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Патент USA US3030890

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April 24, 1962
g
s. E. KEAGLE
3,030,880
HYDRAULIC PREss BRAKE AND HYDRAULIC SYSTEM THEREFOR
Filed Nov. 10, 1960
‘4
2
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3 Sheets-Sheet 1
F1 E6; 1
25'
22
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INVENTOR.
STANLEY E. K5464;
BY
FIG’. 5
April 24, 1962
s. E_ KEAGLE
3,030,880
HYDRAULIC PRESS BRAKE AND HYDRAULIC SYSTEM THEREFOR '
Filed Nov. 10, 1960
3 Sheets-Sheet 2
Q
F5IG.
INVENTOR.
$741M 5X1? (ma:
Jrramvzr:
24,
3,030,880
s. E. KEAGLE
HYDRAULIC PRESS BRAKE AND HYDRAULIC SYSTEM THEREFOR
Filed NOV. 10, 1960
3 Sheets-Sheet 3
A4
wmvron.
5mm” 2-? K6494:
BY
'
Jrramvs r:
United States Patent
C@
3,030,88?
Patented Apr. 24-, 1962
1
2
3,030,880
force exerted by a hydraulic press after the work has
been contacted.
HYDRAULIC PRESS BRAKE AND HYDRAULIC
SYEiTEM THEREFOR
Stanley E. Keagle, 2626 Nassau St, Sarasota, Fla.
Filed Nov. 10, 1960, Ser. No. 68,471
14 Claims. (Cl. 100-269)
This invention has relation to hydraulic press brakes
In the drawings:
FIG. 1 is a front elevational view of a hydraulic press
made according to the present invention with parts broken
away to show a hydraulic pump and control valve;
‘FIG. 2 is a top plan View of the device of FIG. 1;
FIG. 3 is a view taken as on line 3-3 in FIG. 2 with
and more particularly to the type of press brake that
parts in section and parts broken away;
travels a portion of the work stroke unloaded or under 10
FIG. 4 is a sectional view taken as on line 4—4 in
relatively light loads and then must exert a relatively
FIG. 2; and
greater force to accomplish a desired operation.
FIG. 5 is a sectional view taken as on line 5—5 in
Present hydraulic presses use a single stage cylinder
FIG. 4.
for power. In order to have enough force for heavy jobs
Referring to the drawings and the numerals of reference
at a safe working pressure the piston of the power cylin 15 thereon, a hydraulic press 19 includes a frame 11 that
der must be relatively large. The ?lling of the cylinder
has two outer longitudinal members 12, 12 and two in
then tages a considerable amount of time. This slows the
production of the press and limits its output and usefu1~
ness.
A hydraulic press made according to the present inven
tion incorporates a hydraulic power cylinder of relatively
small size that will rapidly advance a press platen to the
ner longitudinal members 18, 18.
Each outer member
and its respective adjacent inner member are ?xedly
joined together adjacent ?rst ends thereof with end mem
bers 13, 13. A cylinder support 14 ?xedly joins the two
inner members adjacent said ?rst ends. An anvil 15 is
?xedly positioned against integral upright portions 16 of
Work and when the force on the work exceeds a prede
the longitudinal members at a second end of said longi-'
termined value an auxiliary hydraulic system becomes
tudinal members.
operative to make the force upon the work a multiplica 25
A hydraulic power cylinder 17 is ?xedly positioned
tion of the force exerted by the hydraulic power cylinder.
against cylinder support 14 and extends toward anvil 15
In the form of the invention as shown, this force multi
between inner members 18, 18. A piston rod 26} is at
plication is obtained through utilization of a two-section
tached to an internal power piston 28 and extends to en
platen that is resiliently held together when the platen is
gage a platen 21 that is slidable on the longitudinal frame
under no load. As disclosed, the piston rod for the main 30 members and extends therebetween. Platen 21 consists
power cylinder is slidably ?tted through the upper platen
section and engages a cylindrical opening that has ‘been
bored into the lower section. The piston rod end surface
acts as a separate piston when it moves within the cylindri
of a ?rst section 22 and a second section 23 that are re-'
siliently urged together by a plurality of springs 24 act
ing on bolts 25 that in turn are slidable in ?rst section
22 and ?xedly attached to said second section 23.
