Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/127—Structure or manufacture of heads, e.g. inductive
  • G11B5/29—Structure or manufacture of unitary devices formed of plural heads for more than one track

Definitions

• This " invention relates in general to multitrack magnetic heads and to methods and parts for forming such heads.
• Linear tape recording of video information implies a simplification of hardware: not only does a lessened information writing speed relax the mechanical demands of the recording operation,
• U.S. Patent 4,084,199 Perhaps the most common technique for forming a multitrack magnetic head is that which is shown generally in U.S. Patent 4,084,199. Such a technique is characterized by the respective winding of coils on discrete cores, and the positioning of the coil-suppor ing cores in thin slots in a head block. Because of the tedium inherent in the winding of coils on tiny cores, and because of the brittleness associated with the slotting of the head block, a head made according to the teaching of U.S. Patent 4,084,199 is generally limited to about 30 tracks per widthwise inch of the reco'rding medium.
• a double helix core-and-coil structure is provided, the preselectable length of such double helix core-and-coil structure determining the number of cores which are to be employed in a head constructed from such core-and-coil structure.
• One helix of the double helix core-and-coil structure constitutes an
• a magnetic head made by the technique disclosed herein will comprise coils which extend virtually the full extent of their supporting cores, despite the fact that (perhaps) only a preselected number of turns of such coils are 30 electrically active.
• Fig. 1 is a side view showing one helix of the double helix core-and-coil structure
• 3 Fig. 2 is a side view showing the double helix core-and-coil structure
• Figs. 3a, 3b and 3c are respectively plan, edge and side views of apparatus employed in the practice of the invention
• Fig. 4 is an edge view, like that of Fig. 3b, but showing a gap-forming cut in the double helix core-and-coil structure;
• Figs. 5a and 5b are edge views like that of Fig. 3b, but showing, respectively, the removal of a mandrel employed as part of the head and gap-forming processes;
• Figs. 6a and 6b are, respectively, edge and under views illustrating additional procedures for forming a gap line in a multitrack magnetic head embodying the invention
• Figs. 7, 8a and 8b are views useful in describing the manner in which electrical contact is made to the electrically conductive helix of the double helix core-and-coil structure;
• Figs. 9 and 10 are side elevational views showing how a multitrack magnetic head embodying the invention may be finished
• Fig. 11 is an edge view useful in describing a presently preferred technique for forming a gap in a multitrack magnetic head according to the invention
• Figs. 12a, 12b and 12c are, respectively, edge, side elevational and schematic perspective views which relate to the showing of Fig. 11 and which are useful in describing the invention.
• Figs. 13 through 16 are illustrations which respectively correspond to the illustrations of Figs. 7 through 10.
• a multitrack magnetic head having 252 coil-wound cores per widthwise inch of the head, and which head embodies the invention, will now be described in terms of its method of manufacture: Referring to Fig. 1, a very fine insulating-covered copper wire 10 (.0023 cm) in diameter) is helically wound into a coil along and about the length of an iron wire 12 (.005 cm in diameter). Then, as depicted in Fig. 2, the coil-supporting iron wire 12 is, itself, helically wound on a mandrel 14, thereby forming the basic double helix core-and-coil structure 15.
• the double helix core-and-coil structure may be provided, and stocked, in large spools and/or skeins thereof, whereby multitrack heads of various numbers of cores may be provided, depending upon the length of the double helix core-and-coil structure which is employed.
• the two pieces 18a and 18b of the jig are positioned (see Fig. 5b) so as to place the cut edges 20a, b in a common plane.
• the edges 20a, b are then lapped flat and thereafter coated with an extremely thin coat (about 1 micron in thickness) of aluminum oxide 22 (or the like), the aluminum oxide serving as a gap spacer for the head under construction.
• the jig parts 18a, b are swung back and positioned so that the edges 20a, b face each other with the gap spacer aluminum oxide therebetween, such positioning causing the cross-section of the double helix core-and-coil structure (10, 12) to collapse into a generally elliptical form.
• the jig parts 18a, b (before, after or during the time they are swung back into position) are relatively shifted longitudinally of the double helix core-and-coil structure by an amount related to the pitch of the iron wire helix, whereby the cut helical iron wire (12) gets converted into a succession of substantially planar, untwisted, core.s having respective gaps (i.e.
• a non-magnetic block 23 (see Fig. 7) having a groove 24 is so bonded to the structure of Figs. 6a and 6b that the unsupported part 26 of the double helix core-and-coil structure (10, 12) resides in and along the length of the groove 24.
• epoxy is employed to hold the wire 28 in place and to fill the voids of the groove 24 of the double helix core-and-coil structure.
• electrical contact to the coils formed from the helically wound electrically conductive wire 10 may be made, simply, by lapping the structure of Fig. 7 to the lap lines 30a, b. While such lapping triangulates (Fig. 8a) the cross-section of the head under construction, it conveniently forms aligned apertures through which rows of copper contact points 32 are exposed on each of two opposing sides of the head; and which contact points comprise respective parts of the double helix core-and-coil structure (10, 12). See Fig. 8b.
• Leads from ribbon cables are then soldered respectively to the rows of copper contact points, (it will be appreciated that, although it will- be usual to bring leads to all of the copper points 32, it will be possible to vary the number and density of the active cores of the head by selectively bonding leads to different ones of the contact points 32. For example, if it is desired to provide a 126-track head, instead of a 252-track head, every other lead of the ribbon cables is simply left opened.) In finishing off the head, block pieces 36a, b and 38a, b are secured .(Fig. 9) to the triangular block of Fig. 8a, the block pieces 38a, b being provided with channels 40a, b through which the leads (42a, b) may pass. Then, finally, the head is contoured as in Fig. 10 to place the gap line 44 at the head surface which is disposed to contact the recording medium.
• the number of discrete cores in a head made as described above depends upon the length of the double helix core-and-coil structure which is employed, the number of turns on each of the cores depends on the lap angle employed to expose the copper contact points 32, as indicated in connection with Fig. 7.
• a transducer gap(s) formed by the head manufacturing technique described above is useful for many purposes, the provision of a high precision gap to optical tolerances is dependent on the ablity of the iron wire 12 to sustain and withstand precision lapping. And, it will be appreciated, the life of such a gap is directly related to and dependent upon the (small) diameter of the iron wire 12 which is used.
• Figs. 1 through 10 may be modified slightly as illustrated in connection with Figs. 11 through 16: After the double helix core-and-coil structure has been longitudinally cut, as was taught in connection with Fig. 4, and the mandrel 14 popped free as in Fig. 5a, a pre-formed pole tip piece 50 (Fig. 11) approximating the dimensions of the cut 20 is placed in pressing relation between the core edges 20a, b.
• the pole tip piece 50 which is best depicted in the perspective showing of Fig.
• 12c is preferably formed from a stack of ferrite pieces 52 interspersed with and bonded to ceramic pieces 54, the stack being longitudinally halved, lapped and reformed with a high reluctance gap spacer 56 between the halves.
• the multitrack head under construction is provided with coil and bias leads; and is contoured, essentially as was described above in connection wth Figs. 7 through 10.
• the parts of Figs. 13 through 16 having correspodning parts in Figs. 7 through 10 are identified with the same, but primed or double-primed, character notations.)
• the invention has been described in detail with particular reference to certain preferred embodi ents thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Magnetic Heads (AREA)

Applications Claiming Priority (1)

Publications (2)

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Family Applications (1)

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Citations (14)

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• 1981
  • 1981-11-24 JP JP50006682A patent/JPS58501642A/ja active Pending
  • 1981-11-24 WO PCT/US1981/001555 patent/WO1983002032A1/en not_active Application Discontinuation
  • 1981-11-24 EP EP19820900072 patent/EP0094382A4/de not_active Withdrawn

Patent Citations (14)

Non-Patent Citations (3)

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