EP0997242B1 - Method and apparatus for cutting tubes - Google Patents

Abstract

Rotating knives (1) make the initial cut in the tube. Each knife is mounted on a pivoting cutter carrier lever (2) activated by an actuator (3), the assembly being arranged on a cutter carrier carriage (4) able to move transversely to a cutting mandrel (5) carrying the tube. A final cut through the remaining thickness is made with rotational locking of the cutters.

Description

The present invention relates to the field of cutting tubes into paper, cardboard, or synthetic material intended for the realization of boxes packaging, drums or the like, and relates to a cutting or cutting process such tubes.

The invention also relates to a cutting device or intersects such tubes for the implementation of this process.

Tubes made of paper, cardboard or synthetic material, which are generally made by continuous longitudinal winding of one or more several contiguous bands and offset on a mandrel of appropriate section up to required thickness, are subsequently cut for the production of sections of identical or different lengths, depending on their final use, using a tube cutting or cutting device.

For this purpose, the tube to be cut is rotated and one or more circular knives penetrate, transversely to the longitudinal axis of the tube, into the material constituting said tube until the cut is made. To avoid the deformation of the tube during cutting, called ovalization, and tearing of the material inside the tube, there is provided in the latter a counterpart called cutting mandrel, which is placed in line with the knife (s).

In the case of a dynamic cut, that is to say a cut on the fly, during which the knife or knives advance together with said tube, the principle cutting is identical. Such a dynamic cut is notably carried out during of tube production online or continuously.

The circular knives used are generally made of steel treated with high hardness and have a single or double bevel intended to facilitate their penetration into the tube to be cut.

Currently, there are different cutting procedures work either one or more circular knives free in rotation, or one or several fixed circular knives, the tube being mounted on a material mandrel synthetic or treated rectified steel with high surface hardness.

In the first case, in the presence of a material cutting mandrel synthetic, the knife or knives make, at each cut, an imprint in the cutting mandrel, which has the effect of generating a significant marking after a number of cuts, this marking resulting in a groove to which corresponds, on the sections of cut tubes, an internal burr due to the tear following the action of the knife (s).

If the cutting mandrel is made of treated steel, the knife (s) circular, coming into contact with said mandrel at the end of each cutting operation, roll on said cutting mandrel and their cutting edge wears out quickly. In effect, due to the contact of the hard edge with a hard surface, said edge crumbles and has degradations similar to tiny sawtooth, so that after a few cutting operations, the appearance of the cuts made is degraded and each cut results in dust generation.

To remedy these drawbacks, it has been proposed in document EP-A-210 118 to use one or more several knives turning to cut almost the entire thickness of the tube, the final or finishing cut being made using another knife. So by example, one or more first knives cut the tube to 1 mm inside diameter of the tube (diameter of the mandrel) and another knife makes the final cut. In such a case, the first knife (s) will not get dull practically not and allow a quality cut for a long time and on most of the cut surface, while the other circular knife wears out quickly on the chuck, but poor cut quality will practically invisible, because the part of the tube concerned is very small.

Such a cutting process has, however, the disadvantage of require at least two knives mounted on one or two knife holders separate knife holders and their adjustment is very difficult to ensure. Furthermore, this device, which is difficult to implement in all cases, is impossible to use for cutting small diameter tubes.

In the second case, namely in the case of using knives fixed circular, the cut obtained is smooth and of very good quality. Usually, the tube is rotatably mounted on a fixed cutting mandrel forming a counterpiece non-rotating and the fixed knives penetrate laterally to the longitudinal axis of the tube in the material thickness of the latter.

In such a case, the knife (s) will heat up, however, quickly in the presence of thick tube to cut, due to friction generated. In addition, the knife (s) are hunting in one direction perpendicular to the cut, which results in a cut of the tube not straight, namely strongly bevelled.

To overcome these drawbacks, it has been proposed to implement, one or more fixed knives when cutting and assigning said knives with a slight rotation during each removal, after the cutting operation. Such a rotation partial, of a predetermined angular value can in particular be obtained by through a ratchet device. Thus, the phenomenon of overheating can be considerably reduced, but the beveled cut, not straight, due to knife that hunts, remains.

The object of the present invention is to overcome these drawbacks by proposing a method and a device for cutting or cutting tubes allowing obtaining cutting surfaces perfectly perpendicular to the longitudinal axis tubes and very good quality, while avoiding premature wear of the cutting knives.

To this end, and according to claim 1, the method of cutting or cutting tubes is characterized in that it consists in making an initial cut of the tube on a major part of its thickness by means of one or more rotary knives and make the final cut of the remaining thickness by means of said knife (s) which have made the initial cut with rotation lock of the or said knives.

The invention also relates to a cutting device or cuts tubes for the implementation of this process, according to claim 2.

la figure 1 est une vue partielle en élévation frontale et en coupe d'un dispositif pour la mise en oeuvre du procédé conforme à l'invention ;

la figure 2 est une vue schématique, à plus grande échelle, représentant un tube avant l'opération finale de coupe de l'épaisseur résiduelle, et

la figure 3 est une vue partielle en élévation latérale et en coupe, à plus grande échelle, du mandrin de coupe.

The invention will be better understood from the description below, which relates to a preferred embodiment, given by way of nonlimiting example, and explained with reference to the appended schematic drawings, in which:

Figure 1 is a partial view in front elevation and in section of a device for implementing the method according to the invention;

FIG. 2 is a diagrammatic view, on a larger scale, showing a tube before the final operation of cutting the residual thickness, and

Figure 3 is a partial side elevational view in section, on a larger scale, of the cutting mandrel.

Figure 1 of the accompanying drawings shows, by way of example, a device for cutting or cutting tubes, which essentially consists of two cutting knives 1, each mounted on a pivoting knife holder lever 2 actuated by means of a jack 3, the assembly being arranged on a knife-carrying carriage 4 movable transversely to a cutting mandrel 5 carrying a tube cut 6. In known manner, the pivoting movement of the knife holder lever 2 is adjustable by means of a stop 7, depending on the thickness of the tube to cut or cut and the prior positioning of the knife holder carriage 4 is carried out by means of an adjustment screw 8 actuated by means of a handwheel or an operating lever 9. The adjusting screw 8 is advantageously of the reverse threads, in the embodiment shown in Figure 1, which highlights works two knife holder carriages 4 each supporting a knife 1, said knives 1 being diametrically opposite with respect to the cutting mandrel 5 carrying the tube to be cut 6.

Of course, the cutting or cutting device can also be of a different type, i.e. have only one knife or have more of two knives. The means for moving the knife-carrying carriage (s) are then adapted to the configuration chosen.

In accordance with the invention, the process for cutting or recutting tubes is characterized in that it consists in making an initial cut of the tube 6 on most of its thickness using one or more knives rotary 1 and to make the final cut of the remaining thickness with locking in rotation of said knife (s) 1.

To this end, the device for implementing this method is characterized in that the cutting knife (s) 1 are rotary and cooperate with at least one means 10 for limiting their rotation for an initial duration of the cutting operation, said means 10 blocking said knife (s) 1 in the final cutting phase.

Figure 2 of the accompanying drawings shows the position of the knife 1 to the end of the initial period of cutting the tube 6, i.e. the cutting with rotation of knife 1. In this position, there remains a thickness d of the total thickness e of tube 6 to be cut. This thickness d is cut while the knife 1 is set to stopping by means 10.

This means 10 is preferably constituted, for each knife 1, in the form of a brake shoe acting on a drum 11 integral with rotation of the knife 1 and actuated by means of a control cylinder 12 mounted on the knife holder lever 2. Thus, after an initial pivoting of the lever 2, during which the knife 1 can rotate freely and penetrate the tube to cut 6, said knife 1, on reaching dimension d corresponding to the thickness remaining to be cut in fixed position of the knife 1, is locked in position and therefore made fixed by clamping the jaw forming the means 10 on the drum 11 at by means of the corresponding jack 12. During the successive pivoting of the knife holder lever 2, the knife 1 is therefore immobilized and makes the final thickness cut d remaining in a fixed position, until it comes into contact with the cutting mandrel 5. It as a result, each knife 1 comes into contact with said mandrel 5 only on a very small portion of the periphery of its edge and that its wear, following this contact is extremely weak and limited.

According to a characteristic of the invention, not shown in the drawings attached, the actuating cylinder 3 for pivoting the knife holder lever 2 or the knife holder lever 2 is provided, on the one hand, with an actuating stop for the jack 12 for controlling the means 10 for limiting the rotation of the knife 1 and, on the other part, of a retraction limit stop of the jack 3 or of the limit switch pivoting of the knife holder lever 2 in the rest position, allowing the triggering of the actuator 12 for controlling the means 10. These stops are advantageously adjustable stops provided with a contactor or the like starting or starting actuation of the cylinder 12, after a stroke of the cylinder 3 or a pivoting of the knife holder lever 2 corresponding to the initial duration of the cutting operation with rotation of the knife 1 or after returning to the position of rest.

In the embodiment shown by way of example in FIG. 1 in the accompanying drawings, the cutting or cutting device comprises two knives 1 diametrically opposite, so that the forces exerted on the mandrel of cuts 5 are completely balanced and that the cut made can be perfect.

According to the preferred embodiment shown in Figure 1 of attached drawings, the knife (s) 1 are advantageously mounted free in rotation on the knife holder lever 2.

However, it is also possible, according to a variant of embodiment of the invention not shown in the accompanying drawings, to mount the or the knives 1 each on a shaft driven in rotation by a device auxiliary motor, the means 10 for limiting rotation for a period initial of the cutting operation can then be constituted, either by the means drive itself, in the form of a stepper motor or a control of impulse rotation, either by an auxiliary means of braking or setting stopping, such as a clutch-brake or the like.

As shown more particularly in Figure 3 of the drawings annexed, the cutting mandrel 5 is preferably constituted by a bar fixed return 13 comprising at its distal end a fixed cutting ring 14 integral with said bar 13, this cutting ring 14 being surrounded, on the one hand, at the free end of the bar 13, of a rotating sleeve 15 mounted on a bearing ball 16 or a plain bearing and, on the other hand, on the side opposite the rotating sleeve 15, a rotating ring 17 mounted on a ball bearing 18 or a bearing. Thus, the cutting ring 14 is fixed with the fixed bar 13 and does not rotate opposite of the knife (s) 1 throughout the duration of the cutting operation, that is to say both while the knives 1 are rotating and during the final cutting of the thickness d, during which said knives 1 are blocked.

The device according to the invention operates in the manner next :

After prior adjustment of the knife carriage 4 so as to bring the knives 1, free to rotate or driven, a few millimeters from the tube to be cut 6, the latter can be rotated and the cutting operations or may begin. Cylinders 3, whose stroke has been adjusted beforehand by means of the corresponding stops 7, then actuate the levers knife holder 2 and cause the knives 1 to plunge into the thickness e of the tube 6. As soon as a cutting depth corresponding to dimension d (figure 2) is reached, the cylinders 3 or the knife holder levers 2 trigger the actuation of the means 10 by means of the jacks 12 and thus block the blades 1 in rotation, the section of the remaining thickness d then being made in this position of blocking.

Thus, during most of the cutting operation of the thickness e of the tube 6, the knives 1 rotate, so that their wear is distributed over their entire periphery and that the friction on the tube and therefore the heating knives 1 are avoided. Knife blocking 1 at the end of the cut, for cutting the remaining thickness d, allows smoothing of the ends of the tube 6 and to prevent said knives from becoming dull by turning against the cutting mandrel 5. It follows that the cut made is straight, the rotary knives 1 not chasing not.

