US2846726A - Method and apparatus for mixing - Google Patents

Description

An 12, 1958 M. M. BEAN 2,846,726

METHOD AND APPARATUS FOR MIXING Original Filed Dec. 2, 1953 2 Sheets-Sheet 1 Fig.1

INVENTOR Mar/Ls M. Beam 660L224, mm 1 J ATTORNEYS Aug. K2, l958 M. M. BEAN 2,846,726

METHOD AND APPARATUS FOR MIXING Original Filed Dec. 2, 1953 2 Sheets-Sheet 2 Z4- 22 f 28 /4 i 36 Fig. 2

lNVENTOR, Mom/s /1 Bean BY (M224 Mama AJ' ATTOR N E Y5 United States Patent METHOD AND APPARATUS FOR NHXJNG Morris M. Bean, Yellow Springs, 0hio, assignor to Morris Bean and Company, Yellow Springs, 0hio,.a corporation of Ohio Original application December 2, 1953, Serial No. 395,737. Divided and this application May. 28, 1957, Serial No. 666,500

2 Claims. (Cl. 1847.5)

This invention relates to apparatus for. thoroughly mixing dry andliquid materials .to form a soft, smooth mix, .and for delivering .the resulting-mix through a convenient conduit. More particularly, the invention relates to. theseparation and injection of slurries of settabl'e materials such as. plaster of Paris-and the like.

.In. the preparation of such mixtures,..difiiculty has been experienced'inso blending dry and wet constituents. as to insurea smooth, uniform mixture freefrom air bubbles. Another difliculty is to reach such smooth uniform con-. sistency before the binder has setup and thereafter to expel the mix from the apparatus before it has set. Where this. problem has been met by using a slow setting mix to give time for the mixing operation plus necessary holding intransit before it is molded, production .hasbeen unduly delayed with serious increase in the capital tied up in. mold equipment (mold is. used broadly herein to include patterns, etc. as. well as external molds).

The present invention aims to provide improved apparatus for effecting a thorough mixing of dry and wet constituents into a slurry and .holding, the slurry ready for molding. during the variable delays normally encountered. in manufacturing and yet to supply the mix on demandin condition for prompt. setting up in a mold;

An.important feature of the'invention is the simple mixing devicewhich not only effects the mixing of the dry and. wet. constituents of the slurry, but. also: subjects the solid particles of, the slurry 'to arubbing. andsqueezing operation, This results both in: improving the uniformity of the mixture and" at the same time in drivingout any gases.

7 Another important feature of .the .invention is the novel ejectionmeans and. its arrangement. in the apparatus.

It.is important also that ,alliparts which contact the mix are so simple and accessible that; an efiective washing, of all operating parts canbe effected by a simple flushing operation.

Further important features are. themaintenance of a controlled head on-xthe slurry'andautomatic supply of materialsto replace: mix withdrawn: from: the machine;

A novel construction of the ejector, particularly of the ejector piston; and the use of the. ejector piston asa valve, are also. important; features;

Another important feature iS thal'S-th'CYCIlDgf of the appurtenant parts being shown diagrammatically, certain parts in phantom and part. of the heat exchanger "b 3 broken away:

Figure 2 is a view, on enlarged scale, mainly invertical section but partly in elevation, of the-mixing ehams ber-and mixing mechanism together with the-ejection pump connected therewith;

Figure 3 is a similarly enlarged sectional detail showing the ejector piston at the lower end of its stroke and with its expansible gland contacting the cylinder wall to prevent by-passing of the slurry around'the piston;

Figure 4 is a sectional view of a modification-in which a fixed ring gear engages pinions on the severalroller shafts to positively determine-the rotation sp'eed ofthe mixing rollers;

Figure 5 is' a fragmentary cross-sectionalview similar to Figure 3 showing a modified expansiblepiston.

In the embodiment of the invention'her'ein illustrated, asuitable frame 8'is provided for supporting the operating parts of-the mechanism. Advantageou'sly, tlrisis a conventional type with an upright pillar mounted'on a base provided with casters for full mobility.- In the'draw ings .as here shown, thi'sframe 8 ispartially'broken away for clear showing of the operating parts.

' Thedevice embodying my invention comprises a mixing chamber 2, in which the constituents of a slurry to be formed are mixed, and mixin'g'means 10 operating in said mixing chamber to crush and' rub the constituents of the slurry against the chamber wall. In this emBodi-J ment, mixingv chamber 2 is shown-asa casting carried by abracket 6 of the frame 8. The mixing chamber is funnel-shaped withthe bottom part 11 of-its walls-' 'at"a greater angle to its axisthan-alo'n'g their major depth.-

The rollers 10- are mounted inibearingsin a yoke "12' which has a hub 14 rotated inbearing 16 supporte'd'on bracketZO; This is also attached to the vertical frame member 8. The belt 22 drives the hub 141f-rompulley 24 on a gearreducer 26 driven by a motor 282- Asshown, the bearings for each of the rollers 10 are eccentrically mounted in a. cylinder 36 fitted in the yoke: 12. These cylinders can be rotated by a-tooi inserted in one of a plurality of holes 38 :and thus the rollers '10 can be adjusted radially to bring them into the desired tangential. contact with-the inner; surface of the mixing chamber 2. Each cylinder 36 can be locked in ad' through the spraynring, 46 and pipez48. The proport-ior'ring of these materialsis advantageously'eifect'ed auto? matically by apparatus such as that disclosed in said: Patent No. 2,574,238. However, in order toxavoid re peat-lug here the extensive description and drawings of" thepropoitioning.apparatus as given: in my patenu l have shown. diagrammatically, in Figure l,. -an"ordinary"proportioning feeder 49-WhiCh. measures "out the powder feed inresponse-to: or in conjunction withifiow-of the liquid, the liquid, in turn or conjointly, being c'ontrolle by a relay and solenoid-valve, .from the'f'eeler circuitfi eluding: probe: 52.. As the level of the. slurry in chamber 2 rises to. that shown at'50, electric probe--52 completes a circuit to actuate a solenoid valve controlling the flow of;

liquid; and,. with. the flow of. liquidrstoppeiino further. proportioning; device until? dry material. can be fed by the the liquidflow isre-established.

If'the proportioning. feed of. PatentNo.-2,57-4;23'8 lis used, the apparatus of Figure 1, except tor'49'istusedwitii the apparatus of the patent above the. -.Wet-coreunih127.

The chute 59 of. thepatentthenbecomes chute 44 'ofis the apparatus herein set forth. and. the water supply-pipes:

72 of the patent and distributor 74 become pipe 48 and distributor 46 above described. The feeding and proportioning apparatus of Figures l-7, 9l2 and 21, as well as the mounting and delivery means of Figures 22-29, can be used substantially as shown in said patent. This combination then would operate as follows:

As the level of the slurry in chamber 2 rises to that shown at 50, electric probe 52 energizes a relay which in turn energizes the timer, which shuts off a motor for a definite time interval allowing the slurry level 50 to drop a short distance, dependin upon the rate of discharge from nozzle 161. This motor drives the plaster meter wheel and the water meter pump geared together to maintain a uniform consistency, and at the expiration of the time interval the motor turns on and the liquid level approaches the electric probe 52.

This mixing chamber as above described makes possible the satisfactory operation at maximum demand, thus requiring very little storage of the mixed material, which would have to be wasted when the production was interrupted for more than a few minutes.

The cylindrical rollers 10 travelling over the conical surface lag behind said surface at the top and turn faster than a rolling speed at the bottom. Thus, a rubbing and smearing action highly effective for mixing the powder into the liquid is achieved. The drag forward on the top of each roller is balanced against the drag back on the bottom of the roller. Only a section near the center of the roller actually rolls on the conical surface of the chamber without slippage. The conical ends of the rollers extending to and even over the outlet from the mixing chamber and rotating at relatively high speed, create a final turbulence in the exit and assure that all material before leaving the mixing chamber will have been rubbed between the rollers and the chamber wall.

The discharge end of the mixing chamber 2 merges into a cylinder 54 provided with an ejector piston 70. The cylinder 54 is secured by a clamping ring 59 bolted over flange 56 and onto the bottom of the chamber 2.

A coupling 66 shown, also in Figure 2, connects the cylinder 54 to the discharge line, including pipes 68, 148 and 160. The inside of this coupling is smooth for streamline flow and is contoured similar to the bottom 78 of piston 70 (see Figure 3).

The probe 69 extending down from piston 70 aids in keeping pipe 68 open.

The piston 70 comprises essentially a gland, here shown as a ring 71 of rubber-like material, advantageously a thick-walled tube of pure gum vulcanized rubber or any elastomer composition sufliciently hard and strong and tough to resist the high fluid pressures encountered 'and the repeated extrusion and retraction from, and between flange 74 and nut 78. In the modified piston shown in Figure 3, a toroidal ring 71a like an automobile tire is used, with its inner rims clamped respectively to the flange 74a and the nut 78a. In either case, when the gland is squeezed, it extrudes laterally into the shape shown in Figure 3. When the flange 74 and nut 78 are moved apart, the gland is extended longitudinally and retracted radially to the shape shown in Figure 2, in which the slurry may by-pass the piston. As shown in greater detail in Figure 3, lateral extrusion and retraction of the piston are effected by the relative movement of the hollow rod 72 and the center rod 76.

Instead of mechanically expanding the piston ring 71, as shown in Figures 2 and 3, this function can be performed pneumatically or hydraulically, e. -g., by using for ring 71b an inflatable annular tube as shown in Figure 5 with an opening at 79 connecting it through the bore of tubular rod 72b, to the hose 140]). The ring 71b is cemented to the rim of flange member 74b, particularly around the hole 79.

Great care must be exercised in design of piston 70 to keep from introducing air between 70 and 71, or to prevent leaks around tube 71a or 71b.

Rod 72 is also flanged at its upper end and rigidly connected to the bottom of the cylinder 82, and rod 76 is connected to piston 80 in the cylinder 82, so that fluid pressure in the cylinder compresses and extrudes ring 71. A spring 84 in this cylinder urges piston 80 and rod 76 downward relative to rod 72, to retract ring 71 to the form shown in Figure 2.

The cylinder 82 is moved bodily by the piston rod 86 driven by piston 88 in cylinder 90 counted on bracket 92 of frame 8. Rod 86 is threaded for adjustment and provided with lock nuts, to control the amount of squeeze on piston ring 71 so as to assure a tight fit in cylinder 54 without excessive friction.

A three way solenoid valve 98 operates to introduce air pressure into the cylinder 82 to extrude ring 71 when its solenoid is energized and to vent air from the cylinder to retract the gland when the solenoid is released.

A four-way solenoid valve 102 introduces air pressure above piston 88 and vents the space below the piston when its solenoid is energized, thus urging piston 70 down into cylinder 54 and imposing a suitable head on the slurry for delivery from the apparatus; when the solenoid is released, valve 102 vents the top and introduces pressure below the piston 88 to lift piston 70. A limit switch 106, normally closed and having one contact positioned to be engaged by finger 108 on cylinder 82, limits the injection stroke of the piston 70 by breaking the energizing circuit of valve 102.

A controlling switch 116 as shown may be put into any of three positions: run, OE, and start. When it is in the start or the run position, it energizes the motor 28, e. g. by conventional circuit connections (not shown).

In the start position this switch makes connections around the relay 123, i. e., the circuit of valve 98 is closed independently of the timer 112; whereas in the run position, the switch connects both solenoid valves 102 and 98 through contacts 126 and 128 of relay 123 thus making them subject to control by the timer. If this switch 116 were left in the start position, the piston 70 would not be etfectively retracted, but would serve only as a stopper. If the switch 116 were left always in the run position, it would not operate valve 98 until relay 123 had received a pulse from the timer; and then pumping would start. The start position of switch 116 provides for operation of fluid motor 80-82 to stopper chamber 2 before the timer 112 is started.

An electronic (or other available) pulse timer 112, operated from the feed line through the wires 114 and 118 and the hand operated switch 122, closes the circuit to the relays 123 for short pulses at time intervals predetermined by the setting of the timer. Contacts 126 and 128 are provided on relay 123 to be closed by its armature; and the connections 130, 132 and the normally closed limit switch 106 provide a holding circuit for the winding of the relay so that, once closed, it remains closed through this holding circuit until switch 106 is opened. Once opened, the relay remains open until a pulse from the timer 112 re-energizes it.

