FR3026336A3 - IMPACT CUTTING THERMOSTATIC MECHANISM - Google Patents

Abstract

A thermostatic cut-off mechanism of a plastic fiber comprising a frame (5) with vertical walls (8), the upper part of which contains a support in which the counterblade (3) is arranged, and the part of which lower part contains a rotating blade holder (2) in which is disposed the blade (1) comprising six heating elements (11): - two or more heating resistors (11) in the rotatable support-blade holder (2), distributed symmetrically along each of its large faces (13) parallel to its axis of rotation and in a plane passing or in proximity to the center of mass, - two or more heating resistors (11) in the counter-blade support (4), distributed symmetrically along each of its large faces (13), in a plane passing through or near the center of mass of the support, and - two or more heating resistors (11) in the frame (5), distributed horizontally on the walls green icals (8) in an area near the plane of passage of the plastic fiber and the impact zone of the blade and against the blade.

Description

TECHNICAL FIELD The present invention relates to an impact-cut mechanism used in plastic bag-making machines, provided with heating devices capable of maintaining or restoring the optimum operating temperature of the cutting heads and the door frame. -head when the machine is disconnected for a while. TECHNICAL BACKGROUND The impact cut of a plastic fiber is impacted by means of a blade mounted on a blade holder which rotates at a certain angular velocity against a rigid, fixed or moving surface, commonly referred to as a blade. against blade. Both elements are mounted on a frame, the first stably and the second movable in a vertical plane. Depending on the configuration of the blade system, complete cutting lines will be generated, in which the plastic fiber is completely divided, or break lines, where the section of the fiber is partial thus constituting a weakened area that facilitates cutting. This type of cut has the advantage of being able to take place without stopping the plastic fiber, which is impossible with other cutting systems. However, it requires an extreme precision of fit between the blade and the impact surface or counter-blade, the two parts to be arranged to make contact over the entire cutting line, with minimal tolerance . This extremely precise setting must not exceed the plane of junction between the edges because they have no elastic property and are therefore incapable of deforming to absorb the energy of the impact which would break them or deform them. permanently. On the contrary, if the tolerance is excessive, the cut will not be made or it will be irregular throughout the blade. This adjustment is so precise that any deformation of the metal parts of the machine due to a change in temperature influences the cutting capacity to such an extent that, if the ambient temperature decreases significantly, the shrinkage of the metal of the frame and the heads cutting increases the separation between the pieces to prevent a correct impact between the blade and counterblade, and therefore a precise cut of the plastic fiber. This effect is of concern when the machine is in cold geographical areas. In these places, the downtimes of the machine, during periods of holidays for example, during weekends or simply during a prolonged stop, are sufficient for a temperature drop to occur which may affect these conditions. cutting mechanisms.

Under these circumstances, restarting the machine requires a gradual adjustment of the blade and counterblade levels to compensate for the misalignment of the metal retraction and at the same time prevent the effect of progressive expansion of the parts. initially cold, the adjustment to be repeated several times until they reach their operating temperature. These adjustments must be carried out by qualified personnel, because if they are not carried out correctly, the longevity of the cutting elements decreases drastically. On the other hand, as these adjustments are made during machine downtimes, they also imply a loss of production.

To solve this problem, some impact cutting mechanisms incorporate an electrical resistance in the body of the blade holder accelerating the temperature measurement, so as to restart the machine without making adjustments. But experience has shown that this system is insufficient since it only improves the dimensional stability of the support of the blade, but not that of the chassis because, since the temperature is not transmitted in the latter, its deformations are not not compensated, and we know that they directly influence the precision of the cut. DESCRIPTION OF THE INVENTION The object of the present invention is a thermostatic impact cutoff mechanism which incorporates a set of electrical resistors strategically disposed on the blade head, in the counterblade holder and in the frame. They evenly distribute the heat to all the elements constituting the cutting mechanism. These resistances can act in two ways; they maintain the working temperature of the cutting mechanism indefinitely when the rest of the machine and its installations are disconnected, they prevent the loss of alignment between the blade and the counter blade as a result of the retraction of the metal, and make it possible to restart the machine without any special precautions, or they raise the temperature of the weatherstripping mechanism to the working temperature in a few minutes, and the misaligned retraction alignment of the metal is compensated automatically: this allows the machine to be relaunched safely and without any intervention. In all cases, the service life of the blade and counterblade assembly is the same as for a machine not subject to thermal variations. Specifically, the new mechanism is constituted by a minimum of six heating elements, preferably electrical resistors, located as follows: - Two heating elements in the support blade holder positioned symmetrically along each of its large faces, and in parallel to the axis of rotation and in the plane passing through or near the center of mass. - Two heating elements in the counterblade support positioned symmetrically along each of its large faces in the plane passing through or near the center of mass of said support. - Two heating elements in the frame of the machine, positioned horizontally in the vertical walls in an area near the plane of passage of the plastic fiber and the impact zone of the blade and against the blade.

With this configuration, the heating elements uniformly distribute the heat in the components of the cutting mechanism so that the expansion of the parts is uniform, perfect dimensional stability is thus achieved over the entire line of impact between the blade and the counter. blade. DESCRIPTION OF THE DRAWINGS FIG. 1 represents an elevation view of an impact cut mechanism according to the invention. FIG. 2 represents a partially cutaway side view of the same impact cut-off device according to the invention. DESCRIPTION OF A PRACTICAL EXAMPLE In the present practical example is shown a type of impact plastic fiber cutting machine having a blade (1) disposed on a rotating blade holder (2), a counterblade (3) placed in a fixed support (4) and a frame (5) formed by vertical walls (8) connected by two transverse sections of rectangular section (6) arranged on the base and three others of circular section (7) arranged in the upper middle zone.

The fixed support (4) bearing against the blade (3) is located in the upper part of the frame (5) and its vertical position can be adjusted by means of two vertical adjustment levers (9) located at the ends and on the face outer walls (8). The blade holder (2) is located in the lower part of the frame (5) and is not adjustable.

Both the fixed support (4) and the blade support (2) have a substantially rectangular structure with widely chamfered corners (12) on the side where the blade (1) and the counterblade (3) are respectively disposed. In this structure are distinguished large faces (13) each having a groove (10) in which there is a heating resistor (11). These resistors are strategically positioned symmetrically near the center of mass of the part so that the heat radiation is distributed uniformly and rapidly, while keeping the temperature constant and uniform. The vertical walls of the frame (8) also comprise grooves (10) in which there are heating elements (11) placed horizontally in the plane of passage of the plastic fiber and the impact zone of the blade (1). and against the blade (3). These resistors retain both the temperature and the dimensional stability of the walls of the frame where the blade holder (2) and the fixed support (4) rest with the counterblade (3) which, following the retraction of the frame by the cold, tend to reduce the vertical rib of their position.

REFERENCE LIST 1 Blade 2 Blade holder 3 Blade guard 4 Fixed bracket 5 Frame 6 Rectangular section cross section 7 Circular cross sectional sections 8 Vertical frame walls.

9 Vertical adjustment levers.

10 Splines 11 Heating Resistors 12 Chamfered Corners 13 Large Faces

Claims (3)

REVENDICATIONS1. A thermostatic cut-off mechanism of a plastic fiber comprising a frame (5) with vertical walls (8), the upper part of which contains a support in which the counterblade (3) is arranged, and the part of which lower part 5 contains a rotary blade holder (2) in which the blade (1) is arranged, characterized by six heating elements (11), resistors located as follows: - two or more heating elements (11) in the door support rotary blade (2), symmetrically distributed along each of its large faces (13) parallel to its axis of rotation and in a plane passing or in proximity to the center of mass, - two or more heating resistors (11) in the counterblade support (4), distributed symmetrically along each of its large faces (13), in a plane passing through or near the center of mass of the support, and two or more heating resistors (11) in the chass is (5), distributed horizontally on the vertical walls (8) in an area near the plane of passage of the plastic fiber and the impact zone of the blade and against the blade. 20 Thermostatic cut-off mechanism according to the first claim, characterized by heating resistors (11) housed in splines (10) of the counterblade support (4), in the blade carrier (2) and in the walls. vertical frame (8). 25 The thermostatic impact cutoff mechanism of claim 1 or claim 2, wherein the resistors are electrical.