US3724821A

US3724821A - Apparatus for automatic regulation of the moisture content of granular material

Info

Publication number: US3724821A
Application number: US00203514A
Authority: US
Inventors: F Szatmari; M Wernli
Original assignee: Georg Fischer AG
Current assignee: Georg Fischer AG
Priority date: 1971-12-01
Filing date: 1971-12-01
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

Apparatus for automatic regulation of the moisture content of granular material, such as molding sand, concrete, or the like, includes an elastically yieldable rod, one end of which is securely fixed and the other end of which extends into the granular material. The rod is moved relative to the granular material and a sensing means detects the amount of elastic deflection of the rod caused by the reaction thereof with the granular material during relative movement. The deflection of the rod is a function of the consistency of the granular material and the output of the sensing means is fed to a controllable valve to control the addition of moistening means to the granular material as a function of the elastic deflection of the rod. A plurality of rods may be provided.

Description

United States Patent 1191 Szatmari et al.

[541 APPARATUS FOR AUTOMATIC REGULATION OF THE MOISTURE CONTENT OF GRANULAR MATERIAL [75] Inventors: Franz Szatmari, Max Wernli, both of Sc haftnausen. Switzerland |73| Assignee: George Fisher Aktiengesellschatt,

, schaffliausen, Switzerland [22] Filed:

Dec. 1, 1971 [21] Appl. No.: 203,514

[52] US. Cl ..259/I49 [51] Int. Cl ..B28c 7/04 [58] Field of Search ..259/168, 154, 149; 73/194, 73/202, 217; 137/92,100, 101.19, 101.21

[ 1 Apr. 3, 1973 3,463,461 8/1969 Kirk ..2s9/154 Primary Examiner-Robert W. Jenkins Attorney-Robert D. Flynn et al.

[57] 1 ABSTRACT Apparatus for automatic regulationof the moisture content of granular material, such as molding sand, concrete, or the like, includes an elastically yieldable rod, one end of which is securely fixed and the other end of which extends into the granular material. The rod is moved relative to the granular material and a sensing means detects the amount of elastic deflection of the rod caused by the reaction thereof with the granular material during relative movement. The deflection of the rod is a function of the consistency of the granular material and the output of the sensing means is fed to a controllable valve to control the addition of moistening means to the granular material as a function of the elastic deflection of the rod. A plurality of rods may be provided.

15 Claims, 4 Drawing Figures PATENIEDAPRB 191a I 3 724 8 21 4 sum 1 [IF 2 PATENIEnAPRa'ma 3, 4, 21

SHEET 2 BF 2 VII/I APPARATUS FOR AUTOMATIC REGULATION OF THE MOISTURE CONTENT OF GRANULAR MATERIAL The present invention relates to a device for automatic regulation of the moisture content of granular material, more particularly of molding sand, concrete or the like, with at least one yieldable sensing element which is acted upon by the granular material by means of a relative motion relative to said material, the sensing element being operatively connected to a valve controlling the introduction of liquid binding means to the granular material.

Devices for the regulation of the moisture content of granular material are known which establish as a criterion for moistening, the actual value of the consistency or plasticity of the material to be mixed, and corresponding to this consistency value, deduce a control instruction for the addition of moistening means to the material. For example, the current consumption of the drive motor of a mixing implement immersed in the material to be mixed may be taken as a measure of the consistency of the material to be mixed. Such a deviceexhibits the disadvantage that only very special types of mixing implements may be utilized, which do not possess the kneading effect of pan or vessel-type mixers. For this reason, devices of this type have not received wide acceptance.

The basic object of the present invention is to provide a device for the regulation of the moisture content of granular material, such as, for example, molding sand, the device being in its manner of operation independent of the type of mixing implement used, and above all, independent of the wear rate of the mixing implements.

SUMMARY OF THE INVENTION Briefly, the apparatus according to the present inven- ,.tion includes a sensing element having at least one elastically flexible rod, one end of which is securely fixed and the other free end of which extends into the granular material. The rod is moved relative to the granular material. A measuring means is provided to detect the amount of elastic deflection of the rod or rods caused by the reaction thereof with the granular material, and the addition of moistening means to the granular material is controlled by a controllable valve as a function of the elastic deflection of the rod or rods.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a first embodiment of a regulator device of the present invention connected to a kneading mixer, shown in side view;

FIG. 2 is a top view of the regulator device shown in FIG. 1;

FIG. 3 illustrates an example of an embodiment of a skimmer connected to the sensing element; and

FIG. 4 illustrates an embodiment of the present invention with a sensing element having two rods, connected with a mixer, shown in side view.

