Patent Publication Number: US-2023150046-A1

Title: Dust collector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation of U.S. patent application Ser. No. 17,582,647, filed Jan. 24, 2022, which in turn is a Continuation of U.S. patent application Ser. No. 17/082,816, filed Oct. 28, 2020, which in turn is a Continuation of U.S. patent application Ser. No. 16/807,584, filed Mar. 3, 2020, which in turn is a Continuation of U.S. patent application Ser. No. 16/672,575, filed Nov. 4, 2019, which in turn is a continuation of U.S. patent application Ser. No. 16/449,788, filed Jun. 24, 2019, which in turn is a Continuation of U.S. patent application Ser. No. 16/140,912 filed Sep. 25, 2018, which is a Continuation of U.S. patent application Ser. No. 15/952,660 filed Apr. 13, 2018, which is a Continuation of U.S. patent application Ser. No. 14/906,413 filed Jan. 20, 2016, which claims the benefit of PCT Application No. PCT/JP2014/070376, filed Aug. 1, 2014, which claims the benefit of Japanese Patent Application No. 2013-161506 filed Aug. 2, 2013 in the Japan Patent Office and Japanese Patent Application No. 2013-161507 filed Aug. 2, 2013 in the Japan Patent Office. The entire disclosure of Japanese Patent Application No. 2013-161506 and the entire disclosure of Japanese Patent Application No. 2013-161507 are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a dust collector that is capable of performing an interlock operation with an electric working machine. 
     BACKGROUND ART 
     A dust collector in one example comprises a communication unit (adapter) that receives a signal wirelessly transmitted from an electric working machine during operation of the electric working machine; the dust collector is configured to be operated when the communication unit receives the signal from the electric working machine (see, for example, Patent Document 1). 
     This dust collector can be operated interlocking with the electric working machine, without providing a signal line for detecting an operation state of the electric working machine between the dust collector and the electric working machine. Accordingly, this dust collector enables an interlock operation with the electric working machine even if, for example, the electric working machine is a chargeable cordless device. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent No. 4955332 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the dust collector in the above-described example starts the interlock operation upon receipt of the single transmitted from the electric working machine. For this reason, if multiple electric working machines that transmit signals for an interlock operation are present around the dust collector, the dust collector may be operated, contrary to the user&#39;s intention, by a signal from an electric working machine that does not require an interlock operation with the dust collector. 
     In one aspect of the present invention, it is desirable to provide the following dust collector: even if multiple electric working machines are present around the dust collector, the dust collector can perform an interlock operation only when the dust collector receives a signal from an electric working machine that requires the interlock operation. 
     Means for Solving the Problems 
     A dust collector in one aspect of the present invention comprises a dust collection portion, a communication portion, and an interlock operation control portion. The dust collection portion sucks dust through a dust collection hose. The communication portion wirelessly communicates with an electric working machine. The interlock operation control portion makes the dust collection portion perform an interlock operation with the electric working machine when the communication portion receives an interlock command transmitted from the electric working machine. The interlock operation control portion comprises a storage portion in which identification information is stored, and the identification information is specific to the electric working machine with which the dust collection portion is to be made to perform the interlock operation. 
     In the dust collector as configured above, the interlock operation control portion can determine whether the electric working machine transmitting the interlock command is a device to be interlocked or a device not to be interlocked. 
     Here, the interlock command transmitted from the electric working machine may include an interlock operation request signal requesting the interlock operation and an identification signal indicating the identification information. 
     In this case, based on the interlock operation request signal and the identification signal, the interlock operation control portion can determine that the interlock command has been transmitted from the electric working machine that requires the interlock operation, so as to make the dust collection portion perform the interlock operation. In addition, a timing of start of the interlock operation by the dust collection portion can be set based on the transmission of the interlock operation request signal from the electric working machine; thus, the dust collection portion can be operated properly. 
     The interlock operation control portion may be further configured such that when the identification information obtained from the identification signal received by the communication portion coincides with the identification information stored in the storage portion and the interlock operation request signal is received by the communication portion, the interlock operation control portion makes the dust collection portion perform the interlock operation. 
     In this case, the interlock operation control portion correctly recognizes that the signal received by the communication portion is the signal from the electric working machine to be interlocked, and the interlock operation can be started by the interlock operation request signal; this can further reduce possibility in which the dust collection portion is erroneously operated. 
     It may be configured such that while the communication portion receives the interlock command periodically and repeatedly transmitted by the electric working machine during operation of the electric working machine, the interlock operation control portion makes the dust collection portion perform the interlock operation. 
     Also, when the communication portion has not received the interlock command for a specified period of time or more, the interlock operation control portion may stop the interlock operation of the dust collection portion. In this case, if the interlock operation of the dust collection portion becomes unnecessary, for example, if the electric working machine stops operating or moves far away, it is possible to stop the operation of the dust collection portion. 
     Accordingly, compared with a configuration in which the electric working machine transmits, as the interlock command, a signal instructing to start and stop the interlock operation and the dust collector controls the start and stop of the interlock operation in accordance with the signal, the operation of the dust collection portion can be reliably stopped. 
     Moreover, the specified period of time before the control portion stops operation of the dust collection portion may be set to be longer than a transmission cycle in which the electric working machine periodically transmits the interlock command. 
     In this case, it can be more reliably determined that the electric working machine stops the interlock command, thereby to stop the operation of the dust collection portion; consequently, it is possible to suppress or inhibit that the operation of the dust collection portion is erroneously stopped. 
     The dust collector may further comprise a registration operation portion configured to input a command for additionally registering the identification information specific to the electric working machine with which the dust collection portion is to be made to perform the interlock operation. Also, the interlock operation control portion may additionally register the identification information in the storage portion in accordance with the command from the registration operation portion. 
     In this case, the electric working machine as an object of the interlock operation can be registered by the dust collector alone and thus, usability of the dust collector can be improved. Moreover, it is not necessary to provide an operation portion for registration of the identification information in the electric working machine. Thus, the electric working machine can be downsized. 
     Furthermore, when receiving the command for additionally register the identification information from the registration operation portion, the interlock operation control portion may transmit an identification information transmission request to a nearby electric working machine via the communication portion; and after the transmission, the interlock operation control portion may additionally register the identification information received by the communication portion in the storage portion. 
     In this case, when a user of the dust collector operates the registration operation portion to register, in the storage portion, the identification information of the electric working machine to be interlocked, it is not necessary to input such identification information by operating the operation portion; thus, registration operation of the identification information to the storage portion can be simplified. 
     Moreover, since the identification information to be registered in the storage portion is transmitted from the electric working machine, it is possible to suppress or inhibit registration of wrong identification information in the storage portion; therefore, the identification information can be correctly registered. 
     A receivable distance at which the electric working machine can receive a signal transmitted from the communication portion may be set to be shorter than a receivable distance at which the communication portion can receive a signal transmitted from the electric working machine. 
     If the receivable distance is set as describe above, the identification information transmission request can be selectively transmitted to the electric working machine(s) located in the vicinity of the dust collector; this can reduce possibility of erroneous registration of identification information of an electric working machine that does not require the interlock operation of the dust collection portion. 
