Patent GB-1181314-A (GB)
Title: Phonograph Tone Arm
IPC: G11B3/28
Filed: 1968-01-17
Abstract: 1,181,314. Record-player tone arms. V-M CORP. 17 Jan., 1968 [26 Jan., 1967]. No. 2643/68. Heading G5R. A record-player tone arm assembly comprises a tone arm having one end arranged for the mounting of a stylus thereon, a mount for the tone arm including a pair of spaced uprights, the tone arm having a portion of it remote from the stylus-attached end provided with spaced depending portions underlying portions of the uprights, and vertically-extending sections of coil wire having their upper end portions longitudinally secured to those portions of the uprights and having their lower end portions longitudinally secured to the tone-arm depending portions, the intermediate portions of the coil springs being axially deflectable and defining between them a pivotal axis about which the tone arm is vertically movable. Stylus pressure on the record may be regulated by a tension spring connected between an adjustable anchorage on the mount and a fixed anchorage on the tone arm As shown in Figs. 1 and 4, a tone-arm mounting member 20 includes a raised plate portion 34 to which is secured a yoke 38 of horizontal U-section, the assembly including two pivot studs 48, 53, seated in recesses 58 and 62, respectively, provided in a bearing post 44 which is staked to a sub-plate 30 and extends through a hole in a base-plate 32. This bearing structure provides for transduciing traverse of the tone arm 22. The tone arm 22 is secured by a screw 70, Fig. 4, to a cradle 74, Figs. 5 and 7, which has two downwardly-extending arms 76, Figs. 5 and 7, one of these arms being forward (in the direction of the stylus end of the tone arm) of the vertical pivot VP, and the other being rearward of this pivot, as seen in section in Fig. 3. Each of these arms has a vertical groove in the outside of an offset portion 78, in which groove is secured, by a clamp 84, and screw, the lower end of a coiled spring 80. The upper end of each coiled spring 80 is similarly secured in a vertical groove in a hanger extension 68, Fig. 3, extending inwards (and either backwards or forwards as the case may be) from an upright 66, Figs. 3 and 7, each upright being integral with the mounting-member structure. The tone arm and cradle are thus able to pivot in a vertical plane about the middle portions 86, Figs. 5 and 7, of springs 80, acting as a hinge and defining the horizontal pivot axis HP, Fig. 3. The axis HP, Fig. 1, is perpendicular to the axis SS, Fig. 1, of the cartridge 24, so the stylus 25 is movable in a vertical plane. The tone arm 22 is initially balanced by an adjustable counterweight 90, 92, Fig. 4. Positive stylus pressure on the record being played may be provided by a tension spring 98 which is anchored between a vertically-adjustable lug 102, Fig. 4, associated with the mounting member 20, and a lug 100 integral with the cradle 74. Thus, during vertical movement of the tone arm, the lug 102, having been adjusted, remains fixed, while lug 100 moves with the tone arm. When a toothed rack 104, Fig. 4, integral with lug 102, is in its lowest position, Fig. 7, the spring 88 intersects the axis HP. In this position, no pressure is exerted by the stylus on the record for any location of the stylus between a height where it engages the highest one of a stack of records and a height where it engages the lowest one of the stack, or the first record on the turntable. The axis HP is vertically located at a height corresponding to the mid-point of the largest stack of records (e.g. six in number) expected to be loaded on to the turntable. The stylus pressure may be varied or preselected by rotating a knob 28 which is connected to a pinion 112 which meshes with rack 104. The stylus pressure increases with increasing height of lug 102. The stylus pressure, once selected, remains constant for the playing of different records at all heights in the stack; also, the stylus pressure does not change during playing of a warped record. Reference has been directed by the Comptroller to Specification 1,096,130.