HEATING DEVICE

Abstract

A heating device with an oven into which a semi-finished product to be heated can be moved in and out, with a wire support formed from several wires spaced apart from one another, and on which the semi-finished product is able to be positioned, and with structure for moving the wire support into the oven and out therefrom. In order to both enable a method with high speeds of travel and at the same time able to use one and the same wire support for differently shaped semi-finished products. The wires can be electrically conductive and the selected wires can be acted upon with a voltage and thereby be heated, wherein the voltage is able to be set and/or controlled in such a way that the wires can adopt a predefinable temperature. Through suitable heating of the wires, the semi-finished product can be fixed on the wire support by fusing.

Claims

1. A heating device with an oven (21), into which a semi-finished product (9) which is to be heated can be moved and moved out, with a wire support (30), which is formed by several wires (32, 32a, 32b) spaced apart from one another, and on which the semi-finished product (9) is able to be positioned, and with means (22) for moving the wire support (30) into the oven (21) and out therefrom, wherein the wires (32, 32a, 32b) are electrically conductive and that selected wires (32, 32a, 32b) can be acted upon with a voltage and thereby heated, wherein the voltage is able to be set and/or able to be controlled in such a way that the wires (32, 32a, 32b) can adopt a predefinable temperature, or the switch-on duration of the voltage source is predefined.

2. The heating device according to claim 1, wherein the wire support (30) is formed from several wires (32) lying parallel to one another.

3. The heating device according to claim 1, wherein the wire support is formed by several wires (32a, 32b) crossing one another, wherein the wires (32a, 32b) cross one another at an angle of 90.

4. The heating device according to claim 1, wherein at one or more of the wires (32, 32a, 32b) respectively a temperature sensor (36) is provided.

5. The heating device according to claim 1, wherein for moving the wire support (30) a carriage (25) is provided, which can be moved on a rail system (23, 24) into the oven (21) and out therefrom.

6. The heating device according to claim 1, wherein a control device (37) is provided, by which the voltage is able to be set and/or is able to be controlled in such a way that the wires (32, 32a, 32b) can maintain a predefinable temperature.

7. An injection moulding machine (1) for the production of plastic moulded parts from a semi-finished product (9), which is overmoulded with a plastic material, comprising a clamping unit, an injection unit, a robot and a heating device according to claim 1.

8. A method for the production of plastic moulded parts from a semi-finished product, which is overmoulded with a plastic material, wherein the semi-finished product is heated by means of a heating device according to claim 1, wherein the voltage of the wires is set to a value at which the wires adopt a temperature which bring about a fusing of the semi-finished product, wherein the heated semi-finished product, after the moving out of the wire support from the oven, is removed from the wire support and is overmoulded with a plastic material in an injection moulding machine.

Description

[0030] The invention is to be described further below with the aid of example embodiments and with reference to the figures. There are shown:

[0031] FIG. 1 injection moulding system with a heating device according to the invention

[0032] FIG. 2 wire support with parallel wires;

[0033] FIG. 3 wire support with crossed wires.

[0034] In FIG. 1 an exemplary injection moulding machine 1 is illustrated. The injection moulding machine 1 has a machine bed 2. On the machine bed 2 a fixed platen 3 is secured and a movable platen 4 is mounted in a linearly displaceable manner. For its linearly displaceable mounting, the movable platen 4 is displaceably mounted along four horizontal columns 5. The movable platen 4 can be moved for example by hydraulic drives, not illustrated in further detail, along the longitudinal extent of the four horizontal columns 5. The movable platen 4 is mounted by linear guides 6 in a horizontally movable manner on the machine bed 2. The above-mentioned components of the injection moulding machine form together the so-called clamping unit. A first injection mould half 7 is fastened on the fixed platen 3. A second injection mould half 8 is fastened on the movable platen 4. In the present example embodiment, the two injection mould halves 7 and 8 are configured to be able to form an organic sheet 9 and to overmould it with thermoplastic material. The organic sheet 9 can be a plate-shaped organic sheet 9, for example. For better clarity, an injection unit, which is usually situated to the right of the fixed platen 3, is not illustrated.

[0035] In FIG. 1 to the right of the injection moulding machine 1 a heating device according to the invention is illustrated, characterized as a whole by reference number 20. This comprises essentially an oven 21, a carriage system 22 with rails 23, 24, and a carriage 25. A wire support 30 according to the invention can become fastened or be fastened on the carriage. More detailed explanations regarding the wire support 30 are to be found further below in the description of FIGS. 2 and 3. An organic sheet 9 or a different semi-finished product can be deposited on the wire support 30. The carriage 25 can be moved by means of suitable drive means into the oven 30 and out therefrom again. In this way, the organic sheet 9 can be moved into the oven, heated therein, and subsequently moved out from the oven again. This travel movement is to be indicated by the double arrow.

