US2037392A - Eddy current control for leers - Google Patents

Description

April 14, 1936. Q RlLEY EDDY CURRENT CONTROL FOR LEERS Filed March 1, 1933 a n llv W35@ egg; im] WW Patented Apr. 14, 1936 I UNITED STATES PATENT OFFICE Clare S. Riley, Hartford, Conn., assignor to Hartford-Empire Company, Hartford, Conn., a corporation of Delaware Application March l, 1933, Serial No. 659,047

I Claims.

This invention relates to a method of and apparatus for controlling and preferably eliminating eddy currents in tunnel type glassware annealing leers, particularly those leers which are 5` heated either by muiile means or leers which are heated by electricity in some manner, in both of which cases combustion products are not brought into the interior of the tunnel into direct contact with the glassware being moved therethrough, so that there is no necessity for any flow of tun- 1 nel atmosphere through the tunnel; and in fact such flow is usually considered undesirable.

In leers of the muiile type and/or those which are electrically heated, drift has been a source of considerable trouble due to the fact that air currents moving through the tunnel from one end to the other thereof have interfered with the temperature gradient control along the tunnel and consequently with the annealing of the glass ary ticles therein. Material improvements have been made in minimizing or wholly stopping such drift throughout the tunnel. Some of these means are shown in the Wadman Patents Nos. 1,808,192, r granted June 2, 1931, and 1,896,874, granted February 7, 1933. Even with these improved devices, however, which minimize or control the overall drift or ow of air currents through the leer, considerable trouble has been encountered due to uncontrolled currents of tunnel atmosphere circulating -in an ungoverned manner through hotter portions of the leer where the glass is most sensitive to variations in temperature. These uncontrolled currents are termed eddy currents both in thepecimzation and appended claims.

Av primary object of the present invention,

therefore, is to provide a method of and appa-l ratus for controlling and preferably eliminating 'these uncontrolled eddy currents of tunnel atmosphere, particularly in the hotter portions of the tunnel of a glasswareannealing leer, thus' overcoming the difficulties existing in the operation of previous types of leers.

movement in a direction longitudinally of the' "tion from that in which the view of Fig. 1 is A further and more specific object of the invention is to establish positive currents of tunnel' structure including the structural members 3 and leer. This method .of eddy current control and the apparatus for use therewith may advantageously be employed in many types lof glassware annealing leers including those shown in the Wadman patents above referred to and in conjunc- 5 tion with the means therein disclosed for controlling overall drift.

A further specific object of the present invention is to establish a current of tunnel atmosphere through the tunnel in a direction at right angles to the path of movement of the ware and in such manner that this current will be substantially stream line in character and will be substantially uniform in velocity transversely of the leer. 15

A further object of the present invention is to provide a means for controlling eddy currents as aforesaid in conjunction with the glassware annealing leer which will not interfere with the normal temperature gradient control therein and further., which preferably will assist in the heat transfer control in the leer. i

Other and more 'specific objects of my present invention will become apparent from a reading of the following specification and appended claims when taken in connection with the accompanying drawing, in which:

Figure 1 is a somewhat diagrammatic view sub-i stantially in vertical longitudinal section of a glassware annealing leer of the muiile, combustion-heated type embodying my invention;

Fig. 2 is a view in vertical section on the line 2--2 of Fig. 1, the lower portion of the leer support being omitted; 35

Fig. 3 is a view in vertical section taken substantially on the line 3-3 of Fig. 1; and

Fig. 4 is a fragmentary view in elevation of a portion of the leer seen from the opposite directaken, showing the driving means for the several fans of the eddy current controlling means.

