US1781098A - Method of and mold for casting piston rings - Google Patents

Description

E. N. BRODERICK El' AL METHOD 0F AND MQLDv FORCASTING PIsToN RINGS Nov. 11, 1930.

Filed Dec.

Patented Nov. 1l, 1930 l UNITED STATES PATENT OFFICE ERNEST N. DRoDnBIcx AND THEOPHEILES D. LUCIER, oF DETROIT, MICHIGAN l w METHOD or AND MOLD FOR CASTINGYPISTON RINGS Application mea December 2o, 1926. serial No. 155,845.

This invention relates/to the casting of cles of molding sand entrapped within the piston rings, its principal object being to prosurface layer during the setting lot the metal. vide an improved method of producing cast- Or if the sand mold be Well made and proings in quantities whereby the metal in each .tected, this sand entrapping may be practiv5 completed ring will `be substantially vfree cally negligible but the oxidizing and chilling 55 from strains, ycementite, sand holes, blow of the. surface will still produce a characterh'oles' and other imperfections common 4to istie hard surface layer. `This harder surstill poured metal and operablev to produce face is hereinafter referred to as the sealev undesirable distortion therein when the ring When piston rings are individually cast, the i is machined or in its subsequent use. common .practice has been to remove the scale 60 Fur-ther objects of the invention are to proof the cast iron from the top and bottom of vide a method of casting rings of the type the ring from its outer periphery, as Well as shown in a copending application, Serial N o. to remove adhering masses of metal or sprues 421,893, filed November 5, 1920 (since pa. from the interior periphery of the ring.

tented July 12,1927, No. 1,635,530), in which This adhering metal may form a portion of 65 a ring is described having certain of its sur the ingate by which the metal has entered the faces provided with a hard, elastic and unmold or may beformed by the overflow in broken scale, except at 'the pointat which the the molding process as will be well underring is split, in order to maintain the warpstood by those acquainted with the art to 59 ing stresses normally present in a cast 'which the invention appertains.

ring inactive to a degree rendering the said `When this internally extending metal is ring proof against such warping after castbroken or cut away from the-inner periphery ing and machining; and to obtain a castlng ofthe ring, the scale of the inne-r periphery which may be machined to meet the usual Iethereof is also broken as a natural consequirements of a piston ring and having such quence, and 4this s cale is verydesirable in an 75 scale protected walls in addition to a softer unbroken condition due to the fact that it Wall onl its outer periphery after machining. will eectivelyl counteract warping stresses Still further objects of the invention are t0 v1n the ring, a ringso treated is readily deprovide a method of producing annular castformed; so thatitjs evident that if uniformings having great homogeneity vof metal 1ty of sprlng tension in the ring is to be se- 80' throughout the casting and in which any eX- 'cured 1t must be so-cast lthat no sprues `or cess of metal and any.7 loose material Within projections requiring removal must be the mold will be carried out of the mold; formed on its inner periphery. These reand to provide means ensuring the compresmarks also apply to the top and bottom of sion of metal inthe molds during casting the ring upon which an unbroken circle of 85 by resisting the release of overflow from the scale is very desirable for similar reasons. molds, g An important feature of our invention is Still further objects subsidiary to and re the securing of the elimination kof sprues or sulting from the above objects, or from the projecting masses of metal upon the inner- 19 construction or operation of the invention as periphery of the ring or upon the top and no it lnav be carried into eiect, will become bottom of the ring adjacent such inner 'peapparent as the said invention is hereinafter riphery. Metal is driven by centrifugal further disclosed. force through an ingate into and around each..

When iron is cast within a mold, the surof a series of annular spaces in a rotating i5 face in contact with the mold is generally mold to an outgate, and the said ingate and 95 harder than the metal within the interior of the outgate orices are connected to each of the casting. This is partially due to the the annular spaces forming the ring molds chilling of the surface layer bycontact with at proximate to their outer peripheries so that the relatively cooler mold surface, and if the sprues will remain attached to the outer vsand molds are used, is partially due to partiedges of the ring blanks. These edges are 'nuo preferably formed 'with an annular rim adapted to be cut away in nishing the rings. It will thus be evident that an inner U-shaped scale forming the inner periphery of the finished ring and the adjacent portions of the top and bottom thereof will be left substantially intact and free from any interruptions or breaks such as result from the removal of sprues formed in the ordinary processes of casting.

The invention is more particularly described and ascertained hereinafter by way of example, having reference to the accompanying drawing, wherein,-

Figure l is a verticalA section through a preferred form of Inold adapted for the carrying out of the said invention, the said section being taken on the line I-I of Fig- Figure 5 is a transverse section of such' blank showing the nature ofthe connection between the two rings, and

Figure 6 is a section on the line VI--VL Figure 5.

Similar characters of reference indicate similar parts in the several figures of the drawing, and Figure 4 is drawn to a larger scale than Figures 1, 2 and 3, and Figures 5 and 6 to a larger scale than is Figure 4.

In the said drawing, there has been shown av form of mold suitable for carrying out of the present process, and the production of ring castings of the type described in our application for Letters Patent Serial No. 421,893, though it will be understood that the invention is not limited to the precise details of the mold herein shown, since it will be apparent that the design of the molds may be varied to suit 'different requirements without departing from the essential features of the process herein described.

l indicates a rotatable driving shaft upon which is mounted a head 2 provided with arms 3 bearing posts l secured thereto by nuts 5, the upper ends of the said posts receiving a yoke 6 which is bored to provide an internally tapered shoulder 7. rIhis shoulder` 7 is adapted to bear against an external tapered shoulder 8 of an annular lrib 9a formed on a two-part casing, the parts 9 and 1() of which together form a vertically parted cylinder. The lower end of the cylinder rests on a circular table 11 provided with a casing-engaging flange 12 and a boss 13 which nests in the upper end of the head2. The yoke 6 forms a clamping means for the two parts of the cylindrical casing, as will be readily-seen from the drawing, and the top of the casing is preferably enclosed except for a central opening 10a provided therein.

Although it is possible to cast rings singly by our process, as will be readily understood, for the purposes of economy it is preferred to cast the rings in plurality or gangs, the said process being particularly adaptable to such form of production; and in the drawing we show an arrangement whereby the upper rings are gated iirpairs and the lower ones in quadruple although the number of rings which may be gated together is only limited by the peculiarities of molding which are well known to those skilled in this art.

To carry out our process with the device under consideration, we provide a core 16 which has formed therein ring channels 16a of a T configuration in cross section, the outer parts of which channels are enlarged to form annular recesses 16, the purpose of which recesses is hereinafter described, and this core is surrounded by a two- part lining 14, 15 within the cylindrical casing? 9, 10. To give access to and egress from the s aid channels 16a gates 16c and 16d are provided in the form of grooves in the core extending between the marginal recessed parts 16b of the said channels.

The core 16 is provided with a central pouring orifice 17 located beneath the opening 10aL in the top of the cylindrical casing, and extending radially from this orifice 17 are ingate openings 18, 19, 20, 21 and 221com- -municating with the grooves forming the gates 16c in the core and incidentally with the associated annular channels in the said core; and on the opposite side of the core outlet openings 24, 25, 26, 27 and 28 are provided leading from the grooves forming the. g'ates 16d and extending radially inward thereof to a riser 30 formed in and extending longitudinally of the said core. This riser is preferably formed with an off-set enlarged channel 8a the purpose of which is hereinafter explained. The table 11 is also provided with an outlet opening 32 contiguous to the foot of the riser 80. 2

The device described is intended to be rotated rapidly on or by the shaft l, during which rotation molten metal is poured through the opening 10a into the orifice 17 of the core and is centrifugally driven through the ingate openings 18, 19, 20, 21 and 22 and through the gate grooves 16c into the channels 16a until the said channels are filled with the molten metal, whereupon the said metal commences to extrude through the openings 24, 25, 26, 27 and 28 toward or into the riser 30.

