U.S. patent number 3,910,087 [Application Number 05/533,992] was granted by the patent office on 1975-10-07 for hydraulic-forming machine.
This patent grant is currently assigned to The Boeing Company. Invention is credited to Everett E. Jones.
United States Patent |
3,910,087 |
Jones |
October 7, 1975 |
Hydraulic-forming machine
Abstract
Hydraulic-forming apparatus for compressively conforming a
workpiece to the contour of a die by applying uniform forming
effort from pressurized hydraulic pressure fluid in a pressure cell
chamber surrounding both the part and die. Pressure is transmitted
to the part and die through a pressure deformable plastic mandrel,
the pressure supporting the part and die in their natural attitudes
and causing the part to conform to the shape of the die without
distorting the adjacent areas of the workpiece. The fluid pressure
system includes means for pressurize the pressure cell chamber to
pump output pressure, a lower pressure amplifier for intermediate
pressurization of the system and a high pressure amplifier to apply
maximum forming pressures to the workpiece. Each amplifier includes
a pressure multiplying apparatus such as a reciprocative piston
assembly in which a larger diameter master piston drives a smaller
diameter slave piston to develop higher hydraulic pressures for use
in the forming apparatus. The fluid pressure amplifiers communicate
with the pressure cell chamber so that reciprocation of each piston
assembly incrementally increases the fluid pressure therein. The
lower pressure amplifier output has a designed maximum pressure at
which the lower pressure amplifier is isolated from the pressure
cell chamber and the higher pressure amplifier operates to further
increase the fluid pressure applied to the pressure cell chamber.
Upon completion of pressurization of the pressure cell chamber to
the desired pressure for forming the workpiece, the hydraulic fluid
activating the higher pressure amplifier is released and is caused
to flow back into a reservoir through a velocity control means in
the conduit. The velocity control means provides a tortuous path
for the hydraulic fluid to prevent damage to the equipment from
sonic or near sonic flow rates.
Inventors: |
Jones; Everett E. (Wichita,
KS) |
Assignee: |
The Boeing Company (Seattle,
WA)
|
Family
ID: |
24128265 |
Appl.
No.: |
05/533,992 |
Filed: |
December 18, 1974 |
Current U.S.
Class: |
72/63; 72/56 |
Current CPC
Class: |
B21D
22/12 (20130101) |
Current International
Class: |
B21D
22/00 (20060101); B21D 22/12 (20060101); B21D
022/10 (); B21D 028/18 () |
Field of
Search: |
;72/56,63,54
;29/421R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: DiPalma; Victor A.
Attorney, Agent or Firm: Christensen, O'Connor, Garrison
& Havelka
Claims
What is claimed is:
1. An apparatus for compressively conforming a metal part to the
contour of a die, a pressure vessel defining a pressure chamber, a
pressure-deformable mandrel enclosed within the chamber, the part
and the die being positionable inside the mandrel, supply means for
supplying pressure fluid, means for selectively connecting the
supply means with the pressure vessel pressure chamber to
prepressurize the pressure vessel pressure chamber;
low pressure amplifier means having an input chamber selectively
connectable with the supply means and an output chamber in
communication with the pressure vessel pressure chamber, the low
pressure amplifier means being operable when the input chamber is
pressurized with pressure fluid from the supply means to increase
the pressure in the pressure vessel pressure chamber for exerting
compressive forming effort through the mandrel upon the part, the
low pressure amplifier means being operable to increase the fluid
pressure in the pressure vessel pressure chamber up to a first
maximum fluid pressure;
high pressure amplifier means having a second input chamber
selectively connectable with the supply means and a second output
chamber in communication with the pressure vessel pressure chamber,
the high pressure amplifier means being operable when the second
input chamber is pressurized with pressure fluid from the supply
means to increase the fluid pressure in the pressure vessel
pressure chamber for exerting compressive effort through the
mandrel upon the part;
control valve actuator means responsive to the transition pressure
means for connecting the supply means with the first-mentioned
input chamber to operate the low pressure amplifier to increase the
fluid pressure in the pressure vessel pressure chamber for selected
forming pressures up to the first maximum pressure, and
alternatively for connecting the supply means with the
first-mentioned input chamber to operate the low pressure amplifier
to increase the fluid pressure in the pressure vessel pressure
chamber up to the first maximum pressure, and then for connecting
the supply means with the second input chamber to operate the high
pressure amplifier to further increase the fluid pressure in the
pressure vessel pressure chamber for selected forming pressures
greater than the first maximum pressure;
the control valve means also being responsive to the pressure
selector means for depressurizing the first-mentioned input
chamber, and alternatively the first-mentioned and second input
chambers when the fluid pressure in the pressure vessel pressure
chamber reaches the selected forming pressure; and,
depressurization means responsive to the pressure selector means
for depressurizing the pressure vessel pressure chamber upon
depressurization of the first-mentioned input chamber and
alternatively with depressurization of the first-mentioned and
second input chambers.
2. The apparatus according to claim 1, wherein the low pressure
amplifier means comprises a reciprocative piston assembly including
a double end face master piston, a single end face slave piston
movable conjointly with the master piston, one end face of the
master piston being exposed to the first-mentioned input chamber,
the other face of the master piston being exposed to a second
chamber, the end face of the slave piston being exposed to the
first-mentioned output chamber, the surface area of the one end
face of the master piston being substantially greater than the
surface area of the end face of the slave piston, and wherein the
control valve means includes means for connecting the supply means
to the first-mentioned input chamber for pressurizing the
first-mentioned input chamber to move the piston assembly in one
direction to increase incrementally the pressure in the
first-mentioned output chamber, and alternately for connecting the
supply means to the second chamber for pressurizing the second
chamber to move the piston assembly in the reverse direction, and
including intermediate valve means intermediate the first-mentioned
output chamber and the pressure vessel pressure chamber for
preventing reduction in fluid pressure in the pressure vessel
pressure chamber during movement of the piston assembly in the
reverse direction, whereby the fluid pressure in the pressure
vessel pressure chamber is increased in increments by moving the
piston assembly in the one and the reverse directions in alternate
sequence.
