US3353302A

US3353302A - Roll grinders

Info

Publication number: US3353302A
Application number: US528664A
Authority: US
Inventors: Paul M Lowy
Original assignee: Mesta Machine Co
Current assignee: Mesta Machine Co
Priority date: 1965-11-23
Filing date: 1965-11-23
Publication date: 1967-11-21
Anticipated expiration: 1984-11-21
Also published as: DE1652121A1

Description

ROLL GRINDERS Filed Nov. 23, 1965 4 Sheets-Sheet 3 Fig.4.

Gen. Field (Generator Amplifier T I 34 Digital to Analog Converter Error Counter Remy I Computer 42 {e k Computer 42 F' g .'5 Wheel Diameter I Preset Diamond Computation Position (Diameter) 7 Wheel Diameter Storage 'lProgram' Conlrol 47 I- Pulse Generator (ROTRAC) I F i Actual Wheel Wheel Position J l Position For Dressing Error Counter-I Digital to Analog Converter INVENTOR 3 34 32 7 Paul M. Lowy ROLL GRINDERS Filed Nov. 25, 1965 4 Sheets-Sheet. 4

Power Line Computer 42 Fig .7.

Grinding wheel Constont Potential Line Radius Computer Motor Field Grmding Dlgltol To Wheel Analog Magnetic Converter with P Built-tn Memory Amphf'er rm Wt Remy Logic Circuits Constant Potential Line INVENTOR 7 Poul M.Lowy

United States Patent Ofifice 3,353,362 Patented Nov. 21, 1967 3,353,302 RGLL GRINDERS Paul M. Lowy, Pittsburgh, Pa., assignor to Mesta Machine Company, a Corporation of Pennsylvania Filed Nov. 23, 1965, Ser. No. 528,664 Claims. (Cl. 51--49) ABSTRACT OF THE DISCLOSURE A roll grinder for automatically grinding the circum ference of rolls having a headstock and an adjustably posititoned spaced tailstock adapted to receive a roll on its axis therebetween, means for driving the headstock for rotating the roll, spaced stands between the headstock and the tailstock receiving the necks of the roll to be ground and supporting the roll between the headstock and the tailstock, grinding means adapted to move parallel to the axis of the roll betWeen the headstock and the tailstock, means for adjusting the grinding means transverse to the axis of the roll to be ground, a measuring means generating a plurality of energy impulses for a given increment of displacement between the roll axis and the grinding means, and a control means actuated by the energy impulses to the grinding means with respect to the rolls.

This application is a continuation-in-part of my copending application Ser. No. 213,294, filed July 30, 1962, and now abandoned.

This invention rel-ates to roll grinders and particularly to automatic roll grinders adapted to automatically align rolls within the grinder and then grind them to desired size and contour.

Roll grinders in which the diameter of the roll is measured and the grinder set accordingly have been previously proposed. However, these prior art grinders depended upon the use of probes which contact the surface of the roll and the grinding wheel. These probes had many defects. For example, a slight bend in a probe or wear on the probe end will throw the measurements out of accuracy and the resulting grind will be in error.

The roll grinder of the present invention eliminates all probes and like devices and provides a grinder mechanism which is accurate and free of the deficiencies of the probe type grinders.

Preferably I provide a headstock and an adjustably positioned spaced tailstock adapted to receive a roll to be ground therebetween, means for driving said headstock to rotate the roll, spaced necking stands between the head- V stock and tailstock receiving the necks of the roll to be ground and supporting said roll, means to shift the neck supporting members transversely of the axis of the roll, grinding means adapted to move parallel to the axis of the headstock between the headstock and tailstock, means for adjusting the grinding means transverse to the axis of i the roll, means generating a plurality of energy pulses for a given increment of distance between the roll axis and the grinding means, means intermittently measuring the diameter of the roll and integrating means relating the diameter of the roll to the position of the grinding means with respect to the roll axis whereby a given relationship between the roll diameter and grinding means may be maintained, and means adapted to adjust the position of the grinding means proportional to wear of the grind: ing means, and means to vary the'rotational speed of the grinding means to maintain a uniform grinding speed.

Preferably the energy pulses are electrical and the means measuring the roll is a measuring wheel of known diameter urged against the roll surface and driving an electrical pulse generator in combination with a pulse generator driven by the roll axis generating pulses in response to rotation of the roll. The grinding means is preferably a rotary grinding wheel. A wheel dressing means is preferably provided adjacent the tailstock at a fixed position from the roll axis whereby the grinding wheel may be automatically dressed under the control of the grinding means pulse generator.

The control circuit of this invention is based primarily upon the use of a roll diameter gauge in combination with a position sensing device such as a Westinghouse Rotrac pulse generator and a digital computer such as a Westinghouse Prodac computer.

An important feature of this invention is its adaptability to changing conditions encountered in the operation. The program which controls the operation is not fixed but is subject to modification in accordance with the result of measurements made during the operation. In conventional automatic machine tools a cutting tool is positioned under control of a programmer to bear against the work piece and made to follow a prescribed path as determined by the program to achieve forming of the workpiece. Since the position of the tool relative to its mounting table is fixed, positioning of the table fixes the position of the tool. In the case of a grinding machine, however, the tool is a relatively soft grinding Wheel which wears appreciably during a pass across the workpiece. As a result, the position of the cutting surface with respect to the workpiece surface cannot be established simply by determining the position of the cross slide 30. Accordingly, it is a purpose of this invention to automatically measure the diameter of the workpiece at intervals to determine the progress of the grinding operation and to alter the program as required to compensate for wear of the grinding wheel.

In the foregoing general description, I have set out certain objects, advantages and purposes of my invention. Other objects, advantages and purposes of this invention will be apparent from a consideration of the following description and the accompanying drawings in which,

FIGURE 1 is a top plan view of a roll grinder according to my invention;

FIGURE 2 is a side elevational View of a roll grinder according to my invention; I v

FIGURE 3 is a schematic wiring diagram of the roll grinder of my invention;

FIGURE 4 is a schematic wiring diagram of the wheel positioning control; I

FIGURE 5 is a schematic wiring diagram of the diamond dressing position control;

FIGURE 6 is a schematic wiring diagram of the carriage drive control; and v 3 FIGURE 7 is a schematic wiring diagram of the wheel speed control. I I

Referring to the drawings, I have illustrated a roll grinder having a bed 10, a headstock 11 and a motor driven traversing tailstock 12. The headstock 11 is provided with a drive motor 13 driving jaws 14 which engage and drive roll 1. Headstock 11 is provided with an end stop 15 and tailstock 12 is provided with an end stop 12a. Necking stands 16 and 17 rest on bed 10' and carry pads 18 and 19 which are shiftable on the necking stands transversely of the axis of the roll. Pads 18 and 19 are mo ed tran vers ly by op ra ion of m tor Z n 21 which are mounted on the necking stands and drive worms or the like which move the pads on ways. Bearing surfaces to support the roll necks are mounted upon pads 18 and 19 to enable the roll to rotate. A roll which is to be ground is placed upon the bearings which are conveniently semicircular bearing surfaces contacting only the lower portion of the roll neck. End movement is limited by stops and 12a, and the roll is rotated on the bearings by jaws 14 driven by motor 13.

A traveling carriage 22 (FIGURE 1) is mounted on ways 23 and 24- fitted on base 10 and is traversed by drive motor 25 acting through pinion 26 engaging rack 27 adjacent the ways and fitted to base 10. Movement of the carriage 22 along

ways

23 and 24 is parallel to the axis of rotation of the headstock. A grinding wheel 29 is mounted on a cross slide 30 on carriage 22 and carries the wheel drive motor 28. The cross slide 30 is driven at right angles to the axis of roll 1. The cross slide 30 is fed by a ball screw 31 driven by a rapid traverse motor 32 acting through a differential drive 33, a worm on drive shaft 35 and worm gear 36 on screw 31. Drive shaft 35 extends from the output of gear box 33. A variable voltage Vernier motor drive 34 acting through the other input of drive 33 also drives shaft 35. Ball screw 31 engages a nut 37 fixed to cross slide 30 but restrained against rotation. The rapid traverse motor 32 moves the carriage and grinding wheel rapidly toward the roll while the vernier motor drive makes micrometer adjustments.

A pulse generator 39, such as a Westinghouse Rotrac, on the ball feed screw 31 gives a multiplicity of electrical pulses for each rotation of feed screw 31. Pulse generator 39 in combination with the computer 42 is used to indicate the distance between the axis of the grinding wheel 29 and the center of the roll being ground.

A calibrated roll diameter measuring Wheel 40 is mounted adjacent the grinding wheel and when required is brought to bear against a roll 1 being measured. A pulse generator 41 is driven by the rotating wheel 40. A roll revolution pulse generator 49 generates a pulse each time an index mark on the headstock 11 passes a fixed refer-v ence line. The pulses generated by the wheel pulse generator 41 are transmited to an integrator which is gated by the roll pulse generator. This roll diameter measuring system is a modification of the measuring system disclosed in my copending application Ser. No. 200,402, filed June 6, 1962, now Patent No. 3,172,208.

The grinding wheel 29 is dressed by traversing the face of wheel 29 across a stationary diamond 43 at the tailstock.

FIGURE 4 illustrates the manner in which Positioning of the wheel takes place in the direction transverse to the axis of the roll. The present Wheel position is constantly monitored and is designated by a count registered in a counter in the computer 42 as described later. When the computer is required to direct the wheel to a new position it subtracts the present wheel position from the desired wheel position and places the difference in the error counter. A digital to analog converter converts the digital error into an analog voltage which is amplified by the amplifier shown. The resulting voltage is applied to both the field of a generator supplying the slow infeed motor and to a relay which selects either the slow or fast infeed motor for energization. If the amplifier voltage is sufficient to actuate the relay the relay contacts energize the fast infeed motor and de-energize the slow infeed motor. For lower voltages the slow infeed motor is energized and the fast infeed motor de-energized. For brevity only one relay is shown. Another is required to reverse the voltage applied to the fast infeed motor when the amplifier voltage reverses. The rectifier selects the proper relay for energization.

The infeed motors drive the cross slide carrying the wheel in the appropriate direction to arrive at the desired position. As the cross slide moves the pulse generator 39 feeds pulses into the computer which directs the error counter to count down in proportion to the pulses received. When the error counter reaches zero the output of the amplifier also goes to zero and the infeed motor stops leaving the cross slide in the desired position.

The following describes the manner in which the position of the grinding wheel is monitored. The pulse generator 39 of this disclosure is a Rotrac pulse generator which is a polarity sensitive pulse generator wherein the direction of rotation of the pulse generator is sensed. Each pulse generated represents an incremental angle of rotation of the pulse generator shaft and each pulse is coded to be positive or negative depending on the direction of the rotational displacement of the shaft, clockwise or counterclockwise, which produces the pulse. The pulses generated are fed to a counter which accumulates the algebraic total of the pulses generated to give an indication of the net angle through which the pulse generator has turned. Because the pulses are coded, the counter will count up for one direction of rotation, for example clockwise, and count down for a counterclockwise rotation of the pulse generator shaft. In this Way the movement of the pulse generator shaft can be traced by referring to the count registered in the counter readout. Since the pulse generator is mechanically connected by gearing to the cross slide which supports the grinding wheel bearings, it is readily seen that with a proper choice of gear ratio and pulse generator angular increment a given lateral displacement of the grinding wheel axis can be made t give a change in count which is a direct measure of the axis displacement, for example, each digit of the counter can be made to represent one-thousandth of an inch of grinding wheel axis displacement. If initially with the grinding wheel against a roll a count is placed into the counter equal to the sum of the radius of the roll and the radius of the grinding wheel in thousandths of an inch then any motion of the grinding wheel axis will cause a corresponding change in the counter reading so that the counter will give a continuous indication of the distance between the axis of grinding wheel 29 and the center of the roll.

FIGURE 5 illustrates the manner in which the computer determines its commands to the wheel position control to position the wheel, in this case, for diamond dressing. The wheel diameter is stored as described elsewhere. The diamond position which is fixed is also stored in a memory location in accordance with well known practice. The computer adds the two values: in storage and divides by two. Division by two is required to obtain the sum of radii instead of sum of diameters which are stored. This gives the desired; position of the wheel axis for dressing. The computer subtracts the actual wheel position from the above value and places the difference in the error counter. Position of the wheel then takes place as described previously.

FIGURE 6 illustrates the means by which the grin g wheel is positioned in the axial direction, that is, parallelto the ways 23and 24. The position of thewheel is monitored by means of limit switches 52 disposed at predetermined locations. along the ways to be actuated by a projection 53 on the carriage 22. The limit switches indicate when the carriage is at a particular location or if not at a particular location they. indicate with the aid of computer logic that the carriage is somewhere between two limit switches. Under normal operation the carriage will not stop between limit switches but will travel between them at a constant speed determined. by the programmer. Actuation of a limit switch can, be used to stop the carriage for a predetermined. time and initiate av subsequent function or to stop and reverse the carriage as required in various grinding sequences. Limit switches are located to establish the ends of the roll, the diameter measuring point and the right and left limits of diamond dressing. All are adjustable to accommodate different lengths of rolls.

. The following is a description of the sequence of events in a grinding operation. Prior to the start of the automatic cycle the following information must be fed into the computer by means of the input dials.

(1) Initial Diameter of Roll.

(2) Amount of Metal to be Removed. Amount Off. 3) Rough Cut Incremental Feed.

(4) Finish Cut Incremental Feeds.

(5) Wheel Dress Incremental Feed.

(6) Number of Wheel Dress Passes.

Next the roll 1 is placed on the hearings on pads 18 and 19. Pad 18 is moved transversely by operation of motor 20 under manual control to obtain a reasonably accurate centering of the end of the roll against the endstop 15 of the headstock 11 as indicated by visual inspection.

Initially pad 19 is moved away from the grinding wheel by means of motor 21 so that a visual inspection clearly indicates that pad 19 is further from the grinding wheel axis than pad 18.

The following alignment procedure takes place automatically. The roll is rotated by the drive motor. The grinding wheel is then brought into contact with the roll at the headstock end until it is under a desired load, such as 20% of full load, for example, as measured by the input to the grinding wheel drive motor. Without changing the cross slide position the grinding wheel is traversed to the tailstock end of the roll and stopped. Motor 21 now drives the pad 19 toward the grinding wheel until the roll contacts the grinding wheel as indicated again by 20% load on the grinding wheel drive motor. The roll is now aligned and grinding may proceed.

The programmer directs the grinding wheel to the measuring point near the end of the roll. A limit switch determines the axial position of the carriage. The radial position is selected to be the same as that which resulted during the neck alignment procedure. The measuring wheel is urged against the roll and the diameter of the roll is measured and stored in the memory of the computer.

The computer determines the number of passes required to remove the amount of metal specified by the setting of the Amount Off dial. This value is obtained by repeated subtractions of the value set up on the Rough Cut dial from the value on the Amount Oif dial. The computer counts the number of subtractions required to bring the result to zero or less. The number of subtractions is the required number of passes across the roll. The grinder proceeds to grind and at the end of each pass the wheel is infed by the amount set up on the Rough Cut dial. After each infeed the count referred to above; that is, the number of subtractions, is reduced by one. When the grinder has made sufficient passes to reduce the above count of zero the grinding passes stop and the carriage returns to the measuring point. The roll diameter is measured again and stored as before. Because of wear of the grinding wheel the change in diameter of the roll will not be equal to the amount of total infeed during the grinding passes. The computer calculates the difference between the new roll diameter and the original diameter less the Amount Off value. The result is the amount of metal yet to be removed. The computer compares this value with a predetermined limiting value and if greater than the limiting value the roughing cycle as described above is repeated including the measurement and comparison to determine if further repetitions are necessary.

When the calculation of amount of metal yet to be removed falls within the prescribed limits the program is permitted to proceed with the wheel dressing cycle. The grinding wheel is directed to the diamond point as described previously. The grinding wheel infeeds the amount set on the Wheel Dressing Increment dial and then is traversed across the diamond to the opposite diamond dressing limit switch. This procedure is repeated according to the value set in on the Number of Passes dial. During the diamond dressing infeeds the Rotrac pulse generator is disabled so that the counter which monitors the transverse position of the wheel does not change its count as the wheel infeeds. The result is a false indication of the position of the wheel with reference to its axis. However, with reference to its cutting surface the counter designation is still valid so that if the wheel table is now returned to the coordinates which it had at the end of the roughing cycle, the wheel will again be in contact with the roll even though its diameter has been reduced by the dressing cycle.

