US3720479A - Devolatilizer rotor assembly - Google Patents

Abstract

A ROTOR ASSEMBLY SUITABLE FOR USE IN A DEVOLATILIZER FOR PROCESSING RELATIVELY VISCOUS MATERIALS TO SEPARATE VOLATILES THEREFROM IS DESCRIBED. THE MOTOR ASSEMBLY INCREASES VAPOR SEPARATION EFFICIENCY AND UTILIZES ON ITS CIRCUMFERENTIAL SHAFT SURFACES AXIALLY EXTENDING, RADIALLY RAISED FLANGED PORTIONS UNDER A PLURALITY OF PLOW BLADES ADAPTED TO EXERT AXIAL AND CIRCUMFERENTIAL FORCE VECTORS ON ALL POINTS OF CYLINDRICAL REGIONS SWEPT BY THE ROTOR ASSEMBLY IN OPERATION.

Description

March 13, 1973 G- A- LATINEN 3,720,479

-'-DEVOLATILIZER ROTOR ASSEMBLY Filed Aug. 16. 1971 6 Sheets-Sheet l INVENTOR GEORGE A. LATINEN ATTORNEY March 13, 1973 G.'A. LATINEN 3,'}20,47 9

DEVOLATILIZER ROTOR ASSEMBLY Filed Aug. 16, 1971 6 Sheets-Sheet 2 'FIG.2

ROTATION I6 I INVENTOR GEORGE A. LATINEN BY fmb 9km ATTORNEY March 13, W73 6. A. LATINEN 3,720,479

DEVOLAT ILI Z ER ROTOR AS S EMBLY Filed Aug. 16. 1.971 6 Sheets-Sheet 3 INPUT CHAMBER 45 26 729 VAPOR SEPARATION CHAMBER VENT | COMPRESSION CHAMBER 50 35 PUMPING CHAMBER l 59 PRODUCT OUT,

SEALING CHAMBER GEORGE A. LATINEN TRANSMISSION MOTOR ATTORNEY March 13, 1973 A- LAT'NEN 3,720,479

DEVOLATILIZER ROTOR ASSEMBLY Filed Aug. 16. 1971 e Sheets-Sheet 4 FEED IN FLUID IN av-FLUID OUT FLUID OUT 29 FIG. 4A

FLUID IN FLUID OUT A MAT L. FLOW INVENT OR GEORGE A.

LATINEN FLUID |N-- 94 ym m ATTORNEY March 13, 1973 G. A. LATINE 3,720,479

DEVOLATILIZER ROTOR ASSEMBLY Filed Aug. 16, 1971 6 Sheets-Sheet 5 FLUID FLUID OUT F I 6.. 4B

2' #Q 35 FliUID I I 57 1 f I I i 58' I I I PRODUCT OUT I TO I I SECOND STAGE I I I J v INVENTOR I GEORGE A. LATINEN 6/ 4,221; #7 BY 62% TRANSMISSION m ATTORNEY March 13, 1973 LATINEN 3,720,479

DEVOLATILIZER ROTOR ASSEMBLY Filed Aug. 16, 1971 6 Sheets-Sheet 6 INVENTOR GEORGE A. LATI NEN ATTORNEY 3,720,479 DEVOLATILIZER ROTOR ASSENBLY George A. Latiuen, deceased, late of Springfield, Mass, by May V. Latinen, administratrix, Springfield, Mass, assignor to Monsanto Company, St. Louis, Mo.

Filed Aug. 16, 1971, Ser. No. 172,058 Int. Cl. F04d 29/38 US. Cl. 416-498 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND Wiped film devolatilizers of the type characteristically used to separate a relatively volatile material from a relatively non-volatile material function by transporting a mixture of such volatile and non-volatile materials into and through a separation chamber wherein conditions are maintained at such elevated temperatures and reduced pressures that the volatile material is above its boiling point, permitting separation of such volatile material as a vapor phase from the non-volatile material. In such United States Patent transporting, a wiped film devolatilizer utilizes a rotor assembly which axially revolves in such separation chamber and which operates to move material axially therethrough and also simultaneously to spread material in the form of a thin film over inside chamber surfaces.

