Winding – tensioning – or guiding – Strand tensioning device – Clamp
Patent
1989-10-20
1992-06-02
Gilreath, Stanley N.
Winding, tensioning, or guiding
Strand tensioning device
Clamp
242 36, 242 37R, 242148, B65H 5922, B65H 6300
Patent
active
051180464
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for detecting yarn movement.
DESCRIPTION OF THE PRIOR ART
According to the prior art, there is known an apparatus for detecting yarn movement comprising a yarn guide unit through which a yarn can be passed, the yarn guide unit having a support surface adapted to be frictionally engaged by the yarn, a converter element associated with the support surface for generating an electrical output signal indicative of a longitudinal yarn movement and a member for biasing the yarn into engagement with the support surface for mechanically amplifying the signal, the member being movably mounted relative to the support surface in the yarn guide unit.
In an apparatus of the type defined as known from Swiss Patent 546,840, a member acting on the yarn is a contact member maintained in point contact with the yarn for biasing it into engagement with a support surface of a friction body by acting directly on the yarn at its contact point with the support surface to thereby amplify the useful signals by increasing the contact pressure of the yarn by mechanical means. The contact member is spring-loaded.
In a yarn monitoring apparatus known from FR-A-1,498,049, the presence and/or movement of the unbroken yarn is detected by guiding it under tension over a support surface belonging to a cantilevered resilient tongue member the other end of which transmits any vibrations directly to the converter element. A large proportion of the energy transmitted by the yarn to the support surface is dissipated by the deformation of the tongue member and its movement about its mounting location. As a result, the useful signal is only of a limited strength.
In an apparatus known from Swiss Patent 479 478 (corresponding to U.S. Pat. No. 3,676,769), a member is a pressure-exerting member biasing the yarn into engagement with a support surface with a sufficient contact pressure. The pressure-exerting member serves the purpose of creating an additional electrostatic charge by frictional engagement with the yarn, resulting in strong potential variations which are readily detectable for thus detecting the movement of the yarn.
In an apparatus known from EP-A 0,139,231 (corresponding to U.S. Pat. No. 4,605,875), the yarn is deflected through a guide ring connected to a foot portion. Provided on the foot portion is a piezo-electric converter element for converting vibrations of the guide ring into electric signals. The longitudinal movement of the yarn results in such vibrations of the guide ring due to its frictional contact therewith. As long as the yarn is not moved, however, this arrangement results in a relatively strong noise signal, so that the output signal of the converter element is difficult to detect or even unfit for use due to the unfavourable signal-to-noise ratio. A movement of a smooth yarn at a slow rate of advance is scarcely detectable.
An apparatus known from DE-B-1,018,644 serves for detecting a yarn or web breakage. In this apparatus, a ball member biased towards a switch contact is prevented from making contact by the yarn or web as long as it is not broken. A movement of the yarn or web is not indicated.
Known from GB-A-2,059,594 is an apparatus for indicating the presence and movement of a yarn by the employ of a piezo-electric converter element directly engaged by the yarn. The converter element is shaped as a cantilevered rod fixedly mounted at one end and contacted by the yarn at its opposite free end. A pre-biased resilient stop member acts on the converter element at a location between its fixed and free ends in a direction substantially parallel to the direction of movement of the yarn. The converter element monitors the yarn directly.
It is an object of the present invention to improve an apparatus of the type described above so as to result in an improved signal-to-noise ratio of the output signal while being of simple construction.
SUMMARY OF THE INVENTION
This object is attained, according to the invention, providing an apparatus for detecting yarn movement comprising a y
REFERENCES:
patent: 3676769 (1972-07-01), Loepfe
patent: 4123014 (1978-10-01), McCullough
patent: 4516738 (1985-05-01), Nurk
Gilreath Stanley N.
Iro AB
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