The invention relates to a device for turning flat mail items through 90° according to the pre-characterising clause of Claim 1.
The present invention relates to the field of postal automation. For automated sorting and distribution of flat mail items such as letters or leaflets, the latter are transported to their target locations—also known as destinations—within a processing and distribution centre by means of conveyors and/or conveying belts. For this purpose it is necessary for the conveying direction to be changed relative to the mail item, e.g. from a vertical conveying direction to a horizontal conveying direction or vice versa.
Transporting flat mail items is demanding in that the dimensions and manipulability of flat sortation items varies widely. On the one hand, in terms of format alone there exists an almost unlimited diversity of width, height and thickness dimensions. In addition, the packaging and stiffness of flat sortation items can also vary greatly, ranging from hard, rigid cardboard envelopes to rather soft film-packaged brochures and magazines. Unpackaged, loose leaflets are also encountered as sortation items. Due to the different sizes of rectangular mail items, it is no easy matter to deflect them from a relatively vertical conveying direction to a horizontal conveying direction at a high conveying speed. Not only does the length-to-width ratio vary comparatively greatly, but the absolute variable of length or width is also wide-ranging, as may be directly seen, for example, from the formats B6 landscape or portrait to the format C3 portrait or landscape. The problem with changing the direction of mail items at high conveying speeds is that, when they are turned through 90°, exceptionally oblong items, for example, must be conveyed away much more quickly in the longitudinal direction than they are conveyed to that deflection point. Within the meaning of this publication, for the sake of simplification only mail items will now be referred to, flat mail items such as letters, leaflets, samples in preferably rectangular format being subsumed under the term “mail items”.
U.S. Pat. No. 6,234,468B1 “Dual Pocket right angle turn for an envelope transport system” proposes a device which conveys envelopes supplied in two rows into a single row, said single row being at an angle of 90° relative to the two rows. However, this device is only suitable for mail items that are to a certain extent homogeneous in terms of size, proportions and mass.
The object of the present invention is therefore to specify a device for changing the conveying direction of flat mail items so as to allow a high throughput irrespective of the masses and proportions of the mail items.
This object is achieved according to the invention by the device set forth in Claim 1.
Conveying the mail items away by means of eccentric rollers ensures that mail items having a wide variety of sizes are reliably transferred from the first direction to a second direction orthogonal thereto, the throughput rate being directly proportional to the rotation speed of the eccentric rollers and therefore easily adjustable. By making eccentric rollers actuatable in two rotational directions corresponding to the second direction, in order to convey the mail items away accordingly to two different points, either the mail items can be further processed generally on two further paths, or “mavericks” such as double withdrawals can be easily removed from onward conveyance.
Advantageous embodiments of the invention are set forth in further Claims.
- i) Due to the fact that the eccentric rollers and the cross belt are mechanically coupled via a free-wheel, so that at higher conveying speed of the eccentric rollers the cross belt is likewise accelerated to the higher conveying speed and the second motor driving the cross belt is not thereby entrained to the higher conveying speed, the mail items are conveyed away from the deflection point reliably and without adversely affecting throughput without complex synchronisation and without the second motor driving the cross belt being thereby entrained to the higher speed (Claim 8).
- ii) Due to the fact that there is provided a nubbed belt containing supports in order to feed the mail items to the deflection point in the first direction, the mail items can be fed to said deflection point in a defined manner, resulting in precise onward conveyance with the eccentric rollers (Claim 10).
- iii) Due to the fact that a feeder (2) is rotationally coupled to the nubbed belt (4) in order to ensure a defined position of the mail items when they are conveyed away by the eccentric rollers (11), the coupling can be provided in such a way that a mail item can be transferred by the feeder via the conveying belt onto the nubbed belt slightly above the support, e.g. 2 cm, so that during onward transportation with the nubbed belt the mail item falls a very short distance onto the support and without rebounding. This results in a defined i.e. horizontal position for conveying away with the eccentric roller means in the transverse direction (Claim 11).
