US2331337A

US2331337A - Method of and machine for reproducing pattern contours

Info

Publication number: US2331337A
Application number: US271868A
Authority: US
Inventors: Arthur A Meyer
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-05-05
Filing date: 1939-05-05
Publication date: 1943-10-12
Anticipated expiration: 1960-10-12

Description

Oct. 12, 1943. I A. A. MEYER 2,331,337

METHOD OF AND MACHINE FOR REPRODUCING PATTERN CONTOURS Filed May 5, 1939 7 Sheets-Sheet l J6, NVBNTOQ/ 20 9 C4r/hw' C4. Wager TTO Eys Oct. 12, 1943. A. A. MEYER 2,331,337

METHOD OF AND MACHINE FOR REPRODUCING PATTERN CONTOURS Filed May 5, 1939 7 Sheets-Sheet 3 7 x v 74 92 7 79 7 94 7 a9 Q0 1 ha 73 a 65 t J .fi 7% 22 ,1 1" 1 I 1:97 ;6a' Vl-:

Y NvL-Z NTOFEJ @Wf/mr G4. Wage)" l Pvt/AM 044M". 7

(fiTro @5 49 Oct. 12, 1943. A, MEYER 2,331,337

METHOD OF AND MACHINE FOR REPRODUCING PATTERN CONTOURS Filed May 5, 1939 7 Sheets-Sheet 4 TO HEAD END OF T3 200 END or To HEAD END OF NS s m UW/hur 64. Qf/egen r4 Pm ch14, m

(flTm Eys 1943. A. AQMEYER 2,331,337

METHOD OF AND MACHINE FOR REPRODUCING PATTERN COIQTOURS Filed May 5, 1959 7 Sheets-Sheet 5 Mr/hur 04. 07/25 22? Oct. 12, 1943.

A. A. MEYER METHOD OF AND MACHINE FOR REPRODUCING PATTERN CONTOURS Filed May 5, 1939 7 Sheets-Sheet 6 MH /MU 6% We en 3 F CUM, Pi 1W OQTTOVQIEXS Oct.- 12, .1943. A. MEYER 2,331,337

METHOD OF AND MACHINE FOR REPRODUCING PATTERN CONTOURS Filed May 5, 1939 7 Sheets-Sheet 7 z zzzwm Wr TTO 4 2.7 5

Patented Oct. 12, 1943 METHOD OF AND MACHINE FOR REPRODUCING PATTERN CONTOURS.

Arthur A. Meyer, South Beloit, 111. Application May 5, 1939, Serial No. 271,868

28 Claims.

This invention relates to a system of control for causing a controlled object to traverse a path corresponding to a pattern outline and has more particular reference to the reproduction of pattern contours by governing the relative movements between a work piece and a tool such as a milling cutter, a cutting torch, a polishing or abrasive Wheel, etc.

One object is to provide a novel method of and machine of the above general character by which a single tracer element will follow the entire periphery of a pattern automatically without the necessity of changing quadrants or otherwise adjusting the control mechanism.

A more detailed object is to govern the relative movements of a controlled object, such as a cutter, in accordance with the mean position of a tracer element which is oscillated back and forth laterally of a pattern outline in directions which are varied automatically with changes in the pattern contour.

Another object is to provide a novel electrical system controlled by a tracer for detecting changes in a pattern contour and to utilize this system in a novel way to control an hydraulic operator which is moved in any one or a combination of four rectangular directions.

Still another object is to provide a novel control system for enabling the movements of a controlled object to reproduce the outline of a pattern in the form of a line inscribed on a transparent medium.

A further object is to utilize a photosensitive cell in a novel way to carry out the foregoing object.

Another object is to provide a novel circuit arrangement for obtaining optimum sensitivity of the electric system controlled by the photosensitive cell.

The invention also resides in the novel manner of varying the direction of oscillation of the tracer element relative to the pattern and in the novel valve arrangement by which precision of control is obtained.

Another object is to provide a control of the above character for reproducing contours incorporating means for selectively adjusting the size of the reproduced path relative to the size of the pattern outline.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a fragmentary perspective view of a machine for practicing the present. invention.

Fig. 2 is a plan view of a pattern. Fig. 3 is an hydraulic circuit diagram.

Fig. 4 is a fragmentary plan sectional view Fig. 8 is a fragmentary sectional view taken along the broken line 8-8 of Fig. 7.

Fig. 9 is an enlarged fragmentary sectional view taken along the line 9-9 of Fig. 7.

Fig. 10 is a section taken along the line l0-l0 of Fig. 7.

Figs. 11, 12, and 13 are sectional views taken along the line ll-l l of Fig. 6 and illustrating diflerent valve positions.

Fig. 14 is a sectional view taken along the line I4|4 of Fig. 13.

Fig. 15 shows graphically the manner of proportioning the fiuid flow to the different hydraulic cylinders.

Figs. 16 to 23 are schematic views showing different positions of the valve and tracer for causing movement of the controlled object in different directions.

Figs. 24, 25,- and 26 are similar views showing different relations of the tracer and valve controller for different applications of the control.

Fig. 27 is a schematic view illustrating the progress of the tracer around a pattern.

Fig. 28 is a wiring diagram.

