DE19809666C1 - Hydraulic mold closure unit for pressure injection molding machine - Google Patents

Abstract

A double-acting displacement piston (7) is connected by its piston rod to one of: the platten (1) and the closure cylinder casing (4). A displacement cylinder casing is connected to the other of : platten (1) and a closure cylinder casing. A displacement cylinder has chambers (9, 10) on the piston and piston rod side for the displacement piston (7). Both chambers (9, 10) of the displacement cylinder can be connected to the tank (T) and/or the pump (P) when required. Preferred features: Chambers (5, 6) of the closure cylinder are interconnected by a line and valve (27, 28, 29). The latter is a pressure converter; on shutting, it produces closure pressure. The valve (28) includes connected high and low pressure pistons. When closure pressure is produced, the high pressure piston enters the high pressure cylinder; this forms a section of line connecting chambers of the closure cylinder. The chamber on the piston rod side of the closure cylinder develops the closure pressure, and the chamber (5) is connected to a pressure maintaining unit. This has a non-return valve opening towards the tank. An alternative arrangement and use of several closure pistons are detailed. Two closure pistons, a compensation piston and an auxiliary piston form a 4-point pattern, the closure pistons being on a diagonal. The compensation closure piston forms the lowest point of the pattern. An integral piston cylinder construction and a variant are described.

Description

The invention relates to a hydraulic mold closing device direction for an injection molding machine, in particular for ver work of plastic, with

• - a movable mold plate,
• - At least one locking piston that over its Locking piston rod is connected to the mold plate,
• - A lock cylinder housing that has a lock cylinder the one with space on the piston side and on the piston rod side for forms the locking piston,
• - a hydraulic tank and
• - a hydraulic pump.

Such a device is for example from DE 31 07 004 C2 known.

The performance of injection molding machines depends not least depending on how quickly the mold opens and can be closed and how quickly the closing builds up pressure. Decisive for both points of view te is the delivery rate of the pump. It is therefore endeavored the individual functions with the lowest possible för to meet the amount of hydraulic fluid.

The invention is based on the object at the outset mentioned mold closing device in this direction develop.

To solve this problem, the above is Mold closing device according to claim 1 characterized by

• - At least one double-acting piston, the via its piston rod with one of the components "Form plate" and "lock cylinder housing" is connected, and
• a driving cylinder housing which is connected to the other of the components "molded plate" and "locking cylinder housing" and forms a driving cylinder with piston-side and piston rod-side space for the driving piston,
  the two spaces of the cylinder can be connected to the tank and / or the pump.

DE 41 17 852 C2 is a double-acting with the movable mold plate connected piston knows that can be controlled independently of the locking piston, however, the two functions are "travel motion" and "Clamping force build-up" interlocked with each other, because the Lock piston as pressure intensifier in the driving piston engages and via this the closing force on the movable Form plate transfers.

In contrast, in the construction according to the invention abge the movements of the movable mold plate completely couples with the function of the closing force. For the The clamping force builds up in its locking cylinder movable locking piston, completely detached from the Generation of driving movements. For the latter is unique and only the piston that is movable in its driving cylinder constantly.

The main advantage is that the two Space of the driving cylinder with extremely small volumes can be tet. So it only needs very little Amounts of hydraulic fluid to meet the required driving to cause movements. A correspondingly high movement range The result is dizziness.

The latter applies in particular if both rooms of the Driving cylinder connected to the pump at the same time the. The hydraulic fluid can then come from the piston rod flow into the piston-side space, whereby the pump only has to deliver the difference.

However, this rapid traverse function can only be used when it is switched off push the piston rod. It offers itself therefore, this direction of movement the opening of the mold assign. There is also a long one in this direction same movement possible, namely if the piston side  Space to the pump and the piston rod side space to the Tank is connected. For the opposite movement direction, the latter two connections are against interchanged.

