A weighing apparatus and a calibration method therefor

Abstract

The invention relates to a weighing apparatus comprising a silo (10) having an inlet (15) for raw material and an outlet (17) equipped with a dosing apparatus (60), a support leg (16) at least partially surrounding the silo (10), and at least one load cell (50) on which the support leg (16) is disposed to measure the weight of the silo (10). The weighing apparatus is wherein the dosing apparatus (60) fixed on the silo (10) includes a determined calibration weight proportional to a predetermined dosing range, and the load cell (50) is calibrated with the calibration weight (40).

Description

[0001] A WEIGHING APPARATUS AND A CALIBRATION METHOD THEREFOR

[0002] TECHNICAL FIELD

[0003] The present invention relates to weighing apparatuses and a calibration method for weighing apparatuses.

[0004] BACKGROUND ART

[0005] Weighing systems are generally in the form of one or more load cells; where the load cells can provide a representation of the force applied to the load cell via the tank, and where the representation can be used to derive a unit representing a load, the weight or mass of the tank and / or the contents of the tank. Weighing systems need to be periodically calibrated to ensure that they accurately represent the mass present within the container. The total measurement error (%RO) (accuracy) of standard load cells is 0.015% of the full-scale weight measurement range. This measurement error consists of errors caused by the manufacturing technique, which are constant with temperature and time, and in addition, errors that vary with time and temperature.

[0006] WO2023067128A1 relates to a weighing device calibration system. The present invention is a calibration device for weighing systems, where the calibration device can be configured to apply a force between a first part and a second part, between a container and a base. The calibration device includes a fixed assembly and a dynamic assembly in use, where the dynamic assembly is configured to move relative to the fixed assembly. The fixed assembly includes: a first connecting piece configured to be connected to a container or a base, an actuator device body, a load cell having a first end and a second (load-receiving) end, where the first end is mechanically connected to the actuator device body and the second end is mechanically connected to the first connecting piece. The dynamic assembly includes: a second connecting piece configured to be connected to a container or a base (foundation), a movable part that moves back and forth along the device body in a force application axis, and a movable rod connected to the movable part and connected to the second connecting piece.

[0007] BRIEF DESCRIPTION OF THE INVENTION

[0008] The object of the invention is to increase the measurement accuracy of a weighing system capable of dosing. In order to achieve the above objective, the invention relates to a weighing apparatus comprising a silo equipped with an inlet for raw material and an outlet equipped with a dosing apparatus, a support leg at least partially surrounding the silo, and at least one load cell on which the support leg is disposed to measure the weight of the silo. The weighing apparatus is wherein the dosing apparatus fixed on the silo having a determined calibration weight proportional to a predetermined dosing weight, and the load cell is calibrated with the calibration weight. This enables achieving higher measurement accuracy in small weight ranges and (in the intended dosing range) by utilizing the continuity / uninterruptedness of the measurement signal and measurement error of the load cell. The number of load cells can be two, three, or four. The load cells can be analog or digital type.

[0009] In a preferred embodiment of the invention, the ratio of the dosing range to the calibration weight is in the range of 0.5 to 1 .5. This ensures that the load cell is calibrated at low weights, thereby reducing the tolerance of the dosed raw material.

[0010] In a preferred embodiment of the invention, it includes at least one calibration weight lifting unit to which the calibration weight is fixed. This enables weight measurement and calibration by hanging the calibration weights removably on the calibration weight lifting unit. The lifting unit can be two, three, or four lifting units disposed at equal angles.

[0011] In a preferred embodiment of the invention, the calibration weight lifting units are provided at opposite ends of the silo. This eliminates errors that may arise from the position of the weight during measurement when the weights are fixed.

[0012] In a preferred embodiment of the invention, by connecting different calibration weights and lifting units to the silo, the system can obtain measurements with similar accuracy in different dosing ranges.

[0013] In a preferred embodiment of the invention, a piston or any lifting system is used as the calibration weight lifting unit. This allows for precise weight measurement.

[0014] In a preferred embodiment of the invention, the load cells are symmetrical with respect to the central axis of the silo. This ensures precise measurement by providing a symmetrical weight balance of the silo at two, three, or four points.

[0015] In a preferred embodiment of the invention, the calibration method includes the step of calibrating the load cells with two measurements taken during the steps of lifting the calibration weights with lifting mechanisms connected to the silo and lowering them back to the ground. This improves measurement accuracy, ensures a low + / - tolerance for the amount of dosed raw material, and minimizes raw material loss.

