US2351262A

US2351262A - Lehr

Info

Publication number: US2351262A
Application number: US378182A
Authority: US
Inventors: Clarence E Hahn
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1941-02-10
Filing date: 1941-02-10
Publication date: 1944-06-13
Anticipated expiration: 1961-06-13

Description

June 13, 1944,. v c. E. HAHN 2,351,262

LEHR

Filed Feb. 10, 1941 3 sheet s-sheet l mi 6% lnven'tor: I Clarence Hahn,

June 13, 1944. HAHN 2,351,262

LEHR

Filed Feb. 10, 1941 3 Sheets-Sheet 2 Inven'fo'r' Clar nce E. Hahn, b W

His AHor-neg June 13, 1944. c. E. HAHN 2,351,262

' LEHR Flled Feb. 10, 1941 3 Sheets-Sheet 3 Figzl.

lnven'for: Clarence E. Hahn,

- His Attorneg.

Patented June 13, 1944 LEHB Clarence E. Hahn, Euclid, Ohio, assigno'r to General Electric Company. a corporation of New York Application February 10, 1941, Serial No. 378,182

6 Claims.

My invention relates to a lehr for heat treating and straightening lengths of vitreous tubing,

and more particularly relates to a lehr for heat treating and straightening comparatively large sizes of vitreous tubing such as those used for the envelopes of incandescent and discharge lamps.

In the manufacture of lamps it becomes necessary to heat treat tubing for several reasons, the most important of which are to relieve the strains therein, bake and otherwise treat colored and fluorescent coatings applied thereto and permit the tubing to be straightened. In such instances, the operations involve the handling of comparatively straight lengths of tubing up to 60 inches in lengthand 2 inches in diameter although the operations are not necessarily limited to tubing of such lengths or sizes.

One object of my invention is to provide a lehr forjheating lengths of tubing uniformly from end to end on such a scale as to be applicable to commercial use. a

Another object of my invention is to provide a lehr for heat treating lengths of tubing more quickly and to higher temperatures than has been possible on a commercial scale heretofore. The ability of the lehr to-introduce heat units into the tubing allows high-temperatures to be applied thereto and increases the speed and reduces the cost of said operation.

Another object of my invention is to provide apparatus for correcting the alignment and avoiding distortion and injury to lengths of vitreous tubing during. the heating thereof.

Still other objects and advantages of my invention will be apparent from the detailed description which follows of the species thereof shown in the attached drawings.

In the drawings, Fig. 1 is a side elevation of a lehr comprising my invention having the forward part of the apparatus in section and amid-portion removed so that the details of said lehr can be shown more clearly; Fig. -2 is a vertical section through said lehr along line 2--2 of Fig.1; Fig. 3 is an end view of the lehr;- Fig. 4 is a plan view of one end of several conveyor rolls and associated apparatus having two of the roll ends in section; Fig. 5 is a vertical section through a portion of the apparatus along line 55 of Fig. 2 showing drive means for the roll rotating chain; and Fig. 6 is a side elevation of the end of heating apparatus and'the adjacent end of cooling apparatus associated therewith. V e.

The lehr in the drawings is considerably longer out from behind the feeding apparatus.

an endless conveyor l0 extending from the front end thereof, at the left of Fig. 1, to the back end, thereof, at the-right of said figure. The conveyor 10 functions as the means of carrying the vitreous tubes ll through the various heat zones in said lehr and extends substantially the full width of the lehr as shown in Figs. 2 and 3 so as to provide a support for the full length of the tubes ll during the heat treatment. In the usual course of events the vitreous tubes H are fed to the conveyor I 0 automatically by the apparatus 12 at the front end of the lehr and are carried through a relatively short idle zone I3, the heating zone ll within the furnace IS, a combination heating and cooling-zone IE (only partially shown) of substantially the same length as the heating zone H and a cooling zone I! by said conveyor I 0. It is also preferred that a cooling conveyor be attached tothe back end of the lehr to receive the tubes H-discharged therefrom.

The operation of feeding the tubes II to the conveyor Ill-is provided for by the apparatus 12 which is comprised of a plurality of inclined rails l8 (Figs. 1 and 3) distributed at desirable intervals across the entire front end of the machine. The rails I8 are supported by upwardly extending arms IQ of the frame (not shown) of the machine and provide an inclined surface which causes the tubes ll placed on an extending portion thereof to roll down to the conveyor Ill. The tube ll must escape from the feeding apparatus separately in order to be fed properly to the conveyor l0 and accordingly must pass below a series 'of fingers 20 mounted at intervals along the cross bar 2| which keep said tubes from climbing over'each other and which only allow single tubes H properly placed on the conveyor 10 to move In the instance shown, the tubes II extend the full width of the lehr and but one tube It can be accommodated crosswise thereof, but in other in stances, shorter tubes are provided and multiples thereof can be accommodated if they can be arranged in end to end relation. In the latter instance the tubes II are placed on the rails l8 of the feeding apparatus in the desired arrangement and pass to the conveyor [0 in exactly the same manner as the longer tubes II.

