Abstract:
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.

Description:
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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 provides a simplified showing of a shutter that includes the present invention. 
     FIG. 2 shows a side view of the simplified shutter. 
     FIG. 3 shows the simplified shutter at an energized position. 
     FIG. 4 shows a front view of another embodiment of the present invention. 
     FIG. 5 shows a side view of the shutter as contemplate by the present invention. 
     FIG. 6 shows the shutter in an open position. 
     FIG. 7 shows a rear view of the shutter. 
     FIG. 8 shows another embodiment of the shutter. 
     FIG. 9 a  and FIG. 9 b  show yet another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 provides a simplified showing of a shutter  20  that includes the present invention. In this figure, a shutter blade  22  is coupled to a motor shaft  24 . The shutter blade  22  is substantially rectangular in shape, with an upper side region cut away, forming an tabbed upper portion  25 . The shutter blade  22  can engage the motor shaft  24  directly using solder or an adhesive such as epoxy, or the shutter blade  22  may engage the motor shaft  24  indirectly using a mounting bracket  26  as shown. A motor  28  driving the shaft  24  may be a DC motor, AC motor, stepper motor or other device capable of rotary motion. 
     FIG. 2 shows a side view of the shutter  20 . A spring  30  is attached to the motor shaft  24 , thereby biasing the shutter blade  22  to a de-energized position shown in FIG.  1 . Thus, when the motor  28  is powered off, the biasing force of the spring  30  moves the shutter blade  22  to the de-energized position. The spring construction may include a coil spring, a hair spring, an elliptic spring, or preferably a spiral spring. The spring  30  may alternatively be attached directly to the shutter blade  22  or another component of the shutter which is responsive to the rotational force of the motor  28 . 
     In FIG. 3, the shutter  20  is shown with the shutter blade  22  at an energized position. At this position, the motor  28  exerts enough force to overcome the biasing force of the spring  30 . A target region  32 , normally obstructed when the shutter is in the de-energized position, is unobstructed when the shutter is moved to the energized position. Thus, an energy beam traveling normal to the shutter blade surface and focused at the target region  32  can only travel past the shutter blade  22  when the shutter blade  22  is at the energized position, and is blocked when the shutter blade  22  is in the de-energized position. The shutter blade&#39;s rotational motion may be limited using a mechanical stop  35  which physically prevents the shutter blade from traveling a complete revolution. 
     FIG. 4 shows a front view of another embodiment of the present invention. A safety shutter  34  includes a shutter blade  36  coupled to a shaft  38 . Preferably, the shutter blade  36  is mounted with screws  40  to a rotating plate  42  which is connected to the shaft  38 . A solenoid  44  is used to rotate the shutter blade  36  over a limited angular range from a de-energized (“closed”) position to an energized (“open”) position. The solenoid  44  is attached to a base  46  having tapped cavities  48  which allow for horizontal and vertical mounting of the safety shutter  34 . 
     FIG. 5 shows a side view of the safety shutter  34 . A spring  50  is connected to the shaft  38  which creates a biasing force when the shaft  38  is rotated. The solenoid  44  includes a wire coil  52  which creates an electrically induced magnetic force when the coil  52  is energized with electric current. Rotational motion is achieved using spiral grooves of gradating depth stamped into the solenoid casing and ball bearings  54  placed within the spiral grooves. When the rotating plate  42  is pulled towards the solenoid by the electrically induced magnetic force of the coil  52 , the rotating plate  42  turns as the ball bearings  54  travel along the spiral grooves. 
     FIG. 6 shows the safety shutter  34  in the open position. As mentioned above, an electric current passing through the coil  52  creates a magnetic force, pulling the rotating plate  42  towards the solenoid  44 . The open position is the point of linear travel where the rotating plate  42  is physically prevented from moving closer to the solenoid  44 . It is contemplated that electric current to the coil  52  may be reduced as the rotating plate  42  reaches the open position. FIG. 7 is a rear view of the safety shutter  34  showing the solenoid  44  secured to the base  46  with a set of mounting nuts  56 . 
     In FIG. 8, another embodiment of the safety shutter  34  is shown. The top end of the shutter blade  36  is partitioned into an first section  58  and a second section  60 . It is contemplated that the first section  58  has different optical properties than the second section  60 . For example, the first section  58  may be reflective and the second section  60  may be non-reflective. In addition, each section may contain optical filters  62  capable of passing a subset of wavelengths in the electromagnetic spectrum. 
     Yet another embodiment of the present invention is shown in FIG. 9 a  and FIG. 9 b . The safety shutter  34  includes a first shutter blade  64  and a second shutter blade  66 . In the closed position, shown in FIG. 9 a , the second shutter blade  66  overlaps the first shutter blade  64 . In the open position, shown in FIG. 9 b , both shutter blades  64  and  66  are rotated opposite each other. This configuration allows the safety shutter  34  to open and close a greater target area  68 . It is contemplated that additional shutter blades may be added to further increase the target area  68 . 
     It is contemplated that the safety shutter of the present invention can be incorporated into a beam steering assembly, with the safety shutter positioned before the energy beam source. The safety shutter can be powered by the same power source of the other beam steering components such that when a power failure to the beam steering components occurs, power failure to the safety shutter also occurs. Such a power failure will cause the shutter blade to spring to the closed position, ensuring the energy beam is blocked from further transmission. 
     Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes, combinations and arrangements of techniques can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed.