DE102022117755A1 - Sensor unit for monitoring a cavity in an injection mold - Google Patents

Abstract

Sensor unit (1) for monitoring a cavity (2) in an injection mold (3). The sensor unit (1) typically comprises a housing (4) which is designed so that it can be arranged in a corresponding opening (5) of the injection mold (3), the housing (4) comprising an end face (6) which is designed so that it can be integrated into a side wall (7) of the cavity (2). The housing (4) comprises a first bore (8) and a second bore (9), which extend to the end face (6) and are spaced apart from one another in a lateral direction (x). A first sensor (10), which is arranged in the first bore (8), is connected to the end face (6) and a second sensor (11), which is arranged in the second bore (9), is connected to the end face ( 6) connected.

Description

AREA OF DISCLOSURE

The present disclosure relates to a sensor unit for monitoring the conditions in a cavity of an injection mold, an injection mold with such a sensor unit, an injection molding device with such an injection mold and a method for monitoring a cavity in such an injection mold.

BACKGROUND OF THE DISCLOSURE

The placement of sensors in relation to a cavity of an injection mold is known from the prior art; examples of this are listed below.

JPH0631764A, published in 1994 in the name of Honda Motor Co. Ltd., relates to a single cavity molding device. A pressure sensor and a temperature sensor are arranged in the cavity. Based on the temperature and pressure state of the resin, the solidified state of the resin in the cavity, the formation state of the hollow part and the like are determined.

EP2212086B1 , published in 2014 on behalf of Priamus Systems Technologies AG, concerns an injection molding machine that has control means. Molten plastic is introduced into a cavity of an injection mold of the injection molding machine, with a viscosity of the plastic in the injection mold being determined from at least one internal mold pressure sensor and a mold wall temperature sensor arranged next to the cavity.

EP3950262A1 , published in February 2022 on behalf of Chung Yuan Christian University, relates to an injection molding device having a mold, an injector and at least one sensor. The shape has a cavity. The injection device is suitable for injecting a material into the cavity of the mold so that the material is formed into a molded part. The at least one sensor is arranged on the mold and is suitable for detecting at least one temperature or a pressure in the cavity of the mold. The at least one sensor is located on an inner surface of the cavity and corresponds to an invisible surface of the molded part.

SUMMARY OF DISCLOSURE

To monitor the production of plastic parts in an injection mold, in particular during the injection of liquefied (viscous) plastic material into at least one cavity of the injection mold, one or more sensors can be arranged which are connected to the at least one cavity. During operation, at least one property of the plastic material injected into the cavity and/or the behavior of the plastic material when injected into a cavity can be determined from the signal from the sensor. Using these characteristics, the process can be adjusted and controlled, and waste and errors can be avoided. The flow of the liquefied plastic material in the cavity during the injection process is rapid and takes place under high pressure and high temperature, which places high demands on the sensors, especially over time, as they typically have to withstand millions of cycles. Two or more sensors may be located near a single cavity to monitor the at least one cavity and the conditions, particularly of the material injected therein, during operation. If several cavities of an injection mold are equipped with sensors, it is possible to compare the conditions in several cavities. What is crucial, however, is that the measurement of the process parameters is accurate and can be compared with one another. If more cavities are monitored, the production consistency of the individual cavities can also be improved.

Good results can be achieved if two sensors are connected to the cavity in a specific way, as described in more detail below. Depending on the geometry of the cavity, which defines the shape of the plastic parts formed in it, placing two individual sensors is complex and in some cases not even possible due to the spatial requirements of both sensors. Particularly if small parts are to be produced, the cavities for their shaping are correspondingly small, which makes it difficult to position two individual holes connected to the cavity in the injection mold for the sensors. If the sensors are to be used to determine process parameters that correlate with the flow behavior of the viscous material (calculated parameters such as shear rate, shear stress, viscosity or flow rate), the position of the individually placed sensors often has to be determined in a complex manner, since the distance between the sensors is is usually an input variable that is needed to determine these process parameters. In addition, the sensors should be easy to install and maintain or replace without compromising their durability to prevent plastic material leakage during production.

