GB2145220A - Yarn fault detector installations - Google Patents

Abstract

A yarn fault detector installation has a plurality of lever means (2) each for guiding a yarn. The lever means (2) are actuated individually in the event of a yarn fault. Baffles (4) are attached to the lever means (2) and can cut a beam of light transmitted through a tube (6) which is detected by a detector (10) when the appropriate lever is actuated, so causing the baffle to move into a slot (36) in the tube (6). Each lever means (2) includes a first lever (14) biased upwardly by an even-centre spring (18), and a second lever (22) coupled to a baffle (4) and resting, when in normal use, on the thread supported by the first lever (14). Excessive tension in the thread will cause the first lever (14) to spring into a downwardly-biased position, allowing the second lever (25), together with the baffle (4), to fall into the alarm position. A yarn break, irrespective of whether preceded by excess tension, will similarly release the second lever (25) to fall to the alarm position. An extension of the baffle (4) may protrude through a slot (40) to give a visual warning and to enable the faulty yarn to be identified. <IMAGE>

Description

SPECIFICATION Yarn fault detector installations The invention relates to yarn fault detector installations for use particularly but not exclusively on knitting machines.

Electro-optical systems for detecting yarn faults are known for example from the Nickell U.S. Patent Specification 3,530,690. These systems are very sensitive and do not detect excessive yarn tension.

The Brooks GB patent Specification 444,128 describes an electro-optic system in which the movement of a dropper or lever actuates a disc to interrupt a light beam. There is considerable friction and inertia and the system cannot be extended easily.

It is amongst the objects of the invention to provide a simple, reliable and versatile yarn fault detecting installation.

According to the invention there is provided a yarn fault detector installation having a plurality of lever means for guiding yarn and actuatable individually in the event of a yarn fault in which baffles are individually associated with the lever means, a beam of light is transmitted through tubes means, and a detector registers a yarn fault whenever one of the baffles interferes with the transmission of light through the tube means. The common beam services a plurality of yarn ends yet a clear ON/OFF signal can be obtained in a simple manner by the baffles.

Preferably each of the lever means include a first resiliently supported lever deflectable in the event of excess yarn tension and a second lever for resting on the yarn and movable in the event yarn breaks or the first lever is deflected and the baffles for each of the lever means is a flag movable conjointly with the second lever. Both excessive tension and slackness or breaking oftheyarn can be detected.

Suitably the tube means includes one or more members having an internal passage with reflective walls and the flags enter through slots in the member to block the transmission of light along the internal passage. The tube means confine the light and permit low light levels to be used. Advantageously the flags and member are shaped so that part of the flag projects for visual fault indication when a particular lever means is actuated. Thus even though there is only one detector for a plurality of yarn ends, nevertheless an operator can easily determine which yarn end is subject to a fault. The tube means also permit a construction in which a LED and photodetector are mounted at the end of the passage(s) and are connected in circuit to arrest the machine and/or provide an audio and/or visual fault indication.The accuracy of the assembly for generating the light beam is thus ensured automatically. Conveniently the members and flags are located substantially internally of a housing to reduce ambient light intrusion.

Drawings: Figure 1 shows a section through a yarn fault detector installation according to the invention illustrating the normal component position; Figure 2 shows a section as shown in Figure 1 but illustrating the actuated position after an excess of yarn tension has occured; and Figure 3 shows a front view of the installation of Figure 1 with a front cover partly removed.

Particular description With reference to Figures 1 to 3, a yarn fault detector installation includes a plurality of lever means. Three such means are shown side by side in Figure 3 but of course any number may be used provided the function is not affected. For each lever means 2 there is also provided a baffle 4 which will operate in a manner to be described. A tube means 6 extends along all of the lever means 2 to convey light from one end generated by a light emitting diode at 8 to a photodetector at the other end 10 (see Figure 3) The lever means 2 are mounted on a U-bracket 12 fastened to a housing 46. The lever means 2 includes a first lever 14 pivotted about 13. A spring 18 extends from a spring anchor 16 on top of the housing 46 to the lower part of a U-support 20 fitted between the mounting bracket 12.On pivotting the lever 14 the spring 18 swings through the dead-centre position so that the lever 14 is resiliently pulled either upwards by the spring at one end of its pivotal movement or sprung downwards by the spring 18 at the opposite end of its pivotal movement.

The lever means 2 includes a second lever 22 consisting of a block 24 into which a pair of wires 25 are fitted to extend out of the housing 46 between the first resilient lever 14. The block 24 also mounts a wire 26 carrying the baffle 4. Because of gravity the lever 22 is always biassed downwards.