The conveyor I0 forms an endless belt type of conveying means in that it is comprised of closely arranged rolls 22 held in place by endless chains 23 attached to the opposite ends thereof. The chains 23 extend about sprockets 24 on the shaft 25 at the front end of the lehr and correthan can be shown andis comprised essentially of 9 11 8 prockets 26 ionly one of which is shown) on shaft 21 at the back end of the lehr and follow a path of movement carry g them to opposite sides of the heated portion of the furnace l3 whereas the rolls 22 pass directly through said furnace l5. The frame of the lehr is the supporting means for the conveyor ill, although it is not directly. connected thereto, and is comprised of a basic unit under the center section of said lehr built up from a series of vertically disposed legs 23 at intervals along each side thereof of structural angle bars, the cross members 23 and the lengthwise disposed members 33. To each corner leg 23 at both ends of this structural unit is attached a bracket 3| which supports a bearing block 32 for an end portion of either shaft 25 or 21. The brackets 3| and hearing blocks "are located just beyond the limits of the conveyor I3 and are completely hidden by motor and speed reducer (not shown), the main driving means of the lehr.

The rolls 22 of the conveyor H) are spaced from each other so as to provide a trench or furrow in which the tube II will remain during the course of travel thereof and correspond in number to the rollers 35 of the chains 23 to which they are attached. The spaced relation of the rolls 22 is therefore established by the links of the means shown in Fig. 5 which is mounted on the frame midway between the. ends of the lehr and which engages the return loop of said chain 33 extending betweenends of the rail 39. The return loop of said chain 33 is kept to its path of movement by the

guide rails

42 and 42 on opposite sides of the driving means and is caused to loop down around the double sprocket 43 by the idler rolls 44 and 45 which are located on opposite sides thereof. A common bracket 46 mounted on a. suspended hanger 4'! of the frame provides the means of supporting one end of the shafts 43 holding the idler rolls and 45 and the shaft 49 supporting .the driven sprocket 43 whereas a second bracket 50 (Fig.2) attached to a side member of the frame provides the means of holding opposite ends of the shafts 43 and49. The

driving sprocket 43 and shaft 49 are actuated separately from. the other parts of the machine in order that the speed of rotation of the conveyor rolls 22 can be controlled more easily and are connected to said means, which is preferably an electric motor and speed reducer, through the sheave 5| and belts 52.

chain 23 and is such that all sizes of tubes H which can be accommodated by the lehr will nest securely therebetween. The connection between the ends of the rolls 22 which are hollow and the chain". 23 is made through studs 33 which have an enlarged portion (Fig. 4) within the end of said rolls 22 and a portion extending endward of said rolls 22 journaled within the rollers of the chains 23.

The heating cycle of the lehr starts at the time the tubes ll come to rest on the conveyor In as the rolls 22 of said conveyor I!) already contain some of the heat they have absorbed during their preceding cycle of operation. This residual heat is. relatively small but means are provided for rotating the rolls 22 so that they will transfer heat to the full periphery of the tubes H and will not in themselves tend to sag or warp. The means of rotatingthe rolls 22 engages portions of the ends of the studs 33 attached to the ends of the rolls 22 at the near side of the lehr in Fig. 1 and at the right side of the lehr in Figs. 2 and 3, which portions extend beyond the chain 23 as shown in detail in Fig. 4. These studs 36 support the sprockets 31 and 31' and are of unequal length so that sprocket 31 on alternate studs 35 engages one section of the chain 33 and the sprockets 31' on the remaining studs 33 engage the other sec tion of. said chain 33. -Both sections of the chain 33 rest on a ridg on a rail 39 lying parallel to length and is straight except for its end portions (only one of which is shown) which follow the curvature of the sprockets 24 and 26 at opposite ends of the lehr. The chain 33 engages a roller 4| held. by the end portions of the rail 39 in pass- The tubes H are fed to a portion of the conveyor I0 held by a section of the chains 23 riding on the sprockets 24 at the front end of the ma-' chine but the movement of said conveyor l9 soon carries it over the highest partpf said sprocket.

of lehr on brackets 40 and on the other side on brackets 54.

