US2678093A - Adjustable scraper blade mechanism for driers - Google Patents

Description

May 11, 1954 A. M. FISCHER 2,678,093

ADJUSTABLE SCRAPER BLADE MECHANISM FOR DRIERS Original Filed April 14, 1943 4 Sheets-Sheet l INVENTOR.

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May 11, 1954 A. M. FISCHER ADJUSTABLE SCRAPER BLADE MECHANISM FOR DRIERS 4 Sheets-Sheet 2 Original Filed April 14, 1945 May 11, 1954 A. M. FISCHER ADJUSTABLE SCRAPER BLADE MECHANISM FOR DRIERS v 4 Sheets-Sheet 3 Original Filed April 14, 1945 QZberZ/YFwc/zer BY 22m Z5 IN VEN TOR May 11, 1954 A. M. FISCHER ADJUSTABLE SCRAPER BLADE MECHANISM FOR DRIERS 4 Sheets-Sheet 4 Original Filed April 14, 1943 INVENTOR. Qlberfi 1260262, BY QM,

Patented May 11, 1954 UNITED STATES PATENT OFFICE ADJUSTABLE SCRAPER BLADE MECHANISM FOR DRIERS Albert M. Fischer, Dowagiac, Mich.

Claims.

The present invention pertains to an improved adjustable scraper blade mechanism for dryers, and is divisional of my copending application on Yeast Drying Apparatus, Serial No. 483,032, filed April 14, 1943, now issued as Patent 2,521,706, granted September 12, 1950.

In that copending application I have disclosed an improved yeast drying apparatus of the revolving drum type in which the yeast is dried on the outer surface of a rotating heated drum at atmospheric pressure. That application disclosed several new and improved features, including an improved adjustable scraper blade mechanism for scraping or stripping the dried yeast from the surface of the heated drum. Such adjustable scraper blade mechanism has been divided out of that application, and now forms the subject matter of the present divisional application.

One of the objects of the invention is to provide improved adjustments for adjusting the scraping blades relatively to the drum.

Another object is to provide improved lifting apparatus for moving the scraping blades into and out of operative engagement with the drum, which lifting apparatus can be given a predetermined setting so thatthe movement of the several blades back into engagement with the drum will be a. sequential operation in which the blades will engage the drum successively instead of simultaneously in order to avoid the placing of an abrupt or abnormal load on the machine. On the other hand, if it is desired that the blades engage the drum simultaneously instead of successively, the lifting apparatus can be given a different setting for obtaining that type of operation.

A further object is to provide a construction in which the tension with which the scraper blades are pressed against the drum can be preset, and therefore an unskilled operator cannot damage the drum surface by application of too heavy a pressure of the scraper blades against the drum.

Other objects, features and advantages of the invention will appear from the following detailed description of one preferred embodiment thereof. In the accompanying drawings illustrating such embodiment:

Figure 1 is an end elevational view of the yeast drying machine, showing the improved adjustable scraper blade mechanism at the left side of the figure;

Figure 2 is a side or front elevational View of the machine, showing the scraper blade mechanism in elevation;

Figure 3 is a fragmentary front elevational view of the scraper blade mechanism on a larger scale;

Figure 4 is an end view thereof on this same larger scale;

Figure 5 is a horizontal sectional view taken approximately on the plane of the line 5-5 of Figure 3;

Figure 6 is a detail sectional view taken on the plane of the line 66 of Figure 3:; and

Figure '7 is a section similar to Figure 6 but taken at another point along the scraper blade mechanism.

Referring first to Figures 1 and 2, the heated drying drum is indicated at 2|, this drum being hollow for the circulation of steam or other heating medium therethrough. Secured to opposite ends of the drum are supporting trunnions 22 and 23 (Figure 2) which are journaled for rotation in bearings 24 and 25 which are mounted on the end standards 26 and 21 of the supporting frame 28. The bearings 24 and 25 are preferably of the self aligning type so as to facilitate assembly and minimize bearing wear. The bearing shaft 22' of the left hand trunnion 22 carries a large spur gear 31 which is driven by a driving pinion 32 which is adapted to be driven at any selected speed through a variable speed drive mechanism 33, the latter receiving its power input from an electric motor or other driving source. The ability to adjust the speed of rotation of the drum 2| through the instrumentality of the variable speed unit 33 enables the apparatus to be adjusted to different total solids of the material to be dried, varying temperatures, humidity conditions, and other variable operating conditions.

