Patent Publication Number: US-8534174-B2

Title: Pyrotechnic actuator and power cutting tool with safety reaction system having such pyrotechnic actuator

Description:
BACKGROUND 
     Many types of power tools have exposed blades, such as table saws and other power cutting tools. Contact between the blade and an object other than a workpiece can be dangerous. Safety systems to mitigate potentially dangerous conditions are continually being developed. Some such safety systems include a blade-drop mechanism that drops the blade below the working surface of the power tool when contact or near-contact with a foreign object is detected, for example. In some instances, such blade-drop mechanisms are actuated by a pyrotechnic actuator. Improved pyrotechnic actuators for these and other applications are needed. 
     SUMMARY 
     In one general aspect, the present disclosure is directed, in part, to a pyrotechnic actuator that can be manufactured with low cost manufacturing processes yet still perform very reliably. In one embodiment, the pyrotechnic actuator can be used in a power cutting tool, such as part of a blade-drop reaction system for a table saw. In such an embodiment, the pyrotechnic actuator can comprise a housing defining a cavity therein, a piston positioned at least partially within the cavity, and an insert-molded unitary assembly positioned within the cavity. The unitary assembly comprises a piston engagement member and a base. A sealed void is defined intermediate the piston engagement member and the base. The unitary assembly comprises a breakable member extending intermediate the piston engagement member and the base and a pyrotechnic initiator positioned at least partially within the base. The pyrotechnic initiator, upon application of a current pulse thereto, is configured to generate a pressurized gas in the sealed void that exerts a force on the piston engagement member and breaks the breakable member, thereby causing the piston engagement member and the piston to move relative to the base and the housing. 
     In another general aspect, the present disclosure is directed, in part, to a pyrotechnic actuator comprising a housing defining a cavity therein and an opening therethrough, and a unibody assembly positioned at least partially within the cavity. The unibody assembly comprises a piston assembly and a base. A portion of the piston assembly is configured to extend through the opening. A void is defined intermediate the piston assembly and the base. The unibody assembly comprises a frangible member extending intermediate the piston assembly and the base and a pyrotechnic initiator. The base is configured to receive at least a portion of the pyrotechnic initiator. The pyrotechnic initiator, upon application of a current pulse thereto, is configured to generate a pressurized gas in the void that exerts a force on the piston assembly and breaks the frangible member thereby causing the piston assembly to move relative to the base and the housing. 
     In another general aspect, the present disclosure is directed, in part, to a power cutting tool comprising a safety reaction system that comprises a pyrotechnic actuator. In such a power cutting tool, the pyrotechnic actuator actuates the safety reaction system that drops the blade out of a danger zone, such as below a tabletop or working surface for a table saw, for example, when a dangerous condition is detected by a detection system. In one embodiment, the power cutting tool comprises a working surface defining an opening therein, a blade configured to extend into the opening, a detection system for detecting a dangerous condition relative to the blade, and a safety reaction system in communication with the detection system. The safety reaction system is configured to cause the blade to move below the working surface when triggered by the detection system. The safety reaction system can comprise the pyrotechnic actuator described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Various non-limiting embodiments of the present disclosure are described herein in conjunction with the following figures, wherein: 
         FIG. 1  is a perspective view of a power cutting tool comprising a detection system and a safety reaction system for a blade in accordance with one non-limiting embodiment; 
         FIG. 2  is an illustration showing certain features of the power cutting tool of  FIG. 1  in accordance with one non-limiting embodiment; 
         FIG. 3  is a side view of a safety reaction system of a power cutting tool, illustrating a blade in a normal operating position in accordance with one non-limiting embodiment; 
         FIG. 4  is a side view of the safety reaction system of  FIG. 3 , illustrating the blade in a partially retracted position in accordance with one non-limiting embodiment; 
         FIG. 5  is a side view of the safety reaction system of  FIG. 3 , illustrating the blade in a fully retracted position in accordance with one non-limiting embodiment; 
         FIG. 6  is a perspective view of a pyrotechnic actuator mounted on a portion of a safety reaction system of a power cutting tool in accordance with one non-limiting embodiment; 
         FIG. 7  is a perspective view of a pyrotechnic actuator, conductors, and a connector interface in accordance with one non-limiting embodiment; 
         FIG. 8  is a perspective view illustrating how a pyrotechnic actuator assembly connects to an electrical system of a safety reaction system and/or detection system of a power cutting tool in accordance with one non-limiting embodiment; 
         FIG. 9  is a side view of the pyrotechnic actuator of  FIG. 7  with part of the housing cut away and the pyrotechnic actuator in the non-deployed position in accordance with one non-limiting embodiment; 
