DE29615506U1 - Knives for use in a processing device for plastic parts and device with such a knife - Google Patents

Description

Knife for use in a processing device for plastic parts and a device with such a knife

The invention relates to a knife for use in a processing device for plastic parts that are coated on the outside with a barrier or oxide layer, such as plastic pipes, in particular for welding two such pipes together or pipes with plastic fittings, sleeves or the like, for removing the barrier or oxide layer on the plastic part before the welding process, wherein the knife has a cutting edge at its lower end facing the plastic part, according to the preamble of claim 1, and to a device with such a knife for processing plastic parts according to the preamble of claim 6.

DE-93 05 220.0-Ul discloses such a device for peeling the surface of plastic pipes, which consists of a clamp-like holder with jaws with roller guides, in which the pipe is partially enclosed. A knife is mounted on the device, which extends radially in the direction of the plastic pipe for peeling off the barrier or oxide layer all around when the device is rotated over the pipe.

DE-8211568.0-U1 discloses a device for stripping plastic-coated cables, in which a three- to five-point double roller bearing is provided in a type of screw clamp on two clamp parts for circular guidance on the cable, and a compression spring and an adjusting spindle are arranged between the clamp parts, and a cutting tool is held in a height-adjustable manner on one clamp part, which has an obliquely radius-shaped, crowned and relief-ground cutting edge, with a support spring arranged between the head of the adjusting spindle and one clamp part. The lateral rollers, seen in the axial feed direction, are arranged directly next to the cutting tool. The rollers preferably have a narrow shape.

DE-8211570.2-Ul discloses another device for manually cutting an electrical cable covered with plastic, consisting of a type of screw clamp made of two clamp parts,

which are held laterally on a guide column, with a multi-point double roller bearing for circular guidance on the cable, whereby a cutting tool is arranged in a tool holder in a bushing on one clamp part, so that it can be adjusted in height and rotated. An adjusting nut is inserted into the bushing, into which a threaded part of the tool holder engages, whereby the clamp parts can be adjusted to the cable diameter using a clamping spindle with a clamping sleeve. The tool is arranged to the side of the guide rollers lying in the feed direction. An angular groove is incorporated in the bushing, whereby an adjusting screw guided in the groove is screwed into the tool, which can be clamped to the outside of the bushing.

EP 0 689 928 A2 discloses a device for processing plastic pipes, which has a knife carrier with a centering mandrel and a peeling knife, with a support sleeve in the end section of each plastic pipe, which is provided with a flange at the end and has at least two different outer diameters.

The known devices have the disadvantage that the knives, which are consumables, on the one hand require precise and complex guidance, and on the other hand are worn out relatively quickly by the abrasive material, so that the known knives and devices are expensive and difficult to handle.

The invention is based on the object of creating a replaceable knife of the type mentioned at the beginning, which allows the quick and safe processing of a plastic part, in particular a plastic pipe, and as a consumable item is inexpensive to manufacture; a device is also to be created for holding such a knife, which allows quick, safe and yet simple handling.

The solution to the problem consists in the fact that in the knife according to the invention shoulders are arranged on both sides of the cutting edge, which run in front of the cutting edge and which serve as a guide and have front surfaces facing the plastic part to be machined, which are inclined at an angle of a small angle (α) and rise forwards in front of the cutting edge,

whereby the cutting edge protrudes between the front faces of the shoulders by the height of its cutting depth.

The device according to the invention for processing plastic parts that are coated on the outside with a barrier or oxide layer, such as plastic pipes, in particular for welding two such pipes together or pipes with plastic fittings, sleeves or the like, for removing the barrier or oxide layer on the plastic part before the welding process, has a replaceable knife which has a cutting edge at its lower end facing the plastic part and which has shoulders on both sides of the cutting edge which run in front of the cutting edge and which have end faces facing the plastic part to be processed and which serve as a guide, which are inclined at a small angle (α) and rise forwards in front of the cutting edge, the cutting edge protruding between the end faces of the shoulders by the height of its cutting depth.

