EP1677963A1

EP1677963A1 - Drive unit

Info

Publication number: EP1677963A1
Application number: EP04802619A
Authority: EP
Inventors: Jörg Dantlgraber
Original assignee: Bosch Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 2003-10-30
Filing date: 2004-10-15
Publication date: 2006-07-12
Also published as: WO2005044539A1; US20060280832A1; US7351053B2

Abstract

Disclosed is a drive unit, especially for a closing unit, an injection unit or an ejecting device of an injection moulding machine. A large axial force can be applied by means of a hydraulic power converter. A cylinder (16) of the power converter (4) can be fixed in relation to the frame of the injection moulding machine by means of a holding device (18) which is functionally separated by the guide (10, 12) of the cylinder (16) on the frame (14) of the injecting moulding machine.

Description

Description of drive unit

The invention relates to a drive unit, in particular for a clamping unit, an injection unit or an ejector, an injection molding machine according to the preamble of patent claim 1.

In recent times there has been a move towards providing injection molding machines with electrical and hydraulic drives, with the electrical drive performing positioning movements at high speed with comparatively low forces, while the hydraulic drive is particularly advantageous when high axial forces are involved in comparatively small actuating movements must be applied.

Such requirements occur, for example, with a clamping unit or an injection unit or when actuating ejectors of a plastic injection molding machine. For example, to inject plastic into a tool cavity, a plasticizing screw is moved towards the mold at a relatively high axial speed until the mold is completely filled with plastic. During the subsequent holding pressure phase, in which the shrinkage of the molded part is compensated for by adding molding compound, a high force must be applied via the injection unit without substantial axial advance of the plasticizing screw.

The requirements for a closing unit for closing the mold of an injection molding machine are similar, the movable clamping plate for closing the Tool is first moved quickly via the electric drive and then only a short remaining stroke has to be carried out to completely close and hold the tool with the required closing force.

From the applicant's DE 101 21 024 AI, a drive unit of an injection molding machine is known in which the comparatively large axial forces are applied during the closing of the injection molding tool or during the holding pressure phase during injection via a hydraulic force translator. This hydraulic power converter has a piston unit with a comparatively small effective area, which is actuated via a spindle arrangement. The smaller piston unit, together with another piston unit with a larger effective area and an axially displaceable cylinder, limits a pressure space. The cylinder can be locked to apply large axial forces so that the axial movement of the smaller piston unit reduces the pressure chamber and, depending on the area difference between the smaller and larger piston units, the latter exerts a high axial force on the unit to be acted on

(Clamping unit / injection unit / ejector) is applied. In the known solution, the cylinder of the force converter is fixed axially by bulging a cylinder wall radially outwards due to the pressure rising in the pressure chamber, so that the cylinder is non-positively fixed in a guide of the cylinder and thus no longer undergoes axial movement. can lead.

A disadvantage of this solution is that the guide surfaces for the cylinder must be designed on the one hand with regard to optimal guidance and on the other hand also with regard to the positive locking of the cylinder. There must therefore be a compromise between optimal guidance and good clamping effect can be found, so that the construction can neither be optimally designed to fulfill one or the other function (clamping, guiding).

In contrast, the invention has for its object to provide a drive unit for an injection molding machine, in which the guidance and the non-positive fixing of an intermediate part of a power converter of the drive unit are improved compared to the prior art.

This object is achieved by a drive unit with the features of claim 1.

The drive unit according to the invention has a force booster with two piston units which are movable relative to one another and have different active surfaces. Together with a displaceably guided intermediate part, these delimit a pressure space. To apply a large axial force, the intermediate part can be fixed via a clamping part to a support element supported on the frame of the injection molding machine. That the elements which form-fit the intermediate part - support element / clamping part - are formed separately from the guidance of the intermediate part, so that these components can be optimally designed for the respective task (guiding / clamping) and no functional compromises are required.

In a preferred embodiment, the support element supported on the frame of the injection molding machine has a support anchor, along which a radially deformable clamping sleeve can be displaced. This clamping sleeve is operatively connected to the intermediate part in such a way that a fixing of the clamping sleeve on the support anchor, the intermediate part is locked in the axial direction.

The radial deformation in the clamping sleeve is preferably carried out hydraulically via the pressure in the pressure chamber. For this purpose, in a preferred solution of the invention, the clamping sleeve is received in a clamping cylinder, the annular pressure chamber of which is connected to the pressure chamber of the force converter via a pressure line.

The intermediate part and also the clamping sleeve or the clamping cylinder are preferably guided via a guide plate which can be guided on spars of the injection molding machine.

In a particularly simple embodiment, this guide plate rests on the one hand on the clamping cylinder and on the other hand on the intermediate part. The outlay in terms of device technology for realizing the invention can be further reduced if the support anchor and / or the clamping sleeve are resiliently prestressed in the direction of their respective support position. The construction according to the invention allows the guide plate to be lubricated, so that the service life of the device was not possible compared to the conventional solution, in which the lubrication of the guide was considerably impaired, since otherwise the clamping effect would have been negatively influenced.

The intermediate part of the force intensifier is preferably designed as a cylinder in which the pistons of the two piston units are designed with a smaller and larger effective area and the pressure chamber. Other advantageous developments of the invention are the subject of further dependent claims.

A preferred exemplary embodiment of the invention is explained in more detail below with reference to a schematic drawing. This shows a schematic sectional illustration of a clamping unit of an injection molding machine. In the figure, only the upper half of the symmetrically constructed drive unit 1 is shown.

The drive unit 1 shown in the single figure is used to actuate the clamping unit of an injection molding machine, with a movable platen 2 initially being moved in the closing direction at a high speed (rapid traverse) and then when the movable half of the mold runs onto the half of the mold clamped on a fixed platen, the remaining stroke and the locking of the tool should be carried out with great force.

The drive unit 1 has a force booster 4, which has a piston unit 6 with a smaller effective area and a force booster piston 8 with a larger effective area. A cylinder 16 of the power converter 4 is guided via a guide plate 10 to spars 12 which are mounted on a frame 14 of the injection molding machine and on which the movable mold mounting plate 2 is also mounted. In order to apply large axial forces to the tool clamping plate 2, the cylinder 16 of the force converter 4 can be fixed with a holding device 18 with reference to the frame 14.

In the exemplary embodiment shown, the force translator 4 is actuated via a spindle drive with a spindle 20 which is driven via an electrical drive (not shown) with a gear wheel or belt drive. is driven. The spindle 20 fixed in the axial direction meshes with a spindle nut 22. In the solution shown, the spindle drive is designed as a recirculating ball drive. The spindle nut 22 has a radially projecting support flange 24 on which a plurality of pistons 26 of the piston unit 6 are supported. Instead of a plurality of pistons 26, a single piston can also be used.

The end section of the pistons 26, which is on the right in the figure, dips into a cylinder space 28, so that, together with the associated piston 26, it delimits a partial pressure space 30. The individual partial pressure spaces 30 of the force booster 4 are hydraulically connected to one another and are part of a pressure space, the volume of which can be changed by axially displacing the pistons 26.

According to the figure, the cylinder 16 encompasses the spindle nut 22 and rests with a contact shoulder 32 on the end face of the support flange 24. In the area of this contact shoulder 32, a clutch 34, preferably an electromagnetic clutch, is provided in the cylinder 16, via which the cylinder 16 can be coupled to the spindle nut 22, so that its axial displacement is transmitted to the cylinder 16.

In the end section of the cylinder 16 remote from the clutch 34, an annular space 36 is formed on the end face, in which a guide section 38 of the force transmission piston 8 designed as a hollow piston is guided. The latter delimits, with the annular space 36, a force booster space 40, which is connected to the partial pressure spaces 30 via a pressure line 42, so that the pressure space of the force booster 4 is formed by these and the force booster space 40. The annular end face of the force booster piston 8 removed from the guide section 38 acts directly or indirectly on the movable platen 2. The force booster piston 8 is biased in the direction of a minimum volume of the force booster chamber 40 via a spring 44 arranged in the annular space 36 and engaging on the guide section 38.

As shown, the cylinder 16 has at its right end portion a radially projecting ^'driving shoulder 46 to which the cylinder 16 is the encompassing guide plate 10 is supported in the axial direction.

In the exemplary embodiment shown, the guide plate 10 has one or more recesses 50 offset with respect to its central axis 48, into each of which a clamping cylinder 52 of the holding device 18 is inserted. It is preferred to distribute several of the clamping cylinders 52 around the circumference; in principle, a single clamping cylinder 52 is sufficient with lower closing forces, which, however, should then act coaxially to the cylinder 16.

