Closing device in an injection moulding machine for synthetic materials

Abstract

The invention relates to a clamping device for an injection molding machine for plastics, including a fixed platen (11) and an end platen (19) which is connected to a moving platen (12) by means of toggle mechanism (13), wherein a hollow-shaft motor (7) with a stator (4) and a rotor (6) interacts with a spindle (21) for operating the toggle mechanism (13). It is proposed that the hollow-shaft motor (7) can be received in a recess of the end platen (19). Moreover, it is proposed that the spindle nut (5, 23) can be received in the inner dimensions of the rotor (6) of the hollow-shaft motor (7).

Description

DESCRIPTION

[0001] The invention relates to a clamping device according to the preamble of claim 1.

[0002] EP 0658 136 B1 discloses a clamping unit for molding tools of injection molding machines, including a clamping system in the form of a toggle mechanism, disposed between the moving platen and an end platen, for displacing the moving platen. Several so-called five-point toggle lever systems are coupled with a common crosshead. A threaded spindle is connected in fixed rotative engagement upon the crosshead and engages a nut which is immobile in axial direction but received in the end platen for rotation. The rotary drive is implemented by coupling the nut to a hollow shaft of an electric motor which is flange-mounted to the outside of the end platen. The hollow shaft is internally so dimensioned as to be suitable to easily receive the entire length of the threaded spindle, when the threaded spindle extends rearwards out of the nut. The toggle lever systems are in symmetric relationship to the force axis of the clamping unit, and the threaded spindle, the spindle nut and the electric motor with its hollow shaft are in alignment with the force axis of the clamping unit. A similar system is described in DE-PS 195 24 314 C1.

[0003] These systems have shortcomings relating to a comparably long construction of the clamping device because the electric motor is arranged outside the end platen and the inner dimension of the hollow shaft is suited to the spindle length.

[0004] The invention is based on the object to provide a clamping device of this type, which is of significantly shorter construction while still allowing a cost-efficient construction.

[0005] This object is realized in accordance with the invention by the features of claim 1 and by the features of further independent claims 16 and 17. Both solutions are hereby based on the common, basic idea to arrange as many components as possible within one another so that their individual axial structural lengths do not add up. The length of the clamping device is then not governed by the sum of the axial dimensions of the individual components but by the longest one of the nested components.

[0006] As the hollow-shaft motor can be received in a recess of the end platen, the structural length of the motor on the outer side of the end platen is absent in comparison to the prior art. Even though a portion of the structural length of the motor extends through the inner side of the end platen, this is still always advantageous when the inner side of the end platen is constructed already with at least some space for receiving the motor. The entire structural length of the injection molding machine is reduced. This reduction of the structural length of the injection molding machine corresponds to the thickness of the end platen.

[0007] The subsequent claims represent advantageous improvements of the invention.

[0008] Preferably, the recess of the end platen is configured as opening through the end platen. In this way, the full thickness of the end platen can be saved as axial structural length of the clamping device.

[0009] Advantageously, the hollow-shaft motor extends hereby through the end platen. Thus, the full thickness of the end platen can be exploited as saving of axial structural length of the clamping device.

[0010] The end platen can be configured in a geometric shape that deviates from the pure plate-shape. Hereby, the end platen has preferably a back wall with a recess in which the hollow-shaft motor can be received. In this way, the full thickness of the end platen can again be saved when the motor is longer than the thickness of the end platen.

[0011] The greatest outer diameter of the hollow-shaft motor is preferably smaller than the smallest inner diameter of the opening through the end platen. This ensures a complete fit of the hollow-shaft motor in the opening through the end platen and a penetration of the hollow-shaft motor through the end platen.

[0012] According to an advantageous configuration of the invention, the end platen includes a preferably cylindrical recess in which the hollow-shaft motor can move into and/or move through. As a consequence of this improvement of the invention, the structural length of the injection molding machine is reduced in any event by the thickness of the end platen. The recognition to configure the end plate with a cylindrical recess in which the hollow-shaft motor can move into, affords the basic idea of the invention to arrange as many components as possible within one another so that their individual structural lengths do not add up, a high practical value in relation to the realization of the construction and enables a significant shortening of the structural space.

