MXPA97007204A - Synchronized variable teeth configurations for sier - Google Patents

Abstract

A variable pitch band saw is provided which has a serrated edge comprising a plurality of recurring groups of teeth. Each group includes a non-fixed front tooth and a plurality of teeth that are fixed laterally to the opposite sides of the saw. Each tooth has a cutting edge disposed in a predetermined cutting plane and an accumulated step distance between the former and the next preceding sawtooth, having a cutting edge in the same plane with the previously determined plane. The size of the throat area of each tooth is made directly proportional to the accumulated step distance of that tooth so that the sizes of the throat areas are the same for all teeth that have the same accumulated step. Each group of teeth may include teeth of varying height and degrees of lateral fixation. Some of the teeth in each group have a step measured from the tip of one of the teeth to the tip of a tooth adjacent to one to avoid uniform tooth separation between all teeth of the group.

Description

CONFIGURATIONS OF SYNCHRONIZED VARIABLE TEETH FOR SAWS This application is a partial continuation of my related Patent Application, Serial Number: 08 / 408,847, filed on: March 23, 1995, entitled: "Synchronized Variable Tooth Arrangements for Saws" which was abandoned in favor of this Application .

FIELD OF THE INVENTION This invention relates to configurations of the teeth for band saw blades, and more particularly, to a sawtooth configuration in which the area of the throat that precedes each of the teeth in the direction cutting, is directly proportional to the distance of accumulated passage of each of said teeth and in which at least some teeth are separated from other teeth by pitch distances that are different in way to inhibit the repetitions in cadence that are generated by the tips of the teeth that make contact with the work.

BACKGROUND OF THE INVENTION [0002] For some time, those skilled in the art of band saw blades have recognized that a sawtooth edge having a "variable pitch" tooth pattern will avoid the problems of excessive noise and viion that they produce the separated teeth equally impacting the work in equal time intervals, the final result being substantially reduced noise levels and the increase of the life of the blade. Although band saw blades have generally developed as a distinct ch of the cutting tool technique, separate from other cutting tools and other types of saws, it has always been common practice to use variable pitch tooth patterns. on the cutting edges of the cylindrical hole saws for more reliable cutting operations. Historically, "variable pitch" sawtooth patterns are composed of repetitive sawtooth groups that are configured with progressive variations in the pitch between successive pairs of teeth in the cutting direction of the saw blade. The variations are in the distances of the passage between the corresponding points of the adjacent teeth, v. gr., the distance of passage between the tips of the adjacent teeth of the saw. The variations in the step begin at the initiating end of the saw and extend towards the terminal end of the sierra; they are generally cyclic from fine to coarse and return to fine again, or vice versa. One skilled in the art of band saw blades will recognize the references of "fine" or "coarse" in relation to a pattern of the saw teeth, such as referring to the pitch distance between an adjacent front pair of teeth that is less or fine in relation to a coarse, or greater pitch distance between another adjacent pair of rear teeth in the pattern. This does not mean that these teeth are higher or lower than others, if measured from a given reference line along the saw. Examples of previous attempts of variable pitch type saw blades, those described in United States of America Patent Number: 2,227,864 and United States of America Patent Number: 2,568,870. Both patents describe saws that have finer teeth at the front end of the blade with teeth that gradually become thicker, after which they again become thin. The cycle is repeated over the entire length of the mountain range. The throats also go along the same progression. Thus, these patents are related to progressively changing the sizes of both the passage and the throat. The Patent of the United States of North America Number: 4,179,967 (republished as Re. 31,433 in 1983) describes a bandsaw blade of variable steps, as shown in Figures 1-3, in which the depth of the throat and the distance of passage between adjacent teeth disposed along the saw first decrease progressively from a non-fixed cleaning tooth 11 which is the thickest tooth, until the finest tooth 15, and then progressively increases again until a tooth has the same characteristics as the front tooth. The teeth also have angles of inclination and the rear teeth are alternately fixed laterally to the same degree. While this latter configuration of the '967 patent offers some advantages over the' 864 and '870 patents mentioned above, particularly with respect to the reduction of noise and vibration, there remains a common trend of reduced cutting speeds in all those sheets of variable pitch, especially when cutting large cross sections of materials difficult to cut. It has been found that these leaf failures occur as a result of some throats that are too "small to accommodate the size of the chipped material that is cut through the leaf, particularly when operated at high feed speeds, as shown in C in Figure 1 DESCRIPTION OF THE INVENTION A principal objective of this invention is to provide an improved sawtooth configuration that overcomes the deficiencies of the variable pitch blades of the prior art while retaining the advantages thereof.