A number of different constructions for wiped film devolatilizers are already known to the art, but it is a general fact that, in all such devices, the rotor assembly employed therein has a profound influence on operating and performance characteristics. Such factors as rotor blade land area and contact angle, rotor shaft speed, and the like, can be critical. The efiectiveness of a rotor assembly in the separation chamber of a given devolatilizer is judged by such factors as these and others known to the art, such as ability to transfer mechanical energy to the material being devolatilized, ability to promote the transfer of thermal energy from the heating medium adjacent separation chamber outside wall through the wall to the material being devolatilized, ability to separate vapor from nonvolatile material within the separation chamber, the rate and steadiness with which material being devolatilized is forwarded through the separation chamber, and the like.

In many cases, devolatilized material from a devolatilizer is fed to a strand die or other shape-forming machine. To operate properly, such a machine requires a steady flow of devolatilized material wherein the flow does not experience short term variations with respect to time. The condition of excessive short term variation in flow with time is called surging as those skilled in the art appreciate, it is highly desirable to avoid surging in feeding a shape-forming machine and in various other situations.

In operation, a rotor assembly develops a moving wave or mass of material before each blades leading edge just in front of the blades land. It has been heretofore discovered that by not using a rotor assembly with continuously extending screw blades, and by using instead a serrated blade, or a series of separate, spaced blade-like members, one can obtain improved energy transfer to the melt and reduced surging, particularly with high viscous fluid materials. Such a discontinuous blade structure, however, has still only at best a somewhat reduced surging characteristic and ability to separate evolved vapor from the non-volatile materials.

There has now been discovered, however, a new and very useful construction for a class of rotor assemblies having interrupted blade structures which construction not only has adequate energy transfer but also greatly reduces surges in the flow of devolatilized material from wiped film devolatilizer constructions wherein used. Furthermore, this class of rotor assemblies generally improves vapor separation in a wiped film devolatilizer separation chamber where cocurrent, as opposed to countercurrent, flow of vapor to non-volatile material takes place, thereby increasing the efficiency of separation of volatile from non-volatile materials in such chamber.

SUMMARY The present invention is directed to a type of flanged rotor assembly adapted for use in the separation chamber of a wiped film devolatilizer, and is particularly suitable for devolatilizing relatively viscous fluid materials. In such rotor assembly, the blades are formed by a series of bladelike separate members which are arranged in axially extending rows positioned on circumferential side wall portions of a central rotor shaft. Radially positioned between the blade-like members and the central rotor shaft are wedge-like, axially extending flange members. The bladelike members are positioned and constructed to exert axial and circumferential force vectors on all regions cylindrically and radially located adjacent the rotor assembly as it rotates. The flange members are positioned and constructed both to direct material being devolatilized to the periphery of a separation chamber where it can be worked by the interaction of blades and separation chamber wall as the rotor assembly rotates and to create a void space therebehind in a wave of material swept thereover by the blades.

DRAWINGS The present invention is better understood by reference to the appended drawings wherein:

FIG. 1 is a representation in side elevation of an embodiment of a rotor assembly of this invention;

FIG. 2 is a developed view of a fragment of the circumferential cylindrical surface of the completed rotor assembly of FIG. 3;

FIG. 3 is a diagrammatic representation in longitudinal section of a wiped film devolatilizer construction wherein a rotor assembly of this invention is employed;

FIGS. 4A and 4B show a detailed longitudinal sectional view through the embodiment shown in FIG. 3; FIG. 4A showing the upper portion of such embodiment, FIG. 4B showing the lower portion thereof, some parts broken away and some parts thereof shown in section, and

FIG. 5 is a vertical sectional view taken along the line 5-5 of FIG. 4A.

DETAILED DESCRIPTION Illustrated in FIGS. 1 and 2 are constructional principles utilized in an embodiment of a rotor assembly of the present invention, such assembly being here designated in its entirety by the numeral 14. Rotor assembly 14 is adapted to be utilized in the separation chamber of a devolatilizer (see FIGS. 4A and 4B). Rotor assembly 14 employs a rotatably mountable cross-sectionally circular shaft means 15 which preferably has generally cylindrical side wall portions 16.

Since the diameter of a shaft means 15 is, or can be, relatively large in an industrial scale rotor assembly 14, it is common and expeditious to construct shaft means 15 as a hollow tube except at the opposite ends thereof.

Thus, at the end thereof chosen to be the input end, a solid, smaller diameter shaft 13 may be secured coaxially with axis 12, while, at the output end, the base or enlarged end portion of a frustoconical shaft section 11 of a compression screw shaft may be secured coaxially with axis 12, thereby fitting rotor assembly 14 for use, for example in a wiped film devolatilizer of the type shown in FIGS. 3-5 described below.

Secured to side wall portions 16 as by welding or the like, in the embodiment shown, are four flanges 17 which axially extend and radially project from shaft means 15. In general, any convenient number of such flanges may be employed on such a shaft means 15, but it is preferred to employ at least two and, more preferably, at least three. On any given shaft means 15, all flanges 17 are preferably similarly dimensioned, and they are circumferentially spaced from one another on side wall portions 16. Preferably, such flanges 17 are circumferentially equally spaced from one another.

Each flange 17 characteristically has a circumferentially rising, ramp-like, circumferentially located outside face 18 which has a leading edge 19 and a trailing edge 20. Both edges 19 and 20 extend axially along side wall portions 16, and a flange 17 is so formed as to have edges 19 and 20 on a given flange 17 be in circumferentially (relative to shaft means 15) spaced, parallel relationship to each other. Each leading edge 19 is generally flush with the surface of side wall portions 16. Each trailing edge defines or sets the maximum radial (with respect to axis 12 of shaft means 15) height of its associated flange 17 above the side wall portions 16. All flanges 17 are so positioned on side wall portions 16 that their respective outside faces 18 all rise in the same circumferential direction (i.e. either clockwise or counterclockwise). Preferably each flange 17 has a planar face 18.

A plurality of blade-like members 21 are located on the outside face 18 of each flange 17, as by welding, or the like. Each such blade-like member 21 extends generally radially outwardly from its associated face 18 and circumferentially somewhere in the region between the leading edge 19 and the trailing edge 20 of its associated flange 17. All the blade like members 21 on any one face 18 are axially spaced from one another. In one preferred embodiment, blade members 21 on a flange 17 are equally axially spaced from one another.

Each blade-like member 21 is typically circumferentially inclined at an angle between about 10 and 89 with respect to the axis 12 of shaft means 5, the exact angle for each blade in any given rotor assembly 14 being a matter of individual choice or preference. All the blade-like members 21 generally have a similar inclination (i.e. a positive or negative slope on a circumference relative to axis 12). A preferred circumferential inclination angle is in the range from about 25 to Each individual blade-like member 21 is in the embodiment shown flattened but it will be appreciated that an individual member 21 may be curved. Each blade-like member 21 has at least one land portion 22 defined on its circumferentially located, radial outer edge. A single such land portion 22 per blade-like member 21 is presently preferred, but more than one such land portion 22 may be on a single member 21 if desired. The circumferentially located, radial outer edge section comprising such land portion 22 is substantially equally radially spaced from axis 12 but generally can have any desired cross-sectional configuration. Optionally, the leading (relative to the direction of rotation of shaft means 15), radially located edge section of a blade-like member 21 can be considered to be, and can be formed into, an extension of a land portion 22. For purposes of the present invention, no particular criticality or novelty is associated with construction, configuration, or location of individual blade-like members 21 on a shaft means 15. It is presently preferred to have all blade-like members 21 on a given shaft means 15 in a given rotor assembly 14 be similar to one another. Conventional blade designs can be utilized as those skilled in the art will readily appreciate.

In general, as shown by FIG. 2, all the blade-like members 21 on any one flange 17 as so positioned relative to the other such blade-like members 21 on the remaining flanges 17 that all cylindrical regions circumferentially located radially opposite shaft means 15 are, or would be, swept by at least one of such land portions 22 during one revolution of a rotor assembly 14 on axis 12. For some applications, all blade-like members 21 on a given flange 17 are substantially parallel to one another. However, it may frequently be desirable to use in a given rotor assembly blades of different size, angular orientation, or land area at diflerent axial locations along the rotor in a separation chamber to achieve a desired vapor separation or material forwarding action, or energy transfer at points along the axial length of a rotor assembly, as those skilled in the art will readily appreciate.

Preferably, in a rotor assembly 14, the ratio of the sum of the surface areas of all land portions 22 in assembly 14 to the total cylindrical surface area swept by a rotor assembly '14 in one revolution thereof ranges from about 0.003 to 1 to 0.15 to 1. Preferably, also in a rotor assembly 14, the ratio of the length of a flange 17 (as being representative of the total functional axial length of a rotor assembly 14) to the maximum diameter (e.g. from land portion 34 to another opposite thereto) of such rotor assembly 24 ranges from about 3 to l to 20 to 1. No particular criticality is associated with the various individual elements, the dimensions thereof, or the interrelationship of such to other such elements employed in a given rotor assembly 24 for purposes of the present invention.

