U.S. patent application number 12/968737 was filed with the patent office on 2011-04-14 for threaded bolt and method for its production.
This patent application is currently assigned to NEWFREY LLC. Invention is credited to Joachim GEIST, Joachim SCHNEIDER, Wolfgang WERNER.
Application Number | 20110086715 12/968737 |
Document ID | / |
Family ID | 39885107 |
Filed Date | 2011-04-14 |
United States Patent
Application |
20110086715 |
Kind Code |
A1 |
GEIST; Joachim ; et
al. |
April 14, 2011 |
THREADED BOLT AND METHOD FOR ITS PRODUCTION
Abstract
A threaded bolt may be produced according to a method including
the steps of: forming a cylindrical bolt blank of metal with a root
end and a head end, and with a section of the bolt blank adjoining
the root end that is reduced in diameter up to a region designed
for the formation of lead-in flights. Then, in a first rolling
phase, partially form the principal thread flights and the lead-in
thread flights using a first pass of flat jaws of a thread rolling
machine. Then, in a second rolling phase, fully form the principal
flights and the lead-in flights and forming grooves.
Inventors: |
GEIST; Joachim; (Muecke,
DE) ; SCHNEIDER; Joachim; (Ehringshausen, DE)
; WERNER; Wolfgang; (Reutlingen, DE) |
Assignee: |
NEWFREY LLC
Newark
DE
|
Family ID: |
39885107 |
Appl. No.: |
12/968737 |
Filed: |
December 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12180030 |
Jul 25, 2008 |
|
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|
12968737 |
|
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Current U.S.
Class: |
470/11 |
Current CPC
Class: |
F16B 33/02 20130101;
F16B 35/007 20130101 |
Class at
Publication: |
470/11 |
International
Class: |
B21H 3/06 20060101
B21H003/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2007 |
DE |
102007036733.5 |
Claims
1. A method of producing a threaded bolt, the method comprising:
forming a cylindrical bolt blank of metal with a root end and a
head end such that a section of the bolt blank adjoining the root
end is reduced in diameter up to a region designed for the
formation of lead-in flights; partially forming principal flights
and the lead-in flights in a first rolling phase using a first pass
of flat jaws of a thread rolling machine; fully forming the
principal flights and the lead-in flights and forming grooves in a
second rolling phase.
2. A method according to claim 1, wherein the flat jaws comprises a
first flat jaw and a second flat jaw; wherein the first flat jaw
has a rolling profile for the formation of the principal flights
and the lead-in flights; wherein the second flat jaw has an initial
section with a thread rolling profile section for the formation of
the principal flights and the lead in flights and an end section
with ribs for the formation of the grooves.
3. A method according to claim 2, wherein the threaded bolt
comprises a shank with a root end and a head end, the shank
including a spiral-shaped external thread; wherein the external
thread includes the principal flights and the lead-in flights, the
lead-in flights adjoining the principal flights and being nearer to
the root end of the shank than the principal flights; wherein the
lead in flights have lead in surfaces which differ from the
principal flight and have a smaller outside diameter than the
principal flight.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional Application of U.S. patent
application Ser. No. 12/180,030, filed Jul. 25, 2008 and now
abandoned, which claims the benefit of German Application No. 10
2007 036 733.5, filed Aug. 3, 2007. The disclosure of the above
application is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a threaded bolt having a shank of
basic cylindrical form, which is provided with a spiral-shaped
external thread that has at least one principal flight and one
lead-in flight with a lead-in surface.
[0003] A threaded bolt of the kind indicated is known from EP
0,840,859. The known design of the threaded bolt is intended to
prevent thread damage when the bolt is screwed with its external
thread into a threaded hole with matching internal thread. Damage
of the thread may occur in threaded elements without lead-in flight
when the central axes of a bolt and a nut are misaligned in such a
way that their threads are displaced with respect to each other by
at least one-half pitch when the threads seek to engage in each
other upon being screwed together. Then, if the two parts are
turned against each other, this may lead to jamming and damage of
the thread, where the flights of external and internal thread cross
over each other. The formation of one or more lead-in flights
ensures correct threading of the flights of internal and external
threads, even in the case of unfavorable alignment, and prevents
damage of the thread when the bolt is screwed in.