While the invention is susceptible of various modifications and alternative constructions and may be practiced in various ways. I have illustrated in the drawings and will herein describe the preferred embodiments and manner of carrying out the invention. It is to be understood that I do not thereby intend to limit the invention by such disclosure but aim to cover all m0difications, alternative constructions, methods, and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Generally stated, the improved method of controlling the relative movements of a controlled object in accordance with a pattern contour comprises oscillating a tracer element back and forth transversely of a pattern outline while relatively moving the element along such outline, changing the angles and relative lengths of the oscillations in accordance with changes in the pattern contour so as to maintain a substantially constant relationship between-the direction of oscillation and the instantaneous curvature of the outline, and relatively moving the controlled object along a path corresponding to the mean path described by said element. The tracer element moves in a small orbital path and the angle of oscillation is varied by changing the portion of the path through which the element oscillates automatically in accordance with changes in the direction of motion of the controlled object so that the entire periphery of the pattern will be traced without the necessity of manual adjustment to change quadrants. This enables a single tracer element and controls permanently associated therewith to'produce movement of the controlled object in all directions in a given plane. I

For purposes of illustrating the invention, the object to be controlled is shown as a metal cutting tool in the form of an oxy-acetylene torch I of Well known construction arranged to direct a cutting flame toward a metal work piece W to cut the latter and reproduce thereon the contour of a pattern 2 (Fig. 2) coacting with the tracer element which, in the present instance, comprises a light beam 3 (Fig. '7) emanating from a casing 1. Preferably, the pattern is simply the inner or outer periphery of an ink or pencil line inscribed on a transparent medium such as a sheet 3 of tracing cloth or paper. Depending on the position of the tracer relative to the pattern, the O beam 3 or a predetermined part thereof will or will not be intercepted by the line 2, and the resulting full-light and reduced light conditions are detected by a light sensitive device 5 and utilized to control a power actuating mechanism by which the controlled object or tool is moved relative to the work piece and the in unison along the pattern outline.

Herein, the pattern carrier 4 is mounted on a transparent plate 6 of glass or the like removably supported at its side edges in a stationary frame 8. The cutter I, in proper operative position relative to the work, is mounted on a carriage 9 which is slidable in ways II on a saddle Ill. The latter and a lateral extension I2 thereof are slidable along ways I3 extending at right angles to the ways II and formed on a suitable base I4.

Feeding of the saddle along the ways I3 and cross feeding of the carriage 9 is accomplished by power actuated means which is relatively sluggish in response to its control so that the carriage does not respond to a measurable degree to the individual oscillations of the tracer. In the present instance, this means comprises two hydraulic actuators having cylinders I5 and I5 respectively secured to the saddle I0 and bed I4 and coacting with pistons I1 and I8 the rods I9 and 29 of which are anchored to the carriag .9 and to the saddle I0.

By supplying pressure fluid through

conduits

23 and 24 to the rod and head ends of the cylinder I6, the saddle I0 supportingthe carriag 9 will be moved relative to the bed in opposite directions which, for the convenience of descrip tion, will be referred to as north and south respectively. Similarly, by introducing fluid through conduits 2| and 22 to the head and rod ends of the cylinder I5, the carriage 9 may be moved in opposite directions, indicated as east and west, along the perpendicular path defined by the ways II. By admitting fluid simultaneously to one end of one cylinder and one end of the other cylinder, and by accurately metering the relative rates of such flow to the respective ends, it will be apparent that the carriage and tracer mounting is fed withdraw oil from a sump saddle may be moved so as to produce a resultant motion of the cutter. and tracer in any NW, SW, NE, or SE direction, that is, at any angle within a complete circle.

Fluid such as oil is placed under pressure by a gear pump 25 driven by an electric motor 26 to 21 and deliver the same to a conduit 28. Regulation of the volume of fluid delivered to one or both of the cylinders to vary the rate of feed of the carriage 9 may be efiected by manual adjustment of a valve 29 through which any selected part of the pump output may be by-passed to the return line 30. In the present instance, the pump 25 and the motor 26 are mounted on the carriage and the

conduits

2I, 22, 23 and 24 are flexible in part to permit movement of the carriage relative to the saddle.

While a single valve unit may be employed for selectively controlling and metering the fluid flow to the cylinder ends, this is accomplished herein by two separated valves 3| and 32 mounted on the carriage 9 and respectively controlling the flow to opposite ends of the east-west cylinder I 5 and the north-south cylinder I6. The valve 32 (see Figs. 6 and 11 to 16) comprises a casing 33 having angularly spaced and 36 extending through its side wall and respectively communicating through suitable fittings with the

conduits

23, 24, and the supply line 28. The passages terminate in the wall of a cylinder 31 in the casing. A passage 38 leading from a branch 39 of the returnline 30 terminates in a port in the bottom of the casing 33 midway between the

passages

34 and 35.

The movable member of the valve 32 is a cylindrical rotor 40 journaled in the cylinder 31 and rigid with a shaft M which projects upwardly through a plug 42 closing the upper end of the casing 33 and carries an arm 41. The rotor is shorter than the cylinder 31 and does not cover the supply passage 36 so that a chamber 43 above the rotor is always under pressure.

Passages

44 and 45 in the rotor open upwardly and also radially so as to connect the pressure chamber 43 with the

passages

34 and 35 in different half portions of the rotor movement. The rotor is cut out to form a segmental recess 46 which is in constant communication with the drain outlet 38 and is adapted to register with one or the other of the

passages

34 and 35. The arm 41 and the valve member 40 oscillat through angles 12. and s. With the arm positioned as shown in Figs. 11 and 16, the

passages

34 and 44 are in full register and the passage 35 is connected to the drain through the recess 46. Fluid flows at a maximum rate from the supply line 28 to the rod end of the cylinder I6 and to 'the drain from the head end resulting in a maximum rate of travel of the saddle I2 in the north direction. As the arm 41 is swung clockwise through the angle n, the flow is decreased progressively to reduce correspondingly the rate or feed in the north direction. The flow is cut of! completely when the arm 41 is in the mid-position shown in Figs. 12 and 18, both

ports

34 and 35 then being covered by the rotor 49. In continued clockwise turning of the arm through the angle s, the passage 45 is brought into register with passage 35, fluid being thereby admitted to the head end of the cylinder I6 and drained from the rod end, thereby initiating movement of the saddle III in the south direction. This feed rate is increased progressively in the continued turning of the arm through the angle passages or bores 34, 35,

s, being a maximum when the rotor is positioned as shown in Figs. 13 and 20.

