Improved portable circular saw

Abstract: This invention is related to a portable circular saw that includes a footplate (24) such that the saw may be operated at an angle of up to sixty degrees from the perpendicular with respect to a board or other workpiece that is to be cut.

Description: This invention is related to portable circular saws. In particular, it is an improved portable circular saw that includes a footplate such that the saw may be operated at an angle of up to sixty degrees from the perpendicular with respect to a board or other workpiece that is to be cut. A portable circular saw comprises a circular saw blade, a motor to drive the blade, typically through reduction gearing, a support structure, a handle, a blade guard, and a foot or footplate. The footplate is typically either a drop foot or a pivot foot, either of which is designed to rest on a surface that is being cut, and is made to move to adjust the depth of cut and provide support for the motor and blade. A drop foot moves essentially parallel to itself and generally perpendicular to the axis of rotation of the saw blade and is often arranged to rotate with respect to a cut line to allow the saw to cut at an angle other than perpendicular to the surface of a workpiece. A pivot foot is constructed to rotate about two axes, one that is parallel to the axis of the saw blade to allow selection of the depth of cut and one that is contained in a plane perpendicular to the axis of the saw blade to allow selection of the angle of cut. The foot supports the portable circular saw on the surface of a workpiece to cut at an angle that may be other than perpendicular to the surface. Portable circular saws are typically made in two styles. One style, called sidewinder, parallel shaft or simply circular saw, has an electric motor that is placed with its shaft parallel to the axis of rotation of a circular saw blade, so that the motor speed is reduced by a set of spur gears, typically, although not necessarily, helical spur gears. The other style of portable circular saw, called a worm drive circular saw, or more recently a hypoid gear variation thereof, has an electric motor that is placed with its shaft in a plane perpendicular to the axis of rotation of the saw blade, so that the speed reduction is produced by a set of worm gears or a hypoid gear set. For either the sidewinder or the worm drive, saw cuts at an angle to the surface of the material being cut are guided by a foot such as those described above. The saw is rotated about front and rear pivot points on an axis parallel to the cut that is to be made and at an angle determinded by a setting of the blade with respect to the foot. Pivotal movement of the motor and blade can also take place about a hinge having an axis parallel to the axis of the rotation of the saw blade. The hinge may be associated with either the front or rear pivot. This pivotal movement is effected in a direction so that the motor is raised from or lowered to the surface of the material being cut. The motor is rotatably adjustable about the front and rear pivot points with respect to the foot and is typically adjustable continuously up to an angle of 45°, since cuts at angles greater than 45° have had to be made by cutting the workpiece while tilting the saw or the workpiece. This is very dangerous and is not recommended. The foot has a quadrant that is usually marked at angles of 0, 15, 30 and 45 degrees and is often fixed with detents to mark these angles for increased convenience in angle cutting. US-A-3,078,885 and US-A-3,733,701 both disclose a circular saw comprising: a footplate with an opening therein to accomodate a saw blade; a motor housing assembly connected to said footplate and accomodating a drive motor; a drive shaft journalled in said housing assembly and being drivable by said motor; a circular saw blade mounted on said drive shaft by a blade bolt and washer; a front and rear pivot point on said footplate and connected to said motor housing assembly for enabling said housing assembly and said attached saw blade to be rotated around an axis parallel to the foot plate and perpendicular to the drive shaft, the rotation axis being located above the footplate; a quadrant indicating the angle over which the housing assembly is pivoted by the front and rear pivot points; pivoting means