EP0148216A1 - Weighing flowable material - Google Patents

Abstract

The apparatus described below is used to weigh a flowable material such as edible grains, crushed ores and liquids. The material enters a region of a hopper (1) and passes through a grid (2). The screen (2) makes it possible to prevent unwanted objects such as animals from entering the edible grains, and also serves to dissipate or scatter the flow of product on the base of the hopper (1). The flow of product passing through the screen (2) is directed by gills (28) so as to indirectly reach new gills (8). These new openings (8) are equidistant and parallel to an entry plane inclined at 35o with respect to the horizontal and defining a plurality of weir-type structures which progressively go up. After leaving the openings (8), the material passes directly down into a weighing tank (15). The weighing tank (15) comprises a row of bars equidistant from each other and placed at right angles to the members of the openings (8). When the flowable material passes through the weighing tank (15), the resistance produced by the passage of the material affects the load cell (9) to which the weighing tank (15) is attached and produces an electrically detectable signal proportional to the flow of the flowing material. The device can have a rectangular or circular shape.

Description

"WEIGHING FLOWABLE MATERIAL" This invention relates to improvements in apparatus for the continuous weighing of flowable materials. Such materials include grains such as wheat and rice, broken mineral such as coal and possibly liquids as well.

BACKGROUND ART The invention particularly relates to apparatus of a known kind which include weigh pans suspended in the material flow path and connected to weight recording apparatus. Unfortunately the prior known devices of this type have been found to be quite inconsistent with their results giving variations as high as 10%. These inconsistencies have been found particularly great at low flow rates. It is. therefore an object of the present invention to provide apparatus which will ameliorate disadvantages of the prior art.

DISCLOSURE OF THE INVENTION Accordingly, in one broad form, the present invention may be said to provide a weigh pan in apparatus for continuous weighing of flowable material, said weigh pan comprising: a rigid support member for attachment to a weight recording device; and at least one pan surface including an array of surface discontinuities arranged symmetrically about a central point or axis.

Preferably the apparatus including the weigh pan described above is such that the at least one pan surface includes two pan surfaces each defined by a two dimensional array of parallel equally separated wires extending perpendicular to a central longitudinal axis, the two pan surfaces extending in mutually opposite directions from the longitudinal axis of the weigh pan; and the apparatus further includes: an array of control louvres disposed in the material flow path immediately before the weigh pan and including a plurality of laterally spaced louvres with their longitudinal axes being parallel to the longitudinal axis of the weigh pan.

It is further preferred that the apparatus includes a dispersal pan disposed in the material flow path immediately before the array of control louvres and adapted to uniformly disperse material flowing thereby on to preselected portions of the array of control louvres. BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, various preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:

Fig. 1 is a view of a preferred embodiment of the invention showing internal detail thereof;

Fig. 2 shows section A-A of the device of Fig. 1; Fig. 3 shows section B-B of the device of Fig. 1; Fig. 4 shows section C-C of the device of Fig. 1; Fig. 5 shows a portion of the device of Fig. 1; Fig. 6 shows a portion of a device common to the embodiments shown in the drawings;

Fig. 7 shows a second embodiment of the invention; Fig. 8 is a view of section E-E of the device of Fig. 7; Fig. 9 shows section D-D of the device of Fig. 7; Fig. 10 shows a third embodiment of the invention; Fig. 11 shows section F-F of the device of Fig. 10; Fig. 12 shows an alternative arrangement to that shown in Fig. 11; Fig. 13 shows section H-H of the device of Fig. 10; Fig. 14 shows a plan view of a further embodiment of the invention;

Fig. 15 shows in section the elevation of the device of Fig. 14; Fig. 16 shows section J-J of the device of Fig. 15; and Fig. 17 shows section K-K of the device of Fig. 15.

BEST MODE OF CARRYING OUT THE INVENTION Flowable material to be weighed enters the apparatus via a hopper type structure 1 which directs the material through a dissipative and direction screen 2 to enter an array of parallel inclined louvers 28. One side wall 3 of the hopper 1 is pivoted at 4 so as to allow the side 3 to be opened for the removal of built up debris which can collect

M above the dissipative screen 2.

