US3115970A

US3115970A - Inspection circuit

Info

Publication number: US3115970A
Application number: US73689A
Authority: US
Inventors: Robert G Husome
Original assignee: Barry Wehmiller Co Inc
Current assignee: Barry Wehmiller Co Inc
Priority date: 1960-12-05
Filing date: 1960-12-05
Publication date: 1963-12-31
Anticipated expiration: 1980-12-31

Description

Dec. 31, 1963 R. G. HusoME 3,115,970

INSPECTION CIRCUIT Filed Dec. 5, 1960 2 Sheets-Sheet 1 FIG. IA.

CONSTANT INVENTOR.

VOLTAGE ROBERT e. HUSOME TRANSFORMER ATTORNEYS.

BY a. I

- United States Patent 3,115,970 INSPECTION CIRCUIT Robert G. Husome, Manhattan Beach, Calif., assignor, by mesne assignments, to Barry-Wehmiller Machinery Filed Dec. 5, 1960, Ser- No. 73,689 Claims. (Cl. 2t)9111.5)

This invention relates to apparatus for inspecting empty bottles for cleanliness and, more particularly, to improvements in the electrical circuits employed therewith.

A preferred method for inspecting empty bottles for cleanliness is to pass these bottles through an inspection zone, which at one side has a source of illumination, usually at the base side of the bottle, and at the neck side contains a photocell arrangement. The presence of dirt or foreign and undesired particles in the bottle is usually sensed by the fact that the illumination falling upon the photocell means is decreased, in response to which detection apparatus is actuated. One of the problems arising with this type of arrangement is that the more sensitive the photocell means are made for the detection of foreign particles, the steadier the source of illumination which must be maintained to avoid false rejects, and maintaining an illumination source steady or constant provides difficulties. Either, sacrifices must be made in the desired sensitivity for the photocell means, or some effort by way of voltage-regulating apparatus for maintaining the illumination constant must be made.

An object of this invention is to provide a novel detection circuit arrangement which automatically compensates for illumination variation while permitting optimum sensitivity to be employed for the photocell detecting means.

Another object of this invention is the provision of a novel and improved circuit arrangement for automatically compensating photocell detecting means for variations in an entire illumination field.

Still another object of the present invention is the provision of novel circuitry which is actuated in response to the photocell detecting means for rejecting or accepting a bottle which eliminates the necessity for auxiliary apparatus for detecting when a bottle is in the inspection zone.

These and other objects of the invention may be achieved in an arrangement wherein the output from each of a plurality of photocells, which are disposed to receive light which has been passed through a bottle, are each applied to a separate amplifying means. The outputs of all these amplifying means are combined and used to control the operating potential applied to all of these photocells in a manner to maintain their over-all output constant, despite variations in the level of illumination of the entire field. This, however, does not prevent the output from any one or more of these photocells, which varies due to the presence of foreign particles, from being detected. Means are provided which are actuated to reject a bottle only in response to the output of the detecting means. These last means effectively include a capacitor which is charged up. When a clean bottle is in the inspection zone, this capacitor is discharged. Such discharge is prevented, however, in the presence of an output from the detecting means. The capacitor, after an interval sufficient to permit a complete inspection of the bottle, is connected to a reject mechanism. If the capacitor remains charged, this reject mechanism is actuated.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a sectional view of bottle-inspection apparatus of the type suitable for employment with this invention;

FIGURE 1A is a plan view of a starwheel used with the apparatus shown in FIGURE 1;

FIGURE 2 shows an arrangement of photocells which are suitable for employment with this invention; and

FIGURE 3 is a circuit diagram of an embodiment of the invention.

The handling of bottles so that they may be passed into and out of an inspection zone and be rejected, if necessary, may be performed most easily by a multipocket starwheel, which overhangs the conveyor such that bottles.

are momentarily passed off the conveyor for inspection. A preferred arrangement is shown which is derived from principles thoroughly described in Patent No. 2,800,226. Accordingly, the details of this inspection machine are only suggested in FIGURE 1, which is a sectional view of an embodiment thereof. A bottle 10 is carried through an inspection zone by a pair of

starwheels

14A, 14B, having

pockets

14A, 14B formed therein for the purpose. The starwheel is attached to a rotor 15 to be driven. For each pocket in the starwheel there is provided a suction cup 12. A vacuum can be applied to this cup through a passageway 13 connected through a valve passageway 13A to a vacuum source, not shown. A valve 17, shown in its nonreject position, normally prevents the vacuum from being applied to a suction cup.

