Abstract:
This invention relates to a power tool ( 1 ) including an operative element ( 4 ) for treating a work piece. The power tool ( 1 ) defines an air passageway and includes propelling means ( 20 ) operative to induce air to flow through the passageway. The passageway direct the induced air over the power tool&#39;s motor ( 14 ) to cool the motor ( 14 ). The air is exhausted from the tool ( 1 ) by exhaust means onto the operative element ( 4 ) and a worked face of the work piece. This cools the operative clement ( 4 ) which prolongs its working life. Furthermore, the exhausted air facilitates removal of swarf from the worked face.

Description:
This application is a continuation of PCT International Application No. PCT/AU01/00254 filed 9 Mar. 2001, which claims priority of Australian Patent Application No. PQ 6188 filed 10 Mar. 2000. 

   FIELD OF THE INVENTION 
   The present invention relates to power tools, and is applicable to such tools that are hand-held, bench mounted, or free standing. The invention is particularly, but not exclusively, concerned with such tools that treat a work piece by, a cutting, grinding, or other material removal, process. 
   RELATED APPLICATIONS 
   The present application is related to the subject matter of provisional patent application entitled “Power Tool Controller” filed on 10, Mar. 2000 by the present applicant, the subject matter of which is incorporated herein by cross-reference. 
   BACKGROUND OF THE INVENTION 
   It will be convenient to hereinafter describe the invention with particular reference to an example power tool of the electrically operated hand-held type, but it needs to be understood that the invention has wider application. An example tool of the foregoing type is an angle grinder. Again, as a matter of convenience, the invention will be hereinafter described with particular reference to such a grinder. 
   Power tools of the foregoing kind tend to develop high temperatures at the work face, and that has the disadvantage of reducing the useful working life of the operative element (e.g., cutting tool, grinding wheel, etc.). In some cases, and particularly relatively large machine tools such as lathes, the temperature problem is attended to by means of a stream of a liquid coolant directed at the work face. That method of cooling is not suited for all types of power tools, and is particularly not suited for use with portable hand-held power tools. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a power tool having an improved working zone cooling system. In that regard, the working zone is to be understood as including the face of the work piece being treated, and the operative element of the tool being used to treat the work face. 
   It is a further object of the invention to provide an electrically powered tool having a cooling system of the foregoing kind, and in which the cooling system also cools the electrical motor of the tool. It is a still further object of the invention to provide a power tool that is convenient and relatively safe to operate. Other objects and advantages of the invention will be apparent from the following description of an example embodiment of the invention. 
   According to one aspect of this invention there is provided a power tool including:
         an operative element for treating a face of a work piece,   an electric motor for driving said operative element,   a chamber,   propelling means operative to induce air to flow into said chamber and to move the inducted air through said chamber,   at least one induction passage arranged to allow the inducted air to flow across and cool said motor and flow into said chamber,   exhaust means arranged to receive air flowing from said chamber and to direct that air into a working zone,   said working zone including said operative element and said face of the work piece.       

   It is preferred that said propelling means operates to pressurize air inducted into said chamber. 
   It is preferred that the power tool include a hollow housing having an air inlet and an air outlet, said propelling means includes a blower device having a rotary impeller mounted within said housing, and said chamber is formed at least in part between said impeller and an internal surface or surfaces of said housing. It is further preferred that said air inlet and said impeller are arranged substantially coaxial and relatively positioned so that inducted air is drawn over said motor before entering said air inlet. 
   It is preferred that the power tool include an automatic shut-down facility that is operative to terminate operation of said operative element in predetermined circumstances, including a circumstance in which said tool is not held properly, or a circumstance in which said tool is dropped. It is further preferred that said shut-down facility includes a member that is movable between a position at which said facility is activated, and a position at which said facility is deactivated, and said tool cannot be operated while said member is in said facility activated position. 
   It is preferred that the shut down facility includes a switch selectively movable between a normal position and a lock position, wherein when the member is in position to deactivate the shut down facility the switch can be moved to the lock position to lock the member in the deactivated position. It is further preferred that the switch is biased towards the normal position such that the switch is moved from the locked position to the normal position automatically after depressing the member. It is further preferred that the switch when in the lock position is manually movable to the normal position. 
