BACKGROUND OF THE INVENTION In conventional saw blades, it is the usual practice, after each of the teeth have been formed at a uniform height, to set the pattern by combining teeth set in a slight bend in the direction of the thickness of the bandsaw blade (the transverse direction) with unset teeth which are not bent in the transverse direction.

When a saw blade is sawing a workpiece, chips are produced which are almost the same thicknesses as the thickness of the backing of the saw blade.

This makes it very difficult to discharge these chips to the outside from the space between the groove formed by the sawing action in the workpiece and the backing of the saw blade. Specifically, the chips have a tendency to collect in the gullet formed between the teeth of a conventional saw blade. Once this gullet is filled with chips, these chips cause the saw blade to be elevated in the feed direction of the cut relative to the workpiece. In proportion to the amount by which the saw blade is elevated, it produces a course deviation to the right or left relative to its direction of travel. Accordingly, in conventional saw blades the problem is produced by which the cut veers to the direction of the deviation.

In addition, in conventional saw blades, when the blade continues to cut the workpiece after chips have collected in the gullet, the chips are compressed so that the problem arises whereby the pressure of the chips cause breakage of the saw teeth. In conventional saw blades, although there are slight differences in height between the tips of the unset teeth and the tips of the oppositely set teeth, for example, when taken from the locus of the center of the thick portion of the unset teeth, the tips of each tooth are almost the same height. Therefore, when the workpiece is being cut, the unset teeth are not always the first teeth to cut into the workpiece. The oppositely set teeth can also be the first to cut into the workpiece. For example, when the left-set teeth are the first to cut into the workpiece, the cutting resistance causes the saw to have the inclination to swing to the right side. Specifically, there is the problem in a conventional saw that vibration and deviation of the cut in the transverse direction is easily produced.

Moreover, the productivity rates desired in cutting of materials have been continually increasing. This increase in productivity has generally been accomplished by using higher cutting speeds or greater down feed pressures (cutting rates). These conditions impose greater demands on the cutting blades. As speeds increase harmonic vibrations within the blade cause teeth to become damaged, high sound levels, and irregular cuts.

In order to meet the production demands of those who need high cutting rates, products are required which will cut quietly with minimum vibration yet at high speeds. Carbide tip products have been introduced which allow for greater loading of the teeth and greater speeds, but top speeds are limited by vibration of the saw. A tooth form is needed which will minimize vibration of the saw, allow high feed rates, maintain a straight cut and yield a smooth cut surface.

PRIOR ART REFERENCES The following patents are related to the present invention as background information: 4,011,783 Mar. 15,1977 Circular Saw 4,423,553 Jan. 3,1984 Blade for a Saw...

4,557,172 Dec. 10,1985 Saw Blade 4,727,788 Mar. 1,1988 Saw Blade 4,813,324 Mar. 21,1989 Saw Blade 4,827,822 May 9,1989 Saw Blade 5,331,876 Jul. 26,1994 Saw Blade...

5,425,296 Jun. 20,1995 Saw Blade 5,477,763 Dec. 26,1995 Saw Blade 5,603,252 Feb. 18,1997 Saw Blade WO 98/07545 Feb. 26,1998 Tooth Structure...

5,832,803 Nov. 10,1998 Tooth Structure...

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a blade that has reduced vibration. It is also an object of this invention to provide a blade that will allow high feed rates and high speed of cutting.

It is a further object to provide a blade that maintains a straight cutting path. It is another object to provide a blade that has an improved surface finish on the cut surface.

This invention thus provides a novel tooth form consisting of a combination of at least two un-set teeth and at least two set teeth. The two un- set teeth are of different height and cut a channel, which stabilizes the cutting blade. The two set teeth are positioned to clear a kerf channel to allow for passage of the blade. The teeth are positioned in such a way as to minimize vibration of the cutting blade. Several benefits result from this invention including a quite operation, enhanced straightness of the cut and a smooth cut surface.

The unique feature on this tooth form is the use of two unset teeth, the first tooth being the highest followed by one that is lower, but wider. Two set teeth that serve to widen the kerf follow these two unset teeth.

