US3048383A

US3048383A - Furnace or like system for gas-supporting and treating flat work

Info

Publication number: US3048383A
Application number: US761873A
Authority: US
Inventors: Champlin John Raymond
Original assignee: SWINDELL DRESSLER CORP
Current assignee: SWINDELL DRESSLER CORP; SWINDELL-DRESSLER Corp
Priority date: 1958-09-18
Filing date: 1958-09-18
Publication date: 1962-08-07
Anticipated expiration: 1979-08-07

Description

Aug. 7, 1962 J. R. CHAMPLIN FURNACE 0R LIKE SYSTEM FOR GAS-SUPPORTING AND TREATING FLAT woRK Filed Sept. 18, 1958 .'5 Sheets-Sheet 2 l fm INVENToR. JoH/J EA YMoA/o CHAMPL/M H/.s A rra/@Nens Aug. 7, 1962 J. R. CHAMPLIN FURNACE OR LIKE SYSTEM FOR GAS-SUPPORTING AND TREATING FLAT WORK Filed Sept. 18, 1958 3 Sheets-Sheet 3 INVE/vron Ja/-lu EA Mann 04AM/:uu

H/.s A Trau/E vs United States Patent 3,048,383 FURNACE R LIKE SYSTEM FOR GAS-SUP- PRTING AND TREATING FLAT WGRK John Raymond Champlin, Fox Chapel, Pa., assignor to Swindell-Dressler Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Sept. 18, 1958, Ser. No. 761,873 7 Claims. (Cl. 266-5) This invention relates to a system for gas-supporting and treating sheets, plates, strip 4and other relatively at shapes in furnaces or the like and adjunct equipment. More particularly, my invention pertains to continuous or batch heat treating of generally flat metal work while it is controllably suspended between air or other gas atmosphere blankets in my apparatus, such gas being conditioned as to temperature and pressure to effect the desired treatment.

Consideration has been given heretofore to heat treat ing metal while it is floating as disclosed in United States Patent No. 1,948,173. However, that operation is relatively uncontrollable, particularly with different weights and sizes of material to be processed. Thus, heating with jets on the underside only is relatively slow-acting and non-uniform. Further, the material heated appears subject to an absence of positional control with fluttering possible, tending to impede or shut down the operation. And, such material must be in continuous strip form with lateral centering thereof dependent upon the engagement means for moving the strip.

In my invention, such deficiencies are overcome and it is possible to relatively rapidly and relatively uniformly heat treat metal whether in continuous strip fform, or in discontinuous sheet or plate Iform with full positional and treatment control. Under my system, the work is pressed between upper and lower temperature-controlled gas blankets supplied through `an upper and a lower hearth and independently regulatable as to the pressure and/ or temperature of such gas. Means may also be provided for effective recirculation of such gas without material loss and with relatively high heating or cooling economy, as the case may be. Hence, irrespective of weight and size of work, such work can be held in a predetermined position relative to each of the hearths and simultaneously treated from both sides, precisely and as respectively desired. Moreover, in the case of sheets and plates or the like to undergo treatment, a succeeding work-piece can be used to push a preceding workpiece along through a furnace of my invention, or separated pieces of such work may be made self-conveying by gently sloping at least the lower hearth in a downward direction toward the exit end of the furnace with gravity seeming to be the force acting upon such work to move it. Further, the accurate positioning achieved in respect of work handled by a device of my invention prevents lateral offcentering, flutter and/or random movement. There is virtually zero friction therein so pickup by the work or by the parts of Ithe furnace that might otherwise occur is eliminated. Still further, with a furnace of my invention, the cost and maintenance expense thereof is materially lower in view, for example, of the lack of need for physical conveying or moving hearth equipment, and, by making such a furnace in sectional form, I can augment the treating control obtainable at respective locations along the path of the work through the furnace as well as increase the efficiency and localizing of the gas recirculation where such is employed.

