DUAL-THREADED SCREW STRUCTURE AND FASTENING STRUCTURE THEREWITH

• US 20200132105A1
• Filed: 03/27/2019
• Published: 04/30/2020
• Est. Priority Date: 06/01/2018
• Status: Active Grant

• Current Assignee: Form Roll Tech., Co., Ltd.
• Original Assignee: Form Roll Tech., Co., Ltd.
• Inventors: Shinbutsu, Toshinaka, Takemasu, Teruie, Amano, Shuichi
• Granted Patent: US 11,293,476 B2
• Time in Patent Office: Days
• CPC Class Codes: F16B 35/00 Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws F16B33/008 takes precedence; joining sheets or plates using screws with two separate threads F16B5/0275; using screws with adjustment sleeves F16B5/0283; thread cutting screws F16B25/00
• CPC Class Codes: F16B 39/16 in which the screw-thread of the locknut differs from that of the nut
• CPC Class Codes: F16B 39/30 Locking exclusively by special shape of the screw-thread
• CPC Class Codes: F16B 5/02 by means of fastening members using screw-thread F16B5/0004 takes precedence; construction of screw-threaded connections F16B25/00 - F16B39/00
• CPC Class Codes: F16B 5/0225 allowing for adjustment parallel to the plane of the plates

Abstract

A dual-threaded screw structure having two kinds of threads formed on a shank, namely, a first thread consisting of one or more threads and a second thread having a lead larger than a lead of the first thread is provided herein. The claimed configuration has a beneficial effect of preventing looseness when the screw structure is fastened with double nuts. One embodiment of the present invention exhibits an example of a dual-threaded screw structure, in which a root diameter between the ridges of the hill-like second thread ridges is formed to be larger by 10% of a height of the ridges than an effective diameter of a first thread. In this case, an inner diameter of an internal thread of a second nut for preventing looseness is formed to be larger than the effective diameter of the first thread by 10% of the height of the ridges.

Claims

1. A dual-threaded screw structure having two kinds of threads formed on a shank, the two kinds of threads comprising:

a first thread including one or more threads of a kind selected from a metric thread, a Whitworth thread, a unified thread, a trapezoidal thread, a pipe thread, a round thread, a ball thread, and an angular thread; and

a second thread having a lead larger than the first thread,

wherein a root diameter of the second thread is larger than an effective diameter of the first thread and smaller than an outer diameter of the first thread.

2. The dual-threaded screw structure according to claim 1,

wherein the first thread is a one-threaded thread, and the second thread is a one-threaded thread or a multiple-threaded thread.

3. The dual-threaded screw structure according to claim 1,

wherein the second thread is a same kind of thread as the first thread.

4. The dual-threaded screw structure according to claim 1,

wherein the root diameter of the second thread is larger in radius than the effective diameter of the first thread by less than 30% of a height of a ridge of the first thread.

5. The dual-threaded screw structure according to claim 1,

wherein the root diameter of the second thread is larger in radius than the effective diameter of the first thread by 10 to 20% of a height of a ridge of the first thread.

6. A fastening structure with a dual-threaded screw structure comprising:

the dual-threaded screw structure having two kinds of threads formed on a shank, the two kinds of threads being a first thread including one or more threads of a kind selected from a metric thread, a Whitworth thread, a unified thread, a trapezoidal thread, a pipe thread, a round thread, a ball thread, and an angular thread, and a second thread having a lead larger than the first thread;

a first nut screwed onto the first thread; and

a second nut screwed onto the second thread,

wherein the dual-threaded screw structure has a strength such that a stress imparted to ridges of the second thread of the dual-threaded screw structure from the second nut is in a range of allowable shearing stress and allowable contact surface pressure of the ridges of the second thread when an allowable maximum axial force is created between the dual-threaded screw structure and the second nut with a rotation torque externally imparted to the dual-threaded screw structure and the second nut.

7. The fastening structure with a dual-threaded screw structure according to claim 6,

wherein a root diameter of the second thread is larger than an effective diameter of the first thread and smaller than an outer diameter of the first thread, in a sectional shape including an axis line of the shank.

8. The fastening structure with a dual-threaded screw structure according to claim 6,

wherein the equation

[(d₂/2)·

tan(α

+ρ

′

)+r₂·

tan ρ

]>

tan ρ

·

r₁

is satisfied when the first nut is rotated when tan ρ

is equal to a friction coefficient μ

, ρ

′

is a friction angle of a contact surface with which the second thread contacts the second nut, r₂ is an averaged radius of a seat with which the second nut contacts a member to be fastened, d₂ is an effective diameter of a thread surface with which the second thread contacts the second nut, α

is a lead angle of the second thread, and r₁ is an averaged radius of a seat with which the first nut contacts the second nut.

9. The fastening structure with a dual-threaded screw structure according to claim 6,

wherein one or more of an irregularity, a flange, and a rough surface is formed on a surface of the second nut contacting the member to be fastened.