Canadian Patents Database / Patent 2371805 Summary

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(12) Patent: (11) CA 2371805
(54) English Title: METHOD AND DEVICE FOR MOULDING TITANIUM PARTS
(54) French Title: PROCEDE ET DISPOSITIF DE MOULAGE DE PIECES EN TITANE
(51) International Patent Classification (IPC):
  • B22D 27/15 (2006.01)
  • B22D 13/04 (2006.01)
  • B22D 21/00 (2006.01)
  • C22F 1/02 (2006.01)
  • C22F 1/18 (2006.01)
  • F27B 14/06 (2006.01)
  • H05B 6/32 (2006.01)
  • F27B 17/02 (2006.01)
  • F27D 3/00 (2006.01)
(72) Inventors :
  • GARNIER, MARCEL (France)
  • GARNIER, CHRISTIAN (France)
  • ERNST, ROLAND (France)
(73) Owners :
  • CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE (France)
(71) Applicants :
  • CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE (France)
(74) Agent: NORTON ROSE FULBRIGHT CANADA LLP/S.E.N.C.R.L., S.R.L.
(74) Associate agent:
(45) Issued: 2009-02-17
(86) PCT Filing Date: 2000-02-18
(87) Open to Public Inspection: 2000-08-24
Examination requested: 2005-01-13
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
99/02318 France 1999-02-19

English Abstract





The invention concerns an appliance for moulding parts made
of very reactive metal or mixture of metals, comprising, inside a
vacuum chamber (15) a cold induction-heated crucible (1) whereof
the base comprises a removable sectored plug (6), said crucible being
configured to enable the levitation of said metal or mixture of metal
in smelted state (5); a mould (20) provided under the crucible (1);
means for driving the mould in rotation; and outside the chamber, a
coil (13) arranged at the lower part of the crucible is designed to heat
by induction said metal or said mixture.


French Abstract

L'invention concerne un appareil de moulage de pièces en un métal ou un mélange de métaux très réactif, comprenant, à l'intérieur d'une enceinte sous vide (15), un creuset froid à chauffage par induction (1) dont le fond comprend un bouchon amovible sectorisé (6), ce creuset étant conformé pour assurer la mise en lévitation dudit métal ou mélange à l'état fondu (5); un moule (20) disposé sous le creuset (1); des moyens pour entraîner le moule en rotation; et, à l'extérieur de l'enceinte, un enroulement (13) disposé à la hauteur de la partie basse du creuset froid est destiné à chauffer par induction ledit métal ou ledit mélange.


Note: Claims are shown in the official language in which they were submitted.




7



CLAIMS



1. A method for casting pieces of a very reactive
metal or metal mixture, including the steps of:
placing in a vacuum chamber (15) a cold induction-
heated crucible (1) containing said metal or said mixture and the
bottom of which includes a removable sectorized plug (6), this
crucible being designed to ensure the levitating of said metal or
mixture in the molten state;
arranging in the chamber, under the cold crucible, a
mould (20) likely to be rotated around a vertical axis (30);
arranging outside of the chamber at the level of the
crucible and especially of the crucible bottom an induction
heating winding (13);
exciting the winding (13) to melt said metal or said
mixture, having it levitate and overheating it by at least 50°C
above its melting point; and
opening the plug (6) to end the levitation and have
said overheated molten metal or mixture flow into the rotating
mould and fill the cavities thereof.

2. The method of claim 1, wherein the very reactive
metal is titanium.

3. The method of claim 1 or 2, wherein the mould is
of the lost wax mould type.

4. The method of any of claims 1 to 3, wherein the
cast pieces are intended for orthopedic applications.

5. The method of claims 2, 3, and 4, wherein the
titanium pieces are intended for dental applications.

6. A device for casting pieces of a very reactive
metal or metal mixture, including:
- inside of a vacuum chamber (15):
a cold induction-heated crucible (1), the bottom of
which includes a removable sectorized plug (6), this crucible
being designed to ensure the levitating of said metal or mixture
in the molten state;
a mould arranged under the crucible;




8



means for rotating the mould;
- outside of the chamber:
a winding (13) arranged at the level of the low portion
of the cold crucible and intended for heating said metal or said
mixture by induction.

