US2132659A - Pattern construction - Google Patents

Description

Oct. 11, 1938. R. D. SPEIRS I 2,132,659

PATTERN G ONSTRUCT ION Filed Dec. 22, 1936 3 Sheets-Sheet 1 I!" will Z "AW 1 40 0 W I INVENTOR.

ATTORNEY.

Oct. 11, 1938. R. D. SPEIRS PATTERN CONSTRUCTION Filed Dec. 22, 1936 3 Sheets-Sheet 2 INVENTOR. Bury D. 51 5135 ATTORNEY.

Oct. 11, w D. SPEIRS PATTERN CONSTRUCTION v Filed Dec. 22, 1936 3 Sheets-Sheet 3 ORNEY.

1N VEN TOR. Ram/H11 PE1R5 Patented Get. 11, 1938 2,132,659 PATTERN CONSTRUCTION 1f Ralph n; Speirs, Hawthorne, N. J.'," assignor to Wright Aeronautical Corporation, a corpora tion of New York .fajlp'ucauon Decemb r 22, 1936, Serial No. 117.110

r 9 Claims. "(01. 22-158) 7 This invention relates to'the, construction of patterns as used in castingmetals and is-gParticularly directedto a novel method of pattern construction by which a plurality of thin, closely 5 spaced fins or web elements may be fabricated in the pattern.

The particular type of pattern for which this invention was developed is one from which cylinder head castings for aircooled aircraft en- 10 gines may be produced. Such cylinder heads are normallycastings of aluminum alloy, the cast-- head. Cylinder heads of generally similar character have been produced for a number of years but the pattern problem for the earlier types was not acute due to the fact that the cooling fins were relatively thick, shallow and widely spaced. 25 As the engine art developed, it became necessary to provide for a much greater cooling surface area upon the cylinder head and accordingly, the spacing of the fins was made smaller, the fins were made deeper, and the thickness of the fins was 30 reduced. This imposed an increasingly difiicult task upon the pattern makers-prior methods of producing patterns of this character became impossible of execution and it was necessary to develop a new technique in the fabrication of pat- 35 terns for the improved type cylinder head.

Prior methods of pattern fabrication generally. consisted in forming a cylinder head body, in forming slots in the body,'and in inserting in said slots fins of appropriate form. Thereupon, 40 a thin soldering iron was inserted between the fins, and solder was run at the joints atthe'base of the fins, and subsequently smoothed by the use of hand tools. As is common in foundry practice for production patterns, metal patterns 45 were the rule in this art by which a plurality of molds could be made without appreciably changing the dimensions of the pattern due to wear.

The order of fin spacing and form may be better appreciated by reciting the approximate diso mensions of the new type of fins in the moderncylinder heads. It is necessary that these fins be of a maximum radial depth of approximatelyZ",

. and that there be between four and five fins per inch. Since each fin is slightly less than A" 55 in thickness, it is apparent that the gap between adjacent fins is of the order of 34;". Obviously such a thin slot between the fins would not permit of the soldering operation above described.

Another method attempted consisted of making up a wooden pattern,-inser,ting' w'ood'fin strips in a body, then making a bronze or brass casting therefrom which was subsequently smoothed to provide a serviceable? production pattern} This procedure was accompanied by difficulties in smoothing the bronze' production pattern due to the fact that slight pits, etc., in the surface of the fins werepractically impossible to eliminate, whereby sandmolds of proper form could not be obtained. One of the essentials, incidentally, in producing a good pattern is toQhave the surface, of the pattern so smooth and regular as to permit of easy withdrawal of the pattern from the sand mold, so that the thin sand sections left by the pattern will be. of adequate mechanical strength to remain intact until the sand mold is baked and'mademechanically strong.

With the above experience in view, I have produced a method of pattern. making which overcomes the difiiculties encountered in past methods, with the result that thousands of cylinder 5 head castings have been produced with patterns constructed according to the methods to be hereinafter described in detail, with a minimum of difficulty and manufacturing loss. It-is an object of this invention toprovide a method of pattern construction which permits ofthe inclusion in the pattern of a plurality of;

closely spaced, deep, fins or'web elements,

It is a further object of the invention ,to pro- 1 videa built-up pattern consisting of a plurality 35 of metallic plates, each of whichhas been previously formed according to the final shape which it must assume in the pattern'.---- I Still another object is to provide a relatively thin plate, preformed at its edges to the form of 40 a thin fin or web, such preforming including allowances for draft of the pattern to draw same from a sand mold which has been rammed upon the pattern as well asfor the formation of proper fillets.

A further object is to provide means; by which abutting fin ends of the parted halves of 'a pattern may be so arranged as to'permit of full fin thickness atthe parting plane in the final casting, regardless of slight misalinement which might occur in the molding process.

Another object is to provide a method of construction for a complex pattern whichwill per-- mit of detail changes in design without the ne- 5 1 plates from which the pattern will be'produced.

Further objects and advantages of the invention will become apparent in reading the annexed detailed description and in viewing the drawings in which:

Fig. 1 is an elevation of a'cylinder head pattern half built in accordance with the teachings .of the invention,

Fig. 2 is an elevation of the pattern viewed from the back thereof,

Figs. '3 to '7 inclusive are perspective views of diiiferent preformed plate elements from which the pattern is assembled,

' Fig. 8 is a section through one of the plates showing the tool used for profiling the fins thereof, and

Fig.9 is another view of the profiling tool.

Referring to Figs. 1 and 2, I show a pattern which simulates the casting for the cylinder head of an aircooled engine. The pattern'as a whole comprises a body portion Ill having a plurality of fins extending therefrom. The lower portion of the body includes horizontal fins ll. Intermediate the height of the pattern is a horizontal fin l2 with certain parts of which vertical fins l3 are in abutment. Angled fins M are located above the fin l2 and to the right and left respectively of the vertical fins l3, the fins I have vertical portions l5 parallel to the fins l3 and have horizontal portions 16 parallel to the fins H and 12. The body portion I0 is provided with solid rocker box portions l1 and I8 upon which certain other fins l9 and are formed. The pitch, or distance from center to center of adjacent fins is of the order of .20" to .25, giving from five to four fins per inch. Should a pattern of this character be attempted according to conventional pattern making practice, the cost thereof would be exorbitant and the difiiculties of its fabrication would be correspondingly great.

Referring to Fig. 2, which is a view toward the parting plane of one of the two substantially similar pattern halves which are adapted'to be assembled at the parting plane or alternately, the halves are utilized by following the known practice of matched plate molding. It will be noted that all ofthe various'finned elements are formed integral with flat plates which are laminated to form the body of the pattern. The plates for the fins II for instance are designated as 22; that for the'fin i2 is designated as 23; those for the fins l3 are designated as 24; those for the'fins M are designated as 25; and those for the fins l9 and 2ll are designated as 26 and 21 respectively. l I

Fig. 3 shows an example of a plate 22, by itself; Fig. 4 shows a plate 23 by itself; Fig. 5 shows a plate 2l by itself; and- Figs. 6 and 7 show examples of plates 25 by themselves.

The procedure used in laying out and in preforming the several plates whichcomprise the pattern is substantially as follows:

The cylinder head is designed in accordance with requirements of engine design, and two alternatives then presentthemselves tothe pattern maker. On the one hand, he may carve from wood or other suitable material, a block which represents the complete envelope of the cylinder head body. This block may the n be sliced to produce a plurality of plates eachvof which will represent the profile for the individualpattern yMetallic plates of a thickness equivalent to the pitch ofthefinal fins may then be scribed in accordance with these primary plates. The metal plates will also be scribed with the lines desighating the form of the outer periphery of the fins.

