Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Reexamination Certificate
1999-11-18
2001-05-08
Barrera, Ray (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
C335S229000, C335S233000
Reexamination Certificate
active
06229421
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of solenoids and specifically to an autosecuring solenoid that prevents unwanted movement of the solenoid plunger that may occur when an external force is applied to the solenoid, displacing the plunger.
DESCRIPTION OF THE RELATED ART
Electronic solenoids are employed in a wide variety of electronic, electrical, and electro-mechanical devices. The basic solenoid has an outer case and an internal cavity. Typically, one or more coils will be located between the cavity and the outer case. A plunger slides within the cavity. At least a portion of the plunger is magnetically permeable, typically this portion is formed from iron or steel. When the coil of the solenoid is energized, the center of the magnetically permeable portion moves or tries to move to the center of the magnetic field produced by the energized coil(s). After removing the magnetic field the plunger remains in position unless an outside force, typically produced by a spring, returns the plunger to its original position. With the solenoid de-energized the movement of the plunger is not restrained, unless a spring or other device limits/restrains the movement of the plunger.
Some solenoids have a magnetic latch that holds the plunger in the energized position even after the solenoid is de-energized. Typically the magnetic latch uses a magnet in one end of the solenoid case, the magnetic field of this magnet is typically aligned with the field produced by the coil when energized to pull the plunger into the solenoid. The plunger will be held in contact with this magnetic latch against the spring force until an opposing magnetic field is induced in the coil. The opposing magnetic field must reduce the magnetic attraction of the plunger to the magnetic latch to the point where the spring can pull the plunger away from the magnetic latch and return the plunger to its original position.
With a solenoid either energized or de-energized the plunger moves when the solenoid is subject to an impact or shock. The plunger will even move when the return spring is used. Both the return spring and an magnetic field produce restorative forces, but even these forces may not be sufficient to prevent undesired plunger movement. The displacement of the plunger during or after a shock impact may be sufficient to cause the plunger to enable and/or actuate the device associated with the plunger. This movement of the plunger is typically undesired.
An example of the effects of undesired plunger movement with the solenoid de-energized may be shown in solenoid actuated electronic locks.
Electronic locks often contain solenoids to open or place the lock in a condition where the operator may open the lock upon entry of a correct combination code. The use of solenoids, in this manner, in electronic locks has been known for some time. In operation, the solenoid typically provides some linear motion for a coupling component, such as a plunger and/or latch, to provide an interlock to a device external to the solenoid, such as a sliding bar, handle, or other mechanical device that places the lock in a condition that allows the bolt to be retracted.
The drawback in utilizing a solenoid in this configuration is that the mass of the solenoid plunger is only constrained by a spring or a magnetic field and may move when subject to external shock, impact, and/or external strikes. The application of an external force to the lock and/or security container develops momentum in the solenoid plunger. Thus, the solenoid plunger may move and place the lock in a condition where the lock may be opened without authorized actuation of the solenoid.
Unauthorized engagement of the aforementioned mechanical means has been accomplished in the prior art by interposing a mechanical stop to prevent movement of the plunger. The mechanical stop has acted to minimize the lateral movement of the solenoid plunger absent authorization, while allowing the plunger to actuate upon entry of the correct predetermined combination code or key code. The mechanical stop has accomplished this by moving in response to the amount of external force applied to the lock to act as a physical barrier set in the pathway of the plunger. However, such a stop adds to the assembly cost and complexity of the lock. Furthermore, the stop is less effective in that it decreases but does not halt movement of the solenoid plunger.
Alternatively, in the prior art, unauthorized engagement of the aforementioned mechanical members has been prevented by use of a second solenoid. The second solenoid provides adequate mechanical reinforcement of the plunger. However, this expends rather than conserves energy as both solenoids require power to operate. This is a significant disadvantage in a self-powered lock, which is constrained by limitations on available power.
In view of the foregoing limitations and shortcomings of the prior art devices, as well as other disadvantages not specifically mentioned above, it should be apparent that there exists a need in the art for a solenoid that prevents undesired solenoid plunger movement.
OBJECTS OF THE INVENTION
It is therefore a primary object of the present invention to provide a secure retaining system for a solenoid plunger to prevent plunger movement caused by application of an external force.
It is a further object of the present invention to provide a device utilizing one or more electrically excited coils to produce one or more magnetic fields for the purpose of moving a solenoid plunger and a interposing device.
It is a further object of the present invention to provide an autosecuring solenoid that can hold the solenoid plunger fixed in more than one position eliminating unauthorized plunger movement while the solenoid is de-energized and also while it is energized.
SUMMARY OF THE INVENTION
Briefly described, these and other objects are accomplished according to the present invention by providing an autosecuring solenoid. This solenoid utilizes an interposing device that restrains the solenoid plunger when the solenoid is de-energized and/or energized, effectively preventing undesired movement of the plunger. When a voltage is applied across the coil, the flowing current creates an magnetic field. This field causes the plunger to slide within the solenoid cavity, unless restrained. This field also causes displacement of a movable magnet in the interposing device. The direction of motion of the movable magnet will depend on the magnetic field orientation of the movable magnet with respect to the magnetic field. Thus, the interposing device may move either toward or away from the plunger. Additionally, if using two interposing devices, one device could move away from the plunger and the second device could move toward the plunger. The second interposing device could even permit the plunger to move until the second interposing device engaged a recess or notch in the plunger. The first and/or second interposing devices may be restored by magnetic attraction between the movable magnet and the plunger or top of the interposing housing when the solenoid is de-energized. Alternatively, there is a second small magnet, spring, or other means in the housing of the interposing device to return the movable magnet to its desired position when the solenoid is de-energized.
While the autosecuring solenoid has immediate application in an electronic lock, it is readily apparent that the autosecuring solenoid is desirable for use in any solenoid operated/accuated device that may be exposed to external forces, attacks, vibration or other interfering stimuli acting to cause potential undesired movement of the solenoid plunger. For this reason, the autosecuring solenoid is not intended to be limited to use in electronic locks. Furthermore, additional benefits and advantages of the present invention will become apparent to one skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.
REFERE
Floyd Tracy
Lowe Tommy
Luciano Joseph
Passafiume John
Arent Fox Kintner & Plotkin & Kahn, PLLC
Barrera Ray
Hill Rustan J.
Mas-Hamilton Group, Inc.
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