Note: Descriptions are shown in the official language in which they were submitted.
DOU~I.E' ACTIO~I PRF~S HAV NG
FLOATI~G PUNCH
The present invention relates to mechanical
presses, and in ~ar~icular to double action presses
wherein a blanking and forming operation is performed
on each cycle o the press.
In ma~ing can ends, ~or example, one slide of
the press performs the blanking operation, which
punches out a circular blank from strip stock, and
the other slide forms the circular blank into a can
end by means of a drawing o~eration. rrhus, both
operations can be performed on a single cycle of
the press.
Due to the fact that the blanking operation
must be carried out prior to the drawing operation,
pres~es of this type are constructed such that the
blanking slide will lead the forming slide. Furthermore,
it is necessary t~ hold the blanked part during at
least a portion of the drawing op~ration so as to
prevent wrinkling. Some prior art presses have accomp-
lished ~his by permitting the blan}cin~ punch to travel
through the tin line and con-tinue to exert pressure
on the blanked part during the drawincJ operation~
By permitting the hlanking punch to overtravel past
the cutting edge, excess$ve wear of the cutting edge
is cau~ed h~ the punch sliding ~ast it. Unless proper
clearance between -the punch and cutting edge can
be maintained at all times, metal to metal contact
betwean the punch and cutting edge will occur during
the o~ertravel portion of the cycle. ~ urther di~advan
tage to overkr~v~l of the hlanking puncll ~s that
the punch will nece~arily have a longe~ re~dence
time beneath the tin line th~n will the eormLng die,
ancl thi~ d~lay~ e~ctlon o~ the einishe~1 part.
In o~cler to avoicl overtravel Oe the blanlcin~
punch, certaLn t~pes of presses ~r:Lve the blankin~
~LS~3~19L
unch slide by means of a cam. The cam is manufactured so
tha-t the blanking punch is caused to dwell a-t the bottom of
its stroke at a point ~ust below the tin line. This
maintains pressure on the blanked part yet avoids overtravel
so that the blanking punch can begin its re-turn stroke at
the same time as or just before the return stroke of the
forming die. In a cam driven press of this type, the mechanism
is quite complicated. Moreover, the fact that the contact
between the cam and connectïn~ rod is only a line contact,
lubrication is difficult and the cam surEaces are subject to
wear.
According to the present invention there is
provided a double action press which has a bed portion, a
blanking slide, a forming slide with drive means connected to
the slides for reciprocating the slides along respective
rectilinear pathsl the drive means including a crankshaft
having at least two eccentrics thereon and at least two
connecting rods connecting respective slides and respective
eccentrics, the drive means causing the blanking slide to lead
the forming slide. A forming die is provided which includes
a first forming tool element connected to the forming slide
and a second forming tool element connected to the bed portion
of the press, the tool elements being adapted to coact with
each other to form a part therebetween when brought together
by the forming slide. A blanking die is provided which
includes a blanking punch connected to the blanking slide and
a blanking tool element connected to the bed portion o~ the
press, the punch and blanking tool element being adapted to
coact with each other to cut out a blank when brought together
by the blanking slide at about the dead center position of
the eccentric driving the blanking slide. The punch is
reciprocally connected to the blanking slide for movement
relative to the blanking slide in a direction parallel to the
rectilinear movement o~ -the blanking slide. The drive means
causes the blanking slide to positively ancl non-yieldably
enga~e khe punch about the dead center po~ition of the
eccen-tric driving the blanking slide to cu-t ou-t a blank. Means
yieldably urges thq punch in the rectilinear direc-tion oE
-kh~. blanking slide away Erom the blanking ~lide to elx-tend
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elative to -the blanking slide and exert a holding force on
the blank as a blanking slide moves away.
