GB2156867A

GB2156867A - A device for positive thread delivery on textile machinery

Info

Publication number: GB2156867A
Application number: GB08508307A
Authority: GB
Inventors: Peter Barth
Original assignee: Sipra Patententwicklungs und Beteiligungs GmbH
Current assignee: Sipra Patententwicklungs und Beteiligungs GmbH
Priority date: 1984-04-04
Filing date: 1985-03-29
Publication date: 1985-10-16
Also published as: GB8508307D0; SE8501100D0; JPS60215853A; SE8501100L; DE3412550A1

Abstract

The thread delivery device includes a guide drum 15 with a thread bearing surface 26 which extends with continuous curvature from an inwardly tapering initial location 25 to an outwardly widening end region 27. The bearing surface 26 is provided, at least in the region of the initial location 25, with a friction- promoting covering, and the thread 23 is fed to the drum 15 by way of a rigid thread guide member 24 which is aligned with the initial location 25 of the guide drum 15 and is drawn off from the drum 15 by way of a thread guide member 28 which is likewise fixed in operation. When thread tension is lacking on the removal side, the thread looped around the guide drum 15 slips into the region of smaller drum diameter and is no longer co-moved by the guide drum 15. <IMAGE>

Description

SPECIFICATION A device for positive thread delivery on textile machinery This invention relates to a device for positive thread delivery on textile machinery comprising a carrier having a drivable guide drum for the thread and thread guide members on the feed side and on the removal side of the guide drum.

In the case of knitting machines, for example, such devices function to constrainedly or positively feed thread to a knitting location so long as the thread is being knitted there. If the knitting operation is interrupted at the knitting location this positive thread feed ceases. In order to achieve the desired change between thread transport by way of a guide drum and interruption of the thread transport and vice versa, various measures have already been proposed. Thus, for example, it is known to bring about positive thread feed by means of a delivery belt which is common to several thread delivery devices and which butts only against a part of the thread bearing surface of the guide drum.

With such a device, the thread can be selectively guided, by means of mechanically or electrbmechanically swingable thread guide members, onto that region of the guide drum which is free from the delivery belt, where it is no longer co-moved by the guide drum, or else it can be moved under the delivery belt which butts against the guide drum so that it is positively fed. The adjusting movement of the relevant thread guide member can, in this respect, be controlled as a function of the tension on the thread (DE-AS 28 36 717).

It is also known to design thread guide members so as to be swingable in the circumferential direction of the guide drum as a function of the thread requirement at a processing location. In this instance the thread will contact the surface of the guide drum over a smaller or a larger circumferential distance and it will be co-moved by the driven guide drum only in the case of the larger contact distance (DE-OS No. 33 01 450). It is also known to provide a part of the cylindrical guide drum with a high friction covering and to make the other part smooth and, by swinging the relevant thread guide members, to cause the thread to be conveyed by abutment against the friction region or to cause it to stand still by abutment against the smooth region of the driven drum.

The aforesaid solutions all have the disadvantage that they necessitate mechanical or electromechanical adjustment of device parts, which not only means considerable technical complexity, but also means that either a certain inertia has to be overcome upon the change-over of these devices from the thread delivery position to the thread rest position, or, if spring bias of thread guide members is used, the thread is exposed to a tensile loading which is increased by this spring bias.

The object of the invention is to design a device, of the kind mentioned at the beginning hereof, which avoids the above-mentioned disadvantages, and which, without adjustment of device parts during operation and solely depending on tension or pull exerted on the thread from a processing location, brings about the switch-over from positive guidance of the thread to non-feeding of the thread and vice versa.

This object is achieved in accordance with the invention, in that the guide drum has a bearing surface extending with continuous curvature from an inwardly tapering initial region to an outwardly widening end region, and having, at least in the vicinity of the initial region, a friction-promoting covering, in that the thread guide members on the feed side and the removal side are arranged so as to be stationary in operation relative to the guide drum, and in that the thread guide member on the feed side is aligned with the initial region of the guide drum.

With the device in accordance with the invention no adjustment of thread guide members takes place during operation. If, from a thread processing location, a pull is exerted on the thread guided over the guide drum, the thread runs positively or constrainedly into the greater diameter initial region of the bearing surface, where the friction-promoting covering of the bearing surface ensures positive entrainment of the thread. If the thread pull is abolished, because no thread is being processed at the processing location, the thread which has become slack (i,e. free of tension) slips from the initial region to the centre of the guide drum, in other words into a guide drum region of smaller diameter.Even if a friction-promoting covering is also present in this region thread entrainment does not take place, but this is especially so if the bearing surface in this region of the guide drum is kept completely smooth. In this respect, the thread reacts rapidly and with fine sensitivity to changes in the thread tension, and immediate stopping or starting of positive thread feed by the driven guide drum ensues.

