KR830000805B1 - Magnetic tape cassette - Google Patents

Abstract

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Description

Magnetic tape cassette

1 is a plan view of a reversible video cassette provided with slides guided on a housing and pivotable guard plates on two sides.

2 is a perspective view of the video cassette of FIG.

FIG. 3 is a perspective view of FIG. 2 with a slide retracted into the housing and an aperture protection plate pivoted in the first position; FIG.

FIG. 4 is a perspective view of FIG. 3 with a pivot plate pivoted in its second position; FIG.

5 is a plan view of a sprue of a video cassette according to the drawings described above.

6 is a cross sectional view according to arrow VI-VI in FIG. 5;

FIG. 7 is a video recorder with a drive unit provided with a cassette support capable of pivotal rotation, a video cassette according to FIGS. 1 to 4 located in the cassette support, and a slide contracting into the housing. Partial view of the cross section of the order.

FIG. 8 is an enlarged view of a portion of FIG. 7 in which the rail center load and video cassette in the cross section seen in the arrow VIII-VIII of FIG. 9 and the cassette supporter are attached in the lower vibration position thereof.

9 is a partial plan view of the video recorder of FIGS. 7 and 8; The video cassette here is arranged on the drive, the cassette supporter oscillates downwards, while the cassette and cassette supporter have been partially omitted so that the portion located below them is visible.

FIG. 10 is a cross sectional view along arrow X-X in FIG.

11 is an actual plan view to allow free operation at the center on the drive spindle.

12 is a partial cross-sectional view of the real hub and drive spindle. The real hub is elastically supported against the stop ring with the aid of a resiliently loaded bowl in the drive spindle.

13 is a similarity of FIG. Here the real hub is magnetically supported against the stop ring.

FIELD OF THE INVENTION The present invention relates to magnetic tape cassettes, and more particularly, to magnetic tape cassettes in which two coaxial planar reel hubs are operated with a planar annular supporter on the cassette's drive spindle.

A) are arranged to cooperate with the magnetic head in first and inverted second positions, the first and second adjacent line hubs being able to rotate about a parallel axis of rotation, each center having at least a substantially circular inner wall A part defining a central centering hole, like at least one driving hole, is located at some radial distance from the centering hole and is parallel to and centered between two end walls of the rail winding part. As with the drive component and the disk-shaped centering device, a so-called "reversible" magnetic tape cassette with a generally circular outer wall and two annular end walls arranged in a plane some distance from each other perpendicular to the axis of rotation; : A first hole coaxial with the first rail hub and a second hole coaxial with the second rail hub First and second parallel balanced plane principal walls which are respectively installed and which actuate the two rail hubs in an axial direction during operation, and two side walls connected to the two principal walls and one rear wall connected to the principal walls. And in this case, the partially open front wall connects the two major surface walls on the front side opposite the rear wall, the length of the magnetic tape being the first end connected to the first rail hub and the first rail connected to the second rail hub. It has two ends, thereby allowing winding of a straight tape portion along the face along the front side of the magnetic tape cassette from the first rail to the rail on the second rail, and into the second rail hub. And the tape portion of the straight tape along the front surface of the magnetic tape cassette from the rail on the first rail hub.

The tape drive further comprises B) centering pins which are arranged to cooperate with the centering hole in the rail hub of the magnetic tape cassette, each of which has a free end, and which is capable of rotating around a parallel axis of rotation. First and second drive spindles and one frame: arranged radially away from the centering pin, resilient and depressed in a direction parallel to the axis of rotation of the drive spindle, and during operation the magnetic tape Cooperate with a drive hole in a rail hub of the cassette, at least one drive pin having a free end on each drive spindle: respectively cooperate with the first or second circumferential wall in its first or second position. Drive spindles and said centering pin of said two drive spindles being connected to said frame for And a cassette supporter for supporting a magnetic tape cassette of the drive company in the operating dentures in the two rail hubs cooperating with the field.

Such a magnetic tape drive is well known from US Patent No. 3027110. In such a magnetic tape drive device, a plurality of drive holes are formed in the disc-shaped centering device and the drive parts at each rail center which are at the same radial distance from the rotational axis of the rail center and separated from each other by the same distance. If two separate winding motors are used for the two rail centers, the spindle of the winding motor can also be used as a centering pin for setting the rail center. The rail hub position in the magnetic tape cassette is determined by the cassette position of the cassette support device.

