CA2780279A1

CA2780279A1 - Nozzle pressing device of an injection moulding machine

Info

Publication number: CA2780279A1
Application number: CA2780279A
Authority: CA
Inventors: Hans Rabe; Steffen Franz; Dirk Issel; Volker Fritzlar; Jorg Meyer; Andreas Fensterer
Original assignee: ZHAFIR PLASTICS MACHINERY GmbH
Current assignee: Haitian Plastics Machinery Group
Priority date: 2009-11-12
Filing date: 2010-11-04
Publication date: 2011-05-19
Anticipated expiration: 2030-11-04
Also published as: JP5608240B2; EP2498969B1; DE102009044506B4; DE102009044506A1; CN102753325A; WO2011057943A1; CA2780279C; CN102753325B; EP2498969A1; JP2013510736A

Abstract

The present invention relates to a nozzle pressing device or a corresponding injection molding machine having an injector unit (3) comprising a nozzle (25) that can be displaced against a mold (30), wherein a drive unit is provided for displacing at least parts of the injector unit having the nozzle relative to the mold, wherein the drive unit comprises two connection sides for connecting to the components to be driven and displaceable relative to each other during driving, wherein a connection side of the drive unit is disposed on a machine frame or machine bed of the injection molding machine and the other connection side is disposed on a displaceable part of the injector unit or is effectively connected thereto, wherein the drive unit having the connection side of the drive unit provided on the machine frame or machine bed is supported by a spring element (10, 10'), such that a nozzle press force is provided by elastically deforming the spring element.

Description

P3924PC00 ZHAFIR Plastics Machinery GmbH
NOZZLE PRESSING DEVICE OF AN INJECTION MOULDING MACHINE

BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION

The present invention relates to an injection moulding machine with an injector unit comprising a nozzle that can be displaced against a mould, and a nozzle pressing device for ensuring that the nozzle is held against the mould during the injection process.

PRIOR ART

Injection moulding machines are widely used, and particularly for producing plastic parts.
The injection moulding machines comprise in this regard essentially two structural units, namely the clamping apparatus for opening and closing a corresponding mould, and an injector unit for injecting flowable material into the mould.

The injector unit is usually displaceable relative to the mould, so that, during the injection process, it is essential that the nozzle through which the material being injected leaves the injector unit presses tightly against the mould, so that the injection pressure can be maintained on one hand and that no material to be injected is lost due to leakage between the nozzle and the mould on the other.
The prior art discloses nozzle pressing devices which ensure that the nozzle presses securely and firmly against the mould during the injection process, and in particular also during post-injection of material to be injected into the mould. Examples of this are given in DE 42 32 533 Al and EP 1 364 765 Al. In the two apparatuses described therein, a drive unit comprising a spindle motor and a threaded spindle for moving the injector unit towards the mould has, between the spindle nut and the displaceable part of the injector unit, which is assigned to the displaceable spindle nut, a spring element in the form of a spiral spring which provides a nozzle press force through its elastic deformation.

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However, a drawback of these nozzle pressing apparatuses is that the nozzle press force is vulnerable to external influences and therefore cannot be adjusted with sufficient precision, as the spring element is arranged between moving parts. Moreover, the spring is arranged offset to the injection axis, as defined by the injection barrel and the nozzle, with the result that additional moments can arise on the injector unit that also affect precise and defined contact of a nozzle press force.

Furthermore, the arrangement of the spring is complicated and the use of coil springs for the intended purpose is unsatisfactory because, for reasons of stiffness, the coil springs usually have to be designed so as to have a relatively long spring displacement and thus the time for force build-up is also long.

DISCLOSURE OF THE INVENTION
OBJECT OF THE INVENTION

It is therefore an object of the present invention to create an injection moulding machine or a corresponding nozzle pressing device which avoids the disadvantages of the prior art and, in particular, facilitates precise and defined application of a nozzle press force and which maintains this nozzle press force, especially without further actuation of the drive unit of the injector unit. In this regard, the corresponding apparatus is to be of simple construction and easy and safe to use.

TECHNICAL SOLUTION
This object is achieved by an injection moulding machine having the characteristics of claim I and a nozzle pressing device having the characteristics of claim 10.
Advantageous embodiments are the object of the dependent claims.

