GB2174195A - An arrangement and a method for the measurement of the weights and/or dimensions and/or volumes of articles - Google Patents

Abstract

For the measurement of their dimensions and/or volumes and/or weights, objects are conveyed e.g. on a conveyor rollers (16), through a measuring frame (10) disposed above a weighing device (24) and having a plurality of emission sources (12) and a plurality of emission detectors (14) arranged in pairs in at least one principal direction. Each detector (14) is adapted each to emit a signal when exposed to emission from the respective source (12). A calculating device receives and compiles the signals from the detectors (14) and the device (24) and based on this information calculates the volume and/or the dimensions and/or the weight of the object. The emission sources (12), which may be infra-red emitters, are arranged to be switched on cyclically in sequence each for a certain time period, and the corresponding detector (14) with which it forms a pair, during the same time period, and only during the specific time period, is effective to detect emission from the source (12) and emit a corresponding signal, which signal is transferred to the calculating unit for the latter to perform its calculations.

Description

SPECIFICATION An arrangement and a method for the measurement of the weights and/or dimensions and/or volumes of articles This invention concerns an arrangement for the measurement of ths weights and/or dimensions and/or volumes of objects conveysd on a conveyor surfacs, comprising a measuring frame having a plurality of emission sources and a plurality of emission detectors, arranged in pairs in at least one principal direction, ths detectors being arranged for emitting a signal when expossd to or shielded from emission from one or more of the sources, such as a light source and/or ultrasonic sources, and a calculating device, which device compiles the signals from the detectors and/or the emission sources and based on this information calculates the volume and/or the dimensions and/or the weight of the object.

The invention also relates to a method of carrying out general measurement of the weights and/or dimensions and/or volumes of objects so conveyed and using such emission sources, detectors and calculating device.

Various arrangements are already known, for effecting volume measurement, incorporating light sources and detectors arranged in pairs in two directions, usually perpendicular to one another. The light beams between the light sources and the detectors form a grid at a measurement station. The volume measuring apparatus also includes some kind of trsnsport means, which progresses objects to be measured through the measurement station. When an object to be measured passes through the measurement station, some of the light beams are interrupted and the corresponding detectors cannot register any light. Consequential signals are transferred to a calculating unit which compiles the signals to a cross-sectional area of the object. A number of crosssectional areas of the object sre calculated in this way until the object has passed through the measuring station.Between each calculated cross-sectional area there is an interval, which may be a time interval or a movement interval. Knowing the speed at, or the distance through which, the object has travelled during the measurement, also the third dimension of the object is determinable and can be used by the calculating unit, which compiles all the information to give as a result of the volume and/or dimensions of the object.

However, this previously known apparatus has several drawbacks. The light sources have to be disposed at least at a minimum distance from each other for space reasons and the detectors cannot be spaced too close to each other, otherwise one or more of the detectors may receive light from a light source other than the corresponding light source(s). Thus, it is not possible to make as accurate a measurement of an object as would be liked.

An object of the present invention is so to improve and develop the previously known arrangement that more accurate measurement of objects can be achieved, with closer distances being possible between the measuring lines of the grid formed at the measurement station. A further object of the invention is to provide a method of operation such an arrangement, to obtain particularly accurate measurement of an object.

Pursuant hereto the present invention provides an arrangement for the measurement of the weights and/or dimensions and/or volumes of objects conveyed on a conveyor surface, comprising a measuring frame with a plurality of emission sources and a plurality of emission detectors, arranged in pairs in at least one principal direction, the detectors being arranged for emitting respective signals when exposed to or shielded from emission from a respective emission source, such as a light and/or an ultrasonic source, and a calculating device, which device compiles the signals from the detectors and/or the emission sources and based on this information calculates the volume and/or the dimensions and/or the weight of the object, said sources being arranged to be switched on cyclically in sequence for a certain time period, with the emission detector belonging to the same pair, during the same time period, and only during that specific time period, being able to detect emission from its source and emit a signal indicative thereof, which signal is transferred to the calculating unit.

The invention further provides a method of measuring the weights and/or dimensions and/or volumes of objects conveyed on a conveyor surface past a measuring frame having a plurality of emission sources and emission dstectors arranged in pairs in at least one principal direction, said detectors being adapted to emit signals, when exposed to or shielded from the respective emission source, such as a light source and/or an ultrasonic source, which signals are transferred to a calculating device which compiles the signals from the detectors and/or the emission sources and calculates the volume and/or the dimensions and/or the weight of the measured object, said sources being switched on cyclically in sequence for a certain time period, with the emission detector belonging to the same pair, during the same time period, and only during that specific time period, detecting emission from the respective source or absence thereof and emitting a signal indicative thereof, which signal is transferred to the calculating unit.

In carrying the invention into effect the arrangement includes a number of emission sources, which are switched on in sequence, preferably each for a very short psriod. The corresponding emission detectors are provided with a switch arrangement such that they can only transmit s signal, indicative of the fact that they are receiving an emission or are shielded therefrom, during the same period as the emission source belonging to the same pair is sending out its emission. This ensures that the emissions from the sources affect any detector other than the one with which the respective source forms a pair. As a result, it is possible to place the detectors very close to each other.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a side view of a first embodiment of the arrangement of the invention; Fig. 2 is a plan view of the arrangement of Fig. 1; Fig. 3 is an end view of the arrangement of Figs. 1 and 2, taken as indicated by the arrows 3-3 of Fig. 1; Fig. 4 is an enlarged section through a frame member of the measurement frame of the arrangement of Figs. 1 to 3, the section being taken on the line 4-4 of Fig. 1; Fig. 5 is an enlarged section through another frame member of the measurement frame of the arrangement of Figs. 1 to 3, the section being taken at 5-5 in Fig. 3; and Fig.

6 is a perspective view illustrating diagrammatically a second embodiment of the arrangement of the invention.

The embodiment shown in Figs. 1 to 5 of the drawings includes a measuring frame 10 having emission sources 12 and emission detectors 14 arrsnged over a transport device or conveyor 16, which in the illustrated case is a roller conveyor comprising rollers 18. The entire arrangement is mounted on a support frame 20 having legs 22. Substantislly centrally disposed beneath the measuring frame there is a weighing device 24 which is carried by the frame 20 and carries both the roller conveyor 16 and the measuring frame. With this arrangement, when an article (not shown) supplied from supply conveyor 26 arrives on the conveyor 16, the weighing device 24 will serve to monitor the weight of said article.

Frovided on frame 28 of the supply conveyor 26 is a housing 30 for control equipment as well as a calculating device or computer (not visible).

The measuring frame 10 comprises two side members 32, 34 and a top member 36 joined together in the form of an inverted U, as well as a bottom member 38, the details of which are shown in Fig. 5. The top member 36 is provided with a fan 40 having an inlet opening 42 provided with an air filter. In the same way the bottom member 38 is provided with a fan 44. The function of these fans 40, 44 will be explained later. In the frame members 32, 34, 36 and 38 there are the emission sources 12 and the detectors 14 which are arranged to face the inner sides of said frame members, at equal intervals. These emission sources and detectors 12, 14 are positioned as indicated by the dotted lines in Figs. 1 and 2, and each emission source 12 is in the form of an infra-red lamp.

Fig. 2 shows how infra-red beams produced by the sources 12 form a grid 46 in the measuring station or area which is defined by or surrounded by the frame 10.

Fig. 4 is a section through the frame member 34, it being understood that the frame member 32 will be a mirror image thereof, and that the frame member 36 will be of comparable construction. As shown, the frame member 34 comprises a supporting U-beam 48. In the interior of the U-section of this beam 48 there is an aluminium or pertinax or like plate 50 on which is mounted a mounting board or card 52, carrying the emission sources 12 and suxiliary components, by means of screws and distance pieces 54. The equipment on the mounting board 52 is connected to a flexible bus lead 56 and a connecting adapter 58.The bus lead 56 provides the equipment on the mounting card 52 with electric power and supplies a signal, which activates, at predetermined intervals, each emission source 12 on one card 52 as well as the corresponding detector 14, which forms the pair with said source 12, on another complementary mounting card mounted in an opposite position in the opposite frame member 32. In Fig. 4, the emission source 12 is shown as comprising a lightemitting diode mounted such that it protrudes into a respective Pole 60 in the plate 50 in alignment with a corresponding hole 62, in the U-beam 48.

When a signal activating any one of the specific emission sources 12 is received by such sources, a beam 64 of short duration is emitted through the respective hole 62. This beam 64 is detected by a respective emission detector 14, such as a photocell, arranged in a corresponding way in a respective hole in an aluminium plate and mounted on a corresponding mounting plate for the light detecting units. It will thus be understood that each emitter 12 in the member 34 has a corresponding detector 14 in the member 32 (these items 12 and 14 constituting a pair) and vice versa.

Suitable, the emission sources 12 end the detectors 14 each have substantially the same radial dimensions, such that they can each be mounted in the same size of hole. Typically, an emission source in the form of a light source and a corresponding light detector may each have a diameter of 3.2 mm end project by a few millimetres into the respective holes which are of substantially the same diameter or slightly bigger. The thickness of each aluminium plate may be about 15 mm, which gives a rigid construction and provides a narrow emission beam from each emission source which may, for instance, alternatively be ultrasonic sources. On each mounting card 52 there may also be printed circuits (not shown) and various auxiliary electronic components (also not shown in detail), such as amplifiers and signal designation units, which are known per se.This electronic equipment is only indicated schematically end has been allocated the common reference numeral 66. Preferably there are sixteen of the emission sources and/or sixteen detectors units mounted on each mounting card 52 which gives a favourable modular configuration for the measuring frame 10.

The necessary number of the cards 52 with their emission sources 12 snd/or detector units 14, are mounted along the U-beams 48 over substantially their full lengths and are connected to the bus lead 56 by the connecting adapters 58. The number of mounting cards 52 may be selected as desired, and is only restricted by the length they have to cover. If there are a great number of the emission sources, the arrangement may be such that emissions are made from two or more of the sources 12 at the same instant in the sequence, provided that there is a sufficient distance between these operative sources, such that there is no risk that an emission beam will be received by the wrong detector.

The open sides of the U-beams 48 of the frame members 32, 34 are covered by reapective cover plates 68 which protect the mounting cards 52 and the components mounted thereon. The U-beams 48 together with the cover plates 68 end end covers (not shown in detail), form enclosed spaces, and the fans 40 and 44 are provided to ventilate snd cool the heat-generating electrical components. The fan 40 connects with an enclosure formed by the top member 36 and side members 32, 34 and the fan 40 is connected to the enclosure within the bottom member 38.

The ventilation and cooling air, which is introduced by these fans 40, 44, escapes through the holes 60 and 62 alongside the emission sources 12 and detectors 14. The ventilation air thus will have the additional effect of preventing dust and dirt from entering the holes 60, 62 end obstructing the emission beams.

It will be observed that the plate 50 is mounted by one edge on one limb of an angle bracket 70 the other limb of which is fixed by a hinge 72 to a mounting block 74 secured by bolts 76 to one side wall of the U-beam 48. Adjacent its other edge, the plate 50 is formed with a hole which engages over a retainer stud 78 provided with a spacer sleeve 80 against which the plate 50 is held stationary by a wing nut 82. Furthermore, the cover plate 68 is connected by one edge to a corresponding side wall of the U-beam 48 by means of a respective hinge 84 and a captive bolt 86 through the plate 50, adjacent its opposite edge, engages into a threaded hole in the mounting block 74 to retain the cover plate 68 in its illustrated closed position.This form of construction, which is employed for the side frame members 32 and 34 as well as the top frame member 36, enables easy access to be had to the components within such members. After the respective cover plate 68 has been released by unscrewing its bolt 86, it can be swung to an open position whereupon the wing nut 82 can be removed from the stud 78 and the plate 50 and the components it carries can be swung to a position in which all of the components are outside the respective member and can be worked upon easily.

Turning now to Fig. 5 of the drawings. This figure illustrates some of the details of the construction of the bottom frame member 38.

In this figure, of course, the same reference numerals have been allocated to parts which are similar to those already described, but of course it is not very convenient to have a pivoted cover requiring an operative to climb underneath the support frame 20. In the frame member 38, therefore, the main structure of the member is provided by a U-beam 88 the sidewalls 90, 90 of which are each located relative to a respective angle member 92, 92 extending transversely of the conveyor 16 by telescopic slides 94, 94 each comprising a plurality of rails 96 each having tracks for balls 98 which enable these slides 94 to be extended so as to bring the U-beam 88 to a laterally-projecting position to one side of the conveyor 16.In this position, it is possible to swing upwards cover plate 100 which is connected to one side wall of the beam 88 by hinge 102 and normally occupies its illustrated closed position under the influence of gravity, and in which it is held by a screw 104 engaging into mounting block 106. The cover 100 having been swung up out of the way, access can be had to the interior of the U-beam 88 to swing up the plate 50 which is pivoted to the mounting block 106 by hinge 108 and engages under gravity with a locating peg 110 on which is a spacer 112.

