METHOD FOR MULTI-GEAR HOBBING AND ITS APPLICATION THEREOF
Technical field of the present invention:
The present invention generally discloses a method for hobbing more than one gear
work-pieces simultaneously using single hob cutter. The present invention mainly
relates to simultaneous hobbing of multiple work-pieces of preferably single type of
gear on state of the art high speed automated dry hobbing machines, being used in
gear hobbing industries. Maximum number of gear work-pieces to be hobbed
simultaneously by the present method herein, preferably depends on the thickness
of single work-piece and the length of the hob cutter in operation therein. The
present invention preferably proposes to hob multiple gear work-pieces
simultaneously on the same platform of the automatic dry hobbing machines. The
process proposed herein significantly increases the quantity of gears manufactured
at modern hobber machines.
Background and object of the present invention:
Gear Hobbing is a machining process for making gears on a hobbing machine,
which is a special type of milling machine. The teeth are progressively cut into the
work-piece by a series ~f cuts made by a teeth cutting tool called a hob or hob cutter.
Compared to other gear forming processes, hobbing is relatively inexpensive but still
quite accurate, thus it is used for a broad range of partsand quantities.
Hobbing is the most widely used gear cutting process for creating spur and helical
gears and more gears are cut by hobbing than any other process since it is relatively
quick.
As gears are very important component for power transmission and especially in
auto industry, huge numbers of gears, in diverse range of dimensions,. are being
manufactures in gear making industries. Apart from maintaining the desired quality
and high abrasion resistance properties of the gears, quick manufacturing of a gear
in least possible time, involving minimum resources is the most important aspect in
cost effective manufacturing of teethed gears.
Due to this reason, in modern practice highly automated software guided hob milling
machines are being used to perform teeth hobbing operations on gear work-pieces.
These hobbing machines are so designed that the strategically assembled hob cutter
is provisioned for cutting teeth on the desired surfaces, preferably on round/circular
surfaces of a gear work-piece, wherein said hob cutter performs the hobbing
operation on the round/circular surface of a gear work-piece of very specific diameter
and of a particular thickness of the work-piece.
In conventional practice the hob cutting machine is so customized for hobbing gear
work-pieces one by one. Such hobbing operations are conventionally automated by
certain software or logic mechanism applicable therein and one cycle of hobbing
operation gets completed within few seconds or within few minutes, depending on
the diameter of the gear work-piece.
The purpose of the present invention is to propose a novel mechanism for
performing hobbing operation on more than one gear work-pieces simultaneously by
operating single hob cutter on them and while performing such simultaneous multihobbing
task, the time involved for one hobbing cycle therein is preferably same or
approximately same as the conventional hobbing cycle for single gear work-piece
undergoing hobbing operation on the same machine therein. Thus the present
invention significantly reduces the hob cycle time for one work-piece hobbled by the
proposed method herein. At the same time the present invention substantially
reduces the other resources involved in the hobbing operation and helps in
increasing the production of gears many times.
Main object of the present invention is to propose a method for performing hobbing
operation on more than one gear work-pieces simultaneously by operating single
hob cutter on them, preferably on an automatic dry hobbing machine.
Another object of the present invention is to propose an optional module towards
loadinglmounting, preferably as vertical or horizontal stacking as the case may be, of
more than one gear work-pieces on the work-arbor simultaneously, preferably the
automatic loading of a set of pre-determined number of gear work-pieces on a
suitable work-arbor
Another object of the present invention is to propose a virtual gear work-piece, as a
virtual cylindrical gear work-piece, which is actually created on the work-arbor of the
hobbing machine therein involved, by stackinglmounting of multiple gear work-pieces
therein, wherein the diameter of the said virtual gear work-piece is similar to each
individual gear work-piece mounted thereof and the thickness of said virtual gear
work-piece is equal to or more than the total sum of the thicknesses of all gear workpieces,
simultaneously mounted on the work arbor for simultaneous hobbing.
Another object of the present invention is to propose the application of certain type of
spacer elements, which are optionally applied in creating the said virtual gear workpieces
on the work-arbor, wherein such spacer elements and gear work-pieces are
simultaneously loadedlmounted on the work arbor one after another alternatively,
and therefore the total thickness of said virtual gear element, made of alternately
arranged gear work-pieces and spacer elements, is more than the sum total of the
thicknesses of the gear work-pieces mounted therein to be hobbed simultaneously.
