AT518646A4 - Vertical clamping unit and method of operating the same - Google Patents

Abstract

Vertical clamping unit for a molding machine with - a stationary platen (2), - a movable platen (3), - at least one hydraulic cylinder (4) for moving the movable platen (3) relative to the fixed platen (2), - a pressure accumulator (5 ), which is hydraulically connected to a lower chamber (6) of the at least one hydraulic cylinder (4), wherein - at least one electrical axis (7) for moving the movable platen (3) relative to the fixed platen (2) is provided and / or - An upper chamber (8) of the at least one hydraulic cylinder (4) with a means of a control or regulating device (9) controlled or controlled pump (10) for conveying a hydraulic fluid is hydraulically connected.

Description

The present invention relates to a vertical clamping unit of a molding machine according to the features of the preamble of claim 1 and to a method of operating such a clamping unit.

Under shaping machines are injection molding machines, transfer molding, pressing and the like to understand.

For example, from JP 0639842 A, it is known to connect the lower chambers of at least one hydraulic cylinder of a rapid stroke of the movable platen with a pressure accumulator.

From DE 102005017878 B3 it is known to provide a proportional or control valve to control or regulate the back pressure in lower chambers of those hydraulic cylinders which are not connected to the pressure accumulator. A disadvantage of the disclosed therein arrangement is the relatively high control effort, which is required by the dynamic pressure control by means of a differential pressure control.

The object of the invention is to provide an alternative to the construction methods of the prior art and to provide an alternative method of operation for such a closing unit.

This object is achieved in terms of the clamping unit with the features of claim 1. With regard to the method, this is achieved by the features of claim 19

On the one hand, this can be achieved by at least one electrical axis for moving the movable platen relative to the fixed platen. Such an embodiment makes it possible to combine the advantages of an electric rapid stroke with the efficiency and simplicity of a hydraulic pressure accumulator.

On the other hand, this can be achieved in that an upper chamber of the at least one hydraulic cylinder is hydraulically connected to a pump controlled or controlled by means of a regulating or control device for conveying a hydraulic fluid. By this measure, the complex control or control of a differential pressure is avoided, wherein the differential pressure between chambers of different hydraulic cylinders is present.

With regard to the method, this is achieved in that a pressure accumulator hydraulically connected to a lower chamber of at least one hydraulic cylinder is loaded so far that by the force of the hydraulic cylinder, a weight of a movable platen together with possibly carried by the platen components in an open position of the movable platen is at least substantially compensated relative to a fixed platen.

In the method according to the invention, the weight compensation is calibrated according to the open position of the movable platen. Under an open position of the movable platen is to be understood that it must be possible to remove the moldings from the tool. This measure has, on the one hand, the advantage that a larger stored pressure is available for the tearing of the tool after the molding has taken place. In addition, changes such as the mold height have less influence on the calibration of the pressure accumulator. By a slight increase in the pressure level in the pressure accumulator so a slightly higher efficiency and easier operation of the machine is achieved.

Protection is also desired for a molding machine with a clamping unit according to the invention.

Further advantageous embodiments will be apparent from the dependent claims.

It can be provided a device for loading the pressure accumulator, which is controlled by the control or regulating device accordingly. Of course, the device for loading the pressure accumulator can also be designed for discharging the pressure accumulator.

The pump or another pump may be part of the device for loading the pressure accumulator, wherein the pump or the further pump is hydraulically connected to the pressure accumulator.

This opens up the possibility of overloading the accumulator - controlled or regulated by the control or regulating device - by means of the pump or the further pump in order to obtain an opening movement of the movable platen. The remaining Ehhubantriebe can be relieved in this way.

The device for loading the pressure accumulator can also have at least one pressure cylinder for a gaseous hydraulic fluid.

It can also be provided that the device for loading the pressure accumulator has a switching valve, by means of which a flow of hydraulic fluid from the pressure accumulator to the device for loading the pressure accumulator is inhibited.