The invention will now be explained in greater detail in an exemplary manner with reference to the accompanying drawings in which:
FIG. 1 shows a view of a conveying section for feeding mail items to a deflection point;
FIG. 2 shows a plan view of a deflection point with three eccentric rollers;
FIG. 3 is an oblique view from below of a deflection point, showing the drive motors and free-wheels;
FIG. 4 is a view of an eccentric roller;
FIG. 5 shows a v-t diagram for a peripheral radial part of an eccentric roller.
FIG. 1 shows a view of a conveying device 1 containing a feeder 2 by means of which mail items are transported singly by a conveying belt 3 to a deflection point 10. The feeder 2 contains a take-off drum 6 with two actuatable grippers 7 for picking up a mail item. The take-off drum 6, the nubbed belt 4 and the conveying belt 3 are synchronously driven by a motor M. The mail items are transferred by a nubbed belt 4 in conveying direction D1. This contains supports 5 for defined feeding to the deflection point 10. As individually described below, the mail items are picked up by at least one eccentric roller 11 and transferred to a cross belt 21 orthogonally with respect to the direction D1. The inventive turning of the mail items is accomplished by means of at least one eccentric roller 11.
FIG. 2 shows a detailed plan view of a deflection point 10. In this exemplary embodiment three eccentric rollers 11 are provided, the two outer ones being disposed on the same horizontal level. Depending on the embodiment, another arrangement of the eccentric rollers 11 in terms of level is also conceivable, e.g. offset in a stepped manner. The inventive teaching also permits a single eccentric roller 11. The deflected direction of the mail items is denoted in FIG. 2 by the reference character D2. In said conveying direction D2 following the eccentric roller 11, there is provided a cross belt 21 for the onward conveyance of the mail items. For picking up the mail items there is provided, opposite each eccentric roller 11, as shown in FIG. 2, a fixed roller 19 which is barely visible in FIG. 2 although the associated axis of rotation is clearly identifiable without a reference character. Alternatively to these rollers it is also possible to provide a metal guide only. As explained below, it is also possible to accomplish the onward conveyance of the mail items in two directions D2 and D2′ at right angles to the in-feed direction, said two directions D2 and D2′ preferably being collinear.
The translation for the rotationally synchronously coupled conveying belt 3, the take-off drum 6 and the nubbed belt 4 and the arrangement of the supports 5 on the nubbed belt 4 must be selected such, when it is being transferred from the conveying belt 3 to the nubbed belt 4, a mail item comes into the region of the nubbed belt 4 about 20 mm above a support 5. The mail items then drops onto the support 5 in the conveying direction. This tightly limited drop ensures that the mail item does not rebound on impact or here on reaching the support 5, thereby ensuring a defined position of the mail item at the moment of pickup by the eccentric roller 11. It is particularly advantageous that the actuation of the eccentric roller 11 takes effect for the mail item at precisely the moment when the mail item has reached the position for horizontal onward conveyance. This means that actuation of the drive motor 14 must take place shortly prior to reaching this position. Thanks to the permanently selected translation, the actuation of the drive motor 14 can be derived directly from the position of a support 5 and the prior pickup of a mail items by a gripper 7. A control actuates the grippers 7; without this actuation, the mail items remain on a stack in the feeder 2. With the supports it can also be achieved that a mail item is not picked up by a single eccentric roller in the case of e.g. two offset eccentric rollers and possibly “bumps” its way through.
FIG. 3 shows an oblique view from below onto a deflection point 10. A first drive motor 14 and a second drive motor 15 are mounted behind flanges 14 and 15 respectively. The eccentric roller 11 or cross belt 21 are driven by means of belts via toothed belt pulleys 18. Behind each flange, a free-wheel is denoted by reference characters 16 and 17. The function of these free-wheels will be explained below in connection with FIG. 5. From FIG. 3 it can be seen that the cross belt 21 is coupled mechanically, i.e. rotationally, to the eccentric rollers 11.
