JPS5966681A - Device for drying and guiding band material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strip drying device, and more particularly to a strip drying device in which a longitudinally moving strip is guided along a curved portion while the strip is supported in a floating state. This invention relates to a material guiding device.

When drying a moving strip of paper or the like, it is often desirable to support the strip from contact during the drying operation to avoid damage to the strip itself or to the ink or coating on the strip. One known device for supporting a strip in a non-contact manner includes upper and lower pairs of air pars extending along a linear, generally horizontal extension of the strip. The air emanating from the lower set of air pars supports the strip in suspension, and the air emanating from the upper set of air pars supports the strip in a generally straight line at a substantially constant distance from both sets of air bars. Stabilize this to hold. The air blown from both sets of air pars is usually heated to speed up the drying of the strip, and the air bar array is usually brought to just below atmospheric pressure by an exhaust blower to remove vapors generated from the strip. placed inside a sealed enclosure maintained at low pressure.

Drying devices that operate on strips extending horizontally in a straight line have the obvious disadvantage of occupying a considerable amount of floor space, so that the inner portion of the strip being dried extends more or less vertically. Much consideration has been given to strip drying devices that are supported with a plurality of extensions.

Where the strip to be dried can be brought into contact with drying rolls, this strip is usually fed through a series of said rolls arranged so as to define a pronounced sinusoidal path relative to the drying roll. be passed around. However, newly printed or newly coated strips of paper or plastic must be supported without contact during drying, and such strips must be placed in a path that occupies a minimum of floor space. , the drying device must include a plurality of non-contacting pivoting guides that cooperate to define the required path of the strip. It will be appreciated that it would be desirable for a non-contact pivoting guide in a strip drying device to provide some drying of the strip in addition to supporting and guiding the strip.

U.S. Pat. No. 3,279,091 discloses an apparatus for drying a strip that is interlocked while contact-free supporting and guiding the strip along a bend. This device is
It includes a non-rotating cylindrical shell of less than full circular shape having a series of circumferentially spaced axially extending air release slots in its outer surface. Each of the slots directs heated compressed air radially outwardly to impinge on the inner surface of a strip partially wrapped around the shell. This shell also has irregularly distributed air ports that provide an exhaust path for heated air. The flanges along the edges of the strip act as air dams that prevent significant amounts of compressed air from escaping from beneath the strip except at the exhaust vents.

The shape of the outlet nozzle is such that the heated air
~6,100m/min (12,000~20,000f
contactless support of the strip, as is clear from the disclosure that it ejects from the exit slot in the form of a long jet with a velocity of This requires a very large pneumatic force to ensure this. The device also applies ``the forces acting radially outwardly on the strip resulting from the air jets acting thereon and the tension in the strip in order to maintain an air cushion capable of acting on the moving strip.'' ``(U.S. Pat. No. 4,218,833).

Another form of apparatus for contact-free supporting a moving strip and drying it while guiding it along a bend is disclosed by U.S. Pat. No. 4,218,833. However, in this case, a plurality of nozzle pairs are arranged in a partially circular row around which the interlocking strip passes. Each nozzle is arranged in pairs such that the two nozzles of each pair each emit a circumferentially diverging stream of air, so that one nozzle in close proximity acts in one circumferential direction while the other in the opposite circular direction. Coanda acting in the circumferential direction
) type nozzle. The nozzle pairs are located alternately around the periphery of the shell with exhaust ports on the shell surface. Converging air streams flow from circumferentially adjacent nozzle pairs to these exhaust ports. The surface of the shell is made of Coand
It defines a continuous arc of uniform radius interrupted only by the a-shaped nozzle and the exhaust port. The circumferential flow of compressed air around the cylindrical shell surface occurs between said surface and the strip, since the pressure on the inner surface of the strip is very small unless the strip is very close to the shell surface. , which acts to levitate the strip a slightly smaller distance from said surface. As a result, the strip tends to drag against the shell at certain locations, particularly near the exhaust inlets, and the device tends to create problems such as strip noise and strip wrinkles; Because of the small pressure applied, the device is unable to levitate a strip under substantially longitudinal tension.

