|Publication number||US3812598 A|
|Publication date||May 28, 1974|
|Filing date||Jan 24, 1973|
|Priority date||Jan 26, 1972|
|Also published as||CA1001405A, CA1001405A1, DE2303503A1|
|Publication number||US 3812598 A, US 3812598A, US-A-3812598, US3812598 A, US3812598A|
|Inventors||Lapierre P, Lefebvre M|
|Original Assignee||Omnium De Prospective Ind Sa|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (15), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1 Lefebvre et al.
[ May 28, 1974 APPARATUS FOR DRYING DAMP WEB MATERIAL Inventors: Michel S. M. Letebvre; Philippe D.
Lapierre, both of Saint-Quentin, France Omnium de Prospective lndustrielle S.A., Neuville Saint-Amand, France Filed: Jan. 24, 1973 Appl. N0.: 326,427
US. Cl. 34/155, 34/156 Int. Cl. F26b 13/00 Field of Search 34/155, 51, 54, 156, 151,
References Cited UNITED STATES PATENTS 7/1963 Morrison et al. 34/68 Eige et al 34/54 Brown 34/156 Daane 34/122 Sutherland et al 34/54 Goodman et al.. 34/155 Daane 34/155 Hamilton et al 34/54 Primary Examinerl(enneth W. Sprague Assistant ExaminerLarry I. Schwartz Attorney, Agent, or Firm-Lewis H. Eslinger, Esq.; Alvin Sinderbrand, Esq.
Apparatus for drying damp web material having a dis- ABSTRACT tribution chamber with inlet and outlet slots through which the material is moved, the chamber having means for receiving compressed gas to which the material is subjected for uniform drying.
10 Claims, 6 Drawing Figures PATENTEUmzs 1974 SL811 2.598
SHEU 1 or 2 APPARATUS FOR DRYING DAMP WEB MATERIAL The present invention relates to a device for drying a web of damp material, i.e. material loaded with liquid or steam.
The problem of drying web material is met with frequently in industry, particularly in the textile industry, for example when it is necessary to decrease the wetness ofa web of fabric leaving a dye bath or, more generally, an apparatus in which it has been subjected to treatment by a liquid or steam.
The same problem exists with strips or yarns, for example warped yarns, so the meaning of the word web in the following text should be defined at this stage. It refers to material which is in the form of a flexible, wide, longitudinally continuous sheet, or of an assembly of longitudinally continuous, narrow strips arranged one beside the other, or of yarns, the width, i.e. the diameter, of which is very small and which are also positioned one beside the other.
Various processes and corresponding apparatus already exist for the pneumatic drying of a web of damp material moving continuously in its own plane. Thus, for example, a table has already been used with which the web moves in contact, holes passing through the said table and forming a large number of orifices connected to a vacuum pump. As it passes over these orifices, the liquid or steam contained in the web is aspirated, this reducing the wetness of the web.
However, such a process is not without disadvantages: in particular its efficiency is very low because the depression is necessarily limited and the energy consumed is badly utilised.
The process consisting of projecting a compressed gas onto the web of damp material is much more efficient and many types of nozzles designed for this treatment have been described.
However, the use of jets of compressed air is not sufficient when the uniform drying of wide webs is required. The apparatus then become more and more complex and less adaptable to the various types of products to be treated.
The present invention is intended to overcome these disadvantages and proposes an efficient apparatus which adapts to the different products to be treated and permits drying of products which are very wide and/or have irregularities. The apparatus for drying a moving web of damp material includes a distribution chamber through which the web to be dried passes and which is adapted to be maintained under pressure, this chamber having means for receiving a compressed gas, for example compressed air, from a calming chamber, and an input and an output passage for the web, each passage consisting of a slot. These slots are of a length of which is substantially equal to the width of the web to be dired and preferably adjustable in order to enable the apparatus to be adapted to the various products to be treated.
The apparatus can also have lateral slots and possibly particular devices for controlling the width of the web.
When the web is very wide, the great width of the apparatus can cause certain elements to bend. Moreover, when the material has irregularities, such as transversal extra thicknesses due for example to seams, auxiliary devices must be provided to correct these defects.
This is the object of a particular embodiment of the invention, in which the distribution chamber is defined by two elements, at least one of which is deformable and is in equilibrium under the influence of on the one hand the pressure in the distribution chamber and on the other hand of an auxiliary balancing force. This force is preferably a counter-pressure applied to the mobile element, for example from an auxiliary gas flow. This gas flow may be constant or otherwise and adjustable or otherwise, depending upon the required working conditions. Furthermore, the apparatus has means for varying the auxiliary balancing force as a function of the pressure in the distribution chamber, for example gasflow transfer channels. The apparatus also has means for locally varying the pressure in the distribution chamber as a function of the local conditions of the gas fed to the said distribution chamber. These means will, for example, be channels creating a charge loss between the feed chamber and the distribution chamber, the latter then having a small cross-section.
