US 4,068,811 A · Hotbox detector

Abstract

An apparatus for determining the temperature of railroad car wheel journals (i.e., "hotbox" detector) includes a sensor including a pyroelectric cell responsive to infrared radiation signals, which are focused onto the cell, to output voltage signals as a function of the radiation signals inputted thereto. The sensor exhibits a nonlinear gain response to different frequencies of input signals and compensation is provided by coupling the output of the sensor to a differentiating circuit which has a similar but relatively negative gain response. The output of the differentiating circuit is a substantial voltage replica of the infrared input signal and this voltage signal may be applied to a suitable utilization device such as one which records journal temperature and/or provides a suitable alarm when a sensed journal temperature exceeds a predetermined value.

Claims10

Dependent claims

An improved circuit for use in apparatus for detecting the temperature of railroad car wheel journals as a train passes a fixed wayside point whereby infrared signals are transmitted from the wheel journals to the apparatus at a frequency corresponding to the rate at which said wheels pass said wayside point, said circuit comprising:

a. sensor means including a pyroelectric cell for outputting a voltage signal having a magnitude which is a function of the infrared input signals applied thereto, said sensor means exhibiting a substantially flat gain response to input signals occurring at frequencies within a first range and a gain response which varies exponentially with an increase in the frequency of the input signals within a second range of frequencies higher than said first range;
and,
b. differentiating means responsive to the output of said sensor means to output a voltage signal having a magnitude porportional to the temperature of the wheel journal, said differentiating means having a substantially flat gain response to signals having a frequency within said first range and a gain response within said second range which varies exponentially at the same rate but in a direction opposite to that of said sensor means.

An improved circuit for use in apparatus for detecting overheated journals in railroad cars comprising:

a. sensor means including a pyroelectric cell for outputting a voltage signal in response to infrared radiation signals inputted thereto, said sensor means exhibiting a substantially flat gain response to input signals occurring within a first frequency range and a gain response which decreases exponentially with increasingly higher frequencies within a second frequency range of higher frequencies than those of said first range;
and,
b. differentiating means coupled to the output of said sensor means, said differentiating means having a substantially flat gain response to input signals having a frequency within said first range and a gain response to input signals within said second range which increases exponentially, with increasing frequencies, at substantially the same rate as the gain of said sensor means decreases whereby the output of said differentiating means is substantially a voltage representation of the infrared signals inputted to said sensor means.

Dependencies are inferred from the claim text.

Hotbox detector

Life of this patent

Hotbox detector

Life of this patent

Abstract

Claims10