Molding apparatus and molding method for precision glass elements

Abstract

According to one example, a molding apparatus can be used to mold one or more glass elements by heating one or more glass materials and pressing the one or more glass materials between an upper mold and a lower mold. The molding apparatus includes: a radiant heating module including a plurality of radiant heating elements, an upper resistance heating module including a first plurality of independently controlled resistance heating elements, and a lower resistance heating module including a second plurality of independently controlled resistance heating elements.

Description

Molding equipment and molding methods for precision glass components This disclosure relates generally to glass molding, and more specifically to molding equipment and molding methods for precision glass components. Cross-references to related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 249,298, filed September 28, 2021, entitled “Molding Apparatus and Molding Method for Precision Glass Elements,” the entire contents of which are incorporated herein by reference. Typically, the molding of precision glass components is performed by heating the glass material above its softening point and pressing the glass material between an upper mold and a lower mold to form a precision glass component. Typical examples of such molding apparatus and methods are described in Japanese Patent No. JP3832986B2; U.S. Patent No. 4,734,118; Japanese Patent No. JP6540684B2; and U.S. Patent No. 6,184,498; each of these patents is incorporated herein by reference in its entirety. However, these typical molding apparatuses and methods may have shortcomings. According to one example, a molding apparatus can be used to mold one or more glass elements by heating one or more glass materials and pressing the one or more glass materials between an upper mold and a lower mold. The molding apparatus includes: a radiant heating module including a plurality of radiant heating elements, an upper resistance heating module including a first plurality of independently controlled resistance heating elements, and a lower resistance heating module including a second plurality of independently controlled resistance heating elements. According to another example, a molding method for molding one or more glass elements includes: heating one or more glass materials using each of a radiant heating module including a plurality of radiant heating elements, an upper resistance heating module including a first plurality of independently controlled resistance heating elements, and a lower resistance heating module including a second plurality of independently controlled resistance heating elements. The molding method further includes pressing one or more glass materials between an upper mold and a lower mold. According to another example, a molding apparatus and molding method can be used to mold precision glass elements by heating one or more glass materials and pressing one or more glass materials between an upper mold comprising one or more molds and a lower mold comprising one or more molds to form one or more glass elements. In this molding apparatus and molding method, heating is achieved through a radiant heating module comprising multiple radiant heating elements, an upper resistance heating module comprising multiple resistance heating elements, and a lower resistance heating module comprising multiple resistance heating elements. In some examples, a combination of heating elements increases the heating rate of the molding method. In some examples, the resistance heating elements and radiant heating elements are independently controlled to obtain a desired temperature gradient for one or more glass elements. According to another example, a molding apparatus and molding method can be used to mold precision glass elements by heating one or more glass materials and pressing one or more glass materials between an upper mold comprising one or more molds and a lower mold comprising one or more molds to form one or more glass elements. In this molding apparatus and molding method, cooling of the glass (or other optical material) is achieved through an inert airflow, an upper resistance heating module comprising multiple resistance heating elements, and a lower resistance heating module comprising multiple multi-resistance heating elements. In some examples, the combination of the inert airflow and the resistance heating elements controls the cooling rate of the glass element. According to another example, a molding apparatus and molding method can be used to mold precision glass elements by heating one or more glass materials and pressing one or more glass materials between an upper mold comprising one or more molds and a lower mold comprising one or more molds to form one or more glass elements. In the molding apparatus and molding method, the temperature is measured by a temperature monitoring device including an infrared camera. In some instances, the infrared camera helps to determine the softening point of the glass material. According to another example, a molding apparatus and molding method can be used to mold precision glass elements by heating one or more glass materials and pressing one or more glass materials between an upper mold comprising one or more molds and a lower mold comprising one or more molds to form one or more glass elements. In this molding apparatus and molding method, the upper mold and the lower mold are aligned by guide pins, wherein the guide pins are connected to positioning devices such that the surface of the guide pins is coplanar with the surface of the molds during heating and then extends from the molds during pressing, thus allowing the guide pins to be used to align holes in the top mold with holes in the bottom mold. According to another example, a molding apparatus and molding method can be used to mold precision glass elements by heating one or more glass materials in a processing chamber and pressing the one or more glass materials