Abstract:
A detachable operating handle for an elongated handheld portable power tool with a nose portion having an output shaft and a slidable operating switch having an outer recess and being configured to slide between on and off positions, the handle comprising a housing configured to cooperatively mate with the power tool housing and be attached at least to the nose portion of the power tool, the housing having an elongated handle portion, a trigger located in the bottom of the handle portion positioned to be moved between depressed and rest positions by a user&#39;s finger while holding the handle portion, a linkage mechanism for interconnecting the trigger and the switch, and the linkage mechanism having a lockout mechanism for preventing the trigger from moving the switch when the lockout mechanism is in a locked position and permitting the trigger to move the switch when in a release position.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to portable handheld power tools. 
     Small handheld power tools that have a rotary output shaft are effective and convenient for using variously shaped cutting and other tools to cut or work with wood and other materials. Such tools are used by tradesman, hobbyists and others in a wide variety of applications and are well known, including those commercialized under the trade names ROTOZIP™ and DREMEL™. If such tools are used with a spiral bit, for example, they can cut materials much the same as is done with a conventional jigsaw, but depth control is difficult unless some type of accessory is provided for that purpose. Also, the convenient use and effective control of the tool can be increased for some cutting and other operations if an accessory handle is attached to the tool which allows for a different hand orientation compared to directly holding the power tool itself. While such accessories have been developed which provide a handle attachment for holding the tool, such known handles require independent operation of the on/off switch of the tool which can be inconvenient to manipulate during use. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention are directed to a detachable operating handle for a power tool of the type that has an elongated housing with a nose portion having an output shaft defining a central longitudinal axis of the tool and a tool bit holding device for securing a tool bit, an operating switch having a switch cap located on the housing near the nose portion, with the switch cap having an outer recess and being configured to slide between on and off positions and be biased toward the off position, the handle comprising a housing configured to cooperatively mate with the power tool housing and be attached at least to the nose portion of the power tool, the housing having an elongated handle portion having a longitudinal axis that is generally perpendicular to the central longitudinal axis of the power tool when the handle is coupled to the power tool, a trigger member located in the bottom of the handle portion positioned to be moved between depressed and rest positions by a user&#39;s finger while holding the handle portion, a linkage mechanism for interconnecting the trigger member and the switch cap for moving the switch cap to its on position, and the linkage mechanism having a lockout mechanism for preventing the trigger member from moving the switch cap when the lockout mechanism is in a locked position and permitting the trigger member to move the switch cap when in a release position. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front left perspective view of a power tool with portions removed, with the tool having a nose portion and an operating switch having a switch cap located near the nose portion; 
         FIG. 2  is a front elevation of the tool shown in  FIG. 1 ; 
         FIG. 3  is a front left perspective view of a detachable operating handle embodying the present invention that is configured to be attached to the tool shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a left side elevation of the detachable operating handle shown in  FIG. 3 ; 
         FIG. 5  is a left side elevation similar to  FIG. 4 , but with portions removed to show the internal construction of the operating handle, particularly illustrating the operating handle trigger in its rest position where the tool operating switch is in an OFF position; 
         FIG. 6  is a view similar to  FIG. 5 , but showing the operating handle having its trigger depressed as required for placing the tool switch in its ON position; 
         FIG. 7  is a perspective view of a portion of a lockout mechanism shown in  FIGS. 3 ,  4  and  5 ; 
         FIG. 8  is a cross-sectional representation of portions of the operating handle, particularly illustrating the lockout mechanism in position to prevent placing the operating switch of the tool in its ON position; and 
         FIG. 9  is a view similar to  FIG. 8 , but illustrating the lockout mechanism having been positioned to permit the trigger to place the operating switch in an ON position, and showing the trigger in its depressed position which moved the switch cap of the operating switch to its ON position. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are directed to a detachable operating handle for use with a power tool of a type that has an elongated housing with a nose portion having an output shaft in a tool bit holding device for securing a tool bit such as a spiral cutting bit to operate in a manner similar to a jigsaw for cutting a work piece. 
