Fabric Pull-off Mechanism, Particularly For Circular Knitting Machines

Abstract

To provide for reliable engagement of the fabric with the pull-off mechanism, and to provide a greater area of contact than a line contact between a pair of rollers, a rotary pull-off means is provided in which the fabric is guided in a path over at least half of the circumference of a roller, or between a pair of endless bands, travelling a parallel path with the fabrics squeezed therebetween. To provide for uniformity of pull-off when the mechanism is intermittently operated, for example by a ratchet or the like, intermittent motion is transferred to a shaft concentric with a pull-off roller, the shaft being connected to the roller over a spiral spring. The tightness of engagement of the intermittently operating mechanism with the pull-off cam track of the machine is adjustable, simultaneous adjustment at both sides of the rollers being provided.

Description

The present invention relates to a fabric pull-off mechanism particularly for circular knitting machines, in which a plurality of pull-off rollers, or pull-off bands are provided which are so arranged that the fabric is engaged over a substantial area thereof.

Customarily, the pull-off mechanisms for circular knitting machines are operated intermittently by levers arranged at both sides of the pull-off rollers; one end of the lever is connected over a one-way clutch with the shaft of the roller, the other, free end of the lever carrying an engagement roller in the form of a cam follower or the like, which bears against an undulating cam track arranged on the machine. As the machine rotates, the lever makes up and down excursions, the one-way clutch converting the oscillating motion of the lever into short rotary increments of shaft rotation for the pull-off roller.

Fabric pull-off mechanisms of this kind, in their simplest form, consist of a pair of parallel, outwardly driven pull-off rollers between which the fabric, in tubular form, is pulled downwardly by friction. To increase the frictional contact, it has been proposed to provide three parallel arranged rollers, the center roller of the three being partly surrounded by the tubular fabric.

Various difficulties have been experienced with fabric pull-off arrangements of this type. To provide for reliable pull-off of the tubular fabric, the outer ends of the outer rollers are pressed together. Since the rather slender rollers are, however, quite elastic, the cunter-pressure of the fabric itself causes deformation of the center of the roller, so that the fabric being pulled off is subjected to a lesser pull at the center, per unit length, than at the end. The ends, however, are pressed together rather strongly. Not only is the tubular fabric insufficiently pulled down in the center, so that it may slip or slide, but additionally the excessive pressure at the two ends of the roller deforms the knit loops at the folded edge, so that it is difficult or even impossible to remove the fold and restore the fabric to flat condition, which interferes with subsequent cutting of the fabric for manufacture into finished goods. Additionally, the material is not pulled off even with the knit loops being knitted, so that a certain bias deformation may result. The pull-off mechanism utilizing three rollers has the additional disadvantage that the tubular fabric always contacts the pull-off roller with one surface, so that only the one side of the tube, which contacts the pull-off roller, is merely carried along, the outer side of the tube being carried along only due to the connection with the inner side, over the double fold at the edge. The outer side of the tubular fabric may, therefore, be retarded in its travel with respect to the inner side which additionally contributes to diametrical asymmetries in the resulting fabric.

The distance between the centers of the pull-off shafts must be variable if the machine is to be used with fabrics of different thicknesses and with different materials. This variation in axial distance of the pull-off rollers greatly interferes, and in some instances completely inhibits synchronization of adjacent pull-off rollers and completely synchronous drive thereof, without play.

Large circular knitting machines effect rotation of the pull-off rollers in many small steps by a lever arrangement, similar to a ratchet, the small steps being so small and so selected that the pull of mechanism approaches a uniform motion. It is necessary, however, to insure that the pull of mechanism is, effectively, always operating, since stoppages, even for short periods of time, interfere with uniformity of the fabric. It has been proposed to provide a pair of lever drives, one on each side of the pull-off rollers, which are out of synchronism with each other, so that they alternately provide pulling movement to increase the number of steps and to thus approach approximately uniform rotation of the pull-off mechanism.

Known pull-off mechanisms utilize, basically, two different types of lever drives; in one type, the stroke of the lever, which is transferred to the roller, is unchanged; in the second, the extent of rotation, that is, the stroke of the pull-off mechanism is automatically adjusted, in dependence on fabric being knitted.

