US3544939A - Electrical pickoff - Google Patents

Electrical pickoff Download PDF

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Publication number
US3544939A
US3544939A US792205*A US3544939DA US3544939A US 3544939 A US3544939 A US 3544939A US 3544939D A US3544939D A US 3544939DA US 3544939 A US3544939 A US 3544939A
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United States
Prior art keywords
armature
output
legs
leg
magnetic circuit
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Expired - Lifetime
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US792205*A
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English (en)
Inventor
Carl C Bath
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Bendix Corp
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Bendix Corp
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/32—Non-reciprocal transmission devices

Definitions

  • the inventive pickoif includes a rotatable armature and a symmetrical magnetic circuit. Rotation of the armature causes an imbalance in the reluctance of the magnetic circuit resulting in an output voltage.
  • the magnitude and polarity of the output are indicative of the angular value and direction of the rotation of the armature.
  • a unique configuration of the armature increases the electrical sensitivity of the pickotf, while decreasing the criticality of its initial balancing in a null position.
  • pickolf devices Many types of electronic control, indicating or measuring systems employ electrical pickolf devices. In many instances the type of system in which the pickolf is employed requires the output of the pickoif to have both an amplitude and a polarity which are indicative of the characteristic under consideration. For this reason, one well known type of pickofl employs a stationary and a rotatable element.
  • the stationary element is a symmetrical magnetic circuit including an input winding and at least one output winding.
  • the rotatable element is situated such that when in a null position the stationary magnetic circuit is in balance and there is no output on the output windings. The movement of the armature due to the function to be measured causes an imbalance in the mag- This output voltage is therefore used as the control or indicating signal.
  • It is another object to provide such a device having an armature whcih is configured to increase the magnetic coupling area of the magnetic circuit and thereby increase the electrical sensitivity while decreasing the critically of the initial balancing in a null position.
  • FIG. 1 is an example of the prior art type device presently existing.
  • FIG. 2 is a preferred embodiment of the instant invention.
  • the prior art configuration shown in FIG. 1 includes a stationary portion and rotatable armature.
  • the stationary portion forms a magnetic circuit which includes a Primary Leg 11 and two Secondary Legs 12 and 13.
  • the Primary Leg 11 and Secondary Legs 12 and 13 are connected by a perpendicular Section 14. All the portions 11 through 14 of the stationary section are made of a magnetic permeable material.
  • a Primary Winding 15 is wound about the Central Post 11 and an alternating input voltage is applied to the Input Terminals 18 and 19.
  • a first Secondary Winding 16 is wound about the Secondary Post 12 and an identical Secondary Winding 17 is wound about the Secondary Post 13.
  • the Secondary Coils 16 and 17 are connected in series with their respective Ends 21 and 22 serving as the output leads of the pickoff device.
  • the Coils 16 and 17 are oppositely wound so that oppositely poled voltages are induced in them.
  • An Armature 23 which is rotatable about an Axis 24 is located between the Secondary Legs 12 and 13. Armature 23 is configured with two Flange Portions 26 and 27 such that there are two degrees of symmetry to the Armature 23. Armature 23 is located with respect to the primary portion of the pickotr, such that there are two Pair Gaps 28 and 29 between Flange 26 and Secondary Legs 12 and 13, respectively.
  • the Armature 23 is located such that there is no output present on Output Leads 21 and 22. This requires the armature to be centered perfectly between the Secondary Legs 12 and 13 in order to balance the two sides of the magnetic circuit. This adjustment is very critical and extremely difiicult to achieve.
  • the Armature 23 is caused to rotate in some manner.
  • the Armature 23 could be caused to rotate by the angular movement of a me chanical member of a system so that the output of the pickott device is a function of the angular movement of said member.
  • the rotation of Armature 23, as an example clockwise, causes a decrease in the portion of Flange 2'6 and Secondary Leg 12 which are adjacent to one another. Consequently, the Air Gap 28 increases thereby increasing the reluctance of this portion of the magnetic circuit.
  • FIG. 2 The inventive embodiment of the pickoff is shown in FIG. 2.
  • the permanently stationed magnetic circuit including Legs 11, 12 and 13 wound with Coils 15, 16 and 17 is identical to the embodiment of FIG. 1.
  • the configuration of Armature 30 is substantially ditferent from the configuration of Armature 23 of the FIG. 1 embodiment.
  • Armature 30 is configured such that its only axis of symmetry is a vertical line, as drawn in FIG. 2. This is different from Armature 23 in that the armature has both a vertical and a horizontal axis of symmetry.
  • Rotation of Armature 30 is about the Axis 24.
  • the top portion of Armature 30 is configured to have two Flat Surfaces 32 and 33 which are respectively adjacent to Secondary Legs 12 and 13.
  • the lengths of Sides 32 and 33 are such that the magnetic coupling between the sides and the Secondary Legs 12 and 13 is substantially increased as compared with that of the FIG. 1 embodiment. Consequently, a change in the width of the Air Gaps 37 and 38 results in a more substantial increase in the reluctance change due to rotation of Armature 30.
  • Armature 30 is also configured to include a Slot 31 symmetrically positioned around the symmetrical axis of the armature. Slot 31 receives Primary Leg 11 such that there is an Air Gap 36 extending along all sides of the Slot 31. Air Gap 36 is therefore cup-shaped when the sensor is in the null position. Although rotation of Armature 30 causes a change in the width of the Air Gap 36 along the sides of Primary Leg 11, the portion of the air gap between the bottom of the Leg 11 and Slot 31 remains substantially constant for all degrees of rotation. Consequently, the magnetic coupling between Primary Leg 11 and Armature 30 remains virtually unchanged. Slot 31 and the end of Leg 11 are dimensioned such that Armature 30 is free to rotate until one of the Sides 32 and 33 contact either of Secondary Legs 12 and 13. In this position, the imbalance of the magnetic circuit is at a maximum.
  • the adjustment of Armature 30 into a null position is substantially easier than that of Armature 23. This is so because the intial adjustment requires equal Air Gaps 37 and 38 but the exact vertical location of Axis 24 is of minor importance. This is ditferent from the embodiment of FIG. 1, wherein the initial adjustment requires both angular and a vertical null position. The vertical location is important because the width of the Air Gaps 28 and 29 substantially affects the sensitivity of the sensor.
  • the initial adjustment of Armature 30 is also facilitated by the Heavy Flange 34 which is formed on the bottom portion of the armature. The heavier portion causes the Armature 30 to naturally hang in a vertical position. This is different from the prior art embodiment of FIG. 1 where the Armature 23 has two degrees of symmetry and therefore will balance in any angular position. If balance is required for a particular application, sufficient external mass may be added to the slotted end of Armature 34.
  • an AC. input must be applied to the Terminals 1'8 and 19.
  • equal and opposite alternating voltages are induced in the Secondaries 16 and 17, resulting in cancellation and thus zero output.
  • a change of the angular position of the rotatable armature would then be indicated by the change of amplitude and phase of the output signal.
  • the invention claimed is: 1. In an electrical pic'kofi' having a stationary element including one leg wound with a first coil and other legs symmetrically positioned about said one leg wound with other coils, and
  • a rotatable armature symmetrically positioned with respect to said other legs in a null position and asymmetrically positioned with respect to said other legs in an output position
  • said armature having only one axis of symmetry said axis of symmetry being perpendicular to the axis of rotation, substantially parallel sides forming air gaps between said sides and said other legs, the lengths of said air gaps being substantially equal when said armature is in said null position and unequal when said armature is in said output position,
  • said armature also including a hollowed notched portion receiving the end of said one leg, said hollowed portion and said end forming a cupshaped air gap, the sides of said cup-shaped air gap being wider than the air gaps between said armature and said other legs.
  • said positioning portion having a mass greater than that of said flux changing portion so that said armature readily assumes a symmetrical position with respect to said stationary element.
US792205*A 1969-01-10 1969-01-10 Electrical pickoff Expired - Lifetime US3544939A (en)

