Strand pelletizer

Abstract

This invention relates to a wire pelletizing machine for granulating wire materials, such as plastic wire materials, into pellets. The machine includes a cutting mechanism with a rotatably driven cutting rotor and a reverse cutter cooperating with the cutting rotor, wherein a cutting gap is formed between the cutting edge of the reverse cutter and the rotor tooth tip of the cutting rotor. According to the invention, at least one sensor is provided on the fixed reverse cutter for determining the cutting gap during operation of the cutting mechanism.

Description

Technical Field

[0001] The present invention relates to a wire pelletizing machine for pelletizing wire materials such as plastic wire into pellets, having a cutting mechanism having a rotatably driven cutting rotor and a reverse cutter cooperating with the cutting rotor, wherein a cutting gap is formed between the cutting edge of the reverse cutter and the rotor tooth tip of the cutting rotor. Prior Technology

[0002] This type of strang granulator is typically used for granulating plastic strangulates produced using a casting machine and associated nozzle plates. The strangulates are then conveyed to the strang granulator via a conveyor trough along with cooling water, depending on the settings or specific processing requirements. See, for example, DE 31 45 613 A1, EP 0 079 609 A1, or US 4,528,157 B1. This strang granulator, which can also perform dry cutting, can also granulate food or pharmaceutical active material strangulates, such as food products (in the form of pasta), into tablets. High throughput can be achieved by feeding multiple adjacent strangulates in parallel to the cutting mechanism.

[0003] Here, the cutting mechanism (Schneidwerk) includes a rotatably driven cutting rotor, which may have rib-like or strip-shaped cutting protrusions or rotor teeth on its circumferential surface. These cutting protrusions or rotor teeth cooperate with a fixed reverse cutter (Gegenmesser). The reverse cutter may essentially consist of a cutter bar (Messerleiste) positioned adjacent to the circumference of the cutting rotor, such that the strip-shaped protrusions or rotor teeth of the passing cutting rotor can knock off the plastic wire on the reverse cutter.

[0004] In order to feed the wire (Strängen) into the working area of ​​the cutting mechanism in a controlled direction and speed, that is, to the area between the reverse cutter and the cutting rotor in a controlled direction and speed, the supply device is located upstream of the cutting mechanism and has counter-rotating supply rollers between which the wire is fed to the cutting mechanism.

[0005] For example, documents DE 101 06 677 C1, DE 34 26 316 A1, DE 31 45 613 A1 and DE 26 00 078 A1 disclose such a cutting mechanism having a pair of upstream supply rollers or supply rollers.

[0006] To achieve high-quality cutting of plastic wire and make the cutting process efficient, the cutting gap between the rotor teeth of the cutting rotor and the cutting edge of the reverse cutter must be set very small and very precisely. This cutting gap should also be kept as consistent as possible over the length of the cutting rotor and the reverse cutter. If the cutting gap is too large, viscoelastic or viscous wire cannot be cleanly sheared, and a clean cutting edge cannot be obtained. Furthermore, because wire material is sheared between the rotor tooth tips and the cutting edge of the reverse cutter, the load on the cutting mechanism increases significantly, which may lead to increased bearing load, vibration, and higher power requirements.

[0007] Conversely, if the cutting gap is set too small, for example, if the cutting gap is initially set very small and then further reduced due to thermal load and the resulting deformation, there is a risk of direct mechanical contact between the rotor tooth tip and the reverse tool.

[0008] As mentioned above, setting the cutting gap of a wire pellet mill is very difficult because the cutting gap should be small but not too small, and it cannot be done perfectly even with a lot of experience. This is because it is difficult to estimate the effects on the cutting gap that occur during operation (such as thermal expansion and different wire materials), especially during the start-up process of the wire pellet mill.

[0009] The cutting gap on a wire rod pelletizer is usually measured manually with the machine stationary using a so-called spionbleche, which has very fine gradations (e.g., a scale of one-hundredth of a millimeter) to precisely set the cutting gap between the cutting rotor and the reverse cutter within 1 / 100th of a millimeter.

[0010] Nevertheless, it is difficult to accurately set the cutting gap due to the dynamic changes during the startup process. The cutting gap changes during machine startup, which negatively impacts the cutting process, due to the influence of hot wire and / or the temperature of the corresponding processing water. Depending on the treatment, such as when using cold or hot processing water, the gap may increase or decrease, where the process is dynamic. This change continues until a steady state is reached, where, in extreme cases, the cutting rotor may come into contact with the reverse cutter and cause corresponding damage.

