Patent Application
20070045257
The present invention relates to safety control systems for use with lasers. In particular, the present invention relates to a safety control system for deactivating a laser based on user proximity to the laser beam.
Lasers generate laser beams that are used for a variety of industrial applications, such as laser welding, soldering, and cutting. Due to the nature of laser beams, numerous safety measures have been implemented to protect users from bodily injury. In response to safety concerns, the American National Standard Institute (ANSI) presented ANSI Z136.1-2000, which provides guidelines and recommendations for the safe use of a variety of lasers.
Nonetheless, a common laser safety issue occurs when users actively work with lasers, such as when a user manipulates work pieces while a laser beam is processing the work pieces. For example, a user may manually hold a work piece with his or her hands and move the work piece around while the laser beam is welding, cutting, or otherwise processing the work piece. This may result in injuries and burns to the user's hands from accidental exposure to the laser beam during the laser processing.
The present invention is a control system and method for use with a laser that generates a laser beam. The control system includes a sensor for sensing a position of a hand of a user, and a control for controlling operation of the laser based on the sensed position of the user's hand. The control system reduces the risk of injuries to the user's hand from accidental exposure to the laser beam during use.
As shown in
Laser 16 is an industrial laser capable of processing metal parts by techniques such as welding, soldering, cutting, machining, and surface treating. Laser 16 is disposed within housing 14 to generate laser beam 18. While laser 16 is shown entirely within housing 14, portions of laser 16 may alternatively be disposed outside of housing 14 so long as laser beam 18 is generated within housing 14.
Laser beam 18 has a maximum power density at focal point 18a, which is the portion of laser beam 18 where the metal parts may be processed. Laser beam 18 also includes converging portion 18b located between laser 16 and focal point 18a, and diverging portion 18c located between focal point 18a and surface 30. At converging portion 18b, the power density of laser beam 18 converges toward focal point 18a. Correspondingly, at diverging portion 18c, the power density of laser beam 18 diverges from focal point 18a.
Laser 16 may be vertically raised and lowered relative to surface 30 to vertically adjust the location of focal point 18a of laser beam 18. This is useful for processing metal parts at different heights. Focal point 18a is offset at a fixed location relative to laser 16 based on optical settings of laser 16. As such, vertical movement of laser 16 results in an equal movement of focal point 18a. Correspondingly, the volumetric dimensions of converging portion 18b remain substantially unchanged when laser 16 is vertically moved. However, the volumetric dimensions of diverging portion 18c will vary based on the distance between laser 16 and surface 30.
An example of suitable volumetric dimensions for converging portion 18b include an inverted cone having a height between laser 16 and focal point 18a ranging from about 5 centimeters to about 15 centimeters and a top base diameter of about 5 centimeters. Examples of suitable volumetric dimensions for diverging portion 18c include a cone having corresponding vectors to converging portion 18b with a height between focal point 18a and surface 30 ranging from about 7 centimeters to about 40 centimeters.
Control 20 is a programmable logic controller (PLC) that controls the operation of laser 16 based on received signals, including signals from pedal actuator 22 and safety system 24. Control 20 may control the operation of laser 16 in a variety of manners. For example, control 20 may cause laser 16 to generate laser beam 18 having an intensity at an operating level. The operating level allows laser beam 18 to laser process the work pieces (e.g., welding, cutting, and surface treating). Additionally, control 20 may cause laser 16 to reduce the intensity of laser beam 18 from the operating level to a standby level, which is a low or zero intensity level. Examples of suitable standby levels for laser beam 18 include intensities that substantially meet the exposure restrictions described in ANSI Z136.1-2000. The intensity of laser beam 18 may be reduced to the standby level by restricting power to laser 16, preventing power to laser 16, defocusing laser beam 18, redirecting laser beam 18, beam dumping (e.g., directing laser beam 18 into a water-cooled beam dump), and combinations thereof.
