Thread cutting and aspiration unit for multiple-feed circular knitting machines

Abstract: The thread cutting and aspiration unit (1) has a vertical cutter supporting post which is shifted towards the axis of a toothed thread trimming disk (4). A cutting blade associated with each cutter (12a) is mounted at the end of a lower L-shaped portion of a corresponding supporting post. The L-shaped portion allows thread to pass beyond the cutter and to be cut by a following blade (12b), so that a considerable length of thread (F) can be aspirated by an aspiration port (15a).

Description: The present invention relates to a thread cutting and aspiration unit for multiple-feed circular knitting machines for manufacturing socks and stockings. In conventional circular knitting machines for manufacturing socks or stockings, with a plurality of thread feeds, the thread is cut and retained by respective aspiration ports to prevent the cut piece of thread from escaping from the corresponding thread guide due to the spontaneous recoil of the thread after cutting. In conventional cutting units, a rotating toothed thread trimming disk moves the thread against a fixed cutter, which is located directly upstream of the aspiration port and cuts the thread that must be aspirated by the respective port: the aspirated portion of thread is very short and often not long enough to ensure a good grip for aspiration, especially in the case of elastic threads or in particular operating conditions. Accordingly, the thread often escapes from the grip of the aspiration port, with the consequent need to stop the machine for rather long periods. US-A-3 557 578 discloses a yarn cutting apparatus for a multiple feed circular knitting machine which includes a rotating toothed cutter ring which transports yarn to a stationary cutter which resiliently abuts the peripheral rim of the cutter ring. The portion of the cutter ring before the cutter is covered by a cover so that upon movement of the yarn guide to either a feeding position or a retracted position the yarn slides on the cover and is not immediately cut by the cutter, but passes first by the cutter and is transported until it again arrives at the same cutter and is then cut so that yarn ends of sufficient length remain for being held by a suction device. US-A-3 157 036 discloses a yarn severing mechanism for a multiple feed circular knitting machine which includes a rotating toothed annulus which carries yarn to cutting element resiliently engaging the upper surface of the annulus. A camming guard plate is provided in association with the yarns at each yarn feed station such that upon movement of a yarn feed finger to an inactive position the yarn engages the guard plate and is prevented from being carried by the toothed annulus and severed by the cutting element at the same station but is instead carried by the annulus to the next adjacent station where it is severed by the cutting element associated with the adjacent station in order that the inactive yarn end will be of sufficient length for remaining held by a suction tube located at the yarn feed station. Alternatively, upon movement of a yarn to knitting position by lowering its feed finger to active position, the yarn is carried by the toothed annulus to be severed by the cutting element at the same feed station. A principal aim of the present invention is to obviate the above mentioned drawbacks of conventional devices and to provide a thread cutting and aspiration unit for multiple-feed circular knitting machines that cuts a portion of thread that is long enough to ensure its effective aspiration. Within the scope of this aim, an object of the present invention is to provide a unit that is simple, relatively easy to execute, safe in use, effective in operation, and has relatively low costs. In accordance with the invention, there is provided a thread cutting and aspiration unit for a multiple-feed circular knitting machine as defined in the appended claims. The characteristics and advantages of the invention will become apparent from the following detailed description of a preferred but not exclusive embodiment of a thread cutting and aspiration unit for a multiple-feed circular knitting machine for manufacturing socks and stockings according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figures 1 and 2 are partially sectional side views, taken along different angles and along vertical planes, of a thread cutting and aspiration unit for a multiple-feed circular knitting machine for manufacturing socks and stockings; figure 3 is a front view of the unit; figure 4 is a plan view of a sector of the circular knitting machine, equipped with two units according to the invention; figure 5 is an enlarged-scale sectional side view of a detail of the main disk and of the secondary disk of the unit; figure 6 is a partially sectional lateral plan view of a thread cutter; figure 7 is a top view of the cutter of figure 6. With particular reference to the above figures, the reference numeral 1 generally designates a thread cutting and aspiration unit for a multiple-feed circular knitting machine for manufacturing socks and stockings, according to the invention. The unit 1 comprises a platen 2, provided with a plurality of radial slots for guiding hooks 3, on which a toothed thread trimming disk 4 is supported so that it can rotate in the direction of the arrow A; said disk has teeth 4a substantially shaped like saw teeth; the reference numerals 5a and 5b designate two successive thread guides, which correspond to the thread feeds of the machine and can be four or more. A coaxial secondary disk 6 is mounted beneath the thread trimming disk 4 and has a slightly smaller radius than the disk 4, so that the external portions of the teeth 4a protrude beyond the outer periphery of the secondary disk 6. A thread cutter 7 is provided at each feed and is constituted by a vertical post 