I have chosen to illustrate my invention in connection with a glassware annealing leer, similar to that shown and described in the patent to Mulholland, No..1,560,481, granted November 3, 1925.

f As shown in the accompanying drawing, this leer comprises an elongate tunnel 1I, which may be built up of a plurality of similar cast iron sec-v tions 2, certain of which in-various zones of the leer'being interchangeable. This tunnel may be supported in any suitable manner, for example,

the ware-entering end, seen at the left in Fig. 1, may be suitably anchored to a suitable supporting the remainder of the tunnel permitted to expand freely from this anchored end, as by providing the several sections with wheels 4 arranged to roll upon suitable rails carried by longitudinally extending channels 5, which may in turn be supported upon suitable pedestals 6.

'I'he tunnel may be insulated as desired, as by the provision of suitable heat insulating material 'I which may be of a pulverulent nature, such as kieselguhr, which may be confined by a suitable light metallic casing 8.

Suitable means may be provided for moving articles of glassware through the leer, such means in the present instance being indicated as a continuous, open work, metallic belt 9 I arranged in sliding relation with the floor of the tunnel I and passing over a plurality of spaced rollers I0 of a packing table in prolongation of the exit end of the leer, as indicated in Fig. 1. Suitable means as indicated generally at II may be em- A ployed for driving the belt 9 by drawing it through the tunnel, the belt returning to the entrance end of the tunnel beneath the same and the return strand being supported in any suitable manner as upon spaced rollers I2. Suitable means may be provided, as indicated generally at I3, for predetermining the slack in the return strand of the conveyor 9.

The leer may be provided with suitable temperature gradient controlling means including one or more longitudinally extending flues I4 arranged beneath the floor thereof to which products of combustion may be supplied from a fire box I5 into which a uid fuel burner I6 may be directed. Suitable means (not shown) may be provided in connection with the re box I5 for introducing a desired amount of air to dilute and cool the products ofv combustion to bring them to the temperature desired at the time they are supplied to the ues I4. Temperature controlling means may be provided at intervals along the flues I4, such means in the present instance comprising spaced air inlet ports I 1, each controlled by a damper I8. In order to provide for the controlled cooling of the ware there may be provided above a desired portion of the tunnel longitudinally extending flues I9 to which atmospheric air may be admitted adjacent to the exit end of the leer, as through the open ends 20 of these flues. may be withdrawn at intervals from the flues I3 through the takeoff passages 2l under control of dampers 22, the passages 2| all. communicating with a longitudinally extending takeoff conduit 23, which communicates adjacent to the exit end of the leer with a wind box 24. The wind box 24 may also communicate with the ilues I4 through saddle pipes, one of which is indicated in dotted lines in Fig. 1 at 25. Gases may be exhausted from the wind box 24 by a suitable exhaust fan 26 driven from any desired source of power, as the motor 21. Adjacent to the exit end of the leer and to the right as seen in Fig. 1 of the communication between the saddle pipes 25 and lthe lower ues I4, these ues may communicate with the atmosphere through an air inlet passage 28 under control of a damper 4ilgf.

'I'hus far the leerwhich I have described is substantially the same as that of the Mulholland patent above referred to. Reference may be made to this patent if desired for a more complete description of this subject matter. 'Ihe leer thus far described forms per se no `part of my present invention and hence will not be described in greater detail.

In order to overcome eddy currents, I provide Air.

means for establishing positive currents of tunnel atmosphere in closed paths each independent of the other and located in spaced zones along that portion of the tunnel in which it is desired that eddy currents be controlled, particularly the hotter portions of the tunnel where the glass is most sensitive to relatively slight variations in temperature such as might be caused by the presence of eddy currents.4

As shown, each section from the second section from the left, as seen in Fig. 1, to a point somewhat beyond the middle of the leer is provided with means for circulating tunnel atmosphere through the tunnel in a direction at right angles to the path of the glass articles therethrough, more particularly in a vertical direction from the top to the bottom of the tunnel. As shown in Fig.

