US3472327A - Precision balance with dual magnetic damping - Google Patents

Precision balance with dual magnetic damping Download PDF

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Publication number
US3472327A
US3472327A US681823A US3472327DA US3472327A US 3472327 A US3472327 A US 3472327A US 681823 A US681823 A US 681823A US 3472327D A US3472327D A US 3472327DA US 3472327 A US3472327 A US 3472327A
Authority
US
United States
Prior art keywords
pendulum
balance
pan
pan carrier
carrier
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.)
Expired - Lifetime
Application number
US681823A
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English (en)
Inventor
Johann Meier
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.)
Mettler Instrumente AG
Original Assignee
Mettler Instrumente AG
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 Mettler Instrumente AG filed Critical Mettler Instrumente AG
Application granted granted Critical
Publication of US3472327A publication Critical patent/US3472327A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G23/00—Auxiliary devices for weighing apparatus
    • G01G23/06—Means for damping oscillations, e.g. of weigh beams
    • G01G23/10—Means for damping oscillations, e.g. of weigh beams by electric or magnetic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G1/00—Weighing apparatus involving the use of a counterweight or other counterbalancing mass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G1/00—Weighing apparatus involving the use of a counterweight or other counterbalancing mass
    • G01G1/18—Balances involving the use of a pivoted beam, i.e. beam balances
    • G01G1/24—Platform-type scales, i.e. having the pans carried above the beam
    • G01G1/243—Platform-type scales, i.e. having the pans carried above the beam having pans carried above the beam
    • 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
    • G01G21/241—Guides or linkages for ensuring parallel motion of the weigh-pans combined with knife-edge bearings

Definitions

  • the scale pan is mounted at the top end of the pan carrier and in the space above the outer knife edge of the beam.
  • the pan carrier is then guided by means of an additional steering lever. Any control weights are deposited on supports on the pan carrier itself.
  • a spring taring device it is preferably a tension spring which acts on the pan carrier in an at least approximately vertical direction and pull it upwards or downwards as required.
  • As the pan carrier is guided parallel it cannot swing like a pendulum, so means for suppressing such swinging are unnecessary.
  • a precision balance comprising a beam which is fulcrumed on the frame of the balance by means of a centre knife edge and which has an outer knife edge from which a pendulum is suspended, a pan carrier linked to the pendulum for movement about an axis of rotation parallel to said knife edges of the beam and carrying a scale pan at its top end, a counterweight mounted at the bottom end of the pan carrier, and a plurality of electromagnetic eddy current brakes which enable the pendulating movements of the pendulum and of the pan carrier to be suppressed independently of one another and each in relation to the frame of the balance.
  • the eddy current brakes comprise permanent magnets fixed in the frame of the balance and metal vanes mounted on the pan carrier and on the pendulum, the vanes entering the magnetic fields of the associated permanent magnets.
  • the axis of rotation of the pan carrier relative to the pendulum is advantageous for the axis of rotation of the pan carrier relative to the pendulum to be below the outer knife edge of the beam.
  • a taring device is provided in the balance frame, it is preferable for a taring spring or taring springs to act on a part of the pendulum located below the outer knife edge of the beam, exerting tension in an at least approximately vertically downward direction.
  • the centre knife edge 2 of the beam 3 is fulcrumed on the frame 1 of the balance. Only one arm of the beam 3 is illustrated which usually is the shorter one. The longer arm provided with a counterweight and a scale is shown only fragmentarily in the drawing.
  • the outer knife edge 4, extending parallel to the centre knife edge 2, is mounted on the shorter arm of the beam.
  • a yoke-shaped pendulum 5, extending below the outer knife edge 4, is seated on the latter again for pivotal movement.
  • the pendulum 5 is provided with two co-axially mounted knives 6, the common axis of the knives being parallel to that of the knives 2. and 4 and being located in the space below the outer knife 4.
  • the pan carrier 7 is pivotally suspended from the knives 6 of the pendulum 5 and carries the scale pan 8, which is located in the space above the outer knife 4 and thus bears on the top end of the pan carrier 7. At the bottom end of the latter and sufficiently far below the knives 4 and 6 there is mounted a counterweight 7.
  • This construction makes it unnecessary for a separate counterweight to be provided on the pendulum 5.
  • the position of stable equilibrium of the pendulum 5 is provided purely by the total weight of the pan carrier 7 suspended from, including its counterweight 7. Hence when there is an eccentric load on the scale pan 8 only the pan carrier 7 will pivot accordingly about the knives 6, while the pendulum 5-once all the pendulating movements have died awaywill remain in its original position on the outer knife edge 4.
  • the pendulating movements of the pan carrier 7 about the knives 6 and of the pendulum 5 about the outer knife 4 are obviously mechanically coupled to one another, and such coupled pendulating movements can be rapidly extinguished only if each is powerfully damped independently of the other.
  • the damping force must be progressive, in the sense that it increases with the amplitude of the pendulating movement.
  • each magnet being rigidly attached to the frame 1 of the balance.
  • Pendulating movements of the pendulum 5 are suppressed by means of the copper of aluminium vane 11 attached thereto, which enters the magnetic field of the magnet 9.
  • the pan carrier 7 is similarly provided with a copper or aluminium vane 12 which can move between the poles of the other magnet 10 without contacting the same.
  • the two magnets 9 and 10 not only suppress the pendulating movements of the pendulum 5 and of the pan carrier 7 but also contribute to effect an aperiodic pivoting movement of the balance beam 3. It may even be possible to dispense with the usual damping means acting between the balance beam 3 and the balance frame 1.
  • the above mentioned electromagnetic eddy current brakes do not require any additional operating member and this results in an automatic suppression of any pendulating movements which may occur.
  • the damping action obtainable can be made so strong that spring taring means can readily be fitted as illustrated in the drawing.
  • These are also merely indicated in a diagrammatic way and comprise the guiding bar 13 which is rigidly fixed in the frame 1 and along which the stretching member 14, mounted thereon, is adapted to move. Such movement is effected by means of a threaded spindle 15 rotatably mounted in the frame 1 of the balance.
  • the taring spring 16 is stretched between the member 14 and a point on the pendulum 5 below the centre knife 4, so that it exerts a downward tensile force on the pendulum 5 at least approximately in a vertical direction.
  • a plurality of taring springs may be used, acting in parallel or in series.
  • the supports to receive them should be mounted as usual on the pendulum 5 and preferably in the space below the knives 6.
  • a precision balance comprising a beam which is fulcrumed on the frame of the balance by means of a centre knife and which has an outer knife from which a pendulum is suspended, a pan carrier linked to said pendulum for movement about an axis of rotation parallel to said knives of the balance beam and carrying a scale pan at its top end, a counterweight mounted at the bottom end of said pan carrier, and a plurality of electromagnetic eddy current brakes which enable the pendulating movements of said pendulum and of said pan carrier to be suppressed independently of one another and each in relation to the frame of the balance.
  • said eddy current brakes comprise two permanent magnets fixed in the balance frame and two metal vanes fixed respectively to said pendulum and to said pan carrier, said vanes entering the magnetic fields of the two permanent magnets respectively.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Vibration Prevention Devices (AREA)
  • Dynamo-Electric Clutches, Dynamo-Electric Brakes (AREA)
US681823A 1967-05-09 1967-11-09 Precision balance with dual magnetic damping Expired - Lifetime US3472327A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH656067A CH449285A (de) 1967-05-09 1967-05-09 Präzisionswaage