The independence of the closing pressure build-up from the driver movements offers the particularly advantageous option of to apply the invention to such systems in which the both rooms of the locking cylinder with one another are connectable in which a shut-off valve is arranged is. This shut-off valve is activated during driving movements open. The hydraulic fluid can therefore between the  overflow both rooms of the locking cylinder. Only when the pressure builds up, the two Spaces from one another by closing the shut-off valve separates.

An overflow of the hydraulic fluid between the Broaching the lock cylinder is known per se, namely in Connection with so-called differential circulation systems. At however, the locking piston takes over these systems at the same time the driving function. He is therefore with an auxiliary connected piston, which ar in a separate auxiliary cylinder prepared and additionally when pushing out the locking piston rod hydraulic fluid is applied. An ent the result is an elongated design. In contrast can the travel drive according to the invention designed and be positioned.

That in the line between the two rooms of the Shut-off valve arranged in the locking cylinder is preferred formed as a pressure intensifier, the shut-off valve builds up the closing pressure through its closing movement. So creates a very compact, aerodynamically favorable Design.

In a further development of the invention, it is proposed that the shut-off valve has a piston element, which forms a high pressure piston and a low pressure piston, the high-pressure piston from when the closing pressure builds up sealingly immersed in a high-pressure cylinder, the Ab cut the two rooms of the lock cylinder together the connecting line forms. Such pressure translators have proven their worth in practice. The piston element is pushed into the by a tubular piston Advanced closing position. Hikes with this movement the low-pressure piston by an enlarged in diameter th room and can get around from the hydraulic fluid be flocked. When the high pressure piston enters the The low-pressure piston also enters the high-pressure cylinder Low pressure cylinder. At the same time, the piston element  radial openings of the tubular piston are released, so that the pump pressure is applied to the low pressure piston. To Be The tubular piston is reversed by the pump disconnected and connected to the tank. The opening movement supply can by a separate, on the piston element piston-cylinder unit can be supported. One out A detailed description of the pressure translator can be found in DE 195 23 420 C1.

In a development of the invention it is proposed that the piston rod-side space of the locking cylinder to open Construction of the closing pressure and that the piston-side space is connected to a pressure maintaining device. At the When the mold is closed, the closing piston pumps the hydraulics liquid from the piston-side space of the locking cylinder via the pressure intensifier into the space on the piston rod side. Since this is smaller than the piston-side space, the Excess hydraulic fluid via the pressure maintenance on direction given. When the form is opened, they reverse Relationships around. It then arises in the piston-side space Deficit in hydraulic fluid that Facility is balanced. The latter determines in all Cases a predetermined filling pressure, which ensures that the cylinder chambers when the hydraulic fluid overflows remain vacuum-free.

As a preferred pressure maintenance device, a com combination of two check valves, of which the one towards the tank and the other towards opens the lock cylinder. Likewise, it can be beneficial be liable that the pressure maintaining device one in the direction check valve opening on the tank and one when opening pressure reducing valve that can be connected to the pump having. In any case, it is ensured that in the Räu of the lock cylinder when the hydraulic flows overflow no vacuum is created.

In an essential further development of the invention, it is provided propose to use at least one compensating locking piston  turn the one axially through the piston-side space of its Compensating lock cylinder going through and out the latter carries out compensating rod, whereby on the one hand the piston side and on the other hand the piston rod-side spaces of the locking cylinder and the Aus same-lock cylinders are interconnected. The we Significant advantage of this construction is that the Compensation amount of hydraulic fluid, on the one hand given to the tank and on the other hand who fed that must be reduced to a minimum. The closing pressure can therefore be built up very quickly. Arithmetically there would be the possibility of reducing the compensation amount to zero to reduce. However, this would result in diameter dimensions with breakage divide by millimeters. Since the latter is not possible remains, albeit a minimal amount of compensation. The arrangement is such that preferably the Sum of the piston-side spaces of the locking cylinder and the Compensation lock cylinder larger than the sum of the pistons rod-side rooms. Their reliable filling is So primarily ensured before the closing pressure in them is built up.

