GB2353297A

GB2353297A - A lockstitch sewing machine comprising a thread gripper

Info

Publication number: GB2353297A
Application number: GB0019746A
Authority: GB
Inventors: Rainer Panhorst; Peter Cygon
Original assignee: Duerkopp Adler AG
Current assignee: Duerkopp Adler AG
Priority date: 1999-08-16
Filing date: 2000-08-10
Publication date: 2001-02-21
Anticipated expiration: 2020-08-10
Also published as: GB0019746D0; GB2353297B; JP2001062180A

Abstract

A lockstitch sewing machine comprises a thread gripper (46) for the looper thread, actuated by a control unit (52) e.g. via a pneumatic cylinder (40). The control unit (52) is supplied with an actual-value signal representing the rotary position of a crank gear (8) for driving the needle bar (13) and a thread lever drive (16) and a set-signal via an input device (53). The control unit (52) actuates the thread gripper (46) so that an initial piece (26) of looper thread is firmly gripped and released during the first rotation of the crank gear (8), when the actual-value signal corresponds to the set-value signal. The controlled spring gripper (46) ensures a reliable beginning to the production of a knitted seam and also, if the set-value signal is suitably preset, enables stitching to begin without an accumulation of looper thread on the underside of the knitted material (55).

Description

2353297 A double lockstitch machine comprising a thread gripper The

invention relates to a double lockstitch machine comprising a thread gripper according to the preamble of 5 claim 1.

DE-PS 171185 (corresponding to US-PS 798 130) discloses a said double lockstitch machine, wherein a thread gripper is proposed for holding the looper thread during the formation of the first of a group of stitchesThe thread gripper is controlled by a component formed with a curved groove, that is in a fixed sequence at the beginning of production of a new group of stitches.

Since the initial piece of looper thread is firmly held during the formation of the first two or three stitches, the said stitches are firmly bound, but a piece of looper thread remains on the underside of the knitted material, resulting inevitably in an accumulation of thread which spoils the appearance of the seam.

Another disadvantage of the known stitching machine is that it is impossible to adjust the operation of the thread gripper to the actual knitting conditions, which are influenced by the friction between the thread and the material for knitting, the nature and thickness of the thread, the thickness of the knitted material, the nature thereof, and the operating speed of the stitching machine.

Owing to the number of influences which cannot be taken into account by the known knitting machine, the only way of accurately beginning a knitting operation is to allow for a relatively long piece of looper thread remainina on the underside of the knitted material.

The aim of the invention is to propose a double 'tch machine comprising a thread gripper which lockstL enables a seam to be made while avoiding an accumulation of looper threads on the underside of the knitted material, so that the knitting operation can begin in a reliable manner and operation can easily be adapted to the actual knitting conditions.

According to the invention, in the case of a double lockstitch machine as per the preamble, the problem is solved by the features in the characterising part of claim 1.

The thread gripper gripping the looper thread is accurately actuated, so that the end of the looper thread can be positioned approximately flush with the underside of the material for knitting. This ensures that the seam begins cleanly on the underside of the knitted material. In addition the knitting process begins in an absolutely reliable manner, thus preventing the looper thread from being completely pulled through on the upper surface of the knitted material when the needle thread begins to be pulled by the thread lever. Another advantage is that the control unit can be adjusted to allow for the actual knitting conditions.

To shorten the thread at the beginning of a seam, it is known from DE 41 32 992 Cl (corresponding to US-PS 345 887) to move the needle thread back by a defined amount at the beginning of production of a seam, so as to avoid an accumulation of excess needle thread on the underside of the knitted material. 5 The additional feature in claim 2 results in a strong gripping force on the thread gripper. The feature in claim 3 results in advantages during production. An example embodiment of the invention will now be explained in further detail with reference to the drawings, in which:

Figure 1 is a front view of a doublelockstitch machine; Figure 2 shows a part of the double lockstitch machine in larger-scale side view in the direction of arrow II in Figure 1; Figure 3 is a plan view of the part shown in Figure 2 in the direction of arrow III; Figure 4 is a diagram of the double lockstitch machine according to the invention with a thread gripper; and Figure 5 shows a piece of material for stitching with the beginning of a seam.