     Turning now to the drawings, and particularly  FIGS. 1 and 2 , such a rotary tool is indicated generally at  10  and has an elongated housing  12  with a nose portion  14  and an output shaft  16 , a tool bit holder such as a collet  18  or the like which is shown with a spiral side cutting bit  20  secured thereto in  FIG. 2 . The tool  10  has an ON/OFF switch with a switch cap, indicated generally at  22 , and is shown in  FIGS. 1 and 2  in an off position. The switch cap  22  has an upper cupped portion  24  shaped to be operated by a user&#39;s thumb or finger, which merges with a outwardly extending ramp portion  26  that in turn merges with a flat portion  28 . The upper cupped portion  24  also has an end surface  30  that is generally perpendicular to the upper cupped portion  24 . The switch cap  22  shown in  FIGS. 1 and 2  is shown in its off position and is moved to an ON position by moving it downward as shown in  FIGS. 1 and 2  to energize the motor of the tool to operate the same. While the switch may be designed and configured to stay in either its ON or OFF positions, it is preferred that it be biased toward its OFF position so that if the user does not continue to hold the switch in an ON position it will automatically be returned to its OFF position if the user releases pressure on the switch cap  22 . 
     The housing  12  preferably has outwardly extending sidewalls  32  for retaining and protecting the switch cap  22  and the housing also has a female portion of a one quarter turn quick fastener  34  located above the switch cap  22  for receiving a male pin portion of the fastener that is provided in the detachable operating handle. Alternatively, a threaded aperture can be provided in the housing  12  for receiving a screw or the like for securing the detachable operating handle to the tool. 
     With regard to the operating handle, it is generally indicated at  40  and has a gripping handle portion  42  that merges with an upper body portion, indicated generally at  44 , as well as with a lower body portion, indicated generally at  46 . The handle portion  42  has a rear end portion  48  as well as a lower generally horizontal support portion  50  that is also interconnected with the lower body portion  46 . The gripping handle portion  42 , rear end portion  48  and lower support portion together define an opening, indicated generally at  52 , which enables a user to hold onto the generally cylindrical gripping handle portion and have the fingers of the user&#39;s hand able to grip the handle portion  42  to guide and control the combination tool  10  and handle portion  40  during use. The forefinger of a user is then positioned to control a depressible trigger  54  that engages a linkage mechanism, indicated generally at  56  and best shown in  FIGS. 5 ,  6 ,  8  and  9 , for controlling the position of the switch cap  22  when the handle  40  is attached to the tool  10 . 
     The lower body portion  46  includes a cylindrical mounting portion  58  having an inner diameter that is sized to receive the nose portion  14  of the tool  10  in fitting engagement, with the cylindrical mounting portion  58  having a split ring front configuration defined by two parallel ears  60  that are spaced from one another and have apertures  62  for receiving a thumb screw or the like which can be tightened to pull the split ring configuration toward one another to firmly grip the nose portion  14  of the tool  10 . 
     It should be understood that while the mounting portion is shown to have a compression type of securing arrangement, other types of engagement may be employed, such as a bayonet type arrangement or a quarter turn accessory coupling arrangement such as is disclosed in U.S. Pat. No. 6,679,658 which is assigned to the same assignee as the present invention. 
     It is preferred that the mounting portion  58  be integrally formed with the lower body portion  46 , but it should also be understood that other arrangements known to those of ordinary skill in the art can be used. The upper body portion  44  and lower body portion  46  have sidewalls  64  that form a channel, indicated generally at  66 , which is sized and configured to receive the tool  10  in cooperative fitting relation so that when the nose portion  14  is placed in the mounting portion  58 , the sidewalls  64  are preferably closely mated with the housing. The upper body portion  44  also has an aperture  68  configured to receive the male portion of the ¼ turn quick fastener  34  (not shown). Alternatively, the aperture  68  may be threaded to receive a screw, bolt or the like in the housing of the tool  10  to firmly attach the upper portion of the tool to the operating handle  40 . The lower body portion  46  has a foot portion, indicated generally at  70 , which includes a front slotted opening  72  that is configured to enable the tool bit  20  to extend below the bottom surface of the foot for cutting. 
