EP2974833A1 - Device and method for determining the state of a blades on a fibre cutting device - Google Patents

Abstract

The invention relates to an apparatus and a method for cutting staple fibers from a bundle of endless fiber strands (5), which are at least partially guided around a rotatable cutting wheel (1), wherein the cutting wheel (1) has a plurality of knives (2 ), which cooperate with a pressure or force loaded pressure element such that the fiber strands (5) between the pressure element and the blades (2) are cut, and a device for detecting the state of the knife (2).

The invention is characterized in that via a change in the distance of the pressure element from the cutting wheel (1) and / or a change in the contact pressure of a printing device on the printing element, the state of the knife (2) can be determined.

Description

The invention relates to a device and a method for determining the state of the knives on a fiber cutting device in which staple fibers are produced from endless fiber strands which are at least partially passed around a cutting wheel and pressed onto the blades by means of a pressure element.

Between the cutting wheel and the pressure roller to run the endless fiber strands, which are divided by the blades - according to the division by the arrangement of the blades on the circumference of the blade carrier - in a predetermined length of staple fibers. Since this process is not classical cutting, but crushing with sliding friction, after a certain time the knives may become dull and even break, whereby the fragments get into the collecting container for the staple fibers and at the same time the staple fibers do not have the predetermined length in one cycle. The presence of the metallic fragments in the container with the staple fibers is undesirable for further processing.

According to the prior art, it is known to arrange a metal detector below the cutting device in the collecting funnel. Small pieces of broken knife edges are not so detectable. Even the condition, for example, the sharpness of the knife can not be determined.

The EP 1877603 B1 describes a method for monitoring the condition of individual knife blades, in which a sensor determines the emissive structure-borne noise of a component and, in the event of a deviation from a desired value, the engine control indicates a fault. The process is very complex, since the smallest changes, for example in the metallic composition of the knives, cause a change in the frequency range, which affect the control / regulation process. In contrast to the aforementioned prior art, the sensitivity is too high in this method to run permanently trouble-free in a robust operation.

The object of the present invention is to provide an inexpensive and robust apparatus and a method for cutting fibers, with which the condition of the knives can be reliably detected or monitored.

The invention solves the problem set by the teaching of claim 1 and 13. Further advantageous features of the invention are characterized by the dependent claims.

According to the teachings of claim 1, the apparatus for cutting staple fibers from a bundle of endless fiber strands comprises at least one rotatable cutting wheel with a plurality of knives about which the fiber strands are at least partially passed. The plurality of knives arranged on the circumference of the cutting wheel cooperate with a pressure or force-loaded pressure element in such a way that the fiber strands are cut between the pressure element and the knives. Furthermore, the apparatus for cutting staple fibers has a device for detecting the condition of the knives.

The invention is characterized in that via a change in the distance of the pressure element from the cutting wheel and / or a change in the contact pressure of a printing device on the printing element, the state of the knife is detectable.

The invention is based on the recognition that in a knife break the distance of the pressure roller to the cutting wheel due to the broken blade at the same point on the circumference of the cutting wheel only gets smaller, but then grows again, since at this point the fiber strands are not cut can.

Alternatively or additionally, the state of the blades can be determined by the change of the contact pressure of a printing device on the printing element. The pressure inevitably increases when the knives are worn or dull or even broken.

For this purpose, advantageously at least one switch, for example a proximity switch, or a sensor is used which can determine small changes in distance, wherein the signals of the at least one switch or sensor are evaluated by the machine control. In contrast to the prior art, the condition or breakage of a knife can be determined very reliably with simple components.

With the features of the invention, it is possible to provide a cheap and robust staple fiber cutter which can reliably detect the condition of the knives.

Preferably, the pressure element is designed as a pressure roller, which is pressed by a cylinder as a pressure device against the cutting wheel.

