Note: Descriptions are shown in the official language in which they were submitted.
3 ~ Do c ke t 1 d~ 7 8
Rail Elead Inductor
This invention relates to an inductor for heating
railroad rail heads to austenizing temperatures and is
particula{ly useful in heat treatments designed t~ harden
the heads for extending the service life of the railsO
In such thermal hardening treatments, the rail
heads are heated to temperatures of up to about 2000F and
then quenched to develop a pearlitic metallurgical structure
in the metal~ U.S. Patents NosO 49099,9~6 and 4,201,602
disclose apparatus for moving the heating source longitudinally
along the rail head to progressively heat the headO Canadian
Patent No, 888,671 and U.S. Patents Nos~ 39266,956 and
3,276,9~ disclose apparatus for longitudinally ~oving the
ralls relative to stationary heat sourcesO Also, U.5.
Patents Nos. 2 7 070~889 and 2,103,716 disclose apparatus for
heating stationary rails with stationary heating sourcesO
The high ~emperatures realized in these processes in~ariably
generate subs~antial ~hermal stresses in the heacls which
tend to horizontally deform the rails. To be acceptable
however~ the hardened rails must be straight. In the
I . ~
1 United States, railrod rails must at least meet the
recommendations of the American Railway Engineering
Association (AREA). The AREA Manual For Railway
Engineering Specification 4-M-6 (1975) recommends that
the lateral sides and top of the hardened rails should
have a certain minimum hardness penetration pattern.
Also, Specification 4-2-6.1 (1983) recommends that the
horizontal misalignment along the lateral side of the
rail head should not exceed 0.030 inches in three
feet. In additional to these and other technical
considerations, economics requires that the rails must
be heated (and then hardened) as quickly and
efficiently as possible.
The inductor of the present invention rapidly
and efficiently generates austenizing temperatures in
rail heads which develop hardness patterns after
quenching meeting the AREA specification. Standard
cabon rails are heated by the inductor at speeds of up
to 24 inches/minute and at heating efficiencies of
about ~0%. The hardened rail heads are substantially
straight and require very little (if any) horizontal
restraightening to meet the AREA specification.
The rail head inductor has an electrical conductor
adapted to carry al-ternating current across the top and
along the lateral sides of the rail head for
concurently inducing a
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magnetic flux in the top and sides of the rail head and
focusing means disposed about the electrical conductor on
both sides of the rail head for concentrating the magnetic
flux concurrently induced in the lateral sides of the rail
head. Preferably there is a second focusing means disposed
about the portion of the electrical conductor extending
across the rail head for concentrating the magnetic flux
induced in the top oE the rail head as well~
Other features~ objects and advantages of the
present inven~ion will become apparent as the following
description of a presen.tly preferred embodiment thereof
proceeds.
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In the accompanying drawings:
Fig. l is a front elevation view showing the
inductor of the present invention and a rail being heated
below,
~ig. 2 is a rear elevation view of the inductor
shown in F ig . l;
Fig. 3 is a bottom Yiew of ~he inductor shown in
Fig. l;
Fig~ 4 is an end view of the inductor shown in
Fig. 1 taken along line IV-IV;
Fig. 5 is a sectional view of the inductor shown in
Fig. 1 taken along line V-V;
~ ig. 6 is a seotional elevation view of the
inductor shown in Fig. 1 taken along line VI-VI;
Fig. 7 is a sectional elevation view of the
inductor shown in Fig. 1 taken along line VII-VII;
Fig. 8 is a sectional side elevation view of the
inductor shown in Fig. 1 taken along line VIII-VIII;
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Fig. ~ is a representation of the flow of electrical
current through the inductor of Fig. l; and
Fig. 10 illustra~es the rail head hardness pattern
used in the railroad industry.
The drawings illustrate an inductor 10 which is
about two to three feet in overall length (including guide
rollers) for progressively heating the upper portion of the
head 52 of a longitudinally moving rail 50 which may be from
about 39 feet long in the case of a nominal rail length up
to about 1660 feet long in the case o a welded string of
track. The inductor can sufficiently heat standard weight
rails moving at speeds of 24 inches per minute and modular
arrangements of these inductors will heat rails moving at
speeds of up to 120 or 180 inches per minute. Alternatively,
the rail could be stationary and an inductor such as that
illustrated could be longitudinally moved along the rail.
Also~ both inductor and rail could be stationary during the
hea~ing step, but this would require an inductor unit
extending the entire length of the rail.
As is illustrated in Figures 1 and 2, the induc~or
10 is suspended over a longitudinally moving rail 50 from a
horizontal base member 20 which is supported by a vertical
board 12 having transv~rse ribs 14. The vertical board 12
is longitudinally immoveably held by a -frame (not shown).
Preferably the base member 20 is fabricated of refractory
L ~
sheet material such as sheet known in the trade as ~zircar~
and the board 12 and ribs 14 are fabricated of a laminated
phenolic material. The base member 20 and the board 12
are fastened together by screws 16 and to ribs 14 by screws
18. The base member 20 has posts 24 of refractory material
such as tha~ known as ~transite" depending from its bot~om
surface 22 and ~astened thereto with screws 26 or other
~uitable fasteners for providing additional support Eor
the inductor 10.
