US2296806A

US2296806A - Apparatus for heating metal objects

Info

Publication number: US2296806A
Application number: US337604A
Authority: US
Inventors: Robert E Buckholdt
Original assignee: SALEM ENGINEERING Co
Current assignee: SALEM ENGINEERING Co
Priority date: 1940-05-28
Filing date: 1940-05-28
Publication date: 1942-09-22
Anticipated expiration: 1959-09-22
Also published as: DE818510C

Description

Sept. 22, 1942- R. E. BUCKHOLDT APPARATUS FOR HEATING METAL OBJECTS Filed May 28, 1940 3 Sheets-Sheet l a? Snnentor R0 BERT. E. BUCKHOLDT Z Gttorneg Sept. 22, 1942- R. E. BUCKHOLDT APPARATUS FOR HEATING METAL OBJECTS Filed May 28, 1940 5 Sheets-Sheet 2 Bnve ntm:

ROBERT E-BL|CKHO LDT Z @Z/VW (Ittorneg l &:

Sept. 22, 1942. R. E. BUCKHOLDT 2,296,306

APPARATUS FOR HEATING METAL OBJECTS Filed May 28, 1940 3 Sheets-Sheet 3 I'mnenfor ROBERT E- EiucKHoLDT Patented Sept. 22, 1942 2,296,806 APPARATUS FOR HEATING METAL OBJECTS Robert E Buckholdt, Salem, Ohio, assignor to Salem Engineering Company, Salem, Ohio, a

proprietorship Application May 28, 1940, Serial No. 337,604

9 Claims.

This invention relates to apparatus for heating metal objects and is particularly concerned with the heating of objects, which are of greatly varying lengths, in a continuous but economical manner. The principles of the invention are particularly applicable in the heat treating of elongated metallic shapes but it should become apparent that, as the disclosure thereof proceeds, the principles are applicable to other specific uses.

Heretofore the uniform and expeditious heating of large tonnages of elongated metal shapes has been accompanied by considerable difficulty due principally to the difficulty of handling the long shapes and maintaining a uniform and controlled heating rate or temperature throughout their entire extent. Such objects, which may comprise beams or sections of various shapes, or tubes, may attain a length of one hundred feet or more and if a continuous furnace of conventional design were employed the length thereof required to effect the proper time temperature relation would be such as to be impractical. It is accordingly the primary object of the invention to provide in a heating furnace an improved arrangement for supporting and moving the objects through the heating zone of the furnace in a uniform and controlled manner but which nevertheless is operative to uniformly heat all of the objects positioned therein throughout their entire extent regardless of the shape or length of the objects.

A further object of the invention is the provision in a material heating furnace of an improved arrangement for directing the heat transferring fluid onto objects of varying and long lengths which are positioned in and moved through the heating chamber of the furnace whereby the objects will be uniformly and expeditiously heated throughout their entire extent.

Another object of the invention is the provision of an improved apparatus for heating elongated metal shapes and consists essentially in apparatus for moving the shapes sideways through the heating chamber of a furnace and for applying a distributed flow of convection heating fluids at locations spaced longitudinally along the objects, the temperature of the fluid being uniformly controlled along the longitudinal axes of the objects.

Yet another object of the invention is the provision of an improved apparatus for uniformly heating objects of varying and long lengths which consists essentially in apparatus for moving the objects sideways through the heating chamber of a furnace and for applying a turbulent flow of convection heating fluids to said objects at locations spaced longitudinally along said objects, the

direction of flow of said fluids over and about said objects being opposite to the direction of movement of the objects through the chamber.

These and other objects and advantages of the invention will become apparent from a consideration of the following detailed specification and the accompanying drawings wherein there is specifically disclosed a preferred embodiment of the invention.

In the drawings:

Figure 1 is a longitudinal sectional view of the material heating furnace of the invention, the view being taken along the line II of Figure 2; Figure 2 is a plan view, partly in horizontal section, of the apparatus of Figure 1; and

Figure 3 is an enlarged view of the furnace hearth operated mechanism.

In the drawings the relative length of the furnace is greatly decreased for better exposition as in actual practice the length of the furnace may be five or six times its width. The furnace consists essentially of a casing Ill which, in accordance with usual practice, may be built up of structural and insulating brick being confined within the buckstays II. The heating chamber l2 as well as all passages for the convection heating fluids employed is preferably lined, as at l3, with chrome alloy sheets which feature is of particular utility in the heating of soft metals, such as aluminum, as it eliminates any scoring and erosion of the surfaces of such objects.

