US2382004A - Method of and apparatus for molding trays - Google Patents

Description

Aug. 14, 1945. F. CURRAN 2,382,004

METHOD OF AND APPARATUS FOR MOLDING TRAYS Filed Nov. 22, 1943 1 i i v y W 7/ 4 I 2 e V 25 12 Patented Aug. 14, 1945 UNITED STATES, PATENT OFFICE METHOD OF AND APPARATUS FOR I MOLDING TRAYS c I I Frank M. Curran,

Grand Rapids, Mich, assignor to Haskelite Manufacturing Corporation, Grand Rapids, Mich, a

corporation of New York Application November 22, 1943, Serial No. 511,289

7 Claims.

The invention relates to molding trays formed of a core of wood with a sheet covering bonded to both faces thereof, r

In molding trays having a rim, 3. bottom and a sloping portion between the bottom and the rim with a core of wood and a preflnished sheet covering, such as paper on which decorations have been lithographed, it is desirable to sub ject the .wood in the rim and the sloping portion to a crushing pressure for stiffening purposes. When the core of wood in the bottom of the dies for molding the tray, showing them in separated relation, and a blank of wood and a sheet of covering interleaved with glue, between the dies. Y

- Fig. 2 is a similar section illustrating the dies after they have been operated to mold thetray.

Fig. 3 is a plan of the female die.

Fig. 4 is a perspective of the finished tray.

In carrying out the invention; a sheet a of suitable paper on which has been lithographed the decoration or ornamentation d desired on the tray is subjected to crushing pressure, wrinkles One object of theinvention is to provide an,

improved method for molding trays of this type from a blank of wood with a finished sheet covering, such as lithographed paper, and thermosetting the glue between the wood and the covering, which densities or crushes the wood in the rim and the sloping portion between the rim and the bottom for stiffening purposes while the bottom of the tray will be subjected to yielding pressure, whereby warping or wrinkling will be avoided, the transfer of the impression of the grain in the core to the cover sheet will be prevented, and varying density in the wood in the bottom will not affect the evenness of the top face of the finished bottom.

Another object of the invention is. to provide improved apparatus for molding trays having arim, a sloping portion inside of the rim and a bottom, all formed of a wood core and a sheet covering on both faces thereof which is bonded to the core, and whereby the bottom of the tray will be subjected to yielding pressure'for preventing wrinkles in Or warping of the bottom, transfer of an impression of the grain in the core to in a single operation during which the wood and the cover sheet, and the unevenness 0n the-top face of the bottom.

Other objects of the invention will appear from the detailed description.

The invention consists in the several novel features hereinafter set forth and more particularly defined by claims at the conclusion hereof.

In the drawing: a

Fig. 1 is a vertical transverse section of the top face of the bottom of the finished tray, is folded around a sheet or blank b of wood which forms a core, and a sheet of glue 0 is folded between the paper and both faces of the wood blank. The tray is molded to its finished shape paper cover are shaped andbonded togetheriry thermosetting of the glue,

The invention is exemplified for molding a tray d having a generally rectangular and circumferential rim d, a flat centrally formed bottom 11 and a sloping portion d between and integral withthe bottom and the rim, all with a core of wood and a finishing cover of paper.

The molding apparatus comprises a male die In and a female die H which can be used in a press of any suitable construction and which is provided with suitable heating means for thermo-setting the, glue while the tray is being shaped and molded. The female die H is supported on a bed I? of the press, and any suitable mechanism may be used for reciprocating the ram to operate the male die In to and from the female die.

The male die i0 is rigid throughout and is provided with a fiat rectangular or marginal rimshaping face l3, an inclined rectangular or marginal face I4 around the insideof the face for shaping the sloping portion 11*, a'fiat bottomformingface l5, offset from the face l3, and which may be provided with ribs for forming grooves or depressions d at the beveled corners of the face It in the-top of the tray.

