Method and device for reducing noise generated during operation of needling machine for production of nonwoven fabrics

Abstract

 The invention relates to method of operation of the needling device (2) for production of nonwoven fabrics (11), whose needle board (23) moves in an enclosed space in periodic straight-lined reversible motion of a high frequency with respect to the surface of the processed web (1) and to the surface of the stripping plate (24). At the reverse motion of the needle board (23) in an enclosed space with atmospheric pressure the air from the decreasing section of an enclosed space under or above the needle board (23) in direction of its motion is expelled into the increasing section of an enclosed space on opposite side of the needle board (23), at the same time this alternately expelled air streams in the mentioned enclosed space, by which the low-frequency noise in surroundings of the machine is limited.
The invention also relates to the device for reduction of low-frequency noise generated at operation of the needling device (2) for production of nonwoven fabrics (11).

Description

Technical field

[0001] The invention relates to the method of operation of the needling device for production of nonwoven fabrics, whose needle board moves in en enclosed space in periodic straight-lined reversible motion of a high frequency with respect to the surface of the processed web and to the surface of the stripping plate.

[0002] The invention also relates to the device for reducing the low frequency noise being generated at operation of needling device for production of nonwoven fabrics, comprising at least one needle board, stripping plate and bed plate, while the needle board is coupled with the driving rods putting the same into a straight-lined reversible motion in direction to the processed fabric and to thestripping plate arranged between the needle board and the web processed, and further comprising a cover delimiting the space in which the needle board is moving.

Background art

[0003] Operation of needling machines for production of nonwoven fabrics is accompanied with intensive noise, which has a very high amplitude at frequency given by a straight-lined reversible motion of the machine needle board. At modern high-speed machines this frequency is higher than 20 Hz, which corresponds to rotation of the machine 1200 min^-1 and lies within the audibility range. The noise is sometimes so intensive, that through its spreading into the vicinity it causes e.g. vibration of structure of a production hall. Due to its low frequency it is very difficult to be dampened, it goes round considerably large obstacles and spreads into a great distance outside a production hall, where it can cause resonant vibrations of buildings, their parts and closed areas. For a man the perception of low-frequency noise is rather bothersome, as it is perceived by organs inside the body and it may cause a fast growth of tiredness.

[0004] At present, reduction of noise is mainly achieved by enclosing the machine into an auxiliary box. Nevertheless the walls of the box may not be thick enough to dampen sufficiently the noise of low frequencies. Moreover it must comprise technological holes, through which the air escapes outside. Therefore only unsubstantial decrease in level of low-frequency noise may be achieved, while the costs for acquisition of such box are inadequate to the result.

[0005] If some of the solution according to the background art, for example CN 2352549, at least marginally solve the problem of reducing the noise of needling machines, they focus to balancing of the driving mechanisms, utilising the silent toothed gearing, etc.

[0006] The topic of air streaming in the space neighbouring with the needle board is published due to removing the separated fibres and cleaning of mouth of needle holes and their vicinity in the stripping plate, e.g. in EU 1384804B1.

[0007] Solution according to the CZ 1998-1523 A3 utilises the compressed air streaming through the nozzles inclined with respect to the direction of passage of the web for support of its motion. Due to the fact that the device here does not utilise the lower needle boards and the needles of the upper needle board are provided with reverse-barbs, the compressed air streaming through the passage holes of the stripping plate at motion of the needle board from the processed web presses the web to the needling pad.

[0008] In such cases this air is transported into the space above the needle board enclosed by a cover from a special source of compressed air and this space is tightly connected with the stripping plate. At time of elaboration of these solutions relatively low frequency of activity of needling device was not a source of low-frequency noise above the audibility limit caused by streaming of air. The particular arrangement of the cover, for example according to CZ 1998-1523 A3, does not deal with the problem of noise, and it does not solve this problem.

