US2415174A

US2415174A - Photoelectric sizing mechanism

Info

Publication number: US2415174A
Application number: US480026A
Authority: US
Inventors: Jr Samuel C Hurley
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-03-22
Filing date: 1943-03-22
Publication date: 1947-02-04
Anticipated expiration: 1964-02-04

Description

Feb. 4, 1947.

s. c. HURLEY, JR

PHOTOELECTRIQ SIZING MECHANISM s Sheets-Sheet 1 mm Samugl C. Hurle: ,Jr.

Filed March 22, 1943 Feb. 4, 1947. 5 HURLEY, JR 2,415,174 I PHOTOELECTRIC SIZING MECHANISM Filed March 22, 1943 v 3 Sheets-Sheet 2 Samuel C. Hurley, Jr.

Feb. 4, 1947. s. c. HURLEY, JR

PHOTOELECTRIC SIZING MECHANISM 3 Sheets-Sheet 3 Filed March 22, 1943 llAAA Gum/Mg ted e d Edd? 2,.dl5,1?d

PRGTOELECTRIC SIZING MECHANISM Samuel E. Hurley, Jim, Danville, 111.

Application March 22, 1943, Serial No. 480,026

(Cl. 209--8Z) 9 illaims. i

This invention relates to photoelectric sizing mechanism and more particularly to a device which will select articles of a predetermined size and reject articles or specimens which are a predetermined amount over or under the desired size. The mechanism causing acceptance or rejection of the specimen is controlled by the passage of the article through a beam of light and no stationary support or rest is required for the specimen being tested. The testing operation may be performed while the specimen is in motion.

In general, the device includes a plurality of phototube bridges, one responsive to the conditions of light and shadow due to the one edge of the article, and another responsive to the conditions of light and shadow due to the other edge of the specimen being tested. The bridges each include a pair of phototubes, each tube forming an arm of the bridge, and if the specimen is of the correct dimension one of the phototubes of each bridge will be in shadow while the other phototube of each bridge is in light. The bridges are so connected as to be unbalanced under these conditions and a selecting mechanism is actuated. If either of the bridges is in balance, that is to say, if the phototubes of either bridge are both in light or both in shadow, a reject mechanism is actuated to reject the article or at least a selecting mechanism is not actuated. The entire device is preferably so arranged and connected that it is necessary to positively actuate a selecting mechanism in order to accept the specimen so that failure of any portion of the device causes the specimens to be rejected.

An object of the present invention is, therefore, to provide an improved sizing mechanism which may operate upon specimens in motion without physical contact between the testing instrumentalities and the article.

Another object of the invention is to provide a phototube sizing device including a plurality of phototube bridges all of which must be in unbalanced condition in order to select the specimen.

Another object of the invention is to provide an improved photoelectric sizing device controlled by passage of an article to be sized through a beam of light and which requires positive actuation of a selecting mechanism in order to accept the specimen being sized so that failure of component parts of the device cause rejection rather than selection of the specimen.

Another object of the invention is to provide a photoelectric sizing mechanism in which a lens system and a plurality of concave mirrors are employed to magnify the departure of an article from a predetermined standard so as to enable the device to work within closed tolerances.

A further object of the invention is to provide an improved sizing device having a. plurality of phototube bridges in which the relative position of the various phototubes and otherelements of the device may be varied to vary the tolerance permitted by the bridge before accepting an article being tested. 7 I

Other objects and advantages of the illVEZl? tion will appear in the following description of the preferred embodiments of the invention shown in the attached drawings, in which Fig. 1 is a schematic view showing the mechanical arrangement of the sizing device of the present invention and an electric circuit associated therewith;

Fig. 2 is a diagrammatic plan view of the me chanical portion of the device;

Fig. 3 is a simplified schematic diagram of the circuits of Fig. 1; and

Fig. 4 is a view similar to 3 showing a modified circuit.

