U.S. patent number RE28,907 [Application Number 05/593,404] was granted by the patent office on 1976-07-20 for self-tapping threaded bushings.
Invention is credited to by Carl-Herwig Eibes, by Christian Eibes, Carl B. H. Eibes, deceased, by Ursula Eibes nee Waschau, by Maria-Theresia Wagner nee Eibes, all legar heirs.
United States Patent |
RE28,907 |
Eibes, deceased , et
al. |
July 20, 1976 |
**Please see images for:
( Certificate of Correction ) ** |
Self-tapping threaded bushings
Abstract
The disclosure relates to a threaded bushing which, upon
entering and turning in the initially smooth bore of the work
piece, will form through its own male thread the corresponding
internal thread within the wall of the work piece bore. The bushing
is formed with one or more exterior bevels or grooves which extend
axially over at least several threads and intersect such threads to
form spoon or cup-shaped frontal areas where each bevel or groove
merges into a respective thread.
Inventors: |
Eibes, deceased; Carl B. H.
(LATE OF Schnalttenback, DT), Eibes nee Waschau; by
Ursula (Schnaittenback, DT), Eibes; by Christian
(Schnaittenback, DT), Eibes; by Carl-Herwig
(Berlin-Schoneberg, DT), Wagner nee Eibes, all legar
heirs; by Maria-Theresia (Amberg, DT) |
Family
ID: |
27211325 |
Appl.
No.: |
05/593,404 |
Filed: |
July 3, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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125260 |
Mar 17, 1971 |
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733562 |
May 13, 1968 |
3597781 |
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Reissue of: |
329952 |
Feb 5, 1973 |
03866510 |
Feb 18, 1975 |
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Foreign Application Priority Data
Current U.S.
Class: |
411/417 |
Current CPC
Class: |
B21H
3/027 (20130101); B23G 7/00 (20130101); F16B
25/0052 (20130101); F16B 25/0078 (20130101); F16B
37/122 (20130101) |
Current International
Class: |
B23G
7/00 (20060101); B21H 3/02 (20060101); B21H
3/00 (20060101); F16B 25/00 (20060101); F16B
37/12 (20060101); F16B 37/00 (20060101); F16B
025/00 () |
Field of
Search: |
;85/47,48 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Frazier; Roy D.
Assistant Examiner: Holko; Thomas J.
Attorney, Agent or Firm: Pollock, Vande Sane &
Priddy
Parent Case Text
This is a continuation of Ser. No. 125,260, filed Mar. 17, 1971,
and now abandoned, which was a division of application Ser. No.
733,562, filed May 13, 1968, and now U.S. Pat. No. 3,597,781,
issued Aug. 10, 1971.
BACKGROUND OF THE INVENTION
Claims
What we claim is:
1. A threaded self-tapping bushing adapted to be secured to a work
piece and comprising,
an elongate member having helical male threads extending over at
least a portion of its axial length, said threads having crests,
roots between said crests, and flanks extending from said crests to
said roots on either side of said crests;
said member having at least one axially extending bevel
intersecting a plurality of successive threads,
the crests and flanks of each said male thread at their
intersection with said bevel defining frontal areas on either side
of said bevel which are concave both along the circumferential
direction of each said male thread and transversely thereto along
the axial direction of the bushing, each said bevel being
approximately as deep as the roots between the crests to ensure
that the roots between successive crests are essentially
discontinuous at each beveled portion, each said frontal area
providing cutting edges along at least a part of its periphery as
defined by said crest, flanks, and bevel,
one of the two said frontal areas formed at the junction of each
said male thread with said bevel having a greater curvature than
the other.
2. The threaded bushing of claim 1 in which the leading frontal
area in the direction of turning said bushing into said work piece
has less curvature than the lagging frontal area.
3. The threaded bushing of claim 1 in which the beveled male thread
profiles at least one end of the bushing are conically tapered
inwardly.
Description
Threaded bushings possessing a self-tapping male thread are usually
manufactured from metals, such as steel, bronze or brass, and serve
to fasten screws, bolts or similar connecting elements within or to
structural members or work pieces which have a lesser hardness than
the bushing material and can consist for example of soft steel or
iron, wood, plastic, light metals and the like. It is the purpose
of such threaded bushings, also called liners, to create within a
relatively soft work piece an internal thread possessing relatively
great strength. This strength is attained not only by this thread
of substantially greater diameter relative to the internal thread
diameter of the bushing but also by avoidance of a severance of the
fibers of the material, and it is one of the purposes of the
invention to avoid this disadvantage.
