# US 5,705,793 A · Thin film electric heater, and method and apparatus for injection molding of plastics using the same

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- Number: US 5,705,793 A
- Document ID: US5705793A
- Status: Granted
- Kind: A
- Application number: 08/654,384
- Filed: 1996-05-28
- Granted: 1998-01-06
- Earliest claimed: 1994-06-06
- Assignees: Daiho Industrial Co., Ltd.
- Inventors: Satoshi Kitaichi; Chiaki Nakamura; Michio Tanaka; Atushi Fukuta
- Web page: https://patentgrep.com/patent/US5705793A

## CPC

- H05B 3/10: Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- B29C 33/08: for dielectric heating
- B29C 33/56: Coatings {, e.g. enameled or galvanised}; Releasing, lubricating or separating agents {(in-mould coating B29C37/0028; using or applying separating agents B29C37/0067)}
- B29C 45/73: of the mould {(B29C45/2642 and B29C45/2737 take precedence)}
- B29C 2045/7356: {the temperature of the mould being near or higher than the melting temperature or glass transition temperature of the moulding material}
- B29C 2045/7393: {alternately heating and cooling}
- Y10S 425/11: Heated mold
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A thin film electric heater employs voltage and current suppressed below values of an allowable voltage and an allowable current. The thin film electric heater includes a thin film electric resistor to be formed directly on a surface of an object to be heated and is energized to effect heating. The resistor has a surface resistivity r, expressed by r=.rho./t (where .rho. is the volume resistivity of the thin film electric resistor and t is the film thickness of the thin film electric resistor), within a range to achieve the heating function of the thin film electric heater while the values of voltage and current applied to the thin film electric heater are suppressed below the values of the allowable voltage and the allowable current.

## Claims

### Claim 1

A thin film electric heater comprising:
a thin film electric resistor to be formed directly on a surface of an object to be heated;
said thin film electric resistor having terminal portions to supply thereto electric power to thereby heat the surface of the object;
said thin film electric resistor having a surface resistivity r of a value defined by: ##EQU2## wherein L is a length between said terminal portions as measured along said thin film electric resistor, D is length of said thin film electric resistor in a direction perpendicular to the direction between said terminal portions, V.sub.a is a maximum value of allowable voltage applied between said terminal portions, I.sub.a is a maximum value of allowable current flowing between said terminal portions, and W.sub.r is an input power per unit area of said thin film electric resistor determined to obtain a desired rate of increase of temperature of the surface of the object.

### Claim 2 (depends on 1)

A thin film electric heater as claimed in claim 1, wherein said thin film electric resistor is formed of a material selected from a group consisting of TiN, TiC, TiCN, TiAlN and CrN.

### Claim 3 (depends on 1)

A thin film electric heater as claimed in claim 1, wherein said surface resistivity r is from 0.05 to 1.0 .OMEGA./.quadrature..

### Claim 4 (depends on 1)

A thin film electric heater as claimed in claim 1, wherein said film electric resistor has a volume resistivity within a range of 10.times.10.sup.-8 to 200.times.10.sup.-8 .OMEGA./.quadrature..