US3646437A

US3646437A - Sand moisture detector including a plow nose housing and roller electrode

Info

Publication number: US3646437A
Application number: US73709A
Authority: US
Inventors: Orville C Nutter
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-09-21
Filing date: 1970-09-21
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28
Also published as: CA920221A; GB1297483A

Abstract

Apparatus is provided for use in a moisture control system which responds to the conductivity of foundry sand disposed between two locations along a reach of a conveyor belt carrying a quantity of foundry sand. At each location there is a device which includes a plow for shaping the sand into a layer or swath of uniform thickness and a rotary electrode which rides in the layer, rotating with the movement of the layer past it. Rotation is achieved either by driving the rotary electrode by an electric motor, or by having the electrode ride on the reach and be driven by the passing belt. Scraper blades keep the exposed surfaces of the rotary electrodes free of adhering sand. The electrodes are mounted at a station which provides means for supporting the electrodes and moving them into position.

Description

Unite States Pate Nutter Feb. 29, 1972 [72] Inventor: Orville C. Nutter, 314 lngalton, West Chicago, Ill. 60185 [22] Filed: Sept. 21, 1970 21 Appl. No.: 73,709

Primary ExaminerEdward E. Kubasiewicz Attorney-Silverman & Cass [57] ABSTRACT Apparatus is provided for use in a moisture control system which responds to the conductivity of foundry sand disposed between two locations along a reach of a conveyor belt carrying a quantity of foundry sand. At each location there is a device which includes a plow for shaping the sand into a layer or swath of uniform thickness and a rotary electrode which rides in the layer, rotating with the movement of the layer past it. Rotation is achieved either by driving the rotary electrode by an electric motor, or by having the electrode ride on the reach and be driven by the passing belt. Scraper blades keep the exposed surfaces of the rotary electrodes free of adhering sand. The electrodes are mounted at a station which provides means for supporting the electrodes and moving them into position.

19 Claims, 9 Drawing Figures PATENTEDFEBZS I972 3,646,437

SHEET 3 OF 3 -Z 170 138 122 2&6 %g

SAND MOISTURE DETECTOR INCLUDING A PLOW NOSE HOUSING AND ROLLER ELECTRODE BACKGROUND OF THE INVENTION This invention finds particular utility in the art of conditioning foundry sand mixtures.

In foundries which are required to make castings on a production basis the sand mixture is used repeatedly and must be conditioned to enable such repetitive use. The finally used mixture must have uniform bulk density and must be of proper temperature and moisture content. Apparatus is known which mixes and mulls the sand and which cools it. Fresh sand and other ingredients may be added in the process of conditioning the sand.

In the process of conditioning sand water is generally added to materials having a variable amount of moisture to reach a preestablished percentage with as close an accuracy as possible to maintain consistent desirable molding properties of the material which is adversely affected by deviations of as little as plus or minus 0.25 percent.

One of the principal problems has been the difficulty of continuously and accurately sensing the moisture content of the material in order to determine the proper amount of moisture to be added to reach the required percentage after a final mixing.

In the prior art, the resistance between two points along a moving layer of sand is a part of an electrical circuit to indicate moisture content and/or to control the water addition required.

A Wheatstone bridge circuit has the sand resistance in one of its arms and a manually adjusted or preset control resistance between two of the arms provides a signal to control the moisture adding apparatus. The manual adjustment is a control potentiometer that in turn positions the degree of opening of a valve. When the bridge is balanced, a set amount of moisture is continuously added to give the desired percentage. The water will be sprayed on the moving mass of sand either before or after the station where the sensing is taking place. This is well known in the prior art.

In order to sense the moisture content of the moving mass of sand, a swath having a uniform layer is plowed at the measuring station, and two probes are provided spaced along the path of movement of the layer on the belt. These probes are electrodes that extend into the layer of sand so that they intercept the moving layer. Since foundry sand is a mixture, including various types of binders, the sand is sticky, even after it has been fluffed and mixed. Accordingly, in the past, the sand mixture adheres to the probes of the prior art, and builds up on these probes, thereby changing their electrical characteristics. For example, it is not unusual for the resistance between a pair of probes at the start of a run to increase several times after a few minutes of use, irrespective of whether there has been a change in the moisture content of the sand mixture. This buildup of a sand mass on one or both of the probes introduces such error into the measurement that the information acquired by the apparatus becomes practically useless. The alternative to such problem is to continuously clean the probes, a process which frustrates the desired benefit of automatic operation.

