Patent Application
20090065407
The invention relates to a device and a method for transporting a flat object, in particular an item of mail, in a specified transport direction.
A device with the features stated in the preamble of claim 1 and a method with the features stated in the preamble of claim 9 are known from DE 19753419 C1. The device described there transports objects in the form of flat items of mail. The transfer module described there comprises two conveyors positioned opposite each other which together transport the items of mail, taking them over from a feeder module and passing them on to a removal module.
The object underlying the invention is to provide a device with the features stated in the preamble of claim 1 and a method with the features stated in claim 9, whereby the transfer module applies lower accelerations to the object without compressing or pulling it.
The object is achieved by a device with the features stated in claim 1 and a method with the features stated in claim 9. Advantageous configurations are stated in the subordinate claims.
In accordance with the invention the transfer module is divided into two transfer components. These two transfer components are controllable independently of each other and in each case exhibit a drive unit and a gripping area.
An object passing through the device in transport direction is first temporarily held and transported by the feeder module, then temporarily held and transported by the first transfer component, then temporarily held and transported by the second transfer component and finally temporarily held and transported by the removal module.
The first transfer component takes the object over from the feeder gripping area and holds it temporarily in the first transfer gripping area. Because the distance from the feeder gripping area to the second transfer gripping area is greater than the length of the object in transport direction, the object is held for a certain period of time only by the first transfer gripping area and during this period of time is neither held in the feeder gripping area nor in the second transfer gripping area. This period of time is between the timepoint at which the object leaves the feeder gripping area and the timepoint at which the object reaches the second transfer gripping area. During this period of time the first transfer component is able to change the transport speed of the object without the object being held and as a result pulled or compressed by a gripping area on another part of the device.
Next the second transfer component takes the object over from the first transfer component and holds it temporarily in the second transfer gripping area. Because the distance from the first transfer gripping area to the removal gripping area is greater than the length of the object in transport direction the object is held for a certain period of time only by the second transfer gripping area. This period of time is between the timepoint at which the object leaves the first transfer gripping area and the timepoint at which the object reaches the removal gripping area. During this period of time the second transfer component is able to change the transport speed of the object without the object being held and as a result pulled or compressed by a gripping area on another part of the device.
Next the second transfer component passes the object on to the removal module with the removal gripping area.
One advantage of the invention is the following: To achieve the same difference between the feed and removal speed the device in accordance with the invention applies a lower acceleration or delay to the object than known devices. This is brought about in particular by the presence of two separate transfer components which change the feed speed to the removal speed in two stages. The lower acceleration is particularly advantageous if the object is sensitive and could be damaged by excessive acceleration.
Preferably the distance from the first transfer gripping area to the second transfer gripping area is smaller than the length of the object. This has the effect that the object is always held by one gripping area as it is being transported by the transfer module.
A further preferred configuration provides that the device is configured in such a way that between the feeder gripping area (Z-K) and the first transfer gripping area (K1) the object travels a distance which is smaller than the length of the object in transport direction (T). The distance which the object travels between the second transfer gripping area (K2) and the removal gripping area (W-K) is also smaller than the length of the object in transport direction (T). This has the effect that the object is always held by one gripping area while it is being transported into and out of the transfer module.
The invention is described below with reference to an exemplary embodiment, in which;
In the exemplary embodiment the device in accordance with the invention is used to transport flat items of mail. The device is installed in a sorting machine for sorting items of mail. The items of mail pass through various subsystems of the sorting machine in a stream of consecutive mail items.
So that these subsystems function reliably there has to be a minimum gap between two consecutive mail items in the stream. This minimum gap is defined as the lower limit for the distance between the rear edge of the item of mail in front and the front edge of the following item of mail. To ensure that the throughput through the sorting machine is and remains adequately high, however, the distance between two consecutive items of mail must not be greater than the specified upper limit.
As items of mail pass through the sorting machine the gap between two consecutive items of mail may be too big or too small. To correct this incorrect distance automatically the sorting machine exhibits at least one gap correction module which the stream of mail passes through. In the exemplary embodiment the device in accordance with the invention functions as this gap correction module.
Before two consecutive items of mail pass through the transfer module of the gap correction module the distance between them is measured. Preferably a light barrier measures this distance. Its beam of light is interrupted by the items of mail. The time span in which the beam of light is not interrupted is measured. The feed speed at which the items of mail pass through the feeder module is known. From this feed speed and the measured time span the distance is calculated.
If the distance is too great the following item of mail is temporarily accelerated relatively to the item of mail in front, which reduces the distance. If, on the other hand, the distance is too small the following item of mail is temporarily delayed, i.e. transported more slowly, which increases the distance.