As can be seen from Fig. 5, the fan 44 is mounted within a casing 114 bolted to the beam 88 by bolts 116, in register with opening 118 in the beam 88, and an air entry 122 to the casing 114 is masked by a filter 120.

Measuring sequences for the emission sources 12 and detectors 14 are started at regular intervals, which correspond to a certain time interval or certain distance of movement for objects (not shown) to be measured.

In the embodiment shown in figures 1 to 5, this can be favourable combined with the drive of the roller conveyor 16 as will be described shortly.

Objects to be measured are supplied to the apparatus by way of the supply conveyor 26 which has a plurality of rollers 121 of which the group, indicated at 123, adjacent to the conveyor 16 are arranged, when the conveyor 26 is being driven, to run at a somewhat faster speed than the rest of such rollers 121.

In register with this group 123 is a photoelectric detector 124 which serves, upon detecting arrival of an object to be measured, to stop the supply conveyor 26 to enable an operative to register an appropriate identification to the object, for instance by means of a datapen reader or laser scanner, which may be hand-held or mounted on the apparatus.

Upon identification being completed, and provided any preceding object or article has been measured at the measuring station and has passed on, the supply conveyor 26 is automatically switched on to cause the identified object to be fed onto the conveyor 16, the faster speed of the roller group 123 ensuring that it is separated from any following objects or articles, the conveyor 26 being stopped again when the next object reaches the photoelectric detector 124.

The roller conveyor 16 is suitable driven from a motor (not shown) through a reduction gearing connected to a chain drive (also not shown) for all of the rollers 18. With the aid of an angle sensor (not shown) signals may be supplied to the calculator or computer indicative of the rotation of the rollers 18 and, thus, of the distance of movement of an object being measured. This signal is calculated by way of suitable leads (not shown) to a logic unit or a microprocessor of the control unit which, of course, is connected to the emission sources 12 and detectors 14 by way of the bus leads 58. A signal from the angle sensor starts a measuring sequence through all the horizontal and vertical pairs of emission sources 12 and detectors 14 in turn and signals are received by the processor indicating if the emission beams are obscured by an object or not.These signals may be stored in the logic unit or microprocessor or are immediately transferred to the computer within the housing 30, which calculates the volume and/or the shape of the object.

A measuring sequence through the side members 32 and 34 may start from the top and progress downwards until one of the detectors 14 does not receive an emission, or the momentary emission form the successive sources may progress ail the way down each of the side members 32, 34 for each sequence. The latter procedure is necessary for the measurement of irregular objects. In the same way, a measuring sequence is performed in the vertical direction from one side to the other. For simple calculations, only the number of emission beam absences (and thus the horizontal extent of an object) is registered and stored in the logic unit, and when the object has passed, the maximum measurement is transferred to the computer for further calculation.

Furthermore, for accurate measurement requirements, not only the horizontal extent of the object but also the distance from the side frames 32, 34 is record ed, i.e. the position of the object. This information is stored by the logic unit or microprocessor or is transferred to the calculating unit which then can calculate the shape and volume of the object.

The first method can be used for example for measuring the dimensions of a parcel, which is progressed through the measuring station with one side approximately parallel to the direction of movement, and the other method can be used for example for calculating the size and volume of a parcel, which is moved through the unit in any direction, or for the measurement of an irregular object. It will be understood that the weighing device 24 transmits a signal indicative of the weight of the object, e.g. to the calculating device.

Suitable the interval (e.g. the distance moved by the object) between the measuring sequences is about one centimetre. With a preferred speed of movement of the article of 16 cm/sec this gives a measuring sequence cycle time of 16 Hz.

