GB811473A - Improvements in or relating to the dressing of abrasive hobs - Google Patents

Abstract

811,473. Dressing abrasive hobs. REISHAUER-WERKZEUGE A.G. Sept. 10, 1956 [June 11, 1966], No. 27603/56. Class 60. Apparatus for dressing the helical thread of abrasive hobs for grinding gears comprises a carriage on which the dressing device is mounted and which is traversed by a lead screw and nut mechanism driven through change gears, the displacement effected by the lead screw and nut per revolution of the abrasive hob being a multiple of the pitch required on the hob and the said displacement being imparted to the carriage through a lever transmission reducing the movement by the rates of said multiple. The abrasive hob 45 is mounted on the end of a shaft 6 driven through gears 40, 41 by a shaft 5 which also drives, through change gears 50, 62, 63, 64, a lead screw 7 ; the shaft 5 is driven through reversing gearing by a shaft 4 driven by a motor 9. The reversing gearing is operated by a piston 37. The dressing tool 98 has the shape of a turning tool the profile of which corresponds to that of the gap of a toothed rack. Th dressing tool 98 is carried by a compound slide, being secured to a top slide 90 movable on ways 901, 902 on a bottom slide 85 movable on ways 1003, 1004 on the machine frame 1. The top slide 90 is formed with a cylinder containing a piston 99 adjustable by a screw 106 journalled in the bottom slide 85 and operated by a handwheel 107. The bottom slide 85 carries a screw 84 rotatable, through gears 86, 87, by a handwheel 39 and engaging the end of a slidable rod 8. The rod 8 is connected at 76 to a lever 75 pivoted at 74, the lever being connected at 77 to the nut 70 on the lead screw 7. Pressure fluid from a pump 122 is supplied to the cylinder containing the piston 37 for operating the reversing gearing and to the cylinder in the top slide 90 under the control of a reversing valve 120 operated, through levers 115, 117 on a shaft 116, by dogs 111, 112 on the lower side 85. Thus, at the end of the working stroke of the dressing tool, the top slide 90 is moved to withdraw the dressing tool from the hob, and the direction of rotation of the lead screw 7 is reversed. At the end of the return stroke, the opposite takes place. In a modification, the lead screw nut is driven in rotation but is restrained axially, whereas the lead screw is restrained from rotation and therefor moves axially. Two dressing tools may be used, each of which operates on one of the two flanks of the hob. Multi-start hobs may be dressed, either indexing means or a number of tools corresponding to the number of starts being used.