EP0060013A1

EP0060013A1 - Method of and apparatus for sorting objects by weight

Info

Publication number: EP0060013A1
Application number: EP19820300084
Authority: EP
Inventors: Taichi Horii; Yasutsugu Obuchi; Katsuhiro Iida
Original assignee: Maki Manufacturing Co Ltd
Current assignee: Maki Manufacturing Co Ltd
Priority date: 1981-03-06
Filing date: 1982-01-08
Publication date: 1982-09-15
Also published as: NZ199446A; DE3265117D1; EP0060013B1

Abstract

A method of and apparatus for sorting objects by weight uses an electronic weighing device 17 in combination with a conveyor system 10 and discharge devices 34. The objects to be sorted are carried one at a time by containers 6 held in mounting members (13) provided at regular intervals along the conveyor. When each container is brought to the weighing device 17, the container is supported solely by the weighing device, free from the influence of vibration of the conveyor itself, with clearances provided between the mounting member 13 and the container 6. This permits an accurate sorting operation. Furthermore, with an electromagnetic force balance device used as the electronic weighing device, the displacement of a weighing receiver plate 18 of the weighing device may be as little as 0.1 mm, or thereabout, permitting the weighing device quickly to stabilize under load, to allow high speed sorting to be performed.

Description

This invention relates to methods of and apparatus for sorting objects on the basis of their weights. The invention is particularly applicable to the sorting of agricultural products such as fruit, by handling each fruit one at a time, determining its weight and then classifying or grading each piece on the basis of the weight thereof.
For the sorting of agricultural products such as fruit on the basis of weight, there are described various apparati on pages 289 - 296 of a publication entitled "SEN-KA HOSO SOCHI NO TEBIKI" (Guide to Fruits Sorting and Packaging Apparati) issued March 20, 1971 by ZEN-KO-REN, SHISETSU-BU, (Department of Facilities, All-Japan Federation of Purchasing Association). Such apparati are in general use and employ weighing instruments of the lever and spring balance type. Furthermore, in recent years, there has appeared an automatic weight sorting apparatus which uses a load cell type of weighing instrument in combination with a conveyor arrangement similar to that of a conventional fruit weight sorting apparatus, as is known for example from Japanese Laid-Open Patent Applications Sho No. 56-97582 and 56-97583.
In many of these conventional apparati for sorting fruit by weight, there is a conveyor system having cup traction shafts mounted at regular intervals on an endless chain arranged to operate in a recirculatory manner. Cups are hinged to the traction shafts and each cup is provided with a finger which is arranged to slide on a weighing instrument, to determine the weight of a carried object.
In another example of the conventional apparatus, cups or weighing buckets are attached to supporting members so as to be able to tilt with respect thereto, constituting a so-called Roberval mechanism. The supporting members are secured to the conveyor chain at regular intervals to form a conveyor system with the weighing cups. In this case, each of the supporting members is provided with a finger or a hook or a sliding piece called a sliding pin which protrudes from a part of the supporting member so as to slide on the weighing instrument while the conveyor system is on the move, so that the fruit can be classified and sorted by weight thereof.
The conventional arrangement thus has cups or weighing buckets kept horizontal and secured to the chain through supporting members either by hinges or fulcrum pins. Therefore, any vibration of the chain on movement thereof is transmitted to the sliding pieces or other elements which are connected to the cups or weighing buckets to allow the detection of weight. The weight detecting elements thus slide on to the weighing instrument while the elements are vibrating, and it has been a shortcoming of the conventional arrangements that considerable weighing errors result from the vibration during the sliding movement on the weighing instrument. This gives rise to inaccurate sorting by weight.
Another problem of the conventional arrangement stems from the fact that each cup or weighing bucket is carried by a fulcrum pin or a hinged Linkage coupling the cup to other components. The freedom of movement or frictional resistance for one cup or bucket may differ significantly from another, especially when there are provided hundreds of cups or buckets. Hence, it has been another shortcoming of the conventional arrangement that weight cannot be measured with precise accuracy, even if the weight of all the cups or weighing buckets are made identical.
Another known arrangement has a small conveyor provided at the weighing receiver plate of a weighing instrument, for conveying to the instrument the objects to be weighed on a piece-by-piece basis. Generally, this arrangement is employed where industrial products are to be subjected to automatic quality control, to determine whether the weight thereof is at a prescribed value or deviates therefrom. A weighing instrument using a conveyor of this type is capable of weighing in a non-contact manner each object-to be tested by removing it from the conveyor, piece-by-piece. However, since the conveyor is incorporated in the weighing mechanism, vibration resulting from the placing of a piece on the conveyor or the removal of a piece therefrom as well as vibration of the conveyor itself can greatly affect the weighing accuracy.
The above stated shortcomings of the conventional known arrangements have rendered the results of sorting operations not always to be entirely satisfactory. This has prevented reliable high speed sorting operations to be performed at increased conveyor speeds. As a result, if accurate sorting of a great number of products is required, it has been necessary to have a plurality of weight sorting apparati all operating at relatively low conveyor speeds, and thus at reduced capacities.
The present invention aims at reducing the shortcomings of the known apparati as discussed above. This is achieved by employing an electronic weighing instrument which is capable of covering a wide range of weight values with only a very slight degree of displacement of a weighing receiver plate. It is therefore a general object of the invention to provide a sorting method and sorting apparatus in which containers for the objects to be sorted can be of simple structure and of uniform weight, allowing the weight of a carried object to be measured at a relatively high speed and then sorted with a high degree of accuracy, whilst allowing simple weight grade adjustments and operation to be performed.
