AT520004A1 - Closing unit of an injection molding machine - Google Patents

Abstract

Closing unit for an injection molding machine, comprising a rotary drive (2), a machine element (3) to be driven to a linear movement and a conversion device (4) for converting a rotary output movement of the rotary drive (2) into a linear drive movement for the machine element (3) the conversion device (4) by means of the rotary drive (2) about a rotation axis (X) rotatable first element (6) and on the machine element (3) and / or a frame (7) of the closing unit (1) directly or indirectly hinging second element (8) and wherein the first element (6) and the second element (8) by a toothing (9) are in a positive-locking coupling, wherein the toothing (9) is at least partially formed as a non-circular toothing.

Description

The present invention relates to a closing unit for an injection molding machine with the features of the preamble of claim 1.

Generic locking units comprise a rotary drive, one to a linear

Movement to be driven machine element and a conversion device for

Implementation of a rotary output movement of the rotary drive in a linear

Drive movement for the machine element. In this case, the conversion device has a first element, which is rotatable about an axis of rotation by means of the rotary drive, and a second element, by means of which the machine element is articulated. Alternatively, can be articulated by the second element on the frame, in which case the first element does the power transmission to the machine element. The first element and the second element are by a toothing in motion-locking coupling.

Simple examples of generic closing units would be those

Clamping units equipped with a turntable driven by a toothed wheel or with ratchet driven (half of) locking nuts

Locking a movable platen with a spar of the clamping unit before Schließkraftbeaufschlagung.

Gears of this type are often used, as they are particularly simple

Represent construction and therefore can be produced and maintained particularly economically.

But there are machine elements on injection molding machines and their closing units, for which until now a toothing could not be used economically in the drive. In particular, these are machine elements that in certain

Movement phases must be moved at high speed and in other phases of the movement sequence with high force.

A classic example would be the movable platen of such a clamping unit. During the closing movement is a relatively high speed (to keep the cycle time as short as possible) necessary, while the

Applying force in the closed position - especially in injection molding - high forces must be exerted on the movable platen.

The object of the invention is to simplify clamping units of the prior art and their drive trains, which have mixed requirements for fast movements and high force application.

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

This is done by the toothing is at least partially (or completely) designed as Unrundverzahnung. Non-round gears are gears that have a variable distance from a pivot point of the first or second element. It is always the same point to use from tooth to tooth for the distance measurement to the respective pivot point - for example, always the tooth base or a certain point in the flank. Due to the variable distance along the length of the teeth arise effectively, depending on the position of the first element or the second element, different over- or reduction ratios. In other words, in different positions of the conversion device creates a different dynamics for different positions.

In other words, the partial curves (equivalent to pitch circles in spur gears) in transmissions with non-circular gears - or generally non-circular gears - be chosen so that on the one hand, the closing speed maximized, but the closing force build-up can also be optimally realized. The instantaneous translation is selected, for example, as a function of the angle of rotation as a division point of the connecting line of the rotation centers of the gear train.

The mentioned, in this way generated variable dynamics along the travel of the machine element is the benefit of the Unrundverzahnung. This is clearly distinguished from classic gears, which undergo changes due to manufacturing deviations or wear. It is therefore a predefined or deliberately non-circular interlocking.

As a rotary drive, for example, an electric drive can be used. Of course, other drives, such as a hydraulic motor, in principle conceivable.

In the context of the invention, the axis of rotation of the first element an imaginary

Axis or a real axis, which may for example be connected to a shaft of the rotary drive or identical.

It should be noted that in the context of the invention, the linear movement of the

Machine element is not necessarily just a linear movement. Of course, rotational movements can also be superimposed. In the context of the invention, however, it is provided that the movement of the machine element has at least a linear proportion of movement, and is optionally stored accordingly.

In general, it should be noted that the machine element can be stored separately from the conversion device.

The invention can basically be used with all tooth flank forms.

Preference involute gears (because of their good manufacturability and

Tolerance with respect to center distance) and / or Wildhaber-Novikov serrations (convexly concave flank contact, because of the high edge carrying capacity especially in the

Closing force) can be used.

It is also possible to change the type of toothing within the toothing, for example to optimize a first part of the toothing on the rapid stroke movement and a second part of the toothing on the power stroke movement.

Preferably, straight or helical gears can be used because they are particularly simple. In principle, however, any shape of the flank line is possible (arrow, bow, sine).

The production of the toothing can, for example, in the single part by

Abzeilen done with conventional end mills. But it is also generally every

Shape of flank line of the meridian section of the machining tool (milling cutter,

Grinding pin, grinding wheel, etc.) conceivable.

