US2529161A

US2529161A - Register control system

Info

Publication number: US2529161A
Application number: US24154A
Authority: US
Inventors: Leroy U C Kelling; Lowell H Sheets
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1948-04-30
Filing date: 1948-04-30
Publication date: 1950-11-07
Anticipated expiration: 1967-11-07

Description

1950 u. c. KELLING ET AL 6 REGISTER CONTROL SYSTEM Filed April 30, 1948 Inventors: Leroy U.C.Kel|in2. Lowell HShee-bs- Theih Attohney Patentecl Nov. 7, 1950 REGISTER CONTROL SYSTEM Leroy U. o. Kelling and Lowell H. Sheets, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York Application April 30, 1M8, Serial-No. 24,154

3 Claims.

This invention relates to control systems, more particularly to register control systems for controlling the positional relationships of a length of material provided with spaced reference marks and an element operating thereon such as a rotating knife for severing the length of material in register with the marks, and it has for an object the provision of an improved control system of this character.

More particularly the-invention rel-ates to register control systems in which the length of material travels at relatively slow or medium speeds and in which but a medium degree of accuracy in'thc positional relationship-of the reference indicia and the operating element is not required.

For example, in machines for wrapping articles such as candy and gum with a label or design appearingfon each wrapper, a strip having labels or designs printed on it in succession is fed into I the cutting and wrapping machine.

knife and the design is required which will insure that the strip is out between the labels or designs.

In such a" machine an accuracy of register between the Usually the required accuracy of cutting varies between one-sixty-fourth inch and one-sixteenth inch. In this relatively low speed field the number of machines is relatively large and consequently low cost of the control is important. Accordingly a further object of the invention is th provision of a'register control system which is simple, reliable and inexpensive.

' In carrying the invention into effect in one form thereof, a photoelectric scanning head respondsto reference marks on the moving length vof material to provide a voltage impulse for each mark. A selector switchingmeans driven by the element which operates on the material produces voltage impulses which are in timed relationship to the'operation of the element. The impulses from the scanning head are supplied to theanode of a mixing'electric valve and the impulses from the selector switch are supplied to the grid. If

error exists, i. e., if the element is'not in correct register with the reference marks on the strip, voltage impulses are received simultaneously onthe grid and anode of the mixing valve. This causes. a triggering circuit to initiate conduction in a thyr atron. A timing circuit maintains the triggering circuit energized fora predetermined interval of time and the triggering circuit in turn maintains the thyratron conducting for the same fixed interval. An electric motor which isenergized in response'to conduction by the thyratron operates through a differential device to introduce a correction in the relative positions of the element and the length of material.

In illustrating the invention in one form thereoiit is shown. as embodied ing cut-off register control system, i..e., a system for controlling a cutter to cut sheets from a moving length of material with the cut edges in correct register with designs previously printed on the material.

For a better and more complete understanding of the invention reference should now be had to the following specification and to the accompanying drawing of which the single figure is a simple schematic diagram of an embodiment of the invention.

Referring now to the drawing, a length of material I, such as a web of paper having a succession of designs printed thereon, is drawn from a roll 2 by means of draw rolls 3 and travels in the directionof thearrow to a cutter .4.

The draw rolls and the cutter are driven by suitable driving means illustrated as an electric motor 5. The drive shaft of the motor is directly connected to the cutter iand through bevel gearing 6 and a mechanicaldifferential device 1 to the draw rolls 3. The differential device comprises an input gear 5a,.anoutputgear lb and a ring gear 'lcwhich is driven by an electric motor 8. The'motor 8'is referred to as the correction motor.

Preferably the ratio of the gearing 6 is such that when the correction motor is at rest, the peripheral speed of the draw rolls exceeds the peripheral speed of the cutter rolls by a small amount, e..g..between .5 per cent and 2 p er cent. "Thus thematerial isoverfed to the cutter so that an error in register between the cutterand the printed designs on the length of material is constantly accumulating.

.As shown, the correction motor 8 is a direct current motor. Power is supplied to its armature from a suitablesource of alternating Voltage such as the supply conductors 9 and it to which the armatur is connected through a, suitable electric valve such as the thyratron II. The thyratron is provided with an anode In, a cathode I lb, and acontrol grid llc. An alternating hold-off voltage is supppliedto the grid and cathode of the thyratron from the secondary winding 42a of a transformer l-Z of which the primary winding l2b is connected to a suitable source which may be and preferably .is the supply conductors .9, ii] from which the thyratron and correcting motor are supplied. The polarity of the connections to the secondary winding are such that the voltage supplied to the grid of the thyratron is out of phase with the anode voltage so that the thyratron is normally non-conductingand the correcting motor is at standstill.

For the purpose of comparing the register, 1. e., the relative positions of the cutter and the designs, the length of material is provided with a succession of reference indicia or register-marks [3 in predetermined relationship with the printed designs. Preferably these marks are printed on the material simultaneously with the printing of thedesigns.

The cutter is provided with means for providand a control grid 310.

the anode 31a to the anode of the amplifier valve '29; and the grid 310 is directly connected through ing an indication of its position. These means 7 are referred to as a selector switch. This selector switch may take the form of a mechanical switching device or it may take form of the photoelectric device which is illustrated in the drawing. It comprises a disk [4 mounted on the cutter shaft and a photoelectric scanning head 15. Preferably V the disk has a dark background upon Which is marked a white segment Ma. The segment may embrace from 10 to 120 of the disk. 7

The register marks [3 pass beneath a photoelectric scanning head" l6 which comprises a lamp I! and a photoelectric cell I8 which is focused on the path of the register marks through a suitable optical system. The photoelectric cell l 8 is connected across a suitable source of direct voltage which is illustrated as a single phase diametric rectifier i3 supplied from a suitable source of alternating voltage which may be and preferably is the source 9, l9. A voltage divider comprising a plurality of resistors 20, 2|, 22, 23, 24 and 25.. is connected across the output terminals of the rectifier. The junction point of

resistors

23 and 24 is grounded. The photoelectric cell It} is connected in a circuit which extends from the point Zila on the divider through the photoelectric .:.c'ell' l8 and resistor 26 to ground. A switch 27 is provided for changing the connection so that the circuit extends from the point 29a on the digrid of an amplifier valve 29 through a capacitor 38, resistor 31 and potentiometer 32. The valve 29 is provided with ananode 290., a cathode 29b and a control grid 2 90 which is directly connected to the slider 32a, of the potentiometer. Avoltage dropping resistor 33 is connected between the anode 29a, and the positive terminal 19a. 'of the rectifier. The cathode 29b is directly connected 'to the point 22a on the voltagedivider. 7 r I As shown, the scanning head of the photoelectric selector switch device l5 comprises a lamp 34 and a photoelectric cell 35. A beam .of light from the lamp 34 passes through focusing lenses to illuminatethe path of the segment [4a, and light is reflected from the segment to the photoelectric cell 35 which is focused upon the seg ment by means of focusing lenses. The photoelectric cell 35 is'connected in series with resistor 36 between the point Zla on the divider and the negative terminal 19b of the rectifier.

For the purpose of comparing the times of currence of signal voltage pulses from the photoelectric cells [8 and'35, an electronic mixer is provided. It comprises the left-hand conducting l path of a twin triode electric valve 31. This left hand path includes an anode 31a, a cathode 311) A capacitor/'38 couples a resistor 38b to the junction point of the resistor 36 and'photoelectric cell 35.

An electronic triggering circuit is controlled by the mixer valve to initiate and maintain conduction in the thyratron H fora predetermined interval of time. It comprises a twin triode electric valve 39, the right-hand conducting path of the valve 3?, and atiming circuit which includes the capacitor 40. The right-hand path valve 3'! includes an anode. 31d, acathode 31c 'and'to their common point 4 and a control grid 31 The anode 31d is connected through two voltage dropping resistors 4| and 42 to the positive terminal We of the rectifier and the cathode 31c is connected to the negative terminal I91). 7

The left-hand conducting path of valve 39 contains an anode 39, a cathode 39b, and a control grid 390. Similarly the right-hand conducting path includes an anode 39d, a cathode 39c and a control grid 39f.

A voltage dropping resistor 43 is connected between the anode 39a and the junction point 41a of resistors 4| and 42, while the cathode 39b is connected through a resistor 44 to the point 24a on the voltage divider. Between the anode 31d and the negative terminal l9b of the rectifier two

resistors

45 and 46 are connected in series, 4511 are connected the cathode 31b of the mixing valve and. the grid 390 of the triggering circuit valve 39.

The timing circuit extends from the positive terminal l9a. of the rectifier through resistor 4|, resistor 43, capacitor 40, adjustable potentiometer ll and resistor 48 to the negative terminal l9b of the rectifier. In this connection one terminal of the timing circuit capacitor 40 is connected to the point 43a which is connected to the anode 39a of valve 39, and the other terminal is connected to the grid 37; of valve 31.

Alternating voltage is supplied tothe righthand conducting path of valve 39 from the secondary winding m of'transformer l2. The cathode 396 is connected to one terminal of the secondary winding and the anode 39d is connected through the primary. winding 49a of a transformer 49 to the other terminal of the secondary winding I20. The grid 39f of the righthand path of valve 39 is connected to the cathode 39b of the left-hand path. The secondary winding 4% of transformer 49 is connected in the grid to cathode circuit of the thyratron ll.

Initially'the relative positions of the scanning heads l5 and 16 with respect to the segment I4a on'the disk and the reference marks on the strip are adjusted so that the voltage pulses produced by the scanning heads do not overlap, i. e., do not occur simultaneously when the cutter 4 is in proper register with the register marks l3.

The voltages applied to the grid 39c and cathode 39b of the triggering valve are selected so that the valve is normally non-conducting. On

the other hand, the voltages applied to the cathode 3le and the grid 31 ofthe timing circuit valve are such that it is normally fully conducting. With the foregoing understanding of the elements, the operation of the system will readily be understood from the following description.

As each reference mark on the strip passes beneath the scanning head IS, the light reflected to the photoelectric cell I8 is decreased thereby decreasing the current through the cell and 'correspondingly decreasing thevoltage drop across the resistor 26 for the period that the reference mark is beneath the photoelectric cell. The resulting negative voltage pulse at the point [8a is indicated graphically in the circle-50. It is transmitted through the coupling condenser 30 and applied as a negative voltage pulse to the control grid 290 of 'the amplifier valve. The signal is amplified and appears as a large positive pulse at the anode terminal 33a of resistor .33. I It is illustrated by the positive voltage pulse in the circle 51'. The amplified voltage pulse is '5 v of the mixing valve 31 as indicated by the pulse within the circle 52.

Once during each revolution of the disk [4, the wh'ite'segment Ida passes beneath the scanning head and increases the light refiected by the disk to the photoelectric cell 35. This increases the current in the photoelectric cell circuit and correspondingly increases the voltage drop across the resistor 36 so that a positive voltage pulse appears at the point a, as represented graphically by the positive pulse within the circle 53. It is applied as a positive pulse (shown within the circle 54) to the control grid 310 of the mixing valve. Owing to the length of the White segment 14a in comparison with the length of a register mark, the pulse applied to the grid 31c is of greater duration than the pulse applied to the anode as indicated by a comparison of the width of the pulses within the

circles

54 and 52.

When the cutter is in proper register with the register marks on the length of material; the pulses applied to the anode 31a and to the grid 370 do not overlap and consequently the lefthand path of valve 31 remains non-conducting. No signal is transmitted to the grid 390 of the triggering circuit valve 39. Consequently the thyratron l'l remains biased to cut-off and the correction motor 8 remains at standstill.

However, since the feed rolls feed a little more than one sheet length of material per machine cycle, i. e., per rotation of the cutting rolls, a condition of misregister soon develops. When a predetermined amount of error, i. e., misregister between the register marks and the cutter, has

accumulated, the voltage pulses supplied from the photoelectric cell I 8 to the anode 31a and from the photoelectric cell 35 to the grid 31c overlap, i. (2., occur simultaneously. This overlap of the voltage pulses on the anode and grid is illustrated graphically within the circle 55.

During the interval that both pulses overlap, the anode 31a and grid 310 are simultaneously positive and current flows in the anode-cathode circuit, thereby increasing the voltage drop across the resistor 46. This results in the voltage at the grid 39c becoming sufliciently positive to render the left-hand path of the triggering circuit valve conducting, which in turn produces a large voltage 'drop'across resistor 43, thereby suddenly making the point 43a more negative by the amount of this voltage drop. Since the condenser 40 cannot discharge instantaneously, the voltage of its terminal 40a suddenly becomes more negative by the amount of the voltage drop across resistor 43. Consequently, the voltage at the grid 31 which is connected to point 40a becomes so negative that the right-hand path becomes non-conductng. When the valve ceases conducton the voltage drop across resistor 42 decreases and the voltage at the point 42a becomes increas ingly positive. This results in maintaining the voltage of the grid 39c sufiiciently positive to maintain conduction in the left-path of valve 39 after the left-hand path of valve 37 has become nonconducting following the termination of the" voltage pulse supplied to its anode.

At the end of a predetermined interval of time from the beginning of conduction in the left- 390 to become sufficiently negative to stop con duction in the left-hand path of valve 35.

The predetermined interval of time during which the left-hand path of valve 39 remains conducting after conduction begins depends upon the rate of discharge of the capacitor 45 which in turn depends upon the adjustment of the potentiometer 47 in the discharge circuit. The voltages at the anode 31d, the grid 31f, the grid 39c and the anode 38a during this predetermined interval of time are illustrated graphically within the circles 56, 51, 58, and respectively.

During the predetermined interval in which the left-hand path of valve 39 is conducting, the voltage drop across the resistor 2 is increased 1 and the. voltage at the point Ma and at the grid hand path of valve the condenser iil has disl.

sister 42 thereby causing the voltage at the grid of the rheostat il.

39f become sufficiently positive to initiate conduction in the right-hand path of the valve 39.

The voltage at the point Ma and at the grid 33 during this interval of time are shown graphical- 1 within the circle GE). The alternating voltage which is supplied to the anode 39d and cathode 396 is rectified by the valve action and the rectified voltage which appears at the anode 35d is illustrated within the circle 61-. Since this rectifled voltage contains a periodically varying component, a periodically varying voltage is induced in the secondary winding 4% which is in phase with the line voltage and therefore out of phase with the hold-off voltage which is supplied to the grid i la of the thyratron from the secondary winding 12a. The alternating hold-off voltage is illustrated within the circle 62' and the periodically varying voltage induced in the secondary winding 4% is illustrated within the circle 53. Since these two voltages are 180 out of phase, the voltage induced in the secondary winding 4% overcomes the bias of the hold-off voltage and the thyratron ll becomes conducting and supplies a rectified voltage to the correction motor 8 for the predetermined interval of time the triggering circuit is active.

In resp-ense to energization, the correction l'llO- tor rotates in a direction such that the revolutions of the output element lb of the differential device 7 are the difference between the revolutions of the input element "Ea and the input element to. Iii-other words, the speed of theudraw rolls is retarded with respect to the speed of the cutting cylinders so that correct register be tween theregister marks and the blades of the cutter is restored. At the end of the predetermind interval of time the thyratron becomes nonconducting and the correction motor :is stopped. 2 Owing .to the overfeed of the strip with respect to the cutter, the register marks again become out of register with the cutter and the operation described in the foregoing is repeated.

The predetermined interval or time during which the correction motor is energized in response to an out-of-register condition may. be

varied by, varying the position of the slider 41a The discharge circuit for the capacitor 45 extends from the lower terminal of the capacitor 40, rheostat 5'1 and resistor 48, to

the negative terminal of the rectifier and from the positive terminal of the rectifier through resistors ii and 53 to the positive terminal of the capacitor. In one embodiment of the invention the resistor i-l is 39,0D0ohms; resistor 169,099 ohms; rheostat 47, 3,000,000 ohms, and resister cs, 100,000 ohms.

After the capacitor has discharged and the ri ht-hand path of the valve 3i has again lacagate come conducting, the capacitor is recharged by grid rectification. The circuit is from the positive terminal of the rectifier through resistors. 4i and 43, capacitor 48, grid 37 cathode 3'le,'to the negative terminals of the rectifier. Thus the greater portion of the high resistance of the discharge circuit is by-passed and the capacitor is recharged in amuch shorter time than was required for the discharge. Thus the system is quickly reset and placed in condition for a subsequent operation, as described in the foregoing. If desired, the control may be arranged for operation With underfeed of the material by selecting a proper ratio of the gearing 6 and by reversing either the field r armature connections to the correction motor 8.

Although in accordance with the provisions of thepatent statutes this invention is described as embodied in concrete form and the principle thereof has been explained together with the best mode in which it is now contemplated applying that principle, it will be understood that the elements shown and described are merely illustrative and that the invention is not limited thereto since alterations and modifications will readily suggest themselves to persons skilled in theart without departing from the true spirit of this invention or from the scope of the annexed claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A control system comprising a source of 'direct voltage, a first electric valve having an anode, a cathode andja control grid and having its anode-cathode circuit connected to be supplied from said source, means for producing a voltage pulse, means for producing another voltage pulse, means responsive to the overlapping in time of said pulses for producing a control voltage pulse, a direct conductor connection from said control voltage pulse producing means to said grid for supplying said control voltage pulse to said grid to initiate conduction of said valve, and means for maintaining said valve conducting for a predetermined fixed interval of time comprising a normally conducting second electric valve provided with an anode, a cathode and a control grid and having its anode-cathode circuit connected to ,be supplied from said source, a connection including a capacitor from the anode of said first valve to the grid of said second valve for rendering said second valve nonconducting in response to initiation of conduction in said first valve, a timing circuit including said capacitor for maintaining said second valve nonconducting for said predetermined interval of time, and a connection from the anode of said second valve to the grid of said first valve for maintaining said first valve conducting for said interval of time and for rendering said first valve nonconducting at the end of said interval.

voltage pulse producing means to said grid for supplying said control voltage pulse to said grid to initiate conduction, of said valve, andmeans for maintaining said 'valve conducting comprising a normally conducting second electric valve having an anode, a cathode and a control grid and having'its anode circuit connected to be supplied from said source, a connection including a capacitor from the anode of said first valve to the, grid of said second valve for rendering said second'valve nonconducting in response to initiation of conduction in said first valve, a timing circuit including said capacitor for maintaining said second valve nonconducting for said predetermined interval of time and a connection from theanode of said second. valveto the-grid of said first valve for supplying a positive bias voltage to the grid of said first valve to maintain said first valve conducting for said interval of time and to render it nonconducting at the end of said interval.

3. A control system comprising a source of direct voltage, a first electric valve having an ahode, a cathode and a controlv grid and having its anode-cathode-circuit connectedto be supplied from said source, a first means for producing a train of periodic voltage pulses, a second means for producing a second train of periodic voltage pulses, means responsive to the overlapping in time of a pulse of said first train and a pulse of said second train for supplying a control voltage pulse to said grid to initiate conduction of said valve comprising a normally nonconducting electric valve having a cathode connected to said grid and to the negative side of said source, an anode connected to said first pulse producing means and a control grid connectedflto. said second pulse producing. means,

and means for maintaining said first valve con ducting for a predetermined interval of time comprising a normally conducting third electric valve having an anode, a cathode and. a control grid and having its anode-cathode circuit connected to be supplied from said source, a connection including a capacitor from the anode of said first valve' to the grid of said third valve for rendering said third valve nonconducting in response I to initiation of conduction in said first valve, a

pulse of said first train and a pulse of said second train for producing a control voltage pulse, a direct conductor connection from said control timing circuit including said capacitor for maintaining said third valve nonconducting for said predetermined interval of time, an adjustable resistor in said timing circuit for. adjusting said interval of time to a desired value, a connection from the anode of said third valve to the grid of said first valve for maintaining said first valve conducting for said predetermined interval of time after initiation of conduction therein and for rendering said first valve nonconducting at the end of said interval.

LEROY U. o. KELLING. LOWELL H. smears. REFERENCES orrizn The following references are of record inythe file Ofthispatent: V

UNITED STATES PATENTS Number Name Date 2,230,715 Cockrell Feb. 4, 1941 2,250,209 Shoults et al July 22, 1941 2,399,135 Miller et al Apr. 23, 1946 2,429,500 V/olfner Oct. 21, 1947 2,444,261 Kelling June 29, 1948