US3770408A

US3770408A - Annealing lehr

Info

Publication number: US3770408A
Application number: US00198849A
Authority: US
Inventors: Cully J Mc
Original assignee: Midland Ross Corp
Current assignee: Surface Combustion Corp; Grimes Aerospace Co
Priority date: 1971-11-15
Filing date: 1971-11-15
Publication date: 1973-11-06
Anticipated expiration: 1990-11-06
Also published as: FR2161563A5; GB1393150A; CA980122A; JPS5755661B2; JPS4859118A

Abstract

An endless belt conveyor annealing lehr having burner means located above the belt. The belt is foraminous and supported throughout the length of the lehr by a system of perforated plates. A shroud extends intermediate the walls of the lehr and a fan is located adjacent to the burner means outlet. This combination results in a continuous circulating atmosphere impinging directly upon the work being conveyed through the lehr. Means is also provided to control the temperature of the work throughout the length of the lehr, particularly at the entrance thereof.

Description

United States Patent 1 Mctlully ANNEALHNG LEHR [75] inventor: Joseph B. McCully, Maumee, Ohio [73] Assignee: Midland-Ross Corporation,

Cleveland, Ohio {22] Filed: Nov. 15, 1971 [2]] Appl. No.: 198,84?

[52] Cl.. :5/]162 65/351 [51] Km. Cl C031) 25/194 [58] Field of Search 65/348, 349, 350, 65/351, 162

[56] References Cited UNITED STATES PATENTS 2,982,052 5/1961 Lawson 65/162 2,544,947 3/1951 Baker 1 65/162 2,725,680 12/1955 Baker 65/351 X [451 Nov6,1973

Primary Examiner-Arthur D. Kellogg Att0rneyPeter Vrahotes [57] ABSTRACT An endless belt conveyor annealing lehr having burner means located above the belt. The belt is foraminous and supported throughout the length of the lehr by a system of perforated plates. A shroud extends intermediate the walls of the lehr and a fan is located adjacent to the burner means outlet. This combination results in a continuous circulating atmosphere impinging directly upon the work being conveyed through the lehr. Means is also provided to control the temperature of the work throughout the length of the lehr, particularly at the entrance thereof.

8 Claims, 7 Drawing Figures a u u I ANNEALING LEHR In the heat treating of work, such as glassware, in an annealing lehr, or furnace, having a continuous belt, it is desirable to obtain efficient heat utilization as well as close temperature control. Prior art annealing lehrs generally utilize direct burner's which emit the products of combustion into the annealing chamber, and the products of combustion are circulated by a fan. Because of the generally random circulation of the products of combustion, a high percentage of the heat is transferred to the surrounding walls, resulting in a large amount of heat being conducted to the glassware radia'ntly. It is preferable to transfer heat by high convection, as it is more efficient for dense loads. Additionally, in the annealing of glassware, sometimes the work is introduced into the lehr at a higher temperature than the temperature required for annealing, and the work must be cooled. As transfer of heat by radiation to dense loads is not as responsive, it again is more desirable to transfer heat by convection.

It is, therefore, an object of this invention to provide an annealing lehr, or furnace, which anneals work with a higher percentage of heat being transferred by convection.

It is another object of this invention to provide an annealing lehr having a close control of temperature from zone to zone.

It is a further object of this invention to provide an annealing lehr having means for releasing hot gases against the base of the workpieces through the support members of the workpieces. i

It is still another object of this invention to provide means for transferring combustion gases from a burner to the work with a minimum temperature drop.

It is still a further object to provide unique burner means for an annealing lehr.

Other and further objects will become obvious when reference is had to the drawings, specification, and claims herein.

In the Drawing:

FIG. 1 is a perspective view of the type of annealing lehr to which the invention is applicable.

FIG. 2 is a partially schematic, longitudinal crosssectional view of the entrance end of an annealing lehr embodying the principles of this invention.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2. v

FIG. 4 is a longitudinal cross-sectional view of the static cooling section of the annealing lehr shown in FIG. 1.

FIG. 5 is a longitudinal cross-sectional view showing a portion of the forced cooling section of the lehr shown in FIG. 1 and the discharge end thereof.

FIG. 6 is a longitudinal cross-sectional view of the entrance end of the annealing lehr shown in FIG. 1 with a unique burner means.

