RU2084970C1 - Unit of rotating video heads - Google Patents

Abstract

FIELD: equipment for magnetic recording, in particular, home and professional video recorders. SUBSTANCE: device has two magnetic heads which are located on mounting plate and have C-shaped half-core, I-shaped half-core and winding which is passed through winding hole which is provided on C-shaped half-core. I-shaped half-cores face each other. Coils of winding of one head are coiled on both half-cores so that their number is reverse proportional to area of cross section of half- cores. In addition device has ring core which is made from ferromagnetic material and has screen, first winding which is shaped as closed coil and second winding which has several coils. Closed coil of first winding of core is passed through winding hole of second head and serves as winding of second head; terminals of second winding of core serve as terminal of second head. Area of winding hole of second head may be less area of winding hole of first head. Winding hole of second have may be made in I-shaped half-core which width is greater than width of I-shaped half-core of first head. EFFECT: increased functional capabilities. 3 cl, 3 dwg

Description

 The invention relates to techniques for magnetic recording and may find application in domestic and professional video recorders.

 The main requirements for the video head blocks, in addition to ensuring a high level of the output signal, are to ensure the greatest isolation between the channels (low level of crosstalk), high technology, high mechanical strength, and protection from radio interference.

 For various reasons, the existing video head blocks are not able to satisfy the complex of these requirements.

 A known unit of rotating video heads [1] containing two magnetic heads (MG) fixed on a mounting plate, consisting of a C-shaped half-cord with a winding window connected to it through a non-magnetic gasket to form a working gap of the I-shaped half-core, and a winding passed through the winding window and located entirely on the C-shaped half-heart, with the I-shaped half-hearts facing each other. With a width of I-shaped half-cores of more than 0.175 mm, this block of video heads provides feedback and friction noises no worse than those of a single head. The disadvantages of the unit include a relatively high level of crosstalk, the absence of radio noise compensation, and the reduced recording efficiency of the second MG due to the fact that the edge of the gap “responsible” for recording is located in a C-shaped half-core with a winding window forming a sharpened magnetic circuit, in which magnetic saturation occurs to a greater extent, especially as the gap depth decreases.

 The closest set of essential features to the claimed one and widely used in practice is a block of rotating video heads [2] containing two MGs fixed to the mounting plate, each of which consists of a C-shaped half-cord with a window for the winding connected to it through a non-magnetic gasket with the formation of the working gap of the I-shaped half-core so that the amount is inversely proportional to the cross-sectional area of the I-shaped and C-shaped half-hearts. This winding allows you to increase the level of the output signal and compensate for radio interference.

The disadvantages of the prototype should include significant crosstalk between the channels. For example, in a block based on MG with windings according to the prototype and the distance between the working gaps d 0.62 mm, the level of these noise when applying to one of the signal heads with an amplitude of 180 mV is up to 30 dB at a frequency of 5 MHz. However, due to the need to wind a large number of turns on closely spaced I-shaped half-hearts, the manufacturability and mechanical strength of the video head unit are low. In practice, the width of the I-shaped half-hearts due to the closure of the windings can hardly be maintained equal to 0.175 mm at d 0.62 mm. With a smaller value of d (for example, for the Video 8 standard, where d is 0.48 mm), it is impossible to implement a design with windings as in the prototype. Another disadvantage of the prototype is the relatively low recording efficiency of the second MG along the rotation, as in the well-known video head unit [1]
Significant crosstalk in the prototype is a consequence of the high mutual induction of the windings, largely determined by the small distance between the windings containing a large number of turns.

 Spacing the windings by placing them entirely on a C-shaped half-core (as in device / 1 /) reduces crosstalk by only about 2dB (7%), while the output signal level is reduced and the ability to compensate for radio interference is lost.

 The task of the invention is to reduce the mutual induction of the windings of the video head unit while maintaining a high level of output signal and the ability to compensate for radio interference.

 This problem is solved by the fact that the block of rotating video heads containing two magnetic heads fixed to the mounting plate, each of which consists of a C-shaped half-cord connected to it with the formation of the working gap of the I-shaped half-cord and a winding passed through the winding window, while I-shaped half-hearts are facing each other, the winding window of one head is made in a C-shaped half-cord, and the turns of its winding are wound on both half-hearts so that their number is inversely proportional to the area of pop cross-sectional cross-sections, additionally contains an annular core of ferromagnetic material with a screen, a first winding in the form of a closed coil and a second winding of several turns, while a closed coil of the first winding of the core is passed through the winding window of the second head and serves as the winding of the second head, and the conclusions of the second winding core are the findings of the second head. The winding window of the second head may have an area smaller than the winding window of the first head. The winding window of the second head with the winding window area smaller than the winding window of the first head can be made in an I-shaped half-cord, the width of which is greater than the width of the T-shaped half-cord of the first head.

 The technical result of the invention is to reduce crosstalk between channels by 6 8 dB while maintaining the ability of the video head block to suppress radio interference, to increase the mechanical strength and durability of the block, to increase the recording efficiency of the second MG along the rotation, as well as to increase the yield of suitable products.

 The achieved technical result can be explained as follows.

 The level of crosstalk between the channels is determined as the result of the interaction of two factors: the distance between the main elements of the heads, subject to mutual induction, and the values of the "studying" surfaces of these elements. The almost identical isolation between the channels of the analogue [1] and prototype [2] is explained by the fact that the first factor acts weakly on the analogue, but the second one is strong (the windings are spaced, but are on C-shaped half-wires with a large radiation surface), and on the prototype it is vice versa (windings are mainly located on I-shaped elements close, but the surface areas of the radiation of these elements are small).

