HYDRAULIC DEVICE FOR FORMING A MACHINE

Abstract

A hydraulic device for a molding machine includes a first pump for a hydraulic fluid, a second pump for the hydraulic fluid, and a drive device for the first pump and the second pump. A first main conduit leads away from the first pump, and a second main conduit leads away from the second pump. A first consumer is connected with the first main conduit via a first opening and a first sub-conduit, and the first consumer is connected with the second main conduit via a second opening and a second sub-conduit. A second consumer is also connected with one of the main conduits via a third opening and a third sub-conduit. The second consumer is connected with the first main conduit via the third opening and the third sub-conduit, and is connected with the second main conduit via a fourth opening and a fourth sub-conduit.

Claims

1. A hydraulic device for a molding machine, in particular an injection molding machine, comprising a first pump for a hydraulic fluid, at least a second pump for the hydraulic fluid, at least one drive device for the first pump and the second pump, a first main conduit which leads away from the first pump, a second main conduit which leads away from the second pump, a first consumer which is connected with the first main conduit via a first opening and a first sub-conduit and which is connected with the second main conduit via a second opening and a second sub-conduit, and at least one second consumer which is also connected with one of the main conduits via a third opening and a third sub-conduit, wherein the second consumer on the one hand is connected with the first main conduit via the third opening and the third sub-conduit and on the other hand is connected with the second main conduit via a fourth opening and a fourth sub-conduit.

2. The hydraulic device according to claim 1, wherein the consumers are formed as piston-cylinder units or as hydro motors.

3. The hydraulic device according to claim 2, wherein the first and third opening each lead to a piston-sided cavity in the cylinder of the respective piston-cylinder unit and the second and fourth opening each lead to a rod-sided cavity in the cylinder of the respective piston-cylinder unit.

4. The hydraulic device according to claim 1, wherein valves, preferably 2/2-way valves, are arranged in each sub-conduit.

5. The hydraulic device according to claim 1, wherein the at least one drive device, which is preferably formed as an electro or hydro motor, drives both pumps.

6. The hydraulic device according to claim 5, wherein both pumps are connected with the one drive device via a common shaft.

7. The hydraulic device according to claim 1, wherein at least two drive devices are provided, wherein each drive device each drives one of the pumps.

8. The hydraulic device according to claim 1, wherein an open or closed loop control unit for controlling or regulating the pumps is provided.

9. The hydraulic device according to claim 8, wherein also the valves can be controlled via the open or closed loop control unit.

10. The hydraulic device according to claim 8, wherein consumer-specific data, for example feeding volumes and/or areal ratios of the consumers, are stored in the open or closed loop control unit.

11. The hydraulic device according to claim 10, wherein the pumps can be controlled by the open or closed loop control unit in dependence of the consumer-specific data.

12. The hydraulic device according to one of the claim 8, wherein the pumps can be controlled by the open or closed loop control unit in dependence of motion profiles of the consumers, preferably stored in a memory.

13. The hydraulic device according to claim 1, wherein the consumers can be sequentially pressurized by the hydraulic fluid via the two pumps.

14. A molding machine, in particular an injection molding machine, comprising a hydraulic device according to claim 1.

Description

[0023] Further details and advantages of the present invention are described more fully hereinafter by means of the specific description with reference to the embodiments illustrated in the drawings, in which:

[0024] FIG. 1 schematically shows a hydraulic device with several consumers and an open or closed loop control unit,

[0025] FIG. 2 shows the hydraulic device according to FIG. 1 when extending the first consumer,

[0026] FIG. 3 shows the hydraulic device according to FIG. 1 when retracting the first consumer,

[0027] FIG. 4 schematically shows a hydraulic device with again several consumers in an open circulation,

[0028] FIG. 5 shows the hydraulic device according to FIG. 4 when extending the second consumer and

[0029] FIG. 6 shows the hydraulic device according to FIG. 4 when retracting the second consumer.

[0030] FIG. 1 shows a hydraulic device 1 which in total comprises four consumers V1-V4. There, the first three consumers V1-V3 are each formed as piston-cylinder units 2, whereas the fourth consumer V4 is formed as hydro motor 3. The piston-cylinder units 2 each comprise a cylinder 8 and a piston 10 together with rod 9 guided in the cylinder 8. The displayed piston-cylinder units 2 are each formed as differential cylinders with different areal ratios (1:2, 1:4 and 0.5:1).

