Patent ID: 7824162

Claim:
A vacuum pump comprising: a pumping chamber, a rotor assembly mounted on a driven shaft for rotation within the pumping chamber, a motor for rotating a drive shaft in forward and reverse directions, a driven member located on or carried by the driven shaft and a drive member located on or carried by the drive shaft for engaging the driven member to couple the driven shaft to the drive shaft, each member having first and second impact surfaces, the members being configured to permit a degree of free angular movement of the drive member relative to the driven member in either the forward or the reverse direction before one of the impact surfaces of the drive member impacts upon a corresponding impact surface of the driven member to transfer angular momentum from the drive member to the driven member, wherein each member comprises an eccentric protrusion located on its respective shaft, the first and second impact surfaces being located on opposing sides of the protrusion, wherein at least one of the members is magnetic, such that the drive member and the driven member are coupled together by a magnetic force at an interface between one of the impact surfaces of the drive member and the corresponding one of the impact surfaces of the driven member, the interface extending in parallel with the drive shaft in an axial direction, thereby creating a stronger magnetic resistance force against a relative, angular movement between the driven member and the drive member than a relative, linear movement therebetween in an axial direction, and wherein before an impact surface of the drive member impacts upon a corresponding impact surface of the driven member the angular movement of the drive member is initially resisted, when rotated in either a forward or reverse direction, due to the magnetic resistance force.