The invention is designed to solve several problems:
1. The internal thread, produced within the bore of the work piece,
is to be produced partially without cutting; for example, by
notching, and partially by cutting, i.e., by metal removal;
2. The entering torque of the threaded bushing is to be kept
relatively low, while the return torque or restoring moment should
be relatively high;
3. The costs for manufacturing the threaded bushing should be as
low as possible.
Self-tapping threaded bushings of various types and designs are
known. For example, there exist threaded bushings which provide, at
least over a portion of the length of the bushing, grooves or slots
which run substantially parallel to its axis and which form cutting
edges together with the webs of the thread, and with the outside of
the penetrating end of the bushing usually designed conically.
These slots or grooves of the known threaded bushings are usually
produced, following the manufacture of the male thread of the
bushing, by milling, grinding or the like. The method of
manufacture is very costly. Furthermore, threaded bushings of this
type will produce the internal thread within the bore of the work
piece almost exclusively by cutting. The forming of the thread by
cutting in the manner described has the disadvantage that the
fibers of the work piece material are severed, thereby lowering its
stability and especially its shearing strength.
SUMMARY OF THE INVENTION
In order to solve the above-described problems, the invention is
based on a threaded bushing possessing bevels, grooves, or the like
which intersect the male thread and form recesses within the
originally round contour, and which extend axially at least over
several threads but preferably over the total axial length of the
threaded bushing, and whereby between the bevel, groove, or the
like on the one hand and the threads on the other hand (i.e., at
the crests of the thread) faces or frontal areas are created which
will produce female threads within the bore of the work piece, the
novel and inventive feature being that the frontal areas of each
thread are bent or curved up, relative to the original contour, and
are formed concavely, similar to a shovel or spoon.
Particularly significant in connection with the threaded bushing
proposed by the invention is the point that the frontal areas of
the thread, facing each other from both sides of a bevel, are bent
or curved up at dissimilar magnitudes relative to the original
contour, and that they are designed in the shape of a shovel or
spoon.
Another specific characteristic, significant in connection with the
invention, of these frontal areas is the fact that they possess
edges which are designed in the form of not too sharply edged
cutting edges, or edges which will help to increase the restoring
moment. These frontal areas are produced by a male thread-rolling
process and appropriate deformation of material; that is, they are
formed by raising from the original surface or contour of the bevel
or the like.
According to the invention, this is accomplished by furnishing a
profile bar which has several axially extending bevels distributed
around its contour (the bevels preferably being axially parallel),
with a male thread by means of rolling tools, whereby the
characteristics of the rolling process, such as rolling pressure,
rolling depth, rolling advance, shape and material of the rolling
tool, and the like, are set and selected in such manner that the
frontal area, created in the zone of transition between an
individual crest of the thread and an individual bevel, is curved
at the thread end to a greater or lesser degree relative to the
original plane or contour of the bevel, or is raised due to the
deformation of material, and that the edges of said frontal areas
project above the areas with the edges not too sharply edged. The
not too sharply edged design is a decisive feature for the creation
of a powerful restoring moment, but it leads also to the other
desired effect, namely that upon entering and turning of the
bushing the internal thread of the work piece is being formed only
partially by cutting but mainly by deformation without cutting.
Preferred basic material to be utilized is profile material, for
example bars or tubes, produced by drawing. Such profile material
will already possess bevels in flat, convex or concave form.
The invention proposes further that during or after the rolling of
the male thread, there are produced in a manner known per se,
adjacent to one or both ends of the threaded bushing, conically
beveled male thread profiles, their outer diameters tapering off
toward the ends. By making the threaded bushing pointed at both
ends, the invention makes it feasible to select one or the other of
a threaded bushing to be entered and turned in the smooth bore of a
work piece, or to fasten it within the work piece, utilizing the
greater or lesser curved frontal area as cutting surface, or the
lesser or greater curved frontal area as means to increase the
restoring torque.
The direction of rolling at the creation of the male thread of the
bushing and the direction of turning of the bushing into the work
piece will either coincide or be opposite to each other, and
accordingly the more heavily curved frontal area will act as
thread-forming means, and the lesser curved frontal area as means
to increase the restoring torque, or vice-versa.
The invention proposes further that the boring of the threaded
bushing and the furnishing of the female thread is accomplished in
a manner known per se either before or after the
thread-rolling.
If applicable, it is further proposed that in case of a threaded
bushing made of steel the male thread or the entire bushing is
tempered after the thread-rolling.
It has been found that such concave or spoon-shaped designs of the
frontal areas which are curved or drawn up relative to the bevel,
groove, or the like possess edges which have, or can perform, at
least partially, the function of cutting and also simultaneously of
displacing material if these frontal areas are utilized as internal
thread-generating means.
At each bevel, groove, or the like, each individual crest of a
thread possesses two frontal areas, and according to the invention
the second area formed in the direction of rolling has a lesser
pitch than the frontal area designed for cutting, but even the
latter is still kept sufficiently concave or spoon-shaped in order
to attain a restoring torque which is greatly improved over the
designs known heretofore. It is also possible, under special
circumstances, to interchange the functions of the two frontal
areas so that the flatter area will act as thread-forming means
when entering and turning in the threaded bushing, with the more
pronouncedly curved frontal area increasing the exit torque during
return movement.
Manufacture is acccomplished by a process covered by the invention,
preferably by thread-rolling. It was found unxpectedly and
surprisingly that in case of basic material possessing the bevels
or grooves at full length, and proper selection of the rolling
surface pressure as well as the other characteristics of the
rolling process, there are created by the thread-rolling curved
frontal areas at the crests of the thread, that is within the zone
of transition between the crest of the thread and the bevel or
groove, a significant feature being that through such rolling
process, correctly set and controlled, said raised edges of the
frontal area are produced. The direction of rolling should
correspond to the direction of turning in of the bushing if it is
desired to use the steeper or more pronouncedly curved
three-forming element (the frontal areas) for the creation of the
internal thread within the smooth bore of the work piece; if it is
desired, in case of special circumstances, to employ the lesser
curved frontal areas as the thread-forming areas, the opposite
rolling direction will be chosen. As ready mentioned, in the latter
case the restoring moment is thus increased still further.
The ratio between the internal thread forming by cutting and by
shaping without cutting will vary, depending for example on the
steepness or height of the frontal area curvature, the sharpness of
the edges of the frontal area, and other characteristics. In any
event, the invention will have the effect of attaining a sufficient
deformation of material without cutting, following, timewise, the
cutting phase of the thread-forming process, so that compacting of
the material as well as an improvement in the fiber structure of
the material of the work piece can be attained. Such deformation of
the material has the additional advantage that the inserted
threaded bushing will be seated more strongly and securely in the
work piece.
If the edges of the frontal areas are not especially sharp, as can
be definitely accomplished by means of a properly controlled
rolling process, any danger of separating the fibers of the work
piece material will be eliminated.
BRIEF DESCRIPTION OF THE DRAWINGS
Specifically, the drawings illustrate:
In FIG. 1, the profile of a solid rod with three uniformly-spaced
bevels in longitudinal direction;
In FIG. 2, a solid rod in profile with slightly convex bevels
running in a longitudinal direction;
In FIG. 3, a solid rod in profile with three uniformly-spaced,
slightly concave bevels running in longitudinal direction;
In FIG. 4, a plan view of a completed threaded bushing;
In FIG. 5, a plan view of another species of a completed
bushing;
In FIG. 6, a completed threaded bushing in perspective;
In FIG. 7, an enlargement of the area VII depicted in FIG. 6;
In FIG. 8, a section along line VIII--VIII of FIG. 7;
In FIG. 9, a section along line IX--IX of FIG. 7;
In FIG. 10, a section along line X--X of FIG. 7; and
In FIG. 11, the insertion and turning process of a bushing into a
work piece.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
FIG. 1 shows rod 1, originally a round bar, provided with flat
bevels 2, spaced uniformly at the contour and running axially
parallel, that is, in a longitudinal direction of the rod.
FIG. 2 shows a substantially identical rod 1', its bevels 2' shaped
slightly in convex form, but otherwise identical with bevels 2.
In FIG. 3 the bevels 2" are shaped concavely at the otherwise
identical rod 1", running again in longitudinal direction, axially
parallel. At area 3 it is indicated that the rod can be hollowed,
whereby the inner wall 3 can be provided with the required internal
thread at the proper stage of the manufacturing process. Usually,
solid rods will be preferable in view of the rolling process
because there exists the danger that a thin-walled tube could be
deformed excessively due to the rolling pressure.
FIG. 4 shows a completed threaded bushing B in plan view, where the
direction of turning is identical with the direction of rolling,
both running in clockwise direction. The rolling direction
illustrated, creating the male thread, causes the above-discussed
bulging, that is, the formation of curved-up or bent-up cutting
edges 13, created by clockwise displacement of material. The
rolling process also has the peculiar consequence that there will
rise in the other direction, that is, opposite to the rolling
direction, a less pronounced curvature at 14, which in this case
represents the restoring edge.
In case of the threaded bushing B', shown in FIG. 5 in the form of
an axial view, the rolling had been performed in opposite
direction, and this figure illustrates that the position of the
edges or frontal areas 13 and 14 becomes reversed, the areas being
designated by numerals 13' and 14'.
