US 3284920 A
Description (OCR text may contain errors)
Nov. 15, 1966 R. HAYRINEN ETAL 3,284,920
APPARATUS FOR DRYING WEB MATERIAL Filed Jan. 21, 1964 mg l -' I m! 8D mum/42m United States Patent Office 3,284,920 APPARATUS FOR DRYING WEB MATERIAL Raimo Ilmari Hiiyrinen and Lauri Jokihaara, Pirkkala, Haikka, Finland, assignors to Valmet y, Helsinki, Finland Filed Jan. 21, 1964, Ser. No. 339,169 3 Claims. (Cl. 34122) In various dryers the moisture content across the width of a web material, e.g., paper web is uneven so that it is greater in the middle portion than at the two edges. E.g., the uneven moisture profile of a paper web impairs some paper technical properties and renders difiicult the aftertreatment of paper. Various apparatuses have been developed for uniformizing the moisture profile. This invention relates to an apparatus of the kind adapted for drying web material, particularly paper web and comprising a hood arranged to extend across the width of the web and divided into sections, blower means for supplying drying medium into said sections and for projecting said medium against the web, e.g., through nozzles or slots, and means for controlling the drying medium amount projected from the said sections against the web. The aforementioned drying medium generally is a mixture of air and steam. By controlling the moisture amounts in the said sections and drying medium it is possible to change the evaporation intensity at different points of the web and thus also to uniformize the moisture profile across the width of the web. In dryers of the stated kind, the control means usually consist of regulating dampers and the like by means of which the amount of drying medium supplied to the sections by pump means has been adjusted. Many disadvantages stem from the fact that the said control means consist of regulating dampers. One of these disadvantages is that the amounts of drying medium admitted to each of the sections cannot be controlled independently of each other, provided a plurality of sections have a blower means in common, for if the amount of drying medium supplied to any one of the sections is decreased the amount of drying medium admitted to the other sections will generally change also. The use of regulating dampers also brings about difiiculties for the reason that the dampers cause clogging, and control in general is difficult to accomplish. Often occurring apparatus-cleaning raises maintenance costs and may deleteriously affect continuous operation. Adjustment by regulating dampers causes losses in output and thus serves to lower the total eiiiciency of the apparatus.
In the apparatus of the instant invention, by section is meant that portion of the apparatus which is in direct connection with only a part of the bottom wall of the means through which the drying medium is projected onto the web. The instant invention has for its object to provide an apparatus without the aforementioned disadvantages for the drying of Web material. The novelty feature of the invention lies in that a blower means is provided in each of the sections of the stated kind of web drying apparatus adapted to project drying medium against the web, the rotation speed of each separate blower means being individually controllable wherefore the drying medium amount projected from each separate section against the Web may be adjusted independently of the other sections. A change in the number of revolutions per minute of a blower means may be brought about so that the rotation speed of the motor is changed and for this reason it is practical to use a reversible motor in the apparatus of the invention. Specifically on using a reversible motor it is also advantageous that the hood is divided into sections so that there are two longitudinally extending halves which are then divided in the transverse direction into sections so that the sections in one of the two halves of the hood are in stepped relation to the sections in the 3,284,920 Patented Nov. 15, 1966 other half of the hood a distance preferably a half of the distance between the oppositely facing wall surfaces of the sections. The invention will now be described more in detail with reference to the accompanying drawing showing an'apparatus embodying the inventon.
In the drawing, FIG. 1 is a top view of the apparatus of the invention for drying web material.
FIG. 2 is a sectional view taken along line IIII of FIG. 1.
The apparatus shown in the drawing includes a hood 1 which partly surrounds a cylinder 2 about which is entrained the web material 3 to be dried, e.g., a paper Web. The bottom wall 4 of the hood 1 is arranged circumferentially with respect to the cylinder 2 and at a spaced distance therefrom so that an interspace 5 is formed between said bottom wall and the cylinder 2. For impinging drying medium against the web the bottom wall 4 is provided with nozzles 6.
The hood 1 is divided into two halves 8a and 8b by partition wall 7 running in the direction of the shaft of the cylinder 2. By means of partition walls 9a and 9b at right angles to the shaft of the cylinder 2 each hood half is respectively divided into sections 10a and 10b so that the sections 10a and 10b in the respective hood halves are in stepped relation to each other a distance which is half the width of the sections in the direction parallel with the shaft of the cylinder 2.