The known magnetic tape drive device is used for recording or reproducing audio signals on magnetic tape. In order to use a video, such a magnetic tape drive is not suitable, since signals of much greater bandwidth must be recorded or reproduced than in audio use. In a magnetic video tape recorder that is commonly used and designed for the consumer market, the signals are recorded on the magnetic tape using a rotating video head as a track in the obliquely extending direction.

These slanted tracks have a width of approximately 18 to 23 microns at a length of approximately 100 mm for some magnetic tape recorders, and two magnetic videos to route the tracks directly connected to each other with no intermediate spacing. Use the head. In order to implement such a magnetic tape drive system, a video cassette recorded on one particular video recorder can be reproduced on the remaining video recorder without any loss, where high accuracy of conveying and delivering the tape is essential. to be. Therefore, fluctuations in the elongation of the magnetic tape and consequent variations in the tension in the magnetic tape are minimized. In fact, the video recorder must be able to read the track recorded on the magnetic tape by the remaining video recorder, and furthermore, the time error that adversely affects the quality of the picture must be eliminated. In light of the exacting compatibility imposed, there is a difficult problem of preventing undetermined friction from affecting the magnetic tape rail. In addition, other causes, such as tape tension variations, should be ruled out as far as possible. Conventional video recorders utilize several servo systems to obtain accurate tape feed rates and minimum tape tension variations. As an example, the rotational speed of the capstan is automatically controlled by the servo system, and at the same time there is another servo system for driving the rotating magnetic head, in which case it is used for controlling the magnetic head and for driving the driving spindle. . As a result of the tension fluctuations occurring in the magnetic tape, the frictional forces acting on the magnetic tape rail also give errors to the last mentioned servo system and other servo systems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic tape cassette which is well suited for use in a video recorder, wherein the drive for carrying out the drive of the present invention is characterized in that each drive spindle has an environmental end wall of the rail hub in order to position the rail hub in the axial direction. A real hub positioning device comprising a stopper and the like that rotates along a drive spindle to cooperate with each other is provided, and also includes an elastic load device for elastically pressing the real hub against the real hub positioning device during operation. In the operating position the rail hub and rail rotate to be completely aligned with the walls of the magnetic tape cassette. In the magnetic tape cassette according to the invention, the tiles in the magnetic tape cassette are supported in a non-contact manner with the remaining portions of the magnetic tape cassette, in particular with the two circumferential walls, during which there is more tension variation in the magnetic tape. Avoided.

In many magnetic video tape recorders, the drive device is a cassette supporter that can move between open and closed positions to hold the magnetic tape cassette in an operating position in the closed position and to insert or remove the magnetic tape cassette in the open position. Doing. One embodiment of the present invention is advantageous for use in a video cassette recorder equipped with such a cassette supporter, which video cassette recorder is adapted to the real hub position device configured with a first and a second real hub load function. On the contrary, it is installed as an elastic load device for elastically pressing the rail hub, and is journaled with the operation in the cassette supporter, and the loads are each provided with a center setting unit for centering the tubular rail winding parts of the rail hub. It is also composed of the first and second compression springs, etc., and cooperates with the real hub load mainly through point contact at the center setting position of the opposite condition of the center setting part. The first advantage of this recorder is that minimizing axial force is exerted on the drive spindle, but no tension force acts on the drive spindle in the meantime. The second advantage is that the load device is rotationally symmetrical and in the end does not allow any unbalance of the rail and is very important for the rapid transfer of magnetic tape during fast forward or reverse winding. This increases the speed up to 2,500 revolutions per minute. This speed corresponds to a tape speed of approximately 3 m per second during fast winding. Another advantage is that the structure is simple and the movement of the magnetic tape cassette is not hindered by the drive spindles.

The following embodiment for the magnetic tape cassette of the present invention has a ground in which the cassette supporter is partially open, the bottom face of which faces the bearing part having the cassette support of the drive unit and the bearing holes for two rail center loadings. The component faces away from the cassette support and can move axially and rotate when the rail center load is operated within the bearing bore in the bearing part, and the real hub load in the bottom direction. A stopper for limiting axial movement in the case, the cassette supporter having an elastic device for promoting the inserted cassette in the bottom direction, the distance between the real hub load and the bottom of the cassette supporter, The size of the tape cassette and the cassette support on the real hub and drive, Magnetic tapes in the open position of the cassette supporter are adapted to each other and are magnetic tapes in the closed position of the cassette supporter in such a way that they can be moved over the bottom of the cassette supporter without contacting the rail center loader. The cassette is supported by the cassette holding device at a location away from the bottom of the cassette supporter and cooperates with the rail hub so that the rail center can move freely in the bearing hole of the bearing part. In this embodiment, the rail center load does not interfere with the insertion of the magnetic tape cassette into the cassette supporter. Moreover, no separate assistance is needed to carry the rail center loader to the rail center. This is because the cassette supporter is automatically affected when it is moved from its open position to the closed position.

Advantages obtained by appropriately using the above embodiment for the present invention are as follows.

The rail-centric drive component defining the disk-shaped centering device and the drive holes has a planar wall portion to cooperate with the drive pins of the drive spindles, the planar wall portion extending substantially radially with respect to the axial direction of the rail center. This prevents the hum from being transferred in the direction other than the tangent direction of the force that the drive pin transfers to the center of the rail. In this embodiment only a very small flow is required between the drive pin and the wall of the drive hole. This is because a tolerance within the radial position of the drive pin is taken by the extension of the drive hole. Because of this, the impact between the drive pin and the wall of the drive hole is minimal when the movement of the rail is reversed during start or stop of the rail, which is advantageous in terms of magnetic tape drive life and accuracy of construction. Another advantage is that the bearing arrangement of the drive spindles is not unnecessarily loaded by non-tangential forces, which does not contribute to the torque applied to the non-tangential forces.

In order to obtain a well-defined position of the magnetic tape rail relative to the drive spindles, this embodiment is considered important and has the following features. An annular end of the center of the rail, having three axially extending protrusions disposed at radially equally spaced apart from the axis of rotation of the reel hub relative to where each of the annular end walls of the rail hub are equally spaced from each other; Each of the stops that rotate along the drive spindles to cooperate with the walls each have an annular stop surface disposed in a plane perpendicular to the front axis of the associated drive spins, whereby the rail center and the stops are connected to each other by a three-point contact. Cooperate. Since real hubs are generally made from thermoplastic plastic materials by an injection molding process, the installation of the axial protrusions knows no practical technical problems. The stopper that rotates along the drive spindles has a precisely machined side of the metal stopper. Also for the present invention, an embodiment is possible in which the real hub ensures a completely free centering on the drive spindle. This embodiment has the following advantages. The centering hole of the rail hub has a much smaller cross-section than the cross-section of the centering pin of the drive unit, and the disc-shaped centering device and the drive components are provided with radially extending grooves in relation to the axis of rotation of the rail hub. Consisting of a shorted part within the centering hole, which is defined, and in order to be able to actuate the drive part and the disk-type centering device which slide on the centering pin of the drive spindles to be blocked there. They are separated from each other by curved grooves.

In addition, this embodiment does not require the use of a real hub load connected to the cassette supporter for the present invention. Such an embodiment has the following advantages. An elastic load device that elastically presses against the reel hub positioning device during operation has a plurality of pressure members, the members being attached on each drive spindle and between a second position near the axis of rotation of the drive spindle relative to the first position. And a resilient device for applying a load to the pressure member toward the first position, the inner wall of the tubular winding part of each rail hub is provided with an annular stop for the pressure part. The bearing, a pressure component on the annular stop, stops the rail hub during operation, and the elastic device exerts the force generated there. At least one of them is directed towards the rail hub position device. Obviously, it is important to avoid suddenly being pushed or pulled by the magnetic tape cassette on the drive spindles or while moving the magnetic tape cassettes from the drive spindles. Thus, the magnetic tape cassettes of the present invention are moved to their first position towards their second position until the annular stopper is reached, as each inner wall of the tubular rail winding parts in each of the two end walls is moved onto the drive. It has a diameter that is gradually lowered to the annular stop to reduce the pressure components to gradually move.

In still another embodiment of the present invention, a resilient load device that resiliently presses against the reel hub positioning device during operation is comprised of components that are arranged at the anchorage of the drive spindle but are not movable all the way. Its characteristics are as follows. The rail hub adjacent to each of the end walls of the tubular rail winding part has an armature ring of magnetizable material, and is joined to each drive spindle armature ring and magnetically opposed to the rail hub positioning device. It has a magnetic device for pulling down. Even when the magnetic device for dragging the real hub against the real hub positioning device in conjunction with the armature ring constitutes an electromagnet, this embodiment switches the current to the electromagnet to move the magnetic tape cassette without expanding the axial force on the drive spindle. You can continue. The magnetic device on the drive spindles also consists of an annular permanent magnet whose outer wall is frustoconical, with the lowest diameter part being the diameter towards the free end of the centering pin, the armature ring being permanent on the drive spindle. It has a conical inner wall corresponding to the outer wall shape of the magnet, and an air gap of substantially uniform thickness is formed in the operating position between the outer wall of each permanent magnet and the inner wall of the armature ring which magnetically cooperates with it. do. The importance of the magnet and the armature ring is mainly due to the fact that a large air cap appears between the permanent magnet and the armature ring of all the real hubs when initially operating the magnetic tape cassette. Thus, the centering device of the rail hub on the routing pins of the drive spindles is not affected by the magnetic force extending to the rail hub during the centering. The shape of the walls and permanent magnets corresponding to the armature ring is chosen in such a way that optimal force path characteristics are obtained. During operation, the permanent magnet on the drive spindle is surrounded by the armature ring of the real hub, so that the stray field can be shielded in a satisfactory manner.

The invention will be described in more detail below with reference to the drawings schematically illustrated in the embodiments.

In the description of the drawings, various parts are indicated by different reference numbers, and when two identical parts are used, the same reference numbers are used, and when they are important for accurate understanding of the drawings, they are distinguished by adding "a" or "b". do.

Video cassette 1 (FIGS. 1-4 and 7-9 are so-called "invertible" magnetic tape cassettes, which are the rotating magnetic heads of the video recorder in a second position inverted from the first position) The cassette has a first and a second closely arranged rail hub 3 which, when rotated around a parallel axis of rotation 2, is a substantially cylindrical rail winding member attached to each of the hubs. (4) has at least a substantially circular inner wall (5), the substantially circular outer wall (6) and the two annular end walls (7) being in a plane some distance from the perpendicular to each other to the axis of rotation (2). The disc-shaped centering and driving member 8 has a part defining the centering hole 9 and the six driving holes 10 at some radial distance from the centering hole 9. Of this rail winding parts It is located in parallel between the end walls 7. A transparent flange 11 is fixed to both sides of the rail hub 3, thereby combining the real hub 3 with the two flanges 11 to form a sprue 12. In order to attach the magnetic tape to the rail hub, the hub has a recess 13 on its circumference The end of the magnetic tape is pressed into the recess and held there by an elastic clamping device although not shown.

In the video cassette, the two sprues 12 are axially bottomed by two parallel plane circumferential walls 14 each having a first hole 15a in operation, and the hole 15a is a second rail hub. Like the second hole 15b which is coaxial with (3b), it is coaxial with the first rail hub 3a. The circumferential wall 14 is interconnected by the wall 16, the back wall 17 and the front wall 18 partially open and disposed on the front side opposite the back wall 17. The magnetic tape cassette of the present invention includes a length of magnetic tape 19, which is connected to a first rail hub 3a attached to the first end and a second rail hub 3b attached to the second end. . As a result, it is wound from the first rail hub 3a to the rail 20b on the second rail hub 3b and rewound from the second rail hub 3b to the rail 20a on the first rail hub 3a. have. The straight tape portion passes along the front of the cassette. The slide 21 is guided to move onto the cassette housing and slides the guard 22 into its retracted position. The protective film is then pivoted in the first direction to open (see FIG. 3) or pivoted in the second direction to open (see FIG. 4). Although this cassette can be reversed, the straight portion of the magnetic tape 19 on the front side of the cassette can always be inserted into the parts of the video recorder from the same side regardless of the cassette position on the drive. The slide 21 is elastically loaded toward the front side by the pressure spring 23 in contact with the spring cup 24. Each side of the cassette has holes 122 and holes 123, and has a slightly larger radius obliquely in the direction parallel to the line connecting between the central portions of the two rail hubs 3. This hole is intended to take the positioning pin of the drive for the invention as described later.

Further information on the video cassette shown in the figure is based on unpublished Dutch patent application no.

The drive device is composed of a frame 25 and two drive spindles 27 and the like, the spindle being able to rotate around a parallel axis of rotation 26 and a central pin 28 wound around a conical free end 29. Each is provided, and cooperates with the center hole 9 in the rail hub 3 of the magnetic tape cassette 1, respectively. It is integral with the porter spins 30 of each electric drive motor 31 of the centering pin 28.

At some radial distance from the centering pin 28, there is a drive pin 32 attached to a rounded free end 33 on each drive spindle 27, which is a buoyancy spring 117. It can be pressed with elasticity in a direction parallel to the axis of rotation 26 of the drive spindle 27 against the force of. This drive pin cooperates with the drive hole 10 in the real hub 3 of the video cassette 1.

Cassette retainers 34 and 35 are provided on the frame 25 to support the video cassette in the first or second position of the video cassette, which can be seen in FIG. As it cooperates with the main wall 14 of the inserted cassette for holding the cassette on the drive in the operating position, there are two rail hubs 3 which are centered pin 28 and drive pin 32. Cooperate with The retaining devices 34 and 35 are composed of protrusions stacked together with the frame 25 and metal fixing pins 36 for the tape guide element 40 fixed in the protrusions 35. These have a conical end 37 and engage with the grooves 39 of the tape guide part 40 of the video cassette attached to the circular portions 38 and 111. This tape guide part extends beyond the main wall 14 of the cassette, whereby the tape guide part 40 is located directly on the cassette support device 35 when the cassette is in its operating position. It is therefore certain that the exact position of the tape guide part is relative to the part of the video recorder, which cooperates with the magnetic tape which is not affected by the tolerances of the video cassette housing.

The tape guide component has some radial axial movement within the circumferential wall 14, and pins 36 fixed thereto are used to secure the cassette housing on the excavation device. For this purpose there is also another securing pin 124 mounted on the plane 25 as can be seen in FIG.

In order to position the rail hub 3 in the axial direction, the drive spindles 27 are constituted by a stopper in the form of an angled stopper 41, the stopper of which is the It rotates along the drive spindle to cooperate with the annular end wall 7. During operation, each of the rail hubs 3 is elastically pressed against the stopper 41 by an elastic load device as described later, and is constituted by a leaf spring 42 like the parts 43. The rail hub 3 is supported at an appropriate height in the cassette 1 so that the sprue 12 travels completely against the walls of the video cassette.

The video recorder has a video cassette operating in a closed position and has an open position (FIG. 7) and a closed position (FIG. 8) to move or insert the video cassette 1 in an open position. It has a cassette support 44 which can be driven between them. The cassette supporter is composed of two side plates 45 separated from each other and connected by a hovering plate 46, by means of the torsional leaf spring 47, the cassette supporter on the strut 48 of the frame 25. Attached. Moreover, this cassette supporter consists of a bottom plate 49 and a connecting part 50, etc., which interconnect the two side plates 45. The resilient load device that presses the rail hub 3 against the stopper 41 during operation includes a load part 43 and the like in the connecting part 50 of the rail center load and the cassette supporter 44 journaled during operation. Consists of. Each of the rail hub loads includes a centering portion 51 for centering the rail hub load machine related to the cylindrical rail winding part of the rail hub 3. The rail hub loads are respectively loaded by the buoyancy springs 42 and cooperate with the rail center load 43 at the centered fixation position opposite the center set part 51 via point contacts, so-called round shoulders 52. It also cooperates with and is disposed on the axis of rotation 26 of the drive spindles 27 in the operating position.

