INJECTION UNIT FOR A MOLDING MACHINE AND MOLDING MACHINE WITH SUCH A

Abstract

Injection unit for a molding machine, wherein the injection unit (1) has an injection element which is suitable for introducing a plastic material into a mold by means of a linear movement of the injection element, wherein the injection element is linearly coupled to a bearing element (8) and at least two linear drives are designed to exert a force on the injection element via the bearing element (8), wherein the force can be transmitted from the at least two linear drives to the bearing element (8) and thus to the injection element by means of a transmission element (4), and at least one clearance (13, 14) is arranged between the bearing element (8) and the transmission element (4) such that deformations of the bearing element (8) are not transmitted to the transmission element (4) or are transmitted to a reduced extent.- openings (6) for receiving the linear drives are provided in the bearing element (8) and - support surfaces (7) are provided between the bearing element (8) and the transmission element (4), characterized in that the support surfaces (7) extend away from the openings (6) transversely to an imaginary connecting line of the openings (6).

Description

The present invention relates to an injection unit for a forming machine having the features of the preamble of claim 1 and a forming machine with such an injection unit. Forming machines can include injection molding machines, injection presses, presses, or similar devices. The following section will describe the state of the art using an injection molding machine as an example. The same applies to general forming machines. US 2001 / 0038868 A1 discloses an injection device for an injection molding machine, wherein injection medium for an injection molding machine with a screw for metering plastic, which is rotatably mounted in a mounting plate which is longitudinally displaceable by means of at least two electrically driven spindles, wherein the pressure exerted by the plastic on the screw is determined by means of at least one sensor which measures the deformation of a connecting ring arranged between a stationary sleeve surrounding the rotary bearing of the screw and the mounting plate; the connecting ring is designed as an annular disk, the inner edge of which is connected to the sleeve and the outer edge of which is connected to the mounting plate. Injection units of this type have an injection element which is suitable for introducing a plastic material into a mold by means of a linear movement, wherein the injection element is linearly coupled to a bearing element and at least two linear drives are designed to exert a force on the injection element via the bearing element. Injection units are typically used to inject a plasticized material (for example, a thermoplastic polymer) into a mold. The plasticization of the material to be plasticized is achieved by supplying energy, which heats the material. Plasticizing screws are widely used for such applications. In this process, the material to be plasticized is plasticized by a rotational movement of the plasticizing screw (through shearing and, if necessary, with additional heating). An axial linear movement then ejects the plasticized material and introduces it into a mold via an injection nozzle. However, there are also other design variants in which plasticized material is fed to an injection cylinder and the injection cylinder, which is constructed like a piston-cylinder unit, introduces the plasticized material into the mold by means of a linear movement. After the plasticized material is fed into the mold, it solidifies within the mold, and a finished product or semi-finished product can be removed for further processing. The hardening of the plasticized material can occur through cooling or a chemical reaction. The linear movement of the injection element results in increased forces, which are usually generated by at least two linear drives. This movement and / or the force generated by the linear drives is transmitted to the injection element via a bearing element, whereby deformations occur in the bearing element due to force application torques and material properties. A disadvantage of this design is that any deformation of the bearing element directly affects the linear drives. With plate-shaped bearing elements, the force applied usually causes the plate to deflect. This deformation of the bearing element subsequently acts as a bending moment on the linear drives, thereby altering the stress conditions on the linear drives. As the power output of linear drives increases over time, the importance of stresses caused by bending moments also grows. The object of the invention is to reduce the stresses caused by bending moments acting back on the linear drives compared to the prior art. This problem is solved by an injection unit for a forming machine having the features of claim 1 and a forming machine having such an injection unit having the features of claim 18. According to the invention, it is provided that the force can be transmitted from the at least two linear drives to the bearing element and thus to the injection element by means of a transmission element, and that at least one clearance between the bearing element and the transmission element is arranged in such a way that deformations of the bearing element are not transmitted to the transmission element or are transmitted to a reduced extent. By providing this additional transmission element, to which the at least two linear drives are attached and which acts on the bearing element, it is possible to decouple the described deformation of the bearing element - at least to a large extent - from the at least two linear drives. Furthermore, gaps between the bearing element and the transmission element can prevent possible wedging of these two components against each other or into each other. By additionally decoupling the linear drives from the bearing element, it is possible to introduce forces more effectively with less material and thus smaller dimensions, since the linear drives are no longer affected by the deformation of the bearing element, which would otherwise subject the linear drives to higher wear and tear and require them to withstand higher stress. In the context of this document, when a plate is mentioned, it should not necessarily be assumed to be a flat, even plate. It may also have depressions and raised areas. Versions with ribs for stabilization are also quite conceivable. The term "molding machines" can refer to injection molding machines, injection presses, presses, or similar equipment. The plasticized material can be, for example, a thermoplastic polymer. Advantageous embodiments of the invention are defined in the dependent claims. It may be provided that the injection element is rotatably mounted on the bearing element. Preferably, the at least one relief is provided - preferably in an imaginary sectional view along the injection element - between a central axis of the injection element and at least one drive axis of at least one of the at least two linear drives. It is possible for at least two linear drives to be connected by a common transmission element. Alternatively, different transmission elements can be provided (for example, separate transmission elements for each linear drive). Preferably, a connection or contact surface – preferably substantially rectangular – is provided between the bearing element and the transmission element. It is also preferable that at least one clearance is arranged next to the connection or contact surface. It may be provided that at least one measuring diaphragm is arranged between at least one of the at least two linear drives and the transmission element. Such a measuring diaphragm can be used, for example, to measure the exerted compressive or tensile forces between the transmission element and the at least one of the at least two linear drives. Preferably, the at least two linear drives are designed as spindle drives, wherein preferably the spindle nut of the spindle drives is connected to the transmission element in a motion-locking manner. The bearing element and / or the transmission element may have a central opening. Preferably, a receptacle for the injection element is provided on the bearing element - essentially centrally. For the purposes of this document, a “centric” arrangement may mean that the relevant element is arranged on an imaginary center line of the injection element. Preferably, the injection element is designed as a plasticizing screw and / or an injection piston. At least one rotary drive can be provided to set the plasticizing screw into a rotary motion. Preferably, the at least one rotary drive is arranged on the transmission element and / or on the bearing element. It may be provided that the injection element is arranged in a mass cylinder. Preferably, the injection element is linearly motion-locked to the bearing element and the mass cylinder is linearly motion-coupled to a mounting plate, wherein the bearing element is linearly displaceable relative to the mounting plate by means of the at least two linear drives, from which the injection element can consequently be displaced in the mass cylinder via a linear movement of the bearing element. It may be provided that at least two drive motors are provided for driving the at least two linear drives, which at least two drive motors are preferably designed as electric motors - particularly preferably three-phase synchronous motors. Preferably, the at least two drive motors are arranged on the mounting plate. Further details and advantages of the present invention are explained in more detail below with reference to the description of the figures and the exemplary embodiments shown in the figures. Figure 1 shows a first exemplary embodiment according to the invention, and Figure 2 shows a perspective view of a bearing element. Fig. 1 shows a cross-sectional illustration of an embodiment of an injection unit 1 according to the invention, wherein the injection unit 1 has two linear drives. In this embodiment, these linear drives are designed as spindle drives 2. These spindle drives 2 are each connected to the transmission element 4 via a spindle nut 3 in a motion-locking manner. Measuring diaphragms 5 are arranged between the transmission element 4 and the spindle nut 3, through which measuring diaphragms 5 a force between spindle drive 2 and transmission element 4 can be measured. Furthermore, the transmission element 4 has openings 6 which are designed to accommodate the spindles of the spindle drives 2 in a retracted position - more precisely: a plasticizing position. The transmission element 4 is connected to the bearing element 8 via the contact surfaces 7, whereby a force from the spindle drive 2 can be transmitted to the bearing element 8 via the transmission element 4. The injection element, designed as a plasticizing screw 9, is rotationally and linearly fixed to the bearing element 8. To ensure the rotational degree of freedom of the plasticizing screw 9, it is connected to the bearing element 8 via the bearings 10. The plasticizing screw 9 can be set into a rotational movement via the pulley 11, which can be connected to a rotary motor via a belt. In this embodiment, the belt drive consists of a pulley 11 and a pinion (not shown for clarity) connected via a belt. As can be clearly seen in Fig. 1, the spindle drives 2 shown here are connected to each other via the common transmission element 4. The stiffening web 12 further stiffens this transmission element 4 in order to withstand the necessary forces. The inner clearance 13 and the outer clearances 14 between the transmission element 4 and the bearing element 8 create the necessary clearance so that any deformation of the bearing element 8 is not directly transferred to the transmission element 4 and thus to the spindle nuts 2 fixed to it. In Fig. 1, the force flow from the plasticizing screw (more precisely: the tip of the plasticizing screw 9) to the spindle drive 2 is indicated by the arrows, which clearly shows how the force coming from the plasticizing screw 9 is redirected or divided at the bearing element 8 and introduced into the spindle drives 2 via the transmission element 4. The plasticizing screw 9 is arranged in a mass cylinder 15, which is attached to a first mounting plate 16. The spindle drives 2 connected to the transmission element 4 are supported on a second mounting plate 17. Thus, the bearing element 8 (and the plasticizing screw 9 linearly connected to the bearing element 8) can be linearly displaced via the second mounting plate 17 relative to the first mounting plate 16 (and the mass cylinder 15 linearly coupled to the first mounting plate 16) by means of the two spindle drives 2. The first mounting plate 16 is connected to the second mounting plate 17 via connecting plates 18. It is also conceivable to use configurations in which the first mounting plate 16 and the second mounting plate 17 are connected by at least one spar, either alternatively or in addition to the connecting plates 18. Fig. 2 shows a perspective view of the bearing element 8, in which an opening for receiving the injection element – ​​more precisely, the plasticizing screw 9 – is provided centrally in the bearing element 8. Openings 6 are provided to the right and left of this to receive the spindles of the spindle drive 2 in a plasticizing position. In Fig. 2, the bearing surfaces 7 arranged on the bearing element 8 are clearly visible, on which (as already explained in Fig. 1) the transmission element 4 rests and thereby creates a certain degree of freedom between bearing element 8 and transmission element 4 - more precisely the spindle drives 2 arranged on the transmission element 4 - so that not every deformation of the bearing element 8 or every deformation is transmitted to the spindle drives to its full extent. Reference symbol list: 1 Injection unit 2 Spindle drive 3 Spindle nut 4 Transmission element 5 Measuring diaphragm 6 Openings 7 Contact surfaces 8 Bearing element 9 Plasticizing screw 10 Bearing 11 Pulley 12 Stiffening rib 13 Inner clearance 14 Outer clearance 15 Mass cylinder 16 First mounting plate 17 Second mounting plate 18 Connecting plate

