Yarn tension or break monitoring apparatus
United States Patent 11 1 Hogan 1 1 YARN TENSION OR BREAK MONITORING APPARATUS [75] Inventor: Edward Merrick Hogan,  
 Wilmington, Del.  
 [73] Assignee: E. I. du Pont de Nemours and Company, Wilmington. Del.  
 [22] Filed: Mar. 25. 1974 [21] App1.No.:454,418  
 [52] US. Cl 73/160; 73/144 [51] Int. Cl. G011 5/04 [58] Field of Search 73/144. 160; 242/45, 148:  
 ZOO/61.13. 61.14. 61.18; 340/259 [56] References Cited UNITED STATES PATENTS 1,757.867 5/1930 Lewellen 73/144 X Primary E.\&#39;anzinerCharles A. Ruehl 57 ABSTRACT A bifunctional stop motion device to detect either tension surges or broken yarn as the yarn is being forwarded in a path of travel from a source to a machine. The device includes a yarn guiding pulley on a counterbalanced arm arranged to pivot for high yarn tension so that it changes the yarn path to cause a conventional feeler riding on the yarn to rotate and actuate a stop motion device shutting down the machine.  
 5 Claims, 2 Drawing Figures SOURCE TEXTILE MACHINE PATENTEDAFRZSIQIS 3,880,001  
  TO SOURCE TEXTILE MACHINE To TROL Cl IT YARN TENSION OR BREAK MONITORING APPARATUS BACKGROUND OF THE INVENTION This invention relates to improved stop motion devices for textile machines and, more particularly, to an apparatus for detecting tension variations and breaks in yarn being forwarded under tension in a path of travel.  
  Typical commercially available stop motion devices rely on a signal or feeler arm supported by the yarn. When the yarn or thread breaks, the tension supporting the feeler arm goes to zero, allowing the arm to drop under gravity and actuate a switching arrangement to stop the yarn and the apparatus as it is being forwarded to what may typically be a knitting machine. There are other devices capable of detecting variations in tension in a thread being forwarded in a path, while still other devices combine the capability of detecting both variations in tension and breaks in a running threadline. These generally are complex and expensive.  
  It is the object of this invention to provide a simple efficient apparatus for detecting an increase in tension or a break in yarn being forwarded under tension in a path.  
 SUMMARY OF THE INVENTION Accordingly, there has been provided an apparatus to detect a variation in tension or a break in yarn being forwarded under tension in a path, said apparatus comprising: a body member located adjacent said path; a first pulley around which said yarn passes rotatably mounted to said body member. an arm pivotally mounted intermediate its ends to said body member at a location spaced from said first pulley; means for biasing said arm against said tension; a second pulley around which said yarn passes rotatably mounted to said arm for swinging movement with said arm toward and away from said path; and means engaging said thread intermediate said first and second pulleys for detecting when the yarn moves more than a predetermined distance away from said path.  
 BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view of one form of apparatus of this invention.  
 FIG. 2 is a plan view of the apparatus of FIG. 1.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, an apparatus generally designated is constructed according to the invention and engages a yarn 12 for determining increases in tension and/or breaks in the yarn which is being forwarded in a path from a source to a textile machine such as a knitting machine (not shown).  
  The apparatus 10 includes a body member 14 located in a fixed position adjacent the path of travel of yarn 12, and a first pulley l6, rotatably mounted to an extension 18 fastened to body 14. An arm 20 extends through the body 14 and is pivotally mounted between its ends to the body. A counterweight 22 is attached to one end of the arm 20 and a second pulley 24 is rotatably mounted to the other end of the arm. A pair of stops 2], 23 is located on either side of body 14 to restrain extent of rotation of arm 20 in either direction. The counterweight serves as a means to bias the arm against stop 23 and against the tendency of the normal LII running threadline tension or gravity topull the pulley downward away from the stop 23 and the normal path of travel of yarn 12. A feeler arm 26, formed of wire with a loop at one end, is looped around and rides on yarn 12 supported by the tension in the yarn. The other end of feeler 26 is pivotally mounted to the body for free movement and enters the body 14 to engage switch 28 which in essence is a simple grounding device actuated by feeler 26 when it moves a predetermined distance from the normal path of travel of yarn 12 such as, for example, when a break occurs in the yarn. Lead 30 typically runs from switch 28 to the control circuit of a textile machine and when grounded by feeler 26 causes the machine to stop.  
