US3455541A - Method of evacuating entrapped gases in liquid cooled furnace rolls and apparatus therefor - Google Patents

Description

y 15, 1959 v T. s. CAVITT 3,455,541

METHOD OF EVACUATING ENTRAPPED G ES LIQUID COOLED FURNACE ROLLS AND APPA US EREFOR Filed July 20, 1967 3 Sheets-Sheet 2 Fig. 3

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METHOD OF EVACUATING ENTRAPPED GASES IN LIQUID COOLED FURNACE ROLLS AND APPARATUS THEREFOR Filed July 20, 1967 3 Sheets-Sheet 5 I N VENTOR. 77404445 .5. CA v/rr BY CAeo-mekse! C'ARon-lse:

1.5 Arron/Eva United States Patent METHOD OF EVACUATING ENTRAPPED GASES IN LIQUID COOLED FURNACE ROLLS AND AP- PARATUS THEREFOR Thomas S. Cavitt, Gibsonia, Pa., assignor to Blaw-Knox Company, Pittsburgh, Pa., a corporation of Delaware Filed July 20, 1967, Ser. No. 654,820 Int. Cl. F27b 1/24; F27d 3/12 U.S. Cl. 263-6 23 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for removal of gas enclosures which collect adjacent the interior cylinder walls of hollow, liquid cooled furnace conveyor rolls.

The gas enclosures which collect adjacent the interior cylindrical wall or the surface to be cooled of the furnace roll are vented directly to the coolant outlet passage at one end of the furnace roll by means of a tube or other passage means.

Cross references U.S. Patent 3,115,335, Dec. 24, 1963, Ornitz et al. (Class 2636).

Background of the invention This invention relates generally to furnace rolls and more particularly to water cooled furnace rolls for use in conveying sheets, plates and the like in high temperature vessels.

The previously cited cross reference should be referred to for knowledge of the evaluation of water cooled furnace rolls to the present day. The conventional water cooled roll consists essentially of a hollow central cylindri cal shaft, hollow roll necks at each end of the shaft providing inlet and outlet ports connected to hollow axial passages with water line fittings. The external periphery of the hollow shaft is provided with spacer lugs over which an outer high temperature alloy sheath is placed. The area therebetween is filled with an insulation. As disclosed in the cross reference, an axial tube having at least one end thereof closed, may be inserted within the hollow shaft in spaced relation from the interior walls thereof. This tube provides a greater velocity or flow of liquid over the interior wall of the hollow shaft which effects more efiicient cooling of the furnace roll.

However, with or without the axial tube, it has been found that gas enclosures become entrapped within the hollow shaft adjacent its interior cylindrical wall. Such furnace rolls are subjected to load bearing temperatures as high as 2400 P. which causes vaporization of the water. Furthermore, water flowing in a fluid system is known to deposit gas inclusions at high points in the system even in the absence of applied heat. Both of these factors are considered to contribute to the presence of such gas entrapments in the conventional furnace roll. The air pockets collect at the high point within the hollow furnace roll adjacent the interior cylinder wall or surface and are concentrated at the outlet end of the roll due to the constant flow of coolant in that direction.

Thus the entrapped air bubbles lie against the inner surface of the hollow shaft where they greatly reduce heat exchange from the shaft to the liquid coolant. This in turn causes the insulation to break down or deteriorate rapidly and weakens the shaft causing a slight bending of the furnace rolls.

The entrapped air collects along the top of the interior of the hollow rotating shaft for a length, measured from the outlet end thereof, proportional to the inlet pressure and water flow. It is therefore obvious that the problem ice is aggravated by reason of the fact that this length of entrapped gases lies continually adjacent and parallel with the tangent line of surface contact on the outer load bearing sleeve between the furnance roll and the hot metal work piece being conveyed.

Summary of invention The present invention provides a method and apparatus for the continuous evacuation of the entrapped gases from the rotating furnace rolls by venting the gases directly to the furnace roll coolant outlet passage. This is accomplished by venting the gases through an independent passage means to the restricted interior of the coolant outlet passage where the fluid static pressure is decreased or by extending the restricted axial outlet passage outwardly within the furnace roll to the interior cylindrical wall such that the entire coolant outlet flow is directed to the cylindrical interior wall adjacent the outlet end to ensure removal of the entrapped gases. The former embodiment utilizes Bernoullis theorem whereas the latter does not.

