AT520004B1 - 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

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

Generic locking units comprise a rotary drive, to be driven to a linear movement machine element and a conversion device for implementing 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 such closing units that have a driven via a gear turntable or driven with racks (halves of) locking nuts for locking a movable platen with a spar of the clamping unit before Schließkraftbeaufschlagung.

Gears of this type are often used because they represent a particularly simple design and therefore can be produced and maintained particularly economically.

However, there are machine elements on injection molding machines and their closing units, for which until now a gearing could not be used economically in the drive. In particular, these are machine elements that have to be moved at high speed in certain phases of the motion sequence and in other phases of the motion sequence with high force application. A classic example would be the movable platen of such a clamping unit. During the closing movement, a relatively high speed (to keep the cycle time as short as possible) is necessary, while high forces must be exerted on the movable platen to apply force in the closed position, especially during injection molding.

Out of round teeth are known in principle in the case of closing units of injection molding machines (JP H058269 A, US Pat. No. 1,110,157 A). In practice, such constructions are not used, partly because they are quite complex.

The object of the invention is to simplify closing 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 maximizes the closing force build-up but also can be optimally realized. The current translation is for example in

Depending on the angle of rotation selected as the division point of the connecting line of the rotation centers of the gear train.

The second element according to the invention has a rack, preferably with variable height, on. Separate devices for converting the rotational movement into a linear movement can then be dispensed with depending on the embodiment.

The mentioned, generated in this way 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 invention, the axis of rotation of the first element may be 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 only 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. Preferably, involute toothings (because of their good manufacturability and tolerance with respect to axial spacing) and / or Wildhaber-Novikov toothings (convex concave edge contact, because of the high edge bearing capacity, especially in the case of clamping force build-up) can be used.

A change of Verzahnungsart within the toothing is possible, for example. To optimize a first part of the toothing on the Eilhubbewegung and a second part of the toothing on the Krafthubbewegung.

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 teeth can be done, for example, in the single part process by trimming with conventional end mills. However, it is also conceivable in general every form of flank line of the meridian section of the machining tool (milling cutter, grinding pin, grinding wheel, etc.).

The articulation of the machine element can be directly or indirectly, that is, the second element can be directly in communication with the machine element in motion 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 Unrundverzahnung can be designed so that in a first part of a travel of the machine element 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 Krafthubbewegung (ie comparatively slow movement with comparatively high power transmission). The invention makes it possible to integrate in the form of clamping plates of injection molding machines classic in Eilhub and power stroke split drive device in a single, without losing the individual benefits of express and power stroke. This principle is, as mentioned, used in movable mold clamping plates as machine elements, but also for example in the pressing movement of injection units.

In other words, the mold clamping plate of an injection molding machine to be moved first in the molding cycle with 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, but the locking nuts towards 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.

It can be provided with a divided second element embodiments, wherein the divided element - a traction means which is about the toothing with the first element in a positive connection, and - another - preferably rotatable - element having, by means of a further toothing in motion-locking coupling is and directs directly or indirectly on the machine element and / or a frame of the clamping unit.

In particular objects can be used as traction means, which are equipped to transmit a tensile force and to enter a spline connection. Examples would be toothed belts and / or roller chains. According to the invention is provided in such an embodiment, a rack as traction means.

It can be provided at least one lever mounted on the second element, which is pivotally connected to the articulation on the machine element and / or on the frame with the machine element and / or 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 an embodiment with a split second element, a rotational movement of the further element can also be transmitted by means of at least one further lever in a linear movement.

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

Geometric dimensions of teeth of the gearing may vary along the gearing in order to meet the different requirements at different Teilun-gene / translations. For example, in the case of involute gearing, a variable modulus along the sub-curve is possible, i. "Small" teeth in the closing movement because of the edge support capability and "large" teeth in the area of closing force due to the Zahnfußfestigkeit. 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. 1 a shows a sequence of movements of a movable platen as

Machine element, Fig. 2a and 2b a further embodiment with a movable Formaufspannplat te as machine element Fig. 3 shows an embodiment according to the invention with a movable mold clamping plate as a machine element, Fig. 4 shows an embodiment of the invention with shared

Nuts as a machine element, Fig. 5 shows an extended embodiment of the invention to that of

Fig. 4 and Fig. 6 shows an embodiment with a split second element.

Figures 1a to 2b and 6 are not part of the invention and are for illustration only.

It has a frame 7, a movable platen and a fixed platen 5. The dashed lines shown rotary actuator 2 rotates a shaft / axis of rotation X. This rotational movement is by the conversion device 4th converted into a 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 / axis of rotation X and is on the non-circular toothing 9 in a positive-locking coupling with the second element 8. The second element 8 is directly connected 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).

Figures 1a to 1f are also schematic in that the conversion device 4 may be present in duplicate (possibly with a common first element 6 and symmetrically with respect. A horizontal and / or vertical plane of symmetry) to reduce unwanted tilting moments or to eliminate.

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.

From the image sequence it can be seen that at the beginning of the movement (Figures 1a to 1c) are much greater distances between those points where the lever 11 are connected to the movable platen (ie the 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). This means that at the same rotational speed of the shaft / rotation axis X at the beginning of the movement there is a higher velocity of the movable platen than at the end of the movement 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 described here of the conversion device 4 is formed by the non-circular toothing 9 and designed as non-circular gears first and second elements 6 and 8. While in the first part of the movement, a relatively large effective radius of the first element 6 and a relatively smaller effective Radius of the second element 8 and thus a translation (high speed at the same drive speed) prevails, is in the second part of the movement, the opposite situation. As can be seen from FIGS. 1 d to 1 f, 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 a 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 to the embodiments described below, the toothing 9 is no longer shown as actual teeth, but as contacting the first member 6 and the second member 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 in which a movable platen acts as a moving machine element 3. The operation of the conversion device 4 is analogous to that of Figures 1 a 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 an 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 a machine element 3. These split lock nuts each have lower halves 13 and upper halves 14. The lower halves 13 and upper halves 14 are each coupled in a positive 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 version of the second element 8, wherein a traction means 15 via the teeth 9 with the first element 6 and the further toothing 14 with another, in this case rotatable , Element 13 is in motion-locking coupling. The rotational movement of the first element 6 is transmitted via the traction means 15 in a rotational movement of the further element 13, 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 of FIGS. 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) is transmitted. Likewise in analogy to the embodiments according to FIGS. 1 a to 1 f and FIGS. 2 a and 2 b, the non-circular toothing is designed in such a way that initially an express stroke (translation) and then a force stroke (reduction) result in the movement sequence.

In this embodiment, the length compensation 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 Unrundverzahnung and at angles of rotation of less than 360 °, one of the Fig. 6 analogous design without a length compensation device 16 can get along.

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 gears with parallel axes are in use. In principle, cutting axes (bevel gearboxes) or skewed axes (hypoid gearboxes) are also possible within the scope of the invention.

Claims (11)

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, wherein the toothing (9) is at least partially formed as a non-circular toothing, characterized in that the second element (8) comprises a toothed rack which preferably has a variable height. 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 machine element to be driven (3) is to be driven to a closing movement movable For maufspannplatte and / or to be driven to a pressing movement 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) is a non-circular gear and / or a non-circular gear segment. 6. 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. 7. Closing unit according to claim 6, characterized in that the at least one lever is attached to the further element of the second element. 8. 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. 9. Closing unit according to one of the preceding claims, characterized in that geometric dimensions of teeth of the toothing (9) vary. 10. 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 to a positive fit and is preferably rotatable about this shaft. 11. Injection molding machine with a clamping unit (1) according to one of the preceding claims.