GB2124380A

GB2124380A - Apparatus for non-contact thickness gauging of disc or sheet objects

Info

Publication number: GB2124380A
Application number: GB08319595A
Authority: GB
Inventors: Leif Duhrin
Original assignee: Esselte Security Systems AB
Current assignee: Esselte Security Systems AB
Priority date: 1982-07-27
Filing date: 1983-07-20
Publication date: 1984-02-15
Also published as: DE3326720A1; SE8204479L; SE454913B; SE8204479D0; GB2124380B; GB8319595D0

Abstract

The apparatus comprises at least two opposed gauges (1, 2), between which the object (3) e.g. a banknote is intended to pass, and a recording or corresponding unit (10). Each gauge (1, 2) of substantially known kind comprises a pneumatically operated gauge head (4, 5), of which the end (6) facing toward the object (3) consists of a preferably axial-symmetric disc- shaped portion (6) with at least one central outlet aperture (7) preferably for compressed air, which portion (6) aerodynamically is designed so that a definite air flow through said outlet aperture (7) is related to a definite distance to the object (3). The gauge head (4) of at least one gauge (1) is movable to and from the object (3), and a transducer unit (9) preferably for inductive measurement of said movement is provided and connected to said recording unit (10). <IMAGE>

Description

SPECIFICATION Apparatus for non-contact thickness gauging of disc or sheet objects This invention relates to an apparatus for gauging of objects of disc or sheet shape, for example of banknotes, the thickness or variations in thickness in a non-contact way, comprising at least two opposed gauges, between which the object is intended to pass, and a recording or corresponding unit for processing the gauging results.

Known methods of banknote thickness gauging are based on mechanic contact with the banknotes. These methods limit the speed of the banknote transport through the gauge.

Opto-electronic devices based on the reflection of light are known for non-contact measuring the variations in height on one side of a banknote, but not for gauging the thickness of the banknote.

Apparatuses of this kind, besides, involve disadvantages in the form of high costs due to high requirements on the precision of prisms and the like, and of a substantial maintenance demand.

The gauging result, moreover, also-can be unsafe, because the light beam reflected from black-print portions is deformed.

Apparatuses for non-contact gauging the thickness of strips are previously known. At some of these apparatuses each gauge consists of a nozzle, by which air is ejected against the object, and a measure of the distance between the nozzle and the object is obtained which is in the form of an air pressure. The variations in thickness are recorded as differences in pressure. Apparatuses of this kind have disadvantages which are connected with the compressibility of the air and the normally small magnitude of the pressure differences to be measured. These disadvantages express themselves in the form of reduced accuracy.

There is therefore a problem to produce an apparatus, which shows high gauging accuracy and low maintenance demand, and which is inexpensive and simple.

The invention relates to an apparatus for noncontact gauging of objects of disc or sheet shape, for example of banknotes, the thickness or variations in thickness, comprising at least two opposed gauges, between which the object is intended to pass, and a recording or corresponding unit for processing the gauging result.

The apparatus according to the invention is particularly characterized in that each gauge comprises a pneumatically operated gauge head, of which the end facing toward the object consists of a preferably axial-symmetric portion of disc shape with at least one central outlet aperture preferably for compressed air, which portion aerodynamically is designed so that a definite air flow through said outlet aperture is corresponded by a definite distance to the object, that the gauge head of at least one gauge is movable to and from the object, and that a transducer unit'preferably for inductive measurement of said movement is provided and connected to said recording unit.

The invention is described in greater detail in the following by way of an embodiment and with reference to the accompanying drawing, in which Fig. 1 is a schematic view of an apparatus according to the invention, seen in the longitudinal and movement direction of an object to be gauged, for example a banknote, Fig. 2 shows a gauging process with building-up portions at the beginning and terminal end of the object, Fig. 3 shows that side of a gauge head which is intended to face toward the object, where a first embodiment of an insert or corresponding detail is provided in the air outlet aperture, and Fig. 4 shows a gauge head in a way corresponding to Fig. 3, where a second embodiment of an insert or corresponding detail is provided in the air outlet aperture.

In Fig. 1 the numeral 1 designates a first one, and the numeral 2 designates a second one of two opposed gauges arranged in a certain spaced relationship. An object 3 of preferably disc or sheet shape, for example a banknote 3, is intended to pass between the gauges for gauging the thickness or variations in thickness of the object 3 by means of the gauges 1, 2.

Each gauge 1, 2 of a kind known per se comprises a pneumatically operated gauge head 4 and, respectively, 5, of which the end 6 facing toward the object 3 consists of a preferably axialsymmetric disc-shaped portion 6. The surface 6' of said portion which is intended to face toward the object is slightly curved, i.e. convex. The portion 6 also can be described as a substantially cylindric portion provided with a flange. 7 designates a central outlet aperture, preferably for compressed air, which opens to the object 3. The compressed air is supplied to the gauges 1, 2 via an intake 8 as indicated in Fig. 1. Each portion 6, of course, may be provided with several outlet apertures. The portion 6 aerodynamically is formed so that a definite air flow determined a.o.

by the air pressure is corresponded by a definite distance to the object 3 to be measured.

According to a first embodiment, the gauge head 4 only of one gauge 1 is movable to and from the object 3. The gauge 1 comprises a transducer unit 9 of substantially known kind for inductive measurement of the movement of the gauge head 4. The transducer unit 9 is connected to a recording unit 10 for processing the result of the gauging. The gauge head 5 of the second gauge 2 is stationary.