The valve 3| is of the same construction as the valve 32 and for convenience the corresponding parts have been indicated by the same but primed reference numerals. The arm 41' is movable through angles e to modulate the flow of fluid through the passages 44' and 34' (Fig. 16) to the head end of the cylinder l and permit the draining of the rod end through the passages 35', the recess 46, and the passage 38'. In the extreme east position (Fig. 18), the passages 34' and f are in full register while in the mid-position of the arm 41' (Fig. 16), the passages 34' and 35' are covered by the rotor and no fluid flows either to or from the cylinder l5. As the arm moves through the angle w, the fluid is permitted to flow to the rod end of the cylinder l5 through the registering passages 35' and 45', a maximum flow occurring in the extreme west position (Fig. 22).

Provision is made for actuating the two valves 3| and 32 from a common member which assumes different positions corresponding to the instantaneous contour of the pattern being traced and accurately positions the two valves to produce a resultant motion of the cutter corresponding tosuch contour. Preferably, the valve actuator is a rotary member and, as shown here in, takes the form of a disk fast on the upper end of a vertical shaft 5| journaled in the forward end of the carriage 9. Fast on the shaft beneath the disk is an eccentric cam 52 acting on follower rings 53 and 54 respectively rigid with

arms

55 and 55 the free ends of which are pivotally connected at 5'! and 58 to the free ends of the arms 41 and 41'.

Since the eccentric 52 is common to both of the followers, the arms 41 and 41' are arranged so that lines through the

pivots

57 and 58 and the eccentric axis will be disposed at right angles to each other as shown in Fig. 16. Also, the throw of the eccentric and the lengths of the arms are such that when the arm 41 is in its opposite limit positions N or S (Figs. 16 and 20), the arm 41' is in its mid-position in which no fluid is flowing to the cylinder l5. Likewise, in the extreme E and W positions of the arm 41' (Figs. 18 and 22) the arm 41 will be in its mid or neutral position. Fig. 15 shows graphically the manner in which the effective volume of oil supplied to the line 28 is proportioned between the two cylinders l5 and I6 for all angular positions of the reference arrow on the valve actuating member 50. For example, in the N position of the member, all of the fluid flows to the rod end of the NS cylinder which causes the saddle H] to move in the north direc tion. As the member moves toward the Wposition, the flow to the cylinder I6 is decreased and that to the rod end of the WE cylinder is increased progressively causing the carriage and saddle to move simultaneously and produce a resultant northwest movement corresponding to the position of the member. From Fig. 15 and the diagrammatic views Figs. 16 to 23, it will be apparent that the described valve actuator provices for selective and simultaneous positioning of the valves 3| and 32 to produce a resultant movement of the cutter in any direction away from the point of intersection of the NS and EW axes, the rate of feed of the cutter being determir. :d by the setting of the by-pass valve 29.

cause the angle of oscillation of the tracer r light beam 3 to change automatically as set forth above, provision is made formoving the tracer in a small orbital path, preferably circu lar, relative to its mounting on the controlled object and in unison with changes in the position of the valve actuating member 50. For this purpose, the conical casing I by which the beam is defined is, in the present instance, attached at one side to an arm 60 (Figs. 7 and 8) the other end of which is fastened to a bar 6! pivotally supported at opposite ends by links 62 constituting one parallel motion device. The other ends of the links are pivotally supported on the short leg of an L-shaped piece 64 the long leg of which is supported by links 63 pivotally supported on the carriageS. The bar 6| has a bore 65 receiving a pin 66 which projects eccentrically from a shaft 61 fastened to the lower end of the shaft 5| 'as by a set screw 68. By loosening the screw, the

collar 61 may be removed and replaced by a collar having a pin 68 of different eccentricity or a given collar may be adjusted angularly to vary the angular position of the eccentric axis 69 relative to the position of the valve actuating member 50. With the casing 1 mounted as above described by the two parallel motion linkages, it will be apparent that the light beam 3 will follow the movements of the eccentric axis 65, describing a complete circle 10 (Fig. 16) about an axis 10 as the valve actuating member 50 turns through a complete revolution.

The tracer element or light beam is sharply defined by a suitable system of lenses TI and 12 for converging the rays of light from a source such as an electric lamp 13 which may be energized from a secondary I02 of a multiple voltage transformer I03 (Fig. 28). To lighten the parts which move with the beam and therefor increase the speed of oscillation of the beam, the lamp is preferably mounted in a tubular casing 14 clamped by a strap 15 against the front of the carriage 9 in substantial axial alinement with the upper open end of the conical casing 1. Part of the lenses are placed in the tube 14. The casing l is thus adapted to oscillate independently of the light source. The side wall 98 (Fig. 9) which defines the hole 99 through which the beam 3 is directed from the casing I is preferably cut back as shown in Fig. 9 to provide a sharply defined beam. The same result may be obtained by making the end of the casing I extremely thin walled.

Various power actuated mechanisms may be employed to effect oscillation of the valve actuating member 50 back and forth in response to full light and no light conditions detected by the tracer. This is accomplished herein by selective energization of a reversible electric motor driving means herein shown as comprising two electromagnetic clutches I04 and I05 for connecting the member 50 for rotation in opposite directions by a constantly rotated driving element. The latter takes the form of a pulley 16 (Fig. 4) driven by a belt 11 from a suitable source of power such as an electric motor 18 on the carriage. A gear 19 rotatable with the pulley meshes with two gears and 8| fast on

shafts

82 and 83 carrying

worms

84 and 85 disposed on diametrically opposite sides of the member 50 and adapted to mesh with teeth v86 cut around the periphery of the member so as to form the clutches l 04 and I05.

