Improved device for the detection of the lack of the needle feeding yarn in circular hosiery machines

Abstract

 Device for the detection of the lack of the piston-type needle (2) feeding yarn (8) in a circular hosiery machine, constituted by a sensor (13) sensible to the motion of a yarn (8), in front of which all the yarns from a same yarn-bearing unit (3) are caused to pass. The sensor (13), is in particular of the electrostatic or of the piezoelectric type.

Description

[0001] The present invention relates to an improved device which allows the lack of the needle feeding yarn in the modern circular hosiery machines operating at high speed to be detected in a reliable and cheap way.

[0002] It is known that in the circular hosiery machines a set of needles positioned along the periphery of a revolv ing cylinder are moved in a vertical direction by suitable drive cams, so as to accomplish the yarn loops. To that purpose, each needle is provided with a latch or tongue freely hinged in the nearby of its own hook, such latch or tongue serving to suitably enclose and guide the fed yarn in cooperation with said hook, as well as to release the formed loop, said latch being driven to its closure po sition and to its opening position by the same yarn loop.

[0003] On the other hand, as in the production of the different parts of a sock, and especially of a women's stock ing, yarns of different counts are generally used, the yarn is supplied to the remaining needles by a yarn-bear ing unit through a plurality of yarn guides, which are as many as the yarn types necessary for the production of the article. To the purpose of reducing the sock production time still more, a plurality of yarn-bearing units are generally used, so as to accomplish at the same time, by each cylinder revolution, as many sticth courses, as the feeds are.

[0004] Now, a quite an important problem in said machine types is caused by the need of detecting the lack of the needle feeding yarn, whose absence, besides causing fault y socks to be formed, can also generate the breakdown of the needles or of other machine components.

[0005] In the present state of the art, the problem is solved by means of an electromechanical system constituted by a feeler which, by being suitably positioned in the zone wherein the needles, while being partially lifted, have their latch kept open by the last formed loop, closes a contact which stops the machine whenever it collides with, and hence detects the presence of a needle latch or tongue in an horizontal position, that is a sure indication of yarn absence. In fact, in the said zone the latch is kept open, and hence turned downwards, by the yarn loop which is being released, whilst, in the absence of yarn, the free latch reaches a horizontal positioning because of the effect of the centrifugal force.

[0006] It should however be kept in mind that the high speed required for the modern circular hosiery machines, which must be capable of operating at 1.000 and more revolutions per minute, imposes that the inertial masses be reduced as much as possible, and hence the needle latches or tongues to be made as small as possible, with consequent greater difficulty in the feeling, which cannot be any longer secured. On the other hand, at the high speeds, the fast beating of the latches causes intolerable damaging and degradation of the yarns, which are in this field delicate, weak, and hence to be handled under the minimum tensioning. It has been hence found it advantageous in the modern high-speed circular machines, to turn from the use of the latch needles to the use of the piston needles, wherein the previous latch function is now carried out by a piston-rod positively cam-driven, and guided in its vertical stroke by a guide slot provided in the shank of the needle.

[0007] But with such needles it is not any longer possible it to detect the presence of the yarn by feeling as in the known art, but using a yarn sensor per eachone of the yarns of each feeder is necessary, and this involves an expensive use of a large number of sensors.

[0008] Purpose of the present invention is precisely to obviate the said drawback and to provide hence a safe and cheap system allowing an efficacious detecting of the lack of the feeding yarn for the piston-type needles in the modern and high-rate circular hosiery machines.

[0009] This is substantially achieved by using a sensor for each yarn-bearing unit instead than for each yarn.

[0010] The whole originates from the consideration that although each yarn-bearing unit must be capable of supplying a plurality of different yarn types according to the sock portion to be accomplished, in practice at each time always one yarn only is used, so that only one type of sensor can be used for all the yarns of a yarn-bearing unit, provided that it is sensible to the motion of the yarn.

[0011] In fact, the lack of the feeding yarn which must be supplied involves that said yarn is stationary like all the other yarns of the same yarn-bearing unit, and hence that no one yarn is being moved, what the sensor detects immediately, stopping the machine. All is on the contrary regular if one yarn is being moved, whichever it may be of the yarn-bearing unit.

[0012] For a better understanding of the invention, it must be kept in mind that such a an arrangement should be necessarily applied for all those feed yarns of which at least one must always be present for the formation of the base knitted fabric.

[0013] If in the feeding yarn-bearing units also other yarns - not intended for the production of the base knitted fabric, but used from time to time to produce e.g. knitted fabric with drawings or other effects - are present, which must anyway be always used together with at least one of the yarns constituting the base knitted fabric, such yarns must be kept under the control by other sensors, not necessarily coordinated with the sensors of yarns intended for the base knitted fabric forming.

