Pumps – Processes
Reexamination Certificate
2001-05-09
2003-07-22
Freay, Charles G. (Department: 3746)
Pumps
Processes
C417S439000, C417S440000, C417S435000
Reexamination Certificate
active
06595758
ABSTRACT:
BACKGROUND
The invention relates to a process for conveying damp gases by means of a conveyor device, which has at least one feed pump with an oscillating displacement piston in a delivery chamber. The invention also relates to a conveyor device, in particular for carrying out the process named at the beginning, with at least one feed pump with an oscillating displacement piston in a delivery chamber, and whose delivery chamber includes an intake with at least one suction valve and an outlet with at least one outlet valve, whereby at least one feed pump of the conveyor device has a ventilation device with a ventilation channel, that opens in an area of the delivery chamber and whereby a ventilation valve is connected intermediately in the ventilation channel, which can be activated as desired, independently of the stroke position of the piston.
From German patent publication DE 296 18 911 U1, it is known to provide a conveyor device of the previously mentioned type with a membrane pump, which conveyor device is, in particular, adapted for evacuation of an oven for the preparation of dentures or denture pieces. For trouble free running of this conveyor device to produce a vacuum, a ventilation valve is provided for the pump working chamber of the membrane pump of te conveyor device. This ventilation valve is connected behind the intake valve in the flow direction to the pump working chamber, so that the suction path of the membrane pump from the ventilation valve is free and the ventilation valve can have no influence on the flow through cross-section of the medium being pumped.
The ventilation valve for the conveyor device known from DE 296 18 911 U1 is intended alone to provide a low cost way, problem-free starting of the pump arrangement when a negative pressure exists in the suction line, and at the same time provide a high pumping performance with low costs. The conveyor device known from DE 296 18 911 U1, is however neither suitable for nor intended for use with damp gases, as required, for example in using an autoclave
Medical instruments and other medical items of daily use are sterilized in autoclaves, which have a sterilization chamber that can be sealed so that it is airtight. Thereafter, the instruments located in the sterilization chamber are first exposed, prior to the sterilization operation, to a so-called fractionated pre-vacuum in which an especially good air removal is achieved even from narrow-orifice instruments, by repeated evacuation of the air in exchange with the periodic inflow of steam. During the sterilization operation, the instruments are exposed in the sterilization chamber to hot water vapor under high pressure. In order to dry the instruments quickly and without residue after sterilization, a so-called post-vacuum is in turn subsequently generated in the sterilization chamber. This post-vacuum should shorten the drying time of the sterilized product and optimize the drying operation.
For the evacuation, the sterilization chamber of these previously known vapor sterilization devices is connected to the conveyor device, which has a vacuum pump. Due to the impingement of the vacuum pump with water vapor, only water ring pumps or membranes have been used until now. Because of the structural dimensions and the disadvantages of a water ring pump, only membrane pumps are possible in the smaller vapor sterilization devices provided, for example, for the doctor's practice.
In the use of customary membrane gas pumps, however, there is the danger that liquid droplets occurring when conveying damp gases can lead to sticking of the gas valves and thus to the interruption of the evacuation process. Moreover, pockets that can hardly be avoided when boring out the flow channels in the cover plate of the pump head can also lead to an accumulation of liquid, whereby additional evacuation is made even more difficult.
In order to achieve a vaporization of the water droplets and to ensure an operation of the prior-art conveyor device that is as free from disruption as possible, the pump heads, especially in the membrane pumps used in vapor sterilization devices, are heated up to approximately 100° C. However, the vaporization of the liquid contained in the conveyor gas is associated with a considerable increase in volume of the conveyed medium, which leads to an increase in the evacuation time. Furthermore, hot pump heads act negatively on the lifetime of the membranes, valves, bearings and other structural parts that are used. These negative effects are amplified further by the already high ambient temperature, which results in the housings of these types of vapor sterilization devices due to the generation of vapor.
Such heads are relatively expensive, because in addition to these heating cartridges, a control device must also be constantly used with a temperature sensor to regulate the temperature of vaporization, and because these heating cartridges require for the most part at least as much electric power as the drive motor of the associated conveyor pump.
The objective of the invention is thus to create a process and a device of the above-named type, with which a simple conveyance of damp gases, which is free from disruption, is possible, without it being associated with an increased use of electrical energy and an increased wear of the feed pump used.
The objective of the invention is achieved in the process of the named type, in particular, in that the delivery chamber of at least one feed pump is ventilated one or more times at intervals during the operation of the conveyor device, as required and independently of the stroke position of the piston oscillating in the delivery chamber.
From U.S. Pat. No. 2,812,893, a device is already known that is constructed as a combination of a suction pump and a compressor. The prior-art device operates as a suction pump during the descending stroke of the piston, while it functions as a compressor during the ascending stroke. Therefore, the piston opens during the descending stroke at the valve openings provided on the cylinder circumference, so that under atmospheric pressure from the outside, additional air flows into the piston-displacement space and can be compressed in the subsequent ascending stroke because the air that is sucked in via the intake valve might not be sufficient by itself for compression.
The prior-art device from U.S. Pat. No. 2,812,893 has compression spring-loaded intake and outlet valves which open briefly at a defined pressure differential. If the outlet valve of the prior-art device opens, for example, at a pressure in excess of 10 bar, then the air quantity that is compressed during the ascending stroke and is over 10 bar is expelled via the outlet valve. Then, in the upper dead space, only the air quantity that is below this pressure limit remains. Since this harmful air volume still has a gas pressure of 10 bar, it would normally press the piston in such a way downwards, that the prior-art device can not assume the function of a suction pump during the descending stroke. The prior-art device thus has a ventilation valve in its pump head which is opened using an activation bar arranged on the piston in the top dead center position. The activation of the ventilation valve used in the prior-art device is thus done cyclically and as a function of the stroke position of the piston.
SUMMARY
In contrast, in the process according to the invention, the delivery chamber of at least one feed pump is ventilated one time or more times at time intervals as required and independently of the stroke position of the piston. In this manner, the liquid droplets that might stay in the delivery chamber are blown out from the conveyor device. The ventilation of the delivery chamber can be done during the operation of the feed pump at one time or more times at time intervals, for example, after certain condensation times or at different pressure levels in a chamber to be evacuated using the conveyor device. Since in the process according to the invention, a fast and targeted pump drying is done, the moisture
Hauser Erwin
Riedlinger Heinz
Freay Charles G.
Gray Michael K.
KNF Neuberger GmbH
Volpe and Koenig P.C.
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