Other objects, features and advantages of my invention will be apparent from the following description and the accompanying drawings, which are illustrative only, in which 3,048,383 Patented Aug. 7, 1962 ICC FIGURE 1 is a view in elevation of a longitudinal section through a heat treating furnace embodiment of my invention shown heat treating a continuous stnp of met-al;

FIGURE 2 is a view in plan, somewhat enlarged, taken along line II-II of FIGURE l;

FIGURE 3 is a view in plan, somewhat enlarged, taken along line III-II-I of FIGURE 1;

FIGURE 4 is a view in elevation, somewhat enlarged, taken along line IV-IV of FIGURE l; w v

FIGURE 5 is a view in elevation, somewh-at enlarged, taken along line V-V of FIGURE 1;

FIGURE 6 is a view of a modified embodiment of a furnace or the like in cross section taken along line VI-VI of FIGURE 7;

FIGURE 7 is a View in elevation of the modi-fied embodiment of FIGURE 6 taken along a longitudinal section line VII--VII of FIGURE 6;

FIGURE 8 is a view in elevation of the modified embodiment of FIGURES 6v and 7 taken -along line VIII- VIII o-f FIGURE 7;

FIGURE 9 is a plan view of a further modification of my invention in the form of a batch furnace for heat treating meta-l shapes such as sheets and plates;

FIGURE 10 is a view in section of the embodiment shown in FIGURE 8 taken generally along line X--X of FIGURE 9; and

FIGURE l1 is a front view of the furnace embodiment shown in FIGURES 9 and 10 taken along line XI-XI of FIGURE 10.

Referring to FIGURES 1 to 5, inclusive, of the draw` ings, the embodiment of this invention therein shown comprises a furnace 10 for annealing, normalizing or otherwise heat treating flat work shown in the form of a continuous steel strip 11 engaged respectively by entry pinch rolls 12 and exit pinch rolls 13. Furnace 10 is provided preferably with a plurality of similar Iheating sections 14 of lany `desired number and one or more cooling sections 15. Such provision of plural heating sections 14 enables work 11 to receive selective varied treatment if desi-red in each of such sections in the course of its passage through the heating portion of furnace 10.

'Fhe furnace 10 is provided with refractory side walls 16 and with a refractory roof 17 and oor 18. In addiv tion, a refractory superstructure casing 21 and refractory substructure casing 22 are provided for the heating sections 14. In the case of the cooling sections 15, the

superstructure 23 and the substructure 24 may be made of a sheet metal. Buckstays 19 and cross girders 20 with suitable auxiliary structural frame binding members tie the furnace structure together.

Refractory front and back walls respectively shown as 25 and 26 are also provided to complete' the furnace enclosure which preferably is gas-tight. AWall 25 is provided with a work inlet 2&7 and wall 26 with a work outlet 28 of suitable dimension. Such inlet and outlet are normally closed by upper and lower asbestos wiper curtains 29 which seal off the work treating chamber 30 extending through furnace 10 between openings 27 and 28. Other sealing means such as seal rolls may be positioned instead in such openings to engage the work 11 and shut oif the interior of furnace 10 from the outside save for leakage to the outside.

Each of the

sections

14 and 15 is shown as separated from an adjoining section by a transverse upper partition wall 31 and lower partition wall 32 extending from side to side of such sections and respectively from the top and bottom to the top'and bottom of =a work treating `space 30. Such partition walls may be made of sheet metal or, if desired, `of refractory in the heating sections. They function to compartment the respective sections and as 3 sist in the achievement of desired control in furnace and uniformity of treatment in a section.

In each

section

14 and 15 there is a lower hearth 33 and an upper hearth 34 in generally horizontal opposed relation defining the top and bottom planes of work charnber 30. Such hearths each comprise an orifice plate having a plurality of orifice openings 35 preferably normal thereto and distributed evenly over the area thereof. Thus, in operation, a gas, which may Ebe a selected atmosphere, or air in some cases, is discharged in jets preterably at right angles to the plane of work 11 as shown by the small arrows in work chamber 30 in FIGURES 1 and 4. And, further as shown, that embodiment has the orifices 35 in

orifice plates

33 and 34 directly opposed, that is, in respective vertical alignment. Each entry side of each orifice plate, that is, the upper side of plate 34 and the lower side of plate 33, is covered by a plenum hood 36 forming a lower plenum chamber 37 land an upper plenum chamber 38 therewith respectively. Supporting members 43 anchor the plenum chambers and orifice plates to the roof and floor of the sections, respectively. The respective plenum hoods are connected to

blowers

39 and 40 independently powered by

motors

41 and 42. In order to independently regulate the gas pressure within the respective plenum chambers, Such motors may be variable speed motors, or dampers 59 in each blower outlet may be provided for such regulation and control.

