Patent Publication Number: US-2023148334-A1

Title: Power tool, power tool accessory and coupling arrangement therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority, under 35 U.S.C. § 119, to UK Patent Application No. 2116001.5 filed Nov. 8, 2021, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a power tool, power tool accessory and coupling arrangement therefor. In particular, the present disclosure relates to coupling arrangement between a rotary hammer and a dust extractor. 
     BACKGROUND 
     Operation of a power tool such as a rotary hammer can often create considerable dust. This is undesirable for the user and therefore a dust extractor may be used to remove dust away from the vicinity of the rotary hammer and the user. 
     Some known dust extractors are mountable to the rotary hammer and are electrically connected to the power supply of the rotary hammer. The dust extractor engages with projecting electrical contacts from the surface of the housing. The projecting electrical contacts can be damaged when the rotatory hammer is placed on a surface. This means that dust extractor may not work properly when mounted on the rotary hammer. 
     Other known dust extractors are engageable with electrical contacts positioned in air vents of the rotary hammer. Whilst this means the electrical contacts are not damaged when the rotary hammer is place on a surface, the airflow through the rotary hammer is restricted when mounted to the dust extractor. 
     SUMMARY 
     Examples of the present disclosure aim to address the aforementioned problems. 
     According to an aspect of the present disclosure there is a power tool comprising: a power source; a power tool housing comprising a first mechanical coupling connectable with a second reciprocal mechanical coupling on a power tool accessory; and a first electrical coupling in electrical connection with the power source and mounted on the first mechanical coupling wherein the first electrical coupling is electrically connectable with a second reciprocal electrical coupling on the power tool accessory. 
     In an embodiment, the first mechanical coupling is a slot or a rail configured to couple with a rail or slot of the second reciprocal mechanical coupling. 
     In an embodiment, the first mechanical coupling is a slot and the second reciprocal mechanical coupling is a rail. 
     In an embodiment, the first mechanical coupling and comprises a first slot a first side of the power tool housing and a second slot on a second side of the power tool housing, the first slot and the second slot respectively configured to couple with a first rail of the second reciprocal mechanical coupling on the first side of the power tool housing and a second rail of the second reciprocal mechanical coupling on the second side of the power tool housing. 
     In an embodiment, the first electrical coupling comprises a plurality of electrical contacts configured to engage a plurality of electrical contacts of the second reciprocal electrical coupling. 
     In an embodiment, the plurality of electrical contacts of the first electrical coupling are mounted on the same surface of the first mechanical coupling. 
     In an embodiment, the plurality of electrical contacts of the second reciprocal electrical coupling are mounted on the same surface of the second reciprocal mechanical coupling. 
     In an embodiment, a distance between a first pair of electrical contacts on the first electrical coupling and the second reciprocal electrical coupling is different from a distance between a second pair of electrical contacts on the first electrical coupling and the second reciprocal electrical coupling. 
     In an embodiment, the plurality of the electrical contacts of the first electrical coupling and the second reciprocal electrical coupling are respectively mounted on a plurality of different surfaces of the first mechanical coupling and the second reciprocal mechanical coupling. 
     In an embodiment, the plurality of electrical contacts of one of the first electrical coupling and the second reciprocal electrical coupling are metal plates. 
     In an embodiment, the plurality of electrical contacts of the other of the first electrical coupling and the second reciprocal electrical coupling are metal springs. 
     In an embodiment, at least one of the electrical contacts is arranged to transmit data between the power tool and the power tool accessory. 
     In an embodiment, the power tool is one of a rotary hammer, a diamond core drill, hammer drill, a router, a reciprocating saw, plunge saw, a circular saw, an impact driver, a drill, a hammer drill, a multitool, an oscillating tool, a chipping hammer. 
     In an embodiment, the power source is a battery is mountable to the power tool housing. 
     In an embodiment, the first mechanical coupling is a slot or a rail comprising a plurality of electrical contacts mounted on the slot or rail. 
