U.S. patent number 10,385,903 [Application Number 15/587,436] was granted by the patent office on 2019-08-20 for metric self-tapping locking screw and the manufacturing method thereof.
This patent grant is currently assigned to Essence Fastening System (Shanghai) Co., Ltd.. The grantee listed for this patent is Essence Fastening System (Shanghai) Co., Ltd.. Invention is credited to Xin'an Li, Huiying Wang, Qinfeng Yi.
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United States Patent |
10,385,903 |
Yi , et al. |
August 20, 2019 |
Metric self-tapping locking screw and the manufacturing method
thereof
Abstract
A metric self-tapping locking screw comprises a screw head which
is connected to a thread locking body by a screw rod. The thread
locking body and the self-tapping tip are provided with a screw
thread on the surface. The self-tapping tip is arranged at the root
of the thread locking body; the screw thread adopts the basic
structure of the standard ordinary triangular thread. The flank
angle back to the fastened surface is 15-20.degree. and the flank
angle of the screw thread facing the fastened surface is
30.degree.. The metric self-tapping locking screw in the Invention
make the installed parts to be fastened have higher axial clamping
force and static loosing moment, which solves the attenuation
problem of axial clamping force and static moment of fastened
parts.
Inventors: |
Yi; Qinfeng (Jiangsu,
CN), Wang; Huiying (Shandong, CN), Li;
Xin'an (Jiangsu, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Essence Fastening System (Shanghai) Co., Ltd. |
Shanghai |
N/A |
CN |
|
|
Assignee: |
Essence Fastening System (Shanghai)
Co., Ltd. (Shanghai, CN)
|
Family
ID: |
61601535 |
Appl.
No.: |
15/587,436 |
Filed: |
May 5, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180223889 A1 |
Aug 9, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 5, 2017 [CN] |
|
|
2017 1 0064953 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21H
3/025 (20130101); B21K 1/46 (20130101); F16B
25/0015 (20130101); B21H 3/027 (20130101); F16B
25/106 (20130101); F16B 25/0021 (20130101); F16B
25/0047 (20130101); F16B 25/0084 (20130101); B21F
5/005 (20130101); F16B 25/10 (20130101) |
Current International
Class: |
F16B
25/10 (20060101); B21F 5/00 (20060101); F16B
25/00 (20060101); B21K 1/46 (20060101); B21H
3/02 (20060101) |
Field of
Search: |
;411/411,414 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Delisle; Roberta S
Claims
What is claimed is:
1. A metric self-tapping locking screw, comprising a screw head, a
screw rod, a thread locking body, a self-tapping tip and a screw
thread; the screw head is connected to the thread locking body with
the screw rod; the thread locking body and the self-tapping tip are
provided with the screw thread on the surface; the self-tapping tip
is arranged at the root of the thread locking body; the screw
thread adopts the basic structure of the standard ordinary
triangular thread; a flank angle of the screw thread back to the
fastened surface is 15-20.degree. and another flank angle of the
screw thread facing the fastened surface is 30.degree.; a crest of
the screw thread is in a plane transition structure or a natural
circular arc transition structure; wherein the screw thread is
divided into eight equal parts by eight mean lines; the eight mean
lines include one-eighth line, two-eighth line, three-eighth line,
four-eighth line, five-eighth line, six-eighth line, seven-eighth
line and eight-eighth line; the intersection of the four-eighth
line and the crest is a first crossing point; the intersection of
the two-eighth line and the flank side back to the fastened surface
is a second crossing point; a tangency arc between the first
crossing point and the second crossing point is a rounded root of
thread; wherein the two-eighth line and the screw thread intersect
at a third tangency point; the three-eighth line and the screw
thread intersect at a fourth crossing point; line connected the
third tangency point and the fourth crossing point forms a thread
root-diameter angle with the two-eighth line; the thread
root-diameter angle is 20.degree..
2. The metric self-tapping locking screw according to claim 1,
wherein the rounded root of thread constitutes the asymmetry
root-diameter structure of the metric self-tapping locking screw
together with the thread root-diameter angle.
