US3341837A - Jam warning control circuit - Google Patents

Description

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United States Patent 3,341,837 JAM WARNING CONTROL CIRCUIT Harold Washington, Broadview, lll., assignor to Instrumentation and Control Systems, Inc., Villa Park, Ill. Filed Feb. 1, 1965, Ser. No. 429,510 12 Claims. (Cl. 340-259) ABSTRACT OF THE DISCLOSURE Electronic circuit control, for monitoring and controlling an automatic fed machine to determine jamming and prevent further use of the machine until malfunction is corrected.

This invention relates to control circuits for automatic machines and more particularly to circuits for controlling automatically fed machines when they jam.

One example of such a machine is a laundry combination comprising a washer-dryer coupled to a folder by a conveyor system. The output of the folder feeds into a stacker. The conveyor might be adapted to sort the wash into various classes and sub-classes. Thus, the laundry class linens might be divided into the sub-classes white and colored responsive to the amount of light reflected from the individual pieces of linen into a photo electric cell.

The control circuit of this invention is designed to monitor the flow of laundry through the conveyor system. When a machine jams, the laundry piles up and might become torn. Worse still, expensive machinery might be damaged or ruined.

Hence, an object of the invention is to detect the jamming of an automatic machine before any damage can occur.

Another object is to stop the products feeding into a jammed machine.

Yet another object is to divert the flow of input goods from the jammed machine into another machine which is not jammed.

These and other objects will become apparent from a study of the attached drawing in which:

The single figure is a schematic diagram showing a jam warning control circuit for a conveyor system associated with an automatic machine.

It should be clearly understood, however, that the control circuit of this invent-ion is not limited to use with this particular conveyor, or with any specific Inachine. Quite the contrary, the invention will find utility with many machines. It will also find utility wherever it is either necessary or desirable to monitor the flow of work pieces and to stop or divert such flow responsive to a congestion of such pieces.

In the drawing, a double, dot-dashed line separates a conveyor system from a jam warning control circuit 11.

The conveyor system 10 comprises a driving source of motive power (such as motor 15), a number of conveyor belts 16, 17 and 18, and a traflic flow selector 20. To make the showing generic, belt 16 is called an input and belts 17 and 18 are called outputs. Each of the conveyors 16, 17 and 18 is here shown as a belt travelling in a direction indicated by an arrow head. For example, the belt 16 travels in the direction indicated by the arrow head 21.

While the nature of associated machinery is not of essential importance to the invention, it is here assumed that a washer-dryer combination deposits laundry on belt 16. symbolically, this depositation is shown by the input arrow 22. It is also assumed that this laundry is conveyed through either of two folding machines by belts 17, 18 to either of two stackers. The output from the 3,341,837 Patented Sept. 12, 1967 folding machines is symbolically represented at 23 and 24.

The trafiic flow selector 20 is shown as a doorlike arrangement 25 which may swing to either of two positions under the control of any suitable device 26. The device 26 is controlled by a signal from a selector SEL (which could be a photo-electric cell). When the device 26 swings the door 25 to the position shown by solid lines, the laundry on conveyor 16 follows the path of the solid line arrow 28 to conveyor 18 in a folding machine and then to a stacker, at 24. When the device 26 swings the door 25 to the position shown by dashed lines, the laundry on conveyor 16 follows the path of the dashed line arrow 29 to conveyor 17 in another folding machine and then to a stacker, at 23. The terms class 1 output and class 2 output are intended as a generic disclosure of any desired sorting. It could be assumed that the class 1 output on conveyor 17 is white linens and the class 2 output on conveyor 18 is colored linens.

Means are provided for monitoring the flow of traflic through the conveyor system. More particularly, one detector 30 provides an output pulse for each item deposited on conveyor 16 by machine 22. Other detectors 31 and 32 provide an output pulse for each item expelled from the folding machines to the stackers, as indicated at 23 or 24. It Will be convenient to refer to the pulses from detector 30 as input pulses and the pulses from detector 31 or 32 as output pulses.

The input and output pulses have opposite effects. One adds and the other subtracts. As long as the input and output pulses tend to be interleaved so that opposites follow each other, the net result might be described as effectively centered at zero. However, if the operating machine (say, conveyor 17) jams, the number of input pulses exceeds the number of output pulses. The cumulative total of the pulses drifts away from zero, and the jam warning circuit 11 commands the conveyor system to take appropriate action. This action could be to stop the conveyor. Or it could be to divert the flow of laundry by changing the position of door 25.