3. The apparatus according to claim 1, wherein the high pressure
amplifier means comprises a reciprocative piston assembly including
a double end face master piston, a single end face slave piston
movable conjointly with the master piston, one end face of the
master piston being exposed to the second input chamber, the other
face of the master piston being exposed to a second chamber, the
end face of the slave piston being exposed to the second output
chamber, the surface area of the one end face of the master piston
being substantially greater than the surface area of the end face
of the slave piston, and wherein the control valve means includes
means for connecting the supply means to the second input chamber
for pressurizing the second input chamber to move the piston
assembly in one direction to increase incrementally the pressure in
the pressure vessel pressure chamber and alternately for connecting
the supply means to the second chamber for pressurizing the second
chamber to move the piston assembly in the reverse direction.
4. The apparatus according to claim 1, wherein the low and high
pressure amplifiers each comprise reciprocative piston assemblies
including master pistons having faces respectively exposed to the
first-mentioned and second input chambers, and wherein the surface
area of the master piston face associated with the high pressure
amplifier is greater than the surface area of the master piston
face associated with the low pressure amplifier.
5. The apparatus according to claim 1, including means defining a
primary flow passage between the second output chamber and the
pressure vessel pressure chamber, and means defining a secondary
flow passage between the first-mentioned output chamber and the
pressure vessel pressure chamber, and wherein the check valve means
includes a one-way valve in the secondary flow passage, the one-way
valve adapted for allowing passage of hydraulic pressure fluid
through the secondary flow conduit only in a direction of flow from
the first-mentioned output chamber to the pressure vessel pressure
chamber.
6. The apparatus according to claim 5, wherein the secondary flow
passage is between the first-mentioned output chamber and the
primary flow passage.
7. The apparatus according to claim 6, wherein the secondary flow
passage is between the first-mentioned output chamber and the
second output chamber.
8. The apparatus according to claim 1, including discharge means
for receiving pressurized pressure fluid flowing from the second
input chamber, valve means intermediate the discharge means and the
second input chamber, the valve means including means for confusing
the flow of pressurized pressure fluid leaving the second input
chamber during depressurization thereof.
9. The apparatus according to claim 8, wherein the confusing means
includes a disc member extending perpendicularly to the flow of
pressurized pressure fluid through the valve means, the disc member
having a plurality of holes therethrough, the holes being of
various diameters and being positioned at various angles relative
to the flow so as to create confusion in the flow through the
holes.
10. The apparatus according to claim 9, including means defining a
bypass flow channel terminating at ports on either side of the disc
member.
11. The apparatus according to claim 1, wherein the pressure vessel
comprises an open ended tubular housing, the housing having a first
inner diameter, first and second end sealing means for respectively
sealing either end of the housing, the mandrel being tubular with a
diameter less than the first inner diameter, the pressure vessel
pressure chamber surrounding the mandrel between the end sealing
means, an elongated part and an elongated die being positionable
inside the mandrel with their lengths extending axially of the
mandrel, first and second clamping means respectively threadedly
coupled with either end of the housing for axially clamping the end
sealing means and the mandrel therebetween, the first and second
clamping means and the end sealing means each having relatively
axially alignable apertures through which the portions of the
elongated part and die on either side of the part section to be
conformed are extendable.
12. The apparatus according to claim 1, wherein the control valve
means comprises a valve selectively operable for connecting the
first-mentioned input chamber with the supply means, and valve
actuator means responsive to the pressure selector means for
operating the valve means.
13. The apparatus according to claim 12, wherein the pressure
selector means includes a time delay relay, the actuator means
being energizable by the time delay relay, the time delay relay
adapted for energizing the actuator means once the pressure chamber
has been prepressured with pressure fluid from the supply
means.
14. The apparatus according to claim 13, wherein the pressure
selector means includes a second time delay relay, the actuator
means also being de-energizable by the second time delay relay, the
second time delay relay adapted for de-energizing the actuator
means once the fluid pressure in the pressure vessel pressure
chamber has been increased by the low pressure amplifier.
15. The apparatus according to claim 12 including discharge means
for receiving pressurized pressure fluid from the first-mentioned
input chamber, and wherein the valve is further selectively
operable for connecting the first-mentioned input chamber to the
discharge means, the actuator means alternatively being responsive
to the transition pressure means for further operating the
valve.
16. The apparatus according to claim 1, wherein the control valve
means comprises a valve selectively operable for connecting the
second input chamber with the supply means, and valve actuator
means responsive to the transition pressure means for operating the
valve means.
17. The apparatus according to claim 16, including discharge means
for receiving pressurized fluid from the second input chamber, and
wherein the valve is further selectively operable for connecting
the second input chamber with the discharge means.
18. The apparatus according to claim 1 including discharge means
for receiving pressurized pressure fluid from the pressure vessel
pressure chamber, and wherein the depressurization means comprises
unload valve means intermediate the discharge means and the
pressure vessel pressure chamber operable for selectively allowing
passage of pressurized pressure fluid from the pressure vessel
pressure chamber, the unload valve means being responsive to the
pressure selector means for allowing flow of pressurized pressure
fluid therethrough simultaneously with depressurization of the
first-mentioned and second input chambers.
19. The apparatus according to claim 18, wherein the discharge
means communicates with the second output chamber.
20. The apparatus according to claim 19, wherein the unload valve
is intermediate the discharge means and the second output
chamber.
