AU720880B2

AU720880B2 - Press

Info

Publication number: AU720880B2
Application number: AU76301/98A
Authority: AU
Inventors: Donald Simpson Mahoney
Original assignee: Becfab Equipment Pty Ltd
Current assignee: ITW Australia Pty Ltd
Priority date: 1997-06-02
Filing date: 1998-06-01
Publication date: 2000-06-15
Anticipated expiration: 2018-06-01
Also published as: AU7630198A

Description

WO 98/55289 PCT/AU98/00401 Press Field of the invention The invention relates generally to a press having a hydraulically controlled platen. More particularly, the press is useful for the manufacture of prefabricated building components (such as trusses) or other building components. It may also be useful in processing other articles (such as plastic sheet, plastic pipe, sheet and metal articles such as aluminium extrusions, laminated and composite timber articles).

Background of the invention Whilst the following discussion illustrates the press used for manufacture of prefabricated building components, it is to be understood that the press may be used in other engineering applications.

Traditionally, trusses that are destined for the building industry may be constructed on-site or prefabricated. Prefabricated trusses of standard designs are very popular as they can be mass-produced by passing the assembled components between a press which fixes the components together at appropriate locations.

Typically, such presses have an upper and/or lower platen against which the fixing occurs.

One form of press, which is in use in the building component prefabrication industry, has a lower platen and an upper moving platen which is designed to press down on the components disposed in between them. The pressing action pushes fasteners into the components to form timber joints of a truss assembly. The components need to be held firmly during the fixing operation to produce strong and uniform trusses. Considerable pressure is applied to the lower platen indirectly during the holding and fixing of the timber joint to achieve this. Further, the fixing is usually localised to relatively small areas of the platen where the joint to be formed is located. This area may vary across the platen depending upon where the proposed joint is positioned.

Consequently, the lower platen has to be supported by devices which prevent it moving or tilting in response to any localised pressure applied to it. A number of these types of devices have been proposed.

2 In Australian patent no. 543663 a hydraulic press is disclosed. A pair of rams are each provided with a hydraulic device under the tool. They are connected by a torsion bar which regulates the fluid flow into the hydraulic rams in the event that it becomes misaligned. A complex combination of bars, rocking members and springs are used to maintain the tool level.

In another arrangement, a series of manually or automatically controlled levers are provided to mechanically regulate the movement and alignment of the platen of a press.

Again, this is complex and is not readily adapted to automate and regulate the pressing function of the machine.

Object of the invention It is an objective of the present invention to provide a press with improved adjustment of the alignment of at least one of its pressing components.

Summary of the invention 0..

Accordingly there is provided a press for fabrication of building components comprising: an upper platen; alowerplaten; the upper platen and/or lower platen movable towards and away from the other; a first and second hydraulic device located on a base, each hydraulic device comprising; 20 a cylinder; (ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and (iii) a piston rod connected to the piston and extending through the second chamber to engage the upper or lower platen wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid Rand the second chamber of the first hydraulic device is in fluid communication with S the first chamber of the second hydraulic device; a pump to pump hydraulic fluid into the first chamber of the first hydraulic device; and a valve in fluid communication with the first chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

In operation, hydraulic fluid is pumped into the first chamber of the first hydraulic device by the pump which causes the piston to move towards the inlet/outlet of the second chamber. The second chamber decreases in volume and forces hydraulic fluid through the inlet/outlet of the second chamber of the first hydraulic device into the first chamber of the second hydraulic device. This in turn, causes a similar displacement of the piston in the second hydraulic device and fluid present in the second chamber of the second hydraulic device flows through the inlet/outlet.

As will be well understood by engineers, hydraulic fluid is substantially incompressible and 15 is a medium which can translate motive forces very well.

According to a preferred form of the invention, there is provided a press for fabrication of building components comprising: an upper platen; a lower platen; the upper platen and/or lower platen movable towards and away from the other; a first and second hydraulic device located on a base, each hydraulic device comprising; a cylinder; (ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and (iii) a piston rod connected to the piston and extending through the second chamber to engage the upper or lower platen wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid and the second chamber of the first hydraulic device is in fluid communication with the first chamber of the second hydraulic device; 4 a pump to pump hydraulic fluid into or from the first chamber of the first hydraulic device to cause the piston rods of both hydraulic device to move the upper and/or lower platen towards or away from the other; and a valve in fluid communication with the first chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

