FORM 2
THE PATENTS ACT 1970 (39 OF 1970)
&
THE PATENTS RULES, 2003


COMPLETE SPECIFICATION (See section 10 and ruie 13)
TITLE OF THE INVENTION
CNC GEAR SHAVING MACHINE MODEL: PSS-300
APPLICANTS
PREMIER LIMITED
AN INDIAN COMPANY
of 58, NARIMAN BHAWAN,
NARIMAN POINT,
MUMBAI-400 021, INDIA

The following specification particularly describes the invention and the manner in
which it is to be performed


CNC GEAR SHAVING MACHINE MODEL : PSS-300 FIELD OF INVENTION:
The present invention is directed to gear tooth finishing process & machine which finish the gears already made by hobbing process. Gear shaving is one of the processes of finishing the gear tooth by using shaving cutter having serrations along the cutter tooth flank which form series of cutting edges that generate the removal of metal in the form of tiny chips.
BACKGROUND OF THE INVENTION;
In the shaving process work-piece and the cutter rotate together like pair of helical gears with crossed axes. The shaving cutter receives the motion from the motor and drives the work piece which is mounted in between two live centers. Rotary shaving cutter operates at up to 500 RPM. The feed is fine and cutter is restricted to a definite zone contact. The cutter removes fine hair like shavings from the gear tooth surfaces. Because of the fine cuts, the tool pressure is low and, therefore there is less tendency of cold working gear tooth.
The relationship of the axis of the cutter to the axis of the work is crossed. In other words, they are set at an angle approximately equal to the difference of their helical angles, usually in the range of 10° -15°. This is primarily to obtain a free cutting action with a minimum of contact pressure, thus eliminating a burnishing effect.
The cutter head slide mounted on the column is swiveled the required angle either left or right & moved in downward direction so that teeth on the cutter will match to that of work piece.

During shaving process both the axes are kept in crossed direction. The reason why axes are crossed is to create an action of reciprocal sliding between the cutter tooth flank and the gear tooth.
TYPES OF CYCLES:
■ Transverse Shaving
■ Diagonal shaving
■ Plunge shaving
■ Underpass shaving
■ Diagonal-Underpass shaving
■ Tangential shaving
■ Crown & Taper Shaving
TRANVERSE SHAVING

The gear to be shaved reciprocates in the direction of its own axis while the gear and the tool are in mesh. With each reciprocation a small amount of radial feeding of the shaving cutter occurs. The theoretical table stroke is as long as the face width of the gear to be shaved and it is recommended to

calculate 1 extra stroke per module in order to guarantee clean shaving of the edges. As illustrated in the above figure, this method is unsuitable for shaving shoulder gears.
DIAGONAL SHAVING

Gear at start of stroke
Point of
contact at end of shaving
Shaving cutter

Gear at end of stroke
Point of contact at beginning of shaving

The gear to be shaved reciprocates obliquely in relation to its own axis while the gear and the tool are in mesh. The diagonal angle is achieved either by positioning the work piece table obliquely or by interpolating two machine axes. With each reciprocation radial feeding of the shaving cutter occurs. In general the diagonal angle can be between 0 and 40 degrees but should not be above 25 degrees for reasons of wear.


With this method there is no worktable translation but only a radial feed of the work piece against the shaving cutter. The shaving cutter must be wider than the gear to be shaved and the serrations of the shaving cutter must be in the form of a helix in order to produce the relative tooth flank feed. Plunge shaving is particularly suited to shaving shoulder gears. In this case, however, all tooth modifications must be made to the shaving cutter as it will not be possible to realize them through axial movements on the machine.


With this method there is no worktable translation but only a radial feed of the work piece against the shaving cutter. The shaving cutter must be wider than the gear to be shaved and the serrations of the shaving cutter must be in the form of a helix in order to produce the relative tooth flank feed. Plunge shaving is particularly suited to shaving shoulder gears. In this case, however, all tooth modifications must be made to the shaving cutter as it will not be possible to realize them through axial movements on the machine.

Diagonal-Underpass shaving is diagonal shaving but with a very large oblique angle. With each reciprocation radial feeding of the shaving cutter occurs. The oblique angle is in general between 40 and 90 degrees. Since the oblique angle may be very large, this method is also suitable for shaving shoulder gears but it is important to use shaving cutters with similar characteristics to plunge-type shaving cutters.


