Patent Publication Number: US-2021170563-A1

Title: Power tool having interchangeable tool heads

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/665,546, filed on Aug. 1, 2017 which claims priority to U.S. patent application Ser. No. 13/671,002, filed on Nov. 7, 2012, now U.S. Pat. No. 9,776,315 and claims the benefit of U.S. Provisional Application No.  61 / 579 , 738 , filed on Dec. 23, 2011 and U.S. Provisional Application No.  61 / 558 , 652  filed on Nov. 11, 2011. The entire disclosures of each of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a power tool which accommodates interchangeable tools heads. 
     BACKGROUND 
     As a result of considerable developments within the field of power tools and the increased demand of the do-it-yourself (DIY) market, the number of different types of power tool available to the consumer has risen considerably in the past decade. Even the most reluctant of DIY enthusiasts will own a power drill and jigsaw, whilst their more enthusiastic counterparts will also require electric sanders, power files, nibblers and other specialized power tools having dedicated purpose. Whilst this considerable array of power tools is often found to be useful, owning such a large number is both expensive and requires a considerable amount of storage space. In addition, having one specialized tool to perform each job often results in significant under-utilization of such a tool which are, generally, all operated by similar motors. Still further, many of today&#39;s power tools are “cordless”, being battery powered by rechargeable batteries, often requiring the user to change the battery pack when changing dedicated tools, or have several ready-charged batteries available for different tools. 
     One approach to address this need has been to design a power tool system that accommodates interchangeable tool heads. The power tool system may include a tool body having a motor with a rotary output and one or more tool heads which detachable couple to the tool body, thereby forming an operational tool. Each tool head includes a tool, such as a drill chuck, a reciprocating saw or a detail sander, which operably couples to the rotary output of the motor. Upon actuation of a trigger switch, the motor is energized which in turn drives the tool. The tool head may further include a tool accessory, such as a work light or fan. Rather than activate the tool accessory using the trigger switch, it is desirable to provide a switch that independently activates the tool accessory integrated into the tool head. 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     A power tool is provided which accommodates interchangeable tool heads. The power tool includes: a tool body having a housing and an electric motor mounted within the housing, as well as a tool head that releasably attaches via a mechanical connection and an electrical connection to the tool body. The tool head includes a tool and a tool accessory. The tool releasably connects to the output shaft of the electric motor when the tool head is attached to the tool body. A tool switch interposed between a power source for the electric motor and the electric motor is operable to supply power from the power source to the electric motor. A tool accessory switch interposed between the tool accessory and the power source for the electric motor is operable to supply power from the power source via the electrical connection to the tool accessory. 
     The electrical connection may be formed by an electrical connector integrated with the tool head and mated with an electrical connector integrated with the tool body. The electrical connection may include a first terminal electrically coupled to the tool accessory switch and a second terminal electrically coupled to the tool switch. The tool accessory switch may be integrated into either the tool head or the tool body. 
     The power tool may further include a controller disposed in the housing of the tool body and configured to receive an identifier for the tool head via the electrical connection from the tool head. The controller can adjust power output by the motor based on the identifier received from the tool head. 
     The power tool may also include a secondary tool switch interposed between the tool switch and the electric motor. In this case, the controller is electrically connected to the secondary tool switch and controls the secondary tool switch based on the identifier received from the tool head. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
         FIG. 1  shows a front perspective view of a body portion of a power tool in accordance with the present disclosure; 
         FIG. 2  shows a part side elevation of a tool head attachment mechanism; 
         FIG. 3  shows a part cut-away side elevation of the body portion of  FIG. 1  having a tool head attached thereto; 
         FIG. 4  shows the part cut away side elevation as shown in  FIG. 3  with the tool head removed; 
         FIG. 5  is a perspective view of the body portion of  FIG. 1  with half the clamshell removed; 
         FIG. 6  is a side elevation of a drill chuck tool head with part clamshell removed; 
         FIG. 7  is a side elevation of a detailed sander tool head with part clamshell removed; 
         FIG. 8 a    is a side view of a reciprocating saw tool head with part clamshell removed; 
         FIG. 8 b    is a schematic view of the drive conversion mechanism of the reciprocating saw tool head of  FIG. 8   a;    
         FIG. 9  is a schematic depicting electronic components in one embodiment of the power tool; and 
         FIG. 10  is a schematic depicting electric components in an alternative embodiment of the power tool. 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts an exemplary power tool  2  comprised of a main body portion  4  conventionally formed from two halves of a plastic clamshell  6 ,  8 . The two halves are fitted together to encapsulate the internal mechanism of the power tool to be described later. The body portion  4  defines a substantially D-shaped body, of which a rear portion  10  defines a conventional pistol grip to be grasped by the user. Projecting inwardly of this rear portion  10  is an actuating trigger  12  which may be operable by the users index finger in a manner conventional to the design of power tools. Such a pistol grip design is conventional and will not be described further in reference to this embodiment. The front portion  14  of the D-shape body serves a dual purpose in providing a guard for the users hand when gripping the pistol grip portion  10  and also serves to accommodate two batteries  26  ( FIG. 5 ) to provide the power source for the tool  2 . The two halves of the clamshell  6 ,  8  define an opening shown generally as  16 , which allows the batteries to be inserted within the tool. Such batteries are releasably restrained within the body portion by a conventional means and it will be appreciated to those skilled in the art that the inclusion of removable batteries (or battery packs) within power tools is well known and the mechanisms used to restrain and release such battery systems are also well known. As such, the batteries per se do not form part of the present disclosure and will not be described in further detail for this present disclosure. 