A better understanding of the invention will be obtained from, and various secondary features and certain particular advantages will become apparent during the course of, the following description of some embodiments, with reference to the attached drawings in which:
FIG. 1 is a schematic, perspective view with a frontal section of an apparatus in accordance with the invention;
FIGS. 2 and 2a are detailed views showing two modifications of the form of the lips of the chamber slots;
FlG. 3 is a cross-section of the apparatus along the line lll [ll of FIG. 1;
FIG. 4 is a partial section of FIG. 3 in the case of a modification;
FIG. 5 is a particular embodiment of the apparatus of FIG. 1.
If reference is made firstly to FIG. 1, it will be seen that the apparatus includes a lower table 1 on which the web to be dried 2 slides continuously. An elongate, hollow element, designated generally by 3, is arranged above web 2 and has at least one gas inlet 4, for example for compressed air. The interior volume of hollow element 3 is preferably divided into two chambers 7 and 8 by a partition 5 having judiciously distributed orifices 6. Chamber 7, known as the calming chamber, partition 5 and orifices 6 ensure suitable distribution of the gas in chamber 8, in such a way that the pressure prevailing in the latter is as uniform as possible.
lt is obvious that element 3 could be the lower element and element 1 the upper element. Similarly, the lower and upper elements could be identical to element 3, with two drying gas supplies.
Chamber 8, known as the distribution chamber, is defined by element 3 itself and by table 1 and is thus traversed by the web to be dried 2.
Table l and element 3 are substantially equal in length to the width of the web to be dried. The input and output passages for the web consist of elongate slots 9a and 9b, the length of which is also substantially equal to thewidth of the web. The thickness of these slots is adjustable, so that the apparatus can easily be adapted to any product to be dried, whatever its thickness may be. Moreover, this facilitates starting of the equipment. In practice, this means that at least one of elements 1 and 3, or only the lips of the slots, must be mobile perpendicularly tothe plane of the web to be dried. The means for effecting this adjustment in .the thickness of the slots can be various and are in any case very simple. It is not, therefore, necessary to describe them here.
These slots can be closed at their lateral ends as shown in FIG. 4 or can, on the contrary, be open, as is the case in the embodiment shown in FIG. 3. In this case they are extended along the lateral extremities of hollow element 3 by slots extending in the direction of passage of the web and between which the lateral margins of the web can move.
These lateral extremities can be used to control the thickness of the web to be dried. As shown in FIG. 3, at least one detector 12 of the position of the margin of the web relative to a fixed reference mark can be provided. This detector, arranged adjacent to the transverseal extremity of element 3, can be of any suitable type, for example optical or mechanical. It is so constructed as to emit an output signal which controls the adjustment of a valve 13 arranged in the gas supply 4. The feed pressure of the gas can thus be controlled into chamber 8 so that transversal stretching of the web is constant.
The arrangement shown in FIG. 4 can also be used. In this case there are no slots at the ends of element 3; on the contrary, these extremities are closed and consist, either on table 1 or on element 3, of full portions 14 forming the lateral walls of the distribution chamber and defining guides for the lateral margins of the web. The distribution chamber then has a length slightly smaller than the width of the web to'be dried.
In the particular embodiment of this apparatus for the treatment of irregular and/or very wide materials, shown in FIG. 5, element 3 which includes the dryinggas supply 4 is the lower element. The calming chamber 7 is connected to distribution chamber 8 by conduits 6 playing approximately the same role as the partition with orifices shown in FIG. 1. The dimensions of these conduits are so determined as to cause the appearance of charge losses in the drying-gas flow and their distribution is judiciously selected for there to be a substantiallyuniform pressure in distribution chamber 8, which itself has a small cross-section. Upper element 22 is mobile between stops 27 and 28 on the upper framework 29. It is made of any locally deformable material, for example a thin metal sheet. This element 22 is subjected on its lower surface 30 to the action of the pressure prevailing in distribution chamber 8. For it to be in equilibrium, it is therefore necessary to apply a secondary, auxiliary force to it. Inthe embodiment shown here, this force is a counter-pressure applied to this element 22. For this purpose, this element 22 has a deformable membrane 31 fixed tightly by any suitable means to a portion of its upper surface 32. As this membrane 31 is deformable, it is possible to form a chamber 33 known as the equilibrium chamber between this membrane 31 and surface 32. This chamber 33 communicates with distribution chamber 8 through orifices 34, the purpose of which becomes apparent below and the dimensions, number and distribution of which are selected as a function of the operating condition of the drying apparatus. Chamber 33, itself deformable, is fed with a stream of auxiliary gas, generally compressed air, the pressure and flow-rate of which are sufficiently low not to modify the action of the drying gas on the material to be treated. The supply of auxiliary gas can be made at any point judiciously selected not to impede the mobility of the lamina. The flow rate of this auxiliary gas can be constant or otherwise, depending upon the operating conditions. It can also be adjustable, for example as a function of certain parameters of the drying conditions.
