Patent GB-804433-A (GB)
Title: Improvements in and relating to surface finishing apparatus
Inventor: MCGIBBON ARCHIE STANLEY
IPC: B24B7/07
Filed: 1954-12-08
Abstract: 804,433. Grinding. LUKENS STEEL CO. Dec. 8, 1954, No. 35602/54. Class 60. [Also in Group XL(b)] A machine for finishing the surface of a workpiece W comprises a supporting structure mounted for controlled movement in a direction parallel to the surface of the workpiece, rotatable means carried by this structure and operative upon the surface, end mechanism accommodating pivotal movement of the rotatable means in a plane substantially perpendicular to the said surface so as to change the angle between the axes of rotation of the rotatable means and the surface. As described, the actual finishing means is an abrasive band 23, Figs. 2 and 3, which is driven over rollers 36, 37, 38, 39 on a frame structure and constitutes the said rotatable means where it passes over the roller 39 at the point of engagement with the workpiece. The frame structure 40, 41 is pivotally supported from the free end of a cantilever 20, Figs. 2 and 4, extending outwardly from a trolley 16 movable on rails 13 on a second trolley 9 similarly movable on longitudinal rails 7. The rails 7, Fig. 2, are supported on beams 6 housed in recesses 5 in a concrete foundation having embedded I-beams for the support of metal plates 2 to which the workpiece W is secured by clamps 4 ; the upper face of the foundation is shaped to provide a space beneath the plates 2 for housing equipment for circulating coolant. The trolley 16 is driven by a motor 17, Fig. 2, controlled by limit switches on the tracks 13 and the trolley 9 by motors 10 controlled by limit switches on the tracks 7. The four rollers 36, 37, 38, 39 are mounted between rigidly-connected side plates 40, 41 supported for pivotal movement on trunnion shafts 111 carried by brackets 110 depending from the cantilever 20 ; the shafts 111 are rotatable in bearings 114 secured in plates 115 connecting the side plates 40, 41. Tilting of the abrasive band structure is controlled by springs 123, 123a, Figs. 3 and 4, which surround a rod 117 extending upwardly from its pivotal mounting 118 on the cantilever and engage on opposite sides of a sleeve 120 fitting on the rod and connected to the plate 41 ; the springs tend to hold the structure with the axes of the rollers horizontal, but permit a restrained tilting movement of the structure as the operative part of the band accommodates itself to variations in the contour of the workpiece. The drive of the band is through the roller 37 which is rotated through a belt drive 47 from an electric motor 24 on the trolley 16, the drive shaft 25 between the motor and belt drive being universally jointed to accommodate tilting movement of the band structure. The band is tensioned or slackened by mounting the roller 38, Fig. 3, so that it can be swung to or from the band by admitting pressure fluid to one end or the other of two pivotally-mounted hydraulic cylinders 59 under the control of a manually-operated valve ; the roller 38 is supported in bearings 50 carried by brackets 51 which can be swung about pivots 52 by the piston rods 58 of the cylinders 59, the fluid admitted to the upper ends of the cylinders to tighten the band being at a much lower pressure than is the fluid admitted to the lower ends of the cylinders to release the band. The bearings of the roller 39 disposed at the operative point of the band and those of the oppositely-positioned roller 36 are mounted, respectively, on two pairs of pivoted arms 64, 65 and 76, 76, Figs. 3 and 4, which are connected by rods 71 for simultaneous upward and downward swinging movement by the action of pivotally-mounted hydraulic cylinders 80 having their piston rods 79 connected with the rods 71 ; stop screws 84 limit the downward movement of the arms. Pressure fluid is supplied to both ends of the cylinders 80 under the control of hand-operated valves, the pressure of the supply to the lower ends of the cylinders being sufficiently greater than that of the supply to the upper ends to ensure that, after taking account of the weight of the rolls and associated parts, there is a net downward pressure of 3 lbs. per square inch. The pressure fluid system also ensures that this downward pressure is maintained constant even should the rollers 37, 39 be raised by the operative part of the band encountering a raised portion of the workpiece, the consequent increase in pressure in the upper ends of the cylinders resulting in the discharge of fluid to the sump until the original pressure balance is restored. The roller 36 is mounted so that it can be oscillated about one end bearing, 62, Fig. 4, (which is of the universal angling type) by having its other end bearing 63, Fig. 3, movable along the top of the arm 64 by the action of a lever 90 operated by the piston rod 93 of an hydraulic cylinder 94 pivoted on the arm 64. Pressure fluid is supplied alternately to opposite ends of the cylinder under the control of a solenoid valve so that the roller is oscillated and the band constantly reciprocated across the roller. The solenoid valve is actuated by relays in an electric circuit, Fig. 13 (not shown) controlled by photo-sensitive units 42, 43, Figs. 2 and 3, disposed near one edge of the band, the light-sensitive element 42a or 43a of each unit being disposed on the opposite side of the band to the corresponding light source 42b or 43b. The units 42, 43 so control the circuit that, as the band moves transversely and thereby affects the light beams of the units, the solenoid valve is alternately energised and de-energised. Rubber, &c. tyres are provided on the three rollers 37, 38, 39, that on the roller 38 being preferably softer and/or thicker than that on the drive roller 37.