Patent Application
20090229436
The invention relates to power tools and more specifically to power tools for installation of flooring.
An undercut saw is a specialty circular power saw used by flooring installers for undercutting walls, moldings, door jams, and cabinetry so that new floors may be installed underneath. When the area is undercut using the saw, the new flooring is simply slid underneath the undercut area, which saves time and presents a visually appealing finish. Without an undercut saw, the flooring should be precisely cut to fit around these areas, which is laborious, costly, and often leaves unsightly gaps.
Most existing undercut saws have been constructed with a fixed blade guard assembly which consists of two telescoping parts that serve both as a blade guard and a height adjustment mechanism for the saw. As shown in
There are practical considerations of this existing height adjusting mechanism with respect to the fasteners used to hold the telescoping members at a desired height. The following is a history of various fastener combinations that have been used. In existing early model undercut saws, the fasteners used were carriage bolts socketed into square holes in the downwardly protruding back edge 240 of the top plate 140. The carriage bolts extending from the back of the top plate passed through slots in the height adjustment skirt forming threaded ends for mounting additional fasteners. First mounted on these threaded ends were so-called “guide washers”, which were specialized cast shapes designed to move within channels formed on a back surface of the height adjustment skirt. Last mounted on these threaded ends were wing nuts which were tightened down on the guide washers. The clamping force generated by the wing nuts pressured the guide washer against an outer surface of the height adjustment skirt, while the downwardly protruding back edge of the top plate was drawn against the inner surface of the height adjustment skirt by the pulling action of the carriage bolt. This clamping force frictionally held the top plate at a desired height within the height adjustment skirt.
In some more recent existing saws, one of which is shown in
Existing guide washers have typically been generally trapezoidal cast shapes with a semi-circular inside surface 315 that precisely mates with the curved outer surface 305 within guide washer channel 380 of the height adjustment skirt 160. Two or three guide washers along with two or three sets of the aforementioned fasteners have been used on existing saws.
Since the rotary power unit 180 and rotatable circular saw blade 220 are fixedly assembled onto top plate 140, the height at which top plate 140 is frictionally held by the fasteners determines the height of cut. The top plate 140 may be frictionally held at any point in a vertical range of about one inch within the height adjustment skirt 160. This enables the height of cut for circular saw blade 220 to be set from floor level (i.e., flush to the floor or no height of cut) to a height of one inch above floor level.
The characteristics of these guide washer and fastener mechanisms for these existing height adjustment mechanisms are as follows: First, the guide washers sometimes do not frictionally hold the assembly together with sufficient force, and the top plate can shift within the height adjustment skirt as the saw is being used. Particularly as the user lifts and places the saw at various locations around a jobsite, the weight of the saw motor can cause the top plate to slip downward within the height adjustment skirt. As a result, in some places the undercut is not of sufficient height, and the user has to re-adjust and re-cut many areas.
Another characteristic of the existing fastening mechanisms and guide washers is that they do little to ensure that the top plate (and thereby the blade) is always parallel with the flat floor surface on which the saw rests during use. The blade should be kept parallel to the floor during undercutting so that the blade will not angle up or down in relation to the floor during a cutting operation. Keeping the blade parallel with the floor surface ensures that the height of undercut will be consistent. Otherwise, angling of the blade may cause the blade to wedge upward or downward. This can result in inconsistent height of cut. Angling of the blade can also bog down the motor during a cutting operation, or even cause the saw to kick back. An improved height adjustment mechanism that worked to prevent the top plate from being set at angles that are not parallel to the floor could prevent undesirable inconsistencies in the height of cut, and would promote safer usage by reducing the possibility of saw kickback.
The use of such existing telescoping height adjustment mechanisms fastened with guide washers and threaded fasteners was preferred for simplicity and low cost. However, various different mechanisms for setting and holding the height of cut for an undercut saw have been designed to address slippage and blade angling during use. Such designs have largely not been adopted because they were impractical for jobsite conditions or too expensive to manufacture. For example, U.S. Pat. No. 5,784,789 to Vargas discloses an undercut saw with a rack-and-pinion mechanism for height adjustment. The undercut saw of this disclosure employs a grinder based power unit. A circular saw blade is mounted onto its spindle. A cylindrical sleeve is mounted to the grinder motor to cover the rotating spindle. The sleeve has a rack formed in its back side. The sleeve is assembled into a base. The base holds the pinion. Thus, as the pinion is turned, the rack on the sleeve causes the power unit and blade to move up or down. The rack and pinion design ensures that blade will move up and down in a precise manner that keeps the blade parallel with the floor at all times. Two screws threaded through the base may contact the sleeve to fix the sleeve at a given height. The rack and pinion mechanism of saw proved too expensive for mass production, and was prone to binding from saw dust. As a result, it was not widely adopted.
