Device for positioning and guiding a magnetic tape around the drum of a

Abstract

Apparatus for positioning and guiding magnetic tape around the drum of a rotary head assembly in a recording and/or reproducing mechanism, particularly for video tapes. At least two guide fingers guide the magnetic tape from a cartridge around at least a portion of the surface of the drum of the rotary head assembly. These guide fingers are mounted for movement between a retracted position where the fingers engage the magnetic tape in a cartridge, and an advanced position where the guide fingers dispose the tape along a predetermined helical path on the drum surface. A self-locking mechanism is provided for holding the guide fingers in the advanced position against the normal retracting forces exerted on the fingers by the tape moving thereover, while permitting limited retracting movement of the fingers in response to excessive retracting forces exerted on the fingers during abnormal tape movement. The self-locking feature is provided by a coupling mechanism which interconnects a pair of drive wheels with the guide fingers. The coupling mechanism includes a connecting rod pivoted to one of the drive wheels so that a half revolution of the drive wheel in a first direction advances the connecting rod to move the corresponding guide finger to its advanced position, and a half revolution of the drive wheel in the opposite direction retracts the connecting rod to move the corresponding guide finger to its retracted position. Stop means associated with each drive wheel stop rotation of the wheel in the first direction slightly beyond the point of maximum advancement of the connecting rod so that any retracting forces exerted on the connecting rod by the guide finger are resisted by the stop means, thereby providing self-locking of the guide fingers. Retracting movement of the guide fingers in response to excessive retracting forces produced by abnormal tape movement is provided by a biased lost motion connection between each connecting rod and the corresponding guide finger. This lost motion connection permits limited retracting movement of the guide fingers in response to retracting forces exerted on the guide fingers in excess of the bias on the lost motion connection.