21. The apparatus according to claim 18, including pressure
responsive actuator means for operating the unload valve means, a
control valve for selectively connecting the supply means with the
pressure responsive actuator means for operating the unload valve
means, the control valve being responsive to the pressure selector
means.
22. The apparatus according to claim 21, wherein the control valve
alternatively connects the supply means with the pressure vessel
pressure chamber.
23. The apparatus according to claim 1, wherein the pressure
selector means comprises a plurality of pressure responsive
switching elements, one group of the switching elements being
responsive to fluid pressure in the first-mentioned input chamber
and another group of the switching elements being responsive to the
fluid pressure in the second input chamber, and means for selecting
one of the switching elements, the control valve means being
responsive to the selected one of the switching elements.
24. The apparatus of claim 1, wherein the transition pressure means
comprises a pressure responsive switch element responsive to
pressure in the first-mentioned input chamber.
25. A method for compressively conforming a portion of a metal
blank to the contour of a die using pressurized pressure fluid
surrounding a pressure deformable mandrel for transmitting
compressive forming effort to the metal blank, first and second
reciprocative pistons each movable in one direction to
incrementally increase the pressure of the pressure fluid and
alternately movable in a reverse direction without increasing the
pressure of the pressure fluid, comprising the steps of:
moving the first piston in one direction to incrementally increase
the pressure of the pressure fluid and alternately moving the first
piston in a reverse direction, and wherein the first piston is
moved in the one direction and then in the reverse direction in
alternate sequence until the pressure of the pressure fluid is
incrementally increased to a desired forming pressure less than a
transition pressure;
alternatively moving the first piston in the one direction and then
in the reverse direction in alternate sequence until the pressure
of the pressure fluid reaches the transition pressure; and
moving the second piston in the one direction so as to further
incrementally increase the pressure of the pressure fluid to a
second desired forming pressure greater than the transition
pressure while simultaneously therewith holding the first piston
stationary.
26. The method of claim 25 including the additional step of moving
the second piston in the reverse direction.
Description
BACKGROUND OF THE INVENTION
This invention relates to hydraulic-forming apparatus of the type
in which forming effort for conforming a metal blank to the contour
of a die is exerted compressively through a pressure deformable
mandrel surrounding the workpiece and die, and more particularly to
multiple stage pressurization systems for controlling the forming
effort exerted and to depressurize the unit after forming is
completed.
Presently-known hydraulic-forming systems typically achieve maximum
forming pressures of from 5,000 pounds per square inch (psi) up to
25,000 psi. For the purpose of forming parts using powder
metallurgy techniques and for workpieces difficult to form, it is
desirable to increase the pressure capability of such systems. This
is especially true in processing workpieces composed of stainless
steel, titanium, hafnium and other exotic metals which require
extremely high forming pressures. Moreover, it is desirable to
increase the versatility of the apparatus to accommodate a wider
variety of shapes and sizes of parts and to achieve a wider range
of formed shapes. One way to achieve these increases in the
apparatus forming pressure capability and accommodations of a press
would be to merely enlarge or increase the scale of presently known
pressure chamber components and the hydraulic pumping and control
systems associated therewith. Such a solution is undesirable from
the standpoint of overall system complexity, compactness, safety,
speed, operating costs and other economic factors. Additional pumps
would be required in the enlarged system to compensate for the
increased compressibility of the pressure exerting system due to
the added amounts of hydraulic pressure fluid and compressible
mandrel material surrounding the blank and die which would be
necessary to fill the added pressure chamber volume. Further, the
extremely high discharge velocities produced by decompression of
the hydraulic pressure fluid, forming core, and associated
relaxation in tension of the pressure chamber during
depressurization of the apparatus at the end of a forming cycle
would endanger operating personnel and equipment unless very large
and costly protective enclosures and safety systems including surge
suppression devices were added to presently-known hydraulic systems
and designs.
It is therefor an object of the present invention to provide
hydraulic-forming apparatus operable at forming pressures
substantially greater than those presently available while
overcoming the aforementioned difficulties of prior art
hydraulic-forming apparatus. A related object is to provide such
apparatus capable of achieving the pressures achieved by forming
pressures substantially higher than the prior art devices.
An additional object is to provide hydraulic-forming apparatus
which is compact, structurally simple, and economical to operate. A
further related object is to provide such apparatus useful to
locally form one section of elongated workpieces. A still further
related object is to provide hydraulic-forming apparatus with
multiple access ports to the pressure chamber which enable rapid
and easy removal or advancement of workpieces and dies through the
apparatus.
Another object is to provide hydraulic-forming apparatus including
surge suppression or control equipment for suppressing or
eliminating catastrophic failures and shock waves in the hydraulic
system and for preventing damage and injury to operating personnel
as a result of rapid depressurization of the apparatus at the
termination of a forming cycle.
Another object is to provide hydraulic-forming apparatus of
increased pressure chamber volume with the capability of
accommodating larger parts wherein the equipment for controlling
and operating the hydraulic system includes a multiple stage
hydraulic fluid supply to first accommodate, by means of a lower
pressure, higher volume hydraulic source, the compressibility of
the hydraulic-forming system; and secondly, apply a substantially
higher hydraulic pressure from a lower-volume, higher-pressure
hydraulic source, thereby achieving a substantially higher
hydraulic-forming pressure in a hydraulic-forming system of
reasonable size and of convenient operability.
