US4517448A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Infrared furnace with atmosphere control capability
Assignee: BTU International Inc
•
Filing: 1981-11-06
•
Granted: 1985-05-14
•
Expires: 2001-11-06
Abstract
Abstract An infrared furnace has a housing with insulated walls defining an elongated straight tunnel disposed on a longitudinal axis between an entrance and an exit. A conveyor continuously moves through the tunnel along the longitudinal axis between the entrance and the exit. A first plurality of elongated tubular infrared heating elements are disposed in the tunnel above the conveyor in spaced apart parallel relationship transverse to the longitudinal axis. A second plurality of tubular elongated infrared heating elements are disposed in the tunnel below the conveyor in spaced apart parallel relationship transverse to the longitudinal axis. The housing has insulated walls each comprising a porous insulative inner panel and a non-porous outer panel. At least one of the outer panels is spaced from its associated inner panel to form a plenum chamber therebetween. The insulated walls define an elongated tunnel in which a source of infrared radiation is disposed. Gas under pressure is supplied to the plenum chamber to induce flow through the inner panel to the tunnel. A first baffle unit has a chamber connectng the entrance of the tunnel to the exterior of the furnace. A second baffle unit has a chamber connecting the exit of the tunnel to the exterior of the furnace such that the conveyor passes through the chambers. Gas is injected onto the conveyor in the chambers to prevent contamination from entering the tunnel. A plurality of parallel spaced apart rods extend through the tunnel parallel to its longitudinal axis directly under the conveyor to support the conveyor. Two of the rods lie near the respective sides of the housing and heating elements are disposed in these rods to compensate for heat loss to the sides of the housing.
Inventors
- 👤 N. Robert Crain
- 👤 Carson T. Richert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 07:47
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/10; H05K3/12; H05K3/1283; H05K3/1291; H10; H10D; H10D84/00; H10D84/01; H05K2203/00; H05K2203/11; H05K2203/1105; H05K2203/1126
Claims Analysis
Total Claims: 50
Claim 1
Independent Claim
189 words
An infrared furnace comprising: an elongated rectangularly shaped heating chamber having its interior top, bottom, side, and end walls formed of sheets of porous insulation; a sheet metal housing enclosing the insulating walls of said heating chamber; a conveyor belt passing into and out of the heating chamber through openings provided in the end walls thereof; a first series of infrared heating elements in said heating chamber transversely disposed above said conveyor belt with their terminal ends extended through the side walls thereof; a second series of infrared heating elements in said heating chamber transversely disposed below said conveyor belt with their terminal ends extending through the side walls thereof; an upper plenum chamber formed between the top insulating wall of said heating chamber and the top wall of said sheet metal housing; a lower plenum chamber formed between the bottom insulating wall of said heating chamber and the bottom wall of said sheet metal housing; and means for introducing a pressurized cover gas into the upper and lower plenum chambers which filters through the porous upper and lower insulating walls of said heating chamber into the interior thereof.
Claim 2
Dependent Claim
189 words
An infrared furnace comprising: an elongated rectangularly shaped heating chamber having its interior top, bottom, side, and end walls formed of sheets of porous insulation; a sheet metal housing enclosing the insulating walls of said heating chamber; a conveyor belt passing into and out of the heating chamber through openings provided in the end walls thereof; a first series of infrared heating elements in said heating chamber transversely disposed above said conveyor belt with their terminal ends extended through the side walls thereof; a second series of infrared heating elements in said heating chamber transversely disposed below said conveyor belt with their terminal ends extending through the side walls thereof; an upper plenum chamber formed between the top insulating wall of said heating chamber and the top wall of said sheet metal housing; a lower plenum chamber formed between the bottom insulating wall of said heating chamber and the bottom wall of said sheet metal housing; and means for introducing a pressurized cover gas into the upper and lower plenum chambers which filters through the porous upper and lower insulating walls of said heating chamber into the interior thereof.
Claim 3
Dependent Claim
125 words
An infrared furnace comprising: an elongated rectangularly shaped heating chamber having its interior top, bottom, side, and end walls formed of sheets of insulation; a sheet metal housing enclosing the insulating walls of said heating chamber; a conveyor belt passing into and out of the heating chamber through openings provided in the end walls thereof; a first series of infrared heating elements in said heating chamber transversely disposed above said conveyor belt with their terminal ends extended through the side walls thereof; a second series of infrared heating elements in said heating chamber transversely disposed below said conveyor belt with their terminal ends extending through the side walls thereof; and elongated quartz rods extending lengthwise through said heating chamber on which said conveyor belt rides.