The invention herein solves the problem and provides a reliable and rugged apparatus for use in a moisture control circuit for foundry sand mixtures.

SUMMARY OF THE INVENTION According to the invention, in place of the prior art probes, the measuring station is provided with a pair of rotary electrodes that are in the form of wheels engaging into the uniform layer of sand provided by plows which are combined with the respective electrodes. The wheels are either mechanically driven by suitable motors or engage against the conveyor belt and are frictionally driven by the passing of the belt. Scraper blades keep the wheels clean of adhering sand. The electrical contact to each of the rotary electrodes is picked up by connecting a conductor to the metal bushing in which the shaft of the wheel is joumaled. This provides a wiping contact between shaft and bushing. The rotary electrode is mounted in a housing which is insulated, the housing in turn being supported in swinging condition from a suitable framework at the measuring station. The wheels of a pair of electrodes are staggered along the length of the moving layer of sand so that the follower electrode engages into a mass of sand that is of uniform thickness and is undisturbed by the passage of the leader electrode. Each electrode has a plow for levelling the sand layer prior to engagement of the electrode therein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a combined rotary electrode and plow with portions broken away to show the constructional details;

FIG. 2 is a top plan view of the combined electrode and plow of FIG. 1 taken generally on the line 22 and in the direction indicated;

FIG. 3 is a fragmentary sectional view taken generally along the line 3-3 of FIG. 1 and in the direction indicated;

FIG. 4 is a sectional view taken generally along the line 4-4 of FIG. 2 and in the direction indicated;

FIG. 5 is a fragmentary sectional view taken generally along the line 5-5 of FIG. I and in the direction indicated;

FIG. 6 is a perspective view of a measuring station using a pair of rotating electrodes, the same being shown with respect to the upper reach of the moving conveyor belt;

FIG. 7 is a side elevational view of a similar but slightly modified installation;

FIG. 8 is a diagrammatic view showing the manner in which the invention is used on a moving mass of sand; and

FIG. 9 is an end elevational view of the structure shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, the invention comprises rotary electrodes which are kept clean so that resistance measurements made by use of these electrodes will be accurate and not affected by any sand buildup. The electrodes are combined with plows that produce uniform thickness layers or swaths of sand into which the electrodes bite. There are at least two electrodes for each installation together with two plows. Electrodes are staggered with respect to the line of movement of the conveyor belt over which the electrodes are disposed so that the rear or followerelectrode will not engage in any grooves produced by the leader electrode. The rotary electrodes may be driven by motors independent of the movement of the belt or they may be driven by the belt itself. In some installations, one electrode may be motor-driven and the other may be friction-driven.

Looking now at FIGS. 1 through 5, there is illustrated a simplified form of a combined electrode and plow designated generally by the reference character 20. A housing 22 is provided for a metal wheel 24 which is suitably mounted for rotation with a substantial portion protruding from the bottom of the housing.

The housing of the structure 20 is formed of a central plate 26 of insulating material sandwiched between the

plates

28 and 30, also of insulating material. Each of the

plates

28 and 30 has a cylindrical bronze bushing mounted therein as shown at 32 and 34 in FIG. 5. The central plate 26 is provided with an arcuate recess 36 which is formed by cutting away the plate. The front end of the housing 22 has a greater vertical dimension than the rear end of the housing 22. A pair of

blocks

38 and 40 are engaged over the

outer plate

28 and 30 respectively to protect and cover the

bushings

32 and 34 respectively, these passing completely through the

respective plates

28 and 30. The

blocks

38 and 40 are held in place by suitable screws such as 42 screw-threaded into the

respective blocks

28 and 30. The

plates

28, 26, and 30 are clamped together by means of

suitable bolts

44 and 46 which pass through the same and are held in place by

nuts

48 and 50 respectively.

A steel wheel 24 has a stub shaft 54 affixed thereto, the stub shaft being journaled at its ends in the

bushings

32 and 34 respectively. A pair of annular spacers 56 center the wheel within the recess 36. The metallic wheel 24 makes a wiping electrical contact with the

bushings

32 and 34, and a screw 58 passing through the corner 68 of one of the

plates

28 and 30 is screw-threaded into the bushing 34 as shown in FIG. 1. An electrical lead 70 connects the screw 58 into the bridge circuit of the moisture-supplying device. Such bridge circuit is well known and hence need not be illustrated.