Contact 126 closes the above mentioned holding circuit for relay 123 and the contact 128 closes circuits to the solenoid valves 98 and 102. At first, the energizing circuit for relay 123 is through the connection 124, timer 112, contacts 122; but when relay 123 is operated the circuit is through connection 130, limit switch 106 and connection 132.

Air-flow control valves are provided at 134 and 136 to regulate the speed of piston 88 and ejector piston 70 connected to it. An air control valve 138 similarly regulates the speed at which the ejector piston 70 is expanded or contracted by movement of piston 80. Air line 140 is a flexible hose or pipe to accommodate vertical movement of the cylinder 82.

In Figure 4 of the drawings is shown a modification of the embodiment shown in Figures 1 to 3 wherein the rollers a are positively rotated by bevel gears 141 which mesh with the fixed ring gear 142'mounted on bracket a so that the rotation of the yoke lz'drives the pinion 141 over the ring gear 142 and thus rotates each of therollers 10a. The ring maybe external or internal. By the proportioning selected for the respective diameters of the pinion gears 141 and the, ring gear 142, any, desired speed of rotation may be given to the. rollers 10a and any desired rubbing action attained.

In the operation of this mechanism, switch 116 is moved to its start position, whereupon the motor 28 is started and solenoid valve 98 is energized to cause the expansion of the injector piston 70. This closes the outlet from the mixing chamber 2.

The liquid and dry materials to be mixed are then introduced by the automatic proportioning device 49 and through the conduit 44 and a spray head 46 respectively. The cylindrical rollers 10 meanwhile have been started in rotation by motor 28, driving through belts 22. The rollers operate against the inner surface of the mixing chamber 2 with both a rolling action to squeeze out any air bubbles, a crushing action to break up any lumps'of the powder, and a rubbing action against the inner surface of the chamber to thoroughly wet the surface of every particle and produce uniform slurry. By reason of the fact that the upper ends of the roller 10 travel around the longer circumference of the top of the funnelshaped chamber 2 while their lower ends traverse a shorter path at the bottom of the chamber, the rubbing action varies both in direction and degree. The frustoconical end 144 of the rollers 10 and the fitting conical bottom 11 of the chamber permits the rolling, rubbing and crushing action to extend substantially to the outlet of the chamber 2 and thus prevents settling out of solids and retards solidification of the slurry when the discharge is shut off.

The introduction of liquid and dry constituents and the mixing continue until the material fills the chamber 2 to the level 50, when it contacts the electrical probe 52 to stop further introduction of the constituents.

When the chamber 2 is thus filled, the switch 116 is moved from start position to run position and the switch 122 is closed to start the timer 112. Removing the switch 116 to the run position releases the solenoid valve 98 permitting exhaust from the cylinder 82 to allow the piston 80 to return and retract the gland 71. As timer 112 moves, it soon sends a pulse to the relay 123. After each pulse, the relay 123 is held energized by the holding circuit through contacts 126, connections 130, 132 and limit switch 106 until limit switch 106 is opened. With contacts 128 closed, both valves 98 and 102 are operated so that piston 80 is moved up, expanding piston 70 to a tight fit in cylinder 54, and piston 88 is driven down causing piston 70 to move down and eject the slurry from cylinder 54 through the line 68, 148 and 160.

At the end of this stroke, a projection 108 on cylinder 82 strikes and opens limit switch 106, which drops relay 123; and solenoids 98 and 102 are thus de-energized which reverses both solenoid valves to retract the piston gland 71 and lift the piston 70.

