GB621559A - Improvements in or relating to drilling and like machine tools - Google Patents

Abstract

621,559. Drilling long holes. IGRANIC ELECTRIC CO., Ltd. Sept. 7, 1945, No. 23122. Convention date, Sept. 11, 1944. [Class 83 (iii)] A drilling or like machine having a worksupporting member, a tool-supporting member and a power drive for effecting forward and return movements of one of said members relative to the other is provided with automatic cyclic control means for said drive affording a given number of different successive operating cycles of said one member differing in the limits of feed range, each cycle comprising traverse at a high rate in the forward direction to bring the tool towards the cutting position, feed at a slow rate in the same direction to cause the tool to cut, and traverse at a high rate in the return direction, and means being provided for ensuring that the high rate traverse in the forward direction of each successive cycle ceases with the tool in predetermined proximity to the position at which the slow rate feed of the preceding cycle ceased. The drill spindle 3, Fig. 1, is rotatably mounted in the sleeve 2 to which is connected by an arm 8 a hydraulic feed piston 7 working in a cylinder 6. Control of fluid to the double-acting piston is effected by electrically operated valves and the electrical circuits used include relays operated by switches 3LS, 2LS, and 1LS, moved by a stop 12 carried by the sleeve. A further stop 20 on the sleeve operates a rack 19 after predetermined downward movement and this rotates the shafts 14, and 16, of an automatic measuring control mechanism 13. This mechanism includes a disc 21 with friction brake shoe 23, a friction clutch 17 under control of solenoid 17a, two cam-controlled limit switches 11LS and 12LS and a spiral return spring 15 for the shaft 14. Operation.-Momentary closure of a forward feed push button conditions electric circuits in conjunction with switch 3LS to energize valves V1 and V3 which admit unrestricted pressure fluid to the top of the piston and give a fast downward feed. The drill 5, Fig. 3, continues its rapid downward feed after striking the switch 1LS to condition certain of the electrical circuits until the stop 20 moves rack 19 and thus shafts 16 and 14 to disengage switch 11LS at the point shown in the diagram. This takes place just prior to the drill entering the work at the surface S1. Valve V1 is then held energized while valves V2 and V3 are in normal position admitting fluid through valve V2 and adjustable throttle valve VT to the top of the cylinder to give a slow working feed, the lower end of the cylinder exhausts through valve V2 and line 11. The slow feed continues until the shaft 14 has rotated sufficiently for the cam 12LSI to close switch 12LS, valve V2 is thus energized and V1 continues energized, admitting pressure fluid to the lower side of the piston for a fast return to position indicated by 1LS, just clear of the work, where this switch is again operated to start a fresh fast downward traverse. Operation of switch 12LS also energizes the solenoid 17a to disconnect the clutch 17, shaft 14 is thus released to return to its initial position for a similar operation by the spring 15, the switch 11LS thus returns to its normally closed position, and switch 12LS to open position. The drive from the rack and pinion 19 and 18 to the clutch 17 is transmitted through a lever 22 positioned between stops 24, 25 on the braked disc 21, and connected thereto by a spring 26 which normally gives the lever a bias to contact the stop 25. On downward movement of the rack the lever is moved against the spring pressure to contact the stop 24 for driving the shaft 24. With the clutch 17 disconnected and the rack released from the stop 20, the spring 26 rotates the lever until it again contacts the stop 25, thus moving the rack upwardly a small amount. This measuring movement ensures that the slow feed is connected at the points 11LS, Fig. 3, just above the previous depth to which the drill has operated. The cyclic feed continues until the switch 2LS is operated when the lower surface S2 of the work has been passed; the drill is then returned at fast traverse to the initial position for the start of another drilling operation. A selector switch is provided to make the machine to operate a single cycle of any required depth and push switches are provided to give immediate fast return of the drill to the upper limit at any time before the lower limit is reached or to stop the feed at any time during working.