Lehr roll cleaning apparatus

Details Lehr roll cleaning apparatus Lehr roll cleaning apparatus

1999-01-25

2001-01-09

Vincent, Sean (Department: 1731)

Glass manufacturing

With positive cleaning means for apparatus

C065S194000, C015S052000, C015S354000, C198S495000, C198S496000

Reexamination Certificate

active

06170293

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to the in-situ maintenance of materials handling equipment and, in particular, to apparatus for cleaning lehr rolls of the type used to carry float glass.
BACKGROUND OF THE INVENTION
Most flat glass is today manufactured by the float production method, developed in England in the late
1950
s. The float process has virtually eliminated production methods, such as sheet or plate glass manufacture. Float glass is made in a float tank, which once placed into operation, is operational 24 hours per day until it is refurbished, which can occur up to a decade later.
The manufacturing process can be broken down into five main stages. The first is the batching of raw materials. In the case of soda lime glass, the main ingredients are silica sand, calcium oxide, soda and magnesium. The components are weighed and mixed into batches to which recycled glass (cullet) is added.
Next the raw materials are loaded into a furnace where they become molten at a temperature of approximately 1550° C. The molten glass “floated” onto a bath of molten tin at a temperature of about 1000° C., forming a large ribbon. The glass is highly viscous and the tin is very fluid. As such, the floating glass does not mix with the tin and the contact surface between the two materials is perfectly flat.
On leaving the bath of molten tin, the glass, now at a temperature of about 600° C., has sufficiently cooled to pass into an annealing chamber called a lehr. Within the lehr, the cooling rate of the ribbon is controlled to obtain annealed material free of internal mechanical stresses, enabling the ribbon to be cut and worked. After cooling, the glass undergoes quality checks prior to being cut into sheets, which are stacked or stored for transport. A conventional apparatus for producing float glass is illustrated and described in U.S. Pat. No. 3,083,551.
The newly formed ribbon of glass is advanced through the annealing lehr on driven conveyor rolls which draw the glass ribbon along the molten metal bath. The glass, which is in a plastic condition as it enters the lehr, is subject to a defect known in the art as “roll print.” Roll print is characterized by distortions or imperfections such as random surface rub marks, fissures, and, in some cases, fractures.
Roll print is often caused by the mechanical contact of the glass ribbon with the lehr conveyor rolls. In time, the rolls tend to accumulate uneven and crusty surface deposits which imprint on the soft undersurface of the newly formed glass ribbon. It is believed that such deposits are formed on the rollers through the collection of oxides, as well as dross and other foreign matter adhering to the soft undersurface of the glass ribbon.
Attempts have been made in the past to remove these crusty deposits from the surfaces of such conveyor rolls in situ. U.S. Pat. No. 3,337,320 teaches a method of removing deposits from the surfaces of lehr rolls by steam. U.S. Pat. No. 3,481,727 discloses the use of a reciprocating abrasive tool for abrading and brushing the crusty deposits from the surfaces of conveyor rolls.
U.S. Pat. No. 4,042,364, describes a system to remove impacted deposits from the surfaces of moderately encrusted conveyor rolls using a floor-mounted mechanism. However, the apparatus is complex and of heavy construction to provide the brushing forces required to remove tenacious deposits from heavily encrusted conveyor rolls. Additionally, since the space between the lehr rolls and the floor is of a very limited height, use of such an approach is not feasible in all circumstances.
U.S. Pat. No. 4,208,754 addresses this problem by providing an off-line lehr conveyor roll cleaning apparatus. The system comprises a mobile lower main unit having a pair of rotating roll supporting stations, one at either of its ends, and an upper removable unit which includes a longitudinally reciprocal, rotary brushing wheel. The lower main unit may include heater devices for heating the roll while it is being cleaned in order to maintain its temperature so that the surface encrustations can better be removed and/or it can be reinstalled in an operating lehr immediately after being cleaned without the usual preheating step.
Although removal of the conveyor roll may ease maintenance of the roll itself, roll removal is not recommended in most cases. Due to its maturity, the manufacture of float glass is a highly competitive process, such that down time must be monitored carefully to maximize throughput and maintain acceptable levels of profitability. Removal of the rollers, though conducive to a high level of surface cleaning, often leads to excessive disruption. The still remains, therefore, for a simple but effective in situ conveyor roll cleaning method and apparatus.
SUMMARY OF THE INVENTION
The subject invention improves upon the prior art by providing in situ roll cleaning apparatus supported within the space between adjacent rolls, thereby consuming little volume in the lehr. More particularly, with respect to a lehr having plurality of parallel, spaced-apart cylindrical rolls used to support a sheet of float glass, roll cleaning apparatus according to the invention includes a carriage supported within the space between first and second adjacent rolls, the carriage having a first set of elements contacting the surface of the first roll and a second set of elements contacting the surface of the second roll, such that the carriage is movable back and forth along a path parallel to the rolls. The invention further includes a mechanism disposed on the carriage for cleaning at least one of the first and second rolls as the carriage moves along the path and in between the adjacent rolls.
The roll-contacting elements, which may take the form of cylindrical or spherical rollers, are preferably supported on one or more pivoting arms, with the apparatus further including means such as a spring for biasing the arms toward the carriage. This forces the carriage away from the roll adjacent the one being cleaned, causing the elements contacting the roll being cleaned to bear against the roll being cleaned. The intimate and controlled contact of the elements against the roll being cleaned precisely positions those portions of the carriage containing the roll-cleaning mechanism with respect to the roll being cleaned, enabling very accurate alignment of the cleaning mechanism relative to the surface of the roll.
The precise positioning of the cleaning mechanism relative to the surface of the roll being cleaned allows the use of mechanisms requiring precise positioning to maintain the roll without scoring, including scrapers or “doctor” blades, rotating cutters or wire wheels, and abrasive particle sprayers. The preferred embodiment also features a fine-adjustment mechanism for further controlling the distance of cleaning device relative to the surface of the roll being cleaned, having forced the elements against the roll being cleaned. In particular, the shaft of the wire wheel extends through a rotatable plate having an eccentric central aperture, such that rotation of the plate causes the wire wheel to move relative to the roll being cleaned.
The preferred apparatus also includes a dust cover disposed over the carriage, and air-inlet and air-output ports formed through the cover, to provide a recirculating air path to cool the inner working of the carriage and remove particulates generated through roll cleaning. The motive power source used to operate the cleaning mechanism is preferably disposed externally of the carriage, with a flexible cable or linkable drive segments being employed to couple the motive power source to the mechanism as the carriage is positioned at different points along its path. The drive cable or shaft may be surrounded by an outer sheath, in which case additional space within the sheath may be used as one of the air-inlet or -outlet paths. In the preferred embodiment, compressed air is forced through the space within the sheath to cool components within the sheath or shafting.


REFERENCES:
patent: 3083551 (

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