SELF-STRAINING BOLTS

• US 3,835,523 A
• Filed: 03/06/1973
• Issued: 09/17/1974
• Est. Priority Date: 03/08/1972
• Status: Expired due to Term

• Current Assignee: Fred Stansfield
• Original Assignee: Fred Stansfield
• Inventors: Stansfield, Fred
• Primary Examiner(s): Smith, Al Lawrence
• Assistant Examiner(s): Smith, Jr., Harold P.
• Application Number:
  US05/338,425
• Time in Patent Office: 560 Days
• Field of Search: 29/252,446,452 254/29A 85/1T,62 81/57.38
• US Class Current: 29/252
• CPC Class Codes: B25B 29/02 Bolt tensioners
• CPC Class Codes: F16J 1/09 with means for guiding fluids F16J1/08 takes precedence
• CPC Class Codes: F16J 15/32 with elastic sealings, e.g. O-rings
• CPC Class Codes: Y10S 411/01 Thread forming, reforming, or cleaning
• CPC Class Codes: Y10S 411/916 Bolt having tension feature
• CPC Class Codes: Y10T 29/49874 Prestressing rod, filament or strand
• CPC Class Codes: Y10T 29/5383 having fluid operator

Abstract

A self-straining bolt includes a shank and a rod of steel or like stiff rigid material which fits with clearance in an axial bore within the shank of the bolt, the bore being closed at one end. A closed cylindrical chamber is secured to the end of the bolt remote from the closed end of the bore, and a piston member which has an overall diameter greater than that of the bore, is fitted in the chamber. The piston member is a close sliding fit in the cylindrical chamber and engages the end of the rod adjacent the chamber. A disc of a resilient material with a hardness in the range of Shore hardness 10 to 100, and preferably 40 to 70, and a thickness of at least 3/8 inch, and preferably at least 1/2 inch, abut the working face of the piston and bears with its periphery against the cylindrical wall of the chamber so as to form a seal. A conduit extends through the wall of the chamber for connecting the chamber to a source of fluid under pressure whereby a pressure can be applied to the piston through the disc to cause the rod to press against the closed end of the bore and strain the shank of the bolt. The disc prevents fluid leaking from the chamber through the space between the piston and the cylindrical wall of the chamber.

Claims

1. A self-straining bolt comprising:

a shank;

an axial bore in said shank, said bore being closed at one end;

a rod of steel or like stiff rigid material fitting with clearance said bore within the shank of the bolt;

a closed chamber with a cylindrical wall rigid with the end of the bolt remote from the closed end of the bore;

a piston member having a working face and sides and having an overall diameter greater than that of said bore, said piston member being provided at the end of the rod adjacent the chamber and being a close sliding fit in the cylindrical chamber;

a disc of a resilient material with a hardness in the range of Shore hardness 10 to 100 and a thickness of at least 3/8 inch abutting the working face of the piston and bearing with its periphery against the cylindrical wall of the chamber so as to form a seal; and

a conduit extending through the wall of the chamber for connecting the chamber to a source of fluid under pressure whereby a pressure can be applied to the piston through the disc to cause the rod to press against the closed end of the bore and strain the shank of the bolt and the disc prevents fluid leaking from the chamber through the space between the piston and the cylindrical wall of the chamber.

2. A bolt according to claim 1 in which the material of the disc has a hardness in the range of Shore hardness 40 to 70.

3. A bolt according to claim 1 in which the edge of the piston member between its working face and its side is relieved to provide an annular space into which material at the periphery of the disc can flow.

4. A bolt according to claim 3 in which said annular space extends axially of the piston for a distance of at least 1/8 inch from the working face of the piston.

5. A bolt according to claim 3 in which the edge is relieved by rounding.

6. A bolt according to claim 1 in which the side of the piston tapers towards the non-working face.

7. A bolt according to claim 1 in which the pressure chamber is provided in a body which is detachable from the shank of thE bolt.

8. A bolt according to claim 7 in which the bolt has an externally screw-threaded head and the body has an internally screw-threaded skirt which can be screwed on the head of the bolt.

9. A bolt according to claim 1 in which a manually operable valve is provided in the conduit.