Winding – tensioning – or guiding – Coil holder or support – Spool or core
Patent
1992-06-22
1994-03-15
Gilreath, Stanley N.
Winding, tensioning, or guiding
Coil holder or support
Spool or core
242 4712, B65H 5120
Patent
active
052940675
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention is directed to a thread storage and feed device.
In the case of a method of the type mentioned at the beginning, which is known from U.S. Pat. No. 4,226,379, the magnets which are fixedly secured to the housing are located radially outside of the group of components, and the magnets arranged in said group of components are located below the storage surface. The magnetic holding forces act at the largest possible distance from the shaft The characteristic curve of the holding force counteracting a rotation of the group of components ascends first flatly and, afterwards, steeply. In the case of modern thread storage and feed devices, high rotational speeds of the shaft occur due to extremely high thread velocities Due to unavoidable unbalanced masses, the thread counterforce which is variable in the direction of rotation, the cantilevered mode of support of the group of components on the shaft, accelerations and decelerations occurring in operation, and other interfering influences, rotary force pulses acting on the group of components may occur, said group of components being then prompted to carry out oscillating movements into both directions of rotation from the holding position defined by the magnets. In view of the holding force characteristic, the group of components will begin building-up rotational vibrations around the desired position, which will reach a resonance state having a large amplitude, e.g. several millimetres. The rotational vibrations cause high strain on the holding means of the magnets, and they make it more difficult to sense the thread supply precisely as well as to maintain a thread take-off tension which is as uniform as possible In cases in which the thread storage and feed device is equipped with an integrated weft thread metering device, the rotational vibrations will interfere with the weft thread metering operation
It is true that German-pat. 28 43 548 discloses a method of holding in position the group of components in a thread storage and feed device; in the case of said method, the group of components is supported on the housing continuously and in a purely mechanical manner Although this method avoids the disadvantage of a magnetic holding force which is weak around the desired position, it results in a complicated and very special structural design of the device
The present invention is based on the task of providing a method of the type mentioned at the beginning, which, when the group of components is held in position by means of magnetic holding forces, will avoid interfering rotational vibrations, as well as a thread storage and feed device, which includes a group of components held in position magnetically and which permits, even at high speeds, an operation largely free from rotational vibrations.
The posed task is solved by the features disclosed by the present invention.
The temporarily established rotational vibration damping connection between the housing and the group of components prevents the building up of rotational vibrations of the group of components against the holding force of the magnets which is weak around the desired position. In view of the fact that the rotational vibrations need a certain amount of time for reaching a resonance state and a troublesome amplitude, the build-up tendency is interfered with from the very beginning by the temporary rotational vibration damping connection so that the generation of detrimental rotational vibrations will be prevented completely The forces applied to the group of components during the temporary rotational vibration damping connection can be comparatively small, since the comparatively free oscillation system of the group of components is influenced by said forces in an extremely efficient manner and in such a way that said group of components can actually no longer be prompted to carry out any noticeable oscillations at all.
In view of the fact that, on the one hand, the thread, which moves continuously around the group of components on its way from the winding-on memb
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patent: 4848417 (1989-07-01), Dekker et al.
patent: 5046537 (1991-09-01), Maina
Josefsson Paer
Tholander Lars H. G.
Gilreath Stanley N.
Iro AB
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