The liquid supplied through the pipe 48 and spray head 46 is advantageously cold enough to substantially retard the setting of the slurry. In the case of plaster of Paris, I thus use water at a temperature about 0 to 20 C. To the same end, the chamber 10 and/or cylinder 54 may be jacketed or provided with a cooling coil and a refrigerant fluid circulated to chill the mix to that range. It is desirable, however, that the slurry set rapidly when it has been introduced into the mold. In the illustrative embodiment of the invention, therefore, a heater 146 is provided so that the slurry is delivered from the discharged nozzle into the mold in a condition ready for quick setting, advantageously 50-65 C. The required temperature is automatically maintained by supplying to a steam jacket 146 saturated steam at a pressure corresponding to a slightly higher temperature, e. g., of a pressure about 2 to 30 p. s. i. above atmospheric. The condensate drains from the low point of this jacket through a pipe 152 :and a thermostatic trap 154 and the discharge pipe 156. A steam gauge 158 shows the pressure and/or temperature. A shut-off valve 150 provides for stopping the heat or reducing the rate ofheating, if the discharge is to be cut off "for any substantial time or unduly retarded.

A flexible tube 160 provided with a nozzle 161 receives the slurry from the tube 148 and enables the operator to deliver it at the desired points in the molds, etc.

The slurry is delivered from the nozzle 161 at a temperature near that of its maximum setting speed and in a stream of about A to /2 diameter or larger, (the particular nozzle being chosen to give the most advantageous size stream for filling the plaster into the detail of the particular mold). The velocity of the stream, which is regulated by the air pressure supplied through the valve 102, is adapted to drive the plaster into the detail by its momentum but without whipping it up so as to entrain any air. Thus, in one preferred embodiment the air supplied by the piston .keeps a head of lbs. per square inch on the slurry.

As one example: A dry mix containing 42% gypsum cement, 47% fine sand, 8% talc and 3% terra alba was mixed with water at 5 C. to the consistency of soft mud or slurry. This could be held safely in the machine for four minutes and it would take about 15 minutes thereafter to set. The chamber 2 was, therefore, designed to hold only enough of the mix for about a two-minute supply for normal use. After this mix had been pumped through the heater 146, its temperature was raised to 50 C. and the mix was then set in 2.8 minutes, thus allowing adequate time for filling it into the mold and for it to flow and form itself into the detail of the mold.

As above pointed out, one of the great advantages of this invention is that slurries such as gypsum plaster can be made and a supply kept at a temperature so low that setting will not occur in the machine and yet will occur promptly after delivery. Because the piston and the mixing device are immersed in the slurry throughout the operation of the apparatus and operate through the open upper surface of the material in the hopper without glands or other devices which could leak air below the surface of the slurry, the danger of introducing air bubbles is substantially entirely eliminated and the mechanical design of the apparatus is greatly simplified by the avoidance of the need for stufling boxes or glands to control such air leakage into the apparatus.

When use of the apparatus is to be discontinued, the feed is cut off and pumping continued until the hopper is substantially emptied.

Water for flushing out the apparatus is run in at 166. This serves to wash out the mixing hopper 2 and to clean the rollers 10 and piston 70 and all parts with which the slurry has been in contact. By leaving the apparatus running while the flushing water is running in and through the apparatus, pump 70 and rollers 10 serve to agitate the water and to give it relatively high velocity along the surfaces which need to be washed and thus facilitate the cleaning of all parts which have been covered by the plaster. Rod 69 also helps in assuring a thorough washing of the pipe 68.

I claim:

1. The process of preparing a settable and moldable slurry including a water-setting constituent, such as gypsum plaster, which consists in mixing the theretofore dry constituents of the slurry with water, chilling the slurry to a temperature sufficiently below atmospheric to strongly retard the setting of the slurry, rubbing and squeezing the wetter solid particles of the slurry during the mixing until occluded gases have been substantially completely expelled while retaining the temperature of 7 the slurry substantially below atmospheric, then ejecting the slurry under pressure into a form with heating of the slurry as it is discharged.

2. The process as defined in claim 19 wherein the amount of slurry being mixed at any time is substantially less than that consumed at the current rate of use within the setting time of the slurry at said low temperature;

References Cited in the file of this patent UNITED STATES PATENTS Lake May 6, 1924 Edwards Aug. 1, 1933 UNITED STATES PATENT ()FFICE CERTIFICATE OF CORRECTION Patent No, 2, 846, 726

August 12, 1958 Morris Mo Bean Column 6 line '73, for "wetter" for th read m Wetted m e claim reference numer column 7, lina 4, al "19" read m 1 o Signed and sealed this 23rd day of Decembevr 1958..

SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Oflicer Commissiongr of Patents

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