US2999675A

US2999675A - Pre-heater or furnace assembly

Info

Publication number: US2999675A
Application number: US391858A
Authority: US
Inventors: Jr John E Erhardt; Elhardt M Siegel
Original assignee: Selas Corp of America
Current assignee: Selas Corp of America
Priority date: 1953-11-13
Filing date: 1953-11-13
Publication date: 1961-09-12
Anticipated expiration: 1978-09-12

Description

Sept 12, 1961 J. E. ERHARDT, JR., ETAL 2,999,675

PRE-HEATER OR FURNACE ASSEMBLY 00 VALL/EBM v ATTORNEYS Sept. 12, 1961 1. E. ERHARDT, JR., ETAL 2,999,675

PRE-HEATER 0R FURNACE ASSEMBLY Filed Nov. 13,I 1953 5 Sheets-Sheet 2 INVENTORS ATTORNEYS Sept. 12, 1961 J. E. ERHARDT, JR., ErAl. 2,999,675

PRE-HEATER 0R FURNACE ASSEMBLY Filed Nov. 15, 1953 5 Sheets-Sheet 3 INVENTORS` ron EEJ' arci, J3'. FIG 2 Ezdmffms'fwez ATTORNEYS 2,999,675 PRE-HEATER R FURNACE ASSEMBLY John E. Erhardt, Jr., and Elhardt M. Siegel, Baltimore,

Md., assignors, by mesne assignments, to Selas Corporation of America, a corporation of Pennsylvania Filed Nov. 13, 1953, Ser. No. 391,858 Claims. (Cl. 263-3) Our present invention relates generally to an improved heater or furnace assembly for use in heat-treating moving continuous lengths of work such as metallic strip and more particularly to such a heater or furnace assembly employed as a pre-heater in an annealing line.

More specifically, our invention relates to the type of pre-heater consisting of a chamber formed by a pair of opposed panels each having a plurality of heating elements or burners facing the sides of an interposed strip of Work. Frequently, pre-heater furnace units receive a strip of work delivered from an entry looper assembly and guide the treated strip into an annealing chamber for subsequent treatment. Such pre-heaters are well known and are customarily utilized as a high temperature and high heat capacity furnace for rapidly elevating the temperature of a moving, continuous-length of Work which must be brought up to the desired temperature for a subsequent heat-treating or annealing operation. The rate at which the work can be heat-treated by such a pre-heater furnace depends upon the distance the heating elements are spaced from the moving strip and the size of the work passed through the effective length of the pre-heater assembly.

In the past, the use of pre-heaters in annealing line installations has been unsatisfactory. Frequent stopping of the strip during heat-treating operations resulted in that portion of the strip under the influence of the high temperature being subjected to such intense heat as to cause oxidation, burning and eventual melting of the strip. Retractable furnace panels have been employed and the retracting of the penals usually was effected by a manual operation, i.e., upon the stopping of the strip an operator or attendant moved the heating panels apart increasing the distance of the furnace from the strip, upsetting the adjusted position of such panels relative to the strip and the strip remained under the inuence of the retracted panels and their respective heating elements or burners. When the strip movement was resumed a dilicult and time-consuming task was presented in restoring the furnace panels to their proper heat-treating position relative to the strip. As the heating elements were not automatically controlled to decrease the temperature of the furnace and the furnace panels remained in the vicinity of the strip, undesriable oxidation and burning continued to be present. Furthermore, uneconomical use of fuel or power resulted from the lack of proper heating element controls.

With the above and other disadvantages of prior art pre-heaters and similar furnaces in mind an object of our invention is to provide a pre-heater assembly of the type described wherein the heating element panels may be united and adjustably secured in fixed positions equally spaced from the surface portions of work being treated and the pre-heater as a unit is automatically retracted to a position entirely removed from heat-treating relation with the strip and the heating of the furnace is decreased upon a stopping of strip movement.