A bottle is moved by the starwheel from a conveyor, through the bottle inspection zone, and then back to the conveyor, or moved to a reject bottle accumulator, not shown. A bottle is held properly in the inspection position over a light source 16 by a spring-loaded bar 19. The starwheel pair 14A, 143 may be changed for runs of different bottle sizes. The bottle 10 in FIGURE 1 is shown being held in the inspection zone. At one side of this inspection zone is a high-intensity incandescent-light source 16, which usually is positioned opposite the bottom of the bottle 10. Since photoelectric cells are being employed for performing the foreign-matter-detection function, variations in intensity of the light source can cause reactions akin to that caused by foreign matter in a bottle, as far as detection function by the photocells is concerned. This may be minimized to a certain extent, although not completely eliminated, by employing a constant-voltage transformer 18, through which power is applied to the light source 16.

The illumination from the light source 16 passes through a diffused opalized glass 24. The function of this glass is to eliminate any false detection which may be occasioned by shadowing of lettering which may appear in the bottom of a bottle. The change in intensity of light of any given photocell, due to the imaging of the smallest particle of foreign matter which is to be detected,

is far greater than the random fluctuations of light intensity on any photocell caused by variations in glass thickness and light transmission between clean bottles of a given type.

Light rays from the bottom of the bottle are collimated by a lens as. The focal length of this lens is equal to the distance of the lens from the bottom of the bottle. The collimated rays then pass through a prism 28. A preferred type of prism is known as the dove prism. This optical component is sometimes called an inverting prism. It is necessary that approximately plane wave fronts be passed through the prism; otherwise, the image on one side of the prism of an object on the other side of the prism will be distorted. The dove prism is mounted in a holder 30, which, in turn, is supported by

bearings

32, 34. The holder of the prism, and therewith the prism, is rotated above the center by means of a belt 36 which passes over the holder 30 and is driven by a pulley 40, which, in turn, is driven by a motor 42.

The collimated light output from the prism is focused, in turn, by another lens 44 upon several photocells supported in a holder 50. In FIGURE 1 the leads 52 of the several photocells may be seen. The function of the lens 44 is to form an image of the bottom of the bottle on the photocells. The prism serves to rotate the image about its axis of symmetry. The image rotates at a speed which is twice that of the prism. It should be noted that the

lenses

26 and 44 are supported in

holders

27, 45 on a shaft 54. Each holder may have several lenses, if desired. The holders are indexed on the support shaft such that any pair of lenses may be aligned concentric with the prism by rotating the shaft and providing a suitable detent. The lens system must be changed to accommodate different bottle heights and diameters. The entire inspection-head structure may be raised or lowered so that the bottom lens just barely clears the bottle. In order to satisfy the requirement of approximately plane wave fronts through the prism, the bottle lens is such that its focal length is just slightly greater than the height of the bottle being inspected. The focal length of the top lens must be such that a constant image diameter is maintained for different bottle sizes.

A small starwheel 56 engages the neck of each bottle which is passed through the inspection zone. FIGURE 1A is a plan view of this starwheel. The starwheel 56 is mounted on a shaft 58, which rotates as a result by being engaged by the bottle passing into and out of the inspection zone. Each time a bottle enters the inspection zone and leaves the inspection zone, a switch 134 is operated. The details of such operation are explained in connection with the explanation of FIGURE 3.

Reference is now made to FIGURE 2, which is a view looking up at the pattern of several photocells. It will be seen that a plurality of

photocells

64A, 64B, 64C, 64D, and 64E are employed for scanning the image of the bottom of the bottle. The photocell pattern preferably is such that the image of the bottom of the bottle may be completely inspected during one rotation of the image about its center.

