GB1563653A - Yarn changing apparatus for knitting machine - Google Patents

Description

(54) YARN CHANGING APPARATUS FOR KNITTING MACHINE (71) We, ASA S.A. a French Body Corporate of, 58 Boulevard Baron du Marais, 42300 ROANNE, France, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for changing the supply yarns in a circular knitting machine having a plurality of knitting systems.

In known apparatus of this type, yarn changing units are carried by a stationary part of the knitting machine and each unit is provided with a movable programming device (such as a drum equipped with pins, perforated film, or a chain with selectively composable links) acting selectively on the corresponding yarn guides, all the devices being themselves controlled, during their movement. by a single control device carried by one of the rotating elements of the machine.

These installations allow several yarn guides to be employed in each yarn changing unit. Also, because the movements are controlled bv the associated programming devices and because of the use of a single control device they offer high operating security, independent of the amplitude of the movement required for the yarn guides.

On the other hand, given the side-by-side arrangement of the various yarn guides of each unit and the synchronisation of their selection and their activation by the same control device, there is a certain imprecision in the engagement of the respective yarns by the needles, the yarns being held differently from one yarn guide to another. Moreover, the necessity of having space available for each knitting system, especially on machines with a large number of systems. limits the allowable space available for each programme device. and, as a consequence. its selection capacity, which considerably reduces the scope of the machine.

Certain types of installations are also known in which each of the yarn changing units has an electro-magnet associated with each yarn guide and the selection takes place prior to the passage of the control device which activates only the yarn guides selected, under the control of a general programme. Since only one programme device is necessary, such installations provide practically unlimited selection possibilities for the machine, whilst simplifying the task of the operator. On the other hand, however, they require the use of a large quantity of selection electro-magnets and of energising circuits with which these have to be associated.

A modified proposal is for the electromagnets for each yarn changer selectively to move the respective yarn guides in front of an additional electro-magnet, which, in replacing the control device, activates only the yarn guide selected at each operation.

However, in addition to an increase in the number of electro-magnets used, this arrangement does not allow the simultaneous use of several yarn guides.

In further proposals, generally intended for knitting machines with stationary needle beds. the yarn changing units are mounted on the rotating cam carrier, and a control cam, common to all the yarn changing units and carried by a stationary portion, can be moved vertically by means of a programme mechanism which is also stationary, in such a way as to act selectively on a portion projecting at the level corresponding to the yarn guide to be selected, and to place the latter in the active position.Again, howev er. this type of installation does not allow the simultaneous use of several yarn guides, while although such installations are suitable for circular machines with stationary needle beds generally having a low density of knitting systems, they are difficult to adapt to machines with rotating needle beds having a large number of systems, in which, whilst being capable of communicating a relatively large amplitude displacement to the yarn guide, the control device must be supported by a rotating part of the machine, and at the same time must be able to be selectively moved with precision between two extreme positions when passing between two consecutive yarn changing units.

According to the present invention there is provided apparatus for changing the supply yarns in a circular knitting machine, having a plurality of knitting systems, the apparatus including yarn changing units to be associated with the knitting systems and each comprising a plurality of yarn guides, each yarn guide being selectively movable between an inactive position and an active position in which, in use yarn is supplied to the needles, the yarn guides being movable by means of a selection device controllable by a programme to act during relative movement between the yarn changing units and the selection device, and including mobile elements respectively associated with the yarn guides and each of which can be moved between two positions without causing movement of the associated yarn guides and to a third position during movement to which it causes the associated yarn guide to move from said inactive to said active position; the selection device including at least one selector effective selectively to place each mobile element in one or other of the said two positions. and a control device effective to move mobile elements which are positioned in a particular one of said two positions into the third position.

With this arrangement small movements in the selection device can give rise to larger but precise movements of the yarn guides, of which several can be employed in each unit. The yarn can be held in the same way by each unit and numerous selection possibilities of yarn are available.

It is advantageous for the mobile elements to be pivotable.

Preferably, the mobile elements are movable in one direction between the said two positions and are movable in a second direction substantially perpendicular to the first direction in movement to the third position.

Preferably, also, there is at least one advance device effective to move the mobile elements from a first to a second of said two positions prior to selection, wherein the selector is effective to move non selected elements back to the first position, and wherein the control device is effective to act on selected elements, which have remained in the second position, in order to move them to their third position.