During the first interval of movement of the tube I|,'it receives only a small portion of the residual heat in the rolls 22 and passes through the idle zone l3 but, following this, it passes into the furnace I5 and into the high temperature zone I 4 thereof. The mouth of the furnace I5 is at the forward edge of a separation between independent upper and lower sections 55 and 53 thereof which have less width than the conveyor l0 and only surround the portion of the blocks of a refractory material which are susing to'and from said bar 39 and is driven by the pended between the side members 30 of the frame,

whereas the upper section 55 of said furnace I5 is supported by the side frames 51 which extend sideward over the ends of the rolls 22, the chains 23-and the roll rotating means of the conveyor II and downward to said side members 30.

, The object of the furnace I5 is to introduce heat in the tubes II as rapidly as said tubes II will absorb it without being injured and accordingly must beat the full periphery thereof as uniformly as possible. The furnace I5 is, therefore, heated by means consisting of a plurality of burners 53 located in a plurality of rows above ports in the upper section 55 thereof and by means consisting of a plurality of burners 53 located below two rows of ports in the lower section 56 thereof. In both instances the flames from the burners 58 and 59 do not touch the tubes l I or the rolls 22 but cause a steady stream of very hot gases to be directed thereagainst. The success of the high speed heat cycle depends on the ability of the furnace II to heat the full the inner surface In their course of travel beyond the furnace ascraea periphery of the tube ll uniformly from-end to end and, in every instance. the burners 58 and 59 are arranged very close to each other in the rows so that said tubes H are heated in this manner. The burners 58 and 59 are attached directly to the manifolds B and SI respectively which are, in turn, connected to means for supplying the combustible gaseous mixture andare preferably controlled automatically by means varying the supply "so that the temperature to which thetubes II are treated can be as near the maximum limit as possible.

mally thought possible, partially because the rolls 22 have relatively thin walls and are made of stainless steel which resists sticking to the vitreous material of the tube H. In fact, the tubes II can be heated above the softening temperature of the vitreous material without danger of collapsing and are normally'heated to a' point where they are straightened by their contact with the rolls 22. In instances when the tubes II are being heated to condition a coating on the inner surface thereof, it is preferred that a current of air be directed through said tubes II I mouth of the'furnace I from a source of air (not shown) and is heated by the furnace I5 so that the air discharged into the tube II is at a fairly high temperature. Along the upper edge of the separation at each side of the furnace I5 is mounted a square tube 62 which helps to seal said opening. Air is blown through the square tube 62' from onev end to the other to keep it cool. The air ducts 62" provide the means of directing jets of air onto the chains 23 to cool them.

Following the high temperature zone l4 in the furnace I5 is a second slightly longer zone I6 which is heated by the flow of gases from zone I4. The temperature gradient in this latter zone I6 is lower as the gases flowing from'zone I4 are gradually relieved of their heat as they pass from the forward end thereof to the exhaust opening 63 along the back edge of the roof-of the furnac l5. This movement of the gases is prefer-l ably produced by an exhaust fan (not shown) connected to the vent pipe 63' attached to the opening 63 in that the leakage of heat from the openings in the furnace II will then be less, and more accurate control of the apparatus will then The temperature of the treatment can be higher than noropposite ends attached to corresponding arms 65 g terval the tubes ll receive only the treatment that results from thejc'ontlnued rotation of the rolls 22.

At this time the conveyor M has completed the effective portion of its cycle of operation and the portion thereof conducting the tubes II to the cooling conveyor has but to return to the feeding apparatus 12 to start the next cycle. In the course of the return movement while the chains 23 are still supportedby the sprockets 26, the roll rotating sprockets 31 and I1 pass from the chain 38 and move into engagement with a double stationary chain 64 which follows A the path of movement thereof. until they are,

again engagedbwthe chain 38. 'I'hechain 64 has at opposite ends of the frame of the lehr and causes the rolls 22 of the conveyor [0 to rotate at a slow rate due to .the rolling motion given to the sprockets 31 and 3i. This final rotativemovement of the rolls 22 keeps them from sagging and warping out of alignment during the major portion of the inactive portion of the cycle of. operation. Support is provided for the straight section of the chain 64 by the guide rail 68 which is attached-directly to the frame. During this" last-interval the chains 23 of theconveyor l0 ride on the guide rails 61 and 68 respectively and are cooled by the air blown from the holes in manifold '69. The guide rails as, 51 and as and manifold 59 are mounted directly on the frame of the lehr. v

The tubes II are still too hot upon leaving the lehr to be handled and it is preferred that they be transferred to a cooling conveyor connected to the end of the lehr. The cooling conveyor can consist, as shown in Fig. 6, of a stationary table "having a lip II extending therefrom which takes the tubes H .from the conveyor it] as it starts to pass down around the. sprocket 26 and preferably includes means 12 v of moving the tubes along the surface of said table 10 and means 13 of directing a cooling The lip II is inclined toward the table 10 so that the tubes ll roll over onto said table 10 by their own weight where they engage the first upright fln-' gers 14 of the moving means 12 of the cool i ing conveyor. v which the tube H rests consists of a series ofa The surface of the table on longitudinally disposed strips in that it must allow the moving means 12 which consists of be afforded. The rate at which the tubes I] are cooled within zone It is of course very slow but suflicient cooling occurs to bring said tubes ll below their strain point before they pass from a plurality of parallel disposed chains 15 having fingers 14 at regular intervals therealong to gain access to the tubes H and must allow the free flow of air from the air duct 16 of the cooling means 13 below said surface to the tubes H.

