FIELD OF THE INVENTION
The present invention relates to a device for concurrent machining of a plurality of thrust bearing pads on a standard vertical boring machine. The invention further relates to a process of concurrent machining of a plurality of thrust bearing pads in a device mountable on a standard vertical boring machine.
BACKGROUND OF THE INVENTION
A stationary bearing pad of a thrust bearing, supports a rotating object such as a shaft via a pressurized fluid such as oil, air or water. Thrust bearings take advantage of the fact that when the rotating object moves, it does not slide along the top of the fluid. Instead, the fluid in contact with the rotating object adheres tightly to the rotating object. Motion is thus accompanied by slip or shear between the fluid particles through the entire height of the fluid film. Thus, if the rotating object and the contacting layer of fluid move at a velocity that is known, the velocity at intermediate heights of the fluid thickness decreases at a known rate until the fluid in contact with the stationary bearing pad adheres to the bearing pad and is motionless. The load resulting from the bearing pads supporting the rotating object causes the bearing pad to deflect at a small angle in respect of the rotating member. Fluid moving with the shaft is drawn into a wedge-shaped opening. Sufficient

pressure is generated in the fluid film to support the load. Both thrust bearings and conventional hydrodynamic journal bearings operate on this principle. Both thrust bearings and radial or journal bearings normally are characterized by shaft supporting pads spaced about an axis. The axis about which the pads are spaced generally corresponds to the longitudinal axis of the shaft to be supported for both thrust and journal bearings.
Each bearing pad 10 includes a leading edge 11 and a trailing edge 12. The leading edge 11 is the edge first approached by a point on the circumference(S) of the shaft (20) as it continues to rotate. Similarly, the trailing edge 12 is the edge approached circumferentially later by the same point on the shaft as it continues to rotate. When the shaft 20 is rotating in the proper direction, it moves, on a fluid film, from the leading edge across the bearing pad and off the trailing edge.
Optimum performance is obtained when a stub-section 13 supports the bearing pad 10 and hence any load, at a point 14 between the circumferential center line of the pad 10 and the trailing edge 12, preferably becomes closer to the centerline.
Referring now to FIGS. 1 and 2, it will be seen that the pad 10 is provided with an accurate face 16 that corresponds essentially to the radius or arc of the outer diameter of the shaft that the pad will be supporting (via the fluid

film), and each pad is defined by axially extending and radially extending edges. The axially extending edges comprise the leading and trailing edges.
Because of its many moving parts and manufacturing tolerances, the tilt-pad design is also the most complex and difficult to manufacture of all journal bearing designs. The design complexity is evident in the number of highly-machined parts required to make up the bearing. Clearance tolerances are additive in the built-up assembly of shell, pivots, and pads, requiring a high degree of manufacturing accuracy to yield acceptable radial shaft clearances. Pad pivot friction under high radial load can also lead to premature wear, or even fatigue failure, which can cause enlarged clearances and thereby increasing rotordynamic unbalance response. All of these multiple requirements to design a tilt-pad bearing, demand maximum attention to design, manufacturing, and selection of materials.
The need for close tolerances manifests itself in known radial pad type bearings, because it has been found necessary to provide an accurately determined clearance between the bearing and the rotating object supported so as to allow an optimum deflection of the bearing pads to form the hydrodynamic wedge. The requirement of close tolerances is particularly troublesome in the manufacture of these bearings pads.
A number of methods of manufacturing of the thrust bearings pads are also contemplated. The selection of a particular method of manufacturing depends

largely on the volume of the particular bearing to be manufactured and the materials used. In low volume applications, the bearings are preferably manufactured through various manufacturing techniques. In intermediate volumes, the bearings of the present invention are preferably manufactured using an investment casting method. In high volume applications, such bearings can be manufactured using a wide variety of materials such as plastics, ceramics, powdered and non-powdered metals, and composites. In high volume applications, a number of manufacturing methods, including injection molding, casting, powdered metal, die casting, and extrusion, can be economically employed.
U.S. Pat. No. 5,489,155, discloses a tilt pad variable geometry bearing having tilting bearing pads and methods of making same however the disclosure mainly focuses on mass production of such bearings through casting/molding procedures which are not economic for producing fewer number of these thrust bearing pads, particularly in hyper specific jobs such as in large size motors or steam turbines.
Since plurality of such pads are used in one bearing, it is difficult to maintain the machining coherency among these pads when machines one at a time. Not only is such technique unworthy for maintaining required close tolerances but also is manhour intensive engaging the machine for a longer period of