         FIG. 10  is a side view of the pyrotechnic actuator of  FIG. 9  in the deployed position in accordance with one non-limiting embodiment; 
         FIG. 11  is a side view of a unibody assembly configured to be positioned at least partially within a housing of a pyrotechnic actuator in accordance with one non-limiting embodiment; 
         FIG. 12  is a cross-sectional view taken along line  12 - 12  of  FIG. 11  in accordance with one non-limiting embodiment; 
         FIG. 13  is a cross-sectional view taken along line  13 - 13  of  FIG. 11  in accordance with one non-limiting embodiment; 
         FIG. 14  is a perspective view of the unibody assembly of  FIG. 11  in accordance with one non-limiting embodiment; 
         FIG. 15  is a view of a pyrotechnic actuator assembly being packaged in accordance with one non-limiting embodiment; and 
         FIG. 16  is a view of the pyrotechnic actuator assembly of  FIG. 15  packaged in accordance with one non-limiting embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various non-limiting embodiments of the present disclosure will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of a pyrotechnic actuator and a power cutting tool comprising the pyrotechnic actuator disclosed herein. One or more examples of these non-limiting embodiments are illustrated in the accompanying drawings. It will be appreciated that the pyrotechnic actuators and power cutting tools specifically described herein and illustrated in the accompanying drawings are non-limiting example embodiments and that the scope of the various non-limiting embodiments of the present disclosure are defined solely by the claims. The features illustrated or described in connection with one non-limiting embodiment can be combined with the features of other non-limiting embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. 
     Various embodiments of the present disclosure are directed to a pyrotechnic actuator. In one application, the pyrotechnic actuator can be utilized to actuate a safety system of a power cutting tool, such as a blade-drop mechanism or safety reaction system of a power cutting tool, such as a table saw, for example. Such safety systems take a danger-mitigating action in response to detection of a dangerous or potentially dangerous condition relative to the blade of the power cutting tool. Before describing the details of the pyrotechnic actuator of the present disclosure, details regarding such a power cutting tool that may employ the pyrotechnic actuator in a safety system are described. 
     In one embodiment, the pyrotechnic actuator can be employed, for example, in a safety system or safety reaction system of a table saw.  FIG. 1  shows one type of example table saw  10 . The table saw  10  comprises a table (or table top)  12  through which a circular blade  14  extends from beneath the table  12 . The table  12  comprises a throat plate  13  that defines an elongated slot through which a portion of the circular blade  14  can extend. A workpiece (not shown), such as a piece of wood, can be placed on the cutting or working surface  15  of the table  12  and can be cut by the portion of the blade  14  extending above the cutting surface  15 . The table  12  and the blade  14  are supported by a housing  16  and legs  18 . The housing  16  can enclose the mechanisms that support, position, and drive the blade  14 . The housing  16  can also comprise a processor-based system for detecting a dangerous condition relative to the blade  14 , as described below, and/or a processor-based system for detecting a condition of the blade  14  (e.g., whether it is spinning). A motor to drive the blade  14  can be positioned in or outside of the housing  16 . A switch  20  can be used to turn the saw on and off, causing the blade  14  to spin when turned on. A handle  22  can be used to manually adjust the position of the blade  14  relative to the table  12 . For example, using the handle  22 , an operator of the table saw  10  can adjust how far the blade  14  extends above the table  12  or how the blade  14  tilts relative to the cutting surface  15  of the table  12 . A user places a workpiece on the table  12  and slides it into the blade  14  to cut the workpiece. Table saws take many different configurations, from large saws sized for industrial use to small saws that can be placed on a bench top or counter, and table saws come with various types of tables and housings. The safety and other mechanisms described herein can be employed in most any type of table saw, as will be apparent from the description below. The table saw  10  can also comprise a riving knife, a blade guard, and/or various other conventional components. 
       FIG. 2  is a diagram showing certain features of the table saw  10  according to various embodiments of the present disclosure. The blade  14  can be mounted to an arbor or a rotatable blade shaft  38 . A motor  40  can drive the arbor  38  to spin the blade  14 . The blade  14  can be directly driven by the motor  40  or indirectly driven through the use of one or more drive belts, chains, and/or gears.  FIG. 2  illustrates that the table saw  10  can comprise a detection system  30  that can be used to detect a potentially dangerous condition with respect to the blade  14 , such as when a foreign object (e.g., an object other than the workpiece) contacts or comes into close proximity to the blade  14 , for example. The detection system  30  is in communication with a safety reaction system  32  (or danger-mitigating system), which takes a danger-mitigating action when triggered and/or actuated by the detection system  30  in response to detection of the dangerous condition. 