This avoids having to constantly activate the pump or the other pump to maintain the pressure level in the accumulator.

It may further be provided that two electrical axes - preferably exactly two electrical axes - and / or two hydraulic cylinders - preferably exactly two hydraulic cylinders - are provided.

The at least one electrical axis may preferably be designed as a spindle drive driven by an electrical machine, which represents a particularly simple design. In this case, the electric machine can be attached to the movable platen or a machine frame. The same applies to the spindle.

But it can also be provided at least one further hydraulic cylinder, which is not hydraulically connected to the pressure accumulator, wherein a lower chamber of the at least one further hydraulic cylinder is hydraulically connected to the or another pump. In this case, preferably two further hydraulic cylinders - preferably exactly two more hydraulic cylinders - may be provided.

A paired arrangement of electric axes or hydraulic cylinders may be advantageous because generic closing units are arranged in a plan view mostly rectangular. This makes it possible to arrange the two electric axes and / or the two hydraulic cylinders and / or the two further hydraulic cylinders diagonally opposite each other in the plan view, which makes it easier to keep the center of gravity of the movable mold clamping plate together with any components on the machine axis.

According to an optional embodiment, upper chambers of the at least one hydraulic cylinder and upper chambers of the at least one further hydraulic cylinder can be hydraulically connected to one another. This makes it possible to distribute the counterforce, which is necessary to close the closing unit against the action of the pressure accumulator, on as many different hydraulic cylinders as possible, whereby the pressure level in the upper chambers of these hydraulic cylinders can be kept lower. In addition, a higher clamping force can be achieved with more hydraulic cylinders, which can be important, for example, in the case of spring preloaded forming tools. The corresponding locking force must then be maintained until it locks.

It may be provided with a regulating or control device valve as an actuator for controlling or controlling a pressurization of the upper chamber of the at least one hydraulic cylinder by the pump, which is preferably designed as a directional control valve.

Alternatively, the upper chamber of the at least one hydraulic cylinder may be directly controlled by a controlled or controlled pump. without using a valve for regulation or control, be pressurized.

It can preferably be provided that the regulating or control device is designed to regulate or control the pressurization of the upper chamber of the at least one hydraulic cylinder so that a minimum pressure in the upper chamber of the at least one hydraulic cylinder is not undershot. If such a minimum pressure is exceeded, it may be that there is cavitation in the hydraulic lines or chambers of the hydraulic cylinder. This is avoided by this measure.

The hydraulic fluid may include a hydraulic oil and / or be gaseous.

The pressure accumulator can be designed as a bladder accumulator, i. a bladder of flexible material in which a compressible medium is enclosed. The accumulator may also include several units of such bladder memory. For a particularly simple and compact design of the pressure accumulator this can be integrated into the lower chamber of the at least one hydraulic cylinder. The accumulator can then be designed as a piston accumulator.

Further advantages and details emerge from the figures and the associated description of the figures. Showing:

1 shows a first embodiment of a clamping unit according to the invention with two electrical axes,

2 shows a further embodiment of a closing unit according to the invention with two electrical axes,

Fig. 3 shows another embodiment of a clamping unit according to the invention with two electrical axes and

Fig. 4 shows an embodiment of a closing unit according to the invention with two further hydraulic cylinders.

1 shows a first embodiment of a closing unit 1 with a fixed platen 2 and a movable platen 3. For loading the movable platen 3 with a closing force, the closing unit 1 has four bars 23 (for clarity, only the two front are shown) , Locking devices 22 and pressure pad 21. In a closed position of the clamping unit 1, that is, when mold half, which are mounted on the movable mold clamping plate 3 and the fixed mold mounting plate 2, touch each other, the movable mold mounting plate 3 by means of the locking devices 22 relative to the Holmen 23 locked. Then, by means of the pressure pad 21, the relatively high closing force can be applied. However, the pressure pads 21 are not suitable for opening the closing unit 1 so far that molded parts can be removed.