The right-hand end of the apparatus 20 of FIGS. 1, 2, and 4 is the leading end and hence the back end is at the left. As seen, a substantial portion of the wheel 24 protrudes at the bottom of the housing 22. The forward end of the housing is tapered to form the plow nose 72 that is intended to part oncoming sand while forming a swath having a uniform thickness. At the back end of the device 20, there is provided a pair of

scraper blades

74 and 76 mounted for scraping the wheel 24 just before the periphery of the wheel passes into the housing 22. These scrapers are formed of some insulating material such as an elastomer and are clamped between the clamping plates 78 and 811 and the

brackets

82 and 34 respectively. These brackets are in the form of strips of metal secured to the surface of the

respective plates

28 and 30 by means of the screws 86 with an intervening layer of insulating material such as an elastomer. The intervening elastomer layers are designated 88 and 90 and are best shown in FIG. 3.

An edge scraper 92 is mounted as shown in FIG. 1 to prevent buildup of sand on the edge of the wheel 24. The edge scraper 92 is secured to the bottom of the housing 22 at its narrower trailing end by means of the screws 94.

An elongate support plate 96 has depending

ears

98 and 100 that are engaged by the

bolts

46 and 44 respectively. At its front end, the support member 96 is provided with an eye 102 to enable the device 20 to be mounted in swinging condition on a suitable support structure. In this way, the weight of the device 20 would keep the wheel 24 riding on the reach of a conveyor belt causing the same to rotate as the belt moves by. Also, the device 20 could be swung up out of the way about the car 102 when it is not in use.

In order to prevent the sand from building up on the device itself, the plow nose 72 and most of the housing 22 is covered by a sheet of synthetic resinous material, such as tetrafluoroethylene. As seen, the protective sheet 104 covers the plow nose 72, the

blocks

38 and 40, and the

brackets

82 and 84. Any suitable means for holding the protective sheet 104 in place may be used, such as screws 106 engaging into various parts of the housing 22. An additional shaped sheet of this same material may be secured to the bottom of the device 20 as shown at 108. The purpose of the bottom sheet is to prevent sand from adhering to the bottom of the housing 22.

In use, the device 20 will ride on a belt 110, the frictional engagement between the belt and the wheel 24 causing the wheel to rotate in the direction indicated by the arrow of FIG. 1 as the belt moves to the left relative to the device 20. The plow nose 72 will divide the sand and provide a layer or swath of uniform thickness which is cut by the wheel 24.

The device 20 is driven by the belt 110, in which case, the wheel 24 is pennitted to contact the belt. By slight modification, it is feasible to have the wheel 24 driven by an electric motor or the like, in which case the wheel 24 will be spaced above the belt 1 slightly.

In use, there will be two electrodes," that is, two of the devices similar to but with the wheels staggered so that the trailing or follower wheel will not engage in a groove produced by the leader or forward wheel.

In FIG. 6, there is illustrated a belt 110 moving on a bed 112 to the left. This is the upper reach of the belt, the lower reach not being shown in this view but it is understood that the lower reach will be moving in the opposite direction. At the measuring station, there is a framework 114 supported by suitable standards 116, the framework carrying two devices, 120 and 122. Each device has some form of

support structure

124 and 126 respectively, such structure being the equivalent of the support plate 96 of FIG. 1. The front end of each of the devices and 122 is pivoted at 128 and 130 respectively, and, in this case, each support structure has a motor mounted thereon. The motor 132 is intended for driving the rotary wheel 134 of the device 120, and the motor 136 is intended to drive the rotary wheel 138 of the device 122. The rear ends of the

respective structures

124 and 126 engage suitable transverse support members such as shown at 140 and 142, such engagement being adjustable in order to adjust the spacing of the respective wheels from the belt 110. If desired the

entire devices

120 or 122 may be swung upon the

respective pivots

128 and 130 out of use. In each case, there is a

belt

144 and 146 driven by the

respective motors

132 and 136, these belts being engaged over suitable sheaves (not shown) secured to the shafts of the respective lheels 134 and 138.

In FIG. 7, a modified form of the structure of FIG. 6 is shown, such modification consisting of remoing the belt 144 and lowering the front device 120 so that the front device 120 has its wheel 134 engaging the belt 110 and is frictionally driven by the belt. As will be seen, the trailing device 122 has its wheel 138 slightly spaced above the belt I10 to permit the motor 136 to drive the wheel 138. In FIG. 6, if the device 120 is connected to be driven by the motor 132, its wheel 134 will also be spaced above the belt 110, but, in FIG. 7, the belt 144 has been removed and the wheel 134 is therefore lowered to come into frictional engagement with the belt 110 so that it is driven by the belt 110 during the movement.

