US 3163502 A
Description (OCR text may contain errors)
Dec. 29,1964 5. J. JUSTUS ETAL 3,163,502
REMOVABLE HOOD FOR A DRYING CYLINDER Filed Oct. 13, 1960 5 Sheets-Sheet 1 Z n. A W
000 ooooe/" ooQo 060000 [UKEHZUPE Dec. 29, 1964 E. J. JUSTUS ETAL 1 5 REMOVABLE noon FOR A DRYING CYLINDER Filed Oct. 13, 1960 5 Shets-Sheet 2 [27252722715 t'glyar I Justus A 0 1/41 6 Haj;
Dec. 29, 1964 E. J. JUSTUS ETAL REMOVABLE noon FOR A DRYING CYLINDER 5 Sheets-Sheet 3 Filed Oct. 13. 1960 Eff 5.
Dec. 29, 1964 E. .1. JUSTUS ETAL.
REMOVABLE HOOD FOR A DRYING CYLINDER 5 Sheets-Sheet 4 Filed Oct. 13, 1960 Dec. 29, 1964 E. J. JUSTUS ETAL 0 REMOVABLE HOOD FOR A DRYING CYLINDER Filed Oct. 13, 1960 5 Sheets-Sheet 5 mum w m U7 fdyar f 7115171; L 0141 H Hess gmi 3,163,502 EMOVABLE HUGE FDR A DRYWG CYLINDER Edgar .lQEustus and Loyal H. Hess, Beioit, Wis, assignors to lileioit Corporation, a corporation of Wisconsin l fiied iIltcta 13, 1960, Ser. No. 62,433
i 2 Unions. (ill. Fla -H4) The present invention relates broadly to impingement air drying of sheet materials, and is more particularly concerned with anovel hood structure especially well-adapted for use with paper drier drums or cylinders and having as one feature thereof a unitary air impingement chamber and air exhaust means therein providing a compact structure of high drying efiiciency.
Numerous attempts have been made in the past to develop a relatively simple hood arrangment for the accelerated drying of paper and related web materials by the use of high velocity-temperature air which is impinged upon the web material so as to penetrate the boundary film layer of vapor which adheres thereto and which normally diminishes by vapor contact the eifect of drying. In many structures complex duotwork is utilized, resulting in heat energy losses and the necessity of excessive quantities of insulation. Other structures known to the art are not readily adapted to exi ting drying apparatus, while in others complex mechanisms are employed to raise and lower the hood relative to the drying cylinder. In allof these, it has been impossible to package all components within the hood or at least in close direct connection thereto, with the result that the prior art hoods have become unduly complex and lacking in a high order of drying efficiency.
It is accordingly an important aim of the present invention to provide a drying apparatus and method which overcomes the noted and other disadvantages of the prior art.
Another object of this invention lies in the provision of a hood structure for location in partial encircling relation to a drying cylinder, and which features a unita-ry air impingement chamber and air exhaust means therein permitting maximum drying eiiiciencies and the packaging of all or essentially all components within the hood itself.
Still another object ofthe instant invention is to provide a hood construction wherein the hood mouth mounts a unitary air supply air exhaust assembly desirably comprised of a pair of spaced curvate plate members mounting a plurality of spaced open-ended exhaust tubes in communication with the hood interior to direct moistureladen air thereto, the space between the plate means com municating with air circulation means and the plate means more closely adjacent the drying drum being passaged to provide a plurality of shaped nozzle openings whereby drying air is impinged against the web in a direction substantially normal thereto and is then withdrawn through the exhaust tubesby the air circulation means for return thereto after passage against air heating means.
A further object of this invention is'to provide a hinged hood arrangement embodying hood elevating and lowering means of high reliabilit rapid action and devoid of structure limiting the degree of wrap of the hood with respect to the drying cylinder.
