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AssigneeRisdon Corporation
InventorAndrew Tscheppe
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Water contamination of the oil in vacuum pumps of high vacuum systems is a major problem in maintaining efficient operation of those pumps. The problem is especially acute where a system includes an evacuated work chamber that must be repeatedly opened for loading products into and unloading them from that chamber where the ambient atmosphere has high humidity. The invention involves utilizing first stage mechanical vacuum pump means in conjunction with final stage high vacuum diffusion pump means, and a cryocoil with fast defrost capability located in the vacuum duct leading from the work chamber to the pumps, in combination with an auxiliary low capacity vacuum pump and a flip/flop valving arrangement which connects the discharge side of the diffusion pump selectively to the first stage mechanical pump or to the auxiliary pump. The flip/flop valving arrangement allows the auxiliary pump to maintain moderate vacuum condition in the diffusion pump during idling periods and also serves as a continuous scavenger of water vapor present in the system, particularly during cycles of defrosting the cryocoil. The invention insures that any water vapor in the system not exhausted by the main pumps to ambient atmosphere or trapped as frost by the cryocoil, is prevented from accumulating in and emulsifying with the oil of the main vacuum pumps. By means of the invention system, any residual water is collected in the sump of the auxiliary pump and is prevented through the provision of the flip/flop valving arrangement from revaporizing and backstreaming through the main pumps during their pump-down cycle. Periodic replacement of the low cost auxiliary pump oil removes the residual water trapped in that pump.
In processing work products in a high vacuum work chamber which is repeatedly opened and closed to atmosphere in loading said products into and unloading them from said chamber, wherein there are employed in conjunction with said chamber first stage and final stage vacuum pump means, a roughing vacuum duct and a shut-off valve therein communicating said first-stage pump with said chamber, and a high vacuum duct and shut-off valve therein communicating said final stage vacuum pump with said chamber, a foreline duct and shut-off valve therein interconnecting the exhaust side of said final stage pump with the vacuum side of said first stage pump, an auxiliary pump and auxiliary vacuum duct connecting said auxiliary pump into said foreline duct between said final-stage pump and foreline shut-off valve, the method of improving the recycle rate of vacuum chamber draw-down after loading said work products into said chamber and closing same to atmosphere which comprises
In the operation of high vacuum processing apparatus incorporating a work chamber adapted to be repeatedly opened to atmosphere for loading, processing and unloading products treated in the chamber, first stage and final stage vacuum pumps, a roughing duct and a roughing duct shut-off valve therein connecting said first stage vacuum pump to said chamber, and a high vacuum duct and a high vacuum duct shut-off valve therein connecting said final stage vacuum pump to said chamber, a foreline and foreline shut-off valve therein interconnecting the exhaust side of said final stage pump with said roughing duct between said roughing duct shut-off valve and said first stage pump, and an auxiliary vacuum pump, auxiliary duct and auxiliary duct shut-off valve therein connected to said foreline between said foreline shut-off valve and said final stage pump, the method which comprises,
In high vacuum processing apparatus incorporating a work chamber adapted to be repeatedly opened to atmosphere for loading, processing and unloading products treated in the chamber, first stage and final stage vacuum pumps, a roughing duct and a roughing duct shut-off valve therein connecting said first stage vacuum pump to said chamber, and a high vacuum duct and a high vacuum duct shut-off valve therein connecting said final stage vacuum pump to said chamber, a foreline duct and foreline shut-off valve therein interconnecting the exhaust side of said final stage pump to said roughing duct between said roughing duct shut-off valve and said first stage pump, and an auxiliary vacuum pump and auxiliary duct connected to said foreline between said foreline shut-off valve and said final stage pump, the improvement which comprises providing a shut-off valve in said auxiliary duct and control means operatively associated with said foreline and auxiliary duct shut-off valves, said control means adapted and arranged to close one of said foreline and auxiliary valves when the other is opened, and vice versa.
Dependencies are inferred from the claim text.