The invention proceeds from the recognition that the drive unit, which enables the injector unit comprising the nozzle to move relative to the mould, can be used simply and effectively to generate a nozzle press force. In this connection, it is assumed that the drive unit is designed to comprise two connection sides which are provided for connection to the components to be driven. Here, the components to be driven can be represented, for example,

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by the injector unit on one hand and by the machine frame or the machine bed of the injection moulding machine on the other, with the injector unit moving relative to the machine frame or to the machine bed. By virtue of the relative movement of the connection sides of the drive unit, which are thus arranged on one hand on the displaceable injector unit and on the other on the stationary machine frame or machine bed, a spring force that can serve as a nozzle press force can be generated by interposing an elastically deformable spring element.

This can be done advantageously as per the invention by providing the spring element on the machine frame or machine bed and connecting a connection side of the drive unit to, or supporting it in the spring element, such that the drive unit can cause the spring element to deform and thus a nozzle press force to be generated. Arranging the spring element on the machine frame or machine bed allows for optimal application of the opposite force into the machine frame or the machine bed and facilitates defined application of a precise nozzle press force, with all kinds of different spring elements lending themselves to this use in respect of type and design of spring element. In addition, arrangement of the spring element is simplified.

The drive unit can be a drive and a unit for generating a translatory motion, wherein diverse embodiments are conceivable. Examples include an actuator that facilitates linear motion of a drive rod, or a spindle motor with a motor-driven threaded spindle, which cooperates with a spindle nut. Rotation of the threaded spindle makes it possible to vary the distance between the spindle nut and spindle motor and so generate a corresponding translatory movement.
Alternatively, in the case of a spindle drive, the spindle nut can be driven instead of the threaded spindle, with the result that the threaded spindle moves linearly relative to the spindle nut. In particular, a spindle drive with a small thread pitch can be used, i.e. in particular a spindle drive whose thread pitch is preferably chosen so as to be small.
Furthermore, many diverse forms of drive unit for generating translatory motion are conceivable. For example, the actuator can be a hydraulic or pneumatic drive, with a piston rod executing the translatory motion.

The above-mentioned connection sides of the drive unit can thus be formed on one hand by the motor, i.e. the spindle motor, and on the other by the spindle nut or by an actuator and an actuating rod which can be moved linearly by it.

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Each connection side of the drive unit can be arranged on the elastic spring element or is effectively connected thereto. For example, in a spindle drive, either the spindle nut or the spindle motor can be fixed in place on the elastic spring element.
The further connection side of the drive unit can be located at any suitable point on the machine frame or machine bed, particularly on traverses of the machine frame or on a stationary platen.

The connection side of the drive unit can be connected direct to the spring element or via correspondingly rigid connecting elements. In particular, the connection side of the drive unit can be supported via a fixed bearing so as to be kinematically determinate.

The spring element can be configured as a rod or plate, for example in the form of a leaf spring or by a correspondingly configured part of the machine frame or machine bed. It is worthy of particular consideration to render traverses of a machine frame transverse to the injection direction appropriately elastic in order that they may act as spring element. A
corresponding elastic configuration can be simply realized by manufacturing in corresponding spring steel.
A corresponding spring element can have short displacement, i.e. elastic deformation, e.g.
maximum deflection, of less than or equal to 10 mm, especially in the range I
to 3 mm, so that short displacement and hence quick force build-up are ensured.

A corresponding spring element can be disposed not only in a simple manner on the injection moulding machine, but in particular can also be provided centrically with the injection axis, such that the spring element has a spring displacement running parallel or concentrically with the injection axis or in a plane that passes through the injection axis. In particular, deflection of the rod or plate in a direction opposite to the injection direction can be provided as spring displacement, such that the correspondingly generated nozzle press force presses the nozzle completely in the direction of the mould.

Accordingly, the spring element and/or the part of the connection side of the drive unit arranged thereon can be provided concentrically with the injection axis or nozzle tip.

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However, the spring element and/or the part of the connection side of the drive unit arranged thereon can be arranged offset from the injection axis, in particular offset in a direction which is transverse to the injection axis, but which passes through the injection axis.