The lever drives in which the stroke is fixed has the disadvantage that, as the material is knitted more or less rapidly, the pull of mechanism is incapable of matching knitting speed (with respect to fabric length); the length of the fabric, per unit time, may change, for example by changing the length of the knit loops, or stitches, adding or subtracting knitting systems on a given machine, or the like. Inability of the pull-off mechanism to adjust to changed fabric length in unit time is undesirable. In the type of pull-off mechanism in which the stroke of the lever is adjustable, it has been customary to include a spring between a fixed point and the lever, the lever having a predetermined stroke, and the spring compensating for variations in fabric length per unit time during operation of the knitting machine. Such arrangements, when utilized with roller drives in which both sides of the rollers are lever driven, have the disadvantage that both levers operate during a short period of time, even though they may be out of phase, or synchronism with respect to each other. During this time of joint operation, the forces of both springs act on the shafts of the pull-off rollers and over those on the knit goods and, by reaction, on the machine. Variations in the amount of pull-off force again interferes with the quality of the fabric being knitted.

SUBJECT MATTER OF THE PRESENT INVENTION

Briefly, the pull-off mechanism is so arranged that a rotary pull-off means, such as rollers or essentially parallel bands are provided, the fabric being pulled off being guided in a path leading over about at least half of the circumference of the pull-off means, that is, half of the parallel portions of the length of the bands, or half of the circumference of a pair of driven pull-off rollers. This increases substantially the frictional contact surface, permits reduction in pressure of the pull-off rollers against each other and avoids one-sided contact of the fabric with a driven element.

To provide for uniformity of pull-off motion, the oscillating or intermittently operating levers are connected to a shaft, and a spring interconnection, preferably a spiral spring, is provided to the pull-off roller, for example by connecting one end of the spiral spring to the shaft stepwise progressively rotating, and the other to the roller, so that the spring can wind and unwind, providing, in effect, practically constant tension and constant rotation to the roller.

DRAWINGS

FIG. 1 is a schematic side view of a fabric pull-off mechanism in which the fabric is pressed by an endless band against a portion of the circumference of a pair of pull-off rollers;

FIG. 2 is a schematic side view in which the fabric is passed between a pair of endless bands, each band, in turn, passing over a pull-off roller;

FIG. 3 is a pull-off arrangement illustrating a spring-loaded pressure roller;

FIG. 4 is a top view of a different embodiment of the present invention;

FIG. 5 is a schematic view, partly in axial vertical section of the embodiment of FIG. 4, with a means to relieve the tension on the fabric;

FIG. 6 is a side view of FIG. 5, to reduced scale, and

FIG. 7 is a perspective view of an adjustment arrangement to control the extent of pull-off of the fabric.

Referring now to FIG. 1: A pair of driven pull-off rollers 2, 3 are provided, the fabric 1 being pressed against the rollers by means of an endless band 4 which is carried around an idler roller 5, against the outer side of the fabric to provide transporting pressure to the outer side, around the first pull-off roller 3, and over the second pull-off roller 2, the endless band itself being wrapped around the pull-off roller. The band is returned over a second idler 6. The roller 3 is preferably driven by means of gears (not shown in the drawing and beyond the frame of the pull-off mechanism) together with roller 2. The axial distance between rollers 2 and 3 may remain constant, the thickness of the fabric being immaterial since the band 4 will provide pressure contacts around rollers 3, and a bearing surface around roller 2 in all instances. The band 4 always has the same speed as the circumferential speed of roller 3. The tubular fabric between band 4 and roller 3 is gripped on both sides and is transported in exactly the same manner on both sides. This provides equal tension to both sides of the flattened tubular fabric. THe elasticity of the band 5 is so selected that, even if the rollers bend through in the middle (as is unavoidable), approximately the same contacting pressure is applied in the center as at the ends of the rollers, so that the specific pull-off force over the entire width of the fabric is uniform. The frictional force in both side walls of the fabric, when flattened, is substantially uniform. Band 4 and the circumferential surface of roller 3 are so selected that they have approximately the same surface characteristics, for example being made of the same material or having a same contacting cover; rubberizing the surface of roller 3, and the band 4 is suitable. The pressure against the edge of the tubular fabric is no greater than that at any other points, and thus the double fold at the edge of the tubular fabric, as it is folded flat, is no greater than the pressure exerted against any other surface area.

