US2622485A - Automatic line tracking machine - Google Patents

Description

Dec. 23, 1952 M. MARTELLOTTI 2,622,435

AUTOMATIC LINE TRACKING MACHINE Filed June 16, 1950 4 Sheets-Sheet 1 IN VEN TOR.

Nfl/F/O MAI? TELL 0 7'7'/ Z7 TTORNEYS Dec. 23, 1952 M. MARTELLOTTI I 2,622,485

I AUTOMATIC LINE TRACKING MACHINE Filed June 16, 1950 4 Sheets-Sheet 2 Fig. 2

INVENTOR. MAR/0 MAR TELL 0 T T/ Dec. 23, 1952 M. MARTELLOTTI 2,622,485

AUTOMATIC LINE TRACKING MACHINE Filed June 16, 1950 4 Sheets-Sheet 3 Fig.4

IN VEN TOR. "/4570 PM? TELLOTT/ flTTOIP/VEYS Dec. 23, 1952 M. MARTELLOTTI 2,622,435

AUTOMATIC LINE TRACKING MACHINE Filed June 16, 1950 I 4 Sheets-Sheet 4 vaz we #h 0' INVENTOR.

A TTOIPN: Y8

Patented Dec. 23, 1952 AUTOMATIC LINE TRACKING MACHINE Mario Martellotti, Cincinnati, Ohio, assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Application June 16, 1950, Serial No. 168,443

Claims.

This invention relates to automatic contouring machines in which a line acts as the pattern controlling element.

It has been conventional practice in this art to utilize as the pattern or control element some form of solid object of the desired shape or contour as the controlling pattern element and to utilize a tracer element in physical contact with the pattern to continuously sense the direction in which the cutting path is to be generated.

There is now developing a demand for a reproducing machine which will eliminate the necessity for making or building a pattern and instead to control the machine directly from a line drawing, which formerly was utilized in making the pattern. By so doing, the intermediate step of making a pattern is eliminated and thus the cost of producing the work is greatly reduced, especially where only a small number of work pieces are to be reproduced from a given pattern.

Reproducing machines designed for following a line are sometimes known as line tracking machines, and, in general, fall into two classes, in one of which, the tracer or sensing means makes physical contact with the drawing and in the other, the sensing means is of such a nature that it is not necessary to make physical contact with the drawing.

This invention relates to the latter type of machine, and more particularly to one in which light or radiant energy is utilized as the sensing means, and although the sensing means does not, in one sense, make physical contact with the line, it is the means which controls or causes the machine to follow a contour and thus in that sense traces or scans the contour, and in this specification is intended to have that meaning.

It is an object of this invention to provide an improved automatic line tracing mechanism of the type utilizing radiant energy as the sensing or control medium.

Another object of this invention is to provide a new and improved mechanism for automatically following an outline or contour without the necessity of physical contact therewith.

A further object of this invention is to provide an improved optical system including a photoelectric cell to maintain follow of the line and detect changes in its direction and correspondingly effect directional control changes in the driving mechanism.

Another object of this invention is to devise an electrical pick-up or scanning system which may be combined with a hydraulic driving system for automatic control thereof to effect contour milling.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is a front elevation of a reproducing machine embodying the principles of this invention. a

Figure 2 is a section through the tracer head of the machine shown in Figure 1.

Figure 3 is a detail section on the line 3--3 of Figure 2.

Figure 4 is a diagrammatic view of the hydraulic operating circuit.

Figure 5 is a diagram of the electrical control circuit.

Figure 6 is a diagrammatic View, showing the relationship of the scanning path to the line being followed and the cutter being controlled.

For the purpose of greater clarity in understanding this invention, it is desirable to review the fundamental principles of a lens or, in its more complicated form, a telescope. Such devices are sighted on an object and thereby produce an image. A telescope may be adjusted or focused to encompass a small circular area in the objective plane, and this small circular area is defined and referred to in this specification as the field of view and for purposes of illustration may be illustrated in the drawings as a small circle F as shown in Figure 6.

If the objective surface ID, in which this circle lies, is a good reflector and is illuminated, the maximum flow of reflected light or radiant energy from the circular field of view will pass to the telescope and thus to a photo-electric cell optically connected therewith. It is contemplated in this invention to impart a planetary motion to this field of view about an axis II normal to the objective plane or surface and to so relate the parts that once during each revolution, or travel through its orbit, the field of view will overlap or scan a portion of a contour line I2 being followed.

