Abstract:
A power tool and system for trimming and cutting vegetation are disclosed. A method of attaching a working assembly, such as blade carrier assembly, to a power tool is also disclosed. The power tool includes interchangeable cutting elements that can be readily attached and detached from a main body portion without any preliminary alignment steps. The main body portion of the power tool includes a selectively actuatable motor including a rotary output and a rotary drive element including a resiliently biased drive pin. Blade carrier assemblies are capable of being selectively and removably attached to the main body portion and each include a moveable blade portion having a drive pin slot. Upon attaching a blade carrier assembly to the main body portion and actuating the motor, the resiliently biased drive pin is rotatable to a position such that the drive pin is resiliently forced into the drive pin slot of the working piece to actuate the working assembly.

Description:
FIELD  
       [0001]     The present teachings relate to a handheld power tool having readily interchangeable cutting elements for trimming and cutting vegetation. More particularly, the present teachings relate to a resiliently biased driving element formed on a main body portion of the power tool that automatically engages various interchangeable blade carrier assemblies to allow a user to perform different types of cutting processes in a quick and safe manner.  
       BACKGROUND  
       [0002]     Known power tools having interchangeable blades are cumbersome and potentially dangerous to manipulate. For example, U.S. Pat. No. 3,959,848 to Irelan et al., discloses a convertible portable electric tool having interchangeable tool pieces. Each of the interchangeable tool pieces include two parts, a stationary element and a moving element, which are pivoted together at a pin. The stationary element includes a comb of teeth and, likewise, the moving element includes a comb of teeth. The rearward end of the moving element includes an elongated opening for receipt of a drive member. The drive member is rotated by a gear and the resulting circular movement oscillates the moving element about the pivot pin. As a result, the stationary element and the moving element lap one another to cut grass between the teeth upon oscillation of the moving element.  
         [0003]     Before attaching a tool piece assembly to the power housing, the user must first rotate the drive member to a predetermined position, such as a top dead center position. Similarly, the user must manually orient the moving element into a predetermined position with respect to the stationary element. After completing these preliminary steps, the drive member can be fitted within the elongated opening of the moving element upon bringing the stationary element into proper registry relative to the power housing. Once the stationary tool element is brought into proper registry and located over guide posts, additional means are provided to maintain the tool piece releasably secured against the housing.  
         [0004]     Accordingly, the attachment of tool pieces to a power housing as disclosed by Irelan et al. is a cumbersome process requiring various manual alignment steps to be performed by the user with respect to both the tool piece and the power housing. Generally, known power tools do not provide fool-proof mechanisms to allow easy, safe, and automatic alignment and attachment of cutting elements. Instead, users are required to spend time handling and adjusting cutting blades and other movable parts until precise alignments are achieved before a cutting element can be properly attached. Not only is this time consuming, but the user is also exposed to sharp cutting surfaces and powered moving parts in the process.  
         [0005]     A need exists for a power tool having interchangeable cutting assemblies that can automatically align themselves into an operative position without requiring cumbersome and dangerous operated-assisted adjustments. A need also exists for interchangeable cutting assemblies that can be readily and safely latched to and selectively released from an operative position whenever desired by the user. There also exists a need for interchangeable cutting assemblies that can be safely and easily manipulated by a user.  
       SUMMARY  
       [0006]     The present teachings relate to a power tool and system having readily interchangeable cutting assemblies for cutting and trimming vegetation. The present teachings also relate to a method of attaching a blade carrier assembly to a power tool main body.  
         [0007]     According to various embodiments, the power tool includes a main body portion including a housing, a selectively actuatable motor operatively arranged with the housing and including a rotary output, and a rotary drive element arranged in operative contact with the rotary output of the motor and including a resiliently biased drive pin. A blade carrier assembly is capable of being selectively and removably attached to the main body portion. The blade carrier assembly includes a moveable blade portion having a drive pin slot. Upon attaching the blade carrier assembly to the main body portion and actuating the motor, the resiliently biased drive pin is rotatable to a position such that the drive pin is resiliently forced into the drive pin slot of the moveable blade portion.  
         [0008]     According to various embodiments, the power tool system includes a main common body portion including a housing, a selectively actuatable motor operatively arranged within the housing and including a rotary output, and a rotary drive element arranged in operative contact with the rotary output of the motor. The rotary drive element includes an engageable drive structure. A plurality of blade carrier assemblies each include a blade carrier cup that is capable of being removably attached to the main common body portion by way of a latching mechanism. The blade carrier cup is arranged to support a cutting blade assembly such that the cutting blade assembly can be safely handled by the user by manipulation of the blade carrier cup. The cutting blade assembly includes a moveable blade portion capable of operative connection with the engageable drive structure of the rotary drive element.  
