Patent Publication Number: US-7211972-B2

Title: Power tool with remote stop

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation of U.S. application Ser. No. 10/898,157, filed Jul. 23, 2004, now U.S. Pat. No. 7,064,502, which is in turn a continuation-in-part of and claims priority under 35 USC § 120 to U.S. application Ser. No. 10/720,022, filed Nov. 21, 2003, now abandoned, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/428,371, filed Nov. 22, 2002. Said U.S. application Ser. Nos. 10/898,157 and 10/720,022 and U.S. Provisional Application Ser. No. 60/428,371 are herein incorporated by reference in their entirety. 

   FIELD OF THE INVENTION 
   The present invention generally relates to the field of power tools, and more particularly to a power tool having a wireless remote stop. 
   BACKGROUND OF THE INVENTION 
   Current power tools typically have a power button located on a main body of the tool. However, the placement of such a button does not allow for remote stopping of a working element of the tool, such as stopping a saw blade of a table saw, or the like. For example, a user may wish to terminate power to a saw blade. Currently, the user must locate the power button on the tool and activate it for stopping the blade. Moreover, a user may desire a different location for the power button. 
   Thus, it would be desirable to provide a remote stop for a power tool, for remotely terminating the flow of electricity to an electric motor driving a working element of the tool. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a power tool including a wireless remote stop for terminating the flow of electricity to an electric motor. In embodiments, the electric motor is configured for operating a working element of a power tool, such as a saw blade of a table saw. For example, the wireless remote stop may be used to terminate power to a motor driving a saw blade via a belt connected to an arbor. In another instance, power is terminated to a motor driving a cutting bit. The wireless remote stop may be implemented as a hand-held device, as a foot pedal disposed of a housing, and the like. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
       FIG. 1  is an isometric view of a table saw including a wireless remote stop in accordance with an exemplary embodiment of the present invention; 
       FIG. 2  is an isometric view of a table saw including a wireless remote stop in accordance with another exemplary embodiment of the present invention; 
       FIG. 3  is a block diagram of transmission circuitry for use with a wireless remote stop in accordance with an exemplary embodiment of the present invention; and 
       FIG. 4  is a block diagram of reception circuitry for use with a power tool including a wireless remote stop in accordance with an exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
   Referring to  FIGS. 1 and 2 , a power tool  100  including a wireless remote stop  108  for terminating the flow of electricity to an electric motor is described in accordance with an exemplary embodiment of the present invention. In embodiments, the electric motor is constructed for operating a working element of a power tool, such as a circular saw blade, a grinding element, a drilling element, a shaping element, or the like for performing a task. In an embodiment, the wireless remote stop is utilized to terminate power to a motor driving a saw blade via a belt connected to an arbor. The working tool assembly/working tool element (e.g. the arbor and circular saw blade or the cutting bit) is for performing a task on a workpiece. For example, the working tool element may shape the workpiece using cutting teeth, abrasive material, and other shaping surfaces. In a presently illustrated embodiment, the power tool  100  including the wireless remote stop  108  is utilized with a power tool such as a table saw  102  having a working tool element such as a saw blade  104 . Those of skill in the art will appreciate that the wireless remote stop of the present invention may be integrated with various other power tools, including band saws, belt sanders, drill presses, grinders, lathes, and the like. 
   The power tool includes a receiver  106  configured to receive a wireless signal from the wireless remote stop. The receiver may include an antenna, an infrared (IR) receiver, a magnetic sensor, and the like. In an embodiment, the receiver may include an antenna configured to receive a radio frequency (RF) signal from the wireless remote stop. In another embodiment, the receiver  106  is configured to sense magnetic flux from a wireless remote stop disposed within a certain distance range of the table saw  102 . In a further embodiment, the receiver is configured to receive an IR signal from the wireless remote stop. A decoder is coupled to the receiver  106  for recognizing an encoded signal wirelessly received by the receiver. In the present example, the decoder is communicatively coupled with a first switch included in the table saw  102  for interrupting power supplied to an electric motor of the table saw. The decoder communicates with the first switch for terminating the flow of electricity to the electric motor upon recognition (via the decoder) of an encoded signal wirelessly received via the receiver  106 . For example, the electric motor of the table saw is operatively connected to the saw blade  104 , e.g. driving a belt connected to the saw blade via an arbor. Thus, mechanical energy supplied to the saw blade is interrupted upon recognition of an encoded wireless signal, eventually causing the saw blade to stop. In further embodiments, an invasive breaking system may be integrated with table saw  102  and the wireless remote stop  108 . For instance, a mechanical break, an electrical break, or another breaking mechanism initiated by the wireless remote stop may be used for stopping the saw blade  104 . 
