US2880485A

US2880485A - Water jacket coring for casting internal combustion engine blocks

Info

Publication number: US2880485A
Application number: US473838A
Authority: US
Inventors: Dolza John
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1954-12-08
Filing date: 1954-12-08
Publication date: 1959-04-07
Anticipated expiration: 1976-04-07

Description

Aprll 7, 1959 J. DOLZA WATER JACKET CORING FOR CASTING INTERNAL COMBUSTION ENGINE BLOCKS Filed Dec. 1954 Attorney United States Patent WATER JACKET CORING FOR CASTING INTER- NAL COMBUSTION ENGINE BLOCKS John Dolza, Davisburg, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 8, 1954, Serial No. 473,838

11 Claims. (Cl. 22-167) This invention relates to coring. for engine castings and particularly to the construction of a reinforced water jacket core for use in casting a cylinder block of an internal combustion engine. The invention also includes a novel method of reinforcing a water jacket core and the process of using such a reinforced core in casting an engine cylinder block.

Recent developments in the foundry industry have resulted in the use of combined barrel and bulkhead cores in the casting of cylinder blocks of V-type internal combustion engines. As a result, some engine manufacturers are now beginning to employ a single thin-walled water jacket core for each cylinder bank in place of the multi-piece water jacket cores previously used. Prior to this development, the smaller water jacket core segments had been separately formed, their mating surfaces subsequently ground, and the core segments pasted together. An example of the new and improved arrangement is disclosed in copending application S.N. 339,098, filed February 26, 1953, now Patent No. 2,783,510, in the names of John Dolza and John B. Burnell.

Moreover, there has been a tendency during recent years to increase the displacement of gasoline engines by greatly increasing cylinder diameters or bores without increasing, or in some cases decreasing, the overall size of the engines. This trend has been particularly evident in the manufacture of V-type engines. In turn, the large bore sizes necessitate the use of water jacket cores having extremely thin walls, especially betweenthe openings in the water jacket cores through which the cylinderdefining barrels of the barrel cores extend. In some instances the core walls between these openings are so thin that they contribute practically no structural strength to the core.

It is obvious that if engines are to be designed so that they have maximum displacement without at the same time increasing the overall size of the cylinder block, the thickness of the walls of the water jacket core must be retained at a minimum. The use of the aforementioned larger thin-Walled water jacket cores, however, increases the likelihood of breakage of these cores during handling or casting operations. For example, the angle at which water jacket cores of V-engines must be placed during core assembly and the manner in which these cores must be supported by transfer or assembly fixtures necessarily subject them to considerable opportunities for breakage.

Furthermore, the hydrostatic pressure exerted by the molten casting metal during and immediately after pouring is appreciable and precludes the use of water jacket cores having walls which are too thin and weak. The molten metal between the water jacket core and the green sand mold exerts pressure laterally and tends to collapse the side walls of the water jacket core if the bores in this core are very large, while the thin core walls between the bores are susceptible to break-down by the pressure of the molten metal between the barrel cores and the water jacket core. During the pouring step, molten cast iron will burn through thin sections of 2,880,485 Patented Apr. 7, 1959 "ice sand and, in combination with the hydrodynamic pressure of the flowing metal, produce core breakage. The resultant castings are defective, of course.

Accordingly, a principal object of the present invention is to provide a reinforced water jacket core for use in casting cylinder blocks of internal combustion engines. Another object of this invention is to provide a method of forming water jacket cores which are less subject to breakage in the course of the manual handling required prior to and during the assembling of these cores in a core transfer mixture, while these cores are in the fixture or being deposited in the drag half of a green sand mold, or during pouring of the molten casting metal. A further object of the present invention is to provide a process forcasting a cylinder block of an internal combustion engine by the use of a water jacket core having a metallic reinforcing portion or core support which becomes integral with the cylinder block casting. A still further object of the invention is to provide a water jacket core which is reinforced by sheet metal in such a manner as to permit casting of a cylinder block of conventional size having maximum cylinder displacement.

