US3078394A - Timer - Google Patents

Description

33,673,394 Patented Feb. 19, 1963 3,678,394 'HMER Melvin iE. iieverenr, St. Clair, Mich., assigner to Diamond (Crystal Sait tlornpany, St. Clair, Mich., a corporation of Michigan Filed May 15, i959, Ser. No. 313,435 8 Claims. (Cl. 3i7--l3tl) This invention relates to electrical timers for establishing a preselected time delay between the occurrence of two events.

In general, the principles of the present invention are applied to a timer for use as an element of a system for dispensing a controlled quantity of liquid into each of a succession of containers. The containers are transported on a continuously moving conveyor system past a liquid dispensing nozzle. When a preselected relationship exists between a container and the nozzle, as determined by a photoeleetric sensing arrangement, a solenoid is actuated to cause the liquid to be discharged into the container. With a constant flow rate, timing of the period of energization of the valve-controlling solenoid permits accurate control of the quantity f liquid which is delivered.

The present invention relates to improved photoelectric sensing, control and timing circuitry adapted for use in such a system, and through its practice improved accuracy and consistency of operation can be achieved with a minimization of maintenance cost and circuit malfunctioning.

rl`he principles, objects and features of the invention will be understood from the following detailed description of a preferred embodiment thereof when read with reference to the drawing in which the single FIGURE illustrates in diagrammatic forni a timing apparatus embodying the principles of the invention.

he system shown in the drawings is energized from an alternating voltage source lil which, upon the closure of switch i2, is connected across the primary winding of transformer ifi. The resultant alternating voltage induced in the center tapped secondary winding of transformer ld is full-wave rectified by means of dual diode ld, is filtered by the capacitor-input resistance-capacitance filter network including capacitors i8 and 2@ and resistors 22 and 24 and is applied across a pair of serially interconnected gaseous discharge voltage regulating devices 26 and 2S. The anode of device 26 is grounded, a regulated negative voltage appears at the cathode of device 2.6 and hence at conductor 30 and a more negative voltage appears at the cathode of device 2S and hence at conductor 32.

The negative voltage between conductor 32 and ground is developed across serially interconnected resistors Sii and 3io which constitute a voltage divider network, with the value of resistor 3d being less than that of resistor 36 so that the voltage at conductor 38, interconnecting re sistors 3tlaud 36, is appreciably negative relative to the voltage on conductor Eil.

A photoelectric tube it? is physically disposed in a position in the path of a light beam so that it is energized, and hence in a low-iinpedanee state, at all times except when the light beam impinging upon that phototube is interrupted as by a can or other container traveling on the conveyor and passing, during its course of travel, through the light beam. The cathode of phototube fltl is connected to conductor 38 and the anode is connected to conductor 3G via conductor dit and resistor d2. When the light beam impinges upon the phototube di) so that its impedance is low, the potential at conductor irl is quite negative relative to the potential at conductor Si) and approaches the potential at conductor 38. When that light beam is interrupted, phototube dil assumes a highimpedance condition, that is, its resistance is high relative to that of resistor d2, little current flows through resistor i2 and the potential at conductor ld is but slightly negative relative to the potential on conductor 30.

A serially interconnected capacitor 56 and resistor 4S are connected in parallel with resistor 42, and resistor i8 is connected between the control grid and cathode of an electron discharge device Srl, which illustratively takes the form of a pentode Vacuum tube. Screen grid bias for tube Se is derived through a potentiometer S2 the resistive element of which is connected between conductor Sil and ground. The suppressor grid is connected to the cathode, and the anode is `connected to ground through the winding of a plate relay 5d having a pair of normally closed contacts 56. Relay S4 has two stables states, energized and released, and contacts 5d have two stable states, open and closed, respectively.

