Yarn speed measurement on the basis of yarn noise

Claim 2

A yarn testing device comprising a pickup member in which an electrical signal is derived from a passing yarn, said signal having a yarn noise signal component produced by the natural irregularities of the yarn and whose amplitude and frequency are proportional to the speed of travel of the yarn, a network coupled to the output of the pickup member for passing the higher frequencies of the yarn signal whereby the yarn noise signal alone is derived at its output, a voltage proportional to a reference yarn speed, and means coupled to the network output for detecting the amplitude or the frequency of said yarn noise signal and for comparing it to the reference voltage to derive a signal proportional to the yarn speed.

Claim 3

A device as claimed in claim 1 wherein the network passing the higher frequencies of the yarn signal includes a signal differentiator.

Claim 4

A device as claimed in claim 2 further comprising means for measuring a length of the yarn comprising, means connecting the output of the means for detecting the amplitude of the yarn noise signal to an integrator, and means connecting the integrator to a start-stop device controlling the integrator and indicating the beginning and the end of the length of yarn to be measured.

Claim 5

A device as claimed in claim 1 further comprising means for measuring a length of yarn comprising, means connecting the yarn noise signal at the output of the network passing the higher frequencies of the yarn signal To a frequency detector followed in cascade by a counting pulse producing device and a counter, said counter being controlled by a start-stop device indicating the beginning and the end of the length of yarn to be measured.

Claim 6

A device as claimed in claim 1 further comprising, an integrator having an automatically adjustable integration time constant, means for applying the yarn signal from the pickup member to an input of the integrator, and means for coupling the yarn speed control signal produced by said detecting means to an input of the integrator so as to vary the integration time constant of the integrator.

Claim 7

A device as claimed in claim 5 in which the pickup member is energized by a source of alternating voltage, and further comprising a device synchronized with the alternating supply voltage and having an output for controlling the operation of the amplitude or frequency detector.

Claim 8

A device as claimed in claim 6 characterized in that the device synchronized by the alternating supply voltage is adjustable by means of a reference speed signal applied to an input thereof.

Claim 9

A device as claimed in claim 7 wherein the device synchronized with the alternating supply voltage includes a multivibrator controlled by the supply voltage and the reference speed signal so that its pulse frequency is determined by the frequency of the alternating supply voltage and the pulse duration is determined by the reference speed signal.

Claim 10

A yarn testing device comprising a pickup member in the path of the yarn for deriving an electric yarn signal that is substantially independent of any physical contact of the moving yarn with a part of the pickup member, said yarn signal including a high frequency yarn noise component that is proportional to yarn speed and which is produced by normal irregularities of the yarn, a high pass network coupled to the output of the pickup member for passing the yarn noise signal component to an output of the network, a source of reference speed signal, and means coupled to the network output and to the reference speed signal source for detecting the yarn noise signal and comparing it with the reference speed signal to derive a yarn speed-control signal that varies with the speed of travel of the yarn.

Claim 11

A yarn testing device comprising a pickup member in the path of the yarn for deriving an electric yarn signal that is substantially independent of any physical contact of the moving yarn with a part of the pickup member, said yarn signal including a high frequency yarn noise component that is proportional to yarn speed and which is produced by normal irregularities of the yarn, a high pass network coupled to the output of the pickup member for passing the yarn noise signal component to an output of the network, a source of reference speed signal, and means coupled to the network output and to the reference speed signal source for detecting the yarn noise signal and comparing it with the reference speed signal to derive a yarn speed-control signal that varies with the speed of travel of the yarn.

Claim 12

A device as claimed in claim 9 wherein said high pass network includes signal differentiating means.

Claim 13

A device as claimed in claim 9 wherein said detecting means comprises, in cascade, an amplitude detector coupled to the network output and an integrator, and Flip-Flop means having an input coupled to the network output and an output coupled to an input of the integrator, and wherein a reference signal related to a desired yarn length is coupled to said integrator in place of the reference speed signal whereby the integrator produces an output signal that is a measure of said yarn length.

Claim 14

A device as claimed in claim 9 further comprising signal integrating means having an electrically adjustable integration time constant, means for coupling the yarn signal from the pickup member to an input of the integrating means, and means for coupling the yarn speed-control signal to an input of the integrating means so as to vary the integration time constant as a function of yarn speed, said integrating means producing an output signal that indicates undesired defects in the yarn and independently of the yarn speed.

Claim 15

A device as claimed in claim 12 wherein said integrating means includes a resistor and a capacitor, and means for applying a given threshold current to said capacitor.

Claim 16

A device as claimed in claim 12 further comprising, a source of pulsatory voltage energizing said pickup member, and means synchronized with the pulsatory voltage source for supplying a gate control signal to an input of the yarn noise signal detecting means to selectively block the passage of given portions of the yarn noise signal.

Claim 17

A device as claimed in claim 14 wherein said gate signal supplying means comprises a multivibrator joiNtly controlled by the pulsatory voltage and the reference speed signal so that the multivibrator pulse frequency is determined by the pulsatory voltage and the pulse width is determined by the reference speed signal.

Claim 18

A device as claimed in claim 15 further comprising a multivibrator interconnected between the output of said detecting means and the input of the integrating means that is used to vary the integration time constant, the pulsatory signal supplied by the multivibrator being variable with the yarn speed.