Patent GB-857603-A (GB)
Title: Improvements in acceleration responsive devices
Inventor: HARDWAY EDWARD VICTOR
IPC: G01P15/08
Filed: 1957-06-11
Abstract: 857,603. Switches operated by vibration; switches, partly electromagnetic; control of motors. ROBERTSHAW-FULTON CONTROLS CO. June 11, 1957 [Sept. 5, 1956], No. 18410/57. Classes 38 (3) and 38 (5). [Also in Group XIX] Switches.-An electric-switch-operating device is connected to a machine, such as a pump, driven by an electric motor, and excessive vibration of the machine operates the switch 110, Fig. 2. An armature 44 is pivoted to a base-plate 20 by means of blocks 28, 36 and a sheet-metal element 30. A compression-spring 62, adjustable by a knob 76 having a pointer co-operating with a dial to vary the sensitivity of the device to vibration, urges the armature counter-clockwise to operate the switch striker 114, its stroke being limited by a latching magnet 90, which retains it in the counter-clockwise vibration - actuated position. The armature carries an auxiliary plate 52 which in the limit clockwise or set position abuts a stop 88 and is spaced from a permanent magnet 84, the magnetic couple in this position being stronger than the spring. The armature can be reset to its clockwise position by a manual reset assembly 96 or by an electromagnet 106. For initial adjustment of the device, the knob 76 is moved to minimum compression and the armature reset. The knob is then rotated until the armature is triggered to actuated position. The knob is then removed from its shaft 74 by loosening a set-screw 78 and re-secured to the shaft with the pointer set to zero, the " no-vibration " setting. The machine is then started and the triggering position of the knob for normal vibration determined. The knob is then rotated further so that triggering will occur with a predetermined excessive vibration. In another form, Fig. 5, the armature 168 is pivoted to an upper plate 154 by a block 160, a sheetmetal element 162 and clamping plates 164, 170. The force of the compression spring 190 is constant and urges the armature clockwise, assisted by a mass assembly comprising elements 184, which can be interchanged, to operate the striker 216 of the switch 212. The permanent magnet 186 attracts the armature, and the counter-clockwise movement of the armature is limited by a stop 198, which is adjustable to vary the sensitivity. Clockwise movement is limited by a set-screw 192. The armature is reset by an electromagnet 208. Control of motors.-An electric motor 258, Fig. 7, drives a machine which it is required should be stopped in the event of excessive vibration, other than during a predetermined period after starting when such vibration is customary. The machine is started by a button 254, whereupon the coil 264 (106, Fig. 2; 208, Fig. 5) is energized and sets the armature to close contacts 270A, energizing a relay 262 and starting the motor, also establishing a circuit through contacts 262D by-passing the start button. The relay 268 is also energized when the start button is depressed, causing contacts 266 to open at the end of said predetermined period. Excessive vibration causes the armature to open contacts 270A and stop the motor. During the starting period, however, the coil 264 prevents the armature from being actuated. In another form, Fig. 8, the circuit is designed to stop the motor 302 when excessive vibration persists over a certain time. On actuating a start button 306, the motor is started, the circuit including normally closed contacts 316 of a thermal time relay 362, and the button 306 is by-passed by a circuit through contacts 320D of a relay 320. Circuit is also made through contacts 332 and a rectifier 336 to a re-set coil 338, which holds the armature in set position with contacts 344 of the switch (110, Fig. 2; 212, Fig. 5) closed to light a neon bulb 350 indicating the position of the armature. Circuit is also made to a relay 328, which after a predetermined delay equivalent to the starting period opens contacts 332 to de-energize the coil 338. Any excessive vibration or shock will then cause contacts 346 to close, energizing a relay 354 to close contacts 356, 358. Contacts 356 complete a circuit to energize the coil 338, open contacts 346 and de-energize the relay 354, while contacts 358 complete a circuit to the thermal relay 362. De-energization of the relay 354 causes contacts 356, 358 to open after a delay period less than the time required for the relay 362 to be heated to its actuating temperature, whereupon the relay 362 is de-energized, as is the coil 338. Any subsequent shock repeats the process. If the average rate of heating of the relay 362 while energized is A, and the rate of its return to normal condition is B, then if during any time period, the contacts 358 are closed for more than B/(A+B) of the period, the relay 362 will open contacts 316 to stop the motor.