[0031] Further displayed in FIG. 1 are a first pump P1 and a second pump P2. Both pumps P1 and P2 are driven in this case by a drive device M1 via a common shaft 7. Only the first pump P1 is connected to the tank 12 for hydraulic fluid via an according tank conduit 13. The first pump P1 can suck and refill hydraulic fluid from this tank 12 via the tank conduit 13. The first main conduit H1 leads away from the first pump P1. Subsequently the first main conduit H1 is connected with the sub-conduits N1, N3, N5 and N7, each of which lead to one of the consumers V1-V4. Valves 6, in this case 2/2-way valves, are arranged in these sub-conduits N1, N3, N5 and N7. The sub-conduits N1, N3, N5 and N7 each enter via an opening O1, O3, O5 and O7 in one of the consumers V1-V4. Concretely, each of the openings O1, O3 and O5 lead in a piston-sided cavity 4 in the cylinder 8 of the respective piston-cylinder units 2. In contrast, the sub-conduits N2, N4 and N6 lead to the rod-sided cavities 5 of the respective piston-cylinder unit 2 via the opening O2, O4 and O6. In an analogous manner the sub-conduit 8 leads to the opening O8 of the hydro motor 3 (consumer V4). All of these sub-conduits N2, N4, N6 and N8 are each connected to the second main conduit H2 which finally leads to the second pump P2.

[0032] In this schematic hydraulic device 1 according to FIG. 1 also the open or closed loop control unit 11 is displayed. In this open or closed loop control unit 11 consumer-specific data like feeding volumes or areal ratios are stored. At least the two pumps P1 and P2 are controlled or regulated by this open or closed loop control unit 11. By the dashed line it is indicated that via this open or closed loop control unit 11 also, preferably all, valves 6 can be controlled or regulated.

[0033] For the function of the hydraulic device 1 it can be exemplary referred to the FIG. 2. For extending the rod 9 of the first consumer V1 the first pump P1, thus, draws hydraulic fluid from the tank 12 and feeds the hydraulic fluid into the first main conduit 1. As the valve 6 in the first sub-conduit N1 is switched correspondingly, the hydraulic fluid reaches the piston-sided cavity 4 of the first consumer V1 via the first opening O1, whereby the piston 10 is moved relative to the cylinder 8 (in this case to the left). By this movement also the hydraulic fluid located in the rod-sided cavity 5 is pressed into the second sub-conduit N2 via the second opening O2 in the cylinder 8. Subsequently, the hydraulic fluid reaches the second pump P2 via the second main conduit H2. In this second pump P2 an energy recovery is possible. As in this case the hydraulic device 1 is formed as a closed circulation, after the second pump P2 the hydraulic fluid again reaches the first main conduit H1 via the circulation conduit 14.

[0034] In FIG. 3 it is illustrated how the consumer is moved in the other direction. In this case the second pump P2 feeds the hydraulic fluid from the closed circulation via the second main conduit H2 to the second sub-conduit N2. From there the hydraulic fluid reaches the rod-sided cavity 5 via the second opening O2, whereby the piston 10 together with the rod 9 is moved relative to the cylinder 8 (in this case to the right). Thereby the hydraulic fluid is subsequently pressed from the piston-sided cavity 4 via the first opening O1 into the first sub-conduit N1. From there the hydraulic fluid again reaches the circulation conduit 14 via the first main conduit H1. Especially when the consumer is formed as a differential cylinder, the first pump P1 takes on the sucking off of the excessive hydraulic fluid into the tank 12. In the illustrated example the maximal stroke volume of the two pumps P1 and P2 have a ratio of 1:1. In order to be able exploit the pumps optimally, these ratios can be adapted to the present system of consumers and, thus, can vary for different systems.

[0035] In FIG. 4 a slightly modified embodiment of the hydraulic device 1 is illustrated schematically. In this case the hydraulic device 1 is formed as an open circulation, wherein both the two pumps P1 and P2 and the hydro motor 3 are each connected to a separate tank 12. Should the two pumps P1 and P2 not be driven by a drive device M1 via a common shaft 7, also a separate drive device M2 (schematically indicated) can be provided. A difference in this FIG. 4 can also be seen in that the hydro motor 3 is connected to the second main conduit H2 only via the sub-conduit N8. An open or closed loop control unit 11 can of course be used in FIG. 4 in the same manner as in FIG. 1. Apart from that, the hydraulic device 1 according to FIG. 4 is identical to the hydraulic device 1 according to FIG. 1.

[0036] For the functionality of this hydraulic device 1 it can be referred to the FIGS. 5 and 6, wherein the sequence of the movement of the consumer V2 is effected analogous to the movement of the consumer V1 according to FIGS. 2 and 3. In particular, according to FIG. 5 the hydraulic fluid (hydraulic oil) is led from the first pump P1 via the first main conduit H1 anddue to the accordingly switched valve 6via the third sub-conduit N3 and the third opening O3 into the piston-sided cavity 4 of the second consumer V2, whereby the piston 10 together with the rod 9 is moved, preferably extended, (in this case) to the left. Thereby, hydraulic fluid is also pressed from the rod-sided cavity 5 via the fourth opening O4 into the fourth sub-conduit N4, from where the hydraulic fluid is further fed via the second main conduit H2 and the second pump P2 into the tank 12. As the piston-cylinder unit 2 of the second consumer V2 is formed as a differential cylinder with a ratio of 1:4, exemplary 100% of hydraulic fluid is fed by the first pump P1, whereas simultaneously 25% of hydraulic fluid is re-fed from the second pump P2 (provided that the two pumps P1 and P2 have the same stroke volume).

