GEAR HOBBING CUTTER WITH NON-CONSTANT WHOLE DEPTHS
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Patent Application No. 62/004,536
filed on May 29, 2014. The disclosure of the above application is incorporated herein by
reference.
FIELD
[0002] The present disclosure relates generally to gear cutting tools and more
specifically, to a gear hobbing apparatus for producing a gear from a blank.
BACKGROUND
[0003] Gears are typically cut from a work piece or blank during a tooth generating
operation called hobbing. A hob cutter is designed to produce a tooth form with a given
tooth height, pressure angle, and tooth thickness. All teeth produced with a typical hob
cutter have the same tooth height, pressure angle, and tooth thickness. The shape of the
features is described by a gear rack. A typical hob is cylindrical in shape and has helical
cutting teeth. These teeth have grooves that run the length of the hob. The grooves can
assist in cutting the blank and facilitate chip removal. During use, the teeth of the hob
can be progressively cut into the work piece by a series of cuts made by the hob.
SUMMARY
[0004] A gear hobbing apparatus for producing a gear from a blank according to one
example of the present disclosure can include a hob, a first series of hob teeth and a
second series of hob teeth. The hob can have a cylindrical hob body. The first series of
hob teeth can extend from the cylindrical hob body and have a first whole depth. The
second series of hob teeth can alternately extend from the cylindrical hob body with the
first series of hob teeth and have a second whole depth. The first and second whole
depths are distinct and configured to create a gear from the blank that has adjacent teeth
having distinct outer diameters.
[0005] According to additional features, the hob has a single start thread. According
to other features, the hob has multiple start threads. The hob can have a first thread
having a first rack profile and a second thread having a second rack profile. The first
thread and the second threads are distinct. The first and second rack profiles are distinct.
In other examples, a hob having three or more threads having three or more rack profiles
is provided.
[0006] A gear hobbing apparatus for producing a gear from a blank constructed in
accordance to additional features of the present disclosure includes a hob, a first tooth
and a second tooth. The hob can have a cylindrical hob body and a cylindrical axis. The
first tooth can extend from the cylindrical hob body and have a first diameter measured
from the cylindrical axis and providing a first whole depth. The second tooth can extend
adjacently from the cylindrical hob body from the first hob tooth and have a second
diameter measured from the cylindrical axis and providing a second whole depth. The
first and second diameters are equivalent. The first and second whole depths are distinct.
The hob is configured to create a gear from the blank that has adjacent teeth having
distinct outer diameters.
[0007] According to additional features, the gear hobbing apparatus can further
include a first series of hob teeth having the first whole depth. The gear hobbing
apparatus can further include a second series of hob teeth alternately extending from the
cylindrical hob body with the first series of hob teeth. The second series of hob teeth can
have the second whole depth.
[0008] According to other features, the hob has a single start thread. In other
arrangements, the hob can have multiple start threads. The hob can have a first thread
having a first rack profile and a second thread having a second rack profile. The first
thread and the second thread are distinct. The first and second rack profiles are distinct.
[0009] A method of producing a gear from a gear blank having a gear blank axis
according to one example of the present disclosure can include, providing a hob having
(i) a cylindrical hob body having a hob axis, (ii) a first series of hob teeth extending from
the cylindrical hob body and having a first whole depth and (iii) a second series of hob
teeth alternately extending from the cylindrical hob body with the first series of hob teeth
and having a second whole depth. The first and second whole depths are distinct. The
hob can be translated across a circumferential face of the gear blank. The hob and the
gear blank can rotate about their respective axes. The gear blank can be cut with the first
and second series of hob teeth. The first and second hob teeth create a gear having
adjacent teeth having distinct outer diameters.
[0010] The hob can have a single start thread in one example. The hob can have
multiple start threads in another example. The hob can have a first thread having a first
rack profile and a second thread having a second rack profile. The first thread and the
second threads can be distinct. The first and second rack profiles can be distinct.
BRIEF DESCRIPTION OF THE DRAWINGS
[001 1] The present disclosure will become more fully understood from the detailed
description and the accompanying drawings, wherein:
[001 2] FIG. 1 is a side view of a hob constructed in accordance to one example of the
present disclosure and shown forming a gear having gear teeth into a blank;
[0013] FIG. 2 is a detail view of the hob and blank of FIG. 1 and shown illustrating
respective hob teeth and gear teeth;
[0014] FIG. 3 is an axial view of the hob of FIG. 1;
[0015] FIG. 4 is another side perspective view of the hob of FIG. 1;
[0016] FIG. 5 is a detail view of one of the teeth extending from the hob of FIG. 4 ;
[0017] FIG. 6 is a sectional view of the hob illustrating adjacent whole depths defined
by adjacent teeth on the hob; and
[001 8] FIG. 7 is a plan view of a resulting gear formed by the hob of FIG. 1 and shown
meshing with an adjacent second gear according to one example of the present
disclosure.
DETAILED DESCRIPTION
[0019] With initial reference to FIGS. 1 and 2, a gear hobbing apparatus or hob
constructed in accordance to one example of the present disclosure is shown and
generally identified at reference numeral 10. The hob 10 can be constructed for producing
a gear 20 from a work piece or blank 22. The hob 10 can be configured to rotate around
a hob spindle 30. The hob 10 has a cylindrical hob body 32 that includes an axis 36 that
is common to a rotational axis of the hob spindle 30. The hob 10 can generally include
hob teeth 40. Gashes 42 are formed longitudinally along the cylindrical hob body 32
between the hob teeth 40.
[0020] As will be described and become more fully appreciated from the following
discussion, the hob 10 is used to form the gear 20 from the blank 22. In this regard, the
gear 20 will have gear teeth 50 formed therearound. The blank 22 can be configured to
rotate about a blank axis 56. The blank 22 can be mounted for rotation with a work piece
spindle 60. As will be described in further detail herein, the gear 20 will be formed by the
hob 10 in a manner such that not all of the gear teeth 50 will have the same outer
diameter.
[0021] The hob 10 is constructed such that the teeth 50 having different outer
diameters can be formed in a single operation without subsequent machining steps. In
this regard, during the formation or hobbing of the gear 20, a first series of hob teeth 40A
can be provided that have a whole depth 70 while a second series of hob teeth 40B have
a whole depth of 72. The first whole depth 70 can generally be defined from a flute 74 on
the hob 10 to a tip 76 on the first tooth 40A. Similarly, the whole depth 72 can be defined
between a flute 77 and a tip 78 of the second tooth 40B. The whole depth 70 and the
whole depth 72 are distinct. Moreover, because the flutes 74 and 77 are at distinct
locations, the root diameter of the first and second series of hob teeth 40A and 40B varies.
The varying root diameter allows for the cutting of the different tooth height teeth 50 in the
gear 20.
[0022] In the example shown, the whole depth 72 is less than the whole depth 70. As
a result, the gear teeth 50 that are formed by the hob 10 will have a first series of gear
teeth 50A and a second series of gear teeth 50B. The first series of gear teeth 50A will
have a diameter 80 measured from the axis 56. The gear teeth 50B will have a diameter
82 measured from the gear axis 56. According to the teachings of the present disclosure,
the gear tooth 50A will have a diameter 80 that is greater than the diameter 82 of the gear
tooth 50B.
[0023] With additional reference now to FIGS. 3-5, additional features of the hob 10
will be described. The hob 10 can define a hole diameter 100 formed through the
cylindrical hob body 32. The hob 10 can define an outside diameter 110. Gash spacing
120 can be radially defined between adjacent flutes 74 and 78. Each hob tooth 40 can
include a radial cutting face 122 and a cam 124.
[0024] The hob 10 can further define a pitch diameter 130, a hub 132, a cutting face
width 134 and a hob length 136. A pressure angle 140 can be defined by the hob teeth
40. Adjacent teeth 40 can define a lead 144. A first thread 150 and a second thread 152
(FIG. 6) can further be provided on the hob 10. With specific reference to FIG. 5, a hob
tooth 40 can further include a tooth thickness 160, a tip radius 162, a hob addendum 164,
and a tip relief modification 168. A whole depth of cut 170 can be defined by each tooth
40.
[0025] Turning now to FIG. 6, the first thread 150 and the second thread 152 are
shown on the cylindrical body 32 of the hob 10. The threads 150 and 152 generally define
a lead angle of the cutting action of the hob 10. Turning now to FIG. 7, the hob 10 is
configured to form the gear 20 having adjacent teeth 50 (such as teeth 50A and 50B)
having distinct diameters 80 and 82. In the example shown, the diameter 80 is larger
than the diameter 82. Because the teeth 50A and 50B, alternately formed around the
gear 20 have distinct diameters, they will have distinct engagement points on mating teeth
200 of a corresponding conventional gear 220 where the teeth 200 have common
diameters. In this regard, the meshing event can have different resonant frequencies
created allowing for a quieter engagement between the respective gears 50 on the gear
20 and the gear teeth 200 on the gear 220.
