Patent Application
20140014200
The invention relates to a throughflow rate limiting device with a spring-loaded valve body which is disposed upstream of a cross-sectional constriction in a flow duct so as to be axially slideable between a first and a second position, where the valve body is loaded by a spring in the direction of the first position and where for a given pressure gradient throughflow in the first position is greater than in the second position, and where the cross-sectional constriction may be bypassed by at least one bypass line, which branches off from the flow duct upstream of the cross-sectional constriction and rejoins the flow duct downstream of the cross-sectional constriction.
From EP 0 969 233 A1 there is known a throughflow limiter with a spring-loaded valve body, where the spring-loaded valve body is located in a constricted part of the flow duct. The nozzle-shaped wall of the housing is provided with longitudinal ribs, which in the closed state of the valve body form flow channels permitting restricted throughflow in the closed position of the valve body.
Throughflow limiting devices with a cross-sectional constriction which can be bypassed by a bypass line, are known from U.S. Pat. Nos. 4,437,493 A, 4,699,166 A and 3,122,162 A.
It is a disadvantage that throughflow limiters of this kind incur relatively high pressure losses in the open state. It is also disadvantageous that known throughflow limiters will switch from the first to the second position only when pressure differences are relatively high. The switching point thus lies at a relatively high pressure difference level.
It is of further disadvantage that known throughflow limiters show relatively strong hysteresis, i.e., the opening movement of the valve body from the closed position is greatly retarded.
It is the object of the present invention to avoid these disadvantages and to configure a throughflow limiting device which has little pressure loss in the open position and little response retardation.
According to the invention this object is achieved by proposing that the valve body have the shape of a double cone. The double-conical shape will result in a design with very small flow losses.
The bypass line may be disposed outside of the flow duct in the housing of the throughflow limiting device.
To permit fast opening from the second position it is of advantage if the valve body is guided by a fixed axial guiding rod, which guiding rod may be provided with a preferably adjustable stop downstream of the valve body, against which the valve body will rest in the second position. The stop may for instance be configured as a sleeve which is axially adjustable on the guiding rod. The sleeve at the same time acts as a counter-bearing for the spring. The sleeve may thus be used both to axially adjust the stop for the valve body and to adjust the preloading of the spring.
When the defined throughflow rate is reached the throughflow limiting device of the invention will abruptly and automatically switch, without external intervention or actuation, the switching force necessary to actuate the valve being entirely derived from flow-dynamical effects.
The defined stop on the guiding rod will prevent the valve body from closely pressing against the housing in its second position. In the second position there will thus remain a defined gap between the valve body and the inner wall of the housing, which will enable very fast opening of the valve body departing from the second position. The inner wall of the housing, which tapers in flow direction, may be configured as a cone or may be nozzle-shaped.
Particularly low flow losses may be achieved if the rotationally symmetrical valve body has a non-linear curve as generatrix. This will permit particularly low throughflow losses in the open state of the throughflow limiting device designed according to the invention.
In a particularly preferred variant it is provided that the switching point between the first and second position is reached when the pressure difference between an area of the flow duct upstream of the throughflow limiting device and an area downstream of the throughflow limiting device is not more than 500 mbar, preferably at most 200 mbar. This will result in a very sensitive response behaviour with little retardation. By comparison, known throughflow limiters usually switch only when a pressure difference of approximately 1,000 mbar has been reached.
Essentially the switching point is determined by the flow-optimized shape of the valve body and the surrounding housing and by the chosen spring force. The switching forces are derived entirely from flow-dynamical effects. In order to achieve only small pressure losses the switching force must be amplified via these flow-dynamical effects. By designing the throughflow limiting device according to the invention the switching point can be realised at a very small pressure difference and completely without actuating means.
The invention will now be described in more detail with reference to the enclosed drawings. There is shown:
The throughflow limiting device 1 illustrated in
The valve body 4 and the cross-sectional constriction 6 can be bypassed by a bypass line 7, which branches off from the flow duct 3 upstream of the valve body 4 and rejoins the flow duct 3 downstream of the cross-sectional constriction 6.
The guiding rod 5 is provided with a sleeve 8 on which is borne a spring 9 which preloads the valve body 4 in a first position shown in
The valve body 4 is essentially designed as a double cone to achieve minimal flow losses.
The sleeve 8 acts as a stop 11 for the valve body 4, the valve body 4 resting against the stop 11 in the second position. The stop 11 is adjusted via the sleeve 8 in such a way that in the second position of the valve body 4 a defined gap is left open between the conical surface 4a of the valve body 4 and a conical wall surface 2a of the housing 2. This gap enables fast opening of the valve body 4 from the second position, such that only little hysteresis will occur. The remaining gap may have non-constant width due to the design of the wall surface 4a of the valve body 4 and the wall surface 2a of the housing 2.
In the first position of the valve body 4 illustrated in
In
As can be seen, the closing/opening characteristic of the valve body 4 is subject to hysteresis. Hysteresis between opening and closing of the valve body 4 is indicated by reference numeral 14. On account of the defined gap in the second position between the valve body 4 and the bypass line 7 hysteresis 14 may be kept at a minimum. Due to the defined gap a small flow is possible even when the valve body 4 is “closed.”
| Number | Date | Country | Kind |
|---|---|---|---|
| A 144/2011 | Feb 2011 | AT | national |
The present application is a National Stage Application of PCT International Application No. PCT/EP2012/051778 (filed on Feb. 2, 2012), under 35 U.S.C. §371, which claims priority to Austrian Patent Application No. A 144/2011 (filed on Feb. 3, 2011), which are each hereby incorporated by reference in their respective entireties.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/051778 | 2/2/2012 | WO | 00 | 10/3/2013 |
