Optical: systems and elements – Optical aperture or tube – or transparent closure
Reexamination Certificate
1999-06-26
2002-06-18
Chang, Audrey (Department: 2872)
Optical: systems and elements
Optical aperture or tube, or transparent closure
C250S496100, C250S506100, C396S490000, C396S484000
Reexamination Certificate
active
06407873
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical and particle beam shutter, and more specifically to a shutter which moves to a closed position when it is de-energized.
2. Relevant Background
Many applications utilize a high energy laser beam or particle stream, herein referred to as an “energy beam”, to carry out certain functions. For example, a high energy laser can be used to cut patterns in fabric during clothing production. In such applications, it is often necessary to quickly stop transmission of the energy beam when an event such as system failure occurs. For example, it is desirable to quickly switch off a laser used for fabric cutting if the laser positioning equipment loses power for some reason, since otherwise the laser beam may stay focused at the same spot for too long and potentially cause the fabric to catch fire.
The most direct method to quickly stop transmission of the energy beam, when possible, is to quickly switch off the power to the energy beam source. This method is not always possible since high energy beam sources often require too long of a period of time to switch off. In addition, high energy beam sources are often powered separately from the beam steering circuitry, and a power failure to the steering circuitry may not necessarily result in a power failure to the energy beam source. Another approach is to intercept the energy beam with an optical/beam shutter. Optical/beam shutters can be designed to absorb or reflect an energy beam and are also referred to as “interlock shutters”, “optical modulators”, or “optical choppers”.
A popular optical shutter design is called a rotating optical shutter. A rotating shutter includes a disk with one or more notches or holes cut into it and is mounted on a motor shaft. When the disk is positioned such that the energy beam passes through one of the notches, the energy beam is unobstructed. To intercept the energy beam, the shutter disk is rotated to a position where the beam no longer passes through the notch and is therefore obstructed by the disk.
One drawback of the rotating shutter design is that power must be present at the shutter motor for the shutter disk to be rotated to a beam-obstructing position. If the rotating shutter loses power, the shutter disk cannot be rotated to an obstructing position and the energy beam will continue to pass through the shutter disk notch, possibly causing damage or injury.
Another optical shutter design utilizes a shutter blade which can be moved from a beam passing position to a beam obstructing position. This type of shutter design is disclosed in U.S. patent application Ser. No. 09/035,766 entitled, “Low Frequency Optical Shutter”, U.S. Pat. No. 6,046,836. This shutter design suffers from the same drawback as the rotating shutter design, where power to the shutter must be present in order to switch the shutter blade to a beam-obstructing position.
There is a need therefore for a low power optical/beam shutter that can obstruct an energy beam quickly and wherein the shutter can switch to a beam-obstructing position when a power loss to the shutter occurs. This helps ensure that energy beam transmission is halted during a power failure to the beam steering equipment, averting possible damage or injury.
SUMMARY OF THE INVENTION
Briefly stated, the present invention teaches a safety shutter suitable for intercepting an energy beam. The safety shutter includes at least one shutter blade having a top end and a bottom end. At least one motor is coupled to the bottom end of the shutter blade such that the motor rotates the shutter blade from a closed position to an open position when energized. The shutter blade is coupled to at least one spring, wherein the spring rotates the shutter blade from the open position to the closed position when the motor is de-energized.
Variations of the present invention may be constructed. For example, the motor can be, but is not limited to, a solenoid, a stepper motor, or a DC motor. Likewise, the shutter blade can be made from reflective material or non-reflective material. The shutter blade may further include at least one optical filter, and the top end of the shutter blade may include a tabbed section. The spring may be a spiral spring, and the optical safety shutter may further include a base attached to the motor.
REFERENCES:
patent: 3697755 (1972-10-01), Boissevain et al.
patent: 3709121 (1973-01-01), Simonson et al.
patent: 4040072 (1977-08-01), Johnson et al.
patent: 4357083 (1982-11-01), Johnson et al.
patent: 5130795 (1992-07-01), Rusche et al.
patent: 5202721 (1993-04-01), Kobayashi et al.
patent: 5701525 (1997-12-01), Caterino et al.
patent: 5828487 (1998-10-01), Greening et al.
Chang Audrey
Electro-Optical Products Corp.
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