GB2193145A

GB2193145A - Blower for blowing a gaseous treatment medium over a moving web

Info

Publication number: GB2193145A
Application number: GB08708676A
Authority: GB
Inventors: Gerhard Trotscher
Original assignee: Lindauer Dornier GmbH
Current assignee: Lindauer Dornier GmbH
Priority date: 1986-08-01
Filing date: 1987-04-10
Publication date: 1988-02-03
Also published as: JPH0461696B2; JPS6342759A; IT8767626A0; GB2193145B; IT1211221B; DE3626171C1; FR2602156A1; GB8708676D0; FR2602156B1

Abstract

The device has a nozzle box (1), two boxes (1) being respectively arranged above and below the web and transversely to it, and each box (1) having a blast nozzle (2), the medium being supplied to the nozzle box from one end (E). Each nozzle box is subdivided in its longitudinal direction into two separate channels (7,8) one above the other by a partition (4), and the medium for both channels is introduced into them simultaneously at one end (E) of the box. At the other end wall (3) of the box, the two channels (7,8) communicate through a gap (9) in the partition (4). In spite of treatment medium being supplied from only one end (E), the flow distribution obtained for the medium leaving the nozzle (2) in the lower channel (8) is the same as that obtained when medium is supplied from the two sides. The device is used for example to heat material in a sheet stretching machine. <IMAGE>

Description

SPECIFICATION Blower device for blowing a treatment medium over a web of material moving in the longitudinal direction This invention relates to a blower device for blowing a treatment medium over a web of material moving in its longitudinal direction, the blowing being by nozzle boxes arranged above and below the web and transversely to it and having blast nozzles. In such a blower device, a gaseous treatment medium supplied from a blower is normally introduced into the nozzle boxes from the side and blow over ~the surface of the web through nozzle opening which are in the form of slots extending transversely across the width of the web.

Nozzle boxes supplied with the medium from one side have the characteristics that the medium is not blown vertically out of the nozzles, but obliquely, and the speed at which it is blown out is uneven. These characteristics are in most cases very troublesome, especially in that the oblique direction of the blast considerably reduces the transfer of heat. In addition, the obliqueness of the direction of flow may adversely affect the quality of the web of material finally obtained, e.g. by formation of creases. The outflow from the blast nozzles can be improved by the installation of baffles such as corrugated sheets or barriers near the nozzles, but these parts must always be individually adjusted to the particular construction or dimensions of the nozzles.

These arrangements have the further disadvantage that cleaning is more difficult.

In the art of treatment of plastic sheets, ever-increasing standards of accuracy are required for the distribution of velocity of the medium discharged from the nozzles and especially its direction of flow. In addition to the nozzle boxes which are subjected with treatment medium from one side, it is also known to use nozzle boxes supplied with the medium from both sides. Such an arrangement does not require additional parts such as the corrugated sheets or barrier plates to ensure that the medium will be discharged from a nozzle perpendicularly to the web of material and with uniform velocity distribution. In some blower devices, however, such an arrangement is impracticable for various reasons.

It is an object of this invention to provide a blower device in which nozzle boxes are supplied with treatment medium from one side and which nevertheless enable the medium to be blown vertically over the material to be treated without requiring special, individually adjusted parts. Further, the whole blower device should be so readily accessible that nozzles can be easily and quickly cleaned.

According to this invention, there is provided a blower device for blowing a gaseous treatment medium over a web of material moving in its longitudinal direction, the blowing being by nozzle boxes arranged above and below the web and transversely to it, and the boxes having blast nozzles and being supplied with the treatment medium from one side, for example for a sheet stretching machine, wherein each nozzle box is subdivided in its longitudinal direction into two channels disposed one above the other by a partition, the treatment medium being supplied simultaneously to both channels from one end of a nozzle box and the two channels being in communication at the other end of the nozzle box through a gap in the partition.

An exemplary embodiment of the invention is described below with reference to the drawings, in which:~ Figure 1 is a schematic longitudinal section through a nozzle box; and Figure 2 is a cross-section through Fig. 1.

A nozzle box 1 has, as is usual, a top wall, two side walls and a bottom wall. Nozzles 2 in the form of slots are arranged in the bottom wall. It is to be understood that the term "slot nozzle" may also apply to a row of individual nozzles. A partition 4 subdivides the nozzle box 1 in its longitudinal direction into two channels 7 and 8 disposed one above the other. This subdivision is substantially carried out in such a manner that the two channels 7 and 8 are of substantially the same crosssection. The partition 4 is situated at about half the height of the nozzle box 1 and extends from the inlet end E to just short of the opposite end wall 3 of the nozzle box. Since the partition 4 is slightly shorter than the box, a gap 9 remains through which the channels 7 and 8 are in communication.A slightly modified arrangement could be used, in that the partition 4 may be in the form of a perforated plate, at least in the region of the end wall 3, this plate having opening for flow of treatment medium. In that case, the gap 9 may be closable to a greater or less extent, e.g. by means of a slide valve 5, so that a degree of adjustment is possible.

Operation is as follows. At the inlet end E, the treatment medium supplied from a fan (not shown) is uniformly fed into the two channels 7 and 8. Medium introduced into the lower channel 8 can leave through the nozzle 2 in the bottom wall. Medium introduced into the upper channel 7 flows along its whole length and is introduced into the lower channel 8 at the other end by way of the gap 9. This arrangement produces the same effect in the channel 8 as the arrangement mentioned above of blowing treatment medium into the channel from both sides. The medium thus flows from both sides into the channel 8 which contains the nozzle 2. Static pressure in the channel 8 is converted into dynamic pres sure at the nozzles, as is usual, i.e. it is con verted into velocity.It has been found in practice that in a small region near the inlet end E, the direction of flow of the ejected medium is subject to a deviation of about 10 , but over most of the length of the slot on nozzle 2 the medium flows out vertically. The velocity distribution along the nozzle is also satisfactory, varying by only about plus or minus 2%.

The partition 4, which is closed and impermeable to air, may be replaced by a perforated plate, which improves velocity distribution, and as regard the direction of outflow it was found that in the initial region near the inlet end E the direction of the blast deviated by only 2 or 30 from the vertical.

A further improvement in the direction of outflow may be achieved by inserting a coarse air restrictor in the form of a perforated plate into the inlet opening of the lower nozzle box 8. This enables the ange of outflow of the treatment medium from the nozzle in the front part to be improved to a deviation of 2 to 30 from the vertical.

An adjustable flap 6 may be arranged at the inlet end E of the channels 7 and 8.

Claims

1. A blower device for blowing a gaseous treatment medium over a web of material moving in its longitudinal, direction, the blowing being by nozzle boxes arranged above and below the web and transversely to it, and the boxes having blast nozzles and being supplied with the treatment medium from one side, for example a sheet stretching machine, wherein each nozzle box is subdivided in its longitudinal direction into two channels disposed one above the other by a partition, the treatment medium being supplied simultaneously to both channels from one end of a nozzle box, and the two channels in communication at the other end of the nozzle box through a gap in the partition.

2. A device according to claim 1, wherein the partition is a perforated plate.

3. A device according to claim 1 or claim 1, wherein the gap in the partition is closable.

4. A device according to any preceding claim, wherein adjustable flaps are arranged at the inlet end of the nozzle channels.

5. A blower device in a sheet stretching machine, the device being constructed and arranged substantially and herein described and shown in the drawings.