Fig. 5 shows a second embodiment of the arrangement of the invention, very schematically, and again similar reference numerals have been allocated to parts which are similar to those already described. For the sake of clarity, the rollers of the roller conveyor 16 are not shown, and its frame 10 is only represented very diagrammatically. In this embodiment the measuring frame 10 is further provided with horizontal frame members 126, 128 in addition to the side members 32, 34 top member 36 and bottom member 38.

Holes for the emission sources 12 and detectors 14 are indicated inside the frame members 32 and 126. In the figure, the weighing area 24 is also visible.

The measurement of an object passing through this unit is somewhat different from the first embodiment, since the third dimension of the object is also measured. Furthermore, in this embodiment it is not necessary to know the speed of the conveyor 16, which will be explained in the following.

Measuring sequences are repeated by the emission sources 12 and corresponding detectors 14 at regular time intervals. When an object enters the measuring zone of the horizontal frame members 126, 128 it will progressively shut off the emission beams as it moves through the measuring station. From this, the speed of the object is detected and calculated by the logic unit or microprocessor or the calculating unit connected thereto. For an object shorter than the measuring length of the frame members 126, 128 the length is directly given by the number of obstructed emission beams. Longer objects are measured by calculating the time during which all the emission beams are covered together with the speed of the object, which is achieved as described above.In the same way the length of the object is calculated when a part of the object is elevated over the measuring level for the horizontal frame members 126, 128. The elevated part of the object firstly breaks the horizontal and vertical emission beams of the vertical measuring area and later the beams of the horizontal measuring area. The time lapse when only the emission beams in the vertical measuring area are obstructed gives the length of the elevated portion of an object. As a check, the speed at which the beams become unobstructed again can also be measured and compared with the speed at which they have been obstructed.

A special feature of the arrangement of the invention is that only one lead in the bus lead 58 is required to trsnsfer signals indicating that emission is passing (i.e. is unobstructed) for an entire group of detectors 14 operating in the same sequence group. Suitably the sequencing is arranged such that a sequence starts at the same time for a horizontal and a vertical row of the detectors 14 at the same time. If there are any measurements along the length of the conveyor 16, these preferably constitute a third sequence group. If the measuring area is very big, or the distance between the measuring lines is very short, it will be necessary to arrange the emission sources 12 and the detectors 14 in more sequence groups in order to be able to complete an entire measuring sequence before it is time to start a new sequence.

For space reasons, it is hardly possible to have a closer distance between adjacent emission sources and detectors than about one centimetre. In order to achieve a closer measuring accuracy, in the arrangement of the invention there may be additional rows of emission sources and detectors off-set sideways and in the measuring direction from the first row of sources and detectors. The distance by which the second or further rows are offset sideways suitably should correspond to an even multiple of the distance which the measured object travels between two consecutive measuring cycles. The distance by which the emission sources and detectors are off-set in the measuring direction preferably is such that the equidistance between all of the measuring points would be the same.For increased accuracy the holes 62 should then be narrow slits in the measuring direction, for instance one millimetre wide.

The sequencing of the emission sources and detectors is suitable provided with the aid of a high-frequency AC current source. Ths AC current suitably has a square wave form and the frequency may be, for instance, 3000 Hz.

Each cycle or period of the AC current activates a new emission source and corresponding detector, which are operative only during the duration of a half cycle or period. In this way, a very long sequence of measuring points can be covered during a short time period. If this is not enough for the measurement requirements, more measuring circuits with the same frequency can be employed, or the frequency can be further increased.

In the preferred arrangement according to the invention, the mounting cards with the emission sources and the mounting cards with the detector units can be exchanged with one another, becuase they are both activated by the same starting impulses. This offers the possibility of arranging emission source cards and emission detector cards so as to alternate along the length of each frame member. This can result in more even heat development in the frame members, since the heat developed by the cards containing the emission sources and the cards containing the detectors will normally be different.

In carrying the invention into effect it is of course possible to carry out the measurements in more than two directions by providing more than one measuring frame on the apparatus or to provide a further off-set system of emission sources and detectors, with the emission beams extending at an oblique angle to the frame. The number of such oblique measuring directions can, of course, be adapted to the needs of the specific measuring task which is to be performed in the measuring apparatus. In this way, also, the volumes and shapes of irregular objects can be measured. However, in the majority of cases, objects to be measured will be rectangular and in many other cases it is the maximum dimensions which are important.

