CA2918826A1

CA2918826A1 - Injection moulding machine having a locking unit

Info

Publication number: CA2918826A1
Application number: CA2918826A
Authority: CA
Inventors: Peter Kobel; Uwe Hanke; Rudolf Neumann
Original assignee: Sumitomo SHI Demag Plastics Machinery GmbH
Current assignee: Sumitomo SHI Demag Plastics Machinery GmbH
Priority date: 2013-07-22
Filing date: 2014-07-21
Publication date: 2015-01-29
Also published as: EP3024628A1; JP3221256U; EP3024628B1; DE102013214244B3; WO2015011102A1; JP2016525033A

Abstract

The invention relates to an injection molding machine comprising a movable die mounting plate (6), a fixed die mounting plate (2), a fixed support plate (5), and a locking unit (7) having a drive element (9), preferably driven parallel to the feeding direction (Z) of the movable mounting plate (6), for initiating an actuating force in the locking unit (7), and having a control arm assembly (12) connected to the drive element (9) in a jointed manner between the support plate (5) and the movable mounting plate (6) and a design of the control arm assembly (12) having three control arms (13, 14, 15) coupled in a jointed manner, namely auxiliary control arm (13), central control arm (14) and output control arm (15) between the central control arm (14) and the movable mounting plate (6), such that the jointed axle (18) between the central (14) and output control arm (15) runs on a non-circular movement track (B), and that, in a closed position of the movable mounting plate (6), the four jointed axles (16, 17, 18, 19) of the control arm assembly (12) formed between the support plate (5), the control arms (13, 14, 15) and the movable mounting plate (6) lie on a straight line (G) which stands perpendicular on a turning point tangent (T) on the movement track (B) of the jointed axle (18) between the central (14) and output control arm (15).

Description

Injection moulding machine having a locking unit The contents of the German patent application 10 2013 214 244.7 is incor-porated herein by way of reference.
The invention relates to an injection moulding machine having the features which are stated in the preamble of Patent Claim 1.
These features represent the fundamental components of injection moulding machines in terms of their movable and fixed moulding platens, a fixed support plate, and a clamping unit for applying the movable moulding platen, such as have been known for a long time from various documents relating to the prior art. Examples of such documents include DE 25 36 880 Al, DE 43 28 844 C2, DE 199 57 485 Al, DE 103 42 012 Al, EP 0 511 170 Bl, or EP 0 775 567 Al. The clamping units of these injection moulding machines have in common that a drive element, for example in the form of a cross head on a spindle drive, which for introducing an actuation force into the clamping unit is driven parallel with the infeed direction of the movable platen in the direction of the fixed platen is provided. The linkage assembly between the support plate and the movable platen, which for transmitting the movement of the drive element to the movable platen in the context of an infeed of the movable platen relative to the fixed platen is connected in an articulated manner to the drive element and in these previously known clamping units is formed by a typical bell-crank lever assembly which has two control arms between the support plate and the movable platen and is complemented by a third control arm to the drive element.

- 2 -Previously known clamping units of this type of an injection moulding machine thus fulfil the primary task of opening and clamping the mould and closing the same while plastics material is injected into the cavity of the mould. On account of the force of the clamping unit being geared, it is possible for a high clamping force to be generated by a comparatively low driving force, this being implemented by employing a bell-crank lever construction, for example also as a double bell-crank lever in the form of four-point or five-point bell-crank levers, such as disclosed in US 5,971,743. Both the high gearing of the force for building up the clamping force as well as closing the mould are ensured by utilizing a reversed state of the bell-crank lever assembly.
This fundamental bell-crank lever concept is also utilized in constructions which somewhat deviate from the above, for example in the double-crank drive for a clamping unit which is disclosed in DE 10 2004 026 450 B4.
These known bell-crank solutions use the reversed state of the movable platen for generating the high clamping forces. It is problematic here that the reversed state cannot be fully utilized. The set-up of the machine is in fact typically performed in such a manner that the operating point lies so as to be shortly prior to or after the reversed state, this in turn limiting the range which is required for building up the closing forces. The gearing of force which is theoretically possible thus cannot be achieved.
A further disadvantage of these previously known bell-crank lever solutions lies in that the movable platen by nature can only be moved out of the reversed state in one direction, namely in the opening direction. This compromises the suitability of such a clamping unit for performing a so-called embossing function in which a further infeed movement in the

