Apparatus For Proportioning Dry Particulate Materials

Abstract

An apparatus for continuously combining and mixing a plurality of dry particulate materials, such as the various constituents in dry concrete or mortar mixes, in accurate preselected proportions. The apparatus includes a separate bin adapted to store a relatively large quantity of each constituent, a rotatable and vibratable screw conveyor for feeding one of the constituents from its bin at a constant preselected volumetric flow rate, and means for feeding a second constituent from its bin at a constant preselected gravimetric flow rate. The gravimetric feeding means includes a conveyor adapted to be translated at a constant speed, means for monitoring the weight of the constituent carried on the conveyor, and control means to adjust the rate of delivery of the constituent onto the conveyor to maintain a substantially constant weight thereof on the conveyor.

Description

The present invention relates to an apparatus for continuously combining and mixing a plurality of differing particulate materials in accurate predetermined proportions. More particularly, the present invention relates to an apparatus for selectively combining and mixing the various constituents of dry concrete or mortar mixes in predetermined proportions.

Dry concrete or mortar mixes which are adapted to be prepared for use by merely adding water are commonly sold in relatively small packages for use by homeowners. A produce of this type is sold under the trademark SAKRETE, and has enjoyed a substantial commercial success in recent years. In producing dry mixes of this type, great care must be exercised in proportioning the several constituents since variations in the constituents will cause corresponding variations in the quality of the resulting concrete or mortar. Typically, mechanical mixers of the batch type are employed for this purpose wherein a definite quantity of each constituent is first deposited in the mixer, then mixed, and finally discharged in batch form at the completion of the mixing operation. While the batch process is able to assure accurate proportioning of the various constituents, its discontinuous operation is entirely too slow for modern production requirements.

To alleviate the problem of limited production associated with batch mixers, it has been proposed to employ a continuous process wherein independent feeding devices for the various constituents are arranged to dispense each constituent into a common hopper in the desired proportions. To obtain accurate proportioning, controls are provided which monitor the weight of one of the constituents being dispensed, and which stop and start the various feeding devices upon the weight becoming excessive or insufficient. However, such stopping and starting of the feeding devices results in an overall reduction in the efficiency of the apparatus, and the desired high production can not be achieved.

Accordingly, it is an object of the present invention to provide an apparatus for continuously combining and mixing a plurality of dry particulate materials and which does not require the stopping and starting of the feeding operations in order to assure the proper proportioning of each of the various constituents.

It is a further object of the present invention to provide an apparatus which is capable of continuously proportioning and mixing relatively large quantities of mixed dry materials in a highly efficient and economical manner.

These and other objects and advantages of the present invention are achieved in the embodiment illustrated herein by the provision of an apparatus which includes a storage bin for individually storing each of the required materials, means for continuously feeding one of the materials at a constant preselected volumetric flow rate, and means for continuously feeding the other required materials from their associated bins at a constant preselected gravimetric flow rate. Each of the gravimetric feeding means includes a translatable conveyor defining a receiving end and a discharge end, and means for translating the conveyor at a constant speed. The weight of the material on the conveyor is monitored, and provision is made for delivering the material onto the conveyor at a variable rate to maintain a substantially uniform weight thereon.

Some of the objects and advantages of the invention having been stated, others will appear as the description proceeds, when taken in connection with the accompanying drawings, in which--

FIG. 1 is a schematic illustration of an apparatus for continuously combining and mixing a plurality of dry particulate materials according to the present invention;

FIG. 2 is an enlarged fragmentary view of the storage and mixing portion of the above apparatus;

FIG. 3 is an enlarged fragmentary side elevational view, partly in section, of the gravimetric feeding means of the present invention;

FIG. 4 is an enlarged fragmentary side elevational view, partly in section, illustrating the volumetric feeding means of the present invention;

FIG. 5 is a schematic illustration of a control panel associated with the present invention;

FIG. 6 is a schematic illustration of the control system associated with the gravimetric feeding means of the present invention.

Referring more specifically to the drawings, the overall apparatus of the present invention is schematically illustrated in FIG. 1 and includes a material delivery system generally indicated at 10. The delivery system includes a hopper 12 adapted to receive one of the constituents from a truck, railroad car, or the like, a conveyor 14 for lifting the constituent into the furnace 16, and a dryer 18 designed to rotate and tumble the heated constituent and thereby remove any excess moisture. From the dryer 18, the constituent is deposited into the secondary hopper 20, and a bucket elevator 22 lifts the same from the hopper 20 onto a vibrating screen separator 24. The separator removes any large particles from the mixture for discharge through the chute 26, and the remaining material is conveyed to a point overlying the storage and mixing apparatus.

