Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Reexamination Certificate
2001-01-18
2003-04-29
Buiz, Michael Powell (Department: 3753)
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
C137S115130, C137S489000, C137S505110
Reexamination Certificate
active
06554017
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a pressure regulating valve having secondary venting measures, comprising a primary duct subject to a primary pressure, a secondary duct rendering possible tapping of a regulated secondary pressure and a movable control member serving for control of the fluid connection between the primary and the secondary duct, the position of said control member being able to be influenced by a moving setting member able to be subjected to an adjustable presetting force, said setting member being constituted by a movable wall section of a comparison chamber communicating with the secondary duct and said setting member furthermore having a venting opening, also under the control of the control member and serving for venting the secondary duct.
THE PRIOR ART
A pressure regulating valve of this type is disclosed in “Der Pneumatic-Katalog 98” pages 9.3/12-1. It is utilized more particularly in connection with compressed air handling in compressed air supply networks, it being employed to hold constant the working pressure, available on the secondary side, in a manner substantially independent of variations in pressure on the secondary side. The secondary venting measures here make possible a reduction of the secondary pressure available in the secondary duct, for instance for venting the connected piping or in the case of pressure increases on the secondary side owing to operation of the driven loads.
In the case of known pressure regulating valves there are substantial oscillation problems owing to variations in the secondary pressure. With an increase in the rate of flow or, respectively, a higher utilized flow of the regulator the tendency to oscillation will increase. For reducing the oscillations it is consequently necessary to make the technical performance data of the pressure regulators, and more particularly the maximum achievable flow rates, less than would be otherwise technically possible.
SHORT SUMMARY OF THE INVENTION
Accordingly one object of the present invention is to provide a pressure regulating valve with a reduced tendency to oscillation.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in accordance with claim
1
herein there is the feature that the venting opening is so arranged on the setting member that it is located outside the comparison chamber either directly in the secondary duct or in a region in communication with the secondary duct.
In the prior art the venting opening provided on the setting member is in the interior of the comparison chamber communicating with the secondary duct via a connecting duct. The vented flow occurring with the venting opening open is therefore from the secondary duct through the communicating duct into the comparison chamber and from same by way of the venting opening to the outside. Owing to the limited cross section of the communicating duct, which can be termed an interrogating duct, the pressure obtaining in the comparison chamber falls more rapidly and to a greater extent during venting than the secondary pressure in the secondary duct. This leads to a overshoot of the regulator or, respectively, of the regulating circuit and oscillation of the regulator will occur. Although such tendency to oscillate may be countered by reduction of the size of the venting opening and also by reduction of the cross section of the connecting duct (i. e. physical damping), this will be at the expense of the response behavior of the pressure regulating valve, the excess pressure coming from the fluid distribution network, connected on the secondary side, being able to be reduced less rapidly. In the case of the design of the invention the venting opening responsible for secondary venting is now no longer in the comparison chamber and is located either directly in the secondary duct or in a region which is connected with the secondary duct, for instance in an additional chamber in communication with the secondary duct by way of a large cross section. The pressure available on the secondary side is now still in the comparison chamber and supplies the force opposing the presetting force, which can be set from the outside and with which the secondary pressure to be regulated may be preset. However the vented secondary flow does not pass through the comparison chamber and the connecting duct preceding it, but bypasses the comparison chamber and escapes by way of the venting opening placed outside it. The interfering influence of secondary venting therefore no longer acts on the setting member, something involving the further advantage that the cross section of any connecting duct present may be reduced so that a physical damping of the regulating circuit will take place. An additional advantage will be that the caliber of the venting opening may be increased so that the secondary venting performance is increased. The tendency of the regulator to oscillate is reduced to such an extent that in operation it will oscillate less or not at all and the regulator may be designed and operated for and, respectively, with substantially larger flow performances.
Further advantageous developments of the invention will appear from the claims.
The control member preferably extends in a control chamber designed as component of the secondary duct, the venting opening being within this control chamber. If the control member is in the form of a plunger, the control chamber can also be termed a plunger chamber.
A particularly advantageous design in accordance with the invention is such that the setting member extends in a sealed manner through a housing wall separating the comparison chamber from the secondary duct and has a head section with the venting opening, said head section extending into the secondary duct. Here it is possible for the head section of the setting member to cooperate with a terminal secondary control section of the control member.
Since the control member, unlike the prior art designs, no longer extends through a partition separating the primary duct from the comparison chamber, and instead conveniently terminates within the secondary duct, its terminal section is preferably provided with a guide member placed in the secondary duct and fixed in relation to the housing. This guide means may comprise a guide insert anchored in the above mentioned partition and extending into the secondary duct.
The comparison chamber is preferably connected by way of at least one connecting duct with the secondary duct. This connecting duct can be termed an interrogation duct, because it samples the pressure obtaining in the secondary duct and passes on the information to the comparison chamber.
The connecting duct preferably has a relatively small cross section something which is preferably ensured by providing a suitable choke means. The maximum venting cross section associated with the venting opening may be made larger than the cross section of the connecting duct.
The setting member functioning as a moving wall section of the comparison chamber may be piston-and/or diaphragm-like. It is preferred for it to possess a principal body containing the venting opening and fixed to the housing in a sealing manner by means of a preferably at least partially rubber-elastically deformable diaphragm. This renders possible a setting movement with very little friction.
Further advantageous developments and convenient forms of the pressure regulating valve will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the accompanying drawing showing a longitudinal section in a single figure.
The drawing shows in longitudinal section a pressure regulating valve generally referenced
1
, which could also be termed a pressure regulator. In the present case it is in the form of a so-called servicing device, which is employed for the production or conditioning of compressed air in supply systems and possesses interfaces
2
and
3
preferably arranged on opposite side thereof and serving for the connection of pressur
Buiz Michael Powell
Festo AG & Co.
Hoffmann & Baron , LLP
Krishnamurthy Ramesh
LandOfFree
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