CA2695641A1

CA2695641A1 - Method for the mould closure of an injection moulding machine and mould closure

Info

Publication number: CA2695641A1
Application number: CA2695641A
Authority: CA
Inventors: Robert Weinmann; Placi Wenzin; Markus Sprecher
Original assignee: Individual
Current assignee: Netstal Maschinen AG
Priority date: 2007-08-13
Filing date: 2008-08-08
Publication date: 2009-02-19
Also published as: WO2009021920A1; AT511639B1; DE112008001581A5; CN101861239A; DE112008001581B4; AT511639A5

Abstract

The invention relates to a method for the mould closure of an injection moulding machine with a support element (1), a movable tool clamping plate (13), 5-point toggle levers and a hydraulic drive (25) for the crosshead (2), in addition a mould closure. The crosshead drive is arranged between the support element (1) and the movable tool clamping plate (13) . The individual 5--point toggle levers are each constructed with a toggle lever (9), a mould movement lever (11, 11') and an expanding bracket (6). The movements for the mould closure are transmitted via expanding brackets (6) to the toggle levers (9). The expanding brackets (6) engage in a central region of the toggle levers (9).
The toggle levers (9) are embodied as articulated forks (20, 21), with the expanding brackets (6) engaging in a crosspiece (22) of the articulated forks. The principal reaction forces from the mould forces are transmitted free of lateral forces and symmetrically onto the support element (1) . The solution allows a maximum pivoting angle for the toggle levers (9), the use of long toggle levers (9) and a maximum opening stroke for the mould halves.

Description

DESCRIPTION
METHOD FOR THE MOULD CLOSURE OF AN INJECTION MOULDING
MACHINE AND MOULD CLOSURE

TECHNICAL FIELD

The invention relates to a method for the mould closure of an injection moulding machine, which has a support element, a movable tool clamping plate, 5-point toggle levers and a hydraulic drive of the crosshead, wherein the crosshead drive is arranged between the support element and the movable tool clamping plate and the movements for the mould closure are transmitted to the toggle levers via expanding brackets.

The invention further relates to a mould closure of an injection moulding machine, which has a support element and a movable tool clamping plate, in addition a hydraulic toggle lever drive arranged between the support element and the tool clamping plate with a crosshead, constructed as 5-point toggle levers with in each case a toggle lever, a mould movement lever and an expanding bracket.

PRIOR ART

Alongside the injection unit and the moulds or respectively the tool, the mould closure is the most important assembly of an injection moulding machine.
The basic requirement for the mould closure is that the mould halves, which in part are very heavy, are brought as quickly as possible with a high acceleration from an open into a closed position and, for removal of the injection-moulded parts, vice versa from the closed position into the open position. The mould halves not only have to be brought with high precision into the injection position, but also held at the high melt pressures of for example 1000 to 2000 bar. For decades, toggle levers and eccentric drives have proved to be successful. These allow the large mould movement to be carried out quickly with a low force and to apply maximum forces for the mould closure in the zero or dead centre position. In the older prior art, the toggle lever mechanism is arranged between the drive support plate or respectively the support element and the movable tool clamping plate, and the drive for the toggle lever mechanism is arranged on the outer side of the drive support plate. Thereby, all the moving parts of the mould closure are readily accessible. The energy supply, whether as hydraulics or as electric current, lies externally and the toggle levers lie with all bearing points internally in the machine. A
disadvantage with this arrangement is, particularly, the length required for the toggle lever drive, which has a direct effect as a corresponding lengthening of the entire machine. The extent of the lengthening can be easily one metre, so that the machine accordingly takes up more base area.

