US3541694A - Dividing head - Google Patents

Description

Nov 24, 1970 w. F. SOHAFER 3,541,694

DIVIDING HEAD Filed July 7, 1969 3 Sheets-Sheet 1 INVENTOR. WALTER E SCHAFER 452 g MM ATTORNEYS Nov. 24, 1970 w. F. SCHAFER 3,541,694

DIVIDING HEAD Filed July 7, 1969 3 Sheets-Sheet 2 FIG. 2 (PRIOR ART) mwszv'ron WALTER F. SCHAFER AT TORNEYS Nov. 24, 1970 w. F. SCHAFER I 3,54

DIVIDING HEAD Filed July 7, 1969 3 Sheets-Sheet 5 INVENTOR. WALTER F. SCHAFER QGJE MM ATTORN EYS United States Patent US. Cl. 33--174 14 Claims ABSTRACT OF THE DISCLOSURE An arm and plug adapted to be secured to one end of the hollow work holding shaft of a dividing head combined with means for measuring its angular deflection. The outer surface of the plug is substantially cylindrical and an aperture extends coaxially through the plug. Slots are cut in one end of the plug, radially of the axis. A screw projects through the aperture and is threaded to a nut having an outer peripheral surface defining the frustrum of a cone which engages the inner surface of the plug adjacent the slots which serves to expand the plug when the screw is tightened. The plug is adapted to be secured within the shaft by tightening the screw which causes the frusto conical surface of the nut to bias the slotted end of the plug into engagement with the inner surface of the shaft. The arm circumscribes and extends radially of the plug and is adjustably fixed to rotate therewith. The measuring means engages the arm at a predetermined position and reflects the angular movement of the arm.

BACKGROUND OF THE INVENTION Dividing heads have long been known and used with milling machines, drill presses, lathes, jig bores, etc., to allow the machinist to drill or cut a work piece at a particular angular relationship with respect to some reference point on the work piece. conventionally, they consist of a main shaft having a chuck on one end for holding the piece to be cut or bored and a transversely extending auxiliary shaft geared to the main shaft in a particular gear ratio. For example, the auxiliary shaft, turned by a manually operable index crank, may rotate forty revolutions for each revolution of the main shaft. An index plunger is associated with the crank adjacent an index plate which has a plurality of holes, angularly spaced around the plate and adapted to receive the plunger.

For example, for the divider head using a forty to one gear ratio between the auxiliary shaft and the main shaft, each revolution of the auxiliary shaft through 360 would be equal to an angular rotation of 9 in the main shaft. The number of equally, angularly spaced holes ordinarily made in the index plate is 9, 18, 27 or 36 to allow for division into smaller angular increments. The angular spacing between apertures in such plates represents an angle on the main shaft of 1, 30', 20' or 15' respectively.

As may be obvious, many more complicated indexing features may be incorporated, for example, one such device includes a complicated set of gear ratios and a plurality of indexing plates each with its own indexing crank whereby one indexing crank would be for degrees, another for minutes and another for seconds. The inventor is aware of such an indexing device whereby the three indexing plates are supported on three concentric auxiliary shafts. Clearly such apparatus will do the job of indexing in an acceptable manner. However, the problems which exist in most shops are increased rather than decreased by this complicated mechanism.

In the first place, the plural indexing plate mechanism is quite delicate and because of the required precise machining, it is also quite expensive. Because it is both deli- Patented Nov. 24, 1970 cate and expensive, it is not economically practical to have such an indexing device on every machine in an average machine shop. Thus, when a machinist is doing ordinary machine work he will have a less complicated indexing mechanism usually consisting of a single indexing plate. However, when precise machining must be done, he will disassemble the single plate indexing device from the dividing head, attach the plural indexing plate device to the head, perform the detailed work necessary, then disassemble it and then reassemble the original.

