HYDRAULIC MACHINE UNIT AND METHOD FOR OPERATING SUCH A MACHINE UNIT

Abstract

A hydraulic machine unit that can be operated with various working forces, in which working medium is selectively delivered, via a pump-piston accumulator system, to a main cylinder and at least one driving cylinder, wherein at least for one working stroke a pump system of the pump-piston accumulator system is used to provide working medium to a piston accumulator of the pump-piston accumulator system, and then at least for the working stroke at least the main cylinder is charged with a working pressure from the piston accumulator, and wherein at least for a return stroke the at least one driving cylinder is charged with a return stroke pressure from the pump-piston accumulator system, can be of structurally simple configuration if, at reduced working forces, the working pressure is reduced with respect to the piston accumulator pressure prevailing in the piston accumulator.

Claims

1. Hydraulic machine unit (1) that can be operated at different working forces, comprising a main cylinder (22) in which a main piston (32) is disposed, at least one drive cylinder (24), the drive piston (34) of which is connected to act together with the main piston (32), and a pump/piston accumulator system (41), which has a pump system (42) and a piston accumulator (44) connected with the pump system (42), as a hydraulic drive (40) for the main cylinder (22) and the at least one drive cylinder (24), wherein the piston accumulator (44) is hydraulically connected with the main cylinder (22) by way of a work stroke control valve (50) comprising a proportional pressure-reducing valve (52).

2. Hydraulic machine unit (1) according to claim 1, comprising precisely two drive cylinders (24).

3. Hydraulic machine unit (1) according to claim 1, wherein the work stroke control valve (50) comprises a bypass valve (54) configured as a way valve, parallel to the proportional pressure-reducing valve (52).

4. Hydraulic machine unit (1) according to claim 1, wherein the proportional pressure-reducing valve (52) can be locked, particularly is combined with a locking way valve (53).

5. Method for operation of a hydraulic machine unit (1) that can be operated at different working forces, in which method a fluid working medium is selectively delivered to a main cylinder (22) and at least one drive cylinder (24), by way of a pump/piston accumulator system (41), wherein working medium is made available in a piston accumulator (44) of the pump/piston accumulator system (41), at least for one work stroke, by way of a pump system (42) of the pump/piston accumulator system (41), and then a working pressure from the piston accumulator (44) is applied at least to the main cylinder (22), at least for the work stroke, and wherein a return stroke pressure from the pump/piston accumulator system (41) is applied to the at least one drive cylinder (24), at least for the return stroke, wherein at reduced working forces, the working pressure is reduced as compared with the piston accumulator pressure prevailing in the piston accumulator (44).

6. Operating method according to claim 5, comprising precisely two drive cylinders (24).

7. Operating method according to claim 5, wherein at maximal working forces, the working medium is delivered to the main cylinder (22) or to the at least one drive cylinder (24) by way of a bypass (74).

8. Operating method according to claim 5, wherein for a reduction of the working pressure, a proportional pressure-reducing valve (52) is placed between the piston accumulator (44) and the main cylinder (22).

9. Hydraulic machine unit (1) according to claim 1, wherein feedback of the proportional pressure-reducing valve (52) takes place on the plunger side.

10. Hydraulic machine unit (1) according to claim 1, wherein the proportional pressure-reducing valve (52) is controlled in a closed regulation circuit.

11. Hydraulic machine unit (1) according to claim 1, wherein the proportional pressure-reducing valve (52) comprises a valve that goes into a floating position, preferably during its reducing function, until the reduced pressure agrees with a predetermined reference value.

12. Hydraulic machine unit (1) according to claim 1, wherein the proportional pressure-reducing valve (52) is pre-controlled.

13. Hydraulic machine unit (1) according to claim 12, wherein the proportional pressure-reducing valve (52) is pre-controlled by means of a control valve (56) and/or by way of a control line (78).

14. Hydraulic machine unit (1) according to claim 1, wherein the hydraulic machine unit (1) is a piston/cylinder system unit, particularly a forming machine, preferably an extruder, particularly a steel extruder, or a forging press, particularly a free-form forging press.

Description

[0033] Further advantages, goals, and properties of the present invention will be explained using the following description of exemplary embodiments, which are particularly also shown in the attached drawing. The drawing shows:

[0034] FIG. 1 a schematic representation of a hydraulic machine unit that can be operated at different working forces;

[0035] FIG. 2 the machine unit according to FIG. 1 at a maximal working force;

[0036] FIG. 3 the machine unit according to FIGS. 1 and 2 at a reduced working force; and

[0037] FIG. 4 the machine unit according to FIGS. 1 to 3 during the return stroke.

[0038] The machine unit 1 shown in the figures is an extruder and comprises a main cylinder 22 also referred to as a plunger cylinder, in which a main piston 32, also referred to as a plunger, is disposed to be displaceable axially in a work direction and in a return stroke direction, wherein drive pistons 34 are provided on the main piston 32 by way of a cross beam 36, which pistons can accordingly be displaced in drive cylinders 24. It is understood that in deviating embodiments, only one drive cylinder, which can also be disposed centrally, can also be provided, if necessary. Because of their lateral placement, the drive cylinders 24 and the drive pistons 34 are frequently also referred to as side cylinders and pistons.

[0039] In order to drive the main piston 32 and the drive pistons 34, a hydraulic drive 40 is provided, which comprises a pump/piston accumulator system 41. The pump/piston accumulator system 41 in turn comprises a pump system 42, on the one hand, in which multiple pumps 43 are switched in parallel by way of pump lines 77, wherein the number of pumps 43 depends on the required pressures and the amounts of working medium to be handled. Furthermore, the pump/piston accumulator system 41 comprises a piston accumulator 44, on the other hand, in which working medium under pressure can be made available in a sufficient volume amount.

[0040] Likewise, the hydraulic drive 40 comprises a tank 40, in which working medium that runs off is collected, and from which the pumps 43 can take up working medium.

[0041] The pump system 42 can be applied to the ring surfaces of the drive pistons 34 by means of a return stroke line 76, by way of a return stroke control valve 46, while it can be applied to a main piston line 71, by way of which the main cylinder 22 can be supplied with a working pressure, by way of a working pressure control valve 47. Both the return stroke control valve 46 and the working pressure control valve 47 are structured as way valves in this exemplary embodiment, and allow emptying of the main piston line 71 or of the return stroke line 76 into the tank 45, in each instance, when pressure is applied to the other one of these lines and this appears practical due to general hydraulic conditions.

[0042] The main piston line 71 is connected with a piston accumulator line 72 by way of a proportional valve 49 and a work stroke control valve 50; this line in turn is connected with the piston accumulator 44. In this manner, the pressure or the volume from the piston accumulator 44 can be delivered to the cylinders 22, 24 by way of the proportional valve 49 and the work stroke control valve 50, or, alternatively, the piston accumulator 44 can be loaded by the pump system 42, wherein the proportional valve 49 particularly serves to prevent overly rapid emptying of the piston accumulator 44, and wherein the work stroke control valve 50 is configured in special manner in the present exemplary embodiment, as will be explained below. When the main piston 32 works, a withdrawal volume 60 is withdrawn from the piston accumulator 44 accordingly.

[0043] The piston accumulator 44 furthermore comprises sensors 48 that record the respective fill level, in this exemplary embodiment a maximal fill level and a minimal fill level, and output it to the controller as an electrical signal.

[0044] Furthermore, the main piston line 71 is also connected with drive cylinder lines 75, which in turn are connected with the drive cylinders 24, so that working pressure can also be delivered to the drive cylinders 24.

[0045] It is understood thatdepending on the concrete embodiment of this exemplary embodimentthe drive cylinders lines 75 and also the return stroke lines 76 can have further valves, which uncouple them from the main piston line 71 or can couple them back to it, if this appears practical for reasons of control technology, weighed against the correspondingly greater construction effort in the hydraulic drive 40 and in its electrical or electronic setup.