When using several locking pistons are advantageous Usually on the one hand the piston side and on the other hand the Spaces of the locking cylinders on the piston rod side with one another connected. The system preferably works with a single one Pressure translator.

A plurality of locking pistons can be several Compensating locking piston be assigned. Can be more advantageous it may be at least one to Set locking piston with an additional locking cylinder set, the piston rod side space with the pistons rod-side rooms of the locking cylinder - and demented speaking with those of the compensating locking cylinder - is connected and its piston-side space with the At related to the atmosphere. This offers the opportunity even when using several locking pistons with a single one  Compensating locking piston, which is an advantage since the latter, compared to an additional locking cylinder, increased design effort.

A construction has proven to be particularly practical proved to be an off at the two locking pistons equal locking piston and an additional locking piston in one 4-point patterns are arranged so that the locking piston lie on a diagonal. Compensating and additional lock pistons are naturally on the other diagonal, whereby the compensating locking piston advantageously on the Operating side facing away from the injection molding machine the un the other point of the pattern.

As already mentioned, there is a high degree of freedom what the design and arrangement of the piston and the As far as the driving cylinder is concerned. It is particularly advantageous however, one consisting of a piston and a cylinder Unit in a lock piston and lock cylinder or best from additional locking piston and additional locking cylinder integrating the existing unit. Such a design bie maximum compactness. Of course you can all units consisting of piston and cylinder associated with the locking piston and locking cylinder or best from additional locking piston and additional locking cylinder existing units can be integrated.

Know a constructive design of this integration is characterized by

• - That the driving cylinder housing from the locking piston stand ge is formed
• - That the piston rod is axially out of the lock piston out through the piston-side space of the lock cylinder extends through and on the lock cylinder housing is attached and
• - That the travel piston rod one optionally to the tank and the pump forms a connectable cavity that over min at least a radial opening on the piston rod side Room of the driving cylinder is connected.

There is no need to mention that this constructive Ge design on additional locking pistons and additional Lock cylinder is applicable. This results in the additional Liche advantage that the piston rod without additional Seal from the piston side space of the additional lock cylinder can be brought out.

The invention is based on a preferred Embodiment in connection with the accompanying Drawing explained in more detail. The drawing shows in:

Fig. 1 is a schematic representation of an inventive mold closing device;

FIG. 2 shows a detail from FIG. 1 on an enlarged scale;

Fig. 3-9 representations corresponding to Fig. 1 in different switching states.

The following description is divided into two parts. In the first part the opening and closing of the mold is described ben, in the second part the building up and down of the closing pressure.

Fig. 1 shows the mold closing device in the retracted form. For this purpose, a movable mold plate 1 has been moved to the left.

The molded plate 1 is connected by two closing piston rods 2 with associated closing piston. 3 The latter are each arranged in a lock cylinder housing 4 and define a piston-side space 5 and a piston rod-side space 6 of the lock cylinder.

To move the mold plate 1 , a travel piston 7 is provided, the travel piston rod 8 of which passes through the space 5 of the locking cylinder and is attached to the locking cylinder housing 4 on the front side.

As can be seen in particular from FIG. 2, the driving cylinder housing of the driving piston 7 is formed by the closing piston rod 2 . The travel piston 7 defines a space 9 on the piston side and a space 10 on the piston rod side.

The piston rod 8 forms a cavity 11 , which is connected to the piston rod-side space 10 of the cylinder via radial bores 12 . Otherwise, the cavities 11 of the two piston rods 8 are connected via a common line 13 to a first control valve 14 . Likewise, the piston-side spaces 9 of the two driving cylinders are connected to the first control valve 14 via a common line 15 . As mentioned, Fig. 1 shows the position when the mold is open. The two lines gene 13 and 15 are connected via the first control valve 14 to a hydraulic tank symbolized by the letter T.