Roller 5, in the example of FIG. 1, increases the angular contact area of fabric 1 with roller 3.

FIG. 2 illustrates an embodiment of the present invention in which the goods 1 are carried between a pair of endless bands 7, 8, the bands pressing against the fabric 1. Endless bands 7, 8 are driven by rollers 9, 10 and/or 11, 12, respectively, the fabric 1 being pressed therebetween being constantly carried by the bands 7, 8. Again, the surface area of contact between the bands and the fabric is substantial.

FIG. 3 illustrates an arrangement in which the goods are carried over a deflection roller 13, which may be an idler and run free; it is then guided around a driven pull-off roller 14 with a circumferential angle .alpha..sub.2 , which extends between a leading contact line A.sub.2 and a trailing contact line B.sub.2. The fabric 1 leaves contact with the roller 14 at line B.sub.2, to then travel along a straight path and be engaged by the likewise driven pull-off roller 15 at line A.sub.3. The roller 15 is covered by the fabric with an angle .alpha..sub.3 which extends between the leading line A.sub.3 and the trailing line B.sub.3, the fabric leaving contact with the driven roller 15 at line B.sub.3, to be then guided to a take-up roll. Before the goods leave the pull-off mechanism, the line C.sub.3 is passed. A pressure roller 16, which is not driven and runs along engages with radial pressure p.sub.1 against the fabric surrounding roller 15. Pressure p.sub.1 is obtained by a spring system 17, the tension of which can be adjusted by means of a set screw 18, as schematically indicated. The angle of circumference between lines A.sub.3 and C.sub.3 is .beta..sub.3.

In contrast to a known arrangement in which the fabric is subjected at two points at a direct radial pressure between metallic portions, only a single pressure to effect pull-off is provided, namely at point C.sub.3. The radial pressure p.sub.1 can be small and, for some applications the roller 16, and with it the radial pressure can be omitted entirely. Radial pressure p.sub.1 in any event is less than pressure of rollers against each other. This is obtained by placing the roller 16 in the vicinity of the trailing line of contact B.sub.3, so that the frictional engagement of the fabric, that is, the force obtainable by the strength of the fabric material itself, can be extended from the line B.sub.3 over the circumferential area given by the axial length of the pull-off rollers and the angle .alpha..sub.2 and .beta..sub.3.

It is customary in circular knitting machines to drive a pull-off mechanism intermittently, in a movement similar to a ratchet movement. In accordance with the embodiment of FIGS. 4-6, the shafts 19, 20 are coupled by means of gears 21, 22 so that they always move in synchronism. They are driven by means of levers 23, 24, which transmit half a cycle of recurring oscillation (in and out of the plane of the drawing FIG. 4) over one-way clutches 25, 26 to shafts 19, 20. As levers 23, 24 oscillate up and down (above and below the plane of the drawing of FIG. 4), and clutches 25, 26 engage in one direction only, shafts 19, 20 are driven in stepwise movement to progress in angular increments. This, fixed and stiff system of shafts is coupled to the pull-off system, that is to rollers 27, 28, which are connected by gear 29, 30, by soft, preferably spirally wound springs 31, 32, which are located within the hollow interior of rollers 27, 28. Thus, elastic coupling is provided by securing one end of 33 of the springs 31, 32, to the shafts 19, 20 respectively, whereas the other end 34 is secured, fixed, to the rollers 27, 28 respectively. Other types of springs than spirally wound springs may be used, and the springs can be located also beyond the rollers and the driven shaft.

In operation, when a greater quantity of material is to be pulled, springs slightly relax and the additional material is pulled off during the expansion of the spring. This slightly decreases the tension on the material; the tension is decreased, however, by an amount which is small in comparison to that which would occur if a stiff coupling were provided. If less material is supplied by the machine, the tension increases slightly, but much less than the increase in tnesion by a stiffly coupled system.

