Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Internally threaded fastener element – e.g. – nut – etc. – Multipart
Patent
1990-05-07
1991-09-10
Wilson, Neill R.
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Internally threaded fastener element, e.g., nut, etc.
Multipart
411916, 411917, F16B 3708
Patent
active
050469061
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to improved force application apparatus.
This invention has particular but not exclusive application to the preloading of mechanical elements, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as the raising of loads.
In the assembly of machinery, it is often difficult to apply the necessary preloads to bolts, studs, shafts and bearings by the use of conventional screwed fasteners, particularly in the case of large machine elements. Hitherto, force applicators of the type using hydraulic pressure to apply preload to machine elements have suffered from a number of drawbacks. They must be pressurised by expensive, specialised pumps and their component shapes render them difficult to construct. Often the configuration of available applicators results in their being inconvenient to use in situations which occur frequently in the assembly and dismantling of machine components.
DESCRIPTION OF THE PRIOR ART
Tensioning nuts for bolts or studs which include hydraulic tensioners are known, but their form and consstructional features result in high manufacturing costs, rendering them useful only in a limited number of applications where their high cost can be justified. Further, the constructional features of current tensioning nut designs result in the generation of undesirably high stresses and deflections within the apparatus, requiring the use of expensive materials and rendering the hydraulic seals susceptible to leakage.
A further problem with current designs of tensioning nut is that differential deflections which occur within the apparatus during the transition from hydraulic tension to mechanical locking with a threaded collar or the like result in a relaxation in the applied tension.
The present invention aims to alleviate the above disadvantages and to provide force application means which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.
SUMMARY OF THE INVENTION
With the foregoing and other objects in view, this invention in one aspect resides broadly in force application apparatus for applying a load to a tensile member relative to a clamping surface through which the tensile member projects, said force application apparatus including:
an annular housing having an annular recess extending inwardly from an end face of said housing;
a piston assembly slidable within said annular recess and sealed thereto;
locating means for locating said force application apparatus about the tensile member, and
pressure application means for applying pressurised fluid to said annular recess to displace said piston relative to said housing.
Preferably the annular recess is a stepped recess having a minor bore disposed along the housing from a major bore and an intermediate step which forms a housing pressure face and wherein the annular piston is a stepped piston having a circular major piston wall and a circular minor piston wall slidably engageable with the minor and major bores respectively and sealed thereto by minor and major sealing means respectively, the stepped piston having an intermediate step between the piston walls which forms a piston pressure face which opposes the housing pressure face. The location means may include an internal thread formed in the annular housing or the annular piston and adapted for engagement with an externally-threaded tensile member.
The piston may include an external thread for engagement with an internally-threaded locking collar. Alternatively, if desired, the annular housing may include an external thread for engagement with an internally-threaded collar. An external locking collar may be included, and may be threadedly engaged with the external thread. The external thread may be of any desired form, but preferably it is a buttress thread having the thrust face of the thread substantially perpendicular to the axis of the thread such that m
REFERENCES:
patent: 2571265 (1951-10-01), Leufven
patent: 3154006 (1964-10-01), Novak
patent: 3837694 (1974-09-01), Frisch
patent: 3841193 (1974-10-01), Ito
patent: 4075923 (1978-02-01), Latham
patent: 4085649 (1978-04-01), Christensson
patent: 4854798 (1989-08-01), Snyder et al.
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