Note: Descriptions are shown in the official language in which they were submitted.
~89.146 BACKGROUND OF INVENTION
The invention herein relates to a bearing construction for rollers
used in supporting and guiding the metal strand formed ;n a continuous casting
process. The process itself and the apparatus used therewith is generally
described in the patent to Jackson, U.S. Patent No. 4,023,612 issued May 17,
1977.
In general, the continuous casting process involves the gravity
pouring of molten metal, such as steel, into the upper end of a box-like mold
which has an open bottom. The mold is cooled, such as by water flowing through
its walls.
As the metal cools, it forms a strand or slab having an outer,
solidified skin that forms where the molten metal contacts thè interior, cooled
walls of the mold, and an inner molten core. This strand emerges downwardly
through the open lower end of the mold. Then the strand is curved into a
horizontal direction. The elongated strand is guided and supported between
roller aprons which comprise a large number of support rollers. Meanwhile,
water sprays are directed, between the rollers, upon the outer surface of the
strand to continue the cooling process so that the strand ultimately becomes
completely solidified.
As the slab or strand moves in the horizontal direction, supported
upon rollers, it i5 cut into lengths. The cut slab lengths are then removed for
further processing, such as for rolling into sheet steel or the like.
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The st:rand or slab :is typi.c~:Lly rectcl.ngular :in cross
sect:ion, as for e~amp.l.e fou:r t.o ni.ne inches in thlckness and about
-three to five feet .in width. The support and guide ~ollers engage
the wide opposi-te Eaces of -the strand. Because of the intense heat,
substantial loads due to -the we.igh-t of the metal and -the tendency of
the strand to bow outwardly under -the internal ferrostatic pressure
of the molten core, and the water and steam atmosphere surrounding
them, the bearing constructions and supports for the rollers tend to
wear out or fail relatively quick:Ly. When this happens, this requires
shut-downs of the operation, replacement of damaged or disabled parts
and then start-ups which are time consuming and difficult because of
the continuous nature of the casting operation.
The rollers are formed oE an inte.rnal, non-rotatable shaft
whose opposite ends are secured to end rails. Each shaft may be
additionally secured between its ends to intermediate rails. Tubular
roller sleeve sections are rotatably mounted upon each shaft. These
roller sleeve sections engage the adjacent metal strand face. Thus,
bearings are arranged between the rotatable sleeve sections and
their shafts upon which they are mounted ~or rotation.
The i.nven-tion herein relates to an improved bearing con-
struction for the rollers, which construction substantially increases
the life of the bearings, as compared to prior bearing constructions.
SUMMARY OF INVENTION
The invention herein contemplates an improved bearing
construction for use between the fixed shaft and the surrounding
rotatable roller sections carried by the shaft. The bearing con-
struction is formed in two parts, namely, a journal type bearing part
and a thrust type bearing part. I'he journal part comprises a bronze
type bearing sleeve press-fitted within the roller sections, at each
end thereof, for a non-slip~ frictional engagement with the interior
wall of the roller sec~ion. The inner wall of the bronze bearing
sleeve is rotatably or slip-fitted upon -the shaft.
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OS9.146 A thin wall liner bushing of a low coefficient of friction material,
such as a "teflon"-bronze impregnated material, is inserted within the bronze
sleeve. The liner flts within a recess in the interior of the bearing sleeve andoccupies roughly half of the interior wall surface thereof. Thus, the inner wallsurface oE the thrust bearing is formed of roughly one-half low coefficient of
friction "teflon"-type material and the other half of bronze bearing material.
The bronze bearing material, being of higher compressive strength, handres more
of the compressive loads while the frictional drag and wear is reduced
considerably by the teflon liner~
In addition to the journal bearing, the thrust bearing part is
arranged to handle the lateral or endwise shifting of the roller sections which
occur in operation. Such thrust bearing is formed of a bored support ring-like
member which is connected to a support rail and through which the shaft passes.
One end of the member is telescopically fitted within an end channel or recess
formed in the roller sleeve. A bronze disk thrust bearing member is arranged
wlthin the recess between the end of the member and ~he adjacent annular end
surface of the bronze hearing sleeve and exposed "teflon" liner. Hence,
movement of the roller section towards the support member results in a bearing
engagement between the disk, the bronze sleeve; the exposed end of the "teflon"
liner, and the adjacent interior wall of the recess formed in the roller section.