Accordingly, one aspect of the invention provides a method for sorting object on the basis of their weights, using apparatus comprising a weighing device and a conveyor system having a plurality of containers each for carrying one object, each container being supported by conveyor means serving to advance each container in sequence to the weighing device and then through a succession of discharge points, the apparatus being arranged to discharge a carried object at one of the discharge points appropriate for the determined weight of that object characterised in that an electronic weighing device is employed and in that at the weighing device each container is lifted clear of the conveyor means so as to be supported solely by the weighing device whilst weighing is being performed, the container being advanced whilst being supported solely by the weighing device by means of an advancing member provided on the conveyor means and imparting a generally horizontal force on the container.
The electronic weighing device may have a slide rail along which each container is in turn slid whilst being supported solely thereby to allow weighing to be performed, in which case it is preferred for there to be clearance between the container and the conveyor means which supports the container other than at the weighing device, which clearance allows the container to move upwardly, downwardly or to either side with respect to the conveyor means. In this way, any vibrations present in the conveyor means will not be imparted to the container during the weighing process. By having an electronic weighing instrument with a weighing receiver plate which is not displaced much by an applied load, each container may simply be slid on to and off the weighing device, with a much reduced likelihood of vibration occurring. Thus the relative level of the receiver plate should set so as to leave upper and lower clearances between the container and a mounting member therefor, on the conveyor means.
According to another aspect of this invention, there is provided apparatus for sorting object on the basis of their weight, the apparatus comprising a weighing device, a conveyor system having a plurality of containers each adapted to carry one object to be sorted, each container being supported by conveyor means arranged to advance the containers in sequence to the weighing device and then through a plurality of spaced discharge points,' discharge means being provided at each discharge point to discharge a carried object .if a discharge signal is directed to that discharge means, and processing means arranged to receive an electric signal from the weighing device and an electric clock signal generated in synchronism with operation of the conveyor means, the processing means generating said discharge signals, which apparatus is characterised in that the weighing device is electronically controlled, in that each container has a receiving pan part, a sliding face and a mounting part, and in that the conveyor means has a plurality of mounting members one associated with each container respectively, each mounting member co-operating with the mounting part of its associated container so as normally to support the container but to permit the container to be lifted clear thereof, the weighing device having weighing means adapted to co-operate with the sliding face of a container thereby to lift a container clear of its mounting member and wholly to support the container and any object carried thereby so as to permit the weighing thereof, there being means co-operating between the mounting member and container mounting part so as to allow the container sliding face to be slid along the weighing means on operation of the conveyor means whilst the container is supported by the weighing means.
Preferably, the mounting member and container mounting part are arranged to define clearances therebetween which permit the container to move upwardly, downwardly or to either side with respect to the mounting member when the container is supported wholly by the weighing means.
The most preferred form of the apparatus has weighing means including a slide rail along which each container is in turn slid as weighing is performed, there being guide means to lift each container clear of its mounting member and on to the slide rail of the weighing device and then to receive each container from the slide rail and lower each container back on to its mounting member.
Most advantageously, the co-operating means between a container and its mounting member comprises a pushing member provided on the mounting member and a thrust-receiving face on the container engaged by the pushing member, one of the pushing member and the thrust-receiving face having an abutment portion which extends generally vertically transverse to the line of advancement of the conveyor means and the other of the pushing member and thrust-receiving face defining a curved surface engaged tangentially with said abutment portion. Thus, the container may define the vertical thrust-receiving face and the pushing member may then be in the form of a freely rotatable roller the periphery of which engages the thrust-receiving face of the container.
It will be appreciated that with the weighing device arranged in this manner, each container is not in contact with its mounting member when the container is slid over the weighing device, whilst carrying the object to be sorted. The container is pushed horizontally by a part of the circumference of the pushing member, in the-direction of advancement of the container. Therefore, there is no adverse effect on the vertical load of the container applied to the weighing device. Further, since the invented arrangement effectively prevents any vibration of the conveying means from being transmitted, sorting by weight - can be carried out at a high degree of accuracy. Besides, the high weighing accuracy permits an increase in the conveyor speed to increase the processing capacity.
By way of example only, certain specific- embodiments of this invention will now be described in detail, reference being made to the accompanying drawings, in which:-

Figure 1 is a plan view showing a first embodiment of the invention which is arranged to have one row of containers travelling linearly, in a recirculatory manner;
Figure 2 is a schematic side view showing the arrangement of the first embodiment;
Figure 3 is a plan view showing a second embodiment of the invention which is arranged to have a plurality of rows of containers travelling linearly in a recirculatory manner;
Figure 4 is a schematic side view showing the arrangement of the second embodiment;
Figure 5 is a plan view of a third embodiment of weight sorting apparatus, arranged to have containers travelling around a horizontal recirculatory path;
Figure 6 is a schematic sectional view showing the essential parts of a sorting and discharge section of the apparatus shown in Figure 5;
Figure 7 is a plan view showing a fourth embodiment of weight sorting apparatus, but of the rotary type and arranged to have containers travelling horizontally around a circular path;
Figure 8 is a schematic sectional view showing the essential parts of the arrangement shown in Figure 7;
Figure 9 is a schematic view of the essential parts of an embodiment of weight sorting apparatus such as is illustrated in Figure 1;
Figures 10 and 11 are schematic views showing the containers as they move past the weighing section of the first embodiment;
Figure 12 is a cross-section through the weighing section of the first embodiment, when a container is located therein;
Figure 13 is a sectional view showing the container conveying device of the first embodiment, at the sorting and discharge section thereof;
Figure 14 is a plan view showing discharge.devices provided beneath the container conveying path of the first embodiment;
Figure 15 is a side view showing the weighing section of the second embodiment;
Figure 16 is a side view showing a part of the conveyor system of the second embodiment;
Figure 17 is a plan view on part of the conveyor system shown in Figure 16;
Figures 18(a) and 18(b) are side views showing a container of the second embodiment, respectively prior to and on being conveyed through the weighing section;
Figures 19(a) and 19(b) are sectional views on Figures 18(a) and 18(b) respectively;
Figures 20 and 21 are schematic views showing the discharge device of the second embodiment; and
Figure 22 is a schematic view showing the details of an electronic weighing instrument for use in embodiments of this invention.

