ELECTROMAGNETIC DRIVE FOR A CUTTING DEVICE OF A TEXTILE MACHINE, CUTTING DEVICE AND YARN CLEARER

Abstract

The invention relates to an electromagnetic drive for a cutting device of a textile machine for severing a thread, to a cutting device having an electromagnetic drive, and to a yarn clearer having a cutting device. In order to provide an electromagnetic drive for a cutting device of a textile machine for severing a thread, the electromagnetic drive enabling particularly efficient, fast and/or precise operation of a cutting device having a cutting blade with large cutting force and also preferably enabling a particularly long uninterrupted and maintenance-free operating time, it is provided that: —the piston is partly guided in a core tube contained by the solenoid, the core tube being formed by the component which is stationary relative to the piston, and the axial air gap extending between the end face of the piston and an end face of the core tube, which end face is formed by the counter face; and/or—the piston is at least partly hollow; and/or—the piston is operatively connected to a returning element for returning the piston after the piston has been moved out of the rest position, the returning element having a progressive and, in particular, non-linear spring characteristic curve; and/or—the piston is surrounded by a solenoid core, which is stationary relative to the piston and which either is produced by powder injection moulding and/or is made from a soft ferrite or is made from a plurality of layers of an electrical steel sheet, more particularly from a non-grain-oriented electrical steel sheet.

Claims

1. An electromagnetic drive (1) for a cutting device of a textile machine configured for severing a thread by means of a solenoid (2), the electromagnetic drive (1) comprising a piston (3) configured to drive a cutting blade carrier (13), wherein the piston (3); is guided for linear movement within the solenoid (2), and is configured to be linearly moved between a rest position and a working position; a coil configured to produce a magnetic field configured to drive the piston (3); and an axial air gap (6), between an end face (7) of the piston (3) and a counter face of a component of the solenoid (2), wherein: the component is stationary relative to the piston (3), and the axial air gap (6) is varied based on movement of the piston, and wherein: the piston (3) is partly guided in a core tube (9) contained by the solenoid (2), in particular by means of a bearing element (11), wherein the core tube (9) is formed by the component, and the axial air gap (6) extends between the end face (7) of the piston (3) and an end face (8) of the core tube (9), wherein the end face (7) of the piston (3) is conical and the end face (8) of the core tube (9) is formed by the counter face and corresponds to the conical end face (7) of the piston (3), the piston (3) is at least partly hollow, the piston (3) is operatively connected to a returning element (12) configured to return the piston (3) after the piston (3) has been moved out of the rest position, the returning element (12) comprising a progressive and non-linear spring characteristic curve, or the piston (3) is surrounded by a solenoid core (5), which is stationary relative to the piston (3), and which: is produced by powder injection moulding, or is made from a soft ferrite, or is made from a plurality of layers of an electrical steel sheet comprising a non-grain-oriented electrical steel sheet.

2. The electromagnetic drive (1) according to claim 1, wherein the piston (3) has a first piston segment (3A) and a second piston segment (3B), wherein: the first piston segment (3A) is positioned outside of the core tube (9), the second piston segment (3B) is fixed to the first piston segment (3A), a free end of the second piston segment (3B) protrudes from the solenoid (2) and extends from the first piston segment (3A) through the core tube (9), and the free end of the second piston segment (3B) being is configured to carry the cutting blade carrier (13).

3. The electromagnetic drive (1) according to claim 2, wherein: the first piston segment (3A) has an axial length greater than or equal to an axial length of an exposed face of the solenoid (2) which faces the first piston segment (3A), and the axial length of the exposed face of the solenoid (2) greater than an axial length of the axial air gap (6) when the piston (3) is in the rest position.

4. The electromagnetic drive (1) according to claim 2, wherein the first piston segment (3A) or the core tube (9); comprises a hot-rolled carbon steel; or has a carbon content: of less than 1%; of less than 0.5%; or in a range from 0.1% to 0.2%.

5. The electromagnetic drive (1) according to claim 2, wherein the second piston segment (3B) comprises a non-magnetic or non-magnetisable metal.