On the side facing away from the cassette support devices 34 and 35, the cassette support 44 has a bearing part 53 connected to the connecting part 50, the bearing parts being connected to the connecting part ( 50 is in the form of bent metal pieces connected to it. A bearing hole 54 in the bearing part 53 is formed for the rail hub load 43, the holes being axially movable when the rail hub load is rotatable and operating in the bearing hole. It has as much diameter. Each of the rail center loads has a stop collar 55 for limiting the movement of the shaft in the direction of the bottom face 49 of the cassette supporter. The cassette located in the cassette supporter presses the tension spring 57 against the bottom face 49 with the aid of the lever 56 and is journaled on the side plate 45. In order to achieve this object, the lever 56 is composed of a pin 58 passing through the hole 59 of the side plate 45, a spring 57 and the like operating thereon. Each lever on the other side is mounted on a bearing plate 112 and is held on the pin by a rotary ring 113. The distance between the rail center load 43 and the bottom surface 49, the size of the magnetic tape cassette 1 and the rail hub 3, the size of the cassette support 44 and the cassette support devices 34 and 35 All allow the video cassette to move beyond the bottom face 49 of the cassette supporter without contacting the real hub loader in the open position of the cassette supporter (FIG. 7), and in the closed position (FIG. 8). Each other is adapted such that the video cassette is supported by the cassette support devices 34 and 35 at a location away from the bottom 49 of the cassette support 44, and the rail hub loading 43 is It can cooperate with the rail hub 3 so that it can move freely in the bearing hole 54 of the bearing component 53. Therefore, undesirable frictional forces or torques that would adversely affect the uniformity of the tape transfer and the tension in the magnetic tape do not reach the sprue 12 during operation.

5 shows that the driving hole 10 in the reel hub 3 is not round but at least elliptical. The drive hole 10 is locally constrained by the planar wall portion 60 to prevent the drive pin 32 of the drive spindles 29 from transmitting non-tangentially directed forces to the reel hub 3 during operation. In relation to the axis of rotation 2 of the reel hub. The ellipsoidal shape, which is excessive or lacking, takes a tolerance within the radial distance of the drive pin 33 relative to the axis of rotation 26 of the drive spindles.

It consists of three axially-directed projections 61 and the like arranged at equally spaced locations from each of the rail hub rotation axes 2 of the annular end wall 7 of the rail hub 3. The annular stops 41 rotating along the drive spindles 27 each have an annular stop surface 62 arranged in a plane perpendicular to the axis of rotation 26 of the drive spindles 27. The rail hub 3 and the stop 41 therefore cooperate with each other by means of a three-point contact, whereby the position of each failure on its clearly defined stop is guaranteed.

9 shows a method of determining the position of a video cassette on cassette support devices 34 and 35. At the fastening point of the cross-sectional view X-X in FIG. 9, the fastening pin 124 having the conical end 125 is engaged with the cassette hole 122, and the cylindrical portion of the fastening pin attached thereto is engaged in the inclined operation. The second securing pins 124 engage with the holes 123 of the video cassette (see FIGS. 4 and 9).

11 shows a disc-shaped centering and drive part 65 having a sprue 114 and a hole 66 extending radially in relation to the axis of rotation of the sprue and shorting in the centering hole 63. ) And the transverse size of the centering hole 63 of the rail hub 64 having a diameter much smaller than the diameter of the centering pin 28 of the drive. Each of the radial grooves 66 shorts in the cross groove 67 on the opposite side of the centering hole 63. By means of these grooves, it is possible to clamp the disc-shaped centering and drive part 65 onto the centering pins 28 of the drive spindles, the parts of which are slightly bent into the grooves 66 and 67. Separated from each other. This allows for excellent centering of the spool. This is because it cannot be operated anywhere between the sprue and the centering pin of the drive. Clearly, in order to align the sprue on such centering pins, a special axial force is required, during which the repositioning of the sprue requires some axial force as well.

