WO2011013156A2

WO2011013156A2 - Circular weft knitting machine provided with improvements for facilitating stitch formation

Info

Publication number: WO2011013156A2
Application number: PCT/IT2010/000329
Authority: WO
Inventors: Renato Pilotelli; Roberto Pilotelli
Original assignee: Pilotelli Macchine Tessili S.R.L.
Priority date: 2009-07-31
Filing date: 2010-07-22
Publication date: 2011-02-03
Also published as: IT1398151B1; ITFI20100023A1; WO2011013156A3

Abstract

A circular weft knitting machine is described, comprising a cylinder (1) of the needles defining a plane (p) for forming jersey. The machine comprises a retaining ring (13) for retaining the fabric having a substantially circular edge coaxial to the cylinder (1) of the needles, said retaining ring (13) preventing the fabric from being lifted by the needles and maintaining the formed fabric below the end (5A) of the open latches of the needles at the end of their lifting path. In this way, the formation of the jersey is facilitated, in particular the beginning of processing of a piece of fabric and the resumption of work in the case of a breakage of a yam.

Description

"CIRCULAR WEFT KNITTING MACHINE PROVIDED WITH IMPROVEMENTS FOR FACILITATING STITCH FORMATION"

DESCRIPTION

Technical field

The present invention refers to single-cylinder circular weft knitting machines.

State of the Art

For the manufacture of knitted fabrics, in particular so-called plain knit "jersey" fabrics, 1/1 or other simple knits, circular machines have long been known and used, which use mutually co-operating needles and sinkers according to an arrangement that is well known to those skilled in the art. In particular, the sinkers serve two functions: creating the stitch formation plane holding the fabric during the sinking movement of the needles and holding the fabric being formed preventing it from being lifted during the lifting path of the needles. Recently some types of such machines that do not use sinkers have also been developed. In this case, the fabric holding function to prevent lifting thereof by the needles is mostly performed by the fabric pulling device, which maintains the fabric under tension in a direction that has at least one component opposite to the rising motion of the needles. For this purpose, the inner surface of the cylinder is conical with a small angle of conicity, for example 24°, and, in correspondence of the stitch formation plane, it ends in proximity to the grooves of the cylinder within which the needles slide. Among other advantages, the elimination of the sinkers enables greatly to simplify the machine, with a reduction in its manufacturing and maintenance cost, lower energy consumption and better knit quality, in particular a knit that is practically devoid of bars.

An example of a machine without sinkers is disclosed in WO-A- 2007/74486.

In the mentioned machines with needles and sinkers, but above all in machines without sinkers, the initial knitting steps of a piece until it reaches the gripping members of the pulling device, and also the resumption of work following the breakage of a yarn that caused a loss of the fabric by even a group of needles, are particularly laborious in that the needles, in their rising motion, tend to rise the row being formed preventing its discharge below the end of open needle latch, and hence preventing the regular formation of the stitches. This requires a manual intervention from an operator, which is time- consuming, with wastage of yarn and possibility of needle breaking.

Objects and summary of the invention

To reduce the drawbacks described above, the present invention provides a single-cylinder knitting machine that comprises a retaining ring for retaining the fabric having a continuous circular edge, coaxial to the needle cylinder, and positioned above and in proximity to the stitch formation plane. Advantageously, said edge can be formed by the intersection of a plane that is orthogonal to the cylinder axis and of a surface that, at least in proximity to said intersection, is cylindrical and is near internally to the upper part of the needles when they are lifting, however without touching them. The retaining ring is positioned in height in such a way that said plane is at a height whose distance from the stitch formation plane is smaller than the distance between the end of the open latches of the needles, in their position of maximum lifting, and the stitch formation plane.

With this arrangement, the retaining ring holds the fabric being formed preventing it from being lifted by the needles in particular in the initial phase of knitting of a piece when the latter has not yet reached the piece-pulling device.

In a preferred embodiment of the invention, unlike known single- cylinder knitting machines without sinkers, the needle-holder cylinder ends superiorly with a plane edge orthogonal to the axis of the cylinder, positioned on the extension of the stope plane of the stitches, i.e. of the upper edge of the grooves within which the needles slide. This edge therefore faces the flat surface of the edge of the above mentioned retaining ring and it is developed radially thereat, so as to define a narrow initial horizontal passage for the fabric that is being formed, thereby holding the fabric to prevent it from being dragged vertically by the motion of the needles, exactly as occurs by means of the sinkers in machines that are provided with them. In practice, a radial extension of this narrow passage from the needles towards the interior of the cylinder is selected that is at least twice the distance of the flat edge of the cylinder from said retaining ring. In this way, when the needles, as they rise, tend to drag the fabric upwards, the portion of fabric adjacent to the needles remains as close as possible to a horizontal plane.

In this way, this function of retaining the fabric is no longer performed by the downwards traction provided by the fabric pulling device, as in traditional single-cylinder machines, and it is possible to limit the function of the piece pulling device simply to the collection of the fabric, avoiding radial overloading of the needles and the fabric, with the advantages of reducing needle and cylinder wear and of improving fabric quality.

This flat upper edge of the cylinder can be obtained by shaping it accordingly or, in the case of a cylinder of a traditional single cylinder machine, placing within the cylinder a ring with appropriate section to obtain an assembly with the desired profile.

Brief description of the drawings

The invention will be easier to understand by means of the description below and the attached drawing, which shows a non-restrictive practical embodiment of the invention.

More in particular, in the drawing

figure 1 shows a partial axial section view of the cylinder of a single cylinder circular weft knitting machine according to a first embodiment of the invention;

figure 2 shows an enlargement of the detail Il of figure 1 ;

figures 3 and 4 show respective views similar to those of figures 1 and 2 for a second embodiment of the invention; and

figure 5 shows a section view similar to that of figure 1 for a particular form of construction of the second embodiment of the invention.

Detailed description of an embodiment of the invention

Referring to figure 1 , a partial axial section is shown of a cylinder of a known single-cylinder circular weft knitting machine without sinkers. In particular, the machine comprises a rotating cylinder 1 with vertical axis X-X having a plurality of grooves 3 for guiding needles 5, uniformly distributed on the outer surface. The needle 5 shown in the drawing is in the uppermost position, with the end of the open latch at a distance hi above the top end of the cylinder 1 , in particular above the end 3A of the grooves of the cylinder which, in this case of a machine without strikers, defines the stitch formation plane P.

To the fixed frame (not shown) of the machine is fixed a ring 7 on whose periphery, in correspondence of each feed, is applied a respective thread guiding member 8 in the lower part of which, near to the needles, are provided at least one hole 9, which may be able to house a ceramic tube, for guiding the bottom yarn that is fed in this feed, and a hole 11 (which may be suitable to receive a ceramic tube) for guiding an elastic yarn to be plated together with said bottom yarn.

According to the invention, the machine comprises a continuous ring 13 arranged above the cylinder 1 , internally and in close proximity to (but not in contact with) the lifting needles 5. In particular, the ring 13 (hereafter also called "press knit" ring or "retaining ring") has a peripheral edge defined by the intersection of a lower plane 13A and of a continuous surface 13B which, at least in proximity to said intersection, is substantially approximately cylindrical and it is inside and in proximity to the needles 5 as they lift.

The ring 13 is fastened to the thread guide ring 7 by at least three brackets 14 and respective vertical bearing screws 15 and horizontal centering screws 17, forming first and second adjustment members. The first adjustment members are used for adjusting the vertical position of the retaining ring 13 with respect to the stitch formation plane of the needle cylinder 1 and the second adjustment members are used for centering the retaining ring 13 with respect to the needle cylinder 1. The brackets 14 are approximately uniformly distanced from each other in plan view along the periphery of the ring and the screws can be fastened in the preferred position by means of nut and locknut or other known means to prevent unscrewing. In this way, with the aid of a dial gauge, it is possible precisely to adjust the centering between the needles and the press knit ring 13 and the vertical position of the latter with respect to the stitch formation plane P.

In particular, as better shown in figure 2, the vertical distance h2 of the plane 13A from the stitch formation plane P is adjusted in such a way as to be smaller than the distance hi of the free end 5A of the fully open latches of the needles 5 from the stitch formation plane P.

With this arrangement, at the start of work on a piece, when the fabric is not yet held under tension by the pulling device of the machine and hence the needles, during their lifting movement for gripping the yarn, tend to drag with them the previously formed rows of stitches, the press knit ring 13 opposes this lifting providing an upward bearing for the just-formed fabric and allowing the discharge of the jersey below the respective latches.

With reference to figures 3 and 4, in a single-cylinder machine provided with a retaining ring 13 as described above, in a second embodiment of the invention the cylinder 19 ends superiorly with a flat surface 19A that lies in a plane that is orthogonal to the axis of the cylinder and therefore parallel to the plane 13A of the retaining ring and that is positioned at a relatively small distance h2 therefrom, in the order of 1mm, sufficient for the passage of the fabric that is formed by the needles 5 but smaller than the distance hi described above. In practice, the radial extension 19C of this passage is at least twice the distance h2 from the flat surface 19A of the cylinder to the plane 13A of the retaining ring 13.

In this way, the narrow passage between the mutually facing flat edges 13A of the retaining ring 13, and 19A of the cylinder 19, substantially limits the possibility of vertical excursion of the fabric, in particular of the stitches thereof engaged to the needles, performing a retaining action similar to the one performed by sinkers in the machines where they are used.

The fabric, after having run through said passage, is deviated downwards by the action of the piece-pulling device to be collected, and the tension exerted by the piece-pulling device on the fabric can be the minimal one necessary to hold the fabric stretched to collect it without wrinkles, avoiding excessively stressing the needles.