More recently, the toggle lever mechanism is successfully arranged differently together with the toggle lever drive in a compact type of construction between the drive support plate and the movable tool clamping plate. The machine can thereby be constructed so as to be shorter. EP 456 335 shows such a device for the closing of moulds. In this publication, one proceeds from an injection moulding machine with a fixed end plate with a tool clamping plate which is movable via a toggle lever mechanism on rails. Each of the four toggle levers is constructed as a double toggle lever and is arranged between the fixed end plate and the tool clamping plate parallel to the machine main axis. It is proposed, for this, to connect two piston-cylinder units on the one hand with the fixed end plate and on the other hand with a single crosshead in a form-fitting manner with the double toggle levers. The crosshead is embodied as a frame structure. The crosshead is guided, for a movement parallel to the machine main axis, via guide rods which are fastened on the fixed end plate. In addition to this, it is alternatively proposed to mount the crosshead displaceably via guide bearings on at least two rails. The movement sequence of the double toggle levers is defined precisely by the double guidance of the crosshead, apart from tolerance errors of the entire machine construction, possible deformations and bearing clearances. The solution has proved to be successful in practice.

More recently, the requirement of a maximum compactness has come to the forefront for the mould closure.
However, this can involve difficulties in several respects. For example, the movement sequence of the toggle levers alone already constitutes a problem in so far as collisions between the components are to be avoided. GM 200 08144 proceeds from an oil pressure cylinder for the drive of an arm structure of an injection moulding machine. This comprises a first, a second and a third arm, wherein the second and the third arm have several articulated plates and are articulated between several fastening plates of a receiving sheet and a movable mould base. An oil pressure cylinder is fastened in the arm structure, in order to move the arm structure and hence the movable mould base. As an improvement, it is proposed that the second arm has two inner articulated plates which are arranged such that they are spaced apart from each other by a space which is somewhat greater than the external diameter of the oil pressure cylinder, in addition two articulations which connect the two second and the two third arms articulatedly and are spaced apart by a space which is somewhat greater than the external diameter of the oil pressure cylinder. In so doing, the articulations of the second and third arms do not collide with the oil pressure cylinder, which is positioned between the receiving sheet and the movable mould base, when the arm structure is actuated, in order to move forwards and back. In this development, the question of space for an ejector, in particular for an ejector plate, is not solved.

With the application PCT / CH 2006 / 000 548, the applicant has attempted to find a compact, favourably priced solution on the basis of a hydraulic drive, which also solves the space problem for an ejector plate. The following partial aims, in particular, formed the basis for this:

= that a best possible accessibility and use of the space is ensured between the drive support plate and the movable tool clamping plate, in addition = that a minimum number of components is achieved for the toggle lever mechanism and for the toggle lever drive, and a maximum compactness is achieved in the withdrawn position and = that an overdeterminacy of the guides of the crosshead or of the toggle lever mechanism is avoided.

On the basis of theoretical considerations, a solution was found in which the toggle lever drive is to engage centrally on the one hand on the drive support plate and on the other hand on a crosshead of the toggle lever mechanism. In contrast to the previously quoted prior art, the engagement point on the toggle lever was arranged in the vicinity of the support element. In addition, a separate crosshead guide was dispensed with. The result was negative and in fact negative such that already when putting a prototype into operation, the solid support element broke open by inner vertical expansion forces.

REPRESENTATION OF THE INVENTION

The aim was now, on the basis of a hydraulic drive within the framework of a generic mould closure, to seek solutions which solve a maximum compactness of the mould closure, a reliable guidance of forces and also the problem of the space question for an ejector plate in a 5-point toggle lever.

The following lay in particular at the centre of the remit for the new invention:

= the primary levers are to transmit the mould closure forces symmetrically, and = a large pivoting angle a(alpha) of the toggle levers is to be aimed for, and a high acceleration is to be achieved at the start of the closing of the mould.
= The necessary closing force is to be applied with a maximum mould opening stroke.

The method according to the invention is characterized in that the toggle levers are embodied in a fork shape on the side of the toggle lever articulation, and the indivi_dual principal reaction forces (PRF) from the mould forces are transmitted symmetrically and free of lateral forces (LF) via the 5-point toggle levers to the support element, wherein the expanding brackets engage in the central region of the articulated forks of the individual toggle levers.

