Abstract:
The power tool includes a body, a trigger mechanism and a manually operated locking member. The trigger mechanism is mounted to the body for rotation about an axis between an actuated position and a non-actuated position. The manually operable locking member is translationally mounted to the body for movement between a first position and a second position. The locking member cooperates with the trigger mechanism to provide first, second and third modes of operation. In the first mode, the locking member is in the first position and articulation of the trigger mechanism from the non-actuated position to the actuated position is precluded. In the second mode, the locking member is in an intermediate position between the first and second positions and the trigger mechanism is freely allowed to articulate between the actuated and non-actuated positions. In the third mode, the locking member is in the second position and the trigger mechanism is prevented from articulating from the non-actuated position to the actuated position.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This invention relates to U.S. Provisional Application No. 60/285,136, filed Apr. 20, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is generally directed to power tools. In particular, the present invention is directed to a power tool having an actuation mechanism including an arrangement for preventing operation of the tool and also maintaining the tool in a continuous operating mode.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional electrical devices frequently include an electrical switch for controlling the operation of the device. Examples of such electrical devices are disclosed in U.S. Pat. Nos. 2,420,585 to Crimmins, 3,378,662 to Sorenson, 4,095,071 to Chamberlain, and 4,454,785 to Pürrer. Examples of electrical switches having a controlled movement include U.S. Pat. Nos. 3,249,725 to Hurt et al., 5,120,922 to Brouillette, and 5,813,522 to Lin.  
           [0004]    Sorenson shows a typical power tool having an ON/OFF switch. This switch is controlled by a linkage including a trigger element, that is retracted into a body of the power tool against the action of a spring. The linkage further includes a plate having a row of serrations and a lock button. This lock button is biased by a spring out of engagement with the serrations. When the power tool is to be operated at a constant speed for extended periods of time, the trigger is retracted a desired distance and the lock button is depressed. This action causes the flange on the lock button to interengage one of the serrations, thus maintaining the trigger in the retracted position. Further retracting the trigger releases this interengagement and the lock button is moved out of engagement by the spring. Thus, the Sorenson linkage provides a consumer convenience feature for avoiding hand fatigue and for providing a mechanism that ensures the power tool can be continuously operated at a constant, predetermined speed for an extended period of time.  
           [0005]    Another known arrangement providing the customer convenience feature of Sorenson is shown in FIG. 1. A power tool is shown to include an actuation mechanism including a trigger and a lock mechanism. In the illustrated position, lock Ad out, the trigger is not able to be actuated. To actuate the trigger, the lock mechanism must be pushed to an intermediate position. Once, the trigger has been fully actuated, the lock mechanism may be pushed to a locking position, continuously engaging the trigger mechanism.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention is to provide a trigger mechanism including a locking device for blocking the movement of the trigger, thus preventing inadvertent operation of a power tool.  
           [0007]    It is another object of the present invention to provide a trigger mechanism that is selectively positionable between a first mode blocking the movement of the trigger, a second mode allowing free manual movement of the trigger, and a third mode retaining the trigger in a position for continuous operation.  
           [0008]    In one form, the present invention provides a power tool, a body, a trigger mechanism and a manually operated locking member. The trigger mechanism is mounted to the body for rotation about an axis between an actuated position and a non-actuated position. The manually operable locking member is translationally mounted to the body for movement between a first position and a second position. The locking member cooperates with the trigger mechanism to provide first, second and third modes of operation. In the first mode, the locking member is in the first position and articulation of the trigger mechanism from the non-actuated position to the actuated position is precluded. In the second mode, the locking member is in an intermediate position between the first and second positions and the trigger mechanism is freely allowed to articulate between the actuated and non-actuated positions. In the third mode, the locking member is in the second position and the trigger mechanism is prevented from articulating from the non-actuated position to the actuated position.  
           [0009]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 is a partial and simplified side view of a prior art actuation mechanism of a power tool known in the art.  
         [0012]    [0012]FIG. 2 is a partial and simplified side view of a power tool showing an actuation mechanism constructed in accordance with the present invention, a trigger of the tool shown in an at rest condition and the locking member shown in a forward position to block actuation of the trigger.  