In the past, the goal was to minimize the air flow required for guidance of the strip for strip drying functions and for sufficient contactless support of the strip as it moves along bends. Various non-contact rotary guides have been devised for guiding the strip. In general, the most satisfactory pivot guides are arranged such that they provide a cushion of compressed air between the strip and the arcuate surface of the device, and require relatively little flow of compressed air to maintain this cushion. It was something. In such a swivel kite, the pressure on the radially inner surface of the strip is, of course, uniform across the width of the strip, especially below its edges, and also over the entire circumference of its curvature. It is necessary. Prior art pivot guides that are well suited for slow air flow and even pressure cushions are disclosed in U.S. Pat. No. 4,182,472, U.S. Pat.
No. 2 and No. 4,288,015. While these pivoting guides have been quite satisfactory as strip guiding devices, the other desirable ability to operate at low air flow rates is that the substantial flow of air in contact with the strip This has not been satisfactory for use as a strip dryer because it is necessary to produce the high rate of heat transfer necessary for rapid drying.

However, these disadvantages outweigh the relatively high cost of the prior art pivot guides mentioned above, since sufficient strip drying can often be obtained in the linear extension of the strip between the pivot guides. There wasn't. As is apparent from the drawings of the three aforementioned US patents, the pivot guides disclosed in these patents were comprised of extruded or molded parts. The tools required to form these parts had to be special for each width and/or radius of the swivel guide, and therefore had to be amortized in relatively small production runs, of course. Although there was an obvious need for a substantially less expensive contactless pivot guide, it was not known how to accomplish this.

In this way, a substantially relatively inexpensive device is provided in which a longitudinally interlocking strip is supported and guided along a bend in a contact-free manner, and also a substantial dryness of the strip can be achieved. The demand for this has so far been unmet. In order for such devices to be satisfactory, they must meet stringent requirements. In order to be intended to function as a drying device, it must provide sufficient flow of heated air in contact with the strip to achieve the necessary heat transfer, but not sufficient for drying to avoid wasting power. No greater airflow rate than is necessary. The device shall, if any, be at least approximately 32 mm (0.1 mm) outward from its surface.
25 inches), preferably about 63 mm (0.25 inches).

If the strip is normally applied to any part of the surface of the device, approximately 3
If they are closer than 2 mm (0.125 inches), the strip may come into contact with the equipment or cause other strip handling problems. Despite this rather large distance between the strip and the surface on which it is guided, it is necessary for the strip to move smoothly and noiselessly. In particular, due to the wide range of band tension and air supply pressure, there should not be any significant edge wobbling. Since low cost is an important goal, the special tooling required to produce the device must be kept to a minimum, and the device can be manufactured in wide swaths to minimize production and inventory costs. It is desirable that it be compatible with the material.

It is a general object of the invention that the strip be supported at a sufficient distance from the device to ensure that the strip is supported at a sufficient distance from the device to counteract its engagement action on the strip even when the strip is under the action of large longitudinal tensions. A low cost device for contact-free guiding of a strip moving longitudinally along a bend, wherein the strip is guided in such a way as to produce a substantially stable and motion-free movement of the strip. It is provided by.

It is also an object of the present invention to provide a strip of sufficient thickness, but not so large as to be uneconomical, to achieve the previously stated objectives and also to ensure sufficient heat transfer for rapid drying. The object of the present invention is to provide an inexpensive strip guiding device of the above-mentioned character which is capable of generating a contact-side air flow.

Another very important object of the present invention is that it can be constructed at low cost by virtue of its almost entirely sheet metal construction and incorporating more or less conventional standard air par construction as the nozzle element. The object of the present invention is to provide a strip guiding device having the above-mentioned characteristics.

It is also an object of the present invention to accommodate strips of different widths and to
~0.36Kg/cm (approximately 21b per inch diameter)
The object of the present invention is to provide a versatile non-contact strip swing guide of the aforementioned character which can be easily adjusted to accommodate strip tensions in the numerical range of ).

Yet another particular object of the invention is to ensure that high precision requirements do not place constraints on the location of other pivoting guide devices placed immediately before and after the device for guiding the strip toward and away from the device. The object of the present invention is to provide a device of the aforementioned character which allows for small variations in the angle at which the strip approaches and leaves the device.