The light which passes through a bottle which is in the inspection zone falls upon the photocells. The arrangement of the photocells is such that a complete scan of the image is made during one rotation. Any pattern of photocells may be chosen as long as every radial increment of the image circle is overlapped by one or more of the photocells when the image is rotated 360 about its axis of symmetry.

The photocells are wired into a circuit such that, when any one of them is momentarily occulted by a dark spot in the image caused by foreign matter obscuring part of the uniform illumination beneath the bottle, the output voltage changes by a percentage which can be detected. Since the image rotates very rapidly, it is essential that the photocells be of a type with a very short time constant. For reliable operation, it is also necessary that the photocells be fairly sensitive, i.e., that they have a reasonable light to dark current ratio. The change in photocell output voltage manifests itself as a short pulse. This pulse is amplified and eventually is enabled to operate a relay amplifier to reject the bottle.

The descriptions which have been made thus far are substantially those of FIGURES l and 2 which appear in an application for a Bottle-Cleanliness Inspection Apparatus, by James H. Wyman, filed April 11, 1960, hearing Serial No. 21,164, and which is assigned to a common assignee. The novel features of this arrangement are claimed therein. The foregoing description has been inse rted by Way of providing a description of a suitable arrangement for utilizing the novel circuitry to be described. However, this preceding description of the photocell detection means should not be construed as a limitation upon this invention, since it will be apparent to those skilled in the art that other photocell arrangements may utilize the embodiment of this invention without departing from the spirit and scope thereof.

Reference is now made to FIGURE 3, which shows a circuit diagram of an embodiment of this invention. The photocells employed in an embodiment of the invention which was built were of the type known as photodiodes, which have the characteristic that their resistance decreases with increasing illumination. One side of all these photodiodes is connected to ground. A bias potential is applied to the other side of these photodiodes from a potential source 70. This is applied through a resistor 72 and through a switch 74 to one side of a plurality of potentiometers, respectively 76A, 76B, 76C, 76D, 76E. A

resistor

78A, 78B, 78C, 78D, 78E connects the other side of each of the potentiometers bearing the associated letters to the

respective photocells

64A, 64B, 64C, 64D, 64E. The slider arm of each of the respective potentiometers is connected to the side of the potentiometer to which potential is applied.

The ungrounded sides of the respective photodiodes 64A through 64E are connected to the bases of associated NPN-type transistors 80A through 80E. Effectively, these transistors act as amplifying devices for amplifying the outputs from the respective photodiodes. The collectors of the respective transistors fiA through SIDE are connected together and to the source of operating potential 70. Each one of the emitters of the respective transistors is connected to a

separate resistor

84A, 84B, 34C, 84D, and ME. Each one of these emitters is also connected to an associated diode, respectively 86A, 86B, 86C, 86D, and 86E.

The ends of the resistors 84A through 84E which are not connected to the respective transistor emitters are connected together and to the base of an NPN-type transister 83. The base of this transistor is also connected through a resistor 90 to ground. The cathodes of the respective diodes 86A through 86E are connected to the base of an NPN-type transistor 92. The base of this transistor is also connected through a resistor 94 to ground. The emitter of transistor 88 is connected to a potentiometer which is connected in series with series-connected resistors, respectively 98, 1%, and 1492. These serve to provide a voltage divider, whereby a bias signal may be derived for the emitter of transistor 83. The resistor '72 is connected to serve as a load resistor for the collector of transistor 88, besides being connected to switch 74.

The emitter of transistor 92 is connected through a resistor 164 to ground. Transistor 92 also receives a biasing potential through a resistor 166 which is connected from the emitter of the transistor to the potential source '70. The collector of transistor 92 is connected through a first resistor 1% to the base of a PNP-type transistor 116 The resistor W8 is connected to another resistor 112, which is connected to operating potential source 76. Therefore, the collector of transistor 92 receives operating potential through

resistors

112 and 108, which are connected in series.

