US2583046A - Apparatus for heat-treating bimetallic strip material - Google Patents

Description

Jan. 22, 1952 APPARATUS FOR Filed May 5, 1949 D. H. GARDNER 2, 83, 6

HEAT-TREATING BIMETALLIC STRIP MATERIAL 6 Sheets-Sheet l INVENTOR. jam/(Z f/ zzd/zer Jan. 1952 D. H. GARDNER 2,583,046

APPARATUS FOR HEAT-TREATING BIMETALLIC STRIP MATERIAL Filed May 5, 1949 6 Sheets-Sheet 2 I N VEN TOR. Jana/(Z //'a2zZ22er B Y ah;

Jan. 22, 1952 D. H. GARDNER 2,583,046 APPARATUS FOR HEAT-TREATING BIMETALLIC STRIP MATERIAL Filed May 5, 1949 6 Sheets-Sheet 3 IN V EN TOR.

Jana/a farazer Jan. 22, 1952 D. H. GARDNER APPARATUS FOR HEAT-TREATING BIMETALLIC STRIP MATERIAL 6 Sheets-Sheet 4 Filed May 5, 1949 v I INVENTOR. Jana/a5 AV 662/0 7-2617 Jan. 22, 1952 D. H. GARDNER APPARATUS FOR HEAT-TREATING BIMETALLIC STRIP MATERIAL Filed May 5, 1949 6 Sheets-Sheet 5 INVENTOR.

Jan. 22, 1952 o. H. GARDNER 2,583,046

APPARATUS FOR HEAT-TREATING BIMETALLIC STRIP MATERIAL Filed May 5, 1949 6 Sheets-Sheet 6 OOOOOOOOQOPOpOOOOOOOO000000? INVENTOR.

Patented Jan. 22. 1952 2,583,046

APPARATUS FOR HEAT-TREATING BIMETALLIC s'rRIP MATERIAL Donald H. Gardner, Detroit, Mich., assignor to Sunbeam Corporation, Chicago, 11]., a corporation of Illinois Application M... a, 1949, Serial No. 91,194

13 Claims. (Cl. zes -s This invention relates to an apparatus for heat treating strips of metal material of the type such as bimetal strips that tend to warp when heated.

In the making of bimetal strips two ormore slabs of preselected metal are placed in side by side relation and are pressed together by a suitable pressure applied at the proper temperature. Thereafter the composite slab is passed through rollers a number of times until the slab is rolled out to the desired thickness; that is, it can be cut into small strips foruse in instruments and the like or can be readily coiled. The characteristics of the bimetal material are such that as it is heated it tends to bend or become deflected, this of course is the basis for its use in industry.

This inherent bending of bimetal material, when heated, presents a real problem in handling during the annealing processes between successive rollings of the slab. Heretofore no satisfactory -means has been available for handling bimetal lic material between the time it is in composite slab form until it is of such thickness that it can be readily used. For example the conventional electric strip annealing furnaces are not suitable for heavy stock due to the high losses of material involved in spot welding short strips together to produce continuous lengths. One of the methods widely used heretofore comprises forcibly coiling the strips in the direction in which they would bend when heated, binding them with wire to prevent uncoiling and then loading the bound coils /into baskets for immersion into oil fired salt pots. To conserve space the strips are generally coiled in decreasing diameter so that one coil can be loaded or supported inside another coil and together thecoils form a comparatively solid unit. Several of these solid coils are then stacked, one upon the other in the basket After these coils have been heated the required length of time the basket is removed from the salt pot and cooled in water to wash off the salt. The coils or strips are then removed from the basket, the binding wire for the individual coils removed and the strips straightened and passed through a special decoiling and cleaning machine. The above process although widely used is objectionable on several grounds. It is obvious that there are many hazards insofar as the safety of the operating personnel is concerned. For example the unloading of the salt furnace involves danger to the personnel due to the fumes and splattering of the salt as the basket is raised from the salt pot. The removing of the coils from the salt these salt pot installations are an eye sore.

