US 2982404 A
Description (OCR text may contain errors)
G. J. HARMON 2,982,404
SPACER AND SORTER FOR SERIALLY CONVEYED UNITS May 2, 1961 Filed May 13, 1955 JIWUJLL, I.
.n y M m Nm w mp t mm M J M y w T k k ats WW 653M mfnro w tfi Patented May 2, 1961 SPACER AND SORTER FOR SERIALLY I CONVEYED UNITS Gregory J. Harmon, Bethesda, Md., assignor to Reed Research, Inc., Washington, D.'C., a corporation of Delaware Filed May 13, 1955, Ser. No. 508,105
2 Claims. (Cl. 209-82) This invention relates to a spacer and length sorter for serially conveyed units, and more particularly to a device and system for insuring that letter-containing envelopes which are being fed on a conveyor to an automatic facing machine are properly spaced and are not of greater length than can be handled by the machine.
The present invention is intended primarily for use with a stamp-sensing machine of the type described in copending applications, Serial Number 460,385, filed October 5, 1954, now Patent No. 2,936,886, issued May 17, 1960, for Stamp Sensing LetterSorter, and Serial Number 478,694, filed December 30, 1954, for Article Handling and Sorting Apparatus. However, it will be apparent that the invention is also applicable to other types of automatic sorting and conveying machines, and to items other than mail envelopes.
letter to be passed. A mechanical selector gate is provided for routing the letters to either the accept or reject position according to signals provided by the photoelectric cells. The arrangement is such that if the trailing edge of a letter has cleared both of the first two light beams before its leading edge intercepts the third light beam, the letter will be accepted, provided that the following letter has not yet reached the first light beam. In all other cases, the letter will be rejected.
It is an important object of the invention to provide means whereby interruptions of the first two light beams establish a rejec conditioning signal, while interruption It is a primary object of the invention to sort all letters which are properly spaced and of the proper length into one conveyor channel for further treatment, and to sort all letters which are improperly spaced or of too great length into another channel which may be termed the reject? channel. Another object is to provide a system for the above purpose which is automatic in operation, simple and inexpensive in construction, and fool-proof in operation.
Still another object is the provision of a photoelectric sensing station arranged to sense letters which are either too long or insufliciently spaced from thenext following letter.
The above identified copending applications relate to a device for automatically facing all of the envelopes of a batch of mail as they are dumped from the mail bag or sack into a conveyor device. It will be apparent that the letters so dumped will be randomly oriented and before they can be fed into the stamp cancelling machine, they must be arranged with all the stamp-bearing corners similarly oriented. This is accomplished automatically by the machine described in the above-referred to applications. However, for proper operation of the machine and particularly to permit time for the selector gates of the machine to move from one selecting position to another, it is necessary that the letters be. spaced by a minimum amount, e.g., five or six inches. 7 Since the machine can only hold letters of a certain maximum length, it is also necessary that letters of greater length than this be rejected. Furthermore, it occasionally happens that letters stick together in overlapping relationship as they move along the conveyor; such letters should, of course, be rejected. This is accomplished, according to the invention, by providing a photoelectric sensing station having three light beams across the path of the letters at three separated points on the conveyor line together with photoelectric means for indicating the presence or absence of a letter at each point by the resulting interruption of the light beam. Two of the light beams are spaced in accordance with the desired gap between successive letters, and the third light beam is spaced from one of the other two in accordance with the desired maximum length of a of the third light beam triggers the mechanical gate for reject operation if the above signal is established or for accept operation in the absence of the above conditioning signal.
A further object is to provide electronic circuit means for insuring positive and definite operation of the gates under all conditions.
The specific nature of the invention as well as other objects and advantages thereof will clearly appear fi'om a description of the preferred embodiment as shown in the accompanying drawings, in which:
Fig. 1 is a schematic diagram showng the principle of operation of the invention;
Fig. 2 is a timing chart showing the relationship of the conditioning and triggering pulses; and
Fig. 3 is a schematic circuit diagram of a practical circuit for carrying out the invention.