Referring to the drawings, the device illustrated in Figs. 1 and 2 includes a source of light iii shown as an electric incandescent lamp, although any other suitable source of concentrated light can be employed. The lamp it has its filament positioned substantially in the optical axis of a pair of condenser lenses H for concentrating the light of the source I0 upon an article it being passed through the beam of light from the condenser lenses H. A projecting lens assembly i3 is mounted so as to have its optical axis in alignment with the optical axis oithe condensing lenses II, and is positioned upon the opposite side of the test zone through which the article 52 is passed. The projecting lens assembly i3 preferably projects a sharply defined shadow of the article being tested upon a plurality of convex mirrors l4 and is shown as being cylindrical mirrors, although other types of convex mirrors, including a spherical mirror, may be employed. That is, the object being tested and the mirrors it and 16 are preferably positioned at the conjugate foci of the lens assembly. The mirrors M and I6 are positioned so-thatfor a perfect article the edge of the shadow cast by the upper edge of the article l2 in Fig. 1 will be approximately centered in a vertical direction upon the mirror !6 when the edge of the shadow cast by the lower edge of the article 12 is approximately 3 centered in a vertical direction upon the mirror- I4. A cylindrical article 12 is shown by way of example, but other shaped articles may be testedit correctly passed through the light beam between the condenser lenses and the projecting lens assembly I3.

Phototubes I1 and I8 are positioned to receive light from the mirror l4 and phototubes l9 and 20 are positioned to receive light from the mirror l6, a light baffle 22 being positioned between the mirrors l4 and I6 to prevent light from mirror I4 from reaching phototubes i9 and. 20 and light from mirror l6 from reaching phctotube H. The phototubes and mirrors are so adjusted that the upper edge of an article which is within the tolerance range and in test position inthe beam of light between the lenses ii and l3 will cause phototube l9 to be in shadow and phototube 20 to be in light while at the same time the lower edge of the article will cause'phototube I8 to be in shadow and phototube H to be in light. This condition is necessary for actuation of the selecting mechanism to accept an article.

The electric circuit for the phototubes and control apparatus is'most clearly shown in Fig. 3 and as shown therein the phototubes l1 and I8 are connected in series across a source of D.-C. potential.

Resistors

23 and 24 are also connected across said source, these resistors being substantially equal, and the midpoint of the resistors is a, control tube 21, preferably of the pentode' type, is connected to the point 28 between the phototubes l1 and I8. The point 28 is normally maintained at ground potential when the voltage drops through the phototubes l1 and I8 are substantially equal, by means of a resistor 29 having a relatively high resistance connected to ground at-3I. It will be apparent that the point 28 and the control grid of the tube 21 remain at substantially ground potential when the phototubes l1 and I8 are non-conducting orwhen both are rendered conducting to approximately the same extent by impingement of light thereon. Thus, the

resistors

23, 24 and the phototubes ll and I8 .form the four arms of a bridge with the resistors 29 connected across the bridge at the junction of the arms remote from the junctures connected to the source of D.-C. potential.

The tube 21 may have its operating voltages obtained from a plurality of voltage dividing \

resistors

32, 33, 34 and 35 connected between the positive terminal 31 of a separate source of D.-C. potential and ground at 3|, the negative terminal of the source of D.-C. potential being connected to ground at 38. The resistors 32 to 35, inclusive, provide proper operating voltages for the tube 21, the anode of this tube being furnished with a relatively high positive potential through a load resistor 39. The screen grid of the tube 21 is connected to a point of somewhat lower positive potential between the

resistors

33 and 34. The cathode of the tube 21 may be connected to a variable slider 4| engaging the resistor 35 at a point which is at a positive potential above ground so as to apply an effective negative. bias to the control grid of the tube 21 with respect to the cathode thereof. The amount of bias thus placed on the control grid is preferably a relatively low negative potential so that considerable current flows in the anode circuit of the tube 21. It will be apparent that this bias is not disturbed as long as phototubes l1 and 18 are nonconducting or conducting to substantially equal extentsbut that the bias on the control grid connected to ground at 26. The control grid of of the tube 21 will be changed if one of the phototubes or I8 is sub-nected to light while the other remains in shadow.

