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Патент USA US3093903

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June 18, 1963
c. A. SPARKS
3,093,890
METHOD FOR IMPACT-FORMING SLIPPER-TYPE PISTONS
Filed March 4, 1958
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INVENTOR.
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BY
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June 18, 1963
c. A. SPARKS
3,093,390
METHOD FOR IMPACT-FORMING sLIPPER-TYPE PISTONS
Filed March 4, 1958
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INVENTOR.
' CLEO/V5 Aer/we Jwrezs
“MQKW7
3,093,890
United States Patent ()?iee
Patented June 18, 1963
1
2
includes preheating of the metal slugs of predetermined
weight, lubrication of the punch ‘and impact forming dur
ing which ?ow of metal into skirt portions is promoted
3,093,890
METHOD FOR IMPACT-FORMING
SLIPPER-TYPE PISTONS
Cleone Arthur Sparks, 1979 E. Colorado Blvd.,
Pasadena, Calif.
Filed Mar. 4, 1958, Ser. No. 719,006
while flow of metal into areas adjacent wrist pin bosses
is restricted and retarded ‘by application of forces which
form contoured end faces of short skirt portions adjacent
the integral bosses. Flow of metal into wrist pin boss
recesses is promoted by venting such recesses. As a result
2 Claims. (€l. 29-—156.5)
This invention relates to a method of and apparatus
for making a forged slipper-type piston having integral
of such concurrent and virtually simultaneous steps, a
10
head, skirt and wrist pin bosses by a single impact ex
trusion operation.
Although many attempts had been made to manufac
dense, strong, lightweight piston blank is obtained which
needs little machining.
An object of the present invention is the provision of a
novel method of an apparatus for producing a forged,
slipper-type piston.
ture forged pistons for internal combustion engines, the
prior attempts required a series of steps and progressive 15
Another object is to provide a method of and apparatus
dies (as in Patent No. 2,344,358) and did not utilize grain
for making differently contoured, forged, slipper-type pis
structure of the metal to good advantage until the advent
of Patent No. 2,740,519 ‘which taught the successful
tons which may be of various sizes.
A further object is the provision of a method of and
manufacture of pistons having integral head, skirt and
apparatus for making a unitary, forged, slipper-type piston
wrist pin bosses by a single impact extrusion operation. 20 with an integral head, skirt and wrist pin bosses, the skirt
Great numbers of pistons have been manufactured ‘by
including skirt portions of short, predetermined length
the method and apparatus of Patent No. 2,740,519, but
the pistons so made were of the normal type wherein the
skirt is of uniform length. More recently, the develop
ment of more compact engines has required the rapid and 25
economical manufacture of pistons of the slipper type ,
wherein the skirt is provided with a long, load~bearing
portion adapted to distribute power stroke pressures upon
the side wall of a cylinder, and with short skirt portions
in the regions of the bosses and a longer skirt in regions
between the bosses.
.
Another object is the provision of 1a method of and ap
paratus for making a forged slipper-type piston whereby
the formed piston blank is easily stripped from the male
punch without damaging the skirt portions of the piston.‘
Another object is the provision of an apparatus for
making a forged, slipper-type piston and having a single
adjacent the wrist pin bosses, these short portions being 30 means for restraining flow of metal into skirt portions
contoured (in most instances) to provide necessary clear
ance for countenweights carried by the crank shaft.
‘_ The present invention embodies the principles of my
prior patent and in addition permits the direct production
of slipper-type pistons without waste of metal and without 35
the necessity of individually machining each piston blank
while enhancing flow of metal into wrist pin boss recesses,
contouring end faces of short skirt portions and for strip‘
ping the piston black ‘from the male punch when it is
withdrawn from the cavity of the die.
Another object is to provide an apparatus for making
a forged, slipper-type piston in which the male forging
to form the cut~away or short skirt portion. The prior
punch has wrist pin boss recesses which are vented to
disclosure (Patent No. 2,740,519) did not teach the appli
promote the ?ow of metal thereinto during the forging
cation of a compressive forming pressure to the end face
operation.
of the skirt; this invention utilizes the step of applying 40
A ?nal and more speci?c object of the present inven
tioniis the provision ‘of‘a method of and apparatus for
making a unitary, forged, slipper-type piston with an in
pressure to desired areas of the end face of the skirt to 7,
.
form strong, dense, short skirt portions. The present
invention also greatly facilitates and insures the complete
tegral head, skirt and wrist pin bosses, the skirt including
?lling of the cavity bet-ween the walls of the die and the
skirt portions of short, predetermined length in the regions
male punch without waste of metal and expeditesthe
of the bosses and a longer skirt in the regions between the
45
manufacture by facilitating the removal of the formed ._ bosses, by a single impact extruction operation of a male
blank from the punch without deformation, splitting or “ punch having Wrist pin boss recesses upon a slug of metal
weakening of the blank.
in a die.