cal opening in the second section. This cylindrical open 35 First section 22 of the platen has two ?xedly attached
ing is connected in parallel with a plurality of auxiliary
guide shafts 26, 26 that extend substantially parallel to the
cylinders bored into the lower section of the platen. The
longitudinal frame members and are slidably mounted
upper section of the platen has an equal number of auxil
through guide blocks 27, 27 each of which is supported
iary pistons ?xedly attached thereto and extending into
by the longitudinal frame members and is ?xedly retained
the respective cylinders in the lower section. The cylinder 40 thereto by notches 29, 29. Guide blocks 27, 27 are braced
in the second section for the power cylinder piston rod
back to end members 13, 13 with struts 30, 30.
and the connecting passages to the auxiliary cylinders con
A ?rst brake block 31, and a second brake block 32 are
tain hydraulic ?uid and form a closed hydraulic system.
pivotally attached to each of guide blocks 27 with a pin
When a predetermined force or pressure has been reached
38 and are positioned to engage each of the guide shafts
in this closed system the upper section of the platen is 45 26. Each of the second brake blocks 32 has a cylinder
locked with respect to the press frame. The power piston
33 bored into it and a pressure tight piston 34 ?tted within
rod continues to move within the cylindrical opening in
said cylinder. A rod 35 is ?xedly attached to the brake
the lower section of the platen, a hydraulic pressure con
piston and extends slidably through ?rst brake block 31.
tinues to be built up within said cylindrical opening and
A nut 36 is threadably ?tted onto rod 35 and engages
an equal pressure will result in each of the auxiliary cylin 50 ?rst brake vblock 31 and moves the blocks toward each
ders. This causes the lower section of the platen to move
other where the piston is acted upon by hydraulic pres
with respect to the upper section against the action of the
sure. An oil passage 37 is located in each of second
resilient means that urges the sections together. The
brake blocks 32 and opens into cylinder 33 between pis~
total force exerted by the lower section will be propor
ton 34 and the interior end of the cylinder.
tional to the number of auxiliary cylinders and their re
Piston rod 20 is slidably ?tted through ?rst section 22
spective cross sectional area in relation to the cross sec
of the platen 21 and extends to slidably engage a master
tional area of the power piston rod acting in its cylindri
cylinder 40 in the second platen section 23. A lower
cal opening in the lower section. The force exerted by
surface 19 of rod 20 acts as a master piston within said
the lower section of the platen is applied directly to the
master cylinder. A plurality of slave pistons 41 are ?x
work. When the power cylinder is retracted the upper 60 edly attached to the ?rst platen section 22 and each ex
section of the platen is released and the two sections are
tends to slidably engage an aligning slave cylinder 42 lo
again resiliently urged together and will move as a unit.
cated in second section 23. A pressure tight element 43
Utilization of auxiliary cylinders and pistons in the
seals each of the slave cylinders 42 and master cylinder
two-section platen will allow any desired multiplication
40 with respect to their respective pistons. A port 44
of force on the work. The movement of the lower sec
connects all of the slave cylinders 42 and master cylinder
tion of the platen with respect to the upper section will
46 in parallel and provides passageway for hydraulic oil
be proportionally less than the movement of the power
to ?ow between said cylinders. A pair of pressure lines
piston rod and this will be dependent on the number of
45, 45 are connected to port 44- and one of said lines is
the auxiliary cylinders in the lower section and their re
connected to passageway 37 in each of the second brake
spective sizes.
70 blocks 32, 32. With the two sections of the platen con
It is an object of the present invention to present a de
tiguous, the pistons 41 extend substantially to the bottom
vice that will automatically provide a multiplication of
of their respective cylinders and the piston rod 20 is posi~
3,030,880
3
tioned with the end surface 19 thereof adjacent the outer
end of master cylinder 40. Port 44, the pressure lines
45, 45 master cylinder 40, slave cylinders 42 and brake
cylinders 33, 33 in each of the brake blocks 32 are ?lled
with hydraulic oil. This system becomes an independent
closed circuit hydraulic system.
A cross arm 46 is ?xedly attached to piston rod 20
and has two bolts 4-7, 47 slidably mounted therein. Bolts
47, 47 are ?xedly attached to ?rst section 22 of the
platen. When the piston rod is retracted, cross arm 46
engages the head portions 50 of the bolts and thereby
moves the platen to a retracted position.
The frame 11 and associated parts are supported by
further sliding movement. As the piston rod 20 con
tinues to slide within master cylinder 4t) the hydraulic
oil within the cylinder will be forced through port 44 to
the slave cylinders 42 and the pressure in the slave cyl
inders 42 will be equal to the pressure in master cylinder
at}. This pressure acting on the slave pistons 41 will
force the second section of the platen to move against
the work and away from the ?rst section of the platen.
