US426375A - grasser - Google Patents

Description

(No Model.) 2 Sheets-Sheet 1.. G. GRASSER. METHOD OF AND APPARATUS FOR MAKING DIES. No. 426,375.

Patented Apr. 22, 1890.

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'2 Sheets-Sheet 2. G. GRASSBR. METHOD OF AND, APPARATUS FOR MAKING DIES. No. 426,375.

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Patented Apr. 22', 189.0.

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UNITED STATES PATENT OFFICE.

CHARLES GRASSER, OF PASSAIC, NEIV JERSEY, ASSIGNOR TO THE SMITH BROTHERS MANUFACTURING COMPANY, OF SAME PLACE.

METHOD OF AND APPARATUS FOR MAKENG DIES.

SPECIFICATION forming part of Letters Patent No. 426,375, dated April 22, 1890.

Application filed July 29, 1889. Serial No. 319,081. (No model.)

To all whom 112'; may concern.-

Be it known that I, CHARLES GRASSER, a citizen of the United States, residing at Passaic, county of Passaic, in the State of New Jersey, have invented a new and useful Method of and Apparatus for Producing Dies for Stamping and Embossing Sheet Metal, of which the following is a specification.

My invention relates to a new and useful art or method of constructing dies for the striking up or embossing of sheet metal by founding or casting such dies of an aluminium bronze or alloy, which at a small fraction of the cost of cut sunk steel dies is their full equal in perfection of finish and their superior in endurance.

From time immemorial down to the present day dies for stamping and embossing sheet metal have been and continue to be laboriously dug out of steel blocks by the class of artistic mechanics known as diesinkers. Die-sinking in its highest depart ments requires a combination of talents, natural and acquired, which commands extremely high wages to the few who possess them. The process of engraving in reverse is slow and hazardous at best, a single mislick often ruining months of most skillful and painstaking labor. Being compelled to cut a desired design in reverse, or intaglio, makes the task peculiarly diiliicult, especially with large deep dies having elaborate patterns. For this reason ornamented articles produced by stamping or pressing have, as a rule, a stiff appearance. Theylack thegraceful and artistic finish which characterizes a work produced in relief by a skillful chaser or repouss worker.

On account of the great cost of steel dies cut into a solid block, suporadded to the lastmentioned diiiiculty, attempts. have been made to produce such dies by casting them in the rough of iron, steel, or hard-metal compositions and finishing them afterward. by the labor of the die-sinker. This mode of making dies carries with it defects which only too often prove that such dies are of inferior finish and endurance. The following explanation will make this clear. The thick heavy blocks of metal which are required for such dies cannot be cast by any of the present known methods with such perfection and sharpness of fine outlines of the design as such dies require. has to be worked over and finished by the die-sinker, which involves nearly as much work as cutting it into solid block. Then it often happens that while working over and finishing a cast die the die-sinker finds underneath the apparently solid surface porous spots or bad places, which render the die useless, and the work so far done is lost. Such a discovery may not be made until the die is almost finished. Another not infrequent source of loss of steel dies is the destruction of the die in the hardening-bath. By means of my invention 1 overcome all the stated existing difficulties and produce dies of a hardness and strength equal to a forged and sunk steel die and obtain a perfection and sharpness of design equal to the artists handwork. By copying my dies from a pattern worked in relief by the chaser or repouss worker I reproduce in intagho the same perfection in design as imparted to the relief.

I will now describe with reference to the accompanying drawings my method of producing perfect dies and molds by means of casting and pressure, using for that purpose an apparatus of peculiar construction.

In said drawings, Figure 1 is a vertical sectional view of an apparatus for carrying out my invention. Fig. 2 is a perspective view thereof. Fig. 3 is an under side "iew of the pattern and its frame. Fig. 4 is a vertical sectional view of the complete apparatus.

The apparatus comprises three principal parts A C E, of cast-iron. or other cast metal, each having a distinct function.