[0009] The background art, probably due to the above mentioned reasons, does not comprise the means, which would solve damping of noise generated from streaming of air, whose source is the periodically moving needle board of the needling machine.

[0010] At motion of the needle board to the stripping plate this air streams mainly in direction of the gap between the needle board and the stripping plate and relatively considerable kinetic energy is imparted to it. This energy through diffusion of the stream changes into a pressure wave. On the contrary, at motion of the needle board from the stripping plate the air is sucked back into the space between the needle board and the stripping plate, nevertheless it is not the same air which was expelled, but the air from a broad vicinity of the gap between the needle board and the stripping plate. Through this an underpressure wave is generated. Periodic generated overpressure and underpressure waves are spread into vicinity of the machine and they express themselves as an intensive low-frequency noise.

[0011] The goal of the invention is to maximally reduce propagation of this noise into a vicinity and to improve the working environment in textile operations of the needling machines.

Principle of the invention

[0012] The goal of the invention has been achieved by a method for operation of the device for production of nonwoven fabrics, whose principle consists in that, at the reverse motion of the needle board in an enclosed space with atmospheric pressure the air from the decreasing section of an enclosed space under or above the needle board in direction of its motion is expelled into the increasing section of an enclosed space on opposite side of the needle board, at the same time this alternately expelled air streams in the mentioned enclosed space, by which the low-frequency noise in vicinity of the machine is limited.

[0013] The goal of the invention has also been achieved by the device for reduction of low-frequency noise generated at operation of the needling device, whose principle consists in that the cover of the machine creates an enclosed space with atmospheric pressure.

[0014] The air expelled from the decreasing space above or under the needle board at the needling device working at high frequency of reversible motion of the needle board thus does not stream into surroundings of the machine by which spreading of pressure waves into surroundings is prevented. Through this the outside noise of the machine is reduced considerably and possible vibration of structures being in vicinity of the machine is prevented.

[0015] It is advantageous if between the cover and the stripping plate a sealing gap is created. A small gap does not cause outflow of a larger quantity of air from space of the cover, at the same time it may have a positive influence on removal of impurities from the space above the stripping plate. It is also advantageous, if between the section of the cover adjacent to the processed web and a surface of the processed web a gap is created, which acts as a further sealing slot preventing an unwilling larger outflow of air from the space inside the cover.

[0016] In alternative embodiment the cover is tightly connected with the stripping plate. This is favourable from the point of view of further decreasing the outflow of compressed air into surroundings of the machine, thus also the noise in surroundings of the machine.

[0017] In the cover around the driving rods of the needle board there are created sleeves with sealing gaps. These create the slot sealing enabling a troublefree operation of driving rods of the needle plate and prevent a larger outflow of air from the space inside the cover.

[0018] In another alternative embodiment the cover is tightly connected to the driving box for drive of the needle board. Through this a total enclosed space of the cover is increased, which reduces fluctuation of pressure inside it, at the same time the pressure waves also do not spread in surroundings of the machine.

[0019] The device according to the invention remedies necessity to surround the machine with a large layer of damping material being disadvantageous both from the point of view of price as well as necessary space.

Description of the drawing

[0020] Exemplary embodiments of the device according to the invention are schematically represented in the drawings by means of longitudinal sections run through axis of the fed processed material, where the Fig. 1 illustrates the basic embodiment, the Fig. 2 embodiment with the bed plate, whose supporting surface is not larger than surface of the stripping plate, the Fig. 3 embodiment with the sealed connection of bottom section of the cover with stripping plate, the Fig. 4 embodiment with shaped cover, the Fig. 5 embodiment with tilting side parts of the cover, the Fig. 6 embodiment with cover attached to the box of the drive, the Fig. 7 embodiment at machine equipped with two needle boards, and the Fig. 8 alternative solution of sealing of the cover with respect to the processed material.