The mould closure according to the invention is characterized in that the toggle levers are embodied in a fork shape at least in the region of the toggle lever articulation, and the expanding brackets engage via an outer expanding bracket bearing in the central region of the articulated fork.

It was found by the inventors, that with a 5-point toggle lever system arranged inside the support element and the movable tool clamping plate, the actual toggle lever is the neuralgic element. With the fork-shaped development of the toggle lever articulation and the mounting of the expanding brackets in the cross-piece of the articulated fork, a whole number of advantages are produced:

- The reaction forces from the melt pressures in the mould cavities can be transmitted symmetrically to the support element.
- The fork shape allows an optimum use of space for the entire 5-point toggle lever system.
- The fork shape is, in itself, resistant to bending, and lateral forces are avoided.
- A longer engagement of the expanding brackets is produced.
- Uncontrolled expanding forces can be at least very greatly reduced.
- The solution allows an optimum use of a "short"
and "thick" hydraulic cylinder. This is with sufficient or respectively maximum driving force.
- In particular, with the new invention, the initial position, for example for a compactness of the mould closure which was not hitherto reached, was able to be created in withdrawn position, and a maximum length of stroke for the movable mould clamping plate, ~ without the question of space for an ejector plate being negatively affected.

The new invention allows a whole number of particularly advantageous developments. Reference is made, in this respect, to Claims 2 to 6 and also 8 to 17.

Quite particularly preferably, each toggle lever is constructed in one piece.

Advantageously, the crosshead is constructed in a cross shape with two vertical and two horizontal arms. The expanding bracket is connected to the upper and lower crosshead arms via corresponding crosshead articulations. The crosshead arms lying horizontally are held in each case in a longitudinal guide fastened on the support element. It has been found that the expanding forces are substantially reduced compared with the applicant's preceding solution. The longitudinal guide of the crosshead proved to be advantageous.

According to a further development, the principal reaction forces from the melt pressures in the mould are transmitted free of lateral forces via the toggle levers and the mould movement levers. The more recent development has shown that any unsymmetrical application of force on the movable tool clamping plate or respectively on the tool has the effect of a fault on the injection moulded parts, as is to be expected according to DE GM 200 8144.

A quite particularly advantageous development idea lies in that the crosshead together with the toggle lever and the expanding bracket and the toggle lever drive, after withdrawal or respectively with the opened mould, is sunk fully into a box-like cavity of the support element. This allows a maximum possible compactness for the mould closure and hence also for the entire machine.

A further advantageous development lies in that the mould plate articulations in relation to a central axis M-M of the injection moulding machine are spaced approximately equally and symmetrically (A') as the inner expanding bracket bearings (A), wherein with extended toggle levers the closing forces are introduced in a region of the mould plate which is approximately half as high as the corresponding distance of the upper and lower support articulations on the side of the support element. It has been found that with regard to the maximum maintaining of dimensional accuracy of the tool, this is the best solution.

In the case of an electromotive drive, for reasons of cost as small a motor as possible is aimed for, so that a sufficient mould closing force can be applied with a smaller torque. In the case of a hydraulic cylinder, the situation is completely different. Here, with good economy, a short, thick cylinder can be selected, so that the necessary force can be applied through a correspondingly greater piston area. It is proposed that the hydraulic toggle lever drive is connected on the one hand with the support element and on the other hand engages on the crosshead, with the hydraulic cylinder projecting on both sides on the crosshead and with the effective length of the hydraulic cylinder preferably corresponding to approximately 4 to 5 times the diameter of the hydraulic cylinder.

The support element has a box shape which is open in the direction of the movable tool clamping plate. In addition, the support element has laterally in each case a vertical support which are arranged so that they form a shared plane together with the upper and lower wall parts of the support element. The forces resulting from the mould closure onto the support element can thus be closed in the manner of a frame on the shortest distance.

