Abstract:
A table saw has a movable cutting tool for cutting a workpiece in a cutting region. The table saw includes a detection system to detect one or more conditions between a person and the cutting tool and a retraction system associated with the detection system. The retraction system retracts the cutting tool away from the cutting region independently of the motor and disengages the cutting tool from driving rotation with the motor upon detection of the one or more conditions by the detection system.

Description:
[0001]    This application claims the benefit of and priority from U.S. Ser. No. 60/444,263 filed Jan. 31, 2003, the entire contents of which is incorporated herein by reference.  
         [0002]    The present invention relates to table saws and more particularly to a table saw with an improved retraction system for the saw blade. 
     
    
     
       BACKGROUND  
         [0003]    Table saws are a type of woodworking machinery used to cut workpieces of wood, plastic, and other materials. Table saws include a flat surface or table with a circular saw blade extending up through a slot in the table. A user slides a workpiece on the table against and past the blade while the blade is spinning to cut the workpiece. It is desirable to provide a system to retract the blade in response to detection of one or more conditions.  
         SUMMARY  
         [0004]    According to the present invention a table saw having a cutting region for cutting workpieces includes a motor driving a movable cutting tool for cutting workpieces in the cutting region, a control system including a logic controller, a detection system adapted to detect one or more conditions between a person and the cutting tool, and a reaction system associated with the detection system and the cutting tool wherein the reaction system is configured to retract the cutting tool at least partially away from the cutting region and to disengage the motor driving the cutting tool upon detection of at least one of the conditions by the detection system. Desirably, the motor indirectly drives the cutting tool so that the time to retract the cutting tool from the cutting region can be reduced. In addition, by providing an indirect driving of the cutting tool, the driving engagement of the cutting tool can be interrupted when the cutting tool is retracted. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 shows an exemplary table saw that incorporates the retraction system of the present invention.  
         [0006]    [0006]FIG. 2 shows another exemplary table saw that incorporates the retraction system of the present invention.  
         [0007]    [0007]FIG. 3 is a schematic block diagram of the table saw in accordance with the present invention.  
         [0008]    [0008]FIG. 4 is a fragmentary schematic perspective view of a table saw with a retraction system and with the blade removed to better show the system.  
         [0009]    [0009]FIG. 5 is a fragmentary schematic side view of a table saw with a retraction system and with the blade in a cutting or operating position.  
         [0010]    [0010]FIG. 6 is a fragmentary schematic side view of a table saw with a retraction system and with the blade in a retracted position. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0011]    Referring now to FIG. 1, one type of table saw  10  is shown and it includes a support frame  20  on which is mounted a working table  24 . As is conventional, the table saw  10  has a cutting assembly  130  which includes a motor  140  and a cutting tool  150  driven by the motor  140  (see FIG. 3). The working table  24  has an elongated generally rectangular opening  26  through which the cutting tool or blade  150  can project. The working table  24  may also have a blade guard  28 , desirably formed of a transparent plastic material, for covering the exposed portion of the saw blade  150 . A blade adjustment mechanism or handle  30  is mounted to the front of the support frame  20 . The blade adjustment mechanism  30  can vary the extent by which the blade  150  projects above the surface of the working table  24  and to vary the inclination of the blade  150  relative the surface of the working table  24 .  
         [0012]    For ease of reference but without limiting the scope of the claims, the present invention will be described in connection with a table saw  10  of the type shown in FIG. 1. It is contemplated, however, that the features of the present invention will be equally applicable to the “contractors” type of table saw  10  depicted in FIG. 2. This type of table saw  10  includes, a working table  24  through which a blade  150  extends from beneath the table through an opening  26 . The table  24  and blade  150  are supported by a frame  20  and legs  22 . The frame  20  encloses the mechanics that support, position, and drive the blade  150 . A motor  140  to drive the blade  150  can be positioned in or outside the frame  20 . A blade adjustment mechanism, such as a handle  30 , is used to adjust the position of the blade  150  relative to the table  24 , for example, how far the blade  150  extends above the table  24  or how the blade  150  tilts relative to the top of the table  24 .  
         [0013]    Turning now to FIG. 3, a schematic of the table saw  10  of the present invention is shown. The table saw  10  includes a power source  32 , a cutting system  130  and a control system  40 . The control system  40  includes a detection subsystem  50 , a logic controller  60 , and a reaction subsystem  70 . The detection system  50  is adapted to detect one or more conditions such as the close proximity between a portion of the human body and the cutting tool  150 . The detection system  50  may also be adapted to detect when the human body or a portion thereof such as a hand, is in close proximity to the opening  26  or the blade cover  28 . When the detection system  40  detects one or more conditions, the control system  40  is configured to retract the blade  150  from a position extending above the top of the table  24  to a position below the table top  24 . One embodiment of the control system is described in U.S. Ser. No. 60/444,263 filed Jan. 31, 2003, the entire contents of which are incorporated herein by reference.  
