Patent Description:
Conventionally, a spinning system has been provided with a cooling unit arranged below a spinning beam having a spinning pack inserted therein including a spinneret for allowing high-temperature molten polymer to be spun therefrom. The cooling unit includes a spinning cylinder surrounding the high-temperature molten polymer spun from the spinneret. The cooling unit is configured to supply cooling air to the spinning cylinder to blow the cooling air on the high-temperature molten polymer so that the molten polymer can be cooled to be solidified, and thereby yarn is formed.

In order to maintain yarn productivity and quality, the above sort of spinning system has undergone maintenance on a regular basis for cleaning a spinneret surface (hereinafter referred to as "surface cleaning") or exchanging a spinning pack. Patent Document <NUM>, e.g., discloses maintenance on a spinning system conducted while a cooling unit is lowered to ensure a working space between the cooling unit and a spinning beam (see paragraph <NUM> in particular). Further, Patent Document <NUM>, e.g., discloses a filament cooling unit elevated and lowered for exchanging a spinning pack or performing surface cleaning (see paragraph <NUM> in particular).

By such a technique as described in Patent Documents <NUM>, <NUM>, however, there has been a probability that, in lowering and elevating the cooling unit, a temperature at the spinneret and an ambient temperature around the spinneret would decrease significantly due to an upward air flow from the spinning cylinder. For a temperature at the spinneret and an ambient temperature around the spinneret decreasing significantly, a time has been taken to return to their respective original levels from the production started after completion of the maintenance. The physical properties of yarn produced in a state of decrease in temperature at the spinneret and in ambient temperature around the spinneret have been degraded to cause technical problems of increase in yarn to be disposed of.

The present invention has been made in view of the above-described technical problems. It is the objective of the present invention to provide a spinning system configured such that decrease in temperature at a spinneret and in ambient temperature around the spinneret can be suppressed.

A first aspect of the present invention is a spinning system comprising:.

According to the above-described first aspect of the spinning system, when the cooling unit having been caused to move for maintenance, air can be blown toward between the spinning beam and the cooling unit in a direction intersecting a yarn path of the molten polymer spun from the spinneret. As a result, air flowing toward the spinneret can be blocked. In other words, as a result of blowing air toward a direction intersecting a yarn path of the molten polymer spun from the spinneret, the flowing of air toward the spinneret can be interrupted or an amount of air flowing toward the spinneret can be reduced. As a consequence, decrease in temperature at the spinneret and in ambient temperature around the spinneret can be suppressed, and therefore a time taken for a temperature at the spinneret and an ambient temperature around the spinneret to return to their respective original levels can be shortened. Eventually, a time taken for yarn to be stabilized in physical properties can be shortened, and therefore an amount of yarn to be disposed of can be reduced.

A second aspect of the spinning system in the above-described first aspect is characterized in that the blower stops operation when the spinning beam and the cooling unit abut each other.

According to the above-described second aspect of the spinning system, the abutting between the spinning beam and the cooling unit closes an upper opening of the spinning cylinder. The closed upper opening of the spinning cylinder causes the cooling air supplied from the cooling unit to mostly flow downward, and therefore decrease in temperature at the spinneret and in ambient temperature around the spinneret can be suppressed. As a result, a time taken for a temperature at the spinneret and an ambient temperature around the spinneret to return to their respective original levels can be shortened, and eventually, a time taken for yarn to be stabilized in physical properties can be shortened.

A third aspect of the spinning system in the above-described first aspect or second aspect is characterized in that the blower is further configured such that a direction of cooling air blown toward the spinneret out of cooling air supplied to the spinning cylinder is changeable.

According to the above-described third aspect of the spinning system, a changeable direction of cooling air toward the spinneret can reduce an amount of air flowing toward the spinneret and an area around the spinneret, or can interrupt the flowing of air, thereby capable of suppressing decrease in temperature at the spinneret and in ambient temperature around the spinneret. Even without stopping of cooling air supplied to the spinning cylinder, decrease in temperature at the spinneret and in ambient temperature around the spinneret can be suppressed by changing a direction of cooling air toward the spinneret. As a result, it becomes possible to reduce time loss to be caused by stopping cooling air and then restarting the flowing of cooling air, and work burden to be required for cooling air and then restarting the flowing of cooling air.

A fourth aspect of the present invention is a method of controlling a spinning system comprising:.

According to the above-described fourth aspect of the controlling method, when the cooling unit having been caused to move down for maintenance, air can be blown toward between the spinning beam and the cooling unit in a direction intersecting a yarn path of the molten polymer spun from the spinneret, and therefore air flowing toward the spinneret can be blocked while its amount being reduced. As a result, decrease in temperature at the spinneret and in ambient temperature around the spinneret can be suppressed, and therefore a time taken for a temperature at the spinneret and an ambient temperature around the spinneret to return to their respective original levels can be shortened. Eventually, a time taken for yarn to be stabilized in physical properties can be shortened, and therefore an amount of yarn to be disposed of can be reduced.

A fifth aspect of the controlling method in the above-described fourth aspect is characterized in that, in the air blowing step, blowing air is finished, during performance of the restoration step, after having undergone maintenance, or when the restoration step having been finished.

According to the above-described fifth aspect of the controlling method, when the restoration step having been finished, an upper opening of the spinning cylinder is closed. The closed upper opening of the spinning cylinder causes the cooling air supplied from the cooling unit to mostly flow downward, and therefore decrease in temperature at the spinneret and in ambient temperature around the spinneret can be suppressed. As a result, a time taken for a temperature at the spinneret and an ambient temperature around the spinneret to return to their respective original levels can be shortened, and eventually, a time taken for yarn to be stabilized in physical properties can be shortened.

A sixth aspect of the controlling method in the above-described fourth aspect or five aspect is characterized in that, in the air blowing step, a direction of cooling air blown toward the spinneret out of cooling air supplied to the spinning cylinder is changeable.

According to the above-described sixth aspect of the controlling method, a changeable direction of cooling air toward the spinneret can reduce an amount of air flowing toward the spinneret and an area around the spinneret, or can interrupt the flowing of air, thereby capable of suppressing decrease in temperature at the spinneret and in ambient temperature around the spinneret. Even without stopping of cooling air supplied to the spinning cylinder, decrease in temperature at the spinneret and in ambient temperature around the spinneret can be suppressed by changing a direction of cooling air toward the spinneret. As a result, it becomes possible to reduce time loss to be caused by stopping cooling air and then restarting the flowing of cooling air, and work burden to be required for cooling air and then restarting the flowing of cooling air.