Figures 1 to 9 all generally illustrate embodiments of the present invention, and the embodiment selected for a particular application will depend upon the kind of objects to be sorted, the quantity of the objects to be processed, the scale of the sorting operation, the size of the available space for installation of the sorting apparatus, the layout of the apparatus, and so on. Through the Figures, like parts are given like reference characters.
The weight sorting apparati generally described below with refernece to Figures 1 to 9 are arranged in various manners, as best appreciated from Figures 1, 3, 5 and 7, respectively. The apparatus 1 shown in each of these drawings has a supply section 3 which is arranged to feed objects 2 to be sorted; a weighing section 4; and a sorting and discharge section 5. Each of these sections 3, 4 and 5 is arranged to extend for the required length.
The apparatus further includes containers 6 each being arranged to carry one piece of the objects to be sorted. Each container 6 is provided with a receiving pan part 7, a sliding face 8 and a mounting part 9. The container 6 may be arranged either to have the receiving-pan part 7, the sliding face 8 and the mounting part 9 formed into a unified body or to have these parts separately formed but assembled with the receiving pan part 7 supported jointly by the mounting part 9 and the sliding face 8, so as to be tiltable to one side. One of these different ways of arranging the container 6 is selected, according to the mode of employment of the invention.
The apparatus has a conveying means 10, which includes either a conveyor chain 11 or. a rotating body 12 such as a turntable, according to the embodiments of the invention. There is provided a mounting member 13 for each of the containers 6, which mounting member 13 co-operates with the mounting part 9 of the container 6 so as to leave clearances a, b, c, d, e and f, respectively above, below, on the right and left sides and on the front and rear sides of the mounting part 9. The container 6 is thus permitted free movement within the range defined by those clearances.
Typically, such clearances may be of the order of several mm.
One of the co-operating mounting part 9 of the container 6 and the mounting member 13 is arranged to be larger than the other, for obtaining the above stated clearances. The shapes and structural arrangement of these parts vary with the particular embodiment of the invention.
The container 6 is provided with a vertical face 15 either on the mounting part 9 or on some other part. The vertical face 15 is directed rearwardly and is disposed to have a part of the circumference of a pushing member 16 in contact therewith. The pushing member 16 is arranged in this manner to maintain the clearances e and f between the mounting member 13_.and the mounting part 9 of the container 6. Each container 6 being thus arranged, many containers are mounted on the conveying means 10 at regular intervals to form a conveyor system 14 with containers 6. The system 14 travels in an endless recirculating manner. The vertical face 15 is disposed below the receiving pan part 7 of the container 6 and above the sliding face 8 - i.e. between the receiving pan part 7 and the sliding face 8 - and may be arranged either in front of, in the middle of or behind the container 6, according to the embodiment of the invention.
The pushing member 16 is.preferably a circular body of low frictional resistance, such as a bearing, a roller or a ball. In some embodiments of the invention, however, the pushing member 16 may take the form of a non-rotating shaft, so that the vertical face 15 is pushed from outside by the non-rotating shaft. In such a case, therefore, the mounting member 13 may be arranged also to serve as the pushing member 16.
Where the vertical face 15 is disposed in front of the mounting part 9, it still should face rearwardly. Then, it is both preferred and economical for the pushing member 16 to be arranged in the form of a roller which enters the mounting part 9, with the mounting member used as a shaft.
It is possible to reverse the above-described relation of a vertical face of the container 6 engaged by a circular front face of the pushing member 16, by making the front of the pushing member 16 into a vertical face while providing the container 6 with a circular protrusion or a roller in place of the vertical face 15.
The weighing section 4 of the apparatus includes an electronic weighing instrument 17 and a weighing receiver plate 18. The receiver plate 18 has sliding measurement rails 19 arranged thereon so as to be able to co-operate with the sliding face 8 of each container 6. The weighing instrument 17 with the receiving plate 18 is disposed beneath the container conveying path 20 of the conveyor system 14 having the containers. The height of the weighing instrument 17 is arranged such that the clearances a, b, c and d mentioned in the foregoing are retained between the mounting member 13 and the mounting part 9 of the container 6 when the container 6 slides on the sliding measurement rails 19. In other words, the weighing instrument is disposed at a height at which the -container _.6 is lifted up by a slight degree from the mounting member 13.
Since the displacement of the weighing receiver plate 18 takes place only to a very slight degree when a vertical load is imposed on the plate 18, the clearance a is retained even when the container with the object to be sorted placed thereon comes on to the sliding measurement rails 19, so that the whole weight of the container 6 can be received by the receiver plate 18 through the measurement rails 19, for accurate measurement of the weight.
The electronic weighing instrument 17 may be either a force-balance type weighing instrument using an electromagnet force-balance device, or a load cell type weighing instrument using a load cell, or a weighing instrument using a differential transformer. In the case -of a high speed weighing operation where 150 to 210 pieces are to be processed per minute - that is, 2.5 to 3.5 pieces per second - the cyclic loading tends to cause the weighing receiver plate 18 to move up and down. This then tends to vibrate,due to its inertia. It is therefore preferable to employ a force-balance type weighing machine using an electromagnetic force-balance device when a high speed operation is to be performed.