United States Patent An even further object of this invention lies in the provision of hood means supported adjacent a drying cylinder, means defining an air discharge chamber extending across and along the mouth of the hood means and being passaged at a plurality of spaced points to provide nozzle openings therein, means in the chamber providing a plurality of individual moisture-bearing air flow paths from the web material tothe interior of the hood means, and means for circulating air into the chamber and through the nozzle openings therein into impingement with the paper Web and thereafter in generally a reverse direction along the moisture-bearing air flow paths to the hood interior and back to the chamber.
Other objects and advantages of the invention will be come more apparent during the course of the following description, particularly when taken in connection with the accompanying drawings.
In the drawings, wherein like numerals designate like parts throughout the same:
FIGURE 1 is a more or less diagrammatic View of a drier section of a paper machine and embodying therein drying means constructed in accordance with the principles of this invention;
FIGURE 2 is a fragmentary plan view of a preferred form of bottom impingement plate used in the hood structure of this invention;
FIGURE 3 is a fragmentary end view of the instant drying apparatus and showing one form of hood pivoting means which can be employed;
FIGURE 4- is a vertical sectional view through approximately one-half of the hood to illustrate further details thereof;
EiGURE 5 is a sectional View of the hood taken substantially along the line V-V of FIGURE 4;
FEGURF 6 is a sectional view of the plate means of FiGURE 2 to more fully illustrate the nozzle openings therein and passage for reception of an exhaust tube mounted in the manner of FIGURES 4 and' 5; and
FIGURES 7 and 8 are detail views of actuating means which may be utilized to raise and lower the hood with respect to the drying cylinder.
Referring now to the drawings, there is shown somewhat diagrammatically in FIGURE 1 a dry end section 10 of drying apparatus of a paper machine with which the instant invention is of important application. The dry end section it comprises a first row of horizontally aligned drying cylinders or drums 1lad of which four are shown in the illustrated exemplary embodiment, and a second row of horizontally aligned drying cylinders 126ld staggered with respect to the drying drums 11 of the first row. A web of paper W passes alternatively about the drying cylinders 11 and 12, and is maintained in contact with the surfaces of the drying cylinders 11a and by a felt l3 and against the surfaces of the drying drums 12a-d by a felt 14. A suitable number of rollers 15 are arranged to guide the felt 13, and rollers 16 guide the felt 1d. The drying arrangement as thus far described will be recognized as of essentially conventional construction, and the general practice in the art is to wrap the web W about the drying cylinders 11 and 12. However, cylinders are not at all times required, and the instant invention can be practiced utilizing a hood positioned with its mouth portion relatively closely adjacent a paper web advanced along a generally straight line, rather than serpentine, path.
Drying apparatus generally designated by the legend A and as constructed in accordance with the principles of this invention, comprises a pair of essentially identical hingedly connected hood sections 28a and Ztib each having a length preferably coextensive with the width of the web W, and together extending a sumcient distance about the cylinder or drum 110 to be coextensive with the wrap of the web W during travel along the circumferential portion of the rotatable drum 11c. Illustratively, the extent of wrap of the web on the drum circumference is approximately The hood sections 2% and 20b are essentially identical as stated, and accordingly, only the details of a single hood section (2%) will be described in the material now to follow.
The hood section 20b shown in FIGURES 4 and 5 comprises a first body portion 21 defining therewithin an I chamber 22 and a pair of second housing por- 55; 23 and 24 connected to opposite ends of the first ousing portion 21 and defining interiorly air supply chambers 25. The first housing portion 21 is provided at opposite ends with a pair of generally arcuate wall portions 26 and 27 to which are connected axially extending and generally similarly shaped top wall portions 26a and 27a. Illustratively, each of the wall portions 26a and 27a may extend approximately one-fourth of the axial length of the drying cylinder 11c, and extending generally radially from the wall portions 26a and 27a are a pair of axially spaced wall portions 26b and 27b which mount a tubular exhaust duct portion 28 communicating with the air supply chambers 25.
