WO1988008511A1

WO1988008511A1 - Method of and an apparatus for checking out-of-roundness

Info

Publication number: WO1988008511A1
Application number: PCT/US1987/001003
Authority: WO
Inventors: Richard T. Gordon
Original assignee: Gordon Richard T
Priority date: 1987-04-27
Filing date: 1987-04-27
Publication date: 1988-11-03

Abstract

A gauge for measuring out-of-roundness of a circular part has a table (40) upwardly from which project 3 posts (72, 74 and 76) arranged substantially at the apices of an equilateral triangle with the post (76) moveable toward and away from an imaginary line extending between post (72) and post (74). A dial indicator (70) is responsive to movement of post (76) to detect out-of-roundness as a part (10) resting on the table and in engagement with the posts is rotated relative thereto.

Description

METHOD OF AND AN APPARATUS FOR CHECKING OUT-OF-ROUNDNESS

Field of Invention

This invention relates to gauging devices and particularly to a gauge for measuring out-of-roundness of circular parts.

Background of the Invention

In machining circular parts it is common practice to hold the work in 3-jaw holding devices such as lathe chucks, internal grinder chucks and the like. In order to securely hold the workpiece the 3-jaws are normally urged either inwardly or outwardly with sufficient pressure to insure adequate retention of the workpiece relative to the jaws. As a result, particularly with thin walled workpieces, the workpiece is disorted into a 3-lobe shape. During the machining operation, such as with a lathe, the part is machined' into a circular configuration so that if measured while in the lathe the part will appear to have a perfectly circular configuration with no out-of-roundness. When the gripping action of the 3-jaws is released the part will, however, spring back to its original shape and will be out-of-round from a truly- round or circular condition. Conventional diameter measuring gauges will not detect this out-of-roundness because the spring back is such that the distance across the part through the center thereof remains essentially constant. However, the distance from the center of the part to the machined surface, if measured throughout the circumference will be found to vary as a result of the lobular disortion of the part during its machining and resulting from its spring back when removed from the 3-jaw chuck.

As far as I am aware there is currently no gauge available on the market for checking out-of-roundness of circular parts, particularly such a gauge as may be readily transported by a machinest and set up near the machine on which he is working and then used to check out-of-roundness of a variety of different size parts. In the prior art, U.S. Patent 1,625,462 has suggested a gauge capable of measuring out-of-roundness but such device requires the use of semi-cicrcular part contacting feelers and would require a different set of such semi-circular feelers for each different diameter part to be checked and as a consequence would be generally impractical if different size parts were to be checked.

U..S. Patent 1,308,324 is a device for measuring the diameter of a circular part and is provided with locators disposed on the same side of the diameter of the part as is a dial indicator.

Other patents of general interest are as follows:

3,751,812 3,913,234 4,128,943 4,137,641 4,280,278 4,326,336

Also of^" interest is a "Tilt-Table" Comparator, model 36B-19 manufactured by Federal Products Corporation, U.S.A.

Summary of the Invention

I overcome the failures of the prior art and provide a portable out-of-roundness ^' checking gauge which may be positioned by the workmen adjacent his machine for checking parts he is machining thereon. My gauge co prises a table having a surface for supporting the part to be checked with at least three contact posts upstanding from the table and adapted to engage the part at three substantially equidistantly spaced points therearound. One of the posts is supported for movement toward and away from an imaginary line extending between the other two posts. Such other two posts are moveable along rectinlinear paths arranged at 60° angular spacing. Dial indicator means responsive to movement of the said one post reads the movement thereof as a part on the table engaging the three posts is rotated. For diameter checking, a fourth post may be provided intermediate the said two posts and cooperating with the said one post whereby the diameter- of a part engaging the said one post and the fourth post may be checked.

Brief Description of the Drawings

Fig. 1 is a plan view of a gauge embodying my invention;

Fig. 2 is a cross-sectional view taken substantially on the line 2-2 of Fig. 1;

Fig. 3 schematicall illustrates the distortion of a workpiece by a 3-jaw chuck during machining of- the workpiece;

Fig. 4 shows the same workpiece after it has been released from the 3-jaw chuck; and >

Fig. 5 is a cross-sectional view taken on the line 5-5 of Fig. 2.

