JPS6245182Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a magnetic detector that uses a bias magnetic field to detect magnetic components contained in paper sheets.

In paper sheet identification devices, it is common practice to detect patterns printed with a minute amount of ferromagnetic material, so-called magnetic ink, etc. contained in paper sheets, and use this as an effective means of identification. In this case, a magnetic head or a detector incorporating a magnetoresistive element such as an InSb crystal as shown in FIG. 1 is used as a detector. In the detector shown in FIG. 1, a magnet 3 made of a permanent magnet or an electromagnet having a magnetically sensitive part 2 made of a magnetic resistance element at the end is arranged in a housing 1 having a U-shaped cross section. This magnet 3 is adapted to apply a bias magnetic field to the magnetically sensitive section 2. Further, a metal plate 4 made of a non-magnetic material such as tungsten is attached to the opening 1a of the housing 1 by appropriate means to protect the magnetically sensitive part 2. In the figure, 5 is a signal line. In this detector, when the paper sheet 6 to be detected passes near the magnetic sensing part 2, the ferromagnetic material in the paper sheet 6 changes the bias magnetic field, and as a result, the resistance of the magnetoresistive element It is configured so that the value changes and is output as an electrical signal from the signal line 5.

However, with this type of magnetic detector, when the paper sheet is dry or electrically charged, the element is affected by electrostatic induction and noise occurs, making it impossible to obtain a stable signal. There were disadvantages such as the trouble of replacing the

This invention was developed based on the above circumstances, and it is possible to eliminate static electricity, which is a source of noise, and easily replace the sliding surface that wears out. Furthermore, the structure is extremely simple, and it is reliable. The object of the present invention is to provide a magnetic detector that can be supplied at low cost with high quality.

This invention will be explained with reference to an embodiment shown in the drawings.

Fig. 2 is a perspective view showing an embodiment of the magnetic detector of this invention, Fig. 3 is a sectional view of the same, Fig. 4 is a perspective view showing a state in which the protection member is moved, and Fig. 5 is a perspective view of the protection member. FIG. In each figure, 10 is a magnetic detector, and this magnetic detector 10 is equipped with a housing 11 having a U-shaped cross section.
1 has a magnetic sensing part 12 at its end consisting of a magnetic resistance element.
A magnet 13, which is a permanent magnet or an electromagnet, is arranged. This magnet 13 is connected to the magnetically sensitive section 12.
A bias magnetic field is applied to the Further, a metal plate 14 made of a non-magnetic material such as tungsten is attached to the opening 11a of the housing 11 by appropriate means to protect the magnetically sensitive part 12. A signal line 15 is connected to the magnetically sensitive section 12 to send a signal to another control device (not shown). Engaging portions, such as grooves 16, are formed on opposing sides of the housing 11, respectively. Engaging portions of a sliding member 17 made of a non-magnetic material such as tungsten, such as protrusions 18, are detachably attached to the grooves 16 (see FIGS. 2 and 4). Projection piece 1 of this sliding member 17
8 is held in the groove 16 of the housing 11 by friction. The sliding member 17 made of a non-magnetic material has a sliding portion 17a that is connected to the metal plate 1 in the front portion of the magnetically sensitive portion 12.
4 and is located in close contact with the sliding member 17
is grounded via a lead wire 20. When the paper sheet 19 passes through this sliding portion 17a, the ferromagnetic material in the paper sheet 19 causes a change in the bias magnetic field, and as a result, the resistance value of the magnetoresistive element changes and the signal line It is configured to output as an electrical signal via 15. Although the sensitivity of such a magnetic detector 10 is somewhat lower than that of a conventional magnetic detector, there is no problem in magnetic detection of paper sheets.

Furthermore, when the sliding portion 17a of the sliding member 17 is worn out by paper sheets 19 when the magnetic detector 10 is used, the sliding portion 17a of the sliding member 17 is moved along the groove 16 of the housing 11. The protruding piece 18 is slid to separate the sliding member 17 from the housing 11 and release the lead wire 20 of the sliding member 17 from the ground. Then, the protruding piece 18 of the new sliding member 17 is inserted into the cut groove 16 of the housing 11.
, the sliding portion 17a of the sliding member 17 is positioned on the magnetically sensitive portion 12 of the housing 11, and the lead wire 20 of the sliding member 17 is grounded.

In the above embodiment, the sliding member 17 is attached by fitting the projection 18 of the sliding member 17 into the groove 16 of the housing 11 and holding it by friction between the two. However, the invention is not limited to this, and as shown in FIG.
Stopper part 2 at one end (upper end in the figure)
1, respectively, prevents displacement in the vertical direction and enables more reliable fixing. Alternatively, the detector and sliding member may be fixed to a support base (not shown) as one body via a fixing device such as a screw (not shown), instead of using frictional fixing as described above. It is also possible to omit the lead wire. Furthermore, the metal plate 14 of the casing 11 of the magnetic detector 10 is not necessarily provided, and if omitted, the gap between the magnetically sensitive part 12 and the sliding member 17 can be reduced, which reduces the sensitivity. This means that it can be prevented.

It should be noted that the above embodiment is merely an example, and it goes without saying that each member can be replaced with another member having the same function.

Since this device is configured as described above, the static electricity charged on the paper sheet is grounded through the sliding member, preventing the generation of noise sources and detecting a stable signal, which eliminates static electricity noise. No special equipment such as a neutralizing roller is required for removal, and when the sliding surface becomes worn due to the sliding of paper sheets, the sliding member can be replaced with a simple operation. , maintenance costs can be significantly lower than conventional ones, which require replacing the entire unit. Moreover, it has excellent effects such as being able to supply a product with an extremely simple structure and extremely high reliability at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a conventional magnetic detector, Fig. 2 is a perspective view showing an embodiment of the magnetic detector of this invention, Fig. 3 is a sectional view thereof, and Fig. 4 shows a protective member. FIG. 5 is a perspective view of the protection member in a moved state. 10... Magnetic detector, 11... Housing, 12...
Magnetic sensing part, 13... magnet, 14... metal plate, 15...
...Signal line, 16...Engaging part, 17...Sliding member,
18... Projection piece, 19... Paper sheet, 20... Lead wire, 21... Stopper portion.

Claims (1)

[Claims for Utility Model Registration] (1) The housing has at least a magnetic bias magnet and a magnetic sensing part, and a bias magnetic field is formed near the detection part to detect minute amounts of magnetic material contained in paper sheets. What is claimed is: 1. A magnetic detector characterized in that a sliding member made of a non-magnetic material that is in close contact with the detection portion and is grounded is removably disposed in a housing. (2) The magnetic detection device according to claim 1 of the utility model registration claim, characterized in that the magnetic detection device is configured to be detachable by a protrusion provided on the sliding member and a cut groove provided in the casing. vessel. (3) The magnetic detector according to claim 1 or 2, wherein the sliding member is grounded via a lead wire.