A further objective of this invention is to provide sawtooth configurations capable of cutting work pieces that are difficult to cut without breaking teeth and feeding speeds comparable to those of the conventional variable step tooth configurations, as found in cutting blades. band saw. Another object of this invention is to provide sawtooth cutting tools that are more effective for cutting work pieces of relatively larger cross sections than hitherto. A further objective of this invention is to provide sawtooth cutting tools that are less prone to lateral deviation and noise generation than conventional variable pitch band saws of the prior art. In accordance with this invention, the cutting edge of a band saw includes a plurality of recurring groups of teeth that are fixed laterally to opposite sides of the blade. Each of the teeth is characterized by having a cutting edge disposed in a predetermined plane and a throat area which is directly proportional to the distance of accumulated passage between that tooth and the next preceding tooth having a cutting edge disposed generally in the same cutting plane as the tooth. As a result, the throat area of each tooth is adapted by a predetermined area to accommodate the depth of the slitting capacity of each tooth. At least some of these teeth are separated from others of these teeth by a step distance that is different from the pitch distances that separate others from these teeth. Thus, the blade has sufficient tooth-to-tooth step variations to inhibit the cadence repetitions generated by the tips of the teeth when contacting the work at uniform time intervals. The above and other objects and advantages of this invention will be more readily apparent from a reading of the following description of an exemplary embodiment thereof taken together with the following drawing.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view of a portion of a prior art saw blade. Figure 2 is a top view of the saw blade portion of Figure 1 with portions thereof in dashed line. Figure 3 is a cross-sectional view, on an enlarged scale, taken along line 3-3 of Figure 2, with portions thereof removed. Figure 4 is a view similar to that of Figure 1 of one embodiment of the present invention.

Figure 5 is a top plan view of the saw blade portion of Figure 4 with portions thereof in dashed line. Figure 6 is a cross-sectional view, on an enlarged scale, taken along line 6-6 of Figure 5, with portions thereof removed. Figure 7 is a diagrammatic view of a throat and tooth configuration illustrative of the parameters involved in the relationship between the passage and throat areas. Figure 8 is a view similar to that of Figure 4 of a further embodiment of the present invention. Figure 9 is a top plan view of the saw blade portion of Figure 8 with portions thereof in broken line; and Figure 10 is a cross-sectional view, on an enlarged scale, taken along line 10-10 of Figure 9.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Shown in Figures 1-3, there is a conventional variable-pitch band saw blade 10 of the prior art, comprising repetitive groups or tooth patterns, each of which includes an unfixed front tooth 11 followed alternately by a plurality of fixed posterior teeth 12-17. The teeth 16L and 17L, shown in Figure 2, are from the group of front teeth, or advance teeth of the main group 11-17 mentioned with reference to Figure 1. As shown in Figures 2 and 3, the unfixed tooth 11 it has a plane of symmetry p_ which defines the saw plane of the sheet and which is parallel to the side surfaces 19 and 21 of the sheet. As shown in Figure 1, all the teeth 11 to 17 are approximately the same height Hl with respect to the trailing edge 24 of the sheet 10. As shown in Figure 3, the tip of the tooth 11 is disposed in the plane v while the teeth 12, 14 and 16 are arranged in the plane w and the teeth 13, 15 and 17 are arranged in the x plane. As best shown in Figure 1, a throat 18 immediately precedes each face of tooth 11_-17_ in which a splinter is formed, as illustrated in C in Figure 1. Thus, for example, as tooth 11 moves to through a workpiece M in a cutting direction a