Device for the vertical stretching of fabric in an automatic knitting machine, in particular flat-bed machine

Abstract: The device, associated with two longitudinal needle beds (1,2) below which the fabric being formed exists, consisting of a series of fabric (3) holding parts (19) arranged below the said needle beds (1,2), appropriately spaced out, and carried by vertically sliding guided supporting parts (8,9). Slide parts (39), fixed to the supporting parts (8,9), slide vertically operated with an alternate motion, between a raised position where the fabric (3) is held and a lowered position when the same fabric (3) is released. Between these holding parts (19) there are gripper parts (50), spaced out uniformly in a longitudinal direction, which when activated hold the fabric when this same fabric is released by the holding parts.

Description: This invention can be classified in the technical sector concerning the production of automatic machines, for example for flat-bed or circular knitting machines. It is known that flat-bed knitting machines generally envisage two needle beds along which a carriage travels longitudinally with alternate motion. The carriage contains appropriate actuator units for the needles that are fitted inside transverse slits at regular distances-along the needle beds. These actuator units actuate the needles in succession, according to the commands provided by an electronic control unit programmed with a suitable fabric knitting program, so as to achieve the formation of a series of so-called fabric rows. The machines mentioned require the vertical stretching of the fabric. Various devices are currently used for this purpose, including generally one or more rollers placed below the needle beds and parallel to these, which are designed to catch and pull the fabric being formed. A device of this type envisages for example a pair of rollers appropriately knurled, mutually tangent and rolling in opposite directions, for a preset time interval, at the end of each carriage stroke. Another known device involves a single rotating roller that stretches along the entire length of a needle bed below which it is fitted and which is equipped with a multitude of pins that penetrate between the fabric stitches. These devices generally produce an uneven stretching in the various machine working areas, giving unsatisfactory results in the fabric weave. There is in fact a progressive slackening in the fabric, with the passage of each operating unit. Furthermore, the known devices are at times exceedingly complex which has negative reflections on their functioning, as well as their cost of production and maintenance. The USA patent no. 4.854.134, belonging to the same applicant, describes a device aimed at making and maintaining the vertical stretching of fabric homogeneous, acting on adjacent sectors of the same fabric. This device envisages a series of coaxial drums with the revolving support of rotating axes and connected to these axes by appropriate elastic parts, each of these drums having a tangential contact with at least two rollers driven by second sprung means; the fabric lies between these drums and the relative presser rollers. Appropriate actuator parts are designed to drive one of the rollers with a rotation of a preset amplitude, to determine the rotation of the relative drum, in phase with the formation of a corresponding portion of the last row of fabric. Another problem that encountered with the traditional stretching devices concerns the different tension that is often found in different areas of fabric, as shown for example in fig. 10, in this case in fact, the known devices are only able to pull the central part of the fabric, while the areas that extend on either side of this central part are not stretched. GB-A-2 013 729 relates to a take-down device for a flat knitting machine and shaped-knitted fabric, the device having reciprocable movable substantially planar elements pivotally biassed for engaging and taking down the fabric. There is also disclosed therein a device for reciprocating the said elements in a preselected manner. Each said element is arranged to be pivotable about an axis extending in the longitudinal direction of the needle beds and parallel to a smooth fabric pressing surface which extends substantially the length of the machine. The aim of this invention is that of producing a device that makes it possible to obtain the uniform stretching of all the adjacent portions of fabric even in the presence of areas of different lengths of this fabric, regardless of the type of fabric or the type of weft of the same. Another aim of this invention is that of proposing a device for the vertical stretching of fabric obtained with a simple, functional and reliable technical solution, which is also versatile to use. The above-mentioned aims are obtained in accordance with is set out in the claims. The characteristics of the invention are described below, with particular reference to the attached drawings, in which: fig. 1 illustrates a cross-section view of the