GB1570010A - Method of producing a magnetic core for a magnetic head - Google Patents

Description

(54) METHOD OF PRODUCING A MAGNETIC CORE FOR A MAGNETIC HEAD (71) We, GRUNDIG E.M.V. ELEK TRO-MECHANISCHE VERSUCHSAN STALT MAX GRUNDIG, a German corporate body of Kurgartenstrasse 37, D-8510 Furth, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a method of reproducing a magnetic core for a magnetic head for recording, reproducing and/or erasing magnetic information.

Mechanical means are used in the methods hitherto known for introducing, into the magnetic core for a magnetic head, the window necessary for the wire coil. In this case, using methods known per se, a groove is introduced into one or both halves of a block from which the magnetic cores are pared, so that after the two halves of the block are joined together to form a uniform body, a closed coil window and the necessary transducing gap result. The individual, thin magnetic cores are obtained by paring from the block and are secured in pairs to head wheels. The required profiling is achieved by a head mirror machining carried out subsequently. In this case, it is a disadvantage that, as a result of deviations from the specified size during the preceding operations, the required values for height of transducing gap and radial dimensions (distance from polished surface of head to centre of wheel) frequently cannot be achieved during this grinding process and, in addition, as a result of the mechanical machining of the grooves in the halves of the block and in particular when paring the individual magnetic cores from the block the edges at the coil window and particularly at the transition to the transducing gap break out or away and this leads to an increased number of rejects in the magnetic-cores or to disadvantageous differences in the electrical head values. A subsequent mechanical introduction of the coil window by the method of machining hitherto used does not overcome this disadvantage because the highly sensitive magnetic cores are destroyed during such operations.

This invention provides a method of producing a magnetic core for a magnetic head for recording, reproducing and/or erasing magnetic information, comprising the steps of providing an initial magnetic core and then using a focussed laser beam to form a coil window therein, or to enlarge a said window in the direction of a taperunning surface of the magnetic core whereby the depth of the transducing gap in the magnetic core is produced to an accuracy of 2-3 Fm. This method eliminates the abovedescribed disadvantage and reduces the cost of production of the magnetic core considerably, with the particular advantage that the transducing gap depth which results, between the tape running surface and the opening face of the window opposite it, can be produced with an error of less than 2-3 Fm.

In general, the magnetic core will be less than 300 Fm in thickness and will be formed of any suitable oxidic, ferromagnetic material.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an initial block, produced in accordance with the prior art hitherto known, for the production of individual magnetic core, Figure 2 shows an initial magnetic core, provided without any window for the wire coil; and Figure 3 shows the magnetic core of Figure 2 after a window for the wire coil has been introduced therein.

Figure 1 shows a ferrite block 1 which has been manufactured in accordance with the known prior art and which already has the outside contours of the later magnetic cores 2, 2', 2" which result from subsequent paring from the block 1. The block 1 is joined together from two members 3 and 4. These each comprise a groove in the plane 6 of the tranducing gaps so that, after the joining together of the two members 3 and 4, a window 5 results for the wire coil associated with the eventual magnetic core. According to the method hitherto known, the necessary radial dimensions were only produced after the magnetic cores had been pared from the ferrite block and secured in pairs to head wheels, by appropriate removal of material from the tape running surface, in which case the transducing gap depth 7 only reached the required value if the position of that edge of the winding space or recess closest the tape running surface displayed no deviations from the desired value.

Figure 2 shows a magnetic core 2 which has been pared from a ferrite block, the two members 3 and 4 of which do not comprise any grooves in the gap region 6.

Figure 3 shows the magnetic core 2 of Figure 2 wherein the coil window, for receiving the wire coil, has been introduced by a focussed laser beam in accordance with the invention so that the transducing gap depth 7 has the necessary final dimensions.

By use of the focussed laser beam, the depth of the transducing gap can be produced with an error of less than 2-3 ssm.

The tape running surface may be given its necessary shape and surface quality on the initial block. Alternatively, it may be given this necessary shape and surface quality when two such magnetic poles are mounted together, as described in connection with Figure 1.