Referring to FIGS. 1 and 2, a mixer l for granular material, for example molding sand, concrete, or the like, is comprised of a vessel or container 2 in which, with the vertical, driven shaft 12 of a crosshead 3, a rotating mixer and kneading implements 4 are arranged. In accordance with a first embodiment of a device for the regulation of the moisture content or moistening rate of the material to be mixed 7, an elastically flexible, rodlike sensing element 5 having for example a rectangular or circular cross section, is connected to crosshead 3 of mixer 1 such that its bottom, free end 6 extends downward into the material to be mixed 7 which is inside of vessel 2. At a predetermined distance in front of sensing element 5 in the direction of rotation as well as a predetermined distance above the bottom end 6 of sensing element 5, there is arranged the bottom end 16 of a scraperlike skimmer 8, which projects up out of the granular material. The lower end 16 of the skimmer 8 extends down into the granular material. A measuring means comprised of elasticity measuring element 10 is arranged immediately adjacent to the place where rod 5 is joined to crosshead 3. Measuring strips 10 vary in their electrical resistance values as a function of applied stress thereto.

The operation of the device of FIGS. 1 and 2 is now described. In rotating crosshead 3, the granular material 7 causes a deflection or bending of the elastically bendable rodlike sensing element 5, thereby influencing the elasticity measuring strips 10 and hence causing an alteration of the electrical resistances thereof. The resulting electrical resistance value is a measurement of the elastic deflection of rod 5 in consequence of the action thereon of the material to be mixed 7. The greater the consistency of the material 7, the greater will be the deflection of rod 5. Thus, the resistance values of strips 10 are a measure of the moisture content of said material.

The change of electrical resistance of strips 10 is conducted over slip rings 11 on shaft 12 to a measuring device, preferably a measuring bridge circuit 13, which is located outside of mixer 1. The output of measuring bridge 13 is fed to an amplifier 14 and the output from the amplifier 14 is conducted to an electrically actuated valve 15 which controls the introduction of liquid, for example water, into the material to be mixed 7 through pipe 17. The controllable valve 15 isopened to pass liquid in an amount correspondingto the values of deflection of rod 5. Liquid flows to the granular material 7 which is inside of vessel 2, until a desired degree-of moistening is achieved, at which time liquid flow is automatically caused to stop.

The measuring bridge circuit 13 is a well known type of circuit. The bridge 13 is adjusted so that when the consistency of the granular material'7 is a predetermined value, which corresponds to a predetermined deflection of the rod 5, the bridge preferably is nulled and produces no output. When the consistency deviates from the desired consistency, the electrical resistance value change in the strips 10 causes the bridge to become unbalanced and to thereby provide an output signal which is fed to the control valve to cause more liquid to be added to the granular material. In this manner, the result is a feedback type of system wherein the liquid is turned off automaticallywhen the granular material reaches the desired consistency, at which point the bridge circuit is nulled and produces no control output.

It is noted that the characteristic of the granular material 7 obtained'by means of the sensing element 5 may also be designated as fluidity. This characteristic is based on the same elementary characteristic of sand or concrete which also determines compressability, bulk density, or siftability, and relates to the same area of observation as the moisture content.

FIG. 3 illustrates a further embodiment of a skimmer in the form of a pipe 27 which is fixed to crosshead 3 of mixer 1 and surrounds rodlike sensing element 5. The bottom end 6 of sensing element projects out by a predetermined distance through the bottom end 28 of the pipelike skimmer 27, whereby the influences of different filling heights of the material 7 are compensated for. During operation of the device, a constant length of the contact surfaces of sensing element 5 is directly exposed to the granular material 7. The pipelike skimmer 27 performs substantially the same function as skimmer or scraper 8 in FIG. 1.

In the embodiment shown in FIG. 4 are two elastically flexible,

rodlike sensing elements

5, 5, which are, in the same way as rod 5 in the embodiment of FIGS. 1 and 3, connected to the crosshead 3 of mixer l and provided with deflection detecting strips 10. The

bottom ends

6, 6 of the two rods extend to different depths into the granular material 7 inside vessel 2. The elasticity strips arranged on the two sensing elements 5, 5' are (analogously as in FIGS. 1 and 2), in a manner not further shown, connected to a measuring bridge and amplifier and in an operational relationship with a preferably electromagnetically actuated valve, which regulates the addition of liquid means to the granular material inside the mixing vessel corresponding to the measured values obtained from the strips 10. Preferably such a circuit is utilized in such a way that for adding of liquid, the difference of the deflection values of the two different rods 5 and 5' acted upon by the material 7 is significant. The arrangement with two sensing elements extending into the granular material 7 at different depths permits the achievement of an especially high degree of accuracy in the regulation of the, moistening rate and the resulting moisture content of thematerial 7, and also largely independent of the filling rate of the mixer, so that under certain circumstancesa skimmer device (such as the one represented in FIG. 4 by scraper 8 and holder rod 9) may be dispensed with.

In the embodiment of FIG. 4, wherein the difference of the deflection values of the two

rods

5 and 5 is used to control the addition of moisture to the granular material 7, the generation of the difference signal may be generated by means of the bridge circuit and/or a differential amplifier. The signal is then amplified and utilized to control addition of moisture to the granular materiaLas desired.

In the above embodiments, the rods 5 are moved relative to the granular material by means of rotation imparted to the cross head 3. Itshould be clear that the rods could be rotated by other means, if desired.

The device of the present invention may be utilized for continuous as wellas charge-wise operation of the mixer.