A very good arrangement is to make the objective surface a good reflector, and the line thereon a. poor reflector, thus establishing a differential between the reflective capacities of each. It should now be evident that by establishing a predetermined overlap of the line per revolution, the

total flux of radiant energy per revolution passing to the photo-electric cell will be less than the maximum referred to supra, but it is capable of being increased by less overlap of the line, or by being decreased by more overlap of the line.

By means of this invention, a photo-electric cell is connected and adjusted in accordance with the amount of light received for the predetermined overlap condition, and the voltage generated by the cell for this condition can be considered as the reference voltage. It now becomes possible for this voltage to automatically increase in response to a decrease in overlap of the line as a result of more light passing to the cell; or for the voltage to automatically decrease in response to increase in overlap of the line as a result of less light passing to the cell.

It has been found practical that rather than illuminate a large area in the objective plane, excellent results can be obtained by confining the illumination to the field of view because the strong concentrated illumination on a small area reduces the effects of variations from the lights and shadows around the machine. This spot illumination is made to follow the scanning orbit or travel of the field of view, and thus, in effect, it would appear to be a rotating spot of light. It will now be seen that by arranging a light sensitive cell, such as a photo-electric cell, in proper position to receive the reflected radiant energy,

' and by providing an objective area of high refiectibility, and a contour line thereon of low reflectibility, that once each revolution an impulse Will be received by the photo-electric cell acting to reduce its voltage.

In accordance with this invention, means are provided for revolving the field of view at a predetermined fast rate with the result that the photo-electric cell is caused to generate a pulsating direct current voltage. Although this voltage is pulsating, it will actually produce an average effective voltage, otherwise known as a root mean square voltage, which may be adjusted to establish a known reference voltage for a predetermined overlap of the line. Under such a condition, either an increase or a decrease in the amount of overlap will cause a decrease or an increase in the effective output voltage of the cell. These variations above or below the reference voltage are utilized as signals to control operation of the machine, and cause the cutting tool to follow a cutting path in accordance with variations in the contour line being followed.

A satisfactory machine for embodying the principles of this invention is shown in Figure 1 of the drawings. In this illustrated machine the reference numeral [5 indicates a bed from the rear of which uprises a column 16. A table I! suitable for supporting a work piece or the like and a pattern or drawing to be reproduced is slidably mounted on suitable guideways l8 formed on the top of the bed l5.

A cross slide [9 is suitably supported on guideways formed on the top of the column 16 for movement crosswise of the table. A spindle carrier 2| is slidably mounted on suitable guideways formed on the front face of the cross slide I5. The spindle carrier journals a spindle 22 and is adapted to be driven by conventional power transmission mechanism for rotating a cutting tool 23.

The spindle carrier, which moves vertically, is provided with a bracket 24 projecting from the side of the spindle carrier for supporting a tracer mechanism so that the tracer mechanism is responsive to both the vertical movements of the spindle carrier and the cross movements of the slide l9. The bracket 24 is provided with a dovetailed guideway 25 upon which is mounted a cross moving slide 26, and this slide, in turn, supports and guides a verticall movable slide 2! which is of right angular shape and has a horizontal guideway 28'. The scanning mechanism housing, indicated generally by the reference numeral 29, is slidably mounted on the guideway 28 and may be adjusted along the guideway by the adjusting screw 30. It will be noted from the relationship of these guideways that the scanning housing may be adjusted in any one of three directions in space relative to the spindle carrier and primarily with respect to the cutting tool 23 so that the tracer mechanism and the cutting tool may be properly aligned with respect to corresponding points on the work and pattern.

A vertical section through the scanning housing is shown in Figure 2 in which the reference numeral 3| indicates a tubular main carrier member which is supported in the housing against axial movement on anti-friction bearings 32 and 33. This member carries a gear 34 attached thereto whereby it may be operatively connected for rotation through suitable gearing 35, Figure 4, to a prime mover such as a hydraulic motor 36.

This motor is not a continuously rotating motor but is a directional control motor and oscillates to maintain the resultant direction of feeding movement in accordance with the direction of the particular section of the contour line being followed.

