US2493439A

US2493439A - Belief duplication

Info

Publication number: US2493439A
Authority: US
Priority date: 1946-09-24
Filing date: 1946-09-24
Publication date: 1950-01-03
Anticipated expiration: 1967-01-03

Description

Jan. 3, W50 J. .J. HRAUND 2,493,439

RELIEF DUPL I CATION Filed Sept. 24, 1946 2 Sheets-Sheet l ELF Jan. 3, 1950 J; BRAUND 2,493,439

RELIEF DUPL ICA'I'ION Filed Sept. 24 1946 2 Sheets-Sheet 2 o o o o m g 9 JUhHJQEdUHd Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE RELIEF DUPLICATION John J. Braund, Washington, D. C. Application September 24, 1946, Serial No. 698,973

26 Claims.

This invention is directed to duplication of relief and particularly to an improved process and machine which will duplicate relief with a high degree of accuracy. The invention is particularly adapted to the reproduction of relief maps, where precision is an indispensible factor, but is also adapted to duplication of other reliefs of utilitarian and ornamental nature.

The general object of the invention is to produce accurate reliefs economically, and to provide a relatively simple and rapid process, and a low cost, easy-operated machine for this purpose.

A further object of the invention is to accurately reproduce reliefs in thermoplastic sheet material.

Still another object of the invention is to produce topographical relief maps and other profiled objects having indicia correlated with the contour thereof, and to mold article blanks upon which the indicia have first been printed or otherwise inscribed in a manner to secure accurate registry of the indicia and contour and cause the indicia to maintain the same positions transversely after deformation of the blank into profile as before, and this regardless of whether the contour is of regular or irregular shape.

A further object of the invention is to secure uniform heating of thermoplastic sheet material in the production of relief therein so that all areas will be softened to the same degree for molding purposes.

Still another object of the invention is to produce relief in thermoplastic sheet material employing a single mold, through the application of vacuum to the side of the sheet facing the mold while subjecting the exposed face of the sheet to uniform heat.

An important additional object of the invention is to mold areas of different amplitude or elevation of a relief in sheet material in progressive order, beginning with areas of lower amplitude or elevation, and to accomplish this by controlling and progressively varying the operating conclitions.

According to my prior Patent No. 2,066,555 granted January 5, 1937, duplicate reliefs are produced by securing a sheet at the edges over a liquid reservoir and deforming the sheet by hot liquid under pressure into an inverted female mold disposed above the sheet. While such procedure has been successful in producing relief with a fair degree of accuracy, the machine required has been found to have been more complicated than desirable in construction and awkward to operate, also less accurate in results when molding either ductile metal or thermoplastic non-metallic sheets. The present invention has all the advantages of my prior patented machine and is a definite improvement thereon from the standpoint of procedure, simplified machine construction, and operation, and duplicating accuracy.

It should be explained preliminarily that the mode of heating thermoplastic sheet material for the production of relief therein is a matter of considerable importance. The heat should be uniformly distributed throughout the entire area of a sheet to be molded. Overheating in local areas is likely to result in blisters and warping and produce a defective product. Underheating of areas is at least as serious since molding operation is likely to cause cracks or ruptures and ruin the sheet.

Again, the heat must be carefully controlled as to temperature. It is very easy to overheat a plastic sheet beyond the temperatures appropriate to molding, and also to heat it above its softening point too rapidly. I found the best results are secured by slowly raising the temperature of a thermoplastic sheet and molding relief areas of different amplitude at different temperatures, starting with low relief areas during initial heating and progressively molding areas of higher amplitude, or elevation as the temperature of the sheet increases. This is particularly important in producing relief maps, to secure relatively uniform expansion of the sheet in adjoining areas of different amplitude so that points of the sheet will be expanded vertically without horizontal shifting and remain in accurate registry with corresponding points of the mold matrix. This cannot be done if the sheet is too hot and too soft or unevenly heated, since under such conditions areas of different amplitude of the sheet are likely to mold simultaneously and result in excessive stretching and thinning of the sheet in one area and little or no stretching in an adjoining area. The resulting relief may be inaccurate, and if indicia are present they will be shifted laterally relative to one another and out of correct registry with the relief.

I have found that heat transmission through a dry gas, ordinarily air, is best suited to the production of relief in thermoplastic sheet material. It is within the scope of the invention to employ various modes of heating depending upon the nature of the relief and the degree of precision required. Radiant heat :from a battery of infrared or other electric lamps, or electrical resistor heating units has been employed successfully, but this is recommended only for work not requiring a high degree of perfection. It is difficult to locate the radiant heating means in spaced relation to a blank sheet to be molded and obtain uniform heating through the area of the sheet. Also, the temperature of the sheet is likely to be raised too rapidly, it being dinicult to properly control such type heating means.

