PNEUMATIC YARN SPLICER

Abstract: A pneumatic yarn splicer comprises a splicer body (6) which defines a splicing chamber in which yarns to be spliced are disposed. The chamber has an open side and open ends, and comprises a first portion (16) extending from one end and merging with a second portion (18) extending from the other end. A pad is provided for closing the open side of the chamber, and a port (10) in the chamber wall normally substantially opposite the open side, provides for delivery of an air blast to splice yarns in the chamber. The cross section of the first chamber portion (16) is restricted relative to that of the second portion (18).

Description: PNEUMATIC YARN SPLICER This invention relates to pneumatic yarn splicing. This process has numerous advantages over traditional methods of joining textile yarns such as knotting, principally because spliced yarns offer improved appearance and processing efficiency. Splicing is firmly established in the textile industry, and in many applications its use is mandatory in order to achieve acceptable standards of yarn quality. In one form of splice, the yarns to be joined are introduced from opposite ends of the splicer. They are laid in a splicing chamber, and the chamber is sealed by a moveable component known as a chamber pad. The waste ends of the two yarns are cut by knives at either end of the chamber. Air is introduced into the chamber as a high pressure blast, which intermingles the fibres of the yarns. When the blast is turned off, the pad is opened to allow the spliced yarn to be removed. The splice is symmetrical in form, and usually has a neat appearance. This form of splice is described as "ends-opposed". In an alternative form of splice, both yarns are introduced from the same end of the splicer. The waste ends of the two yarns are cut at the other end of the chamber. The splice is asymmetrical in form, and usually has a "tail" several millimetres long projecting to one side. This form of splice is described as "ends-together". The ends-together splice has a relatively poor appearance, but it is popular because it is quick to make, and in many situations its inferior appearance is unimportant. Further, some yarns pose technical problems which render ends-together splices the only joints that can be made. When the blast enters the chamber in a splicing process, the yarn components are subjected to a turbulent air-stream, moving at high velocity; the dynamics of the system are very complex. If splicing is to be successfully accomplished, the system must remain relatively stable while certain processes take place. With both ends-opposed and ends-together splices, two separate physical processes must occur in quick succession: a) mixing of the fibres of the yarn components b) intermingling of the fibres of the mixed bundle If either process is deficient, the splice will fail. If the mixing process is unsuccessful, then the intermingling stage is irrelevant; it succeeds only in consolidating each component, but does not join them together. In practice, the two yarn components are quickly blown out of the splicing chamber without a splice being formed. If the mixing process is successful, but the intermingling is poor, then the splice is unsatisfactory. When the splice is withdrawn from the chamber, it may appear acceptable, but it will have little or no strength. Splicing chambers are designed to maximise the efficiency of the two processes of mixing and intermingling. In some respects, however, the performance of splicers is unsatisfactory. In some circumstances, the dynamics of the system within the splicing chamber can become unstable, with the result than the yarns are quickly ejected without a splice being formed. This invention is concerned only with ends-together splicing. In the formation of an ends-together splice the two yarns are introduced to the splicing chamber together, from one side and are secured, usually by yarn clamps. The air blast normally enters the splicing chamber before the yarn bundle is cut, and exhausts roughly equally to left and right of the chamber. With the yarn bundle secured by yarn clamps, the system is in dynamic equilibrium. Once the yarn bundle is cut, the system becomes inherently unstable. The yarn bundle remains secured by a clamp on the entry side of the chamber, but is no longer restrained at the cutting side. If any asymmetries are introduced into the system, the yarn bundle will usually move away from the side which is unrestrained. It will therefore have a tendency to blow out of the chamber on the entry side. If the fibres of the yarns mix and intermingle quickly, then a splice will form by the time the bundle is ejected. If little or no mixing and intermingling takes place, then the two yarns will be ejected as separate entities, without a splice being formed. In general, a satisfactory ends-together splice can be made only if the yarn bundle remains in the chamber for a critical period. To combat the inherent instability, some means of controlling the residence time within the chamber