US2600591A

US2600591A - Device for generating arcs or the like

Info

Publication number: US2600591A
Application number: US81993A
Authority: US
Inventors: Eric H Wang
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-03-17
Filing date: 1949-03-17
Publication date: 1952-06-17
Anticipated expiration: 1969-06-17

Description

June 17, 1952 E. H. WANG 2,600,591

DEVICE FOR GENERATING ARCS OR THE LIKE Filed March 17, 1949 INVENTOR. [If/6 M "4 1%",

ATTORNEY-S- Patented June 17, 1952 DEVICE FOR GENERATING ARCS on THE LIKE Eric H. Wang, Cincinnati, Ohio Application March 17, 1949, Serial No. 81,993

3 Claims.

My invention relates toqa device and process for generating arcs of a radius which is so large that it is impossible or impractical to usethe center of the arc as a pivot point.

In machining, engraving, and other purposes, it is often desirable to generate an arc with the tool wherein the chord or length of the arc is relatively short, but the radius of the arc extremely large, but where the center of the arc is so remote from the machine or engraving apparatus that it is impossible or impractical to use the center as a pivot about which to revolve an arm.

It is an object of my invention to provide a device for generating arcs of large radius to an accuracy sufficient for practical purposes which is located substantially on the are being generated and without the necessity of any portion of the device projecting to or being connected to any center remote from the device.

It is a further object of my invention to provide a process and device for simply and readily generating arcs of sufficient accuracy for practical purposes which is quite simple to construct and maintain and which may be easily altered to generate arcs of different radii and different lengths.

While in the following drawings and description I will show and describe a device primarily for use with a planer or a milling machine, it is to be understood that this is merely exemplary of my process and device since the process and device may be used for many other purposes such as engraving, drawing, or any place where it is desirable to generate an arc of relatively large radius for practical and non-mathematical purposes.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain construction and arrangement of parts of which I shall now describe an exemplary embodiment. Reference is made to the drawings in which:

Figure l is a sketch showing a near approximation to a circular are generated by the tool of my device and a true circular arc of very large radius.

Figure 2 shows the movement of the work piece in reference to the tool whereby the arc is generated.

Figure 3 shows my device as applied to the table and bed of a planer in plane.

Figure 4 shows my device as applied to the table and bed of a planer in elevation.

Figure 5 shows my device as applied to a milling machine in elevation.

Briefly, in the practice of my invention, I have determined that a portion of the loop of a looped trochoid in its special case, an archimedic spiral,

' very closely approaches the true are of a circle of substantial radius in referring to a relatively short chord or are. I have determined that a trochoid can, for example, be generated by translating the work piece in a straight line, while at the same time rotating it through a certain rather small angle and that any tool which is stationary as to its position on the machine will describe in the work piece a part of the trochoidal curve.

The distance to be traveled and the angle through which the work piece must rotate while traveling this distance will be in a constant ratio for each case and will depend on (a) the distance of the lowest point of the trochoid to the center of rotation of the work piece. This is equal to the distance of the points of contact of the tool to the straight line which the center 'of rotation of the 'work piece describes. (b) The radius desired, and (c) the length of the chord between the end points of the are desired.

The calculation is based on a trochoid which coincides in three points with the desired are, preferably a point at or near each end of the desired circular arc and an intermediate point. Computations actually performed show a deviation of only a few thousandthsof an inch down to less than one thousandth of an inch at the place where the trochoid which is generated and the circular are which is desired are furthest apart.

The deviation between the trochoid generated and the circular are desired becomes smaller with increasing radius and relatively diminishing chord. For an arc of 240 inch radius and a chord of inches length, the deviation is less than .001 inch.

Figure 1 shows a piece of work I into which a circular arc 2 is to be cut. Points A and C as well as intermediate B are identical with the are 2 and the trochoid 3 which is generated and indicated by the broken line. The point of greatest deviation between the trochoid 3 and the are 2 is at 4 and as heretofore pointed out is extremely small, and for practical purposes is negligible, diminishing as the radius increases.

