| 摘要 |
FIELD: equipment used in classes. SUBSTANCE: chalk holder is formed as pen made from polystyrene. Pen has body and pusher. Slots made in inner surfaces of opposite side walls are arranged one above the other with uniform space between adjacent slots. Pusher made from polystyrene is formed as parallelepiped with side wall tightly adhering to pen inner surface. W-shaped spring is secured to pusher by rivet. When spring is pressed, pusher moves chalk for distance equal to space between adjacent slots, while pusher itself jumps into adjacent slot. Thus, chalk is advanced for predetermined distance in one direction. EFFECT: increased efficiency, simplified construction and enhanced reliability in operation. |