This arrangement provides the necessary strength and slippage for rotation of the
roller under the load of the metal strand.
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r[~he :Lmproved bear:i.ncJ const:t-uct:i.on herein appears to g:i.ve
a much longer liEe than conventional bear:incJ arrangemenks and more
particularly, permi-ts -the use oE smaller diameter rollers than tha-t
permitted by prior conventional bearing arrangements. Consequent].y,
it is possible to use more rollers on the rol.ler apron, which is a
considerable advan-tage in improving the equipment. That is, with
smaller diameter rollers and with more rollers formed on the roller
aprons, there is less space between -the rollers and more lines o-f
pressure to contain and guide the continuously formed slab, particu-
larly in the areas where the skin is thin and the molten core pres-
sure is still high enough to bow or bulge the slab skin outwardly.
The use of a low coefficient of friction material such as
Teflon* or the Teflon*-bronze impregnated material would ordinarily
not be considered feasible in the environment of roller apron con
structions. That is, the loads, heat, and destructive atmosphere
normally would be expected to rapidly destroy such material and
prevent its use. However, with the constructions as described in
this application, the bearings are unexpectedly stronger and able to
sustain the pressures and loads better -than conventional journal
bearings.
Further objects and ad~antages of this invention will
become apparent upon reading the following description, of which the
attached drawings form a part.
*Trade Mark
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08~.146 DESCRIPTION OF DRAWINGS
Fig. I is a schematic view of the continuous casting process.
Fig. 2 is an enlarged, end view9 schematically showing a pair of
opposed roller apron sections with the continuous cast strand between them.
Fig. 3 is a perspective view of the apron plate or roller support
plate.
Fig. 4 is an enlarged plan view of a two section roller mounted
upon the support plate.
Fig. 5 is a cross sectional, elevational view, of one end and the
middle of the roller illustrated in Fig. 4.
.
Fig. 6 is an enlarged, partly cross sectional, perspective view
showing the disassembled parts which make up the end connection and bearing
construction.
Fig. 7 is an enlarged, partly cross sectioned, perspective view
showing the disassembled parts which make up the middle bearing construction of
a roller.
DETAILED DESCRIPTION
Fig. 1 schema~ically illustrates the continuous steel casting
process. The equipment begins with a ladle 10 which carries molten steel 11
from the furnace to the continuous casting equipment. The mslten steel gravity
drops downwardly from the ladle either through a nozzle 12 or by tipping the
ladle for pourin~ into a tundish 13. A rese~voir of molten steel in the tur,dish
provides the continuous flow of molterl metal downwardly, by gravity, into the
upper, open end of a water cooled continuous casting mold 14.
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0~9.146 The water cooled mold is conventionally made of opposed side
~alls and end walls, connected together to form a box-like construction with
open upper and lower ends. An example oE this type of mold construction is
shown and described in the patent to Floyd R. Gladwin, U.S. Patent No. 3,964,727issued June 22, 1976.
The particular mold used here is imrnaterial to the bearing
construction which is the subject matter of this application. However, the mold
typically forms a continuous strand or slab which is on the order of about four to
nine inches in thickness and three to five feet in width, although the dimensions
may vary considerably from that given above.
When the molten steel is poured into the upper end of the mold,
the portions of the metal in contact with the water cooled mold interior walls
begin to solidify rapidly and form a thin skin. Within the skin is the molten core.
Thus, as the slab or strand 15 gravity rnoves downwardly through
the open lower end of the mold, it comprises a rougly rectangular shaped in cross
section envelope of solidified skin within which is the molten core. The molten
metal within the slab exerts a substantial outward ferrostatic pressure which
tends to bulge the skin outwardly.
The strand passes through cooling plates 18 or cooling rollers or
pull rollers, as ~he case may be depending upon the kind of equipment used.
Frorn that point downwardly, water spray nozzles 19 are directed upon the strandto chill it and continue the cooling of the core. Meanwhile, roller apron guide
rollers 20 guide the strand downwardly and then along a curve until the strand is
arranged horizontally. These guide rollers also hold the strand against bulging
because of the interior ferrostatic pressure.
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38~.146 The roller aprons are forrrled in sections or units, as illustrated for
exarnple in Fig. 2. These units are arranged to form curved upper units 21 and
lower units 22 between which the strand 15 is guidedO
When the strand turns into the horizontal direction, it is carried
upon support rollers 24 which are made in the same way as the guide rollers 20.
However, the support rollers 24 are carried upon suitable support bases or base
construction sections 25. The support rollers move the strand beneath a
conventional cutter 26 which cuts off pre-determined slab lengths 27. These slablengths are then moved into storage or transportation areas for later use in steel
fabrication processes, such as for use in a rolling mill to make sheet material or
the like.
The roller apron sections, each have an apron plate 30 (see Figs. 2
and 3) which is provided with parallel end rails 31 and one or more center rails 32
upon which the rollers are mounted. The plates are also provided with suitable
lar~e openings 33 through which the water spray may be directed, between the
rollers, against the metal strand.
The rollers 20 are each formed of a central steel shaft or axle 35
upon which are rotatably positioned roller sleeve sections 36. The shaft 35 is
fixed against rotation and preferably is chrome plated by any suitable
conventional techniqueO The opposite ends of the shafts are secured to rails 31
by rneans of end support members 38. A bored opening 39 in such member
receives the end portion of a shaft.
The support member is secured to the rail first by means of a
squared section 40 which snugly fits within one of the notches 41 formed in eachof the rails. In ad~ition, an end cap 42, which is cup shaped to fit over and
receive the end of the shaft, is proYided with fastening ears 43 which are secured
to the adjacent r~l portion. Holes 44 formed in each of the ears are aligned with
corresponding holes 45 in the rail so as to receive fastening screws 46 (see Figure
6).
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089.146 Eacll end support rnember 38 inclucles a cylindricaJ end portion 47
which fits into an annular recess or groove 48 formed in the opposite ends of the
roller sleeves 36. One or more conventional autolnotive engine type p;ston rings49, posi~ioned wi~hin grooves formed in the end member cylindrical portion, seals
against the inner surface of the sleeve recess.
A bronze type thrust bearing disk 50 is arranged within the sleeve
recess 48 adjacent the transverse end of the support member cylindrical portion
47. An opening 51 throu~h the disk receives the shaft 35.
The diame$er of the interior surface 55 in the roller sections are
larger than the shafts upon which the roller sections are positioned. Moreover,
enlarged bearing recesses 56 are formed at the opposite ends of the roller sleeve
openings.
Bronze journal type bearing sleeves 58 are press-fitted within the
bearing recesses 56 for non-rotatable, frictional mounting therein. Each bearingsleeve 58 is also provided with an end recess 59 which receives a tubular shaped"teflon" liner 60. The liner is roughly one-half of the length of the sleeve 58 so
that its inner wall surface forms about one-half of the bearing or sli~fit surface
of the journal bearin~ for rotatably enveloping the fixed shaft 35.
By way of example, the "teflon" liner may be on the order of
about 0.125 thick and rnay be bron2e impregnated teflon tubing. This material iscornmercially available, although it has not previt>usly been thought of as a
suitable bearing material f or this environment because of its relative low
strength, etc.
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0~9.146 Th~ fre~, annular ends of the "teflon" liner, surrounding bronze
bearing slee\~e 5S, and an annulal end wall 61 formed within the roller sleeve
recess 4~ provide a coplanar surface for engaging the bronze thrust bearing disk50. Normally, the disk 50 is spaced a short distance from that surface.
Engagement takes place when the roller sleeve section moves in the direction of
the disk which occurs from time to time during operation, but ordinarily not
continuously. Figure 5 illustrates the normal spacing between the disk 50 and the
annular surface withir the roller sleeve recess 48.
The end of the shaft 35 is fixedly connected to the end cap 42 by
means of threaded openings 63 formed in the shaft (see Figure 6) which are
aligned with openings 64 formed in the end cap to receive fastening screws 65.
Further, an O-ring 66 arranged within a ~roove formed in the shaft 35, seals theshaft to the interior of the end cap. An automotive type piston ring of the
appropriate size may be used for such an O-ring seal.