‘
.
The removal of the piston blanks from a punch has
Other objects and many of the‘ attendant advantages
posed difficulties in the past and any application of force
of this invention will be readily appreciated as the same
to the relatively thin edge areas of the skirt normally 50 becomes better understood by reference to the following
produced deformation, splitting or weakening of the skirt. ‘ ‘ detailed description when considered in connection with
This is not true in the instant case because the metal of
the accompanying drawings, wherein:
the skirt portions adjacent the bosses has been subjected
FIG. 1 is a side elevation of an exemplary slipper-type
to impact and forming, and perfect contact exists between
piston.
the slipper-forming elements and such skirt portions, per
FIG. 2 illustrates an exemplary apparatus by which the
mitting ready withdrawal of the male punch from the
method may be carried out, a portion of the ?gure being
formed piston without the ‘generation of any strains in
in side elevation and a portion in vertical section, the
the blank.
punch being shown raised before delivery of its impact
The apparatus, in general, comprises a suitable die and
upon a slug of metal to be formed.
a male punch for cooperation therewith. The die is 60 FIG. 3 is a plan view taken from plane III-III of
preferably provided with a removable liner, so that a ‘ FIG. 2.
single die block may be used in making variously sized
FIG. 4 1s an enlarged vertical section through the es
piston blanks. The male punch is preferably provided
sential portions of the apparatus shown in FIGS. 2 and
with vents which insure complete ?lling of wrist pin boss
3, but with the punch and slipper forming and stripping
recesses with metal; In addition, the apparatus includes
ring in bottom position in the die. The section is along
‘a combined forming and stripping ring which, in combi
nation with the die and punch, forms the short skirt por
a plane as IV-lV of FIG. 3.
FIG. 5 is a vertical section along plane V—V of FIG. 4.
tions, insures that the punch is accurately bottomed (there
FIG. 6 diagrammatically illustrates one relationship
by establishing desired head thickness) and strips the q between die and punch contours along a horizontal plane
Q
formed blank from the punch.
i
such as VI—VI in FIG. 4.
‘The method of operation hereinafter disclosed in detail
FIG. 1 illustrates one exemplary form of a slipperetype
3,093,890
3
piston which .can be made‘ in accordance with this inven
tion. In each instance the piston v1 has .a head .2 (‘which
4
has a contour designed to ?t the valving, combustion cham
cesses 34 and 34' which form the integral wrist pin
bosses of the piston blank, it .has .been found highly de
sirable to provide punch 30 with small bleeder channels
ber dome, etc. of the engine in which it is to be used) and
or vent passageways such as 33 and 33' (shown to best
an integral skirt including integral, opposing wrist pin
advantage in FIG. 4), these passageways communicating
bosses including the wrist pin boss 4 in FIG. 1 the skirt
the innermost portions of the recesses 34 and 34' with
portions 5 adjacent the wrist pin bosses being short and
terminating in contoured end faces 6 while skirt portions
the atmosphere. In many instances, the end face of
the punch 30 is provided with a number of recesses such
as 35 and 36 (as illustrated in FIG. 4), these recesses
7 between said bosses are longer .and thicker. The entire
inner surface 9 is a forged unmachined surface; very little 10 being adapted to form ribs capable of suitably chilling
machining need be done on the external surface and head
or disseminating heat from the piston head. Again, in
of the forged piston blank other than the cutting of the
order to make certain that metal is properly forced into
ring grooves 11, the boring of Wrist pin bores 12 and a
these recesses, additional channels such ‘as 38 may com
?nishing of the end faces 8' of the ‘long skirt portions 7.
municate the recesses 35 and 36 either with the atmos
End faces 6 of the short skirt portions are formed during 15 phere or with the cross-channel 39 leading to the wrist
forging, and very little ifany, ?nishing is required there.
pin boss recesses 34 and 34'.
