US3156361A

US3156361A - Sheet classifying system

Info

Publication number: US3156361A
Application number: US148865A
Authority: US
Inventors: Jim N Moreland; Nybo Paul
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1961-10-31
Filing date: 1961-10-31
Publication date: 1964-11-10
Anticipated expiration: 1981-11-10

Description

J. N. MORELAND ETAL 3,156,361

SHEET CLASSIFYING SYSTEM Nov. 10, 1964 5 Sheets-Sheet 1 Filed Oct. 51. 1961 INVENTORS JIM N.MORELAND PAUL NYBO ATTORNEY a mi F J 55... P56 Edi 22o azooum P530 .rmm E NOV. 1964 J. N. MORELAND ETAL 3,156,361

SHEET CLASSIFYING SYSTEM 5 Sheets-Sheet 2 Filed Oct. 51, 1961 HOLD OFF TIMER H 2 P mm m SI.- QUUQmQOF ommflm PDOZDK Pv R mm 0 9 8 7 cw A 3 2 l O I. O nw 0 O O 0 O O O UmmZ mZ xi 0 no 2030405060 7080 el 0 2.62

TACH VOLTS INVENTOR. J "1 N.MORELAND PAUL NYBO BY Wow ATTORNEY Nov. 10, 1964 J. N. MORELAND ETAL SHEET CLASSIFYING SYSTEM Filed Oct. 51, 1961 5 Sheets-Sheet 3 TOTAL TIMER 2 0 L8 m E (I) l.6 I I 3 L4 (0 Z '2 TIMER g cuRvE STRIP LENGTH TIMER cuRvE TACH VOLTS FIG .3

INVENTOR.

JIM NMORELAND PAUL NYBO fm/wf ATTORNEY Nov. 10, 1964 Filed Oct. 51. 1961 J. N. MORELAND ETAL SHEET CLASSIFYING SYSTEM 5 Sheets-Sheet 4 q- E 0' I m '2 In E 2 I g M h a: a

o Q I W I INVENTOR. JIM NMORELAND PAUL NYBQ BY ATTONEY United States Patent 3,156,361 SHEET CLASSIFYING SYSTEM Jim N. Moreland, Roanoke, and Paul Nybo, Salem, Va, assignors to General Electric Company, a corporation of New York Filed Oct. 31, 1961, Ser. No. 148,865 1 Claim. (Cl. 209-741) This invention relates to a classifying system and more particularly to a classifying system for classifying preselected sheets.

Sheets must often be classified for different reasons. For instance, tin sheets must be classified according to their characteristics. The tin strip is inspected for pinholes, gage, and surface imperfections such as luster, before it is cut into sheets. The tin strip is cut into sheets and they must be classified into a prime stack with sheets having no faults, a secondary stack with sheets having only surface imperfections, and a reject stack with sheets having pinholes.

It is therefore an object of this invention to provide a new and improved classifying system for classifying sheets.

A classifying system capable of handling only one length of sheets operates under a great limitation. For instance, tin sheets are cut into different sizes depending on their intended use and it is impractical to employ a separate classifying system for each length of sheet.

Therefore, an object of this invention is to provide a new and improved classifying system for handling different lengths of sheets.

Heretofore, it has been the practice to employ a classifying system which handles several different lengths of sheets by diverting not only the preselected sheet but also sheets in front and in back of the preselected sheets to insure that the preselected sheet is diverted. Such a system requires further manual sorting of the diverted sheets.

Another object of this invention, therefore, is to provide a new and improved single sheet classifying system capable of diverting only the preselected sheet.

At times the sheet classifier must operate at different speeds and it is therefore an object of this invention to provide a classifying system capable of operating at different speeds.

Usually it is desirable that a classifying system be a single sheet classifier; however, at times it is desirable that the classifying system be capable of classifying not only the preselected sheet but also the sheet in front or in back of the preselected sheet.

It is, therefore, an object of this invention to provide a new and improved classifying system capable of classifying more than one sheet at the same time.

Often the selection of the sheets to be classified is accomplished by detecting faults in a strip before the strip is cut into sheets. The fault may be in any portion of the resulting sheet and it is difficult to divert the proper sheet with the fault in it.

Another object, therefore, of this invention is to provide a new and improved sheet classifying system for classifying sheets according to faults or imperfections detected in a strip before the strip is cut into sheets.

According to the principles of this invention a new and improved sheet classifying system is provided. The sheets to be diverted are preselected. The sheets are diverted by a gate which is normally closed. When the preselected sheet is a predetermined distance from the gate the gate is opened after a predetermined period of time and the preselected sheet is diverted when the sheet reaches the open gate. The predetermined period of time is varied according to the length of sheet being classified and the speed of classification so that different lengths of sheets may be classified at different speeds.

The selection of the sheets to be diverted may be some distance from the gate at which they are to be diverted. When this is the case, information representative of the preselected sheet is stored in a memory register. As the preselected sheet is moved toward the gate the corresponding information is shifted in synchronism in the shift register until the information indicates that the sheet is the predetermined distance from the gate. Then the gate is opened after a predetermined period of time to divert the preselected sheet.

The sheet classifying system constructed in accordance with the pri ciples of this invention accurately classifies sheets of different lengths at different speeds.

When faults .or imperfections are detected in a strip before the strip is cut into sheets, information representative of the fault or imperfection is stored in a memory register. As the fault or imperfection is moved to the cutters where it is cut into sheets and then toward the gate, the corresponding information is shifted in synchronism in the shift register until the information indicates that the fault or imperfection is a predetermined distance from the gate. The gate is opened after a predetermined period of time to divert the sheet with the imperfection or fault.

Sheets with faults or imperfections may be classified with this invention when the fault or imperfection is detected before a strip is cut into sheets.

The novel features .of the invention are set forth with particularity in the appended claim. The invention itelf, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by referring to the following description and the accompanying drawings.

In the drawings:

FiGURE 1 is a diagram of a classifying system constructed in accordance with the principles of this invention.

FIGURE 2 is a graph showing the different holdoif times for different lengths of sheets.

FlGURE 3 is a graph showing the different total times for the different lengths of sheets.

FlGURE 4 is a schematic of a timer suitable for use as a holdolf or total timer.

FIGURE 5 is a drawing used to illustrate the four different lengths of sheets and the different speeds.

FEGURE 6 is a drawing used to illustrate the accuracy of the system.

FIGURE 7 is a graph showing timer curves for the timer illustrated in FIGURE 4.

An understanding of the classifying system may be had by reference to FIGURE 1 wherein a strip 11 is fed from a supply reel 13 having a stock of tin strip material or the like. A visual check of the strip is normally made by manual observation to determine, for example, the degree of luster, as indicated at station 15 in FIGURE 1.. Other examinations of the strip may be made by automatic or semi-automatic devices such as by a pinhole detector 17, as shown at a station 19, and by an X-ray gage 21 as indicated at a station 23 of FIGURE 1. In this manner strip material 11 is delivered to a pair of take-up rolls 25 and 27 and thereafter fed to a series of feed rolls 29 to be acted upon by a flying shear 31 for cutting the strip into predetermined lengths.

The sheets cut from the strip must then be classified according to their characteristics. The sheets with no imperfections are prime stock and must be separated from the other sheets, the sheets which are off gage or have only surface imperfections are satisfactory for some purposes and are called mendor stock, and the sheets with pin holes are useless.

The

gates

33 and 4,3 are magnetic gates which are magnetized to divert sheets from the classifying system. The first gate 33 associated with the first conveyor 35 is magnetized when a sheet with a pinhole is to be diverted and the defective sheet is transferred to a reject conveyor 37 where it is transferred to a reject stack 39. The second gate 43 associated with the second conveyor 41 is magnetized to divert a mendor grade sheet to the mendor conveyor 45 where it is transferred to the mendor stack 47. All other sheets are transferred to the third conveyor 49 and deposited on the prime stock stack 51. In this manner the sheets are classified according to their characteristics.

