US2883172A - Apparatus for the heat treatment of metallic sheet material - Google Patents

Description

April 21, 1959 2,883,172-

APPARATUS FOR THE HEAT TREATMENT OF METALLIC SHEET MATERIAL Filed Aug. 4, 1955 R. N. MI TCHELL 2 Sheets-Sheet 1 INVENTOR.

RANDOLPH N. MITCHELL ATToR NEYT April 21, 1959 R. N. MITCHELL I 2,333,172

APPARATUS FOR Tl-E HEAT TREATMENT OF METALLIC SHEET MATERIAL Filed Au 4,1955 2 Sheets-Sheet '2 53 SHRINKAGE I I I 54 I 54:- LENGTHWISE 52 ALUMINUM I SHEET I j snLisHzs E ALUMINUM g SHEET SHRINKAGE ALUMINUM Fig- SHEET 3 WIDTHWISE 1LBRUSHES INVENTOR.

RANDOLPH. N. MITCHELL ATTORNEY nited Sttes Pater i."

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APPARATUS FOR THE HEAT TREATMENT OF METALLIC SHEET MATERIAL Randolph N. Mitchell, La Grange, Ill., assignor to Reyholds Metals Company, Richmond, Va., a corporation of Delaware Application August 4, 1955, Serial No. 526,419

1 Claim. (Cl. 2636) The present invention relates to means for conveying sheet material and especially to means for conveying sheet material that is susceptible to marking or scratching.

More particularly the present invention has special utility in conveying hot aluminum sheets through an annealing furnace. In the preparation of sheet aluminum it is necessary to convey the sheets from point to point for the purpose of performing various operations on the individual sheets. One such operation is that of annealing. The sheets are conveyed to an annealing furnace which is customarily of considerable length. The conveyor will then pass the sheets through the furnace where they are suitably heated and then conveyed to a cooling chamber.

At the present time, the sheets are generally conveyed by cable conveyors. The conveyor is made of a number of strands of small stainless steel cable upon which the individual sheets are supported. As the sheets are thus transported, the relative movement between the cables and the sheets causes scratching or marking of the undersurface of the sheets. This scratching is primarily due to the relative movement of the sheet and conveyor. This relative movement is always present as the sheet passes through the annealing furnace because of the expansion and contraction of the material. This marking or scratching is further aggravated during the annealing process because the sheets are in a highly heated condition and in a softer state than they are at room temperature. This marking is present in greater or lesser degree in all cable conveyor annealed aluminum and has come to be known to the trade as cable marks.

This scratching of the sheet material is not limited to cable conveyors. When other conveyors such as conventional walking beam or roller hearth types are used, the same problem of abrasion exists. One primary cause of the abrading or scratching is a result of foreign deposits or pickup on the conveyor structure. The relative motion and pressure between the aluminum sheets and the supporting conveyor structure causes aluminum and aluminum oxide to adhere to the supporting surfaces. This is especially true at the high temperatures encountered in the annealing furnace. As these deposits which have come to be known as pickup continue to build up, they abrade and scratch subsequent sheets with increasing severity. In spite of the fact that the speeds of the sheet and supporting conveying means are carefully synchronized, the relative motion therebetween resulting from thermal expansion and contraction of the sheets is suflicient to cause pickup. Of course, if there is relative movement between the conveyor and sheet material due to other causes such as shaking, vibratingor slipping, this too will result in scratching or abrading of the product. Fundamentally, therefore, it is seen that the cause of the problem is the relative movement .of conveyor and sheet. It is to this general problem that the present invention is directed.

It is therefore an object of the present invention to provide an improved conveying mechanism.

Another object of the present invention is to provide a conveying mechanism wherein the conveyed material will not be scratched, marked or abraded.

Another object of the present invention is to provide a conveying mechanism wherein relative movement of the conveyed material and conveying or supporting media is substantially eliminated.

A more specific object of this invention is to provide a conveying device especially adapted for conveying aluminum sheets through an annealing furnace.

In accordance with the above objects, the present invention contemplates a conveyor having a somewhat flexible sheet supporting structure that contacts the conveyed material at a plurality of different points. The flexible character of the supports permits lateral and transverse movement thereof as the point of contact of support and sheet is displaced due to expansion and contraction. In one embodiment of the invention, wire brush surfaces are used to support the aluminum sheet. It should be noted that the pressure which any wire is capable of exerting is limited by the column strength of the wire itself. Each wire is also capable of limited movement in that by bending or deflecting it can follow its point of original contact with the sheet surface through minor speed differentials and sidewise movement resulting from expansion, contraction or from mechanical irregularitim.

The invention will be more fully understood from the following description of a specific embodiment thereof taken with the drawings in which:

Fig. l is a perspective view of a series of brush rolls and driving means embodying the principles of the present invention and shown in a diagrammatically illustrated annealing furnace;

Fig. 2 is a perspective view of a modification of the conveyor of Fig. 1;

Fig. 3 is a detailed cross-sectional view of a brush showing the position of the bristles and the holding means therefor;

Fig. 4 is a perspective view of a further modification of the conveyor of Fig. 1;

Fig. 5 is a side elevation of a further modification of the above forms of the invention;

Figs. 6 and 7 illustrate the manner in which longitudinal and lateral expansion of the sheets is compensated for by the flexibility of the conveyor support means; and

Figs. 8 and 9 illustrate the manner in. which longitudinal and lateral shrinkage or contraction of the sheets is compensated forby the conveyor support means.

Referring now to the drawings and more particularly to Fig. Lnumeral it} represents generally a conveying mechanism comprisinga series of generally parallel rollers 11, 12 and 13. It is of course understood that a larger number of conveyor rollers may be used depending upon the distance the material is to be conveyed, size of the material, etc. For the purposes of description it is suflicient to show three such rollers. These rollers may be suitably mounted within an annealing furnace or heat treating chamber 5 :having an inlet opening 6 for receiv ing aluminum sheets as it is for this operation that the present invention is especially adapted. Sheet, as used in the present description, includes also .plate as known in theitrade (i.e., over A thick). However, it is understood that the principles and structures of the invention as :herein described are not limited to the conveying of aluminum sheets through a furnace. The invention can be equally well employed to convey other materials of other shapes from one location to:another.

Each of the brush rollersvll, 12, 13 is similarly constructed and has disposedlabout theperiphery thereof two (helical brushes 14 and .15. Brush 14 on each roller takes the form .ofa right-hand ahelix .while brush 15 is a left-hand helix. The sheets are conveyed in the direction of arrow 16 and ride on top of the helical brush rollers. Reference will now be made to Fig. 3 in describing the structural details of the brush assembly. A U-shaped channel 17 is provided and has a rod 18 passing lengthwise therethrough. The brush bristles 19 pass aroundthe rod and extend outwardly on both sides thererof as shown in cross-section in Fig. 3. With the bristles 19 and rod 18 in place within the channel, the latter is clamped or squeezed together in such a manner that small tabs 21 are punched out of the channel sides at close equally spaced intervals therealong. These tabs 21 serve to firmly grip the bristles and hold them in place.

The size of brush bristle used may vary widely, and will depend in part on the weight of the sheet being conveyed and the total number of bristles per unit area. Additionally, the surface area of all the bristles should be sufliciently great to support the conveyed sheet without marking the conveyed sheet solely as a result of the weight on the bristle tips. In one practical embodiment of the invention it was found that brushes of stainless steel bristles inch in length and of a gauge between .004 and .006 gave highly successful results.

The brush structure of Fig. 3 is formed into a helix and may be secured to the rollers 11, 12 and 13 in any suitable manner. Any conventional mechanism may be used to drive the rollers and as shown in Fig. 1, a chain drive is employed. Each roller is mounted on a shaft 23 which carries a sprocket on each end thereof. A motor 24 drives brush roller 11 by means of a chain 25. R- tary motion is transmitted to the rollers 12 and 13 through chains 26 and 27 respectively. Alternatively, a belt and pulley driving arrangement could be employed.

It is understood from the above that as the brush rollers turn in a counterclockwise direction as viewed in Fig. 1, the aluminum sheets will pass over the tops of the rollers in the direction of arrow 16. The purpose of the two oppositely wound helices on each roller is to maintain the sheet material in a straight line path. It may be readily seen that a single helical conveying arrangement will exert a force on the material that has a lateral or sidewise component. If this lateral force is not compensated for, the material may move off the side of the conveyor. Thus, there is provided the double helix oppositely wound as above described. Each helix will exert a lateral force on the material in opposite directions which will balance. The only effective propelling force is in the straight line direction of arrow 16.

An alternative arrangement of brushes is shown in Fig. 2. Here, a plurality of axles 28, 29 and 31 are arranged in generally parallel relationship and mounted on suitable supporting structure (not shown). Each axle carries a plurality of brushes 32 which are secured by a hub and set screw 33. Though each axle has been shown as being equipped with three disk-shaped brushes, any convenient number may be so used. The brushes may be constructed as shown in Fig. 3 and can be conveniently placed around a center hub. The axles are driven by a motor 24A, chain 25A and chain 26A similarly to the drive mechanism shown in Fig. 1. The axles 28, 29, 31 and disk brushes 32 rotate in a counterclockwise direction and the aluminum sheet 34 feeds in the direction of the arrow.