Claim 4
Dependent Claim
125 words
An infrared furnace comprising: an elongated rectangularly shaped heating chamber having its interior top, bottom, side, and end walls formed of sheets of insulation; a sheet metal housing enclosing the insulating walls of said heating chamber; a conveyor belt passing into and out of the heating chamber through openings provided in the end walls thereof; a first series of infrared heating elements in said heating chamber transversely disposed above said conveyor belt with their terminal ends extended through the side walls thereof; a second series of infrared heating elements in said heating chamber transversely disposed below said conveyor belt with their terminal ends extending through the side walls thereof; and elongated quartz rods extending lengthwise through said heating chamber on which said conveyor belt rides.
Claim 5
Dependent Claim
28 words
An infrared furnace as defined in claim 2 wherein heater coils are provided within the elongated quartz rods on which the side edges of said conveyor belt ride.
Claim 6
Dependent Claim
91 words
An infrared furnace comprising: a housing having insulated walls defining an elongated tunnel disposed on a longitudinal axis between an entrance and an exit; a conveyor continuously moving through the tunnel along the longitudinal axis between the entrance and the exit; a plurality of parallel spaced apart rods; means for holding the rods to extend through the tunnel parallel to its longitudinal axis directly under the conveyor to support the conveyor such that the rods are free to rotate; and means in the tunnel for radiating infrared energy onto the conveyor.
Claim 7
Dependent Claim
91 words
An infrared furnace comprising: a housing having insulated walls defining an elongated tunnel disposed on a longitudinal axis between an entrance and an exit; a conveyor continuously moving through the tunnel along the longitudinal axis between the entrance and the exit; a plurality of parallel spaced apart rods; means for holding the rods to extend through the tunnel parallel to its longitudinal axis directly under the conveyor to support the conveyor such that the rods are free to rotate; and means in the tunnel for radiating infrared energy onto the conveyor.
Claim 8
Dependent Claim
16 words
The furnace of claim 4, comprising heating means disposed in at least one of the rods.
Claim 9
Dependent Claim
41 words
The furnace of claim 4, in which two of the rods lie near the respective sides of the housing, the furnace additionally comprising heating means disposed in the two rods to compensate for heat loss through the sides of the housing.
Claim 10
Dependent Claim
13 words
The furnace of claim 4, in which the rods are made of quartz.
Claim 11
Dependent Claim
83 words
An infrared furnace comprising: a housing having walls defining an elongated tunnel disposed between an entrance and an exit, the walls each comprising a porous insulative inner panel opening into the tunnel and a non-porous outer panel; a conveyor moving through the tunnel between the entrance and the exit; means for supplying gas under pressure between the inner and outer panels to induce flow through the inner panel to the tunnel; and means in the tunnel for radiating infrared energy onto the conveyor.
Claim 12
Dependent Claim
83 words
An infrared furnace comprising: a housing having walls defining an elongated tunnel disposed between an entrance and an exit, the walls each comprising a porous insulative inner panel opening into the tunnel and a non-porous outer panel; a conveyor moving through the tunnel between the entrance and the exit; means for supplying gas under pressure between the inner and outer panels to induce flow through the inner panel to the tunnel; and means in the tunnel for radiating infrared energy onto the conveyor.
Claim 13
Dependent Claim
71 words
The furnace of claim 8, additionally comprising a first baffle unit having a chamber connecting the entrance of the tunnel to the exterior of the furnace and a second baffle unit having a chamber connecting the exit of the tunnel to the exterior of the furnace such that the conveyor passes through the chambers, the first and second baffle units including means for injecting gas onto the conveyor in the chambers.
Claim 14
Dependent Claim
22 words
The furnace of claim 9, in which the first and second baffle units additionally include means for removing gas from the chambers.
Claim 15
Dependent Claim
28 words
The furnace of claim 8, in which the radiating means comprises a plurality of infrared energy sources distributed on both sides of the conveyor in direct communication therewith.
