Abstract:
A power miter saw of the type which has an upper fixed blade guard and a lower swinging blade guard for covering the lower reach of an installed blade when the saw is in its rest position and for exposing the lower reach of the saw blade when moved to its operational position, the saw comprising an adjustable length elongated linkage mechanism 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 reach of the blade when the saw is in its rest position and uncovers the blade when the saw is moved to its operational position, the linkage mechanism permitting the exposure of 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 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 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 a power miter saw comprise a saw base having a fence for positioning a work piece, a table rotatably connected to the saw base, a miter arm assembly for angularly positioning the table relative to the saw base, a saw blade and motor assembly having a blade arbor on which a blade can be installed and a motor operatively connected to drive the arbor and installed blade; and a frame support on the table for supporting the assembly, including a horizontal shaft about which the assembly is pivotable to move a saw blade vertically between an upper rest position and a lower operational position, the assembly having an upper fixed blade guard for encasing the upper reach of an installed saw blade without encasing the blade arbor, and a lower swinging blade guard pivotally mounted to the assembly around a pivot connection generally concentric with the blade arbor for covering the lower reach of an installed blade when the assembly is in its rest position and for exposing the saw blade when moved to its operational position, the assembly comprising an elongated linkage mechanism interconnecting the frame support and the lower blade guard for moving the lower blade guard in response to movement of the assembly between the rest and operational positions, such that the lower blade guard covers the lower reach of the blade when the assembly is in its rest position and is moved to uncover the lower reach of the blade when the assembly is moved to its operational position, the linkage mechanism being configured to have an adjustable length and be placed in at least first and second positions wherein the first position enables normal movement of the assembly between its rest and operational positions, and the second position wherein the lower blade guard is raised to expose the blade arbor to facilitate changing of the blade. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side plan view or 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 front view of the linkage mechanism shown in  FIGS. 1-3 , and is shown in its retracted position. 
         FIG. 5  is a back view of the linkage mechanism shown in  FIG. 4  and is also shown in the retracted position; 
         FIG. 6  is a front view of the linkage mechanism shown in  FIGS. 4 and 5 , but is shown in its extended position; 
         FIG. 7  is a side plan view of a portion of the locking pin mechanism; 
         FIG. 8  is another side view of the locking pin mechanism, shown in a locked position with first and second links being shown in section; 
         FIG. 9  is a side plan view similar to  FIG. 8 , but shown in an unlocked position permitting the links to be slidable relative to one another in their longitudinal direction; 
         FIG. 10  is a cross-sectional view of an alternative embodiment of one of the elongated links; and 
         FIG. 11  is a view similar to  FIG. 8 , but illustrating the alternative configuration of the elongated links. 
     
    
    
     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 metal 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 around 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  28  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 when the lower blade guard is in its rest position as shown in  FIG. 1  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  1  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 stud 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  28  by a stud or bolt  62  that has a nut  63  which defines a fixed connection point for the linkage mechanism  60 . The stud  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 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 clockwise direction so that the blade is exposed and is enabled to cut a work piece (not shown). 
     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 configured to be adjustable in length and as shown in  FIGS. 4 ,  5  and  6 , and is fabricated of two elongated thin metal links  64  and preferably made of steel. The links  64  and  66  are slideable relative to one another in their longitudinal direction and the left link  64  has an opening  68  at its outer left end portion that is configured to receive a bolt or pivot pin  62  and the right link  66  has an elongated connection slot  70  which houses the bolt or stud  48  that is connected to the plate  52  and also to the lower blade guard  36 . The links  64  and  66  are connected with a releasable locking pin mechanism, indicated generally at  72 , that interacts with both links and can be manipulated to be releasable which enables the two links to slide relative to one another. 
     The locking pin mechanism  72  is shown in detail in  FIGS. 7 ,  8  and  9  and it comprises a head portion  74  that is preferably cylindrically shaped, together with a shank, indicated generally at  76 , with the shank having a narrow preferably cylindrical shaped portion  78  having a length that is slightly larger than the thickness of the link  66  which merges with a larger diameter portion  80 , which in turn is connected to a threaded end portion  82 . It is preferred that the shank  76 , which comprises head portion  74 , enlarged portion  80  and threaded end portion  82  be integrally formed as a single piece that is preferably made of steel or aluminum. 
     As shown in  FIG. 8 , the locking pin mechanism  72  also has a spring  84  which is shown as a wave washer but can be a compression spring if desired. The threaded end portion  82  is shown to have a washer  86  and nut  88  attached thereto. 
     Referring to  FIG. 4 , the right link  66  has a travel slot  90  that extends a distance of approximately two inches and has a width that is slightly larger than the diameter of the narrow portion  78  of the locking pin mechanism  72 . The opposite ends of the travel slot have enlarged portions  92  and  94  which are sized slightly larger than the outside diameter of the enlarged portion  80  of the locking pin mechanism  72 . As shown in  FIG. 8 , the left link  64  has an opening  95  substantially the same size as the openings  92  and  94  so that when the locking pin mechanism is in place as shown in  FIG. 8 , the enlarged portion fits within the opening  95  in the link  64  and in one of the enlarged portions  92  or  94  and locks the two links together so that they cannot slide relative to one another. 
     When a user pushes the head  74  toward the link  66 , the enlarged portion  80  will be released from the enlarged opening in the link  66  so that the portion  78  will be coextensive with the travel slot  90  and enable the links  64 ,  66  to move from the retracted position shown in  FIG. 4 , for example, to the extended position shown in  FIG. 6 . A rear view of the linkage mechanism  60  is shown in  FIG. 5  and in this view it is evident that the link  64  has an elongated slot  98  in which an alignment pin  100  can travel, with the alignment pin being connected to the link  66 . This limits the sliding movement of the two links  64 ,  66  relative to one another in the longitudinal direction and prohibits any angular positioning of the links relative to one another. 
     While the use of the alignment pin  100  shown in the preferred embodiment, it should be understood that an alternative embodiment can be used which is shown in  FIGS. 10 and 11  wherein the cross sectional configuration of the links  64   a  and  66   a  is other than flat and therefore similarly limits sliding movement only in the longitudinal direction. It should be understood that other mechanisms such as an outer bracket that fits around both of the links could be used to limit sliding movement only in the longitudinal direction. If such a bracket were used, then the alignment slot  98  and the alignment pin  100  would be unnecessary. It should also be understood that other alternatives could be used to limit sliding movement only in the longitudinal direction, such as a separate stamped or molded member that covers both links and prevents rotation of them relative to one another. 
     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.