coupled to one of the front and the rear pivot points for enabling the depth of the saw blade extending below the foot plate to be adjusted by pivoting the motor housing assembly about the pivoting means in the plane of the saw blade; a depth of cut indicating bracket mounted on the footplate at the end opposite the pivoting means to indicate the depth of the saw blade extending under the foot plate in length units when the housing assembly is pivoted about the pivoting means. It may be desirable to make a cut with a portable circular saw at an angle as great as 60° to the surface of a workpiece. This would be especially likely in cutting what is often referred to as "two-by" or "2X" lumber in a single cut and would be very advantageous. This would be an advantage in that it would increase efficiency in general carpentry and in particular in framing work, which is a specialized branch of carpentry devoted to erecting wooden frames for structures. The present invention provides a portable circular saw which is characterized in that the pivot points allow said housing assembly and said attached saw blade to be rotated up to 60°; in that the quadrant comprises stop means limiting the pivoting of the housing assembly up to 45°; in that the depth of cut indicating bracket comprises manually operatable means for overriding the stop means and for limiting the pivoting of the housing assembly up to 60°; and in that the depth of cut indicating bracket is provided with an indication of an angle of 60 ° beyond the indicia of length units, and being at such a position that the depth of the saw blade extending beyond the foot plate is sufficient to make a saw cut in wood with the maximal indicated thickness under an angle of 60°. The improved portable circular saw disclosed herein permits rotation of the saw blade up to an angle of 60° from the vertical with respect to the foot and the surface of the workpiece. These and other objects of the present invention will be more fully understood in conjunction with the accompanying drawings in which like numerals represent like components and in which: FIG. 1 is an isometric view of the novel circular saw; FIG. 2 is a side view of the blade side of the novel circular saw; FIG. 3A is a side view of the depth-of-cut bracket associated with the circular saw; FIG. 3B is an end view of the depth-of-cut bracket of FIG. 3A; FIG. 4 is a front view of the quadrant having indicia thereon which indicate the angle of rotation or angle of cut to be made for a given rotation of the motor and saw blade with respect to the footplate; FIG. 5 is a schematic representation of a footplate cross section illustrating the depth-of-cut bracket and the manner of adjusting the depth of cut of the saw by pivoting the saw about a pivot device such as a hinge; FIG. 6A is a schematic representation of a front cross-sectional view of the footplate illustrating the bevel angles of the saw blade with respect to the footplate; FIG. 6B is a schematic representation of a front cross-sectional view of the footplate illustrating the bevel angles of, the saw blade with respect to the footplate when the depth of cut of the saw has been adjusted upwardly to provide clearance between the saw blade and the footplate; FIG. 7 is an isometric view of the spring stop that provides a positive stop at 45° and requires manual operation to allow the saw blade to be adjusted beyond 45° to the 60° position; FIG. 8A is a front view of a forward hinge plate used as a pivoting device about which the motor and saw blade are adjusted for depth of cut; FIG. 8B is a top view of the hinge plate of FIG. 8A; FIG. 9 is a cross-sectional view of the footplate taken along the width of the footplate and illustrating the rear pivot point; FIG. 10A is a front view of the quadrant and hinge with the spring stop in the 0° position; FIG. 10B is a front view of the quadrant with the spring stop at 45°; FIG. 10C is a front view of the quadrant with the spring stop at 60°; FIG. 11 is a plan view of the footplate; and FIG. 12 is a side view of the footplate. The novel circular saw for cutting 60° bevel angles is illustrated in an isometric view in FIG. 1 and in a side view in FIG. 2. The saw 10 includes an upper guard 12 and a lower guard 14 which houses a circular saw blade 16. The saw blade is attached to a motor in guard 18 by