DE29708297U1 - Temperature sensor for injection molds - Google Patents

Description

The invention relates to a temperature sensor for injection molding tools. When using an injection molding tool, it is very important to know the respective temperature (and the temperature profile) of the plastic material injected into the injection mold. The injected plastic part must not be ejected from the tool too early, i.e. when it has not yet cooled sufficiently, and the period within which the plastic can cool down must not be too short. It is therefore desirable to

967

Niemannsweg 133 · D-24105 Kiel · Telephone (04 31) 8 40 75 · Fax (04 31) 8 40 77

MUNICH - BREMEN - BERLIN - DÜSSELDORF - POTSDAM - ALICANTE - BRANDENBURG - HÖHENKIRCHEN - KIEL - LEIPZIG

e-mail: Postma5ter@Boehmert.B0Ehmert.de

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cooling behavior of the plastic material in an injection mold.

Conventional temperature sensors, i.e. thermocouples or resistance thermometers, have been used for this purpose. These have the disadvantage that their response is too low. Furthermore, these thermometers must have mechanical contact with the material to be measured. However, such mechanical contact is problematic if an air gap forms between the shrinking plastic material and the wall of the injection mold.

The invention is therefore based on the object of creating an improved temperature sensor for injection molding tools.

According to the invention, the object is achieved by a cylindrical body, a window made of a material transparent to infrared rays and inserted into a first recess in one end face of the cylindrical body in alignment with this, an infrared measuring element arranged near the window, pointing towards it in a second, deeper recess, an absolute temperature measuring element arranged near the infrared measuring element and a connecting cable fed from the other end face of the body.

A preferred embodiment is characterized by an H-shaped design in which the infrared measuring element (with the window facing upwards) is arranged above the bridge, the absolute temperature measuring element in the area of the bridge and the feed of the connecting cable is arranged below the bridge.

It is further proposed that the window is a plano/convex lens that directs the infrared rays onto the infrared measuring element.

The invention is explained below with reference to a drawing which shows such a temperature sensor for injection molding tools in a schematic sectional view.

The temperature sensor is H-shaped in a sectional view. A first recess 12 is made in one end face (pointing upwards in the drawing), into which a window 14 made of a material that is resistant to high pressure but transparent to infrared rays (e.g. sapphire) is inserted. The disk-shaped window 14 is preferably designed as a lens, the surface of which facing the material in the injection mold (in the drawing, above the window 14) is flat, while the surface facing downwards is convex.

An infrared measuring element 18 is arranged above the web 2 6 of the body 10, which is preferably a thermo-column measuring element, such as is commercially available as a small silicon chip. This infrared measuring element 18 emits a thermo-voltage proportional to the incident heat radiation, which is 0 V if the temperature of the chip (which corresponds to the temperature of the body 10) is that of the object to be measured, in this case the material 10, which is arranged above the window 14 and whose infrared rays are absorbed by the infrared measuring element 18. If, on the other hand, the material is hotter than the housing, the infrared measuring element 18 emits a positive value; if the temperature of the material is lower than that of the body 10,

the infrared measuring element 18 emits a negative voltage.

In the area of the web 2 6 of the body 10, a conventional temperature measuring element 20 is arranged, which measures absolute temperatures, whereby this can be a temperature-sensitive resistor, a thermocouple or even a temperature measuring bridge.

The infrared measuring element 18 and the absolute temperature measuring element 20 are connected via a connecting cable 24, which is led to the body 10 from below, so that the absolute temperature of the body 10 (and thus of the infrared measuring element 18) and the relative temperature of the material outside the window 14 can be led to the outside of the body 10 and calculated there.

The figure further shows that in the embodiment shown, the temperature sensor is firmly connected to a closure piece 28, which holds the body 10 of the temperature sensor in place by means of a pressure screw 30.

Claims (3)

G 5088 Claims 1. Temperature sensor for injection molding tools, characterized by a cylindrical body (3.0) , - a window (14) made of a material transparent to infrared rays and inserted into a first recess (12) in one end face of the cylindrical body (10) in alignment with the latter, an infrared measuring element (18) arranged near the window (14) and pointing towards it in a second, deeper recess (16), an absolute temperature measuring element (20) arranged near the infrared measuring element (18), and - a connecting cable (24) leading from the other end face of the body (10). 2. Temperature sensor according to claim 1, characterized by an H-shaped design, wherein the infrared measuring element (18) (with the window (14) pointing upwards) is arranged above the web (26), the absolute temperature measuring element (22) is arranged in the region of the web (26) and the feed of the connecting cable (24) is arranged below the web (26). 3. Temperature sensor according to claim 1 or 2, characterized in that the window (14) is a plano/convex lens.