SUMMARY OF THE INVENTION
In accordance with the present invention, hydraulic-forming
apparatus particularly useful for compressively conforming a
section of a workpiece to the contour of a die includes a pressure
vessel means defining a pressure chamber surrounding a pressure
deformable mandrel, within which the workpiece and die are
positioned. Compressive forming effort is exerted circumferentially
upon the workpiece and die through the mandrel by increasing the
pressure of hydraulic pressure fluid within the surrounding
pressure chamber. The fluid pressure in the pressure chamber is
first brought up to the maximum output pressure of a hydraulic
fluid source, then incrementally increased by a low pressure
amplifier up to an intermediate fluid pressure, and then is
increased by a high pressure amplifier. The amount of forming
pressure exerted by the pressure amplifiers is controlled by a
pressure selector switch, which is selectively responsive to the
fluid pressure applied to the pressure amplifiers for deactuating
the pressure amplifiers when the fluid pressure reaches the maximum
desired forming pressure. A transition pressure switch, responsive
to fluid pressure applied to the lower pressure amplifier actuates
the high pressure amplifier, as needed, for selected forming
pressures greater than the intermediate fluid pressure developed by
the lower pressure amplifier.
A preferred embodiment of the invention includes three
electromagnetically actuated control valves, two of which are
selectively responsive to the pressure selector and alternatively
responsive to the transition pressure switch elements for actuating
and deactuating the low and high pressure amplifiers. The third
control valve actuates an unload valve for depressurizing the
pressure chamber after the forming cycle is completed. The pressure
amplifiers may include a double-acting master piston, at least one
face of which has a large surface area relative to the surface area
of a slave piston which is movable conjointly with the master
piston. An input pressure chamber and a second pressure chamber,
respectively associated with the large face and an opposite face of
each master piston, are alternately pressurized with hydraulic
pressure fluid in order to produce reciprocative motion of each
piston assembly which thus incrementally increase the pressure in
output chambers respectively associated with each slave piston.
Both output chambers communicate with the pressure chamber
surrounding the mandrel. A check valve means in the hydraulic
conduit from the low pressure amplifier permits repeated cycling of
the low pressure amplifier and isolates the low pressure amplifier
from the pressure vessel pressure chamber during operation of the
high pressure amplifier. A surge control valve positioned in the
exhaust line from the high pressure amplifier controls fluid
velocity and flow regime to eliminate or minimize shock waves
during depressurization. The cylindrical pressure vessel is
provided with two end breach screws for clamping the tubular
mandrel therebetween.
Other objects, advantages and applications of the present invention
will become apparent from the detailed description to follow taken
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a combined partial side elevation and schematic outline
of hydraulic-forming apparatus and control systems according to the
present invention.
FIG. 2 is a cross-sectional view taken along lines 2--2 of FIG. 1
showing the interior of the hydraulic-forming machine pressure
cell.
FIG. 3 is a cross-sectional view taken along lines 3--3 of FIG.
1.
FIG. 4 is a cross-sectional view of the velocity control means
utilized in this invention.
FIG. 5 is a schematic circuit diagram of one portion of the 110
volt segment of the control means used in the preferred embodiment
of this invention.
FIG. 6 is a schematic representation of the lower voltage portion
of the control system of this invention.
FIG. 7 is a schematic representation of another part of the 110
volt portion of the control system utilized in the preferred
embodiment of this invention.
FIG. 8 is a schematic representation of one portion of the
hydraulic circuitry of this invention showing the preloading of the
apparatus with pump pressure.
FIG. 9 is a schematic similar to FIG. 8 showing the mid-range
pressure operation.
FIG. 10 is a schematic similar to FIGS. 8 and 9 showing high
pressure operation of the system.
FIG. 11 is a schematic similar to FIGS. 8, 9 and 10 showing
completion of the forming cycle and release of the pressure from
the forming chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to the drawings wherein like numerals
indicate like parts, there is seen in FIG. 1 an overall schematic
and partial side elevational view of the apparatus of this
invention in the nonpressurized mode such as at completion of a
forming cycle or prior to initiation of a forming cycle. Hydraulic
pump 10 is situated to withdraw hydraulic fluid from reservoir 11
and force the fluid into conduit 62 thus providing the primary
source of hydraulic pressure fluid for the system. Valve 140
permits depressurization of conduit 62 by flow of hydraulic fluid
into return conduit 63. The pressure in conduit 62 may be noted at
pressure gauge 85.
A circumferential pressure cell shown generally at 40 includes a
pressure container 27 surrounding a chamber block 123 which in turn
encloses a hydraulic-forming chamber 12. A pair of breach screws
107 and 107a are shown threaded into the chamber block 123 to hold
the elements of the hydraulic forming cell in place. The hydraulic
duct 28 communicates with fluid chamber 12 which comprises a
substantially cylindrical chamber means bounded on its exterior by
the inner surface of chamber block 123 and on its interior by
bladder 14. Bladder 14 in turn engages the forming core mandrel 105
which comprises a pressure deformable material such as polyurethane
or the like. Positioned inside the mandrel are workpiece 25 and die
26 which are supported by end plates 106 and 106a. The deformable
mandrel 105 surrounds the workpiece 25 and the die 26 so that
pressure imposed upon the mandrel 105 through bladder 14 is equally
distributed circumferentially about the workpiece and die.
In FIGS. 2 and 3, cross-sectional views of the pressure cell 40 are
shown at two locations along the axis of the cell. In FIG. 2,
workpiece 25 is shown in engagement with the contoured surface of
die 26. In FIG. 3, a job 26a in die 26 is shown. Imposition of
pressure from the surrounding deformable mandrel 105 will force
workpiece 25 into engagement with the surface of die 26.
Pressure is supplied to hydraulic duct 28 and thereby to fluid
chamber 12 serially from three sources according to the ultimate
pressure desired. The first source of pressure is via conduit 70
with the hydraulic control system in the preload circuit mode as is
shown in FIG. 8. Valve 101 has been repositioned so that pressure
from pump 10 may flow through valve 101 into conduit 70 and thence
through check valve 15 into the bottom of lower range pressure
intensifier 37, through check valves 18, 19 and 60 and then into
flow chamber 12. In this manner hydraulic fluid at pump output
pressure acts upon the bladder 14 and the mandrel 105 and thereby
upon the workpiece 25 to urge the workpiece 25 into conformance
with the die 26.