means of a bolt 19. The saw is operated by the user grasping handles 20 and 22. A foot or footplate 24 forms the base for the saw 10 and the saw is mounted to foot 24 by front and rear pivots 26 and 28, respectively. As will be more fully described hereafter, these pivot points allow the circular saw blade 16 to be tilted with respect to the foot 24 from the vertical up to 60° for cutting various beveled angles. In addition, the forward end of upper guard 12 of the circular saw 10 is attached at hinge 30 for movement in the vertical plane to regulate the depth of cut. While the hinge 30 is shown attached to the front pivot point 26, it could be attached at the rear pivot point 28 by any type of hinge such as a ball-shaped mounting well-known in the art. A depth-of-cut bracket 40 is associated with rear pivot point 28 and is attached to the saw guard 12 to regulate the depth of cut by pivoting the saw 10 with respect to hinge point 30 in the vertical plane to raise or lower blade 16 with respect to the foot 24. Lower guard 14, as is well known in the art, pivots about the center of the saw blade 16 to uncover the blade as it is fed into the work to cut a particular material. A side view of the depth-of-cut bracket 40 is illustrated in FIG. 3A. The main body 42 of the bracket 40 is arcuate in shape and has a center slot 44 through which a bolt on guard 12 can project with a quick lock thereon to lock the saw at a particular angle as designated on the bracket 40 for regulating the depth of cut of the saw. The bracket is attached to the footplate by flange 46 which has an orifice 48 therein through which the bolt at the rear pivot point 28 is attached. It will be noted that various indicia 50 are imprinted on the bracket 40. Thus, if the saw were tipped upwardly about pivot point 30 to the top of bracket 40, the saw would be set for cutting plywood. As the other indicia indicate, there are locations identified for cutting 6.3 mm material, 9.5 mm material, 12.7 mm material, 15.9 mm material, 19.1 mm material, 25.4 mm material and 50.8 mm material. The notation 60° is also indicated. The 60° graduation mark is at an angle of approximately 7° and 381 m above the horizontal. This is important as will be discussed hereafter. FIG. 3B is an end view of the depth-of-cut bracket 40 illustrating the mounting flange 46 with orifice 48. The quadrant 32 is illustrated in detail in a front view in FIG.4. Front pivot point 26 of the saw 10 illustrated in FIG. 1 and FIG. 2 has a bolt or rivet that passes through orifice 52 of quadrant 32 shown in FIG. 4. The quadrant 32 is attached to footplate 24 in any well-known manner such as by welding, riveting or bolting. Welding is preferred. Note that quadrant 32 has indicia 54 thereon including angles from 0°-60°. It also has a slot 56 therein for purposes that will be discussed hereafter. As stated earlier, the nominal dimension of "2-by" lumber is actually about 25.4-38.1 mm in planed lumber or lumber that has been cut to the plane dimension. In order to cut through a piece of 2X lumber at an angle of 60°, the blade 16 will have to extend below the foot 24 a minimum distance of 76.2 mm. This is true because the hypotenuse of the right triangle formed by the 60° cut times the cosine of 60° will have to equal 25.4-38.1 mm. Since the cosine of 60° is .5, the hypotenuse will have to equal 76.2 mm which would be the vertical depth of the saw extending below footplate 24, as illustrated in FIG. 5. In the schematic illustration as shown in FIG. 5, the saw blade 16 is illustrated in solid lines positioned along line 58 illustrating the angle of tilt about hinge point 30 necessary for a bevel cut at a 60° angle. FIG. 5 also illustrates in dotted lines the position of saw blade 16 at the horizontal line 60 and in dotted lines the position of saw blade 16 along the 2X cut line 62. In each case, the saw would be held at the desired angle by means of a well-known quick-lock bracket attached to the depth-of-cut bracket 40. It is important that the hinge point 30 be of such a distance above footplate 24 that when the saw is adjusted to line 58 designating a 60° bevel cut, the saw blade 16 protrudes below footplate 24 the minimum distance of 76.2 mm. The importance of this requirement will be shown with relation to FIGS. 6A and 6B. FIG. 6A illustrates the saw blade 16 along