2, the side casting 30 of the tunnel is provided f with a passage 3I formed therein which communicates at its upper end with an upper header 32, and at its lower end with a lower header 33. 'I'he lower Wall of the upper header 32, which is common with the roof of the tunnel, is provided with a plurality of perforations 34, which as shown may be of uniform diameter and which may be uniformly spaced. `The header 32 is tapered from the left hand end to the right hand end, as seen in Fig. 2, so that air supplied to its left hand end will be substantially uniformly distributed through the several perforations 34 and so that the currents of tunnel atmosphere flowing downward through the tunnel will move with a substantially stream line iiow and with uniform velocities throughout the width of the tunnel. This is important as it is desirable, if not absolutely necessary, that the temperature conditioning of glass articles in all transverse sections of the tunnel be substantially uniform in order that same result is secured in connection with the lower header, as shown by the provision of perforations or apertures 35 in its upper wall, which is common with the lower wall of the tunnel, of varying effective cross sectional area from the left hand to the right hand ends of the header, as seen in Fig. 2. As shown, these openings are larger in diameter from the left to the right so that the decreasing pull on the air at the right hand end of the headers seen in this figure will be compensated for by perforations of larger diameter. The same result could be accomplished by the prpvision of uniform size openings at closer intervals at the right hand side, as seen in Fig. 2,v

the left hand side. The important factor is that there be a means for insuring a substantially uniform, flow of air as to volume and velocity transversely of the tunnel. With a header having parallel upper and lower walls. as the header 33, this can be effected by providing progressively varying effective cross sectional area of openings per unit of area of the wall in which these openings are formed, which may be done as above set forth either by varying the size of the openings or the spacing thereof, or both.

The use of headers, as shown at 32, having a tapering section from side to side of the leer is preferably Ilimited to portions of the leer wherein the headers are backed only by the heat insulating material as indicated in Fig. 2, while the headers-having parallel sides and the varying cross sectional area of openings and/or varying density thereof, as indicated for the header 33, may be employed when these headers are located intermediate the tunnel and one or-the other o! the articles may be uniformly annealed. This tunity for heat transfer between the ware and the temperature controlling media in the flues is uniform laterally of the'tunnel.

Means .are provided in connection with each of the passages 3i for positively causing circulation of the tunnel atmosphere as aforesaid. Such means in the present instance include fans 31 mounted upon shafts 38 projecting through the side walls of the leer.A Suitable driving means are provided for the fans 31, in the present instance, such means including a common drive for all of the fans. For this purpose th shafts 38 carry bevel gears 39 which mesh with bevel gears 4U mounted upon a common driving shaft 4I which may be driven by any suitable driving means (not shown).

When the fans 31 are in operation, the tunnel atmosphere will be circulated from the fans through the upper portions 42 of the passages 3|, thence through the upper headers 32 or 36,

downwardly through the perforations 34 or 43 in I these headers respectively, thence downwardly through the tunnel in a, stream line i'low extending the entire width of the tunnel and in substantially uniform volume and velocity transversely thereof, thence vthrough the perforations 35 of the lower headers 33, and thence from the end of these lower headers upwardly through the passages 3| back to the fans. A tunnel atmosphere thus circulated will preclude the possibility of eddy currents existing in the portions of the tunnel provided with my novel circulating means as above set forth. -This circulating of tunnel atmosphere will also serve to assist in thel transferring of heat by convection between the glass articles passing through the leer and the nues I4 and I9, which in practice will provide for a more accurate controlled temperature gradient in the leer. The provision of the fans as illustrated and described will insure that all of the tunnel atmosphere being circulated will be posi- I tively forced in its closed paths by the fan, thus prising continuously passing transverse rows of insuring against eddy currents which might exist should at attempt be made to create a circulation by one or more fans located in the tunnel as has been suggested in the prior art for other purposes at which point the fan or fans would be effective either upon only a part of the tunnel atmosphere being circulated or upon air within the tunnel which is not circulated through the closed path, as above set forth, `such structures being liable to increase rather than decrease the eddy currents.