     In one embodiment, the detection system  30  can comprise a contact detection system that detects when a foreign object (e.g., different from the workpiece that is intended to be cut by the blade  14 ) contacts the blade  14 . In other embodiments, the detection system  30  can comprise a proximity detection system that detects when the foreign object is dangerously proximate to the blade  14 . Such a contact detection system can comprise a capacitive contact sensing system that detects contact of the foreign object with the blade  14  based on a change in an electrical signal on the blade  14  due to the change in capacitance when the foreign object contacts the blade  14 . More details regarding such capacitive contact sensing detection systems  30  can be found in the following patent documents, which are hereby incorporated by reference herein in their entirety: (1) U.S. patent application Ser. No. 11/481,549, entitled “Capacitive Sensing System For Power Cutting Tool,” filed on Jul. 6, 2006; (2) U.S. Pat. No. 7,739,934, entitled “Detection System For Power Tool,” issued on Jun. 22, 2010; and (3) U.S. Pat. No. 7,640,835, entitled “Apparatus And Method For Detecting Dangerous Conditions In Power Equipment,” issued on Jan. 5, 2010. Other suitable detection systems, including non-contact detection systems, are described in the following patent documents, which are hereby incorporated by reference herein in their entirety: (1) published PCT WO/2010/059786, entitled “Safety Mechanisms for Power Tools,” filed on Nov. 19, 2009; (2) U.S. Pat. No. 7,421,932, entitled “Power Cutting Tool Comprising A Radar Sensing System,” issued on Sep. 9, 2008; and (3) U.S. Patent Appl. Publ. No. 2010/0037739, entitled “Power Cutting Tool With Overhead Sensing System,” published on Feb. 18, 2010. 
     In various embodiments, still referring to  FIGS. 1 and 2 , the safety reaction system  32  can serve to mitigate the potentially dangerous condition detected by the detection system  30 . In one embodiment, the safety reaction system  32  can drop the blade  14  below the tabletop  12  when triggered or actuated. Examples of such safety reaction systems are described in U.S. Pat. No. 7,628,101, entitled “Pyrotechnic Drop Mechanism For Power Tools,” issued on Dec. 8, 2009, and U.S. Pat. No. 6,922,153, entitled “Safety Detection And Protection System For Power Tools,” issued on Jul. 26, 2005, both of which are hereby incorporated by reference herein in their entirety. 
     In one embodiment, referring to  FIGS. 3-5 , a side view of the safety reaction system  32  for use with a power cutting tool is illustrated. The safety reaction system  32  is indicated generally at  110 . In  FIG. 3 , the blade  14  is in a normal operating position near a riving knife  117 . In  FIG. 4 , the blade  14  is shown to be in a partially retracted position as would occur during operation of the safety reaction system  32 , and in  FIG. 5 , the blade  14  is in a fully retracted position below the working surface  15  of the table top  12 , which is approximately at the elevation shown in  FIGS. 3-5 . The blade  14  rotates on a shaft  116  that is journaled in a generally triangularly shaped arm  118  that has a curved lower surface  120 . The arm  118  rotates around another shaft  122  that is attached to a large plate  124  that is mounted to the table saw  10  by mounting brackets  126  and  128  located on opposite ends of the plate  124 . The plate  124  carries a motor base  130  that is mounted above the elevation of the plate  124  and carries a motor  135  for driving the blade  14 . 
     The output shaft of the motor  135  is not shown, but it can carry a pulley, which drives a belt  134  and a pulley  136  according to various embodiments. The pulley  136  is connected to another pulley or has an extension for driving a belt  138  that in turn drives a pulley  140  that is operatively connected by the shaft  116  to an arbor (not illustrated), but which drives the blade  14 . Since the arm  118  is pivotable about the shaft  122 , it should be understood that the motor  135  is configured to drive the belts  134  and  138  via the motor pulley and the pulley  136  regardless of the vertical position of the blade  14 . Stated another way, the distance between the pulleys  136  and  140  can remain constant, as does the distance between pulley  136  and the motor draft shaft, regardless of the vertical position of the blade  14 . 
