WO2001053224A1 - Mould for making glass products - Google Patents

Abstract

The invention concerns a mould for making glass products comprising a metal casing co-operating with an insert made of a specific alloy. The invention is characterised in that the casing and the insert co-operate through linking mechanical means producing a removable link between them and it further comprises cooling channels arranged preferably substantially parallel to the longitudinal axis XX' of said mould.

Description

 MOLD FOR THE MANUFACTURE OF GLASS PRODUCTS

The present invention relates to the field of manufacturing glass articles such as bottles, flasks, jars ... and, more specifically, the molds used for this purpose.

The conventional processes widely used at present for manufacturing bottles use so-called IS machines and are known by the designations of "blown-blown" and "pressed-blown" processes.

These processes can be broken down into several stages. The most widely used “soufflé-soufflé” process is described below:

• loading: a drop of glass or parison enters under the effect of its own weight in a first mold (rougher), by the upper end of it, corresponding to the bottom of the finished bottle;

• compression: after loading, a rough bottom closes the rough mold; then a blow of compressed air is carried out in the blank mold via the blank bottom to force the glass to penetrate well into the lower part of the mold, which corresponds to the ring of the future article; in addition, this compression ensures good thermal contact between the glass and the mold;

• drilling: a punch, of reduced dimensions, occupying approximately the height of the ring and closing the bottom of the blank mold, withdraws downwards, giving way to a supply of compressed air which drives out in front of it the less viscous hot glass located in the vicinity of the axis of the blank mold; the more viscous cold glass which has been cooled in contact with the mold remains in place; a draft of the future article is thus obtained;

• transfer: when the blank has cooled sufficiently in the blank mold to be able to be handled, it is transferred to a second mold

(finisher) which has the form of the final article;

• elongation and blowing: once placed in the finishing mold, the blank is allowed to lengthen for a certain time before blowing it to give it the form of article; this elongation step makes it possible to distribute the glass well throughout the article;

• extraction: in contact with the finishing mold, the glass cools quickly, and when its viscosity is sufficiently low, the article is extracted from the finishing mold.

The “blown-blown” process differs from the “blown-blown” process only in the blank forming phase, which is obtained by pressing the glass in the closed blank mold, using a punch more or less long which enters the mold from the bottom thereof through the ring mold. There are therefore no compression or drilling steps, the blank of the article being formed in one go, thanks to this pressing.

These methods make it possible to manufacture all forms of articles, whether axisy metric or not.

Cast iron and bronze are frequently used to form the massive molds described above: their thermal conductivities are in fact perfectly suited to the heat transfers sought with respect to glass under the conditions for manufacturing hollow articles, which allows high production rates.

These materials are however imperfect in many ways. In particular, cast iron has grain-shaped surface irregularities which can affect the appearance of the molded product.

On the other hand, the surface of the molds made of these materials is, due to their relative brittleness, especially when hot, likely to be affected more or less seriously in various circumstances, again inevitably causing surface defects in the glass article. . Thus, various production incidents are causing injuries to the molds, requiring the removal of damaged molds for possible repair. The resulting manipulations are again a source of shock, especially since the molds are hot. Furthermore, the aforementioned materials require regular greasing of the roughing and finishing molds to ensure good demolding of the glass without generation of defects on the articles produced, but also to allow good entry of the parisons in the roughing molds, without which the machines for forming could not work continuously. This lubrication is therefore the cause of a drop in manufacturing yield of the order of a few percent, since the first bottles produced after lubrication are discarded because polluted by grease residues. In the long run, the grease residues present on the molds become troublesome for the manufacture (poor quality of appearance of the articles, problems of forming due to blocked exhaust vents) and the molds must be removed for cleaning. This cleaning is relatively aggressive and is one of the main causes of wear of the molds and therefore of their disposal.

Furthermore, no material exhibits a satisfactory compromise in terms of thermal conductivity, resistance to high temperatures, mechanical strength and hot hardness, the ability to implement (machinability, possibility of drilling), surface appearance under acceptable industrial and economic conditions of use.

To remedy the problem set out above, one approach has consisted in coating part or all of the imprint of glassware molds with alloys based on nickel, much harder when hot than cast iron or bronzes, much more resistant. to hot corrosion but also to much more regular surface aspects and therefore better suited to the intended application; these alloys also make it possible to very significantly limit the lubrication of the molds. These alloys were first deposited at the edges, where the molds deteriorate most often, then on all of the imprints.

The German document DE 29717189 illustrates this concept by proposing a mold with insert partially coated with an anti-wear layer, for example in an alloy based on nickel or cobalt. It should be noted that the production of an entire mold in a nickel-based alloy is not realistic because of the difficulties which the foundry molding and the machining of this material present, and the very great difficulty in piercing it. , its high cost, and lower thermal conductivity.