Producing high-quality plastic parts requires accurate and repeated monitoring Relevant physical variables such as temperature, pressure and time (when does the material pass through the individual sensors) of the viscous plastic material that passes the sensor front during an injection cycle and then, for example, during the curing of the material in the holding pressure phase and/or the cooling phase, are advantageous.

One aspect of the present disclosure therefore relates to a sensor unit with at least two sensors for monitoring at least one representative cavity in an injection mold. In a preferred embodiment, the sensor unit comprises a housing with a specific design for arrangement in a corresponding opening of the injection mold, i.e. in a cavity plate of the injection mold. Typically, the opening in which the sensor unit is arranged in the mounted position extends into the cavity and corresponds at least partially to the specific design of the housing in which the sensors are arranged. Typically, the opening is designed so that it leads into the cavity, so that the front side of the housing of the sensor unit forms part of the side wall of the cavity. The opening can also be designed as a blind hole.

The housing of the sensor unit includes an end face that is designed so that it can be integrated into a side wall of the cavity. The housing typically has a first bore and a second bore extending into the end face and spaced apart in a lateral direction. A first sensor is disposed in the first bore connected to the face and a second sensor is disposed in the second bore connected to the face of the housing. Optionally, three or more sensors are arranged in respective bores of the housing in a specific position relative to one another, in particular at a specific distance from one another.

The viscosity of the material is an important factor in monitoring and controlling the consistency of the injection molding process. It is usually determined depending on the shear rate. Viscosity describes dynamic shear stresses that arise from internal friction in moving liquids or in pasty compositions. The definition of viscosity is usually based on Newton's theory, which states that shear stress is proportional to shear rate. The proportionality factor in this case is called viscosity (shear viscosity). The shear stress corresponds to the shear force per unit area and the shear rate corresponds to the quotient v/b, i.e. the change in the displacement speed of one boundary surface relative to the other divided by the distance between the two boundary surfaces (side wall of the cavity). The distance between the first and second sensors serves as the input variable for determining the shear rates (in particular for determining the speed of the injected plastic material). In particular, the distance between the first and second sensors along the flow direction of the plastic material in the cavity.

For example, two sensors arranged laterally at a certain distance from one another, which take into account the production conditions such as pressure, temperature and, if applicable, the sampling rate of the interconnected measuring device, offer significant advantages over the prior art. Preferably, the at least two sensors are arranged in a standardized housing that is part of the sensor unit. The housing can be in one or more parts. A sensor unit that can be easily inserted into a corresponding opening in the injection mold and removed again reduces the disadvantages known from the prior art. Since the physical properties can become largely independent of the rest of the device, the sensor unit can be manufactured, assembled and calibrated independently and outside of the rest of the injection molding device. This offers an advantage over two sensors installed individually in a cavity plate of an injection mold next to a cavity, since the distance between them must be measured after installation. A further advantage arises from the fact that the sensor unit can be replaced by a dummy, at least temporarily, even during production - when operating without sensors. The dummy can be integrated into the manufacturing process and is used to define the geometry of the end face into which the sensors are integrated. If necessary, the sensors can even be integrated into the dummy.

A sensor unit in the sense of the disclosure can, for example, be tested and pre-calibrated outside the injection mold in an auxiliary device before installation in the injection mold, which reduces maintenance and downtimes. If necessary, the sensor unit can be calibrated under operating conditions that exist during the operation of a target shape; in particular, the sensor unit can be precalibrated in an auxiliary device in the form of a test shape. A test form, for example, enables the sensor signals of the sensor unit to be compared with additional sensors that are present in the test form but not in the target form (production form).

Depending on the application, the sensors of the sensor unit can be a pressure sensor sor, in particular a piezoelectric pressure sensor, a temperature sensor, an acceleration sensor, a vibration sensor and a touch sensor or a combination thereof. In a preferred variant, the first sensor is a pressure sensor and the second sensor is a temperature sensor in order to determine a viscosity (or a value that correlates therewith) or a change in viscosity of the injected material from their signals. The temperature sensor is preferably of type K, J, S, L, particularly preferably of type N. Pressure sensors are preferably piezoelectric pressure sensors.