To achieve a medium range of pressures, the lower range pressure
intensifier 37 is utilized. Double-acting piston 32 is adapted to
travel up and down in cylinder 29 due to hydraulic pressure imposed
either in upper chamber 30 or in lower chamber 31. A slave piston
33 having a substantially smaller diameter than master piston 32 is
solidly connected to master piston 32 by piston rod 36. Downward
travel of master piston 32 causes fluid within chamber 39 to become
pressurized and forced into fluid chamber 12. The travel of master
piston 32 and slave piston 33 is controlled by the flow of
hydraulic fluid through valve 102. To cause downward travel of the
piston assembly, valve 102 is switched to the position shown in
FIG. 9 for mid-range pressure. In this position hydraulic fluid
from pump 10 is forced into upper chamber 30 forcing the piston
assembly downward. If it is necessary to cycle the piston assembly
in order to achieve the pressures desired in fluid chamber 12,
valve 102 is returned to the position shown in FIG. 1, thereby
pressurizing the fluid contained in lower chamber 31 and permitting
the hydraulic fluid in upper chamber 30 to exhaust to reservoir 11.
Valve 102 may then be returned to the position shown in FIG. 9 so
as to cause downward travel of the piston assembly and
consequential pressurization of the fluid contained in chamber
39.
For high range pressure, the higher range pressure intensifier 57
is utilized. Similar in structure to the lower range pressure
intensifier 37, the higher range pressure intensifier 57 includes a
piston assembly comprising master piston 52, piston rod 56, and
slave piston 53. Substantial pressure intensification is achieved
by the ratio of the areas of piston 52 and piston 53. Pressure
imposed within upper chamber 50 when the hydraulic circuit is in
the position shown in FIG. 10 causes downward motion of the piston
assembly with consequential pressurization of the fluid contained
in chamber 59, the pressure being transmitted into fluid chamber 12
through hydraulic duct 28.
Once the desired pressure for forming has been achieved, the
pressure in fluid chamber 12 may be relieved by activating the
chamber pressure release system. That system includes the valve
actuator piston 17, unload check valve 16, and conduit 78. By
imposing pump hydraulic fluid under pressure from pump 10 through
valves 101 and 138 into valve actuator 17, the ball valve 16 is
unseated and pressurized fluid permitted to flow through conduits
78 back into reservoir 11.
Both pressure intensifiers have an emergency depressurization
system which permits pressurized fluid to be dumped from both sides
of the upper pistons 52 and 32. This safety system includes valve
130 and conduit 75 connected into higher pressure intensifier 57
through check valves 131 and 132, and into lower pressure
intensifier 37 through check valves 133 and 134. The presence of
these check valves permits pressurization as desired on either side
of the piston; however, upon opening valve 130, the pressure on
each side of the piston will be equalized.
HYDRAULIC CIRCUIT SEQUENCE
The hydraulic system at rest, that is, at the termination of a
forming cycle or at the beginning of the cycle is shown in FIG. 1.
Valve 101 is positioned so that check valve 16 is unseated and any
pressure in fluid chamber 12 is dumped into conduit 63 via conduit
78. The workpiece 25 and die 26 are placed within the pressure
fluid chamber 12 surrounded by deformable mandrel 105. Pump 10 is
then actuated forcing hydraulic fluid into conduit 62 which acts as
a manifold to distribute the hydraulic fluid to the various fluid
pressure users in the system. As shown in FIG. 1, the hydraulic
fluid under pressure enters chamber 31 of lower pressure
intensifier 37 via conduit 74, the lower chamber 51 of pressure
intensifier 57 via conduit 77, and maintains unload check valve 16
in the open position. The hydraulic circuitry is then switched to
the preload circuit as is found in the partial hydraulic circuitry
diagram in FIG. 8. In this condition valve 101 has been switched so
that the pressure on valve actuator piston 17 is relieved and the
unload check valve 16 closed. Conduit 70 is pressurized with
hydraulic fluid which flows into compression chamber 39 through
check valve 15, thence into compression chamber 59 through check
valves 18 and 19, and into fluid chamber 12 through check valve 60
and hydraulic duct 28. In this fashion all of the compression
chambers in the accumulators and the fluid chamber 12 are
pressurized to the output pressure of pump 10. Under some
circumstances, pressure developed by pump 10 may be sufficient to
cause the desired forming effort to be imposed on workpiece 25. In
such an event, the valve 101 would then be switched so that valve
actuator 17 would open unload check valve 16 thereby depressurizing
the system.
In the event that a higher pressure is required for forming the
workpiece 25, the hydraulic circuitry would be switched to that
shown in the partial hydraulic diagram (FIG. 9) in which valve 102
is reversed so that pressure from pump 10 enters conduit 73 and
pressure previously imposed upon conduit 74 is exhausted and
returned to reservoir 11 (not shown). In this mode of operation,
the piston assembly, comprising piston 32, piston rod 36 and slave
piston 33, is caused to move downwardly against the pressure
already imposed upon chamber 39 due to the relief of pressure in
chamber 31 and the imposition of pump pressure in chamber 30 above
the piston 32. Since the upper face of piston 32 is of
substantially greater area than the lower surface of slave piston
33, a substantial intensification of fluid pressure is achieved in
chamber 39. Chamber 39 is in fluid communication with fluid chamber
12 and therefore the pressure in fluid chamber 12 is raised to the
same level as that in compression chamber 39. Piston assembly 32
and slave piston 33 travel downwardly under the influence of
pressure in chamber 30 until either the desired pressure is
achieved, as indicated by pressure responsive means 22, or the
piston assembly makes the full travel along its length to the
position shown in dotted lines. Upon achieving either of these
events, valve 102 is switched so that pressure in chamber 30 is
exhausted to reservoir 11 and pressure from pump 10 is imposed upon
the lower side of piston 32, that is, into chamber 31. This causes
piston 32 to rise, drawing slave piston 33 upward with it. Pressure
of pump 10 remains in conduit 70 causing flow of fluid at pump
pressure into chamber 39. Check valves 18 and 19 prevent blackflow
of the medium pressure hydraulic fluid from fluid chamber 12 into
chamber 39. If desired, the functions of lower range pressure
intensifier 37 may be repeated in order to bring the fluid pressure
in fluid chamber 12 up to the maximum pressure attainable in
intensifier 37 by repeated cycling thereof. This would be the case,
for example, when workpiece 25 must be deformed a large distance to
conform to the die 26, thus requiring a substantial volume of
hydraulic fluid.