With light having iinpinged upon phototube i6 for a period of time and equilibrium conditions having been reached, the potential at the right-hand electrode of capacitor 46 will be substantially equal to the potential on con ductor Sli so that there is substantially zero bias on tube Sil, and the left-hand electrode of capacitor 46 will be at a potential approaching the potential of conductor 38 so that capacitor 46 will be charged with its left-hand elec trode negative with respect to its right-hand electrode. Tube 5l) will, under Zero bias conditions, conduct sutilcient anode current to energize plate relay 54 so as to open the contacts 56, as shown. When the light beam is interrupted as by a traveling object, phototube ttl is converted to a high-impedance condition, and conductor d4 tends instantaneously to change in potential toward the potential of conductor Sil. Since the charge on capacitor lo cannot change instantaneously, the rightJnand electrode of capacitor do tends to be driven in a positive direction instantaneously, making the control grid of tube 5i@ positive relative to the cathode thereof. Since tube Sil is already conducting suiiciently to fully encrgize plate relay 54, this change will not effect the state of relay 54.

lliuring the time that the light directed towards phototube Sti is interrupted, capacitor 46 will tend to discharge through resistors 4Z and With the parameters used in the constructed embodiment of the invention, the time constant of this circuit was but a few milliseconds and kconsequently in normal practice, capacitor i6 would tend to become substantially fully discharged during this interval and tube Sii would be returned substantially to a zerobias condition.

When the impingernent of the light beam upon phototube il? is reestablished, the potential on conductor 44 tends instantaneously to approach the potential on conductor and, since capacitor 46 cannot change charge instantaneously, the right-hand electrode thereof and the control grid of tube 5d are instantaneously driven in a negative direction, establishing a substantial negative bias on tube Sti and driving that tube towards or to grid cutofi or at least to the point at which the anode current is insuiiicient to maintain relay Sli operated. As a result, contacts 56 close. Capacitor lo will then commence to charge through resistor d8 so that the potential at the control grid of tube Sil will gradually become less negative relative to the cathode and, after a preselected short interval, the anode current of tube Sil will increase to the point where plate relay Sd will again operate to again open contacts 56. In the preferred practice, the closed period of contacts S6 is but a few milliseconds in duration.

When contacts 56 are closed, a circuit is completed from ground, through the closed contacts, charging resistor 5S, conductor 60', capacitor 62, and to the negative voltage on conductor 3d. As a result, capacitor 62 is charged with its upper electrode positive relative yto its lower electrode. Conductor 6l), connected to the upper adressa electrode of capacitor 62, will change in potential during this charging period from a substantial negative value towards ground potential. ln a constructed and preferred embodiment of the invention, the time constant of the circuit including resistor 58 and capacitor 62 was greater than the sum of the time constant of the RC circuit at the input of tube d plus the release and operate times of relay 5d so that the extent of the charge on capacitor 62 was determined primarily by the closed time of contacts Se'. While conductor dit does not reach ground potential during this period, it sutiiciently closely approaches ground to bias tubes 64 and 66 quite substantially conductive.

Tubes ed and 66 are illustrated as dual triodes with all four sections connected in parallel, with the control grids connected to conductor 60, with the cathodes connected to ground, and with the anodes being connected through the winding of solenoid 68 to a source of direct voltage comprising a half-wave rectifier itl supplied from source and a lter network comprising capacitors 72 and 7d and resistors '76, the anode to cathode voltage for tubes 64 and 66 being developed across capacitor 74.

When tubes 64 and 66 are rendered conductive, solenoid 68 is actuated. This may be considered to be the load device for the system. Solenoid 6d can be ern` ployed to actuate a valve to cause liquid to be ejected from a nozze, but in the preferred practice, solenoid 63 physically deliects a nozzle through which liquid is continuously owing from a position in which the liquid is directed over a return path to a position in which the liquid is directed into the container. The delay between the reestablishment of the light beam and the instant of actuation of the solenoid may be adjustable if desired.

