JPH0230460Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apron structure of a drafting device in a spinning machine, particularly in a pneumatic high-speed spinning machine.

[Conventional technology]

A draft device in which pairs of rollers in pressure contact with each other are arranged at a plurality of positions, the circumferential speed of each roller is set to increase sequentially in the order of arrangement, and a fiber bundle is passed between the rollers in each pair of rollers to perform drafting. has been known for a long time, but a major problem in this drafting device is how to reduce draft unevenness, which has the greatest effect on yarn quality such as uniformity and strength.

In the three-wire draft device, the rollers are
It is composed of pairs of back, middle, and front rollers, and a belt called an apron is usually attached to the middle roller, and one of the causes of the uneven draft is wear and deformation of the apron.

In particular, compared to ring-type spinning machines, which have a low draft rate, pneumatic spinning machines are faster, and because they directly draft the sliver, the draft rate is very high, and the middle rollers also rotate at high speeds. Therefore, the above-mentioned wear and deformation progresses rapidly.

To explain this using Figures 1 to 3, the first
In the figure, the sliver S drawn out from the can 1 is drafted by passing through a cross roller 2 rotating in pressure contact with each other, a middle roller 4 having an apron 3, and a front roller 5, and further twisted by an air injection nozzle 6. After becoming a spun yarn Y, it is pulled out by a delivery roller 7 and wound into a package P via a yarn clearer 8, a traverse guide 9, and a friction roller 10. In FIG. 2, tension is applied to the aprons 3 and 3 by a cradle 11 and a tensile bar 12, and pins 15 and 16 biased by springs 13 and 14 are in contact with the cradle 11 and the top middle roller shaft 4a, respectively. A pinching force is applied to the sliver S by the aprons 3, 3.

In the apron 3, the frictional deformation portion f
appears along the path of the sliver S as shown in FIG.

Since the apron 3 is usually made by sandwiching and joining the core cord 17 between two rubber layers 18 and 19, the deformed portion is formed on the surface side of the front rubber layer 18, thereby causing a gap between both aprons 3 and 3. Desired contact pressure cannot be maintained. When the surface side rubber layer is made thinner in order to reduce the above-mentioned deformed portion, the shape of the above-mentioned core yarn appears prominently on the rubber layer surface, causing unevenness on the apron surface, which adversely affects the gripping of the sliver and causes cracks. In some cases, there was a deterioration in spinability and spinnability.

To prevent the above frictional deformation, the front rubber layer 1
Although efforts have been made to improve the abrasion resistance of the rubber layer 18, the hardness of the rubber layer 18 inevitably increases, resulting in the occurrence of cracks C shown in FIG. The cracks C are caused by the apron 3 being bent at an acute angle at the X portion in FIG. It causes

Furthermore, accidents such as fibers getting caught in the crack C and wrapping around the apron 3 often occur.

[Problem that the invention attempts to solve]

The present invention is based on the above-mentioned circumstances, and as a result of intensive research, it is an object of the present invention to provide an apron structure that does not cause the above-mentioned frictional deformation and cracks.

[Means for solving problems]

An apron of a drafting device that is attached to the outer periphery of a pair of rollers of a drafting device and pressed against each other via a staple fiber bundle, the apron having a front rubber layer in contact with the fiber bundle and a back rubber layer in contact with the roller. They were connected to each other via a core cord, and the thickness ratio of the front rubber layer and the back rubber layer with a small Poisson's ratio during compression was set to 2.2:7.8 to 1:9.

〔Example〕

To explain the present invention in comparison with a conventional example, as shown in FIG. Therefore, the bending stress b1 in the elongation direction acting on the surface of the front rubber layer 18 at the bent portion When 18 is made of a material with high wear resistance,
The rubber layer 18 has the above-mentioned large bending stress in the elongation direction.
b1 to produce the crack C.

Here, the core cord 17 is actually often made of cotton yarn, etc., and is wound spirally around the apron 3 as shown in FIG. In the example shown in
It acts as a neutral plane for b1 and b2.