A is a frame of such internal shape and size as I desire to give to the die. In the drawings this frame is shown tapering upward toward the open top or mouth, so that dies cast therein will have the customary tapering body. The frame A is provided with an interior lining B of refractory non-conducting material, prefeably either asbestus orcrucible clay. This lining is applied about one-sixteenth of an inch thick. The frame a serves as the mceptacle for the fluid metal,

The design (in intaglt'o) and at the same time answers as the mold to give shape to the body of the die to be cast. The lining B serves to prevent the too rapid cooling of the fluid metal, so as to allow time for the necessary operation of filling the open mold nearly to its brim with molten metal, (aluminium alloy,) removing the dross and other impurities, promptly closing the open mouth of the mold, with the pattern (face downward) clamping said pattern tightly down. upon the asbestus gasket or packing,

so as to close the mouth of the mold, and finally forcing the molten or plastic metal into close and intimate juxtaposition with the pattern by piston-pressure from below, all as hereinafter fully explained.

C is another frame, provided with one flange 0, extending outward to the outer edge of frame A, and another flange 0, extending inward, so that when the frame 0 is attached to frame A by means of screws the said flange 0' forms a portion of a floor or bottom to frame A.

E is a block or piston of such size as to pass loosely through the upper opening of frame 0, and to thus constitutea false bottom and complete the floor of frame A.

D is another block, which is superimposed upon the block E. The block D is kept in place on the piston E by means of'two dowelpins 6. The block E serves as a plunger or piston, by means of which pressure can be applied to the fluid metal when such is poured in and inclosed in frame A. The block D, resting on block E, as indicated, and being forced to enter the mold, as shown in Fig. 4, serves the purpose of taking up the central shrinkage of the metal and insures a perfect counterpart impression of the pattern.

The metal composition which I prefer to use for my said dies is a composition or alloy of ten per cent. aluminium and ninety per cent. copper. This composition has extremehardness, and when founded under my method forms a perfect counterpart of the pattern.

My present invention is largely directed to obtaining a full and accurate impression of the pattern, notwithstanding the tendency of such composition to contract bodily in setting and unequally in different parts of the mass.

To compensate for the slower cooling of the center, and consequently at the place forlast contraction, I use the block D. As stated above, said block being slightly smaller in cross-section than the bottom opening of the frame A it can be forced into the center of the fluid metal during its different stages of cooling until it becomes solidified. As the composition of which the die is made shrinks more than the block D, which is made of castiron, the said block becomes as firmly held as if it had been of the same substance with the die, and so remains an integral part thereof.

One or more downward ly-flared holes (1 may be provided in the blockD to receive portions of the molten metal to still further lock the parts together.

The space between the piston E and the frame (3 serves to receive a fire-proof packing or gasket F for the piston E, which is made by ramming asbestus fiber in the space around said piston. The packing F serves the purpose of preventing the escape of fluid metal from the receptacle or mold A when a high pressure is applied to if.

G is a plain iron frame, which is of the same size onthe outside edge as the frameA on its upper edge. The inside of frame G is about one-half of an inch from the inside edges of frame A. The function of the frame G is to strengthen and hold the relief-pattern H, from which an impression is to be taken, thereby obtaining the intaglio of the pattern.

The relief-pattern H is made of fine plastic clay and burned or baked as hard as what is called by potters biscuit-ware. This clay pattern H is so formed as to have a fiat base or back It. The base or back is exactly of the same thickness as the frame G and a little smaller than the inside of the frame, so that the pattern forming one piece with its base can be placed inside of the frame, leaving about one-eighth of an inch space between the frame and the pattern-base. This space is filled carefully withplaster-of paris, thereby cementing the pattern-base firmly in the frame. When the pattern is thus united with the frame G, a strip of asbestus sheathing is pasted around the edge of the face side to form a packing or gasket J between frame A and frame G when the last-named is placed face down on frame A, as is indicated by the drawing Fig. 4.

After cementing the burnt clay pattern H in the frame G and providing the packingstrips J on the face side the pattern is again well dried to expel all, moisture before using it for the impression.

The frame G has two steady or dyowel pins g on opposite corners. These pins gt loosely in corresponding holes a in the top edge of frame A, so as to permit expeditious and accurate placing of the frame G, with its pattern, in the desired position on the frame A, thus completing a mold for a die to be cast.

The. frame G is useful in protecting the somewhat fragile material of the pattern IIO proper from excessive pressure between the mold and platen.