The pulley shaft and the

shafts

82 and 83 are journaled in bearings in a bar 81, and the shafts are supported for lateral movement by upstanding arms 88 and 89 loose on the shafts adjacent the bar and pivoted at their lower ends on a plate 90 secured to the carriage. The bar 8'! is thus supported for horizontal movement in opposite relay I I1.

directions to carry one or the other of the

worms

84 and 85 into and out of mesh with the worm wheel 50 and thereby actuate the two clutches alternately. Such shifting of the worms is efiected by selective energization of two electromagnets 9| and 92 having

poles

93 and 94 disposed on opposite sides of an upstanding armature 95 fast on one end of a rockshaft 96. The latter is journaled in the plate 90 and has the arm 88 fast on its opposite end. As a result, energization of the magnet 9| will attract the armature and rock the shaft 96 in a direction to shift the worm 84 into mesh with the wheel 50 causing the latter to turn counter-clockwise. When the magnet 92 is energized, the worm 34 is disengaged and the worm 85 shifted into mesh, the member 50 being then driven clockwise. Non-magnetic spring clips 91 on the magnet poles limit the movement of the armature and prevent freezing of the latter against the poles.

The light sensitive device 5 is preferably of the selenium cell type mounted within a holder I00. Herein, the holder is rigid with the outer end of a tube IOI projecting rigidly from the forward end of the carriage 9 beneath the glass panel 6. The effective light sensitive area of the cell 5 is larger than the circle I in which the beam 3 tends to oscillate so that the cell is operative in all of the different positions of the beam.

When the light beam 3 is intercepted by the pattern line 2, the resistance of the photosensitive cell is increased and the current is accordingly decreased. To detect with a high degree of accuracy the rises and falls of the cell current relative to a predetermined adjustable value, one terminal of the cell is grounded and the other terminal is connected by conductor I01 (Fig. 28) to the control grid I08 of a so-called pentode type thermionic tube I09 which may be a type 6J7 tube. The cathode heater IIO of this tube is heated by current derived from a secondary III of the multiple voltage transformer I03. Through a full wave rectifying system indicated generally at II2, the proper voltage is impressed upon the plate II3 of the tube I09. The proper normal grid bias of the tube for different pattern densities is obtained by selective adjustment of rheostats H4 and H5.

When the beam 3 is not intercepted, maximum current will flow through the cell 5. This current, flowing through rheostats II4-I I5, makes more positive the potential impressed upon the grid I08, so that the tube I09 is rendered conductive. The output or plate current from the tube I09 flows through a resistor II3 thus making more negative the potential on control grids I23 of an amplifier tube H6 so that the output plate current of the latter is decreased. The plate circuit of this latter tube is arranged to energize a This tube has been shown as a twin triode and may be a type 53 tube. When the output of the tube H6 is minimum, the coil III will be deenergized and the spring II9 closes the switch I2I. In response to interception of part of the light beam 3 by the pattern line, the resistance of the cell 5 increases resulting in a corresponding decrease in the plate current of the tube I09, and an increase in the tube H6 and the current energizing the relay H1. The coil II'I attracts the armature II8 against the pull of the spring IIS and closes the switch I20.

Selective closure of the switches I20 and I2I is utilized through the medium of a twin triode tube I22 to effect energization of the clutch control magnets 9| and 92. For this purpose, the cathode heater I25 of the tube I22 is energized from the secondary I24 and the plates I26 and I21 of the tube are connected to the

magnets

92 and 9|. The arrangement is such that when the switch l2I is closed current will flow through resistor I2I', thereby-increasing the potential in grid I26 and current flow from the plate I26, which produces effective energization of the magnet 92. Similarly, when the switch I20 is closed, current will flow through resistor I20 increasing the potential of the grid I21 so current flows from plate I21 and the magnet 9I is energized.

As a result of the circuit arrangement above described, the magnet 92 will be energized, the worm and therefore the clutch I04 engaged, and the valve control member 50 rotated in a clockwise direction in response to a continuous full-light condition, that is, when all or a predetermined major portion of the light beam area is exposed to the transparent medium 4. When all or more than said predetermined portion of the light beam area is intercepted by the pattern line 2, which will hereinafter be referred to as the no-light condition, the magnet 9I will be energized and the worm 64 shifted to engage the clutch I05 and turn the valve control member 50 continuously in a counter-clockwise direction. The dividing line between the no-light and fulllight conditions, that is the portion of the light beam which must be intercepted by the pattern line to change from full-light to no-light condition may be varied widely by adjustment of the rheostats H4 and H5 to change the normal grid potential of the tube I09.

By utilizing the switches of the relay II'I through the medium of-the duplex tube I22 instead of directly to control the energization of the magnets 9I and 92, the current burden on the switches is reduced to an extremely low value. This enables the movement of the armature II8 to be reduced to a value, on the order of two thousandths of an inch, without any attendant sparking at or burning of the contact surfaces. The sensitivity of the photoelectric system, that is, its ability to respond to small changes in light intensity and reverse the energization of the magnets 9| and 92, is increased accordingly.

Operation The manner in which a pattern is traced and its outline reproduced by operation of the cutter on the work will be explained with reference to Figs. 16 and 24 to 27. Let it be assumed that the photoelectric cell is associated with the clutch magnets so as to engage the clutch I04 and produce clockwise turning of the valve control member 50 and the light beam in response to detection of a full-light condition, that is, when the beam is not intercepted by the pattern. Rotation of the member 50 continuously under such a condition will result in oscillation of the

Valve arms

41 and 41 back and forth between their extreme positions so that the mean position of each valve arm is its neutral position. This oscillation is so rapid due to the high sensitivity of the electric system and the valve operating and cutter actuating mechanisms are so sluggish due to inertia of the parts, yielding of the hydraulic connections, etc. that no appreciable movement of the carriage 9 and cutter actually takes place. Conversely, iniresponse to a no-light condition, that is, when the beam 3 is partially intercepted by the pattern and the condition of the magnets and clutches is reversed, the member 60 will turn counter-clockwise and the valve rotorswill be oscillated constantly. However, since the admission .of fluid to one end of each cylinder is of the same short duration as that during which fluid is admitted to the other end, the carriage remains substantially stationary.

If, as will usually be the case in flame cutting, the pattern is to be reproduced accurately, that is, the cutting flame directed from the torch I is to describe a path of exactly the same size as the pattern, the eccentric pin 66 will, by adjustment of the collar 61 about the shaft I as permitted by the set screw 68, be adjusted so that when the valve control member 50 is in its east position (Fig. 24), the light beam 3 will lie on a line extending through the axes of revolution of the beam and the member.

