Tilting measurement of a thermoforming mould

Abstract

A thermoforming mould for producing cup-shaped articles from a heated film of plastic is provided. The thermoforming mould comprises a first mould part and a second mould part which are movable in relation to one another, wherein at least one cavity for moulding a cup-shaped article is formed in one of the two mould parts. The thermoforming mould also comprises a measuring device which is designed to determine a tilting of the first mould part and the second mould part with respect to one another. Furthermore, a thermoforming machine comprising the thermoforming mould and also a method for determining a tilting between a first mould part and a second mould part of a thermoforming mould are provided.

Claims

1. A thermoforming mould assembly configured to be installed in a thermoforming machine for producing cup-shaped articles from a heated film of plastic comprising a first mould part and a second mould part, which are movable in relation to one another, wherein at least one cavity for moulding a cup-shaped article is formed in one of the two mould parts, wherein the thermoforming mould comprises a measuring device which is designed to determine a tilting of the first mould part and the second mould part with respect to one another, wherein the measuring device comprises: at least two sensors, wherein the at least two sensors are arranged spaced apart from one another on one of the two mould parts; and at least two reference elements associated with the at least two sensors and arranged on the other one of the two mould parts and opposite to the at least two sensors, wherein each of the at least two sensors is designed to measure a distance to the reference element with which it is associated, wherein the measuring device further comprises an evaluation device designed to determine the tilting of the two mould parts with respect to one another by comparing the measured distances of the at least two sensors to the corresponding reference elements.

2. The thermoforming mould assembly according to claim 1, wherein the at least two sensors comprise an inductive, capacitive, or optical sensor.

3. The thermoforming mould assembly according to claim 1, wherein the thermoforming mould furthermore comprises an optical or acoustic output device that is connected to the measuring device and that is designed to output an optical or acoustic warning signal if the determined tilting exceeds a prespecified limit.

4. The thermoforming mould assembly according to claim 1, wherein the measuring device furthermore comprises a communication interface in order to enable a data transfer between the measuring device and a user end device.

5. A thermoforming machine for producing cup-shaped articles from a heated film of plastic, comprising: the thermoforming mould assembly according to claim 1.

6. A method for determining a tilting between a first mould part and a second mould part of a thermoforming mould assembly installed in a thermoforming machine, the method comprising the following steps: providing a measuring device on the thermoforming mould, wherein the step of providing the measuring device comprises arranging at least two sensors spaced apart from one another on one of the two mould parts, and providing at least two reference elements associated with respective ones of the at least two sensors on the other one of the two mould parts; measuring, by means of each of the at least two sensors of the measuring device, a distance to the reference element with which each sensor is associated; and determining the tilting of the two mould parts with respect to one another by comparing the measured distances of the at least two sensors to the corresponding reference elements.

7. The method according to claim 6, wherein the step of measuring the distance takes place in an inductive, capacitive, or optical manner.

8. The method according to claim 6, wherein the method is carried out while the thermoforming mould is stopped and/or during its operation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a is a sectional view of a thermoforming mould according to the prior art;

(2) FIG. 1b is a sectional view of the thermoforming mould according to FIG. 1a, wherein the upper and the lower mould part have a tilting with respect to one another;

(3) FIG. 2a is a further thermoforming mould with an external dial gauge for the tilting measurement according to the prior art;

(4) FIG. 2b is a sectional view of an excerpt from the thermoforming mould illustrated in FIG. 2a for clarifying the measurement method according to the prior art;

(5) FIG. 3 is a schematic sectional depiction of an excerpt of a thermoforming mould according to the present invention; and,

(6) FIG. 4 is a flow chart for depicting a method for determining a tilting of two mould parts of a thermoforming mould according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIGS. 1a, 1b, 2a and 2b were already described in connection with the prior art. Refer to that portion of the description. A thermoforming mould according to the present invention shall be described in greater detail in the following using FIG. 3.

(8) FIG. 3 depicts an excerpt of a thermoforming mould 300, in cross-section, for producing cup-shaped articles from a heated film of plastic. The thermoforming mould 300 comprises a first mould part 310 and a second mould part 350. According to the illustration in FIG. 3, the first mould part 310 is an upper mould part and the second mould part 350 is a lower mould part of the thermoforming mould 300. The mould parts 310, 350 are arranged movable in relation to one another. According to the illustration in FIG. 3, a plurality of cavities, each for forming a cup-shaped article, are embodied in the second mould part 350. The first mould part 310 and the second mould part 350 can have some or all of the features of the upper mould part 110 or lower mould part 150 of the thermoforming mould 100 described in connection with FIGS. 1a and 1b. Refer to the description of FIG. 1a for a more detailed description of these features.

(9) In contrast to the thermoforming mould 100 in FIGS. 1a and 1b, the thermoforming mould 300 comprises a measuring device 320. The measuring device 320 is designed to determine a tilting of the first mould part 310 and the second mould part 350 with respect to one another. The measuring device 320 comprises at least one sensor 322. The measuring device 320 furthermore comprises at least one reference element 324. According to one preferred variant, the measuring device 320 of the thermoforming mould 300 can comprise at least two sensors 322 spaced apart from one another and at least two reference elements 324, each corresponding to one of the sensors 322. Each of the sensors 322 can be designed to record a measured value for the at least one reference element 324 with which it is associated.

