IL104762A - Sorting device and method - Google Patents

Description

Sorting device and method Natan YEHIMOVITZ C:- 88135 - - SORTING DEVICE AND METHOD FIELD OF THE INVENTION The present invention concerns a device and method for sorting unitary items by weight.

BACKGROUND AND SUMMARY OF THE INVENTION Picked vegetables or fruits have a wide range of sizes and it is usually necessary to sort them either by size or more typically by weight. Sorting is important for a number of reasons. For one, there is a correlation between the size of a fruit or a vegetable and its price. Furthermore, modern packaging means usually dictate that all vegetables or fruits in a single package be of about the same size. It is thus common practice for growers to sort fruits and vegetables by size and market them after sorting, in individual size groups.

It should be noted that inaccurate sorting may at times be rather costly to the grower. If for example, small fruits or vegetables are included in some proportion in a group of bigger fruits or vegetables, this has an overall effect of reducing the quality of his products, and consequently reducing its price. Additionally, inaccurate sorting of large fruits or - - vegetables into a group of small ones, means a loss of revenue which could have been obtained for the high weight fruits or vegetables.

Devices for sorting fruits or vegetables by weight are available but such devices are either not sufficiently accurate or are very complicated and expensive and are thus practical only in large fruit or vegetable packaging plants. Furthermore, such devices are, owing to their manner of operation, noisy.

It is an objection of the present invention to provide sorting means which are accurate on the one hand and relatively inexpensive on the other hand. Other objects of the invention will be clarified by the following description and Claims.

GENERAL DESCRIPTION OF THE INVENTION In accordance with the present invention there is provided a sorting device for sorting unitary items by weight comprising: conveying means for transporting said unitary items, comprising a plurality of compartments equally distanced from one another along its length, each compartment adapted to hold and convey a single unitary item; weighing means situated at the end of said conveyor means so as to receive said unitary items one at a time from said conveyor means, and adapted to hold each unitary item and weigh said item when same is essentially stationery on said weighing means, and emit a weight signal corresponding to the weight of said item; unloading means adapted to remove said item from said weighing means after completion of a weighing operation; a plurality of receiving means each for receiving a different weight range of said unitary items; routing means adapted for receiving said unitary items removed from said weighing means and routing them to one of said receiving means; and - - processor means adapted for receiving said weight signal and emitting a control signal to said routing means to route said unitary item unloaded from said weighing means into one of said receiving means according to its weight.

The present invention further provides a method for sorting unitary items by weight comprising the steps of: (i) conveying unitary items to a weighing means so that they are received on the weighing means one at a time; (ii) keeping each unitary item at rest on said weighing means for a time sufficient to complete the weighing operation by said weighing means; (iii) weighing each item by said weighing means whereby a weight-dependent signal is transmitted to a processor means, said processor means giving out a control signal contingent on said weight signal; and (iv) removing each item off said weighing means and routing it to one of a plurality of receiving means according to the control signal received from the said processor means, each receiving means receiving unitary items of one weight range different than other receiving means.

A preferred but non-limiting embodiment of the present invention is the sorting by weight of fruits or vegetables, to be referred to hereinafter collectively, for the sake of convenience, by the term "fruit(s) ". Other unitary items which may, for example, be sorted by means of the apparatus or method of the invention are eggs, baked products, various other food products, etc.

The present invention thus provides means whereby the sorting is performed by only a few moving components and as a result an apparatus in accordance with the invention is relatively inexpensive. Furthermore, - - another benefit to having only a few moving components is a marked reduction in noise and operational malfunctions. Against this, the device of the present invention allows a very accurate sorting of unitary items.

The invention will in the following be illustrated with reference to a specific, non-limiting embodiment.

BRIEF DESCRIPTION OF THE DRAWING The figure shown in the annexed drawing is an isometric view of a device of the invention intended for sorting fruits by weight.

DESCRIPTION OF A SPECIFIC EMBODIMENT Reference is now made to the annexed drawing showing a device for sorting fruits by weight in accordance with an embodiment of the invention. The device comprises a conveyor generally designated 1 provided with a plurality of compartments 2, each of said compartments adapted for holding only a single fruit 3, which by way of example may be an apple, an orange, a persimmon, etc.

Adjacent the upper end of the conveyor 1 is a collecting surface 4 routing the fruit 3 to a weighing means 6 mounted on a heavy granite plate 7 which is balanced and shock protected by shock absorbers 8. The weighing means has a padded fruit seat 9 adapted to hold a single fruit and has a weight transducer 11 which is electrically connected by line 12 to a processor 13.