[0014] In case the yarn-bearing unit handles a large number of yarns constituting the base knitted fabric, the sensor of the same yarn-bearing unit may also be fractionated into a plurality of feeling positions, through at least one of which the movement runs of one of the base knitted fabric constituting yarns.

[0015] In case in no one of such positions any yarn motions are detected, the sensor stops the machine.

[0016] Summarizing, the device for the detection of the lack of the feeding yarn for needles of the piston-type in a circular hosiery machine operating at high speed and comprising among others at least a yarn-bearing unit, equipped with a plurality of yarn guides fed from cones or bob bins through a yarn-guide plate, is characterized accord ing to the present invention in that it is constituted by as many sensors sensible to the movement of a yarn, as the present yarn-bearing units are, each sensor being interested by all the yarns before it of the respective yarn-bearing unit.

[0017] According to a preferred embodiment of the present invention, the said sensor sensible to the movement of a yarn is then an electrostatic sensor of high impedance sensible to the electrostatic charge carried by a moving yarn. In this case, the absence of the yarn is revealed as electrical charge absence.

[0018] Finally, according to another preferred embodiment of the present invention, the said sensor sensible to the movement of a yarn is a piezoelectric sensor, which detects the vibrations of an idle spindle caused by the movement of the running yarn which lays on it together with the oth er stationary wires of the same wire-bearing unit.

[0019] The invention is now better clarified with reference to the drawing attached, illustrating a preferred embodiment shown to exemplifying and not limitative purposes on ly, in that technical or structural changes may always be provided, without going out the spirit of the invention.

[0020] In said drawing, the figure shows a partial and schematic perspective view of a circular hosiery machine, adopting the feed yarn lack detection system according to the invention.

[0021] Referring to the figure, with 1 the revolving cylinder is indicated of a circular hosiery machine, on whose periphery there are mounted needles 2, which are suitably vertically moved by underlying driving cams not shown in the figure. Said needles 2 are fed with the yarn from a yarn-bearing unit 3 mounted on the stationary support ring 4, and equipped with yarn guides 5 which, as being hinged in 6 to the yarn bearing unit 3, are selectively brought nearer to the needles by means of the tie-rod controls 7. In the figure two yarn-bearing units only are represented, respectively 3 and 3', of them the unit 3' being represent ed only in a schematic way, but more than two of such units could be used in the production of the sock as well, all of them being fed with the respective yarns (five in total) respectively 8₁, 8₂, 8₃, 8₄ and 8₅, which, arriving from bobbins or cones not shown in the figure, are caused to pass through a set of yarn guides 9 of porcelain provided on a yarn-guid plate 10 mounted stationary on a supporting upright 11 solid with the frame of the machine.

[0022] On said upright 11 a shield box 12 too is mounted, within which a sensor 13 sensible to the movement of one of the yarns 8i (with i = 1,...5) is fastened, said yarns being made pass in front of it by being guided by the porcelain yarn guides 14, 15 and 16.

[0023] The sensor 13 shown in the figure is of the electrostatic type, which is sensible to the electrostatic charge borne by one of the moving yarns 8_i, but it could also be of piezoelectric type. In the figure also the sensor 13' is schematically shown in broken lines, it too being shielded by the box 12', which is sensible to the movement of one of the yarns 81 related to the said second yarn-bearing unit 3', in that as many sensors are used, as the adopted yarn-bearing groups are.

Claims

1. Device for the detection of the lack of the feeding yarns for needles of the piston-type in a circular hosiery machine operating at high speed and comprising among others at least a yarn-bearing unit, equipped with a plurality of yarn guides fed from cones or bobbins through a yarn-guide plate, characterized in that it is constituted by as many sensors sensible to the movement of a yarn, as the present yarn-bearing units are, each sensor being interested by all the yarns before it of the respective yarn-bearing unit intended for the production of the base knitted fabric.

2. Device according to claim 1, characterized in that the yarns of each feeding unit, which must be processed together with at least one of the yarns constituting the base knitted fabric are controlled by means of sensors different from those intended for the control of the yarns forming the base knitted fabric.

3. Device according to one or more preceding claims, characterized in that the sensor interested by the yarns constituting the base knitted fabric of the respective yarn-bearing unit is fractionated into a plurality of feeling positions.

4. Device according to one or more preceding claims, characterized in that the said sensor sensible to the mo vement of a yarn is an electrostatic sensor with high im pedance sensible to the electrostatic charge borne by a moving yarn.

5. Device according to one or more preceding claims, characterized in that the said sensor sensible to the mo vement of a yarn is a piezoelectric sensor which detects the vibrations of an idle spindle caused by the motion of the yarn which is laying on it together with the other yarns of the same yarn-bearing unit.

Drawing