Abstract:
A handheld power tool having a detachable tool head is disclosed in which, depending on the type of tool head used, selection of reverse movement of the rotary assembly of the power tool can be prevented. Where reverse movement of the tool head is undesirable, such as for a saw blade, the tool head contains a contact plate that slides a plate member to a position to prevent selection of the reverse direction by the user. However, where reverse movement of a tool head is desired, such as for a drill head, the plate member remains in its original position such that forward and reverse directions can be selected by a user.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application, claims the benefit of and priority to commonly owned U.S. Provisional Application Ser. No. 61/508,962, filed Jul. 18, 2011, which is hereby incorporated by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     TECHNICAL FIELD 
     The present invention relates generally to a handheld power tool having interchangeable tool heads where the direction of rotary movement of the tool head is controllable. 
     BACKGROUND 
     Since their inception, power tools have provided craftsman with improved performance and ease of use. In more recent years, advancements in portable power technology have lead to incorporating the improved performance provided by a power tool into a handheld and often times, cordless configuration. These handheld power tools have provided increased flexibility and freedom of use by operators as well as increased efficiency by craftsman. A handheld power tool generally includes a handle mechanism, a trigger switch, a tool head, and a motor capable of moving the tool head in a desired direction. 
     To further increase ease of use and flexibility, some handheld power tools have advanced so as to permit interchangeability of the tool head. By permitting interchangeability, the same handle mechanism and motor can be used to operate different types of tool heads, such as a drill or driver, a circular saw, a sander, or a jigsaw. While this interchangeability provides convenience to the user, it also introduces the risk of permitting undesirable movement of the tool head, which can lead to serious injury of the tool operator, damage to the power tool, or damage to the surface on which the tool is operating. That is, certain tools heads such as a sander, jigsaw or circular saw are preferably not operated in a reverse direction. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     Embodiments of the present invention are directed to a handheld power tool and a component thereof which restricts selection of reverse movement of the rotary assembly depending on the type of detachable tool head fixed to the power tool. In one aspect, an embodiment of the present invention is directed to a handheld power tool comprising a handle, a tool housing, a rotary assembly having a shaft, a plate member with an opening for regulating movement of the shaft, a detachable tool head capable of contacting the plate member, and a retainer pin positioned within the opening and coupled to a direction-selection switch. Depending on the type of tool head installed on the tool housing and rotary assembly, the plate member may slide axially so as to limit movement of the retainer pin, thereby preventing movement of the direction-selection switch to a position where the shaft of the rotary assembly moves in a reverse direction. 
     In another aspect of the present invention, a plate member for controlling a rotating member of a handheld power tool is disclosed, where the plate member is formed from sheet metal and has an opening located therein, with the opening having a series of edges, where at one end of the opening a retainer pin can move between two positions (forward and neutral) and at an opposing end of the opening, the retainer pin can move between three positions (forward, neutral, and reverse). 
     In yet another aspect, an embodiment of the present invention is directed to a direction-controlling assembly of a handheld power tool comprising a plate member with an opening having a series of edges to define a region in which a retainer pin is permitted to move, where the retainer pin is coupled to a direction-selection switch. The position of the plate member relative to the retainer pin depends on the type of tool head attached to the handheld power tool. Therefore, depending on the type of tool head attached to the power tool, the plate member can slide and restrict movement of the retainer pin and, in turn, the direction-selection switch. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are employed to indicate like parts in the various views: 
         FIG. 1  is a perspective view of handheld power tool assembly and tool head in accordance with an embodiment of the present invention; 
         FIG. 2  is a partial cross section view of a portion of the handheld power tool assembly of  FIG. 1  in accordance with an embodiment of the present invention; 
         FIG. 3  is a fragmentary, cross section view of a portion of the handheld power tool assembly and tool head of  FIG. 1  in which the tool head is shown in a detached position in accordance with an embodiment of the present invention; 
         FIG. 4  is a fragmentary, cross section view of a portion of the handheld power tool assembly and tool head of  FIG. 1  in which the tool head is shown in the process of being attached to the tool housing and rotary assembly in accordance with an embodiment of the present invention; 
         FIG. 5  is a fragmentary, cross section view of a portion of the handheld power tool assembly and tool head of  FIG. 1  in which the tool head is shown attached to the tool housing and rotary assembly in accordance with an embodiment of the present invention; 
         FIG. 6  is a top plan view of a plate member of a handheld power tool assembly in accordance with an embodiment of the present invention; 
         FIG. 7A  is a top plan view of a direction-controlling assembly for use in a handheld power tool assembly in an orientation where rotational movement is not restricted in accordance with an embodiment of the present invention; 
         FIG. 7B  is a top plan view of a direction-controlling assembly for use in a handheld power tool assembly in an orientation where rotational movement is restricted in accordance with an embodiment of the present invention; and, 
         FIGS. 8A, 8B, and 8C  depict top plan views of a direction-controlling assembly for use in a handheld power tool assembly depicting different positions for the plate member in accordance with an embodiment of the present invention. 
