Closed die forging apparatus

A closed die forging apparatus has a fixed bottom die, and a top die at the bottom end of a piston rod depending from a top die carrier rigidly mounted to the underside of a ram. The top die carrier has defined therein a hollow in which a piston is received for up and down motion relative to the top die carrier, with the piston having the piston rod extending downwardly therefrom. A fluid chamber over the piston communicates with a parallel connection of low pressure and high pressure accumulator systems for successively storing the energy of the fluid in the fluid chamber which is pressurized as the ram decends further after moving the top die into contact with the bottom die. The apparatus may further comprise at least one side punch which is forced into and out of the die cavity by an actuating lever acted upon by another fluid cushioned piston built into the top die carrier. A second fluid chamber over this second piston also communicates with an accumulator which stores the fluid pressure developed as the ram descends further after the side punch has been forced fully into the closed die cavity for forging the metal confined therein.

BACKGROUND OF THE INVENTION 
This invention relates to a forging apparatus, or apparatus for causing 
plastic deformation of metals, usually at elevated temperatures, into 
desired shapes by compressive forces exerted through dies, and more 
specifically to such a forging apparatus of the closed die variety. 
Forging machines in general may be classified into open die and closed die 
designs depending upon the type of tooling employed and the way the 
required compressive forces are applied to the workpiece. In an open die 
machine the workpiece is placed between the two dies and squeezed so that 
the metal flows to take up the form in the dies. A certain amount of flash 
is unavoidable as the die faces do not come into contact until forging is 
completed. Closed dies, on the other hand, have their faces in contact 
with each other, completely enclosing the workpiece, before forging 
begins. The plastic deformation of the metal is achieved by means of a 
punch or punches that enter the die cavity from the top, bottom or side 
dependant upon the configuration of the desired component. Flash is very 
much less than with open dies because the die faces are in contact before 
forging begins. 
In conventional closed die forging machines, however, difficulties have 
been encountered in positively holding the dies closed, during the forging 
of the confined metal by the punch or punches, with minimal exertion of 
power on the top die. Additional difficulties manifest themselves in 
connection with machines incorporating a side punch or punches together 
with an associated actuating mechanism or mechanisms for horizontally 
moving the punch or punches into and out of the die cavity. Powered by the 
same ram as the top die, the side punch actuating mechanisms must be so 
designed as to cause the side punch to effectively deform the metal with 
as small power requirement as possible. 
SUMMARY OF THE INVENTION 
The present invention provides an improved closed die forging machine 
having a fluid cushioned top die and accumulator means associated 
therewith, such that the top die can be lowered, and held lowered, with 
minimum energy requirement for the effective forging of the metal or metal 
by a punch or punches. The invention also provides an improved actuating 
mechanism for a side punch, so made that the side punch can be plunged 
into the die cavity in a well controlled manner and with the exertion of 
minimum power from the ram driving the top die. 
Briefly, the improved closed die forging machine according to the invention 
includes a top die carrier rigidly mounted to the underside of a ram for 
up and down motion therewith toward and away from a fixed bottom die. The 
top die carrier has a hollow formed therein in which a piston is slidably 
mounted for up and down motion relative to the top die carrier, with the 
piston defining thereover a fluid chamber to be filled with fluid. The 
piston has a piston rod slidably extending downwardly through the top die 
carrier and projecting therefrom to terminate in a top die movable with 
the piston into and out of contact with the bottom die. Also included are 
low pressure accumulator means and high pressure accumulator means, both 
communicating with the fluid chamber in the top die carrier for storing 
the energy of the fluid pressurized by the piston as the ram descends 
further after moving the top die into contact with the bottom die. Each of 
the low pressure and the high pressure accumulator means comprises a 
pressure tight vessel having a floating piston mounted therein to divide 
the interior thereof into a pair of opposed fluid chambers, one of which 
communicates with the fluid chamber in the top die carrier, and an 
accumulator in communication with the other fluid chamber of the vessel. 
The low pressure accumulator means absorbs a relatively low pressure rise 
in the fluid chamber in the top die carrier, and the high pressure 
accumulator means absorbs a greater pressure rise. 
Thus, with the continued descent of the ram following the movement of the 
top die into contact with the fixed bottom die, the pressure rise in the 
fluid chamber in the top die carrier is absorbed first by the low pressure 
accumulator means and then by the high pressure accumulator means. The 
energy required for holding the dies closed can thus be reduced. The 
particular construction of the low and high pressure accumulator means set 
forth above is well calculated to limit the pressure peaks and pressure 
variations of the fluid in the top die carrier fluid chamber. Further, 
since both low and high pressure accumulator means directly communicate 
with the fluid chamber, any delay between their operations can be avoided. 
The invention further features an improved actuating mechanism for 
thrusting a side punch into the cavity of the dies closed as above. The 
side punch actuating mechanism includes an actuating lever which is 
operatively linked to the side punch and which is driven from another 
fluid cushioned piston built into the top die carrier. The side punch can 
be forced into the die cavity with a very slight displacement of the ram 
toward its lowermost position. 
The above and other features and advantages of this invention and the 
manner of realizing them will become more apparent, and the invention 
itself will best be understood, from a study of the following description 
and appended claims, with reference had to the attached drawings showing a 
preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The closed die forging apparatus in accordance with the invention is shown 
in the drawings as adapted to include a top punch and three side punches 
by way of example. A consideration of FIG. 1 will make clear the general 
organization of the representative forging apparatus. It includes a fixed 
bottom die 10 mounted on a bolster 12 via a baseplate 14. 
Over the bottom die 10 a top die carrier 16 is rigidly mounted to the 
underside of a conventional slide or ram 18 for up and down motion 
therewith toward and away from the bottom die. The top die carrier 16 has 
formed therein a hollow 20 in which a piston 22 is received for up and 
down sliding motion relative to the top die carrier. The piston 22 has a 
piston rod 24 depending therefrom and slidably extending through the top 
die carrier 16 to partly project downwardly therefrom. A top die 26 is 
affixed to this projecting bottom end of the piston rod 24 by means of a 
retainer ring 28. When the top die 26 is moved into contact with the 
bottom die 10, as depicted in the right hand half of FIG. 1, the two dies 
define in combination a cavity 30 of a desired shape into which a 
workpiece is to be formed. A top punch 32 is secured to the understide of 
the ram 18 and slidably extends through the piston 22, piston rod 24, and 
top die 26. Normally held retracted in the top die 26 as shown in the left 
hand half of FIG. 1, a bottom end portion of the top punch 32 is to plunge 
into the die cavity 30 as the ram 18 descents further after moving the top 
die into contact with the bottom die 10, since then the top die is 
displaced upwardly with the piston 22 relative to the top die carrier 16, 
as will be more fully discussed hereafter. 
Slidably engaged in the hollow 20 in the top die carrier 16 as above, the 
piston 22 defines thereover a fluid chamber 34 filled with fluid such as, 
typically, hydraulic oil. This fluid chamber communicates with a parallel 
connection of a low pressure accumulator system 36 and a high pressure 
accumulator system 38. The low pressure accumulator system 36 includes a 
cylinder or pressure tight vessel 40 having a floating piston 42 slidably 
mounted therein to divide the interior thereof into a pair of opposed 
fluid chambers 44 and 46. The fluid chamber 44 is in direct communication 
with the fluid chamber 34 in the top die carrier 16. The other fluid 
chamber 46 is in direct communication with an accumulator 48. 
The high pressure accumulator system 38 is akin in construction to the low 
pressure accumulator system 36, including another cylinder or pressure 
tight vessel 50 of greater diameter than the vessel 40 of the low pressure 
accumulator system. The vessel 50 also has a floating piston 52 slidably 
mounted therein to divide the interior thereof into a pair of opposed 
fluid chambers 54 and 56. The fluid chamber 54 is in direct communication 
with the fluid chamber 34 in the top die carrier 16, and the other fluid 
chamber 56 is in direct communication with an accumulator 58. 
The pressure in the fluid chamber 34 in the top die carrier 16 rises as the 
ram 18 descends further after moving the top die 26 into contact with the 
bottom die 10. Both low pressure accumulator system 36 and high pressure 
accumulator system 38 function to absorb such pressur rise in the fluid 
chamber 34. 
As will be seen from FIGS. 1 and 2, the exemplified forging apparatus is 
shown to have three side punches 60 movable horizontally into and out of 
the die cavity 30. Since the three side punches as well as their actuating 
mechanisms 62 can all be identical, there will be described in detail only 
one of the side punches, seen on the right hand side in FIG. 1, in 
conjunction with the actuating mechanism associated therewith, it being 
understood that the same description applies to the other side punches and 
to the actuating mechanisms therefor. 