For this purpose, the closing unit 1 further Eilhubvorrichtungen. These are in this case two hydraulic cylinders 4 and two electric axes 7. The two hydraulic cylinders 4 each have a lower chamber 6 and an upper chamber 8, wherein the upper chambers 8 are not pressurized in this embodiment.

The lower chambers 6 of the hydraulic cylinders 4 are hydraulically connected to the pressure accumulator designed as two bladder accumulators.

It should be noted that the movable platen 3 and the fixed platen 2 are shown in dashed lines, for better clarity. As can be seen from the illustration in Figure 1, the electric axes 7 and the hydraulic cylinders 4 are arranged diagonally opposite each other in a plan view.

The electric axes 7 are in this case designed as spindles mounted on the fixed platen 2, which are connected to (not shown)

Mutually cooperate, the nuts are driven by the electric machines 18. The stator of the electric machines 18 are fixed to the movable platen 3. Alternatively, the spindles on the movable platen 3 and the stators of the electric machines 18 may be attached to the fixed platen 2.

In the unlocked state of the locking devices 22, the movable platen 23 can therefore be opened and closed by the action of the hydraulic cylinder 4 - supported by the pressure accumulator 5 - and the electric axes.

FIG. 2 shows a further embodiment, which is similar to the embodiment of FIG. The difference is that in the embodiment according to FIG. 2, a device 11 for loading the pressure accumulator 5 is provided. This device includes a - in this embodiment, electrically driven - pump 10 and a switching valve 17. While the loading of the accumulator 5 by the pump 10, the switching valve 17 acts as a check valve, so that the hydraulic fluid for charging the pressure accumulator 5 can not flow back to the pump 10 , As long as the loading of the pressure accumulator 5 is not necessary, the switching valve 17 is closed.

In a further embodiment, which is shown in Figure 3, the hydraulic cylinders 4 are connected so that it is possible to pressurize the upper chambers 8 of the hydraulic cylinder 4 with pressure. For this purpose, a designed as a directional valve valve 16 is available, which is either switched so that in the upper chambers 8 existing pressure is discharged into a tank, or so that by means of the pump pressurization of the upper chambers 8 is completed. As a result, the hydraulic cylinders 8 can assist the electric axes 7 when the closing unit 1 is closed.

FIG. 4 shows an embodiment which is similar to that of FIG. 3. In contrast to that of FIG. 3, the electric axes 7 are replaced by further hydraulic cylinders 12. In the present embodiment, these are

Hydraulic cylinder 12 executed single-acting, that is, the upper chambers 15 are not pressurized.

The lower chambers 13 of the other hydraulic cylinders 15 are connected via the valve 16 to the pump 10 accordingly. Via an additional position of the valve 16, the lower chambers 13 are additionally pressurized.

In the embodiment according to FIG. 4, the upper chambers 8 of the hydraulic cylinders 4 and the upper chambers 15 of the further hydraulic cylinders 12 can be hydraulically connected to one another.

Optionally, in all embodiments in the hydraulic line, which supplies the upper chambers 8 of the hydraulic cylinders 4, a pilot-operated check valve 24 may be provided. The control line 25 is connected to that hydraulic line which supplies the lower chambers 6 of the hydraulic cylinder 4. If a pressure difference between the hydraulic line, which supplies the upper chambers 8 of the hydraulic cylinders 4, and that which supplies the lower chambers 6 of the hydraulic cylinders 4, falls below a certain limit, the blockage by the pilot-operated check valve 24 is released and the pressure in the upper chambers 8 of the hydraulic cylinder 4 can be reduced without resistance by the pilot operated check valve 24.

By a corresponding unlockable check valve 24, a mold can be kept passive closed, which may be advantageous for example in spring-loaded molds.