In especially preferred embodiments of the present invention, one or more of the following modifications may be employed to enhance the performance of the tooth form described herein: (a) chamfer one or more of the teeth, especially the set teeth, for improved surface finish; (b) side grind a clearance into one or more of the teeth, to provide more efficient cutting; (c) the highest tooth can be made wider than the next highest tooth, to provide smoother cutting and less noise; (d) the flat portion of the highest tooth may advantageously be more than 1/3 the width of the tooth, thereby providing greater strength and resistance to breakage.

One or more of these modifications can likewise be used to improve the above-described prior art tooth forms; especially those disclosed in U. S.

4,827,822 and WO 98/07545.

Thus, the present invention includes a tooth form comprising two high guiding teeth followed by one or more sequences of set teeth which are either in pairs or other arrangements, and which optionally include varying set magnitudes and varying number of teeth.

The present invention will serve as the tooth form for a new range of carbide products, including a variable tooth carbide tip product, as well as ground tooth bimetal products including power hacksaw blades and circular saw blades.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1, in views A, B and C, show typical grinding profiles for the teeth used in the invention. View A shows the grinding profile of un-set tooth 1.

View B shows the grinding profile of un-set tooth 2. View C shows the grinding profile of the set teeth 3 & 4.

Figure 2, in views A and B, illustrates the preferred geometry of set tooth 3 (View A) and set tooth 4 (View B) after being set. Note-these could be reversed.

Figure 3, in views A and B, illustrates the preferred relationship of the tooth profiles to one another. This relationship provides the desired PENTA- CHIPrm formation during cutting.

Figure 4, in views A and B, illustrates the preferred tooth form in both plan (View A) and top views (View B).

Figure 5, in views A and B, illustrates further improvements to the preferred tooth form.

Figure 6, in views A, B, C, and D, shows preferred tooth profiles, chamfer angles, side grinding angles, and other specific preferred tooth form details.

Figure 7, in views A and B, shows another embodiment of the present invention, an even pitch, variable pitch 1.4-1.8 carbide tip tooth form.

Figure 8, in views A and B, shows another embodiment of the present invention, an even pitch, variable pitch 2-3 carbide tip tooth form.

Figure 9, in views A and B, shows another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is illustrated in the Figures accompanying this specification. As illustrated therein, this invention covers a special tooth form that is composed of at least two un-set and at least two set teeth arranged so that the un-set teeth cut a channel in the work piece. This channel enhances stability of the blade much the same as a rudder on a ship. The set teeth, in turn clear the kerf for passage of the blade. The use of more than one un-set tooth and having these un-set teeth at various heights and rake angles allows the blade to cut efficiently in a variety of materials.

The variable heights and variable rake angles also permit the blade to cut in a fashion which minimizes vibration of the blade which is detrimental to performance when using hard materials such as carbide. The use of set teeth to clear the kerf area allows for more clearance angle than can normally be achieved through grinding a carbide tip and thereby allows for a smooth cut surface.

The preferred embodiments of the invention have a group of two un-set teeth ground so that the second tooth in the group is lower and wider than the first tooth in the group. This group of un-set teeth is immediately followed by a group of two set teeth, which are of the same shape and height. The height of these set teeth are lower than either of the two un-set teeth and the set magnitude allows the teeth to extend beyond the widest of the two un-set teeth.

One or more of these teeth are side ground such that the widest portion of the tooth is greater than the thickness of the blade. This arrangement results in forming five chips before repeating. Figure 3 shows the preferred overlay of teeth and the five chip, or PENTA-CHIPTM, formation.

Figures 5 and 6 show modifications to the preferred PENTA-CHIP blade design. The specific changes were to increase the flat portion of the highest tooth from 0.017" to 0.022", and to change the height difference between tooth 1 and 2 from 0.002" to 0.0053". These changes match the volume of chips generated by cutting to the volume of the gullet, and will allow for optimum cutting rates. Figures 7-9 show additional embodiments of the blade design.