The articulation of the machine element can be direct or indirect, that is, the second element can directly with the machine element in motion-locking

Connection or indirectly, for example, by gears, levers or the like are interposed.

Further advantageous embodiments of the invention are defined in the dependent claims.

The non-circular toothing can be designed so that in a first part of a

Traversing the machine element a Eilhubbewegung (ie a relatively fast movement with relatively low power transmission) and in a following on the first part second part of the travel a power stroke (ie a relatively slow movement with relatively high power transmission) results. The invention makes it possible with mold platens of

Injection molding machines classic in express stroke and power stroke to integrate two-piece drive device into a single, without losing the individual benefits of express and power stroke. This principle is, as mentioned, in movable platen as

Machine elements, but also, for example, in the pressing movement of

Injection units used.

In other words, the mold clamping plate of an injection molding machine is to be moved first in the molding cycle at a fast traversing speed and be applied later with a high closing force. In the prior art complex constructions with double toggle levers together with a crosshead and a spindle drive or the complete separations between Eilhub and power stroke are common. With the present invention, movable platens and, for example. Injection units can be moved with simpler means according to the requirements.

Also locks of spars or push rods can be easily driven by the invention. In such, often split, locking nuts, it is desirable to first achieve a high speed, the

Locking nuts against the end of the travel but still gently put on the spars or push rods. Even such a kinematic behavior can be easily achieved mechanically by the invention. In previous solutions with normal racks or hydraulic cylinders, this behavior had to be achieved by relatively complex activation of the respective drive.

Other examples of machine elements that can be advantageously driven by the invention are core pullers or ejectors.

Particularly simple are embodiments in which the first element and / or the second element are each non-circular gears and / or non-circular gear segments.

The second element may for example also be a rack, preferably with variable height. Separate devices for converting the rotational movement into a linear movement can then be dispensed with.

Embodiments may be provided with a split second element, wherein the split element has a traction means which is in a motion-positive coupling via the toothing with the first element, and a further element which is preferably rotatable and which by means of a further toothing is in a motion-locked manner Coupling is and directly or indirectly on the machine element and / or a frame of the clamping unit hinges.

In particular objects can be used as traction means, which are equipped to transmit a tensile force and enter into a splined connection. Examples would be toothed belts and / or roller chains. But even rigid traction means, such as a rack, are also conceivable in principle in this embodiment.

At least one lever fastened to the second element can be provided which is pivotably connected to the machine element and / or the frame for articulation on the machine element and / or on the frame.

This is a particularly simple embodiment for transmitting the drive movement to the machine element. In a particularly preferred embodiment, two levers can be provided in toggle lever arrangement.

In a version with a split second element, a rotational movement of the further element can likewise be transmitted by means of at least one further lever into a linear movement.

The mentioned conflicting requirements in parts of the travel path - once high speed, once high force application - can be particularly easily mapped in many cases by at least one meshing area of the teeth with reduction and at least one meshing area with translation are available. Of course, in some cases a variable (pure) translation or translation may be beneficial.

Geometric dimensions of teeth of the teeth can vary along the toothing to accommodate the different requirements at different pitches / translations. For example, in the case of involute gearing, a variable modulus along the sub-curve is possible, i. "Small" teeth in the area of the closing movement because of the edge bearing capacity and "large" teeth in the area of the closing force application because of the tooth root strength. Of course, this basic principle can not only be followed when using involute gearing. Furthermore, the tooth width can be varied along the part curve.

Thus, a reduction of the moment of inertia of the drive can be achieved by utilizing the permissible material stress of the toothing.

Particularly preferred may also be provided that the first element is connected to a shaft of the rotary drive motion fit. In particular, the first element may be attached directly to the shaft of the rotary drive, so that the shaft of the rotary drive forms the axis of rotation of the first element. Alternatively, of course, a transmission of any kind can be connected between the rotary drive and the first element.

Protection is also sought for an injection molding machine with a clamping unit according to the invention.

Further advantages and details of the invention will become apparent from the figures and the associated description of the figures. Showing:

1a - 1f a sequence of movements of an embodiment according to the invention with a movable platen as a machine element,

Fig. 2 shows another embodiment of the invention with a movable platen as a machine element

3 shows a further, inventive embodiment with a movable platen as a machine element,

4 shows an embodiment of the invention with split nuts as a machine element,

Fig. 5 is an expanded embodiment of that of Fig. 4 and

Fig. 6 shows an embodiment of the invention with split second

Element.

It has a frame 7, a movable platen and a fixed platen 5. The dashed rotary drive 2 rotates a shaft / axis of rotation X. This rotational movement is by the conversion device 4 in a implemented linear movement of the movable platen as a machine element 3.