Brief Description of the Preferred Embodiment

In Fig. 3 I have illustrated the distortion, in exaggerated form, of a circular workpiece 10 gripped by a 3-jaw chuck at the points 18, 20 and 22. The jaws may serve to distort the workpiece by, for example, .010 inches inwardly. This will result in a outward distortion or displacement of the workpiece between the jaws at points 2^"4, 26 and 28 of substantially .010 inches from a true circle 30. Thus, a tri-lobular configuration is shown with the lobes at 32, 34 and 36.

Following machining of the workpiece, the part is released from the 3-jaw chuck and springs back to its original position at the 3-points where the chuck jaws were engaging it, i.e. at 18a, 20a and 22a and these points will now lie on the true circle 30. However, the points intermediate these namely at 24a, 26a and 28a will spring inwardly from the true circle 30 by a distance of approximately .010 inches. Thus, the distance D in Fig. 4 illustrates a distortion of substantially .010 inches at a point intermediate the location where the jaws engage the workpiece at 20a and 22a. This distortion will be repeated at the points 24a and 26a. An interesting phenomenon is that if the diameter is measured across the workpiece, for example between points 22a and 26a and compared with the diameter between points 18a and 28a, it will be found that the diameter is substantially the same. Thus, if the workpiece is check by a diameter gauge, out-of-roundness will not be detected. It is only through the use of an out-of-roundness gauge that the distortion in the part can be quickly detected.

As shown - in Fig. 1 my gauge comprises a rectangular table 40 having a smooth- upper surface 42 adapted to support the part whose out-of-roundness is to be checked. Such a part is illustrated in phantom outline at 10. The table is preferably formed with a base member 44 having four feet, one of which is shown at 46 for supporting the table on a surface, such a tool tray which the mechanic may position adjacent his machine. The foot 46 may be provided with- an adjustable pad 50 secured to the lower end of a screw-threaded member 52 threadly disposed within the foot. By rotating the pad 50 it may extended below the leg thereby to correct for any unevenness in the surface 48 of the tool tray or other supporting surface and stabilize the table against rocking.

The table 40 is held on the base 44 by suitable fasteners 54 at the corners of the table. The base is preferably a casting to provide rigidity and good stability for the gauge. The casting may be provided with a pair of laterally extending hand holds 56 and 58 of trough-like configuration which may facilitate grasping the gauge to move it from one machine location to another. The trough-like configuration of the hand holds permits the placement of accessory parts in the upwardly opening pockets 60 and 62. Similar to the hand holds but for a different purpose, the base is provided with a laterally extending integral projection 64 which defines an upwardly opening pocket 66 having a raised peripheral wall 68. The projection 64 ' is intended to function as a guard or protective bumper around the dial indicator 70 so that the same is not damaged or bumped during movement of the gauge from one location to another or during handling of workpieces nearby.

Projecting upwardly from the table 40 are three contact posts 72, 74 and 76. The posts may be arranged at the apices of an imaginary equilateral triangle and are intended to contact the workpiece 10 at 3 substantially equidistantly spaced points around its periphery. In the embodiment shown the posts are intended to engage the internal surface of the workpiece, but it will be apparent to those skilled in the art that the contact posts could as well engage the outer periphery of the workpiece.

The post 76 is supported for rectilinear movement toward, and away from an imaginary line 78 extending between the posts 72 and 74. The movement of the post 76 is in fact substantially perpendicular to the line 78. The dial indicator is responsive to movement of the post 76 to read the movement thereof as a part 10 on the table engaging the 3 posts is rotated. Movement of post 76 toward and away from the line 78 while all three posts engage the part 10 and the part is being rotated, is a measure of the out-of-roundness of the part.

Referring to Fig. 4, the imaginary line 78 has been superimposed thereon and the distance from line 78 to the periphery of the part at point 18a will be found to correspond substantially identically to corresponding dimensions from lines 78a and 78b and the points opposite, namely 22a and 20a. However, it will be observed that when the base line 78 is shifted to lie on the points 28a and 26a as shown by line 78c in Fig. 4, the distance from line 78c to the opposite point 24a will be less than the previous measurements by substantially .010 inches and an out-of-round condition will be clearly detected. Thus, when a part 10 resting on the table and in contact with the posts and is rotated, the geometric relations discussed above will quickly illustrate whether the part is out-of-round.

The posts 72 and 74 are carried by means supporting them for rectilinear movement- along paths angularly spaced by 60°. For this purpose^" the table is provided with rectilinear slots 80 and 82 each of which is provided with a shoulder 84 upon which rests a post supporting block 86 of T-shaped configuration. A cap screw or the like 88 extends down through the block and engages a pad 90 such that upon tightening the screw, the pad is drawn upwardly against the underside of the table to lock the block in adjusted positions along the length of the slot.

The block carries a vertical aperture 92 within which is slideably received the post such as post 74 as shown in Fig. 2. The post includes a cylindrical shank portion 94 topped by a laterally extending contact portion 96. While the contact portion may _. assume various configurations to suit the particular parts being checked, I have found that a contact portion which is in the form of a relatively thin flat circular head at the upper end of the shank 94 is well adapted to engage the internal surfaces of a variety of circular parts and will also be suitable for entering O-ring grooves and the like such as illustrated at 10a in Fig. 2. The post is held in adjusted vertical positions by a set screw 100 threadedly received -at an angle in the block 86 and adapted to bear against the shank 94. The set screw may be provided with a socket for engagement with an alien wrench. It will be noted that the post may be adjustably positioned and locked by the cap screw 88 or the alien screw 100 at any desired position along the length of the slot and at any desired height of the contact portion 96 above the surface of the table.

The post 76 extends through a third slot 122 similar to but longer than slots 80 and 82 and which bisects the 60° angle between slots 80 and 82. The post is carried by a spring supported parallelogram linkage comprising a block 102 supported by a pair of leaf springs 104 and 106 which are attached at the^' bottom to an anchor block 108 in turn secured to the base 44 by fasteners 110. A cam 112 mounted on a shaft 114 journalled in the base, terminates in a handle 116. The cam is disposed between the leafs 104 and 106 to be rotated by the shaft 114. Upon rotation in one direction, the cam will engage the leaf 106 while rotation in the opposite direction will cause the cam to engage a follower portion 118 extending downwardly from the block 102. Thus, by operation of handle 116 in a rotary fashion, the post 76 carried by the block 102 may be shifted toward the base line 78 to permit the part 10 to be placed on the table in surrounding relation to the posts without striking the same. When the part is thus positioned, rotation of the handle 116 in the opposite direction will permit the parrallelogram linkage to move the block 102 in the opposite direction thereby positioning the post 76 so that its contact part 77 may engage the surface of the workpiece 10 for checking. A set screw 119 having an alien wrench receiving end adjustably locks the post in vertically adjusted positions in the block 102.

The dial indicator 70 has an actuating finger 120 to engage the parallel linkage carrying the post 76 whereby movement of the post is sensed by the dial indicator to detect out-of-roundness. In setting up the gauge for measuring out-of-roundness, the posts 72 and 74 are positioned in their slots substantially equidistantly therealong from post 76. The distance selected should be such that with all three posts engaging the workpiece, post 76 will be displaced slightly toward the base line 78 thereby causing the leaf springs 104 and 106 to impose a resilient bias on the post 76 urging it toward and keeping it in contact with the workpiece as the same is rotated on the table. Thus an out-of-roundness will be sensed by the dial indicator as the post tracks the surface of the workpiece as the latter is rotated.

Provision is also made for checking diameters of workpieces. Such is accomplished by the provision of a fourth post 124 slideably supported in the slot 122 upon a support block 126. The support block 126 corresponds in all respects to the support block 86 previously described in connection with the slot _.80. However, the pad 90 shown in Figs. 2 and 5 underlying the table and to which the support block is connected is, in the case of the third slot 122 provided with a lateral extenion 128 to threadedly receive the screw shaft 130. A screw 88a corresponding to the screw 88 previously described, functions to lock the support block 126 in the slot at adjusted positions similar to screw 88. The screw shaft 130 extends through a wall 132 of the base and terminates in a hand knob 134. A collar 135 on the screw shaft bears against the inside of the wall 132, whereby the screw 130 may be rotated to effect adjustment of the post 124 in either direction along the slot. As a result of this construction the post 124 may be locked in adjusted positions along the length of slot 122. Post 124 will cooperate with the post 76 in permitting the measurement of or checking of the diameter of a part 10 positioned on the table.

Claims

Clai s

1. A gauge for checking out-of-roundness of parts comprising, in combination: a table having a surface for supporting the part to be checked; three contact posts upstanding from the table and adapted to engage the part to be checked at three substantially equidistantly spaced points therearound; one of said posts being supported for movement toward and away from an imaginary line extending between the other two posts; and means responsive to movement of said one post to read the movement thereof as a part on the table engaging the three posts is rotated.

2. The invention defined by claim 1 characterized in that said other two posts being adjustable toward and away from said one post to accommodate different diameter parts to be checked. ^•'

3. The invention defined by claim 2 characterized by means for supporting and locking said other two posts in such adjusted positions.

4. The invention defined in claim 1 wherein the posts have a laterally extending contact portion for engaging the part to be checked.

5. The invention defined by claim 4 wherein means are provided for supporting the posts for adjustment relative to the table in a direction to shift said contact toward and away from' the table.

6. The invention defined by claims 1 or 5 characterized by means for shifting said one post toward and away

- from said imaginary line to facilitate placement of a part to be checked on the table and removal therefrom.

7. The^" invention defined in claim 6 wherein said means for shifting said one post includes a manually operable actuator disposed adjacent the table.

8. The invention defined in claim ^"1 wherein said means includes a dial indicator disposed adjacent the table.

9. The invention defined in claim 8 wherein said table includes a guard portion integral therewith and extending around and protecting the dial indicator.

10. The invention defined by claim 1 characterized by a fourth ^"post upstanding from said table intermediate said other^" two posts and opposite said one post for cooperating with the latter in checking the diameter of a part on the table.

11. The invention defined by claim 10 characterized in that said table is provided with a pair of rectinlinear slots therein arranged at 60° angular spacing, and said other two posts supported in said slots for adjustable positioning therealong.

12. The invention defined by claim 11 characterized in that said table is provided with a third slot bisecting the angle between said pair of slots and said one post is disposed in such third slot.

13. The invention defined by claim 10 characterized in that said table is provided with a pair of rectilinear slots arranged at 60° angular relation with one of each of said other two posts supported therein for adjustable positioning therealong and said table provided with a third slot bisecting the angle between said pair of slots, and said one post disposed in such third slot.

14. The invention defined by claim 13 wherein said fourth post is disposed in said third slot and means are provided for shifting said fourth post along said third slot and locking the same therein at adjusted position therealong.

15. The invention defined by claim 1 wherein said table includes feet for supporting the table and wherein one of said feet is provided with an adjustable pad facilitating five point contact with the surface upon which the table is to be supported.

16. The method of checking out-of-roundness of generally circular parts comprising the steps of: arranging three part contacting posts substantially at the apices of an equilateral triangular arrangement; adjusting two of said posts toward and away from the third post along rectilinear paths coincident with the sides of said equilateral triangle to adjust the distance of said two posts from said third post to substantially correspond with coincident equilaterally arranged triangular points on the surface of the part to be checked; positioning the part to be checked in contact with said two posts and moving the third post into contact with said part and resiliently biasing the third post thereagainst; and rotating the part to be checked while maintaining said posts in the aforesaid engagement therewith and reading movement of said third post as a function of of out-of-roundness of said part.