After the detection of the flaw in the strip it is necessary to determine which gate is to be magnetized and when that gate is to be magnetized to remove the sheet with the fiaw in it. The following will describe the control which automatically selects the gate to be magnetized and determines when that gate is to be magnetized to remove a sheet with a predetected flaw. An understanding of the control may be had by reference to FIGURE 1 wherein

pin wheel timers

53 and 55 are conventional pin wheel timers such as the type 132A synchronous timer manufactured by Pratt and Whitney. The pin wheels rotate in synchronism with the travel of the tin strip 11, from the supply 13 through the shear 31, by a mechanical synchronizing linkage 54 which links the drive of the

pin wheel timers

53 and 55 with the drive of the flying shear 31. The pins 54a-54p of pin wheel 53 and pins 56a56p of pin wheel 55 are normally substantially flush with the surface of the pin wheel and may be displaced a predetermined distance by solenoids 57, 59 and 61 when positioned under the solenoids. Solenoid 57 may be energized by an observer closing the circuit to the solenoid 57 by pushing switch 65. Solenoid 59 is energized when X-ray gage 23 detects oif gage of the tin strip 11 and solenoid 61 is energized when pinhole detector 17 detects a pinhole on the tin strip 11.

Each

pin wheel timer

53 and 55 is shown with 16 pins for illustrative purposes while the actual pin wheel timers have more pins. The number of pins depends on the distance from the testing station to the gates and the size into which the tin sheets are cut, as will become apparent later in this description.

After a pin has been displaced by a solenoid in response to the detection of a fault in the tin strip 11 the pin rotates in synchronism with the travel of the fault in the tin strip toward the fiying shear 31.

Normally

open switches

63, 65 and 67 are positioned with respect to the

pin wheel timers

53 and 55 so that the pins substantially flush with the pin wheels do not affect the switches. Displaced pins, however, close the

switches

63, 65 and 67 as the pins are rotated past the switches.

Switch 63 is positioned with respect to the solenoid 57 so that a pin displaced by solenoid 57 when a fault is detected in tin strip 11 is rotated to close switch 63 as the detected fault approaches the second gate 43. In a similar manner switch 65 is positioned with respect to solenoid 61 so that a pin displaced by solenoid 61 in response to the detection of a pinhole is rotated to close switch 65 as the pinhole in the tin strip 11 approaches the first gate 33. Also, in a similar manner, switch 67 is positioned with respect to solenoid 59 so that a pin displaced by solenoid 59 in response to the detection of an off gage is rotated to close switch 67 as the off gage in the tin strip 11 approaches the second gate 43.

The closing of switches 63 and 67 energizes coils 69 and 71 to close normally open contacts 73 and 75 respectively. The closing of switch 65 energizes coils 77 and 79 to close normally open contacts 81 and 83 respec tively. The closing of contacts 73 or 81 connects timers 85 or 87 respectively to tin sheet length selection switch S9. The closing of contacts '75 or 83 connects timers 91 or 93 respectively to tin sheet length selection switch 95.

Timers

85, 87, 91 and 93 are timers of the type shown in FIGURE 4 and described in relation thereto. Each timer is energized when it is connected to a power source and remains energized a period of time approximately inversely proportional to the voltage applied to the timer.

[1 The voltage applied to the timer depends on the speed of the conveyor system and the length of tin sheet being classified.

Tachometer 94 measures the speed of the conveyor system and produces a voltage directly proportional thereto.

The voltage produced by the tachometer 94 is applied to a voltage divider 97 with terminals 970-976 and a voltage divider 99 with terminals 99a-99e. The voltage is divided in the voltage dividers, applying the voltage across a series of resistors and connecting the output terminal to different resistors.

The highest potential in voltage divider 97 is applied to terminal 970, next highest to terminal 971), next highest to terminal 97c, the next highest to terminal 97d and the lowest to terminal 97c.