It is also possible to locate a closed dead air chamber over one side of a thermoplastic sheetand provide electric lamps or other heating means in such chamber in substantially spaced relation to the sheet to secure heating of thesheet by conduction. This mode likewise is recommended only where perfect results are not required since it is subject to the same difficulties as radiant heating above referred to.

I have found that convection. heating is' most satisfactory, and is the only mode which can be employed successfully where a high degree of precision of relief and the absence of flaws are required, as in the case of relief maps. Circulation of dry steam in a closed chamber over the face of a thermoplastic sheet can be employed with opaque sheet material, but it is likely to result in clouding of a transparent sheet, from slight condensation of steam on the sheet surface. I, therefore, prefer to circulate dry hot air over the sheet. I find, further, that better control of the heating temperature to gradually raise the temperature of a sheet may be secured by constantly supplying fresh air, heating it and circulating it over the sheet, and then followin it to escape. If dead hot air is trapped adjacent the face of the sheet circulation is impeded and the temperature of the sheet is likely to be raised too slowly rather than too rapidly.

According to my new process a female mold is provided with the desired relief formed therein. During or after casting of the mold a series of holes are formed at intervals of a few inches, more or less. Such holes will communicate with the deepest and other points of all mold cavities, also with flat areas. Hydrostone, a mixture of plaster of Paris and lime, or other suitable durable plaster, with or without the addition ofasbestos fibers to give added strength and quicker cooling after molding, may be used in formation of the mold.

A flat relatively thin sheet of transparent or opaque thermoplastic material will be employed for the relief. V-inylite or other suitable synthetic resins which are durable and non-warm ing, and which have a relativelylow softening point somewhat above 100 F. are preferred. The thermoplastic sheet is preliminarily inscribed for many but not all reliefs, depending on their nature, by

, printing or otherwise with desired indicia. The

blank sheet is then placed on the mold while in hard state and where indicia are presenttheymust be brought into accurate registry with the corresponding points of the relief of the mold. The sheet is firmly secured in sealing contact with a frame surrounding the mold. A very low preliminary vacuum is then applied to the mold side of the sheet before its temperature has been raised up to the softening point, particularly the V margins of the sheet beyond the mold, to bring the hard sheet into firm contact with the margins of the mold and insure against warping. This will frequently produce a slight dishin effect over all mold cavities also. i

the vacuum to insure accuracy of relief.

Following these initial preparations a progres sive molding operation is carried out. This is accomplished through the simultaneous application of vacuum to the mold side of the sheet and heat to the exposed face of the sheet. Convection heating by circulating warm air over the sheet is preferably employed. Heating gradually raises the temperature of the sheet up to and beyond its softening point. The vacuum is also gradually increased in stages to cause the sheet to first contact the shallower molding surface portions of the mold cavities and thereafter gradually be drawn down into contact with the deepest molding surface portions of the mold cavities. In this manner substantially uniform stretching of the sheet in areas of different elevation is obtained.

.In this manner, also, registry of the indicia, where present, on the sheet with the corresponding points of the mold cavities is preserved.

When the molding operation has been complet ed, a matter of about twenty minutes, heating is discontinued and the completed sheet is cooled and set, preferably by circulating cool air over the exposed face of the sheet while maintaining Cooling is continued until the sheet and the mold are well below the softening point of the sheet, say

to F. or below, also a matter of about twenty or twenty-five minutes. The sheet with the relief permanently set therein is then removed from the mold. The process is repeated with succes sive further sheets until the desired number of duplicates have been obtained. The entire operation requires only about three-quarters of an hour for each duplicate.

The vacuum range and the heating temperature range 'will vary according to characteristics of the particular synthetic resins of which the sheets are formed. Unless sheets of substantial thickness are employed or reliefs of unusual complication are to be produced neither'high vacuum or high temperature is required. For example, in the case of vinylite resin sheets of .015 to .020 inch thickness and. having a softening point of about F., the vacuum employed in the preliminary stage may be about one inch, fo lowing which a lowheat is applied to bring the temperature up to about 109 F. Thereupon the vacuum may be increased to about two inches. When the temperature has further increased upto the softening point of he sheet, about 125 the vacuum may be increased to three inches. When the temperaure has risen to F. the vacuum may be increased to four inches. Heating may be continued to F. as a sufficient maximum. The vacuum then may be again raised to five inches, which has been found the maximum necessary to produce accurate reliefs under the process in many but not in all cases. During the subsequent cooling stage the maximum vacuum is maintained and broken only after the molded sheet has set fully.