stretching device subject of this invention; fig. 2 and 3 illustrate corresponding cross-section views of the device in question, respectively in the fabric holding and in the stretching position; fig. 4 and 5 illustrate, in respective exploded drawings, the holding-jaw activating parts of this device; fig. 6 illustrates a cross-section view of the device along a different plane to the cross-section plane in fig.1, that shows the gripper parts of the same device; fig. 6a illustrates the item 200 of fig. 6 in its inoperative configuration; fig. 7 illustrates, the view of the section VII - VII in fig.6; fig. 8 and 9 illustrate, on an enlarged scale, the opening and closing positions of the gripper parts; fig. 10 illustrates a view of a knitting fabric element to be stretched with the device in question. With reference to the above figures, 1 and 2 indicate the two needle beds of an automatic flat bed knitting machine, and 3 is used to indicate a portion of the knitted fabric in formation. The needle beds 1 and 2 are equipped, in the known manner, with uniformly spaced out transverse slits in which the needles 4 are inserted, actuated by their respective operating systems. The needle beds 1 and 2 are supported by a fixed frame forming a pair of platforms 5 below the same needle beds 1, 2; the platforms 5 are fixed to the needle bed 1, 2 plane by means of a series of spacers parts 6. The platforms 5 are fixed to their respective cross-members 7 that define two opposite vertical surfaces that extend lengthwise along the needle beds 1, 2. Alongside the cross-members 7 two vertically sliding angular elements are fitted, indicated respectively with 8 and 9. The angular elements 8, 9 are joined together, at their tips, by means of a known type of structure, not shown in the drawings. The angular pieces 8, 9 and the cross-members 7 are separated by appropriate pads 10 in antifriction material, designed to reduce the sliding friction. The pads 10 have on one face a narrowed part 10a, that is inserted in a corresponding opening 11 in the angular elements 8, 9, and blocked thereto (see fig. 4). The first angular element 8 is hinged, by means of a pin 290 positioned close to the lower vertical part of the same angular element, to a corner piece 270 arranged in a similar direction to the latter. The horizontal side of the dorner piece 270 is subject to the action of sprung means 380, lying between this same side and the side of the first angular element above 8, as well as the action of a first cam shaft 320, that pushes against these sprung means; this shaft has its rotating support on the end of the structures supporting the angular elements 8, 9 with its horizontal axis arranged lengthwise to the machine. Along the upper edge of the corner piece 270 a series of first jaws 17 are fixed at regular distances. These jaws 17 oscillating in synchrony as a consequence of the oscillation of the corner piece, are designed to act, as described below, in unison with a corresponding second series of oscillating jaws 18, to form an equal number of parts 19 holding the fabric 3 to be stretched. The first and the second jaws 17 and 18 are made up, in a very similar manner, of a ledge 20 protruding from a body 21 that has a pair of holes 22 to fit the relative securing screws 23. The ledge 20 slopes upwards and at the end has a holding surface 24 arranged vertically, and appropriately knurled (fig. 4). The first jaws 17 are screwed to holes 25 in the corner piece 270. The second jaws 18 are screwed into holes 26 of the respective combs 27 that are connected, by relative hinged parts 28, to the second angular element 9. To be precise, the combs 27 have an upper portion 27a, designed to face the cross-member 7 and bearing at its tip the respective second jaw 18, and a lower portion 27b facing downwards; the downward facing portion 27b, when assembled, is below the angular element 9 (see fig. 5). The hinge 28 defines a double seat 28a, 28b for the respective pins 29 and 30 for the hinging to the angular element 9 and a lever 31; the pins 29, 30 have horizontal axes that are longitudinally parallel to the machine. The advantage being that the axis of the pin 29 is positioned at the same height as the axis of the said pin 290. The lever 31 in the form of a kind of beak 31a protrudes over a second cam shaft 32 that has a rotating support, at its extremities, by the said structure that supports the angular elements 8,9 with horizontal axes longitudinal to the machine. The said first and second cam shafts 320, 32 are similar in shape, and operate in synchrony so that the corresponding jaws 17, 18 oscillate while rotating in opposite directions. The lever 31 normally rests against the downward facing part 27b of the comb 27 and is held in position by the action of a spring 33 fitted in a housing 34 made in the same lever 31. The spring 33 is retained, with a counter nut 35, by a knob 36 inserted through a hole 37 of the downward facing portion 27b of the comb 27; the head of this knob 36 rests against the lower surface of the downwards