In order to close the mold, the first control valve 14 is switched to the position shown in FIG. 3. The line 15 remains connected to the tank T, while the line 13 is connected to a hydraulic pump symbolized by the letter P. The hydraulic fluid passes through the cavities 11 of the piston rod 8 into the piston rod-side spaces 10 of the cylinder and cause the locking piston rods 2 to be pulled to the right. In this way, the mold closing device comes into the position according to FIG. 4, in which the mold is closed. The first control valve 14 can be switched back to its rest position.

Figure 5 shows the position of the first control valve 14 required to open the mold slowly. Here, line 15 is connected to pump P, while line 13 remains connected to tank T. The piston-side space 9 of the drive cylinder comes under pressure, while the piston rod-side space 10 is open to the tank.

Fig. 6 shows the associated rapid traverse. Both lines 13 and 15 are connected to the pump P. There is therefore an overflow of the hydraulic fluid from the piston rod-side space 10 into the piston-side space 9 of the driving cylinder, the pump only having to deliver the differential amount of hydraulic fluid. At the end of the opening movement, the position shown in FIG. 7 is reached.

The two driving pistons including their driving cylinders are in the associated locking piston and locking piston rod gene integrated. This results in an extremely compact construction wise. Otherwise, the piston and their Fahrzylin which are dimensioned so that with the lowest possible Lie amount of hydraulic fluid very rapid movements are achievable. Above all, the driving function is complete decoupled from the build-up of the closing force.

As can be seen from the figures, the mold closing device has, in addition to the locking piston 3 and its locking cylinder housing 4, a compensating locking piston 16 which works in a compensating locking cylinder housing 17 ar and defines a piston-side space 18 and a piston rod-side space 19 . The compensating-closing piston 16 carries a compensating rod 20 which extends through the piston-side space 18 and is guided out of the compensating lock cylinder housing 17 in a sealed manner. The balancing locking piston 16 is connected via its balancing locking piston rod 21 with the movable mold plate 1 .

Furthermore, an additional locking piston 22 is provided, which works in an additional locking cylinder housing 23 and defines a space 24 on the piston side and a space 25 on the piston rod side. The additional closing piston 22 is also connected to the movable mold plate 1 via its additional closing piston rod 26 . The piston-side space 24 of the additional lock cylinder housing 23 is closed to the atmosphere.

The figures also show that the piston-side spaces 5 of the lock cylinder housing 4 and the piston-side space 18 of the compensating lock cylinder housing 17 are connected via common line sections 27 to a shut-off valve 28 working as a pressure intensifier.

Likewise, the piston rod-side spaces 6 of the lock cylinder housing 4 are connected together with the piston-side space 19 of the compensating lock cylinder housing 17 and the piston rod-side space 25 of the additional lock cylinder housing 23 via common line sections 29 to the shut-off valve 28 .

All rooms are essentially depressurized during the traversing movements. The shut-off valve 28 assumes its open position in which the line sections 27 and 29 form a common line. The hydraulic fluid speed can flow over between the respective rooms of the cylinder housing, so that a very quick operation can be ensured.

If the device is moved from the position according to FIG. 1 into the position according to FIG. 7, the hydraulic fluid moves from rooms 5 and 18 into rooms 6 , 19 and 25 . The compensating rod 20 ensures that the common volume of rooms 5 and 18 is only slightly larger than that of rooms 6 , 19 and 25 . The excess is delivered to the tank T via a check valve 30 .

If the mold is opened, the hydraulic fluid overflows in the opposite direction. So the rooms 5 and 18 are filled, with a certain deficit in hydraulic fluid must be compensated. This can be done by suction conditions via a check valve 31 . As an alternative, a pressure reducing valve 32 can be provided, which is connected to the pump P when the mold is opened. In each case, the cylinder spaces are kept vacuum-filled while overflowing the hydraulic fluid.