Advantageously, each of the toggle levers is constructed as a cast body in a single piece and on each end side with an articulated fork, for engagement on the bearing sites of the support articulation or respectively of the mould movement lever. The expanding brackets engage on the one hand on the inner expanding bracket bearing and on the other hand on the outer expanding bracket bearing. The expanding brackets are each arranged between the articulated forks, but spaced apart from the hydraulic cylinder, and are preferably mounted so as to be movable rotatably on a shared bearing pin for a symmetrical application of force in relation to the central axis M-M of the injection moulding machine.

A further advantageous development idea lies in that the hydraulic cylinder of the hydraulic drive projects over the crosshead on both sides on the crosshead in the direction of movement. Preferably, the hydraulic cylinder projects on the support element side approximately one quarter, and on the opposite side approximately one half. The hydraulic cylinder is preferably integrated in one piece in the crosshead.
The support element forms an open cavity in the direction of the movable tool clamping plate, with the cavity being constructed in similar shape, corresponding to the outer shape of the crosshead, together with the toggle lever, the expanding bracket and the toggle lever drive in fully withdrawn position.

In the case of a hydraulic drive, the drives for an ejector plate are arranged at a distance above and below the hydraulic cylinder and in a shared vertical plane.

BRIEF DESCRIPTION OF THE INVENTION

The invention is now explained with the aid of some examples with further details, in which:

Figure 1 shows diagrammatically a cut-out of the mould closure side with a 5-point toggle lever;
Figure 2a shows a cut-out of Figure 1 concerning the articulation of the crosshead onto the toggle lever in extended position;
Figure 2b shows the toggle levers in fully withdrawn position or respectively with open mould halves;
Figure 3a shows a single-piece toggle lever with the articulation site for the expanding bracket;
Figure 3b shows a section III-III of Figure 3a;
Figure 4 shows the mould closure side more precisely, with almost extended toggle lever system;
Figure 5 shows a top view from above onto the toggle lever articulations according to arrow V of Figure 6;
Figure 6 shows a section VI-VI of Figure 5;
Figure 7 shows an injection moulding machine without the injection side in perspective illustration;
Figure 8 shows in the manner of an exploded drawing on the left the support element and on the right, "broken out", the toggle lever system in withdrawn position;

Figure 9 shows the support element in modular construction with on both sides in each case a vertical support.

WAYS AND EMBODIMENT OF THE INVENTION
Reference is made in the following to Figure 1. This shows diagrammatically the main elements of the mould closure side with a 5-point toggle lever. On the left in the drawing is a support element 1 on which the drives for a mould height adjustment 26 (Figure 7) and the crosshead drive are articulated. In the crosshead 2, a hydraulic cylinder 3 or respectively a hydraulic drive 25 is integrated, the piston rod 4 of which is articulated on the outer side of the support element 1.
The crosshead 2 has two vertically arranged projections 5, 5, on which the expanding brackets 6 are arranged via an inner expanding bracket bearing 7. The expanding brackets engage on the toggle lever 9 via an outer expanding bracket bearing B. On the left, the toggle lever 9 is articulated on articulation sites 18 of the support element 1 via support articulation axes 15. On the opposite side, the toggle lever 9 is connected via a toggle lever articulation 10 with a mould movement lever 11. On the right-hand side of the drawing, the latter is connected via mould plate articulations 12 with the movable tool clamping plate 13. An ejector plate 14 is only indicated. KM is the central axis of the toggle lever 9 (Figures 2 and 3).

Figure 2a is a cut-out, somewhat enlarged, of Figure 1, with the articulation of the crosshead 2 onto a toggle lever 9. The position drawn in the region of the toggle lever central axis KM and in a central region KMB
(Figure 3a) was determined as a practical best placing of the spreading bracket bearing. This placing is surprisingly advantageous in so far as not only the hitherto mentioned aims were able to be optimally achieved, but that this is, moreover, also optimum with regard to the structural development of the toggle lever 9 as an element in a single piece. The maximum possible pivoting angle for the toggle lever 9 is designated by a (alpha).