In addition to the initial cost of purchasing the expensive set of concentric indexing plates and the labor expense in assembling and disassembling, there is the complication that the angular relationship between each cut or each hold must be calculated with respect to the last cut made. To be more specific, with the complicated con centric indexing plates, the auxiliary shaft calibrated in minutes or the auxiliary shaft calibrated in seconds will rotate the main shaft independent of the auxiliary shaft calibrated in degrees. Thus, when the plunger on the degree indexing plate is moved, for example two degrees, and the plunger on the minute plate is rotated 40 minutes, each indexing plunger will be lodged in a particular aperture in its own indexing plate. Then assume the next cut is to be made two degrees and 40 minutes further around the periphery of the piece to be machined, the degree plunger will be retracted from its two degree hole and rotated two degrees further around the indexing plate at which point it will again drop into the appropriate aperture. Then the plunger for the minute indexing plate will be retracted and rotated forthy more degrees around its indexing plate. Should the machinist then read the two plates, he would read four degrees on the degree plate and twenty minutes on the minute plate, indicating apparently, that an angle of 4 and 20 has been traversed from the starting point of the rotation. This is clearly an error as may be seen by adding the two angles traversed, 2 and 40' for the first angle and 2 and 40' for the second angle, the total is 5 and 20. The problem which this creates is that the machinist cannot glance at his indexing plates and see the angle he has traversed from the beginning.

BRIEF DESCRIPTION OF THE INVENTION Thus, there is a clear need in the art for a simple and inexpensive device which may be kept at the work bench of every machinist which will allow him to adapt his divider head to measure angles of smaller increments than the divider head which he is supplied. Such a device is provided by this invention.

It consists of a radially extending arm which is affixed to the main shaft of the divider head by an expansible plug and a gauge for measuring the angular deflection of the arm.

It is an object of this invention to provide a dividing attachment having two separate means associated with a work holding shaft for measuring the angle of rotation of the shaft. The first means is a conventional, relatively inexpensive auxiliary shaft geared to the main shaft and incorporating an index crank, an indexing plunger and an indexing plate. The second means for measuring the angle of rotation consists of an adjustable radially extending arm fixed to the shaft and gauge means associated with the arm to measure its angular rotation.

Another object of this invention is to provide a device for attachment to a conventional dividing head and indexing device which will allow one to measure the angle of rotation in smaller increments than said conventional structure.

Another object of this invention is to provide an attachment for dividing heads consisting of an arm fric- 3 tionally attached to one end of the main shaft of the dividing head.

Other objects will become obvious from a reading of the detailed description of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a milling machine incorporating a conventional divider head and indexing device with the improved indexing device of this invention;

FIG. 2 is a perspective view of a conventional milling machine, divider head and indexing plate;

FIG. 3 is a fragmentary plan view of the improved indexing device of this invention attached to the main shaft of a conventional dividing head;

FIG. 4 is an elevational view of FIG. 3;

FIG. 5 is a sectional view taken along line 55 of FIG. 3;

FIG. 6 is an elevational view taken along line 66 of FIG. 5; and

FIG. 7 is an exploded view of the arm and the expandable connector plug.

PREFERRED EMBODIMENT FIG. .2 shows a conventional milling machine 10 having associated therewith a conventional indexing head 12. For illustrative purposes only, the milling machine is shown with the cutter 14 machining a work piece 16 with the work piece being secured in the chuck 18 on one end of the spindle or main shaft 20 (FIGS. 1 and 3) of the dividing head.

The main shaft 20 is connected by gear means (not shown) to an auxiliary shaft 24 in a predetermined gear ratio, for example, 40 to 1 is conventional but the particular gearing may vary from one head to another.

At the front of the machine, where the machinist will stand, is an index crank 26 fixed to the auxiliary shaft 24 and oppositely disposed diagonally across the axis of the shaft is an index plunger 28 which is radially adjustable in the slotted bar 30. Such structure is conventional and well known to those having ordinary skill in the art, thus, no detailed description is necessary, The index plunger 28 is adapted to penetrate the adjacent indexing plate 32 through one of the angularly disposed apertures 34. For example, where the gear ratio between the auxiliary shaft 24 and the main shaft 20 is 40 to 1, it is conventional to use a circle of 18 equally spaced apertures 34 through the indexing plate 32. In such an instance, rotation of the auxiliary shaft from one hold to the next turns the main shaft through an angle of minutes.

It is also conventional to provide that the main shaft 20 be hollow, generally as shown in FIG. 3, and include a threaded lock screw 36, best seen in FIG. 1, for locking the main shaft against rotation. The lock screw 36 is tightened when the milling is being performed.