The invention will be understood by reference to the illustrative embodiment of my new machine for carrying out my new process shown in the accompanying drawings and the detailed description following.

In such drawings:

Fig. l is a sectional elevation of a relief duplicating machine according to the present invention;

Fig. 2 is a top plan view of the machine shown in Fig. 1;

Fig. 3 is a fragmentary top plan view of a indicia-bearing relief map; and,

Fig. 4 is a fragmentary sectional elevation of a mold with the relief map of Fig. 3 therein.

The invention will be described in its application to the duplication of relief maps. The original of such a map will preferably be formed of ductilesheet aluminum or copper according to the method of my prior Patent No. 1,866,448, granted July 5, 1932. According thereto such a flat'metal blank is first printed or otherwise inscribed on its rear face with elevation contour lines and elevation and other legends. Such indicia, likewise land and water areas of different elevation, may be printed in different colors. The map blank is then firmly secured around its margin'and placed with its top face down upon a compressible pad and embossed step by step, beginning at the lowest contour line of elevation and progressively pressing the metal to the next succeeding contour line until the highest elevation is reached. This is preferably accomplished with the embossing machine 'of m prior Patent No. 2,029,651, granted February 4, 1936. Such original relief map is then secured upon a rigid backing, the back side of the elevated areas being filled with Hydrostone or other suitable hardening filler for purposes of reinforcement. A suitable frame is then secured around the original map and a mold matrix is then cast thereon and allowed to harden.

A completed mold matrix produced as just described for making duplicates of the original relief map is indicated at I in Figs. 1 and 4. Such mold matrix is provided with a series of holes extending vertically therethrough at the levels of different elevation as illustrated at H, I2, 13 and I l. The number and spacing of such holes will be determined primarily by the character of the contour in any given case, but in general the holes will be located ever few inches and communicate with different elevation levels, but in areas which are fiat a substantially greater spacing of the holes is satisfactory. The holes may be formed incident to casting of the mold matrix by securing small pegs to the original map which are removed when the mold matrix has hardened, or they may be formed by drilling following completion of the mold.

It will be understood that mold matrix It! is a female mold with the points of deepest impression therein representing the points of highest elevation of the map. Such matrix is placed in a rigid frame 15 of my new duplicating machine. As shown in Fig. 1 such frame should be of larger size than the matrix to leave a space between the frame and the sidewalls of the matrix. frame'is provided wth a closed bottom wall I 5 and the matrix is supported in spaced relation thereto b a series of spacer elements ll so that there is a continuous space between the matrix and both the bottom and sides of the frame. Frame 55 is supported in horizontal position in any suitable manner, as by means of table I 8.

Communicating with the interior of frame [5 is a vacuum line I 9 connecting with a vacuum source such as a pump. Also mounted on the frame and communicating with the interior are a vacuum gauge 20 and a bleed valve 2|, Coactive with the upper side of frame I5 is a clamping frame 22 which can be removably secured to the main frame by a series of bolts or other securing elements 23.

Located over the face side of mold matrix If! is a convection air heating space. As shown in Fig. 1 heating of the air may be accomplishedby a battery of infra-red or other suitable electric The ' of mold matrix In so as to avoid hot spots at the molding surface of the matrix. A reflecting hood 26 is associated with the lamps to direct the heated air downwardly towards the mold. Preferably, but not necessarily, such hood extends downwardly to clamping frame 22 to completely close the space over the matrix and provide a hot air chamber 21, thus preventing the uncontrolled escape of heat and enabling the molding operation to be carried out in a shorter time than if an air gap is left between reflector hood 26 and clamping frame 22. Observation and access to the interior of the hood may be provided by a series of transparent hinged windows 28. To insure continuous and uniform circulation ventilators are provided to permit the continuous and controlled discharge of the air flow after passage over the mold. In the present machine windows 28 also serve as such air discharge ventilators, being adjustable to an degree of opening to control temperature. Extending into the interior of the hood is a thermometer 29 to show the interior temperature.

The air heated by lamps 24 is positively circulated by means of an electric circulating fan 30. Preferably, and as shown, such fan will be mounted to circulate air vertically towards the face of matrix I 0 from a point substantially removed therefrom, thereby to insure uniform distribution of the air over the entire area of the matrix. In embodiment shown in Fig. 1 an air inlet conduit 3| to bring fresh air in continually from outside is mounted on the top of hood 2B. Circulating fan 30 is supported adjacent the upper inlet end thereof on a bracket 32, and the supporting frame for the battery of lamps 24 is secured in conduit 3| below the fan. Mounted on the exterior of conduit 3|, or at any other convenient point, are rheostat 33 for varying the speed of fan and electric switch 34 for turning lamps 24 on and off.

