EP1012368A1

EP1012368A1 - Yarn supply method for tufting machines

Info

Publication number: EP1012368A1
Application number: EP98938756A
Authority: EP
Inventors: Michael John Potts
Original assignee: COBBLE BLACKBURN Ltd
Current assignee: Spencer Wright Industries Inc
Priority date: 1997-08-08
Filing date: 1998-08-06
Publication date: 2000-06-28
Anticipated expiration: 2018-08-06
Also published as: GB9716716D0; EP1012368B1; DE69802698D1; WO1999007931A1

Abstract

A method and apparatus for controlling a yarn feed system for a tufting machine is disclosed. The method involves determining a length of yarn required for a particular stitch, selecting a start time at which additional yarn can be introduced into the yarn feed and selecting a rate of supply of additional yarn into the stitch. The method allows precise control of yarn feed even when extreme forms of sliding needlebar movement are used in a tufting machine.

Description

YARN SUPPLY METHOD FOR TUFTING MACHINES

The present invention relates to a method and apparatus for the control

of the yarn feed mechanism of a tufting machine and particularly, but not

exclusively, to such a method and apparatus for use in a tufting machine using

a sliding needlebar.

When a conventional, plain, straight sewing tufting machine is running,

the amount of yarn required by each needle remains constant for each stitch

in the tufted fabric produced on the machine. The yarn supply for each needle

of the tufting machine is conventionally provided by yarn feed rollers which are

geared directly to the machine mainshaft.

When a tufting machine is run using a sliding needlebar to produce a

prescribed geometric stitch pattern, the length of yarn required per stitch

varies stitch by stitch according to whether the stitch is sewn straight or at an

angle by sliding the needlebar. If the correct length of yarn per stitch is not

supplied then the face of the resulting tufted fabric can be uneven which is

clearly undesirable.

Systems for providing yarn feed nominally matched to the usage

requirements of a sliding needlebar stitch pattern are well known. None,

however, work perfectly, partly due to the inability of drive systems to

produce sufficient torque to accelerate or decelerate the yarn feed rollers at

the required rate and partly because of insufficient versatility in the way that

the yarn feed systems are controlled. An additional complication is that yarn

characteristics such as twist, count regularity, stretch, friction, fibre content, tension and propagation characteristics, nominal time taken for a change in

tension or other load on the yarn to be propagated from one end of the yarn

to another vary widely and therefore different yarns require handling in

different ways to obtain the desired length of yarn for a given stitch.

In an existing system the nominal length of yarn used in each type of

stitch occurring within a pattern is calculated and stored in a computer.

Provision is also made to allow manual adjustment of the stored lengths.

These length values are used to control servo controlled drives which operate

the yarn feed mechanism to provide the required length of yarn for each stitch

in sequence. The end result in terms of levelness of the tufted fabric pile face

obtained using this system is unsatisfactory due to both the ability to

sufficiently control the prescription of the input of yarn by the yarn feed

mechanism and also the ability of the drive system to respond to the

prescription on a stitch by stitch basis at machine running speed.

The ability of the drive system to respond is addressed in our co-pending

U.K. Patent Application No. 2297331 -A which describes how the inertia of the

drive system can be reduced.

It is an object of the present invention to provide an improved control

system for the yarn feed systems of tufting machines which enables tufted

fabric of level face to be produced by sliding needlebar machines.

According to a first aspect of the present invention there is provided a

method of controlling a yarn feed system for a tufting machine wherein the

method comprises selecting a length of yarn required for a particular stitch, selecting a starting time (as herein defined) to introduce the additional yarn (as

herein defined) into the stitch, selecting a rate of supply of the additional yarn

into the stitch.

By additional yarn is meant yarn over and above that which would be required for a straight sewn stitch.

By starting time is meant as the point in a stitch cycle at which

additional yarn begins to be supplied into the stitch.

The present invention enables the variable drive of a yarn feed system

to be controlled by way of three parameters. The first parameter, the length

of additional yarn required per stitch, is specified by the length of yarn required

for a particular stitch as in conventional systems. The two additional

parameters allow adjustment of the feed start time of the additional yarn and

the rate at which that additional yarn is supplied. Enabling control of these

features of yarn supply enables fabrics with a good quality face to be

produced even where extreme forms of sliding needlebar movement are used.

By specifying these three parameters it is possible to achieve optimum

conditions for the feeding of a particular fabric, yarn type, and capability of the

yarn feed drive system. This can be achieved by observing the quality of face

of fabric produced and then adjusting one or more of the parameters

accordingly.

The three parameters can be readily understood by tufting machine

setters, whereby they can make appropriate adjustments to the yarn feed

parameters to improve the quality of fabric produced. Such adjustment is not possible with existing equipment where only the yarn length per stitch is

selected.