The conversion device 4 has a first element 6 and a second element 8. The first element 6 and the second element 8 are each formed as non-circular gears, which mesh with each other and thereby form the non-circular toothing 9

The first element 6 is driven directly by the shaft / rotation axis X and is in non-circular engagement with the second element 8 via the non-circular toothing 9. The second element 8 is connected directly to one of two levers 11. The two levers 11 form a toggle for transmitting the rotational movement of the second element 8 to the linear movement of the machine element 3 (the movable platen).

FIGS. 1a to 1f are also schematic in that the

Implementing device 4 may be present in duplicate (possibly with common first element 6 and symmetrical with respect to a horizontal and / or vertical plane of symmetry) to reduce or eliminate unwanted tilting moments.

The mode of operation of the conversion device 4 is illustrated in the (schematic) image sequence of FIGS. 1a to 1f. For the sake of clarity, only elements of the conversion device 4 are shown in FIGS. 1b to 1e.

It can be seen from the image sequence that at the beginning of the movement (FIGS. 1a to 1c), much greater distances lie between those points at which the levers 11 are connected to the movable platen (ie the one on the

Abscissa axis (horizontal) wandering, circled point) than is the case in the later part of the sequence of movements (FIGS. 1d to 1f). That means that at the same

Rotational speed of the shaft / rotation axis X at the beginning of the movement a higher

Speed of the movable platen is present as at the end of

Motion sequence. At the same time, at the end of the sequence of movements (FIG. 1f), a larger lever or a reduction takes place, so that a greater torque or a greater force acts on the movable platen.

The behavior of the conversion device 4 described here arises from the

In the first part of the movement, a relatively large effective radius of the first element 6 and a relatively small effective radius of the second element 8 and thus a translation (high speed at constant drive speed), lies in the second part of the

Movement the opposite situation. As can be seen from FIGS. 1d to 1f, a relatively small radius of the first element 6 and a relatively large radius of the second element 8 are effective in this phase of the movement sequence, which results in higher force application in the mentioned slower speed.

In addition, the mold 12 is shown in dashed lines in Figure 1f. In the closed position of the closing unit 1 shown here, therefore, a relatively high force is exerted on the forming tool 12 by the present reduction, which is necessary, for example, for injection molding processes.

In the figures for the embodiments described below, the toothing 9 is no longer shown as actual toothing, but as contacting of the first element 6 and the second element 8, although of course it is present in the real embodiment. This serves the simple drawing representation and the clarity.

Figures 2a and 2b show schematically a further embodiment of the invention, in which a movable platen acts as a moving machine element 3. The mode of action of the conversion device 4 is analogous to that of FIGS. 1a to 1f. Both in the side view Fig. 2a and in the top view of Fig. 2b, a closed position of the clamping unit 1 in solid lines and an open position are shown in dashed lines.

The embodiment of Fig. 2a and 2b has a double-executed toggle mechanism (reference numeral 11, visible in Fig. 2b) for implementing the rotational movement of the second member 8 in the linear movement of the movable platen.

Figure 3 shows schematically a further embodiment of the invention, wherein the second element 8 is designed as a rack. In order to guarantee the meshing with the first element 6 designed as a non-circular gear, the rack 8 has a variable height. The operation of the non-circular toothing 9 is analogous to that described in connection with FIGS. 1a to 1f.

FIG. 4 schematically shows an embodiment of the invention in which split locking nuts are articulated as machine element 3. This shared

Locking nuts each have lower halves 13 and upper halves 14. The lower halves 13 and the upper halves 14 are each coupled in a motion-locking manner via rods. When the locking nuts are closed, engages an inner profile of the locking nuts in an outer profile of the spars 15. Thus, the spars 15 of the movable platen are locked. The spars 15 can then serve as tie rods for the application of a closing force. Of course, the invention can also be used for locking a central push rod in a running as a 3-plate-clamping unit 1 closing unit.

For moving the lower halves 13 relative to the upper halves 14, as mentioned, a conversion device 4 according to the invention is provided. The first element 6 is designed as a non-circular gear. The second element 8 is in duplicate each before as a rack. Wherein each rack drives one of the upper and lower nut pairs 13 and 14.

In many cases, closing units are equipped with four bars 15. The

Embodiment of Figure 3 can then be used in duplicate, as shown schematically and by way of example in Figure 5. The conversion devices 4 lie crosswise one above the other. The first elements 6 are mounted on the axis of rotation X in 90 ° offset from each other. For the sake of clarity, the other elements have not been provided with reference numerals.

It can also be a single first element 6 is used, by means of which all four locking nuts in the arrangement of Fig. 5 can be driven.

By such an embodiment, it is possible to drive all four locking nuts by a single drive (preferably electrically).