The feeder module, the two transfer components and the removal module in each case comprise at least two endless conveyor belts which in each case run round several rollers and are tensioned to an adequate level of tightness. In each case two conveyor belts positioned opposite each other exert a frictional force on an item of mail that is between them. This enables the two conveyor belts to transport the item of mail without any slip.
In the example shown in
The first transfer component Ü1 comprises
The endless conveyor belt F1-Ü1 runs round the three belt pulleys 3, 4 and 5. The endless conveyor belt F2-Ü1 runs round the three belt conveyors 9, 10 and 11.
The second transfer component Ü2 comprises
The endless conveyor belt F1-Ü2 runs round the three belt pulleys 6, 7 and 8. The endless conveyor belt F2-Ü2 runs round the four belt pulleys 12, 14, 15 and 17. The two idler pulleys 13, 16 tighten the endless conveyor belt F2-Ü2.
In an alternative configuration only the two conveyor belts F1-Ü1 and F1-Ü2 are driven. The two other conveyor belts F2-Ü1 and F2-Ü2 are also turned when the driven conveyor belts F1-Ü1 and F1-Ü2 turn.
In upright position an item of mail is held and transported by in each case two endless conveyor belts positioned opposite each other, with a longitudinal edge of the mail item pointing downwards and a lateral edge pointing forwards in transport direction.
In the exemplary embodiment the conveyor belts exert an influence on the items of mail by means of a friction contact. As a result, four gripping areas Z-K, K1, K2 and W-K are created between in each case two conveyor belts positioned opposite each other.
The feeder gripping zone Z-K of the feeder module is formed by the conveyor belts F1-Z and F2-Z and ends—seen in transport direction Z—in roller 1—more precisely: in a vertical on the parallel conveyor belts F2-Z and F1-Z through the middle point of roller 1. The first transfer gripping area K1 is formed by the conveyor belts F1-Ü1 and F1-Ü2 and is limited by the two rollers 3 and 4 and belongs to the first transfer component. The second transfer gripping zone K2 is formed by the conveyor belts F2-Ü1 and F2-Ü2 and is limited by the two rollers 12 and 17 and belongs to the second transfer component. The removal gripping area W-K of the removal module is formed by the conveyor belts F1-W and F2-W and begins in roller 17.
In the example of
Preferably, items of mail which are shorter than L_min or longer than L_max are sorted out in advance and not transported through the sorting machine, because they are not suitable for machine-processing.
The gap correction module is designed in such a way that each item of mail is always held by at least one gripping area. This is made possible by
The item of mail should not be compressed during transport. A compression would occur if the item of mail were held simultaneously by two conveyor belts turning at different speeds. A suitable control therefore ensures the following:
In the exemplary embodiment the conveyor belts F1-Z, F2-Z, F1-W and F2-W turn at a constant speed in terms of time. It is possible for the four conveyor belts to turn at the same time. It is also possible for the two conveyor belts F1-Z and F2-Z to turn at a feed speed and the two conveyor belts F1-W and F2-W to turn at a removal speed, whereby the feed and removal speed differ.
The speed of the conveyor belts F1-Ü1 and F2-Ü1 of the first transfer component Ü1 can be set and changed independently of the speeds of all the other conveyor belts after the rear edge of the item of mail has left the feeder gripping area Z-K and before the front edge of this item of mail has reached the second transfer gripping area K2. In this period of time the item of mail is exclusively held by the first transfer gripping area K1 and can be accelerated or delayed without being pulled or compressed.
Correspondingly, the speed of conveyor belts F1-Ü2 and F2-Ü2 of the second transfer component Ü2 can be set and changed independently of the speeds of all the other conveyor belts after the rear edge of the item of mail has left the first transfer gripping area K1 and before the front edge of this item of mail has reached the removal gripping area W-K. In this period of time the item of mail is held exclusively by the second transfer gripping area K2.
This control uses as entry variable the position at which an item of mail to be transported finds itself precisely at the time. The device therefore preferably incorporates at least one light barrier Li. This light barrier Li includes a transmitter 20 and a receiver 21. It is arranged at the end of the feeder gripping area Z-K or directly behind it. An item of mail which leaves the feeder gripping area interrupts the beam of light LS emitted by the transmitter 20. This is registered by the receiver 21. Because the speeds at which the transfer components Ü1, Ü2 and the removal module W-K transport the item of mail are known from the control of the drives it can be automatically calculated when the item of mail reaches which gripping area and when it leaves that area.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 034 659.1 | Jul 2007 | DE | national |
