Patent GB-1184921-A (GB)
Title: Improvements in or relating to Drum Tape Recorders
IPC: H04N5/782
Filed: 1967-03-20
Abstract: 1,184,921. Drum type recorder. WESTEL Inc, WESTEL ASSOCIATES, and WESTEL CALIFORNIA INVESTORS. 20 March, 1967 [21 March, 1966; 29 Dec., 1966; 27 Feb., 1967]. No. 12952/67. Heading G5R. In a drum type recorder for recording e.g. video signals in oblique lines on a magnetic tape or for playing back such signals, the drum includes upper and lower stationary drum members and a closely-spaced central rotating drum member which supports one or more magnetic heads and is of sufficient height to give substantial support to the tape and which includes an opening or openings in its periphery adjacent its magnetic head or heads via which air passes outwards to lubricate the tape movement. The drum may be used with systems employing a 180 degree wrap and two heads, or a conventional # wrap with a single head or with systems using more than a 360 degree wrap. In a 540 degree wrap arrangement the drum 72, which increases slightly in diameter with height, includes upper and lower drum members 78, 82 and central member 80 which is made fast to a drive shaft 86. The drive shaft is driven by a D.C., printed circuit motor 156 and supported by the upper and lower drum members which are respectively releasably latched to and secured to the recorder support frame 22. The head 128 is connected to an output plug 140 via a rotary transformer 132, 136 and the speed of the central drum is monitored by photo-cell 148 and lamp 146 which co-operate with a downwardly directed tang 142 on the central drum. Air enters the central drum through apertures 120, 122, 124 and passes outwardly through opening 130 adjacent the head to lubricate the tape. This action is assisted by reducing the diameter of the central drum by about 0À001 inch compared with the upper and lower drum and by using a head which extends beyond the periphery of the drum by about 0.006 inch thereby forming a "tent" in the tape surface. The tape is passed from a supply reel 36 coaxially mounted with take-up reel 38 to a first tape tensioning device 214 then via a first head assembly 216 including audio and video erase heads and capstan 218 to tape entrance guide 182 set at 3 degrees to the vertical. The tape passes 1 ¢ times around the drum to a tape exit guide 184 set at 6 degrees to the vertical and thence via capstan 224, second magnetic head assembly 226, including audio and control signal heads and second tape tension device 228 to take-up reel 38. The audio and control signal heads record on or playback from edge tracks on the tape. The tape is fed on to the drum in overlapping relationship with the preceding convolution but in this arrangement the amount of overlap decreases and disappears before the take off point is reached 180 degrees around the drum. The upper drum is recessed slightly at this take off point and the recess extends beyond the point at which tape overlap ceases. The recess assists in feeding the tape below the preceding convolution during tape rewind. In a second 540 degree wrap arrangement the drum is cylindrical and the tape overlap remains constant between the input and output points. In this arrangement also the upper drum is recessed at the output point and the tape is fed inwardly of the drum before being turned through 360 degrees and fed away from the drum. This makes it possible to feed the tape below the preceding convolution during rewind. The reels 36, 38 are coaxially mounted but separately driven, Fig. 18 (not shown). The upper reel is mounted on a hinged latched plate so that it can be swung aside to allow the lower reel to be loaded.