Firearms
Patent
1996-12-03
1998-05-12
Saether, Flemming
Firearms
411270, F16B 3708
Patent
active
057496919
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a reaction nut, and more particularly to such a nut that can be quickly fastened to and released from an associated bolt, a preferred application of the nut being in a hydraulic bolt tensioning device.
BACKGROUND
A hydraulic bolt tensioning device is basically a hydraulic jack positioned over a nut and bolt assembly with the bolt extending centrally through the jack. Hydraulic pressure is applied to the device such that a load is applied to the bolt to stretch the bolt whereby the associated nut can be tightened down to maintain the joint on release of the hydraulic pressure.
Reaction nuts are conventionally screwed onto the bolt, usually above the tensioning devices, to enable the load to be applied to the bolt.
However, the length of bolt extending through and above the tensioning device can often be quite significant, and the application of the reaction nut to the bolt can be a time consuming and exhaustive exercise, especially if the bolts are of large diameter and/or fine thread. This creates particular problems in hazardous environments, such as sub-sea and nuclear, where the time spent by an operator in potentially dangerous areas must be kept to a minimum.
Various proposals have been made to enable relatively quick application of the reaction nut to the associated bolt. U.S. Pat. No. 4083288 discloses a split nut having two halves which can be located onto a bolt in any axial position therealong, the underside of the nut comprising a conical surface which locates into a complementary recess in a washer or other suitable component, the nut being maintained in threaded engagement with the bolt by co-operation between the corresponding conical surfaces of the nut and washer.
This concept has been applied to hydraulic bolt tensioners, for example as disclosed in UK specification no. 2193549 which shows a split reaction nut having a cam surface for engagement by the surface of a complementary recess in the piston of the tensioner.
U.S. Pat. No. 4438901 and UK specification no. 2143608 disclose bolt tensioning devices in which the reaction nut incorporates a hydraulically-operated collet comprising a plurality of segments which, when activated hydraulically, are urged into engagement with the bolt. This concept is well established in most industries utilising pulling/gripping devices such as rope pullers and the like.
The major disadvantages of these known split nuts are that they require an external force initially to engage the split nut/segments, and the maintenance of this force to keep the nut in position. In the absence of this external force, the split nut and the tensioning device would disengage, thus resulting in these devises being difficult, if not impossible, to use in upside down or horizontal positions without operator intervention. It must also be borne in mind that, in practice, tensioning devices are seldom used singularly, and operator intervention on each of a multitude of tensioning devices is clearly undesirable.
SUMMARY OF THE INVENTION
It would be desirable to be able to provide a reaction nut, in particular for a hydraulic bolt tensioning device, which can be applied onto a bolt quickly and with minimal operator intervention.
According to the present invention there is provided a reaction nut for location on a threaded bolt, the nut comprising a plurality of internally-threaded segments movable between an outermost inoperative position radially spaced from the bolt, and an operative position making threaded engagement with the bolt, said segments having tapering surfaces thereon, and a primary ring member movable axially relative to the segments and having a corresponding tapering surface thereon, characterised by first resilient means biasing the tapering surface of the primary ring member into engagement with the tapering surfaces on said segments, and cam means actuation of which moves the primary ring member from a rest position to an axially displaced position against the bias of said first resilient means whereby the segments
REFERENCES:
patent: 4083288 (1978-04-01), Williams
patent: 4083393 (1978-04-01), Okada
patent: 5118237 (1992-06-01), Wright
patent: 5139381 (1992-08-01), Lubreski
patent: 5282709 (1994-02-01), Chaput
patent: 5378100 (1995-01-01), Fullerton
patent: 5613816 (1997-03-01), Cabahug
Hedley Purvis Ltd A Company of Great Britain and Northern Irelan
Saether Flemming
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