An unloading arm 14 is rigidly attached to the end of an axle 15 which is rotatable by means of a chain of gear and chain-belts generally designated 16 whereby the rotation of arm 14 is coupled to and synchronized with conveyor 1. The coupling ensure that arm 14 performs a complete revolution upon advancement of the conveyor by a distance equal to that of the distance between two adjacent compartments 2, and its - - synchronization ensures so that it comes to the position shown in the figure in which it is about to remove the fruit off seat 9, only after a time sufficient to allow the completion of a weighing operation (see also below).

A guide member 17 is adapted to receive the fruit as it is removed from the seat 9 and deliver it to a routing unit 18. Routing unit 18 comprises a routing member 19 adapted to receive the fruit from guide member 17, which is mounted on an axle 20 of a step motor 21. Situated on top of step motor 21 and rigidly attached thereto is a plate carrying a plurality of sensors 22 which cooperate with an arm 23 fixed on axle 20 to provide an information signal indicating the motor's orientation. The sensors may for example be a proximity sensor, a wide range of which are known. Said motor 21 is connected by an electric command line 24 to processor 13.

A plurality of receptacles 26 are placed so that their receiving ends are radially around routing unit 18, whereby, an item routed by routing member 19 falls into a selected receptacle. Each of the receptacles 26 leads to a packing stand (not shown).

In operation, the fruits are loaded on the conveyor 1 by means known per se. Each compartment 2, holds a single fruit, which fruits are conveyed to the upper end of the conveyor where, each of the fruits in turn falls onto collecting surface 4 and routed towards seat 9 of the weighing means 6.

Once at rest the fruit is weighed by transducer 11 which emits a weight signal to processor 13 through line 12. Contingent with the weight signal the processor determines the category to which the fruits belongs, and a control signal is emitted accordingly and transferred to the step motor which rotates the routing member 19 to an appropriate position whereby, the fruit, after being pushed off from seat 9 by arm 14 is routed to the appropriate receptacle 26. An information signal of the angular orientation of motor 21, arising from sensors 22 which cooperate, for that purpose with - - arm 23, as mentioned above, is transmitted to processor 13 through line 24, thus forming a feedback loop allowing accurate control of the motor's orientation.

The processor, typically comprises a real time clock and has an operating cycle of a time equal to the time the conveyor advances by a distance equal to that between two adjacent compartments 2 on conveyor 1. At an appropriate time in the operation cycle, the processor starts to sample weight signals received from the weighing means through line 12. The processor is programmed to ignore peak weight which happens as a result of the impact of a fruit when it is received on seat 9. When the weight signals received from the weighing means indicate that the weight recorded by the weighing means approaches an asymptote, several consecutive readings are typically averaged, and a control signal, contingent on such an average is transmitted to routing means 18. Consequently routing member 19 is rotated by step motor 21 to an appropriate angular orientation to route the fruit onto the respective receptacle 26 depending on its weight. The processor may also be programmed to correct the position of the routing means should later weight signals indicate that the weight is different than the average recorded previously.

An apparatus in accordance with the invention may suitably comprise also an end of weighing indication means, intended to indicate the processor to perform a last reading of a weight signal shortly before the fruit is removed off the weighing means. An example of such indication means is sensor 30 which cooperates for this purpose with arm 31 rigidly attached to axle 15. When the arm reaches its position shown in the figure, in which it is about to push the fruit off the weighing means, a signal is emitted to the processor as indicated above and the processor performs a final weight reading and if necessary transmits a correction signal to routing means 18.

The speed of operation of the device has in fact two major rate limiting steps: the speed by which the weighing operation is performed and the speed of the routing. Regarding weighing, the speed of weighing can be increased by providing weighing means which are adapted to rapidly damp the oscillations which may arise from the impact of the fruit and thus quickly reach a stable state in which the weighing can be performed. The weighing means is suitably a pressure sensor, e.g. an electromechanical or piezoelectric sensors in which a weighing operation (damping of the movement and then reaching a stable state in which weighing is performed) typically lasts about 0.2 seconds. Regarding routing, the rate of this step may be increased by providing fast server motor for the performance of this step. Furthermore, the rate may also be increased by first providing a control command from the processor which will direct motor 21 to an approximate orientation after performing an initial weight measurement and then at a later stage after performing a more accurate weight measurement correcting the motor's orientation. This may be performed by means of an algorithm which is adapted to calculate a first from a first sample of weight signals and that emits a first control signal contingent on said first average which is transmitted to routing means 18. Thereafter, a second average is calculated from a second set of weight signals and then, if necessary, a correcting control signal is transmitted to the routing means. It is possible also for the algorithm, to be adapted to calculate and emit respective further averages and correcting control signals.