In the former mentioned embodiment, the liquid outlet passage is restricted in cross-sectional area such that it is less than the internal cross-sectional fluid flow area of the hollow cylindrical shaft. A tube means is secured to the furnace roll such that one end is open to the interior of the hollow shaft adjacent the cylinder wall thereof and the other end is open to the restricted outlet passage. By the application of Bernoullis theorem it can be realized that entrapped gases adjacent the cylinder wall will be evacuated due to the static pressure differences at opposite ends of the tube means.

To a small degree, this speed of evacuation may be enhanced by providing a venturi throat at the open outlet end of the tube means in the outlet passage.

The tube means may take on many different structural shapes. It may be in the form of a simple tube secured to the inside of the furnace roll and passing from the larger interior of the hollow shaft into the restricted outlet passage. Upon each revolution of the furnace roll, the tube end adjacent the interior Wall of the hollow shaft will make on pass through the entrapped gases as it rotates through its uppermost point on its circular path of rotation where it will permit the gases to be evacuated.

A single tube has been found sufficient to obtain the desired evacuation of the entrapped air and vapor and is the preferred embodiment. However a plurality of such tubes may be provided by disposing them radially within the furnace roll. The advantage of multiple tubes is that the evacuation process is more uniform or continuous as more tube ends are passing through the entrapped gases for any given revolution of the furnace roll. The disadvantage of multiple tubes is that as the number of tubes increases, the evacuation efficiency of each individual tube decreases and the manufacturing costs increase.

The tubes need not pass internally of the furnace roll, but may also pass externally thereof or even within the walls of the furnace roll itself as by drilling or casting the same therein.

The effect of multiple, radially disposed tubes may be further realized or enhanced by providing a single annular tube formed between two coaxial cylinder or frustum surfaces with the perimeter of one of its ring shaped openings coinciding with the interior cylinder wall of the hollow shaft. For example, the outlet port of the outlet passage, may be frusto conical in shape, tapering from the end of interior cylinder wall of the shaft down to the normal outlet passage diameter. A cone is supported coaxially within the outlet port in spaced relation therefrom to provide a continuous frusto conical shaped tube having a ring shaped opening or cross section. This H j embodiment provides uninterrupted evacuation of the entrapped gases.

Referring to the aforesaid latter mentioned embodiment of the present invention wherein the restricted outlet passage is extended to the interior cylindrical wall of the roll, this embodiment in its most uncomplicated form consists of .a tube which is inserted in and mates the bore of the axial coolant outlet passageand extends into the larger chamber of the furnace roll where it is bent outwardly until its open endlies adjacent the interior cylindrical wall of the furnace roll at its outlet end-This may also be accomplished by casting the coolant outlet passage in the furnace roll with a configuration similar to that of the bent tube. v Other objects and advantages appear hereinafter in the following description and claims.

The accompanying drawings show for the purpose of exemplification, without limitingthe invention thereto,

certain practical embodiments of the present invention wherein: t

FIG. -1 is a ,view in --side elevation; partly in section, of a liquid cooled furnace roll according to the present invention.

FIG. 2 is a sectional view in side elevation of a liquid cooled furnace roll outlet port illustrating a structural variation of the furnace roll shown in FIG. 1.

FIG. 3 is a sectional view in side elevation of a liquid cooled furnace roll outlet port illustrating another embodiment of the present invention.

FIG. 4 is a transverse sectional view of the outlet port illustrated in FIG. 3 as taken along line 44.

FIG. 5 is a sectional view in side elevation of a liquid cooled furnace roll illustrating structural modifications I Water line fittings 17 and 17 are provided at each end of the axial passages 16 and 16', respectively. Each roll neck is provided with a keyway 9 for connection to a drive member, not shown. A hollow axial tube 18 extends axially of the interior of the shaft body 11. The tube 18 is closed at one end by the bulkhead or cap 19 adjacent the inlet port 14 and open at the opposite end. Spacers 20 are provided on the periphery 'of the tube 18 to space the same equidistant from the interior walls of the hollow shaft 11. A spacer ring 21 is threaded onto a threaded neck 22 on the closed end of tube 18 which also receives the cap 19. The spacer ring 21 concentrically supports the closed end of tube 18 within body 11 and prevents the tube ,18 from shifting axially within the cylindrical shaft 11 while permitting the coolant-to flow through its perforated marginal periphery.

The. external periphery of shaft 11 is provided with spacer lugs 24 over which an outer high temperature alloy sheath.25 is provided. The spacerlugs 24 may be coated with a refractory oxide or other heat retarding coating suchas stabilizedzirconia, alumina or the like, to retard the, cooling effect of the lugs 24. The area between the alloy sheath 25 and the outer surface of shaft 11 is filled with an insulation 26 whose nature and density may be variedv to control the amountof cooling effect to be achieved On sheath 25. The coolant such as water, is in- 'troduced under pressurethroughlinlet passage 16 into inlet port 14. The water entering the interior of" the shaft .body 11 passes over the cap 19 through the perforated spacer ring 21 and around tube 18. The coolant leaving m the body 11 fills tube 18 and the excess is permitted to pass out through outletport 15 and outlet passage 16'.

As he seala t passes over t be .8 thra g the o o 4 shaft body 11, gas enclosures within the liquid coolant and vapors are collected along the uppermost portion 30 of the interior volume of the rotating shaft body 11, this being the high point within the furnace conveyor roll. To evacuate these entrapped gases a tube means such as tube 31 is provided in the furnace roll such that the end 32 is open to.the interior of the body 11 adjacent its interior cylindrical wall and its opposite end 33 is open to the outlet passage 16'.

The cross-sectional fluid flow area of the outlet passage 16' is made less than the cross-sectional fluid flow area within the hollow body 11 containing tube 18 such that the coolant is caused to flow through the outlet passage 16' at a greater velocity. The pressure head within the body 11 is thereby converted into a velocity head having a reduced static pressurewithin the outlet passage 16. l: The tube 31 is secured to a sleeve 34 which is in turn secured to the interior of the outlet water fitting 17' as by welding. The additional restriction of the outlet passage 16 caused by the fitting 17' and sleeve 34 provides a small venturi throat within sleeve 34- which gives an additional evacuation efficiency to the tube 31.

Upon each revolution of the furnace roll the tube" end 32 passes through the entrapped gases which have collected along the top portion 30 of the interior chamber of the body 11. Upon each pass of the tube end 32 through the entrapped air, the gases are evacuated by reason of the lower static pressure found Within sleeve 34. This effect may be readily realized by the application of Bernoullis theorem. As previously mentioned the venturi effect of the sleeve 34 will enhance the speed of the evacuation, however, its effect is small in comparison.

The tube 31 along with its connected sleeve 34 provide a further advantage in that they permit furnace conveyor rolls already in use to be readily converted to the practice of the present invention. Such a conversion is accomplished by merely disconnecting the water coupling from the outlet water fitting 17' and inserting the tube 31 and sleeve 34 secured thereto into the outlet passage 16. The sleeve 34 is then secured within the outlet fitting 17 as by welding. However, tubes of shorter length than that of 31 may be employed upon initial construction .of the furnace roll. Such an installation is shown in FIG. 2.

In FIG. 2 the tube means or evacuation tube 31 is provided in multiple and they are disposed radially about the interior of the outlet port 15. In this structure the evacuation process of the entrapped gas is made more continuous by the provision of more than one of the tubes 31. Upon each revolution of body 11 as shown in FIG. 2, two evacuation periods will occur.

The structure of FIG. 2 is. identical to that shown and illustrated in FIG. 2 of the Ornitz et al. cross reference .wherein the perforated spacer 21 is provided at the outlet end of the body 11. The spacer ring 21 shown here is provided with spaced ports 23 about its periphery, the total area of which is equal to or less than the areaof the inlet passage 16 to restrict the flow of the coolant along the surface of the tube 18. The tube ends 32 are preferably provided adjacent the outlet end of the body 11 as the entrapped air is concentrated at this end by reason of the constant fluid flow therethrough in that direction.

In FIGS. 3 and 4, the basic structure of the furnace roll illustrated isv identical to that shown in FIGS. 1 and 2, however, the axial tube 18 within the body 11 is eliminated and the tube means 31 is provided in the configuration of a cone or frustum having an annular passage 34. The tube means 31 consists of a molded or cast conical shaped sleeve 36 having a perforated annular shoulder. 37 at its base which in turn is gripped ,between the body 11 and roll neck 12 a s.indi cated.=at=38 .I.

The conicaltubemeans 31 is preferably molded of ,a metal or plastic such as a polyethylene known on the market under the trade name of Teflon.

The :annular shoulder 37 is provided with a series of ports 45 therearound as defined by the outer ring 39, inner ring 40 and radial web members 41. The outer ring 39 is the portion of the tube means 31 which is actually clamped by the body 11 and roll neck 12 as previously indicated at 38, thereby positioning the annular series of the ports 45 flush with the interior cylinder wall of the body 11. 5 4

Thus the tube means is formed by the annular passage between the frusto-conical surface 42 of the cone 36 and the conical surface of the outlet port 15. The crosssectional fluid flow area of this annular passage 35 is preferably maintained at a constant throughout the length of the passage. Therefore as the conical surface of the outlet port 15 converges towards its apex the conical surface 42 of the tube means 31 must converge at a is permitted to rapidly expand somewhat within the outlet passage 16'. This provides a venturi effect which enhances the rate of avacuationof the gas enclosures passing through the passage 35.

In this structure the annular passage 35 is in substantially continuous contact with the entrapped gases which collect adjacent its opening 32 along the top portion 30 of the interior cylindrical wall of body 11. Thus evacuation of the entrapped gases is an uninterrupted process which provides constant evacuation of the entrapped gas. The tube means as provided by the single tube shown in FIG. 1 is preferred however for its simplicity and, as previously stated, for its venting efliciency due to the fact that a plurality of such tubes decreases the venting efficiency of each individual tube.

The tube means illustrated in FIG. 5 is substantially identical and performs the same function as that shown in FIGS. 3 and 4, however, the outlet passage 16' as shown in FIG. 5 is provided with the diffuser 44 which gradually converts the velocity head found at the nozzle 43 into a pressure head within the passage 16 beyond the diffuser 44 with as little loss as possible. The diffuser 44 therefore increases the efficiency of the venturi illustrated in FIG. 3. The diffuser may be cast in or inserted independently. The diffuser 44 may also be readily employed in the structure of FIG. 1 as by giving sleeve 34 similar configuration.

The tube means 31 may take on many different structural shapes. For example the tube means 31 may be drilled or cast directly into the walls of the roll neck 12 such that one end is open to the interior cylindrical wall of the body 11 and the other end is open to the outlet passage 16'. As an additional example the tube 31 may pass exteriorly of the furnace roll at its outlet end by passing through the walls of the body 11 and returning to the outlet passage 16' through the walls of the hollow roll neck 12. However the latter example is the least desirable since the tube means would be vulnerable to injury.

Referring to FIG. 6, the tube 31' has an outside diameter which is approximately equal to the inside diameter of the outlet passage 16'. Tube 31 is retained in passage 16' either by welding or a force fit. The tube is bent as indicated such that the open end 32' lies closely adjacent the interior cylindrical wall of the body 11 and the outlet port 15.

In this configuration, the entire liquid outflow passing through the body 11, is directed outwardly to the interior cylindrical -wall and tube end 32' for evacuation. Each time tube end 32' rotates through the uppermost portion 30 of the interior of rotating shaft 11, the gas enclosures are drawn into tube 31 along with the liquid coolant. As the entire furnace roll liquid evacuation is concentrated at tube end 32', the evacuation of the gases is very effective with each revolution of the roll.

In place of tube 31', a similar configuration may be cast into roll neck 10 by merely casting axial passage 16' such that it curves outward until it opens adjacent the interior wall of body 11. As another alternative, outlet port 15 may be partially plugged such that only a small segment of its frustoconical surface is exposed from passage 16' to interior wall of shaft 11 to provide the vent tube. The object of embodiment shown in FIG. 6 is to concentrate the liquid coolant outflow to a relatively small area adjacent the interior cylindrical wall of the hollow shaft 11.

The tube 18 as shown in FIGS. 1 and 2, is omitted from the remaining figures to illustrate the fact that its presence is not required for efiicient evacuation of the entrapped gases. It serves mainly to increase the rate of coolant flow over the surface to be cooled, namely the interior wall of body 11.

Although the different figures illustrate the furnace roll with a coolant inlet at one end and a coolant outlet at the other end, this is not required. In some installations it becomes necessary to have the inlet and outlet at the same end. This is accomplished by providing an elongated tube in the furnace roll which is supported coaxially within the hollow shaft 11 and axial outlet passage 16'. The coaxial elongated tube is extended from the fitting 17', where it is connected to a water or coolant source, to outlet port 14. In this type installation, inlet passage 16 is closed.

It should be noted further that the requirement of insulation and an outer sleeve in present day conveyor rolls such as shown in FIG. 1 is optional. The need for such insulation is dependent upon the particular service application and the alloy materials used in the furnace roll.

