Patent GB-294182-A (GB)
Title: Electrical control of planers and like machine tools
IPC: B23Q35/122
Filed: 1928-07-19
Abstract: 294,182. Keller Mechanical Engineering Corporation, (Assignees of Shaw, J. C., and Slaw, R. D.). July 19, 1927. Planing, shaping, and slotting.-In an electrically controlled planing, shaping, slotting or like machine wherein the cut is produced by relative reciprocation between the tool and work, electromagnetic clutches are provided for actuating screw feeds in opposite directions along two perpendicular paths, the circuits to the clutches being controlled by (a; manually - operated switches, or (b) by a tracer partaking of the same movements as the tool and adapted to follow the contour of a pattern or template, or (c) being operated along one path only in the normal manner of a planing machine with automatic feed. The machine cuts on one stroke only, and on the return stroke a dog actuates a switch which sets into operation relay magnets and circuits causing a commutator to be rotated for a single revolution only, the commutator being provided with a conducting strip engaging a brush which causes further circuits to be put into operation for actuating the respective clutches. The conducting strip is tapered so that by adjusting the brush axially along the commutator the extent of the feed during the idle stroke may be varied. The supply to the electromagnetic clutches is preferably from mains at 110 volts and to the relay circuits from a generator at 14 volts. In a planing machine, the tool 104, Fig. 3, is mounted in a clapper-box 105 of usual construction and is adjustable for feeding along vertical guides 107 and horizontal guides 108. A bracket 117 on the tool slide carries a tracer 119 which is adapted to engage a template 122 and is constructed in a similar manner to that described in Specification 233,747. Magnetic clutches 111 rotate a screw 109 for vertical feed of the tool and similar clutches 115 rotate a screw 113 for horizontal feeds. The work 103 is attached to a table 102 reciprocated horizontally beneath the cutter. A drum switch 190 has two sets of contact bars 191, 192 adapted to be moved alternatively into contact with studs 193, the former set being used for tracer control of the feeds and the second for normal planing. The low voltage supply is provided by a generator 188 and the high voltage by mains 189. The commutator 141, Figs. 1 and 3, is loosely mounted on a shaft 145 and is adapted to be driven through a friction clutch 149, spring controlled at 151, worm gearing 148 and change gearing 158 from an electric motor 161 or preferably from the shaft 160 of the low voltage generator at a constant but adjustable speed. A disc 153 attached to the commutator is provided with a peripheral notch into which engages a detent 155, the arrangement being such that the friction clutch slips until the detent is removed by an electromagnet 162. The tapered conducting strip 142 is engaged by a brush 143 adjustable axially along the commutator by rack and pinion gearing 178 hand operated at 179. In operation, for tracer control, the switches 183 and 186, Fig. 3, are moved to the right, the switch 185 is moved to the right or left according to whether the tool is to be fed to the right or left across the work, the main switch 187 is closed and the remaining hand-controlled switches are left open. An earthed lever 125, pivoted at 126 and having a conical socket engaged by the rear pointed end 124 of the tracer 119, carries front and back contacts 127, the former being normally held against a fixed contact 34 by a spring 128 so as to energize a lowvoltage relay magnet 130, S, and cause a switch arm 131 to be thrown and close, the high-voltage circuit 47 to the downwardly-feeding clutch 111, S. A second high-voltage switch 133 which is also required to close the circuit through contact 43, is actuated against its spring by a solenoid 134 when the relay circuit 51 is completed through the commutator 142 during an idle stroke of the machine. The cutter is thus fed vertically downwards at each idle stroke until the tracer engages the template, as shown in Fig. 5, the template being secured by a bracket 123 to a fixed part of the machine and determining the crosssectional profile of the work. The lever 125 is thereupon rocked and the contacts 127, 34 opened, stopping the down feed and also breaking the lowvoltage circuit to an interlock relay solenoid 140<1>, thus permitting a spring 139 to close the highvoltage switch 138 and energize one or other of the clutches 115, according to the setting of the switch 185, and causing a horizontal feed of the cutter when the high-voltage switch 138<1> is closed by the solenoid 136 during an idle stroke, the solenoid 136 being in direct circuit with the commutator. When the horizontal feed relieves the pressure on the tracer, the lever 125 is rocked by its spring 128 to close the contacts 127, 34 and stop the horizontal feed whilst restoring the vertical feed, these two feeds alternating until a flat portion of the template is reached, as in Fig. 6, whereupon the horizontal feed alone operates. On encountering an upward incline, as in Fig. 7, the lateral pressure on the tracer will be great enough to rock it in spherical seat 120 and cause the lever 125 to be oscillated sufficiently to close the back contacts 127, 52, thereby energizing the low-voltage solenoid 130, N, to cause an upward feed of the cutter and also energizing the interluck solenoid 140 to open the high-voltage switch 138 and stop the horizontal feed. As the pressure on the tracer is relieved the contacts 127, 52 are opened and horizontal feed replaces the upward vertical feed, these two feeds alternating until the incline is surmounted. Although the tracer is shown in Figs. 5 and 7 as engaging the template in line with its axis. it is preferably arranged perpendicular to this position, as shown by the dotted circles in the Figures. To impart the required amount of feed to the cutter during the idle stroke, a dog 169, Fig. 3, on the work-table rocks a cam lever 166 on the reversing rock shaft 167 and pushes a bar 164 between spring contacts 163, thus closing the low-voltage circuit through the solenoid 162 and withdrawing the detent 156 from the notched disc 153 on the commutator and allowing the friction clutch 149 to rotate the latter. In its backward movement the detent 156 engages a contact 91 and completes the low-voltage circuit through a solenoid 171. This opens the switch 172 against a spring 173, de-energizing the solenoid 162 and allowing the detent to return to the disc 153 in order to stop it after a single revolution, and also closes the circuit through the solenoid 171 to maintain the circuit 44 to the solenoid 162 open until the switch-bar 164 is removed from the contacts 163 on the next cutting stroke of the table. During its single revolution the conducting strip 142 on the commutator completes the circuit through either the horizontal relay 136 or the vertical relay 134 for a variable length of time, according to the axial setting of the brush 143, and so determines the actual amount of horizontal or vertical feed which is given to the cutter at each idle stroke. When the machine is operated as an ordinary planing machine with automatic vertical feed of the cutter, the switch 182 is moved to the right or left according to whether the feed is to be down or up and the switch 183 is moved to the right. When the feed is required to be horizontal, the switch 185 is moved to the right or left to determine the direction of feed and the switch 186 is moved to the right, in each case the remaining switches, with the exception of the main switch 187, being left open. For hand control of the feeds, the switches 183 and 186 are moved to the left and the switches 181, 181 are operated for actuating the feeds.