As can be seen, for example, in FIGS. 1, 2 and 5 there are three main dimensions influencing the construction and sizes of a set of flanges 17 in a rotor assembly 14. These dimensions are the circumferentially extending width of a flange 17 (labeled a), the circumferential distance between adjacent flanges 17 (labeled b) and the radial maximum height of a flange 17 beyond the wide wall portions 16 (labeled 0). Presently, it is preferred to have dimension a be smaller than dimension b and to have dimension 0 be smaller than dimension b. It is further preferred presently to have each blade like member 21 extend continuously from leading edge 19 to trailing edge 20, as shown. It is still further preferred to have each blade-like member radially extend beyond trailing edge 30 by a distance equal to about /2 to 1 /2 the value of dimension 0. Additionally, it is yet further preferred to have the radius of shaft means 15 be greater than either dimension a or dimension b.

Referring to FIGS. 1 and 2, it is seen that, in the embodiment of rotor assembly 14 shown, the land portion 22 of one blade-like member 21 on one flange 17 ends at trailing edge 20 at a point which, when circumferentially projected over to the leading edge 19 of the next (going in the direction of rotation of shaft means 25) flange 17, marks the beginning of the land portion 34 of another blade-like member 21 on such next adjacent flange 17. If such were not the case, and there were no land portion 34 of a blade-like member 21 on such next adjacent flange 17, then there would be a sort of dead spot on rotor assembly 14 where no material being devolatilized would be contacted or moved by a blade-like 'member 21 until, as rotation of side wall portions 15 continued, still another blade-like member moves into position on a subsequent circumferentially located flange. Such a situation (not illustrated) causes a species of lost motion and serves to increase residence time of material in a separation chamber of a wiped film devolatilizer, which, under certain operating conditions may be desirable or desired.

On the other hand, if such were not the case, and there is an overlap between a pair of circumferentially adja- .ditions, such an overlap may be desirable or desired, as

when viscosity considerations favor such. A presently pre ferred class of rotor assemblies comprises the domain wherein each land portion of all blade-like members on one flange ends where each land portion of all blade-like members on the next adjacent flange begin measured circumferentially up to the situation where each land portion of all blade-like members on one flange ends where each land portion of all blade-like members on the next adjacent flange likewise end, also measured circumferentially.

In FIG. 3 is seen an embodiment of a wiped film devolatilizer incorporating a rotor assembly of the present invention, such devolatilizer being herein designated in its entirety by the numeral 25. Devolatilizer utilizes a housing 26 which in an operative devolatilizer is substantially gas tight and fluid tight. Housing 26 is generally cross-sectionally circular and symmetrical with respect to a common longitudinal axis 27 extending therethrough. Defined within housing 26 at successive adjoining regions along axis 27 are a series of chambers which sequentially comprise an input chamber 28, a vapor separation chamber 29, a compression chamber 30, a pumping chamber 31 and a sealing chamber 32. The housing has defined therein certain apertures. Thus, housing 26 has an input port 33 leading into input chamber 28. A drive shaft entry port 34 is adjacent the sealing chamber 32, though those skilled in the art will appreciate that the drive shaft entry port could be placed at the other end (not shown) of the devolatilizer assembly 25. An output port 35 from pumping chamber 31 is located typically adjacent the sealing chamber 32. A vapor takeoff port 36 is located in separation chamber 29, typically and preferably adjacent compression chamber 30.

Within the input chamber 28 and positioned so as to be generally coaxial with axis 27 is a first shaft 40. A splined bushing construction 41 journals shaft for rotational movements and also permits melt material (not shown) during operation of the devolatilizer 25 entering input chamber 28 to pass from port 33 through input chamber 28 and enter into the separation chamber 29 circumferentially about first shaft 40 (see also, for example, FIG. 4A). Thus, in this embodiment sealing means for first shaft 40 is provided by housing 26 itself during operation of the devolatilizer 25 thereby avoiding the necessity for a separate sealing assembly such as is commonly necessary to obtain a fluid seal between a rotating member and a fixed member, as those skilled in the art will appreciate. Additional constructional details for input chamber 28 are given in greater detail hereinafter.

Within separation chamber 29 and located generally coaxially with axis 27 is rotatable rotor assembly, herein designated in its entirety by the numeral 42. Rotor assembly 42 has an axially extending generally enclosed drum 43 with cylindrical side wall portions 44 and an end wall portion 45. End wall 45 is located adjacent input chamber 28. First shaft 40 projects into the vapor separation chamber 29 and interconnects with the end wall portion 45 of drum 43 so that both drum 43 and first shaft 40 are coaxial with axis 27. It will be appreciated that in place of the first shaft 40 within vapor separation chamber 29, one could employ a stub shaft (not shown) on drum 43 "which is interconnected with first shaft 40.