     In an embodiment, the second mechanical coupling is a slot or a rail comprising a plurality of electrical contacts mounted on the slot or rail. 
     In an embodiment, the power tool and the power tool accessory are only mechanically coupled together with the first mechanical coupling and the second mechanical coupling. 
     In a second aspect of the present disclosure, there is provided a power tool accessory mountable on a power tool for comprising: an accessory housing comprising a second reciprocal mechanical coupling connectable with a first reciprocal mechanical coupling on the power tool; and a second reciprocal electrical coupling mounted on the second reciprocal mechanical coupling wherein the second reciprocal electrical coupling is electrically connectable with a first reciprocal electrical coupling on power tool wherein the first reciprocal electrical coupling is in electrical connection with a power source of the power tool. 
     In an embodiment, the power tool accessory is one of a dust extractor, a water pump, a laser indicator, or an illumination device. 
     In a third aspect of the present disclosure there is provided a power tool assembly comprising: a power tool having: a power tool housing; a power source; a first mechanical coupling on the housing; and a first electrical coupling in electrical connection with the power source and mounted on the first mechanical coupling; and a power tool accessory having: an accessory housing; a second reciprocal mechanical coupling connected with the first mechanical coupling; and a second reciprocal electrical coupling and mounted on the second reciprocal mechanical coupling wherein the second reciprocal electrical coupling is in electrical connection with the first electrical coupling. 
     In a fourth aspect of the present disclosure there is provided a power tool coupling assembly for connecting a power tool to a power tool accessory and mounted on a housing of the power tool, the power tool coupling assembly comprising: a first mechanical coupling connectable with a second reciprocal mechanical coupling on the power tool accessory; and a first electrical coupling in electrical connection with a power source of the power tool and mounted on the first mechanical coupling wherein the first electrical coupling is electrically connectable with a second reciprocal electrical coupling mounted on the second reciprocal mechanical coupling. 
     In a fifth aspect of the present disclosure there is provided an accessory coupling assembly for connecting a power tool accessory to a power tool and mounted on a housing of the power tool accessory, the accessory coupling assembly comprising: a second reciprocal mechanical coupling connectable with a first reciprocal mechanical coupling on the power tool; and a second reciprocal electrical coupling mounted on the second reciprocal mechanical coupling wherein the second reciprocal electrical coupling is electrically connectable with a first reciprocal electrical coupling mounted on the first reciprocal mechanical coupling wherein the first reciprocal electrical coupling is in electrical connection with a power source of the power tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various other aspects and further examples are also described in the following detailed description and in the attached claims with reference to the accompanying drawings, in which: 
         FIG.  1    shows a side view of a power tool according to an example; 
         FIG.  2    shows an exploded perspective view of part of a power tool and a power tool accessory according to an embodiment; 
         FIG.  3    shows a close-up perspective view of a power tool and a power tool accessory according to an embodiment; 
         FIG.  4    shows a close-up perspective view of a power tool accessory according to an embodiment; 
         FIG.  5    shows a close-up perspective view of a power tool according to an embodiment; 
         FIG.  6    shows a partial cross-sectional view of a power tool and a power tool accessory according to an embodiment; 
         FIG.  7    shows another partial cross-sectional view of a power tool and a power tool accessory according to an embodiment; 
         FIG.  8    shows a close-up perspective view of a power tool accessory according to an embodiment; 
         FIG.  9    shows a close-up perspective view of a power tool according to an embodiment; and 
         FIG.  10    shows a side view of a power tool and a power tool accessory according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a side view of a power tool  100 . The power tool  100  as shown in  FIG.  1    is a hammer drill or a rotary hammer. Whilst  FIG.  1    shows a hammer drill, in other examples any other type of power tool  100  can be used. For example, the power tool  100  can be a plunge saw, a reciprocating saw, a circular saw, an impact driver, a drill, a multitool, an oscillating tool, or any other power tool  100 . Hereinafter the term “power tool” will be used to describe the rotary hammer, but this also refers to any other suitable power tool  100 . 
