Method for loading and unloading an isostatic press for compression of pre-formed powder objects

Method for loading and unloading of isostatic presses of the type wherein pre-formed, or equivalent, shapes of powdered metal, ceramics, clay and the like are compressed under very high pressures to form compacts suitable for use as such or for subsequent operations, such as forging, machining, firing or the like as may be appropriate for the particular powdered material. Method is disclosed in connection with the use of an isostatic press having a container including a cylindrical sleeve of elastomeric material for receiving the objects to be compressed under pressure of hydraulic fluid applied to exterior of the container. Bodies of rigid or elastomeric material which also may serve as plugs for the ends of the sleeve are movable from inside to outside the press to positions to receive a pre-form. Method comprises loading of a pre-form onto one of the bodies or plugs, pressing the other onto the pre-form to hold it between the bodies and then moving both bodies with the pre-form held therebetween into the press where it is held by the bodies during the compressing operation which converts the pre-form into a compact. The press is then opened and the two bodies are moved out of the press, holding the compact and placing in a position for removal from the press. Method is of particular value in handling pre-forms which are elongated and unstable when standing on end under influence of gravity alone, the bodies or plugs manipulated according to the method being effective to hold such pre-forms in upright position for loading and compressing and unloading.

RELATED UNITED STATES APPLICATION 
Application Ser. No. 747,915 filed Dec. 6, 1976 is directed to the 
structure of an isostatic press of a type which may be utilized in the 
practice of the method of the present invention. 
BACKGROUND 
Isostatic pressing of objects by the wet bag system involves the placing of 
a pre-formed object in an elastomeric bag which is then placed in the 
cavity of a press and the press is closed. Hydraulic fluid then is 
admitted to the press wetting the outside surface of the bag and as the 
pressure is increased the bag yields to conform to the shape of the object 
whereby the pressure is isostatically exerted upon the object to form it 
into a compact. After pressing and lowering of pressure on the hydraulic 
fluid the bag is removed for extraction of the compact and reloading of 
the bag with another pre-formed shape. This entire operation is inherently 
slow and involves a great amount of manual handling of the bags, 
pre-formed shapes and the compacts. 
In contrast with this, as illustrated in U.S. Pat. Nos. 3,557,405 and 
3,591,903 for example, the isostatic forming and pressing of objects 
directly from powder have been effectively automated being performed in 
multi-cavity presses or in single cavity presses with mechanical 
auxiliaries for loading the cavity or cavities with powder and extracting 
the pressed compacts in cyclic fashion. In devices of the latter type the 
cavity or cavities consist of hollow molds of specific shape for the 
formation of a compact having that shape when pressing is completed. Thus, 
in operation, the mold cavities are opened, a measured amount of powder is 
poured into the cavity and, after closure of the vessel, the pressing step 
is performed. The compact thus formed is removed by manual or automatic 
means either through the same opening used for filling or through an 
oppositely disposed opening as may be preferred or required. 
In devices of the latter type the molds are formed of one or more bodies of 
elastomeric material having hollows therein of the specific shape 
required. Thus, the production is limited to that specific shape and size 
of compact unless a new mold or set of molds is substituted. Also, there 
are limitations on the types of shapes that may be formed and compacted in 
such devices without involving considerable complication such as making 
the molds in several pieces. 
In this background there is need for a method useful with apparatus having 
the relatively great versatility of the wet bag presses to provide 
convenient manual and, if desired automated, loading and unloading of 
pre-formed shapes. 
BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS 
An isostatic press of the type with which this method is useful comprises a 
pressure vessel having a body of generally known design for use in 
pressing and compacting objects under very high pressures, for example 
from about 40,000 p.s.i.g. to 100,000 p.s.i.g. or more. Such body is in 
the form of an open-ended tube made of metal of such specifications and 
thickness as to withstand pressures of the magnitude here involved. The 
open ends of the tube are internally threaded with interrupted threads to 
mate with interrupted threads formed on end closure members whereby the 
closure members may be inserted with threads in non-mating position and 
thereafter closed pressure-tight by turning the closures only a fraction 
of one complete turn, all as is well known in this art. 
The tubular body of such press has positioned therein an assembly 
comprising an imperforate liner fitting snugly within the central bore of 
the body and a canister, perforated radially as is well-known or otherwise 
constructed to permit flow of hydraulic fluid from an annular space 
between the liner and the canister to the inside of the canister. An 
elastomeric membrane consisting of a thin-walled tubular sleeve made of 
rubber-like material, such as urethane, positioned within the canister. 