Hood 26 and the associate parts just described are mounted for vertical movement relative to the position of mold matrix I 0. Any suitable form of mounting may be employed. In the present case a pair of counterweighted cables 35 supported by ceiling-mounted pulleys 36 connect with the upper end of conduit 3| so that the entire reflector hood assembly may be easily raised and lowered. To insure proper registry of hood 26 with frame I5 and 22 the lower end of the hood may be provided with a flange 31 adapted to seat against the upper side of clamping frame 22 and apertured to receive and be secured by bolts 23.

In producing duplicate relief maps withthe machine and according to the process described a flat map blank S of Vinylite is printed or otherwise inscribed on its top face with elevation contour lines L, elevation legends E and any other desired symbols, also with different colored areas if desired, all in exact accordance with the original map previously described. The printed map blank S is shown in Fig. 3.

The flat map blank S is then placed in the machine with its printed face down facing the mold matrix I. Blank S should have a marginal area of at least two inches beyond the mold surface and conform generally to the size of frame l5. Where a series of bolts 23 are used as frame securing means, as shown, the blank can be made small enough to lie within the bolts so as to avoid puncturing the margins of the blank to receive the bolts.

ages-me s Accurate registry-pf the contour lines of map blankiS' with the corresponding contour portionsof the" mold matrix is essential.-'. Tliis can be ac=- complished easily where-blank 'S is of transparent mateniali- When the blank is opaque an' identicalltransparerit' fiat map blank canfir'st'be -1'egis-' tere'd with the matrixand a plurality of pin holes 1 punched' therethrough into the 'topof frame t5, 1 1 following which the transparent*blankfiis "re-" moved andregistered-with the opaque blank-S. '10 Corresponding pin holes will be'punched through bIan-k S and the blank-thenplaced on the frame over the matrix with "the" pin holes therein regis'i tering with those in the frame; Obviously other expedients can be employed-for registering pur 5 poses. r

With themap blank registered with the mo'ld matrixbla'mpingframe22"is placed on the bIafhk margi'njfihe hood 26' "lowered= and bolts 23" insertedthrough frame 22 and into frame was firmly clampthe' margins of the mapblan'k with sealing engagement. "During this installing operation vacuum bleed valve Zls'hould'be entirlY openor the source of "vacuum supplied through line l9 should be cut off. When installationhas 25 been completed vacuum is supplied to the interi'or of frame' le throughlirielfig" Since the vacuum? initially employed -wilbbe less-than that supplied; va1ve"-"2l wilhfirs't "beentirely openg 'and thenzclosed slightly to'supply-a low-'vacuum of about one inchf By reason'of the fact that-the vacuumis sup plied to the" space between the sides" of *matri-x i m ain'd 'frame I'5 the margins-of map blank S are drawn-- into 'lightengagement with the" top mar= gins' of the mold inwardly adjacent the'edgs of the mold This has been found *oiuite important in preventing subsequent formation'of wrinkles in the'marginal portions of the map-blank which engagesuc htop margins'of the mold during *the'" 4 actual molding-"operation; When vacuum is suppliedat this' time to thefac'e of the-blank opposedto the mold matrix a slight deformation of the-"=- blank" into the 'mold' cavities frequently is ob tained-i 1 Switch 34 turned on to energize'the heatirig lamps 24 "and 'rhe'ostat 33*i's turnedup partiall'y to operate circulating fan '30 at only moderate speed. One or'more of hinged windows-28"i"n hood-' 26 should' be' open so 'thatfres'h"air'=drawn in" through "conduit '3 l i's heated by the' lamps 24: circulated through ho'od 2'6 over the'iac'e of sheet s an'd 'allowe'd' to escape" through open"windows 2B. In this manner the temperatureof the'sheet is raisedgradually' up'to and beyond its 'softe'ning point: As the temperature rises 'vac'uum "bleed' valve z I 'moved in intermitte'nt stages towards closed'position to increase the vacuum acting o'n the 'opposite' sid 0f the sheet through'the' holes j in mold matrix It. Thetemperatureofthsheet" and the" amount of vacuum can be watched through'thermometer'ZB'and gauge zllf tem V perature of the sheet canberaisedfasterbrmore slowly" by regulating rheostat' 33" to ad'jiistfthe speed of the fan and the degree of vacuum lcanbe precisely regulated by adjustmentf'bfbleed valve 2|? As previo isly "pointed out a preliminary jlowvacuum is applied: to the sheet before 'softe ning commences; It is extremelyundesirabl e to heat the sheet preliminary to'beingclamped in posi' tion' and drawn into engagement"withthe'mold by th'ewacuum." Asalrady" further pointed out molding'of areas of-map blanks oflow-elevation is carried out after the blank has been raisdto' 'lfi' a temperature shortof its 'sortening 'pomt'butat which under the vacuum it can =be drawn into con-" tact with 'shallower" mold surface areas :1 orthemoldiand each successive area- 0f higher elevation is molded 'successively into contact with deeper mold surfaceareas-as the temperature of a; sheet is brought up to and=beyond its softening point by increasing the degree of vacuum in stages?" In this manner an area of lower elevation of map blank fS is expanded-into the corresponding part of the:mold-landiseatedragainst further expansion before'san adjoining area of higher elevation :is 5 expanded: Areas of maximum elevation will be thelast molded, maximum temperature and'vace uum being 'emp'loyedf or this' purpose. All of this will be 'under'stood by reference to Fig. 4. V Thefnumber 'o'i stages in which the-vacuum is increased; likeWiSe the' amount of =increase'in re=- lationito the rising temperature of the sheet, *wil i be varied-i-depending upon the character of the relief: A relief whi'ch has :only small difff'ences' in elevation between the minimum and-maximum can-be completely molded in fewer stages andwith less'vacuum'end temperature and in less timethan a reliefwhicli has substantialdifferences in elevation. 7