U.S. Pat. No. 6,678,960 to Williams discloses an undercut saw with a housing which rests on a floor surface and itself has a fixed height. A tapped sleeve is mounted on top of the housing. A rotary motor with a central axis and a threaded case may be threaded into the tapped sleeve. The blade when mounted on the central motor armature axis may be moved up and down within the housing as the threaded case is turned within the tapped sleeve. The height is fixed by means of a jam nut also threaded onto the threaded case. This threaded adjustment mechanism ensures that the blade will be kept parallel to the floor at all times. The tapped sleeve and large threads on the motor housing of this design proved too expensive for mass production. This mechanism was also prone to binding from saw dust. Furthermore, the requirement that the blade be mounted on a central armature axis about which the entire assembly turned required that only motors such as routers having a single, central armature axis (without any offset spindle gear) could be employed. Such high RPM low torque motors are not powerful enough for large amounts of undercut sawing. In particular, a great deal of power is used by a saw to undercut an inside corner area. Williams' saw as disclosed could not perform such cuts, due to its bulky blade housing.
Other mechanisms for fixing the height of cut are disclosed within this application, including rack-and-pinion, frictional, interlocking, and lead screw mechanisms. With regard to Williams' lead screw mechanism, this is shown in
A lead screw mechanism such as Williams' “jack screw” generally requires a secondary holding mechanism besides the lead screw to hold the mechanism in position. Otherwise, an accidental bump on the lead screw knob or even vibration during use can cause the mechanism to shift unexpectedly. For Williams, the separate frictional mechanism of clamp 76 provides such a secondary holding mechanism.
Williams' jack screw design presents many manufacturing challenges that make it cost prohibitive. Much as with the threaded case of the embodiment previously discussed, Williams jack screw embodiment has a specialized motor housing having a precisely shaped outer “case” capable of sliding within a sleeve. This is not preferred as most commonly available power units come in the shape of a grinder or circular saw, and such power units have no such precisely shaped case. Furthermore, the tightening clamp used to frictionally hold the case within the sleeve is a large, tight tolerance slide fit mechanism which would entail high machining cost to produce. A lead screw mechanism which did not engage the case of the power unit would be preferred as just about any power unit could be employed.
A lead screw mechanism that worked in conjunction with existing low cost guide washers and fastener assemblies could provide additional support for the existing telescoping top plate and height adjustment skirt at a much lower cost. Such would be preferred as a low cost mechanism to provide the benefits of reduced slippage and angling of the blade. Williams teaches that “peripheral studs” (carriage bolt or wing screw fastener assemblies) or “wing nuts”, are “slow because several fasteners require adjustment” (Background of the Invention, paragraph 3).
Some existing undercut saws have been manufactured with a grinder motor as a power unit. As shown in
Existing grinders typically have a second handle formed in the shape of a threaded post fastenable into tapped holes on either side of the aluminum spindle housing. Such threaded posts extend out quite a distance from either side of the spindle housing, which is preferred during a grinding operation to provide counter leverage for the user. However, such a handle assembly is not suitable for use in undercut saws. The extension of the handle prevents the saw from entering tight areas, such as inside corners.
For this reason, as shown in
The use of bolts 480 and lock washers 460 to bolt a second, forward, movable handle, such as U-shaped handle 440, to spindle housing 420 is preferred for simplicity and low cost. The user can tighten down the bolts 480, and the lock washers 460 tend to hold the handle in place. The handle 440 can also be rotated backward (i.e., towards the first, back handle 380) whenever the saw is used to undercut in a low clearance area, such as underneath the toe-space of a cabinet.
However, if the user pushes excessively hard on U-shaped handle 440, it can rotate forward (towards blade 220). This is not preferred as this puts the user's hand in closer proximity to blade 220. Forward rotation is also not preferred, because whenever the handle is oriented at such an angle, the saw is less able to operate in tight areas, such as inside corners. Some added mechanism to prevent the forward handle of the saw from rotating forward from the normally preferred 90 degree angle would be a usability and safety improvement. A more solid handle and better mounts on the spindle housing could provide such an improvement. However, as previously explained, this handle should also be able to rotate backward for undercutting beneath a toe-space.
