Material sortation system

Details Material sortation system Material sortation system

2003-08-04

2004-10-05

Bidwell, James R. (Department: 3651)

Conveyors: power-driven

Conveyor arrangement for selecting among plural sources or...

By loading or unloading section at selected one of a...

C198S370030

Reexamination Certificate

active

06799672

ABSTRACT:

The present invention relates to a material sortation system and more particularly to a sortation system of the type comprising of a plurality of transport units, and movable on a track. Items to be sorted are loaded onto the transport units and are unloaded at specified addresses or destination ports along the track
In a known material sortation system, each of the transport units comprises a tray which is connected to a tray tilting mechanism. The tray tilting mechanism allows the tray to be tilted to one side, but more usually to both sides, of the direction of travel of the tilt tray units in the track. In this way items loaded onto the trays can be discharged into selected destination ports
In a further known material sortation system, each of the transport units comprises a small conveyor or ‘cross belt’. The conveyor allows items, which are loaded upon it, to be propelled to either side of the direction of travel of the transport units along the track. In this way items loaded onto the conveyors can be discharged into selected destination ports.
Tilt tray and cross belt sorters are well known for their ability to handle a wide variety of products at large throughput rates and high speed with great accuracy. Tilt tray sorters are generally used in luggage handling systems at airports, central distribution warehouses, and parcel handling installations. Cross belts are more commonly used for the sortation of smaller items where the width of the destination port is narrow. The cross belt sorter powers the items into the chute whereas the tilt tray sorter allows product to drop into a destination port under the effect of gravity. As a consequence the width of the destination port can be made narrower for a cross belt sorter.
Tilt tray sorters are in the main mechanically operated, although electrically powered tilt tray units are known.
While an electrically powered tilt tray unit offers many advantages over a mechanical tilt tray unit, there are still some limitations to existing designs. A transmitter must be placed at each tip position along the track to initiate tilting and must be identified to control software within the sorter control system. Anytime a tip position is changed, the transmitter associated with it must be repositioned and changes in the control software need to be made. Furthermore there is considerable installation cost to install tip transmitters in terms of electrical site wiring, software and commissioning.
As a transmitter must be situated immediately adjacent to each tip position, a number of transmitters are required to produce a good fill pattern for wide chutes. Although it is relatively easy to install several transmitters for an electrically powered tilt tray unit, these transmitters all require wiring, software control, installation and commissioning time. There is also a limit on the number of tip positions for a single chute due to the physical size of the transmitters, their mounting brackets and associated wiring.
Once programmed the tip profile of the trays can not be readily changed. Yet it would be beneficial to be able to selectively vary the tray tip profile, for example, to tip a tilt tray more vigorously when luggage became wet, and to tip it gently when fragile items are carried.
One limitation of the throughput of a tilt tray sorter is the sorter speed. The number of items which can be sorted can be no greater than the number of trays passing the sorter loading area in a given time. Yet there is a maximum speed at which trays can safely travel along the track and above this speed there is always the risk that items on the trays will be flung off when the tray travels around bends in the track.
An electrically powered tilt tray sorter is also required to communicate with the sorter control system at specific locations around the sorter track. When the sorter stops the electrical power to the tilt tray units is switched off for safety reasons. When the sorter restarts all of the tilt tray units then need to be reset so that they will respond to tip commands. This function is performed at a certain position by means of a transmitter, which is activated as the tilt tray unit passes over it. Similarly when a tilt tray unit has had a fault, and is in the fault condition, the tilt tray unit is reset in this way.
The tilt tray units once reset, switch on an on board transmitter which signals to the sorter control system that it is ready to receive items. If a tilt tray unit develops a fault the on board transmitter is switched off. The status of the tilt tray units is read at set positions by an in track receiver.
Due to the fact that the transmitters and receivers are read at a limited number of set positions, inherent delays may occur on sorter start up as all of the tilt tray units need to pass the reset position before items can be loaded onto the trays and before tip commands can be passed to individual tilt tray units. If a fault condition occurs a tilt tray unit can not communicate the type of fault, only that a fault has occurred due to the fact that the on-board transmitter provided with it only allows an on or off signal.
For ease of understanding a typical electrically powered tilt tray sorter will now be described with reference to
FIGS. 1 and 2
of the accompanying drawings.
Referring firstly to
FIG. 2
there is shown two electrically powered tilt tray units
101
and
102
which are linked together to form a continuous train. Each tilt tray unit comprises in the lower part thereof an aluminium box section
2
which surrounds a steel plate
1
. The steel plate
1
forms a reaction plate for a linear induction motor. These linear induction motors serve to drive the continuous train around a track (not shown). The speed of the continuous train around the track is determined by sensor means (not shown) on or adjacent to the track which is able to detect the marks on an encoder strip
3
which runs along the side of each box section
2
and a central control then uses this to regulate the speed of the continuous train around the track.
Referring now to
FIG. 1
, each tilt tray unit comprises a braked electric motor
4
which is connected at each end thereof to a pair of arms
5
which in turn support a tray
103
, shown only in
FIG. 1
for ease of illusion. The motor
4
is operable to rotate the tray
103
backwards and forwards about its drive axis, thereby allowing items on the tray
103
to be discharged from it. The tray
103
is normally held in the horizontal position, as shown in
FIG. 1
, by the braked motor
4
.
Each tilt tray unit comprises at the forward end thereof a horizontally extending support bar
104
which carries at each end a roller assembly
105
and
106
. The roller assemblies
105
and
106
are each engageable in a respective channel defined by the aforementioned track. The operation of each tilt tray unit is controlled by receiver and transmitter devices carried by the unit itself and at predetermined locations around the track, as will now be explained.
Each tilt tray unit is reset after a fault condition or the loss of power by the operation of a tray reset transmitter mounted in the track. As a tilt tray unit passes over the reset transmitter, the transmitter is switched on, and a reset receiver (not shown) on the unit itself picks up the signal. The reset receiver outputs a signal to a controller
11
mounted on the tilt tray unit, which controller
11
effects a reset and enables the tilt tray unit. When the tilt tray unit is thus enabled a unit enabled transmitter
9
, carried on the horizontal support bar
104
, is switched on and remains switched on until a fault occurs or the power to the tilt tray unit is switched off.
Also located in the track is a unit enabled receiver which is able to detect the output from each unit enabled transmitter
9
. As each tilt tray unit passes over the unit enabled receiver the status of it's transmitter is detected or “read” and in this way the status of each unit is determined. Those tilt tray units which are determined to be disabled are taken out o

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