Mechanical take down device

Abstract: The invention relates to a mechanical take down device in a circular, particularly double cylinder knitting machine. The device consists of two circular parts (10, 11), where one (11) of them is full and fits into the other part (10), while the fabric (P) passes between them. On one of the parts is formed a screw-like surface (110) and neigh­ bouring surface of the other part is circular and its slant equals that of the screw-like surface. One of the parts does not rotate, while the other forcedly rotates and is coupled with the needle cylinder (1).

Description: The invention relates to a mechanical take down device in a circular knitting machine, particularly a double cylinder knitting machine, according to the first portion of claim 1. From the GB-A-659 999 it is already known such a take down mechanism in a double cylinder knitting machine, comprising two coaxial circular members between which the knitted fabric is passed. The lower member is surrounded by the lower needle cylinder and is formed as a rotating bush having a conical inner surface. The upper member has the shape of a disc and is rotatably mounted by a ball bearing on the obliqued lower end of an axial shiftable pushing rod. The outer conical contact surface of the upper disc member may be provided with concentric or spiral grooves. When both members are in operation the upper disc member rolls obliquely with a local contact on the conical contact surface of the lower member so that an arbitrary contact point travels over the conical surface from one edge to the other along a curved bath. Only in this travelling contact point the knitted fabric will be gripped and drawn inwardly. In the GB-A-432 233 there are described tension means in a knitting machine for drawing the knitted fabric away from the needles of a needle cylinder. One of said tension means is formed as a sleeve having a horizontal ring flange on its upper end portion, and is mounted in the center axis of the lower needle cylinder. The other tension means includes a disc mounted on the lower end of a centrally disposed rod. One of said means is shiftable in the axial direction and both means are provided on its fabric contact or gripping surfaces with spiral grooves and ribs. When the two tension means are in operative relationship the rib formation of one means projects into the groove of the other means, so that the knitted fabric is caused to follow a tortous path between the opposed means, and the fabric is frictionally engaged by the spiral ribs. By the reason of the relative rotation of the co-acting means and the knitted fabric an inwardly directed pull will be exerted on the fabric. During said operation both of the tension means are held stationary and unrotatable. In CS-A-185,999 is described a take down mechanism for a circular knitting machine, in which vertically movable working elements being arranged in a circle. The vertical movement of said working elements is controlled by a stationary cam and springs. Working ends of said elements are made in form of flexible blades. Said device operates reasonably reliably, except for jacquard take down, where bars are sometimes visible. Said bars originate due to uneven take down between neighbouring working elements. The CS-A-221,149 discloses a take down pin for catching up the fabric during welt knitting. During the course of further knitting it takes it down due to the action of a pneumatic mechanism. Said device practically eliminates longitudinal bars, but it is relatively complicated, takes up space and requires the supply of pressure air into the machine. A further disadvantage is that it does not permit to knit panties due to the lift of the device, or the lift may be performed in two parts, of course with the extension of the time to knit one product. When knitting fabric of a low density, i.e. with high extensibility, wrinkling of the fabric takes place. It is an object of the invention to provide a simply constructed take down device, which overcomes the disadvantages of the prior art and which can generate a uniformly and smoothly drawing force in the knitted fabric. This object will be solved by the features of a mechanical take-down device according to claim 1. One advantage of the invention is that the device is very simple and not demanding as to the operation and servicing. Due to the fact that the device acts around the whole periphery of the fabric by a continuous pull, knitted fabrics of high extensibility can taken down without any wrinkling or folding effects. Moreover, it smoothes up the fabric surface and the fabric quality is better. The device does not need to be adjusted and there is practically no wear, what guarantees its long service life. Faults due to the function are also entirely eliminated. The device can operate like upper or lower take down. Exemplary embodiments of the device according to the invention are illustrated in the drawings. It shows: Fig. 1 an axial section of a take down device in operational position in a double cylinder circular knitting machine; Fig. 2 a side view of the both members of a take down device in a non-operational position; Fig. 3 both the take down members of Fig. 2 in the operational position; Fig. 4 a side view of other take down members in a non-operational position, where the working surfaces are formed on the cylindrical surfaces; Fig. 5 the take down members of Fig. 4 in an operational position; Fig. 6 another embodiment of take down members in the operational position; Fig. 7 the lower screw-like surface of the upper take down member of Fig. 6; Fig. 8, 9 another embodiment of the take down members, in which the spiral formed ribs are provided on the lower member. The double cylinder circular knitting machine of Fig. 1 for the production of e.g. socks is provided with a lower and upper needle cylinder 1, 2 for receiving two sets of double-head needles 3 and jacks for controlling said needles 3. For the sake of forming the stitches, the machine is further provided with knock over sinkers 4 in the lower needle cylinder 1 and with stationary presser sinkers 5 in the upper needle cylinder 2. The knock over sinkers 4 are controlled by stationary cam rings 6, 7 fixedly arranged on a non-rotary tube 8. Said knitting machine is equipped with a mechanical take down device comprising the following parts. In the lower needle cylinder 1 there is disposed a member 10 of a funnel-like shape with a central opening for fabric passage fixedly arranged on an internal rotating take down tube 9. In the upper needle cylinder 2 there is arranged an axially shiftable member 11, working part of which has a conical screw-like outer surface 110 provided with a spiral formed rib. Both members 10 and 11 grip into each other, while the slope of internal conical surface 100 (Fig. 2) of the member 10 corresponds to the conical screw-like surface 110 of the other member 11. Both members 10 and 11 are arranged coaxially. The upper member 11 is located rotatably and shiftably in rings 12, 13 which are fixedly arranged in an internal rotary tube 14 of the upper needle cylinder 2. Said internal tube 14 rotates with the needle cylinder 2. In the upper end of the member 11 is arranged a lever 15 located swingably in a stand 16 on an upper flange 17 of the machine. The other arm of the lever 15 is controlled by the machine control drum through a not shown kinematic transmission. Operation of the above-mentioned device is as follows. At the beginning of knitting the fabric, i.e. of the welt, the member 11 is lifted so that the take down device is out of operation. The fabric P grows longer, while it contracts to the center due to laying of elastic thread. After finished knitting of the welt, the member 11 (Fig. 3) is lowered by a command from the control drum. The fabric P is pressed by a conical screw-like surface 110 onto the internal conical surface 100 of the member 10. The pressure of the member 11 causes entrainment of fabric P by rotating the lower member 10. Due to the rotation, the fabric P is in fact screwed into the surface of conical screw-like surface 110 and it is thus in fact tensioned and taken down from the needles 3. After finished knitting the member 11 is lifted by a command from the control drum and the fabric is cast off the needles 3. There exist various modifications, which can be performed within the scope of the invention. The operation of the members 10 and 11 can proceed in opposite sequence. The upper member 11' (Fig. 8) is provided with a conical surface 110' and the lower member 10' with a screw-like conical surface 100'. In case of fit of the member 11' into the member 10' (Fig. 9), the fabric is tensioned and taken down by the member 10'. Another modification representing no change in the principle of the solution consists in that the rotary location is changed. The lower member 10 or 10' is arranged non-rotatably and the upper member 11, 11' is arranged as driven. Further, the surfaces by which the parts fit into each other do not need to be conical, but they may be for example of a cylindrical shape, as evident on members 11a, 10a in Figs. 4 and 5, or they may be formed in adjacent plane faces of parts 11b, 10b (Figs. 6 and 7). Further, the take down device can be arranged for upper take down so that the member 10 with the opening is arranged in the upper needle cylinder and the full member 11 in the lower cylinder. In this case it is possible that the full member in the lower needle cylinder is not axially shiftable and the member with the opening for fabric passage is axially shiftable. The device according to the invention can be used even in single cylinder knitting machines and also in large diameter knitting machines.