A double lockstitch machine 1, hereinafter called a sewing machine 1, is formed in conventional manner with an upper arm 2, a vertical stand 3 and a baseplate 4. An arm shaft 5 is mounted for rotation in the arm 2 and its end emerging from the arm 2 is connected to a drive motor 6. The arm 2 ends in a head 7 for receiving the free end of the arm shaft S and a crank gear 8 firmly connected thereto. A disc 9 is fastened to the arm shaft 5 and is formed with radiating slots at equal angles to one another. A U-shaped light barrier 10 is fastened inside the arm 2 and its limbs surround the disc 9. The disc 9 and the light barrier 10 are components of a rotary position transmitter 11. The arrangement and construction of commercially available rotary position transmitters of this kind are known from DE 40 30 420 C2.

A bearing 12 is formed in the head 7 and receives a movable needle bar 13. An eye 15 of a knitting needle 14 is fastened in the end of the needle bar 13 facing the baseplate 4. The needle bar 13 is connected for drive purposes in known manner to the crank gear 8 via a joint.

The crank gear 8 is also connected for drive purposes to a thread lever drive 16. The thread lever drive 16 is formed with a thread lever 17. The lever has a bore 18 in which a needle thread 19 is guided. The thread lever drive 16 and the construction of the crank gear 8 for driving the needle bar 13 are known from the prior art, for example from DE-AS 1 206 712.

The baseplate 4 is equipped with various drive parts for a feed device 20 and for driving a shuttle 21, the drive motions being transmitted from the arm shaft 5 via a toothed-belt drive disposed in the stand 3. The shuttle 21, for example a barrel shuttle, is known from the prior art. For a further description, see DE- PS 264 e 21 is mounted for reciDroca--- 853. The shutt- -ng rotation n a bearing 22, firmly connected to the basepate 4.

L -L - The shuttle 21 is formed With a tubular container 23 provided with an opening 24. The container 23 receives a supply of looper thread 25, and one end 27 of an initial.

piece 26 of thread extends through the opening 24 out of the container 23.

The shuttle bearing 22 has a surface 28 on to which a plate 29 is fastened by countersunk screws 30. The plate 29 has a projection 31, a projection 32 and a recess 33. The projection 33 has an edge 34. An angle lever 35 is mounted on the projection 32 and can be rotated by means of a screw 36 firmly screwed in a thread.

The angle lever 35 has an arm 37 and a bent arm 38.

The arms 37, 38 extend substantially at right angles to one another. The end of the arm 37 is pivotably connected to the piston 39 of a pneumatic cylinder 40 whose casing 41 is pivotably mounted on the projection 31. The casing 41 is formed with a tube 42 on which a flexible tube 43 is firmly plugged. The pneumatic cylinder 40 contains an internal pressure spring, so that when the pneumatic cylinder 40 is not under pressure the piston 39 is in its retracted position. Furthermore the pneumatic cylinder 40 has a rectangular cross-section and consequently a flat overall shape. The arm 38 has a bent end 44 with an edge 45. The construction and arrangement relative to one another of the edges 34 and 35 results in a thread gripper 46 which can be brought by the pneumatic cylinder 40 into a gripping posi-tion or into a release position.

A stitch plate 47 having a stitch hole 48 for the knitting needle 14 is screwed to the baseplate 4 in the region underneath the head 7 (Figure 4) A thread cutter 49 in the form of a thread burner with a reciprocating burner element is fastened to the baseplate 4 underneath the stitch plate 47. The thread cutter 49 is known from DE 197 15 558 Al (corresponding to US 5 887 537). For a detailed description, see this citation. The pneumatic cylinde-r 40 is connected to a pneumatic valve 50 via the flexible tube 43. The pneumatic valve 50 is a three-way valve actuated by an electromagnet or by spring force and enabling compressed air to flow from a source to the pneumatic cylinder 40 or venting the said cylinder. The pneumatic valve 50 is connected by an electric line 51 to an electronic control unit 52 which comprises an input device 53 in the form of digital switches. The control unit 52 is connected to the rotary position transmitter 11 by an electric line 54.

