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Description  |
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FIELD OF THE INVENTION
The invention relates to a saw blade with a basic body and unset teeth with
cutting edges which are provided in recurring cycles, each of cycle having
at least one group of teeth with at least two teeth in each group, where
these teeth are arranged symmetrically with respect to the basic body. The
invention can be applied to a band saw blade, a hacksaw blade, or a
circular saw blade.
BACKGROUND OF THE INVENTION
The German Offenlegungsscnrift 36 11 063 discloses a saw blade with teeth
in a recurring cycle. Each cycle also comprises a group of teeth, so that
the number of teeth in a group is equal to the number of teeth in a cycle.
The teeth in one group with respect to the cycle of teeth are
differentiated as being either a leading tooth, this being one or more of
the first teeth of a group or cycle, or as being following teeth. The
leading tooth or teeth are often formed as unset teeth, whereas the
following teeth in most cases are formed to be set teeth. Usually all
teeth are of the same width. The leading tooth has the greatest height,
and the height decreases in a group. Sometimes the leading tooth is phased
or its cutting edge is broken by a chip breaking flute . The following
teeth are usually formed as teeth set alternately to the left and right to
create a cutting channel wider than the basic body of the saw blade. When
two leading teeth are provided, these can be stepped like the well known
roughing and finishing teeth of a circular saw blade, by which the
effective edge is distributed between the two leading teeth. The cycle is
completed by the set following teeth, which create a wider cutting
channel. The decrease of height usually occurs in a step-like fashion, but
there are embodiments with teeth which are different with regard to their
height and are arranged in the cycle in a non regular way. In one of the
depicted embodiments seven teeth are provided, with an unset leading
tooth, which has a straight cutting edge the width of the basic body.
Following this leading tooth are three pairs of following teeth, all of
which are set alternately to the left and right.
The last two pairs of following teeth may have identical set width in
conjunction with equal or unequal height of the teeth, so that these last
four following teeth define the width of the cutting channel and work
alternately on the two facing surface planes of the cutting channel. For
instance, the fifth and seventh teeth in a group comprised of seven teeth
will work on the same surface of the cutting channel. The seventh tooth
performes a following work step in relation to the fifth tooth, which
serves to compensate the deviation from the path caused by the fifth
tooth.
In a further embodiment five teeth are provided in a group and therefore in
a cycle. The first tooth is unset, whereas the four following teeth are
set teeth. The setting of the first and fourth following teeth is greater
than that of the second and third following teeth, though. Therefore each
surface of the cutting channel is worked on by a single tooth of the group
only. This is also the case when two set leading teeth are used in place
of one unset leading tooth.
The German Offenlegungsschrift 36 11 063 also describes an illustrative
embodiment which employs no set teeth but only unset teeth in a group of
teeth with respect to a cycle of teeth. In one group two following teeth
are assigned to one leading tooth. The height of the teeth in a group
decreases and the width increases. The last, widest tooth is provided once
only. All the teeth are formed symmetrically with respect to a
longitudinal center plane through the basic body. The present invention
uses such a saw blade as a starting point. The first tooth in a group of
teeth has a straight and continuous cutting edge perpendicular to the
longitudinal center plane of the saw blade. The width of this first tooth
is equal to the width of the basic body. Both of the two following teeth
also have cutting edges perpendicular to the longitudinal center plane of
the basic body, of which, due to the increasing width, only the outer
parts contribute to the cutting process. The following teeth have
differing flank angles and the angle enclosed between flank and cutting
edge is also different for each of the following teeth, but in each case
it is an acute angle. The effective cutting edge decreases in length from
tooth to tooth, so that the main contribution to the cutting process is
provided by the leading tooth and the two following teeth only widen the
cutting channel, so that a clearance cut is achieved. This embodiment of a
saw blade is intended to coincide in function and effect with the
embodiments in which set teeth are used. While set teeth can be
manufactured without too much difficulty, a saw blade with unset teeth of
different width is extremely elaborate in production, it not being clear
how the greater width of the following teeth as compared to the width of
the basic body is to be achieved in the first place. In addition, this
embodiment with unset teeth displays numerous other disadvantages. The
effective part of the cutting edge of the following teeth and their flank
enclose an acute angle, i.e. an angle of less than 90.degree., so that
these lateral tips of the teeth are subjected to substantial wear during
the cutting process, by which the width of the cutting channel rapidly
decreases. With set teeth this disadvantage does not occur to such a great