The proportions of the piston and contour of end faces
Upstanding guide blocks 28, 28' and the like carried
6 will vary. It may be noted that the wall of the piston
by the die block 20 guide the horizontally disposed slip—
in the pad area (where ring grooves 11 are cut) is in
per-forming and stripper ring 40 in its vertical motion.
herently thicker. The forged piston blank is of a prede
Each of the stationary vertically extending guide blocks
termined height or distance from contoured end face 6
to the outer surface of the head 2. The impact forging
28, 28’ and the like, may extend into a grove formed
method of this invention produces lands (between ring
groove being preferably between a pair of cars such as
41 and 42, 41’ and 42’, etc. In order to ‘maintain the
in the outer periphery ‘of the stripping ring 40, such
grooves) in which the ?ow lines are ‘such as to reduce
loading on the lands.
25 ring 40 in an elevated position above the upper surface
An exemplary apparatus by means of which the method
of the present invention can be carried out is illustrated
of a die block, the ring 40 may be suitably urged up
wardly by means of springs. Certain of the cars such
in the drawings. The essential elements comprise a die
as the cars 42 may, for example, carry a downwardly
block 20 and male punch 30 and a slipper-forming and
extending open-ended housing tube 44 containing a spring
blank stripping ring 40 movably mounted between the die 30 45. These housing tubes 44 may extend into suitable
block and the punch when the punch is in raised position
bores formed in the die block 20, the springs 45 thereby
as illustrated in FIG. 2.
It is to vbe understood that the
die block 20 is mounted on a ?rm‘ foundation and the male
punch 30 is actuated by a suitable press. In the manu
‘urging the entire ring upwardly.
In order to limit up
ward movement of the slipper-forming and stripper ring
40, the other set of ears such as the cars 41, 41’ and the
facture of slipper-type pistons from class A forging stock, 35 like, may be provided with vertical bores through which
aluminum alloys, etc., it is desirable to employ a press
extend vertical pins 46, the lower end of each pin being
capable of exerting forging pressures of from about 450
threadedly mounted in die block 20‘ while the upper end
to 900 tons, depending upon size blank which is being
forged.
is provided with a stop head or nut 46’.
The ring 40 is provided with a central aperture or
The die block 20 is provided with a cavity 21; the 40 opening 47 adapted to slida-bly receive the punch 30 and
‘to ?t said punch rather closely when the punch is in its
fully bottomed position as illustrated in FIG. 4. The
ring 40 is also of sufficient width so that in its lower
most position, shown in FIG. 4, it contacts the upper edge
of the liner 22 and the upper surface of the die block 20.
surface of the piston head 'is removably positioned within 45 In such lowermost position, it will be noted that the
the cavity 21, the upper surface of the knock-out block
shoulder 31 of the punch rests upon the ring 40. The
24 and the inner walls of the die liner 22 thereby forming
ring therefore regulates and insures that the punch extend
the walls of the die cavity 21. A vertical reciprocable
into the die cavity a suitable distance.
knock-out bar 26 operates through a suitable bore in the 50
Downwardly extending from the slipper-forming ring
die pad 23 for the purpose of moving the knock-out base
40 are the forming and stripping elements 48 and 48'.
24 upwardly in the cavity at the end of a forming opera
These stripping elements 48 and 48' are diametrically
tion. It ‘will be noted that the present arrangement per
opposed and are positioned to be in transverse alignment
mits various die liners and knock-out bases to be used in p
with the wrist pin forming recesses 34 and 34’ of the
the same die block, thereby permitting a great variety of 55 punch. When the punch is bottomed in its die as indi
pistons, di?ering in shapes and sizes, to be made in the
cated in FIG. 4, these forming elements 48 and 48' of
same die block.
the ring 40 are directly above the wrist pin boss recesses
As more clearly illustrated in FIG. 4, the knock-out
and the lower surfaces of the elements 48 and 48', indi
base 24 may be provided with a small vent channel 27
cated at 49 and 49’, respectively, impart the desired con
for the purpose of eliminating air or preventing any air 60 tour to the short skirt portions 5 of the piston blank and
from being trapped. Such channel 27 may communicate
form the end faces 6 of such short skirt portions.
with the bore in which the knock-out bar 26 operates.
