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DE-102021128687-B4 - Clamping device for a back or bottom thread of a sewing machine

DE102021128687B4DE 102021128687 B4DE102021128687 B4DE 102021128687B4DE-102021128687-B4

Abstract

Clamping device (100) for temporarily clamping a back thread or bobbin thread in a sewing machine, comprising a clamp (102) and an adjusting device (104) for actively adjusting the clamp (102), wherein the adjusting device (104) is configured to adjust the clamp (102) between a clamping position in which the clamp (102) is moved towards or rests against a stitch plate (200) of the sewing machine and thus clamps a back thread or bobbin thread between the stitch plate (200) and the clamp (102), and a release position in which the clamp (102) is moved away from the stitch plate (200) and is thus mounted without contact with it, whereby the back thread or bobbin thread is unclamped, characterized in that a mounting plate (126) is provided and configured to be detachably attached to the stitch plate (200) of the sewing machine, and that the adjusting device (104) is attached between the legs (116) of a double angle (118) attached to the mounting plate (114).

Inventors

  • Andreas Fritsch

Assignees

  • BUNDESDRUCKEREI GMBH

Dates

Publication Date
20260513
Application Date
20211104

Claims (9)

  1. Clamping device (100) for temporarily clamping a back thread or bobbin thread in a sewing machine, comprising a clamp (102) and an adjusting device (104) for actively adjusting the clamp (102), wherein the adjusting device (104) is configured to adjust the clamp (102) between a clamping position in which the clamp (102) is moved towards or rests against a stitch plate (200) of the sewing machine and thus clamps a back thread or bobbin thread between the stitch plate (200) and the clamp (102), and a release position in which the clamp (102) is moved away from the stitch plate (200) and is thus mounted without contact with it, whereby the back thread or bobbin thread is unclamped, characterized in that a mounting plate (126) is provided and configured to be detachably attached to the stitch plate (200) of the sewing machine, and that the Adjustment device (104) is attached between the legs (116) of a double angle (118) attached to the mounting plate (114).
  2. Clamping device (100) according to Claim 1 , characterized in that the clamp (102) is attached to a pivotably mounted rod (106), and that the adjusting device (104) is configured to rotate the rod (106) between different rotational positions in order to pivot the clamp (102) between the clamping position and the release position.
  3. Clamping device (100) according to Claim 2 , characterized in that a rotary lever (108) is connected to the rod (106) in a rotationally fixed manner and which can be actuated by means of the adjusting device (104).
  4. Clamping device (100) according to Claim 3 , characterized in that the adjusting device (104) is formed by a linear actuator with an actuating rod (110) which is coupled to the rotary lever (108) by means of a rotary joint (112).
  5. Clamping device (100) according to Claim 4 , characterized in that the linear actuator comprises pressure medium connections (114) to adjust a piston guided in a cylinder and coupled to the actuating rod (110) between two end positions by means of a pressure medium.
  6. Clamping device (100) according to Claim 5 characterized in that the linear actuator is pneumatically actuated.
  7. Clamping device (100) according to one of the Claims 1 until 6 , characterized in that the adjusting device (104) is pivotably mounted between the legs (116) of the double angle (118).
  8. Stitch plate (200) for a sewing machine with a clamping device (100) according to one of the Claims 1 until 7 , which is fixed to a surface facing away from the fabric surface.
  9. Sewing machine with one stitch plate (200) according to Claim 8 .

Description

The invention relates to a clamping device for temporarily clamping a back thread or bobbin thread in a sewing machine. The invention also relates to a stitch plate with such a clamping device and a sewing machine with such a stitch plate. Sewing machines are used, for example, in the production of passport documents, where the individual passport book pages are sewn together. The production of such documents is highly automated, so it must be ensured that the bobbin thread or backing thread is always available during the sewing process. Sewing machines not used for passport documents typically have a metal spring on the needle plate that passively clamps the sewing thread intermittently. However, such metal springs are not usually used in sewing machines for passport document production because the clamping of the bobbin thread or backing thread cannot be actively controlled. The use of a passive metal spring leads to uneven sewing and a higher rate of rejects. In the DE 10 2016 102 024 A1 A sewing machine is described that includes a clamping device for temporarily clamping a back thread or a bobbin thread. This device uses a leaf spring to clamp the bobbin thread. This leaf spring is actively adjustable between a clamping position and a release position. In the DE 10 2004 015 813 B3 A sewing machine is described that is equipped with a thread clamp for clamping a thread. According to the description, an angled lever may be present to operate the thread clamp and release the thread. In the DE 102 15 011 A1 A sewing machine is also described that includes a thread clamping device for the bobbin thread. By pressing a switch, the clamp can be actively adjusted to clamp or release the bobbin thread. Also in the DE 197 22 395 C1 A sewing machine is described that uses a clamping device to clamp a lower thread using a leaf spring. In the DE 43 23 494 C1 A thread cutting device for a cylinder arm chain stitch sewing machine is described, in which a thread clamp in the form of a leaf spring is located on the thread catcher. Also in the WO 88 / 08 894 A1 A thread cutting device for zigzag sewing machines is described, in which a thread clamp is provided for clamping the lower thread: In the DE 10 2006 059 192 A1 A thread cutting device of a sewing machine is described in which the thread retaining spring is used to pre-tension the movable knife, with an additional knife pressure regulating plate that provides additional pre-tension when the movable knife is extended. Even the EP 1 582 615 B1 describes a sewing machine equipped with a position lock featuring a locking tab on the thread cutting device. It is therefore the object of the present invention to provide a clamping device, a stitch plate and a sewing machine which offer a simplified force application for adjusting the clamping device. This problem is solved with a clamping device for temporarily clamping a lower thread or back thread with the features of claim 1, with a stitch plate with the features of claim 8 and with a sewing machine with the features of claim 9. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. The clamping device according to the invention comprises a clamp and an adjustment device for actively adjusting the clamp, wherein the adjustment device is configured to move the clamp between a clamping position and a release position. In the clamping position, the clamp rests against a stitch plate of the sewing machine or is moved towards the stitch plate and thus clamps a back thread or bobbin thread between the stitch plate and the clamp. In the release position, the clamp is moved away from the stitch plate and is thus mounted without contact with it, with the back thread or bobbin thread being unclamped. This design allows for active control of the clamping mechanism and the clamping force applied. This makes the sewing process more stable and drastically reduces the amount of rejects due to faulty stitching. This design is therefore characterized by increased process reliability. Since sewing machines typically offer very little space for the components of the clamping device, it is advantageous if the clamp is mounted on a swiveling bracket. The rod is attached to the clamping mechanism, and when the adjustment device is set up, the rod is rotated between different positions to pivot the clamp between the clamping and release positions. By using such a rod, the force for adjusting the clamp can be applied offset from the clamp itself, thus making efficient use of the available installation space. In this context, it is also advantageous to have a rotary lever that is fixed to the rod and can be actuated by means of the adjusting device. The use of such a rotary lever has proven beneficial because it allows an actuator to be used to adjust the lever together with the rod, and thus the clamp. It is advantageous if the adjustment device consists of a linear actuator with a