The control tube 21 in conjunction with a similar control tube 42 is employed-to control the action of the power tube 43 which is preferably of the gas filled grid controlled arc discharge type. The control tube 42 is connected with respect to phototubes i9 and 2D in a manner exactly similar to the connection of the control tube 21 with respect to the phototubes [Band II. Thus, the phototubes I9 and 26 are connected in series across the

resistors

23 and 24 so as to also form a bridge therewith. The control grid of the tube 42 is connected to a point 44 between the phototubes l9 and 20 and to ground through a resistor 46 having relatively high resistance so that the normal potential of the control' grid of the tube 42 is substantially that of ground. A plurality of

voltage dividing resistors

41, 48, 49 and 5!] supply proper voltages to the electrodes of the tube 42 in a manner entirely similar to the voltage supply of the tube 21, the anode of the tube 42 being connected to a relatively high positive potential through the load resistor 52.

The tube 43 may have its cathode connected to a relatively low positivepotential maintained by the voltage dividing resistors 53 and 54-connected between the positive terminal 31- of a D.-C. voltage source and ground. The potential of the cathode of the tube 43 is thus maintained positive with respect to the control electrode 56 of the tube 43 and also with respect to the shield electrode 51 of this tube. Thus the control electrode 58 and the shield electrode 51 of the tube 43 normally have sufficient negative bias to maintain the tube 43 in non-conducting condition when the tube is not ionized. A relay coil 58 and a mechanically operated switch 59 are connected in series, one terminal of this circuit being connected to the positive terminal 31 of the source of D.-C. potential and the other terminal being connected to the anode of the tube 43. Thus,

when the tube 43 is in non-conducting condition or switch 59 is open, the coil- 58 is not energized.

but upon closing ofthe switch 59 and rendering the tube 43 conducting, the relay coil 58 is energized to attract an armature 61 opening a circult through normally closed contact 63 and closing a circuit through normally open contact 64. It has been found that the control electrode and shield electrode of certain types of gasfilled tubes may be employed to substantially independently control the ionization of the tube. That is to say, a sufliciently negative bias on either one of these electrodes will prevent ionization irrespective of 6 Whether the other electrode has a positive potential applied thereto with respect to the oathode.

A source of alternating current power shown as an alternating current line 66 hasone side connected to the armature 6| and the other side to a terminal of another mechanically operated switch 61 so that closing of the mechanicalswitch 6'! completes a circuit through one or the other of solenoid operated valves 68 and '69 depending upon which contact 63 or 64 is in engagement with the armature 6| of the relay. The

solenoid valves

69 and 68 control selecting and rejecting mechanisms respectively. Thus, referring to Fig. 1, the

solenoid'valves

68 and 69 may be connected to a, source of fluid pressure (not shown) through a pipe II and maybe provided with discharge pipes 12 and 13, respectively. If the article to be tested is moved. through the light beam in the direction indicated by the arrow is in Fig. 1, immediately after it has been tested a blast of air or other fluid from the pipe 72 may be employed to propel the article i2 into a select receptacle (not shown), or a blast of fluid from the pipe is may be employed to propel the article into a reject receptacle (not shown) depending upon the position of the relay armature ti.

The mechanical switches 5d and ill may be operated by cams M and it, respectively, driven in synchronism, as indicated by the dotted line connecting the two cams, so that the switch 59 is closed when the article reaches the test position in the light beam between the condenser l lenses It and the projecting lens it and the switch it is closed thereafter.