The electromagnetic force-balance device 21 is mounted on a lever 22 to which the weighing receiver plate 18 is attached. The device 21 is arranged to hold and balance the weighing receiver plate 18 always at a prescribed level, pivoting on a fulcrum 23. When the receiver plate 18 is caused by a load to sink, the device 21 acts to lift up the plate 18 by as much as it has sunk. With the device 21 employed, therefore, vibration can be absorbed even where the weighing operation is performed at a high rate exceeding 3 pieces/sec., so that the weighing can be accomplished with a high degree of accuracy.
The electronic weighing instrument 17 is provided with entrance guide rails 24 and exit guide rails 25 which are disposed respectively before and after the sliding measurement rails 19. The rails 24 and 25 are arranged so that each container 6 comes on to and leaves the rails 19 smoothly, without imparting any impact or vibration forces to the weighing instrument 17, the heights of these rails 24 and 25 being adjusted to correspond to the height of the sliding measurement rails 19.
The entrance and exit guide rails 24 and 25 may be mounted on the frame of the conveyor system which is equipped with the containers. However, in view of the importance of the positions of the rails 24 and 25 in relation to the sliding measurement rails 19, the rails 24 and 25 are preferably mounted on the same base as the electronic weighing instrument 17.
The entrance guide rails 24 are arranged to lift in turn each container 6 of the conveyor system 14" by engaging from below the sliding face 8 thereof, and then to cause each container to slide and travel horizontally at a height that maintains the above-stated clearances a and b. Similarly, the exit guide rails 25 are arranged to receive in turn each container 6 as it comes off the sliding measurement rails 19, without changing the height of the container 6 and, after each container has left the rails 19, to guide it smoothly whilst lowering it until the clearance a at the mounting part 9 becomes zero, the mounting part 9 then being supported by the mounting member 13.
A clock means 26 is arranged to produce a pulse signal in synchronism with the movement of the containers 6 and is arranged in association with the conveyor system 14 equipped with the containers. Any suitable known form of clock means may be used for this purpose. The timing of the clock means 26 is adjusted in such a manner that a pulse signal is issued when a container 6 has arrived at a predetermined point on the electronic weighing instrument 17.
The weighing device of the apparatus of this invention is provided with an amplifier 27, which is arranged to amplify an electrical signal produced by the electronic weighing instrument and proportional to the weight of the load imposed on the weighing receiver plate 18. The output signal from the amplifier 27 is converted by a converter 28 into a digital signal which is proportional to the weight.
The electronic weighing instrument 17, the amplifier 27 and the converter 28 constitute a weighing device. The weighing device is connected to an arithmetic unit 29, as is the output of the clock means 26.
The weighing device is arranged as follows. The instant a container 6 slides on to the sliding measurement rails 19 of the electronic weighing instrument 17, the sudden loading causes the weighing receiver plate 18 to vibrate somewhat. At this instant, the clock means 26 produces a pulse signal. With the pulse signal obtained, the converter 28 produces a digital signal corresponding to the weight at the time at which the container 6 has come to travel smoothly on the sliding measurement rails 19, the vibration having been gradually absorbed there.
The arithmetic unit 29 is connected to receive the output of the converter 28 of the weighing device and the output of the clock means 26. The arithmetic unit is mainly composed of a comparison circuit 30; a preset circuit 31 provided for setting standard weight grading values; a discharge position setting circuit 32 for setting a discharge position for each grade; and a shift circuit 33 which is arranged to transmit a discharge instruction signal to each of the set discharge positions in synchronism with the containers. Any suitable known form of arithmetic unit may be employed as the arithmetic unit 29.
Discharge devices 34 are arranged in the sorting and discharge section 5 of the conveyor system 14, and are disposed either on one side of or beneath the container conveying path 20. Each device is allocated to a particular weight grade to discharge an appropriate object. A known form of discharge arrangement may be used for each of the discharge devices 34.
In the arithmetic unit 2.9, the digital signal which is produced by the converter 28 in proportion to the measured weight is counted in the comparison circuit 30 and is compared with the preset values of grades, to determine an appropriate grade. Then, a discharge instruction signal is transmitted to one of the discharge device 34 located at the position of the appropriate grade when the relevant container is at that position.
The discharge devices 34 are arranged to discharge a carried object from the receiving pan part of the containers 6, at the determined positions. The discharging action of each discharge device 34 may be accomplished in one of a number of various manners, such as discharging by tilting a container 6 to one side, discharging by tilting the rear edge of a container 6 downwardly, discharging by pushing a carried object 2 to one side without tilting the container 6, and so on. A suitable discharging manner should be selected according to the mode of employment of the invention,-having regard to the design of the conveyor system having the containers.
A counter which counts the individual pieces sorted in each grade and a printer arranged to record the sorting data may both be connected to the arithmetic unit 29.