The spinning system according to the present invention does not necessarily include all the above-described first aspect to third aspect. The invention in the above-described first aspect, e.g., does not need to encompass both of the invention in the above-described second aspect and the invention in the above-described third aspect. The present invention may be obtained by arbitrarily combining the first aspect and at least a part of the second aspect, or by arbitrarily combining the first aspect and at least a part of the third aspect, or by arbitrarily combining the first aspect, at least a part of the second aspect, and at least a part of the third aspect, to such an extent that consistency can be achieved. In a similar manner, the controlling method according to the present invention does not necessarily include all the above-described fourth aspect to sixth aspect. The invention in the above-described fourth aspect, e.g., does not need to encompass both of the invention in the above-described fifth aspect and the invention in the above-described sixth aspect. The present invention may be obtained by arbitrarily combining the fourth aspect and at least a part of the fifth aspect, or by arbitrarily combining the fourth aspect and at least a part of the sixth aspect, or by arbitrarily combining the fourth aspect, at least a part of the fifth aspect, and at least a part of the sixth aspect, to such an extent that consistency can be achieved.

According to the present invention, it is possible to provide a spinning system configured such that decrease in temperature at a spinneret and in ambient temperature around the spinneret can be suppressed.

An embodiment of the present invention will be described with reference to the drawings hereinafter. For the convenience of description, an up-and-down direction, a left-and-right direction, and a forward-and-backward direction are as shown in their respective drawings to be described later.

First, an outline of a spinning system <NUM> according to an embodiment of the present invention will be described. <FIG> depicts an example of side view taken schematically from a right side with respect to a part of the spinning system <NUM> according to an embodiment of the present invention. <FIG> depicts an example of front view taken schematically from a forward side with respect to a part of the spinning system <NUM> shown in <FIG>. <FIG> depicts an example of schematic view of the spinning system in a state of having caused a cooling unit <NUM> to move down in the spinning system <NUM> shown in <FIG>. The illustrations of a polymer tank <NUM> and a polymer pipe <NUM> shown in <FIG> are omitted from <FIG> and <FIG>. While illustrations of molten polymer P and a yarn Y are omitted from <FIG> for the sake of convenience, the yarn Y may be formed as a result of spinning the molten polymer P from a spinneret <NUM>, when the cooling unit <NUM> is caused to move down, so that the spun molten polymer P is cooled to be solidified through the use of the cooling unit <NUM> or under other conditions.

The spinning system <NUM> according to an embodiment of the present invention is a system for producing a yarn Y made of synthetic fibers. As shown in <FIG>, e.g., the spinning system <NUM> includes a spinning unit <NUM>, a cooling unit <NUM>, a moving mechanism <NUM>, a blower <NUM>, and a controller <NUM> (see <FIG> to be described later). In addition to these structures, the spinning system <NUM> includes an oil-agent application unit <NUM>, a take-up unit (not shown), a winder (not shown), and the like. Descriptions of such structures are however omitted here.

As shown in <FIG> or <FIG>, the spinning unit <NUM> is a melt spinning unit configured to spin molten polymer P as material of a yarn Y. The spinning unit <NUM> includes a spinning beam <NUM> having a substantially rectangular-solid shape, a plurality of pack housings <NUM> formed in the spinning beam <NUM>, a plurality of spinning packs <NUM> (whose number is the same as, e.g., the number of the plurality of pack housings <NUM>) arranged respectively in the plurality of pack housings <NUM>, a polymer tank <NUM> having polymer stored therein, and a plurality of polymer pipes <NUM> connecting between their respective spinning packs <NUM> and the polymer tank <NUM>.

For the sake of convenience, three pack housings <NUM> and three spinning packs <NUM> are shown in <FIG>. However, the invention is not limited to such a configuration. A larger number of pack housings <NUM> and a larger number of spinning packs <NUM> (e.g., twelve) may be provided.

Polymer in the polymer tank <NUM> is fed through the plurality of polymer pipes <NUM> to the plurality of spinning packs <NUM>. In feeding the polymer from the polymer tank <NUM> to the spinning pack <NUM>, the polymer in the polymer tank <NUM> and in the polymer pipe <NUM> is heated by the spinning beam <NUM> to a predetermined temperature (e.g., <NUM>ºC) to become molten polymer.

High-temperature heated molten polymer in a liquid state is supplied through the polymer pipe <NUM> to each spinning pack <NUM>. A spinneret <NUM> is arranged at a lower end portion of each spinning pack <NUM>. That is, the number of the spinnerets <NUM> is the same as that of the spinning packs <NUM>. The spinneret <NUM> has, e.g., a plurality of nozzles (not shown). The spinning pack <NUM> ejects molten polymer P through the plurality of nozzles of the spinneret <NUM> (in other words, spins a plurality of yarns Y). The molten polymer P ejected through the plurality of nozzles is cooled by the cooling unit <NUM> to become the plurality of yarns Y having a plurality of filaments. Specifically, one yarn Y is spun from one spinneret <NUM>. Each spinneret <NUM> is not necessarily required to have a plurality of nozzles but may have only one nozzle. In such a case, the yarn Y is produced as monofilament yarn.

As shown in <FIG>, the cooling unit <NUM> includes a spinning cylinder <NUM> arranged below the spinning unit <NUM>, a duct <NUM> connected to the spinning cylinder <NUM>, and a first compressed-air source <NUM> (see <FIG> to be described later) configured to supply cooling air CF to the spinning cylinder <NUM> through the duct <NUM>. In an embodiment of the present invention, a cyclic yarn cooling unit, e.g., is used as the cooling unit <NUM>. The spinning cylinder <NUM> is e.g. a hollow box body, and extends in an up-and-down direction so as to surround the molten polymer spun from the spinneret <NUM> (so as to locate the molten polymer P in a hollow area CE). The spinning cylinder <NUM> includes a flow straightening plate <NUM> provided therein. Air for cooling (the air will be called "cooling air CF") supplied from the first compressed-air source <NUM> passes through the inside of the duct <NUM> and is supplied into lower space (space under the flow straightening plate <NUM>) of the spinning cylinder <NUM>. The cooling air CF having flowed into the lower space of the spinning cylinder <NUM> passes through the flow straightening plate <NUM> to be straightened upward, and then flows into upper space (space over the flow straightening plate <NUM>) of the spinning cylinder <NUM>. A plurality of partitioning cylinders <NUM> is arranged at a position directly below a filter member <NUM>. The partitioning cylinder <NUM> is configured to prevent transmission of the cooling air CF in a radial direction of the partitioning cylinder <NUM>, thereby preventing the cooling air CF from flowing from the lower space of the spinning cylinder <NUM> directly into the hollow area CE. The cooling air CF having flowed into the upper space of the spinning cylinder <NUM> is straightened in passing through the filter member <NUM> having, e.g., a punching filter and a cooling filter, and then flows into the hollow area CE. In such a manner, the cooling air CF is blown on a yarn material from a periphery of the filter member <NUM>, more specifically, from an entire outer perimeter of the filter member <NUM>. As a result, the yarn material is cooled to become the yarn Y. A sealing member <NUM> is provided at a place where the spinning beam <NUM> and the spinning cylinder <NUM> are in abutting contact with each other. The sealing member <NUM> can be used for preventing leakage from a surface of the abutting contact between the spinning beam <NUM> and the spinning cylinder <NUM>.