At times, the unloading arm, rather than removing a fruit from the weighing means, may accidentally crush a fruit on the weighing means which will give rise to an instantaneous excessive weight recordal. In such a case, it is usually desired to arrest the operation of the device and remove the crushed fruit and its remains. For that purpose the processor is - - preferably programmed to arrest the device's operation where the weight increases beyond a certain prefixed value.

The processor is suitably programmable to perform a variety of processing procedures, each one adapted for different fruits, and also for different grading criteria which may change occasionally depending on the target market segment, (e.g. export or local market) or other considerations.

During operation of the device, the accuracy of weighing may be impaired. Such may be the case for example where the temperature changes, e.g. from a cool morning temperature to a warm afternoon temperature, which may affect the reading of the weighing means owing to its internal physical parameters. Additionally, as a result of some dirt or moisture which may accumulate on the padded seat 9, some load may accumulate and as a result the reading of the fruit's weight may be excessive. In order to avoid same, the processor is preferably adapted to calibrate the zero weight reading at various times during operation. By one example, the processor which continuously samples the weight signals, tests for several consecutive periods in which no fruit was transferred to the weighing means and then all the sampled weight signals are averaged, which average forms the new zero weight or base-line level. It was found, in accordance with the present invention, that a suitable time frame to obtain an accurate zero level reading is 4 "empty" cycles, i.e. 4 cycles in which no fruit was transferred to the weighing means.

By means of the device or method of the present invention, unitary items such as fruits or vegetables can be accurately sorted by weight. The accuracy of the weight sorting can be tailored to specific needs by changing the resolution of the weighing means or by properly programming the processor. Furthermore, a device of the invention may be adapted to sorting unitary items in various numbers of different weight groups, as - - desired, the practical limitation being in fact dictated to a large extent only by the sensitivity of the weighing means.

Claims (10)

CLAIMS:

1. A sorting device for sorting unitary items by weight comprising: conveying means for transporting said unitary items, comprising a plurality of compartments equally distanced from one another along its length, each compartment adapted to hold and convey a single unitary item; weighing means situated at the end of said conveyor means so as to receive said unitary items one at a time from said conveyor means, and adapted to hold each unitary item and weigh said item when same is essentially stationery on said weighing means, and emit a weight signal corresponding to the weight of said item; unloading means adapted to remove said item from said weighing means after completion of a weighing operation; a plurality of receiving means each for receiving a different weight range of said unitary items; routing means adapted for receiving said unitary items removed from said weighing means and routing them to one of said receiving means; and processor means adapted for receiving said weight signal and emitting a control signal to said routing means to route said unitary item unloaded from said weighing means into one of said receiving means according to its weight.

2. A device according to Claim 1 or 2, wherein said processor means is adapted to sample a plurality of consecutive weight signals, and when the value of consecutive readings indicates stabilization of the weight readings, calculating an average of several consecutive signals and issuing said control signal contingent on the average.

3. A device according to Claim 3, wherein said processor means emits a first control signal contingent on a first average and then performing an additional sampling of several consecutive weight signals thereby obtaining a second average thus emits a second control signal contingent on the second average, correcting, if necessary, said first control signal.

4. A device according to any one of the preceding claims, wherein said routing means consist of a routing member mounted on a vertical axle rotatable by an electric motor; there being a plurality of receptacles having a receiving end radially placed around said routing means.

5. A device according to Claim 4, wherein the angular orientation of the routing means is controlled by a feedback.

6. A device according to any one of the preceding claims, wherein the processor means is adapted to arrest operation of the device when weight signals received from said weighing means indicate a weight on said weighing means which exceed a certain prefixed value.

7. A device according to any one of the preceding claims, wherein the processor means is adapted to arrest the operation of the entire device if the weight reading exceeds a certain value indicating jamming.

8. A sorting device according to Claim 1, wherein said unitary items are fruits or vegetables.

9. A method for sorting unitary items by weight comprising the steps of: (i) conveying unitary items to a weighing means so that they are received on the weighing means one at a time; (ii) keeping each unitary item at rest on said weighing means for a time sufficient to complete the weighing operation by said weighing means; (iii) weighing each item by said weighing means whereby a weight-dependent signal is transmitted to a processor means, said processor means giving out a control signal contingent on said weight signal; and (iv) removing each item off said weighing means and routing it to one of a plurality of receiving means according to the control signal received from the said processor means, each receiving means receiving unitary items of one weight range different than other receiving means.

10. A method according to Claim 9, wherein said unitary items are fruits or vegetables. For the Applicants, 8135SPC/DD/be/16.2.1993