Patent Publication Number: US-2010126023-A1

Title: Combination String Trimmer and Blower Tool

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/696,738, filed Jul. 6, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to hand-held lawn and garden tools and more specifically to a combination hand held string trimmer/blower device for use in cutting vegetation and clearing sidewalks, driveways, and the like free from debris. 
     2. Description of Related Art 
     It is known in the art to provide a string trimmer with one or more cutting strings or cutting blades to be used to cut vegetation such as grass and the like. It is also known in the art to use a separate blower device to clear debris from sidewalks, driveways, and the like. There have been several attempts to combine a string trimmer with a blower by attaching a separate blower impeller to the string trimmer. 
     Typically, in order to attach the impeller, the operator would have to remove a fastening device, and then remove the string trimmer head before attaching the blower impeller. This is a very tedious and time-consuming manner in which to convert a string trimmer to a blower. In addition, due to the configuration of the blower attachment, it is likely that the blower attachment will only fit on a limited number of line trimmers. 
     The present invention provides methods and apparatuses for a new and improved combination blower/string trimmer device, which is simple in design, effective in use, and overcomes the aforementioned disadvantages. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is directed to a portable multi-purpose tool. The power tool is powered by an attached power source for use as an air blower capable of delivering a high-velocity stream of air when the multi-purpose tool is in a blower mode of operation and as a rotating string trimmer capable of trimming vegetation when the multi-purpose tool is in a trimmer mode of operation. The multi-purpose tool includes a shaft boom and a drive shaft operatively connected to the power source and configured to be rotated by the power source. The multi-purpose tool also includes an impeller operatively connected to the drive shaft so as to be rotatable by the power source and a trimmer head positioned below the impeller, the trimmer head operatively connected to the drive shaft so as to be selectively rotatable by the power source. The multi-purpose tool also includes a blower housing at a distal end of the shaft boom, the blower housing defining an enclosed chamber and has a plurality of vents leading to the chamber and a blower nozzle for directing air from the chamber, wherein the impeller is rotatably mounted within the chamber, and the housing defines an air pathway between the vents and the impeller. The blower housing is mounted such that the housing is movable between a first and a second position relative the distal end of the shaft boom such that when the multi-purpose tool is in the blower mode of operation, the housing is in the first position and the pathway is open so that air flows through the vents and to the impeller, and when the multi-purpose tool is in the trimmer mode of operation, the housing is in the second position and the pathway is substantially blocked by an air blocking mechanism so that air is substantially prevented from flowing between the vents and the impeller. The multi-purpose tool also includes an actuator that moves the housing between the first position and the second position relative to the distal end of the shaft boom. 
     Another aspect of the invention is directed to portable multi-purpose tool powered by an attached power source for use as an air blower capable of delivering a high-velocity stream of air when the multi-purpose tool is in a blower mode of operation and as a rotating string trimmer capable of trimming vegetation when in a trimmer mode of operation. The multi-purpose tool includes a tubular shaft boom and an internal drive shaft operatively connected to the power source and configured to be rotated by the power source. The multi-purpose tool also includes an impeller operatively connected to the internal drive shaft so as to be rotatable within the chamber and a trimmer head positioned below the impeller, the trimmer head operatively connected to the internal drive shaft so as to be selectively rotatable by the power source. The multi-purpose tool also includes a blower housing at a distal end of the shaft boom having an enclosed chamber, a plurality of vents leading to the chamber, and a blower nozzle for directing air from the chamber, wherein the impeller is rotatably mounted in the chamber such that the housing defines an air pathway between the vents and the impeller, wherein the blower housing is mounted such that the housing is movable between a first and a second position relative the distal end of the shaft boom. The multi-purpose tool has an actuator that moves the housing relative the distal end of the shaft boom between a first position for the blower mode of operation and a second position for the trimmer mode of operation. The multi-purpose tool also has a clutching mechanism configured to selectively clutch the trimmer head when in the trimmer mode of operation and declutch the trimmer head when in the blower mode of operation. The clutching mechanism includes a centrifugal clutch affixed to the internal drive shaft and a clutch drum affixed to the trimmer head, wherein the clutch drum is movable with the blower housing between first and second positions such that the centrifugal clutch nests within and engages the clutch drum when the housing is positioned in the trimmer mode of operation and the centrifugal clutch is positioned outside the clutch drum when the housing is positioned in the blower mode of operation so that the centrifugal clutch does not engage the clutch drum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of the upper side of a trimmer/blower tool; 
         FIG. 2  is a side perspective view of the trimmer/blower tool of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the trimmer/blower tool of  FIG. 1  with portions of the housing removed for clarity; 
         FIG. 4  is an exploded perspective view of the housing illustrating the chamber formed therein; 
         FIG. 5  is a side view showing the trimmer/blower tool in the trimmer mode; 
         FIG. 6  is a side view showing the trimmer/blower tool in the blower mode; 
         FIG. 7  is an exploded perspective view of a second embodiment of the trimmer/blower tool; and 
         FIG. 8  is an exploded perspective view of a third embodiment of the trimmer/blower tool. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the views of the drawings. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description. 
     Referring now to the drawings,  FIGS. 1 and 2  show a portable, hand-held multi-purpose power tool  10  according to one embodiment of the invention that functions as both a string trimmer and an air blower. The power tool  10  is provided with an elongated protective tubular shaft boom  12  with a power source (not shown) positioned at one end of the shaft boom  12  and at least one handle (not shown) for manipulation of the tool  10 . The power source of the tool  10  can be either a gasoline engine or an electric motor, both of which are well known in the art and need not be discussed in further detail. According to the invention, the tool  10  has a blower/trimmer assembly  16  connected to a working end of the shaft boom  12  that is driven by the power source. The blower/trimmer assembly  16  permits the tool  10  to be used either as a hand-held blower capable of delivering a high-velocity stream of air from a blower housing or volute  18  useful for blowing debris off walkways and the like, or as a rotatable string trimmer useful for trimming and cutting vegetation. Desirably, the operator of the tool  10  can quickly and easily manipulate the blower/trimmer assembly  16  to select the desired mode of operation without the need of extra tools or without having to add or remove additional components. 
     Turning now to  FIGS. 3 and 4 , the blower housing  18  (only part of which is illustrated in  FIG. 3  for clarity) contains a rotatable impeller  20  configured to impart energy to the high-velocity stream of air while in the blower mode of operation. Below the housing  18 , the blower/trimmer assembly  16  also has a rotatable string trimmer head  22  used for cutting vegetation. The protective tubular shaft boom  12  houses a rotatable flexible drive shaft (not shown) that extends throughout the shaft boom  12  and operatively connects the power source to an internal drive shaft  26  located within the housing  18 . Flexible drive shafts in and of themselves are known in the art and need not be described in detail. However, means for connecting the flexible drive shaft to selectively engage the impeller  20  and/or the trimmer head  22  so as to provide both blowing and cutting capabilities from the same tool  10  will be described below. The internal drive shaft  26  operatively connects the power source to the impeller  20  and to the string trimmer head  22  to provide the necessary rotating motion as will be set forth more fully below. 
     As best seen in  FIG. 4 , the blower housing  18  forms an enclosed chamber  30  in which the impeller  20  is located. The chamber  30  leads to an outlet nozzle  32  for directing the high velocity stream of air created by the impeller  20 . The outlet nozzle  32  comprises an air outlet for directing air pressurized in the chamber  30  out of the blower housing  18  and is generally tangentially aligned with the outer periphery of impeller  20 . In one embodiment, the nozzle  32  is generally cone shaped and can be threaded onto the blower housing  18  or attached with fasteners to form the air outlet. In operation, air is drawn into the chamber  30  by the impeller  20  and expelled at a relatively higher velocity through the nozzle  32 . The housing  18  has a shroud portion  34  that contains a plurality of vents or windows  35  therein. The vents  35  are designed to permit air to enter the enclosed chamber  30  and reach the impeller  20  when in the blower mode of operation. By an enclosed chamber  30  it is meant that the chamber substantially surrounds the impeller  20  so that the impeller is able to pressurize the air drawn in through the vents  35  and expel the air out of the chamber through the nozzle  32 . 
     The blower housing  18  is desirably fabricated as a two-piece housing  18  formed with mating housing shells  36  and  38 . The blower housing  18  may be made from a suitable polypropylene, polyvinyl chloride (PVC) or other plastic material or the like and is desirably formed by plastic injection molding. Desirably, the blower housing  18  comprises right and left housing shells  36 ,  38  joined together at a flange connection  40  with screws, rivets or other suitable fasteners  42  (seen in  FIG. 7 ). Alternately, the blower housing  18  has a generally concave upper housing shell  36  (i.e., as shown in the embodiment depicted in  FIG. 8 ) and a generally concave lower housing shell  38 . Thus, it is to be understood that the invention is not limited to any particular shape or method of fabrication of the blower housing  18 . As such, the terms “right” and “left” and “upper” and “lower”, as used in describing the housing shells, and any other portion of the tool  10 , are used to aid in describing the housing shells and should not be interpreted as limiting. Other dome or dish geometric shapes for the housing shells can also be used without departing from the scope of the invention. 
     Bearings or bushings  44  permit rotation of the internal drive shaft  26  with respect to the blower housing  18 . The bearings  44  can be sleeve bearings or other conventional bearings chosen with sound engineering judgment. 
     The housing  18  further acts as a debris shield to protect the operator from flying vegetation clippings cut by the trimmer head  22  when the tool  10  is operating in the trimmer mode of operation. As best seen in  FIG. 1 , the debris shield desirably includes the blower housing  18  and an extension guard  49  that extends from the blower housing  18 . The extension guard  49  may be manufactured as a single integrated part of the housing  18  or the extension guard  49  may consist of one or more separate pieces attached to the housing  18 . In such case, the extension guard  49  can be attached to the blower housing  18  by any mechanical means necessary chosen with sound engineering judgment. Preferably, the extension guard  49  is positioned on the housing  18  on the side opposite blower nozzle  32 . 
     As best seen in  FIG. 4  and in the alternate embodiments depicted in  FIGS. 7 and 8 , a spiral partition  50  is formed within the blower housing  18 , so that when the housing shells  36  and  38  are joined, the spiral partition  50  forms the volute shaped chamber  30  having a center coaxial with the impeller  20  and a radius which varies circumferentially around the blower housing  18 . By volute shape, it is meant that the chamber  30  forms a curved funnel generally increasing in area to the air outlet nozzle  32 . In the embodiment illustrated in  FIG. 8 , the spiral partition  50  comprises a wall half formed in the lower shell  38  and half formed in the upper shell  36  so that when joined, the partition  50  extends between upper and lower portions of the housing  18 . However, it is to be understood that the spiral partition  50  may be formed by other means using sound engineering judgment. 
     The impeller  20  resides within the chamber  30  formed by the housing shells  36 ,  38 . The impeller  20  consists of a substantially circular shaped plate  54  mountable on the internal drive shaft  26  so as to be rotatable within the chamber  30 . In one embodiment, the impeller  20  desirably comprises a plurality of airfoils  58  that have an arc-like shape. In the illustrated embodiment, the impeller  20  consists of seven airfoils  58 . However, the impeller  20  may consist of any number of airfoils  58  chosen with sound engineering judgment. The airfoils  58  can be connected to the plate  54  by any mechanical means necessary chosen with sound engineering judgment. When rotated in the blower mode of operation, the impeller  20  is capable of delivering a high-velocity stream of air out of the nozzle  32 . In one embodiment, the tubular shaft boom  12  of the multi-purpose power tool  10  has a bend  64  near its distal end  65  so that a central axis thereof extends generally coaxially through the blower housing  18  and is preferably aligned with the axis of rotation of the impeller  20 . 
     The internal drive shaft  26  engages the impeller  20  and the string trimmer head  22  by any mechanical means chosen with sound engineering judgment. In the illustrated embodiment, the internal drive shaft  26  has an engaging shape and is received within a receiving aperture in the impeller  20  having a corresponding female shape to enable the torque of the internal drive shaft  26  to be passed on to the impeller  20 . The shape of the internal drive shaft  26  may be any shape suitable such as square, star, triangular, octagonal and the like. 
     In one embodiment, a support collar  80  is positioned within the housing  18  above the impeller  20 . The support collar  80  includes a lower restrictor plate  82  and an upper hollow tube section  84  with a ring clamp  86  that affixes the support collar  80  to the distal end  65  of the shaft boom  12 . A handle assembly  88 , broadly an actuator, attaches to the support collar  80 . The handle assembly  88  is used to selectively adjust the position of the housing  18  between a first and a second position relative the boom  12  and support collar  80  as indicated by the arrow A in  FIG. 2  in order to shift the tool  10  between a blower mode of operation and a trimmer mode of operation. As best seen in  FIG. 3 , the handle assembly  88  desirably has a catch  90  that must be pulled back before the handle assembly  88  can be repositioned. The catch  90  discourages inadvertent movement of the handle assembly  88  which could cause undesired engagement of the trimmer head  22  or air discharge from the blower nozzle  32 . The catch  90  locks into a groove (not shown) on the support collar  80 . The handle assembly  88  is pivotably attached to the support collar  80  with a pair of inwardly facing bosses  92  on arms  94  of the handle assembly  88 . The handle assembly  88  is further attached to the housing  18  with guides  93  that move the housing  18  up or down when the handle assembly  88  is pivoted about the bosses  92 . In one embodiment, a biasing spring  95  biases the housing  18  into the trimmer mode position. However, one will understand that the spring  95  may bias the housing  18  into the blower mode position without departing from the scope of the invention. 
     With reference now to  FIGS. 5 and 6 , the restrictor plate  82  fits within the shroud portion  34  of the housing  18  and has an outside diameter that is generally the same as the interior diameter of the shroud portion  34 . When the housing  18  is selectively positioned into the trimmer position as illustrated in  FIG. 5  by positioning the handle assembly  88 , the housing  18  is moved upward relative to the restrictor plate  82  such that the vents  35  become positioned above the restrictor plate  82 . In this orientation, the restrictor plate  82  forms an air blocking mechanism that blocks a substantial amount of the airflow between the vents  35  and the volute chamber  30 . Although the impeller  20  continues to rotate within the volute chamber  30 , the blower function of the tool  10  is essentially disabled as only a limited amount of air, if any, exits the blower nozzle  32 . Alternately, when the handle assembly  88  is selectively positioned into the blower mode position as shown in the embodiment depicted in  FIG. 6  by positioning the handle assembly  88 , the housing  18  moves downward relative the shaft boom  12  and support collar  80  such that the vents  35  are positioned below the restrictor plate  82 . In this orientation, air is free to enter the vents  35  and pass into the air inlet of the volute chamber  30 . Thus, movement of the handle assembly  88  into the blower mode position opens an air path between the air vents  35  and the impeller  20  to pull air into the housing  18  for operation of the tool  10  as an air blower. Conversely, movement of the handle assembly  88  into the trimmer mode position restricts the air path between the air vents  35  and the impeller  20  so that air cannot be pulled into the housing  18 . 
     The string trimmer head  22  is positioned below the blower housing  18 , and as is known in the art, comprises a spool (not shown) of cutting line  96  used to cut vegetation. The cutting line  96  extends from a plurality of apertures  98  located around the circumference of the string trimmer head  22 . The connection of the cutting line  96  within the string trimmer head  22  is commonly known in the art and will not be described herein. In the illustrated embodiment there are two apertures  98  on the string trimmer head  22  to allow the use of two cutting lines  96  to cut the vegetation. However, it should be noted that the trimmer head  22  could operate with one or more cutting lines  96 . Alternately, the trimmer head  22  can receive one or more fixed length cutting lines  96  using means well understood in the art. 
     In one embodiment, the trimmer head  22  is operatively connected to the internal drive shaft  26  through a clutching mechanism  99  configured to selectively clutch the trimmer head  22  when the tool  10  is in the trimmer mode of operation and declutch the trimmer head  22  when in the blower mode of operation. The clutching mechanism  99  contains a clutch drum  100  affixed to an upper portion of the trimmer head  22 . Desirably, the clutch drum  100  and trimmer head  22  are rotatably affixed to the housing  18 , so that the clutch drum  100  is raised and lowered through movement of the housing  18  by selective movement of the handle assembly  88  as described above. A centrifugal clutch  102  adapted to interact with the clutch drum  100  is affixed to the distal end of the internal drive shaft  26  and selectively engages or disengages the trimmer head  22  from the internal drive shaft  26 . In the illustrated embodiment, the centrifugal clutch  102  includes a pair of clutch shoes  103  that expand outward when the internal drive shaft  26  is rotated to engage the clutch drum  100  to thereby transmit rotation of the internal drive shaft  26  to the cutting head  22 . 
     Because the clutch drum  100  is affixed to the housing  18 , the clutch drum  100  moves up and down relative to the internal drive shaft  26  and the centrifugal clutch  102  when the handle assembly  88  is operated to select the desired mode of operation as discussed above. When the tool  10  is operating in the blower mode of operation, the clutch drum  100  is located in a lowered position relative to the centrifugal clutch  102  such that the centrifugal clutch  102  resides above a circumferential wall  105  of the clutch drum  100 . Thus, the centrifugal clutch  102  does not engage the clutch drum  100  in the blower mode and the trimmer head  22  is not rotated by the internal drive shaft  26 . When the handle assembly  88  is repositioned to the trimmer mode position, the housing  18 , and thus the clutch drum  100 , moves upward relative the internal drive shaft  26  and the centrifugal clutch  102 . In this orientation, the clutch drum  100  is raised so that the centrifugal clutch  102  nests within the clutch drum  100 , and when the internal drive shaft  26  is rotated, the clutch shoes  103  expand outward and engage the clutch drum  100 . Thus, the centrifugal clutch  102  only engages the clutch drum  100  in the trimmer mode of operation and the trimmer head  22  is only rotated by the internal drive shaft  26  in the trimmer mode. 
     A clutch retainer  106  positioned adjacent the centrifugal clutch  102  limits the movement of the clutch shoes  103  away from the central axis when the centrifugal clutch  102  is not nested within the clutch drum  100 . The clutch retainer  106  prevents the clutch shoes  103  from continuing to expand outward when the clutch drum  100  is in the lowered position and is thus not in position to check such expansion. The clutch retainer  106  may be a plate that limits the travel of the clutch shoes  103 , or may be a molded feature in the underside of the impeller  20 , or other device chosen using sound engineering judgment. 
     With the components of one embodiment described above, the operation of the combination blower/trimmer assembly  16  will now be explained. As previously mentioned, the handle assembly  88  is used to position the housing  18  between a first and second positions relative the shaft boom  12  and support collar  80 . When the housing  18  is positioned in the first position as illustrated in  FIG. 6  the blower function is operable because air is free to enter the vents  35  and flow to the impeller  20 . In the illustrated embodiment, when the housing  18  is in the first position, the restrictor plate  82  is positioned so that it does not obstruct the flow of air from the vents  35  to the impeller  20 , thereby allowing air to flow into and through the chamber  30  and out the blower nozzle  32 . Additionally, when the housing is in the first position, the trimmer head  22  is inoperable because the clutch mechanism  99  does not transmit rotation of the drive shaft  26  to the trimming head  22 . Conversely, when the operator wishes to use the tool  10  in the string trimmer mode, the operator moves the handle assembly  88  to position the housing  18  into the second position. When the housing  18  is positioned in the second position as illustrated in  FIG. 5 , the blower function is inoperable because the flow path for the air to the impeller  20  is substantially blocked. Specifically, in this position the restrictor plate  82  blocks the flow of air between the vents  35  and the impeller  20 . The trimmer head  22  is operable in the second position because the clutching mechanism  99  engages the trimmer head  22  with the drive shaft  26 . In the illustrated embodiment, the clutch drum  100  is moved up so that the centrifugal clutch  102  engages the clutch chum  100  to enable powered rotation of the trimmer head  22 . 
       FIG. 7  illustrates another embodiment of the tool  10  in which the shaft boom  12  has an extension mechanism comprising an adjustable mount attaching the blower/trimmer assembly  16  to the distal end of the shaft boom  12 . In this embodiment, the blower housing  18  contains a hub  120  that secures the blower/trimmer assembly  16  to the shaft boom  12  in one of two selectable positions. The drive shaft and thus the internal engagement shaft  124  is in a fixed position relative the shaft boom  12 . In a trimmer disengaged position, the hub  120  mounts the blower housing  18  on the distal end of the shaft boom  12  in a first position. In this position, the internal engagement shaft  124  engages the impeller  20  but does not engage the string trimmer head  22 . In a trimmer engaged position, the hub  120  mounts the blower housing  18  in a position such that a portion of the distal end of the shaft boom  12  is received within a pocket in the blower housing  18 . Moving the blower housing  18  from the trimmer disengaged position to the trimmer engaged position therefore causes the internal engagement shaft  124  to move relative to the blower/trimmer assembly  16  such that the internal engagement shaft  124  engages the string trimmer head  22 . In one desired embodiment, the internal engagement shaft  124  only engages the impeller  20  in the trimmer disengaged position and only engages the string trimmer head  22  in the trimmer engaged position. However, the internal engagement shaft  124  can engage both the impeller  20  and the string trimmer head  22  in the trimmer engaged position without departing from the scope on the invention. In this later configuration, similar to the embodiment explained above, an air inlet cover  126  forms an air blocking mechanism. The inlet cover  126  is positioned to cover the vents  35  to block air from entering the chamber  30 , thereby preventing air from moved through the blower housing  18  so that high pressure air does not leave the nozzle  32  of the housing  18 . In one desirable configuration, the act of moving the hub  120  from the disengaged position to the trimmer engaged position simultaneously positions the air inlet cover  126  to block the vents  35 . 
     With the components of this embodiment herein described, the operation of the combination blower/trimmer assembly  16  will now be described. As previously mentioned the hub  120  is rotatable between a first and a second position. When the hub  120  is rotated to the first position, the blower function is operable and the trimmer head  22  is inoperable. Conversely, when the hub  120  is in the second position the blower function is inoperable and tie trimmer head  22  is operable. Furthermore, when the air inlet cover  126  is in the first position the vents  35  are aligned with the air inlet cover  126  such that air is permitted to flow into and through the housing  18  and out the blower outlet  32 . Therefore, in order to use the blower function, the operator, prior to starting the power source (not shown), rotates the hub  120  to the first position. The operator then starts the power source and uses a typical control device (not shown) on the shaft boom  12  to operate the blower  10 . The operation of the power source and control device is commonly known in the art and will not be described herein. When the operator wishes to use the trimmer head  22 , the operator turns off the power source and rotates the hub  120  to the second position so that the drive shaft  124  engages the trimmer head  22 . 
     In an alternate embodiment, as illustrated in  FIG. 8 , the power tool  10  has a boom extension mechanism, indicated generally at  130 , configured to move the internal engagement shaft  124  relative to the string trimmer head  22  and the impeller  20  to selectively operate the desired function of the tool  10 . In one embodiment the boom extension mechanism  130  comprises a boom extender  136  in the tubular shaft boom  12  located between the power source and the blower/trimmer assembly  16 . As the drive shaft located within the shaft boom  12  has a fixed length, changing the length of the shaft boom  12  with the boom extension mechanism  130  has the effect of changing how far the drive shaft  138  extends past the distal end  65  of the shaft boom  12 . 
     When the length of the shaft boom  12  is selected to the longer length, the internal engagement shaft  124  at the end of the drive shaft  138  engages the impeller  20 , but is not long enough to reach the string trimmer head  22 . Thus, in this configuration, the power source causes the impeller  20  to rotate allowing the blower to operate, but the string trimmer head  22  does not rotate. When the length of the shaft boom  12  is selected to the shorter length, the internal engagement shaft  124  extends further past the distal end  65  of the shaft boom  12 . In this configuration, the internal engagement shaft  124  engages the string trimmer head  22  so that operation of the power source causes the string trimmer head  22  to rotate. In one embodiment, the internal engagement shaft  124  is configured to engage either the impeller  20  or the string trimmer head  22 , but not both. Thus, in the second configuration, when the internal engagement shaft  124  engages the string trimmer head  22 , the impeller  20  is not engaged by the internal engagement shaft  124  and does not rotate during trimmer operations. In another embodiment, the internal engagement shaft  124  is configured to engage both the string trimmer head  22  and the impeller  20  in the second configuration. However, in this embodiment, the air inlet cover  126  is positioned to cover the vents  35  to block air from entering the air inlet, thereby preventing air from moved through the blower housing  18  so that high pressure air does not leave the nozzle  32  of the blower. 
     The boom extender  136  is used to selectively lengthen or shorten the length of the tubular shaft boom  12 . As illustrated, the tubular shaft boom  12  comprises a lower shaft boom member  12   a  and an upper shaft boom member  12   b  telescopingly received into the lower shaft boom member  12   a . The lower shaft boom member  12   a  has a pair of holes (not shown) and the upper shaft boom member  12   b  has a spring biased push button  140  configured to be received by one of the holes to lock the upper shaft boom member  12   b  within the lower shaft boom member  12   a  at one of two selectable lengths. However, other adjustment/locking means to selectively adjust the length of the shaft boom  12  are also envisioned. For example, a threaded member may be used to adjust the length of the shaft boom  12  as illustrated in  FIG. 8 . Alternately, a thumb screw (not shown) can be inserted through one of the holes and a cooperating hole (not shown) in the upper shaft boom member  12   b  to adjust the length of the shaft boom  12 . Yet other means for adjusting the length of the shaft boom  12  can be used using sound engineering judgment without departing from the scope of the invention. 
     While this invention has been described in conjunction with the specific embodiments described above, it is evident that many alternatives, combinations, modifications and variations are apparent to those skilled in the art. Accordingly, the preferred embodiments of this invention, as set forth above are intended to be illustrative only, and not in a limiting sense. Various changes can be made without departing from the spirit and scope of this invention.