The applicant has already proposed a thread delivery device in which the bearing surface of the guide drum extends with continuous curvatures from an inwardly tapering initial location to an outwardly widening end region.

However, this proposal was made only for thread storage and delivery devices in which several thread windings are arranged side-byside as stock on a storage drum which windings have to slip downwards on the storage drum in such a way that each individual thread winding does not overlie another. The possibility of guiding a thread by way of such a drum in such a way that it is in certain circumstances moved by contact with the drum and in other circumstances slips over the drum surface was not envisaged at that time.

In the device in accordance with the invention, a thread brake can be connected prior to the thread guide member on the feed side.

The friction-promoting covering on the guide drum can advantageously be in the form of an exchangeable elastically expansible sleeve. Also, the sleeve may advantageously cover only the initial region of the bearing surface of the guide drum, in which case the edge of the sleeve on the bearing surface side will be inserted into a circumferential groove in the bearing surface of the guide drum, so that the continuous curvature of the thread bearing surface of the guide drum is maintained in a stepless manner.

The thread guide member on the feed side, which is preferably rigid, is advantageously shaped as a. thread guide eye. The axis of the thread guide eye is advantageously directed tangentially to the initial region of the bearing surface of the guide drum so as to facilitate the sliding down and sliding up of the thread from or respectively to the initial region of the guide drum as a function of the thread pull at the take-off location.

One of the thread guide members can also be arranged so as to be adjustable around the periphery of the guide drum yet securable for operation in order to be able to adapt the looping region of the thread on the guide drum to the different friction value of different kinds of thread.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematised overall view of a first embodiment of the thread delivery device of the invention; Figure 2 is an enlarged view, half in crosssection, of one type of guide drum which forms part of the device shown in Fig. 1; Figure 3 is a view, similar to Figs. 2, of a second.type of guide drum; Figure 4 is a view from below of a second embodiment of the thread delivery device of the invention which is provided with a thread guide eye which is variable in position.

Fig. 1 shows a device in accordance with the invention for a circular knitting machine.

A device housing 10, which is preferably designed as an elongate hollow body, has a recess 11 adjacent one end into which mounting rail 1 2 of the knitting machine frame (not shown) engages. The device housing 10 can be clamped to this mounting rail 12 by means of a clamping bolt 1 3. Arranged at the other, free end of the elongate device housing 10 is a thread brake 14 which is not shown in detail.

Arranged on the underside of the device housing 10 is a guide drum 1 5 which is securely connected to a vertical shaft 1 6 extending through the device housing 1 0. This shaft 1 6 also carries two belt pulleys 1 7 and 18 on its part which projects above the upper side of the device housing 10. Butting against each belt pulley 17, 1 8 is a respective driving belt 19, 20 each of which is common to several thread guide devices. The two belt pulleys 17, 18 can be selectively coupled to the shaft 1 6 by means of an axially-displaceable clutch disc 21.

Arranged on the upper side of the device housing 10, at the free end thereof, is a first thread guide eye 22 by way of which a thread 23 is supplied to the thread brake 14. The thread 23 is indicated by a dot-dash line and is supplied from a yarn spool (not shown) in the direction of the depicted arrow 24. A further thread guide eye 24 is fixedly attached to the underside of the device housing 10 and it lies behind the thread brake 14 in the thread passage direction.The axis of this thread guide eye 24 is directed tangentially to an initial edge region of a bearing surface 26 of the guide drum 1 5. The bearing surface 26 of the guide drum 1 5 extends with a continuous curvature from the initial edge region 25 to the lower edge 27 of the drum 15, that is to say the drum diameter tapers from the initial edge region 25 inwards and then increases again outwards up to the lower drum edge 27. After the thread 23 has been fed through the rigid thread guide eye 24 it travels a full revolution around the guide drum 1 5 and is drawn off tangentially, and obliquely relative to the lower edge 27 of the guide drum 15, to a thread guide member 28.The thread guide member 28 is anchored on the underside of the device housing 10 at the opposite end to the feed side thread guide eye 24, and after passing therethrough the thread 23 is fed in the direction of the depicted arrow 29a to a knitting location (not shown) of the circular knitting machine.

The enlarged view of the guide drum 1 5 given in Fig. 2 shows the continuously curved course of the thread bearing surface 26 of the guide drum 1 5 from the upper inwardlydirected initial edge region 25 as far as the lower edge 27 of the thread bearing surface 26, where the guide drum 1 5 merges into an edge bead 30. As is evident from the righthand sectioned half of the guide drum 15, the entire drum circumference, including the entire thread bearing surface 26, is covered with a sleeve 31 made from an expansible rubberelastic material, the surface of which has a higher coefficient of friction than, for example, a smooth metal surface.