For the purpose of the invention, the characteristics of the emissions from the emission sources are arbitrary and may be visible light or may be invisible or ultrasonic. In the case where the emission is light, it may be monochromatic or not. For economic reasons, a low cost and low power-consuming light source is preferred, such as a light-emitting diode.

The invention is not limited to the embodiments shown in the drawings and described in the foregoing specification, but can be varied within the scope of the following

Claims (16)

claims. CLAIMS

1. An arrangement for the measurement of the weights and/or dimensions and/or volumes of objects conveyed on a conveyor surface, comprising a measuring frame having a plurality of emission sources and emission detectors, arranged in pairs in at least one principle direction, the detectors being adapted to emit respective signals when exposed to or shielded from emission from the respective emission source, such as a light source and/or an ultrasonic source and a calculating device, which device compiles the signals from the detectors and/or the emission sources and based on this information calculates the volume and/or the dimensions and/or the weight of the object, said sources being arranged to be switched on cyclically in sequence for a certain time period, with the emission detector belonging to the same pair, during the same time period, and only during that specific time period, being able to detect emission from its source and emit a signal indicative thereof, which signal is transferred to the calculating unit.

2. An arrangement as claimed in claim 1, in which the measuring sequences are started at regular time intervals.

3. An arrangement as claimed in claim 1 in which the measuring sequences are started at regular intervals for the conveyed distance of the object.

4. An arrangement as claimed in claim 1, 2 or 3 in which the output signals from a plurality of the emission detectors are transmitted through the same lead to a micro-processor or logic unit.

5. An arrangement as claimed in any preceding claim, in which the emission sources and the emission detectors are arranged in Ubeams having therein holes for the passage of emission beams, the U-beams constituting members of the measuring frame.

6. An arrangement as claimed in claim 5, characterised in that each U-beam is covered at its open side by a cover plate and at its ends to form an enclosed space, and that fans are provided to supply clean air to said enclosed spaces, air exits from said enclosed spaces being through the holes.

7. An arrangement as claimed in claim 6 wherein each cover plate is pivotally mounted so that it can be swung to a position permitting access to the interior of the U-beam.

8. An arrangement as claimed in claim 5, 6 or 7 wherein the emission sources and the detectors are mounted on mounting cards within the U-beams.

9. An arrangement as claimed in claim 8 wherein each mounting card is exchangeable.

10. An arrangement as claimed in claim 8 or 9 wherein the mounting csrds in each Ubeam are mounted upon sn aluminium, pertinax or like plate which can be swung out of the U-beam.

11. An arrangement as claimed in any of claims 5 to 10 wherein the frame includes a bottom member extending transversely of the conveyor surface, beneath the latter, this bottom member comprising a respective said Ubeam which is mounted to be brought to an extended position projecting laterally relative to the conveyor to permit access to the interior of the U-beam.

12. An arrangement as claimed in any preceding claim wherein the conveyor is adapted to be supplied, with successive objects to be measured, from a supply conveyor comprising rollers of which a group is adapted to be driven faster than the rest, so as to separate the object being supplied to the conveyor from following objects.

13. An arrangement as claimed in claim 12 wherein the supply conveyor has a photoelectric detector which arrests the rollers of said conveyor upon arrival of an object to be measured, to permit identification thereof.

14. A method of measuring the weights and/or dimensions and/or volumes of objects conveyed on a conveyor surface past a measuring frame having a plurality of emission sources and emission detectors arranged in pairs in at least one principal direction, said detectors being adapted to emit signals, when exposed to or shielded from the respective emission source, such as a light source and/or an ultrasonic source, which signals are transferred to a calculating device which compiles the signals from the detectors and/or the emission sources and calculates the volume and/or the dimensions and/or the weight of the measured object, said sources being switched on cyclically in sequence for a certain time period with the emission detector belonging to the same pair, during the same tims period, and only during that specific time period, detecting emission from the respective source or absence thereof and emitting a signal indicative thereof, which signal is transferred to the calculating unit.

15. An arrangement for measuring the dimensions and/or volumes and/or weights of objects substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 4 or in Fig. 5 of the accompanying drawings.

16. A method of measuring the dimensions and/or volumes and/or weights of objects substantially as hereinbefore described with reference to the accompanying drawings.