Locking construction for a miter saw having a hinged linear guide mechanism

[0001] The present invention generally relates to power tools, and particularly power miter saws.

[0002] Power miter saws continue to be the subject of research and developmental efforts that are improving the design and operation of such saws. The improved design also improves the accuracy of cuts that are made by the miter saw as well as provide durable and stable operation over an extended useful life. In addition, increased functionality is provided at very little additional cost to the consumer, including the capability of the miter saw to have the blade and motor assembly traverse a generally horizontal path to increase the width of a cut made on a work piece or to cut larger scale crown molding and other trim work that is performed by trim carpenters and other tradesmen.

[0003] Recent developments that have been made by inventors with the Robert Bosch Tool Company utilize horizontal linkages that are combined with transverse linkages which enable such reciprocating movement to have a high degree of stability which contributes to extreme accuracy in the making of cuts on work pieces. Not only that, the use of such linkages eliminates sliding bushings and the like which are relatively more expensive and are prone to having their operability at least partially compromised by exposure to dust, wood cuttings and the like during operation.

[0004] Embodiments of a power miter saw comprise a saw base, 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 operatively connected to the table, a multiple link hinged linear guide mechanism configured to support the saw blade and motor assembly and enable movement of the assembly along a predetermined linear generally horizontal path between extended and retracted positions, the mechanism comprising a first hinge having first and second links pivotably connected together by a first shaft extending through aligned openings therein, the first link being pivotably connected with the assembly by a second shaft and the second link being pivotably connected to the table by a third shaft, the first, second and third shafts being parallel to one another, the second link having at least one outwardly extending mounting tab adjacent the first shaft, and a locking lever having a handle and a locking blade at opposite end portions and a pivot portion with a pivot connection therebetween for pivotably mounting the lever to the tab, the blade being configured to fit within a gap between adjacent surfaces of the first and second links when the guide mechanism is in one of its extended or retracted positions and the lever is moved into a locked position.

[0015] Embodiments of the present invention are disclosed which are directed to a power miter saw that has a base, a rotatable table, a miter arm assembly for angularly positioning the table relative to the base, a saw blade and motor assembly that is operatively connected to the table as well as a multiple hinged linear guide mechanism that is configured to have the saw blade and motor assembly move in a generally horizontal path so that work pieces that are placed on the table that have a width that exceeds the normal width of cutting that can be accomplished by merely moving the blade downwardly into the cutting position. The movement in the horizontal path enables a much wider work piece to be cut.

[0016] With the capability of the linear guide mechanism to move the saw blade and motor assembly between fully extended and fully retracted positions, the size capacity of work pieces that can be cut by the saw is increased as described above. However, there is a desirability for locking guide mechanism in its fully retracted position for performing chop cuts where the horizontal movement along the path is unnecessary. It is also desirable to lock it in its fully extended position for transporting the miter saw to and from a jobsite, for example.

[0017] The embodiments of the present invention include a locking lever that is configured to cooperate with features of the linear guide mechanism which are also part of the embodiments of the present invention, for locking the linear guide mechanism in either its extended or retracted position. The locking lever is operative in an intuitive, easy to use manner and is extremely reliable, inexpensive to manufacture and in connection with the features of the linear guide mechanism, elegant in its design simplicity.

[0018] Turning now to the drawings, and particularly FIG. 1, a miter saw, indicated generally at 10, is illustrated and includes a base 12, a rotatable table 14 that has a top surface 16 upon which a work piece can be placed. The table 14 is pivotably connected to the base 12 for rotation, the rotation of which is controlled by a miter arm assembly, indicated generally at 18. The miter arm assembly 18 generally has the capability of having a quick release for placing the table at an appropriate desired angle so that miter cuts as desired can be made and also has a knob which can be tightened to lock the table in a desired position to cut a particular miter angle. The miter saw 10 preferably has left and right adjustable fence portions 20 and 22, respectively, for holding a work piece in a desired position.

