Patent GB-966676-A (GB)
Title: Apparatus for detecting radiant energy
IPC: G01J5/0805
Filed: 1961-01-09
Abstract: 966,676. Detecting hot bearings. WESTINGHOUSE AIR BRAKE CO. Jan. 9, 1961 [Jan. 7, 1960), No. 811/61. Heading G1A. Apparatus for detecting radiant energy and comprising detector means located, or locatable, adjacent a railway track for producing electrical signals in response to radiant energy from the axle boxes, or wheel portions near the axle boxes, passing on said track, includes interrupting means for interrupting periodically the radiant energy impinging on the detector means, and means for deriving electrical signals dependent on the ambient temperature and the temperatures of a passing axle box and of the interrupting means and for deriving from them an output signal representative of the temperature difference between the passing axle box and the ambient temperature. Heat rays from a portion of the wheel 19, Fig. 1, adjacent the axle box 23 collected through an opening 15b in a casing 15 and a directing tube 25 with filters 29, 31 cutting off radiation of very short wavelength, is reflected by a mirror 17 to an infra-red detecting cell 13. A shutter 15a is operated to close the opening 15b for the period between the passage of successive wheels through the detecting or examining location. The beam to the cell 13 is interrupted by an apertured chopper disc 33 having apertures 33a, Fig. 2, which also function in conjunction with a lamp 37 and photo-cell 39 to provide an alternating reference voltage waveform. The disc 33 is rotated by a motor 35 to provide a reference voltage of about 1000 c.p.s., and the lamp 37 together with the cell 39 are adjustable relative to the apertures 33a so that the positive phase of the reference voltage coincides with the passage of the infra red or heat beam from the wheel portion 19 to the detector 13. In the intervening periods the cell 13 is subject to.the temperature of the chopper disc which is partially representative of the ambient temperature. The output of the photo-cell 39 is fed via an amplifier 45 to a phase comparator and evaluating circuit 47 comprising a transformer with the ends of the secondary winding connected to similarly disposed diode rectifiers 49, 51, Fig. 3, and a central connection 48 from the output of the detector cell 13. The diodes 49, 51 are connected to a smoothing circuit 53, 55, and the periodic output solely from the amplifier 45 produces zero voltage at the output terminal 150 of the circuit 47. A target temperature above the general ambient temperature, i.e. that of the chopper disc 33, results in a positive signal at the terminal 150, at which a negative voltage appears if the target temperature is less than that of the chopper disc 33. The signals from terminal 150 are fed alternatively via a detect gate 69, Fig. 1, or via a non-detect gate 67 and an ambient signal amplifier 115 to a difference amplifier 107 whose output, representing the temperature of the bearing relative to the ambient temperature, is passed to a signal processing circuit. The gates 69, 67 are controlled by detectors 77, 79 in the line of travel of the wheel so that a directional switching member 32 is operated to control a bi-stable multivibrator 73, Figs. 1 and 5, which for the detecting operation provides voltage + E to the point 85, Fig. 5, in detect gate 69 and the point 89 in non-detect gate 67. Also, voltage -E is applied to point 87 in detect gate 69 and to point 91 in non-detect gate 67. With the application of these voltages, the gate 69 can pass voltage from the comparator 47 over lead 98 to the grid of a valve 101 of the difference amplifier 107. At this time the non-detect gate 67 is blocked against passing the output of the comparator 47. When the track detector 79 is actuated, the switch 32 and multivibrator 73 are operated to reverse the potentials applied to the points 85, 87, 89, 91 so that signals cannot be passed over the conductor 98, but those corresponding to the temperature of the chopper disc relative to the ambient temperature are passed to a signal energizing circuit 115 having three integrating circuits 121 and 123, 135 and 137, and 141 and 143, of progressively longer periods, to pass a signal to the grid of a second valve 105 of the difference amplifier 107 producing a final signal proportional to the difference between the axle box and ambient temperatures. In a modification, Fig. 1a (not shown), separate thermistors are included to evaluate directly the difference between the temperature of the chopper disc and the ambient temperature, and this is applied to a difference amplifier also controlled via a detect gate to give the difference between the temperatures of the axle box or wheel and of the chopper disc. The reference voltage may alternatively be generated by a rotating apertured ferro-magnetic disc, Fig. 2a (not shown). Specification 952,996 is referred to.