Patent GB-621214-A (GB)
Title: Automatic electro-mechanical device for cutting gramophone records
IPC: G11B3/08
Filed: 1946-05-23
Abstract: 621,214. Recording apparatus. NINNI, I., and ROLUTI, G. May 23, 1946, No. 15718. Convention date, Dec. 30, 1944. [Class 40 (ii)] In a disc-recording machine of the type in which the cutting member is carried on an arm which is rotatably mounted on a vertical spindle and is driven by a motor, means are provided which, after the arm has rotated through a predetermined angle, switch off the modulating current, increase the transmission ratio between the motor and the arm for the cutting of the higher pitch stopping spiral, and thereafter switch off the driving motor and restore the transmission ratio to normal. As shown, the turntable 2, which is directly driven by the electric motor 9 (Fig. 3), is mounted on a baseplate 1, which also supports, keyed on the shaft 23 (Fig. 7), the arm 3 (Fig. 2) carrying the cutting head 5. The motor 9 (Fig. 3) also drives a pulley 11 (Figs. 3, 4) on the spindle of which is mounted an endless screw 12 engaging a helical wheel 13 keyed on the shaft 14. This shaft also has keyed on it a sliding sleeve 17 comprising two collars 17a, 17b and a conical wheel 20 which is urged downwards (Fig. 4) by the spring 18. Also fitted on the shaft 14 is an endless screw 21 engaging the helical wheel 22 (Fig. 7) loosely mounted on the shaft 23 between two clutch discs 24, 25, of which 24 rests against a hub 26 keyed on the shaft, while 25 is urged against the wheel by the action of the spring 29 pressing on the hub 27 loosely mounted on the shaft, and a spur gear-wheel 28 keyed thereon. A band-brake comprising a metal band 76 passing round a fixed pivot 77 and tensioned by a spring 78 is applied to the hub 26. The spur-wheel 28 engages a toothed wheel 32 provided with conical teeth 33 on one side and loosely mounted on a pivot carried by a support 34 (Fig. 4). The collar 17a engages the fork 35a (Figs. 4, 6) of a rocking member 35, 36 pivoted at 37, a projection 36a of which actuates a switch 38 connected in the modulating current circuit. The arm 36 is normally prevented from actuating the switch by a tooth 39 on a lever 40 which is rotatably mounted on the spindle 41 and may be rotated by a lever 80 (Fig. 2), or by the projection 49a of a plate 49 carried by the wheel 28. The lower portion of the lever 40 has pivoted to it at 42 a bent lever 43, 44. The second collar 17b engages the fork 50 (Figs. 4, 5) fixed to the rocking member 52, 53 which rotates around the spindle 51. A spring 54 (Fig. 3) is fitted between the plate 1 and a notch 52a of the arm 52. The rocking member is normally retained in the full-line position (Fig. 5) by the tooth 55 engaging with the notch 56 of another pivoted member 57, 58 normally maintained in the full-line position by a spring 61. A guiding lever 63 having a slot 64, in which is located a fixed pivot 65, is pivotally mounted on the arm 53 at 62. The wheel 28 carries on the side facing the base-plate (i.e. its upper side), a plate 49 (Fig. 6), and on the other side (a) an arm 67 (Fig. 3), having at its end an adjustable screw 68 which engages the lever 69 during rotation of the wheel, thus switching off the current supply to the motor 9 at switch 70; (b) an arm 71 serving to operate the switches 72, 73 in the motor and modulating current circuits respectively; (c) a plate 74 which normally engages a tooth 75 of the stopping blade 75a; and (d) rollers 60 and 66. Operation. The cutting head is raised manually and moved slightly towards the centre of the turntable, so that the arm 3 rotates, and the shaft 23 and spur-wheel 28 are rotated against the resistance of the stopping blade 75a which is disengaged by riding over the plate 74. The helical wheel 22 which is in mesh with the endless screw 21 remains stationary since its clutch slips. The switches 72, 73 which are operated by the arm 71, switch on the motor and complete the modulating current circuit respectively. The shaft 14 is thereupon set into motion and by means of the endless screw 21 and helical wheel 22 drives the shaft 23. The spur wheel 28 fixed on the shaft 23 also rotates and drives the wheel 32-33 which is not yet in mesh with the wheel 20, but is loose on its pivot. Semi-automatic operation. When recording is completed the lever 80 (Fig. 2) is moved by hand so as to rotate the lever 40 in a clockwise direction (Figs. 3 and 6), thus allowing the fork 35a to move downwards (Fig. 4). The lever 40 returns to its normal position under control of the spring 47 (Fig. 6). The arm 36 opens the switch 38 to prevent further recording. The subsequent movement of the sleeve 17 causes the wheel 20 to engage the conical wheel 33. The ratio between these wheels is 1: 1 and that between wheels 32 and 28 is much greater than that between the endless screw 21 and the helical wheel 22, so that the shaft 23 is driven at a higher speed. During this operation the wheel 22 slips on the shaft 23 and continues to rotate at its previous slower speed. When the spur-wheel 28 has turned through the angle required for tracing the stopping spiral, the roller 60 engages the lever 58 (Fig. 5) and releases the tooth 55 of lever arm 53 from the notch 56. The lever 52, 53 then rotates under control of the spring 54 until the pivot 65 reaches the upper end of the slot 64. During this rotation the fork 50 rises and restores the sleeve 17 (Fig. 4) to its normal position. The subsequent movement of fork 35a serves to restore the member 35, 36 to its original position, thus closing the modulating current circuit at switch 38. Finally, the lever 67 engages the lever 69, thus operating the switch 70 to switch off the motor, and the screw 68 strikes a fixed support (not shown) so as to limit the rotation of the wheel 28 and thus that of arm 3 also. The shaft 23 is stopped by the band-brake 76, 78, but the turntable performs a few more revolutions by inertia and since the cutting head is stationary during these revolutions, the circle required for closing the stopping spiral is cut. The cutting head is then raised manually and the arm 3 is returned to its initial position so that the wheel 28 rotates clockwise (Fig. 5) and the roller 66 moves the lever 53 into its initial position where its tooth 55 engages with notch 56 and the arm 74 engages the tooth 75 (Fig. 3) of the stopping blade 75a. Automatic operation. After a predetermined rotation of the arm 3, the projection 49a of the plate 49 (Fig. 6) strikes the end 44 of the lever 43, 44. Since this lever is prevented from pivoting about 42 by the turned-down ear 46 of the arm 40, it rotates the lever 40 about the pivot 41 and thus initiates the cycle of operations described above for semiautomatic operation. By altering the angular position of the plate 49 with respect to the plate 74, the section of the record in which the stopping channel is to be cut may be varied as desired.