In general, the foregoing and other objects which will become apparent as the description of the invention proceeds, are achieved in the apparatus of the invention, in which the longitudinally interlocking strips along a defined path include: It is supported and guided in suspension along an arcuate curve in said path by compressed air emanating from the interior of the device and forming a cushion behind the concave surface of the strip. The interior of the device includes a prepressure chamber that communicates with a source of compressed air. The devices extend longitudinally parallel to each other across the width of the path of the strips, are located generally on an arc of said curved portion and are laterally separated from each other about said arc. and a plurality of first front surfaces, each of which is flat. A plurality of elongate exit slots open from the interior of the device, each forming a Coanda type nozzle. each said first front face extending along the opposite longitudinal edge of each of said first front faces and arranged to direct diagonally forward and laterally inward flow of compressed air across the surfaces therebetween; There are two exit slots in each. Each end of the device includes an end plate having an edge whose surface is perpendicular to said first front surface and curved concentrically to said arc with a radius substantially equal to the radius of said arc. is present, providing an air dam that obstructs air flow in the longitudinal direction of this concave surface from the space between said first surfaces.

The apparatus also has a plurality of elongated generally planar second front faces, each having a width extending across the spacing between a pair of said first front faces, the second front faces being It is desirable that the second circular arc is concentric with the circular arc of the curved portion, but has a relatively small radius.

The apparatus further includes surfaces each extending in an arc around a front side thereof, following said first front face and providing a surface perpendicular to said first front face, and providing a surface from said front face at right angles to said path. A pair of additional air dams are included laterally adjacent and projecting from behind the strip to restrict the flow of air laterally outwardly.

This device was also disclosed in U.S. Pat. No. 3,384,656 and U.S. Pat. No. 4,187,971. Preferably, the air parser includes a plurality of universally configured air pars, each providing one of said first flat front surfaces and said paired Coanda type nozzles opening at opposite longitudinal edges thereof. This second flat front surface is thus defined by rectangular filling plates, each interposed between a pair of laterally adjacent air bars.

In the accompanying drawings, there is shown what is considered to be one preferred embodiment of the invention.

In one typical application, the drying device 5 of the present invention comprises:
The longitudinally moving strip W is guided along a curve that carries the strip in substantially varying directions as it moves to a vertical dryer 6 and then towards an inclined dryer 7. The arrangement of the drying devices 6 and 7 is intended to tolerate limitations in the dimensions of the chamber both horizontally and vertically;
Since the strip material is provided with a substantial dry mass in the device 5, the device as a whole can be made more compact.

A rather long unsupported and unguided extension 8 of the strip extends vertically upwards from the vertical drying device 6 to the device 5; a likewise unsupported and guided extension 9 is inclined from said device 5. The drying device 7 extends diagonally downward toward the drying device 7. Such an arrangement is possible in the device 5 due to its tolerance to small changes in the angle at which the strip approaches and leaves the device 5.

In general, the device 5 comprises a preload chamber 10 and a plurality of Coanda-type nozzles 29, described below, mounted longitudinally parallel to each other in front of this preload chamber, from which compressed air is received and from which the compressed air is discharged. It consists of an elongated air par 12. The air bars 12 are arranged laterally adjacent to each other in an arc substantially defining the turn or curve of the strip around the device 5, and the air drawn from their Coanta-type nozzles 29 ensures that the strip is An air cushion is provided that is supported in a floating manner along the curved portion.

The compressed air is fed into the rear prepressure chamber 10 via a suitable duct 14 which is connected to a compressed air supply referenced 15. When the strip is dried in the device 5,
It will be appreciated that compressed air source 15 typically includes a heater.

The preload chamber 10 has a non-porous end wall surface 17 and a compressed air duct 1.
The rear wall surface 18 is non-porous except for the inlet where the rear wall surface 4 connects, and the rear wall surface 18 is curved into a substantially circular arc extending from one side edge to the other side edge, thereby forming a side wall surface 20. It is also defined by a front wall surface 19 made of a single metal plate. Furthermore, the front wall surface 19 is bent into a partial polygonal shape when viewed from either end of the preload chamber, so as to have a plurality of flat, generally identical rectangular panels 22 in each of which the air pars 12 are attached. meet at an obtuse corner. Each flat panel 22 extends longitudinally between the end walls 17 and has an extension approximately equal to the width of the air parser disposed thereon. Each panel 22 has a number of evenly distributed perforations 23 through which compressed air flows from inside the prepressure chamber 10 into the inside of its air par 12. These perforations 23 can be formed directly in the front wall 19, or each panel of the front wall can have large openings through which extend screens or sheets 231 that define the perforations. In any case, the passage of the compressed air through the perforations 23 provides an even pressure distribution inside the air bar, so that the perforations make the flow more linear.