         FIG. 9A  is a perspective view of a drill head according to an exemplary embodiment of the present invention; 
         FIG. 9B  is a perspective view of a jigsaw head according to an exemplary embodiment of the present invention; 
         FIG. 9C  is a perspective view of a circular-saw head according to an exemplary embodiment of the present invention; 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the drawings, wherein like reference characters designate like parts throughout the different views, a handheld power tool  100  is depicted in  FIGS. 1-5 . Specifically, the handheld power tool  100  comprises a handle  102 , coupled to a tool housing  104 , where the tool housing  104  is sized to receive a detachable tool head  106  and encloses a rotary assembly  108 . The rotary assembly  108  includes a motor (not shown) which drives a rotatable shaft  110  in both a forward and reverse direction. The rotary assembly also includes an alignment flange  109  which cooperates with the tool head to assure proper orientation of the tool head  106  when coupled with the tool housing  104 . The handle  102  and tool housing  104  may be constructed as one integral part through a casted metal casing or plastic molded construction or alternatively through a mechanical coupling of individual components. 
     Referring to  FIG. 2 , the handheld power tool  100  also comprises a plate member  112 . Further details of the plate member are shown in  FIG. 6  and discussed below. The plate member  112  includes an opening  114  which is sized to limit the movement of a retainer pin  116 , which is positioned within the opening  114 , and is associated with a direction-selection switch  118 . By selectively limiting movement of the direction-selection switch  118 , the plate member  112  is able to control the rotational direction of the shaft  110 . Depending upon the preferred construction, the retainer pin  116  is coupled to the direction-selection switch  118  or formed integral with the direction-selection switch  118 . 
     As previously discussed, the handheld power tool  100  also includes a detachable tool head  106 . However, it is desirable to be able to change the tool head  106  to a different type of tool head depending on the operation to be performed. The detachable tool head  106  is coupled to the rotary assembly  108  and the tool housing  104 . This attachment and detachment process is shown in more detail in  FIGS. 3-5 . The detachable tool head  106  includes a mounting portion  120  which couples with the alignment flange of the rotary assembly  108 , as shown in  FIGS. 1 and 3-5 . 
     In an embodiment of the present invention, the detachable tool head  106  also includes a projection with a contact plate  122  that is capable of contacting the plate member  112 . Depending on the detachable tool head  106  that is selected and coupled with the tool housing  104 , the contact plate  122  may contact the plate member  112  such that the plate member  112  translates axially. The translating or sliding movement of the plate member  112  causes the opening  114  to also translate axially and thereby restrict movement of the retainer pin  116 .  FIGS. 7A and 7B  depict the axial translation of the plate member  112  relative to the retainer pin  116 . Because the retainer pin  116  is coupled to the direction-selection switch  118 , by restricting movement of the retainer pin  116 , selection of the direction of rotation is thereby limited. 
     The size (i.e. length) of the contact plate  122  will determine whether the plate member  112  will move, thereby restricting movement of the retainer pin  116  and selection of a rotational direction of movement for the tool head  106 . Therefore, preventing rotational capability of the tool head is controlled by the size of the contact plate  122 . That is, for tool heads such as drills ( 206 ), where rotational movement in both forward and reverse is desired, the contact plate  122  is sized to not contact the plate member  112  or the contact plate  122  can be omitted altogether. 
     On the other hand, when a tool head  106  such as a sander, jigsaw ( 306 ), or circular saw ( 406 ) is coupled with the tool housing  104 , it is preferred that these tools not operate in a reverse direction. Rotational movement of the shaft in one direction only is desired for use with saw head components because the rotation of the axis in a forward direction causes the saw blade to move in a direction favorable to cutting. Movement in an opposite direction inhibits cutting, and an operator may be inclined to apply more force to try and force the saw to cut, potentially breaking the saw blades or causing other potential injuries. Therefore, in order to prevent rotation in a reverse direction, the contact plate  122  is sized such that when the detachable tool head  106  is coupled with the tool housing  104  and rotary assembly  108  (as shown in  FIG. 5 ), the contact plate  122  contacts the plate member  112 , causing the plate member  112  to translate axially or slide from a position depicted in  FIG. 7A  to a position depicted in  FIG. 7B . In this configuration, the plate member  112  moves due to contact with the contact plate  122  and the retainer pin  116  is only able to toggle between a forward direction position and a neutral, non-rotational position. Furthermore, when the detachable tool head  106  is not attached to the rotary assembly  108 , the retainer pin  116  is in a neutral position, but is permitted to select either a forward and/or reverse direction. An example of this configuration is shown in  FIG. 2 . 
     The handheld power tool  100  also comprises a trigger switch  124  located in the handle  102 . Through the trigger switch  124 , an operator is able to activate and control the motor of the rotary assembly  108  by regulating the power supplied to the motor from a power source (not shown). 
     In an embodiment of the present invention, a plate member  112  for controlling a direction of a rotating member of a power tool is disclosed. The plate member  112  is depicted in  FIG. 6  and comprises a planar member having a thickness and an opening  114  having a first edge  130  and a second edge  132  opposite and generally parallel to the first edge  130 . The opening  114  also comprises a third edge  134  that is generally perpendicular to the first edge  130  and a plurality of fourth edges  136  generally parallel to the third edge  134 . The opening  114  also comprises a fifth edge  138  that extends between the fourth edges  136  and is oriented at an angle relative to the fourth edges  136 . The orientation of the fifth edge at an angle provides a camming surface or way for the plate member  112  to move given the retainer pin  116 . The plate member  112  may be formed out of sheet metal. 
     As shown in  FIG. 6 , the first edge  130  has a first length that is shorter than a second length of the second edge  132 . Referring to  FIGS. 7A and 7B , depending on the position of the plate member  112 , the retainer pin  116  can move between two positions along the first edge  130  and between three positions along the second edge  132 . When the retainer pin  116  is adjacent the first edge  130  (as in  FIG. 7B ), the power tool  100  is capable of operating in forward and neutral positions. Furthermore, when the retainer pin  116  is adjacent the second edge  132  (as in  FIG. 7A ), the power tool  100  is capable of operating in a forward, neutral, and reverse conditions. 
     Located adjacent an end of the plate member  112  is a spring  140  for biasing the plate member  112  in its nominal position, as shown in  FIG. 7A . Referring to  FIGS. 3, 5, 7A, and 7B , the spring  140  is used to bias the plate member  112  in a position permitting three-way movement of the direction-selection switch  118 . However, when the plate member  112  has moved axially rearward with respect to the tool head and downward in the drawings due to a force applied by the contact plate  122 , the spring  140  is compressed, and the position of plate member  112  prevents selection of a reverse direction by the direction-selection switch  118 , as shown in  FIG. 7B , where the retainer pin  116  is located adjacent to the first edge  130  of opening  114 . However, when a non-reverse tool head  106  is removed, the plate member  112  is returned to its previous position, shown in  FIG. 7A , due to the bias of spring  140 . 
     In an embodiment of the present invention, a direction-controlling assembly  130  is disclosed. The direction-controlling assembly  130 , which is depicted in  FIGS. 7A and 7B , comprises the plate member  112  and an opening  114  extending therethrough and located within the plate member  112 . The opening  114  is in accordance with the opening previously described above. The direction-controlling assembly  130  also comprises a direction-selection switch  118  having a retainer pin  116  extending therefrom, with the retainer pin  116  positioned within the opening  114  of the plate member  112 . Movement of the direction-selection switch  118  may be restricted depending on the type of detachable tool head attached to the power tool  100  and the location of the opening  114  of the plate member  112  relative to the retainer pin  116 . 
     The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will become apparent to those of ordinary skill in the art to which the present invention pertains without departing from its scope. Substitutions may be made and equivalents employed herein without departing from the scope of the invention as recited in the claims. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated and within the scope of the claims.