WO1999067135A1

WO1999067135A1 - A channel starvation detector

Info

Publication number: WO1999067135A1
Application number: PCT/IB1999/001162
Authority: WO
Inventors: Klaus Peter Lamm
Original assignee: TOBACCO RESEARCH AND DEVELOPMENT INSTITUTE Ltd
Current assignee: TOBACCO RESEARCH AND DEVELOPMENT INSTITUTE Ltd
Priority date: 1998-06-22
Filing date: 1999-06-21
Publication date: 1999-12-29
Anticipated expiration: 2000-12-22
Also published as: WO1999067135A8; AU4160499A

Abstract

A channel starvation detector (28) for detecting an interruption in the passage of a series or string of cigarettes (22) through a channel (20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7) is provided. The detector (28) includes an optical fibre cable (32) comprising seven individual pairs of transmit (36.1) and receive (36.2) optical fibres positioned to detect variations in received light arising from the steady passage of the cigarettes (22) through the channel (20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7), and to generate an alarm or stop signal in the event of a blockage or void arising in the channel (20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7). The transmit (36.1) and receive (36.2) fibres are positioned to receive a reflected optical signal in such a way that a fluctuating reflected signal arises from the steady passage of the cigarettes (22) through the channel (20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7) and a constant reflected signal arises from a blockage or void in the channel (20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7).

Description

A CHANNEL STARVATION DETECTOR

BACKGROUND TO THE INVENTION

THIS invention relates to a channel starvation detector, and in particular to a channel starvation detector for detecting blockages and the like in the channel through which a series of articles is fed.

After manufacture, cigarettes are typically fed into a hopper, the lower end of which is provided with a series of converging vanes defining a corresponding series of channels for channeling the cigarettes into a configuration in which they are suitable for packing, such as a stacked 7-6-7 configuration. Often, due to the close tolerances involved, blockages arise in the channels. This is known in the industry as "channel starvation". Various different solutions have been proposed and implemented in order to overcome this problem.

One type of detector manufactured by Molins Tobacco Machinery Limited includes a number of L-shaped fingers which are pivoted in such a way that the ends of the fingers abut against the smoking ends of the cigarettes as they are gravity fed down the individual channels. A blockage in the channel upstream of a particular finger will cause the finger to swing inwardly into the space previously occupied by a cigarette end. This inward movement is detected by an optical beam. One disadvantage of this arrangement is that it is only suitable for the detection of a void arising from an upstream blockage. If cigarettes are blocked downstream of the sensing finger, then it will not register anything, as there will be no inward deflection of the finger indicative of a blockage-induced void, and the blocked channel will appear as a channel through which cigarettes are passing at a constant rate. SUMMARY OF THE INVENTION

According to the invention there is provided a channel starvation detector for detecting an interruption in the passage of a series or string of articles through a channel, the detector comprising optical sensing means positioned to detect variations in received light arising from the steady passage of the articles through the channel, and to generate an alarm or stop signal in the event of a blockage or void arising in the channel.

In a preferred form of the invention, the optical sensing means comprises an optical transmitter for transmitting an optical signal onto the articles and an optical receiver for receiving a reflected optical signal from the articles.

Advantageously, the optical transmitter is positioned to transmit the optical signal onto the articles and the optical receiver is positioned to receive the reflected optical signal in such a way that a fluctuating reflected signal arises from the steady passage of the articles through the channel and a constant reflected signal arises from a blockage or void in the channel.

Typically, the articles are rod-like in form, and the optical receiver is arranged to sense fluctuation in reflected light arising from nips or gaps between the articles.

Conveniently, the optical transmitter and the optical receiver are arranged, respectively, to transmit and receive light in a direction normal to the central axes of the rod-like articles.

Preferably, the detector includes a plurality of adjacent channels separated by a series of channel-defining guide vanes, with strings of articles being gravity fed through each of the channels, each of the channels being provided with an optical transmitter and an optical receiver, a plurality of which in combination makes up an array.

Typically, each of the guide vanes are formed with notches and the array of optical transmitters and receivers include a bundle of optical fibre pairs, with each pair terminating in a probe extending in use into a notch.

The array of optical transmitters and receivers may be mounted on a door or flap covering the vanes and arranged to restrict axial movement of the rod-like articles within the vanes.

Typically, the rod-like articles are smoking articles, and the guide vanes form part of a converging guide vane assembly at the base of a smoking article hopper, with a pusher being located at the base of the vanes for cyclically pushing out bundles of smoking articles.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a partly cut-away side view of a channel starvation detector of the invention mounted in position on a guide vane assembly;

Figure 2 shows a partly cross-sectional detail of a single optical sensor mounted in position; and

Figure 3 shows a pictorial detail of one fibre optic sensor forming part of the channel starvation detector of Figures 1 and 2. DESCRIPTION OF EMBODIMENTS

Referring first to Figure 1, a guide vane assembly 10 is shown extending towards the base of a cigarette hopper 12. The vane assembly 10 comprises an outer slanted wall 14, an inner curved wall 16 and a series of six converging vanes 18.1 to 18.6 which define a corresponding array of converging channels 20.1 to 20.7. These channels are each dimensioned to receive a column of cigarettes 22 which are gravity fed downwardly through the channels to a point where the thickness of each vane is reduced to around 0.5mm, at which point a cigarette pusher (not shown) pushes the lowermost three cigarettes in each channel into a cigarette collating turret for subsequent packaging. The cigarette pusher operates cyclically at a constant rate, as a result of which, in the normal course of events, the movement of the column of cigarettes 22 trickling down each channel is fairly constant.

