Patent Description:
In a ring/traveler system of a ring spinning machine, when yarn is wound onto a bobbin, a traveler slides (travels) around a ring. At this time, the sliding surface between the traveler and the ring is susceptible to wear, seizure, and the like due to friction. Particularly in recent years, there has been a tendency to increase the speed at which the traveler moves around the ring in order to improve the productivity of the ring spinning machine, but as a result, wear on the traveler and the ring advances quickly. When wear on the traveler and the ring advances quickly, the useful life of the ring/traveler system decreases, and as a result, components such as the traveler must be replaced frequently. Furthermore, wear on the traveler and the ring typically advances more quickly as frictional force generated on the sliding surface between the two components increases. Therefore, a method of employing a lubricating liquid such as oil, for example, may be used as a method for suppressing wear on the traveler and the ring. With this method, however, the lubricating liquid adheres to and soils the yarn.

Hence, <CIT> describes an invention relating to a ring/traveler system for a ring spinning machine and states that in order to extend the useful life of the ring/traveler system without using a lubricating liquid, "in a ring/traveler system for a ring spinning machine, circular indentations, each having a depth of <NUM> to <NUM> and a diameter of <NUM> to <NUM>, are formed in a sliding surface, which is a surface on which a traveler and a ring slide as the traveler travels, within an area ratio range of <NUM>% to <NUM>%".

<CIT> discloses a ring traveler device having a sliding surface with a low friction portion of a ring. On that sliding surface with the low friction portion a traveler can slide. The low friction portion comprises recesses as dimples. The recesses are circular with a diameter between <NUM> and <NUM> as a spherical concave having a circular opening and a spherical concave surface.

After studying the invention described in <CIT> in depth, however, the inventors found that the shape and arrangement of the indentations (referred to hereafter as "dimples") formed in the sliding surface between the traveler and the ring have not necessarily been considered to a degree enough to extend the useful life of the traveler/ring system.

The present invention has been designed to solve the problem described above, and an object thereof is to provide a ring/traveler system for a ring spinning machine in which the shape and arrangement of dimples that function to resupply an accretion containing a yarn-derived lubricating component to a sliding surface have been studied in depth, with the result that the shape and arrangement of dimples formed on a sliding surface between a traveler and a ring can be optimized, enabling a further extension to the useful life of the ring/traveler system.

The above object is solved by a ring/traveler system for a ring spinning machine having the features of claim <NUM>. A further development is stated in claim <NUM>.

An embodiment of the present invention will be described in detail below with reference to the figures.

<FIG> is a perspective view of a ring in an example configuration of a ring/traveler system for a ring spinning machine. <FIG> is a partially enlarged perspective view of the ring in this example configuration of a ring/traveler system for a ring spinning machine. <FIG> is a schematic perspective view showing a relationship between the traveler and the ring during spinning in this example configuration of a ring/traveler system for a ring spinning machine. The term "ring spinning machine" denotes a spinning machine such as a ring spinning machine or a ring twisting machine in which yarn is wound via a traveler that travels (slides) around a ring that ascends and descends while supported by a ring rail.

In <FIG>, a ring <NUM> and a traveler <NUM> together constitute the ring/traveler system. The ring <NUM> is formed from bearing steel, for example. A flange 11a is formed on the ring <NUM> so as to be structured integrally with the ring <NUM>. The flange 11a is formed to have a T-shaped cross-section.

The traveler <NUM>, meanwhile, is formed from oxidation-treated spring steel, for example. The traveler <NUM> is formed in a C shape. The traveler <NUM> is mounted on the flange 11a of the ring <NUM>.

A chromium plating layer <NUM> is formed on the surface of the flange 11a of the ring <NUM>. The chromium plating layer <NUM> is preferably formed from a hard chromium plating layer with a thickness of approximately <NUM> to <NUM>, for example. A hard chromium plating layer is a plating layer defined in JIS H8615 Chromium plating for engineering purposes. A periodic structure portion <NUM> is formed on the chromium plating layer <NUM> covering the flange 11a in at least a surface layer part of the chromium plating layer <NUM> covering an inner peripheral surface of the flange 11a. The periodic structure portion <NUM> is a part for reducing component wear that occurs when the traveler <NUM> slides around the ring <NUM>.