When contacts 56 open, the above described charging circuit for capacitor 62 is disestablished and that capacitor commences to discharge through a series network, including lxed resistor 78, variable resistor 30 and Calibrating resistor 82, connected in shunt of capacitor 62. As a result of this discharge, the potential on conductor 60 and hence at the control grids of tubes 64 and 66 will gradually become more negative. After capacitor 62 is discharged to a preselected degree, the potential on conductor 60 will have become sufciently negative to reduce the current in tubes dit and 66 to the point where solenoid 63 will release, to close the liquid dispensing controlling valve or to shift the nozzle so that the stream is directed over a return path.

The time constant of the circuit including capacitor 62 and resistors 7S, 80 and S2 is preferably substantially longer than the time constants of the circuit hereinbefore described so that the liquid may be ejected from the nozzle for an appreciable period. In the above noted constructed embodiment, time delays from a few milliseconds to a substantial period were provided.

lt will be observed that the circuit is operated on a direct current basis and that the contacts S6 are only called upon to carry the small amplitude charging currents for capacitor 62 rather than the relatively large amplitude (approaching an ampere) for energizing the solenoid 68.

The arrangement as above described produces actuation of the solenoid 63 in response to the reestablishment of the light beam following an interruption thereof, that is, the action is initiated or triggered in response to movement of the trailing edge of the container past a preselected point. It is also contemplated that the action may be triggered in response to the leading edge of the container, that is, in response to the interruption of the beam following a period of establishment of the beam. This can be accomplished, in one manner, by reversing the connections to the two electrodes of phototube i0 and correspondingly adjusting the direct voltages applied to those electrodes. For example, in the illustrated arrangement, correct operating potentials are applied to the electrodes of tubeid by connecting the anode thereof through resistor 4t2 to conductor 30, the potential of which is negative with respect to ground by the magnitude of the voltage across regulator Z6, and by connecting the cathode to conductor 38. If resistors 34 and 35 were equal (assuming tubes 26 and Z8 to be identical) the potential at conductor 38 would equal that at conductor 30. Consequently, as above noted, resistor 3dis selected to have a smaller value of resistance than resistor 36, with those values being selected to apply a potential to the cathode of tube 40 which is negative relative to the potential at conductor 30 by a preselected amount. To modify the equipment to respond to the leading edge of the container, resistors 34 and 36 can be interchanged and the connections to the anode and cathode of tube i0 reversed. ln a constructed embodiment, resistors 34 and 36 had values of 33,000 ohms and 100,000 ohms, respectively. For the changed mode of operation, resistors 34 and 36 would have representative values of 100,000 ohms and 33,000 ohms, respectively, the anode of tube 40 would be connected to the junction of resistors 34 and 36, and the cathode of tube 4d would be connected to conductor d4. No other circuit changes are necessary.

While it will be apparent that the embodiments of the invention herein disclosed are well calculated to fullill the objects of the invention, it will be appreciated that the invention is susceptible to modication, variation and change without departing from the proper scope or fair meaning or the subjoined claims.

What is claimed is:

l. In a control equipment eifective in response to the transient chance of a licht beam by a movable Object to actuate a load device for a selectable interval of time, the combination of relay means having two stable states, a photoelectric device in the path of the light beam, means including said photoelectric device and iirst timing means responsive to a change of the illumination on said photoelectric device in one direction for changing the state of said relay means from a first to a second state for a pr.,- selected short interval ot time and eiective thereafter even in the absence of a subsequent change of the illumination on said photoeleetric device to change the state of said relay means from said second state to said rst state at the end of said preselected short interval of time, a capacitor, a resistor, a source of energy, means including said relay means and said source and effective while said relay means is in said second state for changing the charge on said capacitor in one direction, means including said resistor eective while said relay means is in said first state for changing the charge on said capacitor in the opposite direction and at a rate controlled by said resistor, and means including amplifying means for operating the load device while the charge on said capacitor differs in one direction from a preselected magnitude and while said relay means remains in said tirst state and for releasing the load device when the charge on said capacitor dilers in the other direction from said preselected magnitude.