An undercut saw is primarily used to undercut walls, door jams, and cabinet areas so that new flooring materials may be fit underneath. Some flooring materials are very thin, such as sheet vinyl or linoleum. To provide the proper undercut for thin sheet vinyl, the undercut saw should cut flush to the floor. For this reason, in most existing saws, as shown in
It is an object to provide an undercut saw with an improved mechanism for guiding the telescoping motion of the top plate and the height adjustment skirt so that during height adjustment the top plate tends to stay parallel with the base of the saw, thereby keeping the blade parallel to the floor surface upon which it is placed during use.
It is an object to provide an undercut saw with an improved mechanism for holding a top plate at a fixed elevation within a height adjustment skirt which is economical enough for mass production.
It is an object to provide an undercut saw with an improved handle fastening mechanism which may be more rigidly fixed to the spindle housing of a grinder motor, which may be adjusted to various angles, but stopped from certain angles that are not preferred.
It is an object to provide an undercut saw with additional safety mechanisms which may be removably mounted to the fixed and movable guards.
The device has several embodiments including an undercut saw with a fixed guard assembly comprising a telescoping top plate and height adjustment skirt, with some embodiments including improved guide washers including an added guide washer slot runner. Certain other embodiments include a lead screw mechanism threaded vertically through the guide washer to assist in setting and holding a height of cut. In certain other embodiments having a right angle grinder motor for their power unit, the saw includes a handle with a pattern of teeth encircling a hole in the handle for mounting the handle to the saw's spindle housing. In addition, a similar pattern of interlocking teeth is formed at a handle mount location on at least one side of the saw's spindle housing. The teeth on the handle and the spindle housing may thus interlock to allow the handle to be fixedly joined at a range of preferred angles. The handle and the spindle housing may additionally include certain bosses acting as stops to prevent the handle from being rotated forward to certain angles which are not preferred. Certain other embodiments include removable cover plates covering the blade to increase safety which may be removed to enable the saw to cut flush to a floor surface.
The improved guide washer may incorporate any one of several added features. The first feature, which will be described herein as a “guide washer slot runner”, is a boss or projection extending from the inner surface of the guide washer. This projection is sufficiently long and has a precise width to extend (with a small degree of play) into its corresponding slot in the height adjustment skirt. In existing saws, the slots in the height adjustment skirt served only to allow passage of the bolts extending through the guide washers to fasten into the downwardly protruding back edge of the top plate. The added guide washer slot runner extends into and may contact the edges of the slots in the height adjustment skirt to guide the telescoping motion of the top plate and the height adjustment skirt during adjustment. This helps keep the base of the height adjustment skirt parallel to the top plate. This helps ensure that the top plate will be adjusted in a manner that keeps the blade parallel to the floor surface.
The guide washer may include an additional tapped hole through a vertical cross section, for receiving an added threaded member. This threaded member may be rotatably fastened on the base of the saw's height adjustment skirt using a collar or other nut type fastener. This threaded member thus forms a lead screw mechanism capable of lifting or lowering the guide washer (and thereby the top plate and blade). Such a lead screw mechanism may be included on one or more guide washers in the assembly, though it is preferred they be used on all such guide washers. This is so the height of cut can be adjusted incrementally on all sides through equal turns of all threaded members. The threaded members provide added support to hold the desired height of cut and prevent slippage. The guide washers may still include the existing fasteners such as wing screws threading into the downwardly protruding back edge of the top plate to provide a second frictional mechanism to hold the height of cut.
In embodiments including a grinder motor for a power unit, the second, forward, movable handle may be affixed to the spindle housing with corresponding circular patterns of interlocking teeth on one or more sides of the handle and the spindle housing. In one embodiment, a two piece handle assembly is provided, made in two halves joined by a pivot pin. The pivoting action of the halves allow the assembly to be closed or opened to enable interlocking or disengagement of the circular tooth patterns on the handle and the spindle housing. When these circular tooth patterns are interlocked, a secure joint is produced between the components preventing unexpected rotation during use. The handle may be pivoted open for adjustment backward to a number of angles to enable the saw to be used in low clearance areas, such as under toe spaces. Added stops on the handle and the spindle housing prevent the handle from rotating to forward angles (acute angles less than 90 degrees) in relation to the long armature axis of the saw.