- 3 -clamping direction takes place after the mould has assumed the clamping position, so as to perform an embossing step on the plastics material which has been injected into the cavity.
Proceeding from the problems of the prior art which have been discussed, the invention is based on the object of providing an injection moulding machine having an improved clamping unit with the aid of which a high gearing of force for generating high clamping forces during a continuous output movement is enabled. Such a continuous output movement is to be understood to mean that the movable platen may be moved out of the range of high gearing of force, that is to say in practical terms in the closing position, in two directions. The closing position is thus no longer to be connected with a reversed state of a usual bell-crank lever assembly.
The object mentioned above is achieved by the features stated in the char-acterizing part of Claim 1, wherein the linkage assembly comprises three control arms which are coupled in an articulated manner, namely an auxil-iary control arm which is articulated on the support plate, a central control arm which is articulated on said auxiliary control arm and which is coupled to the drive element, and an output control arm interdisposed between the central control arm and the movable platen. The control arms here are in-tercoupled in such a manner that the articulation axis between the central control arm and the output control arm runs on a non-circular motion path, wherein in a closing position of the movable platen the four articulation axes of this linkage assembly lie on a straight line which is perpendicular on a reversal point tangent at the motion path of the articulation axis be-tween the central control arm and the output control arm.

- 4 -In other words, the motion path of the articulation axis between the central control arm and the output control arm thus has a reversal point at which the articulation axis precisely lies when the closing position of the clamping unit is assumed. On account of the reversal point the articulation axis between the central control arm and the output control arm, driven by the drive element, may thus be moved both further in the infeed direction, for example for carrying out an embossing step, and counter to the infeed direction, for opening the mould. By aligning the four articulation axes on a straight line the usual self-locking of the gear assembly is nevertheless achieved in an analogous manner to the dead-centre state of a bell-crank lever. The clamping unit is thus located in a position of maximum gearing of force, whereupon an embossing stroke onto the fixed platen may be subsequently implemented from this position.
In summary, an optimal compromise between a high gearing of force in the self-locking closing position and the potential for carrying out an embossing stroke which leads further in the infeed direction from this position is achieved by a targeted design of the motion path of the articulation axis between the central control arm and the output control arm.
One preferred design of the motion path in the infeed direction provides an infeed branch which is substantially linear and runs in an oblique manner to the infeed, a reversal point branch including the reversal point of the motion path, and, adjoining thereto, an embossing branch which runs further in the infeed direction.
The infeed branch and the embossing branch of the motion path may be advantageously oriented such that gearing between the movement of the

- 5 -drive element and the movable platen which is preferably significantly higher than in the embossing branch takes place when the infeed branch is passed. In this way, rapid movement of the movable platen may be achieved during infeed, while a high embossing force may be achieved during embossing.
According to a further preferred embodiment of the invention, in the closing position the auxiliary control arm is oriented in a direction which points away from the movable platen in such a manner that the auxiliary control arm and the central control arm in this closing position are at least partially superimposed. In this way, a compact construction of the clamping mechanism is achieved.
The same purpose is also served by the further preferred design embodiment of the invention, according to which the length of the auxiliary control arm at maximum corresponds to half the length of the central control arm or of the output control arm. Incidentally, this shaping is also influenced by the motion path of the articulation axis that is to be achieved between the central control arm and the output control arm.
Advantageously, the articulation axis between the output control arm and the movable platen in the closing position may be located in the centre of curvature of the motion path of the articulation axis between the central control arm and the output control arm. In this way, the quality of the gearing of force as may be achieved by the clamping unit according to the invention may be significantly increased. On account thereof, the range of high gearing of force prior to and after the operating point of the clamping unit in the closing position is extended.

