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(11) | EP 0 564 041 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Circular knitting machine of elastic needle type with a selection device in the form of a rocking selector |
| (57) A circular knitting machine of elastic needle type in which the selection between
those needles (3) to be flexed and those needles to be left in their normal configuration
and hence travel along different contours of the knitting cams (25,26) is made by
rocking selectors (23) housed in the tricks (2) below each needle (3), to act selectively
so as to flex the needles (3) into their tricks (2) before they rise to seize the
yarn feeds. |
[0001] This invention relates to circular knitting machines and in particular to the selection of needles in such machines for the purpose of producing patterned or reinforced knitwork, and provides a device for selecting those needles which are to seize yarn from the various feed stations to form knitwear.
[0002] Circular knitting machines consist generally of one or two needle cylinders 1 which, as shown in Figure 1, comprise tricks 2 in their outer cylindrical surface. The tricks represent the guides for the needles 3 which during their vertical travel form the stitch loops in cooperation with the sinkers.
[0003] The number of tricks is equal to the number of needles which slide within them with reciprocating motion by the effect of raising and lifting cams not shown in Figure 1. Generally, in hosiery machines the number of tricks and needles is between 200 and 400.
[0004] The cylinder is rotated and with it there rotate the needles which during their reciprocating movement are fed with yarn in fixed angular positions when in their highest point of travel by yarn feed stations consisting of one or more yarn guides which are selectively presented to the needle hooks so that they seize the yarn from them.
[0005] To produce hosiery articles generally only a fraction of the available needles are used at the same time and in the same manner, except for the plain knitwork parts, for which all the needles are operated between their maximum and minimum level, all being fed with yarn at each knitting course, and all being moved in the same manner.
[0006] When the machine is not producing plain knitwork, in order to produce other types of knitwork some needles are required to produce stitch loops and therefore be raised to the maximum level at the feed station in order to seize the yarn, while others have to be raised to an intermediate level to take up yarn without clearing the previous stitch in order to form a tuck stitch, or have to be raised with a certain delay so that they do not seize the yarn fed in that feed station and therefore do not form new loops with it. In other words a needle selection has to be made.
[0007] This means that before each feed it has to be determined which and how many needles must undergo a certain travel and which and how many other needles must undergo a certain different travel or indeed undergo no travel.
[0008] With reference to Figure 1, in the known art this selection is effected by the jacks 4 which slide in the same tricks 2 as the needles lying above them, to urge the needles upwards and move them to a higher level in order to seize the yarn. After seizing the yarn the needles are controlled in their reciprocating movement by their own cams and counter-cams which are fixed relative to the cylinder, and which are not shown in Figure 1 but are shown in the subsequent figures.
[0009] Figure 1 shows an elastic jack 4, able to radially flex its lower end. When the jacks 4 have moved the needle into its working position they withdraw from the needle butt and return downwards.
[0010] If the needle, after completing its task of seizing the yarn and forming the stitch loop and therefore being at its minimum level, is not required to seize a further yarn from another feed it remains at this level until its control jack or other machine members move it upwards again.
[0011] The shank of the jack 4 comprises in its middle part a projection 5, ie the upper guide butt, which comes into engagement with its own control cam 6 for urging the jack downwards when it has completed its task of raising the needle 3. Proceeding downwards along the jack shank there is a lower butt 7 which comes into engagement with the cam ring 8 provided with a raising contour 9 which raises the jack together with its overlying needle, this thus being selected to seize the yarn, and with a contour 10 which with its inner face engages the vertical face of the butt 7 to urge the foot of the elastic jack 4 into the interior of the trick 2. When in this position of approach to the interior, the butt 7 is unable to engage the raising contour 9 of the ring 8 and the jack remains lowered. The lowering cams 6 and the raising and approach contours 9 and 10 are obviously offset angularly and operate at different times on each jack.
[0012] In circular knitting machines, needle selection is generally conducted by maintaining those jacks corresponding to the needles to be raised by the raising butt in a position withdrawn outwards to cause them to engage the raising contours, while maintaining those jacks corresponding to the needles not to be selected in their position of approach to the interior of the trick, whether elastic jacks or conventional rigid jacks are used.
[0013] When elastic jacks are used, they tend spontaneously to move their lower butt 7 outwards to engage the raising contour 9 and be raised, whereas with conventional jacks their approach and withdrawal are effected by suitably positioned cams fixed relative to the cylinder.
[0014] The jacks 4 are maintained in position so that the flexure or displacement of their lower part does not cause their upper part to escape from the trick, this being achieved for example by one or more circular springs 12 rigid with the cylinder and surrounding their upper part. They are held in position by circumferential grooves in the cylinder, so that the springs lie internal to the face of the needle cylinder 1.