It should be clear that various modifications to the present inventive concept may be made without departing from the inventive concept set forth in the claims. For example, the present invention is not limited to drum mixers of the type shown in the above examples, but could be used. with other mixers. Further, the particular type of detection circuitry used in the present invention may be modified, as required.

A typical bridge circuit for use in the present invention is shown in The International Dictionary of Physics and Electronics, Van Nostrand, 1961, p. 165. Other equivalent circuit arrangements could also be used.

We claim 1. Apparatus for automatically regulating the moisture content of granular material comprising:

at least one elongated elastically yieldable member fixed at one end thereof and adapted to extend a predetermined distance into said granular material at the other end thereof; means for moving said yieldable member relative to said granular material; sensing means connected to said yieldable member for detecting the elastic yielding thereof as'a result of said relative rotation;

controllable liquid supply means for introducing liquid means into said granular material; and means responsive to said, sensing means and coupled to said liquid supply means for controlling said introduction of said liquid means to change the consistency of said granular material in accordance with the elastic yielding of said yieldable member.

2. Apparatus according to claim 1, wherein said yieldable member is fixed at said one end thereof to a rotatable cross member, said yieldable member elastically yielding relative to said cross member.

3. Apparatus according to claim 2, wherein said sensing means includes a sensing strip coupled to said yieldable member immediately adjacent the fixed end thereof, an electrical characteristic of said sensing strip being varied in accordance with the elastic yielding of said yieldable member.

4. Apparatus according to claim 3, wherein said electrical characteristic is electrical resistance.

5. Apparatus according to claim 4, wherein said control means includes a bridge circuit for generating an output signal as a function of the electrical resistance of said sensing strip which corresponds to the amount of elastic yielding of said yieldable member.

6. Apparatus according to claim 1, wherein said sensing means includes a sensing strip coupled to said yieldable member, an electrical characteristic of said sensing strip being varied as a response of said elastic yielding of said yieldable member.

7. Apparatus according to claim 1, wherein said controllable liquid supply means includes an electrically controllable valve which supplies liquid in a quantity in accordance with the output of said control means.

8. Apparatus according to claim 1, comprising at least two elongated elastically yieldable members fixed at one end thereof and adapted to extend a predetermined distance into said granular material at the other end thereof, said two members extending to different depths into said granular material.

9. Apparatus according to claim 8, wherein said control means said liquid supply means as a function of the difference between the yielding of said at least two yieldable members.

10. Apparatus according to claim 1, including a skimming means arranged in a predetermined position relative to the position of said yieldable member, the lower edge of said skimming means-extending into said granular material to a lesser degree than the amount said yieldable member extends into said granular material, thereby determining the effective immersion depth of said yieldable member independently of the height of the granular material.

11. Apparatus according to claim 10, wherein said skimming means is a substantially flat member arranged ahead of said yieldable member in the direction of said relative rotation.

12. Apparatus according to claim 10, wherein said skimming means is a hollow pipe means surrounding said yieldable member.

13. Apparatus according to claim 12, wherein said hollow pipe extends into said granular material to a lesser depth than does thelower end of said yieldable member.

14. Method for automatically regulating the moisture content of granular material comprising:

moving an elongated elastically yieldable member relative to the granular material; sensing the elastic deflection of said yieldable member as the result of said relative rotation; and

controlling the amount of liquid introduced into said granular material as a function of said sensed elastic yielding of said yieldable member.

15. Method according to claim 14, comprising moving a pair of different length elongated elastically yieldable members relative to the granular material; and sensing the difference in elastic deflection thereof for controlling the amount of liquid introduced into said granular material.

Claims

1. Apparatus for automatically regulating the moisture content of granular material comprising: at least one elongated elastically yieldable member fixed at one end thereof and adapted to extend a predetermined distance into said granular material at the other end thereof; means for moving said yieldable member relative to said granular material; sensing means connected to said yieldable meMber for detecting the elastic yielding thereof as a result of said relative rotation; controllable liquid supply means for introducing liquid means into said granular material; and means responsive to said sensing means and coupled to said liquid supply means for controlling said introduction of said liquid means to change the consistency of said granular material in accordance with the elastic yielding of said yieldable member.

10. Apparatus according to claim 1, including a skimming means arranged in a predetermined position relative to the position of said yieldable member, the lower edge of said skimming means extending into said granular material to a lesser degree than the amount said yieldable member extends into said granular material, thereby determining the effective immersion depth of said yieldable member independently of the height of the granular material.

13. Apparatus according to claim 12, wherein said hollow pipe extends into said granular material to a lesser depth than does the lower end of said yieldable member.

14. Method for automatically regulating the moisture content of granular material comprising: moving an elongated elastically yieldable member relative to the granular material; sensing the elastic deflection of said yieldable member as the result of said relative rotation; and controlling the amount of liquid introduced into said granular material as a function of said sensed elastic yielding of said yieldable member.

15. Method according to claim 14, comprising moving a pair of different length elongated elastically yieldable members relative to the granular material, and sensing the difference in elastic deflection thereof for controlling the amount of liquid introduced into said granular material.