Claims: Mechanical take-down device in a circular knitting machine, particularly in a double cylinder knitting machine, comprising two take-down members (10, 11) for gripping and drawing-off the knitted fabric (P) therebetween from the needle cylinders (1, 2), one (11, 11') of said take-down members is axially shiftable against the other member and one of said members (10, 10', 10b) is provided with a central opening for the passage of the knitted fabric (P), the first (11, 11b, 10') of said take-down members is provided with a screw-like surface (110, 100') having spiral ribs thereon whereas the second take-down member (10, 11') is provided with a substantially smooth contact surface (100) and fixedly arranged in relation to the needle cylinder of the knitting machine for stationary support of the knitted fabric against the pressure exerted by the first take-down member when the shiftable take-down member (11, 11') is shifted in an operative position, characterised in that both take-down members (10, 11) are arranged coaxially around the central axis of the circular knitting machine and the contact surfaces (100. 110) thereof are in parallel, and the first take-down member (11, 11b, 10') is provided with spiral ribs in contact with the knitted fabric (P) along a length suitable to exert a continuous pull on the knitted fabric around the whole perimeter of the tube being knitted and said first take-down member is mounted for relative circumferential motion against the knitted fabric (P) for forcing the knitted fabric (P) radially inwardly with respect to the central axis of the circular knitting machine. Take-down device according to claim 1, characterised in that one member (11; 11a; 11') is formed for gripping into the central opening of the other member (10; 10a; 10'). Take-down device according to claim 2, characterised in that the member (10, 10', 10a) having the central opening is located in a rotating needle cylinder (1) and the other member (11, 11', 11a) is non-rotatably and axially shiftable located in the other needle cylinder (2). Take-down device according to claims 1 to 3, characterised in that the screw-like surface (110) having the spiral ribs is formed on a full member (11, 11a). Take-down device according to claims 1 to 3, characterised in that the screw-like surface (100) having the spiral ribs is formed on the member (10) having the central opening.

Inventors: CHROMY MIROSLAV, FUCIK MILAN, POHORILSKY JIRI ING, CHROMY, MIROSLAV, FUCIK, MILAN, POHORILSKY, JIRI, ING.
Applicants: UNIPLET AS, UNIPLET A.S.
Application year: 1990
Main classification: D04B15
IPC codes: D04B15