     The power tool  100  comprises a power tool housing  102 . The power tool housing  102  comprises a clam shell type construction having two halves which are fastened together. The halves of the power tool housing  102  are fastened together with screws but in alternative examples any suitable means for fastening the power tool housing  102  together may be used such as glue, clips, bolts and so on. For the purposes of clarity, the fastenings in the power tool housing  102  are not shown in  FIG.  1   . 
     An electric motor (not shown) is mounted in a motor housing portion  104  of the power tool housing  102 . The motor housing portion  104  is integral with the power tool housing  102 . 
     As shown in  FIG.  1   , the power tool housing  102  comprises a handle  110  for the user to grip during use. A trigger button  106  is mounted on the handle  110  which is used by the user to activate the electric motor (not shown). The electric motor is electrically connected to a battery pack  112 . The battery pack  112  is optionally removably mountable to the power tool housing  102  at the base of the handle  110 . In some examples, the battery pack  112  is integral to the power tool housing  102  and not removeable. Alternatively in other examples the power tool  100  is powered additionally or alternatively with mains power (not shown). Where the power tool  100  is powered with mains power, the power tool  100  optionally comprises a rectified for converting AC voltage to DC voltage. In this way, a power tool accessory  200  (as described hereinafter) configured for operation with a DC power source can be powered from the power tool  100 . 
     The electric motor is rotatably coupled to a tool holder  114  via an output drive shaft (not shown). A cutting tool (not shown) such as a drill bit can be mounted in the tool holder  114 . The motor housing portion  104  comprises one or more air vents  108  for cooling the motor. The air vents  108  allow the intake or exhaust of air to increase air circulation around the motor. 
     In some examples a power tool coupling assembly  116  is located on the power tool housing  102  below the air vents  108 . The power tool coupling assembly  116  is arranged to connect the power tool  100  to a power tool accessory  200  (as best shown in  FIG.  2   ). The power tool coupling assembly  116  is arranged to mechanically and electrically connect the power tool  100  to the power tool accessory  200 . 
     The power tool coupling assembly  116  as shown in  FIG.  1    is integral with the power tool housing  102 . In this way, the structure of the power tool coupling assembly  116  is optionally formed when the power tool housing  102  is moulded and the power tool coupling assembly  116  and the power tool housing  102  are a unitary element. However, in some other examples, the power tool coupling assembly  116  is optionally a separate component that is fixed to the surface of the power tool housing  102 . Accordingly, reference to the power tool coupling assembly  116  being mounted on, located on etc the power tool housing  102  can mean the separate component fixed to the power tool housing  102  or an integral part of the power tool housing  102 . 
     The power tool coupling assembly  116  in  FIG.  1    is shown mounted on the motor housing portion  104  below the air vents  108 . However, the power tool coupling assembly  116  can be mounted anywhere on the power tool housing  102 . By mounting the power tool coupling assembly  116  on the power tool  100  below the air vents  108 , the power tool accessory  200  will not obstruct the airflow through the power tool  100  during use. 
     Turning to  FIG.  2   , the power tool accessory  200  and the power tool  100  will now be described in further detail.  FIG.  2    shows an exploded perspective view of part of the power tool  100  and a power tool accessory  200  according to an example. 
     The power tool  100  as shown in  FIG.  2    is partially represented for the purposes of clarity. Specifically, part of the motor housing portion  104  including the tool holder  114  is omitted from  FIG.  2   . The battery pack  112  is also not shown in  FIG.  2   . 
     The power tool accessory  200  as shown in  FIG.  2    is a dust extractor. The dust extractor is arranged to remove dust from the vicinity of the tool holder  114  during operation of the power tool  100 . However, in other examples, the power tool accessory  200  can be another suitable accessory mountable on the power tool  100 . 
