The present invention relates to a spinning ring for textile yarn spinning and more specifically relates to a spinning ring having a low friction, high durability bearing surface for supporting a traveler.
In conventional spinning and twisting operations, spinning or twisting rings are used to support a traveler that moves rapidly around the circumference of the spinning ring. The traveler engages and guides a loose yarn as it is being twisted and wound onto a twisting spindle.
An increase in spinning speed increases the rate at which the traveler rotates around the surface of the spinning ring thereby also increasing the centrifugal force applied between the traveler and the ring. In turn, the greater centrifugal force increases frictional heating of the traveler and the spinning ring while also increasing the abrasive force applied to the traveler and to the spinning ring. Accordingly, spinning speed increases can cause burn-off and/or shortening of the lifetime of the traveler, and also typically decrease the lifetime of the spinning ring because the bearing surface of the ring can spall, chip, or otherwise become roughened.
As spinning speeds are increased the resulting increase in frictional or abrasive forces between the traveler and spinning ring can cause breaks in the yarn being spun or twisted. Yam breaks are particularly undesirable because they lead to downtime in the spinning operation and, thus, a lower manufacturing efficiency. In general, for a given spinning ring and traveler combination, there exists a practical spinning speed limit that cannot be exceeded without frequent breakage of yams. For this reason, the choice of traveler and spinning rings (i.e. the construction of the traveler and spinning rings) can have a substantial impact on manufacturing efficiency.
Spinning ring durability also impacts substantially on manufacturing efficiencies and/or costs. In particular, degradation of the bearing surface of the spinning ring by spalling, chipping or the like, is normally a gradual process. As the bearing surface of the spinning ring degrades, the frictional characteristics of the bearing surface increase. Although in some cases the initial degradation of the spinning ring surface can be addressed by decreasing spinning speeds and/or by selecting travelers of different weight or construction, the manufacturing non-uniformities and potential disruptions associated with changes in the frictional characteristics of the ring surface are costly in many cases and undesirable in any event. Accordingly, the bearing surface of the spinning ring should preferably exhibit uniform frictional characteristics over a substantial period of time, even when the spinning operation is conducted at extremely high speeds.
Attempts to simultaneously address spinning ring surface durability characteristics while also achieving sufficiently low frictional characteristics to allow high spinning speeds have met with only limited success until recent times, due, at least in part, to the contradictory objectives associated with high durability surfaces, and those associated with low friction surfaces. Specifically, high durability surfaces that are resistant to abrasive force typically possess an inherent hardness sufficient to apply significant abrasive forces to a traveler. However, if surface hardness of the ring is decreased in order to decrease the abrasive characteristics of the surface, the durability of the ring surface generally also suffers.
In this regard the textile industry has recently developed spinning rings having ceramic coatings and co-deposited metal/abrasion resistant materials on the bearing surface thereof, to impart superior hardness and superior durability. However, in practice, these spinning rings generally require a substantial break-in period. During the break-in period, the spinning equipment is operated at a relatively low spinning speed because the surface of the spinning ring is initially too rough to allow operation at high speed. The low speed spinning operation allows the initially rough surface of the spinning ring to be conditioned by contact with a moving traveler. Such break-in periods can last for time periods of one month or longer, thus substantially decreasing manufacturing efficiencies.
More recently, spinning rings have been provided that are capable of high-speed operations over a period of several years. These rings have a bearing surface comprising an electrodeposited coating of hard, nodular chromium, and are described in U.S. Pat. No. 5,829,240, entitled xe2x80x9cSpinning Ring Having Improved Traveler Bearing Surfacexe2x80x9d issued Nov. 3, 1998, in the name of inventors Rio H. Benson and Gereon E. Poquette and assigned to A. B. Carter, Incorporated, the assignee of the present invention. In most cases, when these rings are treated in a polishing operation prior to use, only a relatively shortly break-in period is required prior to use of these rings in extremely high speed spinning operations. Nevertheless, in the case of fine yarns, break-in times of 1-2 weeks can be required in order to sufficiently condition the surface of the ring for use in high speed operations due to the relatively low weight travelers used in spinning fine yarns. The lighter travelers apply less conditioning force to the surface of the spinning rings and the lighter travelers are also more susceptible to damage with the result that the break-in period is longer and more travelers are used during the break-in period.