There may be, in the selection device, at least one pusher effective to move those elements previously in their third position away from the control device, and preferably there is also a return cam effective after such movement to bring those elements back to their first position. As the pusher, there may be a member movable by selected elements upon movement to the third position and acting during its movement on these elements already in the third position in order to pivot them within the range of the or a return cam.

The selector may include an electromagnet selectively energisable by the programme during relative movement between the selection device and the yarn changing units to act magnetically on the mobile elements when in their second positions and to retain selected elements in the second position. The ectro-magnet may also be effective to act on elements when in the third position. Alternatively, each mobile element may have a selection stud, the selection studs being staggered relative to one another, and the selection device includes a series of superimposed selectors each associated with a selection stud, and movable between an active position in which it acts on the associated selection stud to make the respective element pivot from the second back to the first position, and an inactive position in which it does not influence the stud so that the element remains in the second position.for the return of the yarn guides, each mobile element may have additional studs in a tiered formation and so arranged that selectors in the inactive positions act on additional studs of any element previously in the third position.

The invention will be more clearly understood from the following description which is given by way of example only with reference to the accompanying drawings in which: Figure 1 is a simplified view, in perspective and radial cross-section of a portion of a circular knitting machine with two beds of rotating needles, showing two yarn changing units of an apparatus in accordance with the invention with which the machine is equipped: Figlo-e 2 is a radial cross-section along the line AA, of the portion of the machine represented by Figure 1. the place of the cross-section also passing through the selection device common to all the yarn changing units: : Figure 3 is a horizontal cross-section along the line BB of Figure 2. showing the selection device as well as the lower portions of three adjacent yarn changing units; Figure 4 is a front view. along the arrow F, of the same selection device; Figure 5 atid 6 show. schematically and in perspective, the arrangement of the principle elements of one of the yarn changing units and of the selection device in the course of two of the operating phases of the apparatus; Figure 7 is a detailed view, in profile cross-section, of the selection device, along the line CC of Figure 4; Figures 8 and 9 illustrate in detail the arrangements for, respectively, holding and controlling the selector organs of the selection device represented in Figures 3, 4 and 7; Figure 10 illustrates an alternative selection device;; Figure 11 is a view in a radial cross-section similar to that of Figure 2, showing an alternative embodiment of apparatus of the invention; Figures 12 and 13 are views respectively in cross-section and in perspective, showing a particular means for returning yarn guides to their inactive position and appropriate to the apparatus of Figure 11; Figure 14 is a plan view, partially in cross-section, of a yarn cutting device which apparatus of the invention may include; and Figure 15 is a radial cross-section of the device of Figure 14.

In the knitting machine partially represented in Figures 1 and 2, vertical needles 1 and horizontal needles 2 are arranged to slide in respective grooves of a rotating cylinder 3 and of a dial 4, which integral with a dish-shaped holder 5. The control of the knitting systems takes place in a conventional manner, by means of cams which are not shown, which are fixed to a stationary vertical cam carrier 6 and to a section assembly 7 external of a horizontal cam carrier 8 which is also stationary. Two knitting systems of the machine are shown in Figure 1 together with yarn guiding components 9, carried by the sections 7 and provided with slits 10 intended to lead a supply yarn to the needles.

Associated with each of the knitting systems is a yarn changing unit 11, 11a these units including four yarn guides 12, 13. 14 and 15 for four separate yarns. One end of each yarn guide is provided with an eyelet 16 for guiding a yarn, and is selectively moveable between an inactive or lower position, otherwise known as a rest position, and an active or upper position, otherwise known as a work position. in which the yarn is supplied to the needles via the guiding component 9. In Figure 1. only the yarn guides 15 and 12 of the yarn changing units 11 and lia respectively are in their work positions, with their eyelets 16 being above the level of the horizontal needles.The other yarn guides are in their rest positions with their eyelets 16 below the level of the horizontal needles, and the corresponding yarns are then held by means of a holding device 17 associated with each unit. This device 17, which can comprise a holding means for each yarn or a single holding means for all the yarns and which can be made integral with a yarn cutting device, is shown schematically.