     Here, to set the receivable distance as described above, for example, transmission power from the communication portion and receiving sensitivity in the communication portion, or transmission power and receiving sensitivity of the electric working machine, etc. may be adjusted. 
     Furthermore, after the interlock operation control portion transmits the identification information transmission request to the nearby electric working machine via the communication portion, when the communication portion receives a plurality of pieces of identification information, the interlock operation control portion may suspend the additional registration of the identification information in the storage portion and notify the suspension via a notification portion. 
     In this case, possibility of erroneous registration of identification information of an electric working machine that does not require the interlock operation of the dust collection portion can be reduced. In addition, failure of additional registration of the identification information is notified; the user can dispose an electric working machine, the identification information of which is desired to be registered, in the vicinity of the dust collector but dispose other electric working machines away from the dust collector, thereby allowing the user to try the registration again. Therefore, it is possible to improve working efficiency in the registration of the identification information. 
     Furthermore, when the identification information is additionally registered in the storage portion, the interlock operation control portion may notify the additional registration via the notification portion. 
     In this case, the user can recognize that additional registration of a new electric working machine, which becomes an object of the interlock operation, is succeeded with respect to the dust collector and therefore, improved working efficiency in the registration of the identification information can be achieved. 
     Furthermore, when the communication portion receives a registration request of the identification information transmitted from the electric working machine, the interlock operation control portion may additionally register the identification information in the storage portion. 
     In this case, although the electric working machine needs to be provided with an operation portion for transmitting the registration request of the identification information, the identification information can be additionally registered to the storage portion in accordance with the request from the electric working machine. Consequently, improved working efficiency in the registration of the identification information can be achieved. 
     In this case, furthermore, after the communication portion receives the registration request of the identification information, the interlock operation control portion may notify, via the notification portion, whether the identification information is additionally registered in the storage portion. 
     The dust collector may further comprise a deletion operation portion that inputs a command for deleting the identification information stored in the storage portion. Moreover, the interlock operation control portion may delete the identification information stored in the storage portion in accordance with the command from the deletion operation portion. 
     In this case, the identification information of the electric working machine to be interlocked, which is registered in the control portion, can be deleted by operating the deletion operation portion. Accordingly, it is possible to easily change an electric working machine that performs the interlock operation of the dust collector. 
     In addition, because unnecessary registration of the identification information in the storage portion can be deleted, a storage capacity of the storage portion can be reduced. 
     Furthermore, when a command for deleting the identification information is inputted from the deletion operation portion while the interlock operation control portion makes the dust collection portion perform the interlock operation, the interlock operation control portion may delete, from the storage portion, the identification information used to make the dust collection portion perform the interlock operation. 
     In this case, it is possible to delete, from the storage portion, the identification number of the electric working machine with which the dust collector is currently made to perform the interlock operation; thus, the identification number of the electric working machine, which is to be deleted, can be easily and correctly specified. 
     The dust collector may comprise a dust collector main body and a communication unit. The dust collector main body may comprise at least the dust collection portion and may operate by receiving a power supply from an external alternating current power source. The communication unit may comprise at least the communication portion; the communication unit may be attached to the dust collector main body and may receive the interlock command wirelessly transmitted from the electric working machine to output an operation command to the dust collector main body. 
     The dust collector main body may comprise an isolation device configured to electrically isolate the alternating current power source from the communication portion. 
     In this case, even if, by any chance, the user touches an internal circuit in the communication unit due to misuse of the communication unit by the user, risk of electrical shock to the user can be suppressed or inhibited. 
     In addition, the dust collector main body is provided as a separate body from the communication unit. Accordingly, the dust collector main body comprises a terminal for inputting/outputting signals to/from the communication unit when the communication unit is attached to the dust collector main body. 
     This terminal is electrically isolated from the alternating current power source. For this reason, even if the user touches the terminal when attaching the communication unit to the dust collector main body, possibility of electrical shock to the user can be reduced or eliminated and therefore, safety of the dust collector can be improved. 
     The isolation device may comprise an isolation transformer, and the isolation transformer may be used to take in the alternating current power inside the dust collector. In this case, not only because the isolation transformer can isolate between the communication unit and the alternating current power source, but also because electric power can be taken in from the alternating current power source via the isolation transformer, it is possible to supply electric power to an internal circuit in the dust collector main body and to the communication unit. 
     The isolation device may comprise a contactless circuit configured to contactlessly transmit a signal between an operation portion and the communication unit, and the operation portion is configured to operate by receiving a power supply from the alternating current power source. 
     In this case, it is possible to suppress or inhibit entry of noise from the alternating current power source into the communication unit via input/output of signals. 
     Moreover, because signals are inputted/outputted contactlessly, possibility of contact failure that occurs between signal input/output terminals can be reduced or eliminated and therefore, reliability of the dust collector can be enhanced. 
     The communication unit may comprise an antenna for wireless communication, a signal input/output portion, and a communication control portion. The signal input/output portion inputs and outputs a signal including the operation command to and from the dust collector main body. The communication control portion controls signals inputted and outputted via the antenna and the signal input/output portion. 
     In this case, the antenna may be disposed on a side opposite to the signal input/output portion across the communication control portion. 
     The signal input/output portion is coupled to a circuit inside the dust collector main body; in many cases, part of the signal input/output portion is a wall inhibiting wireless communication; moreover, the part may be located close to an internal circuit of the dust collector main body, which is a noise source. 
     When the antenna is disposed as described above, the antenna can be located away from the wall inhibiting wireless communication and the noise source, which enables to improve communication quality of the wireless communication with the electric working machine. 
     The dust collector main body may comprise a power supply path and a detection circuit. The power supply path supplies an electric power to the communication unit. The detection circuit detects, based on an electric current flowing to the power supply path, that the communication unit is attached. 
     In this case, it is possible to detect attachment of the communication unit without providing, in the dust collector main body, a terminal dedicated to detection of attachment of the communication unit. Thus, a size of a connecter for attaching the communication unit, which is provided in the dust collector main body, can be reduced, thereby achieving downsize and cost reduction of the dust collector main body. 
     The communication unit may comprise a case, an antenna for wireless communication, a signal input/output portion, and a communication control portion. At least the communication control portion may be covered by a waterproof resin member and housed inside the case. 
     In this case, the communication control portion of the communication unit is provided with two layers of waterproofing, i.e., with the case of the communication unit and with the waterproof resin member. Thus, erroneous operation of the control portion of the communication unit can be more favorably suppressed or inhibited. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a block diagram showing a schematic configuration of a dust collector in a first embodiment and an internal configuration of an electric power tool that makes the dust collector perform an interlock operation. 
         FIG.  1 B  is a block diagram showing an internal configuration of the dust collector. 
         FIG.  2    is an illustrative view illustrating a transmission signal that is transmitted from the electric power tool to the dust collector when the electric power tool and the dust collector operate interlocking with each other. 
         FIG.  3 A  shows flowcharts of a registration request process and an interlock operation request process, which are executed in the electric power tool, and a flowchart of a part of a tool-registration and interlock-operation control process executed in the dust collector in response to the aforementioned request processes. 
