Injection unit for an injection moulding machine

Abstract

The invention describes an injection unit for an injection moulding machine, having a plasticising cylinder (1) and a screw (2), which is operatively connected to a rotary drive (10) and to a linear drive (3) for drive purposes, wherein the linear drive (3) is designed as a hydraulic drive. The invention is characterised in that the linear drive (3) comprises at least two hydraulic cylinder sleeves (4a, 4b, 4c, 4d) that are arranged symmetrically with respect to one another about the longitudinal axis (L) of the screw (2). The hydraulic cylinder sleeves (4a, 4b, 4c, 4d) are arranged between two plates (5a, 5b) and connected thereto. A hydraulically actuatable cylinder piston (16a, 16b, 16c, 16d) having a piston rod (6a, 6b, 6c, 6d) is provided in each of the hydraulic cylinder sleeves (4a, 4b, 4c, 4d). In one of the plates (5b), a recess is provided for each of the piston rods (6a, 6b, 6c, 6d), through which recess the piston rods (6a, 6b, 6c, 6d) are guided and are operatively connected to the screw (2) for drive purposes.

Description

[0001] 77812-WO-KMT / Wl-Wl 21.01.2026

[0002] Description

[0003] Injection unit for an injection molding machine

[0004] The invention relates to an injection unit according to the preamble of claim 1.

[0005] In known injection units, the hydraulic linear drives for moving the screw essentially consist of one or more cast housings with covers on both sides. Within the respective housings between the covers are precision-machined sleeves, in which the pistons and piston rods are located to achieve the linear movement of the screw and thus generate the injection force.

[0006] The disadvantage of this is that such injection units contain a relatively large number of individual components, each of which must be explicitly designed and calculated and requires sufficient installation space. Therefore, such injection units are comparatively expensive to manufacture.

[0007] Based on this, the invention aims to provide an injection unit for an injection molding machine that requires fewer individual components and is comparatively compact in terms of its construction.

[0008] This problem is solved by an injection unit with the features of claim 1. Advantageous embodiments and further developments are specified in the dependent claims. 77812-WO-KMT / Wl-Wl 21.01.2026

[0009] According to a key concept of the present invention, as few individual components as possible should be assembled into a compact, hydraulic linear drive for the screw. Accordingly, at least two, preferably four, hydraulic cylinder sleeves are arranged symmetrically to each other around the longitudinal axis of the screw. However, matching covers are not used on the hydraulic cylinder sleeves. Instead, a first plate and a second plate are provided, and the hydraulic cylinder sleeves are arranged between these two plates and connected to them, for example, by screws. Each of the hydraulic cylinder sleeves contains a hydraulically actuated cylinder piston with a piston rod, and one of the plates has a recess for each piston rod through which the piston rods pass. The piston rods extending from the plate are operatively connected to the screw drive.

[0010] In a preferred embodiment, the linear drive can comprise four hydraulic cylinders, with two piston rods of the first type and two piston rods of the second type being provided, each arranged symmetrically to one another around the longitudinal axis of the screw. The piston rods of the first type can be designed as solid cylinders, and the piston rods of the second type at least partially as hollow cylinders. The hollow cylindrical interior of these piston rods of the second type extends from the cylinder piston, in the manner of a blind hole, to a depth of at least the travel distance of the cylinder piston, the cylinder piston also having an opening corresponding to the diameter of the blind hole. A pressurized fluid can be introduced into the interior of the piston of the second type via the hollow cylindrical interior or the blind hole.This allows the second type of piston rod to be used for an active movement of the screw opposite to the injection direction, provided that suitable measures are taken to ensure that the pressurization in the blind hole results in movement of the second type of piston. For example, the hollow cylindrical interior of the second type of piston rod can be connected to a pipe which is attached to the end of the hydraulic cylinder sleeve opposite the piston rod, the pipe being or being able to be connected to a pressure medium source. 77812-WO-KMT / Wl-Wl 21.01.2026.

[0011] The pipe can extend fluid-tight through the cylinder piston up to or into the blind hole.