3. The metric self-tapping locking screw according to claim 1,
wherein the cross-section of the self-tapping tip is in a
triangular circular arc transition structure and forms an angle of
8-15.degree. with the plane of the thread locking body; the crests
of the self-tapping tip transit to the thread locking body from
small to large in a cone way and the screw threads on the thread
locking body gradually diminish to the self-tapping tip in
compliance with the crest shape; the length of the screw thread on
the self-tapping tip is equal to or less than the nominal diameter
of the screw thread on the thread locking body.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of Chinese Patent
Application No. 201710064953.8 filed on Feb. 5, 2017, the contents
of which are hereby incorporated by reference.
TECHNICAL FIELD
The Invention relates to a screw and its manufacturing method, and
particularly to a metric self-tapping locking screw and the
manufacturing method thereof.
BACKGROUND
As is known to all, threaded fastening has been widely applied in
mechanical equipment, automobile manufacturing, household appliance
and daily life. Moreover, the threaded fastening is requisite for
the fastening and connection between the mechanical parts. In many
industries, self-tapping locking screw is increasingly applied in
order to reduce the intermediate link. Therefore, China has
published such national standards as Screw Thread Shanks for Thread
Forming Screw--Metric Coarse Thread Series (GB/T 6559-1986);
however, these standards cannot satisfy the application
requirements of high mounting torque, high axial clamping force and
high locking performance. Most of fastening technologies
appropriate for application with high requirements are monopolized
by the foreign patents and enterprises. It is urgently needed to
develop a metric coarse-thread self-tapping locking screw and
popularize the fastening technology in manufacturing industry in
China.
SUMMARY OF THE INVENTION
The Invention is to provide a metric self-tapping locking screw and
the manufacturing method appropriate for fastening applications of
base materials such as high-strength cold-rolled steel, aluminum
alloy castings and plastic, and application of the fastening
technology with lower tapping moment and higher static loosing
moment, so that the installed parts to be fastened have higher
axial clamping force, which solves the attenuation problem of axial
clamping force and static moment of fastened parts.
The technical scheme of the Invention is realized as follows: a
metric self-tapping locking screw comprises a screw head, a screw
rod, a thread locking body, a self-tapping tip and a screw thread;
the screw head is connected to the thread locking body with the
screw rod; the thread locking body and the self-tapping tip are
provided with the screw thread on the surface; the self-tapping tip
is arranged at the root of the thread locking body; the screw
thread adopts the basic structure of the standard ordinary
triangular thread; a flank angle of the screw thread back to the
fastened surface is 15-20.degree. and another flank angle of the
screw thread facing the fastened surface is 30.degree.; a crest of
said screw thread is in a plane transition structure or a natural
circular arc transition structure.
Preferably, the screw thread is divided into eight equal parts by
eight mean lines; the eight mean lines include one-eighth line,
two-eighth line, three-eighth line, four-eighth line, five-eighth
line, six-eighth line, seven-eighth line and eight-eighth line; the
intersection of the four-eighth line and the crest is a first
crossing point; the intersection of the two-eighth line and the
crest side back to the fastened surface is a second crossing point;
a tangency arc between the first crossing point and the second
crossing point is a rounded root of thread.
Preferably, the two-eighth line and the screw thread intersect at a
third tangency point; the three-eighth line and the screw thread
intersect at a forth crossing point; a line connected the third
tangency point and the forth crossing point forms a thread
root-diameter angle with the two-eighth line; the thread
root-diameter angle is 20.degree..
Preferably, the rounded root of thread constitutes the asymmetry
root-diameter structure of the metric self-tapping locking screw
together with the thread roof-diameter angle.
Preferably, the horizontal cross-section of said self-tapping tip
is in a triangular circular arc transition structure and forms an
angle of 8-15.degree. with the plane of the thread locking body;
the crests of the self-tapping tip transit to the thread locking
body from small to large in a cone way and the screw threads on the
thread locking body gradually diminish to said self-tapping tip in
compliance with the crest shape. The length of the screw thread on
the self-tapping tip is equal to or less than the nominal diameter
of the screw thread on the thread locking body.
