GB2454469A - Hole detector using transmitted ultraviolet light - Google Patents
Hole detector using transmitted ultraviolet light Download PDFInfo
- Publication number
- GB2454469A GB2454469A GB0721779A GB0721779A GB2454469A GB 2454469 A GB2454469 A GB 2454469A GB 0721779 A GB0721779 A GB 0721779A GB 0721779 A GB0721779 A GB 0721779A GB 2454469 A GB2454469 A GB 2454469A
- Authority
- GB
- United Kingdom
- Prior art keywords
- detector
- hole
- light
- photosensor
- processing means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
- G01N21/8914—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
- G01N21/892—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the flaw, defect or object feature examined
- G01N21/894—Pinholes
-
- G—PHYSICS
- G07—CHECKING-DEVICES
- G07C—TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
- G07C3/00—Registering or indicating the condition or the working of machines or other apparatus, other than vehicles
- G07C3/14—Quality control systems
-
- G—PHYSICS
- G07—CHECKING-DEVICES
- G07C—TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
- G07C3/00—Registering or indicating the condition or the working of machines or other apparatus, other than vehicles
- G07C3/14—Quality control systems
- G07C3/146—Quality control systems during manufacturing process
Abstract
A hole detector for holes punched in plastic packaging comprising an ultraviolet (UV) light source 10 on one side of plastic 14 to be inspected, at least one UV photosensor 12 located on the other side of plastic 14, a filter and a processor 16 for receiving signals representing light intensity detected by the photosensor. The filter only allows light emitted by the light source 10 to reach the photosensor 12. The received signals are compared to a reference signal amplitude or duration (fig. 3) in order to determine whether a hole (20, fig. 3) is present or not and an alarm is used to inform the user. The processor 16 can transmit a signal to the punch 18 to increase the punching force if no hole is detected. An additional photosensor can correct for ambient light levels (fig. 3).
Description
HOLE DETECTOR
This invention relates to a hole detector. The apparatus is particularly applicable for use in detecting holes in plastics which are transparent to visible light.
Plastics are used for packaging goods, such as food. In many instances the plastic is provided with holes. These holes may be punched using a number of different mechanisms1 for example a ball and die. The ball and die system enables holes that typically have a diameter of between 2 and 10mm to be punched on a continuously moving plastic web.
It is important to ensure that the plastic within the holes is removed completely so that the product is not rejected by customers. However, as the holes are punched at a rate of approximately 2000/mm it is not possible to ensure the plastic is completely removed using the eye unless the process is significantly slowed down.
A known method for detecting edges is an air knife system where an air inlet and an air outlet are disposed on opposite sides of the plastic. As a hole passes between the inlet and outlet air coming from the outlet will reach the inlet. A sensor at the inlet can determine the amount of air entering the inlet and therefore the size of the hole. However the time it takes to register the air entering the inlet is too great to allow efficient monitoring of the holes in a web at the speeds desired.
An alternative method of detecting holes in plastic is spark-through detection where the plastic is exposed to an electrical field. The plastic acts as an insulation layer in the electric field. However, air does not have this insulating property and therefore a micro perforation or small hole In plastic exposed to an electric field causes a small spark to be generated.
Detection of the spark can then be used to determine whether there is a hole within the plastic has successfully been created. However, a spark is created regardless of the size of the hole. This means that if the plastic has been punctured but a hole has not been properly created, for example as illustrated in Figure 1, this test will incorrectly determine that a hole is present.
Further conventional methods using photocells and cameras cannot be used to check for holes in transparent films as there is insufficient difference in the level of visible light which is transmitted through the plastic and that which has passed through the hole.
Accordingly there is a need for an improved method for detecting holes within plastics.
According to the present invention there is provided a detector for holes in plastic comprising LJV light source; least one photosensor configured to at least detect UV light; and processing means arranged to receive signals representing light intensity detected by the photosensor from the at least one photosensor, compare the received signals to a reference to determine whether a hole is present or not.
Preferably, the reference includes a threshold duration, the processing means being arranged to determine that a hole is present if a period of increased light intensity lasts longer than the threshold duration.
Preferably, the processing means is configured to determine that a hole is present if the amplitude detected by the photosensor is greater than the amplitude threshold.
Optionally the processing means determines that a hole is present if the period of increased light intensity is greater than a threshold duration and the detected amplitude is greater than an amplitude threshold.
