WO1999049700A2

WO1999049700A2 - Thin film heated fan blade

Info

Publication number: WO1999049700A2
Application number: PCT/US1999/006701
Authority: WO
Inventors: Richard P. Cooper
Original assignee: Thermo•Stone Usa, Llc
Priority date: 1998-03-27
Filing date: 1999-03-26
Publication date: 1999-09-30
Also published as: AU3454099A; WO1999049700A3

Abstract

A thin film heated fan blade including a plurality of fan blades (12) rotatably carried by a slip ring housing (14) that is rotatably secured to a motor (34). Slip rings (32) allow for rotation of fan blades (12) by maintaining electrical contact with leads (30).

Description

THINFILMHEATED FANBLADE

Related Application

This application is based on a provisional US application, Serial No. 60/079,557 filed March 27, 1998, entitled "Thin Film Heated Fan Blade."

Field of the Invention

The present invention pertains to thin film heaters for use as space heaters and for warming nearby objects.

Background Art

U.S. Patent No. 5,616,266, entitled "Resistance Heating Element With Large Area Thin Film and Method," (hereinafter '"266 patent") discloses a heating element that exhibits significant advantages of uniformity of heat distribution over the heater surface area without the need for conductive overlays. The heating element includes a relatively rigid, non-conductive substrate having an electrically conductive, thin film heating element deposited thereon. A pair of spaced apart electrical terminals are connected at opposite ends of the thin film heating element to create electrical resistance heating across the heating element. The disclosed heating element provides uniform heat across its surface area and does so at a relatively low power density. The present invention encompasses a specific application for the thin film heater element disclosed in my above referenced '266 patent.

Summary of the Invention

Briefly described, the fan of the present invention comprises a plurality of fan blades each having a surface area facing an area to be heated, with the surface area of each fan blade having secured thereto a thin film heater covering a substantial portion of said surface area, a housing for rotatably supporting the fan blades, a motor for rotating the fan blades, and means for electrically connecting the thin film heaters to a source of electrical power for heating the thin film heaters as the fan blades rotate.

According to an aspect of the invention, each thin film heater is made of a conductive metal-oxide. Preferably, each thin film heater is made of tin-oxide. It is also preferable that each thin film heater be less than approximately 2 microns in thickness.

According to another aspect of the invention, said means for electrically connecting the thin film heaters includes a slip ring. Preferably, a plurality of slip rings are provided, depending on the voltage supplied to the thin film heaters.

According to another aspect of the invention, a thin conductive protective coating is provided over each thin film heater. Preferably, the protective coating is made of a silicon material.

According to another aspect of the invention, the fan further comprises a switch between a source of electrical power and the thin film heaters, said switch being responsive to rotation of the fan blades. Preferably, the switch is responsive to rotation of the motor. These and other features, advantages, objects of the present invention will become apparent from the following description of the best mode for carrying out the invention, when read in conjunction with the figures, which are incorporated into the summary of the invention.

Brief Description of the Drawings

Throughout the several views, like reference numerals refer to like parts, wherein:

Fig. 1 is a pictorial view of the improved the thin film heated fan blade of the present invention;

Fig. 2 is a sectional view of the thin film heated fan blade of Fig. 1 ;

Fig. 3 is a schematic electrical circuit for the thin film heated fan blade of Fig. l;

Best Mode of Carrying Out the Invention

Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that the described embodiments are not intended to limit the invention specifically to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention.

Fig. 1 shows a ceiling fan 10 having four fan blades 12, and a motor and slip ring housing 14, supported by a vertical pole 16, itself suspended from a ceiling (not shown). Each fan blade 12 includes a thin film heater element 20 of the same general type disclosed in my '266 patent. Each heater element 20 covers the vast majority of the under surface of each fan blade 12 and includes a ceramic insulation layer on which is deposited an electrically conductive, thin, large area film, which is electrically isolated from fan blade 12 by the ceramic layer. The ceramic layer could also be a mica sheet that is attached with the film element facing inward. Each fan blade thin film heater includes a pair of electrical terminals for electrical connection of the film to a source of electrical power.