The Invention also provides a manufacturing method of the metric
self-tapping locking screw, comprising the following steps:
Preparing a wire coil for cold heading to manufacture the cylinder
of the metric self-tapping locking screw; the circular section
diameter of the wire coil for cold heading is equal or greater than
the diameter of the screw head;
Cutting out the wire coil for cold heading by a cold header to
acquire a piece of the wire coil for cold heading with the length
equal to the metric self-tapping locking screw;
Using the main die and the punch die of the cold header for mutual
cold extrusion of the piece of the wire coil; the screw head, the
screw rod, the thread locking body and the self-tapping tip are
formed on the surface of the piece of the wire coil to acquire the
screw blank;
Rolling and extruding the screw blank by thread rolling and molding
equipment and self-tapping screw die so that the screw thread is
formed on the surface of the thread locking body and the
self-tapping tip to acquire the semi-finished screw product;
Conducting carburizing treatment and thermal refining on the
surface of the semi-finished screw product to enhance the hardness
and strength of the semi-finished screw product and acquire the
finished metric self-tapping locking screw.
Preferably, the wire coil for cold heading comprises low-carbon
cold-heading steel, low-carbon alloy steel, martensitic stainless
steel and low austenitic stainless steel.
Preferably, an extrusion forming mode of 1-die 2-punch or 2-die
4-punch is adopted for the mutual cold extraction of the wire coil
by means of the main die and the punch die of the cold header.
Preferably, the screw thread surface is provided with a zinc-nickel
alloy coating.
The positive advantages of the Invention are as follows: the metric
self-tapping locking screw in the Invention is applied to fastening
applications of base materials such as high-strength cold-rolled
steel, aluminum alloy castings and plastic, and application of the
fastening technology with lower tapping moment and higher static
loosing moment, so that the installed parts to be fastened have
higher axial clamping force, which solves the attenuation problem
of axial clamping force and static moment of fastened parts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural diagram of the metric self-tapping locking
screw of the Invention;
FIG. 2 is a structural schematic diagram of the metric self-tapping
locking screw of the Invention;
FIG. 3 is a structural schematic diagram of the thread of the
metric self-tapping locking screw of the Invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The technical scheme of the Invention is further described by the
preferred Embodiments of the Invention in combination with the
Drawings.
As shown in FIG. 1, FIG. 2 and FIG. 3, a metric self-tapping
locking screw of the Invention comprises a screw head 1, a screw
rod 2, a thread locking body 3, a self-tapping tip 4 and a screw
thread 5; the screw head 1 is connected to the thread locking body
3 with the screw rod 2; the thread locking body 3 and the
self-tapping tip 4 are provided with the screw thread 5 on the
surface; the self-tapping tip 4 is arranged at the root of the
thread locking body 3; the screw thread 5 adopts the basic
structure of the standard ordinary triangular thread; a flank angle
.beta. of the screw thread 5 back to the fastened surface is
15-20.degree. and a flank angle .alpha. facing the fastened surface
is 30.degree.; a crest 51 of the screw thread 5 is in a plane
transition structure or a natural circular arc transition
structure.
The screw thread 5 is divided into eight equal parts by eight mean
lines; the eight mean lines include one-eighth line 81, two-eighth
line 82, three-eighth line 83, four-eighth line 84, five-eighth
line 85, six-eighth line 86, seven-eighth line 87 and eight-eighth
line 88; a intersection of the four-eighth line 84 and a crest is
the first crossing point R1; a intersection of the two-eighth line
82 and a flank side back to the fastened surface is the second
crossing point R2; a tangency arc between the first crossing point
R1 and the second crossing point R2 is the rounded root of thread
R; in this way, the fastening performance can be improved.
The two-eighth line 82 and the screw thread 5 intersect at the
third tangency point .gamma.1; the three-eighth line 83 and the
screw thread 5 intersect at the forth crossing point .gamma.2; the
line connected the third tangency point .gamma.1 and the forth
crossing point .gamma.2 forms the thread root-diameter angle
.gamma. with the two-eighth line 82; the thread root-diameter angle
.gamma. is 20.degree..
