US2993688A - Heat treating method - Google Patents

Description

July 25, 1961 K. F. BRAEUNINGER ETAL HEAT TREATING METHOD 5 Sheets-Sheet 1 Filed Aug. 25, 1958 INVENTORS. Aar/ E firaeun/nger' Clare .5. Harris F/TTORNEYS July 25, 1961 K. F. BRAEUNINGER ET AL 2,993,688

HEAT TREATING METHOD Filed Aug. 25, 1958 3 Sheets-Sheet 2 INVENTORS. Kar/ E Braeunr'nger Clare 6. Harris g i g HTTORNEKS July 25, 1961 K. F. BRAEUNINGER ET AL 2,993,688

HEAT TREATING METHOD Filed Aug. 25, 1958 5 Sheets-Sheet 3 52 I INVENTORS 50 n 46 60 MIMI"! Aer/E firaeun/hyer C 0n? 6. Harvvls F2314 W2 M HTTOR/VEYS United States Fatent 2,993,688 HEAT TREATING METHOD Karl F. Braeuninger and Clare S. Harris, Ferguson, Mo., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Aug. 25, 1958, Ser. No. 757,647 4 Claims. (Cl. 263-52) This invention relates to heat treating furnaces and particularly to materials supporting and transporting apparatus for horizontal furnaces which are used in heat treating light metal alloys such as alloys having a base of either aluminum or magnesium.

Extruded sections of light metal alloys and other heat treatable materials often must undergo heat treatment before the sections are suitable for final usage. Such heat treatment is usually accomplished in a horizontal type furnace. Horizontal furnaces are of two conventional types as regards the supporting and transporting structure for the sections while they are within the furnace. In one type of furnace the sections which are to be heat treated are supported on closely spaced rollers which are oscillated constantly during the high temperature cycle to prevent the extrudes from sagging between the rolls or otherwise becoming deformed by acquiring the imprint of the roller member. The trouble encountered when such furnaces are used is that sharp edges of the extnrdes which contact the rolls are damaged by being flattened out until the contacting area is sufficient to bear, without further deformation, the weight of the extrude. This trouble is aggravated when the extrudes are crooked or twisted because such conditions result in fewer rolls being in contact with the extrude.

In the other conventional or common type of horizontal furnace the extrudes are supported on a flat type conveyor. Although the conveyor support elements may be spaced close enough together to eliminate sagging or the flattening of sharp edges of the material being heat treated, the expansion of the extrudes due to temperature changes is suflicient to cause scufiing of the areas in contact with the support elements.

Accordingly, a principal object of this invention is to provide an improved apparatus for transporting and supporting light metal alloys in heat treating furnaces in which the sections carried by the apparatus are subjected to less sagging, flattening, or scufling than has been heretofore obtainable.

In accordance with this invention a horizontal type heat treating furnace is provided with dual acting apparatus for transporting and supporting material to be heat treated in which the sections of metal which are to be heat treated are supported on rolls for the period of heat treatment during which a large part of the thermal expansion of the treated section occurs (before the section is greatly softened by the heat) and then is supported on transversely disposed, flat carrier elements or flow plates. The changeover from rolls to flat carrier elements is effected by relative vertical movement between the rolls and carrier elements. The carrier elements may be stationary and the rolls moveable, or vice versa. The moving apparatus is at the bottom of the furnace structure and is connected to the elements to be moved through suitable linkage.

The invention, as well as additional objects and advan tages thereof will best be understood when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is a simplified-isometric view of materials supporting and transporting apparatus made in accordance with this invention;

FIG. 2 is a side elevational view, partly in section, of apparatus similar to that shown in FIG. 1 and in which the material carried by the apparatus is carried by the rolls;

FIG. 3 is similar to FIG. 2 except that the material is supported principally by the floor plate of the apparatus, and

FIG. 4 is a diagrammatical view showing materials supporting and transporting apparatus in which the rolls are raised and lowered and the floor plate remains stationary.

Referring to FIGS. 1, 2 and 3 there is shown apparatus for transporting and supporting sections or sheets of material, usually but not necessarily of metal, within a horizontal heat treating furnace (the wall enclosure of the furnace not being shown). The apparatus comprises a plurality of roller members 10 which may be supported and driven, if desired, in any suitable manner. The rolls 10 are disposed parallel with respect to one another and their horizontal axes lie in a common plane. Usually, out not necessarily, the rolls 10 are disposed perpendicularly with respect to the centerline of the furnace (not shown) in which the apparatus is used.

