US 4,524,932 A · Railroad car wheel detector using hall effect element

Abstract

A Hall effect element, incorporated into an integrated circuit unit with temperature compensation, voltage regulation, and amplification, is mounted on top of a permanent magnet made of ceramic material with the critical Hall axis aligned with the magnet pole axis. To avoid saturating the Hall cell, it is positioned within a pole-to-pole hole in the magnet, which creates a flux null space. The permanent magnet and Hall cell assembly is mounted on the rail a predetermined distance below the top so that the flange of passing wheels occupies the air gap between the magnet and the rail through which the major portion of the magnet flux flows. Reduction of the air gap increases the level of the magnet flux and thus the level of voltage output of the Hall cell. The output of the Hall cell is applied to a Schmitt trigger whose switching level is set by a threshold voltage unit. Increased Hall output voltage actuates the trigger circuit which applies the signal to a switching transistor whose output in turn is applied to a pulse detector which registers the wheel detection. The magnet, Hall circuit element, and processing network are encapsulated within an epoxy material which is fitted for direct mounting to the base of the track rail on the gauge side.

Claims7

Dependent claims

Wheel detector apparatus for car wheels moving along a railroad track rail, comprising:

(a) a permanent magnet means with an internal hole extending parallel to the pole-to-pole axis for creating a magnetic flux null space along that axis within said hole and externally at both poles,
(b) said magnet means positioned adjacent the gauge side of said rail a predetermined distance below the top of said rail with said pole-to-pole axis in vertical alignment with the flange of each passing car wheel, for generating a first and a second level of magnetic flux when a car wheel is absent and present, respectively,
(c) a Hall effect means positioned at the upper end of said magnet means within said null space and with its critical axis parallel to said pole-to-pole axis,
(d) said Hall effect means responsive to flux from said magnet means for generating an output voltage proportional to the existing flux level, and
(e) a detector network coupled for responding only to said Hall effect means output voltage representing said second flux level to register the passage of a car wheel.

2 more elements

Wheel detector apparatus for registering car wheels moving past a fixed location along a railroad track rail, comprising:

(a) a permanent magnet with a hole parallel to the pole-to-pole axis for creating a null space in the flux pattern within said hole and externally surrounding the extended hole axis,
(b) said magnet positioned adjacent the gauge side of said rail with its pole axis vertical for establishing a first flux path through an air gap and said rail, when no wheel is present at said location, through which a first flux level flows,
(c) said magnet establishing a second flux path, when a wheel is present at that location, through the wheel flange and said rail, having a lower reluctance through which a second higher level flux flows,
(d) a Hall effect means positioned at the top of said magnet within said hole and null space, and with its critical axis parallel to said pole-to-pole axis, and responsive to magnet flux for generating a first and a second output voltage in response to said first and said second flux levels, respectively, and
(e) a monitoring network having a preset threshold voltage level equal to said first output voltage of said Hall effect means and coupled thereto for producing an output to register a car wheel only when said Hall effect means output voltage is at said second level.

2 more elements

Dependencies are inferred from the claim text.

Railroad car wheel detector using hall effect element

Life of this patent

Railroad car wheel detector using hall effect element

Life of this patent

Abstract

Claims7