Another problem inherent in the manufacture of glass products relates to the heat of the molds and in particular the heat evacuation. When the molds have an insert as mentioned above, the insert itself can pose a cooling problem for the mold. Likewise, the respective materials of the insert and of the shell must have thermal compatibilities which avoid any constraint and therefore any embrittlement.

Furthermore, an insert enclosed in a shell requires an efficient evacuation of the heat energy, at least equal to that of a solid mold.

On the other hand, in order to increase the production rates, it is necessary to improve the cooling of the glass, in particular at the level of the cooling rate.

More precisely, it is necessary to reach as quickly as possible the temperature of the glass corresponding to an adequate viscosity, such that the glass product can be released from the mold without collapsing on itself, while maintaining a level of quality. of the formed article.

Concerning more particularly the roughing molds, the viscosity of the body of the article must remain such at the end of the roughing step, that it is possible to finish forming the article. In other words, the cooling of the glass must be limited to the body of the article; the bottle ring must be sufficiently cooled to be able to serve as a hold for the transfer tool (ring mold) to the finishing mold.

A cooling gradient must therefore exist along the axis of the glass product to be formed.

The horizontal thermal distribution must be as homogeneous as possible when the products are axisymmetric, which is mainly the case.

However, if the mold is formed of two half shells, the temperature profile must be adapted accordingly because in this case the joint plane of the two half shells creates a temperature gradient in this area. Various solutions are known to the thermal problem mentioned above.

Thus, patent application FR 2 766 172 filed in the name of the applicant describes a device for cooling mold elements.

This solution recommends using water as a cooling fluid; to do this, cooling channels pass through the body of the molds and they are connected to a cooling water circuit. This concept, although effective, may seem costly. French patent FR 2 321 376 is also known, which describes an air-cooled mold comprising several groups of cooling channels which can be controlled and or adjusted independently of one another.

This solution is sophisticated, delicate to implement, and expensive. Advantageously, the present invention makes it possible to respond to the aforementioned thermal problems.

The present invention indeed represents an effective solution to the various problems mentioned above. It also has great simplicity of manufacture, implementation and execution. Therefore, its cost is low. Very high reliability is attached to this design.

Furthermore, the present invention provides for making one of the elements of the mold removable with respect to the other.

Thus the subject of the present invention is a mold intended for the manufacture of glass products comprising a metal casing cooperating with an insert of a specific alloy.

According to the invention, the envelope and the insert cooperate by means of a mechanical connection means providing a removable connection between them; moreover, the mold according to the invention may comprise cooling channels preferably arranged substantially parallel to the longitudinal axis XX 'of said mold.

According to one embodiment of the invention, the insert is mechanically fixed to the envelope by screwing.

In accordance with another embodiment of the invention, the insert is mechanically fixed to the envelope by welding and / or by riveting.

Preferably, the insert is made of an alloy having a high resistance to oxidation by air and in contact with glass.

In addition, the insert is made of a material having a high thermal conductivity. According to one aspect of the invention, the insert is made of a nickel alloy.

Without departing from the scope of the invention, the insert can be made of cast iron.

In accordance with a feature of the invention, the envelope is made of cast iron. Advantageously, said cooling channels are arranged near the interface between the envelope and the insert.

According to a first application of the invention, the mold may consist of a blank mold intended for the manufacture of hollow glass articles such as flasks, bottles, jars, etc.

In accordance with a second application of the invention, the mold may consist of a finishing mold intended for the manufacture of hollow glass articles such as flasks, bottles, jars, etc.

Other characteristics, details and advantages of the present invention will appear better on reading the description which follows, given by way of illustration and in no way limiting, with reference to the appended drawings in which:

• Figure 1 is a longitudinal section of a mold according to a first embodiment of the invention; and

• Figure 2 is a longitudinal section of a mold according to a second embodiment of the invention.

In Figure 1 schematically appears a first embodiment of the invention which comprises a metal shell (or shell) 1 in which is housed an insert 2 made of an alloy having a high resistance to oxidation by air and in contact with glass. Furthermore, the insert 2 must have a high thermal conductivity, of the order of 45 W / (mK). Cupro-aluminum can be used to form insert 2; as well as cast iron. Without departing from the scope of the invention, a nickel-based alloy can be used, such as for example constituted thus (weight proportions): • at least 80% of Ni,

• from 0.1 to 4% Fe,

• from 1 to 15% of Cr,

• from 1 to 5% of Si,

• from 0 to 0.8% of C, • from 0 to 4% of B and

• usual traces.

According to the invention, the casing 1 and the insert 2 are connected to each other by a mechanical connection means such as a screwing, one or more welds, riveting ... The insert 2 is produced independently of the envelope 1, by molding.

The insert being enclosed in the envelope 1 an efficient evacuation of calories is necessary.

One solution is to provide cooling channels 3 because it is important to be able to cool the mold which is not massive. The invention aims to reproduce in the mold according to the invention the same thermal conditions as in a solid mold which a priori cools more easily.

Preferably, the channels 3 are arranged parallel to the longitudinal axis XX 'of the mold, and regularly distributed angularly. However, the distribution may be irregular around the joint plane of the mold, when the latter is formed from two half-shells.

The channels can be dug partly in the shell 1 and / or partly in the insert 2. Preferably, they will be mainly dug in the insert

2 with through parts hollowed out in the envelope 1. The section of the channels can vary according to their length in order to compensate for the thermal gradient mentioned above.

By way of illustration, the width of the channels 3 can vary from 3 mm to 12 mm. Depending on the exchange surface thus obtained, an appropriate number of channels is chosen. This number can vary between a minimum of 1 and a maximum of 20 per half layer.

Similarly, the flow of cooling air through the channels is modulated by the ventilated air pressure which can be between approximately 8380 Pa and 12748 Pa. According to the embodiment of FIG. 1, the channels 3 are essentially hollowed out in the insert 2 at the interface of the shell 1. They open on each side at the level of the shell 1, either in a direction parallel to the axis XX 'or at an angle with respect to the axis XX '.

These orientations are preferably chosen to adjust the thermal of the mold as well as for machining convenience.

Around the longitudinal axis XX 'appears a cavity 4 which defines the shape of the blank. Above and below the cavity 4, enclosures 5-6 are provided, intended to receive the mold base and the mold respectively. Ring. Above the upper enclosure 5 a circular cavity 7 forms the guide hole of the mold base support.

The thickness of the insert 2 according to the invention can vary from 5 to 30 mm.

FIG. 1 illustrates a mold intended for manufacturing beer bottles of 25 to 33 cl while FIG. 2 relates to a mold for the manufacture of wine bottles of 75 cl and beyond: these examples are of course non-limiting.

The differences between FIGS. 1 and 2 reside first of all in the shape of the interior cavity 4 as well as in the arrangement of the channels 3 which, according to FIG. 2, open at the bottom into the enclosure 6 itself and not in the shell 1. This arrangement is adopted to favor the cooling of the ring mold.

The present invention advantageously makes it possible to have a lower lubrication frequency for the molds than according to the previous article, going from 20-30 minutes to several hours, even several days. Furthermore, the mechanical connection between the shell 1 and the insert 2 makes it possible to separately recover and recycle the materials which constitute them when these are different.

The implementation of the mold according to the invention is also easy, therefore inexpensive. It emerges from the above that one of the major problems of molds comprising an insert is linked to thermal and more particularly to non-homogeneous thermal distribution. This is indeed to cool only the hottest areas and not the others.

The present invention provides a solution that is both simple and effective to all of the problems mentioned above.

All the characteristics and advantages set out above make it possible to define a new interesting and competitive mold vis-à-vis known equivalent products.

Claims

1. Mold intended for the manufacture of glass products comprising a metal casing (1) cooperating with an insert (2) made of a specific alloy, the casing (1) and the insert (2) cooperating by means of a mechanical connection means providing a removable connection between them, and a set of cooling channels (3) preferably arranged substantially parallel to the longitudinal axis XX 'of said mold, characterized in that the insert (2) consists of an alloy having a large resistance to oxidation by air and contact with glass. 2. Mold according to claim 1, characterized in that said cooling channels (3) are arranged near the interface between the casing (1) and the insert (2). 3. Mold according to any one of the preceding claims, characterized in that the insert (2) consists of a material having a high thermal conductivity. 4. Mold according to any one of the preceding claims, characterized in that the insert (2) is made of a nickel alloy 5. Mold according to any one of claims 1 to 3, characterized in that the insert (2) consists of cast iron. 6. Mold according to any one of the preceding claims, characterized in that the envelope (1) consists of cast iron. 7. Mold according to any one of the preceding claims, characterized in that the insert (2) is mechanically fixed to the envelope (1) by screwing. 8. Mold according to any one of claims 1 to 5, characterized in that the insert (2) is mechanically fixed to the envelope (1) by welding and / or by riveting. 9. Mold according to any one of the preceding claims, characterized in that it consists of a blank mold intended for the manufacture of hollow glass articles such as flasks, bottles, pots. 10. Mold according to any one of claims 1 to 8, characterized in that it consists of a finishing mold intended for the manufacture of hollow glass articles such as flasks, bottles, pots.