[0012] According to a further embodiment, the plate located on the side of the cylinder piston facing away from the piston rod can, in at least one of the hydraulic cylinder sleeves, have a recess with a diameter larger than the diameter of the cylinder piston located in that hydraulic cylinder sleeve. Preferably, each of the hydraulic cylinder sleeves can have a recess with a diameter larger than the diameter of the cylinder piston located in that hydraulic cylinder sleeve. The respective cylinder piston, along with its associated piston rod, can be removed from the hydraulic cylinder sleeves via such a recess, for example, for maintenance or repair purposes. In this respect, such an embodiment of an injection unit according to the invention is particularly easy to maintain, which ultimately also has a positive effect on the costs incurred during maintenance and / or repair.

[0013] Each of the plates can have a recess designed to accommodate or allow the plasticizing cylinder to pass through. For example, this recess can be U-shaped, with dimensions such that the plasticizing cylinder can be supported at its base. The plasticizing cylinder can thus be positioned parallel to the cylinder sleeves along the longitudinal axis of the injection unit. This results in a correspondingly reduced installation space along the longitudinal axis of the injection unit.

[0014] A positive-locking and force-transmitting connection between the piston rods and the screw can be formed by means of one or more suitably designed connecting elements. According to a preferred embodiment, a plate-shaped connecting block can be provided as the connecting element, with the piston rods and the screw being attached to the plate-shaped connecting block. 77812-WO-KMT / Wl-Wl 21.01.2026

[0015] The two plates between which the hydraulic cylinder sleeves are mounted can be attached to a support plate or frame. This allows the hydraulic linear drive to be mounted as a unit on the machine bed of the injection molding machine. Linear guides can be provided parallel to each other on the support plate or frame, along which the rotary drive coupled to the screw, as well as the connecting element(s) between the screw and piston rods, can be moved during the injection process.

[0016] The rotary drive can be attached to the plate-shaped connecting block, with a torque-transmitting coupling provided between the worm and the rotary drive, which is rotatably mounted on or in the plate-shaped connecting block.

[0017] The invention will now be described in more detail using an exemplary embodiment and with reference to Figures 1 to 5. These show:

[0018] Figure 1 perspective view of an injection unit according to the invention; Figure 2 view from the direction of arrow P in Figure 1;

[0019] Figure 3 section along line AA in Figure 2;

[0020] Figure 4 View from the direction of arrow P in Figure 1 (= Figure 2);

[0021] Figure 5 section along line AB in Figure 4.

[0022] Figure 1 shows a perspective view of an injection unit designed according to the invention, with a plasticizing cylinder 1 (only partially shown) and a screw 2. The hydraulic linear drive 3 comprises four hydraulic cylinder sleeves 4a, 4b, 4c, and 4d, which are installed, for example, screwed in, between two plates 5a and 5b. A cylinder piston with a piston rod is installed in each of the hydraulic cylinder sleeves (see Figure 5). The piston rods 6a, 6b, 6c, and 6d are guided through suitable openings in the rear plate 5b (viewed from the injection direction) and are operatively connected to the screw 2 via a connecting element 7. The two plates 5a and 5b have a U-shaped recess for receiving the plasticizing cylinder 1 (see also 77812-WO-KMT / Wl-Wl 21.01.2026).

[0023] (Figures 2 and 4). The connecting element 7 can be designed as a plate or a plate-shaped connecting block. The hydraulic cylinder sleeves are open on the side of the front plate 5a. Atmospheric pressure therefore prevails on the side of the cylinder pistons facing away from the piston rods. The arrow pointing to the hydraulic cylinder sleeve 4d indicates the interior of this hydraulic cylinder sleeve. The piston rods 6b and 6d are designed as solid cylinders and can be considered piston rods of the first type. The piston rods 6a and 6c are partially hollow cylindrical, designed like a blind hole, and can be considered piston rods of the second type. In these piston rods 6a and 6c, a tube 8 is provided inside the associated hydraulic cylinder sleeve, with one end of the tube being attached to the front plate 5a via a tube holder 9, and the other end of the tube extending into the blind hole.Further details are described below in connection with Figures 3 and 5. The rotary drive 10 of the worm 2 is attached to the rear of the connecting element 7. The torque is transmitted to the worm 2 via a coupling 14, which is rotatably mounted in the connecting element 7 (see Figure 3). The plates 5a and 5b are mounted on a support plate 11. Two guide rails 12 are also mounted parallel to each other on the support plate 11, with only the front guide rail visible in Figure 1. Guide carriages 13 are attached to the underside of the connecting element 7 and engage with the guide rails 12. When the hydraulic linear drive 3 is operated, the drive force is transmitted to the worm 2 via the piston rods 6a to 6d and the connecting element 7.This involves the movement of the unit consisting of screw 2, connecting element 7, and rotary drive 10 towards the unit consisting of plates 5a, 5b, and hydraulic cylinder sleeves 4a to 4d. The first unit is moved along the guide rails 12. During metering, the first unit is moved in the opposite direction.

