Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
  • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
  • G01L1/2206—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
  • G01L1/2243—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports the supports being parallelogram-shaped
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01G—WEIGHING
  • G01G21/00—Details of weighing apparatus
  • G01G21/24—Guides or linkages for ensuring parallel motion of the weigh-pans
  • G01G21/244—Guides or linkages for ensuring parallel motion of the weigh-pans combined with flexure-plate fulcrums
• • 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
  • G01G3/1402—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
  • G01G3/1412—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports the supports being parallelogram shaped

Definitions

• the invention relates to a force-measuring element for a scale, formed by a beam which takes up the load at one end and has a horizontal recess, on the top and bottom of which bending points are formed by markedly reduced and identical material cross-sections in such a way that between the bending points of the beam two links result in a parallel guide, and in which the measurement signal is derived by strain gauges at the bending points.
• This offset of the center lines of the material cross-section at the bending points by increasing the outer cross-section of the bar or beams results as a result of the shoulder increasing the outer cross-section of a bar, provided that at the bending points the distances between the outer surfaces of the bars and the opening are the same have to be big.
• the offset creates an additional torque, which loads the bending points with an additional bending moment. This can be determined by appropriate dimensioning in such a way that a certain deflection of the point of application of the load on the beam no longer leads to a perceptible change in the derived measurement signal.
• FIG. 2 shows the force-measuring element 10. It is formed by two outer bars 11, 12 and an inner bar 13, which are arranged parallel to one another, are of equal length and are connected to one another by a transverse bar 14 running perpendicularly to them.
• the mold is E-shaped in plan view.
• the two outer beams 11, 12 are fixed with their ends 11', 12' on a bracket 15 by means of screws 16 and 17, respectively.
• the force measuring element 10 takes the load through the pin 19 which is connected to the levers 3 and 4 at their front connection.
• the beams 11, 12, 13 are each provided with an opening 25.
• This is essentially formed by the circular area 25' and the oval area 25'', which are connected to one another via an area 25''' with a rectangular cross-section.
• the areas 25' and 25'' have the same radii.
• bending points 40, 41, 42, 43 are created by markedly reduced material cross sections.
• the material cross sections of the bending points 40 to 43 are the same in each case, as illustrated by the arrows.
• Linkages 50, 51 of a parallel guide are formed between these bending points. In the event of deformation under load, pressure zones and tension zones form in each beam in the links 50, 51 at the bending points 40, 41, 42, 43.
• Two strain gauges 20, 21 are arranged at the bending points 40, 41 on the upper side of the link 50, namely the strain gauge 20 in a tensile zone and the strain gauge 21 in a pressure zone.
• the two strain gauges are connected together with supplementary resistors as a Wheatstone bridge, which is balanced in the unloaded state and in which the measurement signals produced in the strain gauges add up when the load is detuned.
• the point of application of the pin 19 can shift on the right-hand end 13' of the beam 13, as shown in dashed lines at 19' in FIG. Such a shift in the range of only 1/10 mm can easily result from wear. If only two strain gauges 20 and 21 are arranged on the upper side of the link 50 of the beam 13, this results in a change in the measurement signal derived from them. These changes in the strain gauges 20 and 21 are asymmetrical, i.e. the signal changes are not equal in magnitude in the event of a deflection.
• FIG. 6 shows a modification with a slightly different design of the overload stop.
• the overload stop is formed by a stop plate 31, which is arranged on the inner beam 13 by means of the spacer sleeve 30 at a certain distance a' from the top of the inner beam 13 and laterally the outer bars 11, 12 overlaps.
• the two outer ends are seated on the outer beams 11, 12 and thus prevent deflection.
• FIG. 7 shows a second solution to the problem on which the invention is based.
• the step 26 on the underside of the lower link 51 is not formed. Instead, strain gauges 120 and 121 are also provided on the underside.
• the recess 25 is designed symmetrically, i.e. it consists of two circular recesses 25' of the same size and a rectangular recess 25 between them".

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Force In General (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6345968

Family Applications (1)

Country Status (6)

Cited By (1)

Families Citing this family (33)

Citations (7)

Family Cites Families (8)

• 1988
  • 1988-01-26 DE DE3802153A patent/DE3802153A1/de active Granted
• 1989
  • 1989-01-19 EP EP89100864A patent/EP0326017B1/de not_active Expired - Lifetime
  • 1989-01-19 JP JP1501260A patent/JP2521358B2/ja not_active Expired - Fee Related
  • 1989-01-19 WO PCT/EP1989/000057 patent/WO1989007245A1/de not_active Application Discontinuation
  • 1989-01-19 EP EP89901465A patent/EP0397728A1/de active Pending
  • 1989-01-19 ES ES198989100864T patent/ES2030914T3/es not_active Expired - Lifetime
  • 1989-01-19 US US07/499,517 patent/US5183125A/en not_active Expired - Fee Related

Patent Citations (7)

Non-Patent Citations (1)

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