GB483031A - Improvements in and relating to apparatus for stroboscopic observations - Google Patents

Abstract

483,031. Stroboscopes. LIST, H. Oct. 10, 1936, No. 27544. Convention date, April 14. [Class 97 (i)] A stroboscope comprises an oscillating drum shutter with a wide opening 4 and a slit 3 covered by a member 10 with a similar slit. Each slit is partly covered by a finger 5, pivoted on the axis of the drum 1, having an extension 7 with an inclined slot 6 engaging the pin 9 on the spring member 8 or 81. The screw 20, operated in the bearing 12 by the knob 17, produces an axial pressure on the spring 8<1>, also communicated by the rod 54 to the spring 8, for adjustment of the slit widths. The member 10 may be adjusted through a small angle, for example, by the pin 16 mounted eccentrically on the disc 15 rotatable by the knob 13. The frequency of oscillation of the shutter is controlled by the spring 28, deflected during the oscillation by the cam 24. The frequency is varied by the knob 32 which, through the screw 31, moves the slide 29, working in the housing 30, to vary the effective length of the spring. The setting of this control is communicated by the cord 33 to the rotatable scale 37. The housing 30 also serves as a handle for the apparatus. The oscillations are maintained electromagnetically by the armature 45 situated in a magnetic field and fed with a current which is periodically reversed. The finger 49, between two contacts 42 and 43 is attached to the disc 46, frictionally coupled to the shaft 2 by pressure from the spring 48. When the finger 49 makes contact with either 42 or 43 a current flows in one or other direction through the winding 44. When this circuit is completed by movement of the armature, the magnetic force continues the movement (allowed by the slip of the disc 46) until arrested by the increasing stress in the spring 28. The movement is reversed by the force from the spring and the finger 49 then swings on to the other contact and a continuous oscillation is produced. A cam 50 is provided, to make contact with the spring 52 if it turns through more than a certain angle, and so to damp out excessive amplitudes and irregularities of frequency.