EP2363519B1

EP2363519B1 - Yarn gripping and cutting device, particularly for striping yarn fingers for knitting machines or the like

Info

Publication number: EP2363519B1
Application number: EP11154804.6A
Authority: EP
Inventors: Ettore Lonati; Fausto Lonati; Tiberio Lonati
Original assignee: Santoni SpA
Current assignee: Santoni SpA
Priority date: 2010-03-05
Filing date: 2011-02-17
Publication date: 2014-11-26
Anticipated expiration: 2031-02-17
Also published as: KR20110101078A; IT1398548B1; CN102191619B; CN102191619A; EP2363519A1; ITMI20100364A1; TW201144504A

Description

The present invention relates to a yarn gripping and cutting device, particularly for striping yarn fingers for knitting machines or the like.
In the field of knitting machines, yarn fingers are known which are called "striping fingers" and are used generally in assemblies, which, being equipped for each yarn finger with an adapted yarn gripping and cutting device, allow, during production, to change the yarn supplied to the needles at a feed or drop of the machine.
One of these assemblies of striping yarn fingers is disclosed, for example, in EPA 07802212.6 and WO 2008/037339 by the same applicant.
Yarn gripping and cutting devices comprise generally a holding element, which has a laminar body in which a recess is defined, on one side, which is adapted to receive the yarn to be gripped and cut. The holding element is interposed between a gripping element and a cutting element, which also have a laminar body, which face the two opposite sides of the holding element. The gripping element and the holding element are elastically loaded toward each other on their mutually facing sides. The holding element can move with respect to the cutting element and the gripping element along an actuation direction in order to pass from a yarn standby position, in which the portion of the holding element having the cited recess protrudes from the front side of the gripping element and of the cutting element, to a retention position, in which the portion of the holding element with the recess is retracted between the gripping element and the cutting element.
In the standby position, the recess is in a suitable position to receive the yarn to be gripped and cut, which is designed to straddle the recess transversely to the actuation direction of the holding element in relation to the gripping element and the cutting element.
In the transition from the standby position to the retention position, the holding element retracts progressively between the gripping element and the cutting element. In the end portion of this retraction, the yarn, engaged by the holding element, is progressively dragged between the side of the holding element and the side of the gripping element, thus actuating its retention and, immediately thereafter, the yarn is brought into contact with the front side, which constitutes the blade, of the cutting element, actuating its cutting.
These yarn gripping and cutting devices generally have good reliability in gripping of the yarn, and such reliability derives mainly from the elastic load between the holding element and the gripping element.
Such elastic load, which is needed in order to ensure the correct gripping of the yarn, may cause excessive stresses of the yarn, which may cause the fraying or even the breakage of the yarn during its grip when the yarn is dragged, by the movement of the holding element, between the side of the holding element and the side of the gripping element. Breakage of the yarn is not a minor problem, because it causes the loss of the yarn on the part of the respective yarn finger and requires a stop of the machine and the manual intervention of an operator in order to restore the correct feeding of the yarn to the machine. Such problem in practice precludes the use of particularly delicate yarns on knitting machines that use such yarn gripping and cutting devices.
The aim of the present invention is to solve the problems described above, by providing a yarn gripping and cutting device, particularly for striping yarn fingers for knitting machines or the like, which effectively avoids overstraining the yarn during its gripping.
Within this aim, an object of the invention is to provide a yarn gripping and cutting device that makes it possible to use particularly delicate yarns even on machines that use striping yarn finger assemblies of the type described above.
Another object of the invention is to provide a device that can be derived, in an extremely simple manner, from yarn gripping and cutting devices of the known type.
A further object of the invention is to provide a device that can be installed, without problems, on knitting machines as a replacement of the yarn gripping and cutting devices that equip currently commercially available striping yarn finger assemblies.
This aim and these and other objects that will become better apparent hereinafter are achieved by a yarn gripping and cutting device, particularly for striping yarn fingers for knitting machines or the like, comprising an element for holding the yarn which has a laminar body having, on one of its sides, a recess adapted to receive the yarn to be gripped and cut; laterally to said holding element, on mutually opposite sides, being respectively provided a gripping element and a cutting element; said holding element and said gripping element being pushed elastically toward each other on their mutually facing sides; said holding element being movable with respect to said gripping element and to said cutting element along an actuation direction from a standby position, in which said recess is arranged at least partially outside the space occupation of said gripping element and of said cutting element in order to receive the yarn to be gripped and cut, which straddles said recess transversely to said actuation direction, to a retention position, in which said recess is retracted between said gripping element and said cutting element to perform, in succession, the retention of a portion of the yarn, by way of its traction between the mutually facing sides of said holding element and of said gripping element, and the cutting of the yarn, by way of the interference of the yarn with said cutting element, and vice versa, characterized in that it comprises spacing means, which are interposed between said holding element and said gripping element in order to limit the extent of the stresses on the yarn during its traction between said holding element and said gripping element.
Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the device according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic perspective view of the device according to the invention with the holding element in the retention position;
Figure 2 is a schematic perspective view of the device according to the invention with the holding element in the standby position;
Figure 3 is a schematic perspective view of the device according to the invention in a step of transition of the holding element from the standby position to the retention position;
Figure 3a is a sectional view of Figure 3, taken along a plane which is perpendicular to the plane of arrangement of the holding element;
Figure 4 is a schematic perspective view of the device according to the invention in another intermediate step of the transition of the holding element from the standby position to the retention position;
Figure 4a is a sectional view of Figure 4, taken along a plane which is perpendicular to the plane of arrangement of the holding element;
Figure 5 is a schematic perspective view of the device according to the invention at the end of the transition of the holding element from the standby position to the retention position;
Figure 5a is a sectional view of Figure 5, taken along a plane which is perpendicular to the plane of arrangement of the holding element.