pots and then subsequently placing them, in cool water is very dangerous, being almost explosive in nature. Personnel in factories in which salt pots have been utilized have complained of the noise resulting from the immersion of the coils in the salt pot and cool water and also from the fact that the buildings housing this equipment frequently shake rather severely during this process because of the concussion waves resultin from the immersion of the-coils in the salt pots and water. Due to the fact that this process is inherently so dangerous factories utilizing salt pots for-this purpose have found that they have an extremely high labor turnover for operators of salt pots. In addition to presenting hazards to the personnel such salt pots have constituted a fire hazard and in general detract from the appearance of the factory. As a matter of fact In other instances slabs have been stacked one on the other in a furnace with weights distributed over the top of the stack to prevent deflection of the slabs during the heat treating thereof. Preferably, adjacent slabs are placed in side by side relation so that the deflection of one slab counteracts that of another. This method is not satisfactory in that it requires a considerable amount of handling of the bimetal slabs both in preparing the slabs and in placing them in the furnace and in removing the slabs there from Considerable scaling has also been encountered withpprior heat'treating units. One of the big objections to previous constructions for heat treating bimetal slabs has been that they have required a large number of operating personnel.

An object of the invention is to provide a novel annealing furnace means for bimetal and the like materials, that insures that the bimetal strip is uniformly annealed, that the bimetal strip has a bright finish, andprovides for the expeditious handling of the bimetal strip to.

i l I bimtifistrip or slab as itfadvances through the furnace means.

Another object of the invention is the provision of furnace means of the above character for bimetal strips or slabs and the like that requires a minimum of operating personnel.

' Another object of the invention is to provide furnace means of the above character wherein the operation thereof entails a minimum of hazards to the operating personnel, both of the furnace means and adjacent equipment in a fac- .t ry.

Another object of the invention is to provide furnace means of the above character wherein the bimetal strip after passing through the furformed in a furnace IO.

the receiving end of the annealing furnace unit;

, nace per se taken along the section line '|'I in Fig. 8 is a top plan view of the discharge end of the furnace unit;

Fig. 9 is a sectional view taken substantially along the line 9-9 of Fig. 10;

Fig. 10 is a side elevational view of the portion of the furnace unit shown in Fig. 8;

Fig. 1'1 is an enlarged sectional view showing the gas curtain and sealing arrangement for 4 of stock successively through the heating and cooling chambers II and [2 respectively and means for limiting or restraining the distortion or deflection of the bimetal strip as it is heated and subsequently cooled in passing through the heat treating unit.

The heating chamber II in this instance is The chamber H is defined by a suitable thickness of refractory material such as firebrick l1. As shown in Figs. 4 and 7 the chamber II is relatively long and has a generally rectangular cross section with an arched top of conventional construction. The bricks II are encased in suitable insulating material I I, which in turn is'housed in a suitable housing it formed by metallic sheets suitably fastened together. The housing I9 is mounted on suitable cross members 2| spaced lengthwise of the housing and supported by spaced uprights 22 on opposite sides of the housing. The chamber II should be made gas tight so that an atmosphere may be introduced therein.

While any suitable means may be provided for supplying heat to the furnace in this instance it is shown as being heated by electric resistance units 23 and 24. In the present instance four electric resistance units are utilized, two units 23 supported at the top of the chamber II and two units 24 supported at the bottom of the chamber II. The resistance elements '23 are formed by ribbons shaped and positioned as "shown in Fig. 6 and supported on conventional insulated supporting units 28 in turn supported by elements 28 suspended from cross members 3|. The cross members 3| are suitably supported on opposite sides at the top of the chamber I I as by ledges 30 and the side walls defining the chamber II. The ends of the heating elements 23 are connected to conductors 32. The latter project vertically through the top of the furnace unit and terminate'in suitable terminals 33 dispreventing the leakage of gas from the furnace unit, and

Fig. 12 is a sectional view taken substantially along the line l2-l2 of Fig. 11.