Upon attaining the maximum pressure obtainable from lower range
pressure intensifier 37 or upon attaining the pressure necessary to
carry out the forming of workpiece 25, which is achievable at a
level below the maximum pressure provided by intensifier 37, unload
check valve 16 may be activated by valve actuator piston 17 and the
system depressurized. Should a higher pressure be necessary than
that achievable through use of lower range pressure intensifier 37,
the higher range pressure intensifier 57 may be activated by
switching valve 103 to the position shown in FIG. 10. The hydraulic
circuitry shown therein causes fluid at pump pressure to enter
conduit 76 and pass into the upper chamber 50 of higher range
pressure intensifier 57. The hydraulic fluid in chamber 59 would
already be at the maximum output pressure of intensifier 37.
Pressure inside chamber 50 causes piston 52 to travel downwardly
forcing fluid out of the chamber 51 and back into reservoir 11 and
causing slave piston 53 to travel downwardly within chamber 59. Due
to the very substantial greater area of piston 52 as opposed to
slave piston 53, a high pressure intensification is achieved,
whereby the fluid in chamber 59 is raised to a very high pressure
and forced into fluid chamber 12 via hydraulic duct 28. Piston 52
travels downwardly until it either reaches the maximum travel
possible as shown in dotted lines or the desired pressure in
chamber 12 is achieved. At that time valve 103 is again switched to
the position shown in FIG. 1, and pressure fluid in chamber 50
exhausts into reservoir 11 while pump pressure is applied to the
lower surface of piston 51. This causes slave piston 53 to rise in
chamber 59 relieving the pressure therein. At that time valve 101
is returned to the position shown in FIG. 1, causing unload check
valve 16 to be opened permitting the highly pressurized hydraulic
fluid in chamber 12 to exhaust into reservoir 11.
When exhausting hydraulic fluid from cylinder 50, extremely high
flow rates are occasionally encountered. To prevent damage to the
equipment and danger to operating personnel, the flow control
device shown in FIG. 4 is utilized to suppress excessive flow
rates. A plug 42 is placed within the body 43 of the surge control
valve 41. The structure provides a circuitous path for the
hydraulic fluid through ducts 44 to induce turbulence and prevent
unduly high oil velocity. The chamber 45 being of a larger diameter
than fluid conduit 76 further acts to prevent damage to the
apparatus from high oil velocity, frequently approaching sonic
speeds.
Since the ratio of areas of the upper piston and slave piston are
known values, the pressure achieved in fluid chamber 12 may be
readily ascertained by reading the pressure of the fluid in chamber
30 or chamber 50 depending upon which intensifier is being
utilized. For example, pressure switches 22 and 20 may be utilized
to determine the pressure level and then to activate other
functions of the hydraulic system as discussed above.
CONTROL AND OPERATION OF HYDROFORMER
Power to the machine's control circuits is turned off and on
through switches S1 and S1-A, FIG. 5.
The momentary closing of normally open switch S1, FIG. 5, provides
a circuit to relay coil R9. The energized relay coil closes
contacts R9-1 and R9-3 and opens contacts R9-2. The closed contacts
R9-1 provide a holding circuit to the R9 relay coil through
normally closed switch S1-A. The closed contacts R9-3 provide a
closed circuit for the machine operating circuit. The open R9-2
contacts turn the L2 indicator light off, and closed contacts R9-1
turn the L1 indicator light on.
The machine power circuit may be turned "OFF" by momentarily
opening switch S1-A, breaking the holding circuit to power relay
coil R-9 thereby returning the circuit to its normal position, as
shown in FIG. 5.
The machine control circuit is energized by momentarily closing
switch S2, FIG. 5, which energizes relay coil R5 closing contacts
R5-1 and R5-2 and opening contacts R5-3.
The closed contacts R5-1, FIG. 5, provide a holding circuit through
normally closed switch S3 to relay coil R5. The open R5-3 contacts
turn the L5 light off, and the closed contacts R5-1 turn the L3
light on.
The closed contacts R5-2 provide a circuit to the transformer T1
and rectifier RF-1 to provide a 28V DC current to terminals TB5-1
and TB3-1 in the machine sequencing circuit. This DC circuit
energizes relay coil R4, FIG. 6, and closes contacts R4-1, FIG. 5,
setting up a potential circuit for the hydraulic directional
control valves.
The hydraulic pump motor 10, FIG. 5, is started by momentarily
closing switch S5, FIG. 5, which provides an energizing circuit to
relay coil R7, FIG. 5, which closes relay contacts R7-1 and R7-2
and opens R7-3 contacts. The closed R7-1 and R7-2 contacts and
normally closed switch S4, FIG. 5, provide a holding circuit to
relay coil R7 and a sustained circuit to the pump motor and
indicator L6. The opened contacts R7-3 turn the L4 indicator light
off. The pump motor is turned off by momentarily opening the
normally closed switch S4, returning the circuit to its normal
position as shown in FIG. 5.
