Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1998-07-21
2001-03-13
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625650, C251S065000, C251S129100, C251S129190
Reexamination Certificate
active
06199587
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to solenoid valves having permanent magnets.
BACKGROUND OF THE INVENTION
Solenoid valves having permanent magnets as biasing members are known inter alia from U.S. Pat. Nos. 3,202,447, 4,306,589, 4,489,863, 4,561,632, 4,574,841, 4,690,371, 5,318,071, 5,345,968, and 5,351,934.
Conventional solenoid valves comprise three ports, a plunger biased by a spring into a first position, known as the normal position, in which it closes a first port and leaves a fluid path open through the remaining two ports. A solenoid surrounds the plunger, and the plunger essentially forms the core of a magnetic circuit comprising the plunger, the solenoid and further connecting parts of ferrous material, a gap being provided between the plunger and the entrance to one of the two open ports. When current is supplied to the solenoid the plunger moves against the bias of the spring to close the magnetic gap, and thus the first port, previously closed, is opened and one of the other ports is closed, to redirect the fluid path from the newly closed port to the newly opened port. This is the powered position and the valve can only remain in this state as long as the solenoid continues to be powered, otherwise it is returned to the normal position by the bias in the spring. In particular U.S. Pat. No. 5,727,769 discloses a valve which consists of a solenoid which drives a plunger in a yoke to open and close a valve part. A permanent magnet is peripherally positioned around the yoke in a predetermined position such that the magnetic field drives the plunger. The permanent magnet holds the plunger by the position of a groove part in the plunger. The magnetic field forms a loop facing the axial direction of plunger movement with a very short gap.
An advantage of this device is that the system restrains vibration of the plunger by making use of the eddy currents that are generated in proportion to the speed of the plunger. The device is able to achieve a rapid braking of the plunger at a predetermined position. This reduces impact damage on the plunger and thus improves the lifetime of the device.
A disadvantage with many of the devices mentioned above is the amount of energy usage. The solenoid coils are fairly thin and easily heated. A device of this kind may contain or be located very near plastic. In addition heating effects mean that the duty cycle of the device has to be kept below a certain maximum. Furthermore there are many applications in which it is preferable to keep electricity consumption to a minimum, for example in automatic irrigation equipment where the device may be left to operate for several hours a day over a large land area for the duration of the growing season. There are other application where it is essential to keep electricity consumption to a minimum, for example when the valve is located on portable equipment where the only power supply is a battery. Even valves on vehicles that include an alternator to generate electricity from the engine may be required to operate at times when the engine is not operational. For example valves that are part of a system for providing hot water to de-ice the outside of the vehicle are required to operate before the vehicle starts moving. Not only is their electric supply restricted to the vehicle battery but most of the available supply is needed to heat the water.
U.S. Pat. No. 5,727,769 discloses a solenoid valve in which a permanent magnet is placed outside the solenoid in order to damp the oscillation of the coil and thereby to enhance controllablity of the coil.
U.S. Pat. No. 4,295,769 discloses a solenoid valve in which a permanent magnet serves as a latch and in which a detaching coil is provided to generate a magnetic field which partially temporarily nullifies the magnetic field.
SUMMARY OF THE INVENTION
Embodiments of the present invention are designed to overcome these and other problems by providing a solenoid valve having a reversible latching mechanism which, in conjunction with magnetic fluxes of varying strengths provided within the valve in different directions at different times, creates forces to latch the valve in a given position and with reversal of magnetic flux, to force the valve out of the given position.
According to a first aspect of the present invention there is provided a solenoid valve comprising a first coil, a plunger, at least a first and a second opening and a latching mechanism placed in association with the first opening, wherein the latching mechanism causes latching, with a predetermined lathing force, of the plunger to the first opening and energization of the first coil in a predetermined first polarity causes at least a reduction of the latching force.
In an embodiment the latching mechanism comprises a permanent magnet placed in association with the first opening, which permanent magnet serves to provide the latching force, which force is directed towards the first opening, and wherein the first coil is operable to bring about the reduction in the latching force and to pull the plunger towards the second opening.
Preferably the first coil is operable to cancel out the latching force completely. Alternatively, the first coil is operable to change the latching force into a bias towards the second opening.
The solenoid valve may have a third opening, and fluid paths interruptible by the plunger, between the first opening and the third opening and between the second opening and the third opening.
The first coil is preferably remote from the first end of the plunger and a magnetic field extensor may be provided to extend a first pole of the magnetic field produced to the first end of the plunger.
In order to push the plunger away from the latched position, the first pole of the magnetic field produced by the first coil may be of the same polarity as a facing pole of the permanent magnet.
The first coil preferably acts upon an iron core to force the iron core towards the second opening when the first coil is in an energized state. The plunger is connected to the iron core by a biasing connector, for example a spring, and the spring is operative to bias the plunger towards the second opening.
The magnetic field extensor may comprise a hollow cylindrical member of ferrous material terminated by a ferrous endpiece. It may be a single part integral with the core.
The ferrous endpiece may be a ring, and may be mobile with the plunger.
The shape of the ferrous ring or the hollow cylindrical member may be modified and gaps therein may be added or adjusted in order to alter the strength of the magnetic field that appears at the ferrous ring.
The first coil preferably acts upon an iron core to force the iron core towards the second opening when the first coil is in an energized state. The plunger may be connected to the iron core by a biasing connector, and the biasing connector may be operative to bias the plunger against the core towards the second opening.
In an embodiment the hollow cylindrical member is axially slidable with respect to the core. This is preferably done in such a way that flux is able to pass as near as possible unchanged to form an efficient magnetic circuit.
The plunger may be further connected to the iron core by a second biasing connector, and the second biasing connector may be attached to bias the core downwardly with respect to the plunger such that when both plunger and core are moving upwardly and upward motion of the plunger is arrested suddenly, the two biasing connectors are operable to cause a cushioned deceleration of the core. Likewise, when the core is moving downwardly and the downward motion of the core is arrested, the first biasing member may cause downward motion of the plunger.
The biasing connectors may be coiled springs whose characteristics are optimized for any required load.
In a preferred embodiment a second parameter magnet is provided.
Preferably the characteristics of the two biasing connectors are preselected to reduce impact damage to the plunger and to the seats.
Preferably, excitation of the coil is controlled b
Arkashevski Uri
Ivanov Vychislav
Rogozinski Joseph
Shlomi Franco
Gottlieb Rackman & Reisman P.C.
Michalsky Gerald A.
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