Publications (1)

Publication Number Publication Date
US3472327A true US3472327A (en) 1969-10-14

Family

ID=4311511

Family Applications (1)

Application Number Title Priority Date Filing Date
US681823A Expired - Lifetime US3472327A (en) 1967-05-09 1967-11-09 Precision balance with dual magnetic damping

Country Status (4)

Country Link
US (1) US3472327A (de)
CH (1) CH449285A (de)
DE (1) DE1549229A1 (de)
GB (1) GB1152148A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3617370A (en) * 1970-11-17 1971-11-02 Ohaus Scale Corp Apparatus for regulating the operation of a scale
US4696356A (en) * 1985-01-02 1987-09-29 Ellion Dolores D Gun powder dispensing and measuring apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1900641A (en) * 1932-05-21 1933-03-07 Seederer Kohlbusch Inc Magnetic damper for precision balance
US1937223A (en) * 1933-06-26 1933-11-28 Seederer Kohlbusch Inc Magnetic damping apparatus for precision balances
US3403741A (en) * 1967-06-09 1968-10-01 Kern & Sohn Gottlieb Balance

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1900641A (en) * 1932-05-21 1933-03-07 Seederer Kohlbusch Inc Magnetic damper for precision balance
US1937223A (en) * 1933-06-26 1933-11-28 Seederer Kohlbusch Inc Magnetic damping apparatus for precision balances
US3403741A (en) * 1967-06-09 1968-10-01 Kern & Sohn Gottlieb Balance

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3617370A (en) * 1970-11-17 1971-11-02 Ohaus Scale Corp Apparatus for regulating the operation of a scale
US4696356A (en) * 1985-01-02 1987-09-29 Ellion Dolores D Gun powder dispensing and measuring apparatus

Also Published As

Publication number Publication date
DE1549229A1 (de) 1971-04-29
GB1152148A (en) 1969-05-14
CH449285A (de) 1967-12-31

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