A simple mechanism is shown at 143 and in FIG. 7 for adjusting the positions of the

respective support structures

124 and 126 above the belt 110.

Looking now at the diagram of FIG. 8, it can be seen that the belt 110 has a mass of sand 150 moving to the left as viewed in FIG. 8 supported on the belt. The sand is the mixture used for forming molds and ahead of the measuring apparatus it may have masses of nonuniform thicknesses on the belt. The device 120 includes a plow nose 152 and apair of the wheels 134, which are either driven by the electric motor 132 or driven because of frictional engagement with the belt 1 10. The wheels 134 are mounted on a shaft 154, and, for purposes of driving the same by a motor, a sheave is shown at 156. Scraper blades designated are provided to keep each of the wheels 134 clean. Note that two pair of such blades are provided where the device has a pair of electrode wheels.

The plow nose 152 produces a swath of uniform thickness of sand, as indicated at 162. Each of the wheels 134 therefore will always engage into a uniform layer of sand. The trails or grooves caused by the wheels 134 are shown at 164. The follower or trailing device 122 also has a plow nose 166 which maintains the swath of substantially uniform thickness on the belt 1 10, this swath or strip being shown at 168. The trailing or follower wheel 138 thus engages in a layer of sand 168 which is of uniform thickness. It also has the scrapers 170 to keep it clean.

The belt returns in a lower reach 111 as shown in FIGS. 7 and 9.

It will be seen that the

wheels

134 and 138 are staggered with respect to one another along the length of belt 1 10 so that in the event the grooves 164 are not smoothed and filled in by the plow 166, there will still be a clear track for the wheel 138.

In FIG. 7 there is illustrated an electrical lead 172 which connects to the bearing of the wheel 134 by way of a suitable screw 174, and the electrical lead 176, which connects through the screw 178 to the bearing of the wheel 138.

There will be a thermistor engaging into the sand 150 in the vicinity of the measuring station illustrated in FIGS. 6 through 9. This is not shown in the drawings since it forms no part of the invention.

As previously indicated there is a wheatstone bridge for controlling the amount of water that will be added to the sand. One balance leg of the bridge is the sand which is subtended between the electrode wheels of the apparatus, such as for example between the

wheels

134 and 138. The other comtntnm: and

ponents of the bridge are adjusted manually so that a balanced condition will not energize the water-adding apparatus. When an unbalance occurs, as occasioned by an increase in the resistance between the rotary electrodes, water will be added. The conductivity of sand decreases when the moisture content decreases. So long as the electrodes are keptclean, the resistance measured between electrodes will be a substantially true function of the moisture content of the swath of sand and hence will provide reliable and reproducible information,

Various modifications may be made without departing from the scope of the invention as defined in the appended claims.

What it is desired to secure by Letters Patent of the United States is:

1. An apparatus for measuring the moisture content of pulverulent material passing along the reach of a conveyor belt and which includes a measuring station having a pair of electrodes spaced from one another along the length of the belt and adapted to engage the passing mass of material electrically to contact the same for responding to the conductivity of the material between the electrodes, the electrodes each comprising a wheel of conductive material arranged to rotate in a vertical plane normal to the belt reach, and parallel with the line of movement thereof, each electrode having means for supporting the same over the reach and being insulated from said support means, housings carrying the respective electrodes and each having a forwardly directed plow nose spaced above the reach whereby to form a swath of pulverulent material of uniform thickness as the mass passes, each wheel being spaced rearwardly of its plow nose and arranged to engage into a swath, means for connecting an electrical lead to each wheel in a wiping contact, means adjacent the rear edge of each wheel for scraping off any material picked up by the wheel while rotating, and means for rotating each wheel while the belt is moving past the same.

2. The structure as claimed in claim 1 in which said lastmentioned means comprise the belt reach, one of said wheels being frictionally engaged to the belt reach on its bottom edge.

3. The structure as claimed in claim 1 in which said lastmentioned means comprise an independent source of rotation carried on one of said supporting means and mechanically connected to a wheel, the bottom edge of the wheel being slightly spaced above the belt reach.

4. The structure as claimed in claim 1 in which one of said means for rotating comprises an independent source of rotation carried on said supporting means and mechanically connected to one of said wheels with the bottom edge of said one wheel spaced above the belt reach, and the second of said means for rotating comprises the belt reach, the second of said wheels having its bottom edge in engagement with the belt reach.