         [0014]    The logic controller  60  is configured to control the table saw in response to the inputs it receives. For example, the logic controller  60  may be adapted to receive inputs from a variety of sources including the detection subsystem  50 , the reaction subsystem  70 , and the cutting system  130 . The logic controller  60  may also include one or more sensors adapted to monitor selected parameters of the table saw.  
         [0015]    In addition, the logic controller  60  typically includes one or more instruments operable by a user to control the table saw  10 . The instruments may include start/stop switches, speed controls, direction controls, etc. The logic controller  60  may also be connected to receive the user&#39;s inputs via the various instruments as well as inputs from other sources (not shown) such as blade motion sensors, workpiece sensors, etc. to control the cutting system  130  and/or the reaction system  70 . The logic controller  60  may have a predetermined response to the inputs received. For example, the logic controller  60  can activate various features of the reaction subsystem  70  depending on the detection signal received from the detection subsystem  50 . In one embodiment of the control system  40 , an output signal or series of signals activates at least one element within the reaction subsystem  70 .  
         [0016]    In another embodiment, the logic controller  60  can cause the reaction subsystem  70  to activate the retraction subsystem  76 , disable movement of the cutting blade  150 , activate a visual light  72  or audible sound  74 , or rapidly effectuate any combination thereof. When the logic controller  60  outputs a signal to the reaction subsystem  70  to activate the retraction subsystem  76 , the logic controller  60  can also send a signal to the reaction subsystem  70  to activate the retraction system  76 , to provide the user with a visual signal  72  that a body part is in close proximity to the blade  150 , blade guard  28 , opening  26 , or another area near the blade  150 .  
         [0017]    Once activated in response to a signal indicating the presence of one or more conditions, the reaction subsystem  70  is configured to retract the blade  150 . The reaction subsystem  70  is configured to substantially simultaneously retract the blade  150  (move the blade to a position below the table top), disable a restraining mechanism  170 , as well as optionally providing a visual light  72  and/or an audible sound such as a beeper  74 .  
         [0018]    As noted above, the table saw  10  includes a suitable power source  32  to provide power to the cutting system  130  and the control system  40 . The power source  32  may be an external power source such as line current, or an internal power source such as a battery. Alternatively, the power source  32  may include a combination of both external and internal power sources. Furthermore, the power source  32  may include two or more separate power sources, each adapted to power different portions of the table saw  10 .  
         [0019]    Turning now to FIG. 4 one embodiment of a table saw  10  with a reaction subsystem  70  that incorporates a retraction system  76  according to the present invention is shown. Advantageously, according to the retraction system  76  of the present invention, the blade  150  can be retracted below the table  24  without moving the motor  140 . As a result, the energy or force to drop the blade  150  below the table  24  is reduced, which should allow the blade  150  to move downward very rapidly and possibly at a velocity greater than the approach velocity of the user. In addition, because the motor  140  is not moving with the blade  150 , the energy required to be dissipated to stop the downward motion of the blade  150  is less, thus minimizing unwanted rebound of the blade  150 . Moreover, by advantageously configuring the components of the retraction system  76 , when the blade  150  is dropped (retracted), the blade  150  is no longer in driving engagement with the motor  140 . As a result, the blade  150  will stop spinning and the need to dissipate the energy of the spinning motor  140  is eliminated.  
         [0020]    The table saw  10  includes a trunion  100  to carry the motor  140 , a riving knife  120 , and the retraction system  76 . The trunion  100  includes a first side  102 , a second side  104 , a front  106 , a rear  108 , a top  110 , and a bottom  112 . The trunion  100  also has an angled portion  114  that connects the top  110  with the front  106  and below which the blade  150  rests in the retracted position (See FIG. 6). The trunion  100  can be adjusted up or down or at an angle with respect to the top of table  24  by use of the adjustment mechanism or handle  30 , as is known in the art. As a result, the blade  150  can be adjusted with respect to the top of the table  24 .  
         [0021]    The trunion  100  also is provided with an upper stop  116  located on the first side of the trunion  102  where the angled portion of the trunion  114  connects the top of the trunion  110 . The upper stop  116  provides a stop for a swing arm  160  to preclude further upward pivoting of the swing arm  160  and thus further upward movement of the blade  150 .  
         [0022]    In a desired embodiment, the motor  140  indirectly drives the blade  150  through an arbor  152  upon which the blade  150  is secured by a nut  154  or similar fastener. A drive  144  connects the motor shaft  142  with the blade arbor  152 . The drive  144  may be a belt, split-apart gear box, or other known driving mechanisms. The motor  140  is shown as being mounted on a side of the trunion opposite the blade  150  with the motor shaft  142  extending through an opening of the trunion. It will be understood, however, that the motor  140  can be conveniently located so long as motor  140  indirectly drives the blade  150  so that as the blade  150  retracts the blade arbor  152  will not be driven by the motor  140 .  