For supporting the spring element on the machine frame or the machine bed, a moment-free support can be provided that avoids corresponding influences exerted by additional force or moment effects. Were the ends of a spring element, for example, to be rigidly supported on the machine frame or the machine bed, deformation of the spring element would generate additional forces on the support points that would hamper precise setting and determination of the resulting nozzle press force. This is avoided by a corresponding support that permits maximum mobility of the spring element in the support points. For example, a support via rotary joints can be provided on preferably bar-shaped connecting elements, such that the ends of the spring element can rotate freely via the rotary joints, with any displacement of the spring element or parts thereof as a result of deformation of the spring element possibly being at least partially compensated by elastic deformation of the bar-shaped connecting elements.
In connection with the drive unit, a centring arrangement can be provided in the region of the spring element to ensure that the drive unit can continue to move unimpeded if the spring element undergoes elastic deformation.
The present invention can be used in particular on a tiebar-less injection moulding machine, such as is described for example in DE 10 2007 050 689 Al, because the machine frame concept presented therein permits a correspondingly simple arrangement of the spring element and direct application into the machine frame, via the spring element, of the force opposing the nozzle press force. Accordingly, the disclosure content of DE 10 Al is incorporated by reference herein in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, characteristics and features of the present invention are apparent from the following detailed description of embodiments using the enclosed drawings. The drawings show in purely schematic form in Fig. I a perspective illustration of an inventive injection moulding machine;

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Fig. 2 a view of another embodiment of an inventive injection moulding machine from below;

Fig. 3 a view of another embodiment of an inventive injection moulding machine from below;

Fig. 4 a view of a fourth embodiment of an inventive injection moulding machine from below;
Fig. 5 a view of an inventive injection moulding machine similar to that of Figure 4 in the state of pressing the nozzle against a mould;

Fig. 6 a detailed view of the spring element from the injection moulding machine as per Figures 4 or 5, and in Fig. 7 a detailed view of the support of a spring element according to a further embodiment.
Figure 1 shows a perspective illustration of an inventive injection moulding machine 1. Such an injection moulding machine 1, is essentially well known and is described for example in detail in DE 10 2007 050 689 Al, whereby the disclosure of DE 10 2007 050 689 Al is fully incorporated herein by reference.
The injection moulding machine I comprises a clamping unit 2 and an injector unit 33. The injector unit 33 comprises a displaceable injector unit 3, through which, e.g., plasticised polymer is injected via a nozzle into a mould where the plastic solidifies to yield the corresponding plastic injection-moulded product. The clamping unit 2 actuates the mould parts such that the mould opens and the finished plastic injection-moulded product can be removed from the mould. For the next injection operation, the mould is closed accordingly by means of the clamping unit 2. One part of the mould is arranged on the displaceable clamping unit 2, while the other part of the mould is arranged on a stationary platen 11, through which the injector unit 3 comprising the nozzle is in contact with the mould for the purpose of

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injecting the polymer into an opening in the mould. Figure 1 shows the displaceable platen 12 which is arranged on the clamping unit 2 and on which a mould half can be arranged. The stationary platen 11 can be viewed as the separation between injector unit 33 and clamping unit 2.
In accordance with the invention, the injection moulding machine 1 as shown in Figure 1 has a drive unit (not shown in Figure 1) which can move or displace the injector unit 3 towards the stationary platen 11.

In this connection, the drive unit comprising connection sides is on one hand arranged on the displaceable injector unit 3 and on the other is supported against a spring element 10, which is attached as a traverse on the side walls 5 and 6, which enclose the injector unit 3.

In the illustrated embodiment of Figure 1, the injection moulding machine 1 comprises a frame structure with the side walls 5, 6, 4, 7 between which are disposed traverses 13, 14 and 31 and the intervening platen 11. The corresponding frame construction is supported on a machine bed 8, 9, which may have the same design of side walls and traverses.

In addition to the illustrated design of injection moulding machine I with compact frame, in which it is possible to largely dispense with tiebar arrangements for guiding the displaceable injector unit 3 and the corresponding displaceable components of the clamping unit 2, an inventive injection moulding machine can, however, also have the conventional design of an injection moulding machine with appropriate tiebar arrangements. The inventive injection moulding machines thus comprise tiebar-less injection moulding machines and conventional injection moulding machines with arrangements of tiebars.

As is clear from Figure 1, the spring element 10, which is used for generating a nozzle press force, can for example be configured as a traverse of the machine frame and preferably be arranged centrically with the injection axis 15, which passes centrally along the injection barrel and the nozzle in the injection direction.