1~ The inductsr 10 generally comprises an electrical
conductor 30 and focusing means 40 and 41 disposed about ~he
eonductor 30. The details of the inductor 10 may be most
clearly seen in Flgures 3-8~ The general ronfiguration of
conductoE 30 may be most readily seen in Figure 9. Tha
15 depicted conductor 30 is a brazed 1 x 1/2 inch rectangular
copper tube having a 0.125 inch thick wall with the one inch
dimension generally facing the rail 50~
The focusing means 40 disposed at the sides of the
rall head 52 and second focusing means 41 disposad above the
20 rail head 52 about the conductor 30 generally comprise
stacked laminationR of electr.ical steel such as Qilicon-iron
al70y5 sold under the name "Magnesil~. Each lamination i5
an electrically insulated "C~ shaped section having 1~4~ x
1/2~ armq ex~ending from a 1/4a x 1 1/2" cen~ral strlp and
25 a thickness o~ ".007~ Each lamination al50 ha~ copper
keepers 42 on ei~her c;ide for mechanical support and one
* Trade Mark
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mica spacer per inch or breaking the electrical conductivity
through the stack, The focusing means 40 and 41 are preferably
bonded to the electrical conductor 30 by a thermal adhesive.
Preferably the conductor 30 and focusing means 40 and 41 are
coated with a ceramic material. Substantially identical
opposed pairs of laminated stacks are located along the
sides of the rail head 52 so that substantially equal
amounts of heat are induced in the cross section of the rail
head to minimize thermal stresse~ tending to hori~ontally
10 kink the rail.
The inductor 10 is fastened to base 20 by bolts 23
which are soldered to the conductor 30 on both sides of
focusing means 40. Additional support is provided by
soldered bolts 25 which fasten the vertical lengths of
15 conductor 30 to posts 24.
The terminals 34 of conductor 30 are mechanically
supported by vertical board 12~ Each terminal 34 is silver
soldered to a vertical plate 37 having a bracket 39 fastened
~o the board 12 by a screw 13. A mica sheet (not shown) is
disposed between the vertical plates 37 to electrically
insulate the plates and the terminal bolt 35. As may be
seen in Fig. 8, the conductor 30 is further supported on the
undercu~ portion 25 of posts 24. Also, a mica sheet 31 is
disposed between the adjacent lengths of conductor 30 for
electrically insulating these lengths.
The conductor 30 is preferably cooled by water or
other suitable fluid flowing within the rectangular tubeq
As the drawings illustrate, two inlet por ts 36 near the
conductor terminals 34 and two outlet ports 38 provide
coolant to and Erom the conductor 30.
At each end of the inductor lO are plates 44
secured to the bottom surface 22 of the horizontal base
member 20 by bolts 46 or other suitable fasteners for
supporting depending guide rollers which protect the inductor
10 from ~he rail 50. As may be most clearly seen in Fig. 4
horizontal rollers 48 protect the inductor unit from vertical
movements of the rail which could for example result from a
crowning type operation. Vertical rollers 49 extend downwardly
along the sides of the rail and protect the inductor unit
rom lateral movement of the rail . An insulating board (not
shown) may be utilized on the plate 44 at the exit of the
inductor unit to protect the plate 44 from temperatures of
about 2000 F. The rollers 48 and 49 at the entering end
are kept sufficiently cool by the atmosphere.
In a demonstration test of the inductor lO shown
in the drawings, the terminals 34 of the conduct 30 were
energized with 3 KHz current at a power output of about 340
E~ to heat a carbon steel weighing about 132 lbs. per yard
moving along its longitudinal axis at a speed of 24 inches
per minute in a hardening process. The original structure
of the rail head was coarse grained pearlite and the resulting
structure was fine grain pearlite which indicates that the
metal was heated to austeni~ing temperatures before the
L~ ~ 5 ~3
quench. The Rc hardness of the rail along the segments of
the rail head identified in Fig. 10 were as follows:
Dist~ from
Surface 16 ths AO BO CO DO E0_ _ _
1 38 39 38 38 38
2 39 40 39 39 40
3 39 40 39 39 39
3~ ~0 3~ 39 3
3~ 39 37 ~9 38
lo 6 37 39 37 3~ 38
7 37 39 35 38 37
8 36 38 3~ 3~ 37
9 36 38 31 38 36
1~ 35 3~ 30 37 35
11 35 37 28 37 33
12 35 36 2~ 3~ 32
13 33 36 ~5 36 29
1~ 30 35 35 28 -
29 35 34. 27
16 27 34 31
17 26 3~ 29
18 30 29
lg 28 27
~7
Fig. 10 is in accordance with AREA Specifications 4-M~6
which defines segment AE to be 7/8~ below the ball of the
rail head and points B and D to be 5/8 il above segment A~ D
The SpeciEication recommends an aim hardness pattern as
~ollows:
Results
of
~bove
Seqment Depth Brinell Rockwell C Test
~o 6/16~ 321 3~ 37
BO and DO ~ 6 9' 321 34 q 4 37
AO and EO 9/16~9 321 34,4 36
A visual inspection of ~he rail indicated that the rail
would only require touch-up restraightening, if any. This
test indicates that the rails easily mee~t t:he AREA
Specif ication .
-10
While a preferred embodiment of the inductor of
~e present invention has been shown and described above, it
is to be distinctly understood that the invention is not
limited thereto but may be otherwise variously embodied
within the scope of the following claims.
