EP0578938B1 - Cutting device on an extruder for making hollow blocks - Google Patents

Description

The invention relates to a cutting device on an extrusion system for producing perforated bricks with the features according to the preamble of claim 1.

Perforated bricks of larger dimensions and thus greater weight are expediently provided with handle recesses provided on the end faces to facilitate handling. These handle recesses are already incorporated in the manufacture of the perforated brick. For perforated bricks, which are produced in the extrusion process, a cutting device is known in which a cutting wire formed into a loop is inserted and pulled back by an actuating device into the lateral strand flanks of the strand of material emerging from the extruder, so that the later recesses forming the recesses through the handle Movement of the strand itself can be generated (DE-A-35 41 280). It has been shown that - especially after a certain wear of the cutting edge of the cutting loop - those edges and surfaces of the recess that arise in the strand flanks when the cutting loop is inserted and withdrawn can be unclean. The edges or surfaces then run unevenly and have flags or sharp-edged tears that can cause injuries to the fingers.

The object of the invention is to improve a cutting device of this type in a simple manner so that properly bordered handle recesses can be produced.

According to the invention this is achieved by the embodiment specified in the characterizing part of claim 1.

The invention is based on the consideration that the cutting loop - especially after a certain wear of the cutting edge - is elastically deflected in the conveying direction by the moving strand, whereby inevitable inhomogeneities of the raw material in the strand cause an uneven movement when piercing and withdrawing the cutting loop can be out of line. Such uneven movements and the resulting uncontrolled tearing out of the strand surface during the return movement are avoided according to the invention in that the cutting loop is deflected from the outset through the curve from its straight line of motion in the strand movement direction immediately before penetrating the strand flank and is thus elastically pretensioned. By means of the pretensioning, a restoring force acting counter to the strand conveying direction is built up, which is so great that the cutting forces which occur cannot deflect the cutting loop in the strand conveying direction, or only to an insignificant extent.

It is also particularly advantageous to provide a wiping edge on the back of the curve facing the strand, on which the cutting edge slides along the front cutting edge when the loop is pulled back, thereby exerting a scissor effect on the strand skin. Since this scraper edge is very close to the strand flank, the strand skin is cut cleanly in this way and there are no signs of tearing.

In the simplest case, the curve which causes the cutting loop to deflect immediately before it is inserted into the strand flank can be a flat inclined surface rising in the strand conveying direction, on its lower - i.e. closer to the mouthpiece of the extruder - part of the front section of the cutting loop attaches during the plunge movement and then slides along this inclined surface.

• Fig. 1 eine schematische Vorderansicht der Schneidevorrichtung, gesehen entgegen der Strangförderrichtung;
• Fig. 2 eine Seitenansicht der Schneidevorrichtung;
• Fig. 3 eine der Fig. 2 entsprechende Seitenansicht des die Kurve tragenden Bauteils in etwa natürlicher Grösse, jedoch aus zeichnerischen Gründen abgeschnitten dargestellt, und
• Fig. 4 einen Querschnitt des die Kurve tragenden Bauteils längs der Linie IV-IV in Fig. 3.

An embodiment of the cutting device according to the invention is explained in more detail with reference to the accompanying drawings. The drawings show:

• Figure 1 is a schematic front view of the cutting device, seen against the strand conveying direction.
• Fig. 2 is a side view of the cutting device;
• Fig. 3 is a side view corresponding to Fig. 2 of the component bearing the curve in approximately natural size, but shown cut off for drawing reasons, and
• 4 shows a cross section of the component carrying the curve along the line IV-IV in FIG. 3.