[0015] In Figure 1 the selection device, indicated schematically by 11, can either allow the jack 4 to move outwards and rise on the cam 9, or can urge it into its trick so that it remains low.
[0016] Conventional selection uses mechanical selectors acting on a series of intermediate butts, but this type of selection has considerable limits in terms both of operation and of the number of possible selections.
[0017] The most recent machines use electromagnetic selection devices which allow a greater selection speed and a greater number of programmable selections, with advantages in terms of machine productivity and the greater variety of possible patterns.
[0018] These selection devices are divided essentially into two categories, namely fixed devices which do not rotate with the cylinder and are positioned to precede each feed station, and to which the jacks are presented in sequence as they rotate, and selection devices which rotate together with the cylinder (and with its jacks) and which are therefore always positioned at the jacks and can act on them at any moment, rather than only during the very short time in which the jack passes in front of them.
[0019] This second type of selection is also effected before the jacks pass in front of the feed stations, but there is greater freedom with regard to the requirements of synchronization and the constraints on the time available for the selection, however a larger number of selection actuators are required, these being equal in number to the number of needles rather than to the number of feed stations. Needle selection devices and methods of the two described types, operating on both rigid and elastic jacks, are described in European Patent Applications Publication Nrs. 0379234, 0431674, 0441005, 0479371 and Italian Patent Application Nr. 22172 A/90 of the present applicant.
[0020] Those methods which use jacks in circular knitting machines for needle selection involve a selection linkage which is complicated and requires a cylinder 1 of sufficient length to contain the needles 3, the jacks 4 and possibly vertical selection actuators, in accordance with the aforestated patent applications.
[0021] The object of the present invention is to provide a circular knitting machine which does not use vertically moving jacks 4 and instead effects selection directly on the needles. It is described hereinafter with reference to Figures 2a to 3b, which show a typical embodiment thereof by way of non-limiting example.
[0022] According to the scheme of Figures 2a and 2b the cylinder 1 is provided with tricks having an excavated profile 2a which enables the needles 3, which each slide in their own trick, to flex their lower part into the trick and allow their butt 20 to sink into the excavated part 2a. The needle flexure is caused by a rocking selector described hereinafter. The two positions, ie flexed and non-flexed, of a needle 3 are indicated on Figures 2b and 2a, respectively.
[0023] The needle 3 is provided with a butt 20 for engaging its raising and lowering cams. Below the butt 20 there is a nose-shaped projection 22 which engages the nose 24 of a rocking selector 23.
[0024] During the rotation of the cylinder 1, all the needles 3 are lowered by the cam and counter-cam system 29 and 30 described hereinafter, in which position they are subjected to selection.
[0025] In this position of maximum lowering, the nose 22 below the butt 20 of the needle 3 is engaged by the nose 24 of the selector 23.
[0026] At its lower end the selector 23 is shaped with a cavity 12 which rests on an edge provided with a projection 13 of rounded profile matching said cavity, so as to form a hinge which enables upper end of the selector to rock. The extent of rocking of the selector about its lower support is limited by an outer ring 14 and a spring 15 positioned within the trick 2 and urging it towards the ring 14.
[0027] On the outside of the intermediate part of the rocking selector 23 there is a plurality of projections 16 which are used in the same manner as the jack selection butts in the selection processes of the known art. The projections or butts 16 are provided in sufficient number to ensure the desired number of selection combinations. All the butts 16 are removed from each selector 23, except for that or those required to make contact with one or more radial thrust actuators at their level.
[0028] Many types of radial actuators for selecting the butts 16 are known in the art, such as those described in Italian patent appln. Nr. 23287 A/85, Eur. Patent appln. Publ. 0397254 and Eur. Patent 0190803 of the present applicant.
[0029] These actuators therefore act on those selectors 23 whose unremoved butt lies at their level, whereas the other selectors 23 having their residual butts at a different level are not involved.
[0030] When a rocking selector 23 is urged into the trick 2 and flexes its overlying needle 3, the spring 15 becomes elastically loaded.
[0031] When the thrust of the actuator 18 ceases, the energy of the spring 15 is released to thrust the selector towards the ring 14.
[0032] If the selector 23 is thrust inwards, as on Figure 2b the nose 24 engages with its vertical part the vertical part of the nose 22 of the butt 20 and does not allow the butt 20 to rise on the contour of the cam 25 located in the most outer position relative to the needle cylinder, but only on the contour of the cam 26 which is located closer to the cylinder and is of different shape, as described hereinafter.
[0033] If the selector 23 is not thrust inwards, as on Figure 2a the nose 24 does not deviate the movement of the butt 20, which can therefore engage the contour of the cam 25.
[0034] The needles 3 are retained in position by one or more springs 27 which surround their upper part. These springs are held in position by circumferential grooves 28 in the needle cylinder 1.
[0035] The springs have to exert a sufficient opposition to the needle flexure force to enable the selectors 23 to cause flexure rather than cause the upper part of the needles to emerge from the tricks.
[0036] Figure 3b is a side view showing the shape of the cams which move the needles, the selector being shown with only one residual butt, which has been thrust inwards by its actuator. The rotary motion is from right to left. The cams remain at rest and the cylinder rotates with its needles, the butts 20 of which engage the cam contours as they present themselves.
[0037] The butt 20 shown on the far right is engaged by the lower descending contour of the cam 29 until its lowest point is reached, at which it encounters the counter-cam 30. When the needle 3 is in this lowest point, the selector is either thrust or not thrust inwards to effect selection. The selection region is indicated by the segment S. The selection must be made before the needles encounter the assembly comprising the cams 25 and 26.
[0038] If the needle 3 has not been urged into the trick 2 by its selector 23, it remains outwards and its butt 20 travels along the contour of the cam 25, the contour of which is fairly steep and reaches the initial part of the feed region indicated by the segment A, within which the yarn guides are positioned which present the feed yarn to the hook of the needle 3.
[0039] During their rising movement along the cam 25 the needles unload the stitch loops formed during the previous knitting cycle, which move onto the needle shaft, so that only the yarn (or yarns) seized during this raising is present in the needle hook, the previous loop being released on the next lowering of the needle.
[0040] If the needle 3 is engaged via its butt 20 with the nose 24 of the selector 23, its butt 20 projects less outwards then in the previous case. The radial counter-thrust exerted by the flexed needle 3 on the selector 23 is opposed by the thrust of the actuator 18.
[0041] The butt 20 is therefore unable to rise on the ascending contour of the cam 25, but only on the contour of the cam 26 which is closer to the needle cylinder 1. The path followed by the needles rising on the cam 26 and the knitting produced during this path are hence different from those of the needles travelling along the cam 25. The needle 3 is raised and is no longer subjected to the thrust by the nose 24 of the selector 23. The actuator 18 can return to rest having performed its task.
[0042] According to a preferred embodiment of the invention, the cam 26 is provided with an adjustment member to enable it to assume different levels, so as to cause the needles travelling along it to take alternative possible actions, such as:
- unload the stitch and seize a different feed than the needles which have travelled along the cam 25, by rising to the same level as the other needles but with a delay,
- retain the stitch, ie seize the yarn without unloading the previously formed stitch, by rising to an intermediate level,
- pass low without creating a new stitch, because new yarn has not been seized.
1. A circular knitting machine with a needle cylinder provided with tricks (2) within
which needles (3) slide, these being selected to travel either along a path guided
by the contour of a raising cam (25) situated a certain distance from the cylinder,
or along a different path guided by a different contour of a different raising cam,
(26) situated a lesser distance from the cylinder, characterised in that the needles
(3) are elastic needles for which the selection operation is effected by causing them
to either flex to the tricks (2) or not flex, so that their butt (20) projects a lesser
or greater distance from the respective trick (2) the flexed needles being able, via
their butt, to rise only on the contour of the cam (26), whereas the unflexed needles
can rise on the contour of the cam (25), the upward thrust of which commences before
that of the cam (26) and in that the needles (3) are flexed by selectors (23) arranged
below the needles (3) and rocking about the lower fulcrum (13), each needle being
associated with a selector (23) which rocks within the same trick (2) as its associated
needle, and is made to incline or not incline into its trick when the needles (3)
reach their lowest level under the action of the lowering cam (29), the selectors
which are made to incline into their trick (2) being only those which correspond to
the needles to be flexed into the trick, and which cannot therefore slide on the contour
of the cam (25), but only on the contour of the cam (26).
2. A circular knitting machine of the elastic needle type as claimed in claim 1, characterised
in that the trick (2) is formed with an excavated profile (2a) which enables the needle
to flex into it.
3. A circular knitting machine of the elastic needle type as claimed in claim 1, characterised
in that the rocking selectors (23) are provided with one or more butts (16) at the
level of corresponding radial thrust actuators (18), the inclination of the selector
(23) being achieved by presenting an actuator against one of its butts (16), the outward
return of the selector (23), on cessation of action of the actuator (18), being achieved
by a counteracting spring (15) positioned within the trick (2).
4. A circular knitting machine of the elastic needle type as claimed in one or more of
the preceding claims, characterised by comprising an axially shiftable cam (26) able
to assume three levels corresponding to the stitch unloading position, the stitch
retaining position and the inactivity position of the needles travelling via their
butt (20) along the contour of said second cam (26), which is located in correspondence
with the feed stations of the circular knitting machine, said cam (26) having a contour
such that the needles travelling along it are raised with a substantial delay relative
to the raising of the needles travelling along the cam (25).