FIG. 7 is a cross-sectional view of the lehr having the unique burner means shown in FIG. 6 taken along line 77.

Referring now to the drawing, an annealing lehr is shown generally at 10 which comprises a housing 11, or heating chamber, a staticcooling chamber 12, and a forced cooling chamber 13. The housing 11 has a roof 14, a floor 16, first side wall 18, and second side wall 20. The roof l4, floor l6, and walls 18, of the housing 11 are made of refractory insulation 22 which is supported on the outside by a steel casing 24 and on the inside by a metal lining 25. The housing 11 has an entrance opening 26 with an adjustable door 28. There is a second opening 30 at the exit end of the housing 11 'also having an adjustable door 32. Supporting the housing 1 1 are a plurality of laterally extending channel sections 34 which are secured to longitudinally spaced legs 36 which are in contact with the floor of a building or the ground.

Downstream from the housing 11 is the static cooling chamber 12 which has a pair of longitudinally extending channel irons 40 that support transverse channel members 42. Located below the channel members 42 is a plate 44 which, in cooperation with chamber side walls 43, encloses the cooling chamber 12. A plurality of legs 46 support the longitudinally extending channel irons 40 and the static cooling chamber 12 is provided with a roof 48 having a plurality of openings 50 therein,

which openings receive adjustable dampers 52. Downstream from the static cooling chamber 12 is the forced cooling chamber 13, there being an open portion 56 intermediate the static cooling chamber 12 and the forced cooling chamber 13. It will be noted that the plate 44 terminates at the downstream end of the cooling chamber 12 and the balance of the downstream end of the lehr 10 has an open bottom.

The forced cooling chamber. 13 has aroof 60 containing a plurality of openings 62. A plurality'of fan assemblies 64 are disposed on the roof 60, there being a fan assembly located above each of the openings. Situated along the length of the forced cooling chamber 13 i I I are a plurality of flexible curtains 66 which assist in directing the flow of cooling air downwardly.

Located on each end of the lehr l0-

are pipe rollers

68 and 70, there being a drive roller 72, having afriction surface, located below the floor of the furnace and a snub roll 74. A continuous foraminous belt 76, such as a mesh belt, is turned and driven by the

rollers

72, 74 in conveying work 75 through the lehr. In addition, there are a number of rollers 77 having tension means (not' shown) provided to take up slack in the belt 76. The belt 76 is supported within the housing 11 by a longitudinally extending plate 78 which has a plurality of openings 79, or perforations, therein. The plate 78 is, in turn, supported by transversely extending angle irons 80 which are attached to a pair of longitudinally extending support members 81.

Located within the roof 14 of thehousing 11 are a plurality of openings 82. A fan assembly 84 is positioned above each opening 82 and supported by the roof 14. Each fan assembly has a shaft 86 extending through the opening 82 and a fan blade 88 located at the lower end of each shaft. The housing 11 is composed of a plurality of zones, each zone being determined by the location and influence of the fan assemblies 84.

Extending through the side wall 18 at the location of each fan assembly 84 is a ported tube 90 which is supplied with combustible gas from a source 92. Extending the length of the housing 12 is a metallic shroud 94 which is spaced relative to the roof 14,

side walls

18 and 20, and terminates a short distance below the upper location of the belt 76. The shroud 94 has a plurality of first openings 96 which are aligned with the fan blades 88 and a second plurality of openings 97 which receive the ported tubes 90. A plurality of vanes 98 are attached to the shroud 94 and extend from the opening 96 outwardly to direct the wind from the fan blade 88 '3 and intermediate the plenum 100 defined by the shroud 94, roof 14, and

side walls

18, 20. Positioned at locations within the housing 11 to correspond to the locations of the fan assemblies 84 are a plurality of thermocouples 102 which are connected to an instrument 104 which controls the gas source 92 in response to the temperature measured by the thermocouples.

In operation, natural gas is supplied from the source 92 to the ported tube burners 90 wherein the gas is combusted with air as it leaves the ports of the burner. The products of combustion are drawn upwardly by the fan blade 88, mix with the recirculating atmosphere, and subsequently devolve between the plenum 100 defined by the shroud 94 and panels 25. Because ported tube burners 90 are used, the flame is broadly distributed. The recirculating atmosphere then is forced upward from the bottom of the housing 11 by pressure created by the fans 84 and moves upwardly through the perforations 79 in the plate 78. Since the belt is foraminous, the recirculating atmosphere directly contacts the work 75 that is supported upon the belt 76. In this manner there is intimate contact between the work and the recirculating atmosphere so that a high percentage of the heat transferred to the work is by convection. The heat transfer is also aided by the high velocity with which the hot gas impinges against the work 75.