and feeding direction f, the chips C cut from the workpiece are spirally raised along the face of tooth 11 in the throat area of that tooth. It will be recognized that any throat is of insufficient area in the plane of the blade to accommodate the size of the chip that its respective tooth is capable of cutting, then that throat will be, in effect the "weak link" and will be subject to clogging. Should this occur, not only will that throat not be able to perform its function but it may interfere with a series of teeth in the vicinity of the jammed throat being able to make its full cut at work and that condition could result in the wobble sideways to add also to an already difficult task. Each of the groove areas designated respectively A11-A17 for each of the teeth 11-17 of Figure 1 and each of the grooves, is defined as the area in the plane of the leaf corresponding longitudinally to the distance of Step P11-P17. The separation between the tips of the successive teeth and the throat areas depend, therefore, on the depth of the throat h and the radii and the relief angle &;, as also shown in Figure 7. As the distance between the successive teeth of the variable-pitch type band saw blades vary from tooth to tooth, and the respective throats also decrease proportionally in area, as is illustrated in Figure 1, there is a tendency for some throats to get stuck with chips from the material being cut. This is particularly a problem with difficult-to-cut materials, such as metals of relatively large cross section in the direction of cutting movement of the teeth related to the workpiece M as shown in Figure 1. When such a material is cut , the result is generally of spirals C in the form of spiral, unitary, which are formed in each of the throat areas. When cutting larger cross-sectional work pieces, the chips that are being cut will become larger, as long as the tooth remains in contact with the work and the chips are to be transported, or accommodated, in the respective throat of the workpiece. each tooth. In some problematic cutting situations, the throats may become so jammed by the chips of the material being cut that the cutting edge of the respective tooth following that stuck throat area will be unable to cut further into the piece of material. I work until your next cutting step. The effect of these stuck grooves is loss of tracking by those cutting edges, undesirable wobbling, deviations of the saw blade from a straight cutting plane and even premature fracture of the tooth and failure to cut. Despite a disadvantage like this, however, variable pitch blades still prevail in the band saw blade industry due to its vibration reduction, smoother cutting and noise reduction, except for the cases described in the present previously, in which stuck grooves result in wobbling of the blade causing vibration problems and even blade failures. In the present situation, those skilled in the art of cutting tools will recognize that a band saw blade, when linked on driving and static pulleys separated from a band saw, will be driven so that the cutting plane moves unidirectionally in relation to a piece of work, compared to the reciprocal for most other types of saws. While a saw having reciprocal movement during a cutting operation tends to shred and / or clean the chips from the throats generated by that movement, a band saw generally does not tend to shred those chips. Therefore, in the latter type situation, the chip material must be received and contained within each throat area disposed forward of the leading edge or face of each respective cutting tooth within the workpiece and, indeed, causing the same chips to be received in their respective throats. Thus, from the moment a tooth enters the work piece until it leaves the work piece, the splinter will necessarily be carried by the respective throat. That cutting operation will result in splinters that will become too large in cross section to be contained entirely within any of their respective throat areas, the throat areas will become clogged by the splinters with all the terrible consequences that are expected, as mentioned later in the present.

