US3169638A

US3169638A - Piston manufacture

Info

Publication number: US3169638A
Application number: US155014A
Authority: US
Inventors: William C Reinberger
Original assignee: Thompson Ramo Wooldridge Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1961-11-27
Filing date: 1961-11-27
Publication date: 1965-02-16
Anticipated expiration: 1982-02-16

Description

Feb. 16, 1965 w. c. REINBERGER PISTON MANUFACTURE Filed Nov. 27, 1961 2 Sheets-Sheet 1 u mm 6 z z b 2 2 3 2 ,H W ll L a z b rm m m z 2 ar E i m a m a 1i 4: E a Q m g i i W 6 M M m 2.. 1 L I v 3 2 2 z 0 a Z 2 m m u INVENTOR. M'l/fam C. ee/nberyer' United States Patent 3,169,638 PISTON MANUFACTURE William C. Reinherger, Independence, Ghio, assign-or to Thompson Rama Wooldridge Inc, Cleveland, Ohio, a corporation of Ohio Filed Nov. 27, 1961, Ser. No. 155,014 9 Claims. (Cl. 207-) This invention relates to the forging of metal between punch and die assemblies involving an initial free fiow of the metal to create a plastic metal mass which will easily flow between the punch and die for producing the desired shape without requiring special punch and die contours to create a uniform advancing front of extruding metal and to prevent galling. More specifically this invention deals with the manufacture of trunk type pistons from cast aluminum slugs by impact extrusion of the metal slug between a die and a punch shaped to form the desired piston contour and wherein the slug is initially flattened into biscuit form to cooperate with the die and punch for providing spaces for free lateral flow of the metal to create a plastic flowing mass which can easily flow between the die and punch and wherein the advancing wave of flowing metal between the die and punch is restricted by a punch shoulder to form the desired end shape on the piston skirt.

Heretofore, impact forging of metal articles between a die and a punch has required the use of metal preforrns with excess metal masses positioned at areas where flow of metal is difficult. Further, the punch and die configuration could not be dictated alone by the desired shape for the finished article since contours had to be provided to prevent galling and to assist in the formation of a uniform advancing wave front of metal between the die and punch. As a result, the blank obtained by such prior known techniques had to be machine finished into its desired end shape or had to be equipped with metal fillets and the like excess metal areas which are undesirable in the finished article.

The present invention now eliminates the necessity for uneven distribution of metal masses in the preform and for varying the die and punch shapes from the exact desired contour to produce the finished article. According to this invention, the metal preform need only be shaped so as to center itself in the die and to cooperate with the die and punch for providing free spaces for initial flow of metal to create a free flowing plastic mass which can easily rise into the space between the punch and die, According to this invention, there is no need for controlling the advancing wave front of metal between the punch and die since the punch is equipped with a flow stopping shoulder or abutment which will level off the advancing wave front of flowing metal and will at the same time shape the end face of the flowing metal into the desired contour.

A feature of the invention includes the provision of a V slight gap between the punch and die beyond the punch shoulder for receiving flash of excess metal thereby providing a safety valve effect which will insure the supply of sufficient metal to form the complete article without damaging the punch and die in the event an excess of metal is present.

Another feature of the invention resides in the control of the flash thickness between the punch and die so that removal of the flash by a lathe turning operation will simultaneously turn down the circumference of the article to the desired finished shape and size.

Another feature of the invention resides in the endwise impacting of cast metal slugs to form biscuits which will be self-centering in the extrusion die and will cooperate with the punch and die to provide spaces for free lateral flow of metal during the period of initial piercing of the "ice biscuit by the punch to thereby create a free flowing plastic mass that can easily rise into the space between the punch and die. This creation of the free flowing plastic mass of metal makes possible the use of punch and die shapes which are dictated only by the desired shape of the finished article.

Another and still further object of this invention is to provide a new and improved method for manufacturing an internal combustion engine trunk type piston from a suitable material, such as aluminum alloy, brass, magnesium or low carbon steel.

Other and further objects of the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings,

which by way of preferred embodiment, illustrate the method and apparatus of this invention.