The said outlet orifices are somewhat re stricted or of smaller capacity than the inlet orifices so that, upon the centrifugal action referred to being brought into effect and the channels being filled with molten metal, the

compression of the same metal within the said channels is effected due to the centrifugal force and also to the restriction of the outlets from the said channels so that a very compact-casting may be secured; and, furthermore, due to the radiating direction of such force the heavier metal is driven into the channels and the lighter impurities djsplaced thereby from the channels, such impurities finding theii` way through the radial openings and thus freeing the castings therefrom.

An econom of metal is also secured due to the positive lling of the channels irrespective of the complete filling of the central orifice 17 as it will be realized that sufficient metal may be poured into the revolving mold to fill the said channels and wholly or partly fill the gates and inlet and outlet orices without requiring the provision of excess metal in the central pouring orifice. This orifice 17 is preferably tapered upwardly as shown so that the centrifugal whirlpool action of the metal will eHect its flow over the walls of the said orifice and ensure the result last referred to.

In practice it has been found that very eilicient castings can be produced leaving only a thin film of metal on the Walls of the said orifice 17 which film is usually found to contain the impurities displaced by the forces acting upon the metal in the channels and to be perforated by the gases oecluded Y from such metal in the channels.

Figure 4 illustrates a casting so produced wherein it will be seen that the rings 35 as cast are provided withupper and lower peripheral ribs 35at and 35h, respectively, formed by the recesses 16b of the channels 16a, and that the rib 35a ofthe lower ring is connected to the rib 35h of the u per ring by means of gate members 36 an 36a formed by the grooves 16c and 1.6dof the said core, from.`

which gate members sprues 37 and 37a, formed by the inlet and outlet openings of the said core extend. It will also be seen,

.especially from Figur'e 5 and Figure 6, that the said gate members connect with the said case shrinkage losses'transmitted throughout the rings might seriously warp the castings where a large number were being made.

40 indicates reinforcing members extendf` ing upwardly through the core 16 to ensure it against any relative movement or distortion in the liningv 14, 15, and may be used vaccording to necessity'or desirability.

In producing piston ring structures in this particular way, not only is it possible to produce the final casting in such way asto provide the skin effects on the final product heretofore pointed out, but, in addition, the particular method employed in casting ensures that the body of the ringl itself will be of a homogeneous texture throughout, a condition that is more or less difficult when casting by centrifugal action.

This will be readily understood by consid-v ering the conditions 'set up inthe structure shown in Fig. 4, which presents a perspective view of one of the `pairs of'r'ings which are cast in the mold of the remaining figures, and

in which the part 37 may be considered as the inlet sprue and 37a the outlet sprue, the

former being produced in the gate leading.

from the supply, while the latterl sprue is the metal in the gate opening into the channel 30.

As will be understood the centrifugal force is active in both' ofthese gate, being greater in effectin the inflow gate than in the outflow gate, sincesthe former is not only larger in cross-sectional area, but in the infiow gate the body of metal of the supply is being forced outwardly by this action so that there is the force'provided by this larger body acting to force a flow of metal into the cross-connectionsv 36;- outward. pressure is also acribs 35 and 35b solely so that the ring cast-5% tive in thel outflow gate, but here the ings are provided withv surfaces 35, 35d and 35e-the scale of which is unbroken upor-.the

severing of the gate members 36 and 36.i from.

the rings'when the said rings are separated.

ribs 35a and 35h-together with the machining of the outer peripheral face of the said rings, and it will be obvious that after such machining the scale is unbroken on the inner periph-A ery 35d of the rings and that-the scale surfaces 35"Y and 35e will also remain unbroken. Consequently, wnen the ring isparted at any pointas is usual in piston rings this scale forms means positively counti'acting internal stresses in the rings which would otherth'e additional force that is present in the in-v fiow gate, the excess metal being carried into the enlargement 34 by the action of the centrifugal force. Hence, the centrifugal action in the outflow gate serves to set up a counter pressure to the flow of metal toward the outlet, but the value of this pressure is less than that present in the infiow gate. As a result, it will be evident that a flow of metal will be had from the infiow to the outflow, with the flow rate dependent on the differential between these forces.