position 64 which is in the vertical plane. Since this is a diagrammatic representation of the saw taken along a cross section of the footplate 24 from one end, it will be understood that the saw blade 16 can be pivoted to the 45° angle (not shown) and to the 60° angle as illustrated by line 68. Note that at the 60° angle along line 68, the bolt 19 which holds the saw blade 16 on the shaft of the drive motor is in contact with the side of footplate 24. Notice, however, in FIG. 6B that when the saw blade 16 is pivoted about hinge point 30 to the 60° line 58 as illustrated in FIG. 5, that the head of the bolt 19 and the blade washer 21 are raised sufficiently that they clear the side of footplate 24 and neither makes contact. Thus, by adjusting the saw blade 16 to the indicia indicating a 60° cut on depth-of-cut bracket 40 as shown in FIG. 5, and then rotating the saw blade 60° as shown in FIG. 6B, the desired 60° bevel cut through 2X lumber can be made without interference between the blade bolt 19 and washer 21 with the workpiece or the footplate. A spring stop 70 shown in isometric view in FIG. 7 is used in conjunction with the hinge in FIGS. 8A and 8B and the quadrant 32 in FIG. 4 to provide a positive lock at 45° so that the saw blade 16 cannot be tilted beyond 45° until stop spring 70 is physically moved out of place, as will be shown hereafter, to allow the saw to be further tilted to a 60° angle for the 60° cut. Thus, the 45° cut is automatically obtained and the 60° cut must be manually obtained. Thus, hinge 30 illustrated in FIG. 8A has as an integral part thereof a U-shaped bracket 72 with legs 74 and 76 having orifices 78 and 80 respectively therein for mounting the forward end of upper guard 12 to the hinge 30. The orifice 82 is coupled to the front pivot point 26 shown in FIG. 1 and FIG. 2. The hinge 30 has a projecting arm 84 from which extends a projection 86 with an arcuate slot 88 therein. The spring stop 70 is also mounted about pivot orifice 82 of hinge 30 and has a projection 90 which extends through arcuate orifice 88. Because a circular pin 92 on hinge bracket 30 extends through orifice 94 of spring stop 70, spring stop 70 moves with hinge 30 as it pivots about the center of orifice 82. FIG. 10A illustrates the quadrant 32, hinge 30 and spring stop 70 when the saw blade 16 is in the vertical position. A bolt having a head 35 and a body 31 shown in cross-section is part of positive lock arm 33 in FIG. 1 and is slidably mounted in slot 56 of quadrant 32 and slot 88 of hinge 30. As shown in FIG. 10B, when the hinge 30 is pivoted, it carries bolt 31 with it. When hinge 30 has been pivoted sufficiently far that the bolt body 31 contacts the end of slot 56 on quadrant 32, the motor can no longer pivot and the saw blade is at the 45° position. This position is a positive stop. To rotate the motor beyond the 45° position where the motor is now locked, spring stop 70 must be manually depressed so that the projection 90 moves out of slot 88 in hinge 30 and away from the bolt head 35 and the saw guard and blade can then continue rotating to the 60° mark where it automatically locks again when the bottom of slot 88 of hinge 30 contacts bolt body 31. Thus, the saw is automatically positioned at 45° simply by rotating or pivoting the saw and when it reaches 45° it can no longer rotate because spring stop 70 contacts bolt head 35. In this manner, an automatic stop is provided for the 45° position. The position for the automatic stop at 45° is illustrated in FIG. 10B. After the spring stop 70 is manually removed from contact with bolt head 35 in the 45° locked position, the motor can then be rotated to 60° until the bottom of slot 88 of hinge 30 contacts bolt body 31 as illustrated in FIG. 10C. FIG. 9 is a cross-sectional view of footplate 24 illustrating the rear pivot point to which the depth-of-cut bracket 40 is preferably attached by projection 46 and orifice 48 (shown in FIG. 3B). FIG. 11 is a plan view of the footplate 24 that is specially designed for mounting the circular saw 10 such that it can be rotated at an angle to cut a 60° bevel. Note that the foot 24 has strengthening ribs 94 as well as raised edges 95 on the periphery thereof to give rigidity and strength to the foot 24. Front area 98 is the area on which the quadrant 32 is mounted as by riveting or preferably