Although Figure 1 does not show the drive unit for moving the injector unit 3, it is easy to imagine for example that, were the drive unit to be arranged between the rear end 16 of the injector unit 3 and the spring element 10, actuation of the drive unit so as to increase the

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spacing of the connection sides generates a movement which moves the injector unit 3 and the spring element 10 away from each other until the nozzle of the injector unit 3 abuts the mould.
Provided that the drive unit continues to generate a drive force, the spring element 10 then becomes elastically tensioned, with the resultant spring force representing the contact pressure of the nozzle against the mould, said contact pressure being retained when the movement of the drive unit in the corresponding position is stopped. This press force serves to press the nozzle securely against the mould during the injection process and, in particular, to ensure that a post-injection process does not create gaps between the nozzle and the mould through which the material could escape.
Figure 2 shows a more detailed bottom view of further embodiment of an inventive injection moulding machine. In this connection, as also in the subsequent description of the other embodiments, the same reference numerals are used for identical or similar components, with a repeat description of similar or identical components in the following embodiments being eschewed.

Figure 2 shows the injector unit 3, which is displaceable along the injection axis 15 via two displaceable traverses 19 illustrated in Figure 2 , with slide elements 17 being provided on the displaceable traverses 19, said slide elements being provided in corresponding rail arrangements 18 on the side walls 5 and 6 so as to constitute a linear slideway for the injector unit 3.

The injector unit 3 has a nozzle 25 which projects through the stationary platen 11 and makes contact with the injection opening of the mould 30.
For the purpose of moving the injector unit 3 along the rail arrangements 18, provision is made for a drive unit comprising a drive 20, a drive rod 21 and a fastening element 22 for the drive rod 21 on the injector unit 3.

When the drive 20 pushes the drive rod 21 in the direction of the mould 30, the injector unit 3 comprising the nozzle 25 moves in the direction of the mould 30 until the nozzle 25 makes contact with the mould. Further generation of driving force by the drive 20 causes the drive rod to move further and the spring element 10 deflects elastically until the spring force matches the driving force of the drive unit. If the drive rod 21 is then immobilized in this

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position, the spring force of the elastic spring element is retained, such that the spring force presses the nozzle 25 against the mould 30. Accordingly, a simple but effective nozzle pressing device is created.

In particular, the drive 20, the drive rod 21 and the fastening element 22 and the spring element 10 can be arranged centrically, in particular concentrically, with the injection axis 15, such that, when the nozzle press force is exerted due to the elastic deformation of the spring element 10, the nozzle is pressed straight onto the mould 30. The avoidance of moments during application of the nozzle press force makes for extremely precise setting of the nozzle press force. However, it is also possible to arrange the drive unit and/or the spring element 10 offset from the injection axis 15.

The drive 20 can be formed by any suitable drive that enables linear movement of the injector unit 3. This could, for example, be any actuator which can move the drive rod 21 back and forth.

In particular, however, the drive can be a spindle motor which drives a threaded spindle, as shown in the embodiment of Figure 3. Accordingly, the embodiment of Figure 3 differs from that of Figure 2 only in that, instead of a drive 20 in the form of an actuator, a spindle motor 20' is provided, which drives a threaded spindle 21' which cooperates with a spindle nut 23.
The spindle nut 23 is arranged on the fastening element 22 so as to rotate, said spindle nut in turn being firmly connected to the displaceable injector unit 3. Actuation of the threaded spindle 21' via the spindle motor 20' screws the threaded spindle 21' into or out of the spindle nut 23 to displace the injector unit 3 along the injection axis 15 in order that the nozzle 25 may be brought into or out of contact with the mould 30.

In the same manner as in Figure 2, further actuation of the threaded spindle 21 after the nozzle 25 is in contact with the mould 30 bends the spring element 10 such that the elastic spring force generates a nozzle press force which counteracts the injection pressure during injection moulding or the holding pressure during post-injection and thus ensures that the nozzle makes firm contact with the mould.

As is again evident from Figure 3, the spindle motor 20' comprising the threaded spindle 21' is arranged centrically with the injection axis 15 in order that the corresponding forces, i.e. the

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spring force generated by the spring element 10, may be transmitted centrically onto the injector unit 3 and thus onto the nozzle 25. In addition to a completely concentric arrangement of the spindle motor 20' of the threaded spindle 21' and the spindle nut 23 with the injection axis 15 or the nozzle 25, it is also possible to choose a centric arrangement in which the respective components are offset in one direction.

