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WO2019229549A1 - Dispositif de cellule dynamométrique - Google Patents

Dispositif de cellule dynamométrique Download PDF

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Publication number
WO2019229549A1
WO2019229549A1 PCT/IB2019/052695 IB2019052695W WO2019229549A1 WO 2019229549 A1 WO2019229549 A1 WO 2019229549A1 IB 2019052695 W IB2019052695 W IB 2019052695W WO 2019229549 A1 WO2019229549 A1 WO 2019229549A1
Authority
WO
WIPO (PCT)
Prior art keywords
cantilever element
deformable body
load cell
elastically deformable
cantilever
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2019/052695
Other languages
English (en)
Inventor
Gilberto ROMBOLI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nanolever Srl
Original Assignee
Nanolever Srl
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nanolever Srl filed Critical Nanolever Srl
Publication of WO2019229549A1 publication Critical patent/WO2019229549A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
    • G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
    • G01G3/14—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of electrical resistance
    • G01G3/1414—Arrangements for correcting or for compensating for unwanted effects

Definitions

  • the present invention relates in general to the sector of weighing devices for packaging lines and in particular to a load cell capable of eliminating the apparent weight due to the vibrations produced by the automatic machine on which it is installed.
  • a load cell is a transducer used for measuring a force applied to a body.
  • the most common application of load cells is in electronic weighing systems and in the measurement of mechanical compressive and tensile stresses.
  • a load cell generally comprises a measuring body made of metal, typically steel or aluminium, applied on which is a force that causes a deformation thereof.
  • bending-beam load cells In dynamic measurements of weight, so-called bending-beam load cells are used, which comprise a parallelepipedal body made in which is a butterfly-shaped through opening, which enables the body, appropriately mounted in cantilever fashion on a support, to bend with the movement of a parallelogram.
  • bending-beam load cells afford the advantage of not requiring any alignment between the loads applied and the axis of deformation of the body measuring body.
  • a load cell with resistive strain gauges the latter can be glued in appropriate points of the deflecting body in such a way that, by undergoing deformation, they modify their electrical resistance.
  • the variation of voltage is the signal that is amplified and processed so as to be transduced into the value of the weight.
  • Dynamic measurement of weight is carried out on packaging lines provided with a plurality of apparatuses and devices that typically generate vibrations in a very wide frequency spectrum, which ranges from a few hertz up to several kilohertz, the accelerations of which give rise to an apparent weight that adds to the gravitational weight of the object to be measured.
  • the oscillatory forces transmitted to the load cells significantly worsen the standard deviation of the population of the averaged signals all the more the lower the frequency of the vibrations as compared to the sampling frequency .
  • EP 0 635 703 A1 discloses the combination of a weighing cell and a displacement sensor.
  • the weighing cell includes a strain-inducing element having a strain-generating region, where strain is generated in response to application of a load thereto, and a strain gauge for detecting the strain generated in the strain-generating region.
  • the displacement sensor includes a fixed rigid component, a movable rigid component forming a weight element, a generally elongated beam member rigidly secured at one end to the fixed rigid component and at the opposite end to the movable rigid component so as to extend between the fixed rigid component and the movable rigid component, and a displacement-detecting element mounted on the elongated beam member for outputting an electrical signal having an amplitude proportional to the amount of displacement of the movable rigid component in a direction generally perpendicular to the elongated beam member.
  • the strain-inducing element of the weighing cell includes a fixed rigid body, configured for being secured to a base, and a movable rigid body, configured for receiving the load to be measured, and first and second beams, which are rigidly secured at opposite ends to the fixed rigid body and the movable rigid body and extend parallel to one another between the fixed rigid body and the movable rigid body.
  • the displacement sensor is fixedly carried by the fixed rigid body of the weighing cell.
  • the technical problem posed that is solved by the present invention is consequently that of providing a system of load cells that will enable the drawbacks mentioned above with reference to the known art to be overcome .
  • the load cell comprises a bending-beam load cell which is mechanically coupled to a cantilever (springboard-like) element sensorized with strain gauges, in which the cell measures the weight and the cantilever measures the apparent weight to be subtracted from the measurement made by the cell.
  • the instantaneous samples of the apparent weight via a specific procedure, are synchronously subtracted from the samples coming from the load cell, thus eliminating the contribution thereof.
  • the bending-beam load cell and the cantilever which are subjected to the same vibrations, are made in such a way that they oscillate with the same characteristic frequency .
  • the cantilever is set and calibrated with the known procedure used for strain-gauge load cells.
  • the cantilever may have various geometrical shapes, where its function is to oscillate in response to vibration.
  • Figure 1A is a cross-sectional view that shows a load cell according to the invention.
  • Figure IB is a cross-sectional view that shows the sensor for measuring the apparent weight
  • Figures 2A and 2B are cross-sectional views that show a cell with a cantilever element installed in an embodiment alternative to that of Figure 1A;
  • Figure 3 is a cross-sectional view that shows a cell with the cantilever element in the form of load cell
  • Figure 4 provides a simplified diagram of the measurement electronics.
  • a load cell according to the invention is designated as a whole by the reference number 100 and comprises a deformable body 101, which has, for example, a generically parallelepipedal shape and made in which, in the transverse direction Y, is a butterfly-shaped through opening 102.
  • the through opening 102 extends in the longitudinal direction X between a first shoulder 104 and a second shoulder 105 of the deformable body 101.