     The body portion  4  has an enlarged upper body section  18  extending between the front and rear portions  10 ,  14  which houses the power tool motor  20 . Again, the motor  20  employed for this power tool is a conventional electric motor and will not be described in detail herein save for general functional description. This upper body section  18  further comprises a substantially cylindrical opening  22  defined by two halves of the clamshell  6 ,  8  through which access to an output spindle  24  of the motor  20  is provided. 
     Referring now to  FIGS. 3, 4 and 5  the internal mechanism of the tool  2  will be described in more detail. Two batteries  26  (only one of which is shown in  FIGS. 3 and 4 ) are received through the battery opening  16  into the front portion  14  of the body  4  to electrically engage terminals  28 . The batteries  26  are restrained within the tool body  4  by a detent mechanism  30  which is manually operable to facilitate removal of the batteries when so desired. Such a mechanism is conventional within the field of removable battery packs and will not be described further. The electrical terminals  28  are electrically coupled to the motor  20  via the trigger  12  in a conventional manner. (Note, for clarity in the drawings the electrical connections are not shown but comprise insulated wire connections of conventional design.) Upon actuation of the trigger  12  the user selectively couples the motor  20  to the batteries  26  thereby energizing the motor  20  which in turn rotates an output spindle  24  to provide a high speed rotary output drive. 
     The tool body  4  may optionally house a control module or controller. In an exemplary embodiment, the control module is implemented by a microcontroller  21 . In other embodiments, the term control module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
     As is conventional for modem power tools, the motor  20  is provided with a forward/reverse switch  34  which, on operation, facilitates reversal of the terminal connections between the batteries  26  and the motor  20  (via switch  12 ) thereby reversing the direction of rotation of the motor output as desired by the user. Again such a mechanism is conventional within the field of power tools. 
     Referring now to  FIG. 5 , which shows the power tool  2  having one of the clamshells  8  removed to show, in perspective the internal workings of the tool, it will be seen that the motor is supported by conventional clamshell ribs (shown generally at  36  and which are mirrored by compatible ribs on the clamshell  8 ) to restrain the motor within the clamshell. The foremost of these ribs  36   a  ( FIG. 4 ) forms a front extension plate  38  ( FIG. 5 ) which (in conjunction with the comparable front extension plate on the removed clamshell portion  8 ) substantially encloses the front of the motor  40  save for a circular aperture  42  through which the motor spindle  24  projects. The circular aperture  42  is co-axial with the motor spindle axis  49 . The two clamshell halves  6 ,  8  further comprise two semi-circular plates  44  disposed forward of the front extension plate  38  and substantially parallel therewith to form a second, outer extension plate  46  again having a circular aperture  48  to facilitate access to the motor spindle  24 . Both apertures  42  and  48  are disposed co-axially on the axis  49 . As can be seen from  FIG. 4  the two extension plates  38 ,  46  serve to define a chamber  47  about the spindle axis  49 , externally accessible through the aperture  48  and which substantially houses the spindle cog  32 . 
     Furthermore, the outer extension plate  46  is itself recessed within the cylindrical opening  22  (thus forming a substantially cylindrical chamber between the opening  22  and the plate  46 ) so that the spindle cog  32  does not project outwardly of the body portion  4 . The power tool  2  further comprises a plurality of interchangeable tool head attachments (one of which is shown generally as  50  in  FIG. 3 ) which are attachable to the body portion  4  to form a particular type of power tool having a dedicated function. This aspect of the disclosure will be described hereinafter, but for initial reference the particular types of tool head will include, amongst others, a conventional drill chuck, a reciprocating saw drive mechanism and a detail sander. Each of the tool head attachments will have a drive mechanism for engagement with the spindle cog  32  so that the motor  20  will drive the drive mechanism of each tool head. 
     Referring now to  FIG. 2 , each of the tool head attachments (referred to on  50 ) have a uniform connection system  52  shown in  FIG. 2  in solid lines. This tool head connection system  52  comprises a substantially cylindrical outer body portion  54  which is ergonomically designed to match the exterior contours of the body portion  4  when the attachment is connected thereto. This outer body portion  54  design will vary for different types of tool head attachments (as will be seen later) and generally serves to provide a different profile to the power tool dependent on its particular function. The design shown in  FIG. 2  is that intended for use with a drill chuck head attachment. 
     Extended rearwardly of this outer body portion  54  is a substantially cylindrical spigot  56  which is shaped so as to fit snugly within the cylindrical opening  22  of the body portion  4 . As seen in  FIG. 5 , the cylindrical opening  22  of the body portion is defined by a series of inwardly directed ribs  23  forming a substantially cylindrical chamber. This cylindrical spigot  56  has a substantially flat circular rear wall  58  disposed about a head axis  60 . Projecting rearwardly of this wall  58  so as to extend co-axially with the axis  60  is a second, substantially cylindrical and hollow spigot  62  having a diameter substantially less than the diameter of the spigot  56 . This hollow spigot  62  has a series of exterior cylindrical ribs  64  which define an outer cylindrical recess  66 . In addition, the spigot  62 ) has a gradually increasing exterior diameter formed by a series of chamfered steps shown generally at  68  inclined radially outward from the axis  60  in a direction from left to right as viewed in  FIG. 2 . These chamfered steps  68  provide inclined lead-in shoulders on the spigot  62  to form a generally tapered spigot. In addition, the spigot  56  also has a chamfered step  70  again forming an inclined lead-in cam surface. 
     Thus, as the tool attachment  50  is brought into engagement with the body portion  4 , the connection system  52  is inserted into the cylindrical opening  22  of the body portion  4  for the tool attachment axis  60  to extend substantially co-axially with the spindle axis  49 . As the connection system  52  passes into the cylindrical opening  22  the chamfered leading edge  70  may abut the ribs  23  so as to maintain the head attachment  50  co-axial with the spindle axis  49 . As such, the lead-in edge  70  serves as a guide surface. Further insertion of the connection system  52  into the opening  22  will cause the hollow cylindrical spigot  62  to pass through the aperture  48  in the outer extension plate  46  so as to encompass the spindle cog  32 . 
     The power tool  2  also provides an electrical connection between the body portion  4  and the tool head  50 . A first electrical connector  53  is integrated into the body portion  4 , for example protruding outwardly from the outer extension plate  46 . In a reciprocating manner, a second electrical connector  51  is integrated into the tool head  50 , for example protruding outwardly from rear wall  58 . When the tool head  50  is attached to the body portion  4 , the first electrical connector  53  is mated to the second electrical connector, thereby forming an electrical connection between the body portion  4  and the tool head  50 . Accordingly, electric power can be delivered via the electrical connection to the tool head  50 . Additional functionality can be added to the tool head  50 . For example, the drill head attachment shown in  FIG. 6  can include an LED worklight that can be powered via the electrical connection while rotary motion is delivered to the head drive spindle by the mechanical connection. 
     As can be seen from  FIG. 3  the inner aperture  42  of the front extension plate  38  has a smaller diameter than the aperture  48  of the outer extension plate  46 . Furthermore, the remote end  72  of the spigot  62  has a diameter corresponding substantially to the diameter of the aperture  42  whereas the inner diameter of the spigot  62  has a diameter corresponding to the diameter of the aperture  48 . In this manner, as the tapered spigot  62  is inserted into the body portion  4  the spigot  62  will be received in a complimentary fit within the apertures  42  and  48  as shown in  FIG. 3 . In this manner the front extension plate  38  and outer extension plate  46  serve to firmly receive the spigot of the connection system  52  to restrain the connection system from axial displacement within the power tool body portion  4 . Furthermore, this axial support of the connection system is assisted by the snug fit of the spigot  56  within the cylindrical opening  22 . A shoulder portion  74  formed between the outer body portion  54  and the spigot  56  serves to restrain the connection system from further displacement of the connection system axially by its abutment against the outer rim  76  of the clamshell, as shown in  FIG. 3 . 
     To restrain the tool attachment  50  in connection with the body portion  4 , the body portion  4  is further provided with a resiliently biased locking mechanism within the chamber  47  (defined between the front extension plate  38  and outer extension plate  46  ( FIG. 4 )). This locking means (which is not shown in the attached drawings) comprises a resilient mechanism comprising two resiliently biased spring wires and disposed symmetrically about the axis  60  which extend across the apertures  42  and  48  so that as the connection system  52  passes through the aperture  48  the chamfered steps  68  of the spigot  62  will engage the biased wires and deflect them out of the path of the cylindrical spigot  56 . Further insertion of the spigot  62  into the body portion  4  will then enable these resiliently deflected wires to encounter the cylindrical recess  66  on the spigot  56  and, by returning to the resiliently biased position snap engage with this recess  66  to restrain the connection system  52  from further axially displacement. In addition this locking mechanism is provided with a conventional push button (not shown) which extends through an aperture  78  in the body  4  whereby actuation of this push button will cause the two wires to be pushed apart so that they are moved out of engagement with the cylindrical recess  66  in the connection system  52  to thereby release the tool attachment head  50  when required. 
     The power tool  2  is further provided with an intelligent lock-off mechanism ( FIGS. 4, 5 and 6 ) which is intended to prevent actuation of the actuating trigger  12  when there is no tool head attachment  50  connected to the body portion  4 . Such a lock-off mechanism serves a dual purpose of preventing the power tool from being switched on accidentally and thus draining the power source (batteries) whilst it also serves as a safety feature to prevent the power tool being switched on when there is no tool head attached which would present a high speed rotation of the spindle cog  32  (at speeds approaching 15,000 rpm) which could cause serious injury if accidentally touched. 
     The lock-off mechanism  80  comprises a pivoted lever switch member  82  pivotally mounted about a pin  84  which is moulded integrally with the clamshell  6 . The switch member  82  is substantially a elongate plastics pin having at its innermost end a downwardly directed projection  86  which is biased (by a conventional helical spring, not shown) in a downwards direction to the position as shown in  FIG. 4  so as to abut the actuating trigger  12 . The actuating trigger  12  comprises an upstanding projection  88  presenting a rearwardly directed shoulder which engages the pivot pin projection  86  when the lock-off mechanism  80  is in the unactuated position ( FIG. 4 ). 
     In order to operate the actuating trigger  12  it is necessary for the user to depress the trigger  12  with their index finger so as to displace the trigger switch  12  from right to left as viewed in  FIG. 4 . However, the abutment of the trigger projection  88  against the projection  86  of the lock-off mechanism restrains the trigger switch  12  from displacement in this manner. 
     The opposite end of the switch member  82  has an outwardly directed cam surface  90  being inclined to form a substantially wedge shaped profile as seen in  FIG. 4 . 
     Referring now to  FIG. 1  it is seen that the two halves of the clamshell  6  and  8  in the region of the cylindrical opening  22  form a substantially rectangular channel  92  (in cross-section) extending downwardly from the periphery of this cylindrical opening  22  and which is shown generally as  92 . The cam surface  90  is received within this channel  92  so as to be presented outwardly of the body portion  4  ( FIG. 1 ). 
     Referring now to  FIG. 2  the tool attachment  50  has an additional projection  94  which is substantially rectangular in cross-section and presents an inclined cam surface  96  which is inclined radially outwardly from the axis  60  in a direction away from the spigot  62 . This projection  94  has a cross-sectional profile compatible with the rectangular channel  92  of the body  4  and is designed to be received therein. This projection  94  thus serves a dual purpose (i) as an orientation mechanism requiring the tool head to be correctly orientated about its axis  60  relative to the body portion  4  in order that this projection  94  is received within the rectangular channel  92  (which thus serves to position the tool head in a pre-determined alignment relative to the body portion) whilst (ii) the cam surface  96  serves to engage the cam surface  90  of the lock-off mechanism  80  so that continued displacement of the tool attachment  50  towards the body portion  4  causes cam engagement between the cam surfaces  96  and  90 . This cam engagement causes pivotal deflection of the switch member  82  about the pin  84 , (against the resilient biasing of the helical spring (not shown)) and to thus move the projection  86  in an upwards direction (to the actuated position as shown in  FIG. 3 ), thus moving this projection  86  out of engagement with the trigger projection  88  which thus allows the actuating trigger  12  to be displaced as required by the user to switch the power tool on as required. This attachment of the tool head automatically de-activates the lock-off mechanism. 
     Furthermore, for certain tool head attachments a manual, and not automatic, de-activation of the lock-off mechanism. For example, when the tool attachment  50  comprises a reciprocating saw head the projection  94  as shown in  FIG. 2  remains substantially hollow with a front opening to pass over the cam surface  90  so that no cam surface  96  is presented by such a tool head attachment. In such a situation as the tool head attachment  50  is connected to the body portion  4  as previously described the projection  94  serves to orientate the tool head in the correct orientation relative to the tool body by being received within the channel  92 , but such projection  94  is simply received over the switch member cam surface  90  so that this switch member is not actuated, thus leaving the lock-off mechanism in engagement with the trigger switch to prevent accidental activation of this trigger  12 . 