The grinder now proceeds with the finishing cycle. The wheel is infed the amount set in on the first finish cut dial and a pass is made across the wheel. This procedure is repeated using the infeed setting on the second finish cut dial and so on until all finishing cuts have been made. The grinder operation is now completed, the grinder stops and a signal is given.

It is apparent that as the grinding wheel wears down the surface or cutting speed of the wheel will decrease if the angular velocity remains constnat due to the diminishing radius of the wheel. For good grinding, however, the peripheral speed should be maintained at a constant, optimum value. Accordingly, it is a further object of this invention to provide a means for automatically adjusting the angular velocity of the grinding wheel to make its peripheral speed constant. FIGURE 7 illustrates the electrical drive circuit to achieve this aim. The grinding wheel radius is determined by the position of the cross slde 30 when the grnding wheel touches the roll as indicated by the load relay on wheel motor 28 and by the diameter gauge on the roll. The cross slide position is numerically equal to the radius of the roll plus the radius of the grinding Wheel. Since the diameter gauge measures the diameter of the roll then the cross slide position /2 roll diameter=the radius of the grinding wheel. Since the value of radius computed is in digital form a digital to analog computer of conventional form is used to produce an analog voltage proportional to grinding wheel radius. Since the radius is computed intermittently it is necessary to have a memory device to retain the radius value until next roll is measured and the grinding wheel radius recomputed. For a constant peripheral speed 1 of the grinding wheel the angular velocity w of the wheel must be inversely proportional to the radius r of the wheel:

In a similar way for a DC. motor with a constant potential E on the armature, the angular velocity w of the motor is inversely proportional to the field current I of the motor:

e w K f From these relations it is readily seen that to maintain constant peripheral speed of a gradually wearing grinding whel the field current of the motor should be made directly proportional to the wheel radius. Accordingly the analog voltage representing wheel radius is fed to a magnetic amplifier and then applied to the motor field to vary its strength as the wheel radius varies. The maximum value of analog voltage is selected to match the maximum radius of a new wheel. This maximum value must be large enough to give the base speed of the motor. For selecting other speeds such as rough cutting speed and finish cutting speeds a potentiometer P is provided to give some desired portion of the analog voltage. The peripheral speed of the wheel will be changed by the potentiometer but the value chosen will be held constant by the operation described above.

Rolling mill rolls are frequently ground in pairs to make a matched set having identical finished diameters. This is done to insure identical peripheral speeds in the mill when driven by shafts of identical angular velocities. It is a further advantage of this invention that a matched set of rolls can be readily obtained with the subject grinder. It is only necessary to set up the input dials for the first roll as described above. The dials are then left undisturbed for the second roll and the grinder will automatically finish it to the same dimensions as the first.

The following is a detailed explanation of the theory and operation of the roll diameter gauge.

Measuring wheel 40 is accurately machined to a precisely known diameter with a high degree of concentricity. Wheel 40 contacts the roll 1 to be measured and is driven by it with suflicient normal force to insure no slipping of wheel 40 on roll 1. The axes of measuring wheel 40 and roll 1 are parallel. Wheel 40 drives a pulse generator 41 which produces a number of pulses mi proportional to the angular displacement of the measuring wheel 40 A full rotation of the measuring wheel 40 produces in a typical embodiment 5000 pulses. Accordingly, a fractional part of a rotation will give precisely the same fractional part of 5000 pulses to an accuracy of one pulse. It is readily seen that the angular rotation of the measuring wheel can be determined by an accurate count of the pulses generated by pulse generator 41 during the angular rotation of the measuring wheel 40.

Since the diameter of the measuring wheel is accurately known and its angular rotation can be measured as described above, the linear distance traced out by the surface of the measuring wheel over the surface of the roll 1 can be determined from the equation:

If during one exact rotation of roll 1, the measuring wheel 40. causes the pulse generator 41 to produce a number of pulses M then the following equation can be written since the surface of the measuring wheel will have traced out one complete circumference of the roll 1:

D lll 5000 where C represents the circumference of roll 1, D is asabove.

From this the diameter of the roll can be calculated:

where D represents the diameter of the roll.