In another preferred form of the invention there is provided, a press for fabrication of building components comprising: an upper platen connected to an upper part of a frame; a lower platen; the upper platen and lower platen movable towards and away from each other; spaced first and second hydraulic device each connected at one end thereof to the frame and at the other end thereof to the lower platen, each hydraulic device comprising; a cylinder; (ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and 20 (iii) a piston rod connected to the piston at one end thereof and extending from the second chamber; wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid, and the second chamber of the first hydraulic device is in fluid communication with the first chamber of the second hydraulic device; a pump to pump hydraulic fluid into or from the first chamber of the first hydraulic device to cause the piston rods of both hydraulic device to move the upper and/or lower platen towards or away from the other; and a valve in fluid communication with the first chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

In yet another preferred form of the invention there is provided, a press for fabrication of building components comprising: an upper platen connected to an upper frame; a lower platen connected to a lower frame; the upper platen and lower platen movable towards and away from each other by relative movement of the upper frame and lower frame; spaced first and second hydraulic device, each connected at one end thereof to the upper frame and at the other end thereof to the lower frame, each hydraulic device comprising; a cylinder; (ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and (iii) a piston rod connected to the piston at one end thereof and extending from the second chamber; wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid, and the second chamber of the first hydraulic device is in fluid communication with the first chamber of the second hydraulic device; a pump to pump hydraulic fluid into or from the first chamber of the first hydraulic S•device to cause the piston rods of both hydraulic device to move the upper and/or lower platen towards or away from the other; and a valve in fluid communication with the first chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

According to another preferred form of the invention, a press for fabrication of building components is provided comprising: an upper platen; a lower platen; the upper platen and/or lower platen movable towards and away from the other; a first and second hydraulic device located therebetween, each hydraulic device comprising; a cylinder having an partition sealingly engaging the walls of the cylinder and located intermediate the ends of the cylinder, to define first and second chambers of the cylinder; (ii) a first piston located in the first chamber and defining a first subchamber between an end of the cylinder and the first piston and a second sub-chamber between the first piston and the partition, the first piston sealingly engaging the cylinder and movable in the cylinder; (iii) a second piston located in the second chamber and defining a third subbetween the partition and the second piston and a fourth subchamber between the second piston and the other end of the cylinder, the second piston sealingly engaging the cylinder and movable in the cylinder; S" •and (iv) a piston rod connected to the first piston and the second piston and passing through and sealingly contacting the partition, and further extending to S 20 engage the upper or lower platen wherein the first sub-chamber has an inlet for hydraulic fluid, the second subchamber has an outlet for hydraulic fluid, the third sub-chamber has an inlet/outlet for hydraulic fluid and the fourth sub-chamber has an inlet/outlet for hydraulic fluid; and wherein the inlet/outlet of the third sub-chamber of one of the hydraulic device is in fluid communication with the inlet/outlet of the fourth sub-chamber of the other hydraulic device; a pump to pump hydraulic fluid into the first sub-chamber of each of the hydraulic Xdevice; and a valve in fluid communication with the first sub chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first sub chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

s In operation, hydraulic fluid flows into the sub-chamber of each of the hydraulic device to apply a load. Typically the load applied to each hydraulic device is different. The pressure applied causes the first and second piston to move which reduces the volume of the fourth sub-chamber of each hydraulic device; When the load is different on each hydraulic device, the fluid from the fourth sub-chamber which is under the greater pressure, forces fluid into the third sub-chamber of the other hydraulic device. This transmits an additional force to second piston of that other hydraulic device until its fourth sub-chamber has an equal pressure to the fourth sub-chamber of the first hydraulic device.

!i! In this way, the press reacts quickly to equalise the pressure being applied to the platen which minimises potential misalignment of the platen.

The press according to the invention, uses the interaction of the hydraulic fluid in the cylinders as the means to maintain the platen substantially level (horizontal) irrespective of °the localisation of the load imposed by the tool on the platen. Accordingly, the formation of building components, between the upper platen and lower platen over extended periods of use and repetition, is consistently of a high reproducible quality.

o Over time, the seals which form the sealing engagement of the piston with the cylinder will degrade and fluid will leak between the chambers in each hydraulic device. As this occurs, the total volume of fluid which resides in the chambers will change. This results in the 9 S platen becoming tilted.

Accordingly to ameliorate this, the press further comprises a valve which is incorporated to correct any imbalance between the relative position of the pistons in the cylinders.

