US1556138A

US1556138A - Mold and method of casting

Info

Publication number: US1556138A
Application number: US654560A
Authority: US
Inventors: William G Wehr
Original assignee: CLEVELAND ELECTRIC TRAMRAIL CO
Current assignee: CLEVELAND ELECTRIC TRAMRAIL CO
Priority date: 1923-07-30
Filing date: 1923-07-30
Publication date: 1925-10-06
Anticipated expiration: 1942-10-06

Description

w. WEHR MOLD AND METHOD OF CASTING Filed Juljso, 1925 2 sheets-shew 1 W. e, 1925. lmmss W. G. WEHR MOLD AND METHOD OF CASTIR Filed July 50, 1923 2 Sheets-Sheet 2 mW/A , Patented ca. c.1925.

PATENT OFFICE.

-' e. warm, or r cnnvnnann, omo, nssrenon. 'ro THE CLEVELAND ELEC- OF 'WIGKLIFFE, OHIO. i

mean em) i'rn'rncn or cnsrme.

Application filed July 30, 1923. Serial No. 654,560.

To all whom it may concern.

Be it known that LWILLIAM G. WEHR, a citizen of the United States, residing at East Cleveland, in the county of Cuyahoga' and State of Ohio, have invented a certain new and useful Im rovement in Molds and Methods of Casting, of which the following is a full, clear, and exact description.

This invention relates to improvements in molds and to a method of casting, the principal object being to provide means for obtaining a chill on the inner surface, usually an annular surface, of cast iron or semi steel castings, such as are employed to produce wheels, gears and the like, or hubs of the same.

A further object is to materially reduce the cost of wheels and the like adapted to be fitted with ball or roller bearings, particularly bearings of the combined radial and end thrust type, by forming or chilling the metal around the inner bore on a single or double taper so as to enable raceways to be formed directly in the hub portion. Still further the invention aims to do this in amanner such as to reduce the amount of machining or grinding necessary to provide the raceway groove or grooves.

The art of chilling cast iron by use bf metal chills is, of course, old and well known,

but as far as I am aware it has not been feasible to. chill the metal around an inner annular opening because of the stresses in the contractio of the metal causing the metal to grip t e chill and generall result ing in cracking of the casting, or s rinking onto the chill so tightly it cannot be removed. With my invention a metal chill can be used to chill the metal around an inner opening and at the same time the bore is so she. ed as to permit the formation of raceways "rectly in the cast' andthere'fore to subse.-

. quentl provide ,awheel equipped with a ball or roller bearing which is extremely durable and is produced at a relatively low cost as compared with constructions wherein separate inner and outer raceway members formed of hardened steel are required.

The invention may be briefly summarized as consisting in certain novel details of construction, and combinations and arrangements of parts, and in certain novel ste s of the improved method which will be; e-

scribed in the specification and set forth in the appended claims.

In the accompanying sheets of'drawings wh1ch illustrate my invention in a few of the numerous possible modifications, Fig. 1 1s a sectional view through one type of mold which may be utilized, and having a chill formed in accordance with the preferred form of my invention; Fig. 2 is asectional view through a casting produced by the mold and chill of Fig. 1, and showing conventionally the approximate depth of the chill which in this instance, though not necessarily, extends all about the casting; Fig. 3 is asimilar view after the raceways (two raceways in this case) have been ground into the inner chilled surface; Fig. lis asectional view showing a mold in which there is a slight modification-in the shape of casting to be produced; Fig. 5 ma sectional view through'the casting which in this instance constitutes the hub of a gear, this view showmg the racewaygrooves after being ground therein, and showing the gear proper shrunk onto the outer surface of the casting; and Fig. 6 is a sectional view showing my invention'ap'plied to a sand mold.

My invention finds great utility in the pro:

duction of wheels, for vehicles of many different types, including both track and road wheels, or simply the hub portions thereof, in which'event the outer ortions of the wheels are designed to be s runk; or otherwise secured to the inner or hub 'ortions which are cast in accordance with t e presentinvention. The invention is applicable also for the production of such other devices as gear wheels, pulleys and the like, all of which are re arded as embraced under the name wheel wherever used in the specifica 'nated 13, and the upper ta divided-mold is employed having a lower portion or drag 10 and an upper portlon or cope 11. The mold cavity is shown filled with metal indicated at 12.

The chill for chilling the metal around the inner bore or opening of the casting 1n this instance consists of two parts or

members

13 and 14, the member 13 being in the instance carried by the lower part 19, and the member 14 in this instance projecting up through the upper part 11 of the mold and being formed separately thereof and slidable up through the top thereof. The two members 13 and I l-of the chill are in alignment and are held so by the equivalent of a dowel-pin 15, which is preferably fitted tight in one chill member, in this instance the upper member 14, and is slidably fitted into an opening in theother chill member.

In accordance with the present inventionthe chill, i. e. the chill for chilling the metal around the inner boreof the casting is formed with a taper which admits of an axial slippage or relative movement between the chill and the cast metal as it contracts, and thus the gripping of the metal on the chill and danger of the cracking of the casting are avoided.

In this instance the two

chill members

13 and 14. have opposite tapers, and, in fact, each has a double taper, one tapered portion of each chill member being at a different angle than the other. However, I do not regard either of these characteristics as essential, though both are preferred, and when used, certain important advantages are obtained. In other words, I regard it within the scope of my invention in its broader aspects to provide a chill composed of one member havin a continuous taper in one direction, and also regard it as within the scope of my invention when two chill members are provided, such-

asthe members

13 and 14, to provide each with a continous or single taper. As I now re ard the scope of my invention, it is essential only that the .chill member or members have a taper such that when the casting or congealing metal contracts onto the chill there may take place the relative slip age or movement in an axial direction w n the radial stressesoccur due to the shrinkage of the metal onto the chill.

The two chill members, 'such as 13 and 14, are preferably employed when the wheel is to be fitted with two sets or series of bearing members, i. e. balls or rollers, and when it is to be fitted with racewa s to form a part of a double combined ra ial and end thrust bearing for end thrust in either direction. As stated above, each

chill member

13 and 14 is provided with a double taper. In Fig. 1 the ower taper of the member 13 is desigeris designated a corresponding 13". In a similar fas site directions but to have a tapered portions of the upper member 14 are designated 14 and 14". It will be observed that the taper ofthe

portions

13 and 14? is somewhat steeper than the taper of the

portions

13 and 14, That is to say, the inner portions 13 and 14' are inclined to a somewhat greater extent than the

portions

13 and 14. The purpose of this will be explained presently..

When the metal is poured into the mold cavity 12 the metal as it congeals begins to contract around the inner chill. But b tapering the chill members the latter an the casting or contracting metal slip relatively instead of binding tightly and without causing the casting to be cracked as would occur if the taper were not provided. This slip-. page or relative movement occurs in an axial direction and the efiect is to push the upper chill member 14 upwardly slightly through the upper mold member 11, and the'casting itself rises up onto the lower chill 13, lifting slightly the upper mold member 11-.- The upper chill 14 might be formed integral with the upper mold member 11 in the same manner that the lower chill 13 is formed integral with the lower mold 10, but by forming it separately, as shown in Fig. 1, the metal or casting 12 has less weight to lift when it sli s upwardly on the lower chill member 13. s the result of the use of the mold and the method of chilling as described above with the mold shaped as shown in Fig. 1, there is produced a casting such as shown at 16 in Fig. 2. In this figureI have indicated blyl stippling, the a proximate depth of the F c 1 11, and althoug the chill extends all around the casting, as already stated such need not be the case as will ap ear subseof the'casting. Likewise it will be noted that each tapered ortion has two distinct tapers 17 a and 17? ue to the fact that each chill member has portions tapered at different angles. The efi'ect of this is toproduce a casting with an inner or hub portion having a bore which is of minimum diameter at the central plane or where the taper in opposite directions begins (Whichmay or may not be m .the'center plane) and each tapered wall having a general concave shape. That s to say, each wall is not only tapered but dished inwardl somewhat.

As far as the chilling edict is'co'ncerned, the same results would beobtained if each chill member had one continuous taper, but

by providing-the two tapers on each chill member and thus causing the inner wall of the casting not only to be tapered in oppogeneral concave form, less grinding or machining is required, 1. e. less metal is to be cut away, when the It will be understood from the above, that i the casting is to be provided with oppositely tapered portions, each of a general concave nature. This is produced (as shown in the drawings and as described above) by giving each chill member two conical or tapered portions tapered at different angles with respect to the axis of the mold, but it will be obviousthat the same results could be ob tainedif each chill member had more than two conical tapered portions or-Jif the tapered portion were in the form of a continuous curve. Suchmodifications I regard as being clearly within the scope of the present invention.

The casting such as shown in Figsnl, 2 and 3 has been produced by me in great numbers, and is generally employed for the wheels of certain types of cranes and when thus employed the wheel is mounted on a pin or axle preferably provided with hardened steel inner raceway members. When the wheel itself is cast in the manner described above and is provided with raceway grooves, which in the instance shown accommodates ball bearings indicated at 18, the metal forming the grooves is exceedingly hard and desirable in all respects to form bearing raceways, and I am thus able to do away with the necessity of separate outer raceway members. The chill at the periphery of the wheel is desirable to provide a hardened tread. By casting the wheel in the metal mold no machining at all is necessary except that required to grind the race way grooves. v

As reviousl stated, the exterior shape of the w eel or w eel hub may be anything desired, and in Fig. 4 I show a mold used quite extensively by me for the production of a casting 1 the inner part of which-is chilled and shaped like the casting shown in Figs. 2 and 3, but the outer or peripheral part has a portion on which a gear 20 is shrunk, and a portion designated 19 which serves as a tread to run along a trackway.