Between each roll is a load supporting carrier section or floor plate 12 having a planar upper surface 14. Each of the floor plates 12 are secured to leg-like elements 16 which pass through bores 18 in a double faced base plate 29. Bushings or sleeves 22 are provided above and below each bore 18 to assure vertical alignment of the leg-like elements 16. Each of the leglike elements 16 has at its lower end a cap 24 which rests on a coil spring 26. Each coil spring 26 rests upon a frame, indicated generally by the numeral 28, which includes (as shown more clearly in FIG. 1) a pair of I beams 30 which are parallel and aligned with the center-line (not shown) of the apparatus. The I beams 30 are supported by transversely disposed beams 32. As shown in FIGS. 2 and 3 (and as indicated by the arrows 34 in FIG. 1), means for raising and lowering the floor plates 12 with respect to the rolls 10, illustrated as jacks 36, are provided. The jacks 36 may be actuated hydraulically, mechanically or in any suitable manner. Alternatively, raising and lowering means in the form of cams or the like may be used. In FIG. 3 the jacks are extended, raising the floor plates 12 level with the rolls 10. It should be emphasized that the surface 14 of the plates 12 may be raised above the rolls 10, but this results in the loss of the rolls as supporting members.

The jacks 36 are disposed on suitable framing and supporting members 38, which are secured to the base plate 20 by hangars 40.

In operation the sheet or section 42 to be heat treated in the furnace initially rests upon the rollers 10. The rollers may be rotated in one direction to carry the sheet or section 42 into the furnace and then the rolls may be either oscillated or left free running during the time when the section or sheet is raised to, or near to, its softening temperature. The raising means, the jacks 36, are then actuated, raising the floor plates 12 as shown in FIG. 3 until most if not all of the load of the section or sheet 42 is carried by the floor plates 12.

Since most of the expansion of the material in the furnace takes place before the material begins to soften, supporting the material on the rollers 10 prevents the scufiing which would occur if the material were supported during the entire heat treating cycle. Conversely, once the material softens, the floor plate supporting means prevents the sagging or distortion of thin elements or sections which often occurs if only rolls are used to support the material being heat treated.

This invention has thus far been described as apparatus in which the floor plates are raised and lowered with respect to the rolls. FIG. 4 shows, in diagrammatical form, apparatus in which the rolls are raised and lowered with respect to the floor plates.

In FIG. 4 the floor plate assembly 44 is secured to a base plate 46 by the supporting member(s) 48. Jacks 50 (or other suitable raising and lowering means), mounted on the base 46, support a roll supporting frame 52. Motors 54 or other suitable drive means which may be synchronized in speed are coupled through chain belts 56, for example, to pulleys 58 on the shaft 60 of each roll 62. The operation of the apparatus shown in FIG. 4 as regards the way material is handled is generally the same as that of FIGS. 1, 2 and 3 except that the rolls 62 rather than the floor plate assembly 44 is raised and lowered.

While the illustrated embodiments of the invention show the mechanisms for raising or lowering the rolls or floor plate being at the lower part of the apparatus, the raising or lowering could be accomplished by means of retractable rods or cables, for example, extending downwardly from above the rolls. Further, relative movement between the floor plate surface and rolls may be accomplished by movement of both the rolls and floor plates.

This application is a continuation-in-part of my copending application Serial No. 688,043, filed October 3, 1957, now abandoned.

What is claimed is:

1. The method of supporting a light metal section in a horizontally disposed heat treating furnace during a heat treating cycle during which the section is heated at 2,993,688 H g V 4 least near to the range of temperature where softening of the section occurs, comprising supporting the section within the furnace solely on roller-s during the heating cycle until the section approaches its softening temperature range, then supporting the major port of said section on flat surfaces between said rollers while said section is heated to its softening temperature range, and again sup porting said section solely on rollers when said section is cooled below its softening temperature range.

2. The method of claim 1, wherein during the part of said heat treating cycle in which the section is soft the section is supported by said flat surface and by said rollers.

3. The method of claim 1, wherein said light metal section is transported into and out of said furnace on said rollers.

4. The method of claim 1, wherein said rollers are free to rotate during said heat treating cycle.

References Cited in the file of this patent UNITED STATES PATENTS 1,205,690 Wetcke Nov. 21, 1916 2,875,995 Troglione Mar. 3, 1959 2,883,172 Mitchell Apr. 21, 195 9 FOREIGN PATENTS 493,184 Great Britain Oct. 4, 1938 516,683 Great Britain Ian. 9, 194.0

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