Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Patent
1996-07-25
1998-07-14
Falik, Andy
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
242 4701, 139446, D03D 5100
Patent
active
057789436
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a controllable output brake in a thread feed device for projectile or gripper weaving machines, as well as a projectile weaving machine and a gripper weaving machine having such a controllable output brake.
DESCRIPTION OF THE RELATED ART
A controllable output brake on the storage drum of a thread feed device is known for projectile or gripper weaving machines for limiting the balloon during the picking operation and for permitting thread control. The load applied by the output brake to the outgoing thread at the beginning of the picking operation should be very small, especially with regard to the dreaded sudden stretching and with regard to the use of sensitive thread qualities, which may perhaps be of poor quality, and the thread tension should only be increased in the course of the picking operation. This, however, necessitates exactly reproducable and fast responding changes in the braking effect, i.e. changes within a few milliseconds. In the case of the high thread speeds normally used in modern weaving machines of this type, these requirements cannot be met in a satisfactory manner by the output brakes which have been known for more than 20 years.
One example is the output brake according to U.S. Pat. No. 3,411,548 in the case of which guide members projecting outwards from the supporting ring engage oblique slots of the crescent-shaped holding member. The displacement drive is provided with a cam drive for rotating the supporting ring about the drum axis and relative to the holding member. In the course of the rotational movement, the supporting ring is moved forwards or backwards over the slots, depending on the direction of rotation, for varying the braking effect during operation. Comparatively big masses which have to be moved rapidly, energy-consuming rerouting of movements, instable end positions of the supporting ring, etc. are the reasons in view of which this principle, which has been known for a long time, is not used in connection with modern weaving machines.
Another output brake is known from GB-A-13 55 518 for a projectile weaving machine. A rigid balloon limiting cone is adapted to be moved to and fro in the stationary holding member between a position where light braking is effected and an open gap position. The cone has secured thereto an annular armature of a magnetic drive, which, when the coil is acted upon by current, draws the cone against a restoring spring from said gap position into the braking position. Large masses which are to be moved, a comparatively coarsely starting and slowly finishing braking effect and a delayed response behaviour are the reasons for the fact that this output brake is no longer used in modern weaving machines of this type.
A modern controllable output brake is known from FIG. 6 and 7 of WO91/14032. The frusto-conical supporting ring is tiltably supported in the inner circumferential surface of the annular holding member about a line which is defined by openings and webs and which is concentric with the axis of the storage drum. In the tilting area, the supporting ring is secured in position in the holding member without an amount of axial play which would be worth mentioning. In both tilting directions about the tilting line, the amount of space provided for the supporting ring in the holding member exceeds the amount of space that would be necessary for adjusting said supporting ring. The free inner end portion of the thread brake element rests on the brake surface of the storage drum and is acted upon by an actuating element which is located in said holding member behind the supporting ring, said actuating element being e.g. an inflatable and deflatable hose extending in said holding member in the circumferential direction. The hose is adapted to be filled via the drive control unit with a larger or smaller amount of pressurized air or of some other medium, and, via the tilting position of the supporting ring, it determines the magnitude of the contact pressure on the brake surface. The
REFERENCES:
patent: 5343899 (1994-09-01), Jacobsson et al.
patent: 5409043 (1995-04-01), Zeonoi et al.
patent: 5509450 (1996-04-01), Tholander
patent: 5546994 (1996-08-01), Sarfati
patent: 5553641 (1996-09-01), Zenoni
Falik Andy
Iro AB
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