US1781389A - Filter discharger - Google Patents

Description

Nov. 11, 1930. c. c. HERITAGE FILTERYDISCHARGER Filed Nov. 30, 1925 I Ever! 702* 6: GZHE'P/TAGE. y Mia Patented Nov. 11, 193@ PATENT @FFICE CLARK C. HERITAGE, OF. BUFFALO, NEW YORK, ASSIGNOR TO NATIONAL ANILINE d: CHEMICAL 00., 1N0, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK FILTER DISGHARGER Application flied November 30, 1925. Serial No. 72,161).

This invention relates to continuous filters and in particular to filters of the drum type. It relates more particularly to a method and means for removing the filter-cake from the filter medium ofa continuous filter of the drum type, especially in the filtration of crystalline material, or material which is pasty when wet. 7

Among the methods in use for removing o filter-cake from the filter-cloth of a drum type of continuous filter, those principally employed comprise blowing the cake from the cloth by means of a gas under pressure, and scraping the cake from-the cloth by means of 5 a scraper or doctor.

In order to release cake from the cloth of the drum type of continuous filters by the former method, the thickness of cake must be greater than a certain minimumestablished by the tendency of the gas used to blow the caketo blow holes through the cake instead of completely disengaging it from the cloth. This necessity as to thickness of cake greatly limits the use of continuous filters, for they must be operated at a slow speed to build up the required thickness of cake, or they must be periodically stopped and cleaned, since the disengagement of the cake only in spots gradually clogs the cloth and prevents further operation without a thorough cleaning. On the other hand, a knife or doctor can not be effectively substituted for the gas, because the nature of the cloth and its fastening prevent a continuous and uniform direct contact with its surface.

I have discovered that if a roll be mounted to ride on the discharge side of the filter drum and the roll be coated with a thin coating of the material to be removed, the cake will naturally cohere to the thin covering carried by the roll rather than adhere to the filter cloth. The excess of cake material so drawn by the roll from the cloth can be removed readily by means of a scraper.

With the use of this discovery the limitations placed upon the filter speed by the removing means is overcome, as it lends itself to the removal of-thin layers of cake. Consequently the field of application for continuous filters is greatly extended.

terial therefrom is the scraper 6.

As illsutrating an embodiment of the invention, reference is made to the accompanying drawing, in which Fig. l is a partial end view of a filter showing the discharger;

Fig. 2 is a side view of the structure shown in Fig. 1, and

Fig. 3 is a detail.

Near each end of the supporting frame 1 for the filter drum 2 is attached a pillow block 3. Pivoted on this block is an arm 4 which carries at its free end the roll 5 and the scraper 6 associated therewith. An extension 7 from the arm carries a weight 8 for causing pressure of the roll against the drum The pressure can be varied by suspending the weight from any one of a number of holes 9 in the extension.

The roll 5 consists of a steel pipe 10 in each end of which trunnions 11 are riveted. The trunnions rotate in the arms 4 and a bolt 12, with an interposed washer 13, holds the roll in place at each end. The pipe is covered with a chemical hose or equivalent fabric 14, and clamps 15 secure the hose to the pipe.

Cooperating with the roll to remove ma- This scraper is L shaped in cross section, one arm 16 contacting the roll 5. Trunnions 17 support the scraper in the arms 4, and a depending ear 18 has a slot 19 therein whereby the scraper can be adjusted relative to the roll 5 and held in adjusted position by means of a bolt 20 which extends through the slot 19 and the arm 4 for the purpose hereinafter described.

In use, the roll is first covered by plasterin or wetting it with the material to be removed thereby forming in efiect a roll whose outer surface comprises said material. During this operation the material becomes puddled and its adhesiveness is apparently increased. The roll is then applied to the filter cake on the drum, the weight 8 is adjusted to give the desired pressure, the scraper is adjusted to scrape material from the roll 5 while leaving discharging roll presses against the cake, the adhesiveness of the puddled cake on the roll draws the cake from the filter cloth. The pivoted mounting of the roll-carrylng arms I permits the roll to yield with the cloth and thus continue in contact with the cake arried by it. The scraper or doctor in turn re- -moves from the roll the cake that has been abstracted from the'cloth.

The action of the roll is distinctly difierent from that of a gas blower, a suction device or a doctor knife, as the principle of operation which underlies the roll action is the greater natural cohesion of the cake to itself than its adhesion to the filter cloth, and not the forcible separation of the cake from the vcloth.

I claim:

1. A method of removing a filter-cake of pasty material from a continuous drum filter which comprises contacting said cake with a moving body of said material, whereby the cake is removed by cohesion with the body of I material. I

2. A method of operating a continuous drum filter for material forming a pasty filter-cake, which comprises passing the drum in contact with material to .be filtered at a speed forming a thin pasty filter-cake, applying to the cake a roll coated with said cake material, thereby abstracting cake material from said drum, and removing from the roll the cake material abstracted from the drum.

3. A method of discharging a continuous drum filter which comprises plastering a roll with material of the kind to be removed from the drum, applying the plastered roll to the cake of material carried on the drum, thereby abstracting said cake from said drum, and

removing from the roll cake material abstracted from the drum, while leaving a coating of said material on said roll.

In testimony whereof I aflix my signature.

CLARK C. HERITAGE.

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