Any metal or alloy may ‘be used in the manufacture
The vertically reciprocatable male punch 30 has an
of piston blanks; aluminum alloys of the 20-18 and 20-32
external surface which ‘forms the inner surface 9 of the
Class A forging stock type, magnesium alloys, magnesium
walls of the cavity are formed by a removable ‘die liner
22 press ?tted ‘into the die block. Die block and its liner
are then ?rmly mounted upon a die pad 23. A knock-out
base 24 having an upper surface 25 contoured in accord
ance with the shape which is to be imparted to the outer
slipper-type piston blank (the ?nished form of piston 65 thorium alloys, etc., have been used. Preferably, these
being illustrated in FIG. 1). The male punch 30 is
various metals or alloys are ?rst rolled into elongated
therefore provided with a pair of opposing recesses 34
bars so as to have the grain run longitudinally of the
and 34' adapted to form the wrist pin bosses integrally
bars and then the bars are cut into disc-like shapes of
with the skirt and the head. The punch 30 is provided
predetermined weight and thickness. The diameter of
with an outwardly extending .stop shoulder 31 and as 70 these discs is substantially equal to the smallest diameter
previously indicated the entire punch is associated with
of the die cavity and when such disc or slug of metal is
a suitable press for downward movement into the die
placed into the die cavity (in a position indicated ‘by dash
cavity 2'1 so as to perform impact extrusion upon a slug
lines in FIG. 2), the grain now runs axially with respect
of metal placed within the die cavity.
to the die cavity. Preferably, these slugs are preheated
In order to prevent the entrapment of air in the re 75 to a temperature from between about 700° F. to 800° F.
3,093,890
6
5
noted that this time the stationary guides 23 and 28’, and
the like, only extend about 180° around the cavity per
mitting the blank to be readily removed from one side of
the assembly.‘ In some instances, however, the piston
blank remains within the die cavity and the knock-out
During constant operation, the punch develops a tempera
ture of about 600° F. at its head and a temperature of
between about 400° F. and 450° F. immediately above
the wrist pin boss recesses. Suitable temperatures are
maintained in both the punch and the die by ‘suitable
heating and cooling conduits formed in the die block and
in the punch. Reference can be made to my prior patent
bar 26 can then be used to move the knock-out base 24
upwardly- thereby raising the ?nished blank to a discharge
and remove position.
Attention isagain drawn to the fact that in its bot
for an illustration of the manner in which both the die
and the punch may be heated or cooled as the case may
be.
10
In order to insure homogeneity in the piston blank, in
order to make certain that the Wrist pin boss recesses,
inwardly extending radiation ?ns and the like, are com
pletely ?lled and formed, and in order to make certain
that the skirt portions are properly made without weak
nesses, cracks, deformations or wasted metal, the flow of
metal in various parts of the space between the walls of
tomed position the shoulder-31 of the male punch 30
impacts the slipper-forming ring 40 which. in turn is im
pacted against the upper face of the die block and liner
22. A de?nite predetermined positioning of the punch
within the die cavity is thus obtained. The thickness of
the resulting piston head is established within very close
tolerances. Very little machining need be done. The
distance between the formed end face of the short skirt
portions of the piston and the top of the head of the
the die cavity and the punch must be carefully controlled.
piston is also established with a great deal of accuracy.
It is necessary, for example, to restrain and impede the
It is to be understood that during impact forging under
?ow of metal into skirt portions immediately adjacent the
the conditions herein described, high pressures and great
bosses being formed and to facilitate ?ow of metal into
friction stresses are generated. It has been found desir
the recesses of the male punch which form such bosses
able, in order to increase the service life of the punch, to
‘and into the portions of the space in which the thicker,
make the punch with inserts of carbide base material or
longer skirt portions are to be formed. In large part, the
flow of metal is promoted and retarded in the manner 25 other suitable wear-resisting air hardening metallic com
position at its high pressure areas, such as those where
indicated by the use of the principles enunciated in my
the punch forms the ring pad and adjacent the wrist pin
prior Patent No. 2,740,519. For example, in a trans
bosses, where ?ow of metal is restricted. Air hardening
verse plane taken through the punch and die in a zone
metallic compositions which harden by
cooling with
immediately above the wrist pin bosses (as illustrated in
FIG. 4 and FIG. 6), the distance separating the inner wall 30 out quenching are known. Moreover the entire punch
may be chrome plated to good advantage, dull plating
of the cavity from the punch in Zones or ‘areas between
being preferred to bright plating.
wrist pin bosses is appreciably greater than the distance
I claim:
separating the inner wall of the die cavity and the outer
1. The method of making a forged slipperatype piston
surface of the punch in areas immediately adjacent the
blank provided with a head, a skirt of predetermined
wrist pin boss recess. The restriction or reduced width
non-uniform length and integral wrist pin bosses by a
of the space between the punch and the inner walls of
single impact extrusion operation of a male punch against
the cavity immediately adjacent the wrist pin boss re
a slug of metal in a die, comprising: applying impact
cesses, restricts the ?ow of metal out of the recesses into
‘forces to a slug of metal in a single impact extrusion
the space adjacent thereto while the increased width of
such space in zones between the recesses facilitates the 40 operation by impacting a male punch against a slug of
metal in a die to form a piston blank having a head, a
?ow of metal thereinto. Moreover, in accordance with
the present invention, the downward impact of the punch
skirt and integral wrist pin bosses and concurrently pro
?owing into the longer skirt portions.
