EP0988941B1 - Device for cutting hollow profiles made from thermoplastic materials - Google Patents

Abstract

A knife (1) for cutting profiles (6) is clamped in a frame (2-5) with a force NOTLESS 4% of the tensile stress limit of the knife steel. The frame is guided at the sides and during cutting movement runs parallel with the knife.

Description

Plastic profiles are used as continuous products in the Extrusion process manufactured. The products are then by suitable separation units to processable Cut lengths. Usually saws are used for this used. The use of such saws has the Disadvantage that in addition to a large amount of chips considerable noise level arises.

An alternative to using saws is in Use of knives with which a non-cutting separation of the Profiles is possible. For a flawless However, the quality of the cut must be in relation to the knife Saw at a relatively slow speed immersed and also guided exactly.

From the practical experience of those previously available on the market Known cutting systems, the knife is in a guided on the side. The width or the game these guides are partially adjustable. in principle these knives slide freely in their movement.

With an alternative device available on the market is a guidance of the knife with so-called sliding or Ball bushings provided, with this too If at all, put the knife under great effort can be biased.

To ensure a good cut quality, the The demands on the knives are getting bigger. So be For example, ever thinner cutting edges are called for to be able to separate the profiles precisely. This It implies that the actual knife becomes unstable.

Another decisive disadvantage of known knife separation systems is that, especially in the case of so-called main window profiles, door frame profiles or other large-volume and thick-walled building profiles, the knife is immersed in a straight line, but is deflected within the profile during the cut.
The reasons for this are, for example, internal tensions in the profile or insufficient symmetry in the grinding angle of the knife. The knife deflection means that the cutting quality or the cutting angle and the straight course of the cut are in many cases not sufficient for the production requirements. As a result, the use of knife separation in the manufacture of extruded building profiles is excluded in many cases.

The document DE 298 08 312 U discloses the features of Preamble of claim 1. Based on the status of the Technology is the object of the invention is a Knife cutting device to develop so that a Cutting of building profiles can be carried out without cutting, of the quality of such a cut Requirements are sufficient.

This object is achieved according to the invention by a Device with the features of claim 1 solved. at an inventive device, the knife in clamped a stable frame, with the help of which Cut the knife under a certain pretension can be clamped. The preload under which the Knife is held, is based on the Tension limit of the knife steel. That way the knife is always held in a stable position. there the frame is dimensioned so that the required Clamping forces are generated safely by him or by him as well can be safely recorded, such as during the Cutting forces. At the same time, the Stenter moved with the knife, the stenter is guided laterally.

Such a device designed according to the invention allows a straight, right-angled cut even with a stringent requirements quality to perform when the cutting edge of the Knife or its clamping certain geometric Errors.

Practical trials have shown that the usual Even the smallest errors when grinding in the Symmetry of the so-called knife angle with conventional ones Guides could hardly be corrected on average. at previous systems also have extremely low voltages also within the profile or profile asymmetries resulted in a knife in the course of the cut the straight line is distracted. Through the The wedge effect of the cutting angle is considerable Separation forces caused by the inventive extremely stable preload in the cutting area of the knife can be caught.

In a device designed according to the invention make small mistakes in the sharpening of the knife, especially in the symmetry of the knife edge, not to the course of the straight cut. Furthermore has been found that by the very stable Version of the stenter also asymmetrical or with Internal stresses with linear profiles can be cut.

Fig. 1

eine erfindungsgemäße Vorrichtung zum Schneiden von extrudierten Profilen in einer frontalen Ansicht;

Fig. 2

eine alternative Ausführung einer erfindungsgemäßen Vorrichtung zum Schneiden von extrudierten Profilen in einer frontalen Ansicht.

The invention is explained in more detail below on the basis of a drawing illustrating an exemplary embodiment. Show it:

Fig. 1

a device according to the invention for cutting extruded profiles in a frontal view;

Fig. 2

an alternative embodiment of a device according to the invention for cutting extruded profiles in a frontal view.

In the cutting device shown in Figure 1 is a knife 1 clamped in a clamping frame, which is made of two side elements 2 and 4 and a head element 3 and a foot element 5 is constructed. The clamping points 9, 10, on which the knife 1 is connected to the stenter is necessary to achieve the Knife tension close to the diagonal to the cutting direction S running knife edge 1a arranged.