welding, as explained previously. The saw blade 16 extends in a vertical plane through opening 96 with the rear of the saw mounted to pivot point 28 and the front to pivot point 26 on the quadrant bracket 32 when it is attached to area 98. As best seen in FIG. 11, edge 99 of foot 24 has portions 106 and 109 removed sufficiently to allow the upper guard 12 to clear the foot 24 when the saw is in its 60° position. In addition, an elongated recess 110 is formed in one side of opening 96 of footplate 24 to accommodate the lower guard when it is tipped into the 60° position for cutting a 60° bevel. Without having the elongated recess 110, the saw 10 could not rotate sufficiently far to perform a 60° bevel cut. When the saw is at the angle of 60° for cutting a 60° bevel cut, it is important that the lower guard be rotated partially to the rear to widen the gap between the forward end of the lower guard and the underside of foot 24 to provide sufficient clearing between the saw blade 16 and the workpiece. To accomplish that rotational movement of the lower guard 14, a rib 104 is formed on the one side of footplate 24 not only as a strengthener for the narrow side of footplate 24, but also to contact a sloping surface 27 on the lower guard 14 to force the sloping surface and the attached lower guard to move or rotate in the direction of arrow 29 and widen the gap that exists between the front edge 15 of the lower guard 14 and the lower portion of the footplate 24 automatically. The opening 102 in edge 99 allows the sloped surface 27 on the guard to clear the edge 99 and enables the entire saw to be tipped a full 60°. The side view of the footplate 24 is illustrated in FIG. 12 wherein the recessed surface 100 for the blade bolt 19 that holds the saw blade to the motor shaft can be seen. Further, the recesses 106 and 109 which allow the upper guard 12 to be accommodated are also shown. Also, the opening 102 and the rib 104 for causing the lower guard 14 to move such that it opens the gap between the front edge 15 of the guard 14 end the footplate 24 can also be seen. Recess 112 end sloped edge 114 on the other side of opening 96 accommodate the other side of upper guard 12 when the saw is tipped to make the 60° bevel cut. Orifice 116 accommodates the lower leading edge 118 of the upper guard 12 when the unit is tipped in a 60° position. Thus, the entire saw is designed in conjunction with the footplate 24 so that it can be tipped or rotated 60° to perform a 60° bevel cut without any portion of the saw blade or guards contacting the footplate 24. This allows the lower guard 14 to be fully and automatically rotated as needed during making the cut and yet it will restore itself automatically to the shielding position when the saw is removed from the workpiece. In addition, the cut is entirely through a 2X workpiece. Thus, there has been disclosed a novel portable circular saw that can cut a 60° bevel angle on a workpiece and cut entirely through 2X material at the 60° angle. This is accomplished by using an 210 mm diameter blade, mounting the unit on a footplate with front and rear pivot points that are of a distance above the top of the footplate such that at least a minimum amount of the saw blade protrudes below the footplate so that at an angle of 60° the saw can cut entirely through a 2X workpiece. The ability of the novel saw to accomplish this 60° cut includes not only the ability to rotate 60° about front and rear pivot points, but also to pivot upwardly about a hinge or pivoting device so that the various components of the saw which would normally strike the footplate in the 60° position are raised sufficiently to avoid striking the foot piece 24. In conjunction with the ability of the saw to change its depth of cut position to that necessary for enabling a 60° bevel cut and causing the components of the saw that project to the side to miss the footplate 24, portions of the footplate have been removed sufficiently to allow the upper and lower guards 12 and 14 to clear any contact with the footplate 24. Also, there has been disclosed a novel latching mechanism that allows the saw to be rotated to the 60° position but it must come to a positive stop at the 45° position and then be manually released to rotate further to the 60° position. This is a safety feature of the invention which is important.