extent, because the angle between effective cutting edge and flank is
always about 90.degree.. Set following teeth are always unfavorable for
the straight running of a saw blade, though, because lateral forces are
created by them. These forces, acting on one side only, cause a deflection
of the set tooth concerned. This not only results in a poorer surface
quality of the cut face in the cutting channel, but also causes vibrations
of the saw blade. The unset leading tooth has no lateral clearance so that
its flanks cause friction in the cutting channel. The leading tooth must
perform the main cutting work and clear the greatest cross section. The
same holds for more than one leading tooth in a group of teeth; in all
cases the set teeth are loaded less. All embodiments of the known saw
blade attempt to achieve that both leading and following teeth contribute
to the cutting process. The chips are reduced to a small size, which makes
their removal easier and enables a higher cutting speed. By including
buffer teeth, the load on the leading teeth is reduced and distributed
more evenly among all teeth. From the German Offenlegungsschrift 25 16 137
a circular saw blade is known, in which a cycle comprises a group of teeth
having a pre cutter and a final cutter. The pre-cutter and final cutter
teeth have the same tooth-height and their width is the same as that of
the basic body. The pre-cutter and final cutter teeth have differently
angled phases, so that different chips are removed by the respective
cutters in the known way. The achievable surface quality is comparably
poor, due to the fact that there is friction between the basic body and
the adjacent material in the cutting channel.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a saw blade of the type
described above, which provides a stabilized straight movement in
combination with a superior surface quality in the cutting channel. The
roughness of the surface created in the cutting channel is smaller than
previously achieveable.
According to the invention this is achieved by a saw blade of the type
described above, wherein at least two groups of teeth are, preferably
regularly, intermixed in a cycle, with the first group consisting of at
least two teeth with a decreasing height and increasing width graduation,
while the teeth of the second group are formed identically and have the
greatest width.
The invention is based on the idea to have two different groups of teeth in
a cycle, but that these groups should contrary to being arranged one after
the other, as is customary, be intermixed instead. This "overlapping" of
the groups makes sense especially when it is regular. With such a regular
intermixing, there can be, for example, first group consisting of three
teeth, teeth 1, 2 3, which have a from tooth to tooth decreasing height
and increasing width. This first group of three teeth primarily serves to
deepen the cutting channel. The second group of teeth may consist of three
teeth 4, where each tooth 4 has a smaller height but a greater width than
tooth 3 of group one. This second group of teeth serves to finish the
surface of the cutting channel. The two groups are regularly intermixed
when the resulting order of teeth in the cycle becomes 1, 4, 2, 4, 3, 4,
where, for simplicity's sake, a constant pitch is assumed, so that a
complete cycle consists of six teeth. This intermixing or mutual
overlapping of the groups in a cycle, in combination with the advance of
the saw blade, has the extraordinary advantage that the teeth of the first
group remove relatively thick chips and the teeth of the second group
remove relatively thin chips from the cutting channel. When removing thick
chips, wear of the effective cutting edge is not as disadvantageous as
when removing extremely thin chips. This more numerous ocurrance of the
teeth of the second group, which are wider, is responsible for the better
quality surface finish in the cutting channel. Due to this, the invention
clearly stands apart from the case where the widest tooth within a group
of teeth of different width occurs only twice in a double arrangement. In
terms of the above given example this would be an order of 1, 2, 3, 3 in
the cycle. Nevertheless, in accordance with the invention, a double
arrangement of teeth in the intermixing is possible, yielding a first
group of teeth with two second groups of teeth in a cycle, so that for the
example given the order would be 1, 4, 4, 2, 4, 4, 3, 4, 4. Irregular
intermixing of five teeth 1, 2, 3, 4, 5 of a first group with two teeth 6
of the second group resulting in an order 1, 2, 3, 6, 4, 5, 6, also is in
accordance with the invention. The number of teeth in the first group
should be no less than two. The number of teeth in the second group should
also be no less than two. Usually the number of teeth will be the same in
both groups. It is possible to have an equal load on all teeth of group
one and likewise on group two, but with the two loads on each group being
different. The invention may not be confused with the known technology of
pre- and final cutters used on circular saw blades. Circular saw blades
only have two different kinds of teeth, the aforementioned pre- and final
cutters. This can be described as one group consisting of one pre-cutter
and one final cutter. The second group of the cycle is missing. When
intermixing the groups in accordance with this invention, unset teeth are
employed. Nevertheless, interspersing set teeth will not fault the
invention, but also does not lead to an improvement of the qualities.
The individual teeth in the first group are not based on the concept of
leading and following teeth, instead the teeth can be considered to do the
equal work, since all teeth of the first group carry the same load. The
distribution of the contributing cutting edge sections on to the edges of
the teeth of the first group and their relatively wide spacing, e.g. the
distance of two pitches serves the goal to remove chips of relatively
large thicknesses.
The invention can also be applied in combination with the known pre-cutter
and final cutter technology. A simple example is the order: pre-cutter,
widest tooth of the second group, final cutter, widest tooth of the second
group.
It is especially advantageous when the saw blade has unset teeth only and
when the effective cutting edges with respect to the cutting edge sections
are formed by an inflected cutting edge--as opposed to a continuous
straightline cutting edge--, so that each thick chip removed with the
effective cutting edge of a tooth, especially of the first group of teeth,
is subjected to two forces acting in different directions, which act to
break up the chip. This chip-breaking effect is also found with the second
group of teeth, though less pronounced, since this second group removes
thinner chips anyway. The realization of phases on all teeth of both
groups in a symmetric orientation with respect to the longitudinal center
plane serves in a special way to stabilize the forward movement of the saw
blade. A stabilizing wedge action by an even "support" of the teeth of
both groups is achieved in the cutting channel, so that there are no
resulting lateral forces on any tooth. By having symmetrical phases on
each tooth, the two lateral forces on the tooth cancel each other out. The
saw blade therefore has no tendency to run out of a straight line. The
widest tooth in the cycle, which comprises the second group through
repeated use, has as angle between phase and flank greater than
90.degree.. Preferably this angle should be greater than 100.degree. to
further reduce the possibility of wear. In effect it is this outer edge
that works upon the side walls of the cutting channel and is responsible
for the improved surface quality. Since the angle between phase and flank
is substantially greater than 90.degree. at this point, the inevitable
wear on the teeth of the second group is less detrimental than an acute
angle between phase and flank. A more numerous employment of the teeth of
the second group also contributes positively to this cause. The results
are a longer service life of the saw blade as well as surprising surface
quality in the cutting channel. In addition, the obtuse angled geometry
brings about a great stability against material breaking out of the
cutting edge corners, which is of particular importance when using hard
metal cutters.
It should be pointed out that the invention can at first be realized when
applying a constant pitch in a cycle. In this way already, the height
graduation and the width graduation of the teeth in a group produce
reduced sensitivity to vibrations and outstanding straight run
performance, in spite of the similarity in the shaping of the teeth.
However, what is of particular significance, and what the invention
readily allows, is to use the described design in combination with a
variable pitch. Through the use of a variable pitch the teeth of the first
and second group with their intermixing form something like a third group,
which recurrs several times in each cycle. In the above described example
with three teeth 1, 2, 3 of the first group and three teeth 4 of the
second group and the use of 5 different pitches the resulting cycle is
comprised of 30 teeth. The intermixing of the teeth 1, 4, 2, 4, 3, 4 is
repeated five times according to five different pitches.
In a preferred embodiment one tooth of the second group is included between
two teeth of the first group. It is also possible to include two teeth of
the second group between two teeth of the first group. By this measure,
the "effective pitch" between the teeth of the first group is increased,
which in turn produces thicker chips at a constant advancement, while on
the other hand the teeth of the second group will produce even finer chips
in the cutting channel.
The phases on all teeth in both groups can be arranged at a common phase
angle with respect to a straight line perpendicular to the longitudinal
center plane of the basic body. Consequently, these phases run parallel to
each other, on the left hand side and right hand side of the teeth,
respectively, on account of the symmetrical design with respect to the
longitudinal center plane through the basic body. With a uniform height
graduation, a uniform distance from phase to phase is obtained in the
projection, if the point at which the cutting edge is inflected is chosen
correspondingly. If the effective areas cleared by the teeth are regarded,
the design of the teeth in the first group can be arranged so that
identical distributions are distributed over all the teeth in the first
group. It is also possible, however, to provide different distances
between the phases, even while maintaining the same phase angles in the
projection. On the other hand, the phases angles need not necessarily
coincide. The number of points of inflection in an effective, jutting--out
or protruding cutting edge section may also be greater then one. The
second group of teeth is of equal design. Each tooth of the second group
is of the same height, same width and same form of the cutting edge. Since
the teeth of the second group exclusively function to work on the cut
surface, they can be rounded between phase and flank, to further reduce
wear and to obtain a smooth cut surface of the cutting channel.
At least the teeth of the second group should be wider than the basic body,
which does not exclude that the teeth of the first group also be wider
than the basic body. Then a free cut is obtained.
The flanks of all teeth of the second group may be provided at a flank
angle in the range between 3.degree. and 12.degree., in particular
8.degree.. A small flank angle in conjunction with a large phase angle
produces a very stable design of the free corners of the teeth in the
second group. For the corners of the teeth in the first group this is of
minor importance, since these corners, due to their relatively small
width, do not contribute to the cutting work. It is also possible,
however, that the flanks of all the teeth in both groups are provided at a
coinciding flank angle with a congruent projection. This simplifies
production considerably, in that the flanks of all the teeth can be worked
upon with a constant machine setting, e.g. by grinding.
The teeth of both groups may be provided as hard metal tipped, ground
teeth. In conjunction with the phase angle, a width graduation then also
occurs. The teeth are consequently formed with a large overall surface
area and can thus be loaded fully. Generally, the teeth or major parts
thereof are produced by hard metal tipping and by grinding. Beforehand,
the band strip of the basic body is correspondingly prepared by some
milling, punching or grinding process. It is also possible, however, to
use a rolled, conically widened bimetal strip as the basic material, and
to form the teeth of both group by a combined milling/punching/grinding
operation.
Groups which have recurring, variable pitches may be formed in the
recurring cycle of teeth. The number of teeth in the pitch group does then
not necessarily have to coincide with the number of teeth in both groups.
In a pitch group with five different pitches and a first and second group
of teeth with three teeth each, the total number of teeth in the cycle is
thirty. The number of teeth in a cycle is the smallest common multiple of
the number of teeth in the pitch group and the number of teeth in the two
intermixed groups. By having such a high number of teeth in a cycle, the
saw blade becomes less prone to vibrations. It has surprisingly greater
running smoothness with stabilized straight running and a greatly extended
service life compared to standard saw blades. The number of teeth in a
further group of teeth, which is given by the order of variable pitches,
cannot be the same as the number of teeth in the first two groups, thus
the number of teeth in a cycle becomes large, and the saw blade runs very
stable. It is also possible, however, that the number of teeth in this
further group, corresponding to the number of pitches, coincides with the
number of teeth in a cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is further explained and described with reference to a number
of illustrative embodiments. The drawings show in:
FIG. 1 an enlarged partial side cut away view of a saw blade,
FIG. 2 a plan view of the saw blade of FIG. 1,
FIG. 3 a view in the direction of the line III--III in FIG. 1 on a band saw
blade with three teeth each in the first and second group,
FIG. 4 a similar view as FIG. 3, but of a second embodiment of a saw blade,
FIG. 5 a similar view as FIG. 3, but of a third
embodiment,
FIG. 6 a similar view as FIG. 3, but of a fourth embodiment of a saw blade,
FIG. 7 a partial view of a band saw blade of FIGS. 1, 3, or 4 with a
constant pitch,
FIG. 8 a side view of a saw blade with a variable pitch, and
FIG. 9 a side view of a saw blade with a constant pitch as in FIG. 7, but
with a double arrangement of the teeth in the second group.
DETAILED DESCRIPTION
The cut away portion of the band saw blade illustrated in FIG. 1 in a
cutout has a basic body 1 with unset teeth 2, 2', which are provided in
recurring cycles. A first group of teeth 2 is comprised of teeth differing
in height and width. The first tooth 2.sub.n, of such a group is
designated by the index 1, while the last tooth 2.sub.n of a group of
teeth is designated by the index n. A second group of teeth 2* which do
not differ in height or width is also provided. The tooth 2* is lower than
the lowest tooth 2.sub.n of the first group. The tooth 2* is wider than
the widest tooth 2.sub.n of the first group. In a simple case, the number
of teeth in a cycle will be the sum of teeth in the first and second
group, as is the case with constant pitch. Here, the number of teeth in
the first group is two, better three or more. The number of teeth in the
second group is at least two, preferably equal to the number of teeth in
the first group, though. Each tooth 2, 2* possesses a height 3, 3*, with
the same indexing as above. The teeth 2 in the first group have a height
graduation in a way that the height 3 decreases from tooth to tooth. The
height 3.sub.1 of the first tooth 2.sub.1 of the first group is greater
than the height of the second tooth 2.sub.2 of the first group, the height
of the tooth 2.sub.2 is greater than the height of the third tooth
2.sub.3, etc. The heigth 3.sub.n of the last tooth 2.sub.n of the first
group is still higher than the heigth 3* of the teeth of the second group.
The teeth 2 of the first group also are of different width 4, with a width
graduation so that the first tooth 2.sub.1 has the smallest and the last
tooth 2.sub.n the largest width. The tooth 2* in the second group is still
wider than the widest tooth 2.sub.n of the first group, though. Each tooth
2, 2* has an inflected cutting edge 5, 5*, which is formed by an inner
section 6, 6* and an outwardly adjoining phase 7, 7*. The sections 6, 6*
run transverse and perpendicular to a longitudinal center plane 8 through
the basic body 1. The design of each tooth is symmetrical to the
longitudinal center plane 8, so the phases 7, 7* on the left and right of
the tooth 2, 2* are symmetric. As especially FIG. 3-6 show, the phases 7,
7* are inclined towards the basic body 1. This produces a phase angle 9
for all teeth 2, 2* which should be provided in the range between
20.degree. and 60.degree.--preferably about 45.degree.. The phase angle 9
for all teeth 2, 2* is the angle between the phase 7, 7* and a direction
that is perpendicular to the longitudinal center plane 8. The phases 7, 7*
on the individual teeth 2, 2* of both groups are formed in such a way that
the first and highest tooth 2.sub.1 has a comparatively narrow section
6.sub.1 which is smaller than the width of the basic body 1, while the
tooth 2* has a straight section 6* wider than the basic body 1.
The different shaping can be seen most readily in FIG. 3, in which an
embodiment with three teeth 2 in the first group and three teeth 2* in the
second group is depicted. The cycle with six teeth is obtained by
intermixing the two groups of teeth in the following way: 2.sub.1, 2*,
2.sub.2, 2*, 2.sub.3, 2*. In plan view the highest tooth 2.sub.1, with its
relatively small section 6.sub.1 of length a.sub.1, is seen first. This
section 6.sub.1 is adjoined by the relatively long phase 7.sub.1 on the
first tooth 2.sub.1, which in this case has a phase angle 9 of 45.degree..
The phase 7.sub.1 extends to the flank 10.sub.1 of the tooth 2.sub.1. The
flank 10 widens from the basic body 1 in the direction of the tip of the
teeth 2, 2*. The flank has a flank angle 11 with respect to the basic body
1, which in this case is 8.degree.. The flank angle 11 is not indexed,
since it is the same for all teeth 2, 2*. The forming of the flanks 10 is
performed by a grinding operation over all teeth 2, 2* simultaneously. The
first tooth 2.sub.1 cuts only with part of its cutting edge 5.sub.1, that
is the part which extends or projects beyond the outline of the second
tooth 2.sub.2 in the projection. The effective cutting section of tooth
2.sub.1 is comprised of the straight section 6.sub.1 and the adjoining
section 12.sub.1 on both sides. The sections 12.sub.1 end at the
projection intersection 13.