Preferably, the sensor unit has a specific property that can be determined remotely, i.e. if the sensor unit is arranged in a mounted position in the injection mold, the specific property can be determined from the outside of the mold. The specific property can be used, for example, to identify the sensor unit. Good results can be achieved if the specific property is a specific electrical and/or electronic property that is characteristic of the combination of sensors of the sensor unit. The specific electrical characteristic may correlate with at least one specification of the first and/or the second sensor subject to a database in which the specific characteristic is linked to a specification, such as: B. the type of sensor(s) of the sensor unit or the distance between the sensors. Preferably, the specific electrical and/or electronic property of the sensor unit is specific for the combination of the first sensor and the second sensor, so that it is controlled, for example, by an (external) electrical circuit (e.g. a charge amplifier or a control device for the injection mold or an injection molding device, which typically includes a processor and a memory). The electronic circuit can determine the at least one specification of the first and/or the second sensor from the specific property of the sensor unit using reference data.

Alternatively or additionally, another physical quantity or signature of the sensor unit can be recognizable from the outside, which is characteristic of the combination of the first sensor and the second sensor. Optionally, the sensor unit may include an internal electronic circuit that is configured to provide an externally recognizable electronic signature. However, the signature can also be implemented as a barcode, QR code, RFID tag or similar that can be read by an external electrical circuit. The specific electrical and/or electronic property correlates, for example, with a distance between the first and the second sensor. In particular, the specific electrical and/or electronic property correlates with a distance between a first sensor tip of the first sensor and a second sensor tip of the second sensor in the lateral direction.

In some variants, the first and/or the second sensor has a first electrical contact and a second electrical contact and an electrical and/or electronic device arranged therebetween, the electrical and/or electronic device essentially comprising the specific electrical and/or electronic property provides. In a preferred variant, the first electrical contact and the second electrical contact form (part of) an electrical connector. Preferably, the specific property of the sensor unit is independent of the operating conditions, in particular of temperature and pressure in the operating range.

Good results can be achieved if at least one electrical connector is arranged to be accessible from outside the housing, in particular from a rear side of the housing, in order to electrically releasably connect the first and/or the second sensor to the outside. If necessary, one electrical connector (part) per sensor is arranged in the housing, but the sensors can also be connected to one another via a single electrical connector or via one or more cables attached to the sensors, in particular firmly connected to them.

The back of the housing, which is typically located opposite the front, can serve as a mounting surface. When installed in the injection mold, a fastening element preferably engages in this mounting surface in order to press the sensor unit in the axial direction. The fastening element can be designed as an adjusting nut which has an external thread that engages in a corresponding internal thread of the opening of the injection mold. Alternatively or additionally, the sensor unit can be pressed in the axial direction by being clamped in the axial direction between the injection mold and a mounting plate of an injection device.

If the first sensor comprises a first sensor tip and the second sensor comprises a second sensor tip, the sensor tips preferably form part of the geometry of the end face. In this case, the first and second sensors are embedded in the front of the housing, allowing direct contact with the injected material during operation. At the same time, high-quality plastic parts can be produced that leave no or only minimal marks Have sensor tips on their surface if the sensor tips are embedded flush in the end face.

Alternatively, indirect contacting of the first and/or second sensor tip can also be implemented. For example, a protective element can be arranged in the front side in front of the respective sensor tip. In other variants, a surface-forming element can be arranged in the front side in front of a sensor, which enables indirect contact with the injection molding material and thereby creates a desired surface, e.g. a rough surface, on the plastic part.

The geometry of the face may be substantially planar or may have a 3D contour to follow the general contour of the cavity once integrated therein. The front side of the housing is preferably machinable so that the front side can be integrated flush into the geometry of the side wall of the respective cavity. The end face can be machined using a machining process and/or an ECM process (electrochemical machining).