It will be obvious, since the direction of feeding movement may be at any angle throughout 360 degrees in a horizontal plane, that any angular direction of movement must be the resultant of the different rates of movement of the table and the cross slide. As shown in Figure 4, the table I? may be actuated by a hydraulic motor of the piston and cylinder type comprising a cylinder 31 which is suitably fixed in the bed I5 and a contained piston 38 connected by a piston rod 39 to the end of the table 11.

The cross slide [9 may be similarly powered by a piston and cylinder motor comprising a cylinder 40 which is suitably fixed in the column [5 and a contained piston 41 connected by a piston rod 42 to the slide l9.

These cylinders are connected to individual rate and direction control valves, that is, the cylinder 3'! has its opposite ends connected by hydraulic channels 43 and 44 to motor ports 45 and 46 of valve 41. Similarly, opposite ends of cylinder 40 are connected by channels 48 and 49 to motor ports 50 and 5| of valve 52. The valve 41 has pressure ports 53 and 54, and the valve 52 has pressure ports 55 and 55 and all of these pressure ports are connected to a common pressure line 5'! which is supplied by a pump 58. This pump has an intake 59 for withdrawing hydraulic fluid from a suitable reservoir 60 and the delivery of the pump has a relief valve GI connected thereto for controlling the delivered pressure of the pump. The valve 4'! has an exhaust port 62 which is connected by channel 63 to port 64 of a control valve 55, and similarly, the valve 52 has an exhaust port 65 which is also connected by channel 66 to port 61 of the control valve 65.

The valve 4'! has a valve plunger 68 in which is formed annular grooves 69 and 70 forming tapered spools ll, 12, 13, and 14 which act to variably throttle the flow through the various ports. When the valve plunger 68 is in a central position with respect to port 62 the varioustapered spools slightly underlap the respective ports 53. 62. and 54 whereby there is a small continuous flow from the pressure port 53 to the exhaust,

port 62 and from the pressure port 54 to the exhaust port 62, and this creates an intermediate pressure in the two grooves 69 and III which are substantially equal and which are communicated through channels 43 and 44 to opposite ends of the piston 38, thereby holding the piston against movement.

Similarly, the wave 52 has a valve plunger I5 of the same construction so that in a central position equal pressures are established in channels 48 and 49 and thereby on opposite ends of piston 4| to hold the same against movement. The valve plungers I5 and 38 are held bysprings It against a control cam mechanism TI. This cam may be eccentrically adjustable from a position of zero eccentricity in which the valve plungers are held in a neutral position, to a position of maximum eccentricity, and by selecting the amount ofeccentricity the rate of slide movement and thereby the relative feeding rate between the tool and the work may be determined.

Rotation of the cam inversely adjusts the valve plungers I5 and 68 in such a manner as to determine the direction of relative movement between the tool and work.

This cam mechanism is mounted on the rotatable member 3l previously described in connection with Figure 2. Briefly, this mechanism consists of an inner truncated cylinder 18 which is operatively connected by a spline I9 to both the member 3I and gear 34. Thus, the member I8 will simultaneously rotate with the gear 34 and the member 3|. An cuter member 19 has an inclined bore 80 fit-ting the shape of the member I8 whereby as the member 18 is slid up or down on the member 3I it will cause the outer member I9 to move laterally or eccentrically with respect to the axis of the member 3I. The outer member carries two anti-friction bearing ring-s SI and 82 which are engaged respectively by the ends of the valve plungers 38 and I5 and serve as cams for controlling them, and thus constitute the cam mechanism I1.

The inner member 18 is manually adjusted up and down by means of the control 1ever 83 mounted on the end of a shaft 84 which has an eccentric pin 85 located in the end thereof for engaging the shifter groove 88 of the inner member I8. Thus, by means of the rate control lever 83 the eccentricity of the cam mechanism may be manually set, and the automatic rotation of the cam mechanism by the gear 34 will determine the resultant direction of relative movement between cutter and work. As previously stated, th rotation is effected by the motor 36 shown in Figure 4, and this motor is connected by a pair of channels B'I and 88 to ports 89 and 90 of the interlock control valve 35, which serves as a starting valve for initiating automatic feeding by the machine.

