US3054162A - Method and apparatus for descaling strip material, especially strip iron - Google Patents

Description

Sept. 18, 1962 R. J. AMTMANN 3,054,162

METHOD AND APPARATUS FOR DESCALING STRIP MATERIAL, ESPECIALLY STRIP IRON Filed Feb. 17, 195s e sheets-sheet 1 i im? AMTMANN METHOD AND APPARATUS FOR DESCALING STRIP MATERIAL, ESPECIALLY STRIP IRON Filed Feb. 17, 1958 Sept. 18, 1962 6 Sheets-Sheet 2 /NVEA/ro'? Maa/707 hh...

Sept. 18, 1962 Filed Feb. 17, 1958 R .1. AMTMANN 3,054,162

METHOD AND APFARATUS FOR DESCALING STRIP MATERIAL, ESPECIALLY STRIP IRON 6 Sheets-Sheet 3 AMTMANN TUS FOR DESCALING STRIP IRON 6 Sheets-Sheet 4 ECIALLY STRIP D APPARA AL, ESP

Sept. 18, 1962 METHOD MAT Filed Feb. 17, 1958 wf/vra@ rhum; S. Sfffef Sept. 18, 1962 R. 1. AMTMANN 3,054,162

METHOD AND APPARATUS FOR DESCALING STRIP MATERIAL, ESPECIALLY STRIP IRON Filed Feb. 1'?. 1958 6 Sheets-Sheet 5 Sepf- 18, 1962 R. J. AMTMANN 3,054,162

DEscAL METHOD AND APPARATUS F ING STRIP B MATERIAL, ESPECI Y STRIP IRON Filed Feb. 17, 195 6 SheeiS-Sheeb /N VEN/'0,9

y 25324 T Mmm? I /77/1011 STP/'eer iinited States @arent METHOD AND APPARATUS FOR DESCALING STRIP MATERIAL, ESPECIALLY STlRlP IRON Rudolf Josef Amtmann, Herner, Westphalia, Germany,

assigner to Maschinenfabrik August Sentire, Hemer,

Westphalia, Germany Filed Feb. 17, 1958, Ser. No. 715,666 Claims priority, application Germany Feb. 16, 1957 6 Claims. (Cl. 29-S1) The invention relates to a method and an apparatus for continuously descaling strip material and especially strip iron, in which the strip is drawn in zig-zag fashion over deilecting cylinders and mutually displaced and adjustable metal guide bars with curved guide surfaces, and the scale is detached by the guide bars engaging in the vertex of a bending angle formed by the strip.

'I'he invention is based on a former suggestion of the applicant, according to which the strip material is drawn in zig-zag fashion over deflecting cylindersvand mutually displaced and adjustable metal guide bars with curved guide surfaces. The strip is passed over each guide bar at a bending angle which is preferably between 60 and 120. The scale is thereby detached from the surface of the strip by the guide bar arranged in the vertex of the bending angle, a portion of crushed scale being drawn between the bar and the strip to serve as lubricant, for the subsequent removal of which brushes are provided.

An object of the present invention is to improve this `descaling method by feeding water under high pressure (for example 30 to 100 atms.) between the guide surface of the guide bar and the strip, so that a layer or cushion of pressure water is produced on which the strip slides. In this manner the strip is slightly lifted from the guide surface of the guide bar so that it no longer comes in direct contact with the guide surface but slides on the cushion of pressure water located between this surface and the surface of the strip. The `friction between the guide bar andthe surface of the strip is therefore reduced to such an extent that the guide bar is only subjected to slight wear and it is no longer necessary to make the guide bar from hard metal. Due to the cushion of pressure water between the guide bar and the surface of the strip, scraping or scratching of the strip on the guide bar is positively prevented even if, for example in the case of a very thin layer of scale, the quantity of scale drawn between the guide bar and the surface cf the strip is not sufficient to prevent the surface of the strip from being scratched.

As the strip practically floats on the cushion of pressure water between the surface of the strip and the guide bar, the pulling force necessary for moving the strip is, owing to the reduction in friction achieved thereby, considerably less so that pulling devices of a smaller capacity can be used. Owing to the smaller frictional forces which have to be overcome when descaling the strip, the longitudinal expansion and the hardening of the strip resulting therefrom is less than in the case of a descaling method operating without pressure water cushion. By the pressure water fed in the range of the guide bar, the scale detached from the surface of the strip by the bending of the strip is flushed away immediately on becoming detached, so that no'accumulations of scale can form between the guide bar and the surface of the strip, thereby preventing any particles of loose scale from being pressed into the surface of the strip by the high surface pressures existing between the guide bar and the strip. Another advantage of the method according to the invention consists in that the bearing pressure transmitted from the strip on to the guide bar is reduced considerably and the pressure water fed between the guide bar and the strip surface acts as cooling medium which prevents excessive heating of the guide bars.

