GB2042164A

GB2042164A - Testing for container defects

Info

Publication number: GB2042164A
Application number: GB7904049A
Authority: GB
Original assignee: United Glass Ltd
Current assignee: OI Glass Ltd
Priority date: 1979-02-06
Filing date: 1979-02-06
Publication date: 1980-09-17

Abstract

Apparatus for detecting irregularities in a glass surface comprises at least one series of emitters (2a, 2b) arranged in a circle and operative to direct light onto the said glass surface, at least one series of detectors (3a, 3b) arranged in a circle concentric with the emitters and adapted to provide a signal upon detecting reflected light, and means for causing each detector to provide no signal whenever an emitter arranged on the same diameter as the said detector is operative. In one embodiment alternate emitters are arranged to be operative at any one time, the detectors 3b being activated with emitters 2a and vice versa. <IMAGE>

Description

SPECIFICATION Testing for container defects This invention relates to the testing of containers, notably but not exclusively glass containers, for defects, and provides a device for ascertaining the presence or otherwise of defects on the sealing surfaces of containers.

For optimum sealing effect the sealing surfaes of containers, e.g. glass or plastcis containers, should be perfectly smooth and free from surface chips or other irregularities. This is especially the case when the containers in question are to be used for the packaging of carbonated beverages, since any leakage of gas between the sealing surface and the closure cap, or the liner within the cap, will clearly spoil the contents of the container. It has been found that the presence of chips in the sealing surfaces of containers is most marked in those containers which have been sealed by the so-called "crown" caps.

Such caps, which are applied to the filled container by a crimping operation, are normally removed from the container by the use of a bottle opener or by firstly removing a tear-strip formed integrally with the cap. The removal of the crown cap has been observed to scratch or chip the sealing surface of the bottle, so that when such bottles are returned to the filler (for sterilisation and subsequent re-filling) the bottles are imperfect.

Devices are known for detecting chips or scratches on the flat sealing surfaces of containers surrounding the mouths thereof. Such devices comprise a flat pad which is pressed onto the flat sealing surface of the bottle, a source of compressed air to fill the bottle with air under pressure, and a leakage detection device for detecting if the air in the bottle escapes between the pad and the flat sealing surface.

Such devices rely for their operation on a true contact between the pad and the top of the bottle, and the rapid inflow into the bottle of pressure air. It is an object of the invention to provide an efficient device for testing containers for defects which does not rely on any physical contact between the device and the containers.

According to the present invention apparatus for detecting irregularities in a glass surface comprises at least one series of emitters arranged in a circle and operative to direct light onto the said glass surface, at least one series of detectors arranged in a circle concentric with the emitters and adapted to provide a signal upon detecting reflected light, and means for causing each detector to provide no signal whenever an emitter arranged on the same diameter as the said detector is operative.

The device of the invention operates on the basis that a good glass surface reflects light radially but that a defective surface, for example on having chips or scratches in it, deflects the light at an angle to the radial. Thus, we arrange our device to operate such thatwhenver an emitter is operative to direct light, which may be in the visible region or infra-red region, onto the glass surface the detector which is on the same diameter as that emitter (hereafter called "the diametral detector"), and which would detect any radially reflected light from a good surface, is not operative. We are not concerned with such radially reflected light, but only with deflected light, the presence of which indicates a defective surface.Hence, we arrange for the detectors on either side of the diametral detector to be operative, so that any light reflected at an angle to the radial (and denoting a defective surface) will be detected.

In a preferred embodiment of the invention we arrange for alternate emitters to be operative at any one time.

The accompanying drawings illustrate the invention.

In the drawing, Figure 1 is a sectional elevation of a device according to the invention positioned over the top of the glass bottle; Figure 2 is a plan view of the device of Figure 1; Figure 3 is a sectional elevation of another device according to the invention on the lines A-A of Figure 4; and Figure 4 is a plan view of that device.

Referring to Figures 1 and 2, the device of the invention comprises a circular disc 1 of a suitable material, such as aluminium, mild steel or a lightweight alloy, in which are drilled two concentric rings of holes 2,3. The inner series of holes 2 are adapted to receive light emitters, for example the high intensity emitters sold by the Hewlett-Packard Company under the designation HEMT 3300. The outer series of holes are for the reception of detectors, e.g. photodiodes, which will detect light emanating from the emitters and reflected onto them. The emitters and detectors will be contained in a suitable electrical circuit which will control their "on-off" operation and the provision of a signal by the detectors whenever the latter detect reflected light.

The holes 2, 3 are drilled through disc 1 at angles which are determined by the particular shape of the surface the device is required to examine. Thus, in the example shown, the holes 2 are drilled at an angle of 65" to the horizontal, whilst the holes 3 are drilled at an angle of 40 to the horizontal.

In the plan view shown in Figure 2, alternate emitter-receiving holes are marked 2a and 2b; alternate detector-receiving holes are marked 3a and 3b. When emitters 2a are on, emitters 2b are not and only detectors 3b are operative. When emitters 2a are off and 2b are on, detectors 3a only are operative. By this means properly reflected light, e.g.

from an emitter 2a is reflected onto a detector 3b, thus indicating a defect, a signal is provided which may if desired be used to actuate a bottle rejection device. The circuit containing the emitters and detectors may suiably operate at 1 KHz, and the signal on detecting deflected light may be amplified.

The device illustrated in Figures 3 and 4 operates on the same basic principle to that of Figures 1 and 2, but is somewhat more complicated since it is used for observing and testing a portion of the container below the top sealing surface, specifically the underside of an annular shouold beneath which the security ring of a so-called pilferproof closure is crimped. To this end there are provided two concentric series of emitters, 12, 22, and a simple series of detectors 13, the angles of inclination of the emitters and detectors being dependent on the shape of the container being observed. The device is operated as before, with alternate emitters being operative whilst the non-diametral photodetectors are operational.

An alternative operation of the device of Figues 1 and 2 is as follows: (a) All emitters 2a and 2b and all detectors 3a and 3b are on; (b) When a majority of the detectors are receiving a signal then the electronics go to the next operation; (c) Emitters 2a and detectors 3b are left on and the presence of a signal looked for; then (d) Only emitters 2b and detectors 3a are turned on and again the presence of a signal is looked for; (e) (c) and (d) might be repeated several times, and then (f) All inspectors and detectors will be switched on to ascertain whether there is still a bottle present.

If there is then (c) and (d) will again be repeated.

At the switch cycles proposed this whole cycle may be repeated several times even though the container is not halted during passage along the inspection line.

Claims

1. Apparatus for detecting irregularities in a glass surface comprising at least one series of emitters arranged in a circle and operative to direct light onto the said glass surface, at least one series of detectors arranged in a circle concentric with the emitters and adapted to provide a signal upon detecting reflected light, and means for causing each detector to provide no signal whenever an emitter arranged on the same diameter as the said detector is operative.

2. Apparatus as claimed in claim 1 wherein alternate emitters are arrangd to be operative at any one time.

3. Apparatus as claimed in claim 1, substantially as described with reference to Figures 1 and 2, or Figures 3 and 4, ofthe drawings.