With reference directed also to FIGS. 3 and 4 the representative side punch 
60 is supported by a punch holder 64. This punch holder is rigidly mounted 
on a hollow carriage 66 which in turn is slidably mounted on a hollow 
support structure 68 and thereby constrained to horizontal reciprocation 
toward and away from the dies 10 and 26. The support structure 68 is 
mounted on the baseplate 14 in a fixed relation to the bottom die 10. 
The actuating mechanism 62 for the side punch 60 includes an approximately 
T shaped actuating lever 70 pivotally mounted within the hollow support 
structure 68. The actuating lever 70 has three arms 72, 74 and 76 and is 
pivoted on a pin 78 passing the junction of the three arms. The first arm 
72 of the actuating lever 70 is pivotally pinned at 80 to one end of a 
link 82, the other end of which is pivotally pinned at 84 to the carriage 
66. It is thus seen that the link 82 serves to translate the bidirectional 
pivotal motion of the actuating lever 70 into the rectilinear 
reciprocation of the carriage 66 and, consequently, of the side punch 60. 
The side punch 60 enters the die cavity 30 upon counterclockwise turn, as 
viewed in FIG. 1, of the actuating lever 70 and is withdrawn therefrom 
upon clockwise turn of the actuating lever. 
In order to cause the counterclockwise turn of the actuating lever 70, a 
second piston 86 is slidably fitted in a second hollow 88 defined in the 
top die carrier 16. The second piston 86 is movable up and down relative 
to the top die carrier 16 and defines thereover a second pressure tight 
fluid chamber 90 which is filled with hydraulic oil or like fluid and 
which communicates with an accumulator 92. Directed downwardly from the 
second piston 86, a second piston rod 94 slidably extends through the top 
die carrier 16 and projects downwardly therefrom. The projecting end of 
the second piston rod 94 has a pair of thrust pins 96 rigidly attached 
thereto and depending therefrom in parallel spaced relationship to each 
other, with each thrust pin disposed on either side of the support 
structure 68. 
Disposed just under the pair of thrust pins 96 are a pair of abutments 98 
of rectangular shape, seen in both FIGS. 1 and 3, which are mounted on the 
opposite ends of a spindle 100 passing horizontally through the distal end 
of the second arm. Thus as the thrust pins 96 descend with the ram 18, the 
actuating lever 70 is pivoted counterclockwise to cause the side punch 60 
to thrust into the die cavity 30 via the link 82 and carriage 66. A pair 
of stop plates 102 are placed on the baseplate 23, on both sides of the 
support structure 68, so as to underlie the respective abutments 98 on the 
actuating lever arm 74. To be butted on by the abutments 98, the stop 
plates 102 function to positively limit the counterclockwise turn of the 
actuating lever 70 upon descent of the ram 18. The thickness or height of 
the stop plates 102 may be varied as desired to correspondingly change the 
extent to which the actuating lever 70 is allowed to turn counterclockwise 
and, therefore, the extent to which the side punch 60 is thrusted into the 
die cavity 30. 
With reference to both FIGS. 1 and 4 the third arm 76 of the actuating 
lever 70 is bifurcated to rotatably support a roll 104 therebetween. Held 
against this roll 104 is a piston rod 106 of a biasing cylinder 108. The 
biasing cylinder 108 has a head end chamber 110 in communication with an 
accumulator 112. Normally the piston rod 106 of the biasing cylinder is 
held extended to hold the actuating lever 70 pivoted fully in a clockwise 
direction and hence to hold the side punch 60 withdrawn from the die 
cavity 30. 
Operation 
A workpiece to be forged is first placed in the impression in the bottom 
die 10. As the ram 18 is lowered, the top die 26 descends therewith into 
contact with the bottom die 10 thereby confining the workpiece in the 
closed die cavity 30. Upon continued descent of the ram 18 the first 
piston 22 carrying the top die 26 travels upwardly relative to the top die 
carrier 16 against the fluid pressure in the first fluid chamber 34. This 
fluid pressure is effective to hold the top die 26 firmly closed against 
the bottom die 10. 
As the fluid pressure in the first fluid chamber 34 rises with the 
continued descent of the ram 18, the pressure rise is first absorbed by 
the low pressure accumulator system 36 and then by the high pressure 
accumulator system 38. These accumulator systems comprise as aforesaid the 
cylinders or pressure tight vessels 40 and 50, and the accumulators 48 and 
58 in communication with the fluid chambers 46 and 56 of the vessels 40 
and 50, respectively. Consequently the fluid pressure in the first fluid 
chamber 34 in the top die carrier 16 first acts on the floating pistons 42 
and 52 within the vessels 40 and 50 and is then absorbed by the 
accumulators 48 and 58. This manner of pressure absorption is effective to 
reduce pressure peaks and pressure variations in the first fluid chamber 
34. 
