US2518582A

US2518582A - Dehydrating apparatus

Info

Publication number: US2518582A
Application number: US704689A
Authority: US
Inventors: Daniel B Vincent
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-10-21
Filing date: 1946-10-21
Publication date: 1950-08-15
Anticipated expiration: 1967-08-15

Description

1950 D. B. VINCENT 2,518,582

DEHYDRATING APPARATUS Filed Oct. 21, 1946 3 Sheets-Sheet 1 Aug. 15, 1950 D. B. VINCENT DEHYDRATING APPARATUS 3 Sheets-Sheet 2 Filed Oct. 21; 1946 W M w 15, 1950 D. WNCENT DEHYDRATING APPARATUS s Sheets-Sheet 3 Filed Oct. 21, 1946 WT MN Patented Aug. 15, 1950 UNITED STATES PATENT OFFICE DEHYDRATING APPARATUS Daniel B. Vincent, Tampa, Fla.

Application October 21, 1946, Serial No. 704,689

16 Claims.

The present invention relates to dehydrating apparatus and aims generally to improve existing dehydrators to more accurately and economically control the dehydration of moistureladen commodities to a desired content.

One of the primary objects of the invention is the provision of an improved apparatus wherein the material to be dehydrated is pneumatically conveyed in a plurality of directions by a current of heated products of combustion and drying air and in which the temperature and volume of the products of combustion and drying air are controlled according to the unspent drying gases before dehydration is completed.

More specifically, the invention aims to provide an improved apparatus for dehydration of forage and like agricultural products in which the final drying step may be variably controlled by the addition of gases of higher or lower temperature according to an intermediate condition of the drying operation so that the material may be more uniformly and accurately dehydrated to a predetermined moisture content than has heretofore been possible.

The apparatus is particularly adaptable to the uniform dehydration of shredded citrus waste material processed to produce a stock feed according to my Patent No. 2,215,944, which material should be dehydrated to a moisture content of approximately percent to'prevent'spoilage.

Previously, in dehydrating such citrus cannery waste material, the material has been shredded and passed through either open-ended drum dryers or through a three-pass conventional type dryer which is sealed at both ends except for the entering and discharge ports. In both of these prior types of dehydration apparatuses no provision is made to determine the quality or moisture content condition of the material until it passes from the exhaust or discharge end. Since citrus cannery waste is widely variable in moisture content and adaptability to dehydration, dehydrators have produced a considerable quantity of moist material as well as over-dried material.

One triple-pass dehydrating apparatus, above referred to, is illustrated and described in the U. S. patent to Gerald D. Arnold No. 1,988,677 of January 22, 1935. Such triple-pass dryer is preferable to the open-ended drying drum but the change in temperature of the drying gases passing through the machine is indicated and controlled by the temperature of the gases and fuel which have already passed through the dryer. Hence, the subsequent regulation of furnace gases, based on finished material, may lead to 2 trouble or undesirable results on other feed than in the intermediate stage of dehydration within the dryer due to the possibility of difierent moisture content or adaptability to dehydration.

The present invention provides apparatus suitable for rapidly and uniformly dehydrating citrus cannery waste and like material which may vary widely as to moisture content as well as adaptability to dehydration.

The above and other aims and objects of the invention will be apparent to persons skilled in the art from a consideration of the accompanying drawings and annexed description illustrating and describing two forms of apparatus embodying the invention.

' In the drawings Fig. 1 is a side elevation of a dehydrating installation suitable for the dehydration of shredded citrus waste stock feed, parts of the apparatus being broken away and shown in section so as better to illustrate the construction;

Fig. 2 is a transverse sectional elevation taken on the line 22 of Fig. l;

Fig. 3 is an enlarged detail central sectional view of the dehydrator shown in Fig. 1;

Fig. 4 is a diagrammatic view of one suitable system of control;

Fig. 5 is an enlarged fragmental sectional view of one end of a dehydrator drum unit according to an alternative form of apparatus; and

Fig. 6 is an end elevation of the drum unit shown in Fig. 5 as taken on the line 66 of Fig. 5.