The above problems and disadvantages of prior
art double action presses utilized for a blanking and forrning
operation are overcome by driving the two slides by means of
the crankshaft and connecting rod assembly, yet simulates the
dwell achieved by prior art cam driven presses. The blanking
and drawing slides are driven ~y means of a cranksha~t and
connecting rod assembly such as that disclosed in U.S. Letters
Patent 3,902,347, which is owned by the assignee of the
present application. It has been found that this type of
press drive results in a relatively simple, but extremely rigid
structure. Since the'connecting rods surround the crankshaft
throws, a much larger oil film results, thereby reducing wear
between these parts.
I'he dwell produced by prior art cam drives is
simulated by permitting the blanking punch to float within
the guide bushing structure connected to the blanking slide.
The punch is received within the bushing assembly for
reciprocating movement relative to -the blanking slide along,
the same rectilinear direction of movement as the slide. The
upper portion of the blanking punch may be formed as a
piston and reciprocates within a cylinder formed in the
bushing assembly. Pressurized air may be admitted to the
cylinder and continuously urges the punch downwardly. On the
downstroke of the blanking slide, the punch initially contacts
the strip of material, but does not cut through the materia,l
until the blanking slide catches up with it and drives the
punch through the material to cut the blank. The pressurized
air maintains the punch in clamping engagement with the blanked
part during at least a portion of the drawing operation, and
the blanking slide will li~t the punch at the same time as the
forming die is lifted by its slide. Since the blanking punch
and ~ormin~ dic are li~ted togq-ther, the part can be ejected
mu~h more quicl~ly than if khe punch over-traveled as in the case
oE c~rtain prior ar-t p~esses.
~ Eurther advankage to main-tainlng contac-k between
the blan~ing punch and park i9 tha-t i~ facilitates stripping
the park ~rom the lower die. rrhe closer khe punch is to
~0 the drawing die when the par-t is s-tripped, t.he more control
pc/t~
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-:an be maintained on the par-t during -the stripping and
ejecting sequence.
A significant problem with floating punches per
se is that of maintaining alignment and proper clearance
relative to the cutting edge, especially with thin stock.
If proper clearance is not maintained, the punch may contact
the cutting edge during the blanking stroke, thereby
chipping the cutting edge. The punch assembly according
to an embodiment of the present invention overcomes this
problem by providing preloaded antifriction bearings between
the punch and the guide bushing, which very accurately guide
and align the punch. as it reciprocates within the guide
bushing assembly and as it is reciprocated by the bIanking
slide itself.
It is an object of the present invention to
provide a double action press wherein blanking.and forming
operations can be performed in a single cycle of the press,
and wherein overtravel of the blanking punch is avoided.
It is a further object of the present invention
~0 to provide a double action press wherein the dwell of a
blanking punch is accomplished without resorting to the use
of a cam drive. This object is accomplished by utilizing a
crankshaft drive for the slides, wherein the blanking punch
is permitted to reciprocate relative to the blanking slide
against the pressure of a yieldable medium.
These and other objects and features of the
present invention will become apparent from the description .
of the preferred embodiment, taken together with the drawings~
Figure 1 is a front elevational view of a press
.incorporating the present invention;
Figure 2 is an enlarged, fragmentary, sectional
view of the press illustrating the blanking and forming
punch assembly wherein the blanking slide has moved
to the 140 position of its cycle;
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Figure 3 is a view similar to Figure 2 wherein
the blanking slide i5 at bottom clead center or 180
of its cvcle;
Figure 4 is a view sirnilax to Figures 2 and
3 wh~rein the blanking slide is at 254 of its cycle;
Figure 5 is an enlaryed, sectional view o the
liftout mechanism;
Figure 6 is a yraph plo~ing the postions oE
the blanking slide, forming slicle and punch above
bo~tom dead center and abov~ he strip stoc}c for
a complete press cycle; and
Figure 7 is a diagrammatic view o:f the drive
mechanism ~or the lides.
Referring now to the drawings in detail, E'igure
1 illustrates a press 10 comprising a crown 12 connected
to a hed 14, the latter beinc3 sup~orted on legs 16.