The membrane, made of such material will yield and stretch and rebound 
much the same as the rubber-like bags used in the wet-bag procedure. The 
membrane is constructed to be sealed at the opposite ends of the canister 
so that the hydraulic fluid which has access to the outer surface of the 
membrane is confined in a closed system including the openings of 
passageways in the canister, the annular space mentioned above and the 
conventional inlet and outlet passageways, valves and hydraulic pressure 
lines utilized in this type of apparatus. 
The metallic threaded closures mentioned above each have a body such as a 
tapered plug of rigid or of flexible, incompressible elastomeric material, 
such as urethane, secured thereto in position to be forced into the 
respective ends of the membrane in sealing relationship whereby there is 
formed a container for objects to be pressed. When elastomeric plugs are 
used the entire inner surface of the container is defined by elastomeric 
material, that is, by the inner surface of the membrane and the inner 
surfaces of the two elastomeric plugs. 
With only the description so far it will be recognized that the cavity thus 
takes on much the character of a conventional wet bag. That is the 
membrane when placed under hydraulic pressure through the canister will 
collapse inwardly while the end regions thereof lying over rigid plugs 
will conform those plugs. When elastomeric plugs are used the membrane 
will press inwardly on those plugs, distorting the incompressible material 
thereof in the direction in which such material is permitted, and forced, 
to flow under such pressure. In general, the membrane will tend to 
collapse radially of the bore of the vessel while the elastomeric plugs 
will tend to be reduced in diameter thus to elongate inwardly and axially 
of said bore. 
At least one of the metal end closures with the body or plug attached 
thereto is preferably arranged for quick removal from and insertion into 
sealing position. In a preferred form of the invention disclosed and 
claimed in said application Ser. No. 747,915 the closure at the lower end 
of the pressure vessel is made removable and is mounted on the end of a 
vertical rod actuated by a hydraulic cylinder so that it may be removed 
from sealing position and lowered away from the pressure vessel for a 
distance sufficient to permit the positioning on the inner end of the plug 
of the pre-form. The closure is then raised by the hydraulic cylinder to 
position the pre-form in the container or cavity of the vessel whereupon 
the closure is locked by partial rotation. 
When hydraulic fluid is now pumped into the vessel and pressure is raised 
the elastomeric portions of the cavity will press inwardly upon the 
pre-form to compress it isostatically. 
When desired pressure is reached and reduced the bottom closure may be 
unlocked and lowered with the compact resting upon the lower plug in 
position to be removed. 
The plug which closes the upper end of the cavity is carried on the end of 
a rod which is driven vertically by a hydraulic cylinder. When the vessel 
is pressurized the upper plug, like the lower rests against the solid 
metal structure of the associated end closure. During depressurization the 
upper plug is subjected to a downward hydraulic pressure so that the upper 
plug will progressively move downward to continue to press upon the upper 
end of the compact. 
In the practice of the present method when the lower plug is lowered away 
the upper plug continues to be pressed downwardly so that it will follow 
and hold the compact firmly in position during movement of both plugs to 
positions outside the body of the press in which the compact may be 
gripped by hand or mechanical means for removal from the press after the 
upper plug is retracted. 
In the practice of the method conveyors may be provided for supplying and 
taking away the pre-forms and compacts. For complete automation of the 
method a timer and valves operated thereby may be provided.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention will be described in connection with the accompanying 
drawings in which the method is illustrated in connection with the 
compressing of pre-formed shapes (sometimes herein called "pre-forms") 
made of powdered materials such as metal, ceramics, clay and the like to 
produce compacts which may be useful as such without further treatment but 
which usually are adapted for further processing such as forging, heat 
treating, firing, machining and the like. While pre-forms of almost any 
shape and contour may be handled in accordance with the method embodying 
the present invention the invention presents advantage in the handling of 
elongated objects such as a cylindrical rod or other elongated objects 
which it is desired to insert lengthwise into the cavity of the press and 
which have little or no stability when standing on end under the influence 
of gravity alone. For illustrative purposes the present invention is 
diagrammatically illustrated in the handling of a cylindrical rod and a 
somewhat more detailed showing is made of the handling of a lever with 
integral hub, the handle being generally square in cross-section and the 
hub having a transverse circular opening. 