Mounted to the outer wall 14 on a pair of hinges, one of which is shown at 23, is a perspex door 24 through which the cigarette ends can be viewed. The inner surface 26 of the perspex door 24 also serves to restrict axial displacement of the columns of cigarettes as they are passing through the channels. A channel starvation detector 28 of the invention is bolted to the outer surface of the door 24. The channel starvation detector 28 includes an outer housing 30, and a fourteen core optical fibre cable 32 extending into the housing 30 via a cable gland 34, with a bundle of 14 optical fibres 36 extending from an exposed end of the cable. The bundle comprises seven individual pairs of transmit and receive fibres 36.1 and 36.2 which extend obliquely through a sleeve 38 mounted within an angled channel 40 forming part of a sleeve support bracket 42. Each of the transmit and receive fibres 36.1. and 36.2 terminate in an L- shaped probe portion 44 which extends through an aperture 46 formed in the door 24 and terminates within a notch 48 defined within each vane.

The individual transmit and receive optic fibres terminate at a cutout 50, and are arranged, respectively, to direct and receive a beam of light substantially normal to the plane of the cutout 50. Light is transmitted via the transmitting fibre 36.1 in the direction of arrow 52 and is reflected off the paper of the string of cigarettes as they are fed downwardly through the channels. It has been found that the light reflected off the passing cigarettes and received by the optical receiver 36.2 diminishes by about 50% when the transmitted light is directed towards the nips 54 between adjacent cigarettes, with the reflected light reaching a maximum intensity at the so-called tangent of each cigarette, at the point 56 where the outer diameter of each cigarette impinges on or is closest to the side wall of the channel. During normal operation, a received optical signal having a cyclically varying intensity results, cycling between a minimum nip reflection and a maximum tangent reflection. The optical signals are converted to electrical signals, which are processed at a central control unit. The electrical signals may be compared to a set of parameters corresponding to the maximum and minimum expected transition periods between maximum and minimum reflection. In a more sophisticated form of the invention, the signals may be compared with a signal profile stored in a comparator, with the profile corresponding to the variation in signal strength at an ideal feed speed.

In addition to being capable of monitoring feed speed fairly accurately, the channel starvation detector is also able to sense a blockage both upstream and downstream of the optic sensors. In the event of an upstream blockage, a void will exist, with the result that the optical signal will be reflected off the opposite wall of the vane 18.1, in the case of the first channel 20.1. In the case of a matt black wall, the reflected signal will be almost non existent, which will immediately register at the central control unit.

A downstream blockage will cause the column of cigarettes 22 to accumulate in the channel, and, as is the case with an upstream blockage, there will be no variation in the received reflected signal, which will similarly be registered at the control unit. In response to either of these events occurring, the control unit may in turn trigger an alarm signal which will immediately draw the attention of the operator to the problem and allow him or her to stop the machinery and attend to the blockage. Alternatively, and preferably, a stop signal is generated to automatically stop the machinery for a predetermined period, typically corresponding to three transition cycles, after the blockage has been sensed. The signal processing circuitry can be relatively simple, in that it is arranged to sense the receipt of a constant or unwavering signal, which, whatever the amplitude, is indicative of an upstream or downstream blockage.

The invention is not confined to the processing of cigarettes, but may also be used to monitor the progress of any train of substantially identical articles through a channel during or after manufacture and prior to packing thereof.

Claims

1. A channel starvation detector for detecting an interruption in the passage of a series or string of articles through a channel, the detector comprising optical sensing means positioned to detect variations in received light arising from the steady passage of the articles through the channel, and to generate an alarm or stop signal in the event of a blockage or void arising in the channel.

2. A channel starvation detector according to claim 1 in which the optical sensing means comprises an optical transmitter for transmitting an optical signal onto the articles and an optical receiver for receiving a reflected optical signal from the articles.

3. A channel starvation detector according to claim 2 in which the optical transmitter is positioned to transmit the optical signal onto the articles and the optical receiver is positioned to receive the reflected optical signal in such a way that a fluctuating reflected signal arises from the steady passage of the articles through the channel and a constant reflected signal arises from a blockage or void in the channel.

4. A channel starvation detector according to claim 3 in which the articles are rod-like in form, and the optical receiver is arranged to sense fluctuation in reflected light arising from nips or gaps between the articles.

5. A channel starvation detector according to claim 4 in which the optical transmitter and the optical receiver are arranged, respectively, to transmit and receive light in a direction normal to the central axes of the rod-like articles.

6. A channel starvation detector according to any one of the preceding claims 2 to 5 which includes a plurality of adjacent channels separated by a series of channel-defining guide vanes, with strings of articles being gravity fed through each of the channels, each of the channels being provided with an optical transmitter and an optical receiver, a plurality of which in combination makes up an array.

7. A channel starvation detector according to claim 6 in which each of the guide vanes are formed with notches and the array of optical transmitters and receivers include a bundle of optical fibre pairs, with each pair terminating in a probe extending in use into a notch.

8. A channel starvation detector according to claim 7 in which the array of optical transmitters and receivers is mounted on a door or flap covering the vanes and arranged to restrict axial movement of the rod-like articles within the vanes.

9. A channel starvation detector according to claim 8 in which the rod-like articles are smoking articles, and the guide vanes form part of a converging guide vane assembly at the base of a smoking article hopper, with a pusher being located at the base of the vanes for cyclically pushing out bundles of smoking articles.