[0004] It is in addition disclosed in DE 10 2005 017,379 A1 that
threaded bolts may be provided with grooves extending in the
longitudinal direction, which interrupt the flights of the thread
and form free spaces for the accommodation of lacquer, lacquer
residues or dirt. Such a design is advantageous when the nut or
bolt thread has been provided with a coat of lacquer before being
screwed together. In the case of lacquering, the grooves remove
lacquer from the flights and when the bolt is screwed into a
threaded hole, detached particles of lacquer can be deposited in
the grooves, so that they are not caught in between the flights and
thereby hinder screwing of the parts into each other.
[0005] The object of the invention is to make available a threaded
bolt of the kind mentioned at the beginning, which can be screwed
in without the risk of thread damage, does not tend to jam in the
case of a lacquered surface and can be produced especially
inexpensively.
[0006] To accomplish this object, according to the invention there
is provided a threaded bolt having a shank of basic cylindrical
form, which has a root end and a head end and which is provided
with a spiral-shaped external thread that has at least one
principal flight and in the vicinity of the root end has at least
one lead-in flight which is adjoined by the principal flight, where
the lead-in flight has a lead-in surface that differs from the
principal flight, has a smaller outside diameter than the latter
and is formed in order to come into crossing-free engagement with
flights of a complementary internal thread of an element, and where
only the principal flight or the lead-in flight and the principal
flight are interrupted by at least one groove which extends in the
longitudinal direction of the shank, in order to form a free space
for the accommodation of lacquer residues. Here the flights and the
grooves are initially formed by rolling.
[0007] Surprisingly, it has been found that the formation of
lead-in flights and of grooves interrupting them can be matched to
each other so that threaded bolts can be procured which permit
crossing-free engagement of the flights when the bolts are screwed
into a threaded hole and thus reliably avoid damage of the thread.
This was surprising to a person skilled in the art because, owing
to interruption of the flights at the grooves, the possibility of
defective engagement of the flights in case of incorrect alignment
of the threaded bolt is substantially greater than in the case of
threaded bolts without grooves. In unfavorable cases, for example
with small diameters or a large number of grooves, according to one
proposal of the invention, it may be provided that the groove or
grooves interrupt only the principal flight, so that formation and
action of the lead-in flight is not adversely affected by a
groove.
[0008] According to another proposal of the invention, a plurality
of grooves extending in the longitudinal direction of the shank
preferably are provided at a like distance apart from each other,
where each groove preferably runs along a spiral line, the angle of
inclination of which at the outer periphery of the external thread
amounts to about 70.degree. to 85.degree., in particular
80.degree.. The spiral-shaped course of the grooves ensures
continuous rolling of the threaded bolt in the rolling process.
[0009] The depth of the grooves may be substantially equal to the
depth of the thread, and when the diameter of the bolt is
sufficiently great, the depth of the grooves may alternatively be
greater than the depth of the thread.
[0010] A threaded bolt usually has a plurality of principal flights
and alternatively a plurality of lead-in flights, the lead-in
flights having a smaller outside diameter than the principal
flights. For reliable introduction of the threaded bolt into a
threaded hole and avoidance of thread damage, it has in addition
been found to be advantageous when the outside diameter of the
lead-in flights increases over-proportionately in the direction of
the principal flights, i.e., the change in diameter increases from
lead-in flight to lead-in flight.
[0011] The lead-in flights may have a surface arched convex in
profile or a lead-in surface limited laterally by thread flank
sections and flat in profile. Preferably, lead-in flights of both
embodiments are combined with each other, where the lead-in surface
arched convex in profile has a smaller outside diameter than the
lead-in surface flat in profile.