The pre-forms with which this invention may be used may be of any customary 
type, for example they may be made pressing or tamping in molds from 
self-adhesive powdered materials or from a mixture of the desired powdered 
material with a binder of liquid or heat activatable adhesive or they may 
comprise thin plastic, paper or similar containers filled with the desired 
powder, the containers being made in the shape desired for the product. 
The latter procedure may be preferred in those instances wherein adhesive 
or other binding agent may be undesirable or harmful to the final product. 
In FIG. 1 an isostatic press 10, supported in upright position on a frame 
12 is shown in relation with a supply conveyor 14 and takeaway conveyor 
16. The press 10 has a generally cylindrical fluid pressure chamber 18 
closed at the top by a closure 20. A lower closure 22 is mounted on the 
piston rod 24 (see FIG. 3) of a double acting hydraulic cylinder 26 fixed 
in a pit 28. As will be explained below the lower closure 22 is thus 
arranged to be lowered away from the press 10 to a loading position shown 
in FIGS. 1 and 2 and to be raised to closing position as shown in FIG. 3. 
Also, when moved to closing position the lower closure 22 is rotated into 
locking position whereupon hydraulic fluid is pumped into the fluid 
pressure chamber to compress a pre-formed object positioned therein. 
Referring now to FIGS. 4 and 5 there is shown a form of isostatic press 
with which the method of the present invention may be practiced. The 
structure of the press 10 shown in FIGS. 4 and 5 forms the subject matter 
of said copending application s.n. As shown in these FIGS. 4 and 5 the 
press 10 includes a body 30 comprising a thick rigid metal cylinder open 
at both ends and having interior threads for reception of the upper and 
lower closures 20 and 22 respectively. The upper closure 20 is threaded 
into closing position upon assembly of the press 10 and remains in that 
position until disassembly is required. The upper closure 20 comprises a 
threaded tubular sleeve 32, mated with interior threads in body 30, which 
surrounds a heavy metal closure body 34 having an annular flange 36 
against which the tubular sleeve 32 presses to hold the body 34 in 
pressure tight position in the press. The interior of the press 10 
includes a liner sleeve 38 having a predetermined inner diameter and 
within is positioned a perforated canister 40 having an outer diameter 
somewhat less than the inner diameter of liner sleeve 38. This leaves an 
annular space 42 between liner sleeve 38 and canister 40 for flow of 
hydraulic fluid from passageways 44 and 46 which extend through the upper 
closure body 34 and open into the space 42. Pressurized hydraulic fluid 
therefore may be pumped from a suitable hydraulic pump (not shown) through 
one of the passageways 44 or 46 to space 42. The other passageway 44 or 46 
may be left open briefly for bleeding of air, where required, after which 
it is closed and continued admission of fluid will be effective to raise 
fluid pressure within the press 10 to the very high levels, for example 
from about 40,000 p.s.i.g. to 100,000 p.s.i.g. or more, normally utilized 
in this art. 
The perforated canister 40 may be provided with a large number of radial 
openings as is common in this art (see patent 3,537,405 FIG. 4, for 
example). However as shown herein there are only a few radially extending 
passageways 48, 50 and 52 for example which open into the interior of 
canister 40 and into the space 42. As shown most clearly in FIG. 5 these 
passageways communicate directly or indirectly with a continuous helical 
passageway 52 extending from end to end of the interior of canister 40. 
The helical passageway 52 may be in the form of a semi-circular groove 
formed in the inner wall of canister 40. 
A membrane 54 made of elastomeric material which is flexible and will 
stretch and recover, urethane for example, is positioned within the 
canister 40. The membrane 54 is in the form of a sleeve having a 
relatively thin wall of generally cylindrical shape and having integrally 
formed sealing flanges 56 and 58 at opposite ends thereof which fit over 
the ends of canister 40. At the upper end of membrane 54 the flange 56 
fits over the upper end of canister 40 and also is positioned to seal 
against the upper closure body 34 to make the upper end of the fluid 
pressure chamber leak proof. At the lower end of membrane 54 the flange 58 
fits over the lower end of canister 40 and into the space 42. The flange 
58 also is sealed by a washer 60 threaded into the body 30. In this manner 
the lower portion of the fluid pressure chamber of the vessel is made leak 
proof. The hydraulic fluid is thus confined to regions exterior of the 
membrane 54 and within the canister 40 and the space 42 for communication 
with the supply passageways 44 and 46 in the upper closure. Hydraulic 
pressure exerted within this confined region will tend to collapse the 
membrane 54 upon an object that may be placed therein. The membrane 54 is 
open at both opposite ends and in order to close the upper end there is 
provided a plug 62, made of an incompressible elastomeric material such as 
urethane, which is fixed upon a metal disc 64. Disc 64 seats in a recess 
in the upper closure body 34 and is connected to the lower end of a piston 
rod 66 which extends through body 34 and upwardly, see FIG. 1, to a double 
acting hydraulic cylinder 68. The outside of disc 64 and the maximum 
outside diameter of elastomeric plug 62 is such as to move freely 
downwardly through the interior of membrane 54 when the pressure vessel is 
unpressurized as shown in FIG. 4. 