Applications Claiming Priority (1)

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US79220569A 1969-01-10 1969-01-10

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US3544939A true US3544939A (en) 1970-12-01

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US792205*A Expired - Lifetime US3544939A (en) 1969-01-10 1969-01-10 Electrical pickoff

Country Status (4)

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US (1) US3544939A (enrdf_load_stackoverflow)
DE (1) DE2000854A1 (enrdf_load_stackoverflow)
FR (1) FR2033229B1 (enrdf_load_stackoverflow)
GB (1) GB1265461A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3813917A (en) * 1971-05-18 1974-06-04 Applied Magnetics Corp Method and apparatus for measuring strip material kinetic friction
US7273328B2 (en) 2003-03-07 2007-09-25 Next Safety, Inc. Emissive highway markers

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2128752B (en) * 1982-10-20 1987-01-28 Brookes & Gatehouse Electromagnetic angular position sensor
US4584577A (en) * 1982-10-20 1986-04-22 Brookes & Gatehouse Limited Angular position sensor
DE3310386A1 (de) * 1983-03-22 1984-10-04 Mannesmann Rexroth GmbH, 8770 Lohr Hilfskraftlenkung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR14591E (fr) * 1910-04-22 1912-01-11 Giuseppe Del Fu Pietro Fucci Variateur de tension à réluctances variables sonjuguées
FR777638A (fr) * 1933-11-16 1935-02-25 Transformateur statique à tension secondaire réglable
US3152311A (en) * 1957-11-08 1964-10-06 L R Power Corp Variable voltage transformer

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2281453A (en) * 1939-05-11 1942-04-28 Petersen Louis Electromagnetic movement repeating system
GB805466A (en) * 1954-04-15 1958-12-03 Kollsman Instr Corp Improvements in inductive transducers
US3154756A (en) * 1962-02-08 1964-10-27 L R Power Corp Variable voltage transformer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR14591E (fr) * 1910-04-22 1912-01-11 Giuseppe Del Fu Pietro Fucci Variateur de tension à réluctances variables sonjuguées
FR777638A (fr) * 1933-11-16 1935-02-25 Transformateur statique à tension secondaire réglable
US3152311A (en) * 1957-11-08 1964-10-06 L R Power Corp Variable voltage transformer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3813917A (en) * 1971-05-18 1974-06-04 Applied Magnetics Corp Method and apparatus for measuring strip material kinetic friction
US7273328B2 (en) 2003-03-07 2007-09-25 Next Safety, Inc. Emissive highway markers

Also Published As

Publication number Publication date
FR2033229B1 (enrdf_load_stackoverflow) 1973-12-21
DE2000854A1 (de) 1970-08-20
GB1265461A (enrdf_load_stackoverflow) 1972-03-01
FR2033229A1 (enrdf_load_stackoverflow) 1970-12-04

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