For improved guarding, removable cover plates may be added to the bottom of the downwardly protruding back edge of the top plate, the bottom surface of the height adjustment skirt, or the movable guard. These cover plates may be removed to enable flush cutting when installing thin flooring materials, such as sheet vinyl.
As shown in
Top plate 2140 has a downwardly protruding back edge 2240 which forms a semi-circular vertical edge surface. Height adjustment skirt 2160 has an inside face 2260 which also forms a corresponding semi circular vertical edge surface. The downwardly protruding back edge 2240 of top plate 2140 and inside face 2260 of height adjustment skirt 2160 together form precisely mating telescoping surfaces. Base 2450 is an integral part of height adjustment skirt 2160. Base 2450 has a bottom surface 2451 which is the surface upon which the saw rests or is moved while in use.
To fix the height of top plate 2140 in relation to base 2450, top plate 2140 has a tapped hole 2300 which is centered in the location of a corresponding slot 2310 in height adjustment skirt 2160. Wing screw 2280 extends through a horizontal hole 2325 in guide washer 2320 and is threaded into tapped hole 2300 in downwardly protruding back edge 2240 of top plate 2140. Guide washer 2320 has an added guide washer slot runner 2330. As shown in greater detail in
In this embodiment, guide washer slot runner 2330 runs in a slot 2310 to guide the motion of height adjustment skirt 2160 during height adjustment. Others skilled in the art might imagine similar combinations of slots through the height adjustment skirt and bosses (guide washer slot runners) on an inner face of the guide washer which could run in the slots to perform the same function. Such may include multiple slots in the outer face of the height adjustment skirt, for multiple guide washer slot runners on an inner face of the guide washer. One such slot may be the slot provided for passage of a fastener used to fasten the top plate within the height adjustment skirt. Alternatively, the slot may have no other function than for receiving the boss forming a guide washer slot runner. The slot itself may be a slot or a groove of only partial depth in the outer surface of the height adjustment skirt performing the same function of receiving a slot runner. However, the embodiment of
In this embodiment, when height adjustment is performed, normally the saw is turned upside down and rested on the second, forward, movable handle (as shown as undercut saw 100 of
As used herein, and as shown in
As shown in
As shown in
Once inserted in hole 8080, pan head screw 8060 extends vertically up from base 8100 and may be threaded into tapped hole 8040 in guide washer 8020. Next, collar 8210 is fastened onto pan head screw 8060 at an elevation forming a slight gap between the bottom of collar 8210 and a top surface 8260 of base 8100. This gap enables pan head screw 8060 to rotate within hole 8080. (More secure, lower cost alternatives exist for pan head screw 8060 and collar 8210 will be described later.) Finally, for ease of turning, a knob such as three arm knob 8140 may be fastened on top of pan head screw 8060.
The lead screw mechanism formed by a threaded member such as pan head screw 8060 and tapped hole 8040 may be included in one or more of the guide washers included in the fixed guard assembly for the saw. As shown in
In addition to the added lead screw mechanism supporting the height of the guide washer, the guide washer may also include additional frictional mechanisms to further assist in holding the desired height of cut. As shown in
In this embodiment as shown in
In embodiments including both this type of lead screw mechanism as well as a guide washer fastener assembly for frictional holding force (such as wing screw 8160), the guide washer preferably includes a guide washer slot runner such as guide washer slot runner 8025. In such an embodiment, guide washer slot runner 8025 performs a different function in that it prevents guide washer 8020 from rotating when lifting force is applied by pan head screw 8060. The reason such rotation is generated and is not preferred is as follows: Tapped hole 8040 for pan head screw 8060 is offset at least some distance from through hole 8300 for passage of wing screw 8160 through guide washer 8020. Otherwise, these components would interfere with each other and not perform their desired function. With this offset, in the absence of guide washer slot runner 8025, pan head screw 8060 would lift guide washer 8020 on one side, causing it to rotate on wing screw 8160. An added feature on guide washer 8020 resists such rotation. An added guide washer slot runner 8025 can bear against the inner edges of slot 8290 during adjustment, thus preventing such undesirable rotation. Therefore, in such an embodiment, guide washer slot runner 8025 performs an important, though somewhat different function.
