Tension control device for a video tape recording and/or reproducing apparatus

In a magnetic recording and/or reproducing apparatus that includes a cylindrical tape guide drum with at least one rotary magnetic head moved in a circular path substantially coinciding with the periphery of said drum, tape supply means containing a magnetic tape wound on supply and take-up reels and extending therebetween, a capstan spaced from said guide drum, holder means spaced from said guide drum for receiving and positioning said tape supply means;

• a tape loading and unloading device comprising support means rotatable around said drum between inactive and operative positions in an arcuate path that extends adjacent said capstan and said holder means, tape engaging means including a pinch roller mounted on said support means and being movable with the latter in said arcuate path for engaging the tape between the supply and take-up reels of the tape supply means positioned on said holder means with said support means in said inactive position and for withdrawing a progressively extended loop of said tape from said supply means and wrapping one side of the extended tape loop about at least a portion of said periphery of the guide drum in response to movement of said support means from said inactive position to said operative position at which said pinch roller is located within said tape loop adjacent said capstan with the tape of said loop therebetween for driving the tape from said supply reel to said take-up reel, a pivoted tape shifting arm carrying a tape shifting pin and being movable between an inoperative position where said tape shifting pin engages the tape between said reels within said tape supply means and an operative position where said tape shifting pin shifts said one side of the tape loope between said guide drum and said supply reel of the tape supply means in the direction increasing the extent of said portion of the guide drum periphery about which the tape is wrapped in response to movement of said support means to said operative position, means for moving said tape shifting arm between said inoperative and operative positions thereof in response to the rotational positioning of said support means in said inactive position and said operative position, respectively of said support means;
• and a tension control device including a tensioning spring acting to urge said tape shifting pin against the tape in said operative position of said tape shifting arm, braking means controllable by said tape shifting arm in said operative position of the latter for resisting rotation of the supply reel with a braking force which maintains a substantially constant tension in the tape engaged by said pin in dependence on the force of said tensioning spring, an anchor member connected with said tensioning spring and being movable for adjusting said force of the tensioning spring and thereby varying said substantially constant tension maintained in the tape, means substantially counter-balancing the force of said tensioning means in respect to said anchor member, and manually actuable control means coupled with the counter-balanced anchor member for effecting movements of the latter.

A tension control device for controlling the tension in a tape as the latter is being advanced from a supply reel to a take-up reel, comprising a movable tension control arm engageable with a run of the tape between said supply and take-up reels;

• a tensioning spring connected with said arm for urging the latter against the tape so that the positioning of said arm is dependent on the force of said tensioning spring and the tension of said tape run;
• braking means controllable by said positioning of the tension control arm for resisting rotation of the supply reel with a braking force which maintains a substantially constant tension in said tape run;
• an anchor member connected with said tensioning spring and being movable for adjusting the force of said tensioning spring and thereby varying said substantially constant tension maintained in said tape run;
• means substantially counter-balancing the force of said tensioning spring in respect to said anchor member;
• and manually actuable control means coupled with the counter-balanced anchor member for effecting movements of the latter including a manually rotatable control knob having a frictional clutch element rotatably connected thereto, a cam member urged to rotate with said knob by means of said frictional clutch element and a cam follower on said anchor member engaging said cam member, said cam member and cam follower forming irreversible coupling means between said control knob and anchor member for providing a substantial mechanical advantage in respect to the displacement of said control knob relative to the resulting movement of said anchor member.