8 that is pushed downwardly by an upper compression spring 9 having one end abutting the post 8 and another end abutting the end of a seat 13. The post 8 is provided, in a downward region, with an L-shaped portion 10 that defines, at an end portion thereof, a fork in which an oscillating blade 12 is mounted so that it can oscillate about a horizontal-axis pivot 11 (two successive blades 12a, 12b are visible in the figure): the vertical post 8 is guided in the vertical seat 13, and the seat 13 is fixed by means of a screw 14 to an aspiration port 15; with respect to conventional posts, the post according to the invention is shifted towards the axis of the toothed thread trimming disk, and the L-shaped portion 10 allows the thread F to pass beyond the cutter without interfering with the post and being cut, as will become apparent hereinafter, by the following blade, so that the length of thread aspirated by the port is considerably greater. The radius of the secondary disk 6 is slightly greater than the distance from the rotation axis of the machine of the cutting lines of the blades 12 of the cutters, so that the thread F exiting from a thread guide and picked up by the toothed disk slides against the tapered edge of the secondary disk 6 and remains spaced from the cutting line of the cutter 12a that corresponds to the thread guide where the thread exits (for example 5a); the rotation of the disk 4 moves the thread, which is picked up by a tooth 4a, into a condition for being cut by the blade of the following cutter (for example 12b). The aspiration ports 15, one for each feed of the machine, are fixed by screws 16 to the fixed structure of the machine and are essentially constituted by a tubular duct 17 that is tilted slightly with respect to the vertical and is connected to an aspiration unit, which is proximate to the toothed disk 4 in a downward region. In a peripheral region, the bases 18 of the aspiration ports have a circular shape, and their distance from the axis of the machine is greater than the cutting lines of the blades 12 of the cutters and slightly smaller than the radius of the toothed disk 4, so that the thread picked up by the disk 4 first slides against the base, for example 18a, in a condition in which it is spaced from the cutting line of the corresponding cutter, and then, by tilting with respect to an axis lying at right angles to the surface of the disk for the rotation of the thread trimming disk, enters from behind, through a short rising rear profile 19, beneath the base, for example 18b, of the following aspiration port and is engaged by the blade 12b of the corresponding following cutter. The end of the thread F, cut by the blade 12b, is aspirated by the previous port 15a and is long enough to ensure that the port retains it assuredly (the length of the end of the thread is greater than the length obtainable with conventional devices by an extent corresponding to the distance between two successive cutters). It is thus evident that the invention achieves the intended aim and object. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept as defined by the claims. All the details may furthermore be replaced with other technically equivalent ones. In practice, the materials employed, as well as the shapes and the dimensions, may be any according to the requirements without thereby abandoning the scope of the protection of the appended claims. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: Thread cutting and aspiration unit (1) for a multiple-feed circular knitting machine for manufacturing socks and stockings, comprising a rotating toothed thread trimming disk (4) for transporting threads and, at each feed, a thread aspirating port (15) and a vertical cutter (7) supporting post (8) with a cutting blade (12), each vertical cutter (7) supporting post (8) being shifted towards the axis of the toothed thread trimming disk (4) and the cutting blade (12) of each cutter (7) being mounted at the lower end of a L-shaped portion (10) of the corresponding supporting post, said L-shaped portion (10) being adapted to allow the thread (F) to pass beyond the cutter (7) and be cut by the blade (12) of the following cutter (7), a coaxial secondary disk (6) being provided below the toothed thread trimming disk (4), the radius of said secondary disk (6) being slightly smaller than the radius of the trimming disk (4) and being greater than the distance from the rotation axis of the machine to the cutting lines of the cutters (7) that lie above the disk (4), so that the thread (F) exiting from a thread guide (5a) and picked up by the toothed disk (4) is adapted to slide against the secondary disk (6) and remain spaced from the cutting line of the cutter (7) that corresponds to the exit thread guide (5a) of the thread (F), whereas the rotation of the disk (4) is adapted to move the thread into a condition for being cut by the following cutter (7), so that the length of thread aspirated by the port (15) corresponds to the distance between two successive cutters (7). The unit according to claim 1, characterized in that in a peripheral region, the bases (18) of the aspiration ports (15) have a circular shape and a distance from the axis of the machine that is greater than the cutting lines of the cutters (7) and slightly smaller than the radius of the toothed thread trimming disk (4), so that the thread (F) picked up by said disk (4) is adapted to first slide against the base of the aspiration port (15) in a condition in which it is spaced from the cutting line of the corresponding cutter (7) and then is adapted to penetrate below the base of the successive suction port (15) and be engaged by the corresponding following cutter (7), the cut end of the thread being aspirated by the first port (15).

Inventors: ANDO JAN, ANDO, JAN
Applicants: MATEC SPA, MATEC S.P.A.
Application year: 1995
Main classification: D04B15
IPC codes: D04B15