is needed, to inhibit the ejection of the bundle until the fibres have had an opportunity to intermingle. The yarn bundle needs to be restrained. Poor restraint will result in a wide variation of residence time, and splices of variable quality; positive restraint will result in tight control of residence time, and consistent splices. Additionally, the splicing chamber should be configured to encourage the efficient mixing and intermingling of the films. Splicers can be fitted with timers, which control the duration of the blast. With ends-together splices, however, a timer will not control residence time; the yarn will blow out of the chamber if the bundle becomes unstable, no matter what the duration of the blast. The residence time of the ends-together splice can be controlled to some degree by careful choice of the geometry of the splicing chamber, the size of the chamber being chosen to match the yarn very precisely. Friction between the yarn and the chamber wall then inhibits the movement of the yarn bundle. This means of conferring stability is fairly effective, but it demands the use of a large number of chambers if a wide range of yarns is to be spliced. The present invention addresses both the above issues and is directed at a splicer which in a given arrangement, can be used for a wide range of yarn types and sizes, and in which residence time is controlled more precisely by the use of a positive system of restraint. According to the present invention, this is accomplished by dividing the splicing chamber into two portions. A first portion extends from one end, and merges with a second portion extending from the other end, with a port being formed in the chamber wall of the second portion for delivery of an air blast to splice yarns in the chamber. The cross-section of the first chamber portion is restricted relative to that of the second portion and in use, the yarns to be spliced are laid in the first portion with their free ends extending into the second portion, where the splice is in due course formed. This system is essentially a modification of that disclosed in our International Patent Application No. GB95/01481 and offers essentially similar advantages, with the additional advantage of not requiring a restrictor plate to be fitted to one end of the splicing chamber. Thus, the need to select different splicing chambers to suit the characteristics of yarns to be spliced is substantially obviated, and the system is essentially passive, requiring no moving components. It allows the yarns to enter the chamber unhindered, and the completed splice to leave the chamber easily, without undue intervention by the operator. Further, by encouraging the efficient mixing and intermingling of yarns in the enlarged section, and controlling the geometry of the splicing chamber end, the system can substantially ensure retention of the yarns within the chamber for a time which permits the formation of an acceptable splice. In a pneumatic splicer according to the invention, a splicer body defines a splicing chamber for receiving the yarns to be spliced, the chamber having an open side with a pad for closing the open side. The chamber comprises a first portion extending from one end and merging with a second portion extending from the other end, the body being formed with a port in the chamber wall of the second portion for delivery of an air blast to splice yarns in the chamber. The cross-section of the first chamber portion is restricted relative to that of the second portion, to provide the benefits set out above. The cross-section of one or both of the first and second chamber portions is normally substantially uniform along its length. The cross-section of the first portion of the splicing chamber is normally generally V-shaped, preferably taking the form of a trapezium with sides converging towards the base. The trapezium is preferably an isosceles trapezium with a typical apex angle of 20° to 40°. The cross-section of the first chamber portion in a splicer according to the invention is typically around half that of the second portion. The preferred cross- section for the second portion is substantially U-shaped, with the base of the U normally being semi-circular. The base of the first chamber portion is preferably located just below the base of the second portion; ie, further from the closing pad. The invention will now be described by way of example and with reference to the accompanying schematic drawings wherein: Figures 1, 2 and 3 show a transverse cross-sectional view of a splicing chamber in which an "ends-together" splicer is being formed. Figure 4 shows a perspective view of a splicer body in an embodiment of the invention; Figure 5 is a plan view of the splicer body shown in Figure 4 ; and Figure 6 is a sectional view taken on line VI-VI of Figure 4. In Figures 1 to 3 the individual fibres of the two yarns to be spliced are shown in different shades. Initially, the yarns 2 and 4 are laid in the splicing chamber 6 and the open side of the chamber then closed by a chamber pad 8, as