Referring to Fig. 1, a letter 2 is conveyed by any suitable conveyer means 1 in the direction of the arrow successively past stations A, B. and C, at each of which the letter intercepts a light beam from lamps 4, 6 and 8, respectively. Each lamp beam is directed toward a photocell 5, 7, or 9, respectively, so arranged in lines 10, 12, and 39 as shown that interception of the light beam causes an electric pulse in the associated photocell circuit. Assuming the stations to be spaced as indicated, with five inches of spacing between A and B, and twelve inches of spacing between B and C, and assuming in the first place a letter 2 shorter than five inches, the letter will produce a pulse from time t to time t at station A; a pulse from time 1 to time t, at station B; and a pulse from t to at station C. Photocells 5 and 7 are connected in series by line 39, and interception of a light to either one will produce a negative pulse in line 10, therefore with a short letter (less than five inches long) there will be two separate and distinct pulses in line 10 as shown, and sometime later, another short pulse in line v12 leading from station C. The timing relationship of the pulses is shown in full lines in Fig. 2, all pulses being shown positive for convenience. Line 10 is connected through an amplifier 1 4 to a bi-stable trigger or flip-flop arrangement 16, 18, in such fashion that if the amplifier is in the one state (i.e., stimulated or unstimulated), line 20 is at a relatively high potential and line 22 is at a relatively low potential, while if the amplifier is in the other state, line 20 is relatively low and line 22 is relatively high. Normally the amplifier is in the conducting state, and the negative pulse on its input renders it nonconducting as long as the pulse lasts. This causes the potential on line 20 to drop and the potential on line 22 to rise as long as the pulse lasts. Flip-flop 16, 18 is preferably a thyratron device so arranged that normally (with amplifier 14 in the first state) side 18 can be activated and side 16 deactivated. When side 18 is activated, then magnet 26 is energized to operate a mechanical gate' means 40 to direct letter 2 into an accept channel 41; when side 16 is activated, then magnet 24 is energized to direct letter 2 into the diflerent channel designated as the reject channel =41. The voltages on lines 20 and 22 respectively do not per se activate the flip-flop, but only condition the flip-flop for activation. In order to activate the flip-flop, a triggering pulse on the second input into each side of the flip-flop is necessary on line 28; this second input comes from station C, where the leading edge of the pulse from time t to time t is differentiated through differentiator 30 to produce a sharp positive triggering pulse at time t This pulse is applied to both sides of the flip-flop 16, 1S, and will cause the conditioned side of the flip-flop to be activated if it was previously inactive; otherwise there will be no change, that is, if the gate was last on the same side as is now conditioned, then there will be no change produced by the triggering, but if not, then the mechanical gate will change to the opposite position. In our assumed example (letter less than five inches long), the short letter will have cleared both stations A and B before its front edge arrives at station C at time t therefore amplifier 14 will be conducting at time t line 20 will below and line 22 high, as previously explained, and side 18 will be conditioned, so that the pulse from station C at time t produced by differentiation of the leading edge will appear on line 28 and be fed on lines 32 and 34 to both sides 16 and 18, but since 18 is conditioned, will activate side 18 only to energize the accept magnet 26; this is true regardless of which side was previously energized. If magnet 24 was previously energized, it will remain in that state until the triggering pulse on line 28 activates side 16 to flip the energization to magnet 26 and once either side is energized by a pulse from line 28, it remains in that condition until the combination of the other side being conditioned (by line 20 or 22) and triggered (by line 28) causes a change.
The above example assumes that no second letter follows our short letter 2, at such a distance behind letter 2 that the front edge of the following letter was less than 12 inches behind the front edge of letter 2; if that had been the case, then at the time of pulse t from the front edge of letter 2, the light beam at station B would also be interrupted and side 16 of the fiip-flop would be conditioned instead of side 18 so that the letter 2 would be rejected. Therefore it will be seen that unless a letter is spaced from the following letter by at least a minimum distance, it will be rejected, which is one of the objects of the invention. It will also now be apparent that if a letter is greater than twelve inches long, it will be rejected, since in that case, when the front edge produces pulse t at station C, the rear edge will not have cleared station E, and so side 16 will be conditioned to reject the letter.