The machine has two integrated automatic circuits; one for forming
pressures up to 50 KSI known as the low pressure circuit, and a
second circuit for forming pressures above 50 KSI known as the high
pressure circuit. Forming pressures are selected using rotating
switch S36, FIG. 6.
The low pressure forming circuit is as follows: When switch S8,
FIG. 6 is momentarily closed, it starts an automatic pressurization
of chamber 23, FIG. 3, and then a depressurization of chamber 23,
FIG. 2. Its sequence is as follows:
When switch S8 is momentarily closed, FIG. 6, a circuit is provided
to relay coil R3 to close contacts R3-1 and provide a holding
circuit to relay coil R3 through the normally closed contacts R6-1.
This circuit also energizes time delay relay coils R8 and R6 and
normally closed contacts R6-2 to energize the coil of latching
relay R1-A. The time delay relay R6 is set for a longer time delay
than R8, and R8 is delayed until the preload pressure cycle is
completed, FIG. 8.
The energized latching relay coil R1-A closes contacts R1A-2 to
provide a circuit to light indicator light L8, FIG. 6, and R1A-1,
FIG. 5, provides a circuit through previously closed contacts R4-1
to one of the solenoids of hydraulic directional control valve 101.
Fluid under pressure is now directed through preload check valve
15, and transition check valves 18 and 19 and into chamber 23.
Naturally this also pressurizes cylinders 39 and 59, with
pressure. p When these areas are pressurized, time delay relay
contacts R8-1 are closed providing a circuit to energize solenoid
112 of hydraulic directional control valve 102 and shift valve 102
to direct fluid under pressure to the top side of piston 32. When
this has occurred, the time delay relay R6 opens contacts R6-1 and
R6-2, FIG. 6, breaking the holding circuit to the coils of relays
R3, R1-A, R6 and R8. Relays R3, R6 and R8 return to their normal
position as shown in FIG. 6. Relay R1-A, being a latching relay,
will retain the contacts R1A-1 in a closed position even though the
coil is de-energized.
When the energized solenoid 112 in directional control valve 102
shifts the hydraulic valve to direct fluid under pressure to the
top side of piston 32, it forces piston 33 down into cylinder 39
intensifying the pressure in cylinders 39, 59 and chamber 12.
When the fluid pressure against piston 32 is sufficient to actuate
pressure switch 21, a circuit is provided through pressure selector
switch S36 and switch S31. this closed circuit energizes the
latching relay coils R1-B and R2-A.
The energized R2-A relay coil closes contacts R2A-1 and R2A-2. The
closed R2A-1 contacts provide a circuit to light unload indicator
light L7. The closed R2A-2 contacts provide a circuit through
previously closed contacts R4-1 to energize relay coil R11, which
closes contacts R11-1, R11-2 and R11-3. These closed circuits
energize solenoids 113 and 115 in hydraulic directional control
valves 102 and 103, respectively, and solenoid 110 in hydraulic
directional control valve 101, which shifts valves 101 and 102 into
the unload position as shown in FIG. 1. Valve 103 was not moved
because it was in its normal position for low pressure forming and
is only used in high pressure forming which is described later.
The shifted valve 102 now directs fluid under pressure to the
bottom of piston 32, returning it to its normal position. Valve 101
now directs fluid under pressure to piston 17 to force check valves
16 from its seat, FIG. 1, and release the fluid pressure in chamber
12 and cylinder 59.
The manual cycle completion switch S9 is now momentarily closed,
energizing latching relay coil R2-B, opening contacts R2A-2 and
R2A-1 and lighting cycle completion light L9. The opened R2A-1
turns off the unload indicator light L7, FIG. 6. The opened R2A-2
contacts break the circuit to relay coil R11, causing relay
contacts R11-1, R11-2 and R11-3 to open, deenergizing one solenoid
in directional control valves 102 and 103 and one solenoid in
directional control valve 101. The low pressure forming cycle is
now complete.
The high pressure forming cycle is as follows:
The pressure selector switch S36 is set to a pressure in the higher
operating range and in contact with switch S20. When form switch
S8, FIG. 6, is momentarily closed, the coils of relays R3 and R6
are energized, closing contacts R3-1, providing a holding circuit
through normally closed timed delayed relay contacts R6-1 and R6-2
to relay coils R1-A, R3, and R8. R6 and R8 are time delay relays,
and their function is the same as described in the low pressure
circuit. R6 is timed to open and break the holding circuit after R8
has been delayed long enough to preload pressure chamber 12,
chamber 39 and chamber 59 with pump pressure.
The energized latching relay coil R1-A closes contacts R1A-1, FIG.
5. and R1A-2, FIG. 6. R1A-1 closed contacts provide a circuit to
solenoid 111 of valve 101, which directs pump pressure fluid
through preload check valve 15, and transition check valves 18 and
19 into chamber 12. Naturally this also provides pump pressure
fluid in cylinders 39 and 59, FIG. 1.
After these areas have been pressurized with pump pressure, time
delay relay contacts R8-1, FIG. 5, are closed providing a circuit
to one solenoid of directional control valve 102. After this
circuit has been made, time delay relay R6 opens the holding
circuit contacts R6-1 and R6-2, FIG. 6, breaking the holding
circuit to relay coil R3, R1A, R6 and R8, FIG. 6.
Solenoid 112 in directional control valve 102 directs fluid under
pressure to the top side of piston 32 forcing it and piston 33
down, intensifying the pressure in cylinder 39, which in turn
intensifies the pressure in cylinder 59 and chamber 12. When the
fluid pressure against the top of piston 32 is sufficient to
actuate transition pressure switch 22, a 6), through closed R1A-2
contacts and closed pressure switch S22 energizes the coil in relay
R12, closing contacts R12-1 (FIG. 6). R12-2 and R12-3 (FIG. 5).