Another object of our invention is to provide a movable pre-heater assembly for treating a moving continuous length of strip having manually controlled means for automatically positioning the adjusted pre-heater assembly into heat-treating relation with the strip and effecting heat-treating operation of the heating elements.

Patented Sept. 12, 1961 ice A further object of our invention is to provide a movable pre-heater or furnace assembly of the present type having an automatic retracting mechanism controlled by a stopping of strip movement in Which the thermal shock to heating elements and refractory lining materials will be greatly minimized.

A still further object of our invention is to provide a heat-treating assembly for metal strip passing in a continuous path therethrough having means for controlling the temperature and heating capacity of the same in accordance with variations in the rate of movement of the strip, such as and including a stoppage of strip movement.

A still further object of our invention is to provide an apparatus of the type described which is durable and efficient in use, capable of rapid treatment of material and yet relatively economical in manufacture and assembly.

Other advantages and objects of our invention will become apparent from the'following description of a preferred embodiment as presented in the accompanying drawings, in which:

FIGURE l is an endiview in elevation showing the improved and movable pre-heater or furnace assembly of our invention associated with a heat-treating chamber of an annealing line.

FIGURE 2 is a side View in elevation of the movable pre-heater or furnace assembly of FIGURE 1 shown in heat-treating relation with a strip of work.

FIGURE 3 is a side view in elevation similar to FIG. 2, illustrating the pre-heater or furnace assembly of our invention in a retracted position entirely removed from the path of the strip.

FIGURE 4 is a plan view diagrammatically illustrating the manner in which the heating panels of the burner or furnace assembly are associated and illustrated as abutment member for closing the furnace chamber and properly positioning the furnace in strip enclosing and heating position, and

FIGURE 5 is a wiring diagram for a control for the furnace moving means.

Referring to the drawings, particularly FIGURE l, the movable pre-heater or furnace assembly 10 of our invention is preferably employed in an annealing line for heat-treating a moving continuous length of strip metal or work and is shown connected .in the path of movement of a strip 12 ahead of an annealing or heattreating furnace 14 by a horizontally extending strip guiding chamber 16. The strip 12 will be guided for continuous movement through the pre-heater and the annealing furnace by

conventional rolls

18 and 20 as schematically indicated in FIGURE l. It will be understood that a looper or similar strip accumulating mechanism (not shown) may be located ahead of the pre-heater or furnace assembly 10 whereby excessive slack in the moving strip of Work may be taken up Without interrupting the continuous delivery of the strip to the annealing line. The strip 12 will be passed through the pre-heater assembly 10 in such a manner so that the surface portions of the strip move along a vertical centrally located path within the assembly to become properly heated during its passage therethrough. As the annealing furnace or chamber 14 is of a well known conventional gas or electrically fired type it does not form a part of the present invention and hence need not be further described.

Our movable pre-heater or furnace assembly -10 includes 1a pair of opposed vertically disposed

elongated heater panels

22 and 24 of typical construction each having a plurality of heating elements, preferably the gas burner type (not shown), arranged within refractory linings of the same. The construction of the burners or heating elements do .not form an important part of the present invention, since it is obvious that any common present day type of burner, such as a cup burner or the like, may be used. These burners are of course located upon the interior surfaces of the

panels

22 and 24 facing the sides or surface portions 26 and'28 of the centrally interposed strip 12 undergoing treatment. The

panels

22 and 24 are united along adjacent vertical end portions 30 and 32, as more clearly indicated in FIGURE 4, by a plate 34 which may have provis-ion for -spacing the panels in various adjusted positions and controlling the temperature and heat capacity of the assembly. Thus,

panels

22 and 24, which are joined by plate 34, form a U-shaped furnace extending in the direction of strip travel. As shown in the drawing, the legs of the U must be of a width at least equal to the width oflthe strip.