Transistor has its emitter connected to the potential source 70. Its collector is connected through a first resistor 116 to the base of an NPN-type transistor 118 and through a second resistor 120 to ground. The transistor 118 has its emitter connected through a diode 122 to ground. The collector of transistor 118 is connected through a resistor 126 to the source of operating potential '70 and also to the emitter of a unijunction transistor 124. The first base B1 of the unijunction transistor 124- is connected to a resistor 128, the other side of which is connected to ground. The second base B2 of the unijunction transistor is connected to the source of operating potential 70. The control electrode of a silicon control rectifier 130 is connected to the first base of the unijunction transistor 124. The cathode of the silicon control rectifier is connected to ground. The anode of the silicon control rectifier is connected through a resistor 132 to one contact 134D on a switch 134. The other contact 134C of the switch 134 is connected through a resistor 136 to the source of operating potential. A capacitor 138 is connected from the emitter of the unijunction transistor to ground.

The swinger arm of the switch 134 is connected through a capacitor 140 to ground. The switch 134, it will be noted, has four contacts, respectively 134A, 1343, 134C, and 134D. In the position shown in the drawing, the swinger connects together contacts 134A and 13413. It also connects them to the capacitor 140. The switch 134 is operated by the small starwheel 56 and shaft 53 in the manner shown in FIGURE 1. When there is no bottle present in the inspection zone, the swinger arm of the switch 134 remains in the position shown in the drawing, wherein it connects with

contacts

134A and 134B. When a bottle moves into the inspection zone, the starwheel 56 is rotated and moves the swinger arm of the switch to make contact with terminals 134C and 134D. When the bottle moves out of the inspection zone, starwheel 56 rotates again to restore the swinger arm to the position shown in the drawings.

The solenoid 142 of a reject relay has one end connected to the

contacts

134A, 134B and the other end connected to ground. The contacts 142A are connected to reject apparatus 144, which is rendered operative when these are closed.

Each one of the potentiometers 76A through 76B is adjusted to correct for unequal photocell sensitivities. The five transistors 80A through WE are connected as emitter followers to the base of transistor 88. The potential at each one of these transistor emitters is controlled primarily by the amount of light striking its associated photocell. A decrease in light results in a positive-going emitter voltage. The voltage applied to the base of transistor -88, which acts as a common amplifier, is efiectively equal to the sum of the emitter currents of transistors 811A through Sit/E, which are connected to this base and through resistor to ground. As a result, the voltage which is applied across the photodiodes and to the base of transistors 811A through 811E will be a function of the average illumination received by all the photodiodes 64A through 64E, with a decrease in illumination resulting in a positive-going voltage being applied to the base of transistor 88.

Transistor 88 is connected as a common emitter ampliher and is driven by the voltage applied to its base. The sensitivity of transistor 88 may be adjusted by the potentiometer 96. Adjustments of the potentiometers 76A through '7 6E are made with the switch 7 4 operated to the adjust position. With the switch '74 in the operating position, the current drawn through the collector of transistor 38, which is determined by the average illumination, effectively determines the potential being applied to the potentiometer 76A through 76E. Thus, when the illumination level changes, this is sensed by transistor 8'3. The voltage applied across the otentiometers 76A through 7 6E, and thereby the voltage which biases the five photodiodes, is changed to compensate for the change in illumination.

The circuit described provides a feedback loop in which the voltage applied to the base of the transistor 88 will remain essentially constant with Widely varying illumination levels. The voltages on the emitters of transistors 86A through 81113, however, will vary primarily as the result of their respective photocells observing a different amount of light than the average light of all the photocells. The circuit therefore becomes primarily contrast sensitive rather than illumination-level sensitive.

The emitters of transistors 80A through 80E, as has been previously described, are connected through diodes 86A through 861-3 to the base of transistor 92. As a result, the voltage applied to the base of this transistor will represent at any instant the darkest portion of the image under examination. In view of the positive bias applied to the emitter of transistor 92, the voltage applied to its base must exceed a predetermined positive level before the transistor 92 can start conducting. Thus, transistor 92 provides an output signal whenever any one or more of the transistors 811A through E respond to a change in the level of illumination applied to their respective photocells in response to the presence of a foreign particle.

The output of transistor 92 is amplified by transistor 1119. Transistor 118 operates as a shorting switch for discharging capacitor 138 whenever transistor 113 is rendered conductive by an output from transistor 110. The silicon diode 122 in the emitter circuit of transistor 118 serves only to bias the emitter slightly positive (by an amount equal to the forward voltage drop of the diode approximately 0.65 volt), so as to reduce the collector leakage of transistor 118.

