Patent GB-335284-A (GB)
Title: Drilling or tapping machines
IPC: B23B45/14
Filed: 1929-06-28
Abstract: 335,284. Connell, E. L. June 28, 1929. Drilling - machines; bolts, nuts and screws, assembling and screwing-up.-In a drilling, tapping, stud setting. or like machine, an axially movable toolspindle is driven from an electric motor through a switch which is automatically opened when a predetermined motor current is exceeded. the motor circuit being closed to start the drive for a fresh operation by longitudinal withdrawal movement of the tool spindle. The arm 1, adjustable about a supporting column carries a head 2 which carries a bearing sleeve 5 for a rod 6 provided on a sub-frame 7 which is guided at 10 on a part 3. The frame 7 carries a portable electric drill 8 and is normally held in its uppermost position by a spring 11. The sub-frame may be lowered to bring the tool down to the work by means of a lever 13. The control circuit, Fig. 7, comprises alternating current leads 16a, 16b, 16c each in circuit with a contact 18, one of the leads 16a being connected through an overload coil 27. The starting circuit 25 includes a starting switch 26 and the main switch carries an extra set of contacts 20 in circuit with the overload switch 22. A gauge stop 23, emergency stop switch 24 and a relay coil 19 which controls the main switches 18, 20, are also provided. The starting switch, Fig. 2, comprises an insulating block 29 and a pair of conducting segments 30, which may be bridged by a roller 31 carried by a pivoted arm 32 connected to the sub-frame 7. The starting-switch is closed when the tool is in its uppermost position, thus energizing the relay 19 and closing the main switch. In operation, the lever 13 is depressed to engage the tool with the work, the motor circuit being maintained through the circuit 36 even after the roller 31 has passed on to the insulating segment 29. When, for instance, a bolt has been screwed home, the rise of current causes the switch 22 to be broken, whereupon the operator raises the frame 7 to its upper position thereby re-engaging the starting switch 26 ready for a fresh operation. In a modification, Fig. 5, a tool head 40 carries a driving motor 41 geared to a shaft 43 which drives in opposite directions an upper quill 47, and a lower quill 50. A slidable tool-spindle 55, carries a clutch member 54 adapted to engage selectively with teeth on the upper and lower quills and the lower quill is fitted with a collar 56 connected to a pivoted handle 57. An operating handle 65 is pivoted to the handle 57 and carries a push-button 70 adapted to close the starting switch 26 against the resistance of a spring. In operation, the handle 65 is raised, thereby first lifting the spindle to disengage the forward driving clutch 52 and engage the reverse clutch 53. Further upward movement of the handle closes the switch 26 and starts the motor. The handle is then lowered and the tool applied to the work, its advance being stopped while the continued movement of the quills engages the forward clutch 52 whereupon the tool is screwed into the work until the gauge 60 opens the switch 23 or until the torque rise causes the current flowing in the coil 27 to break the switch 22. The operator then raises the handle 65 thereby first engaging the reverse clutch and then closing the starting switch to energize the motor and withdraw the tool from the work.