Figure 2b shows the 5-point toggle lever in withdrawn position, corresponding to opened moulds.

In accordance with Figures 3a and 3b, the toggle lever 9 has on both sides in each case an articulated fork 20, 21, which are connected in the central region by a solid crosspiece 22 to a single-piece element. The articulation site for the expanding brackets 6 forms an articulation pin 23. The illustrated development is optimized with regard to the lever movements, in particular in the withdrawn position, for a maximum pivot angle a of the toggle levers and also for long toggle levers. The toggle lever length is designated by KL.

Further elements of the mould closure side can be seen from Figure 4 in an actual structural development. It is clear from Figure 4 that the space problem for the ejector arrangement 30 is solved efficiently. The stroke Hu-K for the crosshead 2 is approximately equal in size to the stroke Hu-A of the ejector plate 14. The two drive cylinders 31, 31' lie vertically over the hydraulic cylinder 3. The three cylinders do not interfere with each other in the mould closure movements. The piston rod 4 is mounted outside the support element 1 in a solid bearing 32. The support element 1 can be merely supported on the underframe 33 or fastened thereon. The tool clamping plate 13 moves within the toggle lever activation. A further interesting aspect lies in that the inner expanding bracket bearing 7 has approximately the same distance A
from the machine central axis M-M as the mould plate articulations 12 (A') (Figure 1).

Figure 5 shows a plan view over the region of the 5-point toggle lever system and Figure 6 shows a top view according to arrows VI-VI of Figure 5. The toggle levers 9, 9' are illustrated on the left in the drawing of Figure 5, and the two mould movement levers 11, 11' are illustrated on the right. The crosshead has two vertical and two horizontal arms 5, 5' and respectively 40, 40', as can be seen from Figure 6. On both sides, the horizontal arms 40, 40' are held in longitudinal guides 41. In Figure 5, it can be seen that the inner measurement B between the expanding brackets 6, 6' is somewhat greater than the external dimensions C of the hydraulic cylinder 3. The movement of the 5-point articulated lever is thereby in no way disturbed.

Figure 7 shows in perspective the entire mould closure side. The sliding bearing of the movable tool clamping plate 13 is designated by reference number 34, the sliding track by reference number 35, and the rails by reference number 36. The maximum compactness of the entire mould closure can be seen from Figure 7.

With the exploded illustration according to Figure 8, the optimum adaptation of the inner contour of the support element 1 and of the outer contour of the toggle lever system is illustrated, corresponding to the dot-and-dash line 16.

Figure 9 shows a preferred development of the support element 1. This has a box shape which is open in the direction of the 5-point toggle lever. The support articulation axes 15 are indicated above and below. In the extended position of the toggle levers, expanding forces Sp act on the support element 1. These are absorbed directly according to the two arrows 28 via the vertical supports 24. The vertical supports 24 also serve as bearing sites 37 for the two longitudinal guides 41, 41', The bearing sites for the rails are only indicated.

Claims

1. A method for the mould closure of an injection moulding machine, which has a support element (1), a movable tool clamping plate (13), 5-point toggle levers (9) and a hydraulic drive (25) of the crosshead (2) and the movements for the mould closure are transmitted via expanding brackets (6) to the toggle levers (9), characterized in that the crosshead drive is arranged between the support element (1) and the movable tool clamping plate (13) and in combination the crosshead (2) together with the toggle lever (9) and the expanding bracket (6) and the toggle lever drive (25) after withdrawal, or respectively with the opened mould, are sunk completely into a box-like cavity of the support element (1).

2. The method according to Claim 1, characterized in that the head part of the toggle lever drive (25) on the support element side, with opened moulds, is able to be sunk into a corresponding cavity positioned externally in front.

3. The method according to Claim 1 or 2, characterized in that the toggle levers (9) are embodied in a fork shape at least on the side of the toggle lever articulation and the individual principal reaction forces (PRF) are transmitted from the mould forces symmetrically and free of lateral forces (LF) via the 5-point toggle levers (9) to the support element (1), wherein the expanding brackets (6) engage in the central region of the articulated forks of the individual toggle levers (9).

