Classifications

• • D—TEXTILES; PAPER
  • D05—SEWING; EMBROIDERING; TUFTING
  • D05B—SEWING
  • D05B57/00—Loop takers, e.g. loopers
  • D05B57/08—Loop takers, e.g. loopers for lock-stitch sewing machines
  • D05B57/22—Loop takers, e.g. loopers for lock-stitch sewing machines with spool-size bobbin for lower thread

Definitions

• the present invention relates to a rotating hook device, particularly for industrial sewing machines of the knotted- stitch type, embroidering machines, and the like.
• Another aspect of the invention relates to a sewing machine which includes the rotating hook device.
• Conventional knotted-stitch sewing machines essentially include a footing which forms a surface for the sliding of a fabric to be sewn and supports an upper arm with a head which has, at its free end, a needle which can move axially with a reciprocating motion between an upper stroke limit and a lower stroke limit in order to pass a main thread through the fabric.
• a device known as "crochet” is fitted below the sliding surface and detachably encloses a spool of auxiliary thread which interacts with the main thread to form the stitches.
• Conventional crochet devices generally include a substantially cylindrical hollow body, which is mounted in a cantilevered fashion at the end of an axis which is substantially perpendicular to the direction of the movement of the needle or parallel to the needle; such crochet devices are known respectively as “horizontal-axis crochet” and “vertical-axis crochet”.
• the hollow body of the crochet is peripherally provided with a hook-shaped part, which is adapted to engage a loop formed by the main thread after passing through the fabric, and with an axial cavity with a stationary drum on which a likewise stationary case is detachably mounted and rotatably accommodates the spool of auxiliary thread.
• the hollow body oscillates periodically about its own axis with an angle of more than 180°, so as to engage the main thread and move it beyond the semicircle of the spool, guiding it and promoting its full rotation about the spool in order to form a stitch.
• a drawback of the conventional oscillating-shuttle crochet devices is the limited speed at which they can operate, because of the continuous alternating positive and negative accelerations of the shuttle. Accordingly, machines equipped with this crochet device, despite being accurate, are scarcely suited for the high speeds of modern industrial sewing.
• An aim of the present invention is to eliminate the above drawbacks by providing a rotating hook device which is relatively simple and allows to considerably increase the productivity of sewing machines to which it is applied, reducing downtimes.
• An object of the invention is to provide a rotating hook device which is reliable, precise and has a minimum number of moving parts.
• a further object of the invention is to provide a sewing machine which includes a device of the above described type.
• FIG. 1 is a partially sectional front view of a sewing machine with a rotating hook device of the prior art
• Fig. 2 is a partially sectional front view of a sewing machine with a rotating hook device according to the invention
• Fig. 3 is an enlarged-scale schematic side view of the rotating hook device of Fig. 2;
• Fig. 4 is a top view of a detail of the device of Fig. 3 ;
• Figs. 5a to 5e are respective schematic perspective views of the rotating hook device of Fig. 2 in an operating sequence.
• a rotating hook device according to the invention is illustrated and generally designated by the reference numeral 1.
• the device is applied to a knotted-stitch sewing machine which has a needle A which can move in a reciprocating fashion between an upper stroke limit and a lower stroke limit to pass a main thread F through a fabric to be sewn, making it interact with an auxiliary thread F' .
• the device 1 is rigidly coupled in a preset position to the sewing machine below the sliding surface of the fabric and cooperates with other mechanisms of the machine to produce the stitches.
• the device 1 includes a case 2 which is cylindrical or preferably frustum-shaped and tapers upward with a vertical axis 3 which is substantially parallel to the needle A.
• the case 2 is provided with an axial tang 4 in an upward region, and with a resting surface 5 in a downward region and has, on the side wall, an openable portion 6 for the insertion of a spool S of auxiliary thread F 1 .
• the case 2 is removable to facilitate the insertion of the spool during reloading and/or for ordinary maintenance operations.
• the spool S which is also preferably frustum-shaped, can be distinctly larger than the spools commonly used in conventional similar devices of the prior art.
• a rotating hook 7 which can rotate about a second axis 8 which intersects, and is inclined obliquely to, the axis 3 of the case 2 by an angle between 0° and 90°, preferably close to 12°.
• the hook is arranged so that its plane of rotation intersects the case 2 proximate to the centerline thereof.
• the hook 7 is rigidly coupled to the free end of a stem 9 which is fixed, at the opposite end, to a hub 10 which is connected by means of a drive 11 to external motor devices M which are associated with the sewing machine.