. The material to be dehydrated is preferably shredded or comminuted to such size and fineness as to be capable of being, at least momentarily, suspended in a pneumatic current established through the dehydrating chamber. In the case of citrus waste stock feed, shredding or comminution of the orange or grapefruit half sections, as they are received from the canneries, is desirable as it permits of chemical treatment and mechanical pressing or dewatering of a substantial quantity of water from the material, thus reducing the moisture content thereof to approximately to percent as taught in my Patent No. 2,215,944, aforesaid. Such comminuted material necessarily comprises a substantial portion of fines, which are more readily dehydrated than the larger pieces and hence are watering, as referred to above, will vary widely as to moisture content. Hence, the material is variable as to initial moisture content and as to size or adaptability to dehydration.

Broadly, the apparatus of the invention comprises means for establishing a current of heated gas of sub-atmospheric pressure to suspend and move material variable in moisture content and adaptability to dehydration, and means for variably controlling the dehydration of the material at an intermediate stage of dehydration in accordance with the temperature of the material and gases at said intermediate stage of dehydration. Preferably, the material is passed through successive irmer, intermediate and outer dehydration chambers or drums and the temperature of the gases and the rate of dehydration is variably controlled, as by admitting previously unused heated gases or cooling air to the outer drying chamber, varying the volume of the products of combustion in accordance with the temperature of the gases and material emerging from an intermediate dehydrating chamber, varying the frequency at which the material is tumbled in the current, and optionally varying the velocity of the current.

According to the invention, the method may be practiced by suitable apparatus comprising a furnace I of conventional construction fired by suitable means subject to variable control, as for example, a fuel oil burner 2 suppiled with fuel oil through pipe 3 and discharging its products of combustion in the furnace I. The rate of flow of oil through pipe 3 to the burner 2 may be controlled by valve 5 which in turn is controlled by a pressure diaphragm control device 4 supplied with air under pressure by line '6, the pressure in which may be regulated by a switch connected to a source of air under pressure M. The intermediate control devices connecting the air lines 6 and M comprise a control valve I and a controlling thermostat l I, therefor, which thermostat is adapted to be positioned within the drying chamber at a selected intermediate zone of dehydration. I

The control valves and thermostat may be of any of the well known types in the art and preferably are arranged to vary the amount of fuel oil flowing to the burner 2 in accordance with temperature requirements affecting the thermostat II. Thus, as the temperature surrounding the thermostat falls and there is a requirement for more heat, an additional volume of fuel is supplied to the burner 2 resulting in an increase in the volume of products of combustion within the furnace to be supplied to the dehydration apparatus.

The products of combustion of the furnace I are delivered through a hot air duct l2 leading to the inlet end of a dehydrating chamber and the material to be dehydrated may be fed to the hot air duct [2 by a spillway or chute I3 supplied by a feeding hopper I4 and air lock l5 as is usual in the art.

The material is discharged from the dehydrating chamber tln'ough a discharge outlet I! leading to a collector l8 having a. discharge outlet l9 at the lower end thereof. The collector is supplied with suction by means of a fan 20 driven by a motor 2| and connected to duct 22 so as to create a material-conveying current of sub-atmospheric pressure through the dehydrating chamber. The dehydrated material passing through the discharge outlet 19 of the collector I8 is conveyed cessive drums providing correspondingly reduced velocities as established by the suction fan. The forms of drying chambers may vary considerably in construction as shown in the annexed drawings.

Referring to Figs. 1 to 3 inclusive, the dehydrating chamber preferably comprises a stationary casing 30 having end walls 3| and 32. R0- tatably mounted within the casing 30 are a series of concentric drums, herein illustrated as comprising an inner drum 33, an intermediate drum 34 and an outer drum 35. The inner drum 33 comprises a tubular casing having end portions extending through the end walls 3| and 32 and having an inlet end 36 surrounding or aligned with the discharge end of the hot air duct 12 as is clearly shown in Fig. 3. The inner faces of the drums 33, 34 and 35 may be provided with inwardly extending radially disposed paddles or shelves 33 34 and 35 adapted to repeatedly tumble the material to be dried by repeatedly lifting and dropping it across the current of hot drying gases as is customary in the art.