Fig. 4 shows a still further embodiment of the present invention in which a series of straight brushes serve to support and feed the individual sheets. In this form, a pair of shafts 35, 36 are rotatably mounted in the supporting structure, not shown) and carry a pair of friction rollers 37, 38 respectively. An endless belt 39 passes over the rollers and serves to support the series of lateral brush supports 41. These supports may be equally spaced longitudinally of the belt and secured thereto by any convenient means such as screws passing up through the underside of the belt and into the supports 41. The

upper edge of each support carries a straight brush 42 which may be of the general construction shown in Fig. 3. The system may be driven by a motor 24B through a chain 43 which encircles a drive sprocket 44 on the motor shaft and a driven sprocket 45 on roller shaft 35.

Yet another method of embodying the present inven tion would be to use a flat surface (i.e., pallet) with a surface of bristles as one type of conveying surface.

In each of the embodiments thus far described, it was contemplated that the supporting or material engaging elements comprised wire brushes. However, the fundamental principles of this invention are not so limited. The objects of the invention may be realized by other structures, one of which is shown for example in Fig. 5. In this modification, a plurality of rotatably mounted shafts 46, 47 support a series of flexibly mounted fingers 48. The rollers carry a number of rigid stubs 49 to which are secured flexible mountings 51. These mountings may take the form of short lengths of Wire or other flexible material and serve to maintain the individual fingers in a radial position while permitting deflection thereof by the aluminum sheet 50.

Reference will now be made to Figs. 6 and 7 in considering the manner in which the present invention compensates for expansion of the aluminum sheet and avoids scratching or marking thereof. The solid line element 52 indicates the position of the flexible supporting element before expansion of sheet 53 occurs. Element 52 may be either a wire bristle as in Figs. 1, 2 and 4 or it may be a flexible finger as in Fig. 5. For convenience of description, it will be referred to as a bristle. The solid line position of the bristle S2, is the initial relative position it takes in contacting the sheet 53. That is, brush 52 initially contacts sheet 53 at contact point 54. Under the influence of the furnace heat, the sheet may expand longitudinally thereof with the contact point 54 shifting to point 54A. As this point shifts in relative position, the top or contacting point of brush 52 will similarly shift due to the flexible character of the wire bristles. It is seen therefore that there is no rubbing or scraping between the sheet and bristle top. The point of contact remains constant. Consider now the lateral expansion of sheet 53 as illustrated in Fig. 7. The brush bristle 52 initially contacts the sheet at a point shown by the solid line position of the bristle. As the sheet expands laterally, the point of contact moves outwardly to the side but there is no relative movement between the upper contacting point of the bristles and the sheet since the flexible character of the bristle permits a shifting of the end thereof to the dotted line position.

Shrinkage of the sheet 53 is compensated for in the same manner as expansion thereof. In Figs. 8 and 9, the solid line position of bristle 52 represents the position thereof before the expansion. The dotted lines represent the bristle position after expansion. The change of position is of course due to the movement of the contact point. However, the contact point itself does not change because the bristle follows the movement thereof as in the case of sheet expansion.

It is seen therefore that by providing a flexible supporting means for the material, small relative movements of the sheets will be accommodated for by the bending of the support means. Thus the original point of contact remains the same and scratching or abrading of the sheet material is eliminated.

Though the present invention has been disclosed with respect to specific embodiments thereof, it is understood that these are not to be considered as limiting the scope of the invention as defined in the appended claim.

What is claimed is:

In combination with a heat treating chamber for metallic workpieces, conveyor means within said chamber for supporting andadvancing workpieces through said chamber during heat treatment thereof, said conveyor means including supporting means and flexible bristlelike ele- 2,883,172 5 ments projecting from said supporting means with the free marring of the softened supported surfaces: of said workends thereof engageable with the under surfaces of the pieces is avoided. workpieces for supporting the workpieces while being conveyed through said chamber; said flexible elements being References Cited in the file of this patent formed of a metal that is resistant to the heat to which 5 the metallic workpieces are subjected and said elements UNITED STATES PATENTS being bendable to permit their free ends to follow their 1,248,992 Barnett et al Dec. 4, 1917 points of contact with the surfaces of the metallic work- 1,669,902 Kathner May 15, 1928 pieces during relative movement in any direction between 1,906,049 DeBack Apr. 25, 1933 said points of contact and said supporting means, whereby 10 2,755,086 Lubersky July 17, 1956

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