[0024] The sectional view in Figure 3 shows how the worm 2 is operatively connected to the rotary drive 10 via the coupling 14. The coupling 14 is installed in the connecting element 7 via suitable bearings. Due to the U-shaped recess in the plates 5a and 5b, Figure 377812-WO-KMT / Wl-Wl 21.01.2026

[0025] Only the area of ​​plates 5a and 5b located below the plasticizing cylinder 1 is shown hatched.

[0026] The sectional view in Figure 5 shows how the hydraulic cylinder sleeves are screwed to the plates 5a and 5b, although only the hydraulic cylinder sleeves 4b and 4c are visible in this illustration. The connecting element 7 for transmitting the drive force from the piston rods to the worm gear is only partially shown. The piston rod 6b and the cylinder piston 16b are solid cylinders. The piston rod 6c has a blind hole 15, and the cylinder piston 16c has an opening corresponding to the diameter of the blind hole 15. The blind hole 15 extends from the cylinder piston 16c to a depth of at least the travel distance of the cylinder piston 16c. A tube 8 is attached at one end to the front plate 5a via a tube holder 9. The opposite end of the tube 8 extends through the cylinder piston 16c into the blind hole 15. A pressurized fluid, such as oil, can be introduced into the blind hole 15 via the tube 8.This allows the associated piston rods 6a and 6c to be moved in the opposite direction to the injection direction. This makes it possible for the screw 2 to be moved not only backwards by back pressure, i.e., in the opposite direction to the injection direction, but also for an active drive to move the screw 2 in the opposite direction to the injection direction. However, it is also possible to omit the active drive and design all piston rods without blind holes. All piston rods would then be designed as solid cylinders, as shown in piston rods 6b and 6d. In such an embodiment, the screw 2 can only be moved in the opposite direction to the injection direction by back pressure. On the piston rod side, all hydraulic cylinder sleeves 4a to 4d contain oil pressure chambers 17, which can be supplied with hydraulic oil via oil connections 18.These oil pressure chambers 17 can supply oil pressure to the cylinder pistons 16a to 16d and generate a driving force for the movement of the screw 2 in the injection direction. 77812-WO-KMT / Wl-Wl 21.01.2026.

[0027] Reference symbol

[0028] 1 plasticizing cylinder

[0029] 2 snails

[0030] 3 Linear actuator

[0031] 4a -4d hydraulic cylinder sleeves

[0032] 5a Front plate

[0033] 5b Back plate

[0034] 6a Piston rod of the second type (with blind hole) 6b Piston rod of the first type (solid cylinder)

[0035] 6c Piston rod of the second type (with blind hole) 6d Piston rod of the first type (solid cylinder)

[0036] 7 Connecting element or connecting plate 8 Pipe

[0037] 9 Pipe bracket

[0038] 10 Rotary drive

[0039] 11 Support plate

[0040] 12 guide rails

[0041] 13 guide cars

[0042] 14 Clutch

[0043] 15 blind hole

[0044] 16b Cylinder piston of the first type

[0045] 16c cylinder piston of the second type

[0046] 17 Oil pressure chamber

[0047] 18 Oil connection

Claims

77812-WO-KMT / Wl-Wl 21.01.2026 Claims 1. Injection unit for an injection molding machine, comprising a plasticizing cylinder (1) and a screw (2) arranged therein, comprising a first drive as a rotary drive (10) of the screw (2), which is operatively connected to the screw (2) in terms of drive technology, comprising a second drive as a linear drive (3) of the screw (2), which is operatively connected to the screw (2) in terms of drive technology, wherein the linear drive (3) is designed as a hydraulic drive, characterized in that the linear drive (3) comprises at least two, preferably four, hydraulic cylinder sleeves (4a, 4b, 4c, 4d), the hydraulic cylinder sleeves (4a, 4b, 4c, 4d) being arranged symmetrically to each other around the longitudinal axis (L) of the screw (2), a first plate (5a) and a second plate (5b) being provided, the hydraulic cylinder sleeves (4a, 4b, 4c, 4d) being arranged between and connected to these two plates (5a, 5b), a hydraulically actuated cylinder piston (16a, 16b, 16c, 16d) with a piston rod (6a, 6b, 6c, 6d) being provided in each of the hydraulic cylinder sleeves (4a, 4b, 4c, 4d), and a connection being provided in one of the plates (5b) for each of the piston rods (6a, 6b, 6c, 6d). a recess is provided through which the piston rods (6a, 6b, 6c, 6d) are passed, and that the piston rods (6a, 6b, 6c, 6d) are operatively connected to the worm (2) in terms of drive technology.