Preferably, the processing means is arranged to determine whether a hole is present within a predetermined period of time.
Advantageously, the predetermined period of time is calculated from the time that the last hole was detected.
Preferably, the detector is in communication with a punch and predetermined time is calculated from the time that the punch attempted to create a hole in the plastic Optionally, an encoding means determines the speed the plastic moves at. From the speed the expected position of any holes can be determined. This enables the device to determine if a hole has bee created in the expected position.
Preferably, the processing means is arranged to transmit a signal to the punch causing an increase in punching force if no hole is detected.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the foflowing description of specific embodiments of the invention in conjunction with the accompanying figures.
Figure 1 illustrates a plastic where a hole has not been correctly formed; Figure 2 is a side view of the present invention in use; Figure 3 is a birds eye view of the present invention in use; and Figures 4a to 4c illustrate possible signal readings produced by the present invention.
Figures 2 and 3 illustrate an embodiment of the present invention. The detector apparatus includes a light source 10 and at least one photosensor 12. The light source 10 emits light which cannot pass through the plastic to be tested. Advantageously the light source 10 emits UV light as most polymers and plastics are opaque to UV light. Preferably, the UV light is UVC light having a wavelength between l8Onm and 260nm, even more preferably the light has a wavelength of 254nm.
The light source 10 is positioned on one side of the path of the plastic 14 to be inspected.
The photosensor 12 is disposed on the other side of the plastic 14 to the light source 10.
The photosensor 12 is positioned such that light travelling in a straight path from the light source 10 will be detected by the photosensor 12. Preferably, the sensor 12 is provided with a filter (not shown). The filter only allows light at or near the wavelength emitted by the light source 10 to reach the photosensor 12. This minimises the amount of background light radiation to which the photosensor 12 is exposed. The photosensor 12 is able to detect at least a part of the UV light spectrum.
When the plastic 14 moves between the light source 10 and sensor 14 the plastic reflects the light, as discussed above. The reflection of light results in the photosensor 12 sensing only a base line of ambient UV light as shown in Figures 4a to 4c.
When a hole is positioned between the light source 10 and sensor 12 the UV light being transmitted by the light source 10 passes through the break. This causes an increase in the light intensity received by the photosensor 12.
The sensor 12 is connected to processing means 16. The sensor 12 transmits a signal representative of the intensity of UV light sensed. The processing means 16 uses the information contained in the signal to determine whether the desired hole has been made in the plastic 14. The processing means achieves this by comparing the duration for which an increased level of light is received by the photosensor 12 (indicating a perforation in the plastic is present) to a reference duration which indicates how long the increased level of light should occur for if a hole has been correctly made in the plastic 14.
In Figures 2 and 3 the plastic is a web. The web is moved in the direction shown by the arrows. Therefore, the plastic 14 to be monitored by the detecting apparatus is first introduced to a punch 18 where holes 20 are formed in it using any known manner. Once the plastic 14 has holes in it, it is moved to the detecting apparatus to determine whether the desired holes were successfully formed or not.
Figure 4a illustrates the signal received by the processing means when a hole has been correctly cut. As discussed above the increased light intensity lasts for the duration that it takes the hole to pass between the light source and sensor. The time duration that the increased light intensity lasts for is compared by the processor to a reference time which indicates how long the higher light intensity will last if the hole has the desired diameter, If the light intensity duration corresponds to the reference time then the hole in the plastic has been correctly made.
Figure 4b illustrates a signal that might be received by the processing means if a hole such as the one illustrated in Figure 1 passes between the light source and sensor. In this instance, as the increased Jight intensity lasts for the a shorter time than the reference time an incorrectly formed hole can be identified.
Figure 4c illustrates the signal which is received by the processing means when no hole has been cut in the plastic. As there is no break in the plastic, there is no increase in light intensity detected by the photosensor and thus the absence of a correctly made hole can be determined.
In addition to monitoring a timing threshold the system may also monitor the amplitude of light detected. The amplitude having to be greater than a threshold value for a hole to be validly detected. Optionally, the system may only monitor whether the amplitude of the light detected by the photo sensor is greater than an amplitude threshold.