A plurality of radially extending, axially projecting rib members 46 are positioned on end wall 4-5 between shaft 40 and side wall portions 44. Ribs 46 are adapted to deliver material from the region circumferentially located about first shaft 40 to the region circumferentially located adjacent side wall portions 44 of rotor assembly 42.

Integral, radially projecting, blade members 47 are located on side wall portions 44. Blade members 47 terminate in land regions 48 at and in their respective circumferentially located, radial outer edge portions. All individual land regions 48 are substantially equally radially spaced from axis 27. Individual blade members 47 are so arranged on the side wall portions 44 of drum 43 that substantially every inside cylindrical surface portion of housing 26 in vapor separation chamber 29 adjacent said side wall portions 44 is swept by at least one of the land regions 48 during each revolution of rotor assembly 42 during operation of devolatilizer 25.

The rotor assembly 42 during operation of devolatilizer 25 rotates and is adapted thereby to produce simultaneously several different effects. Thus, the rotor assembly 42 is adapted to move melt material through the separation chamber 29 from the input chamber 28 to the compression chamber 30. In addition, rotor assembly 42 is adapted to spread in the form of a thin film (not shown) at least a portion of melt material in the separation chamber 29 over inside cylindrical surface portions of housing 26 in separation chamber 29. Finally, rotor assembly 42 is adapted to produce cocurrent movement of vapors (which have escaped from melt material) and melt material in the separation chamber 29 as the melt material courses through separation chamber 29 to vapor take-off port 36.

Generally positioned within compression chamber 30 and generally coaxial with axis 27 is a compression screw 59. Compression screw 50 has a shaft portion 51 whose diameter is so related to the inside diameter of housing 26 in the region of compression chamber 30 along the axial length thereof that the radial distance 52 between shaft portion 51 and the inside cylindrical surface portions of housing 26 in the region of compression chamher 30 generally continuously declines along axis 27 proceeding in a direction from separation chamber 29 towards pumping chamber 31. Shaft portion 51 adjacent separation chamber 29 is integral with the side 'wall portions 44 of drum 43.

Peripherally located, circumferentially extending, and radially projecting is a helical rib 53 which is integral with shaft portion 51. The width of rib 53 in a radial direction is such as to bring the peripheral outside edge portion or land area of rib 53 proximately to the inside cylindrical surface portions of housing 26 in the region of compression chamber 30. The compression screw 50 is thus adapted to collect, compress and convey melt material from separation chamber 29 to pumping chamber 31 during operation of devolatilizer 25.

Generally positioned within the pumping chamber 31 and generally coaxial with axis 27 is a pump screw 55. Pump screw 55 is of conventional design and is adapted to pressurize and convey melt material from compression chamber 30 to melt output port 35. Pump screw 55 adjacent compression chamber 30 is integral with shaft portion 51.

Generally positioned within sealing chamber 32 and generally coaxial with axis 27 is a second shaft 57. Bearing or journal means 58 generally associated with sealing chamber 32 journals and mounts second shaft 57 for r0- tational movements axially. Adjacent pumping chamber 31, second shaft 57 is integral with pump screw 55.

Generally associated with sealing chamber 32 and adapted to make sealing engagement between second shaft 57 and housing 26 during operation of devolatilizer 25 is a conventional type viscoseal screw assembly 59, though those skilled in the art will appreciate that any conventional sealing means can be used here to achieve sealing engagement between second shaft 57 and housing 26.

Thus, in devolatilizer 25, there is a screw assembly comprising first shaft 40, rotor assembly 42, compression screw 50, pumping screw 55 and second shaft 57. To rotatably drive this screw assembly, power transfer means is provided. In the embodiment shown, such means is provided by short shaft 61 which drives second shaft 57 in a drive such that the screw assembly moves melt material from input port 33 to product output port 35 within housing 26. In turn, shaft 61 is driven by transmission 62, transmission 62 itself being operated by electric motor 63.

Referring to FIGS. 4A and 413, there is seen a detailed view of devolatilizer 25, but equipped with an alternative rotor assembly which is herein designated in its entirety by the numeral 85. For reasons of constructional convenience, it is convenient to manufacture housing 26 in the form of subassembly sections which are assembled together to form completed housing 26. In the region of vapor separation chamber 29, typical section 65 of housing 26 is seen to be of double walled cylindrical construction, there being an interior cylindrical wall 66 and an outer cylindrical wall 67. The walls 66 and 67 are maintained in fixed predetermined spaced relationship one to the other by means of spacer members 68.