[0013] According to a preferred embodiment of the invention, the spindle is arranged in a rotationally fixed manner. The spindle end, facing the moving platen, is hereby in engagement with the rotor of the hollow-shaft motor, advantageously via a spindle nut, and the stator of the hollow-shaft motor is connected to the toggle mechanism. As the motor runs, it moves axially and operates the toggle mechanism. In contrast thereto, the spindle is stationary and barely projects beyond the outer end of the end platen. This means that the structural length of the injection molding machine is essentially bounded by the end platen. The drawback of prior art injection molding machines with a clamping device driven by a spindle and a hollow-shaft motor which is flange-mounted to the outside of the end platen in accordance with the prior art, to have a structural length which is greater than an injection molding machine with belt drive of the clamping device, is thus eliminated. The direct drive via a hollow-shaft motor and a spindle offers, however, many advantages in comparison with a transmission with toothed belt. This drive is safer in operation than a belt drive, which may fail, when the belt is ripped. The direct drive is service friendlier as a retensioning of the belt is eliminated. Compared to a belt drive, it is subjected to less dust because no dust can be encountered as a result of a belt drive. Moreover, it has a greater efficiency and does not cause rolling noises of the belt. The quality of control is significantly improved compared to a belt drive in which a belt acts as elastic element. As a consequence of the high stiffness of the spindle drive, no hysteresis exists. The drive system is faster because, despite higher mass inertia, the comparably smaller rotation speed enables to reach the target speed faster.

[0014] According to a variation of the invention, the spindle can be guided through the end platen and secured in a rotationally fixed manner in an anchor plate.

[0015] According to an alternative preferred embodiment of the invention, the spindle is arranged in a rotationally fixed manner with the rotor of the hollow-shaft motor and meshes with a spindle nut which is connected in a rotationally fixed manner with the end platen. The stator of the hollow-shaft motor is connected with the toggle mechanism. Compared to the first preferred embodiment of the invention, this has the drawback that the spindle is not rotationally fixed and stationary, but projects beyond the end platen, when the clamping device opens and the hollow-shaft motor moves in the direction of the end platen. Thus, the advantage of a smaller structural length is lessened again. The advantage in relation to the first preferred embodiment of the invention resides, however, in the fact that the hollow shaft can be directly connected with the spindle. As a consequence, the spindle nut, connected to the hollow shaft and engaging the spindle, can be omitted. In view of its great mass and its great diameter, this spindle nut has a significant moment of inertia, and thus constitutes a higher dynamic load in comparison to a rotatable spindle. The decrease of the dynamic load in the embodiment of the invention with rotatable spindle enables a quicker movement of the clamping device. The spindle nut, which is connected in this embodiment in a rotationally fixed manner with the end platen, does not pose great demands as far as balancing is concerned. When especially high-quality injection molding machines are involved, in which the demand of space is secondary while very high dynamics should be realized, this alternative embodiment of the invention is especially advantageous.

[0016] In both preferred embodiments of the invention, the hollow-shaft motor is either flange-mounted directly onto the crosshead or integrated therein, for example, by providing the crosshead with a recess for receiving the hollow-shaft motor. As an alternative, the stator may also be coupled directly to the toggle mechanism via suitable connecting elements. As a consequence of the invention, the reaction moment of the drive and the guidance of the crosshead can be realized by a single cost-efficient construction.

[0017] According to a further preferred embodiment of the invention, the stator of the hollow-shaft motor is connected in a rotationally fixed manner with the end platen. The hollow-shaft motor is hereby preferably installed in the recess of the end platen. The spindle is connected in a rotationally fixed manner with the rotor of the hollow-shaft motor. The arrangement has the advantage of a very small mass moment of inertia and is therefore superbly suited for a quick start-up. As the motor runs, the spindle rotates. Engaging the spindle is a spindle nut which is connected to the toggle mechanism preferably via a crosshead. The rotating spindle moves the spindle nut axially and operates hereby the toggle mechanism. In contrast thereto, the stator of the hollow-shaft motor is stationary and projects barely beyond the outer end of the end platen. This means that the structural length of the injection molding machine is bounded essentially by the end platen.

[0018] Based on a clamping device for an injection molding machine for plastics with a fixed platen and an end platen which is connected with a moving platen via a toggle mechanism, according to a further configuration of the general basic inventive idea to arrange as many components as possible within one another so that their individual axial structural lengths do not add up, it is proposed to provide the end platen with a cylindrical prolongation for rotatable support of a sun wheel of an adjustment device of the end platen. The cylindrical prolongation affords the end platen with added stability. For stability reasons, it is therefore proposed to provide a breached end platen preferably with such a cylindrical prolongation. In the event of a configuration with this cylindrical prolongation, it is suitable to use it as receptacle for a sun wheel of an adjustment device of the end platen. A sun wheel of steel and an end platen of spherulitic cast iron provide a good friction pair for a sliding bearing. Hereby only a minimal need for lubrication is required.

[0019] Based on a clamping device for an injection molding machine for plastics with a fixed platen and an end platen which is connected with a moving platen via a toggle mechanism, wherein a hollow-shaft motor with a stator and a rotor is provided and cooperates with a spindle for operating the toggle mechanism, according to a further configuration of the general basic inventive idea to arrange as many components as possible within one another so that their individual axial structural lengths do not add up, it is proposed that a spindle nut can be placed in the inner dimensions of the rotor of the hollow-shaft motor. This constructive configuration has the advantage that the entire structural length of the clamping device according to the invention is shortened by the axial length of the spindle nut, as opposed to those of the prior art.