At the lower end of membrane 54 the open end thereof is adapted to be 
closed and opened at will by an elastomeric plug 70 made of an 
incompressible material such as urethane secured to the heavy rigid body 
72 of the lower closure 22. The plug 70 is tapered to fit snugly into the 
portion of membrane 54 which flares outwardly with the contour of the 
lower end of canister 40 when the lower closure 22 is in closed position 
shown in FIG. 4. 
The membrane 54, upper elastomeric plug 62 and lower elastomeric plug 70 
thus define a wholly elastomeric container within which a pre-form may be 
positioned for compression without coming in contact with the pressurized 
hydraulic fluid. The container thus formed is comparable in function to 
the elastomeric bag customarily used in the well-known wet bag process 
utilized in isostatic presses for handling pre-form objects of almost any 
shape. 
In FIG. 5 the press is shown in pressurized condition wherein the membrane 
54 is collapsed upon a pre-form and upon the plugs 62 and 70. The pre-form 
73 shown in FIGS. 4 and 5 is typical of the shapes for which this method 
is intended, and consists of a lever with an integral hub. The handle 
portion 74 of the lever may be square in cross-section, for example and 
may terminate in a rounded end 76. The hub 78 of the lever may be circular 
in outline and be provided with an opening 80 extending transversely of 
the axis of the handle 74. With a pre-form such as this the inner contour 
of canister 40 and membrane 54 may be shaped to correspond roughly with 
the general shape of the pre-form. Thus in FIGS. 4 and 5 it will be 
observed that the inner diameter of the membrane 54 is smaller in the 
region of handle 74 and is larger in the region of the hub 78. This can be 
done inasmuch as the present invention provides for the loading and 
unloading of pre-forms from the lower end of the press. 
In the unpressurized condition shown in FIG. 4 the preform 73 is supported 
at the lower end upon the plug 70 and is engaged at the upper end with 
plug 62 thus to be firmly held in upright position in the container 
comprising membrane 54 and plugs 70 and 62. As will be disclosed 
hereinbelow holding of the pre-form 73 in upright position forms a part of 
the method of the present invention. When the press is pressurized the 
membrane 54 is progressively collapsed into firm engagement with all 
surfaces of the pre-form 73 and with the outer surfaces of elastomeric 
plugs 62 and 70. Under high pressure the pre-form is compressed by the 
membrane 54 and also by the distortion of plugs 62 and 70 axially of the 
fluid pressure chamber and of the pre-form 73. The pressure thus applied 
axially to the pre-form 73 will compress the pre-form lengthwise. 
When the pressure is reduced in the pressure chamber hydraulic pressure is 
exerted by the upper cylinder 68 to force the upper plug 76 downwardly as 
permitted by progressive relaxation of the membrane 54. In this manner the 
upper plug maintains vertical pressure upon the now compacted pre-form 73 
as the plugs 62 and 70 progressively return to the unpressurized shape 
shown in FIG. 4. If desired the pressure outside the membrane 54 may be 
lowered below that in the interior thereof thus to firmly hold the 
membrane in contact with the inner surfaces of canister 40. 
