Package making – Methods – Gas filling and/or evacuating and closing
Reexamination Certificate
2001-11-06
2003-09-23
Gerrity, Stephen F. (Department: 3721)
Package making
Methods
Gas filling and/or evacuating and closing
C052S171300, C053S079000, C141S005000, C156S109000, C428S034000
Reexamination Certificate
active
06622456
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for insulating glass windows, more particularly, to a method of filling the inner space of sealed insulating glass units with inert gas or mixture of gases.
Sealed insulating glass units typically consist of two parallel spaced apart lites of glass which are sealed along at their periphery such that the space between the lites, or the inner space, is completely enclosed. The inner space is typically filled with air. The transfer of energy through an insulating glass unit of this typical construction is reduced, due to the inclusion of the insulating layer of air in the inner space, as compared to a single lite of glass. The energy transfer may be further reduced by increasing the separation between the lites to increase the insulating blanket of air. There is a limit to the maximum separation beyond which convection within the air between the lites can increase energy transfer. The energy transfer may be further reduced by adding more layers of insulation in the form of additional inner spaces and enclosing glass lites. For example three parallel spaced apart lites of glass separated by two inner spaces and sealed at their periphery. In this manner the separation of the lites is kept below the maximum limit imposed by convection effects in the airspace, yet the overall energy transfer can be further reduced. If further reduction in energy transfer is desired then additional inner spaces can be added.
The energy transfer of sealed insulating glass units may be reduced by substituting the air in a sealed insulated glass window for a denser, lower conductivity gas. Suitable gases should be colorless, non-toxic, non-corrosive, non-flammable, unaffected by exposure to ultraviolet radiation, and denser than air, and of lower conductivity than air. Argon, krypton, xenon, and sulfur hexaflouride are examples of gases which are commonly substituted for air in insulating glass windows to reduce energy transfer.
A great variety of techniques have been developed for filling the inner space of insulating glass units with gas. Typically this is an exchange of gas, where the insulating glass unit originally contains air, present during the construction of the insulating glass units, which must be displaced or exchanged for the fill gas. It is desirable to achieve a high concentration of the fill gas in order to realize the maximum benefit of minimizing the energy transfer of the gas filled insulating glass unit. In practice the exchange of fill gas for air cannot be achieved without some mixing of the gases which results in a final concentration of the fill gas of less than 100%.
Several of the gas filling techniques make use of fact that all of the fill gases mentioned above are denser than air. One conventional technique involves the use of two probes. The first probe is used to feed the gas into the inner space and the second probe is used for exhausting air. The probes are inserted through bores provided in the sealing means at the periphery of the glass units. The bores in the sealing means must be sealed again after the gas exchange has been completed. The insulating glass unit is oriented such that the parallel spaced apart lites are vertical. The gas feeding probe is located at the bottom of the insulating glass unit and the exhausting probe is located near the top of the unit. This method is referred to here as the side filling method. The gas is introduced slowly into the inner space to minimize turbulent flow and to minimize mixing with the air in the inner space. The denser fill gas forces the less dense air towards the top of the airspace where it is exhausted at the exhaust probe. Some mixing with air will always occur and as such the volume of fill gas introduced is typically 1.75 to 2.00 times greater that the volume of the inner space. This over-filling is done in an attempt to also displace as much as possible of the fill gas air mixture such that a final concentration of greater than 90% fill gas is achieved.
In general a significant reduction in energy transfer may be realized for fill gas concentrations between 75% and 100%. However, the sealing means employed for insulating glass units typically have some low permeability which allows the fill gas to diffuse out of the inner space, due to the concentration gradient between the inner space and the ambient atmosphere, very slowly in service. To maintain the desired reduced level of energy transfer over the service life of the insulating glass unit the initial fill gas concentration is desired to be greater than 90% and is most desired to be greater than 95%. Depending on a number of factors associated with the overall design of the insulating glass unit and the edge sealing means the loss by diffusion of the fill gas may be limited such that the concentration of fill gas in the inner space may be maintained above 75% for 10-20 years or longer.
Another method, referred to here as the top filling method, involves orienting the insulating glass unit in the vertical position. Two bores are made in the top of the unit near opposite edges of the unit. A rigid or flexible tube for gas filling is inserted into the inner space and extends to the bottom of the unit along one side. The gas filling tube has multiple holes near the bottom of its length in order to minimize turbulent flow during filling. The tube is inserted into the inner space within two inches of the bottom of the unit. Fill gases, which are again denser than air, are charged through the tube to the bottom of the inner space. The fill gas displaces the air in a manner as described in the side filling method above. The volume of fill gas charged to the inner space is 1.75-2.00 times the volume of the inner space in order to also exhaust the volume of gas which has become partially mixed with air and achieve fill gas concentrations above 90%. The bores in the sealing means must be sealed again after the gas exchange has been completed.
The volume of fill gas to be charged in both of these methods may be calculated based on the size of the insulated glass units and adjusted for the amount of over-filling found through experience to give the typical desired final fill gas concentration. The fill volume is typically regulated by opening a valve in the fill gas supply line for a specified period of time while the gas is charged through a flow regulator set to a predetermined flow rate. Alternatively an oxygen analyzer may be attached to the exhaust port to monitor the oxygen content of the exhaust. The oxygen content is assumed to be proportional to the concentration of air in the mixture of fill gas and air in the exhaust from the inner space. The fill gas supply valve is turned off when the oxygen content in the exhaust falls below a level predetermined to provide the desired fill gas concentration. Using the oxygen analyzer means the size of the inner space to be filled need not be known and the volume of fill gas need not be calculated. Filling continues until the oxygen content, which is inversely proportional to the fill gas concentration, is less than the desired specification.
The maximum flow rate of fill gas into the insulated glass unit in both the side filling and the top filling methods is limited by 1) the desire to minimize turbulent flow, thereby minimizing mixing with the air in the unit; and by 2) the area of the of the exhaust bore or bores which will determine the back pressure within the inner space which if too high may damage the glass lites or the edge seal by forcing the glass lites apart. In general, for both the side filling and top filling method, a slow fill rate can achieve a high concentration of fill gas while limiting the amount of over-fill required. Faster filling rates can reduce the time required but will require higher over-fill rates to achieve the same final fill gas concentration. Even faster filling rates can cause so much turbulence and mixing of the fill gas with air in the inner space that desired fill gas concentrations cannot be achieved without using impr
Gerrity Stephen F.
Renner , Otto, Boisselle & Sklar, LLP
TruSeal Telenologies, Inc.
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