Each thin film heater 20 is preferably made of an extremely thin film of conductive metal-oxide, such as stannic oxide or tin oxide, on the order of 2 microns or less in thickness. The design and preferred method of fabricating the thin film heater are discussed in more detail in my above referenced '266 patent, which is incorporated herein by reference. The particular method for securing the thin film heater to different types of fan blade material should be apparent to those skilled in the art. Preferably, the fan blade 12 forms the non- conductive substrate for receiving the conductive material of the heater element.

Fig. 2 shows a sectional view of fan 10. The leads 30 from the electrical terminals of heater elements 20 are connected to electrical wiring within housing 14 via a slip ring assembly 32. Slip ring assembly 32 includes a slip ring disc for each wire of leads 30. For a 110 volt power supply, two slip rings are needed, whereas for a 230 volt power source, three slip rings are needed.

A motor 34 within housing 14 drives shaft 36, which is connected to a hub 38 on which the four fan blades 12 are mounted. As discussed later, motor 34 and slip rings 32 are connected to a common power source. Fig. 3 shows a schematic electrical diagram for fan blade 10. Fan blade heater elements are designated 1, 2, 3, and 4 and correspond to the heater elements 20 of Fig. 2. Heater elements 1, 2, 3, and 4 are connected in parallel to an electrical power source 40. A pair of slip rings 42, 44 comprise slip ring assembly 32 and are located between heater elements 1 , 2, 3, and 4 and power source 40.

Motor 34 operates off of power source 40 and includes a switch S, that closes when the fan motor is turned on by a remote switch. A second switch or contact S₂ is located in series between power source 40 and slip ring 42 and is logically coupled to motor 34 by any of several methods to ensure rotation of fan blades 12 prior to operation of heater elements 1, 2, 3, and 4. It is well known to those skilled in the art that a current sensor or rotation detector, as well as other devices, can be employed to close switch S₂ prior to operation of the heater elements.

While the heater element disclosed in my '266 patent is designed for low power densities, in the range of 15 watts per square inch or less, the fan blade heater elements of the present invention can utilize much greater power densities due to the inherent convection cooling effect of the rotary motion of the blades. It is believed that power densities in the range of 50 watts can be achieved with no appreciable effect on the integrity of the thin film heater material.

For conventional room ceiling fan applications, where fan blades rotate at approximately 60-200 rpms, it is believed that temperatures in the range of 200°C can be maintained at the surface area of the thin film heaters. The resulting heating effect depends on the size of the heating elements, which can be made to extend across the entire undersurface of the fan blades. Heater elements 20 can be isolated from potential human contact via louvered enclosures or with the application of thin, conductive protective coatings over the heater element surface. Examples of suitable protective coatings are silicone dioxide, mica, and emulsions of silicone nitride, aluminum nitride and zirconia . These can be applied on the order of 1-2 microns thickness directly onto the conductive heater element material.

Another thin film heated fan blade application is for a convection oven heater. In this application, heated air is directed from the fan chamber into the oven enclosure, at elevated temperatures up to approximately 500° F. Other fan blade applications include centrifugal fan blades of the type used for in wall room heaters.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

Claims

What is claimed is:

1. A fan, comprising: a plurality of fan blades each having a surface area facing an area to be heated, a housing for rotatably supporting the fan blades, a motor for rotating the fan blades, said surface area of each fan blade having secured thereto a thin film heater covering a substantial portion of said surface area, and means for electrically connecting the thin film heaters to a source of electrical power for heating the thin film heaters as the fan blades rotate.

2. The fan of claim 1 wherein, each thin film heater is made of a conductive metal-oxide.

3. The fan of claim 2 wherein, each thin film heater is less than 2 microns in thickness.

4. The fan of claim 2 wherein, each thin film heater is made of tin-oxide.

5. The fan of claim 1 wherein, said means for electrically connecting the thin film heaters includes a slip ring.

6. The fan of claim 5 wherein, a plurality of slip rings are provided.

7. The fan of claim 1 and further comprising, a thin conductive protective coating is provided over each thin film heater.

8. The fan of claim 7 wherein, the protective coating is made of a silicon material.

9. The fan of claim 1 and further comprising a switch between a source of electrical power and the thin film heaters, said switch being responsive to rotation of the fan blades.

10. The fan of claim 9 wherein, said switch is responsive to rotation of the motor.