Abstract: A nonmagnetic holder is made having a plurality of precisely located parallel grooves. Each groove has a reference lateral surface provided therein. Individual magnetic transducers are inserted in each groove with a lateral surface abutting the reference lateral surface within that groove. The transducers are preferably made by well known batch fabrication techniques. A locating element, such as a leaf spring, is provided in each groove to urge the transducer core against the reference surface and to firmly hold the transducer in a desired position during alignment and assembly. The modular structure allows inspecting the individual transducers for mechanical or electrical damages and their replacement, if necessary, prior to the final assembly. The multichannel head is then integrally joined together, for example by bonding. The rejection rate of the resulting modular multichannel head is significantly reduced.

Abstract: A dual magnetic head assembly is provided with asymmetrical crosstalk shielding. One of the heads includes a pair of mu-metal washers sandwiching a copper washer, the stacked washers surrounding the portion of the head including the read-write gap. The washers are enclosed within a copper plated mu-metal cap having a central opening through which the gap-containing portion of the head projects for cooperation with a magnetic medium. The other head is unshielded.

Abstract: A semi self-loading air bearing ferrite slider assembly has a tapered leading surface portion extending from a cross rail from which side rails and a middle rail extend rearwardly. The middle rail progressively narrows to form the transducer portion where it extends across the gap between the body portion and core piece near the trailing end of the rail. Etched surfaces between the middle rail and the side rails provides subambient pressure during operation when the slider is in flight whereby the balance between the repelling air bearing surface and attraction of the subambient pressure areas supplements the stabilizing force of the load arm.

Abstract: A method of attaching electrical conductors to a thin film magnetic transducer having a transducing element and a plurality of substantially planar conductive leads formed into a predetermined pattern comprising the steps of mounting the thin film magnetic transducer on a substrate adjacent a medium contacting surface with the conductive leads thereof extending from the medium contacting surface, positioning an electrical circuit member having on one side thereof a plurality of planar connecting elements which have a relatively thin diffusible conductive metal coating contiguous the conductive leads, placing a quantity of curable epoxy bonding material adjacent the plurality of planar connecting elements of the thin film transducer wherein the epoxy bonding material is selected of a material having a curing temperature which is less than the thermal stress temperature of a thin film magnetic transducer wherein at least one of the electrical characteristics and the magnetic characteristics of the thin film mag

Abstract: The present invention relates to a tape recorder and, more particularly, to a tape recorder having an automatic reverse function. The tape recorder has selecting means, a head and a head rotating mechanism. When control buttons are operated by a user, the selecting means can select one of the forward and reverse tape transport directions, and the head rotating mechanism can rotate the head to one of the two positions corresponding to the forward and reverse tape transport directions in accordance with a selection by said selecting means, tape contact surface facing the tape.

Abstract: To reconcile a variety of problems associated with multitrack magnetic heads, modified shields therefor were fabricated. Each such shield is comprised of a plurality of laminations of magnetically, and mechanically, soft material bonded together into a unitary stack of appropriate thickness. The laminations are typically of .mu.-metal; and the stacked laminations are preferably provided with copper cladding as is the practice in the art. At the medium bearing surface of the shield, a cutout is provided; and into such cutout a small insert of magnetically soft, mechanically hard, material, e.g. Sendust, is provided.

Abstract: This invention relates to a rotary head assembly in which a magnetic tape runs while being would helically, consisting of a fixed cylinder 21 having a fixed cylindrical part, and a rotatable rotary member 19 having a diameter approximately equal to that of said fixed cylinder 21, being disposed coaxially with a very small gap and holding a magnetic head 29, wherein pump-out type spiral grooves 20 are provided either partly or wholly on either plane of the confronting planes formed in the relative rotating part between said fixed cylinder 21 and said rotary member 19 in order to create a buoyancy on a running magnetic tape by air pressure not only in the rotary cylinder area but also in the fixed cylinder area, to realize a stable and smooth tape running, and to radically eliminate the tape chirping phenomenon, sticking phenomenon, and tape damage and cylinder wear accompanying sliding.

Abstract: A rotary magnetic head drum apparatus for a video tape recorder of a helical scan type having small projecting members provided on a fixed drum of a rotary magnetic head assembly in the vicinity of the switching positions at the entrance and exit sides for a magnetic tape. The projecting members cause the magnetic tape locally to be displaced radially outward from the surface of the fixed drum so as to reduce longitudinal vibration of the magnetic tape and hence reduce impact error in a signal reproduced on the magnetic tape by two rotary magnetic heads.

Abstract: A magnetic head with the least cross-talk due to leakage magnetic flux in the shield case accommodating therein the magnetic head, the reduction in the cross-talk being realized by chamfering at least one side of an opening formed in the shield case, which are substantially perpendicular to the travelling direction of a magnetic recording medium, in a slant or arcuate surface form.

Abstract: A multitrack magnetic head particularly suitable for automatic assembly comprises a first set of core parts (17) which are rigidly fixed on a first flat base plate (16) and a second set of core parts (31) which are rigidly fixed on a second flat base plate (19). A screening plate (35) is located between cores of the first and second core parts (17,31) and is welded to the flat base plates with its oppositely located longitudinal edges. The screening plate is preferably located with one side against the first base plate and with the oppositely located side against a resilient lug projecting inwardly from the plane of the second base plate.

Abstract: A constrained-layer construction comprising a stiff layer or substrate and a layer of a viscoelastic polymer which is the reaction product of (a) 25 to 75 weight percent of an acryloyl or methacryloyl derivative of at least one oligomer, said oligomer having a glass transition temperature of less than 25.degree. C. and a molecular weight per oligomer of 600 to 20,000, and (b) 75 to 25 weight percent of a copolymerizable monomer whose homopolymer has a glass transition temperature of at least 50.degree. C., the copolymer being suitable for damping vibrations at relatively high temperatures, e.g., 50.degree.-150.degree. C., is disclosed. Also included is a process for damping vibrations in component parts of devices used in automotive, aerospace, and computer industries.

Abstract: A method of manufacturing an integrated magnetic head unit includes providing a substrate which supports a plurality of electromagnetic transducing elements connected to bonding pads. The transducing elements are then covered by a silicon plate which is arranged in good thermally-conducting relationship with the transducing elements and with a housing.

Abstract: A ceramic-ferrite head for use with a flexible data-storage disk comprises a cylindrical body composed of magnetically soft ferrite and formed internally with a cup-shaped recess open at one end and a boss provided with a window at the opposite end. The core assembly is received in this boss and is bonded therein with a glass-resin composition while the coils of the assembly are found in the recess and are connected, together with the ground lead through a cap of the same material as the body, to a printed circuit board on the opposite side of this cap. The recess is lined with a conductive coating which is likewise grounded to the printed circuit board by the ground conductor.

Abstract: A magnetic head for acoustic instruments. The head is composed of at least two units. Each unit, in turn, is composed of a shielding case half, a core holder, cores, etc. The core holder and/or the cores are easily positioned in the shielding case half at the time of assembly of the unit. The units are joined to each other to form a complete magnetic head.

Abstract: Ferrite read and write modules of a magnetic head assembly that are aligned and positioned within a nonferrite housing are clamped by a leaf spring between the walls of the housing. The leaf spring compensates for thermal mismatch between the ferrite modules and the housing, and compensates for stress fluctuation that occurs with temperature change. The clamping force of the leaf spring is precisely controlled.

Abstract: A magnetic head suitable for a reversible stereo cassette tape recorder is disclosed. The magnetic head had a larger operating gap for the recording head than for the reproducing head. This is accomplished by a thicker spacer between the core pieces for the recording head than for the reproducing head. The two spacers are in line, and the core pieces are held on one hand by a common holding member and on the other hand by separate lower and upper holding members.

Abstract: A tape scanning assembly including a fixed drum and a coaxially mounted rotating drum defining a gap therebetween, with the tape wrapped in a helical path around the drums and across the gap, the rotating drum being driven to produce a pressurized gas bearing film between the tape and drums, with the bearing film being vented by the gap to tend to produce a variable film thickness gradient on the upstream side of the gap; the assembly is provided with venting means such as relieved portions or grooves on the rotating drum to reduce said gradient and to control the film thickness upstream from the gap.

Abstract: The temperature of a magnetic head assembly is reduced by active heat transfer accomplished by a thermoelectric cooling element positioned between and in contact with the head assembly housing and the head assembly. The housing serves as a heat sink from which thermal energy is diffused.

Abstract: The head-drum rotary system of a helical scan video recorder is centered on the drive spindle without tilting, by elastic deformation of two wall portions which serve as centering devices. At least one of the centering devices may also function as a clamping element for holding the head-drum system on the spindle.

Abstract: A rotary head assembly having a central stationary shaft one end of which is securely joined to a lower housing, a bearing spacer securely fitted over the stationary shaft at the other end thereof and a rotary sleeve disposed for rotation about the common axis of the stationary shaft and the bearing spacer, whereby a hydraulic bearing is defined by the bearing spacer, the rotary sleeve and a lubricant filled into the space between the bearing spacer and the rotary sleeve, and a hydraulic passage is defined between the stationary shaft and the rotary sleeve. The lower end of the lubricant passage is provided with a magnetic sealing means which seals a magnetic liquid so as to prevent the leakage to the exterior of the magnetic liquid or the lubricant. An upper cylinder which carries one or more video signal recording and reproducing heads is removably mounted on the rotary sleeve.

Abstract: In a rotary head assembly for magnetic recording and reproducing apparatus such as VTR sets, of the type comprising a stationary shaft having its one end securely joined to a stationary member, a rotor fitted over the stationary shaft for rotation, a drive means for driving or spinning the rotor and heads mounted on the rotor, the position N of a thrust support for supporting the rotor is so selected as to coincide with the center of gravity G of the rotor or as to be located between the center of gravity G and the center of gravity G.sub.1 of the rotor except an aggregate of component parts of said drive means mounted on the rotor, the center of gravity G being depending upon the center of gravity G.sub.1 and the center of gravity G.sub.2 of the aggregate of component parts mounted on the rotor, whereby the adverse effects of the precession of the rotor on the precision rotation or spinning thereof can be avoided.

Abstract: Precision machinerycomponents such as a cylinder in a magnetic tape scanning apparatus, a cylinder base and/or a sub-chassis in a video tape recorder, etc. made of cured thermosetting resin composition comprising (A) a resin component comprising, particularly preferably, a terephthalic acid series unsaturated polyester resin, styrene and a saturated polyester resin, (B) an inorganic filler, and (C) short fibrous material such as carbon short fibers, have excellent dimensional accuracy and dimensional stability. When these precision machinery components are used, for example, in a video tape recorder, the same clear VTR picture as in the case of using those made of metal can be obtained.

Abstract: A magnetic head comprises a core holder for holding a magnetic head element and including a first conductive region which is adapted to bear against the magnetic head element, and a shielding case which defines a second conductive region adapted to bear against the first conductive region and covering both the magnetic head element and the core holder to provide a magnetic shielding. In this manner, any static electricity developed on a magnetic tape is conducted to the ground potential of an instrument in which the magnetic head is mounted through the first and the second conductive region.

Abstract: A method for making a multitrack head is disclosed wherein, by use of two separate alignment structures, a head having a large number of perfectly aligned cores, with perfect track-to-track spacing, is provided. The described multitrack head, by virtue of the inventive alignment technique, acquires a plurality of lead-protecting channels, the leads which are associated with the head coils being carried through such channels.

Abstract: A metallic magnetic head core-holder which supports a plurality of head cores of a multi-track head is provided with at least one slot for improving the crosstalk characteristic of the multi-track head. The slot is located between adjacent head cores, and extends along the entire width of a front wall, which is to abut on a magnetic medium, of the core holder. The slot further extends such that each portion of left and right side walls, which are respectively connected to the front wall, of the core holder is removed.

Abstract: A transducer head, and in particular a magnetic reading and/or writing head having a plurality of reading and/or writing tracks has a connector at the rear end thereof having a plurality of pins which are adapted to pierce and engage the conductors of a substantially flat ribbon-type multi-conductor wire. The connecting pins of the connector have generally fork-shaped ends which are adapted to pierce the insulation and engage a conductor between the opposing members of the fork-shaped ends. A cover is provided which is removable only upon application of a predetermined amount of force to prevent accidental or unauthorized opening of the connector.

Abstract: A rotary magnetic head carrier comprises a rotary structure having a cylindrical outer peripheral surface and formed to have at least one cutout or recess into which at least one part of a rotary magnetic head to be mounted on and held by the carrier is fitted. The recess has an opening part at the outer peripheral surface of the rotary structure. Tip edge parts of two side parts disposed on opposite sides of the opening part of the recess and defined by and interposed between the outer peripheral surface and the inner surface of the recess are deformed by pressing inwardly from the outer peripheral surface so as not to project outwardly therefrom.