Each of the air bars 12 is generally similar to the air bars disclosed in U.S. Pat. In this manner, each air par has a pair of flat end walls 25, a pair of elongated side walls 27 which are symmetrically positioned with respect to each other, and a Coanda type nozzle which extends along the entire length of the air par. It consists of a front wall surface 28 that cooperates with a side wall surface 27 to define a pair of slot-shaped air outlets 29 that constitute a. When using a standard air bar, the end wall 17 of each air par lies flat and inwardly adjacent to the end wall 17 of each preload chamber, said end wall being adjacent to its front wall as described below. 19, or the side wall surface 27 and front wall surface 28 of each air bar can extend all the way to the end wall surface 17 of the preload chamber, which wall also serves as the end wall surface of the air par. Become. The front wall surface 28 of each air bar includes a channel member 3 having a hat-shaped cross section.
It forms the center part of 5.

Extending along the rear edge of the side wall surface 27 of each air bar is a panel 2 of the preload chamber on which the air bar is mounted.
a laterally inwardly projecting flange 30 that overlaps flatly with 2;
This flange 30 is fixed to the lower panel by bolts 31 or the like. The side wall surface 27 of each air par is curved at 33 along its entire length to define a ridge projecting outwardly in a V-shaped cross-section spaced therefrom near the leading edge of the side wall surface. A small laterally curved lip 34 extending entirely along the leading edge of the side wall 27 of each air bar cooperates with a channel member 35 of hat-shaped cross section forming the front wall 28. Defining the outlet 29 of the adjacent Coanda type nozzle. Each lip 34 is offset a small distance rearwardly from the flat, forward-facing wall of the front wall 28 of the air bar. Channel members 35 of cap-shaped cross section join the front wall surface 28 at opposite rearwardly projecting rounded corners 37, for cooperating with the lip 34 in defining the outlet 29 of the Coanda-type nozzle. having opposite rearwardly projecting legs 36 from each of which extend laterally to receive a flange 38 in a groove defined by a V-shaped curve 33 in the side wall of the adjacent air bar. Project outward in the direction. The outer edge of each flange 38 is spot welded to the side wall surface 27 of an adjacent air par at intervals along its entire length.

Closely spaced apertures 39 along each flange 38 allow compressed air to enter the flange 38 from the interior of the air bar and from the sides of the adjacent leg 38 of the channel member and its adjacent air bar. It is allowed to flow out from the slot 29 of the Coanda type nozzle through the space between the wall surface 27 and the coanda type nozzle. The lip 34, in conjunction with a curved surface 37, extends away from the nozzle from the slot 29 in a diagonal direction laterally inwardly across the front wall surface 28 of the air bar and in a planar direction toward the strip. It has the known function of creating a flowing air stream. When colliding with the strip, each nozzle 2
The flow exiting from the air outlet 9 splits, a portion of which flows laterally inwardly under the strip in convergent relationship aligned with components of the flow from other air outlets 29 of the air par, and other portions of the air Flows laterally away from the bar.

In some cases, the outlet 4 of the front wall surface 28 of the air parser at regular intervals along its entire length intermediate between the outlet slots 29
1, the air flow converging across the front wall surface 28 through said slot 7 as shown in FIG. 2 and according to the principles described in U.S. Pat. Accordingly, air can flow into the tubular exhaust chamber 42 in the front part of the par. In such a case, the rearwardly extending channel member legs 36
An exhaust chamber 42 is defined by a plate 43 that cooperates with the front wall surface 28 and spans the leg portion 36, and the end wall surface 25 of the air par is an opening through which the tubular exhaust chamber 42 communicates with the atmosphere at both ends thereof. has. The outlet section 41 and its associated exhaust chamber 42 and its vents are of course intended to increase the flow of air in contact with the strip and to ensure that the device 5 is reliable in order to perform critical strip drying. Particularly desirable. opening 4
1 may be omitted (as in the embodiment shown in FIG. 5), although this may prove to be a concern if the device is intended to function solely or primarily as a pivot guide. Alternatively, if not used, the plate 43 can be omitted from each air parlor or replaced by a support column, with the end wall 25 of the air parlage completely closing off its ends.