Referring now to Figures 4-6, a band saw blade 110 of the type of the embodiment of the present invention is presented. Although in some aspects the blade 110 may be similar to the sheet of Figures 1-3, it has some impressive advantages over the prior art, including the variable pitch type band saw blades of the prior art. The band saw blades of the type incorporated in this invention are not only capable of improving the operation of cutting in materials difficult to cut, but the operation is even more impressive when the cutting task is also composed of material difficult to cut. cut cross section larger than usual. As will be demonstrated hereinafter, the sheets of the embodiment of this invention are shown to be fully capable of performing such formidable tasks without stuck chips, tooth fracture, lateral deviation and blade failures. In the preferred embodiment, the invention includes recurring groups of teeth in which each group comprises a plurality of fixed teeth 112-117, alternatively they are fixed to the left and right of the lateral edges of the sheet, as best shown in FIG. Figure 5. Two additional teeth in 116L and 117L are also shown as the last two teeth of the next front group. Preferably, the group includes a non-fixed front tooth 111 followed by six fixed teeth to thereby form recurring groups of seven teeth. As illustrated in Figure 6, the cutting edges of each of the teeth 111-117 are arranged in three separate and distinct cutting planes v, w, and x with the throat area of each tooth being designated A111-A117. It is recognized that many of the cutting problems in the operation of the band saw blades result from failure to accommodate in the actual perspective, the relative importance of the variable pitch and the size of the throat. Then, it was truly credible that the cutting problems associated with band saw blades could be solved by providing the cutting edges with grooves in whose areas the maximum chip size that each respective tooth is capable of producing could be accommodated. In this regard, it was determined that the size capable of being cut by each tooth in the group is a result of the "Bite" or the "depth of cut" (DOC) of that tooth, which, in turn, is directly proportional to the "accumulated step" (Pt) of that particular tooth according to the following equation: DOC = Pt XF / V where: DOC = Depth of cut of each tooth in the pattern; Pt = The accumulated step; F = The feed speed of the blade inside the workpiece (in feed direction f); and V = The velocity of the band (in direction of cut a) • The "accumulated step" for any given tooth in a group can be defined as the total pitch distance between the given tooth and the nearest preceding tooth that has its cutting edge in the same cutting plane as the given tooth. The greater the accumulated pitch of any tooth, the greater the depth of the cut (DOC) or the thickness T (Figure 1) of the slice capable of being cut by that tooth, insofar as, no other cut is available within the accumulated step distance, which will interfere, or compete with that tooth by making a clean cut in its particular cutting plane. The configuration of the tooth, as shown in Figure 4, is essentially the same as that shown in Figure 3, with respect to the coincidence of the cutting planes v,, and x. Consequently, the accumulated step of any fixed right tooth, fixed left tooth or non-fixed tooth of the leaf of Figure 4-6, is the distance between it and the fixed right tooth, the fixed left tooth or the non-fixed tooth, immediately preceding, respectively. In particular, the fixed right tooth (plane w), immediately preceding the right fixed tooth 114 (plane 52), it is the tooth 112 that is (2) further step distances. Teeth 114, 115, 116 and 117 can thus be said to each have a "cumulative pitch" of (2) pitch distances. The teeth 112 and 113 each have an "accumulated passage" of (3) pitch distances, that is, the pitch distance between the teeth 112 and 113 and the teeth 116 and 117L of the preceding tooth pattern. Tooth 111 has an "accumulated passage of (7) pitch distances from tooth 111 to tooth 111. In particular, the area of each throat is proportional to the size of the" bite "taken respectively of each tooth according to the previous equation The "splinter size" (SOC) cut by a given tooth is defined in terms of the area of a splinter taken in the plane of the sheet p and is determined by multiplying the depth of the cut (DOC) by the length of the cross section of the work parallel to the cutting direction a for each cutting step of a given tooth through the work, as shown in Figure 1. The dimension of the grooves in a direction transverse to the plane of the sheet p_ is not included in the equation, nor the width of the chips cut by the tooth of the saw, since they are functions of the thickness of the blade of the saw and as such, remain constant.As a result, all the other variables that are maintained n constant, the greater "accumulated step" of a given tooth, the greater its depth of cut, so that the thickness of the cut of the chips for the same will be, correspondingly, greater. Each