US2924271A - Continuous vacuum dehydrator - Google Patents

Description

Feb. 9, 1960 w. E. CONLEY ETAL 2,924,271

CONTINUOUS VACUUM DEHYDRATOR Filed June 26. 1955 7 Sheets-Sheet 2 FIG.2.

WELD E GONLEY WENZEL P. KOPP' 41 ALBERT M. OLSON LEONARD A BEHN.

INVENTORS 7M mm,

ATTORNEY Feb. 9, 1960 w. E. CONL'EY ETAL 2,924,271

CONTINUOUS VACUUM DEHYDRATOR Filed June 26, 1953 7 Sheets-Sheet 3 Fl WELD E.OONLEY J WENZEL P. KOPP ALBERT M.OLSON LEONARD A.BEHN 3/7 INVENTORS Evil/J ATTORNEY 1960 w. E. CONLEY ETAL 2,924,271

CONTINUOUS VACUUM DEHYDRATOR Filed June 26. 1953 7 Sheets-Sheet 4 /08 F I e 5 78 W 67 42/ Q lZZ IN V EN TORS A23 A35- /?4 WELD CONLEY WENZEL P KOPP ALBERT mimsou BY mwfn zwskzzw" ATTORNEY Feb. 9, 1960 w. E. CONLEY ETAL CONTINUOUS VACUUM DEHYDRATOR w. E. CONLEY ETAL 2,924,271 comnwous VACUUM DEHYDRATOR 7 Sheets-Sheet 7 Feb. 9, 1960 Filed June 26, 1953 INVENTORS WELD E. CONLEY ATTORNEY WENZEL P. KOPP ALBERT M. OLSON LEONARD A. BEHN $64M FIG.I

all, only is small quantities and at great expense.

United States Patent i 2,924,211 CONTINUOUS VACUUM DEHYDRATOR Weld E. Conley, Wauwatosa, Wenzel P. Kopp, Elm Grove, Albert M. Olson, Wauwatosa, and Leonard A. Behn, Milwaukee, Wis., assignors to Chain Belt Company, Milwaukee, Wis., a corporation of Wisconsin Application June 26, 1953, Serial No. 364,458

20 Claims. (Cl. 159-7) This invention relates, generally, to apparatus for dehydrating materials and more particularly to an improved low temperature vacuum dehydrator having a continuously moving belt on which the material reposes while it is being dried.

In drying various materials a great many variables are encountered and it is found that almost every material presents apeculiar drying problem. Materials that are heat sensitive must be dried at low temperatures while some materials must be dried in an air-free atmosphere and some must be cooled immediately after drying to prevent deterioration. Heretofore the successful drying of certain sensitive materials has been accomplished, if at Still other materials, while dried commercially, suffer greatly by loss of properties during drying and the product is not well accepted. Consequently the need for economical low temperature drying apparatus is urgent and has been recognized for many years.

It istherefore a general object of the present invention to provide an improved vacuum dehydrator that is particularly adapted to etfect economical dehydration of sensitive materials.

Another object of the invention is to provide an improved continuous dehydrator for a variety of sensitive materials so arranged that the drying pressure, the drying temperature and the drying rate as well as the temperature of the dried product and other factors may be varied and closely controlled to suit the particular material being dried.

Another object is to provide a dehydrator capable of rapidly applying heat to the material being dried and then rapidly cooling the dried material in a manner to holdthe drying temperature and the drying time at a minimum to best preserve the qualities of the product.

Another object is to provide a dehydrator arranged to dry material continuously from a thin film at low temperature in a vacuum under aseptic conditions, the dried product being cooled rapidly and delivered as discrete, crystalline particles forming a highly soluble powder that is easily transported and stored.

A further object is to provide an improved dehydrator so arranged that its various conditions of operation may be regulated as necessary to adapt the drying process to the special requirements of the particular material being dried for effecting dehydration with the least possible deleterious effect upon the product.

According to this invention, improved apparatus is provided to effect drying of heat sensitive materials and the like under aseptic conditions at low pressure and temperature and out of contact with air. The drying is accomplished continuously from a thin film of wet material ona traveling belt conveyer in a vacuum chamber with the degree of vacuum, the speed of the belt and various other factors under control from the exterior of the chamber. Heat for vaporizing the liquid content is provided by means of a heating drum over which the belt .L, t i

2,924,271 Patented Feb, 1 960 ice travels, the temperature of the drum being controlled to effect the transfer of vaporizing heat as rapidly as possible without deleteriously increasing the temperature of the material. A cooling drum constituting the second? belt pulley, cools the material on the belt as rapidly as ration.

The prepared material to be dried is fed into the vacuum chamber in liquid form and is, preferably de-,

aerated to reduce its tendency to foam under vacuum The liquid material then enters a feed pan and is applied to the outer surface of the drying belt on the under.

side of the conveyer by means of a feeding roller. To regulate the thickness of the film of material on the belt the clearance space between the roller and the belt may be adjusted, together with the speed of rotation of the roller. Both of these adjustments may be made from the exterior of the vacuum chamber while the apparatus is operating. A backing drum is provilded on the upper or inner side of the lower belt run in the region of the feed roller to maintain the belt flat and in a predetermined relationship with the roller. Both the backing drum and the feeding roller may be provided with heat-v ing or cooling means to adapt their temperaturesto the requirements of the material being dried. While passing over the cooling drum, the dried material isyremoved from the belt by means of an oscillating doctor blade.

The angle of contact of the doctorblade and the pressure with which it engages the belt as well as the rate.

scraped from the belt also facilitates its removal and assists in the formation of particles having large surface areas, making them quickly soluble. The drying beltis maintained under tension and is guided by an automatic tracking mechanism in running over the heating and cooling drums. The frame the belt is a rigid structure that rests on three points of support within the vacuum chamber in a mariner to be free from deleterious distortions resulting from the effect for supporting the drums and of changes of temperature and pressure upon the structure of the chamber.

By reason of these several dehydrating apparatus, the particular requirements of any of various materials being dried may be accommodated through mechanism to operate in the manner best suited to effect drying to the desired degree with the least detrimental eifect upon the product.

The foregoing and other objects of this invention will become more fully apparent as the following detailed description of an exemplary embodiment thereof in an improved vacuum dehydrator is read in conjunction with the accompanying illustrative drawings, wherein:

Figure 1 is a view in longitudinal vertical section through an improved vacuum dehydrator embodying the suitably adjusting the elements of the features of the improved present invention, taken on the plane represented by the ing the general arrangementof the housing and the cit-- terior auxiliary equipment; V

.in'gs= as exemplifying the present inventionfor continuous drying in air-free aseptic surroundings vratus is especially arranged to provide for adjustment of the various drying conditions and the final Fig. 3 is an enlarged view in side elevation of part of the interior-equipment illustrated in Fig. 1 andshowing particularly the heating drum and the arrangement for tensiouing andguidingthe. conveyer. belt, some parts having been broken away; v J

Fig. 4 is afragmentary'view of a segment of. the heating drum face withpart of the outer. shellbroken. away to. show the helical bafl le plates;

Fig. SP is a; view in transverse section through the heatiiig drum and its supporting. structure, taken generally onthe plane representedby the line 55 in Fig. 1, some parts having been' broken away; Fig. 6 isya' circuit diagram of limit switch control appa'ratus forstopping the machine in the event the belt runs oif either edge of the heating drum;

Fig, 7' i513. view in transverse section through the app'aratus in the region of the feeding roller, taken gen erally on the plane represented'by'the line 7-7 in Fig. 1;

Fig; 8 is a" fragmentary view showing the feeding roller adjusting": mechanismas viewed from the left. end in Fig- 7; 2 h 'Fig". 9' is an enlarged view in longitudinal section through the sealed shaft bearing shown in Figs. 2 and 7, the" view being taken on the plane represented by the line 99 in Fig. 2-.

Fig. 10 is a view in transverse section through the dehydrating apparatus in the region of the cooling drum may be swung to the side of the machine and entirely clear of the opening23. The door 24 is circularm shapeand is provided with a: circumferential, axially extending flange 27 arranged to abut against a complementary circular gasket 28 mounted on the end of the housing and encircling the opening 23, the door being held in closed position against the gasket by a series of screw clamps 29. Furthermore, when: the chamber is evacuated, the door 24 is pressed strongly against the gasket'ZSby the external atmospheric pressure. t

An observation window 30 is providedin the center of the door 24to enable observationof the operation of the mechanism within the housing. Other similar windows (not shown) are-provided at various appropriate positions in the walls of the housing. 21 to provide for observation of various parts ofthe apparatus from different angles.

