Patent GB-847821-A (GB)
Title: Improvements in tape storage devices
IPC: G11B15/58
Filed: 1956-12-28
Abstract: 847,821. Magnetic recording &c. apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 28, 1956 [Dec. 30, 1955], No. 39531/56. Class 40 (2). [Also in Group XVI] A tape storage device comprises a group of two or more elongated open-ended tape receiving chambers, wherein looped tape sections are formed, means for maintaining tensions on the looped tape sections to cause transfer of the tape between the chambers of the group so as to maintain the looped taped sections equal in length when tape is fed therein to or withdrawn therefrom, and control means for increasing the tension on the looped tape sections in any chamber when the section exceeds a predetermined length. As shown, a supply reel 18 is mounted on a driving-shaft 16, while a take-up reel 23 is mounted on a driving-shaft 17. The shafts 16, 17 can be driven in either direction or braked. For example the shaft 16 is driven by a constant-speed electric motor 24, Fig. 2, through reversing clutches 25 and 26 and can be braked by a brake 27. Magnetic recording tape 19, Fig. 1, unwound from the reel 18, is formed into loops 53 in chambers 39, 40 before passing through a tape reading or recording head 21 and around a reversible capstan 28. The tape is formed into further loops 53 in chambers 41, 42 before being wound on a take-up reel 23. The capstan 28 is driven by a continuously-driven motor 31, Fig. 2, through reversing clutches 32, 33 and can be braked by a brake 34. The clutches 32, 33 and the brake 34 are controlled by a control mechanism which releases the brake 34 and selects the direction of rotation of the capstan as required, for example, by a computer. The periphery of the capstan is perforated and closely spaced from a curved member 37, Fig. 3, supplied with compressed air which causes the tape to be deflected into the perforations in the capstan, thus increasing the frictional contact between the tape and capstan. The chambers 39, 40, 41, 42, Figs. 1 and 2, each include front and rear walls 44, 45, spaced apart a slightly greater distance than the tape width and converging side wall surfaces 46 and 47. The cross-sectional area of each column thus decreases from its upper end 48 towards its lower end 49. The lower ends 49 are connected to a vacuum chamber 50, reservoir 52, and vacuum pump 51. Thus, any slack in the tape between the reels 19 and 23 will be formed into loops 53 in the chambers 39 ... 41. When the reels 19, 23 and the capstan 28 are stationary the tape forms loops 53 of substantially equal length, such that each loop has the same area exposed to vacuum and thus is subject to equal tension. Should the length of one loop vary with respect to another, e.g. as shown in Fig. 5, the tension applied to the loop in chamber 40 is greater than that applied to the loop in chamber 39. The difference in tension causes tape to transfer from the chamber 39 to chamber 40 until the loop lengths are equal. To facilitate tape transfer from chamber to chamber in this manner, the upper end of each partition 54, Fig. 3, has a perforated curved bearing-surface 55 supplied through a pipe 58 with compressed air which opposes the downward pull of the tape to hold the tape out of contact with the bearing- surface 55. The outer extremities of tape is also held out of contact with the side walls of the chambers by compressed air flowing downwardly, thus reducing friction and wear on the tape. Ports 60 and 61, Fig. 2, provided in the rear walls 44 of the chambers 40 and 41, communicate with pressure-responsive bellows 62 and 63, Fig. 10, respectively. The bellows 63 associated with the chamber 40 actuates a double-throw switch 64 having contacts 65 and 66 which complete circuits to operate the brake 27 and counter-clockwise clutch 25, respectively. The lower bellows 62 associated with the chamber 40 actuates a double-throw switch 67 having contacts 68 and 69 which complete a circuit to the switch 64 and operate the clockwise clutch 26, respectively. In operation, if the bottom of the tape loop 53 is positioned at a position A, between the ports 60 and 61, the reduced pressure acting on the bellows 62 closes contact 68, while atmospheric pressure acting on the bellows 63 closes the contact 65 to actuate the brake 27. If the bottom of the tape loop 53 takes up a position B, above the port 61, reduced pressure acts on both bellows 62 and 63, thereby opening contact 65 and closing contact 66 which operates counterclockwise clutch 25 to unwind tape from the supply reel, thereby causing the loop 53 to lengthen. If the bottom of the loop takes up a position C below the port 60, both bellows 62 and 63 are subject to atmospheric pressure, thereby closing contacts 69 and 65. The contact 69 operates the clockwise clutch 26 to rewind tape on the supply reel. The bellows 62 and 63 in the chamber 41 operate in a similar manner, except that the lower bellows 62 controls clockwise rotation of the reel 23 and the bellows 63 counter-clockwise rotation thereof. When the control mechanism, not shown, is operated, the brake 34, Fig. 2, is released and the clutch 32 is actuated to drive the capstan clockwise. The loop in the column 40, Fig. 1, shortens, thereby causing tape from the chamber 39 to pass around the bearing-surface 55 into the chamber 40. Should the capstan 28 continue to rotate the loop 53 in the chamber 40 assumes position B, Fig. 10, thereby causing the supply reel to unwind as previously described. Eventually, providing the capstan 26 continues rotating, the bottom of the loop resumes position A, thereby disconnecting the clutch 25 and causing the brake 27 to stop the supply reel. During this operation, the take-up reel is similarly controlled. Should the loop 53 in the column 40 assume position C, the supply roll is rotated clockwise to rewind tape until the position C is regained. Detectors 70, Fig. 1, engaging the peripheries of the wound tape on the reels 19 and 23 prevent complete unwinding of the tape and may operate through control mechanism 71 to vary the respective reel speeds. If desired, more than two pairs of loop forming chambers may be provided. Reference has been directed by the Comptroller to Specification 733,807.