Further advantageous embodiments of the invention are characterized in the remaining subclaims.

The knife and the device according to the invention have the advantage that the shoulders of the knife on both sides of the cutting edge serve as guides for the plastic part, whereby the part or pipe, in particular PE or PEX pipe, rolls under the slanted end faces of the shoulders and the cutting edge of the knife protrudes by the depth of its penetration into the pipe casing or into the plastic part; the design of the knife effectively prevents the cutting edge of the knife from penetrating deeper into the plastic casing than the free height of the cutting edge below the shoulders. The pipe or the area to be peeled is guided safely and under even pressure to the cutting edge, the cutting depth is always constant, which is a prerequisite for good welding of two plastic parts. In this way, the welding results are improved. Due to the design of the knife, it is no longer possible to accidentally press the knife too deeply into the plastic part or tube with the device according to the invention and thereby create a different chip depth on which welding cannot be carried out properly.

The device also provides a simple and easy-to-use hand-held tool for the surface stripping process of plastic pipes, with the blade of the device being the only wearing part and being easy and inexpensive to replace.
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Short name of the drawing showing: Figure 1 a view of the main surface of a knife Figure 2 a view of Figure 1 folded to the left Figure 3 a plan view from below of Figure 1 Figure 4 a radial section through a device for holding a

such a knife

Figure 5 is a section along the line A-B in Figure 4 and Figure 6 is a section along the line C-D in Figure 4.

Figures 1 to 3 show a knife 1, which is designed here as a cuboid-shaped plate with a large main surface 17, through which a hole 3 is led approximately centrally for screwing the knife to a holder 2 or into a recess 4 thereof using a screw. At its upper end, the knife has two oblique end faces 6, 7 milled into its upper cover surface, which converge at an obtuse angle and which form an anti-twist device in the recess 4 of the holder 2. The lower end of the knife 1 has a cutting edge 13 which projects freely beyond the holder 2.

The cutting edge 13 is formed from the cuboid-shaped knife 1 by introducing a curved recess 12 into the main surface 17 of the knife 1, whereby the surface 11 of the main surface 17, which is set back by the depth of the recess 12, and the original material surfaces of the knife 1 remaining on both sides of the recess 12 and the cutting edge 13, form shoulders 8, 9, which extend downwards on both sides of the surface 11 and the cutting edge 13 in the direction of the plastic part or tube. The shoulders 8, 9 of the cutting edge 13 extend through the recess 12. The shoulders 8, 9 are delimited at their lower ends by end faces 10, 10 directed towards the plastic part or tube 23, which are inclined at an angle a small angle α and rise forwards in front of the cutting edge 13, whereby the cutting edge 13 is recessed by the height of its cutting depth between the

End faces 10,10* of the shoulders 8,9 protrude. The shoulders 8, 9 together with the end faces 10, 10 thus form a guide on both sides of the cutting edge 13 of the knife 1, under which the cutting edge 13 protrudes at the level of its peeling depth. The end faces 10,10' preferably extend behind the cutting edge 13 and run past it, so that a good, flat, one-sided guide of the tube 23 rolling under one of the two end faces 10,10' to the cutting edge 13 of the knife 1 is ensured.

The cutting edge 13 of the knife 1 is formed by the front edge 13 of a front surface 16, which rises to the rear by a small angle β for cutting free, as shown in Figure 2, so that the cutting edge 13 is undercut or free to the rear. It can also be seen from Figure 2 that the front surfaces 10, 10* of the shoulders 8, 9 facing the plastic part or pipe 23 to be processed are directed by a small angle α opposite the inclination of the angle β of the front surface 16 of the cutting edge 13, the two angles α and β being approximately the same size and in the order of 4 to 7 degrees. Preferably, the angle of inclination α of the front surfaces 10, 10' of the shoulders 8, 9 is smaller than the angle of inclination β the front surface 16 after the cutting edge 13. Furthermore, the cutting edge can have short bevels 14, 15 towards the shoulders 8, 9, with which the cutting edge 13 merges on both sides into the planes 10, 10' of the shoulders 8, 9.

A device 18 for processing plastic parts that are coated on the outside with a barrier or oxide layer, such as plastic pipes 23, in particular for welding two such pipes together or pipes with plastic fittings, sleeves or the like, has a replaceable knife 1 for removing the barrier or oxide layer on the plastic part or pipe 23 before the welding process, which knife has a cutting edge 13 on its lower end facing the plastic part or pipe 23 and is shown in Figures 4 to 6; this device 18 has a knife 1 that is shaped as described in Figures 1 to 3.

The device 18 consists of a cylindrical tube 19 with grip recesses 33, with two opposing jaws 20, 21 arranged within the tube 19, of which one jaw 20 has a prismatic recess

29 and the other jaw 21 has a wedge-shaped recess 28 for adjusting the distance between the jaws 20, 21 to different pipe diameters of plastic pipes 23; the recesses 28, 29 run along the axis 30 of the pipe 23.
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The jaws 20, 21 are mounted so that they can move relative to and away from each other, for which purpose the jaws 20, 21 in superposition each have at least one threaded hole with a left-hand and right-hand thread, through which a threaded spindle 26* with a left-hand and right-hand threaded section 31, 32 is guided. When the threaded spindle 26' is rotated by means of a rotary wheel 27 located outside the tube 19, the jaws 20, 21 are moved parallel to each other towards or away from each other, whereby the jaws 20, 21 adapt to different diameters of different plastic pipes 23 and press against the pipe 23.

Preferably, the device 18 has a second guide rod 26 which extends through holes within the jaws 20, 21 for parallel guidance thereof.

Within the casing wall 19 of the pipe, in the area of the jaw 20, there is a recess 34 which partially exposes the jaw 20. The jaw 20 also has a recess 24 in the area of the recess 34 of the pipe 19, forming a flat, approximately radially directed surface on which a knife 1 is held, which is approximately radially directed and extends with its cutting edge 13 along the axis 30 of the plastic pipe 23, as can be seen in Figure 4. In addition to the knife 1, a flat plate 24, which also extends along the axis 30, is mounted in the prismatic recess 29, so that after inserting a plastic pipe 23 and tightening the jaws 20, 21, the plate rests on the plastic pipe 23 along a casing line in the direction of the axis 30; the knife 1 projects beyond the plate 24 by the height of the cutting edge 13.

To peel off the surface of a plastic pipe 23 or a part, the device 18 is placed on the end of the plastic pipe 23 or the part and rotated by hand or by motor, whereby a helical peeling process of the surface is carried out in a simple manner.

of the plastic pipe 23 or the part. Depending on the direction of rotation, one of the two shoulders 8, 9 of the knife 1, namely the leading shoulder, serves to guide the casing wall of the plastic pipe or the part towards the peeling point of the cutting edge 13, the other of the two shoulders 8, 9, namely the trailing shoulder, is free. In this way, the knife 1 and thus the device 18 can be used in any way, clockwise or anticlockwise.

The knife according to the invention is suitable for use in various devices for scraping the surface of flat or curved plastic parts or pipes, also in carriage holders for the knife, which are suitable for guiding the knife in a plane over the plastic part.