6. The electromagnetic drive (1) according to claim 1, wherein an angle of the conical end face (7) of the piston (3) or an angle of a corresponding end face (8) of the core tube (9), with respect to an axial movement axis of the piston (3), is between 15° and 40°.

7. The electromagnetic drive (1) according to claim 1, wherein the piston (3) is positioned so as to be guided within the core tube (9) with a minimal orthogonal distance so that a second, orthogonal air gap (10), extending between the piston (3) and a solenoid core (5) surrounding the core tube (9), is minimized.

8. The electromagnetic drive (1) according claim 1, further comprising a single bearing element (11), positioned in the core tube (9), configured to support the piston (3), wherein the bearing element (11) comprises polyetheretherketone.

9. The electromagnetic drive (1) according to claim 1, wherein a center of mass of the piston (3) remains within the core tube (9) within a bearing element (11) positioned in the core tube (9), during a movement of the piston (3) between the rest position and the cutting position.

10. The electromagnetic drive (1) according to claim 1, wherein a magnetically exposed area in an orthogonal air gap (10) between a solenoid core (5) of the solenoid (2) and the piston (3) is greater than or equal to a magnetically exposed area in the axial air gap (6).

11. The electromagnetic drive (1) according to claim 1, wherein the piston (3) or the core tube (9) comprises a material having: a magnetic saturation level of more than 1.9 T; or a coercive force of less than 1,300 A/m.

12. A cutting device for a textile machine for severing a thread, comprising: an electromagnetic drive (1) according to 1; and a cutting blade carrier (13) with a cutting blade (14), wherein the cutting blade carrier (13) is movable by means of the electromagnetic drive (1) between a rest position and a cutting position.

13. A yarn clearer for a workstation of a textile machine, comprising: an electromagnetic drive (1) according to claim 1; and at least one sensor device configured to detect: a presence or absence of a thread; or a yarn fault.

Description

[0048] The present invention is not limited to the individual embodiments described above. Individual or several embodiments can certainly be combined with each other, whereby an additional preferred embodiment can be achieved.

[0049] An embodiment example of an electromagnetic drive for a cutting device of a textile machine is explained in more detail below with reference to the drawings. In the drawings:

[0050] FIG. 1 shows a schematic view of the top of an electromagnetic drive for a cutting device of a textile machine and

[0051] FIG. 2 shows a sectional view of the electromagnetic drive shown in FIG. 1.

[0052] An electromagnetic drive 1 shown in FIG. 1 is provided for a cutting device of a textile machine that produces thread packages, and said electromagnetic drive 1 has a cutting blade holder 4 for holding the cutting device on a yarn clearer. By means of a cutting blade 14, which is integrated in a cutting blade carrier 13, a thread moving quickly along its central longitudinal axis can be cut or severed, for example when a defect is detected. Because of the high thread running speed, the cutting process must be carried out within a few milliseconds, and therefore particularly fast driving of the cutting blade 14 is required. Furthermore, a certain cutting force and also high precision are required in order to cleanly sever the thread.

[0053] In order to make this possible, the electromagnetic drive 1 has a solenoid 2. A piston 3 is linearly movably arranged in the interior of a solenoid core 5. The piston 3 is composed of a first piston segment 3A and a second piston segment 3B, and a free end of the second piston segment 3B is pressed into a receptacle of the first piston segment 3A and thus is fixed.

[0054] The piston 3 is partly surrounded by a coil, which is not shown in the figures. When the coil is activated, a magnetic field is built up and the piston 3 is moved toward a cutting position. In order to support the piston 3 on the solenoid core 5 precisely and also with minimal friction, the piston 3 is arranged within a core tube 9, into which additionally a bearing element 11 made of polyetheretherketone is pressed. The bearing element 11 linearly guides the piston 3 and prevents tilting.

[0055] The cutting blade carrier 13 is detachably connected to the piston 3, in particular to the other free end of the second piston segment 3B.

[0056] In order to achieve particularly good magnetic interaction between the stationary core tube 9 and the piston 3, the end faces 7, 8 of both the piston 3 or the first piston segment 3A and the core tube 9 are conical. The magnetic interaction between the stationary core tube 9 and the piston 3 occurs primarily within an axial air gap 6, which extends between the end face 7 of the piston 3, which end face 7 is angled with respect to the central longitudinal axis of the piston 3, and the corresponding, likewise angled end face 8 of the core tube 9. The axial air gap 6 changes its volume and its length along the central longitudinal axis or the direction of movement of the piston 3 as the piston 3 is moved from a rest position into a cutting position, in which the thread is severed.

[0057] The two end faces 7, 8 have a flat surface angled by about 30° with respect to the central longitudinal axis of the piston 3, whereby the surfaces are considerably enlarged in comparison with arrangement at an angle of 90°. In this way, the magnetic interaction can be considerably optimised. In order to optimise this interaction further, the bearing element 11, the piston 3 and the solenoid core 5 are formed such that the orthogonal air gap 10 between the piston 3 and the solenoid core 5, which orthogonal air gap 10 surrounds the piston 3 over the full periphery, and the volume of which orthogonal air gap 10 essentially does not change as the piston 3 is moved, is as small as possible.

[0058] As described above, the second piston segment 3B is fixedly set, more particularly pressed, into the first piston segment 3A. The second piston segment 3B is guided in the axial direction by the bearing element 11. Furthermore, the second piston segment 3B is partly hollow or at least partly in the form of a hollow profiled element, and this contributes to further reduction of the moving mass, whereby better acceleration of the moving mass is achieved, leading, in turn, to greater cutting force. In order to avoid magnetic short circuits, the second piston segment 3B is produced from non-magnetic and/or non-magnetisable material, more particularly aluminium or non-magnetic stainless steel. At the same time, the hollowing out of the first piston segment 3A on the side of the piston 3 remote from the second piston segment 3B reduces the eddy current losses and magnetisation losses arising there.

[0059] In order to allow the piston 3 to be reliably and quickly returned from the cutting position to the rest position, a progressive coil spring 12 is arranged surrounding the second piston segment 3B and is increasingly loaded as the piston 3 is moved into the cutting position. As soon as the coil is deactivated, the coil spring 12 presses the piston 3 back into the rest position. A movement cycle of an electromagnetic movement of the piston 3 from the rest position into the cutting position and a spring-force-driven movement of the piston 3 back into the rest position is preferably carried out within 10 ms to at most 15 ms. The coil spring 12 is arranged between the end face 7 of the piston 3 and a spring stop provided in the core tube 9, the spring stop being designed for contact at least in the course of the movement of the piston 3 from the rest position into the cutting position. In another preferred arrangement, the coil spring 12 is retained between the end face 7 of the piston 3 and an end face of the bearing element 11.

[0060] In order to further optimise the magnetic interaction, the first piston segment 3A and the core tube 9 are made of a material having a high magnetic saturation level of more than 1.9 T and having a low coercive force of less than 800 A/m. In this embodiment of the electromagnetic drive 1, hot-rolled carbon steel having a low carbon content of 0.1% to 0.2% is used as the material of the first piston segment 3A and of the core tube 9.

[0061] Furthermore, the solenoid core 5 is formed from a plurality of mutually joined layers of electrical steel sheet, more particularly from non-grain-oriented electrical steel sheet. In another preferred arrangement, the solenoid core 5 is made of a soft ferrite, more particularly Mn—Zn ferrite, Ni—Zn ferrite, yttrium iron garnet or the like, and production by powder injection moulding is particularly advantageous. These measures help, inter alia, to reduce eddy currents and their negative effects on quick acceleration of the piston 3 such that there is no longer any significant effect.

LIST OF REFERENCE SIGNS

[0062] 1 Electromagnetic drive [0063] 2 Solenoid [0064] 3 Piston [0065] 3A First piston segment [0066] 3B Second piston segment [0067] 4 Cutting blade holder [0068] 5 Solenoid core [0069] 6 Axial air gap [0070] 7 End face of the piston [0071] 8 Counter face or end face of the core tube [0072] 9 Core tube [0073] 10 Orthogonal air gap [0074] 11 Bearing element [0075] 12 Returning element/coil spring [0076] 13 Cutting blade carrier [0077] 14 Cutting blade