The female die ll comprises a rectangular frame l6 which is provided with a flat generally rectangular circumferential top-face l! which coacts with the face I3 of the male die to shape the rim d'of the tray, an inclined generally rectangular face l8 substantially parallel to the face H of the male die for shaping the sloping portion d in the tray, and a flexible pad which 'coacts with the flat face 15' of the male die in shaping the'bottom d in the tray. 'lhis pad comprises a shell or container 20 of thin flexible metal, such as 20 gauge steel, and is loaded with a quantity of oil which is not normally .under pressure, and sufficient air to render its top face sufliciently resilient'and flexible while the tray is being molded to uniformly distribute the pressure throughout the bottom of the tray. The sides of the shell 20 extend into a recess 23 and the margins of the pad underlap the face l8 of the frame It. The dies are designed to subject the rim and sloping portion d in the mold to-a crushing pressure, usually about 500 lbs. p. s. i. and the pad is designed so that a lower pressure of ap-' proximately 65 lbs. p. s. i. will be applied to the bottom of the tray. The topface of the shell is sufliciently flexible and resilient, when subjected to this lower pressure, to shape the top face of the tray against the flat rigid face I of the male die, and the flexible face on the female-die will yield to any irregularities in the wood of the core and uniformly distribute the lower pressure throughout the bottom of the tray. Any irregularities or defects which result from the varying density in different portions of the wood will be in the under faced the bottom while its top face will be entirely fiat. This reduced evenly dis-.

tributed pressure against the bottom of the tray also prevents the grain of the wood from being visibly impressed in the paper on the top face of the bottom of the tray. As a result, no defects caused by the quality, varying densities of, or grain in, the wood in the core will be visible on defects as result are visible only on the under tributes this reduced pressure evenly against the underside of the bottom of the tray and yields to any irregularities in thickness or due to different densities in the different portions of the wood. in the bottom, while the paper on the top face of the bottom of the tray will be pressed flat and devoid of defects. I The transfer of impressions of the grain to the paper on the top of the bottom d of the tray will be avoided. Varying densities in the grain of the core of wood in the bottom 11 underthe lower pressure will not result in any fimperfection on the covering on the top face of the bottom of the tray and only on the underside of the bottom where they do not affect the ap-: pearance of the tray. The pressure and heat'to which the bottom of the tray is subjected is sufficient for thermo-setting the glue between the core and the paper cover. After the tray has been molded, the margin of the rim is usually trimmed to a finished edge.

The pad 20 containing a fluid which is usable with heated dies, provides a flexible face on the female die which is preferable to an elastic material, such as rubber, because it has been found in practice that rubber develops irregularities when used with heated dies, such as are necessary for thermo-setting the glue simultaneously with thetop face of the bottom of the tray, and such side of the tray. 1 Heretofore, considerable loss was entailed from the defects which were apparent in the top face of the tray, and these are eliminated by the use of the flexible pad which produces flatness and uniformity, and avoids impres- Q sions of the grain of the wood in the top covering on the top face of the tray. The female die II is provided with dowels 2| which are adapted to enter recesses 25 in the male die for guiding'the male die rectilinearly into conforming relation with the female die. I

In the operation of the apparatus and carrying out the method of the invention, the sheet a of v lithographed paper is folded around the top and the shaping of the tray.

The invention provides for molding in 9. operation a tray having a core formed of a sheet of wood'and covered with prefinished and decorated paper and for subjecting the core of wood in the rim and sloping portion of the tray to a sufliciently high pressure for densifying or crushing it for stiffening purposes, and for molding the flat bottom in the tray with a lower and yielding pressure which results in molding the bottom of the tray with aflat even top face of the paper without transfer of the grain in the core to the top layer ofpaper duringeach thermo-setting of the glue between the core of wood and the r paper. method effects high saving in cost by lowering the percentage of imperfect trays in I rapid production and byrendering fine surfacing bottom of the blank of wood d with an interleaved sheet of glue 0 between the paper and both faces of the blank,'and the assemblyis placed between the dies as illustrated in Fig. 1. The male die is then lowered into the position illustrated in Fig. 2 until a pressure, usually 500 lbs. p. s. i., is exerted on the assembly between the rigid face l3 of the male die and the rigid 'coacting face ll of the female-die and also between the slopeforming face ll of the male die and-the'coacting rigid face l8 of the female die. pressure to which the wood or core in the rim and sloping portion of the tray issubiected is sufliclent to .densify or crush the core of wood between the paper covering in the rim d and the sloping portion :1 of thetray, and the heat from the-dies will thermo-set the interleaved glue. The indentations it will be simultaneously impressed in the corners ofthe slopin portion d. iWhil the scope of the invention.