between an upper mold comprising one or more molds and a lower mold comprising one or more molds to form one or more glass elements. In the molding apparatus and molding method, heating is achieved by a radiant heating module installed in a processing chamber comprising multiple radiant heating elements, the radiant heating module being able to be installed and removed from the processing chamber in a manner that holds the multiple radiant heating elements within the radiant heating module. Examples of this disclosure are best understood by referring to Figures 1-8 of the accompanying drawings, with similar numbers used for similar and corresponding parts of the various figures. The molding of precision glass components is typically achieved through the steps illustrated in Figure 1. As shown in Figure 1, the glass material is first placed in a processing chamber and heated above its softening point. Next, the glass material is pressed between an upper mold and a lower mold to form a glass component, such as a glass lens. Then, the glass component is gradually cooled or annealed below its softening point. Finally, the glass component is rapidly cooled to a lower temperature to be removed from the processing chamber. In some instances, minimizing the time used for the molding process is desirable to increase yield. A typical example of achieving this involves increasing heating power to reduce the time required to heat the glass material. However, shorter heating times can create temperature gradients in the glass material. This can lead to localized melting or cracking, which can create defects in the glass element. Another typical example of minimizing the time used for the molding process involves minimizing the time for the gradual cooling of the glass material. However, rapid gradual cooling can create residual stresses in the glass element, which is undesirable in some applications, such as lenses. Furthermore, typical molding equipment utilizes only radiant heating elements, resulting in limited heating power and making it difficult to control the temperature gradient based on light reflection. In one example, both radiant and resistance heating elements are used; however, heating is achieved through a radiant heating module, an upper resistance heating element, and a lower resistance heating element. Consequently, the temperature gradient within the glass material cannot be controlled. In contrast, the molding equipment and methods discussed herein can address one or more of these drawbacks. For example, the molding equipment and methods described herein allow for precise control of the rate of gradual cooling (and / or heating). This minimizes residual stress, eliminates the need for further annealing of the glass element, and improves accuracy. According to one example, a molding apparatus for precision glass components includes a radiant heating module, an upper resistance heating module in contact with an upper mold, and a lower resistance heating module in contact with a lower mold, wherein each heating module contains multiple heating elements for independent power control. In some examples, the sum of the modules increases the heating power of the molding apparatus, while the independent control of the heating elements reduces the temperature gradient of the glass material. Additionally, the resistance heating elements can be used to control the gradient of the glass material during gradual cooling. This is achieved through a combination of (1) cooling with an inert gas flow and (2) heating with resistance heating elements. In some examples, this achieves shorter heating times while precisely controlling the gradual cooling rate. Figure 2 illustrates an example of a molding apparatus 1 that can be used for molding precision glass components. In the example shown in Figure 2, apparatus 1 has an overall frame 10 surrounding the entire system. The top mold 15 and bottom mold 16 are displaced relative to each other via a servo motor 21, a bearing mechanism 22, a screw jack 23, and a position feedback device (all referred to as a ram 20). The screw jack 23 has sufficient capacity to also press glass materials 40 (e.g., 40a, 40b) with high force. An anvil 30 is mounted to a load detection device 32 for monitoring the force applied to the glass material 40 by the ram 20. The processing chamber 34 is sealed in a manner that allows for a vacuum or inert gas environment during molding. A flexible bellows 50 is used to achieve a seal during movement, but any method used for sealing can be used. For example, in some instances, a sliding mechanical seal may suffice. Processing chamber 34 includes one or more radiant heating elements 60 for heating glass material 40 and molds 15 and 16. The example in Figure 2 shows four radiant heating elements 60 (e.g., 60a-60b), but any number of radiant heating elements 60 can be used. In some examples, the radiant heating elements 60 may be infrared heating lamps, but any other type of radiant heating element 60 can be used. In the example shown, the radiant heating elements 60 are outside the sealed volume of processing chamber 34 and are separated from the sealed volume by a transparent quartz tube 65. In other examples, processing chamber 34 may not include the transparent quartz tube 65. Radiant heating elements 60 may be consumed over time due to the degradation of the filament used in infrared heating lamps. In some examples, the filament is made of tungsten. In some examples, all radiant heating elements 60 can be removed as a single unit to minimize the time required to replace the radiant heating elements 60. Examples of such single units are seen in Figure 3, which shows an example of a radiant heating module 61. The radiant heating module 61 may be a removable single unit comprising each of the radiant heating elements 60. During the installation and removal (e.g., removal) of the radiant heating module 61 from the processing chamber 34, the radiant heating elements 60 may remain mounted on the radiant heating module 61. In the