facing portion 27b. The upper surface of the lever 31 and the angular element 9 are subject to the action of another spring 38. Between the angular elements 8, 9 in correspondence with the ends of the needle beds 1, 2 there are a pair of symmetrical slides 39, only one of which can be seen in the drawings. Each slide 39 has a rack profile 40 on one side that engages with a pinion 41 with a revolving support on the fixed frame 42 of the machine and designed to be intermittently operated by appropriate drive parts. On the side opposite the rack 40, the slide 39 is guided by a counter roller 43, also revolving on a support attached to the frame 42. The action of the rack 40 is also balanced by a spring 44 suspended vertically on the frame 42 and hooked to a pin protruding from the lower end of the slide 39. The slide 39 profile on the sides has opposite shoulders 46, 47 designed to define a resting surface for the angular elements 8 and 9 respectively. The slide 39 is also connected to angular elements 8, 9 by means of screws 48 that pass through the corresponding holes 49 in the same angular elements. The device also envisages a series of gripper parts 50 (fig. 6) designed to hold the fabric 3 firmly. These gripper parts 50 consist of a pair of spring arms 51, 52 made mobile, in synchrony, by an inoperative position I (fig. 6, 8) and by an operative position 0 (fig. 9). The grippers 50 are arranged at equal distances along the cross-members 7, in intermediate positions with respect to the jaws 17, 18, with the arms 51, 52 guided against the lower surface of the needle beds 1, 2 (fig. 6). The arms 51, 52 of the grippers 50 also consist of an shaped element forming at one end a front head 53, that vertically faces the fabric 3 being formed, and in the middle a curved part 54, with the concave part facing upwards, slide fitted in a corresponding slot 60 made in the summit of the relative cross-member 7, with this curved part 54 connected, as a single piece, to an end rod 62. The lower ends 62a of the rods relative to the arms 52, 53 of the same gripper 50 are jointed to the upper ends of relative first arms 63 of the corresponding levers 64 hinged to the shafts 65, attached to the machine frame with horizontal axes arranged longitudinal to the machine. The second arms 66 of the levers 64 are almost horizontal with the free heads 66a facing one another. Above each pair of these latter heads a relative vertical shank 67 is fixed, sliding through a fixed guide part 68, fitted at the top with a plate 67a. Between the plate and the guide part 68 there is a spring 70, within which the shank 67 is inserted, that maintains the same plate in contact with a cam 69a supported by a cam shaft 69 revolving on a support attached to the machine frame and pulled into rotation in synchrony with the said cam shafts 32, 320. The action of the cam 69a, contrasted by the spring 70, gives the shank 67 two extreme positions respectively raised S and lowered A (fig. 6a). The shank 67 in the lowered position A does not intercept the opposing heads 66a (fig. 6a). One of the said second arms 66 is fixed to an electromagnet 71 fitted with a relative mobile anchor 72; when the electromagnet is energized, this mobile anchor adopts an extreme position K (fig. 7) in which the same anchor lies between the lower end 67b of the shank 67 and the relative opposing heads 66a. In this latter case the lower end 67b of the shank 67, during the descent of the latter, intercepts the heads 66a with oscillation of the levers 64 in the opposite directions S1, S2, with transfer of the rods 62 upwards (H direction), and consequent definition of the operative position O for the arms 51, 52 of the gripper 50 (fig. 9). Sprung means (not illustrated) hold the levers 64, when the shank 67 is in the raised position S, in the relative rest position R (indicated with the continuous line in fig. 6) which corresponds to the inoperative position I (fig. 8) for the arms 51, 52 of the gripper 50. It should be noted that the eventual operative position O is commanded by the holding parts 19 in their lowered position and before they open, with this position maintained during the lifting of the same holding parts and until these latter parts close as explained below. In short, with the electromagnet 71 energized, the gripper 50 assumes the operative O and inoperative I position intermittently commanded as a consequence of the rotation of the cam shaft 69, while with the electromagnet 71 de- energized the gripper 50 remains in the inoperative position I. The functioning of the device described is now illustrated starting with the stage in which the holding parts 19 formed by the jaws 17, 18 are opened in a raised position (fig. 1). In this position the aforementioned holding parts 19 are in their topmost position, therefore very close to the area where the so-called rows of fabric 3 are formed, in correspondence with the needle beds 1, 2. In suitably timed rapport with the formation of these rows, the rotation of the cam shafts 32, 320 acting respectively on the levers 31, engaged in correspondence with the respective beaks 31a, and on the corner piece 270 determines in turn the angular rotation of the combs 27, that carry the jaws 18, and the same corner piece that carries the jaws 17. The jaws 17, 18 approach one another blocking the fabric 3. Further rotation of the cam shaft 32 determines subsequently the angular rotation of the levers 31 with respect to the relative combs 27, loading the springs 33, as well as the springs 38 (fig. 2). In this manner an ideal fabric 3 holding tension is obtained, as a function of the action of the springs 33; this holding tension can be appropriately adjusted by means of the knobs 36 holding the same springs 33. Once fabric 3 hold has been established, the command is given for downward sliding of the slides 39 connected to the angular elements 8, 9 that act as supporting parts for the jaws 17, 18, so as to achieve the stretching of the same fabric (fig. 3). This sliding is obtained by the intermittent rotation of the pinions 41 that are engaged in the racks 40 of the slides 39. The intermittent rotation of the pinions 41 and therefore the lowering of the slides 39 is appropriately determined in relation to the characteristics of the fabric being made. When the fabric has been stretched, if necessary the command is given for the closing of the grippers 50 that are open during the stretching stage (fig. 8). The closing of the grippers 50 is commanded as already described, i.e. by energizing the electromagnets 71. The grippers 50 deal with maintaining the fabric 3 taut during the opening of the holding parts 19 and the subsequent rising of the slides 39. A further rotation of the cam shaft 32, that frees the levers 31 (whose return to the rest position (fig. 1) is speeded up by the sprung action of the associated springs 38), and the intermittent rotation in reverse direction of the pinions 41, restores the condition initially described for another stretching phase. To summarize therefore the device in question involves the creation of a sequence of successive stages of lifting of the holding parts 19, closing of the said holding parts 19 (actuated in phase with the opening of the gripper parts 50) and consequent blocking of the fabric 3, descent of the holding parts 19 for the stretching of the fabric, opening of the same holding parts actuated in phase with the closing of the said gripper parts 50. The descent of the holding parts may be achieved in a differential manner. These parts are activated with the carriage, that slides along the needle beds, inverts its stroke (i.e. at the end of the needle beds); in this situation the holding parts descend by a preset amount that is a function of the type of fabric as well as the type of knitting stitches with which the latter is created. During the successive carriage stroke, the said parts are further lowered according to the type of fabric, and the knitting stitches, as well as the number of rows that are formed with each carriage stroke; the number of these rows, as is known, is equal to the operative units envisaged on the carriage. In phase with the new carriage stroke, there is opening of the holding parts 19, actuated in phase with the closing of the gripper parts 50, the rising of said parts to their maximum upper position and finally the closing of the said holding parts in phase with the opening of the gripper parts 50. Therefore the device described makes it possible to obtain the uniform stretching of all the adjacent parts of the fabric, even in the presence of areas of different lengths of the same fabric. Fig. 10 illustrates, as an example, a knitted fabric 68 indicating the front 68a and rear 68b parts, as well as the side parts 68c. Unlike the traditional stretching devices, the alternate movement of the holding parts 19 is able to achieve vertical stretching along the entire length of this fabric, in particular even in correspondence with the side portions 68c. The device is also simple to build, thus reducing considerably the costs of production and maintenance. The inclusion of the gripper parts 50 optimizes the stretching, performed by the holding parts 19, for any type of fabric and/or weft of the latter, regardless of the knitting pattern produced. The applicant has observed that for some types of fabric and/or jersey, the use of the aforementioned gripper parts is not necessary; in these situations it is sufficient to avoid the energizing of the electromagnets, which is achieved, in a simple manner, by adjusting the program controlling the machine. It can also be stressed that with the electromagnets de-energized, the gripper parts 50 remain in their inoperative position I (i.e. open) which facilitates any operations in the working area of the machine involved with the gripper parts 19. In this description the device, subject of this invention, has been proposed associated with a flat-bed machine, for example for knit-wear. This device can be usefully adopted with a circular type knitting machine, or with any kind of machine that produces fabric of whatever kind.

Claims: Device for the vertical stretching of fabric in an automatic knitting machine, in particular a flat-bed knitting machine including two longitudinal needle beds (1,2) below which the fabric (3) being formed exits, holding parts (19) for the fabric (3) arranged below said needle beds (1,2), slides (39) connected to the holding parts (19) and activated to slide vertically with an alternating motion, between a raised position where said fabric (3) is held and a lowered position where the fabric (3) is released; said device being characterised in that it further includes: a first and a second support parts (8,9) arranged facing one another under said needle beds and connected to said slides so as to slide vertically between guides; a first series of regularly spaced out oscillating jaws (17) fixed to an oscillating corner piece (270) joined to said first support part (8) along a first axis (290) longitudinal to the said needle beds (1,2); a second series of regularly spaced out oscillating jaws (18) fixed to a comb (27) that is joined to said second support part (9) along a second axis (29) parallel to the aforementioned first axis, said first and second series of jaws (17,18) forming the said holding parts (19); cams (32,320) designed to provide angular rotation in opposite rotation directions of the said corner piece and the said comb (27) to close the said holding parts (19), in suitable phase with the formation of the rows of the said fabric (3), in the said raised position of the slides (39); a series of gripper parts (50) arranged in intermediate positions with respect to said holding parts (19), regularly spaced out along the lower surface of said needle beds (1,2) and respectively consisting of two sprung arms facing one another (51,52) made mobile, by operative parts, with an inoperative position (I) and an operative position (O) in which the same arms elastically grip the said stretched fabric (3) during the phase in which the same fabric is released by the said holding parts (19). Device as in claim 1, characterised in that said combs (27) are operated by means of levers (31) that are hinged to said second support part (9) and subjected to the action of springs (33) held by the same support part (9), these said levers (31) being operated by said cams (32). Device as in claim 2, characterised in that said springs (33) are inserted in a seat (34) created in said levers (31) and are held, with a counter nut (35), by a knob (36) acting as a counter to the said comb (27) and designed to adjust the action of the same springs (33), so as to adjust the holding tension on the fabric (3) on the part of the said holding parts (19). Device as in claim 1, characterised in that said slides (39) are arranged symmetrically in correspondence with the ends of the needle beds (1,2) and have on one side a rack (40) that engages with a relative pinion (41) revolving on a support attached to the fixed frame (42) of the machine and designed to be activated with alternating motion by appropriate driving parts. Device as in claim 1, characterised in that said support parts (8,9) consist of the respective angular elements, fixed to one another in correspondence with the ends and fitted to slide vertically along the respective fixed cross-members (7) on the intervening pads (10) of antifriction material, blocked to the same angular elements (8,9). Device as in claim 1, characterised in that said jaws (17,18) are similarly made of a ledge (20) protruding from a body (21) designed to be fixed to the summit of said support parts (8,9), said ledge (20) sloping upwards and having a vertical holding surface (24) appropriately knurled. Device as in claim 1, characterised in that said corner element (270) is actuated by the relative cams (320) in contrast with the sprung means (380) lying between the same corner piece and the relative first support part (8). Device as in claim 1, characterised in that said first (27) and second (270) axes are positioned at the same height. Device as in claim 1, characterised in that said arms (51,52) are similarly made of a shaped element forming at one end a front head (53) that vertically faces the fabric (3) being formed, and centrally a curve (54) fitted to slide through a slot (60) made in the summit of a relative cross-member (7) that is an integral part of the support frame of the said needle beds, with this curve connected to a relative end rod (62) subject to the above-mentioned operative parts. Device as in claim 9, characterised in that said operative parts include, for each pair of arms (51,52) relative to the same gripper part: two levers (64) hinged to the relative shafts (65), fixed to the above-mentioned support frame, horizontal and arranged longitudinal to the said needle beds (1,2) with the first arms (63) of these levers (64) joined to the relative lower end (62a) of the said rod (62), and with the second arms (66) of the same levers almost horizontal with the free heads (66a) facing one another; sprung means, associated with said levers (64), for the definition of the inoperative position I of the relative arms (51,52); activating parts operating on said heads facing one another 66a to command, in contrast with the said sprung means, the simultaneous oscillation of the said levers, in the opposite directions (S1,S2), for the definition of the operative position (O) of the aforementioned arms (51,52) . Device as in claim 10, characterised in that said activating parts include: one vertical shank (67) sliding through a fixed guide part (68), arranged in correspondence with the vertical intermediate plane between said heads facing one another (66a), axially moved by a cam shaft (69) in contrast with sprung means (70), by raised position (S) and a lowered position (A), with both of these positions not involving interception between the same shank and the said heads facing one another (66a); and electromagnet (71), fixed to the second arm of a corresponding lever (64), with the relative mobile anchor (72) arranged horizontally so that, if the electromagnet is energised, it will come between said shank (67) and the said heads facing one another (66a), with oscillations of the said lever (64) as a consequence of the passage of the said shank (67) from the raised position (S) to the lowered one (A).

Inventors: STOPPAZZINI BENITO, STOPPAZZINI, BENITO
Applicants: EMM SRL, EMM S.R.L.
Application year: 1992
Main classification: D04B15
IPC codes: D04B15