The opposite end `36 of the pre-heater or

furnace panels

22 and 24 are spaced apart to form a normally closed vertically extending slot 38 permitting the assembly to move in a direction normal to the path of the strip 12 and parallel to the surface portions thereof, without lany portion of the furnace contacting and marring the iinish of the strip. In heat-treating and strip embracing position the furnace assembly moves into contact with a vertical stationary abutment 40 carried by an overhead frame member 42 and closing the slot 38 and properly positioning the assembly in operative position. Thus, the interior of the furnace is formed into a chamber 44 entirely closed at its sides and having openings 46 and 48 yat the top and bottom repectively for permitting passage of the moving strip 12.

A fuel for operating the furnaces, usually of gaseous form, is supplied from any convenient source to the lburners via a conduit 50, a solenoid valve 52, a hand operated shut-cfrr valve 54 a manifold unit 56 and flexible-hose units S8 and conduits 60 through lirechecks 62 and distributing tubes 64. The manifold unit 56 (not clearly shown in the drawings) may merely consist of a tubular casting receiving fuel passing through the shuton valve 54 and distributing the same to the two series of flexible conduits 58 in a manner readily understood by those familiar with the art.

The pre-heater or furnace assembly 10 is movably supported byadjustably spaced apart rail and roller assemblies 66 carried by an overhead frame structure, generally designated by numeral 42, for movement in a horizontal path from the strip treating position embracing the work or strip 12 as shown in FIGURE 2 to furnace retracted position -illustrated in FIGURE 3. In moving to the retracted position the slot 38 located along the vertical end portion 36 of the furnace permits the assembly to move laterally from the strip 12 in the manner previously described. `The rail and roller assemblies 66 are of well known construction and it'will be noted by reference to FIGURES l and 3 that each of the integrally connected

furnace panels

22 and 24 are separately supported from the

respective rails

70 and 72 by a pair of

roller assemblies

74 and 76 journalled within the top of the furnace and located adjacent the opposite ends 36 and 32 of the panels. The overhead frame structure will, of course, be supported by vertically disposed members 84, `86, 38 and 90 to form a rigid structure free of undesirable vibration and similar motions.

The heater assembly is moved horizontally along the supporting

rails

70 and 72 by a chain and sprocket drive mechanism including spaced apart

sprocket assemblies

92 and 94 carried by

shafts

96 and 98 journalled within the opposite end portions of the overhead rails` 70 and 72. A chain or similar exible means 100 is carried by the spaced apart sprocket assemblies and is secured to the opposite end portions of the furnace at

points

102 and 104, as shown in lFIGURE. 3. Power for movi-ng the heater in its horizontal path of movement is provided by a reversible motor 106 having a sprocket Y108 operatively connected to the sprocket assembly 92 by anothere chain or simil-ar flexible drive `110.

For the purpose of detecting a change in the rate of movement or the stopping of the strip of work there is provided a detecting mechanism, generally indicated by numeral 11-2 of FIGURE 1, secured to the guiding chamber 16 adjacent the guide roll 18. The detecting mechanism may comprise lany conventional electrical switch such as the centrifugal type which maybe driven from its pulley, not shown, by a belt 114 and a pulley 116 carried on the shaft of the guide roll 18 in a manner readily understood by those acquainted with the art. Additionally, the detecting mechanism may be employed for actuating either a switch, a rel-ay or a rheostat associated with electrical circuits, presently described, for eiect-ing automatic retraction of the furnace 10 and for decreasing or discontinuing the flow of fuel to the burner elements.

The chamber 16 is sealed at the entrance end of the strip by a pair of

rollers

118 and 120 urged into contact and sealing engagement with the strip -12 by a tension spring 122. The roller 118 may be positively driven through a belt 119 and a pulley 121 carried by the shaft of the guide roll 18. In the present embodiment, the sealing elements are carried adjacent the bottom 48 of the pre-heater furnace 10 upon a frame 124 mounted on the strip guiding chamber 16. This seal for chamber 16 is of conventional form and need not be further described as such merely provides a means of sealing atmospheric gas in the furnace 14 and housing 16.