Each of the sections 1011 and 10b has its own blower 11a and 11b, respectively. Each blower is provided with its own motor 12a and 1212, respectively. The motors are adjustable motors whose rotational speed may be changed whereby is also changed the rotational speed of the blowers driven by the motors. Each of the sections has a pressure chamber 13a (respectively 13b) and a suction chamber 14a (respectively 14b). From the pressure chambers air is supplied through the nozzles to the web. The supplied air passes from the interspace between the bottom wall 4 and the web 3 through holes 15 provided between the nozzles and into the suction chamber and thence into the blower. Thus, it is possible to force drying medium against the web to be dried and to suck the same therefrom.
On the pressure side of the blower is provided an exhaust 16 having a regulating damper arranged therein and on the suction side of the blower is provided an orifice 17 having a regulating damper arranged therein for the admittance of fresh drying medium. With the aid of the said means it is possible to admit the requiste amount of fresh drying medium into the apparatus and also to pass out of the apparatus the desired amount of drying medium holding the moisture evaporated from the web. Thus, when preselected revolutions per minute of blower prevails, it is possible to control the moisture content desired for the drying medium to be forced against the web.
Requisite heating of air takes place in the nozzles 6, a steam pipe being joined by welding to the back of the side Walls of said nozzles. Separate heating units may also he employed for heating the air, the heating arrangement being immaterial from the standpoint of this invention.
As has hereinabove been mentioned the transverse moisture profile of the web is uneven. Generally the middle portion of the web is wetter than its edges. For that reason and in order to enable the web to dry evenly, which is of great importance, separate flows of drying medium must be applied over different portions of the width of the paper. When each section in the apparatus of the invention has its own motor-driven blower whose rotational speed may be changed, a change in the amount of drying medium in any separate section will not afiect the drying medium amount flowing through the other section as has heretofore been the case generally. Thus there is provided means for flowing to different points of the web the drying medium amount requisite each time at thatspecific point and the web is dried more uniformly than heretofore. From the afore-descn'bed arrangement it also follows that when the drying medium amount in any section is lowered, also power consumption will decrease which has not been possible at least to the same extent in prior art dryers. An additional advantage stems from the fact that the apparatus of the invention lacks regulating dampers which become soiled and cause clogging. When the 'hood is divided longitudinally into two halves which in turn are divided into transverse sections so that the sections in the respective halves are in stepped relation to each other, there is gained the advantage the the sections may be made longer in the longitudinal direction which is structurally advantageous and still the drying technical advantages corresponding to those in using shorter sections are gained.
It is to be understood that the invention is not limited to the hereinabove described embodiment for the same may be modified in many different ways within the scope and spirit of the invention. So, e.g., eaoh blower need not have its own blower rfior the main rthing is that the apparatus includes a control means, of any kind, as long as it operates to individually change the rotational speed of the blower independently of the others. The sections to both edges of the dryer need not be provided with a blower. A blower must be provided in each section of the kind wherefrom a flow of drying medium must be produced.
What is claimed is:
1. Apparatus for drying web material comprising, in combination, means for feeding a web of a given width in a given direction; a hood having an open outlet end arranged closely adjacent to and facing one surface of the web fed in said given direction, said open outlet end of said hood having a width substantially equal to that of said web and said outlet end extending longitudinally in said given direction; a first partition extending longitudinally through said hood and dividing the latter into two longitudinally extending halves; a plurality of additional partitions arranged spaced from each other in said longitudinally direction and extendling transverse to said first partition and dividing each of said halves in a plurality of sections; and a plurality of blower means each 00- operating with one of said sections for individually blowing a drying medium through the respective section on to said surface of said web while the latter is fed in said given direction, the rotational speed of each of said blower means being individually adjustable so that the amount of drying medium passing through each section on to said web is adjustable independent of the amount passing through the other sections.
2. An apparatus as set forth in claim 1, wherein said additional partitions extending transversely through one half of said hood are staggered with respect to the additional partitions extending transversely through the other half of said hood.
3. An apparatus as set forth in claim 2, wherein said additional partitions in said one half are substantially uniformly spaced in said longitudinal direction [from eaoh other, and wherein said additional partitions in said other half are spaced in said longitudinal direction [from said partitions in said one half a distance substantially equal to half the spacing between said partitions in said one half.
References Cited by the Examiner UNITED STATES PATENTS 3,078,592 2/1963 Coar 34-122 3,110,575 11/1963 Justus 34111 3,167,408 1/1965 Justus et al. 34122 FREDERICK L. MATTESON, JR., Primary Examiner. WILLIAM F. ODEA, Examiner.
B. L. ADAMS, Assistant Examiner.