JPS5844945B2 - Air column device that supports floating continuous moving strips - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air column device for floatingly supporting a strip, particularly a continuous moving strip, without contact therewith.

The present invention is patent No. 101565, which is an earlier application filed by the applicant of the present invention.
Concerning improvement of No. 7.

The patent relates to an air column device for floating a continuous moving strip, e.g. a flat plate disposed proximate the supported strip with longitudinally extending and spaced curved edges along each of the edges; a pair of air supply nozzles extending lengthwise to form opposed Coanda nozzles for directing a flow of pressurized air toward the strip, with at least a portion of the flow of pressurized air directed toward the center of the strip; The direction indicates a type of air column device designed to allow the direction of flow to be changed.

The fact that the airflow emitted from a nozzle is directed along a curved plate is called the Coanda phenomenon or Coanda effect, and a nozzle that produces this effect is called a Coanda nozzle.

This patent is particularly effectively utilized for drying a strip, in which a high temperature and turbulent air flow is formed between the lower surface of the strip and the plate, but the method is effective in drying the strip at both ends in the width direction (both nozzles). Regarding the point that the air pressure tends to be high at the center of the board in the width direction and low at the center of the board in the width direction, obtaining a uniform supporting force,
and there were some problems in obtaining large airflow and therefore high drying power.

The present invention aims to improve the above-mentioned type of air column device and solve the above-mentioned problems.According to the present invention, in the above-mentioned type of air column device, a an exhaust chamber is formed in the plate, an exhaust passage is formed through the plate approximately at the center of the plate and communicates with the exhaust chamber, and at least a portion of the airflow discharged from the pair of air supply nozzles is provided at the center of the plate. The gases merge and are exhausted into the exhaust chamber through the exhaust passage.

According to the present invention, a decrease in air pressure at the center in the width direction of the plate is prevented, and uniform supporting force can be obtained.

The amount of air supplied from the air supply nozzle can be increased, and therefore high drying power can be obtained when used as a drying device.

The invention will become more apparent from the following description, which refers to the accompanying drawings, which illustrate preferred embodiments thereof.

The high speed web dryer shown as an embodiment of the invention comprises a housing H made of sheet metal and having a front side 1, a rear side 2, a web inlet side 3, a web discharge side 4, and also a bottom 5 and a top 6. .

A strip inlet 11 is provided on the input side 3 of the housing H, and a strip outlet 12 is provided on the discharge side 4 opposite the inlet side.

Exhaust ducts 1-14 extend from the rear side 2 of the housing and communicate with the interior of the housing to continuously exhaust air from the housing.

An upper air column device and supply duct combination UA is provided in the housing, and a pair of duct devices 33, 34 are tapered toward one lengthwise end (discharge side in this case) and have a substantially rectangular cross section. including.

A plurality of hollow tubular air column devices B extend transversely to the direction of movement of the strip in the housing, and duct devices 33, 34
and is in fluid communication with it.

Similarly, the lower air column arrangement and supply duct combination LA
is provided within the housing and includes a plurality of laterally extending air column devices B and a longitudinally extending duct device 43,44 in communication therewith.

An air supply fan F is positioned within the housing and is connected to the duct arrangement 33.3 via the supply duct arrangement 40, 41.42.
4 and 43.44.

Fan F has an air inlet 50 located on one side of the upper and lower air column arrangement and supply duct combination to act to draw return air back to fan F for circulation through the duct system.

A portion of the return air is also exhausted via exhaust duct 14.

Air column devices, as described in U.S. Pat. No. 3,549,070, are suitable for floating support of sheet materials such as strips or webs, and are particularly suitable as high speed dryers. suitable for use.

To form the air column, air is pressurized as shown in FIG. 5 and is ejected through elongated throwers 1-60.61 which extend continuously along both ends of the air column device.

These slots have curved surfaces 60a, 61 in their vicinity.
In cooperation with a, at least a portion of the air flow is made to flow along a curved surface, producing the so-called Coanda effect.

The plate 63 having a curved surface is named a Coanda plate.

The slots 60, 61 act as air supply nozzles forming Coanda nozzles.

The airflow from a pair of opposed Coanda nozzles is directed toward the longitudinal center of the air column in a direction toward each other as shown in FIG.

Centered longitudinally of the Coanda plate 63 is a series of holes or openings 65 extending along the length of the air column and transverse to the direction of movement of the web W.

U.S. Pat. No. 3,549,070 also shows a central aperture, which is used as a means of supplying high-velocity, pressurized air to the surface 63 of the Coanda plate.
This is to create a turbulent flow condition between the belt and the strip.

However, according to the present invention, an exhaust chamber 70 is formed below the Coanda plate 63, and the chamber 70 extends along the length of the air column, the ends of which are defined by the open lower 2 provided in the end wall 73. It is open (Figure 2).

The chamber 70 forms an internal chamber for taking out the dry air discharged towards the strip by two opposed Coanda nozzles 60, 61, and the chamber 70 is fed by the fan F via the open lower 2, as previously mentioned. Or it communicates with the exhaust duct 14.

The exhaust chamber 70 is formed by a Coanda plate 63 and a lower plate 74 that fits within the downwardly curved edge 76 of the Coanda plate, and the plate 74 is secured to the Coanda plate 63.

As shown in FIG. 5, a series of supports 77 extend laterally to the air column device and precisely support the plates 63, 74 to precisely form the Coanda nozzles 60, 61.

Therefore, the Coanda nozzles 60, 61 are not obstructed by the welds, and a smooth and continuous Coanda flow of dry air is formed along the curved surface of the Coanda plate 63.

The support 77 is welded at both ends to the side wall 78 of the air column device.

An air supply nozzle lower 9 is formed in the bottom 79a of the air column device.

The variation shown in FIG. 6 includes a series of tubular exhaust members 81 extending from the exhaust chamber 70 and exhausting air into the interior of the device.

This variant is particularly suitable for drying wide strips, and has the effect of evening out the tendency for the pressure to be high in the center of the exhaust chamber and low toward the ends.

FIG. 8 shows an enlarged view of the upper part of the air column device, in which a high-velocity air stream 82 exiting from the Coanda nozzle 60 flows along the curved surface of the Coanda plate over a short distance and directly impinges on the strip W. Tend.

When air collides with the strip W at high speed, it penetrates the boundary layer along the strip W and the heat transfer coefficient becomes high.

A portion of this high velocity airflow is then diverted inward to the center of the strip and a portion is diverted in the opposite direction along the strip.

A portion of the air directed toward the center of the strip flows along the surface of the strip as shown by the arrow.

Upon reaching the center of the air column, a portion of this airflow is directed towards the exhaust opening 65.

The other part of the air leaving the supply nozzle 60.61 becomes turbulent between the strip and the Coanda plate 63, and this turbulence
It was found that the flow direction is shown by the vortex line in the figure.

FIG. 6a shows an air column device similar to that shown in FIG. 5, with corresponding parts having the same reference numerals.

The shape of the parts near the air supply nozzle 60, 61 is somewhat different.

As shown in FIG. 9, the pressure due to the air jet is very high at the point 84,85 where the jet stream directly impinges.

The pressure between these points initially decreases considerably and then gradually increases until it reaches the central opening 86.

A significant decrease in pressure indicates that the kinetic energy of the air is high.

FIG. 10 shows a graph in which the vertical axis is the ratio to the pressure discharged from the supply nozzle, and the horizontal axis is the ratio of the area AE of the central exhaust opening of the air column to the sum AO of the areas of the two supply nozzles.

As shown by curve 88, the impingement pressure increases from zero (no exhaust opening) and reaches a maximum at an area ratio of approximately 0.75 to 1.0.

The floating pressure is approximately uniform without appreciably decreasing due to the provision of the exhaust opening.

Point 84.8 where air collides with the strip as shown in Figure 9
The pressure at 5 is high and improves heat transfer when used as a dryer.

As is clear from FIG. 10, it can be seen that although the floating pressure is somewhat reduced by providing a central exhaust opening, the effect of air impinging on the strip is improved without significantly affecting the floating characteristics.

According to the invention, the overall heat transfer coefficient is high and the floating pressure is good.

The air between the strip and the surface of the Coanda plate is dynamic in nature and constantly in motion, so that no quiet or turbulent zones are formed.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a main part of a high-speed strip dryer using an air column of the present invention, a part of which is shown in chain lines, Fig. 2 is a partial cross-sectional view of the dryer of Fig. 1, and Fig. 3 1 is a partial perspective view of the dryer shown in FIG. 1, FIG. 4 is an enlarged end view of the air column device that forms the main part of the dryer shown in FIG. 1, FIG. 5 is a sectional view of FIG. 4, and FIG. Fifth
6a is a cross-sectional view of another modified example, FIG. 7 is a vertical cross-sectional view taken approximately along line 7-1 in FIG. 6, and FIG. 8 is a cross-sectional view of another modified example. 5 is a partially enlarged sectional view, FIG. 9 is a graph showing the air pressure distribution at each position corresponding to FIG. 8, and FIG. 10 is a graph showing changes in collision pressure and floating pressure to show the effect of the central exhaust opening. It is. B... Air column device, W... Band-shaped object, 6
0, 61... Supply nozzle, 65... Center exhaust opening (passage), 63... Plate (Coanda plate), 70... Exhaust chamber, 73 ...End wall, 78...Side wall.

Claims (1)

[Claims] 1 having the shape of an elongated closed tube and including opposed end walls, opposed side walls, and a generally flat plate positioned between the side walls, the plates extending longitudinally and spaced apart from each other. Opposed wafers having curved edges and located proximate to the strip to be supported and extending lengthwise along each of the edges to direct the flow of pressurized air toward the strip. a continuous moving band comprising a pair of air supply nozzles forming a Coanda nozzle, such that at least a portion of the flow of pressurized air is directed toward the center of said plate; In an air column device for floating support, an exhaust chamber is formed inside the air column device and below the plate, an exhaust passage passing through the plate at the center of the plate and communicating with the exhaust chamber is formed; The air column device as described above, wherein at least a part of the air flows discharged from the pair of air supply nozzles merge at the center of the plate and are exhausted into the exhaust chamber through the exhaust passage.