of the grooves must therefore have sufficient capacity to receive and carry a chip of the maximum thickness, or depth of cut, that its corresponding tooth is capable of cutting. As shown in Figure 4, the unfixed front tooth 111, which has an "accumulated pitch", or "Pt" of (7) pitch distances will thus take the deepest "bite" of the workpiece and thus should have the largest throat area There of the group. The first pair of back teeth 112 and 113, each of which has a Pt of (3) pitch distances and is indicative of the fact that each of those teeth will take the next longer "bite" and has throat areas A112 and A113, which are essentially of the same area although they are smaller than there. The remaining teeth 114-117, each of which has a Pt of (2) step distances, each will take the smallest bite of the tooth in the group and have the throat areas A114-A117 which are also equal one of another, at the same time that they are smaller than A112 and A113. The group of seven teeth of Figures 4-6 has three different accumulated pitch distances and produces three different sizes of chips. As a result, the pattern has three different sizes of throats, that is, .0185, .0146 and .0112 of previously determined chip storage and / or transport capacity. Moreover, although at least some of the teeth are separated from each other by the pitch distances that are different from the pitch distances between the remaining teeth, this is not the case for all teeth in the group of seven teeth . As best shown in Figure 4, all steps for teeth 114-117 are substantially the same. A problem that can be found with a series of equally spaced teeth is that the tips of each of the teeth will come into contact with the work with repetitions in cadence. As a result, the blade of the saw, like a large spring, will be subjected to unidirectional vibratory sound waves at resonant or harmonic frequencies. It should be noted, in Figure 4, that the Pili step is the largest, as is the throat area corresponding to tooth 111. The pitch for each of the following two teeth 112 and 113, as shown, are equal one another but substantially smaller than Pili. Further, in Figure 4, the measured step-to-tip of the following four teeth P114-P117 are generally equal to each other at the same time that each is substantially smaller than the passages of the two front teeth 112 and 113. Thus, in the embodiment of Figure 4, the size of each of the throat areas A111-A117 is directly proportional to the accumulated pitch of the corresponding teeth 111-117. This is also the case for each of the pitch distances P111-P117 which is directly proportional to the corresponding throat area A111-A117. Finally, as shown in Figure 4, and described above, each group of teeth of the blade 110 includes an unfixed front tooth 111 and, alternatively, six fixed teeth 112-117. Although it has been found that this tooth configuration is an improvement insofar as it solves the problems of cutting speed, tooth tracking, and tooth fracture, as well as the interrelated problems, but also cause difficulty, of noise and vibration of the blade. Other improvements with respect to noise and vibration are still desirable. Excessive vibration and noise are problems that have been solved in the prior art by the use of fixed teeth that first progressively decrease in depth of throat and passage and then progressively grow in throat depth and in passage and in which shorter teeth are given a more positive elevation angle than longer teeth. The configuration of the teeth is described and claimed in the reissued United States Patent Number: 31,433 mentioned above, and illustrated in Figures 1-3. This configuration of the teeth became very well accepted as the state of the art in variable step bandsaw blades. The most important consideration in the limitation, inhibition or nullification of resonant or harmonic frequencies that occur during the operation of the band saw blade, is to avoid repetitions in cadence that are the direct result of equally separated saw teeth. With the blade 110 of Figure 5 driven at a constant speed, so that the teeth 111-117 move in sequence through a workpiece starting with the tooth 111, what follows is a comparative analog sequence in the intervals of time for successive pairs of teeth to engage with the workpiece: d / d / s / d / s / s / s in which "d" means "different" and "s" means "same" with respect to the Time intervals for successive pairs of teeth to move around with work. If this were a pattern of five teeth instead of the seven teeth of Figure 4, but in other aspects similar to the same, the time sequence would be d / d / s / d / s. In any case, it has been found that at least these variations in the step are sufficient to avoid, solve or nullify the occurrence of the repetitions in cadence that can result in the intensification by the reinforcement of the vibratory sound waves for the resonant levels or harmonics According to another feature of this invention, it is possible to change the throat size of any tooth independently of the pitch thereof, such as when the throat areas are synchronized to