The electrical circuits utilized for automatically effecting movement of the pre-heater or furnace assembly 10 into retracted position, restoring the assembly to strip or work treating position and controlling the amount of fuel supplied to the burner elements may be of any design and, a simplified circuit for accomplishing this is shown in FIGURE 5. The switch or`relay of the detecting mechanism V112, upon actuation, will energize a circuit to operate the motor 106 in the direction to move the pre-heater or furnace assembly 10 into the retracted position shown in FIGURE 3 until the furnace contacts normally closed limit switch 126 connectedA in series with the switch 112 to interrupt the power supplied to the motor 106 and discontinue the retracting movement of the assembly. Closing the start switch 127 will energize motor 106 to return the furnace to operating position. Also actuated by switch 112, and in parallel with the motor, is a circuit to control the operation of the solenoid valve 52 to decrease the supply of fuel to the burner elements. When the solenoid is energized, valve 52 will be closed. As an alternate means of effecting fuel control, a rheostat (not shown) may be associated with the detecting mechanism 112 adapted to energize a circuit for progressively closing and opening the solenoid' valve 52 in response to the change in the rate of strip or work movement. In the alternate method of fuel control, the fuel supplied Will be decreased upon a slowing down of the strip, further decreased upon the strip stopping, and increased for normal burner operation as the operating speed of the Vstrip is approached.

It will thus be seen that when the strip 'of work is stopped the supply of fuel to the furnace may be decreased or shut oft and the mechanism may beV operated for moving the pre-heater assembly in a direction lateral to the path of movement and parallel to the surface portions of the strip. Therefore,` the panels of the preheater assembly will be retracted to a position entirely removed from the work and the residual heat of the panels will have no further inuence upon the strip of work.

For the purpose of returning the furnace assembly into strip treating position, preferably, there is provided a manually operated switch '(not shown) employed to reverse the motor and supply current thereto vto etfcct movement of the assembly into-strip embracing position,

Vsuch` manually controlled switch may also control a circuit to open the solenoid valve 52 of the fuel supply and restore the burners to normal operation.

The operation of the present invention is believed to be apparent from the foregoing description wherein it will be seen that the various objects hereinbefore set forth, together with many practical advantages, are successfully achieved. The present pre-heater or furnace assembly makes possible a marked increase in annealing line productions, reduces thermal shock to burner elements and refractory lining materials and eliminates strip oxidation, burning and melting. Furthermore, the adjusted separation of the pre-heater panels is not upset during retracting and work embracing movements of the assembly and, therefore, a more uniform heat treatment of the work is obtained and the time consuming task of manually readjusting the panels into proper heating relation with the strip is eliminated.

It is realized that various possible arrangements and modiiications of the individual features of the invention may be made, all Without departing from the scope thereof, and therefore, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

We claim:

l. An apparatus for heat-treating a continuous length of work comprising, a movable heater having a pair of opposed panels of a size at least equal to the width of the work each carrying a plurality of heating elements facing the sides of an interposed length of Work, means to mount said heater for movement from a rst position with said panels on opposite sides of the work to a second position beyond one edge of the work, means for supplying fuel to said elements in either position of said heater, means responsive to a stopping of work movement to retract the heater assembly laterally from its first position to its second position entirely removed from said work and means effective upon said stopping of the Work to decrease the ow of fuel to said burners.

2. An apparatus for heat-treating continuous lengths of work moving through a path at a high rate of speed, comprising a movable heat-treating chamber located along said path having a pair of opposed vertically disposed elongated heating panels of a Width at least equal to the width of the work means joining said panels along vertical edges at one end, means to mount said chamber for movement from a first position with said panels on opposite sides of the work to a second position beyond one edge of the work, a plurality of heating elements carried by each of said panels facing the sides of an interposed length of work, means for supplying fuel to said elements, and means responsive to a stopping of work movement to retract the chamber laterally from its first position to its second position entirely removed from said strip.