example shown in Figure 2, the glass material 40 comprises two spherical glass materials 40a and 40b. However, any other number of glass materials 40 can be molded using the molding apparatus 1. Furthermore, the glass material 40 can have any size and / or shape suitable for producing glass elements. The size and / or shape of the glass material 40 can affect the size and shape of the glass element (or vice versa). The glass material 40 can be any moldable glass material, such as n-BK7. In the example shown in Figure 2, the glass material 40 is placed on the bottom mold 16, and the top mold 15 is mounted to the slide 20. Between the top mold 15 and the slide 20, a resistance heating module 70a and a cooling plate 72a including channels for inert airflow are mounted. The resistance heating module 70b is mounted between the bottom mold 16 and the anvil 30, and between the cooling plate 72b including channels for inert airflow. The cooling plate 72 may include one or more channels. For example, the cooling plate 72 may include multiple channels. In some instances, the inert gas flow rate in each channel of the cooling plate 72 is individually controlled. A temperature monitoring device 65 can be used to monitor the temperature of molds 15 and 16 and / or glass material 40. In some instances, the temperature monitoring device 65 can be any temperature monitoring device such as a thermocouple. A servo motor 21, a position feedback device, a load detection device 32, a heating element, inert gas flow, and the temperature monitoring device 65 are connected to a controller 90 to achieve the desired temperature and force distribution (see Figure 1). The resistance heating module 70 (e.g., 70a and / or 70b) may include one or more resistance heating elements 80 for controlling the temperature gradient of the glass material 40. In the example shown in FIG. 4, the resistance heating module 70 includes three resistance heating elements 80 (e.g., 80a, 80b, and 80c), but any number greater than one can be used to achieve independent control. In the illustrated example, the three resistance heating elements 80 generate three heating zones: an outer zone generated by resistance heating element 80a, a middle zone generated by resistance heating element 80b, and an inner zone generated by resistance heating element 80c. Each resistance element 80 (and therefore each zone) can be independently controlled to allow each zone to be heated to a different temperature. This allows the device 1 to control (and sometimes eliminate) the temperature gradient of the glass material 40 during heating and / or cooling. In some instances, the resistance heating elements 80 can be used in any step of the molding process, including heating and cooling. In some instances, the resistance heating module 70 (e.g., 70a and / or 70b) may include a tungsten filament embedded in aluminum nitride ceramic. Molds 15 and 16 may each include one or more cavities 55 for molding one or more glass elements. Figure 5 shows an example of molds 15 and 16 with two cavities 55 for molding two glass elements. Molds 15 and 16 may each be made of any material, but are typically made of high-temperature compatible materials such as tungsten carbide or silicon carbide. The illustration in Figure 5 shows two guide pins 75 (e.g., 75a and 75b) which can be used to align the top mold 15 with the bottom mold 16 (and examples of which are described below with reference to Figures 8A and 8B). In the example shown in Figure 5, the glass material 40 is spherical and is placed on the bottom mold 16 at the location of each cavity 55. Temperature monitoring devices 65 are positioned to contact molds 15 and 16 to monitor the temperature gradient of the glass material 40. In the example shown in Figure 5, two temperature monitoring devices 65a and 65b are in contact with the top mold 15, and two temperature monitoring devices 65c and 65d are in contact with the bottom mold 16. In some instances, multiple resistance heating elements 80 allow for control of the thermal gradient across the glass material 40 during heating (and / or cooling). Molds 15 and 16 may each include a plurality of mold pins 17 located within mold plate 18. Figure 5 shows an example of a top mold 15 including two mold pins 17a and 17b placed in mold plate 18a, and a bottom mold 16 including two mold pins 17c and 17d placed in mold plate 18b. In the example of Figure 5, the glass material 40 is spherical and is placed on the bottom mold 16 at the location of each mold pin 17c and 17d. The temperature of the glass material 40 can be monitored by an infrared camera 82, which converts the infrared radiation of the glass material 40 into temperature. In some examples, the infrared camera 82 can be used by a controller 90 to control the temperature on the indoor side. In some examples, the infrared camera can be a Lepton camera manufactured by Flir. In some instances, molds 15 and 16 may each be a single monolithic material piece. Figures 6 and 7 illustrate examples where molds 15 and 16 are each a single monolithic material piece. In the example shown in Figure 6, the glass material 40 is a single piece of glass material 40, and molds 15 and 16 are each a single monolithic material piece including multiple cavities 55 for molding multiple glass elements. In the example shown in Figure 7, the glass material 40 is a single cylindrical disk of glass material 40, and molds 15 and 16 are each a single monolithic material piece including multiple cavities 55 for molding different portions of the single cylindrical disk of glass material 40. In both Figures 6 and 7, in some instances, multiple resistance heating elements 80 allow control of the thermal gradient across the glass material 40 during heating (and / or cooling). As described above, the molding apparatus 1 may include guide pins 75 (e.g., 75a and 75b) to align the top mold 15 with the bottom mold 16. The guide pins 75 may be positioned such that the surface of the guide pins 75 is aligned with the surface of the top mold 15, and then the