Referring now to the drawings, the invention is shown embodied in a heat treating or annealing unit adapted for heat treating bimetal slabs or strips. Such strips may consist of two or more metals laminated together in a conventional manner to form composite strips or slabs. In general these strips or slabs will vary in length from 6 to 35 feet, are A" thick, initially, and are generally somewhat less than a foot wide. They are rolled until the final strip may be approximately .020 inch thick or the like, depending on the ultimate use of the strip.

While the heat treating unit to be described hereinafter is intended primarily for bimetal strips, it is to be understood that any other type of strip may be used if desired particularly where the strips are the type that distort as a result of heating the strip. Inthis embodiment of the invention the heat treating unit in general comprises a heating chamber ll of suitable size to accommodate the material being handled, a cooling chamber l2 of suitable size to accommodate the material being handled adjacent the heating chamber, means for advancing the strip posed in houses 34 mounted on top of the housing l9. In a similar manner the heating elements 24 are formed by ribbons shaped and positioned as shown in Fig. 6. The ribbons are supported on suitable insulating supports 36 mounted on transversely extending ribs 35 on the bottom of the chamber I I. The ends of the ribbon 24 are connected to conductors 31 which project through the bottom of the housing l9 and terminate in terminals 38 located in houses 39 suitably supported on the bottom of the housing I9. By providing four sets of elements as shown, two zones of heating are provided in the furnace, one being used to bring the charge in the furnace up to temperature and the other being used to saturate the charge with heat. The temperature in the furnace may be automatically controlled by any suitable conventional means well known in the art. The latter is not shown for purposes of simplifying the drawings. The power leads for connecting the resistance units in the power system have also been omitted to simplify the drawings, it being understood that' any suitable conventional conductors may be used for this purpose.

The cooling chamber i2 is in axial alinement with the furnace and is positioned at the discharge end thereof. The cooling chamber is defined by a plurality of sections 40 each formed as shown in Figs. 9 and 10 by two generally tubular members ll and 42, disposed one within the other, and each having elongated rectangular cross sections. At the ends of each section 40 the tubular members are joined together as by flanges 42a to form a central axially extending,

passageway 43 opening on both ends oi the section and a water chamber 44 closed at both ends of the section and surrounding the axially extending passageway 43. The sections are suitably supported on spaced rollers 45 (see Fig. supported on frameworks 41 and 48. The sections 48 are rigidly secured together by bolts extending through the flanges 42a on adjacent sections so that the axial passageways 43 are in alinement to define the cooling chamber I2 in turn in alinement with the discharge opening 48 of the furnace. Any suitable connection 58 maybe used for attaching the section 48, adjacent the furnace, to the latter. Water is supplied to each water chamber 44 through an inlet conduit 5| attached to the outer tubular member 44 and is exhausted from the chamber through an exhaust conduit 52. The flow of water to the respective sections 48 may be controlled by any suitable means such as termostatic valves and the like (not shown), so that any desired cooling temperature may be maintained in the cooling chamber I2. Preferably the temperature in the cooling chamber I2 should be such that when the bimetal strip is discharged from the heat treating unit the temperature of the strip is below the oxidizing temperature. Moreover the temperature should be low enough so that the strip can be readily handled and is ready for cold rolling without any further treatment.