The moving mechanism <NUM> having e.g. an air cylinder (the moving mechanism <NUM> will be called an air cylinder <NUM>) is configured to cause the cooling unit <NUM> to move up and down. More specifically, the air cylinder <NUM> is standing upright on, e.g., a floor surface of a factory. The air cylinder <NUM> has a piston rod <NUM> extending longitudinally in an up-and-down direction arranged so as to be expandable/contractible in an up-and-down direction. The spinning cylinder <NUM> has a lower end fixed with a wall member <NUM> extending downward. The wall member <NUM> has a side surface fixed with a tip of the piston rod <NUM>. In such a configuration, the cooling unit <NUM> is entirely movable by the actuation of the air cylinder <NUM> between a first position (see <FIG>) corresponding to an operational state where the spinning system <NUM> is in an operational state and a second position (see <FIG>) below the first position. The cooling unit <NUM> is caused to move up in response to the actuation of the piston rod <NUM> of the air cylinder <NUM> in an expanding direction (upward direction in <FIG>) and is caused to move down in response to the actuation of the piston rod <NUM> in a contracting direction (downward direction in <FIG>). The production of the yarn Y is feasible when the cooling unit <NUM> is at the first position. When the cooling unit <NUM> is at the first position, a force acting upward (toward the spinning beam <NUM>) is applied to the cooling unit <NUM> by the air cylinder <NUM>. When the cooling unit <NUM> is at the second position, a gap is formed as a working space Sw between the spinning unit <NUM> (more specifically, the spinning beam <NUM>) and the cooling unit <NUM> as viewed in an up-and-down direction. Hereinafter, for the sake of convenience, the foregoing "first position" will be called an "upper end" and the foregoing "second position" will be called a "lower end. " However, the "first position" is not limited to the upper end, and the "second position" is not limited to the lower end.

As shown in <FIG>, the blower <NUM> is a device configured to blow side air SF such that the side air SF flows in a substantially horizontal direction in a working space Sw when the cooling unit <NUM> is at the lower end. In this specification, "blowing" of air may also be called "release.

The blower <NUM> includes, e.g., a second compressed-air source <NUM> (see <FIG> to be described later), a plurality of air nozzles <NUM> through which air (e.g., compressed air) supplied from the second compressed-air source <NUM> is releasable as the side air SF, an air pipe <NUM> connecting the second compressed-air source <NUM> and each air nozzle <NUM>, and the like. The plurality of air nozzles <NUM> corresponding to the plurality of spinning packs <NUM>, respectively, are arranged side by side in a left-and-right direction. In an embodiment of the present invention, the plurality of air nozzles <NUM> are arranged so as to cause the side air SF released from the air nozzle <NUM> to flow in one direction from a backward side toward a forward side in a working space Sw formed between the spinning unit <NUM> and the cooling unit <NUM> as viewed in an up-and-down direction. The reason for causing the side air SF released from the plurality of air nozzles <NUM> to flow in one direction is to prevent flows of the cooling air CF directed in different directions from interfering with each other.

It is not necessarily required to arrange the plurality of air nozzles <NUM> so as to cause side air SF to flow from a backward side toward a forward side. The air nozzles <NUM> may be arranged so as to, e.g., cause the side air SF to flow from a forward side toward a background side. The plurality of air nozzles <NUM> may alternatively be arranged so as to cause the side air SF to flow from a left side toward a right side. In consideration of attenuation of the flow rate of the side air SF with a greater distance from the air nozzle <NUM>, however, the plurality of air nozzles <NUM> are preferably arranged so as to cause the side air SF to flow from a backward side toward a forward side, and vice versa.

It is not necessarily required to provide the plurality of air nozzles <NUM> corresponding to the plurality of spinning packs <NUM>, respectively. The plurality of air nozzles <NUM> may be replaced, e.g., with a single flat nozzle having a greater width than a length in a left-and-right direction from a spinning pack <NUM> at the left end to a spinning pack <NUM> at the right end.

The reason for causing the side air SF released from the air nozzle <NUM> to flow in a substantially horizontal direction in a working space Sw is to prevent the side air SF released from the air nozzle <NUM> from going toward the spinneret <NUM> and toward a place around the spinneret <NUM>. Thus, as long as compressed air released from the air nozzle <NUM> does not go toward the spinneret <NUM> and toward a place around the spinneret <NUM>, the air nozzles <NUM> are not necessarily required to be arranged so as to cause the compressed air released from the air nozzles <NUM> to flow as the side air SF in a substantially horizontal direction. The air nozzles <NUM> may be arranged so as to, e.g., cause the compressed air released from the air nozzles <NUM> to flow diagonally downward. In another case, the air nozzles <NUM> may be arranged so as to cause the compressed air released from the air nozzles <NUM> to flow diagonally upward.

In an embodiment of the present invention, the second compressed-air source <NUM> for supplying compressed air to the air nozzle <NUM> and the first compressed-air source <NUM> for supplying the cooling air CF to the spinning cylinder <NUM> are provided separately. However, the invention is not limited to such a configuration. A common compressed-air source may be provided for supplying compressed air to both of the air nozzle <NUM> and the spinning cylinder <NUM>. Further, it is not necessarily required to connect the second compressed-air source <NUM> and each air nozzle <NUM> through the air pipe <NUM>. An air hose, e.g., may be used for the connection.

<FIG> depicts an example of function block diagram schematically showing an electrically-connected configuration of the spinning system <NUM>. The controller <NUM> is configured to perform processing relating to operation of the spinning system <NUM>. The controller <NUM> is responsible for controls such as operation and stop of the spinning of molten polymer P from the spinneret <NUM>, actuation and stop of the air cylinder <NUM>, regulation of the flow rate of cooling air CF supplied to the spinning cylinder <NUM>, i.e., into the hollow area CE, and regulation of the flow rate of compressed air released from the air nozzle <NUM> forming the blower <NUM>.

The controller <NUM> includes a CPU, ROM, RAM, and the like. The controller <NUM> is connected electrically to units including an operation unit <NUM> having buttons and the like operable by an operator, an upper end detection sensor <NUM> for determining that the cooling unit <NUM> is at the upper end, and a lower end detection sensor <NUM> for determining that the cooling unit <NUM> is at the lower end. The controller <NUM> is configured to receive signals from the units including the operation unit <NUM>, the upper end detection sensor <NUM>, and the lower end detection sensor <NUM>.

The controller <NUM> is further connected electrically to units including a gear pump <NUM> capable of causing the spinning of the molten polymer P from the spinneret <NUM>, the first compressed-air source <NUM>, the second compressed-air source <NUM>, and a solenoid <NUM> configured to actuate the air cylinder. On the basis of receipt of various sorts of signals from the units including the operation unit <NUM>, the upper end detection sensor <NUM>, and the lower end detection sensor <NUM>, the controller <NUM> controls the units including the gear pump <NUM>, the first compressed-air source <NUM>, the second compressed-air source <NUM>, and the solenoid <NUM>. The controller <NUM> controls the solenoid <NUM> to control actuation of the air cylinder <NUM>.