These and other objects are attained in accordance with the present invention by the use of a novel reinforced water jacket core for casting the cylinder block of an internal combustion engine. This water jacket core is provided with a thin sheet metal reinforcing layer which supports the core sand of the water jacket core prior to and during the casting operation and which becomes integral with the cylinder block casting upon solidification of the molten casting metal. The sand, which constitutes the principal portion of the water jacket core, is packed around the outer periphery of the core support, the internal contour of the latter being such as to accommodate insertion of the cylinder-defining portions of barrel cores or barrel-bulkhead cores. The molten casting metal, which is subsequently poured between the cylinder bores and the sheet metal core support bonds to or fuses with the latter so that this support becomes an integral part of the cast cylinder block.

Other objects and advantages of this invention will more fully appear from the following detailed description of a preferred embodiment of the invention shown in the accompanying drawing, in which:

Figure 1 is a perspective view of a water jacket core for an internal combustion engine, which water jacket core comprises a reinforcing sheet metal interior layer and'core sand constituting the principal external portion of the core;

Figure 2 is a perspective view of the sheet metal core support shown in Figure 1;

Figure 3 is a fragmentary perspective view, with parts broken away and in section, of a water jacket core generally similar to the core shown in Figure 1 and barrels or cylinder-defining portions of barrel-bulkhead cores which extend through the openings formed in the sheet metal core support; and

Figure 4 is a fragmentary perspective view of a modification of the sheet metal core support shown in Figures 1 through 3.

Referring more particularly to the drawing, in Figure 1 is shown a water jacket core, indicated generally by 10, for use in casting a cylinder block of an internal combustion engine. The water jacket core comprises a destructible outer portion 12 which is formed of core sand and a suitable binder, and an inner reinforcing or supporting portion 14. The latter is preferably formed of sheet metal which is stamped or drawn into the desired shape.

The core support or sleeve 14 is shown in the drawing as including an elongated strip 16 of sheet metal which is contoured to provide the inner surfaces of the cylinder block walls which form the water jacket around the cylinders of the block. Alternatively, the strip 16 may be defined as providing the outer surfaces of the casting walls which form. the cylinders. The strip 16 is shown as being formed of a single sheet, two halves of which are bent back on themselves to form the aforementioned surfaces. The ends of the strip are shaped to provide mating surfaces which may be joined together as shown at 18 by spot welding, brazing or other suitable means. Spacer ribs or ties 20, preferably formed of'the same material as the strip 16, are provided between and connect opposite pairs of inwardly extending portions or indentations 22 of the strip 16. The laterally extending halves of these spacer ribs can be conveniently attached to the indentations 22 by spot welding, although other suitable methods of securing the ribs in place may be employed if desired. The sheet metal parts should be as thin as is compatible with handlingand fabrication problems and their ability to properly support the core.

The reinforced water jacket core may be formed in accordance with the present invention by first fabricating the sheet metal core support 14 in the above-described manner with the ends of the strip 16 being welded together and the spacer ribs 20 being spot welded in place. The resulting core support is placed in a core box which is to be used in forming the sand-binder portion 12 of the water jacket core. Thereafter the core sand constituting the portion 12 is packed, preferably by a blowing operation, around the outside periphery of the support 14. The reinforced water jacket core thus formed is thereafter baked in a conventional manner, such as by the use of av core oven, to cure the sand-binder portion of the core.

As shown in Figure 3, when the completed water jacket core 10 and the other cores which constitute the final cylinder block coring arrangement are assembled, the barrel or cylinder-defining portions 24 of the barrel cores or barrel-bulkhead cores 26 extend through the openings 28 defined by the sheet metal strip 16 and the sheet metal spacers 20. A plurality of generally annular spaces or casting cavities 30 is thus provided between the sheet metal parts and the core sand barrels or cylinder cores 24.

On pouring the molten casting metal intothe space 30 between the barrel cores and the core support 14, the latter fuses with or bonds to the casting metal as it solidifies, thus becoming an integral part of the finished casting. The bond may be either mechanical or chemical. If the sheet metal core support is formed of 'a sufficiently high melting point material, it may become bonded or merely locked to the casting metal Without any appreciable amountof melting of the sheet metal occurring. In any case, because of the necessarily thin and unsup ported sections which form thespacer ribs 20, particularly in the modification shown in the drawings, it is desirable that the-corev support 14. be formed of a metal which does not have a melting point excessively below'the pouring temperature of the casting metal.

However, inasmuch as melting of the sheet metal strip 16 or thejspacer strips 20 would not adversely affect the quality of the casting, provided these parts remain in the solid state for a sufficient period of. time to perform their supporting function, a considerable amount of leeway is permitted in the selection of the material of which the core support 14 can be made. Of course, it is desirable that this metal does not form an alloy with the cast iron having characteristics which would adversely affect the strength of other physical properties of the resultant cylinder block. A ferrous base'metal, suchas sheet steel, is preferred both for reasons of economy and because. of its high melting point since cylinder blocks of internal combustionengines are normally cast of relatively high melting point cast iron.

Although a. core support of sheet steel normally would have a melting point higher than the meltingpoint of the cast ironaof whichcylinder blocks are conventionally formed, there is a tendency for the carbon from the molten cast iron to migrate into the steel and form an alloy which has a melting point lower than the usual pouring temperatures of cast iron. Thus, under some conditions the resulting melting point of the spacer ribs or ties 20 may become too low, and there may be a tendency for these spacers to washout during the pouring operation. Of course, any such premature melting of the reinforcing sheet metal can be eliminated by selection of proper stock thickness, as well as appropriate pouring temperatures and rates of flow of the cast iron during the casting process. It is therefore apparent that, in accordance with the invention, the sheet metal core support may become. merely mechanically locked or bonded to the castiron or it may, actually melt, provided its melting point is not so low that it does not properly support the core until the casting has at least partially solidified. As indicated above,.the problem ofpremature melting is particularly important with respect to the portions of the core support between the openings 28.

Alloying of the cast iron to a sheet steel core support 14 may be facilitated by the use of copper struck steel. A coating of copper or copper base alloy may be applied to the inner surfaces of the core support or, if it is desired to do so because of convenience from a processing standpoint or otherwise, the entire core support may be copper coated. This coating, which preferably has a thickness of only a few hundred-thousandthsof an inch, may be effectively applied by dipping the sheet metal parts. into a copper sulfate solution or by a spraying operation.

It will be evident fromthe above facts, therefore, that the union betweenv the cast iron and the core support may be the result of. rather extensive fusion of these parts, surface bonding, or in some cases merely mechanical locking. Hence, the words bond and fuse, as used in the appended claims, are intended to be. coextensive and each inclusive of these various methods of uniting the cast iron with the supporting portion of the water jacket core.

From a production standpoint, manufacture of the core support 14 can be facilitated by forming two longitudinal halves of the sheet metal strip 16 between rollers. A mating pair of thesestrips each having the corrugations necessary to define the barrelportions of the core thus can. be made of identical shape. The two halves then may be fiash welded together toproduce the final sheet metal reinforcement sleeve or. core support 14. With such an arrangement, the indentations 22 of the strips 16 preferably extend a distancesufficient to permit opposite pairs of this indentation to come into contact upon joining the twolongitudinally extending striphalves. These indentations canthen be flashwelded together, thus completely eliminating the necessity of using the spacer ribs20.

In themodification ofthesheet metal core supportv32 shown in Figure 4, a plurality of tubular sections 34 of equal diameter and length areernployed. These cylindrical tubes may besecured together, preferably by spot welding as-indicated at 36, to form the reinforcing portion of the water jacket core. This-type of construction, of. course, is very inexpensive and simple to fabricate.

It will be appreciated, of course, that the core sand portion 12 of the waterjacket core 10 shown in Figures 1 and. 3 is somewhat schematic and that theouter surfaces of the. core sand 12.areactually provided with various core locators, venting holes and other appropriate recesses necessary to formxa casting of the desired shape. In fact, these changesin contour, which. are necessary to form. a practical. water jacketcore, usually result in making-the walls' of the sand-binder portion of the core 10 considerably thinner than the core walls shown in Figure 1.

While-aspecific embodiment-of my invention has been shownand described-.in..detail, it will beunderstoodthat various changes in the shape and construction of the reinforced water jacket core may be made without departing from the scope of the invention as set forth in the following claims.

I claim:

1. A reinforced water jacket core for use in casting a cylinder block of an internal combustion engine, said water jacket core comprising an elongated thin sheet metal supporting layer shaped to provide outer surfaces of the casting walls which form the cylinders of the engine, said supporting layer having opposite pairs of inwardly extending portions which define with side walls of said layer openings for receiving cylinder-defining portions of barrel cores, and a thin layer of a baked mixture of sand and binder packed around the outer surface of said sheet metal supporting layer.

2. A coring assembly for use in casting a cylinder block of an internal combustion engine, said assembly comprising a barrel core having a generally cylindrical cylinder-defining portion, a reinforced water jacket core having a thin supporting sleeve of sheet metal defining a generally cylindrical opening through which said cylintier-defining portion extends, the diameter of said opening being larger than the diameter of said cylinder-defining portion so as to provide an annular space between said sleeve and said cylinder-defining portion, and a thin layer of a baked mixture of sand and suitable binder adhering to the outer surfaces of said sleeve and contoured to provide the necessary indentations in said water jacket core.

3. A coring assembly including a reinforced multipiece sand and metal foundry core .for use in forming coolant passages in the cylinder block of an internal combustion engine by means of a casting operation, said core comprising a pair of elongated metallic strips formed of a metal having a melting temperature not appreciably lower than the normal pouring temperature of molten cast iron, said strips being provided with indented portions which extend inwardly from the general planes of said strips, oppositely disposed pairs of said indented portions being connected to form separate cham bers, a relatively thin layer of baked core sand and binder packed around the outer surfaces of said joined strips, and barrel cores formed of a baked mixture of sand and binder having cylinder-defining portions extending into said chambers, inner surfaces of said strips being provided with a thin coating of copper.

4. A method of forming a multi-piece reinforced water jacket core for use in casting a cylinder block of an internal combustion engine, said method comprising forming thin-walled sheet metal into a shape having a plurality of openings for receiving cylinder-defining sand cores, thereafter positioning said sheet metal in a core box, thereafter blowing a mixture of core sand and binder into said core box against the outer side surfaces of said sheet metal, and subsequently baking said core to cause said mixture to adhere to said surfaces.

5. A method of reinforcing a thin-walled water jacket core for use in casting a cylinder block of an internal combustion engine, said method comprising fabricating sheet metal members into an assembly having the general shape of walls of the water jacket to be cast, said assembly having a plurality of openings extending therethrough and thin-walled spacer strips separating said openings, positioning said sheet metal assembly into a core box having walls defining the outer contour of the Water jacket core to be formed, subsequently packing a mixture of core sand and binder into said core box around the outer surfaces of said sheet metal assembly and thereafter baking said core in an oven.

6. A method of forming a cylinder block casting by means of a reinforced sand core which comprises forming sheet metal strips into a supporting assembly constituting a plurality of generally cylindrical interconnected sleeves, positioning said assembly in a core box,

packing a mixture of sand and binder around the outer surfaces of said assembly, baking said sand and binder mixture to cure said mixture and cause it to adhere to said surface, thereafter positioning the formed reinforced core around barrel cores so that cylinder-defining portions thereof protrude through openings defined by said sleeves, subsequently pouring molten casting metal between said cylinder-defining portions and said sleeves to thereby bond said'supporting'assembly to said casting metal upon solidification thereof.