Now assume that the machine has been placed in operation with the tracer or light beam operatively associated with a line extending in a true in and out movements will be exactly in proportion to the change in the contour of the then northerly direction. In such a case, the light beam would oscillate inwardly across the outer margin of the line as indicated at I (Fig. 2'7) and then outwardly along a path I3I while simultaneously being advanced along the line 2 in the north direction by movement of the saddle I0 along the bed ways. During the movement of the beam along the path I30, the magnet 92 is energized and the valve control member 50, turning in the same clockwise direction, shifts the valve 3| toward the east position, the rotor of the valve 32 remaining substantially stationary because the eccentric 52 is on dead center with respect to this valve. As soon as a sufiicient area of the beam has been intercepted to produce the no-light condition, this depending on the circuit adjustments, the magnet 92 is deenergized and the magnet 9! is energized, the clutch I05 becoming effective to reverse the rotation of the member 50 and the light beam. The beam then traverses the path i3I under the no-light condition, and the motions of the valve arms 47 and M are similarly reversed. So long as the pattern margin continues in the north direction, the opposite oscillations will be of equal length and the mean position of the light beam will fall on the pattern outline. Also, while the member 50 and the valves actuated thereby are similarly oscillated back and forth across the true northerly position, the movements in Opposite directions beyond such position are of equal lengths with the result that the mean effective flow of fluid is to the rod end of the cylinder I6 onlv which causes the saddle It] to move northward.

As previously pointed out, the oscillations of the valve control member 50 are of short amplitude (on the order of a few thousandths of an inch) and the period of each oscillation (about a sixth of a second) due to the extreme sensitivity of the photoelectric cell and the associated circuits is somewhat less than the interval required for the clutches, the valves and the hydraulic actuators to respond to a change in the position of the tracer. As a result, the only fluid flow which is effective is to the rod end of the cylinder I6 which causes true northerly movement of the saddle I 0 and therof ore of the cutter 8 and the tracer mounting.

When the tracer encounters the portion of the pattern which curves eastward, as it will during the outward movement I33, less movement is rcquired to reach the full-light condition. For the same reason, the inward movements I34 required to detect the no-light condition will be greater.

The changes in the amplitudes of the I active portion of the pattern, the result being to correspondingly change the mean position of the valve control member 50 progressively toward the east. Fluid is thus admitted to the head end of the cylinder I5 and simultaneously the flow to the cylinder I6 is reduced, the relative rates of flow being metered to correspond to changes in the pattern contour.

As an incident to these changes in the mean position of the valve control member 50, the direction of arcuate oscillation of the tracer will be correspondingly changed by virtue of actuation of the tracer mounting from the shaft 5| through the medium of the eccentric. The result is that the angles a: at which the light beam crosses the pattern during its inward movements remain substantially constant. The same is true of the angles which the beam paths make with the path in moving outwardly. That is to say, the range of oscillation of the light beam shifts automatically around the circle III as the pattern contour changes so that there is a substantially constant angular relationship between the inward and outward movements of the tracer and a tangent to the portion of the pattern which is in active control of the light. By thus changing the direction of oscillation of the tracer relative to the pattern automatically to conform to changes in the pattern contour, it is possible to follow completely around the periphery of any pattern, that is, do so-called peri-cutting, Without the necessity of changing quadrants or making other manual adjustments.

By the time the tracer reaches the northeasterly extending portion I35 of the pattern, the parts will be positioned as shown diagrammatically in 1'7. Then, fluid will flow at equal rates into the rod and head ends respectively of the cylinders I6 and I5 producing a resultant northeast movement of the carriage 9. When the tracer encounters the eastwardly extending portion I36 of the pattern, the member 50 and the valves will have been shifted to the east position, there being no effective fluid flow to the cylinder I6. Thus, due to the straightness of the pattern line, the amplitudes of the in and out oscillations l3! and I38 become uniform, thereby maintaining the true east mean position of the valve control member '50 (Fig. 18).

Fig. 27 also illustrates on an exaggerated scale the manner in which the tracer functions to de-- tect a very sharp change in curvature of the pattern. In the case, for. example, of a sharp right angular corner I39, the beam 3 will, following an outward movement H0, berequired to move through a substantial angle along a path MI before encountering the pattern to produce the next no-light condition. This results in turning of the member 50 through an equally large angle producing a suflicient shift in the valve positions to cut off the supply of fluid to the cylinder- I5 and permit the full flow to the head end of the cylinder I6. The'direction of advance of the carriage is thus changed suddenly from a substantially eastward to a southward direction. Thereupon, the tracer oscillations become uniform and the cutter continues southward in accordance with the pattern outline.

The action above described takes place automatically in changing the motion of the controlled object to other quadrants. Thu as the pattern line being traced changes from a south to a southwestward direction, the direction of oscillation of the tracer shifts as shown in Fig. 21, the valve arms 41 and 41' being moved into the south and west segments. The condition of the valves as the direction of oscillation of the light beam to advance the cutter toward the west and northwest respectively are shown in Figs. 22 and 23. It will be apparent therefore that the light beam will follow automatically around the entire periphery of a pattern line,

causing the controlled object to reproduce thepattern on the work with extreme accuracy. When the control described is governed by a pattern of the relatively complicated shape shown in Fig. 2, the cutter will traverse a path which does not depart more than .004 of an inch from the controlling pattern outline. In fact, the control is so sensitive and accurate that the light beam will follow along both sides and around the ends of a single narrow ink line.

It will be apparent that with the method above described, the tracer and the pattern are moved relative to each other longitudinally of the pattern outline and at the same time are continuously moved relat've to each other transversely of the pattern outline to alternately increase and decrease the interception of the contour by the tracer and to vary the amounts of the increases and decreases in accordance with changes in the direction of the pattern outline. These changes are averaged and utilized to vary the direction of the first-mentioned longitudinal movement so that the latter motion is of stepless character and a reproduction of the pattern outline. The transverse relative movements, it will be observed, occur continuously at frequently repeated intervals during which the alternate interception and clearing of the pattern by the tracer occurs at successive points closely spaced progressively along the pattern, each tracer relative to its mounting being alone a predetermined orbital path the tracer mounting.