accommodate the size of the chips to be cut. In Figure 7 two successive saw teeth and their grooves are illustrated. The teeth depicted therein can be any band saw blade, such as the blade 110 and the teeth can also be any type of consecutive teeth, such as 114, 115 and 116. Having recognized the importance of correlating each throat with the size of the cutting capacity of splinter for each of the teeth in a group of teeth, the only remaining question that needs to be answered, is whether there are sufficient step differences between the successive teeth of the blade to inhibit the generation of cadence in the vibration, or the generation of sound waves when the tips of the teeth of the saw come into contact with the work. As described in the present before, the steps P114-P117 of the band saw blade 110 are all the same and if this configuration should cause a problem of noise, or of vibration, it can be overcome by changing the configuration of one of the throats related to the pitch of the tooth that supplies the splinter material inside that throat. More specifically, as shown in Figure 7, the step measured between the tips of the teeth 115 and 114, is P115, and between the tips of the teeth 116 and 115, is P116 '. Step P115 is shown to have a distance greater than P116 '. As illustrated, changing the relief angle. and different radii of curvature, such as that in Rl, R2 and R3 for the throat area of tooth 116, the throat can still be reconfigured as 118 'to remain the same in area to that of the throat for tooth 115 In this way, it has been found that one is able to control the size parameters of the passage and throat independently of one another. In this example, unlike that of Figure 4, where the pitch between the teeth 114, 115 and 116 is the same as the throat areas while, as illustrated in Figure 7, the steps Pl and P2 they are different, the areas of the gorges A115 and A116 are still the same. According to this invention, control over the passage can be maintained while the areas of the gorges are independently controlled. Moreover, it is now possible to obtain the benefit of variable steps without the disadvantages of lower operating speeds and stuck throat problems. The same approach form can be used in relation to the interruption of the uniform pitch of the teeth 211-215, as shown in Figure 8, in which the throat areas are the same as the steps. This sheet would probably have a serious noise and vibration problem when used to cut materials that are difficult to cut. Following the invention, however, as shown in Figure 7, it would be possible to use the method described above to change the pitch of the tooth such as 213 and 214, for example, but reconfiguring its throats. By configuring back the throats, the throat areas A213 and A214 would still be directly proportional to the accumulated passage. Thus, I would be able to implement at least two changes in the pace at the same time to maintain the same throat areas in order to attack both problems: vibration and throat clogging at the same time. This concept contrasts with the prior art sheet of Figures 1-3 in many important ways. In particular, the teeth 12 and 13 of the sheet 10, which have the same accumulated passage, each have different throat areas A12 and A13 although, following the teachings of the present invention, these teeth have the same chip storage requirements and, therefore they should have the same throat areas. Similarly, the teeth 14-17 each having the same accumulated pitch distance, also have different throat areas A14-A17, which, according to the present invention, should all be the same. In addition, the throat areas A114-A117 of teeth 114-116 of the present invention are larger than the smaller throat areas A14 and A15 of the prior art. Accordingly, the tooth pattern of the variable pitch saw blade of the present invention, when compared to the variable pitch designs of the prior art, allows for higher feed speeds and cutting of larger cross-sectional areas with a given tooth pitch. The invention provides these advantages while, at the same time eliminating sticking of the throats, wobbling or deflection of the straight cut of the blade, and excessive wear. Comparative tests were performed on two saw blades having the same general construction as the blades of Figures 1-3 and Figures 4-6, respectively, assuming a constant web speed V a feed speed F and a workpiece M with a length of 5.4 centimeters in the cutting direction of the saw blade. The results are as follows: EXAMPLE 1 (PREVIOUS TECHNIQUE: Figures 1-3) As is apparent from the above data, the teeth 11, which have the largest accumulated pitch, will produce the largest chip of approximately 2.83 square millimeters. Teeth 12 and 13 both have the same "accumulated pitch" and produce essentially the same chip size of approximately 1.4 square millimeters. The teeth 14-17, all have the smallest step gaps and each produces a chip of approximately 0.71-0.77 square millimeters. However, it will be noted that the throat areas A13 and A14 are of different area as are the throat areas of teeth 14, 15 and 16.