[0011] To address these dynamic changes, attempts were made to measure the cutting gap at short intervals to identify what was happening to the cutting gap under given processing conditions. However, this measurement was both cumbersome and relatively inaccurate because the machine cools down or changes temperature rapidly after being shut down, meaning measurements had to be taken very quickly. In fact, the gap changes again once the machine stops and the cutter head opens. Summary of the Invention

[0012] Therefore, the object of the present invention is to create an improved strip granulator of the type described above, which avoids the disadvantages of the prior art and further improves upon it in an advantageous manner. In particular, the setting of the cutting gap should be improved so as to better cope with dynamic changes caused by, for example, temperature variations.

[0013] Therefore, a sensor system suitable for this purpose is proposed to measure the cutting gap between the cutting rotor and the reverse cutter during operation, i.e., when the cutting rotor is running and / or when cutting wire. According to the invention, at least one sensor is provided on the fixed reverse cutter to determine the cutting gap during operation of the cutting mechanism. By means of this at least one sensor operating during the cutting operation, changes in the cutting gap during operation can be detected or monitored, and in particular, dynamic changes in the cutting gap during the start-up process can be detected or monitored. By understanding the dynamic behavior of the cutting gap, the gap size can be set to an optimal value, thereby ensuring high-quality cutting while avoiding the risk of contact between the cutting rotor and the reverse cutter.

[0014] In an improved embodiment of the invention, the at least one sensor is positioned close to or adjacent to the cutting edge of the reverse tool so as to detect changes in the cutting gap as directly as possible.

[0015] In particular, the at least one sensor can be rigidly attached to the reverse tool, such that the sensor follows or experiences changes in the distance between the reverse tool and the cutting rotor in the same manner as the reverse tool.

[0016] Specifically, the at least one sensor may be arranged to be at least partially embedded in the reverse cutter, and with respect to the rotation direction of the cutting rotor, the at least one sensor may be arranged behind or downstream of the cutting edge of the reverse cutter, and toward the rotor teeth that are passing over the reverse cutter. Preferably, the at least one sensor may be located directly below the cutting edge of the reverse cutter, where "below" means that the cutting edge itself protrudes slightly toward the cutting rotor above the sensor, for example, in an overhanging manner, and the rotor teeth that are passing over first glide over the cutting edge itself and then over the sensor.

[0017] The sensor can be positioned on the reverse cutter, for example, such that when the rotor tooth tip is exactly at the cutting edge of the reverse cutter relative to the rotor tooth of the cutting rotor, the rotor tooth rotates by a rotation angle of less than 20º, less than 10º, or less than 5º, the sensor is precisely aligned with the rotor tooth.

[0018] Advantageously, the at least one sensor can be designed to detect the passing rotor tooth tip of the cutting rotor, and in particular, to detect the distance from the rotor tooth tip.

[0019] Advantageously, the at least one sensor is a non-contact distance sensor. In particular, the sensor can be designed in the form of an eddy current sensor.

[0020] This eddy current sensor can determine the distance to conductive rotor teeth, which can be made of, for example, steel or other conductive alloys. Advantageously, in the case of this eddy current sensor, non-conductive media such as water or coolant, as well as materials such as thermoplastic wire, do not affect the measurement results.

[0021] In order to detect rotor tooth tips that typically pass very quickly with sufficient accuracy, the at least one sensor can operate at a relatively high sampling frequency, which in an improved embodiment of the invention is greater than 2 kHz, greater than 5 kHz, or even greater than 10 kHz or even greater than 30 kHz.

[0022] In an advantageous improvement of the invention, multiple sensors are distributed along the cutting gap so that the cutting gap can be measured in different parts of the cutting mechanism. In this way, uneven dynamic changes in the cutting gap can also be accurately detected over the entire width; for example, since the supply at the center is greater than the supply at the left and right edges of the cutting mechanism, the center may experience greater changes than the left and right edges. Simple Explanation of the Diagram

[0023] The present invention will now be explained in more detail with reference to preferred embodiments and related figures. [Figure 1] shows a partially sectional side perspective view of a wire pelletizer according to an advantageous embodiment of the invention, illustrating the cutting mechanism of the wire pelletizer including a cutting rotor and a reverse cutter, and a supply device located upstream of the cutting mechanism including a pair of counter-rotating supply rollers. [Figure 2] shows a partial cross-section of the cutting mechanism and the upstream supply roller, illustrating a distance sensor positioned below the cutting edge of the reverse cutter for detecting the cutting gap size, and [Figure 3] shows a partially enlarged cross-sectional view of the sensor embedded in the reverse cutter in Figure 2, which shows the position of the sensor in the reverse cutter and relative to the tip of the rotor teeth of the cutting rotor. Implementation

[0024] As shown in the figure, the wire pelletizing machine 1 includes a cutting mechanism 2, which has a rotatable cutting rotor 3. The cutting rotor is equipped with a reverse blade 4, so that the wire (e.g., thermoplastic wire) can be cut or sheared by the cutting rotor 3 on the reverse blade 4.