5. The structure as claimed in claim 1 in which the wheels lie in planes which are parallel to and spaced from one another whereby the electrodes are staggered along the belt reach.

6. The structure as claimed in claim 1 in which each supporting means is pivotally mounted to enable the swinging of the electrode housing to carry its electrode into or out of the path of the moving mass of pulverulent material.

7. The structure as claimed in claim 1 in which at least the plow nose is covered by a resinous member that resists adherence of said pulverulent material thereto.

8. The structure as claimed in claim 1 in which said lastmentioned means comprise an independent source of rotation carried on the supporting means of each of said electrodes and being respectively connected to said wheels, the bottom edges of the said wheels being slightly spaced above the belt reach.

9. The structure as claimed in claim 2 in which the supporting means includes a pivotal connection at one end of the housing with the remainder of the housing being free to swing downwardly whereby the weight of the housing and electrode carries the same into said frictional engagement with the belt reach.

10. The structure as claimed in claim 1 in which one wheel is mounted in its housing as a single wheel and the other wheel has a tlurd wheel coaxial therewith m its housing whereby to form a pair of spaced wheels, the plane of the single wheel being parallel with and disposed between the planes of the pair of wheels.

11. The structure as claimed in claim 10 in which the housing with the pair of wheels is forward of the housing with the single wheel whereby the single wheel will not engage any grooves formed in the swath produced by the pair of wheels.

12. The structure as claimed in claim 1 in which said scraping means include blades juxtaposed relative to opposite faces of the wheel.

13. The structure as claimed in claim 1 in which said scraping means include blades juxtaposed relative to opposite faces of the wheel and a scraping member arranged to remove pulverulent material from the edge of the wheel.

14. For use with apparatus for measuring the moisture content of pulverulent material passing along the reach of a conveyor belt, an electrode adapted to engage in said pulverulent material and be supported over the belt to make electrical contact with said material, said electrode comprising:

a housing of insulating material having a recess in the center thereof and a plow nose, a wheel of conducting material joumaled in said recess and having a substantial portion thereof protruding from the bottom of said housing, means for making an electrical wiping contact with said wheel and means at one edge of said wheel arranged to scrape pulverulent material from the exposed portions of said wheel as the wheel is rotated.

15. The electrode of claim 14 in which there is a covering at least over the plow nose which is made of a resinous material to which pulverulent material will not adhere.

16. The electrode of claim 14 in which the means for making contact comprise bushings of conductive materials in said housing, said wheel being journaled in said bushings, and there being a conductive member extending from one of said bushings to the exterior of said housing.

17. The electrode of claim 14 in which the scraping means comprise a pair of opposite blades engaging the exposed faces of the wheel adjacent one edge thereof opposite said plow nose.

18. The electrode of claim 17 in which said blades are formed of an elastomeric material.

19. The electrode of claim 17 in which there is an additional scraper slightly spaced from the said one edge for preventing buildup of pulverulent material on the edge of said wheel.

Claims

2. The structure as claimed in claim 1 in which said last-mentioned means comprise the belt reach, one of said wheels being frictionally engaged to the belt reach on its bottom edge.

3. The structure as claimed in claim 1 in which said last-mentioned means comprise an Independent source of rotation carried on one of said supporting means and mechanically connected to a wheel, the bottom edge of the wheel being slightly spaced above the belt reach.

8. The structure as claimed in claim 1 in which said last-mentioned means comprise an independent source of rotation carried on the supporting means of each of said electrodes and being respectively connected to said wheels, the bottom edges of the said wheels being slightly spaced above the belt reach.

10. The structure as claimed in claim 1 in which one wheel is mounted in its housing as a single wheel and the other wheel has a third wheel coaxial therewith in its housing whereby to form a pair of spaced wheels, the plane of the single wheel being parallel with and disposed between the planes of the pair of wheels.

14. For use with apparatus for measuring the moisture content of pulverulent material passing along the reach of a conveyor belt, an electrode adapted to engage in said pulverulent material and be supported over the belt to make electrical contact with said material, said electrode comprising: a housing of insulating material having a recess in the center thereof and a plow nose, a wheel of conducting material journaled in said recess and having a substantial portion thereof protruding from the bottom of said housing, means for making an electrical wiping contact with said wheel and means at one edge of said wheel arranged to scrape pulverulent material from the exposed portions of said wheel as the wheel is rotated.