Patent GB-971336-A (GB)
Title: Surface grinding machine
IPC: B24B27/00
Filed: 1961-01-26
Abstract: 971,336. Grinding machines. H. E. SJOSTRAND. Jan. 26, 1961, No. 3166/61. Heading B3D. A surface grinder comprises a grinding tool 131, Fig. 1, carried by a rigid arm 101 mounted for vertical adjustment on a column 23 which is itself rotatable in a frame 18 arranged for slidable adjustment on the machine base 10 to and from a rotatable work-table 16, and means for causing the speed of rotation of the tables 16 to be varied in accordance with the momentary radial distance of the grinding tool from the centre of rotation of the table, such means being arranged as to be so effective whatever the distance between the centre of rotation of the workpiece and the column. To compensate for the different adjustment positions of the column the length of the arm 106 is correspondingly adjusted by the insertion or absence of a distance piece between the end of the arm and the grinding head. The table 16 is rotated from a motor 77, Fig. 9, through transverse shafts 79, 82, Fig. 8, associated with an expanding-pulley changespeed device 84 ... 87, and worm gearing 76, 77a. The worm-wheel 76a, which is normally free to rotate on the shaft 53 of the table, is arranged to drive the table through a friction ring 109 when the latter is expanded by a pivoted wedge 111; a cam 116 on a hand-operated shaft 118 co-operates with a spring plunger 112 in the bore of the shaft 53 to actuate a rod 115 controlling the wedge. The expanding-pulley change-speed device 84 . . . 87 comprises pulleys 84, 85 and 86, 87 on the two shafts 79, 82 and a belt 88, the pulleys 85, 87 being respectively axially movable by a spring-pressed lever 91 and a lever 94, 95 controlled by an operating handle 98 to adjust the gear ratio between the two shafts 79, 82 and therefore the speed of the table 16. The shaft 53 of the table 16 is journalled in two bearings 15, Fig. 9, which are provided in a sleeve 14 in the machine base 10 and separated by elastic material 75 to prevent the transmission of vibrations. The underside of the table 16 is provided with an annular depending flange which has grooves 72 and fits between rings 73, 74 upstanding from the bed. The rings 73, 74 serve to retain oil which is forced, during rotation of the table, into the grooves 72 and between the table and bed. The grinding wheel 131, Fig. 1, is secured on the shaft of a motor 129 which is secured on the end of the arm 101 by bolts 128 permitting adjustment of the motor in a vertical plane. The arm 101 has a cylindrical portion 121 embracing the column 23 and arranged for vertical adjustment thereon by an hydraulic cylinder 149, Fig. 1, operated by electrical controls on a panel board 164. A fixed reference point is used with an automatic gauge 160 for determining depth of cut, the initial setting being effected by a knob 180 acting through a rack-and-pinion to adjust the position of the gauge. The frame 18 on which the column 23 is journalled is movable in guides 26 on the machine base 12 in a direction to and from the table 16 by a manually-operable screw 35, Fig. 8, engaging a nut 41 having a pin 42 projecting upwardly into the frame. Swinging movement of the column is derived from the worm-wheel 76a but takes place only when the table 16 is being driven. For this purpose, an eccentric 55, Fig. 10, on the shaft 53 oscillates a slotted lever 61, Fig. 8, and through a rod 58 and reversible pawl-and-ratchet gear 61, operates a shaft 47 coupled by a universal joint 46 to a shaft 31 on which is keyed for relativelysliding motion a worm 30 meshing with a wormwheel on the column 23; an interrupter plate 69 carried by a hand-controlled sleeve 49 on the shaft 47 permits the ratchet action to be adjusted. The above-mentioned speed variation of the table 16 in accordance with the operative position of the grinding tool is effected by a cam 99, Fig. 8, fixed on the column 23 and acting through the jointed lever 94, 95 to control the expanding pulleys. As the column 23 carries the tool away from the centre of the table 16, the cam 99 so adjusts the speed of the latter as to maintain substantially constant the relative velocity between the tool and the momentary coacting part of the workpiece; the joint between the lever parts 94, 95 is controlled by a spring 104 so that it is only effective when the pulley 87 and shafts 79, 82 are rotating. Should the frame 18 and column 23 be displaced further away from the work-table in order that the tool may operate on larger workpieces, the cam 99 (which is displaced with the frame) acts on the jointed lever 94, 95 at a point further from the pulley 87 and so the speed of the table is automatically adjusted in accordance both with the new swing of the arm 101 and the distance between the axes of the column and table. The radius of the sweep of the grinding tool is variable in accordance with the adjusted position of the frame 18 by the insertion of an appropriate distance piece between the motor 129 and end of the arm.