|Publication number||US7594310 B2|
|Application number||US 11/661,797|
|Publication date||Sep 29, 2009|
|Filing date||Sep 2, 2005|
|Priority date||Sep 3, 2004|
|Also published as||CN101014432A, CN101014432B, DE602005013402D1, EP1789218A1, EP1789218B1, US20080236707, WO2006024191A1|
|Publication number||11661797, 661797, PCT/2005/521, PCT/CH/2005/000521, PCT/CH/2005/00521, PCT/CH/5/000521, PCT/CH/5/00521, PCT/CH2005/000521, PCT/CH2005/00521, PCT/CH2005000521, PCT/CH200500521, PCT/CH5/000521, PCT/CH5/00521, PCT/CH5000521, PCT/CH500521, US 7594310 B2, US 7594310B2, US-B2-7594310, US7594310 B2, US7594310B2|
|Original Assignee||Gianfranco Passoni|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (20), Classifications (21), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a national stage completion of PCT/CH2005/000521 filed Sep. 2, 2005 which claims priority from French Application Serial No. 04/09321 filed Sep. 3, 2004.
This invention concerns a method for producing a circular-shaped mechanical part, in particular an annular-shaped part such as a bearing race made of a metal alloy that can undergo at least a hardening heat treatment, in which a blank of this mechanical part is produced through centrifugation in a hollow rotating mold by means of a predetermined volume of this metal alloy brought to a melting temperature T1 and in which this blank is cooled to a temperature T2 lower than this melting temperature T1, at which this blank has a malleable consistency.
It also concerns a device for implementing this method to produce a circular-shaped mechanical part, in particular an annular-shaped part such as a bearing race made of a metal alloy that can undergo at least a heat hardening treatment comprising a hollow rotating mold positioned to receive the pre-determined volume of this metal alloy, heating components to heat this metal alloy to the melting temperature T1 and drive mechanisms to make this hollow mold rotate and produce a blank of the mechanical part via centrifugation.
Finally, it includes a mechanical part produced using this method and this device.
Circular-shaped mechanical parts and in particular annular-shaped parts such as ball or needle bearing races, for example, are generally produced using known cutting methods that involve complex and costly machining of the part from an appropriate metal bar such as chromium steel. By way of example, for a ball bearing race, the machining phases include positioning the metal bar on the mandrel of a lathe, internal piercing, external shaping using a plunge chisel, machining the interior race using a tool that penetrates into the central cavity and that can be moved laterally, machining the grooves for housing the dust caps on either side of the race, cutting the part, washing it and heating treating or tempering it.
The machining operations all produce shavings since they consist in removing material from the full metal bar with a circular section, which is the prime material used to manufacture the part. Since the alloys used are expensive, the production of shavings generates a non-negligible loss, since the amount of shavings produced during machining often weigh more than the part itself. Additionally, for each part diameter, it is necessary to have a raw metal bar with an equal diameter, which means considerable securing and management of stock for various metal alloy bars whose base price is high. Finally, each part corresponds to a range of drilling, milling and other very important tools that must be maintained to guarantee quality production. In particular, cutting machines are expensive, and the investment is relatively large for a manufacturer.
All these disadvantages plus the fact that some extra hard steels do not lend themselves to this type of traditional machining and are therefore not used very much in current industry practices for economic reasons mean that the known methods are difficult to manage in an economic process where productivity has become a major asset.
Relatively satisfactory tests have been conducted, but they have not resulted in satisfactory results with respect to both quality and productivity.
Publication GB 852 359 describes a centrifuge casting method for steel rings in which a pre-determined quantity of molten metal is taken from a tank of melting metal to be poured into a casting crucible. Collecting a pre-determined quantity of molten metal is particularly tricky to do with a pouring-basin equipped with a distribution nozzle and a mechanical stopper.
American patent U.S. Pat. No. 3,927,450 also describes a method for centrifugally casting hollow metal alloy ingots. These ingots are then mechanically machined and cut to form the desired circular-shaped mechanical parts.
French patent FR 2,516,825 also describes a centrifugal casting device. As in the previous documents, the molten alloy is taken from a tank containing the melting material, and the required quantity is removed using an intermediate recipient. This type of supply device is not very precise and is complex and expensive.
