Abstract:
Some embodiments of the invention provide a multipurpose gardening tool having an attachable circular carriage for converting an edge trimmer to a lawnmower for cutting and trimming grass and bushes. The circular carriage has an opening configured for receiving the edge trimmer. The multipurpose gardening tool also includes a coupler. The coupler allows a user to fixedly couple the edge trimmer to the carriage housing without use of any tools. 
     The multipurpose gardening tool further includes wheels for maneuvering the lawnmower. A height adjuster couples these wheels to the carriage. The coupling allows the wheels to be manually and independently controlled for lifting the carriage off the surface of the ground and adjusting the height of the carriage.

Description:
CLAIM OF BENEFIT TO PRIOR APPLICATION 
   This patent application is a continuation-in-part patent application and claims benefit of U.S. patent application Ser. No. 10/211,722, filed on Aug. 2, 2002 now abandoned by the same inventor. 

   FIELD OF INVENTION 
   The invention relates to grass cutting and trimming. The invention also relates to an attachable carriage for converting an edge trimmer to a lawnmower. 
   BACKGROUND OF INVENTION 
   Healthy lawns depicting a well maintained appearance require proper care. This includes cutting the grass and trimming shrubs and weeds that grow on the lawns. These lawns may be categorized into two types; commercial and household lawns. Commercial lawns are very large in size and require heavy industrial lawn maintenance equipment. Household lawns are smaller than commercial lawns and are maintained by manually operated lawnmowers to cut grass and manually operated trimmers to trim shrubs, weeds, and edges. 
   Some manually operated lawnmowers allow a user to attach a trimmer to the lawnmower. This attachment requires use of tools and allows the user to use the lawnmower for cutting grass and detach the trimmer from the lawnmower to trim. Since these manually operated lawnmowers are heavy and consume a large amount of space this attachment poses maneuvering and storage obstacles for homeowners with limited space. In addition use of tools for attachment requires additional time, energy, and complexity. 
   One type of manually operated lawnmower uses a combination of a rectangular shaped carriage and a circular blade attached to the bottom of the rectangular shaped carriage. This combination leaves ample space between the round blade fitted inside the rectangular carriage and the edge of the carriage. Since most home lawns have several sharp corners and edges with limited room to maneuver, the rectangular shaped body of the carriage comes in contact with the corner first and prevents the circular blade inside the rectangular carriage from coming in close proximity to the edges and corners making it impossible to cut the grass in these places. 
   Some existing lawnmowers have sets of front and back wheels that are attached to the carriage at an equidistant height level from ground. Since some lawns exist on angular, non-flat, and uneven terrains, the equidistant height of the wheels prevents the blade from coming in contact with the grass. For example, at the junction of a terrain that has a flat surface joined to a 45-degree incline surface, if front set of wheels are placed on the 45-degree incline surface and the back set of wheels are placed on the flat surface, then the sets of equidistant wheels lift the carriage such that the blade is high enough from the grass preventing it from either touching the grass altogether or touching the grass at the same level that the blade would have touched the grass if the carriage had been completely on the flat surface or the 45-degree inclined surface. This results in the lawn having portions of uncut or uneven grass as the user maneuvers the lawnmower over the uneven terrain. In some instances, some lawnmowers allow wheel height adjustment to raise or lower the lawnmower. However, this type of wheel height adjustment only allows all the wheels to be simultaneously raised thereby raising the lawnmower uniformly. This type of height adjustment does not solve the uneven terrain problem and prevents the lawnmower blade from touching the grass to obtain a uniformly cut lawn. 
   Therefore, there is a need for a carriage that allows easy attachment of a trimmer to trim and cut grass uniformly on all terrains and consume a small amount of storage space. 
   SUMMARY OF THE INVENTION 
   Some embodiments of the invention provide a multipurpose gardening tool having an attachable circular carriage for converting an edge trimmer to a lawnmower for cutting and trimming grass and bushes. The circular carriage has an opening configured for receiving the edge trimmer. The multipurpose gardening tool also includes a coupler. The coupler allows a user to fixedly couple the edge trimmer to the carriage housing without use of any tools. 
   The multipurpose gardening tool further includes wheels for maneuvering the lawnmower. 
   A height adjuster couples these wheels to the carriage. The coupling allows the wheels to be manually and independently controlled for lifting the carriage off the surface of the ground and adjusting the height of the carriage. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of the invention are set forth in the appended claims. However, for purpose of explanation, several embodiments of the invention are set forth in the following figures. 
