US2914109A - Method for making embossed decorative articles - Google Patents

Description

Nov. 24, 1959 MING. c. HSU ET AL 2,914,109

METHOD FOR MAKING EMBOSSED DECORATIVE ARTICLES Filed April 8,. 1957 2 Sheets-Sheet 1 W275; 6/3521 (5 big/m5 yaw ak/Md Z2 Arm/Mfr Nov. 24, 1959 Mm Hsu ETA 2,914,109

METHOD FOR MAKING EMBOSSED DECORATIVE ARTICLES Filed April 8, 1957 2 Sheets-Sheet 2 jg 'l/l/l/l/l/l/ll v 5 'I/ United States Patent METHOD. EORMAKING EMEossED DECORATIVE ARTICLES 1 Application A ils, 1951-, SerialNo. 651,356

sv Claims. (61154-406) 'Ihisinventionu relates to a. method: for making emhossed decorative: articlesand. more particularly to a method" for: making. resilient" decorative. articles having embossed elevated and .depressedrdecorative portions by means-of: dielectric heating.

Dielectric, heating. is; a- .selective heating process wherebyvheatv canbe: developed: within an electrical insulating or;dielectric.material. Since: a: dielectric'material is one which. dOflSmlJOt. normally conduct any appreciable amount of, electrical current, dielectric. heating.does. not result from. the resistance of the material to;current flo,w but. rather, from the. frictional heating; caused by the forced back. and forth: rotating movement: ofqthe molecules' of the. material; The force: that. produces the heating;,will; be uniform throughout the material if the1ma1 teriali has. a uniform molecular; arrangement and. if the electricalv field strength is, uniform;

When thedielectric material isplaced; inan electrical field such as, exists between. two. plates orelectrodes-having avoltage impressed across them, whereby; one of, the planes-is positiveg and the: other is negative, the mole: culesofrthe, dielectric material appear. to-stretch out and elongate. themselves so. that one end ofvthe molecule has: a. positive chargewhichi points towardrthe electrode with. a; negative charge and-.tne other endoi'ithe mole, cule hasua negative char-gee which points towardthe .elec-. trode with .thetpositive charge. Y

If the; charge. between. the plates isreversed: so; that the positiveplate nowbecomesnegative and. vice versa; the, molecules. will. rotate::to realign themselves. if an. alternating; current oii'radiol frequency is? impressed across. the. electrodes, the. electrodes will continually changethein. charge. and. the molecules-oflthe dielectric material willbe. forced to: rotateback' and forth as the electrodes change theincharge. As the. molecules of the dielectriematerial. rotate back; and.- forth, heat will be developed..witl1in.. the. dielectric material, although the Thus,

electrodeswillnotibecomeheated' exceptiby conduction from the heated dielectric material iftthey are-inwont-act therewith Various. methods oftmaking. decorative articles ctr trim assemblies having. elevated and. depressed portions are known and it. is also: known to. make such articles by means of dielectric. heating, However, in. such methods only the depressed portions ofi'the articlesare embossed while the elevated portions. thereof are: not embossed in any manner since they are formed merely as. the result ofjembo'ssingvarious depressed areas or portions. of the articles. The method of this invention. differs from such priorjmethods in that both the elevated and depressed areas of the articles are. embossed so that the finished article includes an integralwell defined decoration; While the method may be used to make various articles, itis ice along; a Y continuous depressed and embossed area and are also-securedtogether by an elevated embossed area within and bounded by the=continuous depressed area.- The backing layer-is compressed within both the depressed and elevated area and the method utilizes dielectric heating.

The primary object of this invention is to provide a new and improved method: for making resilient decorative articles having embossed elevated" and depressed decorative portions. is to. provide a new and improvedmethod for making embossed decorative articlesby means-of dielectric heating. A furtherob'ject OfIithlS. invention is to provide a new and? improved-.methodi for making resilient decorative: articles. having embossed elevated and depressed portions defining asharp' and clearvdesign; These and other objects of: the invention will bereadily apparent from: theafollow-ing specification: anddrawings, in. which:

. Figure '1" is a View oft the: trim assembly positioned within. a dielectric heating: press: prior to the embossment thereof;

Figure 2 is a;p .lan;vie.w= of the die;

Figure. 3; is a-sectional; view taken-on; the plane indi cated by line, 3.-3 of. Figure 2;;

Figure4-isaiview-similar to Figure l and showing. the dielectric, heating pressin. closed position in an interme diate stepnof the.methodpriorto the heat cycle;

Figurej isa ViGW( similar. to-Figure, 4' and showing the heating press. and. the trim assembly during the; heat cycle; and.