The lower closure 22 now may be removed for unloading of the compacted 
pre-form 73. The lower closure 22 may be of the form disclosed in said 
copending application Ser. No. 747,915. In that event the body 72 of 
closure 22 is connected by a spring washer 82 to a threaded sleeve 84 
received in the lower end of the press body 30. Preferably the threads on 
sleeve 84 and within body 30 are interrupted threads such as shown in 
patent 3,730,666, FIG. 6 so that the closure 22 may be inserted linearally 
into the opening almost to closed position and thereafter locked in closed 
position by rotation of sleeve 84 through a small fraction of one complete 
turn. A hydraulically operated means for causing such rotation is provided 
and shown diagrammatically in FIG. 8. Such hydraulic means is very similar 
to that shown in said patent 3,730,666, FIG. 4 and comprises a double 
acting hydraulic actuator 86 having a piston rod 88 connected by a pin 
(not shown) with threaded sleeve 84. The actuator 86 is mounted on a 
cross-member 92 slidably carried on spaced vertical rods 90 and fixed for 
upward and downward movement with the lower closure 22. The actuator 86 is 
operated at proper timed intervals to cause the partial rotation of sleeve 
84 required for locking and unlocking the closure 22. 
The location of hydraulic actuator 86 and the cross-member 92 on which it 
is mounted is also diagrammatically shown in FIG. 1, it being understood 
that these parts move vertically with the lower closure 22 as described 
above. As a result the actuator 86 remains continuously in operative 
engagement with the threaded sleeve 84 for partial rotation of the latter 
between locking and unlocking positions when required. 
As noted above FIGS. 1, 2, 3, 6, 7 and 8 illustrate the method of the 
present invention in connection with the loading of a pre-form and 
unloading of a compact, consisting of the pre-form after compression in 
the isostatic press, wherein the pre-form is a relatively tall slim 
cylinder or rod. It will be apparent that the handling of such a pre-form 
is entirely comparable with the handling of the particular pre-form 73 
shown in FIGS. 4 and 5 insofar as the method is concerned. 
Referring now to FIGS. 1 and 8 a series of cylindrically shaped pre-forms 
94 is brought up to one side of the press 10 by the supply conveyor 14 
which may comprise an endless belt 96 having longitudinally spaced holders 
such as spring clips 98 secured thereto in position to hold the pre-forms 
94 temporarily in upright position as they approach the press 10. The 
takeaway conveyor 16 is positioned on the opposite side of the press 10 
and may comprise an endless belt 100 having longitudinally spaced holders 
such as spring clips 102 secured thereto for receiving and temporarily 
holding the compacts 104 upright as they are moved away from the press by 
movement of belt 100. It should be noted that since the compacts 104 will 
be smaller in size than the pre-forms 94 and the clips or other holders 
102 may be appropriately different in size or design from the clips 98 on 
supply conveyor 14. 
As shown in FIGS. 1 and 8 article gripping and transferring devices are 
provided for moving the pre-forms 94 from conveyor 14 to a position for 
loading into press 10 and for engaging and removing the compacts 104 from 
the press and positioning them on the takeaway conveyor 16. 
Illustratively, the device for loading may comprise a double acting 
hydraulic cylinder 106 having a piston rod 108 which carries a gripping 
device 110 on the outer end of rod 108. The gripping device 110 is movable 
from a retracted position out of the way of incoming pre-forms 94 on 
conveyor 14 (shown in broken lines in FIG. 8) into a position for 
engagement with a pre-form 94 which has been brought to a position in 
lateral alignment with the centerline of the press 10. The gripping device 
110 illustratively may comprise a yoke 112 secured to piston rod 108 and 
carrying a pair of opposed gripping shoes 114 actuated by hydraulic 
pistons, solenoids or the like 116 to close upon the pre-form 94 when the 
yoke 112 moves into the position shown in full lines in FIG. 8. Continued 
movement of the piston rod will be effective to transport pre-form 94 into 
coincidence with the centerline of press 10 as shown in FIG. 1. 
A similar article gripping and transferring device is provided for 
unloading the compacts 104. This comprises a double acting hydraulic 
cylinder 118 with a piston rod 120 carrying a gripping device 122, 
gripping shoes 124 and actuators 126 all as described above in connection 
with the loading device. 
In FIG. 1 the loading gripping device 110 has moved a pre-form 94 to 
loading position resting upon the lower elastomeric plug 70 and is holding 
the pre-form 94 upright. The upper elastomeric plug 62 at this time 
remains positioned above the upper end of pre-form 94 where it has not 
interfered with movement of pre-form 94 into the FIG. 1 position. 
Immediately thereafter the upper elastomeric plug 62 is moved downwardly 
to press vertically upon pre-form 94 after which the gripping device 110 
may be released and moved back to the position shown in FIG. 2. Next, the 
hydraulic piston is energized to raise the lower closure 22 and hydraulic 
pressure on the upper elastomeric plug is overcome or relieved whereby the 
pre-form 94 firmly held by vertical pressure between the plugs 70 and 62 
is raised into the fluid chamber 18 of the press 10. When the parts reach 
the position shown in FIG. 3 the hydraulic activator 86 (FIGS. 1 and 8) is 
energized to lock the lower closure by partial rotation of threaded sleeve 
84. 
