DE10319706A1 - Process for portioning and molding small glass bodies for optical uses comprises preparing a glass melt, removing glass quanta from the melt, and introducing the divided glass quanta into a liquid or onto a liquid surface - Google Patents

Abstract

Process for portioning and molding small glass bodies comprises preparing a glass melt, removing glass quanta from the melt, and introducing the divided glass quanta into a liquid or onto a liquid surface. The liquid is a silicone oil.

Description

The The invention relates to a method for portioning and shaping small vitreous as intermediates for Lenses which in turn for optical applications are intended.

The conventional production of lenses for optical applications from individual complicated processing steps. A possible manufacturing process is that liquid glass poured, molded and afterwards through a complicated and time-consuming cold machining to the desired Lens is finished. Another possibility is that after that Pour out the melt is re-heated glass is pressed.

Be afterwards the compacts through the aforementioned Cold machining process too Ground lenses. A third option is to use the called small vitreous to produce as preforms in that portions from a glass melt equal mass either introduced into a liquid and in it left to sink or applied to a liquid surface levitate there and assume a lenticular shape and subsequently left to sink become; the preforms then become lenses by blank pressing shaped.

• Bereitstellen einer Glasschmelze
• Abtrennen eines kleinen Quantums hieraus
• Ausformen des kleinen Glasquantums durch das genannte Einbringen in eine Flüssigkeit und Sinkenlassen des kleinen Glasquantums derart, daß ohne Zuhilfenahme eines Formwerkzeuges ein fester Vorformling entsteht (sogenanntes Freiformen, Variante A) oder
• Ausformen des kleinen Glasquantums durch das genannte Aufbringen auf eine Flüssigkeitsoberfläche derart, dass es dort infolge der Gasbildung auf der Gasschicht zwischen Flüssigkeit und Glas levitiert und dabei ohne Zuhilfenahme eines Formwerkzeuges ein fester Vorformling entsteht (sogenanntes Freiformen, Variante B), der dann in der Flüssigkeit absinkt.

The invention is concerned with the latter way, in which precise cold machining is avoided. This third way essentially comprises the following individual steps:

• Providing a glass melt
• Detach a small quantum from this
• Forming the small glass quantum by introducing it into a liquid and lowering the small glass quantum in such a way that a solid preform is formed without the aid of a molding tool (so-called free-forming, variant A) or
• Forming the small glass quantum by the aforementioned application onto a liquid surface in such a way that it levitates there between the liquid and the glass due to the gas formation on the gas layer and a solid preform is formed without the aid of a molding tool (so-called free-forming, variant B), which then forms in the liquid decreases.

With regard to the first two individual steps - providing a glass melt and separating a small quantity therefrom - the following prior art has become known:
JP 9110446 . JP 6166521 ,

in this connection becomes the bottom opening of a crucible by periodically moving it up and down of a valve opened and closed. Through this process a certain quantity of glass becomes provided for separation. The separation of the small glass quantum takes place through its own weight through drop formation.

Another option is in JP 8026738 described. A plunger is attached to the feed pipe. The glass melt is conveyed to the opening of the feed pipe by the downward movement of the plunger in connection with the hydrostatic pressure. The glass flow is slowed down by the upward movement of the plunger and the separation of the glass quantity is triggered by the formation of drops due to the weight of the glass in connection with the surface tension.

Show another way JP 06122526 and JP 09052720 , Glass melt flows from a feed pipe onto a collecting device. The amount of glass is weighed and made available for separation. The separation takes place either with the help of a laser beam (heating process) or by a jerky retraction of the mold downwards.

JP 6048746 describes the provision of a small quantity of glass using its own weight. The glass slowly flows out of a feed pipe onto a collecting form and constricts due to the surface tension. The distance between the nozzle and the collecting form is defined so that the glass begins to constrict the first time it comes into contact with the form. The provision is controlled by the weight of the glass and the flow rate per time of the glass melt from the feed pipe. The separation is done by the dead weight.

JP 9235122 uses the dead weight to provide the glass melt and the surface tension of the glass to separate a small quantity of glass. The molten glass emerges from a feed tube as a continuous glass jet. Drops form on the way down.

According to JP 5043258 glass rods are initially manufactured. These rods are fastened vertically and set in rotation. A defined portion of the glass rod is softened by a heating process (laser beam) and made available for separation. The separation is done by the weight of the glass.

According to JP 3295443 The procedure is as follows: The glass melt flows from a crucible to an intermediate storage tank, where an inert gas is applied to the glass surface. The glass melt is controlled by the pressure in the Carrier tube transported. The glass melt flowing out of the feed pipe is separated by its own weight. at JP 3 223 122 pressure is applied to the glass melt on a hermetically sealed melting unit with the aid of hydraulic cylinders in order to make it available at the end of the feed pipe. The separation is carried out subsequently by cutting using a cutting device.

