EP0607720B1 - Drying apparatus for web-like materials, such as paper - Google Patents

Description

The present invention relates to an apparatus for drying sheet materials such as paper or fabric for example.

Apparatuses for drying sheet materials have already been proposed, essentially comprising a rotary cylinder on which the material to be dried is applied and a heat source exerting a heating action inside the cylinder to dry said material.

These devices in which the heat source could be constituted by steam or by a gas burner mounted in the axis of the rotary cylinder, were generally complicated and, very often, were not satisfactory in terms of speed and drying efficiency.

Furthermore, there is described in document US-A-4 688 335 a drying apparatus corresponding to the preamble of claim 1.

The object of the present invention is to remedy the above drawbacks by proposing a drying apparatus having a special but very simple structure and operating by radiation from the heat source in the immediate vicinity of the rotary cylinder, so that the drying of the material applied on and driven by this cylinder is subjected to particularly rapid and effective drying.

To this end, the subject of the invention is an apparatus for drying sheet materials such as paper for example, and of the type comprising a rotary cylinder on which the material to be dried is applied, and a heat source constituted by a first surface. cylindrical fixed; a second fixed cylindrical surface which is externally concentric with the first, which defines therewith a distribution chamber for a combustible gas and which is made of a fibrous, porous and refractory material through which the combustible gas passes; and a means for igniting the combustible gas over the entire outer periphery of said second surface to heat this second surface to very high temperature and produce radiant heat in the annular space between this second surface and the externally concentric rotary cylinder to the latter, characterized in that the first and the second cylindrical surface form a fixed unitary cylinder comprising a recess extending along a generatrix of this cylinder and through which the burnt gases circulating in the abovementioned annular space are discharged.

According to a preferred embodiment of this device, the aforementioned recess communicates with a window formed in the second cylindrical surface to open into the aforementioned annular space and is closed at its ends by the flanges of the aforementioned fixed cylinder, one of these flanges having orifices facing the recess.

According to yet another preferred embodiment of this device, one of the flanges of the rotary cylinder has a plurality of openings arranged in a crown and capable of coming opposite the aforementioned orifices to allow the exhaust of the burnt gases.

The drying apparatus according to this invention also has in a preferred embodiment the characteristic that on the aforementioned fixed unit cylinder is mounted a flame detector projecting from the second cylindrical surface and opening into the aforementioned annular space.

The means for igniting the combustible gas passes through and projects from the aforementioned second cylindrical surface to produce a flame catching on said surface.

However, other advantages of the invention will appear better in the detailed description which follows and which refers to the appended drawings, given solely by way of example, and in which:

Figure 1 is a very schematic perspective view with cutaway of a drying apparatus according to this invention.

Figure 2 is a sectional view along line II-II of Figure 1.

As can be seen in the figures, an apparatus for drying a sheet material such as paper 1, according to this invention, essentially comprises a rotary cylinder 2 on which the material 1 is applied which can be guided by auxiliary rollers such as 3, as well as a fixed cylinder generally identified at 4 which is housed inside the rotary cylinder 2 and which mainly consists of a first cylindrical surface 5 and a second cylindrical surface 6 externally concentric with the first and defining therewith a chamber 7 for distributing the combustible gas.

In the first cylindrical surface 5 opens at 8 a pipe 9 for the supply of combustible gas. More specifically, the pipe 9 consists of a pipe portion 9b extending along the common axis of the rotary cylinder 2 and the fixed cylinder 4, and is connected to a pipe portion 9a extending radially and communicating with the distribution chamber 7 of the combustible gas which, to be precise, is a mixture of combustible gas and combustion air in a proportion close to the stoichiometry.

10 was shown in FIGS. 1 and 2 a cap secured to the first cylindrical surface 5 and favoring the distribution of the combustible gas leaving at 8, in the distribution chamber 7.

The rotary cylinder 2 is supported and driven in rotation by shafts 11 mounted in bearings 30. As it clearly appears in FIG. 1, one of these shafts 11 is axially traversed by the portion 9b of the gas supply pipe combustible. In other words, one of the shafts 11 rotates around the pipe portion 9b, when the apparatus is in operation to allow the drying of the sheet of paper 1.

The unitary and fixed cylinder 4, constituted by the two cylindrical surfaces 5 and 6 is provided with a recess 12 which is particularly clearly visible in FIG. 2. This recess 12 extends along a generatrix of the cylinder 4 and is for example constituted by a sheet having substantially the shape of a V in cross section and to the wings of which V are connected the concentric cylindrical surfaces 5 and 6.

The recess 12 communicates with a window 13 formed in the second cylindrical surface 6, so as to open into an annular space 14 delimited by the second cylindrical surface 6 and the rotary cylinder 2.

As seen in Figure 1, the recess 12 is closed at its ends by the flanges 15, 16 of the fixed cylinder 4. One 16 of these flanges has holes 17 only in its part opposite the recess 12.

The rotary cylinder 2 also includes flanges identified respectively in 2a and 2b in FIG. 1. One 2b of these flanges has a plurality of openings 18 arranged in a crown and capable of coming opposite the orifices 17 during the rotation of the rotary cylinder 2 with respect to the fixed cylinder 4 formed by two cylindrical surfaces 5 and 6. Thus, as will be explained in detail below, the burnt gases circulating in the annular space 14 and passing through the recess 12 via the window 13 can be removed from the rotary cylinder 2.