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

1. That improvement in molding a core of wood with a sheet covering glued on both faces thereof into a tray having a rim, a bottom and a sloping.

portion between the rim and the'bottom which comprises: subjecting the rim and the sloping portion inside of the rim to a sufficiently high l pressure for crushing the portion of the core in the rim and sloping portion of the tray, and shaping the core and covering into the bottom of the ing pressure on the bottom face which localizes rim and sloping portion are formed with this wood densifying and crushing pressure, the flat rigid ;face I! on the male die will exert pressureon the top paper coverin the bottom 11 of the tray but the top face of the shell ll which coacts with the face M on the male die will yield so that the wood in the bottom 41 of the'tray will be subjected to a pressure ransine from appro ma ely 65 lbs. p. s. i. The flexible-top face of the pad disresulting from variations in density in the core,

tray by ri id pressure on the top face and yieldin the bottom face of the tray any irregularities and bonding together the entire core and covering while under such pressures. 2. That improvement inmoldin'g a core of wood with a, sheetcovering glued on both faces thereof into a tray having a rim, a bottom and a sloping portion between the rim and the bottom which comprisesz subjecting the rim and the sloping single not, be understood as rerigid pressure on the. top face and yielding pressure on the bottom face, of approximately 65 lbs. p. s. i., which localizes in the bottom of the tray any irregularities resulting from variations in density in the core, and bonding together the entire core and covering while under such pressures.

3. Apparatus for molding a tray composed of afor shaping the top face of the rim and sloping portion of the tray and densifying the portion of the core in the rim and sloping portion, and with core and a sheet-coveringand having a rim, a

bottom and a sloping portion'between the rim and the bottom, comprising: a male die provided with a rigid face for shaping the top face of the rim, the sloping portion, and the bottom of the tray, and a female die provided with a rigid face portion for coacting with the portion of the male die for shaping the top face of the rim and sloping portion of the tray, for densifying the portion of the core in the rim and sloping portion, and with a flexible face for eoacting with the bottom-forming portion of the male die in shaping the under face of the bottom of the tray to localize in the under face of the bottom any irivegularities resulting fromvarying density in different portions of the core.

4. Apparatus for molding a tray composed of a core and a 'sheet-covering and having a rim, a,

bottom and a sloping portion between the rim and the bottom, comprising: a male die provided with a rigid face for shaming the top face of the rim, the sloping portion and the. bottom of the tray, and a female die provided with a rigid face portion for coacting with the portion of the male die a flexible face for coacting with the bottom-forming portion of the male die in shaping the under face of the bottom of the tray, and localizing in the under face of the bottom anyirregularlties resulting from varying density in different portions of the. core, the dies being adapted to exert -a predetermined high pressure for crushing the core in the rim and sloping portion of the tray and a relatively lower pressure in the bottom of the tray. v.

5. Apparatus for molding a tray composed of a core and a sheet-covering and having a rim, a

' bottom and a sloping portion between the rim and the bottom, comprising: a male die provided with a rigid face for shaping the top face of the rim; the sloping portion and the bottom of the tray, and a female die provided with a rigid face portion for coacting with the portion of the male die for shaping the top face of the rim and sloping portion of the tray and densifying the portion of the 35 in the bottom 0! thetrfly.

FRANK M. CURRAN.

Images