In a further advantageous embodiment, the switch or sensor is arranged on a cylinder, which is the pressure roller against the Cutting wheel presses. Since many cylinders have already integrated the switches for the end positions, their signal can be used to detect the knife breakage. For this purpose, the machine control system has to be provided with modified software that can evaluate the small changes in distance between the pressure roller and the cutting wheel.

A further improvement can be achieved by the switch or sensor cooperates with an actuating rod of the cylinder. The change in distance between the pressure roller and the cutting wheel is thus transmitted linearly.

Advantageously, the cylinder has a magnetic piston as a switching element with which the switch is triggered.

In this case, the switching element cooperate with a further switch, which is also arranged on the cylinder and which stops at an ascended position of the cutting device at least the drive of the cutting wheel.

Characterized in that the pressure roller is pivotally mounted about a pivot point by means of a lever arm, the cylinder can be made very simple mechanically. The pressure roller does not require a guide, along which it is movable on the cutting wheel.

Via a sensor, which determines the contact pressure of the printing device and directs it to a measuring device, the change of the contact pressure can be determined and the state of each individual knife can be determined.

To quickly identify the individual knife, another sensor detects the position of the cutting wheel and passes the signal either to the measuring device or to a controller.

The controller, in turn, can evaluate the changes in position or contact pressure and, via a signal, generate a stop to the machine, an alarm or a warning if certain limits are exceeded.

The method for determining the state of the knives on a fiber cutting device in which staple fibers are produced from endless fiber strands in which the fiber strand is at least partially passed around a cutting wheel and pressed by means of a pressure element on the blades of knives is characterized in that the change in the distance between the pressure element and the cutting wheel and / or by the change in the contact pressure of a printing device on the printing element, the state of the knife is recognizable.

The fact that at a knife break the distance of the pressure roller to the cutting wheel due to the broken blade at the same point on the circumference of the cutting wheel only gets smaller, but then grows again, since at this point the fiber strands can not be cut, can very reliably a knife break be recognized.

By changing the contact pressure of a printing device on the printing element, the state of the knife can alternatively be fixed or fixed. The pressure inevitably increases when the knives are worn or dull or even broken.

Advantageously, the change in the distance is determined by means of at least one switch or sensor whose signals are evaluated by the machine control.

In a preferred embodiment, the at least one switch or sensor cooperates with a printing device designed as a cylinder, which presses the pressure roller against the cutting wheel.

Alternatively or additionally, a sensor determines the position of the cutting wheel and transmitted to a measuring device or control. This way, the condition can be determined and documented for every single knife over one revolution of the cutting wheel.

Particularly preferably, a sensor determines the contact pressure of the printing device and transmits the value to a measuring device. By changing the pressure, the sharpness or damage of the knife blade can be accurately determined.

Figur 1:

eine schematische Prinzipskizze einer Vorrichtung zum Schneiden von Stapelfasern;

Figur 2:

eine schematische Darstellung einer ersten Ausführungsform der erfindungsgemäßen Vorrichtung zum Schneiden von Stapelfasern;

Figur 3:

eine weitere schematische Darstellung der ersten Ausführungsform der erfindungsgemäßen Vorrichtung zum Schneiden von Stapelfasern;

Figur 4:

eine dritte schematische Darstellung der der ersten Ausführungsform der erfindungsgemäßen Vorrichtung zum Schneiden von Stapelfasern;

Figur 5:

eine schematische Darstellung einer zweiten Ausführungsform der erfindungsgemäßen Vorrichtung zum Schneiden von Stapelfasern.

The invention will be explained in more detail with reference to a possible schematically illustrated embodiment. It shows:

FIG. 1:

a schematic schematic diagram of an apparatus for cutting staple fibers;

FIG. 2:

a schematic representation of a first embodiment of the inventive apparatus for cutting staple fibers;

FIG. 3:

a further schematic representation of the first embodiment of the inventive apparatus for cutting staple fibers;

FIG. 4:

a third schematic representation of the first embodiment of the inventive apparatus for cutting staple fibers;

FIG. 5:

a schematic representation of a second embodiment of the inventive apparatus for cutting staple fibers.

FIG. 1 shows an embodiment of a cutting device according to the invention for cutting staple fibers from a bundle of endless fiber strands 5. A rotatable about its axis of rotation 3 and driven by motor cylindrical cutting wheel 1 has on its periphery a plurality of blades 2, with their cutting in the direction of the outer periphery demonstrate. In this embodiment, only four knives 2 out of a total of about 50-90 knives are exemplified. The distance of the knife edges on the outer circumference corresponds to the future cut fiber length. The knives 2 are chambered from below and above with cover plates 4, which protrude in the form of collar and thereby the fiber strands 5 as in a part lead open channel. In this embodiment, the cutting wheel 1 rotates clockwise.

A pressure element is designed in this embodiment as a pressure roller 6, which is acted upon by the pressure device 7 and cooperates with its outer periphery with the cutting edges of the blade 2 on a pitch circle 2a. The pressure roller 6 is rotationally symmetrical in this embodiment and can also be rotatably driven depending on the design with a separate drive, or be carried over the or the fiber strands 5 rotating. The circular pitch circle 2 a is formed by all arranged on the cutting wheel 1 cutting the blade 2. In this case, the pressure roller 6 rotates counterclockwise. Outside its axis of rotation, the pressure roller 6 is pivotably mounted about a pivot point 10 by means of a lever arm 9. The pressure or the force on the pressure roller 6 is applied by an actuating rod 11 which is attached at one end to the pressure roller 6, and at the other end with a cylinder 8, for example a pneumatic or hydraulic cylinder, cooperates.

The fiber strands 5 run continuously tangentially to the circumference of the rotating cutting wheel 1, are guided around the cutting wheel 1, in this embodiment by about 270 °, around and lie on the cutting edges of the knife. Since the blades of the knife 2 are directed to the periphery of the cutting wheel 1, 5 of the pressure of the pressure roller 6 on the fiber strand of this cut. The cut fibers are removed below the cutting wheel 1 through a channel, not shown. The length of the cut fiber corresponds approximately to the distance of the knife edges on the outer circumference of the cutting wheel 1. Uncut individual fibers of the fiber cable gradually wrap around the cutting wheel and are then increased at the next revolution with one Cutting force cut. In order to prevent an excessive knife break, as far as possible no transverse forces should act on the knife edges. For this purpose, the speed of the fiber strands 5 entering the cutting wheel 1 is synchronized with the peripheral speed of the blades 2 at the cutting edges.

The first embodiment of the invention is in the FIGS. 2 to 4 described.

In FIG. 2 the cutting wheel 1 and the fiber strand 5 is shown only symbolically. This figure shows the position of the pressure roller 6, which rests with its outer periphery on the pitch circle 2a. As stated above, the cylinder 8 ensures the required contact pressure, which is exerted on the pressure roller 6 by means of actuating rod 11. The cylinder 8 is fixed by means of a fixed point 15 fixed to a housing of the fiber cutting device, wherein the cylinder 8 is at least partially formed along the actuating rod 11 movable. On the cylinder 8, a first and a second switch 12, 13 are arranged, with which the position of the pressure roller 6 can be determined. The cylinder 8 is mounted axially movably via a center suspension 14. Within the cylinder 8, an unrepresented magnetic piston may be arranged, which cooperates with the switches 12, 13, which may be formed as a proximity switch.

In FIG. 3 the cutting device is shown in the raised position, wherein the cylinder 8 has moved back the actuating rod 11, so that the pressure roller 6 has pivoted about the pivot point 10 around and lifted off the cutting wheel 1. In this position, in which there is a large distance between the knives 2 and the pressure roller 6, for example, the cutting wheel 1 and / or the underlying channel be cleaned and a new fiber strand 5 inserted or the pressure roller 6 are replaced. In this case, the rear switch 13 is actuated by the not shown in the cylinder 8 arranged magnetic piston, so that the machine control stops the speed of the cutting wheel 1 and pressure roller 6 and locks the cutter.

