US3541870A - Coarse and vernier adjustable mechanism - Google Patents

Description

Nov. 24,1970 G. E. LYCNS 3,541,870

COARSE AND VERNIER ADJUSTABLE MECHANISM Filed March 27, 1969 "Ill nul

INVENTOR.

GLENE. LYONS United States Patent 3,541,870 COARSE AND VERNIER ADJUSTABLE MECHANISM Glen E. Lyons, Pensacola, Fla., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed Mar. 27, 1969, Ser. No. 811,010 Int. Cl. F16h 25/18 U.S. Cl. 74-89.15 6 Claims ABSTRACT OF THE DISCLOSURE A cam is pivotally mounted on a movable member. A screw bears on the cam, for coarse direct adjustment of the position of the member carrying the cam. A second screw bears on a lever on the cam, to rotate the cam and provide a vernier adjustment of the position of the member.

The invention relates to a mechanism providing coarse and vernier adjustment of the position of a member, and is illustrated in the context of a precision grinding machine.

In various applications it is desirable to make a rapid coarse adjustment of the position of a member, while still being able to make a vernier adjustment. One example of such an application would be in a precision grinder. As typically constructed a grinder wheel is pivoted into contact with a workpiece by a main cam, there being an adjustable member positioned between the main cam and the chassis carrying the grinding wheel. In one known construction, a slotted sub-frame is bolted to the grinding wheel chassis. A slide member against which the cam acts is attached to a sub-frame by a differential screw, that is, a screw having a first portion with a given pitch threaded into the sub-frame and another portion with a different pitch threaded into the slide. With this construction the vernier adjustment is achieved by rotation of the differential screw. However, the coarse adjustment is not satisfactory since it requires loosening the bolts, sliding the sub-frame, and then retightening the bolts. Since the range of vernier adjustment is very small, it frequently happens that the sub-frame shifts sufiiciently while the bolts were being tightened that the vernier adjustment cannot compensate for the shift.

It has been discovered that a more rapid and simple adjustment can be provided by using a direct acting element (such as a screw) for providing the coarse adjustment, while achieving the vernier adjustment by rotation of a cam positioned between the direct acting means and the member. Advantageously, the cam is rotated by movement of a lever attached to the cam, as by a screw abutting against the lever.

Accordingly a primary object of the invention is to provide a mechanism having novel and improved coarse and vernier adjustments of the position of a member.

A further object is to provide a mechanism of the above character wherein the coarse and vernier adjustments can be made simply and rapidly.

Other objects will in part be disclosed hereinafter, and will in part be obvious from the following disclosure taken in connection with the accompanying drawings, wherein:

FIG. 1 is a simplified perspective view of a precision grinding apparatus incorporating the invention;

FIG. 2 is a plan view, partly broken away, of the preferred adjustable mechanism according to the invention;

FIG. 3 is a side elevation view of the FIG. 2 mechanism; and

FIG. 4 is a fragmentary plan view of an alternative embodiment of the invention.

3,541,870 Patented Nov. 24, 1970 ice As shown generally in FIG. 1, the invention is disclosed in the context of a precision grinding machine wherein various subassemblies are mounted on chassis 20. A first subassembly includes motor 22 driving chuck 24, a workpiece 26 illustrated in the form of a cylindrical rod being mounted in chuck 24. A second subassembly including motor 28 is mounted on chassis 20. Motor 28 drives main cam 30 at a given rate of rotation. A third subassembly is pivotally mounted on chassis 20, and includes bearing 32 rotatably supporting pivot shaft 34, pivot shaft 34 in turn supporting sub-chassis 36. Grinding wheel 38 is driven by motor 40 mounted on one end of sub-chassis 36 adjacent workpiece 26. A cam follower assembly 42 is mounted on the opposite end of sub-chassis 36 for cooperation with main earn 30. The entire third subassembly pivots about the axis of shaft 34, and is resiliently urge toward main cam 30 by spring 44. As main cam 30 rotates, the entire third subassembly rocks or pivots back and forth about shaft 34, feeding grinding wheel 38 against and withdrawing it from workpiece 26. The apparatus as generally described in this paragraph is conventional, although separate motors ordinarily would not be provided for each of the three subassemblies.

The particular cam follower assembly 42 illustrated in FIG. 1 is the preferred embodiment of adjustable mechanism according to the present invention. The function of the adjustable mechanism in the FIG. 1 grinding apparatus is to permit rapid and precise compensation for changes in the diameter of the grinding wheel, the desired depth of grinding on the workpiece, etc. The construction and operation of the adjustable mechanism is illustrated in FIGS. 1-3, wherein the various elements are mounted on a generally U shaped mechanism frame 46. A rod-like member 48 is slidably mounted in a first leg 50 of mechanism frame 46 for movement along its axis. The outer end of member 48 bears against main cam 30 (FIG. 1), while the inner end is slotted in a generally horizontal plane to provide vertically spaced fingers at the end of member 48. Vernier cam 52 is positioned in the slot, and is pivotally retained therein by a vertical pivot pin 54 extending through the fingers and through vernier cam 52. Coarse adjustment means 56 (illustrated as a screw threaded through the second frame leg 58 and abutting cam 52) provides a movable abutment surface for rapidly varying the position of member 48 with respect to leg 58.

Lever arm 60 is integral with cam 52, extending to the right as viewed in FIG. 2. A micrometer screw 62 is mounted in leg 58 with its spindle 63 in alignment with the free end of lever 60. The end of lever 60 may be slidably supported in a horizontal groove in support rod 64, there being no pivot pin such as pin 54 in the free end of lever 60. In the embodiment illustrated, rod 64 extends through a bore in leg 50, and is spring loaded to hold lever 60 against the end of spindle 63.

In the adjustable mechanism as thus described, coarse adjustment of the position of member 48 is accomplished by movement of screw 62, pivoting lever 60 and cam 52 about pivot pin 54.

As cam 52 pivots, the distance between the abutment surface or end of screw 56 and pivot pin 54 is changed by a much smaller amount than the distance through which spindle 63 is moved. The ratio of these distances, and hence the accuracy of the vernier adjustment, depends upon the contour and dimensions of cam 52, and on the length of lever arm 60. In the FIGS. 1-3 embodiment, cam 52 was in the form of a half-inch diameter circle having its center located (as viewed in FIG. 2) on a line parallel to the axis of member 48 and 0.025 inch to the left of the axis of pivot pin 54, and on a line perpendicular to the axis of member 48 and 0.025 inch nearer the end of screw 56 than the axis of pin 54. With the axes of screws 56 and 62 being 2.5 inches apart, movement of screw 62 was about 100 times as large as the resulting movement of pivot pin 54 along the path of member 48.

Although the eccentrically mounted circular vernier cam illustrated is satisfactory for this particular application, it could be formed with a different contour if desired. Various other modifications can be made, one of which is shown in FIG. 4. As illustrated therein, vernier cam 52 is carried by the coarse adjustment means (screw 56) rather than by member 48. In this embodiment, swivel 66 is mounted on the end of screw 56 for rotation about the axis of screw 56. Cam 52 is pivotally mounted on swivel 66 by pivot pin 68, with the cam surface bearing against the inner end of member 48 rather than against the end of screw 56 as in the FIGS. 1-3 embodiment. It is not essential that the vernier cam be attached by a pivot pin to either the member 48 or the coarse adjustment screw, provided the vernier cam separates (determines the distance between) member 48 and means 56, and is movable with them. Various other modifications will occur to those skilled in the art.

I claim:

1. An adjustable mechanism, comprising:

(a) a frame;

(b) a member movable with respect to said frame in a given path;

() a vernier cam pivotally mounted at a point on said member, said cam including a lever arm;

(d) abutment means for engaging said cam, said abutment means being mounted on said frame and adjustable along said path;

(e) means resiliently urging said abutment means and said cam into contact; and

(f) means for adjusting the position of said lever arm whereby the distance from said point to a reference point on said frame can be selectably varied.

2. The mechanism defined in claim 1, wherein said abutment means includes a screw threaded into said frame, and wherein said cam engages one end of said screw.

3. The mechanism defined in claim 1, wherein said means for adjusting the position of said lever arm includes a screw threaded into said frame and engaging the end of said lever.

4. The mechanism defined in claim 1, wherein said cam is an eccentrically mounted circle.

5. The mechanism defined in claim 3, wherein said cam is formed so that movement of said point is substantially proportional to movement of said screw.

6. An adjustable mechanism, comprising:

(a) a frame;

(b) a member movable with respect to said frame in a given path;

(0) coarse adjustment means mounted on said frame and adjustable along said path;

(d) a vernier cam movable with and separating said member and said coarse adjustment means, said vernier cam including a lever arm;

(e) means resiliently urging said coarse adjustment means toward said member; and

(f) means for adjusting the position of said lever arm whereby the distance from said member to a reference point on said frame can be selectably varied.

References Cited UNITED STATES PATENTS 3,339,311 9/1967 Berg 51-33 3,402,613 9/1968 Neusel et al 7489.l5

FOREIGN PATENTS 844,048 8/ 1960 Great Britain. Edqvist.

WESLEY S. RATLIFF, JR., Primary Examiner U.S. Cl. X.R. 5l33

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