US2598061A - Filter sheet - Google Patents

Description

May 27, 1952 D. c. KNOWLTON FILTER SHEET Filed Aug. 5, 1949 WEEK INVENTOR. DAVID C. KNOWLTON BY 6 44mm G MJMQ HIS A'fTORNEY Patented May 27, 1952 UITED STATES ,1;-

TENT OFFICE FILTER SHEET Application August 3, 1949, Serial No. 108,326

6 Claims. 1

This invention relates to a filter sheet provided with deformed portions to make it stretchable longitudinally and transversely, and a filter press having filter sheets of this construction interposed between the recessed plates.

In chamber filter presses with filter sheets disposed between the recessed plates, cloth filter sheets have heretofore been generally used as they have the ability to stretch to a limited extent when forced into the recesses of the recessed plates. However, too great a strain is often exerted upon the cloth where the amount of solids to be separated from the liquid is large, and hence fiush plates are then frequently used with distance or spacing frames inserted between the fiush plates. Paper filter sheets have been used to a limited extent and usually in conjunction with the cloth in those instances where paper sheets have been used. Paper sheets have not been adapted to be used alone because of their inability to stretch longitudinally and transversely, and, therefore, are not strong enough to stand the strain to which they are subjected. Accordingly, when paper sheets are used in conjunction with cloth sheets, they needed to be placed between the cloth sheets so as to be supported by the cloth sheets and be held in place thereby should the paper sheets break, especially where a loose granular filtering material is confined between the filter sheets. Even should the paper sheets not be torn or ruptured in being stretched, they are, thereby, weakened and impaired as are the cloth filter sheets when subjected to too great a strain. This results even with cloth sheets when, as above pointed out, they are subjected to too great a strain, and thus their use with recessed filter plates is limited to the filtering of liquid containing small quantities of solids.

Cloth is expensive and much time and effort are expended in cleaning, and repairing it, when necessary, for reuse. Therefore, it would be highly desirable to use paper filter sheets so that they could be disposed of and replaced with new ones after they have become clogged with accumulated precipitated solids. Accordingly, the paper, in accordance with my invention, is provided with longitudinal and transverse deformed portions, such as crepes or corrugations, for permitting it to be stretched transversely and longitudinally. The extent of the stretch can thus be controlled, and the filter sheets can be constructed to have the necessary stretch to which they will be subjected by reasorf of the recesses in the plates in the filtering operation.

One of the principal objects of my invention is to provide a felted filter sheet which is stretchable longitudinally and transversely.

Another object of the invention is to provide a filter paper suitable for use in a recessed plate filter pressso that it can be disposed of rather than cleaned for reuse.

Another object of the invention is to provide a filter paper which may be used alone with the recessed plates in a filter press.

Another object of the invention is to provide paper sheets for being interposed between the recessed plates of a filter press and be sufiiciently stretchable to conform to the recesses in said recessed plates.

Further objects and objects relating to the details of construction and economies of operation will definitely appear from the detailed description to follow. In one instance I have accomplished the objects of my invention by the device and means set forth in the following specification. My invention is clearly defined and pointed out in the appended claims. Filter sheet structure constituting preferred embodiments of my invention and for carrying out the invention is illustrated in the accompanying drawings forming apart of this specification, in which:

Fig. 1, is a longitudinal cross sectional view of a portion of a filter chamber press, with the recessed plates, equipped with filter sheets embodying my invention.

Fig. 2 is a perspective view of an embodiment of a paper filter sheet embodying my invention.

Fig. 3 is a perspective view of another embodiment of a paper filter sheet embodying my inven-' tion.

Referring specifically to the drawings in which like numerals are used to designate like parts, numeral 2 refers to one of two opposite end plates between which any number of recessed plates 3 are secured with filter sheets 4 interposed between the plates. The end plate is recessed at 5 on the side next to the adjacent recessed plate 3, and each of the plates 3 is recessed on opposite sides with a recess 6, like recess 5, in the inner side of the end plates. The recesses in the end and intermediate plates are bounded by surrounding fianges I which abut when the plates are clamped together to enclose the recesses.

The filter press is of the general type of construction shown and described on pages 345 to 348 of Principles of Chemical Engineering by Walker, Lewis and McAdams (second edition) which was published by McGraw-Hill Book Company, Inc. Reference is made to this publication for incorporation herein as a part of the disclosure for showing chamber filter press constructions with the recessed plates between which filter sheets 4 of the present invention are placed.

. Two filter sheets are placed between the adjacent recessed plates. One sheet 4a, covers the single recess 5 in the end plate, and then the recesses B on opposite sides of the intermediate plates are covered by sheet 4b which is long enough to have an intermediate part draped over the top of an intermediate plate'with the free endsof the sheet extending downwardly over the opposite faces of the recessed plates to be clamped between the adjacent recessed plates.

Each plate is provided with a hole in one corner to register and be in alignment for forming a longitudinal channel 8 through which material to be filtered is flowed between the adjacent re cessed plates and filter sheets to pass through the filter sheets, and a mass of granular material 9 which may, if desired, be contained between the filter sheets, to flow down the bottom walls of the recesses, usually provided with channels, to be discharged out through petcocks in in the bottom of each of the plates.

In the filtering operation, the filter sheets are stretched into the recesses 5' and 6 within the recessed plates, and heretofore only a cloth or textile sheet could be used since it could stand a limited strain. Paper andsuchfeltedmaterial has not been suitable because it could not stand even the limited strain required. Under the conditions in the filtering operation, as noted above, a too great a strain is exerted even upon cloth sheets, and it has been the practice to use flush plates with distance frames interposed, rather than recessed plates, when a large amount of solids needed to be filteredfrom the liquid.

In order to give the filter sheets the ability to stretch in both lateral directionsand prevent tensile strain upon them, they are provided with deformed portions to increase their area. These deformed portions may be crepes ll (Fig. 2) or corrugations i2 (Fig. 3), the erepes or corrugations being arranged-so that there is an increased area surface bothlongitudina-lly and transversely, thereby making provisionfor the paper to be stretched in either or both later-a1 directions without subjecting it to undue strain. There is no tensile strain upon the paper until after the deformed portions have beenstretched to a substantially fiat condition, and thus the deformed portions can be made to give a predetermined stretch and have the paper fiat when it has-been subjected to maximum stretch for conforming to the walls of the recesses. The invention is not limited to any particular shape or arrangement of the crepes or corrugations, and they may be of any size and arrangement and-in regular or irregular pattern or design. Howevenin whatever form or size they are made, they will-besufficient to provide for the necessary stretch'for the paper to conform to the recesses in the recessed plates before being flattened-out. Accordingly, filtersheets so constructed can be stretchedwith out being subjected to'tensile strain thatwould impair their strength and structure. The deformed portions are pressed from the general plane of the sheetto lie in a'plane outside of said general plane. Y

The operation of the filter press with the recessed plates is fully described in the above referred to publication, and'the operationof a filter equipped with the filtersheets as described in the instant case is'ex'actlythe same as when cloth filter sheets are used. The cloth sheets, heretofore, used permitted limited stretch in opposite directions because of the stretchability of the fibers comprising the cloth or the woven structure of the cloth. The cl'oth has not, however,

been provided with deformed portions, such as crinkles, embossments, corrugations and the like which are provided in the filter sheets of the present invention, thereby making paper suitable for use as filter sheets with the recessed filter plates.

The ore es and corrugations may be formed in various ways, and the invention is not limited to any particular way of forming them so long as they are angularly disposed to each other to give stretch horizontally in opposite linear directions. They may be angularly disposed to each other and arranged diagonally rather than lengthwise and crosswise of the sheet. For example, the corrugations may be disposed at right angles to each other as in Fig. 3 but arranged at a 45 angle to the direction of the sheet in being corrugated. Then, too, the sheet may be creped in one direction and corrugated in the other direction rather than be corrugated in both directions as illustrated in Fig. 2. These are suggestions of some variations which may be made in carrying out my invention.

I am aware that the structure herein shown is susceptible of considerable variation and that there may be wide variation in making the deformed portions of the filter sheet without departing from the spirit of my invention and, therefore, I have claimed my invention broadly as indicated in the appended claims.

Having thus described my invention, what I claim as new and useful, and desire to secure by United States Letters Patent, is:

1. In combination with recessed plates of a filter press in which the recesses of the plates are formed by the bottom wall surface in a plane below the face of the surrounding abutting wall on said plates, a felted filter sheet interposed between adjacent plates and bridging the recesses, said filter sheet having portions pressed from its general plane to lie in a plane outside of the general plane for rendering said sheet transversely and longitudinally stretchable.

2. The combination of claim 1 in which the pressed portions are angularly disposed to each other.

3. The combination of claim 1 in which there is at least one filter sheet adjacent each of the recessed plates.

i. The combination of claim 1 in which the pressed portions are transversely and longitudinally disposed.

5. The combination of claim 2 in which pressed portions are transversely and longitudinally disposed.

6. The combination of claim 2 in which there is at least one filter sheet adjacent each of the recessed plates.

DAVID C. KNOWLTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 235,698 Newton Dec. 31, 1880 1,175,001 Mangelsdorff Mar. 14, 1916 1,785,494 Revel Dec. 16, 1930 1,796,794 Koppelman Mar. 17, 1931 2,019,903 Heitmann Novy5, 1935 2,245,014 Sherman June 10, 19 2,298,980 Sloan et a1 0017.13, 1942 2,375,246 Kasten May' 8,1945

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