism connected to the non-magnetic block for rotating the non-magnetic block and therefore the magnetic coupling assembly about an axis of rotation.
2. The magnetic stirrer of claim 1 , wherein the first quadrangle is a first rectangle.
3. The magnetic stirrer of claim 2 , wherein the first rectangle has two sides longer than the other two sides and the magnets of each coupling pair are positioned at the two corners joined by one of the longer sides.
4. The magnetic stirrer of claim 2 , wherein the axis of rotation of the magnetic coupling assembly vertically passes through a point on a line of symmetry of the first rectangle running between the two coupling pairs.
5. The magnetic stirrer of claim 4 , wherein the axis of the rotation of the magnetic coupling assembly passes through the center of the rectangle.
6. The magnetic stirrer of claim 1 , wherein the non-magnetic block of the magnetic coupling assembly is of a circular disc shape.
7. The magnetic stirrer of claim 1 , wherein each of the magnets is embedded in a respective well formed in the non-magnetic block.
8. The magnetic stirrer of claim 1 , wherein the magnets are of a same shape, size and magnetic field potential.
9. The magnetic stirrer of claim 1 , wherein the magnets are permanent magnets.
10. The magnetic stirrer of claim 1 , wherein the magnets are rare-earth magnets.
11. The magnetic stirrer of claim 1 wherein the magnets are neodymium-iron-boron magnets.
12. The magnetic stirrer of claim 1 , wherein the drive mechanism comprises an electric motor and a rotary shaft, to which the non-magnetic block is mounted.
13. The magnetic stirrer of claim 1 , further comprising a third coupling pair of magnets mounted in the top side of the non-magnetic block, wherein
the two magnets of the third coupling pair are oriented such that one has its north pole (N-pole) pointing upwards and the other has its south pole (S-pole) pointing upwards;
the two magnets of the third coupling pair and the two magnets of the second coupling pair are respectively positioned at four corners of an imaginary second quadrangle on the top side of the non-magnetic block; and
the magnets of the second and the third coupling pairs having their respective N-poles pointing upwards are positioned at two adjacent corners and the other two magnets having their respective S-poles pointing upwards are positioned at the other two corners of the second quadrangle.
14. The magnetic stirrer of claim 13 , wherein the second quadrangle is a second rectangle.
15. The magnetic stirrer of claim 13 , wherein the six magnets of the three coupling pairs are positioned on and equiangularly spaced around an imaginary circle on the top side of the non-magnetic block.
16. The magnetic stirrer of claim 15 , wherein the axis of rotation of the magnetic coupling assembly passes through the center of the imaginary circle.
17. The magnetic stirrer of claim 15 , wherein the non-magnetic block of the magnetic coupling assembly is of a circular disc shape.
18. A magnetic stirrer mixer, comprising:
a magnetic coupling assembly comprising:
a non-magnetic block; and
a first coupling pair of magnets and a second coupling pair of magnets mounted in a top side of the non-magnetic block, wherein
the two magnets of each of the two coupling pairs are oriented such that one has its north pole (N-pole) pointing upwards and the other has its south pole (S-pole) pointing upwards;
the four magnets of the two coupling pairs of magnets are respectively positioned at four corners of an imaginary first quadrangle on the top side of the non-magnetic block; and
the two magnets having their respective N-poles pointing upwards are positioned at two adjacent corners of the first quadrangle; and
a drive mechanism connected to the non-magnetic block for rotating the non-magnetic block and therefore the magnetic coupling assembly about an axis of rotation;
a vessel mounted above the magnetic coupling assembly for containing a liquid to be stirred; and
a stir bar inside the vessel to be magnetically coupled and driven by the magnetic coupling assembly to stir the liquid in the vessel.
19. The magnetic stirrer mixer of claim 18 , wherein the magnetic coupling assembly further comprises a third coupling pair of magnets mounted in the top side of the non-magnetic block, wherein
the two magnets of the third coupling pair are oriented such that one has its north pole (N-pole) pointing upwards and the other has its south pole (S-pole) pointing upwards;
the two magnets of the third coupling pair and the two magnets of the second coupling pair are respectively positioned at four corners of an imaginary second quadrangle on the top side of the non-magnetic block; and
the magnets of the second and the third coupling pairs having their respective N-poles pointing upwards are positioned at two adjacent corners and the other two magnets having their respective S-poles pointing upwards are positioned at the other two corners of the second quadrangle.
20. The magnetic stirrer mixer of claim 19 , wherein there are two stir bars in the vessel to be magnetically coupled and driven by the magnetic coupling assembly.
21. The magnetic stirrer mixer of claim 20 , wherein the two stir bars are mounted in tandem with a non-magnetic fixture in the vessel.
22. The magnetic stirrer mixer of claim 21 , wherein an impeller is attached to the non-magnetic fixture.