Patent Application
20060234617
1. Field of the Invention
Exemplary embodiments of the present invention relate to a power tool configured to identify tool accessories and to a method for controlling a power tool having an accessory coupled thereto.
2. Description of the Related Art
Electrical power tools such as variable speed drills, power screw drivers, circular saws, etc., typically are configured to receive various tool accessories. For example, accessories adapted for a variable speed drill includes drill bits, fastening bits and other cut-out tools. A circular saw includes accessories such as saw blades and abrasives. Each accessory has a given speed or rate at which optimum performance is attained, based on the dimensions and specifications of the given tool accessory.
Generally, power tool speed is selected by a user through manual depression of the trigger switch in the tool. If the power tool has an open-loop motor control circuit, the speed of an output spindle of the tool decrease as the tool is loaded, and current drawn by the motor increase. If a relatively constant output speed is desired, the operator can manually compensate for the reduction in motor speed as the tool is loaded by further retracting the trigger switch. This increases the power applied to the motor. Alternatively, if the power tool has a closed-loop motor control circuit, the control circuit can automatically increase the amount of power supplied to the motor as the output spindle of the tool is loaded, so as to maintain the desired speed.
However, the user (or even the control circuit) generally cannot determine the optimum speed of operation for the accessory. Although in some circumstances the speed ranges of a typical variable speed tool are sufficient to span the operational range of a given tool accessory, the speed may not be the optimum operating speed of the accessory. Thus, desired performance and/or efficiency of the tool accessory may not be achieved when operating the tool.
An exemplary embodiment of the present invention is directed to a power tool. The power tool may include a motor, an output spindle actuatable by the motor, and a tool holder connected to the spindle and configured to hold an accessory therein. The power tool includes an accessory reader to decoding an identification device on the accessory.
Another exemplary embodiment of the present invention is directed to a method of controlling a power tool having an accessory operatively coupled thereto. In the method, the accessory is inserted in the tool and a communication interface between the accessory and tool is read. An accessory identification is decoded via an accessory reader of the tool. A tool setting for the power tool may be accessed based on the decoded accessory identification.
Exemplary embodiments of the present invention will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus are not limitative of the exemplary embodiments of the present invention.
As used herein, power tools may be understood as a corded power tool, or a cordless power tool powered by portable power sources such as nickel cadmium (NiCd), nickel metal hydride (NiMH), lead acid and/or lithium-ion (LI-ion) battery packs. Exemplary power tools may include, but are not limited to, drills, high torque impact wrenches, single-handed metal working tools, nailers, hand planers, circular saws, jig saws, variable speed belt sanders, reciprocating saws, two handed drills such as rotary and demolition hammerdrills, routers, cut-off tools, plate joiners, drill presses, table saws, thickness planers, miter saws, metal working tools, chop saws, cut-off machines, bench grinders, etc. Some of these tools are commercially available only in a corded version, but may become cordless. These classifications are not intended to be inclusive of all power tools for which the exemplary embodiments of the present invention are applied, merely illustrative.
Referring to
In
The battery pack 100 may include a battery pack microprocessor 10 to identify the tool accessory and to set the appropriate optimum speed of tool 200. The microprocessor 10 may be embodied in hardware or software as a digital microcontroller, an analog circuit, a digital signal processor or by one or more digital integrated circuits (IC) such as application specific integrated circuit (ASIC) under control of a suitable microcontroller, for example.
The pack microprocessor 10 may be powered by current generated between terminals A and B. The current can be clamped or discontinued by the use of a semiconductor device 20, for example. Semiconductor device 20 may be a metal oxide semiconductor field effect transistor (MOSFET), for example, under the control of the pack microprocessor 10, although device 20 could be another type of switchable device. The semiconductor device 20 may control the voltage applied across the motor 50 in accordance with, for example, a duty cycle of a pulse width modulated (PWM) control signal received from pack microprocessor 10. PWM is modulation in which the duration of pulses vary based on characteristics of a modulating signal, as is known.
During discharge, the pack microprocessor 10 may output pulse width modulation (PWM) control signals to drive the driver circuit 12. A pulsing semiconductor (e.g., pulse width modulator) is commonly used in the electronics industry to create an average voltage, or an average voltage that is proportional to the duty cycle. In either case, the semiconductor devices 20A and 20B (shown as a discharge FET Q1 and charge FET Q2) may be switched between ON and OFF states to create the average voltages.