As previously explained, pan head screw 8060 is rotatably affixed to base 8100 of height adjustment skirt 8120 by collar 8210. Collar 8210 is affixed to pan head screw 8060 at a slight elevation above a surface 8260 on a top face of base 8100 forming a slight gap that permits such rotation. However, when the saw is lifted off the floor, collar 8210 performs the additional function of stopping pan head screw from sliding through countersunk hole 8080 through base 8100. Collar 8210 is affixed to pan head screw 8060 by means of a set screw 8211 which may be tightened down on the threads of pan head screw 8060 at the desired height. However, collar 8210 is an expensive custom component with a set screw 8211 which may come loose and cause the assembly to fail.
As shown in
During height adjustment, as shown in
As defined herein, for the embodiments of
To provide an improved handle for grinder-activated undercut saws, the second, forward, movable handle may be formed from two parts joined by a pivot pin. A toothed surface may be formed on at least one inside surface of a handle which may interlock with a corresponding toothed surface formed on an outer surface of the grinder motor spindle housing. As with existing saws of this kind, and as shown in
The improved handle for the saw is formed from a first, left half 3460, a second, right half 3480, and an upper pivot pin 3500. Left half 3460 is overlapped at relief 3520 with relief 3540 in right half 3480. Pivot pin 3500 is press fit into upper hole 3580 in right half 3480 and through upper hole 3560 in left half 3460 to join the two halves. Thus, the two halves may be pivoted closed to enable interlocking of the circular tooth patterns on the handle and the spindle housing, or pivoted open to permit disengagement or disassembly. This assembly of the left half 3460 and right half 3480 with pivot pin 3500 may be referred to as handle assembly 3510.
Left half 3460 and right half 3480 have circular tooth patterns 3600 and 3620 (respectively) formed on their inside surfaces which may engage corresponding circular tooth patterns 3640, 3660 on the left and right hand sides of spindle housing 3420 (respectively). Threaded four arm screws 3680, 3700 may be inserted through left mounting hole 3720 in left half 3460 and right mounting hole 3740 in right half 3480 (respectively). Threaded four arm screws 3680, 3700 may further thread into a tapped left mounting hole 3760 and tapped right mounting hole 3780 to join handle assembly 3510 to spindle housing 3420.
The circular tooth patterns 3600, 3620 of left half 3460 and right half 3480 are designed to interlock with corresponding circular tooth patterns 3640, 3660 in the left and right sides of spindle housing 3420 and will provide a fixed and solid joint when they are pressed together by threaded four arm screws 3680, 3700. Because these teeth patterns are circular, handle assembly 3510 may interlock and become fixedly joined to spindle housing 3420 at a number of angles. As more clearly illustrated in
As shown in
As shown in
Left half 3460 and right half 3480 may be economically produced as aluminum castings and will easily handle much greater pushing force than existing U-shaped undercut saw handles fastened by lock washers and bolts. A flexible rubber coating such as plastisol may be added to form a softer, slip-resistant gripping surface on the outer surface of handle assembly 3510.
To add removable guarding structures to the bottom portion of the fixed guard of the undercut saw, removable cover plates may be added to any of the height adjustment skirt, movable guard, or top plate. Such removable cover plates may be positioned so as to cover at least a portion of the circumference of the blade past the depth of the teeth. As shown in
As defined herein, in relation to cover plates which may cover the blade, the phrase “past the depth of the teeth” shall describe a cover forming a radius as measured from the center of the circular saw blade which is shorter than a radial distance to the outermost circumference of the circular saw blade. For example, cover plate 4820 mounted on base 4450 covers blade 4810 to a radius alpha (in relation to the center of the circular saw blade 4810). Radius alpha is a shorter radius than radius delta to the outer circumference of the circular saw blade 4810. Similarly, cover plate 4860 mounted on movable guard 4840 covers blade 4810 to a radius beta (in relation to the center of the circular saw blade 4810). Radius beta is a shorter radius than radius delta.
In an another embodiment, as shown in
It will be apparent that various alternatives may be implemented. The Detailed Description discloses a number of additional features, any one of which may be added alone or in any combination to an undercut saw to improve saw design. The handle features and the blade height features may be used separately or together. Although
This application claims priority from U.S. provisional application No. 61/035,704, filed Mar. 11, 2008.
| Number | Date | Country | |
|---|---|---|---|
| 61035704 | Mar 2008 | US |
