Circular mail singulator
BACKGROUND OF THE INVENTION 
     The invention is in the field of automatic mail processing equipment. One portion of the mail handling system in post offices in large cities includes automatic stamp cancelling equipment for envelopes that fall within certain limits as to size standardization. The mail is first hand sorted to eliminate most oversized and undersized envelopes, with the balance being dropped into a 10&#39; long singulator having stationary walls and a moving belt floor. The singulator has periodically extending frictional spring fingers which help to separate side by side and overlapping envelopes so that a single file stream is produced. 
     At the end of this singulator is a rack into which the single file envelopes are stacked, edgewise, and an automatic cancelling machine draws envelopes individually from one end of the stack and cancels the stamp. The cancelling machine is capable of accepting about 38,000 pieces of mail per hour, but the feeding is inadequate and under ordinary conditions of use, at least partially because of the inadequacy of the current signulator, only 14,000 to 20,000 pieces of mail per hour are cancelled. In addition, failure of the singulator to singulate the letter with 100% accuracy from time to time results in the jamming of the cancelling machine which, although it is being overseen by a postal operator, will ordinarily destroy several envelopes and jam up before there is time to stop the system. 
     For these reasons there is a need for an improved singulator which, preferably in the same 10&#39; spaces previously allotted to singulation, produces a stream of singulated envelopes with a non-existent, or virtually non-existent singulation failure rate. 
     SUMMARY OF THE INVENTION 
     The present invention fulfills the above-mentioned need and provides a circular singulator, 10&#39; or less in diameter, which provides over 120&#39; of singulation distance in about the same space allocated for use of previous equipment. 
     The basic elements of the unit are a spiral wall or baffle defining the 120&#39; spiral corridor through which the envelopes pass, and a rotating floor with a frictional surface which draws the mail through the spiral corridor. The mail is delivered to the inner convolution of the spiral by means of a cone which may or may not be caused to rotate in the opposite direction of the rotating floor. The floor rotates in such a direction that mail deposited in the inner convolution from the cone is drawn into the progressively outer convolutions, and therefore picks up a considerable amount of speed over that which it had in the inner convolution due to the unchanged angular velocity coupled with the doubling or so of the diameter of the trajectory. This enables the mail to be deposited on a slow moving portion of the frictional table to ease the transition between the stationary mail and its moving phase, and then the mail is smoothly accelerated to a much higher speed which is adjusted to coincide with the proper speed of delivery into the cancelling machine. 
     An interfacing conveyor belt delivers the singulated envelopes from the outer convolution, with unchanged speed, into the cancelling machine, which is then able to cancel at virtually its maximum rate of 38,000 pieces per hour. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a side elevation of the unit with the left and central portions cut away; 
     FIG. 2 is a top elevation view of the unit with the upper portion of the cone removed; 
     FIG. 3 is a diagrammatic view of a modified form of the spiral baffle in which corridor thickness progressively decreases radially outwardly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The singulator utilizes a framework having a central column 10 and four radial frame members inclusively designated at 12. Each of the frame members 12 supports at its outer end a support roller 14 mounted on a shaft 16 journaled in bearings 18. 
     The rollers are shaped like railroad wheels and both capture and support for rotational movement an overlying annular table 20 which has a frictional coating 22 on its top surface. The table is rotated in the direction indicated by the arrow by means of electric motor 24 mounted beneath one of the frame members 12. By virtue of drive shaft 26 which passes into the central portion of the cone 10 through bushing 28, a bevel gear 30 drives an orthogonally oriented second bevel gear 32 mounted on a shaft 34 which extends up through a reduced diameter upper hollow column 36 and is supported by this column through bearings 38 beneath flange 40. The shaft continues upward and mounts the upper portion of a cone 42 which by virtue of the above-described structure is caused to rotate in the direction opposite the direction of rotation of the annular table 20. 
     Whereas the upper cone portion rotates one direction and the lower table rotates the other, all the structure between the upper cone and the table is stationary and is mounted as follows. Four radial I-beams of decreasing height from inner to outer end extend from the flat sides of the upper column 36 as is best seen in FIG. 2. The principal purpose of these beams is to support, through mounting brackets 46, a spiral baffle 48. This baffle or wall begins at its inner end at 50 and continues outwardly continuously and terminates at 52 to define a continuous corridor between adjacent convolutions of the spiral. 
     Mounted midway out on the radial beams 44 is a frustocone 54 defining a smooth continuation of the surface of the upper cone portion 42 down to the very upper edge of the baffle 48. Where the beams pass through the frustocone they are provided with covers 56, each of which has flanges indicated in FIG. 1 at 58 which are spot welded or otherwise attached to the frustoconical surface so that envelopes sliding down the cone do not get caught in the structure of the I-beams. 
     It can be seen that as the annular floor of the unit rotates in the direction indicated in FIG. 1 and the conical member 42 rotates in the opposite direction, mail dropped on this cone will slide down onto the frustocone 54 and thence into the innermost convolution or corridor 60 where it is engaged by the frictional surface 22 of the table 20 and carried out at increasingly large circles unitl it reaches the outermost limit 52 of the spiral wall. At this point the mail shoots out tangentially of the spiral under the guidance of deflector 62 and chute 64 which delivers the mail, which is now moving at a relatively high speed, onto a high-speed conveyor diagrammatically illustrated at 66. The conveyor then introduces the still moving mail into a cancelling machine. The speed at which the cancelling machine operates is the speed to which the conveyor 66 and the rotating table 20 are synchronized. 
     When the mail is introduced into the inner corridor 60, it is free to overlap one envelope over the other, which condition it is of course the purpose of the singulator to eliminate. As the mail moves outwardly, periodically along the corridor walls are placed spring fingers 68 which have frictional surfaces along their distal ends to delay the innermost envelope of a group of two or more envelopes passing these points. As the speed of a corridor picks up radially outwardly, there is more length along the pathway so that the circular column of envelopes can be expanded to be spaced in single file prior to being ejected onto the conveyor 66. There could, of course, be more spring fingers 68 and other singulation enhancing structures throughout the length of the corridor, as there is plenty of room to incorporate any such structure desired. 
     A structure which has not been heretofore mentioned is a flats extractor which is diagrammatically illustrated in FIG. 2 and will not be described in detail as it is standard equipment in a conventional singulator. This extractor, indicated at 70, is incorporated in the drawing to illustrate that it may be driven off of pulley 72 by the main motor of the instant device. The flats extractor (which has been omitted for clarity in FIG. 1) comprises basically a pair of rollers positioned just high enough to grab the tops of envelopes that are too high and drive them through belts driven by the roller and eject them into a flats hamper 74. 
     Turning to FIG. 3, an alternate orientation of the spiral baffle is shown at 76 in which the distance between adjacent baffle portions decreases progressively toward the outer edge of the annular table. This is essentially a space-saving measure and is made possible by the fact that as the speed of the envelopes increases, and as they are stretched out single file in their respective portions of the corridor, they require less thickness to accomodate them. 
     The invention is thus shown, described and claimed, is exemplary of a number of variations which could clearly be incorporated within the scope of the claims, including means of supporting the baffles and the two cone portions and means of driving those elements which rotate. Additionally, an embodiment to be specifically mentioned herein is one in which the upper portion 42 of the cone is non-rotational and simply is an extension of the frustocone 54. The incorporation of rotation in the upper portion of the cone represents an added feature to prevent the possible hanging up or backing up of the mail, for example on top of the radial beams 44. This problem would be effectively eliminated by the rotation of the upper portion of the cone and in general the singulation of the mail would appear to get an early start by virtue of the counter rotational action of this cone. 
     It should be noted that one side of the spiral baffle could be coated with a slight frictional coating to provide a continuous singulating effect. The spiral could rotate over a stationary table as a possible modification, and dimensions and proportions could be modified to singulate oversized flats, packages, and even non-posted articles of manufacture. 
     By the implementation of the singulator described herein post offices will considerably increase the speed at which their existing cancellation machines operate, enabling them to postpone or avoid entirely purchasing new equipment, and perhaps will even enable them to eliminate an operator whose sole purpose it is to observe the operation of the currently used singulator and its interface with the cancellation machine to prevent disaster in case of jamming or failure of the singulator.