         [0009]     According to various embodiments, the method of attaching a working assembly to a power tool main body is provided. The method includes providing the power tool main body with a selectively actuatable motor arranged to drive a rotary drive element including a resiliently biased drive pin and providing the working assembly, such as a blade carrier assembly, with a moveable working piece portion having a drive pin engageable structure. The method further includes connecting the working assembly to the power tool main body such that the resiliently biased drive pin is displaced if the drive pin is not aligned with the drive pin engageable structure, and then actuating the motor to rotate the rotary drive element to a position such that the drive pin is resiliently forced into the drive pin engageable structure to actuate the working assembly.  
         [0010]     Additional features and advantages of various embodiments will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of various embodiments. The objectives and other advantages of various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description herein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a power tool device and system including an additional, unattached blade carrier assembly according to various embodiments;  
         [0012]      FIG. 2  is a perspective view of the power tool device of  FIG. 1  showing a blade carrier assembly in an unlatched position according to various embodiments;  
         [0013]      FIG. 3  is a top perspective view of an interchangeable blade carrier assembly according to various embodiments;  
         [0014]      FIG. 4  is a bottom perspective view of the main body of the power tool device of  FIG. 1  with the interchangeable blade carrier assembly removed  
         [0015]      FIG. 5  is an exploded perspective view of a drive motor assembly including a first embodiment of a resiliently biased rotary drive element;  
         [0016]      FIG. 6  is a perspective view of a second embodiment of a resiliently biased rotary drive element including a spur gear having a resiliently mounted drive pin arranged thereon; and  
         [0017]      FIG. 7  is a perspective view of the second embodiment of the resiliently biased rotary drive element of  FIG. 6  shown in a disassembled condition. 
     
    
       [0018]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are intended to provide an explanation of various embodiments of the present teachings.  
       DESCRIPTION  
       [0019]     A power tool device  10  and a system for cutting and trimming vegetation is shown in  FIG. 1 . The power tool device  10  can be a handheld unit for cutting grass, weeds, and other types of vegetation around a house or business, or any other location where unwanted growth is found. The power tool device  10  can be part of a system or kit that allows a user to perform various different cutting functions using a common main tool body  12 . The power tool system can include a plurality of interchangeable blade carrier assemblies  14 ,  15  that can be releasably attached to the common main body portion  12 . For example, as shown in  FIG. 1 , the common main tool body  12  is shown attached to an interchangeable blade carrier assembly  14  that comprises a shrubber blade subassembly  16 . Furthermore, adjacent to the power tool device  10  is an unattached interchangeable blade carrier assembly  15  that comprises a shear blade subassembly  17 . Referring to the unattached interchangeable blade carrier assembly  15 , each blade carrier assembly can include a blade carrier cup portion  18  and one of a plurality of different blade subassembly portions  17 . In the preferred embodiment, the blade carrier cup portion  18  is the same for both the shrubber blade  16  interchangeable blade carrier assembly  14  and the shearing blade  17  interchangeable blade carrier assembly  15 . As will be discussed below, the blade carrier cup portion  18  allows the interchangeable blade carrier assembly  14 ,  15  to be safely handled and manipulated by a user, as well as easily attached and removed from the common main tool body portion  12 .  
         [0020]     Referring to  FIG. 2 , a close-up view of the power tool device  10  of  FIG. 1  is provided. The power tool device  10  is shown in a position whereby an interchangeable blade carrier assembly  14  (including a shrubber blade subassembly  16 ) is in the process of being latched onto or unlatched from the common main tool body  12 . The positioning of the structure shown in  FIG. 2  shows how power can be transferred from the common main tool body  12  to the blade subassembly portion  16  of an interchangeable blade carrier assembly  14 .  
         [0021]     On the common main tool body  12 , a trigger switch  24  allows the user to selectively control power to a motor arranged within the housing of the common main tool body  12 . In a preferred embodiment, the main tool body also includes a battery pack for providing energy to the motor enabling the power tool device to be cordless device. The details of the drive motor assembly will be described below with respect to the discussion of  FIG. 4 . According to various embodiments, the motor is operable to rotate a rotary drive element  26 . As shown in  FIG. 2 , the rotary drive element  26  can include a drive plate  28  and a drive pin  30 . The drive pin  30  may be integrally attached or formed with the drive plate  28 . The drive pin  30  can be eccentrically arranged on the drive plate  28 .  
         [0022]     On the interchangeable blade carrier assembly  14 , one or more movable blades  32 ,  33  can be reciprocally arranged with respect to the blade carrier cup  18 . In a preferred embodiment, the power tool device  10  has one moveable blade  32  which sits on top of and works with a stationary blade  33  for providing a cutting action. As shown in  FIG. 2 , the movable blade  32  includes a drive pin slot  34  for engagement with the drive pin  30  of the rotary drive element  26 . The blade carrier cup  18  can attach to the common main tool body  12  by way of a latching mechanism. The latching mechanism may include one or more latch apertures or detents  36  formed on the blade carrier cup  18 . The apertures or detents  36  may be completely cut through the blade carrier cup  18  housing as shown in  FIG. 2  or may be a recess on the interior housing of the blade carrier cup  18  and, therefore, not visible or evident from the exterior housing of the blade carrier cup assembly  18 . The latching mechanism might also include one or more resiliently biased latch elements  38  formed on the common main tool body  12 . The resiliently biased latch elements  38  may be partially or fully retractable into the common main tool body  12  and are resiliently biased outwardly in their non-actuated position. As will be further described in conjunction with  FIG. 3 , the blade carrier cup  18  may have mating hook  40  for mating with and insertion into a recess or aperture in the main tool body  12 . The blade carrier cup  18  is attached to the main tool body  12  by inserting the mating hook  40  into an aperture  45  (see  FIG. 4 ) in the main tool body  12  and then bringing the forward end of the blade carrier cup  18  into engagement with the main tool body  12  until the latch elements  38  snap into engagement with the latch apertures or detents  36  formed on the blade carrier cup  18 . In the engaged position, the power tool device  10  is assembled and ready to perform a cutting operation.  
         [0023]     On the common main tool body  12 , one or more latch release pushbuttons  42  can be arranged in a position for convenient actuation by the fingers and/or thumb of a user. The one or more latch release pushbuttons  42  can be mechanically coupled with the latch elements  38 . Accordingly, the latch elements  38  can be retracted from the blade carrier cup  18  by depressing at least one of the latch release pushbuttons  42  thereby releasing the blade carrier assembly  14  from the common main tool body  12 .  
         [0024]     A detailed top view of a blade carrier cup portion  18  of an interchangeable blade carrier assembly  14  is shown in  FIG. 3 . The blade carrier cup portion  18  may have a concave shape that defines a generally concave interior. The concave interior of the cup portion  18  can be defined by a bottom surface and at least one sidewall surface. The blade carrier cup portion  18  can be arranged to engage a complimentary convex-shaped portion of the main common body portion  12 . In a preferred embodiment, the blade carrier cup  18  is made of a hard resilient plastic which covers the complete underside of the blade subassembly  16 ,  17  (except for the cutting end) to enable a user to grab the blade carrier cup  18  and attach or remove the interchangeable blade carrier assembly  14 ,  15  without needing to touch the blades  32 ,  33 .  
         [0025]     In  FIG. 3 , an interchangeable blade carrier assembly  14 ,  15  is shown with a shrubber blade subassembly  16  operatively connected a bottom interior surface of the blade carrier cup portion  18 . As discussed above, in a preferred embodiment the shrubber blade subassembly  16  may include at least two cutting elements or blades, an upper movable cutting element  32  and a lower stationary cutting element  33 . The lower stationary cutting element  33  can include a stationary blade end  48  that can be secured in the blade carrier cup  18 . A movable blade end  49  of the upper movable cutting element  32  may also be arranged within the blade carrier cup  18 . A drive pin slot  34  may be formed in movable cutting element blade  32  for engagement with the drive pin  30  of the rotary drive element  26 . A track or guide mechanism  52  can be arranged on either side of the stationary cutting element  33  or the movable cutting element  32  for placement during fabrication or to guide the movable cutting element  32  as it reciprocates in a direction into and away from the housing.  
         [0026]     At one end of the blade carrier cup portion  18 , a blade carrier cup hook  40  can be arranged for engagement with the common main tool body  12 . The blade carrier cup hook  40  may be inserted into an aperture  45 , as seen in  FIG. 4 , in the main tool body  12  to provide engagement at the back end of the blade carrier cup  18  with the main tool body  12 . When the blade carrier cup  18  is disengaged the common main tool body  12 , as shown in  FIG. 2 , the blade carrier cup hook  40  can be disengaged from the common main tool body  12  and replaced with a different interchangeable blade carrier assembly  14 ,  15 .  