The inlet end 36 of the inner drum 33 rotates relative to the stationary hot air duct [2 and a rotary bearing support therefor may be provided by an elongated sleeve 31 surrounding and spaced from the drum 33, the portion of the sleeve 3'! exteriorly of the casing 30 being provided with an annular tire 38 supported in driving rollers 39 by means of which the drum is rotated. The end of the sleeve 37 is provided with a plurality of air inlets 40 and the opposite end, within the drum, is provided with air outlets 4|. Accordingly, a current of air is established between inlet end 36 of the inner drum 33 and the sleeve Which maintains the bearing sleeve 3'! much cooler than the inlet end 36 of the drum 33. The current of air is discharged into the dehydrating chamber, preferably in the intermediate drying stage, but it is heated by contact with the inlet end 36 of drum 33 to substantially the temperature of gas in the intermediate drying chamber and hence is not detrimental to the dehydrating action therein.

The intermediate drum 34 may be an imperforate' cylindrical shell surrounding the inner drum 33 and spaced therefrom by supporting members 34 The drum 34 is preferably of less length than the drum 33 and has an open end 42 and a closed end 42 opposite the inlet 36. The inner drum 33 is preferably provided with an end wall or partition 43 and a series of outlet openlngs 44 providing a passage between the inner drum and intermediate drum 34 for the material being dehydrated.

The open end 42 of the intermediate drum is preferably spaced from the end wall 3| of the casing 30 providing an annular control chamber 0 in which the controlling regulator or thermostat H is positioned, and through which the partially dehydrated material must pass in its traverse to the final dehydrating chamber or drum.

The outer dehydrating chamber or drum advantageously may be in the form of an openended shell 35 of substantially cylindrical or polygonal form surrounding the intermediate drum 34 and spaced therefrom by supporting members The drum or shell 35 is preferably of greater length than the intermediate drum providing an overhanging inlet 45 communicating with the control chamber C and an overhanging outlet 46 communicating with the-discharge chamber D which in turn communicates with the outlet 41 by means of openings 48. The outlet 4'! advantageously may be a continuation of the inner drum 33 beyond the end wall 43 which surrounds and is in communication with the discharge outlet ll leading to the collector [8.

The invention thus provides a series of inner, intermediate and outer dehydrating chambers or zones, which advantageously may be concentric and through which the material flows in a tortuous current. The provision of the control chamber C between the intermediate and outer drying chambers 34 and 35 with the control thermostat therein to vary the volume of products of combustion supplied by the burner 2, makes possible the variation in the temperature in the dehydrator prior to the discharge of the material affecting the control. It is thus possible, by the present invention, to correct in the outer dehydrating chamber unsatisfactory dehydrating conditions, as for example by increasing or decreasing the fuel supply and the volume of prod ucts of combustion, subject to the requirements of an intermediate drying stage, and thus produce a more uniformly dehydrated product notwithstanding variations in the moisture content of the raw material fed to the dehydrator.

In addition to varying the heat supplied to the dehydrator it may also be desirable to increase or decrease the temperature of dehydrating gases in the outer drying chamber 35 irrespective of the temperature of the gases in the inner and intermediate chambers 33 and 34. This may be accomplished by admitting previously unused hot furnace gases or room temperature air directly to the control chamber C for passage solely through the drying chamber. This may be accomplished by providing a by-pass 50 from the hot air duct I2 through the casing end 3| and to the control chamber C, and a control damper 5| therein for by-passing a portion of the hot furnace gases directly into the control chamber C. Thus, if the temperature in the outer dehydrating chamber should be increased, the damper 5: may be opened to by-pass furnace gases directly to the control chamber around the inner and intermediate chamber.

The by-pass 55] is also provided with a dampercontroiled fresh air inlet 54 to admit cooling room temperature air to the chamber C when it is desired to reduce the temperature in the outer dehydrating chamber.

Additionally, it may be desirable to variably control the rate or frequency at which the ma terial is tumbled or dropped across the current or dehydrating gases or to vary the velocity of the current of dehydrating gases or both.

According to the present invention, the rotating dehydrating drums or chambers may be rotated by the rollers 39 driven by the chain and sprocket drive 55 from a driven shaft of a suitable variable speed drive, diagrammatically illustrated at 56 and subject to the manual control of the operator by lever 55 or the automatic control of the thermostat l I. By increasing or reducing the speed of rotation of the drums, the frequency of tumbling or dropping the material across the current of dehydrating gases is correspondingly 6 increased or reduced. The larger and heavier particles of material, which are subjected to the tumbling action of the rotating drums, are thus retained in the dehydrating chambers longer as the speed of rotation is reduced and for a lesser period as the speed of rotation is increased.

The more fiocculent and lighter particles of material are supported by the current of drying gases and the duration of dehydrating treatment thereof may be variably controlled to suit existing conditions by varying the velocity of the gas current through the dehydrator. Advantageously, this ma be accomplished by a regulating damper 5'! in the duct controlled by the fan 20, for example, in the exhaust duct 22. As will be apparent, closing the damper 5'! will reduce the velocity of the gas current through the dehydrator, while opening the damper will increase the velocity thereof.

In practicing the invention, the material to be dehydrated is fed from the hopper l4 and chute I3 to the hot air duct I2 in which it is intermixed with the hot furnace gases supplied by the furnace. The system is a substantially closed one by reason of the air lock l5 at the feeding hopper and the air lock 24 at the sacking machine 25 (except for the cooling air current between the inner drum 33 and supporting sleeve 31 (Figs. 1 to 3)) and hence operation of the suction fan establishes a pneumatic current therethrough. This current passes successively through the initial stage in the inner drum 33, the intermediate stage in the intermediate drum 34, the final stage in the outer drum 35 and thence through discharge outlet l'l, collector I8 and offtake 22, and has successively diminishing velocities in the inner, intermediate and outer drums b reason of their respective increased cross sectional areas. The velocity of the current may be variably contro.led by means of the damper 57 in the offtake 22.

The material passing through the inner drum is repeatedly lifted by the buckets or paddles 33 and tumbled or dropped across the pneumatic current of hot gases, and finally is discharged into the intermediate drum 34 in which it is repeatedly lifted and tumbled or dropped while bein conveyed therethrough toward the control chamber C.

The material reaching the control chamber is, of course, relatively dehydrated subject to such final dehydration as to produce a finished product of desired moisture content. The thermostat in said control chamber may be set to maintain a desired temperature therein for entrance into the final or outer dehydrating drum. Optionally, unused hot gases may be by-passed directly thereto by opening the damper 5| to increase the temperature of the gases within the final drum when desired, or cooling air may be admitted thereto by opening damper-controlled inlet 54 to reduce temperature in the final drying stage.

Variation of the frequency of tumbling the material in the current as well as varying the veloc-- ity of the current also aids materially in the accurate control of dehydration.

The various controls above described, such as the dampers 5|, 54 and 51, as well as the variable speed drive for the dehydrator rotating means, may be manually operated by the operator and such manual operation is preferred. However, in certain instances it is desirable to operate these controls automatically and preferably such operation is in response to temperature conditions existing in the control chamber 0,

Preferably, the automatic operation of the controls is subject to the thermostat II as illustrated in Fig. 4.

As illustrated in Fig. 4, the thermostat II may be one of the many conventional types of thermostat, preferably one provided with an adjustment 62 whereby the valve I may be operated at a desired temperature.

When the thermostatically controlled valve is opened in response to requirement for additional heat in the control chamber, air or fluid under pressure may flow from pressure supply line M to the line 6 and branch lines 6, 6 Ii and 6 The branch line 6 leads to the valve casing 4 and provides pressure to lift the valve 5 and admit an additional flow of oil to line 3 leading to the burner 2.

The branch lines 6*, I5 and Ii lead from the line 6 to such other variable controls as are desired. For example, the lines 6 and 6 may control the dampers 51 and BI, respectively, and for this purpose the increased pressure in these branch lines may operate motors 63 having rack and pinion connections with the dampers to rotate them about their pivotal axes.

Similarly, the line 6 may lead to a pressure operated controlling device '64 connected to the operating lever I54 of the variable speed driving mechanism 56 of the drum rotating mechanism for shifting the control lever 56 to vary the speed of rotation of the roller drive 39.

The invention may also be embodied in a somewhat difierent construction of dehydrator in which the outer drum I35 is equipped with tires I38 rolling on and driven by supporting and driving rollers I39. In such dehydrators the outer drum is necessarily imperforate and closed at both ends as shown in Figs. 5 and 6. In such construction the control chamber C between the intermediate and outer drums includes a stationary closure plate I 60, preferably supported on the hot air duct I2, and surrounding the inlet end I36 of the inner drum I33 and overlying the end flanges I3I of the outer drum I35. The relatively movable surfaces at the joints between the closure I5!) and the drum I35 may be sealed against the inlet of outside air as is usual in the art. This stationary closure plate provides a support for the thermostat I I and one end of the by-pass 50 at the control chamber C.

The end closure I60 conveniently may be supported in position by radial arms I52 on a collar I63 surrounding the hot air duct I2 as shown in Figs. 5 and 6.

The dehydrator shown in Figs. 5 and 6 is designed to be supplied with natural and hot furnace gases supplied and controlled by means shown in Figs. 1 and 4, and the dried material is removed therefrom as shown in Fig. 1.

The invention provides an extremely efficient and economical method for the dehydration of moisture-laden materials, such for example as comminuted citrus pulp, shredded forage crops and the like, where materials having varying moisture content may be rapidly dehydrated to a desired moisture content.

While the invention has been described with reference to two forms of apparatus suitable for practicing the method, it is not limited thereto but is intended for illustrative purposes, and I intend that the invention embody other modifications as defined in the appended claims.

I claim:

1. A dehydrator comprising. concentrically arranged inner, intermediate and outer shells,

means for supplying heated gases to one end of said inner shell, means for establishing a pneumatic current of gases successively through said inner, intermediate and outer shells, said intermediate shell being of less length than the outer shell providing a control chamber therebetween at one end thereof, temperature responsive means positioned in said control chamber and means for by-passing previously unused gases from said supplying means to said control chamber.

2. A dehydrator unit comprising concentric inner, intermediate and outer drums, means mounting said drums in spaced-apart relation, said inner drum having an axial inlet adjacent one end and longitudinally spaced radial openings near the opposite end thereof, a partition between said longitudinal spaced openings dividing said inner drum into an initial dehydrating chamber and a discharge chamber, one of said series of radial openings communicating with the intermediate drum and the other of said series of radial openings communicating with said outer drum, and an end closure for the intermediate drum disposed in a plane intermediate said longitudinally spaced radial openings.

3. A dehydrator unit comprising concentric inner, intermediate and outer drums, means mounting said drums in spaced-apart relation, said inner drum having an axial inlet at one end for intermixed material and hot gases, a tubular member surrounding the inlet end of said inner drum and spaced therefrom, means external of said drums for supporting said tubular member, means for admitting cooling air to the space between the inner drum and tubular member, means for discharging heated air from within the tubular member to the intermediate drum, and means for rotating said unit through said tubular supporting member.

4. A dehydrator comprising concentric inner, intermediate and outer drums, means mounting said drums in spaced-apart relation, said inner drum having an inlet adjacent one end thereof, and an annular chamber surrounding said inlet end of the inner drum and communicating with the intermediate and outer drums, a hot air duct for supplying hot furnace gases to the inlet end of said inner drum, means for establishing a pneumatic current of gases successively through said inner drum, intermediate drum, annular chamber and outer drum, and means for by-passing a portion of said gases around said inner drum and into said' chamber for admission into said outer drum.

5. A dehydrator comprising an outer casing and concentric inner, intermediate and outer drums, means mounting said drums in spacedapart relation, said inner drum having an inlet adjacent one end thereof, an annular chamber surrounding said inlet end of the inner drum and communicating with the intermediate and outer drums, means for establishing a pneumatic current of gases successively through said inner drum, intermediate drum, annular chamber and outer drum, and an opening in said outer casing for admitting cooling air directly into said outer drum.

6. A dehydrator comprising concentrically arranged rotary inner and intermediate drums and an outer drum providing respectively initial, intermediate and final dehydrating zones of progressively increased duration and extent, means forming a passageway connecting said inner and intermediate drums adjacent one end of the dehydrator, means including a fixed closure forming a passageway connecting said intermediate and outer drums at an opposite end of said dehydrator, means for supplying heated gases to one end of said inner drum, means for establishing a pneumatic current of gases successively through said inner, intermediate 3 and outer drums, temperature-responsive means fixedly mounted in the fixed closure and having a portion thereof exposed to the passageway connecting said intermediate and outer drums for contact with material-laden gases passing therethrough from said inner and intermediate drums,

and means actuated by said temperature-responsive means in response to the drying conditions in said passageway to vary the temperature of heated gases throughout said initial, intermediate and final dehydrating zones.

'7. A dehydrator comprising concentrically arranged rotary inner and intermediate drums and a fixed outer casing for said drums providing respectively initial, intermediate and final dehydrating zones of progressively increased duration and extent, means forming passageways connecting said inner and intermediate drums at one end and said intermediate drum and outer casing at an opposite end, means for supplying heated gases and material to be dried to one end of said inner drum, means for establishing a pneumatic current of gases successively through said inner and intermediate drums and said outer casing, temperature-responsive means fixedly mounted in the outer casing and having a portion thereof exposed to the passageway connecting said intermediate and outer drums for contact with material-laden gases passing therethrough from said inner and intermediate drums, and means actuated by said temperature-responsive means in response to the drying conditions in said passageway to vary the temperature of heated gases throughout said initial, intermediate and final dehydrating zones.

8. A dehydrator comprising concentrically arranged rotary inner and intermediate drums and an outer drum providing respectively initial, intermediate and final dehydrating zones of progressively increased duration and extent, a fixed closure for said outer drumv means forming a passageway connecting said inner and intermediate drums adjacent one end of the dehydrator, means including said fixed closure forming a passageway connecting said intermediate and outer drums at an opposite end of said dehydrator, means for supplying heated gases to one end of said inner drum, means for establishing a pneumatic current of gases successively through said inner, iiitermediate and outer drums, temperature-responsive means fixedly mounted in the fixed closure and having a portion thereof exposed to passageway connecting said intermediate and outer drums for contact with material-laden gases passing therethrough from said inner and intermediate drums, and means actuated by said temperature-responsive means in response to the drying conditions in said passageway to vary the temperature of heated ases throughout said initial, intermediate and final dehydrating zones.

9. A dehydrator comprising concentrically arran ed rotary inner and intermediat d um a d fixed outer drum provi ing r sp c ively initiel, intermediate and final dehydrating zones of progressively increased duration and extent, means forming a pa sageway connecting said inner and intermediate drums adjacent one end of the dehydrator, means including a fixed closure forming a passageway connecting said intermediate and outer drums at an opposite end of said dehydrator, means for supplying heated gases to one end of said inner drum, means for establishing a pneumatic current of gases successively through said inner, intermediate and outer drums, temperature-responsive means fixedly mounted in the fixed closure and having a portion thereof exposed to the passageway connecting said intermediate and outer drums for contact with material-laden gases passing therethrough from said inner and intermediate drums, and means actuated by said temperature-responsive means in response to the drying conditions in said passageway to vary the velocity of heated gases throughout said initial, intermediate and final dehydrat 'ing zones.

10. A dehydrator comprising concentrically arranged rotary inner and intermediate drums and a fixed outer drum providing respectively initial, intermediate and final dehydrating zones of progressively increased duration and extent, means forming a passageway connecting said inner and intermediate drums adjacent one end of the dehydrator, means including a fixed closure forming a passageway connecting said intermediate and outer drums at an opposite end of said dehydrator, means for supplying heated gases 'to one end of said inner drum, means for establishing a pneumatic current of gases successively through said inner, intermediate and outer drums, said rotary drums having internal material-lifting means for lifting and dropping material across said current, temperature-responsive means fixedly mounted in the fixed closure and having a portion thereof exposed to the passageway connecting said intermediate and outer drums for contact with material-laden gases passing therethrough from said inner and intermediate drums, and means actuated by said temperature-responsive means in response to the drying conditions in said passageway to vary the rate of lifting and dropping material across said current throughout said initial, intermediate and final dehydrating zones.

11. A dehydrator comprising concentrically arranged rotary inner and intermediate drums and a fixed outer drum providing respectively initial, intermediate and final dehydrating zones of progressively increased duration and extent, means forming a passageway connecting sa d inner and intermediate drums adjacent one end of the dehydrator, means including a fixed closure forming a passageway connecting said intermediate and outer drums at an opposite end of said dehydrator, means for supplying heated gases to one end of said inner drum, means for establishing a pneumatic current of gases successively through said inner, intermediate and outer drums, said rotary drums having internal material-lifting means for lifting and dropping material across said current, temperature-responsive means fixedly mounted in the fixed closure and having a portion thereof exposed to the passageway connecting said intermediate and outer drums for contact with material-laden gases passing therethrough from said inner and intermediate drums, and means actuated by said temperature-responsive means in response to the drying conditions in said passageway to vary the rate of lifting and dropping material across said current and the temperature and velocity of heated gases throughout said initial. intermediate and final dehydrating zones.

12. A dehydrator unit comprising concentric inner, intermediate and outer drums, means mounting said drums in spaced-apart relation,

said inner drum having an axial inlet adjacent one end and a plurality of series of longitudinally spaced radial openings near the opposite end thereof, a partition in said inner drum positioned intermediate the adjacent ends of said series of spaced openings and dividing said inner drum into an initial dehydrating chamber communieating with said intermediate drum through one series of openings and a discharge chamber communicating with said outer drum through another series of openings.

13. A dehydrator unit comprising concentric inner, intermediate and outer drums, means mounting said drums in spaced-apart relation, said inner drum having an axial inlet at one end for intermixed material and hot gases, a tubular member surrounding the inlet end of said inner drum and spaced therefrom to form an annular chamber, said tubular member extending within the intermediate drum and having openings at both ends, and means for supporting and rotating said inner and intermediate drums.

14. A dehydrator unit comprising concentric rotary inner and intermediate drums and a fixed outer drum, means mounting said drums in spaced-apart relation, said inner drum having an axial inlet at one end for intermixed material and hot gases, a tubular member surrounding the inlet end of said inner drum and spaced therefrom to form an annular chamber, said tubular member extending within the intermediate drum and having openings at both ends, an annular tire on one end of the tubular member, and a roller drive engaging said tire for supporting and rotating said rotary drums.

15. A dehydrator unit comprising concentric rotary inner and intermediate drums and a fixed outer drum, means mounting said drums in spaced-apart relation, said inner drum having an axial inlet at one end for intermixed material and hot gases, a tubular member surrounding the inlet end of said inner drum and spaced therefrom to form an annular chamber, said tubular member extending within the intermediate drum and being fixed to the inner drum, means for introducing a current of air into the tubular member for insulating it against the heat of the inlet end of the inner drum, and means supporting and rotating said rotary drums through said tubular member.

16. A dehydrator unit comprising concentric rotary inner and intermediate drums and a fixed outer drum, means mounting said drums in spaced-apart relation, said inner drum having an axial inlet at one end for intermixed material and hot gases, a tubular member surrounding the inlet end of said inner drum and spaced therefrom to form an annular chamber, said tubular member extending within the intermediate drum, means for establishing a current of air through said annular chamber between said inner drum and tubular member, and means supporting and rotating said rotary drums through said tubular member.

DANIEL B. VINCENT.

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

UNITED STATES PATENTS Number Name Date 703,508 Ward July 1, 1902 742,265 Wentz Oct. 27, 1903 862,225 Westphal Aug. 6, 1907 1,175,944 Ford et a] Mar. 21, 1916 1,229,524 Rosendahl June 12, 1917 1,326,525 Nordstrom et al Dec. 30, 1919 1,336,422 Burman Apr. 13, 1920 1,988,677 Arnold Jan. 22, 1935 2,038,008 Shodron Apr. 21, 1936 2,132,656 Smith Oct. 11, 1938 2,143,505 Arnold Jan. 10, 19 9 2,173,225 Berry et a1. Sept. 19, 1939 2,226,910 Rice Dec. 31, 1940 2,316,459 Schmidt et a1 Apr. 13, 1943 2,319,673 French May 18, 1943 2,341,101 Howard Feb. 8, 1944 2,409,787 ONeal Oct. 22, 1946 FOREIGN PATENTS Number Country Date 490,373 Great Britain Aug. 12, 1938 Certificate of Correction Patent No. 2,518,582 L August 15, 1950 DANIEL B. VINCENT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correct1on as follows:

Column 5, line 63, for the word or, first occurrence, read of; column 8, line 46, for the indistinct Word after air read duct; column 9, line 58, after to insert the;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 14th day of November, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents.