CA2325456A1 - Mold closing unit for an injection molding machine - Google Patents

Abstract

The invention relates to a mold closing unit which is provided with a clamping device (13) for variably appointing the distance (a) between the stationary mold support (10) and the moveable mold support (11). The clamping device engages with the guide element (12) in an interlocking manner in order to appoint an adjusted distance (a). A fastening device is assigned to the moveable mold support (11). When actuated, said fastening device fixes the moveable mold support (11) in the respective position thereof. The drive (D) for moving the movable mold support (11) varies the distance (a) along a section (12a) of the guide element (12) when the fastening device (14) is actuated and when the clamping device (13) is not engaged. The drive for moving the moveable mold support can also be used for adjusting the height of the mold.

Description

DESCRIPTION
Mould-closina unit for an infection mouldina machine Reference to related aaplications The present application claims the priority of the German patent application 12 741.3, filed on March 24, 1998, the disclosure of which is hereby expressly made the subject matter of the present application.
Field of the invention The invention relates to a mould-closing unit for an injection moulding machine to process plastics materials and other plasticizable masses such as powdery or ceramic masses in accordance with the preamble of claim 1, this mould-closing unit having a mould height adjustment device.
By "mould height" is here understood the height of the mould which is measured in the closing direction and which corresponds to the distance between the move-able mould carrier and the stationary mould carrier when the mould is closed.
Adjusting devices of this kind are first of all necessary in injection moulding ma-chines in which the closing movement and the building-up of the locking pressure takes place via a toggle joint, since the support plate for the toggle joint has to be positioned in relation to the integrated injection moulding tool in such a way that as the tool or the mould is closed, the toggle joint is expanded and thus can apply its maximum locking pressure in each cycle. Furthermore mould height adjusting devices are necessary to optimize the closing path, when moulds with variable mould height are used on the same machine.
Prior Art From PATENT ABSTRACTS OF JAPAN, vol. 16, No. 471 (M-1318),1992-09-30)and JP 04 169216 A is known a mould-closing unit, underlying the preamble of claim 1 and having a mould height adjustment. This mould height adjustment is -c-used as usual in connection with a toggle joint as the closing mechanism. On the moveable mould carrier, an electromagnetically actuatable fixing device is pro-vided and on the support element for the toggle joint mechanism a fixing device is provided which may be actuated manually to detachably fix the support element.
If when the moveable mould carrier is fixed and the support element detached, the closing motor driving the toggle joint is actuated, the support element is dis-placed into the necessary position for the new mould height, in which the locking pressure can be applied with the toggle joint in an expanded position. The support element is not fixed in a positive manner, and thus after a plurality of cycles at least the precision suffers in the repeated application of the locking pressure.
Above all however this mould height adjustment has no influence on the opening path to open the mould, since this is dependent on the movement of the toggle joint and not on the position of the support element.
Mould-closing units with mould height adjustments are known in which there are provided on bars, which are mostly fixed to the stationary mould carrier and serve to guide the moveable mould carrier, threaded portions which are connected with nuts. These nuts are driven via a separate drive to adjust the mould height.
The nuts have on their outer side a ring gear, such that they can be actuated either with a ring gear or with a toothed belt. (US-A 4,281,977; Brochure "Elektra S-Serie" (p.5) of the company Ferromatic Milacron Maschinenbau GmbH, 79364 Malterdingen). During an injection cycle the support element for the moveable mould carriers is hold in position by the nuts. Hence, the closing mechanism moves only the movable mould carrier, whereas the support element is stationary.
Only when the mould height shall be altered, the support element is moved along the guide elements. This is generally the case, when the mould is changed.
For adjusting the mould height and locking a support plate for the closing mecha-nism, the company Engel Vertriebs GmbH, A-4311 Schwertberg, Austria has a known way of providing the bars with grooves and fixing to these grooves two half-nuts by moving the half-nuts in a radial direction towards one another until they come into contact with the grooved region of the guide bars.
Furthermore, from the company Husky Injection Moulding Systems there is a known way of achieving locking of this kind with a bayonet fastening. For this pur-pose, the bar has regions into which a closing piston can engage, as well as re-gions along which the moveable closing piston can slide radially on the guide bars. By turning the closing piston, a positive-locking effect is caused, such that at least a portion of the locking pressure can also be applied to this piston simulta-neously.
From DE 24 29 570 B1 is known an injection moulding machine in which two pressure cylinders are used to close the mould. One pressure cylinder serves to displace the moveable mould plate, a further cylinder to apply the locking pres-sure. Correspondingly, even during the injection moulding cycles, two plates are moved jointly as the moveable mould carrier. A support element which is adjust-able with an alteration of the mould height is not provided. The fixing device is only actuated when the piston of the cylinder has completed its stroke movement and in addition now the locking pressure is to be applied via the piston.
From DE 42 43 735 C2 is known a two-plate machine in which, in order to achieve the mould closure, the moveable mould plate is drawn towards the sta-tionary mould carrier. The moveable mould carrier is separable from the guide bars which are necessary during the application of the locking pressure and can be locked to same. However once the locking has been accomplished, it is only the closing cylinder which is responsible for the mould closing movement and the application of the locking force. Alteration and thus optimization of the locking pressure is thus not possible.
In parallel proceedings, the document DE 30 42 712 C2 was cited, the object of which is completely different however, since there, on engagement grooves of the guide bars, a locking mechanism for the protective bolt is triggered and locked, which covers the mould tentering space.
Summary of the invention Proceeding from this prior art, the object underlying the present invention is to create a mould-closing for many uses.
This object is achieved by a mould-closing unit with the features of claim 1.

