Patent GB-814680-A (GB)
Title: Improvements in tape handling machine
IPC: G11B15/38
Filed: 1956-10-18
Abstract: 814,680. Phonographs &c. SPERRY RAND CORPORATION. Oct. 18, 1956 (Nov. 14, 1955], No. 31771/56. Class 40 (2). [Also in Group XVI] In web-feeding apparatus, such as a tape-recorder wherein a tape 10 is fed past a work station 12 in short fast bursts, the effect of inertia of the supply and take-up reels 11, 13 is eliminated by providing a tapered vacuum box such as 15 into the mouth of which a loop 16 of tape is drawn by reduced pressure applied at the neck 29; due tq the taper, the total force applied across the tape by the pressure difference decreases as the loop approaches the neck, and any deviation from an assumed equilibrium condition is detected by control means actuating the reel, such as 11, to pay out or take up tape to restore the equilibrium condition. The apparatus is stated to allow tape speeds at the work station 12 of 100 inches per second, or more, within 0.001 second from rest, thus giving a minimum wastage of tape between 'bursts of recording or reproduction. Due to the taper of the box 15, which may be linear as shown, or exponentially curved, or steplike (Figs. 2A and 2B, not shown) variations in the force applied across the tape loop 16 will produce corresponding variations in tape tension, which as shown are detected by a pulley 14 mounted on a spring-loaded pivoted arm 32 carrying contacts 34, 42 coacting respectively with fixed contacts 35, 43 to energize the motor 36 of the reel 11 in one direction or the other; this motor, e.g. of the capacitor type, may have its armature spring loaded against a brake disc from which it is axially withdrawn by solenoid action of the field when the motor is energized; the motor 41 of the reel 13 is similarly controlled in response to the tape tension on a pulley 25. Two tapered vacuum boxes 15, 17 and 21, 23 may be provided on each side of the work station 12, and to give maximum actual loop storage on the tape supply side and maximum potential loop storage on the take-up side, the equilibrium positions of the tape may be altered by adjusting the tension of springs 33, 38 according to the direction of travel, e.g. by moving their anchorage 65 about a pivot 66 by means of a solenoid 70 acting against a spring 67. In a modification (Fig. 6, not shown) the contacts 34, 35, 42, 43 are replaced by a pair of carbon pile resistors forming two legs of a bridge circuit having an amplifier which supplies current to the motor 36 when the voltage taken from the common terminal of the resistors differs from a voltage taken by a two-position switch from either of a pair of tappings in a constant resistance forming the other two legs of the bridge circuit, the two-position switch being controlled by relay or other means corresponding to the solenoid 70. To prevent the rapid movement of the tape loops 16 &c. into and out of the tapered boxes 15 &c. from disturbing the pressure difference across the loops when a small-capacity vacuum source is used, the boxes may be connected in mutually-compensating pairs by a wide conduit such as 102. The tape drive shown consists of a pair of capstans 19, 20 continuously rotated in opposite directions by a motor 26; their construction, Fig. 4, includes a stationary shaft 83 cut away at 84 for the admission of positive or negative air pressure to radial passages 88 ... 94 in the rotor, whereby the tape is held away from, or drawn against, the capstan surface; to prevent binding, a second cut-away part 85 in the shaft 83 may be permanently connected either to atmosphere or to a source of positive air pressure. The tape may be further pneumatically controlled by forming the surface of the transducer 12 with apertures 97, Fig. 5, leading to a conduit 98 connectible to sources of positive and negative pressure for respectively freely floating, and braking, the tape; the effect may be increased by adding further apertured members 99, 100 at the sides of the transducer. If the transducer is magnetic, for use with a magnetic tape 10, its coil 96 may be positioned as shown, but the feeding device may also be used for tape impressed by mechanical or photo-electric means.