Inner-circulation high-speed hydraulic system, hydraulic platform, and hydraulic platform assembly

Abstract

An inner-circulating high speed hydraulic system, a hydraulic platform and a hydraulic platform assembly consisting of said systems, wherein the inner-circulating high speed hydraulic system comprises a hydraulic cylinder component and a pressure valve component, the hydraulic cylinder component including a high pressure cylinder, a hydraulic plunger, and a housing, wherein an axial hole and radial holes intersecting with the axial hole are disposed at the top/bottom of the high pressure cylinder and the high pressure cylinder is contained within the housing, wherein the inner-circulating oil chamber may communicate with the axial hole via the radial holes and further communicate with chambers at the top/bottom of the hydraulic plunger, wherein compressed air inlets are disposed on the housing and a lower end of the hydraulic plunger is connected to an actuating element; and a pressure valve component, comprising a pressure servo motor and a pressure plunger driven by the pressure servo motor to move up and down within the axial hole disposed at the top/bottom of the high pressure cylinder. Accurate control on dwell time for pressing at the up and down stop points of the platform, and highly precise adjustment to duration of the dwell time are enabled by the present invention. Thus, a stamping process with high quality is achieved.

Claims

1. An inner-circulating hydraulic system, comprising: a hydraulic cylinder component, including a cylinder, a hydraulic plunger, and a housing, wherein an axial hole disposed near the top of the cylinder communicates with a chamber on the top of the hydraulic plunger, wherein at least one radial hole intersecting the axial hole is also disposed near the top of the cylinder, wherein the hydraulic plunger reciprocates in the cylinder, wherein the housing contains the cylinder and forms a sealed inner-circulating oil chamber outside of the chamber and contained within the housing, wherein the inner-circulating oil chamber fluidly communicates with the axial hole via said radial hole and in turn fluidly communicates with the chamber on the top of the hydraulic plunger, wherein a compressed air inlet is disposed in the upper portion of the housing and a lower end of the hydraulic plunger is connected to a moving platen; and a pressure valve component, comprising a pressure servo motor and a pressure plunger driven by the pressure servo motor to move up and down within the axial hole disposed at the top of the cylinder.

2. The inner-circulating hydraulic system of claim 1, wherein the moving platen is a moving platen of a moving platform.

3. The inner-circulating hydraulic system of claim 2, wherein the hydraulic system further comprises a moving platen lifting component connected to the moving platen, the moving platen lifting component including a lifting servo motor and a lifting mechanism, wherein the lifting mechanism is driven by the lifting servo motor so that the moving platen makes a lifting movement according to a preset lifting curve.

4. The inner-circulating hydraulic system of claim 3, wherein the lifting mechanism comprises a lifting ball screw and a lifting nut engaged with the lifting ball screw for moving, wherein the lifting ball screw is connected to the lifting servo motor while the lifting nut is connected to the moving platen.

5. The inner-circulating hydraulic system of claim 1, wherein a driving mechanism is disposed between the pressure servo motor and the pressure plunger.

6. The inner-circulating hydraulic system of claim 5, wherein the driving mechanism comprises a pressure ball screw and a pressure nut engaged with the pressure ball screw for moving, wherein the pressure ball screw is connected to the pressure servo motor while the pressure nut is connected to the pressure platen.

7. The inner-circulating hydraulic system of claim 1, wherein the pressure plunger is directly driven by a linear servo motor.

8. An inner-circulating hydraulic platform, comprising: an inner-circulating hydraulic moving platform system, comprising: a hydraulic cylinder component, including a cylinder, a hydraulic plunger, and a housing, wherein an axial hole disposed at the bottom of the cylinder communicates with a chamber on the bottom of the hydraulic plunger, wherein at least one radial hole intersecting with the axial hole is also disposed near the bottom of the cylinder, wherein the hydraulic plunger reciprocates in the cylinder, wherein the housing contains the cylinder and forms a sealed inner-circulating oil chamber outside of the chamber and contained within the housing, wherein the inner-circulating oil chamber fluidly communicates with the axial hole via said radial hole and in turn fluidly communicates with the chamber on the bottom of the hydraulic plunger, wherein a compressed air inlet is disposed on the upper portion of the housing and an upper end of the hydraulic plunger is connected to a moving platen; and an upper fixed platform, connected to the inner-circulating hydraulic moving platform system; a moving platen lifting component connected to the moving platen and comprising a lifting servo motor and a lifting mechanism, wherein the lifting mechanism is driven by the lifting servo motor to enable the moving platen to perform lifting movement; and a control system for controlling the above components to act in proper time and controlling the lifting servo motor in the inner-circulating hydraulic moving platform system to operate synchronously.

9. The inner-circulating hydraulic platform of claim 8, wherein the lifting mechanism comprises a lifting ball screw and a lifting nut engaged with the lifting ball screw for moving, wherein the lifting ball screw is connected to the lifting servo motor while the lifting nut is connected to the moving platen.