Preferably the switch 5% is closed just before the article reaches the desired test position and the switch t? is closed just after the article reaches the test position so that the circuit through the tube id is conditioned for operation just prior to the articlereaching the test position in the light beam. The relay coil 58 is not energized unless the article is within the predetermined tolerance range, but if said. article is within the predetermined tolerance range the solenoid coil 59 is energized to attract the armature El and condition the circuit for acceptance of the article by closure of the contact 5t. Subsequent closure of the circuit through the switch til then operates the solenoid valve 63 to select the article. If the article is not within the tolerance range the relay coil 58 is not energized upon closure of switch 59 since the tube 63 has not been rendered conducting and subsequent closure of the switch bl operates the solenoid valve (it to reject the article. It will be noted that the article is always rejected unless the relay coil 58 is energized requiring that both the tube is and relay positively function in order to accept the article. Continued rotation of the cams it and it causes opening of the circuit through the switches to deionize the tube to and open the circuits through either the solenoid valve 68 or valve 6% to condition the device for subsequent test operation.

The bias upon the control grids of the control tubes 2? and ift is normally held at a relatively low negative potential by the connections shown so that a substantial current flows in the anode circuit of these tubes when the bridges including the phototubes ll and t8 and the phototubes l9 and 2d are in balance. This current flowing through the load resistors 3d and 52 of the tubes 2i? and d2, respectively, maintain the control electrode stand shield electrode 57 of tube at at a negative potential with respect to the cathode of'the tube it to prevent ionization of this tube even when the mechanical switch 59 is closed. Thus when both bridge circuits are balanced, closure of mechanical switch 67 will cause operation of the reject solenoid switch 69.

The article to be tested may be passed through the beam of light between the condenser lenses H and the projecting lens it in the direction shown by the arrow l t in Fig. 1. Before the article enters the beam all of the phototubes ll to 29, inclusive, are subjected to light from the light source reflected from the mirrors i l and It and the two phototube bridges are in balance. However, the mechanical switch ill] is open so that there is no operation of the selecting or rejust at this time or shortly potential.

As the article enters the light beam the leading edge of the article reaches a point in which the phototube I1 is placed in shadow while the phototube 18 remains in the light. Even if the mechanical switch 59 were closed at this point no ionization of the tube it would take place as placing the phototube l? in shadow so that the control grid of tube 27 is driven in a positive direction increases the nega tive bias on the control grid to of the tube at. As the article is progressed further into the light beam both phototubes l1 and 3 are placed in shadow so that the bridge containing these tubes again returns to balance, still retaining the bias on the control grid of the tube 43 at a negative During this time the phototubes It and 20 remain in light so that the bridge containing these tubes remains balanced, thus maintaining the negative potential upon the shield electrode 57 of the tube is.

As the article progresses through the light beam it reaches a point at which the phototube i9 is placed in shadow while the phototube 'Ed remains in the light. This unbalances the bridge containing the phototubes l9 and 20 to drive the control grid of the tube Min a negative direction to decrease the anode current through the tube it. This reduces the drop through the load resistor 52 of this tube and allows the shield grid 5? of the tube W to become positive or at least be carried in a positive direction with respect to the cathode of this tube so that the control grid 5% of the tube is conditioned for causing ionization of the tube.

If the article is larger than the predetermined size both phototubes l7 and It remain in shadow so that this bridge remains balanced and the control grid 56 of the tube d3 remains negative. At this time the mechanical switch 59 has been closed but the relay coil 58 is not energized because the tube 63 remains non-conducting. Shortly thereafter the mechanical switch 67 is closed and reject solenoid valve is operated to reject the article as hereinafter described.

7 If the article is within the predetermine tolerance range the phototube I8 is placed in shadow while phototube I1 is still in the light and it will be remembered that the article is in such a position that phototube l 9 is placed in shadow while phototube 20 is in' the light. This unbalances both phototube bridges so that both the control electrode 56 of the tube 43 and the shield electrode 5! are carried in a positive direction. As mechanical switch 5% is closed, the tube 33 ionizes, the. relay coil 58 is energized, and upon closure of mechanical switch 61 the solenoid valve 68 is energized to accept the article.

