Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Reexamination Certificate
1995-11-03
2001-01-16
Hepperle, Stephen M. (Department: 3407)
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
C137S269000, C137S557000, C251S065000
Reexamination Certificate
active
06173729
ABSTRACT:
BACKGROUND OF THE INVENTION
A invention relates to a switch-over device, preferably usable for a gas insufflation device using liquid gas, having at least two inflow channels, each blockable by a valve and at least one outflow channel for alternate removal of a fluid medium from a plurality of containers, and having a switch-over piston movably mounted in a housing and comprising a base member which has at each end a valve closure member in the form of a body of rotation, this switch-over piston being driven by a pressure difference between the flulid media and connecting one of the inflow channels to the outflow channel in each of two switching positions, and with a working chamber which accommodates the switch-over piston, sealing elements being provided for closing off the inflow channels in a pressure-tight manner when the switch-over piston is in the correspondingly closed position and for dividing the working chamber into two portions sealed off from each other.
Switch-over devices for equipment are known which operate with a pressure medium which can be removed from a plurality of pressurised containers, for example a gas from gas bottles. The switch-over device provided ensures that a pressurised container which has been emptied, apart from a certain residue, is disconnected from the plant system and at the same time a full pressurised container is connected up without interrupting the operation of the plant system.
From German patent 29 18 791, a switch-over device is known with which it is possible to remove a pressurised liquid or gaseous medium from batteries of bottle cells or containers in alternating manner. The switch-over device comprises two valve-controlled inlet channels and one outlet channel. Switching the outlet channel from one inlet channel to the other is effected by the fluid medium using a switch-over piston which has a valve closure member at each of its two ends. The corresponding valve seatings are arranged in a chamber which accommodates the switch-over piston within the housing of the switch-over device and are constructed as bushings have a ring seal. The valve closure member is formed by a pin which engages in the correspondingly shaped recess in the bushing when the valve is shut. The end face of the switch-over piston is supported simultaneously on the bushing which forms the valve seating. The fluid medium which brings about the switch-over applies pressure, at the end where the valve is open, to the entire and face of the switching piston, whereas at the end where the valve is closed, only the end face of the valve closure member is subjected to the entry pressure. The chamber which accommodates the switch-over piston is connected, at both ends of the switch-over piston, with a pressure relief valve by means of which the corresponding chamber area can release its pressure into the output line of the switch-over device which supplies the consumer.
The solution described above has the major disadvantage that the desired method of operation is ensured only for a specific flow medium and for given pressure conditions for the switch-over. The use of the switch-over device for a different flow medium and different switch-over conditions requires a different construction both of the switch-over piston and of the housing of the switch-over device.
SUMMARY OF THE INVENTION
Starting from the deficiencies of the prior art an object aim of the invention is to provide a switch-over device of the kind described above which is of simplified construction and which can be adapted without any major constructional problems to different conditions of use, for example when a different fluid medium is to be used or to suit different switch-over conditions.
The above and other objects are accomplished in the context of a switch-over device of the type first described above wherein the switch-over piston and/or the working chamber is constructed so that at least one sealing element can be arranged selectively in different positions, the size and the areas of the switch-over piston which are acted upon by the fluid media and determine the switch-over point, being determined by the position of sealing element.
The invention includes the finding that the force which moves a switch-over piston at a given pressure is directly proportional to an area acted upon by the pressure and, in the case of a switch-over piston having portions of substantially cylindrical or frustoconical construction, the square of a change in diameter goes into the corresponding change in the effective cross-sectional area or circular outer surface area acted upon by a given pressure. Thus, relatively large changes in the effective surface area can be achieved in favourable manner with relatively small changes in diameter.
According to the preferred embodiment of the invention, in a switch-over device having two valve controlled inflow channels and one outflow channel there is provided a switch-over piston having a substantially cylindrical base member at the ends of which are provided, as rotational members, valve closure members constructed to decrease constantly in diameter in the axial direction. The switch-over piston is axially movably mounted within a housing with a suitable mounting of the base member in a working chamber and, as it assumes each end position, it leaves one inflow channel or the other. The particular end position of the switch-over piston is determined by the difference in the pressures in the containers connected to the switch-over device, which contain the particular fluid medium.
The size of the pressure difference at which the switch-over piston moves axially to leave one of the inflow channels and thereby establish a fluidic connection between the other inflow channel and the working chamber, can be adjusted by means of the construction of the valve closure members in connection with the choice of position of the sealing elements used.
Therefore, two sealing elements are provided at the periphery of at least one of the valve closure members. The shape of the sealing elements and their relative axial position determine the size of the area on the switch-over piston which is acted upon by the fluid pressure prevailing in the particular container which is to be connected in the switching operation and, hence, by the force required for axial movement of the switch-over piston. In accordance with the radial dependency of the effective area, the force required for switch-over, and hence the switch-over time or switch-over pressure, can also advantageously be achieved comfortably by changing the position of the sealing elements relative to one another, step by step, in the direction of the longitudinal axis of the switch-over piston. Valve closure members in the form of a truncated cone which tapers in the direction of the free end of the switch-over piston and terminating in a cylindrical pin are particularly advantageous.
According to an advantageous feature of the invention, one of the pins abuts with its end face on the wall of the working chamber in spring loaded manner, so that the switch-over piston assumes a predetermined position which opens the valve of the corresponding inflow channel, irrespective of the pressure, without the switch-over device already being attached to a battery of bottle cells. Because of this constructional feature, the switch-over device is also suitable for systems which have to be supplied with a fluid medium, wherein switch-over is only to a reserve container, for example to supply breathable air to a diver.
O-rings, piston or flange seals may be provided as the sealing elements. O-rings are particularly useful since they can be positioned securely in annular grooves formed in the outer surface of the frustum-shaped valve closure members. For reliable sealing of the inflow channels by means of these valve closure members, which are advantageously self-centering, two sealing elements are provided, inserted in annular grooves, with different axial positions.
The sealing elements consist of VITON fluoroelastomer, EPDM, TEFLON polytetraflu
Dey Uwe
Hartwig Peter
Muller Bernd
Thiel Torsten
Dey Uwe
Hepperle Stephen M.
Kinberg Robert
Spencer George
Venable
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