Connected to the exhaust conduit 28 and providing the outer wall structure for the exhaust chamber 22 is a downwardly inclined wall portion 29 having an inwardly turned wall section 29a, while at the opposite end thereof the wall portion 29 has an upwardly inclined wall section 29b. Connecting with the wall section 2% is an upwardly inclined wall portion 30 and extending therefrom in the direction of the vertical centerline of the drier drum 110 is a wall portion 31. At the opposite end of the wall portion 31, on the other hand, there is provided a downwardly turned wall section 31a providing a surface for connection of the two hood sections 2011 and 20b. The described wall sections are of course generally coextensive with the width of the web W wrapping the drying cylinder 11c, and as appears in FIGURES 4 and 5, the wall sections may be provided by a pair of spaced sheet metal members. As well, between the sheet metal members there is desirably located insulation means 32 to minimize heat losses from within the exhaust air chamber 22.
To provide access to the hood interior the outer wall section 29b may be hingedly connected to the wall section 39 may be constructed to provide a further access opening, as indicated at 30a. A further access opening may be provided in the wall section 2, as indicated at 29c, and this door may be hinged to control the extent of opening so that the amount of make-up air admitted therethrough may be regulated. As appears in FIGURE 4, the exhaust air chamber wall portions 26b and 27b may be apertured as at 33 to provide exhaust air outlets. In the manner known to the art, the exhaust openings 33 may be controlled by damper means in the form of a shiftable plate member or equivalent means.
The air supply housings 23 and 24 are essentially identical, and accordingly, the description will be particularly directed to the housing portion 23 shown in section in FIGURE 5. In the description of the air supply housing 23 now to follow, where applicable like numerals with the sufiix a appended are applied to like parts of the air supply housing 24.
The air supply housing comprises first a sheet metal housing portion 46 connected to the exhaust chamber wall portion 26a. The housing portion 46, two of which are provided at'opposite ends of each hood section 20a and 20b, is connected to a shroud member 35 enclosing blower or fan drive means 36, which is as illustrated a suitable drive motor. The motor means 36 is provided with shaft means 37 mounting pulley means 38 about which is trained belt means 39 also received about pulley means 40 on shaft means 41 mounting fan means 42 at the opposite end thereof. The shaft means 41, as appears in FIGURE 5, is journaled in suitable bearing means 43 and 44. As well, to support the bearing means 43 and 44 shelf means 45 are provided.
The fan or air recirculation means 42 is mounted within the housing portion 46 which in turn receives at its lower end a generally radially extending air supply conduit 47 communicating with an air discharge chamber generally designated by the numeral 48.
The air discharge chamber provided in accordance with the novel concepts of this invention includes top and bottom plate means 49 and 50 of arcuate shape when viewed endwise and extending essentially entirely across the width of the web W wrapping the drying cylinder 11c. Each hood section Zita and 20b is equipped with a pair of radially spaced plate means 49 and 50 of essentially identical construction and each pair of plate means extends along approximately of the circumference of the cylinder 110.
The spaced plate means 49 and 50 may be welded at opposite ends of the two-piece end walls 26 and 27 of the hood sections, and if desired, bracemeans 51 (FIGURE 4) may be welded tothe top plate member 49 and to the exhaust chamber wall portions 26b and 27b. The top plate means 49 is passaged at spaced locations along its length to receive the lower ends of the air supply conduits 47, and radially inwardly of the lower ends of the conduits 47 and generally centrally between the two plate means 49 and 5b are baffle or diverter means 52 functioning to evenly and thoroughly distribute the air flow between the two plate members 49 and 50.
Each of the plate means 49 and 50 is passaged to receive tubular exhaust means 53, each of which is desirably provided with an outwardly flared discharge portion 54 lying against the upper plate member 49 to facilitate welding thereto. Each of the plate members 49 and 50 are passaged to receive therein opposite ends of the exhaust tubes 53, and a preferred configuration for the bottom impingement plate 50 appears in FIGURE 2. In a typical application wherein the plate 50 has a thickness of one-quarter inch, a width of six feet, eight inches, and a length of seventeen feet, nine and three-eighths inches, ninety-six four and one-half inch openings or holes 55 are utilized to receive the lower ends of the exhaust tubes 53. The openings 55 are arranged in the pattern shown to provide eight rows of twelve openings 55 in each row. Likewise, the top plate 49 is provided with openings 56 (FIGURE 5) which align themselves with the openings 55 in the lower plate 50.