To JP 08133751 the glass melt is periodically heated and cooled in a feeder tube (provided using the viscosity and density of the glass). The heated amount of glass separates by its own weight and forms drops.

According to JP 8290920 the glass melt is sucked out of an open crucible through a suction device. The amount of glass sucked out is subsequently expelled and separates due to the formation of drops.

The third individual step, the free-forming according to variant A mentioned, namely by sinking it into a liquid, is over JP 9235122 known. The molten glass emerges from a feed tube as a continuous glass jet. On the way down, drops form and fall into a hot oil. It remains open whether the free-forming is largely in the free. Atmosphere or in oil.

The The methods described above are intended to serve the preform strict requirements with regard to mass, geometry, surface quality and optical Properties to meet. These requirements vary depending on the area of application of those to be manufactured Lenses such as cameras, CD players, Laser applications, microscopes etc.

Typical requirements for the preforms are:
Mass: ± 1% mass deviation is permitted. The masses of the glass drops are typically less than 5 g, depending on the customer's requirements. The smaller the masses become, the more difficult it will be to portion them precisely.
Geometry: The glass drops should be axially symmetrical.
Surface: The glass drops must have no cut marks, no scratches> 0.4 μm and no overlaps.
Optical properties: The optical properties, such as the refractive index, must meet the respective customer requirements.

The previously known methods were complex.

The The invention has for its object to provide a method with which the requirements based on the freeforming described above on if possible inexpensive Way fulfilled can be.

This The object is solved by the features of claim 1.

• – Wärme- und Kältebeständigkeit
• – physiologische Verträglichkeit
• – großer Viskositätsbereich
• – geringe Temperaturabhängigkeit physikalischer Eigenschaften
• – Filmbildungsvermögen
• – hydrophobes Verhalten

The inventors have recognized that the medium in which the sinking process or on which the levitation takes place plays an outstanding role. You chose silicone oil because silicone oils have the following properties:

• - Heat and cold resistance
• - physiological tolerance
• - large viscosity range
• - low temperature dependence of physical properties
• - film formation ability
• - hydrophobic behavior

The Inventors have also recognized the following: during cooling during Sinking process according to the variant A forms a firmer layer on the glass drop. The inner the drop is still molten. With further cooling has the inside glass volume due to its higher temperature striving to become stronger contract than the colder Glass surface. The solid glass surface but resists it. This puts the glass surface under pressure and the inside under tension. So the drop tends to one Cavitation inside the volume. This cavity can the lower side of the drop, i.e. on the flow front while of sinking. There the drop surface meets on its way down always new layers of oil, so there always the greatest temperature difference and thus the greatest cooling rate is present.

The The inventors have learned from this that the oil temperature plays a crucial role.

At the Carry out of the method according to the invention there are various parameters to be considered. The most important is the oil temperature. temperatures from 100 to 200 ° C have proven to be optimal. Basically, the step of freeforming can also be carried out at room temperature of the oil.

The experiments show that the drops cause local evaporation of the oil after application to the oil surface. This evaporation can lead to temporary levitation of the glass items on the oil surface. The tougher the oils become, the longer the drops levitate on the oils. The glass pos cools during levitation ten and takes on a lenticular shape.

The viscosity of oils can also for the roughness of the glass drop surface may be important.

typically, are the roughness values at room temperature of the oil <50 nm (Ra value).

The Surface quality of the drops becomes with increasing viscosity of oils better.

Also the fall height, i.e. the distance that the drop falls before it hits the free fall covered on the oil surface, is important. Fall heights of up to 5 m are possible. With increasing head the drop improves their surface quality.

Claims (5)

Process for portioning and shaping smaller vitreous for optical Applications with the following process steps: 1.1 it a glass melt is provided; 1.2 from the glass melt small glass quanta are separated; 1.3 the single glass quantum is either in a liquid introduced or applied to a liquid surface; 1.4 the glass quantum either immediately drops a certain distance in the liquid bath or only after a levitation phase; 1.5 the liquid is a silicone oil. A method according to claim 1, characterized in that this single glass quantum near the liquid level is separated. A method according to claim 2, characterized in that itself the glass quantum already partially separated on the liquid bath located. Method according to one of claims 1 to 3, characterized in that that the viscosity of the oil between 0.01 and 500 dPa × s lies. Method according to one of claims 1 to 4, characterized in that that the fall height larger than Is 1.5 m.