This action is best illustrated in FIG. 2. The total force
10 exerted on the work is determined by the number of
slave cylinders and the area of said slave cylinders in re
lation to the area of end surface 19 of piston rod 20 and
master cylinder 40. As illustrated, with four slave cyl
inders each with a cross sectional area equal to the cross
a cabinet 51 or other suitable structure. Hydraulic ?uid
under pressure is supplied to the power cylinder 17 by a 15 sectional area of master cylinder 40 the total force
exerted on the work by the second section of the platen
hydraulic pump 52 that is driven by an electric motor 53.
will be four times the force exerted by piston rod 20,
A control valve 54- is employed to divert flow from the
minus the force necessary to overcome the force from
pump selectively through a ?rst oil line 55 or a second
springs 24. Conversely, the movement of the second
oil line 56, each of which are open to the interior cyl
section of the platen with respect to the ?rst section there
inder 17 on opposite sides of the internal piston. A re
of will be one-fourth of the movement of piston rod 20
lief valve 57 is connected in one of the oil lines to pre
within master cylinder 40.
vent excessive pressure buildup in the line.
When oil is diverted from the pump through line 56
Any tendency of the second section of the platen to
cock or bind with respect to the ?rst section is counter
to power cylinder 17 the power piston rod is retracted,
' the pressure in master cylinder 40 is thereby relieved and
acted by pinion gears 58, 58 drivably mounted on a trans
verse torsion shaft 59 that is rotatably mounted on
the brake blocks holding the guide shafts 26, 26 will be
brackets 60, 6t; which in turn are ?xedly attached to the
released. The springs 24 will resiliently urge the two sec
second section 23 of the platen with bolts 61, 61. A
rack 62 is ?xedly attached to each of the outer longi
tudinal members 12 and each rack extends inwardly
therefrom to drivably engage one of pinion gears 58.
Thus, if one of the ends of the second section of the
platen tends to cock when loaded, the unequal movement
of the ends is restrained by the rack and pinion acting
through the torsion shaft 59 and brackets 60. The pinion
gears will not twist with respect to each other but must
rotate together. When the second section of the platen
tends to cock one of the brackets 60 will tend to move
more than the other. This in turn tends to rotate one
of the pinion gears 58 more than the other. The rota
tional movement of the pinion gear is transmitted by shaft
59 to the other pinion gear, thereby equalizing the move
ment of both ends of the second section of the platen
or alternatively equalizing the load exerted at the ends
of the second section if additional movement is not pos
sible. A slot 63 is provided in each of the inner longi
tudinal members 18 for the torsion shaft 59 so that it
may move longitudinally.
Operation
When the press is to be used, as for example to make
permanent a fold in the signatures of a book 64, the
motor 53 is started and the hydraulic pumpv 52 is there
by activated. The book 64 may be placed on the anvil
tions of the platen into contacting relationship. As piston
rod 20 retracts, cross arm 46 will contact bolt heads 50
and the bolts 47 will in turn move the platen away from
the work as the piston rod continues to be retracted
The power cylinder 17 may be of a size to permit rapid
?lling until the work is contacted, thereby making the
unloaded stroke of the platen fast. When the work is
contacted the lower section of the platen will automati
cally move in relation to the ?rst section with a force
multiplication thereby insuring suf?cient power to accom
plish most press brake jobs. The stroke will then also
be proportionately slower to make control of the platen
The return stroke also will be rapid because of
the relatively small size of cylinder 17.
40 easier.
While the device as disclosed is shown operating in a
horizontal position a vertical press brake may utilize the
same type of platen. Also a V-die or other metal form
ing equipment may be inserted into the press brake and
equally excellent results will be obtained. The rapid
return and unloaded strokes of the piston rod greatly
increase the ei?ciency and total output of the press brake.
The total force that may be exerted by the brake will
still be large enough to accomplish most heavy jobs.