     For example, the power tool accessory  200  can be an illumination device, a laser indicator, or any other suitable accessory mechanically and electrically connectable to the power tool  100 . In some other examples, the power tool accessory  200  can be additionally or alternatively a charging mount (not shown) for a mobile phone or a camera or other electronic accessory. The mount for the mobile phone or the camera can comprise a charging socket for charging the mobile phone, camera, or other electronic accessory. The mount can comprise a gripping mechanism for securing the mobile phone or the camera to the mount. The mount can comprise a moveable joint for angling the mobile phone or camera with respect to the power tool  100 . This means that the mobile phone or camera can be positioned to take images or video footage of the operation of the power tool  100 . Alternatively, the mobile phone can be used to display instructions or other information for the user of the power tool  100  during operation of the power tool  100 . In some examples, the power tool accessory  200  can be light or torch. In this way the torch or light can be mounted to the power tool  100  and powered by the power tool  100 . Hereinafter, the term “power tool accessory”  200  will be used to refer to the dust extractor, however this can also be used to describe any other suitable accessory. 
     The power tool accessory  200  is mountable on a front side  118  (as best shown in  FIG.  1   ) of the power tool  100 . This means that the user pushes the power tool  100  into the power tool accessory  200  in a direction towards the tool holder  114 . In some other examples, the power tool accessory  200  is mountable on other parts and sides of the power tool  100 . Although not shown, the power tool accessory  200  is mountable on a rear side  120  adjacent the handle  110 , or the underside  122  adjacent the battery pack  112  or on a top side  124 . 
     The power tool accessory  200  is removably mountable to the power tool  100 . Accordingly, the user can mount the power tool accessory  200  to the power tool  100  to increases the versatility and functionality of the power tool  100  as needed by the user. 
       FIG.  2    shows the power tool accessory  200  having an accessory housing  202 . Similar to the power tool housing  102 , the accessory housing  202  comprises a clam shell type construction having two halves which are fastened together. The halves of the accessory housing  202  are fastened together with screws but in alternative examples any suitable means for fastening the accessory housing  202  together may be used such as glue, clips, bolts and so on. For the purposes of clarity, the fastenings in the accessory housing  202  are not shown in  FIG.  2   . 
     The accessory housing  202  comprises a central recess  204  for receiving the power tool housing  102  when the power tool accessory  200  is engaged with the power tool  100 . The central recess  204  comprises one or more curved walls  206  shaped to complement the shape of the power tool housing  102 . The central recess  204  can optionally comprise curved ribs  208  also arranged to engage the power tool housing  102 . The central recess  204  optionally comprises projecting side walls  218  for overlapping with at least a portion of the power tool housing  102 . When the power tool accessory  200  is mounted on the power tool  100 , the side walls  218  overlap the power tool housing  102  and help limit the movement of the power tool  100  with respect to the power tool accessory  200 . 
     The power tool accessory  200  as shown in  FIG.  2    comprises a motor-fan assembly (not shown) mounted in the accessory housing  202 . The motor-fan assembly is arranged to generate an air flow from a dirty air inlet  210  to a clean air outlet  212 . The dirty air inlet  210  is adjacent to a tool collar  216  arranged to surround the cutting tool mounted in the tool holder  114 . The power tool accessory  200  comprises a removeable dirt container  214  for capturing dirt entrained in the airflow. 
     In some examples an accessory coupling assembly  220  is located on the accessory housing  202  in the central recess  204 . The accessory coupling assembly  220  is arranged to connect the power tool accessory  200  to the power tool  100 . The accessory coupling assembly  220  is arranged to mechanically and electrically connect the power tool accessory  200  to the power tool  100 . 