The means for advancing the bimetal strip through the heating chamber II and the cooling chamber I2 in this instance comprises two endless flexible belts, an upper belt 53 and a lower belt 54 disposed and arranged in coplanar relation as best seen in Figure l. The upper belt 53 is supported on pulleys 55 and 5'! supported at opposite ends of the heat treating unit. The lower belt is supported on pulleys 58 and 59 also supported at opposite ends of the heat treating unit. The mounting pulleys for the upper and lower belt are arranged so that the bottom portion of the upper belt 53 and the top portion of the lower belt 54 are adjacent each other in side by side relation and the bottom portion of the upper belt normally rests on the lower belt. With this construction the belts are so arranged that a strip of metallic stock disposed between the adjacent portions of the upper and lower belts is gripped sufllciently tight so that it is drawn along or advanced in unison with the corresponding gripping portions of the belts. Preferably the belts 53 and 54 are of woven wire construction as best seen in Figs. 6 and 11. The

pulleys 55 and 58 which are the drive pulleys are preferably provided with a layer of friction material on their periphery so as to prevent slippage between the pulleys and the flexible belts 53 and 54. The pulleys 55 and 58 are mounted on shafts GI and 62 respectively supported in suitable bearings mounted on opposite sides of the framework 48. The top portion of the belt 54 is supported by a bottom 63 of a mullle 55 extending through the heating chamber II, the bottom of the cooling chamber l2 and a horizontally extending trough 65a at the charge end of the furnace unit, together forming a guide for the belt 54. As shown in Figs. 4 and 7 the muille 65 is supported by suitably capped spaced ribs 55, projecting upwardly from the bottom of the chamber II and the ends of the furnace so that the mufile is held substantially centrally of the chamber II. The lower portion of the belt 54 is supported by guides 64, 64a and 54b, beneath the he'attreatingunit and suitably supported by the frameworks 41 and 48 and by cross members 88 attached at their opposite ends to uprights 22 beneaththe furnace I5. Rollers 18 at opposite ends of'the heattreating unit also support the belt 54 and provide friction free surfaces for the belt. A tension roll 15 is mounted on the framework 48 to ensage the belt 54 adjacent the pulley 58. The upper portion of the top belt 53 is supported by troughshaped guides 51, 51a and 51b supported on top of the heat treating unit respectively by the frameworks 41 and 48 and cross members 58 on the housin l8 connected on Opp site sides to the uprights 22. Where desired the guides 54, 84a, 64b, 61, 81a and 51b may be replaced by suitable rollers. The belts Sland 54 are arranged so that when they are not advancing a strip of metal the lower portion of the belt 53 normally rests on the top portion of the lower belt 54 as best seen in Fig. 11. To facilitate the placing of the bimetal strip between the conveying belts 53 and 54 the lower belt 54 extends forwardly of the charge end of the furnace a substantially greater distance than the upper belt to define a table for readily receiving the bimetal strip as shown in Figs. 1 and 3.

Provision is made for automatically adjusting the tension in the belts 58 and 54. In this instance automatic tensioning thereof is effected by means of a weight. The tensioning means for the belt 53 is best shown in Figs. 3 and 5. Therein it is seen that the pulley 51 is supported on a shaft ll. The latter is supported at opposite ends in blocks 12 supported between horizontally disposed ways I3 and 14 forming a part of a support or framework 16 at the charge end of the heat treating unit. Attached to each block 12 is an eye 11. A chain I8 is secured at one end to the eye 'I'! and at its opposite end is connected to an eye in a member I8 supporting a weight 88. Between the eye I1 and the weight 88 the chain loops over a sprocket 8| supported on an upright 82 of the support 15 and a sprocket 83 supported on an upright 84 of the support I6 spaced from the upright 82. A turnbuckle 85 is connected in the chain I8 for adjustment purposes. The weight 88 is disposed between the framework 15 and the furnace I5. With this construction whenever there is any change in the length of the belt 53, due to heating of the belt or as it passes through the heating chamber II or the like the weight 88 will move downwardly thereby pulling the blocks I2 and in turn the pulley 51 to the left as shown in Fig. 3 and thereby assure that a desired tension is maintained in the belt 53. Contraction of the belt will cause the weight 88 to be raised. Any desired tension may be obtained in the belt by changing the weight 88.

The tension in the belt 54 is automatically adjusted in the same manner as that described for the belt 53. In this instance the pulley 59 is supported on a shaft 9| supported at opposite ends by slide blocks 82. The latter are supported between horizontally disposed spaced ways 93 and 94 forming a part of the framework 16. An eye 81 is connected with each of the blocks and extends in a direction outwardly from the furnace I5. Attached to each eye is a chain 98 which is connected at its opposite end to an eye of a member 89 supporting a weight I88. Between the eye 9'! and the weight I88 the chain 98 passes over a sprocket I8I suit ably supported on an upright I82 of the framework 15 and a sprocket I83 supported on the upright 82 below the sprocket 8|. A turnbuckle mis connected in the chain for purposes of making adjustments. The weight I causes the pulley 59 to be moved to the left upon ex-' the stretching of the belts. For thispurpose the framework 16 is mounted on suitable slides III' for movement lengthwise toward and away from the furnace I6. Disposed between the slides is a rigid block I01 rigidly fastened to the same support as the slides III; Secured on the block I01 lsa nut I09. "I'hreaded through the nut I08 is a screw I09 having a squared end H0. The squared end 0 is mounted in a bushing II2 for rotational movement but is securely held against longitudinal movement. As shown the squared end I I0 is positioned to be accessible from the extreme front end of the heat treating unit. The bushing H2 is supported on a suitable cross member II3 supported by the spaced uprights I02. With this construction rotation of the screw I09 by means of a wrench or crank attached to the squared head H0 will cause the framework I6 to move towards or away from the charge end of the furnace depending on the direction of rotation of the screw I09 and thereby simultaneously adjust the tension in both belts.

The belts 53 and 54 may be driven by any suitable means. In this instance they are driven by a motor H6 mounted on a platform IIl disposed at one side of the heat treating unit (see Figs. 8 and 10). The motor H6 is connected by a V-belt I20 to a speed change unit H8. The latter in turn is connected by a Vbelt H9 to a speed reducer I2I mounted on the platform H1. The speed reducer unit I2I is connected by means of acoupling I22 to a shaft I23 suitably supported at opposite ends on the platform I I1 and the framework 48. A spur gear I24 is mounted on the shaft I23. Meshingwith the spur gear I24 is a spur gear I26 mounted on a shaft I21 having its ends suitably supported by bearings mounted on the platform H1 and the framework 48. A sprocket I20 is mounted on the shaft I21 in spaced relation to the spur gear I26 and is connected by means of a chain I29 to a sprocket I3I mounted on the shaft 6|. Suitable tensioning means I35 may be provided for the chain I29. A sprocket I32 mounted on the shaft I23 in spaced relation to the spur gear I24 is connected by a chain I30 with a sprocket I33 mounted on the shaft 62. With this arrangement it will be seen that both belts are positively simultaneously driven through the pulleys 56 and'59 from the single motor H6. Suitable tensioning means for the chain I30 ma be provided if desired.

As the bimetal strip passes through the heat treating unit it distorts as it is first heated up. This distortion continues until after what can be considered the critical temperature of the bimetal strip is reached. Thereafter additional heat. 1. e. a higher temperature has little or no effect on the distortion of the bimetal strip.

8 The strip again becomes distorted when the strip passes from the temperatures above the critical temperature down to a lower temperature.- The amount of distortion decreases in this case with a decrease in temperature until at relatively low temperatures the bimetal strip assumes its normal position in which it is relatively free from distortion. While the distortion of the stripxis the prime reason for its use in industry this'inherent .bending of the strip during the heating and cooling steps of the heat treating process has presented a real problem to the industry insofar as handling of it is concerned. Accordingly one phase of the invention is concerned with means for restraining the distortion of the bimetal 'strip as it is advanced successively through the heating chamber II and the cooling chamber I2. This is effected in this instances by limiting the permissible movement of the'bottom portion of the top belt 53 away from the upper portion of the lower belt 54. A top I36 of the muflie (see Figs. 4 and 7) and the bottom 63 is utilized for this purpose in this instance for restraining the defective movement in the heating chamber II. The distance between the top portion I36 and the bottom 63 of the muflle 65 is suflicient to accommodate both thicknesses of the belts 53 and 54 and a bimetal strip disposed therebetween. sufficient clearance being provided to prevent sticking of parts. In a similar manner the top and bottom portions of the inner tubular member 4I provide restraining or distortion limiting means for the belts in the cooling chamber I2. To lower the temperature head required in the heating chamber the bottom portion 63 and top portion I36 are preferably perforated. This allows for better circulation of heat between the heatin elements and the bimetallic strip carried between the belts. A flexible wire belt construction formed as illustrated herein is also advantageous in'that hot air is permitted to circulate freely about the bimetal strip as it passes through the heating chamber. The bottom 63 and the top I36 may be formed in separate sections secured together in any conventional manner or may be formed by a plurality of tubular members welded together at their ends as shown in Fig. 4. v

A preselected atmosphere may be maintained in the furnace. The particular atmosphere may vary considerably for different materials as is well known in the art. Herein the gas for producing the atmosphere may be introduced into the heating chamber II from a header I39 (see Fi 4) through branch lines I39a, I391), I390 and H911. As shown the header I39 is mounted on top of the housing I9 and is connected to a gas supply line I38. A valve I40 may be connected between the header I39 and the line I30 for control purposes. Preferably the branch lines are arranged to be connected to the furnace unit at spaced positions therealong. Thus the branch line I39a is connected to the-section I43 to be in communication with the heating chamber I I at the forward end of the furnace. The branch line I39d is connected to be in communication with the passageway 43 at the discharge end of th furnace. The branch lines I39b and I390 are connected to the chamber II at positions intermediate th ends thereof.

Frequently atmospheres in a furnace are of a relatively explosive character, particularly when mixed with proper-proportions of air. -This is particularly true when a hydrogen atmosphere is employed as is often the case. Accordingly provision is made for preventing the'exhaust of this atmosphere into theroom in which the heat treating unit is disposed. To this end both a felt seal I H and a gas curtain I42 are utilized at both ends of the heat treating unit to prevent the leakage of the atmosphere from the furnace. As best shown in Fig. 11 each felt seal I4I comprises an upper portion I43 and a lower portion I44. These portions are retained between flanges I41 and I48 on extensions I49 and I50 respectively of the muffle Qand project forwardly of the charge end oi the furnace It. The section I43 is formed with a stepped portion I 5 I. With this construction the felts I43 and I44 engage the outer sides of the belts, yet will not provide a friction surface which will interfere with the movement of the belts. The upper felt rests on the top portion of the upper belt 53. In the event of distortion of the strip so that the belt is moved upwardly slightly the end of the felt I43 will be forced into the recess defined by the stepped portion III at the top of the extension I43. The weight of the belts 53 and 54 normally forces the extreme upper end of the felt I44 into the recess defined by the stepped portion I5I. One position of the felts during op- One flame or gas curtain I42 is mounted at the end of the extension I50 and the other is mounted at the end of an extension I55 of the cooling chamber I2. In general the flame curtain comprises spaced tubularmembers I53 having a plurality of ports I51 and closed at one end. At opposite ends the tubular members I53 are held in assembled relation by suitable brackets I54, which are attached to the frameworks I5 and 43 respectively. Gas is supplied to the tubular members I53 by a suitable connection, not shown. During the operation of the heat treating unit the gas curtain burns continually and thus burns any gas such as hydrogen which escapes or leaks from the furnace. By having both the felt seal HI and the gas curtain I42 it will be seen that effectively no furnace atmosphere can escape into the room adjacent the furnace.

As an additional safeguard to operating personnel of the heat treating unit conventional blowout ports I6I are provided adjacent the charge and discharge ends of the furnace l5. In this instanc the blow-out port I5I at the charge end of the furnace is formed in the section I49 between the felt seal HI and the charge end of the furnace I8 (see Fig. '5) and the other blow-out port I is located in the first section 40' of the cooling chamber I2 (see Fig.6).

The operation of the above fumaceisreadilyapparent but may be summarized briefly as follows: The strip of bimetal is placed on the table formed by the belt 54 at the charge end of the heat treating unit. As soon as the belt 54 carries the bimetal forward a suflicient distance the bimetal is gripped securely between the two belts 53 and 54 and is advanced first through the heating chamber I I and then through the cooling chamber l2. As the bimetal heats up in the heating chamber I I it tends to distort. This distortion of the bimetal causes the adjacent portions'of the belts 53 and 54 to spread apart. The distance which the belts may be spread however is limited in this instance by the top I36 and bottom 53 of the inuiiie 65. In effect the deflection movement of the strip is limited. When the temperature in the heating chamber II goes above the critical temperature of the bimetal strip, the forces causing the iseration of the heat treating unit is shown in Fig.

10 tortion are at a minimum and the weight ofthe upper belt itself is probably suiiicient to limit the distorting movement of the bimetal strip- However when the bimetal strip is cooled from the high temperature through the critical temper-a ture to a low temperature in passing through the cooling chamber so that it can be readily handied, the bimetal strip is again distorted. This relatively flat piece of material that is ready for the cold rolling process.

This construction is adaptable for other types of material besides bimetal. The construction described herein may be operated by one person. One of the important advantages of this furnace construction is that the cost of handling bimetal isgreatly decreased and consequently the per'unit cost of bimetal is greatly reduced.

While I have shown one embodiment of my invention I do not wish to be limited thereto since many modifications may be made and I therefore contemplate by the claims to cover such modifications as fall within the true spirit and scope of my invention.

Iclaim:

1. In a furnace for annealing a bimetal and the like strip material that distorts on heating, the combination of a heating chamber. a pair of opposed flexible belts having movable portions disposed in said chamber and spaced apart to receive a strip of said material therebetween and convey the same through said heating chamber. and means associated with said belts and disposed above and below said movable belt portions capable of engaging said belts at an infinite number of points along the length of said heating chamber upon distortion of said strip material to hold said belts in a predetermined spaced relation to limit warpage of said strip as it passes through said heating chamber.

2. In a heat treating unit for annealing bimetal and the like stripmaterial that distorts on heating, the combination of a furnace having a heating chamber therein. a first endless flexible metal belt having a portion extendingwthrough said heating chamber, means on the outside of said chamber for mounting and driving said belt,

a second endless flexible belt having a portion extending through the heating chamber adjacent said portion of the first endless belt to define gripping means to secure a strip of material and advance it through the heating chamber, means on the outside of said chamber for mounting and driving said second belt, and means encasing said portions of the endless belt in the heating chamber to guide the belts, said last mentioned means being continuous in extent throughout said heating chamber and capable of engaging said belts at an infinite number of points therealong and being so dimensioned to limit the separation of said belts to a predetermined amount upon distortion of the strip as the latter advances through the heating chamber.

3. In a heat treating furnace unit for bimetal and the like strip material that distorts on heat ing, the combination of' a heating chamber, a cooling chamber, a pair of flexible endless metallic belts having portions in said heating and l1 cooling chambers in opposed relation to define a gripping means for advancing a strip of said material through the heating and cooling chambers respectively, and rigid means extending for 3 at least the length of said heating chamber encasing said portions and forming a guide for said portions for limiting at any point therealong relative displacement of said portions away from each other whereby to limit the distortion of said strip of material.

4. The combination recited in claim-3 including means for continuously applying a predetermined tension in each of said belts.