Concerning the attachment of this invention, best illustrated in FIGS. 3-7, a radially extending arm 38 circum-, scribes an expansible plug 40 which is adapted to be inserted in the tubular main shaft 20 and expanded into tight frictional engagement, thereby to serve as a shaft extension. While various modifications may be made in the plug 40, the preferred embodiment includes an aperture 42 extending coaxially with the outer plug circumference and counterbores 44 and 46 from each end which form a radially inwardly extending shoulder 48. A screw 49 having a head 50 on one end and being threaded along its shank 52 extends through the aperture 42 and is threaded into a nut 54. The peripheral surface 56 of the nut defines the frustrum of a cone. A cooperatingly shaped frusto conical surface 58 at one end of the plug 40 contacts the peripheral surface 56 of the nut 54. Slots 60 cut in the plug, radially of the axis, divide the end of the plug into segments 61 and allow the segmented end to expand into engagement with the inner surface of the main shaft 20 upon a tightening of the screw 49. Such tightening is accomplished by inserting a conventional Allen wrench (not shown) into the hexagon shaped recess 62 in the head 50 of the screw. This pulls the frusto conical surface 56 of the nut 54 against the frusto conical surface 58 of the plug with a resultant outward biasing of the slotted segments 61 into frictional engagement with the inner surface of the main shaft 20.

The arm 38 circumscribes the plug 40 and is frictionally clamped into place by a screw 64 which is threaded through a split flange 66. When assembling the arm 38 on the plug 40, the screw 64 is tightened by an Allen wrench to frictionally clamp the arm to the plug 40. It is tightened to the extent that the grip of the arm 38 on the plug 40 will cause the arm to rotate with the main shaft 20 but it is loose enough to allow the arm 38 be rotated about the shaft by a manual operation when the main shaft 20 is locked in place by the lock screw 36 or by the plunger 28 being inserted in an aperture 34 in the indexing plate 32. The grip of the arm 38 on the plug 40 may be adjusted by a tightening or loosening of the screw 64.

Near the outer end of the arm 38 is a pin 68 which is adapted to be engaged by an extension 70 of a dial gauge 72. The dial gauge 72 may be calibrated in degrees, minutes, millimeters or any other convenient gauging means as desired. Such dial gauges are readily available in all machine shops.

During the operation of the machine, the work piece is locked into place on the main shaft 20 by the chuck 18 in a conventional and well known manner. Then the indexing head 12, index crank 26 and indexing plate 32 which together comprise the first angle measuring means, are oriented to a given position. All of the cuts or drilled holes may be calculated as to their particular angle relative to the initial position of the work piece 16. The arm 38 and plug 40 are rigidly attached to the opposite end of the main shaft 20. When a particular angular deflection is desired, the hand crank 26 is rotated to the nearest one-half degree (when an l8-hole indexing plate is used) and the indexing plunger 28 slips into the appropriate aperture 34 in the plate 32. The operator then grasps the radially extending arm 38 and manually turns it until it engages a landing 74. When this manual rotation of the arm 38 is performed, the main shaft is locked in position by virtue of the indexing plunger 28 being locked in place in the aperture 34 in the indexing plate 32, the grip of the arm 38 on the plug is not so great as to prevent the manual rotation of the arm and the slippage is between the surface of the plug and the circumscribing clamp of the arm.

When the pin 68 comes into contact with the landing 74, it effectively establishes some constant reference point which may be referred to as a relative zero angle. The extension 70 of the dial gauge 72 is then placed in mmtact with the pin 68 and the indexing plunger 28 is retracted from the aperture 34. Again the index crank 26 is rotated by hand manipulation while the dial gauge 72 is observed and the appropriate angular increment is measured in minutes or seconds, as the case may be. In other words, a small incremental angle less than the angle between adjacent apertures 34 is measured. After the appropriate fractional angle is measured on the second angle measuring means, the main shaft 20 is locked into place by the lock screw 36 and the appropriate Cut is made in the work piece 16 held in the chuck 18.

It should be noted that at this point in the machining operation, the indexing plunger 28 has moved slightly out of position with respect to the initial aperture 34 in which it was inserted. However, the operator of the milling machine may ascertain his angular position with respect to the initial starting point by merely observing the dial gauge 72 and the holes over which the indexing plunger 26 has passed. There is no way for the machinist to lose track of the exact angle he has turned from the starting point. After this milling operation, the lock screw 36 is loosened and the index crank 26 is again rotated to bring the work piece into position for the next cut.

It is important to note that this operation is extremely fast for the operator. He merely turns the crank 26 until the appropriate aperture 34 is reached and immediately manually turns the arms 38 to the point of zero angle on landing 74. However, it is also important that the rotation of the arm 38 not be obstructed when the usual machining and conventional indexing operations are being performed, thus, some movable support means 76 are provided for swinging the extension 70 out of the circumferential area traversed by the pin 68. The landing 74 is similarly removed except at such times as it is being used specifically to measure the smaller angle. Any convenient means for swinging the landing 74 and the dial gauge 72 in and out of operative position is within the contemplation of this invention, the means depicted in the drawings being merely illustrative.

A dial gauge 72 is shown merely as an illustrative example of one angle measuring means which may be employed. In some instances, the dial is calibrated in thousandths of inches and the arm length is so proportioned that a chordal deflection of one-thousandth of an inch is the equivalent of an angle of one minute. It is obvious that such calibration could be made for an angle of one second or ten seconds or any particular deflection desired. It is also obvious that the zero angle landing 74 could be eliminated as the angle being measured is only a relative angle, relative to the stopping point of the index plunger 28. Thus, the extension 70 could be placed into contact with the pin 68 at any time at any angle. The landing 74 is merely a convenient mechanism for establishing the initial zero relative angle. Clearly other means than a dial gauge could be employed for measuring the deflection if desired, and any particular means for measuring the deflection is Within the contemplation of this invention.

For ease of description, the principles of the invention have been set forth in connection with but a single illustrated embodiment. It is not intended that the illustrated embodiment nor the terminology employed in describing it be limiting inasmuch as variations may be made by one having ordinary skill in the art without departing from the scope and spirit of the invention. Rather it is intended that any restrictions on the invention be limited to the spirit and scope of the appended claims.

I claim:

1. Apparatus for dividing a circle into a plurality of distinct angles including,

a work holding shaft, a dividing head operatively connected to rotate said shaft by a transversely extending auxiliary shaft and a means for locking said work holding shaft against rotary movement,

said dividing head including means for turning said auxiliary shaft and measuring the resulting angle of rotation of said work holding shaft,

the improvement comprising a second means for measuring the angle of rotation of said work holding shaft, said second means including an arm adjustably connected directly to and extending radially outward from said work holding shaft, gauge means associated with said arm for measuring its angular deflection.

2. The apparatus of claim 1 including a means for locating the arm at a relative zero angle.

3. The apparatus of claim 2 wherein the arm is rotatable on said shaft by a manual operation to said zero angle.

4. The apparatus of claim 1 wherein the chord of the are traversed by the arm and measured by said gauge means is directly proportional to the subtended angle.

5. The apparatus of claim 4 wherein a chord of 0.001 inch subtends an angle of one minute.

6. The apparatus of claim 1 wherein the arm is clamped around the shaft by means for adjusting the frictional grip of the arm on the shaft.

7. The apparatus of claim 1 wherein the arm includes means forming an aperture, an extension of said shaft projecting through the aperture, a split flange on said arm extending radially from said shaft and means associated with said split flange for adjusting the grip of said arm on said shaft.

8. The apparatus of claim 7 wherein the means for adjusting the grip includes a screw threaded through said flange and extending across said split.

9. The apparatus of claim 1 wherein said second means includes a plug adapted to be secured in one end of the Work holding shaft of a dividing head comprising,

a cylindrical plug having an aperture extending substantially coaxial with its periphery, slots in said plug extending from one end and radially of the plug axis,

a screw projecting through said aperture and threaded to a nut,

the peripheral surface of said nut defining the frustrum of a cone and engaging the inner surface of said plug adjacent the slots, and

the arm being adjustably attached to said plug and extending radially of said axis.

10. The arm and plug of claim 9 wherein the inner surface of said plug adjacent the slots defines the frustrum of a cone.

' 11. The apparatus of claim 1 wherein the work holding shaft is hollow and the arm is connected to the work holding shaft by an expending plug extending into one end thereof.

12. The apparatus of claim 11 wherein the arm circumscribes the plug and is frictionally attached thereto and including means for tightening the grip of said arm on said plug.

13. A dividing head having a main shaft with a chuck on one end for supporting a work piece to be machined,

an auxiliary shaft geared to said main shaft and means associated with said auxiliary shaft for turning it and mesuring the angle of rotation of the main shaft,

means for locking the main shaft in non-rotating position,

an arm adjustably fixed to the main shaft combined with gauging means for measuring the angle of rotation of said main shaft in smaller increments than the means associated with said auxiliary shaft.

14. The dividing head of claim 13 including means for fixing the arm for rotation with the main shaft and when the main shaft is locked against rotation for allowing rela- 55 tive rotation with respect to the shaft.

References Cited UNITED STATES PATENTS 10/1939 Meyer 33-174 9/1944 Hansen 33174 FOREIGN PATENTS SAMUEL S. MATTHEWS, Primary Examiner US. Cl. X.R. 74-813

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