Associated with the moveable mould carrier is a fixing device, such that the moveable mould carrier can be fixed in any way in its current position. If the lock-ing of the drive is detached from the bars, the drive can be adjusted with its re-spective support relative to the bars, such that~a mould height adjustment occurs.
Herein is not essential, whether the injection moulding machine is a two-plate-system, wherein the closing mechanism is arranged on the stationary mould car-rier, or a three-plate-system, wherein a separate support element is provided for the closing device. Since the drive device usually used for a main axis can now be used for a subordinate function, an additional drive for the adjustment of the mould height can be dispensed with. Additional guide elements are not necessary since the guide elements which are present anyway, generally the tie bars, can be used. Through the use of the mould height adjustment device, however, in each - cycle the pressure build-up times can be reduced in the order of several tenths of seconds.
Thus where higher forces have to be applied constantly, i.e. in the standard op-erational state, a positive connection is provided which can be detached as re-quired to adjust the mould height. In the other region, in which the moveable mould carrier only has to be fixed for a short time, in order to effect the adjust-ment of the mould height, the moveable mould carrier can, on the other hand, be fixed on the guide elements or on the machine base merely by a non-positive connection.
In both cases, but above all in the positive operational connection, collet chucks are used to this end. The collet chucks have the advantage, that as a result of the secure clamping, clamping free from play between the guide elements and in par-ticular the support element is guaranteed, since unlike the known threaded ad-justments, no thread play has to be taken into account. By this means, the preci-sion of the whole injection moulding machine can be simultaneously increased despite the existing mould height adjustment. For safety, the devices are so con-structed that the basic function of injection moulding is always adjusted automati-cally under the effect of resilient means.
Further advantages will be apparent from the subclaims.

