Coin handling – Supply level detector – Electric
Patent
1994-04-12
1996-03-26
Bartuska, F. J.
Coin handling
Supply level detector
Electric
2502221, G07F 902
Patent
active
055016332
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to coin mechanisms having one or more coin storage tubes, in which the level of coins stored in the storage tubes is sensed, for example, for the purpose of detecting whether the tube is nearly full, or is nearly empty. For the purposes of this specification the term "tube" is used, as is usual in this art, to mean any structure adapted to accommodate coins stacked face-to-face.
BACKGROUND OF THE INVENTION
As is well known, information about the level of coins in coin tubes may be used, among other things, for the purpose of controlling the delivery of tested and accepted coins to the tubes, and the dispensing of coins from the tubes, so as to avoid the problems of attempting to over-fill a tube, which would cause jamming, and attempting to dispense from an empty tube.
In the applicants' EP-B-0017428 there was disclosed an optical sensor which has proved successful and been widely used, in which a light beam from a light source crosses the tube, is internally reflected twice at the wedge-shaped end portions of a trapezoidal prism, so as to turn the beam through 180.degree., and returns across the tube to a light detector
For the purpose of the present specification the term "light" is not of course confined to the optical part of the spectrum.
The above-mentioned arrangement has certain advantages, such as the folded light beam covering a larger area than a straight beam so as to more reliably sense coins which occasionally are at an angle within the tube, and the fact that the source and detector can be at the same side of the tube so that electrical connections can be made from one side only. The prism can be fitted to, or built into, the tube itself.
It has been found, however, that such detectors have limitations which become more severe as the total length of the path of the light beam from the source to the detector increases. In particular, the power available from the beam for activating the detector falls, and this is aggravated by the fact that small relative misalignments of the source, prism and detector further reduce the power that the detector actually receives.
The first of these problems can be reduced by increasing the power input to the source, but this reduces the useful lifetime of the source itself. The second problem can be reduced by increasing the size of the internally reflecting end faces of the prism, so as to increase the area of the light beam that can traverse the system, but this involves making the prism not-only wider, but also deeper, so that it starts to take up an unacceptable volume within the coin mechanism, where compactness is desired. Further disadvantages of such detectors are that light is lost from the beam where it is transmitted through two surfaces of the prism, where it is reflected at two other surfaces of the prism, and also during its transmission through the material of the prism, which further reduces the power available to activate the detector; and, for a given prism size, the area of the beam that can be reflected through 180.degree. is less than half the area of the entry and exit face of the prism because of the need for two independent reflection steps.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a coin mechanism having an optical coin level sensor which suffers less from these disadvantages.
According to the invention there is provided a coin mechanism having a coin storage tube and an optical sensor for sensing the level of coins in the tube, the sensor comprising a light source arranged to direct a light beam across the tube, means for returning the beam across the tube and a light detector for detecting the returned beam, characterised in that the means for returning the beam is a concave mirror having a curvature such as to give the beam an area, where it approaches the detector, substantially greater than the effective area of the detector.
The concave mirror concentrates the flux of the beam, relative to the prior system where only flat internally reflecting
REFERENCES:
patent: 3419725 (1968-12-01), Dwyer
patent: 4286703 (1981-09-01), Schuller et al.
patent: 4374529 (1983-02-01), Kobayashi et al.
"Coin Sense Unit for Coin Dispenser," IBM Technical Disclosure Bulletin, vol. 29, No. 10B, Mar. 1985, pp. 5956-5957.
Watkins Keith J.
Winstanley Nigel A.
Bartuska F. J.
Mars Incorporated
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