Patent GB-1010160-A (GB)
Title: Improvements in or relating to positioning mechanisms for magnetic head guides
IPC: G11B15/61
Filed: 1964-02-28
Abstract: 1,010,160. Rotary magnetic heads. AMPEX CORPORATION. Feb. 28, 1964 [April 1, 1963], No. 8506/64. Heading G5R. A mechanism for positioning a concave guide to hold a magnetic tape in curved concentric relation to a rotating head assembly, comprises means for adjusting the spacing between the guide and head assembly at the arcuate extremities of the guide, and means for adjusting the spacing between the guide and head assembly at the arcuate mid-portion of the guide, the means being operable independently from one another. In Fig. 1 a rotating head drum 14 is supported from a base-plate 13 to which an arm 33 carrying the concave guide 31 is pivoted by means (Fig. 2, not shown) which allow pivoting and limited universal movement. An air suction line 35 is connected to the guide, and the guide can be rotated from the threading position shown to its operative position where a bearing bolt 42 engages a bearing ball 43 and where the guide is held by latch means (not shown) releasable by a lever 37. Vertical adjustment of guide.-A wedge element 92, Fig. 6, is disposed within a recess 93 on the arm 33 and bears against a bearing pin 94 and a bearing ball 96 extending from the arm. The wedge is retained against the arm by a spring leaf 102 and rests on balls 38 and 39 extending from the base plate 13. The end of the wedge element 92 has a fork 105 engaging a peripheral groove in a knob 41 on a threaded shaft so that rotation of the knob moves the wedge to the left or right in the drawing thereby raising or lowering the guide 31 whilst maintaining the central plane 99 of the guide parallel to the base-plate 13. Raising the guide increases the spacing between the upper end 100 of the guide and the drum 14 and decreases the spacing between the lower end 101 of the guide and the drum, whilst lowering has the opposite effect. Horizontal adjustment of guide.-The bearing ball 43, Fig. 8, which determines the horizontal position of the guide is mounted in a sliding bearing element 133 connected by a spring leaf extension 141 to a block 142. A fixed block 134 forming a guideway for element 133 is similarly connected by a leaf spring 137 to a block 138 and defines a flexible fulcrum for a lever arm 139 to which blocks 138 and 142 are bolted. Thus when the free end of lever arm 139 is moved, the ball 43 moves correspondingly in the opposite direction, and the two spring levers 137 and 141 urge the lever arm in a clockwise direction. In one mode of operation the lever arm 139 is maintained in a pre-set position by its engagement with the end 162 of a shaft 161, the position of the shaft 161 being determined by the engagment of a bearing arm 164 fixed to the shaft with a set screw 166. In an alternative mode of operation the shaft 161 is pushed in and rotated by means of a lever 46 so that the arm 164 bears against a pivoting arm 170 and against lever 139, Figs. 9 and 10 (not shown). The arm 170 may be operated by a servo system so that the head-to-tape pressure is increased, to stretch the tape, if the frequency of played back television signal equalizing pulses is greater than a desired frequency, and reduced if the frequency is less. A pin 174 ensures that the shaft 161 must be pushed in, thereby increasing the spacing of the guide, before it can be rotated to switch from one mode to the other. An eccentrically mounted pin 151 normally prevents the arm 33 from being moved to its operational position, but energization of a solenoid 47, Fig. 1, rotates the pin to allow the arm to move. The solenoid may be connected so that it is deenergized only when the power to the machine is cut off, so that failure of the power causes the guide to be withdrawn.