First Embodiment.

Figures 10 to 14 illustrate in greater detail various features of the conveyor system provided with containers and discharge devices, forming the weight sorting apparatus shown in Figures 1 and 2. In this embodiment of the invention, the receiving pan part 7 of each container is arranged to be-tiltable to one side. The sliding face 8 and the mounting part 9 of the container are formed into one unified body to serve as a supporting body 35 for the pan part 7. A tilting mechanism 36 which is arranged to tilt the receiving pan part 7 is incorporated in the supporting body 35. The receiving pan part 7 is mounted on and connected to the supporting body 35, and also to the tilting mechanism 36 through a link 37 and a pin 38. The tilting mechanism 36 is arranged to urge the receiving pan part to lie horizontal, by means of a spring 39. On discharging an object to be sorted, the receiving pan part 7 is tilted by having a downwardly-protruding pin 40 slid by the discharge device 34 against the force of the spring 39.
The supporting body 35 is mounted by two mounting members 13 each of which is a round rod attached to the chain 11, so as to extend through holes in the mounting part 9. These holes may be formed to have round or square shapes, or indeed other shapes. However, the size of each hole must be determined by adding the required clearances a, b, e and f to the outside diameter of the mounting member 13. In the arrangement shown in Figure 10, the vertical face 15 is provided at the rear of the supporting body 35, a roller 41 being rotatably attached to the chain 11 to serve as the pushing member for pushing the vertical face 15 whilst the container is conveyed horizontally with the clearances e and f being maintained. In the case of Figure 11, the mounting part 9 is formed with square holes 42. The vertical face 15 is formed on the front side of the square hole 42 so as to face rearwardly. A freely rotatable roller 41 is attahced to the mounting -member 13 formed from a round rod and the roller 41 is used as the pushing member.
Figure 12 shows an arrangement in which the container 6 is arranged to have clearances c and d on the left and right sides thereof whilst it is caused to slide along the sliding measurement rails 19 of the electronic weighing instrument 17. However, when the container 6 is travelling along parts of its path other than the weighing section, the container 6 is arranged to be supported on tapered parts 43 provided on both sides thereof, and is thus kept in the middle of the chain conveyor.
Figures 13 and 14 show the discharge device 34 provided beneath the container conveying path 20. The discharge device 34 comprises a lever 44 which when appropriately positioned is arranged to shift the pin 40 provided in the tilting mechanism of the container, a rotary solenoid 45 being provided to move the lever 44. A tilting cam 46 causes the pin 40 to move when directed thereonto by the lever 44. A discharge instruction signal produced by the shift circuit 30 of the arithmetic unit 29 is transmitted in synchronism with the arrival of the appropriate container 6 at the discharge position, so as to actuate the rotary solenoid 45 to cause the lever 44 to turn, thereby guiding the pin 40 on to the tilting cam 46.
The pin 40 thus slides sideways, and the receiving pan part 7 is tilted to discharge the object 2 being sorted.

Second Embodiment.

Figures 15 to 19 show details of the conveyor system with containers as used in the weight sorting apparatus shown in Figures 3 and 4. In this embodiment, the front portion of each mounting member 13 which is coupled with a container is connected through a hinge-pin to an associated metal mounting piece 47 which pieces are provided on the chain 11 at regular intervals. An object to be sorted is discharged from a container by tilting downwardly the rear part of the container. Each container 6 has a receiving pan part 7 disposed in the upper part thereof, a sliding face 8 disposed in a lower part and a mounting part 9 arranged to extend through a body portion disposed between the receiving pan part 7 and the sliding face 8. These parts are formed in one unified body. The mounting member 13 has an arm 49 which carries .a shaft 48 extending into the mounting part 9. The mounting part 9 may be arranged to have round or square holes or holes of some other shapes, in the same manner as has been described in connection with the first embodiment. However, the size of the hole must be determined by adding the clearances a, b, e and f to the outer diameter of the shaft 48. The hole 42 disposed to the front of the mounting member 9 is of a square shape and defines a vertical face 15 formed on the front side thereof, the vertical face 15 thus facing rearwardly. A flanged roller 50 is rotatably mounted on a shaft 48a and thus serves as a pushing member. Shaft 48 has an extension 48b which protrudes outwardly beyond the arm 49 and is carried on a running rail 51. With the extension 48b arranged in this manner, the container is kept horizontal whilst travelling. The front portion of the arm 49 is connected by hinge-pins 52 to a metal mounting piece 47.
Figures 20 and 21 show the discharge device 34 which is disposed below the container conveying path 20, and on one side thereof. A portion of the running rail 51 is here cut out, and is replaced by an ascending-and-descending rail 53, arranged to be movable by means of a solenoid 54. The rail 53 normally has its upper surface 53a kept at the same level as the running rail 51. A discharge instruction signal transmitted in synchronism with the arrival of an appropriate container at the cut-out portion actuates the solenoid 54, so as to cause the rail 53 to ascend. The shaft extension 48b of the container then drops downwardly on to a ramp surface, and further movement of the metal mounting piece 11 causes the rear part of the container to descend. An object to be sorted is thus discharged at this device. Were the object not to be sorted, rail 53 would have been maintained at its lower position (Figure 20).