3. An apparatus for heat-treating continuous lengths of work moving through a path at a high rate of speed, comprising a movable heat-treating chamber surrounding said work and located along said path having a pair of opposed vertically disposed elongated heating panels, means joining said panels along vertical edges at one end, means to mount said chamber for movement from a lirst position with said panels on opposite sides of the work to a second position beyond the `one edge of the work, a plurality of radiant cup burners carried by each of said panels facing the sides of an interposed length of work, means for supplying fuel to said burners, and means responsive to a stopping of work movement to retract the chamber in a direction lateral to the path of movement and parallel to the surface portions of said strip from its first position to its second position removed from the work.

4. An apparatus as set forth in claim 3 wherein means are provided whereby the fuel supplied to the burners is shut olf upon a stopping of work movement.

5. An apparatus for heat-treating continuous lengths of work in strip form moving through a path at a high rate of speed, comprising a movable heat-treating chamber surrounding said work and located along said path having a pair of opposed vertically disposed elongated heating panels, said panels being joined along vertical edges at one end, means to mount said chamber for movement laterally of said Work, a plurality of radiant cup burners carried by each of said panels facing the sides of an interposed strip, means for supplying fuel to said burners, detecting means associated with the strip responsive to a stopping of strip movement, means controlled by said detecting means for retracting the heater assembly in a direction lateral to the path of movement and parallel to the surface portions of said strip beyond the one edge thereof and means controlled by the movement of said chamber upon reaching retracted position to discontinue the retracting movement thereof.

6. An apparatus for heat-treating continuous lengths of work in strip form moving through a path at a high rate of speed comprising, a movable furnace including a pair of opposed panels of a width at least equal to the width of the strip and each having a plurality of radiant cup burners facing the sides of an interposed strip, said panels being joined along common end portions thereof and spaced apart at the opposite end, means to mount said furnace for movement laterally of said work, means for supplying fuel to said burners, a furnace retracting mechanism including a reversing motor, means detecting a change in the rate of movement of the strip, an electrical circuit energized by the detecting means for operating the motor to retract the-heater laterally from around said strip and decrease the ilow of fuel to said burners upon a stoppage of strip movement, a limit switch operated by the heater upon reaching retracted position to deenergize said circuit and render the motor inoperative, and manually-actuated means for reversing the motor to move the heater into strip heating position and provide a normal operating ilow of fuel to the burners.

7. In an annealing line for heat-treating continuous lengths of work in strip form moving through a path at a high rate of speed, a movable furnace comprising, a vertically disposed elongated pair of heater panels of a width at least equal to the Width of the strip, means to mount said furnace for movement laterally of said work, a plurality of burner elements in each panel facing the sides of the strip interposed between the panels, and a source of fuel supply for the burners, the combination of means joining the pair of opposed panels along adjacent vertical end portions thereof, a furnace retracting mechanism including a reversing motor operatively connected to said panels, means for detecting a stopping of strip movement, mechanism actuated by the detecting means for automatically operating the motor to retract the furnace to a position beyond an edge of the Work and reduce the ilow of fuel to said burners, and manually-actuated switch means controlling said mechanism for reversing and operating the mechanism to move the furnace laterally into strip heating position and provide a normal flow lof fuel to said burners.

8. In an apparatus for annealing continuous lengths of work in strip form moving through a path at a high rate of speed including a heat-treating chamber located along the path, a movable furnace located along the path ahead of the heat-treating chamber, said furnace comprising a vertically disposed elongated pair of opposed heater panels, means to mount said furnace for movement laterally of said Work path, a plurality of heating elements facing the sides of a strip interposed between the panels, and a source of fuel supply for the elements, said pair of panels being adjustably joined along adjacent vertical end portions thereof and spaced apart at the opposite end forming a slot to permit movement of the panels from a strip embracing position to a position entirely removed from said strip, a stationary abutment closing said slot of the panels and limiting movement thereof in heat-treating position, a furnace retracting mechanism including a reversing motor operatively Connected to said panels, means for detecting a stopping of strip movement, an electrical circuit energized by the detecting means for automatically operating the motor to retract the furnace panels in a direction lateral to the path of strip movement and parallel to the surface portions thereof and to reduce the ow of fuel to said burners, a limit switch operated by the furnace upon reaching retracted position to deenergize said circuit and render the motor inoperative, and manually-actuated switch means controlling said circuit for reversing and operating the motor to move the furnace into strip heating position and provide a normal ow of fuel to said burners.