 In the proposed solution, the combined effect of these two factors is minimized, since the distance between the main interacting elements — the I-shaped half-core of one head and the additional annular core of the other head — is significantly increased compared to the prototype, and at the same time, the dimensions of one of the interacting elements remain small in difference from analogue [1] It is appropriate to mention here that in the case where both block heads have one turn and additionally annular cores with windings, the decoupling is strongly decreases even relative to the prototype (by 10 dB), which is due to the large size of the interacting elements, although remote over a considerable distance.

 As for the mechanical strength of the proposed device, its increase is achieved by providing the device’s capabilities, its increase is achieved by providing the possibility of increasing the width of the I-shaped half-core of the second head due to the placement of only one coil of the winding in the winding window. At the same time, the wear resistance of the second head increases simultaneously, since most of the I-shaped half-core can be made not of glass, but of ferrite, which has greater wear resistance than glass.

 The presence in the winding window of the second head of only one turn simplifies winding and increases the percentage of suitable products in comparison with the prototype device, the manufacturing process of which is characterized by frequent destruction of the product due to the need for winding multi-turn and closely located windings.

 The possibility of increasing the width of the I-shaped half-core of the second head determines not only an increase in its strength and wear resistance, but also an increase in the reproduction efficiency, which is further facilitated by a decrease in the area of the winding window. When transferring the winding window to the I-shaped half-core, an increase in the recording efficiency of the second head is also achieved in comparison with the prototype.

 The invention is illustrated in FIG. 1 of FIG. 3, which conventionally shows the main options for the implementation of the inventive block of video heads.

 The proposed device (Fig. 1 3) contains the first (I) and second (II) magnetic heads and an annular core 10, mounted on a mounting plate, on which is also fixed an electric board for desoldering the terminals of the windings 2, 5 and 12 (in Fig. 1 3 not shown). In the embodiments of FIG. 1 and FIG. 2, the numbering of the heads (I and II) is conditional, since in these cases the block of heads works the same for any direction of rotation, and in the embodiment of FIG. 3, the direction of rotation is clearly indicated.

 It should be noted that there are other embodiments of the proposed block of video heads that differ from the devices in FIG. 1, 2 and 3 in that the first and second heads are mirror images of the heads II and I, respectively. Moreover, for the video head unit, which is a type of device in FIG. 3, the direction of rotation is reversed.

 Elements of the devices shown in FIG. 2 and 3 have the same numbering as the elements in FIG. one.

 Each head consists of a C-shaped half-heart 1 (9) and an I-shaped half-heart 4 (6). The windings 2 and 5, passed through the winding window 3, are applied to both half-hearts of the first head. The second head has one closed coil 8, passed through the winding window 7 and through the ring core 10 made of magnetically soft material protected by the screen 11, on which the winding 12 is wound, conclusions which are the findings of the second head.

 The winding window 3 of the first head is located in the C-shaped half-core, and the winding window of the second head can be located in both the C-shaped (Fig. 1 and 2) and I-shaped (Fig. 3) half-hearts; in the latter case, the width I -shaped hemispherical necessarily increased, and in the embodiment of FIG. 2 can be increased (shown by a dotted line). The area of the winding window in the cases of FIG. 2 and FIG. 3 several times less than in the case of FIG. one.

 Both heads of the proposed block of video heads operate as universal MGs, providing recording and playback upon contact with magnetic tape.

 In the prototypes of the claimed device, the cores of the magnetic heads are made of a single crystal of manganese-zinc ferrite with a certain orientation of the crystallographic axes of the half-hearts. The dimensions of the cores are shown in FIG. 1. The thickness of the cores is 0.17 mm. The working gap parameters: width 0.35 μm, length 70 ± 4 μm, depth 45 ± 10 μm. The distance between the working gaps of the first and second heads is 0.62 ± 0.01 mm. The inductance of the heads is 2 ± 0.2 μG at a frequency of 3.8 MHz. The number of turns of the winding is indicated in the table.

 The characteristics of the video head blocks with different types of windings are given in the table.

 As can be seen from the table. the isolation between the channels of the head block in the proposed design is increased compared to the prototype by an average of 7.5 dB. There is a slight decrease (15%) in the recoil of the second head, which is explained by a smaller number of turns while ensuring the same inductance. However, with a sufficiently high level of return, this decrease in practice turns out to be insignificant. On the other hand, if necessary, the output signal of the second head can be increased if the area of the winding window is reduced or the thickness of the I-shaped half-heart is increased, which leads to an increase in the efficiency of the magnetic core. As experiments have shown, these measures practically ensure equalization of the recoil of both heads, and the transfer of the winding window of the second head to the I-shaped half-heart contributes to an additional (9 10%) increase in its output signal.

 The description of the proposed device and the test results of the prototypes testify to the industrial feasibility of the invention.

Claims (3)

 1. A rotating video head unit comprising two magnetic heads fixed to a mounting plate, each consisting of a C-shaped half-cord connected to it to form a working gap of an I-shaped half-cord and a winding passed through a winding window, with the I-shaped half-cores facing each other to another, the winding window of one head is made in a C-shaped half-cord, and the turns of its windings are applied to both half-cords so that their number is inversely proportional to the cross-sectional area of the half-cords, characterized in that it additionally contains an annular core of ferromagnetic material with a screen, a first winding in the form of a closed coil and a second winding of several turns, while the closed coil of the first core winding is passed through the winding window of the second head and serves as the winding of the second head, and the conclusions of the second the core windings are the terminals of the second head.  2. The block according to claim 1, characterized in that the winding window of the second head has an area smaller than the area of the winding window of the first head.  3. The block according to claim 2, characterized in that the winding window of the second head is made in an I-shaped half-heart, the width of which is greater than the width of the I-shaped half-heart of the first head.

Images