With reference to the figures, the device according to the invention, generally designated by the reference numeral 1, comprises an element 2 for holding a yarn 3, a gripping element 4 and a cutting element 5.
The holding element 2 has a laminar body which has, on one of its sides, a recess 6 adapted to receive the yarn 3 to be gripped and cut.
The gripping element 4, which also has a laminar body, is arranged laterally to the holding element 2 and faces, with one of its sides, one side of the holding element 2.
The holding element 2 and the gripping element 4 are pushed elastically toward each other on their sides that face each other by means of springs or by using the elastic flexibility of the laminar body of the holding element 2 and/or of the gripping element 4.
The cutting element 5, which also preferably has a laminar body, faces with one of its sides the side of the holding element 2 that is opposite with respect to the side that the gripping element 4 faces.
The holding element 2 can move with respect to the gripping element 4 and the cutting element 5 along an actuation direction, indicated by the arrow 7, in order to pass from a standby position of the yarn 3 to a retention position of said yarn 3.
In the standby position, shown in Figure 2, the holding element 2 is arranged with the recess 6 at least partially outside the space occupation of the gripping element 4 and of the cutting element 5, in a position that is suitable to receive the yarn 3 to be gripped and cut, which is designed to straddle the recess 6 transversely to the actuation direction 7. More clearly, in the standby position, the holding element 2 protrudes, with its recess 6, from the front side of the gripping element 4 and of the cutting element 5.
The expression "front side", in the present description, designates the side of the holding element 2, of the gripping element 4 and of the cutting element 5 that is designed to be directed toward the bed of the machine on which the device according to the invention has to be mounted, i.e., the side of the holding element 2, of the gripping element 4 and of the cutting element 5 that is designed to be directed toward the needles that must be fed by way of the yarn finger assembly that is equipped with the device according to the invention for each one of its yarn fingers.
In order to better illustrate the characteristics and the operation of the device 1 according to the invention, the figures of the accompanying drawings show, besides the device 1, also a yarn finger 8 which is served by the device 1, and Figures 1, 2, 3, 4, 5 also illustrate an assembly of needles 9 of the machine to be fed by way of the yarn finger 8 and an assembly of sinkers 10.
In the retention position, illustrated in Figures 1 and 5, the holding element 2 is arranged with the recess 6 retracted between the gripping element 4 and the cutting element 5.
The movement of the holding element 2 from the standby position to the retention position, which can be actuated by way of means of the known type, particularly by way of the means illustrated in EPA 07802212.6, included herein by reference, causes, in succession, the retention of a portion of yarn 3, by way of its traction between the mutually facing sides of the holding element 2 and of the gripping element 4, and the cutting of the yarn 3, as a consequence of the interference of said yarn 3 against the front side 5a of the cutting element 5, which constitutes the blade of said cutting element 5. In practice, during the traction of the yarn 3 between the gripping element 4 and the cutting element 5, the side of the recess 6 that lies opposite the front side 5a of the cutting element 5 acts as a contrast cutter.
According to the invention, the device 1 comprises spacing means 11, which are interposed between the holding element 2 and the gripping element 4 in order to limit the extent of the stresses on the yarn 3 during its traction between the holding element 2 and the gripping element 4.
Conveniently, the spacing means 11 can be disengaged from the holding element 2 and/or from the gripping element 4 just before the cutting of the yarn 3 by the cutting element 5 so as to ensure effective gripping of the yarn 3, between the holding element 2 and the gripping element 4, before its cutting.
More particularly, the spacing means 11 cited above are constituted by a protrusion 12 that protrudes from the side of the gripping element 4 that faces the holding element 2.
As an alternative, the protrusion 12, instead of being arranged on one side of the gripping element 4, might be arranged on one side of the holding element 2, or there might be two protrusions, one on the holding element 2 and one on the gripping element 4, on their mutually facing sides, which mate with each other.
In the illustrated embodiment, the holding element 2 has a portion 2a that can engage the protrusion 12 in its stroke for transition from the standby position to the retention position with the exception of the end portion of said stroke, because the holding element 2 has, in its region that faces the protrusion 12 when said holding element 2 is in the retention position, a hollow 13, which delimits the portion 2a at the front.
Because of the hollow 13, the holding element 2 disengages from the protrusion 12 just before the interference of the cutting element 5 with the yarn 3 arranged in the recess 6 of the holding element 2.
Preferably, the protrusion 12 is constituted by a punch mark that protrudes from the side of the gripping element 4 that is directed toward the holding element 2.
The device according to the invention is designed to be used in particular with assemblies of yarn fingers 8 to be mounted on knitting machines, particularly circular knitting machines.