Examples of embodiment

[0021] The needling machine serves to produce nonwoven fabrics from a semiproduct, which is a band of nonwoven and relatively little compact fibrous web. Upon needling into the web there penetrates a system of large number of needles provided with reverse barbs and fastened in the needle board, which moves substantially in straight-lined reversible manner in direction perpendicular to surface of band of the web with a high frequency, for example 1400 punctures per minute. During this motion the needles mutually interlace the fibres of the web, hence the web is strengthened and a nonwoven fabric created.

[0022] The Fig. 1 to 8 in various exemplary arrangements represents the working part of needling device according to the invention.

[0023] On entry of the processed web 1 into the needling device 2 there is arranged the feeding mechanism 21, which feeds the web 1 to the bed plate 22 in a fixed manner connected with frame of the machine. The needling device 2 further comprises the needle board 23, in which perpendicularly to its surface a plurality of needles 231 is attached. The needle board 23 with its upper surface is attached to the driving rods 232, which are put into a straight-lined reversible motion by a not represented driving device arranged in the driving box 20. Number of driving rods 232 depends on width of the processed web 1, to which corresponds the longer dimension of the needle board 23. Between the bed plate 22 and the needle board 23 to the frame of the machine in a fixed manner the stripping plate 24 is attached. The bed plate 22 is provided with through holes 221 and the stripping plate 24 is provided with holes 241. Each one above another situated couple of holes 221, 241 is arranged axially with respect to it corresponding needle 231. On exit from the needling device 2 is arranged the draw off mechanism 25 of produced nonwoven fabric 11.

[0024] The needling device 2 further comprises the cover 3 in a fixed manner connected with frame of the machine, in whose upper section are created the sleeves 31 for passage of driving rods 232. Between surface of the driving rods 232 and inner surface of the sleeves 31 the sealing gaps 311 are provided. Circumferential parts of the cover 3 encircle the needle board 23 and the stripping plate 24. Between the outer circumference of the needle board 23 and inner surface of circumferential parts of the cover 3 there is the working gap 26.

[0025] In embodiment represented in the Fig. 1 the cover 3 is provided on the lower side with circumferential border 32, between which and the processed web 1, respectively the produced nonwoven fabric 11, there is the gap 321 continuing into the circumferential sealing gap 322 between the stripping plate 24 and the border 32.

[0026] Embodiment represented in the Fig. 2 from the previous embodiment differs in that the needling device 2 is equipped with the bed plate 22, whose surface adjacent to the processed fabric is identical as ground plane of the bed plate 24. For the reason to provide a suitable gap 321 between the processed web 1, respectively the produced nonwoven fabric 11, and the border 32 of the cover 3 the supporting surface of the bed plate 22 is enlarged so that to circumference of the bed plate 22 the supporting borders 222 are attached.

[0027] In another embodiment represented in the Fig. 3 the cover 3 by its lower border is tightly connected with circumference of the stripping plate 24. This alternative of solution may be realised also in other described arrangements.

[0028] Embodiment according to the Fig. 4 utilises the shaped cover 4, whose annular circumferential cavity 41 has a shape suitable from the point of view of directing the air flow at machine operation.

[0029] The cover 5 in embodiment according to the Fig. 5 comprises at least one tilting side wall 51 serving to facilitate access of attendant during necessary intervention into the inner space of the cover 5.

[0030] In embodiment according to the Fig. 6 the cover 6 is attached with its upper section directly to the driving box 20. This arrangement removes the working gaps 311 between the sleeves 31 of the cover 3, 4, 5 and the driving rods 232, which are necessary at the above mentioned represented embodiments.

[0031] According to the Fig. 7 the needling device 2 is provided with two needle boards 23, corresponding bed plates 22 and the stripping plates 24. The needle boards 23 of the needle machine in such a case usually perform a straight-lined reversible motion with mutually opposite phase. Both needle boards 23 with another means of the needle device 2 are arranged under a common cover 7.

