Title:
Rail flaw detector mechanism
United States Patent 2133687


Abstract:
This invention relates to rail flaw detector mechanisms of the type employed in the Sperry rail flaw detector cars. The general principle underlying the operation cf these cars is well known and consists in energizing the rail by passing current therethrough to establish an electromagnetic...



Inventors:
Drake, Harcourt C.
Application Number:
US1064535A
Publication Date:
10/18/1938
Filing Date:
03/12/1935
Assignee:
SPERRY PROD INC
Primary Class:
Other Classes:
361/170
International Classes:
B61K9/10
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Description:

This invention relates to rail flaw detector mechanisms of the type employed in the Sperry rail flaw detector cars. The general principle underlying the operation cf these cars is well known and consists in energizing the rail by passing current therethrough to establish an electromagnetic field surrounding the same and then exploring said field for irregularities caused by the presence of flaws within the rail. Such irregularities are detected by inductive means which generate an E. M. F. which after being suitably amplified is caused to operate a recorder pen on a chart and at the same time discharge paint on the rail at the point of flaw.

The E. M. F. which is generated by the inductive coil passing through the region of flaw is small and must be amplified by a thermionic amplifier in order to give an output capable of performing the functions stated above, namely, operating pens and rail marking means. It will be understood that the region of magnetic distortion caused by the presence of a flaw is very small in extent and since ihe car is travelling past said region at substantial speed the total time during which the inductive detector means will be affected by the flaw is very small and therefore the duration of the generated E. M. F. will also be small. For this purpose the characteristics of the amplifier are made such that 80 the impulse which is put into the amplifier is prolonged in duration as by inserting a condenser of large capacity in the amplifier circuit with a large resistance leak across the same so that the charge is held for a substantial time. One of the difficulties experienced in rail flaw testing is that surface indications such as burns on the rail surface caused by slipping of driver wheels cause a distortion of the electromagnetic field which is picked up by the detector means and results in a pen mark on the chart and a paint mark on the rail in the same manner as an internal fissure. Operators have been trained to detect such surface indications from their position at the rear of the detector car and such marks are therefore not investigated. However, because of the characteristics of the amplifier which have been described above which prolong the period of an impulse caused by the distortion of the magnetic field, it so happens that a paint mark which is caused by a surface defectwill extend for a distance which may be six or eight inches beyond the surface defect. In other words, the impulse generated by the surface defect is of short duration but because the amplifier prow5 longs this period the paint mark extends for a distance beyond the surface defect. It has been discovered that frequently internal fissures exist close to the surface defect but such internal fissures cannot be detected because the paint mark which originates at the surface defect is prolonged in extent by the amplifier characteristics so that it covers the succeeding portion of the rail in which a real internal defect exists.

It is the principal function of this invention to provide a remedy for the situation described above whereby the impulse passing through the amplifier is limited in extent so that paint marks will be placed only immediately adjacent the internal fissure, or if the paint mark is made at a surface defect such paint mark will not extend beyond the region of the surface defect.

Further objects and advantages of this invention will become apparent in the following detailed description thereof.

In the accompanying drawing, Fig. 1 is a side elevation of a portion of a Sperry rail flaw detector car.

Fig. 2 is a wiring diagram illustrating the principle embodied In this invention.

Referring to Fig. 1 of the drawing, there is disclosed a portion of a Sperry rail flaw detector car comprising the car body 10 within which is mounted a generator G adapted to supply current to the rail to establish an electromagnetic field surrounding the same. The current from generator G may be passed into and out of the rail by means of sets of brushes II and 12 carried by a current brush carriage 15, said carriage being supported from the car body 10 by means such as cables 16 and springs, not shown, which normally maintain the current brush carriage in raised or ineffective position. When it is desired to lower such carriage into engagement with the rail, fluid pressure such as compressed air is supplied to cylinders 17 to depress pistons 18 operating therein, said pistons being connected to the current brush carriage so that said carriage is lowered against the action of the retractile springs. The current brush carriage may be adapted to ride along the rail on means such as flanged wheels 19.