American patent U.S. Pat. No. 3,720,987 describes a method for manufacturing rings, particularly bearing races using carbon steel metal alloys, via centrifugation. This method intends to cause a migration of the steel particles toward the exterior and of the carbon particles toward the interior of the cast part.
American patent U.S. Pat. No. 5,101,547 describes a centrifugal casting method in which the melting material is taken from a molten bath of raw material.
None of these methods are precise and reliable and none allow the rapid, economical and reliable production of precision parts. Bearing races are parts of great expenditure that must be manufactured with tolerances of around 1/000th of a millimeter.
The objective of the invention is to eliminate all of these disadvantages by proposing to replace the standard machining methods that remove metal alloy shards with a simple and economic forming technique allowing the use of any metal alloy, even extra hard alloys, from a reduced stock of raw material and the combination, in certain cases, of this shaping with at least one thermal treatment phase for the part.
This goal is achieved by the method as defined in the introduction and characterized in that the volume of metal alloy to be melted is determined based on a metal alloy bar inserted into a vertical induction oven open at its lower end above the hollow mold. This predetermined volume of metal alloy is brought to the melting temperature T1. The interior shape of this mechanical part is formed using machining components brought into contact with its interior face when this blank has reached temperature T2. This part is extracted from the hollow mold and is brought to a tempering temperature T3 and in that it is cooled in a predetermined manner.
According to an advantageous embodiment, the metal alloy bar is pre-notched circularly in order to define bar segments each corresponding to the predetermined volume of raw material required to produce the mechanical part or to a whole sub-multiple of this volume.
According to a first variant, this predetermined quantity of metal alloy can be introduced into the mold in the form of at least one drop formed by at least one bar segment melted at temperature T1 in the vertical heating oven. This drop is detached by gravity from the metal alloy bar inserted inside the vertical heating oven.
According to a second variant, this predetermined quantity of metal alloy can be introduced into the hollow mold in the form of at least one bar segment. This segment is detached from the bar by heating the bar in the areas where it is pre-scored. This bar segments is then brought to the melting temperature T1 by heating components at least partially surrounding this hollow mold.
This objective is also achieved by the device for implementing this method as defined in the introduction and characterized in that it comprises:
means for determining the volume of metal alloy to be melted from a metal alloy bar;
inducting heating mechanisms to melt this pre-determined volume of metal alloy and bring it to temperature T1 in the hollow mold;
means for cooling this blank obtained by centrifugation of the molten alloy in the hollow mold and bringing it to temperature T2, lower than melting temperature T1, at which this blank has a malleable consistency;
machining mechanisms for forming the interior shape of this mechanical part;
a temperature regulation device to bring the mechanical part obtained from this blank to a tempering temperature T3; and
means for tempering this mechanical part (28) after it is extracted from the hollow mold.
Advantageously, the means for determining the volume of metal alloy to be melted consist of circular preliminary notches made on the bar in order to define bar segments each corresponding either to the volume of raw material required to produce the mechanical part or to a whole sub-multiple of this volume.
In a first embodiment variant, the induction heating components may comprise a vertical induction oven open at its lower end above the hollow mold into which the pre-notched bar of metal alloy is inserted.
In a second embodiment variant, the induction heating mechanisms may comprise a vertical induction oven into which the pre-notched bar of metal alloy is inserted and at least one induction coil at least partially surrounding the hollow mold. The heating temperature in this induction oven being, in this case, determined in order to melt the bar only in the pre-notched areas and to thus allow detachment of the segments necessary to obtain the predetermined volume of metal alloy. These segments then being melted in the mold and brought to the melting temperature T1 by the induction coil.
Preferably, the machining mechanisms comprise a rotating profiled shaping tool combined with drive mechanisms to cause it to rotate and means for axial and lateral movement to bring it up against the interior surface of the blank in order to form the interior shape of this mechanical part.
The hollow mold may be combined with a mask that forms a casting wall for the mechanical part.
Advantageously, the means for tempering the mechanical part include at least one tempering bath.
In all the variants, the hollow mold comprises a crucible designed to contain the predetermined volume of metal alloy and a casting cavity that communicates with this crucible.
In one embodiment variant, the hollow mold may consist of at least two radially mobile segments positioned to allow an opening of this mold, in order to extract the cast part.