tions of said skirt of predetermined length and configura
being urged upwardly by the biasing springs 45. In most
currently promoting ?ow of metal into skirt portions in
reached its upper limit (established by the stop guide rods
46 and nuts 46’), it will be noted that the blank will be
stripped o? the punch, the bottom surfaces of forming
mediately adjacent the wrist pin bosses and preventing
moting ?ow of metal into areas of said blank between
is transmitted to the forming ring 40 and elements 48 and
said wrist pin bosses to form thick skirt portions, restrict
48’ which further impede and restrict the ?ow of metal
immediately adjacent the recesses and actually compact 4.5 ing flow of metal into areas of said blank immediately
adjacent said wrist pin bosses to form thin skirt port-ions
the metal in the thin skirt portions adjacent such recesses.
adjacent each said wrist pin 1boss and preventing ?ow of
The elements 48 and 48’ therefore not only contour the
metal into end face portions of said blank in the skirt
lower faces of the short skirt portions of the slipper-type
adjacent the wrist pin bosses to form said skint of prede
piston but also insure that adequate metal ?ows into the
wrist pin bosses and that the metal is not impeded from 50 termined non-uniform length and to form end face por
tion adjacent said bosses.
Prior to forming of piston blanks in accordance with
2. A method of making a unitary, forged, slipperatype
the method and apparatus hereinabove described, it is
piston
with intergal head, skirt and wrist pin bosses, said
desirable to spray or paint the male punch 30 with a
suitable high temperature lubricant. Moreover, it is de 55 skirt including portions of short, predetermined length
and contour in the region of the bosses and longer skirt
sirable that both the punch and the die be brought up
portions in regions between bosses, comprising: placing a
to near actual working temperatures. Each slug of ma
heated slug of metal in a vfemale die having a non-cylin
terial fed into the die cavity should be properly preheated
drical inner surface and applying a male punch against
and should be of approximately the correct weight to
completely ?ll the cavity when the punch is bottomed (as 60 said slug of metal in a single impact extrustion operation,
said punch having wrist pin boss recesses to vform wrist
illustrated in FIG. 4). At the end of an impact extrusion,
pin bosses in the blank ‘formed by said extrusion and con
the punch is raised and the ring 40 follows the punch
areas of the blank between wrist pin bosses, restricting
instances, the formed blank tends to adhere to the punch
and is raised with the punch. When the ring 40 has 65 ?ow of metal into skirt portions in areas of the blank im
how of metal to the end surface of the skirt being formed
in said blank between the punch ‘and die in areas thereof
adjacent each of said bosses to provide a predetermined
elements 48 and 48’ remaining in contact with and exert
ing pressure upon the end faces of the short skirt portions. 70 length and contour to such skirt in said areas.
The blank is therefore automatically removed and
References Cited in the ?le of this patent
stripped from the male punch and since the stripping
UNITED STATES PATENTS
pressure is applied upon a compacted formed face or end
y1,490,849
Philip ________________ .._ Apr. 15, 1924
face of the piston blank, no deformation, cracking or
(Other references on following page)
other weakening of the blank is obtained. It may be 75
3,093,890
UNITED STATES PATENTS
1,354,271
11,936,598
2,024,286
2,125,068
2,244,954
2,261,304
FOREIGN3PATENTS
Michel ______________ .... Apr. !119, 11932
Handler ____________ __ Nov. 28, 1933
Handler ______________ __ Dec. 17, 1935
Dempsey ____________ __ July 26, 1938
lcnz ________________ __ June ‘10, 1941
2,667,390
2,683,999
Sparks ______________ __ Nov. 4,
Rice ________________ _.. Oct. 19,
Watson ______________ .._ Jan. 26,
Hammond ____________ __ July 20,
2,740,519
Sparks _______________ __ Apr. 3, 1956
2491,51 1
1941
1948
1954
1954 10
176,109
Switzerland __________ .._ Mar. 31, 11935
OTHER REFERENCES
Herb: “Forging Aluminum Aircraft Pistons,” Machin
ery, November 1945, pp. 149-152.
Material and Methods, August 1955, pp, 111-126,
“Impact (Cold) Extruded Parts.”
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