Claims (9)

Expectations: 1. Knife (1) for use in a processing device for plastic parts that are coated on the outside with a barrier or oxide layer, such as plastic pipes, in particular for welding two such pipes together or pipes with plastic fittings, sleeves or the like, for removing the barrier or oxide layer on the plastic part before the welding process, the knife having a cutting edge (13) at its lower end facing the plastic part, characterized in that that shoulders (8,9) are arranged on both sides of the cutting edge (13), which run in front of the cutting edge (13) and have end faces (10,10') serving as a guide and facing the plastic part to be machined, which are inclined at an angle of a small angle (α) and rise forwards in front of the cutting edge (13), the cutting edge (13) protruding by the height of its cutting depth between the end faces (10,10') of the shoulders (8,9). 2. Knife according to claim 1, characterized in that the front surfaces (10,10') of the shoulders (8,9) of the knife (1) extend past the cutting edge (13) to behind the cutting edge (13), the cutting edge protruding between the front surfaces (10,10') of the shoulders (8,9) by the height of its cutting depth. 3. Knife according to claim 1 or 2, characterized in that the cutting edge (13) is the foremost edge (13) of an end face (16) which rises by a small angle (ß) running away to the rear for free cutting, so that the cutting edge (13) is undercut, wherein the end faces (10,10*) of the shoulders (8,9) facing the plastic part to be machined are directed by a small angle (α) opposite to the inclination of the angle (ß) of the end face (16) of the cutting edge (13).
30 4. Knife according to claim 1 or 2 or 3, characterized in that the cutting edge (13) is formed from the cuboid-shaped knife (1) by introducing a curved recess (12) into one of the main surfaces of the knife (1), whereby the original material surfaces of the knife (1) remaining on both sides of the cutting edge (13) form the shoulders (8,9). 5. Knife according to one of the preceding claims, characterized in
that the angle of inclination (ß) of the end face (16) is between 5 and 7 degrees and the angle of inclination (α) of the end faces (10,10') of the shoulders (8,9) is between 4 and 6 degrees and is preferably smaller than the angle of inclination (ß) of the end face (16). 6. Device for processing plastic parts which are coated on the outside with a barrier or oxide layer, such as plastic pipes, in particular for welding two such pipes together or pipes with plastic pittings, sleeves or the like, for removing the barrier or oxide layer on the plastic part before the welding process, with a replaceable knife (1) which has a cutting edge (13) at its lower end facing the plastic part, characterized in that
that shoulders (8,9) are arranged on both sides of the cutting edge (13), which run in front of the cutting edge (13) and which have end faces (10,10*) serving as guides and facing the plastic part to be machined, which are inclined at an angle by a small angle (α) and rise forwards in front of the cutting edge (13), the cutting edge (13) protruding between the end faces (10,10') of the shoulders (8,9) by the height of its cutting depth. 7. Device according to claim 6, characterized in that the front faces (10,10*) of the shoulders (8,9) of the knife (1) extend past the cutting edge (13) to behind the cutting edge (13), the cutting edge protruding between the front faces (10,10') of the shoulders (8,9) by the height of its cutting depth and the cutting edge (13) being the foremost edge (13) of a front face (16) which rises by a small angle (ß) running away to the rear for cutting free, so that the cutting edge (13) is undercut, the front faces (10,10') of the shoulders (8,9) facing the plastic part to be machined being directed by a small angle (α) opposite to the inclination of the angle (ß) of the front face (16) of the cutting edge (13). 8. Device according to claim 6 or 7 for processing plastic pipes, characterized in that that it consists of two jaws (20, 21) which enclose the plastic pipe (23) to be processed and which are mounted so as to be movable relative to and away from each other, wherein in one of the jaws (20, 21) in radial The knife (1) is arranged in a direction inwards towards the other jaw, the cutting edge (13) of which is arranged lengthwise or at a small angle (γ) to the longitudinal axis (30) of the plastic tube (23). 9. Device according to claim 7 or 8, characterized in that the jaws (20,21) together with the knife (1), which is arranged in a recess (22) of the jaw (20) holding the knife (1), are arranged within a tube (21), the jaws (20,21) in superposition each having at least one threaded bore through which a threaded spindle (26,26') each with a left- and right-hand threaded section (31,32) is guided, during the rotation of which the jaws (20,21) can be moved parallel to one another towards or away from one another in order to press the jaws (20,21) onto the plastic tube (23).