[0012] In order to limit the degree of misalignment when a threaded
bolt according to the invention is screwed in, according to an
additional proposal of the invention it is provided that, between
the root end and the lead-in flight adjacent thereto, there is
provided a threadless bolt section, the outside diameter of which
corresponds substantially to the core diameter of the thread.
[0013] For producing the threaded bolt, the present invention
provides a method in which a cylindrical bolt blank of metal is
formed with a root end and a head end, a section of the bolt blank
adjoining the root end is reduced in diameter up to a region
designed for the formation of a lead-in flight and then, in a
thread rolling machine, in one pass by means of flat jaws, in a
first rolling phase principal flights and lead-in flights are
partially and in a second rolling phase are fully initially formed
and, in addition, in the second rolling phase grooves are rolled
into the surface of the bolt blank.
[0014] The method according to the invention has the advantage that
the final form of the threaded bolt can be produced from a
preformed blank in a single, continuous rolling process which
consists of two different rolling phases. The method is therefore
especially rapid and inexpensive to perform. It has further been
found that sufficiently precise forming of the lead-in flights is
obtained with this method, so that crossing-free engagement of the
flights is reliably ensured when the bolt is screwed in.
[0015] According to an additional proposal of the invention, two
unlike flat jaws, namely a first flat jaw with a rolling profile
for formation of principal flights and lead-in flights, and a
second flat jaw, which has an initial section with a rolling
profile for partial formation of principal flights and lead-in
flights, and an end section with ribs for the formation of grooves,
where profile-free jaw sections are provided between the ribs, may
be used for rolling the threaded bolts. This embodiment of the
method has the advantage that the work pieces roll off the flat
jaws trouble-free and the dimensional accuracy of the formed
threaded bolt is great.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention is explained in detail below by an exemplary
embodiment that is shown in the drawing, wherein
[0017] FIG. 1 shows a view of a threaded bolt according to an
exemplary embodiment of the invention,
[0018] FIG. 2, an enlarged longitudinal section of a section
comprising the root end of a threaded bolt according to an
exemplary embodiment of the invention,
[0019] FIG. 3, a schematic representation of the method for rolling
a threaded bolt according to an exemplary embodiment of the
invention,
[0020] FIG. 4, a schematic representation of the flat jaw for the
formation of grooves in the rolling of a threaded bolt according to
an exemplary embodiment of the invention, and
[0021] FIG. 5, a view of an additional threaded bolt according to
an exemplary embodiment of the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0022] The threaded bolt 1 shown in FIG. 1 has a shank 2 of basic
cylindrical form with a root end 3 and a head end 4. Formed on the
head end 4 is a flange 5, which on its side opposite the shank 2
bears a weld-on section 6 with a tapered face 7 for the formation
of an ignition tip 8. At the root end 3, the shank is provided with
a tapered bevel 9 and an adjoining cylindrical section 10.
[0023] Between the section 10 and the flange 5, the shank 2 has a
metric external thread 11 with principal flights 12 and lead-in
flights 13. The lead-in flights 13 are adjacent to the section 10.
They are converted at approximately 14 into the adjoining principal
flights 12. The principal flights 12 correspond in their design to
the standard for metric thread with a pitch of 60.degree..
[0024] The lead-in flights 13 differ in form from the principal
flights 12. The first lead-in flight 13.1 has the smallest outside
diameter and a lead-in surface with convexly arched profile. The
following lead-in flight 13.2 has a somewhat greater outside
diameter. The profile of its lead-in surface is likewise arched
convexly outward, where the curvature may be somewhat greater. The
lead-in flight 13.2 is converted into a lead-in flight 13.3, which
has a still greater outside diameter, but the outside diameter of
which is still distinctly smaller than the outside diameter of the
principal flights 12. The lead-in flight 13.3 already has pitch
sections between which is found a lead-in surface flat in
profile.