After map blank S has 1 been completely molded' switched 'is operated to turn ofi'lamps 24.-

Rhee

stat 33 is turned on full to cause fan 3fi'torapidly circulate incoming cool air through hood =26 'ver moldin'gsheet S. Atthi's time hinged win'dows 28 should befully'o-pen.- Tl'i'evacuum is con tinued as sheet S gradually cool's below its 'soften'=--- I ing point and sets. Cooling is continued a t--1east= down to "F. and can becarrieddoWn to room temperature." When 'cooiin'g hasbeen completed bleed'valve 2l' wi11be open fully'to'eliminatethe vacuum,ibolts;2.3 will be withdrawn, hood' 26 an'd clampingrring: 22 raised and thecompletedrelief map sheet S withdrawn from mold matrix HI. A new'sheet is the'n'placed in the apparatusandthe entire process repeated until 1 the desired riumbei of duplicatefrelieffmaps have been obtained. Of course mold matrix it may be removedfrom the vacuum chamber and replaced by anew matrix at any time;

The process herein described'will produce'relif naps with'grea t accuracy and 'withelevation lines and other indicia exactly in their proper locatlom and this even though comparatively high eIeVations arepresent. Inasmuch as relief mapsre quired forordinary purposes are on' a compara' tively small scale the maximum relief to be molded inlthe sheet will not exceed one or two inches. However, the process has been found adaptable to successful molding to'amplitudes oi five inchesand more provided the processcbejcarm riedyout by raising the temperature and vacuum very gradually." i a The invention has been described in its iapplij cation tothe duplication of relief maps, to em-. phasize its adaptability to precision work. It will be understood; however, that the invention .is equally adaptable to'rnolding other types of relief.. .7 in thermoplastic sheet material, either utilitarian -l or purely ornamental.

The term of the apparatus herein illustrated; and described and the suggested'ranges :of item-W perature and pressure are to be'taken as only] exemplary, all being subject to "considerable Ivaria= tionr depending upon the .nature oftthe the'rmm plastic sheet material" used and thelcharactertoio the relief to beprodu'ced. The scope of .theinvention "isto" be determined by thesappendedal claims.

in molding position across the open side thereof,

a hooded reflector and hot air heating means over- I lying the open face of the box coactive to uniformly heat the entire area of a blank when secured to the box, and means for supplying a varying blank molding vacuum interiorally of the box.

2. A relief duplicating machine comprising a vacuum box having an open side and adapted to support a mold matrix adjacent said open side, means for removably securing a blank sheet to be molded in sealing engagement with the box in molding position across the open side thereof, a hood overlying the open side of the box and defining an air chamber, air heating means mounted in said hood, circulating means for circulating air over the heating means and for causin heated air to flow over a blank when in molding position, and means communicating with the interior of the box for supplying a varying vacuum to the mold side of a blank when in molding position.

3. A relief duplicating machine comprising a vacuum box having an open side and adapted to support a mold matrix adjacent said open side,

means for removably securing a blank sheet to be molded in sealing engagement with the box in molding position across the open side thereof, a hood overlying the open side of the box and defining an air chamber, air heating means mounted in said hood, air inlet means for admittin fresh air into the hood, a fan for drawing air into the hood through said air inlet means and for circulating air over the heating means and over a blank when in moldin position, and means communicating with the interior of the box for supplying a varying vacuum to the mold side of a blank when in molding position.

4. A relief duplicating machine comprising a vacuum box having an open side and adapted to support a mold matrix adjacent said open side, means for removably securing a blank sheet 'to be molded in sealing engagement with the box in molding position across the open side thereof, a closed hood overlyin the open side of the box, means mounting the hood for vertical movement away from the box to permit insertion and 1emoval of blanks, an air inlet in the hood, air heating means and air circulating means mounted in the hood, and air outlet means in the hood, and means communicatin with the interior of the box for supplying a varying vacuum to the mold side of a blank when in molding position.

5. A relief duplicating machine comprising a vacuum box having an open side and adapted to support a mold matrix adjacent said open side, means for removably securing a blank sheet to be molded in sealing engagement with the box in molding position across the open side thereof, variable speed air circulatin means mounted outwardly of the open side of the box adapted to circulate air over a blank when in molding position, means for heating the air to be circulated regulating means for varying the speed of the circulating means adapted to control and vary the temperature of a blank when in molding position, and means communicating with the interior of thebox for supplying a varying vacuum to the mold side of a blank when in molding position.

6. A-relief duplicating machine comprising a relief mold matrix having recurrent ports extending therethrough and communicatin 'with the molding surface, a vacuum box having an open side in which the mold matrix is mounted with its molding surface adjacent said open side, means for removably securing a moldable blank of greater size than the mold to the box in moldin p sition across the open side 'of the box,'the

box being of greater internal dimensions than the mold matrix so as to provide a closed vacuum space around the mold for supplying vacuum through the mold matrix ports to the underside of the area of a moldable blank overlying the mold matrix and also to supply vacuum to the marginal areas of a moldable blank beyond the mold matrix when such a moldable blank is in molding position, means for supplying vacuum to the interior of the box; means for regulating the amount of vacuum in the box, and means for heating a blank when in molding position and while subject to vacuum.

'7. In a relief duplicating machine, a vacuum 'box having an open side and adapted to removably support a mold matrix therein. with the molding surface of the mold facing said open side, means for removably securing a blank sheet to be molded in sealing engagement with the box in molding position across the open side thereof,

means for heating the exposed face of the blank,

an inlet port in the box'for supplying molding vacuum to the box interior, a vent port in the .box and'an adjustable molding vacuum regulating vent valve connecting with said vent port providing communication between the interior 1 of the box and the atmosphere operable during molding tocontrol and varying-the degree of vacuum in the box.

8. A method of producing relief having local areas of different elevation in a blank of thermoplastic sheet material through vacuum and heat which comprises'supporting the blank in the hard state against'the outermost face surfaces of a female relief mold having multiple local molding surface areas of different depth and with the margins of the blank rigidly secured, uniformly heating the side of the blank away from the mold so as'to gradually raise the temperature of the blank and applying vacuum to the mold side of the blank, beginning while the blank is still below its softening point, and as the temperature of the blank rises progressively increasingthe vac- ,uum in controlled amount on the mold side of the blank so as to draw the blank into contact with the local molding surface areas of different depth progressively, starting with molding surface areas of lesser depth. r

9. A method of producing relief according to claim 8, wherein the applied vacuum is progressively increased in controlled amount in intermittent stages.

10. A method ofproducing relief having local areas of different elevation in a blank of thermoplastic sheet material through vacuum and heat which comprises supporting the blank in the hard state against the outermost face surfaces of a V female relief mold having multiple local molding surface areas of different depth and with the margins of the blank rigidly secured, applying a preliminary 0w vacuumto the mold side of the blank while still in the hard state only suflicient to draw the blank against the outermost face surfaces of themold, uniformly heating the side of the blank away from the mold so as to gradually raise the temperatureof the blank and as lesser depth.

starting wit depth.

cei ri if I the temperature cf the blank rises progressively increasing-and controlling-the amount'of vacyy-uumso as to draw the w 7 the localmolding surface 'a reas of different depth .blankinto: contact with progressively, starting with molding areas of 11; method of producing relief having local ;areas of different elevaticn in-a blank of thermoplastic sheet material which comprises supporting the blank in the hard stateagainst theoutermost face surfaces of a female =relif mold having multiple-local molding surface areas of different depth an'd with the margins of the blank extending beyond; the; sides pf the mold-and "yrigidly secured inoutward spaced relation to the sides of the mold; applying heat to the side of the blank away from the mold so as to gradually -raise thetemperature Y 'i'temperaturerises applying vacuum in progressively increased control-led amount to the moldv of the blank and as the side of the blank so as to draw the blank "into contact with the local molding; surface areas of "different depth progressively, starting with molding surface areas-of lesser depth, andthroughout f the blank moldingoperation holding the rigidly secured margins of the'blank beyondthe mold by applying vacuum to the moldside of said'margins.