The rounded root of thread R constitutes the asymmetry
root-diameter structure of the metric self-tapping locking screw
together with the thread roof-diameter angle .gamma.. The helix
angle of the helical line of stressed flank side formed by the
asymmetry root-diameter structure is smaller than the helix angle
of ordinary screw, and the helical line of stressed flank side
formed by the asymmetry root-diameter structure forms the greater
axial clamping force borne by the thread together with the
connected part, resulting in the locking effect without any sliding
or loosening; the asymmetry root-diameter structure is properly
added with the thread root diameter of the screw thread 5 to
improve the rupture moment of the whole metric self-tapping locking
screw.
The cross-section of the self-tapping tip 4 is in a triangular
circular arc transition structure and forms an angle of
8-15.degree. with the plane of the thread locking body 3; the
crests of the self-tapping tip 4 transit to the thread locking body
3 from small to large in a cone way and the screw threads 5 on the
thread locking body 3 gradually diminish to the self-tapping tip 4
in compliance with the crest shape. The length of the screw thread
5 on the self-tapping tip 4 is equal to or less than the nominal
diameter of the screw thread 5 on the thread locking body 3. When
the fastened part passes through the self-tapping tip 4, the thread
is gradually formed from small to large. The crest angle of main
thread is 10-15.degree. smaller than the ordinary triangular
thread; the screwing resistance of the main thread and the
connected part is reduced and the tapping and locking performance
of the thread is greatly improved. Due to the asymmetric angles on
both sides of the main crest of the self-tapping locking thread,
the helical lines formed by tapping and unscrewing are misaligned.
As a result, the frictional force produced by loosening is greater
than that formed by the ordinary triangular self-tapping thread,
which provides a better locking performance.
The manufacturing method of the metric self-tapping locking screw
of the Invention includes the following steps:
Step I: Preparing a wire coil for cold heading to manufacture the
cylinder of the metric self-tapping locking screw; the circular
section diameter of the wire coil for cold heading is equal or
greater than the diameter of the screw head 1;
Step II: Cutting out the wire coil for cold heading by a cold
header to acquire a piece of the wire coil for cold heading with
the length equal to the metric self-tapping locking screw;
Step III: Using the main die and the punch die of the cold header
for mutual cold extrusion of the piece of the wire coil; the screw
head 1, the screw rod 2, the thread locking body 3 and the
self-tapping tip 4 are formed on the surface of the piece of the
wire coil to acquire the screw blank;
Step IV: Rolling and extruding the screw blank by thread rolling
and molding equipment and self-tapping screw die so that the screw
thread 5 is formed on the surface of the thread locking body 3 and
the self-tapping tip 4 to acquire the semi-finished screw
product;
Step V: Conducting carburizing treatment and thermal refining on
the surface of the semi-finished screw product of screw thread 5 to
enhance the hardness and strength of the semi-finished screw
product and acquire the finished metric self-tapping locking
screw.
The wire coil for cold heading includes low-carbon cold-heading
steel, low-carbon alloy steel, martensitic stainless steel and low
austenitic stainless steel. Various raw materials can be used to
manufacture the metric self-tapping locking screw, reducing the
original procurement difficulty of manufacturing of the metric
self-tapping locking screw.
An extrusion forming mode of 1-die 2-punch or 2-die 4-punch is
adopted for the mutual cold extraction of the wire coil by means of
the main die and the punch die of the cold header, which
facilitates machining of wire coil by the cold header and reduces
the production difficulty of the screw blank.
The surface of the screw thread 5 is coated with a zinc-nickel
alloy coating which protects the surface of the screw thread 5 and
provides higher corrosion resistance for the screw thread 5.
In conclusion, the metric self-tapping locking screw in the
Invention is applied to fastening applications of base materials
such as high-strength cold-rolled steel, aluminum alloy castings
and plastic, and application of the fastening technology with lower
tapping moment and higher static loosing moment, so that the
installed parts to be fastened have higher axial clamping force,
which solves the attenuation problem of axial clamping force and
static moment of fastened parts. The manufacturing method of the
metric self-tapping locking screw of the Invention is characterized
by simple steps, low cost and easy operation.
The above embodiments are the further detailed descriptions for the
technical problems, technical schemes and the beneficial effects of
the Invention. It should be understood that the above are the
preferred embodiments rather than the limitations of the Invention.
Any amendment, equivalent replacement and improvement made within
the range of the spirit and rule of the Invention shall be included
in the protection scope of the Invention.
* * * * *