On the drawings:

FIGURE 1 is a fragmentary vertical section of a die and punch having a billet shown in full and dotted lines disposed in a die cavity;

FIGURE 2 is a fragmentary cross sectional view of a die and a punch with the punch shown in elevation for shaping the billet into a hollow type piston;

FIGURE 3 is a fragmentary cross sectional view similar to FIGURE 2 only with the billet being shown partially formed as a result of being struck by the punch and with the punch shown in elevation;

FIGURE 4 is a fragmentary cross sectional view similar to FZGURES 2 and 3 with the punch shown in elevation, and showing the piston blank formed to shape;

FIGURE 5 is a plan view of the piston blank illustrated in FIGURE 4;

FIGURE 6 is an enlarged fragmentary cross sectional view showing a fragment of the piston blank illustrated in FIGURE 4; and

FIGURE 7 is a cross sectional view taken substantially on the line VII-VII looking in the direction indicated by the arrows, as seen in FIGURE 5, only showing the piston turned down to finished diameter and with the flash removed.

As shown on the drawings:

In FIGURE 1, a slug it) is illustrated. This slug may be cut from a solid cast aluminum rod (not shown) which rod may also be made from other suitable materials such as brass, magnesium, or low carbon steel.

In FIGURE 1, an apparatus 11 is illustrated for the purpose of kneading the slug to form a biscuit or billet 12. This billet is of a shorter height and a greater'diameter than the slug as shown by the dotted lines in FIG- URE 1 and the full lines in FIGURE 2. The material used in the manufacture of the slug 16 and the billet 12 may be made from a segment of either cast or wrought bar stock. Cast material is generally preferred because it is less expensive than wrought stock. The billet 12 has a cylindrical side wall 12a with a flat bottom 12b and a convex domed top 120.

The apparatus ll for kneading the slug 10 includes a die member 13 having a die cavity 14 including a flat die bottom 15 which is disposed at an upper end of billet ejector pin 15'. The apparatus 11 further includes a frusto-conical side wall 16 which is joined at one end with the flat bottom 15 and at its opposite end with a circular die Wall 17. A slug punch 18 is vertically movable in the die cavity 14 toward die bottom 15 for the purpose of forming the slug 10 into the billet 12.

Before the slug is formed into the billet 12, it is preheated whereupon it is upset by the apparatus 11 to decrease its length and to increase its radial dimensions, as shown in FIGURE 1. In the operation of the apparatus 11, it will be noted that the cavity 14 of the die that confines the slug is shaped to produce a tapered section or end 12d at one end of the billet. The opposite end has a Preferably spherical or domed surface, as illustrated at 120.

In FIGURES 2-4, an apparatus for forming cup-shaped articles is indicated generally at 23. The apparatus 29 includes a punch 21 and a die 22. The die 22 has a generally cylindrical axially extending die wall 22a as well as a generally radially extending bottom die wall 225. The bottom die wall 221) comprises an upper end surface of a vertically movable piston ejector 2.3, the piston ejec tor being vertically movable after the billet 12 is formed into a piston blank 25 in bore 22a to eject the blank 25 from the apparatus 26. The punch 21 is mounted for reciprocation in a die cavity lie in the formation of the piston blank 25.

The punch 21 is preferably formed with a domed or spherical surface 215 at one end thereof. The punch 21 is further provided with a series of superimposed punch head sections of progressively increasing cross sectional size as identified at 2117, 21c, 21d and 216, the domed surface Ella being disposed on the lowermost punch head section Zlb. Extending vertically on opposite sides of the

punch head sections

21b, 21c and 21d are wrist pin forming portions or notches 21 At the juncture between the

punch head sections

21d and 216, an annular undulated punch shoulder Big is provided which is adapted to axially confront the die cavity bottom 22b.

According to my process, the billet i2 is inserted within the die cavity in such a way that billet surfaces 12:: and 12c are spaced from the die side wall 22a so that as the punch is driven against the blank or billet 12, the blank material is caused to flow from the blank into the spaces around the billet to create a free flowing mass of plastic material as indicated at 12a, 12b and 12d in FIGURE 3. As the movement of the punch is continued, the plastic billet material is caused to flow between the punch and die into the punch notches 21f extruding opposed wrist pin boss portions, as shown in FIGURE 4 whereupon the flow of the plastic material is arrested when it abuts against the undulated punch shoulder 21g.