- 12. Arnethodof producingrelief having local "areas of different elevation in a blank of "thermos.

plastic sheet material, through vacuum and 'heat which comprises supporting the blank against the outermost-face surfaces of a female relif mold having multi'ple l ocal molding surfaces of'different depth and with the rigidly secured, heating the blank by'fcoritinuously circulating a hot dry 'ga's' atsubstantially atmospheric pressure uniformly over""th'e""'side ,Of'the blank away from the nioldsd s tofg'radually raise the temperature of 'the bl'arili and as the temperature of theblank rises applying a -vacuum in progressively increased" controlled amount to the mol'dside of the-blank so as' to mold the blank into contact with -thelocal'iriolding surface areas of different depth progressively,

' 'the mold ing surface areas of lesser '13. A- rnethod1of producing" reliefhaving' local areasof different elevation in a blank of thermoplastic sheet material thr lugli vacuum heat which comprises-supporting the Blank in the hard state against the outermostfaceflsurfaces of a I female relief mold having multiple local mold- 'ing-surfaceareas of difierent depth and with the margins of the blankrig-idlysecured-apply,

' ing a preliminary low vacuum to the mold side of the blank, then circulating a hot dry gas'uniformly over the opposite side of the blank so as to gradually raise the temperature of the blank and as the temperature rises progressively increasing and controlling the amount of vacuum so as to mold theblank into contact 'with thelocal molding surface areas ofdififerent"depth progresslvely, starting with the moldingsurface areas of lesser-depth.

14. A method of prbaucing rner having local argins or th''blank side both at-the margins-and throughout the liminary low vacuum to the blank from th mold entire mold area, then circulatin a hot-dry gas uniformly over the opposite side of the blank so as to gradually raise the temperature o'f the blank and as the temperature ofthe-blank-rises progressively increasing and controllinglthe amount of vacuum so as to moldtheblank'into contact with the local moldin surfaces'of different depth progressively, startingwitli -the molding surface areas of lesser depth. 7

15. A method of producing reliefin ablank of the thermoplastiesheet material through? vacuum and heat which comprises supporting the blank in the hard state against the outermost f face surfaces of a female relief mold arid with, the margins of-the blank rigidly secured, applying a preliminary low vacuum to the mold side of the blank while still in the hard state, heatin lthe side of the blank away from the mold and as the temperature of the blank rises increasingand controlling the amount of vacuum so as to draw the blank into contact with the molding surfaces of the mold.

16. A method of producing relief in a blank of thermoplastic sheet material through vacuum and heat which comprises supporting the blank in the hard state against the outermost face surfaces of a female relief mold and with the 'margins of the blank extending beyondthe sides of the mold and rigidly secured in outward spaced relation to the sides of the moliapplyingla preliminary low vacuum to the mold side of the I blank simultaneously at the margins andthroughout the entire mold area while the'blank is' still in the hard state, heating the side of the-blank away from the mold and as the temperature of the'blank rises applying a higher vacuum to the "mold side of 'theblank so as to draw the blank into contact with moldin surfaces of the mold. 1'7. In the method of producing relief in-a-blank of thermoplastic sheet material, the steps of-supi porting the blank against the marginal face surfaces of a relief mold with the margins of the 'blankextending beyond the sides of the mold and rigidly secured in outward spaced relation to the sides of the mold, molding the blank to the-contour of the mold, and-throughoutmolding holding'the'rigidly secured margins of the blank beyond the sides of the mold by: applyingvacuum to'the mold side of saidirigidly secured margins. 18. A method of producing relief inablank of thermoplastic sheet material through vacuum and heat which comprises supporting the blank in the hard state against'the outermost facesurfaces of-a female reliefmold and with the margins of theblank extending-beyond thesides of the mold and rigidly secured in outward spaced relation to the sides of the' mold, applyingapreliminary low vacuum to themoldside of the margins of the blank, while the blan-k is still in the hard state; heating:thelopposite side of the-blank and as the temperature of thesbl-ank rises applying ahigher vacuum to the mold--side tact with molding surfaces of themold.