The pre-form 94 is now in position to be compacted as has been described 
above in connection with the pre-form 73 and FIGS. 4 and 5. After 
compaction hydraulic pressure is exerted on upper elastomeric plug 62 to 
maintain it in contact with the upper end of the compact as the compacting 
pressure in the press is lowered. The pre-form 94, now identified as a 
compact 104 is ready to be unloaded as shown in FIGS. 6 and 7. 
In FIG. 6 the lower closure 22 has been unlocked and the hydraulic pressure 
on upper elastomeric plug 62 is maintained as the lower closure 22 is 
lowered, thus the grip the compact 104 and hold it upright as shown in 
FIG. 6. The gripping device 122 is now moved toward the left as viewed in 
FIG. 6 to grip the compact 104, the upper elastomeric plug is then moved 
upwardly out of engagement with the compact. The gripping device 122 is 
now moved by cylinder 118 to the position shown in FIG. 7 thus to engage 
the compact 104 in one of the spring clips 102 on conveyor 16. The 
gripping device is then released by energization of actuators 126 and 
continues to move to the broken line position in FIG. 8 to permit the 
takeaway conveyor 16 to advance the compact 104 towards a station (not 
shown) for unloading of the conveyor 16. 
As will be apparent the method hereinabove described may be performed 
manually by operation in predetermined timing and sequence of a plurality 
hydraulic valves, electrical controls and the like. However, for 
achievement of maximum production speed and economical utilization of 
hydraulic pumping equipment, particularly of the very high pressure 
hydraulic pumps which supply the fluid pressure chamber of press 10, it is 
preferred to provide an automatically timed control device for operating 
the equipment in a precisely established program. Such devices are well 
known and available in many specific forms and the selection of suitable 
equipment for use in the present invention will be made obvious upon 
consideration of the diagrammatic showing thereof in FIG. 1. Thus, a 
control box 140 is shown which contains a timer and a plurality of valves 
of on-off and throttling types as required actuated by the timer in the 
desired sequence. A pair of hydraulic lines 142, 144 connects box 140 with 
a high pressure hydraulic pump for supplying fluid to the fluid pressure 
chamber 18 of press 10 and a pair of hydraulic lines 146, 148 connects box 
140 with a lower pressure hydraulic pump for supplying fluid to the 
various cylinders and actuators in the system. These supply lines are 
connected internally of box 140 with the valves aforesaid which distribute 
fluid as required through hydraulic lines to the various components of the 
press described above. Thus, a pair of lines 150, 152 connect box 140 with 
the fluid pressure chamber 18 to supply the high pressure hydraulic fluid 
thereto when and as required. A pair of lines 154, 156 connects box 140 
with the opposite ends of upper hydraulic cylinder 68 for supply and 
control of pressurized low pressure fluid to raise and lower the upper 
elastomeric plug 62 and a similar pair of lines 158, 160 connect box 140 
with the lower hydraulic cylinder 26. A pair of lines 162, 164 connects 
box 140 with the opposite ends of cylinder 106 and a similar pair of lines 
166, 168 connects box 140 with the opposite ends of cylinder 118 for 
supply of low pressure hydraulic fluid to cylinders 106 and 118. A pair of 
lines 170, 172 connects box 140 with the locking and unlocking actuator 86 
for supply of low pressure hydraulic fluid to that actuator. Additional 
hydraulic lines or electrical cables (not shown) may be provided for 
control of the article gripping shoes in the gripping devices 110 and 122 
(see FIG. 8). 
The supply conveyor 14 and takeaway conveyor 16 also must be operated in 
proper timed relation with the operation of the loading cylinder 106 and 
unloading cylinder 118. This may be accomplished manually by operation of 
a switch (not shown) to effect movement of the conveyor 14 to present a 
pre-form in proper position before the loading cylinder 106 is effective 
to transfer the pre-form from the conveyor to the position shown in FIG. 
1. The unloading conveyor 16 may be similarly manually energized to 
present an empty clip 102 in proper position before the cylinder 118 is 
effective to transfer a compact 104 from the FIG. 6 position to the FIG. 7 
position. 