The equation of the trochoid can be developed by using the equation of the involute to start known and may be determined for each individual setting based on the radius of the arc to be cut or generated and the length of the chord.

In Figure 2, the starting position of the work piece I is shown at 5 and the end position of the work piece I is shown at 6. The position of the tool which is stationary is shown at I. The rotating work holder is indicated at 8 and in Figure 2 rotates in a clockwise direction about the center 9 and the distance the tool holder 8'is'translated is-the distance between the centers 9-9 in Figure 2. The broken line 10 indicates the arc (trochoid generated) to be cut by the tool I and is shown completed at ID in Figure 2.

Figures 3 and 4 show my device as applied to a planer having a reciprocating or translating table II and a stationary bed 12. The rotating work holder 8 is positioned on the table II and reciprocates with it. The work I is held in position by suitable clamps 13. The tool 14 is held by the normal tool holder [5.

A gear'l6 mounted on a shaft ll whichrotates the work holder 8 about its centerBby means of mechanismnot showniscommon in the art. A train of gears-lawns from the .gear [6 tea rack l9 which is mounted by means oi brackets 29 to the bed l2.

From the above, it is apparent that by selecting gears of specific relative sizes for thegear train|8 the ratio of translation to rotation of the work I may be adjusted so that the tool M will generate a portion of a specific trochoid 10 in the work I.

Figurefi shows the application of my device to a milling machine having reciprocating or translating table and a stationary base 2!. The leadscrew of the milling machine-22 is connected by gearing 18 to the shaft H which rotates the work holding table 8. The milling cutter 23 rotatestc cut the material but-does not move ina horizontal plane. The action :is the same as that described in reference to the planer, that is, the'ratio of the translation of the table 2| to the rotation of .the work holding table 8 is covered by the gears 18 and is soadjusted that the tool 23'will generate the desired portion ofthe specific trochoid on the work I.

While I have described my invention. as applied to a planer or a milling machine, itis tobe understood that I do not intend to limit myself specifically to these two machines since the application isadaptable to numerous other machine tools as'well asengraving machines and other devices Where it is desirable to have a tool or stylus generate a portion of a trochoid or similar figure.

As is apparent, the device is relatively simple, rugged, and subject to complete control.

It is to be understood that modification may be made in my invention without departing from the spirit thereof. Having thus described my invention in an exemplary embodiment, what I claim as new and desire to secure by Letters Patent is:

1. In a planer or the like a rotatable work holder positioned on the reciprocating table of the planer with its axis of rotation perpendicular to the direction of reciprocation of the table, a rack associated with the stationary planer bed, a train of gears engaging the rack and the work holder for rotation thereof in fixed relation to the translation of the table and a stationary tool positioned over the work holder.

2. In a planer or the like a rotatable work holder positioned on the reciprocating table of the planer with its axis of rotation perpendicular to the direction of reciprocation of the table, a rack associated with the stationary planer bed, a train of gears'engaging the rackv and the work holder for rotation thereof in fixed relation to the translation of the table and a stationary tool positioned over the work holder, said train of gears being variable.

3. In a machine tool or the like, a stationary bed, a rack fixed on the bed, a reciprocating table on the bed, a rotatable Work holder on said table having its axis of rotation perpendicular to the direction of reciprocation of the table, a single series of intermeshing gears, said gears being interconnected with the rotary work holder, the reciprocating table and the stationary rack. whereby said work holder is rotatable and the table reciprocable simultaneously.

ERIC H. WANG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,355,919 Schurr Oct. 19, 1920 1,835,742 Andrew Dec. 8, 1931 1,901,952 Emerson Mar. 21, 1933 2,303,813 Barcus Dec. 1, 1942 2,330,921 Rickenmann Oct. 5, 1943 2,350,428 Torma Jan. 6, 1944 2,366,993 Antos Jan/9, 1945