In these circular knitting machines, the assembly of striping yarn fingers 8 is arranged between the rotation axis of the needle cylinder of the machine and the ideal cylindrical surface along which the needles of the machine are arranged. Each one of the yarn fingers 8, one of which is shown in Figures 1 to 5, is provided with a passage 14 for the yarn 3 and is served by a related device 1 according to the invention, which is arranged so that the actuation direction 7 is oriented radially in relation to the needle cylinder and substantially horizontally.
Each yarn finger 8 can move parallel to the actuation direction 7 in order to pass from a standby position, in which its passage 14 is in a rearward position with respect to the bed, i.e., with respect to the needles 9 of the machine, to a working position, in which its passage 14 is in a forward position toward the bed , i.e., toward the needles 9 of the machine and vice versa. In the transition from the standby position to the working position, the yarn finger 8 also moves along a direction which is perpendicular to the actuation direction 7, i.e., parallel to the needle cylinder axis if the machine is a circular knitting machine, so as to pass over the needles 9, as better described in EPA 07802212.6.
Operation of the device according to the invention is as follows.
As shown in Figure 1, at the beginning of the feeding of the yarn 3 to the needles 9 of the machine, the yarn finger 8 is brought to the working position so as to arrange the portion of yarn 3, which extends from the passage 14 to the device 1, so that it straddles the bed of the machine, i.e., so as to intersect the imaginary cylindrical surface along which the needles 9 of the machine are arranged. In this manner there is the certainty that the needles 9 of the machine, moved to work at the feed or drop, served by the assembly of yarn fingers 8 being considered, grip the yarn 3 fed by the yarn finger 8.
Once the needles 9 have begun to grip the yarn 3, the holding element 2, previously brought to the retention position, is moved, by way of its own movement along the actuation direction 7, in the standby position, as shown in Figure 2. In this position, the holding element 2 has the recess 6 extracted frontally to the gripping element 4 and to the cutting element 5 in a suitable position to receive the portion of yarn 3 that extends from the passage 14 of the yarn finger 8 up to the last needle 9, which has taken the yarn 3 at the feed or drop being considered, when the feeding of the yarn 3 will be interrupted to the needles 9 of the machine.
In order to interrupt the feeding of the yarn 3 to the needles 9 of the machine, the yarn finger 8 is moved backwards in the standby position. This retraction places the portion of the yarn 3 that extends from the passage 14 to the needles 9 of the machine inside the recess 6, as shown in Figures 3 and 3 a.
Subsequently, the holding element 2 is moved from the standby position to the retention position.
During this movement of the holding element 2, the yarn 3 that is placed in the recess 6 is progressively moved closer to the gripping element 4 and to the cutting element 5. It should be noted that during the passage from the standby position to the retention position, the holding element 2 is engaged with its portion 2a against the protrusion 12 and this engagement has the effect of spacing the gripping element 4 from the side of the holding element 2 which it faces. This engagement between the portion 2a of the holding element 2 and the protrusion 12 persists almost until the moment of the interference of the yarn 3 against the front side 5a of the cutting element 5 that constitutes the blade of said cutting element 5. In this manner, the yarn 3 is dragged between the gripping element 4 and the holding element 2 when they are still spaced because of the engagement of the protrusion 12 against the portion 2a of the holding element 2, as shown in Figures 4 and 4a. Thanks to this fact, an excessive stress of the yarn 3, which might produce its fraying or breakage with consequent loss of the yarn 3 on the part of the respective yarn finger 8, is effectively avoided.
Just before the yarn 3 meets the front side 5a, i.e., the blade of the cutting element 5, the portion 2a of the holding element 2 is disengaged from the protrusion 12 and thus the gripping element 4 moves closer almost instantly to the holding element 2, safely gripping the yarn 3 between the gripping element 4 and the holding element 2, as shown in Figures 5 and 5a.
When, during a subsequent feeding of the same yarn 3, the holding element 2 is moved from the retention position to the standby position, the portion 2a of the holding element 2 engages again the protrusion 12, spacing the gripping element 4 from the holding element 2 and thus ensuring the release of the yarn 3.
In practice it has been found that the device according to the invention fully achieves the intended aim, since it avoids effectively any excessive stressing of the yarn, while ensuring an efficient gripping of the yarn, making it possible to use even particularly delicate yarns on machines that use assemblies of yarn fingers that require yarn gripping and cutting devices.
Another advantage of the device according to the invention is that it can be obtained, with modifications that are simple to provide, from yarn gripping and cutting devices of the traditional type.
Although, the device according to the invention has been conceived particularly for striping yarn fingers, it might be used with other types of yarn finger without thereby abandoning the scope of protection of the invention.
The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may further be replaced with other technically equivalent elements.
In practice, the materials used, as well as the dimensions, may be any according to requirements and to the state of the art.
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