- 6 -As is known per se from the prior art, two or more mutually corresponding linkage assemblies may be provided so as to be mirror-symmetrical in relation to the drive axis plane of the drive element and may be coupled to the latter. The infeed direction of the movable platen and thus the orientation of the clamping unit may be horizontally or vertically oriented.
The invention is thus equally suitable for a horizontal and for a vertical embodiment of an injection moulding machine.
Preferred alternatives for the actuation of the drive element are provided by a pneumatic or hydraulic piston-and-cylinder drive, a spindle drive, a rack-and-pinion drive, or a linear motor.
Further features, details, and advantages of the invention are derived from the following description of an exemplary embodiment by means of the appended drawings, in which:
Figs. 1 to 3 show schematic partial side views of an injection moulding machine in various operating positions of the movable moulding platen and of the clamping unit, Fig. 4 shows the injection moulding machine in a view which is horizontally split in two and combines the injection moulding machine of Figs. 2 and 3, in the closing position (bottom) and the embossing position (top) of the movable platen,

- 7 -Fig. 5 shows a partially sectional partial side view of a constructive embodiment of an injection moulding machine in the completely opened position of the movable platen and clamping unit, in an analogous manner to Fig. 1, Fig. 6 shows a partial plan view of the injection moulding machine according to Fig. 5, Fig. 7 shows a view which is analogous to Fig. 5, in the closing position of the movable platen and clamping unit, corresponding to Fig. 2, Fig. 8 shows a view which is analogous to Fig. 5, in a further applied embossing position of the movable platen, corresponding to Fig. 3, Fig. 9 shows a view which is horizontally split in two and combines the clamping unit in the closing position (top) and embossing position (bottom), corresponding to Fig. 4, and Fig. 10 shows a partial plan view in an illustration of the clamping unit in the closing position (top) and the

- 8 -embossing position (bottom), respectively, which is split in two in an analogous manner to Fig. 9.
The in-principle construction of the injection moulding machine which in these illustrations is shown in details and in only a highly schematic manner is to be explained by means of Figs. 1 to 4. The usual injection unit 1 of the injection moulding machine, which externally is attached to the fixed moulding platen 2 by way of a usual nozzle connector 3, is only indicated in a minimalistic manner. A fixed support plate 5 is attached to the fixed platen 2 by way of four parallel spars 4 which are arranged in a quadrangular manner. A movable moulding platen 6 is finally guided on these spars 4, so as to be displaceable in the infeed direction Z, so that a mould, which is not illustrated in detail in Figs. 1 to 4, having a corresponding cavity between two mould halves may be opened and clamped and optionally may be subjected to an embossing step.
The clamping unit which in its entirety is referred to as 7, and which has a spindle drive 8 for a cross head 9 guided thereon as a drive element for introducing an actuation force into the clamping unit 7, serves for driving the movable platen 6. The spindle drive 8 is driven by an electric motor 10 on the fixed support plate 5.
In order for the indexing movement of the cross head 9 to be transmitted to the movable platen 6 in and counter to the infeed direction Z, a linkage assembly 12 is provided so as to be present in duplicate on the top and on the bottom between said platen 6, the cross head 9, and the mounting stays 11 which in the infeed direction Z project from the fixed platen 5. In the following, only that linkage assembly 12 that with reference to Figs. 1 to 4 lies on top will be explained in more detail. The linkage assembly 12 lying

- 9 -on the bottom is constructed so as to be mirror-symmetrical in relation to the horizontal drive axis plane A.
The linkage assembly 12 is assembled from three control arms which are strung together and coupled in an articulated manner, namely an auxiliary control arm 13 which is articulated on the free end of the mounting stay 11 on the support plate 5, and a central control arm 14 which in turn is articulated on said auxiliary control arm 13 and which is also articulated in an articulated manner on the cross head 9 as the drive element.
Furthermore, an output control arm 15 is attached in an articulated manner to the central control arm 14 and the movable platen 6. The corresponding articulation axes are identified with the reference signs 16 for the articulation of the support plate 5 and the auxiliary control arm 13, or articulation axis 17 for the articulation of the auxiliary control arm 13 and the central control arm 14, or articulation axis 18 for the articulation of the central control arm 14 and the output control arm 15, or articulation axis 19 for the articulation of the output control arm 15 and the movable platen 6, or articulation axis 20 for the articulation of the central control arm 14 and the cross head 9, respectively.
The movement of the articulation axis 18 between the central control arm 14 and the output control arm 15, which runs on a non-circular motion path B which is illustrated in Figs. 1 to 4, is important for the functioning of the clamping unit 7. Said motion path B is divided into three branches, namely an infeed branch BZ which in Figs. 1 to 4 is illustrated with short dashed lines and which runs in a substantially linear and oblique manner with respect to the infeed direction Z. A reversal point branch BW is continuing after this infeed branch BZ, in the course of which a reversal point WP is defined. The curvature between the infeed branch BZ and the reversal point