Figure 6 is awiewi ofithe, finished trim assembly.

Referringnow to.Figure l, of the; drawings, a dielectric heatingpress .includeaa, lower electrode lll and an upper. electrode. 1-2, which. lSuSllPPOI'tfid lay-suitable operating means for movement toward and away from the lower electr-Qd 10., Theaheating pressisof a known type which is, commercially availablev and, therefore, it is believed that no further descriptionineed be, given. An alternating current generator 14. is in, series withthe upper and lower. electrodes and is of the type, suitable to impress an alternating current of radio frequency across the, press electrodes; I

'A die 16'is securedin a suitable manner to the upper electrode The die may, be, made of" any suitable thermally and el'e ctricallyconductive material such as steel, copper, brass; bronze, etc. As may be, seen in Figure Z ofth'e drawings, thedie 16' is of V shape and ineludes an outer continuous embossing rib l8 surrounding-an outwardly openingdie cavity 2% of'V-shape and V cross section which! is machined out of' the material of thedie. Although the die is shownof a particular shape for the purposes of description of the subject invention; it will be' understood thatother dies of other shapesmaybeused withxequal success, since the method of? this; invention does: not: depend upon the particular shape. oh the die used; However, it will beunderstood that each diewincludesan-"outer continuous embossing rib whichsurroundsra,die-cavity opening outwardly of the die.;

Referringnow toiFigdrellu ofthe-drawings, one or more bulfenshcetseZtibf siliconezrubber are placed upon the lower." electrode-rl-llrofi thei-press; The buffer sheets act as a resilientwsupportfon the trim: assembly 26 m insure equalfipressure; of: thedie-1 oni alll areas. of the trim assembly engaged: thereby and also acts toprevent arcing betweenrthe:diealfii andi the. lowenpress electrode" 10 when the: press is; in closedposition: and an alternating current. of radiovfrequency is. being impressed across the upper and. lowenelect'rode'si 05 the press. Althoughsilicone rubber. is preferred; thea s-heets. 24' may also be of other materials such as Butyl' rubber.

i The trim assembly 26: which; isasupported on the butter Another object of this invention 3 sheets 24 includes an outer sheet 28 of heat fusible or thermoplastic trim material, an intermediate layer 30 of heat fusible sponge rubber, and a backing sheet 32. The backing sheet 32 is preferably a woven cloth of water absorbent material, such as cotton or other natural fibers, synthetic fibers, or other materials.

The intermediate layer 30 of sponge rubber is preferably processed on the backing sheet 32 when the sponge rubber is produced so that the backing sheet and the layer of sponge rubber are secured together. The sponge rubber is a soft cellular heat fusible sponge-like highly resilient material which may be formed of natural rubber,

various synthetic materials such as Butyl rubber, vinyl chloride resins, neoprene, isocyanate resins, and mixtures of natural rubber and the above synthetic materials. The sponge rubber has a very high resilient property and quickly recovers its shape and form when any deforming pressure is first applied and then removed therefrom. The sponge rubber is also permeable to gases under high pressure conditions with the rate of permeation being very low. The outer sheet 28 may be of any suitable heat fusible or thermoplastic material such as vinyl chloride,

' vinylidene chloride, and other similar synthetics formed into sheet form. If desired, the outer surface of the sheet 28 may be tooled or otherwise provided with various finishes such as a finish simulating leather. It is also preferable that the sheet 28 be secured to the intermediate layer 30 of sponge rubber by a suitable adhesive, whether thermoplastic or otherwise, in order that the sheet 28 may be assembled with the sponge rubber and backing sheet for ease of handling prior to positioning of the trim assembly 26 within the dielectric heating press.