The front and back edges of each of the

orifice plates

33 and 34 are spaced from the respective front and back walls of their particular sections to provide front and

back duct passages

44 and 45 respectively in the upper and lower halves of the heating sections 14.

Similar duct passages

46 and 47 next to the edges of

orifice plates

33 and 34 are in the cooling sections 15 of furnace 10. `

Such ducts

44 and 45 associated with orifice plate 33 are downcomers which lead into a common header 48 leading to the suction side of a respective blower 39 while the

upper ducts

44 and 45 in each heating section 14 are risers communicating with a common header 49 leading to the suction side of a respective blower 40. The

ducts

44 and 45 have transversely extending indirect heating means 50 positioned therein -which are in the form of radiant tubes extending through one of the side walls 16, Such tubes may be heated by burners 51 connected thereto at one end and with the flue gases exiting through the other ends 52 of such tubes for discharge into the mill |building or into a stack collector as desired. Such indirect heating of the circulating gases passing through the orifice plates in each heating section 14 simplifies the problem of control of the work supporting and heating gases which issue, preferably under about the same pressure head, from the respective opposed orifice plates. As will be understood, other heating means such as electric resistance heater grids may be utilized instead as the heating source.

Such gas issuing from each orifice plate in each heating and cooling section tends to remain segregated from the gas issuing from the opposed orifice plate in the same section due to the preferred gas pressure 'balance and the interposition of work 11 therebetween. Such gases from the respective upper and lower halves of each section are returned for the most part to their respective blowers as indicated by the arrows in the respective ducts. Makeup gas may be provided in one or more of the sections of furnace 10 by supplying the same through a pipe 53 leading to the interior of such section. At the same time, there is sufficient communication between the respective upper vand lower halves of each section and between sections to avoid detrimental pressure differentials in the work treating space 30.

Because of the independent regulation of the gas pressure fed to each plenum chamber in each half of each section, gas blankets are formed in each section of selec tive effect on the upper and lower sides of the work going through that section. Consequently, the work, for example, regardless of its width and thickness or specic gravity may be caused to be suspended in spaced relation to lboth upper and lower hearth portions in each section as desired with consequent gain in relative stability and uniformity of treatment in such section. ln the embodiment being described, the speed with which the work strip 11 moves through furnace 10 will be a function of the driving pinch rolls and the amount of temperature change response by the work in each section will be a function of that speed, of the volume of gas circulated by the respective blowers and the temperature at which, in the case of heating sections 14, the radiant tubes 50 are maintained.

Likewise, in the case of the cooling sections 15, the

ducts

46 and 47 are connected in the bottom halves of those sections by headers 54 and in the upper halves by headers 55 leading to the respective cooling section blowers 39 and 4f). The temperature control means 56 in

ducts

46 and 47 may be indirect cooling pipes through which a coolant like water at selected temperature is passed for the respective cooling condition desired in the gas recirculated in those respective halves of cooling sections 15. Normally, the cooling sections 15 reduce the temperature of heat treated work -11 exiting from the rearmost heating section 14 to the selected lower temperature at which it may be passed out into the air on the outer side of the back seals 29.

In the further embodiment illustrated in lFIGURES 6 to 8, parts corresponding generally in construction and functioning tto the first-described embodiment are provided with the same reference numerals with the addition of a prime accent thereto. In such further embodiment, the gas recirculated within each half of the heating section 14 is heated in the ducts `57 by electric resistance grid heaters 58. Moreover, such ducts 57, instead of being transverse at the front and back of each section as are

ducts

44 and 45, extend longitudinally along the side walls 16 of section 14. As a consequence, the

orifice plates

33 and 34 extend the full length of section 14 between the front and back walls thereof but do not extend all the way to the side walls 16' in order to leave room for the respective ducts 57. On the other hand, recirculation ducts for the gases returning to the respective blowers may be provided around all of the edges of each orifice plate, or by ducts extending therethrough in one or more locations within the periphery thereof. The seals at each end of the final heating section 14' are in .the form of sealing rolls 29' at the entrance for work 11 into cooling section 15.