Steam for heating the drum 2| is conducted through supply pipe 36 to a manifold housing 31' which is assembled over the end of the right hand trunnion shaft 23'. This right hand trunnion shaft is hollow for the circulation of steam therethrough into the rotating drum 2 l, and the inner end of the manifold housing 31 is provided with an adjustable stuffing gland 38 for maintaining a steam-tight joint at this point where the manifold housing engages over the end of the rotating trunnion shaft 23. The discharge of condensate and exhaust steam from the drum occurs through a discharge pipe 39 which passes axially through the hollow trunnion 23 in spaced relation to the bore of this hollow trunnion. As indicated in dotted lines, the inner end of this discharge or condensate pipe 39 is provided with a downwardly extending end 39' or any other equivalent device which is adapted to draw the condensate and exhaust steam from the lower interior portion of the drum, these devices being well known and serving to prevent the accumulation of an ex cessive amount of condensate within the drum. The discharge pipe 39 may be connected to a scoop which rotates with the drum, or as shown in the drawing it may be a stationary syphon pipe which has its outer end extending into and through the manifold housing 31. Said manifold housing has attachment to the end frame member 27 through a mounting bracket 42. A drain pipe i3 screws into the outer member of the stuffing gland, in communication with the condensate pipe 39, and conducts the condensate and discharge steam from the end of said condensate pipe down to a T connection 44. Leading from the lower end of T connection fi l is a vent valve 45 which acts as a vent for the drying drum ZI and which serves to discharge condensate, even in the absence of steam pressure. Leading from the lateral port of the T connection 44 is a pipe 46 which is adapted to conduct condensate and exhaust steam into a steam trap 47. From this steam trap the condensate is conducted to the heating jacket of a preheating chamber disposed below the drum ii, for preheating the yeast before it is applied to the drum. The construction and operation of this preheating chamber 5i are fully disclosed in my aforesaid prior application, Serial No. 483,032, now Patent No. 2,521,706, issued September 12, 1950, of which this application is a division. This preheating chamber is not illustrated and described in the present application because it does not affect the construction and operation of the adjustable scraper blade mechanism that constitutes the subject matter of the present application. The same can also be said of numerous other features disclosed in said prior Patent 2,521,706, such as: the circulating compartment for circulating the preheated yeast; the dip or feed trough for applying the preheated yeast to the drum 2I; the spill trough for catching any excess yeast that may be carried up on the drum from the dip trough; the equalizing blade for equalizing and predetermining the thickness of the yeast film on the drying drum 2i; the system for recirculating and screening the yeast accumulating in the spill trough; the end scrapers for removing yeast which might otherwise accumulate on the end surfaces of the drying drum 2 I etc. These other features have not been disclosed in the present application because they are not deemed to be pertinent to the adjustable scraper blade mechanism, but the details of these features can be readily had by reference to said prior Patent 2,521,706.

Referring now. to the improved adjustable scraper blade mechanism for removing the dried yeast from the drying drum 2!, this mechanism is indicated collectively at I60 in Figures 1 and 2, from which it will be seen that it extends across the front of the machine to bear against the lower front side of the drying drum. The scraper mechanism is assembled on a rotatable mounting shaft it! which extends parallel to the drying drum adjacent to the lower front side thereof.

