JP3183233B2 - Article length detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the length of an article in the direction of conveyance while conveying the article by a conveyor such as a belt conveyor.

[0002]

2. Description of the Related Art As a method for detecting the length of an article conveyed by a conveying device in the conveying direction, Japanese Patent Application Laid-Open No. HEI 5-229532 discloses a method.
As shown in the figure, the front and rear ends of the conveyed article are detected by the optical sensor, and the time difference between the detection of the front end of the article and the detection of the rear end of the article and the conveyance speed of the conveyance device and the conveyance speed of the conveyance device. The length in the transport direction is detected.

[0003]

However, according to the above-mentioned method, if the posture of the article is inclined with respect to the transport direction, accurate detection cannot be performed, and the rear end after detecting the front end of the article. The output of the sensor must be checked until the part is detected, it takes a long time to detect, the article must be transported at least for the length of the article for detection, If the front end of the article is brought into contact with the rear surface of a stopper (protruding part) formed on the moving belt, it is difficult to detect the front end of the article.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and requires a shorter conveyance distance and time for detection than in the past, and an article length detection apparatus capable of accurate measurement. The aim is to provide a method.

[0005]

In order to solve the above-mentioned problems, the technical measures taken by the present invention are as follows. Articles are conveyed by moving a front end of an article to a rear end face of a protrusion formed on a surface of an endlessly rotating belt. It is performed in a state where the surfaces are in contact with each other, and the rear end of the article conveyed by the rotation of the endless belt is detected by a sensor, and the length of the article is determined from the detection result of this sensor and the position of the protrusion. It is characterized by detecting. That is, as shown in FIG. 13, a protruding portion T is provided on the surface of the belt conveyor B to abut and support the front end of the article H, and for example, the optical sensor S The light emitter S1 and the light receiver S2 are arranged to face each other, and the conveyor B is run with the front end face of the article H in contact with the rear surface of the protrusion T, and the article H is moved with respect to the position of the light beam K of the optical sensor S. The distance L "between the rear ends of the articles H by the output of the optical sensor S from the point in time when the projecting portion T abutted and supported has relatively passed the predetermined distance L '.
Is measured. That is, the output of the optical sensor S is checked until the output changes from "ON" (the state in which the light ray K is not received by the light receiver S2) to "OFF" (the state in which the light ray K is received by the light receiver S2). Is measured, and the length L of the article H in the transport direction is detected from the distance L ′ and the distance L ″. Note that the distance L ″ from the time when the projecting portion T supporting the article H to the position of the light beam K of the optical sensor S has passed the distance L ′ to the rear end of the article H is measured. The distance L 'is at least smaller than the minimum length LMIN of articles conveyed by the conveyor B.

The optical sensor S may be fixed at a predetermined position on the side of the belt conveyor, or the optical sensor S may be moved by a motor or the like in a direction opposite to the article conveying direction.
In the latter case, the time required for the measurement can be reduced, and when the belt conveyor is a transport conveyor provided on the article loading side of the packaging device, the length of the packaging device can be reduced.

The method of calculating the distance L ″ is to use a stepping motor as a driving source of the conveyor and measure the length of the article by the number of driving pulses, or to measure the length of the optical sensor across the conveyance path of the conveyor. The light emitter and the light receiver are arranged to face each other, and the time from when the projecting portion of the conveyor supporting the article a predetermined distance L 'passes through the light beam of the optical sensor to when the rear end of the article is detected is determined. Any method may be used, such as a method of measuring and calculating the length of an article from the time and the conveyor speed.

According to the above-described means, the article is passed through the detection position by the sensor in a state where the front end of the article is in contact with the rear end face of the protrusion formed on the surface of the endlessly rotating belt. A predetermined distance L 'from the detection position is detected by a sensor, and the rear end of the article is detected to measure the distance L "from the detection start point to the rear end of the article. "And the distance L 'to the protruding portion passing through the detection position of the sensor, the length L of the article in the transport direction can be measured. The distance L 'is known in advance because it is a distance based on the positional relationship between the sensor and the protruding portion. Therefore, the length L of the article in the transport direction is determined by detecting the rear end and measuring the distance L "of the rear half. Therefore, it is possible to measure the length of the moving article without detecting the front end of the article.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 schematically show a packaging apparatus for packaging articles using a stretch film. A belt conveyor 1 for transporting an article a to an elevator head 2 provided inside the machine frame A is provided on the front side of the machine frame A. A packaging part b is provided above the elevator head 2, and further, on the upstream side of the packaging part b in the direction of transporting a film described later (the lower side in FIG. 2 in a direction perpendicular to the belt conveyor). A film holding portion (not shown) for holding a leading end of a film fed from a film roll set in a provided film roll disposing portion (not shown), and a predetermined portion sandwiching the leading end of the film held by the film holding portion. Conveying means 3 for pulling out the length, stretching on the packaging part b, and pre-stretching are arranged to face each other with the packaging part b interposed therebetween. left and right folding plates 5 and 5 'for folding the end of the film 4 covering the upper surface of the product a to the bottom side of the product a, the rear folding plate 6, and a discharge pusher which is located above the rear folding plate 6 and carries out the packaged product. 7 are arranged. Note that the front folding is performed in the process of discharging by the discharge pusher 7.

Further, a position correcting device 8 which corrects the position in the direction orthogonal to the conveying direction of the article and detects the width of the article a is provided on the near side (upstream side) of the belt conveyor 1 of the packaging apparatus. A roller conveyor 9 and a conveying device B having an accumulation conveyor (not shown) arranged upstream thereof are connected to each other, whereby the articles a are centered, and a predetermined interval is provided on the belt conveyor 1 of the packaging apparatus. They are supplied one by one.

The belt conveyor 1 is constituted by arranging a plurality of (four in the drawing) belt-shaped belts in parallel at a predetermined interval in a direction orthogonal to the article conveying direction. A plurality of protrusions 10 are provided at equal intervals on the outer surface of the belt of the belt conveyor 1 and are inserted between the comb-shaped elevator heads 2 divided into a plurality of pieces. (10a in the drawing
, 10b, 10c, and 10d). At the preceding stage of the belt conveyor 1, a second belt conveyor 11 for placing the articles a sent from the above-described conveying device B on the conveyor 1 is arranged in parallel with the unloading side thereof overlapping the loading side of the belt conveyor 1. ing. A roller conveyor 11a for transfer is disposed between the transport device B and the second belt conveyor 11. The belt conveyor 1, the second belt conveyor 11, and the roller conveyor 11a are configured to be driven by a belt conveyor driving motor 12 and a second belt conveyor driving motor 13, respectively.
And the conveying speed of the roller conveyor 11a is made faster than the conveying speed of the belt conveyor 1, whereby the articles a sent from the conveying device B are transferred onto the belt conveyor 1, and the speed difference between the belt conveyor 1 and the second belt conveyor 11 is increased. As a result, the front end of the article a comes into contact with the rear part of the protruding portion 10 during conveyance. The conveying surface of the belt conveyor 1 that conveys the articles a onto the elevator head 2 is located slightly above the elevator head surface before ascending, and the conveying surface of the second belt conveyor 11 is higher than the conveying surface of the belt conveyor 1. It is located slightly above. At a substantially middle side of a section where the belt conveyor 1 and the second belt conveyor 11 overlap, a depth dimension detection sensor 14 for detecting the length (depth dimension) of the article a conveyed by driving the belt conveyor 1 is provided. The light emitting device 14a and the light receiving device 14b are arranged to face each other across the transport path. A height detection sensor (not shown) for detecting the height of the article a is disposed on the side of the entrance of the machine frame A.

Further, the article a of the belt conveyor 1 described above
Is carried on the elevator head 2 and the belt travel path other than the forward movement path until it is mounted on the elevator head 2, that is, a reference for detecting the protruding portion 10 standing and fixed on the belt surface at a predetermined position on the return path. A position detection sensor 15 is provided. When the reference position detection sensor 15 detects the front end of the protrusion 10d, the position of the rear end of the protrusion 10a is defined as the reference point Ro on the elevator head 2, and the position of the rear end of the protrusion 10b is defined as the depth. This is the reference point Qo of the dimension detector. (See FIG. 5) The depth dimension detection sensor 14 is disposed at a distance L1 upstream from the reference point Qo. Also, the conveyor driving motor 12 and the second conveyor driving motor 13 for driving the belt conveyor 1 are controlled to be turned on / off at the same time and to operate for the same period. However, the belt conveyor 1 is driven at 300 mm / sec, and the second belt conveyor 11 is driven.
Is driven at 450 mm / sec in the first half and 600 mm / sec in the second half. The belt surface of the second belt conveyor 11 is made of a net-like cloth so as to be easy to slide on the article a. Thus, after the article a is brought into contact with the projecting portion 10 of the belt conveyor 1, the second belt conveyor 11 rubs the bottom surface of the article a in a section where the article a overlaps with the belt conveyor 1. Can be reduced.

FIG. 3 is an electrical configuration diagram of the above-described packaging apparatus. Control of various operations in the packaging apparatus is performed by microcomputer control. In the figure, reference numeral 16 denotes a CPU (central processing unit) composed of a microcomputer.
The ROM 18, the RAM 19, the operation unit 20, the display unit 21, and the I / O port 22 are connected via the bus 17. The ROM 18 stores control programs executed by the CPU 16 and various tables described later.
Various data preset for each article are stored in the RAM 19, and the data is temporarily stored when the CPU 16 executes the program in the ROM 18. The operation unit 20 is for inputting various commands and data, and the display unit 21 is for inputting commands and data input from the operation unit 20,
Alternatively, in addition to displaying the data stored in the RAM 19 or the operation status of the apparatus, various operations and error messages are displayed in characters and graphics. The I / O boat 22 conceptually shows the entire packaging mechanism section controlled by the CPU 16, and the parts directly related to the present invention include an elevator motor drive circuit 23, a conveyor motor drive circuit 24, a second conveyor It includes a motor drive circuit 25, a reference position detection sensor 15, a depth dimension detection sensor 14, and the like. The control of the entire packaging apparatus is performed based on the count value of the timing pulse generated by the rotary encoder in synchronization with the rotation of the elevator motor. Note that a stepping motor is used for the belt conveyor driving motor 12 and the second belt conveyor driving motor 13, and the transfer distance can be accurately known by counting the number of driving pulses.

The depth dimension detection sensor 14 (S2) is a sensor for detecting the length dimension of the article a to be supplied to the elevator 2 in the transport direction, and is composed of a light emitter and a light receiver. When the article a blocks light from the light emitter, ON ", and" OFF "when the light of the projector is received by the light receiver. Then, the depth dimension of the article a is measured based on the depth dimension detection sensor 14, and based on the depth dimension L (size) of the article a, the carry-in position of the article a on the elevator head, that is, the stop position data “X” is determined, and the stop position of the belt conveyor 1 is controlled based on the data. The details of the process of measuring the depth dimension of the article a and the process of determining the stop position data “X” will be described later.

The reference position detecting sensor 15 (S1) is a sensor comprising a light emitter and a light receiver. When the light from the light emitter is received by the light receiver, that is, when the protrusion 10 is not detected, the output of the sensor is "1". "OFF", when the light of the projector is blocked by the protruding portion 10 and the protruding portion 10 is detected, the output of the sensor is turned "ON", and the detection signal is sent to the CPU 16
Is output to As described above, when the front end of the protrusion 10d attached to the belt conveyor 1 is detected by the reference position detection sensor 15 (Po in the drawing), as shown in FIG. One (10a) is at the reference point Ro on the elevator head 2, and the other protrusion 10 (10b) is at the reference point Qo, that is, the article a conveyed by the second belt conveyor 11 is behind the protrusion 10. Each of them is located at a position in contact with the end face and passing through the depth dimension detection sensor 14 by the distance L1, and after detecting the reference position, the depth dimension L of the immediately preceding article a carried into the elevator head 2 is determined. The belt conveyor 1 is stopped by moving by the stop position data “X” determined based on the above.

Next, the depth measurement processing and the stop position data determination processing of the article in the above-mentioned apparatus will be described with reference to the flowcharts of FIGS. Note that the figure is a flowchart for explanation, and is different from the actual control of the CPU 16. (Start): A description will be given of the case where the packaging apparatus is performing a continuous operation. Immediately before the packaging apparatus starts the next packaging cycle (the packaging operation), the articles a are located at the positions shown in FIG. I have. That is, one on the elevator head 2 (article a1), one on the depth dimension detecting section where the belt conveyor 1 and the second belt conveyor 11 overlap (article a2), and one on the transport device B. (Article a3). As shown in FIG. 7, the projecting portion 10 of the belt conveyor 1 is located at a position where the later-described stop position data X has passed from the reference points Po, Qo, Ro in relation to the positioning of the article a1. The front ends of the a1 and a2 abut on the rear ends of the protruding portions, and the positions thereof are accurately regulated by the protruding portions 10. When the next packaging cycle starts in this state, the following processing is executed. (Step 1) ... The shutter of the conveying device B is lowered to start the insertion of the article a3, and the belt conveyor 1
, And the drive motor 13 of the second belt conveyor 11 is driven to start the belt conveyor 1, the second belt conveyor 11, and the roller conveyor 11a. As a result, the article a2 is started to be loaded onto the elevator head 2 with its front end regulated by the protruding portion 10 of the belt conveyor 1. When the article a1 rises above the elevator head 2, the operation of lifting the article a1 onto the film 4 is started. (Step 2) ... The depth L of the article a2 is measured.
(Details will be described later) (Step 3)... Stop position data X of the article a2 on the elevator head 2 (distance from the reference position Ro on the elevator head) based on the depth dimension L of the article a2 detected in Step 2 above. X) is determined. (Details will be described later.) (Step 4)... It is determined whether or not the article a2 has been transported to the stop position data X determined in Step 3 above.
(The details will be described later.) (Step 5): The judgment result of Step 4 is “YES”,
That is, when it is determined that the article a2 has been transported to the stop position data X, the rotation of the drive motor 12 of the belt conveyor 1 and the drive motor 13 of the second belt conveyor 11 are stopped, and the belt conveyor 1, the second belt conveyor 11, and The roller conveyor 11a is stopped. Thereby, the article a
2 is accurately positioned on the elevator head 2 at a predetermined position corresponding to the depth dimension L of the article a2, that is, a position that has passed a distance X from the reference point Ro on the elevator head 2. It should be noted that the article a3 conveyed from the conveying device B during steps 2, 3, 4, and 5 is the belt conveyor 1 described above.
When the front end of the protruding portion 10 is brought into contact with the rear end of the protruding portion 10 during conveyance due to a speed difference between the belt conveyor 1 and the second belt conveyor 11, and the conveyance by the belt conveyor 1 is stopped in step 5 described above, FIG. It is located at the position of the article a2 indicated by 7, that is, the position which has passed the distance X from the reference point Qo of the depth detecting unit. Then, when the next packaging cycle is started, the above processing is repeated.

Next, the details of step 2 (depth dimension L measurement processing) and step 3 (stop position data X determination processing) will be described with reference to FIG. Note that the depth dimension L measurement processing of the present embodiment measures only the rear dimension L ″ of the article a in order to shorten the time for detection and to shorten the transport distance of the article for detection. Is added to the measurement result and the front dimension L ′ determined in advance is added to the depth dimension L (= L ′).
+ L ″) is detected.
Is measured when the rear end of the article is detected so that the depth L can be accurately measured even when the product is stored in a bent tray having a slit formed in the lateral direction. Instead, the measurement is performed continuously for at least the maximum depth dimension LMAX that can be wrapped by the wrapping device, and the rear end data immediately before the end of the measurement is the rear end of the article. As a result, the processing in step 2 is more complicated than the normal depth dimension measurement processing. (Step 11)... Initial setting (data initialization) is performed. (a) The counter C for counting the number of drive pulses of the drive motor (stepping motor) 12 of the belt conveyor 1 is reset (C = O). (b) Reset the measurement result data L2 (L2 = 0).
The measurement result data L2 is the dimension on the rear side of the article as shown in Fig. 7 (corresponding to the above L "). (C) Reset the measurement distance data l (movement amount) (l =
0). (d) The measurement completion data lMAX is determined by the following equation. lMAX = (LMAX + Y)-(L1 + X) where LMAX is a constant which is the maximum depth dimension that can be packed by this packing apparatus. Y is a constant with a margin. L1 is a constant between the rear end of the belt conveyor 1 and the depth detection sensor 14 when the protrusion 10 is at the reference position (see FIG. 6). X is
The stop position data of the article a1 immediately before the article a2 whose depth dimension is to be measured is a variable, and has already been found in the processing of the above-described step 3 executed in the immediately preceding packaging cycle. In addition,
(L1 + X) corresponds to the dimension L 'on the front side of the article. (Step 12) The drive motor (stepping motor) 12 of the belt conveyor 1 is driven by one step. (Step 13) Count the number of driving steps (C
= C + 1). (Step 14)... Measured distance data (movement amount) 1 is calculated by the following equation. 1 = K * C Here, K is a proportional constant (step 15)... It is determined whether or not the measured distance data (movement amount) 1 has become the measurement completion data lMAX. If the result of this determination is "YES", the flow proceeds to step 18 where "N
If "O", the process jumps to step 16. (Step 16) ... The output of the depth detection sensor 14 is "O
It is determined whether the status has changed from "N" to "OFF". In the illustrated example, the state in which the light from the projector in the depth detection sensor 14 is received by the light receiver is “OFF”, and the state in which the light is not received is “ON”. (Accordingly, when the rear end of the article or the front end of the slit passes the detection sensor 14, the output of the sensor 14 changes from "ON" to "OFF".) When the result of this determination is "YES" The process jumps to step 17 if NO, and to step 12 if NO. (Step 17) ... The measurement result data L2 is calculated by the following equation. L2 = K * (C-1) Note that the dimension L2 detected here is the dimension on the rear side of the article (corresponding to L ") or the length from the detection sensor 14 to the slit of the article. Step 18) Calculate the depth dimension L of the article a by the following formula: L = (L1 + X) + L2 (Step 19) ... The article a calculated in the step 18
The stop position data X (distance X from the reference point Ro on the elevator head 2) of the article a on the elevator head 2 of the belt conveyor 1 is determined based on the depth dimension L of. This determination is performed using a conversion table that determines the stop position X from the depth dimension L stored in the ROM (or RAM).

Next, the stop control process of the belt conveyor 1 which conveys the article "a" for which the measurement of the depth dimension L and the determination of the stop position data X (the reference position R on the elevator head) on the elevator head 2 have been completed (the above steps) Details of step 4, step 5) will be described with reference to FIG. (Step 21) Initial setting (whether the data is initial) is performed. (a) The counter S for counting the number of pulses of the drive motor 12 of the belt conveyor 1 is reset (S = 0). (b) Reset the distance data (movement amount) x (x =
0). (Step 22) The drive motor (stepping motor) 12 of the belt conveyor 1 is driven by one step. (Step 23): It is determined whether the output of the reference position detection sensor 15 has changed from “OFF” to “ON”. In the illustrated example, the state in which the light from the projector in the reference position detection sensor 15 is received by the light receiver is “OFF”, and the state in which the light is not received is “ON”. (Accordingly, when the front end of the protruding portion 10 of the belt conveyor 1 has passed the detection sensor 15, the output of the sensor 14 changes from "OFF" to "ON".) When this determination result is "YES", Jumps to step 24, and if "NO", jumps to step 22. If the result of the determination in step 23 is "YES", as shown in FIG. 5, the other projecting portions 10 of the belt conveyor 1 are connected to the reference point Ro on the elevator head and the depth detection Are located at the reference point Qo and the vertical path of the belt conveyor 1. (Step 24)... It is determined whether or not the measured distance data (movement amount) x is the stop position data determined in step 19. If the result of this determination is "YES", the belt conveyor 1 is stopped and the process is terminated, and if "NO", the process jumps to step S25. (Step 25) The drive motor (stepping motor) 12 of the belt conveyor 1 is driven by one step. (Step 26): Count the number of driving steps (S
= S + 1). (Step 27) ... Distance data (movement amount) x is calculated by the following equation, and thereafter, the process returns to Step 24 to repeat the above processing. x = K * S Here, K is a proportional constant. By the above processing, the article a is accurately positioned and stopped at a position where a distance X has elapsed from the reference point Ro on the elevator head as shown in FIG. In this case, the article a is not positioned by colliding with the stopper as in the conventional packaging apparatus, but only by stopping the belt conveyor 1 that has been conveyed with its front end abutting on the rear end face of the protruding portion 10. Therefore, there is no possibility that the stop position or the stop posture is disturbed by an impact (rebound) when the stopper collides with the stopper, the articles are damaged, or the arrangement of the articles stored in the tray is disturbed.

In the above embodiment, in order to carry a conveyed article onto the elevator head in the packaging machine, the carry-in position on the elevator head is changed based on the size of the article.
Since the conveyor is stopped based on the data of the stop position, the conveyor moves further by the distance X from the reference position detection, and the positional relationship between the depth detection sensor and the protruding portion moves by the distance X each time toward the elevator. That is, the distance L '
Is not a constant but a variable, but the distance between the sensor and the protrusion is known in advance, and the total length can be measured by detecting the dimension from the detection position of the sensor to the rear end of the article. Absent. In the above-described embodiment, the front end of the article is brought into contact with the rear portion of the projecting portion of the belt conveyor by changing the transport speed of the belt conveyor and the second belt conveyor, but the present invention is not limited to this. For example, only the second belt conveyor may be driven to make contact.

[0020]

According to the article length detecting method of the present invention, since it is not necessary to detect the front end of the conveyed article, the front end of the article is brought into contact with the rear of the projecting portion formed on the belt. The length of the article can be accurately detected even in a form in which the article is held. In addition, since the sensor only needs to measure the distance L ″ in the latter half of the conveyed article, the measurement time may be short, and the distance conveyed for measurement may be shorter than the entire length of the article, and the length of the entire conveying apparatus may be shorter. In addition, since the article is conveyed while the front end of the article is in contact with the rear part of the protruding part formed on the belt, the article is conveyed by controlling the stop of the belt. Since the position of the carry-in position can be accurately and accurately determined, it is suitable as a length detecting device arranged at the carry-in end of the packaging device.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a packaging device according to an embodiment of the present invention.

FIG. 2 is a cutaway plan view of the same part.

FIG. 3 is an electrical configuration diagram of the packaging device.

FIG. 4 is an explanatory diagram illustrating a state in which length detection of an article is completed and the article is carried into an elevator.

FIG. 5 is an explanatory diagram showing a state in which a protrusion of the belt conveyor is detected by a reference position detection sensor.

FIG. 6 is an enlarged explanatory view showing a positional relationship between a depth dimension detection sensor and a protruding portion that abuts and supports an article in the state of FIG. 5;

FIG. 7 is an explanatory diagram of a state in which the robot has moved from the reference position by the distance of the stop position data X determined based on the size of the article measured by the depth detection sensor and stopped.

FIG. 8 is an explanatory view showing a state in which after the belt conveyor stops, the elevator is lifted up to push up an article on the stretched film.

FIG. 9 is an explanatory diagram showing a state in which the belt conveyor is driven to measure the length L ″ of the rear half of the article after the elevator descends.

FIG. 10 is a flowchart showing an outline of processing.

FIG. 11 is a flowchart illustrating a depth measurement process and a stop position determination process of an article.

FIG. 12 is a flowchart illustrating stop control processing of a belt conveyor that conveys articles.

13A and 13B are explanatory views showing the principle of the article length detecting method according to the present invention, wherein FIG. 13A is a plan view and FIG. 13B is a side view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Belt conveyor 2 ... Elevator head 10 ... Projection part 11 ... 2nd belt conveyor 14 ... Depth dimension detection sensor 15 ... Reference position detection sensor a ... Article

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-152512 (JP, A) JP-A-4-339709 (JP, A) JP-A-5-229532 (JP, A) 23048 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 21/06 101 G11B 11/04 101 B65B 11/00-11/58 B65B 49/00-49/16 B65B 57 / 00-57/20

Claims (2)

(57) [Claims] An article is conveyed in a state where the front end face of the article is in contact with a rear end face of a protruding portion formed on a surface of an endlessly rotating belt, and is conveyed by the rotation of the endless belt. An article length detecting method comprising: detecting a rear end of an article by a sensor; and detecting a length of the article from a detection result of the sensor and a position of the protrusion. 2. Articles are conveyed with the front end face of the article abutting the rear end face of a protruding portion formed on the surface of the endlessly rotating belt, and conveyed by the rotation of the endless belt. The rear end of the article is detected by a sensor, and the distance L "from the output of the sensor to the rear end of the article from the point in time at which the protruding portion has passed a distance L 'relative to the position of the sensor.
, And the length of the article is detected from the distance L ′ and the distance L ″.