The shut-off valve 28 working as a pressure intensifier has a piston element 33 , which forms a high-pressure piston at its upper end and a low-pressure piston at its lower end. In the rest position, the Kol benelement 33 takes the position shown for example in Fig. 1. The line sections 27 and 29 are connected to each other. Movements of the mold closing device are therefore permitted.

As soon as hydraulic fluid is applied to the shut-off valve, the high-pressure piston of the piston element 33 seals into a high-pressure cylinder 34 and blocks the connection between the line sections 27 and 29 . At the same time, the closing pressure is built up via the line sections 29 , specifically in the kolbenstangenseiti spaces 6 , 19 and 25 of the locking cylinder or the compensating locking cylinder and the additional locking cylinder.

The piston element 33 is driven via a tubular travel piston 35 which is immersed in the piston element 33 on the low pressure side. As soon as the high-pressure piston enters the high-pressure cylinder 34 , the low-pressure piston also moves into its associated low-pressure cylinder. At the same time, the piston element 33 releases radial openings in the tubular travel piston 35 , so that the low-pressure piston is acted upon by hydraulic fluid.

A switchable check valve 36 and a second control valve 37 are used to control the shut-off valve 28 .

If the closing pressure is to be built up, the second control valve 37 is switched from the position shown in FIG. 1 to the position shown in FIG. 7. Thereupon, the check valve 36 opens so that the piston element 33 can carry out its upward movement, namely into the position shown in FIG. 8, whereupon the check valve 36 closes again. The closing force is built up and held. The second Steuererven til 37 can return to its rest position.

To reduce the closing force, the second control valve 37 is switched to the position shown in FIG. 9. The check valve 36 opens and relieves the low pressure piston of the piston element 33 . In this case, the pressure prevailing in the line sections 29 ensures a resetting of the piston element 33 , so that the line sections 29 therefore come back into connection with the line sections 27 . The retraction movement of the piston element 33 can be supported by a piston-cylinder unit 38 .

As soon as the closing pressure has been reduced, the second control valve 37 is switched back into the position shown in FIG. 1, whereby the state according to FIG. 4 is restored.

It should also be mentioned that in the arrangement after the execution Example of the compensating locking piston on the loading the side facing away from the injection molding machine forms the point of the 4-point pattern.

Otherwise, there are others within the scope of the invention Arrangements possible. Above all, it is not necessarily required the piston and cylinder in the Integrate locking pistons and locking cylinders. The The piston rod can then also be attached to the tank and form the connectable cavity that over at least one radial opening on the piston rod side Space of the driving cylinder is connected when the driving piston and drive cylinder not in the locking piston and Lock cylinders are integrated. You can also use a single locking piston in connection with a compensating Locking piston to be worked. One or more Additional locking pistons will be used if there are several Locking piston is worked. Instead of an additional Closing piston is the use of another without further ado Compensating locking piston possible, the diameter of the Compensating rods must be adjusted accordingly. Easier in The structure is of course an additional locking piston. It is suitable is also very good for integrating a piston and a driving cylinder. In the case of the embodiment the mold plate when closing the mold against the Lock cylinder pulled. This is particularly advantageous sticky, but can also work with kinematic reversal become.

Claims (14)

1. Hydraulic mold closing device for an injection molding machine, in particular for processing plastic, with

• 1. a movable mold plate ( 1 ),
• 2. at least one locking piston ( 3 ), which is connected via its locking piston rod ( 2 ) to the mold plate ( 1 ),
• 3. a lock cylinder housing ( 4 ), which forms a lock cylinder with piston-side and piston rod-side space ( 5 , 6 ) for the lock piston ( 3 ),
• 4. a hydraulic tank (T) and
• 5. a hydraulic pump (P),

marked by

• 1. at least one double-acting travel piston ( 7 ), which is connected via its travel piston rod ( 8 ) to one of the components "mold plate" ( 1 ) and "lock cylinder housing" ( 4 ), and
• 2. a travel cylinder housing, which is connected to the other of the components “molded plate” ( 1 ) and “lock cylinder housing” ( 4 ) and a travel cylinder with a piston-side and piston rod-side space ( 9 , 10 ) for the travel piston ( 7 ),
• 3. wherein the two spaces ( 9 , 10 ) of the driving cylinder can optionally be connected to the tank (T) and / or the pump (P).

