Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Torque responsive nut or bolt driving connection – Frangible connection
Patent
1997-05-27
1998-11-24
Wilson, Neill R.
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Torque responsive nut or bolt driving connection
Frangible connection
411411, 248909, 403 2, 403DIG3, 285 2, 285 4, F16B 3100, F16D 900, F16L 3500
Patent
active
058398660
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a mechanical overload protection device of the type adapted to be released when an appearing force exceeds a predetermined value.
2. Description of Related Art including Information Disclosure under 37 CRF 1.97-1.99.
There are several types of overload protection devices used in order to protect equipment against demages due to mechanical overload. It is usual that two or more parts displace themselves mutually when an overload is released, this displacement normally leading to that the overload ceases or becomes harmless.
Shear pins adapted to break upon the occurence of a predetermined shear force represent one of the oldest known mechanical overload protection devices, and shear pins are still much in use.
Also, shear pins are included as functional members in various devices, in which shear pins intentionally are cut as a part of the normal mode of operation of the device. In connection with oil wells, it is e.g. common to lock plugs and other downhole equipment in shear pin devices. Upon the occurence of a force applied thereto, typically through an increase of the pressure in the well liquid, the shear pins are broken and a desired function is effected, such as opening or closing a valve, loosening a plug, uncoupling a coiled tubing from a tool wedged thereto and other things.
Upon the occurence of brief and more or less accidental excesses of the allowed maximum force, it is often desirable that the overload protection device is not activated, i.e. that overload protection devices in some cases should have a certain inertia.
The invention directs itself toward uses where it is usual to use shear pins and may, in many cases, advantageously replace shear pins.
A disadvantage of shear pins is that they often must be overdimensioned in order to avoid that they are broken upon a brief accidental extra strain, and this reduces the security and safety. In many relations it is also a disadvantage of shear pins that they are weakened as soon as the cutting off process has started, a fact that lead to the breakage of the shear pins even if the force is reduced below the upper allowed value.
It is known to combine shear pins having different dimensions or made of various materials in order to achieve a stepwise release of a protection device. The number of shear pins may also be varied. Then, a first set of shear pins are broken at a lower force than a second set of shear pins. This is also utilized in equipment where shear pins are incorporated as a part of the function of the equipment. A first functional step is activated e.g. by breaking one set of shear pins, breaking a second set of shear pins activating the next functional step. In order to obtain a safe function in equipment of this type, it is necessary to have a relatively large difference in shear force between the various sets of shear pins. In connection with downhole operations in oil wells, it has happened that shear pins have released a locking device too soon, with expensive consequences.
SUMMARY OF THE INVENTION
An object of the invention is to provide an overload protection device which is as simple as shear pins, and which simultaneously allows continued functioning after brief excesses of a predetermined upper force value. Another object of the invention is to provide an overload protection device where a possible overload is allowed to act over a predetermined distance before the overload protection device is released. A third object of the invention it that it should absorb substantially more energy than shear pins released upon the occurence of a corresponding load, and that the overload protection device thereby shall be capable of being used to absorb impacts and to retard dangerous mass in motion. A further object of the invention is to provide an overload protection device where the maximum force allowed at any time is a function of a distance over which a possible preceding overload has acted.
The objects are achieved through the features as defined
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Our Customers Wanted A Better Breakaway . . . We Brought Them A Breakthrough, OPW Fueling Components Group, 1987.
Safe-T-Break, Husky Corp., 1986.
Eriksen Erik Peter V.
Gudmestad Tarald
Moen Terje
McClung Guy
Weatherford / Lamb, Inc.
Wilson Neill R.
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