guide pins 75 may be actuated by positioning devices 77 (e.g., 77a and 77b) to extend the guide pins 75 out of the top mold 15 so that they can be used to align holes in the top mold 15 with holes in the bottom mold 16. Figures 8A and 8B illustrate examples of molds, glass elements, and alignment pins that can be used for this purpose. Figure 8A shows the guide pins 75 retracted in the heated position such that the pins 75 do not block radiant light from the lamp. In some instances, blocking can cause a thermal gradient. The pins 75 are located within the top mold 15. The bottom mold 16 includes driven pins 79 (e.g., 79a and 79b) for filling holes in the bottom mold 16 during heating. The driven pin 79 is preloaded relative to the bottom mold 16 by springs 78 (e.g., 78a and 78b). Figure 8B shows guide pins 75 extending to align the top mold 15 and the bottom mold 16. Positioning device 77 is actuated during the molding process, allowing controller 90 to set a retracted position during heating (see Figure 8A) and an extended position during pressing (see Figure 8B). The driven pin 79 is displaced by guide pins 75 during pressing. Modifications, additions, or omissions may be made to the molding apparatus 1 without departing from the scope of this disclosure. Additionally, any suitable logic may perform (and / or control) the functions of the molding apparatus 1 and the components and / or devices within it. Furthermore, one or more components of the molding apparatus 1 may be separated, combined, and / or eliminated. This specification has been prepared with reference to various non-limiting and non-exhaustive examples. However, those skilled in the art will recognize that various substitutions, modifications, or combinations can be made to any of the disclosed examples (or portions thereof) within the scope of this specification. Therefore, it is contemplated and understood that this specification supports additional examples not expressly set forth herein. Such examples may be obtained, for example, by combining, modifying, or recombining any of the disclosed steps, components, elements, features, aspects, characteristics, limitations, etc., of the various non-limiting and non-exhaustive examples described herein. 10: Overall Frame 15: Mold 16: Bottom Mold 17: Mold Pin 17a: Mold Pin 17b: Mold Pin 17c: Mold Pin 17d: Mold Pin 18: Mold Plate 18a: Mold Plate 18b: Mold Plate 20: Slide 21: Servo Motor 22: Bearing Mechanism 23: Screw Jack 30: Anvil 32: Load Detection Device 34: Processing Chamber 40: Glass Material 40a: Spherical Glass Material 40b: Spherical Glass Material 50: Flexible Corrugated Pipe 55: Cavity 60: Radiant Heating Element 60a-60d: Radiant Heating Element 61: Radiant Heating Module 65: Temperature Temperature monitoring device 65a: Temperature monitoring device 65b: Temperature monitoring device 65c: Temperature monitoring device 65d: Temperature monitoring device 70: Resistance heating module 70a: Resistance heating module 70b: Resistance heating module 72: Cooling plate 72a: Cooling plate 72b: Cooling plate 75: Guide pin 75a, 75b: Guide pin 77: Positioning device 77a, 77b: Positioning device 78: Spring 78a, 78b: Spring 79: Follower pin 79a, 79b: Follower pin 80: Resistance heating element 80a-80f: Resistance heating element 82: Infrared camera 90: Controller To gain a more complete understanding of this disclosure and its features and advantages, the following description is now taken in conjunction with the accompanying drawings, in which: [Figure 1] is a curve of the glass element molding cycle using four steps: (1) heating, (2) pressing, (3) gradual cooling, and (4) rapid cooling. [Figure 2] illustrates an exemplary molding apparatus for molding precision glass components using a combination of radiant heating module, upper resistance heating module and lower resistance heating module. [Figure 3] shows an exemplary radiant heating module of the molding apparatus of Figure 2, wherein the radiant heating module can be removed from the heating chamber as a single item. [Figure 4] shows an exemplary resistance heating module of the molding apparatus of Figure 2, wherein the resistance heating module includes three resistance heating elements, each of which can be controlled independently. [Figure 5] shows an example of a mold, a radiant heating element, a resistance heating element, an infrared camera device, and other components that can be used in the molding apparatus of Figure 2, wherein the top mold and the bottom mold each include a plurality of mold pins arranged in a mold plate, and the glass material is a plurality of spheres. [Figure 6] shows another example of a mold, a radiant heating element, a resistance heating element, and other components that can be used in the molding apparatus of Figure 2, wherein the top mold and the bottom mold are each a single monolithic material piece, and the glass material is a plurality of spheres. [Figure 7] shows another example of a mold, a radiant heating element, a resistance heating element, and other components that can be used in the molding apparatus of Figure 2, wherein the top mold and the bottom mold are each a single integral piece of material, and the glass material is a single disk or wafer. [Figure 8A] shows an example of a mold, glass element, and guide pin that can be used in the molding apparatus of Figure 2, wherein the guide pin is in the retracted position for heating. [Figure 8B] shows an example of a mold, glass element, and guide pin that can be used in the molding apparatus of Figure 2, wherein the guide pin extends to align with the top mold and the bottom mold. 10: Overall Framework 15: Mold 16: Bottom mold 20: Slide Pillow 21: Servo Motor 22: Bearing Mechanism 23: Spiral Jack 30: Anvil 32: Load detection device 34: Processing Room 40a: Spherical glass material 40b: Spherical glass material 50: Flexible Corrugated Pipe 60a-60d: Radiant heating element 65: Temperature monitoring device 70a: Resistance heating module 70b: Resistance heating module 72a: Cooling plate 72b: Cooling plate 90: Controller