       FIG. 1  illustrates a one embodiment of a carriage assembly coupled to a trimmer. 
       FIG. 2  illustrates one embodiment of a carriage housing used by the invention. 
       FIG. 3  illustrates an exploded view of the carriage assembly and edge trimmer used by the invention. 
       FIG. 4  illustrates one embodiment of a coupling that uses a snap to couple the trimmer to the carriage. 
       FIG. 5  illustrates one embodiment of a coupling that uses a screw-fastener assembly to couple the trimmer to the carriage. 
       FIG. 6  illustrates one embodiment of a coupling that uses a standoff to couple the trimmer to the carriage. 
       FIG. 7A  illustrates an exploded view of a carriage assembly and a trimmer having a guard according to one embodiment. 
       FIG. 7B  illustrates a one embodiment of a detailed cross section of the trimmer fully inserted and coupled to the carriage housing. 
       FIG. 7C  illustrates rotation of the trimmer&#39;s guard for clearing a path for trimmer insertion into an opening in the carriage according to one embodiment. 
       FIG. 7D  illustrates insertion of the trimmer into the opening in the carriage after the trimmer guard has been fully moved out of the insertion path according to one embodiment. 
       FIG. 7E  illustrates insertion of the trimmer housing snaps and guard snaps into the holes of the carriage assembly for coupling the trimmer and guard to the carriage assembly according to one embodiment. 
       FIG. 7F  illustrate one embodiment of a trimmer and guard coupled to the carriage assembly. 
       FIG. 8  illustrate a carriage having protruding rectangles with each rectangle having a grooved path to guide a wheel for height adjustment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following description, numerous details are set forth for purpose of explanation. However, one of ordinary skill in the art will realize that the invention may be practiced without the use of these specific details. In other instances, well-known structures and devices are shown in a simple diagram form in order not to obscure the description of the invention with unnecessary detail. 
     FIG. 1  illustrates one embodiment of the invention. This figure presents a trimmer  100  coupled to a carriage assembly  105 . The trimmer  100  may be an off the shelf conventional trimmer that includes a handle  110  coupled to a trimmer head assembly  115 . The trimmer head assembly  115  includes a motor placed inside a trimmer housing  120 , a flange formed on the lower portion of the trimmer housing  120 , and a trimmer rotary head located outside the trimmer housing  120  and coupled to the motor inside the trimmer housing  120 . The rotary head includes features for coupling a wire or a blade. The motor spins the trimmer rotary head and thereby the wire or blade that is coupled to the motor and rotated at a speed selected by the user for trimming. Alternatively, other types of trimmers that use electric or gas motor are also contemplated. 
   The carriage assembly  105  includes a carriage housing, several wheels  125  coupled to the carriage housing, and a coupler. The carriage housing  200  as shown in  FIG. 2  is a rigid shell made from a thin plastic or metal. The carriage housing  200  is circular in shape and includes several protruding shapes such as rectangles  210 . Each protrusion  210  blends with the circular carriage  200  and is located on the outer portion of the shell. The protrusion includes features for coupling a wheel as will be described later in more detail. 
   The coupler forms the coupling between the trimmer and the carriage assembly. Once coupled, the carriage assembly and the trimmer form a lawnmower. The lawnmower can be maneuvered by a user pushing the trimmer handle and allowing the wheels of the carriage assembly to roll across a lawn. 
     FIG. 3  shows one embodiment of the carriage assembly and the trimmer. This figure presents an exploded view of a carriage  300 , several wheels  310 , and a trimmer  320 . In this embodiment, the rigid shell of the carriage housing  300  includes a small opening  330  on one side and a large opening on the opposite side. The smaller opening  330  allows the trimmer rotary head  340  to pass therethrough and be exposed from larger opening on the opposite side. This allows the wire or blade coupled to the trimmer rotary head  340  direct access to the grass through the larger opening in the carriage housing  310 . 
   Various types of couplers can be used for coupling the trimmer to the carriage assembly. These couplers allow easy coupling without a need for any tools. This type of coupling prevents the user from spending any extra time, cost, effort or energy that is typically involved with tool usage. These couplers also allow a user to easily detach the trimmer from the carriage without using any tools. Thus a user desiring to trim edges, weeds, shrubs can simply detach the trimmer from the carriage housing by a simple detach operation using the coupler and use the trimmer for trimming. Similarly, the trimmer can be attached to the carriage assembly for mowing the lawn by a simple operational step performed by the user on the coupler. 
     FIGS. 4–6  show these coupling embodiments.  FIG. 4  depicts a coupler that uses a snap feature  400  to couple the trimmer  410  to the carriage  420 . This method of coupling requires a user to align the trimmer rotary head  430  with the small opening in the carriage  420 . Once aligned, the trimmer rotary head  430  is inserted through the small opening allowing a portion of the trimmer flange  440  to push the snap feature aside to clear its way for a complete insertion of the rotary head  430 . 
   As mentioned earlier, the flange  440  is formed within the trimmer&#39;s housing. The flange includes a lower rim  450  and an upper rim  460  and may be one of two types. The first type includes a lower rim  450  that is wider in diameter than the upper rim  460 . In this case, after inserting the rotary head  430  through the small opening, the user aligns the wider lower rim  450  toggling the trimmer back and forth until the wider upper rim  460  is captured by the snap feature  400  in the carriage housing. 
   The second type of flange  440  includes a lower rim that is narrower in diameter than the upper rim. In this case, once the user aligns and inserts the rotary head  430  into the small opening, the lower rims that is wider in diameter than the rotary head  430  pushes the snap feature  400  aside. Once the lower rim of the flange  440  clears the snap feature  400 , the snap  400  retracts to its original position and captures the flange by landing in the area between the narrower lower rim and the wider upper rim thereby fastening the trimmer  410  to the carriage assembly  420 . Furthermore, the wider upper rim which has a surface area that is wider than the small opening comes in contact with the surface of the carriage housing and prevents the rotary head from further insertion into the small opening. 
     FIG. 5  depicts a coupling embodiment similar to a screw-faster assembly. In this embodiment, the carriage  500  and the trimmer  520  both include mating threads  530  and  540  for fastening the trimmer  520  to the carriage  500 . In practice, a user can simply align the trimmer rotary head  550  with the smaller opening in the carriage  500  and insert the trimmer rotary head  550  into the small opening by turning the trimmer  520  in a clockwise direction for fastening. To unfasten or detach the trimmer  520  from the carriage  500 , the trimmer  520  is rotated in an anti-clockwise direction. Alternatively, the mating may also be configured to rotate anti-clockwise for fastening and clockwise for unfastening. 
   The trimmer  520  maybe rotated along the threads  540  in the carriage  500  until the trimmer flange  560  comes to rest on the surface  570  of the carriage shell thereby fastening to the carriage. At this point, the trimmer  520  is coupled to the carriage assembly and a wire or blade  580  attached to the trimmer rotary head  550  is used for cutting the lawn. 
     FIG. 6  depicts an axle assembly used for coupling the trimmer to the carriage assembly. In this embodiment, the carriage assembly  600  includes a carriage  605 , several wheels  610  coupled to the carriage  605 , a sleeve  615 , a standoff  620 , and a standoff capturing snap  625 . The axle assembly  630  includes an axle  635 , a blade  640  coupled to one end of the axle  635 , and an axle head  645  coupled to the other end of the axle  635 . The axle  635  is snuggly fitted within the sleeve  615  of the carriage assembly  600  allowing vertical and rotational motion of the axle assembly  630 . 
   Standoffs  620  with various heights are used to provide a sitting platform for the trimmer  650 . Either a single standoff or multiple standoffs stacked one on top of each other can be used. Each standoff  620  includes a capturing feature  655  on one side and a groove  660  on the other side. A standoff snap capturing snap  625  located on the carriage captures the capturing feature  655  on the standoff to securely couple the standoff  620  to the carriage. The grooves  660  on the other side serve as a sitting platform for the trimmer housing thereby locking independent horizontal movement of the trimmer  650 . Once the trimmer  650  is locked, a horizontal force exerted by the user on the trimmer&#39;s handle moves trimmer and carriage assembly together as one unit in the direction of the force allowing the user to maneuver the lawnmower across the lawn for cutting grass. 
   The axle head  645  is coupled to the trimmer rotary head  657  and receives power through the motor coupled to the trimmer rotary head  657  for spinning. Once the trimmer motor is powered “ON”, the trimmer rotary head  657  coupled to the motor starts rotating. Since the axle head  645  is coupled to the rotary head  657 , rotation of the rotary head  657  also causes the entire axle assemble  660  to rotate. This rotation allows the rotating blade  640  at the end of the axle  635  to rotate and cut the grass as the entire carriage assembly is being maneuvered across a lawn. The embodiments of  FIGS. 5 and 6  also allow a user to adjust the distance between the blade and the grass. The blade is lowered to position A and made closer to the ground to allow for a deeper cut or raised a desired distance to position B from the ground allowing a surface cut. 
   In the embodiment of  FIG. 5 , as discussed earlier, the trimmer rotary head is coupled to the carriage assembly by mating the threads on the trimmer with threads on the carriage and rotating the trimmer in a clockwise direction for fixating it to the carriage assembly. In this embodiment, the trimmer the flange acts as a stop feature preventing the trimmer from being inserted further into the carriage opening. A 100% rotation of the trimmer allows the flange to come in contact with the surface of the carriage shell. Since a blade may be coupled to the trimmer rotary head, with each rotation in the direction of fastening the trimmer to the carriage assembly, the trimmer rotary head and the blade coupled to the trimmer rotary head is also lowered thus allowing for a deeper cut. If the user desires to perform a surface cut or a cut of a determinant height then a standoff with a desired height may be placed between the flange and the surface of the carriage shell. The standoff allows the flange to come to a stop before touching the surface of the carriage shell and raises the height of the blade coupled to the trimmer rotary head for regulating the height of the cut grass. Although the user may determine the height of the standoff, at least a 30% rotational engagement between the trimmer threads and the carriage threads is preferred for locking the trimmer to the carriage. 
   In the embodiment of  FIG. 6 , as discussed earlier, the trimmer rotary head sits on the grooves of the standoff and is coupled to the axle head of the axle assembly. In this embodiment, the height of the standoff can be varied to lower or raise the blade height from the grass. For example, a standoff that has a smaller height provides a sitting platform for the trimmer that is closer to the carriage and lowers the blade closer to the ground to allow for a deeper grass cut. Alternatively, a taller standoff raises the sitting table for the trimmer thereby raising the axle assembly and the blade coupled to the trimmer to allow for a surface cut. 
     FIGS. 7A–7F  illustrate one embodiment of the invention. In progression, these figures present the coupling of a trimmer to a carriage assembly to form a lawnmower.  FIG. 7A  depicts an exploded view  700  of this lawnmower. The carriage assembly  703  includes a carriage  706  and several wheels  709 . The carriage  706  is a rigid shell that is circular in shape and includes several protruding shapes such as rectangles. Each protrusion blends with the circular carriage and includes features for coupling a wheel  709 . The carriage  706  also includes a cut out  711  for receiving the trimmer  715  for coupling. 
   The trimmer  715  includes a housing  720  coupled to a handle  723 . The handle  723  provides a gripping area for a user for maneuvering the trimmer. A motor is housed inside the housing  720  and is coupled to a rotary head  725 . The motor may be battery or electrically powered. A power cord  727  coupled to the trimmer  715  carries power to the motor for its operation. Once powered, the motor rotates the rotary head  725  that is located outside the housing  720  at a user desired speed. The trimmer  715  also includes a flange  730  and a guard  733 . The guard  733  is detachably coupled to the housing  720  and provides a user safety against wire or blade contact while the trimmer is in operation. The guard  733  has features that allow it to be removed from the housing if desired by the user. 
   The flange is formed within the trimmer&#39;s housing and may be circular or of any other shape. As shown in  FIG. 7B , a flange  730  having a circular configuration includes a lower rim  735  that is narrower in diameter than the upper rim  737  of the flange. The area between the lower and upper rim provides a landing area. This landing area is used for coupling the trimmer to the carriage. The upper rim  737  has a surface area that is wider than the small opening comes in contact with the surface of the carriage housing  706  and prevents the rotary head  725  from further insertion into the small opening. 
   The coupling between the trimmer  715  and the carriage assembly  703  is further illustrated in  FIGS. 7C and 7D . The cut out portion  711  of the carriage  706  allows the insertion of the trimmer  715  and the trimmer guard  733  in a horizontal direction for coupling. First, the trimmer guard  733  is rotated counter clockwise as shown in  FIG. 7C . The rotation allows the trimmer  715  to be inserted in the cut out portion  711  removing the trimmer guard  733  out of the path of insertion as shown in  FIG. 7D . Once the trimmer has been fully inserted, a trimmer housing snap  740  that is coupled to the trimmer housing  720  and trimmer guard snaps  745  coupled to the guard  733  capture the holes  750  in the carriage by retracting during the insertion and snapping into the carriage holes  750  once aligned with the carriage holes  750  at the position of full insertion as shown in  FIG. 7E . As shown in  FIG. 7F , the snaps couple the trimmer  715  and the carriage assembly  706  such that they can be operated as one unit. Referring back to  FIG. 7B , the figure illustrates a detail cross section view of the coupling between the trimmer  715  and the carriage assembly  703 . As shown here, the lower rim  735  of the flange  730  is inserted through the small opening in the carriage housing  706 . The insertion places the thin shell of the carriage housing between the lower rim  735  and the upper rim  737 . In addition the insertion allows the housing snap  740  coupled to the trimmer housing to fully inserted into the carriage holes  750  and lock the carriage to the trimmer. In this fully coupled position, the upper rim  737  prevents the trimmer  715  from any downward movement, the housing snap  740  prevents and horizontal movement between the trimmer  715  and the carriage assembly  703 , and the carriage housing  706  trapped between the lower and upper rim obstructs the lower rim  735  from any upward movement thereby completely locking the trimmer  715  to the carriage assembly  703  in all directions. The coupled trimmer along with its guard encapsulates the wire or the blade inside the trimmer such that any debris or cut grass does not fly around. A user may also couple a cut grass collection bag and couple it to the trimmer for grass being collected as it is being cut. 
     FIG. 8  illustrates one embodiment of the invention. This figure presents a carriage  800  having several protruding rectangles  810 . Each protruding rectangle  810  includes a groove  820 . The groove  820  provides a guided path for a wheel  830  and includes several twists and turns. Each wheel  830  includes a wheel shaft  840  that passes thought the center of the wheel  830 . The wheel shaft  840  is captured within the groove  820  such that each wheel  830  can be maneuvered independently within the guided path of the groove from one position to another. 
   The groove  820  also includes a spring detent  850  for locking wheel position. Once the wheel shaft  840  it inserted in a position such as position  1 , the wheel shaft  840  is constrained by the detent  850  and restricted from sliding within the guided path. In addition to the detent  850 , the downward weight force of the carriage forces the wheel shaft  840  upwards towards the end of the groove  820  in position  1  preventing it from sliding. In order to move the wheel  830  from position  1  to position  2 , first a user applies a force on the wheel to move the wheel out of the detent constraint. The move forces the detent aside and allows the wheel shaft  840  to be guided along the groove path. A user can then maneuver the wheel shaft  840  along the groove guided path to a second position where the wheel shaft can be locked by the detent  850 . This movement from one vertical position to another allows the user to adjust the height of the carriage  800  and the blade coupled to the carriage  800 . The blade height adjustment determines the amount of contact a blade will have with the grass and determines the height of cut for the grass. 
   In another embodiment, the carriage  800  includes several holes placed at various horizontal and vertical locations along the carriage  800 . A wheel can be coupled to the carriage by inserting the wheel shaft through any of these holes. A user desiring to adjust the height of the carriage can simply detach the wheel from the carriage  800  and insert the wheel shaft  840  in another hole located at a different vertical location. 
   In addition, the individual movement of each wheel  830  allows the carriage  800  to be balanced even across uneven terrains. By placing one wheel  830  at position  1  and the other at position  2  a user can change the angle of the blade and the carriage and provide a parallel surface between the blade and the grass for a uniformly cut grass on an uneven terrain. Various combinations of angles may also be achieved by adjusting each wheel independently either to keep the blade parallel or at a desired angle for cutting the grass. 
   This wheel assisted lift prevents the blade in the carriage from coming in contact with the ground surface either during operation of the lawnmower or when the lawnmower is in a standing position. Blade contact with the ground surface during operation causes the blade to dig into the ground surface and ruin the lawn by extracting the roots of the grass. Also, if blade contact prevails over time when lawnmower is in a non-operational standing position, this contact can cause either rusting of the blade due to water deposits on ground or blade dullness due to ground contact. In addition, a wheel assisted lift of the carriage prevents a user from exerting energy to lift and push the carriage or accidentally bringing the blade in contact with the ground surface during operation. Also, wheel assisted lift ensures that an even amount of grass is cut as the lawnmower is pushed across the grass which in the case of a user assisted lift would require exact precision in maintaining the exact height from the ground to obtain an even cut.