After leaving the louvers 28 the material enters an enlarged volume 6 with a velocity generally including a horizontal element, during passage through the volume 6 the flowable material is generally redirected so as to include a horizontal value in an opposite direction before entering a further array of louvers 8.

The further array of louvers 8 defines a generally inclined entry area with the upper tips of the individual louvers 8 defining weir type structures of constantly increasing height. In operation it is found that the flowable material firstly finds its way to the lowest opening of the louvers 8 to flow therethrough, once one of the openings of the louvers 8 becomes "full" of flowable material excess material entering the enlarged volume 6 will spill over the next highest weir like structure to exit down the next opening of the louvers 8. Thus in operation there will be material flowing through some number of the openings of louvers 8 with no material flowing through the remaining openings. The number of openings through which material is flowing will be dependent upon the volume of the material entering through hopper like device 1. Furthermore, the openings of the louvers 8 are sized relative to one another so that the velocity of the material flowing out through each of the openings of louvers 8 is equal to the velocity of the material flowing out through the other of the openings of louvers 8.

After the flowable material leaves the louvers 8 it impinges upon the weigh pan 15. The weigh pan 15 is attached via a structure 12 to a load cell 9 which is in turn connected to a weigh pan carriage 11 for vertical adjustment of the positioning of the weigh pan 15. A further adjustment is included in structure 12 to allow adjustment of the inclined angle of the weigh pan 15. The load placed upon load cell 9 will be proportional to the flow rate of the material passing through the device.

A clearer appreciation of the various structures of the device of Fig. 1 is readily obtained by considering Figs. 2 to 4 showing respectively in detail the dissipative screen 2 and associated inclined louvers 28, louvers 8, and weigh pan 15.

In the embodiment of Fig. 1 a weigh pan 15 is seen to comprise an array of parallal equally spaced rods which extend fully across the area exposed to the downwardly falling flowable material. The louvers 8 can be seen in Fig. 3 to be orientated at 90° to the grid pattern of weigh pan 15- Further, the plane of entry into louvers 8 defined by the upper lines of the louvers 8 is parallel to the plane of weigh pan 15. The inclination to the horizontal of these two structures is preferably 35°.

For accurate setting of the device the weigh pan carriage 11 is adjustable vertically and an adjustment scale, shown in Fig. 5, can be seen from the exterior of the device and is calibrated according to the type of material being weighed. It has been found that by adjusting the vertical position of the weigh pan carriage 11 so as to take into account particular grain sizes, moisture content, and density of material being weighed accurate readings for a large variety of flowable materials can be obtained.

The device shown in Fig. 7 can be substantially considered as being two of the devices shown in Fig. 1 combined along side the other. Hopper region 1, dissipative screen 2, inclined louvers 28, second array of louvers 8 and weigh pans 15 are all present.

The actual form of the louvers 8 in the embodiment shown in Fig. 7 is somewhat different from that of Fig. 1 as they are formed from straight plate like structures. However the essential features of the louvers being the equally sized openings therebetween and the inclined entry portion defined by the upper lines of the individual louvers are common to both embodiments. It is further seen that in the volume 6 the flowable material passing through the device is redirected a number of occasions so that it does not fall directly onto the second array of louvers 8.

As seen in Figs. 8 and 9 the various arrays defined by the weigh pan 15, louvers 8, dissipative screen 2 and

OM louvers 28 generally run, in the horizontal plane, at right angles to the respective adjacent arrays. Further the angle to the horizontal weigh pan 15 is again equal to the angle defined by the top lines of the louvers 8, being preferably 35°.

The device is not restricted to rectangular constructions such as those of Figs. 1 and 7 but may be of a circular design as shown in the devices of Figs. 10 and 15. The device shown in Fig. 10 is circular in its symetry and includes a weigh pan 15 which is downwardly convergent. The weigh pan 15 in this case may be generally as shown in Fig. 11 being supported by equally spaced load cells 10. The vertical positions of the three support points being adjusted so that the pan 15 is located horizontally. The pan 15 may also be of the general structure shown in Fig. 12 which has half of the radial bars extending for only half radial distance. This more accurately equalizes the area between adjacent bars along the radial extent of the weigh pan 15. This is found to produce a more accurate result. As shown in Fig. 13 the louvers 8 immediately above the weigh pan 15 comprise a number of concentric rings. These ara again equal spaced so as to provide a constant velocity of flowable material passing therethrough. Furthermore the lines defined by the upper edges of the individual louvers 8 is inclined at approximately 35° being equal to the inclination of the individual bars of the weigh pan 15.

