Patent GB-856944-A (GB)
Title: Improvements in and relating to data storage apparatus including tape drive systems
IPC: B21D28/00
Filed: 1957-10-31
Abstract: 856,944. Driving magnetic tapes. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 31, 1957 [Oct. 31, 1956], No. 34041/57. Class 40 (2). [Also in Groups XVI and XXIX]  A computer utilizing magnetic tape is provided with an hydraulic transmission system for driving the capstan and tape reels. As shown in Fig. 1, tape from a reel 12 is fed over an air bearing 15 to form a loop in a buffer column 16. A magnetic head 17 is positioned above the capstan 18 that drives the tape between the buffer column 16 and a buffer column 19 from which the tape passes over an air bearing 20 to the reel 13. Vacuum ports 21 are gated by the tape loops to actuate vacuum switches. Pumps 29, 35, Fig. 3, are connected in series and supply liquid through a line 31, a start-stop valve 37, and a direction-control valve 38 to an hydraulic motor 39 driving the capstan 18. In order to adjust the speed of motor 39 an adjustable needle-valve 42 is provided in a by-pass line 41. Liquid returning from the motor passes via valves 38, 37 and a return line 40 to a reservoir. Valves 37, 38 are controlled by pilot valves 43, 45 which are actuated by magnets controlled by signals from the computer. A line 47 supplies liquid to the pilot circuit from the return line 40, the needle valve 48 in line 40 controlling the pilot pressure. The tape reel 13 is driven by a motor 39<SP>1</SP> provided with a similar hydraulic system, except that a speed control is provided to compensate for varying diameters of tape on the reel and comprising a by-pass line 56 having parallel connected needle valves 57. The amount of liquid by-passed is varied according to the position of a valve 55 controlled by a sensing-arm 58 engaging the periphery of the tape on the reel. Since maximum torque is required when the reel 13 is being accelerated to the desired speed, a valve 59 is urged by a spring 60 to a position closing the by-pass 56, and is urged to a position to open the by-pass by the pressure of upstream of a needle valve 63 in the return line from the motor 391. A startstop valve 371 and a direction control valve 38<SP>1</SP> are controlled by pilot valves actuated by magnets controlled by vacuum switches in a tape buffer column. In operation, the signal from the computer is applied to magnet 44 to move pilot valve 43 to the right, and pilot pressure moves valve 37 to the right so that the return line from the motor 39 is unblocked and liquid is supplied to the motor, the direction of rotation of the motor being determined by valve 38. A stop-signal applied to magnet 44 moves valve 43 to the left, which moves valve 37 to the left, thus blocking return-flow from the motor and opening the inlet line 31 to the return line 40. The increase in pressure in the return line rapidly stops the capstan. In the operation of the computer, a start signal causes the motor to start after a magnet actuation delay of 1¢ milliseconds. Two milliseconds later the tape has attained full speed, and information may then be recorded or read. When the reading or recording has been completed, a reverse signal is applied to magnet 46 to bring the capstan to full speed in reverse after 5¢ milliseconds. A stop signal is received at this point and the capstan is decelerated to zero velocity in 3¢ milliseconds, stopping the tape just before the end of the information record. This permits successive information records to be placed on the tape with minimum spacing. Specification 733,807 is referred to.