Following the highest tooth 2.sub.1 of the first group is the first tooth
2* of the second group. This tooth 2* has a smaller height 3* than the
teeth 2.sub.1, 2.sub.2 and 2.sub.3 of the first group, but a larger width
4* than these.
The third tooth of the cycle is the second highest tooth 2.sub.2 of the
first group. It has a straight section 6.sub.2 of length a.sub.2, which
again is adjoined by phases 7.sub.2 on both sides in a symmetric fashion.
All phases 7 of all teeth 2 of the first group and 2* of the second group
are parallel to each other. Of the tooth 2.sub.2 as well, only a certain
part cuts, that is the part of the cutting edge 5.sub.2 which extends
beyond the other teeth. This cutting part is comprised of the two cutting
edge sections 14.sub.2 of the section 6.sub.2 and the two adjoining
sections 12.sub.2 of the phases 7.sub.2. The same holds for the third
tooth 2.sub.3 of the first group and the intermixed teeth 2* of the second
group. For the teeth 2* the sections 12* are the same as the phases 7*.
Exending the flanks 10 in the direction of a line through section 6.sub.1
yields a theoretical width b for the teeth 2, 2*.
It can be seen from FIG. 3 that only the outer corners 15* of the teeth 2*
of the second group cut, while the corners 15.sub.1, . . . 15.sub.n of the
teeth 2 move within the cutting channel and do not contribute to the
removal of material. For the service life and the inevitable wear at the
corners 15* it is important to note that the angle between the phase 7*
and the flank 10* is not acute but obtuse, i.e. greater than 90.degree.,
preferably much so.
Also shown in FIG. 3 is the uniform height graduation, which even extends
over the teeth 2 of the first group and the teeth 2* of the second group.
The height and width graduation in conjunction with the phase angle 9 has
been chosen so that each tooth 2, 2* of the two groups removes strips of
material as shown in FIG. 6, where the width of the strip per tooth is
roughly equal, the thickness of material removed being very different,
though. The thickness of the strips is equal for the teeth 2.sub.1,
2.sub.2, 2.sub.3 of the first group; each remove a relatively thick chip
from the material. The thicknesses of the strips 2* are much smaller. It
can be seen that while three thick strips are being removed per unit time
by the teeth 2 of the first group, three thinner strips are being removed
by the teeth 2*. Each chip removed by a tooth 2, 2* is bent in two
different directions at the inflection point 17 of the cutting edge
between the straight section 6 and the effective part of the phase 7. This
contributes to splitting up the individual chips further during removal.
The embodiment of the FIG. 4 is similarly formed as the one in FIG. 3.
However, the phase angle 9 is 30.degree. in this case, while there are
still three teeth 2 in the first group, intermixed with three teeth 2* of
the second group. Furthermore, it is assumed that there is also a constant
pitch so there are still six teeth in a cycle. The height and width
graduations are carried out uniformly over the teeth of both groups.
In the embodiment of FIG. 5 there are three teeth 2.sub.1, 2.sub.2, 2.sub.3
in the first group, intermixed with three teeth 2* of the second group, so
there are also six teeth in the cycle. The phase angle is 45.degree. and
the flank angle 11 has been chosen to be 8.degree.. The cutting edges 5 of
the teeth 2 of the first group are in this case comprised of three
straight sections instead of two, so that there are two inflection points
17.sub.1 and 17.sub.1 ". The first and therefore highest tooth 2.sub.1 has
a straight section 6.sub.1, adjoined by a first phase section 18.sub.1
with a phase angle 9' and then the phase 7.sub.1. The phase 7.sub.1 has a
phase angle 9. The second tooth, the first tooth 2* of the second group,
has a continuous, unbroken straight cutting edge and a rounded off corner
20, which works on the surface of the cutting channel. The following tooth
2.sub.2 of the first group has a straight cutting edge section 14.sub.2, a
first phase section 18.sub.2, and a second phase 72. It can be seen that
the entire phase section 18.sub.2 lies in the region of the effective part
of the cutting edge of the tooth 2.sub.2, while of the phase 7.sub.2 again
only the section 12.sub.2 is effective in a cutting manner. Tooth 2.sub.2
of the first group is again followed by a tooth 2* of the second group,
which in turn is followed by the third tooth 2.sub.3 of the first group.