To notify a user that a product does not have the correct holes the processing means may implement a number of methods. For example, the processing means may be provided with a timer so that it can monitor the frequency at which holes are detected. If a hole does not occur when one is expected then the processing means may, for example, transmit a signal to a control system which causes an appropriate action to occur or cause an alarm to sound at a user interface. The alarm may be a text alert or a sound. The control system may, upon detection of an absence of an expected hole, cause the plastic to stop moving through the detector or to be redirected to a discard pile.
Rather than monitoring the frequency at which the holes occur the processing means may be connected to the punch means. Whenever the punch creates a hole it then sends a signal to the processing means indicating that a hole has been made. The processing means can then signal an alert as described above if a hole is not detected at the time when the hole is expected to pass through the detecting apparatus. The expected time may be transmitted by the punch means, calculated by the processing means (from the speed of the plastic and the distance to the punch means) or set by a user.
Optionally, the processing means may be configured to transmit a signal to the punch means when a hole has not been detected. The signal causing the punch means to increase the punch force or take any other appropriate action to increase the likelihood of a hole being correctly formed. Optionally, the processing means may cause an alarm to sound, or the apparatus to stop, if it has transmitted a certain number of signals, for example, causing an increase in punching force.
The sensor may be provided with a user interface that allows the threshold level for the light intensity to be varied by a user.
The system may be provided with a feedback loop which allows the processing means to cancel out any background light setting a reading of zero when only ambient light is present.
The feedback loop cancels out background UV light at least, although other wavelengths may also be cancelled out. This may be achieved by the use of an additional ambient photosensor connected to the processing means or the presence of control circuitry within the system. The feedback loop also allows for auto correction for different attenuation of light due to the thickness or type of material being monitored.
In one embodiment the sensor includes a single photosensor. The photosensor is arranged to scan across the width of the plastic as the plastic moves between one or more light sources and the photosensor. In another embodiment the sensor may comprise an array of photoserisors and one or more light sources arranged along the width of the plastic. As the processed plastic moves between the photosensors and light source, each of the photosensors transmits a signal indicating the intensity of the light received to a processing means. The processing means then determines whether all the photosensors expected to have an increased intensity of received light are receiving an increased intensity of light, for example, by comparing the received signals to a reference pattern.
Claims (22)
1. A detector for holes in plastic comprising: a. a UV light source; b. at least one photosensor configured to at least detect UV light; and c. processing means arranged to receive signals representing light intensity detected by the photosensor from the at least one photosensor, compare the received signals to a reference to determine whether a hole is present or not.
2. The detector as claimed in Claim I wherein the reference includes a threshold duration, the processing means being arranged to determine that a hole is present if a period of increased light intensity lasts longer than the threshold duration.
3. The detector as claimed in Claim 1 or 2 wherein the reference includes an amplitude threshold, the processing means configured to determine that a hole is present if the amplitude detected by the photosensor is greater than the amplitude threshold.
4. The detector as claimed in Claim 3 when dependent upon Claim 2 wherein the processing means determines that a hole is present if the period of increased light intensity is greater than a threshold duration and the detected amplitude is greater than an amplitude threshold.
5. The detector as claimed in any preceding claim wherein the processing means is arranged to determine whether a hole is present within a predetermined period of time.
6 The detector as claimed Claim 5 wherein the predetermined period of time is calculated from the time that the last hole was detected.
7 The detector as claimed Claim 5 wherein the detector is In communication with a punch and predetermined time is calculated from the time that the punch attempted to create a hole in the plastic.
8. The detector as claimed in any of Claims 5 to 7 wherein an encoding means determines the speed the plastic moves at.
9. The detector as claimed in Claim 7 wherein the processing means is arranged to transmit a signal to the punch causing an increase in punching force if no hole is detected.
10. The detector as claimed in any preceding claim wherein the processing means is arranged to transmit an alert message if no hole is detected.
11 The detector as claimed in any preceding claim wherein the alert message is arranged to cause, an audio alert at a user interface, a text alert at a user interface or a signal to be transmitted to a control means.
12. The detector as claimed in any preceding claim wherein the detector includes a feedback mechanism that deducts ambient light level from the light detected by the photosensor.
13. The detector as claimed in Claim 12 wherein the ambient light level and the detected fight is UV light.
14. The detector as claimed in Claim 12 and 13 wherein the feedback mechanism is connected to an ambient photosensor that is external to the detector.
15. The detector as claimed in Claim 14 wherein the ambient photosensor detects UV light.
16. The detector as claimed in Claim 12 wherein the feedback mechanism is implemented by feedback processing means.
17. The detector as claimed in Claim 14 further including a controller configured to adjust the required time duration specified in the reference.
18. The detector as claimed in any preceding claim wherein the reference includes a threshold light intensity, the processing means being arranged to determine that a hole is present if the increased light is higher than the threshold light intensity.
19. The hole detector as claimed in any preceding claim further including a controller configured to adjust the required light intensity level of the reference.
20. The detector as claimed in any preceding claim wherein the photo detector is provided with a filter to substantially filter out light frequencies not emitted by the UV light source.
21. The detector as claimed in.any preceding claim wherein the light source emits UVC light.
22. A detector substantially as herein described with reference to and as shown in any combination of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0721779A GB2454469A (en) | 2007-11-07 | 2007-11-07 | Hole detector using transmitted ultraviolet light |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0721779A GB2454469A (en) | 2007-11-07 | 2007-11-07 | Hole detector using transmitted ultraviolet light |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0721779D0 GB0721779D0 (en) | 2007-12-19 |
| GB2454469A true GB2454469A (en) | 2009-05-13 |
Family
ID=38858233
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0721779A Withdrawn GB2454469A (en) | 2007-11-07 | 2007-11-07 | Hole detector using transmitted ultraviolet light |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2454469A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112730253A (en) * | 2020-12-31 | 2021-04-30 | 常熟市杜尼电子有限责任公司 | High-precision detection equipment for punching of punching non-standard part |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB756827A (en) * | 1954-11-12 | 1956-09-12 | Linderman Engineering Company | Apparatus for detecting holes in material |
| GB862177A (en) * | 1956-11-20 | 1961-03-01 | Ibm | Improvements in apparatus for detecting perforations in webs, sheets and the like |
| GB1124778A (en) * | 1965-09-23 | 1968-08-21 | Nash & Harrison Ltd | Inspection and sorting of sheet materials by photoelectric means |
| US3700909A (en) * | 1972-03-09 | 1972-10-24 | Columbia Research Corp | Method for detecting pinhole defects in foil material |
| US3755674A (en) * | 1972-03-09 | 1973-08-28 | Columbia Res Corp | Method of detecting pinhole defects in sheet material |
| EP0536695A1 (en) * | 1991-10-08 | 1993-04-14 | Zweckform Büro-Produkte GmbH | Continuous forms, with continuous perforation controll, method and apparatus for their manufacture |
| JPH08338814A (en) * | 1995-06-09 | 1996-12-24 | Toray Ind Inc | Apparatus for detecting defect of film and manufacture for film |
| US20070019187A1 (en) * | 1999-06-10 | 2007-01-25 | Aradigm Corporation | Method and device for non-destructive analysis of perforations in a material |
-
2007
- 2007-11-07 GB GB0721779A patent/GB2454469A/en not_active Withdrawn
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB756827A (en) * | 1954-11-12 | 1956-09-12 | Linderman Engineering Company | Apparatus for detecting holes in material |
| GB862177A (en) * | 1956-11-20 | 1961-03-01 | Ibm | Improvements in apparatus for detecting perforations in webs, sheets and the like |
| GB1124778A (en) * | 1965-09-23 | 1968-08-21 | Nash & Harrison Ltd | Inspection and sorting of sheet materials by photoelectric means |
| US3700909A (en) * | 1972-03-09 | 1972-10-24 | Columbia Research Corp | Method for detecting pinhole defects in foil material |
| US3755674A (en) * | 1972-03-09 | 1973-08-28 | Columbia Res Corp | Method of detecting pinhole defects in sheet material |
| EP0536695A1 (en) * | 1991-10-08 | 1993-04-14 | Zweckform Büro-Produkte GmbH | Continuous forms, with continuous perforation controll, method and apparatus for their manufacture |
| JPH08338814A (en) * | 1995-06-09 | 1996-12-24 | Toray Ind Inc | Apparatus for detecting defect of film and manufacture for film |
| US20070019187A1 (en) * | 1999-06-10 | 2007-01-25 | Aradigm Corporation | Method and device for non-destructive analysis of perforations in a material |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0721779D0 (en) | 2007-12-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |