US2863651A

US2863651A - Solids proportioning and mixing system

Info

Publication number: US2863651A
Application number: US693740A
Authority: US
Inventors: Robert J Mcbride
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-10-31
Filing date: 1957-10-31
Publication date: 1958-12-09
Anticipated expiration: 1975-12-09

Description

Dec. 9, 1958 R. .J. M BRIDE SOLIDS PROPORTIONING AND MIXING SYSTEM Filed oct. :51, 1957 INVENTOR W Eoaser Ma Bans A #0 2 N: V

United States Patent P i s 1C6 2,863,651

Patented Dec. 9, 1958 SOLIDS PROPORTIONING AND MIXING SYSTEM Robert J. McBride, Milwaukee, Wis.

Application October 31, 1957, Serial No. 693,740

4 Claims. (Cl. 259-154) This invention relates to improvements in systems for proportional mixing of solids having different characteristics of flow from bulk containers thereof.

Present sales and distribution practices require the mixing of different solids in given proportions and packaging in containers of a given weight. Examples of such mixtures are plastering compositions including Portland cement, slaked lime and sand, patching cement including Portland cement and sand, and concrete mixes including Portland cement, sand and stone. Portland cement, lime, sand and stone have different characteristics of flow from one another and from even identical bulk bins.

It has been found difficult heretofore to combine known equipment for the bulk handling of solids in such way that accurate control of feeding in stated proportions can be obtained with materials having widely different flow characteristics such as those of the above materials while maintaining nearly continuous operation of the system for securing maximum output at the best rate of operation of such equipment. The difliculty is particularly apparent with Portland cement which bridges or fails to flow and flushes or flows so freely that flow is difiicult to control.

Another difficult condition in devising such systems has been minimization of the number of subassemblies having critical effects on both proportioning accuracy and continuity of operation. Simplification of controls to reduce cost and to minimize the possibilities of failure of the controls, and to reduce the time required for re-adjustments and maintenance of the controls, have also been major difliculties which have heretofore not been overcome.

It is therefore one object of the present invention to provide a system for proportional mixing of dry solids having different flow characteristics, in which actuation of the controls is responsive to the operation of only one of several feeding mechanisms.

Another object of the present invention is to provide a system for proportional feeding of solids having different flow characteristics, in which all but one of a number of feeding mechanisms are operated continuously except upon the occurrence of only one condition of the said one feeding mechanism, and responsive to the delivery of the solid from the said one feeding mechanism.

Another object of the invention is to provide a system for proportional mixing of solids of which the actual discharge of the several solids is severally controlled by vibrating feeders and in which all the vibrating feeders are isolated from one another to some extent, and one feeder particularly is isolated from the others and from the mixing means receiving the discharges of solids whereby transmission to such feeders of shocks and vibration affecting the operations thereof are minimized.

Another object of the invention is to provide a combination of known bin structures and vibrating features for all solids, a rotary vanetype feeder for a varying-flow solid and conveyingmixing means, in which the vibrating feeder for each solid is isolated from the others and from 2 the conveyor-mixer whereby a single balance accurately controls proportional discharge of the solids from all the vibrating feeders and an exceedingly simple electrical system connects the feeders to minimize adjustment and maintenance and supervision of the system and to maintain the system in substantially continuous operation regardless of most bridging or flushing actions of one solid.

Advantages and objects other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing in which: a

Figure 1 diagrammatically illustrates an arrangement of various subassemblies of the present solids mixing system, with a portion of one feeder subassembly shown in section, and

Figure 2 is a diagram of the electrical mechanisms and connections by which the various feeders are controlled responsive to the discharge from a single feeder.

Generally, a number of similarly shaped bins severally receive different solids in a dry state, and each bin discharges its contents on the pan of an electrically operated vibratory feeder associated therewith. The discharge portions of the bins are preferably of substantially uniform shape and size to avoid inducing differences in flow characteristics of the solids, and the vibratory feeders are preferably of the same make and model. The vibrating feeders are each separately supported in such manner as to minimize transmission thereto of shocks and vibration from outside each of the several feeders, i. e., vibration not originating in a feeder being considered. The vibratory feeders severally discharge into a mixing conveyor, preferably of the paddle type which conveys the material by a screw action of the paddles.