' The ends of this shaft are journaled in bearing bosses I52 which are formed integral with webs I63 projecting outwardly and upwardly from adjustable mounting brackets I64. Each mounting bracket IE4 is secured by bolts I65 to the front flange of its respective end frame 26 or 21. The bolts its pass through vertically extending slots I60 in the mounting bracket I64, whereby the mounting bracket can be shifted upwardly or downwardly to different adjusted positions along the inclinedfront flange of the end frame. This vertical adjustment of the mounting brackets and of the mounting shaft It! enables the angle between the scraper blades or knives and the cylindrical surface of the drum to be adjusted as desired, i. e. to adjust the intercepted angle between the scraper knives and the surface of the drum, as viewed from the end of the machine. The scraper knife means I68 is preferably divided into a plurality of blade lengths disposed approximately end to end along the length of the drying drum. By dividing the knife apparatus into a plurality of sections, these sections can be arranged to engage the drum progressively so as to reduce the shock load when starting up the operation of the machine, and the sections are also easier to adjust relatively to the drum, and it takes less expensive equipment to sharpen same. In the illustrated embodiment I have shown the knife assembly divided into three knife sections, consisting of a middle knife I082) and two end knives Ififia and i680 on each side thereof. The middle knife "58b is disposed slightly higher than the end knives so that it can overlap the adjacent extremities of the end knives and thereby avoid leaving any line of the drum which is not stripped by a scraping knife. Each knife section is mounted by substantially the same form of mounting holder or bracket and associated cover plate, and hence I shall only describe one of these assemblies. Each mounting bracket or holder I69 comprises a tilted plate portion I'll (Figures 4, 5 and 6) which extends horizontally substantially the length of its individual knife or blade. A right angle flange I12 projects outwardly from the lower edge of the plate portion I'lI, preferably along substantially the entire length of the holder. Adjacent to each end of the holder circular bosses Il'3 are formed integral with the plate and shelf portion Ill-4'52 and project rearwardly for mounting on the adjustable supporting bar or shaft Itl. These mounting bosses [F3 are freely rotatable on the mounting shaft IEi. Lugs I74 projecting inwardly from the mounting bosses I I3 are apertured at is'5 (Fig. 6) for receiving the hooked upper ends of tension springs I'lt extending downwardly for attachment to spring tensioning devices which I shall presently describe. The action of these springs is that of continuously urging the scraper blades E6805, H382) and I680 resiliently against the surface of the drying drum.

Each knife or blade is assembled against the front face of the plate portion ill and is secured thereto by a clamping cover I18. Referring to Figure 8, each knife or blade 5000-1630 is provided with downwardly projecting extensions or clamping lugs I19, as indicated in dotted lines. These extensions are provided with vertical slots iSi adapted to receive the shanks of cap screws itZ. These cap screws pass through circular holes in the cover plate H8, and then pass through the vertical slots ltl, and then tap into threaded bores in the upwardly extending flange portion ill of the blade holder IE9.

Provision is made for effecting three different scraping adjustments of each scraper blade relatively to the surface of the drum: viz, (1) an independent adjustment of either end of the blade toward or away from the drum substantially in the plane of the blade or in a plane parallel thereto; (2) an independent adjustment of either end of the blade toward or away from the drum in a plane substantially at right angles to the plane of the blade; and (3) an adjustment of the angle intercepted between the plane of the blade and the surface of the drum, this angle being indicated at r in Figures 6 and 7. The first of these adjustments, made in a plane coincident with the plane of the blade, or in a plane parallel thereto, is effected by the two downwardly extending adjusting screws ltd provided at each end of the blade holder 159. These adjusting screws thread through tapped bosses projecting down from the lower edge of the blade holder I69, the upper ends of these screws passing up through the step iiange Hi2 and abutting against the lower edges of the slotted lug extensions H9 projecting down from the blade. It will be evident that upon loosening the clamping screws E32 the adjusting screws Hi4 can be operated selectively to shift either the left hand end or the right hand end of the blade upwardly or downwardly across the face of the mounting flange H- i, thereby adjusting the cutting edge of the blade at either end toward or away from the surface of the drum in a plane coincident with the plane of the blade. After the desired adjustment has been obtained in this plane, the clamping screws I82 are then retightened to retain the blade in its set adjustment.

The second adjustment which occurs in a plane substantially at right angles to the plane of the blade is effected by a plurality of small adjusting screws i236 extending in a horizontal row across the upper edge of the cover plate i725. These adjusting screws thread into tapped bores in the cover plate "58, and are provided with lock nuts I8? adapted to abut against the outer surface of the cover plate. The inner ends of these adjusting screws are adapted to be forced against the outer surface of the blade or knife Nita-i880, whereby to hex any desired portion of the blade toward or away from the surface of the drum in a plane extending at right angles to the plane of the blade. These adjusting screws enable relatively minute adjustments of each blade to be made relatively to the surface of the drum. The third adjustment for varying the intercepted angle :10 (Figures 6 and 7) is effected by loosening the bolts I and sliding the mounting brackets I64 for the mounting shaft ifii upwardly or downwardly along the inclined side surfaces of the end frames 26 and 2?, the slots ififi in the bracket I64 permitting such up and down sliding adjustment. Because of the angular slope of the front surface of each end frame 26, 21, and the angular relationship between the other parts of the assembly, this shifting of the mounting shaft l6! enables the blade to be adjusted for a greater or lesser intercepted angle r. The angle :0

can also be adjusted by turning the two screws I84. These screws will move the blades up or down, thereby decreasing or increasing the angle at. The screws i8 3 serve also to compensate for wear on the blades due to regrinding or sharpening. Either bracket I64 can be adjusted independently of the other, so that either end of the mounting shaft it! can be adjusted slightly relatively to the other end.