Claims: Circular saw (10), comprising: a footplate (24) with an opening therein (96) to accomodate a saw blade (16); a motor housing assembly (18) connected to said footplate (24) and accomodating a drive motor; a drive shaft journalled in said housing assembly (18) and being drivable by said motor; a circular saw blade (16) mounted on said drive shaft by a blade bolt and washer (19,21); a front and rear pivot point (26,28) on said footplate (24) and connected to said motor housing assembly (18) for enabling said housing assembly and said attached saw blade (16) to be rotated around an axis parallel to the foot plate (24) and perpendicular to the drive shaft, the rotation axis being located above the footplate (24); a quadrant (32) indicating the angle over which the housing assembly (18) is pivoted by the front and rear pivot points (26,28); pivoting means (30) coupled to one of the front and the rear pivot points (26,28) for enabling the depth of the saw blade (16) extending below the foot plate (24) to be adjusted by pivoting the motor housing assembly (18) about the pivoting means (30) in the plane of the saw blade (16); a depth of cut indicating bracket (40) mounted on the footplate (24) at the end opposite the pivoting means (30) to indicate the depth of the saw blade (16) extending under the foot plate (24) in length units when the housing assembly (18) is pivoted about the pivoting means (30), characterized in that the pivot points (26,28) allow said housing assembly (18) and said attached saw blade (16) to be rotated up to 60°; that the quadrant (32) comprises stop means (70) limiting the pivoting of the housing assembly (18) up to 45°; that the depth of cut indicating bracket (40) comprises manually operatable means (88,90) for overriding the stop means (70) and for limiting the pivoting of the housing assembly (18) up to 60°; and that the depth of cut indicating bracket (40) is provided with an indication of an angle of 60 ° beyond the indicia (50) of length units, and being at such a position that the depth of the saw blade (16) extending beyond the foot plate (24) is sufficient to make a saw cut in wood with the maximal indicated thickness under an angle of 60°. A circular saw as in claim 1 wherein the pivoting means is a hinge (30) located at the front of the motor housing assembly (18). A circular saw as in claim 2 further including: a lower pivotal saw guard (14) on the housing (18) for shielding the blade (16) when the saw is not in cutting use; means for holding the guard (14) in a first rotated position with respect to the footplate (24) at an angle of the saw of 0° from the vertical; a sloping projection (27) on the lower guard (14); and a rib (104) on the footplate in a location to contact the lower guard (14) sloping projection (27) when the saw blade (16) is tilted to the 60° position to cause the lower guard (14) to move to a second position to facilitate proper operation of the lower guard (14) as the 60° cut is made. A circular saw as in claim 3 further including: a quadrant (32) associated with the front pivot point (26) to indicate the angle of rotation of the motor housing (18) and the saw (16); means (31,33,56) associated with the quadrant (32) for locking the motor housing (18) and saw (16) at 45°; and means (70) associated with the quadrant (32) and locking means to manually override the lock and allow the housing assembly (18) and saw (16) to rotate to 60°. A circular saw as in claim 4 further including means (106,109) for providing sufficent clearance between the lower guard (14) and the footplate (24) when the saw is in the 60° position such that the lower guard (14) automatically returns to its blade-shielding position after a 60° cut is completed. A circular saw as in claim 5 wherein the clearance providing means comprises recesses (106,109) and orifices provided in the footplate (24) at points where interference would normally occur between the footplate (24) and the upper guard (14) and blade bolt and washer (19,21) when the blade (18) is rotated at the 60° angle and tilted about the hinge to the 60° indicia on the depth-of-cut bracket so as to prevent any interference of the footplate (24) with the upper guard (12) assembly and blade bolt and washer (19,21).

Inventors: ESPARZA RAYMOND R, MANGIALARDI GREGG M, TECHTER RONALD R, ESPARZA, RAYMOND R., MANGIALARDI , GREGG M., TECHTER, RONALD R.
Applicants: EMERSON ELECTRIC CO, EMERSON ELECTRIC COMPANY
Application year: 1991
Main classification: B27B9
IPC codes: B27B9