Patent GB-772818-A (GB)
Title: Improvements in or relating to automatic proportional metering, mixing and dispensing system
IPC: G05D11/00
Filed: 1955-02-03
Abstract: 772,818. Mixing liquids. SCHNEIDER, M. Feb. 3, 1955 [Feb. 11, 1954], No. 3225/55. Class 86. A system for mixing two liquids in predetermined proportions comprises two separate feed systems, one for each liquid, and each including a measuring and dispensing means comprising a unit effective on each cycle of operations to dispense a predetermined amount of liquid, a doubleacting interlock being operatively connected between the units and effective to prevent either unit from recycling until the other unit has completed its cycle. The system is described for feeding and mixing a thermosetting resin and a hardener with provision for preventing the mixture from setting while in the apparatus. As shown in Fig. 1, two separate feed systems A, B one for resin and one for hardener lead to a common receptacle C where the two liquids are mixed before being dispensed through a nozle D. 'Each feed system includes a de-aeration chamber F in which the liquid is freed from entrapped water, gas and volatiles, the chamber F being of the type provided with rotary heated plate 2 on which, the liquid is deaerated by being subjected to vacuum through lines .16. 18, The liquid is subsequently transferred to a reservoir G. Each reservoir is connected to the receptacle C through a metering device H controlled by a four-way valve J. When a valve E is opened, mixed liquid flows from the receptacle C under air pressure by way of lines 32, the receptacle receiving fresh supplies of liquid from both metering devices H. Each metering device comprises a base plate 40, Fig. 3, on which two cylinders 42, 42<SP>1</SP> are mounted, each cylinder comprising a jacketed chamber M which contains a bellows 98 connected to a rod 90 and has two openings 68 for supply or discharge of liquid. The upper end of the bellows rod 90 is provided with a roller 112 for engagement with the undersurface of a pivot bar 106. When liquid under pressure enters the left hand chamber M it contracts the associated bellows 98 raising the rod 90 and thereby through the bar 106 lowering the right hand rod 90 and expanding the bellows to discharge liquid from the right hand chamber M. Each rod 90 with its bellows can be adjusted by means of a disc 118 and nuts 116, 120, 122. The disc 118 is adapted on downward movement of the rod 90 to depress the plunger of, and close, a microswitch 126. The openings 68 in each of the chambers M communicate with fittings 70 both connected by line 72, Fig. 1, to the four-way valve J. The valve has four parts, two communicating with lines 72, one with line 30 leading to reservoir G, and one with lines 128, 130. The valve is controlled by an air motor 134 actuated by a solenoid 136. In one position of the valve the line 30 is connected with line 72 of the left hand cylinder 42 while the right hand cylinder 42<SP>1</SP> is connected with line 128, so that liquid is forced into chamber M of the left hand cylinder 42 causing through the pivot bar 106 liquid to be forced out of the chamber M of the cylinder 421 through lines 72, 128, 130 into the receptacle C. In the other position of the valve the liquid is forced out to the receptacle C through the chamber M of the left hand cylinder 42. The valves J in the feed systems A and B are interlocked by means of the solenoids 136 and the microswitches 126 which are connected so that the circuits to terminals 138 or 142 of the solenoids 136 are closed only when both corresponding microswitches 126 in systems A and B are closed. Therefore no matter how soon the metering device H in one of the feed systems may complete its cycle, it cannot recycle until the other metering device H has completed its cycle. In an alternative system each four-way valve J is replaced by two three-way valves mechanically linked together. The mixer C, Fig. 4, comprises a bottom plate 160 and a top plate 162 with three concentric shells 164, 166, 168 mounted between them. The outer shell has apertures 178 to permit entry of heated fluid, the shell 166 is imperforate and the shell 164 has apertures 174, 175. Resin from the feed system A is supplied through one port 184 and hardener from the feed system B is supplied through another port 184 to a chamber between the inner shell 164 and a hollow central shaft 192. The shaft carries impeller blades 202 and is driven by a motor. When no material is being dispensed the liquids in the mixer are circulated downwardly through strainer plates 204 by the impeller blades 202, through apertures 175, then up between the shells 164, 166 and back through apertures 174. The material is dispensed from the mixer when the valve E, Fig. 1 is opened. For preventing setting of the resin-hardener mixture within the mixer C, means are provided which include timers 230, 232, 234, Fig. 5, the timer 232 ("flow" timer) for measuring the time during which dispensing takes place, the timer 234 ("pot life" timer) for measuring the elapsed time and the timer 230 ("delay" timer) for providing a short time delay to enable the other timers to reset themselves. By "pot life" is meant the time taken for a mixture of resin and hardener to set in the mixer. This time can be extended by adding fresh ingredients to replace a withdrawn mixture. Each timer has a clutch CL and a motor M, the clutch CL when energized connecting the motor to the particular timing arrangement and this arrangement in turn actuating certain switches after a predetermined time has been measured. When a clutch CL is de-energized its associated timing mechanism will re-set to zero. The dispensing valve E is normally closed and is adapted to be opened electrically, e.g. by an electromagnet V. When the lines L1 and L2 are energized the clutches CL of the "flow" timer 232 and the "pot life" timer 234 will both be connected across lines L1 L2 via a switch 241 so that that will be energized. Energization of the clutch of liner 234 closes switch 236 where by motor M of timer 234 is energized and timer 234 begins to measure elapsed time. When dispensing is desired switch SW will be operated causing valve E to open and motor M of timer 232 to be energized so that timer 232 begins to measure flow time. Thetimers 232, 234 are set for values of dispensing time and elapsed time respectively to ensure that proper replenishment of the contents of the mixer takes place to have the "pot life" of the mixers' contents restored. Assuming the "pot life" to be thirty minutes and the time to restore the "pot life" to be ten minutes, normally the "flow" timer 232 will measure ten minutes before the "pot life" timer 234 measures thirty minutes, and when the ten minutes are up the circuit between terminals 242 and 244 is opened and switch 241 is opened de-energizing clutches CL of timers 232 and 234 and permitting both to be re-set. Terminals 242 and 246 are now connected whereby the clutch and motor of delay timer 230 are energized. After a delay time of, say, two seconds switch 236 of timer 230 is closed to complete a circuit through clutch CL of timer 232. Energization of this clutch closes switch 241 to form a holding circuit for clutches of both timers 232 and 234. If the dispensing of the mixed material is insufficient to restore its "pot life" the timer 234 will time out before the timer 232. This will cause switch 238 to close causing the switch E to open and dispensing to take place which will continue until timer 232 has timed out. If the level of either the resin or the hardener in its reservoir should fall below a predetermined level a sensing device 254, Fig. 1, in the reservoir will indicate this and will give an appropriate warning. This device may also automatically operate timing mechanism K and start purging the material from the mixed C. Purging may also be accomplished by timing devices after the completion of the day's run of work.