Fluid handling – Line condition change responsive valves – Pop valves
Reexamination Certificate
2000-05-19
2001-02-20
Chambers, A. Michael (Department: 3753)
Fluid handling
Line condition change responsive valves
Pop valves
C137S472000
Reexamination Certificate
active
06189562
ABSTRACT:
FIELD OF APPLICATION
This invention relates to the field of valve technique. It concerns an overflow valve for limiting the pressure in a system in which a liquid is lifted by a positive-displacement pump and flows through the system with varying rates of flow, comprising a valve chamber with an inlet opening bordered by a valve seat for the entry of liquid into the valve chamber and with at least one outlet opening in connection with the runback to the positive-displacement pump for the outlet of the liquid out of the valve chamber, as well as a valve body placed displaceable inside the valve chamber with a valve head, whereby the valve body is pressed by a first spring with the valve head sealing against the valve seat and is lifted off from the valve seat at an opening pressure determined by a first active diameter of the valve head against the force of the first spring and opens the inlet opening.
PRIOR ART
A great number of pump systems with positive-displacement pumps for the lifing of liquids are operated with different rates of flow from the nominal power or maximal power over different throttle states up to the rate of flow zero. Directly acting spring-loaded pressure control valves or overflow valves are used for avoiding an overstressing of the driving gear, for limiting the system pressure and for limiting the volume flow.
Because of the spring power increasing with the opening stroke, these valves cause, after the beginning of the opening, an overflow pressure which is also increasing. This is counteracted in known embodiments, after the beginning of the opening of the valves, by bigger valve surfaces which then become active so that the rise of pressure is reduced or even a decrease of pressure is achieved. Here, the stabilization of the pressure at each operating state raises difficulties. It is known to use hydraulic damping cylinders for stabilizing which then however prevent a quick valve reaction by sudden resistance changes in the system, for example by shutting-off operations, and thus cause undesirable pressure peaks.
For a better understanding of the problems, the widespread operating of gasoline pumps for refueling vehicles can be taken as an example. The pump unit is activated with the removal of the dispensing valve from the Support, and the fuel flows over the overflow valve with a pressure slightly higher than the refueling pressure, the driving energy necessary for this approximately corresponding to the energy demand when refueling. This state has a varying duration.
During the refueling with a fully opened dispensing valve, i.e. with a maximal volume flow and operating pressure and with the use of a gasoline pump which is constructed quite precisely for this capacity, there do not result any problems. However, overdimensioned pumps are very often used in order to cause during the operation already a partial opening of the overflow valve. Due to this measure, the pressure peaks triggered by quick closing dispensing valves should be reduced. This causes a higher energy consumption.
Furthermore, two snap-in positions for the throttled refueling are generally provided on the dispensing valves for the opening lever. Here, the pump is operated with the maximal pressure in connection with the used overflow valves. This pressure encounters a relatively low decrease of pressure, because of the throttled volume flow, so that an unnecessarily high pressure prevails ahead of the dispensing valve. In spite of a low rate of refueling, however with an almost unchanged pump pressure, the energy consumption is unchanged, compared with the throttled refueling, and thus unnecessarily high.
Moreover, for the throttled refueling operations, the high pressure existing at the dispensing valve requires very high throttle cross sections. This causes high rates of low in the dispensing valve which unfavourably result in foam formation and stronger gas evolution in the tank of the vehicle.
Upon the end of the refueling by manual or automatic turning off of the dispensing valve, the same pressure and energy state as before the beginning of the effective refueling is repeated and lasts until the dispensing valve is hung up again into the gasoline pump. Statistical investigations on gasoline pumps have shown that the pump operating time before and after the actual refueling constitutes approximately 30% of the total pump operating time, i.e. represents a great potential of needless lost energy.
A further illustrating field of application of a big range of application relates to heating pumps which are used with liquid as heat transfer media for the heat transport very often to different consumers, for example to heating radiators. The heat demand is variable for different reasons and is adapted to the consumers, for example through thermostatic valves and/or for the whole system by control of the number of revolutions of the pump. With the adaptation of the heat demand, for example only over thermostatic valves, the pressure increases with increasing throttling for the centrifugal pumps commonly used for heating, and undesirable noises arise then because of the pressure differences at the valves which are then big. The energy consumption is getting lower for centrifugal pumps with increasing throttling.
Speed controlled/frequency controlled pump driving gears are used for reducing the pressure and the energy consumption. However, a part of the saved driving energy is lost again due to the frequency control. The use of positive-displacement pumps with a higher efficiency than centrifugal pumps and with a pressure/volume flow lifting characteristic curve almost along the pressure/volume flow resistance characteristic curve of the system would be a considerable improvement with respect to the functional and energy technique compared with the prior art.
A discharge and/or overflow valve, especially for spray guns, is known by DE-U-72 23 233, valve which comprises a hollow valve chamber with an inlet and an outlet which are connected with an inner working room in the valve chamber, a piston slidingly guided in the working room, whereby the valve chamber shows a valve slit, the cross section of which is smaller than the cross section of the piston and which surrounds the inlet, whereby the piston has a section with a smaller diameter which cooperates with the valve seat in order to interrupt the flowing through of a fluid through the valve chamber, the valve chamber having a channel which connects the room between the valve seat and the piston, when the piston is lifted off from the valve seat, with the outlet of the valve chamber, an adjustable device for varying the passage cross section of the channel, a spring placed between the piston and an abutment in the valve chamber for applying a closing pressure onto the piston, and al device which makes it possible to adjust the power applied by the spring so as to vary the force of pressure which must come to effect in the inlet in order to lift off the piston from the valve seat. This should create a discharge valve under spring tension which is so configured that it quickly reduces the operating pressure of the pump installation, as soon as the operation of the spray gun is interrupted. This known valve has a second bigger active diameter. After the valve disk is lifted off from the valve seat when an opening pressure determined by the spring is exceeded, the lower overflow pressure is determined by the piston. Since this by itself causes an unstable state of the valve piston and thus of the overflow valve, the overflowing liquid is guided over a second adjustable valve cross section to the outlet. For each operating state, determined by the volume flow of the pump and the necessary operating pressure for the spray gun, an adjustment of the spring and of the second valve cross section adapted to each other must take place to avoid pressure instability when overflowing. The valve is thus appropriate for overflowing with a stable pressure only by a constant adjusted operating condition and also only by interruption of the fluid flow
Chambers A. Michael
Kueffner Friedrich
McShane Thomas L.
LandOfFree
Overflow valve does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Overflow valve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Overflow valve will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2612053