     The reciprocating saw tool head is then provided with a manually operable switch member (not shown) which comprises a cam surface (similar to cam surface  96  as previously described) compatible with the cam surface  90 . Operation of this switch member services to displace the compatible cam surface through the projection  94 , into engagement with the cam surface  90  when the tool head is attached to the body portion  4  serving to pivotally displace the lock-off mechanism  80  in a manner previously described, so as to release the trigger switch  12 . This manually operable switch will be resiliently biased away from the body portion  4  so that once it has been used to de-activate the lock-off mechanism and the trigger switch  12  displaced so as to activate the power tool, the manually operable switch is released and thus disengages the cam surface  90  whereby the downwardly directed projection  86  of the switch member  82  would then biased towards engagement with the trigger projection  88 . However, at this time since the trigger switch  12  will have been displaced from right to left as shown in  FIG. 3 , the projection  86  will abut an upper surface of the trigger projection  88  while the tool is in use. When the user has finished use of the tool the trigger  12  will be released (and moved from left to right under conventional spring biasing means common to the art) which will then allow the downwardly biased projection  86  to re-engage the shoulder of the trigger projection  88  to restrain the actuating trigger from further activation as previously described. Therefore, if the user wishes to again activate the tool with the reciprocating saw tool head he must manually displace the switch on the tool head so as to de-activate the lock-off mechanism as previously described. This provides the safety feature that when a saw head attachment is connected to the body portion  4  the actuating trigger  12  may not be accidentally switched on. This provides tool heads with automatic or manually operable means for de-activating the lock-off mechanism, i.e. an intelligent lock-off mechanism which is able to identify different tool head functions, and is able to identify situations whereby manual de-activation of the lock-off mechanism is required. 
     Referring now to  FIG. 3 , each of the tool head attachments  50  will have a drive spindle  102  to which is coupled, at its free end, a female cog member  104  which is designed to engaged with the male cog  32  from the motor output spindle  24  ( FIG. 4 ). It will be appreciated that when the male and female cogs of the motor spindle  24  and the drive spindle  102  mate together when the tool head attachment  50  is connected to the body  4 , then actuation of the motor  20  will cause simultaneous rotation of the head drive spindle  102  therefore providing a rotary drive to the tool head drive mechanism (to be described later). 
     As can be seen from  FIG. 3 , which includes a side elevation of a tool head  50  (in this example a drill chuck) it is clearly seen that the female cog member  104  is wholly enclosed within the cylindrical spigot  56  of the connection system  52 . As previously described this cylindrical spigot  56  has a cylindrical end opening to receive the male cog  32  of the motor spindle  24  (as seen in  FIG. 3 ). In addition as can be seen from  FIGS. 1 and 4  the male cog  32  is recessed within the tool body  4  and is accessible only through the cylindrical opening  22  and the aperture  48 . In this manner both of the male and female cogs have severely restricted access to alleviate damage to these potentially delicate parts of the connection mechanism. In particular the male cog  32  is directly attached to the motor spindle and a severe blow to this spindle could damage the motor itself whereby recessing the cog  32  within the tool body  4  the cog itself is protected from receiving any direct blows, for example if the tool body was dropped without a head attachment. Furthermore, by recessing this cog within the tool body (and in the situation whereby the lock-off mechanism was deliberately de-activated—for example by use of a member pushed against the cam surface  90  then even if the motor was able to be activated, the high speed rotation of the cog  24  would not be easily accessible to the user who would thus be protected from potential injury. Thus, by recessing the male and female cogs within the clamshells of the body and the head respectively these delicate parts are protected from external damage which may occur in the work environments in which they are used. 
     Still further, by positioning the female cog  104  within the cylindrical spindle  56  it is automatically aligned substantially with the axis  60  of the tool head  50  which is then automatically aligned with the axis  49  of the motor spindle  24  by virtue of the alignment of the spigot  56  within the aperture  48  so that male and female cog alignment is substantially automatic upon alignment of the tool head with the tool body. 
     Referring now to  FIGS. 6, 7 and 8 , three specific tool head attachments are shown.  FIG. 6  shows a drill tool head attachment (corresponding to that shown in  FIG. 3  generally at  50  with the clamshell portion of the connection system  52  half removed to show, schematically, the drive mechanism of this drill tool head. As previously described, this drill tool head has a connection system  52  having a cylindrical spigot  56  which connects with the tool body  4  as previously described. Housed within the spigot  56  is the head drive spindle  102  having connected thereon a female cog member  104  for engagement with the male cog  32  connected to the motor spindle  24 . The drive spindle  102  has an inner drive cog (not shown) which is designed to drive a conventional sun and planet gear reduction mechanism illustrated generally as  112 . To those skilled in the art, the use of a sun and planetary gear reduction mechanism is standard practice and will not be described in detail here save to explain that the motor output generally employed in such power tools will have an output of approximately 15,000 rpm whereby the gear and planetary reduction mechanism will reduce the rotational speed of the drive mechanism to that required for this specific tool function. In the particular case of a conventional drill this first gear reduction mechanism will have an output of approximately 3,000 rpm, which is then used as an input drive to a second sun and planet gear reduction mechanism to provide a final rotary output of approximately 800 rpm. The exact ratio of gear reduction will be dependent on the number of teeth on the cogs employed in the gear arrangement. The output drive  114  of this gear reduction mechanism  112  then drives a conventional drill chuck  115  in a manner conventional to those skilled in the art. In the particular drill head shown as  110  a clutch mechanism shown generally as  116  (which is again conventional for electric drills and will not be described in any detail here) is disposed between the gear reduction mechanism and the drill chuck. When this drill head attachment is connected to the tool body, the power tool  2  acts as a conventional electric drill with the motor output drive driving the gear reduction mechanism via the male/female cog connection  32 ,  104 . The drill head attachment further includes an LED worklight  117  and a tool accessory switch  118 . The worklight  117  is powered via the electrical connection and may be activated using either the trigger switch  12  or the tool accessory switch  118  as further described below. It is readily understood that the drill head attachment may be equipped with other types of accessories, such as a live wire detection circuit. 