The yarn guides 12 to 15 of each of the units are slidable longitudinally in grooved elements 18, 19 of a housing 20 extending radially above the section assembly 7. To allow access to the sections and to facilitate the introduction of the yarns into the eyelets 16 of the yarn guides, each housing can pivot upwards (Figure 2) about an axis 21 carried by an upper portion of a holder 22 fixed to the horizontal cam carrier 8. This holder 22 comprises a cylindrical downwardly extending portion 23 intersecting the cam carrier 8 and penetrating inside the dishshaped rotating holder 5. An elastically retractable screw 24 is provided in order to hold the housing in its lower position by holding it against the upper portion of the yarn guiding component 9 of the knitting system concerned.

For each yarn guide, the trajectory followed by the end carrying the guiding eyelet 16 in passing from one position to the other, is determined by a longitudinal opening 25 in the yarn guide, the sides of which engage with a pin 26 passing through the housing 20 at the end opposite the point at which it is pivoted. The other end of the yarn guide is hinged on one of the arms 27 of a two-armed lever 28 which is pivotally mounted about the axis 21, and the other arm 29 of which comprises a seat for the upper end of a push-rod 150, the four yarn guides of each unit being associated with respective pushrods 120, 130. 140, 150.This push rod is arranged perpendicularly to the cam carrier 8 and is a free fit in one of the grooves made in the cylindrical part 23 of the holder 22, so that its lower end can pivot radially of the machine between two positions without the position of the yarn guide with which it is associated being affected. whilst it is also capable of sliding vertically whereupon the yarn guide will move from one position to the other.

Figures Sand 6 show that the lower portion of each push-rod is provided with a control butt. respectively 125. 135, 145, 155, with a selection stud 120a, 130b, 140c, 150d, and with three additional studs (respectively 122, 123. 124; 131, 133. and 134; 141, 142 and 144; and 151. 152 and 153). In addition, facing the outside of the machine the pushrods each have a single return stud 126, 136, 146 and 156. The particular arrangement of these various studs, as well as their function, will become evident from the description below in relation to the selection device.

The assembly 30 of the selection device is carried by a plate 31 fixed to the base of the dish-shaped rotating holder 5 and penetrates inside the latter through an opening 32. This selection device 30 comprises an element 33 with a U-shaped profile, and which, with a portion 34 of the same profile arranged concentrically to the dish-shaped rotating holder, makes up an annular guide, inside which the lower ends of the pivoting push rods associated with the yarn guides can move both vertically and radially. The portion 34 of the annular slide can either be incorporated in the base of the dish-shaped holder 5, or made up of several separate elements fixed to this base.The top of the outisde limb of the slide 33 is arranged to be contacted by the bases of the return studs 126, 136, 146 and 156 to determine the inactive position of the respective yarn guides in the case where the push-rods take up the low position and where their lower ends are located nearer the outside of the machine. When the push-rods take up a high position with their lower ends nearer the centre of the machine, it is the top of the inside limb of the annular guide which, contacted this time by the bases of the control studs 125, 135, 145 and 155. determines the active position for the respective yarn guides and holds them in this position.

The inner limb of the guide 33 has an indentation 35 having a horizontal portion positioned slightly below the level of the base of the control studs when in the low position. A ramp 36 leads upwards from the horizontal portion in the direction of rotation of the holder 5 and constitutes a control cam intended to raise the push-rods to their high positions. An advance cam 37 is fixed to the outer limb of the guide 33, opposite the beginning of the indentation 35 in the sense of rotation, and acts on the lower ends of the push-rods in order to urge their lower ends radially towards the centre of the machine so as to place their respective control studs in the path of the ramp 36.

A return cam 38, also fixed to the outside limb of the slide 33, has a descesding ramp 39 downstream of the end of the ascending ramp 36, relative to the direction of rotation of the holder 5. and this ramp 39 acts on the return stud of the push-rods in the high position, which corresponds to the active position of the varn guide. to bring the push-rods back to their low position.

The selection of the push-rods. and consequently of the yarn guides with which they are associated. takes place via four superimposed pivoting selectors 40a. 4()b. 4Oc and 40d. extending radially between two parallel pillars 41 and 42 which fixed to the plate 31 inside the guide 33 (Figures 3. 4. 7, 8). Each selector comprises, at one end, two points 43 which penetrate into conical seats of two regulating screws 44 and 45 carried by the pillars 41 and 42, and defining two horizontally spaced pivots for the selectors.