  • the deformable body 101 is fixed by means of its shoulder 104, whereas the loading area is opposite thereto, where an area that is to receive a load in the vertical direction Z is provided, for example in the form of a plate.
  • the loading plate is set on the top of the deformable body 101 in the proximity of the second shoulder 105 and is fixed thereto, in an example of application, via a threaded through hole 108.
  • the configuration of the load cell illustrated is consequently that of a load cell of the bending-beam type.
  • the bending-beam load cell 100 is fixed in cantilever fashion on a support (not shown) at the end of the shoulder 104 via a through hole 107.
  • the load cell 100 is of the resistive-strain-gauge type and comprises in a known way an electronic control unit 300 housed in a remote position with respect to the cell.
  • the deformable body 101 receives within the through opening 102 a cantilever element 103 (referred to hereinafter for brevity simply as "cantilever") having, in the embodiment illustrated in Figure IB, generically the shape of a parallelepiped elongated in the longitudinal direction X which is bent to form an L-shape in the direction of the axis Z in a terminal part thereof where a through hole 109 is present for fixing to the shoulder 104 via a threaded screw as shown in Figure 1A.
  • a cantilever element 103 referred to hereinafter for brevity simply as "cantilever" having, in the embodiment illustrated in Figure IB, generically the shape of a parallelepiped elongated in the longitudinal direction X which is bent to form an L-shape in the direction of the axis Z in a terminal part thereof where a through hole 109 is present for fixing to the shoulder 104 via a threaded screw as shown in Figure 1A.
  • strain gauges 110 and 111 glued on the cantilever 103 on the opposite sides of its base are two strain gauges 110 and 111 positioned along the longitudinal axis X in the direction of greater deformation of the cantilever.
  • a metal mass 106 constrained to the end of the cantilever 103 that is free to vibrate is a metal mass 106, which can be slid along the length of the cantilever 103, not occupied by the strain gauges 110 and 111, and can be fixed thereto in the preselected position via a threaded through hole 112, the screw of which bears upon the cantilever 103.
  • a force applied on the loading plate constrained to the shoulder 105 via the threaded through hole 108 and acting in the vertical direction Z causes elastic bending of the deformable body 101, which undergoes deformation like a parallelogram whereas the cantilever 103, which is not loaded by any force, remains in its state of rest.
  • Deformation of the bending body 101 is measured, in a known way, via strain gauges glued in positions corresponding to the thinner regions of the body 101, the signals of which are transduced by an appropriate electronics 300 shown in Figure 4 into the value of weight.
  • both the deformable body 101 and the cantilever 103 will forcedly enter into vibration at their respective characteristic frequencies.
  • the deformable body 101 will receive, in the plate connected to the shoulder 105, the object to be weighed, while at the same time the signals produced by the strain gauges of the cantilever 103 in forced vibration will be transduced into apparent weight.
  • the electrical signals coming from the strain gauges of the cantilever 103 and those coming from the strain gauges of the load cell 101 constitute two different sequences or threads, which, acquired synchronously, are processed in parallel by the electronics 300 via a measurement chain that comprises signal amplifiers 302, an analog-to-digital conversion 304, and a microcontroller 306, in which the firmware compensates the signals with respect to one another and averages them.
  • the compensation procedure will subtract from the thread coming from the load cell 101 the thread coming from the cantilever 103 and supplies a signal compensated by the effect of the vibrations.
  • the bending-beam load cell 101 and the cantilever 103 it is necessary for the bending-beam load cell 101 and the cantilever 103 to have the same characteristic frequency. According to the invention, it may be assumed that these two frequencies
  • the first of the two equations yields the characteristic frequency f T of the cantilever 103, whereas the second yields the characteristic frequency f F of the bending-beam load cell, where: E is the Young's modulus of the material; b is the base, h the height, and L the length of the cantilever 103; and m is the weight of the mass 106.
  • E is the Young's modulus of the material
  • b is the base, h the height, and L the length of the cantilever 103
  • m is the weight of the mass 106.
  • K is its stiffness
  • the mass M is the sum of the tare weight of the weighing machine plus the weight of the object being weighed.
  • the cantilever 103 is sized; for example, the mass 106 is set.
  • exact tuning of the frequencies is obtained by displacing along the transverse axis Y of the cantilever 103 the mass 106 until the same frequency is instrumentally obtained.
  • the distance between the free end of the cantilever 103 and the mass 106 determines the range of measurements that the load cell 100 can carry out, keeping the vibrations compensated.
  • the load cell with compensation of vibrations 100 may be configured with the cantilever 103 fixed to the cell 101 via a spacer 109 on the top side (Figure 2A) or the bottom side ( Figure 2B) of the shoulder 104 via the through hole 107.
  • a load cell 100 similar to the load cell 100 of Figure 2B envisages a deflecting body 202 identical to the deflecting body 201 as advantageous embodiment of the cantilever 103 where the deflecting body 201 is the same as the deflecting body 101 already illustrated.
  • the two cells 201 and 202 are constrained together via screws that pass through the through holes 206 and 207 with interposition of an insert 203 that keeps them separate and free to vibrate .
  • the two cells 201, 202 will vibrate at the same characteristic frequency when the mass 210, fixed to the cell 202 via a screw that is tightened in the threaded through hole 208, is equal to the sum of the tare weight and of the weight of the object to be weighed .
  • the cell 100 is mechanically connected to the machine via the same screws as those used for joining the two cells and via the through holes 206 and 207.
  • the load cells 100 according to the invention can be used in a weighing station of a line for packaging products in bulk form, for example ground coffee packaged in pods, medicines packaged in purposely provided containers, and in similar cases where the objects to be weighed always have the same mean weight.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Force In General (AREA)