Unijunction transistor 124, resistor 126, and capacitor 133 form a relaxation oscillator whose period of oscillation is five milliseconds. This corresponds to the time required for one complete optical scan of the bottle under inspection. Each time the unijunction transistor fires, it discharges capac'tor 138 and generates a pulse across resistor 123. This pulse is applied to the control electrode or injector of the silicon control rectifier .130. The capacitor 138 may also be discharged by transistor 118 whenever it is rendered conductive in response to a signal from the preceding transistors. Unijunotion trarisistor 124 will be rendered conductive only if transistor 118 remains nonconductive for a period equal to a period of five milliseconds. That is the amount of time required to charge up capacitor 138 to the voltage value necessary to render unijunotion transistor 124 conductive Thus, during each inspection cycle the unijunotion transistor will become conductive only if an accept condition exists, i.e., no signal indicative of the presence of dirt in a bottle under inspection is received.

The sequence of events during each inspection cycle is essentially as follows:

( 1) A bottle approaches the optical axis of the scanner. The neck of the bottle advances the turnstile, which causes the trigger switch 134 to swing from contacting terminals 134A, 1348 to terminals 134C, 134D.

(2) Capacitor 149 is connected to resistor 136 and resistor 132. This capacitor charges up through resistor 136.

(3) When the bottle reaches the center of the optical axis, one of two conditions can exist: either (a) the bottle under the inspection contains opaque matter, a rejection exists, transistor 11% is not maintained nonconductive for a period of five milliseconds, whereby voltage across capacitor 138 never reaches a level high enough to render unijunetion transistor 124 conductive; or b), the bottle under inspection is clean, an accept condition exists, transistor 118 is turned off for at least one optical scan, or five milliseconds, and the voltage on capacitor 138 reaches a level high enough to fire transistor 124. As a result of the transistor 124 being conductive, a control pulse is injected into the silicon control rectifier to render it conductive, whereby it can rapidly discharge capacitor 140 or reduce it to an extremely low value.

(4) As the bottle continues to move past the optical axis it further advances the turnstile, which returns the switch 134 to its position shown in the drawings. If a reject condition has existed, capacitor 140 is fully charged, and this voltage is applied to relay 142 to energize it and cause it to operate the reject mechanism 144. If the bottle which is passed through the inspection zone has not had any dirt or has been cleaned, then capacitor 140 has been discharged and has insufficient voltage to energize the relay 142 when it is connected thereto.

As a result of the circuitry which comprises this embodiment of the invention, not only is compensation made for the average illumination variations of the field of illumination applied to the bottle, but, also, it is not necessary to specifically detect when a bottle is being inspected. The oscillator formed by the resistor 126, capacitor 133, and unijunction 124 establishes a detection interval, and, if a bottle during that interval can pass inspection, then the reject mechanism is not operated.

There has accordingly been described and shown herein novel and useful circuitry for employment with bottle-inspection apparatus. The types of transistors and photodiodes shown are for purposes of illustration, and not to be construed as a limitation upon the invention.

I claim:

1. An improved circuit for a system for inspecting an empty bottle for cleanliness of the type wherein a bottle passes through an inspection zone including a source of illumination on one side and a plurality of photocells on the other side, said circuit comprising a transistor having base, collector, and emitter electrodes, a resistor having one end connected to said transistor collector, means connected to the other end of said resistor for applying operating potential to said transistor, means for applying operating potential to said photocells from said transistor collector, means for combining all the outputs of said photocells; means for applying said combined photocell outputs to the base of said transistor for varying the current drawn by said transistor through said resistor to maintain the level of the combined photocell outputs substantially constant, means for detecting a variation in the output of one of said photocells due to the presence of an undesired foreign particle in a bottle being inspected, and means for rejecting said bottle responsive to an output from said means for detecting.

2. An improved circuit as recited in claim 1 wherein said means for combining all the outputs of said photocells comprises a plurality of transistors each having a base, emitter, and collector electrode, means connecting the output of a different one of said photocells to the base of a different one of said transistors, means including a resistor connecting the emitters of each of said plurality of transistors to the base of said transistor, and means for applying operating potential between collectors and emitters of said plurality of transistors.