The flat front wall surface 28 of the air bar lies substantially on an arc of a certain area defining the path of the strip as it moves around the device 5. The angle between the front walls 18 of adjacent air bars is related to the radius of curvature of this strip and should, of course, be uniform between the air bars around the perimeter of the assembly. Each degree between the front wall surfaces 28 of adjacent air bars is approximately 20 to 30 degrees.
Good results have been achieved at strip tensions in the range of about 0.5 to 2.0 PLl and strip curvature radii of about 9 to 12 inches. With such parameters, the strip material undergoes a change in the amount of wrapping around the device 5 corresponding to the amount of oscillation of the extensions 8, 9 over an angle of up to approximately 10° (FIG. 1). Even if there was no contact with the device.

Adjacent air bars are at an angle to each other so that a gap exists between them, which gap is filled by a plate 44, each of which bridges the gap between a pair of adjacent air bars and extends over its entire length. . Each plate 44 is placed on the protrusion (formed by the curved portion 33) on the adjacent side wall surface 27 of the air par which it bridges, and is temporarily attached thereto. Thus, the several plates 44 are generally arranged on an arc of relatively small radius but concentric with the front wall surface 28 of the several air pars.

As previously mentioned, a portion of the air flow exiting each outlet slot 29 is deflected away from the air par to side 13 after impacting the strip, thus reducing the gap between the strip and plate 44. flow inside. The front edge of each end wall surface 17 of the preload chamber is curved relative to the circular arc, and on this arc, the outermost part of the end wall surface of the preload chamber in the radial direction protrudes forward from the filter plate 44. The front wall 28 of the air par is generally positioned to act as a fixed air dam 117 along which longitudinally outward air flow is restrained. For manufacturing convenience, the air dams 117 constitute individual plates 17' fixed against the end wall 17 of each preload chamber, which overlap flat outwards as best seen in FIG. I can do it. Each filler plate 44' cooperates with the air dam 117 fixed in this way to provide an air cushion in the space in front of said plate so that the strip is maintained with a uniform curvature over the entire circumference of the device. The goal is to maintain the

If the said gaps between the air bars are left open by omitting the filler plate 44, the strip will tend to have straight flat extensions between adjacent air bars, so that Unless substantially higher pressure values are used than would be required if plate 44 were incorporated, there would be resistance to air par. Thus, plate 44 may be omitted if a relatively high air flow rate in contact with the strip is required for drying the strip, and if relatively high air pressure requirements are acceptable. I can do it. If, on the other hand, the plate 44 were to be moved forward from the position shown, so that said plate would be of more or less the same radius as the front wall 28 of the air par, then the smooth curvature of the strip around the device would be The aim is to reduce the pressure required to maintain and correspondingly reduce the flow rate of air contacting the strip.

To minimize edge sway of the strip, there is an adjustable air dam 45 adjacent the outside of each edge of the strip to direct airflow from behind the strip to the outside. limit. The two adjustable air dams 45 are movable toward and away from each other to accommodate strips of different widths. Each adjustable air dam 45 includes a plate 46 curved into an arc so that the plate can closely overlap the front wall surface 28 of all air bars of the device. Extending along the inner edge of each plate 46 adjacent to and parallel to a portion of the strip is a radially outwardly projecting flange 47 forming the body of the air dam. The flange 47 extends from the front wall 28 of the air par a distance at least equal to the normal maximum clearance of the strip, typically about 6.35 to 19.1 mm (0
．． 25 to 0.75 inches) project radially outwardly beyond its plate 46. The air dams are each approximately 6.35 to 19.1 mm (0.05 mm) from the adjacent edge of the strip.
．． 25 to 0.75 inches) was found to be most effective.