7. The device of claim 6, wherein the very reactive
metal is titanium.

8. The device of claim 6 or 7, wherein the mould is
of the lost wax mould type.

9. The device of any of claims 6 to 8, wherein the
cast pieces are intended for orthopedic applications.

10. The device of claims 7, 8, and 9, wherein the
titanium pieces are intended for dental applications.


Note: Descriptions are shown in the official language in which they were submitted.


CA 02371805 2008-07-04

1
METHOD AND DEVICE FOR MOULDING TITANIUM PARTS

The present invention relates to a method and a device
for casting pieces made of a strongly reactive metal or metal
mixture/alloy, such as titanium.
The use of titanium has often been suggested in fields
where one and/or the other of its specific properties is desired
to be exploited. For e.xample, in the field of aeronautics,
titanium is considered with great interest due to the high value
of the breaking load-to-density ratio. In the field of chemistry,
titanium is advantageous .for its properties of low reactivity
with sane materials. Also, titanium has a good biological
campatibility which makes it adapted to forming prostheses such
as dental protheses. In these various fields, and especially in
the last one, it is often desired to form pieces of small
dimensions and of complex shapes but titanium is a material which
is very difficult to work and tests of direct adaptation of the
various known casting methods result in pieces that are heavily
oxidized in their bulk and/or at their surface.
Thus, the'present invention aims at providing a tita-
nium casting method which ensures a good imnunity against the
axidation of titanium during the melting phase and during the
casting phase.
To achieve this object, the present-invention provides
a method for casting pieces of a very reactive metal or metal


CA 02371805 2001-08-17

2
mixture, including the steps of placing in a vacuum chamber a
cold induction- heated crucible containing said metal or said
mixture and the bottom of which includes a removable sectorized
plug, this crucible being designed to ensure the levitating of
said metal or mixture in the molten state; arranging in the
chamber, under the cold crucible, a mould likely to be rotated
around a vertical axis; arranging outside of the chamber and at
the level of the crucible and especially of the crucible bottom
an induction heating winding; exciting the winding to melt said
metal or said mixture, having it levitate and overheating it by
at least 500C above its melting point; and opening the plug to
end the levitation and have said overheated molten metal or
mixture flow into the rotating mould and fill the cavities
thereof.
According to an embodiment of the present invention,
the very reactive metal is titanium.
According to an embodiment of the present invention,
the mould is of the lost wax mould type.
According to an embodiment of the present invention,
the cast pieces are intended for orthopedic applications.
According to an embodiment of the present invention,
the titanium pieces are intended for dental applications.
The present invention also aims at a device for imple-
menting this method and at the pieces obtained by this method.
An advantage of the titanium pieces obtained by the
method according to the present invention is that they are not
oxidized in their bulk and exhibit an extremely thin surface
oxide layer, only due to possible reactions between the mould and
the molten titanium having penetrated into this mould. Oxide
thicknesses smaller than one micrometer have been obtained while
thicknesses greater than several tens of micrometers are obtained
with conventional methods.
This is an important advantage of the present invention
since it is generally desired to deliver pieces which are not
oxidized at their surface, which requires an operation of sand-
blasting or of polishing by another method, which can be long and


CA 02371805 2001-08-17

3
expensive if the oxide layer and especially the titanium dioxide
layer (Ti02) is thick (of a thickness over a few m) .
The foregoing objects, features and advantages of the
present invention, will be discussed in detail in the following
non-limiting description of specific embodiments in connection
with the accompanying drawings.
Figs. 1A and 1B show a conventional induction furnace
operating in levitation; and
Fig. 2 schematically and partially shows a titanium
melting and casting equipment according to the present invention.
In the following, the present invention will be
explained in relation with the melting and casting of titanium.
More generally, the present invention applies to the melting and
casting of any strongly reactive metal or metal mixture.
To melt a strongly reactive metal or metal mixture,
device of induction-heated cold crucible type, and more specifi-
cally crucibles likely to operate in levitation, are currently
used. Such a crucible is shown in cross-section view in Fig. lA
and in simplified top view in Fig. 1B. Crucible 1 has a rounded
bottom and, as seen from above, is divided into sectors, each
sector being made of a hollow conductive material cooled down by
the circulation of a liquid and electrically isolated from the
adjacent sectors. A winding 3 in which a high-frequency electric
current flows ensures the heating by induction and, due to the
sectorizing and the rounded shape of the crucible bottom, the
levitating of molten substance 5.
The use of such a crucible is described in the art, for
exanple, in US patent 5,058,127 of Marcel Garnier, Isabelle
Gleizes, Patrick Paillere, and Pierre Vernay.
This prior patent, which has some inventors in ccxtIInon
with the present application, more specifically describes the
forming of a crucible including a sectorized bottom forming a
plug, enabling simple opening and fast flow of the levitating
mass, the levitation disappearing when the bottom is opened.
This patent especially suggests in its second exarrple
the melting of a titanium and aluminum mixture. However, this
patent says nothing about the use of a possible mould in which