After the outer sheet 28 of thermoplastic material has been assembled with the intermediate layer 30 of sponge rubber and the backing sheet 32 of water absorbent material, the sheet 32 is moi tened prior to positioning of the trim assembly on the sheets 24 within the dielectric heating press.

Since the method of this invention depends on a very close control of the pressure and temperature within the die cavity 20, as will be hereinafter apparent, the amount of moisture applied to the backing sheet 32 must be carefully controlled. Therefore, it is preferable that from 14 to 18 grams per square foot of water he applied to the backing sheet 32. The water may be applied by any suitable method such as roll coating, and need be applied only to the area of the backing sheet which is positioned below the area of the sponge rubber layer and sheet of thermoplastic material to be subsequently embossed. Since the intermediate layer 30 of sponge rubber is not water absorbent, there is only a very slight and negligible wetting of the outer surface of this layer and for all practical purposes, it may be considered that no moisture is absorbed by this layer.

After the backing sheet 32 has been moistened, the trim assembly 26 is then positioned within the dielectric heating press, as shown in Figure 1, with the backing sheet 32 in engagement with the buffer sheets 24 and the moistened area of the backing sheet in general alignment with the die 16, if only the one area of the backing sheet has been moistened. The upper electrode 12 is thenmoved downwardly until the die 16 engages the trim assembly as shown in Figure 4 of the drawings. When the die engages the assembly, a continuous portion 40 of the sponge rubber layer 30 which is underneath the embossing rib 18 of the die is compressed and is in the shape of a V. The portion 42 of the sponge rubber layer which is within the embossing rib 18 will be forced slightly upwardly within the die cavity 20 of the die and will also force a portion 44 of the sheet 28 upwardly within the die cavity. The pressure of the embossing rib 18 on the area 40 of the sponge rubber layer and the area 46 of the sheet 28 is between 200 and 600 lbs. per square inch with a pressure of 400 lbs. per square inch preferably being used. Since the portion 40 of the sponge rubber layer is compressed and held between the embossing nb 18 of the die and the lower electrode 10 of the press, the cellular construction of this portion is destroyed so that there is no permeation of gases possible therethrough despite the existence of high pressure within the portion 42 of the layer and the die cavity 20 as will be explained.

After the press has been closed as shown in Figure 4, an alternating current of radio frequency is impressed across the upper and lower electrodes of the press by the AC. generator 14 so that an electric field will be generated between the die 16 and the lower electrode 10. The voltage of the field will preferably be in the range from 2,000 to 2,200 volts and the frequency will preferably be in the range from 1 to megacycles with a frequency of 14 megacycles being preferable. As the electric field passes between the die 16 and the lower electrode 10, the water which has been absorbed by the backing 32 of the trim assembly starts to be converted into steam and at the same time the area 46 of the thermoplastic trim material beneath the embossing rib 18 together with the compressed portion 40 of the sponge rubber layer become heated. As the water turns to steam, it will expand as is well known. Since the portion 40 of the sponge rubber is compressed to provide a continuous barrier, the steam cannot escape through this portion of the sponge rubber and, therefore, will force both the portions 44 of the thermoplastic trim material and 42 of the sponge rubber layer 30 upwardly into the die cavity 20 as it expands.

As previously mentioned, the sponge rubber layer 30 is of cellular construction. However, the rate of permeability of the sponge rubber by the steam is such that the steam cannot immediately permeate the sponge rubber to escape into the die cavity 20 and, therefore, the steam will initially force the portion 42 of the sponge rubber layer and the portion 44 of the thermoplastic trim material into the die cavity and compress the portion 42 before there is any substantial permeation of the portion 42 of the sponge rubber layer by the steam. Thus, as the steam is initially formed and expands, it will force the portion 42 of the sponge rubber layer upwardly into the die cavity 20 so that the portion 44 of the thermoplastic trim material will be forced upwardly into substantial conformity with the shape of the die cavity. Since the die 16 is not heated by the electric field passing therebetween and the lower electrode 10, the portion 44 of the thermoplastic trim material will not be heated to its softening temperature by the initial expansion of the steam and therefore will not initially conform to the exact contour of the die cavity, particularly so if the die has sharp corners such as the peak of the V-shaped die cavity 20. The die 16 will also act to quench the portion 44 of the thermoplastic trim material in engagement with the die cavity 20 and the portion 44 of the thermoplastic material in turn will quench the sponge rubber layer immediately adjacent thereto.

