Conveyors – chutes – skids – guides – and ways – Rollerways – Submerging and rising
Reexamination Certificate
2000-04-14
2001-12-25
Bidwell, James R. (Department: 3651)
Conveyors, chutes, skids, guides, and ways
Rollerways
Submerging and rising
C193S037000
Reexamination Certificate
active
06332525
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to a vacuum chamber for flat substrates in which transport rollers provided for transporting the substrates are located above the bottom of the vacuum chamber and held at their two ends by one bearing each.
2. Discussion of the Prior Art
Vacuum chambers of this kind are being used, in particular, as lock chambers for flat glass coating systems, and are in general already known. In order to achieve the greatest possible process speed with installations of this kind, it is necessary to evacuate the vacuum chamber as quickly as possible. This can be achieved by using the smallest possible volume for the vacuum chamber and by using the greatest possible power for the pump which is used to evacuate the vacuum chamber.
At the present time, a drawn-in chamber cover, displacement elements between the transport rollers, and vacuum-tight transport rollers are known as means to reduce the chamber volume. It is possible by these means to reduce the chamber volume significantly. An additional, important reduction in the chamber volume would be possible if transport rollers with a smaller diameter could be used. But this design change is hindered by the fact that the transport rollers can only be supported by bearings at their ends and often must have a length of several meters. But, since they can only have a limited flexure to ensure a safe and direction-stable transport of the flat substrate, the large, free length necessarily requires a relatively large transport roller diameter, often more than 10 cm in today's equipment. An additional transport roller bearing in the middle of the vacuum chamber is not possible with the means available at the present time, because the chamber bottom acts like a membrane and moves by more than 1 mm during evacuation and ventilation.
SUMMARY OF THE INVENTION
The invention is based on the problem of designing a vacuum chamber of the kind described above such that it has the smallest possible chamber volume for a predetermined substrate size.
This problem is solved according to this invention in that the transport rollers are additionally supported between the outer bearings by at least one middle bearing which is located on a plunger which is guided hermetically through an opening of the bottom of the vacuum chamber and is braced against a support underneath the bottom.
According to this invention, due to this additional support of the transport rollers between their outer bearings, it is possible to reduce the diameter of the transport rollers by about half without causing undesirable severe flexure. Since the middle bearing is not braced on the bottom of the vacuum chamber by the supporting plunger, but rather braced outside of the vacuum chamber, for example, against the foundation, the movement of the bottom of the chamber does not lead to a shift of the middle bearing, so that the bottom can be designed as before, and expensive bottom reinforcements can now be omitted.
The sealing of the middle bearing plunger against the bottom of the vacuum chamber could be handled by standard gaskets. The sealing is entirely safe from wear and can be created at low cost if, according to a favorable refinement of the invention, the plunger is connected to the bottom of the vacuum chamber by means of a bellows.
A particularly effective gas seal can be attained when the bellows consists of spring steel.
It is a particularly simple and favorable design when the middle bearing is designed as a support bearing, and has two support rollers resting against the underside of the particular transport roller.
For production reasons, it may be advantageous to supply two mutually aligned transport rollers instead of transport rollers extending across the entire width of the vacuum chamber. This can be achieved by this invention, when the transport rollers are divided between the outer bearings in the vicinity of the middle bearing. In this case, the middle bearing can have two support rings side-by-side on the plunger, into which a transport roller lug will extend.
REFERENCES:
patent: 3807546 (1974-04-01), Lananalo
patent: 4300937 (1981-11-01), Rhonehouse
patent: 5160940 (1992-11-01), Lassou et al.
patent: 32 23 970 A1 (1988-01-01), None
patent: 254 398 B5 (1988-02-01), None
patent: 43 03 462 C2 (1994-03-01), None
Gebele Thomas
Rodling Gert
Bidwell James R.
Leybold Systems GmbH
Smith , Gambrell & Russell, LLP
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