Cutting by use of rotating axially moving tool – Tool or tool with support – Having axial – core-receiving central portion
Reexamination Certificate
2002-05-13
2003-11-04
Bishop, Steven C. (Department: 3722)
Cutting by use of rotating axially moving tool
Tool or tool with support
Having axial, core-receiving central portion
Reexamination Certificate
active
06641338
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to saws used for cutting circular holes through objects made of wood and various other materials, of the type utilizing a cylindrical saw cup coaxially fastened to an arbor holding a pilot drill which protrudes forward of cutting teeth provided on a front annular surface of the saw cup. More particularly the invention relates to a hole saw which automatically ejects a plug sawed from a workpiece, in which hole saw cups of various diameters and having different sized attachment bores may readily be interchangeably mounted on a novel single-ended arbor-holder by a twisting, snapping action.
B. Description of Background Art
In U.S. Pat. Nos. 4,741,651 and 5,096,341, the present inventor disclosed plug ejecting hole saws which utilize a left-hand threaded mandrel or arbor that holds a pilot drill, the shank of which is secured in an enlarged diameter flange or collar located at the front end of the arbor. The arbor is screwed into a threaded, arbor-holder bore disposed coaxially though a bushing or thicker portion of a circular disk-shaped base plate which forms the rear end wall of a cup-shaped saw body which has angled circumferentially spaced apart cutting teeth in the front annular end wall thereof. In a hole saw cup of this type, the front, cup-shaped portion of the saw cup and the thicker rear base plate or arbor-holder bushing are generally fabricated as separate metal parts which are brazed together. Thus, this type of hole saw is sometimes referred to as a “bi-metal” hole saw.
A novel feature of the inventions disclosed in the aforementioned patents of the present inventor comprises left-hand threading of both the outer surface of the arbor and the inner threaded bore through the saw cup base. With this arrangement, when the arbor is threaded counterclockwise into the saw cup arbor-holder bore, as viewed from the front of the saw cup and pilot drill end of the arbor, the front flange portion of the arbor advances rearwardly to seat against the inner front wall surface of the saw cup base. The arbor shank, which protrudes rearwardly from the saw cup base is then secured in the collet of a power drill. When the power drill is powered on to turn the pilot drill bit and saw in the usual clockwise cutting direction, as viewed from the rear, shank end of the bit, a counterclockwise reaction torque is exerted on the saw cup teeth by frictional resistance offered by workpiece in response to the cutting action, tending to further tighten and secure the arbor flange against the inner surface of the saw cup base. When the saw cup has penetrated the thickness of a workpiece such as a door panel, a cylindrically-shaped plug of workpiece material becomes lodged tightly within the saw cup, and in prior art hole saws, is difficult to remove from the saw cup. However, in accordance with the '651 and '341 patents, a plug lodged within the saw cup may readily be ejected by powering the drill in a reverse, i.e., counterclockwise direction after a hole has been bored through a workpiece, while maintaining the saw cup stationary. Rotating the drill shank and arbor in a counterclockwise direction by the power drill causes the arbor to be advanced axially forward within the threaded bore of the saw cup, and the front flange of the arbor to abut the rear surface of the plug and eject it forward out of the saw cup bore.
The above-described plug ejecting feature of hole saws disclosed in the present inventor's '651 and '341 patents has provided a highly effective and widely accepted improvement in bimetal hole saws. Subsequent to issuance of those two patents, U.S. Pat. No. 5,435,672 was issued for adapters having a left-hand threaded arbor-receiving bore, and a right-hand external bore. The adapters were designed to be threaded into right-hand threaded arbor-holder bores of existing saw cups, thus accommodating left-hand threaded arbors and permitting the present inventor's novel plug ejecting function to be accomplished using existing hole saw cups having right-hand threaded arbor-holder bores.
Although the novel plug ejecting hole saws disclosed in the present inventor's '651 and '341 patents constituted a substantial advancement in the art for hole saws having a base provided with a threaded bore for receiving an arbor, there is another type of widely employed hole saw cup which formerly could not utilize the advantageous plug ejecting construction disclosed in those patents. This type of hole saw is sometimes referred to as a “Carbon” type, since it uses hole saw cups fabricated as a unitary structure, e.g., a deep drawn cup, made from high carbon steel. In this type of hole saw, the saw cup base is made of relatively thin stock, thus precluding the use of threaded bore through the base as a means for attaching the saw cup to an arbor. Instead, hole saws with thin base walls are typically provided with a non-circular, e.g., a double-D-shaped central bore through the base, which receives the complementary-shaped, enlarged rear portion of an arbor which is secured to the base by a threaded fastening member.
In response to a need for a plug ejecting hole saw which may utilize thin base wall, non-threaded saw cups of the type described above, the present inventor developed a plug ejecting hole saw which utilizes thin base wall, non-threaded saw cups having an oblong or “double D”-shaped attachment bore. That device, described in U.S. Pat. No. 6,341,925, Plug Ejecting Hole Saw With Twist-Locking Interchangeable Saw Cups, includes an arbor holder comprising a slotted cylindrical body coaxially held in spring biased, longitudinally slidable disposition within a collar. The slotted cylindrical body has a pair of longitudinally disposed, diametrically opposed grooves formed in opposed flats formed in a nose piece portion of the cylindrical body which protrudes forward from the collar. Each longitudinal groove longitudinally slidably holds a locking tab which is spring biased forwardly to an outward position to thereby block an adjacent one of a pair of circumferential grooves formed in two curved portions of the nose piece located between the two flats. The locking tabs are pushed axially rearward against the spring force by a saw cup base to unblock the circumferential grooves, enabling peripheral edge wall surfaces of the saw cup bore to be rotated into the circumferential grooves, thereby preventing relative longitudinal movement between the saw cup and the arbor holder. When the saw cup has been rotated sufficiently far, the locking tabs spring forward into the larger radius, curved portions of the saw cup attachment bore to thereby lock the arbor holder to the saw cup for both clockwise and counterclockwise rotations.
An embodiment of the device disclosed in the '925 patent includes a second, rear nose piece protruding from the cylindrical body at the opposite longitudinal end from the front nose piece, the rear nose piece being of a different size to fit saw cups having a different size attachment bore than the front nose piece, a second spring bias means, a second pair of locking tabs, and frictional means to position the cylindrical body and nose piece portions axially centered within the collar. The present invention was conceived of to provide a plug ejecting hole saw which utilizes a novel single-ended arbor holder that is interchangeably and bi-directionally lockable to saw cups having at least two different sized attachment bores.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a plug ejecting hole saw including an arbor-holder which can be attached to hole saw cups of various body diameters and attachment bore sizes.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which can be secured to the base of a hole saw cup with non-threaded fastening means including a single spring-loaded locking tab.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-h
Bishop Steven C.
Chapin William L.
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