Patent ID: 8833535
Filing Date: 2014-09-16
Classification: G01B

Abstract:
1. A constant-force device comprising: a shaft; a first ratchet wheel mounted rotatably on the shaft, a first ratchet wheel having a plurality of first sawtoothed projections, each of which projects in a first direction along an axis of the shaft; a second ratchet wheel mounted on the shaft so as not to rotate relative to the shaft but to move along the shaft, the second ratchet wheel having a plurality of second sawtoothed projections, each of which projects in a second direction opposite to the first direction; at least one intermediate ratchet wheel mounted on the shaft so as not only to rotate relative to the shaft but also to move along the shaft between the first ratchet wheel and the second ratchet wheel, the intermediate ratchet wheel having a plurality of first intermediate sawtoothed projections and a plurality of second intermediate sawtoothed projections, the first intermediate sawtoothed projections meshing with the first sawtoothed projections of the first ratchet wheel, the second intermediate sawtoothed projections meshing with the second sawtoothed projections of the second ratchet wheel; a biasing member configured to bias the second ratchet wheel towards the first ratchet wheel; and a lock mechanism configured to set at least one of pairs of ratchet wheels which lie adjacent to each other in a connected or unconnected state, wherein a height of each of the first sawtoothed projections is different from a height of each of the second sawtoothed projections.