The locations of the tubes 53 are determined to provide effective distribution of flow of supply air, to obtain substantially uniform exit flow of spent air. from all areas, and to reinforce the plate members 49 and 50 to avoid deflection due to pressures of air within the chamber 48.
As also appears in FIGURE 2, the bottom impingement plate 50 is provided with a plurality of nozzle openings 57, and while for ease of illustration certain of the openings 57 have been eliminated in FIGURE 2, it should be understood that these openings are spaced in the pattern shown entirely across the length and width of the plate 59. Illustratively, the nozzle openings 57 are placed on three inch centers, and 2,176 openings are used, arranged in a pattern of thirty-two rows with sixtyeight openings in each row. While not illustrated, the equilateral triangular arrangement of holes 57 is preferably skewed approximately 5 with respect to the direction of web travel.
The nozzle orifices 57 are desirably rounded entrance openings as appears in FIGURE 6. It may beobserved therefrom that each nozzle opening is defined by an inwardly flared throat portion 58 to provide a roundedapproach orifice as understood by those skilled in the art. It has been found that the illustrated flared configuration reduces orifice losses and permits highvelocity jets of air to operate to scrub away the surface film of saturated moisture vapor traveling with the paper web W. Further, the flared nozzles promote a cyclonic turbulence between the air. jets issuing from the openings 57, this turbulence being indicated generally in the directions of the arrows applied to FIGURE 6.
Experience has further demonstrated that the most desirable results are obtained by relatively close control over the diameter of the openings 57, measured between the points a and b, and over the ratio of area of the openings 57 to total area of the plate 50. Specifically, the desirable range of diameters of the openings 57 is ferred. A ratio of hole or open area to total area of between one and three percent is preferred, and most greferably 1.5% is the optimum in work performed to ate.
The thickness of the bottom impingement plate t? is presently preferred to be one-quarter inch, and the holes or openings 57 therein may be either extruded or drilled, the latter'technique providing a plate having the advantage of better strength and rigidity. The preferred spacing of the exposed surface of the plate 5% from the surface of the web W traveling about the drying cylinder lie is one inch, when the hole diameter and ratio of hole area to total area are within the suggested limits. This spacing appears at present to provide optimum heat transfer and drying rate in accordance with the equation h C1 where h=heat transfer coefiicient in B.t.u. per hour per square foot per degree Fahrenheit, C=coefiicient depending upon hole size and spacing, P=the pumping power required to deliver the air and" iv=an exponent approximately equal to 0.23.
heater ducts 6i) and 61, and of course, each hood section Zha and b is equipped with a pair of heater ducts. Gas heaters of the fire tube type may be substituted. The ducts es and 61 are essentially identical, and each is passaged at opposite ends to communicate the exhaust air chamber 22 and particularly the exhaust air tubes 53 with the exhaust air conduit 28 leading to the fans 42. Each heater conduit mounts at the lower end filter means 62 to prevent the passage of foreign materials such as paper bits, dust and the like to heater means 4 63 within each conduit 60 and 61 or to the tan means 42. The heater means as may take the form of steam coils, as shown.-
The interior of each heater duct 6t and er communicates with the central tubular exhaust air conduit leading to the fans 42. by provision of passages 28a (FlG URE 5) at circumferentially spaced locations along the exhaust conduit 28. As appears in FIGURE 4, the total length of each heater duct 69 or 61 is less than the axial length of the insulated exhaust conduit 28 so that uninterrupted wall portions of the conduit 28 exist outwardly of opposite ends of the duct so and 61. Of course, communication between the heater conduits 69 or 61 and the exhaust air conduit 28 could be eitected in diflerent Ways, however, the illustrated arrangement of interrupting the Wall of the conduit 28 has proven quite eilective in practice.