         [0023]    The blade arbor  152  is carried on a swing arm 160 , which has a first end  160  and a second end  166  with the first end  160  being pivotally connected  164  to the front portion of the trunion  106 . The pivotal connection  164  can be implemented in any known fashion so long as the swing arm  160  is free to pivot from a blade operating position (shown in FIG. 5) to a blade retracted position (shown in FIG. 6). In one embodiment, the swing arm  160  is at an angle of about 27° from the horizontal when the blade  150  is in the operating position. It is contemplated that the swing arm  160  can be provided at different suitable angles depending on the requirements of the table saw  10  and the construction of the trunion  100 .  
         [0024]    A restraining mechanism  170  is operatively associated with the second end of the swing arm  166  to restrain the swing arm  160  from moving to the blade retracted position from the blade operating position. It will be appreciated that during operation of the blade  150  (i.e., cutting movement of the blade), the swing arm  160  will normally be urged in an upward direction. As a result, the restraining mechanism  170  need only provide sufficient force to retain the swing arm  160  and thus the blade  150  in the blade operating position, when the blade  150  is not moving. Suitable restraining mechanisms  170  include, but are not limited to, a shear pin, a spring loaded ball within a detent in the trunion  100  such that the ball engages a detent in the second end of the swing arm, or vice versa, a fusible material such as a nickel chrome wire, stainless steel wire, etc such that the fusible material melts under a predetermined electrical current density, a magnetic solenoid that is demagnetized either upon electrical activation or electrical deactivation or similar apparatus to restrain the swing arm  160  from downward movement.  
         [0025]    The retraction system  76  also includes an actuator  180  that contacts the second end of the swing arm  166  to provide a downward force sufficient to overcome the restraining force of the restraining mechanism  170  to allow the swing arm to swing downwardly or to push the swing arm in a downward direction. For example, if the restraining mechanism  170  is a shear pin, the actuator  180  must provide a sufficient force to shear the pin and force the swing arm  160  in a downward direction. Desirably, in one embodiment, the actuator  180  provides a force greater than the restraining mechanism  170  force such that the additional force aids in the downward movement of the swing arm  160 . Depending on the desired configuration, the actuator  180  may be activated or deactivated depending upon receiving a signal as an indication of detection of one or more conditions.  
         [0026]    The actuator  180  may be any mechanism that can apply a force to the second end of the swing arm  166  sufficient to drive the swing arm  160  in a downward direction. In one embodiment, the actuator  180  is solenoid with a plunger such that when the solenoid is energized the plunger extends outward from the solenoid contacting a portion of the second end of the swing arm  166  to drive the swing arm  160  downward. Alternatively, the solenoid could be configured such that upon deenergization of the solenoid, the plunger extends outward.  
         [0027]    In another embodiment, the actuator  180  may be an explosive charge. The explosive charge may be provided in a cavity formed on a portion of the trunion  100  adjacent the second end of the swing arm  166  such that the detonation energy is forced against the second end of the swing arm  166  to drive the swing arm  160  in a downward direction.  
         [0028]    At least one lower stop  118  is provided to contact and stop the downward movement of the swing arm  160  and thus the saw blade  150  at a retracted position below the top of the table  24 . The lower stop  118  is located on the same side of the trunion  100  as the swing arm  160  and is positioned so that the blade  150  may retract a sufficient distance. Desirably, the lower stop  118  is located such that the swing arm  160  is at angular distance from the horizontal that is less than the angular distance of the swing arm  160  when the blade is in the operating position. For example, if the swing arm  160  is at 27° from the horizontal when the blade is in the operating position, then the swing arm  160  should be at an angular distance less than −27° from the horizontal, e.g., about −25°. Advantageously, by providing this difference in angular distance, the drive  144  coupling motor shaft  142  with the blade arbor  152  will be disengaged (or loosened in the case of the belt) from the motor shaft  142 . In other words, the motor  140  will not be driving the blade  150  when the blade  150  is in the blade retracted position.  
         [0029]    In addition, because the swing arm moves or acts independently of the motor, the swing arm may be accelerated in a downward direction faster than if the swing arm moved with the motor. As a result, the blade should be retracted from the operating position faster than if the swing arm moved with the motor. In other words, the cutting tool and/or swing arm can move independently of the motor which can remain stationary or move independently of the cutting tool and/or swing arm.  
         [0030]    Desirably, the lower stop  118  is formed of any of a number of impact-absorbing materials such as elastomeric materials, rubber, foams, plastics, etc. to minimize any upward rebound or bounce of the swing arm  160 , which might cause the blade  150  to extend above the table top  24 .  
         [0031]    A riving knife  120  is provided at the rear of the trunion  108  and it extends upward from the top of the trunion  110 . The riving knife  120  is secured in position to act as a shield for the rear portion of the blade  150 . The riving knife  120  has a front portion  122  adjacent and spaced from the blade  150 . The riving knife  120  is stationary with respect to the blade  150 . The top of the front portion of the riving knife  122  follows the contour of the blade  150  but it is rearwardly tapered to allow the blade  150  to retract without contacting the riving knife  122 .  
         [0032]    The present invention is applicable to table saws and provides a control system wherein a cutting tool is retracted upon the occurrence of a specified one or more conditions, such as when it is detected that a portion of a human body is in proximity with the cutting tool. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.