METHOD AND APPARATUS FOR THE PRODUCTION OF GLASS TUBES WITH CLOSED ENDS

Abstract

A method for the manufacture of a glass tube with closed ends includes: providing a glass tube with open ends including a first open end and a second open end; closing the first open end of the glass tube while introducing a gas into the glass tube through the second open end; opening a ventilation hole in a wall of the glass tube near one of the open ends; and closing the second open end.

Claims

1. A method for the manufacture of a glass tube with closed ends, comprising: providing a glass tube with open ends comprising a first open end and a second open end; closing the first open end of the glass tube while introducing a gas into the glass tube through the second open end; opening a ventilation hole in a wall of the glass tube near one of the open ends; and closing the second open end.

2. The method of claim 1, wherein the gas introduced has a relative humidity of 5%-20%.

3. The method of claim 1, wherein the gas is introduced by a distribution chamber located near the second open end.

4. The method of claim 3, wherein the distribution chamber is located axially with respect to the glass tube.

5. The method of claim 3, wherein the distribution chamber is formed by a gas exit and a three-sided open chamber enclosing at least part of the second open end.

6. The method of claim 1, wherein the gas is introduced by a nozzle located near the second open end.

7. The method of claim 1, wherein the gas is air.

8. A closed glass tube manufactured according to the method of claim 1.

9. An apparatus for closing a glass tube, comprising: a glass tube transport for transporting the glass tube; a first close tool; a ventilation hole tool; a second close tool; and an air supply positioned opposite from the first close tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of (an) embodiment(s) of the invention taken in conjunction with the accompanying drawing(s), wherein:

[0011] FIGS. 1A-1E show schematically method steps according to the invention;

[0012] FIG. 2 shows an example of an embodiment of a gas supply; and

[0013] FIG. 3 shows a further example of an embodiment of a gas supply.

[0014] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification(s) set out herein illustrate(s) (one) embodiment(s) of the invention (, in one form,) and such exemplification(s) (is) (are) not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The process of manufacturing a glass tube according to an embodiment provided according to the present invention will be shown in reference to FIGS. 1A-E. FIG. 1A shows a glass tube 10, with a length of L, having a first end 30 and a second end 20 at the distal ends of the tube 10. The glass tube 10 has a circumferential wall and encloses an inner space. In this example the length L is around 1.5 m, but other lengths are also possible. Lengths of 0.5 to 2.0 m may be preferable as having the advantage of providing a useful length for transport as well as for further processing.

[0016] The goal is to close both ends 20, 30 of the tube 10 and provide a ventilation hole 32 in the wall of the glass tube 10, where the ventilation hole is in the vicinity of one of the ends 20, 30.

[0017] In a first step, shown in FIG. 1B, the first end 30 is closed using a closing tool 50. During the closing of the first end, gas F is blown into the second end 20 of the glass tube by a gas supply 60. The gas F is blown into the tube 10 in the direction towards the second end 20 in the axial direction of the tube 10, so that the gas F enters the inner space of the tube 10, and optionally fills the inner space of the tube 10. In a variant of this step, the start of blowing of the gas F into the second end 20 is started before the start of the closing of the first end 30. The gas supply 60 is stopped once the first end 30 is fully closed. The now closed first end is indicated as 31 in the FIG. 1B. In a variant of this step, the gas supply can be stopped just before the first end is fully closed.

[0018] In the second step, shown in FIG. 1C, the ventilation hole 32 is made into the wall of the glass tube near the second end 20 of the glass tube 10, by an opening tool 70. During this step, the gas supply 60 can be stopped. In an alternative variant, the gas supply 60 can be kept switched on, and stopped once the ventilation hole 32 has been formed or stopped during the formation of the ventilation hole 32.

[0019] In the third step, shown in FIG. 1D, the second end 20 of the glass tube 10 is closed, also using a closing tool 55, for example of the same type as closing tool 50 used for closing the first end 30 of the glass tube. The now closed second end of the tube 10 is indicated with 21. Optionally, the third step is done within a short period of time after finishing the second step. This short period of time can for example be 5 to 15 seconds.

[0020] After the third step, the result is a glass tube 10 with both ends 21, 31 closed, with a ventilation hole 32 provided near one of the ends 21, shown in FIG. 1E. By having provided gas F into the tube 10 as described above during the closing of the first end 30, the resulting closed tube 10 does not show internal contamination, also after a longer period of storage.