Short descriation of the figures Fig. 1 a schematic representation of an injection moulding machine in side view, in operation Fig. 2 the injection moulding machine according to Fig. 1 with clamped move-able mould carrier, Fig. 3 a representation as per Fig. 1 in operation with adjusted support ele-meet, Figs. 4,5 the collet chuck of the clamping device for fixing the spacing a in the open and closed position, Figs. 6,7 the fixing device on the moveable mould carrier in open and clamped position, Fig. 8 an embodiment of an injection moulding machine without any bars, Detailed description of preferred embodiments The invention will now be explained in greater detail with examples, referring to the attached drawings. The examples of embodiment are only examples and do not limit the inventive concept to a certain physical arrangement.
Fig. 1 shows schematically an injection moulding machine for processing plastics materials and other plasticizable masses, which has an injection moulding unit S
and a mould-closing unit F. The mould-closing unit has a stationary mould carrier 10, whose position e.g. in relation to the machine base is fixed and in the present case is indicated by a fixed bearing. Furthermore, a moveable mould carrier is provided which in the present case is a constructional unit consisting of the clamping plate 23, the cylinder 25 with piston rod 26 of drive D and a backing plate 24. Mould clamping plate and backing plate are braced with one another, such that a precise unit guided on guide elements 12 is produced which forms the moveable mould carrier 11 and has a pre-determined fixed length. The mould clamping plate 23 of the moveable mould carrier 11 and the stationary mould car-rier 10 enclose between themselves the mould teetering space R. In this mould teetering space, injection moulds M of variable height can be used, as in particu-lar Fig. 1 and Fig. 2 make clear. According to the height of the injection mould M, the spacing a between the moveable mould carrier 11 and the stationary mould carrier 10 is greater or smaller. The height of the mould which determines this spacing a is measured in the closing direction s-s.
To move the moveable mould carrier, a drive D is provided which moves the moveable mould carrier in the closing direction s-s towards the stationary mould carrier 10 and away from it again. A part of this drive D is in this embodiment, besides the cylinders 25, the piston rod 26. In the present case of a three-plate-system (stationary mould carrier, moveable mould carrier, support element) the piston rod 26 is supported on the support element 21. It is also conceivable to dispose the closing mechanism on the stationary mould carrier and thus obtain a two-plate system, the device for fixing the spacing a being then allocated as clamping device 13 to the stationary mould carrier 10. Furthermore, the drive D, which is hydraulic here, can also be e.g. electromechanical or pneumatic.
Guide elements 12 configured as tie bars reach through the stationary mould car-rier 10 and the moveable mould carrier 11 in Figs. 1 to 3. They serve as a guide for the moveable mould carrier 11 during its movement and can, as will be gone into later, also serve as a guide for the support element 21 during its movement.
For this purpose, only one portion 12a of the guide element 12 is necessary, so that with other guiding of the moveable mould carrier 11 the rest of the guide ele-ment can be dispensed with (Fig. 8). The support element 21 is in this embodi-ment mounted moveable in relation to the machine base in the closing direction s-s, and this is indicated by the symbol for the corresponding moveable bearing arrangement. The guide elements 12 have at least one portion 12a with which the clamping device 13 between the stationary mould carrier 10 and moveable mould carrier 11 comes into operational connection, as soon as the desired spacing a is set.
In addition, a fixing device 14 is allocated to the moveable mould carrier 11 which, on actuation, fixes the moveable mould carrier 11 in its respective position.
This fixing can be on the guide elements 12, as in the embodiment, however fixing the moveable mould carrier to the machine base or to another suitable stationary lo-cation is also conceivable. As soon as the moveable mould carrier has been fixed, the drive D, which is generally a component of the closing device for moving the moveable mould carrier 11 and for applying the locking pressure, can be actuated when the fixing device 14 is actuated and the clamping device 13 is out of opera-tional connection, in order to move the support element 21 along its guide, here along portions 12a of the guide elements 12, and thus to alter the spacing a for the following injection cycles. This is shown by 1=igs. 1 to 3.
In Fig. 1 the clamping device 13 is fixed on the guide elements 12. Simultane-ously the fixing device 14 is open as the spacing between the clamping jaws and the guide elements 12 in Fig. 1 makes clear. In this state, the moveable mould carrier can be moved along the guide elements by drive D, which produces an optimization in respect of the spacing a of the small mould M shown in Fig. 1.
In Fig. 2 a larger injection mould M is transferred into the mould tentering space R. Here the support element 21 is still in the position of Fig. 1. It becomes clear that in this state no satisfactory opening movement can be brought about for the injection mould M. Therefore, as indicated by the arrows, the fixing device 14 is locked, by which means the moveable mould carrier is held secure in its position.