[0046] In distinction from the state of the art, the work stroke control valve 50 of the present exemplary embodiment comprises a proportional pressure-reducing valve 52 that is combined with a locking way valve 53, a bypass valve 54, and a control valve 56, wherein the proportional pressure-reducing valve 52 is disposed in a reduction line 73 and connected, with feedback, with the piston accumulator line 72, by way of a control line 78 and the control valve 56, and the bypass valve 54 is disposed in a bypass 74, which is switched in parallel with the reduction line 73. Accordingly, the work stroke control valve 50 comprises the proportional pressure-reducing valve 52 and the bypass valve 54, which are switched in parallel with one another, and the control valve 56, which can allow or interrupt feedback of the proportional pressure-reducing valve 52 to the piston accumulator line 72 in the form of a logic way valve.

[0047] In the present exemplary embodiment, the bypass 74 is configured with the least possible pressure loss, in other words as straight-line as possiblesince the maximal working pressure is supposed to be made available by way of the bypass 74 and the bypass valve 54, which is also configured as a way valve, and for this reason, possible pressure losses between the piston accumulator 44 and the main piston line 71 or the drive cylinder lines 75 are supposed to be restricted to a minimum.

[0048] It is understood that a path to the return stroke lines 76, which can be turned on or off, can also be selected by the proportional pressure-reducing valve 52, for example. Likewise, it is conceivable that additional valves are provided, by means of which the pressure reduced by means of the proportional pressure-reducing valve 52 can be delivered to the drive cylinder lines 75 separately, in order to further increase the variability with regard to the working force in this manner, if this appears to be justified in view of the slightly increased construction effort. Likewise, it is conceivable to provide a further proportional pressure-reducing valve 52, if necessary also with a separate control valve 56, for these purposes.

[0049] It is furthermore understood that the return stroke control valve 46 and the working pressure control valve 47 can also be connected slightly differently or, alternatively, with other locations, without losing the advantages of pressure reduction between piston accumulator 44 and the cylinders 22, 24.

[0050] In the present exemplary embodiment, the proportional pressure-reducing valve 52 and the control valve 56 are switched in such a manner that they are each closed, by way of a way valve setting, in the basic position. The bypass valve 54 is also closed in the basic position, wherein corresponding control then prevents simultaneous opening of the valves 52, 54. When the bypass valve 54 is open, the maximal working pressure can be made available by way of the work stroke control valve 50. In an alternative embodiment, it is also conceivable to combine the pressure-reducing valve 52 and the bypass valve 54 in a single way valve. The proportional valve 49 is also closed in its basic position.

[0051] If a reduced working force is to be made available, as compared with the maximal working pressure and the working force resulting from it, the bypass valve 54 is closed and the proportional pressure-reducing valve 52 as well as the control valve 56 are opened, so that feedback of the proportional pressure-reducing valve 52 to the piston accumulator line 72 can take place by way of the control line 78, and a corresponding reduced pressure can be made available as a working pressure by way of the proportional pressure-reducing valve 52. Also, a plunger measurement 81 is performed on the plunger side, which makes it possible to control the proportional pressure-reducing valve 52.

[0052] The proportional pressure-reducing valve 52 goes into a floating position during the reduction function, until the reduced pressure agrees with the predetermined reference value, so that a corresponding default value of the working pressure can be maintained by way of a feedback or by way of a closed regulation circuit.

[0053] As is directly evident, the reduced pressure is measured on the side that runs off with respect to the working medium, in other words on the main piston side, and fed back to the proportional pressure-reducing valve 52.

[0054] It is understood that the hydraulics described above are merely an example and can also be configured differently in detail, as long as the piston accumulator 44, in particular, can act on the main piston 32 with reduced pressure or by way of a proportional pressure-reducing valve 52. In particular, supplemental lines and valves can also be provided, in order to be able to represent yet other operating situations. Likewise, it is understood that safety valves and switches as well as other additional measures can also be implemented. Likewise, it is understood that any working medium that is suitable for hydraulics can be used as a working medium, wherein oil is used in the present exemplary embodiment. Alternatively, water or an emulsion or an oil/water mixture, in particular, can also be used.

