Perforated nut tensioning system

• US 20030086770A1
• Filed: 10/25/2002
• Published: 05/08/2003
• Est. Priority Date: 10/30/2001
• Status: Active Grant

• Current Assignee: Riverhawk Company
• Original Assignee: Riverhawk Company
• Inventors: Trautman, Timothy J., Gibbons, Charles B., Whitney, Robert M.
• Granted Patent: US 6,685,406 B2
• Time in Patent Office: Days
• US Class Current: 411/14.5
• CPC Class Codes: F16B 31/04 for maintaining a tensile load
• CPC Class Codes: Y10S 411/916 Bolt having tension feature
• CPC Class Codes: Y10S 411/917 Nut having tension feature

Abstract

A stud tensioning device includes a nut having internal threads and external threads. The internal threads engage corresponding threads on the stud. At least two axial bores are defined by the nut, and posts are disposed in the bores. Each post at a first end thereof engages a stop surface, and at a second end thereof extends external to the bores and axially beyond a free end of the stud in a direction away from the structural member. A load cell threadingly engages the nut applying an axially-directed force on the posts in a direction toward the structural member and on the nut in a direction away from the structural member to thereby tension the stud.

Claims

1. A stud tensioning device for tensioning a stud having a free end that projects from a structural member, the stud having a central axis, said stud tensioning device comprising:

a nut having internal threads and external threads, said internal threads configured for engaging corresponding threads on the stud, at least two axial bores defined by said nut;

at least two posts, each said post having a respective first and second end, each said post being partially disposed in a corresponding one of said bores, each said first end configured for engaging a stop surface, each said second end being disposed external to said bores and extending axially beyond the free end of the stud in a direction away from the structural member;

a load cell configured for threadingly engaging said external threads of said nut, said load cell applying an axially-directed force on said posts in a direction toward the structural member and on said nut in a direction away from said structural member to thereby tension the stud.

2. The stud tensioning device of claim 1, wherein said load cell comprises a hydraulic load cell.

3. The stud tensioning device of claim 2, wherein said hydraulic load cell comprises:

a cylinder having a closed end and an open end, said open end threadingly engaging said external threads of said nut, said closed end being disposed axially beyond said second end of said posts in a direction away from the structural member, a hydraulic port defined by said cylinder;

a piston disposed within said cylinder, said piston having an inner and an outer surface, said inner surface facing said closed end of said cylinder; and

a hydraulic chamber defined between said inner surface of said piston and said closed end of said cylinder, said hydraulic chamber being radially bounded by a portion of a sidewall of said cylinder, said hydraulic chamber in fluid communication with said hydraulic port.

4. The stud tensioning device of claim 3, wherein said stop surface comprises a washer that is received over the stud, said washer being disposed axially between said first end of said posts and the structural member.

5. The stud tensioning device of claim 4, further comprising a retaining ring, said retaining ring threadingly engaging said external threads of said nut and being disposed axially between said washer and said open end of said cylinder.

6. The stud tensioning device of claim 3, further comprising a retaining ring, said retaining ring threadingly engaging said external threads of said nut and being disposed axially between the structural member and said open end of said cylinder.

7. The stud tensioning device of claim 3, further comprising a support and alignment plate having a top and bottom surface, said plate defining axial plate bores, said posts being received within said plate bores, said plate being disposed axially between said nut and said outer surface of said piston such that said top surface of said plate is opposite said outer surface of said piston.

8. The stud tensioning device of claim 7, wherein said plate bores extend partially through said plate, said second ends of said posts being disposed within said plate bores, said top surface of said plate engaging said outer surface of said piston when said device is actuated.

9. The stud tensioning device of claim 7, wherein said plate bores extend completely through said plate, said second ends of said posts engaging said outer surface of said piston.

10. The stud tensioning device of claim 3, wherein said cylinder includes inner threads that engage said external threads of said nut, said retaining ring includes internal threads that engage said external threads of said nut, each of said internal threads and said external threads of said nut, said internal threads of said cylinder, and said internal threads of said retaining ring include respective thread faces, at least one of said thread faces being substantially perpendicular to the central axis of the stud.