It is obvious that modifications may be made both in the methods hereinl disclosed and in the apparatus by vwhich these methods may be carried out. I do not wish .to be limited, therefore, except by the scope of the appended claims, which are Ato be construed as broadlyas the state of the prior art permits. v

I claim: 1. The method of ,annealing glassware. comglass-articles to be annealed through a tunnel on a mesh conveyor, subjecting all the articles of each transverse row similarly to the temperature modifying effects of successive streams of gaseous medium, each of substantially uniform volume, velocity and temperature across the row, said streams being forcibly moved in substantially vertical directions through the tunnel and between the articles, and so controlling the characteristics of the several streams as to maintain the desired temperature gradient in the ware as it moves through the tunnel.

2. -The method of eliminating eddy currents in a tunnel type glassware annealing leer, which comprises -independently establishing in each oi a plurality of zones longitudinally of the tunnel a positive forced circulation of unaugmented cur. rents of tunnel atmosphere in a closed orbital path including a portion of the tunnel, the tunnel atmosphere being independently circulated in each of said portions from the roof toward the floor of the tunnel, and passing through the tunnel in a substantially stream line flow substantially coextensive with the width of the tunnel and during this portion at least of its circulatory travel having uniform pressure, velocity and direction throughout the width of the tunnel, and 25 l positively moving all the tunnel atmosphere thus circulated by force applied thereto at a portion of its path outside said tunnel.

3. In a leer for annealing glassware, a tunnel having a hotter zone and a cooler zone, a conveyor belt of mesh fabric for conveying ware successively through the said zones, a partition below the ware-bearing strand of said conveyor belt defining the upper wall of a chamber, a second partition above the ware-bearing strand of said conveyor belt and above the path of the ware thereon defining the lower wall of a second chamber, a duct connecting said chambers, flow impelling means interposed in said duct intermediate said chambers, apertures through one of said partitions arranged for the introduction of streams of gaseous medium into the tunnel, said apertured partition being so constructed and arranged that the streams so introduced into the tunnel will be of substantially uniform volume and velocity other of said partition for exhausting the streams, from the tunnel, and means for exhausting gaseous medium, whereby the ,tunnel throughout any cross section in the hotter zo'ne" Vis maintained at a substantially uniform temperature.

4. In a leer for annealing glassware, a leer chamber having a heating zone and a tempering zone, a conveyor belt of light mesh construction for conveying ware through the said zones, a plurality of ducts located above and below the conveyor substantially throughout the length of said zones,'said ducts having openings in the surface thereof adjacent the conveyor, means outside the tunnel for forcibly circulating heated air .through the ducts, through the openings in the Vio i atmosphere through said paththe means forming a part of the path forming means between the portion of the path outside the tunnel and the interior of the tunnel insuring thatv the flow of tunnel atmosphere through the tunnel is substantially uniform in velocity and amount throughout the width of the tunnel considered from the point of view of the direction of movement of the tunnel atmosphere and is in a direction solely at substantially right angles to the Ydirection of movement of the glassware through the tunnel.

6. Apparatus for controlling eddy currents in a tunnel type glassware annealing leer provided with temperature gradient controlling means and means for moving the glassware therethrough,

' comprising means associated with the tunnel forming a closed circuit path for tunnel atmosphere including a portion of the tunnel, means for positively circulating tunnel atmosphere thro-ugh said path, and a perforated ytapered header forming a part of the closed circuit path for the tunnel atmosphere intermediate the portion of its path outside the tunnel and the interior of the tunnel and so constructed and arranged that the amount of air passing through each of the several perforations of the header will be substantially uniform, whereby to produce a uniform flow of air as to velocity and amount across the tunnel in a direction at right angles to the direction of movement of the glassware through the tunnel and substantially coextensive with the Width of the tunnel considered from the point of view of the direction of movement of such tunnel atmosphere.