It is seen that the cutting edge 5 of each tooth can be changed in its
shape by the number of inflection points 17, so that in the limit of
infinitely many inflection points a rounded cutting edge is created for
each tooth 2. But even in this embodiment, with an even height and width
graduation only for the teeth 2 of the first group, thick chips are
removed by the teeth 2, while the teeth 2* still remove thin chips.
FIG. 6 depicts yet another embodiment, which may essentially coincide with
the previously described embodiments. The number of teeth 2 in the first
group is again three. The number of teeth 2* in the second group is also
three, so that there will be six teeth in a cycle with an even pitch. This
time there are no straight, i.e. perpendicular to the longitudinal center
plane 8, sections 6 provided for the teeth 2 of the first group and 2* of
the second group, but instead slightly arrow shaped sections 16 with an
angle 9''. The hatched areas in FIG. 6 depict the stripes 19.sub.1,
19.sub.2, 19.sub.3, and 19* of material removed by the teeth 2.sub.1,
2.sub.2, 2.sub.3, and 2* , respectively.
FIG. 7 shows a side view of FIGS. 1 and 3 over a full cycle, with three
teeth 2.sub.1, 2.sub.2, and 2.sub.3 in the first group and three teeth 2*
in the second group, so that a constant pitch yields a cycle of teeth
2.sub.1, 2*, 2.sub.2, 2*, 2.sub.3, 2*.
FIG. 8 illustrates the superposition of height and width graduation of
teeth 2, 2* as in FIG. 7 with a variable pitch. For simplified
illustration let it be assumed again that with regard to a height
graduation there is a first group of three teeth 2 and a second group of
three teeth 2*' which recurr in the specified sequences and are provided
thus. The total number of teeth in the two groups is thus six. At the same
time, a variable pitch with nine pitches t.sub.1, . . . t.sub.9 is
represented, so that in a group of teeth determined by the pitch, the
number of teeth in such a pitch group is nine. The form of the teeth 2,2*
with regard to the provision of cutting edges 5, sections 6, and phases 7
is precisely the same as described with reference to the preceding
embodiments. The result is a cycle with the smallest common multiple
number of teeth, i.e. 6.times.9=54. Not until the fifty--fifth tooth is
there an exact correspondence with regard to its design, its height, and
its assigned pitch.
FIG. 9 shows another embodiment in side view, for simplicity*s sake with a
constant pitch. A group of three first teeth 2.sub.1, 2.sub.2, 2.sub.3 is
provided. To this a second group of three teeth 2* is assigned. This
second group is formed and provided in a double recurrance. It could also
be said that each tooth 2* appears twice. This causes the distance between
the first tooth 2.sub.1 and the second tooth 2.sub.2 of the first group to
become even larger, so that the chips removed by these teeth become even
thicker. The teeth 2* remove relatively thin chips, with differently thick
chips removed by the two second groups.
While the foregoing specification and drawings disclose preferred
embodiments of the invention, it will be understood by those skilled in
the art that variations and modifications thereof can be made without
departing from the spirit and scope of the invention as set forth in the
following claims.
LIST OF REFERENCE NUMERALS:
1--basic body
2--teeth
3--height
4--width
5--cutting edge
6--section
7--phase
8--longitudinal center plane
9--phase angle
10--flank
11--flank angle
12--section
13--projection intersection
14--cutting edge section
15--corner
16--section
17--inflection point
18--phase section
19--stripe
20--rounded corner
* * * * *
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