         [0013]    [0013]FIG. 3 is a partial and simplified side view similar to FIG. 2, illustrating the trigger in the at rest position and the locking member moved to an intermediate position permitting actuation of the trigger.  
         [0014]    [0014]FIG. 4 is a partial and simplified side view similar to FIG. 3, illustrating the trigger in a fully actuated position.  
         [0015]    [0015]FIG. 5 is a partial and simplified side view similar to FIG. 2, illustrating the trigger in a fully actuated position and the locking member in its rearward position in which the trigger is prevented from freely returning to the at rest position.  
         [0016]    [0016]FIG. 6 is a partial and simplified side view similar to FIG. 5, illustrating the trigger after it has been released by the operator and the trigger engages the locking mechanism to prevent return to the at rest position.  
         [0017]    [0017]FIG. 7 is a perspective view of the trigger according to the present embodiment.  
         [0018]    [0018]FIG. 8 is another second perspective view of the trigger according to the present embodiment.  
         [0019]    [0019]FIG. 9 is a perspective view of the locking member according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0021]    Referring generally to FIGS.  2 - 9  wherein like numbers refer to like features, a portion of a power tool is generally indicated with the reference number  10 . Examples of power tools of the type to which the present invention pertains include outdoor power equipment such as hedge trimmers, chain saws, edgers, grass shears, lawn mowers, lawn vacuums, leaf blowers, sprayers, and string trimmers. Additional examples of such power tools include circular saws, drills, grinders, heat guns, inflators, jig saws, planers, rotary tools, routers, sanders, screwdrivers, and vacuums. The power tool  10  may be powered by electricity (direct or alternating current) or by internal engine. Of course, the teachings of the present invention are also applicable to other types of equipment and tools, and may be used with alternate types of power sources.  
         [0022]    In the exemplary embodiment illustrated, the power tool  10  is a hedge trimmer including a body  11  supporting the components of the hedge trimmer. The power tool  10  generally includes a locking member  12  and a trigger mechanism  14 . The trigger mechanism  14  is pivotally supported on the body  11  for pivotal movement about a transversely extending pivot axis  16  such that the trigger mechanism  14  is divided into two parts, a trigger or actuation portion  18  forward of the pivot axis  16  and a biasing portion  20  rearward of the pivot axis  16 . The trigger mechanism  14  is pivotable between an at rest position in which a motor of the tool  10  is not actuated and a fully actuated position. The at rest position is shown in FIGS. 2 and 3, for example. The fully actuated position is shown in FIGS. 4 and 5, for example.  
         [0023]    The range of movement of the actuation portion  18  is constrained by the locking member  12 . A biasing element  22  normally urges the actuation portion  18  clockwise (as shown in the drawings) when there are no external forces with respect to the power tool  10  that act on the trigger mechanism  14 . According to the preferred embodiment shown in FIG. 1, the biasing element  22  comprises a coil spring. However, it will be understood that alternate biasing members may be used to accomplish to the same function.  
         [0024]    During operation, the power tool&#39;s operator manually engages actuation portion  18  of the trigger mechanism  14  to rotate the trigger mechanism  14  about the pivot axis  16 . The trigger mechanism  14  includes an actuator portion  24  which engages a throw switch  26  of regulator  28 . According to a preferred embodiment of the present invention, a slot  31  (shown in FIG. 8) located in the distal end of actuator portion  24  receives and displaces throw switch  26 . Of course, the trigger mechanism  14  may be configured and located with respect to the body  11  so that actuation portion  18  is engageable by a particular portion of the operator&#39;s body, e.g., one or more fingers. Additionally, trigger mechanism  14  as shown in FIG. 8 includes a guide protruding from the right side of actuator portion  24 . The inclusion of this guide is optional.  
         [0025]    The regulator  28  controlled by the throw switch  26  electrically connects a power source, e.g., a battery (not shown), to an actuator, e.g., a motor (not shown), of the power tool  10 . According to the preferred embodiment shown in FIGS.  2 - 9 , the regulator comprises an electric switch of the single-pole, single-throw type. Thus, the single throw switch  26  is moveable between an OFF position in which the motor is electrically disconnected from the power source, and an ON position in which the motor is electrically connected to the power source.  