The press crankshaft 1~ is driven by an electric
motor 20 connected ~hereto by a belt and pu112y m~chanism
and a clutch (not shown3. Figure 7 illustrates diagram-
matically the connec~ions between crankshaEt 18 and
connecting rods 20, which are connected to the blanking
slide 21 (Figure 1), and connecting rod 22, which
is connected to the forming slid~ 24 (Figure 1).
Outermost eccenkrics 25 are pivotall~ connectecl to
blanking slide connecting rods 20, and innermost
crankpin 28 is pivotally connected to formincJ ~lide
connecting rod 22. Crankpin 28 i5 angularly o~fset
with respect to eccentrics 26 so that connecting
rods 20 and blanking ~lide 21 will lead connecting
rod 22 and ~orming slide 24 as crankshat 18 turns.
Fur-th~rmore, crankpin 28 i.s ~uch -that the total rectilin-
ear tra~el o~ connect:LncJ rod 22 and ~orming 31id~
2~ is gr~atex than the total r~ctilinear trav~l Oe
blanking conneatin~ rod~3 20 and ~31id~ 21. Th~ relative
movem~nt~ Oe blanking ~ 21 and ~orming slide
2~ are Lllustra~d in ~.lgure 6. ~'he ~iqn o~ crank3ha~
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18 to accomplish this rela~ive movement is within
normal engineering expertise.
The shell ty~e bearincJ slaeves 30 are preerably
pressure lubricated through pas~ages 32 connected
s to a lubricant suppl~ (not shown).
Strip stock is fed into prPss 10 by fe2d 36,
and the scrap is cut off by means o~ scrap cutter
38. A liftout mechanism 40 is clriven by means o
chain, ~elt, or other power transmission 42, whicll
is connected to sprocket 4 4 and to sprocket 43, the
latter driv2n by cxanksha~t 18.
Re~erring now to Fi~ures 2, 3 and 4, ~he de~ails
of the punch assembly will be described~ Bolst~r
46 is secured to bed 14 and lowex liftout pin retainer
1~ plate 48 is supported on the upper sllr~ace 4~ thereof.
Draw ring retainer 50 is supported on liftout pin
retainer ~8, and serves to retain draw ring 52 in
position. It will be noted that draw ring 52 includes
an annular upstanding portion 54 around which cuttlng
die retainer 56 is posi~ioned. Cutting die retainer
56 is secured to draw ring re~ainer 50, and includes
an annular step 60 within which annular cutting die
58 is received. Cutting die 58 inclucles a cutting
edge 62, which cooperates with ~he edga ~4 o~ ptmch
66 to stamp out a circular blank when p~nch 66 i~
driven downwardly past cutting edge 62, as wlll be
described below. Filler plate 6n overlies and ls
secur~d to die retainer plate 56, and the upper sur~ace
70 thereof supports the strip stock 240 as it is
advanced through the press in a hoxizontal directionO
Cover plate 72 is rigidly sQcured in posltion/ and
-~he lowe~ sur~ace 74 thereoe 1~ s~aced ro~ the upper
~r~ace 70 o~ r plate 68 ~o as to p~ovide a
,qubstantiall~ planar ~hannel ~hrou~h wlllch ~e ~toc]c
material i~ ~d. The s~aae between ~ureac~ 70 and
74 generally de~ine~ what is known in the lnclu~try
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~L ~ o~314~
as the tin linel a hori~ontal o:r inclined plane -through
which the strip stock is fed hy feed mechanism 36
(Fi~ure 1).