In response to control over the first compressed-air source <NUM>, the flow rate of the cooling air CF (hereinafter referred to as "air volume") supplied to the spinning cylinder <NUM> is controlled. In response to control over the second compressed-air source <NUM>, the flow rate of the side air SF (hereinafter referred to as "air volume" like the cooling air CF) released from the air nozzle <NUM> is controlled.

The cooling air CF supplied to the spinning cylinder <NUM> may be controlled by an automatic valve arranged upstream from the duct <NUM> instead of operation or stop of the first compressed-air source <NUM>. The air volume of the side air SF released from the air nozzle <NUM> may be controlled by an automatic valve arranged upstream from the air nozzle <NUM>.

Second, a maintenance step to be undergone by a spinning system will be described. Before description of such a maintenance step according to an embodiment of the present invention conducted for the spinning system <NUM>, a conventional maintenance step will be described by referring to <FIG>. In describing the conventional maintenance step, signs given to various structures forming the spinning system <NUM> according to an embodiment of the present invention are applied as they are to the corresponding structures (including a spinning unit and a cooling unit) forming a conventional spinning system <NUM>. Meanwhile, the conventional spinning system <NUM> does not include the above-described blower <NUM>.

<FIG> depicts an example of explanatory view of a maintenance step of the conventional spinning system <NUM> schematically showing a part thereof in an operational state. While the spinning system <NUM> is in an operational state, the spinning beam <NUM> and the cooling unit <NUM> are in abutting contact with each other. While the spinning system <NUM> is in operation, the molten polymer P is spun from the spinneret <NUM> and the cooling air CF is supplied from the first compressed-air source <NUM> to the spinning cylinder <NUM> through the duct <NUM>. The cooling air CF supplied to the spinning cylinder <NUM> flows in a substantially horizontal direction into the hollow area CE to cool the molten polymer P spun from the spinneret <NUM>.

<FIG> depicts an example of explanatory view of a maintenance step of the conventional spinning step schematically showing a part thereof in a state of stopping the spinning of molten polymer <NUM> in a state where the spinning of the molten polymer P. For the maintenance on the spinning system <NUM>, the spinning of the molten polymer P from the spinneret <NUM> is stopped first, as shown in <FIG>. The spinning of the molten polymer P is stopped by the controller <NUM> in response to the operation by, e.g., an operator. During the maintenance, supply of the cooling air CF by the cooling unit <NUM> is continued. In the present specification, the maintenance corresponds to, e.g., surface cleaning of the spinneret <NUM> or exchange of the spinning pack <NUM>.

<FIG> depicts an exemplary view of a maintenance step of the conventional spinning system <NUM> schematically showing a part thereof in a state of having caused the cooling unit <NUM> to move down to the lower end with respect to the spinning beam <NUM>. After stopping the spinning of the molten polymer P, the controller <NUM> actuates the air cylinder <NUM> in a contracting direction to lower the cooling unit <NUM> with respect to the spinning beam <NUM>, as shown in <FIG>. Causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM> forms the working space Sw between the spinning unit <NUM> and the cooling unit <NUM> as viewed in the up-and-down direction. When the cooling unit <NUM> is caused to move down with respect to the spinning beam <NUM>, the operator immediately conducts work of covering an upper opening of the spinning cylinder <NUM> with a cover <NUM>. Covering the upper opening of the spinning cylinder <NUM> with the cover <NUM> makes it possible to stop an upward air flow (namely, the cooling air CF) from the upper opening of the spinning cylinder <NUM>.

After covering the upper opening of the spinning cylinder <NUM> with the cover <NUM>, the operator conducts the maintenance. The detail of the maintenance includes surface cleaning of the spinneret <NUM> and exchange of the spinning pack <NUM>. While a time required for the maintenance is determined in a manner depending upon a detail of the maintenance, it is generally <NUM> minutes. The operator conducts surface cleaning of the spinneret <NUM> or exchange of the spinning pack <NUM> in response to purpose. <FIG> depicts an example of explanatory view of a maintenance step of the conventional spinning system <NUM> schematically showing a part thereof in a state of allowing the spinning pack <NUM> to be exchanged.

<FIG> depicts an example of explanatory view of a maintenance step of the conventional spinning system showing a part of the spinning system <NUM> in a state where the spinning of the molten polymer P is restarted. After implementation of the maintenance, in response to operation by the operator, e.g., the controller <NUM> starts (restarts) the spinning of the molten polymer P from the spinneret <NUM>, as shown in <FIG>.

<FIG> depicts an example of explanatory view of the maintenance step of the spinning system <NUM> schematically showing a part thereof in a state of allowing the cover <NUM> for covering the upper opening of the spinning cylinder <NUM> to be detached. As shown in <FIG>, when the spinning of the molten polymer P is restarted, the operator conducts work of detaching the cover <NUM> covering the upper opening of the spinning cylinder <NUM>.

<FIG> depicts an example of explanatory view of the maintenance step of the spinning system <NUM> schematically showing a part thereof in a state of allowing the spinning cylinder <NUM> to have yarn threaded therethrough in yarn threading work. As shown in <FIG>, after implementation of the work of detaching the cover <NUM> covering the upper opening of the spinning cylinder <NUM>, the operator conducts yarn threading work of threading the molten polymer P spun from the spinneret <NUM> (or cooled and solidified yarn Y) through the spinning cylinder <NUM>.

After implementation of the yarn threading work, in response to operation by the operator, e.g., the controller <NUM> actuates the air cylinder <NUM> in an expanding direction to cause the cooling unit <NUM> to move up so as to make the cooling unit <NUM> get closer to the spinning beam <NUM>. When the upper end detection sensor <NUM> (see <FIG>) determines that the cooling unit <NUM> is at the upper end, the controller <NUM> stops actuation of the air cylinder <NUM>, thereby stopping elevation of the cooling unit <NUM>. When the cooling unit <NUM> stops at the upper end, the spinning beam <NUM> and the cooling unit <NUM> abut each other across the sealing member <NUM>. While other preparations for starting production are made in the restoration step, illustrations of these other preparations are omitted.

After implementation of the restoration step, the spinning system <NUM> works normally to be in a state of production. The maintenance on the spinning system <NUM> has conventionally been conducted through the above-described steps.

If restoration is made to a working state after implementation of the maintenance through the above-described conventional maintenance step, the physical properties of yarn are degraded. As shown in <FIG> and <FIG>, e.g., considerable time is required to recover normal physical properties of the yarn (specifically, for the yarn to be determined to be normal). <FIG> depicts an example of schematic diagram showing a result of circular knit staining evaluation changed with the passage of time from the restoration to an operational state after the maintenance in the conventional maintenance step. <FIG> depicts a graph showing a result of thermal stress and de-twisting tension on yarn changed with the passage of time from the restoration to an operational state after the maintenance in the conventional maintenance step.

As shown in <FIG>, the result about circular knit staining evaluation is such that, even after passage of about <NUM> minutes from restoration to a working state, a color is still lighter than a benchmark as a reference (hereinafter called "B. M") so the yarn is not determined to be normal. After passage of about <NUM> minutes from the restoration to the working state, a color approximate to the B. M is obtained so the yarn is determined to be normal.