It will be understood that it would be possible to use any other system applying a uniformly distributed auxiliary force to element 22 to maintain it in equilibrium without departing from the scope of the invention.
When element 22 is in equilibrium, the pressure inside equilibrium chamber 33 is then equal to the pressure on the lower surface 30 of element 22 plus the charge losses to which the auxiliary flow has been subl5 ject in conduits 34. The pressure on lower surface 30,
depending essentially on the pressure prevailing in distribution chamber 8, therefore depends upon two factors: the flow rate of the drying gas and the escape sec tion of this gas, i.e. in fact the distance d between element 3 and mobile element 22. To each pressure in equilibrium chamber 33 corresponds an equilibrium position of element 22, and a drying pressure in distribution chamber 8. It is therefore possible to vary the drying pressure in distribution chamber 8 and the equilibrium position of element 22 by varying the equilibrium pressure in the equilibrium chamber. In the particular embodiment described here, it is sufficient for that purpose to vary the flow rate of auxiliary gas, which is a particularly simple means of adapting the apparatus described to any type of material to be dried.
On the other hand, in addition to this possibility of adjusting the mean distance d between element 3 and mobile element 22, the apparatus described here prevents local variation of d without however preventing general variation in this same distance d. A local variation in dwould be caused, for example, by bending of the fixed'element, which bending will appear all the more rapidly as the apparatus is designed to treat very wide materials. A local variation in d causes a local variation in the flow-rate of the drying air. As the cross section of the distribution chamber is small, there follows a local variation in the drying pressure (by variation of the charge losses in conduits 6) and therefore a local variation in the pressure on the lower surface 30 of element 22. The great flexibility of this element 22 enables it to be deformed locally. It thus prevents local variation in d and remains substantially parallel at all points to element 3, whatever the deformation of the latter may be. It acts to some extent as a corrector of local defects.
The above process is only possible because of the localisation of variations in the drying pressure, (localisation due to the small crosssection of the distribution chamber) in conjunction with uniform distribution of the auxiliary balancing force, this distribution permitting the appearance of local lacks of equilibrium and thus the conformation of the two elements.
On the contrary, this apparatus permits general and momentary variation in the distance d'made necessary in the case of generalised defects. In fact, materials having accidental extra thicknesses have often to be treated, in particular the connecting seams of pieces placed end to end. In this case, the distance d must increase and therefore element 22 move very rapidly out of the way of a defect. However, this element 22 must also return to its equilibrium position immediately after passage of a defect to prevent the formation of wide, badly dried areas behind this defect. Conduits 34 which connect equilibrium chamber 33 and distribution chamber 8 enable the pressure in each of them and, therefore, the pressures balancing mobile element 22 to be compared constantly. Thus they enable practically simultaneous variation of the two equilibrium pressures. When a general defect appears and causes a general variation in the pressure in distribution chamber 8, this variation is transmitted to the pressure in the equilibrium chamber and causes displacement of mobile element 22. The reaction of the apparatus is small that is to say it is immediate and it disappears as soon as the defect which has caused it disappears.
Similarly, it would be possible to make the lower element rather than the upper element mobile. All of the features could also be regrouped on a single element or a device could even be produced with two identical elements, each of them having all of the features described. The apparatus is selected according to the material to be treated and the type of defects to be corrected.
The general operation of the apparatus as illustrated in FIGS. 1 to 5 is, then, as follows.
With web 2 moving in the direction indicated by arrows A, inlet 4 is placed in communication with a compressed-gas source. The gas flows through orifices 6 to distribution chamber 8 and, because of the presence of calming chamber 7, its pressure is substantially uniform in chamber 8. Acceleration of the gas is produced under the effect of expansion actually inside the web to be dried and not outside as happens when compressedair jets directed at the web are used. A first drying action is therefore obtained.
Furthermore, the gas escapes through slots 90 and 9b as well as, where applicable, through the end slots and this action completes drying. The pressure at the inlet is controlled so as to obtain the best efficiency. In the zone of slots 9a and 9b mechanical wringing out of the liquid contained in the web has been noted, favoured by the porosity of the latter, which allows vibrations to appear. In fact the gas passes through the web (which, moreover, in the zone of the input slot travels in the opposite direction to the gas current) so that the latter is not permanently applied to the lower lip of the slot.
