Magnetic Activation System for Switch

The invention relates to the field of activation and indicating systems that operate without mechanical connections to the elements they activate or about which they provide information. The invention particularly relates to the determination of a valve operating condition or state.

The operating state of a valve must often be known for proper operation of a device in which the valve is used. One way to monitor a valve's operating state is with a mechanical connection to a valve component, such as a valve body. However, conventional mechanical connections to valve components require seals that must prevent leakage, yet allow the connection to operate. In valves handling extremely aggressive fluids, seal connections create a risk of damage to other components if the seal connections fail. Thus, it is desirable to use an operating state indicator that does not require such a mechanical connection and its associated seals so that the risk of fluid leakage can be reduced, if not eliminated.

Some prior art remote indicating systems rely on magnets mounted on the valve bodies. While these function satisfactorily in most environments, the magnets can be destroyed in more hostile environments. For example, the hydrazine used in dual-fuel thruster systems can corrode such magnets. There is, therefore, a need for a remote valve status indicating system that does not rely on magnets exposed to the fluid controlled by the valve for which the system provides information.

Additionally, the stroke required by prior art valves to activate their switches requires large valve envelopes or housings. This increases the size of the valve, which results in increased weight and cost. In spacecraft applications, the increased size and weight reduce the amount of payload that can be carried by the spacecraft or increase launching costs. Thus, there is a need for a magnetic switch activation system that allows a valve with a shorter stroke to be used.

A follower is mounted about a valve housing so that it follows a non-magnetic valve body when it travels within the housing. The valve body is made from a ferromagnetic material, and the follower has magnets arranged so that the force of attraction between the valve body and the magnets causes the follower to move in response to movement of the valve body. We prefer to use a pivoting follower in the form of a swingarm mounted to the casing or to the housing of the valve. A switch is mounted near the path of the follower so that the follower can activate the switch. Thus, our device is also a magnetic switch activation system.

As a result of the remote location of the follower, the state of the valve can be determined without a mechanical connection to the valve body. The risk of leakage created by such a mechanical connection is thus eliminated. Also, because of the use of the ferromagnetic valve body and magnetic follower, no magnet need be mounted on the valve body as was required in prior art devices. Our device can, therefore, be used to remotely determine the states of valves that control fluids destructive to magnets, unlike prior art devices. We also eliminate the requirement of mounting a magnet on the valve body and can use parts already present in valves as part of our indicating system. This allows us to retrofit already existing valves with our remote indicating system without disassembling the valves and inserting new parts.

Our system also effectively amplifies the valve stroke since for a given displacement of the valve body, the tip or activating portion of the swingarm is moved through a greater linear distance. This amplification allows the use of a smaller valve stroke, which allows the use of a smaller valve housing or envelope, which in turn results in weight and cost savings. The reduced size and weight is especially important in spacecraft applications since launching costs can be reduced for a given payload or payload can be increased.

FIG. 1 is a cross-sectional view of a valve incorporating our invention.

FIG. 2 is another cross-sectional view of a valve incorporating our invention and focusing on the invention.

FIG. 3 is a view of the valve incorporating our invention taken along line A--A in FIG. 1.

As seen in the accompanying Figures, we use our magnetic activation system in a valve 10, preferably of the poppettype. The valve 10 includes an outer casing 11 that provides support for an energization coil 16 and a valve housing 12 through which fluid travels. A valve body 13 inside the valve housing controls the flow of fluid through the valve housing 12 and is movable between an open position and a closed position in response to the state of the energization coil 16. We make at least a portion of the valve body out of a nonmagnetic, ferromagnetic material, such as iron.

We attach a follower 20, preferably in the form of a swingarm, to a component that is stationary relative to the valve body 13, such as the valve casing 11 and/or the valve housing 12, via a pivot connection 21. The pivot connection 21 can take many forms, but we prefer to use a pin 14 in a mounting bracket 15 attached to the casing 11 and/or housing 12. The preferred swingarm 20 includes a U-shaped portion 22 arranged so that the valve body 13 is between the curved portion of the U-shaped portion 22 and the pivot connection 21. The arms 23 of the U-shaped portion 22 extend toward the pivot connection 21 on either side of the valve body 13 and terminate at the pivot connection 21. In the preferred embodiment, the end of each arm 23 is pivotably connected to the casing 11 and/or housing 12 via the pin 14 of the mounting bracket 15. The follower also preferably includes an upright portion 24 extending from the U-shaped portion 22 and away from the pivot connection 21. Mounted outside of the valve housing 12, the follower 20 remains isolated from the fluid controlled by the valve 10.

To cause the follower 20 to move when the valve body 13 moves, we arrange following magnets 25, preferably rare earth magnets, in the U-shaped portion 22 of the swingarm 20 so that they are substantially equidistant from the valve body 13. Because the valve body 13 is made from a ferromagnetic material, the following magnets 25 are attracted to the valve body 13. When the following magnets 25 are of sufficient strength, the attractive force between the valve body 13 and follower 20 causes the follower 20 to swing about its pivot connection 21 when the valve body 13 moves. Thus, the follower 20 has positions corresponding to the open and closed positions of the valve body 13.

To prevent the follower 20 from traveling too far, we include a limit stop 40.

The upright portion 24 of the swingarm 20 amplifies the valve stroke of the valve 10. The path of the tip of the upright portion 24 moves through an arc, the upright portion 24 lying on a radius of the arc. When the valve body 13 moves, the U-shaped portion 22 of the swingarm 20 moves a similar linear distance, but the upright portion 24 moves a greater linear distance depending on the length of the upright portion. The tip of the upright portion 24 can, therefore, act on an object much farther away from the valve housing 12 than can the valve body 13.

We place a switch 30 near one of the positions of the follower 20 so that the switch is activated by the follower 20 when the valve body 13 is in one of the open and closed positions. In our preferred embodiment, the switch 30 is magnetically activated. To activate the switch 30 in the preferred embodiment, we include an activating magnet 26, preferably a rare earth magnet, in the upright portion 24 of the follower 20. So, if the system is to indicate that the valve 10 is open, the switch 30 is placed near the follower position corresponding to the valve body's open position. When the valve body 13 moves to its open position, the follower 20 moves to its corresponding position, bringing the activating magnet 26 near the switch 30. The switch 30 is closed by the activating magnet 26 so that an indicator 50 attached to the switch 30 can indicate that the valve 10 is open. "Indicator" is used in a broad sense not limited to indicator lights, but including anything that can indicate that the valve 10 is open.

While we prefer to use a magnetically activated switch, the switch 30 could be mechanically activated by the movement of the follower 20, though with inferior results. The follower 20 could also include only one set of magnets to both follow the valve body 13 and activate the switch 30. For example, if only the following magnets 25 were included, upright portion 24 could be left off of the follower 20 and the switch 30 could be moved closer to the valve body 13. The switch 30 would then be activated by the following magnets 25 when the follower 20 reached the appropriate position. This arrangement, however, would probably provide results inferior to our preferred embodiment. Other shapes could also be used for the follower 20, but it is our belief that the shape we have chosen for our preferred embodiment is the most efficient and provides the best results.

10 valve

11 valve casing

12 valve housing

13 valve body

14 pivot pin

15 bracket; pivot mount

16 energization coil

20 follower; swingarm

21 pivot connection between arm and casing

22 U-shaped portion of follower

23 arm of U-shaped portion

24 upright portion of follower

25 following magnet

26 activating magnet

30 switch

40 stop; limit stop

50 indicator