Lower forming die 76, the cross section of which
S is circular in a plane parallel to th~ tin line,
is connected to draw rinc3 52 by screws 78. Thus,
draw ring retainer 50, clraw ring 52, lower formin~ :
die 76, pin retainer plate 48 and bolst~r 46 are
rigidly connected to the press frame. ~ower forming
dia 76 includes an annular bea~ portioll 80, which
forms a corr~spondingly shaped bead 82 in the finished
can end 84 illustrated in Figure 4~
Liftout element 86, which includes a generally
circular base 88 and an upstanding annular rim portion
90, is sliclably received within draw ring 52 ~or
reciprocating movement in the same direction as ~hs
direction of movement of s1ides 21 and 24. Liftout
member S8 is yieldably pulled downwardly by mean~
of liftout stem 92, which is threadedly secured to
the base portion 88, and compression spring 94, which
is disposed between the lower surfac2 96 of pin retainer
plate 48 and a washer lQ0 held in place hy nut 102.
The holding force developeel by spring 94 can be adjusted
by means of nut 102. ~i~tout member 86 slides around
the lower portion 104 o~ lower forming die 76, and
when retracted, its lower sur~ac~ 108 is in abutment
with the upper surface l.L0 o~ draw rlng S2.
Li~tout member 36 is pushe~ to its lntermediate
position by means o~ liEtout pins 112, which are
.~0 slidably received in bushings 114 retained within
pin retainer plate 4~ ietout pin~ :L12 are ~ressed
upwardl!y h~ stems 116, which are ~onnected to piskolls
(not shown~ wikhin pressur~ a~linders L18, the latter
bf3~n~ khreadedly ~ecured to bolst~r 46 an~l seal~d
3S th~3rea(3a~llst b~ 0-~rin~s 120.A eluic1 passa(3e 1~2
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is connected to a source of pressurized air to yieldably
lift the blanked part against the actic)n of uppar
die 170. It will be noted that the upper end of
pin 112 engages the lower surface 10~ of liftout
member 86 so as to raiYe liftout member 86 against
the action of spring 94. Stem 92 is lifted by plate
124, which slides over screws 126 connected to bolster
46. Figure 3 illustrates plata 124 in its Eully
retracted po~ition.
Turning now to the upper portion of the die
set, a housing assembly 128 is slidably disposed
with respect to spindle 130, and retains punch 66
fox slidable movement relative thereto. ~ou~ing
a~sembly 12~ comprices a ~pindle alignment bearing
132 connected to slicle 21 by scraws 134, and a guide
bushing 136 connected to spin~le alignment bearing
by screws 138. The upper por-tion of punch 66 i~
for~ed as an annular piston 140 including seals 141
and 142, and reciprocat~s within an annular cylinder
144 defined by spindle alignment bearing 132 and
an annular step in guide bushing 136. The intermediate
portion 146 of punch 66 i~ annular and cylindrical
in shape, and punch 66 includes a tapered transition
portion 148 between intermediate portion 146 and
the lower cutting portion 150 including cutting edge
64. Air pressure from passage 149 yiQldably and
continuously urges punch 66 downwardly to the positlon
o~ Figure 4.
Punch 66 i~ very accurately guided and aligned
within guide bushing 136 by means of cylindrical
~all bearing as~embly 152, which comprise~ a cylindrical
rat~iner h~ving a plurallty o~ ball b~aring~ 154
aaptu~cl therein. ~ portion of the hall bearings
1$4 ~x~ ln roll:lng enga~amant with the out~r cylindrical
3r~ ~ur~ace 156 o:E the in~ermediate p~r-tlon 146 o~ punch
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66, and the remainder of the ball bearin~s 154 are
in rolling engagement with the inner concave cylindrical
sur~ace 153 of guide bushin~ 136. Bearing assembly
152 is held in place by bearing re~ainer 160, which
5 is secured to guide hushing 136 b~ screws 162. Bear-
ing assembly 15~ is prPferably preloaded so that
very precise tolerances can be maintained with respect
to the position oE the punch 66 relative to cutting
; edge 62. As discussed above, this is important from
the standpoint o~ always ensuring optimum clearance,
which reduces wear on the cuttin~ edges 62 and 64.
Passage 164 provides venting for cylinder 144 when
punch 66 is extencled to the position shown in Figure
~.