Note that in this embodiment, the flange 11a of the ring <NUM> is covered by the chromium plating layer <NUM>, and the periodic structure portion <NUM> is formed on the inner peripheral surface of the flange 11a via the chromium plating layer <NUM>. The film covering the flange 11a is not limited to the chromium plating layer <NUM>, however, and any surface-treated film having either approximately identical mechanical characteristics to the chromium plating layer <NUM> or higher mechanical characteristics than the traveler material, such as nickel plating having a higher hardness than the traveler material, for example, may be used instead.

As shown in <FIG>, when yarn is wound onto a bobbin in the ring spinning machine, yarn Y is passed through the traveler <NUM>. The yarn Y is fed from a drafting device, not shown in the figures, and wound onto a bobbin (not shown) via the traveler <NUM>. At this time, a predetermined tension is applied to the yarn Y passing through the traveler <NUM>. Accordingly, the traveler <NUM> is pulled by the yarn Y so as to contact the flange 11a of the ring <NUM>, and while maintaining this state of contact, moves so as to revolve around the flange 11a. Therefore, while the yarn Y is being wound onto the bobbin, or in other words during spinning, the traveler <NUM> slides (travels) around the ring <NUM>.

Here, a sliding surface on which the traveler <NUM> and the ring <NUM> slide as the traveler <NUM> travels is a surface on which the ring <NUM> and the traveler <NUM> contact each other. Therefore, a sliding surface between the traveler <NUM> and the ring <NUM> exists on both the ring <NUM> and the traveler <NUM>. In this embodiment, as an example, the periodic structure portion <NUM> is formed on the sliding surface on which the ring <NUM> slides relative to the traveler <NUM>. More specifically, a configuration in which the inner peripheral surface of the flange 11a of the ring <NUM> is covered by the chromium plating layer <NUM> and the periodic structure portion <NUM> is formed on the surface of the chromium plating layer <NUM> is employed. In this embodiment, therefore, the periodic structure portion <NUM> on the chromium plating layer <NUM> covering the inner peripheral surface of the flange 11a corresponds to the sliding surface between the traveler <NUM> and the ring <NUM>.

As shown in <FIG>, a plurality of dimples <NUM> are formed in the periodic structure portion <NUM> of the chromium plating layer <NUM>. <FIG> is a front view of the periodic structure portion, and <FIG> is an A-A sectional view of <FIG>.

The periodic structure portion <NUM> is formed by arranging the plurality of dimples <NUM> periodically at a predetermined pitch. In this embodiment, as an example, the plurality of dimples <NUM> are arranged in a staggered pattern. Each dimple <NUM> is formed as a recess in a main surface 14a of the periodic structure portion <NUM>. The main surface 14a of the periodic structure portion <NUM> is a surface excluding the recessed parts formed by the dimples <NUM>. The plurality of dimples <NUM> each have a circular open end 15a. The open end 15a of each dimple <NUM> opens in a circular shape onto the main surface 14a of the periodic structure portion <NUM>. Each dimple <NUM> is formed to have a rounded cone-shaped cross-section. Further, each dimple <NUM> has a wall surface 15b that rises diagonally from a bottom portion of the dimple <NUM> toward the main surface 14a of the periodic structure portion <NUM>.

In this embodiment, the plurality of dimples <NUM> forming the periodic structure portion <NUM> are formed to satisfy the following two conditions simultaneously.

Respective definitions of the dimple wall surface angle, the arrangement pitch of the plurality of dimples <NUM> (also referred to as the "dimple pitch" hereafter), the diameter of the circular open end 15a (also referred to as the "dimple diameter" hereafter), and the depth of the dimple <NUM> (also referred to as the "dimple depth" hereafter) will now be described.

As shown in <FIG>, the dimple wall surface angle is denoted by an angle θ (°) formed by the main surface 14a and the wall surface 15b at the open end 15a where the wall surface 15b of the dimple <NUM> contacts the main surface 14a of the periodic structure portion <NUM>. As illustrated in <FIG>, the dimple pitch is denoted by a center-to-center distance P (µm) between two adjacent dimples <NUM> on the main surface 14a of the periodic structure portion <NUM>. Note that <FIG> show an example in which the arrangement pitch P of the dimples <NUM> is identical in all directions, but the arrangement pitch may be varied according to the direction of the adjacent dimples <NUM>. It should be noted, however, that when two or more different arrangement pitches exist, the value of P/D must satisfy (Condition <NUM>) described above in relation to all of the arrangement pitches. As shown in <FIG>, the dimple diameter is denoted by a diameter D (µm) of the open end 15a of the dimple <NUM>, which opens in a circular shape onto the main surface 14a of the periodic structure portion <NUM>. As shown in <FIG>, the dimple depth is denoted by a maximum depth S (µm) of the dimple <NUM>, using the main surface 14a of the periodic structure portion <NUM> as a reference.