3. An improved circuit for a bottle inspection system of the type wherein a bottle passes through an inspection zone including a source of illumination on one side and photocell means on the other, said circuit comprising a capacitor, means for charging said capacitor, means for discharging said capacitor when its charge exceeds a fixed level, means for detecting an output from said photocell means indicative that a bottle should be rejected and producing an output signal indicative thereof, shorting switch means for preventing said capacitor from charging up to said fixed level in the presence of said output signal, and means operated responsive to said capacitor not attaining said fixed charge level for rejecting said bottle.

4. An improved rejection circuit for a bottle inspection system of the type wherein a bottle passes through an inspection zone including a source of illumination on one side and photocell means on the other side, said circuit comprising a first capacitor, means for charging said first capacitor, means for discharging said capacitor when its charge reaches a predetermined level, a discharge transistor having base, emitter, and collector electrodes, means connecting said discharge transistor collector and emitter electrodes across said first capacitor, means for detecting an output from said photocell means indicative that a bottle should be rejected and producing an output signal indicative thereof, means for applying said output signal to the base of said transistor to render it conductive to thereby prevent said capacitor from charging to said predetermined level, a second capacitor, means for charging said second capacitor, means for discharging said second capacitor responsive to said first capacitor being discharged, and means responsive to said second capacitor being charged for rejecting a bottle.

Q as

5. An improved rejection circuit for a bottle inspection system as recited in claim 4 wherein said means for discharging said first capacitor when its charge reaches a predetermined level comprises a unijunction transistor having an emitter, a first and a second base, a resistor having one end connected to said first base, means connecting said first capacitor between said unijunction transistor emitter and the other end of said resistor; said means for discharging said second capacitor responsive to said first capacitor being discharged comprises a siliconcontrolled rectifier having a control electrode connected to said first base, a cathode connected to said resistor other end, and an anode, and means connecting said second capacitor between said silicon-controlled rectifier anode and cathode.

6. An improved circuit for a system for inspecting an empty bottle for cleanliness of the type wherein a bottle passes through an inspection zone including a source of illumination on one side and a plurality of photocells on the other, said circuit comprising means for combining the outputs of all said photocells, means for maintaining the value of the combined outputs of said photocells substantially constant, means for detecting a variation in the output of a photocell due to the presence of an undesired foreign particle in a bottle being inspected and providing an output signal indicative thereof, a capacitor, means for charging said capacitor, means for periodically discharg ing said capacitor, means responsive to said output signal to render said means for periodically discharging said capacitor inoperative, and means responsive to said capacitor being charged to reject a bottle which has been inspected.

7. An improved circuit for a system for inspecting an empty bottle for cleanliness of the type wherein a bottle passes through an inspection zone including a source of illumination on one side and a plurality of photocells on the other side, said circuit comprising means for combining the outputs of all said photocells, means for maintaining the value of the combined outputs of said photocells substantially constant, means for detecting when the output of one of said photocells is altered due to the presence of unwanted opaque matter in a bottle being inspected and for providing an output signal indicative thereof, a capacitor, means for charging said capacitor, means for discharging said capacitor when its charge reaches a predetermined level, means for preventing said capacitor from charging up to said predetermined level responsive to said output signal, and means operated responsive to said capacitor not attaining said predetermined level for rejecting said bottle.

8. An improved circuit as recited in claim 7 wherein said means for combining the outputs of all said photocells comprises a plurality of transistors each having a base, emitter, and collector electrode, means connecting the output of a different one of said photocells to the base of a diiierent one of said transistors, means including connecting the emitters of each of said transistors to a common junction, said means for maintaining the value of the combined outputs of said photocells substantially constant comprises a control transistor having base, emitter, and collector electrodes, means for applying operating potential to said control transistor including a resistor connected in series with the collector of said control transistor, and means for applying operating potential to said photocells including a connection from the collector of said control transistor to said photocells.