What is claimed is:
1. A hydraulic press brake including a main frame,
a work anvil mounted with respect to said frame, a hy
draulic power cylinder mounted with respect to said
15 and the power cylinder 17 activated by moving the
frame, a power piston slidably mounted in said power
hydraulic control lever to position to divert ?ow through
cylinder, a source of ?uid under pressure, a conduit open
line 55 to the interior of said cylinder. The ?rst and
to said source of fluid under pressure and to the interior
second sections of the platen will be contiguous to form
of said power cylinder, control means in said conduit
a single unit under the action of springs 24 acting through
for selectively diverting said ?uid under pressure to said
bolts 25. The brake blocks 31 and 32 will be released 60 power cylinder, a ?rst platen section slidably mounted
from both guide shafts 26, 26 and the guide shafts may
with respect to said frame, a second platen section slid
move freely in guide blocks 27, 27. The power piston
ably mounted with respect to said ?rst platen section,
28 and the piston rod 20 will be extended by the hy
bias means urging said platen sections together, a piston
draulic pressure in cylinder 17 and will move the platen
rod link operably associated with said power piston, a
toward the anvil by the pressure on the end surface 19
master hydraulic unit comprising 'two master hydraulic
of the piston rod 20 bearing on the column of hydraulic
components, namely a master cylinder and a master
oil in master cylinder 40. The spring 24 holding the two
piston operably associated with said master cylinder, with
platen sections together will be adjusted to counteract
one of said master hydraulic components being operably
the pressure necessary to move the platen under no load,
thereby insuring that the section will move as a unit. 70 associated with said second platen section and the other
of said master hydraulic components being operably asso
When the platen contacts the work piece, the pressure
ciated with said piston rod link, at least one slave hy
within master cylinder 40 will rise and the resulting
draulic unit comprising two slave hydraulic components,
pressure in cylinder 33 in each of the second brake
namely a slave cylinder and a slave piston operably asso
blocks 32, 32 will cause the ?rst and second brake blocks
ciated with said slave cylinder, with one of said slave
to move together and lock each of the guide shafts from
3,030,880
5
hydraulic components operably associated with said ?rst
platen section and the other slave hydraulic component
operably associated with said second platen section, there
being a passageway open to the interior of said master
hydraulic unit and the interior of said slave hydraulic
unit, the interior of said master hydraulic unit, the inte
rior of said slave hydraulic unit and said passageway
6
operable to hold said section immobile responsive to in
crease of pressure in said closed hydraulic system.
5. The combination as speci?ed in claim 4 wherein said
master cylinder is ?xedly mounted with respect to said
second platen section and wherein said brake means is
associated with said ?rst platen section.
6. The combination as speci?ed in claim 5 and means
constituting a closed hydraulic system, and means for
to prevent a ?rst end of said second platen section from
immobilizing with respect to said frame the platen sec
traveling a different distance with respect to said ?rst
tion located farthest away from said anvil responsive to
platen section than a second end of said second platen
increase of pressure in said closed hydraulic system.
section.
2. A hydraulic press brake including a main frame, a
7. A hydraulic press brake including a main frame, a
work anvil mounted with respect to said frame, a hy
work anvil mounted with respect to said frame, a hy
draulic power cylinder mounted with respect to said
draulic power cylinder mounted with respect to said
frame, a power piston slidably mounted in said power 15 frame, a power piston slidably mounted in said cylinder,
cylinder, a piston rod link operably associated with said
a power piston rod ?xedly attached to said power piston,
power piston, a source of ?uid under pressure, a con
duit open to said source of ?uid under pressure and to
pressure source and to the interior of said power cylin
a source of ?uid under pressure, a conduit open to said
the interior of said power cylinder, control means in said
der, control means in said conduit for selectively diverting
conduit for selectively diverting said ?uid under pressure
to said power cylinder, a ?rst platen section slidably
said ?uid under pressure to the interior of said power
mounted with respect to said frame, a second platen sec
tion slidably mounted wtih respect to said ?rst platen
toward said anvil, a ?rst platen section slidably mounted
section, bias means urging said platen sections together,
ably mounted with respect to said ?rst platen section, bias
cylinder and thereby moving said piston and attached rod
with respect to said frame, a second platen section slid
a master hydraulic unit comprising two master hydraulic 25 means resiliently urging said platen sections together, a
components namely a master cylinder and a master piston
master cylinder located in said second section, a master
operably associated with said master cylinder, one of
piston operably engaging said master cylinder, said power
said master hydraulic components being ?xedly attached
piston rod being slidably mounted with respect to said
with respect to said one of said platen sections and the
?rst platen section and operably associated with said
other master hydraulic component being operably asso 30 master piston, a plurality of slave cylinders ?xedly at
tached with respect to one of said platen sections, a plu
ciated with said piston rod link, at least one slave cyl
rality of slave pistons ?xedly attached with respect to
inder mounted With respect to said second platen sec
the platen section not associated with said slave cylinders,
tion, a slave piston operably engaging said ?rst platen
section and operably associated with said slave cylinder,
each of said slave pistons being operably associated with
there being a passageway open to the interior of said 35 one of said slave cylinders, therebeing a passageway open
to the interior of said master cylinder and the interior of
master hydraulic unit and the interior of said slave cyl
inder, the interior of said master hydraulic unit, the inte
rior of said slave cylinder and said passageway con
stituting a closed hydraulic system, and means for im
mobilizing with respect to said frame the platen section
located farthest away from said anvil responsive to in
crease of pressure in said closed hydraulic system.