EXAMPLE 2 (PRESENT INVENTION; FIGS 4 - 6) Referring to EXAMPLE 2, based on the present invention as illustrated, for example, in Figures 4-6, the teeth 111 have the largest accumulated pitch and produce the largest chip, approximately 2.83 square millimeters. Teeth 112 and 113 both have the same "accumulated pitch" of (3) pitch distances and produce essentially the same chip size of approximately 1.29 square millimeters. Teeth 114-117, all have the same "accumulated step" of (2) pitch distances and each produces a chip of approximately 0.77 square millimeters. In another embodiment of this invention, the teeth can be provided with different degrees of height and lateral positioning. For example, as shown in Figures 8-10, a repetitive pattern of five teeth includes a non-fixed front tooth 211 followed alternately by rear teeth 212-215. Referring to Figure 8, the first and last of the rear teeth 212 and 215 are approximately the same height Hl as the non-fixed front tooth 211 and, as shown in Figures 8 and 9, each is provided of a "light" fixation towards the opposite sides of the plane p. The rear teeth 213 and 214 are both of a lower height H-2 than the other teeth of the group and each is provided with a relatively "heavy" attachment to the opposite sides of the plane p. As shown in Figure 9, the cutting tip of each tooth 211-215 in the pattern is disposed in its own cutting plane?, W, x, y; and z, respectively. As mentioned above, the accumulated pitch of each tooth is determined in relation to the next preceding tooth having a cutting edge in the same plane which, in this case, is the corresponding tooth of the preceding tooth pattern. For example, as shown in Figures 7 and 8, the next preceding tooth having a cutting edge in the same plane with the tooth 215 corresponds to the tooth 215L, of the preceding tooth pattern. Since five teeth are arranged between the teeth of the same plane that follow each other, each tooth in the pattern has an "accumulated step" equal to the total of the (5) step distances. Thus, in accordance with the teachings of the present invention, since each tooth has the same accumulated passage, all the teeth would also have the throat areas of equal size and if the passage were proportional to the throat area, the tips of all the teeth would be equally separated and in all probability the noise problem would be substantial when operating this type of blade when cutting materials difficult to cut. To deal with these noise problems and as described above in connection with Figure 7, some changes in the pitch within the sheet 210 may be incorporated, if necessary, to avoid undue cadence repetitions caused by the teeth spaced apart uniform As defined hereinabove, the "throat area" can be defined, for example, with reference to tooth 211, as the area in the plane limited by the front face 211_ of each tooth of the leaf p, by the posterior 215_ of the tooth immediately preceding 211, by the lower edge of the throat as in 218, and by a line that touches the tip of the tooth that is parallel to the trailing edge of the leaf indicative of the height of each tooth. Additional parameters that can be included to determine the throat area include the radii of the lower edge of the throat and its relief angle f. of the tooth of the posterior face in question and the relief angle of the preceding tooth. In particular, the throat areas A211, A212, and A215 of the tallest teeth 211, 212, and 215 are determined using the Hl line while the A213 and A214 areas of the lower teeth 213 and 214 are determined using the H line -2. Consequently, since different height lines are used, the other parameters that affect the throat area, such as throat depth, must be modified to provide uniformity in the tooth-to-tooth area. The prototype band saw blades, produced in accordance with this invention were tested in two different cutting operations for the evaluation of their operation compared to commercially available saw blades. Except that the throat sizes of the prototypes were correlated with the distances of accumulated pitch of each of the teeth thereof, the sheets of the prior art were, in all respects, identical to the prototypes. The previously available leaves were 4.5 meters by 3.45 centimeters by 1.07 millimeters, having a variable pitch pattern of 4/6 teeth by 25.4 millimeters, were tested in comparison with synchronous band saw blades of 4.5 meters by 3.45 centimeters by 1.07 millimeters , with a variable tooth pattern of 4/6 teeth per 25.4 millimeters. In both cases the blades were placed in a Hem Band Saw model 1200, operated at a band saw speed of 20 square meters / minute and a feed rate of 29.2 square centimeters / minute, which were used to cut the same piece of work, that is, iron 5/5 angle A36 with 4 pieces per package. The results were the following: It will be noted that the invention has a longer use life with cutting speeds comparable to those of the prior art sheets. In a second comparative test, the sheets of the prior art and of the prototype, in all cases, were used in a Hem Band Saw Model 1400, and were tested by cutting the same piece of work, that is, I-rod of 45 centimeters x 19.7 centimeters. The span of the cut and the I-rod were oriented to impose the most difficult cutting situation, where the cutting edge of the saw would fit simultaneously into the cross section of the I-rod, including both flanges and the portion of the cutting edge. plot of it. The results of the test listed below clearly establish the superior performance of the configurations of the embodiment of this invention, that is, in a test run, the prior art sheet failed during the first cut. The synchronized blade continued to cut without failure of the teeth for at least four cuts through the rod-1, while the prior art blade No. 2 failed due to the tooth fracture or because it had been dismounted from the saw during the first cut. Furthermore, although the prior art sheet No. 1 did not fail during the cutting test, it will be noted that the prior art sheet made a significantly higher noise level than the synchronized sheet of 100 decibels (db) compared to decibels. In addition, the prior art sheet had a substantially greater transverse deviation from the straight cut achieved by the synchronized sheet. The results of the test were the following: The preferred embodiment of the present invention combines a variable pitch distance between successive teeth other than that of the tooth having the same throat depth, because they have the same accumulated pitch. As a result, the sheets incorporated in this invention have the ability to perform difficult cutting tasks compared to the sheets available up to now. Moreover, these saws are also capable of providing the benefits normally attributed to variable pitch blades, including reduced vibration and noise, as well as less deviation in the cutting plane. However, one skilled in the art should understand that the pitch of the leaf tooth can be varied independently of the area of the throat / accumulated passage as long as the throat area remains in general, the same for all teeth of a given accumulated step and, therefore, remain within the spirit and scope of the present invention. Although the invention has been shown and described with respect to an exemplary embodiment thereof, those skilled in the art should understand that a recurring pattern comprising any number of teeth and various other changes, omissions and additions in the form and detail of they can be made to the present without departing from the spirit and scope of the invention.

Claims (6)

1. A band saw blade comprising: a plurality of saw teeth disposed along the blade and defining a cutting edge thereof, the saw teeth being formed in a plurality of recurring tooth groups including a non-fixed front tooth and a plurality of fixed rear teeth extending laterally outwardly from the blade, each of the teeth being fixed and not stationary, having at least one of the fixed teeth a first accumulated passage and having at least one of the fixed teeth a second accumulated step different from the first accumulated step; and a plurality of grooves disposed along the cutting edge of the sheet, each groove formed between an adjacent pair of teeth and defining a throat area proportional to the accumulated passage of one of the associated teeth.

2. A band saw blade comprising: a plurality of saw teeth disposed along the blade and defining a cutting edge thereof, the saw teeth being configured in a plurality of recurring tooth groups each group including a plurality of fixed teeth extending laterally outwardly from the blade, each of the fixed teeth having an accumulated passage, at least one of the fixed teeth having a first accumulated passage and having at least one of the teeth fixed a second accumulated step different from the first accumulated step, wherein at least some of the teeth have a pitch distance different from others of the teeth, and a plurality of throats disposed along the cutting edge of the blade, each throat formed between an adjacent pair of teeth and defining a throat area proportional to the accumulated passage of one of the associated teeth. The band saw blade of claim 13, wherein each group of teeth comprises a non-fixed front tooth and at least a first and a second pair of fixed teeth, and wherein the non-fixed tooth has an accumulated step of at least 5, the first pair of fixed rear teeth having an accumulated pitch of at least 3, and the second pair of fixed rear teeth having a accumulated pitch of at least 2. The band saw blade of claim 2, wherein each group of teeth comprises a non-fixed front tooth and at least one first, a second and a third pair of fixed rear teeth, and wherein the non-fixed front tooth has a cumulative pitch of 7, the first pair of rear teeth fixed has an accumulated pitch of 3, and the second and third pair of fixed teeth have an accumulated pitch of 2. 5. The band saw blade of claim 2, wherein each group of teeth comprises a non-fixed front tooth. and at least one p first and second pair of fixed rear teeth, each of the first pair of fixed teeth having the same height and each of the second pair of fixed teeth having a lower height than the first pair of fixed teeth. The band saw blade of claim 16, wherein before each of the first pair of fixed teeth was fixed they were substantially the same height as the non-fixed front tooth and each of the second pair of fixed teeth was lower in height that the front tooth is not fixed, and wherein the second pair of fixed teeth extends laterally outwardly from opposite sides of the blade beyond the first pair of fixed teeth.