Figure 4 shows a further inventive injection moulding machine, which differs from the embodiments of Figures 2 and 3 in that the spring element 10' is formed as a separate component and is not formed by a traverse of the machine frame. Accordingly, a special arrangement of the spring element 10' is provided on the machine frame, said arrangement being discussed in detail later.

In addition, the embodiment of Figure 4 differs from those of Figures 2 and 3 in that the drive or spindle motor 20' is not fixed in place on the machine frame or arranged on the machine bed, but rather is arranged on the displaceable injector unit 3, such that it can move along with this.

Through the arrangement of the spindle motor 20' on the traverse 19 of the displaceable injector unit 3, the spindle nut 23 acting in cooperation with the threaded spindle 21' is fixed in place on the spring element 10', which is connected to the machine frame via a support. By means of the drive of the threaded spindle 21', the injector unit 3, to which the spindle motor 20' is firmly attached, is moved back and forth along the rail arrangements 18 via the thread of the threaded spindle 21' acting in cooperation with the spindle nut 23. As soon as the nozzle 25 makes contact with the mould 30 and the spindle motor 20' is moved further so that the injector unit 3 is displaced in the direction of the mould 30, the spring element 10' comes under load and deflects due to elastic deformation. This elastic deformation in turn provides the nozzle press force with which the nozzle 25 is pressed against the mould 30.

This is illustrated in Figure 5, which shows the deflected spring element 10'.
Figure 6 shows the arrangement of the spring element 10' on the traverse 50 of the machine frame in greater detail. Alternatively, the spring element could be arranged on the stationary platen.

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Firmly arranged in place via screw connections on the traverse 50 are two retaining elements 41, which have a bar extending from a square base, and an articulated head 46.
The spring element 10' in each case is accommodated on an articulated head 46 via a rotary joint 40.

Arranged in the middle of the spring element is the threaded nut 23, with an opening provided in the spring element 10' through which the threaded spindle 21' is guided.
The threaded spindle 21' is in engagement with the spindle nut 23, such that the threaded spindle 21' can move back and forth relative to the spindle nut 23 and spring element 10'.

Correspondingly, also provided in the traverse 50 is an opening through which the threaded spindle 21' may be guided.

For the purpose of guiding the threaded spindle 21', a centring unit 42 is arranged on the traverse 50, said unit having a plain bearing bushing 43, which cooperates with a centring pin 44 arranged on the spring element 10'. The centring pin 44 is movably accommodated in the plain bearing bushing 43 such that the centring pin 44 can be axially displaced in the plain bearing bushing 43. The centring pin 44 has a bore through which the threaded spindle 21' can be guided. In other embodiments, in which the threaded spindle need not move through the centring unit, such as when the spindle motor is arranged on the spring element or an actuator is mounted to the injector unit 3 and actuates a piston rod which is attached to the spring element, the bore in the centring pin can be dispensed with. However, even in such a case, a corresponding centring unit can be provided to guide the spring element during deflection.

The plain bearing bushing 43, together with the centring unit 42, makes it possible, in the event of deflection of the spring element 10', for the threaded spindle 21' to be accurately guided through the bore 44, such that no influences due to jamming and the like can occur.
Moreover, the bearing of the spring element 10' on the rotary joints 40 and the retaining elements 41 ensure that a precise and defined nozzle press force can be provided through the deformation of the spring element 10', without any impairment arising due to additional resulting moments or forces. Arranging the spring element 10' via a rotary joint 40 and the articulated head 46 of the retaining element 41 ensures that the respective ends of the spring element 10' can freely rotate about an axis perpendicular to the plane of Figure 6, such that the bearing does not introduce bending moments onto the spring element 10'. In addition, the

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thin bar 47 of the retaining element 41 permits displacement of the rotary joint 40 towards the threaded spindle 21' through corresponding elastic deformation of the bar 47, so that no significant additional forces or moments are applied as a result.
Correspondingly, a fixed connection, instead of a loose support, can be provided between the spring element and the traverse, e.g. with pushing elements, a fact which simplifies the construction.

Whereas, in the embodiment of Figure 6, the retaining elements 41 are arranged directly on a traverse 50 of the machine frame, Figure 7 shows an embodiment in which the retaining elements 41 are arranged on the side walls 5 of the machine frame via angle elements 48.