The user operates laser 16 with pedal actuator 22, which is a pedal-operated actuator switch for operating laser 16. Pedal actuator 22 is disposed adjacent base 12 and communicates with control 20 via line 34. Pedal actuator 22 switches from a first state to a second state when the user depresses pedal actuator 22, where the states of pedal actuator 22 dictate control of laser 16 by control 20. The first state (non-depressed) directs control 20 to deactivate laser 16, or alternatively, cause laser 16 to generate laser beam 18 at the standby level. The second state (depressed) directs control 20 to cause laser 16 to generate laser beam 18 at the operating level. As such, laser 16 requires the user to manually depress pedal actuator 22 to generate laser beam 18 at the operating level for laser processing.
Nominal hazard zone 28 of laser beam 18 is an hourglass-shaped volume located around laser beam 18 that represents a region of greatest risk of skin exposure to laser beam 18. As such, to reduce the risk of direct exposure to laser beam 18 at the operating level, hand 26 of the user should remain outside of nominal hazard zone 28 while laser beam 18 is generated.
Nominal hazard zone 28 is vertically centered around focal point 18a and extends around converging portion 18b and diverging portion 18c. The vertical distances that nominal hazard zone 28 extends above and below focal point 18a may vary based on the power intensity of laser beam 18. In one embodiment, shown in
As further shown in
The remaining volume within housing 14 that is not occupied by nominal hazard zone 28 is referred to as secondary hazard zone 36 of laser beam 18, which is an ocular hazard zone. During laser processing, portions of laser beam 18 may reflect or scatter off the work pieces in a variety of directions. Housing 14 blocks the reflected and scattered portions of laser beam 18 from directly reaching the user's location outside of housing 14, particularly the user's eyes. However, housing 14 does not directly protect hand 26 of the user while disposed within housing 14.
Safety system 24 of the present invention protects hand 26 of the user while disposed within housing 14, such as when the user is manipulating work pieces within housing 14. Safety system 24 includes glove 38, tether 40, pulley 42, magnet 44, sensor 46, and line 48. Glove 38 is a protective barrier capable of receiving hand 26, and is secured to housing 14 around opening 32. Glove 38 includes ribbed portion 50, which is an accordion-like or bellows-like portion of glove 38 that is biased toward housing 14 in the direction of arrow 52. As such, glove 38 is biased toward a retracted position, as shown in
The material of glove 38 absorbs reflected and scattered portions of laser beam 18 within secondary hazard zone 36. This reduces the risk of potential exposure of hand 26 to laser radiation while disposed within housing 14. Examples of suitable materials for glove 38 include standard rubber glove compounds, such as nitrile-based compounds, neoprene-based compounds, styrene butadiene-based compounds, and combinations thereof. In alternative embodiments, glove 38 may be substituted for other protective barriers that provide exposure protection.
In addition to the exposure protection provided by glove 38, safety system 24 also protects the user by reducing the intensity of laser beam 18 to the standby level when hand 26 is within nominal hazard zone 28 of laser beam 18. This is accomplished with magnet 44 and sensor 46, where sensor 46 determines the position of hand 26 within housing 14 based on the distance between magnet 44 and sensor 46. Magnet 44 is a signal-producing component that emits a magnetic field, and is connected to glove 38 via tether 40. Tether 40 includes first end 40a connected to glove 38 and second end 40b connected to magnet 44. In an alternative embodiment, tether 40 may be integrally formed with glove 38. In another alternative embodiment, where glove 38 is not used, first end 40a of tether 40 may be attached to hand 26 of the user (for example, at the wrist). Pulley 42 is rotatably secured at a fixed position that is offset from base 12 and housing 14. Tether 40 extends over pulley 42 such that lateral motion of first end 40a of tether 40 translates to vertical motion of second end 40b of tether 40.
Sensor 46 is a magnetically-actuated switch capable of sensing the magnetic field of magnet 44. Examples of suitable devices for sensor 46 include a Hall sensor and a reed switch. Sensor 46 is secured to base 12 and communicates with control 20 via line 48. Sensor 46 switches between a first state and second state based on whether sensor 46 senses the magnetic field of magnet 44. Sensor 46 is in the first state when the magnetic field is not sensed, and switches to the second state when the magnetic field is sensed.