Four spiral springs Kone at each corner of the apparatusserve the purpose of giving a certain but yielding resistance to the combined frames A, O, and G when pressure is applied on the top. This resistance of the springs is usually very desirable, although under certain modifications of the apparatus it maybe dispensed with.

As seen by the drawings, the whole apparatus rests on the piston E, which is somewhat longer than the depth of packing frame C, which is only prevented from slipping down over the piston E by the friction of the packing F. It is, however, necessary that the combined frames 0 and A, with the pattern-frame G on top, should not move down against the stationary piston until the frame A, forming the mold-walls, is filled with fluid metal from the top and the pattern in frame G has been placed face downward on the same as a cover for the final completion of the mold. The resistance of the springs K mustfor this reason be considerably more than the combined weight of the frames and metal.

The pattern in its frame G, when laid on the filled mold,'is prevented from moving laterally by two steady-pins g.

If the metal-receptacle A is filled and the pattern placed on top as a final cover, (which must be done expeditiously, because refractory metals congeal very rapidly when once poured from the meltingpot,) it is self-evident that no avoidable time should be lost by fastening the frame G firmly to the frame A, so as to prevent the escape of the fluid metal when pressure is applied to it, which is accomplished in my case by placing the whole filled apparatus under a suitable screw-press platen P and forcing the combined mold and pattern downward against the piston E. The surplus resistance of the springs requires a corresponding pressure which is exercised on the frame G, thereby pressing it tightly on the frame A, preventing the escape of the fluid metal.

It may appear at first sight a rather peculiar mode of procedure to force the metalreceptacle downward. It might seem more practical to have the pattern in frame Gfastened at the bottom of the receptacle and pour the fluid metal on the pattern, and then apply the pressure by forcing the piston downward in the metal. However, the great importance of making and manipulating the apparatus as I describe it will presently be clearly seen.

The production of the clay pattern requires little description, because there are several ways to make fine perfect copies from relief designs in plastic clay well known to artisans skilled in the production of ornamented goods made of plastic material. I prefer to take a fine perfect plaster-of-paris mold from the original relief-pattern,which may be modeled in wax or be carved in wood, metal, or other.

suitable substance by the artistic chaser or repouss worker. From such a plaster mold, when well dried, I take fine perfect impressions in plastic clay and harden them by burning in a furnace to the required degree.

Before proceeding to describe the final operation in casting a die with the apparatus described in this specification a few explanations will be given concerning metal compositions used for casting dies and molds, and brief reference made to some of the properties of the above=mentioned al'uminium and copper composition, which I prefer for the material of such cast dies.

1 have heretofore in actual practice cast many dies and molds of cast-iron, of phosphor-bronze, of bell-metal, of aluminium bronze, and even of steel; but I have made such castings by other more familiar methods and by means of other apparatus for applying pressure to the fluid metal, the results of which were not so satisfactory.

In the customary method of pouring the molten metal through gates or sprues into a closed mold several serious difficulties arise. For example, the stream of molten metal is liable to break down or partially obliterate the smaller saliencies in the mold-face. Again, the dross and other impurities form askin or crust which intervenes between the metal and the mold-face and prevents the taking of a sharp impression. Of the metals above cited the first three have not sufiicient strength and hardness to resist the high crushing-pressure required in dies for stamping and embossing metals or pressing other tough materials into the required shape.

Cast-steel, on the other hand, on account of its liability to set except at the extremely high temperature required to melt it, does not cast very sharp nor with even perfect surfaces. The high heat of molten steel, moreover, bites into the pattern, even when the latter is made of the most refractory clay.

It should further be borne in mind that aluminium bronze of the stated mixture is a composition presenting many peculiar features when cast in massive blocks. Metals when poured in a mold in the ordinary way,