- 10 -WP is slightly lower as as the curvature between the reversal point WP and the embossing branch BP following the reversal point branch BW which in Figs. 1 to 4 is illustrated with long dashed lines and which runs substantially parallel with the infeed direction Z
The linkage assembly 12 having the auxiliary, central, and output control arms 13, 14, 15, respectively, in interaction with the attachment to the cross head 9 is conceived such that in the closing position of the movable platen 6 illustrated in Fig. 2 the four articulation axes 16, 17, 18, 19 of the linkage assembly 12 lie on a straight line G which is perpendicular on the tangent T
in the reversal point WP on the motion path B. On account of this conception of the linkage assembly 12 having the corresponding motion path B, the highest gearing of force between the cross head 9 and the movable platen 6 is achieved in the range of this closing position. On account of the arrangement of the four articulation axes 16 to 19 on the straight line G, the clamping unit 7 at the same time is self-locking in this closing position, so that high closing forces on the mould are achieved between the fixed platen 2 and the movable platen 6.
On account of the conception of the motion path B having the reversal point WP the clamping unit 7 may be driven back from the closing position shown in Fig. 2, on the one hand, in that the cross head 9 is again moved counter to the infeed direction Z and is thus displaced in the direction of the open position of the movable platen 6, which is shown in Fig. 1. On the other hand, as opposed to a usual bell-crank lever assembly being moved from the dead-centre position, the movable platen 6 is moved further in the infeed direction Z on the embossing branch BP by a counter-movement of the cross head 9 in the infeed direction Z. On account of the orientation of the embossing branch BP, a slight gearing of the path and a high

11 -embossing force to the movable platen 6 is derived here from the movement of the cross head 9. The clamping unit 7 shown is thus indeed particularly well suited to so-called injection embossing.
Constructive measures for the conception of the motion path B, which are to be briefly explained in the following, are provided in a supporting manner in the region of the linkage assembly 12. The auxiliary control arm 13 during the movement of the clamping unit 7 between the open position according to Fig. 1 and the closing position according to Fig. 2 thus is directed against the infeed direction Z and parallel to same. The main transmission of the movement of the cross head 9 in this case is achieved by the pivoting of the central control arm 14 around the articulation axis 7 during a slight evasion movement of the auxiliary control arm 13 and an according stretching of the central control arm relative to the output control arm 15. In the closing position according to Fig. 2, the auxiliary control arm 13 is then disposed on the straight line G so as to be collinear with the output control arm 15 and the central control arm 14 in relation to the articulation axes 16 to 19, however, points from the articulation axis 16 counter to the infeed direction Z. The auxiliary control arms 13 has a length, which accords half of the length of the central control arm 14 and the output control arm 15 at maximum. The auxiliary control arm 13 and the central control arm 14 are partially mutually overlapping.
It has to be noted with reference to the articulation axis 19 between the output control arm 15 and the movable platen 6 that the former in the closing position according to Fig. 2, respectively, is located in the centre of curvature of the motion path B. This promotes the quality of the gearing of force from the cross head 9 via the linkage assemblies 12 to the movable platen 6.

- 12 -In summary, the clamping unit 7 in comparison with the known bell-crank lever embodiments is distinguished in that the mould in the closing position is closed in an intermediate position of the linkage assembly 12. It is consequently possible for the movable platen 6 to be moved from this closing position for the clamped mould according to Fig. 2, respectively, in which the mechanism is self-locking, by way of an onward movement of the cross head 9 in the infeed direction Z further towards the fixed platen 2, as is illustrated in Figs. 3 and is particularly evident from Fig. 5. There, the assembly is shown in the closing position at the bottom and the assembly in a further converged embossing position at the top. The articulation axis 18 here runs on the motion path B beyond the reversal point WP into the embossing branch BP, a very high gearing of force being still present in particular at the commencement of the onward movement out of the reversal point WP.
If the previously described embossing function is not to be performed, the cross head 9 is returned, as has already been indicated above, and the linkage assembly 12 is moved from the closing position shown in Fig. 2, respectively, in the direction of the open position shown in Fig. 1, respectively. In this way, a usual injection moulding operation may also be performed using the clamping unit 7. To this extent, the construction is universally employable.
A constructive embodiment of the clamping unit 7 which is schematically illustrated in Figs. 1 to 4 is shown in Figs. 5 to 10. Corresponding components here are provided with identical reference signs and need not be listed individually again. It has to be merely highlighted with reference to Figs. 6 and 10 in particular that the upper and lower linkage assemblies 12 have in each case mounting stays 11 which in relation to the central