The lowest potential in voltage divider 99 is applied to terminal 99a, the next lowest to terminal 99b, next lowest to terminal 990, next lowest to terminal 99d and the highest to terminal 99c.

Length selection switches 89 and 95 are moved together so that the corresponding contacts are connected to the two length selection switches 89 and 95 at the same time. That is, contacts 97a is connected to length selection switch 89 at the same time contacts 99a is connected to length selection switch 95. Thus when the highest potential is applied to the holdofif timers 85 and 87, the lowest potential is applied to the two total timers 91 and 93. The reason for such will become apparent later in the description of the control for classifying the tin sheets.

After the first holdolf timer 85 finishes timing, coil 101 is energized and closes normally open contact 103. Contact 103 when closed completes a circuit between

terminals

105 and 107 which are connected to a suitable power supply to energize coil 109. Coil 109 when energized closes normally open contact 111 to energize the first gate magnet 113 which magnetizes the first gate 33 so that the next tin sheet with a pinhole on the conveyor 35 is transferred to the reject conveyor 37 and deposited on the reject stack 39.

After the rejected tin sheet with a pinhole has been transferred to the reject conveyor 37 the first total timer 91 finishes timing and energizes coil 115 which opens normally closed contacts 117 and 119 so that coils 69, 71 and 109 are deenergized. When coil 109 is deenergized contact 111 opens, deenergizing the first gate magnet 113 and demagnetizing gate 33. When coils 69 and 71 are deenergized, contacts 73 and 75 open and no further voltage is applied to the first holdoff timer 85 or the first total timer 91.

In a similar manner, when the second holdolf timer 87 finishes timing, coil 118 is energized to close normally open contact 1.21 and energize coil 123. An energized coil 123 closes normally open contact 125 to energize second gate magnet 127 and magnetize the second gate 43 so that the mendor tin sheet on the second conveyor 41 is transferred to the mendor conveyor 45 and stacked on the mendor stack 47. When the second total timer 93 finishes timing, coil 129 is energized to open normally closed contacts 131 and 133 and deenergize coils 77, 79 and 123. Thus normally open contacts 81 and 83 are opened to stop the application of a voltage to the second gate holdoff timer 87 and the second gate total timer 93. Normally open contact 121 is also opened to deenergize coil 123 and open normally open contact 125, deenergizing second gate magnet 127 to demagnetizc the second gate 43.

The general operation of the tin sheet classifying system has been described. The following discussion and description is directed to the control of the classifying system to handle different lengths of sheets and different speeds of the classifying system.

The two

pin wheel timers

53 and 55 are moved in synchronism with the tin strip 11 and subsequent tin sheets cut from the strip. Thus a pin displaced from one of the

pin wheel timers

53 or 55 in response to the detection of a fault is moved in synchronism with the fault in the tin strip 11 and subsequent tin sheets. Changes in speed of the tin strip and sheets are reflected in the rotation of the

pin wheel timers

53 and 55.

.A magnet is energized when the circuit to the magnet is completed and the gate becomes magnetized later. There is a time delay between the time the magnet is energized and the time the gate becomes magnetized. Conversely, there is a time delay between the time the magnet is deenergized and the time the gate becomes demagnetized. When the gate becomes magnetized it may be said that the gate opens and will attract the desired tin sheet.

The displaced pin representing a fault is moved in synchronism with the fault until the fault reaches one of the gates 33 or 43 where the sheet containing the fault must be removed. As the tin handling apparatus handles different sizes of sheets and operates at different speeds, the gates must be magnetized to remove all defective sheets. Referring to FIGURE 5 the sheets may vary in size from the longest sheet L to the shortest sheet L and the speeds may vary from the fastest speed 5 to the slowest speed S The fault may be in any portion of the sheet, from the head to the tail. The gates must be magnetized a sufficient period of time before the fault reaches the gate to remove all defective t-in sheets. The most difficult sheet to remove is in a condition where the longest sheet L is traveling at the fastest speed S with the fault in the tail of the sheet. The gate magnets must be energized a period of time before the fault actually reaches the gate equal to the length of the longest tin sheet L plus the distance traveled by the sheet after the magnet is energized and before the gate becomes mag.- nctized X, divided by the top speed S Thus equals the time before the fault reaches the gate that the magnet must be energized to remove the longest sheet L traveling at the top speed S with a fault in the tail. If the magnet is so energized, all tin sheets with faults therein will be removed.