As shown in <FIG>, both the de-twisting tension and the thermal stress take values approximate to reference values after passage of about <NUM> to <NUM> minutes from restoration to a working state. As shown in <FIG>, while B. M as a reference value for the de-twisting tension is about <NUM> [cN], e.g., and B. M as a reference value for the thermal stress is about <NUM> [cN], e.g., the B. M changes in response to the sort of yarn, and the like.

As described above, after maintenance is conducted by the conventional maintenance step and then restoration is made to a working state, considerable time is required to recover normal physical properties of yarn. Hence, producing the yarn continuously merely results in increased amount of the yarn to be disposed of. In a case where maintenance is conducted by the conventional maintenance step and then restoration is made to a working state, possible reason for requiring considerable time to recover normal physical properties of the yarn is that temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> decrease seriously in the maintenance step so it takes time for temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> to recover their original temperatures.

<FIG> depicts a graph showing a surface temperature of the spinneret <NUM> changed with the passage of time from the starting of maintenance in the conventional maintenance step. As shown in <FIG>, when the cooling unit <NUM> is caused to move down with respect to the spinning beam <NUM>, surface temperature on the spinneret <NUM> decreases nearly continuously to cause serious decrease of surface temperature on the spinneret <NUM> at a time when the maintenance is finished. When the maintenance is finished and the cooling unit <NUM> is caused to move up so as to get closer to the spinning beam <NUM>, surface temperature on the spinneret <NUM> is recovered gradually. As shown in <FIG>, in order for surface temperature on the spinneret <NUM> to recover its original temperature (e.g., temperature before implementation of the maintenance), a duration of about <NUM> or more is required from start of the elevation of the cooling unit <NUM>.

Possible reason for the serious decrease of surface temperature on the spinneret <NUM> occurring in the conventional maintenance step is that the cooling air CF supplied to the spinning cylinder <NUM> goes upward from the upper opening of the spinning cylinder <NUM>. During implementation of the yarn threading work of threading the molten polymer P spun from the spinneret <NUM> (or cooled and solidified yarn Y) through the spinning cylinder <NUM>, the molten polymer P is cooled and solidified by the cooling air CF (see, e.g., <FIG>) flowing upward from the upper opening of the spinning cylinder <NUM>. In this case, while the operator is allowed to conduct the yarn threading work without using a tool, temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> are unintentionally decreased by the cooling air CF flowing upward from the upper opening of the spinning cylinder <NUM>. This causes serious decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>. Hence, it is considered that, after restoration to a working state, it takes time for temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> to recover their original temperatures.

To solve the above-described problem revealed in the conventional maintenance step, maintenance is conducted on the spinning system <NUM> according to the embodiment of the present invention by a maintenance step described below. The following describes the maintenance step conducted on the spinning system <NUM> according to the embodiment of the present invention.

The maintenance step according to the present invention will be described by referring to <FIG> and <FIG>. The spinning system <NUM> according to the embodiment of the present invention largely differs from the conventional spinning system <NUM> in that it includes the blower <NUM>.

As shown in <FIG>, while the spinning system <NUM> is working, the lower end of the spinning beam <NUM> and the upper end of the cooling unit <NUM> are in abutting contact with each other. While the spinning system <NUM> is working, the molten polymer P is spun from the spinneret <NUM> and the cooling air CF is supplied from the first compressed-air source <NUM> (see <FIG> and the same applies to the following cases) to the spinning cylinder <NUM> through the duct <NUM>. The cooling air CF supplied to the spinning cylinder <NUM> flows in a substantially horizontal direction into the hollow area CE to cool the molten polymer P spun from the spinneret <NUM>. While the spinning system <NUM> is working, the side air SF is not released from the air nozzle <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of stopping the spinning of molten polymer P. For implementation of maintenance on the spinning system <NUM>, the spinning of the molten polymer P from the spinneret <NUM> is stopped first, as shown in <FIG>. The spinning of the molten polymer P is stopped by the controller <NUM> in response to operation by, e.g., an operator. During implementation of the maintenance, supply of the cooling air CF by the cooling unit <NUM> is continued. At this time, the blower <NUM> stops its operation so the side air SF is not released from the air nozzle <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of having caused the cooling unit <NUM> to move down to a lower end with respect to the spinning beam <NUM>. After stopping the spinning of the molten polymer P, the controller <NUM> actuates the air cylinder <NUM> in a contracting direction to lower the cooling unit <NUM> with respect to the spinning beam <NUM>, as shown in <FIG>. Causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM> forms the working space Sw between the spinning unit <NUM> and the cooling unit <NUM> as viewed in an up-and-down direction. When the cooling unit <NUM> starts to be caused to move down with respect to the spinning beam <NUM>, the operator immediately conducts work of covering the upper opening of the spinning cylinder <NUM> with the cover <NUM>. Covering the upper opening of the spinning cylinder <NUM> with the cover <NUM> immediately after starting causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM> makes it possible to stop an upward flow of the cooling air CF from the upper opening of the spinning cylinder <NUM>, thereby preventing the spinneret <NUM> from being cooled by this cooling air CF. At this time, the blower <NUM> stops its operation so the side air SF is not released from the air nozzle <NUM>.

Preferably, timing of stopping the spinning of the molten polymer P coincides with a moment before start of causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM>. However, this is not the only timing but the spinning may be stopped during causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM> or after causing the cooling unit <NUM> to move down to the lower end with respect to the spinning beam <NUM>.

After covering the upper opening of the spinning cylinder <NUM> with the cover <NUM>, the operator conducts the maintenance. The detail of the maintenance includes surface cleaning of the spinneret <NUM> and exchange of the spinning pack <NUM>. While time required for the maintenance is determined in a manner that depends on the detail of the maintenance, it is generally <NUM> minutes. The operator conducts surface cleaning of the spinneret <NUM> or exchange of the spinning pack <NUM> in response to purpose.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of restarting the spinning of molten polymer P. After implementation of the maintenance, in response to operation by the operator, e.g., the controller <NUM> starts (restarts) the spinning of the molten polymer P from the spinneret <NUM>, as shown in <FIG>.

When the spinning of the molten polymer P is restarted, the controller <NUM> starts operation of the blower <NUM>, as shown in <FIG>. As shown in <FIG>, when the operation of the blower <NUM> is started, the side air SF is released in the working space Sw between the spinning unit <NUM> and the cooling unit <NUM> as viewed in the up-and-down direction from the air nozzle <NUM> in a substantially horizontal direction toward the molten polymer P spun from the spinneret <NUM>. Thus, a temperature decrease limiting step includes a blowing step of releasing the side air SF in the working space Sw from the air nozzle <NUM> in a substantially horizontal direction toward the molten polymer P spun from the spinneret <NUM>. Timing of starting releasing of the side air SF from the air nozzle <NUM> will be described later.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of allowing the cover <NUM> for covering the upper opening of the spinning cylinder <NUM> to be detached. When the operation of the blower <NUM> is started (specifically, when release of the side air SF from the air nozzle <NUM> is started), the operator conducts work of detaching the cover <NUM> covering the upper opening of the spinning cylinder <NUM>. When the cover <NUM> covering the upper opening of the spinning cylinder <NUM> is detached, part of the cooling air CF supplied to the spinning cylinder <NUM> goes upward from the upper opening of the spinning cylinder <NUM>. However, a direction of this cooling air CF is changed by the side air SF. Specifically, the cooling air CF going upward can be prevented from reaching the spinneret <NUM> and a place around the spinneret <NUM>. Preferably, the operation of the blower <NUM> is started at least before the cover <NUM> covering the upper opening of the spinning cylinder <NUM> is detached.