2. Mold closing device according to claim 1, characterized in that the two spaces ( 5 , 6 ) of the lock cylinder are connected to each other via a line ( 27 , 29 ) in which a shut-off valve ( 28 ) is arranged. 3. Mold closing device according to claim 2, characterized in that the shut-off valve ( 28 ) is designed as a pressure intensifier and builds up the closing pressure through its closing movement. 4. Mold closing device according to claim 3, characterized in that the shut-off valve ( 28 ) has a piston element ( 33 ) which forms a high pressure piston and a never pressure piston, the high pressure piston sealingly immersed in a high pressure cylinder ( 12 ) when the closing pressure builds up forms a section of the line ( 27 , 29 ) connecting the two spaces of the locking cylinder. 5. Mold closing device according to one of claims 1 to 4, characterized in that the piston rod-side space ( 6 ) of the locking cylinder serves to build up the closing pressure and that the piston-side space ( 5 ) is connected to a pressure-maintaining device. 6. Mold closing device according to claim 5, characterized in that the pressure holding device has a in the direction of the tank (T) opening and in the direction of the lock cylinder opening check valve ( 30 , 31 ). 7. Mold closing device according to claim 5, characterized in that the pressure holding device has a check valve ( 30 ) opening in the direction of the tank (T) and a pressure reducing valve ( 32 ) which can be connected to the pump (P) when the mold is opened. 8. Mold closing device according to one of claims 1 to 7, characterized by at least one compensating closing piston ( 16 ) which carries an axially through the piston-side space ( 18 ) of its compensating locking cylinder and extending out of the latter compensating rod ( 20 ), whereby on the one hand the piston-side and on the other hand the piston rod-side spaces ( 5 , 18 ; 6 , 19 ) of the lock cylinder and the compensating lock cylinder are connected to one another. 9. Mold closing device according to one of claims 1 to 8, characterized in that when using several locking pistons ( 3 ) on the one hand the piston-side and on the other hand the piston rod-side spaces ( 5 , 6 ) of the lock cylinder are interconnected. 10. Mold closing device according to claim 9, characterized by at least one additional locking piston ( 22 ) with an additional locking cylinder, the piston rod side space ( 25 ) with the piston rod side spaces ( 6 ) of the locking cylinder and the piston side space ( 24 ) with the Atmosphere. 11. Mold closing device according to claim 10, characterized in that two closing pistons ( 3 ), a compensating closing piston ( 16 ) and an additional closing piston ( 22 ) are arranged in a 4-point pattern such that the closing piston ( 3 ) lie on a diagonal. 12. Mold closing device according to claim 11, characterized in that the compensating closing piston ( 16 ) on the side facing away from the operating side of the injection molding machine forms the lower point of the pattern. 13. Mold closing device according to one of claims 1 to 12, characterized in that a unit consisting of the driving piston ( 7 ) and the driving cylinder is integrated into a unit consisting of the locking piston ( 3 ) and the locking cylinder or additional locking piston ( 22 ) and the additional locking cylinder . 14. Mold closing device according to claim 13, characterized in

• 1. that the driving cylinder housing is formed by the locking piston rod ( 2 ),
• 2. that the travel piston rod ( 8 ) extends axially out of the locking piston ( 3 ) through the piston-side space ( 5 ) of the locking cylinder and is attached to the lock cylinder housing ( 4 ) and
• 3. that the piston rod ( 8 ) an optional to the tank (T) and the pump (P) connectable cavity ( 11 ) bil det, which is connected via at least one radial opening ( 12 ) to the piston rod side space ( 10 ) of the cylinder is.