Further Blade Modifications: Many cutting blades rely upon setting the teeth to expose the tooth tips and allow efficient cutting. Setting the teeth also serves to cut a width (called "kerf') which is greater than the thickness of the blade and thereby allow more efficient passage of the blade body through the work. Prior art shows arrangements of these set teeth wherein the magnitude of displacement from the side of the blade varies and creates a broaching type of functionality as the kerf generated by the blade is made wider (see, U. S. Patent No. 4,727,788 and U. S. Patent No. 4,813,324).

When setting the teeth of a blade it is common to encounter variations in the magnitude of set and the angle of the set tooth. These variations occur due to minor differences in position of the tooth during setting, variations present in the milling cut that generates the tooth pitch, variations in the mechanical properties of the material, variations in the geometrical characteristics of the blade, variations in the milling cutters used to generate the tooth form, or variations in the setting operation itself. This multitude of variations reduces the chance that the cutting blade will be made to the intended cutting geometry.

One method, which can reduce these variations, involves the use of grinding to generate the required tooth geometry. Grinding is used in high performance products such as a standard triple chip product (see, U. S. Patent No. 4,011,783) to various custom ground configurations (see, U. S. Patent No.

5,425,296 and U. S. Patent No. 5,477,763). While grinding usually increases the cost of the blade it is effective in reducing variability. This generally increases performance consistency and precision.

A combination of grinding and setting has been used to create blades that will clear a larger kerf than would be permitted with a blade that is only form ground. This type of tooth form (see U. S. Patent No. 5,331,876) is still susceptible to the same types of variability mentioned above for standard set type product.

Patents pertaining to the use of grinding to create tooth forms on cutting blades have been generally restricted to creating blades which have symmetrical profiles when the cutting tooth is viewed from the front of the tooth. Exceptions to this statement occur with ground tooth forms such as those shown in U. S.

Patent No. 4,423,553 which combines a ground or filed tooth form with setting of this tooth to create a wide cutting kerf. In some cases, this ground tooth has been combined with relief grinding of the blade such as is seen with standard ground relief jigsaw blades.

Accordingly, the skilled artisan will appreciate the fact that further improvements in performance can be achieved through greater precision in the manufacture of the product. In addition, performance improvements have been obtained using arrangements of teeth, which cut preferred portions of the workpiece. Ground tooth forms that cut designated chips or areas of the kerf will provide cutting consistency and precision benefiting the end user.

EXAMPLES Three blades were tested for cutting rate, noise and surface finish generated during cutting under the following conditions: Machine Daito Downfeed Setting Varied 3 to 6 Tension Setting 18 Speed 112 SFPM (unless modified as noted) Coolant Standard (10%) Test Material T304-4%-inch diameter ground stainless steel bar This testing showed that the 11/2-inch 2.5/3.5 PENTA-CHIPTM blade design was quieter than two commercially available comparison blades (CTIII 11/2 inch 2TPI and 11/2 inch 2 3MR-Simonds Industries, Inc.) as speed was increased.

The CTIII blade cut quietly but had shadowing of the set pattern on the cut surface. Noise was good at 112 SFPM and 138 SFPM but was quite loud and unacceptable when run at 171 SFPM.

The 3MR blade had some squealing on the cuts, which could be due to a lack of break in. The noise was considerable at the 171 SFPM speed setting and would be unacceptable in production.

At 171 SFPM the PENTA-CHIP blade was generally as quiet as the machine. It was noted that when the PENTA-CHIP blade made noise it was for very short time periods (usually only a second or two). Two additional runs were made, one at a lower speed (90 SFPM), which was exceptionally quiet and another at a higher speed (210 SFPM), which was much quieter and tolerable when, compared to the 3MR.

The set teeth on the PENTA-CHIP blade were face ground (7 degrees) before setting. This presents a negative face angle to the cut, which is not commonly used when cutting stainless steel. Ideally, face grinding will be done after setting. The cutting times for the PENTA-CHIP were still better than the comparison bands. After face grinding this blade, it was run at speeds from 90 SFPM to 210 SFPM and was as quiet as the machine at all speeds. Feed rate was varied and did not affect noise of the band. The quality of the cut surface was excellent.