The housing 21 may be evacuated through operation of'a vacuum producinga'nd regulating system comprisingv tion by manipulating acontrol knob and that tune} taken; generallyon theplane; represented by the line 10- I0-in Fig. 1, some partshaving been broken away; Fig; 11 is a" fragmentary viewmostly'in longitudinal section through theapparatusin the region of the prod uct; removal mechanism, taken generally on the plane represented by the line 11-11 in Fig. 10; and,

Fig. 12 is another view in region of'the cooling drum as it is shown in Fig. 10 with part of the outer drum shell broken away to show the double helix bafiie= arrangement.

The improved vacuum dehydrator shown in the drawunder operating conditions that are closely controlled and readily adjustable for accommodating the drying processto the special characteristics and requirements of the particular material being dried. By effecting the drying operation as rapidly as possible under close controlof the temperature, pressure and other variable conditions, it is possible to produce powder dry, high solubleproducts while at the same time avoiding deterioration of heat'sensitive materials and the like. The appatemperatureof the. dried product whereby the drying time and other-important variables may be so regulated as best to suit thearequirements" of dried.

the particular material being Referring more particularly to the drawingsand especially: to Figs. 1 and 2 thereof, the improved dehydrator there; shown isrcapable of continuous operation and is: especially adapted to facilitate the dehydration of perishablematerials. The apparatus comprises in general. a relatively large housing 21 that constitutes the vacuum chamber'and. encloses an improved double drum and belt operating mechanism. As appears in the drawings; the housing 21 is of. generally rectangular shape'and isformedof. welded steel plates suitably reinforced on the exterior by spaced. beams22 that strengthen the fiat surfaces fori better. resisting the external atmospheric pressure; encountered when the chamber is evacuated.

To; permit; moving the internal operating mechanism into and outiof the vacuum chamber, the housing 21 is providedat one end with a large access opening 23. As

housing 21. By means of the creme-arm'25,-the door-l l transverse section in the is arranged convenient in this-instance a multiple stage steam jet vacuum indicated generally bythe reference numeral 41 andthat isconnectedto the housing bym'eans of a relatively large suction pipe 42. For regulating the degree of'fvacuuiti within the housingzl, the vacuum producing system 41 1 is provided with a bypass regulator; indicated in Fig. 2 by the numeral 43, that may be adjusted during opera:

tions to maintain automatically any" de'sired' degree er vacuumlwithin the housing "21up t6" the limit of'the e5 pacity of the pump 41-.

The material supporting apparatus within thehousing 21 comprises essentially a beltuconveyer, carried H byja' rigid steel frame 47-" that rests upon the floor 48" or the housing 21, as shown inFig. l. of a relatively large heating drum- 51 that is rotatably' mounted with its axis horizontaluin the' frame 47 anda' cooperating relatively small cooliug' drum 52 likewise rotatably mounted in the. frame 47 and positioned in parallelhorizontally spaced relationshi'p with the heating drum 51.. ,The spaced: drums-51-and 52 carry a c n-- veyer belt 53 that operates over them to=ca1ry'.thema= terial being dried. Thebelt 53 is preferably a continuous band of. relatively thin, stainless steelor'equivalentmaterial arranged with its lower rundisposed sub stantially horizontal and maintained under tensionby' and52. The material to be dried is'applied tothe under side of the conveyer in liquid form by means of a-feed-' ing mechanism 54; that. feeds it to the under or outer surface of the lower horizontal run-of the belt 53. the material is. carried by. the belt around theheating drum 51, the water vapor or. other solvent is extracted by the actionof thevaouum inthe chamber operating in conjunction. withthe. heat ofvaporization supplied by the heatingeffecbof the. drum. Since=the drying heat is absorbed as theJatentheat of-vaporizatio'ri of the liquid. content, the temperature of the material being dried' remains substantially equal to the: vaporizing tempera' ture at the pressure obtaining within thervacuumchamber until most of the liquid evaporates.

After passing overthe heating drum,.the belt 53 carrie's the warm dried materialwaroundthe cooling drum 52 to cool it as quickly as. possible and to condition it for removal from the belt a by aproduct removal apparatus' 55 including a doctor blade.56"thatscrapesthe1driedmaterial from the belt.just beforfethe belt leaves-the cooling drum. As appearsin-Fig. 1,the-:elements?of thecorr" veyer mechanism and the or installed in thehousing, 21 by passing thcm' through the large access opening 23 whenevernecessaryin connection with the assemblying on maintenance of: the de-: hydrating apparatus. I I i The cooling drum 52 is rotatably mountedjn-horizom tally spaced parallel. i

The conveyer consists,

relationship. with, the heatingldrum 51 by means of bearings'fiI that are fixed intherespec driving gear 63, the gears being substantially equal in a diameter to the diameter of the drum. Each gearv 63 is engaged by a meshing pinion 64, both of said pinions being mounted on a countershaft 65 disposed above and parallel with the drum 52 and rotatably supported in bearings 66 mounted on the opposite sides of theframe 47 above the drum bearings 61. The gears 63 andpinions 64 are preferably of the helical type and the shaft 65 is arrangedfor limited endwise movement to provide for equalized driving action at the respective ends of the drum.

Power for driving the countershaft 65 is derived from a main driving motor 67 mounted on the outside of the housing 21 by means of a supporting bracket 68 as best shown in Fig. 2. A variable speed reducing mechanism 69 also mounted on the bracket 68 is driven by the motor 67 and is adjustable to regulate the speed of the belt 53 by means of a hand wheel 70. From the speed regulating mechanism 69 a shaft 71 projects through the side wall of the housing 21 into the vacuum chamber, a suitable packing gland or" sealed bearing 72 being provided to prevent leakage of air into. the housing along the shaft. Within the housing, the shaft 71 isconnected, as shown in Fig. 10, to the adjacent end of the countershaft 65 by means of a universal joint coupling or connector 73' that provides for relative movement between the wall of the housing 21 and the conveyer supporting frame 47 without danger of exerting binding or cramping action on the shafts. By this arrangement, power for driving the conveyer including the two spaced drums 51 and 52 and the belt 53 is applied to the apparatus in the-region where the greatest resistance is encountered. As appears in the drawing, the frictional or dragging action of "the doctor blade 56 on the belt '53 in scraping the dried product from the belt occurs at the cooling drum and by driving this drum, the tension in the belt in transmitting power between the drums is minimized.

The heating drum 51 is carried on a through shaft 76 that supports hub elements at the respective ends of the drum and is provided on its extending ends with journals rotatably mounted in bearings 77. As best shown in Fig. 3, the housings of the bearings 77 are slidably mounted in yokes or brackets 78 constituting subframes that are in turn pivotally mounted on pins 79 fitted in the sides of the frame 47 at positions spaced from the drum axis. As shown, each subframe or yoke 78 comprises an end plate or base 80 that receives one of the pivot pins 79 and carries upper and lower guide bars 81 which pass through openings in the associated bearing housing 77. This arrangement permits sliding movement of the bearings along the yokes 78 in a generally horizontal direction to provide for moving the heating drum 51 in a direction to tighten the conveyer belt 53. To maintain the sliding hearings in adjusted position, each hearing housing is provided with a threaded rod 82 projecting therefrom through an opening in a place 83 secured to the ends of the guide bars 81 to constitute the outer end of the yoke 78. A nut 84 threaded on the rod 82 is arranged to'bear against the plate 83 for holding the bearing 77 in position to maintain tension in the belt 53.

-'In establishing the desired operating tension in the belt 53, the bearngs 77 are moved in the direction to tension the belt through the action of removable hydraulic jacks 86 provided with pressure. gages 87 by means of pumps the bearings 77 at both ends of the shaft 76 may moved simultaneously. To effect the desired. tension 6 in the belt 53, the gages 87'associa'ted with the two jacks 86 are observed as the pressure is applied until they both indicate predetermined readings. After-the desired tension has been achieved, the nuts '84 on the threaded rods 82 are turned down against the plates 83 and tightened until the gages 87 indicate by falling pressure readings that the forces restraining the bearings 77 in positionare being assumed by the nuts 84. The hydraulic pressure on the jacks 86 is then relieved and the jacks then may be removed from the machine with assurance that'the belt 53 is ready to operate under the desireddegree of tension. i 1

Proper tracking of the belt 53 in running over the drums 51 and 52 may be effected by tilting the heating drum one way or the other as required through up or down pivoting action of one of the bearing supporting yokes under the control of an electrical servo-motor mechanism 85. The yoke 78 at the left end of the shaft 76 as seen in Fig. 5, although pivoted on one of the pins 79, is restrained from pivoting movement relative to the frame 47 by means of an extension 90 projecting from the lower edge of the end plate 83 and secured'to the frame by cap screws 91. At the other or right hand end of the shaft however, the yoke 78 is free to pivot and is provided with an extending arm 92 that is secured to the end plate 83 of the yoke and has a pivotal connection at its outer end, as best shown in Fig; 3, with the lower end of a nut element 93 of the servo or followermechanism 85. The nut element 93 is threaded on a vertically disposed adjusting screw 94 that is rotatably mounted in the top of a bracket 95 fixed on and projecting upward from the side of the frame 47, the arrangement being such that when the screw 94 is rotated in the one or the other direction, the nut 93 is moved up or down to raise or lower the outer end of the yoke 78, thereby tilting the drum 51'to provide for correcting the tracking of the belt 53 in running over the drums.