The bin for any solid which at different times is apt to bridge, i. e., not flow at all, or to flush, i. e., to flow too freely, first discharges into a feeder of the rotary vane type operated by an electric motor and such vane type feeder discharges on a vibratory feeder pan. Assuming that only one bridging solid is involved, such as Portland cement or a mixture of cement and slaked lime, only the vibratory feeder for such material is mounted on a balance. A pointer for the balance moves responsive to changes in weight on the pan of the vibratory cement feeder, between two electrical contacts to control either of two circuits. One circuit controls only the motor of the vane type feeder for the cement, while the other circuit controls all of the vibratory feeders. The essential accuracy of proportions is obtained with a high degree of continuity of operation and consequent high output. I

Referring specifically to the drawing, numerals 5, 6 and 7 respectively, designate bins for a solid likely to stop flowing or to flow too freely as is the case with Portland cement, and for solids having constant free flowing characteristics such as sand and stone of given size range, and which have been dried when the mixture is to be packaged. The cement bin 5 discharges into a rotary vane type feeder which comprises a cylinder 10 with a vane wheel 11 rotatable therein by an electric motor 12. The vane feeder 10, 11 discharges on a pan 13 which is vibrated by an electrical mechanism 14 to discharge the cement from the feeder pan at a given rate so long as at least a given amount of cement is on the pan. Such vibratory feeders are known articles of commerce and need not be more particularly described. The vibratory feeder 13, 14 is mounted on the platform 17 of a balance of a type having its balance indicating mechanism within a column 18 and such balance indicating mechanism includes a pointer 19 moving between and engageable with contacts 20 or 21 under some conditions. The balance is also of the well known construc tion and need not be further described. The balance 17--21 and the vibrating feeder 13, 14 are preferably supported on a foundation separate from other system portions and well isolated from such other system portions.

In the present system, bins 6 and 7 contain dry sand and stone of given size and which are free flowing at all times at substantiallya constant rate, i. e.,' such materials do not bridge or flush. Such bins discharge respectively on vibrating feeders comprising pan 24 and vibrating mechanism 25 and pan 26 and vibrating mechanism 27. Such vibrating feeders are preferably similar to vibrating feeder 13, 14 and are not further described.

Such feeders

24, 25 and 26,27 are also supported sepa rately from and isolated against receipt of shocks and vibration from other'por'tionsof the system. The contact pointer 19 and one terminal of the coil of each of the relays 37, 38 are connected with a source of electric current so that closure of contacts 19 and 20 opens the circuit to the vane'f'eeder motor 12 through relay 37 and closure of contacts 19 and 21 opens the circuit through relay 38 to all of the vibrating

feeders

14, 25 and 27. The pointer 19 will swing counter-clockwise as cement is being delivered by the vane feeder 12 and will cause contact 19 to engage contact if the amount of cement on the vibrating feeder pan is excessive to stop the vane feeder. The pointer 19 will swing counter-clockwise as cement is taken off the pan 13 and until the contact 19 engages contact 21 if the amount of cement is insufficient, the latter movement interrupting operation of all vibrating feeders until the pointer 19 has again swung counterclockwise to leave contact 21 whereupon all the vibrating feeders are again operating. Most of the time the pointer 19 is in mid-position and all the feeders operate continuously. Scale pointer 19 can be set to shift upon fluctuations of only a few ounces. Manually operable switches are provided as is usualin electrical circuits to start and stop the system.

A conveyor is provided comprising a trough 31 with a spout 32 at one end thereof, and a rotatable shaft 33 with blades 34 in staggered relation around the axis of the shaft and longitudinally thereof and extending longitudinally through the trough. The blades are tilted to have a screw effect in moving the solids along the trough toward the spout as the solids are mixed by the blades. The conveyor is supported independently from the bins and feeders and particularly is isolated from the vibrating feeders. Hence, the operation of the conveyor which produces considerable vibration, has no effect whatever on the feeders for the solids and particularly on the feeder for the varying-flow solid. It is believed that isolation of the bins and the vibrating feeders from one another and from the conveyor-mixer are essential factors in obtaining accuracy of proportioning as well as the high rate of output of the present system, with a single balancing means operating the present simplified control, responsive to only the vibrating feeder for the solid having varying-fiow characteristics.

"The simplification of control and control connections is evident from Figure 2,it being understood that the circuit controlled by contacts 19', 20 and 19, 21 are the circuits of relays-operated contactors 37 and 38 which effect opening and closing a circuit to the motor 12 and a circuit to the vibrators 14, and 27, as is usual in electrical control systems.

The operation of the system is as follows: when more than a given amount of cement is on the pan of the vi brating cement feeder therefor, the balance pointer opens the circuit of the vane feeder motor and stops the discharge of cement by the vane feeder. The vibrating cement feeder, however, continues to discharge cement at the present rate and the vibrating feeders for the freeflow materials continue to operate so long as the cement is being discharged by its vibrating feeder. When the amount of cement 'on its vibrating feeder pan is reduced below a given amount, the balance pointer opens the circuit of all of the vibrating feeders while the rotary vane feeder'for cement continues to operate. Assuming that a bridge in the cement breaks so that the rotary vane feeder again receives and discharges cement, the amount of cement on the vibrating feeder pan therefor is again built up to the given value and the circuits for all of the vibrating feeders are again reclosed. Under most conditions of operations, cement bridges collapse after a short time of operation of the rotary vane feeder alone and the system automatically returns to full operation. if the operation of the rotary vane feeder does not cause the cement bridge to collapse, the cement bin may be struck with a heavy hammer or air may be injected to collapse the cement bridge, or other manual action is taken to secure the desired etfect.

