The present disclosure is directed generally to a laser material processing system and, more specifically, to a laser material processing system configured to suppress uncontrolled or self-sustained combustion.
Laser material processing involves imparting laser energy to materials, most often for material removal. These materials are often combustible and also generate volatile compounds as liquid or vapor when interacting with a laser beam which creates a potential for fire. Some existing systems can automatically suppress fires in small enclosures, but these existing systems are typically geared towards cutting machinery, such as Computer Numerical Control (CNC) mills and lathes. In most cases, the material being processed in these existing systems (usually metal) is not flammable, and it is typically only the atomized coolant/lubricant that ignites. Further, these conventional systems do not include active fume extraction continuously drawing fresh air through the system.
The following disclosure describes various types of laser material processing systems configured to suppress self-sustained combustion and associated apparatuses and methods. As used herein, the term “self-sustained combustion” is used to refer to combustion (e.g., fire) that is uncontrolled or otherwise distinguishable over controlled combustion or non-self-sustained combustion ordinarily produced during the processing of materials and generally confined to the point of interaction between a laser beam and a target material. Certain details are set forth in the following description and
Many of the details and features shown in the Figures are merely illustrative of particular embodiments of the technology. Accordingly, other embodiments can have other details and features without departing from the spirit and scope of the present technology. In addition, those of ordinary skill in the art will understand that further embodiments can be practiced without several of the details described below. Furthermore, various embodiments of the technology can include structures other than those illustrated in the Figures and are expressly not limited to the structures shown in the Figures. Moreover, the various elements and features illustrated in the Figures may not be drawn to scale.
In the Figures, identical reference numbers identify identical or at least generally similar elements. To facilitate the discussion of any particular element, the most significant digit or digits of any reference number refer to the Figure in which that element is first introduced. For example, element 110 is first introduced and discussed with reference to
The processing system 100 also includes a pressurized suppressant supply vessel, or suppressant tank 140, in fluid communication with the processing chamber 112 by a valve 142 and external fluid delivery conduit 143 (“external conduit 143”). As described in greater detail below, the suppressant tank 140 can include a suppressant that suppresses self-sustained combustion. The valve 142 is also electrically coupled to a first sensor 150a and a second sensor 150b (collectively “sensors 150”) by a signal cable 152. The first sensor 150a is at least partially disposed in the processing chamber 112, and the second sensor 150b is at least partially disposed in an exhaust outlet 113 in fluid communication with the processing chamber 112. The sensors 150 can include, for example, thermal switches, flame sensors (e.g., ultraviolet (UV) light sensors), thermocouples, smoke detectors, or other suitable sensors or detectors for sensing the presence of self-sustained combustion. In one embodiment, for example, the sensors 150 can be thermal switches (e.g., bi-metal thermal switches) configured to have a specific switching temperature. For example, in some embodiments a thermal switch can have a switching temperature of about 150° F. In addition, although shown in the illustrated embodiment as disposed in the processing chamber 112 and the exhaust outlet 113, the sensors 150 can be positioned at any of a variety of locations within the processing system 100. Further, in several embodiments, the processing system 100 can include a different number of sensors than shown in the illustrated embodiment of
In some embodiments, the processing system 100 can include one or more redundant suppressant supply vessels, or redundant tanks 146 (shown in hidden lines). Each of the redundant tanks 146 can be coupled to the external conduit 143 (or directly to the processing chamber 112) by fluid delivery conduit 148 and a valve manifold 149 containing a plurality of valves (not shown). In use, the valve manifold 149 can automatically or semi-automatically switch over to one of the redundant tanks 146 after another one of the tanks 140, 146 has been discharged. In one aspect of this embodiment, the redundant tanks 146 can reduce system downtime. In particular, the processing system 100 can immediately or nearly immediately resume processing without having to suspend operation until a replacement tank is installed. In an additional or alternative embodiment, the suppressant tank 140 and the redundant tanks 146 can be configured to collectively dispense suppressant into the processing chamber 112 to increase the volume of suppressant delivered during a combustion detection event.
During laser material processing, and as shown by the arrows, air can flow through the processing chamber 112 to remove byproducts of laser material processing (e.g., smoke and fumes) and to draw fresh air into the processing chamber 112. For example, an exhaust air handler 115 (e.g., a blower; shown schematically) can draw fresh air into the processing chamber 112 through an air inlet 116 and out of the processing chamber 112 through a plenum 118 disposed between the processing chamber 112 and the exhaust outlet 113. In one embodiment, the controller 103 can control the exhaust air handler 115 to regulate the flow of air through the processing chamber 112. In another embodiment described in greater detail below, when the presence of self-sustained combustion is detected, the controller 103 can shut off the exhaust air handler 115 and/or close an exhaust flow gate 119a (e.g., a damper) at the exhaust outlet and/or an exhaust flow gate 119b (e.g., a damper) at the air inlet 116. In yet another aspect of this embodiment, the controller 103 can be configured to move the beam delivery apparatus 130 to a position to minimize interference with the deployment of suppressant into the processing chamber 112. As shown in the embodiment of
In general, when an uncontrolled and self-sustaining fire ignites in a conventional laser material processing system, an operator typically must extinguish a fire with an off-the-shelf, manually operated fire extinguisher. One problem with extinguishing fire in this manner, however, is that manual extinguishers can leave messy residue when discharged, which can lead to hours of cleanup and possible damage to the machine system. Another challenge with conventional laser material processing systems is that an operator may not be able to open the processing chamber to extinguish the fire because there may be a risk of exposure to harmful fumes. Because the operator cannot immediately open the processing chamber, it may take longer to extinguish the fire and thus may lead to further damage to the machine system due to prolonged exposure to the fire.