It will be appreciated the metal is conditioned as it flows into the annular space between the

external surfaces

21a, 21b and 21c and the die side wall 22a so that the material will more readily flow along the punch 21 as it continues its stroke (FEGURE 3).

In establishing proper flow of the metal it is important that a suflicient space he provided to allow the metal to start to flow before it is required to fill the relatively thin shaping piston cavity between the punch and the die, such as between the punch surface 211! and the die side wall 22?. This initial unrestricted'flow of the metal makes it possible to use cast stock or to use metal that otherwise could not be extruded by this process.

By practicing the process described above, it is possible to produce the piston blank or cup-shaped blank 25 as shown in FTGURES 4, and 6. The piston blank or cup-shaped blank has a piston head 25a with a depending ring flange 25b and a center skirt 25c. Wrist pin bosses 25d, 25:! extend from the 25a axially along ring flange b and skirt 15c and terminate at the open end of the skirt. The pin bosses are thicker than the skirt and ring flange.

1n the practice of my method, as the metal in the billet is displaced by the forward motion of the punch 21, it flows unrestricted into a narrow space or die flash cavity 26 between the punch and die untilthe faster moving metal reaches the shoulder on the punch. The other spaces where the metal is moving more slowly will then fill out to the desired len th and any excess metal that may have been contained in the billet 12 can extrucle out through the narrow space or die flash cavity 26 (FIG- URE 4) between the punch and the die surface 22a as flash 25s to prevent damage to the punch and die. After the piston blank 25 is removed from the die cavity by Operation of the ejector 23, the flash is then removed. The flash 254: that is extruded out through the narrow space 26 can be removed by the machine or lathe turning operation that reduces the piston to finished diameter as indicated by the trim line 27 in FIGURE 6. Thus the flash thickness is the same as the thickness of the metal that must be removed to reduce the piston to finished iameter. Therefore flash removal and trimming the piston to size are accomplished by the same operation to form the finished cup-shaped article or trunk type hollow piston 23 (FIGURE 7). a The piston 28 may be further processed by cutting piston ring grooves in the ring flange 25b by drilling wrist pin holes in the pin bosses, in a conventional manner as is Well known in this art.

The impact forging operations of this invention are preferably carried out at elevated temperatures best suited for the particular metal being forged. In the case of high silicon aluminum alloy containing around 16% silicon forging temperatures of from 750 to 950 F. are used.

This process therefore produces a piston of the type with a skirt of varying length without special machining operations to produce the desired configuration at the open end. It is capable of producing pistons with essentially no draft or taper on either internal or external surfaces. By this method, pistons may be extruded without compromising the optimum internal or external configuration to control the flow of metal during the forging process.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

1 claim as my invention:

1. The method of making a cup-shaped article which comprises endwise impacting a metal slug to form a flattened-biscuit with a dome top and a tapered bottom, inserting the biscuit in a die sized to position the apex of the dome top at the axial center of the die and to provide a space surrounding the tapered bottom, inserting a punch in the die having a side wall spaced from the die, a nose initially engaging the apex of the dome top of the biscuit'in the die and a shoulder for limiting flow of biscuit metal between the punch and die, forcing the punch into the biscuit to initially flow biscuit metal laterally into the spaces between the punch and die provided by the dome biscuit top and the tapered biscuit bottom to thereby plasticize the metal, continuing the forcing of the punch into the biscuit to flow the plastic metal between the punch and die and against the shoulder of the punch, and extruding flash metal of controlled thickness beyond the shoulder of the punch to accommodate excess biscuit metal without damaging the punch and die.

