Patent GB-532801-A (GB)
Title: Improvements relating to metal cutting or like machine tools
IPC: B23B7/12
Filed: 1939-05-26
Abstract: 532,801. Variable speed reversing gearing. POTTER, W. W. May 26, 1939, No. 15751. Convention date, June 8, 1938. [Class 80 (ii)] [Also in Group XXII] Pre-selective change speed and reversing gearing is described in connection with driving the spindle and feed shaft of an automatic lathe. Driving machine spindle. The spindle 101 is driven through the toothed gear train 102 to 110, Fig. 10, of which the gears 105, 106 are change gears accessible through a cover which controls a switch preventing actuation of the motor when the cover is removed. The gear 109 is driven through variable speed friction gearing 703 from a constant speed motor 112 turning always in one direction when. running. The friction gearing is controlled by a worm and wheel 115 driven through a flexible shaft 116 from a pre-selector 118. Feed shaft drive. The feed shaft has two drives, one geared to the spindle and the other driven from the high-speed reversing motor 144, The spindle drives a shaft 122 through a chain 120 and a pinion 123 on the shaft transmits through a continuously variable gear 126 controlled by a flexible shaft 136 from the preselector. A gear 133 on the shaft 122 drives the annular wheel 132<1> of a differential gear, the sun wheel of which is driven by the gearing 126 and the planet carrier drives the pinion 134 geared to wheel 139 loose on the motor shaft 140 but clutchable to it by a magnetic clutch when the motor is not running. This shaft 140 is coupled to the shaft 160 through a shearing pin coupling. If the shaft 140 has been driven at a high speed by the motor an arm biassed by a spring and carrying planet wheels engaging pinions driven by the shaft 140 and the wheel 139 respectively tends to be moved in a direction to close a switch on a relay circuit to prevent the magnetic clutch from being energized until the speed of the shaft drops to about that of the gear. A stop limits the .movement of the arm in the other direction and a friction device in the differential gear slips when the arm is arrested. A bevel pinion 161 is geared to a shaft 163 driving a control drum 169 through worm gearing 165. The drum has numerous slits 174 for a series of dogs 173 that actuate a series of switches 175 on a fixed support within the drum. The drum is fixed to a spider 170 and is secured to the worm wheel of a screw 172. When the end plate 168 and the screw 172 are removed the spider and drum complete with dogs can be removed and replaced by another already set up for the production of a different part, saving adjusting time for the dogs when a set up requires to be repeated at intervals. The shaft 163 carries a gear 176 with which a pinion 177, Fig. 18, meshes when a shaft 177a is pushed endways to enable the feed shaft to be cranked by hand at 178. In this position a pin 180 opens a switch to prevent any power operation of the feed shaft whilst the gears 176 and 177 are engaged. Pre-selecting devices. The feed and spindle variable speed drives can be controlled through any desired number of pre-set devices, for example three each. The selectors comprise shafts 196 and 196a, Fig. 15, driven by motors 192, 192a and having keyed to them three cam drums 198, controlling stop and direction switches 200 and 201 mounted on arms adjustable as to angular position by worm gearing shaped for operation by a spanner at 204. When a speed change is to be effected the appropriate switches 200 and 201 are rendered operative either by hand or by the control drum and through a system of relays and switches the motor 192 is caused to rotate in one direction or the other according to whether the shaft to be controlled is running faster or slower than the selected speed, the direction switch 201 effecting the change if necessary ; the motor then runs until arrested through the action of the stop switch 200 at which time the friction pinions will have been rocked to the required position. Electrical control. All the parts are controlled by a system of switches and relays which provide all necessary interlocks to secure proper segmental action and prevent actuation of certain parts at improper times or times dangerous to the machine and operator. These devices are actuated by a series of control lines, two of which provide a low pressure A.C. supply derived from a transformer from one phase of the three-phase supply for the spindle, high speed shaft &c. The lubricating motor is driven from the low pressure A.C. lines. A tapping from the secondary of the transformer supplies D.C. lines through a full wave rectifier. These four control lines operate in conjunction with a hand control line and an automatic control line either of which may be rendered operative by a hand actuated two-way switch. When set for hand control the machine is operated by push buttons on the headstock unit, and when set for automatic control a dog drum effects the control, but in this position all the spindle driving and feed gearing may still be controlled by the push buttons except the high speed reverse for the feed shaft. The machine may thus be manually stopped at all times. An under-voltage relay is shunted across the D.C. lines and acts to break the secondary circuit of the transformer and thus renders all the control lines dead. The preselector motors are of the shaded pole type with separate coils for forward and reverse rotation supplied from the A.C. control lines. The forward coils may, however, be supplied from the D.C. lines for braking purposes.