The specific design of the sensor unit includes its shape. To make installation easier, the housing can have an outside (shape) with a mechanical stop, e.g. B. in the form of a projection. The mechanical stop is designed so that in the mounted position it fits into a corresponding counter-stop, e.g. B. in the form of a recess in the opening of the injection mold, intervenes to align the sensor unit with the side wall in the direction of the cavity or vice versa. The at least one projection may be formed integrally by the housing or it may be formed by a separate part attached to the housing. In some variants, the at least one projection is designed as a step. In a preferred variant, the outside comprises two projections which are arranged on opposite sides of the housing in a lateral direction. If the two projections are arranged at different heights in the axial direction (distance from the end face), an installation position for the housing can be defined so that the housing can only be inserted into a corresponding opening of an injection mold in this installation position. The orientation in this case typically refers to a rotational orientation about the axial direction. The outside preferably comprises four side surfaces, with two (adjacent or opposite) side surfaces each having a projection. If present, the other two side surfaces may be substantially planar.

Good results are possible if the outside of the housing has at least one essentially planar side wall, so that rotation in a corresponding opening of an injection mold is prevented. The housing preferably has a rectangular or partially curved cross section that can be easily processed using conventional means. Simplified production is possible if at least some outer edges of the housing, in particular concave and/or convex edges, are rounded. The housing preferably has a tapering cross section in the axial direction towards the end face. In particular, the taper in cross section is formed by the mechanical stop (or the at least one projection), so that the sensor unit can be inserted into the corresponding opening from a rear side of the injection mold (the cavity plate).

Preferably, the first sensor and the second sensor each comprise a sensor housing which is pressed by a fastening means in the axial direction against a stop surface of the respective bore. Typically, the stop surface is arranged in the circumferential direction on an inner wall of the bore. The fastening means can have an external thread that engages with an internal thread arranged on the respective bore. Typically, the fastening means is arranged concentrically to the respective bore. Optionally, the fastening means comprises a central opening that enables access to the at least one electrical connector of the first and/or second sensor.

In order to achieve good results, each sensor housing can have at least one sealing surface which, when assembled, cooperates with the stop surface arranged on an inner projection of the respective bore to form a tight connection. This minimizes the risk of viscous plastic material escaping during operation. If present, the spacer can be arranged between the sealing surface of the sensor housing and the inner projection of the respective bore. In this case, the spacer can act as a sealing ring. In addition, an O-ring can be arranged between the sensor housing or the respective sensor tip and the inner surface of the respective bore to further minimize leakage.

In some variants, a position of the first and/or second sensor in the housing is adjustable in the axial direction (insertion direction) of the first and/or second bore. In this way, in particular, the position of the first and/or the second sensor tip can be adjusted relative to the end face. If the end face is machined so that it can be integrated into the contour of the cavity, it can may be necessary to adjust the position of the first and/or the second sensor. This can be achieved by adjusting the size/height of a spacer, in particular a spacer ring, which is arranged between the first and/or the second sensor and the respective bore.

The longevity can be increased if the sensor housing of the first and/or second sensor is at least partially made of a first material and the housing of the sensor unit is at least partially made of a second material that has a similar degree of nobleness as the first material in order to prevent galvanic corrosion in between to minimize. Typically, both sensor housings and the housing of the sensor unit are made of steel, but protective coatings can also be applied to them.

Another aspect of the disclosure relates to an injection mold with a sensor unit as described above. The sensor unit is arranged in an opening of the injection mold, with the end face of the housing of the sensor unit being integrated into a side wall of the cavity. The injection mold is designed to be arranged within an injection molding device and to connect the sensor unit to an electrical circuit of the injection molding device. If necessary, the housing, in particular the end face, is at least partially made of a material used for the injection mold, such as steel or the like.