The aforementioned tension springs we act on each end of the blade holder and tend to hold the blade against the drum with a resilient pressure during the scraping operation. As shown in Figures 3 and 4, the lower ends of these springs are hooked to eye bolts iili which pass down through apertures 192 in a channel bar its and thread through tapped bosses of adjusting nuts or knobs 194, the latter bearing against the under side of the channel 93. The ends of the channel 193- are secured by bolts I95 to lugs i95a projecting from the webs N3 of the mounting bracket I64. Adjustment of the nuts or hand wheel knobs I94 enables the tension of the springs lit to be increased or decreased for causing either end of the scraper blade to be pressed with a greater or lesser pressure against the surface of the drum.

At the conclusion of an operating cycle it is preferable to swing'the blades i53c-i53e outwardly to inoperative positions, out of contact with the drying drum. This is accomplished by rotation of a hand wheel Hi5 disposed at the right hand end of the machine. This hand wheel revolves a threaded shaft l9? provided with a spherical head iPiS at its inner end, this spherical head seating in a spherical socket it? formed in a bracket fill which is bolted to the end frame N, such mounting of the shaft iii"? permitting the shaft to rotate and also to swing upwardly and downwardly through a limited arc. The threaded shaft screws through a threaded bore in a horizontally ertending trunnion pin 202. The ends of the trunnion pin are journaled in the forked upper end 2533 of an actuating arm 264, which is secured to the mounting shaft liii. It will hence be seen that rotation of the hand Wheel N38 is operative to oscillate the mounting shaft lfil. Such motion of the mounting shaft can be arranged to lift the blades Etta-i630 progressively from the surface of the drum through the instrumentality of three different lifting arms 295, 208 and 2%! which can be set to act in sequence on the respective blade helders. Alternatively, these lifting arms Ede--25? may also be set to engage or release the knives simultaneously, if desired. Each lifting arm is formed as an integral upwardly projecting extension from a collar 26?), Zilii and fill. Each of these collars is fixedly secured to the mounting shaft Si by a set screw Ziit (Figure 4). The lifting arm 205 is positioned to lift blade 580 from the drum; the lifting arin 2:536 is positioned to lift blade ittb from the drum; and the lifting arm 2331 is positioned to lift the blade i580: from the drum. As shown in Figures 6 i, when the lifting arms are set for a progressive engagement of the blades with the drum, the arm 2515 normally stands spaced. a slight distance from the plate portion ill of its respective holder during operation, and the other two lifting arms 2% and 2c? normally stand at increasingly greater distances from the flanges iii of their respective holders. Hence, these lifting arms come into action progressively for lifting the scraping blades progressively from the surface of the drum; and, conversely, in the operation of restoring the blades to scraping position the blades engage the drum successively, thereby minimizing any possibility of imposing an abrupt or shock load on the drum and driving mechanism. When the rying machine is started up after having been shut down for a substantial interval, it is desirable that the drying drum be rotated slowly while it is being brought up to temperature by the steam entering through supply line 36, this preliminary rotation serving to bring about uniform heating and expansion of the drum surface. During this preliminary rotation the scraping blades or knives should not be allowed to contact the drum inasmuch as there is substantial likelihood of damaging the surface of the drum if the scraping blades are permitted to press against the drum when the drum is not carrying any protective film of yeast. As the yeast is brought into contact with the drum,

there may result several idle revolutions of the drum in arriving at proper operating temperatures, adjustments of the equalizer blade 93, etc. This may result in a relatively thick film of yeast becoming encrusted on the drum before the scraping knives i68al 680 are brought into contact with the drum. If the knives were all allowed to engage the drum simultaneously, against this relatively hard encrusted film of yeast, there would result a substantial shock load in the operation of the machine. This is objectionable and is entirely avoided by the above described arrangement of the lifting fingers which result in the blades being brought into operative engagement with the drum in a progressive sequence so that only one blade is brought to bear against the encrusted film at one time.