(10) According to the illustration in FIG. 3, the at least one reference element 324 is arranged on the second mould part 350 and projects therefrom. Alternatively, the at least one reference element 324 can also be a surface or surface segment of the second mould part 350. According to a further alternative, the at least one reference element 324 can be any desired reference object that corresponds to a specific type of sensor so that, using the at least one corresponding sensor 322, at least one measured value can be recorded that indicates a tilting of the mould parts 310, 350 with respect to one another.

(11) The measured value can be a distance between the at least one sensor 322 and the reference element 324 corresponding to the sensor 322. Alternatively, the measured value can be a value that directly indicates the position of the mould parts 310, 350 with respect to one another. Such a value can be recorded using a surface scan of a 3D sensor (3D scanner).

(12) The at least one sensor 322 can be an inductive, capacitive, or optical sensor. Correspondingly, the measured value can be a capacitive value, inductivity value, or run time value (for the optical measurement) that is proportional to the distance to be measured. Alternatively, the at least one sensor can be a 3D scanner (i.e., a camera), a mechanical sensor (e.g. with a spring-loaded measuring rod), a sound sensor, an eddy current sensor, a magneto-resistive sensor, a piezoelectric sensor, or a pressure sensor.

(13) The at least one sensor 322 is designed to record measured values that can be used by an evaluation device (not shown in FIG. 3) of the measuring device 320 to determine a tilting of the two mould parts 310, 350 with respect to one another. The evaluation device can comprise at least one processor (also not shown in FIG. 3) that is designed to process the measured values provided by the at least one sensor.

(14) The thermoforming mould can comprise an optical or acoustic output device (not shown in FIG. 3) that is connected to the measuring device. The output device can be designed to output an optical or acoustic warning signal when a critical tilting of the mould parts has been determined by the evaluation device of the measuring device.

(15) The measuring device 320 can furthermore be designed to communicate with a user end device (for example, a PC, tablet, or smartphone) via a communication interface. The measuring device 320 can receive commands from a user via the end user device. Likewise, the recorded measured values and/or the determined tilting (e.g. the tilt angle α) can be called up by the measuring device 320 via the communication interface and transmitted (e.g. visually) on the end user device.

(16) In connection with FIG. 4, the following describes in greater detail a method 10 for determining a tilting between a first and a second mould part of a thermoforming mould according to the present invention.

(17) In a first step S11, the method 10 comprises providing the measuring device described above on a thermoforming mould. The step S11 of providing the measuring device can comprise attaching at least one sensor to one of the mould parts. In particular, the step of providing the measuring device can comprise mounting the at least one sensor securely to one of the two mould parts. Furthermore, the step S11 of providing the measuring device can comprise (securely) attaching at least one reference element to the mould part opposing the specific sensor.

(18) In a second step S13, the method 10 comprises recording, by means of the measuring device, at least one measured value, wherein the at least one measured value indicates the tilting between the first mould part and the second mould part. The step S13 of recording the at least one measured value can occur with respect to the at least one reference element. Furthermore, the step S13 of recording the at least one measured value can take place in an inductive, capacitive, or optical manner (or, as described briefly in the forgoing, using other types of measurements).

(19) In a third step S15, the method 10 comprises determining a tilting based on the at least one recorded measured value of the measuring device. Determining the tilting can comprise comparing at least two measured values that have been provided by the measuring device. The at least two measured values can preferably come from different sensors. The step of determining the tilting can furthermore comprise calculating a tilt angle α between the mould parts.

(20) The method 10 can also comprise further optional method steps S17, S18, and/or 519 in this or another sequence.

(21) The optional method step S17 can comprise transmitting the determined tilting (e.g. of the calculated tilt angle α) to a user end device. The transmitting can take place continuously during the thermoforming process. Continuous transmission of the determined tilting can inform a user about the tilting of the mould parts at any time (e.g. via the magnitude of the tilting).

(22) According to the method step S18, the method 10 can furthermore comprise outputting a warning signal if the determined tilting (e.g. the tilt angle α) is greater than or equal to a critical tilting (e.g. a critical tilt angle α.sub.krit). The warning signal can comprise an optical and/or acoustic signal.

(23) According to the method step S19, the method 10 can furthermore comprise automatically stopping the thermoforming process if the determined tilting during the thermoforming process reaches or exceeds a critical value. In particular, the machine operation can be stopped automatically if the calculated tilt angle α is greater than or equal to the critical tilt angle=α.sub.krit. Stopping the thermoforming process can comprise turning off the thermoforming machine in which the thermoforming mould is installed.

(24) It is understood that the method for determining the tilting between the first and second mould part of the thermoforming mould can also be performed when the thermoforming machine in which the thermoforming mould is installed is not running.

(25) With the inventive technology, it is possible to detect, rapidly (and precisely), tiltings of mould parts installed in thermoforming machines. Since the measuring device is permanently mounted in the thermoforming mould, the alignment of the thermoforming moulds with respect to one another can be checked even when the thermoforming machine is operating (i.e., during the thermoforming process). Thus continuous monitoring of the mould parts is possible for the first time. Due to the continuous monitoring, critical tiltings of the mould parts with respect to one another can be detected and eliminated early, so that overall wear on the mould parts is reduced.