or when forced in a mold by pressure from an injecting apparatus, are necessarily brought into a state of agitation. In some of the metals and compositions such agitation produces no serious results, because the spattering fragments of metal on entering the mold reunite perfectly with the mass and the casting shows no signs that such spattering or temporary division had taken placegbut in casting aluminium bronze the above-mentioned agitation, spatterin g, and divisionof the metal while entering the mold produce serious defects in the cast-ing. The scattered or divided portions (perhaps owing to superficial oxidation) do not unite perfectly again, and the whole surface, and even the interior portion of the casting, is full of defects, presenting an appearance as if the metal had been loaded with impurities 5 but in reality these spicules prove under close and careful examination to be small portions of the metal itself which have become separated from the mass, and no matter for how short a time such a separation may have been they become surrounded with a film of oxide, which prevents perfect reunion with the mass. It seems to be the same natural cause which is antagonistic to the soldering and welding of aluminium in its pure state. Another serious trouble exists in casting the said aluminium composition, which is the great contraction while cooling. Its shrinkage seems to be nearly double that of other bronze compositions. Furthermore, a mass of this composition cools very unequally. If cast in large blocks, the outside congeals much more rapidly than the center, which causes a drawing away from the pattern or mold, thereby producing imperfection. Pressure applied to the metal through a gate or runner, as it is done by any of thepresent known methods, will not prevent it, because the gate or runner is always smaller than the mass, and consequently congeals sooner than the center of the mass. In the ordinary way of casting aluminium bronze in very open coarse sand molds this defects is greatly remedied by providing numerous sprues in the center; but such open coarse molds will not answer for castings on whose surface the finest line of the pattern must be well defined.

By the use of my herein-described apparatus, and by the fundamental principle of operation, I fully overcome the above-mentioned difficulties of casting aluminium bronze into a perfect die.

The apparatus is plainly shown by the drawings.

The fundamental principle of operation on which success depends is this: I provide a strong vessel open on the top, and which has the same shape as the outside of the die or mold to be cast. Such vessel is provided with a non-combustible lining of weak thermal conductivity. The pattern and the interior of the mold having been heated to incandescence, the molten composition is poured into the mold. After being poured into said vessel time is given for the metallic portion to come to a perfect rest and unity, and for the dross, foam, and other impurities to come to the top. The said impurities are then removed by the operator. The yet open mold is now seen full of clear molten metal. The frame G, with the clay pattern H, is then placed (face down) on top of the frame A. The platen P, being now depressed, holds the frame G, with its inclosed pattern, down and tightly closes the mouth of the mold. Continued depression now of the platen P operates to force the frame G (with its pattern I1) and the frames A and C downward against the piston E, exercising pressure on the still fluid or plastic and now absolutely quiescent metal, which, with a clean surface, comes in contact with and is pressed strongly against the pattern, causing said metal to receive a perfect impression of the same. The contents of receptacle A become congealed on the outside to a certain extent during the performance of the operations of coming to a rest, being skimmed, placing the pattern on top, and applying the pressure; but the piston E and the block D, being smaller than the internal size of the mold, will still force easily into the yet fluid center and exercise the desired pressure on the metal, thereby filling the mold completely, and at the same time taking up and compensating for the tendency to shrinkage in the center of the casting.

Having now fully described the apparatus in its details and functions, and having laid down and explained the principle on which I operate, I will now shortly describe the final operation of casting and pressing a die. The apparatus being complete, as shown in Fig. 1, is placed on an iron plate L, (see Fig. 4,) and the whole inserted in a press M P, which must be provided with a projecting platform or base. Such a press must be of a capacity to exercise a pressure of about four hundred pounds to each square inch of the surface of the die to be cast. This done, the interior lining of the frame A is again heated to expel all moisture. The pattern H in the frame G is then removed and also reheated (preferably by means of a blow-pipe) and laid in readiness to be replaced quickly on top of the frame A. In the meantime, or previously thereto, the aluminium composition has been melted in a proper suitable furnace. Then I fill the frame or receptacle A with the melted metal, making, however, proper allowance for the room or space which will be occupied by the projection of the pattern-that is to say,for the formation of a large deep die the pattern has a corresponding projection, which takes the required space in the frame A. To fill the frame A completely in such a case would cause an overflow when the pattern is put in place, which would cause an objectionable flange 011 the die, and this would be an impediment to its removal from the frame. When the frame A is filled as stated, the metal will bubble and show some agitation, which will, however, subside in afew seconds. As soon as the fluid metal rests quietly all the foam and impurities are quickly skimmed off by means of a suitable tool N, (see Fig. 2,) so as to present a perfectly-clear mirror-like surface of the fluid metal. pattern in the frame G (see Fig. 3) is quickly placed on top (face down) descending gently to its place, guided by the steady-pins g, and thereby closing the mold. The whole apparatus resting on the plate L is then placed under the screw-press P, which is promptly brought into depressing action to the extent required, according to the size of the dies surface. (See Fig. 4c.) The continued action of the press P will move the combined frames A, G, and C against the stationary block D, which will force itself into the rear center of the molten mass, which is the last spot to cool and prevent the central shrinkage and become itself a part of the die. In the course of a few minutes, during which time the pressure is kept up, the metal has cooled enough to be removed by taking the apparatus apart and knocking the die out of the frame A. Should portions of the claypattern adhere to the die, they may be easily removed by a little harfd-work and proper tools. When the clay is removed, it will be found that the die Then the clay or mold is a perfect intaglio copy or counterpart of the claypattern-a copy perfect and true, for example, as in the electrotype production of a' copper shell. The whole surface of the die is free from anyimperfections or defects, and the whole body of the die is as solid. and free from blow-holes as if it had been forged.