9. An improved circuit as recited in claim 7 wherein said means for discharging said capacitor when its charge reaches a predetermined level comprises a unijunction transistor having an emitter and a first and second base, a resistor having one end connected to said first base, means connecting said capacitor between said unijunction transistor emitter and the other end of said resistor; said means for preventing said capacitor from charging up to said predetermined level includes a transistor having an emitter and collector between which said capacitor is connected, and a base to which said output signal is applied.

10. An improved circuit for a system for inspecting an empty bottle for cleanliness of the type wherein a bottle passes through an inspection zone including a source of illumination on one side and a plurality of photocells on the other side, said circuit comprising a transistor having base, collector, and emitter electrodes, a resistor having one end connected to said transistor collector, means connected to the other end of said resistor for applying operating potential to said transistor, means for applying operating potential to said photocells from said transistor collector, means for combining all the outputs of said photocells, a plurality of transistors each having a base, emitter, and collector electrode, means connecting the output of a different one of said photocells to the base of a different one of said transistors, means including a resistor connecting the emitters of each of said plurality of transistors to the base of said transistor, means for applying operating potential between collectors and emitters of said plurality of transistors, means for detecting a change in output of any of said photocells due to the presence of an undesired opaque particle in a bottle being inspected and producing a rejection signal including a separate diode coupling each of the emitters of said plurality of transistors to a junction, and amplifying means connected to said junction, a first capacitor, means for charging said first capacitor, a discharge transistor having base, emitter,

and collector electrodes, means connecting said discharge transistor base to said junction, means connecting said first capacitor between said discharge transistor base and collector, means for discharging said first capacitor when its charge reaches a predetermined level comprising a unijunction transistor having an emitter and a first and second base electrode, a resistor having one end connected to said first base, means connecting said first capacitor between said unijunction transistor emitter and the other end of said resistor, a silicon-controlled rectifier having an anode, cathode, and control electrode, means connecting said silicon-controlled rectifier control electrode to said unijunction transistor first base, means connecting said silicon-controlled rectifier cathode to said other end of said resistor, a second capacitor, means for charging said capacitor, means for rejecting a bottle after inspection operative responsive to said second capacitor being charged up, and switch means operative responsive to a bottle entering said inspection zone for connecting said second capacitor to said means for charging said capacitor and across said silicon-controlled rectifier anode and cathode and responsive to said bottle leaving said inspection zone for connecting said second capacitor to said means for rejecting a bottle.

Weathers July 6, 1943 Bliss Feb. 18, 1958

Claims

1. AN IMPROVED CIRCUIT FOR A SYSTEM FOR INSPECTING AN EMPTY BOTTLE FOR CLEANLINESS OF THE TYPE WHEREIN A BOTTLE PASSES THROUGH AN INSPECTION ZONE INCLUDING A SOURCE OF ILLUMINATION ON ONE SIDE AND A PLURALITY OF PHOTOCELLS ON THE OTHER SIDE, SAID CIRCUIT COMPRISING A TRANSISTOR HAVING BASE, COLLECTOR, AND EMITTER ELECTRODES, A RESISTOR HAVING ONE END CONNECTED TO SAID TRANSISTOR COLLECTOR, MEANS CONNECTED TO THE OTHER END OF SAID RESISTOR FOR APPLYING OPERATING POTENTIAL TO SAID TRANSISTOR, MEANS FOR APPLYING OPERATING POTENTIAL TO SAID PHOTOCELLS FROM SAID TRANSISTOR COLLECTOR, MEANS FOR COMBINING ALL THE OUTPUTS OF SAID PHOTOCELLS; MEANS FOR APPLYING SAID COMBINED PHOTOCELL OUTPUTS TO THE BASE OF SAID TRANSISTOR FOR VARYING THE CURRENT DRAWN BY SAID TRANSISTOR THROUGH SAID RESISTOR TO MAINTAIN THE LEVEL OF THE COMBINED PHOTOCELL OUTPUTS SUBSTANTIALLY CONSTANT, MEANS FOR DETECTING A VARIATION IN THE OUTPUT OF ONE OF SAID PHOTOCELLS DUE TO THE PRESENCE OF AN UNDESIRED FOREIGN PARTICLE IN A BOTTLE