   A remote stop  108  is wirelessly coupled with the receiver  106 . The remote stop includes an encoder for encoding a signal and a transmitter coupled to the encoder. The transmitter is configured to transmit a signal encoded by the encoder. However, the transmitter may also transmit additional wireless signals, including signals for communicating with other receivers. For example, the transmitter may transmit a signal to a third party or to an assembly incorporating an indicator such as a light. The transmitter may include an antenna, an infrared (IR) transmitter, a magnet, and the like. In an embodiment, the receiver may comprise an antenna configured to transmit an RF signal from the wireless remote stop. In another embodiment, the transmitter may be configured to generate magnetic flux to a receiver disposed within a certain distance range of the remote stop  108 . In a further embodiment, the transmitter may be configured to supply an IR signal to the receiver  106 . The remote stop  108  also includes a second switch for initiating wireless transmission via the transmitter of a signal encoded via the encoder. In embodiments, this signal is encoded for recognition by the decoder, which communicates with the first switch for terminating the flow of electricity to the electric motor, as previously described. In this manner, activation of the second switch causes termination of the flow of electricity to the electric motor of the table saw  102 , when the encoded wireless signal is recognized by the decoder in communication with the first switch. 
   In an embodiment, the remote stop  108  is a hand-held fob, having a housing and a button  110 . Alternatively, the remote stop may be implemented as an apparatus including a foot pedal  112 , disposed in a housing and placed on a shop floor, a mat, or the like, such as conveniently placed within reach of an operator&#39;s foot. It will be appreciated that a remote stop may be implemented in a variety of housings for transmitting a wireless signal. The button  110 , the foot pedal  112 , or the like for selective actuation by an operator of the table saw  102 , is coupled to the second switch. For instance, the button  110  may activate the second switch when pressed, while the foot pedal  112  may activate the second switch when stepped on. Alternatively, the second switch may be activated when pressure is released from the button, the foot pedal, or the like. In one instance, continual actuation of the button  110 , the foot pedal  112 , or a like mechanism is required for preventing activation of the second switch. In another embodiment, a device for sensing an abrupt acceleration is employed in combination with the second switch. For example, an accelerometer is implemented with a remote stop for sensing an abrupt motion for triggering the second switch; such as if the remote stop  108  is implemented as a wrist band, or the like. 
   It should be noted that discrete frequency ranges may be used for wireless signals transmitted by various remote stops. For instance, a first frequency range is used for a band saw while another frequency range is used for the table saw  102 . In other embodiments, the signal strength may be varied for preventing unintended activation of the first switch when a remote stop is activated from a distance. For example, a supervisor utilizing a hand-held remote stop from various locations on a shop floor may require a remote stop having a greater signal range than a remote stop placed on the shop floor adjacent to a power tool, such as the table saw  102 . In another instance, the power tool may include components for determining the range of the remote stop  108  from the power tool, such as for ensuring that the remote stop  108  has not been removed from the immediate area. If such determination is made, to for instance, the power tool may terminate power to the motor or prevent the tool from being activated. 
   Preferably, a wireless signal utilized by the power tool  100  including the wireless remote stop  108  is an RF signal, but may comprise another type of wireless signal, such as an infrared signal or the like for wireless communication. Additionally, more than one type of signal may be transmitted by the remote stop. In embodiments, different signals may be used for alerting others of a condition. For instance, a wireless signal may be transmitted for triggering a notification light  112  associated with the table saw  102 . The wireless signal may be the same signal used to stop the saw blade  104 , or possibly of a different type. Further, the wireless signal or another signal may be used to alert a remote monitoring agency, or the like. In such instances, the remote stop may include multiple buttons, foot pedals, or the like, each additional implement for alerting one or more parties. In a still further embodiment, the remote stop may include a microphone and/or a speaker, for allowing direct communication between the user and a third party. For example, the table saw operator may speak with a third party reached through a telephone switch exchange using the power tool  100  including the wireless remote stop  108 . 
