US2758386A - Drier method for veneer - Google Patents

Description

Aug. 14, 1956 J. F. COBB DRIER METHOD FOR VENEER 4 Sheets-Sheet 1 Original Filed Sept. 5, 1951 INVENTOR.

J FORREST COBB AT TOR NEY Aug. 14, 1956 COBB 2,758,386

DRIER METHOD FOR VENEER Original Filed Sept. 5. 1951 4 Sheets-Sheet 2 asaeasceo' INVENTOR.

BY J. FORREST c055 A CM ATTORNEY Aug. 14, 1956 J. F. COBB DRIER METHOD FOR VENEER 4 Sheets-Sheet 3 Original Filed Sept. 5, 1951 1 W M a a i n I a a I :II

INVENTOR J. FORRST COBB MHM mm A: .m

ATTORNEY Aug. 14, 1956 J. F. COBB DRIER METHOD FOR VENEER 4 Sheets-Sheet 4 Original Filed Sept. 5, 1951 INVENTOR.

BY J. FORREST COBB ATTORNEY Uite States DRIER :METHOD FOR VENEER J- F res Cobb, o t and, fi s; M r m R- C ecutrix of said James ForrestjCobb, deceased, assignor to Moore Dry Co. of Oregon, North Portland, Oreg.

application September 5, 19.51, Serial No. 245,105. Divided and hiSaPPlication July 11, 1952, Seria N l-2 2 Claims. (Cl. 3.4--31) This is a division of Serial -No. 245,105 filed September 5, 195-1, now abandoned.

This invention relates to drier method for drying veneer made in the course of manufacturing plywood, which industry has reached important proportions.

More particularly it relates to apparatus with inherent operating methods that are deemed to be of major im portance in theart.

It has long been found useful in some sorts of drying to build an elongated drier, supply it with steam heating coils and pass sheets of material through by means of rollers on plural decks relatively slowly so that it moves constantly in at one end and out of the other; the patent to one Vance, 1,776,014, being an example as shown in Fig. 1 of that patent, though by no means the earliest.

These driers of the prior art were elongated and contained a circulating means for drier atmosphere that served the entire drier at about equal temperature.

It is an object of the present invention to provide a plurality of drier units in side by side relationship, having divisional walls therebetween, with each unit equipped with independent air circulating fans of heretofore unexampled power and air handling capacity in proportion to the cubic capacity of the drier units. Such great air capacity with high velocity makes possible the use of heating radiators of much larger radiating capacity than heretofore thought possible oiexpedient with temperatures so high, of the order of four hundred to-six hundred degrees Fahrenheit, not heretofore deemed possible on account of fire danger. These are used on the green end unit of the drier as a whole, and decrease by-temperature steps to the dry end; the optimum rate of air circulation in those driers showing two fans each, being of the order of thirty thousand cubic feet of air per minute and one-half thatfor those showing but one fan.

The exceedingly high air velocity over, under and between the decks of moving veneer strips as hereinafter described is what makes possible the accompanying high heat, also hereinafter recited, otherwise the veneer strips o ld be everely d mage It is a further object of the invention to provide a plurali ty of drier units in side by side relationship comprising two or more distinct and functionally independent drier units as to temperature, humidity and barometric pressure a d a r han l n e u pm n ith d q at ean for pa in sheet o enee or oth r he t o mat ri wi u stopping, from one end to the other of a relatively long assembly of drier units, applying to the material the hitherto impossible high initial temperature of the order of 600 deg. F. without injury to wood veneer, but which almost instantly volatilizes fractions of pitch as well as free and hydroscopic moisture while constantly moving the veneer to be dried through units which, independently of a succeeding unit, provide a stepped down temperature of drier atmosphere to continue the rapid drying cycle begun in the first drier element .or carried on by a next succeeding drier element to safely ad seriatim steps of progress in the drying procedure to an end unit which maintains, as before, a high drier atmosphere velocity, but of cool air, to bring the product out in excellent flat condition for further processing, with a lower and more uniform moisture content than heretofore deemed practicable, which is a highly favorable change in view of gluing operations which are next following in plywood manufacture.