[0019] The table 14 has a rear bevel adjustment structure, indicated generally at 24, which has a generally horizontal shaft 26 about which a generally vertical extension blasting 28 can be rotated about the shaft 26. The saw 10 includes a saw blade and motor assembly, indicated generally at 30, which includes a housing 32, which includes a motor 34, with the housing 32 including a gear mechanism (not shown) that drives a blade 36. The housing also has a head structure which includes a generally horizontal shaft (not shown) about which the blade and motor assembly can be rotated from an elevated rest position downwardly into a cutting position. A handle 40 is used by an operator to pull the blade and motor assembly downwardly in a cutting position and is preferably biased upwardly toward its rest position.

[0020] The saw 10 includes a multiple link hinged linear guide mechanism, indicated generally at 50, shown in FIGS. 1-5, with FIGS. 2-5 showing the guide mechanism in an enlarged manner. The linear guide mechanism 50 includes a horizontal hinge, indicated generally at 52, comprised of links 54 and 56 which are pivotably connected together by pivot connection 58 that preferably comprises a shaft that is seated in bearings or the like in a manner that substantially eliminates any play in the pivot connection and thereby provides a high degree of accuracy during operation.

[0021] The link 54 is also pivotably connected to the extension casting 28 by a pivot connection 60 and the link 56 is connected to the head structure of blade and motor assembly housing 32 by a pivot connection 62. The pivot connections 58, 60 and 62 are parallel to one another and are generally horizontal in their orientation relative to the table top 16 when the bevel setting is zero, i.e., the extension 28 is also perpendicular to the table top 64.

[0022] The linear guide mechanism 50 also includes a vertical hinge, indicated generally at 66, which includes links 68 and 70 that are connected together by pivot connection 72 with the link 68 also being connected to the extension casting 28 by pivot connection 74 and the link 70 is connected to the housing 32 by pivot connection 76 as best shown in FIGS. 6 and 7. The three pivot connections 72, 74 and 76 are parallel to one another and are generally vertically oriented and also perpendicular to the orientation of the pivot connections 58, 60 and 62 of the horizontal hinge 52. The pivot connection 74 connects the links 68 to a bracket 78 that is formed with the extension casting 28 as best shown in FIGS. 4 and 5.

[0023] All of the pivot connections of the linear guide mechanism are preferably shafts that are journaled in bearings in a configuration whereby there is virtually no play in the joints which would result in anything but pivotal movement of the links relative to one another or to structure to which they are attached so that the stability of the miter saw is excellent which results in accuracy of the cuts that are made by the saw.

[0024] As should be understood from the interaction of the horizontal and vertical hinges 52 and 66, the linear guide mechanism 50 causes the shaft 62 to move in a linear path that is preferably substantially parallel to the plane of the table top 16. The linear guide mechanism 50 enables the blade and motor assembly to be moved from its extended position as shown in FIGS. 1, 4 and 5 where the blade is moved to the right of the fence as shown in FIG. 1 to a retracted position as shown in FIGS. 2, 3 and 6 where the blade is in position to desirably perform chop cuts on work pieces that are placed in abutting contact with the fence 20, 22.

[0025] As previously mentioned, it is desirable to have a miter saw with the reciprocating movement capability as has been described with regard to the saw 10. It is also desirable to be able to lock the linear guide mechanism in its retracted position where chop cuts are made by a user and the linear guide mechanism does not “roll out” from the cutting position. In keeping with the present invention, a locking lever, indicated generally at 80, is provided, which together with the configuration of the links 68 and 70 of the vertical hinge 66 enables the linear guide mechanism to be locked in either of its extended or retracted positions. In this regard, the locking lever 80 is pivotably mounted to the link 68 and can be moved between locked position as shown in FIGS. 1, 3, 5, 6 and 7 or an unlocked position as shown in FIGS. 2 and 4.

