Joints and connections – Articulated members – Lockable at fixed position
Patent
1994-09-30
1996-07-23
Knight, Anthony
Joints and connections
Articulated members
Lockable at fixed position
403374, 280823, 280819, A63C 1122, F16B 714
Patent
active
055383548
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns telescopic rods comprising a plurality of successive tubular sections sliding one inside the other between a retracted position and a deployed position.
Telescopic rods are used in various fields and among other things allow length adjustment within a selected range of variation.
The invention is more particularly concerned with a telescoping tubular assembly of this kind comprising at least one relatively larger diameter first tubular section and one relatively smaller diameter second tubular section, the second tubular section having an inside end accommodated inside the first tubular section and being free to rotate and to slide in the first tubular section between a retracted position and deployed position.
An earlier proposal for locking relative sliding between two successive tubular sections is to use an expandable ring, as described in document EP-A-0 217 556, for example. The ring is mounted inside the first tubular section and is compressed axially between an axial end-piece fastened to the second tubular section and opposed clamping means screwing onto the axial end-piece, corresponding conical bearing surfaces expanding the ends of the ring which are pressed against the inside surface of the first tubular section. Relative rotation between the clamping means and the first tubular section is prevented to cause screwing of the clamping means upon relative rotation of the tubular members. The expansion of the ring produces friction forces opposing axial displacement of the tubular sections relative to each other. However, a prior art expandable ring device of this kind has the drawback that a relatively locking effect is due to a small surface area of the expandable ring. The locking effect is consequently insufficient for many applications.
SUMMARY OF THE INVENTION
The problem to which the present invention is addressed is that of increasing the locking force obtained by means of an expandable locking ring without excessively increasing the number of parts required or the difficulty of manufacture or assembly and without increasing the resistance to axial sliding when the device is unlocked.
To this end, the invention provides means for causing expansion of the ring in two axially offset areas of significantly increased length, distributing the deformation of the ring appropriately and increasing significantly the surface area of friction between the ring and the first tubular section into which it is inserted.
To this end, clamping means are provided comprising a head sliding freely in the first tubular section and bearing against an end surface of the ring. The ring includes a central part in which the axial hole is substantially cylindrical and two end parts in which the axial hole is of greater diameter and is joined to the hole of the central part by respective first and second internal conical bearing surfaces. The first internal conical bearing surface of the ring bears on a corresponding external conical bearing surface of the axial end-piece. The second internal conical bearing surface of the ring bears on a corresponding external conical bearing surface of the head of the clamping means. Longitudinal slits are provided in the ring in the two areas corresponding to the internal conical bearing surfaces of the ring. The slits occupy substantially half the length of the ring, starting from each end, and the internal conical bearing surfaces of the ring are arranged substantially at one third and two thirds of the length of the ring.
Various means may be used to join the head of the clamping means to the second tubular section.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention emerge from the following description of specific embodiments of the invention given with reference to the appended drawings in which:
FIG. 1 is a front view in partial cross-section of the locking area between two successive sections of a telescoping tubular assembly in accordance with the invention;
FIG. 2 is
REFERENCES:
patent: 4134703 (1979-01-01), Hinners
patent: 4238164 (1980-12-01), Mazzolla
patent: 4896687 (1990-01-01), Segal et al.
patent: 5458427 (1995-10-01), Simond
Eilberg William H.
Knight Anthony
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