When the pattern a transparent medium, either side of the line may be traced. In such a case, the light beam moves in opposite directions when tracing the inner and outer sides of the line. This is for the reason that the light beam must move in different directions transversely of the line to detect-either the nolight or the full-light condition. The same effeet will result from reversing the connections to the magnets 9| and 92.

Sometimes it is desirable to cut the work piece larger, by a fixed increment than the controlling pattern, This would be done, for example, in flame cutting where the work piece is to be further machined to produce a final peripheral contour equal to that of the pattern. Or, when the controlled object is a cylindrical milling cutter, as indicated at I43, Figs. and 26, it is necessary to compensate for the radius of the cutter in order to reproduce the pattern contour. Both of these ends may be attained by ofisetting the center of the light beam 3 laterally from a line I44 through the axis 10' of oscillation of the beam 3 and the control member when the latter member is in the extreme east position. To do this, the member 50 is first located in the east position, and then after loosening the set screw 68, the collar 61 is turned relative to the shaft 5| until the beam 3 is offset from the line I44 a distance I45 equal to the radius of th milling cutter I43. For milling cutters of larger size such a is illustrated in Fig. 26, it may be necessary,

transverse motion of the a which is fixed relative to is in the form of a line on in order to obtain the necessary offset I46, to re-,

move the collar 61 and replace it by one having an eccentric pin 66 adapted to produce a greater radius of oscillation of the light beam.

In milling profiles the foregoing method of compensation for the cutter diameter is particularly advantageous in that it simplifies the making of the pattern. The latter may be of the same size as the work contour to be produced.

It is of course desirable, for the sake of obtaining optimum accuracy of pattern reproduc tion, that the orbit in which the light beam oscillates be as small as practicable. With the form of the invention first described, the circle 10 is about .060 of an inch in diameter. In any case, however, the eifective control area of the photoelectric cell is sufficiently large to respond to the light intensity in all position of the beam around its orbital path.

While it is preferred that the tracer element be a light beam, because of the simplicity of the pattern that may be employed and because of the precision obtainable in reproduction, other types of tracers and patterns may be used. For example, the pattern may be a solid of conducting material and the tracer a piece of resilient wire projecting axially from the casing I or equivalent mounting. In such a case, the wire would constitute a laterally yieldable contact coacting with the pattern to form a switch by which one of the magnets 9| or 92 would be energized, the magnet armature being spring urged in the opposite direction. Or, the pattern may be made of non-conducting material operating in conjunction with a yieldable tracer arm carrying both contacts of the control switch which is closed and opened in response to engagement of the tracer arm with or disengagement of the arm from the pattern surface.

I claim as my invention:

1. The method of governing the relative movements between two objects in accordance with the outline of a pattern, said method comprising directing a beam of light toward the pattern, moving one of said objects and the light beam in unison relative to the other object to advance the beam along the pattern outline while continuously and irrespective of the pattern outline oscillatingthe beam transversely of the pattern outline and relative to said one object to alternately and invariably increase and decrease the interception of the beam by said pattern, and changing the direction of relative advance between said objects in accordance with average changes in the lengths of the light increases and decreases.

2. The method of positioning a controlled object in conformance to a pattern contour which comprises directing a beam of light toward'said pattern, effecting relative movement between said beam and the pattern to cause the beam to follow along the pattern contour, simultaneously and continuously moving said beam alternately back and forth across the pattern outline irrespective of the contour of the latter to increase and decrease the interception of the beam by the outline and vary the amounts of the increases and decreases in accordance with changes in the shape of the outline, and controlling the relative positioning of said controlled object in any one or a combination of four rectangular directions selectively in accordance with the mean effective position of said light beam.

3. The method of controlling the relative movements of a controlled object in accordance with a pattern contour which comprises continuously oscillating a control element back and forth in opposite directions transversely of the pattern outline and along different arcuate portions of a complete orbital path which is fixed relative to said object, changing the portions of said path traversed by said control element in accordance with changes in the pattern contour to maintain a generally constant angular relationship between the pattern contour and the path of oscillation of said element, relatively moving said controlled object and simultaneously relatively moving said element and the pattern along the path defined by the mean position of the said element in its successive transverse oscillations whereby to cause said element to follow around the entire perimeter of a pattern.

4. The method of controlling the relative movements between two objects to describe a pattern outline which comprises continuously moving a tracer back and forth repeatedly at substantially regular intervals and in a predetermined orbital path alternately into and out of contact with the peripheral outline of a pattern irrespective of the contour of the latter whereby to shift the range of interception of said pattern contour along said path with changes in the pattern contour, and varying the direction of relative movement between said objects in accordance with the changes in the increases and decreases of pattern interception.

5. The method of governing the relative movements of a controlled object to reproduce a pattern outline, said method comprising relatively moving said controlled object and a light beam in unison to advance the latter along the pattern outline, continuously oscillating the beam back and forth along arcuate paths of predetermined curvature and extending laterally toward and away from said outline, varying the directions and amplitudes of successive oscillations in accordance with changes in the pattern outline, and changing the direction of relative advance of said object and beam to correspond to changes in the mean position of said beam.

6. The method of relatively positioning a controlled object in conformance with a pattern contour which comprises efiecting relative move ment between a pattern element and a tracer element to cause one element to follow the pattern contour while simultaneously and continuously moving the elements intermittently toward and away from each other transversely of said contour and irrespective of the shape of the latter to shift the tracer element relative to said controlled object alternately onto and off from said contour, and controlling the relative movement of said controlled object in any one or a combination of four rectangular directions selectively in accordance with the mean path traversed by the movable element.