Figure 5 shows a particular form of construction of this second embodiment of the invention, in which the retaining ring 13 is held in the desired position by means of a set of brackets 21 , 23 that make it integral to the support structure of the cylinder independently of the ring 7 that bears the thread guide 11. It is thus possible to adjust the position of the retaining ring 13 with adjusting screws 25; 27A₁ 27B in radial direction and in vertical direction, respectively, without influencing the position of the thread guide ring 7.

Additionally, figure 5 shows how to a cylinder 1 of the traditional type (which in a section according to an axial plane ends with a narrow angle in correspondence of the stitch formation plane) a ring 29 can be fastened internally to the cylinder, for example by means of screws, not shown in the drawing, to form with the cylinder 1 an assembly that ends superiorly with a flat edge 29A serving the function of the edge 19A described above.

Thereby, the regular formation of the knitted fabric is assured both during normal production, and in the critical phases of the start of a new piece and of resumption of work following the breakage of a thread, which left one or more groups of needles without the previously produced row or rows of stitches.

It is understood that the drawing only shows an example provided by way of a practical demonstration of the invention, which can vary in forms and arrangement without however departing from the scope of the concept underlying the invention. Any reference numbers in the appended claims are provided for the sole purpose of facilitating reading of the claims in the light of the description and to the drawing, and do not in any manner limit the scope of protection represented by the claims.

Claims

1. A circular weft knitting machine comprising a needle cylinder (1) defining a stitch formation plane (P; 19A, 29A), characterized in that it comprises a retaining ring (13) for retaining the fabric, having a substantially circular edge coaxial to the cylinder (1) of the needles, said retaining ring (13) preventing the fabric from being lifted by the needles and maintaining the formed fabric below the end (5A) of the open latches of the needles at the end of the lifting path of the needles, thus facilitating stitch formation.

2. A machine as claimed in claim 1, characterized in that said substantially circular edge of the retaining ring (13) is formed by the intersection of a plane (13A) orthogonal to the axis (X-X) of the needle cylinder (1) with a surface (13B) which is at least partly substantially cylindrical, facing the needles (5) of said needle cylinder (1).

3. A machine as claimed in claim 2, characterized in that said at least partly substantially cylindrical surface (13B) has a cylindrical shape at least near an edge where said at least partly substantially cylindrical surface intersects said plane (13A).

4. A machine as claimed in claim 2 or 3, characterized in that said plane (13A) is spaced from the stitch formation plane (P) by a height (h2) smaller than the distance (hi) between the free end (5A) of the open latch of the needles (5) in the position of maximum lifting of the needles and said plane (p).

5. A machine as claimed in one or more of the previous claims, characterized in that said retaining ring (13) for retaining the fabric is supported by the thread - guide ring (7) of the machine by means of support brackets (14).

6. A machine as claimed in one or more of the previous claims, characterized in that an adjustment arrangement (17; 15) is provided, for adjusting the position of the retaining ring (13) with respect to the needle cylinder.

7. A machine as claimed in claim 6, characterized in that said adjustment arrangement includes first adjustment members (15; 27A₁ 27B) for adjusting the height (h2) of the retaining ring (13) with respect to the stitch formation plane (P) of said needle cylinder (1) and second adjustment members (17; 25) for centering the retaining ring (13) with respect to the needle cylinder (1).

8. A machine as claimed in one or more of the previous claims, characterized in that said retaining ring (13) is supported by a thread guide supporting ring (7).

9. A machine according to claims 7 and 8, characterized in that said adjustment members (15, 17) are arranged between the retaining ring (13) and the thread guide supporting ring (7).

10. A machine according to one or more of claims 1 to 7, characterized in that said retaining ring (13) is supported by brackets (21, 23) connecting said retaining ring (13) to a support structure of the needle cylinder (1) independently of a thread guide supporting ring (7).

11. A machine according to claim 7 and 9, characterized in that said adjustment members (25, 27A, 27B) are arranged between said retaining ring (13) and said brackets (21 , 23).

12. A machine as claimed in one or more of the previous claims, characterized in that the needle cylinder (19) ends at the top with a flat edge (19A) extending in a plane orthogonal to the axis of the cylinder, which is at a distance (h2) from the plane (13A) of the retaining ring (13), to form a passage having a width (h2) sufficient for the fabric formed by the needles (5), but smaller than the distance (hi) of the end of the open needle latch from the stitch formation plane (19A) when the needles are in the maximum lifting position.

13.A machine as claimed in claim 12, characterized in that the radial extension (19C) of said flat edge (19A) is at least twice the distance (hi) of said edge from the retaining ring.

14. A machine as claimed in claim 12 or 13, , characterized in that said flat edge (19A) is obtained by fixing internally to the upper part of the cylinder (1) a ring (29), flush with the stitch formation plane (29A) of the cylinder.