Heating chamber l2 extends the entire length of the furnace casing and convection heating fluid is supplied thereto by a series of heating units, indicated generally by the reference numeral l4, evenly spaced along the top of the easing Ill. The heating units it each consist of a chamber 15 in which is preferably positioned a number of electrical resistance heating units [6 although it should be understood that any equivalent' heating means, such as liquid or gaseous fuel burners, may be mployed for the purpose. Chambers l5 discharge into the material heating chamber through the vertical ducts i'l extending down along one end wall of the casing in and the heating fluid is withdrawn from the chamber l2 into the chambers l5 through ducts I8 positioned adjacent the opposite end wall of the furnace by the motor driven circulators 19, one of which is provided for each of the heating units. The upper and lower walls of the heating chamber I2 are of saw tooth, formation, as shown at 2i and 22, respectively, with the ribs running longitudinally of the furnace. The ridges 23 of the upper wall are directly above the valleys 24 34 arranged in pairs opposite each other.

of the lower wall to provide in effect a sinous passage for the convection heating fluids transversely of the chamber. This results in a sinous and turbulent flow of the heating fluids over and about th objects passing through the chamber and materially aids intthe efficient and uniform transfer of heat from the fluid to the objects.

The object to be heated which may comprise metal beams, angles, tubes and so forth of varying lengths, are moved into and out of the furnace and through the heating chamber thereof by the mechanism now to be described. Extending on either side of the furnace and substantially throughout the entire length thereof are the shafts 30 which are journaled in suitably fixed pillow blocks 3| and one of the shafts is arranged to be rotated at a uniform controlled rate of speed by the motor 32 through a speed reducing transmission 33. Keyed to the shafts 30 at evenly spaced points are the sprocket wheels Entrained over the sprocket wheels of each pair is a continuous hearth chain 35, the upper reach of which passes through the heating chamber l2 and being operative to support and propel the objects through the chamber, and the lower reach passing below the bottom wall of the heating chamber.

Extending in parallel and horizontally spaced relation at each side of the furnace are the beams 31, the inner one being supported from the buckstays II and the outer one by suitable columns 38. Spanning the beams 31 at uniformly spaced intervals are the shafts 39 each of which rotatably carries a member 40 having a bore of substantial length to receive the shaft 39, an upstanding arm 4| and a pair of depending bearing supports 42. Journaled in the supports 42 of each of the members 40 is a shaft 43 which extends into the furnace heating chamber through vertically elongated apertures 44 in the end walls of the furnace. Keyed to the inner end of each of the shafts 43 is a roll 45 having annular end flanges, as shown. A sprocket wheel 45 is keyed to the outer end of each of the shafts 43 and a chain 41 interconnects each of the wheels 46 with a sprocket assembly 48 rotatably mounted on the associated shaft 39. Each of the sprocket assemblies 48 on either end of the furnace is connected together by a continuous chain 56 so that all of the rolls 45 at either side of the furnace will rotate in unison. One of the assemblies 48 on each end of the furnace is driven by a motor 52 through chain and speed reducing transmission 53.

By referring to Figures 2 and 3, it will be apparent that the inner ends of the shafts 43 and the rolls 45 are positioned intermediate the hearth chains 35. Shafts 43 and consequently rolls 45 are adapted to be raised and lowered by pivotal movement of the members 46 about the shafts 39 and the extent of this movement is such that the upper surfaces of the rolls 45 may be moved from a position below the supporting plane of the chains 35 to a position thereabove and vice versa. To accomplish this purpos the upper ends of the arms 4| of the members 40 along each side of the furnace are pivotally connected to an elongated operating rod 54. The rods 54 are each connected to a piston of an air cylinder 55, which cylinders are independently controlled by suitable valve means, not shown.

In operation the beams or other objects to be heated are moved into the furnace on the conveyor 56 (Figure 2), which may be a motor driven roll table extending from a rolling mill orother equipment of the plant. By admitting fluid pressure to the right side of the cylinder 55 at the charging end of the furnace, as viewed in Figure 2, the rod 54 will be moved to the left and the rolls 45 along the charging end of the furnace will all be raised above the supporting plane of the hearth chains 35. This upper position of the rolls 45 is substantially in horizontal alignment with the conveyor 56 so that the pieces moving into the furnace on the conveyor 56 will be directed onto the rolls 45. All'of the rolls are normally continuously driven by the motors 52bit a uniform rate of speed, which rate of speed is such that the peripheral velocity of the rolls 45 is substantially equal to the peripheral velocity of the driven rolls of the conveyor 56. The pieces are retained on the elevated rolls 45 by the end flanges of th rolls. As the piece approaches its proper position in the furnace, air is admitted to the left side of the cylinder 55 at the charging end of the furnace and consequently the adjacent rolls 45 are moved below the supporting plane of the chains 35. This deposits the piece on the hearth chains and these, being moved at a constant predetermined rate of speed by the motor 32, will move the piece through the heating chamber of the furnace.

