US2746171A - Dryer for powdered material - Google Patents

Description

y 2, 1956 M. T. FLEMING 2,746,171

DRYER FOR POWDEJRED MATERIAL Filed Jan. 8, 1953 3 Sheets-Sheet 1 May 22, 1956 M. T. FLEMING 2,746,171

DRYER FOR POWDERED MATERIAL Filed Jan. 8, 1953 3 Sheets-Sheet 2 May 22, 1956 M. T. FLEMING 2,746,171

DRYER FOR POWDERED MATERIAL Filed Jan. 8, 1953 3 Sheets-Sheet 3 United States DRYER FOR POWDERED MATERIAL Application January 8, 1953, Serial No. 330,289

7 Claims. (Cl. 34233) The present invention relates to new and useful improvements in drying equipment and more particularly to new and useful improvements in equipment for drying a powdered material wherein the powdered material is conveyed through a dryer and has a drying medium passed therethrough.

The most efficient method of drying finely divided powdered material, such as powdered chemicals, is to circulate a drying medium through the material While the material is being conveyed through a dryer housing. Prior to the present invention, it was not possible to dry finely divided powdered material in this manner since there were no conveyors manufactured which had a fine enough mesh to prevent sifting of the material yet permit free circulation of the drying medium. In addition, passing a drying medium such as air through a bed of powdered material produces small eddy currents of air which, in turn, produces a great deal of dust in the dryer housing and prevents the use of this method of drying. A further problem is presented when drying certain types of finely divided chemicals in that the chemicals will react with metals commonly used in dryers, and special metals, such as nickel, must be used for the conveyor and associated parts thereby greatly increasing the cost of the dryer.

With the foregoing in mind, the principal object of the present invention is to provide novel drying apparatus for finely divided powdered materials which will dry materials of this type by circulating a drying medium through the material.

Another object of the present invention is to provide novel drying apparatus wherein the material to be dried is enclosed in an envelope formed of a pair of gas pervious webs which permit free circulation of the drying medium through the material while preventing the escape of the material into the dryer housing. Apparatus of this type permits the use of a conveyor formed of a relatively coarse mesh wire thereby greatly decreasing the initial cost of the dryer.

A further object of the present invention is to provide a novel dryer for powdered chemicals wherein the chemicals conveyed through the dryer are supported on a gas pervious web formed of a disposable material thereby preventing the chemicals from contacting metallic parts of the dryer and also preventing contamination of the chemicals by chemicals which have previously been passed through the dryer.

A still further object of the present invention is to provide a novel drying apparatus having the features and characteristics set forth which is of relatively simplified construction and is entirely eilicient and effective in operation and use.

These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth and described with reference to the accompanying drawings, in which: i

Fig. l is a side elevationalview partially in section of atent 2,746,171 Patented May 22,1956

a dryer made in accordance with the present invention;

Fig. 2 is an enlarged plan view of the feed end of the dryer illustrated in Fig. 1;

Fig. 3 is an enlarged longitudinal sectional view of the feed end of the dryer;

Fig. 4 is an enlarged longitudinal sectional view of the discharge end of the dryer;

Figs. 5 to 7, inclusive, are transverse sectional views taken on corresponding sectional lines of Fig. 3, illustrating the formation of the bottom web of gas pervious material on the bottom web former;

Figs. 8 to 10, inclusive, are transverse sectional views taken on corresponding sectional lines of Fig. 3, illus-' trating the formation of the upper web of gas pervious material on the upper web former; and

Fig. 11 is a transverse sectional View taken on line 11-41, Fig. 1, illustrating the method of enclosing the finely divided powdered material in a gas pervious envelope while the material is being conveyed through the dryer housing.

Referring more specifically to the drawings, and particularly Fig. 1 thereof, a dryer made in accordance with the present invention comprises an enclosed insulated dryer housing 10 through which a conveyor 11 passes. A web l2 of gas pervious material is positioned on the conveyor iii and receives a bed of powdered material M, approximately one inch thick from a feed hopper 13. A second web of gas pervious material 14 is then placed on top of the material to be dried therebycotnpletely enclosing the material in an envelope formed of a pair of gas pervious webs. The webs 12 and 14, and powdered material M are then conveyed through the dryer housing 10 where a drying medium is forced downwardly through the powdered material by means of blowers 15 and a distributor box 16 in order to dry the material.