If, however, the article tubes IT and it are in the light when the leading edge of the article reaches a position such that phototube I9 is in shadow, and phototube ml is in light so that the control electrode 55 of the tube 43 is maintained negative when the shield elecjecting mocha trode 51 thereof is carried in a positive direction.

The tube 43 does not ionize even though the switch 59 is closed and upon closure of the switch 57 the reject solenoid valve 69 is operated.

It will be apparent from the above description of operation, that the only condition under which the accept solenoid valve 68 can be operated is. that the article be of the correct size to place phototube I9 in shadow when phototube 21! is in light while at the same time placing phototube Id in shadow while phototube I! remain; in the light. This means that the article must be withis too small,'both photoin the predetermined tolerances and occupy a predetermined position in the light beam. Thus, the articles can be moved through the light beam in either direction alon a line perpendicular to the axis of the mirrors I4 and I5 in timed relation with properly synchronized mechanical switches in the control circuits and the selecting mechanism will not operate to accept the article unless the above conditions are fulfilled. After th operation of the selecting mechanism to either accept or reject the article, the switch 81 is opened to deenergize the solenoid-valve 68 or 89 operated to either select or reject the article and the switch 59 is opened to deionize the tube 43.

While the switches 59 and 81 must be operated in timed relationship with the passage of articles through the beam of light, their adjustment is not extremely critical. Thus, the switch 59 must be closed while the switch 61 is open at least the switch 51 must not close before the switch 59 closes. It-is merely necessary that the switch 59 open sometime between test operations in order to deionize the tube 43. This switch can be again closed at any time prior to closing of the switch 61 but must be closed at the time the article reaches the test position in the light beam. The switch 61 must not close before the article reaches the may remain closed for a considerable portion of the test cycle.

The device of Fig. 4 is entirely similar to the device of Fig. 3 except that another gas filled tube Bi and relays 82 and 83 are substituted for the mechanical switches 59 and 6T| of Fig. 3 in order to make the operation of the selecting mechanism entirely dependent upon the passage of the article through the light beam so as to avoid the necessity of having a mechanically operated switch synchronized with passage of the article through th light beam. Otherwise the same reference numerals are employed for corresponding parts upon Figs. 3 and 4.

The control electrode 84 of the tube 8| is connected in parallel with the control electrode 56 of tube 43 but has its shield electrode 88 connected to the cathode so that the tube 8| ionizes whenever the control electrode 84 is carried in a positive direction. Thus, unbalance of the bridge including the phototubes I1 and I8 by placing phototube iii in shadow and phototube l1 in light, causes'ionization of tube 8| as above described when its anode circuit is closed, and this can only happen when the article is substantially centrally positioned in the light beam and the lower edge of the article occupies a position where phototube i1 is in light and phototube I8 is in shadow. At this time phototubes l9 and 28 are determining the position of the upper edge of the article. Whentube 8| is thus ionized, as above described, the coil 88 of relay 82 is energized to attract armature 89 to close a circuit through contact 9| of relay 82, and one of the contacts 63 and 64 associated with relay coil 58, and through one of the

solenoid valves

68 or 69 to operate either the selecting mechanism to either accept or reject the article.

If the article is within the tolerange range, the

size or oversize the bridge including phototubes l9 and is in balance at the time tube 8| ionizes so that tube 43 does not ionize and a circuit is completed through the reject solenoid operated valve 69 to reject the article. Operation of relay 82 due to ionization of tube 8| also closes a circuit through contact 93 of relay 82 and the operating coil 94 of relay 95 which causes opening of the anode circuits of the

tubes

43 and 8| at norerances can be set within desired limits.

mally closed contact 980i relay 95. This causes deionization of

tubes

43 and 8| to condition the same for a subsequent operation. Relay is preferably of the delayed action type so that the

tubes

43 and 8| are not deionized until after the selecting mechanism has had an opportunity to operate.

It will be apparent that tube 8| will only ionize and become conducting'when the article is in test position in the light beam and that the ionization of tube 8| completely controls the time of operation of the selecting or rejecting mechanism.

Thus, mere passage of the articles through the light beam not only tests the article for correct size, but also initiates the operation of the selecting mechanism. It will be further apparent that in the device of Fig. 4 the tube 21 and the circuit associated therewith must have sufiicient power to drive the control grids of both

tubes

43 and 8| in a positive direction irrespective of electron flow to these control electrodes when the control electrodes are carried in a positive direction. In

some instances, therefore, it may be necessary to employ a separate amplifying tube .such as 2 for each of the control electrodes of the tubes 43" 28 is essentially similar to the bridge including the tubes i1 and I8 and is only unbalanced in the correct manner'to carry the electrode of a gas filled tube in the positive direction when the article is in thetest position in the light beam, it is also entirely possible to control the tube 8| from the bridge including the phototubes l1 and l8. a

It will thus be seen that the present invention provides a sizing or size determining device which does not require that an article under test be held in a stationary predetermined position. Instead mere passage of an article through a light beam causes acceptance or rejection of the article. Any

known or suitable conveying or article moving means such as a belt or chain can be employed to move the articles through the beam and any suitable accepting and rejecting mechanism can be actuated by the photo cell bridges for directing the tested articles to receivers as they leave the test zone. extremely accurate and the over or under tolbe apparent that it is unnecessary for both edges of the article being measured to be positioned in the same light beam as separate beams can be employed for opposite edges of large articles and furthermore more than one dimension of an article can be simultaneously measured by employing The test for correct size can be made It ,will

a a larger number of phototube circuits and if necessary a plurality of light beams.

While I have disclosed the preferred embodi ments of my invention, it is understood that the details thereof may be varied within the scope of the following claims.

I claim as my invention:

1. In a phototube sizing device, a light sourceand an optical system providing at least one light beam, means for determining whether a dimension of said article intercepting a portion of said beam corresponds to a predetermined dimen'sion comprising a first phototube circuit responsive to light passing one edge of said article for determining when said edge occupies a predetermined position and a second phototube circuit responsive to light passing another edge of said article for simultaneously determining whether said other edge occupies another predetermined position, each of said phototube circuits including a pair of phototubes, one of said phototubes of each circuit being positioned to receive light passing its corresponding edge and the other phototube of each circuit being positioned to be placed in shadow by said corresponding edge when said corresponding edge occupies its predetermined position, each of said photutube circuits being connected to form a bridge so that the bridge of each circuit is substantially in balance when both phototubes thereof receive light or are in shadow and is unbalanced when one phototube thereof receives light and the other phototube thereof is in shadow, and selecting means controlled by both said phototube circuits for accepting said article when both of said bridges are simultaneously unbalanced and rejecting said article when one of said bridges is unbalanced in one direction only and the other of said bridges is in balance.

2. In a phototube sizing device, a light source and an optical system providing at least one light beam, means for determining whether a dimension of said article intercepting a portion of said beam corresponds toa predetermined dimension comprising a first phototube circuit responsive to light passing one edge of said article for determining when said edge occupies a predetermined.

position and a, second phototube circuit responsive to light passing another edge of said article for simultaneously determining whether said othor edge occupies another predetermined position, and selecting means controlled by both said phototube circuits for accepting said article when both said edges simultaneously occupy their corresponding predetermined positions, said selecting means including a control tube of the arc discharge type having a cathode and two control electrodes, electrical circuits and a source of voltage for maintaining each of said electrodes at a voltage with respect to said cathode preventing ionization of said control tube, each of said phototube circuits being connected to one of said control electrodes to carry the voltage thereof in a positive direction when the corresponding edge of said article occupies its predetermined position, whereby said control tube ionizes when said edges simultaneously occupy their predetermined positions only, and selecting means responsive to ionization of said control tube for accepting said article.-