In conclusion, I wish to state that I do not confine my claims to the exact type of appaia tus herein described. By many modifications of the apparatus which will not require special faculties of invention the same method may be adapted to sundry shaped castings of which it is required to have one side of a perfection requiring special hand labor to bring it to such. Forillustration, the frame Gmay inclose a clay mold formed from a pattern which presents two or three ornamented sides or of a peculiar shape. By observing the same rules and principles described the same good resultsare obtained. A mold of an object inclosed in frame G is just as perfectly filled by pressing the metal upward. It remains the same Whether the frame G holds a clay relief pattern or a clay mold or matrix. For example, I produce fine results in cast ing artificial teeth-molds by a slight modification of my apparatus. Such teeth-molds present three sides, which have to be reproduced just like the original mold.

In some applications of my system the piston E may consist of a false bottom or follower so formed. and of such material as after having discharged its functions of forcing the molten and gradually cooling and shrink ing metal against the pattern-face to be withdrawn bodily from the cast die and not contribute to the permanent substance of such die. The pressing action may of course be equally well accomplished by a vice versa of the described action, in which the piston or false bottom is elevated against the superincumbent members, which are held stationary. The extraneous pressure may be derived from any customary source, such as a hydraulic pump, a toggle, or a lever.

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

1. The process or method of forming a die of aluminium composition or alloy, which con sists in filling a mold (which is open at top and has a false bottom) with the molten metal or composition, which is then allowed to settle, skimming off the impurities, closing the open top of the mold with the pattern, (face downward on the clean molten metal,) and pressing the said parts downward against said false bottom, or vice versa, as and for the purposes set forth.

2. The processor method of forming a die of aluminium composition or alloy, which consists in filling an open mold with the molten metal or composition, which is then allowed to settle,s kimming off the impurities, closing the open mouth of the mold with the pattern, and so depressing said parts as to cause the entrance into the central bottom portions of the metal of a two-part plug or piston whose upper portion remains within the die or casting as an integral portion thereof, in the manner explained.

3. A baked-clay pattern fastened within and protected by a surrounding frame of stronger material, in'the manner and for the purpose described.

4:. In combination with a mold and piston, the separable block D,for the purpose explained. 5. In combination with the mold A and piston E, the flanged frame 0, serving asa packing-box for said piston.

(3. The combination of the frames A and O, the piston E, and the separable block D, for the purpose explained.

7 The combination of frames A and G with piston E, and a baked-clay pattern held. in a frame G, forming a complete mold, to which pressure can be applied in the manner specified.

S. The combination of the following elements, to wit: (a) the base or bed plate L, the piston or false bottom E, which rests upon said base, and the springs K, which also rest upon said base 3 (b) the superincumbent members which rest upon the springs K, an d which consist of the frame 0, with its packing it, the frame A, with its packing J, andthe frame G, with its inclosed pattern H; a platen P, depressed by screw or its equivalent, the whole being combined and operating substantially as set forth.

9. The separable block D, having downwardly-fiared orifice d, for the purpose specified.

10. As a new and useful article of manufacture, the die of aluminium alloy or composition, substantially as set forth.

CHARLES GRASSER.

Witnesses:

J. J. 0. SMITH, V. XV. SCOTT.

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