FIG. 5 shows velocity v versus time t for one rotational direction of the eccentric rollers 11. For the other rotational direction, the characteristic is given by mirroring on the t-axis. The values quoted are only given by way of example and reflect the requirements placed on the drive arrangement, i.e. motors and associated open/closed loop control equipment. The characteristic shown refers to one rotation of the eccentric roller 11 measured on the peripheral, radial part 12. It is assumed that, for the conveying away of the mail items, the cross belt is driven under steady state conditions with a velocity of v=2 m/s. A mail item to be turned using the device according to the invention experiences through the eccentric roller 11, apart from slippage, the velocity characteristic according to the curve up to the specified time of 130 ms. Due to the free-wheel 16, from position F16 onwards, the cross belt 21 is likewise subject to the velocity according to the graph. This means that when it is transferred by the eccentric roller 11, the mail item is transiently forwarded by the cross belt 21 with the same velocity. For conveyance away by a following conveying belt, the eccentric roller 11 must in turn be brought into a defined starting position. This means that to complete a single revolution, the eccentric roller 11 must be decelerated to 0 velocity in a very short time, the flattened region 13 being specified approximately parallel to the plane of the mail items or parallel to the plane of the nubbed belt shows the time available for that purpose, which in this example is (147-130) ms=17 ms. Due to the kinetic energy stored in the movement of the cross belt, the cross belt coasts down to the abovementioned 2 m/s. To ensure that the second drive motor 15 is not entrained to the higher speed, a second free-wheel 17 is provided. The decoupling between eccentric roller 11 and free-wheel 17 takes place at the point F17, cf. FIG. 5. It is particularly advantageous to provide a stepping motor for the first drive motor 14 of the eccentric roller(s). FIG. 4 shows the design of an eccentric roller 11. The very high accelerations evident from FIG. 5 require that as little mass is possible has to be accelerated and that therefore the rotational means 11 shall have as low inertia as possible. This is achieved on the one hand by a relatively thin-walled cylinder 22 at the other end of which is mounted a toothed belt pulley. The peripheral part 12 preferably consists of a hard rubber such as vulkollan or adipren. Using segments 20—also known as spokes—on the one hand a considerable reduction in inertia is achieved and, on the other, there is produced an additional elasticity between the fixed reverse side and the eccentric roller for picking up the mail items. This elasticity is achieved in particular by the segments being arranged in a non-radial direction, as shown in FIG. 4 in a spiral-shaped arrangement. This ensures that the mail items are not excessively pressed. This elasticity is therefore also desirable because the mail items generally have different thicknesses. In the case of advertising leaflets this is not so serious, it having to be taken into account that the mail items can also contains small samples which cannot withstand pressures above a limit without damage. The rotational direction of the eccentric roller 11 illustrated in FIG. 4 is clockwise.
Using the two rotational directions of the eccentric rollers, the following advantages can be realised: i) This can be used, for example, when a double withdrawal occurs, to feed this out in the other direction in order to then feed in the fed-out mail item manually to a suitable position in the normal sorting or distribution process in the sense of a re-feed. ii) It is also possible to operate the eccentric rollers generally in both directions, e.g. alternating, and if necessary to provide a cross belt 21 in both directions D2 and D2′. The constructive embodiment of the eccentric roller 11 must be provided in such a way that the segment arrangement ensures the aforesaid elasticity in both rotational directions, e.g. by means of an S-shaped arrangement of the segments.
The abovementioned synchronisation of conveying belt 3, nubbed belt 4 and take-off drum 6 is freely combinable with the above-mentioned special implementations in respect of the bidirectional actuation of the eccentric rollers 11 and of the implementations of said eccentric rollers 11 as well as with the arrangement of a cross belt 21 for conveying away the mail items.
LIST OF REFERENCE CHARACTERS USED
1 Conveying device
2 Feeder
3 Conveying belt
4 Nubbed belt
5 Support on nubbed belt
6 Take-off drum
7 Gripper, actuatable
10 Deflection point
11 Eccentric roller
12 Peripheral, eccentric part
13 Flat section
13.1 First flat section
13.2 Second flat section
14 First drive motor, stepping motor
15 Second drive motor
16 First free-wheel
17 Second free-wheel
18 Toothed belt pulley
19 Roller, opposite eccentric roller
20 Segment, spoke
21 Cross belt
22 Cylinder
23 Bearing
- D1 Conveying direction of nubbed belt to deflection point
- D2, D2′ Conveying directions from deflection point, orthogonal with respect to feeding direction D1.
- F16 Engagement point of free-wheel 16
- F17 Engagement point of free-wheel 17
Patent Application
20050200074