3. A hydraulic press brake including a main frame, a
work anvil mounted with respect to said frame, a hy
draulic power cylinder mounted with respect to said
frame, a power piston slidably mounted in said cylinder,
a piston rod ?xedly attached to said power piston, a
source of ?uid under pressure, a conduit open to said
pressure source and to the interior of said power cylinder,
each of said slave cylinders, brake means ?xedly attached
with respect to said frame and operably associated with
said ?rst platen section, a brake cylinder operably asso
ciated with said brake means, and a passageway open to
the interior of said master cylinder and the interior of
said brake cylinder, the interior of said master cylinder,‘
said passageways, the interior of each of said slave cyliny
ders and the interior of said brake cylinder constituting
a closed hydraulic system, with said brake cylinder posi
tioned to actuate said brake means to hold said ?rst platen
section immobile when the pressure within said closed hy
draulic system exceeds a predetermined level.
8. The combination as speci?ed in claim 7 and means
to prevent a ?rst end of said second platen section from
traveling a different distance than a second end of said
said ?uid under pressure to said power cylinder, a ?rst
second platen section with respect to said ?rst platen sec
platen section slidably mounted with respect to said
tion.
frame, a second platen section slidably mounted with
9. The combination as speci?ed in claim 8 wherein said
respect to said ?rst platen section, bias means urging said 55
means to prevent said ends of said second platen section
platen sections together, a master cylinder ?xedly mount
from traveling different distances with respect to said
ed with respect to one of said platen sections, a master
control means in said conduit for selectively diverting
?rst platen section includes a shaft rotatably mounted
with respect to said second platen section, a pinion gear
said master piston, at least one slave cylinder ?xedly at 60 drivingly mounted adjacent each end of said shaft, and
a rack ?xedly attached with respect to said frame adja
tached with respect to said second platen section, a slave
cent
each end of said shaft and drivingly engaging one of
piston operably engaging said ?rst platen section and op
piston operably associated with said master cylinder,
means operably connecting said power piston rod and
erably associated with said slave cylinder, there being
a passageway open to the interior of said master cylin
der and the interior of said slave cylinder, the interior
of said master cylinder, said passageway and the interior
of said slave cylinder constituting a closed hydraulic sys
said pinion gears.
'
10. A hydraulic press brake including a main frame, a
Work anvil mounted with respect to said frame, a hydrau
lic power cylinder mounted with respect to said frame, a
power piston slidably mounted in said cylinder, a power
piston rod ?xedly attached to said power piston, a source
tem, and means for immobilizing with respect to said
of ?uid under pressure, a conduit open to said pressure
frame the platen section located farthest away from said
source and to the interior of said power cylinder, con
anvil responsive to increase of pressure in said closed hy 70 trol means in said conduit for selectively diverting said
draulic system.