In a typicalembodiment the diameter of the measuring wheel 40. is made to be precisely 5 inches so that the above formula becomes:

It can readily be seen that in this embodiment the total number of pulses stored in the counter 51 during one complete rotation of the roll 1 is equal to the diameter of the roll 1 expressed in thousandths of an inch. The exact determination of the beginning and end of a complete rotation of the roll 1 is made by means of a roll pulse generator 49, typically an Electro-Products Magnetic Pickup. Pulse generator 49 produces a sharp pulse during a very small incremental rotation of roll 1. In this way the pulse defines a point on the circumference of the roll so that the interval, between two successive pulses represents a complete rotation of the roll.

The pulses from pulse generator 49 are used to turn on and turn off a gate 50 which permits the pulses from pulse generator 41 to reach the counter 51. Logic circuits are arranged so that a first pulse from roll pulse generator 49 turns on gate 50 and the next successive pulse from pulse generator 49 turns off the gate 50. In this way only the pulses generated by pulse generator 4-1 during one complete rotation of roll 1 are stored.

In the foregoing specification, I have described a present preferred embodiment of my invention and its operation. It will be understood, however, that this invention may be otherwise embodied within the scope of the following claims.

I claim:

1. A roll grinder comprising a headstock and an adjustably positioned spaced tailstock adapted to receive a roll on its axis therebetween, means for driving said headstock to rotate the roll, spaced necking stands between the headstock and tailstock receiving the necks of the roll to be ground and supporting said roll, grinding means adapted to move parallel to the axis of the roll between the headstock and tailstock, means for adjusting the grinding means transverse to the axis to be ground, a measuring wheel of known diameter, means urging the wheel against the surface of the roll, a rotatable pulse generator means driven by said wheel, a second pulse generator responsive to rotation of the roll, integrating means relating the proportional rotations of the measuring wheel of known diameter and the roll to derive a diameter of the roll and control means acting on the means for transversely adjusting the grinding means.

2. A roll grinder comprising a headstock and an adjustably positioned spaced tailstock adapted to receive a roll on its axis therebetween, means for driving said headstock to rotate the roll, spaced necking stands between the headstock and tailstock receiving the necks of the roll to be ground and supporting said roll, grinding means adapted to move parallel to the axis of the roll between the headstock and tailstock, means for adjusting the grinding means transverse to the axis of the roll to be ground, means generating a plurality of energy impulses for a given increment of movement corresponding to distance between the roll axis and the grinding means, a measuring wheel of known diameter, means urging said wheel against the surface of the roll, rotatable energy impulse generator means driven by said wheel, a second energy impulse generator responsive to rotation of the roll and integrating means converting the energy impulses into control signals positioning the grinding means with respect to the roll to be ground.

3. A roll grinder as claimed in claim 2 wherein the means for adjusting the grinding means transverse to the axis of the roll to be ground is a ball screw driven selectively through a differential drive by a rapid traverse motor and a variable voltage vernier motor.

4. A roll grinder as claimed in claim 3 wherein said means generating a plurality of energy impulses is an electrical pulse generator driven by said ball screw and generating a multiplicity of pulses for each revolution of the screw.

5. A roll grinder comprising a headstock and an adjustably positioned spaced tailstock adapted to receive a roll on its axis therebetween, means for driving said headstock to rotate the roll, spaced necking stands between the headstock and tailstock receiving the necks of the roll to be ground and supporting said roll, grinding means adapted to move parallel to the axis of the roll between the headstock and tailstock, means for adjusting the grinding means transverse to the axis of the roll to be ground, means generating a plurality of energy impulses for a given increment of movement corresponding to distance between the roll axis and the grinding means, a measuring Wheel of known diameter, means urging said wheel against the surface of the roll, energy rotatable impulse generator means driven by said wheel, a second energy impulse generator responsive to rotation of the roll and integrating means converting the energy impulses into control signals positioning the grinding means with respect to the roll to be ground, and adjust the rotational speed of the grinding wheel whereby an optimum uniform peripheral speed is maintained.

References Cited 10 FOREIGN PATENTS 5/1961 Germany.

OTHER REFERENCES Westinghouse Circular LL. 9320-6, Rotrac IIA Pulse Generator, Mar. 29, 1963.

ROBERT C. RIORDON, Primary Examiner.

J. A. MATHEWS, Assistant Examiner.