The conveyor 11 comprises a central portion 17 of woven wire or other foraminous construction supported between a pair of spaced parallel endless chains 18, 18, as illustrated in Fig. 11, and passes over pair of sprockets 21 and 22 mounted on shafts 23 and 24 at the feed and discharge ends, respectively, of the dryer housing 10. Preferably, the shaft 24 at the discharge end of the dryer housing is driven by some suitable drive mechanism (not shown) to pull the upper run of the conveyor through the dryer. During passage through the dryer housing, the upper run of the conveyor is supported on a pair of tracks 25, 25 mounted at opposite sides of the housing and engaged by rollers 26 formed as part of the conveyor chains 18, 18. A plurality of overlapping plates 27 are also mounted on the inner surfaces of the conveyor chains 18, 13, as illustrated in Figs. 2, 3, and 4, to form traveling side guards for the conveyor.

An important feature of the present invention is the provision of the gas pervious web 12 which is positioned entirely across the foraminous central portion 17 of the conveyor 11 and has upturned edge portions inwardly adjacent the conveyor side guards to form a flat U-shaped receptacle to receive and carry the powdered material M. In the illustrated embodiment of the present invention a roll of the web material 12 is mounted on a pedestal 28 beneath the forward end of the dryer and passes upwardly over an idler roll 31 onto a former 32 which folds the side edges of the web 12 upwardly. The former 32, as illustrated in Figs. 2 and 3 comprises a sheet of metal or similar material having a flat downturned forward lip portion 33 and side edge portions 34, 34 which gradually converge inwardly and upwardly to a vertical position, as illustrated, and terminate in spaced parallel relationship. The web 12 is drawn over the former 32 and passes beneath a forming roll 35 which presses the web into the desired cross-sectional configuration.

After the Web 12 has been formed into the desired shape, it is transferred to the feed end of the conveyor 11 and has the powdered material M deposited thereon from the feed hopper 13. An elongated slot 36 is provided in the base of the hopper 13 transversely of the conveyor 12 and a continuously rotating feed screw 37 distributes the powdered material M across the width of the conveyor onto the web 12. The relative speeds of the feed screw and conveyor are adjusted so that a bed of material of the desired thickness is deposited onthe web 12.

Another important feature of the present invention is the provision of the second web 14 which is placed on top of the bed of powdered material before the material enters the dryer housing. As illustrated in Figs. 1 and 3 a roll of the web material 14 is mounted on a support 38 at the feed end of the dryer above the conveyor 11 and passes over an idler roll 41 onto a former 42. The former 42 is constructed similar to the above mentioned former 32 and consists of a sheet of metal or similar material positioned immediately above the conveyor 11 having a flat downturned forward lip portion 43 and side edge portions 44, 44 which gradually converge inwardly and upwardly to a vertical position and terminate in spaced parallel relationship. The web 14 is drawn over the former 42 and passes beneath a forming roll 45 which presses the web into the desired shape. The web 14 is then positioned on top of the bed of powdered material M as illustrated in Fig. 11 with its side edge portions inwardly adjacent the side edge portions of the lower web 12 to form a gas pervious envelope completely enclosing the powdered material before the material enters the dryer housing. If desired, the edges of the webs 12 and 14 may be bent over or interlocked to further prevent the escape of powdered material in the dryer housing. However, the downward flow of drying medium in the dryer housing will normally maintain the upper web 14 in engagement with the powdered material.