Example of the Electronic Weighing Instrument.

Figures 9, 15 and particularly 22 show an example of an electronic weighing instrument 17 which is provided with an electromagnetic force balance device 21, suitable for use with the various types of the weight sorting apparatus 1.
The electronic weighing instrument comprises a lever 22 disposed horizontally to extend across a stand 55 which upstands from and is secured to a base plate. A fulcrum part 55a protrudes from an upper part of the stand 55, the lever 22 and the fulcrum part 55a being connected to each other by a pair of left and right plate springs 56 so as to form a fulcrum 23. One end part of the lever 22 is located a short distance from the fulcrum 23 and is connected to member 57 by a pair of left and right plate springs 58 to give a weight point 59, the receiving member 57 extending up toward the lower part of the weighing receiver plate 18. The upper and lower parts 55b and 55c of the stand 55 are respectively connected to the upper and lower parts 57a and 57b of the receiving member 57 by means of four plate springs 60, disposed parallel to the lever 22 with two thereabove and two therebelow. Each plate spring 60 is reinforced in the middle portion 60a thereof. This arrangement provides the function of the stay of a Roberval mechanism. On the upper surface of'the weighing receiver plate 18, there is mounted the sliding measurement rail 19 which is adapted to receive the sliding face 8 of the container 6. The rail 19 extends horizontally for a distance shorter than the mounting interval P-of adjacent containers 6.
The fore end part 22b of the lever 22 has mounted thereon a balancing core 61 of an electromagnetic force balance device 21. A coil 62 associated with the core 61 is mounted on a coil stand 63 provided on the- base plate, so as to give rise to a force point 64 for electromagnetic force. A differential transformer 65 is attached to a part of the lever 22, to serve as a displacement detector.
When a load imposed on the sliding measurement rail 19 causes the lever 22 to pivot through even to a small degree, there is produced a very small displacement signal (a voltage signal) in the differential transformer 65. This displacement signal is amplified by the amplifier 27 and is converted into a current. The current thus obtained is applied in the correct sense as an exciting current to the coil 62. In this way, the lever 22 is balanced by the electromagnetic force developed at the coil 62.
As has been described in the foregoing, in the embodiments of this invention the containers which carry the objects to be sorted are not fixed to the conveying means (such as a chain) but are arranged so there are clearances therebetween during the weighing operation. Each container is arranged such that it may stand on the weighing device and be pushed horizontally by a pushing member; there is little frictional resistance to such movement over the electronic weighing instrument. Therefore, the load imposed on the electronic weighing instrument is precisely proportional to the weight of the object to be sorted, so that the weight can be measured with a high degree of accuracy.
Furthermore, with the above described electromagnetic- force balance device used as the electronic weighing instrument, the degree of displacement under load of the weighing receiver plate, or the sliding measurement rail, is only 0.1 mm or thereabout. Therefore, the-weighing instrument stabilizes quickly to permit high speed weighing.

Claims

1. A method for sorting objects on the basis of their weights, using apparatus comprising a weighing device and a conveyor system having a plurality of containers each for carrying one object, each container being supported by conveyor means serving to advance each container in sequence to the weighing device and then through a succession of discharge points, the apparatus being arranged to discharge a carried object at one of the discharge points appropriate for the determined weight of that object, characterised in that an electronic weighing device (17, Figure 22) is employed, and in that at the weighing device (17, Figure 22) each container (6) is lifted clear of the conveyor means (10) so as to be supported solely by the weighing device (17) whilst weighing is being performed, the container (6) being advanced whilst being supported solely by the weighing device (17) by means of an advancing member (16, 41, 50) provided on the conveyor means imparting a generally horizontal force on the container.

2. A method according to claim 1 and in which the weighing device has a slide rail (19) along which each container (6) is in turn slid whilst being supported solely thereby to allow weighing to be performed, characterised in that whilst a container (6) is supported solely by the slide rail (19), there is clearance between the container and the conveyor means (10) which'supports the container other than at the weighing device, which clearance allows the container to move upwardly, downwardly or to either side with respect to the conveyor means.

