US2550687A - Method of pressing in a multiple platen press - Google Patents

Description

May 1, 1951 w. c. 6085 METHOD OF PRESSING IN A MULTIPLE PLATEN 'PRESS 2 Sheets-Sheet 1 Filed Nov. 16, 1948 3nnentor 14 0/21 C. Goss V" M Gttorneg Patented May 1, 1951 METHOD OF PRES SING IN A MULTIPLE PLATEN PRESS Worth 0. Goss, Seattle, Wash., assignor to United States Sheetwood Company, Seattle, Wash., a

corporation of Delaware Application November 16, 1948, Serial No. 60,351 3 Claims. (Cl.18-55) This invention relates to improvements in hot pressing, and it has reference more particularly to hot pressing in presses of the multiple opening types such, for example, as presses used in the manufacture of products known in industry as sheet lumber or hard boards and which prod-i ucts' are made from wet or damp fiberized mate rials, formed into pads and the pads compressed between the plates or platens of a multiple open-- ing press under the coalescing action of heat and pressure.

In the consolidating and coalescing of hard boards'and the like from pads of damp ligno-cellulosic .fibers, in hot plate presses, it is customary to place a wire mesh screen between one of the press platens and the pad of damp material in order toprovide for a ready escapement from the pad of the steam that is generated therein in the pressing operation. While screens could advan tageously be'placed at both sides of the pad, the reason for not doing this is the desirability of having boards of this kind formed with one per fectly smooth surface, and such a surface would not; be formed if a screen should be disposed therjeagainst during the pressing operation.

In aco-pending application, filed on July 1,

1946, under .Serial No. 680,838, now abandoned,

noW'in a copending application filed under Serial No. 98,759. I have disclosed the pressing of sheet lumberlfrom a homogeneous mixture of lignocellulosic fibers and a hydro-plastic bonding agent. The agent has been described therein as one having the property of setting while wet and hot and, by reason of this property, to make possible the removal of the consolidated board from the press while still venting steam from its pores. While the provision for safe removal of the board from the press while still venting steam has proven'" to be a great manufacturing advantage, due to the reduction of pressing time, it has been found. further that in presses employing equal temperatures in the plates or platens forboth the steam vented and the unvented sides of the board, the finished products will have opposite surface portions of high density of difierent thicknesses; that is, the fibers of the surface portions of the boards, that by reason of their inti- In another application, filed on July ;1, 1946, under Serial No. 680,839, I disclosedthat in the pressing of sheet lumber in a hot press,'the formation of high density surface layers, or;what I have referred to as flanges, of unequal thickness and density, can be avoided by increasing the temperature of the platen or plate at the steam vented side of the board to a degree sufficient to compensate for the cooling effect of; steam escaping through that surface. I have also disclosed that in the making of a common; type of board according to my method, the increase in temperature should be approximately within a range of 100 F. to 150 F., that is, if the tempera ture of the platen at the unventedside of the board is 350 F., then the temperature of the platen at the vented side should be within the range of, 450 F. to 500 F. in order thata board mate contact with the platens will be more fully V plasticized and coalesced to layers of higher density than the main body portion, will be of unequal thicknesses at opposite sides of the boards, and by reason of this unequal volume of high density flanges, warping of the board to more or less. extent will result uponits removal from the press.

having opposite surface portions or flanges of equal density and thickness shall be formed. The temperatures used are governed somewhat by the thickness of the board and the water content of the pad.

It is desirablafrom the standpoint of economy.

and manufacturing expediency; that multiple opening presses. be used in the making, of the present kind of lumber. Howeven'suchpresses as used heretofore have not provided any means to prevent the formation of surface portions of unequal character. This has been due to the fact that it has been customary to retain the boards in the press until bone dry and baked to the same density throughout, thus eliminating any definite .fianges or surface portions of higherfdensity than body portion.