         FIG.  3 B  is a flowchart of the rest of the tool-registration and interlock-operation control process. 
         FIG.  4 A  shows a flowchart of a part of an identification-number additional registration process executed in the dust collector, and a flowchart of an identification-number transmission process executed in the electric power tool in response to the additional registration process. 
         FIG.  4 B  is a flowchart of the rest of the additional registration process. 
         FIG.  5    is a flowchart of an identification-number deletion process executed in the dust collector. 
         FIG.  6    is a flowchart illustrating a modified example of the identification-number transmission process shown in  FIG.  4 A . 
         FIGS.  7 A and  7 B  are illustrative views each showing a configuration of a communication unit provided in the dust collector. 
         FIGS.  8 A and  8 B  are illustrative views each showing a configuration of a communication unit provided in the electric power tool. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
       2  . . . electric power tool,  4  . . . dust collector,  10  . . . tool main body,  12 . . . cutting grindstone,  14 . . . motor,  16  . . . drive circuit,  18  . . . trigger switch,  20 . . . battery pack,  22 . . . battery,  30 . . . communication unit,  32 . . . operation detection circuit,  33 . . . antenna,  34 . . . transmission and reception circuit,  36 . . . control circuit,  37 . . . identification-number setting portion,  38 . . . SW circuit,  40 . . . dust-collector main body,  41 . . . dust collection hose,  42 . . . dust collection motor,  44 . . . dust collection motor driving circuit,  45 . . . power plug,  46 . . . changeover SW,  48 . . . signal isolation circuit,  50 . . . control circuit,  52 . . . isolated control power source,  52 . . . control circuit,  53 . . . power outlet,  54 ,  56 . . . current detection circuit,  58 . . . IF circuit,  60 . . . communication unit,  61 . . . antenna,  62 . . . transmission and reception circuit,  64 . . . control circuit,  66 . . . IF circuit,  68 . . . memory,  70 . . . SW circuit,  72 . . . notification circuit,  80 ,  90 . . . circuit board,  82 . . . component mounting area,  84 ,  92 . . . resin case,  86 ,  94 . . . outer case,  95 ,  96 . . . attachment portion. 
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, exemplified embodiments of the present invention will be described with reference to the drawings. 
     First Embodiment 
     As shown in  FIG.  1 A , a dust collector  4  of the first embodiment comprises a dust collection hose  41 , a tip end of which is disposed in the vicinity of an electric power tool  2 . The dust collector  4  is configured to suck, through the dust collection hose  41 , dust including powder dust or cutting chips discharged from the electric power tool  2 . Also, the dust collector  4  comprises a dust-collector main body  40  and a communication unit  60 . 
     The electric power tool  2  is a grinder that cuts a workpiece to be processed, by rotating a cutting grindstone  12  by a motor  14 . The electric power tool  2  comprises a tool main body  10 , a battery pack  20  that supplies electric power to the tool main body  10 , and a communication unit  30  provided between the tool main body  10  and the battery pack  20 . 
     The tool main body  10  comprises the motor  14 , a power transmitter (not shown) that transmits rotation of the motor  14  to the cutting grindstone  12 , a drive circuit  16  that drives the motor  14  upon receipt of power supply from the battery pack  20 , and a trigger switch  18  that is operated by a user to input a drive command for the motor  14 . 
     The communication unit  30  comprises an operation detection circuit  32  that detects a drive state of the motor  14 , a transmission and reception circuit  34  that wirelessly communicates with the communication unit  60  in the dust collector  4  via an antenna  33 , and a control circuit  36 . 
     The operation detection circuit  32  is configured to detect the drive state of the motor  14  based on an electric current flowing through a power supply path from a battery  22  inside the battery pack  20  to the drive circuit  16 . 
     When the operation detection circuit  32  detects driving of the motor  14  (in other words, operation of the tool main body  10 ), the control circuit  36  makes the transmission and reception circuit  34  transmit an interlock command to the communication unit  60  in the dust collector  4 , thereby making the dust collector  4  perform an interlock operation. 
     Moreover, when transmitting the interlock command to the communication unit  60  in the dust collector  4 , the communication unit  30  periodically transmits a signal (interlock command), which include an interlock operation request signal and an identification number signal, at a specified time interval, as shown in  FIG.  2   . The interlock operation request signal is a signal having a specified bit length. The identification number signal is a signal having a specified bit length indicating an identification number (for example, product serial number) of the communication unit  30 . 
     For this reason, the communication unit  30  comprises an identification-number setting portion  37  in which an identification number of the communication unit  30  itself has been set beforehand. 
     Upon detection of the operation of the tool main body  10  by the operation detection circuit  32 , the control circuit  36  reads out the identification number from the identification-number setting portion  37 ; then, the control circuit  36  periodically outputs, to the transmission and reception circuit  34 , the read identification number as identification information specific to the electric power tool  2 , together with the interlock operation request signal. The control circuit  36  of the first embodiment is configured as a microcomputer. However, the control circuit  36  may be configured by combining separate various electronic parts; alternatively, the control circuit  36  may be an ASIC (Application Specified Integrated Circuit), a programmable logic device, such as FPGA (Field Programmable Gate Array), etc., or any combination thereof. 
     Consequently, while the tool main body  10  is operating, the interlock command shown in  FIG.  2    is periodically transmitted from the communication unit  30  to the communication unit  60  in the dust collector  4  (see, an interlock operation request process shown in  FIG.  3   ). 
     Moreover, the communication unit  30  comprises an SW circuit  38  provided with an operation SW (SW is abbreviation of “switch”); the operation SW is used to input a command (registration command) for registering, in the dust collector  4 , the identification number of the communication unit  30  itself as the identification information specific to the electric power tool  2 . 
     When an identification-number registration command is inputted from the SW circuit  38  when the operation of the electric power tool  2  is stopped, the control circuit  36  reads out the identification number from the identification-number setting portion  37  and outputs, to the transmission and reception circuit  34 , an identification-number registration signal including an identification-number registration request signal and the identification number signal, thereby transmitting an identification-number registration request from the communication unit  30  to the communication unit  60  in the dust-collector main body  40  (see, a registration request process shown in  FIG.  3   ). 
     Next, the dust-collector main body  40  comprises a dust collection motor  42  for sucking dust including powder dust or cutting chips discharged from the electric power tool  2 , a dust collection motor driving circuit  44  that drives the dust collection motor  42 , and a power plug  45  that is inserted into an external power outlet to receive power supply from an alternating-current power source so as to supply the received power to the dust collection motor driving circuit  44 . 
     Provided on an alternating current power transmission path extending from the power plug  45  to the dust collection motor driving circuit  44  is a changeover SW  46 ; the changeover SW  46  is to be changed among three states: making the dust collector  4  operate interlocking with the operation of the electric power tool  2 ; inhibiting the interlock operation (i.e., making “Uninterlock”); and stopping the operation of the dust collector  4  (i.e., turning “OFF”). 
     If the changeover SW  46  is not in an OFF state (i.e., “Interlock” or “Uninterlock”), an alternating current voltage inputted from the power plug  45  is outputted to the dust collection motor driving circuit  44 . 
