Patent GB-679759-A (GB)
Title: Improvements in or relating to belt grinders for grinding turbine blades and other irregularly-shaped articles
IPC: B24B21/00
Filed: 1950-05-05
Abstract: 679,759. Grinding turbine blades. UNITED AIRCRAFT CORPORATION. May 5, 1950 [May 17, 1949], No. 11157/50. Class 60. A method of grinding irregularly-shaped articles such as turbine blades comprises positioning the articles on a work support 32 adjacent a grinding belt 20, positioning a form 28 on the opposite side of the belt to hold the latter against the article, effecting relative movement in timed relation between the work support and form during each of a series of 'grinding operations, and feeding the form towards the support after each grinding operation. The belt 20, Fig. 1, passes over a pulley 22 which is driven by a motor 30, centering pulley 24, tensioning pulley 26 and form roll 28. The motor 30 and pulleys 22, 26 are mounted on a carriage 46 which may be clamped in adjusted position on columns 36, 38, and the pulley 24 and roll 28 are carried by a slide 50 movable vertically in guides 52 on the carriage. The slide 50 is constantly urged upwardly by a piston-and-cylinder device 62 and is moved downwardly in steps by an intermittentlyrotated cam 54; Fig. 4, carried by the carriage and co-operating with a follower 56 mounted freely on a spindle 58 in the slide; this spindle 58 also carries the form roll 28. The work support 32 is mounted on a spindle 68, Fig. 4, arranged for oscillation in bearings in a fixed frame 70 as a result of the coaction of a gear 72 on the spindle with a rack 74, Fig. 7, mounted on a slide 76. This slide is reciprocated by a motor 92 acting through pin-and-crank mechanism 44 and a second slide 80 which is normally coupled to the slide 76 by a latch 82 urged to locking position by a spring 88. The form roll 28 is oscillated in timed relation with the work support 32 by a gear 102 on the spindle 58 coacting with a rack 104 carried by a slide 106. When the slide 50 is in'its lowered operative position, the slide 106 is connected to, and driven from, the slide 76 by means of pins 110 entering sockets 112 in the slide 76. When the slide 50 is raised to inoperative position, a catch 114 on the slide 106 acts to disengage the latch 82 and thereby stop the drive to both slides; a spring plunger 90 holds the latch in both engaged and disengaged positions. In operation, the work 31, Fig. 4, is secured by a clamp 66 on locating pins 64 on the support 32, and the cam 54 is intermittently rotated to advance the slide 50 in steps at the end of each oscillation of the support 32 and roll 28 by means of a roller 130, Fig. 5, carried by an arm 128 on the shaft 58 striking against one or the other of two projections 136, 138 depending from two spring- pressed slides 132, 134 reciprocable in the carriage 46. Both slides 132, 134 carry racks 148, 160 co-operating through pawl and ratchet mechanism 150-156 to drive the shaft 126 of the cam 54 so that, whichever of these slides is operated at the end of an oscillation of the shaft 58, the cam 54 is rotated always in the same direction and lowers the form roll 28 in steps. The position of an adjustable stop 146 co-operating with the slide 132 determines the amount of each movement of the cam 54. The crank mechanism 44 is adjusted so that the extent of oscillation of the workpiece and roll 28 is such that the workpiece is moved out of contact with the belt at each end of the oscillation, and the advance of the cam 54 and roll 28 takes place with the belt out of contact with the workpiece. Lever mechanism 170, Fig. 5, is provided to enable the pawl and ratchet mechanism 150-156 to be disengaged and thereby permit manual adjustment of the cam shaft 126 and roll 28. To enable the use of a form roll 28 of approximately cylindrical shape, the follower roll 56 may be replaced by an auxiliary cam, which is fixed on the oscillating shaft 58 and, by coaction with the cam 54, moves the roll 28 towards the workpiece as it approaches the end of each oscillation. The centering pulley 24 is mounted on a yoke 194, Figs. 1 and 4, pivoted for oscillation transversely of the belt under the control of a double-acting piston in a cylinder 190 supplied with air under pressure. Separate bleed lines from opposite ends of the cylinder lead to two sets of nozzles 186, Fig. 1, which are located on opposite sides of the centre line of the belt so that their outlets are normally closed by the belt. Should the belt become mis-aligned, one or more of the nozzles in either set are uncovered and the piston is operated to move the pulley and restore the belt to its central position. The tensioning pulley 26 is mounted on a pivoted plate 214, Fig. 1, which is acted upon by a weighted cord 218 passing over a pulley 320. The form roll 28 may be initially ground to shape by inserting a master blade in the support 32, reversing the belt so that its abrasive surface is adjacent the roll, and then setting the machine into operation. The final size of the finished workpiece may be determined by proper initial positioning of the carriage 46 on the columns 36, 38 by means of a screw 60, or a switch 222, Fig. 4, mounted on the carriage 46 may be opened automatically when the roll 28 reaches a pre-determined position so as to shut off power to the belt. In a modification, the work support 32 and form roll 28 may be arranged to make complete revolutions, being driven in timed relation by a gear train arranged to permit vertical movement between the members. Two or more workpieces may then be carried by the work support. Specification 586,490 is referred to.