The different chains 15 of the moving means each v extend about a sprocket TI on the shaft 18 which is held by'the cooling conveyor and which isdriven through the chain 18. and sprockets 80 and, by the lehr. This manner of operation causes the fingers 14 on the chains 15 to swing up through the surface of the table 10 behind each tube H as rapidly as they are received from the lehr and causes' the tubes II to be pushed along'the surface of said table Ill by the movement of the fingers I4. The tubes ll actuthe tube ll, correcting linear alignment thereofand heat treating fiuoretscent material placed on t ereo IS, the tubes II are in the open air and continue to cool to a point where they are not in-'- 'jured when discharged therefrom. In this in- 76 ally roll along said surface so that the full pe-' riphery thereof are subjectedto the now of air from the cooling means 13. The length of said conveyor is preferably such that the tubes II are cooled to a point where there they can be handled conveniently when discharged thererom.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A lehr for heat treating vitreous tubes comprising a furnace adapted to produce heat treating temperatures above the softening temperature of the tubes, 'and a conveyor extending through said furnace comprising a series of uniformly spaced rolls disposed in a substantially horizontal position and adapted to support the full length of each of a plurality of tubes placed longitudinally between successive rolls, means for carrying said rolls through the furnace at a desired rate of speed to soften the tubes, and means for rotating said rolls during said movement to cause the tubes to be rotated during the heat treatment so that distorted tubes are straightened by their contact with the rolls.

2. A lehr for heat treating vitreous tubes comprising a furnace adapted to produce heat treating temperatures above the softening temperature of the tubes, and a conveyor extending through said furnace comprising a series of uniiormly spaced hollow rolls disposed in a substantially horizontal position and adapted to support the full length of each of a plurality of tubes placed longitudinally between successive rolls, means for keeping the rolls in alignment with each other and carrying said rolls through the furnace at a desired rate of speed to soften the tubes, and means for rotating said rolls during said movement to cause the tubes to be rotated during the heat treatment so that distorted tubes are straightened by their contact with the rolls.

3. In a lehr for heat-treating vitreous tubing, an endless conveyor, a furnace through which said conveyor travels adapted to heat the tubes above their softening point, said conveyor comprisinga series of uniformly spaced rolls of hollow sheet metaltubing arranged to support the full length of each of a plurality of vitreous tubes placed longitudinally between successive rolls, meansfor moving said rolls through said furnace, and means for rotating said rolls about their axes at a comparatively slow speed during the period of their travel outside said furnace and means for rotating said rolls at a higher speed during the period of their travel withfrom warping during their period of travel outin the furnace whereby distorted tubes are straightened within the furnace by their contact with the rolls and the rolls are prevented side the furnace.

4. A lehr for heat-treating vitreous tubes comprising a furnace adapted to heat the tubes above their softening point, and a conveyor extending through said furnace comprising a series of spaced rolls arranged to support the full length of each of a plurality of tubes placedlongitudinally between successive rolls, means for rotating said rolls about their axes to cause the tubes to be rotated during the heat treatment so that distorted tubes are straightened by their contact with' the rolls, and means, independent of the said rotation of said rolls, for moving said tubes through the furnace.

5. A lehr comprising a furnace, and a conveyor for carrying vitreous tubes through the furnace comprising an endless chain mechanism carrying a series of uniformly spaced horizontal rolls arranged to support tubes placed horizontallybetween adjacent rolls, means operable upon those rolls which at a given time are located within the furnace for rotating said rolls about their own axes independently of any such rotation which might be effected only by movement of the conveyor, and means operable upon those rolls located outside the furnace for rotating said rolls at a lower speed.

6. A lehr comprising a furnace, and a conveyor for carrying vitreous tubes through the furnace comprising an endless chain mechanism carrying a series of uniformly spaced horizontal rolls arranged to support tubes placed horizontally between adjacent rolls, said rolls having sprockets at an end thereof, a second chain mechanism engaging the sprockets of those rolls which at a given time are located within the furnace, means for moving said second chain mechanism independently of the movement of the first-mentioned chain mechanism to rotate said rolls about their own axes, and a third chain arranged to engage the sprockets of those rolls located outside the furnace to rotate said rolls at a lower speed.

CLARENCE E. HAHN.