The states of sensor 46 direct the control of laser 16 by control 20. The first state of sensor 46 does not direct control 20 to control laser 16 in any particular manner. As such, laser 16 generates laser beam 18 at the operating level when the user depresses pedal actuator 22. The second state of sensor 46, however, directs control 20 to cause laser 16 to reduce the intensity of laser beam 18 from the operating level to the standby level, regardless of the other received signals. As such, the signal associated with the second state of sensor 46 overrides signals from pedal actuator 22, and reduces the intensity of the laser beam 18 to the standby level even when pedal actuator 22 is in the second state.
Whether sensor 46 senses the magnetic field of magnet 44 is generally based on the distance between magnet 44 and sensor 46, which is correspondingly based on the position of hand 26 of the user. For example, when hand 26 is in the retracted position shown in
In alternative embodiments of the present invention, magnet 44 and sensor 46 may be substituted with other forms of signal-producing components and corresponding sensors, such as linear encoders, signal-threshold sensors that compare signal strengths to minimum signal thresholds, and other components known in the art. Additionally, magnet 44 may be movably connected to a guide rail to limit the range of lateral motion of magnet 44. Furthermore, glove 38 may be physically restrained by a tie back (e.g., a chain or a cable) connected to housing 14. The length of the tie back between housing 14 and glove 38 may be selected to physically prevent glove 38 from entering nominal hazard zone 28.
In one embodiment of the present invention, magnet 44 and sensor 46 are positioned such that sensor 46 senses the magnetic field of magnet 44 and switches states when hand 26 of the user enters nominal hazard zone 28. When the user extends hand 26 from the retracted position toward nominal hazard zone 28, magnet 44 vertically raises. As such, magnet 44 moves closer to sensor 46. When hand 26 reaches nominal hazard zone 28, magnet 44 is close enough to sensor 46 for sensor 46 to sense the magnetic field of magnet 44. Control 20 then causes laser 16 to reduce the intensity of laser beam 18 to the standby level, as discussed above. This automatically reduces the intensity of laser beam 18 to a safe or zero-intensity level while hand 26 of the user is disposed within nominal hazard zone 28. Therefore, the user is not required to manually deactivate laser 16 to work within nominal hazard zone 28.
When the user moves hand 26 toward the retracted position, magnet 44 vertically lowers, thereby moving away from sensor 46. When hand 26 exits nominal hazard zone 28, sensor 46 no longer senses the magnetic field of magnet 44. Sensor 46 then switches back to the first state, and the intensity of laser beam 18 increases back to the operating level in response to the user depressing pedal actuator 22. As such, while depressing pedal actuator 22, the user may repeatedly move hand 26 in and out nominal hazard zone 28 without the worry of accidental exposure to laser beam 18. Safety system 24 reduces the intensity of laser beam 18 to a safe or zero-intensity level while hand 26 is within nominal hazard zone 28 and allows the intensity of laser 16 increase back to the operating level when hand 26 leaves nominal hazard zone 28. This reduces the risk of exposure to laser beam 18, thereby increasing safety when working with laser 16.
Glove 138 functions in the same manner as discussed above in
The fluorescent materials allow glove 138 to emit light at a particular wavelength (referred to herein as “signal-wavelength light”) when glove 138 absorbs UV-wavelength light. In particular, when UV-wavelength light is directed at glove 138, electrons of the fluorescent materials in glove 138 absorb photons from the UV-wavelength light, causing the electrons to jump from their original energy states to higher energy states. Photons are then released from glove 138 when the electrons drop down to lower energy states. However, the lower energy states obtained differ from the original energy states, which results in the released photons having longer wavelengths than the UV-wavelength light. The particular wavelength of the photons emitted from glove 138 (i.e., the signal-wavelength light) generally depends on the types and concentrations of the fluorescent materials used.
Emitter/sensor 154 is disposed within housing 114 and is a combined emitter/sensor system that includes Lw-beam emitter 156 and sensor 158. Example of suitable systems for emitter/sensor 154 include the trade designated “UVX 100” and “UVX 300” Luminescence Sensors, which are commercially available from EMX Industries, Inc., Cleveland, Ohio.
UV-beam emitter 156 is a signal-producing component that emits UV beam 160. UV beam 160 is a diverging beam directed toward surface 130, and which extends around laser beam 118, as shown in
UV beam 160 is desirably positioned such that it encompasses focal point 118a of laser beam 118, which is the location of the maximum power density of laser beam 118. Even more desirably, UV beam 160 is positioned such that it substantially encompasses a nominal hazard zone of laser beam 118 (not shown), similar to nominal hazard zone 28 discussed above in
Sensor 158 is a sensor for sensing signal-wavelength light emitted toward emitter/sensor 154. Sensor 158 includes electronics that generate an output signal to control 120 via line 148. The output signal has a first state and a second state based on whether sensor 158 senses signal-wavelength light having an intensity that equals or exceeds a preset threshold. The output signal of sensor 158 is in the first state when sensor 158 does not sense any signal-wavelength light or when the intensity of sensed signal-wavelength light does not exceed the preset threshold. The output signal of sensor 158 switches to the second state when the intensity of sensed signal-wavelength light equals or exceeds the preset threshold.
The preset threshold prevents the output signal of sensor 158 from accidentally switching to the second state due to the detection of background signal-wavelength light. For example, during a laser operation such as welding, a measurable amount of signal-wavelength light may be emitted from melted metal of the work pieces. Therefore, the preset threshold is desirably set above the intensity of such background signal-wavelength light. This allows sensor 158 to discriminate between sensed signal-wavelength light emitted from glove 138 and background signal-wavelength light. Accordingly, UV-beam emitter 156 desirably emits UV beam 160 at an intensity that allows glove 138 to emit signal-wavelength light at an intensity that is greater than the preset threshold. This allows the portions of signal-wavelength light emitted from glove 138 toward emitter/sensor 154 to exceed the preset threshold.
The states of the output signal of sensor 158 direct the control of laser 116 by control 120 in a similar manner to that discussed above in
Whether sensor 158 senses signal-wavelength light is generally based on the position of hand 126 of the user and glove 138. For example, when glove 138 is in the retracted position shown in
When the user extends hand 126 within UV beam 160, portions of UV beam 160 absorb into glove 138, which causes signal-wavelength light to emit from glove 138. While the emitted signal-wavelength light is scattered within housing 114, portions of signal-wavelength light are directed toward emitter/sensor 154. Sensor 158 then senses these portions of signal-wavelength light. Because the sensed portions of signal-wavelength light are emitted from glove 138, the intensities exceed the preset threshold. Control 120 then correspondingly causes laser 116 to reduce the intensity of laser beam 118 to the standby level. This automatically reduces the intensity of laser beam 118 to a safe or zero-intensity level while hand 126 of the user is disposed within UV beam 160. Therefore, the user is not required to manually deactivate laser 116 to work within the region of UV beam 160.
When the user moves hand 126 toward the retracted position, glove 138 exits UV beam 160. As a result, sensor 158 no longer senses signal-wavelength light. The output signal of sensor 158 then switches back to the first state, and the intensity of laser beam 118 increases back to the operating level in response to the user depressing pedal actuator 122. As such, while depressing pedal actuator 122, the user may repeatedly move hand 126 in and out UV beam 160 without the worry of accidental exposure to laser beam 118. Safety system 153 reduces the intensity of laser beam 118 to a safe or zero-intensity level while hand 126 is within UV beam 160 and allows the intensity of laser 116 increase back to the operating level when hand 126 leaves UV beam 160. This reduces the risk of exposure to laser beam 118, thereby increasing safety when working with laser 116.
In an alternative embodiment to that disclosed in
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, while laser apparatuses 10 and 110 are each disclosed above as having a single safety system (e.g., safety systems 24 and 152), multiple safety systems of the present invention may be used. In particular, a pair of safety systems 24 of the present invention are desirably used so that the user may safely work with both hands within housing 14. Alternatively, multiple safety systems 152 may be used to increase the volumetric coverage of UV beams 160. Additionally, while the present invention is disclosed in use with a laser processing system, the present invention is suitable for use with any system that employs a laser.