CA 02371805 2001-08-17
4

the obtained material would be poured. Indeed, this patent
considers levitation essentially in that it enables ensuring a
stirring in conditions of great purity to abtain a homogeneous
mixture/alloy of several metals.
On the other hand, this patent does not describe how
the inductive windings are arranged around the crucible. It can
thus be thought that these windings are arranged conventionally,
around the crucible and as close as possible to the crucible.
The present invention aims at using a bottom-opening
crucible of the type described in the above-mentioned patent, but
which is adapted to a casting operation after the melting.
For this purpose, the present invention provides a
device, the general diagram of which is symbolically shown in
Fig. 2. In this drawing, the means for supporting the various
elements are not shown but can be easily implemented by those
skilled in the art.
Fig. 2 shows a crucible 1 of the same type as that
illustrated in Fig. 1A and 1B containing a liquid mass 5 likely
to levitate. Bottom 6 of the crucible, in accordance with the
teachings of US patent 5,058,127, includes a cooled down and
removable sectorized plug 6. Plug 6 for example moves along with
a rotating arm 8 articulated around an axis 9. Arm 8 is driven by
mechanical, electromechanical, or magneto-mechanical means to be
able to very quickly tip over. It should be noted that axis 9 is
also linked to water supply means (not shown) for cooling down
sectorized bottom 6. Similarly, water supply means for the
sectors of crucible 1 have not been shown.
According to the present invention, inductive windings
13 are arranged outside of the vertical walls of a chamber 15.
This is different from conventional assemblies in which, as
illustrated in Fig. 1A, windings 3 are arranged inmediately
around the crucible. Chamber 15 includes a bottam 17 and a cover
(not shown) which can be connected thereto by seals to create
vacuum inside of it. The chamber is connected to outlet means
intended for forming a primary vacuum therein. These means are
not shown either.


CA 02371805 2001-08-17

The present inventors have found that, conversely to an
established prejudice, the fact of arranging windings 13 outside
of the walls of chamber 15 does not modify the possibility of
obtaining a heating by induction and a levitating of mass 5. The
5 power applied to the winding just has to be slightly increased.
It should be noted that induction systems in which an inductive
winding is placed outside of a chamber for heating are known
(see, for exanple, US-A-4,609,402) but not in levitation systems.
The fact of arranging the windings outside of the
chamber has several advantages.
According to a first advantage, it is useless to
provide crossings of the chamber, which is particularly eco-
nomical, in particular in the case where the chamber is made of
quartz.
According to a second advantage, this avoids risks of
creating a plasma or causing electric breakdowns. Indeed, when
the winding is arranged inside of the vacuum chamber, especially
in the case where the metal to be molten is titanium, a very fast
vaporization of this titanium appears, whereby a reactive plasma
may be created and there are strong risks of short-circuits
between the conductors of the inductive winding, within the
chamber. To solve this problem, various ways of protecting the
windings have been tried in prior art, for example, by embedding
them in an isolator. This however has proven difficult to imple-
ment and often inefficient.
Further, the present invention provides arranging under
the opening provided in the bottam of crucible 1 a mould 20. This
mould includes an inner cylindrical neck 21 having a relatively
large diameter, to ensure that when the titanium flows through
opening 6, it entirely penetrates into the neck. The mould
preferably is a mould obtained by the so-called lost wax
technique and includes various hollowings of calibrated shapes,
two of which, 23 and 24, are visible in the cross-section view.
Mould 20 is assembled on a rotating device not shown and rotates
relatively fast around axis 30 of the device. Thus, the molten
titanium penetrates into openings 23, 24 and fills them up. There
is no air discharge and oxidation problem since the entire system