FIG. 6 shows the tapering of the lower threads within area 12, a
feature which is known per se and which can be accomplished for
example by proper turning or grinding.
We wish to mention that the preferred basic material is a rod,
manufactured by drawing and formed as shown in FIGS. 1-3. A
significant feature of the invention is the fact that the frontal
areas 13 as well as the opposite areas 14, created at the
intersections between the bevels 2, the flanks 15a and 15b and the
crests 15 of each thread at the zone of transition toward the bevel
2 or the like, have a concave shape, similar to a spoon, for
example, an internal surface in the form of a spade or scoop; in
other words, areas are curved inwards spherically and cup-like.
Also, the roots 11 between successive threads are essentially
discontinuous at bevel 2.
FIGS. 7 and 8 illustrate these points in a particularly clear
manner. The frontal areas 13 possess a spherical concavity of the
frontal edge or area of the crest 15 of the thread. The frontal
areas 14 are shaped in the same manner although less pronouncedly.
The edges 13' and 13" of said frontal areas 13 are formed at the
intersection of flanks 15a and 15b with bevel 2 and are upwardly
forced, narrow crests which act in a certain manner as cutting
edges, that is, metal-removing edges; however, since they do not
possess the sharpness of a knife, they will fulfill the desired
effect of not only removing metal by cutting but to begin, and at
least carry out partially, the process of deforming material during
the formation of the female thread within the work piece. Likewise,
the edges or rims 14' and 14" of the frontal areas 14 will form not
too sharp cutting edges, so that these frontal areas 14 will
increase significantly the restoring moment during the back-out,
assuming that the direction of entry and turning corresponds to the
arrow E in FIG. 7. Obviously, in case of the opposite direction of
turning, as indicated by arrow E', the frontal area 14 will be the
area forming the female thread, and areas 13 the back-out areas,
causing a particularly great increase in the restoring moment.
FIGS. 9 and 10 illustrate the sectional views along the lines
depicted in FIG. 7. It should be noted that within the lower region
12 (see FIG. 6), the crests of the thread are flattened, that is,
designed in tapered shape, as indicated by the broken line 17 in
FIG. 10 (note shown in FIG. 9).
FIG. 11 shows how a threaded bushing B is introduced and turned in
work piece 19 in direction E by a turning tool 18 of known
construction, the work piece possessing a known smooth bore 20, the
bore diameter being smaller than the widest part of the outer
diameter of bushing B. The bushing B, illustrated in FIG. 11, has
for example the thread-forming frontal areas 13 and the back-out
areas 14, as shown in FIG. 6.
According to a preferred embodiment, the bushings of the present
invention are made from a length of rod of basic circular cross
section which has been provided with longitudinal planar bevels
generally as shown, for example, in FIG. 1. As shown in FIGS. 4, 5,
7, and 8, the longitudinal planar bevels are located on chords of
the basic circular cross section of the rod which are at a depth
within the circular cross section sufficient to ensure that
subsequent thread-rolling on the circular cross section does not
produce any threads whose roots extend completely across the
bevelled portions. In other words, the thread root radius is chosen
to be at least as large as the minimum radius between the center of
the circular cross section and the planar bevel. Thread rolling is
properly carried out by the well-known means of three rollers
spaced circumferentially about the rod, and preferably the
direction of thread rolling is clockwise, that is, in the direction
of turning of the bushing into the work piece. The thread rolling
rollers are adjusted as required by the particular thread geometry
and the rod material so that the conventional thread rolling
surfaces do not roll any thread roots completely across the area in
which the planar bevels are located on the rod, in a manner that
will be appreciated by those skilled in the thread-rolling art.
After the threads have been rolled onto the rod, the then-threaded
rod is cut into a plurality of pieces each of which comprises a
single bushing.
Also covered by the invention is the manufacture of threaded
bushings possessing one or more of the above discussed features in
that manner that first pieces of bushing length are cut off from a
rod or tube section possessing a round contour, the pieces are then
provided with bevels (2,2') and with a male thread by rolling, the
internal thread being created in usual manner.
Finally, another manufacturing process within the framework of the
invention could utilize pressure die casting with the pressure die
casting tools or molds being shaped and designed in such manner
that the above-discussed physical features, in particular the
scoop-shaped form of the frontal areas 13, 14, will be created.
Having described an improved self-tapping bushing as one
improvement of this invention, we desire it to be understood that
various other modifications and alterations may be made departing
the specific forms shown without departing from the scope of the
invention.
* * * * *