7. Apparatus for controlling eddy currents in the tunnel type glassware annealing leer provided with temperature gradient controlling means and means for moving the glassware therethrough, comprising means associated with the tunnel forming a closed circuit path for tunnel atmosphere including a portion of the tunnel, means for positively circulating tunnel atmosphere through said path, and a header forming a portion of said path between that portion thereof outside the tunnel and the interior of the tunnel and provided with perforations of varying size transversely of the tunnel', said header and the perforations thereof being so constructed and arranged that the flow of air across the tunnel will be in a-direction at rightangles to the direction of movement of the glassware through the tunnel and will be substantially uniform as to velocity and amount transversely of the tunnel.

8. Apparatus for controlling eddy currents in a tunnel type glassware annealing leer provided with temperature gradient controlling means and means for moving glassware therethrough, comprising means associated with the tunnel forming a closed circuit path for tunnel atmosphere including a portion of the tunnel, means for positively circulating tunnel atmosphere through said path, a tapered header having perforations therein forming ,a part of the vpath forming means intermediate the portion of the path outside Vthe tunnel and the interior of the tunnel, and another header having perforations of varying sizes transversely of the tunnel forming another portion of the closed circuit path between the portion thereof outside the tunnel and the interior of the tunnel, said headers and the perforations thereof being so constructed and arranged that the flow of tunnel atmosphere across said. tunnel will be substantially coextensive with the width thereof considered from the point of view of the direction of movement of the tunnel atmosphere, will be in a direction at right angles to the direction of movement of the glassware through the ltunnel, and will be substantially uniform asl to velocity and amount transversely of the tunnel.

9. Apparatus for controlling eddy currents in a tunnel type glass annealing leer provided with a mutlle flue associated with the tunnel for controlling t-he temperature gradient therein and with means for moving the glassware therethrough, comprising means associated with the tunnel forming a closed circuit path for tunnel atmosphere including a portion of the tunnel, means for positively circulating tunnel atmos- 'phere through said path, a header forming a part of said closed circuit path intermediate the portion of said path outside the tunnel and the interior ofthe tunnel and having a perforated wall common with the tunnel and a wall parallel thereto common with at least a portion of the flue by which the temperature gradient in the tunnel is controlled, the perforations in the wall of said header being of different diameters transversely of the tunnel, whereby the circulation of tunnel atmosphere through the tunnel may be uniform as to velocity and amount transversely thereof and the temperatures existing in the tunnel opposite said header will be substantially uniform transversely thereof due to all transverse portions being equally exposed to the flue portion on the opposite side of said header for the transfer of heat therebetween.

l0. Apparatus for controlling eddy currents in a tunnel type glassware annealing leer provided with temperature gradient controlling means and means for moving the glassware therethrough, comprising means associated with the tunnel forming a plurality of independent closed circuit paths at zones spaced along the tunnel for the circulation of unaugmented currents of tunnel atmosphere, each path including a portion of the tunnel, a fan in each of said paths in a portion thereof outside said tunnel for positively circulating tunnel atmosphere through the respective paths and in such a manner that in passing through the tunnel portion, the tunnel atmosphere will move with a substantially stream line flow coextensive with the width of the tunnel considered from the point of view of the direction of movement of such tunnel atmosphere and in a direction solely at substantially right angles to the direction of movement of the glassware through the tunnel, and, a common driving means for all said fans.

11. Apparatus for controlling eddy currents in a tunnel type glass annealing leer provided with a'longltudinally extending heating flue associated with the floor of the tunnel and having the side and top walls-of the tunnel unheated, and means for moving the glassware through the tunnel, comprising a passage built in one of the side walls of the tunnel at a desired portion thereof, headers associated with the floor and roof of this portion of the tunnel and communieating with said passage and with the interior of the tunnel through perforations in the walls of the headers common with the tunnel, the

tunnel, said headers and said passage forming collectively a closed circuit' path for tunnel atmosphere, and means associated with said passage for causing a circulation of tunnel' atmosphere downward through the tunnel, through perforations in a portion of the floor of the tunforated, a fan associated with said passage for nel intothe lower header, upward vthrough said passage and thence through the upper header and the perforations in the roof portion of the tunnel thereof into the tunnel in a downward direction, whereby to create a positive forced circulation of tunnel atmosphere through the tunnel in a direction opposite to that which would be taken by'normal convection currents shouldthe header and passages be unobstructed and unprovided with circulation causing means, the

flow of gases through the tunnel being substantially coextensive with the width thereof, whereby positively to prevent the existence ofeddy currents in the tunnel.