Abstract

L'invention concerne une cellule dynamométrique (100) comportant: i) un corps élastiquement déformable (101), où sont placées des jauges de déformation à résistance électrique; ii) un élément (103) en porte-à-faux fixé au corps élastiquement déformable (101), où sont placées des jauges respectives de déformation à résistance électrique; et iii) une unité de commande électronique logée dans une position distante par rapport à la cellule dynamométrique (100); l'élément déformable (103) en porte-à-faux étant monté à l'intérieur d'une ouverture débouchante (102) du corps élastiquement déformable (101) ou se trouvant sur le dessus de celui-ci par l'intermédiaire d'une entretoise et mécaniquement contraint par rapport à celui-ci, le corps élastiquement déformable (101) et l'élément (103) en porte-à-faux étant affectés de la même façon par les vibrations et pouvant être accordés à la même fréquence caractéristique. Les signaux enregistrés par les jauges de déformation de l'élément (103) en porte-à-faux sont soustraits des signaux provenant des jauges de déformation du corps déformable (101).
PCT/IB2019/052695 2018-05-31 2019-04-02 Dispositif de cellule dynamométrique Ceased WO2019229549A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT201800005923 2018-05-31
IT102018000005923 2018-05-31

Publications (1)

Publication Number Publication Date
WO2019229549A1 true WO2019229549A1 (fr) 2019-12-05

Family

ID=63491862

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2019/052695 Ceased WO2019229549A1 (fr) 2018-05-31 2019-04-02 Dispositif de cellule dynamométrique

Country Status (1)

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WO (1) WO2019229549A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT202000004741A1 (it) 2020-03-05 2021-09-05 Nanolever S R L Apparecchiatura per trattare prodotti alimentari e corrispondente procedimento

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0635703A1 (fr) 1993-07-22 1995-01-25 ISHIDA CO., Ltd. Détecteur de charge avec capteur de déplacement et dispositif de pesage l'utilisant

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0635703A1 (fr) 1993-07-22 1995-01-25 ISHIDA CO., Ltd. Détecteur de charge avec capteur de déplacement et dispositif de pesage l'utilisant

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT202000004741A1 (it) 2020-03-05 2021-09-05 Nanolever S R L Apparecchiatura per trattare prodotti alimentari e corrispondente procedimento

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