At the ends opposite their pivoting axes, the selectors are each provided with a control lug 46 having a ramp 47, and intended to act on the selection studs 120a, 130b, 140c and 150d, as will be described later. The amplitude of the vertical displacement allowed for the control lugs 46, when the selectors pivot, is determined by the respective sides of a series of tiered grooves 48 formed in lateral shoulders 49 and 50 of the two pillars (Figure 7).

For the selective control of the selectors, four electro-magnets 51a, 51b, 51c and 51d are arranged side by side on the plate 31 between the two pillars 41 and 42, each electro-magnet comprising a mobile armature 52a, 52b, 52c and 52d linked by a clip 53 to the corresponding selector, the mobile armatures, and consequently the selectors, being urged upwards by means of tension springs 54.

Figure 10 illustrates a variation in the method of fixing the selectors which in this case consist of spring blades 55, fixed ends of which are held in a strut 56 between the two pillars 41 and 42, this eliminating the return springs.

Selective energising of the windings of the electro-magnets. and consequently pivoting of the selectors downwards in opposition to the force of the springs 54, is carried out by reading of an information programme carried by a stationary device, by means of electric wires 57 joined to brushes 58a, 58b, 58c and 58d, carried by a sleeve 59 of the stationary horizontal cam carrier 8 and urged by springs against collector rings 60a, 60b, 60c, 60d and 60n, centered on the holder 5 and linked by other electric wires 61 to the respective electro-magnets. The stationary programme device can employ for example an optical film. a punched tape, a matrix or any other known information carrier.

Whereas the control studs 125, 135, 145 and 155 are all situated at the same level, the various selection studs 120a, 130b. 140c and 15()d are staggered from one push-rod to the other, in such a way that when the yarn guides are in the rest position, these studs correspond to the respective levels of the control lugs 46 of the four pivoting selectors 40a. 40b, 40c and 40d when. as is usual. they are urged upwards under the action of their return springs. In addition, the four studs have sufficient vertical space between them to avoid any contact with the control lugs of the selectors when these are moved downwards under the action of the mobile armature of the corresponding electro-magnets.This arrangement of the selection studs is particularly clear in Figure 5, which also illustrates the method by which the selection of one of the yarn guides of a yarn changing unit is effected.

The selection device carried by the dishshaped rotating holder 5 moves in the direction of the arrow G. Assuming that initially the four yarn guides of the unit in question are all in the rest position, the lower ends of the respective push-rods are engaged between the two uprights of the annular guide 34, as shown by the broken line in Figure 2. The advance cam 37 acts successively on the lower ends of the four push-rods and pivots them towards the centre of the machine, so that their respective control studs 125, 135, 145, and 155 are engaged with the horizontal portion of the indentation 35 of the guide 33. As illustrated in Figure 5, the selector 40b has in opposition to its return spring 54, been displaced downwards by the movement of the mobile armature 52b of the electro-magnet 51b which is selectively energised.During the revolution of the holder 5, the control lug 46 of the selector 40b passes below the corresponding selection stud 130b and so the push rod 130 remains in the same position, and its control stud 135 is subsequently engaged by the ramp 36 and then slides onto the inside limb of the annular guide 33. The push-rod thus moves the yarn guide 13 with which it is associated, during its upward movement. so as to place that yarn guide in its active position where it ensures a supply of yarn to the needles of the machine (Figure 2).On the other hand. the selection studs 120a, 140c and 150d, of the three other push rods are pushed back by the ramps 47 of the control lugs 46 of the associated selectors 40a, 40c and 40d and the push-rods 120, 140 and 150 pivot back to their initial positions, so that the yarn guides 13, 14 and 15 with which they are associated remain in the rest position.

The arrangement and the method use of the three additional studs 122. 123 and 124: 131, 133 and 134: and 141. 142 and 144 and 151, 152 and 153 of the push-rods 120. 130.

140 and 150 are illustrated more particularly in Figures 5 and 6. On each push rod. these three additional studs are placed between the control stud and the selection stud at levels such that. if the push-rod in question has been moved to its high position bv the ascending ramp 36. each of the additional studs will be positioned on a level with one of the control lugs 46 of the other three selectors with which it is not normally associated when these selectors are moved downwards, that is to sav they are selected by their respective electro-mignets.