Claims

1. A molding apparatus for molding one or more glass elements by heating one or more glass materials and pressing the one or more glass materials between an upper mold and a lower mold, the molding apparatus comprising: A radiant heating module that includes multiple radiant heating elements; The system includes an upper resistance heating module comprising a first plurality of independently controlled resistance heating elements; and a lower resistance heating module comprising a second plurality of independently controlled resistance heating elements; and a controller, wherein the controller is configured to: control the operation of at least one of the first plurality of independently controlled resistance heating elements or the second plurality of independently controlled resistance heating elements to heat the one or more glass materials during cooling of the one or more glass elements; and control an inert gas flow to the one or more glass materials during cooling of the one or more glass elements such that the heating of the one or more glass materials by at least one of the first plurality of independently controlled resistance heating elements or the second plurality of independently controlled resistance heating elements and the inert gas flow form a selected temperature distribution in the one or more glass materials.

2. The molding apparatus according to claim 1, further comprising an upper mold and a lower mold, wherein each of the upper mold and the lower mold is a single integral material part.

3. The molding apparatus according to claim 1, further comprising an upper mold and a lower mold, wherein each of the upper mold and the lower mold includes a plurality of mold pins arranged in a mold plate.

4. The molding apparatus according to claim 1, wherein each of the upper resistance heating module and the lower resistance heating module is in contact with a plate having one or more channels for inert airflow.

5. The molding apparatus according to claim 1, further comprising: An upper mold; and a slide block for displacing the upper mold relative to the lower mold, wherein the slide block includes a screw, a motor, and a bearing assembly.

6. The molding apparatus according to claim 1, further comprising a sealed processing chamber for molding the one or more glass elements.

7. The molding apparatus according to claim 1, wherein the one or more glass materials comprise one or more spherical glass materials.

8. The molding apparatus according to claim 1, wherein the one or more glass materials comprise a single cylindrical disk of glass material.

9. The molding apparatus according to claim 1, wherein the plurality of radiant heating elements comprises a plurality of independently controlled radiant heating elements.

10. A molding apparatus for molding precision glass elements by heating one or more glass materials and pressing the one or more glass materials between an upper mold comprising one or more molds and a lower mold comprising one or more molds to form one or more glass elements, the upper mold and the lower mold being aligned by guide pins, wherein the guide pins are connected to positioning devices such that the surface of the guide pin is aligned with the surface of the mold and then extends out of the mold, thereby enabling the guide pins to be used to align holes in the upper mold with holes in the lower mold.

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