[0025] In a manner known per se, the cutting rotor 3 has circumferential cutting protrusions or rotor teeth 5, which may be designed as strips and may extend substantially along the entire length of the cutting rotor 3. Here, the cutting protrusions or rotor teeth 5 may be arranged substantially parallel to the longitudinal roller axis of the cutting rotor 3, but may also extend at an angle relative to the longitudinal axis or extend slightly helically along the cylindrical envelope of the cutting rotor 3. Referring to Figures 2 and 3, in cross-section, the rotor teeth may be generally tapered and / or arranged obliquely relative to the radial direction, such that the tooth tips are slightly forward-tilted with respect to the rotation direction 7 of the cutting rotor 3 in order to "bite" into the wire.

[0026] The reverse cutter is arranged on the envelope of the cutting rotor 3 and can be designed as a strip or form a plate-shaped blade, with the rotor teeth 5 of the cutting rotor 3 passing beside the reverse cutter. In particular, the reverse cutter 4 can have a cutting edge 8 that extends along the envelope of the cutting rotor 3, specifically parallel to the axis of rotation of the cutting rotor 3, and referring to Figure 2, the cutting edge can be progressively cut or "sharpened" at a slightly acute angle.

[0027] A cutting gap is defined between the cutting edge 8 of the reverse cutter 4 and the tooth tip 6 of the rotor tooth 5 of the cutting rotor 3. The size of this cutting gap can be in the range of a few percent of a millimeter.

[0028] To feed the wire (e.g., thermoplastic wire or food strip) to the cutting mechanism 2 at a controlled speed and direction, a supply device 10 is provided upstream of the cutting mechanism 2. This supply device 10 includes two counter-rotating supply rollers 11 and 12, which feed the strip between them and deliver it to the cutting mechanism 2. As shown in Figure 2, a counter-rotating cutter 4 is located in the transport area of ​​the supply rollers 11 and 12 and is arranged between the supply rollers 11 and 12 and the cutting rotor 3.

[0029] As is known, referring to Figure 1, the granulated strips from the continuous casting machine can reach the supply device via a conveying device such as a conveyor trough 9.

[0030] Referring to Figures 2 and 3, in order to determine the gap size of the cutting gap between the cutting edge 8 of the reverse cutter 4 and the tooth tip 6 of the cutting rotor 3 even during operation of the cutting mechanism 2, the cutting mechanism 2 is equipped with a sensor system having at least one sensor 13 disposed on the fixed reverse cutter 4. Advantageously, multiple sensors 13 can be distributed along the length of the cutting gap so that the gap size can be determined in different parts of the cutting mechanism 2.

[0031] As shown in Figures 2 and 3, the sensor 13 is advantageously mounted on the reverse cutter 4 and directly adjacent to the cutting edge 8, such that the sensor 13 follows changes in the distance of the reverse cutter 4 from the cutting rotor 3. In particular, the at least one sensor 13 is positioned on the lower portion of the reverse cutter 4 and, with respect to the rotation direction 7 of the cutting rotor 3, directly behind or downstream of the cutting edge 8, which is the portion reached by the individual rotor teeth 5 after passing the cutting edge 8.

[0032] As shown in Figures 2 and 3, sensor 13 can be advantageously arranged to be at least partially embedded in the reverse cutter 4, wherein the reverse cutter 4 may have a hole (e.g., a blind hole) opening towards the cutting rotor 3, in which the sensor can be arranged to be embedded. If the sensor is equipped with a data cable, a through hole or lateral hole may also be provided on the reverse cutter to lead out the data cable. However, the sensor may also have a wireless data transmission module, such as Bluetooth or a radio interface.

[0033] The sensor head of the sensor 13 can be oriented toward the passing rotor tooth 5, wherein, referring to Figures 2 and 3, the sensor head can be arranged to be exposed to or flush with the side of the reverse cutter facing the cutting rotor 3.