[0020] According to an advantageous configuration of the invention, the spindle nut is fixedly connected with the rotor of the hollow-shaft motor. This is preferably implemented in the embodiments of the clamping device with axially movable hollow-shaft motor which is connected with the toggle mechanism. This embodiment has the advantage of a particularly short axial structural length of the clamping device.

[0021] According to an alternative advantageous embodiment of the invention, the spindle nut can move into the interior space of the rotor of the hollow-shaft motor. This technique finds preferably application in the configuration of the clamping device in which the stator of the hollow-shaft motor is connected in a rotationally fixed manner with the end platen and the spindle nut is connected in a rotationally fixed manner with the toggle mechanism. The spindle is here connected in a rotationally fixed manner with the rotor of the hollow-shaft motor. This arrangement has the advantage of a very slight mass moment of inertia as the spindle nut does not rotate, and is therefore superbly suitable for a quick start-up. The rotating spindle moves the spindle nut axially and operates thereby the toggle mechanism. When the clamping device is completely opened, i.e. the toggle levers are drawn completely in the direction of the end platen, the spindle nut plunges into the hollow-shaft motor. The entire structural length of the clamping device according to the invention is shortened in this embodiment by the axial depth of penetration in comparison to those of the prior art.

[0022] Preferably, the configurations of the general basic inventive ides to arrange as many components as possible within one another so that their individual axial structural lengths do not add up, are combined. As a result, a clamping device is implemented in which the spindle nut can be received in the inner dimensions of the rotor of the hollow-shaft motor, and the hollow-shaft motor can be received in a recess of the end platen. Thus, the spindle nut, the hollow-shaft motor and the end platen can nest within one another, when the clamping device is open.

[0023] Exemplified embodiments of the invention are shown in the drawings, in which:

[0024] FIG. 1 shows a cross section of a clamping device according to the invention,

[0025] FIG. 2 shows a variation of the clamping device according to the invention of FIG. 1 with rotatable spindle,

[0026] FIG. 3 shows a variation of the clamping device according to the invention of FIG. 2 with rotatable spindle in which the hollow-shaft motor is received in a cylindrical recess of the end platen.

[0027] An example of the invention is illustrated in the attached FIG. 1. Arranged on a machine bed 16 is a fixed platen 11, whereby a movable platen 12 is able to move axially relative to the fixed platen by a toggle mechanism 13. The fixed platen 11 is connected via the machine bed 16 with an end platen 19. A spindle 21 is guided with its end distal to the moving platen 12 through the end platen 19 and is arranged in a rotationally fixed manner in an anchor plate 3. Arranged on the other end of the spindle 21 is a hollow-shaft motor 7 which is axially movable on guide bars which are arranged on both sides of the spindle 21 and fixed in the end platen 19 so that they are invisible in FIG. 1. A spindle nut 5 is coupled with the hollow shaft or the rotor 6 of the hollow-shaft motor 7 and is in engagement with the spindle 21. The stator 4 of the hollow-shaft motor 7 is flange-mounted to the toggle mechanism 13. In this way, the functions of the crosshead and of the drive motor are united.

[0028] FIG. 2 shows an alternative embodiment of the invention in which the spindle 21 is connected in a rotationally fixed manner with the rotor 6 and meshes with a nut 22 which is connected in a rotationally fixed manner to the end platen 19. The stator 4 of the hollow-shaft motor 7 is connected to the toggle mechanism 13. The spindle 21 and thus the hollow-shaft motor 7 moves axially as the rotor rotates. The clamping device is opened and closed, respectively, via the toggle mechanism 13. When the clamping device opens, whereby the hollow-shaft motor 7 moves in the direction of the end platen 19, the spindle 21 projects beyond the end platen 19.

[0029] FIG. 3 shows a further variation of the clamping device according to the invention. The hollow-shaft motor 7 is hereby received in a recess of the end platen 19. The stator 4 of the hollow-shaft motor 7 is hereby connected in a rotationally fixed manner with the end platen 19. The rotor 6 of the hollow-shaft motor 7 is connected in a rotationally fixed manner with the spindle 21. The spindle 21 meshes with a spindle nut 23 which is connected in a rotationally fixed manner with the toggle mechanism 13. Depending on the rotation direction of the motor, the spindle nut 23 moves in closing or opening direction of the clamping device. The clamping device is opened by fully moving the spindle nut 23 back in the direction of the hollow-shaft motor 7. Finally, the spindle nut 23 plunges into the hollow-shaft motor 7. The interior space of the rotor 6 of the hollow-shaft motor 7 is so configured that the spindle nut 23 can move into it. This arrangement has the advantage of a very slight mass moment of inertia as the spindle 23 does not rotate, and is therefore superbly suitable for a quick start-up. When the clamping device is open, the spindle nut 23, the hollow-shaft motor 7 and the end platen 19 are nested within one another.