Laser material processing systems configured in accordance with several embodiments of the present technology, however, address these and other limitations of conventional laser material processing systems. In one aspect of this embodiment, the suppressant 263 can be selected such that there is little or no clean-up after it has been dispensed. For example, inert gases or liquid-phase suppressants can leave little or virtually no residue in the processing chamber 112. Another advantage of the laser material processing systems of the various embodiments is that the operator does not need to open the access port 120 in order to suppress self-sustained combustion with a manual fire extinguisher.
In another aspect of this embodiment, the nozzles 160 can be configured to provide a high volumetric flow of the suppressant 263, but without substantially atomizing or vaporizing the suppressant 263. When in a liquid phase, the suppressant does not substantially atomize or vaporize (if at all). As such, the suppressant 263 can mostly flow downwardly and across the work plane 102 to smother or suppress self-sustained combustion. Also, the liquid-phase suppressant 263 is not rapidly drawn out of the processing chamber 112 by the exhaust.
In various embodiments, the sensors 150 can be configured to distinguish between expected combustion (e.g., non-self-sustained combustion) in the processing chamber 112 and self-sustained combustion that is not expected. More specifically, the sensors 150 can be configured to distinguish between localized combustion at the point of interaction between the laser and the material to be laser processed and the combustion associated with self-sustained combustion, such as fire, that has spread beyond the point of interaction. For example, in one embodiment, if only the sensor proximal to the point of interaction (e.g., the first sensor 150a) detects combustion, the processing system 100 does not dispense the suppressant 263. However, if a less proximal sensor also detects combustion (e.g., the second sensor 150b and/or another sensor in the processing chamber 112), this can indicate that fire has spread beyond the point of interaction with the material to be laser processed, and the processing system can dispense the suppressant 263. As described in greater detail below with reference to
If the presence of self-sustained combustion is detected (decision block 574), the method 570 proceeds to block 576 at which point the suppressant 263 is delivered to the processing chamber 112 (block 576). As discussed above, at least one the sensors 150 can send a signal over the signal cable 152 which causes the valve 142 of the suppressant tank 140 to open and thereby dispense the suppressant 263 into the processing chamber 112 via the nozzles 160. In one embodiment, the valve 142 can remain open such that substantially all of the suppressant in the suppressant tank 140 is dispensed into the processing chamber 112. In an additional or alternate embodiment, the suppressant 263 can be dispensed for a predetermined duration of time (e.g., a dispense time in the range of about 15 to 30 seconds).
In some embodiments, the sensors 150 can open the valve 142 even if the controller 103 were to malfunction or otherwise fail. For example, in the illustrated embodiments, the sensors 150 are not connected to the controller 103. Instead, the signal cable 152 directly connects the sensors 150 to the valve 142. In other embodiments, however, the controller 103 can be an intermediary between the sensors 150 and the valve 142.
In several embodiments, the controller 103 can carry out certain functions when the presence of self-sustained combustion is detected. For example, the controller 103 can produce a signal that causes an audible and/or visible alarm to activate, one or both of the exhaust flow gates 119a and 119b to close, and/or the beam delivery apparatus 130 to move to a predetermined position, such as the home position H shown in
Referring first to
Referring again to
In some embodiments, the processing system 700 can determine the presence of self-sustained combustion based on the rate in change of detected temperature over time (ΔT/t) and by comparing this measurement to a threshold value, such as a threshold rate of change in temperature. For example, the processing system 700 can determine the presence of self-sustained combustion when two or more of the sensors 750 detect a rapid change in temperature that exceeds the threshold. In addition or alternately, the processing system 700 can determine the presence of self-sustained combustion based on the relative location of the triggered sensors. For example, if sensors 750c and 750d detect combustion at the same time, this could be indicative of expected combustion. However, if sensors 750c and 750e (or even further spaced apart sensors) detect combustion at the same time, the could be indicative of the presence of self-sustained combustion.
From the foregoing, it will be appreciated that specific embodiments of the present technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the various embodiments of the present technology. Moreover, because many of the basic structures and functions of laser material processing systems are known, they have not been shown or described in further detail to avoid unnecessarily obscuring the described embodiments. Further, while various advantages and features associated with certain embodiments of the disclosure have been described above in the context of those embodiments, other embodiments may also exhibit such advantages and/or features, and not all embodiments need necessarily exhibit such advantages and/or features to fall within the scope of the disclosure.
The present application claims priority to U.S. Provisional Application No. 61/916,025, filed Dec. 13, 2013, which is incorporated herein by reference in its entirety.
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