   It is preferred that the power tool include a start button that is manually operable to cause operation of said tool, provided said shut-down facility is deactivated. 
   It is preferred that the power tool include a body portion containing said chamber and said propelling means, and a head portion carrying said operative element and being connected to said body portion. It is further preferred that said connection enables the position of said head portion to be adjusted relative to said body portion. It is further preferred that said adjustment involves rotational movement of the head portion relative to the body portion, and head locking means is operable to releasably hold said head portion in any one of two or more positions or rotation relative to said body portion. It is further preferred that the power tool include head locking means including at least one detent mounted on the head portion, and two or more cooperative recesses provided in said body potion, said detent being engagable within a selected one of said recesses so as to thereby releasably hold said head portion in a selected one of said positions of rotation. It is further preferred that said head locking means includes two said detents, each detent being located on a respective one of two opposite sides of the head portion, and means biasing each said detent biased towards an engaging position at which it engages a selected said recess. 
   It is preferred that the power tool includes a handle attached to the head portion, the handle being movable relative to the head portion so as to adopt any one of two or more positions, relative to the head portion. It is further preferred that the power tool includes handle locking means operable to releasably lock said handle in a selected said position. It is preferred that the handle locking means includes a lever associated with the handle, the lever having a lug which is locatable in a hole in the head portion, the lever being movable between a locked position wherein the lug is located in the hole in the head portion, and an unlocked position wherein the lug is separated from the hole in the head portion. It is preferred that the tool includes lever biasing means for biasing the lever towards the locked position. It is further preferred that the head portion includes two or more holes to provide the two or more positions of adjustability for the handle relative to the head portion. 
   It is preferred that the tool be in the form of a grinder and the operative element be in the form of a grinding or cutting disc. 
   It will be convenient to hereinafter describe the invention in greater detail by reference to the accompanying drawings showing one form of hand-held power tool incorporating an embodiment of the invention. The particularity of those drawings and the related detailed description is not to be understood as superseding the generality of the definition of the invention as given by the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front schematic view of a hand-held tool according to one embodiment of the invention; 
       FIG. 2  is a side schematic view of the tool of  FIG. 1 ; 
       FIG. 3  is a side plan view of the tool of  FIG. 1 ; 
       FIG. 4  is a bottom plan view of the tool of  FIG. 1 ; 
       FIG. 5  is a bottom horizontal sectional view of the tool of  FIG. 1 ; 
       FIG. 6  is a front vertical sectional view of the tool of  FIG. 1 ; 
       FIG. 7  is a top horizontal partial sectional view of a front portion of the tool of  FIG. 1 ; 
       FIG. 8  is a front vertical partial sectional view of a rear portion of the tool of  FIG. 1 ; 
       FIG. 9  is a side vertical partial sectional view of a detent for connecting a head portion  3  and body portion  2  of the tool of  FIG. 1 ; and 
       FIG. 10  is a front vertical partial sectional view of one end  10  of handle  9  secured to the head portion  3  of the tool of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
     FIGS. 1 to 4  show an example hand-held tool incorporating one embodiment of the invention. That example tool is an angle-grinder, and it is to be understood that the invention can be applied to other types of tools, whether they be hand-held, bench mounted, or free standing. 
   The tool  1  shown by  FIGS. 1 to 4  includes a body portion  2  and a head portion  3 . An operative element in the form of a rotatable grinding disc  4  is carried by the head portion  3 , and a protective guard or shroud  5  overlies and surrounds a substantial part of the disc  4 . In that regard, a plate section  6  of the shroud  5  overlies the upper surface of the disc  4 , and a skirt  7  of the shroud  5  extends around the periphery of the disc  4 . An opening  8  is provided at the front of the shroud  5  to enable engagement between the disc  4  and a work piece (not shown). The disc  4  is arranged for rotation about an axis extending transverse to the longitudinal axis of the tool  1 . 
   It is preferred that the shroud  5  is adjustable so as to enable the opening  8  to be placed at a convenient position relative to the longitudinal axis of the tool  1 . By way of example, it may be convenient to place the opening  8  at one side of the tool  1  rather than at the front as shown by  FIG. 1 . For that purpose, the shroud  5  is capable of rotation about an axis substantially coincident with the rotational axis of the disc  4 . In accordance with conventional practice, the shroud  5  may be releasably secured in a selected rotational position by means of a clamping plate (not shown) engaging against the under surface of the plate section  6 . Fastening screws may be used to press the clamping plate against the plate section  6  and thereby hold the shroud  5  against rotation. 