Depending on the form of embodiment, the means for cooling the blank may be positioned to cool the exterior walls of the mold and/or the mask.
This invention and its advantages will be better understood by reading the detailed description of a form of implementation of the method of the invention and its variants in reference to the appended drawings given by way of non-limiting example, wherein:
In reference to
These operations are performed automatically at a rapid rhythm on digital control machines. They generate a large quantity of metal shards and the machining tools must be sharpened regularly and their position must be adjusted to offset their wear.
The method according to the invention makes it possible to do away with all the constraints tied to this manufacturing process by further improving the known method of centrifugally casting parts. The dimensions of the parts obtained using the known method cannot be guaranteed, for measurement of the parts to be cast is not very reliable. In the method of the invention, this disadvantage is eliminated by the fact that the volume of metal alloy to be melted is determined using a metal bar inserted inside a vertical induction oven, this bar being divided into equal, pre-cut sections which will make it possible to obtain a predetermined volume of metal alloy that is always identical. This predetermined volume of metal alloy is then brought to the alloy's melting temperature to form a blank via centrifugation in a rotating mold. While the blank is still malleable, the interior shape of the desired mechanical part is formed using a machining tool such as a rotating profiled shaping tool brought into contact with its interior surface and after the part is extracted from the mold, it is immersed in a tempering bath.
This method may be used on a device illustrated in
Above this equipment there is a feed device for the raw material used to produce the mechanical part, in this case a metal alloy that is presented, for example, in the form of a bar 20 that is formed of segments 21 connected to one another by peripheral grooves 22. In practice, a milling device (not shown) machines the peripheral grooves 22 in a predetermined manner automatically controlled to define the segments 21. This bar 20 is inserted into a vertical induction oven 23 so that a quantity of raw material is melted and falls into the crucible 13 of the rotating hollow mold 11.
For this purpose, the vertical induction oven 23 comprises induction coils 24 whose axes are vertical and correspond to the axis of the central channel 25, which corresponds more or less to the axis of the hollow mold. The induction coils 24 are arranged so that the segments 21 of the bar 20 that are automatically moved in the direction of the arrows are first pre-heated, then melted. Each segment 21 preferably has an equal volume or a volume that corresponds to a whole sub-multiple of the volume of raw material necessary to produce the mechanical part.
The functioning of this device is explained below in reference to the Figs., which represent the different stages of the process.
These different phases of the process may be carried out in a controlled atmosphere to prevent oxidation or corrosion depending on the metal alloy used.
In a second embodiment of the device as illustrated in
The other components of the device are more or less the same and, when the metal alloy is melted, centrifugation by rotation of the hollow mold around its axis produces a blank 26 whose treatment is the same as that described above to produce the final part.
In the two variants of the device according to the invention described previously, the hollow mold is topped by a mask 15. The part can be removed from the mold after this mask is removed.
The preferred embodiments described may undergo different modifications and may be incorporated in a carrousel equipped with different workstations. It is also possible to use an alloy in the form of divided particles, for example grains or granules, contained in a feed regulator. In this case, the quantity of particles necessary can be measured by weighing or by volume measurement, so that the volume of particles corresponds to the volume of the part to be produced. The particles of raw material are poured cold into the crucible of a hollow mold equipped with heating components as described in reference to the second form of embodiment.
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|FR2516825A1||Title not available|
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|GB852359A||Title not available|
|JP2004098090A||Title not available|
|JPH038546A *||Title not available|
|JPS5978764A *||Title not available|
|U.S. Classification||29/33.00C, 164/133, 164/297, 164/80, 164/286, 29/898.066, 164/335, 29/DIG.6, 29/527.6, 29/898.12|
|International Classification||B22D13/04, F16C33/64, B23P23/00, B22D13/10|
|Cooperative Classification||Y10T29/49989, Y10T29/49705, Y10T29/5184, F16C33/64, Y10T29/49689, Y10S29/006|
|May 10, 2013||REMI||Maintenance fee reminder mailed|
|Sep 29, 2013||LAPS||Lapse for failure to pay maintenance fees|
|Nov 19, 2013||FP||Expired due to failure to pay maintenance fee|
Effective date: 20130929