Pumps – One fluid pumped by contact or entrainment with another – Jet
Reexamination Certificate
1999-11-24
2001-10-02
Tyler, Cheryl J. (Department: 3746)
Pumps
One fluid pumped by contact or entrainment with another
Jet
C417S198000
Reexamination Certificate
active
06296454
ABSTRACT:
BACKGROUND OF THE INVENTION
The subject of the invention is a suction jet pump with an improved suction action. Suction jet pumps are used, for example, in fuel tanks of motor vehicles, in order to convey fuel out of one region of the fuel tank into another region.
Suction jet pumps are nowadays employed in fuel tanks of motor vehicles and are therefore known. They have the task of conveying fuel out of distant and lower regions of the fuel tank to the feed unit or into a baffle. The suction jet pump consists, in this case, essentially of a propulsion jet tube, an intake orifice and a mixing tube. The liquid quantity supplied to the suction jet pump via the propulsion jet tube emerges under pressure from the propulsion jet nozzle delimiting the propulsion jet tube and subsequently enters the mixing tube. The intake orifice for the liquid to be conveyed is arranged between the propulsion jet nozzle and the mixing tube. The propulsion jet entering the mixing tube generates a vacuum upstream of the latter, so that the liquid to be conveyed is sucked into the mixing tube via the intake orifice. The efficiency of a suction jet pump, in this case, depends on many factors. Thus, for example, the length of the mixing tube and other geometric factors influence the efficiency. The general disadvantage of suction jet pumps is their relatively low efficiency of about 20 to 30%.
It is known that a good suction action is achieved if the mixing tube length amounts to more than ten times the mixing tube diameter. On account of the conditions of space in a fuel tank, however, precisely these geometric requirements often cannot be implemented, so that the efficiency, which is low in any case, is impaired even further.
The object on which this invention is based is, therefore, to provide a suction jet pump with improved suction action, which has a simple design and does not take up a large construction space.
BRIEF SUMMARY OF THE INVENTION
It was found, surprisingly, that the problem on which the invention is based is solved by means of a suction jet pump, the propulsion jet nozzle and diffuser of which are designed in such a way that, as early as in the diffuser, the propulsion jet is laid completely onto the circumference of the latter. This results in a very rapid liquid seal which leads to a very high vacuum. It is essential to the invention that the propulsion jet nozzle and the diffuser be coordinated with one another. In particular, the shape of the propulsion jet nozzle makes it possible to widen the propulsion jet just after it has left the propulsion jet nozzle.
The advantage of the suction jet pump according to the invention is its suction action which is improved as compared with known suction jet pumps, and which is attributed to the rapid liquid seal in the diffuser. Furthermore, the suction jet pump has a very simple design and takes up little space.
In a particularly advantageous refinement, the nozzle orifice of the propulsion jet nozzle is designed in such a way that it generates a flat jet. In this case, the diffuser possesses an elliptical inflow cone adapted to the flat jet.
It is particularly advantageous to have a nozzle orifice which possesses a notch running transversely. The propulsion jet is thereby widened into a fanlike manner. In other refinements, a web is arranged in the nozzle orifice, said web dividing the propulsion jet and thus generating the flat jet. It may also be envisaged, however, to have a nozzle orifice possessing a plurality of orifices arranged in a line, so that the individual jets form themselves into a flat jet.
A likewise rapid liquid seal in the mixing tube is achieved when the axis of the propulsion jet nozzle is at a small angle to the axis of the mixing tube. As a result, the propulsion jet does not impinge onto the mixing tube axially, but obliquely. This increase in the impingement angle results in even more rapid sealing-off of liquid in the mixing tube, in order thereby likewise to lead to an improved suction action.
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Kürmann Ludger
Lepper Joachim
Planck Wolfgang
Schmid Rene
Mannesmann VDO AG
Mayer Brown & Platt
Speer Richard A.
Tyler Cheryl J.
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