Method and Apparatus for Inspecting the Bottoms of Hollow Glass Articles

This invention relates generally to an apparatus and method for inspecting glassware for the presence of tramp glass or fused glass and in particular to the inspection of glassware for the presence of tramp glass or fused glass on the inside bottom surface of the glassware. In order to ensure maximum consumer protection, it is desirable that all surfaces of a glass container be inspected for defects. These defects may take the form of checks, birdswings, tramp glass, fused glass, and many others. Various methods have evolved to inspect glassware for such manufacturing defects; however, the inventor is unaware of any method or apparatus for inspecting the inside bottom surface of glassware for the presence of tramp glass or fused glass. For the purposes of this invention, it is essential that checks be distinguished from tramp glass and fused glass.

Most glassware is manufactured to bear some indication of its origin by placement of certain mold markings on the outside base of the container. These markings may take the form of letters, numbers, or abstract designs. The presence of the various types of markings plus the fact that the same markings do not always appear in the same physical location has made inspection of glass bottoms inherently difficult. A discussion of a couple of the state-of-the-art devices may aid in appreciating the present invention.

There are light operative means for inspecting the "heel" area of glassware for checks. In one such apparatus the light is directed into the glassware and reflected therefrom (ideally) only when there is a check present. A check is a fracture line which normally occurs internal to the glassware and is not a surface defect. When the light strikes the check, the air-check layer causes the light to be reflected from the plane of the check. The reflected light is sensed and a reject signal generated to ultimately cause the subject ware to be discarded.

Another method for inspection of glassware with light is disclosed by U.S. Pat. No. 3,887,285. The invention is directed to inspection of flasks for checks occurring in the neck of the flask. Light is directed through the outer surface of the flask and focused onto the wall of the container opposite thereto and passes therethrough. The presence of a check causes the direction of the light to be significantly redirected and ultimately detected by a light sensing means.

The angle of incidence of the light is such that the light "enters" the wall of the glass container, i.e., the light is not reflected by the primary surface of the container. When the light strikes a check it is reflected from within the wall and emerges from within the wall to be sensed by a light sensor. The angles involved and the suspected angle of the check are critical since the angle of incidence, the angle of the check, and the resulting angle of reflection are all dependent.

Should the teaching of U.S. Pat. No. 3,887,285 be applied to the bottom of a container, the lettering, mold markings, or pertubations present on the bottom would cause reflections not indicative of errors. Additionally small imperfections such as seeds and blisters within ranges of acceptability would indicate defective ware.

It is an object of this invention to provide a method and apparatus for inspecting the bottom of glass containers for tramp glass or fused glass.

It is a further object of this invention to inspect such glassware by directing light through the outside walls of the glassware and onto the inside bottom surface of the glassware.

It is yet another object of the present invention to inspect such glassware by directing light onto the inside bottom surface in such a manner whereby substantially all of the light is reflected unless tramp glass or fused glass is present in the container.

My invention is a method and apparatus for inspecting the bottom of glassware for imperfections. In particular, the present invention detects the presence of tramp glass, fused glass, or similar imperfections. A plurality of light sources are positioned to uniformly irradiate the interior surface of the bottom of the glassware. The angle of incidence is predetermined to obtain maximum reflection from the interior surface of the bottom and, consequently minimum transmission of the light through the bottom of the glassware. The light sources provide directed light to effectively illuminate the entire bottom of the container. Any tramp glass or fused glass present on the inside bottom of the glassware will cause the light incident thereon to be bent, refracted, or reflected in such a way that light will be transmitted through the base of the container instead of being reflected by the base of the container. A light sensitive means is used to sense the presence of transmitted light and ultimately cause the related glassware to be rejected.

Other objects, features, and advantages of the present invention will become more fully apparent from the appended claims and the accompanying drawings in which:

FIG. 1 is a prospective view and partial block diagram of a preferred embodiment of the present invention; and

FIG. 2 is a top view schematic diagram of the present invention.