The novel drying process hereinafter described and .explained in detail, to make it available to those skilled in the drying art, is in outline as follows: A method of uniformly drying veneer which essentially includes passing a plurality of vertically spaced courses of green, water saturated veneer stock through a series of drying units that are functionally independent of each other, starting with a unit in which the drying temperature is of the order of 600 deg. F. and the air circulating volume of the order of thirty thousand cubic feet of heated atmosphere per minute, and, without stopping the flow of said courses of veneer stock, passing them through a succession of other drying units provided with downwardly stepped temperatures and with suitable air circulation velocities and volumes, until a final or end unit cooling is reached and passed, it being much better when the circulation is reversed repeatedly, .by which the veneer is brought down to a safe cool point'where it does not readily absorb moisture from surrounding normal atmosphere; plus, additionally, the novel equipment found expedient to carry out the steps of the drying process in commercially practical volume.

The apparatus and method have been made and 'installed in various places and the accompanying drawings are such modifications of working drawings used in building these various drying plants as render them suitable for patent drawings. Many of the details are conventional representations of known equipment as will be stated infra, and others are so well known as not to need indentification.

The elongated drier, with roller means for continuously moving sheet material through for drying, is broadly old and not claimed herein but in general the same external outlines divided up into a series of side-by-side drier units, each functionally independent as to heating and circulation means, each with independent controls, starting the drying cycle with a four hundred to six hundred degree heat, the wood being protected by its high initial moisture content and terrific velocity of drier atmosphere, produces a highly desirable result in only a fraction of the time required by theoriginal drier supra, that externally greatly resembles it.

The best structure now known to carry out the drying process is illustrated in the accompanying drawings, in which:

Fig. 1 is a plan view of an assembly of drier units constituting a single drier apparatus, to be explained in detail.

Fig. 2 is an elevation of the structure shown in Fig. 1.

Fig. 3 is aperspective view of the basic structure shown in Figs. 1 and 2 showing the external appearance and the green end of the structure.

Fig. 4, on the same sheet as the previously noted figures, is a sectional view taken on the plane 4-4, Fig. 2, and is a cross-sectional elevation, showing a typical cross-section of any of the drier units, varying only in minor details with the relative position of the unit.

Fig. 5 is a sectional elevation taken on the plane 5-5 of Fig. 4, showing an end view of a typical reheater such as positioned by dotted outlines in Fig. 1.

Fig. 6 is an enlarged partial view of the top of the reheater taken on the plane 6--6, Fig. 7.

Fig. 7 is an end view of the reheater taken on plane 7-7 of Fig. 5, at reduced scale, showing its relative position in the top of the drier unit, of which it is an important part.

Fig. 8 is a typical cross-section of a four deck drier unit of the fast drying type, such as the first six, left to right in Fig. 1, showing the spaced position of the roller courses with veneer lines thereoetween that define the decks and intermediate piping for steam heat. The air circulation means at the top is omitted in this figure.

Fig. 9 is a section taken on plane 9-9 of Fig. 8.

Fig. 10 is a view taken on plane 10-14) of Fig. 9, showing a typical plan of intermediate radiation steam piping, shown by fragmentary indications to be on both sides of each deck to supplement the reheaters as explained infra.

Fig. 11 is a view showing typical star wheels, taken on plane 11-41 of Fig. 8, for causing constant motion of upper and lower rolls, the rolls themselves constitutmg the decks referred to supra.

Fig. 12 is one of the most important of any of the views in the series of drawings, showing means for passing the sheets of veneer through the intermediate walls between drier units and at the same time maintaining substantially perfect isolation of the drier atmosphere with respect to adjacent units or outside air.

Fig. 13 is a fragmentary view of the structure shown in Fig. 12, taken from the plane 13-43 of Fig. 12.

