U.S. patent number 3,659,069 [Application Number 05/095,503] was granted by the patent office on 1972-04-25 for inductor for heating an elongated workpiece having a varied profile.
This patent grant is currently assigned to Park-Ohio Industries, Inc.. Invention is credited to Norbert R. Balzer, George M. Mucha.
United States Patent |
3,659,069 |
Balzer , et al. |
April 25, 1972 |
INDUCTOR FOR HEATING AN ELONGATED WORKPIECE HAVING A VARIED
PROFILE
Abstract
An induction heating inductor for heating an elongated workpiece
having a varied profile which inductor includes two generally
parallel conductors extending the portion of the workpiece to be
heated and generally U-shaped flux concentrators around these
conductors with spaced legs facing the workpiece and wherein the
length of the legs are varied to form substantially a mirror image
of the workpiece profile.
Inventors: |
Balzer; Norbert R. (Parma,
OH), Mucha; George M. (Parma Heights, OH) |
Assignee: |
Park-Ohio Industries, Inc.
(Cleveland, OH)
|
Family
ID: |
22252299 |
Appl.
No.: |
05/095,503 |
Filed: |
December 7, 1970 |
Current U.S.
Class: |
219/673; 219/639;
219/660 |
Current CPC
Class: |
H05B
6/102 (20130101) |
Current International
Class: |
H05B
6/02 (20060101); H05b 009/02 () |
Field of
Search: |
;219/10.43,10.79,8.5,10.57 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truhe; J. V.
Assistant Examiner: Jaeger; Hugh D.
Claims
Having thus described our invention, we claim:
1. An induction heating inductor for heating an elongated workpiece
having a given length to be heated, a central axis and an outer
surface with a preselected axially extending profile whereby some
portions are more close to said axis than other portions of said
surface, said inductor comprising at least one generally straight
conductor extending axially along said surface for said given
length and a generally U-shaped flux concentrator over said
conductor with two legs spaced facing said workpiece surface, the
improvement comprising: said legs of said concentrator having
varied lengths and forming a profile approximately the mirror image
of said surface profile.
2. The improvement as defined in claim 1 wherein said concentrator
is formed at least in part from a plurality of generally U-shaped
iron laminations.
3. The improvement as defined in claim 1 wherein said concentrator
included interrupted portions along its profile.
Description
The invention relates to the art of induction heating and primarily
to an inductor for heating an elongated workpiece having a varied
profile.
The invention is particularly applicable for inductively heating a
shaft-like workpiece having a tapered profile, and it will be
described with particular reference thereto; however, it should be
appreciated that the invention has much broader applications and
may be used for inductively heating a variety of elongated
workpieces having varied profiles along their lengths.
In hardening elongated, shaft-like workpieces it has become
somewhat common to use a single turn inductor having two parallel
conductors extending the length of the workpiece. The workpiece is
rotated adjacent the energized parallel conductors to heat
inductively the portion of the elongated workpiece adjacent the
conductors. Thereafter, appropriate means is used to quench harden
the heated portion of the workpiece. The present invention relates
to an improvement in an inductor of the type including two
generally parallel conductors formed into a single loop and
energized by an alternating frequency power source. Heretofore,
when the profile of the elongated workpiece was varied to include
axial tapers or stepped portions along the length of the workpiece,
the heating effect along the parallel conductors was not varied.
This resulted in un-uniform surface heating of the workpiece as it
was rotated. To overcome this difficulty, it has been suggested to
modify the parallel conductors extending along the length of the
workpiece to correspond with the profile of the workpiece. As is
obvious, this solution substantially increased the difficulty
experienced in forming the inductor and added to its expense. Also,
it was difficult to modify such an inductor to compensate for
engineering variables or to change the inductor for use in
different workpieces.
All of these difficulties have been overcome by the present
invention which relates to a single turn inductor for use in
heating an elongated workpiece, which inductor is modified to
change the heating effect along its parallel conductors in
accordance with the profile of the workpiece to be heated.
In accordance with the present invention, there is provided an
improvement in an induction heating inductor for heating an
elongated workpiece having a given length to be heated, a central
axis and an outer surface with a generally preselected axially
extending profile, which inductor includes at least one generally
straight conductor extending axially along the surface of the
workpiece and carrying a generally U-shaped flux concentrator with
two spaced legs facing the workpiece surface. The improvement, in
accordance with the invention, includes varying the length of the
legs of the concentrator to form a profile for these legs, which
profile approximates the mirror image of the surface profile of the
workpiece. In this manner, the heating effect along the length of
the workpiece is substantially uniform without requiring
modification of the parallel conductors.
The primary object of the present invention is the provision of a
single turn inductor for heating an elongated workpiece having a
varied profile, which inductor includes flux concentrator means for
varying the heating effect along the conductor in accordance with
the profile of the workpiece.