Adjustable air dams 45 prevent significant wastage of compressed air when the width of the strip being dried is substantially less than the length of the air bar of the device, but this is due to the curved plates of these air dams. 46 overlaps with the then unused ends of the outlet slots 29 of the air par, so that the air flow from each such slot is not substantially more than sufficient to impinge upon the entire width of the strip. It is. curved plate 46
need not be sealingly engaged with the unused portion of the outlet slot of the air bar, and if it overlaps with the front wall of the air bar, any waste of compressed air from the unused portion of the slot will be eliminated. This will reduce the outflow to the point where it can be ignored. Each curved portion 46 also cooperates with its adjacent fixed air dam 117 to define a pocket for capturing compressed air in a space located forward of the plate 44 but outside each edge of the strip. It will become clear.

The device 5 of the present invention is constructed according to FIG.
Tests have confirmed that it attempts to maintain the strip at the desired gap distance from the front wall surface 28 of the air bar even when the tension in the strip varies considerably. The stability of the gap in this band depends on the preferred relationship between the gap distance and the pressure of the air cushion between the band and the front wall 28.

If no changes in compressed air are directed against the air bar, a small increase in the gap distance of the strip will result in a rapid relatively large increase in the pressure of the air cushion, and a small increase in the gap distance will result in an immediate increase in the cushion pressure. resulting in a substantial decrease in The apparatus attempts to maintain a state of equilibrium between the air cushioning force of the radially external force on the strip and the radially inward acting force component of the tension in the strip. If the tension in the band increases and this equilibrium is reversed in the direction of decreasing the gap distance in the band, the resulting rapid increase in the pressure of the air cushion below the band will result in a decrease in the gap distance. is small enough to retain the strip without making sufficient contact with the surface of the device 5. This corrective action is
This occurs automatically without the need for changes in the compressed air source or any other operating variables. Thus, in the case of certain conventional pivot guides, "the impossibly fine tension control required..." (U.S. Pat. No. 4,218,8
The problem of No. 33) is avoided by the device of the present invention.

The device 5 of the invention may be partially enclosed within an exhaust hood or the like (not shown), thereby allowing to blow away the air entrained with the steam brought into contact with the strip. It should be obvious. It is also possible to thoroughly dry the strip by sequentially feeding the strip over two or more devices 5 of the invention arranged to feed the strip through the bend first in one direction and then in the other direction. It should be clear that it can be done. Furthermore, the device 5 may blow a stream of dry air against the front surface of the strip at the bend in any suitable manner in order to provide a sufficient supporting force against the concave rear surface of the strip. I can do it.

Comparing the description with the drawings, the present invention provides a simple, inexpensive and highly effective method by which a longitudinally moving strip is supported in a floating state while being guided along a bend. It is clear that the invention provides a strip drying device. The apparatus of the invention accommodates strips of different widths under different longitudinal tensions and provides sufficient heat for rapid drying of the strips with a moderate air flow rate. It will be seen that transmission is ensured.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one type of strip drying device in which the apparatus of the present invention can be incorporated; FIG. 2 is a perspective view of a non-contact strip guide device embodying the principles of the present invention; FIG. 4 is a front view of the device according to the invention on a slightly smaller scale than in FIG. 3, and FIG. 5 is a modification of the device according to the invention in a plane parallel to the end wall surface. It is a partial perspective view which shows an example. 5-7...Drying device, 8,9...Strip material extension, l0
... Precompression chamber, 12 ... Air par, 14 ... Duct, 15 ... Compressed air supply source, 17 ... End wall surface, 18
... Rear wall surface, 19 ... Front wall surface, 20 ... Side wall surface,
22: Rectangular panel, 23... Perforation, 25... End wall surface, 27... Side wall surface, 28...
Front wall surface, 23... Coanda type nozzle, 30... flange, 33... curved part, 34... lip part, 35...
... Channel member, 36 ... Leg part, 37 ... Corner part,
38... Flange, 38... Opening, 41... Outlet part, 42... Exhaust chamber, 43... Plate, 44... Plate,
45...Air dam, 46...Plate, 47...Flange, 117...Air dam. Patent applicant: D.A. R. Grace &
Company agent Patent attorney Heikichi Odashima