According to a second aspect of the present invention there is provided

apparatus for controlling a yarn feed system for a tufting machine wherein the

yarn feed system is controlled in dependence upon selected values of the

length of yarn required for a particular stitch, the starting time (as herein

defined) for additional yarn supply (as herein defined) and the rate of supply

of the additional yarn.

The apparatus preferably comprises a computer which is arranged to

calculate the appropriate control parameters, based on a particular fabric

design. Provision to manually adjust each of the parameters is preferably also

provided.

The apparatus preferably includes a display means which may take the

form of a computer monitor. The display means is preferably arranged to

show a selection diagram which enables an operator to select the start point

in the stitch cycle for the extra yarn input, and also the rate of the extra yarn

input.

The apparatus of the present invention provides a convenient way for

a machine operator to select the operational parameters of a yarn feed system

for a tufting machine. The selection of the three above defined parameters

gives an operator far more control over a yarn feed system than with

conventional yarn feed system control equipment. This enables an improved fabric or carpet to be produced, particularly the control apparatus enables a

fabric with a fiat face to be produced by a sliding needlebar tufting machine.

In order that the invention be more clearly understood there is now

described an embodiment thereof, by way of example, with reference to the

accompanying drawing which illustrates an on screen selection diagram to

facilitate selection of start point and yarn input rate.

Yarn feed control apparatus is provided by a computer. The computer

serves a similar function as an existing pattern control computer used in

conjunction with a tufting machine. The computer is arranged to convert any

specific pattern of needle placement for a prescribed needle gauge and stitch

rate along the fabric into a list of yarn control parameters. The yarn control

parameters include a list of the required lengths of yarn, stitch by stitch,

throughout the pattern, selectable yarn feed start times which specifies the

point in a stitch cycle at which the yarn required, additional to that required

to form a normal straight stitch, is introduced and selectable additional yarn

introduction rates. These three parameters are used to control the operation

of the servo-controlled drive of a yarn feed system.

There is also provided provision for manual adjustment of these

parameters, to enable account to be taken of fabric type, condition etc.

Referring to the drawing there is illustrated an on screen selection

diagram, displayed by the apparatus. The diagram comprises a yarn feed rate

graph 1 and a yarn introduction curve 2.

The yarn feed rate graph represents along the horizontal axis 3 one stitch cycle. The vertical axis 4 represents the amount of additional yarn

introduced. Ten possible yarn introduction rates 5 are illustrated, these may

be selected by use of a cursor or inputting a number into the computer.

The yarn introduction curve 2 represents stitch cycles and illustrates the

movement of a needle through one stitch cycle from its uppermost 6 to its

lowest 7 position and return to the upper position 8. The point in the cycle at

which the additional yarn is introduced is selected by positioning arrow 9 on

the curve 2. The position of the arrow may be selected by use of cursor keys

or a computer mouse.

In use the control apparatus would be provided with fabric pattern

details and optionally, information regarding the yarn to be used from which

the control parameters are calculated, at which point the control parameters

may be manually revised. An operator would then operate a tufting machine

in accordance with the control parameters to produce a sample length of

fabric. Adjustments to the control parameters may then be made by the

operator on the basis of the fabric sample to optimise the produced fabric.

The present invention allows more control to be exercised over the

fabric feed to a tufting machine and enables improved carpets and fabrics to

be produced. Control is exercised by three parameters which are well

understood by persons skilled in the art and more particularly tufting machine

operators and setters. This enables the machine operator to easily make

adjustments to the machine control to rectify faults in and improve fabric

production. The above embodiment is described by way of example only, many

variations are possible, without departing from the invention.

Claims

1 . A method of controlling a yarn feed system for a tufting machine

wherein the method comprises selecting a length of yarn required for a

particular stitch, selecting a starting time (as herein defined) to introduce the

additional yarn (as herein defined) into the stitch, selecting a rate of supply of

the additional yarn into the stitch.

2. Apparatus for controlling a yarn feed system for a tufting machine

wherein the yarn feed system is controlled in dependence upon selected values

of the length of yarn required for a particular stitch, the starting time (as herein

defined) for additional yarn supply (as herein defined) and the rate of supply

of the additional yarn.

3. Apparatus according to claim 2 comprising a computer which is

arranged to calculate appropriate control parameters, based upon a particular

fabric design or characteristic.

4. Apparatus according to claim 2 or claim 3, wherein means to manually

adjust each of the parameters is added to the apparatus.

5. Apparatus accordingly to any one of claims 2 to 4, wherein the

apparatus includes a display means.

6. Apparatus according to claim 5, wherein the display means comprises

a computer monitor.

7. Apparatus according to claim 5 or claim 6, wherein the display means

is arranged to show a relevant diagram which enables an operator to select the

start point in the stitch cycle for the extra yarn input, and also the rate of extra yam input.

8. A method of controlling a yarn feed system of a tufting machine

substantially as hereinbefore described with reference to the accompanying

drawings.

9. Apparatus for controlling a yarn feed system of a tufting machine

substantially as hereinbefore described with reference to the accompanying drawings.