7. A method of casting a cylinder block of an internal combustion engine by means of a reinforced thin-walled water jacket core, said method including the steps of fabricating-an elongated sheet steel assembly into the general shape'of the walls of the water jacket to be cast, said assembly having transversely extending thinwalled spacer strips which define with other portions of said assembly a plurality of openings, positioning said sheet steel assembly into a core box having walls defining the outer contour of the water jacket core to be formed, blowing a mixture of core sand and binder into said core box and around the outer surfaces of said sheet steel assembly, baking the formed water jacket core in a core oven to cure the sand and binder portion of said core, subsequently inserting cylinder-defining portions of barrel cores into said openings to thereby provide a plurality of annular spaces between said sheet steel assembly and said cylinder-defining portions, and thereafter pouring molten cast iron into said annular spaces.

8. In a process for casting a cylinder block of an internal combustion engine by means of a thin-walled reinforced water jacket core, the steps of fabricating sheet steel strips into a core support having the general shape of walls of the water jacket to be formed, said core support being provided with a plurality of openings extending therethro-ugh separated by thin-walled sheet steel spacer portions of said support, positioning said core support in a core box having side walls defining the outer side contour of the water jacket core to be formed, thereafter blowing a suitable mixture of core sand and binder into said core box around the outer surfaces of said support, baking the resultant reinforced water jacket core to cure the sand-binder portion thereof, subsequently positioning baked sand barrel cores so that cylinder-defining portions thereof extend through the openings in said core support to provide a plurality of generally annular spaces between said support and cylinder-defining portions, thereafter pouring molten cast iron into said spaces, and permitting said core support to fuse with the casting metal during solidification thereof to thereby cause said core support to become an integral part of the finished cylinder block casting.

9. A reinforced water jacket core for use in casting a cylinder block of an internal combustion engine, said water jacket core comprising an elongated, thin, sheet metal supporting layer shaped to provide outer surfaces of the casting walls which form the cylinders of the engine, said supporting layer having wall portions extending generally transversely relative to the core, said wall portions and side Walls of said layer defining openings for receiving cylinder-defining portions of barrel cores, and a thin layer of a baked mixture of sand and binder packed around the outer surface of said sheet metal supporting layer.

10. A coring assembly including a reinforced multipiece sand and metal foundry core for use in forming coolant passages in the cylinder block of an internal combustion engine by means of a casting operation, said core comprising an elongated, thin, sheet metal supporting sleeve shaped to provide a plurality of openings extending generally transversely relative to said sleeve, said sleeve being formed of a ferrous metal having a melting temperature not appreciably lower than the normal pouring temperature of molten cast iron, a relatively thin layer of baked core sand and binder packed around the outer surfaces of saidsleeve, and barrel cores formed of a baked mixture of sand and binder having cylinderdefining portions extending into said openings.

11. A coring assembly including a reinforced sand and metal foundry core for use in forming coolant passages in the cylinder block of an internal combustion engine by means of a casting operation, said core comprising an elongated thin-Walled supporting sleeve having laterally extending portions which form with other portions of said sleeve a plurality of transverse openings, said sleeve being formed of sheet steel having a melting temperature not appreciably lower than the normal pouring temperature of molten cast iron, a relatively thin layer of baked core sand and binder packed against all outer side surfaces of said sleeve, and a plurality of barrel cores formed of a baked mixture of sandand binder each having a cylinder-defining portion extending into one of said openings, said cylinder-defining portions being spatially separated from said sleeve to provide a series of interjacent annular spaces for receiving molten cast iron.

References Cited in the file of this patent UNITED STATES PATENTS