According to the representation in Fig. 1, the cutting device consists essentially of a frame 1, which is attached to the mouthpiece-side part of an only schematically drawn extruder 2 so that a whole designated 3 actuating device for two rectangular cutting loops 4 directly at the outlet of the Raw material strand 5 from the mouthpiece 6 of the extruder 2 is arranged. The cutting loops 4 are the assigned opposite lateral flanks of the strand 5 and can be controlled by the actuating device 3, cyclically controlled, inserted into the strand flanks, held in it for a while and then withdrawn again. As a result of the strand conveying movement (to the left in FIG. 2), a piece of raw material is cut out during the holding period of the cutting loops 4 in the strand and removed therefrom when the cutting loops are withdrawn.

The cutting loops 4 are each fastened to the end of a swivel arm 8 which can be swiveled about an axis 9 directed parallel to the strand conveying direction. A piston / cylinder arrangement 10 acts on the swivel arm 8. By extending the piston rod 11, the swivel arm and thus the cutting loop 4 is moved towards the strand flank and pressed into it; by retracting the piston rod 11, the cutting loop 4 is retracted again from the strand flank.

Each rectangular loop 4 is assigned a component 12 fastened to the mouthpiece 6, which has a deflection curve for the cutting loop 4. The component 12 consists essentially of a vertical flat piece 13, on the rear side facing the mouthpiece 6 of which two bolts 14 are welded, which are fixed in ring plates 15 of the mouthpiece 6 by nuts 16. The flat piece 13 has the cross section shown in Fig. 4, i.e. it has a flat inclined surface 20 which serves as a deflection curve for the front cutting edge 21 of the cutting loop 4. The inclined surface 20 rises in the direction of the strand movement X (FIG. 4).

The ring tabs 15 are dimensioned such that the component 12 lies in the assembled state with the inclined surface 20 in the path of movement of the associated cutting loop 4. Due to the alignment of the pivot axis 9 parallel to the strand movement direction, this movement path is theoretically oriented perpendicular to the strand longitudinal axis.

Due to the inevitable elasticities and play in the swivel arm 8 and in the cutting loop 4 itself, however, an elastic adjustment in the direction X of the strand movement is possible. When the cutting loop 4 approaches the strand flank, the cutting edge 21 strikes the lower end of the inclined surface 20, but is increasingly deflected in the course of the approach movement parallel to the strand movement direction. As a result, existing games between swivel arm and swivel axis 9 are consumed and, in addition, an elastic pretension is generated in these parts and in the cutting loop 4 itself, before the cutting edge penetrates into the strand flank running immediately behind the flat piece 13. Because of this pretension, the cutting force in the raw material of the strand causes little or no additional deflection of the cutting loop 4 in the direction of the strand movement.

The edge 22 of the side surface of the flat piece 13 facing the strand, which is downstream with respect to the strand movement, is formed with sharp edges. The cutting edge 21 of the cutting loop 4 slides past this edge, which is located immediately adjacent to the strand flank, when it is pulled back, so that a shear effect is thereby created. This shear effect causes the strand skin to be cut smoothly and prevents parts from breaking out or being torn out of the strand flank.

Claims (4)

1. A cutting device on an extrusion press for making perforated bricks, comprising a cutting loop (4) for cutting recesses out of the side of the extrusion, which form gripping recesses on the finished perforated bricks, and comprising an actuating device which cyclically controlledly moves the cutting loop (4) forwards and back in a direction perpendicular to the side of the extrusion, characterised in that arranged in the path of movement of the cutting loop (4) and directly beside the side of the extrusion is a cam (20) which deflects the cutting loop in the direction of movement of the extrusion (5) before penetrating into the side of the extrusion, and thereby elastically prestresses it.
2. A device according to claim 1 characterised in that the cutting loop (4) is of rectangular shape and the cam is an inclined surface (20) arranged parallel to the front cutting edge (21) of the cutting loop.
3. A device according to claim 1 or claim 2 characterised in that provided at the side of the cam which is towards the extrusion is a stripping edge (22) over which the cutting loop slides when moving back from the extrusion.
4. A device according to claim 3 characterised in that the stripping edge is provided on the component (12) carrying the cam.

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