Abstract: A magnetic head mount assembly for accessing data tracks recorded on a magnetic medium includes a mounting post, an arm element which engages the post, and a yoke on which circuit elements are disposed. An end portion of the post is slotted to receive electrical leads for connection to the magnetic head, which is supported by an air bearing slider positioned over the slotted end portion. The arm element is preferably frustoconical to reduce mass and weight, thereby enhancing access time.

Abstract: A multiple leg magnetic transducer has two corresponding core portions abutting at a transducing gap plane. Each portion has a transducing gap defining pole and a multiple leg back core contiguous with the pole. A nonmagnetic side piece supports the pole and intermediate leg portions while a rear leg portion most distant from the pole is unsupported by the side piece. The thusly supported portions are pressed together in a direction towards the transducing gap plane while the rear leg portions flex in the opposite direction to obtain an intimate contact between all corresponding end faces of the abutting core portions. In the preferred embodiment the flexed leg portions are firmly supported by a bonding material.

Abstract: The transducer has a pole tip plate containing magnetic pole tips defining transducing gaps and a core housing providing electric shielding and containing magnetic cores engaging the poles. The tip plate has a first part of a wear-resistant, nonmagnetic, machinable material in the transducer-to-medium interface area, providing long wear, and an integrally joined contiguous second part of a conductive, nonmagnetic, machinable material, providing electric shielding.In accordance with the method, corresponding surfaces of a first block portion made of nonmagnetic, wear-resistant, machinable material and of a second block portion made of a nonmagnetic, conductive, machinable material are integrally joined together. Pole tips are secured into parallel grooves machined transversely to the joined surfaces to form a half-tip plate.

Abstract: A combined magnetic tape head having a recording head and a reproducing head disposed in a side by side relationship with a recessed wedge shaped area therebetween. A shielding plate is interposed between the heads to reduce cross feed therebetween. The top portion of the shielding plate is bent into L-shape so that the bent tip confronts the recording head. The remainder of the wedge shaped area is covered with a resin material, or an auxiliary plate can be positioned over the plate extending between the heads. In order to maintain the combined head free from dust accumulation, the top portion of the L-shaped shielding plate or the auxiliary plate is tapered so that it has a substantially trapezoidal cross-section with either straight or curved inclining sides.

Abstract: A combined magnetic tape head for use in recording equipment comprises a recording head covered by a shield case, a playback head covered by a shield case and a flat chip for providing a preferable wrap angle of recording tape. The recording and the playback heads are combined into a unitary element by means of a tightening mechanism and/or adhesive agnets. The shield cases are provided at their arcuate front surfaces facing the recording tape with cut portions which are adapted to receive the flat chip, thereby making it possible to readily position the flat chip at a desired position.

Abstract: A fly off transducer platform or carrier according to the invention comprises a platform for supporting at least one transducer for reading and writing from and onto a data carrier such as a magnetic disc which is driven past the transducer in a given direction and sense. The platform has on its face adjacent the data carrier at least one air gap carried by a skid whose major dimension is parallel to the said given direction. The front face of the said skid, with reference to the said sense of movement of the data carrier, forms a diverter blade to force any unwanted contaminant material to at least one side of the said skid and thus prevents this material from collecting at the air gap.

Abstract: A rotary headwheel assembly is described for magnetic recording on a magnetic tape. The headwheel includes a plurality of heads distributed about the periphery of the wheel and means for clamping the wheel to a rotary motor for rotating the wheel at high speeds and magnetically recording or playing signals on the tape. A headwheel cover is placed over the headwheel for providing the safety from fly away pieces from the headwheel or rotating assembly. The buildup of debris due to the close contact of the tape with the headwheel when the headwheel is rotating at high speed is prevented by narrow apertures in the cover and impeller means coupled to the rotating shaft of the headwheel for driving air current through the slots.

Abstract: A magnetic transducer head having, at the face end wall, at least one pair of transducer pole piece portions extending in the direction of movement of the tape and having a gap between them. The pole pieces are tangent, at the gap, to a base plane parallel to the general direction of movement of the tape. In the example illustrated, the pole piece portions are disposed at approximately 13.degree. relative to the base plane so that the spacing between the pole piece portions and the base plane increases with distance from the gap on both the approach to and retreat from the gap. The casing has a tape guide surface which overlies the pole piece portions at the face end wall and determines the angle of approach to and retreat from the pole piece portions. This guide surface is cylindrical in the example illustrated, providing an approximately 7.degree. angle of approach and retreat of the tape relative to the base plane, this being substantially less than the 13.degree.

Abstract: A magnetic head assembly includes read/write pole elements having tip structure flush with slide surfaces on separate mounts, the latter mounting erase poles having ends at opposite sides of the read/write pole tip structure. Separate coils may be located about the erase poles; and notches may be located in the mounts at opposite sides of the read/write pole elements to provide a controlled throat dimension.

Abstract: A magnetic head for tape recorders and the like is manufactured with cores made of alloys of elements such as Al and Fe which have relatively large potential differences. In order to avoid the galvanic effect which may be produced by segregation and impurities in the alloys, a part of the tape sliding surface is made of an element such as Zn which is lower in galvanic potential than elements forming the cores, and that part of the tape sliding surface is made electrically conductive to the cores.

Abstract: A magnetic head comprises a magnetic core having a sliding surface on which a magnetic tape moves sliding, a casing for enclosing said magnetic core, and a fixing material used to secure said magnetic core within said casing, said fixing material essentially consisting of a resin, a filler and MoS.sub.2 added as an additional filler.

Abstract: A protective arrangement for a cassette tape recorder in which a magnetic head has a face side facing upwards, and is located within the recorder. A protective hood covers the face side of the magnetic head, and is rotatably located about a horizontal axis which is perpendicular to the gap plane of the magnetic head. A coiled spring engages the protective hood, and urges it into a closed position. A switch for connecting the recorder to a power supply line, is connected to the protective hood, by a connection located so that upon moving the switch to an ON position, the protective hood is moved to an open position against the action of the spring. When the switch is moved to an OFF position, the movement of the protective hood to its closed position is released. A stop located on the protective hood, enters behind the cassette placed in the recorder in the opening position of the protective hood.

Abstract: A spring retaining clip resiliently urges the back bar core piece of a magnetic head assembly into contact with the back ends of two other core pieces whose front ends define the head gap. Use of the clip permits installation of the head coil on one of the core pieces and installation of the back bar after the core pieces have been secured, ground and lapped in the head housing, thus simplifying the manufacturing process. In a preferred embodiment the retainer clip has a first surface member for engaging or being glued to the side of the back bar, and a pair of resilient tabs for engaging the back ends of the pole pieces when the back bar is installed with the clip holding the back bar and the pole pieces tightly together. A grounding wire for the core can be soldered to the retaining clip.

Abstract: A magnetic information card encoding apparatus wherein the train of clock pulses used to synchronize the release of binary data from a storage register to a recorder head is generated by the motion of the card itself. Structural means forms a card receiving slot into which the card is manually inserted and removed. A rotatable carriage assembly consists of a drive shaft, photoelectric means responsive to rotation of the drive shaft for generating the clock pulse train, an idler wheel, and spring biasing means for urging the idler wheel against the drive shaft in a friction drive relationship. A second spring biasing means urges the carriage assembly to rotate such that the idler wheel frictionally engages the card so as to be driven thereby. A switch is actuated by the leading edge of the card to provide a signal defining the position of the card in the slot. The arrangement is such that the information card is erased on insertion and encoded on withdrawal.

Abstract: A method of making a thin film magnetic head assembly having a spaced substrate and superstrate with a thin film magnetic transducer mounted therebetween by the steps of positioning at least one spacing member between the substrate and superstrate, placing a quantity of insulating bonding material of selected characteristics adjacent the spaced substrate and superstrate and controllably heating the substrate, superstrate, thin film magnetic transducer and spacing member sub-assembly to a bonding temperature located in a bonding temperature range and maintaining the sub-assembly at a bonding temperature to enable the bonding material to substantially fill the space by capillary action thereby encapsulating the thin film magnetic transducer bonding the substrate, superstrate and thin film magnetic transducer into an integral assembly is shown.