A yarn gripping and cutting device, particularly for striping yarn fingers for knitting machines or the like, comprising an element (2) for holding the yarn (3) which has a laminar body having, on one of its sides, a recess (6) adapted to receive the yarn (3) to be gripped and cut; laterally to said holding element (2), on mutually opposite sides, being respectively provided a gripping element (4) and a cutting element (5); said holding element (2) and said gripping element (4) being pushed elastically toward each other on their mutually facing sides; said holding element (2) being movable with respect to said gripping element (4) and to said cutting element (5) along an actuation direction (7) from a standby position, in which said recess (6) is arranged at least partially outside the space occupation of said gripping element (4) and of said cutting element (5) in order to receive the yarn (3) to be gripped and cut, which straddles said recess (6) transversely to said actuation direction (7), to a retention position, in which said recess (6) is retracted between said gripping element (4) and said cutting element (5) to perform, in succession, the retention of a portion of the yarn (3), by way of its traction between the mutually facing sides of said holding element (2) and of said gripping element (4), and the cutting of the yarn (3), by way of the interference of the yarn (3) with said cutting element (5), and vice versa, characterized in that it comprises spacing means (11), which are interposed between said holding element (2) and said gripping element (4) in order to limit the extent of the stresses on the yarn (3) during its traction between said holding element (2) and said gripping element (4).
The device according to claim 1, characterized in that said spacing means (11) can be disengaged from said holding element (2) and/or from said gripping element (4) just before the cutting of the yarn (3) by said cutting element (5), i.e., just before the interference of the yarn (3), arranged in the recess (6) of said holding element (2), with said cutting element (5).
The device according to claims 1 and 2, characterized in that said gripping element (4) has a laminar body which faces a side of said holding element (2), said spacing means (11) being constituted by a protrusion (12) on the side of said gripping element (4) that faces said holding element (2).
The device according to claim 3, characterized in that said holding element (2) has a portion (2a) that can engage said protrusion (12) in its stroke for passing from said standby position to said retention position, except for the end portion of said stroke.
The device according to claim 4, characterized in that said portion (2a) of the holding element (2) disengages from said protrusion (12) just before said cutting element (5) interferes with the yarn (3) arranged in the recess (6) of said grip element (2).
The device according to one or more of claims 3 to 5, characterized in that said protrusion (12) is constituted by a punch mark that protrudes from the side of said gripping element (4) that is directed toward said holding element (2).
The device according to one or more of the preceding claims, characterized in that at least one between the laminar body of said holding element (2) and/or the laminar body of said gripping element (4) is elastically flexible and is loaded elastically against the other body.