Thereafter, as the heating continues, the steam will gradually permeate the portion 42 of the sponge rubber layer and come into contact directly with the portion 44 of the sheet 28 of thermoplastic material in engagement with the die cavity. 20. This will soften the portion 44 of the thermoplastic material so that the material will exactly conform to any sharp contours of the die cavity under the pressure of the steam acting directly thereagainst and the pressure of the portion 42 of the sponge rubber layer. The permeation of the portion 42 of the sponge rubber layer by the steam will also fuse this portion under compression so that the portion will retain its compressed shape after removal of the trim assembly from the die.

The heating cycle during which the alternating current of radio frequency is impressed across the upper and lower electrodes will preferably be a period of 15 seconds. Thereafter, the electric field is turned off but the die 16- is not'movedout of engagerrrent withthetrim assembly for a periodof another Ssecorids. Duringthis latter seconds, theportionAZ. of the thermoplastic trim material in engagemenrwith the die cavity is quenched by the die so asuto' retainrits'shape after removal of the trim assembly from the die. g

During the formation of the elevatedportion of. the decorative article, as previously explaihed, the portion 40 of the sponge rubber layer which is fcompressed-be tween the embossing rib Idofhthejdie and the lower press electrode is heated dielectrically, and also somewhat by the entrapped steam, so,thatthis; layer will be fused while compressed. The area 46 of the thermoplastic material immediately beneath the embossingjrib. is also softened dielectrically so as to be msea1 tothe sponge rubber layer. j

Thereafter, when the press is opened, the finished trim assembly may be removed. As shown particularly in Figure 6 of the drawings, the trim assembly includes an elevated portion 50 of V shape and also V cross section which conforms exactly to the shape of the die cavity 20 of die 16, with this elevated portion being bounded by a continuous depressed portion 52 of the shape of the embossing rib 18 of the die 16. The elevated portion 50 is comprised of an outer covering of thermoplastic trim material conforming exactly to the contour of die cavity 20 and a backing layer of fused and compressed sponge rubber, with the degree of compression being greatest immediately adjacent the depressed portion 52 and least adjacent the apex of the V cross section. The depressed portion'SZ is also comprised of an outer covering of thermoplastic trim material and a backing layer of fused and substantially totally compressed sponge rubber.

As previously mentioned, the method of this invention depends on a very close control of the pressure and temperature within the die cavity 20, and therefore the amount of moisture applied to the backing sheet must be carefully controlled. If insufiicient moisture is applied to the backing sheet, then the volume of steam may not be sufficient to compress the portion 42 of the sponge rubber layer 30 within the die cavity to force the portion 44 of the sheet 28 of thermoplastic material to conform to the contour of the die cavity. Also, the reduced volume of steam will not permeate the sponge rubber layer to any extent so as to fuse this layer while under compression and will also not soften the portion 44 of the sheet of thermoplastic material. Thus, the assembly will not retain its shape after removal from the press.

Likewise, if there is an excess volume of steam caused by the application of excess water to the backing sheet 32, then the portion 42 of the layer of sponge rubber may become so compressed by the initial expansion of the steam to prevent any permeation and fusion thereof by the steam, except perhaps for the immediate surface layer adjacent the backing sheet 32. This will also prevent the steam from softening the portion 44 of the sheet of thermoplastic material to cause this portion to conform exactly to the shape of the die cavity 20.

The amount of water applied to the backing sheet 32 also controls the temperature of the sponge rubber layer during the compression and fusion thereof. This temperature must be kept below the degradation temperature of the sponge rubber or otherwise the sponge rubber will become charred or destroyed. In the particular assembly shown herein, the temperature of the sponge rubber is approximately 300 F. during the compression and fusion steps of the method. It will also be noted that the portion 44 of the thermoplastic trim material will also be destroyed if the temperature of the adjacent portion of the portion 42 of the sponge rubber layer becomes heated to an extremely high temperature.