11. The stud tensioning device of claim 3, further comprising a piston protection washer disposed between said second end of said posts and said outer surface of said piston.

12. The stud tensioning device of claim 1, further comprising a support and alignment plate having a top and bottom surface, said plate defining axial plate bores, said posts being received within said plate bores, said plate being disposed axially between said nut and said load cell.

13. The stud tensioning device of claim 12, wherein said plate bores extend partially through said plate, said second ends of said posts being disposed within said plate bores, said top surface of said plate engaging said outer surface of said piston when said device is actuated.

14. The stud tensioning device of claim 12, wherein said plate bores extend completely through said plate, said second ends of said posts engaging said outer surface of said piston.

15. The stud tensioning device of claim 1, wherein said load cell comprises a mechanical load cell.

16. The stud tensioning device of claim 15, wherein said mechanical load cell comprises:

a cylinder having a closed end and an open end, said open end threadingly engaging said external threads of said nut, said closed end being disposed axially beyond said second end of said posts in a direction away from the structural member;

a piston disposed within said cylinder, said piston having an inner and an outer surface, said inner surface facing said closed end of said cylinder; and

actuating means forcing said cylinder and piston apart in an axial direction.

17. The stud tensioning device of claim 16, wherein said stop surface comprises a washer that is received over the stud, said washer being disposed axially between said posts and the structural member.

18. The stud tensioning device of claim 17, further comprising a retaining ring, said retaining ring threadingly engaging said external threads of said nut and being disposed axially between said washer and said cylinder.

19. The stud tensioning device of claim 16, further comprising a retaining ring, said retaining ring threadingly engaging said external threads of said nut and being disposed axially between the structural member and said cylinder.

20. The stud tensioning device of claim 16, further comprising a support and alignment plate having a top and bottom surface, said plate defining axial plate bores, said posts being received within said plate bores, said plate being disposed axially between said nut and said outer surface of said piston such that said top surface of said plate is opposite said outer surface of said piston.

21. The stud tensioning device of claim 20, wherein said plate bores extend partially through said plate, said second ends of said posts being disposed within said plate bores, said top surface of said plate engaging said outer surface of said piston when said device is actuated.

22. The stud tensioning device of claim 20, wherein said plate bores extend completely through said plate, said second ends of said posts engaging said outer surface of said piston.

23. The stud tensioning device of claim 16, wherein said actuating means comprises an actuator screw.

24. The stud tensioning device of claim 23, further comprising a worm and worm gear engaging said actuator screw.

25. The stud tensioning device of claim 16, further comprising a piston protection washer disposed between said second end of said posts and said outer surface of said piston.

26. The stud tensioning device of claim 16, wherein said cylinder includes inner threads that engage said external threads of said nut, said retaining ring includes internal threads that engage said external threads of said nut, each of said internal threads and said external threads of said nut, said internal threads of said cylinder, and said internal threads of said retaining ring include respective thread faces, at least one of said thread faces being substantially perpendicular to the central axis of the stud.

27. A method of tensioning an externally threaded stud projecting from a structural member, said method comprising the steps of:

disposing a washer over the stud and adjacent the structural member;

threadingly engaging a nut onto the external threads of the stud, the nut having internal and external threads and defining at least two bores;

threadingly engaging a retaining ring onto the external threads of the nut;

disposing a respective post in each of said at least two bores, said posts extending through said bores and engaging the washer, said posts extending axially outside of the nut in a direction away from the structural member;

threadingly engaging an open end of a load cell onto the external threads of the nut, a closed end of said load cell being disposed axially beyond the stud relative to the structural member;

actuating the load cell thereby exerting axially directed and opposed forces upon the posts and the nut;

maintaining the stud in the tensioned condition by turning the retaining ring down into engagement with said washer and, thereby, the washer into engagement with the structural member; and

removing the load cell from engagement with the stud.