The gear to be shaved reciprocates in the direction of its own axis while the gear and the tool are in mesh. With each reciprocation a small amount of radial feeding of the shaving cutter occurs. The theoretical table stroke is as long as the face width of the gear to be shaved and it is recommended to calculate 1 extra stroke per module in order to guarantee clean shaving of the edges. As illustrated in the above figure, this method is unsuitable for shaving shoulder gears.
CROWN SHAVING & TAPER SHAVING
Crown Shaving & Taper Shaving can be achieved by interpolating the three axes that is 'X', 'Y' & T
20 AUG 2009

CONDITION OF WORKPIECE
Shaving being a precision finishing operation is not intended to remove very great amounts of stock from previously hobbed or shaped gears. Consequently, prior gear cutting tolerances should be held to reasonable commercial limits. The closer these tolerance the easier and faster it is to reduce shaved gear tolerance to any desired minimum
Shaving depends upon the character and machinability of the gear materials. Also the accuracy of the blank from which the gear was cut.
Profile of the hobbed gear should be similar to the desired form of the finished gear so that the stock removed is even during the shaving operation. Shaving reduces the profile error of hobbed gear to 66% or more.
SUMMARY OF THE INVENTION:
The present invention provides the possibility of all the above mentioned cycles. The CNC Gear Shaving Machine comprising: a table supported by a supporting bed, a pair of tailstocks on said table, a column vertically installed on said supporting bed, a cutter head which is lifted and lowered on said column by a driving motor, a rotary cutter for finishing gears which can be loaded to a spindle mounted on said spindle housing.
Feed motor is provided to each axis which is directly coupled to the ball screw. Vertical axis ('x' axis) is provided with brake motor.
The axes movement is controlled by A.C. servo motor and for its positioning by precision ground ball screw. Drive to the ball screw is through

coupling. The rapid travel rate for vertical axis ('x' axis) is more to reduce the auxiliary time during non-cutting period
Said cutter head assembly comprising a spindle, spindle housing, a clamping & de clamping mechanism; the clamping & de clamping mechanism comprising a four cylinders mounted on cutter head slide; disc spring is provided for clamping the spindle housing with cutter head slide, de clamping is done hydraulically, the spindle being rotated by a drive which rotates the cutter mounted on a spindle shaft.
Work piece is supported in between two tailstock centers which is mounted on the table. Work piece is rotated through cutter which receives the motion from the motor. Cutter having serrations along the cutter tooth flank which form series of cutting edges that generate the removal of metal in the form of tiny chips.
A control means such as computerized system for example computer numerical control (CNC) or equivalent electronic calculating means appropriate controllable drive unit such as electrically powered motors to provide the necessary linear and rotational movements refer to above
With the machine of the present invention, the difficulties and in accuracies refer to above are eliminated. Resulting in a more precise, structurally sound and strip machine, i.e. mechanically simpler than the Gear Shaving Machine of the prior art.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention:

Fig 1 (a) & (b) schematically illustrates General layout of the present invention.
Fig 2 illustrates the linear (X) axis lay out of the Gear Shaving Machine according to the present invention;
Fig 3 illustrates the linear (Y) axis layout of the Gear Shaving machine according to the present invention;
Fig 4 illustrates the linear (Z) axis layout of the Gear Shaving machine according to the present invention;
Fig 5 illustrates the Spindle axis layout of the Gear Shaving machine according to the present invention;
Fig 6(a) schematically illustrates the drive chain for the cutter rotation.
Fig 6(b) schematically illustrates the drive chain for the 'Y' & 'Z' axes rotation according to the present invention;
Fig 6(b) schematically illustrates the drive chain for the 'X' axis rotation according to the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:
The present invention will now be discussed with reference to the accompanying drawing. The preferred embodiment of the present invention is shown in fig 1(a) and 1(b). The inventive CNC Gear Shaving Machine comprises a column with cutter head & saddle located on a generally "T" shape type machine bed which is mounded on leveling wedges. Cutter head slide which is mounted on the column slides up & down vertically. Spindle housing along with the spindle is mounted on the cutter slide.
As per one aspect of the present invention the machine for providing shaving of gears, said machine consist of a work piece mounted in between the two tailstock centers which are fixed on the table. Work piece receives the motion from the cutter. Cutter mounted on the spindle shaft gets the motion from the spindle motor.
For swiveling of the cutter head slide worm & worm wheel mechanism is provided. A magnetic scale is mounted on the spindle housing through which we can read the required swivel angle.
As shown in FIG (2) 'X' axis layout consist of column with LM guide ways & ball screw coupled to the feed motor. Said cutter head slide with spindle housing slides along this axis. A support bracket is provided at the bottom of the ball screw.
FIG (3) shows 'Y' axis layout. Said layout consist of Bed with LM guide ways & ball screw which is coupled to the feed motor. Said saddle moves along this axis which gives the cross feed to the work piece.

FIG (4) illustrates the 'Z' axis layout for the CNC Gear Shaving Machine. Said layout consists of a Table which moves linearly along the LM mounted on the saddle & gives longitudinal movement to the work piece.
As shown in FIG (5) the spindle axis layout for the CNC Gear Shaving Machine. Comprising of spindle enclosed in spindle housing. Said spindle housing is fitted to the cutter head slide through LM guide ways for vertical movement of the cutter head slide. Swivel angle required for the swiveling of the cutter slide is calculated from the work piece swivel angle & cutter helix angle. The calculated swivel angle is given to the cutter head slide. Worm & worm wheel arrangement is provided to give the required swivel angle. The machine can have a swivel angle up to ±25°. Rotary magnetic scale & digital read out is provided to see the required reading. Accuracy provided for the measurement of swivel angle is about 1". The relative movement of the shaving cutter and the work piece are controller by electronic means from outside such as CNC etc.
FIG 6(a), (b), (c) jointly represents the kinematics for the CNC Gear Shaving Machine. As shown in Fig 6(a) the drive chain mechanism for the cutter rotation Siemens consist of a spindle motor coupled to the 21 teeth pinion. Pinion transmits the motion to the 63 teeth gear. Reduction ratio is 1:3. So, as the rated speed of the spindle is 1500 RPM, spindle will rotate to a maximum speed of 500 RPM.
Fig 6(b) illustrates schematically the drive chain mechanism for 'Y' & 'Z' axes, wherein an AC servomotor is coupled to precision ball screw by coupling. It is the direct drive to ball screw which results higher rapid travel for 'Y' & 'Z' axes. V axis ball screw moves the saddle towards & away from the operator.

Which gives the cross feed to the work piece. Z' axis ball screw moves the table & hence the work piece longitudinally.
Fig 6(c) illustrates schematically the drive chain mechanism for 'X' axis, wherein an AC servomotor is coupled to precision ball screw by coupling. It is the direct drive to ball screw which results higher rapid travel for 'X' axis. As the ball screw rotates cutter slide moves perpendicular to the work piece axis vertically.
The present invention represent an advance over machines of the prior art by providing a mechanically stiffer machine exhibiting improved dynamic characteristics and yet one which is less costly to produce. The inventive machine can be made more reliable than the shaving machine of the prior art.
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

claim:
1. A CNC Gear Saving Machine Comprising:
A support bed, a table and vertical column supported by said support
bed, a pair of tailstocks centers on said table. A cutter head slide
mounted on said column for vertical movement by a driving motor. A
shaving cutter mounted on a spindle shaft which rotates by a spindle
motor.
a work piece mounted on the table has longitudinal as well as
transverse movement.
a work-piece and the cutter rotate together like pair of helical gears
with crossed axes. The shaving cutter receives the motion from the
motor and drives the work piece which is mounted in between two live
centers.
Said machine comprising 3 axes along with one swiveling axis.
Vertical axis (column axis) - 'X' axis
Horizontal axis (table axis) - T axis
Horizontal axis (saddle axis) - 'Y' axis
Swiveling axis (cutter head slide) -'S' axis
2. A machine as defined in claim 1 in which said work piece its axis parallel to the table axis, said cutter comprising it's axis parallel to work piece & table axis.
3. The machine as claimed in claim 1 wherein said control means further comprises of an electronic calculating means.
4. The machine as claimed in claim 2 wherein said electronic calculating
means comprises a CNC.
5. A Gear Shaving Machine for shaving to already produced gears, said
machine comprising:

a machine bed;
a column located on said machine bed, said saddle being movable in transverse direction along said Z' axis, said table including a means for mounting a work piece for rotation about an axis of rotation of said work-piece;
a cutter head slide located on said column, said cutter head slide being movable along a said 'X' axis in a direction perpendicular to both T & Z' axis.
a spindle housing comprising a means for mounting of spindle which comprising a means for mounting of cutter for rotation about an axis of rotation of said shaving cutter.
means for controlling the movement of saddle in a direction along an axis 'Y' means for controlling the movement of said work piece in a transverse direction, means for controlling the movement of table in a direction along an axis 'Z' means for controlling the movement of said work piece in longitudinal direction.
6. The machine as claimed in claim 5 wherein said shaving cutter is a cutting tool having serrations along the cutter tooth flank which form series of cutting edges that generate the removal of metal in the form of tiny chips.
7. The machine as claimed in claim 5 wherein said shaving cutter is driven
by a motor located behind the spindle housing.
8. The machine as claimed in claim 5 wherein a said bed is in "T" type
shape.

9. The machine as claimed in claim 5 wherein a said spindle housing is swivellable in an angle between ±25° w.r.t cutter head slide mounted on a column.
10. The machine as claimed in claim 5 wherein a said spindle housing is fitted to the cutter head slide. A said cutter head assembly comprising a hydraulic cylinder with disc spring at the top of the cutter head slide for clamping & de clamping of the spindle housing with cutter slide; clamping of housing is done by disc spring & de clamping of housing is done hydraulically.
11. The said machine comprising a separate coolant tank & magnetic chip
conveyor for the removal of chips.