As the dried yeast is stripped from the surface of the drum it falls outwardly over the outer surfaces of the scraping blades and drops down into a longitudinal conveyor 2E8 which extends along the front side of the machine below the scraping blades (Figure 1). Front and rear deflector panels 2 and 212 direct all of the yeast down into the conveyor. A conveyor screw 2&3 extends along the arcuate bottom surface of the conveyor trough, and serves to propel the dried yeast toward one end of the trough. A cooling jacket 2M embraces the lower portion of the trough and is provided with suitable pipe connections 255 and 255 (Figure 2) for conducting cold Water or other cooling medium through said jacket. For the purpose of preventing any loss of the heat labile vitamins, it is desirable to cool the dried yeast before it is fed to the pulverlzer. The left hand end of the feed screw 253 is provided with a shaft 25? projecting beyond this end of the conveyor trough 21a. The shaft 2!; carries a sprocket wheel 2H8 over which passes the drive chain 6'! which is driven by the sprocket Wheel 68 on a trunnion shaft 22 of the drying drum. The feed screw 253 conveys the naked yeast toward the right hand end of the trough, from whence the yeast is conveyed in any suitable manner to a pulverizer or to a place of storage. In typical or preferred installations, the trough 21K) is arranged to discharge into an elevator which carries the dried product up to an elevated inlet of a motor-driven pulverizing unit which breaks up the flaked yeast into very small particles. From this pulverizer the yeast can be conveyed to a place of storage, or can be packaged in bags, boxes or the like.

While this invention has been illustrated in connection with a yeast drying machine, it is understood that it is by no means limited to this particular application, and that it can be usefully employed in drying apparatus for other products such as milk, blood, cereals, paint, etc.

While I have illustrated and described What I regard to be the preferred embodiment of my invention, nevertheless it will be understood that such is merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention.

I claim:

1. In drying apparatus of the class described including a cylindrical drying drum rotatably mounted in a supporting frame and adapted to receive a liquid material for drying thereon, the combination therewith of adjustable scraper blade mechanism for scraping the dried material from said drum, comprising a mounting shaft extending substantially parallel to the cylindrical outer surface of said drum, a plurality of separate blade holders each provided with rearwardly projecting apertured bosses mounted for independent pivotal movement on said mounting shaft, each of said blade holders comprising a blade mounting plate portion and an outwardly projecting step flange at the lower edge of said plate portion, a scraper blade clamped fiat against the outer surface of each blade mounting plate portion with the lower edge of the blade disposed adjacent to said step flange and with the upper edge projecting upwardly above said plate portion for engagement with the drying drum at a level above the blade holder, a clamping cover and clamping screw coacting with said blade holder for clamping the scraper blade against said plate portion, the blade mounting plate portion on one of said holders being spaced outwardly a greater distance from the axis of said mounting shaft than the blade mounting plate portion on the next adjacent holder, thereby enabling the blade mounted on the first of such holders to engage said drum at a higher level than the blade on said next adjacent holder but with both blades engaging the drum at substantially the same angle, the blade which engages the drum at the higher level having an overhanging end portion which overlaps the end of the next adjacent blade so that there will be no area of drum surface between said blades that is not scraped by said blades, separate springs connected to each of said blade holders for independently revolving each of said blade holders relatively to said shaft in a direction tending to hold the upper edges of their respective scraper blades pressed resiliently against the drying drum, adjusting screws threading upwardly through the step flanges of said blade holders and adapted to contact the lower edges of said blades for adjusting the blades in planes substantially parallel to the blade mounting plate portions of said holders, adjusting screws threading transversely through said clamping covers and adapted to contact the front sides of said scraper blades at levels above said blade mounting plate portions for adjusting the upper edges of said blades in planes substantially at right angles to said plate portions, brackets mounted on said supporting frame for rotatably supporting said mounting shaft, means enabling said brackets to be adjusted on said supporting frame for shifting the position of said shaft to adjust the intercepted angle between said scraper blades and the cylindrical surface of said drying drum, separate lifters on said mounting shaft for imparting pivotal movement to said blade holders in opposition to the action of said springs for lifting the upper edges of said scraper blades out of contact with said drum, said lifter members being secured to said shaft in different angular positions whereby in one direction of rotation of said shaft said blades are lifted successively from the surface of the drum and in the other direction of rotation the blades are restored successively into scraping engagement with the drum, and means for rotating said shaft in opposite directions.