Closed contacts R12-1 provide a holding circuit to R12 coil. Closed
R12-2 contacts, FIG. 5, provide a circuit to solenoid 114 of
directional control hydraulic valve 103. Closed R12-3 contacts
provide a circuit to solenoid 113 of directional control hydraulic
valve 102. The valve directs fluid to the bottom of piston 32
bringing it back to its normal position.
Valve 103 directs fluid to the top of piston 52 forcing piston 52
and piston 53 down, intensifying the pressure in cylinder 59 and
chamber 12. When pump pressure on the top side of piston 52 is
sufficient to actuate pressure switch 20, a circuit is provided to
latching relay coils R2-A and R1-B, which opens R1A-2 contacts
breaking the holding circuit to R12 relay coil, FIG. 6, which opens
contacts R12-1 (FIG. 6), R12-2 and R12-3 (FIG. 5) to de-energize
solenoids 113 and 114 of valves 102 and 103, respectively.
The energized coil of relay R2-A, FIG. 6, also closes contacts
R2A-2, FIG. 5, to provide a circuit to relay coil R11 which closes
contacts R11-1, R11-2 and R11-3, which in turn provide circuits to
solenoid 113 of valve 102, solenoid 115 of valve 103 and solenoid
110 of valve 101 (FIG. 5). These valves unload the forming pressure
in the chamber 12, FIG. 1. Valve 103 reverses the pressure on
piston 52 returning it to its normal position. Valve 101 applies
pressure to piston 17 to force check valve 16 from its seat and
release the remaining pressure in chamber 12. Solenoid 113 in valve
102 had previously been energized to return the piston 32 to its
normal position.
Emergency unload switch S7, FIG. 6, can be actuated anytime during
a forming cycle to duplicate this pressure unloading operation
because it duplicates the circuit provided by pressure switches 20
or 21.
The machine can be operated manually as well as automatically. To
manually preload the system, switch S33 is momentarily closed
energizing relay coil R-10, closing contacts R10-1 and R10-2
establishing a holding circuit through normally closed switch S34,
to solenoid 111 of valve 101 to preload cylinders 39, 59 and
chamber 12, FIG. 3, with pump pressure. L14 and L15 are lighted.
This pressure can be unloaded through unload check valve 16 when
switch S34 is momentarily opened and combined switch S37 is
momentarily closed. The opening of switch S34 breaks the holding
circuit to solenoid 111 of valve 101 and momentarily closed switch
S37 energizes solenoid 110 of valve 101 to shift the directional
control valve 101 and pressurize piston 17 to force check valve 16
from its seat and release the pressurized fluid in cylinders 39 and
59 and chamber 12.
To manually operate the machine, the manual piston control switch
S40 is actuated, setting up a start circuit as previously
described. The preload valve switch S33 is actuated setting up the
preload circuit and preloading the hydraulic working area as
previously described.
Forming pressures in the medium pressure range are developed by
momentarily closing piston forward switch S42, FIG. 7. The
momentary closing of switch S42 energizes relay coil R14 closing
contacts R14-1 and opening contacts R14-2. The closed R14-1
contacts provide a holding circuit to relay coil R14, and a circuit
through previously closed contacts R16-1 to energize solenoid 112
of valve 102, so that fluid pressure is now directed to the top
side of piston 32 forcing it down, intensifying the pressure in
cylinders 39 and 59, and chamber 12. The pressure intensification
is measured by the pump pressure gauge 85. If pressures above the
medium pressure range are desired, the piston forward switch S44,
FIG. 7, is momentarily closed after piston 32 reaches its maximum
pressure.
The momentary closing of switch S44, FIG. 7, energizes relay coil
R15, closing contacts R15-1 and opening contacts R15-2. The closed
R15-1 contacts and normally closed switch S45, FIG. 7, provide a
holding circuit to relay coil R15, and they also provide a circuit
through previously closed contacts R17-2, to solenoid 114 of valve
103, to direct fluid pressure to the top of piston 52 to push
piston 52 forward and intensify the pressure in cylinder 59 and
chamber 12. The intensified pressure is read on the pump pressure
gauge 85.
To unload the pressure circuit, switch S43 is momentarily opened
breaking the holding circuit to relay coil R14 and opening contacts
R14-1 and closing contacts R14-2. The closed contacts R14-2 provide
a circuit through normally closed switch S43 and previously closed
contacts R16-2 to solenoid 113 of valve 102, which shifts the
directional control valve and direct fluid pressure to the bottom
of piston 32, returning it to its retracted position.
Switch S45, FIG. 7, is now momentarily opened breaking the holding
circuit to relay coil R15, opening contacts R15-1 and closing
contacts R15-2. A circuit is now provided through normally closed
switch S45 through closed contacts R15-2 and previously closed
contacts R17-1 to solenoid 115 of directional control valve 103 to
shift the valve and direct fluid pressure to the bottom of piston
52, returning it to its retracted position, reducing the pressure
in chamber 12 and cylinder 59.
The combined switches S34 and S37 are now actuated. The normally
closed switch S34 is opened breaking the holding circuit to relay
coil R10, opening contact R10-1, de-energizing solenoid 111 of
valve 101. The closing of switch S37 provides a circuit to solenoid
110 of valve 101 shifting the directional control valve 101 to
direct fluid pressure to the piston 17 which pushes the ball check
16 from its seat and releases the pressurized fluid in cylinder 59
and chamber 12.
While the inventor has set forth the preferred embodiments of his
invention herein, it will be apparent to one skilled in the art
that this invention may be practiced in variant forms all within
the scope of the appended claims.
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