- 13 -plane M are present in pairs and have auxiliary control arms 13 articulated thereto in pairs and a common solid central control arm 14. Mounting appendages 21, 22, 23 (Fig. 10) are moulded to the latter in the centre and externally on both sides in front thereof, between which the output control arms 15, which are again fitted in pairs, are coupled while configuring the articulation axis 18. The articulation axis 19 between these pairs of output control arms 15 and the movable platen 6 is again formed by three mounting appendages 24, 25, 26 (Fig. 10) which are fitted thereto and between which the pairs of output control arms 15 are in each case rotatably mounted.

Claims

1. Injection moulding machine comprising:
- a movable moulding platen (6), - a fixed moulding platen (2), - a fixed support plate (5), and - a clamping unit (7) having = a drive element (9) which is preferably driven parallel with the infeed direction (Z) of the movable platen (6) in order to introduce an actuating force into the clamping unit (7), and = a linkage assembly (12) between the support plate (5) and the movable platen (6), which, for transmitting the movement of the drive element (9) to the movable platen (6) in the context of an infeed movement of the movable platen (6) relative to the fixed platen (2), is connected in an articulated manner to the drive element (9), characterized by - a configuration of the linkage assembly (12) having three control arms (13, 14, 15), comprising = an auxiliary control arm (13) which is articulated on the support plate (5), = a central control arm (14) which is articulated on said auxiliary control arm (13) and is coupled to the drive element (9), and = an output control arm (15) interdisposed between the central control arm (14) and the movable platen (6), and being coupled in an articulated manner such - that the articulation axis (18) between the central control arm (14) and the output control arm (15) runs on a non-circular motion path (B), and

2. that in a closing position of the movable platen (6) the four articulation axes (16, 17, 18, 19) of the linkage assembly (12) which are in each case formed between the support plate (5), the control arms (13, 14, 15), and the movable platen (6) lie on a straight line (G) which is perpendicular on a reversal point tangent (T) on the motion path (B) of the articulation axis (18) between the central control arm (14) and the output control arm (15).
Injection moulding machine according to claim 1, characterized in that the motion path (B) in the infeed direction (Z) has an infeed branch (BZ) which is substantially linear and running obliquely related to the infeed direction (Z), a reversal point branch (BW) continuing to the infeed branch (BZ) and including the reversal point (WP) of the motion path (b), and, adjoining in turn thereto, an embossing branch (BP) which runs further in the infeed direction (Z).

3. Injection moulding machine according to Claim 2, characterized in that the infeed branch (BZ) as compared with the embossing branch (BP) is conceived in such a manner that the gearing ratio between the movement of the drive element (9) and the movable platen (6) is higher in the infeed branch (BZ) than in the embossing branch (BP).

4. Injection moulding machine according to one of the preceding claims, characterized in that in the closing position the auxiliary control arm (13) is oriented in a direction which points away from the movable platen (6) in such a manner that the auxiliary control arm (13) and the central control arm (14) in the closing position are at least partially su-perimposed.

5. Injection moulding machine according to one of the preceding claims, characterized in that the length of the auxiliary control arm (13) at maximum corresponds to half the length of the central control arm (14) or of the output control arm (15).

6. Injection moulding machine according to one of the preceding claims, characterized in that the articulation axis (19) between the output con-trol arm (15) and the movable platen (6) in the closing position is locat-ed in the centre of curvature of the motion path (B).

7. Injection moulding machine according to one of the preceding claims, characterized in that at least two mutually corresponding linkage as-semblies (12) are provided so as to be mirror-symmetrical in relation to the drive axis plane (A) of the drive element (9).

8. Injection moulding machine according to one of the preceding claims, characterized in that the infeed direction (Z) of the movable platen (6) is horizontally or vertically oriented.

9. Injection moulding machine according to one of the preceding claims, characterized in that the drive element is driven by a pneumatic or hydraulic piston-and-cylinder drive, a cross head (9) having a spindle drive (8), a rack-and-pinion drive, or a linear motor.