Switches

63, 65 and 67 in FIGURE 1 are thus placed so that they are closed by a displaced pin when the corresponding fault is the distance X +L from the appropriate gate. This is called the pin Wheel interlock. Again L equals the length of the longest sheet to be classified and X equals the distance the fault travels at the top speed from the time the magnet is energized until the gate becomes magnetized. As a result, for a longest sheet L traveling at the highest speed S the magnet will be energized a period of time equal to before the fault in the tail of a sheet reaches the gate in a manner to be described.

When shorter tin sheets are being classified or tin sheets arebeing classified at slower speeds the

switches

63, 65 and 67 in FIGURE 1 are closed when the fault is a distance X +L from the gate at the pin wheel interlock.

It is not practical to change the position of the switches for each length of sheet being classified and for each speed of which the conveyor system operates. Therefore, apparatus of this invention operates according to the following principles.

Referring again to FIGURE 5 for condition 2. When a shorter sheet L is being classified at the same top speed :3 the magnet may be energized when the fault is closer to the gate to remove a sheet with the fault in the tail. Rather than moving the switches the magnet may be energized a period of time after it would have been energized 6 for the longest sheet L Sucha period of time may be called the holdotf time T ho and for a shorter sheet L traveling top speed S the holdolf time is equal to S S Similarly, for condition 3 in FIGURE 5, if the longest sheets L are being classified at a slower speed S the magnet may be energized when the fault is closer to the gate. The holdofi time T ho, for the longest sheets L traveling at a slower speed S is equal to 2L2 S2 1 In a similar manner for condition 4 in FIGURE 5, when a shorter sheet L; is being classified at a slower speed S the magnet is not energized for a holdolf time T equal to For condition 1 where:

the longest sheet L is traveling at top speed S where the distance the sheet travels from the time the magnet is energized until the gate becomes magnetized is X. The magnet is energized the following period of time before the fault reaches the gate:

X +L t For condition 2 where: a shorter sheet L is traveling at top speed S and the energization of the magnet is held off for a period of time after the magnet would have been energized for condition 1. This period of time is the first holdofi' time T ho.

For condition 3 where:

the longest sheet L is traveling at a slower speed .8 and the energization of .the magnet is held off for a period of time after the magnet would have been energized for condition 1. This period of time is the second holdolf timeT ho.

T iw=s For condition 4 where: a shorter sheet L is traveling at a lower speed S and the energization of the magnet is held ofi fora period of time after the magnet would have been energized for condition 1. This period of time is the third holdoli time T 110.

T3hO= TghO After the magnet has been energized it should remain energized for an energization period to keep the gate magnetized until the selected sheet has been removed. The gate should remain magnetized for a certain period of time after the tail of the selected sheet reaches the gate to insure that the seleceted sheet is removed, and inthis particular embodiment this is one half of the length of the sheet being classified, divided by the speed 2 X SX Also after the magnet has been deenergized, a certain period of time Td is required for the gate to become demagnetized and this time Td may be subtracted from the time the magnet is energized to keep the gate magnetized.

For condition 1 the period of time that the magnet is energized for the longest sheet L traveling at the top speed S is from the time the fault reaches the distance L +X from the gate until the magnet is deenergized. This time may be expressed as:

X l L L 1 S! 2 81 Td For condition 1 this time may also be termed the total time.

For condition 2 where a shorter sheet L is traveling at the top speed S the period of time that the magnet must remain energized is from the time the fault reaches the distance X-i-L from the gate until the magnet is deenergized, minus the first holdofi time T 710. From the time the fault reaches the distance X+L from the gate until the magnet is deenergized is known as the first total time T t and for a shorter sheet L traveling at top speed S is:

The energization period for condition 2 is the first total time T t minus the first holdotf time T 110.

Similarly for condition 3, the period of time from the time the fault reaches the distance X+L from the gate until the magnet is deenergized is known as the second total time T t and for the longest sheet L traveling at the slower speed S is:

S2 2 x Td The energization period for condition 3 is the second total time T t minus the second holdoff time T ho.

In a similar manner for condition 4, the period of time from the time the fault reaches the distance X+L from the gate until the magnet is deenergized is known as the third total time T and for the shorter sheet L traveling at the slower speed S is:

X L L 1 ai 2 X 2) Td The energization period for condition 3 is the third total time T t minus the third holdoff time T ho.

Thus the period of time the magnet is energized for the four different conditions is the total time minus the holdoff time.

In the particular embodiment described herein a total timer 91 or 93 in FIGURE 1 is energized as described previously when the displaced pin in

pin wheel

53 or 55 closes switch 63, 65 or 67 indicating that a fault in a sheet is a distance X-i-L from the appropriate gate. As described, the holdotf timers 85 or 87 are energized at the same time.

The holdoff timers 85 and 87 actuate a time delay from the time when the fault in a sheet reaches the distance X-l-L from a gate until the magnet is energized. This time, as explained earlier, varies according to the length of sheets being classified and the speed of the sheet.

The total timers 91 and 93 actuate a time delay from the time when the fault in a sheet reaches the distance X+L from a gate until the magnet is deenergized. This time, as explained earlier, varies according to the length of sheets being classified and the speed of the sheet.

As described in more detail with reference to FIGURE 4, the holdotf timers 85 and 87 and the total timers 91 and 93 are timers which measure a period of time approximately inversely proportional to the voltage applied.

The voltage applied to the timers is determined by the setting of

switches

89 and 95 and the speed of the system as measured by the tachometer 94. Table 1 shows the setting of switches 89 and 94 for the different lengths of tin strip to be classified.

Switches

89 and 95 are tied together so they are connected to corresponding contacts.

The voltage applied to the timers is dependent on tachometer voltage and which contact in the voltage dividing networks 97 and 99 the timers are connected to.

The timers were selected by taking the equations described earlier for the holdofi times and the total times. To select the times for the holdotf timers the holdoff time in seconds was recalculated for the longest strip traveling at different speeds. A curve was plotted using the different points arrived at. The other lengths to be classified were so used to calculate the holdoif time for each of these lengths for different speeds. Curves were also plotted for each of the different lengths. The resultant curves for the different lengths are shown in FIGURE 2.

For each sheet length, 18 inches, 22.87 inches, 27.75 inches, 32.62 inches and 37.5 inches, the holdotf time in seconds was plotted against the speed in percent of tachometer volts delivered from the tachometer.

A timer was selected that could be adjusted to time the required time in seconds in response to the selected combined length and speed. The timer curve in FIGURE 2 is shown timing zero seconds with an tach volts input to approximately 0.8 second with zero tach volts input.

As shown when contact 97a is connected to the holdoff timer, when 37.5 inch sheets are being classified the holdolf time in seconds varies from zero seconds for tach volts input to approximately 0.3 second holdoff time for a 40% tach volts input.

The longer holdoif times for the shorter lengths were obtained by the voltage divider network 97 applying less voltage to the timers for the shorter lengths for the same percent of input tach volts.

The same procedure was followed in calculating the total times for the different lengths and plotting the curves as shown in FIGURE 3. The timer curve varies from approximately 0.3 second at 100% tach volts input to approximately 1.8 seconds at zero tach volts input. The voltage applied to the timer from the tachometer was varied for the different lengths by the contact to which the timer was connected in the voltage divider network 99.

Five lengths of sheets are shown being classified by the apparatus shown. In the voltage divider and FIG-

URES

2 and 3 it can be seen that independent of the voltage from tachometer 94 the greatest voltage is applied to switch 8% from contact 7a to the holdotf timers at the same time the smallest voltage is applied to the total timer from contact 99a. As switches 89 and are moved for the different lengths to different contacts, inverse voltages are applied to the timers except when the same voltages are applied from contacts 970 and 990. This is because the timers time a time delay approximately inversely proportional to the voltage applied and as the length being classified becomes less the holdoff times become greater as shown in FIGURE 2, requiring less voltage and the total time becomes less as shown in FIGURE 3, requiring more voltage. Examination of the equations for deriving the holdoif and total times also shows this.

The operation of the classifying system for classifying sheets of different lengths and at different speeds has been explained. It can be seen that in the embodiment described,

connected switches

89 and 95 must be moved for the different lengths. This may be made manually or automatically if the lengths were measured automatically by measuring means such as photoelectric cells. The adjustment as to speed is made automatically by the tachometer output.

The accuracy of the classifying system is dependent on the separation between the sheets and the opening of the gate. FIGURE 6 shows three sheets in row A separated by a distance Z and the same three sheets in row B after they have traveled a distance equal to Z. X is the distance the sheet travels after energization of the magnet before the gate becomes magnetized. Y is the opening of the gate. If the fault is in the tail of the sheet the holdoit" time will be sufiicient to catch the head of the sheet, but the total time will catch the following sheet if one half of the length of the sheet L/ 2 is greater than the separation Z of the sheets. For instance in FIGURE 6 where the separation Z between the sheets is less than one half of the length of the sheets L/2 the gate will remain magnetized to point W and will catch the following sheet. Therefore, Z (separation between the sheets) should be greater than L/ 2 (half the length of the sheet being classified).

Conversely, if Y (the opening of the gate) is greater than Z (the separation between the sheets) the total time specified will catch the selected sheet and not the following sheet, but will catch the preceding sheet. So, for accuracy, Z (separation between the sheets) should be greater than Y (opening of the gate).

The classifier as described is a one sheet classifier with one selected sheet being removed. It may be desirable to remove more than one sheet at a time and it can be seen that by making Z (the separation between the sheets) smaller than L/2 (one half of the length of the sheet being classified) two sheets will be removed at a time, the selected sheet and the following sheet. Also by making Y (gate opening) larger than Z (separation between the sheets) two sheets will be removed at a time, the selected sheet and the preceding sheet. By doing both together three sheets, the selected sheet, the following and the preceding sheet, will be removed. So the classifier may either be a one, two or three sheet classifier depending on the need.

The electronic timer shown in FIGURE 4 provides a time delay approximately inversely proportional to the input voltage. Minimum time delay corresponding to the maximum input voltage and the maximum time delay corresponding to the minimum input voltage are both adjustable. FIGURE 7 shows a graph where the time from zero to eight seconds is plotted against the input voltage applied from zero percent to 100 percent. The times may be adjusted so a curve may exist between zero input volts and other selected percent input volts provided the zero input voltage of the curve is not higher than the other selected percent input voltage end of the curve. Adjusted timer curves are shown in FIGURES 2 and 3. In FIGURE 2 the timer curve is from approximately 0.8 second time delay for zero input volts to zero seconds time delay for 80 percent input voltage. In FIGURE 3 the timer is adjusted so the timer curve is from 1.8 seconds time delay at zero input voltage to approximately 0.3 second time delay at 100 percent voltage input.

Referring again to FIGURE 4 terminal 141 is connected to a normally open contact 73, 75, 81 or 83 (FIGURE 1) and not normally connected to the input voltage. Normally open contacts 143 and 145 (FIG URE 4) and normally closed contacts 147 and 149 (FIGURE 4) are physically connected to a normally open contact 73, 75, 81 or 83 (FIGURE 1) and are closed or opened when the normally open contacts 73, 75, 81 or 83 (FIGURE 1) are closed. Referring now to FIGURE 4, before the initiating coil is energized capacitor 151 is charged (using normally closed contacts 147 and 149) through diode 153, diode 155 and resistor 157. Capacitor 151 charges until its voltage exceeds the zener breakdown voltage volts) of zener diode 161. During the half cycle when point 159 1s positive, diode 153 prevents capacitor 151 from .discharging through the zener diode 161. After capacitor 151 is charged, the current flows through zener diode 161, diode 155 and resistor 157 which limits the flow. The charge time of capacitor 151, reset time, is the time of the positive half cycle (no conduction) plus approxiptat iely 5 milliseconds, or approximately 14 milliseconds ota.