In addition, in the areas of the two slots, a depression zone is formed due to the presence of the divergent resulting from the form of the slots; this favours evaporation of the liquid, or at least of the water which it may contain.
These two effects are again reinforced by the presence of grooves or baffles 11 in the lips of the slots which favour the appearance both of vibrations and of localised depression zones. Moreover, the presence of these grooves decreases the mechanical friction of the web on the lips, thus facilitating its movement.
The apparatus also enables the width of the web to be controlled and thus facilitates its winding on a takeup roll or, more generally, its subsequent use.
In the case of FIG. 3, an extension effect of the web controlled by the detector 12 has been noted at the lateral extremities of chamber 8.
In the case of FIG. 4, the edges of chamber 8 directly gauge the web.
The large number of alternative constructions of this apparatus enable it to be adapted to any type of product to be treated.
What is claimed is:
1. Apparatus for pneumatically drying a web of porous damp material moving through said apparatus in a predetermined direction, said apparatus comprising first and second frame elements, said first frame element including means for providing a web engaging surface along which the web being dried moves during operation of the apparatus and said second frame element including means cooperating with said web engaging surface for forming an air distribution chamber in said apparatus through which said web moves, and an air supply chamber formed therein in communication with said air distribution chamber for uniformly supplying pressurized air from a source thereof to said distribution chamber; said frame elements being spaced from each other a predetermined distance to define therebetween inlet and outlet slots on opposite sides of said distribution chamber transversely to the direction of movement of said web through the apparatus and through which said web passes, said slots having a height dimension selected to be substantially equal to the thickness of the web being treated, whereby pressurized air supplied to said distribution chamber is forced into the web to escape from said distribution chamber through said slots, thereby to remove liquid from said web.
2. The apparatus as defined in claim 1 wherein said web engaging surface is substantially air-impervious whereby said pressurized air squeezes said web in said distribution chamber forcing liquid out of the web and through said slots as the pressurized air escapes therefrom.
3. The apparatus as defined in claim I wherein said first and second frame elements include substantially superimposed spaced wall portions defining said inlet and outlet slots, at least one of said wall portions having a plurality of grooves formed therein extending transversely of the direction of travel of said web whereby transversely extending baffles are defined in said at least one wall portion.
4. The apparatus as defined in claim 1 wherein said first and second frame elements include opposed wall portions extending generally parallel to the path of travel of said web through the apparatus and on opposite sides thereof, said opposed wall portions being spaced from each other to define auxiliary slots in said apparatus which receive edge portions of said web and permit escape of part of the pressurized air from said distribution chamber.
5. The apparatus as defined in claim 1 wherein said means providing said web engaging surface is mounted in said first frame element for movement with respect to said second frame element in a direction generally perpendicular to the plane of said surface, under the influence of the pressurized air in said distribution chamber; and means for producing an auxiliary balancing force for maintaining said web engaging surface in a predetermined balanced position with respect to said second frame element.
6. The apparatus as defined in claim 5 wherein said means providing said web engaging surface is formed of a flexible material and is locally deformable.
7. The apparatus as defined in claim 5 wherein said means for producing said auxiliary balancing force includes means for regulating said force as a function of the pressure in the distribution chamber.
8. The apparatus as defined in claim wherein said first frame element has an auxiliary air chamber formed therein adapted to be connected to a source of pressurized air and located adjacent said means providing said web engaging surface, and on the opposite side thereof 5 from said surface, whereby the air pressure in said auxiliary chamber produces said balancing force.
9. The apparatus as defined in claim 8 wherein said means providing said web engaging surface has a plurality of apertures therein providing air communication between said auxiliary chamber and said air distribution chamber whereby air in said auxiliary chamber escapes therefrom through said apertures in accordance with the air pressure in said distribution chamber, thereby to vary the pressure in said auxiliary chamber and the balancing foce produced thereby.
10. The apparatus as defined in claim 1 wherein said first frame element has an auxiliary air chamber formed therein opening towards said air distribution chamber and said means providing said web engaging surface comprises a plate formed'of a flexible material movably mounted in said first frame adjacent said auxiliary air chamber for movement towards and away from said second frame element, said auxiliary air chamber being operatively connected to a source of air whereby an auxiliary balancing force is produced on said plate for maintaining said web engaging surface in a predetermined balanced position with respect to said air distribution chamber-under the influence of the air pressure in said air distribution chamber; said plate having a plurality of apertures therein providing air communication between said auxiliary chamber and said air distribution chamber whereby air in said auxiliary chamber escapes therefrom through said apertures in accordance with the air pressure in said distribution chamber, thereby to vary the pressure in said auxiliary chamber and the balancing force produced thereby.
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|International Classification||D06B15/09, D06B15/00, F26B13/10|