Abstract:
A circular saw includes a machine base, a sliding unit including a slide shaft slidably inserted through the machine base and a stationary mount fixedly mounted at one end of the slide shaft and defining a datum plane, and a cutting unit including a supporting arm pivotally connected to the stationary mount and a saw blade pivotally connected to the supporting arm. The saw blade is movable by the supporting arm up and down relative to the machine base between a lower limit position and an upper limit position so that the saw blade may intersect with the datum plane or be kept in a tangential relationship relative to the datum plane when it reaches the lower limit position. Thus, the circular saw has a compact size, low vibration level and high precision characteristics.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims, under 35 U.S.C. §119(e), priority to U.S. Provisional Application No. 61/635,990, filed Apr. 20, 2012, which application is hereby incorporated by reference in its entirety, inclusive of the specification, claims, and drawings. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of saw machines, and more particularly to a circular saw having a compact size, low vibration level and high precision characteristics. 
       BACKGROUND 
       [0003]    Both U.S. Pat. No. 5,241,888 and U.S. Application Publication Number 2007/0163409 disclose a slidable miter saw. However, the saws disclosed in these two prior art designs exhibit certain drawbacks, such as bulk size and high operating vibration, which affect the cutting precision. Specifically, according to the aforesaid two prior art saws, the cutting unit must be kept within a limited cutting stroke, and the length of the sliding stroke of the slide bars of the sliding mechanism must be fixed. Further, the supporting arm that extends from the front side of the sliding mechanism must be properly defined. 
         [0004]    If the length of the supporting arm that extends from the front side of the sliding mechanism is excessively long, the size of the worktable must be relatively increased to fit the stroke of the cutting unit and to give sufficient support to the workpiece. However, increasing the size of the worktable relatively increases the storage and delivery cost of the miter saw. According to the aforesaid prior art saws, the length of the arm of force of the cutting unit is determined subject to the extending distance of the sliding mechanism. In order to increase the arm of force of the cutting unit, the extending distance of the sliding mechanism cannot be reduced, thus resulting in a high level of operating vibration that correspondingly affects the precision of the cutting operation. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a circular saw, which has the characteristics of compact size, low operating vibration and high cutting precision. 
         [0006]    To achieve this and other objects of the present invention, a circular saw comprises a machine base, a sliding unit, and a cutting unit. The sliding unit comprises at least one slide shaft and a stationary mount. The slide shaft is axially movably inserted through the machine base. The stationary mount comprises a mounting portion affixed to one end of the slide shaft for enabling the stationary mount to be moved by the slide shaft relative to the machine base. The cutting unit comprises a supporting arm pivotally connected to the stationary mount, and a saw blade pivotally connected to the supporting arm. Thus, the saw blade is movable by the supporting arm relative to the machine base between an upper limit position and a lower limit position. 
         [0007]    Further, the mounting portion of the stationary mount of the sliding unit has a front side facing toward the saw blade and defining a datum plane. When the saw blade reaches the lower limit position, the saw blade and the datum plane intersect with each other, or alternatively may be kept in a tangential relationship. Thus, the circular saw advantageously has compact size, low vibration level and high precision characteristics. 
         [0008]    It is another object of the present invention to provide a circular saw which enhances the operating smoothness. To achieve this and other objects of the present invention, the circular saw further comprises a guard mechanism. The guard mechanism comprises a saw blade guard and a link. The saw blade guard is pivotally connected to the supporting arm to surround the saw blade. The stationary mount defines a guide groove and a bearing groove. The link has its one end pivotally connected to the saw blade guard, and its other end providing a protruded guide portion and a protruded bearing portion. The protruded guide portion is coupled to and movable along the guide groove. The protruded bearing portion is coupled to and movable along the bearing groove. When the saw blade is biased from the upper limit position to the lower limit position, the saw blade guard will correspondingly be biased by the link relative to the saw blade to expose the saw blade, thus achieving enhanced operating smoothness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other advantages and features of the present invention will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure. 
           [0010]      FIG. 1  is an elevational view illustrating a saw blade of a circular saw kept in an upper limit position in accordance with the present invention. 
           [0011]      FIG. 2  is an elevational view of the circular saw of  FIG. 1 , illustrating the saw blade of the circular saw biased from the upper limit position to an intermediate position. 
           [0012]      FIG. 3  is an elevational view of the circular saw of  FIG. 1 , illustrating the saw blade of the circular saw biased from the upper limit position to a lower limit position. 
           [0013]      FIG. 4  is an elevational view of the circular saw of  FIG. 1 , illustrating the cutting unit moved relative to the worktable. 
       
    
    
       [0014]    It should be noted that the drawing figures are not necessarily drawn to scale, but instead are drawn to provide a better understanding of the components thereof, and are not intended to be limiting in scope, but rather to provide exemplary illustrations. It should further be noted that the figures illustrate exemplary embodiments of a circular saw and the components thereof, and in no way limit the structures or configurations of a circular saw and components thereof according to the present disclosure. 
       DETAILED DESCRIPTION 
       [0015]    While the disclosure may be susceptible to various modifications and alternative constructions, certain illustrative embodiments are shown in the drawings and are described in detail below. It should be understood, however, that there is no intention to limit the disclosure to the specific embodiments disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure. 
         [0016]    It will be understood that, unless a term is expressly defined in this disclosure to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning 
         [0017]    Referring to  FIG. 1 , a circular saw in accordance with the present invention is shown. As illustrated, the circular saw  10  comprises a machine base  20 , a sliding unit  30 , a cutting unit  40 , and a guard mechanism  50 . The machine base  20  is mounted at a tabletop or any other support surface means for holding the workpiece to be cut, and comprises a bracket  22  upwardly extended from a rear side thereof. 
         [0018]    The sliding unit  30  comprises at least one slide shaft  32  and a stationary mount  34 . The slide shaft  32  is axially slidably inserted through the bracket  22 , enabling the sliding unit  30  to be moved linearly relative to the bracket  22  along a predetermined traveling path to achieve a predetermined cutting stroke. The stationary mount  34  comprises a mounting portion  342  and an extension portion  348 . The mounting portion  342  of the stationary mount  34  is affixed to one end of the slide shaft  32 , thus enabling the stationary mount  34  to be moved by the slide shaft  32  relative to the machine base  20 . Further, the mounting portion  342  of the stationary mount  34  has a front side  344  and a rear side  346 . The front side  344  of the stationary mount  34  defines a datum plane P remotely located from the slide shaft  32 . This datum plane P is substantially perpendicular to the axial direction of the slide shaft  32 . The rear side  346  of the mounting portion  342  defines a rear plane PR located adjacent to the slide shaft  32 . This rear plane PR is substantially parallel to the datum plane P. The extension portion  348  extends from the mounting portion  342  in a direction away from the rear side  346  of the mounting portion  342  and along the axial direction of the slide shaft  32 . 
         [0019]    The cutting unit  40  comprises a supporting arm  42  and a saw blade  44 . The supporting arm  42  is pivotally coupled to the extension portion  348  of the stationary mount  34  by a rotating shaft  46  at a rear side relative to the rear plane PR of the mounting portion  342 . The saw blade  44  has a radius R, and is pivotally connected to the supporting arm  42  by a pivot axle  442 . Thus, the saw blade  44  can be moved by the supporting arm  42  up and down relative to the datum plane P of the stationary mount  34  between an upper limit position P 1  and a lower limit position P 2 . Further, the saw blade  44  and the stationary mount  34  are arranged relative to each other in order to avoid interfering with each other. When the saw blade  44  reaches the upper limit position P 1 , as shown in  FIG. 1 , the saw blade  44  and the datum plane P intersect. 
         [0020]    Similarly, when the saw blade  44  reaches the lower limit position P 2 , as shown in  FIG. 3 , the saw blade  44  and the datum plane P intersect. At this time, a horizontal distance L 1  is defined between the pivot axle  422  and the rotating shaft  46 , a horizontal distance L 2  is defined between the rotating shaft  46  and the datum plane P, and a horizontal distance L 3  is defined between the datum plane P and the pivot axle  442 . These three horizontal distances L 1 , L 2 , L 3  exhibit a relationship wherein L 3 =L 1 -L 2 , i.e., the horizontal distance L 3  between the datum plane P and the pivot axle  442  is equal to the horizontal distance L 1  between the pivot axle  442  and the rotating shaft  46  minus the horizontal distance L 2  between the rotating shaft  46  and the datum plane P. Thus, the horizontal distance L 3  is smaller than the radius R of the saw blade  44 . Alternatively, it should be appreciated that the horizontal distance L 3  may be defined to be equal to the radius R of the saw blade  44 . In this alternative case, the saw blade  44  and the datum plane P have a tangential relationship. 
         [0021]    The guard mechanism  50  comprises a saw blade guard  51 , a support  52 , and a link  53 . The saw blade guard  51  is pivotally connected to the supporting arm  42  to surround the saw blade  44 . The support  52  is mounted at the top side of the stationary mount  34 , defining a guide groove  54  and a bearing groove  55 . The bearing groove  55  is an elongated groove having a first sloping segment  56  and a second sloping segment  57 . The first sloping segment  56  slopes downwardly from a location close to the datum plane P to a location far from the datum plane P. The second sloping segment  57  is kept in communication with the first sloping segment  56 . Further, the second sloping segment  57  obliquely extends downwardly from the bottom end of the first sloping segment  56  in the direction toward the datum plane P. The link  53  has one end thereof pivotally connected to the saw blade guard  51 . An opposite second end of the link  53  is provided with a protruded guide portion  58  and a protruded bearing portion  59 . Both the protruded guide portion  58  and the protruded bearing portion  59  protrude from one side of the opposite second end of the link  53 . Moreover, the protruded guide portion  58  is slidably coupled to the guide groove  54 , and the protruded bearing portion  59  is slidably coupled to the bearing groove  55 . 
         [0022]    Referring again to  FIG. 1 , the saw blade  44  is kept in the upper limit position P 1  before application. At this time, the protruded bearing portion  59  of the link  53  is positioned in the top end of the first sloping segment  56  of the bearing groove  55 . When using the saw machine, the supporting arm  42  is biased downwardly toward the machine base  20  to move the saw blade  44  from the upper limit position P 1  toward the lower limit position P 2 , as shown in  FIG. 3 . This movement forces the protruded bearing portion  59  of the link  53  to move downwardly along the first sloping segment  56  of the bearing groove  55 , and the protruded guide portion  58  of the link  53  to move backwardly along the guide groove  54 , as shown in  FIG. 2 . Additionally, the resisting force produced between the protruded bearing portion  59  of the link  53  and the first sloping segment  56  of the bearing groove  55  at this time is imparted to the saw blade guard  51  to bias the saw blade guard  51  relative to the saw blade  44 , thus increasing the exposed part of the saw blade  44 . 
         [0023]    By continuously biasing the supporting arm  42  downward, the protruded bearing portion  59  of the link  53  will be moved downwardly along the second sloping segment  57  of the bearing groove  55  and kept stopped against the second sloping segment  57  of the bearing groove  55 , as shown in  FIG. 3 . This enables the link  53  to keep biasing the saw blade guard  51  relative to the saw blade  44 , and therefore continuously increase the exposed area of the saw blade  44 . When the protruded bearing portion  59  of the link  53  reaches the bottom end of the second sloping segment  57  of the bearing groove  55 , the saw blade  44  intersects with the datum plane P of the stationary mount  34 , as shown in  FIG. 3 . At this time, the cutting unit  40  can be moved relative to the machine base  20  by the slide shaft  32 . When the cutting unit  40  reaches the rear limit position during its cutting stroke, the rear side  346  of the mounting portion  342  of the stationary mount  34  is substantially rested on the bracket  22  of the machine base  20 , as shown in  FIG. 4 . During this movement, the exposed part of the saw blade  44  is forced to cut the workpiece. 
         [0024]    The design of the circular saw  10  in accordance with the present invention greatly shortens the distance in which the cutting unit  40  extends out of the sliding unit  30  during its cutting stroke, thus enabling the total dimensions of the circular saw to be effectively reduced. Further, shortening the arm of force can reduce the operating vibration to enhance the cutting precision. Also, the link  53  of the circular saw  10  in accordance with the present invention provides a protruded guide portion  58  and a protruded bearing portion  59  that smoothly match with the guide groove  54  and the bearing groove  55 , respectively, for enabling the saw blade guard  51  to be biased smoothly relative to the support  52 . 
         [0025]    Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.