| 摘要 |
502,177. Copying milling - machines. ATKINS, H. F. Aug. 11, 1937, No. 22062. [Class 83 (iii)] In a copying milling- machine of the kind wherein the work and pattern are mounted in superimposed position on a slide which is traversed diametrically across a table and then held stationary whilst the table is rotated through half a revolution to enable the cutter and tracer, which are mounted concentrically on a swinging arm, to follow the semi-circular ends of the work and pattern, the slide is traversed by one or two hydraulic pistons whose fluid supply is controlled automatically by the intermittent rotation of the table. The table 1 is mounted in roller bearings on a stationary support 4 and has worm wheel teeth 6 engaged by a worm 5. The pattern is secured between the work 22 and the slide 7 which is traversable in diametrical guides 7<1> on the table 1. Cylinders 8, 9 in the table hold double-acting plungers 10, 11 each plunger carrying a freely rotatable pinion 12 which rolls on a fixed rack on the table and engages a rack on the slide to traverse the slide at twice the speed of the plungers. Passages 16, 17 at the ends of the cylinders lead to axial passages 18 in the table, the passage 18 at one side of the table being brought opposite an inlet 28, Fig. 4, in the stationary support 4 whilst the other is connected to exhaust. In operation, the table is held stationary by a pivoted stop 21 engaging one of the dogs 19, 20 whilst the slide is being traversed, the fluid proceeding through aligned passages 29 in a spring pressed valve 31 and aligned passages 32a in a spring pressed valve 32 in the table. On reaching the end of the traverse a dog 26 on the slide engages an abutment 27 on the stop 21 to release it from the dog 20 and simultaneously starts rotation of 'the worm 5 through automatic mechanism (not shown). Rotation of the table breaks the connection between the valves 31, 32 and allows the springs to close the passages 29, 32a, thus shutting off the supply from 28 and holding the plungers in their end position. When the table has rotated through half a revolution to machine a semicircular end on the work the stop 21 is restored to operative position by a spring or weight, rotation of the worm 5 is stopped, the valve 31 makes communication with the valve 32 at the other side of the table, and the slide is again traversed to machine the other side of the work. According to the Provisional Specification, the plungers 10, 11 may operate the slide 7 directly. Speed-controlling mechanism.-In order to maintain a constant speed of cutting irrespective of variations in resistance to the cutter, a byepass valve 33 normally returns part of the supply from 28 to 34 but if the tool meets undue resistance a rise of pressure in the fluid at 29 closes the valve against its spring and enables a greater fluid pressure to be applied to the plungers 10, 11. The invention is stated to be applicable to the machine described in Specification 502,176, which includes mechanism for surmounting abrupt portions of the pattern. |