The spring, which transmits the pull-off force can readily be released from spring pressure in case the machine is to be stopped for an appreciable period of time, so that it is undesirable to maintain a pull-off tension on the material between the knitting positions on the machine and the first pull-off roller. Such uninterrupted and continued pull has an undesirable effect on the knitted fabric. FIGS. 5 and 6 illustrate, to a different scale, one each of the two pull-off rollers 27, 28 with the coupling spring 31 located therein. A gear 29 is secured to roller 27 which meshes with a meshing gear 35, having a shaft 36 which extends beyond the wall 37 of the housing of the fabric pull-off mechanism. A lever 38 is secured to the end of shaft 36, the lever serving to release the tension due to the spring when the machine is stopped for an appreciable period of time. Pin 39 can be removed, permitting relative rotation of shaft 36 counter the normal direction of rotation. To prevent lever 38 from moving, in operation of the machine, it can be removed from shaft 36.

After the machine has been stopped, and when the machine is to be started again, lever 38 is moved, or rotated back to its original position, and is then removed from shaft 36. The fabric is now under the desired pull-off tension.

It is desirable that the stroke of the pull-off mechanism be adjustable, to provide for uniform tension, even if the fabric length per unit-time changes. To provide for uniformity of pull-off, even with intermittently and out-off phase operation of the oscillating pull-off mechanism, an adjustment mechanism is provided which is illustrated, in perspective and schematic form in FIG. 7. A shaft 40 has a pair of pulleys 41 arranged at its end, about which a tension cable 42 is passed, which runs over an idler pulley 43 and is then connected to a spring 45. Springs 45 engage the drive levers 44, the other end 49 of which is engaged by the pull-off operating cam track of the machine, a fragment of which is illustrated at 46. Such cam tracks to operate pull-off mechanisms are known and further description is not necessary. The cam track itself is undulating, so that the cam follower roller end 49 will make an up-down movement. The extent of engagement of roller 49 with cam track 6 will determine the stroke. Adjusting the tension of springs 45, thus, determines the engagement, force, and length and thus affects the stroke length. To compensate for change in length of cable 42 engaging spring 45, a counter-length adjusting spring is provided. The length of both levers, on the right and on the left side of the rollers is adjusted simultaneously by means of a gear drive schematically indicated as a worm gear 47, operated by a handle. The adjustment is thus common to both sides of the rollers, simultaneously changing the spring tension of springs 45, and thus providing for synchronized adjustment of the springs which affect the pull-off force and stroke.

Pull-off mechanisms for textile machinery, and particularly for circular knitting machines, should be able to pull off the material over the entire width with the same force, at any one point transverse to the width; it should not damage the goods at the bend, where a tube is flattened; in multiple ply, such as flat and tubular fabrics, the same tension should be applied to both top and bottom (or front and back) layers of the tube; the pull-off mechanism should be completely synchronized at both ends, and with respect to stroke, and provide uniform pull-off tension and pull-off force at all strokes; and all contacting surfaces should be as large as possible. These objects are achieved by providing a large angle of contact of the rollers, spring interconnection of intermittent pull-off force and pull-off rollers, and completely synchronized and balanced adjustments of pull-off force and stroke.

Various changes may be made within the scope of the inventive concept.

The detailed specification is directed to that portion of the machine in which the apparatus of the present invention is incorporated and with which the method of the present invention is useful. For a complete discussion of knitting machines, reference may be had to "Double Knit Fabric Manual," copyright 1961, and "Knitting Dictionary," copyright 1966, both published by the National Knitted Outerwear Association; "Technologie der Rundstrickerei" by Albert Diebler, Konradin-Verlag, Stuttgart, particularly vols. 9, 10 and 11; U.S. Pat. Nos. 2,169,801, 2,697,336; and British Pat. Nos. 874,719 (which dicloses a system to control the dial needles), and 996,291, from which well known parts of the machines, the cooperation of the apparatus of the present invention with known parts of knitting machines, and application of the invention to other machines and operating elements thereof, will be obvious. Typical knitting machines are, for example, Type SMH, SMJH, and other interlock circular knitting machines, eight lock circular knitting machines, single knit machines and the like made by Fouquet-Werke Frauz & Planck described in detail in their "Betriebsanleitung" ("Operating Instructions") and "Montage-und Betriebsanleitung" ("Installation and Operating Instructions").