The webs 12 and 14 may be any air or gas pervious strip of material in which the size and arrangement of the openings or passages through the material are too small to permit passage of the material being dried yet are sufiicient in size and number to not materially impede or hinder the flow of the drying medium. One class of material that may be used effectively for the webs is the material used as infusers for tea bags and the like which is a bonded material consisting of textile or paper fibers and potentially adhesive fibers, the fibers in the product being bonded as a result of the activation of the potentially adhesive fibers by a solvent or heat. Examples of the potentially adhesive fibers which may be present in the material are cellulose derivative fibers, i. e. cellulose esters and ethers, cellulose acetate and ethyl cellulose being typical, and fibers formed from synthetic resins such as vinyl resins, for instance, a' copolymer of vinyl chloride and vinyl acetate, vinyl'idine resins, nylon type resins and ac-rylate resins such as methyl methacrylate. Advantageously, the potentially adhesive fibers are thermoplastic, i. e. activatible by heat, in which case they should have a softening point higher than the temperature encountered in the use of the Web in the drying apparatus. Likewise, certain loosely constructed standard wet strength papers have been used successfully.

Webs formed of the above-described materials are relatively cheap and maybe disposed of after they are used thereby preventing any of the powdered material from making subsequent passes through the dryer housing and contaminating the rest of the material to be dried. If desired, the webs 12 and 14 may be formed of a fabric and, instead of being wound in roll form, may be endless and thus continuously pass through the dryer housing. Webs of this type will be used when there is no danger of contaminating the material being dried.

With reference to Fig. 4, after the conveyor 11 leaves the discharge end of the dryer housing, the upper web 14 is passed between a pair of friction rolls 46 and 47 and is wound on a spool 48 mounted on a support on the dryer housing above the conveyor 11. The lower web 12 continues passage in a straight line and passes over an idler roll 4-9, causing the powdered material M to drop into a hopper 51 which has a feed screw 52 therein that removes the powdered material and conveys the material to some subsequent treating operation. The lower web 12 then passes between a pair of friction rolls 53 and '54 and is wound onto a spool 55 mounted on a pedestal 56 beneath the discharge end of the conveyor 11.

The pairs of friction rolls 46 and 47 and 53 and 54 should be drivably connected to the discharge end of the conveyor in such a manner that their peripheral speed is equal to the rate of travel of the conveyor. In addition, the spools 43 and 55 on which the webs 14 and 12, respectively, are wound should have a friction drive or a slip drive which would continuously take up any slack in the webs 12 and 14. After the spools 48 and 55 are fully wound, they may be removed from their respective supports and the web material disposed of.

From the foregoing it will be observed that the present invention provides a novel dryer for finely divided powdered material such as powdered chemicals wherein the powdered material is held captive in an envelope formed of a gas pervious material so that a drying medium at a relatively high velocity can be forced through the powdered material in order to dry the same. In addition, the present invention also provides a novel dryer for powdered materials wherein the material may be conveyed through the dryer without contacting any metallic parts of the dryer thereby providing a dryer which is particularly adapted for use in drying chemicals which would react with the metallic materials usually found in dryers.

While particular embodiments of the present invention have been described and illustrated herein, it is not intended to limit the invention to such a disclosure, and changes and modifications may be incorporated and embodied therein within the scope of the following claims.

I claim:

1. In a dryer for powdered material comprising a dryer housing in which a drying medium is circulated, an endless foraminous conveyor having an upper run thereof mounted for passage through the dryer housing, a web of gas pervious material positioned on top of said conveyor upper run, said web having upwardly extending side edge portions at opposite sides of said conveyor to carry a bed of powdered material, a second web of gas pervious ma terial positioned on top of said bed of powdered material and having upwardly extending side edge portions inwardly adjacent the side edge portions of said first web to form an envelope of gas pervious material completely enclosing the bed of powdered material prior to passage of the same through the dryer housing, blower means in said dryer housing operable to force the drying medium through the powdered material, webs and conveyor to dry the powdered material, and means at the discharge end of the dryer housing to remove the powdered material from said webs.

2. In a dryer for powdered material comprising a dryer housing in which a drying medium is circulated, a conveyor having an upper run mounted for passage through the dryer housing, a first web of gas pervious material carried by the upper run' of said conveyor, forming means mounted adjacent the forward end of said conveyor operable to bend the side edge portions of said web upwardly and form a U-shaped receptacle for the powdered material, a second web of gas pervious material positioned on top of said powdered material to form an envelope of gas pervious material completely enclosing the powdered material prior to passage of the same through the dryer hous ing, and blower means in the dryer housing operable to force the drying medium through the powdered material, webs and conveyor to dry the powdered material.