     In one embodiment, when the blade  14  is in the normal operating position as illustrated in  FIG. 3 , the top right surface of the arm  118  abuts against a stop member  141  that is mounted to the plate  124  by a mounting bracket  142  using bolts  144 . The arm  118  is held in the upper position as shown in  FIG. 3  by a detent assembly, indicated generally at  146 , that comprises a main bracket that is bolted to the plate  124  by bolts  150 , wherein a detent rod  152  engages a V-shaped recess  154 . The detent rod  152  is biased into engagement with the recess  154  by a spring  156  that is seated on a bolt  158  and which is adjustable to vary the biasing force that is applied to the detent rod  152 . The detent assembly  146  is therefore designed and configured to maintain the arm  118  in its normal operating position unless it is rotated downwardly with sufficient force to depress the detent rod  152  away from the V-shaped recess  154  and release the arm  118  for rotation. 
     The force that is necessary to overcome the detent assembly  146  is provided by a firing mechanism or a pyrotechnic actuator that is indicated generally at  160 . Various embodiments of pyrotechnic actuators will be discussed in greater detail below.  FIGS. 4 and 5  illustrate an example embodiment of a pyrotechnic actuator  160  being actuated. As the piston  180  of the pyrotechnic actuator  160  is deployed from a housing of the pyrotechnic actuator  160 , a hammer  183  is driven in the leftward direction causing the arm  118  to rotate in the clockwise direction around the shaft  122  and drop and/or fire the blade  14  into the retracted position below the working surface  15 . Support members  198  are bolted to the plate  124  by bolts  200 . 
     In one embodiment, an anvil  202  is connected to the arm  118  by a pair of pins  204 , a pair of bolts  206 , as well as by a strap  208  that is bolted on opposite ends to the anvil  202  and the arm  118 . It should be apparent that the front surface of the hammer  183  is in contact with the adjoining surface of the anvil  202  so that when the pyrotechnic actuator  160  is activated, the piston  180  will cause the hammer  183  to move the anvil  202  and the arm  118  in a clockwise direction so as to retract the blade  14  below the table  12  or working surface  15  thereof before an operator is injured by the blade  14 . 
     When the pyrotechnic actuator  160  receives a current pulse initiated from the detection system  30 , the piston  180  is forced outwardly to move the anvil  202  as it does so. This pushing force overrides the detent assembly  146  and the arm  118  rotates and/or is fired in a clockwise direction. Since the arm  118  and the hammer  183  are not physically connected, (i.e., they only touch) the arm  118  is free to continue rotating even though the piston  180  stops moving after being fully deployed. The arm  118  continues to rotate until it contacts a mechanical stop that is not shown, at which time its movement ends. 
     Various pyrotechnic actuators that are currently available may not be considered for use in many high volume applications due to the high costs of designing and manufacturing such actuators. The pyrotechnic actuators of the present disclosure, however, incorporate unique features which allow low cost design and manufacturing methods to be utilized without compromising safety, quality, and/or design integrity. Some features of the pyrotechnic actuators of the present disclosure are that they can be constructed to be tamper-proof and can be viewed to determine whether they have been actuated. 
     In one embodiment, referring to  FIG. 6 , a pyrotechnic actuator  260  of the present disclosure is illustrated positioned within a safety reaction system  132  on a table saw. The safety reaction system  132  can comprise similar components as that described above in relation to  FIGS. 3-5  and the safety reaction system  32 . 
     In one embodiment, referring to  FIGS. 7-14 , the pyrotechnic actuators of the present disclosure will now be described in greater detail. In various embodiments, the pyrotechnic actuator  260  can comprise a housing  282  having a cavity  284  defined therein. The housing  282  can also define an opening  286  defined therethrough on an end thereof or at another suitable location. In various embodiments, the housing  282  can be comprised of a metallic material, such as aluminum, for example. In one embodiment, a portion of the generally cylindrical piston  280  can extend from the housing  282  even when the piston  280  is in the non-deployed position (see e.g.,  FIGS. 7-9 ). In other various embodiments, the piston  280  can be positioned inside the housing  282  when the piston  280  is in the non-deployed position. The piston  280  can be attached to or formed with a unitary assembly, as discussed below. 
     In one embodiment, referring to  FIGS. 8 and 12 , the pyrotechnic actuator  260  can be in communication with a connector interface  288  through conductors  290 . The conductors  290  are configured to transmit a current pulse from the connector interface  288  to an initiator  292 , such as a pyrotechnic initiator, for example, within the housing  282  to cause the piston  280  to move from the non-deployed position into the deployed position. The current pulse can be initiated from the detection system  30  when a dangerous condition is detected. In various embodiments, the initiator  292  can be a conventional initiator or a pyrotechnic initiator. In one embodiment, the connector interface  288  can be connected to a mating connector  294  (see,  FIG. 8 ) attached to conductors  296  in electrical communication with, for example, an amplifier (not shown) that amplifies the signal from the detection system  30  of the power cutting tool. In one embodiment, the connector interface  288  can have male pins while the mating connector  294  can be configured to receive such male pins or, in other embodiments, the mating connector  294  can have male pins while the connector interface  288  can be configured to receive such male pins. As a result, when the detection system  30  detects a dangerous condition, a current pulse can be delivered through the conductors  296 , through the mating connector  294 , through the connector interface  288 , through the conductors  290 , through a ferrite filter  291 , and to the initiator  292  within the housing  282 . 