   In the arrangement shown, a loop-type handle  9  extends transversely across the top of the head portion  3  and has each of its ends  10  attached to respective opposite sides of the head portion  3  as hereinafter described. Other types of handles could be used. By way of example, one or more laterally projecting stub handles of a conventional kind could be attached to the head portion  3 . Selection of a particular type of handle may be influenced by the nature of the tool being used. 
   In the example tool shown, a press-button  11  is accessible at the top of the head portion  3 . The button  11  is manually depressed to lock the disc  4  against rotation when the disc is being removed from or attached to the head portion  3 . In accordance with standard practice, the button  11  is spring influenced to return to an inactive position when pressure is removed. 
   The example tool shown is electrically powered, and is connectable to a source of AC power through a flexible cord  12  extending from the rear of the body portion  2 . A cord storage groove  13  may be provided at the rear underside of the body portion  2  so as to enable convenient wrapping of the cord  12  when the tool is not in use. That is, the cord  12  may be wound about the tool  1  by being looped over the shroud  5  and through the groove  13 , and is thereby retained in a stored condition. 
   Power is connected to the drive motor  14  ( FIG. 5 ) of the tool  1  by depressing a start button  15 , which in the example shown is located at the top-front of the body portion  2 . Other locations could be adopted. It is preferred however, that simple depression of the button  15  is not sufficient to operate the tool  1 . In the arrangement shown, an automatic shut-down facility needs to be deactivated prior to depressing the start button  15 . Such deactivation may be achieved by depressing a lever  16  ( FIGS. 3 and 4 ) positioned at the underside of the body portion  2 . 
   The lever  16  is arranged to automatically return to a non-depressed condition if the user of the tool releases grip on the body portion  2 , or does not grip that body portion correctly. Under those circumstances, the shut-down facility is activated and power is disconnected from the drive motor  14 . 
   If desired, an interlock switch  17  ( FIG. 4 ) may be provided at the underside of the body portion  2  adjacent the lever  16 . The switch  17  is selectively movable between a normal position and a lever lock position. When the switch  17  is in the normal position, the shut-down facility functions as described above. When the switch  17  is in the lever lock position, it locks-the lever  16  in a depressed condition and thereby retains the shut-down facility in a deactivated condition. It is preferred that the switch  17  automatically returns to the normal position if the lever  16  is depressed while the switch  17  is in the lever lock position. 
   Tool function indicators  18  and  19  may be located adjacent the start button  15  as best seen in  FIGS. 1 and 2 . The indicator  18  may provide a visible signal when the tool  1  is subjected to maximum load during operation. The indicator  19  may provide a visible and/or audible signal when the tool reaches an overload condition. Maximum and overload conditions may be determined by monitoring the current being drawn by the tool. 
   It is a feature of the tool  1  that it includes propelling means operative to direct a flow of air over the working zone of the tool. In that regard, the working zone includes the face of the work piece being treated, and also includes the operative element of the tool  1 , which is the disc  4  in the example tool shown. 
   It is preferred, but not essential, that the propelling means includes a blower-type device  20  ( FIGS. 5 and 6 ). In the example shown, the blower  20  includes an impeller  21  rotatably mounted within a hollow housing  22  having an air inlet  23  ( FIG. 5 ) and an air outlet  24  ( FIG. 6 ). It is preferred, as shown, that both the impeller  21  and the inlet  23  are arranged substantially co-axial with the drive motor  14 . It is further preferred that the impeller  21  is connected to a spindle  25  of the motor  14  so as to be driven by the motor  14 . 
   A chamber  26  is formed between the periphery of the impeller  21  and an inner surface  27  of the housing  22 . The impeller  21  includes a plurality of vanes  28 , and the number and configuration of those vanes is selected to assist achievement of the result hereafter described. Similarly, proper selection of the space between the periphery of the impeller  21  and the housing surface  27  may influence achievement of the desired result. In the example arrangement shown by  FIG. 6 , it is intended that the impeller  21  be driven to rotate in a clockwise direction. 
