GB2204128A - Neck-in can automatic discriminator - Google Patents

Description

Title :- NECK-IN CAN AUTOMATIC DISCRIMINATOR The present invention relates to a neck-in can automatic discriminator for detecting whether or not a crease exists in the neck of a neck-in can (a can whose mouth and the circumference near to the mouth are squeezed inside to form a neck), or whether : he crease exceeds a predetermined allowable crease. Thus during production of neck-in cans defective cans can be detected and separated from normal cans.

Generally, neck-in cans are typically punched out from material such as aluminium, to a required volume, and then formed to a required shape with the mouth and the circumference near to'the mouth squeezed inwardly by a squeezer to form a neck. During squeezing creases sometimes occur in the neck.

Creases are generated by various causes, e. g. a flaw in the squeezer itself or its temporary malfunction, or improper positioning of the can with an unformed neck in the squeezer.

The crease in the neck-in may affect the airtight sealing properties of the can when the can is sealed with a suitable cap in a later automatic operating step, with a possible fouling of the contents. It is of course necessary to prevent crease formation, but it is also necessary not to allow cans having creases to be transferred for subsequent operating steps.

Currently, however, there are only means to detect whether or not there is a flange crack at the mouth of the neck-in can and to detect whether or not the flange length is suitable so as to discriminate good from bad.

There is no device for detecting whether or not a crease exists and for discriminating effectively good from bad.

An object of the present invention is to provide a neck-in can automatic discriminator which is capable of automatically distinguishing cans having creases as rejects by detecting the presence of creases in the cans effectively.2 The invention provides an automatic discriminator for neck-in cans having at least one step in the necks thereof, the discriminator comprising a turning mechanism for rotating one or more neck-in cans arranged in a conveyor line about the central axis of rotation of the can ; at least one detection circuit each corresponding to a step in the neck of the can and comprising light irradiation means for irradiating light to the neck of a rotating neck-in can and photosensing means for receiving the reflected light of the irradiated light and for photoelectrically converting the light : a discriminator circuit for discriminating between the presence or absence of a crease in the neck depending on the photoelectrically converted output pattern of the or each photosensing means : and a rejection mechanism for ejecting a neck-in can from the conveyor line when the can is judged to have a crease, or a crease above a predetermined allowable limit, by said discriminator circuit, wherein the at least one detection circuit is or are arranged so that the light irradiation means irradiates light to the neck from outside the rotat. ing neck-in can and photosensing means are arranged on both sides of the irradiation means so that the or each pair of photosensing means receives the reflected light, and the discrimination circuit compares the photoelectrically converted output of the or each pair of photosensing means and judges that a crease is present when the corresponding photoelectrically converted output or outputs are not uniform.

Accordingly, the neck-in can automatic discriminator of the present invention can effectively detect a crease inflicted by some cause while the neck-in can is formed by a squeezer and reject the defective can through an effective detection with the resultant great improvement of product yield.

Since optical means are used in the present invention to detect whether or not a crease is present, detection can be made effectively and accurately regardless of the material of the can such as tin or aluminum.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a sectional view showing an example of a neck-in can ; Figure 2 is a schematic view showing an embodiment of a neck-in can automatic discriminator of the present invention ; Figure 3 illustrates crease detection principle of the embodiment shown in Figure 2 : Figure 4 is a plan and a side view showing an example of the crease detection sensor employed in the embodiment shown in Figure 2 : Figure 5 is a block diagram showing a example of the discriminator circuit employed in the embodiment shown in Figure 2 ; and Figure 6 is a plan and a side view showing particularly an example of the crease detection sensor used in other embodiment of the neck-in can automatic discriminator of the present invention.

In Figure 1 a neck-in can has a trunk TR, a neck NC, and a mouth or opening OP. In this example, the neck NC is squeezed in three steps to form a required shape of the neck-in can.

In the overall arrangement of the embodiment shown in Figure 2, a conveyor 1 has guide rollers 2a, 2b attached thereto which hold the neck-in can so as to be rotatable about the axis of rotation, i. e. the centre axis of that can. The neck-in cans which have been squeezed as required by the squeezer (not shown) are transferred from the directions F1, F2 indicated by arrows in Figure 2 to the conveyor. The cans are inserted between the guide rollers 2a, 2b sequentially as shown as the conveyor 1 rotates in the direction of arrow F3.

Sensors 3a, 3b, e. g. limit switches or photosensors, are provided for detecting whether or not neck-in cans are actually present on the conveyor 1 (more precisely on the guide rollers 2a 2b). Turning rollers 4a 4b rotate in the direction of arrow F4 in mutually interlocked relation and rotate the neck-in cans in the direction of arrow F5 about the axis of rotation (the central axis of the can).

Crease detection sensors Sa, 5b for detecting creases in the neck-in cans are each provided with a light irradiation means for irradiating light from inside the can to the neck NC (Figure 1) of the neck-in can being rotated by the turning rollers 4a, 4b and a photosensing means for receiving the reflected light of the irradiated light and photoelectrically converting the light. A discriminator circuit 6 is provided for receiving photoelectric conversion output of the photo-sensing means of the sensors 5a, 5b and discriminating presence or absence of a crease in the neck-in can. Rejectors 7a, 7b eject crease-free neck-in cans at positions indicated by a continuous line in the directions of arrows F6a and F6b, which are conveyance lines for transferring the neck-in cans to the next operation stage, or, depending on the result at the discriminator circuit 6, reject the neck-in cans having creases at the position indicated by a broken line in the direction of arrows F7a and F7b through the conveyance line as rejects.

For the device shown in Figure 2, a 12-pocket double index (150 stop) type is employed. The insertion of the sensors 5a, 5b into the neck-in cans, the operation of the sensors 5a, 5b. and the operation of the rejectors 7a, 7b are suitably controlled dependent on the machine timing.

The sensors 5a, 5b (hereinafter referred to as the sensor 5) and the discriminator circuit 6, which are the main parts of the present invention, will be described in detail with reference to Figures 3 to 5.

The neck-in can crease detection principle by the utilization of the sensor 5 and the discriminator circuit 6 will be described with reference to Figure 3.

In Figure 3 (a), the light irradiation means of the sensor 5 comprises a lamp L, an optical fibre OF, and an irradiation head 51. The photosensing means of the sensor 5 comprises a photosensor head 52, an optical fibre OF, and a phototransistor FT. The neck NC of the neck-in can has an inner wall IW.

If the output of the phototransistor FT is detected while the inner wall IW is moved in the direction of arrow F5, i. e. while the neck-in can is being rotated (Figure 2), and is fed to an electric circuit as shown in Figure 3tub), irregular reflection will occur only when there is a crease Cr as shown in Figure 3 (a) on the inner wall IW, and the quantity of light received each time by the photosensing means will be greatly reduced.

As a result, the input signal of the electric circuit of Figure 3 (b) will take the pattern of the signal S1 shown in Figure 3 (b).

The change component is extracted from the signal by means of a capacitor Cl which functions as a filter of that circuit. The extracted signal S2 is amplified to a specified level at an amplifier AMP, and peak hold is performed at a capacitor C2. A signal having a voltage level corresponding to the largest crease Cr like a signal S3, particularly at point P is obtained.

Accordingly, if the voltage level of a suitable voltage setter is set a level corresponding to a crease of a pre-determined size, and the set voltage level and the voltage level of the extracted signal are compared from time to time by a comparator, it can be ascertained whether the neck-in can is acceptable or not depending on the comparator output.

Figures 4 and 5 respectively show an example of the sensor 5 and the circuit 6 based on the aforementioned principle.

In Figure 4, irradiation heads 51a-51d are provided corresponding to each step of the neck NC of the neck-in can, and photosensor heads 52a-52d are similarly provided. The heads 52a-52d are fixedly supported by a head support member 50 so that when the neck of the neck-in can is free of crease, light irradiated through the irradiation heads 51a to 51d is reflected fully to the corresponding photosensor heads 52a through 52d.

The support member 50 is moved in the direction of arrow F8 (Figure 4 (b)) by means of a suitable cam mechanism (not shown), thereby controlling the insertion and removal of each head into and from the neck-in can.

In Figure 5, a CPU (central processing unit) 60 performs overall control of discrimination of presence/absence of creases and operation of the rejectors 7a, 7b depending on the discrimination result. Pick-up information processing circuits 610, 620,630,640 of similar configuration process pick-up information from the individual photosensor heads 52a-52d of the sensor 5. A multiplexer 61 batch transfers information processed at the processing circuits 610-640 based on the command from the CPU 60. An A/D converter converts the information transferred from the multiplexer 61 and transmits the resultant digital information to the CPU 60. Setters 611, 621. 631, 641, in which information processed at the pick-up information processing circuits 610-640, that is, level information corresponding to individual allowable crease ranges, are preset corresponding to the peak hold signal given relative to the aforementioned principle. A sensor 63 detects the machine timing of the embodiment shown in Figure 2. A rejector solenoid 64 controls the driving of the rejectors 7a, 7b (Figure 2) dependent on the command from the CPU 60. Indicators 65 indicate visibly and in a suitable manner the machine timing, the driving mode of the rejectors 7a, 7b, lamp blow-out in the light irradiating means, neck-in can acceptable/unacceptable, and so forth.

The CPU 60, which plays the central role in the discriminator circuit 6, compares the output of the A/D converter 62, that is, the largest crease detection information in each step of the neck NC of the neck-in can picked up at each pick-up information processing circuit 610,620,630,640 with each level information preset to the setter, 611, 621, 631, 641. The CPU 60 operates so as to reject the neck-in can associated with the detection information exceeding the preset level information driving the rejector 7a or 7b as appropriate via the solenoid 64 when the neck-in can is ejected through the conveyance line (arrows F6a, F6b in Figure 2). A signal line LN shown in Figure 5 is for checking if the lamp in each light irradiation means has blown or not.

In summary, the device of the above-mentoned embodiment enables accurate discrimination between a crease-free can or a can having an allowable crease and an unacceptable can having a crease beyond the allowable limit.

In this embodiment, the construction of the conveyor 1 shown in Figure 2, the conveying method and ejecting method of the neck-in can are optional, and any suitable construction and method may be selected.

In addition, the crease detection and discrimination methods are not limited to those employed by the embodiment. For example, the detection and discrimination of creases may be made using the sensor 8 as shown in Figure 6.

In Figure 6 the sensor 8 comprises a lamp 81 disposed so as to be able to irradiate light at least to the neck NC of the neck-in can, a lens 82 for converging the irradiated rays of the lamp 81, solar cells 83a, 83b for receiving the reflected light of the irradiated light from the surface of the neck-in can through the respective slits S, and a differential amplifier capable of comparing the photoelectric conversion outputs of the solar cells 83a, 83b.

These components of the sensor 8 are accommodated integrally in a case 80 in the manner as shown. A discriminator circuit (not shown) monitors the output of a differential amplifier 84, and when the output level exceeds a predetermined value, that is, when the difference between the photoelectric conversion outputs of the corresponding solar cells exceeds a predetermined value due to the irregular reflection caused by a crease on the surface of the neck-in can, the discriminator operates so as to reject that neck-in can as a reject.

The discrimination may be made effectively likewise by the above means.

Claims (3)

1. CLAIMS: 1. An automatic discriminator for neck-in cans having at least one step in the necks thereof, the discriminator comprising a turning mechanism for rotating one or more neck-in cans arranged in a conveyor line about the central axis of rotation of the can ; at least one detection circuit each corresponding to a step in the neck of the can and comprising light irradiation means for irradiating light to the neck of a rotating neck-in can and photosensing means for receiving the reflected light of the irradiated light and for photoelectrically converting the light : a discriminator circuit for discriminating between the presence or absence of a crease in the neck depending on the photoelectrically converted output pattern of the or each photosensing means ; and a rejection mechanism for ejecting a neck-in can from the conveyor line when the can is judged to have a crease, or a crease above a predetermined allowable limit, by said discriminator circuit, wherein the at least one detection circuit is or are arranged so that the light irradiation means irradiates light to the neck from outside the rotating neck-in can and photosensing means are arranged on both sides of the irradiation means so that the or each pair of photosensing means receives the reflected light, and the discrimination circuit compares the photoelectrically converted output of the or each pair of photosensing means and judges that a crease is present when the corresponding photoelectrically converted output or outputs are not uniform.
2. 2. A neck-in can automatic discriminator as claimed in claim 1, wherein each photosensing means comprises solar cells.
3. 3. A neck-in can automatic discriminator substantially as hereinbefore described with reference to any one of the embodiments shown in the accompanying drawings.