. 3. In a phototube sizing device, a light source and an optical system providing at least one light beam, means for determining whether a dimension of said article intercepting a portion of said beam corresponds to a predetermined dimension asserts comprising a first phototube circuit responsive to light passing one edge of said article for determining when said edge occupies a, predetermined position and a second phototube circuit responsive to light passing another edge of said article for simultaneously determining whether said other edge occupies another predetermined position,

and selecting means controlled by both said phototube circuits for accepting said article when both said edges simultaneously occupy their corresponding predetermined positions, said selecting means including a control tube of the grid controlled arc discharge type having a cathode, a control electrode and a shield electrode, electrical circuits and a source of voltage for maintaining each of said electrodes at a voltage with respect to said cathode preventing ionization of said control tube, one of said phototube circuits being connected to said control electrode to carry the voltage thereof in a, positive direction when its corresponding edge is in said predetermined position, and the other of said phototube circuits being connected to said shield electrode to carry the voltage thereof in a positive direction when its corresponding edge occupies its predetermined position, whereby said tube ionizes when said edges simultaneously occupy their predetermined positions only, and means responsive to ionization of said control tube for accepting said article.

4. In a phototube sizing device, a light source and an optical system providing at least one light beam, means for determining whether a, dimension of said article intercepting a portion of said beam corresponds to a predetermined dimension comprising a first phototube circuit responsive to light passing one edge of said article for determining when said edge occupies a predetermined position and a second phototube circuit responsive to light passing another edge of said article for simultaneously determining whether said other edge occupies another predetermined position, and selecting means controlled by both said phototube circuits for accepting said article when both said edges simultaneously occupy their corresponding predetermined positions, said selecting means including a control tube of the arc discharge type having a cathode and two control electrodes, electrical circuits and a source of voltage for maintaining each of said electrodes at a voltage with respect to said cathode preventing ionization of said control tube, each of said phototube circuits being connected to one of said control electrodes to carry the voltage thereof in a positive direction when the corresponding edge of said article occupies its predetermined position, whereby said control tube ionizes when said edges simultaneously occupy their predetermined positions only, and selecting means responsive to ionization of said control tube for accepting said article and rejecting said article when said control tube fails to ionize, said last named means including a second control tube responsive to one of said phototube circuits for sion of said article interceptin a portion of saidbeam corresponds to a predetermined dimension comprising a first phototube circuit responsive to light passing one edge of said article for determining-when said edge occupies a predetermined position and a second phototube circuit position, and selecting means controlled by both said phototube circuits for accepting said article when both said edges simultaneously occupy their corresponding predetermined positions, said selecting means including a control tube of the arc discharge type having a cathode and twocontrol electrodes, electrical circuits and a source of voltage for maintaining each of said electrodes at a voltage with respect to said cathode pre-; venting ionization of said control tube, each of said phototube circuits being connected to one of said control electrode: to carry the voltage thereof in a positive direction when the corresponding edge of said article occupies its predetermined position, whereby said control tube ionizes when said edges simultaneously occupy their predetermined positions only, and selecting means responsive to ionization of said control tube for accepting said article and rejecting said article when said control tub fails to ionize, said last named means including a second control tube of the arc discharge type having a control electrode connected to one of said phototube circuits to cause ionization of said second control tube when one of said edges occupies its predetermined position irrespective of the position of the other of said edges, means responsive to ioniza-- tion of said second control tube for initiating operation of said selecting means and for thereafter causing deionization of both said control tubes.