[0030] Position List

[0031] Injection Molding Machine

11 fixed platen
12 moving platen
13 toggle mechanism
16 machine bed
19 end platen
22 spindle nut

[0032] Drive

4  stator of the hollow-shaft motor
5  spindle nut
6  rotor of the hollow-shaft motor
7  hollow-shaft motor
21 spindle
23 spindle nut

Claims

1. Clamping device for an injection molding machine for plastics, comprising a fixed paten (11) and an end platen (19), which is connected via a toggle mechanism with a moving platen (12), wherein a hollow-shaft motor (7) with a stator (4) and a rotor (6) interacts with a spindle (21) for operating the toggle mechanism (13), characterized in that the hollow-shaft motor (7) can be received movably or fixedly in a recess of the end platen (19).

2. Clamping device according to claim 1, characterized in that the recess of the end platen (19) is configured as opening through the end platen (19).

3. Clamping device according to claim 1 or 2, characterized in that the hollow-shaft motor (7) extends through the end platen (19).

4. Clamping device according to one of the preceding claims, characterized in that the end platen (19) has a back wall with a recess in which the hollow-shaft motor (7) can be received movably or fixedly.

5. Clamping device according to one of the preceding claims, characterized in that the greatest diameter of the hollow-shaft motor (7) is smaller than the smallest inner diameter of the opening through the end platen (19).

6. Clamping device according to one of the preceding claims, characterized in that the hollow-shaft motor (7) can move in and/or move through the recess of the end platen (19).

7. Clamping device according to one of the preceding claims, characterized in that the spindle (21) is arranged in a rotationally fixed manner, that the end of the spindle (21), facing the moving platen (12), is in engagement with the rotor (6) of the hollow-shaft motor (7), and that the stator (4) of the hollow-shaft motor is connected with the toggle mechanism (13).

8. Clamping device according to one of the preceding claims, characterized in that the spindle (21) is guided through an end platen (19) and secured in a rotationally fixed manner in an anchor plate (3).

9. Clamping device according to one of the claims, 1-6 characterized in that the spindle (21) is connected in a rotationally fixed manner with the rotor (6) of the hollow-shaft motor (7) and meshes with a spindle nut (22) which is connected in a rotationally fixed manner with the end platen (19), and that the stator (4) of the hollow-shaft motor (7) is connected with the toggle mechanism (13).

10. Clamping device according to one of the preceding claims, characterized in that the toggle mechanism (13) is coupled to a crosshead, and that the hollow-shaft motor (7) is flange-mounted to the crosshead.

11. Clamping device according to one of the claims 1-6, characterized in that the toggle mechanism (13) is coupled to a crosshead, and that the crosshead has a recess for receiving the hollow-shaft motor (7).

12. Clamping device according to one of the claims 1-9, characterized in that the toggle mechanism (13) is coupled directly to the stator (4) of the hollow-shaft motor (7).

13. Clamping device according to claim 12, characterized in that the stator (4) of the hollow-shaft motor (7) is movably supported on laterally arranged guides.

14. Clamping device according to claim 12 or 13, characterized in that the moving platen (12) is movably guided on several columns, and that the stator (4) of the hollow-shaft motor (7) is movably guided on one or more of these columns.

15. Clamping device according to one of the claims 1-4, characterized in that the stator (4) of the hollow-shaft motor (7) is connected in a rotationally fixed manner with the end platen (19).

16. Clamping device for an injection molding machine for plastics, comprising a fixed paten (11) and an end platen (19), which is connected via a toggle mechanism with a moving platen (12), characterized in that the end platen (19) has a cylindrical prolongation for rotatable support of a sun wheel of an adjustment device of the end platen (19).

17. Clamping device for an injection molding machine for plastics, comprising a fixed paten (11) and an end platen (19), which is connected via a toggle mechanism with a moving platen (12), wherein a hollow-shaft motor (7) with a stator (4) and a rotor (6) interacts with a spindle (21) for operating the toggle mechanism (13), characterized in that a spindle nut (5, 23) can be received in the inner dimensions of the rotor (6) of the hollow-shaft motor (7).

18. Clamping device according to claim 17, characterized in that the spindle nut (5) is fixedly connected with the rotor (6) of the hollow-shaft motor (7).

19. Clamping device according to claim 17, characterized in that the spindle nut (23) can move into the interior space of the rotor (6) of the hollow-shaft motor (7).

20. Clamping device according to one of the claims 17-19, characterized in that the hollow-shaft motor (7) can be received in a recess of the end platen (19).