Coil 163 is energized when the grid voltage of tube 165 exceeds approximately 5 volts. Coil 163 corresponds to coil 1G1, 119, or 129 (FIGURE 1) depending on which timer the timer in FIGURE 4 is used as and the results of the energization of

coils

101, 119, 115 and 129 has been described elsewhere.

When the appropriate coil (69, 71, 77 or 79 in FIG- URE 1) has been energized terminal 141 is connected to the input voltage, contacts 147 and 149 are opened, and contacts 143 and are closed. The voltage between the grid and cathode of tube is composed of two parts, that due to the input volts is positive, point 167 to 169, and the charge on capacitor 151 is negative, point 171 to 167. As long as the voltage on capacitor 151 exceeds the input volts, the grid is negative and coil 163 remains deenergized.

At the beginning of a timing cycle capacitor 151 is fully charged. The length of the time interval is determined by the RC time constant of capacitor 151, resistor 1'73 and potentiometer 175, and by the level of the input voltage. When the input voltage equals the voltage on capacitor 151, the time interval is zero, and when the input voltage is low, a maximum length of time determined by the setting of potentiometer 173 is required to discharge capacitor 151. For explanation of minimum time adjustment, assume that input voltage is maximum and equal to that on capacitor 151 at the beginning of the time interval. If potentiometer 177 is turned clockwise, less than the maximum input voltage exists between points 167 and 169. It would thus take a small amount of time for capacitor 151 to discharge down to the reduced voltage, the time depending on the setting of potentiometer 177.

The storage means used in this embodiment are mechanical pin wheel timers. Other storage means of the electronic type may be used such as magnetic core shift registers, magnetic tapes, and magnetic drums. Other timers may also be used such as digital counters.

In summary, new and improved classifying apparatus for diverting preselected sheets from a conveyor system has been described. The invention has been applied to a tin sheet classifying operation. Only the selected sheet is diverted from the conveyor system. Sheets of different lengths may be sorted at different speeds.

While this invention has been explained and described with the aid of a particular embodiment thereof, it will be understood that the invention is not limited thereby and that many modifications will occur to those skilled in the art. It is therefore contemplated by the appended claim to cover all such modifications as fall within the scope and spirit of the invention.

What is claimed is:

In a sheet classifying system for classifying sheets including magnetic gating means for diverting sheets having faults therein from the classifying system, a pin wheel timer, means for displacing a pin in said pin wheel timer to select a sheet to be diverted by said magnetic gating means, means for moving said pin in said pin wheel timer in synchronism with the movement of the selected sheet in said classifying system, select means for producing a select signal when said pin has been moved to a position indicating that the corresponding selected sheet has moved to a predetermined distance from said magnetic gating means, hold-off timing means responsive to said select signal to magnetize said magnetic gating means after a first predetermined period of time as the head of the sheet with the fault therein approaches said magnetic gating means, total timing means responsive to said select signal to demagnetize said magnetic gating means after a second predetermined period of time as the tail of the sheet with the fault therein clears said magnetic gating means, means for producing length signals indicating the length of sheets being classified, means for producing speed signals indicating the speed of the classifying system and means responsive to said length and speed signals for varying said first and second predetermined periods of time to insure that all sheets with faults therein are diverted from the classifying system.

Rei'erences Qited by the Examiner UNITED STATES PATENTS SAMUEL F. COLEMAN, Acting Primary Examiner.

FRANK L. ABBOTT, ERNEST A. FALLER, JR,

Examiners.