' In view of the above, it has been the principal object of the present invention to provide a method of pressing in a multiple opening press for the simultaneous compression and coalescing of a plurality of pads or sheets of damp, fibrated material as arranged alternately therewith, into boards or sheets of lumber, each board to have one smooth surface, and wherein means for the venting of steam from the pads are associated with alternate platens of the series, and the temperature of said alternate platens of the series will be of such degree above that of the others as to insure the formation of surface flanges of the same density and thickness at the steam vented sides as at the other sides of the boards. Furthermore, it is an object of the invention to so establish the temperatures of the platens at the vented and unvented sides of the boards, respectively, that in accordance with the character and thickness of the board being made, uniformity of surface structure at both sides of each compressed sheet will result and all tendency of the finished sheet to warp by reason of the formation of unequal surface flanges will be avoided. Further objects and advantages of the invention are to be found in the combination and relationship in a multiple opening pressof this kind, of platens or"- high and of lower temperature, alternating in the series, and steam venting screens associated with the platens of higher temperature only for the simultaneous production of two or more sheets or boards, each with one smooth surface.

In accomplishing these and other objects of the invention, I have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawings. wherein:

Fig. 1 is a side View of a multiple platen press embodied by the present invention.

Fig. 2 is a horizontal section taken on line 2-'2 in Fig. 1.

Fig. 3 is a perspective view of a detail of the platen bracket design.

Fig. l is a horizontal sectional detail of platen construction.

Referring more in detail to the drawings:

The present press comprises a rectangular, horizontally disposed base structure Ill and a top structure H, these parts being joined in fixed, vertically spaced relationship by tie bolts l2, passed therethrough at their four corners.

Mounted in the base structure II] are paired hydraulic jacks i k-Hi which support thereon a horizontal plate or frame l5 on which the lower platen I6 of the press is horizontally mounted. "Secured to the underside of the top structure H is a horizontally disposed press platen l8, and arranged between the platens l6 and [8 are independently movable platens is, and 2i; all platens of the press are of the same length and width and all are in vertical alignment. The platens i9, 20 and 2| are equipped at their four corners with brackets 22 whereby they are mounted for vertical, guided movements in opening and closin operations, on vertical guide bars 24 that are extended'between and fixed to the base and top-portions iii and II at opposite ends of the press as will best be understood by reference to Fig. 1.

When the plate [5 is fully lowered, the platens IS, I9, 20, 2i and i8 will be supported in spaced relationship as noted in Fig. l. The platens l6, I9, 20 and 2! will be held in proper spacing by the engaging of the brackets 22 at their ends with upwardly facing shoulders 29 On thevertical guide bars 2G. These stop shoulders of the bars are in stepped relationship and so arranged that the spacing of all the platens of the series will be equal and to such amount that the prepared pads of material to be simultaneously pressed between the succession of plates may be readily placed between them for consolidation upon closing the press.

It is to be explained also that all intermediate platens, as well as the upper and lower platens, are heated and, for my presentpurpose,'the lowermost platen will be heated toa temperature of about 500 F. The next higher platen will be heated to a temperature of about 350 F, the next higher to about 500 and so on through the series. Higher or lower temperatures may be employed, depending upon the character or thickness of board being made. The means for heating the platens may be electric elements located in the platens or superheated steam admitted to passages provided therefor in the platens. In the present instance I have indicated the platens as being steam heated, each having steam channels 34, opening to anend thereof and to which flexible pipe connections, designated generally at 35, leading from separate supply lines 36 and 31, are joined, thus to maintain steam circulation and maintain proper platen temperatures at all times.

Pressure medium for control of the jacks l4-l4 is delivered through supply .pipe 40 and a pressure pump AI and is admitted to or released from the jacks under control of a control valve 42. In connection with this hydraulic mechanism, suitable pressure gauges, not shown, would be employed to indicate pressing pressures being used. Also, indicators or other means would be used to show platen temperatures at all times.