The storage and mixing apparatus comprises a cement storage bin 28, a mortar storage bin 30, and four constituent storage bins positioned in close proximity to each other. In particular, the four storage bins include a rock storage bin 31, a mortar sand storage bin 32, a concrete sand storage bin 33, and a specialty sand storage bin 34.

The constituents are selectivity directed into the appropriate storage bin from the screen separator 24 by an arrangement which includes a first conduit 36 directed toward the bins 31 and 32, and a second conduit 38 directed toward the bins 33 and 34. The first conduit 36 includes a divided lower portion, with the segment 40 leading to bin 31 and the segment 42 leading to the bin 32. The second conduit 38 is similarly divided, with the segment 44 directed to bin 33 and segment 46 directed to bin 34. Three flapper valves are positioned within this system to selectively direct the constituent into the proper bin. In particular, a flapper valve 48 is positioned at the top of the system to direct the constituent into either the conduit 36 or 38. Also, a flapper valve 49 is positioned to selectively direct the constituent between the conduit segments 40 and 42, and a flapper valve 50 is positioned to selectively direct the constituent into the segments 44 or 46. An independent system (not shown) is employed for directing the cement and mortar into their respective bins 28 and 30.

A discharge chute extends from the bottom of each of the four constituent bins 31-34 in the manner as seen in FIG. 2. More particularly, discharge chutes 51 and 52 extend from the bins 31 and 32 respectively, and communicate with a first common discharge chute 56. Discharge chutes 53 and 54 lead from the bins 33 and 34 respectively and communicate with a second common discharge chute 58. The lower end of each bin 31-34 further includes a gate, numbered 61, 62, 63 and 64 respectively, for selectively opening the bin to its associated discharge chute. By this arrangement, it will be seen that either the rock or mortar sand may be fed into common chute 56, while either the concrete sand or specialty sand may be fed to chute 58. Viewing FIG. 2, it will be noted that the bin 34 also includes an additional discharge chute 66 and associated flapper valve 68 for selectively directing the specialty sand either through the chute 54 or 66.

In accordance with the present invention, provision is made for feeding selected constituents from the bins 31-34 or certain combinations of constituents, into a hopper 70 at a constant preselected gravimetric flow rate. For this purpose, a pair of oppositely directed conveyors 72 and 74 are positioned such that the receiving end of the conveyor 72 underlies the chute 56, and the receiving end of a conveyor 74 underlies the chute 58. The discharge end of both conveyors overlies the hopper 70 such that a constituent being conveyed along either conveyor will fall into the hopper. As seen in FIGS. 2 and 3, the chutes 56 and 58 extend downwardly and open onto the conveyor receiving end. In each case, a side wall opening (not numbered) at the lower end of the chute communicates with the conveyor and faces the discharge end thereof, and a translatable gate 76 is positioned at the lower end of the chute for varying the extend of the opening. Since the speed of the conveyor is designed to be constant, it will be apparent that the position of the gate 76 will in each case determine the amount of the constituent delivered to the conveyor.

The system for monitoring the weight of the constituent positioned on conveyor 72 is illustrated schematically in FIG. 6, it being understood that the system for monitoring the weight on conveyor 74 is a duplicate of that shown. Also, a control panel 78 for both of the conveyors is shown in FIG. 5, with the right half serving conveyor 72 and the left half (having primed numerals) serving the conveyor 74. As shown in FIG. 6, the monitoring system includes a pneumatic load cell 80 positioned to support the discharge end of the conveyor 72 and thereby sense the total weight thereof. The load cell 80 is supplied with pneumatic pressure from the supply line 81, and converts the weight of the conveyor into a first pneumatic signal representative of the weight of the constituent carried on the conveyor. This signal is transmitted to the biasing regulator 82 through line 84, which serves to correct the signal from the load cell for any error resulting from material accumulating on the frame or other parts of the conveyor during use. Thus periodically the conveyor is run empty and the biasing regulator 82 is employed to zero the signal from the load cell 80 and thereby adjust for the excess weight.