A pressure sensor 26 on the lower chamber 13 of the other hydraulic cylinders 12 is sufficient to bring the pressure accumulator 5 to the respective optimum biasing pressure depending on the weight of the mold and the opening stroke.

The weight of the movable platen 3 is in the open position, depending on the charge of the pressure accumulator 5 more or less by the piston force of

Hydraulic cylinder 4 and / or the other hydraulic cylinder 12 is held. If the pressure in the cylinders in the open state of the engine is at a minimum or even zero, this means that virtually all the weight is held by the cylinders and thus by the storage preload.

Thus, at engine start or after a tool change on the device 11 for loading and unloading the pressure accumulator 5 and a corresponding pump control the pressure accumulator 5 must be charged or discharged until the pressure transducer 26 indicates a minimum pressure (for example: 20 bar).

A certain minimum pressure is necessary to ensure that: - the other hydraulic cylinders 12 are securely filled with oil and may not even kavitieren by overcharging the pressure accumulator 5 piston side and - the pressure changes resulting inevitably in the pressure accumulator 5 due to the opening and closing process can be.

Since both the variable volume of the hydraulic cylinders 4 and the other hydraulic cylinders 12 via the stroke, as well as the number of accumulator units, the volume and the charge of the pressure accumulator 5 are known, also the maximum possible change in the pressure in the lower chambers 6 and 13th the hydraulic cylinder 4 and the other hydraulic cylinder 12 known about the stroke. Thus, the optimum minimum pressure can also be calculated as a function of the opening stroke and the optimum charge of the pressure accumulator 5 is completely independent of the current opening stroke possible.

Calculation example: - the calculation of the pressure change in the pressure accumulator 5 by moving the entire stroke of the hydraulic cylinders 4 and 12 gives eg: 20 bar - the maximum travel is 1000 mm - the desired minimum pressure in the lower chambers 6 and 13 of the hydraulic cylinders 4 and 12 is 10 bar - the minimum pressure in the cylinders occurs logically in the fully closed (hydraulic cylinders 4 and 12 fully retracted) state, since here the pressure accumulator 5 are the highest loaded and therefore more force is taken over by the hydraulic cylinders 4 and 12

With these assumptions, the minimum optimum pressure of 10 bar in the completely closed state would act in the lower chambers 6 and 13 of the hydraulic cylinders 4 and 12, in the fully open state 30 bar (assuming that all 4 hydraulic cylinders 4 and 12 have the same piston diameter if, for example, the hydraulic cylinders 4 and the further hydraulic cylinders 12 had different diameters, these area ratios would have to be taken into account accordingly). From this, the ideal charge pressure can be calculated for any stroke. Similar calculation methods can also be used in the other embodiments with electric axes 19. Instead of the pressure transducer 26, torque measurements or strain gauges can be used, by means of which the respective prevailing force can be measured.

In all embodiments, oil is used as the hydraulic medium. The accumulator 5 is designed as a plurality of bladder memory.

However, the invention is not limited to the embodiments shown here. For example, the upper chambers 15 of the further hydraulic cylinders 12 and the upper chambers 8 of the hydraulic cylinders 4 could be hydraulically connected to each other (whereby the other hydraulic cylinders 12 would be double-acting). The pressure accumulator 5 could also be integrated into the lower chambers 6 of the hydraulic cylinders 4.

Claims (19)

claims 1. vertical clamping unit for a molding machine with - a fixed platen (2), - a movable platen (3), - at least one hydraulic cylinder (4) for moving the movable platen (3) relative to the fixed platen (2), - a pressure accumulator (5), which is hydraulically connected to a lower chamber (6) of the at least one hydraulic cylinder (4), characterized in that - at least one electrical axis (7) for moving the movable platen (3) relative to the fixed platen (2) is provided and / or - an upper chamber (8) of the at least one hydraulic cylinder (4) with a means of a control or control device (9) controlled or controlled pump (10) for conveying a hydraulic fluid is hydraulically connected. 2. Closing unit according to claim 1, characterized in that a device (11) for loading the pressure accumulator (5) is provided and that the control or regulating device (9) is adapted to load the pressure accumulator (5) to the extent that a Weight of the movable platen (3) together with possibly supported by the platen components - preferably in an open position of the movable platen (3) relative to the fixed platen (2) -at least substantially compensated. 3. Closing unit according to claim 1 or 2, characterized in that two electric axes (7) - preferably exactly two electric axes (7) and / or two hydraulic cylinders (4) - preferably exactly two hydraulic cylinders (4) - are provided. 4. Closing unit according to one of claims 1 to 3, characterized in that at least one further hydraulic cylinder (12) is provided, which is not hydraulically connected to the pressure accumulator (5), wherein a lower chamber (13) of the at least one further hydraulic cylinder ( 12) is hydraulically connected to the or a further pump (10). 5. Closing unit according to claim 4, characterized in that two further hydraulic cylinders (12) - preferably exactly two further hydraulic cylinders (12) - are provided. 6. Closing unit according to claim 3 or 5, characterized in that the two electrical axes (7) and / or the two hydraulic cylinders (4) and / or the two further hydraulic cylinders (12) are each arranged diagonally opposite each other in a plan view. 7. Closing unit according to one of claims 4 to 6, characterized in that upper chambers (8) of the at least one hydraulic cylinder (4) and upper chambers (15) of the at least one further hydraulic cylinder (12) are hydraulically connected to each other. 8. Closing unit according to one of claims 1 to 7, characterized in that with the control or control device (9) connected to the valve (16) as an actuator for regulating or controlling a pressurization of the upper chamber (8) of the at least one hydraulic cylinder ( 4) is provided by the pump (10). 9. Closing unit according to claim 8, characterized in that the valve (16) is a directional control valve. 10.Schließeinheit according to claim 8 or 9, characterized in that the regulating or control device (9) is adapted to control the pressurization of the upper chamber (8) of the at least one hydraulic cylinder (4) so that a minimum pressure in the upper chamber (8) of the at least one hydraulic cylinder (4) is not exceeded. 11 .Schließeinheit according to one of claims 1 to 10, characterized in that the hydraulic fluid includes a hydraulic oil and / or is gaseous. 12. Closing unit according to one of claims 1 to 11, characterized in that the pressure accumulator (5) in the lower chamber (6) of the at least one hydraulic cylinder (4) is integrated. 13.Schließeinheit according to claim 2, characterized in that the pump or another pump (10) is part of the device (11) for loading the pressure accumulator (5), wherein the pump (10) or the further pump with the pressure accumulator (5 ) is hydraulically connected. 14.Schließeinheit according to claim 13, characterized in that the regulating or control device (9) is adapted to overload the pressure accumulator (5) by means of the pump (10) or the further pump to effect an opening movement of the movable platen (3) , 15. Closing unit according to one of claims 1 to 14, characterized in that the device for loading the pressure accumulator has at least one pressure bottle for a gaseous hydraulic fluid. 16. Closing unit according to one of claims 1 to 15, characterized in that the device (11) for loading the pressure accumulator (5) has a switching valve (17), by means of which a flow of hydraulic fluid from the pressure accumulator (5) to the device (11). for loading the pressure accumulator (5) can be inhibited. 17. Closing unit according to one of claims 1 to 16, characterized in that the at least one electrical axis (7) as one of an electric machine (18) driven spindle drive (19) is executed. 18. Forming machine with a closing unit according to one of claims 1 to 17. 19. A method for operating a vertical clamping unit, in particular according to one of claims 1 to 17, characterized in that with a lower chamber (6) at least one hydraulic cylinder (4) hydraulically connected pressure accumulator (5) is loaded so far that by the force effect a weight of a movable platen (3) together with any components carried by the platen in an open position of the movable platen (3) relative to a fixed Platen (2) is at least substantially compensated for by the hydraulic cylinder (4).