I claim:

1. A liquid cooled furnace conveyor roll having a hollow cylindrical body with end inlet and outlet coolant passages, said outlet passage having a cross-sectional fluid flow area smaller than the internal cross-sectional fluid flow area of the cylindrical body, characterized by tube means secured to said furnace roll and having an inlet open to the interior of said body adjacent its cylinder wall and outlet end and an outlet open to the interior of said outlet passage to remove gas enclosures adjacent said cylinder wall.

2. The furnace roll of claim 1 characterized by at least one tube providing said tube means.

3. The furnace roll of claim 2 wherein said tube is smaller in cross section than and lies within said outlet passage and extends into said body interior.

4. The furnace roll of claim 2 wherein said tube lies external of said conveyor roll.

5. The furnace roll of claim 2 wherein said tube is imbedded in the walls of said conveyor roll.

6. The furnace roll of claim 1 characterized by a coaxial sleeve mounted in said outlet passage and spaced from the walls thereof to provide said tube means therebetween.

7. The furnace roll of claim 6 characterized in that said sleeve is frustoconical having its restricted end farthermost from said body interior.

8. The furnace roll of claim 7 wherein said tube means is of substantially constant cross-sectional area throughout its length.

9. The furnace roll of claim 8 wherein said tube means cross-sectional area is smaller than that of said outlet passage.

10. The furnace roll of claim 1 characterized in that said tube means is of smaller cross-sectional fluid flow area than said outlet passage.

11. The furnace roll of claim 10 characterized by a venturi restriction in said outlet passage where said tube means opens thereto.

12. The furnace roll of claim 11 characterized by a diffuser in said outlet passage extending outwardly from said venturi restriction.

13. The furnace roll of claim 1 characterized by an axially extending tube imperforate intermediate the ends thereof in said body and spaced from said cylindrical wall and forming an annular passage therebetween through which the coolant is passed.

14. The furnace conveyor roll of claim 1 characterized by a tube providing said tube means, said tube having its outlet mated with said outlet passage to provide a continuation thereof.

'15. A furnace conveyor roll adapted to carry a coolant comprising a hollow cylindrical body having axial inlet and outlet ports, inlet and outlet passages leading from said ports respectively, tube means secured to saidfurnace roll and having one end open to the interior of said body adjacent the cylinder wall and outlet end thereof and the other end open to the interior of said outlet passage, said outlet passage being sufliciently restricted in cross-sectional area to provide a lower fluid static pressure at the said other end of said tube means than at the said one end thereof and a load bearing surface on said body.

. 16. The furnace conveyor roll of claim 15 characterized by an axially extending tube imperforate intermediate the ends thereof in said body spaced from the interior walls thereof and forming an annular passage therebetween through which the coolant is passed.

17. A liquid cooled furnace conveyor roll having a hollow cylindrical body with axial inlet and outlet coolant passages, said outlet passage having a cross-sectional fluid flow area less than that of the hollow fluid flow interior of said body, characterized by a vent tube having its inlet adjacent the interior cylinder wall of said body and its outlet in said coolant outlet passage to remove gas enclosures adjacent said cylinder wall.

18. The liquid cooled furnace conveyor roll of claim 17 wherein said vent tube outlet mates with said outlet passage to provide a continuation thereof.

19. The liquid cooled furnace conveyor roll of claim 17 wherein said vent tube inlet is also adjacent the outlet end of said hollow cylindrical body.

. 20. The method of removing gas enclosures adjacent the interior walls'of a hollow liquid cooled furnace conveyor roll having an inlet and an outlet passage, comprising the steps of decreasing the static pressure of the liquid flowing through the furnace roll in the outlet passage by restricting its cross-sectional area, and inde pendently venting the gasenclosures to this decreased pressure area in the outlet passage to remove the gas enclosures.

' 21. The method of'claim 20 including the step of thereafter diffusing the liquid of low static pressure.

22. The method of removing gas enclosures adjacent the interior walls of a hollow liquid cooled furnace conveyor roll having restricted axial inlet and outlet coolant passages, comprising the step of venting the gas enclosures directly to the interior of the restricted outlet coolant passage.

23. The liquid cooled furnace roll of claim 17 characterized in that said tube vent is secured to said body for axial rotation therewith.

References Cited UNITED STATES PATENTS 3,058,731 10/1962 Bloom.

US. or. X.R. 263-44

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