The front switch 12 monitors the fed state of the pressure roller 6. He is set back so far that during normal operation, the switching position is not covered, or the switch does not trigger. In a knife break the fiber strand 5 can not be cut. The missing edge of the blade 2 may cause the pressure roller 6 to cover the pitch circle 2a during the first revolution of the non-cut fiber strand 5 since the pressure roller 6 can dip into the gap of the broken blade 2. Only when there are several revolutions with wound fiber strands, the force on the pressure roller 6, whereby this is pressed against the pressure of the cylinder 8 locally away from the pitch circle 2a, so that the distance between the cutting wheel 1 and pressure roller 6 increases. This slight lifting of the pressure roller 6 from the pitch circle 2a of the cutting wheel 1, which is formed by the blades of the blade 2, is detected by a second switch 12 and forwarded to the machine control, which then displays an error message. Due to the distance of the pressure roller 6 from the pitch circle 2a, the switch can be adjusted so that a single wrapping of the cutting wheel 1 with a non-cut fiber strand 5 does not lead to a triggering of the switch 2. Only a repeated wrapping of the cutting wheel 1 with parts of the fiber strand 5 leads to a greater distance of the pressure roller 6 from the pitch circle 2a and the triggering of the switch 12. Depending on the fiber thickness of the switch 12 can be adjusted so that a false alarm can be avoided.

According to the invention, a knife break can be reliably determined via the determination of the distance of the pressure roller 6 from the cutting wheel, in particular from the pitch circle 2a or via the deviation from the theoretical distance from the blades of the knife 2, without the need for further devices such as metal sensors or other sensors. The arranged on a cylinder 8 or integrated sensors 12, 13 and their signals can be used to detect a possible knife break with the machine control.

Alternatively, the switches or sensors can also be arranged as Drehweggeber example in the pivot point 10 of the lever arm. A further arrangement can also be made on the lever arm 10 or in the region of the bearing of the pressure roller 6. The switches 12, 13 or sensors on the cylinder 8 have the advantage that they can already be integrated in or on the cylinder and only a connection with the machine control and an additional adaptation of a software allows detection of a knife breakage.

In the second embodiment of the FIG. 5 the change in the contact pressure of the pressure element or the printing device 7 is used to monitor the state of the knife 2, in particular the breakage of the knife 2. For this purpose, a sensor 16 determines the actual contact pressure of the printing device 7, for example of the cylinder 8, and forwards the signal to a measuring device 18 which generates a signal 20 by means of a controller 19 or a controller if limit values are exceeded. The controller 19 detects deviations from a target size, which then conclude whether a blade 2 is blunt or possibly broken with an even greater deviation. A second sensor 17, which may be designed as an incremental encoder and is arranged on the cutting wheel 1, continuously transmits its position or the position of the cutting wheel 1 to the measuring device 18. The measuring device 18 can with both sensor values for each knife 2 the Save current state and transmit the data to the controller. This results in a fully automatic knife monitoring for the cutting machine, which can determine the state of each individual knife 2 within a revolution of the cutting wheel 1. A significant advantage over the prior art is the exact display of the defective blade 2 and the early display of dull blades 2 before they break. This allows early planning a maintenance interval for all become problematic knife 2, which due to the exact indication of which knife 2 is affected, can reduce the maintenance time. An analysis of the cut cable length per knife makes it possible to build up a traceable and documentable quality assurance system, for example, when the supplier or the batch of blades changes. The downtime is thus minimized and there is an optimal use of the blades 2. The measuring device 18 can graphically represent and monitor the cutting forces of each blade 2, wherein the control 19 limits for a warning, an alarm or a stop or knife break in Dependence of the fibers to be cut are adjustable.