When automatic operation is utilized suitable switches will be provided in 
box 140 (FIG. 1) and operated by the timer therein to move the conveyors 
14 and 16 by increments at appropriate times. Alternatively, in automatic 
operation the conveyors 14 and 16 may be continuously driven at a speed 
precisely synchronized with the timer in box 140 whereby to present a 
pre-form 94 on conveyor 14 or an empty clip 102 on conveyor 16 at the 
proper time with relation to performance of the loading and unloading 
steps. 
For economic reasons it may be preferred to provide two or more complete 
isostatic presses of the type utilized herein to share the services of a 
single source of high pressure hydraulic fluid. In such event the timers 
in the boxes 140 of each press will be interlocked in such manner that 
while one press is loading and unloading the other is in that portion of 
its cycle wherein high pressure fluid is being supplied to the fluid 
pressure chamber thereof. In this connection it will be appreciated that a 
substantial portion of the complete cycle of each press is devoted to 
depressurizing of the fluid pressure chamber, unlocking and lowering of 
the lower closure 22, transfer of the compact 104 to the takeaway 
conveyor, transfer of a pre-form 94 to loading position, raising of the 
pre-form 94 into the fluid pressure chamber 18 and locking of the lower 
closure 22. If the time required for these loading and unloading 
operations is somewhat more than one-half of the total cycle the high 
pressure hydraulic source may be utilized for pressurization of one 
additional press having a similar time cycle and interlocked for operation 
in opposite phase. If the time required for loading and unloading 
constitutes a substantially greater fraction of the total time cycle a 
proportionately greater number of presses may be interlocked for properly 
phased operation. Obviously also the time required for loading and 
unloading may be deliberately stretched somewhat to permit operation of 
one or more additional presses from a single source of high pressure 
hydraulic fluid, in any instance wherein the slightly reduced total output 
of compacts from each press would be offset by the obviously more 
efficient utilization of the costly, and high energy consuming source of 
high pressure hydraulic fluid. 
While the isostatic press chosen for illustration herein to be utilized in 
practice of the method of the present invention has been shown as an 
upright, bottom loading press it will be apparent that the method is 
equally useful in connection with a top loading press of the same general 
type or a horizontally disposed press of the same general type which loads 
from either of its ends. For example the press 10 shown herein could be 
bodily inverted to load and unload at the top by use of conveyors and 
transfer devices identical with the conveyors and transfer devices shown 
herein. Also, with some obvious modification of the conveyors the press 10 
could be laid on its side to be loaded and unloaded from either end. The 
important point here is that the present method provides positive 
engagement with and control of the pre-forms and compacts at all times 
whereby gravity plays no part in the positioning or movement thereof. 
The foregoing detailed description has been made in connection with the 
utilization of a press wherein the plugs 70 and 62 are made of elastomeric 
material. As is the case in said copending application Ser. No. 747,915 
the plugs may be made of rigid material such as metal or they may be 
bodies capable of engaging and holding the pre-form or compact without 
necessarily performing the function of closing the opposite ends of the 
membrane or sleeve 54. When rigid plugs or bodies are thus used the method 
of loading and unloading is substantially unaffected. However, inasmuch as 
rigid plugs, of shape such as 70 and 62, will not be distorted when 
pressure is applied to membrane 54 the latter will conform to the shape of 
the plugs and will collapse upon the pre-formed object held therebetween. 
The resultant compressing of the pre-form will not reduce the lengthwise 
dimension thereof but rather will force the opposite ends of the pre-form 
against the unyielding surfaces of the rigid plugs. The pre-form will thus 
be compressed in all directions including lengthwise but without change in 
length. 
When rigid plugs or bodies are used instead of the elastomeric plugs 62 and 
70 the upper plug corresponding with 62 will remain in continuous contact 
with the upper end of the pre-form whereby, when the unloading steps are 
initiated it is not necessary to apply hydraulic pressure to the plug to 
make it compensate for lengthwise shrinking of the compact and recovery of 
shape of an elastomeric plug. However, hydraulic pressure will be applied 
to the upper rigid plug to make it follow the compact as it is withdrawn 
from the press thus to insure that at all times the compact is held by 
lengthwise or axial pressure between the upper and lower plugs. While this 
pressure is unyielding it is the full equivalent, insofar as the method is 
concerned, of the yielding pressure which is exerted upon the pre-form or 
compact by elastomeric plugs.