At the end of the tube cutting, the knives 1 return to the position of departure, according to a known command sequence, and the means 10 are unlocked, again allowing the blades to rotate 1.

The centering of the tube to be cut 6 on the cutting ring 14 mounted on the mandrel return bar 13, in line with the knives and inside the tube 6 prevents overwriting and simultaneously improves the quality of chopped off.

Thanks to the invention, it is possible to produce a cutting device or cutting tubes with one or more knives, generally two knives placed in opposition, making it possible to cut perfectly flat and smooth ends of pipe sections, without internal burrs and with knife wear reduced to a minimum.

As a result, the efficiency of machines equipped with such devices can be significantly improved, maintenance work, namely the replacement and adjustment of knives, being significantly reduced.

Of course, the invention is not limited to the embodiment described and shown in the accompanying drawings. Modifications are still possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention according to the claims.

Claims (8)

1. Tube cutting or recutting process with one or several rotary blade(s) characterised in that it consists in making an initial cut in a tube (6) through most of its thickness by means of one or more rotary blades (1), and making the final cut through the residual thickness (d) by means of said blade(s) which carried out the initial cut with the blade(s) (1) prevented from rotating.
2. Tube cutting or recutting device for implementing the process according to Claim 1, essentially consisting of at least one rotary cutting blade (1) mounted on a pivoting blade-support lever actuated by means of a jack (3), the whole being arranged on a blade-holding carriage (4) that can move transversely to a cutting mandrel (5) carrying a tube (6) to be cut, characterised in that the rotary blade(s) (1) cooperate(s) with at least one means (10) for limiting its/their rotation during an initial stage of the cutting operation, such that the said means (10) lock the blade(s) (1) during the final phase of cutting.
3. Device according to Claim 2, characterised in that the means (10) for limiting the rotation of the blade(s) (1) during an initial stage of the cutting operation consist, for each blade (1), in a brake jaw that acts on a drum (11) attached to and rotating with the blade (1), which is actuated via a control jack (12) mounted on the blade-support lever (2).
4. Device according to either of Claims 2 and 3, characterised in that the jack (3) which actuates the pivoting of the blade-support lever (2), or the blade-support lever (2) itself, is provided on the one hand with an actuation abutment for the control jack (12) of the means (10) for limiting the rotation of the blade (1), and on the other hand with an abutment terminating the retraction travel of the jack (3) or terminating the pivoting travel of the blade-support lever (2) at a rest position that enables disengagement of the control jack (12) for the means (10).
5. Device according to Claim 4, characterised in that the actuating and travel terminating abutments are adjustable abutments provided with a contact or similar which engages or disengages the actuation of the control jack (12) for the means (10) after a travel of the jack (3) that actuates the pivoting of the blade-support lever (2) or a pivoting of the blade-support lever (2) corresponding to the initial duration of the cutting operation with rotation of the blade (1) or after the return to the rest position.
6. Device according to any of Claims 2 to 4, characterised in that the blade(s) (1) is/are mounted to rotate freely on the blade-support lever (2).
7. Device according to any of Claims 2 to 4, characterised in that the blade(s) (1) is/are mounted each on a spindle moved in rotation by an associated motorisation device, and the means (10) of limiting the rotation during an initial period of the cutting operation consist either of the drive means itself in the form of a step by step motor, or of a pulse-type rotation control, or of an associated braking or stopping means such as a clutch brake or similar.
8. Device according to Claim 2, characterised in that the cutting mandrel (5) consists of a fixed restoring bar (13) having at its distal end a fixed cutting ring (14) attached to the said fixed restoring bar (13), this cutting ring (14) being surrounded on the one hand at the free end of the fixed restoring bar (13) by a rotating sleeve (15) mounted on a ball bearing (16) or a smooth bearing, and on the other hand, on the side opposite the rotating sleeve (15), by a rotating ring (17) mounted on a ball bearing (18) or a smooth bearing.

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