US3425168A

US3425168A - Work follower rests

Info

Publication number: US3425168A
Application number: US573625A
Authority: US
Inventors: Gordon H Porath
Original assignee: Babcock and Wilcox Co
Current assignee: Acme Precision Products Inc
Priority date: 1966-08-19
Filing date: 1966-08-19
Publication date: 1969-02-04
Anticipated expiration: 1986-02-04
Also published as: GB1184584A; DE1627998A1

Description

b- 1969 G. H. PORATH WORK FOLLOWER RESTS Sheet Filed Aug; 19. 1966 SERVO R E .H u P M A FIG. 3

GORDON H. gg l l-i Ms-M ATTORNEYS.

G. H. PORATH WORK FOLLOWER RESTS Feb. 4,- 1969 Sheet Filed Aug. 19, 1966 GORDON H. gK%l-\ ATTORNE Y5 FIG. 5

Feb. 4, 1969 G. H. PORATH WORK FOLLOWER RESTS Sheet -3 of 4 Filed Aug. 19. 1966 Goaoow H. Pdi i k' i ATTQRNEYS Feb. 4, 1969 G. H. PORATH WORK FOLLOWER RESTS Sheet 4- 0 4 Filed Aug. 19, 1966 FIG. 9

W Ws-M ATTORNEYS Claims ABSTRACT OF THE DISCLOSURE A follower rest which is brought into position adjacent but in spaced relation to the workpiece having a plurality of surfaces, each of which has at least one pressure pad therein. A restrictor is associated with each pressure pad and liquid is provided to each restrictor. When the workpiece is in position adjacent the follower rest and the work performing tool is brought into contact with the workpiece, liquid is supplied to each of the pressure pads and a film of liquid flows continuously at a low velocity between the adjacent surfaces of the follower rest and the workpiece in such a manner that the liquid dissipates its pressure a short distance from the pressure pad.

This invention relates to back up supports or work follower rests for supporting inter-mediate portions of workpieces as they are operated upon by a work performing tool such as a grinding wheel.

In the shaping of workpieces such as cam shafts, it is conventional to support the workpiece on a machine at its ends and to bring a work performing tool such as a grinding wheel into position adjacent the periphery of the workpiece and move the workpiece or the grinding wheel transversely to remove or shape portions of the workpiece. Because of the large forces involved, it is also conventional to cause a follower rest to mechanically engage the workpiece in the area directly diametrically opposite the work performing tool aligned or axially spaced relation thereto in order to prevent deflection of the workpiece. Obviously, such mechanical contact of the follower rest with the workpiece is undesirable since it tends to mar the surface of the workpiece and create high frictional forces. Further, the follower rest is subject to wear and must be refinished or replaced periodically.

Among the objects of the invention are to provide follower rests which will effectively support the workpiece and at the same time will eliminate the problems of detrimentally affecting the surface of the workpiece, high friction between the follower rest and the workpiece, and frequent replacement or repair of the follower rest.

Basically, the follower rest embodying the invention comprises surface which are brought into position adjacent but in spaced relation to the workpiece, each surface having at least one presure pad therein. A restrictor is associated with each pressure pad and liquid is provided to each restrictor. When the workpiece is in position adjacent the follower rest and the work performing tool is brought into contact with the workpiece, liquid is supplied to each of the pressure pads and a film of liquid flows continuously at a low velocity between the adjacent surfaces of the follower rest and the workpiece in such a manner that the liquid dissipates its pressure a short distance from the pressure pad. The forces of the work performing tool which tend to distort the workpiece are opposed by the pressure in the pads. Any increase in pressure due to distortion of the workpiece causes increased pressure in the pads tending to return the workpiece to its original position. As the periphery of the workpiece changes, for example if the diameter is reduced by grinding, the follower rest is moved inwardly a corresponding distance so United States Patent that it continues to perform its function. Because there is never any metal-to-metal contact, there is neither any undesirable frictional load nor any wear on the workpiece or the follower rest.

In the drawings:

FIG. 1 is a partly diagrammatic plan view of a machine embodying the invention.

FIG. 2 is a fragmentary side sectional view taken along the line 2-2 in FIG. 1.

FIG. 3 is a view similar to FIG. 2 of a modified form of the invention.

FIG. 4 is a fragmentary sectional view on enlarged scale similar to FIG. 2.

FIG. 4A is a fragmentary sectional view on an enlarged scale of a portion of the machine shown in FIG. 4.

FIG. 5 is a view similar to FIGS. 2 and 4 of a further modified form of the invention.

FIG. 6 is a fragmentary exploded view of a portion of the apparatus shown in FIG. 5.

FIG. 7 is a part sectional view similar to FIGS. 1, 4, and 5 of a further modified for-m of the invention.

FIG. 8 is a fragmentary sectional view on an enlarged scale of a portion of apparatus shown in FIG. 7.

FIG. 9 is a part sectional view similar to FIGS. 1, 4, 5, and 7 of a further modified form of the invention.

FIG. 10 is a fragmentary exploded perspective view of a portion of the apparatus shown in FIG. 9.

FIG. 11 is a part sectional view of a further modified form of the invention.

FIG. 12 is a part sectional view of a further modified form of the invention.

FIG. 13 is a perspective view of the form of the invention shown in FIG. 12.

Referring to FIG. 1, the invention is adapted to be used in conjunction with a machine 10 that comprises a headstock 11 and tailstock 12 on which a workpiece W is supported for rotation. The machine further includes a work performing tool such as a grinding wheel 13 that is mounted on the slide 14 for movement transversely of the workpiece W. In directly opposed relation to the work performing tool 13, there is provided a follower rest 15 that is supported on a slide 16 for movement transverse to the workpiece W. In practice, the slide 16 is moved inwardly toward the workpiece W by spring means 17 (FIG. 2), a fluid operated cylinder 18 (FIG. 3) or similar device. As will be hereinafter set forth, the follower rest 15 is preferably moved inwardly toward the workpiece W in direct relation and response to the move ment of the work performing tool 13 inwardly toward the workpiece W.

As shown in FIGS. 2 and 4, the follower rest 15 comprises a body 20 having an arcuate surface 21 that is adapted to be brought into close proximity to the periphcry of the workpiece W. Specifically, the arcuate surface 21 includes

opposed surface portions

22, 23 that have one predetermined radius and an intermediate surface portion 24 that has :a lesser radius. Each of the

surface portions

22, 23, 24 is formed with at least one pressure pocket which cooperates with the adjacent surface portions to form a pressure pad 25. A restrictor 26 shown diametrically in FIG. 4 is provided in association with each pressure pad 25 and as shown in FIG. 40, comprises an orifice or capillary 27 in a threaded member 28 that is threaded into the base of a passage 29 extending to each pressure pocket. Liquid under pressure from a source not shown is supplied to each passage 29 through a conduit 30. The liquid preferably comprises the coolant for the work operation or some material that may be safely mixed with the coolant.

In practice, after a workpiece W has been placed in position on the machine, the follower rest is brought into position adjacent the periphery of the workpiece W and liquid under pressure is Supplied to each pressure pad. In the initial set up of the machine, the sizes of the orifices 26 are selected such that the pressure in the pressure pads is preferably substantially equal. This can be readily determined by mounting a pressure gauge 31 in association with each pressure pocket, the pressure gauge being connected through passage 32 to its respective pressure pocket.

As liquid flows through each pressure pocket, it passes in a thin laminar film outwardly from the pressure pocket thereby maintaining the workpiece W in a spaced relation to the surface 21 of the follower rest. As the grinding wheel 13 applies a force to the workpiece W tending to distort the workpiece, the pressure in one or more of the pads in the direction in which the workpiece is being distorted will increase presenting a force that tends to return the workpiece to its original position.

As the diameter of the workpiece W is reduced, the effectiveness of the pressure pads in the

surfaces

22, 23 will be diminished, the remaining forces will be mainly horizontal and the pressure pad in the surface 24 will then predominate in providing a resistance to distortion of the workpiece.

It should be understood that as the grinding wheel moves inwardly, the follower rest 15 is also moved inwardly by the spring 17 or the piston in the cylinder 18.

In the preferred form shown in FIG. 3, the cylinder 18 is responsive to the movement of the grinding wheel 13 to move the follower rests 15 inwardly a corresponding distance. One or more of the pressure pads controls a servo valve through a servo amplifier to in turn control movement of the cylinder 18.

In the form of the invention shown in FIGS. and 6, two circumferentially spaced pressure .pads and associated restrictors are provided in the body 20. This arrangement can be utilized where the workpiece W has a substantially smaller diameter.

In the form of the invention shown in FIGS. 7 and 8, the follower rest 40 comprises hinged

sections

41, 42 that have

arcuate surfaces

43, 44. A bolt 45 extends through clearance opening 46 in section 41 and is threaded into the section 42. A spring 47 yieldingly urges the section 41 toward the section 42 and in turn causes the

surfaces

43, 44 to move toward the workpiece W with a predetermined force. Each

surface

43, 44 is formed with at least one pressure pad 45 having an orifice or capillary restrictor 48 associated therewith. As in the previous form of the invention, as a workpiece tends to distort due to the action of the grinding wheel 13, pressure in one or more of the pads 45 is increased to produce a force that tends to return the workpiece to its original position transversely of the machine. As the work operation on the workpiece progresses and the diameter of the workpiece is reduced, the spring 47 urges the

sections

41, 42 toward the workpiece to accommodate to the changing diameter.

In the form of the invention shown in FIG. 9 and 10, the follower rest 50 is provided with a plurality of shoes 51 that are positioned in depressions 52. The shoes are 'held in position by pins 53 extending into grooves 54 into the shoes. Springs 55 yieldingly urge the shoes outwardly toward the workpiece W. Each shoe is formed with an arcuate surface 56 having a pressure pad 57 therein with an orifice -or restrictor 58 associated therewith. As the work operation on the workpiece progresses and the diameter of the workpiece is reduced, the shoes accommodate to the changing diameter.

The curvature of surfaces such as 56 and 43 is preferably shaped to the best average circular size. The surfaces may have their centers offset from the center of the workpiece or may be non-circular in curvature in order to obtain adequate film engagement over a range of workpiece sizes.

In the form of the invention shown in FIG. 11, a single pressure pocket 60 of substantially arcuate extent cooperates with short adjacent surfaces 61 to provide a pressure pad that is substantially degrees in arcuate extent. A restrictor 62 provides fluid under pressure to the pocket in order to support the workpiece W when it is being acted upon in a machining operation such as the action of a grinding wheel 13. This form of the invention is particularly applicable to finish grinding wherein the diameter of the workpiece is not changed substantially.

In the form of the invention shown in FIGS. 12 and 13, a central pressure pocket 65 is supplied with fluid under pressure from a restrictor 66. The fluid then flows through capillary grooves 67 to pressure pockets 68. Thus, the work follower rest comprises three pressure pads in a manner similar to the form of the invention shown in FIG. 4 except that only one separate restrictor is provided and the fluid is metered to the pressure pockets 68 by capillary groves 67 that form the secondary restrictors.

Although the follower rest embodying the invention has been shown as being applied in direct dianietric opposition to the work performing tool, it can be appreciated that the follower rest may be axially displaced from the work performing tool in accordance with well-known practice.

I claim:

1. The combination comprising a machine for performing an operation on a workpiece which includes means for supporting the workpiece for rotation about an axis,

a work performing tool,

and means for moving the tool generally transversely to the axis of rotation,

a follower rest,

means for moving said follower rest transversely toward the workpiece in a direction generally opposite to the direction of movement of the work performing tool toward said workpiece,

said follower rest having an arcuate work engaging surface,

at least one pressure pad in said surface,

a restrictor associated with each pressure pad,

and means for supplying liquid under pressure to each said restrictor whereby when said follower rest is positioned adjacent said workpiece and liquid is supplied to said restrictors, a pressurized film of liquid flows continuously through the pressure pads between the surface of the follower rest and the workpiece so that forces applied to the workpiece by said work engaging tool are opposed by the pressure of said film of liquid and the workpiece is stabilized in its position in the machine,

said follower rest being made of two relative movable parts,

each part having a surface portion with at least one pressure pad therein,

said parts being yieldingly urged toward one another and in opposition to the pressure formed in said pressure pads when the follower rest is in position adjacent a workpiece.

2. The combination set forth in claim 1 wherein said sections of said follower rest are hinged to one another.

3. The combination comprising a machine for performing an operation on a workpiece which includes means for supporting the workpiece for rotation about an axis,

a work performing tool,

and means for moving the tool generally transversely to the axis of rotation,

a follower rest,

said follower rest having an arcuate work engaging surface,

at least one pressure pad in said surface,

a restrictor associated with each pressure pad,

said means for yieldingly urging said follower rest toward said workpiece comprising a fluid operated motor,

means responsive to the pressure in at least one of said pressure pads for controlling the application of fluid to said fluid operated motor.

4. For use with a machine for performing an operation on a workpiece which includes means for supporting the workpiece for rotation about an axis, a work performing tool, and means for moving the tool generally transversely to the axis of rotation,

a follower rest, means for moving said follower rest transversely toward the workpiece in a direction generally opposite to the direction of movement of the work performing tool toward said workpiece, said follower rest having an arcuate work engaging surface, at least one pressure pad in said surface, a restrictor associated with each said pressure pad, and means for supplying liquid under pressure to each said restrictor whereby when said follower rest is positioned adjacent said workpiece and liquid is supplied to said restrictors, a pressurized film of liquid flows continuously through the pressure pads between the surface of the follower rest and the workpiece so that forces applied to the workpiece by said work engaging tool are opposed by the pressure of said film of liquid and the workpiece is stabilized in its position in the machine,

said follower rest being made of two relative movable parts,

each part having a surface portion with at least one pressure pad therein,

said parts being yieldingly urged toward one another and in opposition to the pressure formed in said pressure pads when the follower rest is in position adjacent a workpiece. 5. The combination set forth in claim 4 wherein said sections of said follower rest are hinged to one another. 6. For use with a machine for performing an operation on a workpiece which includes means for supporting the workpiece for rotation about an axis, a work performing tool, and means for moving the tool generally transversely to the axis of rotation,

a follower rest, means for moving said follower rest transversely toward the workpiece in a direction generally opposite to the direction of movement of the work performing tool toward said workpiece, said follower rest having an arcuate work engaging surface, at least one pressure pad in said surface, a restrictor associated with each said pressure pad, and means for supplying liquid under pressure to each said restrictor whereby when said follower rest is positioned adjacent said workpiece and liquid is supplied to said restrictors, a pressurized film of liquid flows continuously through the pressure pads between the surface of the follower rest and the workpiece so that forces applied to the workpiece by said work engaging tool are opposed by the pressure of said film of liquid and the workpiece is stabilized in its position in the machine, said means for yieldingly urging said follower rest toward said workpiece comprising a fluid operated motor, means responsive to the pressure in at least one of said pressure pads for controlling the application of fluid to said fluid operated motor.

References Cited UNITED STATES PATENTS 712,815 11/1902 Landis 51-238 1,875,486 9/1932 Peaslee 51238 2,718,168 9/1955 Kendall et al 51238 X 3,118,258 1/1964 Price et al. 51-105 3,145,513 8/1964 Porath 51238 LESTER M. SWINGLE, Primary Examiner.

US. Cl. X.R.