Note that <FIG> shows an example in which the dimples <NUM> have a rounded cone-shaped cross-section, but the present invention is not limited thereto, and instead, the employed dimples <NUM> may have a pointed cone-shaped cross-section, as shown in <FIG>, or a trapezoidal cross-section, as shown in <FIG>. Regardless of the employed sectional shape, the open end 15a of the dimple <NUM> is circular.

The term "circular" used to describe the opening shape of the open end 15a preferably denotes a perfect circle. The present invention is not limited thereto, however, and the term "circular" may denote an ellipse having an ellipticity of at least <NUM>, for example. As regards the dimple wall surface angle θ in this case, the dimple wall surface angle θ should satisfy the condition of being not less than <NUM>° and not more than <NUM>° in at least one of a long axis direction and a short axis direction of the ellipse. Further, as regards the dimple diameter, the condition according to which the value of P/D is not less than <NUM> and not more than <NUM> should be satisfied when the length of at least one of a long axis and a short axis of the ellipse is applied as the dimple diameter D (µm).

The dimple depth S of each of the plurality of dimples <NUM> is preferably not less than <NUM>. Further, the dimple diameter D is not less than <NUM> and not more than <NUM>. Furthermore, a dimple area ratio of the periodic structure portion <NUM> is preferably not less than <NUM>% and not more than <NUM>%. The dimple area ratio is a value expressing the ratio of the entire surface area of the dimples <NUM> to the entire surface area of the sliding surface between the traveler <NUM> and the ring <NUM> as a percentage.

The plurality of dimples <NUM> can be formed by laser processing, for example. When the dimples <NUM> are formed by laser processing, picosecond laser processing using picosecond pulsed laser light is preferably applied. In picosecond laser processing, the position in which the workpiece is irradiated with the laser light can be varied by controlling the orientation of the picosecond pulsed laser light emitted by a laser oscillator using a galvanometer optical system. Hence, when the periodic structure portion <NUM> is to be provided on the ring <NUM>, the plurality of dimples <NUM> can be formed in a desired arrangement by irradiating the sliding surface of the ring <NUM> with picosecond pulsed laser light using a galvanometer optical system and successively shifting the irradiation position using the galvanometer optical system.

A mechanism by which the periodic structure portion <NUM> reduces wear will now be described.

First, in this embodiment, the sliding surface between the ring <NUM> and the traveler <NUM> is a surface on which sliding is performed in an environment without liquid lubrication. "Without liquid lubrication" indicates a state in which no liquid lubricant exists. Typically, when metals slide against each other in an environment without liquid lubrication, severe wear occurs on the sliding surface. In a ring/traveler system, the traveler <NUM> revolves around the ring <NUM> at a particularly high speed, and therefore wear may be expected to advance rapidly on the sliding surfaces of the two components, leading to seizure occurring within a period of several minutes to several hours. In an actual ring/traveler system, however, contrary to expectation, wear advances slowly. During cotton spinning, for example, the traveler <NUM> can often be used for up to one or two weeks without being replaced. In tribological terms, therefore, the sliding surface between the ring <NUM> and the traveler <NUM> is believed to be in a boundary lubrication state rather than a non-lubricated state. More specifically, it is assumed that due to a lubricating function realized when an accretion containing a yarn-derived lubricating component (mainly carbon) adheres to the travel surface by which the traveler <NUM> travels around the ring <NUM> and spreads thinly and evenly over the travel surface, solid contact between the metals constituting the ring <NUM> and the traveler <NUM> is suppressed, with the result that wear on the sliding surface is reduced. Further, it is assumed that the accretion is generated when cellulose fibers separate from the yarn Y that passes through the traveler <NUM> during spinning and these fibers becomes intertwined with wear debris from the traveler and so on. In Reference Document <NUM>, described below, it is reported that the frictional force generated between the ring <NUM> and the traveler <NUM> during spinning using a single spinning machine was half the frictional force of a test machine in which spinning was not performed. In Reference Document <NUM>, described below, it is reported that due to the lubricating function realized during spinning, the wear speed of the traveler <NUM> was lower than the wear speed of a test machine in which spinning was not performed. It is therefore evident that due to the lubricating function typically realized during spinning, frictional force can be reduced in comparison with a test machine in which spinning is not performed, with the result that wear can be suppressed, but wear cannot be prevented completely, meaning that solid contact cannot be prevented sufficiently. According to the present invention, the typical lubricating function of a ring/traveler system can be greatly improved by employing dimples.