The embodiment of FIG. 6 is a schematically illustrated example of a split embodiment of the second element 8, wherein a traction means 15 via the toothing 9 with the first element 6 and the further toothing 14 with a further, in this case rotatable element 13th is in motion-locking coupling. The rotational movement of the first element 6 is via the traction means 15 in a

Rotary movement of the further element 13 transmitted, depending on the position of the first element 6 different translations or ratios. The length change in the traction means resulting from the non-circular toothing 9-more precisely, the change in length of the free part of the traction means 15-is compensated by a length compensating device 16. About the lever 11 of the conversion device 4, analogous to the

Embodiments according to Fig. 1a to 1f and Fig. 2a and 2b, the rotational movement of the further element 13 in the linear movement of the machine element 5 (here a movable platen) transmitted. Also analogous to the

Embodiments according to Fig. 1a to 1f and Fig. 2a and 2b, the non-circular toothing is formed so that in the sequence of movement initially an Eilhub (translation) and then a power stroke (reduction) results.

In this embodiment, the length compensating device 16 is formed by a spring-loaded pivotable roller. Of course, other length compensation devices 16 can be used.

The traction means 16 may be formed for example by a roller chain and / or a toothed belt. In principle, however, all traction means 16 are conceivable, which are just equipped to transmit a tensile force and the occurrence of a splined connection.

With a suitable choice of the non-circular toothing and with angles of rotation of less than 360 °, an analogous embodiment of FIG. 6 can also do without a length compensating device 16.

The invention can also be used, for example, in ejectors.

For example, in an ejector first large forces can be achieved to overcome any sticking of a molded part in the mold and then to achieve a fast ejection speed.

In the illustrated and described embodiments, non-circular parallel axis transmissions are in use. In principle, cutting axes (bevel gearboxes) or skewed axes (hypoid gearboxes) are also possible within the scope of the invention.

Innsbruck, May 19, 2017

Claims (14)

claims 1. Closing unit for an injection molding machine, comprising - a rotary drive (2), - a machine element to be driven to a linear movement (3) and - a conversion device (4) for implementing a rotary output movement of the rotary drive (2) in a linear drive movement for the machine element (3), wherein the conversion device (4) by means of the rotary drive (2) about a rotation axis (X) rotatable first element (6) and on the machine element (3) and / or a frame (7) of the clamping unit (1) directly or indirectly articulating second element (8) and wherein the first element (6) and the second element (8) by a toothing (9) are in a positive-locking coupling, characterized in that the toothing (9) is at least partially formed as a non-circular toothing , 2. Closing unit according to claim 1, characterized in that the non-circular toothing is formed so that in a first part of a travel of the machine element (3) Eilhubbewegung and in a following on the first part second part of the travel results in a Krafthubbewegung. 3. Closing unit according to claim 1 or 2, characterized in that the driven machine element (3) is to be driven to a closing movement movable platen and / or to be driven to a contact pressure injection unit. 4. Closing unit according to one of the preceding claims, characterized in that the machine element to be driven (3) is a locking nut or an ejector. 5. Closing unit according to one of the preceding claims, characterized in that the first element (6) and / or the second element (8) is in each case a non-circular gear and / or a non-circular gear segment. 6. Closing unit according to one of the preceding claims, characterized in that the second element (8) is a rack, which preferably has a variable height. 7. Closing unit according to one of the preceding claims, characterized in that the second element - is divided, - a traction means (15) which is about the toothing (9) with the first element (6) in a motion-locking coupling, and - a further - preferably rotatable - element (13) which by means of a further toothing (14) is in a positive connection and directly or indirectly on the machine element (3) and / or a frame (7) of the closing unit (1) articulates. 8. Closing unit according to claim 7, characterized in that the traction means (15) is designed as a toothed belt and / or roller chain. 9. Closing unit according to one of the preceding claims, characterized in that at least one on the second element (8) fixed lever (11) is provided, for articulation on the machine element (3) and / or on the frame (7) with the machine element (3 ) and / or the frame (7) is pivotally connected. 10. Closing unit according to claim 7 or 8 and claim 9, characterized in that the at least one lever is attached to the further element of the second element. 11. Closing unit according to one of the preceding claims, characterized in that the non-circular toothing (9) is formed so that at least one meshing region of the toothing (9) with reduction and at least one meshing region with translation are present. 12. Closing unit according to one of the preceding claims, characterized in that geometric dimensions of teeth of the toothing (9) vary. 13. Closing unit according to one of the preceding claims, characterized in that the first element (6) with a shaft of the rotary drive (2) is connected in a rotationally locking manner and is preferably rotatable about this shaft. 14. Injection molding machine with a closing unit (1) according to one of the preceding claims.