When the fan means 42 in each hoodsection 20a and Zilb are operated, and the heater means 63 energized, high velocity-temperature air flow paths'are provided in the directions indicated by the arrows to which the numeral 65 has been applied. The heated air passes downwardly or radially inwardly through the air supply conduits 47 and is diverted by the bailie means 52 in opposed directions both axially of the length of the drying cylinder 11c and circumferentially thereof generally within the limits of each hood section as defined by the wall sections 2% and 310. thereof. In this regard, it should be emphasized that the upright or radially extending exhaust tubes 53 received in the spaced plate means 49 and 5 break.
' pair of hinge portions 71 and 72 welded or otherwise sed 54) eiifectively bathe and distribute the supply air to equalize the high velocity air how, so that the delivery from the nozzle openings 57 in p the bottom impingement plate 59 to the web is at all times uniform. As well, the exhaust tubes 53 provide a high degree of structural stiltness for the air supply chamber 48 to permit a continuous crosswise and longitudinal plenum. in addition, the exhaust tubes provide for uniform distribution of the discharge of the spent air from the zone between the drying cylinder lie and the bottom irn ingement plate 56. The heated supply air moves in the directions indicated by the arrows 65 from the supply conduits 47 to between the plates 49 and Sil, issuing at high velocities through the rounded entrance orifices 57 to impinge upon the moist paper web W so as to penetrate the boundary film layer of vapor which adheres to the paper web, and which normally diminishes the eifect of drying by vapor contact. The moisture-bearing or spent air is then withdrawn under action of the fan means 42 radially outwardly or upwardly through the exhaust tubes 53, following the path indicated by the arrows to which the numeral as has been applied. It may be observed that the moisture-bearing air is withdrawn through the exhaust tubes 53 toward the heater conduits 6t) and 61 and through said conduits to the passages 28a in the axially extending exhaust air conduit 28 communicating with the fan housings 46 anddan As was noted, a portion of the spent air may be exhausted through the opening 33,,and by means of the access opening 29c, make-up air may be added to the moving' air stream to maintain a proper balance in the recirculating air system.
lt'may be found necessary upon occasion to clean paper bits and the like from the air discharge chamber 4%. For this purpose, the opposite end walls 26 and 27 of a each hood section Zita and 20b may be passaged as at 7% (FIGURES 3 and 4) to permit access to the space between the plate means 49 and 56.
The hood sections 24in and 20b are hingedly connected to permit raising and lowering of the hood sections when it is desired to obtain access to the space between the bottom impingement plate 50 and the circumference of the drying cylinder 110. Such access may be desired when the paper web W is being threaded onto the drying cylinder, either during initial start-up or following a sheet The hinge means for this purpose comprises a cured to the hood wall sections 31a, the hinge portions 71 and 72 being connected by pin means 73 providing a pivot point for the hinge sections 2012 and 2%.
To effect a raising or lowering action of the hood sections 26k: and Ztib about the hinge point 73, various types of actuating means may be employed. A first form appears in FIGURES 3 and 4, and comprises bracket means 75 at opposite ends of the hood sections and supported upon frame structure 76 mounting the drier cylinder 11c through suitable bearing structure to be later noted. Each of the bracket means at opposite ends of the hood sections Ztla and 201; receives pin means 77 to which is connected a link member .78, the opposite end of which receives pin means 79 to connect the link member 78 to one end of a threaded rod member 30, forming a part of screw jack means generally designated by the numeral 81. v
The screw jack means 81 further includes a suitable housing 82, and within the housing is a pair of fixed flange portions'83 and 84. The screw rod member is threaded for meshing engagement with sprocket means 85 mounted upon shaft means 85 supported by the screw jack housing 32. The sprocket means 85 has trained thereabout chain means d7, which also wraps sprocket means 88 carried upon shaft means 89 extending generally entirely along the length of the drying cylinder 11c.