On the other hand the body fin periphery form maybe'determined by calculation or by descriptive geometry at the several contour levels pertaining to the several fins, and these forms laid out upon the plates which will comprise the pattern. Plates such as 25 may then be bent as necessary, and the fin form machined on each plate subsequent to cutting of the plate to the ultimate platesis to use a cutter such as 29 comprising a shank to which a cutting blade 30 is attached. The blade is profiled at. its cutting edgell in accordance with the desired form of the fin. The tool 29 ,is held ina vertical milling machine, drill press or other suitable machine tool, and the plate 22, while the tool 29 is rotating may then be movedso' that the edge of the cutter 30 follows the line on the plate, which has been laid out previouslyto designate the body contour of the pattern. This milling operation is carried out throughout most of the fins, but where thefins terminate at the parting plane as at 32 in Fig. 4, the tool '29 is raised a small amount so that the fin, at-and near the parting plane, will be oi increased thickness, as at 33. This will leave a step 34 on the plate which may be subsequently smoothly finished and tapered off by hand. The purpose of thisthickened portion 33 is to allow for slight maladjustment of mold assembly after the molds have been made from the pattern, so that the casting resulting from the mold will have fins at the parting plane. whose thickness is at least equal to the thickness of fins at other parts of the casting. Redundant thickness of fins at the parting plane is thereafter dressed down by means of high speed tapered cutters which may be utilized when cleaning up the casting.

The horizontal fin l2 shown'in Fig. 1 and also shown in Fig. 4, is provided with a plurality of corrugations 35, the tops" of these corrugations being fiat and being coplanar with the body of the plate 23, to receive in abutting relationship, the bottom edge 31 of vertical fins I2-,-such fins being shown in Fig. 5. r

In the fabrication of plates 25 which carry the angled fins M, the fiat faces of the fins are profiled by the tool 29 as previously described, while the angled portions of these plates may be properly formed by a tapered milling cutter,

whose axis is substantially parallel to a line through the bend in the plate.

The small fin elements is and 20 are also formed on plates in the same manner as previously described.

, The rocker box units 11 and I8 are preferably formed of hollow bronze castings, subsequently machined and smoothed to proper form, these castings being assembled to the various fin ele- I rn ents in a manner to be described shortly.

Figs. 1 and 2 show a bottom reenforcing fin.

whose periphery is substantially coextensive with reenforcement to protect the fins I I from damage. The fin 40 will appear in a casting resulting from the use of the patternand may subsequently be cut down to the lineindicated at 4| which forms the normal reenforcing bead or bolting flange on the bottom part of the cylinder head when it is attached to a cylinder barrel.

Fig. 2 shows, in dotted lines, the various screws and dowel pins used in assembling the various preformed pattern plate elements into a-finished pattern. Both screws and dowels are used in the assembly and for the sake of simplicity screws have been shown on' the left of Fig. 2 and dowels on the right, although in practice, these screws and dowels are used throughout the pattern in assembly.

The first step in assembly consists in loosely inserting a bolt 42 downwardly through the plate 23, and thereafter building up on the plate 23, the plates 24, 25 and 28'. The rocker box units I! and 18 are then bolted to the assembled plates. Thereafter the horizontal plates 22 are assembled upon the bolts 42 and are properly secured. Bolts 43 may be loosely placed through one of the lower plates 22 for later securement to a cylindrical member 44 adapted to form part of the sprue and riser system for casting. I

When the several angled plates 25 are assembled upon one another, substantially crescent shaped spaces 45 will be left between adjacent corners. These spaces 45 shown in the left hand side of Fig. 2, may be filled with fitted brass gussets or with soft solder as shown in 46 at the right hand side of Fig. 2.

It will be appreciated that the pattern is readily disassembled after it has once been assembled, which is a very advantageous feature. Should changes in design of the body form or fin form of the cylinder head become necessary, the pattern may be disassembled and certain portions of the pattern may be built up with soft solder or brazing on the plate elements when separated from one another, or portions of the plates or fins may be further cut away in accordance with the design changes necessary. Thereupon, the pattern may be reassembled without having necessitated the complete building of a new pattern,

as would be necessary if the pattern were constructed in a unitary manner.

A further advantage flows in the construction herein outlined in that all of the separate fin elements of the pattern may be accurately machined and highly polished whereby the resultant castings will be accurate and smooth with a minimum of manufacturing loss due to faulty molds. In the production of molds from patterns of this character, a high degree of care and technique is essential to preserve the thin mold sections which define the spaces within which metal is poured to produce the fins. Imperfectly finished fins on the patterns cause difiiculties in good molding, so that the smoothly finished patterns which this invention-makes possible permit of distinct improvement in foundry practice.

While I have described my invention in. detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

1 What I claim is:

1. In a split pattern, a body and a plurality of thinfins extending therefrom, certain of the fins being interrupted in the parting plane of the pattern components, said certain fins being thickened at and near the parting plane, whereby, if opposed fins are misalined upon assembly of the pattern halves, said thickened fins will be in overlapping relation to provide a net thickness of section at least equal to the-normal thickness of the fin proper.

2. A pattern assembly comprising a plurality of fiat plates stacked upon one another, a second plurality of fiat stacked plates having coplanar edges in abutment with the topmost plate of the first plurality, the plates of the respective pluralities being at an angle to one another, and each of the several plates being formed with an edged fin of less thickness than the plate thickness.

3. In a pattern assembly, a plurality of stacked plates parallel to a first plane, a second plurality of stacked plates parallel to a second plane and normal to the first plane, and a third plurality of stacked plates each plate thereof having a portion parallel to the first said plane and having a portion parallel to the second said plane.

4. In-a pattern assembly, a plurality of stacked plates parallel to a first plane, a second plurality of stacked plates parallel to a second plane and normal to thefirst plane, and a third plurality of stacked plates each plate thereof having a portion parallel to the first said plane and having a portionparallel to the second said plane, each said plate being formed at part of its periphery to provide a fin of less thickness than the thickness of the respective plate, the central portions of said stacked plates being. attached to one another to form the sole body portion of the pattern.

5. In a pattern for a finned cylinder head, the head comprising a body portion and sets of cooling fins extending therefrom at variant angles but all fins lying normal to a central plane through the cylinder, a composite pattern comprising a plurality of sets of plates in laminated relation together forming the cylinder body and fins, each plate having a thickness equivalent to the pitch of the cylinder fins and having a curved edge of reduced thickness to comprise a fin, tlze several sets of said plates and fins being in the planes of the corresponding finsof the cylinder head.

6. In a pattern for a finned cylinder head, semicylindrical pattern halves each comprising a plurality of stacked plates, each plate being substantially semi-circularand having its arcuate edge -formed as a fin thinner than the plate central portion, the fins having a uniform tapered profile throughout the mamr Outltlfll portion of the semi-circle and being thickened at portions adjacent to the base diameter, to provide a draft taper on said fins on a l e normal to the base diameter, and to provide for overlap of said thickened finned portions when the pattern halves are assembled in approximate registry with one another.

7. A pattern assembly comprising a first plurality of stacked plates, and a second plurality of stacked plates having coplanar edges in abutment as with the topmost plate of the first plurality, each of the several plates being formed with an edge fin of less thickness than the plate thickness, and the fin of the topmost plate of the first plurality having projections in abutment with the fin edges of the second plurality.

8. In a pattern assembly, pluralities of stacked plates, the pluralities disposed at an angle to each thereof formed as fins 01' less thickness than the thickness of the plate, and the plate edges of one plurality abutting an end plate of one other plurality, said end plate having fllleted grooves therein, the inter-groove projections torming termm for the fin ends of the one plurality,

RALPH D. SPEIRB.

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