[0016] BRIEF DESCRIPTION OF THE FIGURES

[0017] Figure 1 schematically shows the weighing system according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In this detailed description, the development according to the invention is explained with reference to examples, without any restriction and only to better illustrate the subject matter. Figure 1 schematically shows the weighing apparatus according to the invention. The weighing apparatus includes a silo (10) in which raw material in liquid, powder, or granular form is supplied. A first support arm (12) is provided on a first lateral wall (11 ) of the silo (10). A second support arm (14) is provided on a second lateral wall (13) of the silo (10). The first and second support arms (12, 14) are located symmetrically with respect to the central axis of the silo (10). The necessary raw materials are supplied into the silo (10) from a raw material inlet (15) provided at an upper end (18). The raw materials supplied from the raw material inlet (15) are discharged by the force of gravity from a feeding outlet (17) provided at a lower end (19). The feeding inlet (15) and the feeding outlet (17) are located on the silo (10). The feeding outlet (17) of the silo (10) extends outwards. The circumference of the silo (10) is surrounded by a support leg (16) in the form of a flange that at least partially surrounds it. A lifting unit (20) is fixed at a fixed end (22) to the first support arm (12) of the silo (10). A calibration weight (40) is attached to a free end (24) of the lifting unit (20). A second lifting unit (30) is fixed at a fixed end (32) to the second support arm (14) of the silo (10). A calibration weight (40) is attached to a free end (34) of the second lifting unit (30). A load cell (50) is disposed on an extension (162) of the support leg (16) of the silo (10). Two, three, or four load cells (50) are provided symmetrically with respect to the central axis of the silo (10). The load cells (50) are fixed on a base (70). The raw materials are dosed from the outlet part of the silo (10) by a dosing apparatus (60). The dosing apparatus can be a screw feeder, a vibratory feeder, a rotary feeder, or a valve for liquid dosing.

[0019] In the calibration method, the calibration weights (40) are removably attached to the lifting unit (20) and the second lifting unit (30) provided on the first and second support arms (14, 12) on the silo (10). The weight information read from the load cells (50) on the silo (10) with the calibration weights (40) attached is recorded, then the weight information read from the load cells (50) after being lifted by the lifting units (20, 30) is also recorded. The load cell (50) is calibrated by the ratio of the first and second weight measurement results.

[0020] In an exemplary calibration method, in a silo (10) whose total weight with the raw material inside reaches 10,000 kg, the difference between the read weight and the actual weight of the raw material in the silo (10) can vary between minus 1 .5 kg and plus 1 .5 kg. For example, when 15 kg of raw material is dosed from the silo, the actual weight of the dosed raw material can vary between 13.5 kg and 16.5 kg. This weighing accuracy, when calculated as a percentage of the weighed raw material, is 10%. A load cell (50) that makes a +-1.5 kg error throughout the entire measurement range, for example, will have a smaller measurement error in the range of 8,000 kg to 8,200 kg. A measurement that makes a +1.5 kg error at 8,000 kg will make a +1.4 kg error at 8,200 kg, meaning the measurement error varies not in the +-1 .5 kg range but in the +1.4 to +1.5 range. When we calibrate the load cell (50) within this range, the measurement error will be ((1 .5-1 .4) / 2=0.05) +-0.05 kg. In this way, when 15 kg of raw material is dosed from the silo (10), a measurement error of +-0.05 kg is obtained, and the actual weight of the dosed raw material varies between 14.95 kg and 15.05 kg. In this case, the weighing accuracy, when calculated as a percentage of the weighed raw material, will be 0.33% (0.05 / 15=0.0033). To dose raw material between 0-20 kg from a 10,000 kg capacity silo, a calibration weight of around 20-25 kg is attached to the silo (10). This calibration weight is connected to the lifting units (20, 30) attached to the silo (10). The load cell is calibrated using the ratio when the calibration weights are attached and not attached in the 20-25 kg weight range.

[0021] REFERENCE NUMBERS

[0022] 10 Silo 20 Lifting Unit

[0023] 11 First Lateral Wall 22 Fixed End

[0024] 12 First Support Arm 24 Free End

[0025] 13 Second Lateral Wall 30 Second Lifting Unit

[0026] 14 Second Support Arm 32 Fixed End

[0027] 15 Raw Material Inlet 34 Free end

[0028] 16 Support Leg 40 Calibration Weight

[0029] 162 Extension 50 Load Cell

[0030] 17 Outlet 60 Dosing Apparatus

[0031] 18 Upper End 70 Base

[0032] 19 Lower End

Claims

CLAIMS1. A weighing apparatus comprising a silo (10) having an inlet (15) for raw material and an outlet (17) equipped with a dosing apparatus (60), a support leg (16) at least partially surrounding the silo (10), and at least one load cell (50) on which the support leg (16) is disposed to measure the weight of the silo (10) characterized in that the dosing apparatus (60) fixed on the silo (10) having a determined calibration weight (40) proportional to a predetermined dosing range, and the load cell (50) is calibrated with the calibration weight (40).

2. A weighing apparatus according to Claim 1 , wherein the ratio of the dosing weight to the calibration weight is in the range of 0.5 to 1 .5.

3. A weighing apparatus according to any of the preceding claims, the calibration weight is fixed to at least one lifting unit (20, 30) to which.

4. A weighing apparatus according to Claim 3-4, wherein a piston is utilized as the lifting unit (20, 30).

5. A weighing apparatus according to any of the preceding claims, wherein the load cells (50) are symmetrical with respect to the central axis of the silo (10).

6. A weighing apparatus according to any of the preceding claims, wherein the support leg (16) has a flange structure.

7. A weighing apparatus according to any of the preceding claims, wherein the inlet part (15) of the silo (10) is provided at an upper end (18), and the outlet part is provided at a lower end (19) provided opposite to the upper end (18).

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