   In the arrangement shown, the housing outlet  24  communicates with exhaust means including a duct  29  extending downwardly towards the shroud  5 . The shroud plate section  6  includes a plurality of openings  30  to allow air to pass from the duct  29  to the upper surface and periphery of the disc  4 . Such openings  30  may be provided around substantially the full extent of the plate section  6 . It is preferred that an angled louvre  31  extends over each opening  30 . Each louvre  31  is arranged to urge the air to flow through the respective opening  30  in a direction that is generally the same as the direction of rotation of the disc  4 . Such an arrangement promotes attachment between the disc  4  and the air flowing into the shroud  5  through the openings  30 , and thereby maximizes the cooling influence of that air flow. By way of example only, the louvres  31  may be disposed at approximately 45 degrees relative to the body of the plate section  6 . 
   The head portion  3  of the tool  1  may be movable relative to the body portion  2  so as to allow selection of any one of a number of dispositions for the disc  4 . In the arrangement shown, the head portion  3  is mounted on the body portion  2  for relative rotation about an axis substantially coincident with the axis of the motor spindle  25 . Other arrangements could be adopted. 
   As best seen in  FIG. 7 , which is a diagrammatic illustration, the rotatable connection between the head portion  3  and the body portion  2  may include a bearing collar  32  secured to the body of the head portion  3 , and two half-ring bearings  33  secured to a wall  34  of the body portion  2 . It may be convenient to secure each half-ring bearing  33  to the body portion by means of fastening screws  35 , as shown by  FIG. 5 . The collar  32  may have a channel section  36  ( FIG. 7 ) to provide a location for the half-ring bearings  33 . 
   Any suitable means may be adopted to selectively lock the head portion  3  in any one of the available positions of rotation. Also, the number of such positions can be selected to suit requirements. In the example embodiment shown, the head portion  3  is capable of 360 degree rotation relative to the body portion  2 , and can be locked in any one of twelve equally spaced positions of rotation. 
   The head locking means for the head portion  3  may include a spring influenced detent that is engagable in any one of a number of co-operative openings, or recesses, provided in an indexing member. In the example arrangement shown, an end surface  37  ( FIGS. 8 and 9 ) of the body portion  2  forms the indexing member, but other arrangements could be adopted. A series of equally spaced recess  38  is formed in the surface  37 , and it is preferred that twelve recesses  38  constitute that series. 
   A spring influenced detent  39  mounted on the head portion  3  is adapted to engage in a selected one of the recesses  38  and thereby hold the head portion  3  against rotation relative to the body portion  2 .  FIG. 9  illustrates, in a diagrammatic manner, one particular arrangement of the detent  39 . In that arrangement, the detent  39  is slidably mounted on the head portion  3  so as to be movable into and out of any one of the recesses  38 . A compression spring  40  urges the detent  39  towards the surface  37 , and into a recess  38  when the detent  39  is correctly aligned with that recess. Release movement of the detent  39  is achieved by applying finger pressure against an arm  41  connected to and extending laterally from the detent  39 . When that finger pressure is removed, the spring  40  urges the detent  39  back towards the surface  37  so that it can again lock in any one of the recesses  38 . 
   It is preferred that a detent  39  is provided at each of two opposite sides of the tool  1 , and such an arrangement is shown by  FIG. 5 . The arrangement of the detent  39  at each side may be as described above in relation to  FIG. 9 . 
   Means may be provided to enable the handle  9  to be moved relative to the head portion  3  so as to adopt any one of two or more relative positions. The position of the handle  9  shown by  FIGS. 1 to 4 , can be regarded as the normal position of the handle  9 . 
   In the example arrangement shown, each end  10  of the handle  9  is pivotally connected to a respective one of the two sides of the head portion  3 . That pivotal connection can be achieved in any suitable manner. A preferred form of pivotal connection is shown, in diagrammatic form, by  FIG. 10 . An internally threaded sleeve  42  having a flange  43  at one end, is secured to each side of the head portion  3  in a manner such as to be held against rotation. As shown by  FIG. 10 , the flange  43  bears against an outside surface of the head portion  3 . Each end  10  of the handle  9  is secured to a respective one of the sleeves  42  by means of a fastening screw  44 . It is preferred that a spacer sleeve  45 , is located between the head  46  of the screw  44  and the flange  43  so as to ensure that the handle end  10  is left sufficiently free to be rotatable about the axis of the screw  44 . 
   Handle locking means may be provided to enable the handle  9  to be releasably locked in any one of two or more positions of rotation relative to the head portion  3 . In the  FIG. 10  arrangement, the handle locking mean includes a lever  47  mounted between the handle end  10  and the pivot mounting flange  43  in a manner such as to be movable between lock and release positions. Lever  47  is mounted on the handle end  10  in such a way that it cannot rotate relative to that end  10  about the axis  48  of the pivotal connection.  FIG. 10  shows the lever  47  in the release position, and  FIG. 5  shows the lever  47  in the lock position. As shown by  FIG. 5 , it is preferred that handle locking means is provided at each end  10  of the handle  9 . 
   Lever  47  is biased towards the lock position by suitable biasing means, which in the example shown includes a hollow resilient member  49  interposed between the lever  47  and an opposed surface  50  of the handle  9 . The biasing member  49  collapses in the axial direction when the lever  47  is manually lifted into the release position as shown by  FIG. 10 . When manual pressure is released, internal stress within the member  49  causes that member to expand axially and thereby push the lever  47  back to the lock position as shown by  FIG. 5 . In the lock position, a laterally projecting lug  51  of the lever  47  locates in a recess or hole  52  provided in the flange  43  as shown by  FIG. 5 . Since the lever  47  cannot rotate relative to the handle end  10 , and the sleeve  42  cannot rotate relative to the head portion  3 , location of the lug  51  in the recess or hole  52  prevents rotation of the handle  9  about the pivot axis  48 . 
   In circumstances where the handle  9  is to be capable of being locked in more than one position, the flange  43  will be provided with a number of recesses or holes  52 , and that number will be equal to the number of handle positions. The spacing between those recesses or holes  52  can be determined according to the desired positions of the handle  9 . By way of example, in one such position, the handle  9  may be located forwardly of the normal position as shown by  FIGS. 1 to 4 , so as to provide a surface engaging rest if the tool is to be supported on a surface in an upside down position. When the handle  9  is in that forward location, the handle  9  and the top surface of the body portion  2  can engage an underlying surface to support the tool  1  in a substantially horizontal inverted disposition. 
   It is preferred that the head portion detents  39  cannot be released, at least in a convenient manner, while the handle  9  is in the normal position as shown by  FIGS. 1 to 4 . Release of the detents  39  is made possible, or convenient to achieve, by moving the handle  9  out of the normal position, and preferably forward of that position. 
   The pivot mountings for the handle ends  10  are preferably constructed so as to be capable of accepting the fastening screw of a standard stub handle. That permits one or two stub handles to be substituted for the loop handle  9 . If desired, one or more additional handle mounting points may be provided around the head portion  3  so as to extend the choice of the positions for stub handles, and possibly also provide two or more alternative positions for the loop handle. 
   When the tool  1  as described above is operated, rotation of the impeller  21  causes air to be induced to flow into the body portion  2  through openings  53  provided at or near the rear end of the tool  1 . The inducted air flows from the openings  53  to the housing inlet  23  by way of a passage or passages  54 . Air flow through the passage or passages  54  has a cooling influence on the motor  14 . Air received within the housing  22  is driven to the outlet  24 , possibly in a compressed state, and from there into the shroud  5  by way of the duct  29  and the shroud openings  30 . The air flow into the shroud  5  provides a cooling influence at the working zone of the tool. 
   Rotation of the disc  4  in the shroud  5  also tends to induce air to flow into the shroud  5  by way of the openings  30 . 
   Swarf and debris tends to be removed from the disc  4  by centrifugal action, but air flow through the shroud  5  can-assist that removal and also assist in removing swarf and debris from the working zone in general. 
   It is an aim of the tool design to maximise air flow to the working zone, and thereby maximise the cooling influence of the air flow. Factors contributing to that result include the design of the impeller  21  and the design of the housing  22 . 
   It will be apparent from the foregoing description that a power tool incorporating the invention has several benefits. Cooling at the working zone is particularly beneficial in that it promotes a longer working life for the operative element of the tool. The automatic shut-down facility has a valuable safety benefit, and adjustment of the head position and the handle position enables the tool to be used with maximum comfort and efficiency in a wide variety of working situations. 
   It is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of the parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.