The device shown in Fig. 5 is employed by' me as a driving gear on an electrically propelled crane tro ey. In Fig. 4 the lower and upper mold members are designated 21 .and 22, and the chills are designated by the are precisely the same as reference characters 23 and 24.

The function of these chills and the method of casting reviously described, and further descri tion of the construction and operation is t erefore unnecessar Iii the figures so far described, metal molds are shown, but as already stated, my method may be utilized with sand molds,

and in Fig. 6'I have illustrated one way in which this may be done. The flask here shown has a drag 25.and a cope 26. In this instance the chill for chilling the metal around the inner bore of the, casting, which is here designated 26, consists of two members as before, i. e. a lower chill 27 carried by the drag, and an upper chill 28 carried by the cope. In this instance I employ also an outer chill29 for chilling a portion of the periphery of the casting, but this is not cssential, and, if desired, only the metal surrounding the inner bore may be chilled in accordance with my invention.

With this mold the metal surrounding the inner bore is chilled precisely the same 'way as before described by a slippage or relative movement in an axial direction between the shrinking cast metal and the

chill members

27 and 28. To'permit or accommodate this, the chill members may be forced outwardly into the sand a slight distance, or the cope may be lifted slightly from the drag when the relative movement occurs, or both may occur, this depending to a large extent on the manner in which the sand is rammed.

Itwill thus be seen that I have provided an improved mold and an improved method of casting having very important advantages in the production of certain kinds of castings, particularly wheels designed to be "ings because of the little machine work and small waste of material, while at the same time, raceways are provided, admirably adapted for this purpose by their wear resistlng qualities.

As before stated, this'invention is very useful in the production of cast iron or semisteel castings, but particularly of cast iron castings preferably of low silicon content to i get the desired depth of chill.

While I have shown the preferred form and certain modifications of my invention,

I do not desire to be confined to the precise details shown, but aim in my claims to cover all modifications which do not involve a departure from the spirit and $00 of my invention as defined 1n the appen ed claims.

Having described my invention, I claim: 1. A mold having a chill for'chilling the metal around the wall of an inner o enin 2. A mold having a chill for chilling the metal around an inner opening, said chill being tapered in such a manner as to produce in the casting a tapered opening with a general concave form.

3. A mold having a chill for chilling the metal around an inner opening, said chill having inner and outer portions tapered at different angles, the inner portion having a greater taper than the outer.

.1-. A mold having a chill for chilling the metal around an inner opening, said chill serving to impart to the chilled metal a double taper, the two portions being tapered in opposite directions and each being of general concave form.

5. A mold having a chill for chilling the metal around an inner opening, said chill composed of two ali ed tapered members having a taper such t at they are caused by the gripping action of the coolingcastln to have relative movement during the chilfing operation in a direction axially of said opening, said members imparting oppositely disposed tapers to the chilled metal. 1

6. A mold having a chill for chilling the metal around an inner opening, said chill composed of two aligned tapered members relatively movable during the chilling oper ation in a direction axially of said openlng', said members imparting oppositely disposed tapers to the chilled metal, each tapered portion being of a general concave form.

7 A mold composed of upper and lower members, each carrying a chill adapted to be arranged end to end and having inner ends tapered at an angle such that the gripping action of the cooling casting will cause the chills to move apart.

nsaeuss 8. A mold composed of upper and lower members, each having a tapered chill for chilling the metal around an inner opening of the casting, the chill carried byone memher being movable relative to said member during the chilling operation in a direction axially of said opening.

9. mold composed of u per and lower members and a chill for ch1 ling the metal around an inner opening of the casting, said chill composed of two pa s, one fixed into the lower member and t e other movably supported in the upper member.

10. The method of producing a chill in the metal around an inner opening of a casting, which comprises pouring the metal in a mold around a chill and permitting a slippage between the contracting metal and chill to prevent the metal gripping the chill and cracking the casting.

11. The method of producing a casting with a chilled portion around an inner opening, which comprises pouring the metal in a mold cavity around a chill and preventing cracking of the casting by causing the forces incident to contraction to produce a relative movement in an axial direction between the contracting metal and chill.

12. The method of producing castings having a chilled wall around an inner 0pening which consists in pouring the metal in a mold cavity around a chill and utilizing the forces incident to contraction of the metal to cause a relative shifting between the cast metal and chill in a direction axially of said opening. 7

In testimony whereof, I hereunto ailix my signature.

- WILLIAM G. WEHR.