US 2586829 A
Description (OCR text may contain errors)
Feb. 26, 1952 w. KELSEY PAPER MACHINE DRIER 2 SHEETS--SHEEIT 1 Filed Dec. 8. 1949 Feb. 26, 1952 w. KELSEY 2,586,829
PAPER MACHINE DRIER Filed Dec. 8. 1949 2 SI-IEETS--SHEET 2 Patented F eb. 26, 1 952 UNITED STATES ATENT OFFICE PAPER MACHINE DRIER Walter Kelsey, New York, N. Y.
Application December 8, 1949, Serial N0. 131,880
' 1 Claim. (01. 34-124) This invention relates to paper machine driers and more particularly to means of introducing heat into such paper machine dryers.
Heretofore, the common practice was to heat paper machine dryers by steam introduced into the inside of the revolving dryer cylinder, this steam heating both the cylindrical paper web drying surface and the ends of the dryers or cylinders, the steam condensate (water) being removed by syphons or dippers operated through the center of the end of the dryer. This method of heating the dryers has failings which became more and more apparent as the speed was increased, which required more heat. The steam connections at the end of the dryer were always troublesome and the condensate removing syphon or dipper was not one hundred per cent efiicient, leaving a layer of steam condensate (water) on the inside surface of the revolving cylinder. This water layer was detrimental to the efficient transfer of heat from the steam to the dryer shell. This layer of Water was at the steam temperature, but as it was between the dryer shell and the steam, the reservoir of latent heat of the steam Was thus kept away from direct action on the dryer cylinder, and the transfer of heat was retarded by the slow transfer of heat through the water layer. This demand for more heat at the dryer surface was met by increasing the steam pressure, and the heat of the steam, to a point at which further increase of pressure would have necessitated radical modification in the cylinder construction to safely stand the increased pressure.
This invention contemplates the use of a revolving dryer cylinder not subjected to internal steam pressure, this cylinder being constructed to carry only its own weight and to withstand the centrifugal action and the pull of the paper web and carrying felt. This permits the construction of a light weight and thin cylinder giving as little resistance as possible for the transfer of heat from the inside of the cylinder to the paper web carrying surface.
There is provided an inner stationary cylinder, which forms with the revolving dryer cylinder, a circumferential air chamber inclosing heating units which heat the enclosed air, which in turn heats the inner surface of the revolving dryer cylinder. The heating units spaced centrally between the two cylindrical walls supported on the stationary cylinder are steam pipes carrying a flow of steam at such pressure and temperature as to heat the air in the chamber and ultimately the revolving dryer cylinder to the desired temperature. The total area of the external surface of the pipe heating units is at least as large as the area of the inside surface of the revolving outer cylindrical wall of the air chamber.
Where desirable to use another heat power flow, as for instance, electrical power conveying current, the heating units are demountable electrical resistance heating units spaced centrally in the air chamber between the two cylindrical walls, and supported on the stationary cylinder.
The air in the air chamber is kept from escaping from the chamber and from passing in and out of the chamber, through the clearance spaces between the two cylinders, by closing ofi the free passage of air through one cylinder bearing and including a running clearance space between the two adjacent solid cylinder ends, thus preventing the loss of heat through the changing of air in the air chamber. Air in the chamber between the moving and the stationary cylinder walls will be drawn along by the moving wall and retarded by the stationary wall. Between these two actions there will be a continual turbulence or rolling agitation of the air, picking up heat from the heating units and transferring it to the moving paper web contacting wall. Heat is likewise transferred to the surface of the inner cylindrical wall. This inner wall is polished to throw as much heat as possible to the outer wall which has a heat retaining surface. The inside or concave side of this inner cylindrical wall and the outside of the end walls of the cylindrical chamber are covered with materials retarding heat transmission. This construction forces a very large per cent of the heat to pass through the outer cylindrical wall which is the paper web drying area. The distribution of heat is uniform over the whole surface and coextensive with the width of the paper web, a definite requirement in paper drying.
To maintain control of the temperature, flowing saturated steam is used. The steam passage through each of the heating unit groups is relatively short. The steam supply for each group is taken from a steam manifold and the steam dis charge from each group is collected into a discharge manifold and from that manifold the steam is carried on to other dryers or for further use in the plant. Thus the steam heating units or group become part of a through steam pipe line taking steam from an outside source piping through the hollow shaft and discharging the steam, and piping the same out through the hol low shaft. The object of this multiplicity of short steam passes is to make sure of live and dry steam in each heating unit group. A the con densation of steam will be very rapid, drain pipes are run from the low point of each loop in the groups of heating units. These drain pipes discharge into a drain header or drain headers maintained at a steam pressure lower than that in the heating units, the difference in pressure being such as to force the (water) condensate out of each loop in the groups of heating units.