Abstract: An arrangement for recording information on a magnetic record carrier, having at least one magnetic recording head which incorporates an electromagnet having a core, wherein said arrangement includes a magnetic shunt, said magnetic shunt and the magnetic core of the electromagnet being adapted to be arranged on either side of said record carrier and close thereto, so as to form a closed magnetic circuit in which the magnetic flux is substantially perpendicular to the surface of the carrier, the said core having a recording pole and a flux-closing pole and the cross-section of the recording pole being smaller than that of the flux-closing pole.

Abstract: In a magnetic head having a tape contact face, a non-ferromagnetic unitary housing has a cavity for receiving a coil and has a slot for receiving at least one C-core of the magnetic circuit. The slot extends in a side face of the housing and debouches at one end into the cavity and at the other end into the tape contact face.

Abstract: A magnetic sensor includes a housing in which flux producing means which comprises an electromagnet or a permanent magnet is received. A pair of magnetoelectric transducer elements are secured to a surface of the flux producing means which represents a magnetic pole, with a given spacing between the elements. In order to dispose the magnetoelectric transducer elements as close as possible to the outer surface of the housing, the latter is formed with a through opening at a corresponding position. The through opening is covered by a thin shield cap to protect the magnetoelectric transducer elements from a member being detected which is passed in sliding contact with or very close to the outer surface of the housing and to provide an enclosed construction for the housing.

Abstract: An adjustable holder for mounting a magnetic head so that it can be adjusted for both lateral and angular deviation with respect to the center line of a recording track. The holder includes a carriage adapted to receive guide pins and a yoke carrying the magnetic head on a leg at one end. The yoke is attached to the carriage by a fastener which permits vertical and rotational displacement. The leg of the yoke includes three equally-spaced openings to receive rotational coupling elements, each of which includes a shank having an enlarged head at one end and a flange with a diametrical groove at the other end. The carriage has three fixed pins received within the grooves of respective coupling elements. The axes of the coupling elements define the corners of one equilateral triangle while the axes of the fixed pins define the corners of a similar but non-congruent equilateral triangle.

Abstract: A magnetic ink character reading system is provided in which multi-element read heads are positioned in a spaced apart and staggered arrangement. Data signals occurring in the analog responses of the read heads are detected, and converted to discrete logic level signals under the control of a dynamically adjustable threshold. The logic level signals of each read head are sampled in response to independent data sample signals which are phase locked to the data rate of the respective read head. NRZ (non-return-to-zero) data signals formed thereby are synchronized to a common fixed frequency, and serialized faithfully to represent the characters appearing on documents passing the read heads.

Abstract: Write windings are deposited on a ferrite half yoke mounted on a titanium body, and magnetoresistive elements are deposited on another ferrite half yoke mounted on another titanium body. A center section comprising a sandwich of silver-copper shielding material between two ferrite sheets has glass-filled slots cut on one side thereof. The center shield is placed between the write and read sides with the write windings placed between pairs of glass-filled slots and with the magnetoresistive elements in contact with the opposite surface of the center shield. The write windings and the magnetoresistive elements are connected to connector blocks prior to final assembly, and the write and read sides and the center section are pressured together by bolts through two end pieces, forming a vise-like structure.

Abstract: This magnetic head construction includes two or more elements defining a transducing gap which are positioned and held together within a shell by a wedge.The magnetic head assembly disclosed normally includes a shell structure, a pair of transducer elements defining a transducing gap, a wedge and a wedge follower. The wedge follower may be present as either a separate element or as a surface carried by one of the transducer elements. The assembly is normally formed by the process of disposing the transducer elements, and the wedge follower, if present, within the shell wall, and then rough positioning these elements within the shell, followed by the insertion of the wedge against the wedge following surface to bring the parts into final position in a locked relationship. Generally speaking, locking is achieved by selecting the wedge angle, .theta. as a function of the coefficients of friction of the mating surfaces according to given formulae.

Abstract: In magnetic disk equipment or the like, the read/write magnetic heads are each bonded to the wall of a thru-hole of a carrier plate adapted to act as a "flying" member maintained by an aerodynamical action in close proximity to the surface of the rotating disk. In a device according to the invention, the bond between the lateral surface of the head and said wall is made to ensure magnetostatic and electrostatic shielding of the head against spurious magnetic, electromagnetic and electrostatic fields. Said bond may comprise thin films of a high permeability anisotropic material coating at least the facing surfaces of the head and the wall and a layer of solder intervening between said films. Such a shield may partially extend over selected areas of the rear faces of the plate and head.