[0034] The sensor 13 is advantageously designed as a non-contact distance sensor, particularly in the form of an eddy current sensor, which can detect the distance between the sensor head and the tip 6 of the rotor tooth 5 that is passing by, and thus the distance between the reverse cutter 4 and the tip 6 of the rotor tooth 5 that is passing by. The sensor head of the sensor 13 generates an eddy current field pointing towards the rotor tooth 5, which is influenced by the ferromagnetic rotor tooth according to the distance between the ferromagnetic rotor tooth and the sensor head, so that the sensor 13 can provide a sensing signal for characterizing the distance.

[0035] Advantageously, the sensor 13 operates at a sufficiently high sampling frequency (e.g., greater than 5 kHz or greater than 100 kHz) in order to accurately detect the rapidly passing tooth tip 6.

[0036] Advantageously, the gap size of the cutting gap measured online can be used to appropriately set the gap size by adjusting the position of the cutting rotor 3 and / or the reverse cutter 4. This can be advantageously done during the operation of the cutting mechanism, but can also be done in a stopped state. In this case, the feed device with the adjustment driver can be controlled by the control device according to the signal from the sensor 13 to move the cutting rotor 3 closer to or away from the reverse cutter 4. The reverse cutter 4 can also be moved accordingly if necessary.

[0037] 1: Wire pelletizing machine 2: Cutting mechanism 3: Cutting the rotor 4: Reverse tool 5: Rotor teeth 6: Tooth cusp 7: Rotation direction 8: Blade 9: Conveying trough 10: Supply device 11: Supply Roller 12: Supply Roller 13: Sensor

Claims

1. A wire pelletizing machine for granulating wire into pellets, the wire pelletizing machine having a cutting mechanism (2), the cutting mechanism comprising a rotatably driven cutting rotor (3) and a reverse cutting tool (4) cooperating with the cutting rotor, wherein, A cutting gap is formed between the cutting edge (8) of the reverse cutter (4) and the rotor tooth tip (6) of the cutting rotor (3), characterized in that at least one sensor (13) is provided on the fixed reverse cutter (4) for determining the gap size of the cutting gap during operation of the cutting mechanism (2); wherein the at least one sensor (13) is arranged on the side portion of the reverse cutter (4), and the rotor tooth (5) reaches the side portion with a rotation angle of less than 5º relative to the cutting rotor position when the rotor tooth tip (6) of the rotor tooth (5) is exactly at the cutting edge (8) of the reverse cutter (4); wherein the at least one sensor (13) has a sampling frequency greater than 30 kHz; wherein during the operation, i.e. when the cutting rotor (3) is running and when cutting wire; wherein the sensor (13) is arranged downstream of the cutting edge (8); wherein the cutting edge (8) protrudes slightly above the sensor (13) toward the cutting rotor (3).

2. The wire pelletizing machine according to claim 1, wherein, The at least one sensor (13) is designed as a non-contact distance sensor.

3. The wire pelletizing machine according to claim 1 or 2, wherein, The at least one sensor (13) is designed as an eddy current sensor.

4. The wire pelletizing machine according to claim 1 or 2, wherein, The at least one sensor (13) is arranged on the reverse cutting tool (4) and adjacent to the cutting edge (8) of the reverse cutting tool (4).

5. The wire pelletizing machine according to claim 1 or 2, wherein, The at least one sensor (13) is directed toward the passing rotor tooth tip (6) of the cutting rotor (3) and / or detects the distance of the passing rotor tooth tip (6) from the sensor head of the sensor (13) and / or the reverse cutter (4).

6. The wire pelletizing machine according to claim 1 or 2, wherein, The at least one sensor (13) is arranged to be at least partially embedded in the reverse cutter (4) and is positioned behind the cutting edge (8) of the reverse cutter (4) and toward the cutting rotor (3) with respect to the rotational direction (7) of the cutting rotor (3).

7. The wire pelletizer according to claim 1 or 2, wherein, Multiple sensors (13) are distributed along the length of the cutting gap and mounted on the reverse cutter (4).

8. The wire pelletizer according to claim 1 or 2, wherein, The device is equipped with a cutting gap adjustment device and a feeding device. The cutting gap adjustment device is used to adjust the gap size of the cutting gap, and the feeding device is used to feed the cutting rotor (3) to make it closer to or farther away from the reverse tool (4) and / or to feed the reverse tool (4) to make it closer to or farther away from the cutting rotor (3).

9. The wire pelletizing machine according to claim 8, wherein, The feeding device includes an adjustment driver and a control device, the control device being used to control the adjustment driver to adjust the cutting gap according to a signal from the at least one sensor (13) during operation of the cutting mechanism (2).

10. The wire pelletizing machine according to claim 1 or 2, wherein, The wire material is plastic wire material.

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