time. The present invention provides a device for concurrent machining of such thrust bearing pads with little effort and in a minimum amount of time.
Also since a lot of machining operations are required to be performed on the thrust bearing pad so as to provide passage for lubricant and dissipation of heat, it is required to rigidly hold the thrust bearing pad to apply machining process.
Within the objects of this invention, it is sought to cure the defects existing in the art as mentioned in part above, and to provide a method and means of machining of thrust bearing pads having low initial cost and upkeep, great and continuing accuracy inherent in its design and operation, ruggedness and simplicity in its construction and operation, all to the ultimate end of faithfully and consistently reproducing quality thrust bearing pads.
OBJECT OF THE INVENTION
It is, therefore, an object and purpose of the present invention to propose a device for concurrent machining of a plurality of thrust bearing pads on a standard vertical boring machine.
Another object of the present invention is to propose a device for concurrent machining of a plurality of thrust bearing pads on a standard vertical boring machine, which allows to achieve uniformity in dimensions for all thrust

bearing pads within a close tolerance such that all the bearing pads are in parallel planes which are perpendicular to the axis of rotation.
A further object of the invention is to propose the invention further relates to a process of concurrent machining of a plurality of thrust bearing pads in a device mountable on a standard vertical boring machine.
A still further object of the invention is to propose the invention further relates to a process of concurrent machining of a plurality of thrust bearing pads in a device mountable on a standard vertical boring machine, which enables the machine tool to accurately reproduce the desired profile on the thrust bearing pads.
These and other objects of the invention will be apparent from the specification which follows and from the drawings wherein like numerals are used throughout to identify like parts.
BRIEF DESCRIPTION OF THE ACCOMPANIED DRAWINGS
The foregoing and other features of the invention will be apparent from the following more particular description of the invention, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different figures. The drawings are not necessarily to

scale, emphasis instead being placed upon illustrating the principles of the invention.
FIG. 1 is an illustration representing a shaft being support through thrust pad bearing
FIG. 2,3 is an illustration representing pad of a thrust pad bearing.
FIGS. 4 is an illustration representing details of base plate of the developed device.
FIGS. 5 is an illustration representing details of inside clamping ring in accordance to present invention.
FIG. 6 is an illustration representing details of complete thrust pad clamping arrangement in accordance to present invention.
FIG. 7 is an illustration representing packing support in accordance to present invention.
FIG. 8 is an illustration representing details of coupling segment in accordance to present invention.

DETAILED DESCRIPTION OF THE INVENTION
Before describing in detail, the means for machining thrust bearing pad in accordance with the present invention, it should be observed that the present invention resides primarily in a novel and non-obvious combination of hardware elements and method steps. Accordingly, these elements and steps have been represented by conventional elements and steps in the drawings, showing only those specific details that are pertinent to the present invention so as not to obscure the disclosure with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
The present invention is directed to solve the above-described problems of the prior art and to provide a method and means of machining thrust bearing pad in accordance with the present invention and to enable to accurately machine thrust bearing pad easily and in short time.
During the machining of thrust bearing pad 10, the machining forces shall be directed radially outward or inwards. Therefore suitable resistive provisions are required to be made for accommodating these machining forces. These provisions are manifested through clamping arrangements on outer and inner

periphery of the job to accommodate radially inward and outward machining forces respectively. Also, clamping arrangements are provided on mid-segment of the thrust bearing pad 10 so as to accommodate any linearly upward or downward machining forces. These clamping mechanisms shall be discussed in detail as hereunder.
Referring to figure 3 in detail, a stepped base plate 20 is shown. This base plate can be flame cut out of any a metal sheet of suitable thickness as raw material as per the size of thrust bearing pad 10, flame cut a circular plate of required diameter.
This base plate, acting as the base of the complete fixture F, utilizes plurality of arrayed rectangular slots 21 to rigidly hold the base plate 20 or in-turn entire fixture F on any standard machine T-slot table. Plurality of circularly segmented thrust bearing pad are placed in a circular array on the extruded surface 20’ of base plate 20 in a way that a gap G is maintained between the plurality of segmented thrust bearing pad.
Steps 26 and 27 are provided on the outer and inner half of the base plate 20 respectively. These steps are mandatorily required to accommodate the tool overrun during thrust bearing pad machining and thereby insuring that machine tool does not hit and damage the machine table T.
When the machining is to be performed on the inner diameter, plurality of thrust bearing pad 10 placed on the extruded surface 20’ of base plate are

required to be rigidly held in such a way that inner diameter surface is freely available for unrestricted tool movement. For the same to happen, end 221 of the Coupling segment 22 is placed on groove support S1, generally available on outer periphery of the molded thrust bearing pad received for finish machining, while the other end 222 of the Coupling segment 22 is placed on a packing support 23. In other words, Coupling segment 22 is simply supported on groove support S1 and packing support 23 through its ends 221 and 222 respectively. In this case, packing support 23 is placed over outer step 26. Coupling segment 22, through slot 223, receives fastening means 24 that forms a threaded connection with pairing threaded hole 25.
Correspondingly, when the machining is to be performed on the outer diameter, plurality of thrust bearing pad placed on the surface 20’ are required to be rigidly held in such a way that outer diameter surface is freely available for unrestricted tool movement. For the same to happen, end 221 of the coupling segment 22 is placed on groove support S2, generally available on inner periphery of the molded thrust bearing pad received for finish machining while the other end 222 of the Coupling segment 22 is placed on a packing support 23. In other words, Coupling segment 22 is simply supported on groove support S2 and packing support 23 through its ends 221 and 222 respectively. In this case, packing support 23 is placed on inner step 27. The Coupling segment 22, through slot 223, receives fastening means 24 that

forms a threaded connection with pairing threaded hole 29 on step 27 of base plate 20.
As mentioned, steps 26 and 27 are provided on the outer and inner half of the base plate 20 respectively to accommodate the tool overrun during thrust bearing pad machining thereby insuring that machine tool does not hit or damage the machine table T. Thus the differential height H between surface 20’ of base plate 20 and surface 26’ and 27’ of steps 26 and 27 shall depend upon factors such as thrust bearing pad size, corresponding machine tool size etc. If the differential height H is too large, provisions of inside clamping ring will be required to be placed on step 27 in such a way that hole 29’ of inside clamping ring 30 and threaded hole 29 on step 27 matches.
The height of packing support 23 and inside clamping ring 30 is to be selected in such a way that coupling segment 22 and base plate 20 maintain a parallel spatial relationship.
The fastening means 24, while passing through slot 223, is threadedly received by pairing holes 25, 29 in a way that the head of the fastening means 24 abuts the surface 22’ of coupling segment 22 and that it applies a downward pressing force on the thrust bearing pad upon tightening since the downward movement of coupling segment 22 is restricted by packing support 23 and groove supports S1, S2.

Similar coupling segment 22 are also placed in gap G over accurate surface 16 of thrust bearing pad 10 wherein Coupling segment 22, through slot 223, receives fastening means 24 that forms a threaded connection with pairing threaded hole 28. The fastening means 24 is threadedly received by pairing hole 28 in such a way that the head of the fastening means 24 abuts the surface 22’ of coupling segment 22 and that it applies a downward pressing force on the thrust bearing pad upon tightening.
Thus depending upon the machining requirements on inner, outer or top surface of the thrust bearing pad, the clamping arrangements can be made in conjunction to the base plate and inside clamping ring.
Although the present discussion relates to improved method and means for concurrent machining of plurality of thrust bearing pad, more particularly, the method and means shall enable machining of such pads in close tolerances which is of utmost importance for their operational capability. It will be appreciated that the device and methods discussed may be readily adapted for use with other similar procedures. Not only the methods and the tools devised thereof for quality concurrent machining of thrust bearing pad is cheap and easy to manufacture but also will provide safer and ergonomic means for the operators to deal with the clamping and machining operation. It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.

Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention 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. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

WE CLAIM:
1. A device for concurrent machining of a plurality of thrust bearing pads on a standard vertical boring machine, comprising:
- a stepped base plate 20 having at least one surface (20’) provided with steps 26 and 27 on the outer and inner side of the base plate 20 respectively; each step (26,27) having at least one surface (26’,27’);
- a plurality of rectangular slots 21 configured on the base plate 20;
- coupling arrangements including a plurality of coupling segments 22, each having a slot 223;
- a plurality of packing support 23 including inside clamping ring 30 having a hole 29’ placed over the base plate steps 26, 27 to provide support to the coupling segments 22;
- a plurality of fastening means 24 matching with the plurality of threaded holes 25, 28, 29 on the base plate (20), wherein the differential height between the surface 20’ of the base plate 20 and the surfaces 26’ and 27’ are selected based on depend upon thrust bearing pad size, and corresponding machine tool size, wherein, the inside clamping ring 30 is placed on the step 27 and that the hole 29’ of inside the clamping ring 30 and the threaded hole 29 on the step 27 matches.

2. The invention further relates to a process of concurrent machining of a plurality of thrust bearing pads in a device mountable on a standard vertical boring machine, comprising :
- fixing the base plate 20 on machine bed using the rectangular slots 21;
- placing plurality of circularly segmented thrust bearing pad 10 in a circular array on the surface 20’ of the base plate 20 while maintaining a gap G between each and placing the packing support 23 adjacent said thrust bearing pad 10;
- placing the coupling segment 22 over the thrust bearing pad such that one end 221 of said coupling segment is placed on support S1 or S2 available on the thrust bearing pad while the other end 222 of the Coupling segment 22 is placed on the packing support 23, either on the outer step 26 or the inward step 27;
- holding the thrust bearing pad 10 at its position by applying a downward pressing force, on its distal ends as well as on the mid segment, generated upon tightening of the fastening means 24 and the pairing holes 25, 28, 29; wherein, steps 26 and 27 are provided on the outer and inner half of the base plate 20 respectively to accommodate the tool overrun during thrust bearing pad machining thereby insuring that machine tool does not hit or damage the machine table T.

3. The process as claimed in claim 2, wherein, the height of the packing support 23 and inside clamping ring 30 is to be selected in such a way that the coupling segment 22 and the base plate 20 are in same plane.