     The accessory coupling assembly  220  as shown in  FIG.  2    is optionally integral with the accessory housing  202 . In this way, the structure of accessory coupling assembly  220  is formed when the accessory housing  202  is moulded and the accessory coupling assembly  220  and accessory housing  202  are a unitary element. However, in some other examples, the accessory coupling assembly  220  is optionally a separate component that is fixed to the surface of the accessory housing  202 . Accordingly, reference to the accessory coupling assembly  220  being mounted on, located on etc the accessory housing  202  can mean the separate component fixed to the power tool housing  102  or an integral part of the accessory housing  202 . 
     Turning to  FIGS.  3 ,  4  and  5   , the engagement between the power tool  100  and the power tool accessory  200  will now be discussed in more detail.  FIG.  3    shows a close-up perspective view of the power tool  100  and the power tool accessory  200  according to an example.  FIG.  3    is a close up of  FIG.  2    as indicated by the dotted box labelled A in  FIG.  2   .  FIG.  4    shows a close-up perspective view of the power tool accessory  200  as indicated by the dotted box labelled B in  FIG.  3   .  FIG.  5    shows a close-up perspective view of a power tool  100  as indicated by the dotted box labelled C in  FIG.  3   . 
     The power tool housing  102  comprises a first mechanical coupling  300 . The first mechanical coupling  300  as shown in  FIG.  3    is a first slot  302 . In some examples, the first mechanical coupling  300  comprises a pair of slots  302 ,  700  on either side of the power tool housing  102 . 
     The pair of slots  302 ,  700  are best shown in  FIG.  7   .  FIG.  7    shows another partial cross-sectional view of the power tool  100  and the power tool accessory  200  according to an example. Accordingly, the first slot  302  is positioned on a first side  702  of the power tool housing  102  and a second slot  700  is positioned on a second side  704  of the power tool housing  102 . As can be seen from  FIG.  7   , the first slot  302  and the second slot  700  are positioned along the axis X-X. The first slot  302  and the second slot  700  are located on opposite sides  702 ,  704  of the power tool housing  102 . In this way, the first and second slots  302 ,  700  limit the movement of the power tool  100  with respect to the power tool accessory  200  when the power tool  100  is mounted to the power tool accessory  200 . 
     Whilst  FIG.  7    shows the first mechanical coupling  300  mounted on the power tool housing  102  comprise a first slot  302  and a second slot  700 , in other examples different mechanical coupling mechanisms can be used. For example, in some alternatives the first mechanical coupling  300  comprises a single slot (not shown). In this example with a single slot, the single slot may optionally comprise a “T” cross-sectional shape or an “I” cross-sectional shape. 
     In some other examples, there are additional slots mounted on the power tool housing  102  in addition to the first and second slots  302 ,  700 . Indeed, there can be any number of slots to increase the frictional forces between the power tool  100  and the power tool accessory  200 . 
     Turning back to  FIG.  3   , the mechanical engagement between the power tool  100  and the power tool accessory  200  will be further discussed. 
     The power tool accessory  200  comprises second reciprocal mechanical coupling  304 . The second reciprocal mechanical coupling  304  is connectable with the first mechanical coupling  300  on the power tool  100 . 
     The second reciprocal mechanical coupling  304  as shown in  FIG.  3    is a first rail  306  projecting from side wall  218  of the accessory housing  202 . The first rail  306  is arranged to mechanically engage the first slot  302 . In some examples, the second reciprocal mechanical coupling  304  comprises a pair of rails  306 ,  706  on either side wall  218  of the accessory housing  202 . Similarly, the first and second rails  306 ,  706  are arranged to respectively mechanically engage the first and second slots  302 ,  700 . 
     The pair of rails  306 ,  706  are best shown in  FIG.  7   . Accordingly, the first rail  306  is positioned on the first side  702  of the power tool housing  102  and a second rail  706  is positioned on the second side  704  of the power tool housing  102 . As can be seen from  FIG.  7   , the first rail  306  and the second rail  706  are positioned along the axis X-X. The first rail  306  and the second rail  706  are located on opposite sides  702 ,  704  of the accessory housing  202 . In this way, the first and second rails  306 ,  706  limit the movement of the power tool  100  with respect to the power tool accessory  200  when the power tool  100  is mounted to the power tool accessory  200 . 