In the stop position of the valve, as shown, the ports 89 and 90 are connected by valve grooves 9I and 92 to ports 93 and 94 which lea-d to the return channel 95. When the valve plunger 96 of valve 65 is moved downward to its running position, the ports 89 and 90 are connected by the grooves 9I and 92 to ports 91 and 98 which, in turn, are connected by channels 99 and I00 to motor ports IM and I02 of the master control valve I03.- This valve has two pressure ports I04 and as an exhaust port I06. The valve plunger III! of this valve has a pair of annular grooves I08 and I09 for alternately connecting the pressure ports I04 and I05 to the motor ports IN and I02. The position of this valve is controlled by eccentric cam I I0 shown in Figure 3, which is oscillated by an electric motor III. This motor is the connecting link between the electrical scanning system shown in Figure 5 and the hydraulicoperating system shown in Figure 4. In other words, the control signals from the photo-electric cell are utilized to operate this motor, which, in turn, through valve I03 controls rotation of the hydraulic motor 33, which, in turn, sets the direction of feeding movement through cam mechanism TI.

The photo-eelctric scanning system is carried by the member 3I including the photo-electric cell and the means for creating a spot of light, and this system is connected by the electrical circuit shown in Figure 5 in a manner to control rotation of the electric motor I I I and thereby control the operation of the machine. Thephotoelectric system comprises a photo-electric tube II2 which is suitably mounted in the axial bore of the member 3I. In addition, the member 3I supports two tubular members H3 and H4 arranged normal to its axis of rotation, and in the outer end of each of these tubular members is mounted a source of light in the form of a light bulb Il5.

' At the intersection of these tubular members with the axial bore IIB of the member 3I there are mounted two mirrors II! and H8 which are angularly positioned at such an angle that light from the bulbs I I5 passing through the tubes I I3 and I M will be reflected downward by the respective mirrors to a mirror I I9. This mirror is positioned substantially at an angle of 45 degrees of the axis of the member 3| and the mirror is carried by a separate rotatable head indicated gen erally by the reference numeral I20. The member 3I has a lower cylindrical section I2I upon the periphery of which is mounted a truncated cylinder I22 which is vertically slid'able on the portion I2I. A cooperating member I23 has a diagonally extending bore fitting the periphery of the member I22 and at such an angle that upon axial adjustment of the member I22 the member I23 may be adjusted eccentrically with respect to the axis of rotation of the member 3 I.

The member I23 is held against axial movement by means of a flange I 24 formed on its upper end which overlaps a flange I25 carried by the part I26 which is integral with the member BI and which is rotatable therewith.

The member I22 is shifted axially by a pin I 21 formed eccentrically on the rotatable member I28 which is also mounted in an integral part of the member 3 I. The pin I 21 engages a shifter groove I29 formed in the periphery of the upper end of the member I22.

The member I28 has a hexagonal head I29 whereby it may be rotated, and a sleeve lock nut I30. The object of eccentrically adjusting the member I23 is that a drive pulley I3I is anti-friction-ally mounted on the periphery of the member I23 and is driven by a belt I 32 which is connected to an electric motor I33 which, as shown in Figure 1 of the drawings, is carried by a fixed part of the tracer housing 29. By eccentrically adjusting the member I23 the slack in the belt I32 may be taken out, thereby insuring a more positive drive. The pulley I3I has the rotatable head I20 integrally may be rotated at a continuous fast rate inde- 7 pendent of the slow rotation or oscillation of the member 3 I.

The head I20 supports a pair of mirrors I34 and I35 which are angularly related so that light striking the mirror II9 will be reflected by the mirror I34 to the mirror I35, and this, in turn, will reflect the light to a mirror I36 located in the upper end of the sighting tube I31. This tube may contain suitable lenses, if necessary, to concentrate the light.

Reflected light from the pattern will return through the tube I31 and be reflected, in turn, by the mirrors I36, I35, I34, and H9 to the axial bore II6 of the member 3I and thereby to the photo-electric cell II2 located in the upper part of the bore of the member 3 I.

Variations in light intensity on the photo-electric cell II2 are translated by the electrical circuit shown in Figure into motion of the master control valve motor III. To this end a source of rectified D. C. current is obtained by connecting the primary I31 of a transformer I38 to a source of A. C. indicated by the lines I39 and I40. Opposite ends of the secondary I4I are connected to separate plates of the by-phase valve rectifier tube I42. The cathode I43 of this tube is connected by line I44 to a filter indicated generally by the reference numeral I45. A line I46 is con nected to the midpoint of the secondary MI and constitutes the negative side of the rectified D. C. circuit, while the line I41 forming the output from the filter represents the positive side of the D. C. circuit.

These two lines are directly connected to opposite ends of the field I48 of the motor II I. Thus, the field of the motor is continuously energized by rectified D. C. current.

The terminals I49 and I50 of the photo-electric tube II2 are connected across the D. C. circuit, the terminal I49 being connected by a resistor I5I to line I46, and the terminal I50 being connected by a resistor I5I to line I46, and the terminal I50 being connected by a resistor I52 to a source of constant potential at I53. The plate of the photo-electric tube is connected by line I54 to the control grid I55 of pentode tube I56. This tube forms part of an amplifying circuit for controlling the grids I51 and I58 of tubes I59 and I60 in the sense that the variations in the rather weak current from the photo-electric cell are enabled to control and cause variations in the plate circuit of the tube I56.

The plate I6I of tube I56 is connected to the grid I51 of tube I59 through line I62 and resistor I63. The grid I58 of tube I60 is connected by line I14 to a source of constant voltage represented by the line I53. A voltage regulator tube I61 is connected between line I46 and a point I68, this point being connected to the D. C. output line I41 by the resistance I69 so that a steady D. C. voltage is obtained between the points I68 and the line I46, any variance in voltage will now appear across the resistance I69. It will now be seen that there is a constant voltage circuit from line I46 through rheostat I64, resistor I65, line I53, and resistor I66 to the point I68. By means of the rheostat I64, a voltage is selected for the cathode circuit of tube I56, the rheostat being connected through a resistor I to the cathode I10. The plate I6I of tube I56 is maintained positive by its connection through line HI and resistor I12 to the constant voltage point I68 which, in turn, is connected to positive D. C. line I41 by resistor I69.

Thus, with a steady potential on the grid I55 and by adjusting the rheostat I64 to give a de'-'- sired potential on the grids of tubes I59 and I60 which are substantially equal, a predetermined starting condition for operation of the circuit may be established.

The cathodes of the tubes I59 and I60 are connected to a common point I15 which, in turn, is connected by a resistor I16 to the negative D. C. line I46 which thereby establishes a negative potential on the cathodes.

There will now be an equal flow of current from the negative line I46 through resistor I16, through the parallelly connected tubes I59 and I60 to the plates I11 and I18 of the respective tubes which plates, in turn, are connected by lines I19 and I to separate saturable reactors I6I and I82 to control the flow of A. C. current through the reactors. Since a small direct current in the D. C. winding of a saturable reactor can control a large flow of A. C. current through the reactor, it will be seen that an amplifying effect is obtained since small variations in the D. C. current of the control tubes I59 and I60 is made to effect variations in the large flow of A. C. current in the reactors.

These reactors are operatively connected to the motor III, one reactor for causing rotation of the motor in one direction, and the other reactor for causing rotation in the opposite direction.

When the illumination on the photo-tube II2 increases above a predetermined norm, determined from the predetermined overlap of the line, it causes the reference voltage on grid I55 to rise, and more current will fiow from line I46 to the constant voltage point I68. The increased flow of current through the tube I56 lowers the potential at point I13 and thus lowers the potential of the grid I51 of tube I59. This will decrease the current fiowing through tube I59. This, in turn, will increase the cathode potential at point I15 and increase the flow of current in the tube I60 because the grid potential in this tube remains constant.

By keeping the potential on the grid I58 substantially constant, the grid I51 of the other tube may be varied with respect to it, and in so doing controls the flow through tube I60 indirectly by raising or lowering the cathode potential of the tube as represented by the point I15.

It should now be evident that the photo-electric cell directly controls the grid potential of one tube I59, and thus the flow of current therethrough, and indirectly and inversely controls and varies the current flow through the other tube, I60, by controlling or varying the cathode potential of that tube. By this unique arrangement when the current fiow through one tube is increased, the current fiow through the other tube is automatically decreased.

The saturable reactor I82 has its A. C. winding I83 connected to opposite ends of a secondary I84 of an A. C. transformer I85, the primary coil I86 of which is connected to the A. C. supply lines I39 and I40. Similarly, the reactor I8I has its A. C. winding I81 connected to opposite ends of the secondary I88 of an alternating current transformer I89, the primary coil I90 of which is connected to the A. C. supply lines I39 and I40.