[0055] If the main piston 32 is to be moved in the work stroke direction 65 with maximal working force, then for this purpose, as shown in FIG. 2,. the working pressure control valve 47 is opened, and the return stroke control valve 46 is closed, so that the return stroke line 76 to the tank 45 is open. Likewise, the valve 52 and 56 are closed, and the bypass valve 54 is opened. The pump system 42 then acts directly on the cylinders 22, 24, while the speed of the main piston 32 can be mastered by way of the proportional valve 49, which ultimately acts as an adjustable shutter. It is understood that reduced working force levels can be achieved, if necessary, in that the return stroke control valve 46 is also opened, and thereby the pump system 42 can also act on the ring surface of the drive piston 34. Likewise, if necessary, valves can also be provided in the drive cylinder lines 75, which are closed, if necessary, in order to also lower the working force in step-like manner.

[0056] Actually, however, in the present exemplary embodiment, the working force is reduced by way of the proportional pressure-reducing valve 52, as shown in FIG. 3. For this purpose, the bypass valve 54 is closed and the control valve 56 is opened, so that a pressure from the piston accumulator 44, which also acts on the main piston 32 by way of the proportional valve 49, which pressure is reduced in desired manner, can be made available at the proportional pressure-reducing valve 52. With regard to valve control of the working pressure control valve 47, the return stroke control valve 46, and the proportional valve 49, it is then possible to proceed, ultimately, as in the case of maximal working force, in order to guarantee the desired movement of the main piston 32 at the given reduced working force.

[0057] If necessary, only hydraulic control of the drive cylinders 24 can also take place for a fast stroke in the work stroke direction 65, if the main piston ultimately has the required volume made available to it from the pump/piston accumulator system 41 or from the piston accumulator 44, if necessary at a reduced pressure and, if necessary, also with slight suction. For this purpose, further valves and lines can also be provided, if necessary.

[0058] For the return stroke in the return stroke direction 66, as shown in FIG. 4, the return stroke control valve 46 is opened and the working pressure control valve 47 as well as the proportional valve 49 are closed, so that the main piston line 71 and the drive cylinder lines 75 are relieved of stress into the tank 45, while the piston accumulator 44 does not lose any further pressure. The pump system 42 of the pump/piston accumulator system 41 then acts on the ring surfaces of the drive pistons 24 and pushes the main piston 32 in the return stroke direction. It is conceivable, if applicable, that during this time, the piston accumulator 44 is loaded up again by way of a line that can be turned on separately, something that otherwise can take place, of course, during possible dead times or auxiliary process times, by way of the piston accumulator line 72, by means of the proportional valve 49 and the bypass valve 54.

[0059] It is understood that instead of the machine unit described above, configured as an extruder, a corresponding hydraulic drive can also be used in other types of machine units, particularly in the case of other piston accumulator system units or forming machines, for example in forging presses.

[0060] Reference Symbol List:

[0061] 1 machine unit

[0062] 22 main cylinder

[0063] 24 drive cylinder

[0064] 32 main piston

[0065] 34 drive piston

[0066] 36 cross beam

[0067] 40 oil-hydraulic drive

[0068] 41 pump/piston accumulator system

[0069] 42 pump system

[0070] 43 pump

[0071] 44 piston accumulator

[0072] 45 tank

[0073] 46 return stroke control valve

[0074] 47 working pressure control valve

[0075] 48 sensor

[0076] 49 proportional valve

[0077] 50 work stroke control valve

[0078] 52 proportional pressure-reducing valve

[0079] 53 locking way valve

[0080] 54 bypass valve

[0081] 56 control valve

[0082] 60 withdrawal volume

[0083] 65 work stroke direction

[0084] 66 return stroke direction

[0085] 71 main piston line

[0086] 72 piston accumulator line

[0087] 73 reduction line

[0088] 74 bypass

[0089] 75 drive cylinder line

[0090] 76 return stroke line

[0091] 77 pump line

[0092] 78 control line

[0093] 81 pressure measurement