Material for knitting 55 lies on the baseplate 4 in the region under the knitting needle 14 and is held down and guided by a pressure foot 56 on the feed device 20.

Operation is as follows: It is assumed that the knitting machine 1 is inoperative, and the knitting needle 14 is positioned outside the material 55 for knitting, the initial piece 26 of looper thread 25 extends from the opening 24 to the thread gripper 46, the controll unit 52 supplies the pneumatic valve 50 with electricity, so that the pneumatic cylinder 40 causes the angle lever 35 to rotate anticlockwise (Figures 3 and 4) with the result that the initial piece 26 is gripped in the thread gripper 46 as shown in Figures 2 and 3, and - a set-value signal in the form of an item of information is delivered to the control unit 52 by the device 53.

After an order to start has been given to the control unit 52, the arm shaft 5 is rotated by the motor 6, and the rotary position transmitter 11 constantly supplies the control unit 52 with a signal representing the actual rotary position of the arm shaft 5.

When the arm shaft 5 rotates the needle 14 pricks into the material 55 for knitting, so that when the needle 14 rises again in known manner, the loop of needle thread 19 forming on the needle 14 is received by the shuttle 21. During this process the initial piece 26 of looper thread 25 is acquired by the loop of needle thread 19 and pulled through the stitch hole 48 into the material 55, whereas the end 27 is firmly gripped as before by the thread gripper 46.

As soon as the control unit 52 ascertains that the actual-value signal is the same as the set-value signal, the pneumatic valve 50 is switched over, thus moving the thread gripper 46 from the gripping position -Into the free posction. Figure 4 shows the time immediatel_y before the pneumatic valIve 50 has switched over.

After the change-over, the thread gripper 46 occupies its free position, so that the regular knitting operation can continue. The free position of the thread gripper 46 is indicated in Figure 3 by a chain-dotted part of the arm 38 in its pivoted position. Since the setvalue signal can be preset on the input device 53, the amount of shuttle thread 25 remaining on the underside 55 of the material, for knitting can be exactly monitored at the beginning of production of a seam (Figure 5).

After the seam has been made, the thread is cut by the thread cutter 49 in known manner. When the burner element pivots into the region where the threads 19 and 25 for cutting extend, the looper thread is positioned so that it comes within working range of the thread gripper 46, so that the looper thread 45, before 'being cut, is first gripped in the thread gripper 46, on suitable actuation of the pneumatic cylinder 40, and is then cut. The initial piece 26 is thus in the gripped state shown in Figures 2 and 3, when the end 27 projects upwards about one and a half millimetres from the thread gripper 46.

Claims

Claims:

1 A double lockstizch machine comprising a thread gripper for the looper thread, having the following features:

- an arm shaft with a crank gear for driving a needle bar and a knitting needle vertically in reciprocation, - a thread lever drive connected for drive purposes to the crank gear and comprising a thread lever which supplies a needle thread to the knitting needle, - a stitch plate holding the material for stitching and having a stitch hole for the knitting needle to pass through, a shuttle co-operating with the sewing needle and having a supply of looper thread is provided under the stitch plate, - the thread gripper is formed with a drive and is disposed in the region of the stitch hole between the stitch plate and the shuttle, - a cutter for the looper thread is provided between the stitch plate and the thread gripper, and - a control unit for moving the thread gripper into a position for gripping the looper thread or into a position for releasing the looper thread, - a rotary position transmitter for transmitting an actual-value signal representing the rotary position of the crank gear, the control unit with a device for inputting a set- value signal,-, the control is connected in circuit to the drIve of the thread gripper, in order to switch the thread gripper over from the gripping position to the free position when the actual-value signal corresponds to the set-value signal.

2. A double lockstitch machine according to claim 1, in which the drive for the thread gripper comprises a pneumatic cylinder.

3. A double lockstitch machine according to claim 1, characterised in that the thread gripper is disposed on a bearing for the shuttle.

4. A double lockstitch machine substantially as described herein with reference to and as illustrated in the accompanying drawings.