Loosening prevention screw

• US 5,569,009 A
• Filed: 11/23/1993
• Issued: 10/29/1996
• Est. Priority Date: 11/26/1992
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Suzuki Rashi Seisakusho
• Original Assignee: Kabushiki Kaisha Suzuki Rashi Seisakusho
• Inventors: Suzuki, Yasuo
• Primary Examiner(s): Saether, Flemming
• Application Number:
  US08/156,044
• Time in Patent Office: 1,071 Days
• Field of Search: 411/411-415, 411/307-310, 411/168
• US Class Current: 411/413
• CPC Class Codes: F16B 25/0031 the screw being designed to be screwed into different materials, e.g. a layered structure or through metallic and wooden parts
• CPC Class Codes: F16B 25/0047 the ridge being characterised by its cross-section in the plane of the shaft axis
• CPC Class Codes: F16B 25/0068 with multiple-threads, e.g. a double thread screws
• CPC Class Codes: F16B 25/0073 characterised by its pitch, e.g. a varying pitch
• CPC Class Codes: F16B 39/30 Locking exclusively by special shape of the screw-thread

Abstract

The screw of this invention can be used for fastening members of a variety of materials and reliably prevent loosening of the screw. The screw shank is formed with two threads, a main thread for driving the screw and a sub-thread which extends in the same direction as the main thread, is smaller in outer diameter than the main thread and has a pitch different from the main thread. The inclination of the slant surface of the sub-thread is set steep on the loosening side and moderate on the fastening side. The pitch of the main thread is set larger than that of the sub-thread. When the tightened screw is applied a loosening torque, the sub-thread bites into the inner wall of the hole, preventing the screw from being loosened.

Claims

1. A loosening prevention screw comprising:

a main thread for driving the screw into a hole; and

a sub-thread running in the same direction as the main thread, being smaller in outer diameter than the main thread, and having a pitch different from that of the main thread;

wherein the main thread and the sub-thread are formed over substantially a same longitudinal distance on a same shank of the screw, and;

wherein the pitch of the main thread is coarser that the pitch of the sub-thread.

2. A loosening prevention screw according to claim 1, wherein the inclination of a slant surface of the sub-thread is set steep on the loosening side and moderate on the fastening side.

3. A loosening prevention screw according to claim 1, wherein the main thread is an isosceles triangle in cross section while the sub-thread is a scalene triangle in cross section.