4. The method according to one of Claims 1 to 3, characterized in that the mould plate articulations (12) in relation to a central axis M-M of the injection moulding machine are spaced approximately equally and symmetrically (A') as the inner expanding bracket bearings (7) A.

5. The method according to one of Claims 1 to 4, characterized in that with extended toggle levers (9) the closing forces are introduced in a region of the mould plate which is approximately half as high as the corresponding distance of the upper and lower support articulations (15) on the side of the support element (1).

6. The method according to one of Claims 1 to 5, characterized in that the hydraulic toggle lever drive (25) is connected on the one hand with the support element (1) and on the other hand engages on the crosshead (2), wherein the hydraulic cylinder (3) projects on both sides on the crosshead (2) and the effective length of the hydraulic cylinder (3) corresponds preferably approximately 4 to 5 times to the diameter of the hydraulic cylinder (3).

7. A mould closure of an injection moulding machine, which has a support element (1) and a movable tool clamping plate (13), in addition a hydraulic toggle lever drive (25) with a crosshead (2) which are embodied as 5-point toggle levers each with a toggle lever (9), a mould movement lever (11, 11') and an expanding bracket (6), characterized in that the hydraulic toggle lever drive (25) with the crosshead (2) is arranged between the support element (1) and the tool clamping plate (13) and in combination the crosshead (2) together with the toggle lever (9) and the expanding bracket (6) and the toggle lever drive (25) after withdrawal, or respectively with the opened mould, is sunk completely into a box-like cavity of the support element (1).

8. The mould closure according to Claim 7, characterized in that the box-like cavity is open in the direction of the movable tool clamping plate (13).

9. The mould closure according to Claim 7 or 8, characterized in that the box-like cavity is constructed in a similar shape, corresponding to the outer shape of the crosshead (2) with the toggle lever (9), the expanding bracket (6) and the toggle lever drive in fully withdrawn position.

10. The mould closure according to one of Claims 7 to 9, characterized in that the toggle levers (9) are embodied in a fork shape at least in the region of the toggle lever articulation and the expanding brackets (6) engage via an outer expanding bracket bearing (8) in the central region of the articulated forks (20, 21).

11. The mould closure according to Claim 10, characterized in that the axis of the outer expanding bracket bearings (8) is arranged approximately on the longitudinal central axis of the toggle lever (9).

12. The mould closure according to one of Claims 10 or 11, characterized in that each toggle lever (9) is constructed on each end side with an articulated fork (20, 21), for engagement at the bearing sites of the support articulation (15) or respectively of the mould movement lever (11, 11), wherein each toggle lever (9) is constructed in one piece, in particular as a single-piece cast body.

13. The mould closure according to Claim 12, characterized in that the horizontal spacing of the single-piece toggle levers (9) is greater than the outer contours of the hydraulic cylinder (3).

14. The mould closure according to one of Claims 7 to 13, characterized in that the crosshead (2) has two vertical and two horizontal arms, wherein the expanding brackets (6) engage on the vertical arms and the horizontal arms (40, 40') are held on longitudinal guides (41) which are fastened on the support element (1).

15. The mould closure according to one of Claims 7 to 14, characterized in that the hydraulic cylinder (3) of the hydraulic drive projects over the crosshead (2) on both sides on the crosshead (2) in the direction of movement.

16. The mould closure according to Claim 15, characterized in that the hydraulic cylinder (3) projects on the support element side approximately one quarter and on the opposite side approximately half, with the hydraulic cylinder (3) being integrated in one piece into the crosshead (2).

17. The mould closure according to one of Claims 7 to 16, characterized in that the drives for an ejector plate (14) are arranged at a distance above and below the hydraulic cylinder (3) and in a shared vertical plane to the hydraulic cylinder (3).