Another object of the present invention is to provide an apparatus for continuously descaling strip material, particularly strip iron, which comprises in the region of the curved guide surface of each guide bar at least one passage extending substantially perpendicularly to the surface of the strip for feeding the pressure water between the guide bar and the surface of the strip. In order, particularly in the case of relatively wide strips, to obtain as far as possible a pressure water cushion of uniform conguration over the entire width of the strip, it is advisable to equip each guide bar with several feed passages distributed over its length, which passages are connected to a common feed conduit for the pressure Water. The feed passages are preferably constructed as nozzles and arranged with their axes in the longitudinal central plane of the guide bar, so that the strip is lflushed with water jets projected with great force, practically over its entire width, and the scale detached from the surface of the strip by bending the strip is iiushed out of the pores of the strip and washed away. The mouths of the nozzles are preferably widened in fan-shape in the longitudinal direction of the guide bars so that, to obtain the same descaling effect, a smaller number of nozzles is required.

In another form of construction the apparatus according to the invention is provided with at least one elongated pressure water chamber extending in the longitudinal direction of the guide bar, which pressure water chamber is open toward the guide surface of the bar and connected to a pressure water feed conduit. In order to obtain a uniform distribution of pressure water on the entire width of the strip, it is preferable to provide several pressure water chambers arranged one behind the other in the longitudinal direction of each guide bar, which chambers extend over a considerable portion of the width of the strip and are connected by short connection 'passages to a distributor passage of relatively large cross section arranged under the guide bar and extending in the longitudinal direction thereof.

According to an alternative embodiment of the invention, the apparatus can be so constructed that adjacent each of the longitudinal sides of each guide bar preferably several spraying nozzles are arranged within the bending angle formed by the strip, and distributed over the width of the strip, which nozzles squirt pressure water jets between the facing surfaces of the strip and guide bar. Also in this case it is advisable to spread the pressure water jets in fan-fashion parallel to the apex of the guide bar so as to obtain the greatest possible effect with the smallest possible number of nozzles and a relatively Small quantity of water. Distributing pipes carrying the Spray nozzles and extending adjacent both sides of the guide bars are preferably constructed so that they are vertically and laterally adjustable and rotatable about their longitudinal axis so as to enable the direction of the pressure water jets to be adjusted in relation to the bending angle of the strip actually chosen.

With the 'aid of the invention metal strips with a very wide range of thicknesses, for example strip iron from about 0.5 to l0 and even more mms. in thickness can be descaled. The size of the bending angle depends upon the material and the thickness of the strip, and also upon the thickness and composition of the layer of scale. In most cases the most favorable bending angle lies between about 60 and 120, but deviations from these values are conceivable. r

Several preferred embodiments of the invention are illustrated by way of example in the accompanying drawings, in which:

FIG. l is a diagram showing the general layout of a descaling apparatus according to the invention;

FIGS. 2 and 3 are vertical central sections showing the descaling apparatus in greater detail, FIG. 2 showing a first portion and FIG. 3 a second portion of the apparatus;

FIG. 4 is a cross section through a guide bar equipped with pressure water nozzles;

FIG. 5 is a top plan view of FIG. 4;

FIG. 6 is a cross section through a modified guide bar equipped with pressure water chambers;

FIG. 7 is a top plan view of FIG. 6;

FIG. 8 is a cross section through another modification of guide bar equipped with spraying nozzles on both sides, and

FIG. 9 is a top plan view of FIG. 8.