     In one embodiment, referring to  FIGS. 9-14 , a unitary assembly or an insert-molded unitary assembly  300  can be positioned within the housing  282 . In various embodiments, the unitary assembly  300  can comprise a piston assembly  302  comprising a piston engagement member  304  and the piston  280 . In various embodiments, the piston assembly  302  can be formed of a single component or material comprising the piston  280  and the piston engagement member  304  or, in other embodiments, can be formed of more than one component or material comprising the piston  280  and the piston engagement member  304 . In one embodiment, the piston engagement member  304  can be formed separate from the piston  280 , but attached to the piston  280 . In an embodiment where the piston engagement member  304  is attached to the piston  280 , the piston engagement member  304  can comprise an annular groove  306  in a face thereof and the piston  280  can comprise an annular projection  308  extending from an end thereof (see,  FIG. 12 ). The annular projection  308  is configured to be engaged with the annular groove  306  to engage the piston  280  with the piston engagement member  304  in an interlocking fashion. In one embodiment, an adhesive can be used to aid the engagement of the annular projection  308  with the annular groove  306 . In other various embodiments, the piston  280  can be engaged with or connected to the piston engagement member  304  in other suitable ways known to those of skill in the art. In one embodiment, the piston assembly  302 , the piston  280 , and/or the piston engagement member  304  can comprise an annular groove  303  configured to receive a sealing member, such as an o-ring, for example. The piston assembly  302  and/or the piston  280  can comprise a ramped portion  305 . In one embodiment, the piston  280  can be a cold-drawn piston and the piston engagement member  304  can be formed with the unitary assembly  300 . In various embodiments, the piston  280  can be comprised of a metallic material, while the unitary assembly  300  can be comprised of a non-metallic material, such as nylon 70G, for example. 
     In one embodiment, referring to  FIGS. 9-14 , the unitary assembly  300  can comprise a base  310  on an opposite end as the piston assembly  302 . The initiator, or micro-gas generator,  292  is positioned on the base  310  or is positioned at least partially or fully within a cavity formed in the base  310 . The conductors  290  can extend through the base  310  to the initiator  292  and can be configured to direct a current pulse from, for example, an amplifier (not shown) that amplifies a signal from the detection system  30  to the initiator  292 . The base  310  can comprise an annular groove  312  defined therein which is configured to receive a sealing member, such as an o-ring, for example. In one embodiment, the base  310  can house a ferrite filter  291  in communication with the conductors  290  and the initiator  292 . 
     In one embodiment, still referring to  FIGS. 9-14 , the unitary assembly  300  can comprise at least one frangible, separatable, and/or breakable member  314  (hereafter “frangible member”). The at least one frangible member  314  can extend from the base  310  to the piston engagement member  304  or to the piston assembly  302 , if the piston  280  is formed with the piston engagement member  304 . In various embodiments, the frangible member  314  can comprise a plurality of frangible struts, such as two to four, for example, extending between the base  310  and the piston engagement member  304  or the piston assembly  302 . The plurality of frangible struts can be arranged in any suitable configuration, such as the configuration illustrated in  FIG. 13 , for example. In various embodiments, the frangible members  314  can comprise a portion that is frangible, separatable, and/or breakable, while the remainder of the frangible members  314  are not frangible, separatable, and/or breakable. In other various embodiments, the frangible members  314  can comprise score lines, reduced material portions (e.g., smaller perimeter, diameter, and/or thickness), weakened portions, and/or perforated portions. In such an embodiment, the frangible members  314  can be configured to break along or about such score lines, reduced material portions, weakened portions, and/or perforated portions after ignition of the initiator  292 . In still other various embodiments, the frangible members  314  can break at or proximate to their attachment to the base  310  or the piston assembly  302  or the piston engagement member  304 . In one embodiment, the frangible members  314  can be comprised of a non-metallic material, such as Nylon 70G, for example. In various embodiments, the frangible members  314  can be formed of the same materials as the piston assembly  302 , the piston engagement member  304 , the piston  280 , and/or the base  310 . The frangible members  314  can have any suitable cross-sectional shape, such as round, ovate, rectangular, square, and/or triangular, for example, and can have any suitable length between the base  310  and the piston assembly  302  based on the size and purpose of a particular pyrotechnic actuator. The frangible members  314  can be configured and constructed such that they will only break upon actuation of the pyrotechnic initiator  292 . 
