A SYSTEM AND METHOD FOR CONTROLLING OPERATION OF CROSS-RAIL IN VERTICAL BORING MACHINE
FIELD OF INVENTION
[001] The present invention in general relates to an electric control system and method for preventing mechanical damage to components of vertical boring machine. In particular, the present invention relates to an electrical control system to avoid over compression of disc springs inside lead screw housing which thereby prevents mechanical damage of disc springs.

BACKGROUND OF THE INVENTION
[002] A vertical boring machine is used to machine parts of any material to get the uniform size. On a Vertical Boring Machine (VBM), the work which is to be machined is fastened on a horizontal revolving table and then cutting tools of VBM advances vertically into it as the table revolves. Vertical Boring Machines have two designs: Single Column VBM and Double Column VBM.
[003] In a double column VBM, the horizontal cross- rail is carried on vertical slide-ways and carries tool holder slide or slides. The cross-rail is supported from the cross-rail drive assembly with the help of lead screw rods and nuts. The leadscrew is of the standard type having a thread of slow helix angle and having a nut thereon with an internal thread which mates with that of the screw and to be driven thereby. The nut has a housing. The lead screw nut housing contains the nut and disc springs for pre-loading of the nut. When, up/down command of cross rail is given, the cross-rail first moves up until the disc springs are fully unclamped on either sides. Then the up/down command to the next position is executed. During movement of the cross-rail, incidents may arise during which the disc springs are compressed more than the limit due to malfunctioning or overloading.
[004] Excessive compression of the disc spring leads to transmission of load to the lead screw and subsequently to the top cross-rail drive assembly plate holding the cross rail. This can result in bending of lead screws and top cross-rail drive assembly plate which can lead to major mechanical damage of the VBM.
[005] Therefore, there is need to provide for a safe and full proof environment in industries of cross-rail operation in VBM.

OBJECTIVE
[006] A main objective of the present invention is to provide for an electrical control system for controlling cross rail operation of VBM to avoid over compression of disc springs inside lead screw housing.
[007] Another objective of the present invention is to provide for an electrical control system which ensures safe and full proof environment in industries for cross-rail operation in VBM.

SUMMARY OF THE INVENTION:
[008] The present invention concerns a system for controlling operation of cross-rail in Vertical Boring Machine. The system has a nut housing assembly enclosing the leadscrew nut and a disc spring and a control device coupled to the nut housing. The controlling device have a plurality of limit switches which is positioned on the nut housing, where the plurality of limit switches is coupled with control system of the Vertical Boring Machine.
[009] The plurality of limit switches is mechanically actuated when the disc spring is compressed more than a predefined threshold limit, wherein upon actuation, the plurality of limit switches transmit an emergency stop signal to the control system to stop the cross rail. The device comprises a plurality of limit switches and wirings, incorporated with a logic rule to restrict the operation of the cross-rail in unsafe zones and shall enable normal operation of the cross-rail when the cross-rail is moved away from the unsafe zone
[0010] In accordance with a preferred embodiment of the invention, the cross rail lead screw nut housing on both right and left had side has mounted thereon a normally closed limit switch which is opened when any abnormal operation of cross-rail happens and the spring discs are compressed more than the safety limit. This limit switch is in circuit with the emergency system so that when the disc springs are compressed beyond the predetermined distance the limit switch associated therewith is opened and prevents the mechanical system from extensive damages.
[0011] As will be apparent form the detailed description, the system of the present invention provides an additional safety feature that monitors the compression of disc spring continuously and stops the machine operation of any abnormality in disc spring loading is observed.
[0012] The drawings are illustrative only but not used to limit scope of the present subject matter.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0013] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0014] Fig. 1 schematically illustrates selected portions of an embodiment of a Double Column VBM to which the present invention is applicable.
[0015] Fig. 2 is a schematic view of a cross-rail mounting bracket mounted over screw-rod of a Double Column VBM wherein the present invention is applicable.
[0016] Fig. 3. is a cross-sectional view of a lead screw nut housing assembly mounted over the left lead screw rod of a Vertical Boring Machine.
[0017] Fig.4 is a schematic view of a lead screw nut housing assembly having the electric control system along with limit switch mounted thereon.
[0018] Fig. 5 is schematic diagram of an interlock circuit for the limit switch apparatus shown in the Fig 4 to restrict cross-rail operation in unsafe zones accordingly to the invention.