As best shown in Fig. 3, the upper end of the rotatable screw 94 is connected by means of a universal joint coupling or connector 96 to a shaft 97 extendingupward through a packing gland or sealed bearing 98 in the top 26 of the housing 21. The upper end of the shaft 97 is connected by means of a torque limiting or shear pin device 99 to and driven by an external gear reduction reduction mechanism 100 are mounted on the top 26 of the housing 21 outside of the vacuum chamber. By energizing the motor 102 for operation in the one or the other direction, the pivoted yoke 78 and the corresponding end of the drum shaft 76 can be raised or lowered to tilt the drum 51 for correcting the tracking of the belt. The bearings 77 are preferably of the self-aligning type to permit the limited canting of the shaft 76 that occurs when the drum is tilted. A

To control the belt tracking operation there is provided a follower roller 103 positioned to engage one edge of the belt 53 and rotatably mounted on the lower end of an arm 104 that is pivotally mounted for swinging movement on a bracket 105 secured to and extending downward from the top 26 of the housing. Thearm 104 is arranged to control the belt tracking servo-mechanism by its swinging movement under the influence of the I shifting belt edge in engagement with the roller 103 to register changes in the tracking of the belt 53 on-the drums. This swinging movement is transmitted through a jointed shaft 106 to a horizontally disposed arm 107, shown best in Fig. 5, the outer end of which is connected to a vertically disposed control rod 108. The control rod 108 carries a weight 109 which functions to bias the arm 107 and the shaft 106 indirection to maintain the roller 103 in contact with the edge of the belt.

The lower end of the control rod 108 is provided with 112; and: a :doWif switchsl li both'mounted oni a; switch bracket 114:that.-is. securedto the: arm92' on the pivoted bean'ngyoke-78. By-this. arrangement, when the belt.53 departs from itscentral position and approaches the near sideoftheheating drum 51, for example, asseen in Fig. 3, theactionofrtheroller 103 in followingthe belt edge turnsrthe: shaft 106 indirection to'lift the control rod 108 whereupon thedisc 1'11 efiects closing of. the up switch 112. Conversely, movement. ofthe. belt in the; other direction' causes the control rod to move. down and close thefdown switch; 113. Electrical conductors 115 and 116 lead from the up switch and the down switch respectively'through a conduit 117 to alcontrol box 118 associated with thetracking motor 102. When theup switch is closed it completes an, electrical circuit through the conductor 115 that operates. in. the: control box 118.

to cause the motor 102 to turn in the direction causing the elevating screw- 94 to lift the bearing yoke 78 for-tile ing the drum 51. to. correct. the belt tracking. This upward movement of the yoke 78also effects movement of the switch bracket114 in the same direction therebymovingithe up" switch 112 away from the control disc 111 to open the circuit and stop the motor 102 as. soon as suflicient movement has been effected. In a similar manner,rwhen the belt shifts inlthe other directiomthe down switch 113 is closed causing the yoke 78 to move downwardithereby-tilting the drum in thedirection to correct the tracking and at the same" time. moving; the down switch. away from the. control disc 111 to permit it'to open. again. Accordingly, whenever the belt 53 moves appreciably to. the one or the other side of the central running position on the drum 51 the follower control or servo mechanism. 85 operates automatically to effect tilting of the drum 51 in the proper direction to guide the belt back to its. central position. The exact position at which the belt normally runs on the drums may be adjusted by adjusting-the position of the. control disc 111 on the control rod-108. I,

To stop the conveyer in the event of failure of the follower trackingv mechanism 85, or if for, some other reasonthe belt.53 shouldrun off the edge. of the drum 51, limitv switch operators 121 and 122are provided at the respectiveedges of the drum. Upon being contacted by the belt edge, either of these limit switch operators will operate to open a control circuit for stopping the conveyer. driving motor 67. As shown in the wiring diagram in Fig. 6, the limit switch operators 121 and .122 arearranged to actuate normally closed switch contacts 123 and 124 in a control circuit 125 connected. to actuate a motor controller 126 that isoperatively connected to start and stop the belt driving motor 67 and also an auxiliary motor 127 that operates to effect oscillation of i the doctor blade 56. As can be seen in Fig. 6,.whenever the belt 53. runs off either edge of the drum 51 it will engage with the limit switch operator 121 or the limit switch operator 122 and by opening the corresponding. switch contacts 123 or 124 operate to open the con- ,might cause the belt to run off the edgeof. the drums.

Since the. chamber 21 is evacuated and is also subjected to changes in temperature, thefloor 48 and the walls of the chamber are. subjected todeflectiou's in the nature of warping or bending. actions. To avoid transmitting the housing deflections resulting from the changes in pressure and temperature to the drum supporting structure, the frame ,47 is in the form of a rigid unitary member en-. tirely separate from the housing 21 and mounted as a unit' on the floor 48 by means. of three spaced feet. to constitute a three pointsupporting arrangement. 7

As shown in Fig. 1; the'left" end of the frame 47 is provided-with-arsinglecentral supporting-tooth: theform a. a shot-apiece; of: round: shafting; 131. disposed; 1am:

tudinally of; the frame at; righaangles: to. the drum axes and; secured as by welding .to they lower surface, of the.

frame. cross; member to constitute one: point of support.

. Thetsupporting foot or shaft 131 fits! into a comple- 47, as seen in Fig. 1 and which is foreshortened to provide more room for the feeding mechanism 54 and. theprodq uct removal apparatus: 55, is supported by, a pair of spaced feet constituting; the.- other. two. points. of support and formed by short pieces of round shafting. 1 34am" ranged; in axial alignment at'spaced positions underthe outer. edgesof the frameand between the drums asshown in Figs 5. 7 These two. cylindrical feet134 fit in complementary grooves: or sockets in lugs or pads. 135 thatare secured to .channelmembers 136; mounted on; the; floor 48 in parallel. relationship. with. the channel 133. The

cylindrical feet 134-.permit limited; longitudinal tilting or weaving naovement-ofl the: frame about their aligned transverse axis but, prevent endvwi'sei movement of the frame within. the housing 21 By reason of. this. three point support ng rrange ent it. is p a nt. that 6.0%

siderable warpingortwisting movement of. the housing floor. 48 may occur as a result of. changesin temperature or. pressure: without causing. corresponding deflections of the frame 47.. Furthermore, the pivoting actions per.- mitted bythe threeeylindrical supporting. feet allow. both longitudinal and transverse tilting movements of the r conveyer apparatus to. occur without causing deflections ofthe. frame 47. p r

The material to. be dried is fed into the drying appa ratus, assho wnin Fig. 2, by meansiof a feed pump 141 that. receives the liquid material through an. inlet pipe 142 and serves as a metering pump: to deliver it under moderate pressure at a predeterminedv rate, through a feed pipe143. When the material enters. the housing 21 it is, of course, subjectito the vacuum in the chamber. and this results in the release of occluded air causing'foaming of thematerial and makingit dilficult to control inthe feeding. mechanism 54. Accordingly, since it tends to preserve the quality of the. material as wellastopreverit foaming, it is preferable. to deaerate the material. before it reachesthe feedingmechanism, As the first step in deaerating, it is desirable to warm the! liquid material and this isaccomplished in aheating unit 144 intolwhich the feeding pipe 143 delivers thematerial from the pump 141.. From. the heating unit 144,a pipe 145 includinga control. valve 146 extends abovethe top of the housing 21 and enters through the top .26. thereof to deliver the material intothe vacuum chamber. Power for. driving the feed pump 141is' derived froman electric motor 148 that drives a gear reduction unit 149 coupled to the pump 141 by abelt transmission 150. By suitably regu lating the speed atwhich the pump 141 is driven and the setting of:the control. valve 146 the rate at which. the liquid materialis :delivered into thedehydrating chamber may be controlled and coordinated. withthe rate at which it is applied to the. drying belt 53 by the feeding mechanism. 54.

As best shown in Fig.1. the liquid material entering the top. of the vacuum chamber 21 through the pipe 145 flows into a deaerating apparatus comprising-a relatively large vertically disposed pipe 152 suspended from the top of the. housing by brackets 153 and open at its upper end, the pipe being preferably of glass or some other inert substance. 'Theliquid material' fromthe pipe 145 passes through a spray nozzle 154 located within the upper end of the dcaerat'or and. is sprayed thereby onto the innerwall of the open large pipe 152; the spray pf material being subject to the vaeuum within the chamber. The action of the vacuum upon the finely divided material in the spray removes the air that was occluded in the material thereby greatly reducing the tendency of the liquid to foam as it is being fed onto the belt 53. The sprayed material collects on the inside of the deaerator pipe 152 and flows down to the closed bottom end thereof from which the liquid is conducted through a smaller pipe 155 into the outer end of a long sloping drip trough and feed pan 157. The drip trough or'pan 157 is suspended from the frame 47 beneath the heating drum 51 and slopes downwardly toward the feeding mechanism 54. The liquid material flows by gravity along the trough into the lower feed pan or hopper portion thereof beneath'the lower run of the belt 53 about midway between the cooling drum 52 and the heating drum 51. v

A feeding roller 159, preferably "of stainless steel and presenting a sand blasted periphery, is rotatably mounted within the feed pan 157 in position to be partially submerged in the liquid material therein and is operative to carry the liquid upward'on'its' periphery and apply it to the lower surface of-the belt 53. As the applicator roller 159 turns within the feed pan 157 it applies to the mo'ving'belt 53 a thin uniform layer of the material to be dried, the material being applied-to the belt before it contacts the heating druml' Any material which may drip from the belt or be blown off by vapor formed in the materialupon contact of the belt with the heating drum 51 falls back into the drip trough 157 and returns with the incoming material along-the sloping feed pan to the feeding roller 159. The portion ofthe belt 53 to which the material is appliedis relatively cool since it has previously been in contact with the cooling drum 52 and its surface has been prepared to receive the liquid by action of the doctor blade 56 in scraping the previously dried material from the belt. Since the material is applied to the 'belt 53 at a position prior to its contact 'with the heating drum 51, full advantage is taken of the heat transferring effect of the drum. I

To stabilize the lower run of the belt 53 and cause it to follow a predetermined path relative to the appli cator roller 159 there is provided above the belt in the region of the feed roller a backing drum 160 that is rotatably mounted at its ends in the frame 47 as shown in Fig. 7. The backing drum 160 engages the inner or upper surface of the lower run of the belt as appears in Fig. 1 with sufiicient pressure to'defiect it somewhat for maintaining its lower surface fiat and running in a fixed path for the purpose of l receiving from the feeding roller 159 a material film of uniform; predetermined character.

As best shown in Figs. 7 and 8 the feeding roller 159 is rotatably mounted in bearings 162 thatcooperate with journals on a through shaft 163 which serves to drive the roller. 1 As in the case of the heatingdrum, the bearings 162 of the applicator roller are carried in pivotally mounted sub-frames or brackets 164 each pivoted to the main frame 47 at-one' end to constitute a pivot point spaced horizontally from the axis of the roller. By this arrangement the roller I59 maybe positioned closer to or farther from the surface of the belt 53 through pivoting the brackets164 about thepivot pins 165. This provides for regulatingthe thickness of the film of material applied to the beltin, order that the film may be of the characteristics best suited to the requirements of the ma- 'terial being dried. q I

In order that the roller 159 may move within the feed pan 157 in effecting adjustment relative to the belt, the sides of the pan 157 are slotted fromthe top down.- ward' to receive the shaft 163 near bothends of the roller. To' prevent the escape of liquid material along the shaft '163 and through the slots in the pan, the-shaft is provided inwardly of the slots at each side of the pan with a sliiiger 'dis'c'166i "'Ihe'discs 166 are so arranged thatany liquid "material reaching either-disctends'to drip 'or'bezthrown from -itsperiphery to forestall further-creepage of -the material along the shaft from the ends-of the roller 159. The depth of the material within the pan 157 may be regulated by adjusting the rate of delivery to the deaerator as previously explained and is indicated in the drawings by the dot dash line 167. A drain valve 168 in the bottom of the pan 157 is arranged to be operated from the outside of the housing 21 by means of an actuating rod 169 and may be opened to drain the pan 157 through a drain connection 170 leading through the floor 48 of the housing.

. Movement of the applicator roller 159 in adjusting its position relative to the belt 53is effected by screw and nut mechanisms operating on the ends of the brackets 164 remote from the ends thereof engaged by the pivot pins 165, there being a separate adjusting means-at each end of the rollerto provide for correcting'inequalities in the thickness of the material film across the face of the belt 53. As best shown in Fig. 8, the end of each bracket 164 carries a nut element 172 that engages complementary threads on a vertically disposed screw shaft 173, the upper end of which is provided with a step bearing that engages a bracket 174 secured to the frame 47. In order that adjustment of the feed roller'spacing may be effected while thedehydrating apparatus is in operation, the screw shafts 173 extend downward through the floor 48' of the housing, packing glands 175 being provided to prevent leakage of air into the housing while per-'mitting'rota't'ion of the shafts. The lower end of each adjusting shaft 173 is provided with an actuating handle 176 and an indicating dial 177 whereby precise independent adjustment of the position of each end of the applicator rollerl59 may be effected without interferring with the operation of the drying apparatus.

The feed roller driving shaft 163 is connected by a universal joint connector 180 to a shaft 181 that extends through a packing gland and sealed bearing 182 in the slde wall of the housing 21,-the sealing arrangement bemg shown in detail in Fig. 9. As shown in Fig. 2 the shaft 181 is connected at its outer end to a gear reduction mechanism 183 driven by a motor 184 both mounted on a bracket 185 secured to the outside of the housing 21. The gear reduction mechanism 183 is of the variable speed type and is operated to turn the feeding roller 159 in a manner to cause its upper surface to 'move in the direction of travel of the belt 53 and at a somewhat faster-speed. The speed may be regulated by manipulat mg a speed controlling hand wheel 186 on the variable speed gear reduction mechanism 183. By adjusting the speed changing gearing 183 in this manner, the speed of rotation. of the roller 159 may be regulated'from the exterior of the chamber without interferring with the operation of the dehydrator. Thus by changing both the'spacing of the feeding'roller 159 relative to the belt 53 and the speed of rotation of the roller, the amount of material applied to the belt 53 and the characteristics of the resulting film of material on the belt may be regulated as the drying operation proceeds to effect application of the material film in the manner best suited for efficient drying of the particular material under the conditions then prevailing within the vacuum chamber.

Furthermore, the temperature of both the feeding roller 159 and the backing drum 160 may be controlled as desired to best adapt them for handling the particular liquid materialubeing applied to the belt. The backing drum 160 may be of hollow construction and maybe cooled or heated by heat exchanging liquid that maybe introduced through a rotary joint or coupling 188 at the right end as shown in Fig. 7 and that flows off through a imilar rotary coupling 189 at the left end of the drum structure. The applicator roller 159 may also be holcoupling 190presenting :a conduit 191 through which heat the speed of oscillation of'the doctor blade may be adjusted by manipulating a speed changing hand wheel 230 on the reduction gearing 221 while the apparatus is in operation to establish the speed best suited to'the circumstances. Oscillation of the doctor blade reduces the frictional drag upon the belt 53 and thereby reduces the tendency of the blade to chatter'as well as distributing the wearing actionon both the blade and the belt. In addition to adjusting the'pressure'exerted by the blade and its rate of oscillation from outside of the housing it is also desirable to adjust the angle of contact or the angle of attack of the blade relative to the belt. To accomplish this each end of the blade carrying shaft 207 is rotatably mounted in a bearing bracket 227 that is slidably mounted for vertical movement on thefrarne 47 as shown in Figs. 10, l1 and 12. By sliding the brackets 227 up or down along the frame 47 the shaft 207 is moved closer to or farther from the drum 52 thereby causing the blade 56 .to assume different angles of contact with the belt. This, of course, results in turning the shaft 207 slightly which is accommodated by corresponding movement of the pressure actuated piston rods 209 without materially changing the pressure between the blade and the belt.

As shown in Fig. 12 eachbearing bracket 227 has rotatably connected to it the upper end of a vertically disposed adjusting shaft 228 that extends downward through the floor 48 of'the housing, the usual packing I glands 229 being provided to prevent leakagei Each adjusting shaft 228 has threaded engagement with'a nut 231 secured to the frame 47,- the arrangement being such that when the shaft is rotated in the nutthe' bracket 227 is raised or lowered. The lower exposed end of each adjusting shaft 228 is provided as shown in Fig. with an actuating handle 232 and a cooperating indicating dial 233 which may be graduated to indicate the angle of incidence of the doctor blade'with the surface of the belt. Thus by turning the actuating handles 232 and refer- I ring to the indicating dials 233 the angle of incidence of the doctor blade 56 may be adjusted at any time during operation of the machine to the angle best suited for removing from the belt ,the granular particles of the particular material being dried in the dehydrator.

As the dried product is scraped from the belt 53 by the doctor blade 56 it falls into a product receiving pan or trough 236 formed semicircular at its bottom to receive a rotary screw conveyor 237 disposed'transversely of the machine parallel with the axis of the drum 52. As shown in Fig. 1l,'one wall of the trough 2 36'is formed by a removable chute or plate 238 that constitutes the face of a magnetic separator 239 for removing magnetic impurities such as tramp iron particles from the product as it falls away from the doctor blade. The magnetic clamping action of an angle iron frame 241. The frame 241 is secured at each end to a vertically disposed supporting plate 242 that is pivotally connected at its lower end by apivot pin 243 to a bracket 244, the arrangernent being such that the entire magnetic separator 239 including the plate 238 may be swung about the pivot pin 243 to open the product receiving trough thereby providing accessability for cleaning or for adjustment of the doctor blade 56 or the like. The supporting brackets 244 are adjustably secured to the frame 47 by bolts 245 that pass through longitudinal slots 246 in the frame. By loosening the bolts 245 and sliding the brackets 244 along the frame, the position of'the magnetic separator relative to the doctor blade may be adjusted in order to provide the-best action in guiding'the dried product intothe conveyor 237 and in removing magnetic particles from the product.

As shown in Fig. 10, the transverse screw conveyer 237 operates to move the dried prpduct along the trough product into the one of the other chute.

236 toward the left and into an inclined rotary 'ball 'mill or similar grinding device 250. The ball mill 250 discharges into a coaxial rotary screen 251 through which the product is shifted into a divided discharging hopper 252. Although both the grinding mill 250 and the rotary screen 251 are shown in the drawing, it is to be under stood that different dried products require different kinds of treatment and it may be desirable to substitute for the grinder a plain rotary conveyer tube which may in some cases be further extended to replace the screen also, thereby discharging the product from the conveyer screw 237 directly into the product hopper 252. Likewise-the grinder 250 may be utilized by itself without the rotary screen 251 if desired.

As best shown in Fig. 10, both the screw conveyer 237 and the rotary grinder and screen are driven from the main countershaft 65 that drives the cooling drum 52. To this end, the countershaft 65 is provided with a sprocket wheel 255 that is operatively connected by a transmission chain 256 to a sprocket 257 on an extending shaft at the rightend of the conveyer screw 237. A second sprocket 258 on the screw conveyershaft is connected by a chain 259 with a sprocket 260 on the end of a jointed transmission shaft 261 extending transversely of the apparatus beneath the screw conveyer 237. At its left end, the jointed shaft 261 is inclined parallel with the grinder and screen and is provided with a belt pulley 262 that transmits motion through a belt 263 to a pulley 264 encircling and mounted on the rotary grinder 250.

By this arrangement, the screw conveyer 237 and the grinding and screening apparatus are always driven in proper synchronism with the conveyer belt 53 to convey away the dried material'as rapidly as it is scraped from the belt and regardless of changes in the belt speed that may be effected by changing the adjustment of the belt driving transmission mechanism 69. In the event that it is desired to change the relationship between the speed of the screw conveyer and the speed of the conveyer belt 53 this, may be accomplished by substituting a different sprocket for either the sprocket 255 or 257 or both to change the driving ratio. Likewise the speed of rotation of the rotary grinder 250 relative to the screw conveyer may be changed by changing the sprocket 258 or 260. This may be desirable in some instances to control the amount of grinding and thereby assist in controlling the density of the powdered product being delivered to the hopper 252.

In some instances it may be desirable to further cool the powdered product after it has been scraped from the belt to prevent melting and sticking of thermoplastic material in the product removal apparatus. For this purpose the screw conveyer 237 may be provided with a hollow shaft presenting a longitudinal passageway 266 as indicated in Fig. 11 through which cooling water may be circulated in the manner in which it is circulated through the cooling drum 52 or the backing drum for example. Further cooling may be effected by cooling pipes 267 arranged along the outer surface of the product receiving pan 236 and along the doctor blade bracket 206, as indicated diagrammatically in Fig. 11.

As best shown in Fig. 1, the product receiving hopper 252 is divided at its lower end into two discharge chutes 271 and 272 a deflector plate or gate 273 being pivotally mounted between the chutes and arranged to divert the The gate 273 is carried on a shaft 274 extending through and journalled in the sides of the hopper 252 as shown in Figs. 1 and 10. A jointed shaft 275 connects the shaft 274 with an actuating shaft 276 that passes through a packing gland 277 in the wall of the housing 21 and is provided at its outer end with an actuating lever 278. By swinging the lever 278 from side to side, the gate 273 may be caused to swing across the hopper 252 for diverting the dried product into the one or the other of the chutes 271 or 272.

ble P b e P ct cei n P9 3 9? sh ts hsrs 212 each chute being provided with ashut off valve 2801 that may be closed to prevent leakage of air intothe vacuum chamber while changing containers. For example, when the container 279 on the chute 271 becomes. filled with material, the gate 273 is swung over to divert the product into the chute 272 for filling another co ntainer279. The shut 01f valve 280 in the chute 271 is. then closed and the vacuum in the filled container is. broken, pref.- erably by admitting an inert gas. The filled. container is then removed from the machine, and an empty container is substituted for it, the closedvalve 28.0 in the ehute 271 preventing leakage of air into the vacuum; chamber during the change. The substituted empty container 279 is then secured on the chute 271 and evacuated after which the valve 280 in the chute is opened to prepare it for receiving the product again as, soon; as the container on the chute 272 is filled. i

The various sealed bearings and packing glands that are utilized throughout the apparatus tor passing rotary and oscillating shafts through the wall of the vacuum chamber are exemplified by the feed, roller shaft hearing m s shown hdh i in F 9- As l s Show the sealed bearing. 182. comprises acylindrical. bearing casing 281 that is securely. mounted. in the wall of. the housing 21 in a. manner to prevent leakage of air. around it. The bearing casing 281 carries at eacher d an. antifriction bearing 282 which bearings rotatably support the shaft 181 at spaced positions, At its inner end the casing 281 carries a packing gland283 that engages the shaft 181 to prevent leakagev into. thevacuum. chamber.

At its outer end the casing 281 is. provided with an oil seal 284. to prevent the escape of oilfrom the bearings. In order to insure against leakage of air into the vacuum chamber, the space within the casing 281 between the two bearings 282 is completely filled with oilor some equivalent fluid that is admitted through anoil cup 285 on. the outer end of the casing. By maintaining the oil cup. 285 filled with oil the possibilityof air-entering through the casing 281' is obviated. Even in th e event that the packing gland 283 should: leak somewhat, no air'will be admitted and whatever oil leaks through the packing will be apparent upon, observing the inner eiid of the packing gland through one of the. observationPQ ts such as the window 30 and will serve as a reminder .to

tighten the gland 283.

As previously mentioned, the: cooling drum 5 2 carried by a through shaft 62 that is provided at its ends with a water intake rotary coupling 196 a.water discharge rotary coupling. 197, respectively, As indicated in Fig. 10, the shaft 62 is fitted with two spaced hub elements 286 positioned inwardly of the ends of the drum. From each hub .2 86, six spokes 287 radiate-to and support a cylindrical inner shell member 288.. End rings 289 secured to the. ends of the inner shell 288 projec't radially to the ends of an outer. shell 291 that is spaced outwardly from the inner shell and thatfeon stitutes the belt engaging surface of the drum. The outer shell 291 is preferably of material having good. heat transmitting properties such as copper.

The space between the inner shell 2 88 and the outer shell 291 and enclosed. by theend; rings 289 constitutes a chamber 292 for the cooling water that serves to cool the dried material on the belt 53. As shown in Fig. 1 0, the cooling water which enters through the eontrol'fvalve 194, the pipe 195 and the rotary coupling. 1 96. flows through a passageway 294 that is bored into the end of theshaft 62 and extends inwardly just beyondthe hub 286. From the passageway 294, the cooling 'water flows into two radial fittings 295 disposed at 180"v toeachother and from each of which. a branching conduit leads to the cooling chamber 292. As shown,- one branch. condu 296 leads o h 'c amhe 9. in he e h 1 l t n 0. h dr m n aho her hr h h co dui 2 insi ts the shaoh at the islit sail-9i QQEQHW- y when his arrans m htt the .294? 1cm. th v 1IPi r she f i -li f e fi. uni rml h qlhe l of h rum areeool Q cqt lallyto. avoid'any inequality in expansion u i ht b p wih htsrf r with groper tracking 9 the belt nrunnin'g over the. drum 52 The cooling "wa hith sh tt hhhssts with; he new howling h u h h as a na i s h d nt he pipe, 198leading'tliroi1g h? floor. 481 Qf= the. housing. B wit hu hs' h. sro h v iil-r h s f h dw t 5% an -distorti n h e u t in tw -mi existing between the ends of me drum and: the mid-porhn resul lsr h li ht awnin es h the drain wh c w ll: 71 a ver e! htkshthe hperatioh of the belt53 in runnin 4; over. the drum; In assembling hsshumfiz... the ha s hr at he sa in 28 a 't he ham; Plates? ans-flan e??? r mhc i h h ah acc r t hs s a e 99 sup t th o e sh a ter hichthaqha manna o rh a eat shh hswh h with he PaiP a ew the e d in s: n h afiie s r h wt s s l, the sa rihssh s i ahls hea n at hashin rings "eon ceutric "with. the

i'i h is eg s heat h q i ahs sta s that: the was ng co act..