Turning now to the drawings wherein like components are designated by like reference numerals throughout the various figures, a glassware bottom inspector according to the present invention is disclosed. Referring to FIG. 1, glassware 2 is inverted by conventional means before it arrives at the inspection zone 4. The glassware is not stopped during the inspection cycle. Glassware position sensing means 6 senses the presence of the glassware in the inspection zone and causes the inspection sequence to take place. The position sensing means may cause the light sensing means 8 to become active or, assuming the light sensing means always to be active, the position sensing means may cause the light sources to be pulsed during the inspection cycle. The inspection cycle may be defined as the interval of time the glassware is in such a position that light emanating from light sources 10, 12, and 14 will strike bottom 16 of a select piece of glassware.

Pulsing the light sources may be a preferred approach. The heat generated by the lights would not build-up as much if the lights are pulsed as if they were energized all of the time. Additionally, substantially the same power may be used to generate high intensity pulsed light during the inspection cycle as would be required to provide medium or low intensity light continuously. Regardless of the approach selected, conventional circuitry (not shown) may be used to either pulse the light sources or the light sensing means. In either embodiments, it is never required that the glass-ware be stopped.

Infrared light may be used as the light sources to simplify the detection procedure. Ambient light present in most glass manufacturing plants does not contain significant amounts of infrared. Accordingly, an infrared light sensing means would not be sensitive to extraneous light received from sources within the plant. There would be no need to shroud the inspection area as may be necessary if ordinary light is utilized for the inspection procedure.

It has been determined for flint glass that the angles of incidence A.sub.1, A.sub.2, and A.sub.3 should be between 5 degrees and 30 degrees preferably 15 degrees. The exact angle will vary depending on the glass and the wavelength of the light used. For example, the reflectivity of infrared would be different than the reflectivity of the light produced by a Xenon flash tube.

Light sources 10, 12, and 14 are adjustably mounted. Thus, the angles of incidence may be easily varied to accommodate set-up.

Light sources 10, 12, and 14 irradiate the inside surface 16 of glassware 2. Ideally, three light sources are utilized. The light is dispersed such that three light sources are sufficient to irradiate the desired area. In the absence of tramp glass or similar matter, substantially all of the light is reflected by surface 16. If tramp glass is present, the light striking same will be reflected and transmitted through the bottom surface. A sufficient amount of light will be transmitted to cause a response by light sensing means 8 which would then cause the rejection means 18 to reject the subject ware. Light sensor 8 may be a single light sensor or a plurality of light sensitive components. It may also be a television camera. Utilization of a television camera provides the operator with a visual output during set-up and also provides a selectable field of view. Conveniently, the camera may be positioned to receive light from any area of surface 16.

The present invention operates in a manner quite dissimilar to conventional check inspectors. A check inspector detects a check if light is reflected. The present invention detects tramp glass or fused glass if light is transmitted. A check is a flaw within the wall of the glassware, whereas tramp glass or fused glass is an imperfection external to the wall of the glassware.

The present invention is not severely limited nor is accurate inspection jeopardized by the presence of lettering on the sides or bottom of the container. The light being directed at the bottom of the container will not be significantly distorted by lettering appearing on the sides of the container. Of course, there could be sufficient lettering or designs on the side of the glassware to cause the light to be unduly attenuated.

The lettering on the outside surface of the bottom of the container does not interact with the light except when the light is being transmitted through the bottom, i.e., when tramp glass or its equivalent is present. When the light is being transmitted the lettering acts to disperse the light but does not prevent the light from reaching the light sensing means 8. Accordingly, the present invention permits the inspection of the bottom of glassware which carries lettering.

The present invention will function equally as well with glassware which does not have straight walls as it does with glassware that does have straight walls. An extremely convex container may cause the light to deviate in such a manner that irradiation of the bottom surface at the desired angle would be virtually impossible. The present invention will function well with flasks and other glassware not symmetrical in design.

FIG. 2 is a top view of the present invention and discloses the position of a piece of glassware during the inspection cycle.