A combination in the evaluation of the data is useful, so to combine the change in contact pressure with the change in the position of the pressure element, as this reliably a false alarm can be avoided in a possible knife break, as in possible defects in the hardness of the fiber strand a change in the Contact pressure can be displayed without changing the position of the pressure element.

A partial combination is also possible in which, for example, the change in position of the pressure element is combined with the sensor 17 in order to be able to directly determine the position of the broken blade.

reference numeral

1

cutting wheel

2

knife

2a

pitch circle

3

axis of rotation

4

cover sheet

5

tow

6

pressure roller

7

printing device

8th

cylinder

9

lever arm

10

pivot point

11

actuating rod

12

switch

13

switch

14

center suspension

15

fixed point

16

sensor

17

sensor

18

measuring device

19

control

20

signal

Claims (18)

Apparatus for cutting staple fibers from a bundle of endless fiber strands (5) which are at least partially passed around a rotatable cutting wheel (1), the cutting wheel (1) having on its circumference a multiplicity of knives (2) which are subjected to a pressure - or force-loaded pressure element cooperate in such a way that the fiber strands (5) between the pressure element and the knives (2) are cut, and a device for detecting the state of the knife (2), which is characterized in that a change in the Distance of the pressure element from the cutting wheel (1) and / or a change in the contact pressure of a printing device on the printing element, the state of the knife (2) can be determined. Apparatus according to claim 1, characterized in that the change in the distance of the pressure element from the cutting wheel (1) by means of at least one switch (12) or sensor is determined. Device according to one of the preceding claims, characterized in that the pressure element is designed as a pressure roller (6). Device according to one of the preceding claims, characterized in that the printing device is designed as a cylinder (8). Device according to one of the preceding claims, characterized in that the switch (12) or sensor is arranged on the cylinder (8). Apparatus according to claim 4 or 5, characterized in that the switch (12) or sensor cooperates with an actuating rod (11) of the cylinder (8). Device according to one of the preceding claims, characterized in that the cylinder (8) has a switching element which cooperates at least with the switch (12). Device according to one of the preceding claims, characterized in that the cylinder (8) has a switch (13) which stops at least the drive of the cutting wheel (1) at an ascended position of the cutting device. Device according to one of the preceding claims, characterized in that the pressure roller (6) by means of a lever arm (9) about a pivot point (10) is pivotally mounted. Apparatus according to claim 1, characterized in that a sensor (16) determines the contact pressure of the printing device and the signal to a measuring device (18) passes. Apparatus according to claim 1, characterized in that a sensor (17) passes the position of the cutting wheel (1) to a measuring device (18) or a controller. Device according to one of the preceding claims, characterized in that a controller (19) evaluates changes in the position of the pressure element or changes in the contact pressure and generates a signal (20). Method for determining the condition of the knives on a fiber cutting device, in which endless fiber strands (5) which are at least partially passed around a cutting wheel (1) and Staple fiber are produced by means of a pressure element on the blades of knife (2), characterized in that by changing the distance between the pressure element and the cutting wheel (1) and / or by changing the contact pressure of a printing device on the pressure element of Condition of the knife (2) is recognizable. A method according to claim 13, characterized in that the change in the distance by means of at least one switch (12) or sensor is determined, the signals of which are evaluated by a controller. A method according to claim 14, characterized in that the at least one switch (12) or sensor cooperates with a cylinder (8) designed as a printing device which presses the pressure element against the cutting wheel (1). A method according to claim 13, characterized in that a sensor (17) detects the position of the cutting wheel (1) and transmitted to a measuring device (18) or control. A method according to claim 13, characterized in that a sensor (16) determines the contact pressure of the printing device and transmits the value to a measuring device (18). Method according to one of claims 13 to 17, characterized in that the state of each individual knife (2) within one revolution of the cutting wheel (1) can be determined.

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