Abstract:
A press for fabrication of building components including: 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 including; a cylinder; 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 a piston rod connected to the piston and extending through the second chamber to engage the upper or lower platen; 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.

Description:
BACKGROUND OF THE INVENTION 
     1. 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 aluminum extrusions, laminated and composite timber articles). 
     2. Description of the Related Art 
     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 localized 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 localized pressure applied to it. A number of these types of devices have been proposed. 
     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. 
     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 
     Accordingly there is provided a press for fabrication of building components including: (a) an upper platen; (b) a lower platen; (c) first and second hydraulic devices each including; (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, 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; and each piston rod of each hydraulic device extends in engagement with one and the same of the upper or lower platens, whereby the hydraulic devices are operable to shift the upper or lower platen the piston rods engage, relatively toward or away from the other of the upper or lower platens, (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 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 is a medium which can translate motive forces very well. 
     In another preferred form of the invention there is provided, a press for fabrication of building components including: (a) an upper platen connected to an upper part of a frame; (b) a lower platen; (c) spaced first and second hydraulic devices each connected at one and the same end thereof to the frame and each including; (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 through the second chamber into engagement with the lower platen at the other end of the device to that connected to the frame; 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 device to cause the piston rods of both hydraulic devices to move and to shift the upper or lower platen relatively towards or away from the other platen; 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 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 including: (a) an upper platen connected to an upper frame; (b) a lower platen connected to a lower frame; (c) spaced first and second hydraulic devices, each including; (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 through 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; and each of the hydraulic devices is connected at one end to the upper frame and at the other end to the lower frame, one of the connections being with the end of the piston rods extending from the second chambers, and the devices being operable by extension or retraction of the piston rods thereof to shift the upper or lower platen relatively toward or away from the other; (d) a pump to pump hydraulic fluid into or from the first chamber of the first hydraulic devices to cause the piston rods of both hydraulic devices to move and to shift the upper or lower platen relatively towards or away from the other platen; 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 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 including: (a) an upper platen; and (b) a lower platen; (c) first and second hydraulic devices each including; (i) a cylinder having a 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) a first sub-chamber between an end of the cylinder and the first piston and (b) 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 (c) a third sub-chamber between the partition and the second piston and (d) 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 from the fourth sub-chamber; 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 the inlet/outlet of the third sub-chamber of one of the hydraulic devices is in fluid communication with the inlet/outlet of the fourth sub-chamber of the other hydraulic device; and each of the hydraulic devices is connected at one end to the upper frame and at the other end to the lower frame, one of the connections being with the end of the piston rods extending from the fourth sub-chamber and each device is operable by extension or retraction of the piston rods thereof to shift the upper or lower platens relatively toward or away from the other; (d) a pump to pump hydraulic fluid into the first sub-chamber of each of the hydraulic devices; and (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. 
     In operation, hydraulic fluid flows into the sub-chamber of each of the hydraulic devices 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 the 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. 
     In this way, the press reacts quickly to equalize the pressure being applied to the platen which minimizes 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 localization 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. 
     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 platen becoming tilted. 
     Accordingly, to ameliorate this the valve 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 and under predetermined pressure conditions permits hydraulic fluid to pass from one chamber to another. 
     In an alternate embodiment, the valve is located externally of the cylinders in a hydraulic fluid line which communicates with a reservoir of 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 hydraulic fluid lines which communicate between the hydraulic devices. 
     In another alternate embodiment, the valve may be actuated in response to sensor signals. Sensors (e.g. 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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be further explained and illustrated by reference to the accompanying drawings in which: 
     FIG. 1 is a simplified front view of a press; 
     FIG. 2 is a simplified front view of the press of FIG. 1 with a misaligned platen; 
     FIG. 3 is a front view of a press according to a first form of the invention; 
     FIG. 4 is a front view of a press according to a second form of the invention; 
     FIG. 5 is a front view of a press according to a third form of the invention; 
     FIG. 6 is a front view of a press according to a fourth form of the invention; 
     FIG. 7 is a front view of a press according to a fifth form of the invention; 
     FIG. 8 is a side view of the press of FIG. 7; 
     FIG. 9 is a front view of a press according to a sixth form of the invention; 
     FIG. 10 is a side view of the press of FIG. 9; 
     FIG. 11 is a conceptual illustration of a press according to a seventh form of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the drawings like elements are designated by the same numbers. FIGS. 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 localized impact forces may occur across the lower platen  3 . These localized forces may cause the platens  2  and  3  to become misaligned as shown in FIG.  2 . If the machine is automated and is carrying out repetitive fabrication steps, the integrity of the fabrication may be adversely affected. 
     FIG. 3 shows a form of press  100  according to the invention. Like parts from FIGS. 1 and 2 have the same reference numerals, plus  100 . Lower platen  103  is supported by a pair of hydraulic cylinders  105  and  106 . Cylinders  105  and  106  are connected to the lower platen  103  by piston rods  107  and  108 . Piston rods  107  and  108  are connected to pistons  109  and  110  which are in sealing engagement with the walls of cylinders  105  and  106 . Piston  109  defines chambers  111  and  112  in cylinder  105 . Piston  110  defines chambers  113  and  114  in cylinder  106 . 
     Cylinder  105  has a fluid inlet/outlet  115  in chamber  111  and a fluid inlet/outlet  116  in chamber  112 . Cylinder  106  has a fluid inlet/outlet  117  in chamber  113  and a fluid inlet/outlet  118  in chamber  114 . 
     Fluid line  119  connects inlet/outlet  116  to inlet/outlet  117 . Fluid line  120  connects the inlet/outlet  118  to a reservoir/pump  121 . Fluid line  122  connects reservoir/pump  121  to inlet/outlet  115 . 
     In operation if the platen  103  is subjected to a localized load, the pressure will be spread differentially across the platen and transmitted differentially to the two piston rods  107  and  108 . Assuming the greater load is transferred to the cylinder  106 , the piston rod  108  causes the piston  110  to move against the fluid in the chamber  113 . The residue of the load is applied to the piston rod  107  which in turn attempts to move the piston  109 . Chamber  113  of cylinder  106  is in fluid communication with the chamber  112  of cylinder  105  via fluid line  119 . Any movement of the two pistons is matched by the flow of fluid from the chamber  113  into chamber  112 . The platen  103  is thereby maintained substantially level (horizontal) and does not tilt. 
     Likewise to raise platen  103  to carry out the fabrication, hydraulic fluid is pumped from reservoir/pump  121  through fluid line  122  into chamber  111 . This urges piston  109  up and hydraulic fluid in chamber  112  is displaced to chamber  113  via fluid line  119 . This in turn forces piston  110  up and hydraulic fluid is expelled to the reservoir/pump  121  via fluid line  120 . In this way a distributed lifting force is applied across platen  103  to ensure that it remains substantially horizontal. To lower platen  103  the reverse procedure is carried out. 
     In FIG. 4 a press  200  includes many of the features of FIGS. 1 to  3  and those features have the same third, or second and third numbers. A recycling valve  223  is interposed into fluid line  220  and a branch fluid line  224  extends from the recycling valve  223  to fluid line  222 . In operation, when platen  203  is being raised, the volume of hydraulic fluid which is being pumped from the reservoir/pump  221  to cylinder  205  can be significantly reduced by opening recycle valve  223  to allow fluid being expelled through inlet/outlet  218  to flow via fluid lines  220 ,  224  and  222  to inlet/outlet  215 . 
     In FIG. 5 a press  300  is shown with the same reference numeral structure as FIG.  4 . This arrangement  300  is appropriate to compensate for any leaks in the seal between the pistons  309  and  310  and the cylinders  305  and  306  respectively. Over time, these seals will degrade and fluid will leak between the chambers  311  and  312  and/or chambers  313  and  314 . As this occurs, the total volume of fluid which resides in chambers  312 ,  313  and/or chambers  313 ,  314  and fluid line  319  increases. As such, the relative position of the pistons  309  and  310  will change and platen  303  will be tilted. 
     To compensate for these leaks, one or more valves can be incorporated which are either pressure actuated or actuated using remotely generated signals. As shown in FIG. 5, fluid lines  326  and  328  are connected to chambers  311  and  313 , respectively and also connect to valve  325 . In the event that the chambers  311  and  313  are out of balance, valve  325  opens either or both fluid lines  326  and  328  to permit pistons  309  and  310  to again be in a balanced relationship by hydraulic fluid flowing through fluid line  327 . 
     Likewise, a compensation circuit is connected to chambers  312  and  314  via fluid lines  330  and  331 . These fluid lines  330  and  331  are both connected to valve  329  which can selectively permit fluid to flow from either or both chambers  312  and  314  to fluid line  332 . 
     In FIG. 6 a press  400  is shown, with the same reference numeral structure as FIG.  4 . An alternate compensating arrangement is shown. For simplicity only, none of the external circuit is shown. However, the external circuitry as shown in FIG.  3 . would be suitable. The internal compensatory circuit uses valves  435  and  436  disposed in passageways  433  and  434 . As shown, the pistons  409  and  410  are out of alignment due to wearing of the seals (not shown). By opening valve  435  fluid can flow from chamber  412  to chamber  411 . By opening valve  436  fluid can flow from chamber  414  to chamber  413 . Typically the valves  435  and  436  are pressure actuated and only open for a time sufficient to permit the pistons  409  and  410  to be rebalanced. 
     FIGS. 7 and 8 show a practical arrangement of a press  500  according to the invention. The circuitry is not shown but would typically be that disclosed in FIG.  4 . The press  500  is mounted on a carriage  537  which has four wheels  538 . The wheels  538  engage and roll along a pair of lower flanges of rails  539 . The wheels  538  are connected by axles  540 . 
     The carriage  537  has a base frame which is composed of a pair of spaced upright plates  541  which are connected by platen  542  (which is also the upper platen) and a pair of plates  543 . A recess is formed by the plates  541  and platen  542  in which a hydraulic power pack  544  resides. Hydraulic power pack  544  controls the fluid circuitry (not shown). 
     Located in between the plates  541  is a lower sub-frame  545 . Hydraulic cylinders  505  and  506  are connected to sub-frame  545  whilst the piston rods  507  and  508  are connected to plates  543  in the base frame. Sub-frame  545  has a lower platen  546 . In operation, the article  547  to be fabricated is to be held between upper platen  542  and lower platen  546 . To move the lower platen  546  upward, fluid is pumped into chamber  512  (as shown in FIG. 4) and accordingly fluid is displaced from chamber  511  to chamber  514 . The upper platen  542  is initially lowered until it rests on the article  547 . The lower platen  546  is then raised to sandwich article  547  with upper platen  542  and lift the four wheels  538  off the rails  539 . The reverse procedure is followed to lower the lower platen  546 . 
     FIGS. 9 and 10 show another practical arrangement of a press  600  according to the invention. Again the circuitry is not shown but would typically be that disclosed in FIG.  4 . The press  600  is mounted on a carriage  637  which has four wheels  638 . The wheels  638  engage and roll along a pair of lower flanges of rails  639 . The wheels  638  are connected by axles  640  which are in turn connected to the lower platen  648 . 
     The carriage  637  has a base frame which is composed of a pair of spaced upright plates  641  which are connected by platen  642  (which is also the upper platen) and a pair of plates  643 . A recess is formed by the plates  641  and platen  642  in which a hydraulic power pack  644  resides. Hydraulic power pack  644  controls the fluid circuitry (not shown). 
     Located in-between the plates  641  and on the plates  643  are hydraulic cylinders  605  and  606 . Piston rods  607  and  608  are connected to lower platen  648 . In operation, the article  647  to be fabricated is between upper platen  642  and lower platen  648 . To initially move the upper platen  642  downward and then move the lower platen upward, fluid is pumped into chamber  611  (equivalent to chamber  211  as shown in FIG. 4) and accordingly fluid is displaced from chamber  612  to chamber  613 . The lower platen  648  is finally raised to sandwich article  647  with upper platen  642  which movement raises the wheels  638  off the rails  639 . The reverse procedure is followed to lower the lower platen  648 . 
     FIG. 11 shows conceptually another alternative. Press  700  has a lower platen  702  and an upper platen  703 . Both platens  702  and  703  are movable towards one another. An article (not shown) to be fabricated is disposed in the space  704 . As the platens  702  and  703  converge, they hold the article in position to permit fasteners or the like to penetrate the article at the desired position. This means that localized impact forces may occur across the lower platen  703 . These localized forces may cause the platens  702  and  703  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  703  is controlled by a pair of hydraulic cylinders  705  and  706 . Cylinders  705  and  706  are connected to the upper platen  703  by piston rods  707  and  708 . Piston rods  707  and  708  are connected to pistons  709  and  710  in cylinder  705  and pistons  711  and  712  of cylinder  706  respectively. These pistons are in sealing engagement with the walls of the cylinders. 
     Intermediate piston  709  and  710  is partition  713 , whilst intermediate pistons  711  and  712  is partition  714 . These partitions  713  and  714  sealingly engage cylinders  705  and  706  and also permit piston rods to pass therethrough in a sealed arrangement. 
     The upper ends of cylinders  705  and  706  define first sub-chambers A and B with pistons  710  and  712  respectively. The pistons  710  and  712  define second sub-chambers C and D with partitions  713  and  714  respectively. The pistons  709  and  711  define third sub-chambers E and F with partitions  710  and  712  respectively. The lower ends of cylinders  705  and  706  define fourth sub-chambers G and H with pistons  709  and  711  respectively. 
     The first sub-chambers A and B have an inlet  715  and  716  for hydraulic fluid from a hydraulic fluid pump  717 . The second sub-chambers C and D have an outlet  718  and  719  for hydraulic fluid. The third sub-chambers have an inlet/outlet  720  and  721  for hydraulic fluid. The fourth sub-chambers have an inlet/outlet  722  and  723  for hydraulic fluid. Fluid line  724  connects inlet/outlet  721  and  722 , whilst fluid line  725  connects inlet/outlet  720  and  723 . 
     To compensate for any leaks between the sub-chambers, one or more valves  726  can be incorporated which are either pressure actuated or actuated using remotely generated signals. Also, valve lines  727  and  728  may be provided to connect the first sub-chambers A and B with a valve  729 , so that if chambers A and B are out of balance, valve  729  opens either or both of fluid lines  727  and  728  to permit pistons  710  and  712  to be balanced by fluid flowing through line  730 . This arrangement is effectively the same as that shown in FIG. 5 in relation to the valve  325 . 
     In operation, hydraulic fluid flows into the first sub-chamber A and B of each of the hydraulic cylinders  705  and  706  to apply a load. The load applied to each cylinder  705  and  706  is invariably different. The pressure applied causes the pistons  709  and  710 , and  711  and  712  to move which reduces the volume of the fourth sub-chambers G and H. 
     When the load is larger in hydraulic cylinder  705  than in hydraulic cylinder  706 , the fluid from the fourth sub-chamber G of cylinder  705 , forces fluid into the third sub-chamber (F) of cylinder  706 . This transmits an additional force to piston  711  of cylinder  706  until fourth sub-chamber H has an equal pressure to the fourth sub-chamber G of cylinder  705 . 
     In this way, the press reacts quickly to equalize the pressure being applied to the platen which minimizes potential misalignment of the platen. 
     Presses according to the invention, use the interaction of the hydraulic fluid in the cylinders as the means to maintain the platen substantially level (horizontal) irrespective of the localization of the load imposed by the tool on the platen. Improvements and modifications will be readily apparent to those skilled in the art and are considered to be within the scope and spirit of the invention.