Device with a heating press

Abstract

Device with a heating press (1) which has a vulcanization mold (2) for vulcanizing heating bladder blanks (5) consisting of at least one rubber mixture, characterized by that it has a programmable logic controller (4) with an input module which has at least one temperature sensor (3) which detects the temperature at a point within the material of the heating bladder blank (5) during a heating cycle, further comprising a central unit which processes the input signals of the temperature sensor (3) according to a control algorithm and with an output module which controls or adjusts the heating time of the heating press (1) via control signals.

Description

[0001] The invention relates to a device with a heating press which has a vulcanization mold for vulcanizing heating bladder blanks consisting of at least one rubber mixture.

[0002] The vulcanization process of heating bladders is influenced by a number of parameters, such as the temperature in the vulcanization mold, design details and specific features of the vulcanization mold, and the vulcanization properties of the rubber compounds from which the heating bladders are made. The influence of these diverse individual parameters and factors affects the vulcanization process of the respective heating cycle and, consequently, also the subsequent heating cycles. Currently, the length of the heating time of the vulcanization process is determined by the operating personnel before the start of vulcanization. It is therefore not possible to determine the actual state of the vulcanization process during vulcanization, and there is no way to influence the vulcanization parameters, such as time and temperature, during a heating cycle.The bladders vulcanized one after the other in a heating press can therefore differ from one another in terms of their properties and often do not have the optimal properties for a long service life.

[0003] The invention is therefore based on the object of providing a device in which heating bladder blanks can be vulcanized to heating bladders of high and consistent quality.

[0004] The object is achieved according to the invention in that the device has a programmable logic controller with an input module which has at least one temperature sensor which detects the temperature at a point within the material of the heating bladder blank during a heating cycle, further comprising a central unit which processes the input signals of the temperature sensor according to a control algorithm and with an output module which controls or adjusts the heating time of the heating press via control signals.

[0005] The programmable logic controller allows the length of the heating time to be controlled using temperature as an input variable. The optimal heating time for a heating cycle is continuously recalculated, and the heating cycle is terminated when the predefined degree of vulcanization is reached. The bladders vulcanized in this way exhibit the desired mechanical and physical properties.

[0006] Particularly preferred is an embodiment in which the control algorithm is created on the basis of a temperature profile which is determined on the basis of a heating cycle of a heating bulb blank running under laboratory conditions.

[0007] In a particularly advantageous embodiment, the temperature sensor or one of the temperature sensors measures the temperature within the base area of ​​the heating bladder blank. The base area of ​​the heating bladder is known to be particularly critical for optimal vulcanization.

[0008] A preferred embodiment is one in which the temperature sensor has an RTD sensor that extends into the base area of ​​the heating bulb blank when it is molded into the vulcanization mold. This ensures particularly reliable and accurate temperature determination within the relevant temperature range.

[0009] Further features, advantages and details of the invention will now be described in more detail with reference to the drawing, which schematically illustrates an embodiment of the invention. Fig. 1 a diagram of a device according to the invention and Fig. 2 a part of a vulcanization mold for a bladder.

[0010] Fig. Figure 1 shows a diagram of the device according to the invention with a heating press 1 having a vulcanization mold 2 for a heating bladder 5. Heating bladders, for example in the vulcanization of pneumatic vehicle tires, have the task of receiving a heating medium, for example water or steam, and transferring both the pressure and the temperature of the medium to the inner wall of the object to be vulcanized, i.e., the green tire. Heating bladders are produced by vulcanization in appropriately designed vulcanization molds from heating bladder blanks consisting of rubber mixtures. The essential components of the overall system according to Fig. 1 includes, in addition to the heating press 1, at least one temperature sensor 3 positioned within the vulcanization mold 2 and a control system 4.

[0011] According to the invention, the controller is a programmable logic controller 4. Programmable logic controllers are known to contain all the necessary modules for implementing the respective closed automation circuit. These modules include at least one input module, which has at least one sensor, and at least one output module, which has an actuator. A central unit processes the input signals according to a programmed control algorithm and forwards the corresponding control signals to the actuator(s) via the output module. The central unit consists of powerful microprocessors, which enable correspondingly fast processing of the individual functions, arithmetic operations, time functions, and the like. The central unit has an operating system, which enables the programming of the control algorithm, a user software.