2. Injection unit according to claim 1 , characterized by the fact that that the linear drive (3) comprises four hydraulic cylinder sleeves (4a, 4b, 4c, 4d), that two piston rods of the first type (6b, 6d) and two piston rods of the second type (6a, 6c) are provided, each arranged symmetrically to one another around the longitudinal axis (L) of the screw (2), that the piston rods of the first type (6b, 6d) are designed as solid cylinders and that the piston rods of the second type (6a, 6c) are designed at least partially as hollow cylinders, the hollow cylindrical interior of these piston rods of the second type (6a, 6c) extending from the cylinder piston (16a, 16c) in the manner of a blind hole (15) to a depth of at least the travel distance of the cylinder piston (16a, 16c). 77812-WO-KMT / Wl-Wl 21.01.2026 3. Injection unit according to claim 2, characterized by the fact that the hollow cylindrical interior of the piston rods of the second type or the respective blind hole (15) is connected to a tube (8) which is attached to the end of the hydraulic cylinder sleeve (4a, 4c) facing away from the piston rod (16a, 16c), wherein the tube (8) is or can be connected to a pressure medium source.

4. Injection unit according to claim 3, characterized by the fact that the pipe (8) extends fluid-tight through the cylinder piston (16a, 16c) to the blind hole (15) or into the blind hole (15).

5. Injection unit according to one of the preceding claims, characterized by the fact that the plate (5a) which is located on the side of the cylinder pistons (16a, 16b, 16c, 16d) facing away from the piston rods (6a, 6b, 6c, 6d) has a recess with a diameter Da in at least one of the hydraulic cylinder sleeves (4a, 4b, 4c, 4d) which is larger than the diameter Dz of the cylinder piston (16a, 16b, 16c, 16d) located in this hydraulic cylinder sleeve (4a, 4b, 4c, 4d).

6. Injection unit according to claim 5, characterized by the fact that Each of the hydraulic cylinder sleeves (4a, 4b, 4c, 4d) has a recess with a diameter Da which is larger than the diameter Dz of the cylinder piston (16a, 16b, 16c, 16d) located in this hydraulic cylinder sleeve (4a, 4b, 4c, 4d).

7. Injection unit according to one of the preceding claims, characterized by the fact that that each plate (5a, 5b) has a recess designed to receive or allow the plasticizer cylinder (1) to pass through, for example, a U-shaped recess. 77812-WO-KMT / Wl-Wl 21.01.2026 8. Injection unit according to one of the preceding claims, characterized by the fact that one or more connecting elements are provided which form a positive locking and force-transmitting connection between the piston rods (6a, 6b, 6c, 6d) and the screw (2).

9. Injection unit according to claim 8, characterized by the fact that a plate-shaped connecting block (7) is provided as a connecting element, wherein the piston rods (6a, 6b, 6c, 6d) and the worm (2) are attached to the plate-shaped connecting block (7).

10. Injection unit according to one of the preceding claims, characterized by the fact that the two plates (5a, 5b) are attached to a support plate (11) or a support frame.

11. Injection unit according to one of the preceding claims, characterized by the fact that Linear guides (12) are provided on the support plate (11) or the support frame, parallel to each other, on which the rotary drive (10) which is operatively connected to the screw (2) and the connecting element(s) between the screw (2) and the piston rods (6a, 6b, 6c, 6d) can be moved during the injection process.

12. Injection unit according to one of claims 9 to 11 , characterized by the fact that the rotary drive (10) is attached to the plate-shaped connecting block (7), wherein a torque-transmitting coupling (14) is provided between the worm (2) and the rotary drive (10), which is rotatably mounted on or in the plate-shaped connecting block (7).

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