[0036] Between the heating device 20 and the injection moulding machine 1, a robot 40 is arranged which is configured for the handling of the organic sheets 9 and in particular has a suitable gripping device 41. By means of the robot 40, an organic sheet 9 which is to be heated can be removed from a storage stacknot illustrated hereand placed onto an empty wire support 30. After the organic sheet 9 has been heated and moved out from the oven 20 again, the heated organic sheet 9 can be brought by means of the same robot 40 into the space between the open mould halves 7 and 8 and fixed there in its position for an injection moulding process. Of course, several robots, also several different robots, can be provided in order to accomplish the handling of the stored organic sheets, of the heated organic sheets and of the finished plastic moulded parts.

[0037] FIG. 2 shows a first embodiment of a wire support 30 according to the invention. Several wires 32 are clamped in a frame 31, arranged parallel to one another and at an equal distance from one another. An organic sheet 9 is laid centrally on the wire support 30. The wires 32 are connected to a voltage source 35 via connecting cables 33 and 34. In FIG. 2, for the sake of simplicity, the voltage source 35 is illustrated as a separate battery. Of course, any other suitable voltage source can also be provided, which is suitable to act upon the wires 32 with a suitable voltage for this and to heat them with the effect of resistance heating. Preferably, a temperature sensor 36 is provided at one or more of the wires 32, the values of which temperature sensor can be evaluated by a controller 37, so that the voltage source 35 can be operated in a suitable manner. The controller 37 or respectively the control device 37 preferably serves for the voltage to be adjustable and/or controllable in such a way that the wires 32 maintain a predefinable temperature.

[0038] Steps can be taken in order to set the temperature of the wires 32 in a suitable manner, namely: [0039] Preheating the wires to a temperature above the melting temperature of the organic sheet. For a polyamide organic sheet for example 260 C. [0040] The controlling of the temperature of the wire grid takes place here via at least one thermal element, which is or are fastened on one or respectively on one wire in each case. Preferably, thermal elements with small dimensions are to be used for this, in order to keep the thermal mass as small as possible. [0041] Together with a suitable switching element such as a solid state relay (SSR), the temperature increase can now be measured and controlled via the duration of the application with electrical voltage. It is likewise conceivable to adapt the voltage or current intensity accordingly. [0042] A temperature control via the switch-on duration is already known for example in the temperature control of ceramic heating bands or infrared emitters, and prior art [0043] Therefore at the time of laying the organic sheet onto the oven grid, a wire support which is temperature-controlled above the melting temperature is present [0044] Through the contact between organic sheet and wire support, a heat transfer results from the wire support to the organic sheet, and the organic sheet, or respectively the matrix material contained in the organic sheet, melts [0045] Due to the melting process, a form fit results between the placed organic sheet and the wire support.

[0046] This form fit leads to a reliable fixing of the organic sheet on the wire support and enables a quick movement of travel of the wire support without displacement of the organic sheet on the oven grid.

[0047] FIG. 3 shows a second embodiment of a wire support 30 according to the invention. In contrast to FIG. 2, the wire support is formed from several wires 32a and 32b crossing one another, wherein the wires cross one another at an angle of 90. A suitable insulation is provided at the crossing points.

[0048] The wire support 30 according to the invention is used in a method for the production of plastic moulded parts from an organic sheet 9 or from another semi-finished product, which is overmoulded, or respectively is to be overmoulded, with a plastic material. Here, an organic sheet 9 or respectively the semi-finished product is heated by means of a heating device of the type previously described. The voltage of the wires 32 or 32a/32b is set to a value at which the wires adopt a temperature which brings about a fusing of the organic sheet 9. The carriage 25 can therefore be moved at a comparatively high speed of travel into the oven 20 and, after heating of the organic sheet 9, can be moved out therefrom again. After the moving of the wire support 30 or respectively 32a/32b out from the oven 20, the organic sheet 9 is removed from the wire support and is overmoulded with a plastic material in the injection moulding machine 1.

LIST OF REFERENCE NUMBERS

[0049] 1 injection moulding machine

[0050] 2 machine bed

[0051] 3 fixed platen

[0052] 4 movable platen

[0053] 5 horizontal columns

[0054] 6 linear guides

[0055] 7 first injection mould half

[0056] 8 second injection mould half

[0057] 9 organic sheet

[0058] 20 heating device

[0059] 21 oven

[0060] 22 carriage system

[0061] 23 rail

[0062] 24 rail

[0063] 25 carriage

[0064] 30 wire support

[0065] 31 frame

[0066] 32 wires

[0067] 32a wires

[0068] 32b wires

[0069] 33 connecting cable

[0070] 34 connecting cable

[0071] 35 voltage source

[0072] 36 temperature sensor

[0073] 37 controller

[0074] 40 robot

[0075] 41 gripping device