2. In drying apparatus of the class described including a cylindrical drying drum rotatably mounted in a supporting frame and adapted to receive a liquid material for drying thereon, the combination therewith of adjustable scraper blade mechanism for scraping the dried material from said drum, comprising a mounting shaft extending substantially parallel to the cylindrical outer surface of said drum, aplurality of separate blade holders each provided with mounting apertures mounted for independent pivotal movement on said mounting shaft, each of said blade holders comprising'a blade mounting plate portion and an outwardly projecting step flange at the lower edge of said plate portion, a scraper blade clamped flat agaist the outer surface of each blade mounting plate portion with the lower edge of the blade disposed adjacent to said step flange and with the upper edge projecting upwardly above said plate portion for engagement with the drying drum at a level above the blade holder, a clamping cover and clamping screu coacting with said blade holder for clamping the scraper blade against said plate portion, the blade mounting plate portion on one of said holders be ing spaced outwardly a greater distance from the axis of said mounting shaft than the blade mounting plate portion on the next adjacent holder, thereby enabling the blade mounted on the first of said holders to engage said drum at a higher level than the blade on said next adjacent holder but with both blades engaging the drum at substantially the same angle, the blade which engages the drum at the higher level having an overhanging end portion which overlaps the end of the next adjacent blade so that there will be no area of drum surface between said blades that is not scraped by said blades, separate springs connected to each of said blade holders for independently revolving each of said blade holders relatively to said shaft in a direction tending to hold the upper edges of their respec tive scraper blades pressed resiliently against the drying drum, adjusting screws threading upwardly through the step flanges of said blade holders and adapted to contact the lower edges of said blades for adjusting the blades in planes substantially parallel to the blade mounting plate portions of said holders, adjusting screws thread- -ing transversely through said clamping covers and adapted to contact the front sides of said scraper blades at levels above said blade mounting plate portions for adjusting the upper edges of said blades in planes substantially at right angles to said plate portions, separate lifters on said mounting shaft for imparting pivotal movement to said. blade holders in opposition to the action of said springs for lifting the upper edges of said scraper blades out of contact with said drum, said lifter members being secured to said shaft in different angular positions whereby in one direction of rotation of said shaft said blades are lifted successively from the surface of the drum and in the other direction of rotation the blades are restored successively into scraping engagement with the drum, and means for rotating said shaft in opposite directions.

3. In drying apparatus of the class described including a cylindrical drying drum rotatably mounted in a supporting frame and adapted to receive a liquid material for drying thereon, the combination therewith of adjustable scraper blade mechanism for scraping the dried material from said drum, comprising a mounting shaft extending substantially parallel to the cylindrical outer surface of said drum, a plurality of separate blade holders each provided with mounting apertures mounted for independent pivotal movement on said mounting shaft, each of said blade holders comprising a blade mounting plate portion and an outwardly projecting step flange at the lower edge of said plate portion, a scraper blade clamped flat against the outer surface of each blade mounting plate portion with the lower edge of the blade disposed adjacent to said step 10 flange and with the upper edge projecting upwardly above said plate portion for engagement with the drying drum at a level above the blade holder, a clamping cover and clamping screw coacting with said blade holder for clamping the scraper blade against said plate portion, the blade mounting plate portion on one of said holders being spaced outwardly a greater distance from the axis of said mounting shaft than the blade mounting plate portion on the: next adjacent holder, thereby enabling the blade mounted on the first of said holders to engage said drum at a higher level than the blade on said next adjacent holder but with both blades engaging the drum at substantially the same angle, the blade which engages the drum at the higher level having an overhanging end portion which overlaps the end of the next adjacent blade so that there will be no area of drum surface between said blades that is not scraped by said blades, separate springs connected to each of said blade holders for independently revolving each of said blade holders relatively to said shaft in a direc tion tending to hold the upper edges of their respective scraper blades pressed resiliently against the drying drum, adjusting screws threading transversely through said clamping covers upwardly through the step flanges of said blade holders and adapted to contact the front edges of said scraper blades at levels above the blade mounting plate portions for adjusting the blades in planes substantially parallel to the blade mounting plate portions of said holders, separate lifters on said mounting shaft for imparting pivotal movement to said blade holders in opposition to the action of said springs for lifting the upper edges of said scraper blades out of contact with said drum, said lifter members being secured to said shaft in different angular positions whereby in one direction of rotation of said shaft said blades are lifted successively from the surface of the drum and in the other direction of rotation the blades are restored successively into scraping engagement with the drum, and means for rotating said shaft in opposite directions.

