GB2151835A

GB2151835A - Magnetic head device

Info

Publication number: GB2151835A
Application number: GB08423471A
Authority: GB
Inventors: Michio Kamimura; Kiyoshi Matsui
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1983-12-22
Filing date: 1984-09-17
Publication date: 1985-07-24
Also published as: JPH0313848Y2; JPS60106211U; KR850009658U; KR900008851Y1; GB8423471D0; GB2151835B

Abstract

A magnetic head device includes a magnetic head (1,2) mounted on a head-mounting member (3) with a gap provided therebetween. A vibration damper (5) is inserted in the gap for damping any microvibration transmitted from the head-mounting member (3). Magnetic head (1,2) may be a composite structure of a recording/reproducing head (1) and an erasing head (2). Head-mounting member (3) may be a conductor at ground potential. Either one of head (1) and head (2) may be secured to the head-mounting member (3), and the gap may be provided between the other head and the head-mounting member (3). Magnetic head (1,2) may be electrically connected to member (3) through an electrically-conductive spacer for forming the gap. Damper (5) may be a silicone resin elastomer. <IMAGE>

Description

SPECIFICATION Magnetic head device Background of the invention Field of the invention The present invention relates to a magnetic head device, for example, a sound/control/erasing head for videotape recording.

Description of the prior art Figure 1 is a front elevational view of a magnetic head device of the kind mentioned above. A recording/reproducing head 1 and a sound erasing head 2 are connected together in highly accurate positional relation to each other. Further, in order to allow this composite structure to be easily mounted on the chassis of an apparatus, the composite structure is secured at, for example, the recording/reproducing head 1 to a head mounting plate 3 by means of a screw 4 with high positioning accuracy. It is to be noted that, in the Figure, the reference numerals la, 1 b and 2a respectively denote a magnetic gap for sound, a magnetic gap for control and a magnetic gap for erasing sound.

Such an apparatus as a videotape recorder in which the magnetic head device is used has a tendency to reduce its weight, width and size. For this reason, the mechanical strength of each of the parts employed in such apparatus has been lowered.

Further, from the viewpoint of space, the distance has become relatively short between a vibration source, such as a motor or a solenoid, and the magnetic head device. Further, since handy or portable products have spread, it has become frequent that the apparatus employing the magnetic head device is carried about. With these points as background, the vibration transmitted to the magnetic head device is undesirably increased, which adversely affects the characteristics of the magnetic head device.

If the vibration frequency of a vibration source, such as a motor, mounted on the apparatus is coincident with or close to the natural frequency of the magnetic head device, the vibration transmitted from the vibration source inconveniently causes the magnetic head device to vibrate sympathetically or in a manner close to resonance.

To prevent such vibration of the magnetic head device, it is conventional practice that, as shown in Figure 1, a weight 6 is mounted on the respective upper sides of the heads 1, 2 and is secured by means of a screw 7, in order to move the natural frequency of the magnetic head device including the weight 6 away from the vibration frequency of the vibration source, thereby preventing any resonance from arising.

According to the above-described conventional arrangement, however, it is necessary to adjust the weight of the weight 6 such that the natural frequency of the magnetic head device including the weight 6 is not coincident with the vibration frequency of any one of the vibration sources mounted on the pertinent apparatus. Since it is generally often that various types of apparatus in which the magnetic head device is used differ from one another in the kind and number of vibrations sources, it is necessary to properly design the weight for each type of apparatus, which is extremely troublesome.

Moreover, the provision of the weight disadvantageously suppresses the above-described reduction in weight, width and size of the apparatus in which the magnetic head device is used, which is also disadvantage from the viewpoint of design. Furthermore, there is a need for a screw and a tapping operation in order to secure the weight, which unfavourably increases the number of required parts and the number of working steps, resulting disadvantageously in an increase in production cost.

Summary of the invention Accordingly, a primary object of the invention is to provide a magnetic head device which is hardly caused to vibrate by any externally transmitted vibration, that is, a magnetic head device which is capable of improving the intermodulation distortion, thereby overcoming the above-described disadvantages of the prior art.

To this end, according to the invention, there is provided a magnetic head device comprising: a hard head-mounting member constituted by, for example, a metal plate; a magnetic head mounted on the head mounting member with a gap provided therebetween; and a vibration damper for damping any microvibration transmitted from the head mounting member, the vibration damper being inserted in the gap and constituted by an elastic member of, for example, a silicone resin elastomer.

The above and other objects, features and advantages of the invention will become clear from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.

Brief description of the drawings Figure 1 is a front elevational view of a conventional magnetic head device; Figures 2 and 3 are front elevational views of magnetic head devices in accordance with embodiments of the invention, respectively; and Figures 4 and 5 are characteristic charts respec tivelyshowing intermodulation distortions measured in the case where the magnetic head device in accordance with one embodiment of the invention is mounted on a videotape recorder.

Description of the preferred embodiments Embodiments of the invention will be described hereinunder with reference to the accompanying drawings.

Referring now to Figure 2 which is an illustration showing a first embodiment of the invention, a recording/reproducing head 1 and a sound erasing head 2 are connected together in highly accurate positional relation to each other similar to the conventional arrangement. Further, the composite structure of these members is secured to a head mounting plate 3 by means of a screw 4 with high positioning accuracy. In this case, a gap is provided between the sound erasing head 2 and the head mounting plate 3 and is filled with an elastic member 5 of an RTV type silicone resin elastomer (KE347, the name of a product manufactured by Shin-etsu Chemical Industry Co., Ltd.). The elastic member 5 has a specific gravity of 1.04, a tensile strength of 20 Kg/cm2, an elongation percentage of 300 % and a hardness (JIS-C-2123) of 30.In the case of this embodiment, the recording/reproducing head 1 is in direct contact with the head mounting plate 3 of a metal which is at the ground potential, thereby allowing the head 1,2 to be grounded.

Figure 3 is an illustration showing a second embodiment of the invention in which the composite structure of the recording/reproducing head 1 and the sound erasing head 2 is secured to the head mounting plate 3 by means of the screw 4through a ring-shaped spacer 8. Accordingly, the spacer 8 is formed with a through hole for receiving the screw 4.

The existence of the spacer 8 having a relatively small diameter provides a gap between the recording/reproducing head 1 and the head mounting plate 3, and the gap is filled with the elastic member 5 of an RTV type silicone resin elastomer (KE347, the name of a product manufactured by Shin-etsu Chemical Industry Co., Ltd.). In the case of this embodiment, since the spacer 8 is made of an electrically-conductive material, such as a metal, the heads 1,2 are electrically connected through the spacer 8 to the head moutning plate 3 of a metal which is at the ground potential.

Figures 4 and 5 and characteristic charts respectively showing intermodulation distortions measured in relation to the structure shown in Figure 2 in which an RTV type silicone resin elastomer (KE347, the name of a product manufactured by Shin-etsu Chemical Industry Co., Ltd.) was employed as the elastic member 5 and iron (in the case of Figure 4) and aluminum (in the case of Figure 5) were employed as the head mounting plate 3.

More specifically, a magnetic head device having the structure shown in Figure 2 was mounted on the rotary head cylinder of the videotape recorder, and a magnetic tape on which a signal of a frequency of 3 KHz has been recorded was traveled by the videotape records. Then, the waveform of the output from the magnetic head device was measured for each of the cases where as the head mounting plate 3 iron was employed (Figure 4) and aluminum was employed (Figure 5).

As will be clear from these Figures, the crest value of the modulated wave is low: in the case of Figure 4, the difference between the fundamental wave and second harmonic of the input signal is 45 dB; in the case of Figure 5, the difference is 43 d B. On the other hand, when the intermodulation distortion of the conventional magnetic head device shown in Figure 1 was measured, the crest value of each modulated wave was high, since the magnetic head device resonated during use. Although not shown, the difference between the fundamental wave and second harmonic of the input signal (3 KHz) is about 28 dB in the case of the conventional magnetic head device.Accordingly, twill be understood that the intermodulation distortion is improved by about 17 dB in the case of Figure 4 and about 15 dB in the case of Figure 5.

The RTV type silicone elastomer employed in the above-described embodiments is formed in such a manner that a polysiloxane prepolymer having a reactive group such as SI-OH, Si-OR, Si-H or Si-CH=CH2 is allowed to react with a silicone resin elastomer at its end at room temperature so that the elastomer possesses a three-dimensional stucture through elongation and crosslinking of molecular chains. RTV is an abbreviation of ROOM TEMPERA TURE VULCANIZATION.

According to the invention having the abovedescribed construction, it is advantageously possible to reduce the vibration with a simple structure even if vibration sources have vibration frequencies over a wide range, and it conveniently becomes possible to reduce the weight, width and size of the magnetic head device.

Claims

1. A magnetic head device comprising: a hard head-mounting member; a magnetic head mounted on said head mounting member with a gap provided therebetween; and a vibration damper for damping any microvibration transmitted from said head mounting member, said vibration damper being inserted in said gap.

2. A magnetic head device according to claim 1, wherein said magnetic head is constituted by a composite structure which is composed of a recording/reproducing head and an erasing head connected to said recording/reproducing head, and said head mounting member is constituted by a conductor which is at the ground potential, and wherein either one of said recording/reproducing head and said erasing head is secured to said head mounting member, and said gap is provided between the other head and said head mounting member and is filled with said vibration damper.

3 A magnetic head device according to claim 1, wherein said head mounting member is constituted by a conductor which is at the ground potential, and said magnetic head is electrically connected to said head mounting member through an electricallyconductive spacer for forming a gap, into which gap said vibration damper is filled.

4. A magnetic head device according to claim 1, wherein said vibration damper is constituted by a silicone resin elastomer.

5. A magnetic head device according to claim 4, wherein said silicone resin elastomer is an RTV type silicone resin elastomer.

6. A magnetic head device substantially as hereinbefore described, with reference to Figures 2 to 5 of the accompanying drawings.