     Moreover, the dust-collector main body  40  comprises: a control circuit  50  that controls driving of the dust collection motor  42  by the dust collection motor driving circuit  44 ; an isolated control power source  52  that generates a direct-current power supply voltage to be supplied to the control circuit  50  and to the communication unit  60  attached to the dust-collector main body  40 ; and a power outlet  53  that supplies an alternating current power to an external device. Although the control circuit  50  of the first embodiment is configured as a microcomputer, the control circuit  50  may be configured by combining separate various electronic parts; alternatively, the control circuit  50  may be an ASIC, a programmable logic device, such as FPGA, or any combination thereof. 
     When the changeover SW  46  has been changed to “Interlock” or “Uninterlock”, the alternating current power inputted from the power plug  45  is also supplied to the isolated control power source  52  and the power outlet  53  via the changeover switch  46 . 
     Provided on an alternating current power supply path extending from the changeover SW  46  to the power outlet  53  is a current detection circuit  54  that detects an alternating current to be supplied to the external device via the power outlet  53 . 
     Moreover, the dust-collector main body  40  comprises an interface circuit (IF circuit)  58 ; the IF circuit  58  is configured to supply, as a power source voltage, the direct current voltage generated by the isolated control power source  52  to the communication unit  60 ; also, the IF circuit  58  is configured to transmit/receive, to/from the communication unit  60 , the interlock command transmitted from the communication unit  30  in the electric power tool  2  and information such as a drive state of the dust collection motor  42 , etc. 
     Provided on a direct-current power supply path extending from the isolated control power source  52  to the IF circuit  58  is a current detection circuit  56  that detects a direct current to be supplied to the communication unit  60 . From this current detection circuit  56 , detection results of the direct current are inputted to the control circuit  50 . 
     Moreover, results of current detection by the current detection circuit  54  and a changeover state of the changeover SW  46  are inputted to the control circuit  50  via a signal isolation circuit  48  comprising a photocoupler. 
     The control circuit  50  drives the dust collection motor  42  via the dust collection motor driving circuit  44 , based on the changeover state of the changeover SW  46  (in this case, “Interlock” or “Uninterlock”) as well as a current value of the alternating current supplied from the power outlet  53  to the external device. 
     Also, the control circuit  50  determines whether the communication unit  60  is attached to the IF circuit  58  based on a current value of the direct current detected by the current detection circuit  56 . If the communication unit  60  is attached and the changeover SW  46  has been changed to “Interlock”, the control circuit  50  drives the dust collection motor  42  via the dust collection motor driving circuit  44  in accordance with a drive command inputted from the communication unit  60 . 
     Moreover, a control signal, which is outputted from the control circuit  50  to the dust collection motor driving circuit  44 , is also inputted to the dust collection motor driving circuit  44  via the signal isolation circuit  48  comprising the photocoupler. 
     This is because, by means of the signal isolation circuit  48  and the isolated control power source  52 , the communication unit  60  to be coupled to the IF circuit  58  is made to be electrically isolated from a path of the alternating current voltage supplied from the external alternating-current power source via the power plug  45 . 
     That is to say, in the first embodiment, the signal isolation circuit  48  and the isolated control power source  52  allow the internal circuits in the dust-collector main body  40 , which receive power supply from the external alternating-current power source, to supply electric power to the communication unit  60  or to transmit/receive signals to/from the communication unit  60  while the internal circuits are being isolated from the alternating-current power source. With this configuration, risk of electrical shock to the user when the user touches the IF circuit  58  is to be suppressed or inhibited. 
     Moreover, the isolated control power source  52  includes an isolation transformer; the isolation transformer receives power supply from the alternating-current power source by dropping the alternating current voltage. Alternatively, an isolating switching power source may be used as the isolated control power source  52  so as to supply a constant voltage direct-current power to the control circuit  50 . 
     Next, the communication unit  60  comprises an IF circuit  66  that comprises a terminal portion attachable to the IF circuit  58  in the dust-collector main body  40 , a transmission and reception circuit  62  that wirelessly communicates with the communication unit  30  in the electric power tool  2  via an antenna  61 , and a control circuit  64  that is provided between the transmission and reception circuit and the IF circuit  66 . 
     The control circuit  64  is configured to control transmission/reception signals by the transmission and reception circuit  62  and input/output signals by the IF circuit  66 . 
     Specifically, when the transmission and reception circuit  62  receives the interlock operation request signal transmitted from the communication unit  30  of the electric power tool  2 , the control circuit  64  determines, based on the identification number signal transmitted together with the interlock operation request signal, whether the electric power tool  2  is an electric power tool as an object of the interlock operation. 
     If the electric power tool  2  is to be interlocked, the drive command of the dust collection motor  42  is outputted to the control circuit  50  in the dust-collector main body  40  to make the dust collection motor  42  perform the interlock operation. 
     To enable this, the communication unit  60  comprises a non-volatile memory (hereinafter, simply referred to as a memory)  68  for storing an identification number of the electric power tool as the object of the interlock operation. 
     When the transmission and reception circuit  62  receives the identification number transmitted from the electric power tool  2 , the control circuit  64  determines whether this identification number coincides with the identification number in the memory  68 ; if these identification numbers coincide, the control circuit  64  makes the dust collection motor  42  perform the interlock operation (see, a tool-registration and interlock-operation control process shown in  FIG.  3   ). Here, the control circuit  64  in the first embodiment is configured as a microcomputer. However, the control circuit  64  may be configured by combining separate various electronic parts; alternatively, the control circuit  64  may be an ASIC, a programmable logic device, such as FPGA, etc., or any combination thereof. 
     Moreover, the memory  68  for storing the identification number comprises, for example, an EEPROM, a flash memory, or the like, which is capable of additionally registering the identification number and deleting the identification number. 
     Furthermore, when the identification-number registration request is transmitted to the control circuit  64  from the communication unit  30  in the electric power tool  2 , the control circuit  64  additionally registers in the memory  68  the identification number included in this registration request (see the tool-registration and interlock-operation control process shown in  FIG.  3   ). 
     Moreover, the communication unit  60  comprises a SW circuit  70  and a notification circuit  72 ; the SW circuit  70  comprises a registration SW for instructing additional registration of the identification number in the memory  68  and a deletion SW for instructing deletion of the identification number registered in the memory  68 ; the notification circuit  72  is to notify registration results and deletion results of the identification number in the memory  68 . 
     When an additional registration command of the identification number is inputted from the registration SW inside the SW circuit  70 , the control circuit  64  executes an additional registration process (see  FIG.  4   ) to obtain the identification number from the electric power tool  2  located around the dust collector  4  and register the identification number in the memory  68 . Meanwhile, when a deletion command of the identification number is inputted from the deletion SW inside the SW circuit  70 , the control circuit  64  executes an identification-number deletion process (see  FIG.  5   ) to delete the identification number from the memory  68 . 
     Next, referring to  FIGS.  3 A and  3 B , the registration request process and the interlock operation request process, which are executed in the control circuit  36  inside the communication unit  30  of the electric power tool  2 , and the tool-registration and interlock-operation control process, which is executed in the control circuit  64  inside the communication unit  60  of the dust collector  4 , will be described. 