Referring now more particularly to the drawings, FIG. l shows a descaling apparatus in which a strip of band iron 1 running off a reel, not shown in the drawings, is first passed through a braking device 2 composed of four mutually adjustable cylinders. By adjusting the cylinders of the braking device 2 in the directions x-x1 the tractional resistance of the strip can be regulated. A dressing or straightening mechanism which is not driven can, for example, also be used as braking device. An upper cylinder 2a of the braking device 2 serves at the same time as guiding and deectng cylinder for the strip 1 which is subsequently passed in Izig-zag fashion over a guide bar 3 which is detachably mounted on a carrier 4 adjustable in the directions y-y1. The guide bar 3, as can be seen from FIGS. 1 and 4, engages the surface of the strip in the vertex of the bending angle a formed by the strip 1. The size of the bending angle a depends partly upon the material of the strip to be descaled, the thickness of the strip and also the composition and thickness of the scale layer and generally lies between 60 and 120 in the case of iron strip about l to 10 mms. in thickness. By adjusting the carrier 4 in the directions y-yl the bending angle of the strip 1 can be adjusted within a range of, for example, about 60 to 150. The bending angle a is changed when a strip of a different thickness and/or with a different scale composition is to be passed through the descaling apparatus.

Behind the guide bar 3 engaging the under side of the strip in FIG. 1, the strip 1 is again deflected by a cylinder 5 and then runs through a pulling device 6, which, in the example illustrated in FIG. 1, consists of two cylinders at least one of which is driven and which are mutually adjustable in the directions z-z1. By changing the spacing and the speed of rotation of the cylinders mounted in the pulling device 6, the tensional force irnparted to the band 1 can be regulated. Behind the pulling device 6, the strip 1 is preferably guided over another deecting cylinder 7 and subsequently over a second guide bar 3a displaced in relation thereto, which bar engages the upper side of the strip. By the guide bar 3a the strip 1 is bent in zig-zag fashion in the opposite direction, the bending angle al formed at the guide bar 3a being of the same dimension as as the bending angle a at the guide bar 3. The guide bar 3a is, just like the guide bar 3, exchangeably mounted on a carrier 4a adjustable in the directions y-y1. Behind the guide bar 3a the strip is returned into the horizontal plane of travel of the strip by a deflecting cylinder 8 and subsequently runs through a second pulling device 9 which, like the pulling device 6, consists of cylinders adjustable in relation to each other in the directions z-z1, at least one of said cylinders being driven at an adjustable speed of rotation.

In the descaling apparatus illustrated in FIGS. 2 and 3, the first guide bar 3, contrary to the arrangement shown in FIG. l, is arranged above the strip 1, whereas the second guide bar 3a shown in FIG. 3 is below the strip. It is immaterial whether the arrangement raccording to FIG. 1 or that according to FIGS. 2 and 3 is chosen. As can be seen from FIG. 2 the strip 1, in entering the apparatus, rst passes between a pair of feed-in cylinders 33, at least one of which is driven. These feed-in cylinders are followed by the cylinders of the braking device 2. In the present case five cylinders are provided some of which are braked directly or on their ends. These cylinders also serve for straightening the strip. Means for braking the cylinders of the braking device are indicated at 34. The braking force can be adjusted by spring pressure. The strip 1 passes from the braking device 2 into a first descaling unit 35- of the apparatus in which the strip is guided over cylinders 36 and 5. The guide bar 3 is arranged between these cylinders 36 and 5 and is adjustable in vertical direction by means of a spindle 37. The cylinders 36 and 5 can be adjusted in vertical direction with the aid of spindles 38. A rotary brush 19 is mounted above the cylinder 5 and driven by a motor 33. After the removal of scale on one side of the strip 1, the latter passes from the descaling unit 35 into the pulling device 6 which has driven cylinders 39 around which the strip is passed so as to be pulled through the unit 35 against the resistance of the braking device 2.

For descaling the other side of the strip 1, the strip travels first through another braking device 40 following the pulling device 6 and corresponding substantially to the braking device 2. As shown in FIG. 3, the strip 1 then enters a second descaling unit 41 of the apparatus in which the guide bar 3a is arranged. This guide bar 3a is located between guide cylinders 42 and 3. A rotary brush 26 is coordinated to the cylinder 8 and driven by a motor 43. Two further units 44 and 45 are connected up in series behind the second descaling unit 41. The units 44 and 45 include driven brushes 46 and 47 which cooperate with adjustable guide cylinders 48 and 49 respectively. Spraying devices 50 are provided for supplying water under suciently high pressure to cach of the brushes 46 and 47. These spraying devices can be coordinated to the upper and lower sides of the strip. Nozzles for spraying water under pressure are also coordinated to the already mentioned guide bars 3 and 3a. The special forms of construction and arrangement will be hereinafter described. Behind the unit 45 the pulling device 9 is provided which corresponds in construction to the pulling device 6 of FIG. 2.

As can be seen from FIGS. 4, 6 and 8, the guide bar 3 has a curved guide surface 10. This guide surface 10 is cambered according to a radius 1' which is differently dimensioned in guide bars serving for descaling strips of different thicknesses. It has been found advantageous to make the radius r about four times as great as the actual thickness s of the strip.

In the form of construction of the descaling apparatus illustrated in FIGS. 4 and 5, the guide bar 3 and the similarly constructed guide bar 3a are provided with several nozzles or jets 11 arranged at regular intervals apart in the longitudinal direction of the bar, through which nozzles water under high pressure of about 30 to 100 atms. for example, can be fed between the guide surface 1t) and the surface of the strip, The nozzles 11 are arranged with their aXes in the longitudinal central plane a-a of the guide bar 3. These nozzles 11 are connected by means of short passages 12 to a distributor passage 13 of relatively large cross section passing through the guide bar over its entire length and extending parallel to the guide surface 10. The distributor passage 13 is, as can be seen from FIG. 5, connected at both ends to a feed conduit 14 and 14a respectively for the pressure water.

The pressure water is fed to the guide bars 3, 3a preferably by a high-pressure pump which is not shown on the drawings but which is so constructed that the pressure and quantity of the water fed can regulated, preferably continuously, within wide limits. It is evident that it is also possible to provide for the regulation of the pressure and/ or the quantity of water fed to the nozzles 11 of the guide bars 3, 3a, throttle element elements fitted in the feed conduit 14, 14a.

As shown in FIG. 5, the nozzles 11 arranged one behind the other in the longitudinal direction of the guide bar 3, are uniformly distributed over a range corresponding to the total width b of the strip 1, so that a uniform layer of pressure water forms over the entire width of the strip between the guide surface and the surface of the strip 1. As can be seen from FIG. 5, the nozzles 11 have their mouths 11a widened in fan-fashion in the longitudinal direction of the guide bars 3, 3a, whereby the mouths 11a of adjacent nozzles overlap slightly. As a result the jets of pressure water passing out of the nozzles 11 at a high speed spread in fan-fashion in the longitudinal direction of the guide bars 3 and 3a respectively, so that, even if adjacent nozzles 11 rare spaced apart at relatively Wide spaces c, the whole width b of the strip is sprayed with water jets emerging with a considerable amount of kinetic energy. The pressure water fed by the nozzles 11 forms between the curved guide surface 10 and the surface of the strip 1 facing this guide surface, a pressure water cushion by which the strip is lifted oif the guide surface 10. The water flows off laterally on both sides of the guide surface 10 in the direction w--wl and perpendicularly thereto.

Y In the embodiment illustrated in FIGS. 4 and 5, the guide bar 3 is exchangeably iixed on the carrier 4 by bolts 15. Thus, the guide bar can be easily exchanged when descaling strips o-f different materials, different thicknesses, different widths and with different scale formations.

In the construction illustrated in FIGS. 6 and 7, the guide bar 3 is composed of two halves 31 and 32, being divided along a plane extending parallel to the longitudinal central plane 1 -a, which halves are clamped between jaws 23, 24. The clampin- g jaws 23, 24 are drawn together by screws 25. The facing contact surfaces of the guide bar halves 31 and 32 are ground and when in clamped position are pressed tightly one against the other by the jaws 23, 24. It is evident that it is also possible to provide packings between the contacting surfaces of the guide bars 31 and 32.

In the crown or apex of the curved guide surface 10 two elognated pressure water chambers 26, 26a are arranged one behind the other in the longitudinal direction of the guide bar 3. These pressure water chambers 26, 26a are open toward vthe guide surface 19, reach to the Vfull height of the guide bar 3 and together extend over about three-quarters of the -strip width. The division plane of the guide bar 3 coincides with one of the longitudinal walls of the pressure water chambers 26, 26a. On Yboth sides of the pressure water chambers 26, 26a the crown of the guide bar 3 is provided with a longitudinal groove 27 corresponding approximately to the width of the chambers, which groove is only shallow, being e.g. about 2 mms. in depth. With the aid of this shallow longitudinal groove a uniform pressure water cushion is formed at the crown Vof the lguide bar 3 on each side of the pressure water chambers 26, 26a so that the scale will be washed away on both sides in the longitudinal vdirection of the guide bar.