[0026] When the locking lever 80 is in its locked position, it fits within two adjacent gapped surfaces of links 68 and 70 which prevents the pivot connection 72 from pivoting. The configuration of the links near the pivot connection 72 is important. Referring initially to FIGS. 2 and 3, it is shown that the link 70 has upper and lower end portions 82 and 84 with a recess 86 therebetween in which a tongue portion 88 of the link 68 fits. It should be apparent that the pivot connection 72 fits within openings in the upper and lower end portions as well as the tongue portion 88 to define the pivot connection.

[0027] The link 68 has an outwardly extending tab portion 90 that has an aperture 92 therein for receiving a pin or bolt 92 for providing a pivot connection to the locking lever 80. The locking lever 80 is shown in detail in FIGS. 8 and 9 and has a handle portion 94 at its right end thereof, a locking blade 96 at the left end portion thereof and a pivot portion 98 between the handle and blade 94 and 96. The pivot portion 98 has a lower portion 100 with a reduced thickness in which a nut for a bolt used to interconnect the locking lever 80 with the tab 90 can reside without extending beyond the outermost surface of the portion 98.

[0028] The blade portion 96 has opposite faces 104 and 106 which are slightly inclined to more easily be rotated into locking engagement. The pivot portion 98 also has a stop extension 108 with a back surface 110, an end surface 112 and a stop surface 114 which is configured to prevent the locking lever from rotating more than approximately 60° when it is in its unlocked position as shown in FIG. 2, for example. The mass of the blade portion 96 relative to the pivot portion 98, as best shown in FIG. 9, enables the design of the locking lever to be such that the center of gravity prevents the locking lever 80 from engaging due to gravity when it is in the disengaged or unlocked position.

[0029] Alternative embodiments can utilize a spring clip 120 such as is shown in detail in FIG. 10 and also in FIGS. 2-5. The clip includes a base portion 122 having side wings 124 with apertures 126 which are configured to be spaced apart to enable the locking lever 80 to fit between the wings 124 and be held in place by the pin or bolt that interconnects the locking lever 80 with the tab 90. The clip 120 has a forward extension 126 and a clamping portion, indicated generally at 128, that includes angled surfaces 130, 132, 134 and 136 for engaging the surfaces 108, 110, 112 and 114 of the pivot portion 98 of the locking lever 80. For example, as shown in FIG. 2, when the locking lever 80 is in its disengaged or unlocked position, it is apparent that the inside surfaces of portions 132 and 134 of the clip 120 are in contact with the back surface 110 of the pivot portion 98 of the locking lever 80. Also, as is evident from FIG. 3, when the locking lever is in its locked position, the surface 134 of the clip 120 is contacting the end surface 112 of the pivot portion 98 of the locking lever 80. The spring clip 120 is preferably configured to require an operator to impose a force significantly greater than gravity to engage and disengage the locking lever 80.

[0030] As previously mentioned, the configuration of the links 68 and 70 is designed to interact with the locking lever 80 to lock the linear guide mechanism 50 in either its extended or retracted positions. This is best shown in FIGS. 6 and 7 which is a top view of the links 68 and 70 together with the locking lever 80 shown in its locked position, with FIG. 6 showing it being locked in the retracted position and FIG. 7 in its extended position. The link 68 which has the tab 90 upon which the locking lever 80 is pivotably connected has a surface 140 that is configured to engage the surface 104 of the blade portion 96 whether it is locked in the extended or the retracted position.

[0031] When it is in the retracted position and referring to FIG. 6, the surface 106 of the blade 96 is positioned to engage a surface 142 of the link 70. The distance between the adjacent surfaces 140 and 142 defines a gap that is generally slightly larger than the thickness of the blade portion 96 at its maximum dimension, i.e., at the top of the blade portion 96 as shown in FIG. 9. When the linear guide mechanism is placed in its extended position, and referring to FIG. 7, then a surface 144 is positioned to contact the surface 106 of the locking lever 80.

[0032] A rubber bumper 150 may be provided which as shown in FIG. 6 would tend to urge the links 68 and 70 apart which would apply some degree of compression of the blade 96 to hold it in a locked position if the embodiment did not include a spring clip 120.

[0033] 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.

[0034] Various features of the invention are set forth in the following claims.