     The first mechanical coupling  300  and the second reciprocal mechanical coupling  304  engage each other. A frictional force between the first mechanical coupling  300  and the second reciprocal mechanical coupling  304  prevents the first mechanical coupling  300  and the second reciprocal mechanical coupling  304  from accidentally separating. In some other examples, in additional to the frictional forces between the first mechanical coupling  300  and the second reciprocal mechanical coupling  304  optionally one or more mechanisms for providing a positive engagement are provided. For example, a detent (not shown) on the first or second rails  306 ,  706  can engage with reciprocal recess on the first or second slots  302 ,  700 . Additionally, or alternatively, the power tool accessory  200  can be secured to the power tool  100  with clips or a latch mechanism (not shown). 
     In the previously mentioned example where the first mechanical coupling  300  comprises a single slot (not shown), a single rail (not shown) is also provided on one side of the power tool accessory  200 . In this example with a single slot, the single slot may optionally comprise a “T” cross-sectional shape or an “I” cross-sectional shape. Similarly, the single rail comprises a reciprocal “T” cross-sectional shape or an “I” cross-sectional shape for a sliding fit into the single rail. 
     As shown in Figures, the first mechanical coupling  300  and the second reciprocal mechanical coupling  304  are respectively a pair of slots  302 ,  700  and a pair of rails  306 ,  706 . However, in alternative examples not illustrated in the Figure, the first mechanical coupling  300  on the power tool housing  102  comprises a pair of rails. Similarly, the second reciprocal mechanical coupling  304  comprises a pair of slots. Furthermore, in some alternative examples, the first mechanical coupling  300  and the second reciprocal mechanical coupling  304  each comprise one slot and one rail. 
     In addition to the previously described mechanical engagement, the power tool coupling assembly  116  and the accessory coupling assembly  220  are electrically connectable. The electrical connection between the power tool  100  and the power tool accessory  200  will now be discussed. 
     The power tool coupling assembly  116  comprises a first electrical coupling  500  as shown in  FIG.  5   . The first electrical coupling  500  is in electrical connection with the battery pack  112 . This means that the power tool  100  can supply power to the power tool accessory  200  when electrically connected to the first electrical coupling  500 . 
     The first electrical coupling  500  is mounted on the first mechanical coupling  300 .  FIG.  5    shows a plurality of electrical contacts e.g. a first electrical contact  502 , a second electrical contact  504 , and a third electrical contact  506 . The plurality of electrical contacts  502 ,  504 ,  506  are mounted on different surfaces of the first slot  302 . In some examples, the first electrical contact  502 , the second electrical contact  504 , and the third electrical contact  506  are respectively mounted on a lower slot surface  508 , a vertical slot surface  510  and an upper slot surface  512 . By locating the plurality of electrical contacts  502 ,  504 ,  506  on different surfaces of the first slot  302 , the power tool accessory  200  is not able to accidentally short circuit across the incorrect electrical contact when mounting the power tool accessory  200  on the power tool  100 . 
     In some examples, the plurality of electrical contacts  502 ,  504 ,  506  are spring biased for engagement with a reciprocal electrical contact. As can be seen from  FIG.  5   , the first electrical contact  502 , the second electrical contact  504 , and the third electrical contact  506  comprise a flat plate portion connected to a spring biased free end. However, in some alternative examples the first electrical contact  502 , the second electrical contact  504 , and the third electrical contact  506  are flat metal plates. 
     Similarly, the accessory coupling assembly  220  as shown in  FIG.  4    comprises a second reciprocal electrical coupling  400  as shown in  FIG.  4   . When the first electrical coupling  500  is electrically connected with the second reciprocal electrical coupling  400 , the power tool accessory  200  receives power from the power source of the power tool  100 . In some examples this is a battery pack  112 , but in other examples this is mains voltage. 