     In one embodiment, a bushing  316 , such as a step bushing, for example, can be positioned within the cavity  284  of the housing  282 . The bushing  316  can be positioned on an end of the housing  282  most distal from the base  310 . The bushing  316  can define a bore  318  therethrough configured to receive a portion of the piston  280 . The bore  318  can be aligned with the opening  286  in the housing  282 , such that, upon actuation of the pyrotechnic actuator  260 , the piston  280  can extend longitudinally through the bore  318  and the opening  286 . In one embodiment, referring to  FIGS. 7 and 8 , when the piston  280  of the pyrotechnic actuator  260  is in the non-deployed position, the piston  280  can at least partially extend through the bore  318  and the opening  286 . In one embodiment, the piston  280  can extend from the housing  282  a first distance prior to actuation of the pyrotechnic initiator  292  (see,  FIG. 9 ) and can extend from the housing  282  a second distance after actuation of the pyrotechnic initiator  292  (see,  FIG. 10 ). In one embodiment, the piston assembly  302  and/or the piston  280  can be in a first position relative to the base  310  and/or the housing  282  prior to ignition of the pyrotechnic initiator  292  and can be in a second position relative to the base  310  and/or the housing  282  after ignition of the pyrotechnic initiator  292 . 
     In one embodiment, the bushing  316  can be comprised of a rubber material and can be used to decelerate the piston  280  and/or the piston assembly  302  as the piston  280  and/or the piston assembly  302  is moved or fired into the deployed position after actuation of the pyrotechnic initiator  292 . In various embodiments, the piston  280  and/or the piston assembly  302  can be decelerated when the ramped portion  305  engages a portion of the bushing  316  distal from the opening  286  in the housing  282 . In one embodiment, the bushing  316  can serve as an environmental seal to prevent, or at least inhibit, foreign materials from entering the cavity  284  of the housing  282 . The bushing  316  can also be used to prevent, or at least inhibit, flames from escaping out of the cavity  282  during actuation of the initiator  292 . The bushing  316  can have different shapes and sizes based on a particular application. 
     In one embodiment, referring to  FIGS. 7-10 , the housing  282  can comprise an exterior wall  320  and an interior wall  322 . The exterior wall  320  can comprise at least one annular groove therein. In one embodiment, the exterior wall  320  can comprise a first annular groove  324  and a second annular groove  326 . The first and second annular grooves  324  and  326  can be formed by crimping the housing  282 , for example, or through other suitable methods. In one embodiment, through formation of the first and second annular grooves  324  and  326 , annular lips or projections can be formed in the interior wall  322 . The annular lips or projections can also be formed using other methods. A first lip or projection  328  can be formed by the first annular groove  324  and a second lip or projection  330  can be formed by the second annular groove  326 . The first and second lips or projections  328  and  330  can each extend inwardly into the cavity  284  toward the unitary assembly  300 . The first lip or projection  328  can engage the base  310  prior to and after actuation of the pyrotechnic initiator  292 . In essence, the first lip or projection  328  can maintain the base  310  in position during and after actuation of the pyrotechnic initiator  292  by contacting the base  310  and preventing, or at least inhibiting, the base  310  from moving toward the opening  286  in the housing  282 . The second lip or projection  330  can engage the piston  280  and/or the piston assembly  302  after actuation of the pyrotechnic initiator  292 . Stated another way, the second lip or projection  330  can engage the piston  280  and/or the piston assembly  302  to help decelerate and/or stop the piston  280  and/or the piston assembly  302  after actuation of the pyrotechnic initiator  292 . In one embodiment, the second lip or projection  330  can be positioned proximate to the bushing  316 . In various embodiments, the ramped portion  305  of the piston  280  and/or the piston assembly  302  can engage the second lip or projection  330  to decelerate and/or stop the piston  280  and/or the piston assembly  302  after actuation of the pyrotechnic initiator  292 . In one embodiment, the lips or projections  328  and  330  may not be provided. In such an embodiment, the base  310  can be glued or otherwise fixed to the housing  282  as the same location as illustrated and the bushing  316  can act to decelerate the piston  280  and/or the piston assembly  302 . 