In this .condition of a flow of metal the casting ofthe rings in'pairs or multiples and the use of the cross connections 36 and 36a is of importance. This will be' understood from the fact that the cross-connections have'their outer face coincident` in plane with the o uter face of the rings and therefore have the same centrifugal force value as is present in the rings themselves, and also to the location of the cross connections.

As will be understood, the radial How of metal is in a direction such as to be entirely outside of the ring cavities, so thatthere is no radial pressure present within ythe said cavities other than is set up by the thickness of the cavities, the additional pressure being placed on the metal in the crossconnections. Hence, the flow of metal within the ring cav,- ities. is not materially disturbed by the centrifugal force, the latter tending to produce an equal pressure within the -ring cavities. But this condition, as. an aid to the homogeneous texture'is amplified by the fact that the flow of metal to the ring cavities is lateral and in the plane of the'ring, with .the same character of action present at the outlet of the ring cavities into the cross-connections, the opposing streams of metal which meet at such outlet, not meeting as the end of a path of movement, but coming together and providingr the lateral ilow through the outlet intothe cross` connection, so that'the juncture is made of a flowing metal instead of a static' metal, the counter pressure preventing a too rapid low and thus ensuring that the texture at both the entrance to and outlet from a ring cavity will be similar to that of the remainder of the ring, and preventing the production of any blow-holes, etc., through trapped air, etc., the latter being driven out ahead of the -liowing metal.

`vided paths, and which are subjected to the radial pressures of differential values. 4

-One advantage in this respect is the fact that because the result is obtained byv a flow of metal in this way, the length of time the mold is rotated to produce the centrifugal action is not required to be so accurately gaged,

assuming a sufficient amount of metal is present. As will be understood, an excess period of rotation does not change the texture conditions,.'since the metal will continue to flow while the rotation continues, with the result that a greater amount of excess metal will' pass through the outlet as the rotation is continued beyond that which would be normallyrequired., Assurance can'thus be had of a the presence of the excess will indicate'that -which it connects. complete and proper casting-operation, since the ring cavities are properly filled and Will remain so as long as there is metal present in the supply to set up the major pressure of the prising a core having an annular channelformed therein and a pouring orifice formed Within said channel, said channel having marginal extensions,` and gates connecting said orice exclusively wlth said ymarginal extensions, said gates having a depth notI greater than the width of said marginal extensions atV the point of connection therewith. 3. A mold for casting piston rings comprising a core having an annular channel formed therein and a pouring oriiice formed Within said channel, a gate connecting said orifice with said channel, and an outlet from said channel, said outlet being restricted relatively to said gate in order to provide back pressure.

4. A mold for casting piston rings in m'ultiple, comprising a core having a series of annular channels formed therein and a pouring orifice formed within the confines of said channels, gates connecting said orifice to saidl channels, outlets extending from said channels, a riser' formed longitudinally of said core and connected to4 said outlets, said riser having an offset enlarged portion for the purpose describedy I 5.- In the art of casting piston rings in multiple by centrifugal action, a rotatable mold having ,spaced ring-cavities connected by spaced connection cavities, a supply cavity,

an outlet passage, a connection between the supply cavity and a connection cavity, and a second connection between the outlet passage and a second connection cavity, the ringv and connection cavities being located in a zone of greater centrifugal pressure than the similar pressures of the supply cavity and the outlet passage.v

6. -A mold as in claim 5 characterized in ythat the location of the outlet passage is in a zone of greater centrifugal pressure than the similar pressurelof the supply cavity.