This positive way of getting the (water) condensate out of. the steam heating units aids in maintaining dry steam in the heating units. The object of maintaining a flow of steam in the heating units and this means of removing condensate or water from the heating units is to keep live dry steam with its reservoir of latent heat at the inside surface of the pipes of the heating units, thus giving the most efficient transfer of heat to the turbulent air in the cylindrie cal air chamber.
The important feature of the invention whether carried out with enclosed steam piping heating units or with electrical heating units, is to have the heating units spaced from the outer surface of the inner cylinder and from the inner surface ofthe outer cylinder, preferably equally spaced from said surfaces, for the purpose of making available the quick heat transfer of a fast moving air flow, which transfers heat faster than when the air travels slowly. This turbulent condition of the air in the cylindrical chamber acts likewise to accelerate the flow of heat from the air to the cylindrical walls.
The invention will be more fully described hereinafter, embodiments thereof shown in the drawings, and the invention will be finally pointed out in the claims.
In the accompanying drawings,
Fig. 1 is a vertical section taken on line of Fig. 2 showing the open spoke spider for the fixed cylinder and steam pipes in the pipe space between the open spoke spider support of the fixed cylinder and the demountable sectional head of the rotating cylinder;
Fig. 2 is a longitudinal section taken on line 2-2 of Fig. 1 of the dryer and equipment.
Fig. 3 is a typical plan taken on line 3-3 of Fig. 1 of a group of heating units showing the looping arrangements;
Fig. 4 is an end view taken on line 44 of Fig. 2 showing the demountable end support of the rotating cylinder;
Fig. 5 is an end view taken on line 5-5 of Fig. 2 showing the dryer support and clamp for th fixed hollow shaft;
Fig. 6 is a plan of group of heating units showing supports and slides;
Fig. '7 is a cross-section view taken on line in Fig. 6 showing a group of heating units with supports in the cylindrical air chamber;
Fig. 8 is a longitudinal section taken on line 88 of Fig. 6 showing supporting guides between the loops of heating units;
Fig. 9 is a longitudinal section taken on line 9-9 of Fig. 6 showing support of a loop of heating unit;
Fig. 10 is a view of steam pipe T fitting in hollow shaft;
Fig. 11 is a section taken on line in Fig. 10 showing steam pipe T fitting in hollow shaft;
Fig. 12 is a view of an electrical unit held by plates to the inner cylinder, and
Fig. 13 is a fragmentary radial section of an electrical conductor in the space between the cylinders.
Similar characters of reference indicate corresponding parts throughout the various views.
Referring to the drawings and more particularly to Figs. 1, 2 and 4, a paper machine dryer is shown, consisting of an outer rotating dryer cylinder 20, longer than the width of the paper web, a solid airtight supporting disk head 2|, an opposite supporting head 22 built up of several fitted and connectingparts 23 (Fig. 4), each having its peripheral part solid with a spoke section connecting to a hub 24 having preferably flat faces. Each part 23 of the head 22 is made removable without displacing the other parts of the cylinder 20. Each cylinder head is supported on the fixed bushed hollow shaft 25 through bearings 26 (Fig. 4). An inner fixed cylindrical shell 21 extends between the two supporting heads 2| and 22 of the rotating cylinder and is supported from and fixed to the fixed hollow shaft 25 by one solid disk 28 and one spider 29 of open spoke construction. The outer or drying cylinder is rotated by force applied to the spur gear 39 mounted on the hub 3| which is part of the supporting end disk 2|. The hollow shaft 25 and inner cylinder 21 can be rotated, for installation purposes, by
the worm gear 32 attached to the shaft 25, and worm 33, hand operated by suitable means and attached to the dryer bed plate 36. This worm gear and worm may be removed when the dryer is in operation. The dryer 20 can be held in a fixed position by locking the driving gear by suitsupport the dryer.
if The collar 39 can be reached through a covered hand hole (not shown) in the end supporting disk side of the cylinders.
2|. A thrust collar 40 is adjusted from the in- Supports 28 and 29 or" the cylinders are provided to slide on the shaft 25 to meet changes in length of cylinders due to temperature conditions.
Between the outer surface of the inner cylinder wall 21 and the inner surface of the outer revolving cylinder wall 20, (Fig. 2) in the space between these two walls and between the end walls 22a and 2|a, a chamber A is formed. It is closed by a circumferential inwardly extending flange 221) on the wall 22, and by a circumferential inwardly extending flange 2|b on the wall 2|, each flange being in line with and separated from or clearing the end of the wall forming the inner cylinder 21.