5. The combination recited in claim 3 with manual means for simultaneously adjusting the tension in both belts.

6. In a heat treating furnace unit for bimetal and the like material that distorts on heating, the combination of a heating chamber. a cooling chamber, a pair of flexible endless metallic belts having portions in said heating and cooling chamber in opposed relation to define a gripping means for advancing a strip of material through the heating and cooling chambers respectively, means for continuously applying a predetermined tension to said belts, manual means for simultaneously adjusting said last mentioned means, and rigid means extending throughout the length of said furnace unit for completely encasing said portions thereby forming a guide for said portions and limiting at any point therealong relative displacement of the belts away from each other to limit the distortion of said strip.

7. In a heat treating furnace unit for bimetal and the like strip material, the combination of a furnace having an elongated heating chamber, a muille extending through said chamber having a passageway therethrough defined by top and bottom surfaces in closely spaced relation, an elongated cooling chamber in alinement with said passageway defined in part by top and bottom surfaces in closely spaced relation and forming a continuation of the top and bottom surfaces of the muiile, a pair of flexible endless belts having portions extending through said passageway and said chamber in adjacent relation defining opposed gripping surfaces for holding a strip of material, pulley means on the outside of said heating chamber and said cooling chamber for mounting said belts, and driving means for driving said pulley means to advance said gripping surfaces successively through the heating chamber and the cooling chamber, said top and bottom surfaces defining continuous restraining means engageable with said belts respectively to limit the distortion of said strip as it passes through the heating and cooling chambers.

8. The combination recited in claim 7 in which a portion of the muflie is perforated.

9. In a heat treating unit for bimetal and the like material, the combination of a treating chamber having openings at opposite ends and adapted to contain an atmosphere, a pair of endless belts having portions movable through said chamber in overlying relation to define top and bottom gripping portions for advancing a strip of material through said chamber, tubular means encasing substantial length of said portions of 12 the belts defining a guide ton-said portions of the belts, said tubular means defining continuous restraining means for limiting distortion of said strip as it passes through said chamber, and resilient felt seal means mounted on said tubular means to be engageable with the top and bottom portions of the belts respectively to minimize leakage of atmosphere through said openings for any relative position of the belts due to distortion of the strip.

10. The combination recited in claim 9 in which a gas curtain is in spaced relation with each of said felt seal means and together with said felt means effectively prevents leakage of furnace atmosphere to the atmosphere surrounding the heat treating unit.

11. The combination recited in claim 9 in which the felt seal means have ends projecting inwardly of the topand bottom portions of the tubular means to engage the top and bottom portions of the belts respectively and in which the top and bottom portions of the tubular means are formed with recesses to receive the end portions of the felt seals when the belts are in side by side sliding movement with the top or bottom portions of the tubular means respectively to provide substantially friction free surfaces for said portions of the belts.

12. In a furnace for annealing relatively short lengths of strip material such as a bimetallic material that distorts when subjected to temperature changes, the combination of a chamber for causing a substantial change in temperature of said strip material when passing therethrough, a pairof opposed flexible belts having movable portions disposed in said chamber and spaced apart to receive a strip of said material therebetween and convey the same through said chamber, and means associated with said belts extending continuously through said chamber and disposed above and below said movable belt portions to engage said belts upon distortion of said strip material at an infinite number of points therealong to hold said belts in a predetermined spaced relation to limit distortion of said strip as it passes through said chamber.

13. The combination recited in claim 12 in which the flexible belts permit air circulation therethrough.

DONALD H. GARDNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 890,252 Thompson June 9, 1908 1,319,085 Jacobson Oct. 21, 1919 1,367,049 Jackman et al Feb. 1, 1921 1,714,040 Naugle et al May 21, 1929 1,753,828 Greer et al. Apr. 8, 1930 2,061,910 Kingston Nov. 24, 1936 2,101,065 Hayes Dec. 7, 1937 2,237,966 Koehring Apr. 8, 1941 2,319,300 Cook May 18, 1943

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