   In embodiments, the remote stop  108 , held or worn by the operator or implemented as a foot pedal, is activated by the operator for terminating the flow of electricity to the electric motor of the table saw  102 . The activation may be performed by depressing the button  110 , stepping on the foot pedal  112 , or removing a foot from the foot pedal  112 . Alternatively, the activation may be performed when pressure is released from the button, the foot pedal, or another mechanism. For instance, a pressure sensitive mat may be placed adjacent to the table saw  102 , such that power is terminated if an operator steps off of the mat. The signal is encoded and transmitted as a wireless signal. The wireless signal is received and then decoded for terminating the flow of electricity to the electric motor via the first switch. The process of encoding and decoding ensures that the wireless signal is an expected signal and not a stray signal, in order to ensure that a wireless signal received for terminating power to the motor is a valid signal. 
   The remote stop  108  may be configured for sending a wireless signal by reloading software code into an internal processor or memory, setting a transmission pulse length, setting a level of transmission power, selecting options such as whether to send a signal to an external indicator or provide an alert to an external device, setting a range, identifying a receiver device by an address, identifying a receiver device by a serial number and revision number, and the like. A determination is made as to whether manual activation of the remote stop has occurred. A determination may also be made as to whether a condition has occurred within the remote stop to warrant the transmission of a wireless signal. For example, the remote stop  108  may transmit a signal indicating a low battery condition, or another condition requiring the attention of an operator. If not, the remote stop may enter or remain in a low power mode, such as for extending battery life. If activation has occurred, a signal may be encoded and transmitted. 
   The wireless sensor/receiver of the power tool  100  including the wireless remote stop  108  may be mounted on the table saw  102 . In embodiments, the power to the table saw is controlled through a control device including the first switch, such as a high current relay coupled with the receiver. For example, the first switch may be integrated into a controller (such as a controller including an on and off switch, a toggle switch, or the like) for supplying power to the electric motor, terminating power to the electric motor, and/or controlling a level of power supplied to the electric motor. Such a controller may include a power button or the like for controlling the supply of power to the motor. The first switch may be integrated into the controller, coupled between the controller and the motor, or supplied with the motor. An operator may install or carry the remote stop  108  to remote locations. For example the remote stop may be worn at waist level. The remote stop may attach to the operator&#39;s belt or waistband of clothing by various mechanical attachments, such as a clasp to the operator&#39;s belt. In an additional embodiment, a remote stop is worn on the wrist of the operator by a strap or the like. The remote stop may also be worn on an operator&#39;s head. For example, the remote stop may be incorporated in various apparel or eyewear. In another alternative, the foot pedal  112  is utilized. The foot pedal may activate a switch for transmitting the wireless signal when depressed. For example, an operator may step onto or off of the foot pedal  112 . A spring return mechanism, a plastic bellows, or another similar mechanism may be used to maintain the foot pedal in a normally open (i.e. non-activated) position. An external indicator  114  may be provided externally to the table saw  102  and the operator for alerting the operator to a pending condition or alerting co-workers to a condition. The indicator may be a steady light, a flashing/strobe light, a buzzer, or another similar indicator. 
   Preferably, the first switch is integrated in the electric system included in the table saw  102 . In embodiments, the electric system of the table saw  102  is coupled with a power source, such as an alternating current (AC) power outlet. Each receptacle of the AC power outlet has two or three slots or holes to accept the prongs of a power cord included with the table saw  102 . In an embodiment, the first switch is installed on or within a housing of the table saw  102 , through which the electrical power supply is supplied to the tool. The housing may also contain a power supply controller. The first switch and the power supply controller may be housed separately. 