Other possible stops or tension points for the Knives 1 are in FIG. 1 by reference numerals 11 to 15 characterized.

In the area of the clamping points 9 to 15 can not here shown clamping devices are attached, wherein the fixation of the knife 1 in the clamping points 9 to 15 for example with a quick release device can be done.

The stenter has in this example Execution on the upper left side a pivot point 7, around which the left side element 4 is pivotable. By one working against the foot element 5 of the frame Screw 6, the frame can be clamped. Since doing that Knife 1 on the one hand, for example, at the clamping point 10 firmly with the pivotable about the pivot point 7 Side element 4 connected and on the other hand simultaneously for example at the fixed point 9 at the fixed point Side element 2 is held by the bracing of the pivotable side element 4, the knife 1 as well biased. The tension reached in the knife 1 corresponds to at least 4% of the invention Tensile strength of the steel from which the knife 1 is made.

A groove 8 is exemplary in the right side spar 2 shown. The groove 8 forms a lateral guide for the frame.

As alternative tours can not laterally here Ball bushing guides shown are used also function free of the knife clamping forces.

A profile 16 is guided through the stenter, which is cut to length by means of the knife 1.

1 it is clear that in which stable lateral holder the knife 1 is led to the occurring on the knife 1 to absorb acting forces so that the cutting edge 1a basically makes a straight cut.

Extensive tests have shown that all so far cut profiles with this version straight and could be cut at right angles. There were different angles for the knife geometry used, with hardly any influence on the straightness the cut was as long as one symmetrical grinding was carried out. In contrast to conventional cutting devices in question standing type was the requirement on the symmetry of the However, grinding is considerably lower. Residual stresses in the profile showed no influence on the straightness of the cut.

The separating device according to the invention is suitable basically also for cutting pipes or similar extruded hollow chamber products. It is chipless Separation not only possible with PVC profiles, but also can in principle almost all plastics with this be separated. The quality of the separation quality then depends still depends primarily on the separation speed.

In the second exemplary embodiment according to FIG. 2 there is one scissor-shaped arrangement of the clamping device realized. The knife 27 is in the two z-shaped Frames 17 and 18 at stops 24 and 25 excited, which is arranged near the knife edge 27a are and in which the knife 27 with the respective lower Arm of the z-shaped frame 17, 18 are connected. The z-shaped Frames 17 and 18 are common Pivotal point 19 can be pivoted like a pair of scissors, that when the upper arms 17a, 18a approach each other Frame 17, 18 the lower arms 17b, 18b of frame 17, 18 separate from each other. In addition, the frames are 17, 18 at the upper end of their upper arms 17b, 18b via a upper cross frame 23 connected to one another Separating force is applied to the upper arms 17b, 18b to move pivot point 19. The connection is over the two free slot connections 20 and 21 manufactured.

The device shown in FIG. 2 is biased via a clamping device 22, not shown in detail. This tensioning device 22 pulls for tensioning the Knife 27, the upper arms 17b, 18b of the frames 17 and 18 together around pivot point 19 so that the lower arms 17a, 18a of the frames 17, 18 are moved apart. On in this way the knife 27 becomes transverse to the cutting direction 26 biased until subjected to tension which is at least 4% of the tensile stress of the steel, from which the knife 27 is made.

The knife drive takes place during a cutting process in Cutting direction 26. The z-shaped frames 17 and 18 also serve to manage the overall system, the frame 17, 18 in guides, not shown are led.

Claims (4)

1. A device for cutting lengths of hollow-chamber profiles (6), particularly window and door-frame profiles, made of thermoplastic materials, using a knife (1) for cutting the profile (6), characterised in that the knife (1) is clamped in a stable frame and the prestress on the knife (1) is equal to at least 4% of the tensile stress limit of the knife steel and the frame is laterally guided and runs parallel with the knife during the cutting movement.
2. A device according to claim 1, characterised in that the frame is rectangular and closed on all sides, is used for prestressing the knife (1) and is laterally guided.
3. A device according to claims 1 and 2, characterised in that the cut-guiding means are free from tensile stresses on the knife.
4. A device according to claim 1, characterised in that the knife (1) is clamped in a scissors-like device, so that the clamping frame is open downwards in the cutting direction and the scissor arms are laterally guided.

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