One end of section 65 ends in a male flange member 70, while the other end thereof ends in a female flange member 71. In the flat facing portion of flange 70, a circular groove 72 is provided for receipt of a seal 73. Thus, in an assembled housing 26, flanges 70 and 71, one each on abutting sections 67 (paired), matingly engage into a sealed relationship between one another by means of seal 73.

It will be appreciated that a devolatilizer 25 is conveniently formed of steel with individual pieces being welded or clamped together. Thus, adjacent sections 65 are conveniently secured together by clamping means, welding, or the like.

The flanges 70 and 71 on a pair of abutting sections 65 may be conveniently secured together by C-clamps, nut and bolt assemblies, or the like (not shown). Section 65 is conveniently constructed so that inner-cylindrical wall 66 and outer-cylindrical Wall 67 are in fluid tight relationship to one another, in cooperation with flanges 70 and 71 and spacer members 68 so that an appropriate heating or cooling fluid (not shown) can be circulated in the open spaces of a section 65 between walls 66 and 67, thereby to heat or cool a section 65 in a controllable manner. Typically, when a devolatilizer 25 is being used with a polymer melt, a section 65 is maintained in a heated condition relative to the surrounding ambient embodiment, the heating being accomplished by using heated water, oil, or the like, as those skilled in the art appreciate. Such a temperature controlling fluid is conveniently injected into a section 65 through an input nozzle 37 and removed therefrom through an output nozzle 38.

In order to control the temperature of the melt material passing through a devolatilizer 25, it is also desirable to jacket housing 26 in the regions of input chamber 28, compression chamber 30, and pumping chamber 31. Typically, in a devolatilization operation being performed on a polymer in devolatilizer 25, these chambers, like separation chamber 29, are maintained in a heated condition. Thus, input chamber 28 is equipped with jacket assembly 75 and compression chamber 30 and pumping chamber 31 are equipped with jacket assembly 76. Flow paths for fluids into and from jackets 75 and 76 are indicated. Conveniently located, in proximity to a devolatilizer 25 when a heating fluid is employed is apparatus (not shown) for heating such a temperature control fluid and for maintaining such fluid at a predetermined feed temperature to devolatilizer 25, as those skilled in the art will fully appreciate. Because of the possibility of excessive heat buildup in an operating devolatilizer 25 in the region of sealing chamber 3 2, suitable cooling means for this chamber 32 is preferably provided, such as by cold fingers 117, for which refrigeration apparatus (not shown) for cooling a coolant (not shown) and for maintaining such coolant at a predetermined feed temperature is provided located in proximity to a devolatilizer 25.

Bridging the region between separation chamber 29 and input chamber 28 is a cap plate 74 which joins together a first section 65 and a shell 77 which forms the wall of input chamber 28. Shell 77 is jacketed by jacket assembly 75 in the region of input chamber 28. Interior cylindrical wall surfaces of shell 77 are lined by a splined bushing 41, the bushing 41 being conveniently maintained in position by a ring and key assembly 79. Positioned in input chamber 28 so as to be generally coaxial with shell 77 and splined bushing 41 is first shaft 40. When a hot melt (not shown) enters input chamber 28, such passes through and over the axially extending groove spaces 80 existing between shaft 40 and splined bushing 41. Such a melt further serves to lubricate splined bushing 41. Thus, a melt from input chamber 28 is circumferentially fed into vapor separation chamber 29 about first shaft 40.

Those skilled in the art will appreciate that, in place of the splined bushing 41, one can employ any one of a number of different but functionally equivalent mechanical arrangements in order to achieve delivery, as desired, of melt material from input chamber 28 to separation chamber 29 circumferentially of a first shaft 40.

In general, any arrangement of elements which will permit one to deliver melt material from an input port through an input chamber to a vapor separation chamber in a man ner so as to be circumferentially located about a rotatable shaft may be used in practicing the present invention.

As a rotor assembly 42 for use in vapor separation chamber 29, one may employ any one of anumber of different but functionally equivalent means in order to process melt material in the vapor separation chamber 29, as described. One preferred rotor assembly is seen in the embodiment shown in FIGS. 4A and 4B and is herein designated in its entirety by the numeral 85. In rotor assembly 85, a drum 43 is employed whose side wall portions 44 extend radially outwardly a plurality of discrete blade-like members 86. These blade members 86 are arranged into four axially extending rows. These rows are in circumferentially spaced relationship to one another and each now contains approximately an equal number of blade members 86. Although the embodiment shown utilizes four rows, it will be appreciated that any convenient number of rows can be used from 2 to about 8, 3 or 4 rows presently being preferred. Allblade members 86 are circumferentially inclined at an angle between about 10 to 89 with respect to rotor assembly axis 27. In the embodiment shown, each blade member is inclined at a fixed angle of about 30. Each of the blade members 86 in any given row are generally equally axially spaced from one another. Each blade member 86 has a land portion 87 defined on its circumferentially extending radially outward edge portion. All the land areas of the individual blade members 86 are substantially equally radially spaced from axis 27. In general, the blade like flattened members 86 are so arranged on side wall portions 44 that substantially all cylindrical regions on the inside walls of separation chamber 29 adjacent the side wall portions 44 of drum 43are swept by at least one land portion 87 during a single rotation of rotor assembly 85. Thus, each point in the separation chamber 27 adjacent side wallportions 44 has both an axial and a circumferential force vector exterted thereon during rotational movements of the rotor assembly 85.

In rotor assembly 85, between blade member 86 and the side wall portions 44 of drum 43 is an axially extending flange '88 which extends axially under each row of blade members 86. Each flange '86 defines a circumferentially rising ramp-like outside face 89 and has a leading edge 114 and a trailing edge 115. Edges 114 and 115 extend axially and are in circumferentially spaced, parallel relationship to one another. The direction of circumferential rise for all outside faces 89 is substantially the same. The number of flanges 88 employed in a given rotor assembly 85 can vary, the number being generally equal to the number of rows of blade members 86 employed in a given rotor assembly 85.

With rotor assembly '85, as shown in FIGS. 4A and 4B, there are employed a compression screw 50 and a pumping screw 55 each of which is like the corresponding membersused in the embodiment of FIG. 3 for rotor assembly 42. In FIG. 4B, it is seen that a thrust bearing assembly 58 for shaft 57 is employed.

One preferred construction for the region in the vicinity of the vapor take-off port 36- in housing 26 is illustrated by FIG. 4A. Extending through a section 65 is an appropriately shaped mounting flange 90. Connected to flange 90 is an elbow pipe 91 which, at its respective input and output ends, is equipped with respective flanges 92 and 93. Extending through flange 93 to couple elbow pipe 91 to flange 90 are a series of bolts 94 which threadably engage mating threading recesses in flange 90. Positioned between flange 93 and flange 90 is a ring 95 of metal. Connected (as by welding or the like) to the interior circumference of ring 95 is a sleeve 96. Mounted on the inside circumferential surface portion of sleeve 96 are two wedge-shaped flanges 98 which act as bafiles to reject melt material within separation chamber 29 which might tend to enter and pass through the vapor take-off port 36 during rotational movements of rotor assembly 85 in operation of devolatilizer 25. While the devolatilizer 25 is operable Without flange 98 since by the present invention there is only slight tendency for melt material to enter through vapor take-off port 36 from vapor separation chamber 29, it will be appreciated that the efliciency of operation of devolatilizer 25 is improved by the presence of flanges '98, or equivalent assembly, in a devolatilizer 25.

Housing 26 as illustrated in FIGS. 4A and 4B in devolatilizer 25 is generally conically shaped in the region of compression chamber 30, being tapered from a maximum diameter adjacent the region of separation chamber 29 to a final minimum diameter adjacent the region of pumping chamber 31. The thickness of housing 26 in the region of pumping chamber 31 is increased so that housing 26 can withstand the pressures developed here during operation of devolatilizer 25. A single jacket assembly 76 circumferentially embraces housing 26 in the adjoining regions of the compression chamber 30 and the pumping chamber 31.

The operation of a rotor assembly, such as rotor assembly 42, in the separation chamber 29 of a devolatilizer 25 is illustrated in 'FIG. 5. In FIG. is shown the appearance of a melt material as such moves axially through the separation chamber 29. As the melt material moves in the downward direction shown, for example, in FIG. 1, such melt material is seen to be distributed in the form of a thin film 119 on the inside cylindrical surface portions of housing 26 within the separation chamber 29. Concurrently, as the rotor assembly 42 turns, a species of wave 120 exists just in front of the land region 48 on each blade member 47. What happens in operation when devolatilizing a relatively viscous liquid as a rotor assembly 85 revolves in a separation chamber is illustrated in FIG. 5. As a viscous liquid passes over a flange 88 a void space 5 is created adjacent the trailing edge of flange 88 behind blade 86, thereby creating a zone where a high liquid surface area exposed to a vapor phase exists, enhancing devolatilization, as those skilled in the art will readily appreciate.