Figure 6, which shows what happens when a new selection is made. in this case the selector 40d has been moved downwards by the movement of the mobile armature ot the electro-magnet 52d. While the push-rod 130 which was selected during the previous operation, has remained in the high position during the rotation of the holder 5, the three push-rods 120, 140 and 150 have again been pivoted towards the direction of the centre of the machine under the action of the advance cam 37.During the passage of the selectors, only the selection studs 120a and 140c of the push rods 120 and 140 are pushed back by the control lugs 46 of the selectors 40a and 40c, whilst the selection stud 150d of the push-rod 150 is not acted upon by the selector 40d and it engages with the ascending ramp 36, so that the corresponding yarn guide 15 is placed in the active position to feed the needles with a new yarn.

The lug 46 of the selector organ 40d, on the other hand, pushes back the additional stud 134 of the previously raised push-rod 130, which has the result of pivoting the latter towards the outside of the machine, whereupon its return stud 136 is engaged by the return cam 38 and the push-rod 130 returns to its low position, causing the yarn guide 13 to return to the inactive or rest position.

This particular use of three additional studs therefore allows an easy exchange of yarn guides under the sole control of the selection programme. without it being necessary for a supplementary mechanism to be introduced.

In the embodiment illustrated by Figures 11 to 13, which is generally the same as that previously described, the assembly of superimposed selectors has been replaced by a single electromagnetic selector 62 acting directly on the push-rods associated with the yarn guides. The electro-magnet 62 is controlled by pulses synchronised to the passage of the selector in front of the push-rods and transmitted by reading the programme using brushes 63 and 64 rubbing against two collector rings 65 and 66 on the rotating holder 5. Each push-rod. 220, 230, 240 and 250, is provided with an elastically deformable portion 67 and has but one stud 68.The selector comprises a permanent magnet 69 against which all the studs 68 are applied by the action of the advance cam 37 acting on the lower parts of the push-rods, an electromagnet 70 controlled selectively by the pulses of the programme. and a second permanent magnet 71 for the purpose of temporarily holding the push-rods selected by the electro-magnet. The selection device comprises a push cam 72 intended to deform the elastic portions 67 whilst the control studs 68 are acted upon magnetically. The push-rods which are not held selectively by the electro-magnet 70 return to their initial position under the relaxation effect of their elastic portions 67. whilst selected push rods are lifted up by the ascending rap 36.

Figure 11 shows that in order to provide for the return of the push-rods, and consequently the yarn guides, under the control of the selection programme, the push cam 72 has a height sufficient to deform the elastically deformable portions 67, whether the push-rods are in their low position or whether they are in their high position. The push-rods are available to be subjected to the effect of the electro-magnet 70 at each rotation of the dish-shaped holder 5, while push-rods placed in the high position during a previous selection and which are not held magnetically by the electro-magnet 70, pivot towards the outside of the machine, so that their respective return studs are placed within range of the return cam 38.

Figures 12 and 13 illustrate the return of the push-rods under the control of the selection programme. For reasons of convenience, the principle elements represented in Figure 12 are assumed to be viewed from inside the machine. The control stud 68 of each push-rod has a notch 74, into which can be located a pivoting member 73 carried by the inside limb of the guide 33 and placed in the indentation 35. Each time that a control stud 68 is engaged by the ascending ramp 36, it lifts the member 73.

The upper part of the member 73 has an inclined surface 75 which engages the bases of the control studs 68 of any push rods which were placed in the high position during a previous selection, and causes these push-rods to pivot towards the outside of the machine so that their respective return studs are placed within range of the return cam 38.

In known yarn changers each unit or even each yarn guide has an associated means of holding tye yarn. and a yarn cutting device comprising a fixed blade and a mobile blade which is activated by means of a mechanical system which takes up too much space to be mounted in a machine having a multitude of knitting systems.

In the installation described herein. each yarn changing device has, as represented in Figures 14 and 15. a means for holding the yarn 80 which includes two plastic components 81, for example made of "Vulkolan".

pressed into a housing 82 in opposition to springs 83. The two components 81 are held in their housing 82 by the fixed blade 84 of the varn cutting device. A mobile blade is in the form of a roller 85 fixed via a spring 87 on to the same support 88 as a yarn taker 89, the support 88 being fixed to a rotating part of the knitting machine. There is only a single mobile blade for all the yarn changing units.

