GB213629A - Improvements in testing machines - Google Patents

Abstract

213,629. British Cotton Industry Research Association, and Oxley, A. E. Nov. 1, 1922. Testing yarns a n d threads.-The machine iipplies a cyclical variation of stress to a length o f thread suspended therein. The stress may be applied mechanically or electromagnetically, and means are provided for indicating or recording the strain,. and for preventing untwisting of the thread. Fig. 1 shows an arrangement in which the test piece of thread 1 is suspended from a clamp 2 and carries an armature 3 adapted to be attracted by an electromagnet 4 excited by a variable or alternating current. When the armature contacts with the magnet a. circuit is closed which energizes a magnetic clutch 12 for the purpose of raising slightly the rod 8 carrying the clamp 2. A screw-threaded part of the rod 8 passes through a nut in the bearing 9, and a worm wheel 23, Fig. 3, on the rod meshes with a worm on the shaft 18 on which is mounted the armature 17 of the magnetic clutch. The part 13 of the clutch., which is supplied by current through rings 24. is mounted on a shaft 14 which is rotated continuously by gearing 15, 16. In operation, stress is applied repeatedly by the electromagnet 4, and extension of the thread is taken up when the supporting rod 8 is raised slightly by the gear controlled by the magnetic clutch. For measuring the extension of the thread, the worm wheel 23 mav have graduations on its upper surface, a vertical scale 26 being provided. Fig. 7 shows a modification in which the rod 8 is rotated intermittently by spur gearing 37, 38 from the shaft 14 through the magnetic clutch 12. The gear 38 carries a pencil 39 arranged to make a moving strip of paper 40 and so produce a record. The bar 28 to which the clamp 2 is secured slides through a member 29 in which rotation is prevented by a feather, and is connected to the rod 8 by a swivel joint 7. Fig. 6 shows a modified arrangement of the electromagnet for applying the stresses. The electromagnet 4 is excited by a continuous current, and to the end of the thread is clamped an insulating plate 31 which carries a solenoid 32 excited by an alternating current. Contacts 11 control the magnetic clutch, and wings 34 and stops 35 prevent untwisting of the thread. The stresses may be applied mechanically as shown in Fig. 9. The test pieces are supported by slides 51 which are reciprocated by connecting rods 49 and cranks on a rotating shaft 46. Weights 55 are suspended from the lower .ends of the threads by bi-filar suspensions passing through guide tubes 57 in order to prevent untwisting of the threads. The cyclical variation of tension in the test pieces is produced by the inertia of the moving weights. When a test piece breaks, its weight 55 falls on a spring-pressed stud 61 and completes the' circuit of a cut out device which stops the driving motor. _