'7. Mechanism for causing one object to move relative to another object and traverse a path corresponding to a pattern outline having, in combination, a control member, hydraulic actuating means for relatively moving said objects in any planar direction, valve means positioned in accordance with changes in the position of said member and controlling said hydraulic means to cause relative movement of the objects in a direction determined by the instantaneous posl-' tion of said member, a photosensitive cell, a light beam directed toward said cell and oscillated back and forth along diflerent parts of a complete predetermined orbital path, said beam being movable in unison with said member, a pattern coacting with said tracer to determine the extent of each oscillatory motion thereof, an electrical system having two windings energized selectively in accordance with changes in the light intensity on said cell, and reversible driving means for said member controlled by said windings, the frequency of oscillation of said beam and the inertia of said actuating means being sufliciently high that said controlled object is not responsive to the individual oscillations of said light beam.

8. A machine for causing relative movement between two objects to reproduce a pattern contour having, in combination, a pattern, a tracer including a light beam directed toward the outline of said pattern, a mounting movable in unison with one of said objects and supporting said tracer for movement of said beam in an orbital path relative to said pattern, a photosensitive cell on the opposite side of said pattern having an efiective control area greater than the orbit described by the light beam in moving completely around said path, means for oscillating said tracer relative to said' mounting transversely of the pattern outline and for shifting the range of such oscillation along different portions of said path automatically with changes in the pattern contour, and power actuated mechanism controlled by said cell and operating to cause one of said objects and said tracer mounting to move relative to the other object and follow the changes in the mean position of said tracer.

9. Mechanism for relatively moving a controlled object having, in combination, a transparent medium having contiguous relatively light and dark areas the junction of which defines a pattern outline, a tracer device for directing a beam of light through said medium, a light sensitive device disposed on the opposite side of said medium for impingement of the beam thereon. mechanism controlled by said light sensitive device ior invariably causing intermittent relative oscillation of said devices in a zigzag path around the pattern outline including straight portions of the latter, and power actuated means controlled by said mechanism for causing said controlled object to traverse the mean path described by the oscillated device.

l0. Mechanism for causing one object to move relative to another object and traverse a path corresponding to a a pattern outline having, in combination, an hydraulic actuator for relatively moving said objects, means controlling said actuator selectively to cause relative movement of said objects in different directions including two windings, and an electrical system controlling the selective energization of said windings in cluding a tracer supported by one of said objects and continuously oscillated back and forth transversely of the pattern outline and relative to its supporting object, the period of oscillation of said tracer being less than the response of said actuator to changes in the energization of said windings whereby no relative movement occurs in response to the individual oscillations of said tracer but follows only the changes in the mean position thereof.

11. Mechanism for causing one object to move relative to another object and traverse a path corresponding to a pattern outline having, in combination, a rotary control member, hydraulically actuated means operating continuously to relatively move said objects in a direction corresponding to the instantaneous position of said member, valve means positioned selectively in accordance with the angular position of said member to meter the flow of pressure fluid to said hydraulically actuated means and cause said relative movement in any one or any combination of four rectangular directions, a tracer movable in unison with the rotary motion of said member, a pattern having a peripheral outline interposed in the path of said tracer, reversible electric motor driving means for said member having two windings selectively energizable to cause turning of the member in opposite directions, and means responsive to movements of said tracer in oppositie directions into and out of contact with the outline of said pattern to control the alternate energization of said windings.

12. Mechanism for causing one object to move relative to another object and traverse a path corresponding to a pattern outline having, in combination, a rotary control member, hydraulic actuating means to relatively move said objects in any planar direction, valve means actuated by said member and controlling said actuating means to cause said relative movement in accordance with the instantaneous angular position of said member, a pattern, a tracer movable in unison with the rotary motion of said member in an orbital path extending transversely of the peripheral outline of said pattern, and means controlled by said tracer'to cause said member to turn alternately in opposite directions in response to movement of said tracer into and out of contact with said pattern ouline.

13. Mechanism for causing one object to move relative to another object and traverse a path corresponding to a pattern outline having, in combination, a rotary control member, power actuated means operating continuously'to relatively move said objects in any direction determined by the instantaneous angular position of said member, a pattern, a tracer movable in unison with the rotary motion of said member in an orbital path extending transversely of the peripheral outline of said pattern, and means con trolled by said tracer to cause said member to i turn alternately in opposite directions in response to movement of said tracer into and out of contact with said pattern outline.

14. Mechanism for, relatively positioning a controlled object in conformance to a pattern contour having, in combination, a pattern element, a tracer element, means for efiecting relative movement between said elements to cause one element to follow completely around the pattern contour, means supporting one of said elements for independent movement transversely of the pattern contour and relative to said controlled object, means operating continuously to move the movable element relative to its support to alternately increase and decrease the interception of the contour by the tracer element and vary the amounts of the increases and decreases as the contour changes, and power actuated means responsive to said transverse movements and operable to relatively move said controlled object in any one or a combination of four rectangular directions selectively in accordance with the mean path traversed by the movable element.

15. Mechanism for controlling the relative movements of a controlled object in accordance with a p'attem contour having, in combination, a control element mounted for oscillation relative to said controlled object transversely of the pattern outline, means for oscillating said element continuously, means controlled by said element for changing the angle of its oscillation in accordance with changes in the pattern contour to maintain a generally constant angular relationship between the path of oscillation and the effective portion of the pattern, and power actuated mechanism controlled by said element and operating to relatively move said controlled object and simultaneously to relatively move said element and the pattern along the path defined by the mean position of the said element in its successive oscillations whereby to cause said element to follow around the entire perimeter of a pattern. I

16. Mechanism for causing one object to move relative to another object and traverse a path corresponding to a pattern outline having, in combination, a control member, power actuated means for moving said object in any planar direction, means positioned in accordance with changes'in the position of said member and controlling said power actuated means to cause relative movement between said objects in a direction determined by the instantaneous position of said member, a tracer oscillated back and forth. along different parts of a complete predetermined orbital path and movable in unison with said member, a pattern coacting with said tracer to determine the extent of each oscillatory motion thereof, and means for positioning said member in accordance with the mean position of said tracer.