The plate circuit I80 from tube I59 is connected to one end of the direct current winding I9I of the reactor I82, while the other end is connected to the positive D. C. line I41. Similarly, plate circuit I19 from tube I80 is connected to one end of the D. C. winding I92 of reactor I8I, while the other end is connected to the positive D. C. line I41. Thus, when the D. C. current in the winding I9I is increased, the alternating current flow through the A. C. winding is simultaneously increased, but at the same time the D. C. current will be decreased in the D. C. winding I92 of the reactor I8I, decreasing the A. C. current flow through the winding I81.

A pair of Thyratron tubes I93 and I9 3 are connected back to back between line I95 and line I96. Line I96 is connected by branch line I91 to the armature I08 of the motor III, the other end of the armature being connected by line I99 and inductance 200 to the A. C. supply line I39. The line I95 is connected by a branch line 20I to the A. C. supply line I 40.

Thus, we have an armature circuit starting from the A. C. line I40 through lines 20I and I95 to the two tubes I93 and I94, and from these tubes through lines I96 and I91 to the armature I98, the circuit being completed through line I99 and inductance 200 to the other A. C. line I39. Since the tubes I93 and I99 are connected back to back, current will flow through the tube I93, when the tube is fired, in the direction toward its plate 202, thus causing or tending to cause rotation of the armature in one direction, while current flow in the tube I94 toward its plate 203, will cause or tend to cause rotation of the armature I90 in the opposite direction, The firing of these tubes is controlled by their grids 294 and 205 respectively.

Each grid circuit is connected across a bridge to obtain a phase changing effect. The grid 204 of tube I93 is connected by a grid resistor 206 and a grid condenser 201 arranged in parallel to a point 299, forming one midpoint of the bridge. The cathode 209 of tube I93 is connected by line I95 to point 2I0 forming the other midpoint of the bridge circuit. One leg of the bridge, between points 208 and 2I0 includes one-half of the secondary I04 indicated by the reference numeral 2H, and the fixed resistor 2I2. The other leg includes the other half of the secondary I64 indicated by the reference numeral 2 I3, and the A. C. winding I83 of the saturable reactor I62. It will be noted that the A. C. winding I83 constitutes the variable part of the bridge circuit.

Similarly, the grid 205 is connected by a grid resistor 2I4 and grid condenser 2I9, arranged in parallel, to a point 2I6 forming one midpoint of the bridge. The cathode 2I1 of tube I94 is connected by line 2I9 to point 2I9 forming the other midpoint of the bridge. One leg of the bridge circuit from point 2I9 includes one-half 2200f the secondary I88 and the fixed resistor 22 I. The other leg includes the other half 222 of the secondary I99 and the A. C. winding I91 of the saturable reactor I6I. It wil be noted that the A. C. winding I81 constitutes the variable element of this bridge circuit.

When the same D. C. voltage is applied to each saturable reactor by the tubes I59 and I60, the Thyratron tubes I 94 and I 93 will fire at the same time. By properly adjusting the voltage the tubes will fire at the same point in the cycle, preferably midway of the positive half of the A. C. cycle. The result, however, will be that the amount of current flowing from the plate 202 into line I91 will be equal to the amount of current flowing in the opposite direction, that is, from the line I91 to the cathode of tube I99. These currents will balance one another and therefore no rotation will be'produced in the armature I98 of motor III.

1 When, however, the DC. current on one r actor is increased, and on the other reactor decreased, by the tubes I59 and I60, the effect on the reactors in their respective bridge circuits is to cause one of the tubes I93 or I94 to fire ahead of the other, whereby a flow of current in one direction through line I91 is created for a greater time than the current flowing in the opposite direction, thus producing rotation of the motor. Obviously, the direction in which the greater current flows through line I91 determines the direction of rotation of the motor.

As previously set forth, the motor III and its connected cam IIll controls the position of the master control valve plunger I01 shown in Figures 2 and 4 of the drawings. Normally, during operation of the machine, this cam is in its neutral position, that is, in a position to hold the master control valve in its neutral position and thus cause the hydraulic motor 96 to remain stationary.

In setting up the machine for operation, the machine slides are adjusted to put the spot of light in the necessary relationship with respect to the line to be followed.

Referring to Figure 6, very satisfactory results can be obtained by spacing the axis I3 of the sighting tube I31 from the edge of the line I2 a radial distance R equal to the radius R of the cutter 23. Since the cutter and sighting tube are on the same support for joint movement, they will always be in the same relation to corresponding points on the work and pattern. The circle I4 representsthe path of travel or orbit of the axis I3 which is the center of the field of view, and by keeping this circle tangent to the line being followed, one-half of the field of View will overlap on the line each revolution. This makes a very satisfactory or normal condition for tracing or following the line.

Under the conditions illustrated in Figure 6, the feed. direction setting of the directional control cam 11 is represented by the arrow 224. If the line deviates from this direction, as represented by the line I2a, then the overlap of the line would increase, and an automatic adjustment would be effected to change the direction of feed of the cutter to that represented by the arrow 224a. When the line deviates as represented by the line I2b, the overlap of the line by the field of view is decreased and an adjustment is efiected to change the direction of feed to that represented by the arrow 22427.

The sighting tube I31 is slidably mounted in its upport so that the radius R may be adjusted to suit the radius of the cutter utilized therewith.

t will now be seen that each revolution of the spot of light or field of view will intersect or overlap a predetermined portion of the line, and the electrical circuit is adjusted for this condition so that the electric motor I II will be balanced and held against rotation.

The hand wheel 223, which is operatively connected to the member 3| carrying the cam 11, is rotated or adjusted so that the direction arrow 224 on the hand wheel, as shown in Figure 4, points in a direction substantially parallel to the line to be followed. The start valve 96 is moved to its lower position by clockwise rotation of the bell crank 225, as shown in Figure 4, and a spring 226 will move the plunger down upon release of the latch 221. This will result in operatively connecting the hydraulic motor 36 to the master control valve, but with the master control valve motor would take place.

11 now eccentrically adjusted by its control 83 to establish a given feed rate in the direction as determined by the arrow 224.

With the electric motor I33 set into operation for rotating the scanning tube, the feeding movement between the tool and work continues in the direction in accordance with the relative position of the two directional control valves 47 and 52, their positions being determined by the cam 11.

With the electric lights H illuminated to create the spot of light it will be seen that the photo-electric cell starts to function and be responsive to variations in the amount of light reflected from the field of view as variations occur caused by increase or decrease in the amount of line overlap caused by variations in the direction of the line. It has been described in connection with the electrical circuit shown in Figure 5 how increases or decreases in the amount of reflected light on the photo-electric cell cause rotation of the electrical motor I II in one or the other direction to position the control cam H0 and move the valve plunger I01 above or below its neutral position. If it moves below its neutral position, such as that shown in Figure 4, fluid pressure from the pump 58 will flow through port I04 and groove I09 of the valve plunger to motor port IBI so that the fluid pressure will continue through line 99, interconnected ports 91 and 89 of valve 65 and line 81 to the hydraulic motor 36.

The return fluid will pass through line 88, interconnected ports 90 and 98 of valve 65 to line I00 and pass to reservoir through interconnected ports I02 and I06 of the master control valve. This will cause rotation of the cam 11 in the proper direction to reposition the directional control valves and thereby change the direction of relative movement between the tool and work to make it conform to the new direction of the particular line section being followed. If the master cam H0 is rotated in a direction to raise the master control valve above its neutral position, the motor port Ifll will then become an exhaust port through interconnection with port I06 and the motor port I02 will be connected to pressure through its interconnection with port I05. The result will be that the cam 11 will be rotated in the opposite direction.

When the change in the direction of feed has been brought into parallelism with the portion of the line being followed, it will be obvious that the reaction on the photo-electric cell will neutralize the electrical circuit to hold the parts in their new position.

It will be noted at this point, that just previous to the neutralization of the electric circuit, that the motor II I has been driving the cam H0 in one direction or the other and therefore at the moment of neutralization of the circuit the control valve is off center with respect to its neutral position. It is, therefore, necessary to immediately return the valve to its neutral position in order to stop further rotation of the hydraulic motor.

This is accomplished by providing centralizing springs 228 as shown in Figure 3 which are attached at one end to adjusting screws 229 threaded in a fixed part of the motor support, and at the other end, connected to a pin 23D projecting from the face of the cam H0. The springs are adjusted to hold the cam and thereby the control valve in its neutral position. Thus, when the valve is moved to an off-center position and the motor HI deenergized, the springs will rotate the cam as well as the motor armature immediately to reposition the valve plunger I01 with the aid of spring 23! to its neutral position and stop further rotation of the hydraulic motor 36.

Thus, the action of the motor HI is always that of moving the master control valve out of its neutral position to start actuation of the hydraulic motor to change the direction of feed while the neutralizing springs act to return the control valve to its neutral position and thus hold the direction control mechanism in its new position.