Periodic tests are made to insure accurate proportion-- ing of the solids. However, accuracy of proportioning. of solids is best shown by the sale in three months 'of nearly 300,000 pounds of mixture toonly four customers (among others) who continuously test samples of each: product for assurance that each product meets its speci-- fications. The rate of output of applicants present system has averaged over 4600 pounds per hour but larger equipment would provide a larger output. However, continuity of operation is shown by the fact that no adjustment of the control, requiring. interruption of operation, has been needed in over five and a half months since the system has been moved from an experimental location to its present location for full scale use.

Although but one embodiment of'the present invention has been illustrated and described, it will be ap parent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. In a system for the proportional mixing of solids including at least one free-flow solid and a solid having varying-fiow characteristics, a bin for each of the solids, an electrically operated vibrating feeder receiving and discharging the free-flow solid only during energization of said feeder, a rotary vane feeder receiving and discharging the varying-flow solid, an electric motor operating the vane feeder, an electrically operated vibrating feeder receiving the varying-flow solid from the vane feeder and discharging upon energization of the vibrating feeder only, a single balance having a plurality of stationary contacts and a contact movable responsive only to the weight of the varying-flow solid on the vibrating feeder therefor, the movable contact engaging one stationary contact to open the motor circuit when such weight exceeds and engaging another stationary contact to open the circuit of all vibrating feeders when such weight falls below a given value, and a mixing conveyor receiving the solids from all vibrating feeders.

2. In a system for the proportional mixing of solids including at least one free-flow solid and a solid having varying-flow characteristics, a bin for each of the solids, an electrically operated vibrating feeder receiving and discharging the free-flow solid only during energization of said feeder, a rotary vane feeder receiving and discharging the varying-fio-w solid, an electric motor operating the vane feeder, an electrically operated vibrating feeder receiving the varying-flow solid from the vane feeder and discharging upon energization of the vibrating feeder only, a single balance supporting the vibrating feeder for u e varyingflow solid, the balance having a plurality of stationary contacts and a contact movable responsive only to the weight of the varying-flow solid on the vibrating feeder therefor, the movable contact engaging one stationary contact to open the motor circuit when such weight exceeds and engaging another stationary contact to open the circuit of all vibrating feeders when such weight falls below a given value, and

a mixing conveyor receiving the solids from all vibrating feeders, the vibrating feeder for the varying-flow solid and the balance therefor being supported for reducing transmission thereto'of shocks and vibrations.

3. In a system for the proportional mixing of solids including at least one free-flow solid and a solid having varying-flow characteristics, a bin for each of the solids, an electrically operated vibrating feeder receiving and discharging the free-flow solid only during energization of said feeder, a rotary vane-feeder receiving and discharging the varying-flow solids, an electric motor operating the vane feeder, an electrically operated vibrating feeder receiving the varying-flow solid from the vane feeder and discharging upon energization of the vibrat ing feeder only, a single balance supporting the vibrating feeder for the varying-flow solid, the vibrating feeder for the varying-flow solid and the balance therefor being separately supported for isolation therefrom of shocks and vibrations of other portions of the system, the balance having a plurality of stationary contacts and a con tact movable responsive only to the weight of the varyingfiow solid on the vibrating feeder therefor, the movable contact engaging one stationary contact to open the motor circuit when such weight exceeds and engaging another stationary contact to open the circuit of all vibrating feeders when such weight falls below a given value, and a mixing conveyor receiving the solids from all vibrating feeders.

4. In a system for the proportional mixing of solids including at least one free-flow solid and a solid having varying-flow characteristics, a bin for each of the solids, an electrically operated vibrating feeder receiving and discharging the free-flow solid only during energization of said feeder, a rotary vane feeder receiving and discharging the varying-flow solid, an electric motor operating the vane feeder, an electrically operated vibrating feeder receiving the varying-flow solid from the vane feeder and discharging upon energization of the vibrating feeder only, a single balance supporting the vibrating feeder for the varying-flow solid, the vibrating feeder for each of the solids being isolated from all other portions of the system for minimizing the transmission of shocks and vibrations to such feeders, the balance having a plurality of stationary contacts and a contact movable responsive only to the weight of the varying-flow solid on the vibrating feeder therefor, the movable contact engaging one stationary contact to open the motor circuit when such weight exceeds and engaging another stationary contact to open the circuit of all vibrating feeders when such weight falls below a given value, and a mixing conveyor receiving the solids from all vibrating feeders.

References Cited in the file of this patent UNITED STATES PATENTS