Skewing detection mechanism for printer employing continuous recording form

Claim 1

A skewing detection mechanism for a printer of the type wherein an image is formed on a continuous recording form, said mechanism comprising: pivotally moveable sensor means arranged in abutted and biased relation to said continuous recording form as said form is transported along a predetermined transport path; means for detecting pivotal movement of said sensor means; shaft means having an axis that extends perpendicularly to said predetermined transport path, said sensor means being mounted on said shaft means for pivotal movement about said axis; spring means associated with said sensor means for biasing said sensor means in such a manner that said sensor means is abutted against said continuous recording form; wherein said means for detecting is associated with said sensor means for detecting said pivotal movement of said sensor means about said axis of said shaft means under the biasing force of said spring means at the time that said sensor means is released from abutting against the continuous recording form; said sensor means includes a pair of sensor elements mounted on said shaft means for pivotally moving about said axis of said shaft means in spaced relation to each other along said shaft means, and said spring means includes a pair of spring members associated, respectively, with said pair of sensor elements, said pair of sensor elements being respectively abutted against opposite side edge portions of said continuous recording form under the biasing forces of said spring members such that when at least one of said pair of sensor elements is released from abutting against a corresponding one of said opposite side edge portions of said continuous recording form and is pivotally moved about said axis of said shaft means under the biasing force of a corresponding one of said spring members, said detecting means detect said pivotal movement of said sensor element to output a signal that is representative of the occurrence of a transport abnormality of said continuous recording form; each of said pair of sensor elements includes a boss mounted on said shaft means and a first arm that extends from said boss, said first arm having a free end face, a part of said end face being abutted against a corresponding one of said opposite side edge portions of said continuous recording form under the biasing force of a corresponding one of said pair of spring members, while a remaining part of said free end face extends outwardly from a side edge of said corresponding side edge portion of the continuous recording form; said means for detecting includes a moveable element and a detector for detecting movement of said moveable element and means for transmitting said pivotal movement of at least one of said pair of sensor elements to said moveable element of said detecting means, wherein pivotal movement of said at least one sensor element is transmitted to said moveable element of said detecting means through said transmission means so as to move said moveable element; said moveable element of said detecting means comprises a shutter plate, and said detector comprises a photointerrupter, said shutter plate being moveable between an inoperative position within a detecting region of said photointerrupter and an operative position out of said detecting region thereof, wherein said shutter plate is normally in said inoperative position, while when said shutter plate is moved to said operative position, said photointerrupter outputs a signal indicative of the occurrence of an abnormality in transporting said continuous recording form; and wherein in each sensor element further includes a second arm projecting from said boss of said sensor element in a direction that is substantially opposite to that in which said first arm of said sensor element extends from said boss, said transmission means including a crank bar comprising opposite axial end portions having their common axis extending perpendicularly to said predetermined transport path and an eccentric shaft section extending between said opposite axial end portions, said shutter plate being mounted on one of said opposite axial end portions of said crank bar for pivotally moving about said common axis, said eccentric shaft section resting upon said second arms of respective sensor elements, wherein said pivotal movement of at least one of said pair of sensor elements causes said second arms to move said crank bar angularly about said common axis, thereby angularly moving said shutter plate from said inoperative position to said operative position.