US2995362A

US2995362A - Letter feeder

Info

Publication number: US2995362A
Application number: US856269A
Authority: US
Inventors: Maurice M Levy
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-11-30
Filing date: 1959-11-30
Publication date: 1961-08-08
Anticipated expiration: 1978-08-08

Description

M. M. LEVY LETTER FEEDER Aug. 8, 1961 9 Sheets-Sheet 1 Filed Nov. 30, 1959 M. M. LEVY LETTER FEEDER Aug. 8, 1961 9 Sheets-Sheet 2 Filed Nov. 30, 1959 M. M. LEVY LETTER FEEDER Aug. 8, 1961 9 Sheets-Sheet 3 Filed Nov. 30, 1959 Ba \K /I all I zisa I L Ill 1951 M. M. LEVY 2,995,362

LETTER FEEDER Filed Nov. 50, 1959 9 s s 4 H/S ATTORNEYS 1951 M. M. LEVY 2,995,362

LETTER FEEDER Filed Nov. 50, 1959 9 Sheets-Sheet 5 Aug. 8, 1961 M. M. LEVY 2,995,362

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LETTER FEEDER Filed Nov. 30, 1959 9 Sheets-Sheet 9 mad-A270 United States Patent 2,995,362 LETTER FEEDER Maurice M. Levy, Ottawa, Ontario, Canada, assignor to Her Majesty The Queen in The Right of Canada as represented by the Postmaster General, Ottawa, Ontario,

Canada Filed Nov. 30, 1959, Ser. No. 856,269 Claims. (Cl. 271-36) This invention relates to a feeder for letter mail and like articles. The principal characteristic that distinguishes mail from most other flat articles (such as punch cards and similar information-storing records that require to be sorted and otherwise handled by feeding mechanisms) is the widely varying dimensions of the articles. Letter mail, which is assumed to include post cards, but is distinguished from parcel mail (with which this invention is not concerned) varies from piece to piece in length, height, thickness and weight as well as in surface coefiicient of friction. Consequently it has presented many problems in the design of mechanical feeding devices that will accept and handle reliably and uniformly pieces of mail of widely varying characteristics received in a random order.

The modern mechanisation of postal operations requires letter feeders that are both versatile and reliable. Machines are now in existence for automatically franking and cancelling the stamps on letters. Machines have also been developed for applying coded addresses to letters and for automatically reading such codes and sorting the letters accordingly. One of the merits of such machines is that they operate at high speeds; but, on the other hand, they require that successive letters be fed to them with a high degree of precision in the timing between letters. Some machines require letters to be fed so that there is a constant distance between the trailing edge of each letter and the leading edge of the next letter; other machines, particularly sorting machines, require the letters to be fed to them with equal spacing between the leading edges of successive letters, regardless of the variations in the lengths of the letters. It is with a feeder designed to produce this latter type of feed that the present invention is concerned. It will be appreciated that normally the letters will initially be arranged in the form of a stack, with the letters lying face to face, and it is the function of the feeder to change them from this orientation to a series of spaced letters arranged end to end.

That is to say, the primary object of the invention is to provide a feeder that can pass a series of letters sequentially to a further instrumentality where they are either to be franked, coded, sorted or otherwise manipulated, such feeder ensuring an accurately determined time interval between presentation of successive leading edges of the letters to a datum position at the input of such further instrumentality, or, to be more exact, at the output of the feeder itself. In practice, this latter alternative amounts to the same thing because the output of the feeder will either coincide with the input to the other instrumentality or will be connected thereto by a constant speed conveyor.

Feeders designed to perform in this manner have al ready been proposed, but they have all suffered to a greater or lesser extent from one or other of the following disadvantages: lack of accuracy; a tendency to jam and damage the letters (at the speeds involved, say ten letters a second, a jam may seriously mutilate one or more pieces of mail, which is an event that cannot be tolerated); a tendency to feed doubles (that is two or more letters that have become interlocked with each other or have otherwise adhered to each other, and tend to travel as a single unit); excessive wear on the mechani- 2,995,362 Patented Aug. 8, 1961 cal parts (in some feeders it has been found necessary to replace critical propelling surfaces, which are usually made of rubber, as often as daily).

The object of the present invention may thus be further stated as the provision of improvements in regard to these disadvantages, more specifically the provision of an increase in the precision of letter spacing, while permitting a more reliable high speed operation than has heretofore been found practicable. A subsidiary object is the reduction of wear on the parts, or at least the distribution of wear over larger areas of the parts so as to extend their useful life. A still further object is the minimisation of the feeding of doubles to the receiving instrumentality. A certain number of doubles can be tolerated, because provision will normally be made to detect and reject doubles in the instrumentalities carrying out the subsequent manipulations. Nevertheless each double fed forward and later rejected represents a reduction in the efficiency of the system, and is therefore to be avoided as far as possible.

A feeder exhibiting the many features of the invention is illustrated by way of example in the accompanying drawings.

FIGURE 1 is a plan view, with the top cover removed, of the overall feeder mechanism;

FIGURE 2 is a fragment of FIGURE 1 showing the parts in a different position;

FIGURE 3 is a section on the line HIIII in FIG- URE 1;

FIGURE 4 is the same section showing the parts in a different position, being taken on the line IVIV in FIGURE 2;

FIGURE 5 is a section on the line VV in FIG- URE 1;

FIGURE 6 is a partial side view of FIGURE 1 as seen on the line VI-VI;

FIGURE 7 is a section on the line VIIVII in FIG- URE 1;

FIGURE 8 is a simplified diagrammatic representation of the feeder showing an initial stage of a feeding operation in progress, identified subsequently as Time 1;

FIGURE 9 is a similar diagram showing the position of the parts and a letter at a later stage identified as Time 2;

FIGURE 10 is a similar diagram showing conditions at a stage just after that of Time 2, identified as Time 2A;

FIGURE 11 is a further such diagram showing the position of a letter that has been correctly fed, at a later stage known as Time 3;

FIGURE 12 is a digram of the conditions prevailing at Time 3, if the letter is not correctly fed forward;

FIGURE 13 is a circuit used in the apparatus;

FIGURE 14 is a diagram illustrating the cycle of operations of the apparatus;

FIGURE 15 is a further view similar to FIGURES 8 to 12 showing an improved construction; and

FIGURE 16 corresponds to FIGURE 15 with the parts in a different position.

The feeder may be considered for convenience to consist of three parts, a preliminary feeding station, a main feeding station and an output station.

The principal components of the main feeding station (FIGURES 1 and 3) are a main feeding roller A mounted on and driven through a ratchet or like conventional form of overhauling mechanism 9 (that is a mechanism that drives positively in one direction while permitting a free-wheeling action in the other direction), the mechanism 9 being connected to a cam E that is mounted on a shaft 10 which is fixed in position in the framework of the apparatus; a pair of coaxial idler rollers B mounted on the free ends of a forked member 11 pivoted about pin 12; and a reverse driving roller C mounted on a pair of spaced arms 13 pivoted on a pin 14 and driven by shaft 8 connected by universal joint 7 to further shaft 6.

The principal components of the output station are a pair of fast driven, forward drive rollers D1 and D2 mounted on respective drive shafts 15 and 16 (FIG. The shaft 15 is mounted in fixed position in the framework and the shaft 16 is supported between spaced arms 17 that are secured to the pin 14.

The arms 13 that control the position of the reverse driving roller C are acted upon by a yoke 18 pivotally mounted on the end of a rod 19 that is free to slide through a conventional bearing 20 to an extent limited in one direction by an adjustable stop 21, and is urged in that direction by a coil spring 22. By this method of mounting, the reverse driving roller C is free to be pushed back resiliently by rollers B so as to be out of contact with the main feeding roller A. This is the condition illustrated in FIGURES l, 3 and 5 and its purpose will later be explained in detail. Whenever this pressure from rollers B is removed, roller C will be urged by spring 22 to project into contact with roller A, as shown in FIGURES 2 and 4.

Roller D2 is urged firmly against roller D1 by a further spring 23 acting at one end on an arm 24 secured to the pin 14 to which the arms 17 supporting roller D2 are connected. The other end of spring 23 is connected to a similar but fixed arm 24a. A plate 33 is mounted to move with arms 13 and hence with roller C, this plate being apertured for the projection through it of the appropriate peripheral locations of rollers C and D2. Roller C has three projecting peripheral portions, two end portions which engage the spaced rollers B and a central portion which engages the main roller A. All three such portions are, however, firmly supported on a common core and always rotate together. As an alternative, the central portion of roller C which engages the main roller A may be separate from the outer portions and be arranged to be fixed against any rotation.

As already mentioned, the cam E is mounted con centrically on the shaft with the main feeding roller A to turn in a clockwise direction as seen in FIGS. 1 and 2. Cam E cooperates with a cam follower 25 secured to one arm of the forked member 11 carrying rollers B. The cam E thus controls the position of rollers B; whether they are withdrawn as shown in FIG. 2, or projecting as in FIGURE 1. On an extension 26 of the forked member 11, there is mounted a boss 27 secured to a rod 28 slidable in frame bracket 29. Boss 27 is acted on by a spring 30 which thus serves to press the cam follower 25 firmly against the cam E. A continuation 28a of rod 28 acts through an arm 31 pivoted at 31a on the actuating plunger 32 of a switch S mounted on the frame. FIGURES 1 and 2 show this actuating plunger in its two positions. In the FIGURE 2 position switch S is open; in the FIGURE 1 position it is closed.

Before letters are engaged by the rollers that have already been described, they are moved forward from a preliminary feeding station comprising a vacuum chamber V (see FIGURES l, 6 and 7) in which is mounted a pair of coaxial preliminary feed rollers F straddling a control finger G which is mounted on a spindle 40 that can be turned anti-clockwise from the position seen in FIGURE 1 by a crank 41 connected by a link 42 to a conventional rotary type solenoid M1. When the solenoid is energized, spindle 40 is turned to cause finger G to project beyond the peripheries of rollers F. (The effect of this action is described later in connection with FIGURE 12.) Rollers F rotate together, being fixedly mounted on a common driven shaft 43, the direction of rotation being clockwise as seen in FIGURE 1.

The pressure within vacuum chamber is controlled by a rotary valve H, the position of which is determined by a crank arm 44, link 45 and a second rotary type .4 solenoid M2. In the position of the valve H shown in FIGURES 1 and 7, a port 46 in valve member 47 connects the interior of chamber V to a suction pipe 49 that leads to a vacuum source (not shown). This position is the energised position of solenoid M2. When solenoid M2 is released to permit link 44 to turn clockwise under the action of a spring incorporated in the solenoid M2, ports 46 and 48 are brought out of register with each other, while a port 50 in a second valve member 51 of valve H is brought into register with a port 52 fixed in chamber V and communicating with atmosphere through vent 53. Thus when solenoid M2 is de-energised, the vacuum is released.

The framework which supports all the parts heretofore described includes a vertically disposed, smoothly polished face plate 54 which is apertured only sufliciently to allow the peripheries of rollers A, B, D1 and F and finger G to project beyond its outer surface. Plate 54 cooperates with plate 33 to form a channel over the latter part of the path of travel of a letter, a short portion of a fixed plate 55 (FIGURE 1) also being provided as a continuation of the movable plate 33 to cooperate with the extreme end of plate 54 to provide a discharge channel at the output station of the device. The letters travel standing vertically between these plates, their lower edges resting on a smoothly polished horizontal plate 56. These various plates thus cooperate to define a path of travel for letters from the preliminary feeding station of rollers F, through the main feeding station of rollers A, B and C, to the output station of rollers D1 and D2.

The feeding of letters to the preliminary feeding station is effected by a conventional spring urged arm K. This type of feed, which presents a new letter to the roller F after each previous letter has been fed forward, is well known in mail handling machines and need not be considered in further detail since the inventive features with which the present application is concerned reside elsewhere in the apparatus.

Shafts 6, 10, 15, 16 and 43 are all driven from a motor (not shown) through a gear box 59 (FIGURE 1).

Three photo-electric cells P1, P2 and P3 are provided. Cell P1 is seen in FIGURE 5 and cell P3 is seen in FIG-

URES

3 and 4. Cell P2 is arranged between cells P1 and P3, as is illustrated in the diagrammatic views of FIG- URES 8 to 12. Each cell has an associated lamp R R and R The effective optical lines of these three photoelectric systems are best appreciated from the simplified illustrations of FIGURES 8 to 12 to which reference will be made when explaining the manner of operation of the device. However, in addition to these latter figures which show the positions of the various parts of the apparatus at specific times during an operating cycle, there is provide, as FIGURE 14, an explanatory diagram showing a cycle of operations.

It will therefore be desirable first to explain FIGURE 14 in general terms, after which it will be explained in greater detail along with FIGURES 8 to 12.

The

number

1, 2, 2A, 3,. 4A and 4 at the top of FIG URE l4 refer to specific Times in the cycle, as determined by the position of the cam E, similar numbers having been applied to points on the periphery of the cam E in FIGURES 1 and 2. When each of these given numbered points on the cam E is in contact with the cam follower 25, the parts will be in the condition shown on FIGURE 14 under the same number. FIGURES l and 8 show the conditions at Time 1; FIGURE 9 shows them at Time 2; FIGURE 10 at Time 2A; FIGURE 2 at Time 3; and FIGURES 11 and 12 both at Time 4, FIGURE 11 showing conditions when forward feeding takes place correctly, while FIGURE 12 shows conditions if incorrect operation occurs.

Considering now the beginning of a feeding cycle at Time 1, reference should be made to FIGURE 8 where it will be seen that the idler rollers B are projecting into engagement with the reverse driving roller C, thus h0lding such roller C out of contact with the main feeding roller A. Reverse driving roller C is driven clockwise, so it induces anti-clockwise rotation of idler rollers B. Photo-cell P3 is energised, since no letter obscures its optical line. This cell is connected to solenoid M2 which is accordingly energised to turn the valve H to apply vacuum to the chamber V. As a result the first letter L1 in the stack of letters L is drawn by suction into a position extending across the mouth of the chamber V. The letter is thus drawn against the preliminary feed rollers F which are driven clockwise. Consequently the letter is fed forward towards the rollers B and C which, as already explained, are now rotating in a direction to reject the letter. As a result it remains, waiting, adjacent the jaws of the rollers B and C which constitute the input area of the main feeding station. The main feeding roller A is rotated blockwise continuously, but it can have no propelling action on the letter at this time, because there is no roller cooperating with it to hold the letter against it. A roller will have no propelling eflfect on a letter unless the letter is pressed against the roller. As the letter approaches this waiting position, it cuts the optical line of photo-cell P3, thus deenergising solenoid M2 and releases the vacuum in chamber V. Preliminary feed rollers F, although continuing to rotate, thus have no further forceful propelling action on this letter, which as a result is not subjected to any buckling forces. Alternatively, the valve H may be adjusted to leave a slight vacuum in the chamber V in order to ensure that the letter will be urged gently by the rollers F into the input area of the main feeding station.

These events take place between Time 1 and Time 2, that is between movement of the cam E from the position seen in FIGURE 8 to that seen in FIGURE 9, this period comprising the Preliminary feeding period and the first part of the Waiting period shown on FIGURE 14.

At Time 2, the cam follower 25 is just on the point of moving onto the depression on the cam E. As FIGURE 14 shows, this produces a withdrawal of rollers B, which movement is followed by the spring urged roller C. Very shortly after this movement begins, roller C comes to bear against the main roller A, or, more accurately, comes to rest against one face of the letter L1 while forcing the opposite face of such letter against roller A. The exact moment at which this pressure is applied, is dependent on the thickness of the letter, and cannot therefore be defined with certainty on the cam E. A typical such moment has been designated as Time 2A in FIG- URE 14, and is illustrated in FIGURE 10. Nevertheless, the variations between Times 2A from letter to letter are so small in practice as to have no appreciable effect on the desired accuracy of letter feeding periodicity.

At approximately the same time as this pressure is applied, the switch S is opened by the movement of rod 28, such movement being brought about by pivoting of the forked member 11 which carries the cam follower 25, in the manner already explained.

The Main synchronised feeding period starts at Time 2A and continues until Time 4A which shortly precedes Time 4 in the same manner that Time 2A follows Time 2. Like Time 2A, Time 4A is not uniquely determinable, because it will depend on the thickness of the letter and whether or not the letter has already been removed from between rollers A and C by the output rollers D1 and D2, a consideration that will depend on the length of the letter. Output rollers D1 and D2 which drive faster than the main feeding roller A should, if the operation has been performed correctly, have seized the letter towards the end of the Main synchronised feeding period and thereby have initiated the Fast feeding period shown in FIGURE 14. This function will now be described in more detail.

During the Main synchronised feeding period from Time 2A to Time 4A, the cam follower 2,5 is riding on the depression of the cam B so that the rollers B are withdrawn and rollers A and C control the movement of the letter. These latter rollers are both rotating clockwise so as to have opposite propelling effects on the letter. The surface of the main feeding roller A is made of rubber or other material, having a comparatively high co efiicient of friction, while that of reverse driving roller C is composed of a material having a comparatively low coefiicient of friction, with the result that the roller A predominates in its effect on the letter which is thus fed forward at a speed determined by the speed of rotation of shaft 10. However, the reverse rotation of roller C has a useful tendency to separate or weaken the interlock between a double, if one has been fed forward from the preliminary feeding station.

Towards the end of the Main synchronised feeding period (somewhere between Times 3 and 4A), the leading edge of the letter will reach (assuming correct operation) the jaws of rollers D1 and D2 which are pressed together with a great deal more pressure than are rollers A and C. Moreover rollers D1 and D2 have a high coefficient of friction and are rotated with a peripheral speed substantially greater than that of roller A so that they seize the letter and eject it rapidly from the output station of the apparatus. FIGURE 11 shows this operation in progess at Time 4. If the trailing end of the letter is still in engagement with the roller A when the rollers D1 and D2 seize the leading end, which will depend on the length of the letter, the pull of the letter will induce a short overhauling movement of the roller A, since the roller A is free to turn relative to its shaft 10 in a clockwise direction by virtue of ratchet mechanism 9. This overhauling movement will continue until the end of the letter has passed beyond the roller A. If the letter is short, this. movement may be small or even non-existent. The longer the letter, the more appreciable the advancement of roller A relative to its shaft 10 and hence cam E at this point in the cycle. In practice there will be a sufficient number of letters of long and medium length to ensure a steady and random advancement of the roller A in relation to the cam E. Since the timing of the cycle of operations is controlled by the cam E, this advancement of the roller A in relation to the cam ensures that over a period of time the whole surface of the roller A shares the wear that results from contact with the letters, especially the wear which is found to be the consequence of initial engagement with and disengagement from the letter. Such operation necessarily requires the roller A to have a truly cylindrical peripheral surface, so that any part of such surface can perform a letter propelling function as well as any other part.

In prior forms of feeders employing letter engaging and propelling rollers or like members that engage each successive letter at exactly the same position on the surface of the member, excessive wear at this position has been experienced. The letter engaging surfaces are usually made of rubber to afford an adequate frictional grip, and it has sometimes been found necessary to replace such parts in prior forms of feeder as often as daily. It must be remembered that feeders of this class are required to operate at high speeds, feeding as many as 10 letters per second which is many hundreds of thousands of letters per day.

The manner in which the present construction avoids this localisation of roller wear by automatically inducing rotation of the roller A at least occasionally relative to the timing cam, is a valuable feature of improvement over earlier feeders. Since roller A is the roller that propels the letters forward at an exact periodicity determined by cam E, it would otherwise be most prone to localised wear.

As will be apparent, the rotational cycles of roller A and cam E could be arranged in some other way to be different, as by interposing between such parts a drive ratio slightly greater or less than unity. Such an arrangement would at least distribute the wear around roller A, although at discrete points. The random elfect of an overhauling mechanism is preferred, however, and is mechanically somewhat simpler to employ.

As far as the foregoing description is concerned, which presupposes correct operation of the device, there is little more to be said about the remainder of the cycle which soon returns to Time 1 to repeat the feeding op eration with the next letter in the stack. As the trailing edge of each letter passes beyond the optical line of cell P3 (somewhere between Time 4 and Time 1), the vacuum is reapplied in chamber V by solenoid M2 to begin the feeding cycle for the next letter. Each successive letter is thus fed forward by roller A and finally ejected from the feeder by output rollers D1 and D2 at a periodicity measured at the leading edges of the moving letters and determined by the rate of rotation of the cam E.

Now suppose that a letter is not properly grasped by the fast turning rollers D1 and D2. It will tend to remain somewhere in the space between rollers D1 and D2, and roller C during the latter part of the Main synchronised feeding period. Such a situation may be due to some irregularity in the operation of the mechanism, or in the dimensions of the letter; or it may be due to the feeding of a double. The latter is an especially likely cause. When a double is fed forward by the preliminary feeding rollers F (an occasional occurrence that it is virtually impossible to prevent by reason of the loose edges that envelopes inevitably exhibit from time to time and the tendency for such edges to become interlocked), the two letters that comprise the double will seldom have their leading edges aligned. As a result the more forward one will be grasped by rollers D1 and D2. The second one may be carried forward by the first one, in which case a double will have been fed and will have to be detected and rejected by a subsequent instrumentality which will normally be fitted with a device for detecting doubles. On the other hand, often the acceleration of the leading letter induced by rollers DE and D2 unlocks the double and leaves the second letter somewhere short of the rollers D1 and D2. If the proper periodicity of feeding is not to be interfered with, it is necessary that such second letter, or a single letter that has not proceeded properly to the jaws of rollers D1 and D2 and has thus failed to be fed forward at the correct moment, be returned to the input side of the main feeding roller A, so that it will be fed forward again on the next rotation of cam E from the correct initial input position. mediate position extending partly through rollers A and C when the latter come together again at Time 2A in the next cycle, then the timing of the discharge of such letter from the output feeder rollers would be incorrect. It should be understood that no great inconvenience results if no letter is fed at one of the predetermined moments when a letter should be fed. There is merely a gap in the sequence and the sorter or other instrumentality that follows the feeder is inetfective for one cycle. The important requirement of the feeder is that it should never feed a letter other than at one of the predetermined moments.

FIGURE 11 shows correct feeding at Time 4. By contrast, FIGURE 12 shows the result at the same time in the cycle of an incorrect feed, that is a letter not being grasped by rollers D1 and D2. At Time 4A roller C again comes under the influence of rollers B, as the depression on cam E approaches its end. Roller C is thus moved out of engagement with roller A and rollers B and C close over and control further movement of the letter. This action commences the Return period and FIGURE 12 shows the condition at Time 4 after this action has been in operation for a short time. Roller C is driven clockwise, so the letter is moved in reverse until it reaches a position at the input area just on the input side of rollers B and C, in the same position as a newly If it were to be in some inter-.

fed letter takes up during the Waiting period." There the returned letter waits until Time 2A of the next cycle when a second attempt to feed it forward properly is made in the same manner as before.

It is during this return movement that photo-cells P1 and P2 are effective. When the letter is in the position shown in FIGURE 12, it will obscure the optical line of cell P2 but not of cell P1. This results in a positive signal from cell P1 and a negative signal from cell P2. FIG URE 13 shows the circuit by which these two cells feed into a conventional And gate W1 which is so set as to emit a positive output signal only when it receives this particular combination of input signals (positive from cell P1, negative from cell P2). Gate W1 feeds to a second conventional And gate W2 which also receives a signal from switch S when the latter is closed. Gate W2 is set to emit an output signal only when it receives this particular combination of signals (positive from gate W1 and positive from switch S). The output pulse from gate W2 is fed to a conventional flip-flop circuit Y which in turn feeds to an amplifier Z which energises solenoid M1. As already explained, energisation of solenoid M1 will cause the finger G to be extended. Thus, as the letter is returned, it is held by finger G out of contact with rollers F, as shown in FIGURE 12. If this were not done, there might be a tendency for the returning letter to be buckled, since the rollers F would be tending to urge it forward while the roller C is driving it in reverse. At the same time finger G will tend to hold the next letter in the stack L away from the rollers F, if it should be well advanced before the returning letter has begun to move back. In this way there can be no possibility of another letter starting to feed forward until the returning letter has been disposed of.

Switch S prevents the photo-cell circuit being effective during normal forward feeding. This switch is held open by cam E from approximately Time 2A to Time 4A, by which latter time the rollers D1 and D2 will have seized and taken charge of the letter, if operation is correct. The photocell circuit cannot be operated when the switch S is open because gate W2 will not then emit, and it will not be operated once the rollers D1 and D2 have taken over the letter, because the optical line of cell P1 will be obscured by the letter so that its signal will be negative which is incompatible with operation of gate W1, and finally the trailing edge of the letter will pass beyond the optical line of cell P2. This cell will then give a positive signal which is also incompatible with operation of gate W1.

It will be noted that the optical line of cell P3 remains obscured during all the return movement (FIGURE 12) so that solenoid M2 controlling the vacuum remains deenergised not only throughout the Return period but also into the next Preliminary feeding period, unless the letter is returned with so much momentum that it moves appreciably beyond the roller C, in which case cell P3 will again be effective to apply vacuum to chamber V and thus cause the letter to be fed forward again by rollers F to the correct waiting position at the jaws of rollers B and C. This operation prevents overshooting of the return feed. Finger G will not interfere with this latter operation because it will have been retracted as soon as the returning letter has passed beyond the optical line of cell P2, because then the signals from cells P1 and P2 will both be positive and gate W1 will emit no output signal. Hence gate W2 will also be inactive. The flip-flop circuit Y will include a conventional automatic resetting control so as to return to its initial condition and deenergise solenoid M1, when no signal is received form gate W2.

FIGURE 15 illustrates a modification to the construction. This modification employs the same parts as the construction already described with the addition of a further roller N which is mounted on the free end of an arm 60 pivoted at 61 and urged towards the plate 54 by a compression spring 62. A stop 63 defines the limit of inward movement of the arm 60. Roller N is mounted on the arm 60 by means of a ratchet mechanism which prevents anti-clockwise rotation while permitting free clockwise rotation. This additional roller N represents a further device for minimising the feeding of doubles. In the forward direction of feed, if a second letter L2 adheres to the principal letter L1 being fed, such second letter L2 will be on the side of the principal letter adjacent roller N. The spacing of roller N from plate 54, as determined by the stop 63 is adjusted to permit ready entry of the leading edge of the first letter L1 but to tend to obstruct entry of the leading edge of the second letter L2. The second letter, if it is to travel forward, must be dragged along the face of roller N which will not turn anti-clockwise, an action that will tend to dislodge it from the principal letter through which any forward propelling force must be transmitted. The roller N will present some resistance to forward movement of a single letter if the letter is comparatively thick, but this resistance, while normally suflicient to dislodge a loosely attached second letter, will be insufficient to overcome the main forward drive of rollers F. When an incorrectly fed letter is being returned in the manner described above, as shown in FIGURE 16, the roller N presents no substantial resistance to the return movement of the letter,

since it can turn freely clockwise in rolling contact with the letter.

I claim:

1. A feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity, comprising a preliminary feeding station, a main feeding station, an output station and means defining a path of travel for said articles from said preliminary feeding station through said main feeding station to said output station, said preliminary feeding station comprising preliminary feeding means for presenting said articles seriatim to an input area of the main feeding station, said main feeding station comprising a main feeding roller having a truly cylindrical article-engaging and propelling surface of high frictional grip, a selected peripheral location of said main feeding roller projecting into said path of travel, means for driving said main feeding roller in a direction to cause its surface at said selected location to travel towards said output station, reverse driving means having an article-engaging surface of frictional grip lower than the article-engaging surface of said main feeding roller, a selected location of said reverse driving means projecting into said path of travel and into engagement with the surface of said main feeding roller to define therewith said input area of said main feeding station, means for driving said reverse driving means in a direction to cause its surface at said last mentioned selected location to travel away from said output station, separating means for holding the surfaces of said main feeding roller and said reverse driving means apart, closing means for overriding said separating means with a regular periodicity to move said surfaces together to urge a said article waiting at said input area into driving relation with said main feeding roller and for maintaining said surfaces in such engaged position for a predetermined time interval of length sufiicient to ensure presentation to said output station of a said article fed forward norm-ally by said main feeding roller, said output station including output feeding means for seizing and advancing articles so presented to it, said main feeding station further including means cooperating with said reverse driving means to urge an article not seized by said output feeding means at the end of said time interval into driving relation with said reverse driving means for return to said input area to await the next operation of said closing means, and means interconnecting said main feeding roller and said closing means for ensuring at least occasionally lack of synchronism between the rotation of said main feeding roller and the periodicity of said closing means whereby to distribute around said main feeding roller the pc- 16 ripheral areas thereof in contact with an article during successive said time intervals.

2. A feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity, comprising a preliminary feeding station, a main feeding station, an output station and means defining a path of travel for said articles from said preliminary feeding station through said main feeding station to said output station, said preliminary feeding station comprising preliminary feeding means for presenting said articles seriatim to an input area of the main feeding station, said main feeding station comprising a main feeding roller having a truly cylindrical article-engaging and propelling surface of high frictional grip, a selected peripheral location of said main feeding roller projecting into said path of travel, means for driving said main feeding roller in a direction to cause its surface at said selected location to travel towards said output station, reverse driving means having an articleengaging surface of frictional grip lower than the articleengaging surface of said main feeding roller, a selected lo cation of said reverse driving means projecting into said path of travel and into engagement with the surface of said main feeding roller to define therewith said input area of said main feeding station, means for driving said reverse driving means in a direction to cause its surface at said last mentioned selected location to travel away from said output station, separating means for holding the surfaces of said main feeding roller and said reverse driving means apart, closing means for overriding said separating means with a regular periodicity to move said surfaces together to urge a said article waiting at said input area into driving relation with said main feeding roller and for maintaining said surfaces in such engaged position for a predetermined time interval of length sufficient to ensure presentation to said output station of a said article fed forward normally by said main feeding roller, said output station including output feeding means for seizing and advancing articles so presented to it, said main feeding station further including means cooperating with said reverse driving means to urge an article not seized by said output feeding means at the end of said time interval into driving relation with said reverse driving means for return to said input area to await the next operation of said closing means, means driving said output feeding means to advance said articles faster than by said main feeding roller, and means interconnecting said closing means with said means for driving said main feeding roller to relate the periodicity of operation of said closing means to the rotation of said last-mentioned driving means, said last-mentioned driving means including an overhauling mechanism whereby the increased velocity of an article simultaneously engaging both said output feeding means and said main feeding roller will rotationally advance said main feeding roller in relation to its driving means to give rise to a random relationship between the rotation of said main feeding roller and the periodicity of said closing means in order to distribute around said main feeding roller the peripheral areas thereof in contact with an article during successive said time intervals.

3. A feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity, comprising a preliminary feeding station, a main feeding station, an output station and means defining a path of travel for said articles from said preliminary feeding station through said main feeding station to said output station, said preliminary feeding station comprising preliminary feeding means for presenting said articles seriatim to an input area of the main feeding station, said main feeding station comprising a main feeding roller having a truly cylindrical article-engaging and propelling periphery of high frictional coeflicient, a peripheral location of said main feeding roller projecting into said path of travel, means for driving said roller in a direction to cause its periphery at said peripheral location to travel towards said output station, a reverse driving roller having an article-engaging periphery of frictional coefficient lower than that of said main feeding roller, a peripheral location of said reverse driving roller projecting into said path of travel and into engagement with the periphery of said main feeding roller to define therewith said input area of said main feeding station, means for driving said reverse driving roller in a direction to cause its periphery at said last-mentioned peripheral location to travel away from said output station, separating means for holding the peripheries of said rollers apart, closing means for overriding said separating means with a regular periodicity to move said peripheries together to urge a said article waiting at said input area into driving relation with said main feeding roller and for maintaining said peripheries in such engaged position for a predetermined time interval of length sufiicient to ensure presentation to said output station of a said article fed forward normally by said main feeding roller, said output station including output feeding means for seizing and advancing articles so presented to it, said main feeding station further including means cooperating with said reverse driving roller to urge an article not seized by said output feeding means at the end of said time interval into driving relation with said reverse driving roller for return to said input area to await the next operation of said closing means, and means interconnecting said niain feeding roller and said closing means for ensuring at least occasionally lack of synchronism between the rotation of said main feeding roller and the periodicity of said closing means whereby to distribute around said main feeding roller the peripheral areas thereof in contact with an article during successive said time intervals.

4. A feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity, comprising a preliminary feeding station, a main feeding station, an output station and means defining a path of travel for said articles from said preliminary feeding station through said main feeding station to said output station, said preliminary feeding station comprising preliminary feeding means for presenting said articles seriatim to an input area of the main feeding station, said main feeding station comprising a main feeding roller having a truly cylindrical article-engaging and propelling periphery of high frictional coefficient, a peripheral location of said main feeding roller projecting into said path of travel, means for driving saidroller in a direction to cause its periphery at said peripheral location to travel towards said output station, a reverse driving roller having an article-engaging periphery of frictional coeflicient lower than that of said main feeding roller, a peripheral location of said reverse driving roller projecting into said path of travel and into engagement with the periphery of said main feeding roller to define therewith said input area of said main feeding station, means for driving said reverse driving roller in a direction to cause its periphery at said last-mentioned peripheral location to travel away from said output station, separating means for holding the peripheries of said rollers apart, closing means for overriding said separating means with a regular periodicity to move said peripheries together to urge a said article waiting at said input area into driving relation with said main feeding roller and for maintaining said peripheries in such engaged position for a predetermined time interval of length sufiicient to ensure presentation to said output station of a said article fed forward normally by said main feeding roller, said output station including output feeding means for seizing and advancing articles so presented to it, said main feeding station further including means cooperating with said reverse driving roller to urge an article i not seized by said output feeding means at the end of said time interval into driving relation with said reverse driving roller for return to said input area to await the next operation of said closing means, means driving said output feeding means to advance said articles faster than by said main feeding roller, and means interconnecting said closing means with said means for driving said main feeding roller to relate the periodicity of operation of said closing means to the rotation of said last-mentioned driving means, said last-mentioned driving means including an overhauling mechanism whereby the increased velocity 'of an article simultaneously engaging both said output feeding means and said main feeding roller will rotationally advance said main feeding roller in relation to its driving means to give rise to a random relationship between the rotation of said main feeding roller and the periodicity of said closing means in order to distribute around said main feeding roller the peripheral areas thereof in contact with an article during successive said time intervals.

5. A feeder according to claim 3, including means sensitive during the periods intermediate said time intervals to the presence of an incorrectly fed article disposed between said main feeding station and said output station but out of engagement with said output feeding means, and means connecting said sensitive means to said preliminary feeding means to render the same inoperative and unrresistant to the return of said article by said reverse driving roller.

6. A feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity, comprising a preliminary feeding station, a main feeding sta tion, an output station and means defining a path of travel for said articles from said preliminary feeding station through said main feeding station to said output station, said preliminary feeding station comprising preliminary feeding means for presenting said articles seriatim to an input area of said main feeding stations, said main feeding station comprising a main feeding roller having a truly cylindrical article-engaging and propelling periphery of high frictional coeflicient, a peripheral location of said main feeding roller projecting into said path of travel, means for driving said roller in a direction to cause its periphery at said peripheral location to travel towards said output station, a reverse driving roller having an article-engaging periphery of frictional coeflicient lower than that of said main feeding roller, a peripheral location of said reverse driving roller projecting into said path of travel, means for driving said reverse driving roller in a direction to cause its periphery at said lastmentioned peripheral location to travel away from said output station, resilient means urging said reverse driving roller into peripheral engagement with said main feeding roller at said peripheral locations to define therewith said input area of said main feeding station, a cam, means driving said cam at a constant speed, a cam follower bearing on the operative surface of said cam, a free-running idler roller, a member connected to said cam follower and mounting said idler roller movably between a withdrawn and a projecting position under the control of said cam, said projecting position being such that said idler roller engages the periphery of said reverse driving roller to move the same against the action of said resilient means out of engagement with said main feeding roller, and said withdrawn position being such that said idler roller is withdrawn from engagement with the periphery of said reverse driving roller to'permit the same to engage said main feeding roller, said cam being such as normally to hold said idler roller in projecting position but to move said idler roller to withdrawn position with a regular periodicity to bring said reverse driving roller and said main feeding roller into pressure engagement about a said article waiting at said input area and to maintain said idler roller in withdrawn position for a predetermined time interval of length sufiicient to ensure presentation to said output station of a said article fed forward normally by said main feeding roller, said output station including output feeding means for seizing and advancing articles so presented to it, said idler roller returning to projecting position at the end of said time interval to cooperate with said reverse driving roller to urge an article not then seized by said output feeding means into driving relation with said reverse driving roller for return to said input area to await the next movement of said idler roller to its withdrawn position, and means inter-connecting said main feeding roller and said cam driving means for ensuring at least occasionally lack of synchronism between the rotation of said main feeding roller and the periodicity of said cam whereby to distribute around said main feeding roller the peripheral areas thereof in contact with an article during successive said time intervals.

7. A feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity, comprising a preliminary feeding station, a main feeding station, an output station and means defining a path of travel for said articles from said preliminary feeding station through said main feeding station to said output station, said preliminary feeding station comprising preliminary feeding means for presenting said articles seriatim to an input area of said main feeding station, said main feeding station comprising a main feeding roller having a truly cylindrical article-engaging and propelling periphery of high frictional coefiicient, a peripheral location of said main feeding roller projecting into said path of travel, means for driving said roller in a direction to cause its periphery at said peripheral location to travel towards said output station, a reverse driving roller having an article-engaging periphery of frictional coefiicient lower than that of said main feeding roller, a peripheral location of said reverse driving roller projecting into said path of travel, means for driving said reverse driving roller in a direction to cause its periphery at said lastmentioned peripheral location to travel away from said output station, resilient means urging said reverse drivig roller into peripheral engagement with said main feeding roller at said peripheral locations to define therewith said input area of said main feeding station, a cam, means driving said cam at a constant speed, a cam follower bearing on the operative surface of said cam, a free-running idler roller, a member connected to said cam follower and mounting said idler roller movably between a withdrawn and a projecting position under the control of said cam, said projecting position being such that said idler roller engages the periphery of said reverse driving roller to move the same against the action of said resilient means out of engagement with said main feeding roller, and said withdrawn position being such that said idler roller is withdrawn from engagement with the periphery of said reverse driving roller to permit the same to engage said main feeding roller, said cam being such as normally to hold said idler roller in projecting position but to move said idler roller to withdrawn position with a regular periodicity to bring said reverse driving roller and said main feeding roller into pressure engagement about a said article waiting at said input area and to maintain said idler roller in withdrawn position for a predetermined time interval of length sufiicient to ensure presentation to said output station of a said article fed forward normally by said main feeding roller, said output station including output feeding means for seizing and advancing articles so presented to it, said idler roller returning to projecting position at the end of said time interval to cooperate with said reverse driving roller to urge an article not then seized by said output feeding means into driving relation with said reverse driving roller for return to said input area to await the next movement of said idler roller to its withdrawn position, means driving said output feeding means to advance said articles faster than by said main feeding roller, and means interconnecting said cam driving means with said means for driving said main feeding roller to relate the speed of rotation of said cam to the rotation of said last-mentioned driving means, said last-mentioned driving means including an overhauling mechanism whereby the increased velocity of an article i4 simultaneously engaging both said output feeding means and said main feeding roller will rotationally advance said main feeding roller in relation to the rotational position of the cam to give rise of a random relationship between the rotation of said main feeding roller and said cam in order to distribute around said main feeding roller [the peripheral areas thereof in contact with an article during successive said time intervals.

8. In a feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity along a path of travel, a main feeding station comprising a main feeding roller having a truly cylindrical articleengaging and propelling surface of high frictional grip, means mounting said main feeding roller for projection of a selected peripheral location of said roller into said path of travel, means for driving said main feeding roller in a direction to cause its surface at said selected location to travel in forward direction along said path of travel, reverse driving means having an article-engaging surface of frictional grip lower than the article-engaging surface of said main feeding roller, means mounting said reverse driving means for engagement with the surface of said main feeding roller at said selected location, means for driving said reverse driving means in a direction to cause its surface at said location to travel in the opposite direction from the direction of travel of the surface of said main feeding roller, separating means for holding the surfaces of said main feeding roller and said reverse driving means apart, closing means for overriding said separating means with a regular periodicity to move said surfaces together to urge a waiting article into driving relation with said main feeding roller for forward feeding of said article along said path of travel and means including means interconnecting said main feeding roller and said closing means for ensuring at least occasionally lack of synchronism between the rotation of said main feeding roller and the periodicity of said closing means whereby to distribute around said main feeding roller the peripheral areas thereof in contact with an article during successive operations of said closing means.

9. In a feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity along a path of travel, a main feeding station comprising a main feeding means having a continuous, uniform, article-engaging and propelling surface of high frictional grip, means mounting said main feeding means for projection into a selected location along said path of travel, means for driving said main feeding means in a direction to cause its surface at said selected location to travel in forward direction along said path of travel, reverse driving means having an article-engaging surface of frictional grip lower than the article-engaging surface of said main feeding means, means mounting said reverse driving means for engagement with the surface of said main feeding means at said selected location, means for driving said reverse driving means in a direction to cause its surface at said location to travel in the opposite direction from the direction of travel of the surface of said main feeding means, separating means for holding the surfaces of said main feeding means and said reverse driving means apart, closing means for overriding said separating means with a regular periodicity to move said surfaces together to urge a waiting article into driving relation with said main feeding means for forward feeding of said article along said path of travel, and means including means interconnecting said main feeding means and said closing means for ensuring at least occasionally lack of synchronism between the movement of said main feeding means and the periodicity of said closing means whereby to distribute along said main feeding means the surface areas thereof in contact with an article during successive operations of said closing means.

10. In a feeder for delivering a series of letter-like articles sequentially and with a predetermined periodicity along a path of travel, feeding means having a continuous, uniform, article-engaging and propelling surface of high frictional grip, means mounting said feeding means for projection into a selected location along said path of travel, means for driving said feeding means in a direction to cause its surface at said selected location to travel in forward direction along said path of travel, means for positioning a said articleat said location in said path of travel for engagement by said feeding means, separating means for holding the surface of said feeding means out of contact with a said article at said location, closing means for overriding said separating means with a regular periodicity to move said surface into engagement with a waiting article at said location for forward feeding of said article along said path of travel, and means including means interconnecting said feeding means and said closing means for ensuring at least occasionally lack of synchronism between the movement of said feeding means and the periodicity of said closing means whereby to distribute along said feeding means the surface areas thereof in contact with an article during successive operations of said closing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,791,425 Ford et a1. May 7, 1957 2,836,416 Van Marie May 27, 1958