10. The inner-circulating hydraulic platform of claim 8, further comprising: a pressure valve component, comprising a pressure servo motor and a pressure plunger driven by the pressure servo motor to move up and down within the axial hole disposed at the bottom of the cylinder; and wherein the control system comprises a controller, a first driver corresponding to the pressure servo motor, and a second driver corresponding to the lifting servo motor, wherein the controller is configured to: send actuating commands to the second driver corresponding to the lifting servo motor so that the hydraulic plunger is driven to move downward, which in turn brings the moving platen to move downward; when the moving platen stops moving downward, the controller receives an in-position signal from the second driver of the lifting servo motor and sends commands to the first driver of the pressure servo motor for synchronously running so as to synchronously drive the pressure plunger to enter into the chamber and seal the radial hole; send commands to the first driver of the pressure servo motor for synchronously reverse running so as to synchronously drive the pressure plunger to exit the chamber upward; and send commands to the second driver of the lifting servo motor for driving the hydraulic plunger to move reversely, and bringing the moving platen to move upward.

11. The inner-circulating hydraulic platform of claim 10, wherein the controller is a PLC or a motion controller.

12. The inner-circulating hydraulic platform of claim 8, further comprising: a connecting mechanism connecting and fixing the upper fixed platform and a lower fixed platform; wherein when the moving platen reciprocates to a lower stop point, the moving platen contacts the lower fixed platform with zero speed and tightly presses it; and the housing of the hydraulic cylinder is fixed to the upper fixed platform, wherein the cylinder is contained in an aperture formed in the upper fixed platform and also fixed to the upper fixed platform.

13. The inner-circulating hydraulic platform of claim 12, wherein the connecting mechanism comprises a right wallboard and a left wallboard which are connected between the upper fixed platform and lower fixed platform.

14. An inner-circulating hydraulic platform, comprising: a lower fixed platform, the lower fixed platform connected to: at least one inner-circulating moving platform hydraulic system, comprising: a hydraulic cylinder component, including a cylinder, a hydraulic plunger, and a housing, wherein an axial hole disposed at the bottom of the cylinder communicates with a chamber on the bottom of the hydraulic plunger, wherein at least one radial hole intersecting with the axial hole is also disposed near the bottom of the cylinder, wherein the hydraulic plunger reciprocates in the cylinder, wherein the housing contains the cylinder and forms a sealed inner-circulating oil chamber outside of the chamber and contained within the housing, wherein the inner-circulating oil chamber fluidly communicates with the axial hole via said radial hole and in turn fluidly communicates with the chamber on the bottom of the hydraulic plunger, wherein a compressed air inlet is disposed on the upper portion of the housing and an upper end of the hydraulic plunger is connected to a moving platen; and a pressure valve component, comprising a pressure servo motor and a pressure plunger driven by the pressure servo motor to move up and down within the axial hole disposed at the bottom of the cylinder; a moving platen lifting component connected to the moving platen and comprising a lifting servo motor and a lifting mechanism, wherein the lifting mechanism is driven by the lifting servo motor to enable the moving platen to perform lifting movement; and a control system for controlling the above components to act in proper time and controlling the pressure and lifting servo motors in the inner-circulating hydraulic moving platform system to operate synchronously.

15. The inner-circulating hydraulic platform of claim 14, wherein the lifting mechanism comprises a lifting ball screw and a lifting nut engaged with the lifting ball screw for moving, wherein the lifting ball screw is connected to the lifting servo motor while the lifting nut is connected to the moving platen.

16. The inner-circulating hydraulic platform of claim 14, wherein the control system comprises a controller, a first driver corresponding to the pressure servo motor of the at least one inner-circulating hydraulic moving platform system, and a second driver corresponding to the lifting servo motor, wherein the controller is configured to: send actuating commands to the second driver corresponding to the lifting servo motor so that the hydraulic plunger is driven to move upward, which in turn drives the moving platen to move upward; when the moving platen stops moving upward, the controller receives an in-position signal from the second driver of the lifting servo motor and sends commands to the first driver of the pressure servo motor for synchronously running to synchronously drive the pressure plunger to enter into the chamber and seal the radial hole; send commands to the first driver of the pressure servo motor for synchronously reverse running to synchronously drive the pressure plunger exiting the chamber downward; and send commands to the second driver of the lifting servo motor for driving the hydraulic plunger to move reversely, which in turn brings the moving platen to move downward.

17. The inner-circulating hydraulic platform of claim 14, wherein the controller is a PLC or a motion controller.

18. The inner-circulating hydraulic platform of claim 14, further comprising: a connecting mechanism connecting and fixing the lower fixed platform and an upper fixed platform; wherein when the moving platen reciprocates to a lower stop point, the moving platen contacts the upper fixed platform with zero speed and tightly presses it; wherein the housing of the hydraulic cylinder is fixed to the lower fixed platform, and wherein the pressure valve component passes through an aperture formed in the lower fixed platform and is fixed to the lower fixed platform.

19. The inner-circulating hydraulic platform of claim 18, wherein the connecting mechanism comprises a right wallboard and a left wallboard, both wallboards connected between the lower fixed platform and the upper fixed platform.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will become more obvious from the detailed description set forth below when taken in conjunction with the drawings. In the drawings:

(2) FIG. 1 illustrates a perspective view of an inner-circulating high speed hydraulic platform according to a first embodiment of the present invention, wherein a support for fixing the inner-circulating high speed hydraulic platform to a stamping machine, a control system, a moving platen and a lower fixed platform are omitted for clarity;

(3) FIG. 2 is a static section view of an inner-circulating high speed hydraulic system according to a first embodiment of the present invention;

(4) FIG. 3 is a section view of an inner-circulating high speed hydraulic system in a pressured state according to the first embodiment of the present invention;

(5) FIG. 4 is a section view of an inner-circulating high speed hydraulic system in a pressure-released state according to the first embodiment of the present invention;

(6) FIGS. 5-7 are section views of an inner-circulating high speed hydraulic platform comprising four inner-circulating high speed hydraulic systems in various states according to the present invention;

(7) FIG. 8 illustrates a perspective view of an inner-circulating high speed hydraulic platform according to a second embodiment of the present invention, wherein a support for fixing the inner-circulating high speed hydraulic platform to a stamping machine, a control system, a moving platen and an upper fixed platform are omitted for clarity; and

(8) FIGS. 9-11 are section views of an inner-circulating high speed hydraulic platform in various states according to the second embodiment of the present invention.

DETAILED DESCRIPTION

(9) FIG. 1 shows a perspective view of an inner-circulating high speed hydraulic platform according to a first embodiment of the present invention. The inner-circulating high speed hydraulic platform mainly comprises: an upper fixed platform 13, a moving platen lifting component, a plurality of inner-circulating high speed hydraulic systems (for example, 2, 3, and 5 etc. and specifically 4 in the present embodiment) mounted to the upper fixed platform 13, and a control system (not shown). The moving platen lifting component is used for pushing a moving platen 16 to move toward a lower fixed platform 17 and contact the lower fixed platform 17 with zero speed (See FIG. 2). The inner-circulating high speed hydraulic systems are used for supplying fluids to the hydraulic system when pushing the moving platen 16 toward the lower fixed platform 17 and applying pressure on the lower fixed platform 17 after the moving platen 16 contacts the lower fixed platform 17. The control system is used for sending corresponding commands to the respective components according to action requirements and receiving related feedback information so as to ensure reliable operation of the inner-circulating high speed hydraulic platform with high speed, high pressure and high precision.

(10) In this embodiment, the inner-circulating high speed hydraulic platform comprises four identical inner-circulating high speed hydraulic systems. However, it should be understood that the present invention is not limited to four identical inner-circulating high speed hydraulic systems, but may have any appropriate number of systems, such as 2, 3, etc. Those four identical inner-circulating high speed hydraulic systems have same structures and operational processes. Herein, only one of the systems is described in details with reference to FIGS. 2-4.

(11) FIG. 2 shows a stationary state of an inner-circulating high speed hydraulic system as well as a moving platen lifting component according to a first embodiment of the present invention. The inner-circulating high speed hydraulic system includes a hydraulic cylinder component and a pressure valve component.

(12) The hydraulic cylinder component includes: a high pressure cylinder 11, a hydraulic plunger 15, and a housing 6. An axial hole, disposed on the top of the high pressure cylinder 11, may communicate with a chamber on the top of the hydraulic plunger 15. At least one radial hole(s) 12 intersecting with the axial hole is also disposed near the top of the high pressure cylinder 11. The plunger 15 reciprocates in the high pressure cylinder 11 and the lower end of the plunger 15 may connect to an actuating element, which in a preferred embodiment is a moving platen 16. The housing 6 contains the high pressure cylinder and forms a sealed inner-circulating oil chamber outside. The inner-circulating oil chamber may communicate with the axial hole with the aforementioned at least one radial hole 12 and in turn communicate with the top of the hydraulic plunger 15. In addition, a compressed air inlet 7 is disposed in the upper portion of the housing 6 for introducing compressed air.

(13) A pressure valve component comprising a pressure servo motor 5 and a pressure plunger 10 is disposed on the top of the hydraulic cylinder component. The pressure plunger 10 may be driven by the pressure servo motor 5 to move up and down within an axial hole disposed on the top of the high pressure cylinder 11. In this embodiment, a driving mechanism may be disposed between the pressure servo motor 5 and the pressure plunger 10. The driving mechanism comprises a pressure ball screw 8 and a pressure nut 9 engaged with the pressure ball screw 8 for moving. The pressure ball screw 8 is connected to the pressure servo motor 5 and supported by a bearing to rotate. The pressure nut 9 is connected to a pressure plunger 10.

(14) It should be understood that the pressure plunger 10 may be directly driven by servo motor 5, if desired.

(15) The functions of the pressure valve component are as follows. The pressure servo motor 5 enables the pressure plunger 10 to appropriately turn off hydraulic oil in at least one radial hole 12 of the hydraulic cylinder component according to command(s) received from the control system, which in turn enables the pressure plunger 10 to move into the high pressure oil chamber 22 at the top of the hydraulic plunger 15. When the pressure plunger continues to move downward, the low pressure hydraulic oil 21 in the top of the hydraulic plunger 15 will be compressed, which will increase the pressure in the seal chamber (up to 400 kg/cm.sup.2) and generate a significant thrust on the hydraulic plunger 15. Provided that the moving distance of the pressure plunger 10 toward the hydraulic plunger 15 is controlled, the generated thrust of the hydraulic plunger 15 and its highly precise position (for example, with a positional repeatability of 0.01 mm) may be controlled.

(16) FIG. 2 also shows a moving platen lifting component. The moving platen lifting component is connected to said moving platen 16, comprising: a lifting servo motor 20 and a lifting mechanism. The lifting mechanism may be driven by the lifting servo motor 20, causing the moving platen 16 to perform lifting motion according to a preset lifting curve. In this embodiment, the lifting mechanism comprises a lifting ball screw 18 and a lifting nut 19 engaged with the lifting ball screw 18 for moving. The lifting ball screw 18 is connected to the lifting servo motor 20 while the lifting nut 19 is connected to the moving platen 16.

(17) The moving platen lifting component enables the moving platen 16 to approach the fixed platform with high speed and zero-speed contact with the fixed platform with high precision and press it tightly. Meanwhile, the hydraulic plunger 15 fixed on the moving platen 16 is pulled to have oil supplied or discharged from the high pressure hydraulic cylinder 11 thereon.

(18) Hereinafter, the action process of the hydraulic system according to a preferred embodiment of the present invention will be described with respect to FIGS. 2-4.

(19) In FIG. 2, the hydraulic system is in a stationary state. In this state, low pressure compressed air enters an inner-circulating oil chamber via a compressed air inlet 7, causing the hydraulic oil 21 to flow into the top of the hydraulic plunger 15 through radial holes 12 along direction A so that the hydraulic plunger 15 is enabled to generate a low pressure thrust downward. At this time, the moving platen lifting component is constrained by a static torque generated from the servo motor 20, which in turn constrains the moving platen 16 and the hydraulic plunger 15 to maintain in a stationary state as shown in FIG. 2. This state is referred as origin state for the hydraulic system in the present invention.

(20) With reference to FIG. 3, the hydraulic oil 21 propelled by the low pressure compressed air flows into the top of the hydraulic plunger 15 through the radial holes 12. At this time, the lifting servo motor 20 rotates according to the command sent from the control system, causing the lifting ball screw 18 to engage with the lifting ball nut 19, which in turn propels the moving platen 16 fixed to the hydraulic plunger 15 to move toward the lower fixed platform 17 according to a preset downward curve for approaching and pressing the lower fixed platform 17 without shocks. Thus, the action of oil supplying with low pressure is completed. Subsequently, the pressure servo motor 5 is initiated to drive the pressure ball screw 8 to rotate so that the pressure nut 9 propels the pressure plunger 10 to move downward in the figure. During the movement of the pressure plunger 10, it will firstly turn off the radial hole 12 at the top of the hydraulic plunger 15 so as to form a sealed high pressure cylinder on the top of the hydraulic plunger 15. When the pressure plunger 10 continues to move downward, the hydraulic oil in the sealed high pressure cylinder is compressed to generate a high pressure (for example, 400 kg/cm.sup.2) within the high pressure cylinder, which in turn enables the hydraulic plunger 15 to generate a huge thrust. Provided that the rotation angle of the pressure servo motor 5 is changed, the moving position of the pressure plunger 10 might be changed and accordingly the thrust and position of the hydraulic plunger might also be changed.

(21) With reference to FIG. 4, when the moving platen 16 is required to move upward back to the stationary state as shown in FIG. 2, the pressure servo motor 5 drives the pressure ball screw to rotate reversely. Then the pressure nut 9 will bring the pressure plunge 10 to move upward. When the pressure plunger 10 arrives at a position at which the radial hole 12 begins to be exposed, high pressure oil in said high pressure cylinder will discharge oil to the inter-circulating chamber along the direction B.

(22) At this time, the lifting servo motor 20 rotates reversely, bringing the moving platen 16 together with the plunger 15 to move upward so that the hydraulic oil 21 may be completely discharged via the radial holes 12. Thus, all actions within a stroke are completed. Then, the platform returns back to the state shown in FIG. 2, waiting for next active command.

(23) FIGS. 5-7 are section views of an inner-circulating high speed hydraulic platform comprising 4 inner-circulating high speed hydraulic systems (only two systems are shown in the figures while others are covered) in various states according to the present invention.

(24) In addition to the inner-circulating high speed hydraulic platform, a lower fixed platform 17, a right wallboard 14 and a left wallboard 14A are also illustrated in FIGS. 5-7, wherein a platform supporting system consisting of an upper fixed platform 13, the lower fixed platform 17, the right wallboard 14 and the left wallboard 14A is used for fixing the inner-circulating high speed hydraulic platform to a device it applied, such as a stamping machine. The right wallboard 14 and the left wallboard 14A are vertically connected between the upper fixed platform 13 and the lower fixed platform 17 so that the relative positions of the upper and lower fixed platform 13, 17 are fixed and a space for containing the housing of the high pressure oil chamber 22 and the moving platen 16 reciprocating therein is formed. Furthermore, housings 6 of the hydraulic cylinder components are connected to the upper fixed platform 13 through fixtures such as bolt, rivet or the like. The cylinder of the high pressure oil chamber 22 is contained in a via formed in the upper fixed platform 13 and also fixed to the upper fixed platform 13. Undoubtedly, it should be understood that the housings 6 of the hydraulic cylinder components or the cylinder of the high pressure oil chamber 22 may also be formed with the upper fixed platform 13 integrally. The inner-circulating high speed hydraulic platform and the supporting system connected as above form an integral inner-circulating high speed hydraulic platform assembly. In this way, the so-constructed inner-circulating high speed hydraulic platform assembly has a compact structure and decreases the overall height of the assembly, and is easy for transportation.

(25) Further, FIGS. 5-7 show a control system of the inner-circulating high speed hydraulic platform. With reference to FIG. 5, the control system comprises a controller 1, a driver 3 for the servo motor 20 corresponding to the moving platen lifting component, and drivers (only two drivers 2 and 4 are shown in the figure) for the servo motors 5 corresponding to the hydraulic cylinder components. According to the action requirements, the control system is used for sending corresponding commands to the servo motor 5 of the pressure valve components of the hydraulic cylinder components, the servo motor 20 of the moving platen lifting component, and other actuators, as well as receiving related feedback information therefrom, to ensure reliable operation of the inner-circulating high speed hydraulic platform with high speed, high pressure and high precision.

(26) Next, the operational process of the inner-circulating high speed hydraulic platform under the control of the control system will be descried with reference to FIGS. 5-7.

(27) FIG. 5 shows states of the respective components when the platform begins to move downward. When the moving platen 16 begins to press downward, a driving command for driving servo motor 20 to rotate is sent from the controller 1 to the driver 3 according to the preset action program. The rotation brings the lifting ball screw 18 to rotate and thus brings the engaged lifting nut 19 to follow an acceleration and deceleration curve preset by controller 1, causing the moving platen 16 to approach the lower fixed platform 17 with zero speed and press the lower fixed platform 17, i.e., arriving a state as shown in FIG. 6. With the downward movement of the moving platen 16, the compressed air is enabled to compress hydraulic oil 21 through compressed air inlets 7 of the inner-circulating high speed hydraulic system, causing the hydraulic oil 21 to rapidly enter the high pressure oil chamber 11 via the holes 12, thereby completing a downward stroke of the platform for oil supplying.

(28) With reference to FIG. 6, when the lifting servo motor 20 arrives zero speed, the driver 3 may send an in-position signal to the controller 1 which simultaneously sends commands to drivers 2 and 4 for synchronously rotating the pressure servo motors 5. At this time, the pressure servo motors 5 operate synchronously and drive each pressure ball screw 3, thereby bring each pressure nut 9 to move linearly and propel the pressure plungers 10, which may firstly seal the holes 12 and compress the hydraulic oil in each high pressure cylinder 11 at the same time, thereby generate high pressure. It should be understood that the approach for synchronizing pressure servo motors 5 may use any method well known in the art, such as parallel control, master-slave control, cross-coupling control, virtual line-shaft control, relative coupling control, and so on.

(29) With reference to FIG. 7, after all actions shown in FIG. 6 are completed, the controller 1 firstly may send rotation command to drivers 2 and 4. At this time, the pressure servo motors 5 also rotate according to the lifting curve preset by controller 1, bringing each pressure ball screw 8, respectively, to drive each pressure nut 9 and thus propel the pressure plungers 10 to make upward linear movement. When the plungers move and then stop at the position as shown in FIG. 7, the controller 1 may promptly send commands to the driver 3 for rotating the lifting servo motor 20. At this time, the lifting servo motors 20 drive the lifting servo ball screws 18, which in turn enable the lifting nuts 19 to bring the moving platen 16 and the hydraulic plunger 15 to move upward. At this time, the hydraulic oil 21 in the high pressure cylinder 11 is discharged back into the inner-circulating oil chamber through the holes 12. At this moment, all actions in the upward and downward strokes have been completed.

(30) Although the present invention is described with reference to a first embodiment of an inner-circulating high speed hydraulic platform comprising four inner-circulating high speed hydraulic systems, the number of the inner-circulating high speed hydraulic systems in the present invention is not limited to four, but may be any number more than one.

(31) It should be understood that the controller described herein may be implemented as a well known controller in the art, such as PLC, motion controller, and so on.

(32) Descriptions regarding upward/upper and downward/lower used herein are not intended to limit the direction of components in figures during usage. It will be understood by those skilled in the art that the above system may be used inversely by modification, as will be describe with respect to the second embodiment below.

(33) FIG. 8 shows a perspective view of an inner-circulating high speed hydraulic platform according to a second embodiment of the present invention. The inner-circulating high speed hydraulic platform mainly comprises: a lower fixed platform 13, a moving platen lifting component, a plurality of inner-circulating high speed hydraulic systems (for example, 2, 3, 5 etc. and specifically 4 in the present embodiment) mounted to the lower fixed platform 13, and a control system (not shown). The moving platen lifting component is used for pushing a moving platen 16 to move toward an upper fixed platform 17 and contact it with zero speed (See, FIG. 9). The inner-circulating high speed hydraulic systems are used for supplying fluid to the hydraulic system when pushing the moving platen 16 toward the upper fixed platform 17 and applying pressure on the upper fixed platform 17 after contacting the moving platen 16. The control system is used for sending corresponding commands to components according to action requirements and receiving related feedback information so as to ensure reliable operation of the inner-circulating high speed hydraulic platform with high speed, high pressure and high precision.

(34) FIGS. 9-11 are section views of an inner-circulating high speed hydraulic platform comprising 4 inner-circulating high speed hydraulic systems (only two systems are shown in the figures while others are covered) in various states according to the present invention.

(35) In this embodiment, the inner-circulating high speed hydraulic platform comprises four identical inner-circulating high speed hydraulic systems. However, it should be understood that the present invention is not limited to four identical inner-circulating high speed hydraulic systems but may take any appropriate number of systems, such as 2, 3, etc. The four inner-circulating high speed hydraulic systems may have similar structure and operational process to those of the first embodiment. Herein, only one of the systems is described in details with reference to FIG. 9.

(36) Taking the hydraulic cylinder component shown in the left side of the FIG. 9 as an example, it comprises a high pressure cylinder 11, a hydraulic plunger 15, and a housing 6. An axial hole, disposed at the bottom of the high pressure cylinder 11, may communicate with a chamber on the bottom of the hydraulic plunger 15. At least one radial hole(s) 12 intersecting with the axial hole is also disposed near the bottom of the high pressure cylinder 11. The plunger 15 reciprocates in the high pressure cylinder 11, the upper end of which may connect to an actuating element, which in the preferred embodiment is a moving platen 16. The housing 6 contains the high pressure cylinder 11 and form a sealed inner-circulating chamber outside. The inner-circulating chamber may communicate with the axial hole via the aforementioned at least one radial hole 12 and in turn communicate with the bottom of the hydraulic plunger 15. In addition, a compressed air inlet 7 is disposed at the top of the housing 6 for introducing compressed air.

(37) A pressure valve component comprising a pressure servo motor 5 and a pressure plunger 10 is disposed at the bottom of the hydraulic cylinder component. The pressure plunger 10 may be driven by the pressure servo motor 5 to move up and down within an axial hole disposed at the bottom of the high pressure cylinder 11. In this embodiment, a driving mechanism may be disposed between the pressure servo motor 5 and the pressure plunger 10. The driving mechanism comprises a pressure ball screw 8 and a pressure nut 9 which is engaged with the pressure ball screw 8 for moving. The pressure ball screw 8 is connected to the pressure servo motor 5 and supported by a bearing to rotate. The pressure nut 9 is connected to a pressure plunger 10.

(38) It should be understood that the pressure plunger 10 may be directly driven by servo motor 5, if desired.

(39) The functions of the pressure valve component are as follows. The pressure servo motor 5 enables the pressure plunger 10 to appropriately turn off hydraulic oil in at least one radial hole 12 of the hydraulic cylinder component according to command(s) received from the control system, which in turn enables the pressure plunger 10 to move into the high pressure chamber 22 at the bottom of the hydraulic plunger 15. When the pressure plunger 10 continues to move upward, the low pressure hydraulic oil 21 at the bottom of the hydraulic plunger 15 will be compressed, which will increase the pressure in the sealed chamber (up to 400 kg/cm.sup.2) and cause a significant thrust on the hydraulic plunger 15. Provided that the moving distance of the pressure plunger 10 toward the top of the hydraulic plunger 15 is controlled, the generated thrust of the hydraulic plunger 15 and its highly precise position (for example, with a positional repeatability of 0.01 mm) may be controlled.

(40) FIG. 9 also show a moving platen lifting component. The moving platen lifting component is connected to said moving platen 16, comprising: a lifting servo motor 20 and a lifting mechanism. The lifting mechanism may be driven by the lifting servo motor 20, causing the moving platen 16 to perform lifting movement according to a preset lifting curve. In this embodiment, the lifting mechanism comprises a lifting ball screw 18 and a lifting nut 19 engaged with the lifting ball screw 18 for moving. The lifting ball screw 18 is connected to the lifting servo motor 20 while the lifting nut 9 is connected to the moving platen 16.

(41) The moving platen lifting component enables the moving platen 16 to approach the fixed platen with high speed and zero-speed contact with the fixed platen with high precision and press it tightly. Meanwhile, the hydraulic plunger 15 fixed on the moving platen 16 is pulled to have the high pressure hydraulic cylinder 11 thereon oil supplied or discharged.

(42) Hereinafter, the action process of the hydraulic system according to a preferred embodiment of the present invention will be described with respect to FIGS. 9-11.

(43) In FIG. 9, the hydraulic system is in a static state. In this state, low pressure compressed air enters an inner-circulating oil chamber via a compressed air inlet 7, causing the hydraulic oil 21 to flow into the bottom of the hydraulic plunger 15 through the radial holes 12 along direction A so that the hydraulic plunger 15 is enabled to generate an upward low pressure thrust. At this time, the moving platen lifting component is constrained by a static torque generated from the servo motor 20, which in turn constrains the moving platen 16 and the hydraulic plunger 15 to maintain in a static state as shown in FIG. 9. This state is referred as state of origin for the hydraulic system in the present invention.

(44) With reference to FIG. 10, the hydraulic oil 21 propelled by the low pressure compressed air flows into the bottom of the hydraulic plunger 15 through the radial hole 12. At this time, the lifting servo motor 20 rotates according to the commands sent from the control system, causing the lifting ball screw 18 to engage with the lifting ball nut 19, which in turn propels the moving platen 16 fixed to the hydraulic plunger 15 to move toward the upper fixed platform 17 according to a preset downward curve for approaching and tightly pressing the upper fixed platform 17 without shock. Thus, the action of oil supplying with low pressure is completed. Subsequently, the pressure servo motor 5 is initiated to drive the pressure ball screw 8 to rotate so that the pressure nut 9 propels the pressure plunger 10 to move upward in the figure. During the movement of the pressure plunger 10, it will firstly turn off the radial hole 12 at the bottom of the hydraulic plunger 15 so as to form a sealed high pressure cylinder below the bottom of the hydraulic plunger 15. When the pressure plunger 10 continues to move upward, the hydraulic oil in the sealed high pressure cylinder is compressed to generate a high pressure (for example, 400 kg/cm.sup.2), which in turn enables the hydraulic plunger 15 to generate a huge thrust. Provided that the rotation angle of the pressure servo motor 5 is changed, the moving position of the pressure plunger 10 might be changed, and accordingly the thrust and position of the hydraulic plunger might also be changed.

(45) With reference to FIG. 11, when the moving platen 16 is required to move downward to return to the stationary state as shown in FIG. 9, the pressure servo motor 5 drives the pressure ball screw to rotate reversely. Then the pressure nut 9 will bring the pressure plunge 10 to move downward. When the pressure plunger 10 moves to a position at which the radial hole 12 begins to be exposed, high pressure oils in said high pressure cylinder will discharge oil to the inter-circulating chamber.

(46) At this time, the lifting servo motor 20 rotates reversely, bringing the moving platen 16 together with the plunger 15 to move downward so that the hydraulic oil 21 may be completely discharged via the radial hole 12. Thus, all actions within a stroke are completed. Then, the platform returns back to the state shown in FIG. 9 waiting for next action command.

(47) In addition to the inner-circulating high speed hydraulic platform, an upper fixed platform 17, a right wallboard 14 and a left wallboard 14A are also illustrated in FIGS. 9-11, wherein a platform supporting system consisting of an lower fixed platform 13, the upper fixed platform 17, the right wallboard 14 and the left wallboard 14A is used for fixing the inner-circulating high speed hydraulic platform to a device, such as a stamping machine, to which it applied. The right wallboard 14 and the left wallboard 14A are vertically connected between the lower fixed platform 13 and the upper fixed platform 17 so that the relative positions of the lower and upper fixed platform 13, 17 are fixed and a space for containing the housing of the high pressure oil chamber 22 and the moving platen 16 reciprocating therein is formed. Furthermore, housings 6 of the hydraulic cylinder component are connected to the lower fixed platform 13 through fixtures such as bolt, rivet or the like. The pressure valve component passes through a via formed in the lower fixed platform 13 and is also fixed to the lower fixed platform 13. Undoubtedly, it should be understood that the housings 6 of the hydraulic cylinder component or the cylinder of the high pressure oil chamber 22 may also be formed with the lower fixed platform 13 integrally. The inner-circulating high speed hydraulic platform and the supporting system connected as above form an integral inner-circulating high speed hydraulic platform assembly. In this way, the so-constructed inner-circulating high speed hydraulic platform assembly has a compact structure, decreases the overall height of the assembly, and thereby is easy for transportation.

(48) Further, FIGS. 9-11 also show a control system of the inner-circulating high speed hydraulic platform. With reference to FIG. 9, the control system of the present invention comprises a controller 1, a driver 3 for the servo motor 20 corresponding to the moving platen lifting component, and drivers (only two drivers 2 and 4 are shown in the figure) for the servo motor 5 corresponding to the hydraulic cylinder components. According to the action requirements, the control system is used for sending corresponding commands to the servo motor 5 of the pressure valve components of the hydraulic cylinder components, the servo motor 20 of the moving platen lifting component, and other actuators, as well as receiving related feedback information therefrom, to ensure reliable operation of the inner-circulating high speed hydraulic platform with high speed, high pressure and high precision.

(49) Next, the operational process of the inner-circulating high speed hydraulic platform under the control of the control system will be descried with reference to FIGS. 9-11.

(50) FIG. 9 shows states of components when the platform begins to move upward. When the moving platen 16 begins to press upward, a driving command for driving servo motor 20 to rotate is sent from the controller 1 to the driver 3 according to the preset action program. The rotation brings the lifting ball screw 18 to rotate and thus brings the engaged lifting ball nut 19 to follow an acceleration and deceleration curve preset by controller 1, causing the moving platen 16 to approach the upper fixed platform 17 with zero speed and tightly press the upper fixed platform 17, i.e., arriving a state as shown in FIG. 10. With the upward movement of the moving platen 16, the compressed air is enabled to compress hydraulic oil 21 through compressed air inlets 7 of the inner-circulating high speed hydraulic system, causing hydraulic oil 21 to rapidly enter a high pressure oil chamber 11 through the holes 12, thereby completing an upward stroke of the platform for oil supplying.

(51) With reference to FIG. 10, when the lifting servo motor 20 arrives zero speed, the driver 3 sends an in-position signal to the controller 1 which simultaneously sends commands to drivers 2 and 4 for synchronously rotating the pressure servo motors 5. At this time, the pressure servo motors 5 operate synchronously and drive each pressure ball screw 3, respectively to bring each pressure nut 9 to move linearly and propel the pressure plungers 10, which may firstly seal the holes 12 and compress the hydraulic oil in each high pressure cylinder 11 at the same time, thereby generating high pressure. It should be understood that the approach for synchronizing pressure servo motors 5 may use any method well known in the art, such as parallel control, master-slave control, cross-coupling control, virtual line-shaft control, relative coupling control, and so on.

(52) With reference to FIG. 11, after all actions shown in FIG. 10 are completed, the controller 1 firstly sends rotation commands to drivers 2 and 4. At this time, the pressure servo motors 5 also rotate according to the lifting curve preset by controller 1, bringing each pressure ball screw 8, respectively, to drive each pressure nut 9 and propel the pressure plungers 10 to make downward linear movement. When the pressure plungers 10 move and stop the position as shown in FIG. 11, the controller may send commands to the driver 3 for rotating the lifting servo motor 20. At this time, the lifting servo motors 20 drive the lifting servo ball screws 18 to enable the lifting nuts 19 to bring the moving platen 16 and the hydraulic plunger 15 to move downward. At this time, the hydraulic oil 21 in the high pressure cylinder 11 is discharged back into the inner-circulating oil chamber through the holes 12. At this moment, all actions in the downward strokes have been completed.

(53) Although the present invention is described with reference to a second embodiment of an inner-circulating high speed hydraulic platform comprising four inner-circulating high speed hydraulic systems, the number of the inner-circulating high speed hydraulic systems in the present invention is not limited to four, but may be any number more than one.

(54) It should be understood that the controller described herein may be implemented as a well known controller in the art, such as PLC, motion controller, and so on.

(55) Descriptions regarding upward/upper and downward/lower used herein are not intended to limit the direction of components in figures during usage.

(56) While the present invention is specifically described with respect to the preferred embodiments, it should be understood by those skilled that various changes and modifications could be made on the basis of the aforementioned disclosure without departing from the essential thereof. Thus, the scope of the invention is defined by the appended claims.