Another aspect of the disclosure relates to an injection molding device with an injection mold as described above. Preferably, the first and/or the second sensor are electrically connected to an electrical circuit configured to determine at least one process parameter based on the signals received from the first and/or the second sensor. If present, the electrical circuit typically includes at least one processor and at least one memory. Reference data is preferably stored in the memory, which relates a specific electrical property to a property of a sensor unit, as described above. Depending on the area of application, the processor is designed to determine at least one process parameter from the received sensor signals, the determined specific electrical properties and the reference data stored in the memory. Good results are possible when the processor is configured to control the injection of viscous plastic material based on the determined process parameter so that the process parameter remains within a predefined range.

The variants of the sensor unit described above simultaneously reveal correspondingly designed variants of the injection mold and the injection molding machine and vice versa.

One aspect of the disclosure relates to a method for monitoring a cavity of an injection mold, the method comprising the following steps. Providing the injection mold with a sensor unit as described above, the sensor unit being arranged in an opening of the injection mold, the end face of the housing of the sensor unit being integrated into a side wall of the cavity. Further steps include detecting a specific electrical property of the sensor unit in an electrical circuit connected to the sensor unit and determining at least one property of the sensor unit through the electrical circuit based on the detected specific electrical property using reference data.

A high performance is achieved if the property determined by the electrical circuit is a lateral distance between the first and the second sensor, in particular a distance between a first sensor tip of the first sensor and a second sensor tip of the second sensor along the front side of the housing. This allows the electrical (or electronic) circuit to independently determine a value for the lateral distance based on stored reference data. This makes manual entry unnecessary. The sensor unit can function as a viscosity sensor.

The previously described variants of the sensor unit and the injection mold simultaneously reveal corresponding variants for carrying out the method according to the disclosure and vice versa.

It is to be understood that both the foregoing general description and the following detailed description are embodiments and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings serve for further understanding and are part of this description and are incorporated into it. The drawings illustrate various embodiments and, together with the description, serve to explain the principles and operation of the concepts disclosed.

BRIEF DESCRIPTION OF DRAWINGS

• 1 eine perspektivische und teilweise geschnittene Ansicht einer ersten Variante einer Spritzgiessform mit einer ersten Variante einer Sensoreinheit gemäss der Offenbarung;
• 2 eine Detailansicht der ersten Variante von 1, die dort mit dem Buchstaben O bezeichnet ist;
• 3 eine perspektivische und teilweise geschnittene Ansicht einer zweiten Variante einer Spritzgiessform mit einer zweiten Variante einer Sensoreinheit gemäss der Offenbarung;
• 4 eine Schnittansicht der zweiten Variante von 3, die in dieser mit der Schnittlinie NN dargestellt ist;
• 5 eine perspektivische und teilweise geschnittene Ansicht einer dritten Variante einer Sensoreinheit gemäss der Offenbarung;
• 6 eine perspektivische und teilweise geschnittene Ansicht einer vierten Variante einer Sensoreinheit gemäss der Offenbarung;
• 7 eine Explosions- und Teilschnittdarstellung der ersten Variante der Sensoreinheit von 1 und 2; und
• 8 eine schematische Ansicht einer Spritzgiessvorrichtung gemäss der Offenbarung.

The disclosure described herein will be better understood from the following detailed description and the accompanying drawings, which should not be construed as limiting the disclosure described in the appended claims. The drawings show:

• 1 a perspective and partially sectioned view of a first variant of an injection mold with a first variant of a sensor unit according to the disclosure;
• 2 a detailed view of the first variant of 1 , which is designated there by the letter O;
• 3 a perspective and partially sectioned view of a second variant of an injection mold with a second variant of a sensor unit according to the disclosure;
• 4 a sectional view of the second variant of 3 , which is shown in this with the section line NN;
• 5 a perspective and partially sectioned view of a third variant of a sensor unit according to the disclosure;
• 6 a perspective and partially sectioned view of a fourth variant of a sensor unit according to the disclosure;
• 7 an exploded and partial sectional view of the first variant of the sensor unit 1 and 2 ; and
• 8th a schematic view of an injection molding device according to the disclosure.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to specific embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all, features are shown. In fact, the embodiments disclosed herein may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, the same reference numbers are used to refer to the same components or parts.