In accordance with another object of the present invention there is
provided a single turn inductor for heating an elongated workpiece
having a varied profile, which inductor includes a flux
concentrator extending along the length of the parallel conductors
and having a varied profile that is the mirror image of the
workpiece profile.
These and other objects and advantages will become apparent from
the following description used in conjunction with the accompanying
drawings, in which:
FIG. 1 is a pictorial view showing, somewhat schematically, the
preferred embodiment of the present invention;
FIG. 2 is an enlarged cross-sectional view taken generally along
line 2--2 of FIG. 3;
FIG. 3 is an enlarged plan view taken generally along line 3--3 of
FIG. 2;
FIG. 4 is an enlarged cross-sectional view taken generally along
line 4--4 of FIG. 3;
FIG. 5 is an enlarged cross-sectional view taken generally along
line 5--5 of FIG. 3; and,
FIG. 6 is a top elevational view showing, somewhat schematically, a
modification of the present invention.
Referring now to the drawings wherein the showings are for the
purpose of illustrating a preferred embodiment of the invention
only and not for the purpose of limiting same, FIGS. 1-5 show an
induction heating apparatus A for inductively heating an elongated
workpiece B having an outer surface profile 10 including a
cylindrical portion 12 and a tapered portion 14. The workpiece has
spaced ends 16, 18 and a length L to be heated between these ends.
Centers 20, 22 locate the workpiece on its axis a for rotation by
an appropriate means, schematically indicated as driven motor 24.
An inductor C is used for inductively heating the workpiece. This
inductor includes two parallel spaced conductors 30, 32, a first
cross-over conductor 34 at end 18 and a second cross-over conductor
36 at end 16. These conductors form a single turn loop having a
well known construction. To energize this loop, there is a
discontinuity portion 40 dividing cross-over conductor 36 into two
sections, 36a, 36b. This discontinuity portion could be located at
various positions within the loop formed by the conductors of the
inductor. Leads 50, 52 connect the sections 36a, 36b with a power
supply, schematically represented as generator 54, having a power
factor correcting capacitor 56. The structure so far described is
essentially the same as now being used for inductively heating
shaft-like workpieces.
In accordance with normal practice, there are provided two flux
concentrators 60, 62 having U-shaped legs 60a, 60b and 62a, 62b,
respectively which legs face toward the workpiece B. The U-shaped
concentrators could be formed by a plurality of adjacent soft iron
laminations or other high permeability material, such as ferrites.
In accordance with the present invention, the legs of the flux
concentrators are modified to provide profiles 70, 72 for
concentrators 60, 62, respectively. These profiles are
substantially mirror images of the profile 10 formed by the outer
surface of workpiece B. Of course, in the illustrated embodiment
the profiles 70, 72 could be formed by a plurality of steps or by
gradual changing of the lengths for the legs of the concentrators.
The term "mirror image" is used to indicate that the profiles 70,
72 have essentially the reverse shape of the workpiece profile 10,
but not that this shape is identical from a dimensional standpoint.
It could vary to provide basically the function described
later.
Referring now to FIGS. 4 and 5, the effect of the varied contour
for the flux concentrator legs is schematically illustrated. As
shown in FIG. 4, if the legs 60a, 60b, 62a, 62b have their longest
lengths, the flux fields x are concentrated to provide a heating
pattern generally shown by the dashed lines within the portion 12
of workpiece B. With these flux concentrator legs retracted, as
shown in FIG. 5, the flux density of each field y is reduced so
that, in the smaller portion 14, of the workpiece B the heating
depth is somewhat reduced beyond that which would have been caused
hy the leg being at the length shown in FIG. 4. This causes the
heating pattern shown by the dashed lines which is substantially
the same as the heating pattern in the larger cylindrical portion
12. In this manner, there is a modification of the flux fields
emanating from the parallel conductors 30, 32 which variation
attempts to compensate for the variations in the cross-section of
the workpiece B along the length L. After the workpiece B is
heated, is is then quench hardened according to known
practices.
Referring now to FIG. 6 a modification of the invention is
illustrated. The same parts as shown in the preferred embodiment
bear like numbers. The workpiece B' includes stepped portions 80,
82 and 84. The inductor C' includes flux concentrators 90, 92 on
conductor 30 and concentrators 94, 96 on conductor 32. These flux
conductors are formed into U-shaped configurations, as were
concentrators 60, 62, and are positioned opposite the enlarged
portions 80, 84 of workpiece B'. The intermediate openings 100, 102
are adjacent the reduced portion 82 of workpiece B'. These openings
could be filled by flux concentrators having shorter legs, as is
apparent from the description of the preferred embodiment of the
present invention. The operating characteristics of this
modification are substantially identical to the operating
characteristics as explained in connection with the preferred
embodiment of the invention as shown in FIGS. 1-5.
* * * * *