Method of obtaining a thread running signal

• US 5,164,710 A
• Filed: 04/10/1992
• Issued: 11/17/1992
• Est. Priority Date: 12/22/1989
• Status: Expired due to Fees

• Current Assignee: Maschinenfabrik Rieter AG (Rieter Holding AG)
• Original Assignee: Maschinenfabrik Rieter AG (Rieter Holding AG)
• Inventors: Anderegg, Peter, Oehy, Peter
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): MULLEN, THOMAS J
• Application Number:
  US07/867,294
• Time in Patent Office: 221 Days
• Field of Search: 340/677, 340/668, 340/825.71, 310/323, 200/61.14, 200/61.18, 112/278
• US Class Current: 340/677
• CPC Class Codes: B65H 2513/11 angular
• CPC Class Codes: B65H 2515/31 Tensile forces
• CPC Class Codes: B65H 2553/26 Piezoelectric sensors
• CPC Class Codes: B65H 2701/31 Textiles threads or artificial strands of filaments
• CPC Class Codes: B65H 59/40 Applications of tension indicators
• CPC Class Codes: B65H 63/0327 using piezoelectric sensing means
• CPC Class Codes: D01H 13/1633 Electronic actuators

Abstract

In a method of obtaining a thread tension signal a sensor in the form of a piezofoil is attached to a thread guide or to its mounting and delivers a signal which reflects, amongst other things, the oscillations induced in the thread guide by the thread movement. In order to obtain a signal which corresponds to the thread tension either the frequency of an element which winds up the thread and/or harmonics of this frequency is filtered out of the sensor signal and the level of this frequency or the level of these frequencies is measured.

Claims

1. A method of measuring the tension in a running thread on a textile machine having means for winding said running thread, a thread guide for guiding said thread and a sensor connected to said thread guide for sensing oscillations of said thread guide, said sensor comprising a piezofoil disposed in a plane which is parallel to a plane in which said running thread is situated, comprising the steps of:

(a) supplying a running thread to said textile machine;

(b) winding said running thread onto a cop;

(c) passing said running thread through said thread guide;

(d) sensing oscillations of said thread guide and producing a signal corresponding to said oscillations and the tension in said running thread; and

(e) filtering said signal to obtain elements of said signal corresponding to a basic frequency of operation of said winding means or an harmonic thereof and obtaining from said filtered out frequency a signal corresponding to said tension in said running thread.

2. A method as set forth in claim 1, further including the step of amplifying said signal.

3. A method as set forth in claim 1, further including the step of converting said signal to a digital form.

4. A method as set forth in claim 1, further including the step of comparing said signal to a reference signal.

5. A method as set forth in claim 4, further including the step of adjusting the level of said reference signal in accordance with an operating state of said textile machine.

6. A method as set forth in claim 4, further including the step of generating said reference signal with a reference sensor disposed on a thread guide which has no running thread passing through it.

7. A thread tension sensor for sensing tension in a running thread on a textile machine which has a winding element that is operable at least one basic frequency for winding said running thread onto a package, comprising:

(a) a thread guide for guiding said running thread on said textile machine;

(b) mounting means for supporting said thread guide on said textile machine to permit said thread guide to oscillate;

(c) a piezofoil sensing element disposed on said thread guide in a plane which is parallel to a plane through which said running thread passes for generating an electrical signal corresponding to oscillations of said thread guide;

(d) a tune filter for filtering said electrical signal to produce and transmit an output signal;

(e) means for tuning said filter in accordance with the prevailing basic frequency of said winding element or an harmonic frequency of said prevailing frequency; and

(f) means for measuring the level of said output signal corresponding to the level of tension in said running thread.

8. A thread tension sensor as set forth in claim 7 wherein said tuned filter is a filter in switch capacitor form.

9. A tread tension sensor as set forth in claim 7, wherein said tuned filter has a frequency band width in the region of between 5 and 15 percent of a selected harmonic frequency of said winding element.

10. A thread tension sensor as set forth in claim 9, wherein a selected transmission range of said filter lies in the upper part of its band width.

11. A thread tension sensor as set forth in claim 7, wherein said thread guide is in the form of a pigtail.

12. A tread tension sensor as set forth in claim 7, wherein said mounting means is formed in one piece with the thread guide in the shape of a leaf spring and said sensing element is attached to said spring.

13. A tread tension sensor as set forth in claim 7, wherein a reference sensor is disposed on said textile machine in a position where it is subjected to vibrations of said machine but it is not subjected to vibrations induced by a running thread.

14. A tread tension sensor as set forth in claim 13 further comprising means for comparing said electrical signal to a reference signal to produce said output signal.

15. A tread tension sensor as set forth in claim 14, including means for using said reference signal as a threshold value for generating a binary thread break signal.

16. A tread tension sensor as set forth in claim 13, including means in said reference sensor for excluding environmental signals above a predetermined level.

17. A tread tension sensor as set forth in claim 7, wherein said thread tension sensor is enclosed in a housing attached to said textile machine and acoustic insulation is disposed between said housing and said textile machine.

18. A tread tension sensor as set forth in claim 7, including means for amplifying said electrical signal before transmitting said signal to said tuned filter.

19. A tread tension sensor as set forth in claim 18, further comprising a microcontroller for evaluating said electrical signal.