Then the clamping device 13, which is allocated to each guide element 12, is un-locked. If drive D is now actuated, there is no movement of the moveable mould carrier because it is clamped. Instead, the support element 21 is now moved in the closing direction s-s, such that a position of the support element as per Fig. 3 is produced, which position is adapted to the corresponding mould height. In order to make an injection moulding process possible again, the support element 21 is locked with the clamping element 13 and the fixing device 14 is unlocked. Now the further process of manufacturing injection moulded parts can take place, adapted to the altered mould height.
To be precise, the spacing a between the stationary mould carrier 10 and the moveable mould carrier 11 is adjusted by drive D, which in a small injection mould with a small mould height, has to cover a larger movement path than in an injec-tion mould with a large mould height. However if an unaltered movement path of the moveable mould carrier 11 is assumed, an alteration of spacing a takes place, as a comparison between Figs. 1 and 3 shows. However the spacing between support element 21 and stationary mould carrier 10 has also changed as has the distance b of the guide elements 12 projecting beyond the support element. To this extent, one could also talk about an adjusting device to adjust the length b of the projecting guide elements 12, optimizing the amount of oil with an unaltered movement path of drive D.
Naturally, the fixing device 14 has to be arranged only on any part of the move-able mould carrier, and it can comprise a single or a plurality of fixing devices. In the embodiment they are arranged on the backing plate 24, however they can also be arranged directly on the mould clamping plate 23. It must just be ensured that the movement of the moveable mould carrier can be temporarily prevented by the fixing device.
Portion 12a of the guide element 12 has an altered cross-section, it being in-tended that this cross-section alteration should contribute to making possible a positive operational connection with the clamping device 13 to fix the spacing a. A
positive connection free from play is desired at this location, since high forces have to be applied during the injection cycle, to which the clamping device 13 must be equal. The cross-sectional alteration can be grooves or, in this embodi-ment, a thread 12b. A thread has the advantage that it can be manufactured very precisely as a result of continuous manufacturing in thread cutting. The fixing de-vice 14 on the other hand is fixed in a non-positive manner, since this device is open during the injection cycle and only low forces are applied during the secon-dary function of the adjustment of the mould height. In this respect the non-positive connection is adequate for this purpose.
Figs. 4 and 5 show preferred embodiments of the clamping device 13 to fix spac-ing a free from play. As clamping device 13, an actuating element 15 for a first collet chuck 38 is provided which element is disposed coaxially to the guide ele-ments 12 in the region of portion 12a. The collet chuck has a threaded bush 16 which enters positive operational connection with the thread 12b of portion 12a when the collet chuck is actuated. The clamping device 13 is so constructed that it automatically remains in the locked position under the force of a resilient means 22 held on pins 37. Unlocking to adjust the mould height or to adjust spacing a takes place under the effect of a hydraulic medium. This hydraulic medium is led via the hydraulic connection 29 into the annular hydraulic chamber 27. As a com-parison between Fig. 4 and Fig. 5 shows, the application of this hydraulic medium leads to an axial movement of the annular piston 17 against the force of the resil-ient means 22. During this movement, the conical portion 17a of the annular pis-ton 17 moves out of engagement and the conical region 16a of the collet chuck moves into engagement. Consequently, the threaded bush 16 is expanded by the cone ring 31 and a relative movement between support element 21 and guide element 12 is rendered possible. If the hydraulic pressure in the hydraulic cham-ber 27 is reduced, as a result of the resilient means 22 mounted in recess 21 a of the support element 21, resetting of the annular piston 17 into a position as per Fig. 5 comes about. In this movement, the cone ring 31 connected via fastening means 32 to the annular piston 17 is also moved axially with said piston. On the other hand, the movement of the (double) annular piston 17 is ended by the coni-cal region 16b and the conical portion 17a coming together. The hydraulic cham-ber 27 is also limited in an axial direction by a closing element 33.
Figs. 6 and 7 show the fixing device 14. This fixing device 14 has a second collet chuck 19, which is disposed in the embodiment coaxially to a guide element 12 and is fixed on the moveable mould carrier 11, or more precisely on the backing plate 24 in a recess 24a. The fixing device has a housing 36 which encloses a hydraulic chamber 28 radially towards the outside, to which chamber hydraulic medium can be applied via a hydraulic connection 30. The second collet chuck has a conical region 19a which causes the clamping with a conical portion 18a of the hydraulically actuated annular piston 18. The return into the non-clamped po-sition takes place under the effect of an additional resilient means 20. As a com-parison between Figs. 6 and 7 shows, the movement of the annular piston is lim-ited on the one hand by a stop on the housing 36 and on the other hand by the conical portion 18a and conical region 19a coming into contact with one another.
The elastic means 20 is mounted in a closing element 34 which is connected to the housing 36 via securing means 35.
Fig. 8 shows a further embodiment in which the piston rod 26 of drive D serves as the guide element, and comes into positive operational connection with the clamping device 13 via a portion 26a which in this respect can be equated with the previously-mentioned portion 12a.