Claims (1)

[Claims] 1. An apparatus in which a strip is supported and guided in a suspended state as it moves longitudinally along a bend in a defined path, comprising: A. a plurality of air bars, each elongated, each having: (1) opposing side wall surfaces; (2) a pair of air outlet loss slots disposed between and spaced from the side wall surfaces; a front wall surface having opposite longitudinally extending edges cooperating with said side wall surface in defining an air bar, each of said outlet slots extending the entire length of said air bar; The edges are wide such that each of the outlet slots defines a Coanda-type nozzle for directing compressed air from the interior of the air bar forwardly and laterally across the front wall to other outlet slots. Curved backwards in direction B. Apparatus is provided in which the air bars are supported in longitudinally parallel relation to one another to define a preload chamber extending across the width of the passageway, the front wall of the preload chamber substantially extending from the curved portion. located substantially on a convex arc of a radius defining a pre-pressure chamber, the pre-pressure chamber being in communication with a source of compressed air at its interior and communicating with the interior of each air bar at its rear; C. perpendicular to the longitudinal direction of the air par and arranged adjacent to the ends of the air bar and extending edgewise across the space therebetween so as to extend in the longitudinal direction of the air par; Apparatus characterized in that it is provided with an air dam plate having a surface defining an air dam that restricts the flow of compressed air outwardly from the space. 2. Furthermore, D. in the space between each pair of adjacent air bars, extending laterally from one of said adjacent air bars to the other and extending longitudinally from one of said air dam plates to the other; a second circular arc substantially concentric with the convex arc and having a relatively small radius; An apparatus according to claim 1, characterized in that: 3. Further, (1) each of the opposing sidewall surfaces of each air bar defines a ridge that curves along its length and projects laterally outwardly, and (2) the device 3. The apparatus of claim 2, wherein the air bar is spanned between each adjacent pair of air bars forming a filling plate supported by one of the ridges in each of the air bars. 4. A strip moving longitudinally along a defined path is supported and guided in suspension along an arcuate bend in said path by compressed air acting against a concave back surface of the strip at the bend. A. B. an apparatus defining a source of compressed air and a preload chamber capable of continuous pain; B. defining a plurality of elongated generally flat first front surfaces on the preload chambers, the preload chambers (1) extending longitudinally parallel to each other across the width of the passage; (2) located substantially in an arc of the curved portion; (3) laterally spaced apart from each other at intervals along the arc; C. Apparatus is provided for cooperating with each of said first front surfaces to define a pair of elongate exit slots from the interior of said preload chamber, each said preload chamber extending along opposite longitudinal edges of said surface. D. a Coanda-type nozzle arranged to direct a flow of compressed air extending across said surface and converging diagonally forward and laterally inward; The strip guiding device is provided with a device defining a plurality of elongated substantially planar second front surfaces, each of the second front surfaces having a width equal to that of the pair of first front surfaces. E. extending across a spacing between surfaces, said second surface lying substantially on an arc of a concentric but relatively small radius with said arc of curvature; At each end of each of said second front surfaces there is provided an air dam arrangement defining an air dam surface substantially perpendicular thereto and projecting forwardly therefrom, so that air is directed along said second front surface in the longitudinal direction thereof. A device that is patented to be restricted to flow away from the second front surface. 5. Furthermore, F. a pair of adjustable air dams are provided, each of the air dams: (1) each curved along the length of the arc of the curved portion to tightly overlap the first front surface; a plate having a length extending across all of said outlet slots and having a ridge covering an end of each said outlet slot; (2) at an inner edge of said plate and radially outward of said edge; a flange projecting from the strip to provide an air dam that restricts the flow of compressed air outwardly through the adjacent edges of the strip; G. The air dam is adjustable in a direction parallel to the axis of the inner arc such that the air dam can have its flanges disposed outwardly adjacent to the side edges of the guided strip. 5. The apparatus of claim 4, further comprising means for releasably securing each said air dam in one of a number of selectable positions. 6. Further, (1) each of the first front surface and two adjacent air outlet slots is defined by an air bar; and (2) each of the second front surfaces is laterally adjacent. 5. Device according to claim 4, characterized in that it is defined by plates extending edgewise between the air bars.