If a letter is less than twelve inches, say eleven inches long, it will be accepted, as its trailing edge will have cleared station B at time t unless a following letter has entered station A, in which case it will be rejected. It will thus be seen that even with the greatest letter that can be accepted, there must be a space of more than five inches between it and the next following letter for the letter to be accepted.
The rejected letters can be sent along a separate conveyor, preferably slower than the main conveyor, and the very long ones manually picked out, while the overlapping short ones can be returned to the main feeder from which letters are supplied to the conveyor; since a relatively small percentage of the letters are thus overlapped, the probability is that these will be adequately spaced on the second trip, and if not, by the third, etc., trip around. The treatment of rejected letters, however, is a matter of choice, and not a part of the present invention; which is concerned with the separation and rejection of letters which might cause trouble in the sensing operation which follows.
It should be explained that prior to arrival at station A, the letters have been subjected to a mechanical spacing treatment which properly spaces the great majority of them, but since over-length letters are occasionally found and since occasional overlapping of even short letters can occur, the present device is necessary to insure proper operation of the sensing machine.
Fig. 2 shows the timing relation between letters of various length. Since the speed of the conveyor system is constant, it will be noted that for a given letter, times t and t always have the same relation corresponding to the spacing of the stations, while times t t and t have also the same relation to each other, but not to times 11, t and t Note that for very short letters (heavy solid line in Fig. 2) and for ordinary letters (dash line) there is no overlapping at time t but for very long letters (broken line) time 12; does not occur until after time t so that the letter is rejected; likewise if a following letter is properly spaced, its leading edge arrives at station A at time T but after t but if the gap between the letters is too small, it arrives at time T before t has occurred, and the leading letter is rejected.
Fig. 3 shows the details of a circuit in accordance with the block diagram of Fig. 1. Corresponding parts will be given the same reference characters as in Fig. 1, with a prime added. Note that the negative pulse on line 10' is applied to the grid of amplifier tube 14', the cathode of which is returned to 5 volts through resistance 15, producing a cathode follower effect whereby changes in the potential on line 22 follow the changes in potential on line 10', while potential changes on plate line 20 are of opposite sign, to produce the effect described in connection with Fig. 1. A neon lamp 21 is used to provide a simple direct current coupling to conditioning grid 17' of thyratron 16, as there is a constant voltage drop across the neon lamp (70 volts for type NE-2 lamp), which transfers the sensing effect of the photocells 5 and 7 to the grid 17', providing effective voltage regulation.
At station C, a double photocell (type 55 84) is used of a type having two slits spaced about A; inch, so that at the conveyor speeds (approximately ten feet per second), the effect is substantially that of a single pulse, so far as time is concerned, the output of each photocell being supplied to one of the control grids 97 and 98 of thyratrons 16 and 18' respectively. This insures isolation between the grids 17 and 19' so that the change in voltage due to the inductive condition of either thyratron does not affect the grid of the other'tube. The plate circuits of the two thyratrons 16 and 18' are coupled through a 0.1 microfarad condenser 23 to provide the desired flip-flop action whereby only one tube can be energized at a time, as is well-known in the art. The actual mechanical gates energized by magnets 24' and 26' are preferably of the type shown in copending application, Serial Number 478,694, filed December 30, 1954, for Article Handling and Sorting Apparatusv In order to clarify the operation of applicants apparatus and claim the combinations thereof in terms of the functional relationships disclosed above, the following terms are defined: the conditioning circuit means 42 comprises elements 14', 15, 21, and their associated connections as shown in Figure 3; the gate operating circuits comprise (1) elements 16, 24, and their associated connections as shown in Figure 3, and (2) elements 18', 26', and their associated connections as shown in Figure 3; and the electrical signal circuits comprise (1) elements 5, 39, and their associated power supply, (2) elements 7, 10, and their associated power supply, and (3) elements 9, 12, and their associated power supply, as best shown in Figure 1.