Preferably, the valve is located in either or both the pistons and is pressure actuated. In this embodiment, the pistons are preferably provided with a passageway which communicates between the chambers of the cylinder. The valve is located in the passageway PCT/AU98/00401 Received 15 March 1999 8 and under predetermined pressure conditions permits hydraulic fluid to pass from one chamber to another.

In an alternate embodiment, the valve is preferably located externally of the cylinders in a hydraulic fluid line which communicates with a reservoir for hydraulic fluid. The fluid line is connected to each of the cylinders. If the fluid pressure exceeds the predetermined amount in a cylinder, the valve opens to permit hydraulic fluid to flow out and correct any imbalance between the relative positions of the pistons in the cylinders.

In another alternate embodiment, the valve is externally of the cylinders in a hydraulic fluid lines which communicate between the hydraulic device.

In another alternate embodiment, the valve may be actuated in response to sensor signals.

Sensors (eg. electrical limit switches) are positioned to detect the position or alignment of the platen. If predetermined limits are exceeded, the sensors cause the valve or valves associated with either or both the cylinders to open. The pistons are therefore rebalanced to restore the desired alignment.

Description of the drawings The invention will now be further explained and illustrated by reference to the accompanying drawings in which: Figure 1 is a simplified front view of a press; Figure 2 is a simplified front view of the press of figure 1 with a misaligned platen; Figure 3 is a front view of a press according to a first form of the invention; Figure 4 is a front view of a press according to a second form of the invention; Figure 5 is a front view of a press according to a third form of the invention; Figure 6 is a front view of a press according to a fourth form of the invention; Figure 7 is a front view of a press according to a fifth form of the invention; Figure 8 is a side view of the press of figure 7.

SFigure 9 is a front view of a press according to a sixth form of the invention; AMENDED SHEET (Article 34) (IPEA/AU) S. PCT/AU98/00401 Received 15 March 1999 9 Figure 10 is a side view of the press of figure 9.

Figure 11 is a conceptual illustration of a press according to a seventh form of the invention.

In the drawings like elements are designated by the same numbers. Figures 1 and 2 are conceptual illustrations of a press 1 in different positions. Press 1 has an upper platen 2 and a lower platen 3. Both platens 2 and 3 are movable towards one another. An article (not shown) to be fabricated is disposed in the space 4. As the platens 2 and 3 converge, they hold the article in position to permit fasteners or the like to penetrate the article at the desired position. This means that localised impact forces may occur across the lower platen 3. These localised forces may cause the platens 2 and 3 to become misaligned as shown in figure 2. If the machine is automated and is carrying out repetitive fabrication steps, the integrity of the fabrication may be adversely affected.

Figure 3 shows a form of press 1 according to the invention. Lower platen 3 is supported by a pair of hydraulic cylinders 5 and 6. Cylinders 5 and 6 are connected to the lower platen 3 by piston rods 7 and 8. Piston rods 7 and 8 are connected to pistons 9 and 10 which are in sealing engagement with the walls of cylinders 5 and 6. Piston 9 defines chambers 11 and 12 in cylinder 5. Piston 10 defines chambers 13 and 14 in cylinder 6.

Cylinder 5 has a fluid inlet/outlet 15 in chamber 10 and a fluid inlet/outlet 16 in chamber 11.

Cylinder 6 has a fluid inlet/outlet 17 in chamber 13 and a fluid inlet/outlet 18 in chamber 14.

Fluid line 19 connects inlet/outlet 16 to inlet/outlet 17. Fluid line 20 connects the inlet/outlet 18 to a reservoir/pump 21. Fluid line 22 connects reservoir/pump 21 to inlet/outlet In operation if the platen 3 is subjected to a localised load, the pressure will be spread differentially across the platen and transmitted differentially to the two piston rods 7 and 8.

Assuming the greater load is transferred to the cylinder 6, the piston rod 8 causes the piston to move against the fluid in the chamber 13. The residue of the load is applied to the piston rod 7 which in turn attempts to move the piston 9. Chamber 13 of cylinder 6 is in fluid communication with the chamber 12 of cylinder 5 via fluid line 19. Any movement of the two pistons is matched by the flow of fluid from the chamber 13 into chamber 12. The platen 3 is thereby maintained substantially level (horizontal) and does not tilt.

AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00401 Received 15 March 1999 Likewise to raise platen 3 to carry out the fabrication, hydraulic fluid is pumped from reservoir/pump 21 through fluid line 22 into chamber 11. This urges piston 9 up and hydraulic fluid in chamber 12 is displaced to chamber 13 via fluid line 19. This in turn forces piston 10 up and hydraulic fluid is expelled to the reservoir/pump 21 via fluid line 20. In this way a distributed lifting force is applied across platen 3 to ensure that it remains substantially horizontal. To lower platen 3 the reverse procedure is carried out.

In figure 4, a recycling valve 23 is interposed into fluid line 20 and a branch fluid line 24 extends from the recycling valve 23 to fluid line 22. In operation, when platen 3 is being raised, the volume of hydraulic fluid which is being pumped from the reservoir/pump 21 to cylinder 5 can be significantly reduced by opening recycle valve 23 to allow fluid being expelled through inlet/outlet 18 to flow via fluid lines 20, 24 and 22 to inlet/outlet In figure 5 an arrangement is shown to compensate for any leaks in the seal between the pistons 9 and 10 and the cylinders 5 and 6 respectively. Over time, these seals will degrade and fluid will leak between the chambers 11 and 12 and/or chambers 13 and 14. As this occurs, the total volume of fluid which resides in chambers 12, 13 and/or chambers 13, 14 and fluid line 19 increases. As such, the relative position of the pistons 9 and 10 will change and platen 3 will be tilted.

To allow for these leaks to be compensated for, one or more valves can be incorporated which are either pressure actuated or actuated using remotely generated signals. As shown in figure 5, fluid lines 26 and 28 are connected to chambers 11 and 13, respectively and also connect to valve 25. In the event that the chambers 11 and 13 are out of balance, valve opens either or both fluid lines 26 and 28 to permit pistons 9 and 10 to again be in a balanced relationship by hydraulic fluid flowing through fluid line 27.

Likewise, a compensation circuit is connected to chambers 12 and 14 via fluid lines 30 and 31. These fluid lines 30 and 31 are both connected to valve 29 which can selectively permit fluid to flow from either or both chambers 12 and 14 to fluid line 32.

In figure 6, an alternate compensating arrangement is shown. For simplicity only, none of the external circuit is shown. However, the external circuitry as shown in figure 3 would be suitable. The internal compensatory circuit uses valves 35 and 36 disposed in passageways 33 and 34. As shown, the pistons 9 and 10 are out of alignment due to wearing of the seals AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00401 Received 15 March 1999 11 (not shown). By opening valve 35 fluid can flow from chamber 12 to chamber 11. By opening valve 36 fluid can flow from chamber 14 to chamber 13. Typically the valves and 36 are pressure actuated and only open for a time sufficient to permit the pistons 9 and to be rebalanced.

Figures 7 and 8 show a practical arrangement of a press 1 according to the invention, The circuity is not shown but would typically be that disclosed in figure 4. The press 1 is mounted on a carriage 37 which has four wheels 38. The wheels 38 engage and roll Is along a pair of lower flanges of rails 39. The wheels 38 are connected by axles The carriage 37 has a base frame which is composed of a pair of spaced upright plates 41 which are connected by plate 42 (which is also the upper platen) and a pair of plates 43. A recess is formed by the plates 41 and plate 42 in which a hydraulic power pack 44 resides.

Hydraulic power pack 44 controls the fluid circuitry (not shown).

Located in between the plates 41 is a lower sub-frame 45. Hydraulic cylinders 5 and 6 are connected to sub-frame 45 whilst the piston rods 7 and 8 are connected to plates 43 in the base frame. Sub-frame 45 has a lower platen 46. In operation, the article 47 to be fabricated is to be held between upper platen 42 and lower platen 46. To move the lower platen 46 upward, fluid is pumped into chamber 12 (as shown in figure 4) and accordingly fluid is displaced from chamber 11 to chamber 14. The upper platen 42 is initially lowered until it rests on the article 47. The lower platen 46 is then raised to sandwich article 47 with upper platen 42 and lift the four wheels 38 off the rails 39. The reverse procedure is followed to lower the lower platen 46.

Figures 9 and 10 show another practical arrangement of a press 1 according to the invention. Again the circuity is not shown but would typically be that disclosed in figure 4.

The press 1 is mounted on a carriage 37 which has four wheels 38. The wheels 38 engage and roll along a pair of lower flanges of rails 39. The wheels 38 are connected by axles which are in turn connected to the lower platen 48.

The carriage 37 has a base frame which is composed of a pair of spaced upright plates 41 which are connected by plate 42 (which is also the upper platen) and a pair of plates 43. A recess is formed by the plates 41 and plate 42 in which a hydraulic power pack 44 resides.

Hydraulic power pack 44 controls the fluid circuitry not shown).

AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00401 Received 15 March 1999 12 Located in-between the plates 41 and on the plates 43 are hydraulic cylinders 5 and 6.

Piston rods 7 and 8 are connected to lower platen 48. In operation, the article 47 to be fabricated is between upper platen 42 and lower platen 48. To initially move the upper platen 42 downward and then move the lower platen upward, fluid is pumped into chamber 11 (as shown in figure 4) and accordingly fluid is displaced from chamber 12 to chamber 13.

The lower platen 46 is finally raised to sandwich article 47 with upper platen 42 which movement raises the wheels 38 off the rails 39. The reverse procedure is followed to lower the lower platen 48.

Figures 11 show conceptually another alternative. Press 1 has a lower platen 2 and a upper platen 3. Both platens 2 and 3 are movable towards one another. An article (not shown) to be fabricated is disposed in the space 4. As the platens 2 and 3 converge, they hold the article in position to permit fasteners or the like to penetrate the article at the desired position. This means that localised impact forces may occur across the lower platen 3.

These localised forces may cause the platens 2 and 3 to become misaligned. If the machine is automated and is carrying out repetitive fabrication steps, the integrity of the fabrication may be adversely affected.

Upper platen 3 is controlled by a pair of hydraulic cylinders 5 and 6. Cylinders 5 and 6 are connected to the upper platen 3 by piston rods 7 and 8. Piston rods 7 and 8 are connected to pistons 9 and 10 in cylinder 5 and pistons 11 and 12 of cylinder 6 respectively. These pistons are in sealing engagement with the walls of the cylinders.

Intermediate piston 9 and 10 is partition 13, whilst intermediate pistons 11 and 12 is partition 14. These partitions 13 and 14 sealingly engage cylinders 5 and 6 and also permit piston rods to pass therethrough in a sealed arrangement.

The upper ends of cylinders 5 and 6 define first sub-chambers A and B with pistons 10 and 12 respectively. The pistons 10 and 12 define second sub-chambers C and D with partitions 13 and 14 respectively. The pistons 9 and 11 define third sub-chambers E and F with partitions 10 and 12 respectively. The lower ends of cylinders 5 and 6 define fourth subchambers G and H with pistons 9 and 11 respectively.

The first sub-chambers A and B have an inlet 15 and 16 for hydraulic fluid from a hydraulic fluid pump 17. The second sub-chambers C and D have an outlet 18 and 19 for hydraulic AMENDED SHEET (Article 34) (IPEA/AU) fluid. The third sub-chambers have an inlet/outlet 20 and 21 for hydraulic fluid. The fourth sub-chambers have an inlet/outlet 22 and 23 for hydraulic fluid. Fluid line 24 connects inlet/outlet 21 and 22, whilst fluid line 25 connects inlet/outlet 20 and 23.

To allow for any leaks between the sub-chambers to be compensated for, one or more valves 26 can be incorporated which are either pressure actuated or actuated using remotely generated signals.

In operation, hydraulic fluid flows into the first sub-chamber A and B of each of the hydraulic cylinders 5 and 6 to apply a load. The load applied to each cylinder 5 and 6 is invariably different. The pressure applied causes the pistons 9 and 10, and 11 and 12 to move which reduces the volume of the fourth sub-chambers G and H.

When the load is larger in hydraulic cylinder 5 than on 6, the fluid from the fourth subchamber G of cylinder 5, forces fluid into the third sub-chamber of cylinder 6. This transmits an additional force to piston 11 of cylinder 6 until fourth sub-chamber H has an equal pressure to the fourth sub-chamber G of cylinder In this way, the press reacts quickly to equalise the pressure being applied to the platen which minimises potential misalignment of the platen.

The press according to the invention, uses the interaction of the hydraulic fluid in the cylinders as the means to maintain the platen substantially level (horizontal) irrespective of the localisation of the load imposed by the tool on the platen. Improvements and ooo* modifications will be readily apparent to those skilled in the art and are considered to be within the scope and spirit of the invention.

o .The word 'comprising' or forms of the word 'comprising' as used in this description and in •the claims do not limit the invention claimed to exclude any variants or additions.

Claims

1. A press comprising: a) an upper platen; b) a lower platen; the upper platen and/or lower platen movable towards and away from the other; c) a first and second hydraulic device located on a base, each hydraulic device comprising; i) a cylinder; ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and iii) a piston rod connected to the piston and extending through the second chamber to engage the upper or lower platen i 15 wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid and the second chamber of the first hydraulic device is in fluid communication with the first chamber of the second hydraulic device; d) a pump to pump hydraulic fluid into the first chamber of the first hydraulic device; and e) a valve in fluid communication with the first chambers of the first and S-second hydraulic devices to selectively withdraw hydraulic fluid from the first chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

2. A press according to claim 1 wherein the pump is additionally adapted to pump S' 25 hydraulic fluid from the first chamber of the first hydraulic means.

3. A press comprising: a) an upper platen connected to an upper part of a frame; b) a lower platen; the upper platen and lower platen movable towards and away from each other; c) spaced first and second hydraulic device each connected at one end thereof to the frame and at the other end thereof to the lower platen, each hydraulic device comprising; i) a cylinder; ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and iii) a piston rod connected to the piston at one end thereof and extending from the second chamber; wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid, and the second chamber of the first hydraulic device is in fluid communication with the first chamber of the second hydraulic device; d) a pump to pump hydraulic fluid into or from the first chamber of the first hydraulic means to cause the piston rods of both hydraulic means to move the upper and/or lower platen towards or away from the other; e) a valve in fluid communication with the first chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first chamber of either or both the first and second hydraulic devices to align the upper and lower platens. o4. A press comprising: a) an upper platen connected to an upper frame; 000"b) a lower platen connected to a lower frame; S the upper platen and lower platen movable towards and away from each other by relative movement of the upper frame and lower frame; c) spaced first and second hydraulic device, each connected at one end thereof to the upper frame and at the other end thereof to the lower frame, each hydraulic device comprising; i) a cylinder; ii) a piston located in the cylinder defining a first and a second chamber in the cylinder, the piston sealingly engaging the cylinder and movable in the cylinder; and iii) a piston rod connected to the piston at one end thereof and extending from the second chamber; wherein the first and second chambers, each have an inlet/outlet for hydraulic fluid, and the second chamber of the first hydraulic device is in fluid communication with the first chamber of the second hydraulic device; d) a pump to pump hydraulic fluid into or from the first chamber of the first hydraulic means to cause the piston rods of both hydraulic means to move the upper and/or lower platen towards or away from the other; and e) a valve in fluid communication with the first chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the 0 first chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

5. A press comprising: a) an upper platen; b) a lower platen; 20 the upper platen and/or lower platen movable towards and away from the other; c) a first and second hydraulic device located therebetween, each hydraulic S device comprising; •oS i) a cylinder having an partition sealingly engaging the walls of the cylinder and located intermediate the ends of the cylinder, to define first and second chambers of the cylinder; ii) a first piston located in the first chamber and defining a first sub-chamber between an end of the cylinder and the first piston and a second sub-chamber between the first piston and the partition, the first piston sealingly engaging the cylinder and _movable in the cylinder; PCT/AU98/00401 Received 15 March 1999 17 iii) a second piston located in the second chamber and defining a third sub-chamber between the partition and the second piston and a fourth sub-chamber between the second piston and the other end of the cylinder, the second piston sealingly engaging the cylinder and movable in the cylinder; and iv) a piston rod connected to the first piston and the second piston and passing through and sealingly contacting the partition, and further extending to engage the upper or lower platen wherein the first sub-chamber has an inlet for hydraulic fluid, the second sub-chamber has an outlet for hydraulic fluid, the third sub-chamber has an inlet/outlet for hydraulic fluid and the fourth sub-chamber has an inlet/outlet for hydraulic fluid; and wherein the inlet/outlet of the third sub-chamber of one of the hydraulic device is in fluid communication with the inlet/outlet of the fourth sub- chamber of the other hydraulic device; d) a pump to pump hydraulic fluid into the first sub-chamber of each of the hydraulic device e) a valve in fluid communication with the first sub chambers of the first and second hydraulic devices to selectively withdraw hydraulic fluid from the first sub chamber of either or both the first and second hydraulic devices to align the upper and lower platens.

6. A press according to claim 5 wherein the valve is located externally of the cylinders in a hydraulic fluid line connected to each of the cylinders which communicates with a reservoir for hydraulic fluid.

7. A press according to claim 5 wherein the valve is located externally of the cylinders in a hydraulic fluid line which communicates between the hydraulic devices.

8. A press according to claim 5 wherein the valve is actuated in response to sensor signals. AMENDED SHEET (Article 34) (IPEA/AU)