FORM 2
THE PATENTS ACT 1970 (39of 1970)
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE
A cutter slide assembly for key way machining operations
APPLICANTS
Tata Motors Limited, of Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai - 400001, India, an Indian company
INVENTORS
Under Section 28(2)
Koshy Thomas and Abhijit Borkar, C/o Tata Motors Limited, of Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai-400001, Maharashtra, India, both Indian nationals

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


This invention relates to a cutter slide assembly for key way machining operation. In general engineering, particularly in automobile engineering key way machining is carried out for producing woodruff key which is mainly used for transmission of power to and from pulleys rotating at high speed.
Conventionally, key way cutting is carried out by rotating a cutter held in a collet. This rotation may be either in vertical or horizontal axis. Rotating cutter advances to a job which is clamped firmly to cut the key way. After completing the job, the cutter retracts and the job is declamped to be replaced by the next job.
Conventional cutter slide assembly has the following components. A collet is mounted on the output shaft of a geared motor. This collet holds the shank of the key way cutter slide which abutts against the positive step in the collet. The non driven end of the cutter is supported by a centre which freely rotates and is supported by bearings mounted in a housing. An adjustment screw provided at the base of the centre keeps the non driven end of the cutter in contact with the centre.
During machining operations, the job is held in a chuck and the cutter is driven to advance the cutter slide to the job. After completing the machining, a forward limit switch gets actuated to activate a solenoid valve which reverses the direction of movement of the cutter slide which returns to its initial position.
The main drawback observed while using the conventional cutter slide assembly is improper machining of the key way. The centre may move down due to damaged bearings in its housing, or due to loosening of the centre adjusting screw. The cutter gets deflected due to this resulting in off set key way machining. A job with such improgper maching of key way gets rejected.
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The main object of this invention is to develop a cutter slide assembly which will avoid offset key machining.
The cutter slide assembly for key way machining operations according to this invention comprises a drivable cutter slide, one end of which is rotatably mounted on a drive means, the other end being in contact with a rotatable and adjustable centre assembly, drive means for forward and backward movement of said cutter slide controlled by respective solenoid valves, said centre assembly having a rotatable disc provided with sensor means mounted thereon, a proximity switch for sensing the position and rotation of said sensor means, said proximity switch being connected to a control relay circuit and a comparator for controlling the forward and backward movement of said slider.
This invention and its method of operation will now be described with reference to the figures in the accompanying drawings, in which
Fig. I is a schematic drawing of the cutter slide assembly according to this invention.
Fig. II is the relay circuit diagram and
Fig. Ill is the circuit diagram for the comparator.
In Fig. I reference numeral 1 represents the geared motor which drives the cutter slide 3. Reference numeral 2 is a collet which is mounted on the output shaft of the geared motor. Numeral 4 shows the job or work piece which is to be machined. The centre which is in contact normally with the cutter is shown by 6 while numeral 5 shows the bearings inside the housing of the centre. Reference numeral 7 is the adjustable screw which enables the centre to be in contact.
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The centre when in contact with the cutter is in friction with the cutter driven by it. The drive means which may be a pressurized hydraulic cylinder is shown by numeral 8 and numeral 9 is the solenoid valve which controls the forward and backward movement of the hydraulic cylinder and therethough the cutter slide. Numeral 10 is the pump for pressurizing hydraulic oil to activate the hydraulic cylinder. Reference numeral 11 is El which is the forward limiting switch. A proximity switch 12 is mounted for sensing the position or rotation of a sensor provided on a disc which is indicated by reference number 14. Reference number 13 shows the wires from the proximity switch which are connected to the relay circuit and the comparator.
Fig. II shows the relay circuit diagram of the cutter slide assembly which is connected to the proximity switch. JLS is the job clamped limit switch. PBC and PBS are the push buttons for cycle stop and cycle start when the job is clamped on the assembly contacts 1 and 2 close and the contactor CI becomes on and the cutter starts rotating. 3, 4 are push button contacts for emergency stopping of the machine. Contacts 5 and 6 close when the start press button is operated. Contacts 7 and 8 also closes and solenoid SI of the cutter slide gets operative. Hydraulic cylinder of the cutter slide assembly moves forward and machining starts and continues till the cutter slide forward limit switch is reached. In the event of the centre point moving down, due to faulty bearings, loosening of the adjusting screw or for any other reason, the proximity switch (numeral 12) looses contact with the sensor mounted on the disc. Zero speed sensor comes into operation and the solenoid valve S2 gets actuated through RL2 establishing contacts between 11 and 12. Hydraulic cylinder of the cutter assembly retracts the cutter slide by moving backward.
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Fig III shows the comparator provided with set value of pulses. When the actual pulse sensed by the sensor is below this value, RL2 gets activated and the cutter retracts to its initial position. This reversal of the cutter slide prevents any damage to the work piece and off set key way machining.
Though the invention has been described hereinabove with reference to specific embodiments, alterations and variations known to persons skilled in the art are within the scope of the appended claims.

WE CLAIM:
1. A cutter slide assembly for key way machining operations comprising a drivable cutter slide, one end of which is rotatably mounted on a drive means, the other end being in contact with a rotatable and adjustable centre assembly, drive means for forward and backward movement of said cutter slide controlled by respective solenoid valves, said cutter assembly having rotatable disc provided with sensor means mounted thereon, a proximity switch for sensing the position and rotation of said sensor means, said proximity switch being connected to a control relay circuit and a comparator for controlling the forward and backward movement of said slider.
2. The cutter slide assembly as claimed in claim 1 wherein a geared motor is provided for driving said cutter slide which is mounted on a collet connected to the output shaft of said geared motor.
3. The cutter slide assembly as claimed in claims 1 and 2 wherein said drive means for forward and backward movement of said cutter assembly is a hydraulic cylinder, u
4. The cutter slide assembly as claimed in claims 1 to 3 wherein said sensor means has zero speed sensors.
5. The cutter slide assembly as claimed in claims 1 to 4 wherein said adjustable centre assembly has a centre in contact with said cutter in its normal position, which is mounted in a housing provided with bearings and an adjustable screw.


6. The cutter slide assembly as claimed in claims 1 to 5 wherein said comparator is provided with a set value of pulses.
7. A cutter slide assembly for key way machining operations substantially as herein described and illustrated in the accompanying drawings.

Dated this 1st day of December 2003.

(Arindam Paul)
of DePENNING & DePENNING
Agent for the Applicants