[0021] Methods and devices for closing ends of glass tubes as mentioned before as the use of a closing tool to close the end of the glass tube are known in the art, for example from U.S. Pat. No. 10,315,946. In general, the end to be closed is heated up (for example with a gas burner) so that the glass is softened, and the end is closed using either a forming tool to physically form the closure or let the now softened end fall in on itself due to gravity thereby closing off the end of the glass tube. During these kind of closing methods, the glass tubes can be rotated around their circumferential axis to improve the closing process. According to the invention, any suitable closing method or device can be used.

[0022] The ventilation hole is applied by the opening tool 70, such tools are known in the art, for using a spot burner. Optionally, the burner is located above the glass tube when opening the hole, but other positions are also usable. The location of the ventilation hole is optionally near the closed end of the glass tube, as the section of the tube between the ventilation hole and the closest closed end of the glass tube can typically not be further processed.

[0023] The gas F used is optionally a non-reactive gas, that does not interfere with the closing process or interfere with the surface of the glass tube. One example is air, with a low relative humidity of 5%-20% at 20 C. room temperature. In absolute humidity terms, the air is optionally between 0.05 to 5 g/m3. Other examples would be nitrogen gas, carbon dioxide gas, or a mixture thereof, also with a low relative humidity (water vapor content). Other non-reactive engineering gases (like noble gasses like argon) can be used, optionally with a water content (i.e. humidity) within the range of 5%-20% at 20 C. room temperature. Gasses that are reactive in the sense that they bind with water can also be used, as the use of these also reduces the humidity of the gas. Blowing the gas into the glass tube during processing leads to a significant reduction or full elimination of internal contamination of the closed tube. Optionally, the gas is filtered to prevent unwanted particles to enter the glass tube to be closed. Gas filtration methods are known in the art, for example by a physical filter.

[0024] In FIG. 2, an example of an embodiment of a gas supply 601 provided according to the invention is shown. In this embodiment, the gas supply 601 is provided with an inlet 602 that is connected to a gas source 603, that provides the gas F under pressure. This can, for example, be done using a gas compressor. The gas source 603 can be provided with a gas pressure regulator that regulates the pressure of the gas to be supplied as well as an opening and closing mechanism that can open and close the gas source. Such gas sources are well known in the art. The gas source can also comprise a flow meter.

[0025] The inlet 602 is communicatively connected to an outlet 604 where the gas F leaves the gas supply 601 to enter the open end of the glass tube. In the embodiment shown in FIG. 2, the gas supply comprises a nozzle 605. The outlet 604 of the nozzle 605 is placed so that the gas F expelled from the outlet 604 of the nozzle 605 can enter the tube end 20 of the tube 10. Optionally, the nozzle 605 is lined up with the axial direction of the tube 10. The outlet 604 of the nozzle 605 is place at some distance from the tube end 20 to enable the gas F to freely enter the glass tube 10.

[0026] In the embodiment shown in FIG. 3, the gas supply 701 comprises an outlet 704 that expels the gas F into a distribution chamber 707. This distribution chamber 707 is optionally made as a cylindrical chamber with an open end 709 at the end facing away from the outlet 704, with the outlet 704 placed in or near the center of the chamber 707 at the closed end of the chamber. The open end 709 of the distribution chamber 707 is placed near or around the end 20 of the glass tube 10, so that the gas F leaving the outlet 704 and being gathered into the distribution chamber 707 can enter the glass tube 10 freely. Around the open end 709 of the distribution chamber 707 a circumferential shield 708 can be placed. The shield 708 extends during the supply of gas F to the glass tube 10 around the end section 20 of the tube 10. The shield 708 creates a chamber that retains the gas F in an overpressure situation (compared to the ambient air pressure) so that the ambient air is prevented from entering the glass tube 10, or at least the amount of ambient air entering is reduced. The circumference of the shield 708 is optionally larger in diameter than the open end 709 of the distribution chamber 707. The shield 708 does not need to be contiguous around the circumference and can be provided with additional openings to change gas flow to improve the flow of the gas F so that it easily enters the glass tube 10.

[0027] The invention can also be implemented by adding an air supply provided according to the invention to an existing closing apparatus. In that case, the air supply should be added to the existing apparatus so that the air supply lines up with the end of the tube at the point where the end is going to be closed.

[0028] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.