Claims

Injection unit for a molding machine, wherein the injection unit (1) has an injection element which is suitable for introducing a plastic material into a mold by means of a linear movement of the injection element, wherein the injection element is linearly coupled to a bearing element (8) and at least two linear drives are designed to exert a force on the injection element via the bearing element (8), wherein the force can be transmitted from the at least two linear drives to the bearing element (8) and thus to the injection element by means of a transmission element (4), and at least one clearance (13, 14) is arranged between the bearing element (8) and the transmission element (4) such that deformations of the bearing element (8) are not transmitted to the transmission element (4) or are transmitted to a reduced extent.- openings (6) for receiving the linear drives are provided in the bearing element (8) and - support surfaces (7) are provided between the bearing element (8) and the transmission element (4), characterized in that the support surfaces (7) extend away from the openings (6) transversely to an imaginary connecting line of the openings (6). Injection unit according to the preceding claim, characterized in that the injection element is rotatably mounted on the bearing element (8). Injection unit according to at least one of the preceding claims, characterized in that the at least one clearance (13) is arranged between a central axis of the injection element and at least one drive axis of at least one of the at least two linear drives. Injection unit according to at least one of the preceding claims, characterized in that the at least two linear drives are connected to a common transmission element (4). Injection unit according to at least one of the preceding claims, characterized in that the contact surfaces provided between the bearing element (8) and the transmission element (4) are essentially rectangular. Injection unit according to the preceding claim, characterized in that the at least one relief (13, 14) is arranged next to the connection or contact surface (7). Injection unit according to at least one of the preceding claims, characterized in that at least one measuring diaphragm (5) is provided between at least one of the at least two linear drives and the transmission element (4). Injection unit according to at least one of the preceding claims, characterized in that the at least two linear drives are designed as spindle drives (2), wherein preferably the spindle nuts (3) of the spindle drives (2) are connected to the transmission element (4) in a motion-locking manner. Injection unit according to at least one of the preceding claims, characterized in that the bearing element (8) and / or the transmission element (4) have a central opening. Injection unit according to at least one of the preceding claims, characterized in that a receptacle for the injection element is provided substantially centrally on the bearing element (8). Injection unit according to at least one of the preceding claims, characterized in that the injection element is designed as a plasticizing screw (9) and / or an injection piston. Injection unit according to the preceding claim, characterized in that at least one rotary drive is provided to set the plasticizing screw (9) into a rotary motion. Injection unit according to the preceding claim, characterized in that the at least one rotary drive is arranged on the transmission element (4) and / or on the bearing element (8). Injection unit according to at least one of the preceding claims, characterized in that the injection element is arranged in a mass cylinder. Injection unit according to the preceding claim, characterized in that the injection element is linearly motion-locked to the bearing element (8) and the mass cylinder is linearly motion-coupled to a mounting plate, wherein the bearing element (8) is linearly displaceable relative to the mounting plate by means of the at least two linear drives. Injection unit according to at least one of the preceding claims, characterized in that at least two drive motors are provided for driving the at least two linear drives, which at least two drive motors are preferably designed as electric motors - particularly preferably three-phase synchronous motors. Injection unit according to the preceding claim, characterized in that the at least two drive motors are arranged on a mounting plate. Forming machine for the production of molded parts from plasticized material with at least one injection unit (1) according to one of the preceding claims.

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