Although various conventional spinning rings can minimize or even eliminate break-in time for fine yarn spinning operations, these rings typically suffer from the undesirably low durability properties associated with spinning rings of conventional construction. For example, spinning rings described in U.S. Pat. No. 5,086,615, entitled xe2x80x9cCoated Spinning Rings and Travelersxe2x80x9d, issued in the name of inventor Bodnar, on Feb. 11, 1992, that have a surface coating with a particulate polymeric fluorocarbon dispersed in a metallic matrix, can have a very short break-in time requirement, but also typically have a useful life of less than about one year.
As detailed above, the textile industry desires a spinning ring that can impart increased durability and spinning speed over prolonged use periods without increasing the inefficient break-in period required to operate the device at standard productivity spinning speeds. To date, the successful modifications that have been used in conjunction with the spinning ring to improve durability and useful spinning speed have been hampered by typically requiring costly and sophisticated coating processes, modifications to the travelers used with the spinning rings and/or increased periods of break-in.
The present invention provides spinning rings having a traveler bearing surface that can be used at high productivity spinning speeds without spalling or cracking of the bearing surface of the spinning ring. The spinning rings of the present invention can be used in the as-manufactured state for high speed spinning of fine yarns; that is, no break-in period is required in order to achieve high speed spinning of fine yarns. Nevertheless, the spinning rings of the present invention have a hard and durable traveler bearing surface such that the rings can be used for high speed spinning without substantial degradation of the frictional characteristics of the traveler bearing surface of the spinning rings for periods of greater than about one year, typically longer.
The spinning rings of the present invention comprise an electroplated, hard amorphous chromium coating having a thickness of between about 0.05 mil (0.00005 in.) and about 1.5 mil (0.0015 in.), preferably between about 0.2 mil (0.0002 in.) and about 0.4 (0.0004 in.). The chromium plating can be applied to spinning rings formed from conventional base metals such as carbon steels and steel alloys. The frictional characteristics of the traveler bearing surface of the spinning ring are such that the ring can be used for high speed spinning in the as-plated state without the necessity of a polishing or conditioning treatment.
In particular, spinning rings of the present invention are capable of immediate use in a high speed spinning operation in which a 50 cotton count yarn is spun at a spinning speed such that the traveler moves at a velocity of at least about 35 meters per second for a period of at least about 3 days without burn-off of the traveler or other degradation of the traveler sufficient to require traveler replacement.
Preferably, the amorphous chromium coating applied to the spinning ring surface has a hardness exceeding at least about 900 Vickers hardness (HRc67), more preferably about 1,070 Vickers hardness (HRc70) or greater. Despite the extremely hard and durable surface of the spinning ring, the ring can be used with conventional travelers at high speeds without break-in or conditioning of the spinning ring surface.
The amorphous, hard chromium coatings employed in the present invention can be smooth or nodular, preferably smooth. However, the coatings generally exhibit a bright satin white appearance having a brightness less than that of the bright, mirror-like surface of conventional bright chromium plating. As compared to the nodular, crystalline, hard chromium coatings employed in Applicant""s assignee""s commercially available high durability spinning rings, the chromium coatings employed in the present invention are generally brighter in the as-plated state, even in the case of a nodular amorphous chromium coating.
The improved durability of the chromium coatings employed in the present invention is believed to be due to the absence of shear planes within the matrix of the chromium coating. In particular, conventional electrodeposited hard chromium coatings are crystalline in nature with the result that stresses applied to the chromium coating are concentrated along the shear planes of the crystalline chromium coating matrix. The absence of a crystalline structure in the chromium coatings employed in the present invention greatly improves stress distribution because there is no stress concentration along shear planes so that fatigue cracking which is characteristic of conventional chromium coatings, is avoided in the spinning rings of the present invention.
The spinning rings of the present invention can be prepared using known commercially available technologies. Hard amorphous chromium plating technology is well known in the art and can be applied according to various processes including electroplating processes, incorporating an organic additive in a somewhat modified conventional hard chromium plating process.
Amorphous chromium coated spinning rings according to the present invention provide numerous benefits and advantages. The elimination of the necessity for a break-in, or conditioning period can substantially improve manufacturing efficiencies in the spinning operation. The time and costs associated with manufacture of the spinning rings of the present invention are substantially improved since polishing operations for improving surface finish prior to use of the spinning rings are not necessary.