Twin vane rotary vacuum pump

1. A vacuum pump, comprising:

a housing having an inlet and an outlet;

a chamber within the housing;

a rotor configured to undergo rotational movement about a rotational axis within the chamber, and

at least a first vane and a second vane, the first vane and the second vane being received, respectively, in a first slot and a second slot, the first slot and the second slot being formed in the rotor,

wherein the first slot and the second slot are substantially parallel to each other,

wherein a length of the first vane is greater than a length of the first slot,

wherein a length of the second vane is greater than a length of the second slot, and

wherein the first slot and the second slot are formed as secants and are symmetrical to each other about the rotational axis of the rotor.

2. The vacuum pump according to claim 1 ,

wherein the length of the first vane and the length of the second vane are greater than a diameter of the rotor.

3. The vacuum pump according to claim 2 , wherein a ratio of a maximum length of a portion of the first vane external to the first slot to a radius of the rotor is between 1 and 1.3.

4. The vacuum pump according to claim 2 , wherein a center of gravity of each of the first vane and the second vane is offset towards a respective vane tip.

5. The vacuum pump according to claim 2 , further comprising biasing means configured to bias at least the first or the second vane into an extended position.

6. The vacuum pump according to claim 2 , wherein the biasing means comprise an oil supply to an abutment of one or more of the first vane and the second vane.

7. The vacuum pump according to claim 2 , wherein the chamber comprises a chamber profile having a circular arc portion corresponding to a section in a range of at least 90° to 135°.

8. The vacuum pump according to claim 7 , wherein the chamber profile comprises a widening portion corresponding to a section in a range of 10° to 40°.

9. The vacuum pump according to claim 2 , wherein the rotor is connected to a drive shaft by over moulding.

10. The vacuum pump according to claim 9 , wherein the shaft comprises a flattened tang portion extending into a central solid portion of the rotor.

11. A vacuum pump, comprising:

a housing having an inlet and an outlet;

a chamber within the housing;

a rotor configured to undergo rotational movement about a rotational axis within the chamber, and

at least a first vane and a second vane, the first vane and the second vane being received, respectively, in a first slot and a second slot, the first slot and the second slot being formed in the rotor,

wherein the first slot and the second slot are substantially parallel to each other,

wherein a length of the first vane is greater than a length of the first slot,

wherein a length of the second vane is greater than a length of the second slot,

wherein the rotor comprises first and second bridges, and

wherein the first bridge intersects the first slot and the second bridge intersects the second slot for connecting opposing portions of the rotor.

12. The vacuum pump according to claim 11 , wherein the first vane comprises a first recess that corresponds to the first bridge and the second vane comprises a second recess that corresponds to the second bridge such that the first vane and the second vane are able to slide, respectively, within the first slot and the second slot.

13. The vacuum pump according to claim 12 , wherein the first bridge and the second bridge form abutments for restricting movement of the first vane and the second vane.

14. The vacuum pump according to claim 13 , wherein the abutments are formed such that a center of gravity of the first vane and a center of gravity of the second vane are always kept on a same side of a radial plane through the rotor perpendicular to the first slot and the second slot.

15. A production method for manufacturing a vacuum pump comprising:

providing a housing having an inlet and an outlet, the housing defining a chamber therein;

providing a drive shaft;

over moulding a rotor on the drive shaft, the rotor having a first slot and a second slot, wherein the first slot and the second slot are substantially parallel to each other; and

providing a first vane and a second vane received, respectively, in the first slot and the second slot, wherein a length of the first vane is greater than a length of the first slot, wherein a length of the second vane is greater than a length of the second slot, and wherein the first slot and the second slot are formed as secants and are symmetrical to each other about a rotational axis of the rotor.

16. The production method according to claim 15 , further comprising:

forging a flattened tang portion on the drive shaft before over moulding the rotor.

17. A vacuum pump, comprising:

a housing having an inlet and an outlet;

a chamber within the housing;

a rotor configured to undergo rotational movement about a rotational axis within the chamber, and

at least a first vane and a second vane, the first vane and the second vane being received, respectively, in a first slot and a second slot, the first slot and the second slot being formed in the rotor,

wherein the first slot and the second slot are substantially parallel to each other,

wherein a length of the first vane is greater than a length of the first slot,

wherein a length of the second vane is greater than a length of the second slot,

wherein the first slot includes a radially inner surface that extends, in a plane perpendicular to the rotational axis, from a first point on a circumference of the rotor to a second point on the circumference of the rotor thereby forming a first secant line in the plane perpendicular to the rotational axis, and

wherein the second slot includes a radially inner surface that extends, in the plane perpendicular to the rotational axis, from a third point on the circumference of the rotor to a fourth point on the circumference of the rotor thereby forming a second secant line in the plane perpendicular to the rotational axis.

18. The vacuum pump according to claim 17 , wherein the first secant line and the second secant line are parallel, and

wherein the diameter of the rotor defines a line that lies between the first secant line and the second secant line.

19. The vacuum pump according to claim 18 , wherein the rotor includes a center section that separates the first slot from the second slot,

wherein a width of the center section is defined by a distance between the first secant line and the second secant line.

20. The vacuum pump according to claim 17 , wherein a distance between the first and second points on the circumference of the rotor is smaller than the diameter of the rotor.