[0032] At the cover 8 according to the Fig. 8, when compared with the previous embodiments, the border of its lower section is replaced with tiltable slats 81 in a roof-like manner arranged in direction of motion of the processed web 1, respectively of the produced nonwoven fabric 11, and connected with the side walls of the cover 8 by means of hinges 82. In the not represented embodiment the slats 81 are made of flexible plastic and their borders adjacent to the cover 8 are without hinges fastened to the side walls of the cover 8. At least a part of the tiltable or flexible slats 81 is oriented so that by a possible excessive short-term overpressure in the space inside the cover 3 their borders are lifted.

[0033] In the not represented embodiments the whole devices are arranged in a vertical opposite manner. The stripping plate 24, the needle board 23 and the driving box 20 are under the processed web 1, while the bed plate 22 is positioned above the web 1.

[0034] At operation of the needling device 2 the processed web 1 is in a interrupted manner shifted by the feeding mechanism 21 in cooperation with the draw off mechanism 25 into the space between the needle board 23 and the stripping plate 24. At resting status of the device in the inner space of the cover 3, 4, 5, 6, 7, 8 atmospheric pressure is present. Approximately at the moment of beginning of motion of the needle board 23 from the upper dead centre of its straight-lined reversible motion in vertical direction to the stripping plate 24 the web 1 stops. The needles 231 are passing through holes 241 of the stripping plate 24, penetrate the whole thickness of the standing web 1 and enter the holes 221 of the bed plate 22. After reaching the lower dead centre the needle board 23 moves back into the upper dead centre, in which the needles 231 are outside the web 1 and further shifting of the web 1 occurs by the feeding mechanism 21 and the draw off mechanism 25. At their straight-lined reversible motion the tip and the not represented reverse barbs of the needle 231 in a known manner strengthen the web 1 and create the nonwoven fabric 11 for further use.

[0035] The frequency of running the needle board 23 in an exemplary embodiment is 1400 cycles per minute. At motion of the needle board 23 in direction to puncture of needles 231, this is in direction to the bed plate 22, the space between the needle board 23 and the stripping plate 24 decreases quickly, at the same time expelled air flows from this space through the circumferential working gap 26 to opposite side of the needle board 23 in practically enclosed space inside the cover 3, 4, 5, 7, 8. Partial air pressures in various sections of space of the cover 3, 4, 5, 7, 8 are changed during operation of the device, nevertheless an average pressure is practically always on the level of atmospheric pressure. Circumferential gap 26 is of a sufficiently great diameter, so that no excessive throttling of air flow occurs. Total volume of air in the space inside the cover 3, 4, 5, 6, 7, 8 at operation of the needling device 2 changes only by an insignificant change in volume of inner sections of the driving rods 232. The air only transfers from the space under the needle board 23 into the space above the needle board 23 and vice versa. At embodiment according to the Fig. 6 through connection of inner space of the cover 6 with inner space of the driving box 20 the common enclosed space is created. Naturally, the principle of operation of the needling device 2 is not changed.

[0036] From the space inside the cover 3, 4, 5, 7, 8 only relatively small quantity of air escapes through the gap 322 between the lower border 32 of the cover and circumference of the stripping plate 24 and the gap 321 between the lower border 32 of the cover and surface of the processed web 1, respectively of the produced nonwoven fabric 11, through the circumferential gaps between the needles 231 and holes 241 and the sealing gap 311 of substantially slot sealing between surface of the driving rod 232 and inner diameter of the sleeve 31 of cover. At embodiment, which corresponds to the Fig. 3, the quantity of air leakage outside the cover 3, 4, 5, 7 is yet reduced by leakage through the gap 321 as a result of a tight connection of lower section of the cover 3, 4, 5, 7 with the stripping plate 24. This further reduces noise in vicinity of the machine. At embodiment according to the Fig. 6, a small quantity of air may leak from area above the needle board 23 around the driving box or through the space of the driving box 20 caused by untightness.