shown in Figure 1. The air blast port 10 is shown at the base of the chamber, opposite the open side. When the air blast 12 enters the chamber 6 as shown in Figure 2, the coherence of each yarn is disturbed; the fibres are separated, and move so that the fibres of one yarn become intimately mixed with those of the other. This process continues until the mixed fibres align themselves in the respective yarns, and intermingle as shown in Figure 3. The completed splice can then be withdrawn from the chamber 6, either through the open side after removal of the pad 8, or through the open end from which the spliced yarns enter. Without a restraint system, there is a risk that the yarns will be ejected from the chamber through the respective open end without or prior to the splice being formed. In the embodiment of the invention illustrated in Figures 4 to 6, the splicing chamber is divided into two portions 16 and 18. The first portion 16 has a uniform cross-section in the form of an isosceles trapezium with an apex angle of 30°. The cross-section of the second portion 18 is substantially U-shaped, with the base of the U being substantially semi-circular. As can be seen, the base 20 of the first chamber portion is substantially flat, and located just below the base of the second portion 18. The air blast port 10 is located in the second portion 18 close to the junction with the first portion, and typically substantially equidistant from the two ends of the splicing chamber, as shown in Figure 5. To use the splicer, yarns are laid in the first chamber portion 16 with their ends extending into the second portion 18 and normally beyond the section containing the air blast port 10. The chamber is then closed by lowering of the pad (not shown in Figures 4 to 6) , and the air blast delivered. When the blast enters the chamber, the restricted cross-section of the first portion 16 effectively directs exhaust air out through the wider open end of the second portion 18 where most of the air will leave. This generates a biasing force towards that end, which assists in retaining the yarn bundle in the chamber while the splice is made. Since the yarn bundle cannot easily blow out of the chamber, the fibres are given time to mix and intermingle. With continuous filament yarns, as mixing and intermingling proceeds, the bundle begins to twist up and, as it contracts, is drawn back across the blast hole. With staple yarns loose fibres are blown away during this phase. The length of the yarn bundle on the knife or cutting side reduces, and the biasing force reduces correspondingly. Finally, the force is exceeded by that acting back toward the entry side. The yarns are pushed back towards the entry side, and expelled. Although the splicer described herein is particularly useful for yarns of larger diameters it can be used very effectively with quite small yarns. The differential between the cross-sections of the two chamber portions and the location of the air blast port create a pressure balance within the chamber that encourages tidy and self-regulating splicing for a wide range of yarn sizes and types.

Claims: CLAIMS 1. A pneumatic yarn splicer in which a splicer body defines a splicing chamber for receiving yarns to be spliced, the chamber having an open side with a pad for closing the open side, and comprising a first portion extending from one end and merging with a second portion extending from the other end, the body being formed with a port in the chamber wall of the second portion for delivery of an air blast to splice yarns in the chamber, wherein the cross-section of the first chamber portion is restricted relative to that of the second portion. 2. A yarn splicer according to Claim 1 wherein the cross-section of at least one of the first and second chamber portions is substantially uniform along its length. 3. A yarn splicer according to Claim 1 or Claim 2 wherein the cross-section of the first portion of the splicing chamber is a trapezium. 4. A yarn splicer according to Claim 3 wherein the trapezium is an isosceles trapezium. 5. A yarn splicer according to Claim 4 wherein the apex angle of the trapezium is in the range 20° to 40°. 6. A yarn splicer according to any preceding Claim wherein the cross-section of the first chamber portion is substantially half that of the second portion. 7. A yarn splicer according to any preceding Claim wherein the cross-section of the second chamber portion is substantially U-shaped. 8. A yarn splicer according to Claim 7 wherein the base of the U-shape is a semi-circle. 9. A yarn splicer according to Claim 3 and Claim 8 wherein the apex of the trapezium is below the base of the U-shape. 10. A yarn splicer according to any preceding Claim wherein the junction between the first and second chamber portions is substantially midway between the chamber ends.

Inventors: WATERS GRAHAM THOMAS, WATERS, GRAHAM, THOMAS
Applicants: PENTWYN PRECISION LTD, WATERS GRAHAM THOMAS, PENTWYN PRECISION LTD., WATERS, GRAHAM, THOMAS
Application year: 1995
Main classification: B65H69
IPC codes: B65H69