US3089293A

US3089293A - Automatic control mechanism for roll grinder

Info

Publication number: US3089293A
Application number: US143138A
Authority: US
Inventors: Walter A Hoier; George W Marshall; Milton V Waters
Original assignee: Cincinnati Milling Machine Co
Current assignee: Milacron Inc
Priority date: 1961-10-05
Filing date: 1961-10-05
Publication date: 1963-05-14
Anticipated expiration: 1980-05-14
Also published as: DE1427473A1; GB959428A; DE1427473B2

Description

May 14, 1963 w. A. HOlER ETAL 3,089,293

AUTOMATIC CONTROL MECHANISM FOR ROLL GRINDER I Filed Oct. 5, 1961 6 Sheets-Sheet 1 mvcm'ons WALTER A.HO\ER c EORGE w. MARSHALL MILTON V.WAT I38 2% 7 122%:

ATTORNEYS May 14, 1963 w. A. HOIER ETAL 3,089,293

AUTOMATIC CONTROL MECHANISM FOR ROLL GRINDER 6 Sheets-Sheet 2 Filed 001;. 5, 1961 v w NM. J I l I l I l I l i I ll 5 on \h @N H. I I mm w I 2 oh. a I X 6 mm Q0 no 0o v= \LK LI 2%? MN ow H v I 3 3 I MI 9 mm May 14, 1963 W. A. HOIER ETAL AUTOMATIC CONTROL MECHANISM FOR ROLL GRINDER Filed Oct. 5, 1961 6 Sheets-Sheet 6 In; v

TARRY TIMER.8I.. 86 T TRA TRT 87 H|O3CR COUNTS ROUGH GRIND 88 PA$$ES.6I,'

"[O4CR IOSCR IOGCR CLUTCH-1.2 89 COUNTS FINISH GRIND 9 IO5CR -PASSES.62. v

4l0- pi409 1 9| I.

GR GL v SERIES FIELD CARRIAGE MOTOR 2M 92. IF

85 GL c 93 R O v SHUNT FIELD 96 EK GRINDING QMKS WHEEL MOTOR lM SHUNT SHUNT 2 SHUNT 4 97 L k I L- s7 r as a9 90 98 iOlCR 103CR zuca loo lCM-R uvLuJ 4 k LUZ U no I/I' Egg HiGH 99 mu 98 96 SCRUB OUGH IRY 30 I02 2M 3 2 4RY 3RY 22 4RY 5302. 107 A SRY mime. 6RY LQjJOZ.

United States Patent 3,989,293 AUTOMATEC (IONTRQL MECHANISM FGR ROLL GRENDER Waiter A. Hoier and George W. Marshall, Qincinnati,

and Milton V. Waters, Silver-ton, Ohio, assignors to The Cincinnati Milling Machine Co., Cincinnati, (ihio,

a corporation of Qhio Filed Oct. 5, 1961, Ser. No. 143,138 8 Claims. er. 51-165) This invention relates to improvements in roll grinders and, more particularly, to an automatic control system for roll grinders which is effective to maintain an established load on the grinding wheel motor during both of two distinct cycles of operation, which are herein designated as the scrub grinding and the rough grinding programs of the machine.

In the past, the technique of regrinding worn mill rolls to restore them to the proper geometry has been primarily a matter of operator experience, skill, and vigilance. This is mostly due to the fact that the regrinding of used or worn rolls involves many intangibles which can be recognized and allowed for by an experienced operator but which can not easily be handled by automatic control equipment.

It is, therefore, an object of the present invention to provide a control mechanism for roll grinders which will automatically adapt itself to the different conditions of the rolls to be ground and enable the grinding operation to be accomplished in a more expeditious manner than heretofore.

Another object of the invention is to provide an automatic control mechanism for roll grinders which is sensitive to changes in the torque on the grinding wheel drive motor but which is insensitive to flat spots on the face of the roll.

Another object of the invention is to provide an automatic control mechanism which will effect pick-feeding of the grinding wheel and reversal of the grinding wheel oarriage in response to a change in spindle motor current without being subject to false indications caused by fiat spots in the roll face.

Another object of the invention is to provide an automatic control mechanism of the type set forth in the preceding object, together with means to prevent a second reversal of the grinding wheel cariage until after the grinding wheel has reached the end of the roll face.

Another object of the invention is to provide an automatic control mechanism which will provide in-feeding of the grinding wheel during rough grinding operations to the extent required in order to compensate for wear of the grinding wheel.

With these and other objects in view, which will become apparent from the following description, the invention includes certain novel features of construction and combinations of parts, the essential elements of which are set forth in the appended claims and a preferred form or embodiment of which will hereinafter be described with reference to the drawings which accompany and form a part of this specification.

In the drawings:

FIG. 1 is a plan view of a roll grinder incorporating the present invention.

FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. 1.

FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG. 1.

FIG. 4 is a hydraulic diagram of the pick-feeding mechanism.

FIG. 5 is a diagrammatic view illustrating the scrub grinding program.

3-,h39,293 Patented May 14,1963

FIGS. 6a-6d together constitute a wiring diagram of the automatic control circuits for the roll grinder.

FIG. 7 is a table showing the sequence of operation of the timer and counter contacts.

The present invention is shown herein as applied to'a traveling wheelhead type of roll grinder. However, it will be appreciated as the description proceeds, that the invention might equally well be applied to a grinding machine of the type in which the wheelhead remains stationary while the workpiece moves relative thereto.

As shown in FIG. 1, the roll grinder includes a headstock 10 and a tailstock 11 between which a workpiece such as a roll (not shown) may be supported for rotation about its longitudinal axis in the customary manner. The headstock is provided with a drive motor 12 for rotating the workpiece as it is being abraded by the grinding wheel.

The machine also includes a bed 15 provided with ways '16 and 17 on which a carriage 1% is supported for longitudinal movement in a direction parallel to the axis of the workpiece. Movement of the carriage along the ways is eifected by an electric motor 2M on the carriage which drives a pinion 20 (FIG. 2) meshing with a nack 19 on the bed 115. The drive from the motor to the pinion is effected through a train of speed reducing gears including a pinion 2i, gear 22, worm 23 wormwheel 24, gear 25' and gear 26. For the purposes of this disclosure the carriage is shown provided with a pair of limit switches 11.8 and ZLS (FIG. 1) which cooperate with

dogs

27 and 28 adjustably attached to the bed 15 so as to limit the movement of the carriage in its travel along the ways 16 and '17 in accordance with the length of the roll. As viewed from the front of the machine, which is at the top of FIG. 1, the limit switch 1LS and dog 27 limit movement of the carriage to the right while the limit switch 21.8 and dog 28 limit movement of the carriage to the left.

Also mounted on the carriage 18 is a cross feed slide 29 supported on ways 3-1 and 32 ('FIG. 3) for movement transversely of the axis of the workpiece. The slide 29 provides support for a grinding wheel drive motor 1M (FIG. 1) which is connected by a series of V-belts housed in a guard 33 with a grinding wheel spindle on which the grinding wheel 34 is mounted. The slide is arranged to be driven along the

ways

31 and 32 either by an electric power cross-feed motor 3M or by a hydnaulic pick-feed motor MP. In either case, a shaft 36 journaled in the cross feedslide is rotated to effect translation of the slide by means of a worm 37 on the shaft meshing with a worm wheel 38 attached to a nut 39 embracing a screw 40 which is nonrotata'bly secured to the carriage '18.

Shaft 36 is connected through a magnetic clutch lMC with a shaft 45 which is connected by

bevel gears

46 and 47 with a vertically extending shaft 48. At its upper end the shaft 48 is connected by additional bevel gears (not shown) with a handwheel 49. The hydraulic motor MF may also be selectively connected to the shaft 48 by a bevel gear 50 on the motor shaft meshing'wit'n a bevel gear 51 affixed to a shaft on which is secured a worm 52. The worm 52 meshes with a worm wheel 53 which is secured to the casing of a magnetic clutch EMC. The armature 54 of the clutch is keyed to the shaft 48 for rotation therewith. Hence, when the clutches IMC and 3MC are both energized, operation of the pick feed motor MF will cause rotation of the shaft 36 and cross feeding movement of the slide 29. When the clutch SMC is deenergized, feeding movement of the slide may be effected by rotation of the hand wheel 49. As will hereinafter be described in connection with the wiring diagram, both of the clutches IMC and 3M0 are automatically deenergized when motor 3M is energized, and power feeding of the slide by the motor 3M may take place without rotation of either the hand wheel 49 or the hydraulic pick feed motor MP.

A hydraulic circuit for controlling the operation of motor MP is illustrated in FIG. 4 of the drawings. As there shown, a pump 58 withdraws hydraulic fluid from a reservoir 59 and delivers it to a line 69 at a pressure determined by a relief valve 61. The pressure line 60 is connected to a port on a solenoid valve 62 which controls the application of pressure to a motor line 63. The line 63 is connected to one side of the hydraulic motor MF through a flow control valve 64, the other side of the motor being connected to reserovir through an exhaust line 65. When the solenoid 1SOL of the valve 62 is deenergized, as shown in FIG. 4, the motor line 63 is connected to reservoir through a return line 66. Hence, both sides of the motor will be connected to reservoir and the motor will remain idle. However, when the solenoid ISOL is energized, the valve will con nect the pressure line 60 with the motor line 63 and cause the motor to run at a speed determined by the setting of the valve 64. Hence, pick feed of the slide 29 will take place and the amount of pick feed will be determined by the length of time that the solenoid llSOL remains energized. This feature of the apparatus will be made clear in a later portion of the description.

An understanding of the purpose and mode of operation of the scrub grinding program of the machine may best be understood by referring to FIG. 5. In this figure, there is shown a roll 70 mounted on the grinding machine with the grinding wheel 34 positioned adjacent one end of the roll ready to take the first out. The solid lines represent the roll in its worn condition as it is received in the roll shop prior to regrinding. In this condition of the roll, both ends are high and the center section is worn away. The dotted lines in FIG. 5 represent the shape of the roll after it has been reground. It will be understood that the configurations depicted in FIG. 5 are greatly exaggerated in order to illustrate clearly the deteriorated condition of the roll before it is reground and the crown produced thereon by the grinding operation.

To restore the proper geometry to the face of the roll, whether it be straight, convex, or concave, a method known as scrubbing may be used. By this method, a cut is established starting at one end of the roll face, as indicated by reference numeral 71, and traversing the grinding wheel toward the center of the roll. When the cut deteriorates as, for example, at the position indicated by reference numeral 72, the carriage is stopped, the wheel is pick fed into the work a predetermined amount to reestablish the cut, and the carriage is returned to the end of the roll face. At the end of the roll face 71, the carriage is again reversed and the wheel is once more fed into the work to re-establish the cut. The carriage is again traversed toward the center of the roll until the out again deteriorates, for instance at the position indicated by reference numeral 73. The carriage movement is again reversed after pick-feeding of the grinding Wheel. This operation is again repeated at position 74 and again at position 75, the latter position representing the low point on the surface of the roll. The operator now stops the machine and repeats the scrubbing operation from the opposite end of the roll face until the desired geometry of the roll has finally been established.

The next step is to improve the quality of the finish by removing the least possible amount of material from the roll face while maintaining the previously established geometry. This is effected by the rough grinding program and consists in establishing adetermined value of stock removal starting at one end of the roll face and traversing the wheel along the full length of the roll with the automatic control mechanism compensating for wheel wear by further infeeding of the grinding wheel as necessary during the traversing movement. After rough grinding, the roll is finish ground by following a procedure similar to the rough grinding program but without the automatic infeeding of the grinding wheel during traversal of the roll face to compensate. for wheel wear. A more complete understanding of the machine operation will be obtained from a study of the electrical control circuits which will now be described.

Electrical Control Circuits In FIGS. 6a6d of the drawings is shown an acrossthe-line wiring diagram of the electrical circuits of the machine. The energizing conductors extend lengthwise of the sheet and are continued from one sheet to the next. The numbers arranged along the lefthand margin of each sheet designate the lines of the diagram in which the various components, relays, relay contacts, etc., appear. The numbers in the right-hand margin below the legends refer to the lines in which the relay contacts are found, the underscored numbers designating normally closed contacts.

Referring to the diagram, electric current for energizing the control circuits is derived from a suitable theephase souce to which the

conductors

80, 81 and 82 are connected as shown in FIG. 6a. Two of these conductors are connected to the primary winding 83 of a transformer 84, the secondary winding of which is connected to

conductors

114 and 30 to provide a suitable source of single-phase A.C. potential for energizing the various control circuits.

The operator of the machine can select either a manual cycle or a program cycle by means of a selector switch ZSEL (ll). In the Manual position of the switch, a relay ltltiCR will be energized thereby closing the contacts lfifiCR in line 15. Hence, when either of the power cross feed pushbuttons 15PB or 16PB is depressed, a timer relay 3TR will be energized and time closed its delay contacts in line 13. A circuit will thereby be completed through the depressed pushbutton and a relay 3MP or 3MR so as to energize the relay and close its contacts in lines 2-7. These contacts control the operation of the power cross feed motor 3M and cause the cross feed slide 29 to move in when the relay 3MP is energized and to move out when the relay 3MR is energized. The time delay provided by relay 3TR prevents any inadvertent, momentary depression of the pushbuttons from operating the slide.

When relays 3MP and 3MR are both deenergized, their contacts in line -17 will be closed and supply energizing potential to the rectifier lRECT. The output leads 103 and 104 of the rectifier are connected across the clutch winding 1M0 and cause the clutch to be energized thereby enabling manual adjustment of the cross feed slide by handwheel 49. When a pick feed timer tl-TR (49) is energized, its contacts in line 19 are closed thereby energizing the clutch coil 3MC also whereby operation of pick feed motor MF will cause feeding movement of the cross feed slide. The pick feed timer 0TR is a commercially available unit and may be of the type shown and described in US. Patent No. 2,175,865, patented October 10, 1939, to Eagle Signal Corporation of Moline, Illinois.

The carriage motor 2M (91) is a DC. motor and is adapted to be energized from

conductors

409 and 41% connected to a suitable source of direct current. The speed of the motor is capable of being varied by means of a rheostat 85 and the direction of current flow through the armature of the motor is under the control of relay-s GR (78) and GL (79) which have contacts in

lines

91 and 92. When relay GR is energized, the motor will drive the carriage 18 to the right and when the relay GL is energized, the motor will drive the carriage to the left. The relay GR is in turn controlled by a relay CRR (40) while the relay GL is controlled by a relay CRL (69). This portion of the control circuit will be described hereinafter in greater detail.

The grinding wheel drive motor 1M (96) is also a DC. motor and like the motor 2M, is connected across the conductors 499 and 410. The motor 1M is adapted to be started and stopped by a pair of ganged switch contacts 9MKS (96) and may be adjusted to a selected speed by means of a rheostat 86. A series of

shunts

87, 88, 8? and 90 are connected in series with the armature circuit of the motor 1M and are utilized in a manner hereinafter to be described to control the operation of the machine during the grinding cycle.

Manual Cycle Energization of relay IOGCR with selector switch ZSEL turned to Manual also closes contacts ltlfiCR in

lines

42 and 73 so as to enable the carriage Feed Right push button 201 8 (40 and 69) and the carriage Feed Left pushbutton 221 3 (70 and 40). This permits feeding movement of the carriage to the right or left to be controlled manually by means of the pushbuttons.

Manual relay ltltlCR also has two pairs of normally opened contacts in line 46 which cause a relay CRA to be energized when either of the pushbuttons ZtlPB or ZZPB is depressed with relay ltltlCR energized. In this case, depression of a pushbutton will cause relay CRR or CRL to be energized and close contacts CRR in line 42 or contacts CRL in line 68. This furnishes a path for current to flow from conductor 114 through the depressed pushbutton and the above mentioned contacts of relays CRR and CRL to a conductor 12s which is connected by the closed contacts itltlCR (46) with relay CRA. When this relay is energized, it closes its contacts in line 46 and opens its contacts in

lines

42 and 71. Consequently, conductor 114 will now be connected through contacts CRA (46) to conductor 12% to provide a holding circuit for relay CRA when the pushbutton is released. Also, current can now fiow from conductor 114 through conductor 120 and the closed contacts of relay CRR (42) or CRL (68) to maintain the appropriate relay CRR or CRL energized after the pushbutton is released. Hence, the carriage will continue its travel to the opposite end of the roll where limit switch contacts 1L5 (40) or 2L5 (69) will open so as to deenergize relay CRR or CRL and stop the carriage. At the same time, the limit switch contacts 1L5 or 2L8 in

line

27 or 29, respectively, will close and energize a relay 105CR or 196CR. Thus, the contacts 196CR (38) or 165CR (75) will close and energize the other relay CRR or CRL to cause the carriage to start toward the opposite end of the roll. As soon as the appropriate relay CRR or CRL is energized, its contacts in

line

42 or 68 will be closed and provide a holding circuit for the relay around the 186CR or NSCR contacts which will open as soon as the carriage moves off of the limit switch. Hence, the carriage will continue its movement along the face of the roll until it reaches the opposite end where the limit switch will be operated and cause another automatic reversal of the carriage. This automatic traversing of the carriage will continue until the selector switch ZSEL (11) is turned to the Off position to deenergize relay ltltlCR. It will be noted that the direction of carriage travel during manual cycling may be reversed at any time by depressing the appropriate pushbutton ZtlPB or 221 B.

Each reversal of the carriage during Manual may, if desired, be accompanied by an automatic pick feed of the grinding Wheel toward the work. With the selector switch 4SEL (51) set on Auto, a circuit will be established from conductor 114 through contacts l lblCR in

lines

46 and 49 to a relay CRX (53). The contacts CRX in line 52 will thereby be closed and when, at the end of a traverse, both pairs of contacts ZZCRL and ZCRR in line 52 are closed as well as the contacts of timer TRA in line 50. the clutch and timing motor of timer tl-TR (49) will be energized and initiate a pick feed. is effected in the following manner:

The CLC contacts of timer tl-TR in line 55 will close (see FIG. 7) and energize a timer relay 105TR which will close its instantaneous contacts in line 52 so as to energize relay 113CR. The contacts of this relay in line 51 will close and energize the solenoid ISOL which will actuate the valve 62 (FIG. 4) and start the pick feed motor MF.

Although, in a manual cycle, both pairs of contacts ZCRL and ZCRR in line 52 remain closed only for an instant, the timer contacts TRA will remain closed during pick feed so that energization of the timer tl-TR will be maintained until after it has timed out and closed its COC contacts in line 64. This will energize relay 116CR (67) through the CRX contacts in line 66 and cause the contacts 116CR in line 83 to close thus conditioning the relays GR and GL for energization when the tarry timer contacts TRT in line 81 close at the end of the tarry period. At this time, the contacts CRR or CRL in lines 78-81 will already be closed and relay GR or GL will therefore be energized along with timer relay TRA. The contacts of the latter relay in line 86 will time open after a short delay to allow time for relay GR or GL and relay GlCR to pick up before the contacts TRT (81) open. When relay GR or GL is energized, its contacts in lines 76-79 will close and provide a circuit from wire 112 through these contacts to latching relay GECR. The latter relay provides a circuit from conductor 114 to wire 112 and relays GR and GL after the tarry timer contacts TRT in line 81 have opened.

When the pick-feed selector switch 4SEL is turned to Off with the machine set for a manual cycle, relay CRX will be deenergized and its contacts in line 67 will be closed. Thereby, relay llCR will be held energized through the contacts ltltlCR in line 66 so as to enable carriage traverse to begin as soon as the tarry timer TRT times out and closes its contacts TRT in line 81.

Thus, in a manual cycle of the machine, the grinding wheel carriage 18 will travel back and forth between the limit stops 27 and 28 (FIG. 1) with either automatic pick feed of the cross feed slide 29 on each reversal of the carriage, or with manual feed by hand wheel 49 or, finally, with power feed by motor 3M under the control of pushbuttons MP3 or 161 B (l4). Carriage reversal may be effected at any point in the traverse by depression of pushbut-ton 281 13 (40) or 221 13 and the carriage may be stopped by moving switch ZSEL (11) to Off.

Meter Relays The meter relays used to control the traverse and pick feed functions of the machine are connected across the shunts 87-90 as shown in FIG. 6a. The three meter relays utilized in this connection are designated as ICMR, Low Scrub; ZCMR, High Scrub; and SCMR, High Rough. These relays each consist of a DArsonval type meter movement with contacts on the indicating pointer and on a manually adjustable set-point arm. A locking coil, wound on the same bobbin as the measuring coil, is utilized to maintain firrn pressure on the contacts once they have been closed. Two types of contacts are provided, high limit contacts and low limit contacts. These devices are commercially available, one supplier thereof being Assembly Products, Inc, of Chesterland, Ohio.

Each of the meter relays has two additional relays associated with it; a sampling relay for periodically breaking the circuit through the locking coil, and an operating relay controlled by the contacts of the meter relay. Herein, the sampling relays are designated as 4RY, SRY and 6RY (107), and the operating relays as lRY, ZRY, and BRY (102).

Looking first at the low scrub relay circuit, it will be observed that this circuit is only operative when the scrub control relay 1l2CR (22) is energized thereby closing its contacts in

lines

98 and 108. When the relay contacts iltlZCR in line 108 are closed, a DC. chargingcircuit for a capacitor C will be established from positive and

negative supply terminals

94 and 95 through normally closed contacts RY and resistor R As the capacitor charges, the relay 4RY will be energized whereupon the contacts 4RY in line will open and break the charging circuit. The charge on the capacitor C then will discharge through the relay coil and maintain the relay energized for a predetermined interval of time after which the relay Will drop out and the charging cycle will be repeated.

When relay 4RY is energized, its contacts in line 102 will close and, if the high limit contacts 96 of meter relay ICMR are closed by the action of the measuring coil 97, as they normally will be during a scrubbing operation, a charging circuit for the capacitor C will be established from terminal 95 through locking coil 98 and resistor R The time required for the capacitor C to charge is less than the on time of relay 4RY. When the relay 4RY is deenergized, the contacts 4RY (102) will be open and break the circuit through the locking coil. However, the time required for the relay lRY to drop out is longer that the time interval during which relay 4RY is deenergized, the off period of relay 4RY being very short as compared to its on period. Hence, the circuit controlled by relay IRY will not be interrupted so long as the current through the measuring coil is sufiicient to hold the contacts 96 closed during the break interval, i.e., when contacts 4RY (102) are open. If the current is not sufiicient then the contacts 96 will open during the break so that capacitor C cannot be charged and relay TRY will drop out.

The circuit for the high scrub meter relay ZCMR, which is enabled by the contacts of relay ltllCR in

lines

98 and 108, is similar to the circuit just described except for the fact that the low limit contacts 99 of relay ZMCR are used instead of the high limit contacts. In the present control circuit, the low limit contacts are normally closed during all programs i.e., scrub, rough, and finish, the relay functioning as an over current safety device to stop the program should the load on the grinding wheel become excessive. Hence, the relay ZRY like the relay lRY is normally held energized.

The circuit for the high rough meter relay SCMR is enabled by the contacts of relay 103CR in

lines

98 and 108 and is similar to the circuit previously described in connection with relay ZCMR, the low limit contacts 100 of this relay being utilized for control. In this circuit, however, the contacts 100 are normally open and the relay 3RY is normally deenergized. This is due to the fact that the current drawn by motor 1M during the rough grind program is normally slightly greater than the setting of the set-point arm on relay 3CMR.

Scrub Program With the carriage at either end of its travel along the

ways

16 and 17, a scrub program may be initiated by setting selector switch ZSEL (11) to Program which energizes relay 101CR and closes its contacts in

lines

23, 45, 49, 54-, 83, 98 and 108. The machine is thereby conditioned for either a scrub, rough, or finish program as compared to a manual cycle. Selector switch 3SEL (23) is then set to scrub which causes scrub program relay 102CR to be energized. To start the scrub program, a Program Start pushbutton 21PB (60) is depressed. This will cause the relay 114CR (60) to be energized through the closed contacts 101CR (54), Wire 357, contacts 105CR (59) or 106CR (60), 21PB, 25PB, 105TR, 102CR and 108CR. Contacts 114CR (62) will close and hold the relay energized around the pushbutton 21PB and the contacts 105CR or 106CR. As indicated in the wiring diagram, the relay 114CR has additional contacts in

lines

54 and 55 which enable automatic pick feed during the scrub and rough programs. Since relay 100TR (62) will be picked up at the same time as relay 11.4CR, i.e. when the Program Start pushbutton is depressed, the contacts 100TR in line 54 will close and initiate a pick feed with the grinding wheel in contact with the end of the roll face as indicated in FIG. 5. Relay lM-CR also has contacts in

lines

42 and 45 which serve to energize conductor 120 and pick up relay CRA (46).

When relay 102CR is energized, the contacts 102012 in line 30 are closed thereby conditioning the low scrub contacts lRY in this same line for control of timer relay 102TR. The latter relay prevents pick feed and carriage reversal from occurring until a predetermined time interval has elapsed after the low scrub meter relay signals a loss of torque on the grinding wheel motor. This is to prevent false reversals from occurring due to flat spots in the surface of the roll. For this purpose, relay 102TR is set to provide a time delay approximately equal to the time required for the workpiece to rotate 180". Since the normally open contacts IRY (30) are ordinarily held closed due to energization of the relay lRY (102), relay 102TR is customarily energized during the scrub program thereby maintaining the contacts 102TR (31) closed and relay ltWCR energized. However, when the current to the grinding wheel motor 1M falls below the set point on meter relay ICMR, the contacts IRY will open and drop out relay 102TR. The contacts 102TR in line 31 will time open after approximately one half revolution of the workpiece and drop out relay 107CR. This relay has normally open contacts in

lines

38 and 69 which serve as holding contacts for the traverse relays CRR and CRL. Hence, when relay 107CR is deenergized, these relays will drop out and the carriage will stop and reverse its direction of travel after a pick feed of the grinding wheel has occurred.

The scrub program relay 1020K also has normally open contacts in

lines

37 and 74 which provide a circuit around the relay contacts 106GB (38) and CR (75) and enable the relays CRR and CRL to be energized with the carriage in an intermediate position along the roll face as well as in either end position. This is made possible by relays CR (34) and lllCR (36) which are conditioned for operation during the scrub program by relay contacts 102CR (34). Relay 110CR, when energized signifies that the carriage has been running right and this relay will remain energized until the carriage reaches an end position even though a reversal of direction should take place in the meantime. Similarly, the relay fillCR signifies that the carriage has been running left and it too will remain energized until the carriage arrives at an end position. These relays have contacts in

lines

41 and 72 which provide an initial energizing circuit for relays CRR and CRL by way of contacts 102CR, CRA, lllCR or 110CR, 116CR and 1LS or 2L8. The relays lllCR and 1100K have additional contacts in

lines

39 and 70 which provide a holding circuit around the contacts 107CR and permit continued energization' of relay CRR or CRL in case the contacts 1.07CR should open as a result of reduced current to the grinding wheel motor 1M after the carriage has reversed and is moving from the center of the roll face out toward one end of the roll face.

It will be noted that only one reversal can occur with this arrangement. In other words, when the carriage moves olt of a limit switch, say 2L3, and travels to the right with relays CRR and 1l0CR energized, if the low scrub relay lRY drops out due to reduced current to the grinding wheel drive motor 1M, the contacts 107CR (38) will open and drop out relay CRR. Since both pairs of contacts CRR and CRL in line 62 are now closed, timer relay 100TR will be energized and close its contacts in line 54. This will energize pick feed timer 0-TR and feed the grinding wheel into the work which will cause relay 107CR to again become energized. At the end of the pick feed, the COC contacts (64) of timer 0*TR will close and energize relay 116CR which will close its contacts in

lines

71 and 83. Closing of contacts 116CR in line 71 will establish a circuit to relay CRL through the contacts 110CR in line 72. Hence, this relay will be energized and close its contacts in lines 79 and 8-1.

When relay CRR dropped out, timer relay TRA (81) also dropped out and started tarry timer TRT (86). At the end of the tarry period, which is normally somewhat longer than the time set on timer O-TR for pick feed,

the contacts TRT in line 81 will close and energize relay GL which will drive the carriage to the left. Relay 110CR will remain energized. Therefore, if the current to motor 1M is again reduced to the point of causing relay 107CR to drop out, this will have no effect since the contacts lltlCR (70) are closed around the 107CR contacts (69) and maintain the relay CRL energized. Hence, the carriage will continue its travel to the left until it reaches the end of the workpiece where it will operate limit switch ZLS and drop out relay CRL.

After the scrub operation has been completed on one half of the roll (FIG. the program may be stopped ei her manually by the operator or automatically by meter relay ZCMR due to an overload on the grinding wheel motor 1M. An excessive flow of current through the motor will cause the low limit contacts 99' (100) to open and drop out relay ZRY. Closure of contacts 2RY in line 32 will energize relay 108CR through contacts IOICR (23) and wire 302 and open contacts 108CR in line 60 so as to drop out relay 114CR and stop the program. When relay 1 14CR is deenergized, its contacts in line 42 will open thereby deenergizing relay CRA. This will cause the CRA contacts in

lines

38 and 74 to open and drop out whichever traverse relay CRR or CRL is energized thereby stopping the carriage. The grinding wheel is then retracted and moved to the other end of the roll Where the Program Start pushbutton (60) is depressed to cause scrubbing of the other half of the roll.

Rough Program After the roll has been scrubbed, it is ready for a rough grinding operation. To accomplish this, the operator moves the selector switch 3SEL (23) to Rough which energizes relay 103CR and closes its contacts in

lines

33, 41, 55, 65, 72, 84, 87, 98, and 108. The closure of the 103CR contacts in

lines

33, 98, and 108 places the relay 109CR (33) under the control of meter relay 3CMR. The set pointer on this relay should be adjusted to a position which is slightly below the current expected to be drawn by the grinding wheel motor during the rough grinding operation. Thereby, the low limit contacts 100 (100) will normaly be open and relay 109CR will normally be held energized. If at any time the motor current should fall below that set on the meter relay 3CMR, relay 109CR will drop out and cause infeed of the crossfeed slide as will hereinafter be described.

Closure of contacts 103CR in line 87 will cause the clutch coil of a rough grind counter 107 to be energized thereby closing the COB contacts of this counter in line 61. Hence, when the Program Start pushbutton (60) is depressed with the carriage at the end of the roll, relay 114CR will be energized and close its contacts in

lines

42 and 45. The relay CRA (46) will thus be energized and close a circuit to relay CRR or CRL depending on whether the carriage is at the right or left-hand end of the roll. 'If it is at the left-hand end, the circuit will be esablished through the contacts 106CR (38), CRA, 106CR (40), 103CR (41), lLS (40) and CRL. If the carriage is at the right-hand end of the roll, the circuit will be established through the contacts 105CR (75), CRA (74), 105CR (71), 103CR (72), 2LS (69) and CRR. Since the 103CR contacts in

lines

41, 72, and 84 are closed around the 116CR contacts, the carriage can start its traversing movement without waiting for the pickfeed timer 0-TR (49) to time out. The tarry timer TRT (86) will still control the start of carriage traverse, however, so that a preselected tarry time from zero to say 12 seconds, for example, may be established at the end of each traverse across the face of the roll. At the end of each traverse, the contacts 105CR and 106CR will break the circuit to the count coil of the rough grind counter 107 and cause a count to be entered. After a preselected number of passes, the counter will count out and open its COB contacts in line 61 thereby stopping the program with the carriage at the end of the roll.

Infeeding of the grinding Wheel is effected during the rough grinding program under the control of the meter relay 3CMR. As previously mentioned, relay 109CR (33) is normally energized during rough grinding but will drop out whenever the current of motor 1M falls below the preselected value. In this event, the contacts 109CR (55) will close and establish an energizing circuit for pickfeed timer G-TR through contacts 181CR (54), ltiSCR (55), 114CR, 106CR or CR, or IG'BTR (57), and 109CR. The timer will run as long as contacts 1tl9CR remain closed but will be stopped and reset whenever the contacts open upon the motor current being brought back to the preset value. Since the motor current will fall off rather quickly when the grinding wheel reaches the end of the roll, the infeed will be initiated through the 169CR contacts (55) and the 106CR or IGSCR contacts (55) and will continue until either the pick-feed timer times out or until the contacts 1G6CR or 105CR open upon movement of the carriage at the end of the tarry time set on timer TRT. Normally, the tarry timer is set fora zero time interval during the rough grind operation to prevent infeeding of the grinding wheel at the end of the roll since improvement in the finish of the roll face with a minimum amount of stock removal is desired during this operation. Should the current to motor 1M fall olf during a traverse of the grinding wheel across the roll face, the cont-atcs 109CR will close in

lines

36 and 55 and energize the pick-feed timer after the timer 1G3TR times out. Infeed will continue until the current of motor 1M is restored to normal. The delay provided by timer 103TR is for the same purpose as the delay provided by the scrub infed dwell timer 102TR (30) narnely, to prevent pick feed until the roll has revolved approxi mately so that a flat spot on the roll will not be effective to initiate an undesired infeed of the grinding wheel.

Finish Program After the roll has been rough ground, the operator moves the selector switch 3SEL (23) :to Finish thereby energizing relay 104CR and closing the contacts of this relay in

lines

48, 51, 67, 85, and 89 and opening its contaots in line 94. When the IMCR contacts are closed in line 89, the clutch coil of a finish grind counter 10 8 is energized and the COB contacts of the counter in line 62 are closed. Hence, when the Program Start pushbu-tton (60) is depressed with the carriage on a limit switch 1L8 or 2L5, relay 114-011 will be energized and close its contacts in

lines

42 and 45 Relay CRA will thereby be energized and close its contacts in

lines

38 and 74. Accordingly, when the 116CR contacts in

lines

40 and 71 are closed, a circuit will be established through the 106CR or 1050K contacts to the traverse relay CRR or CRL and movement of the carriage will begin. If the selector switch 4S'EL (51) is set for Auto, an energizing circuit will be provided for pick feed timer tl-TR through contacts 104CR (48), 1 14CR, CRX (52), 'ZCRL and ZCRR, or TRA (50), and 104CR. After a pick feed is completed, the COC contacts of timer d-TR in line 64 will close thereby energizing relay 106CR and closing its contacts

i-n linw

40 and 71. If the switch 4SEL is turned to Off so as to eliminate automatic pick feed at the end of each traverse of the grinding wheel, the relay CRX will be deenergized and relay HGCR will be energized through the CRX and IMCR contacts in line 67. Hence, carriage traverse can start as soon as the tarry timer TRT (86) times out.

During finish grinding, the operator may observe the arnmeter H0 (99) connected to shunt 90 to determine the amount of the cut and, when he notices the current beginning to fall off due to Wear on the grinding wheel, he may then manually infeed the wheel to restore the current to its previous value. After the carriage has completed the number of passes set up on the finish grind counter,

1 1 the COB contacts in line 62 will open and stop the program.

It is to be understood, of course, that the foregoing disclosure of the new automatic control mechanism for roll grinders is intended to be illustrative only and that changes and modifications may be resorted to without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

l. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

(a) means for supporting the workpiece to be ground for rotation about its longitudinal axis,

(b) a grinding wheel,

() traversing means for effecting longitudinal movement of the grinding wheel relative to the workpiece,

(d) a drive motor for the grinding wheel,

(e) means for disabling said traversing means in response to a reduction in the torque on said drive motor below a predetermined value, and

(f) delay means for inhibiting the operation of said disabling means for a preselected time interval after the torque has fallen below said valve and for preventing said disabling means from becoming effective if the torque is restored to said valve within said time interval.

2. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

(12) a grinding wheel,

(c) reversible traversing means for effecting longitudinal movement of the grinding wheel relative to the workpiece,

(d) a driving motor for the grinding wheel,

(e) means for reversing the traversing means in response to a reduction in torque on said drive motor below a predetermined value, and

(f) delay means for inhibiting the operation on said reversing means for a preselected time interval after the torque has fallen below said value and for preventing said reversing means for becoming eifective if the torque is restored to said value within said time interval.

3. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

(b) a grinding wheel,

(c) traversing means for effecting longitudinal movement of the grinding wheel relative to the workpiece,

(d) a drive motor for the grinding wheel,

(:2) means for disabling said traversing means in response to a reduction in the torque on said drive motor below a predetermined value,

( means rendered effective upon the operation of said disabling means for advancing the grinding wheel a selected distance toward the axis of the workpiece, and

(g) delay means for inhibiting the operation of said disabling means for a preselected time interval after a reduction in the torque below said value and for preventing said disabling means from becoming effective if the torque is restored to said value within said time interval.

4. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

(b) a grinding wheel,

(0) reversible traversing means for eflfecting longitudinal movement of the grinding wheel relative to the workpiece,

(d) a drive motor for the grinding wheel,

(e) means for reversing the traversing means in response to a reduction in torque on said drive motor below a predetermined value,

(f) means for preventing a second reversal of said traversing means in response to a second reduction in torque on the drive motor below said predetermined value, and

(g) delay means for inhibiting the operation of said reversing means for a preselected time interval after the torque has fallen below said value and for preventing said reversing means from becoming eifective,

if the torque is restored to said value within said time interval. 5. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

(b) a grinding wheel,

(c) reversible traversing means for effecting longitudinal movement of the grinding wheel relative to the workpiece toward the center thereof and return,

(d) means signifying the direction of movement of the grinding wheel relative to the workpiece as it moves from one end toward the center thereof,

(e) a grinding wheel drive motor, and

(f) mean-s rendered effective by said signifying means to reverse said traversing means in response to a re duction in the torque on said drive motor below a predetermined value as the grinding wheel moves toward the center of the workpiece and to prevent a second reversal of said traversing means upon a reduction in torque as the grinding wheel moves toward said one end of the workpiece.

6. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

. (b) a grinding wheel,

(0) reversible traversing means for eifecting longitudinal movement of the grinding wheel relative to the workpiece from one end of the workpiece toward the center thereof and return,

(d) a grinding wheel drive motor,

(e) means for disabling said traversing means in response to a reduction in torque on said drive motor below a predetermined value,

(1) means rendered effective upon the operation of said disabling means to advance the grinding wheel a selected distance toward the workpiece,

(g) means to signify the direction of movement of the grinding wheel relative to the workpiece as it moves from one end thereof toward the center, and

(/1) means rendered effective by said signifying means at the conclusion of the operation of said advancing means to reverse said traversing means and prevent a second operation of said disabling means as the grinding wheel moves toward said one end of the workpiece.

7. A machine for grinding the peripheral face of a cylindrical workpiece comprising in combination:

(b) a grinding wheel,

(c) traversing means for eifecting longitudinal movement of the grinding wheel relative to the workpiece,

(d) a drive motor for the grinding wheel,

(e) normally inactive means for advancing the grinding wheel toward the workpiece,

( means responsive to the torque on said drive motor for initiating operation of said advancing means when the torque is reduced below a predetermined value to cause feeding of the grinding wheel toward the workpiece and for stopping said advancing means when the torque is restored to said predetermined value to stop feeding of the grinding wheel, and

(g) a timer for limiting the infeed movement of the grinding Wheel by said advancing means to a predetermined maximum amount.

8. The grinding machine of claim 7 including:

(a) delay means for inhibiting the operation of said initiating means for a preselected time interval after the torque has fallen below said predetermined value ing efiective if the torque is restored to said value within said time interval.

References Cited in the file of this patent and for preventing said initiating means from becom- 10 2,96 ,808

UNITED STATES PATENTS Taylor Jan. 29, 1929 Hall i Aug. 8, 1939 Smith Apr. 7, 1953 Dunigan Nov. 29, 1960

Claims

1. A MACHINE FOR GRINDING THE PERIPHERAL FACE OF A CYLINDRICAL WORKPIECE COMPRISING IN COMBINATION: (A) MEANS FOR SUPPORTING THE WORKPIECE TO BE GROUND FOR ROTATION ABOUT ITS LONGITUDINAL AXIS, (B) A GRINDING WHEEL, (C) TRAVERSING MEANS FOR EFFECTING LONGITUDINAL MOVEMENT OF THE GRINDING WHEEL RELATIVE TO THE WORKPIECE, (D) A DRIVE MOTOR FOR THE GRINDING WHEEL, (E) MEANS FOR DISABLING SAID TRAVERSING MEANS IN RESPONSE TO A REDUCTION IN THE TORQUE ON SAID DRIVE MOTOR BELOW A PREDETERMINED VALUE, AND (F) DELAY MEANS FOR INHIBITING THE OPERATION OF SAID DISABLING MEANS FOR A PRESELECTED TIME INTERVAL AFTER THE TORQUE HAS FALLEN BELOW SAID VALVE AND FOR PREVENTING SAID DISABLING MEANS FROM BECOMING EFFECTIVE IF THE TORQUE IS RESTORED TO SAID VALVE WITHIN SAID TIME INTERVAL.