This also applies to the case of two embodiments for the present invention, i.e., the case shown in FIG. 12 and FIG. FIG. 12 shows the cooperative relationship between the centering pin 115 and the reel hub 68, which differs from the reel center 3 just described in this regard. The rail hub 68 also has a center routing hole 69, similarly to the six drive holes 70 in the disc-shaped centering and drive component 71. The tubular rail winding part 72 has a rail flange 73 on both sides, one of which is shown partially in the cross section in the figure. The rail 75 is wound on the cylindrical outer wall 74 of the rail winding part 72. The component 76 is clamped onto the center line setting pin 115 and forms part of the drive spindles 116. The flanged portion 77 of the component 76 constitutes an annular stop surface 82 on its upper limit side, which surface is disposed in a plane perpendicular to the axis of rotation 79 of the centerline setting pin 115. In this embodiment, the resilient device for elastically pressing the reel hub 68 against the stop 77 during operation consists of a plurality of load components in the form of a bowl 80, which is arranged on each drive spindle. It is mounted to and can move to a limited range between a first or external position and a second or internal position near the rotary shaft 79. These parts are loaded by their pressure springs 81 towards their outer position. The tubular rail winding part 72 of the rail hub 68 is provided with an annular stopping device 83 internal to the bowl 80 near its end wall 82. As shown in FIG. 11, the bowl 80 discards the annular stop 83 during operation. They exert a force on the stop having a component directly directed towards the stop 77. The stops 83 are in contact with each other on the conical surface in that they are located below the center of the bowl.

The tubular rail winding part 72 near the end wall 82 of the rail hub 68 has a conical inner wall 84, the diameter of which decreases less than the annular stop 83. The inner wall serves to gradually move the bowl 80 from the outer position to the inner position until the annular stop 83 arrives on the drive during positioning of the magnetic tape cassette. The inner wall 83 belongs to a metal ring 85 which forms a part of the tubular rail winding part 72 of the rail hub 68. The circular metal sleeve 86 on the part 76 belonging to the drive spindles 116 is adapted to hold the bowl 80. In the fixing position of the bowl 80, a round hole 87 is formed in the sleeve having a diameter slightly smaller than the maximum diameter of the bowl 80. As a result, the bowl may protrude from the sleeve, but cannot be pressed out of the hole by the spring 81. Drive pin 88 is secured to ring 89 inside part 76. The pressure spring 90 pushes the ring 89 upward and discards the stop ring 91 attached to the other end. As a result of this structure, the drive pin 88 can be elastically compressed in a region limited in the direction of the rotation axis.

In FIG. 13, the real hub 92 is substantially the same as that of FIG. 11 except that the metal ring 85 is used instead of the metal ring 92 of a different type. This ring acts as an armature ring and is made of a self-loading metal that cooperates with the organ device in the form of a permanent magnet 94, which forms part of the drive spindles 95 and the metal electric hook 93 Is pulled out with respect to the stopper 96 serving as a rail hub positioning device. This stop forms part of the component 98 secured to the motor spindles 100, which acts as a centering pin with the aid of the screw 99. Although not shown, the permanent magnet 94 is fixed to the plastic support 101 by a screw device, and is connected to the stopper 96. The component 98 has a threaded portion 102 to which a cap 103 is attached. A ring 104 is disposed directly below the cap, to which the drive spindles 105 are fixed. The pressure spring 106 is supported by the plastic support 101 by pressing the ring 104 upward.

The permanent magnet 94 on the drive spindles 95 is annular and has an outer wall 107 in the frustoconical shape, the part of which is in contact with the minimum diameter of the outer wall near the free end 108 of the centering pin 100. Is located in. The armature ring 93 has a conical inner wall 109 corresponding to the shape of the outer wall 107 of the permanent magnet 94 on the drive spindles 95. In the operating position (see FIG. 12), an air cap 110 of substantially uniform thickness is formed between the outer wall 107 of the permanent magnet 94 and the inner wall 109 of the armature 93. The permanent magnet on its surface 107 has a plurality of alternating north and south poles, whereby the magnetic field lines in the operating position are accurately shielded by the armature ring 93, which is undesirable. It is confirmed that no problems can arise as a result of the stray magnetic field. In addition, the cap 103 and the stopper 96 are also made of a magnetizable metal.

Claims (1)

In a magnetic tape cassette in which two coaxial planar reel hubs (3) composed of at least one annular end wall (7) operate together with a planar stop (41) on drive spindles (27) of the cassette, A magnetic tape set comprising a subwall (7) formed of three axially extending protrusions (61) to come into contact with the stopper (41).

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