Within this chamber A, a group of pipe heating units 4| such as shown-in Fig. 3 and extending the length of the chamber is arranged in multiple form around and within the chamber, the steam being within the pipes 4|, and giving up its heat to the air in the chamber. In doing so, the steam condenses, and the condensate (water) is discharged through the drain connections D.
To facilitate installation and maintenance of the heating units 4|, and to provide for the speci fied flow of steam through these units, the units are joined in pairs forming a U loop with the steam supply and steam discharge ends in the pipe space between the two cylinder en ds 22, and
- 29 inFig. 2 The heating units. at their, steam,
5. entrances connect through flange couplings 46 to the fixed steam supply header S3, and the steam discharge ends connect through flange couplings 41 to the fixed steam discharge header SDs. Each loop may be connected individually to the same supply header S3 and to the steam discharge header SDs, or may be joined with another loop or loops forming a group (Figs. 3 and 6), the outer ends of a group are connected to the steam supply header S3 and to the steam discharge header SDs. The steam supply header S3 is connected with the branch S2, which is connected with the steam supply line S through the T 48b in the hollow shaft 25. The discharge header SDs is connected with the branch SDz, which is connected with the steam discharge line SD through the T 48a in the hollow shaft 25. The
total loops consist of an even number and all.
groups to have the same number of loops. All groups and piping are symmetrical with respect to a vertical median line, and all U loops are spaced in equal distance center to center of the loops. To remove any loop or group of heating units 4| from the dryer, the fixed shaft is turned to bring the loop or group to a top position, a section 23 of the cylinder end 22 is turned to a top position, and this section 23 (Fig. 4) removed. By disconnecting the flange couplings 46 and 41 (Fig. 2) of the loop or group to be removed, the loop or group (Figs. 2 and 6) is pulled out of the dryer. In placing a loop or group in position in the dryer the proceeding is reversed. Thus, the headers S3 and SDs, which are at one end of the cylinders and in fixed position, by virtue of the proximate couplings 46 and 41, may be disconnected and connected to the heating units, so that these may be mounted and demounted. The arrangement shown in Figs. 1 and 2, shows disposition of the headers S3 and SD:; in relation to the heat distributors 4|.
Drain lines D from the low point of each loop are provided with disconnecting unions and are run through the pipe space and the hollow shaft 25. The drain pipes D are shown in outline in Figs. 1 and 2 by the dash line. In the drawings, the drain piping is shown passing out of one end of the hollow shaft. The drain piping is then connected with a receiver at lower pressure than that in the distributing units 4|. This receiver is not shown in the drawings. It is important, to remove the condensates, so that the full heating action of the live steam may be obtained.
It may be more convenient to divide the piping running part to each end of the shaft.
The offset T (Figs. 10 and 11) connection 480. and 48b in the steam supply line S and steam discharge line SD at the point where these lines branch and leave the hollow shaft 25 makes it possible to run these two main steam lines or branches out of the shaft through the same end of the hollow shaft 25. In this drawing (Fig. 2) both steam supply line S and steam discharge line SD are shown running out of the hollow shaft 25 through one end. They could run out of both ends.
In the embodiment, these pipe heating units 4|, are joined together in pairs to form U loops. The sides of these loops 4i are spaced from the cylinder wall 21 and are held in position by supports 42 connected in pairs to cross base bars 43, the projecting ends of which are held in cleats 44 running the length of and attached to the fixed cylinder 21 by bolts 45, (Figs. 6, '7, and 8). Electrical heating units 4 la (Fig. 13) when used may be. mounted likewise preferably in loops supported 6'- on the supports 42a, but these supports 42a are then of insulating material, and the base bars 43 will be replaced by a base plate 43a for the length of the cleats 44, the projecting edges of the base plate being held by the said cleats (Fig. 12).
Heat may be lost at the ends of the confined air space due to the surface loss from the outer shell and ends and to the unavoidable change of air through the running clearance space. In this invention an excess of heating element is made by the U bend at each end with the idea of overcoming this heat loss. This excess can be increased or decreased to give a resulting even heat extending out to the edge of the drying surface. It is important that the heat emission of the outside surface of the outer shell or cylinder be uniform, continuous, and uninterrupted spatially across the full width of the sheet to provide uniform drying of the sheet.
The base bars 13, and supports 42 and 42a are staggered so that adjacent supports will not be in the same plane perpendicular to the axis of the cylinders. This staggering is made to prevent a possible dead spot or line in the heated air by breaking up the established pattern of turbuience in the air.