     In one embodiment, although not illustrated, the first and second annular grooves  324  and  326  may not be provided on the exterior wall  320  of the housing  282 . Lips or projections, however, may still be formed on the interior wall  322 . In one embodiment, the lips or projections formed on the interior wall  322  can be discontinuous about the perimeter of the interior wall  322 . For example, the lips or projections may only extend about a portion of the perimeter of the interior wall  322 , such as about 50%. In other embodiments, the first lip or projection  328  and/or the second lip or projection  330  can be formed of a plurality of discontinuous portions. The lips or projections can have any suitable size and shape. In one embodiment, the lips or projections can have a wedge or triangular shaped cross-section such that they can better maintain the base  310  in the suitable position and decelerate the piston  280  and/or the piston assembly  302 . 
     In one embodiment, referring to  FIG. 9 , a void  332  or a sealed void can be defined intermediate the base  310  and the piston assembly  302  and/or the base  310  and the piston engagement member  304 . The initiator  292  can be in fluid communication with the void  332  to allow gas generated by the initiator  292 , upon actuation, to fill the void  332 . Eventually the gas will fill the void  332  and pressurize the void  332  to such an extent as to cause the frangible member  314  to break, thereby allowing the piston assembly  302  to move relative to the base  310  and/or move away from the base  310 . In one embodiment, an outer perimeter of the base  310 , an outer perimeter of the piston assembly  302 , an outer perimeter of the piston engagement member  304 , and/or an outer perimeter of the piston  280  can sealably engage the interior wall  322  of the housing  282 , such that the void  332  can be sealed from the remainder of the cavity  284  for pressurization. In most instances, if the void  332  is not sealed from the remainder of the cavity  284 , the pyrotechnic actuator  260  will not function property as the pressure differential between the void  332  and the remainder of the cavity  284  may not be sufficient to deploy the piston  280  and/or the piston assembly  302  by breaking the frangible member  314 . 
     In one embodiment, referring to  FIGS. 9-11 , the annular groove  303  in the piston  280 , the piston engagement member  304 , and/or the piston assembly  302  and the annular groove  312  in the base  310  can each be configured to receive a sealing member, such as an o-ring, for example. Such annular grooves  303  and  312  can be omitted, in various embodiments, if sealing members are not provided. A first sealing member  334  can be positioned in the annular groove  303  and a second sealing member  336  can be positioned in the annular groove  312 . In one embodiment, the first sealing member  334  and the second sealing member  336  can be adhesively fixed and/or positioned at least partially within their respective annular grooves  303  and  312 . The first sealing member  334 , when positioned at least partially within the annular groove  303 , can be compressed by the interior wall  322  of the housing  282  to create a seal between the piston  280 , the piston engagement member  304 , and/or the piston assembly  302  and the interior wall  322 . The second sealing member  336 , when positioned at least partially within the annular groove  312 , can be compressed by the interior wall  322  of the housing  282  to create a seal between the body  310  and the interior wall  322 . Such seals can create the sealed void  332 . As discussed above, the sealed void  332  can house pressurized gas generated by the initiator  292  until such time as the at least one frangible member  314  breaks, thereby moving the piston assembly  302  into the deployed position. 
     In one embodiment, when the detection system  30  detects a dangerous condition proximate to the blade  14  or detects a foreign object in contact with or proximate to the blade  14 , the safety reaction system  32  can be activated by the current pulse. The current pulse can be conducted through the conductors  296 , the mating connector  294 , the connector interface  288 , the conductors  290 , the ferrite filter  291  in the conductors  290 , to the initiator  292  to cause the initiator  292  to activate, causing a pyrotechnic explosion. The pyrotechnic explosion generates pressurized gas in the void  332  that eventually causes the frangible members  314  to break owing to the pressure within the void  332  and owing to the force that the pressure creates on the piston engagement member  304  and/or the piston assembly  302 . The base  310  is fixed within the housing  282  by the lip or projection  328  and, as a result, to release the pressure within the void  332 , the piston assembly  302  and/or the piston engagement member  304  moves away from the base  310 . Once the frangible members are broken, the piston assembly  302  and/or the piston engagement member  304  is forced away longitudinally from the body  310  and into the deployed position. In the deployed position, the piston  280  contacts the hammer  183  to cause the safety reaction system  32  to drop or fire the blade  14  below the working surface  15  to prevent, or at least inhibit, contact of the foreign object with the blade  14 . In one embodiment, the pyrotechnic actuator  260  can actuate in less than five (5) milliseconds, for example. Of course, other actuation times are within the scope of the present disclosure based on the particular application of a pyrotechnic actuator. 