     Referring now to  FIG. 7 , which shows a detail sander tool head  120  one half of the clamshell is removed to allow the drive mechanism is to be shown schematically. This tool head  120  has the connection system  52  as previously described together with the cam projection  94  required for de-activation of the lock-off mechanism as previously described. However, it will be noted here that the outer peripheral design of this tool head varies to the drill tool head  110  but is again designed to be flush fit with the body portion  4  so as to present a comfortable ergonomic design for a detailed sander once this head is connected to the body. To this end, each of the tool head clamshell designs ensures that once that tool head is connected to the tool body, then the overall shape of the power tool is ergonomically favourable to the function of that power tool to allow the tool to be used to its maximum efficiency. 
     Again, the detailed sander tool head  120  has a drive shaft with female cog member  104  which again is connected to a conventional gear reduction mechanism  112  (conventional sun and planet gear reduction mechanism) to provide a rotary output speed of approximately 3,000 rpm. The gear reduction output  122  is then employed to drive a conventional eccentrically driven plate on which the detailed sander platen  124  is mounted. The gear reduction and drive mechanism of the tool head  120  is conventional to that employed in a detail sander having an eccentrically driven platen. As such, this drive mechanism will not be described herein in any detail since it is commonplace in the art. The sander tool head attachment  120  further includes an LED worklight  125  and a tool accessory switch  126 . The worklight  125  is powered via the electrical connection and may be activated using either the trigger switch  12  or the tool accessory switch  126  as further described below. It is readily understood that the sander tool head attachment may be equipped with other types of accessories, such as a fan or dust blower. 
       FIG. 8A  shows a reciprocating saw tool head attachment  130  having the conventional connection system  52  connection with the tool body  4 . Again the tool connection system  52  will house the drive spindle  102  with female cog member  104  connected to a gear reduction mechanism  112  to reduce the speed of the head drive mechanism to approximately 3,000 rpm. The gear reduction mechanism  112  then has a rotary output connected to a drive conversion mechanism shown generally at  132  which is used to convert the rotary output of the gear reduction mechanism to linear motion to drive the saw blade  134  in a linear reciprocating motion indicated generally by the arrow  136 . Whilst is can be seen from  FIG. 8A  that this reciprocating motion is not parallel with the axis of the tool head, this is merely a preference for the ergonomic design of this particular tool head  130  although, if necessary, the reciprocating motion could be made parallel with the tool head (and subsequently motor drive) axis  60 . The tool head  130  itself is a conventional design for a reciprocating or pad saw having a base plate  138  which is brought into contact with the surface to be cut to stabilize the tool (if required) and again the exterior shape of this tool head has been chosen for ergonomic preference. 
     The drive conversion mechanism  132  utilizes a conventional reciprocating space crank illustrated, for clarity, schematically in  FIG. 8B . The drive conversion mechanism  132  will have a rotary input  140  (which for this particular tool head will be the gear reduction mechanism output at a speed of approximately 3,000 rpm and which is co-axial with the axis of rotation of the motor of the tool itself). The rotary input  140  is connected to a link plate  142  having an inclined front face  144  (inclined relative to the axis of rotation of the input). Mounted to project proud of the surface  144  is a tubular pin  146  which is caused to wobble in reference to the axis of rotation of the input  140 . Freely mounted on this pin  146  is a link member  148  which is free to rotate about the pin  146 . However, this link member  148  is restrained from rotation about the drive axis  140  by engagement with a slot within a plate member  150 . This plate member  150  is free (in the embodiment of  FIG. 8 a   ) to move only in a direction parallel with the axis of rotation of the input  140 . Thus, the wobble of the pin  146  is translated to linear reciprocating motion of the plate  150  via the link member  148 . This particular mechanism for converting rotary to linear motion is conventional and has only been shown schematically for clarification of the mechanism  132  employed in this particular saw head attachment  130 . 
     In the saw head  130  the plate  150  is provided for reciprocating linear motion between the two restraining members  160  and has attached at a free end thereof a blade locking mechanism  162  for engaging a conventional saw blade  164  in standard manner. Thus the tool head  130  employs both a gear reduction mechanism and a drive conversion mechanism for converting the rotary output of the motor to a linear reciprocating motion of the blade. 
     Furthermore, the reciprocating saw tool head  130  has a projection  94  for orientating the tool head  130  relative to the body of the power tool  4 . However, as previously described, this projection  94  (for this particular tool head) is hollow so as not to engage the cam surface  90  of the lock-off mechanism  80 . This tool head is then provided with an additional manually operable button  166  which, on operation by the user, will enable a spring biased member (not shown) to pass through the hollow projection  94  when the head  130  is attached to the body  4  so as to engage the cam surface  90  of the lock-off mechanism  80  to manually de-activate the lock-off mechanism when power is required to drive the reciprocating saw (as previously described). 
     The reciprocating saw tool head  130  further includes a laser  168  and a tool accessory switch  169 . The laser  168  serves as a guide or alignment feature for the blade on the workpiece. The laser  168  is powered via the electrical connection and may be activated using either the trigger switch  12  or the tool accessory switch  169  as further described below. It is readily understood that the reciprocating saw tool head attachment may be equipped with other types of accessories, such as a fan or dust blower. 
     Although three specific tool head embodiments have been shown in  FIGS. 6, 7 and 8 , the present disclosure is by no means limited to three such tool heads. In particular, a complete range of tool head attachments may be connected to the tool body to obtain a functional tool which is currently available as an existing single function power tool. Exemplary head attachments include but are not limited to an oscillating head, a hammer drill, a trim saw, an inflator, scissors, a flashlight, a scrubber, a router, a hedge trimmer, a string trimmer, etc. It will be appreciated by those skilled in the art that the particular embodiments of the tool head attachment described herein are by way of example only and merely serve to describe tool head attachments which employ (i) no gear reduction or drive conversion mechanisms, (ii) those which have simple gear reduction mechanisms and (iii) those which have both gear reduction and drive conversion mechanism for converting the rotary to non-rotary output. Thus, a power tool system is provided which provides for a plurality of power tool functions having different output functions, all driven by a single speed motor. 
     Furthermore, it will be appreciated that the drive conversion mechanisms described with reference to the tool heads described herein are conventional and provided by way of example only. It will be appreciated that any conventional drive conversion mechanism for converting rotary to linear reciprocating motion may be used in place of those systems described herein. Furthermore, alternative gear reduction mechanisms may be utilized to replace the conventional sun and planet gear reduction mechanisms referred to for these particular embodiments. 
     In addition, whilst the specific embodiments of the tool have referred to the power source as batteries, and such batteries may be conventional or rechargeable, it will also be appreciated that the present disclosure will relate to a power tool having a conventional mains input or for use with alternative heavy duty battery packs. 
     While reference has been made to a particular power tool, it is understood that the concepts described herein are also extendable to other types of power tools having interchangeable tool heads. For example, it is readily understood how the connection scheme could be adapted for use in a drill having a conventional pistol grip configuration. Such an exemplary power tool is described in commonly owned U.S. patent application Ser. No. 13/530,629 which was filed on Jun. 22, 2012 and is incorporated herein by reference. 
     Electronic components of the power tool  2  are further described in relation to  FIG. 9 . In an exemplary embodiment, the tool body  4  houses the electric motor  20 , a motor control circuit  202 , batteries  26 , a discharge control circuit  204 , a trigger switch  12  and a controller  21 . During operation, the motor drive circuit  202  enables voltage from the batteries  26  to be applied across the motor  20  in either direction. The motor  20  in turn drives the output spindle  24 . In the exemplary embodiment, the motor drive circuit  202  is an H-bridge circuit arrangement although other circuit arrangements are contemplated. Although a few of the primary components of the power tool  2  are discussed herein, it is readily understood that other components may be needed to construct the power tool  2 . 
     Electric power may also be supplied from the tool body  4  via an electrical connection to an attached tool head. Electrical connector  53  mates with electrical connector  51  when the tool head  50  is attached to the tool body  4 , thereby forming the electrical connection. In an exemplary embodiment, the electrical connectors  51 ,  53  provide three pins or terminals although connectors having more or less pins are contemplated by this disclosure. Electric power can be delivered via the electrical connection to the tool head  50 , thereby enabling additional functionality to be integrated into the tool head  50 . 
     In the exemplary embodiment, a tool accessory switch  206  enables the tool operator to independently activate one or more tool accessories integrated into the tool head  50 . To do so, the tool accessory switch  206  is interposed between the power source (i.e., batteries  26 ) and a tool accessory  210 . The tool accessory switch  206  is preferably implemented by a non-momentary or latching switch. One terminal of the tool accessory switch  206  is electrically coupled to the discharge control circuit  204 ; whereas, the other terminal of the tool accessory switch  206  is electrically coupled to the tool accessory  210 . In the exemplary embodiment, the tool accessory switch  206  is mounted on the tool head  50 . In other embodiments, the tool accessory switch  206  may optionally be disposed on the tool body  4 . 
     Upon actuation of the tool accessory switch  206 , the switch  206  closes and power is delivered from the power source to the tool accessory  210 . The tool accessory  210  remains activated until the tool accessory switch  206  is actuated a second time. In this way, the tool accessory switch  206  enables the tool accessory  210  to be activated independently from the tool (e.g., drill bit). Additionally, type of tool accessory switch  206  (and its location) can be tailored to the type of accessory being controlled. For example, it may be preferable to use a momentary switch for some types of accessories. To the extent that more than one tool accessory is integrated into the tool head  50 , a separate accessory switch may be used for each of the different accessories. 
     In some embodiments, it may be preferable to activate the accessory  210 ′ using the trigger switch  12 . In this case, a second terminal of the electrical connectors  51 ,  53  can be used to supply power from a terminal of the trigger switch  12  to the tool accessory  210 ′. Upon actuation of the trigger switch  12 , the switch  12  closes and power is delivered to the tool accessory  210 ′ as well as to the motor  20 . For example, the saw tool attachment  130  may include a laser that serves as a guide or alignment feature for the blade on the workpiece. In this example, the laser may be activated by the trigger switch  12  rather than an independent accessory switch. When the trigger switch is released, the switch  12  is opened and power is no longer delivered to the tool accessory  210 ′. 
     With reference to  FIG. 10 , the electrical connection may further include a data terminal  211  coupled between the tool body  4  and the tool head  50 . In some embodiments, the data terminal may be established through a separate connection or connector. The data terminal  211  may be used to communicate data about the tool head  50  to the controller  21  of the power tool. For example, because the tool body  4  can be interfaced with many different types of tool heads  50 , the data terminal may be used to provide an indicator for the type of tool head (i.e., drill head, sander head, saw, inflator, etc.) and/or various operating parameters. Operating parameters may include but are not limited to whether the power tool head require electricity from the electrical connection, a mechanical rotational input from the motor through the mechanical connection or both, the speed or range of speeds for operating the motor and the torque or range of torques for the motor. It is envisioned that other types of data may be communicated via the data terminal between the tool body  4  and the tool head  50 . 
     In an exemplary embodiment, a resistor  212  may be used to identify the type of tool head. The resistor  212  is electrically coupled via the data terminal to the controller  21  of the power tool. Different types of tool heads will be configured with resistors having different resistance values. By determining the resistance value of the resistor  212 , the controller  21  can determine the type of tool head. Other techniques for identifying the type of tool head, such as a magnet, a memory unit or a mechanical feature, also fall within the broader aspects of this disclosure. 
     Depending on the tool head type, the tool may operate differently. For example, the controller  21  may adjust the power output by the motor  20  based on the type of tool head. Assuming 20 volts of available power, the controller  21  may interface with the motor control circuit  202  such that all of the available power (e.g. 20 volts) is applied to the motor  20  when the type of tool is a router. In contrast, the controller  21  may interface with the motor control circuit  202  to reduce the voltage applied to the motor to 14 volts for a different type of tool, such as a drill. In other words, the motor output can be optimized or tailored to the desired performance of the respective tool head. Techniques for controlling motor output of an electric motor are readily understood in the art. 
     Certain types of tool heads may not include tools which are driven by the motor. For example, the tool head  50  may include a live wire detection circuitry and/or stud detection circuitry (not shown). In this example, there is no need to drive the motor  20  but it may be desirable to activate these detection functions using the trigger switch  12 . To accommodate such tool heads, the tool body  4  may be equipped with a secondary tool switch  214  (e.g., a FET) placed in series with the trigger switch  12 . The controller  21  can be electrically connected to a control terminal of the secondary tool switch  214  to open or close the switch. In operation, the controller  21  determines the type of tool head in the manner set forth above and controls the secondary tool switch  214  based on the type of tool head attached to the tool body  4 . For tools heads which do not require use of the motor, the controller  21  opens the secondary tool switch  214 ; otherwise, the secondary tool switch  214  remains closed. Upon actuation of the trigger switch  12 , power is supplied via the second terminal to a tool accessory  210 ′ (i.e., detection circuitry), but not to the motor  20 . In this way, the trigger switch can be used to activate the functions in the tool head  50  while the motor is not driven unnecessarily. 
     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.