Fig. 8 also shows that use of clamping device 13 and fixing device 14 is also pos-sible on a machine without bars, in which instead of tie bars, a force transmission element 40 guides the forces occurring during injection moulding around the mould tentering space R to achieve better accessibility. This force transmission element, possibly also multipart, is hinged on' one hand to the stationary mould carrier 10. On the other hand, drive D is supported on its opposite end 42 associ-ated with the moveable mould carrier 11. Here the clamping device 13 can be provided which co-operates with portion 26a. If the clamping device 13 is open and the fixing device 14 engaging on the guide element 41 is locked, the drive D
can displace portion 26a of the piston rod 26 relative to the clamping device.
Thus altered movement paths of the moveable mould carrier are produced for subse-quent injection cycles.

Claims (14)

Claims

1. Mould-closing unit for an injection moulding machine for processing plastics materials and other plasticizable masses, having - a stationary mould carrier (10), - a moveable mould carrier (11) which has between itself and the stationary mould carrier (10) a mould tentering space (R) to accommodate injection moulds (M) of variable height, measured in a closing direction (s-s), - a drive (D) to move the moveable mould carrier (11) in the closing direction (s-s) towards the stationary mould carrier (10) and away from the stationary mould carrier, which drive has at least two parts operationally connected to one another, of which one part is supported on a support element (21), and the other part is connected to the moveable mould carrier (11), - guide elements (12) which guide the moveable mould carrier (11) during its movement in the closing direction (s-s), having at least one portion (12a, 26a) - a device for variably fixing the spacing (a) between the stationary mould carrier (10) and the moveable mould carrier (11) measured with the injection mould (M) closed and assuming a movement path of the moveable mould carrier unaltered in relation to a state before alteration of the spacing (a), which device is a clamping device (13) and enters operational positive connection with the portion (12a, 26a) of the guide elements (12) to fix the spacing (a) set, - a fixing device (14) allocated to the moveable mould carrier (11) which, on actuation, fixes the moveable mould carrier (11) in its respective position, - wherein drive (D), when the fixing device (14) is actuated and the clamping device (13) is out of operational connection, itself alters the spacing (a) by displacing the clamping device (13) along portion (12a, 26a), characterized in that at least one of the two parts of the drive (D) for the movement of the moveable mould carrier (11) extends in a linear manner in the closing direction even during the closing movement.

2. Mould-closing unit according to claim 1, characterized in that the drive (D) is a hydraulic drive and that the parts of the drive (D) are the cylinder (25) and piston rod (26) of a hydraulic piston-cylinder unit.

3. Mould-closing unit according to claim 1, characterized in that the drive (D) is an electromechanical drive.

4. Mould-closing unit according to claim 1, characterized in that, in connection with the drive (D), the spacing (a) is variable by alternate actuation of the clamping device (13) and of the fixing device (14).

5. Mould-closing unit according to claim 1, characterized in that the clamping device (13) has a first collet chuck (37) which is disposed coaxially to the guide element (12) in the region of portion (12a) and can be transferred with portion (12a) into positive operational connection free from play.

6. Mould-closing unit according to claim 5, characterized in that the first collet chuck (38) has a conical region (16a) which, in order to release the tension, comes hydraulically into operational connection with a cone ring (31) connected to an annular piston (17) and under the force of resilient means (22), the annular piston (17) being axially moveable to a limited extent along the guide element (12).

7. Mould-closing unit according to claim 1, characterized in that portion (12a) of the guide elements (12) has a thread (12b) to form a positive operational connection with a threaded bush (16) of the clamping device (13).

8. Mould-closing unit according to claim 1, characterized in that the actuated fixing device (14) fixes the moveable mould carrier (11) in a non-positive manner to the guide elements (12).

9. Mould-closing unit according to claim 1, characterized in that the fixing device (14) has a second collet chuck (19) which is disposed coaxially to a guide element (12) and is fixed on the moveable mould carrier (11).

10. Mould-closing unit according to claim 9; characterized in that the second collet chuck (19) has a conical region (19a) and in that a second hydraulically actuated annular piston (18) with a conical portion (18a) effects the clamping with the conical region (19a) when hydraulic pressure is applied.

11. Mould closing unit according to claim 10, characterized in that the additional annular piston (18) being able to be reset via an additional resilient element (20).

12. Mould closing unit according to claim 1, characterized in that the clamping device (13) is allocated to the support element (21).

13. Mould-closing unit according to claim 1, characterized in that the guide element is a piston rod (26) of the drive, which rod comes into operational connection with the clamping device (13) via a portion (26a).

14. Mould-closing unit according to claim 1, characterized in that that there is hinged to the stationary mould carrier (10) a force transmission element (40), at the opposite end (42) of which, associated with the moveable mould carrier (11), is disposed the clamping device (13) which co-operates with portion (26a).