In operation yarn 28 extends over a smooth V-shaped part at the end of the first lever 14 and under the hooked part of the wires 25.

The tube means 6 include one or more tube members 30 which may be of a convenient length to ensure that the light is transmitted without excessive loss. The tube memember 30 (see Figure 3) has internal passages 32 with reflective walls 34. The tube member 30 is provided with slots 36 so as to permit the baffles 4 to enter and extend transversely across the internal passages 32 so as to block the transmission of light through it. The baffle 4 is made longer than necessary to block the passage 32. The extra part passes over the internal passage 32 and projects through a slot 40 in the housing 46 at its far end 38.

A light emitting diode can be fitted inside a housing which is plugged into the internal passage 32. The front of the housing 46 may be closed off by a cover 48 provided with windows 49 through which the yarn engaging parts of the lever 14 and lever 22 may project for operation.

In normal operation the lever means 2 are in the position illustrated in Figure 1. The tension of the spring 18 may be adjustable so as to vary the overcentre force. The baffle end 38 is over the internal passage 32 and fully inside the housing 46.

The lever 14 is held up by the spring 18 and the lever 22 including the wire 26 mounting the baffle 4 is held in its position by the length of yarn extending between both legs of the lever 14 (see the right-most lever means 2 in Figure 3).

Figure 2 shows the position occupied by the lever means 2 following the occurrence of excessive yarn tension. As a result of the excessive yarn tension the yarn pulls down the lever 14 until it can slip offthe end of the lever 14. In so doing the yarn tension overcomesthetension imparted by the spring 18. As a result of the lowering of the lever 14 and thereby the yarn, nothing resists the downward movement of the lever 22 as a result of gravity. Consequently the block 24 with the wires 25 and the wire 26 is pivotted so that the baffle 4 blocks the internal passage 32 of the tube member 30. At the same time the end 38 of the baffle 4 projects through a slot 40 in the housing 46 to indicate visually which of the lever means 2 has been subjected to a yarn fault.

In the event that a yarn were to break, the lever 14 would remain in the position illustrated in Figure 1.

However the restraint against downward movement of the lever 22 would be removed. The lever 22 would pivot bodily with the baffle 4 so that the same end result would emerge as that described with reference to Figure 2.

In Figure 3 the position shown in Figure 1 is shown on the left hand side of the Figure. The position shown in Figure 2 is shown in the middle Figure. The position shown on the right hand side corresponds to that shown on the left hand side, but shows the yarn passing over the first lever 14.

Using the installation described a plurality of lever means 2 can be monitored using a singie light source 8 and detector 10. By the aid of the tube means 6 it is possible to detect the insertion of a baffle 4 across the internal passage 32 in a reliable simple fashion even though the light source has to transmit light along a considerable length. The arrangement is constructionally very simple and the optical components do not have to be mounted with a very high accuracy.

The invention may be modified in a variety of ways. The lever 22 may consist of a single wire 20 that may be integral with the baffle 4. The tube means 6 may include a tube member of square cross section for enhanced strength and ease of mounting but be provided with an internal passage 32 of round or other suitable cross section. Light may be retro reflected through the tube.

Claims (7)

1. A yarn fault detector installation having a plurality of lever means for guiding yarn and actuatable individually in the event of a yarn fault in which baffles are individually associated with the lever means, a beam of light is transmitted through tube means, and a detector registers a yarn fault whenever one of the baffles interferes with the transmission of light through the tube means.

2. A yarn fault detector installation according to claim 1 in which each of the lever means include a first resiliently supported lever deflectable in the event of excess yarn tension and a second lever for resting on the yarn and movable in the event yarn breaks or the first lever is deflected and the baffles for each of the lever means is a flag movable conjointly with the second lever.

3. A yarn fault detector installation according to claim 2 in which the tube means includes one or more members having an internal passage with reflective walls and the flags enter through slots in the member to block the transmission of light along the internal passage.

4. A yarn fault detector installation according to claim 3 in which the flags and member are shaped so that part of the flag projects for visual fault indication when a particular lever means is actuated.

5. A yarn fault detector installation according to claim 3 or claim 4 in which a LED and photodetector are mounted at the end of the passages and are connected in circuit to arrest the machine and/or provide an audio and/or visual fault indication.

6. Ayarn fault detector installation according to any of claims 3 to 5 in which the members and flags are located substantially internally of a housing to reduce ambient light intrusion.

7. A yarn fault detector installation substantially as described herein and shown with reference to the Figures.