         [0027]      FIG. 4 , provides a perspective view of the bottom of the main body  12  of the power tool device  10 . The drive pin  30 , drive plate  28  and rotary drive element  26  can be seen as the interchangeable working assembly  14 ,  15  is removed. Further, the latch release pushbuttons  42  may be mechanically coupled with the latch elements  38  for securing and releasing the interchangeable working assemblies or blade assemblies  14 ,  15 . In addition, the main body  12  includes an aperture  45  for mating with and receiving the cup hook portion  40  of the blade carrier cup  18 .  
         [0028]     Referring to  FIG. 5 , a drive motor assembly  50  for the power tool device  10  is shown. The drive motor assembly  50  may include an electric motor  56  that can power a resiliently biased rotary drive element  26 . As shown in  FIG. 5 , the electric motor  56  can be operatively attached to a gearbox assembly  58  that can provide power to a drive gear  66 . The gearbox assembly  58  may include a gear train, including, for example, a planetary gear arrangement  60 . A support surface  62  can be arranged along a portion of the drivetrain of the drive motor assembly. For example, the support surface  62  can be arranged adjacent to the planetary gear arrangement  60 . The support surface  62  can provide a smooth surface upon which a spring  64 , such as, for example, a spring washer  64 , can be supported.  
         [0029]     The drive gear  66  can be operatively connected with the planetary gear arrangement  60  and can provide rotary power to the rotary drive element  26 . As shown in  FIGS. 2, 4  and  5 , the rotary drive element  26  can include a drive plate  28  having an eccentrically arranged drive pin  30  arranged or formed thereon. The rotary drive element  26  can rotate with respect to a rotary drive element housing  68 . The rotary drive element housing  68  can attach with the gearbox assembly  58  to form the drive motor assembly structure.  
         [0030]     In the assembled state of the drive motor assembly  50  structure, the spring  64  resiliently forces the rotary drive element  26  in a direction away from the motor  56  such that the rotary drive element  26  is forced against the rotary drive element housing  68 . The rotary drive element  26  can move a distance into the rotary drive element housing  68  against the resilient force of the spring  64 . For example, referring to  FIGS. 2, 4 , and  5 , the rotary drive element  26  would be forced into the rotary drive element housing  68  against the force of spring  64 , if the drive pin  30  is not aligned with the drive pin slot  34  of moveable blade  32  when the blade carrier assembly  14  is brought into engagement with the main tool body  12 . When the motor  56  is energized by having the user depress the trigger  24 , the drive plate  28 , and in turn, the drive pin  30  are rotated until the resiliently biased drive pin  30  snaps or clicks into the drive pin slot  34  of one or more moveable blades  32 . Once engaged in the drive pin slot  34 , the drive pin  30  can continue to be rotated by the motor  56  to reciprocate moveable blade  32  and achieve a cutting action against stationary blade  33 . Thus, there is no need for the user to make any preliminary alignments with respect to the drive pin  30 , the drive pin slot  34 , or the blade carrier assembly  14 ,  15 .  
         [0031]     To replace or interchange blade carrier assemblies  14 ,  15 , for example, to change from a shrubber blade assembly  14  to a shear blade assembly  15 , the user can depress one or more of the latch release pushbuttons  42 . Depressing the latch release pushbuttons  42  results in the latch elements  38  being retracted such that they no longer project into or through the latch apertures or detents  36  formed on the blade carrier cup portion  18  of the blade carrier assembly  14 ,  15 . The user can then remove the blade carrier assembly  14  by moving the blade carrier cup  18  downwardly with respect to the common main tool body  12  and removing the cup mating hook  40  from the recess or aperture  45  within the main tool body  12 . At this point, the blade carrier assembly  14  can be safely detached from the common main tool body  12  and discarded by grasping the blade carrier cup portion  18  and removing it from the common main tool body  12 .  
         [0032]     A new blade carrier assembly  14 ,  15  can then be attached to the common main tool body  12  by the user grasping the blade carrier cup portion  18  and placing the blade carrier cup hook  40  into the main tool body recess or aperture  45  within the common main tool body  12 . The front portion of the blade carrier cup portion  18  can then be brought into engagement with the main tool body  12  until the resilient latch elements  38  engage with the latch apertures or detents  36  formed on the carrier cup  18 . As discussed above, when the trigger  24  is depressed, the resiliently biased rotary drive element  26  will rotate until the spring biased drive pin  30  snaps or clicks into engagement with the moveable blade drive slot  34  of the blade assembly  16 .  