The pressure water chambers 26, 26a are each connected by two connection passages 28, 28a provided in the clamping jaw 24 to a distributor passage 29 of relatively large cross section extending through the clamping jaw 24 in the longitudinal direction of the guide bar 3. The distributor passage 29, as in the .embodiment illustrated in FIGS. 4 and 5, is connected at both ends to pressure water feed conduits 14, 14a.

In the form of construction illustrated in FIGS. 8 and 9, the guide bar 3 is solid, that is without passages or chambers, but is also clamped between two jaws 23, 24 which are adjustable in relation to each other by means of clamping screws 25. Distributor pipes 30, 30a of relatively large cross section are arranged one on each of the longitudinal sides of the guide bar 3 parallel with the apex of the guide bar. Spraying nozzles 31, 31a are arranged on the periphery of distribution pipes 30, 30a

one behind the other in the longitudinal direction of each pipe, the longitudinal axes of these nozzles being located in the longitudinal central plane of their respective distributor pipes. It is evident that any desired number of spraying nozzles can be provided distributed over the width of the strip. The spraying nozzles 31, 31a have a mouth widened in fan-fashion in the longitudinal direction of the distributor pipes 30, 30a, so that Water jets 32, 32a passing out therefrom are spread in fan shape parallel to the crown of the guide bar 3. As can be seen from FIG. 8, the water jets 32, 32a are sprayed with high pressure between the facing surfaces of the strip 1 and the guide bar 3 overrthe entire width of the strip. By means of the high pressure water jets 32, 32a impinging with great force in the space between the strip 1 and the guide surface 10, a pressure water cushion forms between the guide surface 10 and the surface of the strip facing it, which cushion lifts the strip, slightly olf the guide bar and washes away the scale loosened by the bending of the strip. Y

As indicated by arrows in FIG. 8, the distributor pipes 30, 30a are adjustable in height and laterally andare mounted so that they can be turned about their longitudinal axis, so that the pressure water jets 32, 32a can always be accurately directed to the gap between the stripV 1 and the curved guide surface 10 of the guide bar 3. The adjustment of the distributor pipes 30, '30a is also necessary to enable the `direction of the high pressure water jets 32, 32a to be adapted tothe actual bending angle x when changing this angle. The distributor pipes 30, 30a are connected at one end to a high pressure water conduit, not shown in the drawings.

As. shown particularly in FIG. 1, but also in FIGS. 2 and 3, each of the guide bars 3 and 3a is followed by a spraying device 16 and 16a respectively, providedwith a plurality of nozzles distributed over the Ywidth b of the strip and by which the surface of the strip actually descaled is again sprayed with jets of water under high pressure. `Such a spraying device 16 or 16a can obviously also lbe used when the guide bars are constructed as in the embodiments illustrated in FIGS. 6 to 9. The nozzles of the .spraying device 16 or 16a, which are not shown in detail in FIGS. 1 to 3, are connected by a common distributor pipe and by a connection conduit 17 or 17a thereon, to awater feed conduit 1'8 or 18a leading to a high pressure pump, not shown in the drawings, like the connection conduits 14, 14a of the nozzles 11 or the chambers 26, 26a, or the distributor pipes 30, 30u.

The strip 1, after passing the spraying device 16 or 16a, is fed between at least one deflecting cylinder 5 or 8 and a brush 19 or 20 respectively. The brushes 19, 20 engage the descaled surface of the strip sprayed by the preceding spraying device .16 or 16a and are adjustable in the direction t-t1. Approximately tangential to the periphery of the brushes 19 and 20 respectively one or more adjustable nozzles 21, 21a are arranged in the range'between the strip and the periphery of the brushes, by which nozzles the contact area between the brushes and the surface of the strip is ushed by jets of Water under pressure directed substantially tangentially to the periphery of the brushes. By these pressure Water jets an improved brushing effect and a continuous cleaning of the rotating brushes 19, 20 from particles of scale are attained. The spraying nozzles 21 and 21a respectively are, in the form of construction illustrated in FIGS. l to 3, connected to the same pressure Water feeding conduits 18, 18a as the connecting conduits 14, 14a of the guide bars 3, 3a or the connecting conduits 17, 17a of the spraying devices 16, 16a. As the pressure of the water fed through the nozzles 21, 21a may be considerably lower than that of the water fed in the region of the guide bars 3, 3a and through the spraying devices 16, 16a, the nozzles 21, 21a are connected to feed conduits 22, 22av provided with throttle devices. Furthermore, independently adjustable throttle devices can also be arranged in the connection conduits 14, 14a and 17,

17a in order to enable the pressure and/or the quantity of water fed in the region of the guide bars 3, 3a and through the spraying devices 16, 16a to be regulated independently of each other. For the nozzles 21, 21a, however, a separate water feed conduit under lower pressure can also be provided.