9. In apparatus for heat treating a strip of material, means to guide the material through a straight path portion, a. heating chamber including a U-shaped heater structure movable between a strip-heating position With the legs of the U extending the Width of the material and on opposite sides of the material and a second position distant from one edge of the strip and in which the heater structure will not heat the material, a stationary abutment adjacent to an edge of the strip adapted to be contacted in sealing relation by said heater structure when the latter is in strip heating position, means to support said heater for movement between said two positions in a plane parallel to said material path, and means responsive to stopping of the material to move said heater structure away from said material by movement along a line lying in said plane and normal to the direction of said material path.

10. Apparatus for heating a portion of a strip moving through a vertical path including structure forming a vertically elongated furnace chamber rectangular in section, one Wall of said structure extending along the edge of said strip being xed in position, the remaining walls of said structure forming a rigid unit and being separate from said one wall, a pair of tracks extending transversely to said strip on ropposite sides thereof and beyond the edge opposite said one edge, means to mount the remaining walls of said structure for movement along said track from a position in which they engage said one Wall to a position removed from said strip, and means responsive to movement of said strip to control movement of said remaining walls on said track.

ll. Apparatus for heating a strip of material moving through a vertical path comprising a U-shaped furnace with the legs thereof extending on opposite sides of said strip through a portion of said path, an .abutment extending parallel to said strip adjacent to one edge thereof, said abutment being engaged -by the ends of the legs of said furnace when it is surrounding said strip to form a rectangular furnace chamber through which the furnace travels, a track extending transversely of said strip, means to mount said furnace for movement on said track 8 from a position in which the ends of said legs engage said abutment vtov a position beyond the opposite edge ofsaid-strip Where the strip will not be heated, a reversible motor `connected to move said furnace, and means to actuate said motor.

l2. Apparatus for heating a strip of material moving in a vertical path comprising a U-shaped furnace, the legs of which form panels extending in the direction of strip travel and of a width a-t least equal to the Width of the strip, a pair of horizontally extending tracks, one on each side of the strip, said tracts extending from one edge of the strip to beyond the other edge thereof, rollers attached to one end of each of said panels riding onsaidl tracks to support said panels for movement from a position in front of said strip to a position beyond the edge thereof, a reversible motor to move said furnace between said two positions, and means responsive to movement of said strip through said furnace to control the operation of said motor.

13. The combination of claim 12 including burners in said panelsto heat said strip, means to supply fuel to said burners in `any position of said furnace, and means operated by said responsive means to control said supply of fuel.

14. An apparatus for heat treating a continuous moving length of Work comprising, a movable heater surrounding said Work and having a plurality of heating elements, means to mount said heater for movement from a first-position surrounding said Work to a second position removed beyond one edge of said work, means for heating said elements and means responsive to a change in the rate of movement of the Work to retract the heater assembly laterally from its first position to its second position entirely removed from said Work.

l5. Apparatus as set forth in claim 14, wherein means are provided for decreasing the heat of said elements upon a decrease in the rate of movement.

References Cited in the le of this patent UNITED STATES PATENTS 2,210,032 Hess Aug. 6, 1940 2,409,431 Hess Oct. 15, 1946 2,448,009 Baker Aug. 31, 1948 '2,666,003 Dougherty et al. Ian. 12, 1954 2,668,700 Zimmerman Feb. 9, 1954 l2,668,701 Dietrich Feb. 9, 1954 2,742,274 Edvar Apr. 17, 1956 FOREIGN PATENTS 409,909 Great Britain M-ay 10, 1934