     In one embodiment, a power cutting tool, such as the table saw  10 , for example, can comprise a working surface  15  comprising a throat plate  13  defining an opening therein. The power cutting tool can comprise the blade  14  which is configured to extend into the opening, the detection system  30  for detecting a dangerous condition relative to the blade  14 , and the safety reaction system  32  in communication with the detection system  30 . The safety reaction system  32  can be configured to cause the blade  14  to quickly move below the working surface  15  when the safety reaction system  32  is activated by the detection system  30 . The safety reaction system  32  can comprise the pyrotechnic actuator  260  comprising the housing  282 , the piston  280  positioned at least partially within the housing  282 , and an insert-molded unitary assembly  300  positioned at least partially within the housing  282 . The unitary assembly  300  can comprise the piston engagement member  304  and the base  310 . The void  332  can be defined intermediate the piston engagement member  304  and the base  310 . The unitary assembly  300  can comprise the at least one frangible member  314  extending intermediate the piston engagement member  304  and the base  310  and the pyrotechnic initiator  292  positioned at least partially within or on the base  310 . The pyrotechnic initiator  292 , upon application of a current pulse thereto, can be configured to generate a pressurized gas in the void  332  that exerts a force on the piston engagement member  304  to break the frangible member  304 , thereby causing the piston engagement member  304  and the piston  280  to move relative to the base  310  and/or the housing  282 . 
     In one embodiment, a pyrotechnic actuator assembly of the present disclosure can be easily replaced after it is actuated. The pyrotechnic actuator assembly can comprise the pyrotechnic actuator  260 , the connector interface  288 , and the conductors  290 . By merely separating the connector interface  288  from the mating connector  294  and removing the pyrotechnic actuator assembly from the safety reaction system  32 , the pyrotechnic actuator assembly can be replaced with another pyrotechnic actuator assembly comprising the same or similar components. In one embodiment, referring to  FIGS. 15 and 16 , example packaging  338  for the pyrotechnic actuator assembly is disclosed.  FIG. 15  illustrates an exploded view of the packaging  338  and the pyrotechnic actuator assembly, while  FIG. 16  illustrates a perspective view of the pyrotechnic actuator assembly within the packaging  338 . In various embodiments, the packaging  338  can comprise a backsheet  340  and a cover sheet  342 . The backsheet  340  can be comprised of cardboard, other paper-like material, and/or plastic. In one embodiment, the cover sheet  342  can be transparent and can be comprised of plastic or similar material. To assemble the packaging  338 , the pyrotechnic actuator assembly can inserted into recesses within the cover sheet  342  and then the cover sheet  342  can be attached to the backsheet  340  using conventional packaging techniques. 
     Although the pyrotechnic actuators of the present disclosure have been described for use with a power cutting tool, use of such pyrotechnic actuators is not so limited. In fact, many suitable uses exist for the pyrotechnic actuators of the present disclosure. Some example uses include automotive safety restraint systems, defense and aerospace rocket controlled guidance systems, cable cutters, deep hole drilling and mining applications, and fire suppression systems. 
     Various embodiments are also directed to a method of making the pyrotechnic actuator  260 . First, the unibody assembly  300  can be insert-injection molded using a polymer, such as high impact nylon, for example. Other materials that can be used for similar applications include polycarbonate and polyphthalamide. As an alternative to injection molding, reaction injection molding (RIM) can also be used with suitable thermosetting polymers. Also, in various embodiments, die casting processes and powder metal formation processes can be used to form portions of the pyrotechnic initiators of the present disclosure. The unibody assembly  300  can then be installed into the housing  282 , with or without the first and second sealing members  334  and  336 , depending on the intended application of that particular pyrotechnic actuator. The housing  282  can be pre-formed on the end that receives the base  310 . A bushing  316  can be installed in the end of the housing  282  that defines the opening  284 . The end of the housing  282  that defines the opening  284  can then be formed to enclose the unibody assembly  300 . The at least one annular groove  303  or  312  can then be formed on the exterior wall  320  of the housing  282  to form the lips or projections  328  or  330 . 
     All documents cited in the Detailed Description are, in relevant part, incorporated herein by reference in their entirety. The citation of any document is not to be construed as an admission that it is prior art with respect to the present disclosure. To the extent that any meaning or definition of a term in the present disclosure conflicts with any meaning or definition of the term in a document incorporated by reference, the meaning or definition assigned to the term in the present disclosure shall govern. 
     While particular non-limiting embodiments of the present disclosure have been illustrated and described, those of skill in the art will recognize that various other changes and modifications can be made without departing from the spirit and scope of the present disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of the present disclosure.