It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of my invention as defined in the appended claims.
1. In combination with means for conveying a series of separate articles in a fixed path of motion, said path of motion having a direction, said articles having been previously subjected to a mechanical spacing treatment which properly spaced the great majority of them, a plurality of sensing stations spaced along said means for conveying and including at least a first station, and a second station spaced from said first station forwardly along said path in the direction of motion of said articles by a fixed distance corresponding to a critical length of said articles, two channels spaced forwardly of both said first and second stations with respect to the direction of motion of said articles, article selecting gate means operative to allow communication between said path and one of said two channels, each of said first and second stations comprising electrical sensing means connected in an electrical signal circuit and operable during the time of passage of any of said articles past said station to produce an electrical signal in its associated signal circuit, article selecting gate control means openatively associated with said sensing means of said first and second stations and said gate means, said gate control means comprising two gate operating'circuits connected to said signal circuits for operating said gate means to a first state in which said articles are allowed communication only with one of said two channels or to a second state in which said articles are allowed communication only with the other of said two channels, conditioning circuit means connected to the signal circuit of said first station for conditioning one of said two gate operating circuits for operation in the absence of a signal from said sensing means of said first station at the time of the signal caused by an article reaching said sensing means of said second station, or for conditioning the other of said two gate operating circuits for operation upon the occurrence of a' signal from said sensing means of said first station at the time of the signal caused by an article reaching said sensing means of said second station, actuating circuit means connected to said signal circuit of said second station for actuating only the conditioned one of said two gate operating circuits in response to the signal caused by an article reaching said sensing means of said second station, and aspacer-sensing station spaced along said means for conveying rearwardly with respect to said direction of motion of said articles from said first station by a distance corresponding to a minimum predetermined required spacing between articles, said spacer-sensing station comprising electrical sensing means connected in an electrical spacersignal circuit and operable during the time of passage of any of said articles past said station to produce an electrical signal in said spacer-signal circuit, and means connecting said spacer-signal circuit to' said conditioning circuit means to permit the conditioning of said one of said two gate operating circuits for operation in the absence of a signal from said sensing means of said spacersensing station at the time of the signal caused by an article reaching said sensing means of said second station,
, or to permit the conditioning of said other of said two gate operating circuits for operation upon the occurrence of a signal from said sensing means for said spacer-sensing station at the time of the signal caused byan article reaching said sensing means of said second station, whereby a signal from either said sensing means of said spacer-sensing station or from said sensing means of said first sensing station will have the same effect in conditioning said gate operating circuits.
2. In combination with means for conveying a series of separate articles in a fixed path of motion, said path of motion having a direction, a plurality of sensing stations spaced along said means for conveying and including at least a first station, and a second station spaced from said first station forwardly along the direction of motion of said articles by a fixed distance corresponding to a critical length of said articles, each of said first and second stations comprising electrical sensing means connected in an electrical signal circuit and operable during the time of passage of any of said articles past said station to produce an electrical signal in its associated signal circuit, article selecting control means operatively associated with said sensing means of said first and second sensing stations, said control means comprising two operating circuits connected to said signal circuits for activating said control means to a first state or to a second state, conditioning circuit means connected to the signal circuit of said first station for conditioning one of said two operating circuits for operation in the absence of a signal from said sensing means of said first station at the time of the signal caused by an article reaching said sensing means of said second station, or for conditioning the other of said two operating circuits for operation upon the occurrence of a signal from said sensing means of said first station at the time of the signal caused by an article reaching said sensing means of said second station, actuating circuit means connected to the signal circuit of said second station and to said control means for actuating only the conditioned one of said two operating circuits in response to the signal caused by an article reaching said sensing means of said second station.
OTHER REFERENCES Circuit Theory of Electron Devices by Boone, copyright 1950.