As indicated in Figure 1 of the drawings, the direction of material travel through the heating chamber of the furnace is opposite to the direction of flow of the convection heating fluid therethrough. By providing a saw tooth configuration to the top and bottom walls of the heating chamber, substantially as shown, the convection heating fluid will be caused to move through the chamber along a turbulent and sinuous path of travel, thereby uniformly applying heat to all the surfaces of the beams or other pieces being heated. A temperature responsive element 58 is located adjacent the exit end of each of the fluid heating chambers l5 and through the medium of conventional control apparatus, not shown, control the operation of the respective heating elements l6. Thus the fluid coming into contact with the objects being heated at the discharge side of the furnace is of accurately controlled temperature and therefore the final temperature given the objects may be accurately controlled. 7

' As the objects which have moved through the heating chamber reach a position above the lowered rolls 45 along the discharge side of the furnace, these rolls are all elevated by admitting air to the proper end of the cylinder 55 of the discharge side of the fumace'and, as the rolls 45 are raised, they will support the objects free of the chains 35. The rolls 45, being continuously driven by the adjacent motor 52, will pro,

pel the objects out of the furnace onto the discharge conveyor 65 which may lead to quenching equipment or other station in the plant. If desired, suitable mechanism, responsive to the advanced position of the objects, may be pro vided to admit air to the proper side of the cylinder 55 at the discharge end of the furnace to automatically raise the rotating discharge rolls 45 when the objects have reached a position thereabove. Also, it should be apparent that automatic means may be provided to lower the charging rolls 45 so that the furnace may be arranged for entirely automatic operation.

An important advantage of the apparatus of the applicant's invention is that the objects to be heated, regardless of their length, may be very rapidly moved into and out of the heating chamber of the furnace, thereby enabling the heating to be started along the entire extent of the objects at the same time and insuring a final uniform temperature throughout the objects. This minimizes the distortion of the shaped objects and is of particular advantage in hardening operations. Also, ment enables these desirable results to be accomplished while using apparatus of economical design and practical size and, by enabling the material charging and discharging ports to be kept relatively small, a good overall efficiency may be maintained.

It should be observed that the furnace of this invention is uniformly operative, regardless of the length of the objects to be heated. This is accomplished in part by spacing the chains 35 and the rolls 45 at short intervals so that short pieces may be adequately supported. In a representative installation of the furnace which has a hearth length of one hundred and three feet and a width of eight feet the chains and rollers are positioned on two feet centers. In this furnace seven heating units, as described above, were employed and it was found that the temperature of the heating fluid was very uniform throughout the entire length of the hearth and it should therefore be obvious that short stock lengths will be uniformly heated, regardless of their particular location on the hearth. The furnace may thus be employed to heat miscellaneous shapes of varying lengths to a maximum substantially equal to the length of the hearth and, when shorter pieces are to be charged, these may be charged in groups having a combined length of similar proportions. The furnace is so constructed and normally operated that the length of time each individual piece remains in the heating chamber is the same and it is therefore possible to arrrange the apparatus for efficient automatic operation. The temperatures maintained at the thermocouples 58, the speed of movement of the chains 35 and rotation of the rolls 45 may be controlled at will to effect a proper balance between the various factors involved.

The above specifically described embodiment of the invention should be considered as illustrative only as obviously many changes may be made therein without departing from the spirit or scope of the invention. For example, other means than that specifically disclosed may be employed to distribute the convection heating fluid over the objects to be heated and various mechanical changes may be made in the object handling and moving means. Reference should the arrangetherefore be had to the subjoined claims in de- I termining the scope of the invention.

What I claim is:

1. Apparatus of the character described comprising in combination a casing having a heating chamber therein, means to circulate convection heating fluid through said chamber, means to move objects to be heated longitudinally into one end of said chamber along one side thereof, comprising a series of driven rolls, means to raise and lower the axes of rotation of said rolls, a series of movable hearth chains spanning said chamber and positioned in part intermediate said rolls whereby objects to be heated coming into said chamber on said rolls will be deposited on said chains when said rolls are lowered, a second similar series of rolls positioned intermediate the chains at the opposite end of said chamber along the other side thereof and operative to propel the objects out of the chamber, the axes of rotation of said rolls being substantially paralleLvvith the direction of movement of said chains.

2. Apparatus of the character described comprising in combination a. casing having a heating chamber therein, means to circulate convection heating fluid through said chamber, means to move elongated objects to be heated into one end of said chamber along one side thereof comprising a series of driven supported rolls, said rolls being carried by the inner ends of shafts extending from outside of to within said casing and chamber and journaled at their outer ends in pivotally mounted members adapted to move about axes parallel with the axes of rotation of said shafts, means mechanically connecting each of said members whereby said members will be moved and said rolls raised and lowered in unison, means to move said objects laterally through said chamber, the arrangement of the parts being such that when said rolls are lowered objects positioned thereon will be deposited on said laterally movable means, and means at the other end of said chamber along the other side thereof to support and move the objects longitudinally out of said chamber after they have traveled through said chamber.

3. Apparatus of the character described comprising in combination a casing having a heating chamber therein, means to supply convection heating fluid to said chamber and to circulate said fluid therethrough, means to move elongated metal shapes longitudinally into one end of said chamber along one side thereof comprising a series of driven rolls extending along one side of said chamber, means in said chamber to move the objects laterally through said chamber, means to raise and lower said rolls, the arrangement of the parts being such that as said rolls are lowered the objects supported thereon will be deposited on said laterally movable means, and means at the opposite side of said chamber to move said objects longitudinally out of said chamber along said opposite side thereof.

4. Apparatus of the character described comprising in combination a casing having a heating chamber therein, means to move elongated metal objects to be heated longitudinally into one end of said chamber along one side thereof, means to move the objects laterally through said chamber, means at the other side of said chamber to move the objects longitudinally out of said chamber, and a plurality of heating units positioned above said chamber and evenly spaced along the transverse axis of the laterally moving means; each of said units comprising a convection heating fluid moving means, a convection fluid heating means, a fluid discharge outlet adjacent the last mentioned side of said chamber, and a fluid return duct adjacent the first mentioned end of said chamber.

5. Apparatus of the character described comprising a casing having a heating chamber therein, means to move elongated metal shaped longitudinally into one end of said chamber along one side thereof comprising a plurality of parallel shafts extending from outside of to within the said one side of said chamber and each carrying at its inner end an object supporting roll, said shafts being disposed substantially at right angles to the direction of movement of the shapes into said chamber, means to rotate said shafts in unison, means to move said elongated shapes laterally through said chamber, means to move whereby said rolls may be simultaneously moved below the supporting plane of said laterally moving means, and meansatthe other side of said chamber to move said elongated shapeslongitudinally out of said chamber.

6. Apparatus of the character described comprising a heating chamber, a movable hearth in said chamber, means to move elongated metal shapes longitudinally onto one end of said hearth comprising a plurality of spaced parallel shafts positioned outside of said chamber, a member pivoteddintermediate its end on each of said shafts, a shaft journaled in one end of each of said members and extending into said chamber, a supporting roll keyed on the inner end of each of said last mentioned shafts and a sprocket keyed on the same shaft, a. sprocket rotatably mounted on each of said first mentioned shafts, means to rotate each of-said sprockets in unison, means to mechanically connect the other ends of said member with a moving means whereby said members may be rocked and their supported roll carrying shafts raised and lowered, and means to move the elongated shapes longitudinally away from the other end of said hearth.

7. Apparatus of the character described comprising in combination a casing having a heating chamber therein, means to circulate convection heating fluid through said chamber, a continuously moving hearth operative to move objects from one side of said chamber to the other side 2,296,808 the axes of rotation of said shafts in'unison thereof, means to move elongated objects to be heated longitudinally into said chamber and to deposit the same. onto said hearth along one side of said chamber, and means to raise said objects from said hearth and to move the obthe other side thereof.

8. Apparatus of the character described comprising in combination a casing having a heating chamber therein, means to circulate convection heating fluid through said chamber, a continuously moving hearth operative to move objects from one side of said chamber to the other side thereof, means to move elongated objects to be heated longitudinally into said chamber and to deposit the same onto said hearth along one side of said chamber, and means to support said objects and to move said objects longitudinally out of said casing along the other side thereofu 9. Apparatus of the character described comprising in combination a casing having a heating chamber therein, means to heat said chamber uniformly throughout its length, a continuously moving hearth operative to move elongated objects laterally from one side of said chamber to the other side thereof means to move said elongated objects longitu ally into said chamber and to deposit the same onto said hearth along one sideof said chamber, and means to support said objects and to move said objects longitudinally out of said chamber along the other side thereof.

ROBERT E. BUCKHOLDT.