Fig. 14 is a view taken on the plane 1414 of Fig. 13, showing the position of one end of the rolls which define decks and their relative spacing from the side walls of the drier units.

Describing the structure shown in the drawings in greater detail: The general idea of a greatly elongated drier, the outline of which is adopted here, is broadly old and well known, though the principle of internal partitions, as referred to in the foreword of this specification, is believed to be novel. For the high temperatures hereinafter described under which operation is planned and needful, the drier construction must be of metal and omits burnable material altogether, also in the interest of economy and to the end that the immediate vicinity may be occupied by an operator, the external surfaces are insulated with insulation material suitable for the temperatures involved; but the insulation is not shown in the drawings.

A heat supplier or steam boiler furnishing dry saturated steam at preferably three hundred pounds gauge is suitable as the source of heat supply as the steam delivered to the drier will be enough higher than 400 degrees F. to permit regulation. Lower steam pressures may be used with superheat.

To avoid complication of the drawings, no insulation has been shown; the fans, being a commercial product, are represented by known symbols and the drive motors therefor, likewise.

An elongated drier structure as shown in Figs. 1 and 2, is built as an assembly of separated drier units represented by numerals 2, 3, 4, 5, 6, 7 and 8, the last one, 8, being a cooling unit. More or fewer units may be used, but eight in assembly constitutes a typical assembly of drier units according to the invention.

Describing unit numbered 2 at the left hand side of Fig. l and Fig. 2, and referring to the typical dimensions taken from the shop drawing: In plan it was about ten feet six inches wide and a bit more than twice that dimension in length. The height would vary as a function of the number of decks used, in this case four. The four decks are defined by four lines of pairs of rollers, each pair comprising a lower roller 10 and an upper roller 11.

These numerals are applied to any pair of rollers, not necessarily the same pair, in Fig. 2 and Fig. 8 and in particular in Figs. 12 and 13. The rollers are preferably drawn steel tubing with heads and stub shafts welded or otherwise secured in alignment. One end of each lower roller stub shaft 12 will have mounted thereon a sprocket for chain drive 13 and the upper reach of a chain 14 will engage all of the sprockets and suitable means not shown will be provided over each sprocket to prevent the chain jumping 21 sprocket tooth as the construction is Well known. j

The lower reversely running reach of the same chain, numbered 15, will run back to the main speed change box 16, where the bight of the chain, 14-15, will pass over a suitable inside drive sprocket, not shown, and all of the chains, in this'case four, one for each deck of rollers, will be driven by a motor 17 indirectly through a Reeves or equivalent speed changer 18 adjacent the dry or right hand end of the drier assembly as shown in Figs. 1 and 2. The rollers and chain drive are an old expedient, in the public domain. Passageways for carrying the chains through the divisional Walls are provided.

The opposite ends of both rollers such as 10 and 11 are equipped with star wheels, a form of intermeshing gears with long teeth, as shown in Fig. 11 at 19', to permit the upper roll 11 to raise under the lifting effect of a sheet of veneer passing between the rolls 10 and 11 without depriving the upper roll 11 of a positive drive by the teeth going out of mesh, as would be the case with standard gearing.

The decks of rollers and the chain drive are common to all of the separate drier units such as 2, 3, 4 and to the end of the drier and pass through the divisional walls 19 by virtue of a special arrangement of cooperative parts with a pair of rollers 10 and 11 positioned very closely to the divisional wall proper, shown in this instance as being a plurality of channel shaped longitudinal baffles 20 as in Figs. 12 and 13.

Suitable partition members such as the beam 21 and the vertical support 22, form a support for the sealing plates 20, which will be made of proportionately lighter material than the drawing might seem to indicate.