The electromagnetic field surrounding the rail is uniform as long as there are no flaws. When flaws occur there is a distortion of the electromagnetic field in the region of the flaw and such distortions are designed to be detected by induction means which may comprise a pair of opposed induction coils 20 supported in a housing 21, carried by a detector carriage 22 which is designed to be supported on the current brush carriage for movement independent thereof by means such as loose-fitting bolts 23 and springs 24 constituting limited universal joints. The detector carriage 22 may be supported on the rail surface by means such as rollers 25. It will now be seen that as the car travels along the rail R the inductive means 20 are maintained a constant distance above the rail surface and will normally cut a constant number of lines of force. When a region of flaw is encountered one of the coils will cut a different number of lines of force and there will be generated a differential E. M. F. which after being amplified by an amplifier may be caused to operate indicating means such as pens operating on a moving chart and rail-marking means such as a paint gun.

Referring to Fig. 2, it will be seen that the detector unit is arranged to impress the differential E. M. F. on the amplifier, which may be an ordinary cascade type of resistance coupled amplifier.

The duration of the impulse into the amplifier is prolonged by means such as a large capacity condenser C and high resistance S, so that the charge placed upon C will slowly leak off the high resistance. The output of the amplifier is shown as energizing a magnet 30 which closes the circuit through a pen magnet 31 which actuates pen P. At the same time that the pen magnet 31 80 is energized, there is also energized a paint-gun magnet 35 which controls the energization of a paint gun 40 by actuating a valve-stem 41 therein so that the paint gun is operated to discharge paint on the rail. The paint gun is mounted as 85 shown in Fig. 1 so as to compensate for the travel of the car and for the lag in operation of the gun whereby a paint mark is obtained at the region of magnetic distortion caused by a flaw or surface defect.

As stated in the introduction to this specification, it is desirable for the reasons therein set forth to limit the duration of the output to such an extent that the output from the amplifier will cease as soon as the pens and the paint magnet have been energized.

For this purpose we have placed in the circuit controlled by the output of the amplifier an additional magnet 45 of slightly greater strength than the magnet 30 and the paint magnet so that 0o said additional magnet will be energized only after the pen magnet and the paint magnet have been energized. Said additional magnet controls an auxiliary circuit which is normally open and adapted to be closed at a set of contacts 46 when the additional magnet is energized. Said auxiliary circuit short-circuits the condenser C to cause the same to discharge quickly instead of d'scharging slowly by way of the large resistance S. As a result, there is obtained a limitation of the output of the amplifier, said limitation becoming effective immediately after the pens and the paint gun have been energized.

In accordance with the provisions of the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other equivalent means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and Tg others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is: 1. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means for prolonging the duration of said impulse and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means for rendering said prolonging means ineffective.

2. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means for prolonging the duration of said impulse and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means controlled by the output of said amplifier for limiting the duration of said output. 3. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means for prolonging the duration of said impulse and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means controlled by the output of said amplifier for rendering said prolonging means ineffective.

4. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means for prolonging the duration of said impulse and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means controlled by a predetermined output of said amplifier for rendering said prolonging means ineffective.

5. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means for prolonging the duration of said impulse and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means, adapted to be rendered effective when the output of said amplifier is sufficient to actuate said indicating means, for rendering said prolonging means ineffective.

6. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means including a condenser of large capacity and a high resistance leak therefor whereby the duration of said pulse is prolonged and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means for rendering said condenser ineffective.

7. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means including a condenser of large capacity and a high resistance leak therefor whereby the duration of said pulse is prolonged and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named means including means for short-circuiting said condenser.

8. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means including a condenser of large capacity and a high resistance leak therefor whereby the duration of said pulse is prolonged, and indicating means actuated by the outpt of said amplifier, means for limiting the actuation of said indicating means, said lastnamed means including means controlled by the output of said amplifier for short-circuiting said condenser.

9. In a rail flaw responsive mechanism havi2 Ing means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means including a condenser of large capacity and a high resistance leak therefor whereby the duration of said pulse is prolonged and indicating means actuated by S the output of said amplifier, means for limiting the actuation of said indicating means, said lastnamed means including means controlled by a predetermined output of said amplifier for shortcircuiting said condenser. 10. In a rail flaw responsive mechanism having means which responds to flaw by generating an electrical impulse of relatively short duration, an amplifier for amplifying said impulse, said amplifier having means including a condenser of 1i large capacity and a high resistance leak therefor whereby the duration of said pulse is prolonged and indicating means actuated by the output of said amplifier, means for limiting the actuation of said indicating means, said last-named' 2 means including means adapted to be rendered effective when the output of said amplifier is sumcient to actuate said indicating means for shortcircuiting said condenser.

HARCOURT C. DRAKE.