Chain-cutting device for single-thread sewing machines

Abstract: This invention concerns a chain-cutting device able, when activated, to automatically carry out a series of operations in rapid succession, namely hooking up the thread which comes off the reel, blocking it on the work top, and immediately afterwards, cutting it just below the blocking point, in such a way that the thread is kept constantly stretched, even while sewing is suspended to enable the item just completed to be separated from the one following.

Description: This patent application for an industrial invention concerns a chain-cutting device, designed to cut off the thread in stitching, which protrudes from the fabric, forming chains. Therefore, the device in question, is intended to be fitted to sewing machines, with a single thread, which is normally drawn from below, by means of a special hook needle, able to effect chain stitching, often used as embroidery, either alone or accompanying other embroidering materials. Once the stitching of the piece is concluded, it is necessary to cut the thread while keeping it constantly stretched, so as to ensure that the working of the subsequent piece is correctly started off. Currently to do this, the operator must grip and manually pull the thread, holding it firm in such a way that the thread coming off the reel, stays stretched even during cutting, which obviously is effected along the piece of thread which extends beyond the gripping point. Machines for cutting and separating sewn pieces on sewing machines exist already on the market. Patent FR-A-2142449 describes a cutting device in which a blade, rotating on a horizontal plane, intersects intermittently with a fixed blade; said device includes a mechanism for operating the rotating blade and a brake for stopping the blade, which is automatically disconnected when said operating device is activated. This well-know device with rotating blade can in no way however resolve the problem which this invention aims at resolving. The problem this invention aims at resolving is not simply that of automatically cutting the stitching thread once a part has been sewn, but rather to cut the thread in such a way that the end of the thread from the reel is stretched horizontally so as to correctly resume sewing on the next piece to be sewn. As previously mentioned, there are no cutting devices in existence capable of cutting the thread while stretching the section of thread being cut, to the extent that to date the operator has had to pull the thread horizontally by hand before the thread was cut. The aim of this invention is actually to create an automatic chain-cutting device, which at the right moment, is able to carry out the aforementioned actions in rapid succession, namely hooking up and pulling the thread coming off the reel, temporarily blocking it on the work top and cutting it off immediately at a point just below the end blocked on the work top. The device in question is essentially composed of a flat arm with a hooked end, screwed in a radial position to the top of a small shaft, on a vertical axis, which, when activated, as required, rotates 360°, during which it also translates vertically, up and down, by means of a cam and related tappet. Said arm at rest is positioned within a sunken 'U' shaped nest, on the edge of a platform designed to be installed next to the work top, in such a way that the work top and the platform are perfectly coplanar. The platform must be placed in such way as regards the sewing needle, that during a complete turn by the small shaft, the radial arm can also turn and position itself above the work top, so as to be able to grip the thread with its hooked end thus pulling it sideways, where it must pass under a momentarily raised blade, provided for the purpose on the work top near the needle. Before completing rotation, the arm passes over a blade, positioned within the aforementioned nest, which cuts off the thread, the end of which remains blocked on the work top, due to the fact that said blade moves down and just before cutting, grips and blocks the thread drawn by the arm. In other words, the thread coming off the reel, is first of all stretched and blocked on the work top and then cut at a point below said blade, which holds it blocked on the work top, in such a way that the thread is stretched to the right extent, ensuring that the subsequent stitching operation can be started off without problems or delays. For further clarity of explanation, the description of the invention continues with reference to the attached drawings, reproduced for illustrative and not limitative purposes, wherein; Fig.1, is an axonometric protection of the chain cutting device according to the invention, drawn schematically; Fig.2, shows the chain-cutting device according to the invention, seen from above - the arm is illustrated by an uninterrupted line when at rest, and by a dotted line, in the several different positions assumed during its 360° rotation. With reference to the aforementioned drawings, the chain-cutting device according to the invention, comprises a bearing platform (1), to be installed at the side of the sewing machine work top, in such a way that the top surface (1a) of the platform (1), is on the same level as the top surface of the work top (P.L.). On the edge of said platform (1), there is a sunken 'U' shaped slot (1b), within which a flat arm (2) is positioned it being radially screwed to the top of a small vertical shaft (3), near the edge (1c) of the platform (1), which meets the side edge of the work top (P.L.) Said shaft (3) has an annular groove (3a) which together with a fixed tappet (4) with a corrugated section, is able to make the shaft (3) at each turn, carry out an upwards movement followed by a descending return stroke. Therefore, during one complete turn of the small shaft (3) there is a gradual lifting of the arm (2), which comes out of its sunken slot (1b), stays in the air for a certain time and finally returns to its original position, following the gradual descent of the small shaft (3), during the last part of its rotation. The dimensions of the arm (2) and the position of the platform (1) with regard to the sewing thread (F) are such that, during a complete turn of the arm (2), the hooked end (2a) of the arm passes exactly over the hole (5) crossed by the thread (F). Within the sunken slot (1b) a blade (6) is lodged, which is touched by the arm during the last part of its rotation as it gradually descends. With particular reference to Fig.2, the instructions for use of the chain-cutting device in question will be briefly described : to this end, three positions will be considered which are assumed one after the other by the arm (2) while in rotation, these having been illustrated by the dotted line in Fig.2 and indicated by the ordinal numbers I, II and III. The arm (2) when at rest, remains within the sunken slot (1b), an area almost diametrically opposite the point on the work top (P.L.) where the hole (5), crossed by the thread is situated. After rotating slightly more than 180°, the arm (2), which in the meantime, has reached sufficient height to be able to pass over the work top (P.L.) takes up position I, and at this point, it grips the sewing thread (F) with its hooked end (2a). Having hooked the thread (F), the arm (2), while continuing to rotate, draws and pulls the thread (F), which just after emerging from the hole (5) assumes a horizontal position, the direction of which may vary coinciding with as many radial directions starting from the centra which is formed by the hole (5). While moving from position II to position III, the arm (2) translates the thread (F), in such a way that it passes below a blade (7) on the work top (P.L.), this blade being lowered and only ascending after the arm (2) has reached position II. Just before the arm (2) reaches the cutting station, said blade (7), activated by a control rod (7a) is automatically lowered, so that the thread (7) coming off the reel is blocked on the work top before this self same thread is cut. In the right of this description with reference to the attached drawings, it now becomes clear how the device in question is able to carry out, automatically and in quick succession, the thread hooking operation, the blocking of the thread on the work top and immediately the cutting action below the blocked point, so that the thread coming off the reel is constantly stretched even in the period of time during which the stitching operation has to be suspended temporarily to allow the piece just finished to be separated from the subsequent piece. In Fig.2, it is supposed that along the work top there is a line of sewing machines in operation, therefore, other holes (5) and blades(7) are also visible. In this case, the work top (P.L.) is motorised and slides in such a way that the thread to be cut is brough before the fixed chain-cutting device each time.

Claims: Chain-cutting device for single thread sewing machines characterized by the following: a platform (1) whose surface (1a), near the edge (1c) has a sunken "U" shaped slot (1b) within which a blade (6) is fixed; a radial arm (2) having a hooked end (2a), housed in the slot (1b) and fixed to the top of a supporting shaft (3) with vertical axis and annular groove (3a) characterized by a corrugated section coupled to a fixed tappet (4) which forces the shaft (3) to perform an upward movement followed by a descending return stroke, with every rotation; a blade (7) placed on the work top (P.L.) positioned next to edge (1c) and fixed to the top of a control rod (7a) having a vertical axis and alternating perpendicular movement; the perpendicular alternating movement of the control rod (7a) being synchronized with the rotary movement of the shaft (3) so that the blade (7), which is normally lowered and does not protrude from the work top (P.L.), lifts only after the radial arm (2) has passed over the same and lowers again, to fasten the thread "F" to the work top (P.L.) before the blade (6) cuts the thread (F) hooked to the radial arm (2).

Inventors: GALLUCCI GIANNI, GALLUCCI, GIANNI
Applicants: TESEO SRL, TESEO -S.R.L.
Application year: 1990
Main classification: D05B65
IPC codes: D05B65, D05B73