3. In a dryer for powdered material comprising a dryer housing in which a drying medium is circulated, a conveyor having an upper run mounted for passage through the dryer housing, a first web of gas pervious material carried by the upper run of said conveyor, forming means mounted adjacent the forward end of said conveyor operable to bend the side edge portions of said web upwardiy and form a U-shaped receptacle for the powdered material, a second Web of gas pervious material positioned on top of said bed of powdered material, and second forming means mounted above said conveyor to bend the side edge portions of said second web upwardly inwardly adjacent the side edge portions of said first web to form an envelope of gas pervious material completely enclosing the powdered material prior to passage of the sam through the dryer housing.

4. In a dryer for powdered material comprising a dryer housing in which a drying medium is circulated, an endless foraminous conveyor having an upper run mounted for passage through the dryer housing, a first web of gas pervious material carried by the upper run of said conveyor, forming means mounted adjacent the forward end of said conveyor operable to bend the side edge portions of said web upwardly and form a U-shaped receptacle for the powdered material, a feed hopper positioned above said conveyor operable to deposit a uniform bed of powdered material between the upturned edge portions of said web, a second web of gas pervious material positioned on top of said bed of powdered material, second forming means mounted adjacent said feed hopper to bend the side edge portions of said second web upwardly inwardly adjacent the side edge portions of said first web to form an envelope of gas pervious material completely enclosing the powdered material prior to passage of the same through the dryer housing, blower means in said housing to force the drying medium downwardly through the powdered material, webs and conveyor to dry the powdered material, and means at the discharge end of the dryer housing to remove the powdered material from said webs.

5. In a dryer for powdered material comprising a dryer housing in which a drying medium is circulated, an endless foraminous conveyor having an upper run thereof mounted for passage through the dryer housing, a web of gas-pervious material carried by said upper run of the conveyor to carry a bed of powdered material through said dryer housing, said web having its opposite side edge portions disposed angularly relative to the plane of said conveyor, means to deposit the powdered material on said web, a second web of gas-pervious material positioned on top of said bed of powdered material and having side edge portions engaging the side edge portions of said first web to form an envelope of gas-pervious material completely enclosing the bed of powdered material prior to passage of the same through the dryer housing, means engaging the side edge portions of at least one of said webs operable to maintain the side edge portions of said webs in engagement with each other, and blower means in said dryer housing operable to force the drying medium through the powdered material, webs and conveyor to dry the powdered material.

6. A dryer for powdered material as defined in claim 5, wherein the first-mentioned web of gas-pervious material has its opposite side edge portions disposed angularly upward relative to the plane of said conveyor.

7. In a dryer for powdered material comprising a dryer housing in which a drying medium is circulated, an endless foraminous conveyor having an upper run thereof mounted for passage through the dryer housing, a web of gas-pervious material carried by said upper run of the conveyor to carry a bed of powdered material through said dryer housing, means to deposit the powdered material on said web, a second web of gas-pervious material positioned on top of said bed of powdered material, forming means mounted adjacent the forward end of said dryer housing operable to engage and bend the side edge portions of at least one of said webs angularly relative to said conveyor to form an envelope of gas-pervious material completely enclosing the powdered material prior to passage of the same through the dryer housing, means engaging the side edge portions of at least one of said Webs operable to maintain the adjacent side edge portions of said webs in engagement with each other during passage of the same through the dryer housing, and blower means in said dryer housing operable to force the drying medium through the powdered material, webs and conveyor to dry the powdered material.

References Cited in the file of this patent UNITED STATES PATENTS 347,360 Lorimer Aug. 17, 1886 791,029 Johnson May 30, 1905 1,626,041 Kyle et al.. Apr. 26, 1927 1,773,852 Parkes Aug. 26, 1930 1,929,090 Bryant Oct. 3, 1933 2,067,115 Bogaty Jan. 5, 1937 2,152,939 Wentworth Apr. 4, 1939

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