As stated previously, the furnace housing is divided into zones, each being defined by the location of a fan assembly 84. The temperature of each zone is controlled by the thermocouples 102 through the controller 104. When the selected temperature of each zone is measured as too high, the respective source of gas will be discontinued and, conversely, gas will be supplied to the burners 90 after the temperature falls before a preset minimum. It will be appreciated that the work 75 will at times enter the first zone at a temperature above the desired annealing temperature. With the present arrangement the entrance zone may be operated in such a manner as to cool the incoming work 75 when required, by omitting the source of heat and allowing the first zone to act as a cooling zone.

ALTERNATE BURNER MEANS An alternate burner means 105 for providing combustion gases to the fan assemblies 84 for circulation is shown in FIGS. 6 and 7. The burner means 105 comprises a combustor 106 secured to the roof 14 of the housing 11. The combustor is supplied with a gas line 107, which communicates with the source 92, and an air line 109. The combustor emits combusting gases into an annular chamber 108 that is received within an opening 110 of the roof. The chamber l08'has a refractory lining 112 which serves to prevent loss of heat and protect the roof from heat damage. Depending from each chamber 108 are a plurality of straps 114 which have a shoe 116 attached to the lower ends thereof, each of which shoes opens in the direction of its associated fan assembly 84. As can be determined from the drawing, hot gases are directed downwardly from the chamber 108 and are deflected into a horizontal direction by the shoes 116. The gases are then drawn by the fan blades 88 and circulated as described previously.

The advantage of this type of burner means 105 is that of safety. With the ported tubes 90, as well as prior art burners, structures project from the side of the lehr 10 where they act as a hazard with regard to collisions by personnel and exposure of operatorsto heat. The

burner means 105 just described is supported by the roof 14 and is thus removed as a hazard. The burner means 105 also has an advantage in that a broad path is provided for the hot gases.

What is claimed is:

1. A lehr for heatftreating in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor,'an entrance opening and an exit opening, support means disposed along the length of the housing intermediate the roof and the floor, a foraminous belt received within the housing and supported along the length thereof by said support means, means for conveying the belt through said furnace, a plurality of longitudinally spaced-fans received within the roof, a longitudinally extending shroud within the housing spaced relative to the roof and the side walls and terminating above the floor to define a plenum in combination with said side walls androof and an opening in combination with said floor, said shroud having a plurality of openings which are aligned with said fans, a plurality of longitudinally spaced burners received within and extending into said housing, said burners being mounted in such a manner that the productsof combustion are drawn into the circulating path generated by said fans, means for supplying fuel to said burners, means for sensing the temperature along the length of the furnace, and means for controlling the supply of fuel in response to the temperature sensing means.

2. The lehr of claim 1 wherein said support means is aperforated plate.

3. The lehr of claim 1 wherein said burners are located at the locations of said fans.

4. A lehr for heat treating of work in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor, an entrance opening and an exit opening, a longitudinally extending, porous plate received within said housing, an endless foraminous belt supported by said plate, means for conveying said belt along said plate, a plurality of longitudinally spaced fans received within said roof, a shroud extending within the length of the housing spaced relative to the roof and side walls to define a plenum therebetween, said shroud terminating at approximately the location of said plate to define an opening therebetween, said shroud having an opening at each location of said fans, a plurality of longitudinally spaced burners received within one of said side walls and extending intermediate said belt and said fans, said burners being mounted in such a manner that the products of combustion are drawn into the circulating path generated by said fans, means for supplying fuel to said burners, means for sensing the temperature along the length of said housing, and means for supplying fuel to said burners in response to said sensing means.