When a yarn guide is brought back to the rest position, the varn taker engages the yarn and carries it into the gripping device 80 and brings it also into contact with the fixed blade 84. The mobile blade 85. which arrives a little later, then cuts the yarn which remains held in the gripping device 80.

Since the control of the yarn guides is not carried out directly, but via mobile elements which have been previously selected in selection movements which can be of low amplitude, the apparatus is of particular interest when applied to circular knitting machines with a great number of knitting systems, in which the yarn changing units are very close together.

It goes without saying that other embodiments can be envisaged without going outside the scope of the invention. For example it would be possible to use, insofar as the push-rods associated with the yarn guides are concerned, mobile elements which are not linked directly to the yarn guides, in which case means to hold the yarn guides separately would be provided. In the same way, the advance cam, designed to be common to all the mobile elements, could be eliminated by providing a spring associated with each element. Where, as described. the selection of the mobile elements is by one or more electro-magnets, alternative means of transmitting both the selective digital signals and the energy required could be envisaged. The electrical connections between the stationary portions and the rotating portions of the apparatus could be obtained by, for example, induction.

WHAT WE CLAIM IS: 1. Apparatus for changing the supply warns in a circular knitting machine. having a plurality of knitting systems, the apparatus including yarn changing units to be associated with the knitting systems and each comprising a plurality of yarn guides, each yarn guide being selectively movable between an inactive position and an active position in which, in use yarn is supplied to the needles, the yarn guides being movable bv means of a selection device controllable by a programme to act during relative movement between the yarn changing units and the selection device, and including mobile elements respectively associated with the yarn guides and each of which can be moved between two positions without causing movement of the associated yarn guides and to a third position during movement which it causes the associated yarn guide to move from said inactive to said active position: the selection device including at least one selector effective selectively to place each mobile element in one or other of the said two positions, and a control device effective to move mobile elements which are positioned in a particular one of said two positions into the third position.

2. Apparatus according to claim 1 wherein the mobile elements are movable in one direction between the said two positions and are movable in a second direction

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

**WARNING** start of CLMS field may overlap end of DESC **. for the return of the push-rods, and consequently the yarn guides, under the control of the selection programme, the push cam 72 has a height sufficient to deform the elastically deformable portions 67, whether the push-rods are in their low position or whether they are in their high position. The push-rods are available to be subjected to the effect of the electro-magnet 70 at each rotation of the dish-shaped holder 5, while push-rods placed in the high position during a previous selection and which are not held magnetically by the electro-magnet 70, pivot towards the outside of the machine, so that their respective return studs are placed within range of the return cam 38. Figures 12 and 13 illustrate the return of the push-rods under the control of the selection programme. For reasons of convenience, the principle elements represented in Figure 12 are assumed to be viewed from inside the machine. The control stud 68 of each push-rod has a notch 74, into which can be located a pivoting member 73 carried by the inside limb of the guide 33 and placed in the indentation 35. Each time that a control stud 68 is engaged by the ascending ramp 36, it lifts the member 73. The upper part of the member 73 has an inclined surface 75 which engages the bases of the control studs 68 of any push rods which were placed in the high position during a previous selection, and causes these push-rods to pivot towards the outside of the machine so that their respective return studs are placed within range of the return cam 38. In known yarn changers each unit or even each yarn guide has an associated means of holding tye yarn. and a yarn cutting device comprising a fixed blade and a mobile blade which is activated by means of a mechanical system which takes up too much space to be mounted in a machine having a multitude of knitting systems. In the installation described herein. each yarn changing device has, as represented in Figures 14 and 15. a means for holding the yarn 80 which includes two plastic components 81, for example made of "Vulkolan". pressed into a housing 82 in opposition to springs 83. The two components 81 are held in their housing 82 by the fixed blade 84 of the varn cutting device. A mobile blade is in the form of a roller 85 fixed via a spring 87 on to the same support 88 as a yarn taker 89, the support 88 being fixed to a rotating part of the knitting machine. There is only a single mobile blade for all the yarn changing units. When a yarn guide is brought back to the rest position, the varn taker engages the yarn and carries it into the gripping device 80 and brings it also into contact with the fixed blade 84. The mobile blade 85. which arrives a little later, then cuts the yarn which remains held in the gripping device 80. Since the control of the yarn guides is not carried out directly, but via mobile elements which have been previously selected in selection movements which can be of low amplitude, the apparatus is of particular interest when applied to circular knitting machines with a great number of knitting systems, in which the yarn changing units are very close together. It goes without saying that other embodiments can be envisaged without going outside the scope of the invention. For example it would be possible to use, insofar as the push-rods associated with the yarn guides are concerned, mobile elements which are not linked directly to the yarn guides, in which case means to hold the yarn guides separately would be provided. In the same way, the advance cam, designed to be common to all the mobile elements, could be eliminated by providing a spring associated with each element. Where, as described. the selection of the mobile elements is by one or more electro-magnets, alternative means of transmitting both the selective digital signals and the energy required could be envisaged. The electrical connections between the stationary portions and the rotating portions of the apparatus could be obtained by, for example, induction. WHAT WE CLAIM IS:

1. Apparatus for changing the supply warns in a circular knitting machine. having a plurality of knitting systems, the apparatus including yarn changing units to be associated with the knitting systems and each comprising a plurality of yarn guides, each yarn guide being selectively movable between an inactive position and an active position in which, in use yarn is supplied to the needles, the yarn guides being movable bv means of a selection device controllable by a programme to act during relative movement between the yarn changing units and the selection device, and including mobile elements respectively associated with the yarn guides and each of which can be moved between two positions without causing movement of the associated yarn guides and to a third position during movement which it causes the associated yarn guide to move from said inactive to said active position: the selection device including at least one selector effective selectively to place each mobile element in one or other of the said two positions, and a control device effective to move mobile elements which are positioned in a particular one of said two positions into the third position.

2. Apparatus according to claim 1 wherein the mobile elements are movable in one direction between the said two positions and are movable in a second direction

substantially perpendicular to the first direction in movement to the third position.

3. Apparatus according to claim 1 or 2 including at least one advance device effective to move the mobile elements from a first to a second of said two positions prior to selection, wherein the selector is effective to move non selected elements back to the first position, and wherein the control device is effective to act on selected elements, which have remained in the second position, in order to move them to their third position.

4. Apparatus according to claim 3 inclouding. in the selection device, at least one pusher effective to move those elements previously in their third position away from the control device.

5. Apparatus according to claim 4 including a return cam effective after such movement to bring those elements back to their first position.

6. Apparatus according to claim 4 or 5 including as the pusher, a member movable by selected elements upon movement to the third position and acting during its movement on those elements alreadv in the third position in order to pivot them within the range of the or a return cam.

7. Apparatus according to claim 3, 4. 5 or 6 wherein the selector includes an electro-magnet selectively energisable by the programme during relative movement between the selection device and the yarn changing units to act magnetically on the mobile elements when in their second positions and to retain selected elements in the second position.

8. Apparatus according to claim 7 wherein the electro-magnet is also effective to act on elements when in the third position.

9. Apparatus according to claim 3, 4. 5 or 6 wherein each mobile element has a selection stud. the selection studs being staggered relative to one another, and the selection device includes a series of superimposed selectors each associated with a selection stud, and movable between an active position in which it acts on the associated selection stud to make the respective element pivot from the respective element pivot from the second back to the first position, and an inactive position to which it does not influence the stud so that the element remains in the second position.

10. Apparatus according to claim 9 including electro-magnets to control the selectors.

11. Apparatus according to claim 9 or 10 wherein for the return of the yarn guides to the inactive position under the control of the programme. each mobile element has additional studs in a tiered formation and so arranged that selectors in the inactive positions act on additional studs of any element previously in the third position.

12. Apparatus according to any preceding claim wherein each mobile element is pivotable.

13. Apparatus according to claim 12 wherein each mobile element is linked to the corresponding yarn guide or an associated intermediate element by a hinge which defines the element pivot point.

14. Apparatus according to any preceding claim wherein the control device is a cam.

15. Apparatus for changing the supply yarns in a circular knitting machine, such apparatus being constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 9 of the accompanying drawings.

16. Apparatus according to claim 15 modified substantially as hereinbefore described with reference to and as illustrated in Figure 10 of the accompanying drawings.

17. Apparatus for changing the supply yarns in a circular knitting machine, such apparatus being constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 11, 12 and 13 of the accompanying drawings,.

18. Apparatus according to claim 15, 16, or 17 and including a yarn cutting and holding device constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figure 14 and 15 of the accompanying drawings.

19. A circular knitting machine including apparatus according to any preceding claim.