6. In a phototube sizing device, a light source and an optical system providing at least one light beam, means for determining whether a dimension of said article intercepting a portion of said beam corresponds to a predetermined dimension comprising a first,phototube circuit responsive to light passing one edge of said article for determining when said edge occupies a predetermined position and a second phototube circuit responsive to light passing another edge of said article for simultaneouslydetermining whether said other edge occupies another predetermined position, each of said phototube circuits including a pair of phototubes, one of said phototubes of each circuit being positioned'to receive light passing its corresponding edge and the other phototube of each circuit being positioned to be.

placed in shadow by said corresponding edge when said corresponding edge occupies its predetermined position, each of said phototube circuits being connected to form a bridge so that the bridgeof each circuit is substantially in balance when both phototubes thereof receive.

light or are in shadow and is unbalanced when one phototube thereof receives light and the other phototube thereof is in shadow and selecting means controlled by both said phototube circuits for accepting said article when both said bridges are simultaneously unbalanced, said device having a convex mirror individual to each of said phototube circuits and a projecting lens for focusin the shadow of the corresponding edge of said article upon the corresponding mirror, the phototubes of each circuit being positioned to I receive reflected light or shadow from said mirror corresponding to its circuit.

7. In a phototube sizing device, a light source mension comprising a first phototube circuit responsive to light passing one edge of said article for determining when said edge occupies a predetermined position and a second phototube circuit responsive to light passing another edge of said article for simultaneously determining whether said other edge occupies another predetermined position, each of said phototube circuits including a pair of phototubes, one of said phototubes of each circuit being positioned to receive light passing its corresponding edge and the other phototubeof each circuit being positioned to be placed in shadow by said corresponding edge when said corresponding edge occupies its predetermined position, each of said phototube circuits being connected to form a bridge so that the bridge of each circuit is substantially in balance whenboth phototubes thereof and an optical system providing at least one light beam, means for determining whether a dimension of said article intercepting a portion of said beam corresponds to a. predetermined direceive light or are in shadow and is unbalanced when one phototube thereof receives light and the other phototube thereof is in shadow, and

selecting means controlled by both said phototube circuits for accepting said article when said bridges are simultaneously unbalanced, said device having a convex mirror individualto each of said phototube circuits and a projecting lens for focusing the shadow of the corresponding edge of said article upon the corresponding mirror, the phototubes of each circuit being positioned to receive reflected light or shadow from said mirror corresponding to its circuit.

8. In a photoelectric sizing device, a light source and an optical system providing a light beam, means for determining the size of an article intercepting a portion of the light in said'beam including a phototube circuit responsive to light passing one edge of said article for determining the position of said-edge, said circuit including a pair of phototubes one of which receives light passing said edge and the other of which is placed in the shadow of said edge when said edge is in a predetermined position, a second phototube circuit responsive to light passing another edge of selecting said article when both said edges of said article simultaneously occupy said predetermined positions and rejecting said article when one of said edges occupies its predetermined position and the other of said edges fails to occupy its predetermined position, said last named means-including a control tube of the are discharge type having a control electrode and a shield electrode, one of said circuits controlling the potential of one of said electrodes and the other of said circuits controlling the potential of the other oi said electrodes to provide for ionization of said tube when said edges simultaneously occupy said predetermined positions only and means responsive to ionization of said control tube for accepting said article.

9. In a phototube sizing device, a light source and an optical system providing at least one light beam, means for determining whether a dimension of said article intercepting a portion of said beam corresponds to a predetermined dimension, comprising a first phototube bridge circuit responsive to'light passing one edge of said article tion of the indicating means when one of said bridge circuits is balanced or is unbalanced in a 10 direction of potential opposite that for actuating the indicating means.

SAMUEL c. HURLEY. JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,237,811 Cockre11 Apr. 8, 1941 2,033,645 Parkhill Mar. 10, 1936 2,114,867 Wilson Apr.. 19, 1938 2,304,814 Glasser -Dec. 15, 1942 2,188,159 Rockwood -Jan. 23, 1940 2,085,671 Powers June: 29, 1937 1,873,315

Dreyer Aug. 23, 1932