     As shown in  FIGS.  3 A and  3 B , the registration request process is a process to be executed as one of main routines in the control circuit  36  when the motor  14  in the electric power tool  2  is stopped. Upon start of this process, in S 110  (S represents a step), it is determined whether the identification-number registration command has been inputted from the SW circuit  38 . 
     If the identification-number registration command has not been inputted, S 110  is executed again to wait for the registration command to be inputted. However, if it is determined in S 110  that the identification-number registration command has been inputted from the SW circuit  38 , the process proceeds to S 120 . 
     In S 120 , the above-described signal including the identification-number registration request signal and the identification number signal is outputted to the transmission and reception circuit  34 , thereby transmitting the identification-number registration request from the communication unit  30 . After the identification-number registration request is transmitted in S 120 , the process returns to S 110 . 
     Next, the interlock operation request process is a process to be executed as one of main routines in the control circuit  36  when the trigger switch  18  is operated to drive the motor  14 . Upon start of this process, in S 130 , it is determined whether a tool current (electric current flowing to the motor  14  via the drive circuit  16 ), which is detected by the operation detection circuit  32 , has exceeded a threshold value pre-set for determining operations of the electric power tool  2 . 
     If the tool current does not exceed the threshold value, S 130  is executed again to wait until the tool current exceeds the threshold value (i.e., wait until the electric power tool  2  starts a normal processing operation). If the tool current exceeds the threshold value, the process proceeds to S 140 . 
     In S 140 , the interlock command shown in  FIG.  2    is outputted to the transmission and reception circuit  34 , thereby transmitting the interlock command from the communication unit  30 . 
     In the subsequent S 150 , after the transmission of the interlock command, the process waits until a specified time T 1  has passed. When the specified time T 1  has passed, the process returns to S 130 . 
     As a result, in the interlock operation request process, when the tool current exceeds the threshold value (i.e., while the electric power tool  2  is operating), an interlock operation request is to be periodically and repeatedly transmitted at the following time interval; the time interval is obtained by adding the specified time T 1  to a transmission time necessary to output the interlock command to the transmission and reception circuit  34 , the interlock command including the interlock operation request signal and the identification number signal. 
     Next, the tool-registration and interlock-operation control process is a process to be repeatedly executed as one of main routines in the control circuit  64 . Upon start of this process, in S 210 , it is determined whether the identification-number registration request has been received in the transmission and reception circuit  62 . 
     Then, if the identification-number registration request has been received in the transmission and reception circuit  62 , the process proceeds to S 220  to determine whether the identification number transmitted from the electric power tool  2  side has been received in the transmission and reception circuit  62 . 
     In S 220 , if it is determined that the identification number has been received, the process proceeds to S 230  to store (additionally register) the received identification number in the memory  68 . In the subsequent S 240 , completion of storing the identification number is notified (for example, by lighting a success indication lamp comprising an LED, etc.) via the notification circuit  72  and then, the process returns to S 210 . 
     However, if it is determined in S 220  that the identification number has not been received, in S 250 , failure of storing the identification number is notified (for example, by lighting an error indication lamp comprising an LED, etc.) via the notification circuit  72  and then, the process returns to S 210 . 
     On the other hand, in S 210 , if it is determined that the identification-number registration request has not been received, the process proceeds to S 260  to determine whether the interlock operation request has been received in the transmission and reception circuit  62 . 
     If the interlock operation request has been received in the transmission and reception circuit  62 , the process proceeds to in S 270  to determine whether the identification number transmitted from the electric power tool  2  side has been received in the transmission and reception circuit  62 . 
     If it is determined in S 270  that the identification number has been received, the process proceeds to S 280  to determine whether the received identification number is stored (registered) in the memory  68 , thereby determining whether the electric power tool  2  that transmitted the interlock operation request is an electric power tool that is an object of the interlock operation. 
     Then, in S 280 , if it is determined that the received identification number this time is stored (registered) in the memory  68 , the electric power tool that transmitted the identification number is confirmed as the object of the interlock operation; thus, the process proceeds to S 290 . 
     In S 290 , the control circuit  50  in the dust-collector main body  40  is instructed to drive the dust collection motor  42  via the IF circuits  66  and  58 , thereby making the dust collection motor  42  (and therefore, the dust collector  4 ) perform the interlock operation. 
     After the process in S 290  is performed, in S 300 , the process waits until a specified time T 2  has passed. When the specified time T 2  has passed, the process returns to S 210 . 
     In this regard, the specified time T 2  is a time for executing a series of processes S 210  to S 290  in a time period that is longer than a transmission cycle in which the communication unit  30  in the electric power tool  2  periodically transmits the interlock operation request by the interlock operation request process. 
     For this reason, the specified time T 2  is set to be longer than the specified time T 1  during which the process waits in S 150  of the interlock operation request process. 
     However, when negative determination is made in any of S 260 , S 270 , and S 280 , i.e., when the interlock operation is not requested from the electric power tool, when the identification number cannot be received properly, or when the received identification number is not from the electric power tool as the object of the interlock operation, the process proceeds to S 310 . 
     In S 310 , a stop command of the dust collection motor  42  is outputted to the control circuit  50  of the dust-collector main body  40  via the IF circuits  66  and  58 , thereby stopping driving of the dust collection motor  42 ; then, the process returns to S 210 . 
     Next, with reference to  FIGS.  4 A and  4 B , an identification-number additional registration process and an identification-number transmission process will be explained; the identification-number additional registration process is executed in the control circuit  64  when the additional registration command of the identification number is inputted from the registration SW inside the SW circuit  70  provided in the communication unit  60  of the dust collector  4 ; and in conjunction with the identification-number additional registration process, the identification-number transmission process is executed in the control circuit  36  inside the communication unit  30  of the electric power tool  2 . 
     The additional registration process is a process to be executed as one of main routines in the control circuit  64 , together with the above-described tool-registration and interlock-operation control process. Upon start of the additional registration process, in S 410 , it is determined whether the registration SW inside the SW circuit  38  is in an ON state. 
     If the registration SW is not in the ON state, S 410  is executed again to wait for the registration SW to be changed to the ON state. When it is determined in S 410  that the registration SW is in the ON state, the process proceeds to S 420 . 
     In S 420 , an identification-number transmission request is outputted to the transmission and reception circuit  62 , thereby making the transmission and reception circuit  62  transmit a transmission request for the identification number to the electric power tool  2  located around the dust collector  4 . 
     On the other hand, in the communication unit  30  provided in the electric power tool  2 , the control circuit  36  is configured to execute the identification-number transmission process shown in  FIG.  4 A  as one of main routines. 
     In this identification-number transmission process, in S 510 , it is determined whether the transmission and reception circuit  62  has received the identification-number transmission request transmitted from the communication unit  60  in the dust collector  4 , thereby waiting for the identification-number transmission request to be received in the transmission and reception circuit  62 . 