um r ssh s th rsw bi m a f a i l f we ho t i sats in his lltar hmd in, a g la w s re a onship hhs ara s hsth hush ali ned q e in e Web of he seats an; n hshnsra'ii s les 30 s r th aihhsr urf e c the sperms? 18 h holes in t e has? m y h s hhs t d q Pr ide an r a i ls h shth th zs ars is; t e Purp e eliminatihs hshh hsh and sh ats 1.9 the van sh apparatus shbwht s pl hs d um 51 s am 0 hhh n ameter and i slish x l nger thanh wi t t t b w sh in h sh nss-i i hh e atls dr m 5 s n many ahhl Sim? ilar. in construction tothecooling drum. 5,2 but is larger,

being in this apparatus feet in. diameter. "As best.

shown in Fig 5, .theidrprn .51 is. supported on the trans W3 thiq'h h sh iUh P W9 1 1198? hi l? f sh' sh h 3 .5 disposed in-spaced relationship approximately in line with .Fig. 4f the bafile ,plate321 .eater ds continuously across h f t? e than: a 81 2 3?! AS Previously mentioned stearntor he atmg the drum. is admitted throughthe automatic. pressure regulating valve 200 (Fig. 5) and theverticalpipe201 to therotary connection 202 from which it flows through a passageway 323 bored into 1116? n iof shaftt 7 6 to a position beneath the hub 315. Radial passageways 324 in the shaft 7 6 permit the steam to flow frprngthe passageway .323 into the interior sha 2 m h sh w s in a 1 shrunlgi on the drum it is sealed: to

st h ends 9 h '17 steam flows outwardly through all of the hollow, spokes 316, associated therewith, into the right end of the heating chamber 320 as seen in Fig. 5. In order that the steam may be distributed rapidly across the face of the drum, the inner edges of the helical baflie plates 321 are notched in axial alignment with each spoke 316 to constitute a transverse steam passage 325.

Water which condenses from the steam when its latent heat is released to the belt 53 collects in the bottom of the chamber 320 between the turns of the helical baffle plate 321. Since the helix formed by the baffle plate 321 extends from side to side of the drum the condensate which collects is urged toward the left as seen in Fig. as the drum turns and is discharged from the left end of the drum. As appears in Fig. 4, the helical baffie plate 321 terminates in apocket or dipper space 326 that communicates with one of the hollow spo'kes 315 at the discharge side of the drum, the other .seven spokes at this side being closed at their ends. Upon each revolution of the drum 51 the water which finds its way to the dipper space 326 at the end of the helix drains away through the hollow spoke 316 as soon as the dipper space arrives at a position above the axis of the drum. From the hollow spoke 316 the water flows into the hollow hub 315 and thence'through radial passageways 327 into a bore 328 in the left end of the shaft 76 that constitutes a passageway leading to the rotary coupling 203 from which the water discharges through the pipe 204 to the exterior of the housing 21.

In fabricating the heating drum, the end plates 318 and the helical baffle plate 321 are secured to the periphery of the inner drum shell 317 preferably by welding. Two diametrically opposed transverse backing strips 329 are then fitted to the periphery of the bafile plates-by suitably notching the plates and welding the strips in the notches as shown in Figs. 3 and 4. The periphery of the baffle plates including the transverse backing strips is then machined to accurately cylindrical shape for receiving the outer shell 319. In this drum the outer shell is preferably formed of stainless steel and is applied in two semi-cylindrical segments joined at their ends over the two backing strips 329. In applying the two semi-cylindrical stainless steel sheets or segments to the drum they are first clamped in position preferably by clamp hoops Wrapped around the segments and drawn tight as by nuts threaded on their ends. The two segments are then welded together over one of the backing strips leaving the other two ends free in spaced relationship over the other backing strip. Both of the stainless steel sheets are then heated as by playing gas torches over them to expand them a predetermined amount whereupon their free ends are welded together. Heating of the shell is then discontinued and the clamping hoops are removed. Both welds are then completed to join the two segments securely together and to the two backing strips by deposits of weld metal. As the stainless steel segments cool, circumferential residual tension stresses are established within them insuring close conformity of the outer shell 319 to the outer periphery of the baflle plate and end rings despite the differences in external and internal pressures and variations which may occur in the temperature of the drum during operation. The edges of the outer shell 319 are then welded to the end rings 318 and the periphery of the drum is then machined to accurately cylindrical shape concentric with the journals of the shaft 76 to provide a surface suitable for good heat transferring contact with the material conveying belt 53.

In applying the belt 53 to the heating drum 51 and the cooling drum 52, a long strip of suitable stainless steel sheet material is passed around the drums and cut to the required length with accurately squared ends. With the heating drum in its retracted position, the ends of the belt strip are joined by butt welding to form a continuous endless band trained about the drums. The heating drum is then moved along its supporting brackets 78 to tighten the belt as previously explained. As is evident from the description, and generally well known, establishing accurately cylindrical smoothsurfaces on the heatingand cooling drums is a troublesome and expensive procedure. One of the great advantages of using the conveyor belt 53 to suppo'rt the material being dried as compared with a drum dryer for instance is that the belt serves to protect the accurately formed cylindrical surfaces of the drums. Hence should any injury befall the material receiving and transporting surface, it can be renewed readily and inexpensively simply by removing the damaged belt and replacing it with a new' one. This is accomplished without the necessity of dismounting the drums or operating upon their peripheral surfaces.

As another guard against injury to the drum surfaces, each drum is provided with an auxiliary scraper for tomoving any debris which may accumulate on the drum face thereby preventing it from building up between the drum and the belt. drum 52 is engaged by a transversely disposed auxiliary scraping blade 332 beneath which 'is arranged a catch pan 333 to 'receive any debris scraped from the drum surface. Likewise the backing drum is provided with an auxiliary scraping blade 334 and a cooperating catch pan 3%. As best shown in Fig. 3 the heating drum 51 is provided with an auxiliary scraper blade 336 that is pivotally mounted on the frame 47 and resiliently held in engagement with the drum periphery by a spring 337, thearrangement being such that the spring retains the blade in proper contact with the drum periphery regardless of tilting movement of the drum axis in effectingtracking of the belt as previously explained. A suitable catch pan 338 is also provided to receive debris from the blade 336. Likewise the follower roller 103 contacting the edge of the belt 53 is fitted with a scraper blade 339 to remove debris which might otherwise accumulate thereon and interfere with its belt guiding action. Thus the dehydrator may be operated continuously over long periods of time without the necessity of shutting down for cleaning operations.

From the foregoing description and explanation of operation of the exemplary dehydrating apparatus set forth herein it will be apparent that the improved mate- I rial drying equipment provided by this invention is especially adapted to effect the drying of a large variety of heat sensitive'materials and the like because of the fact that it is possible to control closely the drying pressure and temperature, the rate of drying and the temperature of the product while effecting dehydration at low temperature under aseptic conditions in vacuo. By effecting thorough dehydration while avoiding overheating or 'oxi-' dation of'the material being dried, the resulting product retains the texture, color and flavor of the original material with its moisture content so reduced as to effect greatly improved storage properties and having a high degree of solubility for complete and rapid reconstitution of the material.

Furthermore, because of the construction features described, the apparatus has the ability to operate continuously over relatively long periods of time, so that after the chamber is'initially evacuated, the material may be fed to the belt without interruption for a long run ning period and the machine shut down only when good practice demands a complete cleaning of the material contacting components. Apparatus of the size and op erating as described herein is capable, for instance, of producing sixty to sixty-fivepounds of coffee powder per hour from an extract concentrated to about 40% solids in commercial operations. I

Although a single example of dehydrating apparatus illustrative of the present invention has been set forth in considerable detail by way of a full disclosure of a practical, useful embodiment of the invention, it is to be understood that other arrangements of the apparatus and different proportional relationshipsof its elements may As shown in Fig. 1, the cooling een' fully described, what tionship, with said heating drum, a material conveying belt trained over said heating drum and said cooling drum, power actuated means operatively connected to drive said drums and said belt, a feeding. roller disposed with its periphery 'in cooperating relationship with the outer side of the run of said belt moving from said coolingdrum to said heating drum and at asubstantial distance from said heating drum and rotatably mounted for applying material to be dried to said belt, a backup drum disposed to engage. the inner side of said run. of said; beltin the region of said feeding roller for-maintaining. said-belt in predetermined relationship with said-feeding roller, means to apply liquid'material to. the .periph'erypf said feeding roller for application: thereby to said. belt, vari: able speedpower. actuated driving mechanism operatively. connected to ,turn said feeding roller at selected speed in a manner to move its feeding periphery in the direction oftravel of ,said beltforapplying material to said belt, control means to adjust thespeed of rotation, ofsaid feeding roller, and. adjusting means to adjust the I clearance distance between said: feeding roller. and said belt, the arrangement being such that thethicknessof the film of material applied to said beltmay be regulated during operation of the dehydrator. by adjusting the speed of rotation of said feed roller and the clearance between it and said belt.