[0037] Contrary, only 25% of the feeding volume of the second pump P2 is required for the movement of the piston 10 of the second consumer V2 to the right in order to re-fed 100% of hydraulic fluid via the first pump P1, as it is the case according to FIG. 6. With this hydraulic device 1, thus, consumers with different areal ratios can be driven, preferably sequentially, in an easy manner. Consumers can also be driven in a closed or in an open circulation.

[0038] Generally it has yet to be noted that in a particularly preferred embodiment a third consumer V3 is provided which is connected to the first main conduit H1 via a fifth opening O5 and a fifth sub-conduit N5 and which is connected to the second main conduit H2 via a sixth opening O6 and a sixth sub-conduit N6. In addition, yet also a fourth consumer V4 can be provided which is connected to the first main conduit H1 via a seventh opening O7 and a seventh sub-conduit N7 and which is connected to the second main conduit H2 via an eighth opening O8 and an eighth sub-conduit N8. Preferably also these consumers V3 and V4 are driven sequentially by the pumps P1 and P2.

[0039] With other words the present invention can also be expressed as follows:

[0040] The present invention can particularly be used for multiple-axis systems. A central pumping station (servo motor+regulation pump) supplies several hydraulic axes (consumers V1-V4) via long conduits and corresponding switching elements (valves 6). Two regulation pumps (pumps P1 and P2), driven by an electro motor (asynchronous or synchronous motor), are used in order to drive a hydraulic actuator. The positioning of this actuator (consumer) is effected by a corresponding regulation. By the use of a second pump P2 there is the possibility of energy recovery. In order to be able to operate several hydraulic axes with one drive system, switching elements are necessary to direct the supply of the actuators correspondingly. In this case the axes do not have to be compact axes. In particular in the case of a use in an injection molding machine there is a central pumping station from which the consumers are supplied with long conduits. The control technology can be effected by a central open or closed loop control unit 11, whereby especially the switching between different consumers V1-V4 is carried out.

[0041] In particular the system can be formed in such a way that either a motor (drive device M1) with two regulation pumps (pumps P1 and P2) or two motors (drive devices M1 and M2) with constant pumps (pumps P1 and P2) are driving at least two consumers from the group of consumers V1-V4. The consumers V1-V4 can have different volume requirements and can be driven by volume and pressure control. Exemplary volume ratios of the cylinder chambers are illustrated in the drawings. The direction reversal is not implemented by way valves but is effected only by the control of the pumps P1 and P2. The different consumers from the group of consumers V1-V4 are driven preferably only sequentially. This is preferably effected by simple on-off valves, whereby the individual consumers V1-V4 are connected to or separated from the supplying system. Optionally, also seat valves can be used for this purpose in order to lock the position. Preferably the open or closed loop control unit possesses at each point of time the information which consumer from the group of consumers V1-V4 is driven. The movement is regulated or followed via ramps (force or way ramps).

[0042] In the case of the first variant according to the FIGS. 1 to 3 the hydraulic device 1 works in a semi-open circulation, wherein only one pump (first pump P1) is directly connected to the tank 12. This pump P1 compensates the different required amounts between the cylinder chambers 4 and 5. Thus, the first pump P1 sucks hydraulic fluid volume from the system if the piston 10 of the consumer is retracted and feeds hydraulic fluid volume into the system if the piston 10 is extended. In the case of this system the hydro motor 3 can be driven both in an open and in a closed circulation.

[0043] In the case of variant 2 (FIGS. 4 to 6) the hydraulic device 1 comprises two pumps P1 and P2 each of which is connected to the tank 12. Preferably the pumps P1 and P2 are used with different stroke volumes in order to enable an optimal adaptation to the different volume requirements of the respective cylinder chambers 4 and 5. In the case of this system the hydro motor 3 is driven in an open circulation.

[0044] With the present invention in contrast to the state of the art it is, thus, not only possible to drive one consumer but to drive several consumers. This is controlled or regulated in that one pump is switched to the intake side and the other pump is switched to the discharge side of the consumer. For the control direction of the further consumers no 4/3-way valves are responsible but via the pumps the desired movement direction follows depending on which pump is feeding and which pump is sucking. The separation of the consumers from the pressure is not effected by 4/3-way valves but by 2/2-way valves.