The signal from the biasing regulator 82 is transmitted to the pneumatic controller 86 which balances this signal against a preset second pneumatic signal emanating from the regulator 88. The signal from the regulator 88 is initially set by closing the button 89 of the three-way switch 90 to direct the output pressure to the recorder 92, which in turn gives a visual reading on the control panel 78, note FIG. 5. Thus, by changing the output of the regulator 88, the weight indicated by the recorder 92 may be adjusted to a preselected valve. Upon release of the button 89, the preset signal from the regulator 88 is transmitted to the controller 86. The controller thus receives two signals, one from the load cell 80 and another from the regulator 88. The controller 86 is designed to sense a pressure differential between these two signals and to send a correcting pressure signal through the three way toggle switch 93, past gauge 94, and to the gate positioner air motor 96. As the positioner 96 moves, it translates the gate 76 and effectively opens or closes the side wall opening in the chute 56 to thus change the amount of the constituent being delivered onto the conveyor. By this arrangement, a constant preselected gravimetric flow rate is obtained, which is independent of changing densities of the constituent, or its delivery rate into the chute 56.

To feed the cement or mortar to the hopper 70 from the associated bins 28 and 30, there is provided a feeding system which is designed to feed the material at a constant preselected volumetric flow rate. This system is illustrated schematically in FIGS. 1 and 2 and more specifically in FIG. 4. It will be appreciated that the system as shown in FIGS. 1 and 2 is rotated 90.degree. from its actual position in relation to the bins 31-34 for purposes of clarity in illustration.

Each of the two volumetric feeding systems includes a rotatable screw conveyor 100 having a receiving end in communication with the associated bin, and a discharge end overlying a flexible downwardly directed conduit 102. The flexible conduit 102 communicates with a vibrating screw conveyor 104 which is rotated and vibrated by an arrangement which includes the motor 105 and eccentric weight 106 positioned on the central shaft thereof. The discharge end of the conveyor 104 communicates with the chute 108 to direct the material into the hopper 70. The hopper 70 in turn communicates with a rotatable screw conveyor 110 for mixing the various constituents received therein, and for delivering the same to a dispensing apparatus 112 which is designed to dispense preselected quantities of the material into individual bags or the like in the conventional manner.

In describing the operation of the illustrated apparatus, it will be appreciated that the apparatus is designed to selectively combine and mix various combinations of constituents in accurate preselected proportions. For example, commercial dry concrete and mortar mixes are commonly sold in the following forms:

1. Mortar Mix; comprising mortar and mortar sand.

2. Cement Mix; comprising cement and concrete sand.

3. Concrete Mix; comprising cement, concrete sand, and rock.

In addition, it is common to sell the specialty sand in bin 34 separately. Obviously, a number of other constituents could be positioned in bins 31-34, and a number of other combinations of these constituents could be prepared utilizing the illustrated apparatus.

If it is desired to dispense for example mortar mix, the apparatus is programmed to dispense mortar from bin 30 into the hopper 70 at a constant preselected volumetric flow rate, and to dispense mortar sand along the conveyor 72 and into the hopper 70 at a preselected gravimetric flow rate. The two constituents are mixed by the screw conveyor 110 and dispensed by the dispensing apparatus 112 into individual bags.

Similarly, if it is desired to prepare cement mix, the cement is dispensed from bin 28 at a constant volumetric flow rate, and the concrete sand is dispensed from bin 33 at a constant gravimetric flow rate. In dispensing the concrete mix, rock is delivered from bin 31 at a predetermined gravimetric flow rate concurrently with the sand which is dispensed from the bin 33 at a predetermined gravimetric flow rate. If it is desired to dispense the specialty sand alone, the sand may be directed through the separate chute 66 into the hopper 70, or it may be dispensed along the chute 54 and conveyor 74 into the hopper.

The electrical control system for opening and closing the various gates and flapper valves as described above, and for selectively operating the various components of the apparatus, are of conventional design well known to those skilled in the art and will therefore not be specifically described herein.

In the drawings and specification, there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

What is claimed is:

1. An apparatus for continuously combining at least two different essentially dry particulate materials in predetermined proportions comprising

a storage bin for individually storing each of said materials,

means for continuously feeding a first material at a constant flow rate from its associated storage bin,

means for feeding a second material at a constant flow rate from its associated storage bin and including a translatable conveyor defining a receiving end and a discharge end, means for translating said conveyor at a constant speed, means for delivering the second material onto said conveyor receiving end at a variable rate, means for monitoring the weight of the second material positioned on said conveyor, and control means operatively associated with said monitoring means for controlling said delivering means to maintain a substantially constant weight of the second material on said conveyor, and

means for receiving said first and second materials from the associated feeding means.

