Patent GB-229800-A (GB)
Title: Improvements in or relating to phonographic sound-boxes
IPC: G11B3/46
Filed: 1923-12-19
Abstract: 229,800. Grissinger, E. Dec. 19, 1923. Tool-arms and mountings.-Relates to vibration-transmitting devices in phonographic recording or reproducing sound-boxes, of the kind in which a lever controlled by restoring springs which oppose its vibrations is held against its bearings by means applying great pressure approximately in the line of the pivotal axis of the lever. According to the invention, the pressureapplying means has no restoring spring effect, and the restoring springs have no action in holding the lever on its bearings. Fig. 2 is a side elevation of a sound-box, looking in the direction of the. needle, Fig. 4 being a central section. Lateral arms 12 of the stylus-lever 15 have conical recesses 25 engaging bearing points 24, the arms being pulled strongly against the bearings 24 by means of spring wires 23, which are looped through holes in the arms 12 and attached to tensioning screws 22. The restoring springs consist of a pair of steel rods 27 (such as sewing-needles cut to the required length) clamped to the lever by plates 28, the free ends of the rods being sprung against opposite sides of lugs 30. The lugs are preferably conical-ended adjustable screws. An adjustable connection between the lever arm 15 and the diaphragm 3 is made by a screw 17 and pairs of nuts 18, 19. A single central spring may be used instead of the two bearing spring wires 23. In a modification, coiled wires are substituted for the straight wires 23, and the restoring springs consist of a pair of leaf springs, each of which engages with the conical end of an adjustable screw. The end of the stylus-bar is in this case secured directly to the diaphragm by a small screw. Edge bearings, swivelled in screw supports, may be substituted for the bearing-points 24. Figs. 9, 11, 12, and 13 show a further modification in which the stylus-arm 113 is fixed to a box member 112, to which the stylus-holder 109 is screwed, and which has lateral arms 114 screwed thereto. These arms are held upon point bearings 116 by pressure (which may be very great) applied by means of a bar 118 upon a short rigid or slightly resilient rod 117 passing through the member 112, Fig. 13. The thrust is preferably applied to the rod 117 by a rod 122 at right-angles thereto, secured in the end of the bar 118. The latter is adjustably secured by a nut 119 to a bar 121, which also carries the bearings 116. Restoring springs, arranged in oppositely-disposed pairs 128, 129, have their ends attached to the bar 121 and the arms 114 respectively, these springs encircling the arms 114 ; the attachments to the bar 121 are made adjustable by means of screws 132 passing through slots in the springs. The bar 121 has trunnions 124 fitting in split bearings 107 in which they are secured by locking screws 126 after the assembled parts have been so adjusted as to leave the diaphragm free from initial stress. The end of the stylus-arm 113 is preferably attached to the diaphragm 103 by means of a clamping device such as is shown in Fig. 15, comprising nuts 150 which are threaded on the arm and are rounded so as to engage in depressions in washers 160 gripping the diaphragm.