1 shows a perspective and partially sectioned view of a first variant of an injection mold 3, which includes a first variant of a sensor unit 1 according to the disclosure, and 2 shows a detailed view of the first variant of 1 , which is indicated therein by the circle O. Similarly shows 3 a perspective and partially sectioned view of a second variant of an injection mold 3, which includes a second variant of a sensor unit 1 according to the disclosure, and 4 a sectional view of the second variant of 3 , which is indicated therein by the cutting line NN. 5 shows a third embodiment of a sensor unit 1 according to the invention in a perspective and partially sectioned view. 6 shows a fourth variant of a sensor unit 1 according to the disclosure, in a perspective and partially sectioned view. In 7 is an exploded and partial sectional view of the first variant of the sensor unit 1 1 and 2 shown. 8th shows a schematic view of an injection mold 3 according to the disclosure in an injection molding device 31.

The variants of the sensor units 1 shown include a housing 4, which is to be arranged in an opening 5 of the injection mold 3, as in the and is best seen. The housing 4 has an end face 6, which is integrated into the side wall 7 of a cavity 2 of the injection mold 3, typically close to or adjacent to the cavity 2. Preferably, the end face 6 can be integrated flush into a geometry of the side wall 7 of the adjacent cavity 2, as in 2 shown. The housing 4 includes a first bore 8 which extends into the end face 6 and in which a first sensor 10 is arranged. A second bore 9 of the housing 4 is arranged at a distance from the first bore 8 in a lateral direction x and extends into the end face 6. A second sensor 11 is arranged in the second bore 9.

The variants of injection molds 3 shown include at least one of the variants of a sensor unit 1 described above. Typically, each variant of the injection molds 3 comprises at least a first and at least a second mold half, which are displaceable relative to one another between an open and a closed position. The at least one sensor unit 1 is integrated into the first and/or second mold half and preferably forms part of the contour of the mold halves (cavity half) (cavity side wall 7). In the closed position, the cavity 2 formed by the mold halves is suitable for receiving viscous plastic material. A flow path of the plastic material is in 4 represented by arrows with dashed lines. The viscous plastic material is injected through at least one injection nozzle 29, which is in fluid communication with the cavity 2, to fill the cavity 2 and form plastic parts. Good results are possible if the first and second sensors 10, 11 are arranged one behind the other in the direction of the flow path, so that the plastic material passes through the first and second sensors 10, 11 one after the other. This makes it possible, for example, to determine the viscosity of the plastic material during injection.

8th shows a first variant of an injection molding device 31, in which the sensor unit 1 is connected to an electrical circuit 28 via electrical connections 26 (on the sensor unit side), 30 (on the electrical connector side). The electrical circuit 28 is preferably designed to determine at least one process parameter (temperature, pressure, shear rate, shear stress, viscosity, flow rate, cooling rate, shrinkage, etc.) based on signals from the first and/or the second sensor 10, 11. Optionally, the electrical circuit 28 is configured to control the injection of viscous plastic material based on the determined process parameter, as indicated by the solid line between the electrical circuit 28 and an injector 29.

In the first variant of the sensor unit 1 shown, the first sensor 10 is a pressure sensor and the second sensor 11 is a temperature sensor. In the second variant of the sensor unit 1 shown, the first sensor 10 is a temperature sensor and the second sensor 11 is a pressure sensor. In the third and fourth variants of the sensor unit 1 shown, the first sensor 10 and the second sensor 11 are each a temperature sensor.

Like in the 2 and 7 best seen, the first sensor 10 and the second sensor 11 each include a sensor housing 21, which is pressed by a fastening means 22 in the axial direction z against a stop surface 23, which is arranged on an inner projection 25 of the respective bore 8, 9 is. In the assembled state, a sealing surface 24 of each of the sensor housings 21 interacts with the stop surface 23 of the respective bore 8, 9 to form a sealing connection. This is particularly the case when the fastening means 22 presses the sensor housing 21 in the axial direction z against the end face 6 of the housing 4.

The outside 18 of the housing 4 typically has at least one projection 19 (partial or in the circumferential direction) which engages in a corresponding recess 20 of the opening 5 of the injection mold 3 when it is installed therein. The variants shown each have two projections 19 which extend along the outside 18 and have a step-shaped geometry. The projections 19 each form an alignment platform, as in 7 shown, whereby the distance of the first projection (the one next to the first bore 8) in the axial direction x to the end face 6 is greater than the distance of the second projection 19 (the one next to the second bore 9) to the end face 6. Typically, the outside 18 consists of four side surfaces and a back 27, with two side surfaces each having a projection, as described, and the other two side surfaces being planar to ensure good alignment of the opening 5. This predetermines (similar to a Poka-Yoke plug) an installation position and orientation of the housing 4 and thus of the sensor unit 1 in the opening 5 of the injection mold 3, as in 2 shown. Typically, the sensor unit 1 is inserted into the corresponding opening from the back of the injection mold 3 (the cavity plate). This is in the 1 and 3 can be seen, whereby the respective sensor unit 1 is installed in the axial direction z by first lowering the sensor unit 1 with its end face 6 into the opening 5 until the projection 19 or the sealing surface 24 arranged thereon has a corresponding surface on the recess 20 the opening 5 comes into engagement.

6 shows a variant of the sensor unit 1, in which both the first and the second sensor 10, 11 have an electrical connection 26, which consists of a first electrical contact 12 and a second electrical contact 13. Depending on the sensors used, an electrical device 14 can be arranged between the first and second electrical contacts 12, 13. In the first variant, which is in 7 is shown, the electrical device 14 arranged between the first and the second electrical contact 12, 13 of the second sensor 11, which is a piezoelectric pressure sensor, has a specific electrical property that can be detected from the outside. This specific electrical property correlates with the distance 15 between the first sensor tip 16 and the second sensor tip 17 along the end face 6, as in 5 you can see. How out 2 As can be seen, this corresponds to the distance 15 between the sensor tips 16 and 17 along the flow path during operation of the injection mold 3.

Rather, the words used in the specification are descriptive rather than restrictive, and it is understood that various changes may be made without departing from the scope of the disclosure.

LIST OF REFERENCE SYMBOLS

1

Sensor unit

2

cavity

3

Injection mold

4

Housing

5

Opening (injection mold)

6

Front side (housing)

7

side wall (cavity)

8th

First hole

9

Second hole

10

First sensor

11

Second sensor

12

first electrical contact

13

second electrical contact

14

Electrical device (electrical property)

15

Distance (between the first and second sensors)

16

first sensor tip

17

Second sensor tip

18

Outside (housing)

19

Projection (outside of the housing)

20

Deepening (opening, injection mold)

21

Sensor housing

22

Fasteners

23

Stop surface (inner projection, hole)

24

Sealing surface (sensor housing)

25

Inner projection (hole)

26

Electrical connector (sensor)

27

Back (housing)

28

electrical circuit

29

injector

30

Electrical connector (electrical circuit)

31

Injection molding device

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2212086 B1 [0004]
• EP 3950262 A1 [0005]

Claims (17)