With the continued descent of the ram 18 after the movement of the top die 
26 into contact with the bottom die 10, the top punch 32 rigidly attached 
to the ram is forced into the closed die cavity 30 to cause deformation of 
the workpiece confined therein. 
The pistons 86 associated with the three side punches 60 also descend with 
the ram 18. The thrust pins 96 depending from the piston rods 94 act on 
the abutments 98 on the second arms 74 of the actuating levers 70 thereby 
causing the same to pivot in a counterclockwise direction, as viewed in 
FIG. 1, against the effect of the biasing cylinders 108 until the 
abutments hit the stop plates 102. The link 82 translates this 
counterclockwise turn of the actuating lever 70 into the linear leftward 
travel of the carriage 66. Thus the side punches 60 plunge into the closed 
die cavity 30 and deforms the metal into the required shape in coaction 
with the top punch 32. The reactive forces exerted on the side punches 60 
by the metal are borne by the fluid in the fluid chambers 90 in the top 
die carrier 16. The stroke of the side punches 60 may be readily varied as 
required by altering the height of the stop plates 102. 
The descent of the ram 18 after the actuating lever 70 has been turned 
fully in a counterclockwise direction as above results in the 
pressurization of the fluid in the fluid chambers 90 in the top die 
carrier 16. The pressure rise in the fluid chambers 90 is absorbed by the 
accumulator 92. The side punches 60 remain inserted in the die cavity 30 
under fluid pressure exerted through the carriage 66 during the ram 
descent over the additional distance. 
When the ram 18 is raised upon completion of forging, the top punch 32 is 
first withdrawn from the die cavity 30. Then the top die 26 travels 
upwardly with the piston 22, out of contact with the bottom die 10, 
causing a pressure drop in the fluid chamber 34 in the top die carrier 16. 
Thereupon the presurized fluid that has been stored in the two accumulator 
systems 36 and 38 returns to the fluid chamber 34. The thrust pins 96 also 
ascend with the associated pistons 86. Freed from the upward forces from 
the actuating levers 70, the pictons 86 allow the fluid to return from the 
accumulator 92 to the fluid chambers 90. Further, when the thrust pins 96 
move out of contact with the abutments 98, the accumulator 112 returns the 
fluid to the biasing cylinders 108 thereby causing the same to turn the 
actuating levers 70 in a clockwise direction, with the consequent 
withdrawal of the side punches 60 from the die cavity 30. The foregoing 
cycle of operation is repeated to forge the successive workpieces. 
In the above forging operation by the improved apparatus of this invention, 
the position where each side punch 60 is stopped on its forward stroke 
depends upon the height of the stop plates 102. Accordingly, if the stroke 
of the ram 18 is constant, the height of the stop plates 102 determines 
the extent to which the pistons 86 associated with the side punches 60 are 
displaced upwardly relative to the top die carrier 16 against the fluid 
pressure in the fluid chambers 90. It is thus seen that the period of time 
during which the side punches 60 are held at a standstill in the die 
cavity 30 is readily variable as required by changing the height of the 
stop plates 102. 
With reference to FIG. 1 the capital L indicates the distance between the 
axis of each actuating lever 30 and the center of the pin 80 connecting 
the first arm 72 of the actuating lever to the link 82. The small letter l 
denotes the distance between the axis of each actuating lever 30 and the 
center of the spindle 100 connecting the second arm 74 of the actuating 
lever to the pair of abutments 98. Optimumly, for reducing the power 
requirement of each side punche 60, the distance L should be greater than 
the distance l. With the relative distances L and l so determined, each 
actuating lever 30 will be required to turn a correspondingly smaller 
angle for a given stroke of the associated side punch 60. Consequently the 
ram 18 will be required to power the actuating lever while traveling a 
small distance toward the end of its downward stroke. 
Although the forging apparatus in accordance with the present invention has 
been shown and described in terms of a specific example thereof having a 
top punch and three side punches, it is understood that the number and 
arrangement of the punches are merely illustrative and not to impose 
limitations upon the invention because they are subject to change 
depending upon the forging to be made. Additional modifications or 
alterations of the illustrated embodiment will readily occur to the 
specialists without departing from the scope of the invention.