JPH0250542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video tape recorder, particularly a rotating cylinder mounted on a rotating shaft rotated by a drive source, and a rotating cylinder arranged concentrically with a gap of a predetermined width formed with respect to the rotating cylinder. a fixed cylinder arranged;
The present invention relates to a rotary head drum for magnetic recording and reproducing having a plurality of magnetic video heads fixed to a rotary cylinder in a predetermined phase relationship in this gap.

Conventionally, in this type of head drum, in order to make the magnetic tape run smoothly with less frictional force, an air flow is formed between the drum surface and the tape surface, and the air film effect reduces the mechanical strength between the drum surface and the tape surface. There are methods that reduce contact (for example, see Japanese Patent Application Laid-Open No. 52-24506 or 52-24507).
Such devices are equipped with a fan or blower to generate airflow, or are provided with a large number of radial grooves on the surface of the rotating cylinder facing the stationary cylinder. As a result, the overall size of the device has increased, and reliability has deteriorated and maintenance has been difficult due to the accumulation of dirt and oil in the many grooves. These problems are particularly acute in so-called home video systems, where miniaturization and ease of maintenance are particularly required.

Furthermore, in drum assemblies with a larger number (for example, four) of magnetic heads than the conventionally used two magnetic heads on a single rotating cylinder, the diameter of the cylinder is small and the cylinder rotates at high speed. However, the angle of the sector formed by the area in contact with the tape on the outer peripheral surface of the drum,
The so-called tape wrapping angle increases (for example, 4
(270 degrees or more on the drum of a magnetic head), which may impede the smooth running of the tape and cause jitter to appear in the video signal. Even in such an apparatus, it is desired to realize smooth running of the tape with a simple and compact structure.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome these drawbacks of the prior art and to provide a small and highly reliable rotary head drum for magnetic recording and playback that can run the tape smoothly with less frictional force. .

This object is achieved by a rotary head drum for magnetic recording and reproduction according to the present invention as follows. That is, in this rotating head drum, the rotating cylinder has a first conical surface whose surface facing the fixed cylinder has a substantially conical shape as a whole, and the fixed cylinder is connected to a gap of a predetermined width and is connected to the first conical surface. It has a second conical surface forming a complementary substantially conical cavity. As a result, the airflow generated in the gap as the rotating cylinder rotates flows out from the gap, and the magnetic tape runs smoothly on the outer peripheral surfaces of the rotating cylinder and the fixed cylinder. This is particularly true when the stationary cylinder and rotating cylinder have substantially the same outer diameter.

Next, embodiments of the rotary head drum for magnetic recording and playback according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram for explaining the principle of the present invention. In the figure, a rotating drum head 10 schematically drawn includes a fixed cylinder 12 having a conical inner surface and a rotating cylinder 16 attached to a rotating shaft 14 whose center coincides with the center line of the cone. The conical surface 18 of the rotating cylinder 16, together with the conical surface 20 of the stationary cylinder 12, forms a substantially constant air gap 22 as shown. Therefore, when the rotating shaft 14 is rotated by an external drive system (not shown) in the direction of arrow A in FIG.
As shown by V2 and V2, there is a difference in the linear speed of rotation in the circumferential direction between the upper and lower sides of the surface of the conical surface 18 in the figure.
As shown, an air flow from the bottom to the top is generated in the gap 22 and is blown out from the slit 24 between the fixed cylinder 12 and the rotating cylinder 16 to the outside, for example, as shown by arrow B4. The amount of this air flow depends on the diameter of the conical surface 18 or 20, the difference between its upper and lower sides, and the rotational speed of the rotating cylinder 16.

An embodiment of a two-head rotary head drum assembly for a video tape recorder incorporating the principles of the present invention is shown in FIG. 2, in which similar components to those in FIG. 1 are designated by the same reference numerals. In the figure, the fixed cylinder 12 is fixed to the casing 30. A rotating shaft 1 defining a slit 24 of a rotating cylinder 16 attached to the rotating shaft 14
4, two magnetic video heads 32 and 34 are mounted with a phase difference of 180° in the circumferential direction of the cylinder 16, as shown in FIG.
It is attached with. A tension regulator mechanism (not shown) is attached to the outer periphery of the cylinder 16 so that a guide pole 38 (a second
The other guide pole is omitted in the figure, and the tape 3
A part of 7 is at the position of the guide pole at the dotted line 37A
is shown. ) is arranged, and when the rotary shaft 14 rotates in the direction of arrow A while the tape 37 is being recorded/played, the tape 37 travels in the direction of arrow C and rotates from the guide pole 38 toward the back of the cylinder 16 in the figure. It is designed so that it can be slipped through to the left.

The conical surfaces 18 and 20 of the rotating cylinder 16 and the fixed cylinder 12 are provided with grooves 40, 42 and 44, 46 in the circumferential direction, respectively.
A coil winding is disposed in and 44, and shot rings are disposed in grooves 42 and 46 and fixed therein with a fixing agent such as resin or adhesive, thereby forming a rotary transformer. Therefore, the surface of these fixatives has a smooth conical surface 18.
or forming part of 20.

When the rotary cylinder 16 rotates in the direction of the arrow A in the recording/playback state, an air flow from the bottom to the top is generated in the gap 22 due to the difference in linear speed of rotation between the top and bottom of the conical surface 18, and flows out from the slit 24. do. While the tape 37 travels in the direction of arrow C, a force is applied to it by a tension regulator mechanism (not shown) via a guide pole such as 38 so as to contact the outer surface of the cylinder 16. Due to the air film effect caused by the air flow blown out from the slit 24, a gap on the order of .mu.m is created between the outer peripheral surfaces of the cylinder 16 and the casing 30 and the tape recording surface. The size of this gap can be varied by adjusting the tension regulator mechanism. This allows the tape 37 to run smoothly with less frictional force even when the length around the rotating drum 10 becomes long, such as in the case of a four-head rotating drum, that is, even when the tape wrapping angle becomes large. be able to. Note that if the air flow rate blown out from the slit 24 is not sufficient to obtain an air film effect, a fan (not shown) may be installed near the position indicated by the lower part 48 of the cylinder 12 of the rotating shaft 14 to promote the air flow. May be worn.

The rotary head drum according to the present invention is configured as described above, so that the tape can be smoothly run with less frictional force. Furthermore, it is possible to provide a reliable and compact device with a simple configuration without providing a large number of grooves, blowers, etc. to generate airflow. Particularly in the case of an embodiment in which a rotary transformer is provided in the conical portion of the cylinder, the diameter of the rotating drum can be reduced without interfering with the airflow, and the head assembly can be made compact. The present invention is particularly effective for drum assemblies in which a single rotating drum is provided with a large number (eg, four) of magnetic heads.

Although the invention has been described with respect to specific embodiments, the concept of the invention is not limited thereto. For example, in the illustrated embodiment, the relative positional relationship between the rotating and fixed cylinders is an upper drum rotating system, but it may also be a middle drum rotating system. Further, in the illustrated embodiment, the conical surfaces 18 and 20 have a conical shape as a whole or a conical shape including a truncated cone, but as can be understood from the principle of the present invention, the generatrix thereof does not necessarily have to be a straight line. Even if the generating line of the truncated cone forms a gentle curve, the principle of the present invention can be applied as long as there is a difference in linear velocity above and below it.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram for explaining the operating principle of a rotary head drum according to the present invention, and FIG. 2 is a partially cutaway sectional view showing an embodiment of the rotary head drum according to the present invention. Explanation of the symbols of the main parts 12...Fixed cylinder,
14... Rotating shaft, 16... Rotating cylinder, 18, 20
...Conical surface, 22...Gap, 24...Slit, 32...
Magnetic video head.

Claims (1)

[Scope of Claims] 1. A rotating cylinder attached to a rotating shaft rotated by a drive source, a fixed cylinder arranged concentrically with a gap of a predetermined width with respect to the rotating cylinder, A rotary head drum for magnetic recording and playback including a plurality of magnetic video heads fixed to the rotary cylinder in a predetermined phase relationship in the gap, wherein the rotary cylinder has a first head whose surface facing the fixed cylinder has a substantially conical shape. the fixed cylinder has a second conical surface connected to the gap and complementary to the first conical surface forming a substantially conical gap; A rotary transformer means for circuitly coupling the plurality of magnetic video heads to an external circuit is disposed on the conical surface of the fixed cylinder, and the fixed cylinder has an opening near the top of the second conical surface to fill the air gap. A rotary head drum for magnetic recording and reproducing, characterized in that an opening is formed to communicate with the outside, and when the rotary cylinder rotates, air flows into the gap through the opening and blows out from the gap. 2. In the rotary head drum according to claim 1, the first conical surface has a concentric first surface.
A first winding constituting one coil of the rotary transformer means is fixed to the first groove by a fixing agent, and the second conical surface has a concentric second groove. 1. A rotary head drum for magnetic recording and reproducing, characterized in that the drum has a groove, and a second winding constituting the other coil of the rotary transformer means is fixed to the second groove with a fixing agent. 3. The rotary head drum for magnetic recording and reproduction according to claim 1, wherein the fixed cylinder has substantially the same outer diameter as the rotary cylinder.