Abstract:
Embodiments of a power miter saw of the type which has an upper fixed blade guard for encasing upper reaches of an installed saw blade without encasing the blade arbor, and a lower swinging blade guard for covering the lower reaches of an installed blade when saw is in its rest position and for exposing the saw blade when moved to its operational position, the saw comprising an elongated linkage mechanism having opposite end portions interconnecting a frame support and the lower blade guard for moving the lower blade guard in response to movement of the saw between the rest and operational positions, such that the lower blade guard covers the lower reaches of the blade when the saw is in its rest position and uncovers the lower reaches of the blade when the saw is moved to its operational position, the linkage mechanism being configured to be selectively detachable from the frame support, thereby enabling the lower blade guard to be placed in at least first and second positions wherein the first position enables normal movement of the saw between its rest and operational positions, and the second position wherein the lower blade guard is raised to expose a blade arbor to facilitate changing of the blade.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to power miter saws and similar power saws. 
     The design and development of power tools and particularly power saws, such as miter saws, for example, have produced saws that are extremely sophisticated and not only provide reliable and accurate cutting of work pieces, but also are much safer to operate. Such safety considerations have greatly changed the configuration of miter saws over several decades. One of the major changes involves the protection of a user from the rotating saw blade by having not only an upper generally fixed blade guard as part of the design of the motor and blade assembly, but also a swinging lower blade guard that is pivoted out of the way to expose the lower portion or reach of the blade for cutting as the motor and blade assembly is lowered into its operating position to cut a work piece. When the cut is completed and the motor and blade assembly rotated upwardly to return to its normal rest position, the lower blade guard is automatically rotated into position to cover the lower reach of the blade. 
     As is the case for some known miter saws that are currently marketed, the geometry of the miter saw prevents a lower guard from rolling back away from the saw blade for the purpose of having access to the blade arbor as required when it is desired to change the blade. The actuating link of the lower guard is connected to a frame support and does not normally permit this type of movement. For many designs, it is therefore necessary to at least partially disassemble the saw in order to obtain access to the arbor so that the blade can be changed. The amount of disassembly varies depending upon the particular saw, but is often inconvenient and time consuming. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention permit the lower guard linkage linking mechanism to be easily manipulated to place the lower guard to be rotated out of the way and be temporarily held in a position which exposes the blade and arbor to permit the user to change the blade. 
     Embodiments of the present invention is directed to a power miter saw of the type which has an upper fixed blade guard for encasing upper reaches of an installed saw blade without encasing the blade arbor, and a lower swinging blade guard for covering the lower reaches of an installed blade when saw is in its rest position and for exposing the saw blade when moved to its operational position. The saw includes an elongated linkage mechanism having opposite end portions interconnecting a frame support and the lower blade guard for moving the lower blade guard in response to movement of the saw between the rest and operational positions, such that the lower blade guard covers the lower reaches of the blade when the saw is in its rest position and uncovers the lower reaches of the blade when the saw is moved to its operational position. The linkage mechanism is configured to be selectively detachable from the frame support, thereby enabling the lower blade guard to be placed in at least first and second positions wherein the first position enables normal movement of the saw between its rest and operational positions, and the second position wherein the lower blade guard is raised to expose a blade arbor to facilitate changing of the blade. 
     One embodiment of the invention has a linkage mechanism that has one end that can be easily detached so that the lower blade guard can be raised to the second position and then reattached to hold it in the second position. 
     Another embodiment has a linkage mechanism that has one end that can be easily detached so that the lower blade guard can be raised to the second position and then conveniently uses an opening in the linkage in combination with a necessarily loosened screw to hold the lower blade guard in the second position. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side plan view of a portion of a compound miter saw, particularly illustrating a portion of the saw base and table and a frame support supporting a blade and motor assembly, and also illustrating a linkage mechanism for a lower swinging blade guard, with the motor and blade assembly in a rest or non-operating position; 
         FIG. 2  is a side plan view similar to  FIG. 1 , but illustrating the saw with the blade and motor assembly pivoted downwardly into an operating position; 
         FIG. 3  is a side plan view of the saw shown in  FIGS. 1 and 2 , but illustrating the lower swinging blade guard pivoted to a position that exposes the blade arbor and blade thereby enabling a user to change the blade without interference from the swinging lower plate guard; 
         FIG. 4  is a cross-section taken through the snap-fit connection of a link to a post on the miter saw; 
         FIG. 5  is a plan view of a portion of the link together with the snap-fit connection; 
         FIG. 6  is a side plan view of another preferred embodiment showing a portion of a compound miter saw, particularly illustrating a portion of the saw base and table and a frame support supporting a blade and motor assembly, and also illustrating a linkage mechanism for a lower swinging blade guard, with the motor and blade assembly in a rest or non-operating position; 
         FIG. 7  is a side plan view similar to  FIG. 6 , but illustrating the saw with the blade and motor assembly pivoted downwardly into an operating position; 
         FIG. 8  is a side plan view of the saw shown in  FIGS. 6 and 7 , but illustrating the lower swinging blade guard pivoted to a position that exposes the blade arbor and blade thereby enabling a user to change the blade without interference from the swinging lower plate guard; and 
         FIG. 9  is a side view of a thumb screw used in the embodiment shown in  FIGS. 6-8  to attach one end of the link to the miter saw. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is particularly suited for use in a power miter saw of the type which has a compound action as well as being adjustable to perform cuts at different miter angles as well as different bevel angles. With the miter saw having a motor and blade assembly that is pivotable along a generally horizontal axis downwardly into contact with a work piece that is placed on a table of the miter saw and wherein the motor and blade assembly includes an upper fixed blade guard as well as a swingable (i.e., rotatable) lower blade guard that is configured to completely encase the blade so that a user cannot contact the blade when the motor and blade assembly is in its upper rest position. However, the present invention includes embodiments that are useful in other types of saws of the type which have a lower blade guard associated with them. 
     Turning now to the drawings, and particularly  FIG. 1 , a compound miter saw, indicated generally at  10 , that includes a partially shown base  12 , a rotatable table  14  that has a hub  16  which is connected to a vertical stand  18  to which a pair of rods  20  (only one of which is visible in  FIG. 1 ) can move horizontally to provide compound action of the saw to increase the length of cut that is possible with the saw. The forward end of the rods  20  are connected to a frame support  22  that has a horizontal shaft  24  that pivotally supports a motor and blade assembly that is indicated generally at  26 . It should be understood that the present invention can also be used for a non-sliding type of miter saw. 
     As is typical, the table  14  has a fence  28  which is provided to anchor a work piece that may be placed on the table  14 . The frame support  22  has a rearward extension  29  that is preferably integrally formed with the frame support  22 . The motor and blade assembly  26  has a handle  30  as well as a carry handle portion  30   a . The handle  30  is used by a user to pivot the motor and blade assembly  26  downwardly toward the table  14  for cutting a work piece that is positioned on the table. The motor and blade assembly  26  preferably has an upper blade guard portion that is preferably cast together with other components to include the motor (not shown), a dust collecting portion  34 . 
     A rotatable lower blade guard  36  is shown with the blade  38  being visible, preferably because the lower blade guard  36  is formed of a transparent or nearly transparent plastic material so that a user can see if the blade  38  is moving or not. The lower blade guard  36  has a small roller  40  located on its bottom which acts as a bumper for contacting the top surface of the table  14  when the motor and blade assembly is brought down into cutting position as shown in  FIG. 2 . 
     The lower blade guard pivots around an axis  42  that is generally concentric with the axis of an arbor  44  (see  FIG. 3 ) to which the blade  38  is mounted. The pivot  42 , however, is secured to the upper blade guard  32  and is not attached to the arbor  44 . The pivot  42  has a generally circular hub portion  46  which has a post or bolt  48  that is preferably threaded to receive a nut  50  which defines an attachment pin for an elongated linkage mechanism, indicated generally at  60 , the other end of which is connected to the rearward extension  29  that has a post  62  to which a snap-fit connector, indicated generally at  64  can be removably attached and which defines a connection point for the linkage mechanism  60 . 
     The upper post  48  is attached to a flat plate  52  that is generally shaped commensurate with a raised bead  54  outline as shown in  FIG. 3  that is very generally shown as being rectangular. The plate  52  has its right end portion secured in the upper blade guard by a screw  56  and its opposite end portion secured by a screw  58 . 
     The screw  58  fits within an opening  59  in the upper blade guard  32  as is particularly shown in  FIG. 3 , wherein the screw  58  has been removed from the opening  59  and the screw  56  has been loosened slightly so that the plate  52  is rotated about the screw  56  in a counter-clockwise direction thereby enabling the lower blade guard  36  to be rotated further away from the arbor  42  thereby enabling the arbor to be accessed and the blade removed or replaced if desired. 
     As is shown by comparing  FIGS. 1  with  2 , when the motor and blade assembly  26  is in its rest position shown in  FIG. 1  where the blade is elevated relative to the table, the linkage mechanism  60  is positioned to have the lower blade guard  36  positioned as shown where it totally encloses the blade  38 . However, when the handle  30  is moved downwardly to bring the blade in near contact with the upper surface of the table  14 , the linkage mechanism  60 , by virtue of the connection  48 , rotates the lower blade assembly in a counter clockwise direction so that the lower reach of the blade is exposed and is enabled to cut a work piece (not shown). 
     To access the arbor and remove or replace the blade  38 , the motor and blade assembly  26  is placed in its rest position and the linkage mechanism  60  is detached from the post  62 . The lower blade guard  36  then is rotated in a counterclockwise direction so that the blade  38  is exposed, and the linkage mechanism is reattached to the post  62 . In this manner, the lower blade guard  36  is maintained in the position that exposes the blade  38  and the plate  52  covering the arbor. 
     As is evident from  FIGS. 1 and 2  showing the motor and blade assembly in the uppermost rest position and in an operating lower position, respectively, it is apparent that the arbor is covered by the lower blade assembly. 
     The elongated linkage mechanism  60  is preferably fabricated from steel and has an opening  66  (see  FIG. 4 ) at the lower end of the linkage mechanism that is preferably a circular opening sized to receive the snap fit connector  64 . The snap fit connection  64  is comprised of an inner component  68  and an outer component  70  which have a generally cylindrical configuration and snap fit together with each component extending through the opening  66  of the elongated linkage mechanism  60 . More particularly, the outer component  70  has a number of fingers  72  with an outwardly extending ear  74  defining a shoulder  76  that is configured to engage corresponding ears  78  of outer periphery  80  of the inner component  68 . The inner component has a number of recesses  82 . 
     The inner component  68  has a number of fingers  84  that are spaced apart from one another and which generally surround the cylindrical post  62 , i.e., they have an inside diameter that is approximately equal to the outside diameter of the post  62 . The post has an outer free end  86  with a generally flat end surface  88  which preferably has a rounded curved periphery  90  that facilitates matching the snap fit connector onto the post  62 . The post also has an annular groove  92  near the outer end surface  88 . The groove has sloped sides  94  to facilitate attachment and detachment of the snap fit connection on the post. The fingers  84  have an inwardly directed protrusion  96  with sloped side portions  98  that are preferably angled generally the same as the angle of the sloped side portions of the groove  92  to also facilitate sliding attachment and detachment of the snap fit connector from the post  62 . It should be understood that the snap fit connector is fabricated from a plastic or plastic-like material so that the fingers have resilience and are preferably made of polypropylene or similar material. 
     It should be understood that while the construction of the snap fit connector has inner and outer components that snap together and are more or less permanently retained in the opening  66  of the elongated linkage mechanism  60 , it should be understood that alternative constructions for such a snap fit connection can be used, including forming a one piece snap fit connection around the opening  66  and end of the elongated linkage mechanism  60 . 
     The second embodiment of the present invention is shown in  FIGS. 6-9  and is directed to another type of compound miter saw and is indicated generally at  110  that includes a partially shown base  112 , a rotatable table  114  that rotates around a hub  116  which is connected to a vertical stand  118  to which a pair of multilink hinges  120  and  121  are provided. The two hinges are oriented approximately 90° relative to one another and operate to move ahead support  122  in a horizontal direction. The head support  122  has a horizontal shaft  124  that pivotally supports a motor and blade assembly, indicated generally at  126 . It should be understood that the present invention can also be used for a non-compound type of miter saw. 
     As is typical, the table  114  has a fence  128  which is provided to anchor a work piece that may be placed on the table  114 . The motor and blade assembly  126  has a handle  130  which is used by a user to pivot the motor and blade assembly  126  downwardly toward the table  114  for cutting the work piece and is positioned on the table. The motor and blade assembly  126  preferably has an upper blade guard portion that is preferably an aluminum casting that also includes an extension  132  that carries a motor  134 . 
     A rotatable lower blade guard  136  is shown with the blade  138  being visible, preferably because the lower blade guard  136  is formed of a transparent or nearly transparent plastic material so that a user can see if the blade  138  is moving or not. The lower blade guard  136  has a small roller  140  located on its bottom which acts as a bumper for contacting the top surface of the table  114  when the motor and blade assembly  126  is brought down into a cutting position as shown in  FIG. 7 . 
     The lower blade guard pivots around an axis  142  that is generally concentric with the axis of an arbor  144  (see  FIG. 8 ) to which the blade  138  is mounted. The pivot  142 , however, is secured in the upper blade guard  132  and is not attached to the arbor  144 . The pivot  142  has a generally circular hub portion  146  which has a post or bolt  148  that is preferably threaded to receive a nut  150  which defines an attachment point for an elongated linkage mechanism, indicated generally at  160 , the other end of which is connected to a post  162  located on the head portion  122 , to which a thumb screw, indicated generally at  164 , can be removably attached and which defines a connection point for the linkage mechanism  160 . 
     The upper post  148  is attached to a flat plate  152  that is generally shaped commensurate with a raised bead  154  outlined which is shown in  FIG. 8  that is very generally shown as being rectangular. The plate  152  has its right end portion secured in the upper blade guard  132  by a screw  156  and its opposite end portion secured by a screw  158 . 
     The screw  158  is threaded into the upper blade guard  132  and cooperates with a spot  159 , the upper blade guard  132  is shown in  FIG. 8  as being slightly angled so that as the plate  152  is rotated in a clockwise manner, the slot will be coextensive with the screw  158  so that it can be tightened to hold the plate  152  in place. 
     As was the case with the embodiment shown in  FIGS. 1-4 ,  FIG. 6  shows the motor and blade assembly  126  in its rest position, whereas  FIG. 7  shows the same in an operational positional wherein the linkage mechanism  160  rotates the lower blade assembly in a counterclockwise direction so that the lower reach of the blade is exposed enabling it to cut a work piece (not shown). 
     As is evident from  FIGS. 6-8 , the elongated linkage mechanism  160  is not straight as it is in the embodiment of  FIGS. 1-5 , but is grooved in the general shape of a semi-circle that extends through approximately ⅔ of the center portion of the length of it. The linkage mechanism  160  also has an enlarged aperture  170  located at the base of the curve near the thumb screw  164 . The aperture  170  is sized to be larger than the screw  158  and is conveniently placed so that it will hold the lower blade guard in its upper position as shown in  FIG. 8 . The thumb screw has been removed from the head  122 . Thus, the lower guard  138  is held in the blade changing position by placing the hole  190  over the screw  158  that was loosened to permit the plate  152  to be rotated in a counterclockwise direction to the blade changing position. 
     With regard to the thumb screw  164 , it is shown in detail in  FIG. 9  and comprises an enlarged cylindrical head portion  174  which preferably has a narrowed outer surface to facilitate easy gripping by a user for attaching and removing the same. The head  174  has a cylindrical shoulder portion  176  that has an annular groove  178  which then terminates in a threaded end portion  180 . A retaining ring  182  is provided in the groove  178  which has an outer diameter that is larger than the opening  166  in which the thumb screw is attached. The length of the shoulder portion  176  is greater than the thickness of the length so that the thumb screw can be easily rotated to engage or disengage the threaded opening emboss of the head portion  122 . The retaining ring is provided so that the thumb screw will remain attached to the elongated linkage mechanism  160 . The retaining ring  182  is preferably a metal split-type retaining ring that has an inside diameter that can pass over the threaded end portion  180  and be fixed into the groove  178  of the shoulder screw. 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
     Various features of the invention are set forth in the following claims.