The air chamber between the cylindrical walls El and 20 cannot be made air tight as a running clearance is required between the inner wall 21 and the abutting flanges 2 lb and 22b on the outer wall heads 2! and 22. To reduce the forces producing air change in this chamber to a minimum the diameter of the abutting flanges on the heads of the outer wall is the same, thus keeping the centrifugal action on the air the same at each end of the dryer. Also the projection of the abutting fianges 2!?) and 22b on the heads of the outer shell are the same for both heads of any one dryer to give a balanced air action for the two ends. In the embodiment, the radial thickness of the flanges 21b and 22b, are such as to overlap the abutting cleats (Fig. 2).
The enlarged diagram Fig. 13, of the end of F the air chamber or compartment A, shows the outer revolving cylindrical shell 20 with the end support 22, the circumferential inwardly extending flange 22b, the matching stationary inner cylinder 21 with its support 29. Materials 5| to retard heat transmission are shown at the outside end and at the inside surface of the inner stationary cylinder. The electrical heating unit 41a is shown midway between the cylindrical walls 29 and 21 with the insulating supports 42a connecting to the base plate 43a. A part of the paper web is shown at 52. The running clearance 53, between the flange 22b and inner cylinder 21, is made as small as mechanically advisable, in the manner as the running clearances shown in the embodiment of Fig. 2. Conductors, not shown, may pass through the shaft 25, and are connected with the input and output ends of the units 4 la, as shown in Fig. 12, and these conductors from the shaft to these ends, are supported by the inner cylinder, in substantially the same general manner as the headers described, and the units 41a are connected detachably thereto, to enable the replacement of any unit.
The invention contemplates the provision of a cylindrical chamber of a length considerably longer than its depth, formed by an outer cylindrical wall with heads and rotating in respect to an inner cylindrical wall which is stationary and extends between the two rotating heads of the outer cylindrical wall, and completes the inclosure of the cylindrical chamber. This stationary inner wall supports the piping or power units which supply heat energy to the stationary heat distributing units for heating the cylindrical chamber, said heat distributing units being supported on the convex side of the inner cylindrical wall.
This rotating cylindrical wall at its outer side functions as a pulley acting as a belt picking up the web of paper carrying it for about three quarters of a revolution whence it is run oil to a following cylinder.
The function of the inclosed cylindrical compartment or chamber filled with air surrounding the heat distributing units is to convey the heat from the heat distributing units to the outer cylindrical wall, thence through this wall to the paper Web to dry said paper web. Air in the chamber between the moving and the stationary walls will be drawn along by the moving wall and retarded by the stationary wall. Between these two actions there will be a continual IClling agitation of the air picking up heat from the heat distributing units and transferring it to the paper contacting wall. The inn-er cylindrical wail the space within will become heated to such an extent that heat will be conveyed from the inner wall to the outer wall by the air in the chamber. The only real loss of heat will be through the end walls of the cylinders. This distribution of heat to the outer cylindrical'wall which is paper drying area, is uniform over the whole surface and coextensive with the width of the paper, a definite requirement in paper drying.
In these drawings many common and necessary piping supports and bolts and welds are not shown.
This is a continuation in part of my co-pending, application, Serial Number 37,718, filed July 8, 1948, for Electrically Operated Paper Machine Dryers and Method of Drying Paper, which has been confined to a method, this application embodying the apparatus structure of that application, together with improvements thereon.
I wish it to be understood that I do not desire 4 to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.
In a paper machine dryer having concentric cylinders including an outer cylinder and an inner cylinder, with horizontal coincident axes, closing means at the ends of the cylinders for forming a fluid substantially closed chamber between the cylinders, means supporting the inner cylinder in a stationary position, and means rotating the outer cylinder around the inner cylinder, the combination of heat distributing members spaced from both cylinders and fixed intermediate of both cylinders and supported by the inner cylinder, and means for rotating said outer cylinder at paper drying speed, whereb the air in the chamber is drawn from the outer surface of said inner cylinder, by the outer cylinder in a circumferential direction and around said spaced heat distributing members, said heat distributing members forming a plurality of heat distributor units, each unit independent of the other, and each having a heat power supply end, a return power flow end, means detachably supporting each of said units on said stationary cylinder, means on the stationary cylinder for supplying heat to each heat supply end of each unit, means on the stationary cylinder for the return of the return flow end of each unit, detachable means connecting said supply and return end of each of said units, to said last named means respectively, whereby each of said units may be removed and replaced from said static-nary cylinder after detaching said detachable means, and condensate drains connected with said steam pipes, said drains removing the condensate, to enable the live steam pipes to be free of said condensate.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 963,942 Richardson July 12, 1910 1,675,274 Miller June 26, 1928 1,899,256 Brannen Feb. 28, 1933 2,367,578 Helin Jan. 16, 1945