   Preferably, the remote stop is formed of plastic or the like, with button  110  prominently disposed in the housing of the remote stop  108 . In an advantageous embodiment, the button  110  is large enough in comparison to the housing and conveniently located for access without causing undue false tripping. In the present embodiment, the remote stop  108  is powered by a battery. Additionally, an indicator, such as a light  116 , may be provided to notify an operator of low battery conditions. Control elements may also be placed on the remote stop  108  to change characteristics, such as the length and intensity of the wireless signal pulse. The control elements may include enablement or disablement of certain functions, such as providing a signal to an external alert mechanism. Suitable control elements include rotary knobs, push button switches, or the like. In further embodiments, the remote stop may be implemented to vibrate, such as to gain attention when an audible warning would be ineffective. 
     FIG. 3  illustrates an exemplary embodiment  200  of transmission circuitry for use with a wireless remote stop in accordance with an exemplary embodiment of the present invention. When the button is pressed, switch  202  is activated, and a change of voltage level is presented to a processor  204 . In embodiments, a normally closed switch or a normally open switch may be used. Instead of a manually activated switch, a switch may be used which is activated when not substantially oriented in a desired orientation; for example, a switch may be activated when the remote stop  108  is inverted, rapidly accelerated, or the like. The processor  204  may be a Programmable Interrupt Controller (PIC) or other microprocessor. Software code may be downloaded onto the microprocessor to perform the functions of the remote stop  108 . The processor  204  provides a signal to the encoder  206  that then provides an encoded signal to the transmitter/antenna  208 . Alternatively, an infrared light emitting diode may be used for infrared communications. Booster circuitry may be incorporated as needed or desired; for example, a booster transistor may be used to supply greater current to the transmitter/antenna  208 . The power source of the remote stop is preferably a battery. The remote stop may also have a battery backup. In an additional embodiment, a low battery detector circuit may be provided. For example, a low battery detector circuit may include a voltage divider formed of two resistors providing a voltage to the base (or gate) of a transistor. Either or both resistors may be made variable to adjust the voltage applied to the base. When the base voltage drops below a threshold (such as if the power source decreases), the transistor is turned on. This causes a current to flow through the indicator, such as a light emitting diode (LED). The diode is used to isolate the battery from an electrolytic capacitor. The electrolytic capacitor helps to supply sufficient current to the indicator when the battery grows too weak. 
     FIG. 4  illustrates an exemplary embodiment  300  of reception circuitry for use with a power tool including a wireless remote stop in accordance with an exemplary embodiment of the present invention. An antenna  302  receives a radio frequency signal. In the current embodiment, the antenna is coupled to a receiver module that provides a signal to a decoder  304 . The radio frequency signal is decoded by the decoder  304 . A processor  306  included in the table saw  102  including the wireless remote stop  108  determines the command associated with the signal. A power cut-off signal may be transmitted directly to a switch  308  to cut off the power supplied to the power tool. Alternatively, the power cut-off command may be latched by a latch that then controls the actuator of the cut off switch. Another switch may determine whether a latched control signal, a momentary signal, or a signal of limited duration is applied to the switch  308 . The signal selection made by switch may be set manually by a Dual In-line Package (DIP) switch or may be set through the processor  306 . The switch  308  may be opened automatically or may be limited to manual release only. Various glue logic, booster circuits, protective circuits, and the like are contemplated by the present invention. 
   Those of skill in the art will appreciate that while preferred embodiments of the power tool  100  including the wireless remote stop  108  have been described as including an encoder for encoding a signal and a decoder for decoding a signal, the use of such an encoder and decoder is not necessary for the functioning of the present invention. For example, an RF signal may be transmitted on a pre-selected discrete wavelength or range of wavelengths for receipt by the receiver  106 . Upon receipt of a signal transmitted on the pre-selected wavelength, the first switch may be activated for terminating power to the working tool element of the power tool. For instance, the receiver  106  is communicatively coupled with the first switch included in the table saw  102  for interrupting power supplied to the electric motor of the table saw. The receiver communicates with the first switch for terminating the flow of electricity to the electric motor upon receipt of a wireless signal transmitted on the pre-selected wavelength. Similarly, the transmitter may be coupled with the second switch, for transmitting a signal on the pre-selected wavelength when the second switch is activated. It will be appreciated that other signals may be used as well, including RF signals, magnetic signals, and the like for being received by the receiver  106 . 
   It is believed that the present invention and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes.