Abstract:
A modular power tool incorporates a modular drive system and modular handle set that is reversible for use with both a left hand and right hand configuration. The modular drive system and handle set of the modular power tool of this invention reduces the need for derivative circular saw designs by introducing common components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 10/165,167, filed on Jun. 7, 2002, the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a modular power tool. In particular, the present invention relates to a modular circular saw wherein the handle supports the drive assembly and is adaptable to be fastened on either side of the saw blade, providing a right hand and left hand assembly. 
     BACKGROUND OF THE INVENTION 
     Circular saws are known in the art. A growth in circular saw applications has created many derivative circular saw designs for each specific type of use. Many of these applications require changes to motor platforms, blade guarding and gear cases. Specifically, most circular saw designs do not allow different motor sizes to fit the same housing. This requires a housing redesign and a new transmission for each different or new motor size. The transmission or gear case is typically the most complex component to develop and dimensionally qualify because it has the most stringent tolerances and becomes the foundation for all the other structure that is mounted to it. Hence, the product development time for a derivative circular saw is extensive and somewhat prohibitive. 
     In addition, there is a need for a left and right hand blade applications with respect to the handle set for many circular saw designs, which usually requires a handle set redesign. The design of the handle set is complicated because generally battery applications or power sources fit onto the handle set. Thus, development of a new handle set for each circular saw product creates a tremendous amount of design resources, tooling cost and development time. 
     Accordingly, a need exists for a modular power tool for a circular saw application having the ability to incorporate numerous gear cases, motor platforms and guard designs, with a handle operable in both a left hand and right hand configuration. 
     SUMMARY OF THE INVENTION 
     The present invention provides a modular power tool for a circular saw application. The modular power tool incorporates a modular drive system that employs a mounting flange portion with a common hole pattern for coupling motors of various sizes to a universal gear case. The handle set of the modular power tool is designed with a cavity through which the drive system passes. The handle set further includes a universal mating portion for receipt of a variety of battery and power sources. The handle set is also reversible for use with both a left hand and right hand configuration. The modular drive system and handle set of the modular power tool of this invention reduces the need for derivative circular saw designs by introducing common components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is an exploded perspective view of a modular power tool in a left hand orientation according to the principles of the present invention; 
         FIG. 2  is an exploded view of the modular power tool in a right hand orientation; 
         FIG. 3  is a side view of a handle set according to the principles of the present invention; 
         FIG. 4  is a front view of a gear case according to the principles of the present invention; 
         FIG. 5  is a perspective view of the modular circular saw in a left hand configuration; 
         FIG. 6  is a perspective view of the right hand configuration of the modular circular saw according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring generally to  FIGS. 1 and 2 , an exploded view of a first embodiment of a modular power tool  10  is shown. The present invention is directed towards a circular saw, however, it is to be understood that the principles embodied herein are equally applicable to other types of power tools as well. 
     The modular power tool or power circular saw  10  includes a reversible clam shell handle set  12  with a symmetrical motor housing  14 . A universal drive train platform is provided with a motor case  18  which has a flange  20  and mounting hole pattern which is designed for the largest motor, such that smaller motors can be provided with the same flange and hole pattern. The universal drive train platform also includes a universal gear case  22 . Various guards  24  and shoe assemblies  26  can be provided for a specific saw application such as right and left hand blade applications, wood or metal cutting, etc. Fasteners  28  extend through mounting holes  30 , provided in the symmetrical motor housing  14 , holes  32 , provided in the reversible clam shell handle set  12 , holes  34 , provided in the flange  20  of the motor case  18 , mounting holes  36 , provided in the universal gear case  22  and finally into mounting holes  38  provided in guard  24 . 
     The symmetrical motor housing  14  can be made out of one or two pieces. The symmetrical motor housing  14  is generally made from plastic and encloses an end of the motor case  18 . Different size symmetrical motor housings  14  can be optionally used to reduce the size of the assembly for different motor sizes. This reduces the cost and development time required of an entire new housing tool. The symmetrical motor housing  14  is coupled to the two-piece clam shell handle set  12 . 
     The two-piece clam shell handle set  12  incorporates an identical and symmetrical mounting pattern on both sides of each clam shell portion  12   a ,  12   b . This clam shell handle set  12  has an opening  40  that allows the entire range of desired motor cases  18  to pass through it for mounting onto the universal gear case  22 . The clam shell handle set  12  also supports the motor case  18  for coupling to the symmetrical motor housing  14 . In addition, clam shell handle set  12  has an open end cavity  42  (best shown in  FIG. 2 ) designed so that different mold inserts can be used for different battery and power sources to be connected to the power circular saw  10 . Clam shell handle set  12  further includes a trigger  44  and a safety  46  (best shown in  FIG. 3 ). Both trigger  44  and safety  46  are generally made from plastic. Safety  46  extends through the clam shell handle set  12 , and must be held for the trigger  44  to release. 
     The modular universal transmission and gear case  22  is symmetrical and has the ability to incorporate numerous gear ratios, motor platforms and guard designs. In addition, as shown in  FIG. 4 , the universal gear case  22  has symmetrical air flow vents  39  with fins and ribbing  48  that can direct air to remove dust and debris from a cutting line in both right and left handed blade applications. 
     Referring generally to  FIGS. 1 and 2 , the assembly of power circular saw  10  generally involves inserting motor case  18  through the cavity  40  of the clam shell handle set  12 . The motor case  18  has a flange  20  with holes  34  which couple the universal gear case  22  to the motor case  18 . The universal gear case  22  is further coupled to the guard and shoe assembly  24 ,  26 . Symmetrical motor housing  14  is fixed to the end of the clam shell handle set  12  such that it covers the rest of the motor case  18 . The symmetrical motor housing  14  provides the starting point for the fasteners  28 , specifically fasteners  28  are threaded though the symmetrical motor housing  14  via holes  30  into the clam shell handle set  12  via holes  32 , through motor assembly holes  34 , the gear case holes  36  and into the guard  24 . The battery  50  ( FIGS. 5 and 6 ) or other power source are mounted onto cavity  42 . The left hand assembly for the power circular saw  10  is shown  FIG. 5 . The right hand assembly for the power circular saw  10  is shown in  FIG. 6  and is achieved by reversing the orientation of the clam shell handle set  12 . 
     The design of the present invention allows the clam shell handle set  12  to be mounted either to the left or to the right of the blade and gear case. Features that allow this arrangement include the identical and symmetrical mounting fasteners on both sides of each handle clam shell. In addition, the handle set defines an opening that is large enough for the entire range of different sized motor assemblies to pass through it. Furthermore, the motor housing and gear case are symmetrically designed for left hand and right hand use. The blade guard and shoe can be changed for different uses and for left or right hand orientations. 
     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.