The focussed laser beam may be used to form the entire coil window, or alternatively it may be used simply to widen out or enlarge an existing window in the direction of the tape running surface. The window may be enlarged only after the wire coil has been fitted.

WHAT WE CLAIM IS: 1. A method of producing a magnetic core for a magnetic head for recording, reproducing and/or erasing magnetic information, comprising the steps of providing an initial magnetic core and then using a focussed laser beam to form a coil window therein, or to enlarge a said window in the direction of a tape-running surface of the magnetic core, whereby the depth of the transducing gap in the magnetic core is produced to an accuracy of 2-3 Rm.

2. A method as claimed in claim 1, in which said initial magnetic core is formed by paring from an initial block.

3. A method as claimed in claim 2, in which said block comprises two members joined together on a plane extending through the transducing gaps of the magnetic cores pared therefrom.

4. A method as claimed in claim 3 or 4, in which the tape running surface is given its necessary shape and surface quality on said initial block.

5. A method as claimed in claim 1, 2 or 3, in which the tape running surface is given its necessary shape and surface quality when two such magnetic cores are mounted together.

6. A method as claimed in any preceding claim, in which the coil window is enlarged by said focussed laser beam only after the coil has been fitted.

7. A method as claimed in any preceding claim, in which said magnetic core is less than 300 Fm in thickness.

8. A method as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.

9. A magnetic core produced by a method as claimed in any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. Figure 1 shows a ferrite block 1 which has been manufactured in accordance with the known prior art and which already has the outside contours of the later magnetic cores 2, 2', 2" which result from subsequent paring from the block 1. The block 1 is joined together from two members 3 and 4. These each comprise a groove in the plane 6 of the tranducing gaps so that, after the joining together of the two members 3 and 4, a window 5 results for the wire coil associated with the eventual magnetic core. According to the method hitherto known, the necessary radial dimensions were only produced after the magnetic cores had been pared from the ferrite block and secured in pairs to head wheels, by appropriate removal of material from the tape running surface, in which case the transducing gap depth 7 only reached the required value if the position of that edge of the winding space or recess closest the tape running surface displayed no deviations from the desired value. Figure 2 shows a magnetic core 2 which has been pared from a ferrite block, the two members 3 and 4 of which do not comprise any grooves in the gap region 6. Figure 3 shows the magnetic core 2 of Figure 2 wherein the coil window, for receiving the wire coil, has been introduced by a focussed laser beam in accordance with the invention so that the transducing gap depth 7 has the necessary final dimensions. By use of the focussed laser beam, the depth of the transducing gap can be produced with an error of less than 2-3 ssm. The tape running surface may be given its necessary shape and surface quality on the initial block. Alternatively, it may be given this necessary shape and surface quality when two such magnetic poles are mounted together, as described in connection with Figure 1. The focussed laser beam may be used to form the entire coil window, or alternatively it may be used simply to widen out or enlarge an existing window in the direction of the tape running surface. The window may be enlarged only after the wire coil has been fitted. WHAT WE CLAIM IS:

1. A method of producing a magnetic core for a magnetic head for recording, reproducing and/or erasing magnetic information, comprising the steps of providing an initial magnetic core and then using a focussed laser beam to form a coil window therein, or to enlarge a said window in the direction of a tape-running surface of the magnetic core, whereby the depth of the transducing gap in the magnetic core is produced to an accuracy of 2-3 Rm.

2. A method as claimed in claim 1, in which said initial magnetic core is formed by paring from an initial block.

3. A method as claimed in claim 2, in which said block comprises two members joined together on a plane extending through the transducing gaps of the magnetic cores pared therefrom.

4. A method as claimed in claim 3 or 4, in which the tape running surface is given its necessary shape and surface quality on said initial block.

5. A method as claimed in claim 1, 2 or 3, in which the tape running surface is given its necessary shape and surface quality when two such magnetic cores are mounted together.

6. A method as claimed in any preceding claim, in which the coil window is enlarged by said focussed laser beam only after the coil has been fitted.

7. A method as claimed in any preceding claim, in which said magnetic core is less than 300 Fm in thickness.

8. A method as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.

9. A magnetic core produced by a method as claimed in any one of the preceding claims.