• the hook 7, by rotating, enters a loop formed by the main thread F after the needle A has passed through the fabric and pulls the main thread F around the case 2, tying it to the auxiliary thread F'.
• the device includes a unit for supporting the case 2 which acts selectively at its longitudinal ends to support it in a stationary position, allowing the free rotation of the hook 7 and of the thread F about the case 2 as well as the extraction of the knotted threads F and F' toward the outside of the tang 4.
• the supporting unit includes a pair of grip members 12, which interact in a cyclic fashion with the tang 4 of the case 2, and a pusher 13 which acts in a cyclic fashion on the lower supporting surface 5 of the case 2.
• the grip members 12 and the pusher 13 cooperate selectively in order to suspend the case 2 in a substantially stationary position with respect to the hook 7.
• the grip members 12 are constituted by two jaws 12', 12" which can move alternately between a first clamping position and a second release position of the tang 4, and the pusher 13 is constituted by a disk 14 which is rigidly coupled to the end of a lever 15 which can move alternately between a lower position, which is spaced from the lower surface 5 of the case, and an upper position, which is in contact therewith.
• the grip members 12 and the pusher 13 are synchronized so that the clamping position of the former coincides with the spaced position of the latter.
• Units are provided for actuating the grip members 12 and the pusher 13 and are constituted by one or more cams 16, 16 ⁇ which are operatively connected to the motor M of the sewing machine and act according to a preset criterion synchronously with the rotary motion of the hook 7 and the reciprocating motion of the needle A.
• cams which are drum-shaped and/or have complementary profiles and act by means of adapted transmission means on the jaws 12', 12" and on the lever 15.
• the actuation units can be of the electromagnetic or pneumatic type.
• first guiding units constituted by a spacer 17 made of rigid metal wire which is substantially V-shaped, with its ends rigidly coupled to the case 2 and the vertex arranged so as to protrude toward the outside of the case.
• second units 18 for guiding the auxiliary thread F' which are mounted inside the case 2 and are suitable to release in a controlled manner the thread F', keeping its tension and unwinding speed constant.
• These second guiding units are constituted by a substantially horizontal elongated member 19, which is rotatably and coaxially pivoted to the upper end of the case 2 and has, at its free end, an eyelet 20 in which the auxiliary thread F" unwound from the spool is passed.
• the elongated member 19 is coupled to an adjustable tensioning spring 21 which acts on the thread F'.
• Figs. 5a to 5e illustrate an operating sequence of the rotating hook device according to the invention.
• the device according to the invention allows to reduce the downtimes of the sewing machines to which it is applied, considerably increasing their productivity by virtue of the fact that the case can accommodate spools which have a distinctly higher capacity than the spools that are normally used.
• the constructive simplicity and the reduced number of moving parts allow to achieve high sewing rates, ensuring reliability and precision.
• the resulting seams are free from thread interruptions, as instead occurred in the past, and therefore are stronger and more pleasant from an aesthetic point of view.
• a knotted- stitch sewing machine includes a rotating hook device of the type described above and includes a head T which is joined to a footing B by means of an arm C.
• the head T supports a thread tensioning lever 22 which can move reciprocatingly between an upper position, in which the main thread F is stretched, and a lower position for the release of the previously stretched portion of thread used to form a stitch.
• the thread tensioning lever 22 has at least two thread passage eyelets 23 and 24 which are formed at the free end of the lever at a short distance from each other for the insertion of respective loops of thread, so as to tension/release, at each stroke, a portion of thread which is twice that of conventional thread tensioning levers of the past which had the same length but had a single thread passage eyelet.
• the end of the head can be split in two, with one eyelet for each part.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Sewing Machines And Sewing (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=11426121

Family Applications (1)

Country Status (6)

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Family Cites Families (5)

• 1996
  • 1996-07-24 IT IT96VI000120A patent/IT1287321B1/it active IP Right Grant
• 1997
  • 1997-07-17 JP JP10506544A patent/JP2000514685A/ja active Pending
  • 1997-07-17 AU AU37678/97A patent/AU3767897A/en not_active Abandoned
  • 1997-07-17 WO PCT/EP1997/003825 patent/WO1998003714A1/en not_active Application Discontinuation
  • 1997-07-17 CN CN 97196671 patent/CN1226295A/zh active Pending
  • 1997-07-17 EP EP97934478A patent/EP0918899A1/en not_active Ceased

Non-Patent Citations (1)

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