Apparatus for Reversing the Direction of Flat Items

This application claims the priority of German Application No. P 43 15 053.5 filed May 6, 1993, which is incorporated herein by reference.

The present invention relates to an apparatus for reversing the direction (orientation) of flat items for mail-sorting systems.

In mail-sorting systems, flat items are typically supplied to mark recognition or identification devices that allow the distribution of the items according to the different information written on the surface thereof. In such conventional systems the problem arises that a portion of the items are transported in the conveyor means in such a way that the item surface provided with the necessary information is not in the processing position (that is, in a position that allows processing by the mark recognition device). An item not located in the processing position can be brought into the processing position by being rotated about its longitudinal and/or vertical axis. Because of such rotations the clearance between the items changes, possibly even resulting in overlapping of the items, which can lead to jams and functional breakdowns of the system.

It is an object of the present invention to provide an apparatus with which items can be rotated quickly and reliably about their vertical axis, that is, the axis perpendicular to and passing through the largest plane defined by each of the flat items.

A further object of the invention is to provide an apparatus with which the rotation of items around their vertical axis takes place in such a way that the clearances between the items are identical prior to and following rotation.

These objects and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the apparatus for reversing an orientation of flat items includes a first conveyor driven with a first speed; a second conveyor adjoining the first conveyor such that items discharged by the first conveyor are introduced into the second conveyor; a third conveyor driven with a second speed and adjoining the second conveyor such that items discharged by the second conveyor are introduced into the third conveyor; a sensor for determining a moment when a trailing edge of an item leaves the first conveyor; and a control arrangement connected to the sensor and the second conveyor for driving the second conveyor with the first speed as an item enters the second conveyor from the first conveyor, for decelerating the second conveyor when the sensor determines the moment when a trailing item edge passes by, for reversing a direction of motion of the second conveyor after deceleration and for accelerating the second conveyor to the second speed as an item enters the third conveyor from the second conveyor.

Thus, the direction reversing apparatus is effective for reversing a direction of each of the items by interchanging the front edge of a given items with the rear edge of that item.

It is a particularly advantageous feature of the invention that the items are guided inside the device reliably and without jars and shocks. Moreover, the items are continuously frictionally gripped in a force transmitting relation within the device and are thus never permitted to move freely therein. As a result of this last measure, high precision in the control of the movement of the items is achieved, and disturbances in item travel are avoided. The device slows and accelerates the items in a gentle manner, and it also permits the return of an item into its original space in the item flow.

FIG. 1 is a schematic side elevational view of a preferred embodiment of a direction reversing apparatus according to the invention.

FIG. 2 is a path-time diagram showing the respective position/time graphs of two successive items whose directions are to be reversed.

FIG. 3 is a schematic illustration of a combination of two direction reversing apparatus in accordance with the invention.

FIGS. 4a, 4b and 4c are schematic illustrations similar to FIG. 3, showing additional embodiments as variations of the combination of FIG. 3.

In the device shown in its principal design in FIG. 1, the items to be rotated are supplied to a first conveyor channel 1 and therefrom in the direction of the arrow A to a second conveyor channel 2. The first conveyor channel 1 is defined on one side thereof by a run of a conveyor belt 3 driven by two guiding rollers 4 and 5, and on another side thereof by a run of a further conveyor belt 6 driven by guiding rollers 7, 8 and 9. Conveyor channel 1 thus constitutes a first conveying means for the item. The, channel-forming runs of the two conveyor belts 3 and 6 are disposed parallel to one another such that they form the narrow conveyor channel 1 in which an item to be transported is guided and advanced by the belts 3 and 6 which are in frictional force-transmitting contact with opposite item surfaces. A third conveyor channel 10, defined on one side thereof by a run of conveyor belt 6 and on another side thereof by a run of a conveyor belt 11, driven by guiding rollers 12 and 13, receive items from the second conveyor channel 2 which is defined by runs of conveyor belts 14 and 17 driven by guiding rollers 15, 16, and 18, 19, respectively. Conveyor channel 2 and conveyor channel 10 thus constitute a second and third conveying means, respectively. The items are guided within each conveyor channel 1, 2 and 10 by being frictionally gripped on opposite faces by the respective belt runs.

An item to be reversed by the apparatus is supplied to conveyor channel 2 by conveyor channel 1 at a predetermined, preferably constant velocity. The belts 14, 17 defining conveyor channel 2 are controlled and, at the moment of transfer, move in the same direction and at the same velocity as the belts 3, 6 of conveyor channel 1. The item is therefore received within channel 2 reliably and without jars or shocks. As soon as the rear item edge has left conveyor channel 1, the item is slowed by conveyor belts 14 and 17. The velocity of the conveyor belts 14 and 17 is controlled according to a predetermined reversal velocity profile. After the item has been decelerated, the conveying direction is reversed and the item is accelerated to a second predetermined reversal velocity in accordance with the predetermined velocity profile. Thereafter, the items are received by the third conveyor channel 10 from the second conveyor channel 2, that is, in between conveyor belts 6 and 11 which move the items at the second predetermined velocity in the direction of arrow B in order to assure an impact-free and reliable transfer thereof into channel 10. The point in time when the rear item edge leaves first conveyor channel 1 is preferably detected by a light detection device (optical barrier) 19 coupled to a control device 30 which may include a computer in which the velocity course (profiles) are programmed. The device 30 is connected to a motor 31 which operates conveyor belts 3, 6, 11 and a motor 32 which operates conveyor belts 14, 17.

