Patent GB-909959-A (GB)
Title: Apparatus and method for polishing articles
IPC: B24B21/00
Filed: 1960-06-27
Abstract: 909,959. Polishing apparatus. HI-LITE POLISHING MACHINE CO. Inc. June 27, 1960 [June 30, 1959], No. 22387/60. Class 60. An apparatus for polishing a workpiece comprises means for moving an abrasive belt along the surface of a workpiece while the latter is being rotated by a chuck, means for urging the abrasive member into contact with the surface during such movement, means for preventing movement of the belt to maintain a given surface area of the belt in contact with the surface of the workpiece, and means for indexing the belt between successive polishing operations. The apparatus is described as provided with separate abrasive belts for polishing the inner side wall and bottom respectively of a cylindrical pan 3, Fig. 1, held by vacuum means in a chuck 5 which is driven by an hydraulic motor. The means for polishing the side wall of the pan is that portion of a stationary abrasive belt 27 where it passes over a rubber shoe 58 and that for polishing the bottom of the pan the portion of a similar belt 145 where it passes over a rubber shoe 149. The abrasive belts are mounted on frame structures on a vertical member 10 which can be swung about a vertical axis 11 by an air cylinder 15, Fig. 5, to move the operative portions of the belts into and out of the pan. The belt 27 is positioned on a frame 26 which is pivotally mounted on a bolt 52 on a slide 25 arranged for horizontal reciprocation on guideways 40 on a member 24 which is mounted at one side of the vertical member 10 for adjustment both vertically and tiltably in a vertical plane so as to deal with pans of different sizes and shapes. The belt is led on the frame 26 from a reel 66 over rollers 67, 69 and around the rubber shoe 58 which straddles two belt guides at the end of an elongated extension 54 of the frame, the shoe and guides being arranged so that in action the operative part of the belt runs generally parallel to the direction of rotation of the pan. With the member 10 swung to its inner position, the operative portion of the belt is moved axially along the side wall of the pan by reciprocating the slide 25 on the guideways 40 by means of an hydraulic cylinder 45; the forward stroke of the slide is slowed down in order to intensify the polishing action by causing a cam 106 on the slide to contact a follower 105 on the member 24 and so control a valve in the supply to the hydraulic cylinder 45, the length of the cam determining the period over which the speed is reduced, and its depth the speed during this time. An air cylinder 60 is also provided for tilting the frame 26 about the bolt 52 and therefore moving the operative portion of the belt into and out of floating contact with the side wall of the pan. After passage over the rubber shoe 58 the belt is led between rollers 70, 71 of which the roller 70 is indexed forwardly between polishing operations by a pawl-andratchet device 76 actuated by an air cylinder 78 to present new sections of the belt to the shoe. The belt 145 is carried on a frame 127 which is supported by a linkage 128, 130, 132, 135, Fig. 5 from the end of a slide 114 arranged for reciprocation in guideways 112 on a horizontal plate 110 extending from the vertical member 10. The belt is led from a reel 150 around a roller 152 through a slot 153 in the frame 127 and then over rollers 154, 156 and around the shoe 149 which is retained between flanges 148 at the end of an elongated extension 146 of the frame. The slide 114 is reciprocated by an hydraulic cylinder 119 to reciprocate the operative portion of the belt between the centre and periphery of the bottom of the pan, when the member 10 has been swung to its inner position, and an air cylinder 136 is employed to pivot the linkage and so move the operative portion of the belt into and out of floating contact with the pan. Upon leaving the shoe 149 the belt is led between rollers 158, 159 of which the roller 158 is indexed forward similarly to the roller 170 between polishing operations to present new sections of the belt to the shoe. If polishing is carried out under wet conditions a coolant is sprayed into the pan through a nozzle 174, and hoods 176, 177 are provided to prevent spattering of the slurry. The machine is arranged for automatic operation by a control circuit including limit switches actuated by the inward swinging action of the vertical member 10 and movement of the slides 25, 114. In the case of the slide 25, two switches 95, 98 are provided on the member 24 for respective actuation at the outer and inner ends of the strokes of the slide by corresponding nut members 93, 97 adjustable on a screwed spindle consisting of two telescopic screw parts 90, 91 mounted between brackets 89 on the slide; the end of the part 91 serves as a positive outer stop in conjunction with a fixed plate 39 and the nut member 97 similarly co-operates with a plate 104 to fix the inner limit of stroke. Switches 183, 187, Fig. 5, provided on the plate 110 are similarly actuated by nut members on a twopart spindle 179, 180 on the slide 114. At the start of an automatic cycle the vertical member 10 is swung inwardly by the air cylinder 15 and, with the belts 27, 145 then disposed in initial polishing position, actuates a switch 22, Fig. 1, to start the chuck-driving motor, open a valve for the passage of coolant to the nozzle 174, and cause the hydraulic motors 45, 119 to move the slides 25, 114 so that the operative parts of the respective belts 27, 145 move inwardly of the wall and from the centre to the periphery of the pan. The slides, at the start of this movement, actuate the switches 95, 183 to cause the air cylinders 60, 136 to bias the belts into engagement with the respective parts of the pan. On approaching the end of this movement the slides actuate the switches 98, 187 to cause the air cylinders first to release this bias and then re-establish it, and this action is followed by reversal of fluid flow to the hydraulic cylinders 45, 119 to move the respective belts outwardly along the wall of the pan and from its periphery to the centre, whereupon actuation of the switches 95, 183 releases the air cylinders, stops the chuck-driving motor and supply of coolant, and causes the air cylinder 15 to swing the member 10 outwardly to permit withdrawal of the pan from the chuck. To meet the case in which the side wall or bottom of the pan is stepped, the two-part spindles 90, 91 and 179, 180 are each provided with a bevelled nut for the purpose of actuating the corresponding switch to effect release of the air pressure on the belt as the latter rides over the step. The control circuit also includes manually-operable switches for varying the action of the air cylinders 60, 136 in establishing bias upon the belts, as for example when, in dealing with pans having outwardly-flared edges, bias is to be maintained upon the belt 27 throughout its outward travel and beyond the point at which the switch 95 is normally effective. A timer is also arranged to be switched into the circuit when it is desired to subject a pan to more than one polishing cycle without retracting the member 10. The invention may be adapted for the polishing of the exterior surfaces of a pan.