     The second reciprocal electrical coupling  400  is mounted on the second reciprocal mechanical coupling  304 .  FIG.  4    shows a plurality of reciprocal electrical contacts  402 ,  404 ,  406  e.g. a first reciprocal electrical contact  402 , a second reciprocal electrical contact  404 , and a third reciprocal electrical contact  406 . The plurality of reciprocal electrical contacts  402 ,  404 ,  404  are mounted on different surfaces of the first rail  306 . In some examples, the first reciprocal electrical contact  402 , the second reciprocal electrical contact  404 , and the third reciprocal electrical contact  406  are respectively mounted on a lower rail surface  408 , a vertical rail surface  410  and an upper rail surface  412 . By locating the plurality of reciprocal electrical contacts  402 ,  404 ,  406  on different surfaces of the first rail  306 , the power tool accessory  200  is not able to accidentally short circuit across the incorrect electrical contact when mounting the power tool accessory  200  on the power tool  100 . 
     Accordingly, the first reciprocal electrical contact  402 , the second reciprocal electrical contact  404 , and the third reciprocal electrical contact  406  are arranged to electrically connect respectively to the first electrical contact  502 , the second electrical contact  504 , and the third electrical contact  506 . This is best shown in  FIG.  6    which shows the power tool  100  and the power tool accessory  200  in mechanical and electrical engagement.  FIG.  6    shows a partial cross-sectional view of the power tool  100  and the power tool accessory  200  along the axis Y-Y in  FIG.  7   . 
     In some examples, the first reciprocal electrical contact  402  and the first electrical contact  502  and the second reciprocal electrical contact  404  and the second electrical contact  504  are configured to transmit power from the battery pack  112  to the power tool accessory  200 . In some examples, the third reciprocal electrical contact  406  and the third electrical contact  506  are configured to provide information about the power tool accessory  200  to a controller (not shown) of the power tool accessory  200  and/or the power tool  100 . 
     In some examples, the third reciprocal electrical contact  406  and the third electrical contact  506  provide an ON/OFF signal that the indicates whether the power tool accessory  200  is mounted to the power tool  100 . In some other examples, the third reciprocal electrical contact  406  and the third electrical contact  506  are a data connection between the power tool accessory  200  and the power tool  100 . In this way, status information or any other information of the power tool accessory  200  and the power tool  100  can be transmitted between the power tool accessory  200  and the power tool  100 . This can help the power tool  100  manage the power requirements of the power tool  100  and the power tool accessory  200  during operation. 
     As shown in  FIGS.  6  and  7   , the plurality of electrical contacts  502 ,  504 ,  506  are mounted on the first slot  302  and the plurality of reciprocal electrical contacts  402 ,  404 ,  406  are mounted on the first rail  306 . This keeps the routing of the electrical wiring within the power tool accessory  200  simpler. However, in some examples only some of the plurality of electrical contacts  502 ,  504 ,  506  and the plurality of reciprocal electrical contacts  402 ,  404 ,  406  are mounted on the first slot  302  and the first rail  306 . At the same time one of the plurality of electrical contacts  502 ,  504 ,  506  and one of the plurality of reciprocal electrical contacts  402 ,  404 ,  406  are respectively mounted on the second slot  700  and the second rail  706 . By mounting some of the plurality of electrical contacts  502 ,  504 ,  506  and the plurality of reciprocal electrical contacts  402 ,  404 ,  406  on each of the first slot  302 , the first rail  306 , the second slot  700  and the second rail  706 , this again reduces the chances of accidentally causing a short circuit when the power tool accessory  200  is mounted on the power tool  100 . 