The jam warning control circuit for accomplishing this function comprises a gate circuit 40, a memory circuit 41, a jam detector 42, a timer circuit 43, and an output control circuit 44. The input gate circuit includes an electronic switch 50, here shown as an NPN transistor which is normally biased to an off condition by 12 volts applied to its base via resistor 51.

When a piece of laundry is fed into the machine, the detector 30 provides an input pulse. Then the timer 52 responds and applies a ground potential to the upper end of resistor 53 for a period of 150 milliseconds. The two series connected resistors 51 and 53 divide the voltage and apply a forward bias potential to the base of transistor 50, which turns on.

When the electronic switch turns on, a 12 volt potential is applied to the lower end of a voltage divider formed by the two resistors 55 and 56. The voltage division is such that a forward bias appears on the control electrode of a constant current generator device, (which is here shown as including a PNP transistor 57).

Means are provided for remembering the number of pieces of laundry in the machine at any given time. This the switch 57 turns off, the incremental charge remains stored on the capacitor.

The folding machine will process an average number of pieces of laundry during any given period of time. However, the number of pieces may vary at any instant as compared with any other instant according to the time required to complete the folding of the individual pieces. Therefore, in effect, the conveyor system 16-18 stores laundry while the folding machine is processing it and the detectors may send more input than output pulses. The capacitor 60 thus receives more than one incremental charge.

Under normal operation, however, the folder soon completes its cycle and sends a folded piece of laundry to the stacker, as symbolically shown by the arrows 23 or 24. As the laundry leaves the folder, the detector cuit 11. Then, the capacitor 60 is partially discharged. 31 sends an output pulse to the jam warning control cir- Thereafter, on the average, one piece of laundry leaves the folding machine every time that another piece of laundry enters it. Thus, the input and output pulses will tend to follow each other. Otherwise, pieces of laundry collect in the folder and it jams.

Assume first that the machine does not jam and a folded piece of laundry passes out of the folder every time that a piece enters. When the contacts 31 or 32 close, a timer, such as 65, applies a strong negative pulse (in the order of 24 volts, for this circuit) to an OR gate 66 at the input of the timer circuit 43.

The timer circuit 43 is shown as a monostable circuit having two active elements which are a PNP transistor 67 and a unijunction transistor 68. A series of three resistors 69, 70 and 71 form a voltage divider connected between 12 and 12 volts, for normally applying a reverse bias to the base of the transistor 67. The resistors 72-75 form a bias network which provides the potentials that normally hold the unijunction transistor 68 in an off condition.

When either of the timers 65 or 76 applies a high negative voltage to the lower end of the resistor 70, the transistor 67 turns on. This generates a voltage pulse which passes over the circuit from ground G1 through the emitter-collector of transistor 67, and capacitor 77 to the base B2 on the unijunction transistor 68. This pulse reduces the voltage difference between base B2 and emitter E to turn on the transistor 68.

Before the unijunction transistor 68 turns on, the upper plate of capacitor 78 is standing at a potential which is set by the voltage divider 73, 75. The lower plate is at 12 volts. After the transistor 68 turns on, the capacitor 78 discharges into the emitter E for holding the unijunction transistor 68 on for a predetermined period of time. After the capacitor 78 discharges sufficiently, the emitter current reduces, and the transistor 68 turns off. The monostable timer circuit 43 then returns to normal with both of the transistors 67 and 68 turned off.

While the transistor 68 is on, a ground pulse is sent over wire 79 and into the control electrode of an elec tronic switch, here shown as an NPN transistor 80. This pulse makes the base positive relative to the emitter, and the transistor 80 turns on. The emitter and collector of the transistor 80 are connected through a current limiting resistor 81 to discharge the capacitor 60. The circuit values are selected so that the potential which drains olf the capacitor 60 is exactly equal to the incremental charge stored on the capacitor when a piece of laundry trips the input detector 30.