If a pull is exerted on the thread 23 in the direction of the arrow 29a from a thread processing location, the thread 23 assumes the run-off course shown with a dot-dash line in Fig. 2. The thread thus extends around the entire guide drum 1 5 in the upper initial edge region 25 with its relatively larger drum diameter and is then drawn off from the drum 1 5 obliquely downwards in the direction of the thread guide member 28. In this respect, because of the thread tension or pull a snug abutment of the thread 23 against the thread bearing surface 26, which is formed by the sleeve 31 of the guide drum 15, is achieved, which leads to slipfree entrainment of the thread 23 by the rotating guide drum 1 5.

When operation of the knitting machine or other textile machine at the thread processing location is interrupted, or the machine is switched off, the pull on the thread in the direction of the arrow 29a ceases, and the thread 23 slips downwards from the initial edge region 25 of the inwardly-curved thread bearing surface 26 into the central reduced diameter region of the guide drum 1 5 and remains there approximately on the thread course which is shown with a broken line and identified by the reference number 23a in Fig.

2. In this slack or tension-free state the thread 23 slips on the thread bearing surface 26 despite the sleeve 31 and it is not entrained by the guide drum 1 5 which continues to rotate. As soon as tension or pull in the direction of the arrow 29a from the processing location becomes effective again on the thread 23, the thread again assumes the path shown in dot-dash lines and is co-conveyed by the guide drum 1 5.

Fig. 3 shows a guide drum 15' which is composed of two halves 15a' and 15b'. The dividing line 32 between the two drum halves 15a' and 15b' extends perpendicularly to the axis of the shaft 1 6 somewhat above the minimum diamter location of the thread bearing surface 26'. In this embodiment, only the upper half 15a' of the drum is covered by a sleeve 31' made of rubber-elastic material. In other words only the upper initial region 25' of the bearing surface 26' is provided with a surface covering which increases the thread bearing friction, whilst the thread bearing surface region 33 located thereunder has a smooth polished surface.The lower edge 34 of the sleeve 31' is inserted into an annular groove 35 formed in the surface of the guide drum 15' along the dividing line 32 in such a way that over the entire width of the thread bearing surface 26' a smooth stepless curvature is still afforded. In this embodiment, when thread tension (pull) is lacking the thread 23 looped around the drum 15' slips down from the course which is shown in dotdash lines in the bearing region 25' onto the course 23a which is shown in broken lines and is in the smooth bearing region 33.

A thread drum having a curvature course as disclosed in DE-AS 27 43 749 has also proved to be advantageous when carrying out the present invention.

In the embodiment shown in Fig. 4, the thread guide eye 28" on the thread removal side is mounted on an arm 36 which is swingable coaxially relative to the guide drum 15" but is capable of being secured for operation, so that the looping angle for the thread 23 on the guide drum 15" can be adjusted. In other words, the arm 36 can be adjusted for take-off from the drum at any desired location so that the looped path of the thread around the drum may be varied.

Claims

1. A device for positive thread delivery on textile machinery comprising a carrier having a drivable guide drum for the thread and thread guide members on the feed side and on the removal side of the guide drum, characterised in that the guide drum has a bearing surface extending with continuous curvature from an inwardly tapering initial region to an outwardly widening end region, and having, at least in the vicinity of the initial region, a friction-promoting covering, in that the thread guide members on the feed side and the removal side are arranged so as to be stationary in operation relative to the guide drum, and in that the thread guide member on the feed side is aligned with the initial region of the guide drum.

2. A device as claimed in claim 1, characterised in that a thread brake is connected prior to the thread guide member on the feed side.

3. A device as claimed in claim 1 or 2, characterised in that the friction-promoting covering is in the form of an exchangeable elastically expandable sleeve.

4. A device as claimed in claim 3, characterised in that the sleeve covers only the initial region of the bearing surface and its edge on the bearing surface side is inserted into a groove in the bearing surface of the guide drum.

5. A device as claimed in any of claims 1 to 4, characterised in that the rigid thread guide member on the feed side is shaped as a thread guide eye, the axis of which is directed tangentially to the initial region of the bearing surface of the guide drum.

6. A device as claimed in any of claims 1 to 5, characterised in that one of the thread guide members is arranged so as to be adjustable around the periphery of the guide drum yet securable for operation.

7. A device for positive thread delivery on textile machinery substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2, or Figs. 1 and 3, or Fig. 4.

of the accompanying drawings.