  A pulley 17 mounted coaxially with pulley 16 on extension 18 is used to provide the particular thread path shown (around pulley 16 then pulley 24 and finally back to and around pulley 17). This particular arrangement is preferred over one in which the threadline passes around only pulleys 16, 24 and then leaves from pulley 24. The sensitivity of the preferred embodiment is independent of the mounting position relative to the fixed positions of the yarn on either side of the device. This occurs because the angle of wrap of yarn around pulley 24 does not change for the preferred embodiment and therefore the torque on arm 20 depends solely on yarn tension.  
  In operation, the apparatus 10 is located adjacent the path of travel of yarn 12 in such a manner that the yarn may be passed first partially around pulley 16 then around pulley 24 and back to and around pulley 17; then it leaves pulley 17 toward a textile machine (not shown). When a preselected yarn tension is exceeded, as determined by the counterweight 22, one of the yarn guide points, i.e., pulley 24 moves downward to the alternate position shown in FIG. 1 with arm 20 resting against stop 21. The feeler arm 26 riding on yarn 12 moves downward with the yarn and in the alternate position shown grounds wire 30 by contacting an appendage of the wire 30, i.e., switch 28 within body member 14, thus, shutting down the textile machine involved. The above described motion changes the yarn path enough to activate the feeler 26 and stop the machine before the yarn breaks.  
  Various equivalent arrangements are possible within the scope of this invention. For example, the counterweight 22 and its function may be replaced by a spring between the arm 20 and body member 14 to give automatic reset when excess tension is released. A further alternate would employ a magnetic biasing means of suitable strength. This arrangement would also be independent of mounting orientation but only to the extent that will allow the feeler arm 26 to drop under the influence of gravity in case of complete break in the yarn. Alternatively, the arm 20 may be replaced bya flexible member and the motion of the member itself may act as a switch to shut off the machine rather than using a separate feeler arm 26. In this manner, the geometric relation of the components may be rearranged to suit the needs of the machine without need for the influence of gravity in the operation if the yarn breaks.  
 What is claimed is:  
  1. An apparatus to detect a variation in tension or a break in yarn being forwarded under tension in a path, said apparatus comprising: a body member located adjacent said path; a first pulley around which said yarn passes rotatably mounted to said body member, an arm mounted to said body member at a location spaced from said first pulley; means for biasing said arm against said tension; a second pulley around which said yarn passes rotatably mounted to said arm for swinging movement with said arm toward and away from said path; and means engaging said yarn intermediate said first and second pulleys for detecting when the yarn moves more than a predetermined distance away from said path.  
  2. An apparatus to detect a variation in tension or a break in yarn being forwarded under tension in a path, said apparatus comprising: a body member located adjacent said path; a first pulley around which said yarn passes rotatably mounted to said body member, an arm pivotally mounted intermediate its ends to said body member at a location spaced from said first pulley; means for biasing said arm against said tension; a second pulley around which said yarn passes rotatably mounted to said arm for swinging movement with said arm toward and away from said path; and means engaging said yarn intermediate said first and second pulleys for detecting when the yarn moves more than a predetermined distance away from said path.  
  3. The apparatus as defined in claim 2, including a third pulley coaxially mounted with said first pulley around which said yarn passes after it leaves said second pulley.  
  4. The apparatus as defined in claim 2, said means for biasing comprising a counterweight attached to one end of said arm.  
 5. The apparatus as defined in claim 2, said variation in tension being an increase in tension.