Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
2000-04-20
2001-09-25
Rivell, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625690, C137S625650, C251S129060
Reexamination Certificate
active
06293308
ABSTRACT:
The invention relates to a miniaturized valve mechanism with a small-size linear motor for the actuation of the valve.
The smallest possible size of valves of conventional design is determined by the size of the control mechanism, where smaller sizes are made possible by direct-action solenoid drives.
New technologies, such as the micro systems technology, create a demand for ever smaller and more complex devices, machines and systems. Areas of application for some of these can already be found in medical, measurement, communications and biotechnological fields, as well as in physics and in chemistry.
The need arises in some of these areas to meter, mix, etc. extremely small amounts of fluids, and to this purpose there is a trend to develop valves and applications of very small size.
A linear motor of small size is known, where the mode of operation is based on the piezoelectric effect. This very small linear motor is already used for measurement and positioning applications in the nanometer range.
A driver is radially enclosed by a small piezoelectric tube with two electrodes. If a voltage is applied to the two electrodes, the piezoelectric tube will expand. This expansion is transmitted to the driver, which is pushed out of the piezoelectric tube. If the linear motor is subjected to voltage pulses, longer strokes can be achieved. Because of its mass moment of inertia, the driver does not follow the rapid movements of the piezoelectric crystal, but continues its movement in relation to the piezoelectric unit by a small amount with every voltage pulse applied, and when these pulses are repeated, the movement extends into the millimeter range. Under no-voltage conditions, the driver of the miniaturized linear motor remains locked in its acquired position with sufficient firmness to prevent the heaviest load that it is capable of lifting from pushing the driver back. The linear motor can be calibrated down into the nanometer range.
It is the object of the invention to provide a valve mechanism which is driven by a linear micro motor and that can be produced in the smallest possible size. Miniaturized valve mechanisms produced according to the invention may be made in a great variety of embodiments.
One embodiment of a micro valve mechanism has two plate shaped valve elements, of which one, containing a plurality of trapezoidal valve seats, is firmly connected to the housing. The second element contains an equal number of closing bodies in a complementary arrangement with the valve seats. According to the invention, this closing body element is firmly connected to a moving part which, in turn, is connected to the driver of the linear motor, or to a driver extension carrier tube, respectively, preferably by means of a screwed joint. This measure provides a simple way to separate the piezoelectric drive from the fluidic part of the valve without having to interfere with the fluid circuit. To this purpose, the fluid housing is separated from the miniaturized linear motor by means of sealing joints.
According to the invention, a simple 2-way or 3-way open/close valve can be achieved in that the driver of the miniaturized linear motor is calibrated to two defined end positions. One or more voltage pulses open the valve up to the pre-defined end position, and voltage pulses of opposed polarity once again close the valve.
On the basis of the proposed arrangement, it is furthermore an easy matter to produce a proportional flow valve. The driver of the linear motor moves the device governing the opening and closing of the valve proportionally to a pre-determined standard value.
A further valve mechanism embodiment, in accordance with the invention, is obtained when the miniaturized linear motor is used in conjunction with a toggle valve. Such valves are known from DE 44 25 540 A1, and are characterized by their modular construction and their reduced space requirement. The fluidic part with at least one inlet and one outlet port contains, for the purpose of opening and closing the valve, a toggle member consisting of a magnetizable metal which is held in a defined position by means of a spring. The fluid housing is separated from the drive by means of a metallic plate. This plate is non-magnetic and contains two magnetic inserts arranged above the toggle member.
For the purpose of opening and closing the valve, the driver of the miniaturized linear motor moves a magnetic system friction-free between lateral guides over this plate.
The valve mechanism according to the invention and in its starting position is deenergized. The driver of the miniaturized linear motor keeps the permanent system on the non-magnetized part of the separating plate. The toggle member is held in a holding position by means of a return spring. The piezoelectric tube is now subjected to as many voltage pulses as are required until the driver of the linear motor has moved the magnetic system over the magnetic parts of the separating plate. Magnetic energy is then allowed to flow and tends to close the magnetic circuit. The toggle member is attracted against the holding force of the return spring and opens one valve port whilst closing the other. The driver of the linear motor with the magnetic system, remain in this position until once again voltage pulses of opposed polarity return the driver, together with the magnetic system, to its starting position. The magnetic force becomes smaller than the force of the return springs and the toggle member is therefore reset into its starting position.
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Burkert Werke GmbH & Co.
Friedman Stuart J.
Nixon & Peabody LLP
Rivell John
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