Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1997-12-10
2000-02-01
Wyszomierski, George
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
29896411, 29447, 368280, C21D 900, F16B 400
Patent
active
060198605
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method for fixing two elements together, in particular links of a metal wristwatch strap, according to which a metal pin made of a moulding memory alloy with large hysteresis--programmed such that it turns from the martensitic structure to the austenitic structure in a first temperature range which is situated above the service temperature of the elements and whereby its thickness increases, and such that it is turns back from the austenitic structure to the martensitic structure in a second temperature range which is situated under the above-mentioned service temperature --is put in the martensitic structure in at least one either or not blind hole in at least one of the elements to be linked; the pin is subsequently heated to a temperature higher than the first temperature range, such that the thickness of the pin is increased, whereby the clamping force between pin and hole becomes very large; and the pin is finally cooled down to service temperature.
Thanks to the use of moulding memory alloys, the mere mechanical clamping of the pins in the holes can be improved, since it is possible to obtain much greater clamping forces.
The working of moulding memory alloys is based on a change in the metal structure, i.e. a martensitic structure changes in an austenitic structure at a certain temperature during heating, and it turns back to the martensitic structure when the temperature drops again. It is possible to associate a specific shape or diameter of a pin made of such material with each of the metal structures. This implies that during the transition from a low to a high temperature or vice versa, the shape or diameter of the pin will change or, if this change is prevented during the heating, a force will be created.
When such a memory alloy is heated, the transition to the austenitic structure and thus the deformation starts, at a temperature A.sub.s. This transition lasts until the abovementioned higher temperature A.sub.f is reached. When the alloy is cooled down again, the transition back to the martensitic structure will not start at the latter temperature, but at a lower return temperature, called the martensitic starting temperature M.sub.s, which phenomenon is called hysteresis. The return to the martensitic structure is ended at a still lower temperature M.sub.f.
Examples of such alloys are: Cu--Zn, Cu--Zn--Al, Cu--Zn--Si, Cu--Au--Zn, Cu--Al, Cu--Al--Ni, Ni--Ti, Ni--Ti--Cu, Ni--Ti--Fe, Ni--Ti--Nb, Ni--Ti--Zr, Ni--Ti--Hf, Fe--Ni--Al, Fe--Ni--Al--Ti, Fe--Ni--Co--Ti, Fe--Mn--Si, Ag--Cd, Au--Cd, Cu--Sn, Cu--Au--Zn, Cu--Zn--Be, Cu--Zr, Ni--Al, Fe--Mn--Si--Cr--Ni, both single crystalline and polycrystalline.
A method for fixing links together whereby use is made of pins made of such moulding memory alloys is described in WO-A-94/23214.
In this known method, pins are used whose thickness is smaller than the width of the holes in the martensitic structure, such that the pins can be put loosely in the holes without any force being required. When the pins have the austenitic structure, they jam in the holes.
However, this jamming is restricted since a considerable part of the increase in thickness of the pin is required to make the pin fill the hole, whereas only a part of the increase, which is prevented when the hole is filled, is used to cause the clamping force in the hole.
Also, the invention aims to provide a method for fixing two elements together, in particular links of a wristwatch strap, making use of a pin made of a moulding memory alloy with which a better clamping is obtained.
This aim is reached according to the invention in that the pin with a martensitic structure has a thickness which is slightly larger than the width of the hole.
This implies that the pin has to be inserted in the hole with a certain force. The entire tendency to an increase in thickness as a result of the transition from the martensitic to the austenitic structure is transformed in clamping force, so that an excellent clamping is obtained, which cannot be obtained when a pin is pressed in
REFERENCES:
patent: 2737843 (1956-03-01), Koehl
patent: 3837163 (1974-09-01), Fujimori
patent: 3913444 (1975-10-01), Otte
patent: 4036669 (1977-07-01), Brook et al.
patent: 5617377 (1997-04-01), Perret
Moorleghem Wilfried Van
Schwob Jean
Turler Willy A.
Advanced Materials and Technologies, afgekort "A.M.T.", naamloze
Gay Freres Vente et Exportation S.A.
Wyszomierski George
LandOfFree
Method for fixing two elements together, in particular links of does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for fixing two elements together, in particular links of , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for fixing two elements together, in particular links of will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-934615