2. ln a control equipment effective in response to the transient change of a light beam by a moving object to actuate a load device for a selectable interval of time, the combination of first timing means for operating the load device for the selectable interval of time, an electron discharge device having conductive and noneonductive states, a pair of contacts, means including said electron discharge device for switching said contacts from one to another oi two stable states in response to changes of the state of said electron discharge device, a photoelectric device in the path of said beam, and means including said photoelectric device and second timing means for biasing said electron discharge device to one of said states and er'liective in response to the transient change of the light beam for changing the state of said electron discharge device fron a first to a second one of said states for a preselected short interval of time and etlective thereafter even in the absence of a subsequent change in the illumination on said photoelectric device and independently of said first timing means to change the state of said electron discharge device back to said first state at the end of said preselected short interval of time, said preselected short interval of time being short relative to said selectable interval of time, said first timing means being controlled by said eiectron discharge device and comprising a capacitor, means effective while said contacts are in one of said states for changing the magnitude of the charge on said capacitor in one direction, means effective while said contacts are in the other one of said states for changing the magnitude of the charge on said capacitor in the other direction, and means effective only while the charge on said capacitor exceeds a preselected magnitude for operating the load device.

3. In a control equipment effective in response to the transient change of a light beam by a moving object to actuate a load device for a selectable interval of time, the combination of an electron discharge device having conductive and nonconductive states, a pair of contacts, means including said electron discharge device for switching said contacts from one to another of two stable states in response to changes of the state of said electron discharge device, a photoelectric device in the path of said beam, means including said photoelectric device and rst timing means for biasing said electron discharge device to one of said states and effective in response to the restoration of the light beam following interruption of the light beam for changing the state of said electron discharge device for a preselected short interval of time the duration of which is independent of the duration of interruption of the light beam, a load device, and means including second timing means effective after and in response to a change of said first contact from said one to said other of said stable states followed by a change from said other to said one stable state for operating said load device for a different preselected interval of time.

4. In a control equipment effective in response to the transient interruption of a light beam by a moving object to actuate a load device for a selectable interval of time, the combination of an electron discharge device having conductive and nonconductive states, a pair of contacts, means including said electron discharge device for switching said contacts from one to another of two stable states in response to the changes of the state of said electron discharge device, a photoelectric device in the path of said beam, means including said photoelectric device and first timing means for biasing said electron discharge device to one of said states and effective in response to the restoration of the light beam following interruption of the light beam for changing the state of said electron discharge device from a first to a second one of said states for a preselected short interval of time the duration of which is independent of the duration of the interruption of the light beam and independent of the duration of the restored illumination from the light beam and second timing means controlled by said contacts for operating the load device for the selectable interval of time comprising a capacitor, a first resistor, a source of energy, means including said contacts and effective while said contacts are in said other state for effecting a charging circuit for said capacitor including said first resistor and said source, a second resistor, means including said second resistor connected in shunt of said capacitor effective while said contacts are in said one state for discharging said capacitor at a rate controlled by said second resistor,

another electron discharge device, and means including said other electron discharge device having the load device in the anode circuit thereof effective only while the charge on said capacitor exceeds a preselected magnitude for operating the load device.

5. In a control equipment effective in response to the transient interruption of a light beam by a moving object to actuate a load device for a selectable interval of time, the combination of an electron discharge device having conductive and nonconductive states, a pair of contacts, means including said electron discharge device for switching said contacts from one to another of two stable states in response to changes of the state of said electron discharge device, a photoelectric device in the path of said beam, means including said photoelectric device and first timing means for biasing said electron discharge device to one of said states and effective in response to the interruption of the light beam for changing the state of said electron discharge device for a preselected short interval of time the duration of which is independent of the duration of interruption of the light beam, a load device, and means including second timing means effective after and in response to a change of said contacts from said one to said other of said stable states followed by a change from said other to said one stable state for operating said load device for a different preselected interval of time.