CA 02371805 2001-08-17

6
is under vacuum. Thus, at the end of the operation, there only is
a thin titanium layer on the inner walls of neck 21 of the
chamber and in each of casting openings 24.
According to an inportant aspect of the present inven-
tion, before opening plug 6 to let the titanium flow into lost
wax mould 20, this titanium is overheated much higher than its
melting temperature. For example, if for pure titanium the melt-
ing temperature is on the order of 16600C, the titanium is
preferably heated up to a temperature on the order of from 1700
to 1800 C. All the disadvantages which would be due to a prema-
ture cooling down in a contact of the molten titanium with the
mould before this titanium completely fills the casting cavities
are thus avoided.

A single figure which represents the drawing illustrating the invention.

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Admin Status

Title Date
Forecasted Issue Date 2009-02-17
(86) PCT Filing Date 2000-02-18
(87) PCT Publication Date 2000-08-24
(85) National Entry 2001-08-17
Examination Requested 2005-01-13
(45) Issued 2009-02-17

Abandonment History

Abandonment Date Reason Reinstatement Date
2002-02-18 FAILURE TO PAY APPLICATION MAINTENANCE FEE 2002-12-05

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Filing $300.00 2001-08-17
Registration of Documents $100.00 2002-08-06
Reinstatement: Failure to Pay Application Maintenance Fees $200.00 2002-12-05
Maintenance Fee - Application - New Act 2 2002-02-18 $100.00 2002-12-05
Maintenance Fee - Application - New Act 3 2003-02-18 $100.00 2003-01-22
Maintenance Fee - Application - New Act 4 2004-02-18 $100.00 2004-01-29
Request for Examination $800.00 2005-01-13
Maintenance Fee - Application - New Act 5 2005-02-18 $200.00 2005-01-26
Maintenance Fee - Application - New Act 6 2006-02-20 $200.00 2006-01-25
Maintenance Fee - Application - New Act 7 2007-02-19 $200.00 2007-01-26
Maintenance Fee - Application - New Act 8 2008-02-18 $200.00 2008-01-29
Final Fee $300.00 2008-12-03
Maintenance Fee - Patent - New Act 9 2009-02-18 $200.00 2009-01-26
Maintenance Fee - Patent - New Act 10 2010-02-18 $250.00 2010-01-25
Maintenance Fee - Patent - New Act 11 2011-02-18 $250.00 2011-01-25
Maintenance Fee - Patent - New Act 12 2012-02-20 $250.00 2012-01-25
Maintenance Fee - Patent - New Act 13 2013-02-18 $250.00 2013-01-31
Maintenance Fee - Patent - New Act 14 2014-02-18 $250.00 2014-01-22
Maintenance Fee - Patent - New Act 15 2015-02-18 $450.00 2015-01-23
Maintenance Fee - Patent - New Act 16 2016-02-18 $450.00 2016-01-21
Maintenance Fee - Patent - New Act 17 2017-02-20 $450.00 2017-02-17
Maintenance Fee - Patent - New Act 18 2018-02-19 $450.00 2018-01-22
Maintenance Fee - Patent - New Act 19 2019-02-18 $450.00 2019-01-18
Current owners on record shown in alphabetical order.
Current Owners on Record
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Past owners on record shown in alphabetical order.
Past Owners on Record
ERNST, ROLAND
GARNIER, CHRISTIAN
GARNIER, MARCEL
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Description
Date
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Cover Page 2002-03-22 2 40
Drawings 2001-08-17 2 27
Abstract 2001-08-17 1 70
Claims 2001-08-17 2 61
Representative Drawing 2002-03-21 1 5
Description 2001-08-17 6 296
Description 2008-07-04 6 296
Representative Drawing 2009-01-27 1 6
Cover Page 2009-01-27 1 40
PCT 2001-08-17 9 335
Assignment 2001-08-17 4 138
Correspondence 2002-03-19 1 32
Assignment 2002-08-06 2 87
Fees 2002-12-05 1 40
Prosecution-Amendment 2005-01-13 1 37
PCT 2001-08-18 5 214
Correspondence 2008-06-06 1 32
Correspondence 2008-07-04 2 77
Correspondence 2008-12-03 2 69