Here, too, just as in the previous embodiments, it is ensured that the force acting on the counter-support in the form of the support arrangement for the elastic spring element 10 or 10' is applied direct into the machine frame, which acts as a compact and stable frame for the entire injection moulding machine.
Although the present invention, as already stated above, can also be used in connection with other injection moulding machines which have a tiebar structure, use in the case of a tiebar-less injection moulding machine having the compact and stable machine frame construction, as shown for example in Figure 1, is particularly preferred, as this ensures optimum application of the force of the nozzle press force or the corresponding opposing force into the machine frame. Nevertheless, the advantages of the invention can also be used in other types of injection moulding machines having tiebars if the drive unit with a connection side, i.e. the spindle nut or a spindle motor, is arranged on a machine bed via a spring element.

Although the present invention has been described in detail with reference to the embodiments, it is self-evident to a person skilled in the art that the invention is not limited to these embodiments, but rather that modifications involving the omission of individual characteristics are possible, or that other types of combinations of the presented characteristics can be made without departing from the scope of the appended claims. The invention comprises in particular all combinations of individual characteristics presented.

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Claims

1. Injection moulding machine comprising an injector unit (3) having a nozzle (25) that can be displaced against a mould (30), wherein a drive unit is provided for displacing at least parts of the injector unit having the nozzle relative to the mould, wherein the drive unit comprises two connection sides for connecting to the components to be driven and displaceable relative to each other during driving, wherein a connection side of the drive unit is disposed on a machine frame or machine bed of the injection moulding machine and the other connection side is disposed on a displaceable part of the injector unit or is effectively connected thereto, characterised by the fact that the drive unit having the connection side of the drive unit provided on the machine frame or machine bed is supported by a spring element (10, 10'), such that a nozzle press force is provided by elastically deforming the spring element.

2. Injection moulding machine in accordance with claim 1, characterised by the fact that the drive unit comprises a drive (20, 20') and a unit for generating a translatory motion, especially a motor and a threaded spindle (21, 21') driven by the motor, and a spindle nut (23) acting in cooperation with the threaded spindle.

3. Injection moulding machine in accordance with claim 2, characterised by the fact that the drive, particularly the motor of the drive unit, or the displaceable end of the unit for generating a translatory motion (21, 21'), particularly the spindle nut, are arranged on the spring element (10, 10').

4. Injection moulding machine in accordance with any of the previous claims, characterised by the fact that that connection side (23; 20, 20') of the drive unit which is connected to the spring element (10, 10') is connected direct to the spring element, particularly in the form of a fixed bearing.

5. Injection moulding machine in accordance with any of the previous claims, characterised by the fact that the spring element (10, 10') is formed as a rod or plate, particularly by a part of the machine frame or machine bed, preferably by a traverse arranged transversely to the injection direction.

6. Injection moulding machine in accordance with any of the previous claims, characterised by the fact that the spring element (10, 10') has a spring displacement, which is parallel or concentric with the injection axis, particularly constituting a deflection of a rod or a plate in a direction opposite the injection direction.

7. Injection moulding machine in accordance with any of the previous claims, characterised by the fact that the spring element (10, 10') and/or that part (23; 20, 20') of a connection side of the drive unit which is arranged thereon are arranged concentrically with the injection axis or nozzle tip or, along an axis of symmetry offset from the injection axis or the centre point of the nozzle.

8. Injection moulding machine in accordance with any of the previous claims, characterised by the fact that the spring element (10, 10') is supported such that, where the spring element is elastically deformed as per a default spring displacement on the support points of the spring element, no force acts to falsify the elastic deformation of the intended spring displacement, in particular a support is provided via rotary joints on preferably bar-shaped connecting elements.

9. Injection moulding machine in accordance with any of the previous claims, characterised by the fact that a centring arrangement for the drive unit is provided in the region of the spring element.

10. Nozzle pressing device for pressing a nozzle (25) of an injection moulding machine against a mould (30) having a drive unit (20, 20'; 21, 21'; 23), which comprises two connection sides for connecting to the components to be driven and displaceable relative to each other during driving, wherein a connection side of the drive unit is disposed on a machine frame or machine bed of the injection moulding machine and the other connection side is disposed on a displaceable part of an injector unit or injection moulding machine or is effectively connected thereto, characterised by the fact that a spring element is provided on that connection side of the drive unit which is provided on the machine frame or machine bed, such that that connection side of the drive unit which is provided on the machine frame or machine bed is supported via the spring element, such that a nozzle press force can be provided by elastically deforming the spring element, particularly comprising the characteristics of claims 2 to 9.