It should now be clear how the jam warning control circuit 11 operates when there is no jam in the folding machine. Each time that a piece of laundry enters the folding machine, detector 30 sends an input signal and an incremental charge is stored on the capacitor 60. Each time that a piece of laundry leaves the folding machine contacts 31 or 32 close, and transistor 80 conducts to discharge the capacitor 60 by one incremental charge.

For any one of many reasons, which are not essential to the invention, it is desirable for the circuit to give a jam warning only after a predetermined number of incremental charges have been stored on the capacitor 60 with no intervening discharges through the transistor 80. Thus, the circuit values are selected so that the total charge on capacitor 60 reaches a threshold potential after a predetermined number of incremental charges are stored. An adjustment of the potentiometer 58 selects the exact number of incremental charges required to reach this threshold potential. In one machine, this number could be varied from four to six.

Means are provided for detecting a jammed condition responsive to the charge on capacitor 60 reaching the threshold potential. In greater detail, the jam detector circuit comprises a silicon controlled switch (SCS) 82 biased to an off condition by the resistors 83a and 83b. A SCS such as this will turn on when the voltage at its anode A exceeds the voltage at its gate G. Thus, the circuit values are selected so that the SCS 82 turns on responsiveto the storage of the threshold potential on the capacitor 60. The capacitor 84 slows the voltage change across the SCS 82 so that it will not fire on a lower than usual potential owing to its rate sensitivity. Also, the resistor 83a, in series with the capacitor 84, acts as a filter to pass transients which might otherwise turn off the SCS 82.

Once the SCS 82 turns on, current flows through the bias resistor 83b and a coupling resistor 85 to cause the output control circuit 44 to operate.

The output control circuit 44 includes a relay connected in parallel with a spark suppression diode 91 and a current dividing resistor 92. The current through this parallel circuit is manually controlled at a pushbutton 95 and automatically controlled by an electronic switch, such as a silicon controlled rectifier (SCR) 96. The current through resistor 92 holds the SCR on after it turns on. A capacitor 97 is connected across SCR 96 to slow the rise time of the applied firing voltage and pass transients.

The operation of the output control circuit 44 begins when the SCS 81 turns on to apply a voltage through the resistor 85. This turns on the SCR 96. When the SCR conducts, current divides between the relay 90 and the resistor 92. The current through resistor 92 latches the SCR 96 in its on condition unti-l pushbutton 95 is pushed.

The relay 90 operates. At contacts 96, it opens a circu t to prevent the normal selection of a folding machine conveyor belt 17 or 18. At contacts 97, it transfers the laundry input from the jam-med folding machine belt to the other non-jammed machine belt. Contacts 98 open to remove electrical power from the motor 15 and thereby stopthe jammed folding machine. The contacts 99 close to give an alarm which could be to light (or turn off) a lamp 100.

Maintenance personnel respond to the alarm and remove the jammed laundry from the machine. Then, the pushbutton 95 and 101 is pushed. The interruption of current at 95 turns off the previously latched SCR 96 and releases the relay 90. The closing of contacts 101 discharges the capacitor 60. The circuit is now normal.

If the power is removed, the charge on the capacitor 60 leaks off through the diode 105. This diode is poled with a reverse bias polarity. Thus, the capacitor 60 can only discharge through the diode 105 at the very slow rate allowed by the extremely low, reverse bias, leakage current. Therefore, the riode has no real effect as long as the machine continues to operate.

- While the foregoing description has referred to laundry machines, the invention will find utility wherever it is necessary to monitor a flow of input and output signals. Those skilled in the art wiil readily perceive many needs for such monitoring. Hence, the attached claims are to be construed broadly enough to cover all equivalents reasonably included within the true spirit of the invention.

I claim:

1. An automatic machine comprising a conveyor system for transporting work pieces, said system having an input and a plurality of outputs, means for directing the flow of said work pieces from said input to a particular one of said outputs, means for detecting jam conditions during which said work pieces ceases to flow to one of said outputs, and means responsive to said detection for giving an alarm and transferring said flow of said work pieces to another of said outputs.

2. The machine of claim 1 wherein said work pieces are pieces of laundry and said conveyor system transports said pieces of laundry through a folding machine.

3. A jam warning system for monitoring the flow of Work pieces through a machine, means responsive to an entrance of a work piece into said machine for storing a memory of said entrance, means responsive to an exit of a work piece from said machine for canceling said memory, alarm means responsive to the memory storage of the entrance of a predetermined number of said work pieces without an exit of any pieces for giving an alarm, and means responsive to said alarm means for transferring said flow of work pieces from said machine to another machine.

4. An automatic laundry system comprising means for conveying pieces of laundry through a folding machine to a stacker, means for monitoring the flow of traffic through said conveyor, memory means for storing a memory of each piece of laundry entering said conveyor, and for canceling the storage of said memory responsive to each piece of laundry leaving said machine, said memory means comprising a capacitor, gate means for applying a pulse to said capacitor responsive to the entry of each of said pieces of laundry on said conveyor, means responsive to each exit of a piece of said laundry from said conveyor for discharging said capacitor, and means responsive to the storage of a predetermined number of pulses on said capacitor for giving said jam warning.

5. The system of claim 4 wherein said discharging means comprises a monostable circuit triggered by said exit of said piece of laundry, and an electronic switch in series with a current limiting device, said series circuit being connected across said capacitor, means responsive to the triggering of said monostable circuit for turning on said switch for the unstable period of said monostable circuit.

6. The system of claim 5 and means for adjusting the potential stored on said capacitor responsive to each of said pulses to select the number of pieces of laundry required to be in said machine simultaneously to give said jam warning.

7. A jam warning system comprising means for monitoring the flow of work pieces passing through an automatically fed machine, means responsive to each entrance of a work piece into said machine for storing a memory of said entrance, said memory means comprises a capacitor and a gate means for applying a voltage pulse having a predetermined volt-second characteristic to said capacitor responsive to the entry of each of said work pieces into said machine, means responsive to each exit of a work piece from said machine for triggering a monostable timing circuit, an electronic switch controlled by said monostable circuit and connected in series with a current limiter, said series circuit being connected across said capacitor, the circuit values being such that the triggering of said monostable circuit drains a charge having said volt-second characteristic from said capacitor, and alarm means operated responsive to the storage of predetermined number of said voltage pulses without an exit of any work pieces for giving an alarm.

8. The system of claim 7 and means responsive to said alarm means for transferring said flow of work pieces from said machine to another machine.

9. A monitor circuit for observing the flow of trafiic through an automatic machine, means for storing a memory of each piece of trafilc entering said observed flow, said memory means comprises a capacitor, gate means for applying a pulse of a predetermined characteristic to said capacitor responsive to the entry of each of said pieces of trafiic into said observed flow, means responsive to each piece of traific leaving said observed flow for partially discharging said capacitor to cancel the storage of one of said pulses on said capacitor, and means responsive to the storage of a predetermined voltage on said capacitor for giving an alarm signal.

10. The system of claim 9 wherein said discharging means comprises a monostable circuit triggered by said piece of traflic leaving said observed flow, and an electronic switch in series with a current limiting device, said series being connected across said capacitor, and means responsive to the triggering of said monostable circuit for turning on said switch for the unstable period of said monostable circuit.

11. The system of claim 10 wherein said alarm means comprises a silicon controlled switch connected to fire and latch when the voltage on said capacitor reaches a predetermined level.

12. The system of claim 11 and means for manually unlatching said switch to cancel said alarm signal.

References Cited FOREIGN PATENTS 764,607 6/1954 England.

NEIL C. READ, Primary Examiner. D. L. TRAFTON, Assistant Examiner.

Claims (1)

1. 3. A JAM WARNING SYSTEM FOR MONITORING THE FLOW OF WORK PIECES THROUGH A MACHINE, MEANS RESPONSIVE TO AN ENTRANCE OF A WORK PIECE INTO SAID MACHINE FOR STORING A MEMORY OF SAID ENTRANCE, MEANS RESPONSIVE TO AN EXIT OF A WORK PIECE FROM SAID MACHINE FOR CANCELING SAID MEMORY, ALARM MEANS RESPONSIVE TO THE MEMORY STORAGE OF THE ENTRANCE OF A PREDETERMINED NUMBER OF SAID WORK PIECES WITHOUT AN EXIT OF ANY PIECES FOR GIVING AN ALARM, AND MEANS RESPONSIVE TO SAID ALARM MEANS FOR TRANSFERRING SAID FLOW OF WORK PIECES FROM SAID MACHINE TO ANOTHER MACHINE.

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