Comparison of 3MR product to PENTA-CHIP Product The table below compares important geometric features of the 3MR tooth form to the PENTA-CHIP tooth form: Geometrical Parameter 3MR Product Special Titanium Grind PENTA-CHIP Grind Face Rake Angle6TF Primary Back Angle 20° 14° 22° Secondary Back Angle 40° 40° 45°/52° High-Low height Diff. 003". 007". 002" The PENTA-CHIP design can thus be considered a"next generation"of the Simonds 3MR product. The two highest teeth in the PENTA-CHIP design do most of the cutting while the two set teeth serve to only widen the kerf to allow easy passage of the blade through the work. Due to this unique cutting arrangement, the effective pitch of the PENTA-CHIP blade is considerably coarser than one would expect upon initial examination. The 2.5/3.5 pitch, which has 4 teeth in a 1.407 distance, would normally be considered to have an effective tooth pitch of 2.8 TPI. However, the two set teeth cannot be considered cutting teeth which leaves the cutting rate and aggressiveness of the blade related to the two high teeth. This implies that the blade will have the cutting action of 2 teeth in the repeat length for an effective pitch of 0.7 TPI.

One advantage of the PENTA-CHIP over the 3MR product arises from the infeed moderating effects caused by the set teeth. Whereas a coarse pitch blade like the 0.7 TPI mentioned above would feed without much control particularly in thin sections, the PENTA-CHIP product will have an additional two teeth in the work to prevent a feed rate that would damage the blade. This feed control could be adjusted by changing the primary back angle of the set teeth (teeth 3 and 4) or through the use of more pairs of ground and set teeth.

A negative effect also occurs due to this unique design. The wear rate or effective service life of the blade is determined by the wear rate of the two high teeth. It is known that a blade with more cutting teeth will offer greater overall life at the sacrifice of cutting speed. The PENTA-CHIP blade would be expected to have the life of a carbide tip 3MR blade having a pitch of 7 TPI. However, because of the increased number of teeth due to the set teeth, it can be used in applications where such a coarse pitch would be prohibitive.

CHROME/COBALT CUTTING TEST One PENTA-CHIP band of 1-1/2"x. 055 2.5/3.5 18'10-1/2"was tested on a Cosen AH-2028H Bandsaw. The band had been face ground to 7 degrees, after setting.

The testers noted that prior to this cutting test, they had never had a blade cut the Chrome with Cobalt Experimental materials as fast (19 minutes).

When lightly loaded the PENTA-CHIP blade tended to squeal, but when loaded it quieted down.

GULLET VOLUME STUDIES Area calculations on the gullet of the PENTA-CHIPTM tooth form are shown below. In order to optimize performance of this product, it is believed that the volume of the chip made by each tooth (Chip area x gullet length) should be related to the gullet volume (gullet area x band thickness).

Such ratios have been calculated for the 0.002-inch difference between the high tooth to the lower tooth that was used for early versions of the PENTA- CHIP product. Next such ratios were calculated for a theoretical optimum difference of 0.007 inches.

Relationship between Chip Volume and Gullet Volume For two variations of the 2.5/3.5 PENTA-CHIP Tooth Form The following calculations are based upon a 0.002-inch difference in height between tooth 1 and tooth 2: Tooth No. 1 2 3 4 Chip Volume 0. 0000446 0. 0000661 0. 0000075 0.0000087 Chip Vol Ratio 100.0% 148.1% 16.8% 19.5% Gullet Volume 0. 0019952 0. 0015508 0. 0008075 0.0010905 Ratio 100.0% 77.7% 40.5% 54.7% The following calculations are based on a 0.007-inch difference in height between tooth 1 and tooth 2: Tooth No. 1 2 3 4 ChipVolume 0. 0000659 0. 0000472 0. 0000075 0.0000087 Chip Vol Ratio 100.0% 71.7% 11.4% 13.2% GulletVolume 0. 0019952 0. 0015508 0. 0008075 0. 0010905 Ratio 100.0% 77.7% 40.5% 54.7% These calculations suggest that much more set can be put on the product without fear of filling the small gullets, or conversely, that modifications could be made on tooth cutting.

The present invention has been described in detail, including the preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on this invention and still be within the scope and spirit of this invention as set forth in the following claims.