GB663815A - Improvements in grinding machines - Google Patents

Abstract

663,815. Pllilling-machines. SJOSTRAND, H. E. May 23, 1946, No. 15705/46. [A Specification was laid open to inspection under Sect. 91 of the Acts, May 23, 1946.] Class 83 (iii). [Also in Group XXIII] The invention is described with reference to grinding-machines but the Specification as open to inspection under Sect. 91 states that the grinding-wheel may be replaced by a cutting- tool, for instance a milling-cutter having hard metal cutters. This subject matter does not appear in the Specification as accepted. A machine for grinding plane surfaces comprises in combination a frame, a rigid arm mounted on the frame to swing about a stationary axis, a first spindle mounted with its axis in fixed position in the frame, a second spindle mounted at the free end of the swinging arm so that its axis maintains a fixed position with respect to the arm, a grinding-wheel mounted on one spindle and a work-holder on the other; the axis of the spindle carrying the work-holder being parallel with the swinging axis of the rigid arm, means to rotate the grinding-spindle at a high speed and the work-spindle at a lowspeed, means for adjusting the position of the rigid arm in the direction of its swinging axis, thereby enabling the distance between the grinding-wheel and the work-holder to be adjusted, and means for holding the rigid arm in fixed axial position after adjustment. A grinding-wheel 21, Figs. 1, 3, which may be a cup wheel, is secured to the shaft of an electric motor 20 which is mounted on, and for adjustment about the axis of, a horizontally-extending cylindrical arm 7 carried by a vertical shaft 6 journalled at its ends in a frame 2 so that the grinding - wheel may be .swung in a horizontal plane across work carried on a table 45 rotatable, about a vertical axis, on the machine base. The arm 7, and thus the grinding- wheel 21, is vertically adjustable on the shaft 6 by means of a nut carried by the arm 7 and running on a screw 24 fixed to lateral extensions of the shaft 6. The work-table 45, which may be a magnetic chuck, is driven from the grinding-wheel motor 20 through a flexible shaft and gearing 52, 54. The grinding-wheel 21 is automatically swung across the work at a speed which increases as the wheel approaches the centre of the work-table by mechanism comprising a link 76 attached at one end to a lateral arm 23 of the vertical shaft 6 and at the other end adjustably to a slotted arm 75, secured to the upper end of a shaft 71 slowly rotated by cam and pawl-and-ratchet means from the work-table. Instead of driving the work-holder at a constant speed and varying the rate of swinging of the grinding-wheel arm 7 the grinding-wheel may be swung at a constant speed and the speed of rotation of the workpiece increased as the wheel approaches the centre of the work-holder, in which case the work-holder is driven through gears 103, 104, Fig. 8, and a friction disc 105 driven at a variable speed by a friction wheel 106 which is rotated by a flexible shaft 50 from the grinding- wheel motor and is carried at the end of a pivoted arm 107 swung across the friction disc 105 by a cam 112 mounted on an extension of the swinging shaft 6, an eccentrically journalled cylinder 111 holding the wheel 106 in engagement with the friction disc 105, and cam 115 contacting a finger 114 on the arm 107 serving, if required, to reverse the direction of rotation of the work-holder. Instead of a single workpiece secured to the holder a number of small work-pieces may be secured thereto to form a ring around the centre. In the machine described with reference to Figs. 1-3, the automatic swinging mechanism for the arm 7 may be disconnected and a hand-operated screw-andnut device mounted on the machine, to swing the arm for surface grinding or to move it to a fixed position for cylinder grinding. For cylinder grinding the arm 7 and grinding-wheel 21 may be moved vertically either manually or automatically by mechanism, Fig. 6, in which a cam 101 on a rotating shaft 49 on the grinding- wheel head operates a reversible ratchet-and pawl device 90, 96 to rotate a nut 25 on the screw 24, a cam 98 reversing the feed by bring- ing another pawl into action. If the machine is to be used to grind non-circular sectioned cylinders a follower arm is secured to the swinging shaft 6 to engage a template secured to the work-table. If the machine is either to grind non-cylindrical bodies of rotation, in which case the work is mounted on the rotating holder, or to form-grind one side of a workpiece secured directly to the table of the machine an upright template is secured to machine table and a follower arm on the swinging shaft 6 contacts it. In an alternative construction the grinding-wheel is journalled in the machine frame and the work-holder is swingable and vertically adjustable, separate motors for the wheel and holder being provided, of which the work-holder motor may be an oil turbine, the speed of which is varied by automatically choking the oil supply through a regulating valve connected with the swingable supporting member. When grinding with a cup wheel the motor shaft which is turned to be at right angles to the work-holder has a spring-pressed double axial bearing, Fig. 13 (not shown). A pump 77, Fig. 3, operated from the work-holder drive, pumps soapy water or other coolant through a pipe 155, Fig. 14, to bores in the grinding-wheel hub, whence it is centrifugally thrown on to the working edge of the wheel 152. Specification 663,908, [Group XXIII], is referred to.