The size of an opening at the air nozzle <NUM>, specifically, the area of the opening through which the side air SF is released is extremely smaller than the area of the upper opening of the spinning cylinder <NUM>. Thus, the flow rate of the side air SF released from the air nozzle <NUM> is extremely higher than the flow rate of the cooling air CF going from the upper opening of the spinning cylinder <NUM> toward the spinneret <NUM>. This makes it possible to change a direction of flow of the cooling air CF going upward from the upper opening of the spinning cylinder <NUM> using the side air SF released in a substantially horizontal direction from the air nozzle <NUM>. In this way, the side air SF functions as a barrier to interrupt flow of the cooling air CF toward the spinneret <NUM> or to reduce the air volume of the cooling air CF going toward the spinneret <NUM>. Furthermore, making the air volume of the side air SF per unit time released from the air nozzle <NUM> larger than the air volume of the cooling air CF per unit time going toward the spinneret <NUM> makes it possible to reduce the air volume of the cooling air CF going toward the spinneret <NUM>. In this way, the cooling air CF going upward from the upper opening of the spinning cylinder <NUM> can be blocked from moving toward the spinneret <NUM> and a place around the spinneret <NUM>. The side air SF released in a substantially horizontal direction from the air nozzle <NUM> further has the function of cooling and solidifying the molten polymer P spun from the spinneret <NUM>. It becomes more difficult to cool the molten polymer P with a greater diameter of the molten polymer P. Thus, the blower <NUM> preferably has the function of changing the air volume of the side air SF per unit time released from the air nozzle <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of allowing the spinning cylinder <NUM> to have yarn threaded therethrough in yarn threading work. As shown in <FIG>, after implementation of the work of detaching the cover <NUM> covering the upper opening of the spinning cylinder <NUM>, the operator conducts yarn threading work of threading the molten polymer P spun from the spinneret <NUM> (or cooled and solidified yarn Y) through the spinning cylinder <NUM>. At this time, once the yarn Y is threaded through the spinning cylinder <NUM>, the yarn Y is then carried by the cooling air CF flowing downward that is part of the cooling air CF supplied to the spinning cylinder <NUM>. The molten polymer P spun from the spinneret <NUM> is cooled and solidified by the side air SF or the cooling air CF, or by the side air SF and the cooling air CF. This allows the operator to conduct the yarn threading work without using a tool.

After implementation of the yarn threading work, in response to operation by the operator, e.g., the controller <NUM> actuates the air cylinder <NUM> in an expanding direction to cause the cooling unit <NUM> to move up so as to make the cooling unit <NUM> get closer to the spinning beam <NUM>. When the spinning beam <NUM> and the cooling unit <NUM> abut each other, the controller <NUM> stops actuation of the air cylinder <NUM> to stop elevation of the cooling unit <NUM>, and then makes restoration to a working state.

When the spinning beam <NUM> and the cooling unit <NUM> abut each other and elevation of the cooling unit <NUM> is stopped, the controller <NUM> stops operation of the blower <NUM> to stop release of the side air SF from the air nozzle <NUM>, thereby finishing the blowing step. Preferably, timing of stopping release of the side air SF from the air nozzle <NUM> coincides with a moment when the spinning beam <NUM> and the cooling unit <NUM> abut each other and elevation of the cooling unit <NUM> is stopped or a moment after stop of the elevation. The reason for this is that, as the abutting contact between the spinning beam <NUM> and the cooling unit <NUM> closes the upper opening of the spinning cylinder <NUM> to cause the cooling air CF flowing into the hollow area CE to go downward entirely or mostly, it is still possible to limit decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> even after the blowing step is finished. As a result, it becomes possible to shorten time for temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> to recover their original temperatures, eventually, shorten time for stabilizing the physical properties of yarn. In another case, release of the side air SF from the air nozzle <NUM> may be stopped during elevation of the cooling unit <NUM> so as to make the cooling unit <NUM> get closer to the spinning beam <NUM>, while this may reduce the effect of limiting decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> compared to a case where release of the side air SF from the blower <NUM> is stopped when elevation of the cooling unit <NUM> is stopped.

After elevation of the cooling unit <NUM> with respect to the spinning beam <NUM> is stopped, the operator stretches the yarn around the oil applicator <NUM>. Timing of stretching the yarn around the oil applicator <NUM> is not limited to a moment after the cooling unit <NUM> has been caused to move up with respect to the spinning beam <NUM> but may coincide with a moment before elevation of the cooling unit <NUM> with respect to the spinning beam <NUM> is started or with a period when the cooling unit <NUM> is being caused to move up with respect to the spinning beam <NUM>. However, this timing preferably coincides with a moment after release of the side air SF from the air nozzle <NUM> is stopped.

While other preparations for starting production are made in the restoration step, illustrations of these other preparations are omitted. After implementation of the restoration step, the spinning system <NUM> works normally to be in a state of production.

As described above, in the maintenance step according to the present invention, the side air SF released from the air nozzle <NUM> functions as a barrier to interrupt flow of the cooling air CF toward the spinneret <NUM> or to reduce the air volume of the cooling air CF going toward the spinneret <NUM>. This makes it possible to prevent serious decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>. Thus, time for temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> to recover their original temperatures can be shortened after restoration to a working state to allow reduction in the amount of yarn to be disposed of.

As long as release of the side air SF from the air nozzle <NUM> is started at least before detachment of the cover <NUM> covering the upper opening of the spinning cylinder <NUM>, this timing of the release may coincide with a moment either before or after the spinning of the molten polymer P is restarted.

While the maintenance step according to the present invention is as has been described above, this is not the only maintenance step for solving the problem revealed in the conventional maintenance step. The following describes a maintenance step according to a modification.

The maintenance step according to the modification will be described by referring to <FIG>. The state of the spinning system <NUM> during production or in a working state is the same as that of <FIG>, so that a drawing showing the state of the spinning system <NUM> in a working state is omitted.

The maintenance step according to the modification largely differs from the maintenance step according to the present invention in that supply of the cooling air CF to the spinning cylinder <NUM> is stopped in the maintenance step. Like the spinning system <NUM> according to the embodiment of the present invention, the spinning system <NUM> according to the modification includes the blower <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of stopping the spinning of molten polymer P. For implementation of maintenance on the spinning system <NUM>, the spinning of the molten polymer P from the spinneret <NUM> is stopped first, as shown in <FIG>. The spinning of the molten polymer P is stopped by the controller <NUM> in response to operation by, e.g., an operator. The blower <NUM> stops its operation and air is not supplied from the second compressed-air source <NUM> to the air nozzle <NUM>, so that the side air SF is not released from the air nozzle <NUM>.

