DESC:FIELD OF INVENTION
The present invention relates to a high capacity headstock for four guide way lathe machine. Further the present invention relates to a method of working of the four guideway lathe machine with high capacity headstock.

BACKGROUND OF INVENTION
The lathe is commonly used for the primary machining process of cylindrical jobs. Conventional lathe machines are configured to perform various metal cutting operations such as turning, facing, thread cutting, knurling, and drilling. The traditional heavy-duty lathe consists of the head stock, bed, tail stock, saddle, cross slide and tool post/tool turret. The bed consists of flat and V turcite guideways to facilitate the movement of the saddle. The cross slide along with the tool post is mounted on the saddle. The headstock can be optionally provided with hydraulic/pneumatic/manually operated chuck. The job will be held between the head stock and tail stock. The tail stock can be moved to different positions along the bed to accommodate different lengths of jobs. The primary motion which is the rotation of the work piece is provided by the movement of the main spindle which is driven by a series of gear arrangement. The spindle can be run in different speed ranges by engaging the different combinations of the gear stages, which are mounted inside the headstock. These gears are driven by an electric motor, which in turn rotates the main spindle. The nominal weight of the job the headstock can rotate is 3 ton without steady rest and up to 5 ton with two steady rests.

The four guideway lathe consists of all the parts similar to the heavy-duty lathe, except there will be 4 guideways, where one pair of guideways will be used for the movement of the saddle and the other pair of guideways are for the tail stock movement. All four guideways are mounted on bed in parallel. All the axes movements and spindle rotation are driven by siemens AC servo/spindle motors and all the axes/spindle and other machine functions are controlled by Siemens make CNC system and Drive. The programmable logic controller (PLC) is integrated in CNC system.

In a case of large-sized jobs weighing in several tons, all lathe operations cannot be performed easily, because the present 4-guideway lathe machines cannot accommodate such huge capacity.

There exists a need for a high capacity head stock for four guideway lathe machines for machining higher capacity work pieces. Further there exists a need for the method of working of the high capacity head stock for four guide way lathe machine.

OBJECTS OF INVENTION:
It is the primary object of the present invention to provide a high capacity head stock for four guide way lathe machine for machining higher capacity work pieces.

It is another object of the present invention to provide a four guideway lathe machine with high metal removing capabilities.

It is another object of the present invention to provide high level of accuracy, rigidity and reliability spindle design.

It is another object of the present invention, wherein the robust headstock allows high load carrying capacity between centers and by the fact that such characteristic allow work pieces of large dimension.

It is another object of the present invention, wherein the lathe machine is designed to perform turning, facing, threading, OD contouring and ID contouring on jobs held between chuck and centers or between centers with appropriate face clamping with 20 tons load carrying capacity.

SUMMARY OF THE INVENTION:
One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention.
It is the primary aspect of the present invention to provide a high capacity headstock [1] for four guideway lathe machine, comprising:
a main spindle [2];
one or more spindle bearings/roller bearings [3];
one or more gear arrangement units [4];
a lubrication unit [5];
a rotary encoder [7] for spindle speed feedback;
one or more hydraulic cylinders [8] for gear shifting; and
characterized in that
the motor is coupled through gears with proportioned transmission of 5.6 and 48.12 for speed range of 5-100 rpm and 100-400 rpm or with proportioned transmission of 17.69 for the speed range of 85-270rpm,
wherein the headstock spindle [2] with A2-15 size is mounted on high precision double row cylindrical roller bearings [3] at the front and double row roller bearings at the rear along with thrust ball bearing,
wherein the actual spindle speed feedback is taken from the rotary encoder [7] which is mounted on the head stock [1] through a 1:1 ratio pulley driven through a timer belt connected to the main spindle [2],
wherein the spindle motor is coupled to the main spindle [2], through a set of gear arrangement units [4] which are mounted on six or more shafts, and
wherein the head stock [1] is operated with 5-400 rpm/ 85-270 rpm speed range of the spindle [2], the proportioned transmission for head stock with spindle speed of 5-400 rpm is in two gear stages with gear ratio of 5.6 and 48.12 with a speed range of 5-100 rpm and 100-400 rpm respectively and the proportioned transmission for head stock with spindle speed of 85-270 is in one gear stage with 17.69 gear ratio, and the spindle gear stage selection is done by using auxiliary codes.

It is another aspect of the present invention, wherein the power of spindle [2] is 74kW.

It is another aspect of the present invention, wherein the spindle gear stage is changed through the hydraulic cylinders [8] by actuating a combination of hydraulic solenoids by a programmable logic controller (PLC).

It is another aspect of the present invention, wherein the lubrication unit [5] comprises of a lubrication tank, a pump, a 3 phase AC induction motor and the flow switch [6].