2. The apparatus as defined in claim 1 wherein the storage bin associated with the second material is positioned above said conveyor, and

said delivering means comprises an open chute extending downwardly from said storage bin and onto said conveyor receiving end, means defining an opening at the lower end of said chute in communication with said conveyor and facing said discharge end, and translatable gate means positioned at the lower end of said chute for varying the extend of said opening.

3. The apparatus as defined in claim 2 wherein said monitoring means comprises means mounted at the discharge end of said conveyor for generating a first pneumatic signal representative of the weight of the second material carried by said conveyor, and

said control means comprises means for generating a second pneumatic signal representative of a preselected weight of the second material carried by said conveyor, means for sensing a pressure differential between said first and second pneumatic signals, and means responsive to said sensing means for translating said gate means to thereby change the extend of said opening and thus the amount of said second material delivered to said conveyor until the preselected weight is present on said conveyor.

4. An apparatus for continuously combining and mixing at least two essentially dry particulate materials in preselected proportions to obtain a substantially homogeneous mixture comprising

a first bin adapted to store a relatively large quantity of a first material,

a second bin adapted to store a relatively large quantity of a second material,

means for feeding the first material from said first bin at a constant preselected volumetric flow rate,

means for feeding the second material from said second bin at a constant preselected gravimetric flow rate and including a translatable conveyor defining a receiving end and a discharge end, means for translating said conveyor at a constant speed, means for delivering the second material onto said conveyor at a variable rate, means for monitoring the weight of said second material carried on said conveyor, and control means operatively associated with said monitoring means for controlling said delivering means to maintain a substantially constant weight of the second material on said conveyor, and

means for receiving said first and second materials from the associated feeding means and for mixing the same.

5. The apparatus as defined in claim 4 wherein said means for receiving and mixing said first and second materials comprises a hopper and means for dispensing the materials therefrom.

6. The apparatus as defined in claim 5 wherein said means for feeding the first material from said first bin comprises a rotatable and vibratable screw conveyor and means for rotating and vibrating the same.

7. An apparatus for continuously combining and mixing a plurality of essentially dry particulate materials in predetermined proportions to obtain a substantially homogeneous mixture comprising

a mortar storage bin,

a cement storage bin,

a plurality of constituent storage bins positioned in close proximity to each other and including a first constituent storage bin, a second constituent storage bin, and a third constituent storage bin,

means for selectively feeding mortar from said mortar storage bin at a preselected volumetric flow rate,

means for selectively feeding cement from said cement storage bin at a preselected volumetric flow rate,

first feeding means including a discharge chute extending from each of said first and second constituent bins and communicating with a first common discharge chute for selectively feeding either the first or second constituent from the associated storage bin at preselected gravimetric flow rate,

second feeding means including discharge chute extending from said third constituent bin and communicating with a second common discharge chute for selectively feeding the third constituent from said third storage bin at a preselected gravimetric flow rate,

control means for selectively feeding either mortar or cement from the associated storage bins, and for selectively operating either said first feeding means independently, said second feeding means independently, or said first and second feeding means concurrently, and

means for receiving the selected materials from the associated feeding means.

8. The apparatus as defined in claim 7 wherein said plurality of constituent storage bins further includes a fourth constituent storage bin, and said second feeding means includes a discharge chute extending from said fourth constituent bin to said second common discharge chute and further including means for selectively feeding either the third or fourth constituent from the associated storage bin at a preselected gravimetric flow rate.

9. The apparatus as defined in claim 8 further comprising means for selectively delivering the first, second, third, and fourth constituents into their respective constituent bins, and including means for transporting a selected one of said constituents along a predetermined path of travel to a point overlying said four constituent bins, first conduit means communicating with said first and second bins for selectively transferring the selected constituent into said first or second bins, second conduit means communicating with said third and fourth bins for selectively transferring the selected constituent into said third or fourth bins, and means for selectivity connecting either said first or said second conduit means to said path of travel to thereby permit the conveying of the selected constituent into any of said four constituent bins.

10. The apparatus as defined in claim 9 wherein said means for transporting a selected constituent includes drying means positioned along said path of travel for removing excess moisture from the selected constituent.