4. In drying apparatus of the class described including a cylindrical drying drum. rotatably mounted in a supporting frame and adapted to receive a liquid material for drying thereon, the combination therewith of adjustable scraper blade mechanism for scraping the dried material from said drum, comprising a mounting shaft extending substantially parallel to the cylindrical outer surface of said drum, a plurality of separate blade holders each provided with mounting apertures mounted for independent pivotal movement on said mounting shaft, each of said blade holders comprising a blade mounting plate portion, a scraper blade clamped flat against the outer surface of each blade mounting plate portion with the upper edge projecting upwardly above said plate portion for engagement with the drying drum at a level above the blade holder, a clamping cover and clamping screw coasting with said blade holder for clamping the scraper blade against said plate portion, the blade mounting plate portion on one of said holders being spaced outwardly a greater distance from the axis of said mounting shaft than the blade mounting plate portion on the next adjacent holder, thereby enabling the blade mounted on the first of such holders to engage said drum at a higher level than the blades on said next adjacent holder but with both blades engaging the drum at substantially the same angle, the blade which engages the drum at the higher level having an overhanging end portion which overlaps the end of the next adjacent blade so that there will be no area of drum surface between said blades that is not scraped by said blades, separate springs connected to each of said blade holders for independently revolving each of said blade holders relatively to said shaft in a direction tending to hold the upper edges of their respective scraper blades pressed resiliently against the drying drum, adjusting screws threading transversely through said clamping covers and adapted to contact the front edges of said scraper blades at levels above the blade mounting plate portions for adjusting the blades in planes substantially parallel to the blade mounting plate portions of said holders, separate lifters on said mounting shaft for imparting pivotal movement to said blade holders in opposition to the action of said springs for lifting the upper edges of said scraper blades out of contact with said drum, said lifter members being secured to said shaft in different angular positions whereby in one direction of rotation of said shaft said blades are lifted successively from the surface of the drum and in the other direction of rotation the blades are restored successively into scraping engagement with the drum, and means for rotating said shaft in opposite directions.

5. In drying apparatus of the class described including a cylindrical drying drum rotatably mounted in a supporting frame and adapted to receive a liquid material for drying thereon, the combination therewith of adjustable scraper blade mechanism for scraping the dried material from said drum, comprising a mounting shaft extending substantially parallel to the cylindrical outer surface of said drum, a plurality of separate blade holders each provided with mounting apertures mounted for independent pivotal movement on said mounting shaft, each of said blade holders comprising a blade mounting plate portion and an outwardly projecting step flange at the lower edge of said plate portion, a scraper blade clamped fiat against the outer surface of each blade mounting plate portion with the lower edge of the blade disposed adjacent to said step flange and with its upper edge projecting upwardly above said plate portion for engagement with the drying drum at a level above the blade holder, a clamping cover and clamping screw coacting with said blade holder for clamping the scraper blade against said plate portion, the blade mounting plate portion on one of said holders being spaced outwardly a greater distance from the axis of said mounting shaft than the blade mounting plate portion on the next adjacent holder thereby enabling the blade mounted on the first of said holders to engage said drum at a higher level than the blade on said next adjacent holder but with both blades engaging the drum at substantially the same angle, the blade which engages the drum at the higher level having an overhanging end portion which overlaps the end of the next adjacent blade so that there will be no area of drum surface between said blades that is not scraped by said blades, separate springs connected to each of said blade holders for independently revolving each of said blade holders relatively to said shaft in a direction tending to hold the upper edges of their respective scraper blades pressed resiliently against the drying drum, adjusting screws threading upwardly through the step flanges of said blade holders and adapted to contact the lower edges of said blades for adjusting the blades in planes substantially parallel to the blade mounting plate portions of said holders, and adjusting screws threading transversely through said clamping covers and adapted to contact the front sides of said scraper blades at levels above said blade mounting plate portions for adjusting the upper edges of said blades in planes substantially at right angles to said plate portions.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 65,377 Guenther June 4, 1867 691,210 Venuleth Jan. .14, 1902 927,169 Roeh July 6, 1909 1,591,053 Reavell July 6, 1926 1,853,451 Overton Apr. 12, 1932 1,927,694 Wood Sept. 19, 1933 2,117,958 Hershey May 17, 1938 2,376,502 Overton May 22, 1945 2,521,706 Fischer Sept. 12, 1950 FOREIGN PATENTS Number Country Date 10,852 Denmark May 18, 1908 313,817 Great Britain June 20, 1929 406,305 Great Britain Feb. 23, 1934 438,251 Germany Dec. 11, 1926

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