DETAILED DESCRIPTION OF THE CURRENT INVESTIGATION
[0019] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
[0020] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and detailed in the following description. Descriptions of well-known components and processing techniques are omitted to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0021] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0022] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0023] The present subject matter herein relates to an electric control system (400) for controlling movement of cross rail (104) of vertical boring machine (100). The vertical boring machine (100) is a double column design for the application of the present invention. As per Fig. 1 the Double Column Vertical Boring Machine (VBM) (100) which has columns (101a and 101b) and table (102) mounted on a bed (103). It is provided with a cross-rail (104) supported on the left and right hand side vertical columns (101a and 101b). The cross rail (104) is moved up or down to the desired position depending on the machining job dimensions using the lead screws and nuts on either sides of the cross-rail. Leadscrews are essentially accurate screws used to move a nut attached to a load, and they have been used for centuries to convert rotary motion into linear motion. The cross-rail carries the tool holder slides (105). The holder slides (105) moves horizontally to the left and right on the X-axis and forward and rearward on the Y-axis. The movement of cross rail (104) is supported by lead screw rods (106a and 106b).
[0024] Fig. 2 illustrates a cross rail mounting bracket (201) that is mounted over lead screw rod (106a). Cross-rail mounting bracket (201) is pressed at the instance of compression.
[0025] Fig. 3 illustrates a detailed view of a nut housing assembly in reference to Fig. 1 and 4, showing a nut housing assembly (404) that is installed on the lead screws rod (106a and 106b) as shown in Fig. 1. The nut housing assembly comprises of a lead screw nut (302) and disc springs (303). The leadscrews nut (302) move along screw rods (106a) as they rotate to move the cross-rail up or down. A screw is essentially a rotary wedge; it converts rotary motion into linear motion by the action of the inclined plane of one thread on another. The lead screw nut is preloaded with the disc spring elements (303). When a linear motion application requires high thrust force and rigidity along with good positioning accuracy, a preloaded lead screw assembly is necessary. The primary reason for using a preloaded lead screw is to reduce internal clearance between the raceways of the nut and screw, which causes axial play (backlash). Reducing or eliminating backlash in turns improves the repeatability of the screw assembly, since there is no “lost motion” when the direction of travel is reversed. Higher preload also correlates with higher nut rigidity, which improves the rigidity of the complete screw assembly.
[0026] Fig. 4 is a schematic view of the lead screw nut housing assembly (404) having the limit switch apparatus (402) in accordance with the present invention mounted thereon. It shows the electrical control system (400), emphasizing the Limit Switches (402) with Metal Plunger (403) installed in the cross-rail lead screw nut housing assembly (404) including the corresponding actuating cams incorporated in the device according to the invention. The limit switch (402) is mounted on the top of the nut housing assembly using a mounting plate (401).
[0027] During cross-rail operation, when there is malfunctioning or overloading, the disc springs (303) are compressed more than the permissible limit, in such cases, the limit switch (402) is actuated and the metal plunger (403) gets pressed against the cross rail mounting bracket (201). When the plunger (403) is pressed, an electrical signal is passed on to the control system (400) for emergency stop of the cross rail (104) of the Vertical Boring Machine (100).
[0028] The disc spring compression happens during instances in which the cross-rail is standstill, but the nut rotation is not yet stopped. In such cases, as the nut keeps on rotating, the disc spring starts getting loaded up and the distance between the limit switch plunger (403) and the Cross-rail mounting bracket (201) starts decreasing. Beyond the permissible compression limit of the disc spring, the limit switch plunger is pressed against the Cross-rail mounting bracket (201), thereby sending the Emergency Stop signal to the control system (400).
[0029] Fig. 5 shows an interlock circuit (500) for defining the functions performed by the limit switch apparatus (402) as shown in the Fig. 4 to restrict cross-rail operation in unsafe zones according to the present invention. The interlock circuit (500) is connected to a 24VDC power supply (501) and to the normally closed switches LS1 and LS2 (502). The limit switches LS1, LS2 are mechanically actuated and used to perform the logical operation.
[0030] Reference numerals:
100- Vertical Boring Machine
101 (a, b) - Vertical Columns
102- Table
103- Bed
104- Cross Rails
105- Tool Holder Slides
106 (a, b)- Leadscrews
201- Cross Rail Mounting Bracket
302- Leadscrews Nut
303- Disc Spring
400- Electric Control System
401- Limit Switch Mounting Plate
402- Limit Switch
403- Limit Switch Metal Plunger
404- Nut housing assembly
500- Interlock circuit
501- Power supply
502a, 502 b- Limit Switches LS1, LS2

We claim:

1. A system for controlling operation of cross-rail (104) in Vertical Boring Machine (100), the system (400) comprising:
a limit switch mounting plate (401);
a limit switch (402); and
a limit switch metal plunger (403);
wherein the limit switch (402) is mounted over the mounting plate (401) and is actuated mechanically to control the operation of cross rail (104) in Vertical Boring Machine (100).
2. The system as claimed in claim 1, wherein the system (400) is mounted over a nut housing assembly (404) that is installed on lead screws (106 a, b) of the Vertical Boring machine (100).
3. The system as claimed in claim 1, wherein the nut housing (404) encloses a disc spring (303) that is compressed and expanded facilitating movement of cross rail (104) of the Vertical Boring Machine (100).
4. The system as claimed in claim 1, wherein the system (400) further comprises of an interlock circuit (500) for defining logical operation.
5. The system as claimed in claim 1, wherein the interlock circuit (500) generates emergency stop signal resulting in stopping of the cross rail (104).
6. The system as claimed in claim 1, wherein the interlock circuit (500) is further connected to a 24VDC power supply (501).
7. A method for controlling operation of cross-rail (104) in Vertical Boring Machine (100), the method comprising:
actuating of the limit switch (402);
pressing of the limit switch metal plunger (403);
passing of a signal to the cross rail (104) of Vertical Boring Machine (100); and
stopping of cross rail (104) of the Vertical Boring Machine (100).
wherein pressing of metal plunger (403) results in generation of an emergency stop signal which controls the operation of to the cross rail (104) of the Vertical Boring Machine (100).
8. The method as claimed in claim 7, wherein the limit switch (402) is actuated at the instance of pressing of a cross-rail mounting bracket (201) on the compression of disc spring (303).
9. The method as claimed in claim 7, wherein the limit switch metal plunger (403) is pressed against a cross-rail mounting bracket (201) when disc springs (303) are pressed beyond permissible compression limit.
10. The method as claimed in claim 7, wherein the pressed metal plunger (403) sends signal to stop the cross rail (104).