It may now beobserved that when a rotative force is applied to the sprocket means 88, the sprocket means 85 is caused to rotate in engagement with the screw member 80, causing linear movement of the rod member 8t relative to the housing flange portions 83 and 84. As the rod member 86 moves linearly, as in a raising action, the link member 7 8 connected to the rod member 8% swings about a fixed pivot 77, pivoting the hood sections a and 26b connected to the pin means 79 about the hinge point 73. Of course, the reverse action occurs during a lowering action.
In substitution for the screw jack means just described, hydraulic or pneumatic means may be employed. Referring now to FIGURE 7, the frame structure 76 may mount at opposite ends thereof bracket means 90 to which is connected by pin means 91 a link member 92 connected at its opposite end by pin means 93 to a piston 94 reciprocal within a cylinder 95 connected to the frame structure 76 by pin means or the like 96. Actuation of the cylinder 95 causes reciprocation of the piston 94 therein swinging the hood section 2011 connected to the pin means 93 about the pivot point at upon the hinge point 73. In the arrangement of FIGURE 7, as well as with the screw jack means of FIGURES 3 and 4, it is important to note that the link members 92 or 78 therein perform an effective latching action during hood raising. More specifically, when the link arm 78 is raised by the screw jack means 81, or the link arm 92 raised by the piston means 84, and the respective links are on line with an imaginary line extending between the hinge point 72 and either the pin means 77 or 91, a stable linkage is provided and no further means are required to maintain the hood sections 20a and 20b in raised positions. In other words, the hinge portions 71 and 72 connecting the hood sections remain in elevated positions Without the requirement for auxiliary support or latch means. The important advantage of this is that the hood sections can be raised or lowered much more quickly upon demand than would be the case if auxiliary fastening or safety devices were employed, which necessarily must be re leased either manually or automatically.
Another form of actuating means for efiecting a raising or lowering action of the hood sections 20a and 20b appears in FIGURE 8, to which reference is now made. The frame structure 76 mounts bracket means 97 receiving pin means 98 for connecting a lever arm 99 to the bracket member 97 for pivotal movement thereon. The bracket member 99 generally centrally thereof is connected to the hood section 20a by fixed pin means 160, while at the end of the lever arm 99 opposite the pin connection 98 the lever arm receives pin means 101 to provide a connection with piston means 102 reciprocal within an actuator cylinder 103 fixedly connected to the frame structure 76, as at 104. Quite clearly, the cylinder 95 of FIGURE 7 and the cylinder 103 of FIGURE 8 may be either of the pneumatic or hydraulic type. And of course, the actuating means of FIGURES 7 and 8 are provided at both ends of each hood section 26a and 20b.
The various forms of hood elevating and lowering means described in connection with FIGURES 3, 4, 7 and 8 may be under the control of the machine operator, and as Well, the actuating means may be responsive to web break detection means in the manner now known to the art. More specifically, upon occasion of a sheet break, it is desirable to effect a rapid raising action of the hood sections and essentially simultaneous stopping of the fan means to prevent broken piecesof the web from passing into the heating means, or at least jamming the nozzle structure. Accordingly, the described actuating means may be electrically connected through suitable circuitry to known web break detection means, and the same can be the case with respect to the motor means 36 in control of the fan means 42.
It should be observed that by the particular construction of air discharge 48 and tubular exhaust means 53 therein the heater means 63, fan means 42 and drive means 36 therefor, filter means 62 and recirculating ductwork can now all be packaged within the hood itself, producing a unit having as an important advantage minimum use of insulation and minimum heat losses. The insulation 32 employed in the exhaust housing portion 22 has been earlier noted, and may now be seen to be minimum in amount. As well, it is desirable in order to conserve the heat energies that the exhaust tubes 53 receive thereon insulating sleeves or jackets 105, as appears in FIG- URES 4 and 5. However, it is apparent that since the length and diameter of each exhaust tube 53 is at the minimum required for effective air circulation, the insulation sleeves 105 need not be excessively great in wall thickness.