Cooling section 15', as more particularly shown in FIG- URE 8, is an air cooling section of the non-recirculating type with ducts 57a extending longitudinally along sides 16 in vthe manner of ducts 57. Thus, such sections 14' and 15 in furnace 10 have longitudinally continuous opposed sets of section hearths with the exhaust ducts for the gas issuing from each orifice plate to each side thereof. Although the Work passing through furnace 10 and modification 10 is shown in the form of a continuous strip of metal, it will be understood that such furnaces may be operated continuously on sheets or plates suspended between such hearths in the same manner with the preceding sheet or plate being pushed bythe one behind.

In the still further embodiment illustrated in FIGURES 9 to 1l, inclusive, a batch operation in accordance with the principles of this invention may be practiced. Parts in `the further modification of FIGURES 9 to l1 corresponding generally in construction and functioning to parts illustrated in the first-described embodiment are provided with the same reference numerals with the addition of a double prime accent thereto. Such still further embodiment is particularly useful for the heat treating sheets and plates 11l on a time cycle basis and may be used in conjunction with an entry roller or transfer table 60 and an exit roller or -transfer table 61. And, as shown more particularly in lFIGURE 9, fthe orifices 35a along the side edges of at least the lower orifice plate 33 may be somewhat smaller in effective diameter than the remaining orices 35 therein. In that way, any tendency that a sheet or plate 11" might yotherwise have to become laterally olfcentered will be prevented by the higher velocity gas jets issuing from such bordering side orifices 35a. Normally, however, I have lfound that with the upper and lower gas blankets between the hearths, the positional control of the work, even when in separated pieces, is such that it will follow the desired work path through the new furnace or the like even when all the orifices are the same size.

Such tables 60 and `61 are respectively in alignment with the inlet opening 27 to heating section 14" and with the outlet opening 28" from the cooling section 15". Such openings are provided respectively with

doors

62 and 63 and a further door -64 is provided to close the .opening between sections 14" and 15". Each such door is hung from a laterally spaced pair of rods 65 pivotally connected thereto. The upper ends of such rods are respectively connected to inwardly extending arms 66 rigidly connected tto a cross shaft 68 pivotally supported at 67 in bearings supported by the tops of the respective sections. The outer ends of each cross shaft 68' are provided with opposed arms 69 from which ring rods 70 depend. Any ring rod connected to any shaft 68 can be pulled downwardly by an operator 'on either side to open ithe particular door connected to that shaft. Conversely, the door may close when an operator allows the ring rod 70 to rise. If desired, suitable counterweights for the respective doors may be provided to lessen the effort required to manually open one or more of them las selected.

In addition, a laterally spaced pair of chains 71 is connected to the upper edge of each door and respectively extend around pulleys 72 in an automatic cycle operator 73. The cycle operators 73 are interconnected electrically, hydraulically or pneumatically, as will be understood, in the desired timing or sequence for the opening and closing of the respective doors 62', 64 and 63 for whatever operation in furnace 16 is selected when it is on automatic or semiautomatic rather than manual control.

Further, the hearths 33" and 34" in each of the sections 14" and 15 are parallel to each other, respectively, and titlted or sloped somewhat downwardly in a longitudinal rearward direction. As a consequence, in an operation of furnace 10, a plate 11 which has been sufliciently reduced in temperature in air cooling section 15 may be discharged onto table 1 by opening door 63. When that door rises above suspended plate 11, plate 11 will ride out by itself onto table 61. Then if door 63 is closed and door y64 is opened when the time heating cycle in section 14" is ended, the sheet or plate 11" in section 14 will feed itself while suspended out of the heat-treating space 30 between the hearths in section 14" and into the Work cooling space 30 between the hearths in section 15". Such last-mentioned plate 11" will come to rest in section 15" when the forward edge thereof engages the inside of door 63, or other suitable stop means may be provided. The rearwardly downward slope of the hearths is gentle enough so that the movement of work 11l against the inside of door 63 will not damage such door. And, the inner side of door 64 may be used as a stop in the same manner with respect to heating section 14.

When section 14" has been emptied, door 64 is reclosed and door 62 is then opened so that heating section 14" may receive the next piece of work 11" from table 607 such piece of work coming to rest after it has moved in suspended fashion between hearths 33" and 34 in section 14" when its forward edge engages the inside of door 64. At that point, door 62 is closed and the heatingcycle on workpiece 11" in section 14" is underway. As shown, work 11" in section 15, like section 15 in FIGURE 8, is supported and cooled directly by ambient air surround- 6 ing and taken into blowers 39" and 40". Suchl cooling air leaving work space 30 between

orifice plates

33 and 34 in section 1S is discharged through the upper and lower ducts 46 and 4 respectively to the outside of furnace 10". It will be recognized that such an air cooling section 15 is utilized where the heat treated plate 11 exiting from section 14 may be air-quenched in that manner without harm to the desired physical or metallurgical properties wanted in the treated plate or sheet 11". As soon as the desired cooling in section l5 has been completed, the fully treated work 11 is discharged onto table 61 as described above.