2. In a vacuum dehydrator for continuously drying from a liquid condition any of various heat sensitive materials. having different dryingcharacteristics, an enclosing vacuum chamber, evacuating apparatus operatively connected to effect evacuation of said'chamber, a: control system arranged-to control said evacuating. apparatus in a mannerto maintain a desired degree of vacuum within said, chamber, means to. adjust said control system to regulate the degree of vacuum to the necessities of the material being dried, a heating drum rotatably mounted within said chamber, a cooling drum rotatably mounted in spaced parallel relationship with said heating drum, a material conveying belt trained about and run ning over said spacedjdrums, regulatable heating means arranged to effect heating of said heating drum to a selected temperature adapted to cooperate. with the selected degree of vacuum in said chamber to effect drying of the material on said'belt in the most expeditiousmanner consistent with the least deleterious effect upon the quality. of the dried material, regulatable cooling means arranged toeffect cooling of said cooling drum to a selected temperature adapted to cool said belt and the dried material thereon to prevent overheating'the mate-v rial and to facilitate removal thereof from said belt, means. to remove the dried material from said belt after it is cooled on said cooling drum, a feeding. roller, disposed with its periphery in cooperating relationship with the outer surface of the run'of said conveyor belt moving from said coolingsdrum to said heating drum and at,

a substantial distance from said heating. drum for. applying to said cooled belt the liquid material to'be dried,

driving means, adjustable from the exterior of'said cham-. I

her and operative to turn said feeding roller. at selected; speed in. thedirection. totmoveits feeding periphery in the direction of travel of said. belt,;positioning means operable to adjust the clearance, between said feeding material having characteristics best adapted for drying under the selected conditions of heat and vacuum, and a backing drum rotatably mounted to engage the inner side of said belt in the region of said feeding roller to roller and said belt for. cooperating with the speed of rotation toietfect'the application to said beltjofa film of stabilize saidbelt' and maintain it'in position to receive the. film' .of material applied by said roller.

3'; In dehydratingfapparatus fordrying material from a liquid conditionpa; of drums. rotatably mounted in parallel spaced relationship, a "conveyer belt trained about said spaceda drums =for co1'1veying material being dried, a'feeding roller rotatably mounted .withits, periph-. cry in rollin'gcoopcrating relationship withsaid belt. for

applying to. said belt the liquid material to. be dried, and control apparatus connected to effect precise independent adjustment oftli'e spacing betweenteach end respectively of said feeding roller and said beltto regulate the thickness of the, film of material applied to said belt by said roller, whereby the film thickness maybe regulated throughout; the width of said belt while the dehydrating apparatus is in operation.

4. In dehydrating apparatus, a rotatably mounted drum, a second drum rotatably mounted in spaced parallel relatipnshipj with said first drum andrarranged for-tilting movement, a. drying conveyer belt running over said spaced drums for advancing material being dried, a follower mechanism responsive tothe position of said belt axially of said drums, tracking mechanism responsive to said follower mechanism and operative in accordance therewith to effect tilting of said second drum in a mannerto maintain correct tracking of said belt in running over said drums, a scraper blade pivotally mounted and resiliently held ,in, position to engage and scrape the periphery of said tilting second drum at a position thereon not engaged by; said belt and-regardless oftilting movement of saiddrum, whereby accumulation of debris between said beltand said drum may be prevented. I j

-, 5. In a, dehydrator for the continuous drying of mate;

rials from a liquid condition, a pair of drums'rotatably mounted 'in parallel spaced relationship, a continuous conveyer belttrained over said drums a backup drum disposed to engage. the inner. surface of one run. of said conveyer sen, betweenv said ,spaced drums tornaintain said belt .in a fixed. track in the region thereof, a feeding roller rotatably, mounted adjacent, the outer surface of said; beltiu the region maintained in a fixed track by said rotation ofQsaid feeding roller, the arrangement being such: that by adjusting thc.clearance between said feeding roller and said, belt and adjusting the speed of rotation of said reller during a drying operation the characteristics of the film of material applied to said belt by said roller may. be regulated in a (manner best adapted to facilitate the drying of the particular material being dried. V j

6., The deaerator as set forth in claim 5 in which the drums are mounted in horizontally spaced relationship.

7. Invacuum dehydrating apparatus, a vacuum chamber, evacuating means operatively connectedto evacuate said chamber, a heater arranged to warm liquid material to be ;dried, a conduit connected to feed the warmed liquid material from said heater into said vacuum chamber, a deaerator within said vacuum chamber connected toreceive-the warm liquid material from said conduit to deaeratefit, conduit means connected; to the lower end of. said deaerator to receive deaerated liquid; therefrom, a feeding pan" within said chamber connected to-receive deaerated liquid material from said conduit means, said deaerator deaerating said liquid material andsaid'conduit means deliveringlydeaerated liquid to'said feeding pan, whereby frothing in said feeding pan'jisjprevented, a

device presenting amoving drying-surfacemcuntedl 21 within said vacuum chamber, feeding means arranged to receive liquid material from said feeding pan and to apply it to said moving drying surface, and collecting means arranged to collect dried material from said moving drying surface, the arrangement being such that ohjectionable foaming of the liquid material in said feeding pan under the influence of the vacuum in said chamher is obviated by deaerating the liquid in said deaerator before it reaches said feeding pan.

8. In a dehydrating apparatus, a pair of spaced, generally parallel drums, a drying belt trained over said parallel drums, power actuated driving mechanism operatively connected to drive said drums and said belt, means to apply liquid material to be dried to said belt, means to scrape dried material from said belt, a conveyer disposed to collect the dried material scraped from said belt, grinding means disposed to receive dried material from said conveyer to grind it, power transmitting mechanism connected to be driven by said power actuated belt driving means and connected to drive said conveyer and said grinding meansin synchronism with said belt, said power transmitting mechanism including a speed changing device arranged to provide for varying the ratio between the speed of said belt and the speed of said conveyer and said grinding means, and a product discharging device disposed to receive the dried product from said grinding means to discharge it from said apparatus. 7

9. In a belt dehydrator, a pair of spaced belt drums, a belt running over said spaced drums, means to apply material to be dried to said belt including an applicator roller disposed in feeding relationship with the outer surface of one run of said belt, means to adjust the position of said roller relative to said belt, means to drive said roller, control means operative to adjust the speed of rotation of said roller, the arrangement being such that the amount of material fed to said belt may be regulated by adjusting the spacing of said roller relative to said belt and the speed of said roller, a backing drum disposed to engage the inner surface of said run of said belt in position to stabilize said belt in the region of said applicator roller, and means to regulate the temperature of said backing drum to cool or warm said belt selectively at the position of receivingthe material to be dried.

10. A drying apparatus comprising a first drum, a second drum disposed in parallel relationship with said first drum, a material conveying belt trained around and running over said parallel drums, a backing drum mounted to engage the inner surface of one run of said belt to stabilize it, a scraper blade mounted in position to engage and scrape the periphery of each of said drums at a point thereon not engaged by said belt, and a drip pan disposed to catch debris scraped from said drums by said blades, whereby the debris is prevented from accumulating between the inner surface of said belt and the outer surfaces of said drums.

11. In a belt drying apparatus, a first rotatably mounted drum, a second drum rotatably mounted in parallel spaced relationship with said first drum, a conveyer belt trained over and running on said spaced drums, means to remove dried material from said belt, a feeding roller arranged to cooperate with the outer surface of said belt between said drums and operative to apply to said belt a film of liquid material to be dried, a backing drum rotatably mounted to engage the inner surface of said belt in the region of said feeding roller to stabilize said belt in relation to said roller, and means to regulate the temperatures of said feeding roller and of said backing drum to control the characteristics of the film of material being applied to said belt by said feeding roller, whereby the film applied to said belt may be of the nature best suited to the requirements of the particular material being dried.

12. In a belt type of dehydrator, a pair of spaced belt drums, a'belt running over said spaced drums, means to apply material to be dried to 'said belt between said horizontally spaced drums including an applicator roller disposed with its periphery in feeding relationship with the outer surface of one run of said belt between said spaced drums, means to adjust the position of said roller relative to said belt, variable speed driving means to drive said roller in a manner to roll upon said belt with its feeding periphery moving in the direction of travel of-said belt, and control means operative to regulate said variable speed driving means to adjust the speed of'rotation of said roller, the arrangement being such that the amount of material fed to said belt may be regulated by adjusting the spacing of said roller relative to said belt and the speed of rotation of said roller.

13. In a belt dehydrator, a pair of spaced belt drums, a belt running over said spaced drums, means to apply material to be-dried to said belt including an applicator roller disposed in feeding relationship with the outer surface of one run of said belt, means to adjust the position of said roller relative to said belt, the arrangement being such that the amount of material fed to said belt may be regulated by adjusting the spacing of said roller relative to said belt, a backing drum disposed to engage the inner surface of said run of said belt in position to stabilize said belt in the region of said applicator roller in a manner to maintain the adjusted spacing between said roller and said belt, and means to regulate the temperature of said backing drum to cool or warm said belt selectively at the position of receiving the material to be dried. 1

14. In vacuum drying apparatus, a vacuum chamber, an evacuating system operatively connected to evacuate said chamber, material conveyingmechanism within said vacuumchamber presenting a moving drying surface, a doctor blade disposed to scrape dried material from said moving drying surface, adjusting means operative from the exterior of said-vacuum chamber to adjust the angle of contact of said blade with said surface in selecting the most advantageous angle for removing a particular dried material in the course of a drying-operation,

fluid pressure actuating mechanism operative upon said doctor blade to effect movement of said blade into engagement with said drying surface, control mechanism operative from the exterior of said vacuum chamber to regulate said fluid pressure actuating mechanism for establishing the degree of pressurewith which said blade engages said moving drying surface, a power operated 0scillating mechanism mounted on the exterior of said vacuum chamber, control means operative from the exterior of said vacuum chamber to control the speed of operation of said oscillating mechanism, and a universal coupling mechanism operatively connecting said externally mounted oscillating mechanism to oscillate said doctor blade transversely of said drying surface for facilitating the removal of dried material from said surface, Whereby the angle of contact of said blade and the position thereof relative to said drying surface may be adjusted without interfering with the transverse oscillation of said blade relative to said drying surface.

,15. In a dehydrating apparatus a rotatably mounted drum, a second drum rotatably mounted in spaced parallel relationship with said first drum, means for adjusting the relative angular position of the axis of said second drum with respect to the axis of said first drum, a belt trained around said spaced drums for advancing material being dried, and a scraper blade pivotally mount-.

ed and resiliently held in position to engage and scrape the periphery of said second drum at a position thereon not engaged by said belt and independently of the relative angular adjustment of said drum, whereby accumulation of debris between said belt and said drum may be prevented. 1

16. In a dehydrating apparatus, a pair of spaced, generally parallel drums, a drying belt trained over said parallel drums, a power-actuated driving mechanism opmeans to scrape dried material from said' belt, a conveyor disposed to collectthe dried material scraped from said belt, a screening device disposed to receive dried material from said conveyor to screen it, power-transmitting mechanism connee-ted to be driven by said. poweractuated belt driving means'and connected to drive said conveyorand said screening deviee in synchronisrn with said belt, said power-transmitting mechanism including a speed-changing device arranged to provide for varying the ratio between the speed of said belt and the speed of said conveyor and said'screening device, and a product discharging device disposed to receive the dried product from said screening device toydisc'harg'eit from said apparatus. 7 I

a 17. In a vacuumdehydrator ahousi'ng including walls constituting a vacuum chamber, one of said walls pres'enting a shaft-received aperture and janother of said walls having an observation window, an evacuating system operativelyconnected to evacuate said chamber for drying material therein, a drying conveyor apparatus within said chamber arranged to carry the material being dried under vacuum thereimmaterial feeding' mean'sdisposed to feed onto said conveyor apparatusliquid material to be dried thereon, product removal apparatus dis posed to remove dried product from said conveyor apparatus, power-actuated driving mechanism mounted externally of said housing for driving said internal conveyor apparatus, a power transmitting shaft passing through said aperture in said wall of said housing and arranged to operatively connect said external driving mechanism to said driven conveyor apparatus within said housing, a sealed bearingstruc-ture mounted in said'housing Wall aperture to support said shaft, said bearing structure comprising a cylindrical casing fixed in said "wallaperture, spaced bearings mounted within said cylindrical casing and rotatably supporting said shaft, an oil seal associated with one of said bearings at the outer end of said cylindrical casing to prevent leakage of oil therefrom, a packing gland arrangedin said casing inwardly of the other of said spaced bearings at the inner end thereof and engaging said shaft to prevent leakage along said shaft into said housing, and an oil reservoir on said casing externally of said housing and connected to maintain a body of oil within saidcylindrical casing between said spaced bearings, whereby leakage of 'air into said vacuum chamber along said shaft is prevented andany leakage of oil which may occur through said packing gland is observable through said observation window and may be checked by tightening 's'aid packing gland.

18. In a drying apparatus, a pair of drums rotatably mounted in parallel, spaced relationship, a conveyor belt trainedaround and running over said drums, a backup drum rotatably mounted between said spaced drums in position to engage and roll upon the inner surface of one run of said belt between said spaced drums to stabilize said belt, a feeding roller rotatably mounted in position to cooperate with the outer surface of said run of said belt in the region stabilized by said independently effecting adjustment of the respective ad-.v

justably-mounted supporting means to vary the spacing drum, a material conveying belt trained over said heating drum and said cooling drum, power actuated means operatively connected todrive' said drums and said belt,

' and feeding means disposed in cooperating relationship between each end of said feeding roller and said belt to regulate the thickness of the film of the material ap plied to said belt by said roller, and means to apply material to be dried to said rotatable feeding roller for transfer thereby to said belt.

19. In a dehydrator for drying liquid materials, a rotatably mounted heating drum, a rotatably mounted cooling drum in parallel spaced relationship with said heating with the outersurface of the ,funof said belt moving from the cooling drain to the heating drum and at a substantial distance from said heating drum for applying liquid 'tobe dried to'the belt, wherebythe liquid is applied to the belt before it is substantially heated by the heating r 20. In a dehydratingapparatus, avacuum chamber, a drum and belt drying conveyor mounted within said vacuum chamber, means to drivesaid conveyor, feeding means arranged to feed liquidflmaterial onto said belt for drying, a doctor blade disposed in cooperating relationship with said conveyor belt to scrape dried material therefrom, means operative from the exterior of said vacuum chamber to change the peripheral position and the angle of incidence of said doctor blade in adjusting its relationship with, said conveyor belt, power actuated oscillating mechanism mounted on the exterior of said 1,005,963 Groat 0a. 17, .1911 1,078,603 Amundsen Nov. 18, 1913 1,081,338 Sleeper- Dec. 16, 1913 1,163,439 Naumann Dec. 7, 1915 1,200,116 Johnson Oct. 3, 1916 1,225,282 Stevens" May 8,1917 1,353,980 Yahn Sept.28, 1920 1,507,238 Kocourek Sept. 2, 1924 r 1,577,709 Glessner Mar. 23, 1926 1,583,333 Bigum May 4, 1926 1,588,159 Bolgiano June 8, 1926 1,713,171 Dawkins May 14, 1929 1,717,491 Bouda et al. June .18, 1929 1,726,751 Miles Sept. 3, 1929 1,933,819 Miles r Nov. 7, 1933, 2,030,982 Grossenbacher Feb; 18, 1936 7 2,117,958 Hershey May 1 7, 1938 2,119,594 McLean June 7, 1938 2,131,666 McDougall Sept. 27,1938 2,139,628 Terry t Dec. 6,l 1938 r 2,155,963 Watson a Apr. 25, 1939 2,191,366 Buccione Feb. 20, 1940 2,294,996 Mercier Sept. 8, 1942. 2,300,908 Broughton Nov. 3, 1942 2,304,843 Nordquist Dec; 15, 1942 2,311,928 Buehler Feb. 23, 1943 2,449,574 Wilcox Sept. 21, 1948 2,457,537 Douglass "Dec. 28, 1948 2,486,719 Messinger Nov. 1, 1949 2,488,294 Hornbostel Nov. 15, 1949 2,498,662 Eaby -3 Feb. 28, 1950 2,519,608 Stilson Aug. 22, 1950 2,528,476 Roos Oct. 31, 1950 2,566,811 Stevenson Sept. 4, 1951. 2,576,036 Ostertog et al Nov.-20, 1951 2,600,273 Seifried .a June, 10, 1952 2,606,156 Davis Aug. 5, 1952 2,661,545 Messinger Dec. 8,1953 2,728,387 Smith Decz 27, 1955. 2,798,544 Davis -2 July 9, 1957:

. 1, FOREIGN PATENTS r a 594,923 France Iulyj6, 1925 21,426, Australia Dec. 3, 1935 599,269 G reat Britaina u Mar. 9, 1948. 132,406 Australia May 2, 1949 UNITED STATES PATENT OFFICE QERTIFICATE OF CORRECTION Patent N0a 23241 271 February 9, 1960 Weld Ea Conley et alt.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column 2 line 23 for "provild'ed" read provided "3 column 3 line 47., for "high read highly column line 59 for "place read plate line 65 for "bearngs read bearings line 72 for 'puump" read pump column 14, line 4 for "shifted" read sifted --Q Signed and sealed this 2nd day of August 1960.,

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents

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