According to a preferred embodiment, the window 13 can be obtained by a plate or the like 13a (FIG. 2) partially covering the open side of the V12-shaped recess.

The second cylindrical surface 6 of the fixed cylinder 4 is made of a fibrous material which is refractory and porous, so that the combustible gas distributed in the chamber 7 can pass through said material.

There is shown in 19 in Figure 1 an ignition means forming a kind of candle capable of causing combustion. This means 19 is mounted on and projects from the second cylindrical surface 6, so that the combustible gas passing through said surface will be ignited, and the flame will catch on the entire outer periphery of this cylindrical surface. In other words, the cylindrical surface 6 will be brought to a very high temperature, close to 800 ° C., and thus the heat produced by the flame will radiate in the direction of the rotary cylinder 2, in the annular space 14.

We still see at 20 in FIGS. 1 and 2, a flame detector integral with the fixed cylinder 4 and projecting from the second cylindrical surface 6 to open into the annular space 14.

However, for a better understanding of the invention, the operation and the advantages of the drying apparatus described above will be briefly explained below.

The combustible gas, or rather the gas-air mixture, feeds the device through line 9, while the rotary cylinder 2 on which a sheet of paper 1 is applied, is rotated by any suitable means and not shown.

This gas-air mixture leaving at 8 is distributed in a homogeneous manner, before combustion, in the chamber 7, and it crosses the cylindrical surface 6 which is made of a fibrous, porous and refractory material.

The candle 19 causes the ignition of the gas mixture passing through the cylindrical surface 6, and the flame will thus hang over the entire outer periphery of said surface.

Consequently, the heat produced will radiate in the annular space 14 to allow homogeneous and effective heating of the cylindrical wall constituting the rotary cylinder 2, that is to say rapid and efficient drying of the sheet of paper 1.

The gases burned in the annular space 14 will be evacuated through the window 13, the recess 12, the orifices 17 and the openings 18 communicating with a system (not shown) external to the rotary cylinder 2 and allowing the evacuation of the fumes.

It will be observed here that the system for evacuating the burnt gases constituted by the window 13, the recess 12 and the orifices and openings 17 and 18 will favor, because of its design and its geometry, the acceleration of the speed of entry of the burnt gases into the recess 12 and therefore good circulation of these gases in the annular space 14. In other words, the burnt gases will be somehow sucked through the slot 13 to then flow into the recess 12 before be discharged through the openings 17 and the openings 18.

An apparatus for drying sheet materials has therefore been produced according to the invention which, because of its particular and simple design, makes it possible to obtain homogeneous and controllable temperatures around the periphery of the rotary cylinder, so as to thus allow drying. fast and efficient web materials.

Of course, the invention is in no way limited to the embodiment described and illustrated, which has been given only by way of example.

This is how the rotary cylinder rotation drive system, as well as the smoke evacuation system of this device can be any. Also, the device can include any various insulating means, and the assembly of the constituent elements, namely in particular the assembly of the elements constituting the fixed cylinder inside the rotary cylinder, can also be arbitrary.

Claims (5)

1. Apparatus for the drying of sheet materials such as paper for example and of the type comprising a rotary cylinder (2) onto which the material to be dried (1) is applied and a heat source constituted by a first stationary cylindrical surface (5); a second stationary cylindrical surface (6) which is externally concentric to the first one, which defines with the latter a distribution chamber (7) for a combustible gas and which is of a fibrous, porous and refractory material through which the combustible gas is flowing; and a means (19) for the ignition of the combustible gas over the whole external periphery of the said second surface (6) to heat that second surface to a very high temperature and to produce heat radiating in the annular space (14) comprised between that second surface (6) and the rotary cylinder (2) externally concentric thereto, characterized in that the first and the second cylindrical surfaces (5) and (6) form a unitary stationary cylinder (4) comprising a recess (12) extending along one generating line of this cylinder and through which are discharged the burnt gases circulating in the aforesaid annular space (14).
2. Drying apparatus according to claim 1, characterized in that the aforesaid recess (12) communicates with a window (13) formed in the second cylindrical surface (6) to open into the aforesaid annular space (14) and is closed at its ends by cheeks (15, 16) of the aforesaid stationary cylinder (4), one (16) of these cheeks comprising openings (17) in front of the recess (12).
3. Drying apparatus according to claim 2, characterized in that the rotary cylinder (2) also comprises cheeks (2a, 2b), one (2b) of these cheeks (2a, 2b) of the rotary cylinder comprising a plurality of circumferentially arranged apertures (18) adapted to come in front of the aforesaid openings (17) for the exhaust of the burnt gases.
4. Apparatus according to one of the foregoing claims, characterized in that onto the aforesaid unitary and stationary cylinder (4) is mounted a flame sensor (20) projecting from the second cylindrical surface (6) and opening into the aforesaid annular space (14).
5. Apparatus according to one of the foregoing claims, characterized in that the means (19) for the ignition of the combustible gas extends through and projects from the aforesaid second cylindrical surface (6) to produce a flame clinging to the said surface.

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