JPH04250040A - Air foil nozzle - Google Patents

Abstract

PURPOSE:To increase the thermal transmission rate of a nozzle pocket part and provide an air foil nozzle which does not allow the flapping motion of a web to occur. CONSTITUTION:This air foil nozzle consists of a main nozzle system 1 which communicates with a hot blast intake duct 7 where hot blast blow-out orifices such as slits 3a, 14b open in the width direction of a web 6, facing the latter 6 and a hot blast discharge groove 13 extended in the width direction of the web 6, facing the web 6 and both ends are open, are alternately arranged. In addition, the nozzle has the cross section, of the hot blast blow-out orifice 14 in the center, which is smaller than the cross section of the hot blast blow-out orifice 3a at both sides.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a paper coater dryer,
This is related to airfoil nozzles in dryers for offset rotary presses, etc., and is used for strip-shaped plastic films, etc.
It can also be applied to a dryer nozzle with a thin plate structure.

0002

2. Description of the Related Art Generally, in an offset rotary press, ink is applied to a web and then dried by passing it through a dryer. The hot air nozzle used in this dryer is an airfoil type, and as shown in FIG. A box 4 is installed, curved surfaces 5 for jet deflection are formed on both sides of the pocket box 4, and the nozzle bodies 1 are alternately arranged above and below the web 6 (staggered arrangement). After the hot air enters the chamber 8 and is rectified through the rectifier plate 9, it is made to collide with the web 6 through the slits 3, 3, becomes a wall jet on the web 6, and is then released through the hot air outlet 10. At that time, the hot air jetted from the slits 3, 3 is caused by the Coanda effect (when the hot air blows out, a low-pressure vortex is created between the hot air and the curved surface 5, and the hot air is bent toward the curved surface 5).
The web 6 is deflected and flows out into the pocket area 11, and the floating of the web 6 is achieved by the dynamic pressure in the collision area 12 from the slit 3 and the static pressure in the pocket area 11.

0003

SUMMARY OF THE INVENTION The above-mentioned prior art has the following problems. When the local heat transfer coefficient of the conventional nozzle is measured, as shown in FIG. 6, the heat transfer at the junction is good, but the heat transfer in the pocket region is significantly worse due to the retention of hot air. As a result, the nozzle average heat transfer coefficient decreases, requiring larger dryers for printing presses.

An object of the present invention is to provide an airfoil nozzle that increases the heat transfer coefficient in this pocket area and that does not cause web flapping.

[0005]

[Means for solving the problem] 1. Multi-row slit groups and circular hole groups are provided in the pocket portion of the nozzle. 2. In order to prevent interference of hot air between the slits or between the slit holes, a groove having an appropriate width and depth in the width direction is provided between the slits or between the slit holes. 3. Provide a step between the slit exit on both sides of the nozzle and the pocket slit exit.

[0006]

[Effect] 1. The pocket portion of the nozzle can be supplemented with slits or holes to improve heat transfer in the pocket area. 2. By providing grooves in the width direction of the nozzle between the slits or circular slit holes, the hot air accumulated in the pocket area can be expelled and the pressure distribution in the web width direction can be maintained evenly, so the sheet runs stably. Furthermore, it is possible to prevent a decrease in heat transfer coefficient due to retention of hot air. 3. By creating a height difference between the slit exits on both sides of the nozzle and the pocket slit exit, the hot air coming out of the slits on both sides is blown out to the center of the nozzle due to the Coanda effect. 4. The slit width (or hole exit diameter) of the nozzle pocket is narrower at the center than at both sides. Therefore, in the central slit portion, the flow velocity at the slit exit (or the flow velocity at the circular hole exit) is less attenuated by the pocket static pressure.

[0007]

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 3. 1 is an overall side view, FIG. 2 is a detailed view of the pocket portion shown in FIG. 1, and FIG. 3 is an enlarged view of the slit 14 and groove 13 of the pocket portion shown in FIG. 2. Note that both ends of the groove 13 of the nozzle pocket portion 4a are open.

In such a device, hot air entering the hot air chamber 8 in the nozzle body 1 passes through the baffle plate 9 and is discharged from the slits 3a on both sides of the nozzle and the slit group 14 of the nozzle pocket 4a. The width of the slit in the nozzle pocket portion 4a is such that the central slit 14b is narrower than the slits 14a on both sides, and the slit 14a is narrower than the slit 3a. Furthermore, the width of the slits 3a on both sides of the nozzle can be adjusted using screws 15 and nuts 16. Furthermore, since the hot air discharged from the slits 3a on both sides is configured such that the slit outlet position is lower than the blowout position of the central slits 14a and 14b, the hot air is jetted onto the heated object 6 due to the Coanda effect. Collision occurs and a high heat transfer coefficient is obtained. Of the hot air discharged from chamber 8,
The material 17 directed toward the inside of the pocket portion 4a enters the groove 13 and is discharged into the dryer from both open ends thereof. On the other hand, the one 18 facing the outside of the pocket portion 4a is
After flowing along the web 6, it is discharged into the dryer through the hot air outlet 10.

In FIG. 2, in the slit group of the nozzle pocket portion 4a, the slit width x on both sides is wider than the slit width y at the center (x>y) to stabilize the sheet running. . The reason for this is that if the width of the center slit is equal to or greater than the width of the slits at both ends, the static pressure peak will appear above the slits by the same number of slits, which will increase the fluttering due to fluctuations in the static pressure of the sheet. It is.

For example, the slit width at both ends is 2 mm, the blowing speed is 60 m/s (at 200° C.), and the slit width at the center is 1 m.
When there are m×2 slits, the heat transfer coefficient is improved by about 30% compared to when there is no central slit. FIG. 4 shows a nozzle pocket portion 4b having a structure different from that of the above embodiment. The structure other than the nozzle pocket portion 4b is the same as that shown in FIGS. 1 to 3.

FIG. 4 shows a nozzle pocket in which the hot air outlet is a circular hole 14, which has the same effect as the embodiment shown in FIGS. 1 to 3.

0012

[Effects of the Invention] The airfoil nozzle according to the present invention has a hot air exhaust groove that is open at both ends, such as a slit that faces the web and opens in the width direction of the web, in the nozzle body that communicates with the hot air intake duct. By alternately installing the hot air outlets and making the cross-sectional area of the hot air outlet in the center smaller than the cross-sectional area of the hot air outlets on both sides, the following effects can be obtained.

[0013] The length of the dryer can be shortened. It is possible to prevent hot air from stagnation in the nozzle pocket, make the pressure distribution uniform in the width direction of the nozzle, and safely float the web.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view along the web traveling direction in an embodiment of the present invention.

FIG. 2 is an enlarged view of the nozzle pocket in FIG. 1.

FIG. 3 is a perspective view of the slit and groove portions in FIG. 2;

FIG. 4 is a perspective view showing another structure of the slit and groove shown in FIG. 3;

FIG. 5 is a sectional view showing a conventional hot air nozzle.

FIG. 6 is a distribution diagram of heat transfer in a conventional hot air nozzle.

[Explanation of symbols]

1 Nozzle body 4a Nozzle pocket part 6. Web 7 Hot air intake duct 3a slit 14 Slit 13 Hot air exhaust groove

Claims (1)

[Claims] Claim 1: A hot air outlet, such as a slit, which faces the web and opens in the width direction of the web, in a nozzle body that communicates with the hot air intake duct, and a hot air outlet that faces the web and extends in the width direction of the web. An airfoil nozzle characterized in that hot air exhaust grooves with open ends are arranged alternately, and the cross-sectional area of the hot air outlet in the center is smaller than the cross-sectional area of the hot air outlets on both sides.