There has thus been provided a new and improved device of the character described, which is particularly useful for machining irregular shapes from a line drawing and which embodies a new and improved system for following a line, and one which is contrived so that it may control a hydraulic actuating system for the working elements of a machine and govern the direction of generation of a cutting path in accordance with the line being followed.

What is claimed is:

1. In a machine tool having a pair of slides movable normally one with respect to the other and a rotatable cutter carried by one of said slides for operation on work carried by the other slide, the combination with power operable means for moving said slides, of means on said other slide for supporting a pattern surface having a contour line delineated thereon, means on said one slide for rotating a spot of light on said surface about an axis spaced from the edge of said line substantially equal to the radius of said cutter to elfect a predetermined overlap of the spot of light on said line once each revolution, a photo-electric cell operatively connected for continuously viewing said spot of light and establishing a reference voltage in accordance with the average reflected illumination from said pattern per revolution of the spot of light and, a control circuit for said power operable means operatively connected to said cell and responsive to variations in voltage with respect to said reference voltage for determining the direction of relative movement effected by said power operable means between the cutter support and work support.

2. A machine for causing relative movement between two supports to reproduce a contour comprising, in combination, means on the one support for supporting a pattern surface having a delineated line thereon forming the contour to be reproduced, means for projecting a spot of light on said surface, power operable means for rotating said projecting means about an axis of revolution spaced from the edge of said line to eifect periodic overlap of the line by said spot of light, a photo-electric cell optically connected for continuously viewing the spot of light and establishing an average reference voltage for the average return of light per revolution, and a control circuit operatively connected to the cell having means responsive to voltage variations with respect to said reference voltage for controlling the direction of said relative movement.

3. A machine for causing relative movement between two supports to reproduce a contour having, in combination, means on one support for supporting a pattern surface having a delineated line thereon forming the contour to be produced, a tracer mechanism carried by the other support including an enclosed photo-electric cell, a line viewing tube optically connected to said cell and having an optical axis normal to said .pattern surface, said tube being adjusted to have a field of view on said pattern forming a scanning circle, means defining the axis of revolution for said tube eccentric to its optical axis, said axis of revolution being spaced from the edge of said line, means to adjust said tube relative to its axis of revolution in accordance with the radius of the cutter utilized therewith, means for illuminating the area of said circle, means forrotating said tube about said axis of revolution to efiect periodic overlap of the circle on said line and establish a reference voltage in said cell, and means to utilize increases or decreases in voltage with respect to said reference Voltage as correction signals for determining the direction of said relative movement.

4. A machine tool for causing relative movement between two supports to reproduce a contour comprising in combination means on the one support for supporting a pattern surface having a delineated line thereon forming the contour to be reproduced, means projectin a spot of light on the pattern surface, power operable means for rotating said projecting means about an axis spaced from said line to effect periodic overlap of said spot of light on said line per revolution, a photo-electric cell continuously responsive to reflected light from said spot for establishing an average reference voltage for a predetermined overlap of said line, whereby changes in voltage with respect to said reference voltage may be utilized as control signals for determining changes in the direction of said relative movement.

5. In a machine tool for causing relative movement between two supports to reproduce a contour from a delineated line on a pattern surface carried by one support, the combination of means for automatically controlling the direction of relative movement between said supports comprising a scanning tube optically connected to a photo-electric cell for scanning the marginal area adjacent said line, means to illuminate the area being scanned, means to rotate said tube about an axis intersecting said area to effect periodic overlap of said line to modify the fiux of radiant energy passing to the photo-electric cell per revolution and establish a predetermined average control voltage, and electrical means responsive to increases or decreases in said voltage to change the direction of said relative movement.

MARIO MARTELLOTTI.

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

UNITED STATES PATENTS Number Name Date 2,068,889 Roehm Jan. 26, 1937 2,154,974 Cook Apr. 18, 1939 2,172,313 Young Sept, 5, 1939 2,226,677 Vickham Dec. 31, 1940 2,239,625 Roehm Apr. 22, 1941 2,331,337 Meyer Oct. 12, 1943 2,332,533 Roehm Oct. 26, 1943 2,397,933 Fowle et al. Apr. 9, 1946 2,521,946 Ptathje Sept. 12, 1950 2,532,421 Rathje Dec. 5, 1950

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