Upper forming die 170 is rigidly connecte~ to
spindle 130 by retainin~ rod 172, which is threadedl~
secured at its lower end 174 to forming die 170,
and is held against spindle 130 a~ its upper end
by nut 176. Spindle 130 is connected to ~op plate
178 by screws 179, and plate 178 is connected to
slide 24 by bolts 180 and nuts 182. Dowel 184 prevents
rotation bet~een formin~ die 170 and spindle 130.
It will be noted that forming die 170 compri.ses an
annular bead portion 186 around its periphery and
an ~nnular groove 188 ad~acent bead 186.
With reference to Figure 5, the li~tout mechanis~
40 comprises a bracket 1~0 secured to the bed 14
of press 10 by bolts 192, which are received within
sleeves 194 and held in place by nuts 196. Washers
197 and 198 are positioned between bolts 19~ and
bed 14, and between nuts 196 and brac};et 190, xespectivel~.
aam sh~t ~0 i~ rotatably ~upportcd by hearing~
2~2 conn~ctecl to legr3 16 (Fi~ure 1), and te~mlnate~3
in ~3procket 4~, which is in enga~ement with chain
~2. Since chain ~2 i~ driven b~ ~prock~t 43, whlch
i~ connected ko cr.mksha~t 1~, the rotation Oe cam
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sha~t 200 will be synchronized wi~h that o-E cranksha-Et
18 so that li.ftout occurs at the proper time in the
press cycle. Cam 206 is connected to shaft 200 by
an interference fit sleeve ~OA, which is scr~wed
to cam 206. Sleeve 208 is connectecl to cam 206 by
screws 210.
Cushion cylinder 212 is connected to the
upper surace 213 of bracket 190 by screws 214, and
includes a double ended cushion stem 216 connected
to a piston ~not shown) within cylinder 212. Cylinder
: 212, which is supplied with pressurized air from
a suitable source of supply, exerts cons~ant downward
pressure on stem 21fi. The lower end o~ stem 216
is threadedly secured tv follower yoke 218, and locked
thereagainst by lock nut 220. Cam follower 222 is
rotatably supported on shaft 224, the latter ~xtending
through yoke 218 and secured thereto by nut 226.
As cam 206 is rotated, cam follower 222 will roll
on its peripheral surface 228 and cause stem 216
to be lifted and lowered at the appropriate times
in the press cycle.
The upper end oE stem 216 is connected to plat~
.24 by stem retainer 230, which is connected to plate
124 by screws 232. The lower end 234 o stem 92
i~ contacted by the upper sur~ace o~ plate 12~ when
~tem 216, yoke 21~ ancl followex 222 are pushed upwal.dly
by cam 206.
With reference now to Ficlures ~, 3, 4 and 6,
the operation o~ pr~ss 10 will be described. The
steel or aluminum strip material 240 i~ advanced
by ~eed meahani~m 36 ~o that an unblanked portion
is po~i-tloned wi~hin ~he di~ ~et. r~eanwhlle, blankincJ
~lide ~1 and eormincJ ~ 24 ar~ movin~ downwa.rdly
und~r tha aation o:~ cranksha~t 1~, wlkh blankinq
~l.id~ 21 leading eormincl ~lld~ 2~ sll~hkly a~ ~hown
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in Figure 6. It will also he appreciated that the
total travel of forming slide 24 is greater than
the total travel oE blanking 51icle 21, a situakion
which is necessitated hy the crreater travel requirea
for the drawing operation.
As blan~in~ slide 21 moves downwardly, the lo~.~er
edge of punch 66 will contact and re~t on the upper
surface of strip material 240, hut no cu~ting of
the strip material will occur at this time because
blanking slides 21 and guide hushing 136 hava not
yet caught up to punch 66. At a~proximately 140
of the pres~ c~cle, the ~urface 242 of quide bushing
132 will contact the upper surace of the piston
portion 140 o~ punch 66 and drive cutting edge 64
1.5 downwardly past the cutting edge 62 of cutting die
58 so as to blank out a circular disk 84 rom the
strip material 240. The press in thi~ position is
illustrated in Figure 2 wherein the punch ~6 has
just cut through the ~trip material 240.