1'7. A machine for causing relative movement of a controlled object to reproduce a pattern contour having, in combination, a tracer, a mounting movable in unison with said controlled object and supporting said tracer for movement independently of the controlled object in a predetermined circular path relative to said pattern, means for oscillating said tracer relative to its mounting back and forth relative to the pattern outline, power actuated mechanism to relatively advance said object and said tracer mounting in accordance with changes in the mean position of said tracer, and means for varying the angle of the tracer oscillations in conformance with changes in the pattern contour.

18. Mechanism for causing relative movement of a controlled object corresponding to a pattern outline having, in combination, a rotary control member, power actuated means for operating automatically to relatively move said object in any direction determined by the instantaneous angular position of said member, an eccentric rotatable with said member, a pattern, a tracer therefor moved in an orbital path by said eccentric, and means controlled by said tracer to cause said member to turn in opposite directions when said tracer is disposed on opposite sides of said pattern outline.

19. In a tracer control of the character described, a source of light, means receiving rays of light from said source and converging the same to form a beam constituting a pattern tracer, and means supporting said last mentioned means for movement in an orbital path independently of said light source whereby to minimize-the weight of the parts required to be moved to oscillate said beam in said path.

20. A machine for efiecting relative movement between two objects to reproduce a pattern contour having, in combination, a tracer, means supporting said tracer on one of said objects and for independent oscillatory movement relative to its support transversely of a pattern outline and at variable angles, means for continuously moving said tracer relative to its mounting back and forth transversely of the pattern outline and irrespective of the contour of the latter while maintaining asubstantially constant angle between such movements and the pattern outline, and power actuated mechanism to advance said one object and the tracer mounting relative to the other object and in accordance with changes in the mean position of the tracer.

21. The method of controlling the tracing of a contour which comprises relatively moving said contour and a tracer longitudinally of the con tour, and during such relative movement continuously imparting other relative movement between said tracer and said contour transversely of the contour to alternately increase and decrease the interception of the contour by the tracer and to vary the amounts of the increases and decreases in accordance with changes in the direction of the contour, and varying the direction of said first mentioned relative movement in accordance with the changes in the amounts of the increases and decreases.

22. The method of controlling the tracing of a contour which comprises relatively moving said contour and a tracer longitudinally of the contour, and during such relative movement continuously imparting other relative movement between said tracer and said contour transversely of the contour along a predetermined orbital path to alternately increase and decrease the interception of the contour by the tracer with changes in the direction of the contour, and varying the direction of said first mentioned relative movement in accordance with changes in the increases and decreases in interception of the contour.

23. The method of controlling the tracing of a contour which comprises relatively moving said contour and a tracer longitudinally of the contour, and during such relative movement continuously imparting other relative movement between said tracer and said contour transversely of the contour to alternately increase and decrease the interception of the contour by the tracer at successive points closely spaced progressively along the contour and to vary the amounts of the increases and decreases in accordance with changes in direction of the contour, and varying the direction of said first mentioned relative movement in accordance with changes in the amounts of the increases and decreases of interception due to changes in the contour.

24. The method of controlling tracing of a contour which comprises relatively moving said contour and a light beam longitudinally of the contour, and during such relative movement, continuously moving said beam and contour relative to each other transversely of the contour to alternately increase and decrease the interception of the beam by said contour and to vary the amounts of the increases and decreases in accordance with changes in the direction of the contour, and varying the direction of said first mentioned relative movement in accordance with the changes in the amounts of the increases and decreases in light interception.

25. Mechanism for governing the relative movements between work and tool supports to reproduce a pattern outline comprising, in combination, power actuated means for effecting relative movement between said supports in any direction in a plane, one of said supports providing a mounting for said pattern, means on the other of said supports adapted to rotate in a circle which is fixed relative to the latter support and to direct a beam of light toward said pattern, power actuated mechanism for relatively moving said beam and pattern along said circle to alternately intercept and clear the pattern, a photosensitive device fixed on said other support and responsive to the varying amounts of pattern interception by said light beam, and means controlled by said device and governing the direction of relative advance of said supports by said power actuated means to reproduce the pattern outline and cause relative motion between said beam and pattern longitudinally of the latter.

26. In a mechanism for controlling the repro- -duction of a contour, the combination of, a

tracer, power actuated means for moving said tracer and contour relative to each other along the contour, power actuated means operable continuously to move said tracer and contour relative to each other transversely of said first mentioned relative movement and alternately onto and off from the contour to increase and decrease the interception and vary the amounts of the increases and decreases as the contour changes, and means for varying the direction of said first mentioned relative movement in accordance with variations in the interception of said contour by said tracer.

2'7. In a mechanism for controlling the reproduction of a contour, the combination of, a tracer comprising a beam of light projected toward said contour, means for relatively moving said contour and light beam along the contour, means operable during such relative movement for continuously imparting other relative movement between said tracer and contour transversely of the contour to alternately increase and decrease the interception of the light beam by the contour and vary the amounts of the increases and decreases as the contour changes, and mechanism including a light sensitive device responsive to the varying amounts of light interception by said contour and operable to vary the direction of said first mentioned relative movement and thereby follow changes in the direction of said contour.

28. In a mechanism for controlling the reproduction of a contour, the combination of a tracer, a tool, and a workpiece, means for moving said tracer and contour relative to each other along the contour, means operable continuously to move said tracer and contour relative to each other transversely of said first mentioned relative movement and alternately onto and off from the contour to increase and decrease the interception and vary the amounts of the increases and decreases as the contour changes, means for varying the direction of said first mentioned relative movement in accordance with variations in the interception of said contour by the tracer, means controlled by both of said relative movements for relatively moving said tool and workpiece in a path to reproduce said contour, and means for adjusting said mechanism to vary the range of said path relative to the size of said contour.

ARTHUR A. MEYER.