[0026] A method for producing the gear 20 using the hob 10 according to one example
of the present disclosure will now be described. At the outset the hob 10 is selected
having characteristics suitable for producing the desired gear 20. In this regard, the hob
10 is selected having a desired pitch diameter 130, cutting face width 134, hob length
136, pressure angle 140, tooth thickness 160, tip radius 162, hob addendum 164, tip relief
modification 168 and whole depth of cut 170 for each resulting tooth. The first series of
hob teeth 40A have the whole depth 70 that is greater than the whole depth 72 provided
by the alternating second series of teeth 40B.
[0027] The hob spindle 30 can be fixed for rotation around the axis 36. The hob
spindle 30 can be rotated by a drive motor (not specifically shown). The work piece
spindle 60 can be fixed for rotation around the gear axis 56. The hob 10 is translated
across a circumferential face of the work piece 22 while the hob 10 rotates about the axis
36 and the work piece 22 rotates about the axis 56. The first and second series of hob
teeth 40A and 40B have distinct whole depths 70 and 72. The first and second series of
hob teeth 40A and 40B cut the work piece 22 creating the gear 20 having alternating gear
teeth 50A and 50B. The gear teeth 50A and 50B have distinct outer diameters.
[0028] The foregoing description of the embodiments has been provided for purposes
of illustration and description. It is not intended to be exhaustive or to limit the disclosure.
Individual elements or features of a particular embodiment are generally not limited to
that particular embodiment, but, where applicable, are interchangeable and can be used
in a selected embodiment, even if not specifically shown or described. The same may
also be varied in many ways. Such variations are not to be regarded as a departure from
the disclosure, and all such modifications are intended to be included within the scope of
the disclosure.

CLAIMS
What is claimed is:
1. A gear hobbing apparatus for producing a gear from a blank, the gear
hobbing apparatus comprising:
a hob having a cylindrical hob body;
a first series of hob teeth extending from the cylindrical hob body and having
a first whole depth; and
a second series of hob teeth alternately extending from the cylindrical hob
body with the first series of hob teeth and having a second whole depth;
wherein the first and second whole depths are distinct and configured to
create a gear from the blank that has adjacent teeth having distinct outer diameters.
2 . The gear hobbing apparatus of claim 1 wherein the hob has a single start
thread.
3. The gear hobbing apparatus of claim 1 wherein the hob has multiple start
threads.
4 . The gear hobbing apparatus of claim 1 wherein the hob has a first thread
having a first rack profile and a second thread having a second rack profile, wherein the
first and second threads are distinct.
5. The gear hobbing apparatus of claim 4 wherein the first and second rack
profiles are distinct.
6 . A gear hobbing apparatus for producing a gear from a blank, the gear
hobbing apparatus comprising:
a hob having a cylindrical hob body and a cylindrical axis;
a first tooth extending from the cylindrical hob body and having a first
diameter measured from the cylindrical axis and providing a first whole depth;
a second tooth adjacently extending from the cylindrical hob body from the
first hob tooth and having a second diameter measured from the cylindrical axis and
providing a second whole depth; and
wherein the first and second diameters are equivalent, the first and second
whole depths are distinct and wherein the hob is configured to create a gear from the
blank that has adjacent teeth having distinct outer diameters.
7. The gear hobbing apparatus of claim 6 further comprising a first series of
hob teeth having the first whole depth and a second series of hob teeth alternately
extending from the cylindrical hob body with the first series of hob teeth, the second series
of hob teeth having the second whole depth.
8. The gear hobbing apparatus of claim 6 wherein the hob has a single start
thread.
9. The gear hobbing apparatus of claim 6 wherein the hob has multiple start
threads.
10. The gear hobbing apparatus of claim 6 wherein the hob has a first thread
having a first rack profile and a second thread having a second rack profile, wherein the
first and second threads are distinct.
11. The gear hobbing apparatus of claim 10 wherein the first and second rack
profiles are distinct.
12. A method of producing a gear from a gear blank having a gear blank axis,
the method consisting of:
providing a hob having (i) a cylindrical hob body having a hob axis, (ii) a first
series of hob teeth extending from the cylindrical hob body and having a first whole depth
and (iii) a second series of hob teeth alternately extending from the cylindrical hob body
with the first series of hob teeth and having a second whole depth, wherein the first and
second whole depths are distinct;
translating the hob across a circumferential face of the gear blank wherein
the hob and the gear blank rotate about their respective axes; and
cutting the gear blank with the first and second series of hob teeth wherein
the first and second hob teeth create a gear having adjacent teeth having distinct outer
diameters.
13. The method of claim 12 wherein the hob has a single start thread.
14. The method of claim 12 wherein the hob has multiple start threads.
15. The method of claim 12 wherein the hob has a first thread having a first rack
profile and a second thread having a second rack profile, wherein the first thread and the
second threads are distinct.
16. The method of claim 12 wherein the first and second rack profiles are
distinct.