The clamping cylinder 52 dips with a stepped-down end section 54 into the recess 50 of the guide plate 10. A spring 56, for example a plate spring arrangement, is placed on the end section 54 of the clamping cylinder 52, which is supported on the one hand on a ring 58 and on the other hand engages the guide plate 10, so that the clamping cylinder 52 is biased against the guide plate 10 with a shoulder 60. The recess 50 is formed with a certain clearance to the outer circumference of the end section 54 of the clamping cylinder 52, so that a certain adjustment of the axial position (axis 62) of the clamping cylinder 52 is made possible by means of the spring 56. In this clamping cylinder 52, a clamping sleeve 64 is inserted which, together with the jacket of the clamping cylinder 52, delimits an annular space 66 which is connected to the partial pressure spaces 30 via a connecting channel 68. In the embodiment shown, the connecting channel 68 extends from the cylinder 16 into the clamping cylinder 52 via the guide plate 10. The annular space 66 is sealed off from the outside via sealing arrangements 70, 72. The clamping sleeve 64 is designed such that it can be deformed in the radial direction when the annular space 66 is subjected to a predetermined minimum pressure and can thus be clamped on a support anchor 74. This positive connection is designed in such a way that the supporting forces resulting from the locking force can be transmitted.

The clamping sleeve 64 engages around the rod-shaped support anchor 74, the end section of which on the right in the illustration also passes through the guide plate 10. The support anchor 74 is supported on one side by a support device 76 on the frame 14 of the injection molding machine. In the illustrated embodiment, the support device 76 has a support bracket 78 anchored to the frame 14, on which a biasing spring 80 is supported. This engages on a support ring 82 which is placed on the support armature 74 and is supported there, for example via a spring ring 84, in the axial direction. The end face of the support armature 74, which is on the left in the illustration, is prestressed against a contact face 86 of the frame 14 by means of the prestressing spring 80.

The resilient positional positioning of the support armature 74 and the clamping cylinder 52 makes it easy to compensate for manufacturing tolerances, since the springs allow centering along the common axis 62. The springs 56, 80 must be designed so strong that when opening the forces occurring due to friction on the form and in the guide are overcome. In the illustrated embodiment, a plurality of pistons 26 are used. Instead of these pistons, a single hollow piston can also be used, the annular end face of which has a substantially smaller effective area than the end face of the force transmission piston 8 received in the annular space 36.

The function of the drive unit 1 is explained for better understanding. It is assumed that the tool clamped on the tool clamping plates is open, the cylinder 16 either assuming the position shown when the tool is open or being shifted further to the left in contact with the frame 14.

To close the tool in rapid traverse, the clutch 34 is first engaged so that the cylinder 16 is connected to the spindle nut 22. At the same time, the drive motor of the spindle 20 is actuated and the latter is rotated, so that the spindle nut 24 accordingly carries out an axial feed to the right (illustration). The cylinder 16 is carried along via the clutch 34, so that the entire force converter 4 is shifted to the right and the tool mounting plate 2 is moved in the closing direction. This closing movement takes place at a comparatively high speed, with only a small force being transmitted via the spindle drive.

During this axial shift in the rapid traverse, the volume changes through the partial pressure spaces 28 and

Force translator chamber 40 formed pressure chamber of the cylinder not 16, so that accordingly the pressure in the pressure chamber remains constant.

When the tool is closed, the clutch 34 is released to apply a high locking force, so that the cylinder 16 is no longer carried along by the spindle nut 22 during the remaining stroke. As a result, the pistons 26 dive into the cylinder spaces 28, so that the volume of the partial pressure spaces 30 is reduced and the pressure in the pressure space of the cylinder 16 increases accordingly.

In order to prevent the cylinder 16 from moving to the left, it is clamped in place via the holding device 18. In the exemplary embodiment shown, this is done in that the clamping sleeve 66 is deformed radially inwards and positively on the outer circumference of the support rod 74 by the pressure rising in the pressure chamber (partial pressure chambers 28, force transmission chamber 40), which is also present in the annular chamber 66 via the connecting channel 68 is set. The preloaded spring 44 ensures that a clamping force is built up before the closing force occurs. The clamping action is sufficient to fix the cylinder 16 to build up the locking force in the axial direction. Due to the increasing pressure in the pressure chamber 68, the force booster piston 8, which has a much larger effective area than the pistons 26, is subjected to a large force in the closing direction of the tool, depending on the area ratio of the effective areas, the stroke correspondingly being reduced

Speed.

During the entire closing movement and during the

Structure of the locking force, the cylinder 16 is guided exactly on the rigid bars 12 via the guide plate 10.