At least the movable gauge head 4 is designed so as to have low weight, and preferably it is manufactured of plastic or the like whereby building-up processes 11, 12 in Fig. 2 of only a small extent are obtained primarily at great position changes of the gauge head, as at position changes A, B corresponding to the ends of the object 3. In Fig. 2 a corresponds to movement, and t to time.

The recording unit is arranged in a known suitable manner so that measuring results sequential during a predetermined time, such as the time p in Fig. 2, after a gauge head movement of predetermined amplitude are excepted from processing. Hereby the effect of the beginning end of the object, at A in Fig. 2, and of the terminal end, at B in Fig. 2, is eliminated.

According to a second embodiment, also the gauge head 5 is movable, as indicated by a dashed arrow in Fig. 1. The gauge head, of course, also is designed to have low weight. Even at this embodiment, however, preferably only one gauge head, for example gauge head 4, is provided with a transducer unit 9 connected to the recording unit.

In Figs. 3 and 4 preferred embodiments of the air outlets of the portions 6 are shown. At the embodiment according to Fig. 3, a substantially circular insert 1 3 is located in the aperture 7 so that a circular gap 14 is formed, through which air is intended to flow out. At the embodiment according to Fig. 4, in the aperture 7 an insert 1 5 of substantially circular sector shape is located, the pointed portion of which preferably is directed to the direction, indicated by a dashed arrow, in which the object 3 is intended to be moved past the gauge head.

At one embodiment of the apparatus according to the invention, the movable gauge head 4 carrying a transducer unit is provided with an insert 13, Fig. 3, and the opposed gauge head 5 is provided with an insert 15, Fig. 4.

The mode of operation of the apparatus according to the invention substantially should have become apparent from the aforesaid. The object 3, for example a banknote, is caused to pass between the gauge heads 4, 5. When the gauge head 5 is stationary, the object 3 due to the configuration of the portion 6 is sucked inward to the gauge head 5 and maintained at well-defined distance therefrom. In this way a well-defined reference position of the object 3 is obtained. The movable gauge head 4, due to the configuration of the portion 6, remains at a definite distance from the surface of the object 3 facing toward the gauge head 4.The movement of the gauge head 4 is measured by means of the inductive transducer 9, and the results of the measuring are transferred to and processed by the recording unit where the movement is a measure of the thickness or variation in thickness of the object 3.

At the embodiment where each of two opposed gauge heads 4, 5 are movable, the positions of the object and gauge heads in a corresponding manner are adjusted so that the distance of the heads to the respective object side is maintained constant, and the movements of the gauge head 4 are recorded.

The apparatus is a very simple, inexpensive and reliable equipment for gauging the thickness and variations in thickness of sheet objects, for example banknotes. The equipment is adapted for recording rapid processes and, therefore, a high object speed can be used.

The invention has been described above with reference to some embodiments. It is, of course, possible to imagine more embodiments and minor alterations without abandoning the invention idea.

The movement of a movable gauge head, for example, can be measured in a way other than inductive, for example in a mechanic way. Also more than two gauge heads, for example four, can be imagined be comprised in an apparatus according to the invention, in which case the recording unit is fed from more transducers.

The invention, thus, must not be regarded restricted to the embodiments set forth above.

Claims

1. An apparatus for rion-contact gauging of objects of disc or sheet shape, for example banknotes, the thickness or variations in thickness, comprising at least two opposed gauges, between which the object is intended to pass, and a recording or corresponding unit for processing the gauging results, characterized in that each gauge (1, 2) comprises a pneumatically operated gauge head (4, 5), of which the end (6) facing toward the object (3) consists of a preferably axial-symmetric disc-shaped portion (6) with at least one central outlet aperture (7) preferably for compressed air, which portion (6) aerodynamically is designed so that a definite air flow through said outlet aperture (7) is corresponded by a definite distance to the object (3), that the gauge head (4) of at least one gauge (1) is movable to and from the object (3), and that a transducer unit (9) preferably for inductive measurement of said movement is provided and connected to said recording unit (10).

2. An apparatus as defined in claim 1, characterized in that said outlet aperture (7) is substantially circular and comprises an insert (13, 15) or corresponding detail with either substantially circular configuration so that a circular outlet gap is formed, or with substantially the configuration of a circular sector where the pointed portion of the insert (1 5) is directed preferably to the direction, in which an object (3) is intended to be moved past the gauge head.

3. An apparatus as defined in claim 1 or 2, characterized in that each of two opposed gauged heads (4, 5) are movable to and from the object (3).

4. An apparatus as defined in claim 3, characterized in that the outlet aperture (7) of one gauge head (4) comprises a circular insert (13), and the outlet aperture (7) of the second gauge head (5) comprises a sector-shaped insert (1 5).

5. An apparatus as defined in claim 1, 2, 3 or 4, characterized in that at least each movable gauge head (4) is designed so as to have low weight, for example manufacture of plastic or the like, whereby building-up processes of only a small extent are obtained at position changes of the gauge head (4), such as at position changes (A, B) corresponding to the ends of the object (3).

6. An apparatus as defined in claim 1, 2, 3, 4 or 5, characterized in that said recording unit (10) is designed so that gauging results sequential during a predetermined time (p) after a gauge head movement of a predetermined amplitude are excepted from processing, whereby the effect of the beginning and terminal end of the object is eliminated.

7. An apparatus for non-contact gauging of objects of disc or sheet shape, substantially as any described herein with reference to the accompanying drawings.