It is another aspect of the present invention, wherein the spindle is supported by the taper roller bearing to withstand both axial and radial forces.

BRIEF DESCRIPTION OF DRAWINGS:
So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawing, which form a part of this specification. It is to be noted, however, that the drawing illustrates only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.
Figure 1 is the front view of the Four Guide way lathe with 20-ton capacity headstock according to one embodiment of the present invention.
Figure. 2 is the top view of the Four Guide way lathe with lubrication unit for 20-ton capacity headstock according to one embodiment of the present invention.
Figure. 3 is the top view of the 20-ton capacity headstock for four guideway lathe machines with main spindle, gear arrangements, bearings, rotary encoder, hydraulic cylinders and flow switch according to another embodiment of the present invention.
Figure. 4 is the perspective view of the 20-ton capacity headstock for four guideway lathe machines from rear side according to one embodiment of the present invention.
Figure. 5 is the perspective view of the 20-ton capacity headstock for four guideway lathe machine from front side according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The present invention relates to a high capacity headstock for four guide way lathe machine. Further the present invention relates to a method of working of the four guideway lathe machine with high capacity headstock.

The headstock housing consists of all the transmission devices like shafts, gears and other elements which are used to drive the main spindle. The headstock [1] is made of stress relieved high grade cast iron, oil-tight, and high rigidity. The main spindle [2] is hardened and ground of extreme rigidity and coupled to high torque 74kW AC spindle motor. The torque produced in the spindle end is capable of handling higher material removal rate. Hence the four guideway lathe machine with this high capacity headstock provides high metal removing capabilities.

The spindle speed feedback unit is through a rotary encoder [7] to facilitate accurate thread cutting. The headstock [1] made of high grade cast iron, duly stress relieved, oil tight, of highest rigidity carrying all the transmission devices like shafts, gears and other elements to drive the main spindle [2] and the headstock gear/ speed change is automatic.

The main spindle [2] with A2-15 size is mounted on high precision double row cylindrical roller bearings [3] at the front and double row roller bearings at the rear along with thrust ball bearing. Both the front and rear bearings are aligned for optimum performance and normally these bearings do not require any further adjustment.As the spindle is supported by taper roller bearing which can withstand both axial and radial forces, this new design of high capacity head stock provides high level of accuracy, rigidity and reliable spindle design.

The spindle motor is coupled to the driven pulley by a belt drive. The driven pulley is connected to the main spindle [2], through a set of gear arrangements [4] which are mounted on 6 shafts. the proportioned transmission for the speed range of 5-400 rpm in two gear stages, 5.6 and 48.12 gear ratio with a speed range of 5-100 rpm and 100-400 rpm or for the speed range of 85-270 in one gear stage with 17.69 gear ratio. I.e. the same head stock [1] can be used for 2 types of spindle speed ranges, 1. spindle speed 5-400 rpm or 2. spindle speed of 85-270rpm. The selection speed range is achieved by engaging a set of gears to the gear mounted on the main spindle. The proximities mounted inside the head stock gives the current gear stage. The spindle speed range selection is done by using auxiliary codes (M codes) in the CNC program. The spindle gear stage (for the programmed spindle speed) is engaged through hydraulic cylinders [8] by actuating a combination of hydraulic solenoids by PLC.

The four guide way lathe machine with the high capacity head stock performs turning, facing, threading, OD contouring and ID contouring on jobs held between chuck and centers or between centers with appropriate face clamping with 20 tons load carrying capacity.

The gears and bearings inside the headstock [1] are to be lubricated continuously with the help of a lubrication unit [5] for the healthy running of the head stock [1] and for the long life of gears and bearings. The lubrication unit [5] consists of a lubrication tank, pump, 3 phase AC induction motor and a flow switch [6]. The lubrication unit starts working with the machine ON. The presence of lubrication is continuously monitored by using the flow switch [6]. The required flow rate to be monitored will be set on the flow switch [6]. The feedback from the flow switch [6] is connected to the PLC input, failure of which stops the rotation of the main spindle immediately.

The rotary encoder [7] within the Siemens AC spindle motor only gives the speed feedback from spindle motor. As there are gears involved in speed transmission from motor to the main spindle [2], the feedback from the rotary encoder [7] on the motor will not be the actual main spindle rpm. CNC system requires the actual spindle speed for some of the machining operations like thread cutting. The actual spindle speed feedback is taken from a rotary encoder [7] which is mounted on the head stock [1] through a 1:1 ratio pulley driven through a timer belt connected to the main spindle [2]. This gives the actual spindle speed feed back to the CNC system. The lubrication unit [5] is provided on the head stock [1] for lubricating gears and bearings along with the flow switch [6] to monitor the continuous lubrication.

The four guideway lathe machine consists of all the parts similar to the heavy-duty lathe, except there will be 4 guideways, where one pair of guideways will be used for the movement of the saddle and the other pair of guideways are used for the tail stock movement. All four guideways are mounted on bed in parallel. All the axes movements and spindle rotation are driven by siemens AC servo/spindle motors and all the axes/spindle and other machine functions are controlled by Siemens make CNC system and Drive. The programmable logic controller (PLC) is integrated in CNC system.

The four guideway lathe machine is equipped with four station programmable tool turret. Based on operation, the required tool is brought into the machining area by indexing the turret to the station having the tool. The main spindle speed is calculated based on the tool selection, operation, cutting parameters etc. The spindle speed is programmed in CNC using S code. Before programming the spindle speed, the required gear stage is programmed using M- Codes M41 and M42, M41 for gear stage 1 and M42 for gear stage 2. On execution of M code the CNC gives the command to the PLC to shift the gear stage. The PLC in turn energies a set of solenoids to actuate the cylinders for the movement of shift fork to engage the required gear pair according to the programmed gear stage. The feedback of gear shifting is taken from a set of proximity switches mounted inside the headstock and gear shifting completed signal is given from PLC to CNC. The selected gear stage number is displayed on the CNC display unit. After receiving the gear shifting completed feedback signal from PLC, the CNC continues machining operation by moving the axes as per the part program.

The lubrication pump is switched on simultaneously with machine on. The required lubrication flow rate is set in the flow switch which is mounted inside the headstock. The flow switch signal is connected to the PLC and is monitored continuously. Whenever the required flow goes below the set level the PLC immediately stops the machining operation including main spindle rotation and alarm text is displayed on the CNC display unit. The help text for the alarm is viewed by pressing help key on the CNC key board. The help text describes the reason for the alarm and the remedies to clear the alarm.

Technical Parameters:
Sl. No. Description Specification
1 Swing over carriage 750 mm (min)
2 Depth of cut (On radius) 10 mm (max.)
3 Spindle speed (infinitely variable) 5 to 400 rpm/
85-270rpm
4 Through bore in spindle 150 mm
5 Main spindle motor drive rating 75 kW
6 2000 mm/min 2000 mm/min
7 Loading capacity with two steady rest 20 MT
8 Cutting force 19,471 N
9 Feed Force 3171 N

Advantages:
• Headstock can accommodate work pieces of large dimension with 20 tons of load.
• High metal removing capability
• High level of accuracy, rigidity and reliability.

Although, the invention has been described and illustrated with respect to the exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. ,CLAIMS:WE CLAIM:
1. A high capacity headstock [1] for four guideway lathe machine, comprising:
a main spindle [2];
one or more spindle bearings/roller bearings [3];
one or more gear arrangement units [4];
a lubrication unit [5];
a rotary encoder [7] for spindle speed feedback;
one or more hydraulic cylinders [8] for gear shifting; and
characterized in that
the motor is coupled through gears with proportioned transmission of 5.6 and 48.12 for speed range of 5-100 rpm and 100-400 rpm or with proportioned transmission of 17.69 for the speed range of 85-270rpm,
wherein the headstock spindle [2] with A2-15 size is mounted on high precision double row cylindrical roller bearings [3] at the front and double row roller bearings at the rear along with thrust ball bearing,
wherein the actual spindle speed feedback is taken from the rotary encoder [7] which is mounted on the head stock [1] through a 1:1 ratio pulley driven through a timer belt connected to the main spindle [2],
wherein the spindle motor is coupled to the main spindle [2], through a set of gear arrangement units [4] which are mounted on six or more shafts, and
wherein the head stock [1] is operated with 5-400 rpm/ 85-270 rpm speed range of the spindle [2], the proportioned transmission for head stock with spindle speed of 5-400 rpm is in two gear stages with gear ratio of 5.6 and 48.12 with a speed range of 5-100 rpm and 100-400 rpm respectively and the proportioned transmission for head stock with spindle speed of 85-270 is in one gear stage with 17.69 gear ratio, and the spindle gear stage selection is done by using auxiliary codes.

2. The high capacity headstock [1] for four guideway lathe machine as claimed in claim 1, wherein the power of spindle [2] is 74 kW.

3. The high capacity headstock [1] for four guideway lathe machine as claimed in claim 1, wherein the spindle gear speed is changed through the hydraulic cylinders [8] by actuating a combination of hydraulic solenoids by a programmable logic controller (PLC).

4. The high capacity headstock [1] for four guideway lathe machine as claimed in claim 1, wherein the lubrication unit [5]comprises of a lubrication tank, a pump, a 3 phase AC induction motor and the flow switch [6].

5. The high capacity headstock [1] for four guideway lathe machine as claimed in claim 1, wherein the spindle is supported by the taper roller bearing to withstand both axial and radial forces.