17. A mold as in claim 5 characterized in that the outleJ passage includes a lateral extension leading in the direction vof greater centrifugal pressure.

8. A mold as in claim' characterized in that-the outer face of a connection cavity is alined with the outer face of the ring cavities 9. .In the art of casting piston rings in multlple by centrlfugal action, a rotatable mold having ring cavities spaced the maximum distance from the axis of rotation, the ring cavities of a multiple group being spaced apart and connected together at spaced points, the outer face of the ring and connec-v tionVK cavities being alined, a central supply cavity, a connection between the supply cavity and one of the connection cavities to provide an inflow gate for the metal to the cavities, and an outlet passage for excess metal located intermediate a second connection cavity and the axis of rotation, said passage being connected with such second connection cavity by an' outflow connection, whereby a flow path is established between the supply cavity and the outlet passage with the ring and connection cavities located in a zone of centrifugal pressure greater than that of the supply cavity and the outlet passa e.

t). A mold as in claim 9 characterized in that the outlet passage includes a lateral extension leading in the direction of greater centrifugal pressure.

11. In the art of casting piston rings or the like by centrifugal action, the process which consists in establishing a flow-path for the ring metal, the metal in said flow-path being subject to centrifugal action,said iowpath including an intermediate annular por.

tion having the cross-section of the desired cast product,A said annular portion -having the maximum centrifugal force pressure applied uniformly as respects the direction of length of the annular portion, the flow of metal to and from the annular portion being in directions lateral of the annular portion and having centrifugal force pressure of similar value to that of the annular portion of the How-path with the entrance to and exit from the annular portion open to the free passage ofl metal therethrough, said entrance and exit being substantially diametrically opposite each other relative to the annular ortion, the ends of the flow-path extending substantially radial to the lateral portions of the Aflow-path, whereby the flow of metal through the entrance to the annular portion ofthe How-path will freely divide vand pass in opposite directions toward the exit with the excess metal passing through the exit in a lateral direction intothe exit end of the flow-path to complete the metal of the desired cast product intermediate to and connected with vthe metal of the lateral portions of the How-path at the conclusion of the centrifugal action.

12. A process as in claim 11 characterized in that the end of the outlet portion of the How-path terminates at a greater distance from the axis of rotation of the ow path than the inlet end portion of such path, whereby the metal of the radial portion of the outflow will exert a counter pressure to the discharging metal of less value than the pressure exerted bythe metal of the radial portion of the inow of metal.

13. In the art of casting piston rings or the like in multiple by centrifugal action, the process which consists in establishing a flow-path for the ring metal, the metal in said path being subject to centrifugal action, said flow-path including an intermediate portion temporarily divided to form individual paths within such intermediate portion, said individual paths being subjected to the maximum centrifugal force pressures and including the mold cavities of adjacent spaced-apart axiallysalined ring cavities extending in parallelism, the undivided vend portions of the flow-path being subject to centrifugal force pressures oflless pressure value the outlet end portion serving to set up a counter-pressure activity, the individual paths being connected together at oppositely-spaced points with the connections ex- Y tending laterally between the paths in the zone of maximum centrifugal force pressure and forming the sections of the {low-path from and to which the individual-paths lead.

14;. A process as in claim 13 characterized in that the out-let end of the flow path terminates a greater distance from thel axis of the individual paths'than the entrance to the inlet end portion of the flow-path, whereby the counter-pressure is of lesser valuev as a pressure source.

15. AA process as in claim 13 characterized in that the outlet end of the flow path terminates at a greater distance from the axis of the individual paths than the entrance to the inlet end of such flow-path, the outlet end portion terminating in a cavity. zone leading laterally in the direction of greater centrifugal force pressure, whereby the metal discharged from the outlet will be ineffective to increase the counter-pressure force of the outlet portion of the path.

In testimony whereof we aflix our signatures.

^ ERNEST N. BRODERICK. THEOPHEILES D. LUCIER.

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