Sensor unit (1) for monitoring a cavity (2) in an injection mold (3), the sensor unit (1) comprising: a. a housing (4) which is designed so that it can be arranged in a corresponding opening (5) of the injection mold (3), the housing (4) having an end face (6) which is designed so that it is in a side wall (7) of the cavity (2) can be integrated; b. the housing (4) has a first bore (8) and a second bore (9) which extend to the end face (6) and are spaced apart from one another in a lateral direction (x); c. a first sensor (10) arranged in the first bore (8) and connected to the end face (6); d. a second sensor (11), which is arranged in the second bore (9) and connected to the end face (6). Sensor unit (1). Claim 1 , wherein the sensor unit (1) has a specific property that can be determined remotely, in particular when the sensor unit (1) is arranged in a mounted position from the outside of the injection mold (3). Sensor unit (1). Claim 2 , wherein the specific property is a specific electrical and/or electronic property that is characteristic of the combination of the first sensor and the second sensor (10, 11). Sensor unit (1). Claim 3 , wherein the first and/or the second sensor (10, 11) has a first electrical contact (12) and a second electrical contact (13) and an electrical and/or electronic device (14) arranged therebetween, the electrical device ( 14) essentially provides the specific electrical and/or electronic property. Sensor unit (1). Claim 3 or Claim 4 ,wherein the specific electrical and/or electronic property correlates with a distance (15) between the first and the second sensor. Sensor unit (1) according to at least one of the preceding claims, wherein the first sensor (10) has a first sensor tip (16) and the second sensor (11) has a second sensor tip (17), which are part of a geometry of the end face (6). Sensor unit (1) according to at least one of the preceding claims, wherein the end face (6) of the housing (4) can be processed so that the end face (6) can be integrated flush into a geometry of the side wall (7) of the adjacent cavity (2). Sensor unit (1) according to at least one of the preceding claims, wherein the housing (4) has an outside (18) with at least one projection (19) which is connected to a corresponding recess (20) of the opening (5) of the injection mold (3). Intervention can be brought to align the sensor unit (1) with the side wall (7) of the cavity (2). Sensor unit (1) according to at least one of the preceding claims, wherein a position of the first and/or the second sensor (10, 11) in the housing (4) in the axial direction (z) of the first and/or the second bore (8, 9 ) is arranged adjustable. Sensor unit (1) according to at least one of the preceding claims, wherein the first sensor (10) and / or the second sensor (11) each have a sensor housing (21) which is secured against in an axial direction (z) by a fastening means (22). a stop surface (23) of the respective bore (8, 9) is pressed. Sensor unit (1). Claim 10 , wherein each sensor housing (21) has at least one sealing surface (24) which, in the assembled state, cooperates with the stop surface (23) arranged on an inner projection (25) of the respective bore (8, 9) to form a tight connection. Sensor unit (1) according to one of the Claims 10 or 11 , wherein the sensor housing (21) of the first and / or the second sensor (10, 11) is at least partially made of a first material and the housing (4) of the sensor unit (1) is at least partially made of a second material, which is a has a similar degree of nobleness as the first material in order to minimize galvanic corrosion in between. Sensor unit (1) according to at least one of the preceding claims, wherein at least one electrical connector (26) is arranged to be accessible from outside the housing (4), in particular from a rear side (27) of the housing (4), in order to connect the first and/or to electrically connect the second sensor (10, 11) to the outside in a detachable manner. Injection mold (3) with a sensor unit (1) according to at least one of the preceding Claims 1 until 13 which is arranged in an opening (5) of the injection mold (3), the end face (6) of the housing (4) of the sensor unit (1) being integrated into a side wall (7) of the cavity (2). Injection molding device (31) with an injection mold (3). Claim 14 , where the first and/or the second sensor (10, 11) are electrically connected to an electrical circuit (28) which is configured to determine at least one process parameter based on the data from the first and/or the second sensor (10, 11). received signals. Method for monitoring a cavity (2) of an injection mold (3), the method comprising the following steps: a. Providing the injection mold (3) with a sensor unit (1) according to at least one of the preceding Claims 1 until 13 which is arranged in an opening (5) of the injection mold (3), the end face (6) of the housing (4) of the sensor unit (1) being integrated into a side wall (7) of the cavity (2); b. Detecting a specific electrical property of the sensor unit (1) in an electrical circuit (28) connected to the sensor unit (1); and c. Determining at least one property of the sensor unit (1) by the electrical circuit (28) based on the detected specific electrical property using reference data. Procedure according to Claim 16 , wherein the property obtained by the electrical circuit (28) is a lateral distance between the first and the second sensor (10, 11), in particular a distance (15) between a first sensor tip (16) of the first sensor (10) and a second sensor tip (17) of the second sensor (11) along the end face (6) of the housing (4).

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