Apparatus for forming an erasable record of the value of a measured quantity

In a recording apparatus operative for making and erasing records of the values of a measured quantity on a transported record carrier of the type having characteristics alterable by means of magnetic fields, particularly a record carrier made of a material which can be caused to assume a first state by passing a magnetic field through the record carrier normal thereto and which can be caused to assume a visually distinguishable second state by establishing in the general plane of the record carrier two magnetic fields which are oriented generally perpendicular to each other, in combination, a writing unit operative for forming a recording trace on the record carrier during record carrier transport, the writing unit comprising first means operative for generating a radial field lying in the general plane of the record carrier, the field because it is radial being comprised of field components which are oriented generally perpendicular to each other and which furthermore are oriented at angles to the record carrier transport direction;

• and an erasing unit for erasing the recording traces formed by the writing unit, the erasing unit comprising second means for operative for establishing a magnetic field which extends transverse to the record carrier transport direction and which is comprised of field lines passing through the record carrier normal thereto, the first means forming a magnetic circuit and being comprised of a permanent magnet, a cup-shaped flux return body having an annular end, and a ferromagnetic writing element arranged concentric to the return body, the end of the writing element and the annular end of the cup-shaped return body together defining an annular air gap.

In a recording apparatus operative for making and erasing records of the values of a measured quantity on a transported record carrier of the type having characteristics alterable by means of magnetic fields, particularly a record carrier made of a material which can be caused to assume a first state by passing a magnetic field through the record carrier normal thereto and which can be caused to assume a visually distinguishable second state by establishing in the general plane of the record carrier two magnetic fields which are oriented generally perpendicular to each other, in combination, a writing unit operative for forming a recording trace on the record carrier during record carrier transport, the writing unit comprising first means operative for generating a radial field lying in the general plane of the record carrier, the field because it is radial being comprised of field components which are oriented generally perpendicular to each other and which furthermore are oriented at angles to the record carrier transport direction and an erasing unit for erasing the recording traces formed by the writing unit, the erasing unit comprising second means operative for establishing a magnetic field which extends transverse to the record carrier transport direction and which is comprised of field lines passing through the record carrier normal thereto, the first means forming a magnetic circuit and being comprised of an electrically controllable magnet, a cup-shaped flux return body having an annular end, and a ferromagnetic writing element arranged concentric to the return body, the end of the writing element and the annular end of the cup-shaped return body together defining an annular air gap.

In a recording apparatus operative for making and erasing records of the values of a measured quantity on a transported record carrier of the type having characteristics alterable by means of magnetic fields, particularly a record carrier made of a material which can be caused to assume a first state by passing a magnetic field through the record carrier normal thereto and which can be caused to assume a visually distinguishable second state by establishing in the general plane of the record carrier two magnetic fields which are oriented generally perpendicular to each other, in combination, a writing unit operative for forming a recording trace on the record carrier during record carrier transport, the writing unit comprising first means operative for generating a radial field lying in the general plane of the record carrier, the field because it is radial being comprised of field components which are oriented generally perpendicular to each other and which furthermore are oriented at angles to the record carrier transport direction;

• and an erasing unit for erasing the recording traces formed by the writing unit, the erasing unit comprising second means operative for establishing a magnetic field which extends transverse to the record carrier transport direction and which is comprised of field lines passing through the record carrier normal thereto, the first means forming a magnetic circuit and being comprised of two pole plates located in parallel planes, a permanent magnet intermediate the pole plates, and a ferromagnetic writing element mounted on one pole plate, the other pole plate having an aperture, and the writing element extending from the one pole plate through the aperture in the other pole plate and toward the record carrier, the outer periphery of the writing element and the rim of the aperture together forming an annular air gap.