5. The lehr ofv claim 4 wherein said burners are ported tube burners.

6. A lehr for heat treating in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor, an entrance opening and an exit opening, support means disposed along the length -of the housing intermediate the roof and the floor, a foraminous belt received within the housing and supported along the-length thereof by said support means, means for conveying the belt through said housing, a plurality of spaced fans received within the roof, a longitudinally extending shroud within the housing spaced relative to the roof and the side walls and terminating above the floor to define a plenum in combination with said side walls and roof and an opening in combination with said floor, said shroud having a first plurality of openings whichare aligned with said fans and a second plurality of openings, a plurality of longitudinally spaced burners received within said roof and extending into said housing and said shroud through said second plurality of openings, said burners being mounted in such a manner that the products of combustion are drawn into the circulating path generated by said fans, means for supplying fuel to said burners, means for sensing the temperature along the length of the furnace, and means for controlling the supply of fuel in response to the temperature sensing means.

7. The lehr of claim 6 wherein said support means is a perforated plate.

8. A lehr for heat treating work in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor, an entrance opening and an exit opening, a longitudinally extending, porous plate received within said housing, an endless foraminous belt supported by said plate, means for conveying said belt along said plate, a plurality of longitudinally spaced fans received within said roof, a shroud extending within the length of the housing spaced relative to the roof and side walls to define a plenum therebetween, said shroud terminating at approximately the location of said plate to define an opening therebetween, said shroud having a first series of openings at each location of said fans, a plurality of longitudinally spaced combustors received within said roof and operative to direct combusting gases downwardly, said shroud having a second series of openings at each location of said combustor, a shoe located beneath each combustor having means to deflect gases from the com bustor horizontally into the circulating path generated by said fans, means for supplying fuel to said combustors, means for sensing the temperature along the length of said housing, and means for supplying fuel to said combustors in response to said sensing means.

Claims

1. A lehr for heat treating in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor, an entrance opening and an exit opening, support means disposed along the length of the housing intermediate the roof and the floor, a foraminous belt received within the housing and supported along the length thereof by said support means, means for conveying the belt through said furnace, a plurality of longitudinally spaced fans received within the roof, a longitudinally extending shroud within the housing spaced relative to the roof and the sidE walls and terminating above the floor to define a plenum in combination with said side walls and roof and an opening in combination with said floor, said shroud having a plurality of openings which are aligned with said fans, a plurality of longitudinally spaced burners received within and extending into said housing, said burners being mounted in such a manner that the products of combustion are drawn into the circulating path generated by said fans, means for supplying fuel to said burners, means for sensing the temperature along the length of the furnace, and means for controlling the supply of fuel in response to the temperature sensing means.

2. The lehr of claim 1 wherein said support means is a perforated plate.

5. The lehr of claim 4 wherein said burners are ported tube burners.

6. A lehr for heat treating in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor, an entrance opening and an exit opening, support means disposed along the length of the housing intermediate the roof and the floor, a foraminous belt received within the housing and supported along the length thereof by said support means, means for conveying the belt through said housing, a plurality of spaced fans received within the roof, a longitudinally extending shroud within the housing spaced relative to the roof and the side walls and terminating above the floor to define a plenum in combination with said side walls and roof and an opening in combination with said floor, said shroud having a first plurality of openings which are aligned with said fans and a second plurality of openings, a plurality of longitudinally spaced burners received within said roof and extending into said housing and said shroud through said second plurality of openings, said burners being mounted in such a manner that the products of combustion are drawn into the circulating path generated by said fans, means for supplying fuel to said burners, means for sensing the temperature along the length of the furnace, and means for controlling the supply of fuel in response to the temperature sensing means.

7. The lehr of claim 6 wherein said support means is a perforated plate.

8. A lehr for heat treating work in a continuous operation, comprising: an elongated housing having a roof, spaced side walls, a floor, an entrance opening and an exit opening, a longitudinally extending, porous plate received within said housing, an endless foraminous belt supported by said plate, means for conveying said belt along said plate, a plurality of longitudinally spaced fans received within said roof, a shroud extending within the length of the housing spaced relative to the roof and side walls to define a plenum therebetween, said shroud terminating at apProximately the location of said plate to define an opening therebetween, said shroud having a first series of openings at each location of said fans, a plurality of longitudinally spaced combustors received within said roof and operative to direct combusting gases downwardly, said shroud having a second series of openings at each location of said combustor, a shoe located beneath each combustor having means to deflect gases from the combustor horizontally into the circulating path generated by said fans, means for supplying fuel to said combustors, means for sensing the temperature along the length of said housing, and means for supplying fuel to said combustors in response to said sensing means.