In the ring/traveler system according to this embodiment, the plurality of dimples <NUM> are formed on the sliding surface on which the ring <NUM> and the traveler <NUM> slide as the traveler <NUM> travels. The yarn Y wound onto the bobbin via the traveler <NUM> generates wear debris in the form of cellulose fibers by sliding along the traveler <NUM>, which possesses surface roughness. At this time, fluff previously integrated with the yarn Y is sheared so as to separate from the yarn Y. Cellulose fibers in the wear debris, the fluff, and so on are generated in the sliding sites between the ring <NUM> and the traveler <NUM> and also fly out to the periphery thereof. Hence, when the cellulose fibers that separate from the yarn Y enter the sliding surface between the ring <NUM> and the traveler <NUM>, some of the fibers flow into the dimples <NUM> formed in the sliding surface, while the majority of the fibers move within the sliding surface such that a yarn-derived lubricating component contained in the fibers spreads over the sliding surface between the ring <NUM> and the traveler <NUM> and the inner surfaces of the dimples <NUM> in the form of a thin film. In other words, the cellulose fibers containing the yarn-derived lubricating component are believed to adhere in part to the dimples <NUM> so as to be held therein, and to flow while spreading over the sliding surface between the ring <NUM> and the traveler <NUM> in the form of a thin film. As a result, a film of accretion containing cellulose fibers is formed on the sliding surface between the ring <NUM> and the traveler <NUM>, and due to the lubricating function of the film, as well as a function thereof for preventing direct contact between the ring <NUM> and the traveler <NUM>, a wear-reducing effect is obtained. Hence, wear on the ring <NUM> and the traveler <NUM> can be suppressed even in an environment without liquid lubrication. In a typical ring <NUM> not having the dimples <NUM>, spaces for holding adhered cellulose fibers are limited to extremely small spaces that are formed between the ring <NUM> and the traveler <NUM> by the roughness on the respective surfaces thereof. When a ring <NUM> not having the dimples <NUM> is used, therefore, the volume of the spaces for holding adhered cellulose fibers is greatly reduced in comparison with a case where the ring <NUM> having the dimples <NUM> is used. As a result, when a ring <NUM> not having the dimples <NUM> is used, the surface area of the film believed to be formed by expansion of the accretion is extremely small in comparison with a case where the ring <NUM> having the dimples <NUM> is used, and this can be interpreted as the reason why the surface area of solid contact between the ring <NUM> and the traveler <NUM> increases.

To ensure that the lubricating function realized by the accretion remains in a favorable state, the dimples <NUM> must fulfill a function for storing the accretion containing the yarn-derived lubricating component and a function for resupplying the stored accretion to the sliding surface. In other words, the dimples <NUM> serve to maintain the lubricating function realized by the accretion by taking in and storing the accretion generated during spinning and resupplying the stored accretion to the sliding surface. Following in-depth study, the inventors found that the dimple wall surface angle θ and the value of P/D, as described above, are both closely related to the accretion storing function and the accretion resupplying function, as shown in <FIG>.