[0037] Air streaming at the needling device 2 with two one after another arranged needle boards 23 according to the Fig. 7 is considerably more complicated. Portion of the air here at a certain moment flows from the space between the needle board 23 and the stripping plate 24 of that section of the device whose needle board 23 moves in direction to the corresponding stripping plate 24 into the space between the needle board 23 and the stripping plate 24 of the second section of the device, because the second needle board 23 moves in direction from to it corresponding stripping plate 24. Nevertheless function of the cover 7 from the point of view of reducing the low-frequency noise is very similar to other embodiments.

[0038] Pressure waves generated upon exit of air expelled from the space between the needle board 23 and the stripping plate 24, or vice versa of the air sucked into this space, are not spread into vicinity of the machine and do not border the surroundings with intensive noise. This solution also removes the danger of possible damage of structure of production hall of the textile operations by kinetic energy, as the described pneumatic effect may be a source of this kinetic energy.

List of referential markings

[0039] 

1

web

11

nonwoven fabric

2

needling device

20

driving box

21

feeding mechanism

22

bed plate

221

hole (in bed plate for needle)

222

supporting border (of bed plate)

23

needle board

231

needle

232

driving rod

24

stripping plate

25

draw off mechanism

26

working gap

241

hole (in stripping plate for needle)

3

cover

31

sleeve (of cover for driving rod)

311

sealing gap (between the sleeve of cover and the driving rod)

32

circumferential border (of lower section of the cover)

321

gap (between web or fabric and the circumferential border of lower section of the cover)

322

sealing gap (between stripping plate and circumferential border of lower section of the cover)

4

cover (shaped)

41

circumferential cavity (of shaped cover)

5

cover (with tilting side wall)

51

tilting side wall (of cover)

6

cover (sealed with respect to the driving box)

7

cover (device with two needle boards)

8

cover (with sealing tiltable slats)

81

tiltable slat

82

hinge (of tiltable slat)

Claims

1. Method of operation of the needling device (2) for production of nonwoven fabrics (11), whose needle board (23) moves in an enclosed space in periodic straight-lined reversible motion of a high frequency with respect to the surface of the processed web (1) and to the surface of the stripping plate (24), characterised in that, at the reversible motion of the needle board (23) in an enclosed space with atmospheric pressure the air from the decreasing section of an enclosed space under or above the needle board (23) in direction of its motion is expelled into the increasing section of an enclosed space on opposite side of the needle board (23), at the same time this alternately expelled air streams in the mentioned enclosed space, by which the low-frequency noise in vicinity of the machine is limited.

2. The device for reduction of low-frequency noise generated at operation of the needling device (2) for production of nonwoven fabrics (11), comprising at least one needle board (23), the stripping plate (24) and the bed plate (22), at the same time the needle board (23) is coupled with the driving rods (232) putting the same into a straight-lined reversible motion in direction to the processed web (1) and to the stripping plate (24) arranged between the needle board and the processed web (1), while the device further comprises the cover (3, 4, 5, 6, 7, 8) delimiting the space, in which the needle board (23) moves, characterised in that, the cover (3, 4, 5, 6, 7, 8) creates an enclosed space with atmospheric pressure.

3. The device according to the claim 2, characterised in that, between the cover (3, 4, 5, 6, 7, 8) and the stripping plate (24) the sealing gap (322) is provided.

4. The device according to the claim 3, characterised in that, between section of the cover (3, 4, 5, 6, 7, 8) adjacent to the processed web (1) and surface of the processed web (1) the gap (321) is provided.

5. The device according to the claim 2, characterised in that, the cover (3) is tightly connected with the stripping plate (24).

6. The device according to any of the claims 2 to 5, characterised in that, in the cover (3, 4, 5, 7, 8) around the driving rods (232) of the needle board (23) the sleeves (31) with sealing gaps (311) are created.

7. The device according to any of the claims 2 to 6, characterised in that, the cover (6) is tightly connected to the driving box (20) of drive of the needle board (23).

Drawing