[0012] The programmable logic controller 4 provided in the system according to the invention processes the signals from the temperature sensor 3 and adjusts the heating time according to the user software programmed in the central unit.

[0013] To program the software, a temperature profile determined from a running heating cycle (determined by temperature sensors at critical points on the bladder) is converted into an equivalent heating time, preferably at 200°C, using the Arrhenius equation, which has been modified to reflect real-world heating conditions. This value is the key parameter for the software. The optimal value for the equivalent heating time, for example, 4.5 minutes at 200°C, is defined under laboratory conditions and is a fixed value that depends on the compound properties of the rubber compound of the bladder blank. The user software programmed in the programmable logic controller 4 contains this value as a key parameter to be achieved.If the mixture composition is changed, a new temperature profile is created under laboratory conditions to determine the effect on the value of the equivalent heating time.

[0014] During bladder vulcanization, the user software ensures that the heating time is adjusted and modified in such a way that the bladder exhibits the specified and desired mechanical and physical properties. The optimal heating time for each heating cycle is continuously recalculated and terminated when the defined vulcanization status is reached. The programmable logic controller therefore allows automation of the heating process with regard to the optimal heating time to achieve the desired properties of the vulcanized end product.

[0015] The capabilities of the programmable logic controller can be expanded by increasing the number of measuring points, for example the number of temperature sensors positioned in the vulcanization mold and protruding into the material (a raw rubber mixture) of the heating bladder blank at different points, or by taking additional variables, such as the pressure of the heating medium, into account in the user software and incorporating them into the calculation of an optimal heating time.

[0016] Fig. Figure 2 shows a possible positioning of a temperature sensor 3 in a molded part 6 of the vulcanization mold 2. The temperature sensor 3 has a sensor receptacle 7 for an RTD sensor 8 and is made, in particular, of a high-temperature-resistant plastic material with low thermal conductivity. The RTD sensor 8 protrudes at the tip of the sensor receptacle 7. The sensor receptacle 7 is connected to a metallic holder 9, which is provided with a threaded portion 9a. The temperature sensor 3 is inserted into a through-bore 10 of the molded part 6, which has an internal thread in a widened end portion, so that the temperature sensor 3 can be connected to the molded part 6 via a fixed screw connection. In the Fig.The embodiment shown in Figure 2 also shows that part of a heating bladder blank 5 that includes a widened base region 5a. The RTD sensor 8 extends into the rubber compound material of the base region 5a and thus allows the temperature profile to be monitored during vulcanization in the sensitive base region 5a. List of reference numbers 1 heating press 2 Vulcanization mold 3 temperature sensors 4 Control device 5 Heating bulb blank 5a Foot area 6 molded part 7 Sensor recording 8 RTD sensor 9a Threaded section 10 Hole

Claims

[1] Device with a heating press (1) which has a vulcanization mold (2) for vulcanizing heating bladder blanks (5) consisting of at least one rubber mixture, characterized by , that it has a programmable logic controller (4) with an input module which has at least one temperature sensor (3) which detects the temperature at a point within the material of the heating bladder blank (5) during a heating cycle, further comprising a central unit which processes the input signals of the temperature sensor (3) according to a control algorithm and with an output module which controls or adjusts the heating time of the heating press (1) via control signals. [2] Device according to claim 1, characterized bythat the control algorithm is created on the basis of a temperature profile which is determined on the basis of a heating cycle of a heating bulb blank (5) running under laboratory conditions. [3] Device according to claim 1, characterized by that the or one of the temperature sensors (3) detects the temperature within the base area (5a) of the heating bulb blank (5). [4] Device according to claim 1 or 3, characterized by that the temperature sensor has an RTD sensor (8) which projects into the foot region (5a) of the heating bladder blank (5) when the heating bladder blank (5) is molded into the vulcanization mold (2).

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