Although the furnace embodiments illustrated have involved a plurality of sections, for some purposes a single temperature control section may be suiiicient to comprise the entire device used. Further, Work-suspending embodiments employing this invention may be constructed for treating work in a way which does not involve changing the temperature of the work, as, for example, the application to such work of cer-tain coating substances which may be supplied with the supporting gas or introduced into the work space separately and directly. Again, while reference has been made to moving work longitudinally relative to devices of this invention, it will be noted that such term is relative and that work may be introduced through one side and discharged through another side of such a device, or by control of the tilting of respective section hearths may be moved in an angular path within respective portions of such device. The work discussed above as flat work may of course include work having a relatively large area by comparison with thickness and in which the upper or lower surfaces, or portions thereof, or both, are not fully planar as in the case of work having corrugated ridges or undulations on one side, or the other, or both.

Thus, various changes in the illustrated embodiments may be made and still other embodiments may be devised without departing from the spirit of my invention or the scope of the appended claims.

I claim:

l. In a furnace or like system for gas-supporting and treating at solid metal work or the like, apparatus comprising, in combination, a plurality of heating sections in longitudinal alignment, at least one cooling section adjoining the rearmost heating section in longitudinal alignment therewith, each section having a longitudinally extending work treating space defined by upper and lower plenum chambers in opposed relation, said plenum chambers in each section respectively having la llat orifice plate dening the top and bottom planes of said 4work treating space, said orifice plates being substantially horizontal and having only substantially vertical orifices therethrough in uniformly distributed arrangement over said work treating space, means for supplying a gas to each said plenum chamber for discharge through said orifices Kat a predetermined pressure sufficient to suspend work in each section at a predetermined height between said orice plates and within said work treating space, transverse upper and lower separator means between said sections, heat exchange gas temperature regulating means positioned transversely and outside of said `work treating space along opposed walls in each of said sections adjacent said plenum chambers to control the temperature of gas supplied to said sections respectively without forming combustion products in situ, header means connecting said temperature regulating means with said tiret-named means to provide a recirculation circuit for said gas, horizontally and longitudinally aligned Work inlet and outlet openings at respective ends of said furnace or like system, and means for enclosing the interior of said furnace and said work treating space.

2. In a furnace or like system for gas-supporting and treating substantially flat solid metal or the like, apparatus comprising, in combination, a heating section, a cooling section adjoining said heating section, each section having a longitudinaly extending work treating space defined by upper and lower plenum chambers in opposed relation, said plenum chambers in each section respectively having an orifice plate defining the top and bottom of said work treating space, said orifice plates being substantially horizontal and having only substantially vertical orifices `therethrougl'i in distributed arrangement, means for supplying a gas to each said plenum chamber for discharge through said orifices at a predetermined pressure suicient to suspend work in each section at a predetermined height between said orifice plates and within said work treating space, transverse upper and lower separator means between said sections, indirect heat exchange gas temperature lregulating means positioned outside of said work treating space along at least one `wall of said heating section, means connecting said temperature regulating means with said first-named means to provide a recirculation circuit Vfor said gas, horizontally and longitudinally aligned work inlet and outlet openings at respective ends of said furnace or like system, and means for substantially sealing the interior of said furnace and said work treating space.

3. In an enclosed -furnace or like system for gas-supporting and treating stiff fiat work, apparatus comprising, in combination, a treating chamber having a work space defined by upper and lower horizontal hearths in spaced relation defining the top and bottom of said work space, said hearths comprising orifice plates with discharge orifices only therethrough distributed over said work space, means for supplying gas respectively to each orifice plate for discharge through said orifices into said work space at a predetermined pressure sufficient to suspend work in said work space at a predetermined height I between said orifice plates, said work space having ingress and egress openings in a horizontal plane, and means for controlling the `temperature of said work without subjecting it to combustion products formed in situ.

