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Miniaturized fan for printed circuit boards
| Details |
Inventors: Cox, Ned;
Assignee: Texas Instruments Incorporated (Dallas, TX)
Primary Examiner: Salce; Patrick R.
Assistant Examiner: Rebsch; D. L.
Attorney, Agent or Firm: McAndrews; James P., Haug; John A., Sharp; Melvin
A fan for mounting on and use in connection with cooling of components on a PWB comprising a PWB having an aperture therein for receiving a bearing holder with a bearing rotatable within the holder. An annular multipole permanent magnet is secured to the bearing for rotation in the bearing holder. An impeller in the form of radially and outwardly extending vanes, aligned with a central point but spaced from said point, is secured to an outer surface of the permanent magnet and rotates therewith. A housing is secured to the PWB, the housing being disposed over the impeller and the magnet and having two openings, one in the region above the central point of the vanes and a second opening facing along the surface of the PWB. Four electromagnets are secured to the side of the PWB opposite the magnet, the electromagnets being positioned at the four corners of a square and beneath the magnet. A nonmagnetic spacer surrounds the electromagnets with a stator positioned thereover and beneath the electromagnets, the stator being secured to the bearing holder by means of a threaded member. The electromagnets are pulsed serially by a pulse circuit disposed on the surface of the PWB, the pulses being applied to the electromagnets via conductive paths of the PWB. |
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DETAILED DESCRIPTION In accordance with the present invention, the above noted problems of the prior art are minimized and there is provided a fan for cooling of components mounted on a PWB, said fan being of small dimension, being mounted directly onto the PWB and being under control of electronic circuitry mounted on the PWB itself.
Briefly, the above is accomplished by providing a PWB having an aperture therein for receiving a bearing holder with a bearing therein rotatable within the bearing holder.
An annular multipole permanent magnet with north and south poles 120 degrees apart is secured to the bearing for rotation therewith in the bearing holder.
An impeller in the form of a plurality of radially and outwardly extending vanes extending to a central point but spaced from said point is secured to an outer surface of the permanent magnet and rotates therewith.
A housing is secured to the PWB, the housing being disposed over the impeller and the magnet and having two openings therein, one in the region above the central point of the vanes and a second opening facing along the surface of the PWB.
Four electromagnets are secured to the surface of the PWB opposite the magnet, the electromagnets being positioned at the four corners of a square and beneath the magnet.
A non-magnetic spacer surrounds the electromagnets with a stator of a material so as not to impede rotation positioned thereover and beneath the electromagnets, the stator being secured to the bearing holder by means of a threaded member.
The electromagnets are pulsed serially by a pulse circuit disposed on the surface of the PWB, the pulses being applied to the electromagnets via conductive paths of the PWB.
In operation, when current pulses are applied to the electromagnets, a magnetic field is set up to cause rotation of the rotor and impeller.
The rotation of the impeller forces air therein which is between the vanes out of the second opening and along the surface of the PWB.
This air movement forms a slight vacuum in the region of the impeller between the vanes and causes air to travel through the first opening to the region between the vanes
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Generators or Motors 