After stopping the spinning of the molten polymer P, the controller <NUM> stops operation of the first compressed-air source <NUM> to stop supply of the cooling air CF to the spinning cylinder <NUM>. Stopping supply of the cooling air CF to the spinning cylinder <NUM> makes it possible to prevent the cooling air CF from going from the upper opening of the spinning cylinder <NUM> toward the spinneret <NUM>, thereby preventing serious decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of having caused the cooling unit <NUM> to move down to a lower end with respect to the spinning beam <NUM>. After stopping supply of the cooling air CF to the spinning cylinder <NUM>, the controller <NUM> actuates the air cylinder <NUM> in a contracting direction to lower the cooling unit <NUM> with respect to the spinning beam <NUM>, as shown in <FIG>. Causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM> forms the working space Sw between the spinning unit <NUM> and the cooling unit <NUM> as viewed in an up-and-down direction. When the cooling unit <NUM> is caused to move down with respect to the spinning beam <NUM>, the operator conducts work of covering the upper opening of the spinning cylinder <NUM> with the cover <NUM>. However, it is not necessarily required to conduct the work of covering the upper opening of the spinning cylinder <NUM> with the cover <NUM> as supply of the cooling air CF to the spinning cylinder <NUM> is stopped. The blower <NUM> stops its operation and compressed air is not supplied from the second compressed-air source <NUM> to the air nozzle <NUM>, so that the side air SF is not released from the air nozzle <NUM>.

Preferably, timing of stopping the spinning of the molten polymer P coincides with a moment before start of causing the cooling unit <NUM> to move down with respect to the spinning beam <NUM>. However, this is not the only timing but the spinning may be stopped during causing the cooling unit <NUM> with respect to the spinning beam <NUM> or after causing the cooling unit <NUM> to move down to the lower end with respect to the spinning beam <NUM>.

Timing of stopping supply of the cooling air CF to the spinning cylinder <NUM> is not limited to a moment after the spinning of the molten polymer P is stopped but may coincide with a moment before the spinning of the molten polymer P is stopped or with a moment substantially simultaneous with stop of the spinning of the molten polymer P.

After the cooling unit <NUM> has been caused to move down with respect to the spinning beam <NUM> and the upper opening of the spinning cylinder <NUM> is covered with the cover <NUM> while this covering is not absolute necessity, the operator conducts the maintenance such as surface cleaning of the spinneret <NUM> or exchange of the spinning pack <NUM> in response to purpose. While time required for the maintenance is determined in a manner that depends on the detail of the maintenance, it is generally <NUM> minutes.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of restarting the spinning of molten polymer P. After implementation of the maintenance, in response to operation by the operator, e.g., the controller <NUM> starts (restarts) the spinning of the molten polymer P from the spinneret <NUM>, as shown in <FIG>. If the upper opening of the spinning cylinder <NUM> is covered with the cover <NUM>, the operator conducts work of detaching the cover <NUM> covering the upper opening of the spinning cylinder <NUM>.

The foregoing step of stopping supply of the cooling air CF to the spinning cylinder <NUM> is included in a temperature decrease limiting step. Timing of stopping supply of the cooling air CF to the spinning cylinder <NUM> is as has been described above. If the upper opening of the spinning cylinder <NUM> is covered with the cover <NUM>, however, it is only required to stop supply of the cooling air CF to the spinning cylinder <NUM> at least before detachment of the cover <NUM>. The reason for this is that, while the upper opening of the spinning cylinder <NUM> is covered with the cover <NUM>, the cover <NUM> can function to prevent the cooling air CF from going from the upper opening of the spinning cylinder <NUM> toward the spinneret <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of causing the blower <NUM> to start operation. After restarting the spinning of the molten polymer P, the controller <NUM> starts operation of the blower <NUM>. When the operation of the blower <NUM> is started, the side air SF is released in the working space Sw between the spinning unit <NUM> and the cooling unit <NUM> as viewed in an up-and-down direction from the air nozzle <NUM> in a substantially horizontal direction toward the molten polymer P spun from the spinneret <NUM>. A step of releasing the side air SF in the working space Sw from the air nozzle <NUM> is also included in the temperature decrease limiting step.

Operation of the blower <NUM> may be started after detachment of the cover <NUM> covering the upper opening of the spinning cylinder <NUM> or before detachment of the cover <NUM> covering the upper opening of the spinning cylinder <NUM>. The reason for this is that, as there is no supply of the cooling air CF to the spinning cylinder <NUM>, serious decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> is not caused by the cooling air CF going upward from the upper opening of the spinning cylinder <NUM>.

Timing of starting operation of the blower <NUM> is not limited to a moment after the spinning of the molten polymer P is restarted but may coincide with a moment before the spinning of the molten polymer P from the spinneret <NUM> is restarted.

As described above, stopping supply of the cooling air CF to the spinning cylinder <NUM> makes it possible to limit decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>. On the other hand, stopping supply of the cooling air CF to the spinning cylinder <NUM> makes it impossible to cool and solidify the molten polymer P spun from the spinneret <NUM> using the cooling air CF supplied to the spinning cylinder <NUM>. Not cooling and solidifying the molten polymer P spun from the spinneret <NUM> might impose difficulty in conducting yarn threading through the spinning cylinder <NUM> after the maintenance is finished. In this regard, releasing the side air SF in the working space Sw from the air nozzle <NUM> toward the molten polymer P spun from the spinneret <NUM> allows cooling and solidification of the molten polymer P spun from the spinneret <NUM>. As a result, it becomes possible to facilitate yarn threading through the spinning cylinder <NUM> conducted after the maintenance is finished while limiting decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of allowing the spinning cylinder <NUM> to have yarn threaded therethrough in yarn threading work. As shown in <FIG>, when release of the side air SF from the air nozzle <NUM> is started, the operator conducts yarn threading work of threading the molten polymer P spun from the spinneret <NUM> (or cooled and solidified yarn Y) through the spinning cylinder <NUM>. At this time, the molten polymer P spun from the spinneret <NUM> is cooled and solidified by the side air SF released from the air nozzle <NUM>. This allows the operator to conduct the yarn threading work without using a tool.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of having caused the cooling unit <NUM> to move up to the upper end with respect to the spinning beam <NUM>. As shown in <FIG>, after implementation of the work of threading the yarn through the spinning cylinder <NUM>, in response to operation by the operator, e.g., the controller <NUM> actuates the air cylinder <NUM> in an expanding direction to cause the cooling unit <NUM> to move up so as to make the cooling unit <NUM> get closer to the spinning beam <NUM>. When the spinning beam <NUM> and the cooling unit <NUM> abut each other, the controller <NUM> stops actuation of the air cylinder <NUM> to stop elevation of the cooling unit <NUM>. Furthermore, when the spinning beam <NUM> and the cooling unit <NUM> abut each other and elevation of the cooling unit <NUM> is stopped, the controller <NUM> stops operation of the blower <NUM> to stop release of the side air SF from the air nozzle <NUM>. Preferably, timing of stopping release of the side air SF from the air nozzle <NUM> coincides with a moment when the spinning beam <NUM> and the cooling unit <NUM> abut each other and elevation of the cooling unit <NUM> is stopped or a moment after stop of the elevation, as it allows cooling and solidification of the molten polymer P spun from the spinneret <NUM>. In another case, release of the side air SF from the air nozzle <NUM> may be stopped before elevation of the cooling unit <NUM> with respect to the spinning beam <NUM> is started or during elevation of the cooling unit <NUM> so as to make the cooling unit <NUM> get closer to the spinning beam <NUM>.