When considering the accretion storing function and the accretion resupplying function, it is necessary to ascertain the flow behavior of the accretion in the spaces between the traveler <NUM> and the ring <NUM>. Centrifugal force from the traveler <NUM> acts on the accretion as force (referred to hereafter as "vertical force") acting on the ring <NUM> in a vertical direction, while rotary force generated in the traveler <NUM> when the yarn Y is wound onto the bobbin acts on the accretion as shearing force. Hence, compressive force and shearing force act on the accretion simultaneously. Since wear is observed on the traveler <NUM>, it is clear that sufficient strength for preventing solid contact between the ring <NUM> and the traveler <NUM> is not generated when the aforesaid vertical force and shearing force act on the accretion. Accordingly, the accretion is believed to flow as the traveler <NUM> moves, thereby becoming sandwiched between the traveler <NUM> and the ring <NUM> so as to suppress solid contact. When the dimple wall surface angle θ is small, resistance to the flow of the accretion is low, and therefore the accretion moves more easily. When the dimple wall surface angle θ is large, on the other hand, resistance to the flow of the accretion is high, and therefore the accretion moves less easily. When the resistance is extremely high, it is thought that the accretion flows over the surface of the ring <NUM> while the cellulose that has accumulated in the dimples remains therein. The value of P/D, meanwhile, denotes a ratio of the length of the surface on which solid contact occurs to the length of the accretion stored in the dimples <NUM>. It is assumed, from the resulting increase in the useful life of the traveler <NUM>, that there is a period in which the accretion sandwiched between the ring <NUM> and the traveler <NUM> suppresses solid contact by forming a space while moving within a range of the length of the surface on which solid contact occurs.

It is believed that although vertical force acts on the ring <NUM> from the traveler <NUM>, an opposing force equaling or exceeding the vertical force is generated by the flow of the accretion. When the value of P/D is small, the accretion flows within the dimples such that the generated opposing force is insufficient, leading to a relative increase in surface pressure outside the dimples, and as a result, the accretion is removed, making solid contact between the ring <NUM> and the traveler <NUM> more likely to occur. When the value of P/D is large, the length on which the opposing force is generated increases, but since the amount of cellulose stored in the dimples is small, the space between the ring <NUM> and the traveler <NUM> in which the accretion spreads evenly is small, and as a result, solid contact is more likely to occur. The dimple wall surface angle θ and the value of P/D, i.e. the two elements required to store and resupply the accretion, are both linked to the flow of the accretion and must therefore be satisfied simultaneously. In a ring spinning machine, as is evident from the high-speed photographs of the traveler behavior shown in Reference Document <NUM>, described below, and the contact sites of the traveler in Reference Document <NUM>, described above, the contact sites of the traveler are not fixed. Hence, the dimple wall surface angle θ and the value of P/D cannot be determined by calculation, and therefore numerical values thereof are determined by experiment. More specifically, when the dimple wall surface angle θ is too large or too small, the accretion cannot be stored easily in the dimples and cannot be resupplied easily to the sliding surface. Likewise when the value of P/D is too large or too small, the accretion cannot be stored easily in the dimples and cannot be resupplied easily to the sliding surface. Therefore, the dimple wall surface angle θ is preferably not less than <NUM>° and not more than <NUM>°, and the value of P/D is preferably not less than <NUM> and not more than <NUM>. By prescribing the dimple wall surface angle θ and the value of P/D thus, the accretion can be stored easily in the dimples <NUM>, and the stored accretion can be resupplied easily to the sliding surface. Hence, the lubricating function realized by the accretion can be maintained in a favorable state, and as a result, the useful life of the ring/traveler system can be further extended. (Reference Document <NUM>) <NPL>.

To confirm the wear-reducing effect of the periodic structure portion <NUM>, the inventors evaluated the useful life of the components using rings <NUM> having dimples <NUM> formed under different conditions. Results are shown in <FIG>.

In <FIG>, the evaluation subject component is divided into example <NUM>, example <NUM>, example <NUM>, example <NUM>, example <NUM>, comparative example <NUM>, comparative example <NUM>, comparative example <NUM>, and comparative example <NUM>. In examples <NUM> to <NUM> and comparative examples <NUM> to <NUM> of these examples, the dimple sectional shape is a rounded cone shape. In example <NUM>, the dimple sectional shape is trapezoidal, and in comparative example <NUM>, the dimple sectional shape is rectangular. The formation conditions of the dimples <NUM> will be described in detail below.

In example <NUM>, the dimples <NUM> were formed under the following conditions: dimple wall surface angle = <NUM>°; P/D = <NUM>; dimple area ratio = <NUM>%; dimple diameter = <NUM>; dimple depth = <NUM>; dimple pitch = <NUM>. <FIG> is a front view of the dimples formed under the conditions of example <NUM>, and <FIG> is a sectional view of the dimples.

In comparative example <NUM>, the dimples <NUM> were formed under the following conditions: dimple wall surface angle = <NUM>°; P/D = <NUM>; dimple area ratio = <NUM>%; dimple diameter = <NUM>; dimple depth = <NUM>; dimple pitch = <NUM>. <FIG> is a front view of the dimples formed under the conditions of comparative example <NUM>, and <FIG> is a sectional view of the dimples.

Note that <FIG> do not necessarily show the dimensions of the dimples at the correct scale.

To evaluate the useful life, an unused traveler <NUM> was attached to each of the rings <NUM> in which the dimples <NUM> were formed under different conditions, as described above, and the useful life of the traveler <NUM> was checked in an actual machine test. The actual machine test was implemented in a dry condition environment using a ring spinning machine (RX240) manufactured by Toyota Industries Corporation, with the rotation speed of a spindle set at <NUM> rpm. The spindle rotates integrally with the bobbin while supporting the bobbin. The useful life of the traveler <NUM> was determined on the basis of the wear level of the traveler <NUM>. More specifically, the traveler <NUM> was determined to have reached the end of its useful life when the thickness of the traveler <NUM> decreased to half the initial thickness of the traveler <NUM> at the start of the test.

Further, to evaluate the useful life, the distance traveled by the traveler at the end of the useful life of the traveler <NUM> in an actual machine test implemented using a ring <NUM> not formed with the dimples <NUM> was set as a reference distance L (km). An actual machine test was then implemented for each of examples <NUM> to <NUM> and comparative examples <NUM> to <NUM>, and a result obtained by dividing the distance traveled by the traveler in each example and each comparative example by the aforesaid reference distance L was set as a useful life ratio.

As is evident from <FIG>, examples <NUM> to <NUM> satisfy both condition <NUM>, according to which the dimple wall surface angle θ is not less than <NUM>° and not more than <NUM>°, and condition <NUM>, according to which the value of P/D is not less than <NUM> and not more than <NUM>. Comparative example <NUM> and comparative example <NUM>, meanwhile, satisfy condition <NUM> but do not satisfy condition <NUM>. Comparative example <NUM> satisfies neither condition <NUM> nor condition <NUM>. Comparative example <NUM> satisfies condition <NUM> but does not satisfy condition <NUM>.

As regards the useful life, meanwhile, the useful life ratio is <NUM> in all of comparative examples <NUM> to <NUM>. Therefore, even when the dimples <NUM> are formed under the conditions of comparative examples <NUM> to <NUM>, the useful life of the ring/traveler system cannot be extended. In particular, it was learned that when the value of P/D is smaller than <NUM>, as in comparative examples <NUM> and <NUM>, the useful life of the traveler <NUM> does not increase even though the dimple wall surface angle θ satisfies condition <NUM>. It was also learned that the useful life of the traveler <NUM> does not increase when the value of P/D is larger than <NUM>, as in comparative example <NUM>. Hence, to extend the useful life of the traveler <NUM>, the value of P/D must be held within a range of not less than <NUM> and not more than <NUM>.

In all of examples <NUM> to <NUM>, on the other hand, the useful life ratio equals or exceeds <NUM>. Hence, by forming the dimples <NUM> under the conditions of examples <NUM> to <NUM>, the useful life of the ring/traveler system can be extended by a multiple of two or more in comparison with comparative examples <NUM> to <NUM>. In particular, when the dimples <NUM> are formed under conditions of dimple wall surface angle = <NUM>° and P/D = <NUM>, as in example <NUM>, the useful life of the traveler <NUM> increases by a multiple of <NUM>. Note that when the dimples <NUM> were formed under the conditions of examples <NUM> to <NUM>, the accretion generated during spinning spreads thinly over the sliding surface by a coverage of at least <NUM>%, or even at least <NUM>%, and this is assumed to lead to a further increase in the useful life of the ring/traveler system.

Further, the accretion generated during spinning is stored temporarily in the dimples <NUM>, but when the dimples <NUM> are too shallow at this time, the accretion may be stored in the dimples <NUM> in an insufficient amount. Therefore, the dimple depth S is preferably at least <NUM>, more preferably at least <NUM>, and even more preferably at least <NUM>. Note, however, that when the dimples <NUM> are too deep, it may be difficult to resupply the accretion to the sliding surface. Therefore, the dimple depth S preferably satisfies a condition of being not more than <NUM>.