It can be seen that the chrome plated shaft 3S is non-rotatably
secured to the rails so as to span a pair of spaced apart end rails. Meanwhile, a
number of sleeve sections 36, rotatably supported upon the shaft, may
independently rotate thereonO The number of roller sleeve sections may be
varied and typically would be on the order of 2, 3 or 4 sections, depending uponthe span required. Each of the roller sleeve sections is provlded with the interior
journal bearing construction descrlbed above as well as the thrust bearing
construction. To form the thrust bearing construction between the ends of the
shaft, that is at the middle rails 32, the end support member is slightly mod;fied
to form a middle support mernber 68, as shown in Fi~ure 7. Such middle support
member includes the squared section 40 and the cylindrical portion 47, but
includes a second cylindrical portion 47a which also has one or more pis~on ringtypes of seals 49, as described above. Otherwise, the middle support member 68
is the same in construction as that o~ the end support member 38.
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089.146 The squared portion 40 of the middle support mernber 68 snugly
fits into one of the notches 41 formed in the center rail 32. It is locked in the
notch by means of a lock bar 70 which rests upon the upper surface of the rail
and the upper flat surface of the squared portion 40. The lock bar is secured tothe rail by means of screws 71 extending through aligned holes 72 and 73 in the
lock bar and ~he rail, respectively. The lock bar may be in the forrn of short
lengths or of one long length to match the length of the central r~il. ~
Where the rollers are formed of more than two roller sleeve
sections, additional middle rails 32 are moun~ed upon the apron plate 30. The
rails 32, as well as the end rails 31, may be suitably welded to the plate or
o~erwise permanently affixed thereto.
The space between the interior of the tubular roller sleeves and
the shaft upon which :the sleeves are mounted, is packed with a suitable high
temperature lubricant or grease. This lubricant is applied throu~h an axially
extending hole 75 formed in each shaft. Transverse holes 76 carry the lubricant
from ~e hole 75 into the spaces between the adjacent inner wall surfaces of the
roller sleeve sections and the outer surface of the shaft, as well as in the small
spaces between the journal bearings and the shaft. The lubricant is applied, when
necessary, through a central opening 77 forrned in the end cap, which is ali~nedwith the opening 75 in the shaft. The end cap opening is normally closed by a
screw type closure 78 (see Figures 5 and 6).
Although the dimensions may vary considerably, by way of
illustration for the purposes of determinin~ relationships of parts, a roller rnade
ln accordance with ~e construction described herein may comprise a shaft of
about five feet in length with an O.D. of about 3 1/2 inches. The roller sleeve
3~
089.146 may have an O.D. of abou~ 7 1/4 inches and if three sections are used, each
would be sligh~ly less than 16 inches in length with a wall thickness of about 3/4
inch. The bron~e journal bearings may be on the order of about two inches in
axial len~th and about 1/4 to 3/8 inches in wall thickness. The liner of "teflon"
material may be on the order of about one inch in axial length and about 1/10
inch, e.g., .125, in wall thickness and may be made of a split ring configuration,
that is, a length of sheet material which is rolled into a circular cross-sectional
shape.
Conventional rollers are ordinarily of a considerably greater
diameter. Thus, the bearing construction herein permits the reduction in O.D.
of the rollers, thereby permitting more rollers to be used along the length of the
continuously cast strand, with a space in between the rollers being much reducedas compared ~o the conventional aprons.
In operation, the apron sections are suitably supported upon a
framework (not shown) which is conventional so as to form parallel, spaced apart,
arrangements between which the strand passes (see Figure 2). The rails of each
apron are curved, either concave or convex, so as to mount the rollers 20 in a
similar curved path. Thus, as the strand emerges downwardly from the mold 14,
it begins curving due to the guiding of the rollers. The rollers are subjected to
considerable forces or loads due to the weight of the metal as well as ~e
tendency of the metal to bulge or bow outwardly because of the f errostatic
pressure of the molten core within the surrounding skin. However, as the skin
thickens, along the downward curved path of the strand~ the core pressure is
contained within the skin itself. Nevertheless, the load upon the rollers and the
adverse atmosphere within which it operates would normally tend to rapidly
destroy the bearing constructions. However, the bearing construction herein,
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089.146 despite the much limited compression or load resistance o~ ~he "teflon" bearing
section as compared with the bronze section, provides a much greater life than
an all bronze bearing, unexpectedly. Thus, the roller apron may be used for many
more continuous casting production hours than the previously known
constructions. Then, when the bearings ultimately begin to fail, the operation
may be shut down and the roller sleeve sections, which normally are made of a
suitable steel material, may be removed from the shafts and the bearings rebuilt
relatively easily because of ~heir simplified construction.
Having fully described an operative embodiment of this invention,
I now claim:
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