Joints and connections – Interfitted members – Radially interposed shim or bushing
Patent
1991-04-23
1992-08-25
Reese, Randolph A.
Joints and connections
Interfitted members
Radially interposed shim or bushing
403371, 403374, 4034091, 254 29H, F16B 702
Patent
active
051413566
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a locking device for an elongated reinforcement under tension, such as a tension rod, strand, cable or similar.
Such locking devices are known which comprise in a general manner a support plate perforated by at least one flared opening, into which there penetrates a wedge of complementary shape which is crossed axially by the reinforcement with which it comes to engage by means of an internal toothing, said wedge being intended to be driven by force into the opening by an initial pressure and then by the tension of the reinforcement.
In his previous patent application FR-A-2,625,241, the applicant described a wedge comprising on at least a part of its external surface an anti-return toothing which is intended to come to engage with the internal wall of the opening of the support plate when this wedge has been driven into said opening.
Such a toothing, the teeth of which bite into the metal of said internal wall, exerts the anti-return effect desired and holds the reinforcement in place in relation to the support plate, even if this reinforcement is no longer tensioned for whatever reason it may be, vibrations, aging of the work concerned, etc.
Such a toothing therefore provides satisfaction and serves the function for which it has been designed.
However, at the time of tensioning of the reinforcement and at the end of this operation, the teeth of this toothing, which start to bite into the metal of the internal wall of the support plate, have a tendency to oppose a deeper penetration of the wedge into the opening. Thus, and in relation to a wedge of which the external surface is smooth, a wedge of which the external surface comprises an anti-return toothing involves the risk of being driven in less for a given driving pressure, or can only be driven in in the same manner by a greater driving pressure.
The applicant has thus sought to improve said wedge in order to propose a wedge which makes it possible to maximize the anti-return grip of the teeth of the external toothing in the opening of the support plate, while minimizing the force necessary to drive in this wedge.
According to the invention, the locking device of the abovementioned type is characterized in that this toothing has, in the direction of the length of the wedge, toothed zones alternated with recessed untoothed zones.
As a result of the presence of the recessed untoothed zones, the surface of contact of the teeth of the external surface of the wedge with the internal wall of the opening of the support plate is substantially reduced, and the teeth, reduced in number, exert a resistance to the driving in of the wedge which is substantially reduced in relation to the earlier wedge. It can thus be said that the wedge is driven in and slides more easily inside the opening.
Similarly, the clamping force exerted by the support plate on the external surface of the wedge is in fact exerted on a reduced tooth surface. This thus creates a contact pressure between the teeth and the wall of the opening which is proportional to that obtained in the case of the earlier wedge in a ratio which is the inverse of the ratio between the respective tooth surfaces. The teeth thus bite more deeply into the metal of the wall of the opening in order to anchor themselves better in the metal and have a more powerful anti-return effect.
Moreover, the following surprising effect is observed. As a result of the increased pressure exerted by the teeth, creep of the metal of the wall of the opening takes place; the metal, pushed away by the teeth, creeps towards the zones of the wall situated opposite the recessed untoothed zones and there creates protuberances projecting towards the inside of the opening in relation to the surface of the initial wall of the opening; these protuberances thus constitute, with the adjacent teeth, anchorages exerting a very significant additional anti-return effect.
According to an advantageous alternative of the invention, the teeth of the external toothing are regularly spaced and extend from the essentially
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patent: 3447784 (1969-06-01), Launay
patent: 3703748 (1972-11-01), Kelly
patent: 4146951 (1979-04-01), Howlett
patent: 4209661 (1980-06-01), Pate et al.
patent: 4662134 (1987-05-01), Illgner
Chun Heather
Reese Randolph A.
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