[0025] In the region of the external thread 11, the shank 2 in
addition has a plurality of grooves 15, which extend in the
longitudinal direction and run along a spiral line about the
longitudinal axis of the shank 2. The angle of inclination of the
spiral line of the grooves 15, that is, the angle that upon
unwinding forms the spiral line of a peripheral line, amounts to
about 80.degree., but may alternatively be smaller or greater. The
depth of the grooves 15 corresponds substantially to the depth of
the external thread 11. The principal flights 12 and the lead-in
flights 13 are therefore interrupted by the grooves 15 and
subdivided into individual flight sections. The grooves 15 have the
task, when the threaded bolt 1 is screwed into a threaded hole, of
accommodating lacquer residues that become detached from the
previously lacquered surfaces of the threaded bolt and/or the
threaded hole.
[0026] FIG. 2 shows a cross section through the front end of the
bolt 1. Here, the unlike form of the lead-in flights 13.1, 13.2 and
13.3 is clearly visible, where the lead-in surface of the first
lead-in flight 13.1 has not been fully formed out in rolling and
therefore does not have the provided convex arching. However, this
is not disadvantageous for screwing in, since the thereby still
flatter lead-in flight 13.1 is able to promote rather than hinder
automatic alignment of the bolt 1. The first principal flight 12.1,
in contrast to the following principal flights 12, is likewise not
fully formed out in its tip region. Such small deviations from the
form sought may result, however, due to slight dimensional
deviations and inhomogeneities of the blank in subsequent
deformation of the threaded bolt.
[0027] The principle of the rolling method with flat jaws used
according to the invention is illustrated in FIG. 3. A lower flat
jaw 20 is arranged stationary and has on its upper side a
development of the thread profile. Over the jaw 20 is seated
movable in the longitudinal direction an upper flat jaw 21, which
on its underside has a distortion of the thread profile. The
movable seating of the upper jaw 21 is designed so that in the
starting position of the jaw 21 a cylindrical blank can be inserted
between the jaws. With continued movement of the jaw 21 in the
direction of the arrow 22, the distance between the jaws 20, 21 is
reduced, so that the thread profile of the jaws penetrates into the
surface of the blank and while the blank rolls on the jaws, the
thread is formed out more and more strongly up to its final
definition. The drawing shows the end of the thread rolling process
with the blank formed into the threaded bolt 23.
[0028] FIG. 4 illustrates the construction of a flat jaw 25, which
is designed for producing a threaded bolt according to the
invention. The flat jaw 25 has an initial section 26 with a thread
rolling profile, where the thread rolling profile has a region 26.1
for the formation of principal flights and a region 26.2 for the
formation of lead-in flights. The initial section 26 is adjoined by
an end section 27, which is provided with ribs 28 for the formation
of grooves. Between the ribs 28 are found deeper, profile-free
sections 29, into which the formed-out sections of the flights,
which are found between the grooves, can penetrate. The jaw 25 is
used together with a second flat jaw, which on its entire length
has a thread rolling profile suitable for the formation of
principal flights and lead-in flights.
[0029] FIG. 5 shows a threaded bolt 31, which is like the threaded
bolt 1 up to the formation of grooves. The threaded bolt 31 has a
shank 32 with a root end 33 and a head end 34, which is provided
with a flange 35 and a weld-on section 36. The shank bears a metric
external thread 37 with principal flights 38 and, between the
flights 38 and the root end 33, lead-in flights 39.
[0030] In the case of the threaded bolt 31, only the principal
flights 38 are interrupted by a plurality of grooves 40. The
grooves 40 extend along a spiral line with like angle of
inclination and have a like distance apart from each other. The
grooves 40 end at the lead-in flights 39, so that the lead-in
flights 39 are fully formed. This has the advantage that, in case
of unfavorable conditions of thread-to-shank diameter and in case
of an unfavorable number of grooves referred to shank diameter, a
more precise configuration and better action of the lead-in flights
39 can be obtained. Since the lead-in flights 39 are not fully
formed flights, the absence of grooves 40 in this region is not
disadvantageous.
* * * * *