Although preferred heating cycle quench cycle times have been hereinbefore mentioned, these times are necessarily dependent on each particular trim assembly, particularly so depending on the depth of the sponge rubber layer 30. In-the arrangement shown-,this layer is approximately 55 thick, and the times hereinbefore specitied may be used with of this thickness. Thus, this invention provides an improved method for making decorativearticles having embossed elevated and depressed areas so that the finished article includes an integral and well-defined decoration. I

What is claimed is: a

l. A method ofmaking an article having an elevated decorative portion formed thereon comprising, coating one surface of a gas and vapor p'ervious cellularheat fusible resilient material with about 14 to I8 grams per square foot of a liquid which is convertible into vapor upon the application of heat and which is chemically inert with respect to said resilient material, causingthe opposite surface of said material to be engaged with a die structure having a die cavity opening in face-to-face relation with the said portion of the article to be decorated, relatively moving said die to compress said material sufficiently to destroy the cellular structure of said material about the periphery of said decorative portion so as to leave a pocket of said cellular material within said compressed periphery, dielectrically heating said material sutficiently to convert said'liquid to vapor, said vapor initially acting upon the liquid coated surface of said material to urge the material in said pocket upwardly into intimate engagement with the die cavity, continued dielectrically heating of said material causing said vapor to permeate and heat the cellular material within said pocket whereby the compressed portion of said material will be fused and the material in said pocket caused to retain the shape of the die cavity.

2. A method for making an article having an elevated decorative portion integral therewith comprising, coating one surface of a portion of a gas and vapor pervious cellular heat fusible resilient material with about 14 to 18 grams per square foot of a liquid which is convertible into vapor upon the application of heat and which is chemically, inert with respect to said resilient material, confining the portion of the article to be formed into the elevated portion by compressing said material within a substantially closed die structure having a die cavity of the decorative portion opening to the opposite surface of said material, and thereafter dielectrically heating the liquid Within the die structure to convert the liquid to heated vapor, the confined vapor initially acting on the liquid coated surface to urge the confined material into intimate engagement with the die cavity, continued dielectric heating of said material causing said vapor to permeate and heat the confined cellular material whereby the cellular material adjacent said die will be fused upon itself to retain the shape of the die cavity.

3. A method for making a resilient laminated article having elevated decorative portions integral therewith comprising, assembling a sheet of thermoplastic material with a backing of a gas and vapor pervious cellular heat fusible resilient material, coating the surface of the cellular material opposite said sheet material with a liquid which is convertible into vapor upon the application of heat and which is chemically inert with respect to said sheet and said resilient material, compressing a continuous boundary area of a portion of the laminate within a die having a die cavity of the desired decorative configuration opening to the thermoplastic sheet material, and thereafter dielectrically heating the liquid within the die to convert the liquid to vapor whereby the confined vapor pressure will initially act against the liquid coated surface of the cellular material compressing this material so as to force the thermoplastic material within the die cavity, continued dielectric heating of the materials causing said vapor to permeate and heat the cellular material whereby the compressed portion of the latter material will fuse upon itself and the sheet material will fuse to successon a sponge rubber layer the subadiacent cellularmaterialcausing the laminate to retain the shape of the die cavity, the amount of said liquid coated onthe surface of the cellular material being such as-to-produce-sufiicient vapor pressure toforce the thermoplastic material into conformity with the die cavity while leaving'the cellular material gas and vapor pervious.

4. A method. of making an article as set forth in claim 3 in which the liquid is applied to the surface of said cellular material in the amount of between 14 to 18 grams per squarefoot of said surface, and further in which said material is compressed between 200 and 600 pounds per square inch.

5. A method of making an article as set forth in claim 3 in which the liquid is applied to thesurface of said cellular material inv the amount of between 14 to 18 grams per square foot of said surface, and in which the temperature ,of said material is approximately 300 F. duringihezcompress'ion and fusion steps.

References cr ed in the file of this patent I =UNIDED'5STATESPA'11ENTS .1949, George.Allen,&,Unwin Ltd., London, pp. 170-171. Dakin et all: Ind. & Eng. Chem., Dielectric Heating, vol. 37. No. 3,, pp. 268-7275.

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