The sealing plates may be attached to the support members in any suitable way to substantially close the openings 23 between their edges 24, with their fiat sides very close to the perimeters of the rollers, or in contact. It will be seen at once that by cooperation of the adjacent rollers 10 and 11, in actual contact with the sealing plates 20, the opening for passing. veneer sheets 25 through the divisional wall 19 will be closed whether or not a flow of veneer is passing through the roller deck from the outside of the first drier unit, through a pair of rollers that are reversed duplicates of those shown in Figs. 12 and 13. The feeding in employs the same mechanical principle.

Since drier unit 3 will ordinarily be operated at a somewhat lower temperature step than drier unit 2, for example, and heat leakage through the first divisional wall 19, or in fact any divisional wall 19, is unimportant, these divisional walls need not be heat insulated, which is the case with all of the divisional walls 19.

Since the upper rollers 11 must yield to permit the passage of veneer sheets of varying thickness, each end of these rollers is provided with a stub shaft that may freely move up to allow a sheet of veneer to pass under it in slotted bearings 26 (Fig. 11), all of which has been taken from the known art.

Each drier unit will contain suitable piping such as shown at 27 in Figs. 8 to 10 inclusive and each separate drier unit will be equipped with separate steam radiator reheaters such as shown in Figs. 5, 6, and 7, identified by numeral 28 regardless of size and placed substantially as shown in Fig. 4 as to relative vertical position and as indicated by dotted outlines in plan in Fig. 1. Fig 1 also indicates the decreasing size of these reheaters required as the drying method progresses toward completion. Also it is to be noted that there are none shown in the drier unit at the extreme right, which has a powerful fan 29 for cooling the unit and the veneer strips as they enter from the last preceding .drier unit.

It will be observed that each drier unit is equipped with one or more fans 29 for circulating drier atmosphere, there being pairs of fans 29 in each of units 2, 3 and 4 and single fans in other units. This arrangement is not vital and may be varied but the schematic showing indicates decreasing temperatures and enough circulation to protect the veneer against temperatures that would still be dangerous without high velocities of drier atmosphere.

It will be advantageous to place the fans as shown so that the circulation over the veneer is reversed as it passes from one drier unit to the next succeeding one, which promotes a uniformly low final moisture content.

Each drier unit will be equipped with a stack, insulated, to a point beyond which it could be dangerous on account of temperatures given by discharged drier atmosphere in which the extracted moisture has been transformed to superheated steam. The stacks are indicated by numeral 30 and may be equipped with regulating means, as schematically shown at 31. When a stack serves two zones as illustrated in Figs. 1 and 2, a means 31, Fig. 4, is shown where the fan blast is intercepted by a means tending to lower barometric pressure within the affected drier zone. Hinged doors 32 may be placed at both ends of each drier unit to aflford timely access thereto.

Having fully described my novel drier unit apparatus and the results made possible by novel construction with its inherent mode of operation and entirely new result, what I claim as new and desire to secure by Letters Patent, is:

1. The method of drying sheets of wood veneer which comprises moving a plurality of such sheets through a succession of drying zones, said movement being uninterrupted while maintaining isolation between zones in the matter of temperature and high air volume circulation in said zones, the heat being arranged according to conditions and variety of wood from 400 degrees F. or higher by downward temperature steps, while maintaining a volume of atmosphere cross-circulation volume of thirty thousand cubic feet per minute in at least two of said zones, to achieve rapid evaporation of contained moisture from said sheets and to prevent damage to the wood fibres.

2. The method as claimed in claim 1 and including the variation of reversing the direction of circulation in adjacent zones.

References Cited in the file of this patent UNITED STATES PATENTS 1,050,151 Loomis Jan. 14, 1913 1,541,889 Baltz June 16, 1925 1,567,023 Larsson Dec. 22, 1925 1,656,802 Vance Jan. 17, 1928 1,668,314 Harvey May 1, 1928 1,725,708 Fowler Aug. 20, 1929 1,751,552 Kehoe Mar. 25, 1930 1,777,764 Olson Oct. 7, 1930 2,659,162 Katz Nov.- 17, 1953

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