In the form of construction illustrated by way of example in FIG. 1, a brush is arranged behind each spraying device 16, 16a. In cases where exceptionally exigent requirements are placed on the surface condition of the strips, it is evident that two or more brushes 19 or 20 can be provided which are connected up in series. Furthermore, dry-operating brushes can also be provided instead of or in addition to the wet-operating brushes for polishing the strips. It is likewise possible to dry the descaled wet bands in a drying device, for example a continuous heating furnace, so as to avoid the formation of rust.

In order to improve the descaling effect, tine abrasives, such as corundum powder, steel turnings or the like, can be added to the water fed onto the surface of the strip in the region of the guide bars 3, 3a and/or through the spraying devices 16, 16a. In such cases, it is advisable to make the nozzles of the guide bars 3, 3a as well as those of the distributor pipes 30, a and the spraying devices 16, 16a from wear-resistant and abrasion-proof material. In some cases, it will also be advisable to add to the water anticorrosive agents so as ot prevent the formation of rust during the descaling of strip iron.

The invention may be embodied in other specific forms without departing from the spirit or essential characterf istics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

I claim:

l. A method for descaling str-ip material comprising the steps of guiding the strip material along a selected path; `bending the strip material during the passage thereof over a bending surface; building a layer of liquid between said bending surface and the surface of said str-ip material and preventing direct contact between said surfaces by directing a liquid under suicient continuous pressure between said surfaces to maintain said layer and thereby prevent said direct contact.

2. A method for descaling strip material comprising the steps of guiding the strip material along a selected path; bending the strip material during the passage thereof over a bending surface; and directing liquid under pressure of between 30 to 100 atmospheres between said bending surface and the surface of the strip material adjacent to it to build a cushion of liquid between said surfaces and to prevent direct contact between the same.

3. A method for descaling strip material comprising the steps of guiding the strip rnaterialalong a selected path; bending the strip material during the passage thereof over a bending surface; and directing liquid containing an abrasive material under pressure between said bending surface and the surface of the strip material adjacent to it to build a cushion of liquid between said surfaces and to prevent direct contact between the same.

4. A method for descaling strip material comprising the steps of guiding the strip material along a selected path; bending the strip material during the passage thereof over a bending surface; and directing liquid containing abrasive material under pressure of between 30 to 100 atmospheres between said bending surface and the surface of the strip material adjacent to it to build a cushion of liquid between said surfaces and to prevent direct contact between the same.

5. A method for descaling strip material comprising the steps of guiding the strip material along a selected path; bending the strip material through an angle of between and 150 during the passage thereof over a bending surface; and directing liquid under pressure of at least 30 atmospheres between said bending surface and the surface of the strip material adjacent to it to build a cushion of liquid between said surfaces and to prevent direct contact between the same.

6. Method for the continuous removal of scaly matter from the surface of strip material, comprising the steps of pulling the baud under tension over guide rollers and over an arc-shaped slide surface of guide bars mutually displaced and adjustably arranged with respect to said guide rollers in zig-zag `formation with said arc-shaped slide surfaces, each of said arc-shaped slide surfaces being arranged in the vertex of the angle of deflection formed by the band, and simultaneously feeding water under a pressure of 30 to 100 atmospheres between said slide surfaces of each guide bar and the adjacent surface L of the band, thereby forming a layer of pressure water on which the band glides.

References Cited in the file of this patent UNITED STATES PATENTS 295,217 York Mar. 18, 1884 874,692 Lundstrand Dec. 24, 1907 896,638 Hock Aug. 18, 1908 1,896,674 Longwell Feb. 7, 1933 2,140,289 Hurtt Dec. 13, 1938 2,152,842 Evans Apr. 4, 1939 2,203,751 Simons June 11, 1940 2,256,520 Johansen Sept. 23, 1941 2,318,432 Stanier May 4, 1943 2,319,309 Emigh May 18, 1943 2,335,196 Pecsok Nov. 23, 1943 2,680,938 Peterson .lune 15, 1954 2,857,655 Greenberger Oct. 28, 1958 2,877,534 Larson Mar. 17, 1959 2,913,808 Thomas NOV. 24, 1959 FOREIGN PATENTS 22,055 Sweden Nov. 2, 1905

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