The drying cylinder 11c, as well as the other cylinders 11 and 12 of the dry end section 10 of FIGURE 1 are mounted by frame structure in any manner conventional the art. As appears in FIGURES 3 and 4, the bearing means is designated generally by the numeral 110, and a detailed description thereof is not believed necessary since this structure forms no part of the instant invention. As well, and as also appears in these same views, fluid to heat the drying cylinders to the desired temperature is admitted to the drum or cylinder interior through inlet means 115.
.It may now be seen that there is herein provided a high velocity and high temperature recirculating air hood which is adaptable to either existing or new machines without interference with crane travel or with other equipment already installed. There is no exterior ducting to cause such interference, and as appears particularly well in FIGURES 1 and 3, the drying apparatus A has a minimum profile. By eliminating complex duotwork, the heat losses are held to an absolute minimum and the insulation requirements are markedly reduced. The lift means for elevating and lowering the hood sections 2011 and 2312 are simple in construction and reliable in action, and further place no limitation on the degree of wrap of the hood sections with respect to the drying drum. The lift means additionally, as was noted, render unnecessary auxiliary latching or safety devices to maintain the hood sections in an open position.
Certain modifications to the structure herein described have been pointed out above, and these and other changes can of course be effected without departing from the novel concepts of this invention.
We claim as our invention:
1. In a dryer particularly adapted to dry fibrous webs of paper and in combination with a rotatable drying cylinder having a fibrous web of paper Wrapped thereabout,
(a) a supporting frame structure for said drying cylinder,
([1) a pair of individual hood sections mounted on said supporting frame structure in end-to-end relation and extending about a portion of the circumference of said drying cylinder,
(0) a transverse hinge pin hingedly connecting the adjacent ends of said hood sections together,
(d) said hood sections each having air impingement nozzles opening toward said drying cylinder and impinging air on the web traveling thereabout,
(e) and means supporting the free ends of said pivotally connected hood sections on said supporting frame structure and pivoting said hood sections away from said dryer drum about the axis of said transverse pivot pin comprising,
(f) individual screw jacks for supporting said hood sections on said supporting frame structure and having threaded extensible power members mounted on said supporting frame structure on opposite sides of said dryer drum and extensibly and retractibly movable with respect to said supporting frame structure,
(g) link members pivotally connected to said supporting frame structure at points spaced outwardly of the free ends of said hood sections for movement about axes parallel to the axis of said transverse hinge pin 9 16 and spaced on opposite sides of said hinge pin, equal inclined with respect to said supporting frame structure distances from the axis of said hinge pin, and hood sections and extend in the general direction of (h) pivot pins pivotally connecting said link members outward and upward movement of said hood sections to said hood sections adjacent the free ends thereof, about said transverse hinge pin. (1') said threaded extensible power members having 5 pivotal connection with said hood sections coaxial References flied in the file of this Patent with the axes of said pivot pins connecting said link U I AT PATENTS members to said hood sections and having sutficient a travel to position the axes of said pivot pins upward- 22 5 5g f? ly beyond lines extending through the pivotal axis of 10 1 613 i Z 1951 said hinge pin and the axes of connection of said 15 5 3 S oolner 1959 link members to said supporting frame structure, and g g M 1960 thereby cooperate with the over-center positions of 3O12335 Allard; D 1061 said link members to provide a self-locking structure 3052991 G 6 3 locking said hood sections in elevated relation with 15 r 9 respect to said drying cylinder. FOREIGN PATENTS 2. A dryer in accordance with claim 1 wherein said 710,353 Ggrmany Sept 11 1941 threaded extensible power members are mounted on said 931,286 Germany 4 1955 supporting frame structure inwardly of the inner margins 1,267,995 France Feb 1960 of said hood sections and are outwardly and upwardly 20