In the embodiment of the device according to FIG. 1, the conveying directions in conveyor channels 1 and 2 form an angle .alpha., and the conveying directions in conveyor channels 2 and 10 together form an angle .beta. which is smaller than angle .alpha.. During the transfer of the items to either conveyor channel 2 or conveyor channel 10, the items are first moved in these channels in the direction in which they were being moved in the previous conveyor channel. It is thus ensured that an item can be reliably guided out of conveyor channel 1 into conveyor channel 2, or out of conveyor channel 2 into conveyor channel 10 without necessitating additional measures for influencing the direction of the items, such as deflector plates or the like. It is noted, however, that the invention may be practiced with the use of such additional measures as well.

Thus, to assure reliable guidance of the items, two controlled conveyor belts 14 and 17 are used to define conveyor channel 2. However, one of the two controlled belts can also be replaced with a single conveyor roller or a plurality of serially arranged conveyor rollers without a fundamental change in function. It is also possible in principle to replace both controlled belts with two controlled conveyor rollers or two series of such rollers between which the item to be reversed is guided.

FIG. 2 shows a path/time diagram for two successive items whose directions are to be reversed. In this instance the dashed line indicates the idealized position versus time graph of the item mid-point. The vertical axis corresponds to the location x of items I1 and I2, and the horizontal line RL corresponds to a theoretical reversal line of the items, which are separated by a gap d. The midpoint of each of the items is indicated by IMP. An impact-free reversal of two items in the device as shown in FIG. 2 requires that the reversed item is already outside the reversing mechanism comprising belts 14 and 17 before the second item enters therein. Because of the high conveying velocities conventionally used today, this may lead to an excessive required minimum gap between successive items.

FIG. 3 shows an embodiment with which successive items may be reversed while keeping a significantly smaller gap between items than is feasible with the earlier-described embodiment shown in FIG. 1. In the FIG. 3 embodiment, two reversing units 20 and 21 are used, each being constructed, for example, in accordance with the embodiment shown in FIG. 1. The items are advanced on an inlet conveyor (track) 24 from which, by means of a switch 22, items may be selectively directed to the first reversing unit 20 (that is, introduced into the conveyor channel 1 thereof). Other items proceed on the continuation of the inlet conveyor 24 where, downstream of the switch 22 a further switch 23 is provided by means of which items may be selectively directed to the second reversing unit 21. Other items continue on a delaying conveyor (track) 26. The outlet of the first reversing unit 20 and the second reversing unit 21 as well as the delaying conveyor 26 merge at different locations in an outlet conveyor (track) 25. A sensor 27 situated upstream of the switch 22 in the inlet conveyor 24 determines the spacing between consecutive items and also determines whether the item is properly aligned for address-reading in the processing position or whether its position should be corrected by the reversing arrangement. Thus, items which need not be reversed circumvent the first and second reversing units 20, 21. A control device 33 coupled to the switches 22, 23, to the sensor 27 as well as to the first and second reversing units 20 and 21 directs the items to be reversed alternatingly into the first and the second reversing units 20, 21 or forwards the other items through the delaying track 26 to the outlet conveyor 25. Also, as a function of the signals received from the sensor 27, the control device 33 ensures that the spacing of the items in the outlet conveyor 25 will be the same as in the inlet conveyor 24. Thus, items to be reversed travel out of the reversing unit 20 or 21 backward with respect to their prior orientation; the former rear edge of each item thus becomes its new front edge. The flow of reversed items then rejoins the unreversed items in outlet conveyor 25. If the gap between two items to be transported to the same reversing device is too small, an impact between the items can be avoided by moving the second item to the delay conveyor 25 and separating it out later.

FIGS. 4a through 4c show further advantageous embodiments of the combination of two reversing units 20 and 21. Instead of providing three paths defined by reversing units 20, 21 and delaying conveyor 26, a straight path (without reversal) can also be followed through units 20 and 21 and these two item flows can join the reversed flows after suitable deviation.

In present-day mail-sorting systems it is conventional to provide constant gaps between the items of an item flow to be processed. To make it possible for an item to return into its original space after its direction is reversed, the mid-points of the adjacent items must be relatively in the same position with respect to one another and have the same velocity after leaving the reversing apparatus. This can be realized with very different velocity profiles of the items inside the reversing apparatus. FIG. 2 shows by way of an example a possible course in time of the location of the item mid-point inside the reversing apparatus.

In one embodiment of the invention, in accordance with FIG. 1, the exact velocity profile of the belt movement in the reversing mechanism is determined as a function of the item length, the belt velocity in the rest of the system, and the time at which the rear edge of an item exits from conveyor channel 1, which time is detected by light detection device 19. The determination of this velocity profile is preferably done on-line by a processor. The calculated course of the belt movement then serves as a nominal value for the cascade control of the setting drive for conveyor channel 2. It is therefore possible to accurately reposition into the item flow those items which, because of disturbances, previously shifted slightly in the item flow. In this manner gap corrections may be effected.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.