Punch 66 continues to travel past cutting edge
62 by a slight amount to the bottom dead center posi tion
illustrated in Figure ~. At the same time, forming
slide 24 will cause the upper forming die 170 to
pass by the lower edcre of punah 66 and draw the blank
84 to the shape illu~ratecl in Figure 3. In forminy
this shape, beacl 186 pres~e~ liftout member 90 down-~ :
wardly against the action o~ liftou~ pins 112 and
forms a bead 244 into the blank 84 a~ it passes into
th~ annular ~pace b~tweon draw rin~ 54 and lower
formin~ die 76. At the same time, groove 188 cooperate~
with bead 80 to form bead ~2.
Whil~ the draw.lncJ operation i-q ocaurrincr, blanklng
~llcle 21 h~gins to mov~ upwar~l~ a~ ~hown in Figux~,
6, but ~he aix pr~ure within c~llncler 144 hold~
the low~r ecl~Je o~ punch 66 acrain~t blank 8~ during
at lo~t a portion o~ the drawin~ operatlon. Formin~
slide 24 then also be~ins to move upwardly at about
the ~ame time that yuide bushing 136 begins to liEt
punch 66, which is just a few degre~s past bottom
dead center. Forming die 170 an~ punch 66 move upwardly
together, and at the same time cam 206 begins to
lii-t ~ollower 222, yoke 218, ~t(3m ~16, plate 124
and stem 92, which li~ts li~tout member ~6 and ~trips
the part ~4 from lower die 76 to the position sho~7n
in Fi~ure g. During strippin~ of part 84, both punGh
1~ 66 and upper forming die 170 ar~ maintained in close
contact with part 84 so that maximum control is realized.
When part a4 has been lifted to the position shown
in Fi~ure 4, it is eJected by a mechanical 15icker,
or by a blast oE air, or by ~ravity, a~ in the case
o~ an inclined press, or by a combination of any
two or all three oE thas~ means.
As cam 206 continues to rotate, spring 94 will
cause liftout member 86 to be re~racte~ below the
tin line, and another segment of strip material 240
is fed into the die. The press then recycles to
again perform the operations described above.
Although springs and pressuriz~d air have been
used for various biasing functions i~ the press described
above, in some cases thcy are interchangeable. For
exrample, spring pre~sur~ could be utiliæed to bias
punch 66 downwardlv rather than pres3urizecl air as
in the preferred embodiment. The ball bearin~ as~embly
152 utili2ed to guide punch 66 can be any one o~
a variety oE commercially available bearings, such
as those manuEaatured by Lempco Industrie~s Inc.
Althouc~h an open back inclinahl~, clouhl~ action
pr~s 10 ha~ b~n d~scribed in connQctlorl with khe
lnventlon, tha lnv~ntion i~ not c;o llmited to thi~
typ~ o~ pr~s~. E'urth~rmorc, th~ invantion could
be utlllzecl ~or marlufacturincJ parts other than can
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ends, ancl the particular blanking and forming operations
described a~ove are merely exemplar~ an~ are not
intended to limit the invention in its ~roa~est orm.
Tlle invention also encompasses presses llaving a l~luralit~
of punches in the die set.
While this invention has been descxibed as having
a preferred design, it will be understood that it
is capa~le of further modification. This application
is, therefore, intended to cover any variations,
uses, or adaptations of the invention ~ollowin~ ~he
~eneral principles thereof and inc~udin~ such departures
from the present disclosure as come ~it!~in ktlown
or customar~ nractice in the art -to ~ ich this invention
~ertains and fall within the limits of the apnendecl
claims.
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