The force translator 4 through the pressure in the force Setzerraum 40 generated, acting on the movable tool half supporting force is transmitted via the cylinder 16, the driving shoulder 46, the guide plate 10 and over the shoulder 60 to the clamping cylinder 52 and further via the clamping sleeve 64 to the support anchor 74 and via the contact surface 86 in the Frame 14 of the injection molding machine initiated, so that a secure locking of the tool is guaranteed even with high closing forces.

The construction according to the invention is distinguished by an extremely simple construction, wherein high tolerance requirements for the construction can be avoided by the loose mounting of the support armature 74 and the clamping cylinder 52 with prestressed springs 80, 56. The requirements for these springs 56, 80 are comparatively low, since they only have to transmit the frictional force and the forces for opening the tool. Since the leadership of the cylinder 16 is functionally different from that

Clamping is separated, the guides between the guide plate 10 and the spars 12 can be lubricated in an optimal manner. When the cylinder 16 is fixed, the deformations of the bars 12 are minimal, since the geometric accuracy of the holding device 18 is very high and the clamping cylinder 52 and the support anchors 74 can be optimally adjusted to one another and to the bars 12 by the loose mounting. The illustrated one-sided mounting of the components furthermore enables good access to the drive unit and simple assembly and disassembly, so that maintenance is made easier. Disclosed is a drive unit, in particular for a clamping unit, an injection unit or an evaluation fer, an injection molding machine in which a large axial force can be applied via a hydraulic force intensifier. A cylinder of the force intensifier can be fixed in relation to a frame of the injection molding machine by means of a holding device which is functionally separate from the guidance of the cylinder on the frame of the injection molding machine.

LIST OF REFERENCE NUMBERS

Drive unit tool mounting plate power booster piston unit power booster piston0 guide plate2 spar4 frame6 cylinder8 holding device0 spindle2 spindle nut4 support flange6 piston8 cylinder chamber0 partial pressure chamber2 contact shoulder4 clutch6 annulus8 guide section0 force translator chamber2 pressure line4 spring6 driving shoulder8 central axis0 shoulder0 recesses2 axis8 clamping sleeve4 annulus

connecting channel

sealing arrangement

Stutz anchor

supporting device

support bracket

biasing spring

support ring

spring washer

contact surface

Claims

claims

1. Drive unit, in particular for a clamping unit, an injection unit or ejector of an injection molding machine, with a hydraulic force intensifier (4), with two piston units (26, 8) which are movable relative to one another and have different active surfaces, which together with an axially displaceable Guide means (10, 12) guided intermediate part (16) delimit a pressure chamber (28, 36), the smaller piston unit (6) preferably being electrically driven and the intermediate part (16) for applying an axial force via a holding device (18) Reference to a stationary frame (14) can be determined, characterized in that the holding device (18) has at least one support element (74) supported on the frame (14), which has a positive fit with a jointly displaceable jointly with the intermediate part (16) essentially functionally separate clamping part (64) can be connected.

2. Drive unit according to claim 1, wherein the support element has at least one parallel to the intermediate part (16) spars (12) extending support anchor (74), along which a radially deformable clamping sleeve (64) is displaceable.

3. Drive unit according to claim 2, wherein the clamping sleeve (64) is received in a clamping cylinder (52), the annular space (66) is partially delimited by the clamping sleeve (64), which is connected via a connecting channel (68) to the pressure chamber (28, 40) of the force translator is connected.

Drive unit according to claim 3, wherein the intermediate part (16) and the clamping cylinder (52) are guided via a guide plate (10) on at least one spar (12) of the injection molding machine.

Drive unit according to claim 4, wherein the guide plate (10) in the axial direction on the clamping cylinder (52) on the one hand and on the intermediate part (46) on the other.

6. Drive unit according to one of the claims 2 to 5, wherein the support anchor (74) is supported on one side on the frame (14) and the clamping sleeve (64) can be displaced along a free end section of the support anchor (74).

7. Drive unit according to one of claims 2 to 6, wherein the support armature (74) and / or the clamping sleeve (64) are resiliently biased into a support position.

8. Drive unit according to one of claims 4 to 7, wherein the guide between the spar (12) and the guide plate (10) is lubricated.

9. Drive unit according to one of claims 3 to 8, wherein the intermediate part is a cylinder (16) in which the two piston units (6, 8) with a smaller and larger effective area and the pressure chamber (28, 40) are accommodated, the cylinder (16) has a pressure connection which is connected to the pressure chamber (28, 40) and which is connected to the annular space (66) of the clamping cylinder (52) via the connecting channel (68).