?uid under pressure to said cylinder and thereby moving
4. The combination as speci?ed in claim 3 wherein said
said piston and attached rod toward said anvil, a ?rst
means for immobilizing said platen section includes brake
platen section slidably mounted with respect to said frame,
means ?xedly attached with respect to said frame and as
at least one guide block ?xedly attached with respect to
sociated With said platen section, said brake means being " said frame, at least one guide rod ?xedly attached to said
spanner;
7
?rst platen section and slidably mounted through said
guide block, a second platen section siidably mounted
and a master piston operably associated with said master
cylinder, with one of said master hydraulic components
with respect to said ?rst platen section, bias means res'li
being operably associated with said second platen sec
tion and the other of said master hydraulic components
being operably associated with said piston rod link, at
least one slave hydraulic unit comprising two slave hy
ently urging said second platen section into contacting
relationship with said ?rst platen section, a master cylinder
located in said second platen section, said power piston
draulic components, namely a slave cylinder and a slave
piston operably associated with said slave cylinder, with
tion with the lower portion of said power piston rod con
one of said slave hydraulic components operably associ
stituted as a master piston operably engaging said master
cylinder, a plurality of slave cylinders located in said sec 10 ated with said ?rst platen section and the other slave hy
rod being slidably mounted through said ?rst platen sec
ond platen section, a plurality of slave pistons ?xedly at
tached with respect to said ?rst platen section and each
operably associated with one of said slave cylinders, brake
draulic component operably associated with said second
means mounted on said guide block and operably engag
platen section, therebeing a passageway open to the
interior of said master hydraulic unit and the interior
of said slave hydraulic unit, the interior of said master
ing said guide rod, a brake actuating cylinder operably
hydraulic unit, the interior of said slave hydraulic unit
associated with said brake means, and therebeing a pas
and said passageway constituting a closed hydraulic sys
tem, and means for immobilizing with respect to said
frame the platen section located farthest away from
said anvil responsive to increase of pressure in said closed
sageway connecting the interior of said master cylinder,
the interior of each of said slave cylinders, and the interior
of said brake cylinder in parallel, said passageway and said
parallel connected cylinders thereby forming a closed hy
draulic circuit, with said brake means engaging said guide
rods and holding said ?rst section of said platen immobile
hydraulic system.
14. A press brake including a main frame, a work
anvil mounted with respect to said frame, a ?rst platen
section slidably mounted with respect to said frame, a
second platen section slidably mounted with respect to
said ?rst platen section, bias means urging said platen
sections together, power thrust means mounted with
respect to said frame, a piston rod link operably associ
when the pressure within said closed hydraulic system ex
ceeds a predetermined level.
11. The combination as speci?ed in claim 10 wherein
said bias means includes a plurality of coil springs posi
tioned to urge the platen sections together.
12. The combination as speci?ed in claim 10 wherein
said brake means includes a pair of brake blocks piv
unit comprising two master hydraulic components, namely
otally attached with respect to said guide block and with
respect to each other and substantially encircling said
a master cylinder and a master piston operably associ
ated with said master cylinder, one of said master hy
guide rod, said brake cylinder being ?xedly attached with
draulic components being operably associated with said
second platen section and the other of said master hy
draulic components being associated with said piston rod
link, at least one slave hydraulic unit comprising two
respect to a ?rst of said brake blocks and having an in
ternal piston with attached piston rod positioned to oper
ably engage a second of said brake blocks and to move
ated with said power thrust means, a master hydraulic
said blocks together to lock said guide rod when the
slave hydraulic components, namely a slave cylinder and
pressure within said closed hydraulic system exceeds a
a slave piston operably associated with said cylinder,
with one of said slave hydraulic components operably as
sociated with said ?rst platen section and the other slave
hydraulic component operably associated with said sec
ond platen section, t-herebeing a passageway open to the
interior of said master hydraulic unit and the interior of
said slave hydraulic unit, the interior of said master
hydraulic unit, the interior of said slave hydraulic unit
and said passageway constituting a closed hydraulic sys
tem, and means for immobilizing with respect to said
frame the platen section located farthest away from said
anvil responsive to increase of pressure in said closed
predetermined level.
13. A hydraulic press brake including a main frame,
a work anvil mounted with respect to said frame, a power
hydraulic unit comprising two power hydraulic com
ponents, namely a power hydraulic cylinder and a power
piston slidably mounted in said power cylinder, a ?rst
of said power hydraulic components being mounted with
respect to said frame, a piston rod link operable associ
ated with a second of said hydraulic components, a source
of ?uid under pressure, a conduit open to said source of
?uid under pressure and to the interior of said power cylin
hydraulic system.
der, control means in said conduit for selectively diverting
said ?uid under pressure to said power cylinder, a ?rst 50
References Cited in the ?le of this patent
platen section slidably mounted with respect to said frame,
a second platen section slidably mounted with respect to
said ?rst platen section, bias means urging said platen
sections together, a master hydraulic unit comprising two
master hydraulic components, namely a master cylinder
UNITED STATES PATENTS
2,302,953
2,603,176
2,855,628
Popock ____________ __ Nov. 24, 1942
Sebring et a1. ________ __ July 15, ‘1952
Lassman ____________ __ Oct. 14, 1958
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