12. Apparatus for controlling eddy currents in a tunnel type glassware annealing lee'r, provided with a longitudinally extendingv cooling said passage, through the upper header, downward through the tunnel, through the lower header and back into said passage, the'ilow of tunnel atmosphere through the tunnel being substantially vertically downward for preventing the existence of eddy currents in the tunnel, and the upper header having parallel upper and lower sides, the perforations in the latter of which are of varying average area per unit of area of' the surface, whereby the circulation of tunnel'atmosphere through the tunnel may be maintained substantially uniform in velocity and amount from side to side, thereof, and whereu by the heatltransfer between the articles of glassware being annealed and the upper cooling iiue will be uniform transversely of the tunnell 13. Apparatus for controlling eddy currents in a tunnel type glassware annealing leer provided with temperature gradient controlling means including a longitudinally extending heating ue associated with the floor of the tunnel and a longitudinally extending cooling flue assoc'iated with at. least a portion of the roof of the tunnel and means for moving glassware therethrough, comprising 'a passage associated with a side wall of the tnnnel, a header communicating` with said passage and interposed between the longitudinally extending heating flue and the floor of the tunnel, a second header communicating with said passage and interposed between the longitudinally extending cooling ue and the roof of the tunnel, the common walls between said headers and theoor land roof of the tunnel respectively being percirculating tunnel atmosphere in a closed path including a portion of the tunnel, said headers and said passage, and means for driving such fan to cause a circulation of tunnel atmosphere such that there will be a flow thereof downwardly through the tunnel from the upper header'to the lower header and substantially 'co- .extensive with the width of said tunnel, the' now-being substantially stream line in passing through the tunnel and being substantially'uniform as to velocity and amount transverselyy thereof, whereby eddy currents in the tunnel will beprevented without interfering with the lateral uniformity of heat conditions in the tunnel.

1'4. Apparatus for controlling eddy'currents in a tunnel type glassware annealing leer pro-I vided with temperature gradient controllir" means including a longitudinally extending heating flue associated with the floor of the tunnel and a longitudinally extending cooling ueV associated With at least a part of the roof of the tunnel and provided with means for moving the.

glassware therethrough, comprising' means associated with a plurality of spaced vfones'longitudinally of the tunnel for creati.. in each of said zones a closed circulation of tunnel atmosphere in a closed path, each of said paths including a portion of the tunnel, each path including a passage in the side wall of said tunnel, 5 a header associated with the roof of said tunnel and having avcommon wall therewith provided with perforations, and a second header associated with the floor of said tunnel and having a common wall therewith provided withperforations, said headers and the perforations thcreof being so constructed and arranged as to provide for a substantially uniform stream line flow of tunnel atmosphere transversely of the tunnel as to volume and velocity, a fan associated with each of said .passages forcausing the tunnel atmosphere to move upwardly in said passages and downwardly in said tunnel, and a common driving means for all said fans, whereby to preclude the existence lof eddy currents in the portions of the tunnel provided with circulating means for tunnel atmosphere as aforesaid.

15. In a leer for annealing glassware, a leer chamber having a heating zone and a tempering zone, a conveyor belt for conveying ware through the said zones, a, plurality of ducts located above andl below the conveyor substantially throughout the length of said zones, said ducts having openings in the surface thereof adjacent the conveyor, means for forcibly circuu' lating heated air. through the ducts, through the openings in the ducts and through the conveyor belt transverselyv to -the direction of movement of the belt whereby substantially all movement of the air in the direction of movementof the conveyor belt is eliminated.

^ .CLARE S. RILEY.`

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