3. A method according to claim 1 or claim 2, further characterised in that a clock signal (26) is generated in synchronism with a container being supported by the weighing device, and in that the determined weight is processed in conjunction with the clock signals generated as the conveyor means (10) is operated to advance the containers (6), a discharge signal being produced to --actuate discharge means (34) at the appropriate discharge point for a particular object (2) when the container carrying that object is determined as being present at that discharge point.

4. A method according to claim 3, characterised in that the weighing device (17) determines the weight of a container (6) and the object (2) carried therein, the determined weight being processed to classify the weight of a carried object (2) into one of a number of pre-set grades of weight corresponding one to each discharge point, a discharge signal for the discharge point appropriate for the classified weight being produced by processing the classified weight in conjunction with the clock signals generated as the conveyor means is operated to advance the containers.

5. A method according to claim 3 or claim 4, characterised in that generation of the discharge signal operates the discharge means (34) either to tilt a container (6) sideways or to swing downwardly, with respect to the conveyor means (10), in either case to discharge a carried object from the container.

6. Apparatus for sorting objects on the basis of their weight, which apparatus comprises a weighing device, a conveyor system having a plurality of containers each adapted to carry one object to be sorted, each container being supported by conveyor means arranged to advance the containers in sequence to the weighing device and then through a plurality of spaced discharge points, discharge means being provided at each discharge point to discharge a carried object if a discharge signal is directed to that discharge means, and processing means arranged to receive an electric signal from the weighing device and an electric clock-signal generated in synchronism with operation of the conveyor means, the processing means generating said discharge signals, characterised in that the weighing device (17) is electronically controlled, in that each container (6) has a receiving pan part (7), a sliding face (8).and a mounting part (9), and in that the conveyor means (10) has a plurality of mounting members (13) one associated with each container respectively, each mounting member (13) co-operating with the mounting part (9) of its associated container (6) so as normally to support the container but to permit the container to he __ lifted clear thereof, the electronic weighing device (17) having weighing means (18, 19) adapted to co-operate with the sliding face (8) of a container (6) thereby to lift a container clear of its mounting member (13) and wholly to support the container and any object (2) carried thereby so as to permit the weighing thereof, there being means (15, 16 or 15, 41) co-operating between the mounting member (13) and container mounting part (9) so as to slide the container sliding face (8) along the weighing means on operation of the conveyor means whilst the container is supported by the weighing means.

7. Apparatus according to claim 6, further characterised in that the mounting member (13) and container mounting part (9) are arranged to define clearances (a, b, c, d, e and f) therebetween which permit the container to move upwardly, downwardly or to either side with respect to the mounting member when the container is supported wholly by the weighing means.

8. Apparatus according to claim 6 or claim 7, further characterised in that the weighing means (17) of the weighing device is in the form of a slide rail (19) along which each container (6) is in turn slid as weighing is performed, there being guide means (24, 25) to lift each -container clear of its mounting member and on to the slide, rail (19) of the weighing device and then to receive each container from the slide rail (19) and lower each container back on to its mounting member.

9. Apparatus according to any of claims 6 to 8, characterised in that each container has a supporting body defining the sliding face (8) and mounting part (9), the receiving pan part (7) being pivotally connected to the supporting body to permit pivoting of the pan part at a discharge point to discharge a carried object (2).

10. Apparatus according to any of claims & to 8, characterised in that each mounting member (13) is pivotally connected to the conveyor means (10) to permit pivoting of both the mounting member (13) and its associated container (6) at a discharge point to discharge a carried object.

11. Apparatus according to any of claims 6 to 10, characterised in that the co-operating means between a container and its mounting member comprises a pushing member (16 or 41) provided on the mounting member and a thrust-receiving face (15) on the container engaged by the pushing member, one of the pushing member and thrust-receiving face having an abutment portion which extends generally vertically transverse to the line of advancement of the conveyor means and the other of the pushing member and thrust-receiving face defining a curved surface engaged tangentially with said abutment portion.

12. Apparatus according to claim 11, further characterised in that said other of the pushing member and thrust-receiving-face comprises a freely rotatable roller (41) the axis of which is substantially horizontal and the periphery of which engages the generally vertically extending -abutment portion (15).

13. Apparatus according to claim 12, characterised in that the container (6) has a supporting body in which there are provided two transverse apertures (41), the mounting member having a pair of shafts (13 or 48) extending one through each aperture respectively, the freely rotatable roller being mounted on one of the shafts and the apertures being so dimensioned as to permit the container (6) freedom of movement upwardly, downwardly and to either side when the container is lifted by its slide face vertically off the shafts.