2. The method of making die forged pistons from slugs which comprises the steps of heating a cylindrical slug to forging temperatures, forging said slug endwise to decrease the height and increase the diameter thereof and simultaneously to form on one end thereof a domed contour and on an opposite end thereof a tapered contour, centering the resulting billet in a die to cooperate therewith in forming spaces between them for free flow of metal, causing the billet to be forged around a punch initially flowing metal from the billet into the spaces around the billet to create a free flowing mass of plastic material, continuing to punch the billet causing the plastic material to flow between the punch and die extruding opposed wrist pin boss portions and then arresting the flow of metal against a shoulder on the punch to form a skirt, allowing excess billet metal comprising flash to flow axially past said shoulder radially outwardly of said shoulder between the punch and die, and controlling the thickness of the flash so that said thickness is equal to or less than the depth of a cut to be made during subsequent turning of the piston.

3. The method of making die forged pistons from slugs which comprises the steps of heating a cylindrical slug to forging temperatures, forging said slug endwise to decrease the height and increase the diameter thereof forming one end with a domed contour and an opposite end with a beveled contour, centering the resulting billet in a die leaving spaces between them for free flow of metal, causing the billet to be forged around a punch initially flowing metal from the billet laterally into the spaces around the billet to create a free flowing mass of plastic material, continuing to punch the billet causing the plastic material to flow between the punch and die extruding opposed wrist pin boss portions and then arresting the flow of metal against a shoulder on the punch forming a cylindrical skirt and forming an end of the skirt at the open end 'of the piston blank to final shape, and allowing excess billet metal to flow axially past said shoulder radially outwardly of said shoulder between the punch and die.

4. The method of making die forged pistons from slugs which comprises the steps of heating a cylindrical slug to forging temperatures, forging said slug endwise to decrease the height and increase the diameter thereof forming one end with a domed contour and an opposite end with a beveled contour, centering the resulting billet in a die leaving spaces between them for free flow of metal, causing the billet to be forged around a punch initially flowing metal from the billet laterally into the spaces around the billet to create a free flowing mass of plastic material, continuing to punch the billet causing the plastic material to flow between the punch and die extruding opposed wrist pin boss portions and then arresting the flow of metal against a shoulder on the punch forming a cylindrical skirt and forming an end of the skirt at the open end of the piston blank to final shape while allowing excess billet metal to flow axially past said shoulder radially outwardly of said shoulder between the punch and die, arresting the flow of metal initially against portions of a shoulder axially opposite the wrist pin boss portions with the metal then being flowed to fill out the die between the wrist pin portions and allowing excess billet metal to flow amally past and radially outwardly of the shoulder with the piston blank being thereby formed with an annular undulated shoulder at its open end with portions of the shoulders extending axially beyond the bosses to a greater extent circumferentially between the bosses as opposed to portions of the shoulder axially opposite the bosses.

5. An apparatus for manufacturing cup-shaped forged piston blanks having excess flash located along its outside diameter comprising a die and a forging punch mounted for reciprocation in a die cavity defined by the die, the punch having a series of axially related sections of progressively increasing diameter for movement of metal in said die cavity and with an annular undulated shoulder disposed at a lowermost end of the uppermost of said sections, the punch having circumferentially spaced Wrist pin recesses extending axially in said sections terminating axially below said undulated shoulder, the uppermost of said sections having a diameter slightly smaller than said die cavity providing a flash cavity therebetween permitting excess billet material to be extruded axially of said punch shoulder as a billet is forged by said punch.

6. An apparatus for manufacturing cup-shaped forged piston blanks having excess flash located along its outside diameter comprising a die and a forging punch mounted for reciprocation in a die cavity defined by the die, the punch having a series of axially related sections of progressively increasing diameter for movement of metal in said die cavity and with an annular undulated shoulder disposed at a lowermost end of the uppermost of said sections, the punch having circumferentially spaced wrist pin recesses extending axially in said sections terminating axially below said undulated shoulder, the uppermost of said sections having a diameter slightly smaller than said die cavity providing a flash cavity therebetween permitting excess billet material to be extruded axially of said punch shoulder asa billet is forged by said punch, said undulated shoulder having lower shoulder portions disposed in close adjacency to said wrist pin notches and having other shoulder portions spaced axially from the wrist pin notches a greater distance than said lower shoulder portions for forming a cup-shaped piston blank with an undulated piston blank shoulder at its open end.