19. Amethod of producing-relief in-ablank of thermoplastic sheet ,material jthrough-- vacuum relief mold and withthe margins of:-the-blank -=rigid1y secured, heating theblank by continuand heat which comprises supportingthe-blank against theoutermost face surfaces of a female ously circulating hot'dry-gas at substantially at- 'mosphere pressure, overtheside of-th+b1ank away from-the-mold so as to raise the temperature of the blank uniformly over the entire mold and simultaneously applying a controlled vacuum to the mold side of the blank to draw the blank underheating into contact with molding surfaces of the mold.

20. A method of producing relief in a blank of thermoplastic sheet material through vacuum and heat which comprises supporting the blank against the outermost face surfaces of a female relief mold and with the margins of the blank rigidly secured, heating the blank by flowing a continuously replenished stream of hot air over the side of the blank away from the mold to gradually raise the temperature of the blank, continuousl'y removing at least a portion of the hot air after flowing over the blank and applying vacuum to the mold side of the heated blank to draw the blank into contact with the molding surfaces of the mold.

21. A method of producing an article having relief and containing correlated visible indicia in accurate registry with the relief which comprises supporting a blank of thermoplastic sheet material inscribed with the correlated indicia and in hard state against the outermost face, surfaces of a female relief mold with the indicia of the blank in accurate registry with corresponding points of the relief of the mold and with the margins of the blank rigidly secured, uniformly heating the side of the inscribed blank away from the mold so as to gradually raise the temperature of the blank and applying vacuum to the mold side of the blank, beginning while the blank is below its softening point, and as the temperature of the blank rises progressively increasing the vacuum in controlled amount on the mold side of the blank so as to draw the blank into contact with the relief molding surfaces of the mold of different depth progressively, starting with the molding surfaces of lesser depth, and maintain accurate registry of the correlated indicia with corresponding points of relief of the mold.

22. A method of producing an article having relief according to claim 21 wherein hot air is circulated over the side of the blank away from the mold to uniformly heat and gradually raise the temperature of the blank.

23. A method of duplicating a topographical relief map which comprises supporting a map blank of thermoplastic sheet material inscribed with topographical indicia of the desired map and in hard state against the outermost face surfaces of a female relief mold having the relief of the desired map with the topographical indicia in accurate registry with corresponding points of the mold relief and with the margins of the blank rigidly secured, uniformly heatin the side of the blank away from the mold so as to gradually raise the temperature of the blank and applying vacuum to the mold side of the blank, beginning while the blank is below its softening point, and as the temperature of the blank rises progressively increasing the vacuum controlled amount on the mold side of the blank so as to draw the blank into contact with the relief molding surfaces of the mold of different depth progressively, starting with the molding surfaces of lesser depth, and maintain accurate registry of the topographical indicia with corresponding points of the relief of the mold.

24. A method of duplicating a topographical relief map according to claim 23, wherein hot air is circulated over the side of the map blank away from the mold to uniformly heat and gradually raise the temperature of the blank.

25. A relief map duplicating machine comprising a vacuum box having an open side and adapted to support a mold matrix therein adjacent said open side, means for removably securing a blank sheet to be molded in sealin engagement with the box in molding position across the open side thereof, regulatable means communicating with the atmosphere for continuously flowing a controlled and varying amount of hot air at substantially atmospheric pressure uniformly on the outer face of the blank when in molding position, and means communicating with the interior of the box regulatable to supply a varying vacuum to the mold side of a blank during heating in molding position to draw the blank into the mold.

26. A relief duplicating machine comprising a vacuum box having an open side and adapted to support a mold matrix adjacent said open side, means for removably securing a blank sheet to be molded in sealing engagement with the box in molding position across the open side thereof, means communicating with the atmosphere located outwardly of the open side of the box operable to continuously flow hot dry fluid at substantially atmospheric pressure uniformly on the outer face of the blank when in molding position, and means communicating with the interior of the box for supplying a varying vacuum to the mold side of a blank during heating in molding position to draw the blank into the mold.

JOHN J. BRAUND.

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

UNITED STATES PATENTS Number Name Date 130,140 Judson Aug. 6, 1872 597,929 Burns et al. Jan. 25, 1898 1,387,805 Roberts Aug. 16, 1921 1,737,874 Busch Dec. 3, 1929 2,345,112 Grundel Mar. 28, 1944 2,377,946 Leary June 12, 1945