Claims

We claim:

1. Pull-off mechanism for circular knitting machine comprising

two pull-off roller (14, 15) adjacently located and driven to rotate in opposite directions;

guide means guiding the fabric (1) being pulled off the machine in a path leading over more than one half the circumference of the first (14) of said rollers, with respect to the pull-off path of the fabric, including an idler roller (13) having its center located in advance of, and laterally offset with respect to the center of the first pull-off roller (14) to change the direction of the arriving fabric and guide the fabric against the surface portion of the pull-off roller so that the fabric will form, at its contact point with the pull-off roller, an angle with respect to the direction of the arriving fabric, and thus to increase the surface contact of the fabric with the first pull-off roller;

the second pull-off roller (15) being located, with respect to the direction of the arriving fabric, laterally adjacent the first pull-off roler (14) so that the path of the arriving fabric will be deflected by said idler roller (13) to engage the first pull-off roller over an angular extent of its circumference in excess of 180.degree., and the fabric will then engage the second pull-off roller over an angular extent of about in the order of 180.degree.; and

a presser idler roller (16) pressing the fabric against the second pull-off roller (15) in the region adjacent to, but not beyond the separation line of the fabric with the second pull-off roller (15) as the fabric is being removed from the second pull-off roller.

2. Mechanism according to claim 1

including operating means for said pull-off rollers, comprising

oscillating means (23, 24, 25, 26) converting swinging, oscillating motion into intermittent progressive rotary motion;

a shaft (19, 20) connected to said oscillating means;

and spring means (31, 32) interconnecting the shaft (19, 20) and at least one of the rollers to provide for essentially uniform application of pull-off force to the respective roller although the shaft is advanced intermittently.

3. Mechanism according to claim 2 wherein the roller is hollow and concentric with the shaft;

and the spring means comprises a spiral spring wound about the shaft and secured at one end to the shaft and at the other end to the roller.

4. Mechanism according to claim 3 wherein a pair of power-driven rollers and a pair of shafts are provided, the shafts being interconnected by gears (21, 22).

5. Mechanism according to claim 3 wherein a pair of power-driven rollers and a pair of shafts are provided, the rollers being interconnected by gears (29, 30).

6. Mechanism according to claim 2 including (FIGS. 5, 6) means (38) permitting manual rotary displacement of the roller (27) with respect to a respective shaft (19).

7. Mechanism according to claim 6 including a gear (29) secured to the roller (27) subject to displacement;

a meshing gear (35), the means permitting manual displacement of the roller (27) comprising a removable handle (38) coupled to the meshing gear (35).

8. Mechanism according to claim 7 wherein the removable handle is removably secured to the meshing gear (35) to rotate therewith, and a fixed stop (39) for the handle (38), when secured to the gear (35), is provided on the machine.

9. Mechanism according to claim 1 (FIG. 7)

including operating means for said pull-off rollers adapted to be driven intermittently by the machine, comprising

oscillating means (44, 49, 46) converting swinging, oscillating motion into intermittent progressive rotary motion including a pair of levers (44, 49), one each arranged at an end of the respective driven pull-off roller and forming a pair of cam followers;

a pair of cam tracks (46), one each engaged by one of said cam followers;

spring means (45) connected to each said cam followers and pressing the cam followers against the cam tracks;

and an adjustment means to adjust the spring pressure of said cam followers comprising an adjustment shaft (40) extending essentially parallel to the main axis of the roller, connection means (50, 42, 43) engaging each spring for each cam follower and coupled to the ends of the adjustment shaft and means (47) adjusting the angular position of said adjustment shaft (40) to provide for uniform change of spring pressure pressing each said cam followers against the cam track, and thus effect uniformity of adjustment of both cam followers, synchronously and simultaneously.