7. An apparatus for manufacturing cup-shaped articles having excess flash located along its outside diameter comprising a die and a forging punch mounted for reciprocaticn in a die cavity defined by the die, the punch having a series of axially related sections of progressively increasing diameter for moving metal insaid die cavity and with an annular shoulder disposed at a lowermost end of the uppermost of said sections, the uppermost of said sections having a diameter slightly smaller than said die cavity providing a hash cavity therebetween permitting excess billet material to be extruded axially of said punch shoulder as a billet is forged by said punch said shoulder having an annular undulated conformation corresponding to a shape to be imparted to an axial shoulder of a center skirt on a cup-shaped piston blank.

8. The method of making die forged pistons from slugs which comprises the steps of heating a cylindrical slug to forging temperatures, forging said slug endwise to decrease the height and increase the diameter thereof, centering the resulting billet in a die to cooperate therewith in forming spaces between them for free flow of metal, causing the billet to be forged around a punch initially kowing metal from the billet into the spaces around the billet to create a free flowing mass of plastic material, continuing to punch the billet causing the plastic material to flow between the punch and die extruding opposed wrist pin boss portions and then arresting the flow of metal against a shoulder on the punch to form a skirt, allowing excess billet metal comprising flash to flow axially past said shoulder radially outwardly of said shoulder between the punch and die, and controlling the thickness of the flash so that said thickness is equal to or less than the depth of a cut to be made during subsequent turning of the piston.

9. The method of making die forged pistons from slugs which comprises the steps of heating a cylindrical slug to forging temperatures, forging said slug endwise to decrease the height and increase the diameter thereof to form a billet, centering the billet in a die with the outer walls of the billet being spaced radially inwardly from the die walls to provide free space between the die and the billet, inserting a punch in the die with the side wall of the punch being spaced a predetermined distance from the die and having a nose initially engaging one end of the billet in a die and a shoulder for limiting the flow of billet metal between the punch and the die, punching the billet and initially radially flowing metal from the billet into the free space around the billet to create a free flowing mass of plastic material, continuing to punch the billet and causing the plastic material to flow between the punch and die extruding opposed wrist pin boss portions, and arresting the flow of metal against a shoulder on the punch to form a skirt.

References Qited in the file of this patent UNITED STATES PATENTS 1,720,722 Dean July 16, 1927 2,360,354 Lyon Oct. 17, 1944 2,679,931 Cigliano June 1, 1954 2,740,519 Sparks Apr. 3, 1956 2,795,467 Colwell June 11, 1957 FOREIGN PATENTS 94,882 Switzerland June 1, 1922

Claims

1. THE METHOD OF MAKING A CUP-SHAPED ARTICLE WHICH COMPRISES ENDWISE IMPACTING A METAL SLUG TO FORM A FLATTENED BISCUIT WITH A DOME TOP AND A TAPERED BOTTOM, INSERTING THE BISCUIT IN A DIE SIZED TO POSITION TH APEX OF THE DOME TOP AT THE AXIAL CENTER OF THE DIE AND TO PROVIDE A SPACE SURROUNDING THE TAPERED BOTTOM, INSERTING A PUNCH IN THE DIE HAVING A SIDE WALL SPACED FROM THE DIE, A NOSE INITIALLY ENGAGING THE APEX OF THE DOME TOP OF THE BISCUIT IN THE DIE AND A SHOULDER FOR LIMITING FLOW OF BISCUIT METAL BETWEEN THE PUNCH AND DIE, FORCING THE PUNCH INTO THE BISCUIT TO INITIALLY FLOW BISCUIT METAL LATERALLY INTO THE SPACES BETWEEN THE PUNCH AND DIE PROVIDED BY THE DOME BISCUIT TOP AND TAPERED BISCUIT BOTTOM TO THEREBY PASTICIZE THE METAL, CONTINUING THE FORCING OF THE PUNCH INTO THE BISCUIT TO FLOW THE PLASTIC METAL BETWEEN THE PUNCH AND DIE AND AGAINST THE SOULDER OF THE PUNCH, AND EXTRUDING FLASH METAL OF CONTROLLED THICKNESS BEYOND THE SHOULDER OF THE PUNCH TO ACCOMMODATE EXCESS BISCUIT METAL WITHOUT DAMAGING THE PUNCH AND DIE.