         [0026]    It is also envisioned that a variable resistance or other type of infinitely variable switch could be used to gradually vary the connection between the power source and the actuator. Such an infinitely variable switch would be able to adjustably control the speed or some other characteristic of the actuator. In the case of an internal combustion engine actuator, the regulator may comprise a carburetor controllingly connecting a power source, e.g., fuel supply, to the internal combustion engine. Of course, the carburetor could either provide discrete levels of internal combustion engine operation, or provide a gradually varying connection between the fuel supply and the internal combustion engine.  
         [0027]    In the exemplary embodiment illustrated, the trigger mechanism  14  and its pivoting connection about pivot axis  16  define a control linkage for conveying the manipulations of the power tool&#39;s operator to the regulator  28 . Of course, the linkage may alternatively include additional links and, as noted above, the actuation portion  18  may be supported with respect to the body  11  for other types of relative movement, e.g., linear translation. As such, the control linkage would comprise a sliding connection between the actuation portion  18  and the body  11 , rather than the pivoting connection about the pivot axis  16 . The locking member  12  is captured in a groove for manual movement between a forward position and a rearward position. The forward position is shown in FIG. 2. The rearward position is shown in FIGS. 5 and 6. The intermediate position is shown in FIGS. 3 and 4.  
         [0028]    According to a preferred embodiment of the present invention, the locking member  12  is translatable between the forward or first position and the rearward or second position against the urging of a resilient biasing member  30 , e.g., coil spring. Alternatively, the resilient biasing member  30  may include other members known to provide translation biasing. In operation, the power tool&#39;s operator engages a contact part  32  to slide the locking member  12  toward the second position, and the resilient biasing member  30  returns the locking member  12  toward the first position. Of course, it is envisioned that different types of relative movement other than translation, e.g., pivoting or rotating, could occur between the locking member  12  and the body  11 .  
         [0029]    The trigger mechanism  14  and the locking member  12  include cooperating elements for controlling the mode of operation of the actuation portion  18 . In a first mode of operation, the trigger is precluded from actuating the motor. In a second mode of operation, the trigger is freely allowed to move between actuated and non-actuated positions. In a third mode of operation, the trigger is retained in the actuated position.  
         [0030]    The trigger mechanism includes a first portion or latching element  34  and a second portion or blocking element  36 . The first portion  34  upwardly extends toward the locking member  12  and is generally hook shaped. The second portion  36  defines a blocking surface.  
         [0031]    The locking member includes a first portion  40  and a second portion  42 . The first portion  40  downwardly extends toward the trigger mechanism  14 . The second portion  42  downwardly extends toward the trigger mechanism  14  and is generally hook shaped.  
         [0032]    As particularly shown in FIG. 2, the power tool  10  is in its first mode of operation in which the actuation portion  18  is precluded from actuating the motor. The trigger mechanism  14  is therefore in its non-actuated position. The locking member  12  is in its forward position. A forwardly extending leg  44  of the first portion  40  of the locking member  12  abuts an upper surface  46  of the first portion  34  of the trigger mechanism  14 . Additional blocking contact is provided through engagement of a rearwardly extending leg  48  of the second portion  42  of the locking member  12  and an upper surface of the second portion  36  of the trigger mechanism  14 .  
         [0033]    An additional benefit of this embodiment is visible in FIG. 2. The locking member  12  and specifically the rearwardly extending leg  48 , and the trigger mechanism  14  and specifically the upper surface of the second portion  36 , are positioned so that they are as close as practical to the throw switch  26  of the regulator  28 . This minimizes the lever arm of the trigger mechanism  14 , thereby maximizing the force required to override the lock off position.  
         [0034]    Turning to FIG. 3, the power tool is shown in its second mode of operation in which the actuation portion  18  of trigger mechanism  14  is freely allowed to move between its actuated and non-actuated positions. The locking member  12  is shown translated rearward in the direction of arrow A from its forward position of FIG. 2 to its intermediate position in which the first portion  34  of the trigger mechanism  14  is positioned between the first and second portions  40  and  42  of the locking member  12 . FIG. 4 similarly shows power tool  10  in the second mode of operation but illustrates the actuation portion  18  articulated to its first actuated position.  
         [0035]    With reference to FIG. 5, the locking member  12  is translated rearwardly against the bias of the resilient biasing member  30  to its rear position and the power tool  10  is now in its third mode of operation in which the trigger mechanism  14  will be prevented from return to its non-actuated position.  
         [0036]    An additional benefit of the preferred embodiment of the present invention is visible in FIGS. 4, 5, and  6 . As the trigger mechanism  14  is actuated through its range of motion (as shown in these figures), the distal end of the actuator portion  24  moves through an arc about the pivot axis  16 . The amount of displacement of the throw switch  26  does not vary with additional rotation in either direction of trigger mechanism  14 , so long as the trigger mechanism  14  is in the range of motion that engages the distal end of actuator portion  24  with the throw switch  26  of regulator  28  to its ON position. This allows for more economically produced parts, in higher volumes, with the associated increase in variation of the exact sizes and shapes of these parts, without increasing the likelihood that the entire lock on/lock off mechanism will not operate as desired.  
         [0037]    In FIG. 6, the trigger mechanism  14  is shown released by the tool user such that the actuation portion  18  rotates slightly in a clockwise direction and the hook-shaped portions  34  and  42  of the trigger mechanism  14  and locking member  12 , respectively, engage. Through such engagement, the biasing force of the resilient biasing member  30  is prevented from otherwise returning the locking member  12  to its forward position. Additionally, biasing force of biasing element  22  prevents the trigger mechanism  14  to its original position  
         [0038]    Disengagement of the hook-shaped portions  34  and  42  is accomplished by manual grasping of the actuator portion  18  by the tool user such that the trigger mechanism  14  rotates counterclockwise about pivot axis  16  to the position shown in FIG. 4. At this point, resilient biasing member  30  forwardly biases the lock member  12  to its intermediate position. The trigger mechanism  14  can now freely return to its non-actuated position upon release of the actuator portion  18  by the user. When this happens, the first portion  34  of the trigger mechanism  14  clears the forwardly extending leg  44  (shown in FIG. 2) of the first portion  40  of the lock member  12  and the spring bias of the resilient biasing member  30  now returns the locking member  12  to its forward position.  
         [0039]    In the preferred embodiment of the present invention, the power tool  10  will now be understood to include a locking member  12  and a trigger mechanism  14  which cooperate to lock out the actuation portion  18  and provide continuous operation with reduced operator fatigue. The present invention provides a blocking feature for lock out of the trigger. Additionally, the present invention provides an improved switching feature. Furthermore, the present invention allows for a preferred movement of the locking member  12  between distinct positions for locking out actuation of the actuation portion  18  and maintaining actuation of the actuation portion  18 .  
         [0040]    When a user picks up the power tool, the locking member  12  in its forward position and inadvertent actuation of the motor is precluded through the engagement of the forwardly extending leg  44  with the first portion  34  of the trigger mechanism  14  and engagement of the rearwardly extending leg  48  with the second portion  36  of the trigger mechanism  14 . When the user desires to actuate the motor, the locking member  12  is rearwardly translated to its intermediate position such that the first portion  34  of the trigger mechanism  14  is positioned between the first and second portions  40  and  42  of the locking member  12 . At this point, the user can squeeze the actuation portion  18  and articulate the trigger mechanism  14  counterclockwise about the pivot axis  16 . If continuous operation of the motor is desired by the user, the locking member  12  can be further rearwardly translated such that the cooperating hook-shaped portions  34  and  42  of the trigger mechanism  14  and locking member  12 , respectfully, overlap. When the user releases his or her grasp of the actuation portion  18  the hook-shaped portions  34  and  42  engage and prevent the trigger mechanism  14  from further rotating clockwise to thereby cease actuation of the motor. To discontinue the continuous operation of the motor without grasping the trigger mechanism  14 , the user squeezes the trigger mechanism  14  to rotate the trigger mechanism  14  counterclockwise about the pivot access  16  and release engagement of the hook-shaped portions  34  and  42 . This action causes the locking member  12  to forwardly translate to its intermediate position such that the trigger mechanism  14  can be freely articulated between actuated and non-actuated positions. As such, manual release of the trigger mechanism  14  allows the trigger mechanism  14  to fully rotate in a clockwise direction about the pivot axis  16  and the locking member  12  to further translate to its full forward position in which actuation of the motor is normally precluded.  
         [0041]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.