Owing to the fluid mechanical nature of the melt material, in the course of a plurality of revolutions of rotor assembly 42, the melt material comprising a thin fihn 119 gradually becomes caught up and becomes a part of wave 120, only to be redeposited at a further point on the side wall of housing 26 in vapor separation chamber 29 at a further point on downwardly in the vapor separation chamber 29. The process is gradually repeated for all melt material in vapor separation 29 until all material entering input chamber 28 is expelled through the product output 10 port 35. Typical circumferentially exerted force vectors in film 119 are suggested by the arrows shown adjacent land region 48. In the region immediately adjacent housing 26, very little fluid movement occurs in film 119, but the rate of fluid movement in thin film 119 increases as one moves toward a land region 48.

Although the housing 26 is externally tapered downwardly about compression chamber 30 from a maximum to a minimum cross-sectional diameter in the region of pumping chamber 31, such a taper is not necessary in order to practice the present invention. Thus, for example, one may employ a housing whose cross-sectional diameter substantially is constant through the various chambers.

From the foregoing description, it will be appreciated that a rotor assembly of this invention may be used in a separation chamber regardless of how melt material is fed thereto, how melt material and vapors evolved therefrom flow through a separation chamber, how melt is collected and/ or compressed after traversing a separation chamber, or the like. For example, material flow through a separation chamber may be vertical (upwards or downwards) horizontal, or the like.

It will be appreciated that, while the embodiments of the present invention, as shown and described herein are necessarily limited to a few forms of the present invention, many variations and modifications thereof are feasible and practical without departing from the spirit and scope of the present invention disclosed and claimed herein.

What is claimed is:

1. A rotor assembly adapted for use in a devolatilizer of the wiped film type for the processing of relatively viscous fluid materials, said rotor assembly comprising:

(A) a rotatably mountable shaft means having generally circularly symmetrical side wall portions,

(B) at least two axially extending similarly dimensioned, circumferentially spaced parallel, radially outwardly projecting flanges on said side wall portions,

( 1) each flange defining a circumferentially rising, ramp-like, circumferentially located outside face which has a leading edge and a trailing edge, both such edges extending axially and being in circumferentially spaced, parallel relationship to each other, said leading edge being generally flush with the circumferential surface of said side wall portions, said trailing edge defining the maximum. radial height of its associated flange above said side wall portions,

(2) all said flanges being similarly oriented so as to have their respective said outside faces all rise in the same circumferential direction, and

(C) a plurality of axially spaced, radially extending blade-like members,

(1) each such member extending generally radially outwardly from the said outside face of each of said flange,

(2) each such member extending circumferentially in the region between the said leading edge and the said trailing edge of its associated flange at an angle ranging from about 10 to 89 with respect to the axis of said shaft means, all such members having a similar inclination,

(3) all such members on any one said flanges being axially spaced from one another,

(4) each such member being circumferentially inclined at an angle between about 10 and 89 with respect to the axis of said shaft means, all such members having a similar inclination,

(5) each such member having a land portion defined at its circumferentially located, radial outer edge, each such land portion being substantially equally radially spaced from said axis, and being adapted to apply both an axial and a circumferential force vector when said rotor assembly revolves on said axis, and

(6) all such members on any one of said flanges being so positioned relative to the other such members on the remaining flanges that all cylindrical regions circumferentially located radially opposite said shaft means about said rotor assembly are swept by at least one of said 1 land portions during one revolution of said rotor assembly on said axis.

2. The rotor assembly of claim 1 wherein each of said outside faces is generally planar.

3. The rotor assembly of claim 1 wherein a portion of all said blade-like members on any one flange are substantially parallel to one another.

4. The rotor assembly of claim 1 wherein the land portion of one of said blade-like members on one of said flanges either meets or overlaps on the area covered by the land area another of said blade-like members on References Cited UNITED STATES PATENTS 4/1955 Mayer-Ortiz et a1. 416198 1903 Taplin 416198 CARLTON R. CROYLE, Primary Examiner R. E. GARRETT, Assistant Examiner US. Cl. X.R. 4l6-175, 176

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