         [0033]     Referring to  FIGS. 6 and 7 , another embodiment of a resiliently biased rotary drive element is shown. The resiliently biased rotary drive element can include a spur gear  72  that can be driven by a drive motor assembly by way of a drive gear  90 . The spur gear  72  can be arranged to support an eccentrically located and resiliently biased drive pin  74 . The drive pin  74  can be resiliently biased in a direction away from the spur gear  72  and can be pushed in a direction towards and into the spur gear  72  against the resilient force. Thus, the resiliently biased rotary drive element includes a rotatable spur gear  72  and a resiliently biased drive pin  74  supported thereon.  
         [0034]     Referring to  FIG. 7 , details of the resiliently biased rotary drive element are shown. To more clearly show the structural details, the drive pin  74  is shown removed from a countersunk or stepped aperture formed in the spur gear  72 , along with a disassembled C-clip  78  and spring  76 . The drive pin  74  can include a shaft portion  75  and an enlarged head portion. In an operative position, the shaft portion  75  of the drive pin  74  can be arranged to extend in a throughhole  82  that passes through the spur gear  72 . An enlarged, coaxially arranged borehole  84  formed in the spur gear  72  can accommodate the enlarged head portion of the drive pin  74 .  
         [0035]     The drive pin  74  can be resiliently biased by way of a spring  76 . One end of the spring  76  can engage a flat surface formed at the intersection between the throughhole  82  and the enlarged aperture borehole  84 , and the other end of the spring  76  can engage a backside of the head portion of the drive pin  74 . The spring  76  can be arranged about the shaft portion  75  and is operable to bias the drive pin  74  such that the enlarged head portion is forced beyond a surface of the spur gear  72 .  
         [0036]     To secure the drive pin  74  within the aperture of the spur gear  72 , a drive pin securing mechanism  78 , such as a C-clip, can be used to engage an end of the shaft portion  75  of the drive pin  74 . The C-clip  78  can clamp onto the drive pin  74  at the back side of the spur gear  72 . For example, the C-clamp  78  can clamp into a groove  80  formed on the end of the drive pin  74 . The securing mechanism  78  operates to prevent the spring  76  from forcing the drive pin  76  out of the aperture formed in the spur gear  72 .  
         [0037]     Referring to  FIG. 7 , an exemplary gear train arrangement for transferring power from the motor (not shown) to the spur gear  72  is shown. The gear train arrangement can include a motor-driven input drive gear  86 , a lower gear  88 , and an upper gear  90  coaxially arranged with the lower gear  88  and in driving engagement with the spur gear  72 . According to various embodiments, other gear train arrangements could also be employed to drive the spur gear  72 .  
         [0038]     The attachment of an interchangeable blade carrier assembly  14  to the main body portion including the resiliently biased rotary drive element of  FIGS. 6 and 7  will now be described. As shown in  FIG. 6 , the resiliently biased drive pin  74  will be forced into the spur gear  72  if the drive pin  74  is misaligned with the drive pin slot  34  of the moveable blade  32 . In such a misaligned position, when the motor is energized, the spur gear  72 , and in turn, the drive pin  74  are rotated until the resiliently biased drive pin  74  snaps or clicks into the drive pin slot  34  of moveable blade  32 . Once engaged in the drive pin slot  34 , the drive pin  74  can continue to be rotated by the motor thereby reciprocating moveable blade  32  and providing a cutting action against stationary blade  33 . Thus, there is no need for the user to make any initial alignment of the drive pin  74  with the drive pin slot  34 .  
         [0039]     The present invention provides the user with a hassle-free working assembly or blade assembly attachment mechanism and process which provides automatic engagement between the motor and drive pin to the working assembly or blade assembly. Further, the partial housing or casing around the blade assembly enables the user to attach and remove the interchangeable blades without the concern of touching the working members or blades. Still further, the quick release and latch mechanisms enable the user to quickly and easily disengage the working assemblies through the use of the release buttons or mechanism which are located separate from the working assemblies providing a safe release mechanism enabling the user to release and remove the working assemblies without the need to contact the working members or blades.  
         [0040]     Those skilled in the art can appreciate from the foregoing description that the present teachings can be implemented in a variety of forms. Therefore, while these teachings have been described in connection with particular embodiments and examples thereof, the true scope of the present teachings should not be so limited. Various changes and modifications may be made without departing from the scope of the teachings herein.