     If it is determined in S 510  that the identification-number transmission request has been received in the transmission and reception circuit  62 , the process proceeds to S 520 ; in S 520 , from the identification-number setting portion  37 , the identification number of itself is read out and then outputted to the transmission and reception circuit  34 , so as to make the transmission and reception circuit  34  transmit the identification number; then, the present identification-number transmission process is terminated. 
     Here, after the termination, the identification-number transmission process is restarted after a specified waiting time has elapsed, and is executed in the same manner as described above. 
     For this reason, in the additional registration process in the dust collector  4  side, in S 420 , the transmission request of the identification number is transmitted from the transmission and reception circuit  62 ; thereafter, in S 430 , the identification number is transmitted from the nearby electric power tool  2  and then, it is determined whether a prescribed time necessary for the transmission and reception circuit  62  to receive this identification number has passed. 
     When the prescribed time has not yet been passed, it is determined in S 440  whether the identification number has been received. If the identification number has been received, in S 450 , a number of the identification numbers received before the prescribed time has passed (“Received Number”) is counted and then, the process returns to S 430 . Also, if it is determined in S 440  that the identification number has not yet been received, the process proceeds to S 430 . 
     Here, a transmission power of the transmission and reception circuit  62  is set to be low, compared with the transmission and reception circuit  34  inside the communication unit  30  provided in the electric power tool  2 . 
     This is because, a receivable distance at which the electric power tool  2  is capable of receiving the transmission request of the identification number is made to be shorter than a receivable distance at which the communication unit  60  of the dust collector  4  can properly receive an electric wave transmitted from the transmission and reception circuit inside the communication unit  30 . 
     Specifically, a transmission power from the communication unit  30  in the electric power tool  2  is set to correspond to a length of the dust collection hose  41  (for example, 5 to 10 m), so that even if the dust collection hose  41  is fully extended, the communication unit  60  in the dust collector  4  can receive an electric wave transmitted from the electric power tool  2  in relation to which the tip end of the dust collection hose  41  is disposed. 
     On the other hand, a transmission power from the communication unit  60  in the dust collector  4  is set such that the receivable distance at which the electric power tool  2  side is capable of receiving is sufficiently shorter (for example, about 1 m) than the length of the dust collection hose  41 . 
     As a result, when the user operates the registration SW to store (register) the identification number of the electric power tool  2  in the memory  68 , the electric power tool  2  to be registered is made close to the dust collector  4 , thereby allowing an electric wave transmitted from the communication unit  60  of the dust collector  4  to reach the electric power tool  2  to be registered, while making it difficult for this electric wave to reach an electric power tool  2  that does not require the interlock operation with the dust collector  4 . 
     Next, in S 430 , if it is determined that the prescribed time has passed, the process proceeds to S 460  to determine whether the Received Number of the identification number counted in S 450  is “1”. If “Received Number=1” is satisfied, the process proceeds to S 470  to store (additionally register) the received identification number in the memory  68 . 
     In the subsequent S 480 , as in the above-described S 240 , completion of storing the identification number is notified via the notification circuit  72  and then, the present additional registration process is terminated. 
     However, if it is determined in S 460  that the Received Number of the identification number is not “1”, i.e., if the identification number cannot be received or if a plurality of the identification numbers are received, the process proceeds to S 490  to notify, as in the above-described S 250 , failure of storing the identification number via the notification circuit  72  and then, the present additional registration process is terminated. 
     Here, after the termination, the additional registration process is restarted after a specified waiting time has elapsed, and is executed in the same manner as described above. 
     Next, the identification-number deletion process will be explained with reference to  FIG.  5   ; the identification-number deletion process is executed in the control circuit  64  when the deletion command of the identification number is inputted from the deletion SW inside the SW circuit  70  provided in the communication unit  60  of the dust collector  4 . 
     The identification-number deletion process is a process to be executed as one of main routines in the control circuit  64 , together with the above-described tool-registration and interlock-operation control process and the additional registration process. Upon start of the identification-number deletion process, in S 610 , it is determined whether the deletion SW inside the SW circuit  38  is in an ON state. 
     If the deletion SW is not in the ON state, S 610  is executed again to wait for the registration SW to become the ON state. If it is determined in S 610  that the registration SW is in the ON state, the process proceeds to S 620 . 
     In S 620 , it is determined whether the dust collection motor  42  in the dust-collector main body  40  is currently being driven (i.e., whether the dust collection motor  42  is performing the interlock operation). If the dust collection motor  42  is performing the interlock operation, the process proceeds to S 630 . 
     In S 630 , the identification number of the electric power tool  2  with which the dust collection motor  42  is currently made to perform the interlock operation is confirmed, and this identification number is deleted from the memory  68 , thereby erasing the registration of this electric power tool  2 . 
     Then in S 640 , the deletion of the identification number from the memory  68  is notified via the notification circuit  72  and then, the present identification-number deletion process is terminated. 
     However, if it is determined in S 620  that the dust collection motor  42  is not currently made to perform the interlock operation, the identification number to be deleted from the memory  68  cannot be identified and thus, failure of deletion of the identification number is notified via the notification circuit  72 ; then, the present identification-number deletion process is terminated. 
     Here, after the termination, the identification-number deletion process is restarted after a specified waiting time has elapsed, and is executed in the same manner as described above. 
     As explained above, in the dust collector  4  of the first embodiment, the control circuit  64  inside the communication unit  60  executes the above-described tool-registration and interlock-operation control process; accordingly, the dust collector  4  can be made to perform the interlock operation only when the electric power tool  2  that sent the interlock operation request is the electric power tool pre-stored in the memory  68  as an object of the interlock operation. 
     For this reason, even if a plurality of electric power tools that transmit the interlock operation requests are present around the dust collector  4 , it is possible to suppress or inhibit the dust collector  4  from being operated contrary to the user&#39;s intention, by the interlock operation request from the electric power tools. 
     Moreover, the interlock operation request from the electric power tool  2  is made by periodically transmitting the signal including the interlock operation request signal and the identification signal. Therefore, in the dust collector  4  side, operation of the dust collection motor  42  can be started at a timing of receipt of the signal and also, a start timing of the interlock operation can be made to correspond to operation of the electric power tool  2 . 
     Furthermore, the electric power tool  2  periodically and repeatedly transmits the interlock operation request. Meanwhile, when the dust collector  4  cannot receive the interlock operation request, driving of the dust collection motor  42  (in other words, the interlock operation of the dust collector  4 ) is stopped. 
     Accordingly, compared with a case where the electric power tool  2  is configured to transmit a signal instructing start and a signal instructing stop of the interlock operation, the interlock operation of the dust collector  4  can be reliably stopped. 
     That is, in the case where the electric power tool  2  is configured to transmit a signal instructing start and a signal instructing stop of the interlock operation, if the transmission and reception circuit  62  cannot receive a stop command from the electric power tool  2  due to change in a communication condition between the dust collector  4  and the electric power tool  2 , it is impossible to stop the driving of the dust collection motor  42 . 
     However, according to the dust collector  4  of the first embodiment, it is possible to reliably stop the driving of the dust collection motor  42  without causing the aforementioned problem. 
     Moreover, in the dust collector  4 , the identification number of the electric power tool  2  as an object of the interlock operation can be additionally registered in accordance with a command from the SW circuit  38  provided in the communication unit  30  of the electric power tool  2  or from the SW circuit  70  (specifically, the registration SW) provided in the communication unit  60  of the dust collector  4 . 
     Furthermore, the registration of the identification number of the electric power tool  2  as an object of the interlock operation can be removed by a command from the SW circuit  70  (specifically, the deletion SW) provided in the communication unit  60  of the dust collector  4 . 
     Accordingly, the user can arbitrarily set, in the dust collector  4 , the electric power tool  2  as an object of the interlock operation and also, the setting operation can be easily made by operating a switch in the electric power tool  2  side or the dust collector  4  side. 
     Moreover, whether or not this operation of the switch can property register or delete the identification information is notified (in the first embodiment, displayed by lighting an LED, etc.) via the notification circuit  72  provided in the communication unit  60  of the dust collector  4 . Therefore, the user can confirm registration results or deletion results of the identification information by confirming the state of the notification. 
     Thus, the dust collector  4  of the first embodiment provides excellent usability to the users. 
     Here, in the first embodiment, the dust collection hose  41  and the dust collection motor  42  correspond to one example of a dust collection portion of the present invention; the antenna  61  and the transmission and reception circuit  62  in the communication unit  60  correspond to one example of a communication portion of the present invention; the control circuit  64  in the communication unit  60  and the control circuit  50  in the dust-collector main body  40  correspond to one example of an interlock operation control portion of the present invention; and the memory  68  in the communication unit  60  corresponds to one example of a storage portion of the present invention. 
     Moreover, the registration SW in the SW circuit  70  provided in the communication unit  60  corresponds to one example of a registration operation portion of the present invention; likewise, the deletion SW corresponds to one example of a deletion operation portion of the present invention; and the notification circuit  72  corresponds to one example of a notification portion of the present invention. 
     Second Embodiment 
     The second embodiment is made by modifying part of respective configurations of the electric power tool  2  and the dust collector  4  in the first embodiment. Accordingly, in the following description, the same configurations as those of the first embodiment are assigned with the same reference numerals as those used in the first embodiment, and will not be explained; only different configurations will be explained. 
     In the communication unit  60  of the second embodiment, the antenna  61 , the transmission and reception circuit  62 , the control circuit  64 , the IF circuit  66 , the memory  68 , the SW circuit  70 , and the notification circuit  72  are all formed by a circuit pattern(s) of a circuit board  80  shown in  FIG.  7 A  and electronic components mounted on the circuit board  80 . 
     As shown in  FIG.  7 A , the antenna  61  and the IF circuit  66  (specifically, a connector for connection to the dust-collector main body  40 ) are mounted, respectively, on both ends of the circuit board  80 . In the circuit board  80 , a component mounting area  82  is set between the antenna  61  and the IF circuit  66 ; the component mounting area  82  is provided for electronic components forming the transmission and reception circuit  62 , the control circuit  64 , the memory  68 , the SW circuit  70 , and the notification circuit  72 . 
     Moreover, a resin case  84  for waterproofing is to be attached to the circuit board  80  so as to cover the component mounting area  82  on which respective electronic components of the aforementioned circuits are mounted. 
     Moreover, the resin case  84  is configured to cover, in addition to the component mounting area  82 , part of the IF circuit  66  excluding a connection portion to the dust-collector main body  40 . 
     As shown in  FIG.  7 B , the circuit board  80  with the component mounting area  82  being covered by the resin case  84  for waterproofing is housed in an outer case  86  made of synthetic resin. 
     The outer case  86  is formed in a shape allowing the connection portion of the IF circuit  66  to protrude outside therefrom, and via this connection portion, the communication unit  60  is coupled to the IF circuit  58  of the dust-collector main body  40 . 
     In the communication unit  30  of the second embodiment, as in the communication unit  60  of the dust collector  4 , electronic components that form the operation detection circuit  32 , the antenna  33 , the transmission and reception circuit  34 , the control circuit  36 , the SW circuit  38 , and the identification-number setting portion  37  are mounted on a circuit board  90  shown in  FIG.  8 A . 
     As shown in  FIG.  8 A , the antenna  33  is mounted on an end of the circuit board  90 , and the electronic components excluding the antenna  33  are mounted on a component mounting area in a central part of the circuit board  90 . Moreover, as in the communication unit  60  of the dust collector  4 , the component mounting area is covered by a resin case  92  for waterproofing. 
     The above-described circuit board  90 , on which the electronic components are mounted and to which the resin case  92  is attached so as to cover the electronic components excluding the antenna  33 , is housed in an outer case  94 , as in the communication unit  60  of the dust collector  4 . 
     In order to have a function of coupling the tool main body  10  to the battery pack  20 , as shown in  FIG.  8 B , the outer case  94  comprises an attachment portion  95  for the tool main body  10 , which is formed at a side where a mounting surface for the electronic components exists in the circuit board  90 , and an attachment portion  96  for the battery pack  20 , which is formed in an opposite side to the mounting surface. 
     A rear end side of the tool main body  10  is to be attached to the attachment portion  95  in a state where the tip end side of the tool main body  10 , to which the cutting grindstone  12  is to be attached, is protruded from an opposite side to the antenna  33 . The battery pack  20  is to be attached to the attachment portion  96 . 
     As explained above, in the dust collector  4  of the second embodiment, the signal isolation circuit  48  comprising a photocoupler and the isolated control power source  52  comprising an isolation transformer are provided inside the dust-collector main body  40 ; with these components, a path of an alternating current voltage supplied from the external alternating-current power source is electrically isolated from the communication unit  60 . 
     For this reason, by supplying electric power and transmitting/receiving signals to/from the communication unit  60  that is isolated from the alternating-current power source, it becomes possible to eliminate or reduce risk of electrical shock in a case where the user touches a terminal of the IF circuit  58  when attaching the communication unit  60  to the dust-collector main body  40 ; consequently, improved safety can be achieved. 
     Moreover, in the communication unit  60 , the antenna  61  is disposed, across the internal circuits such as the control circuit  64 , at an opposite side to the IF circuit  66  that is a signal input/output portion in the communication unit  60  side. For this reason, the antenna  61  can be disposed away from a connection portion to the dust-collector main body  40 , which may interfere with the wireless communication; thus, the wireless communication by the antenna  61  can be favorably achieved. 
     Furthermore, in the communication unit  60 , all of the constituent components (electronic components) excluding the antenna  61  and the connector of the IF circuit  66  are to be covered by the resin case  84  for waterproofing on the circuit board  80 . Thus, waterproof properties of the communication unit  60  can be enhanced. 
     Moreover, especially, the communication unit  30  of the electric power tool  2  is likely to be splashed with water when the electric power tool  2  is used. However, also in the communication unit  30 , constituent components (electronic components) excluding the antenna  33  are to be covered by the resin case  92  for waterproofing on the circuit board  90 . Thus, waterproof properties can be enhanced, and malfunctions caused by splashing water to the communication unit  30  can be reduced. 
     Also, in the dust-collector main body  40 , the current detection circuit  56  is provided on the path for the direct current power supplied from the isolated control power source  52  to the communication unit  60 . The control circuit  50  is configured to detect that the communication unit  60  has been attached based on the detected electric current by the current detection circuit  56 . 
     With this configuration, it is possible to detect attachment of the communication unit without providing, in the dust-collector main body  40 , a terminal dedicated to detection of attachment of the communication unit  60 . Thus, a size of a connector constituting the IF circuit  58  can be reduced, thereby facilitating downsizing and cost reduction of the dust-collector main body  40 . 
     Here, in the present embodiment, the isolated control power source  52  and the signal isolation circuit  48  correspond to one example of an isolation device of the present invention; and among these two, especially, the signal isolation circuit  48  corresponds to one example of a contactless circuit of the present invention. Moreover, the IF circuit  66  corresponds to one example of a signal input portion of the present invention; and the control circuit  64  corresponds to one example of a communication control portion of the present invention. 
     The exemplified embodiments of the present invention have been described as above; however, the present invention should not be limited to the above-described first and second embodiments, but can take various forms within the scope not departing from the spirit of the present invention. 
     For example, in the above-described embodiments, the electric working machine as an object of the interlock operation with the dust collector  4  is a grinder; however, any electric working machine in other forms, such as a circular saw, a plane, etc., which discharges powder dust or cutting chips during the operation. 
     Moreover, in the above-described embodiments, the dust collector  4  comprises the dust-collector main body  40  and the communication unit  60  that is separately provided from and is detachably attached to the dust-collector main body  40 . However, the dust collector  4  may contain a communication circuit having the same communication function as that of the communication unit  60 . 
     In above-described embodiments, the dust collector  4  is configured to be able to additionally register and delete, in and from the memory  68 , the identification number of the electric power tool  2  as an object of the interlock operation; however, the dust collector  4  may be configured not to perform part or all of the above-described additional registration and deletion of the identification number. 
     For example, according to the dust collector  4  of the above-described embodiments, the user can operate the registration SW of the SW circuit  70  provided in the communication unit  60  to make the control circuit  64  execute the additional registration process shown in  FIGS.  4 A and  4 B , thereby additional registering the identification number of the electric power tool  2 . 
     Therefore, it is not absolutely necessary to provide the SW circuit  38  for registration of the identification number in the communication unit  30  of the electric power tool  2 . In other words, it is not necessary to use the SW circuit  38  to make the control circuit  36  in the electric power tool  2  execute the registration request process shown in  FIG.  3 A , thereby making the control circuit  64  of the dust collector  4  register the identification number of the electric power tool  2 . 
     As described above, if the SW circuit  38  is not provided in the communication unit  30  of the electric power tool  2 , downsizing and cost reduction of the communication unit  30  can be achieved and therefore, demand for reducing size and weight of the electric power tool  2  can be met. 
     Moreover, in the above-described embodiments, the identification number (product serial number, etc.) of the communication unit  30  is stored as the identification information of the electric power tool  2  in the memory  68  and based on this identification number, it is determined whether to make the dust collection motor  42  perform the interlock operation; however, any identification information that can be used to identify an electric working machine as an object of the interlock operation may be stored in the memory  68 . 
     Meanwhile, in the above-described embodiments, the identification-number transmission process shown in  FIG.  4 A , which is executed by the control circuit  36  inside the communication unit  30  of the electric power tool  2 , may be modified as shown in  FIG.  6   . 
     Specifically, in the identification-number transmission process shown in  FIG.  6   , if it is determined in S 510  that the identification-number transmission request has been received in the transmission and reception circuit  62 , the process proceeds to S 515  to determine whether the trigger switch  18  is in an ON state. 
     If the trigger switch  18  is in the ON state, the process proceeds to S 520  to transmit the identification number of the communication unit  30  from the transmission and reception circuit  34 . However, if the trigger switch  18  is not in the ON state, the current identification-number transmission process is terminated without transmitting the identification number. 
     If the identification-number transmission process, which is executed in the control circuit  36  in the electric power tool  2 , is modified as described above, it is possible to reduce a number of the electric power tools  2  that send the identification number in response to the identification-number transmission request transmitted by the additional registration process shown in  FIGS.  4 A and  4 B , thereby increasing possibility for the control circuit  64  to additionally register the identification number in the memory  68 . 
     Specifically, in the additional registration process shown in  FIGS.  4 A  and  4 B, the identification-number transmission request is transmitted to an area around the dust collector  4  via the transmission and reception circuit  62 , so that the identification number of the electric power tool  2  located in the aforementioned area can be obtained and additionally registered in the memory  68 . However, if multiple identification numbers are obtained, the identification number to be additionally registered cannot be identified; therefore, the additional registration to the memory  68  is inhibited. 
     In this regard, if the identification-number transmission process executed in the electric power tool  2  is modified as shown in  FIG.  6   , the identification number is transmitted on the condition that the trigger switch  18  is in the ON state. Accordingly, it is possible to reduce possibility for the multiple electric power tools  2  to transmit the identification numbers, thereby facilitating additional registration of the identification number in the memory  68 . 
     Moreover, when the user operates the trigger switch  18  of the electric power tool  2 , the identification number of which is desired to be registered, simultaneously with or immediately after operating the registration SW of the dust collector  4 , the identification number of this electric power tool  2  can be additionally registered in the memory  68  of the dust collector  4 . 
     Thus, the user can more reliably register a desired electric power tool  2  as a tool with which the dust collector  4  is made to perform the interlock operation. In addition, it is possible to further reduce possibility of erroneous registration of an electric power tool that is not an object of the interlock operation. 
     Moreover, in the above-described first and second embodiments, in order to isolate between the communication unit  60  and the external alternating-current power source, the isolated control power source  52  comprising the isolation transformer and the signal isolation circuit  48  comprising the photocoupler are provided in the dust-collector main body  40 . However, an isolation transformer and a photocoupler may be provided in the IF circuit  58 , thereby electrically isolating between the dust-collector main body  40  and the communication unit  60 . 
     In addition, this isolation is sufficient when a leakage current flowing from the dust-collector main body  40  to the communication unit  60  is limited to a specified value or below. Thus, for example, a capacitor or a resistor may be provided in the current path so that the current path has impedance. 
     Moreover, as the isolated control power source  52 , an isolating switching power supply may be used. 
     Furthermore, in the above-described first and second embodiments, a direct current voltage generated by the isolated control power source  52  is supplied, as a power source voltage, to the communication unit  60 . However, it is not absolutely necessarily to supply power from the dust-collector main body  40  to the communication unit  60 , and the communication unit  60  may be configured to contain a battery as a direct-current power source. 
     In this configuration, by simply providing a photocoupler, etc. between the dust-collector main body  40  and the communication unit  60 , it is possible to isolate between the alternating-current power source and the communication unit  60 ; consequently, a function as an isolation device can be very easily obtained. 
     Furthermore, in the second embodiment, it has been described that in the communication units  30  and  60 , the antennas  33  and  61  are, respectively disposed outside the resin cases  84  and  92 ; however, the antennas  33  and  61  may be housed inside the resin cases  84  and  92 , respectively.