     As can be seen from  FIG.  4   , the first reciprocal electrical contact  402 , the second reciprocal electrical contact  404 , and the third reciprocal electrical contact  406  comprise a flat plate portion connected to a spring biased free end. However, in some alternative examples the first reciprocal electrical contact  402 , the second reciprocal electrical contact  404 , and the third reciprocal electrical contact  406  are flat metal plates. 
     In some examples, the first electrical coupling  500  and the second reciprocal electrical coupling  400  are mounted on surfaces such that the first electrical coupling  500  and the second reciprocal electrical coupling  400  do not project outwardly from the power tool housing  102  or the accessory housing  202 . Accordingly, when either the power tool  100  or the power tool accessory is placed on a surface, the first electrical coupling  500  and the second reciprocal electrical coupling  400  are protected. This improves the lifetime of the electrical connection between the power tool  100  and the power tool accessory  200 . 
     Turning to  FIGS.  8  and  9   , an alternative example will now be discussed.  FIG.  8    shows a close-up perspective view of the power tool accessory  200  according to an example and  FIG.  9    shows a close-up perspective view of the power tool  100  according to an example. The example shown in  FIGS.  8  and  9    is the same as discussed with respect to the previous Figures except that the arrangement of the plurality of electrical contacts  502 ,  504 ,  506  and the plurality of reciprocal electrical contacts  402 ,  404 ,  406  is different. 
     The plurality of electrical contacts  502 ,  504 ,  506  are mounted on the upper slot surface  512  as shown in  FIG.  9   . The plurality of reciprocal electrical contacts  402 ,  404 ,  406  are mounted on the upper rail surface  412 . In this way, the plurality of the electrical contacts  502 ,  504 ,  506  are all mounted on the same surface. Likewise, the plurality of reciprocal electrical contacts  402 ,  404 ,  406  are all mounted on the same surface. 
     The plurality of electrical contacts  502 ,  504 ,  506  are not equally spaced along the upper slot surface  512 . Indeed, the first electrical contact  502  and the second electrical contact  504  are separated by a first distance d 1 . The second electrical contact  504  and the third electrical contact  506  are separated by a second distance d 2 . In some examples, the first and the second distances d 1 , d 2  are not equal. As shown in  FIG.  9   , the first distance d 1  is less than the second distance d 2 . Alternatively, the first distance d 1  is greater than the second distance d 2 . 
     Turning to  FIG.  8   , likewise the plurality of reciprocal electrical contacts  402 ,  404 ,  406  are not equally spaced along the upper rail surface  412 . Similarly, the first reciprocal electrical contact  402  and the second reciprocal electrical contact  404  are separated by the first distance d 1 . The second reciprocal electrical contact  404  and the third reciprocal electrical contact  406  are separated by the second distance d 2 . 
     Accordingly, when mounting the power tool accessory  200  on the power tool  100 , the plurality of electrical contacts  502 ,  504 ,  506  and the plurality of reciprocal electrical contacts  402 ,  404 ,  406  will not accidentally short circuit. 
     Another example will be discussed with reference to  FIG.  10   .  FIG.  10    shows a side view of the power tool  100  and a power tool accessory  1000  according to an example. 
     The example as shown in  FIG.  10    is the same as discussed in reference to the previous examples, however the power tool accessory  1000  is a different power tool accessory. The power tool accessory  1000  engages the power tool  100  using the same mechanical and electrical features as discussed in the previous examples. 
     In  FIG.  10    the power tool accessory  1000  comprises an illumination device  1002  which illuminates and area  1004  around the tool holder  114  and the cutting tool. This means that the user can better see the workpiece during operation of the power tool  100 . Alternatively, the illumination device  1002  can be a laser indicator arranged to display a target intersection point on the workpiece. As can be seen from  FIG.  10   , the power tool accessory  1000  comprises a smaller form factor when compared to the power tool accessory  200  as shown in the previous examples. 
     In another example, two or more examples are combined. Features of one example can be combined with features of other examples. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.