Patent GB-750167-A (GB)
Title: Improvements in and relating to apparatus for testing yarns, threads, fibres, filaments and the like
Inventor: COTTON LAURIE
IPC: G01N3/08
Filed: 1953-07-13
Abstract: 750,167. Photo-electric apparatus for thread testing. COURTAULDS, Ltd. July 12, 1954 [July 13, 1953], No. 19325/53. Class 40 (3). [Also in Group XIX] Apparatus for measuring the breaking load and extension of a thread when stretched at a constant rate comprises a member to which one end of the thread is anchored and which is deflected in accordance with thread tension, a loading mechanism fixed to the other end of the thread to produce the constant rate of extension, a counter operated by a mechanism producing a number of pulses corresponding to deflection of the member, a further counter operated by pulses generated by movement of the loading mechanism and means for stopping both counters when the thread breaks. The loading mechanism may be a constant speed electric motor or, as shown (Fig. 1) a piston supplied via valve 9 with fluid from a constant delivery rate pump, its movement being measured by rack and pinion driven cam 38 which periodically breaks the circuit at 35 to the actuating coil 45 of a counter. The deflecting member may be a metal ring 1 (Fig. 1) rigidly fixed to a support 2. The distortion of the ring is communicated through channel member 21 (Fig. 4) to ring 20 on racked rod 14 which rotates perforated disc 16 in front of an aperture 28 between a light source 27 and photo-cell 29 whereby the latter is illuminated every time a perforation coincides with aperture 28. In an alternative arrangement (Fig. 6) a beam of light from mercury vapour lamp 55 is monochromatised by filter 57 and plane polarized by polarizing film or prism 58 at an angle of 45 degrees to the optical axes of a set of calcite prisms 51, 52, 53 through which it is projected perpendicular to these axes. The state of polarization of the emergent beam rapidly alternates between plane polarized parallel and perpendicular to the plane of the incident beam with intermediate states of elliptical polarization as the length of the light path in calcite is varied by the motion of the prisms 51, 52 mounted on rod 14. The emergent beam passes through polarizing film or prism 59, set to completely extinguish light in one of the states of plane polarization, to photo-cell 29. In a further modification, rod 14 carries a screen bearing a series of parallel uniformly spaced transparent lines corresponding with a similar series of lines on an adjacent fixed screen. A photo-cell on one side of the screens is illuminated by a lamp on the opposite side every time the two series of parallel lines are in register. In all the above cases the photocell is illuminated by flashes of light, the number of which corresponds to the deflection of the ring. The photo-cell forms part of the grid circuit of a cathode follower valve 42, the output of which is amplified in valve 43 in the anode circuit of which is. the coil 44 of an electromagnetic counter so that the counter is operated each time the cell is illuminated. When the thread 12 breaks ring 1 resumes its unstrained position and carries contact 25 away from ring 20 until the rod is returned to its original position by tension spring 24, thereby open circuiting at 25 a relay 47 the normally open contacts S1, S2 of which complete the circuits to the coils of the two counters which are therefore immobilised throughout this period. Contacts S3 are also opened so that relay 47 is not re-operated when contact 25 closes until press-button 46 is pushed. In a further alternative the disc 16 may be replaced by a rotary electric switch which directly makes and breaks the circuit of a counter operating coil. The ring 1 may be replaced by a cantilever, by a beam supported at both ends or by a U-shaped member, in which case the lower limb of the U is fixed while the thread is anchored to the inner part of the upper limb, the extremity of which drives a racked rod as before through contacts which break when the thread snaps. This arrangement amplifies the movement of the deflecting member. The clamps 3, 4 which hold the ends of the thread may be pneumatically or electromagnetically operated.