Improvement in the device for cutting threads in circular stocking knitting machines

Abstract: A device for cutting threads in circular stocking knitting machines, which includes a circular saw (11) having teeth (12) on its periphery and at least one knife. Each tooth of the saw has a cutting zone (17) away from and moved back with respect to the front part (15). The front part is intended for gripping and dragging along the thread towards the knife (13). Between the front part and the said cutting zone of each tooth, there is provided a notch or step, which is intended for holding a piece of thread without being intercepted by the said knife (13). The cutting zone (17) interacts with the said knife (13) for cutting the thread away from the front dragging part, when the thread rests on the said cutting zone.

Description: The present invention refers to the sector of circular stocking knitting machines and more specifically it pertains to an improvement in the device for cutting the threads in such circular machines during knitting. The circular stocking knitting machines, whether they are single feed or multiple feed, are usually provided with a device for cutting the threads, which consists of a circular saw having teeth facing towards the outside and of one or more knives having the function of a counterblade. The saw is fixed and rotates with the plate, while the knife remains stationary. Therefore, any tooth of the saw can, with its front part, intercept the thread that comes close to it as a result of an appropriate movement of the relative thread guide, and interacting with the fixed knife, cuts the thread (see DE-A-3830079). Normally, the length of the tail of the thread that remains when cut is that from the outlet point of the thread from the needles to the cutting of the tooth of the saw, which coincides with the front part of the tooth which grips the thread and which interacts with the knife for the cutting. However, the distance between the needles and the saw teeth is often limited, and the tail of the cut threads can be too short. Therefore, in some knitting operations, especially in the presence of elastic threads, such a tail of the threads, if it is too short after the cutting, can become unthreaded from the knitting, passing from the reverse side to the right side of the manufactured article. It is an object of the present invention to remedy such a drawback through a new, original structure of the saw and more specifically of its teeth. Another object of the present invention is to propose a thread-cutting saw for circular stocking knitting machines modified in such a way that each of its teeth, in addition to dragging along, with its upper part, the thread to be cut towards the fixed knife, is able to hold a piece of thread horizontally before this piece is cut with the aid of the knife, so as to increase the length of the tail of the remaining thread. According to the present invention, the objects are achieved by moving back the cutting zone of each tooth of the saw as regards the front part of the tooth which is intended for gripping and dragging along the thread towards the knife, by making, between the front part and the cutting zone of the tooth, a notch or step, in which a piece of thread is carefully placed above the cutting zone, and by cutting the thread with the aid of the knife at the level of the cutting zone of the tooth away from the front part for dragging the thread. Therefore, the thread is cut by means of the knife away from the front part of the tooth, which drags along the thread towards the knife, and the length of the remaining thread tail is no longer, as usual, equal to the distance between the needles and the saw teeth, that is, between the point of outlet of the thread from the needles of the machine and the front part of the tooth, but it is equal to such an increased distance of the piece of thread that is held by the notch or step of the tooth, that is to say, increased in the distance between the front part and the cutting zone of the tooth. Therefore, with a suitable selection of the distance between the front part and the cutting zone, that is, of the length of the notch or step, the threads, even elastic threads, can be cut to a length such that their tails do not become unthreaded from the knitting and pass from the reverse side to the right side. The accompanying drawings illustrate, by way of example, on embodiment of the invention, and precisely: Figure 1 is a section of the saw in an enlarged perspective view; Figure 2 is a plane view of a part of the saw in Figure ; Figure 3 is an enlarged section according to the arrows III-III in Figure 2; and Figure 4 is a section, also enlarged, according to the arrows IV-IV in Figure 3. The saw consists of an annular body 11, having on its periphery a plurality of teeth 12. The saw is fixed and rotates with the plate of a circular stocking knitting machine, and its teeth are intended for interacting with at least one fixed knife 13, which acts as a counterblade, for the cutting of threads 14. Considering the direction F of rotation of the saw, each tooth 12 of the saw has a radial front part 15 intended for gripping the thread 14 to be cut and for dragging it along towards the knife 13 when the thread guide moves the thread into a position of interception by any tooth of the saw. The knife 13 is usually arranged above the saw in correspondence to the teeth 12 so as to touch their upper surface 16 while the saw rotates with the plate, to which it is fixed. According to the present invention and as shown in the drawings, a notch or step 17, which extends backwards (with respect to the direction of rotation) from the front part 15 up to a cutting zone 18, is made on the upper surface 16 of each tooth 12. The cutting zone 18 of each tooth is thus spaced away (backwards) from the front part 15, and the notch or step 17 can hold a corresponding piece of thread 14. The fixed knife 13 passes over the notch or step 17 without affecting the thread 14. Moreover, the knife 13, when it corresponds to the cutting zone 18, touches it, and interacting with same as blade-counterblade, cuts the thread (cf. Figure 4). The thread is thus cut away from the front part of the tooth that drags it along, for which reason the remaining tail of the thread will certainly be longer than it would be if the thread were cut at the level of the front part of the tooth as occurs with the prior-art saws.

Claims: A device for cutting threads in circular knitting machines, comprising a circular saw having peripherical teeth (11,12) and at least one knife (13) acting as a counterblade, and where the saw is fixed for rotation with a circular knitting machine plate, the knife is fixed, each tooth (12) of said saw includes a front part (15) for gripping and is dragging a thread toward the knife and the knife is positioned for touching an upper surface of teeth of said saw, characterized in that a recess or each tooth (12) of the saw includes a cutting zone (18) spaced away from said front part (15) and designed for gripping and dragging the thread toward the knife, notch (17) for holding a piece of thread above said cutting zone without being intercepted by said knife, said notch being disposed between said front part (15) and said cutting zone (18) of each tooth (12), said cutting zone interacts with said knife for cutting a thread away from said front dragging part, when said thread rests on said cutting zone. A device according to claim 1, wherein said recess or notch is formed on a surface of said tooth facing said knife, and said knife is positioned in order to touch said cutting zone a distance from said front part for dragging.

Inventors: SANGIACOMO FULVIO, SANGIACOMO, FULVIO
Applicants: SANGIACOMO SPA, SANGIACOMO S.P.A.
Application year: 1995
Main classification: D05B1
IPC codes: D04B15