Insulating glass fibers are currently produced by internal centrifuging in a fiberizer, i.e., by introducing a thin stream of molten glass into a centrifuger, also known as a fiber spinner, rotating at high speed and having a large number of orifices on its sidewall. Under the effect of centrifugal force, the glass is projected through these orifices in the form of filaments. In addition to the centrifugal force, the fibers are often also drawn by a high temperature and velocity gaseous current, which is emitted tangentially to the perforated wall of the spinner by an annular burner. This gaseous current maintains the spinner sidewall at a temperature suitable for centrifuging the glass and also maintains the primary fibers emanating from the spinner in a plastic state to enable further attenuation into secondary fibers. Often, within the fiberizer, there is also an annular blower proximate to the sidewall of the spinner, which emits relatively cool air and serves to further attenuate the fibers.
Good fiber quality depends on several factors, e.g., the proper temperature in and around the spinner, the rotational speed of the spinner, the viscosity of the molten glass, and the air pressure around the spinner. These factors, in turn, depend on the proper operation of the spinner, the annular burner, and the blower. Thus, the fiber forming process is regulated by controlling the various process variables, such as the temperature and volume of the gaseous current from the annular burner, the temperature of air from the blower, the temperature and viscosity of the molten glass, and the rotation rate of the spinner, for example.
With respect to the temperature within and around the fiberizer, such temperature is sensitive to a large number of factors including, for example, the operation of the annular burner and the hot attenuating gases which are emitted from the burner to aid in drawing the fibers, the temperature of the glass, the flow rate of the glass, the relatively hot atmosphere prevailing around the spinner, the relatively intense cooling owing to the relatively high rotational velocity, the temperature of the air from the blower, and the spinner itself which may become deformed after a given amount of operating time and may consequently react differently to the effect of heating by the burners. Due to these various factors, there may be a fairly wide temperature gradient around the spinner to which the fibers are exposed during their formation.
Unsatisfactory temperatures may cause large-scale disturbance of the fiber-drawing process. If the spinner, for example, is too cold, devitrification may begin which renders the glass unsuitable for fiber-drawing. A spinner that is too hot and is at the thermal fracture limit may lead to the formation of undesirable non-fibered portions or extremely fine fibers due to the glass being too highly fluid.
The ability to accurately monitor and access the operating conditions, such as the temperature, in and around the spinner is thus crucial to regulating such operating conditions so that desirable fiber quality can be obtained or maintained. Values that fluctuate or deviate from the desirable values of pressure and temperature, for example, for the gaseous blast, diminish the quality of the fibers, produce waste and reduce the life of the spinner.
Certain prior art devices have been developed to monitor the temperature or other conditions of a fiberizer. For example, attempts have been made to position thermocouples or other process monitoring devices on the spinner or at fixed positions within the annular burner or in the path of the attenuating gases emerging from the annular burner. The fixed position of these devices only allows for a measurement at a specific location or measurements within a narrow range of locations. Generally, these devices fail to provide a broad picture of the processing conditions in the fiberizer.
There is a need for a means for more accurately and completely monitoring the operating conditions in fiberizers for use in determining and regulating the properties of fibers being produced, such as the diameter, length or the like, of such fibers. More particularly, there is a need for facilitating the measurement of different operating conditions, such as the gas temperature, gas pressure, spinner rotational speed, etc., the measured values being used for assessing, monitoring and regulating the operation of the fiberizer. Such a means may also allow for the attainment of an extended view of the environment that fibers face as they are formed at the spinner side wall, attenuated into primary and secondary fiber form, and distributed to a collection means either as chopped fibers or elongated filament strands.