Thus, the driver circuit 12 may shift the PWM output of pack microprocessor 10 so as to drive the gate of semiconductor device 20A, cycling the semiconductor device 20A ON and OFF depending on sensed conditions. The semiconductor device 20B may pass current with only a diode drop in voltage, since semiconductor device 20B is reverse-biased. If lower losses are required, the pack microprocessor 10 outputs a command to the driver circuit 12 which maintains the semiconductor device 20B ON during the PWM action. This may result in a controlled discharge with lower losses through the semiconductor device 20B, for example.
During charge, a reverse logic can be applied. Semiconductor device 20A is reversed-biased with respect to current flow, whereas semiconductor device 20B can control the charge current based on information from the microprocessor 10 via driver circuit 12. The component arrangement that comprises the driver circuit 12 is known in the art and not described herein for purposes of brevity.
The pack microprocessor 10 may be powered by an internal power supply. Battery pack 100 may further include a current sensor (not shown) to sense current and provide a signal to the microprocessor 10. Semiconductor devices 20A and/or 20B may include a pull down resistor to act as a bypass for semiconductor device 20 when power is OFF and the pack 100 is dormant.
The battery pack 100 may include one or more temperature sensors (not shown). The temperature sensor(s) may communicate the temperature inside the battery pack 100 to the pack microprocessor 10 and/or an attached tool 200, for example.
Referring to
The pack microprocessor 10 may also access the memory 25 to read a plurality of values stored in a look-up table therein, which may represent varying speeds for a particular tool accessory 60. The memory 25 is operatively connected to the microprocessor 10. The memory 25 may be any non-volatile memory, such as, but not limited, to EPROM and EEPROM. Memory 25 stores information relating to the battery pack 100, such as, but not limited, type of pack, pack capacity and/or charging process. Similarly, the pack microprocessor 10 may direct information related to a charger (not shown) to be stored in memory 25, such as, but not limited to, number of batteries charged, number of times switch was on or activated (i.e., the number of times a refresh mode was selected), number of times the charging process was delayed to allow cooling of the batteries, etc. Further, the pack microprocessor 10 may designate a string of memory slots or “buckets” for storing related information. A detailed teaching of the use of buckets for storing information is described in U.S. Pat. No. 6,218,806 to Brotto et al., which is hereby incorporated by reference in its entirety.
The pack microprocessor 10 can be responsive to a variable speed potentiometer 80 (which may be a variable resistor, for example) located in the tool 200, when pressure is applied to a trigger on tool 200 for desired speed. The variable speed potentiometer 80 measures the value of resistance so as to identify the amount of desired speed. The pack microprocessor 10 may be programmable so as to read a trigger position from analog signals at terminals C and D. Based on the trigger position data, the pack microprocessor 10 varies the pulse width modulation (PWM) duty cycle of semiconductor device 20 to obtain the desired speed of the motor 50.
A tool accessory 60 may interface with power tool 200. The tool accessory 60 may be embodied as one or more drill bits, fastening bits and/or other cut-out tools for a variable speed drill, for example, and/or saw blades and abrasives for a circular saw, for example. It should be understood that many other types of accessories 60 are usable with the power tool 200. Indirectly, the accessory 60 may be connected to a gear train of the motor 50 to produce rotation and torque.
Accessory 60 may include an identification device (hole 505 in
The identification device 505/605 may be decoded by an accessory sensor 70. The sensor 70 may be embodied as a radio frequency sensor, a bar-code reader, an emitter sensor, an optical sensor, (such as a light reader), and/or a magnetic sensor such as a hall-effect sensor or a magneto-resistive sensor. Each sensor may include a respective modulator/demodulator. Other sensors may be implemented, so long as the sensor decodes the information stored in the identification device 505/605. The sensor 70 may be immune to vibration caused in the tool 200 and may provide electrical isolation for other tool components, for example.
Further, known modulation techniques may be used to modulate the data on the tool accessory 60, such as pulse width modulation (PWM), pulse code modulation, amplitude modulation and frequency modulation (in the case of analog signals) and/or, multiple frequency modulation (MFM), run length limited (RLL), on-off keying (OOK), phase-shift-keying (PSK), multiple-phase-shift-keying (MPSK) and frequency-shift-keying (FSK), (in the case of digital signals).
For a RF communications interface, any one of the above modulation schemes may be used to ensure reliable data. The tool accessory 60 and sensor 70 may each have an RF connection point such as an antenna, instead of a magnetic connection point. In an optical communication interface, any one of the above modulation schemes may also be used, with the tool accessory 60 and sensor 70 each having an optical connection point such as a light source and/or optical receiver, as opposed to a magnetic connection point.
The data communication interface between the accessory sensor 70 and the pack microprocessor 10 may illustratively be a two wire system via terminals E and F. However, other interfaces can be used, such as, by way of example and not of limitation, a single wire system, a three-wire system, a synchronous system, and/or an asynchronous system. The interface may illustratively be hardwired or wireless. Further, the data could be multiplexed or modulated over other lines, such as the power lines connected via terminals A and B.
Once the identification device 505/605 on the accessory 60 has been identified by sensor 70, tool settings are determined (S140) based on the decoded identification signal. The settings may be implemented by the pack microprocessor 10. These settings are accessible from a suitable look-up table stored in the pack microprocessor 10, for example. Hence, the tool settings may be implemented (S150) to obtain the desired performance of the tool accessory 60.
Referring to
The tool microprocessor 30 and pack microprocessor 10 may read and send data using, for example, digital communication. One of the pack microprocessor 10 and the tool microprocessor 30 may be designated as a “smart” controller that controls and/or sets the desired parameter, such as the speed to operate the tool accessory 60. If the tool microprocessor 30 fails to detect that battery pack 100 has a smart microprocessor 10, then tool microprocessor 30 checks to determine if battery pack 100 has a memory 25 (such as EEPROM) in which information about the accessory 60 is stored. If the battery pack 100 has a memory 25, the tool microprocessor 30 sets the desired and/or optimum speed of the power tool 200 based on the information stored in memory 25.
The data communication interface between the tool microprocessor 30 and the pack microprocessor 10 may illustratively be a two-wire system over serial data paths via terminals E and F, for example. However, other interfaces can be used, such as, by way of example and not of limitation, a single wire system, a three-wire system, a synchronous system or an asynchronous system. The interface may be a hardwired or wireless interface, for example.
The tool microprocessor 30 may also interface with the variable speed resistor potentiometer 80 to provide a user with the capability of adjusting speed. The tool microprocessor 30 may be programmable so as to read a trigger position of a trigger in tool 200 and report the trigger position via serial data paths. Based on the trigger position, the tool microprocessor 30 sends a command to pack microprocessor 10 to vary the PWM duty cycle of semiconductor device 20 so as to achieve the desired speed of motor 50.
The tool microprocessor 30 may query the battery pack 100 using digital communications, for example, to determine whether there is a microprocessor in battery 100 (S240). If the microprocessor 30 detects that battery pack 100 has a pack microprocessor 10 (output of S240 is ‘YES’) and determines that the pack microprocessor 10 is a smart controller (S245), then tool microprocessor 30 determines whether pack microprocessor 10 will control the tool settings or whether it will control the tool settings (S250).
At this point, control may be allocated to the selected microprocessor 10 or 30 depending on the determination at S250. Once control is allocated to the proper microprocessor 10 or 30, the tool setting parameters are initialized based on information obtained from the sensor 70, and may be set to the desired setting (S260) to obtain the desired performance of the tool 200.
If the tool microprocessor 30 does not detect that battery pack 100 includes a smart microprocessor 10 (output of S240 is ‘NO’), then tool microprocessor 30 may check to determine if battery pack 100 has a memory 25 (S270), such as an EEPROM, which stores information of the tool accessory 60. If battery pack 100 has a memory (output of S270 is ‘YES’), then the tool microprocessor 30 reads the memory 25 (S280) to access a look-up table (S290) and initialize tool setting parameters (S260) based on the information obtained from the look-up table in memory 25 (S260).
The sensor 70 may read the bar code 503 with an optical reader or bar code scanner, for example. The sensor 70 (e.g. an optical reader or bar code scanner) may include a source that emits radiation in a range of wavelengths, a device for scanning the radiation across the bar code, and a detector that receives the reflected radiation. The sensor 70 may decode the information of the saw blade 501 from electrical signals produced by the detector, since the reflectance from the black bars may be significantly different than that from the white bars. Bar code scanning technology is known in the art and will not be described further herein for reasons of brevity.
Another example accessory saw (blade 502) is shown in
The hole sensing technique may involve the use of an optical source of radiation and a detector that receives the reflected radiation. The optical sensor 510 may decode the information from the electrical signal produced by the detector, since the reflectance from hole 505 will be significantly different than that of the surrounding blade 500 material. The timing of the reflectance changes may allow the optical sensor 510 to decode the pertinent information from the tool accessory (i.e., saw blade 500).
Other hole sensing techniques may use a source of magnetic radiation, and a detector that measures the radiation. The optical sensor 510 may decode the information from the electrical signal produced by the detector since the magnetic signature of the hole may be significantly different than that of the surrounding material, such as a ferrous material.
The optical sensor 510 may produce a magnetic field and be perturbed by the passing saw blade 500. The hole 505, being a non-ferrous material, would produce a detection signal that is substantially differentiated from the surrounding metal saw blade 500 material (e.g., ferrous). Once the blade speed is determined as stable by monitoring a synchronizing signal, the detector signal may be monitored to determine the point at which the optical sensor 510 is transitioning from a ferrous region (solid) on the blade 500 to a non-ferrous region (hole 505) and then back again. As the different signal levels are read, time may also be recorded. The timing of the transition points along with a synchronization signal may allow the optical sensor 510 to determine the relative position and distance of all the holes 505 on the blade 500 which may essentially decode the pertinent information from the tool accessory (blade 402 in
Each Hall Effect sensor 610 may project a field varying in space in a fixed frame of reference. The pattern of variation in space for a given Hall Effect sensor 610 may be different than the pattern of variation for one or more other Hall Effect sensors 610. For example, the Hall Effect sensors 610 may be identical to one another, but disposed at different locations or in different orientations. The field patterns of the Hall Effect sensors 610 may thus be displaced or rotated relative to one another, which may be relative to a fixed frame of reference.
Each Hall Effect sensor 610 may emit a series of pulses to the pack microprocessor 10 or to the tool microprocessor 30. The pulses are representative of the frequency of rotation of the motor 50. The Hall Effect sensors 610 can be driven at different frequencies so that a signal which varies at different frequencies represents the field at the object from different transmitters. Based on the detected parameters of the field from the individual hall effect sensor 610 and the known pattern of variation of the field from each hall effect sensor 610, the given microprocessor 10 or 30 may calculate the position and/or orientation of the magnet(s) 605, and hence the position of the object bearing the magnet(s) 605, in the fixed frame of reference of the hall effect sensor 610.
In an alternative embodiment, a plurality of Hall Effect sensors 610 may be disposed at various locations and/or orientations in the fixed frame of reference. The location and/or orientation may be deduced from signals representing the parameter of the field prevailing at the various magnets 605. In a further example embodiment, the decoding technique may include detecting the presence and/or location of holes 505 (in the tool accessory of
The data radius 740 (which may be surrounded by the sync radius 720) may contain information including, but not necessarily limited to type, make, model number, size, optimum speed, temperature limits, voltage limits, current limits, serial identification numbers, hardware revision numbers, software revision numbers, fault conditions, and/or any other detailed information regarding the tool accessory 700. A single radius 700 or 740 may be used to obtain the information of the tool accessory 700. Alternatively, more than two radii may be used to obtain the accessory 700 information.
The tool accessory 700 may include at least one magnet (725 and/or 745) placed “x” degrees apart on each radius, where x is any positive integer value. For example, a sync magnet 725 may be the “zero” point (base reference) while an encode magnet 745 may be placed x degrees apart. With the determination of the location of each magnet 725, 745, the pack microprocessor 10 or tool microprocessor 30 may identify the tool accessory 700 to the power tool 200 by the number of degrees the magnets 725, 745 are separated.
Additional information may be added by adding more magnets 725, 745 in the same radius path, or by adding additional magnets 725, 745 at different radius paths. In another example, the magnets 725, 745 may be replaced by holes and/or other marks so that a sensor such as a Hall Effect sensor 610 may decode the holes magnetic codes. It should further be understood that holes, magnets and/or marks may be used in any combination.
The pack microprocessor 10 or tool microprocessor 30 may initially detect accessory speed stabilization by monitoring the time between sync radius magnet pulses (S810). Once the speed is stabilized, the given microprocessor 10/30 waits for the time to be constant (S820) to determine a base reference point so that decoding can commence. Decoding may be performed by measuring the time between the sync radius magnet 725 pulse and the data radius magnet 745 pulse (S830). The time may be divided by the time between the sync radius magnet 725 pulse (time for one revolution) (S840). This data may be multiplied by 360 to convert to degrees or by 2π to convert to radians (S850). Accordingly, the calculated magnet location (which can be stored) data may be used to obtain information of the tool accessory.
Initially, a variable Time1 is initialized at zero (S860). Before a time measurement can be performed, a pulse timer is reset to zero (S861). Next, a loop is executed (e.g., reading the sync radius sensor 720) until there is a sync pulse event (S862 and S863). Once an event has occurred, a variable Time2 is set to the elapsed time and the pulse timer is reset to zero (S864).
At this point, the current sync magnet 725 pulse separation time is compared with the previous time of the sync pulse event to determine if the tool accessory speed has stabilized (S865). If the two times (Time1 and Time2) are not close enough in time, (e.g., current sync magnet pulse and previous time sync pulse) stabilization has not been reached and the value of variable Time2 is shifted to Time1 (S866). In an example, Time 1=Time 2 satisfies this threshold. Then, control is returned to S862 until stabilization is achieved. However, if stabilization has been reached and Time1 and Time2 are close enough (S865), stabilization has been reached and control is passed to the data pulse event loop (S867 and S868).
The loop operations at 5867 and 5868 continue until there is a data pulse event (output of S868 is ‘YES’). Next, the pulse timer value representing the difference in time between the sync and data magnets 725, 745 is stored in memory 25 to obtain a Decode variable (S869). Then, the angle in degrees of difference between the two magnets 725, 745 is multiplied by 360 times the Decode value, divided by Time2 (S870) (e.g., radians of separation between sync and data magnets=360×(Decode variable/Time2)). Alternatively, the angle in radians may be 2π times Decode value divided by Time2 (S871) (e.g., radians of separation between sync and data magnets=2π×(Decode variable/Time2)). Accordingly, the calculated data may be used to obtain information of the tool accessory.
The tool accessory 913 includes (resistor 914), which may have a given value which represents an identification, embedded in its core at an end that is inserted into the chuck 912. One end 914A of the resistor 914 may be electrically connected to the metal shank of the tool accessory 913, and the other end 914B may be electrically isolated from the shank of accessory 913 but exposed at the tip of the accessory 913 so as to be electrically connected to the electrical core conductor 910 in the center of the transmission output shaft 911. As assembled, the accessory 913 is inserted into the chuck 912, and the chuck jaws 915 are tightened down on the shank of tool accessory 913.
To determine the resistance value of ID resistor 914, an electrical path exists starting at any point (911a, 911b, 911c) on the exterior of output shaft 911. The electrical path is through the output shaft 911 and a threaded interface 916 of the output shaft 911 and chuck 912 (also indicated as 911c). The electrical path continues through the chuck 912 to the chuck jaws 915 and then to the accessory 913 clamped in the chuck jaws 915.
The electrical path is created through the accessory 913 to one end of the ID resistor 914 embedded in the accessory 913, continuing through the ID resistor 914 and engaged with the electrical core conductor 910 of the transmission output shaft 911. The core conductor 910 may extend through the output shaft 911 and out the back of the output shaft 911. By passing a known current through the ID resistor 914 and reading the voltage across the resistor 914, the resistance value of the ID resistor 914 can be determined using Ohms Law calculations (R=E/I). There are numerous methods of determining resistance values as known in the art. As such a detailed description will not be described herein for reasons of brevity.
The exemplary embodiments of the present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the spirit and scope of the exemplary embodiments of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
This application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/665,087, filed Mar. 25, 2005 to Jeffrey FRANCIS et al. and entitled “POWER TOOL ACCESSORY IDENTIFICATION SYSTEM, the entire contents of which is hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 60665087 | Mar 2005 | US |