Claim 16
Dependent Claim
47 words
The furnace of claim 8 additionally comprising means for sensing the temperature in at least one zone of the tunnel and means responsive to the temperature sensing means for controlling the infrared energy radiated onto the conveyor so as to maintain the temperature in the zone constant.
Claim 17
Dependent Claim
86 words
The furnace of claim 8, in which the means for radiating infrared energy comprises a plurality of elongated, tubular infrared heating elements disposed in the tunnel in direct communication with the conveyor, means for applying electrical energy to the heating elements to energize them, means for sensing the temperature in at least one zone of the tunnel, and means responsive to the temperature sensing means for controlling the voltage of the electrical energy applied to the heating elements to maintain the temperature in the zone constant.
Claim 18
Dependent Claim
25 words
The furnace of claim 13 in which the sensing means maintains the temperature in the zone constant at a temperature between 1120° to 1170° K.
Claim 19
Dependent Claim
30 words
The apparatus of claim 13 in which the controlling means controls the voltage applied to the heating elements to maintain their temperature of the order of 1400° to 2000° K.
Claim 20
Dependent Claim
28 words
The furnace of claim 13, additionally comprising one or more rods extending through the tunnel parallel to its longitudinal axis directly under the conveyor to support the conveyor.
Claim 21
Dependent Claim
22 words
The furnace of claim 13, in which the sources are tungsten filaments enclosed in a sealed quartz envelope with an inert gas.
Claim 22
Dependent Claim
23 words
The furnace of claim 17, in which the temperature of the infrared sources is of the order of 1400° K. to 2000° K.
Claim 23
Dependent Claim
25 words
The furnace of claim 18, in which the temperature in the interior of the tunnel is of the order of 1120° K. to 1170° K.
Claim 24
Dependent Claim
31 words
The furnace of claim 13, additionally comprising a plurality of parallel spaced apart rods extending through the tunnel parallel to its longitudinal axis directly under the conveyor to support the conveyor.
Claim 25
Dependent Claim
16 words
The furnace of claim 20, comprising heating means disposed in at least one of the rods.
Claim 26
Dependent Claim
43 words
The furnace of claim 20, in which two of the rods lie near the respective side walls of the housing, the furnace additionally comprising heating means disposed in the two rods to compensate for heat loss through the side walls of the housing.
Claim 27
Dependent Claim
48 words
The furnace of claim 13, in which the walls defining the tunnel comprise approximately horizontal top and bottom walls and approximately vertical side walls together forming a rectangular cross section and the heating elements are parallel to the top and bottom walls and perpendicular to the side walls.
Claim 28
Dependent Claim
19 words
The furnace of claim 23, in which the ends of the heating elements are supported by the side walls.
Claim 29
Dependent Claim
80 words
The furnace of claim 23, in which the ends of the heating elements pass through the side walls to the exterior of the housing, the furnace additionally comprising an outer enclosure surrounding the top, bottom, and side walls in spaced relationship from the side walls; means for applying electrical energy to the ends of the heating elements to energize them; and means for blowing air between the enclosure and the side walls to cool the ends of the heating elements.
Claim 30
Dependent Claim
71 words
The furnace of claim 13, additionally comprising a first baffle unit having a chamber connecting the entrance of the tunnel to the exterior of the furnace and a second baffle unit having a chamber connecting the exit of the tunnel to the exterior of the furnace such that the conveyor passes through the chambers, the first and second baffle units including means for injecting gas onto the conveyor in the chambers.
Claim 31
Dependent Claim
22 words
The furnace of claim 26, in which the first and second baffle units additionally include means for removing gas from the chambers.
Claim 32
Dependent Claim
32 words
The furnace of claim 27, in which each removing means comprises an upwardly extending duct opening into the chamber between the point of injection of gas and the exterior of the furnace.
Claim 33
Dependent Claim
23 words
The furnace of claim 28, in which the first and second baffle units additionally comprise means for creating turbulence in the injected gas.
Claim 34
Dependent Claim
31 words
The furnace of claim 29, in which the first and second baffle units each additionally comprise a plurality of baffle walls between the point of injection of gas and the tunnel.
Claim 35
Dependent Claim
41 words
The apparatus of claim 13, in which the controlling means controls the voltage of the energy applied to the heating elements so the heating elements radiate infrared radiation with energy concentration in a wavelength band of approximately 0.7 to 2.5 microns.
Claim 36
Dependent Claim
117 words
An infrared furnace comprising: an elongated rectangularly shaped heating chamber having its interior top, bottom, side, and end walls formed of sheets of insulation in the form of compressed, white alumina fiber; a sheet metal housing enclosing the insulating walls of said heating chamber; a conveyor belt passing into and out of the heating chamber through openings provided in the end walls thereof; a first series of infrared heating elements in said heating chamber transversely disposed above said conveyor belt with their terminal ends extended through the walls thereof; and a second series of infrared heating elements in said heating chamber transversely disposed below said conveyor belt with their terminal ends extending through the side walls thereof.
Claim 37
Dependent Claim
117 words
An infrared furnace comprising: an elongated rectangularly shaped heating chamber having its interior top, bottom, side, and end walls formed of sheets of insulation in the form of compressed, white alumina fiber; a sheet metal housing enclosing the insulating walls of said heating chamber; a conveyor belt passing into and out of the heating chamber through openings provided in the end walls thereof; a first series of infrared heating elements in said heating chamber transversely disposed above said conveyor belt with their terminal ends extended through the walls thereof; and a second series of infrared heating elements in said heating chamber transversely disposed below said conveyor belt with their terminal ends extending through the side walls thereof.
Claim 38
Dependent Claim
27 words
An infrared furnace as defined in claim 32 wherein the sheets of insulation forming the interior walls of said heating chamber have a rating of 3000° F.
Claim 39
Dependent Claim
39 words
An infrared furnace as defined in claim 32 wherein the top and bottom walls of said heating chamber are formed of two sheets of insulation and wherein the side walls thereof are formed of a single sheet of insulation.
Claim 40
Dependent Claim
70 words
An infrared furnace as defined in claim 32 wherein said sheet metal housing includes: side walls and end walls covering the corresponding insulating walls of said heating chamber; a top cover which fits over the top portion of said heating chamber; a bottom cover which fits over the bottom portion of said heating chamber; and means for connecting said top and bottom covers to said side walls and end walls.
Claim 41
Dependent Claim
46 words
An infrared furnace as defined in claim 32 including: outwardly extending tray members attached to the sides of said sheet metal housing; and ceramic connectors mounted on the outer ends of said tray members to which the terminal leads of said infrared heating elements are connected.
Claim 42
Dependent Claim
21 words
An infrared furnace as defined in claim 32 including baffle means at the entrance and exit ends of said heating chamber.
Claim 43
Dependent Claim
38 words
An infrared furnace as defined in claim 37 wherein each of said baffle means includes: a baffle housing through which said conveyor belt passes; and a vertically disposed exhaust duct on the outer end of said baffle housing.
Claim 44
Dependent Claim
54 words
An infrared furnace as defined in claim 38 wherein said baffle housing includes: an upper plenum chamber and a lower plenum chamber; said upper and lower plenum chambers having apertures respectively disposed above and below said conveyor belt; and means for introducing a pressurized baffle gas into each said upper and lower plenum chambers.
Claim 45
Dependent Claim
27 words
An infrared furnace as defined in claim 39 wherein said upper plenum chamber has a plurality of transversely disposed vertical baffle walls depending from the bottom thereof.
Claim 46
Dependent Claim
40 words
An infrared furnace as defined in claim 40 wherein the bottom wall of said upper plenum chamber is vertically adjustable to vary the depth to which the baffle walls depending therefrom extend into the baffle housing above said conveyor belt.
Claim 47
Dependent Claim
44 words
An infrared furnace as defined in claim 32 including a rectangular framework having longitudinal extending side members; said heating chamber positioned within said rectangular framework and supported on the side members thereof by bracket means attached to the corners of said sheet metal housing.
Claim 48
Dependent Claim
34 words
The furnace of claim 32, additionally comprising means for introducing a pressurized cover gas between the sheet metal housing and the insulating walls which filters through the sheets of insulation into the heating chamber.
Claim 49
Dependent Claim
12 words
The furnace of claim 43, in which the cover gas is inert.
Claim 50
Dependent Claim
12 words
The furnace of claim 44, in which the cover gas is nitrogen.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-05-13 | 1988-11-12 | 1989-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-13 | 1992-11-12 | 1993-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-13 | 1996-11-12 | 1997-05-14 | $7700.00 | Window Closed / Lapsed |