RULER BALANCING DEVICE IN UNIVERSAL PARALLEL RULER

摘要

PURPOSE:To balance a ruler under a simple constitution by displacing the action point of a spring on a lever in a direction in which a radius varies as an element of generating the torque of the lever, instead of displacing the spring in its longitudinal direction when torque is adjusted. CONSTITUTION:A circular, eccentric cam 22 and a handle 24 are fixed on the top of a vertical axis 20 rotatably supported by a head base 18, and a ruler fitting plate 28 is fixed on the bottom of the vertical axis 20. The shape and radium of the cam 22 are determined so that the torque of the cam 22 forms a sine curve when the cam 22 is rotated. When a motor 40 is rotated, a piece 46 moves along a spring 38, and the acting point 34 of a coil spring 42 on a lever 34 shifts because of this movement in a direction in which the radium varies as the element of generating the rotary torque of the lever 34. Consequently, a straight line indicating characteristics such as the flexure of spring force and its change varies proportionally with respect to a straight line indicating unadjusted characteristics. Rotational torque caused by the spring 42 of the cam 22 varies with the rotation of a ruler in the form of a sine curve, the balance of the ruler, that is, the vertical axis 20, is maintained.