     It should be understood that when the tool  10  is attached to the handle  40 , the switch cap  22  is positioned inside of the channel  66  and is unaccessable for independent operation. It is highly desirable that the trigger  54  be the only means for turning the tool  10  on and off and the preferred embodiment of the present invention exhibits this desirable feature. 
     As best shown in  FIG. 5 , the lower body portion  46  has an internal channel  76  configured to receive a stem portion  78  of the foot  70 . The stem portion is generally perpendicular to the plane of the bottom surface  74  of the foot  70  and is vertically adjustable within the channel  76  to vary the depth of cut of a tool bit  20  that is mounted in the tool  10 . This is accomplished by the stem portion  78  having an elongated slot  80  which is aligned with an aperture  82  in the far side of the lower body portion which is configured to retain a thumb screw or the like that can be loosened to adjust the vertical position of the shoe relative to the lower body portion  46  and be tightened to secure it in a desired position. 
     As is also shown in  FIG. 5 , the trigger  54  is pivotally mounted in the handle portion  42  around pivot  84 . While not shown in  FIGS. 5 and 6 , it has a recessed top surface  86  as shown in  FIGS. 8 and 9  configured to engage an elongated lever  88  at its bottom surface  90 . The lever  88  is pivotally connected to the upper body portion  44  by pivot  92  and also has a top end portion  94  with an outer tip portion  96  which extends into the channel  66  of the top body portion  44 . The pivot  92  may be outwardly extending hubs that engage corresponding recess in the top body portion  44 , with the hubs being integrally formed with the lever  88 . Alternatively, a suitable separate pivot pin could be employed. 
     The end portion  94  is angled at approximately 45 degrees so that the tip portion  96  is approximately horizontal as shown. The upper end portion  94  also has a lower extension  98  with a bottom surface  100  that is provided for engaging a lockout member indicated generally at  102 . When the trigger  54  is depressed or moved upwardly as shown in  FIG. 6 , the lever  88  is rotated in a counterclockwise direction around the pivot  92  so that the tip portion  96  will be moved downwardly. 
     In this regard, the tip portion  96  is configured to engage the top surface  30  of the switch button  22  so that when the trigger  54  is depressed, the switch button  22  will be moved to its ON position. This assumes, of course, that the lockout button  102  is not positioned to prevent such movement. 
     The linkage mechanism  56  also includes a compression spring  104 , the upper end of which is confined in a recess  106  in the handle portion  42  and the lower end of which fits around a tab  108  provided on the lever  88 . The compression spring  104  is configured and sized sufficient to put a biasing force on the linkage mechanism  56  to hold the mechanism in its position shown in  FIG. 5  where the tip portion  96  is in its highest position, i.e., the switch button gap  22  is in its OFF position. 
     With regard to the lockout member  102 , it is shown in  FIG. 3  to be mounted in the upper body portion and extends through openings therein so that it is accessible by a user and can be slidably moved in either direction by a user using either their thumb or forefinger to slide the lockout member  102  into and out of its lockout position. 
     The lockout member is shown in detail in  FIG. 7  and has a width that is slightly larger than the width of the upper body portion  44  with end surfaces  110  and  112 , a center upper extension  114  with a contact surface  116  that is configured to engage the lower extension  98  of the tip portion  96  of the lever  88 . This is diagrammatically illustrated in  FIG. 8  where the lockout member  102  is shown to be engaged with the lower extension  98 . In this position, the switch cap  22  is in its OFF position and the lockout member  102  would prevent from being moved by if the user were to attempt to depress the trigger  54 . The lockout member is shown to be in contact with the lower extension in  FIG. 3 . The width of the extension  114  is such that movement in one direction or another by the user pushing on one of the contact surfaces  110  or  112  will move it out of engagement with the lower extension  98  and enable depression of the trigger  54  to move the switch cap  22  as is diagrammatically shown in  FIG. 9 . 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention. Various features of the invention are set forth in the following claims.