6. The combination of claim 1 further including a second resistor connected in shunt of said capacitor and in which said amplifying means comprises another electron discharge device having the load device in the output circuit thereof.

7. In a control equipment effective in response to the transient change of a light beam by a movable object to actuate a load device for a selectable interval of time, the combination of relay means having two stable states, a photoelectric device in the path of the light beam, means including said photoelectric device and first timing means responsive to a change of the illumination on said photoelectric device in one direction for changing the state of said relay means from a first to a second state for a preselected short interval of time determined by said first timing means and effective thereafter even in the absence of a subsequent change of the illumination on said photoelectric device to change the state of said relay means from said second state back to said first state at the end of said preselected short interval of time, and second timing means controlled by said relay means and effective in response to the change of state of said relay means from said first state to said second state and back to said first state for operating the load device for a selectable length of time longer than said preselected short period of time.

8. The combination of claim 7 in which each of' said first and said second timing means includes a resistor and a capacitor connected in a change-of-charge circuit with said resistor.

References Cited in the file of this patent UNITED STATES PATENTS 2,165,048 Gulliksen July 4, 1939 2,621,808 Blakeney Dec. 16, 1952 2,738,448 Bokser Mar. 13, 1956 2,869,044 Horwege et al. Jan. 13, 1959 OTHER REFERENCES Garner: A Transistor Timer, Radio and Television News, October 1953, pages 68, 69 and 187.

Claims (1)

1. IN A CONTROL EQUIPMENT EFFECTIVE IN RESPONSE TO THE TRANSIENT CHANGE OF A LIGHT BEAM BY A MOVABLE OBJECT TO ACTUATE A LOAD DEVICE FOR A SELECTABLE INTERVAL OF TIME, THE COMBINATION OF RELAY MEANS HAVING TWO STABLE STATES, A PHOTOELECTRIC DEVICE IN THE PATH OF THE LIGHT BEAM, MEANS INCLUDING SAID PHOTOELECTRIC DEVICE AND FIRST TIMING MEANS RESPONSIVE TO A CHANGE OF THE ILLUMINATION ON SAID PHOTOELECTRIC DEVICE IN ONE DIRECTION FOR CHANGING THE STATE OF SAID RELAY MEANS FROM A FIRST TO A SECOND STATE FOR A PRESELECTED SHORT INTERVAL OF TIME AND EFFECTIVE THEREAFTER EVEN IN THE ABSENCE OF A SUBSEQUENT CHANGE OF THE ILLUMINATION ON SAID PHOTOELECTRIC DEVICE TO CHANGE THE STATE OF SAID RELAY MEANS FROM SAID SECOND STATE TO SAID FIRST STATE AT THE END OF SAID PRESELECTED SHORT INTERVAL OF TIME, A CAPACITOR, A RESISTOR, A SOURCE OF ENERGY, MEANS INCLUDING SAID RELAY MEANS AND SAID SOURCE AND EFFECTIVE WHILE SAID RELAY MEANS IS IN SAID SECOND STATE FOR CHANGING THE CHARGE ON SAID CAPACITOR IN ONE DIRECTION, MEANS INCLUDING SAID RESISTOR EFFECTIVE WHILE SAID RELAY MEANS IS IN SAID FIRST STATE FOR CHANGING THE CHARGE ON SAID CAPACITOR IN THE OPPOSITE DIRECTION AND AT A RATE CONTROLLED BY SAID RESISTOR, AND MEANS INCLUDING AMPLIFYING MEANS FOR OPERATING THE LOAD DEVICE WHILE THE CHARGE ON SAID CAPACITOR DIFFERS IN ONE DIRECTION FROM A PRESELECTED MAGNITUDE AND WHILE SAID RELAY MEANS REMAINS IN SAID FIRST STATE AND FOR RELEASING THE LOAD DEVICE WHEN THE CHARGE ON SAID CAPACITOR DIFFERS IN THE OTHER DIRECTION FROM SAID PRESELECTED MAGNITUDE.

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