It will-be understood that with the press so designed, it can be fully opened by the lowering of the jack supported plate I5 to its lower limit. Then, with the press open, and the succession of platens in the relationship shown in Fig. 1, the pads of material to be pressed, here designated by reference numeral 45, are disposed between the platens, and steam-venting screens 46 are placed between the pads and the platens of higher temperature only. If additional means for steam escapement is necessary or desirable, this may be accomplished by providing those faces of the platens that are engaged by the screens, with a plurality of cross channels with slit-like openings to the platen faces and with ends open to the sides of the platens, as has been described and illustrated in my co-pending applications above mentioned.

With the pads of damp fibrous material in place, then the platens are moved toward each other by applying pressure medium to the jacks to lift plate [5. With the final closing of the press, all pads will be substantially equally compressed and their fibers coalesced under the simultaneous application of heat and pressure.

By reason of the use of the stated higher platen temperature at the steam vented sides of the pads, the cooling effect of escaping steam will be compensated for. After a few trial operations, the temperatures of platens of the two series that will insure formation of flanges of equal thickness may be very accurately established. The increase of temperature of the platen at the steam vented side is more or less in accordance with the increase or decrease of board thickness and the moisture content. The range herein given is practical for boards of inch to inch thickness.

Presses of this kind may be advantageously employed in the making of boards using a damp fibrated material as described in my applications above mentioned, or a material like that disclosed in the various patents of Mason, for example, as in United States Patents Nos. 1,663,503, 1,663,504 and 1,663,505.

Presses using the above described relationship of platens of different temperatures may be made in various designs, sizes and to receive various numbers of pads simultaneously. The essence of the present invention resides in the arrangement and use of steam vented platens of increased temperature, in alternate relationship with platens of a designated, substantially lower temperature, to bring about the formation of boards wherein the high density surface portions, or flanges, will be of substantially the same thickness, or at least will be of such structure as to equalize each other in so far as their tendency to cause warping of the board is concerned.

Having thus described my invention, what I claim as new therein and desire to secure by Letters Patent is:

1. A method of simultaneously compressing and drying a plurality of compressible moisture containing pads, comprising, subjecting single pads to heat and pressure between the successive plates of a multiple opening press wherein alternate plates of the press are smooth surfaced for direct contact with the pads and heated to one degree of steam generating heat and the other platens are heated to a higher degree of heat, and wherein steam venting screens are located only between the pads and plates of the higher degree of heat; the temperature of said other plates being above that of the smooth surfaced plates sufficient to compensate for the cooling effect of escaping steam thereon.

2. A method for the simultaneous production of a plurality of compressed fiber boards, each having one smooth surface and both sides formed with dense surface flanges of equal thickness and a less dense body portion, comprising subjecting single pads simultaneously to heat and pressure between the successive plates of a multiple opening press wherein alternate plates are heated to a degree range between 300 F. and 350 F.,

and the other plates of the series are heated to a degree range between 400 F. and 500 F. and approximately F. higher than the other plates, and wherein the plates of the lower degree range are smooth surfaced, and steam venting 6 means are provided at the surfaces of the plates of the higher degree range; the pressing operation being discontinued before the pressed pads become entirely dry.

3. A method for the simultaneous production of a plurality of boards from compressible moisture containing pads of bondable fibrous material, each board having at least one smooth surface and having dense surface flanges of equal thickness at opposite sides and a less dense body portion; the method comprising subjecting the individual pads to compression and heat between the successive plates of a multiple opening press wherein alternate plates are smooth surfaced to give the smooth surfaces to the boards, and heated to steam generating heat of a predetermined degree, and the other plates surface vented for escapement of steam from the boards along said vented surfaces, and heated to a degree of heat above that of the smooth surfaced plates sufiicient to compensate for the cooling effect of the escaping steam.

WORTH C. GOSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,894,778 Mason Jan. 1'7, 1933 1,942,251 Mains Jan. 2, 1934 2,161,653 Ellis June 6, 1939

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