The flowable material passing through the device of Fig. 10 passes the dissipative screen 2 to be deflected outwardly before travelling down a converging channel directing the material inwardly. The flowable material, as in the previously described embodiments, therefore does not fall directly onto the louvers 8.

The device shown in Fig. 15 is another circular based device but with a downwardly diverging weigh pan 15. The first louvers 28 and intermediate louvers 8 are shaped somewhat differently from those of the embodiment shown in Fig. 10, but as it will be seen, has a similar effect of controlling the exit velocity from louvers 8 before impinging upon the weigh pan 15. The device of Fig. 15 may be suspended by a single centre load cell 10 and it has been found that small pendulum type movements of weigh pan 15 do not deteriorate the accuracy of the device.

Common to all of the above described devices is an electronic unit, the face of which is shown in Fig. 6, for calibration of the device and forming a human readable output. Primarily the electronic unit receives information from the load cell to produce pulses representing a preselected mass. By counting the numbers of pulses in any given time period the total mass of material for that time period can be measured and further the average or instantaneous flow rate can be determined. The device may include card stamping facilities and similar so as to produce permanent hard record of the amount of material received from the weighing unit.

The electronic unit can be calibrated so as to take into account any temperature changes which might effect the device. Further, by including moisture measuring apparatus 26, electrically connected to the electronic device, the real mass of wet or damped material passing through the device can be instantly calculated rather than having to rely on the weight of the material plus unwanted moisture therein.

As can be seen the invention may be embodied in a number of varying shaped devices. It can also be made in a number of sizes to accommodate different capacities- Smaller devices will be easily transportable while the actual weight of larger devices would make then permanent. Various parts of each of the embodiments may be hinged or removable so as to provide access for cleaning.

It has been found that due to the stress applied to a number of the components that high tensile steel is required in a number of components. Of course future technology may well provide economical feasible alternatives to high tensile steel which could advantageously be used as a substitute.

Claims

1. A weigh pan in apparatus for continuous weighing of flowable material, said weigh pan comprising: a rigid support member for attachment to a weight recording device; and at least one pan surface including an array of surface discontinuities arranged symmetrically about a central point or access.

2. Apparatus including the weigh pan of claim 1 and an array of control louvers disposed in the material flow path immediately before the weigh pan, the control louvers including a plurality of laterally spaced louvers with their longitudinal axes being perpendicular to the longitudinal direction of said surface discontinuities.

3. Apparatus as defined in claim 2 wherein a dissipative screen is included in the material flow path immediately before said array of control louvers and adapted to uniformally dispers material flowing therethrough.

4. Apparatus as defined in claim 2 or 3 wherein said weigh pan is substantially rectangular comprising an array of parallel equally spaced bars.

5. Apparatus as defined in any one of the claims 2 to 3 wherein said weigh pan is of a frustro conical construction comprising an array of equally angularly spaced radial bars.

6. Apparatus as defined in any one of the claims 2 to 5 wherein said array of control louvers includes upper edges of the individual louvers being aligned to form an inclined upper plane angled at 35° to the horizontal.

7. Apparatus as defined in claim 6 wherein the plane defined by said weigh pan is parallel to the plane defined by the upper edges of the individual louvers of said array of control louvers.

8. Apparatus as defined in claim 7 wherein the louvers of said array of control louvers are equally spaced from one another so that material to be weighed passing therethrough exits from said control louvers at a controlled speed being equal for all said louvers.

9. Apparatus as defined in claim 3 wherein there is

OMPI disposed between said dissipative screen and said control louvers means directing the flow of material flowing therethrough so as not to impinge directly onto said control louvers.

10. Apparatus as defined in claim 9 wherein said means directing the flow comprise a further array of inclined louvers.

OMP