FIG. 5B shows an apron 3 according to the present invention, in which the thickness ratio a1:a2 of the rubber layers 18, 19 on the front side and the back side is set between 3:7 and 1:9.
In this case, it means that the core cord 17 serving as the neutral plane has moved to the front side compared to the case shown in FIG. changes as shown in the figure, and the bending stress b3 on the surface of the front rubber layer 18 becomes considerably smaller than that in the case shown in FIG. 5A. Therefore, irrespective of the material of the front rubber layer 18, the occurrence of cracks C is suppressed, draft unevenness is eliminated, and stable drafting can be performed.

Normally, each of the rubber layers 18 and 19 is made of a material mainly composed of NBR, and the front rubber layer 18 is made of a high nitrile material to improve wear resistance. However, as a result of various experiments using these general materials, the above thickness ratio
The occurrence rate of cracks C decreases as the thickness ratio a1 of the front rubber layer 18 in a1:a2 becomes smaller, and especially when the thickness ratio a1:a2 becomes 3:7, especially from 2.2:7.8 to 2.2:7.8. At a ratio of 1:9, we were able to obtain results that could withstand actual use.

That is, although it depends on the material of the rubber, if draft operation is performed with the above thickness ratio set to 5:5, in extreme cases, crack C will occur within a few hours after the start of use, and the apron 3 will have to be replaced. However, if the thickness ratio a1 of the front rubber layer 18 is set to 3 or less,
Can withstand continuous draft operation for at least 90 days,
In particular, it was confirmed that α1 was set to 2.2 to 1 in good condition, and it became clear that it could be used stably with regular maintenance once every three months in a spinning field where continuous operation is often performed day and night. .

At the same time, it has been confirmed that when the thickness ratio a1 of the front rubber layer 18 is set to 1 or less, another problem described below occurs.

In other words, if the thickness ratio a1 is too small, the core cord 17 will come close to the surface of the apron 3, resulting in a decrease in the strength of the front rubber layer 18, making it easy to tear, and making it difficult to manufacture. As shown, the surface of the front rubber layer 18 protrudes in a striped manner only in the portion where the core cord 17 is present, and the front rubber layer 18 is bent in a fine wave shape, so that the bending stress in the elongation direction is concentrated in the striped portion l. This is the bending stress in the elongation direction explained in Figure 5.
This overlaps with b1 and b3 and destroys the front rubber layer 18, causing cracks C to occur. Cracks C due to this cause can be almost eliminated by setting the thickness ratio a1 of the front side rubber layer 18 to 1 or more.

Although it is difficult to quantitatively show the occurrence of the crack C described above, it will be quantified by the method described below, and an example of an experiment conducted on the correlation with the thickness ratio is shown in the graph of FIG.

The apron 3 of the sample was a very common one with the shore hardness of the front rubber layer 18 being 78.0, the inner diameter of the apron was φ37 mm, the width of the apron was 32 mm, and the results of continuous operation for 500 hours at an apron surface speed of 6 m/min are shown. be.

In the figure, "total crack length" means each crack C.
The lengths were measured and the sum of the lengths was obtained, and it is clearly shown that the thickness ratio a1/a2 takes the lowest value in the period of 1/9 to 2.2/7.8. In this experiment, the above thickness ratio a1/a2 was 4/
When it is 6 or more, a large crack C occurs at both the end and the center of apron 3, and it is 2.2/7.8 to 1/9.
In this case, a small number of cracks C of minute length were generated at the ends of the apron, and a relatively large number of excellent cracks C were generated over the entire apron, especially between 2.2/7.8 and 1/9.

In addition, in order to make the surface of the front rubber layer 18 as smooth as possible by reducing the linear portion l, and to strengthen the function of the core cord 17 as the neutral surface, the thread used for the core cord 17 is It is desirable to tightly wrap a thin and strong material, and it is also possible to use cloth or synthetic leather, and it is of course effective to reduce the thickness of the apron 3 itself, regardless of the above thickness ratio. However, these methods also have limitations, and cannot significantly change the effect of setting the thickness ratio of the rubber layers 18 and 19 described above.