<FIG> depicts an example of view schematically showing a part of the spinning system <NUM> in a state of being restored to an operational state. When the lower end of the spinning beam <NUM> and the upper end of the cooling unit <NUM> abut each other and elevation of the cooling unit <NUM> is stopped, the controller <NUM> restarts operation of the first compressed-air source <NUM> to start supply of the cooling air CF to the spinning cylinder <NUM>.

Timing of starting supply of the cooling air CF to the spinning cylinder <NUM> is not limited to a moment when the lower end of the spinning beam <NUM> and the upper end of the cooling unit <NUM> abut each other and elevation of the cooling unit <NUM> is stopped. For example, if the side air SF released from the air nozzle <NUM> flows between the spinning unit <NUM> and the cooling unit <NUM> as viewed in an up-and-down direction, supply of the cooling air CF to the spinning cylinder <NUM> may be started while the cooling unit <NUM> is at the lower end. Starting supply of the cooling air CF to the spinning cylinder <NUM> while the cooling unit <NUM> is at the lower end makes it likely that the cooling air CF will flow from the upper opening of the spinning cylinder <NUM> toward the spinneret <NUM>. However, as the side air SF released from the air nozzle <NUM> functions as a barrier, it is possible to limit decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>.

In the maintenance step according to the modification described above, at least in a state where the cooling unit <NUM> has been moved downward with respect to the spinning beam <NUM>, supply of the cooling air CF to the spinning cylinder <NUM> is stopped. This allows the cooling air CF to be stopped from flowing from the upper opening of the spinning cylinder <NUM> toward the spinneret <NUM>. As a result, it is possible to limit decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>.

The foregoing maintenance step according to the modification has been described on the assumption that supply of the cooling air CF to the spinning cylinder <NUM> is stopped. However, instead of stopping supply of the cooling air CF to the spinning cylinder <NUM>, the air volume of the cooling air CF to be supplied to the spinning cylinder <NUM> may be reduced. Reducing the air volume of the cooling air CF to be supplied to the spinning cylinder <NUM> reduces the air volume of the cooling air CF to flow from the upper opening of the spinning cylinder <NUM> toward the spinneret <NUM>, making it possible to limit decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>. Regarding reduction in the air volume of the cooling air CF to be supplied to the spinning cylinder <NUM>, this air volume may be reduced at least compared to an air volume during production, namely, before stop of the spinning of the molten polymer P.

Stopping supply of the cooling air CF to the spinning cylinder <NUM> or reducing the volume of supply of the cooling air CF during implementation of maintenance on the spinning system <NUM> might result in the failure to cool and solidify the molten polymer P spun from the spinneret <NUM> to impose difficulty in the work of threading yarn through the spinning cylinder <NUM> conducted after the maintenance is finished. However, as the side air SF released from the air nozzle <NUM> flows toward a direction intersecting a yarn path of the molten polymer P spun from the spinneret <NUM>, it is possible to cool and solidify the molten polymer P spun from the spinneret <NUM>. This allows yarn threading through the spinning cylinder to be conducted easily after the maintenance is finished while limiting decrease of temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM>. As a result, after restoration is made to a working state, it becomes possible to shorten time for temperature at the spinneret <NUM> and ambient temperature around the spinneret <NUM> to recover their original temperatures to allow reduction in the amount of yarn to be disposed of.

As a result of implementation of maintenance by the maintenance step according to the present invention or implementation of maintenance by the maintenance step according to the modification described above, it was possible to shorten time required to recover normal physical properties of yarn after restoration to a working state. <FIG> is a schematic view showing result about circular knit staining evaluation that is changed with passage of time from restoration to a working state after implementation of maintenance by the maintenance step according to the present invention. <FIG> is a graph showing an example of result about thermal stress and de-twisting tension on yarn that are changed with passage of time from restoration to a working state in each of a case where maintenance is conducted by the conventional maintenance step and a case where maintenance is conducted by the maintenance step according to the modification.

As shown in <FIG>, in the result about circular knit staining evaluation, a color approximate to B. M is obtained roughly after <NUM> minutes from restoration to a working state so the yarn is determined to be normal. In this way, it was possible to shorten time considerably required for the yarn to be determined to be normal, compared to implementation of the maintenance by the conventional maintenance step.

As clearly understood from <FIG>, both the de-twisting tension and the thermal stress fulfill more favorable results in the case of implementation of maintenance by the maintenance step of the modification than in the case of implementation of maintenance by the conventional maintenance step.

<FIG> is a graph showing change in surface temperature on the spinneret <NUM> responsive to passage of time from when maintenance is started by each of the conventional maintenance step, the maintenance step of the present invention, and the maintenance step of the modification. In <FIG>, (a) shows exemplary change in surface temperature on the spinneret <NUM> responsive to passage of time from when the maintenance is started by the conventional maintenance step. In <FIG>, (b) shows exemplary change in surface temperature on the spinneret <NUM> responsive to passage of time from when the maintenance is started by the maintenance step according to the present invention. In <FIG>, (c) shows exemplary change in surface temperature on the spinneret <NUM> responsive to passage of time from when the maintenance is started by the maintenance step according to the modification.

Claim 1:
A spinning system (<NUM>) comprising:
a spinning beam (<NUM>) having a spinning pack (<NUM>) inserted therein including a spinneret (<NUM>) for allowing molten polymer (P) to be spun downward;
a cooling unit (<NUM>) arranged below the spinning beam (<NUM>), including a spinning cylinder (<NUM>) extending in an up-and-down direction so as to surround the molten polymer (P) spun from the spinneret (<NUM>), configured to cool the molten polymer (P) through the use of cooling air (CF) supplied from a periphery of the spinning cylinder (<NUM>);
a moving mechanism (<NUM>) configured to cause the cooling unit (<NUM>) to move downward with respect to the spinning beam (<NUM>) so as to form a gap between the cooling unit (<NUM>) and the spinning beam (<NUM>); and
a blower (<NUM>) configured to, at least when the cooling unit (<NUM>) having been caused to move downward with respect to the spinning beam (<NUM>), blow air toward between the spinning beam (<NUM>) and the cooling unit (<NUM>) in a direction intersecting a yarn path of the molten polymer (P) spun from the spinneret (<NUM>).