4. In an enclosed furnace or like system for gas-supporting and treating flat work, apparatus comprising, in combination, a heating chamber having a work space defined by upper and lower horizontal hearths in spaced relation defining the top and `bottom of said work space, said hearths comprising orifice plates with discharge orifices only therethrough distributed over said work space, means for supplying gas to each orifice plate `for discharge through said orifices at a predetermined direction and pressure sufficient to suspend work in said work space at predetermined location and height bet-Ween said orifice plates, indirect heater means `for said gas positioned -in said heating charnber outside said work space, horizontally aligned work inlet and outlet openings in said chamber at opposite ends of said work space, said orifice plates being gently sloped downwardly in a rearward direction to cause work like plates and sheet to move toward the back of said heating chamber.

5. In an enclosed furnace or like system for gas-supporting and treating fiat substantially solid work such as plates, strips and sheets, apparatus comprising, in con1,l

bination, a heating chamber having a iwork space defined by upper and lower horizontal hearths in -spaced relation defining the top and bottom of said work space, said hearths comprising orifice plates with discharge orifices only therethrough in a distributed arrangement, meansf I for supplying a selected gas to each orifice plate for discharge through said orifices in an opposing direction at predetermined pressures sufficient to suspend work in said work space at a predetermined location and height between said orifice plates, said orifices along the side edges of said heating chamber being sized smaller than the remainder of said orifices to guard against lateral oficentering of said work, said work space having ingress and egress openings on the same level, heater means for said gas positioned in said heating chamber outside said work space to control the temperature of said vgas without forming combustion products in situ, and means for recirculating said gas respectively to said orifice plates past said heater means.

6. In an enclosed system for gas-supporting and treating substantially solid surface area Iwork, apparatus comprising, in combination, a treating chamber having a work space defined by upper and lower substantially horizontal hearths in spaced relation defining the top and bottom of said work space, said hearths comprising orifice plates with orifices therethrough distributed over said work space, means for supplying gas to each orifice plate for discharge through said orifices in an opposing direction and at a predetermined pressure sufficient to suspend work in said work space at a predetermined height between said orifice plates, work inlet and outlet openings in said chamber on the same level for said work space, and further means for conditioning said gas to treat said work without forming combustion products in situ.

7. In an enclosed lfurnace or like system for gas-supporting and treating substantially flat solid metal work, apparatus comprising, in combination, a heating section having enclosed .walls including front and back walls, upper and lower generally horizontal hear-tbs in said heating section comprising opposed orifice plates having discharge orifices only distributed thereover, a plenum chamber on the entry side of each said orifice plate, independently regulatable means for supplying a selected gas at a predetermined pressure to each said plenum chamber sufiicient to suspend work at a predetermined height between said hearths, generally vertical ducts at opposite edges of said orifice plate and alongside opposite sides of said plenum chambers, radiant tube or electric heating means positioned in said ducts to heat said gas to heat treat said work, a header in communication with said ducts above said upper orifice plate, a further header in communication with said ducts below said lower orifice plate, -said headers being connected to Said independently regulatable means respectively -to separately control supporting gas forces operative through said orifice plates above and below said work, said front and back ywalls having inlet and outlet openings on the same level respectively for work to pass therethrough, and means for causing work to be heated to move through said section while in gas-supported predetermined spaced relation to said orifice plates and to the sides of said heating section.

References Cited in the file of this patent UNITED STATES PATENTS 1,948,173 Hagan Feb. 20, 1934 2,144,919 Gautreau J an. 24, 1939 2,519,059 MacConnell Aug. 15, 1950 2,525,112 Baker 2---- Oct. 10, 1950 2,525,203 Bostroem Oct. 10, 1950 2,669,068 Wambreuze Feb. 16, 1954 FOREIGN PATENTS 652,038 Germany e Oct. 23, 1937 167,413 Austria Ian. l0, 1951 UNITED STATES PATENT oEFICE CERTIFICATE 0F CORRECTION Patent No., 3,048,383 August 7, 1962 John Raymond Champlin It is hereby,r certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 50, for "table l" read table 6l mg column 6, line 74, after "metalIl insert, work --g column 7, line 48, after "at," insert a column 8, line 30, for "enclosed" read enclosing Signed and sealed this 20th day of November 1962.

(SEAL) Attest:

ERNEST w. swlDER DAVID L- LADD Atteting Ufficer Commissioner of Patents