Furthermore, in order to further suppress cracks C occurring at the ends of the apron 3, the back side rubber layer 19 is made of a material having a small Poisson's ratio when compressed. In other words, the thickness ratio a1 of the front rubber layer 18 is reduced,
When the thickness ratio a2 of the back side rubber layer 19 is increased,
As explained in FIG. 5, the bending stress b3 of the front side rubber layer 18 becomes small, and the rubber layer 18 as a whole becomes less likely to cause cracks C, but on the contrary, the bending stress b4 of the back side rubber layer 19 in the compression direction is relatively large.

The above materials used for the rubber layers 18 and 19
Synthetic rubber such as NBR and thermoplastic resin have better compressive properties than tensile properties, so even if the stress b4 becomes somewhat large, cracks C due to compression will not occur in the back side rubber layer 19, but the rubber layer If the Poisson's ratio of 19 is large, the entire apron 3 will expand excessively in its width direction, and as shown in FIG.
This causes the phenomenon that . That is, when the Poisson's ratio is large, the back rubber layer 19 easily bulges outward at the bent portion X, pushing up the end of the front rubber layer 18, and bending stress in the elongation direction is applied to the pushed-up angular portion. As a result, a condition is created in which crack C is likely to occur.

In order to reduce the Poisson's ratio, the back side rubber layer 19
It is effective to reduce the degree of freedom of the rubber layer 19 by dispersing short fibers, such as polyester filaments, into the rubber layer 19.

[Effect of idea]

As explained above, in the apron of the present invention, the front side rubber layer and the back side rubber layer in contact with the roller are connected to each other via a thin core cord that is tightly wound to the extent that they touch each other, so that the rubber layer is formed thin. Also, the streaky portion does not become large and the unevenness of the surface layer can be reduced, and the unevenness of the core yarn appears on the surface and cracks occur when the surface layer is thin due to the tensile force of the apron generated during rotation of the apron. It is possible to prevent a situation that would lead to deterioration in spinnability. In addition, by setting the thickness ratio between the front rubber layer and the back rubber layer with a small Poisson's ratio during compression to 2.2:7.8 to 1:9, the occurrence of cracks in the front rubber layer can be greatly suppressed, and the apron Stable spinning can be ensured by preventing damage and uneven drafting. In addition, in the case of the apron of the present invention, the core cord is thin and the thin core cords are tightly wound to the extent that they touch each other, so even if the inner layer rubber is made thin, the streaks will not become large and will not cause cracks. This has the effect that it is difficult to occur.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the outline of the pneumatic spinning machine, Fig. 2 is a side view showing its middle roller portion, and Fig. 3 is a perspective view showing the outline of the pneumatic spinning machine.
The figure shows the state of frictional deformation when an apron with low wear resistance is used. This figure shows the state of the crack when a high apron is used. Figure A is a plan view of the apron, Figure B is a cross-sectional view taken along the - line, and Figure 5 is a side cross-sectional view showing the bent part of the apron. , Figure A shows a conventional example, Figure B shows an example of the present invention, Figure 6 is a plan view of an apron to explain the core cord, and Figure 7 shows an apron with a thinner front rubber layer. FIG. 8 is a graph showing the thickness ratio of the rubber layer and the occurrence of cracks, and FIG. 9 is a front view of the apron bend. 3... Apron, 17... Core cord, 18... Front rubber layer, 19... Back rubber layer.

Claims (1)

[Scope of utility model registration request] An apron of a drafting device that is attached to the outer periphery of a pair of rollers of a drafting device and pressed against each other via a staple fiber bundle, the apron having a front rubber layer in contact with the fiber bundle and a back rubber layer in contact with the roller. They are connected to each other via thin core cords that are tightly wound to the extent that they touch each other, and the thickness ratio between the front rubber layer and the back rubber layer with a small Poisson's ratio when compressed is 2.2:7.8 to 1: An apron of a draft device characterized by being set at 9.