An electrically operated driving shaft control device for a window blind, comprising:
- a casing having a driving shaft vertically journalled in said casing;
- means for rotating said driving shaft;
- a plate member provided in said casing and having a top and bottom side, a front end with a projecting plate extending upward therefrom and a rear end, said plate member having a bearing seat formed on said top side and a pair of first oval-shaped openings substantially aligned with said projecting plate on both sides of said bearing seat, said projecting plate having at least three holes formed therethrough, and a micro-switch assembly being attached to said bottom side of said plate member adjacent to said front end thereof, said plate member having an opening formed between said projecting plate and said bearing seat;
- a stationary plate provided on said plate member and having a front end spaced from said projecting plate of said plate member and a rear end fixed to said casing, said front end having two upward spaced projections and a downward projecting rod extending through said opening of said plate member and vertically aligned with said micro-switch assembly, said opening of said plate member being bigger than said downward projecting rod permitting said projecting rod to move within said opening, said stationary plate having a second oval-shaped opening bigger than said bearing seat and two threaded holes smaller than and substantially aligned with said pair of first oval- o shaped openings of said plate member on both sides of said second oval-shaped opening;
- a pair of engaging screws passing through said first oval-shaped openings of said plate member and said two threaded, holes, of said stationary plate to engage said plate member and said stationary plate, said driving shaft passing through said bearing seat of said plate member and said second oval-shaped opening of said stationary plate;
- a guiding roller fixed to said driving shaft on said stationary plate;
- a pair of resilient plates each having a roller at one end and another end attached to said front end of said stationary plate with said rollers biasing said guiding roller;
- a rope provided frictionally around said guiding roller and having two end portions each passing through one of said rollers and said guiding roller to attach said window blind, said guiding roller having means for guiding said rope therearound and said driving shaft being movable in said second oval-shaped opening of said stationary plate when said rope being rotated by said driving shaft;
- a partition plate provided between said front end of said stationary plate and said projecting plate adjacent to said two upward spaced projections and having a pair of holes therethrough respectively aligned with two outer holes of said three holes on said projecting plate;
- a pair of first pins each with a head respectively passing through said pair of holes of said partition plate and said two outer holes of said projecting plate and a first compression spring sleeved therearound, two ends of said first compressing spring abutting said projecting plate and said partition plate in such a manner that said partition plate being pressed against said two upward spaced projections and a second pin including a head and having a second compression spring sleeved, therearound, inserted through the intermediate hole of said three holes on said projecting plate abutting said projecting plate and said head of said second pin;
- means for preventing said second pin disengaging from and keeping said projecting plate at a predetermined distance away from said head of said second pin with a clearance being formed between said head and said partition plate;
- and
- means for turning off said driving means upon reaching a predetermined tension at one end portion of said rope due to the rotation of said driving shaft, said predetermined tension pulling said driving shaft in said second oval-shaped opening, moving said rear end of said plate member towards said rear end of said stationary plate so that said micro-switch assembly contacts with said downward projecting rod of said stationary plate.