Meanwhile, in examples <NUM> to <NUM>, the relationship between the dimple diameter and the useful life ratio is such that when the dimple diameter D is not less than <NUM> and not more than <NUM>, the useful life ratio equals or exceeds <NUM>. In examples <NUM> and <NUM> in particular, in which the dimple diameter D satisfies a condition of being not less than <NUM> and not more than <NUM>, the useful life ratio equals or exceeds a multiple of <NUM>. Hence, the dimple diameter D is preferably not less than <NUM> and not more than <NUM>, and more preferably not less than <NUM> and not more than <NUM>.

Furthermore, when the dimple area ratio is compared between comparative examples <NUM> to <NUM> and examples <NUM> to <NUM>, the dimple area ratio exceeds <NUM>% in comparative examples <NUM> and <NUM> and is <NUM>% in comparative example <NUM>, whereas in examples <NUM> to <NUM>, the dimple area ratio satisfies a condition of being not less than <NUM>% and not more than <NUM>%. In examples <NUM> to <NUM>, the useful life ratio is at least <NUM> times greater than in comparative examples <NUM> to <NUM>, and in examples <NUM> and <NUM> in particular, the useful life ratio equals or exceeds a multiple of <NUM>. Hence, the dimple area ratio is preferably not less than <NUM>% and not more than <NUM>%, and more preferably not less than <NUM>% and not more than <NUM>%.

In this embodiment of the present invention, the plurality of dimples <NUM> formed in the sliding surface between the ring <NUM> and the traveler <NUM> satisfy a condition according to which the dimple wall surface angle θ is not less than <NUM>° and not more than <NUM>° and a condition according to which the value of P/D is not less than <NUM> and not more than <NUM>. As a result, the accretion generated during spinning can be stored easily in the dimples <NUM>, and the stored accretion can be resupplied easily to the sliding surface. Hence, the lubricating function realized by the accretion can be maintained in a favorable state, enabling a large reduction in wear on the components of the ring/traveler system. According to this embodiment, therefore, the shape and arrangement of the dimples formed in the sliding surface between the traveler and the ring can be optimized, enabling a further increase in the useful life of the ring/traveler system.

The technical scope of the present invention is not limited to the embodiment described above and also includes embodiments realized by applying various modifications and amendments within a scope from which the specific effects obtained by the constituent elements of the invention and combinations thereof can be derived.

For example, in the above embodiment, an example in which the plurality of dimples <NUM> are arranged in a staggered pattern was described, but the present invention is not limited thereto, and the plurality of dimples <NUM> may be arranged in a lattice shape, for example.

Further, the spun yarn is not limited to cotton, and hemp, silk, wool, or chemical fiber (rayon, nylon, vinylon, or fleece), for example, may be used instead. Among these materials, cotton and hemp are preferable in consideration of the ease with which the accretion spreads over the sliding surface.

Moreover, the ring <NUM> forming the ring/traveler system is not limited to a ring including the flange 11a having a T-shaped cross-section and may be a ring including a tapered flange, for example. In this case, a traveler having a suitable shape for the tapered flange is used.

Claim 1:
A ring/traveler system for a ring spinning machine in which sliding is performed in an environment without liquid lubrication,
wherein a plurality of dimples (<NUM>), each having a circular open end (15a), are formed in a sliding surface on which a traveler (<NUM>) and a ring (<NUM>) slide as the traveler (<NUM>) travels,
wherein a periodic structure portion (<NUM>) is formed by arranging the plurality of dimples (<NUM>) periodically at a predetermined pitch, and
the plurality of dimples (<NUM>) satisfy a condition according to which a dimple wall surface angle (θ) is not less than <NUM>° and not more than <NUM>° and satisfy a condition according to which a value of P/D, where P is a pitch (µm) at which the plurality of dimples (<NUM>) are arranged over the periodic structure portion (<NUM>) and D is a diameter (µm) of the circular open end (15a), is not less than <NUM> and not more than <NUM>,
wherein the plurality of dimples (<NUM>) satisfy a condition according to which a diameter (D) of the circular open end (15a) is not less than <NUM> and not more than <NUM>,
wherein the dimple wall surface angle is denoted by an angle θ (°) formed by a main surface (14a) of the periodic structure portion (<NUM>) and a wall surface (15b) at the open end (15a) where the wall surface (15b) of the dimple (<NUM>) contacts the main surface (14a) of the periodic structure portion (<NUM>), characterized in that,
the cross-section of the dimples (<NUM>) is rounded cone shaped, pointed cone shaped or trapezoidal.