Another object of the present invention is to propose a work-arbor, which is capable
of holding and handling said virtual cylindrical gear work-piece, comprising of
multiple gear work-pieces and optionally multiple spacer elements therein, during the
simultaneous hobbing operation using single hob cutter on them; wherein it is
capable of performing its pre-defined mechanical functions and movements to
support the proposed hobbing operation herein, in co-ordination with the functional
hob cutter therein.
Another object of the present invention is to propose a hob or hob cutter, wherein
said single hob or hob cutter is capable of cutting teeth on the cylindrical round
surface of the virtual cylindrical gear work-piece, comprising of multiple gear workpieces
and optionally multiple spacer elements therein, mounted on the work-arbor;
wherein it is capable of performing its pre-defined mechanical hob cutting functions
and movements thereto to support the proposed hobbing operation herein, in coordination
with the functional work-arbor therein.
Another object of the present invention is to propose an optional module towards
automatic unloading of simultaneously hobbed multiple gears from the work arbor of
the hobbing machine.
Another object of the present invention is to propose an effective fume control
module including an effective exhaust fan therein, which is required in the automatic
dry hobbing machines.
Statement of the invention:
The present invention is intended to propose:
A method for performing hobbing operation on more than one gear workpieces
simultaneously by operating single hob cutter on them, ,preferably on
an automatic dry hobbing machine;
An optional module towards loadinglmounting, preferably as vertical or
horizontal stacking as the case may be, of more than one gear work-pieces
on the work-arbor simultaneously, preferably the automatic loading of a set of
pre-determined number of gear work-pieces on a suitable work-arbor;
A virtual gear work-piece, as a virtual cylindrical gear work-piece, which is
actually created on the work-arbor of the hobbing machine therein involved,
by stackinglmounting of multiple gear work-pieces therein, wherein the
diameter of the said virtual gear work-piece is similar to each individual gear
work-piece mounted thereof and the thickness of said virtual gear work-piece
is equal to or more than the total sum of the thicknesses of all gear workpieces,
simultaneously mounted on the work-arbor for simultaneous hobbing; . -
The application of certain type of spacer elements, which are optionally
applied in creating the said virtual gear work-pieces on the work-arbor,
wherein such spacer elements and gear work-pieces are simultaneously
loaded/mounted on the work arbor one after another alterinatively, and
therefore the total thickness of said virtual gear element, made of alternately
arranged gear work-pieces and spacer elements, is more than the sum total
of the thicknesses of the gear work-pieces mounted therein to be hobbed
simultaneously;
A work-arbor, which is capable of holding and handling said virtual cylindrical
gear work-piece, comprising of multiple gear work-pieces and optionally
multiple spacer elements therein, preferably during the simultaneous hobbing
operation using single hob cutter on them; wherein it is capable of performing
its pre-defined mechanical functions and movements to support 'the proposed
hobbing operation herein, in co-ordination with the functional hob cutter
therein;
A hob or hob cutter, wherein said single hob or hob cutter is capable of cutting
teeth on the cylindrical round surface of the virtual cylindrical gear work-piece,
comprising of multiple gear work-pieces and optionally multiple spacer
elements therein, mounted on the work-arbor; wherein it is capable of
performing its pre-defined mechanical hob cutting functions and movements
thereto to support the proposed hobbing operation herein, in co-ordination
with the functional work-arbor therein;
An optional module towards automatic unloading of simultaneously hobbed
multiple gears from the work-arbor of the hobbing machine; and
An effective fume control module including an effective exhaust fan therein,
that is required in the automatic dry hobbing machines.
Description of the present invention:
The present invention generally relates to a novel automatic hobbing operation on a
gear hobbing machine wherein more than one gear work pieces are simultaneously
mounted on a suitably designed and structured work-arbor. The work-arbor is so
designed, that it can effectively hold plurality of gear work-pieces and can carry out
its pre-defined mechanical functions and movements towards performing
simultaneous hobbing operation on multiple gear work-pieces therein. Such
simultaneous multi hobbing operation is applicable for several types of gears, viz.
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spur and helical gears, crowned and tapered gears, worm gears, pinions etc.;
wherein the teeth profile is to be created on the round cylindrical surface of each of
them, simultaneously mounted as a virtual cylindrical gear work piece on the workarbor.
Once the gear work pieces, preferably in a particular number according to the
dimension and functional abilities of the work-arbor and the hob cutter thereof, are
mounted on the work-arbor of the automated software guided hob milling machines,
a virtual cylindrical gear work-piece gets created there, wherein the complete
cylindrical surface of said virtual cylindrical gear work piece is subjected to a single
hob cutter. Said hob cutter is of such a dimension, preferably of its hob cutting teeth
profile, length of hob cutter and the diameter of said hob cutting teeth profile thereof ,
that it can cut corresponding teeth profiles on all the gear work pieces
simultaneously in the desired manner and angles. For such simultaneous hobbing
operation on said virtual cylindrical gear work piece is suitably programmed to
perform mutual verticallhorizontal movements of hob cutter and the work-arbor, RPM
of hob cutter therein, frequency of work-arbor towards its rotational motion therein
etc.
The frequency of performing hob action is regulated by certain software andlor
suitable logic program.
In a particular preferred exemplary instance of simultaneous hobbing operation on
said virtual cylindrical gear work piece, the process proceeds in following stepwise
manner:
Step I: Preparation of gear blank work pieces for hobbing,, mainly by forging
operations;
Step II: Mounting of a particular number of gear work-pieces on the work-arbor,
preferably in vertical position on the work-arbor and creating a virtual cylindrical gear
work-piece therein, preferably automatically;
Step Ill: Preferably in automatic manner, subjecting the set of said particular number
of gear work pieces, as the virtual cylindrical gear work-piece therein to a functional
cylindrical Hob cutter, preferably positioned in horizontallvertical or angular direction,
towards simultaneous hobbing operation on those gear work pieces for generating
corresponding teeth on the complete cylindrical surface of said virtual cylindrical
gear.
Step IV: After simultaneous hobbing of multiple gear work pieces, removal of finished
gears from the work-arbor and reloading of same number of gear work pieces on
same work-arbor, preferably automatically.
As the contact area and time between the virtual gear work piece and the hob cutter
is considerably increased in the present proposed simultaneous hobbing operation
on multiple gear work pieces, therefore it is likely that substantially large volume of
fumes gets generated .and considerably high heat is evolved during the operation.
Therefore it is important to apply an effective module for expelling said fumes and
heat generated, preferably in a dry manner. An effective exhaust fan and effective air
circulation duct is provisioned around the action area of the hob cutter in use.
For one preferred exemplary embodiment of a gear work piece being hobbed herein,
preferably on a dry automatic Liebherr hob milling machine, the thickness or length
of the cylindrical surface of the gear work piece is 12mm and its diameter is in a
range of 40 to 50 mm. It is important that the hob milling machine chosen herein is of
same platform, which -is conventionally applicable for hobbing similar gear work
pieces one-by-one and not simultaneously. Therefore the total thickness or the
length of the cylindrical round surface of said virtual cylindrical gear work piece,
made of five individual gear work pieces thereof, is 60mm. The diameter of said
virtual cylindrical gear work piece is same as all five individual gear work pieces
mounted therein on the work-arbor, that is in the range of 40 to 50 mm.
If hobbing operation is performed in conventional manner on the same automatic dry
hobbing machine, only'one gear work piece would be hobbed by consuming time of
one hobbing cycle and this time is preferably 75 seconds. But as per the proposed
method of simultaneous hobbing of multiple gear work pieces herein, the total time
consumed in one complete hobbing cycle for creating teeth on the complete
cylindrical surface of said virtual cylindrical gear work piece herein, which comprises
of five individual gear work pieces, is also preferably 75 seconds. Therefore the time
consumed for one hobbing cycle of one gear work piece of thickness 12mm remains
one fifth of the total 75 seconds consumed for hobbing of said virtual cylindrical gear
work piece, that is, only. 15 second.
Again, in another preferred exemplary instance of simultaneous hobbing operation,
the gear work pieces are such that there are certain lugs provisioned on one of its
flat surfaces. As the surfaces of the gear work pieces are not smooth and are not
suitable for stacking of multiple pieces of said gear pieces and therefore certain
spacer elements are sandwiched between two gear work pieces, leading to a proper
virtual cylindrical gear work piece. Thus a preferred exemplary embodiment of virtual
cylindrical gear work piece gets created comprising of alternately arranged individual
actual gear work pieces and spacer elements, wherein the number of individual gear
work-pieces are pre-determined. Such virtual cylindrical gear work piece, made up of
multiple gear work pieces and multiple spacer elements suitably undergoes
simultaneous hobbing operation, as herein proposed.
Scope of the present invention:
Although the invention has been described with reference to specific embodiments,
this description is not meant to be construed in a limiting sense. Various
modifications of the disclosed embodiments, as well as alternate embodiments of the
invention, will become apparent to persons skilled in the art upon reference to the
description of the invention. It is therefore contemplated that such modifications can
be made without departing from the spirit or scope of the present invention as
defined.

We claim:
1. A method for multi-gear hobbing and its application thereof towards hobbing
more than one gear work-pieces simultaneously using single hob cutter,
preferably on an automatic dry hob milling machine; wherein said hobbing
operation mainly involves:
(i) a work-arbor loaded with a virtual gear work piece comprising of
preferably plurality of gear work-pieces, with or without plurality of
spacer elements therein, stacked together on the work-arbor,
(ii) a hob cutter suitable for hobbing on the complete cylindrical surface of
said virtual gear work-piece, and
(iii) effective fume control module and air cooling system, preferably as
essential part of the automatic dry hobbing machines;
wherein said method of multi-gear hobbing is characterized by, at least one
operations among other things, optional module towards loadinglmounting of
more than one gear work-pieces on the work-arbor simultaneously;
stackinglmounting of said virtual gear work-piece on a suitable work-arbor;
simultaneous hobbing of plurality of gear work pieces stackedlmounted on the
work-arbor as said virtual gear work piece; optional module towards automatic
unloading of habbed multiple gears from said work-arbor of the hobbing
machine; and functioning of a module for fume control and air cooling system,
preferably in an automatic dry hobbing machine.
2. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein the hobbing operation herein is characterized by
simultaneous hobbing on more than one gear work-pieces mountedlstacked
on one suitable work-arbor, by operating single hob cutter on them, preferably
on an automaticdry hobbing machine.
3.' A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein the hobbing machine optionally comprises of a module
towards loadinglmounting, preferably as vertical or horizontal stacking, as the
case may be, of .more than one gear work-pieces on the work-arbor
simultaneously, preferably the automatic loading of a set of pre-determined
number of gear work-pieces on a suitable work-arbor therein.
4. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein the virtual gear work-piece, as a virtual cylindrical gear workpiece,
is actually created on the work-arbor of the hobbing machine therein,
by stackinglmounting of multiple gear work-pieces therein, wherein said virtual
gear work-piece is characterized by its diameter being same as to each
individual gear work-piece mounted therein and its thickness being equal to or
more than the total sum of the thicknesses of all individual gear work-pieces,
simultaneously mounted on said work-arbor for simultaneous hobbing.
5. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein said spacer elements, preferably in plurality, are optionally
applied in creating the said virtual gear work-pieces on the said work-arbor,
wherein such spacer elements and gear work-pieces ,are simultaneously
stackedlmounted on the work-arbor one after another, and therefore the total
thickness of said virtual gear element, made of alternately
arranged/stacked/mounted gear work-pieces and spacer elements, is more
than the sum total of the thicknesses of individual gear work-pieces,
simultaneously mounted therein.
6. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein the work-arbor of the hobbing machine is characterized by its
capability of holding and handling said virtual gear work-piece during the
simultaneous hobbing operation using single hob cutter; wherein said workarbor
is further characterized by is capability of performing its pre-defined
mechanical functions and movements to support the proposed hobbing
operation herein, in co-ordination with the functional single hob cutter therein.
7. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein said single hob or hob cutter of the hobbing machine is
characterized by its capability of cutting teeth on the cylindrical round surface
of said virtual gear work-piece, comprising of multiple individual gear workpieces
and optionally multiple spacer elements therein, mounted on the workarbor;
wherein said hob or hob cutter is further characterized by its capability
of performing .its pre-defined mechanical hob cutting functions and
movements thereto to support the proposed simultaneous hobbing operation
herein, in co-ordination with the functional work-arbor therein.
8. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein the hobbing machine optionally comprises of an optional
module towards automatic unloading of simultaneously hobbed multiple gears
from the work-arbor of said hobbing machine. .
9. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1, wherein the hobbing machine preferably comprises of a fume control
module and air cooling system, wherein it including an effective exhaust fan
and effective air circulation duct around the action area of the hob cutter in
use therein.
10. A method for multi-gear hobbing and its application thereof, as claimed in
claim 1 and as substantially described and illustrated hereinabove. I
Date: 07.06.201 2